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bacteria swim in a very different manner to macroscopic animals because , at micron length scales , inertial effects are negligible compared to viscous forces . in this , the zero reynolds number limit , the navier - stokes equations reduce to the stokes equations , which are time reversal invariant .
this leads immediately to the scallop theorem @xcite , that any swimming stroke must be non - reciprocal look different when run forwards or backwards in time if it is to result in a net motion .
examples of strategies developed by microorganisms to overcome the scallop theorem are rotating flagella , waving cilia and surface waves .
moreover initial experiments have shown that it is possible to design tiny swimming robots which may be developed for drug delivery or manipulating payloads in microchannels @xcite .
to gain insight into the generic behaviour of microscopic swimmers several model systems have been defined and studied both analytically and numerically .
these include squirmers @xcite , purcell s three link swimmer @xcite , three linked spheres @xcite and the ` pushmepullyou ' swimmer @xcite .
all of these systems are polar swimmers , in that they undergo a non - reciprocal stroke , which picks out a preferred direction in time and hence results in swimming .
indeed , the scallop theorem suggests that apolar models should be immediately discounted as they will not swim .
however , as pointed out by koiller _
@xcite , although this is true for a single apolar swimmer , a collection of such swimmers _ can _ swim . if their swimming strokes are not in phase , the motion taken as a whole is not reciprocal in time , and motility is possible .
the physical mechanism which turns the motion of an apolar swimmer into a net displacement is the hydrodynamic forces between the swimmers . in this paper
we study the simplest model of an apolar swimmer , oscillating dumb - bells .
we give an analytic solution for the motion of a pair of dumb - bells , in the oseen tensor limit , and valid for large separations . by numerically iterating these results we are able to gain insight into how the orbits of two swimmers depend on their relative positions , separations , and phases .
we then consider regular arrays of swimmers and , in particular , suggest a way in which tethered swimmers could be used as a micropump .
we next present results for suspensions where the dumb - bells are initially placed randomly with random relative phases . the collective behaviour of such groups of self - propelled organisms has received a lot of interest in the past decade .
remarkably , the dynamics of systems as seemingly unrelated as flocks of birds , swarms of bacteria and vibrated rods can be treated within the common theoretical framework of active fluids @xcite . within this class
a distinction has been made between systems where the order is polar , for example , flocks of birds , and those with apolar order , such as vibrated rods .
since a dumb - bell is intrinsically apolar , a suspension of them provides a minimal microscopic model of an active _ apolar _ fluid .
we present results comparing the behaviour of a suspension of interacting dumb - bells to that of a suspension of three - linked - sphere swimmers @xcite , which is a simple microscopic model of an active _ polar _ fluid .
we first describe the motility of oscillating dumb - bells at zero reynolds number .
each dumb - bell comprises two spheres , of radius @xmath0 , joined by a thin , rigid rod , whose length varies sinusoidally as @xmath1 .
we stress the importance of the relative phase of the two dumb - bells : if they oscillate in phase or @xmath2 out of phase then their combined movements remain reciprocal and the scallop theorem prevents any net motion @xcite
. however , for other values of the relative phase , motion will occur . to show this we use the oseen tensor formulation of hydrodynamics , valid in the limit of zero reynolds number @xcite .
we present anaytic calculations , valid for large separations , and numerical results , valid for separations down to of order the size of a dumb - bell .
linearity of the stokes equations which govern zero reynolds number flows allows the fluid velocity to be written as a linear combination of the forces , @xmath3 , acting on the fluid due to the motion of the swimmers @xmath4 \ ; .
\label{eq : flow}\ ] ] here the subscript @xmath5 labels the dumb - bells and the superscripts @xmath6 label the spheres of an individual dumb - bell . for spheres
whose radii @xmath0 is small compared to their separation the greens function , @xmath7 , may be taken to be the oseen tensor , @xmath8 \ ; , \quad & \text{otherwise , } \end{cases } \label{eq : oseentensor}\ ] ] where @xmath9 .
the motion of the dumb - bells through the fluid is then determined by three ingredients ; consistency of the fluid flow with the change in shape , i.e. , the change in rod length , the constraint that each dumb - bell is force free , @xmath10 , and the constraint that each dumb - bell is torque free , @xmath11 .
a short calculation then leads to an expression for the forces @xmath12 where terms of @xmath13 $ ] have been omitted .
the unit vector @xmath14 gives the direction of sphere @xmath15 relative to sphere @xmath16 and thus describes the orientation of the dumb - bell .
applying the torque free constraint determines the angular velocity , @xmath17 , from which we obtain an equation for the evolution of the dumb - bell s orientation @xmath18 \\ & \quad \times \sum_{b \not = a } \bigl\ { g^1_b({\bf x}^2_a ) - g^1_b({\bf x}^1_a ) \\ & \qquad - g^2_b({\bf x}^2_a ) + g^2_b({\bf x}^1_a ) \bigr\ } { \bf f}^1_b \ ; . \end{split } \label{eq : rotate}\end{aligned}\ ] ] finally , the translational motion of each dumb - bell is given by @xmath19 where @xmath20 denotes the ` centre ' of the dumb - bell , @xmath21 . as expected , the motion described by eqns . and arises solely through interactions with other dumb - bells .
we assume that the dumb - bells are in a dilute suspension so that the separation , @xmath22 , of any given dumb - bell from its nearest neighbour may be assumed to be large compared to its size , @xmath23 . under such circumstances the interactions between the dumb - bells
may be expanded in a power series in @xmath24 and only the leading contributions retained . integrating over a complete cycle leads to expressions for the changes in position and orientation of the dumb - bells after a single swimming stroke : @xmath25 @xmath26 \\ & \ ; + 2{\bf n}_a \bigl [ ( { \bf n}_a \cdot \hat{{\bf r}}_{ba } ) + 2({\bf n}_a \cdot { \bf n}_b)({\bf n}_b \cdot \hat{{\bf r}}_{ba } ) \\ & \;\ ; - 5({\bf n}_a \cdot \hat{{\bf r}}_{ba})({\bf n}_b \cdot \hat{{\bf r}}_{ba})^2 \bigr ] \bigr\ } \ ; , \end{split } \label{eq : updatex}\ ] ] where @xmath27 is the position vector of @xmath28 relative to @xmath5 .
the amplitude @xmath29 is given by @xmath30 where @xmath31 is the phase of @xmath28 s swimming stroke relative to @xmath5 s .
the long time behaviour of a group of dumb - bells may be determined by numerically iterating eqns . and to find the new positions and orientations of all the dumb - bells after each swimming cycle .
at the origin and @xmath28 placed at the corresponding point in the diagram .
several regimes of long time behaviour are found . in region
p the two dumb - bells adopt a stable perpendicular configuration as exemplified by ( i ) .
this type of behaviour is also found in the shaded regions , however , before acquiring the perpendicular configuration the two dumb - bells tumble for a period of time , as shown in ( ii ) . in the regions labelled o the dumb - bells move along parallel trajectories with an oscillatory motion , as illustrated in ( iii ) .
finally , along each of the dashed lines there is no rotational interaction and the dumb - bells undergo a pure translation along straight parallel paths . ]
we first consider two dumb - bells lying in the @xmath32plane and both oriented along the @xmath33direction .
dumb - bell @xmath5 is initially at the origin and dumb - bell @xmath28 is placed on a circle of radius @xmath34 centred on the origin . for two dumb - bells , varying the relative phase does not lead to any qualitative changes in behaviour and therefore we consider only the case @xmath35 . the sole free parameter is the angle , @xmath36 , that the position vector of @xmath28 makes with the @xmath37direction . as this angle
is varied the hydrodynamic interactions between the dumb - bells change leading to different long time behaviour , which we illustrate in fig .
[ fig : pair ] .
the predominant behaviour is for the two dumb - bells to adopt a perpendicular configuration in which one dumb - bell is oriented parallel and the other perpendicular to their relative position vector .
this stable arrangement appears at long times for all initial configurations in the regions labelled p in fig .
[ fig : pair ] .
an exemplary time series showing how the perpendicular configuration is reached is shown in fig .
[ fig : pair](i ) .
the stability of this state may be seen from a linear stability analysis of eq . .
similarly , linear stability analysis reveals that the rotational fixed point at @xmath38 is unstable . however , small deviations away from this fixed point do not lead smoothly to the stable perpendicular configuration .
instead there is an initial period during which the dumb - bells tumble , often several times , before they finally settle down , as illustrated in fig .
[ fig : pair](ii ) .
exactly at the fixed point , and in the absence of any fluctuations , the dumb - bells undergo a pure translational motion , swimming cooperatively in the direction of the dumb - bell with positive relative phase .
the fully aligned configuration with @xmath39 is also a rotational fixed point and again , exactly at this angle , the motion is purely translational with both dumb - bells moving in the same direction .
however , in this case , the fixed point is a centre and small deviations away from it lead to an oscillatory cooperative motion , an exemplary time series of which is shown in fig .
[ fig : pair](iii ) .
this oscillatory motion occurs throughout the regions labelled o in fig .
[ fig : pair ] and is separated from the p regions by an additional rotational fixed point at @xmath40 .
we now present examples of the cooperative effects of the hydrodynamic interaction between many apolar swimmers , for first regular , and then random , distributions of swimmers . consider a chain of @xmath41 identical dumb - bells all oriented along the @xmath33direction and initially positioned at equally spaced intervals of @xmath42 along the @xmath37axis . to optimise the hydrodynamic interactions between nearest neighbours the relative phase between any two neighbouring dumb - bells
is set to @xmath43 , increasing in the positive @xmath37direction .
although this is a highly artificial configuration , the lack of any rotation greatly simplifies the dynamics , allowing for the effect of changing @xmath41 to be clearly quantified .
we show in fig .
[ fig : chainconfig ] the initial configuration of the chain and the distances moved by each of the dumb - bells as their total number increases .
two features are particularly noteworthy : firstly the behaviour for @xmath44 is significantly different from that for @xmath45 , and secondly the general behaviour for @xmath46 shows only minor variations , indicating that an asymptotic limit is being approached . swimming strokes for chains with different numbers of dumb - bells . ] the evolution of the pattern of swimmers may be understood by noting that there is a fundamental distinction between dumb - bells with two nearest neighbours and those with only one .
the former constitute what we shall call the _ bulk _ of the chain , while the latter form the _
boundary_. a dumb - bell in the bulk not only gets pulled along by its neighbour in front of it , but is also pushed by its neighbour from behind .
these two interactions add constructively leading to a member of the bulk moving faster than a single isolated pair . by contrast a dumb - bell which is on the boundary only has one nearest neighbour and
hence does not benefit from this added boost .
thus the bulk moves faster than the boundary .
this has the effect of introducing an asymmetry between the two boundaries ; the dumb - bell on the trailing boundary gets left behind while that on the leading boundary is caught up . from eq .
we see that the strength of interactions depends on the separation of the dumb - bells as @xmath47 , so that as the trailing dumb - bell gets left behind , the pull it receives from the bulk rapidly diminishes until it becomes isolated and can no longer move . at the same time
the distance between the leading dumb - bell and the bulk decreases yielding a sharp increase in the strength of interaction between itself and its neighbour . as a result the leading pair speed up significantly and are ejected from the front of the chain .
the cooperative motion of one dimensional chains carries over to regular arrays in two dimensions . as an example , consider a square lattice of dumb - bells all oriented in the @xmath33direction and with @xmath48 positions @xmath49 , where @xmath50 is the lattice constant and @xmath51 are integers .
co - operative directed motion can be induced by defining the phase of each dumb - bell to be @xmath52 .
the entire lattice then moves uniformly along the @xmath53 $ ] direction . for a system of real swimmers this state
could not be sustained ; we have found that it is unstable to any imperfections of the lattice such as boundaries or fluctuations in the position of the swimmers .
this instability of long range coherent states is in agreement with analytic work by ramaswamy and co - workers @xcite and numerical simulations of saintillan and shelly @xcite .
however one might envisage tethering fabricated dipolar swimmers to a substrate and aligning and activating them with a magnetic field .
such a set - up would act as a micon - scale pump .
we estimate @xmath54 , which is similar to the velocities achieved by bacteria .
it should be noted that the interactions scale with separation as @xmath47 , so that a small decrease in lattice spacing will provide a substantial increase in flow speed .
) and 0.02 ( @xmath55 ) .
bottom : diffusion constant for increasing number of swimmers . ]
we consider a suspension of @xmath41 dumb - bells initially dispersed throughout a cubic box of side @xmath56 with random positions , orientations and relative phases . to avoid singularities in the hydrodynamic interactions a short distance cut - off
is employed when the separation between any two dumb - bells becomes less than @xmath57 . at separations of order
@xmath23 an expansion of the oseen tensor in powers of @xmath58 does not converge rapidly . to overcome these difficulties we instead use an expansion in powers of @xmath59 to better describe the near field hydrodynamics .
the combination of a random initial configuration and apolar symmetry means that there is no prefered direction for the motion , and on average the velocity is zero . in continuum models of apolar active fluids
spontaneous symmetry breaking can lead to a state with non - zero average velocity @xcite , however we have not observed any such transitions in our simulations of dumb - bells . in the absence of a net velocity , the mean speed provides a measure of the degree of collective activity . fig .
[ fig : collective](i ) shows that the mean speed of the dumb - bells increases linearly with the number density @xmath60 .
this agrees with a simple scaling argument : since every dumb - bell will interact with every other one , the total number of interactions scales as @xmath61 . balancing
this against the kinetic energy predicts that the mean speed should increase linearly with @xmath62 .
the same linear scaling , but tending to a finite value as @xmath63 because of the finite speed of a single swimmer , is also found for a suspension of polar swimmers ( fig . [
fig : collective](ii ) ) .
a measure of the nature of the collective motion generated by the interacting dumb - bells is the mean square displacement , @xmath64 , where @xmath65 denotes an ensemble average .
this is plotted in fig .
[ fig : collective ] for number densities of @xmath66 and @xmath67 . at long times , and for large number densities , a scaling form @xmath68 develops , with an exponent of @xmath69 indicating that the suspension of dumb - bells is behaving diffusively . at smaller number densities
the behaviour is more sporadic because the large average separation between dumb - bells greatly reduces the strength of the interactions between them .
the collective motion is then dominated by those fluctuations in the local number density which bring two dumb - bells close enough to allow them to move appreciably .
the mean square displacement of a suspension of dumb - bells shows qualitatively different behaviour to that of a suspension of polar swimmers . in the latter case , shown in fig .
[ fig : collective](ii ) , the mean square displacement is ballistic at short times ( @xmath70 ) , with a cross - over to diffusion ( @xmath69 ) at longer times .
moreover , since this cross - over is due to the randomisation of swimmer orientations through hydrodynamic interactions , it occurs at later and later times as the number density is reduced . for polar swimmers
this leads to a diffusion constant which decreases as the number density is increased . for apolar swimmers
the oppposite is true ; their motion arises solely from hydrodynamic interactions and the diffusion constant increases with increasing number density .
the aim of this letter is to discuss the motion of a simple model of apolar swimmers , systems which move at zero reynolds number _ only _ in the presence of other swimmers .
we have demonstrated that , as is the case for colloids @xcite and polar swimmmers @xcite , hydrodynamic interactions lead to complex collective behaviour .
particular observations are that , for two dumb - bell swimmers which are initially parallel , the most likely final state corresponds to the axes of the swimmers lying at right angles .
oscillatory trajectories are also observed . for regular arrays of swimmers cooperation between hydrodynamic pair interactions can lead to simple flow fields .
in particular a square array of dumb - bells produces a constant flow and hence , if the dumb - bells were fixed in position , could act as a pump . for a large number of dumb - bell swimmers , initialised with random positions and phases , the mean speed is linear in the number of dumb - bells , reflecting the energy pumped into the system by the hydrodynamic interactions .
the mean - square displacement evolves linearly in time showing the expected diffusive behaviour .
there is much further work to the done to explore the phase space of apolar swimmers , for example considering initial configurations for which pairs move out of the plane , three dumb - bell orbits , and the role of the distribution of phases on multi - dumb - bell motion . for more than two dumb - bells the relative phase becomes an important variable ; since the pairwise interactions between three or more dumb - bells can not simultaneously take their maximum value the system exhibits a type of frustration .
it is also interesting to consider the effect of moving away from the zero reynolds number limit @xcite , and to ask which of the properties of dumb - bells provide a generic representation of the class of apolar swimmers .
comparing simple microscopic models of polar and apolar swimming may help to formulate the correct continuum theory of swimmers , and to link the microscopic and continuum length scales .
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|
we investigate the way in which oscillating dumb - bells , a simple microscopic model of apolar swimmers , move at low reynold s number . in accordance with purcell s scallop theorem a single dumb - bell can not swim because its stroke is reciprocal in time . however
the motion of two or more dumb - bells , with mutual phase differences , is not time reversal invariant , and hence swimming is possible .
we use analytical and numerical solutions of the stokes equations to calculate the hydrodynamic interaction between two dumb - bell swimmers and to discuss their relative motion .
the cooperative effect of interactions between swimmers is explored by considering first regular , and then random arrays of dumb - bells .
we find that a square array acts as a micropump .
the long time behaviour of suspensions of dumb - bells is investigated and compared to that of model polar swimmers .
|
• Host DJ Martin Solveig has since apologised for his comment • Luka Modric won men’s award to break Ronaldo-Messi duopoly • The 100 best female footballers in the world 2018: part one
Luka Modric ended a decade of dominance by Lionel Messi and Cristiano Ronaldo in the Ballon d’Or but the Croatian’s win was overshadowed when the inaugural winner of the women’s award, Ada Hegerberg, was asked to twerk live on stage by the host DJ, Martin Solveig.
The 100 best female footballers in the world 2018 Read more
Hegerberg, who helped Lyon to the French title and Champions League, scoring in the final, pipped Denmark’s Pernille Harder to the prize but appeared embarrassed when asked by Solveig if she wanted to dance in celebration and “knew how to twerk”.
The 23-year-old said “no” and seemed to attempt to leave the stage, before reluctantly agreeing to dance to another song with Solveig. Solveig tweeted shortly after the ceremony, saying he had apologised to Hegerberg for the remark.
“I explained to [Ada] and she told me she understood it was a joke,” Solveig wrote. “Nevertheless, my apologies to anyone who may have been offended. Most importantly, congratulations to Ada.”
The Norwegian forward said: “He came to me afterwards and was really sad that it went that way. I didn’t really consider it sexual harassment or anything in the moment. I was just happy to do the dance and win the Ballon d’Or.”
Play Video 1:01 Ada Hegerberg's Ballon d'Or triumph and fight for equality in football – video profile
Hegerberg added she was extremely proud to be named the first female winner. “It’s incredible,” she said. “This is a great motivation to continue working hard and we will continue to work together to win more titles. I wanted to end with some words for young girls around the world: believe in yourselves.”
Andy Murray was among those on social media who criticised Solveig’s comment, calling it “another example of the ridiculous sexism in sport.”
“What questions did they ask Mbappé and Modric?” the British tennis player added on Instagram. “I’d imagine something to do with football. And to everyone who thinks I’m overreacting and it was just a joke ... it wasn’t. I’ve been involved in sport my whole life and the level of sexism is unreal.”
Ada Hegerberg stepped forward for women’s football, but sexism kicked her back | Suzanne Wrack Read more
Modric won a third straight Champions League title and inspired his country to reach the World Cup final, and there are few who will begrudge his victory, with Ronaldo in second. Lionel Messi only came fifth, finishing behind France duo Antoine Griezmann and Kylian Mbappé – the first time since 2006 that the Argentina forward has not finished in the top three.
There had been a clue that there would be a new winner in the 63rd edition of this award – Blackpool’s Stanley Matthews was the first in 1956 – when neither Ronaldo nor Messi were present at the Grand Palais in Paris, although in typically humble fashion Modric admitted he had been pleasantly surprised to be recognised after being congratulated on his victory by Croatia president Kolinda Grabar-Kitarovic.
Play Video 0:49 Luka Modric 'honoured' after winning men's 2018 Ballon d'Or – video
Having become the first teenager to score in a World Cup final since Pelé in 1958 as France won their second title in Russia, Paris Saint-Germain’s forward Mbappé was the runaway winner of the inaugural Kopa Trophy for the best player under the age of 21, ahead of Liverpool’s Trent Alexander-Arnold. Mohamed Salah finished in sixth place in the men’s award in recognition of his fantastic debut season at Anfield, in which he scored 32 Premier League goals and helped the team reach the Champions League final.
Quick guide Ballon d'Or: Full results Show Hide Men's award – top five 1) Luka Modric (Croatia and Real Madrid)
2) Cristiano Ronaldo (Portugal and Juventus)
3) Antoine Griezmann (France and Atlético Madrid)
4) Kylian Mbappé (France and PSG)
5) Lionel Messi (Argentina and Barcelona) England's Harry Kane was 10th, Wales's Gareth Bale joint 17th Women's award – top five 1) Ada Hegerberg (Norway and Lyon)
2) Pernille Harder (Denmark and Wolfsburg)
3) Dzsenifer Maroszan (Germany and Lyon)
4) Marta (Brazil and Orlando Pride)
5) Sam Kerr (Australia and Chicago Red Stars) England's Lucy Bronze and Fran Kirby finished sixth and 14th Kopa award for best young player The inaugural award for the best under-21 player in the world was won by France and PSG forward Kylian Mbappé. The men's award: how the rest finished 6 Mohamed Salah 7 Raphaël Varane 8 Eden Hazard 9 Kevin De Bruyne 10 Harry Kane 11 N'Golo Kanté 12 Neymar 13 Luis Suárez 14 Thibaut Courtois 15 Paul Pogba 16 Sergio Agüero =17 Karim Benzema, Gareth Bale =19 Roberto Firmino, Ivan Rakitic, Sergio Ramos =22 Marcelo, Edinson Cavani, Sadio Mané =25 Alisson, Jan Oblak, Mario Mandzukic 28 Diego Godín =29 Isco, Hugo Lloris. Photograph: Aurélien Meunier/Getty Images Europe
Salah was the highest-ranked player from the Premier League, with Chelsea’s Eden Hazard eighth, Kevin De Bruyne of Manchester City ninth and Tottenham’s Harry Kane – who won the Golden Boot in Russia – 10th. ||||| Olympique Lyonnais' Ada Hegerberg celebrates with the Women's Ballon d'Or award during the Golden Ball award ceremony at the Grand Palais in Paris, France, Monday, Dec. 3, 2018. Awarded every year by... (Associated Press)
Olympique Lyonnais' Ada Hegerberg celebrates with the Women's Ballon d'Or award during the Golden Ball award ceremony at the Grand Palais in Paris, France, Monday, Dec. 3, 2018. Awarded every year by France Football magazine since Stanley Matthews won it in 1956, the Ballon d'Or, Golden Ball for the... (Associated Press)
PARIS (AP) — Luka Modric ended the long reign of Lionel Messi and Cristiano Ronaldo by winning the Ballon d'Or for the first time on Monday, while another first saw Norwegian forward Ada Hegerberg win the inaugural women's trophy.
Messi and Ronaldo had won every Ballon d'Or since 2008, and usually fought only each other for the greatest recognition among soccer's elite. Women's fight for recognition on the biggest stage took a big step with Hegerberg's award.
Modric won the Champions League with Real Madrid and then guided Croatia to the World Cup final in July. The midfielder was voted player of the tournament.
"As a kid we all have dreams. My dream was to play for a big club and win important trophies," Modric said. "The Ballon d'Or was more than just a dream for me and it is really an honor and a privilege to hold this trophy."
Ronaldo was second in the polling followed by France forward Antoine Griezmann. France's teen star, Kylian Mbappe, was fourth. Brazil star Neymar was third last year but only 12th this time. Messi was fifth in the voting, having been runner-up to Ronaldo the past two years and in the top three every year since 2007. Modric had never previously been in the top three.
"2018 is a dream year for me," the 33-year-old Modric said. "Throughout my career I realized hard work, persistence and belief in yourself in difficult moments are the foundations of success."
Modric's father was shown on the big screen wiping away tears during the ceremony at the imperious Grand Palais in Paris.
Ronaldo missed out on a record sixth award, which would have moved him one ahead of Messi. The last player to win it before those two started dominating world soccer awards was Brazil midfielder Kaka with AC Milan in 2007.
Ronaldo also won the Champions League last season with Modric, before leaving to join Juventus. He scored a hat trick against Spain at the World Cup but he failed to make an impression when Portugal lost to Uruguay in the round of 16.
Mbappe and Griezmann scored in the 4-2 World Cup final win against Croatia. Mbappe earned a domestic treble with Paris Saint-Germain. Griezmann also scored twice for Atletico Madrid in the Europa League final win against Marseille.
France coach Didier Deschamps said a France player should have won the award.
"They deserve it because of what they did with the national team at the World Cup and also because of the trophies they won with their clubs," Deschamps said.
The 19-year-old Mbappe — the youngest player to score in a World Cup final — won the Raymond Kopa Trophy awarded to the best young player.
France Football magazine has been awarding the Ballon d'Or since 1956, and created a women's award for the first time this year.
Hegerberg is a three-time Women's Champions League winner with French side Lyon and scored a tournament-record 15 times last season.
"I want to say thanks to France Football. It's a huge step for women's football," Hegerberg said. "I want to end this speech with a message to all young girls in the world. Believe in yourselves."
The outspoken 23-year-old Hegerberg said she won't play for Norway at the Women's World Cup in France next June.
Taking a stand against what she describes as a lack of respect for female players in Norway, she hasn't played for the national team since 2017 when it crashed out of the group stage of the Women's European Championship without scoring a goal.
Speaking in an interview shortly before collecting her Ballon d'Or, Hegerberg told The Associated Press on Monday she has no plans to reconsider her decision taken to preserve her "authenticity and my values, as a person, as a footballer."
"A lot of things need to be done to make the conditions better for women who play football," she said. "It's all about how we respect women's football. I don't think the respect has been there.
"Sometimes you have to take tough decisions to stay true to yourself. I let them know, quite clearly, what I found wasn't working."
___
More AP sports: https://apnews.com/apf-sports and https://twitter.com/AP_Sports ||||| One of the most prestigious soccer awards ceremonies in the world sparked outrage Monday night when the first-ever women’s soccer player of the year was asked to twerk on stage by a male presenter.
Norwegian striker Ada Hegerberg, 23, had just accepted her trophy when the presenter, Martin Solveig, a DJ and producer, asked her in French if “she could twerk”. Visibly irritated, Hegerberg declined. With an abrupt “no,” she turned and left.
Hegerberg had just been crowned the first ever recipient of the Women’s Ballon D’or – an annual soccer award that until this year only recognized the best male player in the world. Hegerberg was the leading scorer with 15 goals as her team, Lyon, won the Champions League for the third year in a row.
France Football has awarded the Ballon d’Or to a male player every year since 1956, but this is the first year there has been a women’s award.
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Before Solveig’s intervention, Hegerberg thanked all who had helped her to the achievement.
“I want to say thanks to my team-mates because this would not have been possible without them, my coach or our president Jean-Michel Aulas,” Hegerberg said.
“I also want to thank France Football. This is a huge step for women’s football.”
But what should have been a celebratory and historic evening quickly descended into awkwardness and uncomfortable silence. Soccer, like many sports, has a problem with sexism. Solveig’s comments were met with stunned silence in the audience. The ceremony, which took place in Paris, appeared to be cut short after the incident.
In a video posted to Twitter shortly after, Solveig said “he [hadn’t] wanted to offend anyone,” and that the question, intended as a joke, had been misconstrued.
In an interview with the BBC later on Monday, Hegerberg sought to play down the moment.
“He came to me afterwards and was really sad that it went that way. I didn’t really think about it at the time to be honest. I didn’t really consider it a sexual harassment or anything in the moment.
“I was just happy to do the dance and win the Ballon d’Or to be honest. I will have a glass of champagne when I get back,” she said.
On the same night, Luka Modric, who lead Croatia to their first ever World Cup Final and won an unprecedented third Champions League trophy with Spanish club Real Madrid, was named the world’s best male player. Cristiano Ronaldo, who has won the Ballon D’or five times – a record he shares with Barcelona striker Lionel Messi – placed a distant 5th.
It was the first time in ten years that neither player has won the award.
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– It was, as Norwegian soccer great Ada Hegerberg told the audience, "a huge step for women's football." The 23-year-old had just become the first woman to win the prestigious Ballon D'or in France, which recognizes the greatest soccer player in the world. And then the event's host tried to be funny: French DJ Martin Solveig asked Hegerberg to dance and wondered if she knew how to twerk, reports Time. Hegerberg responded "no" and began walking off stage, the moment captured here, though she did remain to dance with Solveig to a Frank Sinatra song. The "twerk" question, though, exploded on social media, with Solveig coming under worldwide criticism for sexism. “This is disgusting,” tweeted US soccer great Abby Wambach. “Imagine having just been given the best award for your craft/job/passion, and this is the question you’re asked?!" From the tennis world, Andy Murray called it “another example of the ridiculous sexism in sport," per the Guardian. Solveig tweeted an apology video, saying it was a "bad joke" and not meant to offend, and Hegerberg herself told the BBC that she didn't perceive it as an insult in the moment. "I was just happy to do the dance and win the Ballon d'Or, to be honest." Though Hegerberg isn't joining the anti-Solveig bandwagon, she is a big proponent for women's equality in sport. The AP reports, for example, that she won't play for Norway in next year's Women's World Cup because she thinks the team's players aren't treated fairly. "It's all about how we respect women's football," she said. "I don't think the respect has been there." (People were miffed about US soccer star Brandi Chastain's likeness on a plaque.)
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epigenetics represents the field of study of heritable changes in gene expression which are not directly related to dna and it studies : histone modifications , short interfering rnas etc . , micrornas ( mirnas ) .
these are small noncoding rnas , 21 to 23 nucleotides in length , which either inhibit translation or affect mrna stability and degradation .
there are mirnas involved in the animal and human diabetes mellitus ( type 1 or 2 ) .
microrna-9 ( mir-9 ) has been correlated with modifications in glucose - stimulated insulin release ( gsis ) .
. demonstrated , in the rat -cell line ins-1e , that higher levels of mir-9 decrease the expression of the onecut-2 ( oc2 ) gene which determines an increase in granuphilin , exerting a negative control on insulin exocytosis .
the authors have stipulated that , although mir-9 expression is higher in neurons than in -cells , the lack of granuphilin expression in the former allows neurons to support these higher concentrations .
more recently , ramachandran et al . showed , in vivo , on -cells from adult swiss male mice , that mir-9 levels increase during the falling phase of insulin secretion .
the same group has also shown that mir-9 negatively regulates sirt1 by targeting its 3utr region thus affecting gsis in -islets .
sirt1 represents a mammalian class - iii protein deacetylase that has also been linked to senescence and to cognitive functioning in an analysis of the leiden 85-plus study .
it has also been shown that sirt1 is correlated with depression in two japanese human studies , one including patients with major depressive disorder or bipolar disorder , but not correlated to the therapeutic response to selective serotonine reuptake inhibitors ( ssris ) .
as such , mir-9 , through its effects on oc2 and especially sirt1 plays important roles both in insulin release and in depression , with much still to be learned about the molecular pathways through which these effects are obtained .
advanced glycation end products ( ages ) represent important molecules in the pathology of diabetes that act through the receptor for advanced glycation end products ( rage ) to induce cyclooxygenase-2 ( cox-2 ) , an inflammatory gene .
s100 is a ligand of rage that can increase cox-2 in different tissues , including pancreatic islets .
physiologically , microrna-16 ( mir-16 ) can promote a rapid degradation of cox-2 mrna but this process is blocked , in vitro , by s100b which inhibits mir-16 expression .
a recent study by baudry et al . on mice showed that chronic treatment with fluoxetine ( a ssri ) increased mir-16 levels in serotonergic raphe nuclei thus reducing the levels of the serotonin transporter ( sert ) , whilst the raphe released the molecule s100 , previously shown to be implicated in diabetic complications .
s100 decreased mir-16 levels , promoting the expression of the serotonergic functions in noradrenergic neurons .
the study also proved the implication of the wnt receptor and of the connection between the locus coeruleus and the raphe in the treatment of depression with fluoxetine .
this study is the first to prove the role of micrornas in the treatment of depression and it might explain the delayed onset of action of ssris in treating depression , at least in part .
while s100 is believed to have only a paracrine / autocrine function , it has already been demonstrated that this protein , through the immune reactions towards it , might represent a factor in parkinson s disease and the impaired insulin response that occurs in this disease .
s100 has already been associated with depression , as shown previously , with a recent study demonstrating this association in patients with end - stage renal disease as well .
s100 has also been shown to be involved in mental stress , neurodegenerative disorders [ 16,18 , 19 ] , brain injury , head injury , and schizophrenia .
as such , s100 is already of interest as a treatment for several neurological and psychiatric diseases .
while this organ is known for its regenerative capabilities , so far neurogenin3 ( ngn3 ) is the only molecule that is expressed only during the pancreas development and not during its regeneration .
a recent study performed by joglekar et al . has shown that during pancreas regeneration in mice , several micrornas , including mir-16 , activate an alternate , new pathway , which does not involve ngn3 , thus offering new therapeutic options for type 1 and 2 diabetes mellitus .
in the past years , the dysfunction of circadian rhythms has been shown to play a role in major depression ( md ) .
the first proof of microrna-132 ( mir-132 ) being involved in the circadian rhythms has come from cheng et al . who have shown that mir-132 is induced by photic stimulation through several pathways . in a more recent human study including 359 patients with md and 341 controls , saus et al .
we suggest a precise posttranscriptional regulation of circadian rhythms by mirnas with a role of rs76481776 snp [ single nucleotide polymorphism ] in the control of sleep awake rhythm .
recently , yang et al . have also proven that mir-132 represents an important factor in the differentiation of embryonic stem cells into dopamine neurons through a direct regulation of the expression of the nuclear receptor sub - family 4 group a member 2 ( nr4a2 , also known as nurr1 ) .
reports regarding the function of mir-132 in diabetes and insulin signaling are diverse : numakawa et al .
did not find insulin - like growth factor-1 ( igf-1 ) to have an effect in mir-132 regulation , while the in vivo experiments on goto - kakizaki ( gk ) rats of esguerra et al .
have shown that the expression of rno - mir-132 is upregulated by hyperglycemia , although during prolonged exposure to hyperglycemic conditions , the gk islets strived to reset the levels of mirnas to that of the controls .
this last result is also confirmed by results obtained in isolated pancreatic islets of other mouse models .
an interesting finding is related to a study of gestational diabetes mellitus ( gdm ) in which the levels of mir-132 were significantly decreased in gdm patients in comparison with controls ( p=0.042 ) , the authors suggesting the utility of mir-132 as a serum - based non - invasive biomarker during early second trimester .
there have been numerous studies in which malnutrition of the mother during pregnancy or malnutrition of the child in the first years of life has been linked to diabetes .
an ethiopian study including 107 patients showed that diabetes was strongly associated ( odds ratio= 5.5 , 95% ci : 1.57.8 ) with a history of childhood malnutrition , while two studies of mexican patients have suggested that early impaired nutrition in extrauterine life is correlated with insulin anomalies in young adult males and that there is a decreased activity of beta - cell function and increased insulin sensitivity in stunted children . a historical cohort study of 300.000 men exposed to
the dutch famine of 19441945 showed that nutritional deprivation in the first half of the pregnancy resulted in higher obesity rates ( p<0.0005 ) , while exposure in the last trimester of pregnancy and the first months of life led to lower obesity rates ( p<0.005 ) .
one of the possible explanations for this association is gene methylation in utero which was demonstrated by a study done by lillycrop et al . which shows that an unbalanced prenatal nutrition induces persistent , gene - specific epigenetic changes that alter mrna expression .
recent studies support the results of ravelli et al . that both malnutrition and over - nutrition act through epigenetic mechanisms leading to an increased risk of diabetes .
another study on the dutch famine has shown that people conceived during the famine were at increased risk for schizophrenia and depression , possibly through inheritable epigenetic mechanisms .
the protein proopiomelanocortin ( pomc ) seems to play an important role in the presented pathology as it is involved in energy homeostasis and has been recently shown to be modulated by epigenetic changes , as shown by a recent study in patients with anorexia nervosa . a recent review analyses the strong associations between prenatal famine , diabetes and schizophrenia , a thorough review of under - nutrition effects , as well as the homocysteine hypothesis of depression elaborated by folstein et al . .
as it may be seen from the information presented , the field of mirnas in the diagnosis and the pathology of psychiatric diseases , as well as in diabetes mellitus , is still new , but researchers have already identified several such molecules that are involved in both conditions .
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diabetes mellitus is one of the most cited non communicable diseases and the most common metabolic disorder .
epigenetics represents the field of study of heritable changes in gene expression which are not directly related to dna .
epigenetics is concerned , alongside histone modifications , short interfering rnas etc .
, with micrornas ( mirnas ) as well
. these are small noncoding rnas , 21 to 23 nucleotides in length , which either inhibit translation or affect mrna stability and degradation . at present , there are dozens of mirnas which have been proven to be involved in the animal and human pathology of diabetes ( type 1 or 2 ) .
this review focuses on the mirnas which have been identified as playing a role in both psychiatric diseases and diabetes .
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there are several extensions of the standard model ( sm ) with an enlarged scalar sector .
some of these extensions allow for higgs with reduced or even no couplings to the fermions .
they are referred to as fermiophobic higgs scenarios in the literature @xcite .
the d0 collaboration has recently presented new results on fermiophobic higgs searches @xcite . in @xcite
they have searched for a fermiophobic higgs produced in association with a charged higgs .
the full process is @xmath9 and was proposed in @xcite .
d0 required at least three photons in the final state for maximizing signal efficiency . for each pair of values of @xmath10
a bound on the fermiophobic higgs mass was set . in @xcite ,
d0 has performed a search for the inclusive production of di - photon final states via the higgsstrahlung and vector boson fusion processes : @xmath11 and @xmath12 , respectively , with a total integrated luminosity of 1.10 @xmath13 0.07 @xmath14 . a lower @xmath15 bound of 100 gev
was obtained in a benchmark scenario that assumes hvv ( v= w , z ) couplings to be exactly the same as in the sm and all fermion branching ratios to be exactly zero .
+ all lep collaborations have searched for a fermiophobic higgs in the channel @xmath16 @xcite . the combination of all results @xcite yielded the lower bound for the fermiophobic higgs mass of 109.7 gev , at 95% confidence level , which again is valid only in the above benchmark scenario .
searches in the @xmath17 channel were also performed at lep with lower bounds derived for @xmath18 ( see references @xcite for details ) .
the new d0 bound @xcite on @xmath15 is weaker but a larger region of the model s parameter space is covered .
the channel @xmath19 had already been used at the tevatron by the cdf @xcite and by the d0 @xcite collaborations to set limits of 78.5 gev and 82 gev at 95% confidence level , respectively , on the fermiophobic higgs mass .
it is expected @xcite that all tevatron bounds will improve once the data collected at @xmath20 luminosity is analyzed .
+ there are however other ways of producing a four photon final state in a fermiophobic scenario . in this letter
we will consider all fermiophobic higgs production processes with at least three photons in the final state produced via gluon fusion .
as shown in @xcite , a signal with at least three photons is very easy to extract at the tevatron .
the most relevant process for the analysis is @xmath21 but we can also have @xmath22 and @xmath23 .
we will show that both the tevatron and the large hadron collider ( lhc ) can probe a substantial region of the parameter space .
we will discuss as well the complementarity between the different production modes .
+ this paper is structured as follows : we will review the fermiophobic model in section ii and then proceed to look at the all available theoretical and experimental bounds in section iii . in section iv
, we will discuss in detail the production process and in section v the signal .
analysis of the results and conclusions will be presented in section vi .
to define our notation we start with a brief review of the two - higgs doublet potential used here .
the potential chosen is the most general , renormalizable , cp - conserving potential , invariant under @xmath24 that one can build with two complex higgs doublets .
it can be written as @xmath25 & & \lambda_{4}(|\phi_{1}|^2 |\phi_{2}|^2 - |\phi_{1}^+\phi_{2}|^2 ) + \lambda_{5 } [ \re e(\phi^+_{1}\phi_{2 } ) -v_{1}v_{2}]^2 + \lambda_{6 } [ \im m(\phi^+_{1}\phi_{2})]^2 \label{higgspot}\end{aligned}\ ] ] where @xmath26 and @xmath27 have weak hypercharge y=1 , @xmath28 and @xmath29 are respectively the vacuum expectation values of @xmath26 and @xmath27 and the @xmath30 are real valued parameters .
note that this potential violates the discrete symmetry @xmath31 only softly by the dimension two term @xmath32 .
the hard breaking terms ( dimension four ) of the discrete symmetry have been set to zero .
as in all other thdm , we end up with two cp - even higgs states usually denoted by @xmath33 and @xmath34 , one cp - odd state , @xmath35 and two charged higgs bosons , @xmath36 .
the potential in eq .
( [ higgspot ] ) has 8 parameters ( including @xmath28 and @xmath29 ) .
the combination @xmath37 is fixed as usual by the electroweak breaking scale through @xmath38 .
we are thus left with 7 independent parameters ; namely @xmath39 , and @xmath40 .
equivalently , we can take instead @xmath41 as the 7 independent parameters .
the angle @xmath42 is the rotation angle from the group eigenstates to mass eigenstates in the cp - odd and charged sector .
the angle @xmath43 is the corresponding rotation angle for the cp - even sector .
+ in a general thdm it is possible to couple just one doublet to all fermions by choosing an appropriate symmetry for both the fermions and the scalars .
this model is known as thdm type i in the literature .
like in the sm , where just one doublet couples to all fermions , each scalar couples to the different fermions with the same coupling constant . however , unlike the sm , the couplings are now proportional to the rotation angles @xmath43 and @xmath42 .
for instance , the lightest cp - even higgs couples to the fermions as @xmath44 . by choosing @xmath45 , the lightest cp - even higgs decouples from all fermions .
it is usually referred to as a fermiophobic higgs scalar @xcite . this way the heavy cp - even scalar will acquire larger couplings to the fermions than the corresponding sm couplings .
the remaining scalars are not affected by this choice as they do not couple proportionally to @xmath43 .
however , @xmath33 can still decay to two fermion pairs via or
. we will include these decays in our analysis .
it is worth pointing out that these processes occur near the @xmath46 threshold .
decays of @xmath33 to two fermions can also be induced by scalar and gauge boson loops ( see e.g. fig . [
fig : fig_hff ] ) . in the thdm ,
the angle @xmath43 has to be renormalized to render @xmath47 finite .
however , at @xmath48 , all one - loop decays @xmath49 are finite .
thus we can impose the following condition for the renormalization constant @xmath50 : the renormalized one - loop decay width for @xmath47 is equal to the finite unrenormalized decay width .
this condition is equivalent to setting @xmath51_{\alpha=\pi/2}=0 $ ] . in @xcite
we have checked that this condition holds for all fermions .
the only relevant one - loop decay is @xmath52 due to a large contribution of the feynman diagram shown in fig .
[ fig : fig_hff ] to the total decay width $ ] is proportional to the @xmath53-quark mass . ] .
thus , on one hand , @xmath33 is not completely fermiophobic at @xmath48 , and on the other hand , all decays @xmath47 but @xmath54 are almost zero even at one - loop level .
nevertheless it is possible , although hard , to find regions of the parameter space where @xmath55 has a sizeable effect in the fermiophobic higgs signature . with this in mind
it is obvious that we are working with a version of the model with one less parameter than the general cp - conserving thdm .
[ sec : bounds ] in our analysis we take into account the following experimental and theoretical constraints .
note however that we will use the theoretical constraints as guides and explain in each case how they would affect the results given in the plots .
we believe that if nature did not provide a fermiophobic higgs it should be disallowed ultimately by experiment . * experimental bounds from lep ;
the lep collaborations have set bounds on the mass of a fermiophobic higgs as a function of @xmath56 .
the most stringent bound comes from the combination of all lep experiments given in @xcite .
the 95% cl limit on @xmath56 is about 18 for @xmath57 gev . from @xmath57 gev until @xmath58 gev , the bound oscillates about @xmath59 . for @xmath60 gev
, @xmath61 is already a conservative bound . in the plots @xmath62
is used because much higher values of @xmath56 would violate perturbativity constraints .
note however that as we will show , @xmath63 is independent of @xmath56 and for @xmath64 the dependence of all other relevant processes is negligible . + there is another bound on the fermiophobic higgs coming from @xmath65 production at lep which constrains severely the value of @xmath66 especially for small @xmath33 masses .
if however we take the @xmath35 mass to be above 150 gev , the @xmath65 production is no longer a constraint for all values of @xmath56 .
+ finally , if @xmath56 is large , the @xmath67 coupling is suppressed while the non - fermiophobic cp - even higgs @xmath34 will couple to the @xmath68 bosons with almost the sm strength .
therefore , in the plots shown , the minimum value of the @xmath34 mass is 100 gev and most cases presented are for an @xmath34 mass above 120 gev . + * as already stated in the introduction , the d0 and cdf experiments recently reported searches for a fermiophobic higgs in two different channels . d0 searched @xcite for the inclusive production of di - photon final states via the higgsstrahlung and vector boson fusion .
the bound with the model benchmark described in the introduction is weaker than the lep bound but it spans a larger region of the parameter space .
the search @xcite in the @xmath69 channel sets a bound on the fermiophobic higgs mass for each pair of values of @xmath10
. we will take all these bounds into consideration in our analysis .
* the extra contributions to the @xmath70 parameter from the higgs scalars @xcite should not exceed the current limits from precision measurements @xcite : @xmath71 .
such an extra contribution to @xmath70 vanishes in the limit @xmath72 . to ensure that @xmath70 will be within the allowed range whenever possible we allow only a small splitting between @xmath73 and @xmath74 . *
recently , it has been shown in ref .
@xcite that for thdm models of the type ii , data on @xmath75 imposes a lower limit of @xmath76gev . in thdm type i
, there is no such constraint on the charged higgs mass .
therefore , in our numerical analysis which is valid for thdm type i we will ignore the limit on the charged higgs . * the scalar sector
can also be constrained using perturbativity constraints on @xmath30 @xcite . in the present study
we will not impose those constraints in order to quantify the optimal cross sections and scan over all parameters space .
in fact , in the fermiophobic limit , the process @xmath77 for example depends only on @xmath15 , @xmath78 and @xmath79 .
as we will explain later , the @xmath80 dependence in @xmath81 drops out . as a result , for a given @xmath15 , @xmath78 and @xmath79 , one can tune @xmath80 , @xmath82 and @xmath83 in order to satisfy perturbativity constraints . * from the requirement of perturbativity for the top and bottom yukawa couplings @xcite , @xmath80 is constrained to lie in the range @xmath84 .
but it turns out that from perturbativity argument on @xmath30 , moderate values of @xmath80 less than about 10 are preferred . in order to respect perturbativity constraints we will use moderate values for @xmath85 , @xmath86 , @xmath87 and @xmath88
the process @xmath89 has both tree level contributions mediated by higgs exchange from @xmath90 and one loop contributions from gluon fusion @xmath91 .
the tree level contribution is proportional to the quark masses which will be neglected for the tevatron energies .
we have also checked that even in the large @xmath56 limit the production process @xmath92 is also negligible for the lhc when compared to @xmath93 .
the process @xmath94 occurs only at the one - loop level .
as we will see , even if loop suppressed , this process can still be enhanced by the strong qcd coupling as well as by the heavy higgs @xmath34 resonant effect when it can decay to two light cp even @xmath33 scalars .
there are two types of diagrams that participate in the process @xmath94 . the box diagram , as shown in fig [ fig : fig_boxhhgg ] represents just a generic contribution to the process .
we have also included all other quarks and because both the initial and the final state have identical particles , there is a total of six diagrams for each flavor .
the second type are the vertex diagrams which again are six for each flavor . in fig .
[ fig : fig_verthhgg ] we show just the representative diagrams with a generic fermion in the loop . in the fermiophobic limit ,
the top loop is always the dominant contribution .
the other two processes , @xmath95 and @xmath96 have a similar structure ( vertex and box ) to @xmath97 , except for one additional contribution to the vertex diagrams in @xmath98 which is the @xmath68 boson and the goldstone boson s - channel exchange .
+ however , in the fermiophobic limit , all box contributions vanish and the same is true for all vertex contribution with s - channel higgs ( @xmath33 ) exchange due to the fact that the fermiophobic higgs coupling to fermions is zero . since the box contributions drop out in the fermiophobic limit , the two processes @xmath99 are directly proportional to the pure scalar couplings @xmath100 and @xmath101 .
the third process @xmath102 is sensitive both to pure scalar couplings @xmath103 and @xmath104 as well as to the gauge coupling @xmath105 .
hereafter we list the pure scalar coupling in the fermiophobic limit ( fl ) needed for our study : @xmath106 \label{aal}\\ \lambda_{a g h}^{fl } & = & \frac{e \ , \sin \beta}{2 m_w s_w}\bigg ( m^2_{a } - m^2_{h}\bigg)\label{agl}\\ \lambda_{hh^\pm h^\mp}^{fl}&= & \frac{e}{2 m_w s_w\sin 2\beta}\bigg[2 \sin^3\beta m^2_{h } - \lambda_5 v^2 \sin\beta- 2 \sin{2\beta } \cos{\beta } m^2_{h^\pm } \bigg]\label{lhphm}\end{aligned}\ ] ] note that the @xmath107 and @xmath101 couplings are directly proportional to @xmath79 while the @xmath103 coupling depend both on @xmath79 , @xmath74 as well as on @xmath108 .
it is clear that in the case of exact discrete @xmath109 symmetry ( @xmath110 ) , both @xmath100 and @xmath101 would vanish . in the fermiophobic limit , all fermions couple to each scalar with the same strength .
the @xmath111 coupling is proportional to @xmath112 .
therefore from eq .
[ hll ] we conclude that the @xmath42 angle dependence cancels out in the cross section , _ that is _ , @xmath113 depends only on @xmath15 , @xmath78 and @xmath79 .
the @xmath114 coupling is proportional to @xmath115 which means that in the large @xmath56 limit the @xmath42 angle dependence is also very mild except for very large @xmath33 and/or @xmath35 masses . those cases
will not be included in our study . finally , note that not only @xmath113 vanishes in the limit @xmath110 but also @xmath116 , in the high @xmath56 limit becomes negligible when @xmath117 due to to the smallness of the values of the masses involved .
+ the one - loop amplitudes were generated and calculated with the packages feynarts @xcite and formcalc @xcite .
the scalar integrals were evaluated with looptools @xcite . in this section
, we present our numerical results . as stated earlier , to avoid the lep bounds on the fermiophobic higgs we will fix @xmath80 to be of the order 10 for the processes @xmath118 and @xmath119 .
this way we suppress the @xmath67 coupling while keeping perturbativity bounds on @xmath30 within the allowed range .
+ the first consequence of this choice of @xmath120 is that the coupling @xmath121 is enhanced ( @xmath122 ) while @xmath123 is suppressed ( see eqs .
[ hll ] , [ hhl ] ) . as we have discussed , in the fermiophobic limit , the process @xmath124 has only vertex contribution through s - channel heavy higgs ( @xmath34 ) exchange .
therefore , the cross section for @xmath125 depend both on @xmath78 as well as on @xmath121 coupling which is proportional to @xmath79 .
there are two sources of enhancements for @xmath124 .
the first one is to take @xmath121 ( or equivalently @xmath79 ) as large as possible .
the second one is when @xmath126 production is resonant , that is , @xmath127 . for the tevatron in units of @xmath128 as a function of the fermiophobic higgs mass with @xmath129 and @xmath130 .
on the left the mass of the heavier cp - even higgs boson is twice the fermiophobic higgs mass , i.e. , on threshold , and on the right it is fixed ( 120 gev).,title="fig:",height=259 ] for the tevatron in units of @xmath128 as a function of the fermiophobic higgs mass with @xmath129 and @xmath130 . on the left the mass of the heavier cp -
even higgs boson is twice the fermiophobic higgs mass , i.e. , on threshold , and on the right it is fixed ( 120 gev).,title="fig:",height=259 ] for the lhc in units of pb as a function of the fermiophobic higgs mass with @xmath131 , @xmath132 and @xmath130 . on the left the mass of the heavier cp -
even higgs boson is twice the fermiophobic higgs mass , i.e. , on the threshold , and on the right it is fixed ( 120 gev).,title="fig:",height=259 ] for the lhc in units of pb as a function of the fermiophobic higgs mass with @xmath131 , @xmath132 and @xmath130 . on the left the mass of the heavier cp -
even higgs boson is twice the fermiophobic higgs mass , i.e. , on the threshold , and on the right it is fixed ( 120 gev).,title="fig:",height=259 ] we first discuss @xmath133 production . in fig .
[ plot1 ] ( left ) we illustrate the cross section of @xmath134 as a function of the fermiophobic higgs mass @xmath15 for two representative values of @xmath135 and @xmath136 .
the other heavy cp even mass is taken to be @xmath137 such that the resonant channel @xmath138 is open .
the other parameters are : @xmath139 gev . on the @xmath34 resonance ,
the cross section is enhanced and can reach a few hundreds of picobarn for a very light fermiophobic higgs @xmath140 gev .
even for @xmath15 of the order of 100 gev , the cross section is still larger than 0.1 @xmath128 which would give thousands of produced events for the planned tevatron luminosity of @xmath141 .
as can be seen from the analytic expression of the coupling @xmath107 , the large @xmath79 is the large is the coupling @xmath107 and so is the @xmath97 cross section .
the observed kinks at @xmath142 and 182 gev in the left plot are due to the opening of the decay channels @xmath143 and @xmath144 . on the right - hand side of fig .
[ plot1 ] we show the same cross section , the only difference being the @xmath34 mass which is now fixed at 120 gev .
it is clear that even away from the @xmath34 resonance a significant set of fermiophobic higgs masses and @xmath79 values can still be probed at the tevatron . the behavior with @xmath79 changes at threshold due to the @xmath34 width effect on the cross section . above threshold the @xmath145 channel
is closed , the @xmath34 width is then very small .
therefore in that region the cross section is just proportional to @xmath146 .
below threshold , the @xmath145 channel is open and the width in the @xmath34 propagator starts to play a role which makes the dependence with @xmath79 no longer trivial .
+ in fig .
[ plot2 ] we show the same plots as in fig . [ plot1 ] but for the lhc .
as expected the plots are re - scaled by more than one order of magnitude . for the values
shown , all masses between 10 and 100 gev can be probed for most values of @xmath79 . even for @xmath131
the smallest cross section value is of the order of 10 @xmath147 . for the tevatron ( left ) and for the lhc ( right ) in units of @xmath128 as a function of the heavier cp - even higgs mass with @xmath148 and a fermiophobic higgs mass of 60 gev.,title="fig:",height=259 ] for the tevatron ( left ) and for the lhc ( right ) in units of @xmath128 as a function of the heavier cp - even higgs mass with @xmath148 and a fermiophobic higgs mass of 60 gev.,title="fig:",height=259 ] and @xmath149 for the tevatron ( left ) and for the lhc ( right ) in units of @xmath128 as a function of the fermiophobic higgs mass with @xmath150 , @xmath151 , @xmath152 gev and @xmath153 gev.,title="fig:",height=259 ] and @xmath149 for the tevatron ( left ) and for the lhc ( right ) in units of @xmath128 as a function of the fermiophobic higgs mass with @xmath150 , @xmath151 , @xmath152 gev and @xmath153 gev.,title="fig:",height=259 ] in fig .
[ plot3 ] we show the cross section of @xmath154 as a function of the resonant higgs mass @xmath78 for @xmath155 and for a fermiophobic higgs @xmath156 gev , for the tevatron ( left ) and for the lhc ( right ) .
as one can see , away from the resonance @xmath157 , the cross section is of the order a few @xmath147 for the tevatron and a few @xmath128 for the lhc .
once we cross the resonance , one can see a spectacular pick for @xmath158 gev which is due to the opening of the decay channel @xmath159 .
the peak is very sharp because the total width of @xmath34 is very narrow for @xmath160 , less than @xmath161 gev .
once the decay channel @xmath159 is open for @xmath162 the decay width of @xmath34 increase suddenly to more than 100 gev .
this is manifestly seen in the plot by a dramatic decrease of the cross section from few hundred pb to @xmath161 pb .
finally we present the @xmath163 and @xmath164 reactions .
it is clear from both plots presented in fig .
[ plot4 ] that the cross section for @xmath165 production is negligible for most of the parameter space . on the contrary , the cross section for @xmath65 production can be very large and still within the tevatron reach .
the cross section @xmath166 can be several orders of magnitude larger than the corresponding @xmath167 ( see ref .
. we will show in the next section that taking into account the pseudo - scalar branching ratios , the decay @xmath168 can be the dominant one , and so the channel @xmath169 is still worth exploring at the tevatron .
finally , we have checked that the contribution from @xmath170 was negligible .
having established that @xmath63 and @xmath166 are worth studying both at the tevatron and at the lhc we now turn to the experimental signatures for the fermiophobic higgs and for the pseudo - scalar in the parameter space under study . in the fermiophobic limit
there is a dramatic change in the fermiophobic higgs signatures . for smaller fermiophobic higgs masses ,
the main decay is to two photons ( through w and charged higgs loops ) until the ww channel starts to dominate .
the crossing point of the branching ratios depends on the parameters of the scalar potential which enters the game through the charged higgs contribution to @xmath171 .
those parameters are mainly the charged higgs mass , @xmath79 , @xmath80 and the fermiophobic higgs mass ( see eq.([lhphm ] ) ) .
recently a detailed study of @xmath172 appeared in @xcite .
due to all experimental and theoretical constraints , for a fermiophobic higgs with mass between 10 and 100 gev , @xmath173 except in a tiny neighborhood of @xmath174 . in this neighborhood ,
all cross sections are extremely small . therefore there will always be a tiny region around @xmath110 that will not be probed with the processes proposed here . for illustration
, we show in fig .
[ plot5 ] ( left ) the fermiophobic higgs branching ratio as a function of @xmath79 .
we have checked that the larger @xmath66 is the higher the value of the @xmath175 branching ratio .
@xmath176 decreases with the fermiophobic higgs mass , but for @xmath177 gev the plot looks almost the same . regarding the pseudo - scalar decays , as one can see in fig .
[ plot5 ] ( right ) , one can have @xmath178 if the decay @xmath179 is kinematically forbidden .
we have checked that changes in @xmath56 , @xmath79 and the @xmath35 mass produce negligible changes in the branching ratio provided the charged higgs channel @xmath179 is kept closed .
therefore , the 4 @xmath180 final state is by far the dominant one . and of the cp - odd scalar as a function of the fermiophobic higgs mass .
both plots are for @xmath62 , @xmath148 , @xmath181 gev.,title="fig:",height=259 ] and of the cp - odd scalar as a function of the fermiophobic higgs mass .
both plots are for @xmath62 , @xmath148 , @xmath181 gev.,title="fig:",height=259 ]
in this work we have shown that there are alternative channels to search for fermiophobic higgs with a multi - photon signature .
a vast region of the parameter space of the fermiophobic thdm can be probed at the tevatron and the analysis can easily be extended for the lhc . in the fermiophobic limit ,
the angle @xmath42 is already very constrained .
lep @xcite has set a limit of @xmath182 for almost all values of the fermiophobic higgs masses up to 100 gev .
for some masses the bound is even stronger . on the other hand theoretical constraints tell us that these values can not be too high .
this implies that @xmath63 and @xmath183 will be large while @xmath184 will be negligible .
note however that the @xmath63 cross section does not depend on @xmath80 and that the @xmath183 dependence on @xmath56 for values above 10 is negligible . regarding the @xmath79 dependence ,
we have shown that there is a `` tiny to small '' region around @xmath110 that can not be probed .
this is especially true for @xmath126 productions but @xmath166 decreases with @xmath79 as well
. + the process @xmath185 proposed in @xcite and studied in @xcite is complementary to the processes we propose in this work .
we probe the region of small @xmath34 and/or @xmath35 masses while @xcite probes the small charged higgs mass region .
the advantage in our case is that our study is independent of @xmath56 while their process does not depend on @xmath79 .
finally if all higgs scalars besides the fermiophobic higgs are very heavy , only the two photon search can exclude a fermiophobic higgs . +
as expected and as it was shown in @xcite the background for a 3 or 4 photon final state is easy to control . in the case of the 3 photon final state
the main background contribution comes from the direct tri - photon production ( see @xcite for details ) .
our thanks to andrew akeroyd and pedro teixeira - dias for a careful reading of the manuscript and many interesting discussions .
this work is supported by fundao para a cincia e tecnologia under contract poci / fis/59741/2004 .
is supported by fct under contract sfrh / bpd/23427/2005 .
is supported by fct under contract sfrh / bd/19781/2004 .
is supported by the national science council of r.o.c under grant number : nsc96 - 2811-m-033 - 005 .
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in this study , we propose new higgs production mechanisms with multi - photon final states in the fermiophobic limit of the two higgs doublet model .
the processes are : @xmath0 , @xmath1 followed by @xmath2 and @xmath3 followed by @xmath4 . in the fermiophobic limit , @xmath5 and @xmath6 would give rise to 4@xmath7 signature while @xmath8 can give a 6@xmath7 final state .
we show that both the fermilab tevatron and cern s large hadron collider can probe a substantial slice of the parameter space in this fermiophobic scenario of the two higgs doublet model .
if observed the above processes can give some information on the triple higgs couplings involved .
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[ cols="^,^,^",options="header " , ]
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we demonstrate experimentally that the spectral broadening of cw supercontinuum can be controlled by using photonic crystal fibers with two zero - dispersion wavelengths pumped by an yb fiber laser at 1064 nm .
the spectrum is bounded by two dispersive waves whose spectral location depends on the two zero - dispersion wavelengths of the fiber .
the bandwidth of the generated spectrum and the spectral power density may thus be tailored for particular applications , such as high - resolution optical coherence tomography or optical spectroscopy .
the continuous - wave ( cw ) pumping regime has been recently proposed as an interesting alternative to pulsed lasers for the generation of strong supercontinuum ( sc ) @xcite .
sources based on cw sc are characterized by a substantial lower intensity noise , a lower coherence length , a higher stability and a higher spectral power density than their pulsed counterparts .
additionally , photonic crystal fibers ( pcfs ) can be spliced to recently developed cw fiber lasers , preserving the all - fiber format .
these features are of particular interest for ultrahigh resolution optical coherence tomography for instance .
sc spectra generated with a pcf pumped by a cw yb fiber laser were reported in refs .
@xcite and @xcite .
about 700 nm - wide spectra with high spectral power densities ( in the order of 10 mw / nm ) were obtained .
but one drawback of these configurations is that the bandwidth of the sc spectrum is not easily adjustable to the one required for a particular application . as a consequence
the pump power budget is not optimized if the application requires a given spectral power density over a particular spectral range , as this is actually the case for many potential applications . quite recently
, it has however been numerically demonstrated that a simple scheme based on a pcf with two - zero dispersion wavelengths allows a tailoring of the sc spectrum extent , and consequently of the spectral power density @xcite .
these numerical results are of great potential interest for the reasons stated before . in this paper
, we provide an experimental proof - of - principle of this novel technique by pumping pcfs with a cw yb fiber laser .
we experimentally show that the generated sc spectrum can be tailored through a suitable design of the group velocity dispersion ( gvd ) of the fiber , and in particular of the position of its two zdws , as predicted numerically @xcite .
we report the generation of 200 nm and 500 nm wide spectra in two slightly different pcfs with two zero - dispersion wavelengths ( zdws ) .
the sc is achieved by pumping in the anomalous dispersion region , just between the two zdws .
we showed that a slight modification of the dispersion curve allows the control of the sc extension and consequently permits to optimize the pump power budget for particular applications .
for the sake of simplicity and clarity , we recall here only on the basic mechanisms involved in sc generation in cw pumping regime . a detailed theoretical analysis of the sc formation is given in ref . @xcite . in the first stage ,
modulational instability converts the cw field into a train of quasi - solitonic pulses of a few picoseconds duration @xcite .
these pulses experience higher - order linear and nonlinear effects so that they become unstable .
consequently , they shed energy away to dispersive waves ( dws ) which are phase - matched with the solitonic waves @xcite . from this phase - matching condition that depends on the gvd and on the nonlinear phase mismatch of the solitonic waves @xcite , one can estimate the spectral position of the dws . on the contrary to fibers with a single zdw
where only one dw is phase - matched with one solitonic pulse , in fibers with two zdws there are two wavelengths for which the phase - matching condition is satisfied . consequently , two dws are generated : one is located on the blue side of the lower zdw and the other one is located on the red side of the higher zdw . additionally the stimulated raman scattering shifts the solitons towards longer wavelengths @xcite .
this so - called soliton self - frequency shift stops just below the second zdw because a balance is achieved between the red shift due to srs and the blue shift due to spectral recoil when the dispersion slope of the fiber is negative @xcite .
it is worth noting that even more complex nonlinear interactions should occur during the propagation of such strong pulses in a low dispersion region , such as soliton collisions that can reinforce the frequency shift towards long wavelengths @xcite . providing that the pump wavelength is located between both zdws in a low anomalous dispersion regime
, one can simply summarize that the sc extension is roughly limited by the spectral separation between the two dws . in order to experimentally demonstrate the numerical results predicted in ref .
@xcite , we designed two pcfs with two zdws from part to part of the pump wavelength at 1064 nm , and a low anomalous dispersion region at this wavelength .
this can be achieved for a relatively small hole - to - hole spacing @xmath0 in the order of 1.6 @xmath1 m , and a @xmath2 value of about 0.4 , with @xmath3 being the hole diameter @xcite . for
a reasonable number of seven air - hole rings , such a small pitch leads to relatively important confinement losses around 1500 nm , where the sc is expected to extend .
we numerically evaluated these losses with a finite - elements method ( fem ) , and we found that they were in the order of 1000 db / km at 1500 nm . to overcome this problem , we replaced the seventh air - hole period with a ring of larger air holes ( @xmath4 ) , as can be seen in the scanning electron micrograph ( sem ) represented in the inset of fig .
[ fig1 ] .
confinement losses were thus reduced to about 1 db / km at 1500 nm , which is an acceptable value for experiments performed in tens of meters long fibers , as required for cw sc generation . another way to reduce confinement losses without adding such an air - clad structure would be to use a higher number of uniform air - hole rings ( typically ten or eleven ) . however
, this would make the fabrication process a lot trickier since this would approximately double the total number of holes in the cladding .
we fabricated two pcfs labeled fiber a and fiber b in what follows .
they were designed to exhibit a gvd curve similar to that of pcf1 and pcf2 in ref .
@xcite .
the gvd curves of the fabricated fibers were calculated from high resolution sems with a fem package .
they are represented in fig .
[ fig1 ] together with an example of sem for fiber b in inset .
they both exhibit a convex shape with two zdws located on each side of the pump wavelength ( represented by the vertical dashed line in fig .
[ fig1 ] ) .
the basic characteristics of the fabricated pcfs are also summarized in table [ tab1 ] for the sake of clarity .
it can be seen from this table that the parameters of fibers a and b are very close to those of pcf1 and pcf2 of ref .
@xcite respectively .
the nonlinear coefficient @xmath5 was deduced from the computed effective area at 1064 nm , by taking the typical value of @xmath6 = 2.6@xmath710@xmath8 [email protected]@xmath10 for the nonlinear refractive index of silica @xcite . the nonlinear coefficient of both pcfs was in the order of 25 [email protected]@xmath10 at 1064 nm .
note that this value is about twice higher than the nonlinear coefficient of pcfs with a single zdw around 1064 nm usually designed for sc generation @xcite . since the two zdws of fiber a are closer than the ones of fiber b , a broader sc is expected in fiber b according to the theoretical study summarized above and detailed in ref .
@xcite .
the pcfs were pumped with a linearly polarized cw yb fiber laser ( ipg ) delivering 20 w at 1064 nm with a full width half maximum of 0.5 nm .
the setup is displayed in fig .
[ fig2](a ) .
the collimated beam with a 5 mm diameter ( at @xmath11 ) was sent through an afocal setup made of two ir - coated lenses in order to reduce the spot size by a factor of 2 .
about 70 % of the pump power was launched into the fibers by using appropriate aspherical lens . however , even though most of the pump power is coupled into the core of the pcfs , there is a small amount of pump power launched and guided in the inner cladding because of the last ring of holes ( larger air holes with @xmath4 ) .
consequently the total power of 14 w launched into the fibers does not contribute completely to the sc generation .
the output light was butt - coupled to a standard single - mode pigtail in order to record the spectra with an optical spectrum analyzer ( osa ) .
figure [ fig2 ] shows the spectra measured for the two pcfs under investigation .
in fiber a ( with the zdws separated by only 161 nm ) , we obtained a relatively narrow spectrum ranging from 1000 nm to about 1200 nm it is important to note that the upper limit of the sc ( @xmath121200 nm ) is well below the oh absorption peak ( 1380 nm ) , which can consequently not be involved to explain the limitation of the sc extension .
the total average output power was 9 w. in fiber b ( with the zdws separated by 285 nm ) , the sc spectrum is much broader than in fiber a. it spans from 1050 nm to 1550 nm , with an important dip around 1400 nm due to important losses at this wavelength due to water absorption ( measured to be about 300 db / km at 1380 nm ) .
as a consequence , the average output power is reduced to 6.3 w. note that the spectrum generated in fiber b is limited by the pump on the low wavelength side rather than by the blue - shifted dw .
this is due to the fact that this blue - shifted dw is very weak because its spectral shift with the soliton is very important @xcite .
it is also important to note that the spectral boundaries of both experimental spectra are in very good agreement with the ones predicted by numerical simulations for corresponding pcfs in ref .
@xcite .
our experimental results thus clearly reveal that the sc spectrum is actually bounded by the presence of two dws as expected . for both fibers
, we checked that the general shape of the output spectrum and especially its upper and lower limits did not change when fibers longer than 60 m were used . in that case
, there was only a reduction of the output power due to absorption losses , and more pump power was converted in the sc . on the contrary , by shortening the fiber length to less than 60 m , the bandwidth of the sc was strongly reduced and most of the output power was located in the vicinity of the pump wavelength .
we found that a length of 60 m was a good compromise between the output power and the conversion efficiency of the pump power into the sc . above the fundamental study and
the experimental demonstration reported in the present paper , we believe that sc - based sources with a controllable generated spectrum would be of great interest for numerous applications . however , this would require a very good temporal stability and an improved flatness of the output spectrum . indeed , in the case of the `` free space '' injection setup used in our study , the output spectrum was stable just over a few minutes at full pump power .
after this duration , the output power and the stability of the spectrum began to decay because of thermal effects at the fiber input . although the stability over a few minutes is sufficient to record the spectrum with an osa without any trouble , it will not be suitable for most of potential applications .
this crucial limitation could be overcome by directly splicing the pcf to the fiber laser output .
a careful splice would also present the advantage of increasing the amount of pump power launched into the core by limiting the power coupled into the inner cladding .
this would consequently improve the conversion of the pump power into the sc , _
i.e. _ the spectral power density at the fiber output .
finally , the dip around 1400 nm in the spectrum could be removed by reducing the oh contamination with a suitable cleaning of the stacked pcf preform @xcite . in conclusion , we have studied cw sc generation in pcfs with two zero - dispersion wavelengths located around the pump wavelength . by a suitable control of the position of both zdws and of the dispersion value at the pump wavelength , we evidenced experimentally for the fisrt time to our knowledge the possibility of tailoring the sc spectrum . by this way
, the sc extension and the output power can be adjusted over the spectral range of interest required for a particular application in the near ir .
this represents an important step towards optimizing the pump power budget for a given application of sc - based sources .
next steps will consist in improving the flatness of the sc by reducing the water contamination and to directly splice the laser source with the pcf .
we believe that this all fiber sc light source would become an useful tool for oct applications for example .
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nadph oxidases ( noxs ) comprise a family of multicomponent enzymatic systems that catalyze the reduction of molecular oxygen to superoxide anion radical [ 13 ] . the best characterized and studied member of the nox family is nox2 , which is expressed in phagocytic cells and has its primordial microbicidal function in the innate immune system as the primary source of reactive oxygen species ( ros ) .
nox2 is comprised by cytosolic factors p47phox , p67phox , and p40phox and the membrane - linked p22phox and gp91phox factors , which are the catalytic subunit .
nox2 also has a regulatory gtpase , rac2 ( in neutrophils ) , or rac1 ( in monocytes ) [ 4 , 5 ] .
noxs , including nox2 , are also expressed in endothelial cells and have direct influence in the oxidative imbalance , which is considered a pivotal event in the endothelial dysfunction and , consequently , in the initiation and/or progression of chronic inflammatory and vascular diseases .
hence , the inhibition or modulation of noxs activities may have direct benefit in the treatment of these pathologies . apocynin ( 4-hydroxy-3-methoxyacetophenone ) is widely used as an inhibitor of noxs and of the concomitant ros production in experimental models involving phagocytic [ 68 ] and nonphagocytic cells [ 913 ] .
the effects of apocynin include the reduction of p47phox expression and membrane translocation , inhibition of nf-b activation and expression , interference in arachidonic acid metabolism , inhibition of phagocytosis of opsonized microorganisms , inhibition of hocl production by phagocytes , and reduction of cytokine release by monocytes and t cells [ 7 , 1517 ] .
there is evidence of the role of the neutrophil peroxidase , myeloperoxidase ( mpo ) in the inhibitory mechanism of apocynin in phagocytic cells [ 9 , 18 ] .
however , the effect of apocynin in nonphagocytic cells , which do not contain mpo , is still controversial .
some authors suggest that in nonphagocytic cells apocynin does not inhibit nadph oxidase system but acts as an antioxidant or even as stimulator of ros production [ 10 , 11 ] , and others suggest that apocynin and its dimer do inhibit nadph oxidase system even in the absence of mpo [ 9 , 13 ] . here , we addressed these questions using cells with different content of mpo and comparing the inhibitory potency of apocynin .
additionally , we evaluated if the apocynin effect on nox2 could be related to a regulation of gene expression for its components gp91phox , p47phox , p22phox , and p67phox in nonstimulated cells .
apocynin , phorbol 12-myristate 13-acetate ( pma ) , dihydrorhodamine 123 , paraformaldehyde , zymosan , azide , 3,3,5,5-tetramethylbenzidine ( tmb ) , lucigenin , dextran , horseradish peroxidase ( hrp ) , and rpmi-1640 medium were purchased from sigma - aldrich ( st . louis , mo , usa ) .
hydrogen peroxide was prepared by diluting a 30% stock solution and calculating its concentration using its absorption at 240 nm ( 240 nm = 43.6 m cm ) .
apocynin stock solution was prepared by dissolving the compound in dimethyl sulfoxide ( dmso ) .
tmb solution was prepared dissolving 10 mm tmb and 100 m potassium iodide in 50% dimethylformamide and 50% acetic acid ( 800 mm ) ( v / v ) .
human serum - opsonized zymosan was prepared as described in a final concentration of 10 mg / ml .
hl-60 cells were obtained from atcc and kept in culture in rpmi 1640 medium supplemented with 10% fetal bovine serum , 2.0 mm l - glutamine , 10 u / ml penicillin , and 100 g / ml streptomycin , in humidified atmosphere , with 5% co2 at 37c .
hl-60 differentiation was induced by 1.3% dmso or 200 u / ml ifn- and 1000 u / ml tnf-. cells were cultured during 5 days , and the medium was replaced every 2 or 3 days .
cell differentiation was accompanied by cytochemical test to monitor peroxidase - positive granules , and microscopic indicators of cell differentiation , like reduction of the nucleus : cytoplasm ratio and changes in the pattern of azurophilic granules .
after differentiation , cells were incubated with 100 m or 1.0 mm apocynin during 15 minutes , 2 or 4 hours .
polymorphonuclear ( pmn ) and peripheral blood mononuclear cells ( pbmcs ) were separated by ficoll - paque ( 1.119 and 1.077 g / ml , resp . )
density gradient centrifugation from 20 ml of blood from healthy donors ( n = 6 for each experiment ) .
after isolation , the cells were resuspended in phosphate buffered saline ( pbs ) supplemented with 1.0 mm calcium chloride , 0.5 mm magnesium chloride , and 1.0 mg / ml glucose ( supplemented pbs ) or rpmi-1640 supplemented with 10% fetal bovine serum , 2.0 mm l - glutamine , 100 u / ml streptomycin , and 100 u / ml penicillin for longer culture periods .
flow cytometry assays were developed with total blood or total leukocytes in which erythrocytes were lysed with rbd lysis buffer according to the needs of the evaluation .
the determination of mpo activity in the different cell populations studied was based on tmb oxidation .
400 l of phosphate buffer 100 mm ph 5.4 and the cationic detergent cetrimide 0.3% were added to 1.0 10 cells .
samples were centrifuged ( 10.000 rpm ) and the pellet discarded . in a 1.0 ml cuvette , 150 l of the supernatant , 745 l of phosphate buffer , and 80 l of tetramethylbenzidine ( tmb ) in dimethylformamide ( dmf ) were homogenized , and 25 l of h2o2 12 mm was added at the moment of the reading , what was performed at 655 nm and took place every 1 minute during 30 minutes .
dihydrorhodamine 123 ( dhr ) is largely used in the detection of intracellular oxidant species production by cell systems .
dhr oxidation by ros results in the formation of rhodamine , a highly fluorescent component .
total leukocytes were incubated with apocynin ( 1.0 mm ) for 2 h and then stimulated with pma ( 400 nm ) for 10 min .
after pma stimulation , cells were incubated with dhr ( 10 mg / ml ) for 5 min , washed once with pbs , and suspended in pbs / bsa / azide buffer .
fluorescence of gated pmn was detected at fl1 , counting 30,000 events / gate , in an facs canto flow cytometer ( bd , franklin lakes , nj , usa ) .
, ashlan , or , usa ) , and results were recorded as fluorescence intensity and percentage of positive cells in the sample .
lucigenin - dependent chemiluminescence is a sensitive , reproducible , and reliable technique for superoxide detection . in this reaction
, superoxide reduces lucigenin to its cation radical , which reacts with a second superoxide anion to form the energy - rich dioxetane molecule emitting a photon . in our assay ,
pmn cells and pbmc ( 1.0 10 cells / ml ) were preincubated with apocynin ( 100 m ) for 15 min in supplemented pbs .
next , lucigenin ( 5.0 m ) and opsonized zymosan ( 1.0 mg / ml ) were added , and the light emission was measured for 30 min at 37c ( centro microplate luminometer lb960 , berthold technologies , tn , usa ) .
the inhibitory potency was calculated by accounting for the light emission generated by the control , in which the cells were incubated in the absence of the tested compounds .
gp91phox , p47phox , p22phox , and p67phox gene expression was performed by real - time pcr .
this methodology is based on monitoring the fluorescence emitted during the polymerizing chain reaction ( pcr ) by the binding of a fluorescent dye ( sybr green ) at the newly synthesized strand .
briefly , rna was extracted from treated cells using trizol kit ( invitrogen , catalog no .
15596 - 026 ) , and reverse transcription reaction was performed using the superscript ii rt kit ( gibco brl , gaithersburg , md ) and random hexamers .
primers specific for the target genes were designed using the primer express software ( applied biosystems , foster city , ca , usa ) , and -actin gene expression was used as standard control .
real - time pcr was performed in duplicate using the sybr green master mix ( applied biosystems ) in a 7500 sequence detector system ( applied biosystems ) . in order to confirm pcr specificity and reproducibility ,
comparisons among samples treated with apocynin and control samples ( incubated with the vehicle ) were made using the mann - whitney test for unpaired data .
hl-60 cells were differentiated with 1.3% dmso or 100 u / ml ifn- and 1000 u / ml tnf- during 5 days .
this procedure resulted in two populations with different levels of mpo ( figure 1(a ) ) .
the mpo activity of differentiated hl-60 cells was also compared with leukocytes obtained from the blood of healthy donors .
we found that pbmc and dmso - differentiated hl-60 cells presented the same level of mpo activity .
pmn cells showed mpo activity increased even when compared to ifn-/tnf--differentiated hl-60 cells . in resume
, the following crescent order for mpo activity was observed : pbmc = hl60 dmso < hl60 ifn/tnf < pmn . in the sequence ,
the cells were activated with pma , and the inhibitory potency of apocynin was measured .
apocynin strongly inhibited the intracellular ros production by pmn cells ( around 80% ) and ifn-/tnf--differentiated hl-60 cells ( around 45% ) but showed a subtle effect in pbmc and dmso - differentiated hl-60 cells ( around 20% ) ( figure 1(b ) ) .
mpo is relevant for apocynin mechanism , since apocynin inhibitory effect was increased in cells with increased mpo activity . in order to confirm the role of mpo on apocynin mechanism of action , we pharmacologically simulated an increase in peroxidase activity by adding hrp to the pbmc .
the cells were incubated with apocynin ( 100 m ) and hrp ( 400 nm ) during 15 minutes and then stimulated with opsonized zymosan .
hrp significantly increased the inhibitory effect of apocynin on superoxide anion release ( figure 2(a ) ) .
additionally , we evaluated the apocynin effect on superoxide anion release in pmn incubated with the mpo inhibitor , azide .
the cells were incubated with apocynin ( 100 m ) and sodium azide ( 5.0 mm ) during 15 minutes , and superoxide production was stimulated by opsonized zymosan ( 10 g / ml ) .
azide significantly reversed the inhibitory effect of apocynin on superoxide anion release ( figure 2(b ) ) .
in the sequence , we evaluated if the apocynin effect on nadph oxidase activity could be related to a regulation of nadph oxidase gene expression . for this purpose , we determined gene expression of the components gp91phox , p47phox , p22phox , and p67phox of nadph oxidase by resting cells incubated with apocynin .
pbmc , pmn , and differentiated hl-60 cells were incubated with apocynin during 4 hours , and gp91phox , p47phox , p22phox , and p67phox were determined using real - time pcr .
apocynin did not change gp91phox , p47phox or p22phox gene expression in pbmc , hl60 dmso , hl60 ifn-/tnf- , and pmn cells ( figures 3(a ) , 3(b ) , and 3(c ) ) , but increased p67phox gene expression in hl60 ifn-/tnf- ( figure 3(d ) ) .
the major oxidant system in leukocytes is constituted by nadph oxidase and mpo , which are the key enzymes in a cascade of reaction leading to ros as h2o2 , hypochlorous acid ( hocl ) , hypobromous acid ( hobr ) , and hypothiocyanous acid [ 2426 ] . in this concern , these enzymes are target in the development of new drugs for treatment of chronic inflammatory pathologies .
apocynin is one of these drugs for which many attentions have been given in the last few years .
curiously , the mechanism of action of apocynin involves both mpo and nadph oxidase , since its oxidation catalyzed by mpo seems crucial for the inhibition of nadph oxidase via formation of a dimeric oxidation product and/or the generation of a transient pro - oxidant apocynin radical . in the first case
, there is evidence that the dimeric product is more potent than apocynin itself , or in other words , apocynin could be assigned as a prodrug . in the second proposal , the pro - oxidant apocynin radical could oxidize essential sulfhydryl residues in the components of nadph oxidase , leading to its inactivation . in a recent paper ,
the importance of the oxidation of apocynin was reinforced , since apocynin - derived oligophenols were still more potent than apocynin in endothelial cells where mpo is not expressed . despite the exact mechanism
, the fact is that the oxidation products or yet the transient species generated during the oxidation apocynin inside the cells impede the migration of the component p47phox to the membrane avoiding the nadph assembly . in agreement with that , here we have confirmed the importance of mpo in the inhibition process of apocynin . however , more than just confirmed , we obtained a direct relationship between the cellular mpo level and the inhibition of ros generation using differentiated promyelomonocytic hl-60 cells and peripheral blood leukocytes .
this dependence of mpo is not an isolated case . indeed , mpo - mediated oxidation is part of the mechanism of activation or metabolism / deactivation of several drugs .
for instance , mpo mediated the oxidation of nimesulide , carbamazepine , and mitoxantrone leading to the formation of even more active products [ 2931 ] .
the oxidation of doxorubicine , daunorrubicine , and 2 adrenergic agonists by mpo inactivates the drugs , turning them nontoxic to mpo - rich cells . besides the activation / inactivation of its cytosolic components , the enzymatic activity of the nadph oxidase system can be also altered at transcriptional level by phytochemicals .
for instance , berberine , an alkaloid traditionally used in chinese ayurvedic and north american medicine to the treatment of diarrhea , reduces gp91phox expression in lps - stimulated macrophages , an effect that can be related to its anti - inflammatory and antiproliferative properties .
polyphenols , abundant in tea , cocoa , and red fruits , and known by its anti - inflammatory , antitrombotic , anti - ischemic , antioxidant , and vasorelaxing properties , reduce p22phox , gp91phox and p47phox , and nadph oxidase activity in phagocytes .
for instance , the reduction of gp91phox gene expression in lps - stimulated pbmc ; decreased p47phox and gp91phox in rat kidney and aorta treated with aldosterone ; in pma - differentiated thp-1 cells apocynin potentiates testosterone - induced inhibition of p47phox gene expression . here , we found that apocynin did not change gp91phox , p22phox , and p47phox in all cell populations studied but slightly increased p67phox gene expression in ifn-tnf--differentiated hl-60 cells .
we also observed that , unlike the inhibition of nadph oxidase activity , the apocynin effect on nadph oxidase gene expression in resting cells is not related to the level of mpo activity .
this difference amongst our results and the literature can be due to the activation state of the studied cells , since we evaluated apocynin effect in differentiated , but not stimulated cells . in conclusion , our results shed some light on apocynin mechanism of action .
we have demonstrated that mpo activity is a key factor for apocynin effect on nadph oxidase activity , but this concept does not extend to the nadph oxidase transcriptional regulation in nonstimulated cells .
considering the role of mpo in the inhibitory mechanism of apocynin and its increasing application as anti - inflammatory drug , the results from this work suggest that a rational search for better inhibitors of nadph oxidase in leukocytes should include a correlation with its affinity as a substrate for mpo .
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apocynin is widely used as an inhibitor of the nadph oxidase . since myeloperoxidase ( mpo ) has been considered as essential for the mechanism of action of apocynin , here we used cells with different levels of mpo and compared their sensitivity to apocynin .
hl-60 cells were differentiated with dmso or ifn/tnf and compared with peripheral mononuclear ( pbmc ) and polymorphonuclear cells ( pmn ) .
the relative mpo activity was pbmc = hl60 dmso
< hl60 ifn < pmn .
apocynin inhibited the intracellular reactive oxygen species production by pmn ( 80% ) and ifn/tnf-differentiated hl-60 cells ( 45% ) but showed a minor effect in pbmc and dmso differentiated hl-60 cells ( 20% ) .
the addition of azide decreased the efficiency of apocynin in pmn and the addition of peroxidase increased the inhibition in pbmc .
we also determined the gene expression of the components gp91phox , p47phox , p22phox and p67phox in the resting cells
. apocynin did not change gp91phox , p47phox or p22phox gene expression in nonstimulated pbmc , hl60 dmso , hl60 ifn/tnf , and pmn and has a subtle increase in p67phox in hl60 ifn/tnf. the results from this work suggest that a rational search for better inhibitors of nadph oxidase in leukocytes should include a correlation with their affinity as substrates for mpo .
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kounis syndrome is the concurrence of acute coronary syndromes ( acs ) with conditions associated with mast cell activation including allergic or hypersensitivity as well as anaphylactic or anaphylactoid reaction.1)2 ) there have been a few reports on extraordinary causes other than wasp stings leading to a drug - eluting stent ( des ) thrombosis as a manifestation of kounis syndrome.3 - 6 ) as far as we knew , very late stent thrombosis ( st ) in a second - generation des following wasp stings has not yet been reported .
we describe a case of very late st in an everolimus - eluting stent as a consequence of wasp stings and present the pathophysiology and clinical implications of this syndrome with a review of the literature .
a 56-year old man was referred by an emergency physician to our hospital with an impression of st - segment elevation myocardial infarction ( stemi ) .
the patient was stung on the arm , neck and head several times by wasps while working on his field about 7 hours prior to admission .
he had a mild allergic reaction involving local pain and urticarial swelling immediately after the incident without signs of anaphylaxis or shock .
just a few minutes after being stung , he started complaining of chest pain and called the emergency service .
his blood pressure was 120/80 mm hg , pulse rate was 90 beats per minute and electrocardiogram revealed st - segment elevation with q wave formation in the anterior leads and reciprocal st - segment depression in the inferior leads ( fig .
his troponin t level was elevated to 1.86 ng / ml . after being given intravenous dexamethasone and antihistamine ,
he had undergone an everolimus - eluting 3.515 mm stent placement ( promus , boston scientific , mn , usa ) in the mid - left anterior descending ( lad ) artery for stable angina 3 years prior in our hospital .
clopidogrel ( 75 mg / d ) was withdrawn 24 months after stent implantation , while aspirin ( 100 mg / d ) had been continued until that day .
coronary angiography demonstrated a thrombosis in the previous stent in the lad artery , completely occluding the vessel ( fig .
the lesion was crossed with a runthrough ns guidewire ( terumo ) and sequential inflations using nimbus pico ( bard ) 1.2512 mm , followed by 2.012 mm balloons to disperse the thrombus .
next , thrombus aspiration with a thrombus aspiration catheter ( thrombuster ii , kaneka corp .
abciximab infusion was started , of which half of the initial bolus was given directly into the left coronary system .
however , thrombolysis in myocardial infarction flow 3 was not established despite these measures . in the end , an everolimus - eluting 3.515 mm stent ( promus element , boston scientific , mn
we did not measure serum tryptase and histamine levels with a half life of 90 minutes and of less than 30 minutes respectively because 7 hours had passed after the onset of symptoms .
he was discharged from the hospital 6 days after the index procedure with dual anti - platelet therapy ( dapt ) .
the patient is currently doing well and is being followed up in the outpatient department .
stent thrombosis is the primary concern regarding long - term safety outcome in the current des era , which is a fatal complication that often leads to myocardial infarction or death .
early st is likely due to clinical factors such as stemi , chronic kidney disease or premature discontinuation of clopidogrel and procedural issues such as stent malapposition , plaque protrusion or vessel dissection , while late or very late st is associated with late - acquired stent malapposition , delayed reendothelialization and neoatherosclerosis with plaque rupture.7 ) the occurrence of acs during the course of an allergic reaction constitutes kounis syndrome.1)2)8 ) st in des due to hypersensitivity reactions to components of des ( metallic strut , impregnated drug and especially polymer ) is known as type iii kounis syndrome.9)10 ) other types include patients with normal coronary arteries ( type i ) and patients with quiescent , pre - existing atheromatous disease ( type ii ) .
these include drugs ( antibiotics , analgesics , non - steroidal anti - inflammatory drugs ) , conditions ( asthma , food allergy , urticaria ) or environmental exposures ( hymenoptera and others stings , shellfish consumption , latex contact).1)2)8 ) myocardial infarction following hymenoptera stings ( bees , wasps and hornets ) is rare with less than twenty documented reports in the literature.11 - 14 ) furthermore , st in des leading to myocardial infarction secondary to wasp envenomation is much rarer and existing report was about first - generation des.15 ) to the best of our knowledge , this case is the first description of very late st in a second - generation des caused by wasp stings as a manifestation of kounis syndrome .
although the exact mechanism of kounis syndrome is still under discussion , mast cell degranulation following an allergic insult is known to play a key role .
chemical mediators released from mast cells such as histamine , neutral proteases ( tryptase and chymase ) , platelet activating factors , cytokines , chemokines and metabolites of arachidonic acid ( leukotrienes and thromboxane ) have been incriminated to induce coronary artery spasm , to promote platelets aggregation , and to transform a pre - existing stable atheromatous plaque to a vulnerable plaque leading to rupture.2)6)9)11 ) other possible mechanisms involve : 1 ) the direct action of wasp venom constituents such as histamine and phospholipase a2,13 ) 2 ) the anaphylactic reaction itself with severe hypotension , and 3 ) adrenalin use which can induce coronary spasm and myocardial damage.16 ) our patient had previously undergone short and large - diameter ( 3.515 mm ) stent implantation without underexpansion or dissection under non - acs conditions .
the current guideline recommends at least 12 months of dapt after des implantation,17 ) and he had received dapt for 2 years and then aspirin until the day of admission .
he developed chest pain just a few minutes after being stung by wasps , had no signs of anaphylaxis or shock and did not receive therapeutic adrenaline .
based on these observations , it is reasonable that we can classify our patient as having kounis syndrome . in the present case ,
recent studies have shown that second - generation dess ( everolimus - eluting or zotarolimuseluting stent ) lead to more favorable healing profiles18 ) and are associated with lower rates of st compared with first - generation dess.19)20 ) in conclusion , kounis syndrome is an uncommon clinical entity , and its diagnosis is difficult to make owing to its variable manifestations .
it is important for clinicians to keep this potential fatal scenario in mind while treating an allergic reaction associated with acute chest pain .
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kounis syndrome is the concurrence of acute coronary syndromes with conditions associated with mast cell activation following an allergic insult .
we report a 56-year - old man who experienced a st - segment elevation myocardial infarction after wasp stings .
the patient presented without signs of anaphylaxis or shock .
coronary angiography showed an everolimus - eluting stent thrombosis ( st ) of the left anterior descending artery occluding the vessel completely which was deployed for stable angina 3 years ago .
the patient had been compliant with anti - platelet therapy , and no relevant cardiovascular events occurred until the day of admission .
we interpreted our patient 's condition as a manifestation of kounis syndrome .
to our knowledge , this is the first case of kounis syndrome showing very late st in a second - generation drug - eluting stent caused by wasp stings .
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(Scott Sommerdorf | The Salt Lake Tribune) Defendant Tyerell Joe Przybycien, 18, of Spanish Fork, returns to court follo... (Scott Sommerdorf | The Salt Lake Tribune) Defendant Tyerell Joe Przybycien, 18, of Spanish Fork, returns to court follo... (Scott Sommerdorf | The Salt Lake Tribune) Defendant Tyerell Joe Przybycien, 18, of Spanish Fork, returns to court follo... (Scott Sommerdorf | The Salt Lake Tribune) Defendant Tyerell Joe Przybycien, 18, of Spanish Fork, returns to court follo... (Scott Sommerdorf | The Salt Lake Tribune) Defendant Tyerell Joe Przybycien, 18, of Spanish Fork, sits without showing a... (Scott Sommerdorf | The Salt Lake Tribune) Defendant Tyerell Joe Przybycien, 18, of Spanish Fork, speaks with his defens... (Scott Sommerdorf | The Salt Lake Tribune) Attorney Neil Skousen speaks with his client defendant Tyerell Joe Przybycien... (Scott Sommerdorf | The Salt Lake Tribune) Defendant Tyerell Joe Przybycien, 18, of Spanish Fork, sits during his prelim... (Scott Sommerdorf | The Salt Lake Tribune) Detective David Sorenson of the Utah County Sheriff's office glances over at ... (Scott Sommerdorf | The Salt Lake Tribune) Judge James Brady speaks with prosecution attorneys during the preliminary hea... (Scott Sommerdorf | The Salt Lake Tribune) Defendant Tyerell Joe Przybycien, 18, of Spanish Fork, sits during his prelim... (Scott Sommerdorf | The Salt Lake Tribune) Defendant Tyerell Joe Przybycien, 18, of Spanish Fork, sits during his prelim... (Scott Sommerdorf | The Salt Lake Tribune) Judge James Brady looks on during the preliminary hearing for Defendant Tyerel... (Scott Sommerdorf | The Salt Lake Tribune) Judge James Brady of Provo's 4th District denies the admissibility of some ev... (Scott Sommerdorf | The Salt Lake Tribune) Defendant Tyerell Joe Przybycien glances back into the courtroom as he exits ... (Scott Sommerdorf | The Salt Lake Tribune) Detective David Sorenson of the Utah County Sheriff's office answers question... (Scott Sommerdorf | The Salt Lake Tribune) Defendant Tyerell Joe Przybycien, 18, of Spanish Fork, returns to court follo... (Scott Sommerdorf | The Salt Lake Tribune) Wesley Stickley, the self-described best friend of defendant Tyerell Joe Przy... (Scott Sommerdorf | The Salt Lake Tribune) Wesley Stickley, the self-described best friend of defendant Tyerell Joe Przy... (Scott Sommerdorf | The Salt Lake Tribune) Judge James Brady speaks with prosecution and defense attorneys at the end of ...
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– What a Utah man should've done, at least per one friend's advice, when 16-year-old Jchandra Brown told him she wanted to kill herself: talk her out of it. What Tyerell Przybycien is charged with doing instead: helping her set up and carry out her suicide, the Daily Herald reports. On Tuesday, a 4th District Court judge ruled there was "reasonable belief" that enough evidence exists to send the Spanish Fork man to trial for Jchandra's death, charging him with first-degree murder and failure to report a dead body, both felonies. If convicted, he could face 15 years to life in prison. In court documents cited in the Washington Post, prosecutors say when Jchandra told Przybycien of her plans, the 18-year-old texted another friend to ask what he should do, and the friend told him he should persuade her otherwise. Przybycien, however, reportedly had the reverse reaction. "It be awesome," he texted back, noting he wanted to help her carry out her plan. "Like getting away with murder." Those records also detail Przybycien's alleged role, including mapping out Jchandra's suicide, picking her up from work May 5, and buying rope and compressed air. He's then accused of taking Jchandra to the Maple Lake Campground in Payson, setting up a noose for her, and filming her as she inhaled the compressed air, passed out, and fell off a wooden pedestal, hanging herself in the process. The Salt Lake Tribune has reported he also provided running commentary through the video found on her cellphone, including noting at one point: "That's when the brain stops getting oxygen." Przybycien's lawyer argues his client didn't actually carry out the actions that killed her, but Judge James Brady says Przybycien's help was a "substantial factor" in her death. Przybycien's arraignment is set for Oct. 24. (Radio host Delilah revealed the contents of her son's "goodbye note.")
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SECTION 1. SHORT TITLE.
This Act may be cited as the ``Charitable Volunteers Tax Credit
Incentive Act of 1995''.
SEC. 2. CREDIT FOR CHARITABLE CONTRIBUTIONS TO CERTAIN PRIVATE
CHARITIES PROVIDING ASSISTANCE TO THE POOR.
(a) In General.--Subpart A of part IV of subchapter A of chapter 1
of the Internal Revenue Code of 1986 (relating to nonrefundable
personal credits) is amended by inserting after section 22 the
following new section:
``SEC. 23. CREDIT FOR CERTAIN CHARITABLE CONTRIBUTIONS.
``(a) In General.--In the case of an eligible taxpayer, there shall
be allowed as a credit against the tax imposed by this chapter for the
taxable year an amount equal to so much of the qualified charitable
contributions which are paid by the taxpayer to 1 qualified charity as
do not exceed $500.
``(b) Eligible Taxpayer.--For purposes of this section, the term
`eligible taxpayer' means any individual who has worked at least 50
hours at the qualified charity identified under subsection (c) during
the taxable year.
``(c) Qualified Charitable Contribution.--For the purposes of this
section, the term `qualified charitable contribution' means any
charitable contribution (as defined in section 170(c)) made in cash,
but only if the amount of such contribution, the qualified charity, and
the number of hours worked by the taxpayer at the qualified charity are
identified on the return for the taxable year during which such
contribution is made.
``(d) Qualified Charity.--
``(1) In general.--For purposes of this section, the term
`qualified charity' means, with respect to the taxpayer, any
organization described in section 501(c)(3) and exempt from tax
under section 501(a)--
``(A) which is certified by the Secretary as
meeting the requirements of paragraphs (2) and (3); and
``(B) which is organized under the laws of a State
at the time the contribution is made and is exempt from
income taxation (if any) by such State.
``(2) Charity must primarily assist the poor.--An
organization meets the requirements of this paragraph only if
the predominant activity of such organization is the provision
of services to individuals whose annual incomes do not exceed
150 percent of the official poverty line (as defined by the
Office of Management and Budget).
``(3) Minimum expenditure requirement.--
``(A) In general.--An organization meets the
requirements of this paragraph only if the Secretary
reasonably expects that the annual exempt purpose
expenditures of such organization will not be less than
70 percent of the annual aggregate expenditures of such
organization.
``(B) Exempt purpose expenditure.--For purposes of
subparagraph A--
``(i) In general.--The term `exempt purpose
expenditure' means any expenditure to carry out
the activity referred to in paragraph (2).
``(ii) Exceptions.--Such term shall not
include--
``(I) any administrative expense;
``(II) any expenses for the purpose
of influencing legislation (as defined
in section 4911(d));
``(III) any expense primarily for
the purpose of fundraising; and
``(IV) any expense for a legal
service provided on behalf of any
individual referred to in paragraph
(2).
``(e) Donor May Not Have Financial Interest in Charity.--
``(1) In general.--No credit shall be allowed under this
section for any contribution made to an organization if the
donor or any member of the donor's family is an officer or
employee of such organization.
``(2) Self-dealing.--To the extent provided by the
Secretary by regulation, no credit shall be allowed under this
section for any contribution made to an organization if--
``(A) the donor,
``(B) any member of the family of the donor, or
``(C) any thirty-five percent controlled entity of
persons described in subparagraph (A) or (B), engages
in significant activities with respect to such
organization which are a type described in section
4941(d) (relating to self-dealing).
``(3) 35-percent controlled entity.--
``(A) In general.--For purposes of paragraph (2),
the term `35-percent controlled entity' means--
``(i) a corporation in which persons
described in subparagraph (A) or (B) of
paragraph (2) own more than 35 percent of the
combined voting power,
``(ii) a partnership in which such persons
own more than 35 percent of the profits
interest, and
``(iii) a trust or estate in which such
persons own more than 35 percent of the
beneficial interest.
``(B) Constructive ownership rules.--Rules similar
to the rules of paragraphs (3) and (4) of section
4946(a) shall apply for purposes of this paragraph.
``(4) Member of the family.--For the purposes of this
subsection, the members of an individual's family shall be
determined under section 4946(d).
``(f) Coordination With Deduction for Charitable Contributions.--
``(1) Credit in lieu of deductions.--The credit provided by
subsection (a) for any qualified charitable deduction shall be
in lieu of any deduction otherwise allowable under this chapter
for such contribution.
``(2) Election to have this section not apply.--A taxpayer
may elect for any taxable year to have this section not
apply.''.
(b) Qualified Charities Required To Provide Copies of Annual
Return.--Subsection (e) of section 6104 of such code (relating to
public inspection of certain annual returns and applications for
exemption) is amended by adding at the end the following new paragraph:
``(3) Charities receiving creditable contributions required
to provide copies of annual return.--
``(A) In general.--Every qualified charity (as
defined in section 23(d)) shall, upon request of an
individual made at an office where such organization's
annual return filed under section 6033 is required
under paragraph (1) to be available for inspection,
shall provide a copy of such return to such individual
without charge other than a reasonable fee for any
reproduction and mailing costs. If the request is made
in person, such copies shall be provided immediately
and, if made other than in person, shall be provided
within 30 days.
``(B) Period of availability.--Subparagraph (A)
shall only apply during the 3-year period beginning on
the filing date (as defined in paragraph (1)(D) of the
return requested).''.
(c) Clerical Amendment.--The table of sections for subpart A of
part IV of subchapter A of chapter of such Code is amended by inserting
after the item relating to section 22 the following new item:
``Sec. 23. Credit for certain charitable contributions.''.
(d) Effective Date.--The amendments made by this section shall
apply to contributions made and work performed after the 90th day after
the date of the enactment of this Act, in taxable years ending after
such date.
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Amends the Internal Revenue Code to create a tax credit not to exceed $500 (in lieu of a deduction) for cash contributions made by an individual to a tax-exempt private charitable organization primarily assisting the poor, for which the individual must also have worked at least 50 hours.
Denies such credit if the donor or a family member is an officer or employee of such organization, or has another specified relationship with the organization that would involve self-dealing.
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the discovery that at the heart of virtually all early - type galaxies in the local universe , lie supermassive nuclear black holes ( sbhs ) has led to the general consensus that black holes play a pivotal role in the formation and evolution of galaxies .
the well - known correlation between the black hole mass , m@xmath7 , and the host galaxy s stellar velocity dispersion , @xmath8 ( gebhardt et al .
2000 ; ferrarese & merritt 2000 ) implies that black hole growth and the build - up of galaxy bulges go hand - in - hand , perhaps as feedback from the active galactic nucleus ( agn ) regulates the surrounding star formation in the host galaxy ( e.g. silk & rees 1998 ; kauffmann & haehnelt 2000 ) .
the connection between black hole growth and galaxy bulges is further intimated by the fact that virtually all _ currently _ known actively accreting black holes i.e. agn - in the local universe are found in galaxies with prominent bulges ( e.g. heckman 1980a ; ho , filippenko , & sargent 1997 ; kauffmann et al .
it is unclear how common it is for bulgeless galaxies to contain sbhs and of those that do , whether they are actively accreting .
m33 , the best studied nearby bulgeless galaxy , shows no evidence of a sbh and the upper limit on the mass is significantly below that predicted by the m@xmath7-@xmath8 relation established in early - type galaxies ( gebhardt et al .
2001 ; merritt et al .
2001 ) . amongst the population of known agn , there are possibly a handful of extremely late - type galaxies that may show subtle signs of agn activity in their optical narrow - line nuclear spectra ( ho et al .
the best - studied definitive case of an agn in a purely bulgeless galaxy is the galaxy ngc 4395 , which shows an unmistakable seyfert 1 spectrum .
the inferred black hole mass in this dwarf galaxy is 3.6 @xmath2 10@xmath9 m@xmath6 ( peterson et al .
2005 ) , much less massive than black holes found in galaxies with massive bulges , and comparable to the inferred black hole mass in the other well - know dwarf galaxy with an agn , pox 52 ( barth et al .
greene & ho ( 2004 ) recently searched the first data release of the sloan digital sky survey for galaxies with similar intermediate mass black holes and found only 19 broad - line agn , suggesting that they are uncommon .
subsequent stellar velocity dispersion measurements revealed that these objects follow the extrapolation of the m@xmath7-@xmath8 relation ( barth et al .
it is unclear if the hosts are late - type galaxies since the sloan images are of insufficient spatial resolution to confirm their morphological type .
are agn uncommon in bulgeless galaxies ? is a bulge necessary for a black hole to form and grow ?
these questions can not be definitively answered with the current suite of observations , which are largely carried out at optical wavelengths .
such studies can be severely limited in the study of bulgeless galaxies , where a putative agn is likely to be both energetically weak and deeply embedded in the center of a dusty late - type spiral .
in such systems , the traditional optical emission lines used to identify agn can be dominated by emission from star formation regions , in addition to being significantly attenuated by dust in the host galaxy .
indeed searching for agn under these circumstances poses unique challenges . although x - ray observations can be a powerful tool in finding optically obscured agn in the non - compton - thick regime , the x - ray luminosities of weak agn will be low and comparable to and therefore indistinguishable from x - ray binaries in the host galaxy .
similarly , the radio emission can be dominated by and indistinguishable from compact nuclear starbursts ( e.g. , condon et al . , 1991 ) .
_ spitzer _ mid - ir spectroscopy is the ideal tool to search for agn in such galaxies .
as has been shown in previous works , agn show prominent high excitation fine structure line emission but starburst and normal galaxies are characterized by a lower excitation spectra characteristic of hii regions ionized by young stars ( e.g. , genzel et al .
1998 ; sturm et al . 2002 ; satyapal et al . 2004 ) .
in particular , the [ nev ] 14 @xmath0 m ( ionization potential 96 ev ) line is not produced in hii regions surrounding young stars , the dominant energy source in starburst galaxies , since even hot massive stars emit very few photons with energy sufficient for the production of this ion .
the detection of this line in a galaxy is therefore definitive proof of an agn . in this _ letter _ , we report the discovery of an agn in the galaxy ngc 3621 .
ngc 3621 is a relatively isolated nearby ( 6.2 mpc ; rawson et al .
1997 ) sad iii - iv ( third reference catalogue of bright galaxies rc3 ; de vaucouleurs et al .
1991 ) galaxy with no previous published evidence for nuclear activity .
the observations presented here add to the growing evidence that a black hole can form and grow in a galaxy with little or no bulge .
ngc 3621 was observed by the infrared spectrometer ( houck et al .
2004 ) on board _
spitzer _ using the short - wavelength high - resolution ( sh ; [email protected] , 9.9 - 19.6 @xmath0 m ) and the long - wavelength high - resolution ( lh ; [email protected] , 18.7 - 37.2 @xmath0 m ) modules as part of the sings legacy proposal ( program i d 159 ; kennicutt et al .
2003 ) on 2004 june 28 .
these modules have a spectral resolution of r @xmath1 600 .
the observations were executed in spectral mapping mode , in which the spacecraft moves in a raster pattern of discrete steps in order to construct a rectangular map of the targeted region .
the sh and lh maps included 3 pointings parallel to and 5 pointings perpendicular to the major axis of the slit , with half slit - length and half - slit width steps , respectively .
the integration time per pointing was approximately 60s , with each position being covered twice for the sh observations .
the total duration for the high resolution observations of ngc 3621 was 2915s .
we used bcd - level data products downloaded from the _ spitzer _ archive in conjunction with _
_ v.1.0.2 ( kennicutt et al . 2003 ; smith et al . 2004 ) to construct the high - resolution spectral cubes for ngc 3621 .
the bcd - level products were pre - processed by the _ spitzer _ pipeline , version 13.2 prior to download .
the overall flux calibration uncertainty is 25 to 30% . a detailed description of the post - processing steps included in _
cubism _ is given in smith et al .
( 2004 ) .
the final full cube map size for sh corresponds to @[email protected] , while the final full cube map size for lh corresponds to @[email protected] . at the distance of ngc 3621
, this corresponds to a physical size of 742pc@xmath2405pc and 1341pc@xmath2923pc .
given the small spatial extent of both the sh and lh maps , we were unable to perform in - situ background subtraction , since the full extent of each map is confined within the galaxy .
the post - bcd software smart , v.5.5.7 ( higdon et al . , 2004 ) , was then used to obtain line fluxes from the extracted 1d spectra .
when line ratios were calculated , the line flux was obtained from spectra extracted from the same - sized aperture in both modules corresponding to the same physical region on the galaxy .
this aperture can range from a minimum of @xmath1 9@xmath29 , below which artifacts introduced by an undersampled psf can distort the spectrum , to a maximum of [email protected]
i.e. , roughly the full extent of the sh map .
the fits output images from _ cubism _ were smoothed within _
ds9 _ using a gaussian kernel of 2-pixel width .
finally , the line map plots were created using the iraf routine _ rotate _ in conjunction with _
in figure 1 , we show spectra extracted from the full aperture of the sh and lh maps near 14 @xmath0 m , 24 @xmath0 m , and 26@xmath0 m . as can be seen , there are clear detections of the [ nev]14@xmath0 m ( 4@xmath8 ) , [ nev]24@xmath0 m ( 6@xmath8 ) , and the [ oiv ] 25.9@xmath0 m ( 10@xmath8 ) lines , providing strong evidence for the presence of an agn .
continuum - subtracted spectral images reveal that the emission is centrally concentrated and peaks at the position of the nucleus determined from the 2mass coordinates , as can be seen in figure 2 . since the ratio of high to low excitation lines depends on the nature of the ionizing source , the [ nev]14@xmath0m/[neii]12.8@xmath0 m and the [ oiv]25.9@xmath0m/[neii]12.8@xmath0 m line flux ratios have been used to characterize the nature of the dominant ionizing source in galaxies ( e.g. , genzel et al .
1998 ; sturm et al . 2002 ; satyapal et al . 2004 ; dale et al . 2006 ) .
the [ nev]/[neii ] ratio for the 13 agn with both [ nev ] and [ neii ] detections by the _ infrared space observatory ( iso ) _ ranges from 0.06 to 2.11 , with a median value of 0.47 ( sturm et al .
the [ nev]/[neii ] ratio corresponding to the maximum aperture ( [email protected] ) for this galaxy is 0.06 , similar to the lowest value observed in a similar aperture ( 27@xmath214 ) by _ iso_. the [ nev]/[neii ] ratio does not increase substantially as the aperture size is reduced ; the line ratio corresponding to the minimum aperture ( 9@xmath29 ) is 0.064 .
the [ oiv]/[neii ] ratio for the 17 agn with both lines detected by _ iso
_ ranges from 0.15 to 8.33 , with a median value of 1.73 ( sturm et al . 2002 ) .
the [ oiv]/[neii ] line flux ratio corresponding to the maximum aperture in ngc 3621 is 0.23 , again within the range but at the low end of the observed values in the nearby powerful agn observed by _
the [ oiv]/[neii ] flux ratio corresponding to the minimum aperture ( 9@xmath29 ) is 0.3 , only marginally larger than the ratio obtained from the larger aperture . for comparison ,
the few starburst galaxies that show detectable [ oiv ] emission have [ oiv]/[neii ] line flux ratios that range from 0.006 to 0.647 ( median = 0.019 ; verma et al .
2003 ) but no [ nev ] emission .
we note that the fact that the [ nev]/[neii ] and [ oiv]/[neii ] line flux ratios are very low suggests that the _ spitzer _
spectrum is dominated by regions of star formation , and that significant contamination from star formation exists even at the smallest _ spitzer _ apertures ( 9@xmath29@xmath1 270pc@xmath2270pc )
we note that there is currently no published optical spectrum of ngc 3621 .
however , an optical spectrum has been obtained by the sings team which does show a very low - power seyfert , but it becomes inconspicuous for an aperture size of @xmath1 1kpc due to contamination from star formation in the host galaxy ( moustakas et al .
2007 in prep . ) . in the general case , for such low luminosity agn
, the standard optical or uv emission lines can be ambiguous indicators of agn activity because they can all be produced in starburst models ( e.g. , terlevich et al .
1992 ) , a problem that is exacerbated in weak agn .
however , the detection of the two [ nev ] lines by _ spitzer _ provides firm evidence for an agn in this galaxy and demonstrates that _ spitzer _ _ can _ find agn in galaxies even when the agn is energetically minor compared to star formation , regardless of the aperture size from which the spectrum is obtained . [ cols="^,^,^ " , ] since there are currently no published optical spectroscopic observations of ngc 3621 , it is not possible to estimate the bolometric luminosity of the agn using traditional optical calibration factors ( e.g. kaspi et al .
however , we can get an order of magnitude estimate of the bolometric luminosity of the agn using the [ nev ] line luminosity since this line is not contaminated by emission from the host galaxy and can therefore be assumed to be associated exclusively with the agn . using the [ nev ] 14@xmath0 m fluxes from a large sample of agn recently observed by _ spitzer _
( dudik et al . 2007 ; gorjian et al .
2007 ) , we can determine the relationship between the line luminosity and the nuclear bolometric luminosity of the agn . selecting only those galaxies with published bolometric luminosities obtained through direct integration of a well - sampled nuclear spectral energy distribution ( sed ) , we plot in figure 2 , l@xmath10}$ ] vs. l@xmath11 , demonstrating that there is a clear correlation .
the bolometric luminosities for this sample ranged from @xmath1 2@xmath210@xmath12 ergs s@xmath4 to 4@xmath210@xmath13 ergs s@xmath4 and the black hole masses ranged from @xmath1 7@xmath210@xmath14m@xmath6to 7@xmath210@xmath15m@xmath6 .
the best - fit linear relation yields : @xmath16 } ) + 6.317\ ] ] assuming this relationship extends to lower values of l@xmath10}$ ] , the total [ nev ] 14@xmath0 m luminosity from the entire map of ngc 3621 of @xmath1 5@xmath210@xmath17 ergs s@xmath4 corresponds to a nuclear bolometric luminosity of @xmath1 5@xmath210@xmath3 ergs s@xmath4 .
if we assume that the agn is radiating at the eddington limit , this yields a lower limit to the mass of the black hole of @xmath1 4@xmath210@xmath5m@xmath6 .
line luminosity as a function of nuclear bolometric luminosity in known agn that currently have [ nev ] observations ( dudik et al . 2007 ; gorjian et al .
the bolometric luminosities were taken from woo & urry ( 2002 ) and were obtained by direct flux integration of a well - sampled sed .
the figure clearly shows a strong correlation , demonstrating that the [ nev ] luminosity can be used to estimate the bolometric luminosity of the agn in the proposed sample .
, title="fig:",width=264 ] does this lower mass limit allow us to make any statement on the location of ngc 3621 on the m@xmath18
@xmath8 plane ?
there are no previously published high spectral resolution optical observations from which the stellar velocity dispersion in this galaxy can be determined . in the absence of an explicit bulge - disk decomposition from the surface photometry , we can get an order of magnitude estimate of the bulge luminosity using the morphological type of the galaxy and its total luminosity .
we adopt the empirical relation given in simien & de vaucouleurs ( 1986 ) to estimate the contribution of the disk to the total luminosity of a disk galaxy : if 3 @xmath19 t @xmath19 7 : @xmath20 = 0.324(t + 5 ) 0.054(t + 5)@xmath21 + 0.0047(t + 5)@xmath5 , where t is the numerical hubble type index , as given in the rc3 .
the bulge absolute magnitudes is then given by : @xmath22(bul ) = @xmath23 + @xmath24 .
using the apparent magnitude from the rc3 catalog of b@xmath25=9.20 and hubble index of 7 , yields @xmath22(bul)=15.52 mag . using the updated calibration of the magorrian relationship from ferrarese & ford ( 2005 ) ,
the expected black hole mass is m@xmath18= 3.1@xmath210@xmath14 m@xmath6 , approximately three orders of magnitude higher than the lower mass limit derived from the eddington limit .
since the scatter in the m@xmath18- m@xmath26 relation is significantly higher than that in the m@xmath18 @xmath8relation ( e.g. ferrarese & merritt 2000 ) , we can attempt to get an estimate of @xmath8 using the maximum rotational velocity , @xmath27 .
the maximum rotational velocity has been shown to follow a tight correlation with the stellar velocity dispersion in spiral galaxies in which extended rotation curves are available ( ferrarese 2002 ; baes et al .
2003 ; courteau et al .
2007 ) . as part of the sings data deliveries , h@xmath28 rotation curves are available for ngc 3621 ( daigle et al . 2006 ) .
the maximum rotational velocity obtained from this rotation curve is 180 kms@xmath4 , which assuming an inclination angle of 65 degrees ( daigle et a. 2006 ) corresponds to an inclination - corrected velocity of @xmath1 200 kms@xmath4 .
however , the h@xmath28 data cover only the inner @xmath16 kpc of the galaxy , which unfortunately does not extend to the flat part of the rotation curve . noting that this is an underestimate of @xmath27 , the value of @xmath8 obtained using the v@xmath29 @xmath8 relation from courteau et al .
2007 , shown in spiral galaxies to depend on the bulge - to - total ( b / t ) light ratio , is @xmath1 102 km / s .
the corresponding black hole mass is @xmath1 6@xmath210@xmath14 m@xmath6 , again significantly larger than the lower mass limit derived from the eddington limit .
we note that all of these methods to estimate the black hole mass are indirect and subject to large uncertainties .
some spiral galaxies of hubble type sd can contain nuclear star clusters and no bulge , some have bulges and no nuclear star clusters , and some possess both ( boker , stanek , & van der marel 2003 ) . a detailed high
spatial resolution surface brightness profile analysis is required to determine the bulge and nuclear star cluster content in ngc 3621 .
the discovery of an agn in ngc 3621 adds to the growing evidence that a black hole can form and grow in a galaxy with no or minimal bulge component .
our estimate for the bolometric luminosity of the agn is approximately two orders of magnitude greater than that of ngc 4395 ( peterson et al . 2005 ) , the best - studied example of a bulgeless galaxy hosting an agn .
these observations suggests that perhaps it is not the bulge but the dark matter halo of the host galaxy that determines the presence and activity level of sbhs , as suggested by recent theoretical models for the formation of supermassive black holes ( e.g. , adams , graff , & richstone 2001 ; natarajan , sigurdsson , & silk 1998 ) .
follow - up multiwavlength observations of ngc 3621 are required to obtain more precise estimates of the bulge mass , black hole mass , accretion rate , and nuclear bolometric luminosity .
are agn in bulgeless galaxies more common than once thought ?
since the optical emission lines in weak agn may be dominated by star formation in the host galaxy , it is possible that agn are missed in optical spectroscopic surveys and that they are perhaps more common than current optical surveys suggest .
moreover , it is well known that the infrared ( ir ) excess observed in galaxies increases along the hubble sequence implying that late - type galaxies are dusty ( e.g. sauvage & thuan 1994 ) . in order to truly determine how common sbhs and agn activity are in bulgeless galaxies and
whether or not the dark matter mass instead of the bulge mass determines the presence and activity level of a sbh , an infrared spectroscopic study is crucial .
future studies with _ spitzer _ will allow us to gain further insight into these fundamental questions and expand our understanding of the formation and growth of sbhs in low bulge environments .
we are very thankful to joel green , dan watson , jackie fischer , mario gliozzi , mike eracleous , and rita sambruna for their invaluable help in the data analysis , and for their enlightening and thoughtful comments .
the excellent suggestions of an anonymous referee helped improve this letter .
ss gratefully acknowledges financial support from nasa grant nag5 - 11432 .
rpd gratefully acknowledges financial support from the nasa graduate student research program .
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we report the discovery of an active galactic nucleus ( agn ) in the nearby sad galaxy ngc 3621 using _ spitzer _ high spectral resolution observations .
these observations reveal the presence of [ nev ] 14 @xmath0 m and 24 @xmath0 m emission which is centrally concentrated and peaks at the position of the near - infrared nucleus . using the [ nev ] line luminosity
, we estimate that the nuclear bolometric luminosity of the agn is @xmath1 5@xmath210@xmath3 ergs s@xmath4 , which corresponds based on the eddington limit to a lower mass limit of the black hole of @xmath1 4@xmath210@xmath5m@xmath6 . using an order of magnitude estimate for the bulge mass based on the hubble type of the galaxy , we find that this lower mass limit does not put a strain on the well - known relationship between the black hole mass and the host galaxy s stellar velocity dispersion established in predominantly early - type galaxies .
mutliwavelength follow - up observations of ngc 3621 are required to obtain more precise estimates of the bulge mass , black hole mass , accretion rate , and nuclear bolometric luminosity .
the discovery reported here adds to the growing evidence that a black hole _ can _ form and grow in a galaxy with no or minimal bulge .
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much attention has been given to a resurgence of neural networks , deep learning ( dl ) in particular , which can be of unsupervised @xcite , supervised @xcite , or a hybrid form @xcite .
significant performance gain has been observed , especially in the presence of large amount of training data , when deep learning techniques are used for image classification @xcite and speech recognition @xcite . on the one hand ,
hierarchical and recursive networks @xcite have demonstrated great promise in automatically learning thousands or even millions of features for pattern recognition ; on the other hand concerns about deep learning have been raised and many fundamental questions remain open . some potential problems with the current dl frameworks include : reduced transparency and discriminativeness of the features learned at hidden layers @xcite ; training difficulty due to exploding and vanishing gradients @xcite ; lack of a thorough mathematical understanding about the algorithmic behavior , despite of some attempts made on the theoretical side @xcite ; dependence on the availability of large amount of training data @xcite ; complexity of manual tuning during training @xcite .
nevertheless , dl is capable of automatically learning and fusing rich hierarchical features in an integrated framework .
recent activities in open - sourcing and experience sharing @xcite have also greatly helped the adopting and advancing of dl in the machine learning community and beyond .
several techniques , such as dropout @xcite , dropconnect @xcite , pre - training @xcite , and data augmentation @xcite , have been proposed to enhance the performance of dl from various angles , in addition to a variety of engineering tricks used to fine - tune feature scale , step size , and convergence rate .
features learned automatically by the cnn algorithm @xcite are intuitive @xcite .
some portion of features , especially for those in the early layers , also demonstrate certain degree of opacity @xcite .
this finding is also consistent with an observation that different initializations of the feature learning at the early layers make negligible difference to the final classification @xcite .
in addition , the presence of vanishing gradients also makes the dl training slow and ineffective @xcite . in this paper
, we address the feature learning problem in dl by presenting a new algorithm , deeply - supervised nets ( dsn ) , which enforces direct and early supervision for both the hidden layers and the output layer .
we introduce _ companion objective _ to the individual hidden layers , which is used as an additional constraint ( or a new regularization ) to the learning process .
our new formulation significantly enhances the performance of existing supervised dl methods .
we also make an attempt to provide justification for our formulation using stochastic gradient techniques .
we show an improvement of the convergence rate of the proposed method over standard ones , assuming local strong convexity of the optimization function ( a very loose assumption but pointing to a promising direction ) .
several existing approaches are particularly worth mentioning and comparing with . in @xcite ,
layer - wise supervised pre - training is performed .
our proposed method does not perform pre - training and it emphasizes the importance of minimizing the output classification error while reducing the prediction error of each individual layer .
this is important as the backpropagation is performed altogether in an integrated framework . in @xcite ,
label information is used for unsupervised learning .
semi - supervised learning is carried in deep learning @xcite . in @xcite ,
an svm classifier is used for the output layer , instead of the standard softmax function in the cnn @xcite . our framework ( dsn ) , with the choice of using svm , softmax or other classifiers , emphasizes the direct supervision of each intermediate layer . in the experiments , we show consistent improvement of dsn - svm and dsn - softmax over cnn - svm and cnn - softmax respectively .
we observe all state - of - the - art results on mnist , cifar-10 , cifar-100 , and svhn .
it is also worth mentioning that our formulation is inclusive to various techniques proposed recently such as averaging @xcite , dropconnect @xcite , and maxout @xcite .
we expect to see more classification error reduction with careful engineering for dsn .
in this section , we give the main formulation of the proposed deeply - supervised nets ( dsn ) .
we focus on building our infrastructure around supervised cnn style frameworks @xcite by introducing classifier , e.g. svm model @xcite , to each layer . an early attempt to combine svm with dl
was made in @xcite , which however has a different motivation with ours and only studies the output layer with some preliminary experimental results . [ cols= "
< , < " , ] street view house numbers ( svhn ) dataset consists of @xmath0 digits for training , @xmath1 digits for testing , and @xmath2 extra training samples on @xmath3 color images .
we followed the previous works for data preparation , namely : we select 400 samples per class from the training set and 200 samples per class from the extra set .
the remaining 598,388 images are used for training .
we followed @xcite to preprocess the dataset by local contrast normalization ( lcn ) .
we do not do data augmentation in training and use only a single model in testing .
table [ svhn - table ] shows recent comparable results .
note that dropconnect @xcite uses data augmentation and multiple model voting .
in this paper , we have presented a new formulation , deeply - supervised nets ( dsn ) , attempting to make a more transparent learning process for deep learning .
evident performance enhancement over existing approaches has been obtained .
a stochastic gradient view also sheds light to the understanding of our formulation .
this work is supported by nsf award iis-1216528 ( iis-1360566 ) and nsf award iis-0844566 ( iis-1360568 ) .
we thank min lin , naiyan wang , baoyuan wang , jingdong wang , liwei wang , and david wipf for help discussions .
we are greatful for the generous donation of the gpus by nvidia .
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our proposed deeply - supervised nets ( dsn ) method simultaneously minimizes classification error while making the learning process of hidden layers direct and transparent .
we make an attempt to boost the classification performance by studying a new formulation in deep networks .
three aspects in convolutional neural networks ( cnn ) style architectures are being looked at : ( 1 ) transparency of the intermediate layers to the overall classification ; ( 2 ) discriminativeness and robustness of learned features , especially in the early layers ; ( 3 ) effectiveness in training due to the presence of the exploding and vanishing gradients .
we introduce `` companion objective '' to the individual hidden layers , in addition to the overall objective at the output layer ( a different strategy to layer - wise pre - training ) .
we extend techniques from stochastic gradient methods to analyze our algorithm .
the advantage of our method is evident and our experimental result on benchmark datasets shows significant performance gain over existing methods ( e.g. all state - of - the - art results on mnist , cifar-10 , cifar-100 , and svhn ) .
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SECTION 1. SHORT TITLE.
This Act may be cited as the ``Helping Ensure Life- and Limb-Saving
Access to Podiatric Physicians Act'' or the ``HELLPP Act''.
SEC. 2. INCLUDING PODIATRISTS AS PHYSICIANS UNDER THE MEDICAID PROGRAM.
(a) In General.--Section 1905(a)(5)(A) of the Social Security Act
(42 U.S.C. 1396d(a)(5)(A)) is amended by striking ``section
1861(r)(1)'' and inserting ``paragraphs (1) and (3) of section
1861(r)''.
(b) Effective Date.--
(1) In general.--Except as provided in paragraph (2), the
amendment made by subsection (a) shall apply to services
furnished on or after January 1, 2014.
(2) Extension of effective date for state law amendment.--
In the case of a State plan under title XIX of the Social
Security Act (42 U.S.C. 1396 et seq.) which the Secretary of
Health and Human Services determines requires State legislation
in order for the plan to meet the additional requirement
imposed by the amendment made by subsection (a), the State plan
shall not be regarded as failing to comply with the
requirements of such title solely on the basis of its failure
to meet these additional requirements before the first day of
the first calendar quarter beginning after the close of the
first regular session of the State legislature that begins
after the date of enactment of this Act. For purposes of the
previous sentence, in the case of a State that has a 2-year
legislative session, each year of the session is considered to
be a separate regular session of the State legislature.
SEC. 3. MODIFICATIONS TO REQUIREMENTS FOR DIABETIC SHOES TO BE INCLUDED
UNDER MEDICAL AND OTHER HEALTH SERVICES UNDER MEDICARE.
(a) In General.--Section 1861(s)(12) of the Social Security Act (42
U.S.C. 1395x(s)(12)) is amended to read as follows:
``(12) subject to section 4072(e) of the Omnibus Budget
Reconciliation Act of 1987, extra-depth shoes with inserts or
custom molded shoes (in this paragraph referred to as
`therapeutic shoes') with inserts for an individual with
diabetes, if--
``(A) the physician who is managing the
individual's diabetic condition--
``(i) documents that the individual has
diabetes;
``(ii) certifies that the individual is
under a comprehensive plan of care related to
the individual's diabetic condition; and
``(iii) documents agreement with the
prescribing podiatrist or other qualified
physician (as established by the Secretary)
that it is medically necessary for the
individual to have such extra-depth shoes with
inserts of custom molded shoes with inserts;
``(B) the therapeutic shoes are prescribed by a
podiatrist or other qualified physician (as established
by the Secretary) who--
``(i) examines the individual and
determines the medical necessity for the
individual to receive the therapeutic shoes;
and
``(ii) communicates in writing the medical
necessity to a certifying doctor of medicine or
osteopathy for the individual to have
therapeutic shoes along with findings that the
individual has peripheral neuropathy with
evidence of callus formation, a history of pre-
ulcerative calluses, a history of previous
ulceration, foot deformity, previous
amputation, or poor circulation; and
``(C) the therapeutic shoes are fitted and
furnished by a podiatrist or other qualified supplier
individual (as established by the Secretary), such as a
pedorthist or orthotist, who is not the physician
described in subparagraph (A) (unless the Secretary
finds that the physician is the only such qualified
individual in the area);''.
(b) Effective Date.--The amendment made by subsection (a) shall
apply with respect to items and services furnished on or after January
1, 2014.
SEC. 4. BUDGET SAVINGS: STRENGTHENING MEDICAID PROGRAM INTEGRITY
THROUGH CONTINUOUS LEVY ON PAYMENTS TO MEDICAID PROVIDERS
AND SUPPLIERS.
(a) In General.--Section 6331(h)(2) of the Internal Revenue Code of
1986 (defining specified payment) is amended by striking ``and'' at the
end of subparagraph (B), by striking the period at the end of
subparagraph (C) and inserting ``, and'', and by adding at the end the
following new subparagraph:
``(D) any payment to any Medicaid provider or
supplier under a State plan under title XIX of the
Social Security Act.''.
(b) Effective Date.--The amendments made by this section shall
apply to levies issued after the date of the enactment of this Act.
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Helping Ensure Life- and Limb-Saving Access to Podiatric Physicians Act or HELLPP Act - Amends title XIX (Medicaid) of the Social Security Act (SSA) to include podiatrists as physicians in order to cover their services under the Medicaid program. Amends SSA title XVIII (Medicare) to revise requirements for coverage of therapeutic shoes for individuals with diabetes regarding the processes of: (1) documentation by a physician of, and certification of a comprehensive plan of care related to, the diabetic condition; (2) prescription by a podiatrist or other qualified physician upon a finding of the medical necessity for the therapeutic shoes, including findings communicated to a certifying doctor of medicine or osteopathy of certain related foot conditions; and (3) fitting and supplying the shoes. Amends the Internal Revenue Code to subject to the continuing levy upon property and property rights, for collection of unpaid taxes, any payments made to a Medicaid provider or supplier.
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type ia supernovae ( sne ia ) have been successfully utilized over the past decade to measure the cosmic expansion history @xcite and explore the nature of dark energy ( e.g. , * ? ? ?
* ; * ? ? ?
* ; * ? ? ?
* ; * ? ? ?
the foundation for the utility of sne ia as a cosmological tool is that some distance - independent observables , such as the light - curve shape parameters @xcite , the color parameters @xcite , or both @xcite , have been found to correlate with their peak luminosity . these empirical correlations can be used to calibrate the luminosities of sne ia and measure their distances with a precision of @xmath19% .
a recent result suggests that the luminosity standardization of sne ia can be improved to a level of @xmath16% by separating the sne into two groups based on a spectroscopic criterion [ for details , see @xcite , hereafter w09 ] .
the expansion velocity ( @xmath0 ) of the sn ejecta is inferred from the blueshift of the absorption minimum of siii @xmath96355 , and the sne are divided into one group with normal @xmath0 ( hereafter normal " sne ia ) and the other group with high @xmath0 ( hereafter hv " sne ia ) .
w09 found that the two groups have either different extinction laws or color evolution .
the cause for such a dichotomy might be related to the properties of their progenitors .
the hv sne ia are characterized by stronger absorption features of intermediate - mass elements ( imes , such as si , s , and ca ) at higher velocities as well as a red @xmath10 color around maximum brightness .
sn 2002bo and sn 2006x are two of the best - studied examples of this class @xcite .
in particular , the interstellar na i d lines were found to show significant variations in the spectra of sn 2006x , likely pointing to the presence of csm produced by the progenitor system @xcite .
the possible detection of csm around sn 2006x is also supported by a flat evolution of the late - time light curve @xcite and a detection of light echoes @xcite .
similar variability of the na i d lines was also observed in sne 1999cl and 2007le @xcite , two other members of the hv sn ia class .
contrasting with this , multi - epoch , high - resolution spectral observations of sn 2007af , a normal sn ia , do not reveal any significant signature of csm absorption @xcite .
this raises the possibility that csm might be preferentially present for the sne ia in the hv class . in this paper
, we present optical observations of another member of the hv sn ia class , sn 2007gi .
our goal is to increase the sample and understand the properties of well - observed hv sne ia .
observation and data reductions are described in 2 , while 3 presents the @xmath11 light curves , color curves , reddening estimate , and an analysis of the rise time .
section 4 presents the spectral evolution .
our discussions and conclusions are given in 5 .
sn 2007gi was discovered by k. itagaki ( iauc 8864 ) on july 23.49 ( ut dates are used throughout this paper ) at @xmath12 = 12@xmath1301@[email protected] , @xmath16 = + 61@xmath1753@[email protected] ( j2000.0 ) in the lenticular galaxy ngc 4036 .
an optical spectrum taken on 2007 aug .
4.90 revealed that sn 2007gi was a very young sn ia at a phase @xmath110 days before maximum brightness @xcite , with an expansion velocity measured from the absorption minimum of si ii @xmath96355 as @xmath120,500 km s@xmath2 .
this velocity is much higher than what is observed for a normal sn ia at a similar phase , but is typical for members of the hv sn ia class , such as sne 1983 g , 1997bp , and 2006x @xcite .
photometry of sn 2007gi was obtained primarily with the 0.8-m tsinghua - naoc telescope ( tnt ) located at naoc xinglong observatory .
this telescope is equipped with a @xmath20 pixel back - illuminated ccd , with a field of view ( fov ) of @xmath21 ( scale @xmath22 pixel@xmath2 ) .
observations of sn 2007gi began on 2007 aug .
8 , @xmath16 days before @xmath3-band maximum , and continued for the next 6 months .
sn 2007gi was also observed during its early rising phase ( from @xmath23 to @xmath247 days ) with the ultraviolet / optical telescope [ uvot ; @xcite ] onboard the _ swift _ observatory . as shown in figure 1 ,
sn 2007gi is located just outside the central bulge of ngc 4036 . to remove the light contamination from the host galaxy , we applied an image - subtraction technique before performing the photometry .
template images of ngc 4036 were obtained on 2008 may 24 , roughly 300 days after maximum brightness . to perform the image subtraction ,
the image containing sn 2007gi is first geometrically registered to the corresponding template image ; the fluxes of the foreground stars in the images are then scaled to the same level .
the point - spread functions ( psfs ) of these two images are convolved to match , and the template
is then subtracted from the sn images .
we finally performed standard psf - fitting photometry to obtain the instrumental magnitudes for the sn and the local standard stars with the iraf daophot package @xcite .
transformations from the instrumental magnitudes to the standard johnson @xmath25 @xcite and kron - cousins @xmath26 @xcite systems were established by observing on photometric nights a series of @xcite standard stars covering a wide range of air masses and colors .
a total of 4 photometric nights were used to calibrate 8 local standard stars in the field of sn 2007gi .
table 1 lists their final calibrated @xmath11 magnitudes @xcite .
these local stars are then used to transform the instrumental magnitudes of sn 2007gi to the standard @xmath11 system , and the final results of the photometry are listed in table 2 . the error bars ( in parentheses ) include both the uncertainty in the calibration of the local standard stars and the uncertainty of the instrumental magnitudes due to photon noise and image subtraction . the @xmath3- and @xmath27-band magnitude obtained by uvot on three earlier epochs
are also listed in table 2 .
the swift / uvot photometry was reduced in a manner similar to that described in @xcite and using the photometric zeropoints of @xcite . in the absence of template images of the host galaxy
, regions around the galaxy at the same distance from the nucleus as the sn were used to estimate the underlying count rate and its uncertainty .
given the sparse spectroscopic observations of sn 2007gi ( 4 ) , no @xmath28- or @xmath29-corrections were applied to the photometry presented in this paper .
optical spectra of sn 2007gi were obtained primarily with the 3-m shane telescope at lick observatory using the kast double spectrograph @xcite .
a spectrum was also obtained on 2007 nov .
12 with the low resolution imaging spectrometer ( lris ; @xcite ] mounted on the 10 m keck i telescope on mauna kea , hawaii .
the journal of spectroscopic observations is given in table 3 .
all of the spectra were reduced by standard iraf routines . in order to avoid contamination from the host galaxy ,
each spectrum of the sn was extracted carefully , and the flux calibration was done with spectra of standard stars observed on the same night at similar air masses .
the spectra were corrected for continuum atmospheric extinction using mean extinction curves for lick observatory , and telluric lines were removed from the data . during the observations , the slit was always aligned near the parallactic angle to avoid chromatic losses due to atmospheric dispersion @xcite .
the @xmath11 light curves of sn 2007gi are presented in figure 2 . a polynomial fit to the @xmath3-band light curve around
maximum brightness yields @xmath30 = [email protected] mag on jd 2,454,[email protected] ( 2007 august 14.5 ) .
this indicates that our observations started from about @xmath2411 days and extended to + 188 days with respect to the @xmath3-band maximum .
the @xmath27-band light curve reached a peak magnitude of [email protected] mag on jd 2,454,[email protected] , about 1.5 days after @xmath31(b ) . using a template - fitting method [ similar to that used in hamuy et al .
( 1996 ) but expanded to include more templates ] to fit the @xmath3- and @xmath27-band light curves , we derived @xmath32 = [email protected] mag and @xmath33 = [email protected] mag .
the @xmath10 color around the maximum is found to be slightly redder than the unreddened loci @xcite , suggesting some reddening toward sn 2007gi .
the salt2 method @xcite yields a best - fit stretch factor of @xmath34 = [email protected] , which corresponds to @xmath35(b ) = [email protected] from the transforming relation between @xmath34 and @xmath35(b ) by @xcite .
the best - fit templates from mlcs2k2 @xcite are also overplotted in figure 2 .
one can see that the light curves of sn 2007gi can be well fit by both salt2 and mlcs2k2 . in figure 3 , we compare the light curves of sn 2007gi with those having similar @xmath32 values : sne 1994d @xcite , 1996x @xcite , 2002bo @xcite , 2002dj @xcite , 2002er @xcite , 2004eo @xcite , and 2006x @xcite . among these objects ,
sne 2002bo , 2002dj , 2006x , and 2007gi belong to the hv group , while sne 1994d , 1996x , and 2004eo belong to the normal group .
sn 2002er may be a transitional object linking the normal and hv groups ( w09 ) .
compared to the normal sne ia in the @xmath3 band , sn 2007gi appears relatively brighter and declines slowly when entering the nebular phase . for convenience of comparison
, we introduce a quantity @xmath36 , which is the flux ratio measured at @xmath37 and @xmath6 days with respect to the @xmath3 maximum .
the ratio @xmath36 is found to be [email protected] for sn 2007gi , which is similar to that of sn 2006x ( [email protected] ) but noticeably smaller than that of sn 1994d ( [email protected] ) , sn 1996x ( [email protected] ) , and sn 2004eo ( [email protected] ) .
thus , the hv objects seem to have systematically smaller peak - to - tail contrast than the normal objects . close inspection of figure 3a also reveals that there may be a break in the light - curve evolution for sn 2007gi at @xmath38 days . the decay rate @xmath39 is found to be [email protected] mag ( 100 days)@xmath2 during the period from @xmath40 days to @xmath41 days , similar to that measured for sn 1984a and sn 2002bo at the same phase . the decay becomes steeper after @xmath41 days , with @xmath39 = [email protected] mag ( 100 days)@xmath2 .
such a two - stage evolution also exists in sn 2006x , but it is not unambiguously present in the cases of sne 1984a and 2002bo due to poor photometric coverage in the nebular phase .
future observations will be needed to determine whether this trend is universal for all hv sne ia . in contrary to the @xmath3-band light curve
, the @xmath42-band light curves of sn 2007gi do not exhibit a two - stage evolution in the nebular phase ( see figure 3b d ) . neither the flux contrast between the tail and peak nor the decay rate of the tail show significant differences among the objects in the comparison .
a noticeable difference is that the secondary shoulder / maximum features at around + 25 days in the @xmath42 bands appear more pronounced in the hv objects than those in the normal ones ( see figures 3c and 3d ) .
part of this effect could be caused by significant extinction which shifts the effective passband to redder wavelengths [ e.g. , @xcite ] .
as the extinction suffered by sn 2007gi is relatively low ( 3.2 ) , its prominent secondary shoulder is likely to be mostly intrinsic .
according to @xcite , the variation of the secondary maximum of the near - infrared ( nir ) light curves is caused by the abundance stratification in sne ia and/or the progenitor metallicity .
one feature in figures 3(a)(d ) , though not easily discernible due to the crowdness of the data points , is that the hv sne 2007gi , 2006x , and 2002bo seem to rise to the maximum at a faster rate than the normal objects .
such a trend was also mentioned by @xcite in the qualitative comparison of sn 2002dj .
a quantitative analysis of the rise time is given in 3.3 .
figure 4 presents the optical color curves of sn 2007gi ( @xmath43 , @xmath44 , @xmath45 ) .
overplotted are the color curves of the other sne in the light - curve comparison in figure 3 .
all of the color curves are shifted to match the observed values of sn 2007gi at @xmath3 maximum . for the @xmath10 color
, sn 2007gi exhibited a similar color evolution as the other sne in the early phase ( @xmath46 days ) . at @xmath47 days , it has the reddest color of all the sne .
after the red peak at @xmath48 25 days , sn 2007gi seems to become progressively bluer than the other sne in the comparison , so by @xmath40 days it has the bluest color .
unfortunately , there is a gap in the range @xmath4960 days when sn 2007gi was behind the sun , so the detailed evolution during this phase is not clear .
the slope measured during @xmath690 days is @xmath50 mag day@xmath2 , steeper than the lira - phillips relation [ e.g. , @xmath51 mag day@xmath2 ; @xcite ] .
this was also noticed by @xcite in the comparison study of sn 2006x .
in fact , a steeper @xmath10 color - change slope than the lira - phillips relation in the nebular phase is found to be the case for most of the hv events ( wang , x. , et al .
2009c , in preparation ) , suggesting that the reddening derived for them from their tail colors might be potentially biased toward a lower value .
despite the relatively large differences seen in the @xmath10 color evolution , the two classes of sne ia ( hv and normal ) share similar @xmath52 and @xmath53 color evolution ( figures 4b c ) .
the galactic extinction toward ngc 4036/sn 2007gi is @xmath54 mag @xcite , corresponding to a color excess of @xmath55 mag [ adopting the standard reddening law of @xcite ] .
the peak @xmath10 color , corrected for the galactic reddening , is [email protected] mag .
this corresponds to a host - galaxy reddening of @xmath56 mag under the assumption that the hv sne ia have intrinsic @xmath10 colors similar to those of the normal objects near maximum brightness ( w09 ) .
assuming @xmath57 , as suggested by w09 for the hv sne ia , the extinction caused by the dust within the host galaxy of sn 2007gi is @xmath58 mag
. the late - time evolution of sne can provide valuable constraints on the sn environments as well as their explosion models [ e.g. , @xcite ] .
the field of sn 2007gi was imaged with the wide field planetary camera 2 ( wfpc2 ) onboard the _ hubble space telescope ( hst ) _ on 2009 march 26 , @xmath1600 days after discovery , as part of _ hst _ program go-10877 ( pi : weidong li ) .
a cosmic - ray - split pair of observations was observed with each of the f435w , f555w , f675w , and f814w filters . to locate sn 2007gi on these wfpc2 images
, we follow the technique detailed by @xcite .
we use an @xmath8-band image of sn 2007gi taken with the lick observatory 1-m nickel telescope on 2007 dec .
15 , and identify four stars that are present in the wfpc2 images .
an astrometric solution using these four stars yields a relatively poor precision of @xmath59 due to the faintness of the stars and the resolution of the nickel image .
nevertheless , within the 1@xmath60 error radius of the astrometric solution , we identify a single star which we presume to be sn 2007gi .
figure 5 demonstrates this process . to measure the magnitudes of sn 2007gi in the wfpc2 images
, we have used the
hstphot " package developed by @xcite . after performing the preprocessing suggested by the hstphot manual , including removal of cosmic rays , defects , bad pixels , and hot pixels
, we measure the magnitudes in the wfpc2 system .
these magnitudes are then converted to the ground - based broad - band @xmath11 magnitudes using the procedure described by @xcite .
we measure the following magnitudes for sn 2007gi : @xmath3 = [email protected] , @xmath27 = [email protected] , @xmath8 = [email protected] , and @xmath61 = [email protected] .
sn 2007gi was found to decline by @xmath111.1 mag in the @xmath27 band by 590 days after the @xmath3 maximum .
this flux drop is consistent with the corresponding values observed in sn 1996x and sn 2003hv at comparable phases @xcite .
sn 1991 t and 1998bu , which showed evidence for the presence of light echoes @xcite , declined by @xmath62 mag within 590 days since the maximum .
in addition , the @xmath10 color of sn 2007gi in the nebular phase is found to be inconsistent with that predicted by the light - echo scenario . thus .
we conclude that an interstellar echo may not be present in sn 2007gi . the time spent by a sn from explosion to maximum brightness
is defined as the rise time @xmath63 , an important parameter that links the explosion physics to the progenitors of sne ia @xcite .
the rise time of a sn ia is determined primarily by the rate at which the interior energy is released and subsequently diffuses to the surface of the supernova .
assuming that the luminosity of a sn ia evolves as an expanding fireball at very early phases @xcite , the rise time @xmath63 can be derived from the relation @xcite @xmath64 where @xmath12 is the `` speed '' of the rise of the luminosity and @xmath65 is the time elapsed since maximum brightness . in this subsection , we attempt to examine the difference in @xmath66 between hv and normal sne ia .
instead of adopting the @xmath3-band light curve @xcite , our analysis uses the @xmath8-band light curve , as our earliest photometric data points are usually obtained with a clear filter ( used in our sn search ) which is very close to broad - band @xmath8 @xcite . only those data obtained earlier than one week before the @xmath8-band maximum are used in the fitting .
the computed rise times for sn 2007gi and several other well - observed sne ia are plotted against the decline rate @xmath5 in figure 6 .
the sne are divided into the hv ( filled circles ) and normal ( open squares ) groups according to the classification scheme defined by w09 . in each group
, @xmath63 correlates with @xmath32 : slower decliners have longer rise times .
the hv sne ia appear to have a faster ( i.e. , shorter ) rise time than the normal ones at the same @xmath32 with the exception of sn 1994d , which lacks published photometry during the very early phases .
a similar trend was also noted by @xcite .
assuming comparable amounts of nickel are synthesized during the explosion , the rise time of a sn ia is affected by the efficiency of the photon diffusion , which depends on the opacity and the location of the photosphere .
a shorter @xmath63 could indicate that compared with a normal sn ia , the photosphere of a hv sn ia is less effectively heated by the @xmath67-ray photons inside the ejecta , or becomes optically thin at a faster pace due to the more rapid expansion ( see the discussion in 4.3 ) .
we have 5 optical spectra of sn 2007gi obtained with the 3.0-m shane telescope at lick observatory and the keck i 10-m telescope at the w. m. keck observatory , spanning from @xmath68 to @xmath69 days since @xmath3-band maximum brightness .
as shown in figure 7 , the spectral evolution around maximum brightness generally follows that of a normal sn ia but is characterized by very broad and highly blueshifted absorption features at 3600 (ca ii h&k ) , 6000 ( si ii @xmath96355 ) , and 8000 ( ca ii nir triplet ) . in figure 8 , we compare the spectra of sn 2007gi with those of sne ia having similar @xmath35 values at four selected epochs ( @xmath70 , @xmath71 , + 6 , and + 3 months since the @xmath3 maximum ) .
all spectra have been corrected for the reddening and the redshifts of the host galaxies .
the reddening of each comparison sn ia is taken from table 1 in w09 , and the @xmath72 value is assumed to be 1.57 for the hv sne ia and 2.36 for the normal objects according to the analysis w09 . at @xmath73 days ( figure 8a ) , the spectrum of sn 2007gi is characterized by lines of singly ionized imes ( si , s , mg , and ca ) . the absorption features of si ii @xmath96355 and ca ii h&k in sn 2007gi are deep and broad , comparable to those in the hv sn ia 2002bo but significantly stronger than those in the normal sne 1994d , 2002er , and 2004eo .
around maximum brightness ( figure 8b ) , we measured a line - strength ratio of si ii @xmath95972 to si ii @xmath96355 , known as @xmath74(si ii ) @xcite , to be @xmath75 for sn 2007gi .
this is a relatively small @xmath74(si ii ) value and usually indicates an overluminous event @xcite .
similar low values of @xmath74(si ii ) are observed for the other two hv objects , sne 2006x and 2002bo . by one week
after maximum ( figure 8c ) , the strong absorptions of si ii and ca ii lines are still present in the hv objects ( sne 2007gi , 2002bo , 2002dj , and 2006x ) , but the w - shape s ii lines have almost vanished . at @xmath76 months ( figure 8d ) ,
the spectra are dominated by iron lines whose strength is similar in all of the objects , and a strong ca ii nir absorption trough .
sn 2006x was found to show a prominent near - uv excess starting from @xmath77 days , perhaps due to a local light echo or an interaction of the sn ejecta with circumstellar material @xcite .
close inspection of the @xmath78 day spectrum of sn 2007gi reveals a flux excess at the blue end when compared to the normal sne ia , consistent with its bluer @xmath79 color at this phase ( 3.2 ) .
the blueshift of the absorption minima of some spectral features may approximately trace the location of the photosphere in the early phases of a sn . in this subsection
, we examine some strong lines such as si ii @xmath96355 and ca ii h & k , as well as a weak line s ii @xmath95640 .
the derived evolution of the expansion velocity ( @xmath0 ) of the sne is shown in figure 9 .
all of the velocities have been corrected for the redshifts of the host galaxies .
sn 2007gi is one of the objects with the highest expansion velocities in the comparison , with @xmath0 = 15,500 @xmath4 300 km s@xmath2 at @xmath80 day . by comparison ,
the typical value of @xmath0 for a normal sn ia is 10,600 @xmath4 400 km s@xmath2 at this epoch ( w09 ) .
the velocities inferred from the ca ii h @xmath81 k and s ii @xmath95640 lines are about 21,500 km s@xmath2 and 12,800 km s@xmath2 near maximum , respectively , which are also significantly higher than those of the normal sne ia .
these high @xmath0 values of the imes ( si , s , and ca ) can often be interpreted as being caused by a density / abundance enhancement in the outer ejecta of the sne @xcite .
several scenarios have been proposed to account for such an enhancement .
the metallicity effect was examined by @xcite , who found that increasing the metallicity in the c+o layers by a factor of 10 is still far from explaining the high @xmath0 seen in sn 2002bo .
the delayed detonation models were proposed to explain the hv features in sn 1984a and sn 2002bo @xcite , as intense nucleosynthesis in the outer layers results in an enhancement of the density of the imes at higher velocities , which subsequently increases the opacity in the outer regions and results in a photosphere that is moving at a high velocity .
an interaction between the sn ejecta and csm could produce the high - velocity ca ii lines @xcite and may also affect the si ii lines @xcite .
detailed analysis of the reasons for the hv features is beyond the scope of this paper .
as discussed by @xcite , @xcite , and @xcite , the flux ratio @xmath74(si ii ) between si ii @xmath95972 and si ii @xmath96355 is an indicator of the photospheric temperature and the luminosity of a sn ia : a value of @xmath74(si ii ) means a more luminous sn ia with a higher photospheric temperature .
the unusually low @xmath74(si ii ) value of @xmath10.07 for sn 2007gi at @xmath80 day thus suggests a rather high photospheric temperature . on the other hand , the strength of si iii @xmath94560 (
actually si iii @xmath824553 , 4568 ) has been proposed as another photospheric temperature tracer @xcite , and is stronger for a sn ia having a higher temperature .
the si iii @xmath94560 line is weak in sn 2007gi , suggesting a rather low photospheric temperature .
the two temperature indicators thus provide conflicting results for sn 2007gi . in an attempt to further constrain the photospheric temperature in sn 2007gi
, we used the parameterized resonance scattering synthetic - spectrum code synow @xcite to fit the near - maximum spectra of sn 2007gi .
the basic input parameters are taken from table 1 in @xcite , with the blackbody temperature @xmath83 and the velocity at the photosphere @xmath84 as free parameters .
figure 10 shows our best synow fit for the @xmath80 day spectrum , with @xmath84 = 15,500 km s@xmath2 and @xmath85 k. the high @xmath84 is consistent with the high @xmath0 measured directly from the spectrum ( 4.2 ) .
the blackbody temperature @xmath83 , on the other hand , is rather typical of other sne ia at this phase .
for example , @xcite estimated @xmath86 k for the normal sn ia 1994d at @xmath87 day , while our best synow fit to a spectrum of the normal sn ia 2004eo at @xmath88 day yields @xmath89 k. our synow analysis thus suggests that @xmath74(si ii ) is not a good photospheric temperature indicator for the hv sne ia .
the exact cause for this is not clear .
one possibility is contamination by fe ii and fe iii lines .
@xcite suggested that the fe lines might weaken the si ii @xmath95972 absorption line even at low @xmath83 .
in this paper , we present optical photometry and spectroscopy of sn 2007gi , a sn ia with an extremely high expansion velocity measured from imes ( si , ca , and s ) . we also conduct a comparison study for a sample of sne ia with high and normal expansion velocities ( hv and normal , respectively ) to investigate differences in their photometric and spectroscopic behaviors .
the @xmath3-band light curve of sn 2007gi shows a two - stage evolution : a decay rate of @xmath90 mag ( 100 days)@xmath2 during @xmath9190 days and @xmath92 ( 100 days)@xmath2 thereafter .
the latter decay rate is similar to those observed in normal sne ia .
this two - stage evolution is also present in the hv sn ia 2006x .
more late - time observations of the hv objects are necessary to establish whether this is a universal property .
the @xmath93 color of sn 2007gi is found to evolve at a faster slope than that of normal sne ia during the nebular phase , a trend that is also observed for the hv sn ia 2006x @xcite and most of the other hv events ( wang , x. , et al .
2009c , in preparation ) .
sn 2007gi was detected at @xmath94 days after @xmath3 maximum in _
hst_/wfpc2 images . the magnitudes and colors at this very late - time epoch suggest that sn 2007gi may not be contaminated by a light echo on interstellar scales .
using a dozen well - observed sne ia , we confirm the previous claim that hv sne ia tend to have a faster rise time than normal sne ia @xcite : at the same value of @xmath35 , the rise time of the hv objects is shorter than that of the normal objects by 12 days .
the spectral evolution of sn 2007gi is characterized by high expansion velocities measured from the absorption lines .
the value of @xmath0 is measured to be 15,500 km s@xmath2 at @xmath80 day , @xmath150% higher than what is observed for normal sne ia . a small flux ratio @xmath74(si ii ) = [email protected]
is observed , which traditionally means a hot photospheric temperature in the sn ejecta .
our synthetic spectral analysis using the synow code , on the other hand , suggests that sn 2007gi has a typical photospheric temperature compared with other normal sne ia .
the two - stage evolution in the @xmath3-band light curve of sn 2007gi may suggest that an additional energy source besides radioactive decay plays a role in the nebular phase .
dust scattering ( a light echo ) seems unlikely because the tail luminosity would have remained nearly constant for a long time , which is not the case for sn 2007gi .
nevertheless , the possibility of a local light echo on a small scale ( due to csm dust ) can not be completely ruled out .
another potential energy source is interaction with csm ; detection of variable sodium lines in the spectra of some hv events provides some evidence for this scenario . assuming that the csm lies at a distance of @xmath95 cm from the supernova , it is expected that the outermost ejecta will begin to interact with the csm at @xmath130 days after the @xmath3 maximum .
this naturally accounts for a flatter evolution seen in the @xmath3-band light curve of the hv sne ia after @xmath96 days .
the difficulty with this scenario is the lack of convincing observational evidence for stripped material , such as low - velocity h@xmath12 emission in the nebular spectra [ e.g. , @xcite , but see @xcite for alternative explanations regarding the observed lack of hydrogen ] , and the lack of spectral evidence in support of ongoing csm interaction .
a possible explanation for the hv features observed in the hv sne ia is that there are density enhancements of the imes in the outer layers of the ejecta of the hv objects ( due to a metallicity effect , delayed detonations , or csm interaction ) ; the @xmath67-ray heating is less effective , and the photosphere is formed at an outer layer with a higher expansion velocity compared to the normal objects .
we thank peter nugent for help with the synow fitting .
this study is supported by the chinese national natural science foundation through grants 10673007 , 10673012 , and 10603006 , and by the china-973 program 2009cb824800 .
a.v.f.s group at u.c .
berkeley is grateful for nsf grants ast-0607485 and ast-0908886 , the tabasgo foundation , and us department of energy grants de - fc02 - 06er41453 ( scidac ) and de - fg02 - 08er41563 .
financial support for this work was also provided by nasa through grant go-10877 from the space telescope science institute , which is operated by associated universities for research in astronomy , inc .
, under nasa contract nas 5 - 26555 . the work of l.w .
is supported by nsf grant ast-0708873 .
j.d . and y.q .
are supported by the nsfc grant no .
10673014 and the china-973 program 2009cb824800 .
some of the data presented herein were obtained at the w. m. keck observatory , which is operated as a scientific partnership among the california institute of technology , the university of california , and nasa ; the observatory was made possible by the generous financial support of the w. m. keck foundation .
we are grateful to the staffs at the lick and keck observatories for their assistance with the observations . , @xmath44 , and @xmath45 color curves of sn 2007gi compared with those of sne 1994d , 1996x , 2002bo , 2002er , 2002dj , 2004eo , and 2006x .
all of the comparison sne have been dereddened .
the solid line in the @xmath10 panel shows the unreddened lira - phillips locus .
the data sources are cited in the text.,width=566 ] region of an @xmath8-band image taken with the lick observatory 1-m nickel telescope , and the _
hst_/wfpc2 f450w image , respectively , after the images have been astrometrically registered .
the position of sn 2007gi in the nickel image is marked as a circle in the middle panel .
the right panel shows a @xmath97 region around the site of sn 2007gi in the wfpc2/f450w image .
the location of sn 2007gi is marked with a circle having a radius that is three times the astrometric precision .
there is a single object near the center of the circle which we identify as sn 2007gi.,width=566 ] -band rise time of sn 2007gi and other sne ia .
the sample is divided into two groups : hv ( solid circles ) [ sne 2002bo @xcite , 2003w @xcite , 2006le @xcite , 2006x @xcite , 2007gi ( this paper ) ] and normal ( open squares ) [ sne 1990n @xcite , 1994d @xcite , 2001el @xcite , 2002er @xcite , 2003cg @xcite , 2004eo @xcite , 2005cf @xcite , 2007af @xcite and sne 1999cp , 2001en , 2001ep , 2002dj , 2002eb , 2003fa , 2006gr ( ganeshalingam et al .
2009 , in preparation ; wang x. et al .
2009c , in preparation)].,width=566 ] , @xmath71 , + 6 , and + 3 months from @xmath3-band maximum , from top to bottom ) , compared to those of sne 1994d @xcite , 1996x @xcite , 2002bo @xcite , 2002dj @xcite , 2002er @xcite , 2004eo @xcite , and 2006x @xcite at the same phase .
all of the spectra have been corrected for reddening and host - galaxy redshift , and shifted in the vertical direction for clarity.,width=566 ] lcccccc star & @xmath27 & @xmath43 & @xmath98 & @xmath44 & @xmath45 + 1 & 13.860(002 ) & 0.823(003 ) & 2.392(016 ) & 0.475(002 ) & 0.726(002 ) + 2 & 14.233(002 ) & 0.860(003 ) & 2.702(020 ) & 0.482(003 ) & 0.697(002 ) + 3 & 14.833(002 ) & 0.742(004 ) & 2.399(022 ) & 0.395(004 ) & 0.585(004 ) + 4 & 15.375(004 ) & 1.413(008 ) & 3.367(067 ) & 0.929(005 ) & 1.363(004 ) + 5 & 15.298(003 ) & 0.800(006 ) & 2.532(032 ) & 0.443(005 ) & 0.648(005 ) + 6 & 15.408(004 ) & 0.762(007 ) & 2.538(034 ) & 0.451(005 ) & 0.654(006 ) + 7 & 15.869(005 ) & 0.878(009 ) & 2.655(045 ) & 0.522(007 ) & 0.783(007 ) + 8 & 16.175(006 ) & 0.781(010 ) & 2.474(047 ) & 0.410(009 ) & 0.611(010 ) + lcrcccc ut date & jd @xmath24 2,450,000 & phase & @xmath3 ( mag ) & @xmath27 ( mag ) & @xmath8 ( mag ) & @xmath61 ( mag ) + 2007 aug 3 & 4316.17 & -10.85 & 15.170(0.048 ) & 14.940(0.055 ) & & + 2007 aug 4 & 4317.70 & -9.32 & 14.510(0.050 ) & 14.420(0.045 ) & & + 2007 aug 7 & 4320.18 & -6.84 & 13.870(0.052 ) & 13.840(0.053 ) & & + 2007 aug 8 & 4321.02 & -6.00 & 13.678(0.016 ) & 13.615(0.029 ) & 13.488(0.021 ) & 13.553(0.035 ) + 2007 aug 9 & 4322.03 & -4.99 & 13.505(0.015 ) & 13.450(0.028 ) & 13.391(0.034 ) & 13.446(0.029 ) + 2007 aug 11 & 4324.03 & -2.99 & 13.323(0.021 ) & 13.269(0.048 ) & 13.190(0.018 ) & + 2007 aug 12 & 4325.02 & -2.00 & 13.321(0.023 ) & 13.189(0.028 ) & 13.197(0.017 ) & 13.320(0.014 ) + 2007 aug 14 & 4327.01 & -0.01 & 13.259(0.037 ) & 13.106(0.052 ) & 13.153(0.023 ) & 13.383(0.023 ) + 2007 aug 15 & 4328.01 & + 0.99 & 13.237(0.028 ) & 13.077(0.029 ) & 13.130(0.033 ) & 13.374(0.032 ) + 2007 aug 21 & 4334.00 & + 6.98 & 13.571(0.023 ) & 13.238(0.018 ) & 13.347(0.067 ) & 13.647(0.095 ) + 2007 sep 3 & 4347.02 & + 20.00 & 15.236(0.024 ) & 13.899(0.015 ) & 13.769(0.028 ) & 13.642(0.018 ) + 2007 sep 4 & 4347.99 & + 20.97 & 15.330(0.029 ) & 13.944(0.018 ) & 13.753(0.045 ) & 13.612(0.033 ) + 2007 sep 5 & 4348.99 & + 21.97 & 15.414(0.028 ) & 13.997(0.025 ) & 13.756(0.036 ) & + 2007 sep 6 & 4349.99 & + 22.97 & 15.533(0.047 ) & 14.089(0.041 ) & 13.804(0.050 ) & + 2007 oct 13 & 4387.30 & + 60.28 & 16.514(0.020 ) & 15.753(0.012 ) & 15.572(0.017 ) & 15.671(0.026 ) + 2007 oct 16 & 4390.36 & + 63.34 & 16.532(0.035 ) & 15.807(0.014 ) & 15.695(0.027 ) & 15.791(0.036 ) + 2007 oct 21 & 4395.39 & + 68.37 & 16.586(0.020 ) & 15.972(0.013 ) & 15.846(0.019 ) & 15.973(0.035 ) + 2007 oct 22 & 4396.34 & + 69.32 & 16.626(0.021 ) & 15.986(0.013 ) & 15.893(0.026 ) & 16.015(0.031 ) + 2007 oct 24 & 4398.34 & + 71.32 & 16.613(0.031 ) & 16.014(0.012 ) & 15.980(0.038 ) & 16.128(0.047 ) + 2007 oct 25 & 4399.36 & + 72.34 & 16.622(0.033 ) & 16.034(0.019 ) & 16.000(0.049 ) & 16.154(0.050 ) + 2007 oct 29 & 4403.40 & + 76.38 & 16.736(0.059 ) & 16.179(0.081 ) & 16.228(0.081 ) & + 2007 nov 12 & 4417.38 & + 90.36 & 16.857(0.016 ) & 16.551(0.020 ) & 16.612(0.017 ) & 16.643(0.056 ) + 2007 nov 20 & 4425.36 & + 98.34 & 17.028(0.014 ) & 16.735(0.010 ) & 16.889(0.014 ) & 16.979(0.027 ) + 2007 nov 28 & 4433.36 & + 106.34 & 17.174(0.033 ) & 16.961(0.022 ) & 17.120(0.020 ) & 17.145(0.035 ) + 2007 dec 22 & 4457.36 & + 130.34 & 17.606(0.049 ) & 17.425(0.053 ) & 17.771(0.041 ) & 17.729(0.057 ) + 2008 jan 6 & 4472.36 & + 145.34 & 17.845(0.023 ) & 17.861(0.032 ) & 18.301(0.044 ) & 18.218(0.086 ) + 2008 jan 9 & 4475.26 & + 148.24 & 17.852(0.057 ) & 17.907(0.058 ) & 18.315(0.065 ) & 18.274(0.140 ) + 2008 feb 18 & 4515.29 & + 188.27 & 18.480(0.030 ) & 18.520(0.126 ) & & + cccccc stretch & @xmath35 & @xmath99 & explosion velocity & @xmath100 & temperature + & mag & mag & km s@xmath2 & mag & k + 0.88 @xmath4 0.02 & 1.31 @xmath4 0.09 & -19.26 @xmath4 0.10 & 15 , 500 @xmath4 300 & 0.17 @xmath4 0.04 & 11 , 500 + lcrlc ut date & jd @xmath24 2,450,000 & phase & range( ) & resolution( ) + 2007 aug 7 & 4319.50 & -7.52 & 330010,000 & 5 - 12 + 2007 aug 14 & 4326.50 & -0.52 & 330010,000 & 5 - 12 + 2007 aug 21 & 4333.50 & + 6.48 & 330010,000 & 5 - 12 + 2007 nov 12 & 4416.50 & + 89.48 & 31009200 & 6 + 2008 jan 15 & 4480.50 & + 153.48&330010,000 & 5 - 12 + altavilla , g. , et al .
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we present optical photometry and spectra for the type ia supernova ( sn ia ) 2007gi in the nearby galaxy ngc 4036 .
sn 2007gi is characterized by extremely high - velocity ( hv ) features of the intermediate - mass elements ( si , ca , and s ) , with expansion velocities ( @xmath0 ) approaching @xmath115,500 km s@xmath2 near maximum brightness ( compared to @xmath110,600 km s@xmath2 for sne ia with normal @xmath0 ) .
sn 2007gi reached a @xmath3-band peak magnitude of [email protected] mag with a decline rate of @xmath5(true ) = [email protected] mag .
the @xmath3-band light curve of sn 2007gi demonstrated an interesting two - stage evolution during the nebular phase , with a decay rate of [email protected] mag ( 100 days)@xmath2 during @xmath690 days and 1.61@xmath7 mag ( 100 days)@xmath2 thereafter .
such a behavior was also observed in the hv sn ia 2006x , and might be caused by the interaction between supernova ejecta and circumstellar material ( csm ) around hv sne ia .
based on a sample of a dozen well - observed @xmath8-band ( or unfiltered ) light curves of sne ia , we confirm that the hv events may have a faster rise time to maximum than the ones with normal @xmath0 .
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SECTION 1. SHORT TITLE.
This Act may be cited as the ``Contracting Data and Bundling
Accountability Act of 2014''.
SEC. 2. PLAN FOR IMPROVING DATA ON BUNDLED AND CONSOLIDATED CONTRACTS.
Section 15 of the Small Business Act (15 U.S.C. 644) is amended by
adding at the end the following new subsection:
``(s) Data Quality Improvement Plan.--
``(1) In general.--Not later than the first day of fiscal
year 2016, the Administrator of the Small Business
Administration, in consultation with the Small Business
Procurement Advisory Council, the Administrator of the Office
of Federal Procurement Policy, and the Administrator of the
General Services Administration shall develop a plan to improve
the quality of data reported on bundled and consolidated
contracts in the Federal procurement data system.
``(2) Plan requirements.--The plan shall--
``(A) describe the roles and responsibilities of
the Administrator of the Small Business Administration,
the Directors of the Offices of Small and Disadvantaged
Business Utilization, the Small Business Procurement
Advisory Council, the Administrator of the Office of
Federal Procurement Policy, the Administrator of the
General Services Administration, the senior procurement
executives, and Chief Acquisition Officers in
implementing the plan described in paragraph (1) and
contributing to the annual report required by
subsection (p)(4);
``(B) make necessary changes to policies and
procedures on proper identification and mitigation of
contract bundling and consolidation, and to training
procedures of relevant personnel on proper
identification and mitigation of contract bundling and
consolidation;
``(C) establish consequences for failure to
properly identify contracts as bundled or consolidated;
``(D) establish requirements for periodic and
statistically valid data verification and validation;
and
``(E) assign clear data verification
responsibilities.
``(3) Committee briefing.--Once finalized and by not later
than 90 days prior to implementation, the plan described in
this subsection shall be presented to the Committee on Small
Business of the House of Representatives and the Committee on
Small Business and Entrepreneurship of the Senate.
``(4) Implementation.--Not later than the first day of
fiscal year 2017, the Administrator of the Small Business
Administration shall implement the plan described in this
subsection.
``(5) Certification.--The Administrator shall annually
provide to the Committee on Small Business of the House of
Representatives and the Committee on Small Business and
Entrepreneurship of the Senate certification of the accuracy
and completeness of data reported on bundled and consolidated
contracts.
``(6) GAO study and report.--
``(A) Study.--Not later than the first day of
fiscal year 2018, the Comptroller General of the United
States shall initiate a study on the effectiveness of
the plan described in this subsection that shall assess
whether contracts were accurately labeled as bundled or
consolidated.
``(B) Contracts evaluated.--For the purposes of
conducting the study described in subparagraph (A), the
Comptroller General of the United States--
``(i) shall evaluate, for work in each of
sectors 23, 33, 54, and 56 (as defined by the
North American Industry Classification System),
not fewer than 100 contracts in each sector;
``(ii) shall evaluate only those
contracts--
``(I) awarded by an agency listed
in section 901(b) of title 31, United
States Code; and
``(II) that have a Base and
Exercised Options Value, an Action
Obligation, or a Base and All Options
Value; and
``(iii) shall not evaluate contracts that
have used any set aside authority.
``(C) Report.--Not later than 12 months after
initiating the study required by subparagraph (A), the
Comptroller General of the United States shall report
to the Committee on Small Business of the House of
Representatives and the Committee on Small Business and
Entrepreneurship of the Senate on the results from such
study and, if warranted, any recommendations on how to
improve the quality of data reported on bundled and
consolidated contracts.
``(7) Definitions.--In this subsection the following
definitions shall apply:
``(A) Chief acquisition officer; senior procurement
executive.--The terms `Chief Acquisition Officer' and
`senior procurement executive' have the meanings given
such terms in section 44 of this Act.
``(B) Federal procurement data system
definitions.--The terms `Base and Exercised Options
Value', `Action Obligation', `Base and All Options
Value', and `set aside authority' have the meanings
given such terms by the Administrator for Federal
Procurement Policy in the Federal procurement data
system on October 1, 2013, or subsequent equivalent
terms.''.
|
Contracting Data and Bundling Accountability Act of 2014 - Amends the Small Business Act to direct the Administrator of the Small Business Administration (SBA) to develop a plan to improve the quality of data reported on bundled and consolidated contracts in the federal procurement data system. Requires the plan to: (1) describe the roles and responsibilities of the Administrator, the Directors of the Offices of Small and Disadvantaged Business Utilization, the Small Business Procurement Advisory Council, the Administrator of the Office of Federal Procurement Policy, the Administrator of the General Services Administration, the senior procurement executives, and Chief Acquisition Officers in implementing the plan and contributing to the annual report; (2) make necessary changes to policies and procedures on proper identification and mitigation of contract bundling and consolidation, and to training procedures of relevant personnel on proper identification and mitigation of contract bundling and consolidation; (3) establish consequences for failure to properly identify contracts as bundled or consolidated; (4) establish requirements for periodic and statistically valid data verification and validation; and (5) assign clear data verification responsibilities. Requires the finalized plan to be presented to the House and Senate small business committees by not later than 90 days prior to implementation. Directs the Administrator to: (1) implement the plan by the first day of FY2017, and (2) annually provide to such committees certification of the accuracy and completeness of data reported on bundled and consolidated contracts. Directs the Comptroller General (GAO): (1) to initiate a study by the first day of FY2018 on the effectiveness of the plan that shall assess whether contracts were accurately labeled as bundled or consolidated; and (2) not later than 12 months after initiating the study, to report to the small business committees on the results from such study and, if warranted, any recommendations on how to improve the quality of data reported on bundled and consolidated contracts.
|
extracting the parameters , such as masses , widths , and form factors , associated with the @xmath6 and @xmath7 resonances ( collectively referred to as @xmath5 ) from the data of meson - production reactions is an important task for understanding quantum chromodynamics ( qcd ) in the nonperturbative domain .
it is usually done by performing a comprehensive partial - wave analysis of @xmath8 and @xmath9 reactions with various final states including @xmath8 , @xmath10 , @xmath11 , @xmath12 , @xmath13 , and @xmath14 etc . within the on - shell @xmath15-matrix approaches @xcite and the dynamical - model approaches @xcite . here , the unitarity is a key essential element in accomplishing such a comprehensive analysis and making a reliable extraction of resonance parameters , because it not only ensures the conservation of probability in multichannel reaction processes but also properly defines the analytic structure of the scattering amplitudes in the complex - energy plane .
the latter is crucial for extracting from the data correctly the resonance parameters defined at the poles of scattering amplitudes . among the @xmath5 resonance parameters , transition amplitudes for the photo- and electro - excitation of the nucleon to @xmath5 resonances , @xmath16 ,
have been a particular focus of interest in the @xmath5 spectroscopy because of its crucial role in understanding the electromagnetic properties as well as the quark - gluon substructure of @xmath5 resonances ( see , e.g. , ref .
in fact , the dynamical - model studies @xcite of photon- and electron - induced meson - production reactions off the proton target revealed the large meson - cloud effect on the transition amplitudes at low @xmath17 whereas it decreases when @xmath17 is increased , implying that the ( constituent ) quark - gluon core of @xmath5 surrounded by dense meson clouds at long distance scales gradually emerges at shorter distance scales . in this
regard , new extensive measurements of @xmath18 with @xmath19 are planned at clas12 @xcite , aiming at precise determinations of the @xmath20 transition amplitudes in the @xmath17 region where such a transition to the `` core - dominated '' region is expected to occur .
however , for the @xmath4 @xmath5 resonances , the @xmath16 transition amplitudes for both the proton ( @xmath21 ) and neutron ( @xmath22 ) are necessary to uniquely determine the isospin structure of the photo- and electro - excitation couplings .
the information on such isospin - decomposed transition amplitudes are also important for investigating the neutrino - induced reactions in the @xmath5 resonance region ( see , e.g. , ref .
@xcite ) because those are the basic ingredients for constructing the vector - current matrix elements associated with the weak interactions .
the analysis of the photo- and electro - production reactions on both the proton and neutron targets is required to determine the isospin structure of the @xmath16 transition amplitudes for the @xmath4 @xmath5 resonances @xmath5 resonances , the @xmath20 and @xmath23 transition amplitudes are the same , and thus in principle only the data for either the proton- or neutron - target reaction is required .
however , it is still highly desirable to have the data for both reactions so that one can have more constraints on the transition amplitudes for @xmath24 @xmath5 resonances as well . ] , and such combined analyses have been done so far by several analysis groups @xcite within the coupled - channels framework . in ref .
@xcite , we reported on the @xmath5 parameters extracted within the dynamical coupled - channels ( dcc ) model developed in ref .
our approach is to fit the meson production data and to also search for the resonance poles by solving the following coupled integral equations for the partial - wave amplitudes , @xmath25 , which are specified by the total angular momentum @xmath26 , parity @xmath27 , and total isospin @xmath28 ( these indices are suppressed in the following equations ) , @xmath29 with @xmath30 here , the subscripts @xmath31 represent reaction channels considered , for which the @xmath32 , @xmath33 , and @xmath34 channels are the resonant components of the three - body @xmath10 channel .
[ indices for the orbital angular momentum ( @xmath35 ) and total spin ( @xmath36 ) of each reaction channel are suppressed . ]
@xmath37 is the green s function of channel @xmath38 ; @xmath39 is the mass of the @xmath40th bare excited nucleon state @xmath41 in a given partial wave ; the hadron - exchange potential @xmath42 is derived from the effective lagrangians by making use of the unitary transformation method @xcite ; the energy - dependent @xmath43 term @xcite is the effective one - particle - exchange potential that is derived with the projection operator method @xcite and produces the three - body @xmath44 cut ; the vertex interaction @xmath45 defines the @xmath46 decay ( note @xmath47 ) .
similar approach is also taken in ref .
the differences between our approach and the other coupled - channels analyses @xcite , which only consider the on - shell matrix elements of @xmath48 , have been discussed in detail in refs .
here we only mention that these models can be qualitatively obtained from eq .
( [ eq : teq ] ) by keeping only the on - shell part of the propagator @xmath49 , and refs .
@xcite further replace the hadron - exchange interaction @xmath50 by phenomenological forms such as the polynomials of on - shell momenta . if the data are _ complete _ ( as explained , e.g. , in ref .
@xcite ) and the high accuracy fits can be achieved , all approaches are acceptable for extracting the resonance pole positions
. however , more investigations are needed to examine under what ideal conditions all approaches should give the same resonance parameters defined at the poles of the scattering amplitudes .
furthermore , it is practically impossible to get _ complete _ data .
thus it is essential to impose theoretical constraints on both the determinations of the partial - wave amplitudes and the extractions of @xmath5 parameters .
this is accomplished in our approach by implementing the well - established hadron - exchange mechanisms , as defined by @xmath42 in eq .
( [ eq : veq ] ) , in the fits .
this also allows us to provide interpretations of the structure of the extracted @xmath5 resonances , such as the meson - cloud effects on the @xmath16 transitions . for the calculations of the @xmath9 reaction amplitudes , we use the so - called helicity-@xmath51 mixed - representation @xcite , in which the initial @xmath9 state is specified by their helicities , @xmath52 and @xmath53 , while the final meson - baryon state is specified by @xmath35 , @xmath36 , @xmath26 and @xmath28 as in eq .
( [ eq : teq ] ) , @xmath54 @xmath55 where @xmath56 . here
we note that the summation in eq .
( [ eq : teq2 ] ) runs over only hadronic meson - baryon channels .
we take @xmath9 channel perturbatively since the electromagnetic interactions are much smaller than the strong ones and their effect on the resonance parameters are expected to be just the order of isospin breaking .
the potential @xmath57 is again derived from the effective lagrangians by making use of the unitary transformation method . on the other hand , in ref .
@xcite the potential for electromagnetic interaction is simply parametrized with polynomials . in our previous work
performed in ref .
@xcite , we analyzed the available data of @xmath58 reactions in the region of @xmath59 2.1 gev .
then 24 physical @xmath5 resonances , which are defined at the poles of the scattering amplitudes in the complex energy plane , were successfully extracted .
their properties , including the @xmath2 transition amplitudes , were also extracted by evaluating the residues of the scattering amplitudes at the resonance poles . as a first step towards understanding the isospin structure of the photo- and electro - excitation of the nucleon to the @xmath4 @xmath5 resonances , in this work we extend our previous dcc analysis @xcite by further including the available data of @xmath0 photoproductions off the neutron and making a combined analysis of meson production reactions off the proton and neutron targets .
we then present the extracted @xmath60 transition amplitudes , together with the improved results for resonance pole masses , @xmath8 elastic residues , and the @xmath2 transition amplitudes . in this work ,
we focus on studying the transition amplitudes at the photon point , @xmath61 .
our procedures of resonance extraction have been given in detail in refs .
we therefore will only recall in sec .
[ sec : formulas ] the formulae that are needed for presenting the parameters of the extracted @xmath62 transitions . in sec .
[ sec : fit ] , we present our fits to the data . the extracted @xmath63 transition amplitudes are presented in sec . [
sec : respar ] , along with the revised values of resonance pole positions and the @xmath64 transition amplitudes presented in ref .
@xcite . in sec .
[ sec : summary ] , we give a summary and discussions on the necessary future works .
to define the @xmath3 transition amplitudes , we recall here some formula that can be derived @xcite from eqs .
( [ eq : teq ] ) and ( [ eq : teq2 ] ) within the considered dynamical coupled - channels model .
the on - shell @xmath36 matrix elements of the meson - baryon reactions , @xmath65 , in the center - of - mass system are given for each partial wave by @xmath66 here @xmath67 is the total scattering energy and we have suppressed indices for the angular momenta , parity , and isospin quantum numbers associated with the channels @xmath68 and @xmath69 .
the on - shell scattering amplitudes @xmath70 are related to the @xmath71 matrix elements given by eq .
( [ eq : teq ] ) as follows : @xmath72^{1/2 } t_{m'b',mb}(k_{m'b'}^{\text{on } } , k_{mb}^{\text{on } } ; w ) [ \rho_{mb}(k_{mb}^{\text{on}};w)]^{1/2 } , \label{eq : f - t}\ ] ] with @xmath73 where @xmath74 is the energy of a particle @xmath75 with mass @xmath76 and three - momentum @xmath77 ( @xmath78 ) . for a given @xmath67 , which can be complex ,
the on - shell momentum for the channel @xmath68 , @xmath79 , is defined by @xmath80 .
as the energy @xmath67 approaches to a pole position @xmath81 in the complex @xmath67 plane , the scattering amplitudes take the following form , @xmath82 where @xmath83 is the residue of @xmath70 at the resonance pole @xmath81 and @xmath84 is the `` background '' contribution .
both @xmath83 and @xmath84 are constant and in general complex .
the pole position ( @xmath81 ) and the residue ( @xmath83 ) are fundamental quantities that characterize the extracted resonance . the residues @xmath83 defined in eq .
( [ eq : f - pole ] ) can be calculated by using the definition @xmath85 , \label{eq : residue_def}\ ] ] where @xmath86 is an appropriate closed - path in the neighborhood of the point @xmath87 , circling @xmath87 in a counterclockwise manner .
it can be shown that for partial waves with one or more bare states ( this is the case of our current model for all partial waves ) , @xmath83 can also be calculated @xcite with @xmath88^{1/2 } \bar \gamma^r_{m'b'}(k_{m'b'}^{\text{on}};m_r ) \bar \gamma^r_{mb}(k_{mb}^{\text{on}};m_r ) [ \rho_{mb}(k_{mb}^{\text{on}};m_r)]^{1/2}. \label{eq : residue2}\ ] ] here @xmath89 is the ( renormalized ) dressed @xmath90 vertex that contains the meson cloud arising from the coupling to the meson - baryon continuum states .
as for the @xmath91 reactions , the on - shell scattering amplitudes are given in the helicity-@xmath51 mixed - representation by @xmath92^{1/2 } t_{m'b',\gamma n(\lambda)}(k_{m'b'}^{\text{on } } , k_{\gamma n}^{\text{on } } ; w ) [ \rho_{\gamma n}(k_{\gamma n}^{\text{on}};w)]^{1/2 } , \label{eq : f - t - ele}\ ] ] where @xmath93 is given by @xmath94 .
the amplitude @xmath95 also has a form close to the resonance pole position @xmath81 , @xmath96 then , the residue at the resonance pole @xmath81 , @xmath97 , can be calculated using the same formula ( [ eq : residue_def ] ) as the @xmath98 cases , or can be calculated using the similar formula to eq .
( [ eq : residue2 ] ) , @xmath99^{1/2 } \bar \gamma^r_{m'b'}(k_{m'b'}^{\text{on}};m_r ) \bar \gamma^r_{\gamma n(\lambda)}(k_{\gamma n}^{\text{on}};m_r ) [ \rho_{\gamma n}(k_{\gamma n}^{\text{on}};m_r)]^{1/2 } , \label{eq : residue2g}\ ] ] where the quantity @xmath100 is the dressed @xmath3 vertex , as illustrated in fig .
[ fig : dressed - v ] , multiplied by an appropriate wave - function renormalization factor .
the details on how to compute @xmath89 and @xmath100 etc . have been given in refs .
@xcite .
graphical representation of dressed @xmath101 transition vertex.,scaledwidth=60.0% ] with the renormalized vertex @xmath102 , the helicity amplitudes for the @xmath3 transitions evaluated at the resonance pole position @xmath81 , @xmath103 and @xmath104 , can be written as @xcite @xmath105 with @xmath106 where @xmath107 is the spin of the resonance state and @xmath108 . by fitting to the data , the model parameters included in the potentials ( [ eq : veq ] ) and ( [ eq : veq2 ] )
are determined .
we then can compute the on - shell dressed @xmath3 vertices at the resonance pole position @xmath109 and determine the helicity amplitudes @xmath110 by using eqs .
( [ eq : a32])-([eq : coef - c ] ) . in practice , however , we use an alternative formula from ref . @xcite to calculate the helicity amplitudes and unambiguously fix their phases .
the formula is given with the residues @xmath111 and @xmath112 as follows : @xmath113 @xmath114 with @xmath115 for @xmath28=3/2 @xmath5 and @xmath116 for @xmath28=1/2 @xmath5 ; the phase is fixed so that @xmath117 .
.[tab : data - chi2 ] observables and number of the data points considered in this coupled - channels analysis .
the data are taken from the database of the ins dac services @xcite . [
cols="<,^,^",options="header " , ] the extracted @xmath60 transition amplitudes are listed in table [ tab : helicity_n ] . here
only the results for the isospin @xmath4 nucleon resonances are presented because @xmath118 and @xmath119 give the same value . in the same table
, we also present the results obtained by the bonn - gatchina ( boga ) analysis @xcite for a comparison .
the results from ours and boga show a reasonable agreement for the transition amplitudes , for which the boga analysis assigns relatively small uncertainties for the extracted amplitudes . in particular , our results for the first @xmath120 ,
@xmath121 , and @xmath122 resonances , which correspond respectively to @xmath123 , @xmath124 , and @xmath125 in the pdg notation , are in good agreement with the boga results .
however , some disagreement is also seen for several @xmath5 resonances .
the boga analysis gives positive @xmath126 for the second @xmath120 resonance , while in our analysis @xmath126 is negative and very small . to obtain a more conclusive result for this transition amplitude , however , we would also need to take into account @xmath127 photoproduction data , as discussed in ref .
we hope to make this extended analysis by directly analyzing @xmath128 reactions , rather than analyzing the @xmath129 data provided by other experiment / analysis groups , and this will be presented elsewhere .
the origin of a significant disagreement in the transition amplitudes for the @xmath130 resonances would also come from a couple of reasons : ( a ) the pole mass of the second @xmath130 resonance from two analyses is different ; i.e. , @xmath131 mev from our analysis and @xmath132 mev from boga .
since the value of the residue has a strong correlation with the pole mass and more sensitive to the analysis model used in each analysis , one should first determine the pole mass well to accomplish a precise determination of the residues .
( b ) the @xmath130 resonances are found to give a small contribution to the @xmath133 reactions within our dcc model , and thus the @xmath60 transition amplitudes are not well constrained by the @xmath133 data .
therefore , to get more convergent results , we would need to further include the data associated with the other meson photoproductions off the neutron , such as @xmath134 , @xmath135 , and @xmath15 productions , into our fits to get convergent results .
however , as already mentioned , this is beyond the scope of the current work and will be performed elsewhere .
combining the @xmath60 and @xmath2 transition amplitudes listed in tables [ tab : helicity_p ] and [ tab : helicity_n ] , we can obtain the isovector ( @xmath136 ) and isoscalar ( @xmath137 ) parts of the @xmath62 amplitude for @xmath28=1/2 @xmath5 by using the following well - known relations : @xmath138 where @xmath139 and @xmath140 are helicity amplitudes for @xmath64 and @xmath63 transitions , respectively .
the resulting values of the isospin - decomposed transition amplitudes within our current dcc analysis is presented in table [ tab : helicity_n - iso ] as a reference .
in this work , we have extended our dcc analysis @xcite of the @xmath58 reactions by further including the data for pion photoproductions off the neutron target , @xmath133 , in the fits .
the helicity amplitudes for the @xmath60 transition , defined by the residues of the poles of the scattering amplitudes , have then been extracted . through this combined analysis of both the proton- and neutron - target reactions ,
the resonance pole masses and the @xmath2 transition amplitudes extracted from our previous analysis @xcite have also been revised accordingly .
our results allow an isospin decomposition of the @xmath101 transitions , which is needed for testing the hadron structure calculations and investigating the neutrino - induced reactions @xcite .
the extracted @xmath60 transition amplitudes are compared with the results of the boga analysis .
it is found that two results are consistent with each other overall .
however , some significant disagreements also exist for several @xmath5 resonances , implying that further extensions of both analyses to analyze more complete data on the neutron target will be needed to make progress .
as mentioned throughout this paper , in our current analysis we have used the @xmath141 data extracted from the @xmath142 data by other experiment / analysis groups . in most experimental analyses , the @xmath133
cross sections and polarization observables are extracted by simply applying momentum cuts to the deuteron data and choosing the kinematics where the quasi - free mechanisms are assumed to dominate the reaction processes .
effects of the nucleon fermi motion inside the deuteron have also been included in some analyses , but final @xmath143 interactions are usually neglected . on the other hand , several theoretical investigations @xcite have shown that the @xmath143 final - state interaction has very large effects on the @xmath144 reaction .
similar large effects are expected also for the other neutral - meson productions such as @xmath145 with @xmath146 . to make further progress in the study of the @xmath5 spectroscopy ,
an approach for investigating these meson production reactions off the deuteron must be developed .
since the accuracy of the extracted @xmath133 data depends on the way of unfolding the many body effects from the raw data , it is highly desirable to analyze directly the data of @xmath142 reactions based on a well - developed reaction model .
the dcc model employed in our analysis is particularly useful for the analysis of @xmath147-d and also @xmath147-nuclei reactions since the necessary off - shell amplitudes are readily available . to complete such a analysis , a method to describe
the @xmath143 dynamics in the @xmath7 and higher @xmath5 resonance region has to be explored .
these necessary tasks towards determining electromagnetic interactions associated with the @xmath5 resonances will be taken step by step and presented elsewhere .
this work was supported by the japan society for the promotion of science ( jsps ) kakenhi grant no .
25800149 ( h.k . ) and no .
16k05354 ( t.s . ) , the mext kakenhi grant no .
25105010 ( t.s . ) , and by the u.s .
department of energy , office of nuclear physics division , under contract no .
de - ac02 - 06ch11357 .
this research used resources of the national energy research scientific computing center , which is supported by the office of science of the u.s .
department of energy under contract no .
de - ac02 - 05ch11231 , and resources provided on blues and/or fusion , high - performance computing cluster operated by the laboratory computing resource center at argonne national laboratory .
r. l. workman , m. w. paris , w. j. briscoe , and i. i. strakovsky , phys .
c * 86 * , 015202 ( 2012 ) ; r. l. workman , r. a. arndt , w. j. briscoe , m. w. paris , and i. i. strakovsky , _ ibid .
_ , * 86 * , 035202 ( 2012 ) .
d. rnchen , m. dring , h. haberzettl , j. haidenbauer , u .- g .
meiner , and k. nakayama , eur .
phys . j. a * 51 * , 70 ( 2015 ) ; d. rnchen , m. dring , f. huang , h. haberzettl , j. haidenbauer , c. hanhart , s. krewald , u .- g .
meiner , and k. nakayama , _ ibid . _ * 50 * , 101 ( 2014 ) ; * 49 * , 44 ( 2013 ) .
l. tiator , s. s. kamalov , s. ceci , g. y. chen , d. drechsel , a. svarc , and s. n. yang , phys .
c * 82 * , 055203 ( 2010 ) ; g. y. chen , s. s. kamalov , s. n. yang , d. drechsel , and l. tiator , _ ibid .
_ , * 76 * , 035206 ( 2007 ) .
r. gothe _ et al .
_ , nucleon resonance studies with clas12 ( jlab e12 - 09 - 003 ) , https://www.jlab.org/exp_prog/proposals/09/pr12-09-003.pdf ; d. s. carman _ el al .
_ , exclusive @xmath148 studies with clas12 ( jlab e12 - 06 - 108a ) , https://www.jlab.org/exp_prog/proposals/14/e12-06-108a.pdf .
r. a. arndt , j. m. ford , and l. d. roper , phys .
d 32 , 1085 ( 1985 ) ; r. a. arndt , w. j. briscoe , i. i. strakovsky , and r. l. workman , phys .
c 74 , 045205 ( 2006 ) , and references therein ; cns data analysis center , george washington university university , http://gwdac.phys.gwu.edu the values for the model parameters determined by the analysis performed in this work are included as the supplemental material in the submission of the paper and can be provided by the authors upon request .
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by extending the dynamical coupled - channels analysis performed in our previous work [ phys .
rev .
c * 88 * , 035209 ( 2013 ) ] to include the available data of photoproduction of @xmath0 meson off the neutron , the transition amplitudes for the photo - excitation of the neutron to nucleon resonances , @xmath1 , at the resonance pole positions are determined .
the combined fits to the data for both the proton- and neutron - target reactions also revise our results for the resonance pole positions and the @xmath2 transition amplitudes .
our results allow an isospin decomposition of the @xmath3 transition amplitudes for the isospin @xmath4 @xmath5 resonances , which is necessary for testing hadron structure models and gives crucial inputs for constructing models of neutrino - induced reactions in the nucleon resonance region .
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SECTION 1. SHORT TITLE.
This Act may be cited as the ``Eastern Band of Cherokee Indians
Land Exchange Act of 2002''.
SEC. 2. FINDINGS AND PURPOSES.
(a) Findings.--Congress finds the following:
(1) Since time immemorial, the ancestors of the Eastern
Band of Cherokee Indians have lived in the Great Smoky
Mountains of North Carolina. The Eastern Band's ancestral
homeland includes much of seven eastern States and the land
that now constitutes the Great Smoky Mountains National Park.
(2) The Eastern Band has proposed a land exchange with the
National Park Service and has spent over $1,500,000 for studies
to thoroughly inventory the environmental and cultural
resources of the proposed land exchange parcels.
(3) Such land exchange would benefit the American public by
enabling the National Park Service to acquire the Yellow Face
tract, comprising 218 acres of land adjacent to the Blue Ridge
Parkway.
(4) Acquisition of the Yellow Face tract for protection by
the National Park Service would serve the public interest by
preserving important views for Blue Ridge Parkway visitors,
preserving habitat for endangered species and threatened
species including the northern flying squirrel and the rock
gnome lichen, preserving valuable high altitude wetland seeps,
and preserving the property from rapidly advancing residential
development.
(5) The proposed land exchange would also benefit the
Eastern Band by allowing it to reclaim the Ravensford tract,
comprising 144 acres adjacent to the Tribe's trust territory in
Cherokee, North Carolina, and currently within the Great Smoky
Mountains National Park. The Ravensford tract is part of the
Tribe's ancestral homeland as evidenced by archaeological finds
dating back no less than 6,000 years.
(6) The Eastern Band has a critical need to replace the
current Cherokee Elementary School, which was built by the
Department of the Interior over 40 years ago with a capacity of
480 students. The school now hosts 794 students in dilapidated
buildings and mobile classrooms at a dangerous highway
intersection in downtown Cherokee, North Carolina.
(7) The Eastern Band ultimately intends to build a new
three-school campus to serve as an environmental, cultural, and
educational ``village,'' where Cherokee language and culture
can be taught alongside the standard curriculum.
(8) The land exchange and construction of this educational
village will benefit the American public by preserving Cherokee
traditions and fostering a vibrant, modern, and well-educated
Indian nation.
(9) The land exchange will also reunify tribal lands now
separated between the Big Cove Community and the balance of the
Qualla Boundary, reestablishing the territorial integrity of
the Eastern Band.
(10) The Ravensford tract contains no threatened species or
endangered species listed pursuant to the Endangered Species
Act of 1973. The 218-acre Yellow Face tract has a number of
listed threatened species and endangered species and a higher
appraised value than the 144-acre Ravensford tract.
(11) The Congress and the Department of the Interior have
approved land exchanges in the past when the benefits to the
public and requesting party are clear, as they are in this
case.
(b) Purposes.--The purposes of this Act are the following:
(1) To acquire the Yellow Face tract for protection by the
National Park Service, in order to preserve the Waterrock Knob
area's spectacular views, pristine wetlands, and endangered
species and threatened species from encroachment by housing
development, for the benefit and enjoyment of the American public.
(2) To transfer the Ravensford tract, to be held in trust
by the Department of the Interior for the benefit of the
Eastern Band of Cherokee Indians, in order to provide for an
education facility that promotes the cultural integrity of the
Eastern Band and to reunify two Cherokee communities that were
historically contiguous.
(3) To promote cooperative activities and partnerships
between the Eastern Band and the National Park Service within
the Eastern Band's ancestral homelands.
SEC. 3. LAND EXCHANGE.
(a) In General.--Within 90 days after the effective date of this
Act, the Secretary of the Interior shall exchange the Ravensford tract,
currently in the Great Smoky Mountains National Park, for the Yellow
Face tract adjacent to the Waterrock Knob Visitor Center on the Blue
Ridge Parkway.
(b) Treatment of Exchanged Lands.--Effective upon receipt by the
Secretary of a deed for the lands comprising the Yellow Face tract (as
described in subsection (c)) to the United States, all right, title,
and interest of the United States in and to the Ravensford tract, (as
described in subsection (d)), including all improvements and
appurtenances, are declared to be held in trust by the United States
for the benefit of the Eastern Band of Cherokee Indians as part of the
Cherokee Indian Reservation.
(c) Yellow Face Tract.--To effectuate this land exchange, the
Eastern Band shall cause the following lands to be deeded to the United
States. Parcels 88 and 89 of the Hornbuckle Tract, Yellow Face Section,
Qualla Township, Jackson County, North Carolina, consisting
respectively of 110.4 and 108.2 acres more or less, together with all
improvements and appurtenances thereto. The lands shall thereafter be
included within the boundary of and managed as part of the Blue Ridge
Parkway by the National Park Service.
(d) Ravensford Tract.--The lands declared by subsection (b) to be
held in trust for the Eastern Band of Cherokee Indians are as follows:
The tract currently located within the Great Smoky Mountains National
Park and identified on Map No. 133/80020, entitled ``Ravensford Land
Exchange Tract'', as on file and available for public inspection in the
appropriate offices of the National Park Service and the Bureau of
Indian Affairs, consisting of 144 acres more or less.
(e) Legal Descriptions.--Not later than 1 year after the date of
enactment of this Act, the Secretary of the Interior shall file a legal
description of the areas described in subsections (c) and (d) with the
Committee on Resources of the House of Representatives and the
Committee on Indian Affairs and the Committee on Energy and Natural
Resources of the Senate. Such legal descriptions shall have the same
force and effect as if the information contained in the description
were included in those subsections except that the Secretary may
correct clerical and typographical errors in such legal descriptions.
The legal descriptions shall be on file and available for public
inspection in the offices of the National Park Service and the Bureau
of Indian Affairs.
SEC. 4. IMPLEMENTATION PROCESS.
(a) Government-to-Government Agreements.--In order to fulfill the
purposes of this Act and to establish cooperative partnerships for
purposes of this Act the Director of the National Park Service and the
Eastern Band of Cherokee Indians shall enter into government-to-
government consultations and shall develop protocols to review planned
construction on the Ravensford tract. The Director of the National Park
Service is authorized to enter into cooperative agreements with the
Eastern Band for the purpose of providing training, management,
protection, and preservation of the natural and cultural resources on
the Ravensford tract.
(b) Construction Standards.--The National Park Service and the
Eastern Band shall develop mutually agreed upon standards for size,
impact, and design of construction consistent with the purposes of this
Act on the Ravensford tract. The standards shall be consistent with the
Eastern Band's need to develop educational facilities and support
infrastructure adequate for current and future generations and shall
otherwise minimize or mitigate any adverse impacts on natural or
cultural resources. The standards shall be based on recognized best
practices for environmental sustainability and shall be reviewed
periodically and revised as necessary. All development on the
Ravensford tract shall be conducted in a manner consistent with such
standards.
(c) Tribal Employment.--In employing individuals to perform any
construction, maintenance, interpretation, or other service in the
Great Smoky Mountains National Park, the Secretary of the Interior
shall, insofar as practicable, give first preference to qualified
members of the Eastern Band.
SEC. 5. GAMING PROHIBITION.
Nothing in this Act shall be construed to satisfy the terms for an
exception under section 20(b)(1) of the Indian Gaming Regulatory Act
(25 U.S.C. 2719(b)(1)) to the prohibition on gaming on lands acquired
by the Secretary of the Interior in trust for the benefit of an Indian
tribe after October 17, 1988, under section 20(a) of such Act (25
U.S.C. 2719(a)).
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Eastern Band of Cherokee Indians Land Exchange Act of 2002 - Requires the Secretary of the Interior to exchange the Ravensford tract, currently in the Great Smoky Mountains National Park, for the Yellow Face tract adjacent to the Waterrock Knob Visitor Center on the Blue Ridge Parkway.Requires the Eastern Band of Cherokee Indians (Eastern Band) to deed specified parcels of land to the United States. Requires the deeds for specified lands be held in trust by the United States for the benefit of the Eastern Band as part of the Cherokee Indian Reservation.Requires the Secretary to file a legal description of the areas held in trust by the United States for the benefit of the Eastern Band.Requires the Director of the National Park Service and the Eastern Band to: (1) enter into government-to-government consultations and develop protocols to review planned construction on the Ravensford tract; and (2) develop mutually agreed upon standards for size, impact, and design of construction consistent with the Eastern Band's need to develop educational facilities and support infrastructure.Authorizes the Director to enter into cooperative agreements with the Eastern Band for the purpose of providing training, management, protection, and preservation of the natural and cultural resources on the Ravensford tract.Requires the Secretary to give first preference of employment for service in the Great Smoky Mountains National Park to qualified members of the Eastern Band.
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SECTION 1. SHORT TITLE.
This Act may be cited as the ``Veterans E-Health and Telemedicine
Support Act of 2017'' or the ``VETS Act of 2017''.
SEC. 2. LICENSURE OF HEALTH CARE PROFESSIONALS OF THE DEPARTMENT OF
VETERANS AFFAIRS PROVIDING TREATMENT VIA TELEMEDICINE.
(a) In General.--Chapter 17 of title 38, United States Code, is
amended by inserting after section 1730A the following new section:
``Sec. 1730B. Licensure of health care professionals providing
treatment via telemedicine
``(a) In General.--Notwithstanding any provision of law regarding
the licensure of health care professionals, a covered health care
professional may practice the health care profession of the health care
professional at any location in any State, regardless of where the
covered health care professional or the patient is located, if the
covered health care professional is using telemedicine to provide
treatment to an individual under this chapter.
``(b) Property of Federal Government.--Subsection (a) shall apply
to a covered health care professional providing treatment to a patient
regardless of whether the covered health care professional or patient
is located in a facility owned by the Federal Government during such
treatment.
``(c) Construction.--Nothing in this section may be construed to
remove, limit, or otherwise affect any obligation of a covered health
care professional under the Controlled Substances Act (21 U.S.C. 801 et
seq.).
``(d) Covered Health Care Professional Defined.--In this section,
the term `covered health care professional' means a health care
professional who--
``(1) is an employee of the Department appointed under the
authority under sections 7306, 7401, 7405, 7406, or 7408 of
this title, or title 5;
``(2) is authorized by the Secretary to provide health care
under this chapter;
``(3) is required to adhere to all quality standards
relating to the provision of telemedicine in accordance with
applicable policies of the Department; and
``(4) has an active, current, full, and unrestricted
license, registration, or certification in a State to practice
the health care profession of the health care professional.''.
(b) Clerical Amendment.--The table of sections at the beginning of
chapter 17 of such title is amended by inserting after the item
relating to section 1730A the following new item:
``1730B. Licensure of health care professionals providing treatment via
telemedicine.''.
(c) Report on Telemedicine.--
(1) In general.--Not later than 1 year after the date of
the enactment of this Act, the Secretary of Veterans Affairs
shall submit to the Committee on Veterans' Affairs of the
Senate and the Committee on Veterans' Affairs of the House of
Representatives a report on the effectiveness of the use of
telemedicine by the Department of Veterans Affairs.
(2) Elements.--The report required by paragraph (1) shall
include an assessment of the following:
(A) The satisfaction of veterans with telemedicine
furnished by the Department.
(B) The satisfaction of health care providers in
providing telemedicine furnished by the Department.
(C) The effect of telemedicine furnished by the
Department on the following:
(i) The ability of veterans to access
health care, whether from the Department or
from non-Department health care providers.
(ii) The frequency of use by veterans of
telemedicine.
(iii) The productivity of health care
providers.
(iv) Wait times for an appointment for the
receipt of health care from the Department.
(v) The reduction, if any, in the use by
veterans of in-person services at Department
facilities and non-Department facilities.
(D) The types of appointments for the receipt of
telemedicine furnished by the Department that were
provided during the 1-year period preceding the
submittal of the report.
(E) The number of appointments for the receipt of
telemedicine furnished by the Department that were
requested during such period, disaggregated by Veterans
Integrated Service Network.
(F) Savings by the Department, if any, including
travel costs, of furnishing health care
through the use of telemedicine during such period.
Passed the House of Representatives November 7, 2017.
Attest:
KAREN L. HAAS,
Clerk.
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. Veterans E-Health and Telemedicine Support Act of 2017 or the VETS Act of 2017 (Sec. 2) This bill allows a licensed health care professional of the Department of Veterans Affairs (VA) to practice his or her profession using telemedicine at any location in any state regardless of where the professional or patient is located if the covered health care professional is using telemedicine to provide VA medical or health services. Such authority shall apply to a covered health care professional regardless of whether the covered health care professional or patient is located in a federally-owned facility. The bill defines "covered health care professional" as a health care professional who: (1) is a VA employee appointed under specified VA authorities or under the civil service; (2) is authorized by the VA to provide health care; (3) is required to adhere to all telemedicine quality standards; and (4) has an active, current, full, and unrestricted state license, registration, or certification for such health care profession. The VA shall report to Congress on the effectiveness of the VA's use of telemedicine.
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accidents can take place in a wide variety of environments and settings ; however , the home , which people regard as the safest place , is the most likely location .
home accidents comprise 35% of all unintentional injuries in childhood , and the majority of victims are toddlers and pre - school children .
televisions ( tv ) have become ubiquitous in households all around the world [ 35 ] . over the past several years
, tvs have grown larger in size and shape , which has made them unstable and susceptible to toppling [ 6 , 7 ] .
falling tvs have created a potential risk for significant injury to children in households . however , despite the danger , only a few studies have been reported in the literature regarding this source of risk [ 1 , 311 ] . furthermore , several home safety guidelines for parents do not include how to prevent tv - related injuries [ 12 , 13 ] .
the purpose of this study was to quantify injuries in children that result from toppled televisions and to highlight the significance of this mechanism of injury .
this is a retrospective chart review study for which we collected data from our emergency department s digital patient database for the september 2008september 2009 period .
all children under 15 years of age who presented to the ed with injuries casued by a falling television were included in this study .
patients were identified and selected from the digital database using the chief complaint upon arrival .
demographic information , injured body region and diagnosis , surgical intervention , admission to the intensive care unit ( icu ) , glasgow coma scale ( gcs ) score , length of hospital stay ( los ) , in - hospital mortality , and disposition at hospital discharge were analysed .
a descriptive analysis of the continuous and categorical data was performed using proportions , frequency distributions , means , and standard deviations .
during the 12-month period under investigation , 3,856 children were admitted to our ed with injuries sustained at home . of these 3,856 admissions , 71 ( 1.8% ) were becasue of tv - related injuries , and thus these patients were included in this analysis .
the mean age was 39.79 20.14 months ( sd ) , with more than half ( 53.5% ) of the children aged 12 to 36 months .
table 1age and gender of the patientsage ( months)girlsboystotal<120121224491325365202537484374960491361721567384326>84011total215071 age and gender of the patients almost three - quarters of the children ( 49/71 ) sustained various head and facial injuries .
the most common site for a scalp hematoma was the occipital region ( 55% ) , followed by the temporal , frontal , and parietal regions .
the most common site for a scalp laceration was the frontal region ( 57% ) , followed by the temporal , occipital , and parietal regions .
there were 18 skull fractures ( 8 occipital bone , 4 temporal bone , 3 frontal bone , and 3 parietal bone ) .
traumatic brain injury occurred in 14 patients ( 4 subarachnoid bleeding , 1 epidural hematoma , 1 subdural hematoma , and 8 cerebral contusions ) .
the average gcs score was 13.3 ( range , 315 ) in head trauma patients .
one patient had a skin laceration over the midfoot that was sutured in the ed .
there were seven patients with fractures , which were all treated with casting and/or closed reduction .
two of them had superficial skin lacerations over the abdominal wall that did not reach the intra - abdominal cavity .
one patient had a minor liver laceration , and two patients had free fluid in the abdomen detected with ultrasonography .
the mean length of stay was 15.6 h ( 124 h ) in these patients .
sixteen patients were hospitalised , and 14 of them required follow - up in the icu .
two patients ( one with an epidural hematoma and one with a subdural hematoma ) underwent surgical intervention .
four patients with subarachnoid bleeding died ( mean age , 30.25 months , range 2731 ) .
one of them died immediately upon arrival , and the other three died in the icu .
the mean los was 71.25 h ( range , 48168 h ) in the hospitalised patients .
the number of injuries may add up to more than the number of cases because of multiple injuriesinjured body regionnumber of casesdescription of the injurieshead and facial injuries49*scalp and facial injuries31 patients , scalp hematoma 14 patients , scalp laceration6 patients , nasal contusion2 patients , forehead laceration1 patient , lip laceration*skull fractures8 patients , nondisplaced linear skull fracture10 patients , basilar skull fracture*traumatic brain injury4 patients , subarachnoid bleeding1 patient , epidural hematoma1 patient , subdural hematoma8 patients , cerebral contusionchest injuries132 patients , rib fracture11 patients , chest wall contusionabdominal injuries101 patient , grade 1 liver laceration 2 patients , abdominal wall laceration7 patients abdominal wall contusionextremity injuries30*upper extremity17 patients , soft tissue injuries1 patient , clavicular fracture1 patient , radius distal torus fracture*lower extremity5 patients , soft tissue injuries1 patient , skin laceration over midfoot2 patients , closed tibia fracture2 patients , closed metatarsal fracture1 patient , closed femur fracture distribution and description of injured body regions .
the number of injuries may add up to more than the number of cases because of multiple injuries
most accidents take place in the home environment , especially in toddlers and pre - schoolers as they spend most of their time there [ 1 , 2 , 11 ] .
this study showed that children aged 12 to 36 months of both genders had the highest overall injury rate resulting from tv - related injuries .
children s relative lack of coordination at this stage of development and their still undeveloped cognitive hazard awareness and avoidance skills are the major reasons for the accumulation of injuries at this age .
previous studies on tv - related injuries have had comparable results to those of our study [ 1 , 6 , 8 ] .
reported that more than half ( 57.4% ) of the children were boys , and more than three quarters ( 76.0% ) were 1 to 4 years of age .
similarly , yahya et al . reported that 7 out of 18 children with tv - related head injuries were younger than 36 months of age , and more severe injuries occurred in this age group in their series .
although home accidents can occur in all children , current evidence indicates that this specific mechanism of injury particularly affects boys younger than 36 months of age .
previous retrospective descriptions and a prospective study have confirmed that a tv tip - over usually occurs when a curious toddler attempts to climb onto furniture , typically a dresser , on which the tv sits , causing the furniture and the tv to fall onto the child [ 1 , 5 ] .
cathode ray tube tvs are not stable due to the imbalance of the intrinsic weight distribution of their design [ 6 , 7 ] .
constructed a static model of a climbing child to simulate a tv tip - over and investigated how much weight was enough to topple a tv .
suprisingly , they found that 90% of the accessible televisions could be tipped by a child 4 years of age with weight in the 90th percentile .
sikron et al . reported that nearly three - quarters of the children ( 73.3% ) sustained head / neck injuries , with almost half of these having a definite traumatic brain injury . our results and the other relevant studies supported this evidence [ 5 , 11 ] .
there may be two reasons ; either the tv falls onto the child s head , or the child hits his head on the ground during the fall
we further analysed our data and found that occipital and frontal lesions , involving scalp haematomas , lacerations , and cranial fractures , were more common than lesions in other head regions .
the presence of frontal lacerations , nasal contusions , and forehead and lip lacerations are indications of the first scenario , while the presence of occipital hematomas and fractures point to the second .
mortality and substantial long - term sequelae in tv - related injuries can be attributed to traumatic brain injuries [ 9 , 10 ] .
other injuries , including those of the abdomen , chest , and extremities , were mild to moderate in this study .
reported the highest mortality rate ( 38.3% ) among studies concerning tv - related injuries .
however , crush type injuries were also responsible for half of the mortality in their study .
therefore , victims of tv - related injury should be carefully examined for possible fatal abdominal and thoracic injuries .
we could not obtain a detailed history from the parents at the time of admission .
we do not know the tv screen sizes , what the tvs were placed on , and the circumstances surrounding the injury scene .
furthermore , data were extracted from our digital patient database , and some cases may have been missed , which may have affected the results .
prospective studies are necessary to have a more realistic understanding of the mechanism of injury . in conclusion ,
falling tvs may cause significant morbidity and mortality in children , particularly those younger than 3 years old .
head and facial injuries are the most commonly encountered , followed by injuries to the extremities .
preventive measures taken in the home and , more importantly , increased awareness of this potential risk of injury by the parents are the key solutions to this problem .
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backgroundfemoral artery pseudoaneurysm following cardiac catheterization is a serious groin complication requiring careful assessment and prompt intervention.aimsthe risk of femoral artery pseudoaneurysm is estimated at 0.6 to 17% following diagnostic and interventional procedures.methodsthe clinical use of bedside ultrasonography as part of the physical examination by attending emergency physicians has increased significantly over recent years.resultsbedside emergency department ultrasonography provides the clinician with critical information noninvasively , rapidly determining various anatomical structures.conclusionswe present the case of a patient with femoral artery pseudoaneurysm detected by bedside emergency department ultrasonography secondary to angiographic catheterization .
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we give a breezy , qualitative overview of some of our recent results @xcite on studying jet stopping in strongly - coupled plasmas using gauge - gravity duality .
previously , people have found that the maximum stopping distance in such plasmas scales with energy as @xmath0 . we show that there is an important distinction between typical and maximum stopping distances . for the strongly - coupled excitations that we study , we find that the typical stopping distance scales with energy as @xmath1 .
how far does a high - energy excitation travel through a quark - gluon plasma , before it stops in the medium and thermalizes ? to get the discussion started , consider the weak - coupling picture of energy loss depicted in fig .
[ fig : brem ] , which is dominated by nearly - collinear bremsstrahlung at high energy .
what sets the scale for the running coupling constant in this process ? as the particle flies along , it picks up small kicks from the medium , which change its direction , which is a form of acceleration , and so a source for bremsstrahlung .
the individual kicks are dominated by relatively soft momentum scales for which @xmath2 is of order @xmath3 ( shown in red ) . but now consider the @xmath2 ( shown in blue ) associated with the emission of the bremsstrahlung gluon .
its scale is plausibly set by the relative transverse momenta @xmath4 of the two daughter particles after the splitting .
is the typical transverse momentum picked up during the formation time of the bremsstrahlung gluon . ] in an infinite medium ( the relevant case if the medium is thick enough for a jet to actually stop ) , the typical @xmath4 grows slowly with particle energy as @xmath5 .. this relation follows from the usual lpm relations that ( for the case @xmath6 of interest ) @xmath7 and ( for an infinite medium ) @xmath8 , where @xmath9 is the formation time . ]
the scaling of the stopping distance @xmath10 depends on the size of @xmath2 at these two scales @xmath11 and @xmath4 . *
_ weak coupling _ : if @xmath12 are both small , then @xmath13 ( up to logarithms ) .
this scaling is a corollary of the early work of baier et al .
( bdmps ) @xcite and zakharov @xcite on the lpm effect in qcd .
( for specific formulas for the stopping distance in weakly - coupled qcd , see ref .
@xcite . ) * _ mixed coupling _ :
if @xmath3 is large and @xmath14 is small , various people have argued that the stopping distance still scales as @xmath13 and that the strong - coupling dynamics of the problem can be isolated into the value of @xmath15 .
this is related , for example , to the motivation of liu , rajagopal , and wiedemann @xcite to find the value of @xmath15 in strongly - coupled theories via ads / cft . * _ all strong coupling _ : for @xmath16 very large , very large for large-@xmath17 @xmath18 super yang mills .
] progress has been made in theories such as @xmath18 super yang mills ( and its close cousins ) , where calculations are possible using gauge - gravity duality . in this case
, people have found that the stopping distance has a different scaling with energy : @xmath19 @xcite . in this article
, we will focus on the last , all strong - coupling case .
what is interesting about this result is its demonstration that the exponent @xmath20 in @xmath21 can depend on @xmath2 .
we will see that the strong - coupling case has an even richer set of exponents than @xmath19 to describe jet stopping .
weak - coupling picture of energy loss due to bremsstrahlung . ] think about the finite - temperature 3 + 1 dimensional field theory , and imagine what happens if you very energetically kick the medium is some way at @xmath22 , creating a localized excitation that moves through the medium , as depicted in fig .
[ fig : kick ] . at later times
, one looks at the progress of the excitation through the medium by following some conserved density such as energy or momentum or charge density . for the purpose of this figure , it will be simplest if we think of charge density . as time passes , the charge density moves in a pulse that eventually slows down ( because of energy loss ) and then stops as the energy in the excitation thermalizes , after which the charge diffuses outward .
the distance from the kick to the center of the late - time diffusion cloud of charge is the stopping distance .
evolution in time of a local excitation of some conserved charge created by a high - energy kick to the plasma .
here @xmath23 means the third spatial coordinate , and the eyeball represents a late - time observation of the system . ] as an example of previous calculations of jet stopping in ads / cft which found @xmath19 , we briefly review in fig.[fig : string ] how chesler , jensen , karch , and yaffe @xcite set up the problem for light - quark jets . a classical string in the 5-dimensional gravity theory is used to describe a state analogous to a @xmath24 pair in qcd .
the string is initialized in a way that its end points fly apart , analogous to a high - energy back - to - back quark and anti - quark .
as the ends fly apart , the string also falls in the fifth dimension towards the black brane horizon , as depicted by the time - series of curves , from top to bottom , in fig .
[ fig : string]a .
the presence of the string disturbs the background gravitational and other fields , and so causes a deformation of the fields on the boundary , as depicted in fig .
[ fig : string]b . as in fig .
[ fig : kick ] , it will be pictorially simplest to discuss observing conserved charge densities which diffuse ( rather than energy or momentum density , which can create sound waves ) . in the case of chesler et .
al , the relevant global charge is `` baryon '' number .
as the string falls toward the horizon , its effect on the boundary becomes more and more red - shifted , and so spreads out to longer and longer wavelengths .
this is how the falling string produces diffusion of the charge density seen in the boundary theory .
a cartoon of ( a ) the falling string of chesler et . al @xcite and ( b ) its effect on baryon number charge density on the boundary .
see ref .
@xcite for their own versions of these cartoons . ]
there is one just slightly dissatisfying aspect of this very nice picture : the initial configuration of the system has been specified in the language of the gravity dual rather than directly in the 3 + 1 dimensional field theory .
our goal is to avoid this by finding a way to formulate some `` jet '' stopping problem from beginning to end in the field theory .
we will only use the gravity dual as a means to solve that field - theory problem . to understand our method
, it helps to first think impessionistically of the decay of a very high energy , slightly virtual photon , or of a very high energy @xmath25 boson , in a qcd quark - gluon plasma .
fig .
[ fig : decay ] shows the corresponding processes for weak coupling .
each creates a localized , high - energy , high - momentum excitation in the plasma , moving towards the right of the figure ( the @xmath26 direction ) .
we will loosely call such an excitation a `` jet . '' in weakly - coupled qcd , the jet produced in fig.[fig : decay ] starts out as a nearly - collinear @xmath27 pair . in strongly - coupled @xmath18 sym ,
the analogy is a localized excitation of strongly interacting gluons , gluinos , and adjoint scalars .
now treat the red photon or @xmath28 line in fig .
[ fig : decay ] as an external field in the form of a high - energy plane wave @xmath29 with @xmath30 .
however , we will also approximately localize that external field , so that we know where the jet it creates starts from .
that way , when we later see where the jet stops and thermalizes , we will be able to extract the stopping distance from the difference .
put all together , we replace the photon or @xmath28 by adding a source term to the lagrangian : @xmath31 with @xmath32 the factor @xmath33 is the external field , where @xmath34 is a smooth envelope function which localizes the source to a region of size @xmath35 around the origin in both space and time .
the @xmath36 is the field - theory operator the external field couples to , such as @xmath37 in the examples of fig .
[ fig : decay ] , and corresponds to the vertex in fig .
[ fig : decay ] .
the decay of a high - energy slightly - virtual photon , or of a high - energy @xmath25 , in a qcd quark - gluon plasma . ]
it turns out that the response to such a source is measured by a _
3-point correlator _ in the field theory .
a crude but simple way to understand this is given in fig .
[ fig:3point ] .
the boot represents the source operator in ( [ eq : source ] ) .
we apply this operator to a generic state of the thermal plasma to create our localized , high - energy `` jet '' state , as in fig .
[ fig:3point]a .
we then want the expectation value in this state of some conserved density energy or momentum or charge represented by the eyeball operator in fig . [ fig:3point]b . substituting fig .
[ fig:3point]a into the left - hand side of fig .
[ fig:3point]b yields the right - hand side of fig .
[ fig:3point]b , which is a 3-point correlator of the boot , the eyeball , and the boot - conjugate , calculated for an equilibrium plasma . for _ finite - temperature _ ads / cft calculations
, there is a great deal in the literature on computing 2-point correlators , but until recently almost nothing carried through to specific results for 3-point correlators . schematic picture of how the expectation of an observable ( eyeball ) in a jet state created by some operator ( boot ) can be related to a 3-point equilibrium correlator .
] to compute this field - theory three - point correlator , we use gauge - gravity duality to relate it to a three - point boundary correlator in ads@xmath38-schwarzschild space , as depicted in fig . [
fig : ads3point ] . here
@xmath39 is the space - time point where we make our observation , and @xmath40 and @xmath41 are integrated over the source region .
recall that gauge - gravity duality relates the strongly - coupled field theory problem to a problem in _ classical _ gravity , which means tree diagrams in the gravity problem . in fig .
[ fig : ads3point ] , we therefore have a three - leaf tree diagram made up of the dashed lines meeting at a vertex in the bulk .
the vertex represents a cubic term in the 5-dimensional supergravity action .
the dashed lines are bulk - to - boundary propagators and in our calculation are given by _
_ functions .
heun functions are obscure generalizations of hypergeometric functions which are difficult to work with . as a result , it is difficult to make analytic progress in calculating generic 3-point functions , which requires integrating over the vertex position . it is also difficult to evaluate such integrals numerically in our problem because the fact that our source is high energy , and the fact that we are looking at real - time correlations , means that the bulk - to - boundary propagators associated with the boots are very highly oscillatory functions and so very difficult to integrate
. fortunately , this very problem also points the way to a solution .
the ( red ) dashed lines in fig .
[ fig : ads3point ] associated with the boots are high - energy / momentum propagators , and we may make a corresponding high-@xmath42 wkb - like approximation , which gives them a relatively simple analytic form . for the remaining ( green ) dashed line in fig . [
fig : ads3point ] , recall that the technique for measuring the stopping distance is to look for the spatial center of late - time charge diffusion , as depicted by the last curve in fig .
[ fig : kick ] .
this corresponds to measurements of large wavelengths and so small wave numbers of the late - time response of the system . as a result
, we may use a low-@xmath42 approximation to the ( green ) dashed line associated with the eyeball in fig .
[ fig : ads3point ] .
the low-@xmath42 limit also gives a relatively simple analytic expression for the propagator .
these approximations , appropriate for the problem we want to solve , turn out to be enough to make it possible to analytically integrate over the bulk vertex position and compute the 3-point correlator .
[ by the way , it is easy to see now why this physics could not possibly be captured by a 2-point correlator .
if we took a 2-point correlator of a boot ( source ) and an eyeball ( measurement ) , there would be a mismatch between the high - momentum of the boot and the low wave - numbers of interest for the eyeball , and so the 2-point correlator would vanish by momentum conservation . ]
3-leaf tree diagram that gives the 3-point correlator in the gravity dual theory . ] the results @xcite of using this method to calculate the jet stopping distance are summarized in fig.[fig : result ] , which shows a probability distribution for the jet stopping distance .
there is indeed a `` maximum '' stopping distance that scales like @xmath0 , beyond which the probability distribution falls off exponentially .
however , this is not the _ typical _ stopping distance of the jets created .
almost all of the jets created by our kick ( [ eq : source ] ) instead stop sooner at a distance scale proportional to @xmath43 , where @xmath35 is the size of the space - time region in which the jet was initially created ( i.e. the size of the toe of our boot and the duration of the kick ) . is often instead used to stand for the thickness of the medium .
this has nothing to do with our @xmath35 here : in our problem , we are considering jet stopping in an infinite medium . ] between the scales @xmath43 and @xmath0 , the probability distribution falls algebraically , with the power law depending on the conformal dimension of the source operator @xcite . qualitative picture of the probability distribution of jet stopping distances , where @xmath35 is the source size .
the power - law fall - off @xmath44 shown for the intermediate region is for the specific source operator analyzed in ref .
@xcite ; the more general case is given in ref .
@xcite . ] by the way , for the @xmath45 case , which dominates the probability distribution shown in fig .
[ fig : result ] , the calculation can be made even simpler than the forgoing discussion . in this limit
, it turns out that one can use the approximation of geometric optics and replace the 3-point calculation of fig .
[ fig : ads3point ] by a simple classical calculation of a 5-dimensional particle falling toward the horizon in ads@xmath38-schwarzschild space .
see ref .
@xcite for details .
readers may wonder what the size @xmath35 of the source has to do with how far jets propagate ?
the answer is that @xmath35 determines the virtuality of the source .
recall that in ( [ eq : source ] ) we chose a source proportional to @xmath33 with @xmath46 .
the envelope function @xmath34 localized the source to a region of size @xmath35 and so , by the uncertainty principle , introduces a spread in momentum of size @xmath47 .
fig .
[ fig : momentum ] gives a qualitative picture of the region of momentum space that contributes to @xmath33 .
generic momenta in this region are not exactly on the light cone , and we demonstrate in ref . @xcite that the @xmath43 scaling of the typical stopping distance really means @xmath48 , where @xmath49 is the typical virtuality of the source : @xmath50 qualitative picture of the region in 4-momentum where the source ( [ eq : source ] ) has support . ]
studying jet stopping in the strongly - coupled limit is a useful theoretical exercise in order to sharpen our understanding of the role that coupling @xmath2 plays in the scaling of jet stopping with energy .
it also provides an interesting test case for optimists , or a straw man for cynics , for phenomenological comparisons with data : regardless of one s point of view , ads / cft results inspire the question of whether experiment can differentiate between @xmath51 and @xmath0 or other scaling for jet stopping distances , or between non - standard scaling laws for other measurements related to energy loss . for some work along these lines ,
see refs .
@xcite .
readers who toy with such questions might naturally ask what happens if we now put @xmath52 into ( [ eq : stop ] ) , since @xmath52 is the virtuality scale of processes creating high - energy jets at mid - rapidity in actual relativistic heavy ion collisions .
the corresponding running coupling constant associated with the initial moments of such jet creation is @xmath53 , rather than the couplings @xmath3 or @xmath14 reviewed in the introduction .
whatever one may think of the theoretical or perhaps phenomenological utility of investigating jet stopping in strongly - coupled theories , it seems implausible that @xmath54 can be approximated as infinite for high energy jets .
if there is any phenomenological application for the results presented here , one should likely avoid treating the system as strongly coupled until enough time has passed that the initial virtuality @xmath52 associated with jet creation has dropped to some lower virtuality where one is willing to at least entertain the possibility that the @xmath2 associated with the emission of a bremsstrahlung gluon might be effectively strongly coupled .
this work was supported , in part , by the u.s .
department of energy under grant no .
de - fg02 - 97er41027 and by a jeffress research grant , gf12334 .
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the discovery of cosmic acceleration @xcite has become one of the main challenges for modern theoretical physics , because it has put forward the problem of the so called dark energy , responsible for this acceleration .
this dark energy should possess a negative pressure such that the relation between pressure and energy density is less than @xmath0 @xcite .
a considerable amount of dark energy models was proposed ( see , e.g. @xcite ) , which now have to confront with growing quantity of observational data .
being enigmatic by itself , the phenomenon of the cosmic acceleration - dark energy - negative pressure hides inside another subphenomenon , which is not yet so well confirmed experimentally , but if confirmed , it would become , perhaps , more intriguing than all the preceeding cosmological puzzles .
we mean here , the phenomenon of the so called phantom dark energy , i.e. the matter with the relation between the pressure and dark energy @xmath1 less than @xmath2 @xcite .
some observations indicate that the present day value of the parameter @xmath3 provides the best fit . according to some authors
, the analysis of observations , permits to specify the existence of the moment when the universe changes the value of the parameter @xmath4 from that the region @xmath5 to @xmath3 @xcite .
this transition is called `` the crossing of the phantom divide line '' .
other authors speak about double crossing of the phantom divide line ( @xcite ) . in any case
the existence of the phantom phase of cosmological evolution put forward some important theoretical problems .
for example , considering a perfect fluid with barotropic equation of state , where @xmath6 and @xmath3 one can easily see that a universe during its evolution after a finite amount of time encounters a special kind of cosmological singularity , characterized by an infinite value of the velocity of expansion , which has been dubbed `` big rip '' @xcite .
being a little bit unusual in comparison with well accepted big bang and big crunch singularities , the big rip singularity is quite similar to them from the formal ( geometrical ) point of view .
notice , that in the modern cosmological literature also other `` exotic '' types of singularities are under consideration @xcite .
another difficulty connected with the problem of phantom energy has a more fundamental character .
it is well - known that the models with minimally coupled scalar field are very efficient both for the description of the inflationary stage of the development of the early universe and for the explanation of the late - time cosmic acceleration phenomenon @xcite .
however , it is easy to see , that the standard minimally coupled scalar field can not give rise to the phantom dark energy , because in this model the absolute value of energy density is always greater than that of pressure , i.e. @xmath7 . a possible way out of this situation is the consideration of the scalar field models with the negative kinetic term .
again , being a little unusual from the point of view of common wisdom , these models have become quite popular novadays . perhaps , the most thrilling problem arising in connection with the phantom energy is the crossing of the phantom divide line .
the general belief is that this crossing is not admissible in simple minimally coupled models and explanation of this phenomenon requieres more complicated models such a multifield ones or models with non - minimal coupling between scalar field and gravity ( see e.g. @xcite ) . in the present paper
, we would like to explore the consequences of the possibility of existence of simple minimally coupled scalar field models allowing the crossing of the phantom divide line . as a matter of fact
, we would like to present some toy examples , suggesting that such a crossing could be unavoidable and dictated by the continuity of the solution of einstein equations . in the next section we discuss in some detail a simple toy model , giving an illustration of the change of sign of the kinetic term in the scalar field cosmology . in the third section we sketch some other models and in the last section we attempt to discuss the above consideration in a more general context .
let us consider a simple cosmological model , representing a flat friedmann universe with a metric @xmath8 filled with a barotropic fluid with an equation of state @xmath9 where @xmath10 and @xmath11 are energy density and pressure of the fluid respectively and @xmath12 .
choosing conveniently the normalisation of the constants in the theory one can write the friedmann equation in a simple form @xmath13 where the hubble variable is defined as @xmath14 .
the energy conservation law is @xmath15 which together with eq .
( [ barotropic ] ) gives immediately @xmath16 from eqs .
( [ energy1 ] ) and ( [ friedmann1 ] ) one gets @xmath17 or , in other terms , @xmath18 another useful equation obtained by differentiation of the eq . ( [ friedmann1 ] ) and substitution into it eq .
( [ energy ] ) reads : @xmath19 the pressure can be written down as @xmath20 it is well known that for a given cosmological evolution @xmath21 satisfying some simple conditions one can find a minimally coupled scalar field cosmological model with lagrangian @xmath22 which contains this evolution as a particular solution , provided suitable initial conditions are chosen ( see , e.g. @xcite and references therein ) .
the energy density and pressure of the scalar field ( [ lagrange ] ) are @xmath23 @xmath24 from eqs .
( [ energy - scal ] ) , ( [ pressure - scal ] ) , ( [ friedmann1 ] ) and ( [ pressure ] )
one has @xmath25 @xmath26 equation ( [ scal1 ] ) gives the potential @xmath27 as a function of @xmath28 .
finding @xmath29 by integrating eq .
( [ scal ] ) , inverting this function and substituting a function @xmath30 into eq .
( [ scal1 ] ) , one finds the potential @xmath31 as a function of the scalar field @xmath32 .
sometimes this can be done explicitly .
for example , the evolution ( [ hubble ] ) could be reproduced in the extensively studied @xcite cosmological model with an exponential potential @xmath33 apparently , the super - accelerated evolution ( [ hubble ] ) with @xmath3 can not be reproduced by means of the minimally coupled scalar field model ( [ lagrange ] ) , but can be easily obtained in the framework of the model with phantom scalar field @xmath34 our starting point is the remark made in @xcite , attracting the attention to some interesting features of the potential ( [ scal1 ] ) represented as a function of time @xmath28 .
the point is that the volume function @xmath35 satisfies a simple second - order differential equation @xmath36 which can be easily obtained from eq .
( [ scal1 ] ) .
as has been already noticed above , the potential @xmath27 is chosen in such a way to provide a given cosmological evolution .
for example , for the evolution ( [ hubble ] ) the form of the potential is @xmath37 for simple forms of the potential one can find the general solution of eq .
( [ equation ] ) , which contains together with the solution used for the construction of this potential also another independent solution .
for the potential ( [ pot - time ] ) the general solution looks like @xmath38 where @xmath39 and @xmath40 are nonnegative constants .
( in papers @xcite the solution ( [ solution ] ) was written down for the case of dust @xmath41 . ) now , knowing @xmath42 one can find @xmath43 and @xmath44 . substituting the obtained @xmath45 into eq .
( [ scal1 ] ) one can try to find the dependence @xmath29 .
inversion of this dependence @xmath30 and its substitution into the expression for the potential as a function of time ( [ pot - time ] ) would have given the potential @xmath46 , whose form is different from the exponential one ( [ exponent ] ) when @xmath47 .
one can derive the equation for the functions @xmath30 compatible with the potential @xmath27 from eq .
( [ exponent ] ) .
first of all , notice that the field @xmath32 should satisfy the klein - gordon equation @xmath48 dividing eq .
( [ kg ] ) by @xmath49 one has @xmath50 it is convenient to rewrite the second time derivative of the scalar field as @xmath51 where we have used the relation @xmath52 with the `` prime '' denoting the differentiation with respect to the scalar field @xmath32 .
now , we would like to take the time derivative of eq .
( [ kg1 ] ) .
the first term gives @xmath53 then , using the relations ( [ scal1 ] ) and ( [ prime ] ) one gets @xmath54 then we make the following transformation : @xmath55 the time derivative of the expression in the left hand side of eq .
( [ thirdterm ] ) is @xmath56 combining expressions ( [ firstterm]),([secondterm ] ) and ( [ thirdterm1 ] ) , using the explicit form of the potential ( [ pot - time ] ) and multiplying the resulting equation by @xmath57 one arrives to the following equation : @xmath58 particular solutions of this equation being substituted into eq .
( [ pot - time ] ) generate different potentials @xmath46 corresponding to different cosmological evolutions ( [ solution ] ) .
it is easy to check that the solution @xmath59 corresponding to the potential ( [ exponent ] ) and to the evolution with @xmath60 , satisfies eq .
( [ nonlinear ] ) . instead of looking for other exact solutions ( which is not an easy task ) we concentrate now on the qualitative study of eq .
( [ nonlinear ] ) or its equivalents .
first of all , let us notice that the solution ( [ solution ] ) tacitly assumes that the time parameter runs from @xmath61 to @xmath62 .
when @xmath63 one can neglect the influence of the second term in the solution ( [ solution ] ) .
thus , the potential @xmath46 in this limit has the asymptotic form ( [ exponent ] ) .
it is possible to calculate also the subleading term .
the form of the hubble variable corresponding to the evolution ( [ solution ] ) is @xmath64 while its time derivative is @xmath65 at large values of @xmath66 written down up to the first non - leading term reads : @xmath67 substituting the expression ( [ hubble4 ] ) into eq .
( [ scal1 ] ) one finds the subleading correction to the scalar field @xmath32 as a function of @xmath28 . inverting this relation and inserting the result into eq .
( [ pot - time ] ) we obtain the potential @xmath46 including the first nonleading term : @xmath68 the above formula can be elucidated as follows : if one consider the cosmological evolution described by eq .
( [ solution ] ) with non - zero value of the parameter @xmath40 , one can state that there exists a potential describing this evolution . in spite of the absence of an explicit expression for this potential
we know that its asymptotic behaviour is described by the formula ( [ subleading ] ) .
now , let us consider the evolution of a cosmological model , which is characterized by eq .
( [ hubble1 ] ) and the potential whose asymptotic form is given by eq .
( [ subleading ] ) .
it is easy to show that at some moment @xmath69 , such as @xmath70 , the time derivative of the hubble variable vanished .
indeed , a simple analysis of the formula ( [ hubble3 ] ) gives this value @xmath71 obviously , @xmath69 exists for any value of @xmath47 .
the evolution of the model given by eq .
( [ hubble1 ] ) is consistently defined at @xmath72 in the standard scalar model ( [ lagrange ] ) with a potential whose asymptotic form at large values of @xmath28 was presented above ( [ subleading ] ) .
( the consistency is based on the fact that at @xmath72 the time derivative of the hubble constant is always negative ) .
it is possible also to find the approximate expression for the potential @xmath46 for @xmath73 .
it is well known that the klein - gordon and friedmann equations allow a shift of the scalar field by some constant .
it is convenient to fix the scalar field as @xmath74 when @xmath73 .
the time derivative of the hubble variable at @xmath73 behaves as @xmath75 where @xmath76 substituting the expression ( [ hubble5 ] ) into eq .
( [ scal1 ] ) one can integrate the latter , getting @xmath77 whose inversion gives @xmath78 thus , the potential results @xmath79 it is rather straightforward to verify that the expressions for @xmath80 and the potential @xmath46 are regular when @xmath73 while the derivative @xmath81 and @xmath82 are singular . now , before discussing the subtle question of the behavior of the cosmological model under consideration at @xmath83 and of the possibility of crossing this point , we shall study briefly another branch of the evolution ( [ hubble1 ] ) : namely , that where @xmath84 . for small values of @xmath28 to reproduce the evolution ( [ solution ] ) one should use the phantom lagrangian ( [ lagrange1 ] ) .
proceeding in the similar way one can find the corresponding potential of the phantom field in the subleading approximation : @xmath85 one can easily describe what is going on in the model characterized by a negative kinetic term and the potential whose asymptotic form is given by ( [ pot - zero1 ] ) in the vicinity of the point @xmath86 .
now , we are in a position to scrutinize the possibility of matching these two branches of the evolution ( [ solution ] ) at @xmath84 and @xmath72 .
are they really incompatible ?
let us consider a scalar field model with a negative kinetic term and a potential whose asymptotic form is that of eq .
( [ pot - zero1 ] ) .
further , let us suppose that at some moment @xmath84 one has initial conditions on the values of @xmath87 and @xmath49 which provide the evolution ( [ solution ] ) where the values of the parameters are consistent with those of the potential @xmath46 .
then approaching the time moment @xmath86 one arrives to the regime when @xmath88 and @xmath49 tend to vanish .
nevertheless , all the geometric characteristics of the spacetime remain well defined ( due to homogeneity and isotropy of the friedmann cosmology all the curvature invariants are expressible through the cosmological factor @xmath89 and its time derivatives , which are obviously finite ) . in contradistinction ,
the second time derivative of the scalar field at @xmath83 and @xmath81 diverge , but this divergence is an integrable one .
this offers us an opportunity ( and , perhaps , necessity ) of a continuation of the spacetime geometry and field configurations beyound this `` divide line '' .
clearly , such a smooth dynamical continuation which respects einstein equations , entails the change of the sign of the kinetic term and the transition to the regime for @xmath72 described above .
the cosmological evolution presented in the preceding section describes the following scenario : the universe begins its evolution from the cosmological singularity of the `` anti - big rip '' type and its squeezing is driven by a scalar field with a negative kinetic term .
then at the moment ( easily calculated from eq .
( [ hubble1 ] ) ) @xmath90 the contraction of the universe is replaced by an expansion . at the moment @xmath91
( [ time - phantom ] ) the kinetic term of the scalar field changes sign .
then , with the time growing the universe undergoes an infinite power - law expansion .
the graphic of the time dependence of @xmath21 is presented in fig . 1 . changing the sign of time parameter in all the equations the range @xmath92 one can consider the cosmological evolution running from @xmath93 to @xmath94 .
it begins from the non - singular contraction and ends in a `` standard '' big rip singularity . in this case at the moment @xmath95 the scalar field undergoes the `` phantomization '' , while the transition at the moment @xmath83 , considered in the preceeding section can be called `` dephantomization '' .
the toy model discussed above prrovides an illustration of these phenomena of phantomization and dephantomization , but from observational point of view , it would be more interesting to get an evolution beginning from the big bang and ending in the big rip singularity , after undergoing a phantomization transition . instead of trying to construct some potential and cosmological evolution describing such a process we shall limit ourselves to giving a graphical presentation of the @xmath21 -dependence which could be responsible for such a scenario ( see fig .
2 ) . this picture represents the function @xmath96 . here
the moment @xmath97 is the moment of big rip , while the the moment of phantomization is @xmath98 . in principle
, the function @xmath21 determines the model completely , including the form of the potential , even if when it is not written explicitly .
as has been already mentioned in introduction , some observations favor double crossing of the phantom divide line @xcite .
the corresponding graphic @xmath21 is presented in fig .
3 . also to this time dependence of @xmath21 one can associate some potential and the evolution , in course of which the scalar field undergoes two smooth transitions : phantomization at the point of mimimum of the curve @xmath21 and the subsequent dephantomization at the point of its maximum .
it is suggestive to remark that the diagram fig.3 reminds topologically the well - known van der waals isoterm curve .
the part of the van der waals curve situated between the maximum and minimum , describing a metastable state ( of supercool vapor or superheated liquid ) , is analogous to the phantom phase in our fig .
models with double crossing of the phantom divide line were considered also in @xcite .
the idea in @xcite consisted in cutting off the phantom piece of the evolution with the subsequent sewing of remaining branches of the trajectory removes the problems connected with the crossing of the phantom divide line .
in other terms , the trajectories , considered in @xcite correspond graphically to @xmath21 which instead of one maximum and one minimum ( see fig .
3 ) have one inflection point . continuing the analogy with the van der waals isoterms
, one sees that this curves corresponds to the critical van der waals curve .
surely , such models can be studied , but their existence does not exclude the existence of models described by fig . 3 and in a frame of a concrete model with fixed lagrangian and initial conditions these two types of trajectories can not be transformed one into other .
above we have discussed the properties of some simple cosmological models based on minimally coupled scalar fields , which could , in our opinion , describe the crossing of the phantom divide line , changing the sign of the kinetic term in the corresponding lagrangian . as a starting point of our consideration
we have used the observation @xcite that having a simple form of the scalar field potential , written as a function of time @xmath27 , one can find the general solution of the einstein ( friedmann ) equations for the hubble variable @xmath21 ( see eq .
( [ solution ] ) .
different particular solutions describing the evolution of the hubble variable correspond to different potentials as functions of the scalar field @xmath46 .
all these solutions ( excluding the obvious , when @xmath99 ) contain the time moment when the time derivative of the hubble variable vanishes ( see eq .
( [ time - phantom ] ) ) and the only consistent way of passing of this point respecting the continuity of the einstein equations is the change of the sign of the kinetic term for the scalar field .
this change can be called ( de)-phantomization of the field .
all above are of technical nature and are confirmed by a direct analysis of the corresponding differential equations .
as far as physical interpretation is concerned one has two alternatives .
one can say that the sign of the kinetic term should be fixed a priori ( see , e.g. @xcite ) ) and , hence the models , which imply the change of this sign should be discarded as non - physical ones . here , we attempted to treat another alternative : i.e. to take this theory seriously because from mathematical point of view it looks consistent . in choosing this alternative
we were guided by a belief that einstein equations are more fundamental then the concrete form of the action for other fields .
the idea about the dominant role of einstein equations goes back to the classical works by einstein , infeld and hoffmann @xcite , where it was shown that the motions of mass points ( geodesics law ) are determined by the einstein equations for the gravitational field .
later this approach was confirmed in works by lanczos @xcite , fock @xcite and others . in this respect
the general relativity is quite different from electrodynamics , where the lorentz s force law is quite independent of the maxwell field equations ( for a discussion see e.g. @xcite ) .
the derivability of the equation of motion for particles is based on the fact that the einstein equations are non - linear and also they are subject to additional identities , namely the bianchi identities which reduce the number of independent equations .
these bianchi identities imply conservation laws for matter , present in the model under consideration .
in fact , the argumentation , based on the bianchi identities could be used also for getting information about the possible field configurations for non - gravitational fields .
indeed , the einstein equations for fields , minimally coupled to gravity , have the form @xmath100 the bianchi identities @xmath101 imply some kind of the energy - momentum conservation law : @xmath102 for the case of the minimally coupled spatially homogeneous time - dependent scalar field with the standard sign of the kinetic term eq .
( [ conserv ] ) is reduced to @xmath103 which is equivalent to the klein - gordon equation when @xmath104 . for the phantom scalar field one
has similarly @xmath105 the comparison between eqs .
( [ conserv1 ] ) and ( [ conserv2 ] ) points to the opportunity of the change of type of the klein - gordon equation at the moment when @xmath106 . in other words , while the einstein equations require the change of the type of the scalar field lagrangian provided some form of the scalar field potential and the cosmological evolution are chosen , the bianchi identities show why this transformation is possible . before concluding , let us notice that we have shown that simple scalar field models driving the universe through the phantom divide line do exist .
however , the natural question arises : given the potential as a function of the scalar field ( not of the time ) how general are the initial conditions providing the reaching of the point @xmath106 .
in other words , do we need the fine tuning ( cf .
@xcite ) ? .
the answer to this question is not simple technically and , perhaps , is worth further investigations .
another interesting question is concerned with an opportunity of using some kind of modified local lagrangian formalism for the description of smooth dynamical transition from one form kinetic term to another one .
the authors are grateful to a.a .
starobinsky for a useful discussion .
was partially supported by rfbr , grant no .
05 - 02 - 17477 and by the programme
ur , grant no . 02.01.299 .
was partially supported by rfbr , grant no .
05 - 02 - 17450and by the research programme `` astronomy '' of the ras .
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simple scalar field cosmological models are considered describing gravity assisted crossing of the phantom divide line .
this crossing or ( de)-phantomization characterized by the change of the sign of the kinetic term of the scalar field is smooth and driven dynamically by the einstein equations .
different cosmological scenarios , including the phantom phase of matter are sketched .
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This combination of images made on Tuesday, Sept. 26, 2017, from propaganda video released by North Korea state-run media shows a simulation of a B-1B bomber being hit by a missile. Military analysts... (Associated Press)
SEOUL, South Korea (AP) — Military analysts say North Korea doesn't have either the capability or the intent to attack U.S. bombers and fighter jets, despite the country's top diplomat saying it has every right do so.
They view the remark by North Korean Foreign Minister Ri Yong Ho and a recent propaganda video simulating such an attack as tit-for-tat responses to fiery rhetoric by U.S. President Donald Trump and his hardening stance against the North's nuclear weapons program.
By highlighting the possibility of a potential military clash on the Korean Peninsula, North Korea may be trying to create a distraction as it works behind the scenes to advance its nuclear weapons development, said Du Hyeogn Cha, a visiting scholar at Seoul's Asan Institute for Policy Studies. Another possibility is that North Korea is trying to win space to save face as it contemplates whether to de-escalate its standoff with Washington, he said Tuesday.
Speaking to reporters before leaving a U.N. meeting in New York, Ri said Trump had "declared war" on his country by tweeting that North Korean leader Kim Jong Un "won't be around much longer." Ri said North Korea has "every right" to take countermeasures, including shooting down U.S. strategic bombers, even when they're not in North Korean airspace.
The U.S. frequently sends advanced warplanes to the Korean Peninsula for patrols or drills during times of animosity. Last weekend, U.S. bombers and fighter escorts flew in international airspace east of North Korea to the farthest point north of the border between North and South Korea that they have in this century, according to the Pentagon.
Hours after the flights Sunday, a North Korean government propaganda website posted a video portraying U.S. warplanes and an aircraft carrier being destroyed by attacks. The video on DPRK Today, which was patched together from photos and crude computer-generated animation, also included footage of North Korean solid-fuel missiles being fired from land mobile launchers and a submarine. The North was clearly trying to claim it has the ability to conduct retaliatory strikes against U.S. attacks, said Hong Min, an analyst at Seoul's Korea Institute for National Unification.
Moon Seong Mook, a former South Korean military official and current senior analyst for the Seoul-based Korea Research Institute for National Strategy, said it's highly unlikely North Korea has the real-world capability to match Ri's words. North Korea's aging MiG fighters won't stance a chance against much more powerful U.S. fighters escorting long-range bombers. And while North Korea touted in May that it's ready to deploy new surface-to-air missiles that analysts say could potentially hit targets as far as 150 kilometers (93 miles) away, it's questionable how much of a threat the unproven system could pose to U.S. aircraft operating far off the country's coast, Moon said.
It's also unclear whether North Korea would be able to even see the advanced U.S. warplanes when they come. South Korea's National Intelligence Service told lawmakers in a closed-door briefing on Tuesday that the North's inadequate radar systems failed to detect the B-1B bombers as they flew east of North Korea.
The last time North Korea fired on a U.S. aircraft was in 1994 when it shot down a U.S. Army helicopter around the heavily armed inter-Korean border, killing one of the pilots and capturing the other. The surviving pilot said after his release he was pressured by North Korean officials to confess that the helicopter had crossed into North Korea. In 1969, a North Korean fighter jet shot down an unarmed U.S. reconnaissance plane and killed all 31 crewmembers on board.
It's highly unlikely North Korea would attempt a similar attack now, experts say. Amid tension created by the North's nuclear weapons tests and threat to detonate a thermonuclear missile over the Pacific Ocean, such an attack would pretty much guarantee retaliation from the United States that could lead to war, Cha said.
"The most obvious reason Ri made those comments was because North Korea simply can't tolerate such high-profile insults to its supreme leadership," Cha said. It's also possible that the North is trying to fan concerns about a potential military clash in the region now so that it can win room to save face later when it tries to de-escalate, he said.
"If Kim Jong Un ever offers a moratorium on his missile tests or makes whatever other compromise, he could say made a big-picture decision to reduce military tension in the Korean Peninsula," Cha said. He said Ri's comments also allow China and Russian to restate their calls for a "dual suspension" of North Korean weapons tests and displays of military capability by the U.S. and South Korea.
The Trump administration's stance on North Korea has been hardening in recent months as the North has been stepping up the aggressiveness of its nuclear and missile tests. It conducted its sixth and most powerful nuclear test on Sept. 3, which it said was a thermonuclear weapon built for intercontinental ballistic missiles. It tested two ICBMs in July, displaying their potential ability to reach deep into the continental United States. North Korea has also fired two powerful midrange missiles over Japan in recent weeks.
Trump in a speech at the United Nations General Assembly last week said the United States would "totally destroy" North Korea if provoked, which prompted Kim to pledge to take the "highest-level" action against the United States. Ri then said North Korea might conduct the "most powerful" atmospheric hydrogen bomb test in the Pacific Ocean, but added that no one knew what Kim would decide. ||||| WASHINGTON (Reuters) - President Donald Trump warned North Korea on Tuesday that any U.S. military option would be “devastating” for Pyongyang, but said the use of force was not Washington’s first option to deal with the country’s ballistic and nuclear weapons program.
“We are totally prepared for the second option, not a preferred option,” Trump said at a White House news conference, referring to military force. “But if we take that option, it will be devastating, I can tell you that, devastating for North Korea. That’s called the military option. If we have to take it, we will.”
Bellicose statements by Trump and North Korean leader Kim Jong Un in recent weeks have created fears that a miscalculation could lead to action with untold ramifications, particularly since Pyongyang conducted its sixth and most powerful nuclear test on Sept. 3.
Despite the increased tension, the United States has not detected any change in North Korea’s military posture reflecting an increased threat, the top U.S. military officer said on Tuesday.
The assessment by Marine Corps General Joseph Dunford, chairman of the U.S. Joint Chiefs of Staff, about Pyongyang’s military stance was in contrast to a South Korean lawmaker who said Pyongyang had boosted defenses on its east coast.
“While the political space is clearly very charged right now, we haven’t seen a change in the posture of North Korean forces, and we watch that very closely,” Dunford told a Senate Armed Services Committee hearing on his reappointment to his post.
In terms of a sense of urgency, “North Korea certainly poses the greatest threat today,” Dunford testified.
A U.S. official speaking on the condition of anonymity said satellite imagery had detected a small number of North Korean military aircraft moving to the North’s east coast. However the official said the activity did not change their assessment of Pyongyang’s military posture.
North Korean Foreign Minister Ri Yong Ho on Monday accused Trump of declaring war on the North and threatened that Pyongyang would shoot down U.S. warplanes flying near the Korean Peninsula after American bombers flew close to it last Saturday. Ri was reacting to Trump’s Twitter comments that Kim and Ri “won’t be around much longer” if they acted on their threats toward the United States.
North Korea has been working to develop nuclear-tipped missiles capable of hitting the U.S. mainland, which Trump has said he will never allow. Dunford said Pyongyang will have a nuclear-capable intercontinental ballistic missile “soon,” and it was only a matter of a “very short time”.
“We clearly have postured our forces to respond in the event of a provocation or a conflict,” the general said, adding that the United States has taken “all proper measures to protect our allies” including South Korean and Japan.
“It would be an incredibly provocative thing for them to conduct a nuclear test in the Pacific as they have suggested, and I think the North Korean people would have to realize how serious that would be, not only for the United States but for the international community,” Dunford said.
South Korean lawmaker Lee Cheol-uoo, briefed by the country’s spy agency, said North Korea was bolstering its defenses by moving aircraft to its east coast and taking other measures after the flight by U.S. bombers. Lee said the United States appeared to have disclosed the flight route intentionally because North Korea seemed to be unaware.
U.S. Air Force B-1B Lancer bombers, escorted by fighter jets, flew east of North Korea in a show of force after the heated exchange of rhetoric between Trump and Kim.
The United States has imposed sanctions on 26 people as part of its non-proliferation designations for North Korea and nine banks, including some with ties to China, the U.S. Treasury Department’s Office Of Foreign Assets Control Sanctions said on Tuesday.
The U.S. sanctions target people in North Korea and some North Korean nationals in China, Russia, Libya and Dubai, according to a list posted on the agency’s website.
U.S. President Donald Trump speaks during a news conference with Spanish Prime Minister Mariano Rajoy in the Rose Garden at the White House in Washington, U.S., September 26, 2017. REUTERS/Joshua Roberts
‘CAPABILITY TO DETER’
U.S. Secretary of State Rex Tillerson will visit China from Thursday to Saturday for talks with senior officials that will include the crisis over North Korea and trade, the State Department said on Tuesday.
Evans Revere, a former senior diplomat who met with a North Korean delegation in Switzerland this month, said that Pyongyang had been reaching out to “organizations and individuals” to encourage talks with former U.S. officials to get a sense of the Trump administration’s thinking.
“They’ve also been accepting invitations to attend dialogues hosted by others, including the Swiss and the Russians,” he said.
Revere said his best guess for why the North Koreans were doing this was because they were “puzzled by the unconventional way that President Trump has been handling the North Korea issue” and were eager to use “informal and unofficial meetings to gain a better understanding of what is motivating Trump and his administration”.
During a visit to India, U.S. Defense Secretary Jim Mattis said diplomatic efforts continued.
Speaking in Beijing, Chinese Foreign Ministry spokesman Lu Kang said war on the Korean Peninsula would have no winner.
“We hope the U.S. and North Korean politicians have sufficient political judgment to realize that resorting to military force will never be a viable way to resolve the peninsula issue and their own concerns,” Lu said.
South Korean President Moon Jae-in urged Kim Jong Un to resume military talks and reunions of families split by the 1950-53 Korean War to ease tension.
Slideshow (8 Images)
“Like I’ve said multiple times before, if North Korea stops its reckless choices, the table for talks and negotiations always remains open,” Moon said.
In Moscow, Russia’s Foreign Ministry said it was working behind the scenes to find a political solution and that it plans to hold talks with a representative of North Korea’s foreign ministry who is due to arrive in Moscow on Tuesday, the RIA news agency cited the North’s embassy to Russia as saying.
The United States and South Korea are technically still at war with North Korea after the 1950-53 conflict ended in a truce and not a peace treaty.
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– The promised countermeasures to President Trump's supposed "declaration of war" on North Korea may already be in the works. A South Korean lawmaker briefed by the country's spy agency says North Korea is moving aircraft to its east coast in an effort to bolster its defenses, per Reuters. The revelation comes days after US bombers flew in international airspace east of North Korea, prompting Foreign Minister Ri Yong Ho to warn the North would shoot down US planes "even when they are not inside the airspace border of our country." Adding to the tension: a recent propaganda video released by the North Korean regime—using photos and simple animation—shows US warplanes and an aircraft carrier under attack, reports the AP. Despite that, military analysts don't believe there's any real risk to US planes. For one thing, South Korean intelligence suggests North Korean radar missed Sunday's flights by US planes. For another, it isn't clear if North Korea has the technological capabilities to bring down planes outside its airspace. According to some analysts, North Korea might simply be blowing smoke in an effort to divert attention away from its nuclear weapons program. The country might also be trying to save face. "The most obvious reason Ri made those comments was because North Korea simply can't tolerate such high-profile insults to its supreme leadership," Du Hyeogn Cha of Seoul's Asan Institute for Policy Studies tells the AP.
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the apparent existence of metal - insulator transitions in two - dimensions @xcite has generated a lot of interest recently on the problem of interplay between interaction and disorder . however , the consequences of a highly non - trivial , non - gaussian distribution of conductances @xmath0 for even non - interacting electrons at arbitrary disorder at zero temperature in two or three dimensions remains poorly understood .
in particular , several novel features in @xmath0 have recently been discovered @xcite , including a non - analyticity in @xmath0 near @xmath1 in the insulating regime @xcite , a ` one - sided ' log - normal distribution @xcite near the metal - insulator crossover regime in quasi one dimension ( q1d ) as well as strong deviations from the expected log - normal distribution for an anderson insulator @xcite in three dimensions ( 3d ) .
they raise serious questions about the effect of such broad asymmetric distributions on e.g. the anderson metal - insulator transition in particular and on quantum phase transitions @xcite in general .
although there is a significant body of numerical work available @xcite , analytic study of the full distribution @xmath0 in 3d at arbitrary disorder is beyond the scope of the conventional field theory framework altshuler , shapiro .
the novel features in @xmath0 mentioned above were obtained directly from the joint probability distribution @xmath2 of the @xmath3 transmission eigenvalues @xmath4 , @xmath5 , for an @xmath3-channel disordered conductor , via the landauer formula@xcite [ landauer ] p(g)_a^n dx_a p(*x * ) ( g-_i sech^2x_i ) .
[ pofg - def ] the n - dimensional integral was evaluated using a saddle point method @xcite , while the distribution @xmath2 was obtained from the q1d dmpk equation @xcite and its 3d generalization obtained recently @xcite . for a conductor of fixed cross section @xmath6
, it describes the evolution with length @xmath7 of the joint probability distribution @xmath8 based on a ` local ' maximum entropy ansatz @xcite .
the generalized dmpk ( gdmpk ) equation reads @xcite @xmath9p(\textbf{x},t ) \end{aligned}\ ] ] where & -&_i < j _
ij |^2 x_j-^2 x_i| & -&_i |2x_i | . in the above , @xmath10 where
@xmath11 is the mean free path , @xmath12 where @xmath13 is a phenomenological matrix @xcite defined in terms of certain eigenvector correlations that can be explicitly evaluated numerically and contains information about dimensionality .
the q1d dmpk equation is recovered when @xmath14 ( we only consider orthogonal symmetry ) .
recently a direct numerical solution of eq .
( [ gdmpk ] ) has been obtained @xcite by mapping it onto a langevin equation .
the numerical results confirm that the gdmpk equation indeed distinguishes between two and three dimensional models with the same number of transmission channels . with detailed comparisons
, the study confirms that : ( i ) eq . ( [ gdmpk ] ) correctly describes the full @xmath0 not only in the strongly localized regime but also near the critical regime in 3d , and ( ii ) two parameters , @xmath15 and @xmath16 , are enough to model the entire matrix @xmath17 at least in these regimes . in ref .
[ ] it was shown that at least two parameters are needed in order to guarantee the conservation of probability , so this can be considered as a minimalistic model . within this approximation ,
disorder is characterized by @xmath18 . in the insulating regime
one can interpret @xmath19 as the localization length , giving @xmath20 .
the other independent parameter @xmath21 , so that @xmath22 depends only on the geometry of the system .
therefore for a cubic system , within this approximation , the entire distribution is characterized by a single disorder parameter @xmath23 . as shown in refs .
[ ] the parameter @xmath24 , where @xmath25 is the cross - sectional dimension , contains information about the dimensionality of the system via the dimension - dependent eigenvector correlations that define the matrix @xmath26 . in particular in 3d , k_11 & & 1/l^0 , insulating regime , & & 1/l^1 , at critical point , & & 1/l^2 , metallic regime , such that the quantity @xmath27 is zero in the metallic regime as well as at the critical point , but it is finite for insulators . clearly
the parameter @xmath28 can be considered as an order parameter for the anderson transition .
we can therefore expect that eq .
( [ gdmpk ] ) can be used as the starting point for studying the anderson transition in terms of the full distribution of conductances , starting from the insulating limit . however , unlike the q1d dmpk equation , a general analytic solution of the gdmpk equation for arbitrary disorder is not yet available . in this paper
we will obtain an analytic perturbative solution of the gdmpk equation for @xmath3 transmission channels valid in the strongly disordered regime @xmath29 .
the solution is based on a mapping of the equation on to an imaginary time schrdinger equation @xcite , describing @xmath3 interacting bosons in one dimension evolving from a delta function initial condition and satisfying some singular boundary conditions . in ref .
[ ] , the full @xmath0 in 3d was evaluated based on a solution of the gdmpk equation in the limit where the interaction between the eigenvalues was totally neglected . in this work ,
we include the interaction and show that it changes the qualitative features of the distribution .
we begin by developing a systematic perturbation theory method to obtain the @xmath3-particle greens function . as a first check ,
we show that our solutions agree where exact solutions are available , namely for the special cases of @xmath30 @xcite .
we then use the @xmath3-particle greens function to obtain the joint probability distribution of the eigenvalues @xmath31 , @xmath32 , analytically .
we show that in particular , the density of the eigenvalues remains uniform , independent of disorder , with an exponential gap at the origin that increases with increasing disorder .
indeed , it is this feature which is at the heart of many novel properties in the distribution of conductances in 3d .
it suggests that the anderson metal to insulator transition can be viewed as the opening of a finite gap in the density of the eigenvalues at the origin .
finally , we do the @xmath3-dimensional integral of eq .
( [ pofg - def ] ) approximately to show that the distribution of conductance agrees with the numerical results , improving on the approximate solution obtained in ref . [ ] where the distribution was found to be much broader . in particular , we obtain the variance @xmath33 as well as the skewness @xmath34 .
we find that asymptotically the variance is not a simple power law although numerical data can be fitted with a power law in limited regimes .
we also find that asymptotically the skewness goes as a positive constant .
further , the skewness changes sign from positive to negative well before the metal - insulator transition point .
a short version containing some of the above results was published in ref .
here we provide details of the calculation and also these new results .
the paper is organized as follows . after a brief introduction in section i
, we discuss the mapping of the gdmpk equation on to a schrdinger equation in section ii . in section iii
we show how a systematic perturbation theory can be developed and point out how a resummation of the perturbative expansion is essential in order to satisfy certain boundary conditions .
we will use the results obtained in section iii to obtain the joint probability distribution of transmission eigenvalues in section iv and then the full distribution of conductances in section v. section vi contains summary and conclusions . in appendix
a we discuss how to include systematic corrections to the leading order results of section iii .
within the approximation that only two independent matrix elements @xmath35 and @xmath16 can describe the entire @xmath26-matrix , eq .
( [ gdmpk ] ) can be written in the form = _
i=1^n p(*x*,t ) & - & _ i < j | ^2 x_j-^2 x_i | & - & _ i |2x_i | . where @xmath36 , and @xmath37 .
the initial condition is given by : p(*x*,t=0)=(*x * ) and the boundary conditions are _
x_i0 p = 0 ; _ x_ip=0 .
following ref .
[ ] we map the equation for @xmath38 on to an imaginary time schrdinger equation .
first we use a factorization [ pofxyt ] p(*x*,t|*y*)=(*x*)g_n(*x*;t|*y*)^-1(*y * ) ; e^-/2 . the @xmath3-particle greens function @xmath39 then satisfies the imaginary time schrdinger equation in the variables @xmath40 , given by -g_n / t = hg_n [ eqofgn ] where @xmath41+\sum_{i < j}v(x_i , x_j ) .
\ee and the single particle potential and the interaction terms are given by \begin{eqnarray } \label{potentials } u(x_i ) & \equiv & \frac{\lambda_u}{\sinh^2 2x_i}\cr v(x_i , x_j ) & \equiv & \lambda_v [ \frac{1}{% \sinh^2(x_i - x_j)}\cr & + & \frac{1}{\sinh^2(x_i+x_j ) } ] .
\end{eqnarray } here \bea
\lambda_u & \equiv & -k/2 \cr \lambda_v & \equiv & k\gamma(\gamma-2)/8 \eea the greens function $ g_n(\textbf{x};t|\textbf{y})$ will then have the initial condition \be g_n(\textbf{x } ; t=0|\textbf{y } ) = \frac{1}{n!}\sum_{\pi(y)}\epsilon_{s , as}(\textbf{y } ) \prod_{i=1}^n \delta(x_i - y_i ) \ee where the subscripts $ s$ and $ as$ refer to the symmetric and antisymmetric initial conditions , respectively , depending on whether $ \omega$ is symmetric or antisymmetric in its variables and $ \pi$ stands for permutations . in the small $ y$ limit
, this recovers the proper initial conditions on $ p$. the boundary conditions become \be \lim_{x_i\rightarrow 0}\left[\frac{\partial g_n}{\partial x_i}-\frac{g_n}{\sinh 2x_i}\right ] = 0 .
\ee note that the factorization requires defining a new set of variables $ y_i$ , but in the end we will be interested in the $ y\to 0 $ limit \be p(\textbf{x},t)=p(\textbf{x},t|\textbf{y}=0 ) .
\ee therefore , we will be interested in the $ y\to 0 $ limit of the $ n$-particle greens function $ g_n(\textbf{x};t|\textbf{y})$ as well . according to the construction of eq.~(\ref{pofxyt } ) , $ p(\textbf{x},t|\textbf{y})$ looks highly singular in the limit $ y\to 0 $ , given by \begin{eqnarray}\label{singular } p(\textbf{x},t|\textbf{y } ) & = & \frac{\prod_{i < j}|\sinh^2x_j-\sinh^2x_i|^{\frac{\gamma}{2 } } \prod_i|\sinh 2x_i|^{\frac{1}{2 } } } { \prod_{i < j}|\sinh^2y_j-\sinh^2y_i|^{\frac{\gamma}{2 } } \prod_i|\sinh2y_i|^{\frac{1}{2}}}\cr & \times & g_n(\textbf{x},t|\textbf{y } ) .
\end{eqnarray } however , it turns out that the complete $ n$-particle greens function can be obtained exactly for the special values $ \gamma = 1 , 2 , 4$. in these special cases \cite{beenakker } the small $ y_m$ limit of $ g_n$ has the form \begin{eqnarray}\label{symmetry } g_n(\textbf{x},t|\textbf{y } ) & \propto & \prod_{i < j}|\sinh^2y_j-\sinh^2y_i|^{\frac{\gamma}{2}}\cr & \times & \prod_i|\sinh 2y_i|^{\frac{1}{2 } } ; \;\;\ ; y_m \ll 1 .
\end{eqnarray } thus the $ g_n$ for these $ \gamma$ cancel the singularity arising from $ \xi^{-1}(\textbf{y})$ exactly as $ y_m\rightarrow 0 $ and yields a finite result for $ p(\textbf{x},t)$. this is a highly non - trivial result , and typically an approximate evaluation of the $ n$-particle greens function will not have the same property , rendering the extraction of $ p(\textbf{x},t)$ impossible . in
what follows , we will organize the perturbative series for $ g_n$ in such a fashion as to conform to this symmetry . \section{the greens function } as given in eq.~(\ref{eqofgn } ) , the $ n$-particle greens function satisfies a differential equation which is different from the usual many - body greens function defined in terms of time - ordered annihilation and creation operators .
in fact it satisfies the differential equation obeyed by n - particle propagator . taking a cue from this
, one can straightforwardly verify that $ g_n$ can be written as : \begin{eqnarray } g_n(\textbf{x},t|\textbf{y } ) = \frac{1}{n!}\langle \textbf{0}|\prod_{m=1}^n\psi(x_m ) e^{-ht } \prod_{n=1}^n \psi^{\dagger}(y_n)|\textbf{0}\rangle \label{prop } \end{eqnarray } where $ |\textbf{0}\rangle$ is the $ n$-particle vacuum and \begin{eqnarray } h & = & \int_{-\infty}^{\infty}dx \psi^{\dagger}(x ) \left[-\frac{k}{4}\frac{\partial^2}{\partial x^2}+u(x)\right]\psi(x ) \cr & + & \frac{1}{2}\int_{-\infty}^{\infty}dx\int_{-\infty}^{\infty}dx ' \psi^{\dagger}(x ) \psi^{\dagger}(x')\cr & \times & v(x , x')\psi(x ' ) \psi(x ) .
\end{eqnarray } this marks a distinction between the $ g_n$ of eq.~(\ref{prop } ) and more typical many - body green 's functions in that the expectation in this case is against the vacuum , rather than the many - body ground state .
as we will see , this will have dramatic consequences for the diagrammatic expansion of $ g_n$. now as usual we would like to go to the interaction picture , and so we define the interaction picture imaginary time evolution operator : \begin{eqnarray } s(t_2 , t_1 ) = t\exp \left\ { { - \int\limits_{t_1 } ^{t_2 } { dt'\,h ' } ( t ' ) } \right\ } \end{eqnarray } where $ h'$ is the perturbation in the interaction picture . taking advantage of the fact that $ h'$ annihilates the vacuum , and that t is always greater than 0 , we can write eq.~(\ref{prop } ) as : \bea g_n ( { \bf{x}},t|{\bf{y } } ) & = & \frac{1}{{n!}}\left\langle { \bf{0 } } \right|ts(\infty , 0)\prod\limits_{m = 1}^n { \psi ( x_m , t ) } \cr & \times&\prod\limits_{n = 1}^n { \psi ^\dag ( y_n , 0 ) } \,\left| { \bf{0 } } \right\rangle \eea from the standard theory of non - equilibrium green 's functions , the diagrammatic expansion of $ g_n$ follows .
we would compute all diagrams with n external legs $ x_i$ , and n external legs $ y_i$ as illustrated in fig.~\ref{bubble}. \begin{figure } \includegraphics[angle=0,width=0.35\textwidth]{g_n - expansion.eps } \caption{diagrammatic expansion of $ g_n$ } \label{bubble } \end{figure } and we would connect them via the external potential and interaction vertices shown in fig.~\ref{vertices}. \begin{figure } \includegraphics[angle=0,width=0.45\textwidth]{vertices.eps } \caption{vertices appearing in diagrammatic expansion of $ g_n$ } \label{vertices } \end{figure } finally , the unperturbed green 's function would be given by : \begin{eqnarray } g_0 ( t_1 , t_2 ) = - \left\langle 0 \right|t\psi ( t_1 ) \psi ^\dag ( t_2 ) \left| 0 \right\rangle \end{eqnarray } % as illustrated in fig \ref{g_0}. % \begin{figure } % \includegraphics[angle=0,width=0.35\textwidth]{g_0.eps } % \caption{unperturbed green 's function $ g_0 $ } % \label{g_0 } % \end{figure } we would integrate these diagrams over all space and over time from 0 to $ \infty$. but we will observe that $ g_0 $ is zero for negative times $ t_1-t_2 $ , and so this will allow us to integrate over all time as well without error .
\subsection{simplification of the diagrammatic expansion } the fact that the expectation is taken against the vacuum has a few important consequences for the diagrammatic expansion .
first we will find that we have no self - energy corrections to $ g_0$. this is because the self - energy is due to the interaction of the particle with the background state .
but since there are no particles in our background state , the self - energy vanishes . also ,
because $ g_0 $ does not allow negative times , all diagrams must proceed forward in time .
this will rule out all crossed diagrams , vertex corrections , etc .
the vacuum expectation dramatically simplifies the diagrammatic expansion , and we can determine its general form from the following argument . taking $ n=3 $ for illustrative purposes (
the argument for general n is completely analogous ) , $ g_3 $ can be constructed via the expansion in fig .
\ref{dyson - expansion}. \begin{figure } \includegraphics[angle=0,width=0.47\textwidth]{dyson - expansion.eps } \caption{dyson expansion of $ g_3$. $ g_3 $ is represented by the bold lines . }
\label{dyson - expansion }
\end{figure } the proof is straightforward .
simply write out the expansion algebraically , and then act on both sides of the equation with the operator $ -\partial/\partial t - h_0 $ , where $ h_0 $ is the kinetic energy term
. the result will be the equation \begin{eqnarray } \left [ { - \frac{\partial } { { \partial t } } - h_0 - \sum\limits_{i = 1}^3 { u(x_i ) } - \sum\limits_{i < j}^3 { \upsilon ( x_i , x_j ) } } \right]g_3 = \cr \delta ( t)\delta ( x_1 , x_2 , x_3 |y_1 , y_2 , y_3 ) \label{dyson - expasion - eq } \end{eqnarray } which is indeed the desired differential equation for times greater than 0 .
\subsection{exponential expansion } we will find it most convenient to analyze the series expansion of the green 's function in terms of an exponential series ( defined below ) , rather than a taylor series .
one reason is that we will find the individual diagrams in the taylor expansion diverge logarithmically ( for our potentials ) for small y. yet when exponentiated , the diagrams will give logical , finite results . additionally , we will need to extract from the taylor expansion the non - perturbative symmetry required in eq.~(\ref{symmetry } ) , and this is perhaps most directly accomplished using the exponential series .
to that end it is useful to consider the following .
each diagram in the taylor expansion of $ g_n$ can be labelled according to the number of single particle potential lines on each particle , and the number of interaction lines between each pair of particles . for convenience
we will then label each diagram , $ w$ , in the taylor expansion according to the following notation : \ [ \\w^{\{u_i\}}_{\{v_j\}}. \ ] the superscripts , $ \{u_i\}$ , label the number of external potential lines on each particle , $ i = 1 ... n$.
the subscripts $ \{v_j\}$ label the number of interaction lines between each pair of particles $ j = 1 ... n(n-1)/2$. for instance , the diagram in fig.\ref{worder } \begin{figure } \includegraphics[angle=0,width=0.30\textwidth]{worder.eps } \caption{typical diagram , w , in taylor expansion of $ g_n$ } \label{worder } \end{figure } would be labelled $ w^{211}_{102}$ since it has two u 's on particle 1 , one u on particle 2 , and one u on particle 3 , as well as one v between the first particle pair ( 12 ) , 0 v 's between the second particle pair ( 13 ) , and two v 's between the third particle pair ( 23 ) .
other diagrams obtained by rearranging the potential lines on this diagram would be of the same order . using this notation ,
the taylor series expansion of the n - particle green 's function could be written as \begin{equation } g_n = g_n^{(0 ) } + \sum\limits_{\{u_i\ } = 0}^\infty \sum\limits_{\{v_j\ } = 0}^\infty { w_{\{v_j\ } } ^{\{u_i\ } } } \label{tay - expansion}\ ] ] where @xmath42 is the unperturbed n - particle green s function . in preparation for the next step
, we ll divide through by @xmath42 to get @xmath43 where we define the dimensionless diagram @xmath44 .
now we d like to re - express this taylor series as an exponential series .
so we write , @xmath45.\ ] ] to define @xmath46 with respect to @xmath47 we equate both expressions and solve for @xmath46 in terms of @xmath47 order by order , where order is understood in the sense of the subscripts / superscripts @xmath48 .
this process in general defines @xmath46 in the exponent .
formal rules can be worked out and they are as follows : the n - particle green s function is given by : @xmath49 \label{g_nform}\ ] ] where the superscripts @xmath50 label the number of external potential lines on each particle with @xmath51 , and the subscripts @xmath52 label the number of interaction lines between each pair of particles with @xmath53 . there is a one - to - one correspondance between a particular dimensionless diagram , @xmath47 , in the taylor series expansion of @xmath54 , and a particular term @xmath46 in the exponential series expansion .
the rules for constructing the @xmath46 corresponding to the @xmath47 are as follows : * start with the basic diagram @xmath55 * vertically cut @xmath55 inbetween interaction and potential lines , into all distinct diagram factorizations ( daughter diagrams ) such that the sum of the corresponding indices in each daughter diagram adds up to : @xmath56 * for each daughter diagram , each @xmath47 receives a ( - ) sign . * for each daughter diagram , let @xmath57 be the number of @xmath47 s in the daughter diagram . then divide by @xmath57 . to illustrate , consider the particular diagram in the taylor series expansion in fig .
( [ wparent ] ) ( for n = 3 ) .
, scaledwidth=30.0% ] we can cut this diagram in 3 different ways .
one way is between the two interaction lines in fig .
( [ wdaughter1 ] ) , between the last interaction line and the external potential line in fig .
( [ wdaughter2 ] ) , and between both , fig .
( [ wdaughter3 ] ) , resulting in the following expression for @xmath46 : f_020 ^ 010 & = & - w_020 ^ 010 + w_010 ^ 000 w_010 ^ 010 + w_020 ^ 000 w_000 ^ 010 & - & w_000 ^ 010 w_010 ^ 000 w_010 ^ 000 .
we recall that @xmath58 in this case .
there is a set of @xmath46 s appearing in the exponential series of @xmath54 that we can sum exactly .
these are the ones which give us the exact single particle green s function , @xmath59 , and two - particle green s function @xmath60 .
it turns out that these terms are also responsable for the asymptotic behavior in eq .
( [ symmetry ] ) .
going back to eq .
( [ g_nform ] ) , consider the set of diagrams parameterized by @xmath61 .
this set has @xmath62 external potential lines on particle one , and nothing else on the other n-1 particle lines .
if we add these diagrams up , then we get : @xmath63 similarly , adding up @xmath64 would give us @xmath65 . now consider the set of diagrams given by @xmath66 .
this would correspond to the set of interaction ladders between the first pair of particles , say particles 1 and 2 .
and there would be no interaction lines between any other pair of particles ( and no external potential lines for that matter ) .
if we add these up , we will obtain @xmath67 and similarly for @xmath68 , etc .
therefore let us separate the @xmath46-terms with only one non - zero index from the rest , which we ll denote by @xmath69 . after adding up the one - index @xmath46 s we will obtain , @xmath70\cr & = & g_n^{(0 ) } \prod\limits_i { \frac{{g_1 ( i)}}{{g_1 ^ 0 ( i ) } } } \prod\limits_{i < j } { \frac{{g_2 ( i , j)}}{{g_2 ^ 0 ( i , j)}}}\cr & \times & \exp \left [ { \sum\limits_{\ { v_j \ } = 0}^\infty { \sum\limits_{\ { u_j \ } = 0}^\infty { f'\,_{\ { v_j \ } } ^{\ { u_j \ } } } } } \right ] .
\label{g_nfinal } \end{aligned}\ ] ] this is our main result for the green s function , @xmath54 .
again , @xmath69 consists of all diagrams which do nt consist purely of external potential lines on one particle , or interactions lines between one pair of particles . the first order contribution to @xmath69
will be considered in the appendix . on a general note , the unperturbed basis , @xmath71
, does not have to be the free particle basis ; any basis will suffice . given a choice for @xmath71 ,
@xmath71 will define @xmath72 , and will be the basis in which the diagrams in @xmath69 are expanded .
@xmath59 would be defined via @xmath73 , where @xmath74 is the single particle perturbation .
@xmath60 would be defined via @xmath75 , where @xmath76 is the two - particle interaction .
for instance , if the single particle potential is simple enough , then the exact single particle basis may be convenient to use . in that case
, there would be no external potential lines appearing in the the @xmath69 diagrams , only interaction lines
. it will be evident that the terms to the left of the exponential in eq .
( [ g_nfinal ] ) possess the symmetry present in eq .
( [ symmetry ] ) , and as such would constitute a natural first order approximation , though they contain contributions up to infinite order in both @xmath77 and @xmath78 .
the @xmath69 terms in the exponent are corrections to this approximation .
as evidence of the adequacy of this first order approximation , we adduce the fact that by itself , it reproduces the solution of the q1d dmpk equation for the distinctly non - perturbative values of @xmath79 .
this in itself is remarkable , since the dmpk equation is a many - body problem , but the solution , at least in the metallic and insulating regimes , can apparently be factored into 1 and 2 body green s functions .
thus , the first order approximation may be more generally accurate than it might seem .
indeed , the first order approximation treats all one and two particle correlations exactly to infinite order , and approximates all higher order correlations as products of these lower order correlations .
the @xmath69 diagrams correct this approximation .
so if three particle correlations are important then the @xmath69 terms will need to be included .
but if not , then we may expect that our first order approximation may be highly accurate - even for non - perturbative interactions .
now we would like to apply this formalism to our problem of calculating @xmath80 . to wit
, we need to calculate the 1 and 2 particle green s functions .
since the single particle potential @xmath81 is not small , we would like to include it in our basis hamiltonian , @xmath71 .
@xmath82 will satisfy the differential equation , @xmath83g_1^{(0)}\ ] ] this equation has been solved in the literature @xcite .
the un - normalized eigenfunctions are @xmath84 where @xmath85 , and @xmath86 is a legendre function .
the small / large x behavior of the eigenfunctions is given by @xmath87 , \;\;\ ; x > 1 .
\end{aligned}\ ] ] for large times ( lengths ) @xmath88 , only the lowest lying eigenstates @xmath89 are important to the green s function , and we will make this approximation on the @xmath23 function so that @xmath90 . normalizing the eigenfunction and evaluating the green s function we obtain , in the large x / small y limit : @xmath91 next we need the two - particle green s function .
since we re using the exact single particle basis , the external potential @xmath81 will appear in the equation for @xmath60 , @xmath92g_2 .\ ] ] this equation would be rather difficult to solve , so we will use an approximation afforded to us in our region of interest . note above in eq.([g_1ass ] ) , that @xmath93 for @xmath94 and @xmath95 .
since we re concerned with the insulating state behavior , we will naturally be considering only large x. therefore we may replace the external potential @xmath81 with the boundary condition that @xmath96 . given this
, we can evaluate the @xmath71 two - particle green s function in the large x , small y limit , @xmath97.\ ] ] @xmath60 will then be defined through @xmath98g_2\ ] ] such that we use @xmath99 as the free basis .
this equation can now be solved .
we first change variables to @xmath100 and @xmath101 .
then the equation is separable , and may write @xmath102 where @xmath103 satisfes , @xmath104g.\ ] ] analogous to the single particle case , un - normalized eigenfunctions are given by @xmath105 , & & z > 1 . \end{aligned}\ ] ] to evaluate @xmath103 in the insulating limit , we let @xmath106 and @xmath107 as well . with this approximation , @xmath108 , and upon normalization of the @xmath109 , we can construct the green s function @xmath103 .
now the green s function @xmath110 does not satisfy the effective boundary conditions imposed by @xmath81 . to satisfy these
, we can add to this solution green s functions corresponding to image charges outside the boundary @xmath111 .
then we will have : @xmath112 finally , forming the ratio @xmath113 and taking the small y limit , we obtain , [ g_2ass ] & & t_(x_1 + x_2 ) t_(|x_1 - x_2 | ) & & |y_1 ^ 2 - y_2 ^ 2 |^/2 where @xmath114 is defined as : @xmath115 and we have defined @xmath116 left out of eq .
( [ g_2ass ] ) are the additional terms coming from the effect of the boundaries
. these also have the appropriate symmetry , but are negligible when @xmath94 .
ultimately , we could have ignored the external potential , as we did in our previous paper,@xcite , for purposes of calculating @xmath60 , since it has effect only near the origin , but in the insulating regime , only @xmath117 is of consequence . from @xmath59 and @xmath60 and using eq .
( [ g_nfinal ] ) we can construct the approximate n - particle green s function to first order , @xmath119 observe that we have the requisite symmetry in the small y limit , as required by eq .
( [ symmetry ] ) .
now from this we may construct @xmath118 using eq.([singular ] ) .
we obtain , @xmath120 we can write the eigenvalue distribution in the form of a classical partition function . first recall that the time variable is the longitudinal length of the conductor @xmath121 .
so we have , @xmath122 now we may write p(*x * ) as , @xmath123\ ] ] where we have defined : @xmath124 .
\end{aligned}\ ] ] in the insulating limit , @xmath107 , the @xmath40 s are large , and the conductance is dominated by the smallest eigenvalue
. therefore the conductance is given by @xmath125 .
in this case , we can obtain the full distribution @xmath0 by considering the contribution from @xmath126 alone .
we can approximately obtain @xmath127 via the following procedure .
we order the eigenvalues from least to greatest , separate out @xmath126 , and then integrate over the rest , @xmath128 where @xmath129 and p_n - 1 ( * x * ) & = & .
we can consider @xmath130 to be the partition function of a classical gas of @xmath131 particles constrained between @xmath126 and @xmath132 .
calculating this classical partition function is non - trivial in itself .
though the interaction is weak , a cluster expansion will not work because the interaction is long - ranged ; the individual terms in the expansion will diverge with the particle number . barring a more accurate method , we will use the mean - field approximation @xcite .
the basic idea is that @xmath133 where @xmath134 is the expectation of the energy of these particles with respect to @xmath135 , @xmath136 is the entropy , and @xmath135 is the probability distribution function for the @xmath131 particles that minimizes the free energy @xmath137 .
the mean - field approximation consists of postulating a trial @xmath135 : @xmath138 where the @xmath139 is normalized to @xmath131 , and then minimizing @xmath137 with respect to @xmath57 . forming @xmath137 with our trial @xmath135 , we obtain , @xmath140\cr & + & \frac{1}{2}\int\limits_{x_1}^\infty { dx\int\limits_{x_1 } ^\infty { dy\,n(x)n(y)\,v(x , y ) } } \ , \cr & + & \int\limits_{x_1 } ^\infty { dx\,n(x)\ln\frac{{n(x)}}{{n - 1}}}. \end{aligned}\ ] ] to find the @xmath139 which minimizes @xmath141 , we take a functional derivative with respect to @xmath57 and set it to 0 , subject to the constraint that @xmath139 be normalized to @xmath131 .
we obtain the following equation , @xmath142 where @xmath143 is the lagrange multiplier enforcing the normalization constraint .
we now turn to evaluating the eigenvalue density , @xmath139 .
one can numerically solve this equation , but it is possible to make reasonable approximations based on the qualitative picture that for @xmath144 close to @xmath126 , the external potential determines the form of the density while for large @xmath144 , the interaction dominates , crystallizing the eigenvalues into a kind of lattice .
given the fact that we expect @xmath126 to be large , we may make the following approximation on the interaction .
first , we may neglect the @xmath145 interaction as it is rather small in comparison to the @xmath146 interaction .
secondly , we may make the approximation that @xmath147 .
on the external potential , we may make the following saddle point approximation : @xmath148 where , @xmath149 all of these approximations are quite good in the insulating regime .
following this , our density equation becomes , & & _
x_1 ^x dyxn(y ) + _ x^ & & + u_sp ( x ) + + = 0 this non - linear integral equation can now be reduced to a first order non - linear differential equation .
to do so , we will first need the following boundary conditions imposed by the integral equation itself . for @xmath144 close to @xmath126 ,
the entropy ( @xmath150 ) term will dominate over the interaction ( integral ) term and we ll have , @xmath151 , \;\;\;\;\;\;\ ; x \to x_1.\ ] ] for large @xmath144 , the interaction will dominate over the entropy , and we ll have : @xmath152 now we take two derivatives of our integral equation for @xmath139 .
this results in the 2nd order non - linear differential equation : @xmath153 happily , this equation is autonomous in @xmath144 , so we can change the independent variable to @xmath57 , and the dependent variable to @xmath154 .
this will give a bernoulli differential equation in @xmath38 .
using the boundary condition in eq .
( [ boundary2 ] ) , we can obtain the following differential equation for @xmath57 .
@xmath155 the full solution to this equation is unknown , but in the insulating state , it is the small @xmath156 behavior that is important since only the lowest lying eigenvalues control the conductance . for @xmath144 close to @xmath126 , and therefore small @xmath57 , the @xmath157 term dominates the @xmath57 term in the square root . neglecting the linear term
, we can perform the integral .
employing the boundary condition eq .
( [ boundary1 ] ) , we obtain , @xmath158 the numerical solution to this equation is shown in our previous paper @xcite for two different values of @xmath23 .
it illustrates that the density is roughly constant with an exponential gap from the origin that increases with increasing disorder .
in contrast , the density in the metallic regime is also constant , but starting at the origin .
thus our result suggests that the opening of a gap in the eigenvalue spectrum could be considered as a signature of the metal - insulator anderson transition .
now that we have determined the density of eigenvalues for @xmath144 close to @xmath126 , we can use it to evaluate @xmath137 in this same region .
we obtain , @xmath159.\ ] ] finally , this brings us to our result for @xmath160 . using eq .
( [ px1 ] ) , we obtain , @xmath161\cr f(x ) & = & u(x ) - \frac{{\sqrt \pi } } { { 8e\gamma \sqrt { \gamma ' } } } { \mathop{\rm erfc}\nolimits } \left [ { ( x - x'_{sp } ) \sqrt { \gamma ' } } \right].\cr \end{aligned}\ ] ]
to obtain the probability distribution of the conductance in the insulating state , we use the aformentioned fact that the dominant contribution to @xmath162 comes from the first eigenvalue , @xmath126 .
therefore @xmath163 , which implies @xmath164 . and so , @xmath165.\ ] ] this is our expression for the conductance distribution in the insulating state . in fig .
[ p(g)graph ] , we compare the analytical formula in eq .
( [ final ] ) to numerical results and also to the distribution obtained from the gdmpk equation neglecting the interaction . in the insulating regime for two values of disorder ,
@xmath166 ( solid red line ) and @xmath167 ( dotted green line ) , corresponding to @xmath168 and @xmath169 , respectively .
the numerical data points are from ref .
[ ] for the same value of @xmath170 .
the dashed blue curve is the gdmpk prediction of @xmath171 for @xmath172 neglecting the eigenvalue interaction , scaledwidth=45.0% ] examining eq .
( [ final ] ) we find the distribution has a gaussian tail in @xmath173 for very small @xmath162 .
we can calculate the expectation of @xmath173 as a function of @xmath23 .
the result , to leading order , is @xmath174 .
\label{lng_gamma}\ ] ] one may also calculate the variance of @xmath173 in terms of @xmath175 .
we find that asymptotically , @xmath176 current numerical simulations @xcite suggest rather that the variance of @xmath173 goes as @xmath177 . in our previous paper @xcite
we found a power law consistent with @xmath178 .
it is a consequence of eq.([var_gamma ] ) that different power laws can be fitted over different ranges of @xmath173 . to illustrate we plot @xmath179 vs. @xmath180 in fig .
( [ varlng ] ) , and in the insert , over a shorter range of @xmath173 , we plot @xmath179 vs. @xmath181 which is actually a better fit over that shorter range . plotted as a function of @xmath180 .
the points are calculated from eq.([final ] ) .
the line is a best fit .
variance of @xmath173 is plotted as a function of @xmath182 in the insert , scaledwidth=45.0% ] so the discrepancy could be the result of the range of current numerical simulations ( as the analytic solution seems to match with different power laws in different regimes ) , or the result of the series of approximations made in calculating the partition function , which provides motivation for further work in this area .
a major prediction of eq . ( [ final ] ) is the resulting novel disorder dependence of the skewness of the distribution . as shown in ref .
[ ] , the skewness is positive in the deeply insulating regime and seems to tend to a constant value as disorder increases . from eq .
( [ final ] ) , one can calculate the skewness and confirm that it does approach a constant value , @xmath183 .
the convergence to the asymptote is logarithmic , as illustrated in fig.[skewness ] . .
note the asymptote at @xmath184.,scaledwidth=45.0% ] as disorder decreases the skewness eventually changes sign while still in the insulating regime .
this change of sign occurs well before the anderson metal - insulator transition point . unfortunately due to
the approximations used to obtain the density of eigenvalues , we can not trust eq .
( [ final ] ) to describe the distribution at the transition point itself .
in this work we start with the assumption , well supported numerically , that the generalized dmpk equation ( gdmpk ) with two scale - dependent parameters correctly describes the evolution of transmission eigenvalues with increasing length in a 3d disordered conductor . taking advantage of a mapping of the gdmpk equation on to an imaginary time schrdinger equation for a system of bosons interacting via a short range interaction in 1d ,
we then develop a systematic perturbation theory to solve for the full distribution of the eigenvalues in terms of the @xmath3-particle greens function describing the system ( eq .
( [ g_nfinal ] ) ) . in the strong disorder regime
the strength of the interaction between bosons is small , which we use as the small parameter in our perturbation theory .
in particular , we make sure that the @xmath3-particle greens function satisfies a highly non - trivial boundary condition . to
leading order which includes at least all two - particle correlations , we obtain the distribution of the eigenvalues in the strong disorder regime , where all eigenvalues are exponentially large . writing the eigenvalue distribution in the form of a classical partition function , we then separate out the smallest eigenvalue @xmath126 which dominates the distribution , and use a mean field approximation that allows us to evaluate the density of the eigenvalues ( eq .
( [ eq - density ] ) ) and the free energy close to @xmath126 .
finally , using landauer formula connecting conductance with the transmission eigenvalues , we arrive at our expression for the full distriburtion of conductance , given by eq .
( [ final ] ) .
it turns out that the final distribution can be expressed in terms of a single disorder parameter .
we use eq .
( [ final ] ) to compare directly with conductance distributions evaluted numerically from three dimensional tight binding anderson model in the insulating regime .
once the parameter of the theory is fixed to give the correct mean value of the distribution , the entire distribution is reproduced very well .
in addition , we evaluate the variance and skewness as a function of disorder . while the numerical data for the variance is usually fitted with power laws , we find that the asymptotic behavior is perhaps more complex , given by eq .
( [ var_gamma ] ) , which can be fitted with different power laws in different regimes .
we predict the skewness approaches a constant value in the deeply insulating regime , and changes sign as the disorder is decreased from deeply insulating regime towards the anderson transition point .
our expression becomes less applicable as one approaches the transition , but the change in sign occurs well before the transition .
the theory can in principle be improved by keeping higher order terms in the perturbation expansion , as shown in appendix a. however , even though the perturbation parameter remains small up to the anderson transition point , the partition function and hence the density of the eigenvalues can not be evaluated very accurately as the system approaches the transition .
it is not clear at this point how to improve the calculation of the partition function beyond the mean field approximation used here .
nevertheless , starting at the strongly insulating regime , the present approach already predicts highly non - trivial changes in the conductance distribution as one decreases the disorder towards the anderson transition .
if we want to include three - particle correlations , then to leading order they would come from the following type of diagram ( fig .
( [ threepart ] ) ) with two interaction lines .
permutation refers to the same graphs but with the order of the first and second interactions switched .
there would be the same set of diagrams for every distinct triple of particles within the set of @xmath3 .
the first dimensionless graph would correspond to an @xmath46 of : @xmath185 let us call this term @xmath186 .
each of the other five graphs is simply a permutation of the arguments of the first .
for instance , switching the order of the interaction lines of @xmath187 would give us : @xmath188 .
the second @xmath46 would be @xmath189 , and its permutation would be @xmath190
. the third @xmath46 would be @xmath191 and its permutation would be @xmath192 .
let @xmath193 denote the sum of these 6 @xmath46 s . then using eq.([g_nfinal ] )
we can write out the expression for @xmath54 correct to second order in the interaction : @xmath194 in order to calculate these diagrams it is convenient to go to a plane - wave basis
. unfortunately , the potentials in eq .
( [ potentials ] ) do not possess well - defined fourier transforms due to the @xmath195 singularity at the origin .
even then , we have found that a good representation of the fourier transform is given by the following relations : @xmath196 the large @xmath197 behavior of these potentials result in ln - divergences of the first order ( and probably higher order too ) dimensionless diagrams , @xmath47 .
but the corresponding @xmath46 s result in well - defined , indeed necessary , terms by taking the divergences to the exponent .
this is one of the advantages of the exponential expansion , the divergences are resummed to give finite results order by order which we see accumulated in @xmath59 and @xmath60 . on the other hand ,
if one is not interested in the small @xmath40 or small @xmath198 behavior ( this ought to be taken care of via @xmath59 and @xmath60 in any event ) , we may approximate these fourier transforms by their small @xmath197 limit @xmath199 this is equivalent to approximating the potentials with a delta function which gives the same phase shift . since the potentials are very short ranged , this should be adequate .
whichever set of expressions we use , the feynman rules in frequency space would be given in fig .
( [ g0 ] ) , and fig .
( [ vinteraction ] ) .
the first vertex corresponds to the interaction potential @xmath200 , and the solid vertex corresponds to the interaction potential @xmath201 .
the latter can be incorporated into fourier space provided we associate it with momentum @xmath197 flowing from the center outwards towards both @xmath126 and @xmath202 , rather than with momentum @xmath197 flowing from @xmath126 to @xmath202 as with the difference potential .
momentum would be conserved at all intersections as usual .
p. marko , _ conductance statistics near the anderson transition _ in t. brandes and s. ketteman ( editors ) _ anderson localization and its ramifications _ , lectures notes in physics 630 , springer 2003 ; p. marko , phys .
lett . * 83 * , 588 ( 1999 ) ; m. rhlander , p. marko and c.m .
soukoulis , phys .
b * 64 * , 212202 ( 2001 ) ; p.
marko , phys .
b * 65 * , 104207 ( 2002 ) ; i. travenec and p. marko , phys . rev .
b * 65 * , 113109 ( 2002 ) ; p. marko and b. kramer , philos . mag . * 68 * , 357 ( 1993 ) ; k. slevin , p. marko , t. ohtsuki , phys .
* 86 * , 3594 ( 2001 ) ; k. slevin , p. marko , t. ohtsuki , phys .
b * 67 * , 155106 ( 2003 ) ; p. marko , j. phys .
a : math . gen . * 33 * , l393 ( 2000 ) ; p. marko , ann .
physik ( leipzig ) * 8 * si=185 ( 1999 ) .
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we develop a systematic perturbative method to obtain analytic solution of the generalized dorokhov - mello - pereyra - kumar ( dmpk ) equation in the strongly disordered regime which describes the evolution of the joint probability distribution of the transmission eigenvalues with system size .
the solution allows us to obtain the distribution of conductance analytically in the insulating regime .
our results are consistent with existing numerical simulations of the three dimensional tight binding anderson model , and suggests a possible description of the anderson transition in the presence of a very broad , highly asymmetric conductance distribution .
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in addition to bringing down the prolactin levels , they also reduce tumor size ( 5075% by bromocriptine and 90% by cabergoline ) . in women with prolactinomas , stimulatory effects of the hormonal milieu of pregnancy result in significant tumor enlargement during gestation .
a 20-year - old housewife presented with secondary amenorrhea for 2 years in july 2001 .
she consulted neurosurgery department in this hospital , where she was found to have prolactin level of 150 ng / ml ( normal 525 ng / ml , clia ) .
her magnetic resonance imaging ( mri ) brain showed a microadenoma of about 4 mm in the left half of the pituitary gland .
she was started on bromocriptine 2.5 mg daily , which was stepped up to 7.5 mg subsequently . at 3 months of treatment , she had two menstrual cycles and her prolactin was 25 ng / ml . then , she did not follow - up for 1 year , but she continued the drug .
repeat mri in april 2004 showed microadenoma of size 4 mm , which was the same as previous scan . in february 2004 ,
after 2 months of stopping breastfeeding , her prolactin was > 150 ng / ml .
she stopped bromocriptine on her own in june 2006 and presented in september with headache , blurring of vision and amenorrhea of 3 months duration .
mri showed pituitary macroadenoma of 1.2 1.6 1.1 cm in the sellar region with suprasellar extension abutting of left side of optic chiasma [ figure 1 ] .
the patient was admitted in the hospital where she was started on low dose of bromocriptine and the dose was slowly increased to 7.5 mg / day .
bromocriptine was stopped and she was advised to breastfeed the baby under close monitoring of visual field and symptoms .
mri was repeated after 3 months of delivery , which showed almost complete disappearance of the tumor [ figures 25 ] .
magnetic resonance imaging at presentation showing a microadenoma of about 4 mm in the left half of the pituitary gland magnetic resonance imaging after first delivery , showing a microadenoma of about 4 mm in the left half of the pituitary gland magnetic resonance imaging showing a pituitary macroadenoma 1.2 1.6 1.1 cm in the sellar region with suprasellar extension abutting of left side of optic chiasma , after second pregnancy ( spontaneous abortion ) , after stopping bromocriptine magnetic resonance imaging in february 2007 , during third pregnancy , after 6 weeks of bromocriptine magnetic resonance imaging 3 months after delivery , showing complete disappearance of tumor
pituitary gland enlarges during pregnancy , and by the end of pregnancy , it increases by 136% .
mandel et al . , summarizing 19 series , found that out of 376 cases of microprolactinoma , 6 ( 1.3% ) had symptomatic tumor enlargement .
though dopamine agonists have been used during pregnancy to prevent tumor growth , it is prudent to reduce fetal exposure to drugs . in patients with microprolactinoma
, they are advised to have menstrual periods occur naturally for a period of time ( 34 months ) long enough to predict that a missed period may be due to pregnancy .
, these drugs will have been given only for 34 weeks of gestation . in 6239 pregnancies of patients managed in this manner
, there was no increased incidence of abortions , prematurity , multiple births or fetal malformations above that expected in the control population .
there is no evidence that other dopamine agonists are less safe , but exposure to other agents during pregnancy is not well described .
such patients should be seen in each trimester and assessed for symptoms such as headache or visual problems .
treatment options for patients when the tumor is large or extends to the optic chiasma or cavernous sinus are 1 ) prepregnancy tumor debulking , 2 ) intensive monitoring without bromocriptine therapy and 3 ) continuous bromocriptine .
the safety of the last approach is not established , though it seems to be safe based on case reports .
mean offspring birth weight of the babies was normal in a series of 53 patients receiving bromocriptine .
long - term follow - up studies of 64 children of age between 6 months and 9 years whose mothers took bromocriptine have shown no ill effects .
patients with macroadenomas should be seen monthly for clinical assessment and visual fields are to be tested during each trimester .
prolactin levels have little value in pregnancy . when there is evidence of tumor enlargement during pregnancy , bromocriptine therapy is to be reinstituted immediately and the dosage increased as rapidly as possible .
if there is no clinical response to bromocriptine on close monitoring , switching to cabergoline , transsphenoidal surgery or delivery ( if the pregnancy is far enough advanced ) should be considered .
the effects of transsphenoidal surgery during gestation are not known specifically , but would not be expected to be significantly different from the effects of other kinds of surgery .
cabergoline has been shown to cross the placenta in animal studies , but such data are lacking in humans .
the data on safety of cabergoline during pregnancy and its effects on fetal development are scarce .
the frequency of spontaneous abortions in pregnant women under cabergoline treatment in various series ranges from 7.2 to 10%.[815 ] in a series of 6329 patients treated with bromocriptine , guillam et al . found the risk of spontaneous abortions to be 9.9% . in the general population , nybo andersen et al .
also , the risk of embryo - fetal malformation does not look elevated based on the present data.[111820 ] though cabergoline database is small , for a woman who is intolerant to bromocriptine and doing well with cabergoline , continuing cabergoline may be reasonable .
it has been shown that cabergoline treatment causes further shrinkage of tumor in patients previously treated with bromocriptine and those considered resistant to dopamine agonists .
cabergoline has a high affinity to 5ht2b receptors besides d2 receptors , and this forms the basis of action of cabergoline on cardiac valves .
valvular regurgitation and restrictive valvulopathy has been described in parkinson 's patients receiving high doses of cabergoline ( nearly 20 times the typical doses used for prolactinoma ) .
literature review shows that 11 studies have assessed the potential association between valve regurgitation and the use of cabergoline in patients treated for prolactinoma . in total , 795 patients , treated with cabergoline at a median cumulative dose of 290 mg and a median duration of 59 months , and 1202 healthy control individuals were included in these studies .
five of these studies did not report any relevant cardiac findings , although increased prevalence of regurgitation in any valve was reported in five studies , and one study reported an increased tenting of the mitral valve . in light of these data , it is controversial whether prolactinoma patients receiving cabergoline for long term should be monitored with echocardiography or not .
although suckling stimulates prolactin secretion in normal women for the first few weeks to month postpartum , there are no data suggesting that breastfeeding can cause tumor growth .
the possibility of the enlargement being entirely due to lymphocytic hypophysitis , which is known to present with mass lesion during pregnancy and spontaneously resolves postpartum , was considered in our patient . however , serum cortisol and thyroid functions which were normal are not in keeping with the diagnosis of lymphocytic hypophysitis this case report illustrates an unusual presentation of microprolactinoma which had symptomatic enlargement during pregnancy , which resolved completely in the postpartum period with medical line of therapy .
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a patient with microprolactinoma , who had two successful pregnancies , is described for management issues .
first pregnancy was uneventful . during the second pregnancy ,
the tumor enlarged to macroprolactinoma with headache and blurring of vision which was managed successfully with bromocriptine .
post delivery , complete disappearance of the tumor was documented .
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HONOLULU -- A man who suffered a heart attack shortly after Hawaii mistakenly issued an alert about a ballistic missile filed a lawsuit against the state on Tuesday. The false missile alert and the state's failure to cancel it in a timely manner was a substantial factor in causing James Sean Shields' heart attack on Jan. 13, the lawsuit said.
His girlfriend Brenda Reichel joined the lawsuit, having suffered "emotional upset" from watching him almost die on several occasions. Their lawsuit names the state of Hawaii and the then-administrator of the Hawaii Emergency Management Agency, Vern Miyagi.
The lawsuit also names unidentified state employees, individuals and entities responsible for the missile alert. The suit seeks unspecified damages.
"We're going to reserve any comment until we have had a chance to review the claims," said Richard Rapoza, a spokesman for the Hawaii Emergency Management Agency State attorney general spokesman Krishna F. Jayaram said the office will review the complaint carefully and respond in due course.
Miyagi declined to comment. A Hawaii Emergency Management Agency employee mistakenly sent the missile alert to cellphones and broadcasters on Jan. 13, triggering widespread panic until the agency sent another message 38 minutes later notifying people it was a false alarm.
The lawsuit recounts how the couple was heading from their townhome in Hawaii Kai to Sandy Beach on that Saturday morning when they received the alert on their cellphones. "Both plaintiffs believe this message to be true and were extremely frightened and thought they were shortly going to die," the lawsuit said.
This smartphone screen capture shows a false incoming ballistic missile emergency alert sent from the Hawaii Emergency Management Agency system on Saturday, Jan. 13, 2018. Caleb Jones / AP
They decided if they were going to die, they might as well die together on the beach, the lawsuit said. Reichel's son, who is in the Hawaii Army National Guard, called her saying the threat was real and asked what they planned to do to seek shelter.
The couple called their loved ones as they drove to the beach. Shields began to feel a severe and painful burning in his chest after he called his son and daughter.
Shortly after, he went to a community clinic, where he suffered cardiac arrest. A doctor resuscitated him, while arriving paramedics assisted him further.
He was diagnosed with a myocardial infarction or heart attack after he arrived at Straub Hospital, the lawsuit said. CBS affiliate KGMB-TV reports that paramedics responded to three other incidents that day that the patients or members of their family blamed on the missile alert.
The other incidents were an 89-year-old man who fell, a 37-year-old woman in a car accident and a 38-year-old woman who was experiencing anxiety, KGMB-TV reports. ||||| “There are probably thousands of people out there who suffered either financial or physical injuries as a result of what happened," Rosenberg said. "I’m aware, for example, of several car accidents that occurred on the day that the missile alert came up because people were rushing around trying to either get home or get to loved ones or get as far away from the downtown area as possible. So there are a number of car accidents. Those, in my opinion, are all attributable to the state.”
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– A Hawaii man claims that a false alert about incoming ballistic missiles issued in that state earlier this year caused him to have a heart attack. On Jan. 13, Hawaii’s Emergency Management Agency fired off an alert to cellphones warning, “Ballistic missile threat inbound to Hawaii. Seek immediate shelter. This is not a drill.” A lawsuit filed Tuesday says James Sean Shields and Brenda Reichel, both listed as plaintiffs, “believed the message to be true and were extremely frightened and thought they were going to die,” NBC reports. According to the suit, the pair, who lived in Honolulu, were heading to Sandy Beach when the alert came, per KGMB. “If they were going to die,” the suit says, “They might as well die together on the beach.” So they continued to the beach. Once they arrived, they began to call loved ones.” After calling his kids, Shields began to have severe chest pains, per CBS. He went to a clinic, where he suffered cardiac arrest and was resuscitated. Around the same time, some 30 minutes after the missile alert, the state sent another message saying the alert was sent in error. Per KGMB, the suit says that Shields hadn’t had any heart conditions previously. Vern T. Miyagi, former Emergency Management Agency administrator, as well as unnamed state employees are named in the suit, which seeks unspecified damages. “We’re going to reserve any comment until we have had a chance to review the claims," a state attorney tells CBS. According to reports, an elderly man fell, a 37-year-old woman had a car accident, and a 37-year-old woman called 911 with anxiety in connection to the false alarm. (This man claims that licorice caused his heart problems.)
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in recent years the presence of antiprotons @xmath3 s ) in the cosmic ray ( cr ) flux incident upon the earth has been firmly established by a series of balloon borne experiments ( golden et al .
1979 ; bogomolov et al .
1979 ; bogomolov et al .
1987 ; bogomolov et al .
1990 ; hof et al .
1996 ; mitchell et al . 1996 ; moiseev et al . 1997 ; yoshimura et al . 1995 ; boezio et al . 1997 ; matsunaga et al .
the measurements are summarized in table 1 .
the observed cr @xmath0 ratio has been shown to be in approximate agreement with predictions based on the leaky box model ( lbm ) ( stephens 1981 ; stephens & golden 1987 ; webber & potgieter 1989 ; gaisser & schaefer 1992 ) , which assumes that the @xmath1 s originate from proton interactions in the interstellar medium ( ism ) .
the @xmath1 s then propagate within the galaxy until they `` leak out '' by diffusion and convection with the characteristic cr galactic escape time @xmath4 million years ( myr ) ( webber & potgieter 1989 ; gaisser & schaefer 1992 ) . if the @xmath1 lifetime @xmath5 is not long compared to @xmath6 the predicted @xmath0 spectrum will be modified .
the agreement of the lbm predictions with the observed @xmath0 spectrum has therefore been used to argue that @xmath7 myr ( golden et al .
1979 ; bogomolov et al .
1979 ; stephens 1981 ; stephens & golden 1987 ) .
this estimated limit is based on early cr @xmath1 data and does not take into account the reduction of the @xmath1 decay rate due to time dilation , the effect of the heliosphere on the observed @xmath0 spectrum , or the systematic uncertainties associated with the predictions . in this paper
we compare recent cr data with the predictions of an improved lbm extended to permit a finite @xmath5 .
heliospheric corrections and systematic uncertainties are taken into account . assuming a stable @xmath1
, we find excellent agreement between our predictions and the cr observations .
allowing the @xmath1 to decay , we obtain a lower limit on @xmath5 which is significantly more stringent than current laboratory bounds obtained from searches for @xmath1 decay in ion traps ( gabrielse et al . 1996 ) and storage rings ( geer et al .
1994 ; hu et al .
the analysis presented in this paper improves on our earlier analysis ( geer & kennedy 1998 ) by including new data from matsunaga et al .
( 1998 ) .
cpt invariance requires @xmath5 = @xmath8 , where the proton lifetime @xmath8 is known to exceed @xmath9 yr ( caso et al . 1998 ) .
although there is no compelling theoretical motivation to suspect a violation of cpt invariance , and hence a short @xmath1 lifetime , it should be noted that string theories can accommodate cpt violation .
consider a mass dimension@xmath10 cpt violating quantum field operator suppressed by the characteristic scale @xmath11 , with @xmath12 4 .
dimensional analysis provides the estimate @xmath13^{2n-8}$ ] , yielding @xmath14^{1/(2n-8)}$ ] ( kennedy 1999 ) . for a given lower limit on @xmath5 ,
the implied lower limit on @xmath11 is most stringent for @xmath10 = 5 . note that if @xmath11 is at the planck scale @xmath15 gev/@xmath16 and @xmath10 = 5 , the expected @xmath5 would be @xmath17 10 myr .
hence , a search for @xmath1 decay with a lifetime approaching 10 myr provides a test for cpt violation well beyond the scale accessible at high energy colliders .
finally , since the antiproton is the only long lived antiparticle that could decay into other known particles without violating charge conservation , a search for a modification of the cr @xmath1 spectrum by @xmath1 decay provides a unique test of the stability of antimatter .
in the lbm the ism @xmath1 s are produced by the interactions of cr @xmath18 s ( stephens 1981 ; stephens & golden 1987 ; webber & potgieter 1989 ; gaisser & schaefer 1992 ) : @xmath19 where @xmath20 is a nucleus of charge @xmath21 , and @xmath22 is anything .
our calculations use the elemental ism abundances given in webber & potgieter ( 1989 ) and gaisser & schaefer ( 1992 ) , and the measured cross sections for @xmath21 = 1 ( the dominant contribution ) given in stephens ( 1981 ) . for @xmath23 1
, we have used the `` wounded nucleon '' results also used by gaisser & schaefer ( 1992 ) .
the @xmath1 s are assumed to propagate within the galaxy until they are lost either by leakage into intergalactic space or by @xmath24 annihilation .
the dominant loss process is leakage .
energy loss is included in the model .
comparisons between predicted and observed cr isotopic abundances imply that reacceleration can be neglected ( webber et al .
reacceleration is not included in our calculation .
the lbm incorporates space - dependent diffusive and convective cr leakage into a single escape term with a single characteristic escape time .
this picture is known to be too simple . a more accurate picture of galactic crs ( webber et al .
1992 ) is provided by a two - zone diffusion - convection model which we refer to as the _ inhomogeneous leaky disk model _
the model is based on a @xmath25 100 pc - thick matter disk ( radius @xmath26 20 kpc ) , with a halo extending above and below the disk by @xmath27 kpc .
the crs diffuse off the disk into the halo by magnetic turbulence .
it has been shown that convection driven by the galactic wind can be neglected ( bloemen 1993 ) .
the ildm _ disk _ storage time @xmath28 where the diffusion transverse to the galactic disk @xmath29 @xmath30 m@xmath31 sec@xmath32 ( bloemen 1989 ; webber et al .
the ildm with these parameters @xmath33 has been numerically solved by chardonnet et al .
( 1996 ) for the secondary cr @xmath1 spectrum .
although the ildm provides a more realistic physical description of cr propagation than the lbm , chardonnet et al . found that the fluxes in the galactic disk predicted by the ildm are reproduced within uncertainties by a modified lbm ( mlbm ) in which the momentum - dependent escape time @xmath34 is given by : @xmath35 ( 13 myr ) @xmath36^{-0.6}$ ] .
this escape time is longer than that used by webber & potgieter ( 1989 ) and gaisser & schaefer ( 1992 ) and , since the @xmath1 flux is proportional to @xmath34 , raises the predicted @xmath1 flux and continues the trend of the last two decades toward longer cr escape times / lengths , as discussed by these authors .
the uncertainties on the parameters of the mlbm result in uncertainties on the normalization of the predicted @xmath0 ratio but , to a good approximation , do not introduce significant uncertainties in the shape of the predicted spectrum .
uncertainties on four parameters must be considered : ( i ) the storage time ( @xmath3767% ) ( webber et al . 1992 ) , ( ii ) the ism primary @xmath18 flux ( @xmath3735% ) ( gaisser & schaefer 1992 ) , ( iii ) the @xmath1 production cross section ( @xmath3710% ) ( stephens 1981 ; gaisser & schaefer 1992 ) , and ( iv ) the composition of the ism , which introduces an uncertainty of @xmath38% on the predicted @xmath1 flux ( gaisser & schaefer 1992 ) .
we neglect the last of these uncertainties since it is relatively small . within the quoted fractional uncertainties on the other three parameters we treat all values as being a priori equally likely .
note that the predicted @xmath0 ratio is approximately proportional to each of the parameters under consideration .
the solid curves in figure 1 show the mlbm @xmath0 spectra for the parameter choices that result in the largest and smallest @xmath0 predictions . the predicted ism spectrum does not give a good description of the observed distribution at the top of the atmosphere .
good agreement is not expected because the cr spectra observed at the earth are modulated as the particles propagate through the heliosphere , which consists of the solar magnetic field @xmath39 and solar wind ( stix 1989 ; encrenaz et al .
1990 ; longair 1992 ) .
the wind , assumed to blow radially outwards , has equatorial speed @xmath40 400 km sec@xmath32 .
_ ulysses _ has found a latitude - dependent @xmath41 . at high latitudes
@xmath42 , @xmath40 750 km sec@xmath32 ( smith et al . 1995 ; marsden et al .
1996 ; ulysses 1999 ) .
the latitude - dependent solar rotation @xmath43 ( howard 1984 ) twists the field lines into a parker spiral . the smoothed heliomagnetic field ( @xmath44 5 nt at the earth s orbit ) declines as it changes from radial at the sun to azimuthal in the outer solar system .
the heliomagnetic polarity @xmath45 is opposite in northern and southern solar hemispheres and switches sign somewhat after sunspot maximum .
note that @xmath46 0 in the 1990 - 99 epoch .
the regions of opposite magnetic polarity are separated by an approximately equatorial , unstable neutral current sheet .
the sheet is spiraled and wavy ; its waviness is measured by the tilt angle @xmath47 , which relaxes from @xmath48 @xmath49 at polarity reversal to @xmath48 @xmath50 just before reversal . the wavy sheet locus in heliographic co -
ordinates is @xmath51 $ ] = 0 ( jokipii & kopriva 1979 ; encrenaz et al .
1990 ; nso 1999 ) .
cosmic rays enter the heliosphere on ballistic trajectories and are then transported by drift and diffusion ( jokipii & kopriva 1979 ; risken 1984 ) .
the transport model includes energy loss as crs perform work against the wind , cr solar wind convection , drift of crs across inhomogeneous field lines , and diffusive scattering by field turbulence .
particles with @xmath52 @xmath53 drift in along a polar ( sheet ) route .
since the polar @xmath54 is approximately twice the equatorial @xmath54 , particles with @xmath55 0 find it more difficult to drift in along a polar route than do @xmath56 0 particles along a sheet route . in the following ,
we restrict our analysis to cr @xmath18 s and @xmath1 s with kinetic energies @xmath57 500 mev . at these energies ,
( a ) the wind and magnetic drift ( isenberg & jokipii 1979 , 1981 ) dominate the transport ; and ( b ) the diffusion is charge
symmetric and , for a given rigidity , modulates the @xmath18 s and @xmath1 s by the same factor , and hence cancels in the ratio of fluxes ( see ulysses @xmath58 and @xmath18 scans : smith et al .
1995 ; marsden et al . 1996
; fisk et al .
1998 ) .
we compute the modulation of the cr fluxes by the method of characteristics , numerically implemented in three dimensions by a combination of runge kutta and richardson burlich stoer techniques ( press et al .
the calculation is based on the heliospheric transport model of jokipii & kopriva ( 1979 ) , jokipii & thomas ( 1981 ) , and jokipii & davila ( 1981 ) , but that model has been updated with _
pioneer , voyager , helios , imp _ and _ ulysses _ heliospheric measurements ( smith et al . 1995 ; marsden et al .
1996 ; nssdc 1999 ; sec 1999 ) .
the improvements include the latitude - dependent @xmath41 and @xmath43 .
the calculation is simplified by ignoring diffusion where its effects on the @xmath0 ratio are small , which for our energy range means everywhere except across the sheet ( jokipii & thomas 1981 ) .
the effects of diffusion away from the sheet are essential for particles with energies below the range we are considering . for particles with speed @xmath59 the across - sheet diffusion coefficient @xmath60 = @xmath61 m@xmath31/sec@xmath62[b_\oplus /b(r)](p/{\rm gev})^{1/3}(v / c)$ ] is used ( smith et al .
1995 ; marsden et al .
the implied field fluctuation spectral index is the kolmogorov value of 5/3 .
the modulated fluxes at earth depend only weakly on @xmath60 in our energy range , for this and larger values of @xmath60 .
we use the data sets recorded by the mass91 , imax , bess , and caprice experiments ( table 1 ) .
these data were recorded in the period 19911995 , corresponding to a well behaved part of the solar cycle for which the heliospheric modulation corrections can be confidently calculated . to explore the dependence of the predicted spectrum on the heliospheric parameters ( equatorial @xmath54 , polar @xmath54 , and @xmath63 ) we have computed the modulated spectra for 11 parameter sets ( f1 f11 ) that span the range of acceptable parameter values ( table 2 ) . using the central parameter values for our mlbm , and assuming a stable antiproton , the predicted modulated @xmath0 spectra for a fixed time in the solar cycle ( july 1995 ) are shown in figure 2 for each of the 11 heliospheric parameter sets .
figure 2 also shows the epoch corrected measured cr spectra , obtained by multiplying each measurement by the factor @xmath64july 1995@xmath65 , where @xmath66 is the predicted @xmath0 ratio at time @xmath67 .
the factors @xmath68 , which are shown in table 1 and have been computed using the f6 parameters , vary by up to @xmath69 with the parameter set choice .
the mlbm predicted @xmath0 spectra give an excellent description of the measurements .
there is no evidence for an unstable @xmath1 . to obtain a limit on @xmath5 we add to the mlbm one additional loss mechanism , @xmath1 decay .
the results from maximum likelihood fits to the measurements are shown in figure 3 as a function of the assumed @xmath5 for the 11 heliospheric parameter sets .
the fits , which take account of the poisson statistical fluctuations on the number of observed events and the background subtraction for each data set ( table 1 ) , also allow the normalization of the mlbm predictions to vary within the acceptable range ( figure 1 ) .
for a stable @xmath1 , at the 95% c.l .
all of the heliospheric parameter sets yield predictions that give reasonable descriptions of the observed @xmath0 spectrum .
allowing for a finite @xmath5 , the heliospheric parameter sets with larger wind speeds permit lower @xmath1 lifetimes .
this can be understood by noting that , as the wind speed increases , the predicted flux of polar routed particles ( protons in the present solar cycle ) is depleted at kinetic energies @xmath70 10 gev , which increases the predicted @xmath0 ratio in this energy range . antiproton decay would compensate for this distortion in the predicted spectrum . hence our fits using the extreme parameter set f11 determine the limits on @xmath5 . under the assumption that there are no significant non
standard sources of cosmic ray antiprotons , we obtain the bounds : @xmath71 our simple dimensional analysis suggests that if a dimension@xmath10 cpt violating coupling results in antiproton decay , the mass scale @xmath11 at which this new physics takes place exceeds @xmath72
gev/@xmath73 @xmath74 gev/@xmath75 $ ] , for @xmath10 = 5 ( 6 ) . the limits ( 1 ) are significantly more stringent than those obtained from the most sensitive laboratory search for inclusive @xmath1 decay ( @xmath76 months ) ( gabrielse et al . 1996 ) or the most sensitive search for an exclusive @xmath1 decay mode ( @xmath77 myr ) ( hu et al .
note however that these limits are less restrictive than the estimate @xmath5 @xmath78 10 myr given in caso et al .
( 1998 ) , which takes no account of time dilation , systematic uncertainties , or propagation effects and which is therefore overconstraining .
it is a pleasure to thank j. r. jokipii ( lunar & planetary laboratory , univ .
arizona ) and e. j. smith ( jet propulsion laboratory / caltech ) for their insights .
this work was supported at fermilab under grants u.s .
doe de - ac02 - 76ch03000 and nasa nag5 - 2788 and at the univ .
florida , institute for fundamental theory , under grant u.s .
doe de - fg05 - 86er40272 .
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measurements of the cosmic ray @xmath0 ratio are compared to predictions from an inhomogeneous disk - diffusion model of @xmath1 production and propagation within the galaxy , combined with a calculation of the modulation of the interstellar cosmic ray spectra as the particles propagate through the heliosphere to the earth .
the predictions agree with the observed @xmath0 spectrum . adding a finite @xmath1 lifetime to the model
, we obtain the limit @xmath2 0.8 myr ( 90% c.l . ) .
= cmr10 scaled 1200 = cmr10 scaled 800 -40pt published in * the astrophysical journal * : 20 march 2000
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NEW YORK (Reuters) - Surviving members of Lynyrd Skynyrd have filed a lawsuit against the Southern rock band’s former drummer to halt the production of a movie depicting the 1977 plane crash that killed lead singer Ronnie Van Zant.
FILE PHOTO - Singer Kid Rock (L) performs with Johnny Van Zant (R) and his band Lynyrd Skynyrd on ABC's "Good Morning America" in New York, U.S. on August 22, 2008. REUTERS/Brendan McDermid/File Photo
Lead guitarist Gary Rossington, Ronnie’s brother and current lead singer Johnny Van Zant, and others contend that “Street Survivors: The True Story of the Lynyrd Skynyrd Plane Crash,” based on recollections of former drummer Artimus Pyle, violated a 1988 consent order governing the use of the band’s name.
The lawsuit against Pyle and co-defendant Cleopatra Records Inc was made public on Friday in the U.S. district court in Manhattan. A trial is scheduled for July 11, court records show.
Pyle could not immediately be reached for comment. It is unclear whether he has a lawyer.
Brian Perera, Cleopatra’s president, said in an interview he would be willing to settle, but added, “I understood my First Amendment rights. Filmmakers can make biopics.”
Known for such songs as “Sweet Home Alabama” and “Free Bird,” Lynyrd Skynyrd went on hiatus after its touring plane crashed in Mississippi on Oct. 20, 1977, killing Ronnie Van Zant, guitarist Steven Gaines and four others. Twenty people, including Pyle, survived.
In 1987, surviving band members reunited for a “tribute tour,” prompting litigation that led to the consent order.
The plaintiffs, who include representatives of the estates of Ronnie Van Zant, Gaines and late guitarist Allen Collins, said they had issued a cease-and-desist letter last summer to halt the defendants’ plan for a movie titled “Free Bird.”
They said that while Pyle, who left the band in 1991, “is free to exploit his own personal life story,” the retitled movie would destroy their right to use the name and history of Lynyrd Skynyrd, causing “incalculable” loss and irreparable harm.
Such a movie “may contain a potentially inaccurate or skewed portrayal of Lynyrd Skynyrd’s story as filtered solely through the eyes of Pyle masquerading as the ‘True Story’ of a defining moment in the band’s history,” the plaintiffs said.
“Street Survivors” is now being edited, and could be ready for theaters in 2018, Perera said.
The case was assigned to U.S. District Judge Robert Sweet, who oversaw the 1988 consent order.
The case is Ronnie Van Zant Inc et al v. Pyle et al, U.S. District Court, Southern District of New York, No. 17-03360. ||||| MANHATTAN (CN) – Hoping to shut down an upcoming movie about the 1977 plane crash that killed members of the band Lynyrd Skynyrd, widow Judith Van Zant testified Tuesday that the film sensationalizes a tragedy governed by a decades-old settlement.
“Not in a million years would I have consented to it,” Van Zant said of the upcoming film “Street Survivors: The True Story of the Lynyrd Skynyrd Plane Crash.”
Back in 1988, representatives of several living and deceased members of the band reached a settlement governing the use of the band’s name along with the “name, likeness, portrait, picture, performances or biographical material” of Ronnie Van Zant, who founded the band and wrote most of their songs, and guitarist Steve Gaines.
Former drummer Artimus Pyle advised the upcoming film by Cleopatra Records but did not appear at Tuesday’s hearing, where Judith Van Zant called the movie a “compressed” and “sensationalized” story that fails to highlight Lynyrd Skynyrd’s greatness.
Among other things, she said the film incorrectly portrays the plane’s pilots as intoxicated, despite a toxicology report by the National Transportation Safety Board that disputes any allegations of alcohol or drugs and attributes the crash to strictly running out of fuel.
Pyle was reportedly playing a prototype of the 1970s video game “Pong” on board when the plane crashed in rural Mississippi. He survived the plane crash with less-serious injuries than those sustained by his fellow bandmates and road crew, only to be shot by a farmer while seeking help in the aftermath of the crash. The former drummer now lives outside of Ashville in Black Mountain, North Carolina.
U.S. District Judge Robert Sweet has presided over both the 1988 civil action and the current dispute.
To delineate the pre-crash and post-crash eras of the iconic Southern rock band, the 1988 consent decree requires post-crash incarnations of Lynyrd Skynyrd to include the year after the band name.
Van Zant’s widow testified today that the band dropped the year in the name around 1993.
She holds a 50 percent share of Ronnie Van Zant Inc., split with two of the songwriter’s daughters.
Ronnie Van Zant Inc. is named as co-plaintiff in the lawsuit along with current Lynyrd Skynyrd musicians Gary Rossington and Jonny Van Zant, and representatives for deceased members Allen Collins and Steve Gaines.
Butting heads with attorneys in cross-examination, Judith Van Zant appeared frustrated in trying to explain multiple times that she and the Estate of Ronnie Van Zant treat documentaries about the band differently than feature films using the names and likenesses the Ronnie Van Zant and Steve Gaines.
Van Zant described one band-approved movie about the band, currently in the treatment stage, as a passion project for producer Jeff Waxman, who previously produced the 1996 Lynyrd Skynyrd documentary “Freebird … The Movie.”
In a May 11 opposition brief, attorneys for Cleopatra Records argued that there is no risk of confusion “because Cleopatra is going to explicitly advise viewers at the outset of the film that it has not been authorized by the band or any of its members.”
Cleopatra’s attorneys have demanded that the script of their unreleased “Street Survivors” stay sealed during the trial.
Appeared via television link from Los Angeles, Cleopatra CEO Brian Perera testified Tuesday about Pyle’s role in “Street Survivors” as co-producer or consultant.
Perera said Pyle had been interviewed for details about the week leading up to the plane crash but did not write any of the film’s script.
Lynyrd Skynyrd still performs today, with Gary Rossington serving as the lone original founding member still with the band. Ronnie Van Zant’s brother Johnny took over on vocals for the band’s reunion in 1987, marking the 10th anniversary of the plane crash.
Founded as an obscure rock record label in 1992, Cleopatra Records recently acquired all U.S. rights to Morrissey biopic “Steven” with Jack Lowden as the legendary British singer and frontman of The Smiths. Following a number of smaller direct-to-video ventures and partnerships on indie titles, the acquisition marks the company’s expansion into film distribution and production.
Further testimony in the case is expected Wednesday.
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– Current members of Lynyrd Skynyrd, along with representatives of members now deceased, are suing to block a new documentary, claiming it tells only a "compressed" and "sensationalized" story about the group. Judith Van Zant—the widow of Lynyrd Skynyrd founder Ronnie Van Zant, one of six people killed when the band's touring plane crashed in Mississippi in 1977—argued in a Manhattan court Tuesday that Cleopatra Records' Street Survivors: The True Story of the Lynyrd Skynyrd Plane Crash wrongly suggests the pilots were intoxicated. What's more, Van Zant says the film also violates a 1988 consent order governing use of the band's name, along with the name, likeness, and biography of her former husband, reports Courthouse News. Band members Johnny Van Zant (Ronnie's brother) and Gary Rossington, as well as representatives for deceased members Allen Collins and Steve Gaines (who died in the crash), also protest the film, which offers former Lynyrd Skynyrd drummer Artimus Pyle's opinion on what happened. Pyle, one of 20 people to survive the crash, "is free to exploit his own personal life story," but the film's improper use of the name and history of Lynyrd Skynyrd and its "potentially inaccurate or skewed portrayal … of a defining moment in the band's history" will cause considerable loss and harm, the plaintiffs say, per Reuters. Cleopatra CEO Brian Perera maintains he's not in the wrong. He hopes to release the film, which Cleopatra lawyers say will clearly acknowledge it's not authorized by the band, in 2018.
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a 44-year - old male patient was admitted to our hospital with vague pelvic pain and questionable prostate symptoms .
his vital signs and physical examination , as well as the basic biochemical and complete blood count examinations , were within normal limits .
the patient was referred to our department by the attending physician for a ct examination to check for abdominal pathology .
ct examination revealed a centrally hypodense lesion that measured 8 cm in diameter with well - defined borders and an enhancing peripheral portion that radiated centrally to almost completely fill the splenic parenchyma ( fig .
mri study confirmed the ct findings , revealing a lesion with heterogeneous intensity with a centrally scattered hyperintense signal on the precontrast fat saturated t1-weighted images ; this was suggestive of hemorrhagic components , which were confirmed by pathologic analysis ( fig .
1c ) , the lesion appeared peripherally hyperintense and centrally hypointense with radiating enhanced areas towards the center of the lesion , which appeared hyperintense .
1d , e ) showed peripheral enhancement with progressive central progression in a radiating fashion on the late phase images , and this resembled a spoke - wheel pattern .
the central portion was not completely filled on the late phase images , and this was consistent with fibrosis , which was confirmed by the pathology report .
there was no lympadenaopathy or any other focal solid organ lesion that was suggestive of metastasis .
the gross examination revealed an enlarged spleen weighing 650 gr . a whitish firm nodule with hemorrhagic spiculations extending towards the normal splenic parenchyma was seen on the gross cut section .
microscopic examination depicted that the lesion was primarily composed of multiple angiomatoid nodules that were separated by sclerotic fibrous stroma .
round - shaped vascular spaces lined by endothelial cells were noted to be centrally circumscribed by granulomatoid structures ; these were the most prominent morphological features of these nodules .
the cells within the nodules had vesicular nuclei and they rarely contain eosinophilic nucleoli with rare mitosis .
immunohistochemical studies of the nodules revealed cd34-positive , cd31-positive and cd8-negative cells in the peripheral sector , while the central portion was mainly comprised of cd31-positive , cd34- and cd8- negative cells .
the patient did well during the post - surgical period and he was discharged four days after the surgery without any complications .
non - lymphomatoid tumors of the spleen are unusual and these are primarily of a vascular origin ( 4 ) .
most of these lesions are comprised of cavernous hemangiomas , while other disorders of this class , namely , hemangioendothelioma , littoral cell angiomas and hamartomas are rare .
sant of the spleen is a newly defined distinct pathological vascular disorder of the spleen by martel et al . ( 2 ) in 2004 ; the pathological analysis of this new entity was described in detail in their series of 25 patients .
they also concluded in their study that sant of the spleen is a benign disorder with no tendency for recurrence , and splenectomy offered complete cure to patients . in another manuscript by li et al .
( 3 ) , the ct findings were described together with an in - depth pathological analysis of a patient .
the reported lesion was hypodense , as in our patient , with an internal calcific focus that became indistinguishable from the surrounding splenic parenchyma on the late portal phase images . in our patient ,
the lesion demonstrated diffuse peripheral enhancement on the early arterial phase with progressive centripedal filling in a radiating pattern , while its center remained hypodense and hypointense on the late phase images of ct and mri , respectively . to the best of our knowledge ,
although rare , sant should be considered in the differential diagnosis for hypervascular lesions of the spleen .
sant was reported to cause no symptoms in the affected patients and it is generally incidentally detected .
its clinical prognosis was reported to be excellent with complete cure after splenectomy ( 2 ) .
making the differential diagnosis among the other benign and malignant vascular lesions of the spleen may be difficult .
angiosarcoma , the most prevalent primary malignant vascular entity , may sometimes be difficult to differentiate from other benign lesions .
however , considering their highly aggressive biological nature , it would be highly unusual to see an angiosarcoma of this size to be restricted to only the spleen without any distant metastasis .
littorall cell angioma may be differentiated due to its typical multiple hypodense nodules and considering the solitary appearance of sant of the spleen ( 2 ) .
although lymphoma must also be kept in mind for splenic lesions , the absence of splenomegaly , the solitary character of the lesion and the absence of any associated intraabdominal lympadenopathy may be helpful clues for making the differential diagnosis ( 2 ) .
also , the general well - being of the patient and the absence of any other clinical symptoms regarding lymphoma may be other supportive findings against the diagnosis of lymphoma .
it may be difficult or impossible to confidently differentiate sant of the spleen from other benign disorders of the spleen like hamartoma and inflammatory pseudotumor of the spleen with using only the images .
the scarcity of data on the imaging characteristics of the sant of the spleen make this even more problematic .
so , we think that pathological examination and invasive treatment may be almost always indicated for making the correct diagnosis with the currently available data . in conclusion , sant is a rare vascular lesion of the spleen and its incidence may increase , after its recent description as a separate clinico - pathologic entity .
mri may be helpful for the diagnosis of splenic nodular angiomatoid transformation by demonstrating a spoke - wheel pattern on mri with centripedal filling in a radiating pattern , and the splenic mass may contain fibrotic and hemorrhagic components . the description of the radiological and clinical features of this entity in a large series may also increase the recognition of sant by practicing radiologists .
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sclerosing angiomatoid nodular transformation of the spleen is a recently described benign pathologic entity that is characterized by round shaped vascular spaces that are lined by endothelial cells , and the spaces are circumscribed by granulomatoid structures .
microscopically , all the reported cases had multiple angiomatoid nodules in a fibrosclerotic stroma .
each angiomatoid nodule was made up of slit - like , round or irregular shaped vascular spaces that were lined by endothelial cells and interspersed ovoid cells .
we present here the ct and dynamic gadolinium - enhanced mr findings of a patient with sclerosing angiomatoid nodular transformation .
the spoke - wheel pattern that was observed on mri in this case may be an important imaging clue for making the correct diagnosis of this benign lesion .
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pyogenic liver abscess ( pla ) is a crucial clinical disease that can be fatal without prompt recognition and treatment .
an increasing number of studies have demonstrated that pla in western and asian countries differs in many aspects , including demographic characteristics , etiological factors , and clinical manifestations .
for example , a significant proportion of pla in asia is associated with klebsiella pneumoniae infection , whereas escherichia coli is the predominant pathogen found in pla in western countries . moreover , pla in asia is typically associated with diabetes or a cryptogenic etiology , compared with the biliary etiology observed in western countries .
colonic diverticular diseases are a relatively common health care problem and the most frequently reported pathology in routine colonoscopy .
autopsy studies have estimated the diverticular - disease prevalence at 5% to 52% in western countries , and 1% to 19% in asia . approximately one - third of the population older than 45 years is estimated to have diverticular disease .
diverticular diseases can lead to disruption of the colonic mucosal barrier and therefore major clinical morbidities , including inflammation , obstruction , infection , hemorrhage , fistula formation , perforation , and peritonitis .
previous studies have demonstrated that the hematogenous spread of pathogens to the liver is a critical pathogenic factor for pla , and colonic mucosal defects might be a route for bacterial invasion into the portal system . in a relatively small cohort study ,
however , no study has been conducted in asia to investigate the epidemiologic association between diverticular diseases and pla by using a nationwide population - based dataset .
we therefore hypothesized that patients with diverticular diseases may have a higher risk of pla than patients without diverticular diseases and conducted this study by analyzing data from taiwan 's national health insurance research database ( nhird ) , which is composed of deidentified medical claims from 99% of the 23 million residents of taiwan .
the national health insurance ( nhi ) program was implemented in taiwan on march 1 , 1995 , and provides insurance coverage for approximately 99% of the population of taiwan ( ref1 ) .
the national health research institutes ( nhri ) maintains the nhird , comprising the administrative and health claims data of the nhi program , and makes it available for medical research . in this study , we used a subset of the nhird that includes files of inpatient claims from the registry of beneficiaries .
the identification numbers of patients were scrambled before being released to users to protect the privacy of the insurant .
diseases are coded according to the international classification of diseases , ninth revision , clinical modification ( icd-9-cm ) .
this study was approved to fulfill the condition for exemption by the institutional review board ( irb ) of china medical university ( cmuh-104-rec2115 ) .
we identified patients with newly diagnosed diverticular diseases , including diverticulosis ( icd-9-cm codes 562.10 , 562.12 ) and diverticulitis ( icd-9-cm codes 562.11 , 562.13 ) , from 2000 to 2011 , from inpatient claims data .
the initial date of hospitalization with a diagnosis of diverticular - disease was defined as the index date .
patients with history of pla ( icd-9-cm code 572.0 ) or amebic liver abscess ( icd-9-cm code 006.3 ) , missing data for sex or date of birth , or aged younger than 20 years were excluded from our study .
nhi beneficiaries aged 20 years and older without diverticular were randomly selected for inclusion in a nondiverticulosis cohort and frequency matched with the patients in the diverticular cohort at a 4:1 ratio according to age ( in 5-year bands ) , sex , history of diabetes mellitus ( icd-9-cm code 250 ) , and index year , and the same exclusion criteria were applied .
person - years of follow - up were calculated for each patient until pla diagnosis or censoring because of loss to follow - up , death , withdrawal from the insurance program , or the end of 2011 .
the comorbidities comprised well - known risk factors for pla , namely , alcoholic liver disease ( icd-9-cm codes 571.0 , 571.1 , 571.3 ) , cholecystitis ( icd-9-cm code 575 ) , cancer ( icd-9-cm codes 140 - 208 ) , chronic obstructive pulmonary disease ( copd ) ( icd-9-cm codes 491 , 492 , 496 ) , choledocholithiasis ( icd-9-cm code 574 ) , cholangitis ( icd-9-cm code 576.1 ) , diabetes mellitus ( icd-9-cm code 250 ) , hyperlipidemia ( icd-9-cm code 272 ) , hypertension ( icd-9-cm codes 401 - 405 ) , heart failure ( icd-9-cm code 428 ) , liver cirrhosis ( icd-9-cm codes 571.2 , 571.5 , 571.6 ) , and pancreatic diseases ( icd-9-cm code 577 ) .
student t - tests and chi - square tests were used to examine the differences in the demographic characteristics and comorbidities between the diverticular - disease and nondiverticular - disease cohorts .
the incidence density rates ( per 10,000 person - year ) of pla were estimated for both cohorts according to sex , age , and comorbidities .
univariate and multivariate cox proportional hazards regression analysis was used to assess the risk of developing pla associated with diverticular diseases , compared with the nondiverticular - disease cohort .
the hazard ratios ( hrs ) and 95% confidence intervals ( cis ) were estimated in the cox model .
the multivariate models were simultaneously adjusted for age , sex , and comorbidities of diabetes mellitus , hypertension , hyperlipidemia , cancer , copd , heart failure , choledocholithiasis , alcoholic liver disease , liver cirrhosis , cholangitis , cholecystitis , and pancreatic diseases .
all data processing and statistical analyses were performed using sas version 9.4 ( sas institute , inc . , cary , nc ) ; 2-tailed p < .05 was considered statistically significant .
the national health insurance ( nhi ) program was implemented in taiwan on march 1 , 1995 , and provides insurance coverage for approximately 99% of the population of taiwan ( ref1 ) .
the national health research institutes ( nhri ) maintains the nhird , comprising the administrative and health claims data of the nhi program , and makes it available for medical research . in this study , we used a subset of the nhird that includes files of inpatient claims from the registry of beneficiaries .
the identification numbers of patients were scrambled before being released to users to protect the privacy of the insurant .
diseases are coded according to the international classification of diseases , ninth revision , clinical modification ( icd-9-cm ) .
this study was approved to fulfill the condition for exemption by the institutional review board ( irb ) of china medical university ( cmuh-104-rec2115 ) .
we identified patients with newly diagnosed diverticular diseases , including diverticulosis ( icd-9-cm codes 562.10 , 562.12 ) and diverticulitis ( icd-9-cm codes 562.11 , 562.13 ) , from 2000 to 2011 , from inpatient claims data .
the initial date of hospitalization with a diagnosis of diverticular - disease was defined as the index date .
patients with history of pla ( icd-9-cm code 572.0 ) or amebic liver abscess ( icd-9-cm code 006.3 ) , missing data for sex or date of birth , or aged younger than 20 years were excluded from our study .
nhi beneficiaries aged 20 years and older without diverticular were randomly selected for inclusion in a nondiverticulosis cohort and frequency matched with the patients in the diverticular cohort at a 4:1 ratio according to age ( in 5-year bands ) , sex , history of diabetes mellitus ( icd-9-cm code 250 ) , and index year , and the same exclusion criteria were applied .
person - years of follow - up were calculated for each patient until pla diagnosis or censoring because of loss to follow - up , death , withdrawal from the insurance program , or the end of 2011 .
the comorbidities comprised well - known risk factors for pla , namely , alcoholic liver disease ( icd-9-cm codes 571.0 , 571.1 , 571.3 ) , cholecystitis ( icd-9-cm code 575 ) , cancer ( icd-9-cm codes 140 - 208 ) , chronic obstructive pulmonary disease ( copd ) ( icd-9-cm codes 491 , 492 , 496 ) , choledocholithiasis ( icd-9-cm code 574 ) , cholangitis ( icd-9-cm code 576.1 ) , diabetes mellitus ( icd-9-cm code 250 ) , hyperlipidemia ( icd-9-cm code 272 ) , hypertension ( icd-9-cm codes 401 - 405 ) , heart failure ( icd-9-cm code 428 ) , liver cirrhosis ( icd-9-cm codes 571.2 , 571.5 , 571.6 ) , and pancreatic diseases ( icd-9-cm code 577 ) .
student t - tests and chi - square tests were used to examine the differences in the demographic characteristics and comorbidities between the diverticular - disease and nondiverticular - disease cohorts .
the incidence density rates ( per 10,000 person - year ) of pla were estimated for both cohorts according to sex , age , and comorbidities .
univariate and multivariate cox proportional hazards regression analysis was used to assess the risk of developing pla associated with diverticular diseases , compared with the nondiverticular - disease cohort .
the hazard ratios ( hrs ) and 95% confidence intervals ( cis ) were estimated in the cox model .
the multivariate models were simultaneously adjusted for age , sex , and comorbidities of diabetes mellitus , hypertension , hyperlipidemia , cancer , copd , heart failure , choledocholithiasis , alcoholic liver disease , liver cirrhosis , cholangitis , cholecystitis , and pancreatic diseases .
all data processing and statistical analyses were performed using sas version 9.4 ( sas institute , inc . , cary , nc ) ; 2-tailed p < .05 was considered statistically significant .
table 1 shows comparisons of the demographic characteristics and comorbidities of the diverticular - disease and nondiverticular - disease patients .
the mean ( standard deviation [ sd ] ) age of the diverticular - disease cohort was 57.7(18.1 ) years and that of the nondiverticular - disease cohort was 57.2(18.1 ) years , with 37.1% of the patients aged 49 years .
women were predominant ( 55.8% vs 44.2% ) . the principal diseases including hypertension , hyperlipidemia , cancer , copd , heart failure , choledocholithiasis , alcoholic liver disease , liver cirrhosis , cholangitis , cholecystitis , pancreatic diseases , and percutaneous aspiration of the gallbladder and biliary tract in diverticular - disease patients were higher than those in the nondiverticular - disease cohort ( table 1 ) .
the mean follow - up periods were 4.79 3.12 years for the diverticular cohort and 5.09 3.06 years for the nondiverticular cohort .
characteristics of patients between patients with diverticular and patients without diverticular then , we determined the incidence of pla in both groups and found that diverticular diseases were associated with a significantly elevated risk of pla ( table 2 ) .
the crude incidence of pla was 2.44-fold higher in the diverticular - disease cohort than in the nondiverticular - disease cohort ( 11.5 vs 4.65 per 10,000 person - year ) ( table 2 ) .
after adjustment for age , sex , and comorbidities , the adjusted hr ( ahr ) for developing pla during follow - up was 2.10 ( 95% ci , 1.812.44 ) for the diverticular - disease cohort , as compared with the nondiverticular - disease cohort .
incidence and hazard ratio of pyogenic liver abscess between patients with diverticular and without diverticular stratification analyses were performed to evaluate the risk of pla in the subgroups stratified according to their sexes , ages , and comorbidities ( table 2 ) .
our results showed that the elevated risk of pla in patients with diverticular diseases could be observed in every stratification analysis .
the risk of pla in patients with diverticular diseases was significantly higher than in patients without diverticular disease , after stratification for sex ( ahr , 1.83 , 95% ci , 1.432.43 for women ; ahr , 2.27 , 95% ci , 1.882.75 for men ) , age ( ahr , 4.03 , 95% ci , 2.775.85 for patients aged 49 years ; ahr , 2.17 , 95% ci , 1.642.28 for patients aged 5064 years ; ahr , 1.65 , 95% ci , 1.342.03 for the group aged 65 years ) , and comorbidities ( ahr , 2.94 , 95% ci , 2.323.73 for patients without comorbidities ; ahr , 1.65 , 95% ci , 1.371.98 for patients with comorbidities ) .
we then explored whether the inflammation of colonic diverticula was associated with pla risks . the incidence and relative risks of pla in patients with diverticulosis and diverticulitis
compared with the nondiverticular - disease cohort , patients with diverticulosis had a significantly increased risk of pla ( ahr , 2.26 , 95% ci , 1.862.75 ) , followed by patients with diverticulitis ( ahr , 1.98 , 95% ci , 1.652.38 ) .
incidence and hazard ratio of pyogenic liver abscess between different entities diverticular diseases finally , we would like to validate the accountability of our results by calculating the risk of pla in the patients with some known risk factors of pla .
theoretically , we should be able to demonstrate that patients with pla risk factors , such as cholangitis , cholelithiasis , and diabetes mellitus , exhibited relatively high ahrs .
on the other hand , patients with comorbidities not related to pla should have lower ahrs of pla . compared with the patients without diverticular diseases and comorbidities , those with only cholangitis had a higher risk of pla ( ahr , 29.8 , 95% ci , 7.39120.1 ) followed by those with only diabetes mellitus ( ahr , 3.35 , 95% ci , 2.494.51 ) , those with only choledocholithiasis ( ahr , 2.50 , 95% ci , 1.185.31 ) , and those with only copd ( ahr , 2.33 , 95% ci , 1.194.56 ) ( table 4 ) . moreover , compared with the diverticular - disease patients without these comorbidities , among the diverticular - disease patients , those with 5 or more comorbidities had a significantly increased risk of pla ( ahr , 8.08 , 95% ci , 4.3814.9 ) , followed by those with 4 comorbidities ( ahr , 5.30 , 95% ci , 3.079.15 ) , those with 3 comorbidities ( ahr , 4.06 , 95% ci , 2.696.14 ) , those with any 2 comorbidities ( ahr , 4.53 , 95% ci , 3.366.60 ) , and those with 1 comorbidity ( ahr , 4.26 , 95% ci , 3.325.47 ) , regardless of comorbidity type .
joint effects for acute coronary syndrome between diverticular and acute coronary syndrome - associated risk factor
this study is the first to address the long - term risk of pla in asian patients with diverticular diseases through analysis of a nationwide database with widespread coverage and complete follow - up evaluation .
this population - based cohort study demonstrates that the diverticular - disease cohort exhibited a significantly elevated risk of pla ; after mortality was accounted for as a competing cause of risk and multiple known confounding factors were adjusted for .
additional clinical and basic studies are warranted for further investigation of the underlying causes of the observation in the present study .
studies have reported that pla can occur secondary to asymptomatic sigmoid diverticulitis and colon cancer .
the present study , in analyzing a 13-year longitudinal database , further established a link between pla and diverticular diseases .
the large sample sizes collected in the present study enabled a highly reliable statistical analysis for assessing the pla risk in patients with diverticular diseases and therefore avoided selection and recall biases . over the past few decades
, the mortality associated with pla has decreased gradually from more than 50% before the 1980s .
however , recent studies have reported that pla has continued to have a significant in - hospital mortality rate since 2000 , ranging from 2.5% to 10% .
the presentation of pla is often nonspecific , and its diagnosis requires a high degree of clinical suspicion .
the median symptomatic duration prior to the diagnosis of pla has been reported as approximately 1 week , whereas only 15% to 55% of pla patients present with localized right upper quadrant tenderness .
therefore , identifying groups of patients who are at a risk of pla is imperative .
based on the observations in this study , patients with diverticular diseases should undergo image screening for pla when there is any clinical suspicion .
diverticular diseases are associated with old age and diabetes , which was also found in the present study .
moreover , 10% to 25% of patients with diverticular diseases experience diverticulitis and its related complications , and therefore may undergo surgery at some point . therefore , these unfavorable factors may compromise a patient 's immunity and predispose the occurrence of pla .
as mentioned , a substantial proportion of patients with diverticular diseases encounter colonic inflammation , bleeding , and even perforation .
theoretically , mucosal disruption and underlying blood vessel exposure caused by diverticular inflammation may facilitate hematogenous spreading of colonic bacteria into portal circulation and the liver parenchyma .
this hypothesis is further supported by a previous observation that nearly one - fourth of patients with cryptogenic pla had a colonic cause when they underwent colonoscopic investigation .
in addition to translocation via the mucosal defects , some intestinal bacteria , including k. pneumoniae , could also enter the bloodstream directly without breaking the mucosal integrity . in - vitro and
in - vivo studies suggested that k. pneumoniae could translocate across the colonic epithelium via rho gtpase - and phosphatidylinositol 3-kinase / akt - dependent mechanisms .
other studies have reported that the expression of rho gtpase and phosphatidylinositol 3-kinase / akt activities were both enhanced within inflamed colonic segments .
it will be of clinical interest to investigate whether direct bacterial translocation via intact intestinal mucosa contributes to the occurrence of pla in patients with diverticular diseases .
one possible confounding factor in our observation is that the diverticular - disease cohort may have had a higher risk of colorectal cancer , which is known as a risk factor for pla .
whether colonic diverticular diseases are associated with an increased risk of colorectal cancer remains controversial .
diverticular diseases have been suggested to be a predisposing factor for left - side colorectal cancer . in a case control study , sigmoid diverticulitis was associated with a significantly higher risk of left - side colorectal cancer , with an odds ratio of 4.2 .
conversely , our previous study did not reveal any association between diverticular diseases and colorectal cancer . because we adjusted for cancer as comorbidity ,
there are some study limitations : the database has no detailed data about the smoking , alcohol , exercise , incomes , and diabetes mellitus control , which may the potentially confounding factors regarding the study biases ; no detailed data in eastern populations the to do further analyses about the prevalence and pattern of diverticular diseases , usually in the right - side colon .
in addition , the pathogens of pla may be different based on the location ; we could not to confirm the diagnoses of pla and diverticular diseases by checking the individual patient 's medical record .
however , these hospitalized patients whose diagnoses were strictly audited for reimbursement in this study ; these patients were included from the database of inpatient admission , which is the potential selection bias .
all of the above these study limitations might cause underestimated or overestimated the association between diverticular diseases and the risk of pla . in summary
, we determined that asian patients with diverticular diseases have a significantly increased risk of pla . based on our findings , further study on the rates of pla for patients with diverticular diseases
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abstractwhether patients with diverticular diseases exhibit a higher risk of developing pyogenic liver abscess ( pla ) remains inconclusive.from the inpatient claims in taiwan 's national health insurance research database , we identified 54,147 patients diagnosed with diverticulosis in the 1998 to 2010 period and 216,588 controls without the disorder .
the 2 cohorts were matched by age , sex , and admission year , and were followed up until the end of 2010 to estimate the risk of pla.overall , the incidence of pla was 2.44-fold higher in the diverticular - disease group than in the controls ( 11.5 vs 4.65 per 10,000 person - year ) .
the adjusted hazard ratio ( ahr ) of pla was 2.11 ( 95% confidence interval [ ci ] , 1.812.44 ) for the diverticular - disease group , according to a multivariate cox proportional hazards regression model .
the age - specific data showed that the ahr for the diverticular - disease group , compared with the controls , was the highest inpatients younger than 50 years old ( ahr , 4.03 ; 95% ci , 2.775.85 ) .
further analysis showed that the diverticular - disease group exhibited an elevated risk of pla regardless of whether patients had diverticulitis.the patients with diverticular diseases exhibited a higher risk of pla .
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we thank h. chen , a. e. hosoi , c. pipe , m. roper and h. stone for useful discussions . this work was supported in part by the charles reed fund at mit and by the national science foundation ( cts-0624830 ) g. segre and a. silberberg .
behaviour of macroscopic rigid spheres in poiseuille flow .
determination of local concentration by statistical analysis of particle passages through crossed light beams .
, 14:115 135 , 1962 .
s. childress .
forward flapping flight as a bifurcation in the frequency reynolds number . in s .-
sohn j. r. kweon , s .- c .
kim , editor , _ proceedings of the 2004 international workshop on mathematical fluid dynamics and applications _ , pages 921
. 2004 . in a related study , m. roper and h. a. stone ( personal communication )
have recently shown that the reciprocal oscillatory translation of a solid body could lead to a net rotation for arbitrarily small values of the frequency reynolds number .
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purcell s scallop theorem defines the type of motions of a solid body - reciprocal motions - which can not propel the body in a viscous fluid with zero reynolds number .
for example , the flapping of a wing is reciprocal and , as was recently shown , can lead to directed motion only if its frequency reynolds number , @xmath0 , is above a critical value of order one . using elementary examples
, we show the existence of oscillatory reciprocal motions which are effective for all arbitrarily small values of the frequency reynolds number and induce net velocities scaling as @xmath1 ( @xmath2 ) .
this demonstrates a continuous breakdown of the scallop theorem with inertia .
a large variety of biological movements occur in a fluid environment , from swimming bacteria to whales . in many cases ,
the study of fluid forces is crucial to the understanding of animal locomotion @xcite . because of the large range of relevant length scales in biological motility - eight orders of magnitude in size , from less than a hundred nanometers to tens of meters - fluid mechanics occurs in distinct regimes with important mechanical consequences . on small length scales ,
the relevant reynolds number is usually very small ( @xmath3 for swimming _ e. coli _ ) and viscous forces are dominant .
this is the stokesian realm of swimming microorganisms such as bacteria , spermatozoa , and ciliated cells . at the opposite end of the range of length scales ,
the reynolds numbers are typically very large ( @xmath4 for a swimming tuna ) and inertial forces are dominant .
this is the eulerian realm of flying birds and swimming fishes . in this paper
, we address the transition from the stokesian to the eulerian realm , and show that , in some situations , this transition can take place continuously with an increase of the relevant reynolds number . in his 1977 lecture _ life at low reynolds numbers _
, edward purcell introduced the scallop theorem " @xcite .
he observed that the stokes equations , which govern fluid flows at zero reynolds numbers and are both linear and independent of time , are identical under time reversal .
consequently , there exists a certain geometrical class of motion ( or , more generally , actuation of a solid body ) , termed `` reciprocal motion '' , which can not lead to any locomotion in this limit . a reciprocal motion ( or actuation ) is a motion in which the geometrical paths followed by various material points on the body are identical when viewed under time reversal . by symmetry , such motion can only lead to a net movement equal to minus itself , and therefore , no net movement at all ( see also refs .
@xcite ) .
the simplest example of a reciprocal motion is a periodic motion composed of two distinct parts . in the first part
, the body moves in a certain prescribed way , and in the second part , the body moves in a manner which is identical to the first - part as seen under time reversal .
a scallop opening and closing belongs to this subclass of reciprocal motion and , independently of the rate of opening and closing , the scallop can not move .
another example of reciprocal motion - or , in this case , reciprocal actuation - is a flapping body .
consider a solid body oscillated up and down in translation in a prescribed manner by an external means .
since the motion going up is the time - reversal symmetry of the motion going down , the flapping body does not move on average in the limit of zero reynolds numbers . however , large animals such as birds use flapping wings for locomotion , and so clearly a thin flapping body must be effective in the eulerian realm .
the question then arises : when does a flapping body - or more generally a reciprocal motion - become effective ?
how much inertial force is necessary to break the constraints of the scallop theorem ?
this question was first formulated and studied by childress and dudley @xcite .
the mollusc _
clione antarctica _ was observed to possess two modes of locomotion .
the first is non - reciprocal and uses cilia distributed along the body of the mollusc .
the second is reciprocal and consists of two flapping wings .
the flapping - wing mode was observed to be predominant for the large swimming velocities . using both experimental observations and fluid mechanics models
, the authors postulated that reciprocal motions are ineffective in producing any net motion unless the relevant frequency - or `` flapping '' - reynolds number , @xmath0 , is sufficiently large ( order unity ) .
in other words , the transition from no - motion to motion occurs at a finite value of @xmath0 and the breakdown of the scallop theorem is discontinuous .
this idea was subsequently studied in laboratory experiments @xcite and numerical simulations @xcite of flapping symmetric bodies , both of which confirmed the transition to directed motion as a symmetry - breaking instability occurring at a finite value of the frequency reynolds number , as well as the robustness of this transition to a change in a variety of geometrical and mechanical parameters . in this paper , we consider a series of elementary oscillatory reciprocal motions of a solid body with broken spatial symmetries and show that they become effective in producing a net translation of the body for arbitrarily small values of the frequency reynolds number , with induced velocities scaling as @xmath1 ( @xmath2 , _ inertial creep _ @xcite ) .
this demonstrates a continuous breakdown of the scallop theorem with inertia .
the examples we propose rely on classical results of lift forces for the motion of spherical particles at small reynolds number @xcite .
we consider a solid spherical particle ( density @xmath5 , radius @xmath6 ) oscillating with frequency @xmath7 and amplitude @xmath8 in a fluid of density @xmath9 and shear viscosity @xmath10 .
the three different setups we propose are described below , and we start by some general remarks . in the case of purely translational motion , including the effect of inertia on the particle motion can be done in a number of limits , as there are in general three relevant reynolds numbers .
firstly , the unsteady term in the navier - stokes equations scales as @xmath11 ( where @xmath12 is the typical speed of translation ) , and is smaller than the typical viscous term , of order @xmath13 , by a factor of @xmath14 , where @xmath15 is the kinematic viscosity .
secondly , the nonlinear advective term in the navier - stokes equations scales with @xmath16 , and is smaller than the viscous term by a factor of @xmath17 , which is the flapping ( or `` frequency '' ) reynolds number @xcite .
thirdly , the particle inertia is quantified by a particle reynolds number , @xmath18 , the ratio of the typical rate of change of the particle momentum , @xmath19 , to the typical viscous forces on the particle , @xmath20 . in this paper , we will consider the asymptotic limit where @xmath21 so that the motion of the flapper is quasi - static and the leading - order departure of the fluid forces from the stokes laws is due to the nonlinear advective term in the navier - stokes equations @xcite .
the limit described by eq .
is equivalent to that of small frequency reynolds number ( @xmath22 ) and large flapping amplitude ( @xmath23 and @xmath24 ) .
note that this is a different limit from the work in refs .
@xcite where body inertia likely played an important role .
we consider below three examples of such large - amplitude low-@xmath0 reciprocal flapping which lead to directed motion for arbitrarily small values of @xmath25 . ) for arbitrarily small values of the frequency reynolds number . in each example , the reciprocal motion is composed of the periodic repetition of two distinct parts , with the second part ( bottom ) being identical to the first part ( top ) as seen under time reversal : ( a ) oscillation in vertical position of a sphere parallel to a solid surface leads to motion perpendicular to the surface ; ( b ) in - phase oscillations in translation and rotation of a sphere leads to motion perpendicular to both the directions of translation and rotation ; ( c ) oscillation in vertical position of a sphere in an oscillating shear flow ( in phase ) leads to motion perpendicular to the direction of translation ; in all cases , @xmath26 denotes the ( small ) sphere velocity induced by inertial forces . in case ( a ) , the distance to the solid surface is denoted @xmath27 . ]
the first example is that of a flapper near a wall . specifically , we consider the reciprocal oscillation in vertical position of the solid sphere with velocity @xmath28 parallel to a stationary solid surface and free to move in the @xmath29 and @xmath30 directions ( see notations in fig .
[ mainfig]a ) .
in the stokes flow limit ( @xmath31 ) , the sphere experiences no lift force , and remains at a constant distance , @xmath27 , to the solid surface .
the first effect of inertia on this problem , in the limit set by eq . , is the appearance of a lift force , directed away from the solid surface , and independent of the sign of @xmath32 @xcite .
such a limit is captured when the oseen length scale @xmath33 , the distance away from the sphere where inertial forces become important , is much larger than all relevant length scales of the problem , _
i.e. _ the sphere radius , @xmath6 , and its distance to the surface , @xmath27 . in the simple case where @xmath34 , the lift force leads to a low - reynolds number lift velocity for
the particle @xcite @xmath35 always directed away from the surface . for an oscillatory motion ,
@xmath36 , the lift velocity away from the surface averages over one period to @xmath37 a flapper near a wall performing a reciprocal translational motion is therefore able to move forward ( away from the wall ) for arbitrarily small values of the frequency reynolds number .
this inertial migration decreases to zero with the first power of the reynolds number ( @xmath38 ) , and the stokes limit is recovered when we formally set @xmath31 in eq . .
our second example is that of a rotating flapper .
we consider the case where the solid sphere is oscillating both in translation and rotation , with velocity and rotation rates given by @xmath39 and @xmath40 , and is free to move in the @xmath29 and @xmath30 direction ( see fig .
[ mainfig]b ) .
if the two oscillations are in phase , the actuation of the sphere is reciprocal , which we will assume here , and no average motion is obtained in the stokes limit .
if @xmath41 is the typical magnitude of @xmath42 , the rotation reynolds number @xmath43 measures the importance of inertial forces due to the rotational motion . in the asymptotic limit set by eq . , and for @xmath44 , the first effect of inertia is the appearance of a lift force perpendicular to both the directions of translation and rotation @xcite and given by @xmath45 .
this results in a low - reynolds number lift velocity @xmath46 when @xmath47 , we obtain an average translational velocity , along the @xmath29 direction , given by @xmath48 here again , the reciprocal translational and rotational motion of the solid sphere leads to a directed motion for arbitrarily small values of the reynolds number .
the magnitude of this directed motion also decreases to zero with the first power of @xmath0 ( @xmath49 ) . as a final example , we show that these results are also valid when the fluid in the far - field is not quiescent by considering a flapper in a shear flow .
specifically , as shown in fig .
[ mainfig]c , we consider the case when the solid sphere is oscillating in vertical position with a prescribed velocity , @xmath50 , in a shear flow described by the far - field undisturbed flow field @xmath51 ( the center of the sphere is located at @xmath52 ) and is free to move in the @xmath29 and @xmath30 directions .
if the two oscillations are in phase , the motion of the sphere is reciprocal , which we assume here , and no average motion is obtained in the limit of zero reynolds number .
we also assume that the sphere is far away from the surfaces responsible for the creation of the shear flow and therefore ignore wall effects @xcite .
if @xmath53 denotes the typical magnitude of @xmath54 , an additional reynolds number , @xmath55 , needs to be introduced . here , the first effect of inertia is the appearance of a lift force directed across the undisturbed streamlines @xcite .
the original study , due to saffman @xcite , calculated this lift force in the limit where @xmath56 , and in this case the lift force is moving the sphere in the direction opposite to its translational velocity .
we consider here the same asymptotic limit , together with the limit assumed in eq . .
in this case , and if @xmath57 , the sphere experiences a low - reynolds number lift velocity given by @xmath58 where @xmath59 is a numerical coefficient . for an oscillatory motion @xmath60 , and with @xmath61 to satisfy saffman s asymptotic limit , we get an average velocity , along the @xmath29 direction , given by @xmath62 where @xmath63 . as in the previous cases , the actuation of the sphere is reciprocal and yet it leads to a directed motion for arbitrarily small values of the frequency reynolds number @xmath0 . here , however , the magnitude of the induced velocity decreases to zero with the square - root of the reynolds number ( @xmath64 ) . also , in this case , the motion will continue until the point along the @xmath29 axis where the local velocity from the shear flow cancels out the translational velocity of the sphere . as a summary
, we have presented elementary examples of oscillatory reciprocal forcing of a solid body leading to net translational motion of the body for arbitrarily small values of the frequency reynolds number , @xmath0 . when the frequency reynolds number is formally set to zero
, the effect disappears as dictated by the scallop theorem , but it remains non - zero for all non - zero values of @xmath0 .
the induced average velocities scale as @xmath1 ( @xmath2 ) , corresponding to the limit of asymptotically large strouhal number , @xmath65 .
this demonstrates that the breakdown of purcell s scallop theorem with inertia can take place in a continuous way without a finite onset of translational motion . as our examples show , a directed motion on the order of the flapping velocity will take place when @xmath66 .
moreover , the mechanical efficiencies of the examples above - ratio of the useful work to the total work done by the flapper - scale as @xmath67 so that order one efficiencies should also be expected for order one reynolds numbers . from a biological perspective , both these observations suggest that reciprocal gaits are very inefficient for small reynolds number and become advantageous only when @xmath66 . consequently , and even in the absence of a mathematical bifurcation , the onset of an appropriately defined `` efficient flapping flight '' is expected occur at a finite value of @xmath0 @xcite .
furthermore , it is important to note that all of our examples display some spatial broken symmetries which govern the direction of the net motion of the solid body : ( a ) the location of the wall , ( b ) the direction of the rotation rate , and ( c ) the direction of the shear flow .
this is somewhat different from the `` flapping wing '' setup studied experimentally in refs .
@xcite and numerically in refs .
@xcite where both the shape and the actuation of the wing are symmetric and where locomotion is a result of a hydrodynamic instability @xcite .
finally , we have considered examples leading to net translational motion , but similar examples exploiting lift forces and torques on asymmetric particles @xcite could be devised leading to a net rotation , or combined translation and rotation , of the solid body @xcite .
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SECTION 1. SHORT TITLE.
That this Act may be cited as the ``Assets for Independence Act
Amendments of 2000''.
SEC. 2. MATCHING CONTRIBUTIONS UNAVAILABLE FOR EMERGENCY WITHDRAWALS.
Section 404(5)(A)(v) of the Assets for Independence Act (42 U.S.C.
604 note) is amended by striking ``, or enabling the eligible
individual to make an emergency withdrawal''.
SEC. 3. ADDITIONAL QUALIFIED ENTITIES.
Section 404(7)(A) of the Assets for Independence Act (42 U.S.C. 604
note) is amended--
(1) in clause (i), by striking ``or'' at the end thereof;
(2) in clause (ii), by striking the period at the end and
inserting ``; or''; and
(3) by adding at the end the following new clause:
``(iii) an entity that--
``(I) is--
``(aa) a credit union
designated as a low-income
credit union by the National
Credit Union Administration
(NCUA); or
``(bb) an organization
designated as a community
development financial
institution by the Secretary of
the Treasury (or the Community
Development Financial
Institutions Fund); and
``(II) can demonstrate a
collaborative relationship with a local
community-based organization whose
activities are designed to address
poverty in the community and the needs
of community members for economic
independence and stability.''.
SEC. 4. HOME PURCHASE COSTS.
Section 404(8)(B)(i) of the Assets for Independence Act (42 U.S.C.
604 note) is amended by striking ``100'' and inserting ``120''.
SEC. 5. INCREASED SET-ASIDE FOR ECONOMIC LITERACY TRAINING AND
ADMINISTRATIVE COSTS.
Section 407(c)(3) of the Assets for Independence Act (42 U.S.C. 604
note) is amended--
(1) by striking ``9.5'' and inserting ``15''; and
(2) by inserting after the first sentence the following:
``Of the total amount specified in this paragraph, not more
than 7.5 percent shall be used for administrative functions
under paragraph (1)(C), including program management, reporting
requirements, recruitment and enrollment of individuals, and
monitoring. The remainder of the total amount specified in this
paragraph (not including the amount specified for use for the
purposes described in paragraph (1)(D)) shall be used for
nonadministrative functions described in paragraph (1)(A),
including case management, budgeting, economic literacy, and
credit counseling. If the cost of nonadministrative functions
described in paragraph (1)(A) is less than 5.5 percent of the
total amount specified in this paragraph, such excess funds may
be used for administrative functions.''.
SEC. 6. ALTERNATIVE ELIGIBILITY CRITERIA.
Section 408(a)(1) of the Assets for Independence Act (42 U.S.C. 604
note) is amended by striking ``does not exceed'' and inserting ``is
equal to or less than 200 percent of the poverty line (as determined by
the Office of Management and Budget) or''.
SEC. 7. REVISED ANNUAL PROGRESS REPORT DEADLINE.
(a) In General.--Section 412(c) of the Assets for Independence Act
(42 U.S.C. 604 note) is amended by striking ``calendar'' and inserting
``project''.
(b) Transitional Deadline.--Notwithstanding the amendment made by
subsection (a), the submission of the initial report of a qualified
entity under section 412(c) shall not be required prior to the date
that is 90 days after the date of enactment of this Act.
SEC. 8. REVISED INTERIM EVALUATION REPORT DEADLINE.
(a) In General.--Section 414(d)(1) of the Assets for Independence
Act (42 U.S.C. 604 note) is amended by striking ``calendar'' and
inserting ``project''.
(b) Transitional Deadline.--Notwithstanding the amendment made by
subsection (a), the submission of the initial interim report of the
Secretary under section 412(c) shall not be required prior to the date
that is 90 days after the date of enactment of this Act.
SEC. 9. INCREASED APPROPRIATIONS FOR EVALUATION EXPENSES.
Subsection (e) of section 414 of the Assets for Independence Act
(42 U.S.C. 604 note) is amended to read as follows:
``(e) Evaluation Expenses.--Of the amount appropriated under
section 416 for a fiscal year, the Secretary may expend not more than
$500,000 for such fiscal year to carry out the objectives of this
section.''.
SEC. 10. NO REDUCTION IN BENEFITS.
Section 415 of the Assets for Independence Act (42 U.S.C. 604 note)
is amended to read as follows:
``SEC. 415. NO REDUCTION IN BENEFITS.
``Notwithstanding any other provision of Federal law (other than
the Internal Revenue Code of 1986) that requires consideration of 1 or
more financial circumstances of an individual, for the purpose of
determining eligibility to receive, or the amount of, any assistance or
benefit authorized by such law to be provided to or for the benefit of
such individual, funds (including interest accruing) in an individual
development account under this Act shall be disregarded for such
purpose with respect to any period during which such individual
maintains or makes contributions into such an account.''.
|
Excludes funds attributable to matching contributions by qualified entities from IDA emergency withdrawals.
Includes among eligible grantees low-income credit unions and community development financial institutions.
Revises requirements for withdrawals from IDA accounts for the purchase of a home.
Increases the amount of funds set aside for economic literacy training and administrative costs.
Includes a Federal poverty measure among alternative eligibility criteria.
Declares that funds in an IDA shall be disregarded entirely for purposes of determining eligibility for Federal programs based on need.
|
Seattle defense attorney John Henry Browne said today he’ll represent the Joint Base Lewis-McChord staff sergeant suspected of killing 16 civilians in Afghanistan.
Browne said he talked to the soldier over the phone early this morning and is making arrangements to meet with him soon, possibly in Kuwait.
“We’re making contingency arrangements right now,” said Browne, who was at the County-City Building in downtown Tacoma on a separate matter. “We don’t know where he’s going to be tried.”
The attorney said the staff sergeant, a married father who’s trained as a sniper, asked for him specifically during talks with military officials.
“He’s from here, and he knows who I am,” said Browne, who has represented a number of high-profile clients in the past, most recently “Barefoot Bandit” Colton Harris-Moore.
The staff sergeant is currently being represented by a military attorney, Browne added.
He declined to divulge any more information about his client or his state of mind, saying he’s worried for the safety of the soldier and his family.
Browne said he was girding himself for a case he called “more political than legal.” ||||| The Seattle lawyer representing a U.S. soldier accused of killing 16 Afghan civilians has only appeared in military court a handful of times in a career spanning 40-plus years, but he's no stranger to high-profile clients.
FILE - In this Dec. 16, 2011 file photo, attorney John Henry Browne, representing Colton Harris-Moore, who is also known as the "Barefoot Bandit," appears in Island County Superior Court in Coupeville,... (Associated Press)
FILE - In this July 22, 2010, file photo, attorney John Henry Browne speaks with reporters in Seattle. Browne said Thursday, March 15, 2012 that he's been asked to represent the American soldier accused... (Associated Press)
FILE - In this June 9, 2011 file photo, attorney John Henry Browne answers questions from the media about his client, “Barefoot Bandit” Colton Harris-Moore, outside U.S. District Court in Seattle. Browne... (Associated Press)
John Henry Browne has tried over 250 criminal cases to verdict, representing clients ranging from serial killer Ted Bundy to Colton Harris-Moore, known as the "Barefoot Bandit."
The 65-year-old said he has only handled three or four military cases. The soldier will also have at least one military lawyer.
Browne has been a prominent figure in Washington state legal circles since the 1970s. Tall and stylish, he's known equally for his zeal in representing his clients and his flair before television cameras.
He has handled some of the most high-profile criminal cases in state. In addition to being a lawyer for Bundy, in 1983 he helped Benjamin Ng avoid the death penalty following his conviction in Washington's worst mass killing, the massacre of 13 people at a Seattle restaurant.
In one of his greatest legal victories, Browne ensured that a man who fled to Brazil after setting a fire that killed four firefighters would not face murder charges upon his return because the extraditing country _ Brazil _ did not have a felony murder statute equivalent to Washington's.
Browne recently represented Colton Harris-Moore, who gained international attention for stealing airplanes, boats and cars during a two-year run from the law. Browne and his co-counsel, Emma Scanlan, helped Harris-Moore reach state and federal plea deals, then persuaded a state judge to give him the low end of the sentencing range: seven years in prison.
Browne graduated from American University School of Law in 1971 and went on to be a Ford Foundation Fellow at Northwestern University School of Law. He began his legal career as an assistant attorney general in Olympia, Wash., the state capital.
|
– We still don't know the name of the US soldier accused of killing 16 people in Afghanistan, but one of his attorneys certainly has a high profile. Seattle's John Henry Browne tells the News Tribune of Tacoma that he will assist military attorneys with the defense. Browne has defended a slew of big-name clients, most recently the Barefoot Bandit. Years ago, he represented serial killer Ted Bundy, notes AP. He wouldn't divulge any information about the 38-year-old soldier, other than to say he's from the Tacoma area and sought out Browne via the military because of his reputation. “He’s from here, and he knows who I am,” Browne told the local newspaper, adding that the case is "more political than legal." One possible avenue of defense is the brain injury that the soldier suffered on a previous tour of duty.
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SECTION 1. SHORT TITLE.
This Act may be cited as the ``Drunk Driving Repeat Offender
Prevention Act of 2013''.
SEC. 2. USE OF IGNITION INTERLOCK DEVICES TO PREVENT REPEAT INTOXICATED
DRIVING.
(a) In General.--Chapter 1 of title 23, United States Code, is
amended by inserting after section 159 the following:
``Sec. 160. Use of ignition interlock devices to prevent repeat
intoxicated driving
``(a) Definitions.--In this section:
``(1) Alcohol concentration.--The term `alcohol
concentration' means grams of alcohol per 100 milliliters of
blood or grams of alcohol per 210 liters of breath.
``(2) Driving while intoxicated; driving under the
influence.--The terms `driving while intoxicated' and `driving
under the influence' mean driving or being in actual physical
control of a motor vehicle in a State while having a blood
alcohol concentration of 0.08 percent or greater.
``(3) Ignition interlock device.--The term `ignition
interlock device' means an in-vehicle device that requires a
driver to provide a breath sample prior to the motor vehicle
starting, and that prevents a motor vehicle from starting if
the alcohol concentration of the driver is above the legal
limit.
``(4) Motor vehicle.--
``(A) In general.--The term `motor vehicle' means a
vehicle driven or drawn by mechanical power and
manufactured primarily for use on public highways.
``(B) Exclusions.--The term `motor vehicle' does
not include--
``(i) a vehicle operated solely on a rail
line; or
``(ii) a commercial vehicle.
``(b) Laws Requiring Ignition Interlock Devices.--
``(1) In general.--Subject to paragraph (2), a State meets
the requirements of this subsection if the State has enacted
and is enforcing a law that requires throughout the State the
installation of an ignition interlock device for a minimum of
180 days on each motor vehicle operated by an individual who is
convicted of driving while intoxicated or driving under the
influence.
``(2) Exception.--The 180-day period referred to in
paragraph (1) for the installation of an ignition interlock
device may be reduced to period of not fewer than 90 days, if--
``(A) the driver's licence of the individual is
suspended for a minimum of 180 days as a result of the
conviction; and
``(B) the period for the installation of an
ignition interlock device begins after the last day of
the suspension.
``(c) Withholding of Funds for Noncompliance.--
``(1) Fiscal year 2016.--On October 1, 2015, the Secretary
shall withhold 1 percent of the amount required to be
apportioned to a State under each of paragraphs (1) and (2) of
section 104(b) if the State does not meet the requirements of
subsection (b).
``(2) Fiscal year 2017.--On October 1, 2016, the Secretary
shall withhold 3 percent of the amount required to be
apportioned to a State under each of paragraphs (1) and (2) of
section 104(b) if the State does not meet the requirements of
subsection (b).
``(3) Fiscal year 2018 and thereafter.--On October 1, 2017,
and on October 1 of each fiscal year thereafter, the Secretary
shall withhold 5 percent of the amount required to be
apportioned to a State under each of paragraphs (1) and (2) of
section 104(b) if the State does not meet the requirements of
subsection (b).
``(d) Period of Availability of Withheld Funds; Effect of
Compliance and Noncompliance.--
``(1) Period of availability of withheld funds.--Any funds
withheld under subsection (c) from apportionment to a State
shall remain available for apportionment to the State until the
end of the third fiscal year following the fiscal year for
which the funds are authorized to be appropriated.
``(2) Apportionment of withheld funds after compliance.--
If, before the last day of the period for which funds withheld
under subsection (c) from apportionment are to remain available
for apportionment to a State under paragraph (1), the State
meets the requirements of subsection (b), the Secretary shall,
on the first day on which the State meets the requirements of
subsection (b), apportion to the State the funds withheld under
subsection (c) that remain available for apportionment to the
State.
``(3) Period of availability of subsequently apportioned
funds.--Any funds apportioned pursuant to paragraph (2)--
``(A) shall remain available for expenditure until
the end of the third fiscal year following the fiscal
year in which the funds are so apportioned; and
``(B) if not apportioned at the end of that period,
shall lapse.
``(4) Effect of noncompliance.--If, at the end of the
period for which funds withheld under subsection (c) from
apportionment are available for apportionment to a State under
paragraph (1), the State does not meet the requirements of
subsection (b), the funds shall lapse.''.
(b) Conforming Amendment.--The analysis for such chapter is amended
by inserting after the item relating to section 159 the following:
``Sec. 160. Use of ignition interlock devices to prevent repeat
intoxicated driving.''.
|
Drunk Driving Repeat Offender Prevention Act of 2013 - Directs the Secretary of Transportation (DOT) to withhold specified graduated percentages of a state's apportionment of certain federal-aid highway funds for FY2016-FY2018 if the state has not enacted and is not enforcing a law requiring the installation of an ignition interlock device for a minimum of 180 days on each motor vehicle operated by an individual convicted of driving while intoxicated or driving under the influence (having a blood alcohol concentration of 0.08% or greater). Authorizes reduction of the 180-day period to 90 days if: (1) the driver's license is suspended for a minimum of 180 days as a result of the conviction, and (2) the period for installation of an ignition interlock device begins after the last day of the suspension.
|
SECTION 1. SHORT TITLE.
This Act may be cited as the ``Empower Employees Act of 2014''.
SEC. 2. LABOR ORGANIZATION DUES NOT DEDUCTIBLE FROM PAY.
(a) Agencies Generally.--
(1) In general.--Chapter 71 of title 5, United States Code,
is amended by striking section 7115 and inserting the
following:
``Sec. 7115. Labor organization dues not deductible from pay
``(a) In General.--An agency may not deduct any amount from the pay
of an employee for the dues of a labor organization.
``(b) Restriction.--Appropriated funds may not be used to pay an
employee who makes deductions described in subsection (a).
``(c) Definition.--For purposes of this section, the term `agency'
means--
``(1) an Executive agency (as defined in section 105), the
United States Postal Service, and the Postal Regulatory
Commission;
``(2) an office, agency, or other establishment in the
legislative branch;
``(3) an office, agency, or other establishment in the
judicial branch; and
``(4) the government of the District of Columbia.''.
(2) Clerical amendment.--The table of sections for chapter
71 of title 5, United States Code, is amended by striking the
item relating to section 7115 and inserting the following:
``7115. Labor organization dues not deductible from pay.''.
(b) Postal Service Amendment.--
(1) In general.--Section 1205 of title 39, United States
Code, is repealed.
(2) Clerical amendment.--The table of sections for chapter
12 of title 39, United States Code, is amended by striking the
item relating to section 1205.
SEC. 3. EFFECTIVE DATES; TRANSITION PROVISIONS.
(a) Effective Date.--The amendments made by this Act shall take
effect on the date of enactment of this Act.
(b) Transition Provisions.--
(1) Current deductions for dues of an exclusive
representative.--Nothing in this Act shall, in the case of an
assignment received before the date of enactment of this Act
under subsection (a) of section 7115 of title 5, United States
Code (as then in effect), cause the termination of such
assignment before--
(A) the date on which such assignment is revoked,
in accordance with the last sentence of such subsection
(a) (as last in effect before such date of enactment);
or
(B) if earlier, the date determined under paragraph
(1) or (2) of subsection (b) of such section 7115 (as
last in effect before such date of enactment).
(2) Current deductions for dues of other labor
organizations.--Nothing in this Act shall, in the case of a
voluntary allotment made before the date of enactment of this
Act under subsection (c) of section 7115 of title 5, United
States Code (as then in effect), cause the termination of such
allotment before the date on which the underlying agreement
(under authority of which such allotment is being made) ceases
to have effect, whether by reason of section 7115(c)(2)(B) of
such title 5 (as last in effect before such date of enactment)
or otherwise.
(3) Current deductions for dues of a labor organization
from postal service employees.--Nothing in this Act shall, in
the case of a written assignment received before the date of
enactment of this Act under section 1205 of title 39, United
States Code (as then in effect), cause the termination of such
assignment before the date on which such assignment--
(A) is revoked in accordance with such section (as
last in effect before such date of enactment); or
(B) otherwise expires.
(c) Nonrenewability.--
(1) In general.--An agreement between an agency and a labor
organization, entered into before the date of enactment of this
Act under subsection (a) or (c) of section 7115 of such title 5
(as then in effect), shall not, to the extent that it relates
to deductions for the payment of dues of such labor
organization, be subject to renewal or extension.
(2) Postal service.--A written assignment received by the
United States Postal Service under section 1205 of title 39,
United States Code (as then in effect) or an agreement between
the United States Postal Service and any organization of
employees in effect pursuant to 1205(b) of such title (as then
in effect), shall not, to the extent that it relates to
deductions for the payment of dues of such organization, be
subject to renewal or extension.
(d) Definitions.--For purposes of this section, the terms
``agency'', ``exclusive representative'', and ``labor organization''
have the meanings given such terms in section 7103 of title 5, United
States Code.
|
Empower Employees Act of 2014 - Prohibits federal agencies, including executive, legislative, and judicial agencies, the United States Postal Service (USPO), the Postal Regulatory Commission (PRC), and the government of the District of Columbia, from deducting labor organization fees from the salaries of their employees.
|
it has long been widely accepted that active galactic nuclei are powered by gravitationally liberated energy from accretion discs around massive black holes @xcite . while the study of accretion is an interesting prospect in itself , the feedback it ensues is significantly consequential for the evolution of galaxies
as well ( e.g. * ? ? ?
* ) . to truly gauge the effect of feedback requires highly detailed cosmological hydrodynamic simulations that self - consistently track the growth of black holes and the emission from their accretion discs
even the most state - of - the - art simulations presently ( e.g. * ? ? ?
* ; * ? ? ?
* ) are unable to resolve accretion discs , and must use subresolution models to describe their physics ( e.g. * ? ? ?
* ; * ? ? ?
* ) , in a similar vein to semi - analytic models ( e.g. * ? ? ?
* ; * ? ? ?
an analytic understanding of the functioning of accretion discs is hence key for this cause . in the simple picture of a thin accretion disc ,
particles quasi - statically shrink on equatorial , circular orbits , where pressure forces are assumed negligible , until they reach the orbit of lowest energy , after which they are assumed to be captured by the black hole @xcite . in doing so
, those particles must be liberated of their angular momentum . either angular momentum is lost through the disc out to higher radii , or it is emitted vertically and removed from the disc entirely .
the latter occurs naturally through thermal emission of the disc and through scattering of photons if the disc is subject to irradiation from an external source .
it is of interest then to assess the contribution of angular - momentum liberation that photons provide in order to better understand the process of accretion itself .
this paper aims to calculate exactly this , using purely general relativistic arguments . in section [ sec : math ] of this paper ,
relevant mathematical formulae for studying accretion discs are outlined .
general relativistic calculations are performed based on these formulae in section [ sec : main ] , where limiting cases for the liberation of angular momentum via photons , as well as from the standard @xcite disc , are considered .
concluding remarks are provided in section [ sec : conclusion ] .
the unique metric for spacetime around a ( non - charged ) rotating source mass ( e.g. a black hole ) was first discovered by @xcite , usually now written in boyer - linquist coordinates @xcite , for which the invariant interval is [ eq : interval ] @xmath4 @xmath5 where @xmath6 is the speed of light , @xmath7 is the schwarzschild radius , and @xmath8 is the spin parameter ( specific angular momentum ) of the source of mass @xmath9 and angular momentum @xmath10 .
the metric is stationary , axisymmetric , and , as @xcite showed ( but see also * ? ? ?
* ) , exhibits four constants of motion .
two of these constants are the azimuthal and time components of covariant four - momentum . taking the limit @xmath11 ,
one finds these to be relativistic analogues of energy and azimuthal angular momentum , usually referred to as the energy and angular momentum `` at infinity '' .
often the `` at infinity '' is dropped for brevity , and the usual symbols for these quantities are used , i.e. @xmath12 when discussing the emission or transport of energy or angular momentum in accretion discs ( or kerr geometry in general ) , these are the quantities that are meant . throughout the rest of this paper , most quantities will be expressed in a dimensionless form , represented by a bar placed on the quantity of interest . for quantities with dimensions of distance , this means normalising to half the schwarzschild radius , e.g. @xmath13 , @xmath14 , in line with literature convention . equation [ eq : el ] covers quantities with other dimensions . by analysing equations of motion for particles in a kerr spacetime ,
@xcite obtained expressions for the energy and specific angular momentum for circular ( i.e. @xmath15 ) , equatorial ( i.e. @xmath16 and @xmath17 ) , keplerian ( i.e. gravity is entirely centrifugally balanced ) orbits : [ eq : el ] @xmath18 @xmath19 where upper signs are for prograde orbits and lower signs retrograde . note that @xmath20 represents the _ rest _ mass of a particle ( at infinity ) , _ not _ its _ inertial _ mass . by checking the derivatives of these quantities , [ eq : del ] @xmath21 @xmath22 \bigg\}\ ; \end{gathered}\ ] ] @xmath23^{3/2}\ , \ ] ] one finds these two relations share a common minimum , referred to in the literature as the innermost stable circular orbit ( isco ) , where @xmath24 is given by equation 2.21 of @xcite .
and @xmath25 are equivalent to @xmath24 and @xmath26 here , respectively . ] under the picture where particles transit between infinitesimally adjacent orbits in the process of accretion ( until they reach the isco ) , the above equations provide the starting point for calculating how much specific angular momentum can be lost from photon emission and/or scattering .
hereafter , the use of @xmath27 and @xmath28 ( with or without bars , but without further subscripts ) refers to the orbiting states for which these equations ( [ eq : el][eq : del ] ) apply .
in each of the following subsections , the relative specific - angular - momentum loss to photons in an accretion disc , @xmath29 ( where subscript @xmath30 is for photons ) , as a function of radius , is calculated for a different idealised situation , where each builds on the last . each result
is plotted in fig .
[ fig : dl ] for @xmath31 , allowing for comparisons between each individual case .
the models considered here are all of thin , relativistic accretion discs , whereby the mathematics of section [ sec : math ] is applicable . before considering consequences for other forms of energy transport ,
the energy carried away by a photon supplied by a particle moving to an adjacent lower - energy circular orbit should , at most , be the energy difference between the orbits .
this can be written in terms of differentials as @xmath32 if this energy is lost primarily through radiation , one expects each photon to be emitted with statistical isotropy from the frame of the emitting particle . for a non - rotating disc
, this would make the average direction of emission from each face of the disc vertical ( i.e. initially completely in the @xmath33-direction ) .
for a rotating disc perceived from an external frame ( i.e. one static with the boyer - lindquist coordinates ) , this can then be modelled by stating that photons are emitted in the @xmath34@xmath35 `` plane '' with a three - velocity in the @xmath34-direction equivalent to that of the disc , naturally a function of radius .
this ( angular ) velocity is found as @xmath36 .
recognising @xmath37 and @xmath38 ( cf .
equations [ eq : interval ] and [ eq : eldef ] ) , obtaining the contravariant metric components by taking the matrix inverse of equation [ eq : interval ] , and expanding and simplifying with equation [ eq : el ] , one concludes consistently with @xcite that @xmath39 let us write the ( contravariant ) four - momentum components of an emitted photon as @xmath40 .
one can then simultaneously solve @xmath41 and equation [ eq : omega ] ( for the latter , the left - hand side now reads @xmath42 ) to obtain explicit functions for @xmath43 and @xmath44 . further calculating @xmath45 ,
one obtains @xmath46 consistent with the report of @xcite .
now through equation [ eq : ee ] , combined with use of equation [ eq : del ] , one finds an explicit form of @xmath29 , as presented by the dot - dashed lines in fig .
[ fig : dl ] . for non - spinning black holes ,
the analytic relation simplifies to @xmath47 which further reduces to the newtonian case presented by @xcite for @xmath48 .
( the maximum of * ? ? ?
the dot - dashed curves assume photons are emitted with energy equal to the difference of the orbits and are angled to the accretion disc plane such that the @xmath34-velocity of the photons matches that of the disc itself ( see section [ ssec : isotropic ] ) .
the solid curves follow the solution of @xcite , which include effects of internal torques ( outlined further in section [ ssec : viscosity ] )
. the dashed curves also account for internal torques , and show the upper limit of scattering , where the momentum imparted on photons is parallel to the @xmath34-direction ( section [ ssec : scattering]).,scaledwidth=48.0% ] under this picture , one finds that specific - angular - momentum removal by photons is important beyond the percent level out to @xmath1@xmath49 . for non - spinning holes , as particles approach the isco , the radiative efficiency of angular momentum approaches 25% , while for maximally spinning black holes , the efficiency approaches 87% .
already from this analysis , it is clear , and perhaps unsurprising , that radiation is insufficient by itself to liberate an accretion disc of its necessary specific angular momentum .
the previous subsection considered a limiting role of photons without any additional form of angular - momentum transport .
because photons are unable to remove all the necessary angular momentum if they remove all the necessary energy , some other mechanism must remove angular momentum , which consequently must alter the energy liberated by photons too .
the standard model of thin accretion discs proposed by @xcite , and extended to be relativistic by @xcite , considers angular momentum to be transported radially through internal torques ( generated by magnetically induced
see * ? ? ?
* ; * ? ? ?
* ; * ? ? ?
* ) , in addition to removal from photons , in an accretion disc whose structure is completely stable ( i.e. not a function of time ) .
if @xmath50 represents the radial _ net removal _ of specific angular momentum from internal torques during a particle transition to an infinitesimally adjacent orbit , then it must hold that @xmath51 with some small rearranging , the solution derived purely from the continuity equations of rest mass , angular momentum , and energy by @xcite provides [ eq : nt ] @xmath52 @xmath53 where @xmath54 , @xmath55 , and @xmath56 are dimensionless quantities that approach unity for increasing @xmath57 : the reader is referred to equation 5.4.1 of @xcite for their formal definitions . , but using that provides different results and does not satisfy equation [ eq : lll ] , whereas numerically integrating the equations of @xcite does . for an alternate parametrisation ,
see @xcite . ] as for the previous subsection , @xmath29 is presented for the @xcite model in fig .
[ fig : dl ] as solid lines . for non - spinning black holes ,
the liberation of angular momentum from photons at low radii is noticeably less effective than the previous limiting case .
faster spinning holes reach a peak efficiency of radiative angular - momentum removal of nearly 40% .
navely , one may have expected the solid lines in fig .
[ fig : dl ] to lie underneath the dot - dashed lines ( i.e. the result of section [ ssec : isotropic ] ) , because a new mode of angular - momentum transport has been introduced since section [ ssec : isotropic ] .
however , as noted by @xcite , internal angular - momentum transport provides a net energy _ source _ for @xmath58 , meaning more angular momentum must be liberated by photons , specifically by a factor of 3 .
this is reconcilable by considering an energy outflow balance equation ( i.e. an energy version of equation [ eq : lll ] ) , @xmath59 using a combination of equations [ eq : del]a , [ eq : dle_iso ] , and [ eq : nt]b , one can determine @xmath60 to show that indeed this asymptotes to a value of 3 .
this is plotted in fig .
[ fig : eph ] ( solid curves ) . when interpreting fig .
[ fig : eph ] , one should appreciate that the _ absolute _ energy gap between adjacent orbits tends to zero as @xmath61 , and that thin discs have higher densities toward their centres . ) and a maximally scattering - dominant disc with internal angular - momentum transport ( dashed curves , section [ ssec : scattering ] ) around non - spinning ( thick curves ) and maximally spinning ( thin curves ) black holes . where the curves pass above a value of 1 ( dot - dashed line ) , extra energy is radiated away , transferred internally within the disc .
the dotted line indicates an asymptote ; at large radii , a massive particle in the disc emits a photon with thrice the necessary energy to reach its adjacent lower orbit to account for energy supplied by internal transport.,scaledwidth=48.0% ] if an accretion disc is irradiated by an external source , incoming photons can be absorbed or scattered , causing particles in the disc to lose angular momentum , la the poynting - robertson effect @xcite . in the absorption case , where the motive absorbing particles re - emit the radiation , the analysis of section [ ssec : viscosity ] remains sound
however , it could also transpire that charged particles in the disc anisotropically transfer their energy to the incoming photons via inverse compton scattering .
an external irradiative source is observationally motivated by x - ray reflection spectra generated by an accretion disc s corona , which provide a means for measuring black holes spins ( for a review , see * ? ? ?
* ) . at very high redshift
, the cosmic background radiation could also provide an irradiative source ( e.g. * ? ? ?
* ; * ? ? ?
* ) , although far more modest in temperature .
for fast - spinning holes , a notable portion of emitted radiation from accretion discs is expected to fall back on the discs as well @xcite . so long as the thomson regime is applicable in the scattering particle s reference frame , the scattered photon can have its energy significantly multiplied and be beamed in the direction of the scatterer s motion as perceived by an external observer ( see * ? ? ? * ) . while the precise direction of the photon s change of momentum would depend on its initial energy relative to the scattering particle
, one can consider the extreme upper limit where this is the @xmath34-direction , as shown immediately below .
let us now write the four - momentum components of that imparted on the scattered photon as @xmath40 [ it is very important to note that this is the _ change _ in photon s momentum from scattering ; when considering radiation , this was the momentum of the ( average ) photon itself , as it did not exist prior ( i.e. it had no initial momentum ) ] . because photons have no rest mass
, it must hold that @xmath62 , where the @xmath63 terms are the metric components obtainable from equation [ eq : interval ] , hence @xmath64 simultaneously solving equations [ eq : deg ] and [ eq : sim ] , recognising @xmath65 in this maximal limit ( cf .
equation [ eq : eldef ] ) , and using equation [ eq : ee ] , one obtains @xmath66 one can consider taking the same energy lost to photons from section [ ssec : viscosity ] but instead using it to kick ( scatter ) photons in the @xmath34-direction . the relative increase in specific - angular - momentum loss
can then be found by taking the ratio of equation [ eq : dle_phi ] to equation [ eq : dle_iso ] .
however , by increasing @xmath67 , it must be true that @xmath50 decreases , in order to satisfy conservation of angular momentum ( equation [ eq : lll ] ) .
if @xmath50 decreases , then so must @xmath68 by an amount found by taking the ratio of equation [ eq : lll ] to equation [ eq : eee ] after making the internal - torque terms the arguments for each : @xmath69 where subscript
[ ssec : viscosity ] implies the quantities as determined from section [ ssec : viscosity ] .
consequently @xmath70 must increase from energy conservation ( equation [ eq : eee ] ) , and therefore @xmath67 must be higher than initially calculated .
one can iteratively work through these calculations until finding a converged result . in the iterations , but the end result is the same . ] using the above method , one can calculate the maximum @xmath29 for photon scattering with the effects of internal transport included .
this is shown by the dashed lines in fig .
[ fig : dl ] . consistent with the above results , under this maximal regime
, accretion discs can remain efficient above the percent level for @xmath29 beyond @xmath71 . as was the case for the standard @xcite disc , @xmath60 asymptotically approaches a value of 3 for increasing radii , but does so more slowly .
it also exceeds a value of 1 at the same radius , as displayed by the dashed curves in fig .
[ fig : eph ] .
it should again be stressed that the calculations in this subsection are an upper limit . in truth
, one should expect the relevant curve on fig .
[ fig : dl ] to lie between the solid and dashed ones presented , with a bias towards the former .
as material accretes onto massive black holes , there must be a process by which specific angular momentum is removed from the system .
as accretion discs are known to be bright sources of radiation , the emission of photons provides one channel for this angular - momentum loss .
if a disc is irradiated , inverse compton scattering provides another channel .
this paper has provided calculations of the contribution of angular - momentum liberation through photons in thin , relativistic accretion discs . in addtion to situations where transport by internal torques was included , such that the usual conservation laws of physics were satisfied , these calculations included limiting situations where photon emission was responsible for all the necessary energy removal and where photon scattering was angled to remove maximal angular momentum . on scales up to the order of a hundred schwarzschild radii , photons remove a small ( @xmath72 ) percentage of angular momentum in accretion discs that emit in an expected fashion , but beyond this contribute negligibly . at the absolute most , discs subject to strong irradiation are potentially capable of scattering away angular momentum as efficiently out two orders of magntiude farther from the black hole .
the contribution in both cases becomes stronger near the horizon of a fast rotating black hole , especially in the latter case ( @xmath7360% , cf .
thin dashed line , fig .
[ fig : dl ] ) . by and large though
, angular momentum is transported far more efficiently through the disc internally , rather than liberated from the disc electromagnetically .
thanks must go to donald lynden - bell , mitch begelman , and especially the anonymous referee for their constructive thoughts on this manuscript , which inevitably lead to improvement of its content .
thanks also to darren croton for his continued academic support during the publishing of this paper .
bardeen , j. m. 1970 , natur , 226 , 64 bardeen , j. m. , press , w. h. , & teukolsky , s. a. 1972 , apj , 178 , 347 benson , a. j. 2012 , newa , 17 , 175 booth , c. m. , & schaye , j. 2009 , mnras , 398 , 53 boyer , r. h. , & lindquist , r. w. 1967 , jmp , 8 , 265 burns , j. a. , lamy , p. l. , & soter , s. 1979 , icar , 40 , 1 carter , b. 1968 , phrv , 174 , 1559 croton , d. j. , springel , v. , white , s. d. m. , et al . 2006 ,
mnras , 365 , 11 cunningham , c. 1976 , apj , 208 , 534 di matteo , t. , springel , v. , & hernquist , l. 2005 , natur , 433 , 604 fukue , j. , & umemura , m. 1994 , pasj , 46 , 87 johnson , j. l. 2011 , an , 332 , 841 kerr , r. p. 1963 ,
phrvl , 11 , 237 lin , f. , liu , s. , & xiaoqing , l. 2013 , newa , 21 , 40 lynden - bell , d. 1969 , natur , 223 , 690 lynden - bell , d. 1986 , in _ gravitation in astrophysics , cargse 1986 _ eds . b. carter & j. b. hartle ( new york : plenum press ) mineshige , s. , tsuribe , t. , & umemura , m. 1998 , pasj , 50 , 233 misner , c. w. , thorne , k. s. , & wheeler , j. a. 1973 , _ gravitation _
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a key component of explaining the array of galaxies observed in the universe is the feedback of active galactic nuclei , each powered by a massive black hole s accretion disc . for accretion to occur
, angular momentum must be lost by that which is accreted .
electromagnetic radiation must offer some respite in this regard , the contribution for which is quantified in this paper , using solely general relativity , under the thin - disc regime .
herein , i calculate extremised situations where photons are entirely responsible for energy removal in the disc and then extend and relate this to the standard relativistic accretion disc outlined by @xcite , which includes internal angular - momentum transport .
while there is potential for the contribution of angular - momentum removal from photons to be @xmath01% out to @xmath110@xmath2 schwarzschild radii if the disc is irradiated and maximally liberated of angular momentum through inverse compton scattering , it is more likely of order @xmath3 schwarzschild radii if thermal emission from the disc itself is stronger .
the effect of radiation / scattering is stronger near the horizons of fast - spinning black holes , but , ultimately , other mechanisms must drive angular - momentum liberation / transport in accretion discs .
accretion , accretion discs black hole physics
galaxies : active galaxies : nuclei relativistic processes quasars : general
|
binary stars are common in the universe and their evolution is important to many astrophysical phenomena including supernova rates , enrichment of the interstellar medium , and the formation of x - ray binaries and blue stragglers .
pinsonneault & stanek ( 2006 , hereafter ps06 ) discussed the importance of the distribution of binary mass ratios to understanding binary evolution : binaries with similar - mass components ( twins ) undergo qualitatively different evolution than binaries whose two components are quite different in mass .
this affects all aspects of binary evolution , and is of particular interest to the formation of double compact objects , which are potential sources of gravitational waves ( ps06 ) .
the size of the twin population is therefore important to understanding and modeling a wide range of astrophysical phenomena ; see ps06 for an overview of the important role of twins .
ps06 studied the distribution of mass ratios ( @xmath0 ) of ob binaries in the small magellanic cloud ( smc ) , using the sample of eclipsing binaries published in harries et al .
( 2003 , hereafter hhh03 ) and hilditch et al .
( 2005 , hereafter hhh05 ) .
ps06 divides this sample into detached and semidetached binaries and finds a very large proportion of twins among detached binaries : they estimate that 45% of detached binaries have @xmath1 .
by contrast , they find that the semidetached systems have a low rate of twins , with a distribution of @xmath2 peaked near 0.6 .
they argue that the difference between the two samples can not be due to an observational bias and that the detached sample reflects the true proportion of twins among detached binaries in the smc .
ps06 argued that the twin population is a dominant feature , not just of their sample , but of previously studied binary samples .
they specifically claim that a similar twin population is present in the samples of lucy & ricco ( 1979 , henceforth lr79 ) , tokovinin ( 2000 , henceforth t00 ) , and halbwachs et al .
( 2003 , henceforth hmua03 ) .
indeed , lr79 and t00 find twin populations similar to that in ps06 , as does lucy ( 2006 , henceforth l06 ) ; hmua03 also finds an excess of twins , though their results are not directly comparable due to a different selection of primary masses and the inclusion of single - lined spectroscopic binaries ( sb1s ) in their sample .
hmua03 shows that the sb1s have systematically lower mass ratios than the double - lined spectroscopic binaries ( sb2s ) , leading to a lower number of twins in their overall population .
since sb1s have systematically lower @xmath2 than sb2s , samples consisting entirely of sb2s ( including lr79 , t00 , l06 and ps06 ) overestimate the true size of the twin population . although l06 makes a compelling case for the statistical significance of the twin population
, they do not consider the bias introduced by using a sample consisting only of sb2s .
raghavan et al .
( 2010 ) did a comprehensive multiplicity study of nearby stars and found a smaller twin population than appears in studies of sb2s ; though they find evidence that this population increases at short orbital periods , their sample at these periods is extremely small .
sana et al .
( 2012 , henceforth s12 ) observed a sample of ob stars and performed a statistical analysis of the full population ( sb2s , sb1s and single stars ) ; they find that the underlying distribution of @xmath2 is close to flat and does not show clear evidence for a twin population . in this paper , we argue that samples of sb2s are biased in favor of binaries whose components have similar brightnesses , rather than similar masses _ per se_. we show that the full sample of ps06 detached and semidetached consists of binaries whose components are similar in brightness .
we present a monte carlo model showing that a consistent bias based on brightness ratio will affect the distribution of @xmath2 differently depending on the evolutionary status of the binaries .
our model reproduces both the abundance of twins in the detached population and the lack of twins in the semidetached population .
we conclude that the data used by ps06 are consistent with a far smaller twin population than they find .
the ob binaries analyzed by ps06 were initially discovered as eclipsing binaries . given the quality of the photometry in hhh03 & hhh05 , non - twins ( @xmath3 ) should be easily detected through their eclipses .
however , their sample is further selected by the fact that they only obtained orbital solutions for the sb2s . specifically , hhh03 and hhh05 obtained spectroscopy for 169 binaries , @xmath4 of which received detailed followup , and only 50 of which ( all sb2s ) appear in the final sample used by ps06 . samples of sb2s are known to be biased towards twins : in samples including both sb1s and sb2s , the sb1s have systematically lower mass ratios .
for example , the sb1s in hmua03 have @xmath5 , while their sb2s have @xmath6 ( their fig .
the 119 binaries not in their final sample are presumably sb1s and likely have lower mass ratios than the sb2s studied by ps06 . in general , we would expect a sample of sb2s to favor binaries in which both components contribute significantly to the observed spectrum .
since hhh03 and hhh05 obtained spectroscopy at @xmath7 , this would bias their sample towards systems whose components have similar b - band magnitudes .
if such a bias is present , we would expect the sb2s in hhh05 and hhh03 to have brightness ratios near 1 , even in cases where the mass ratio is significantly below 1 .
1 shows histograms of mass ratio and b - band brightness ratio ( @xmath8 ) ; following ps06 , we split the sample into detached and semidetached binaries .
we computed absolute b - band magnitudes using the spectral types and radii listed in hhh03 and hhh05 , together with the values of @xmath9 and @xmath10 given in popper ( 1980 ) .
we exclude the two contact binaries , because the possibility of distortion makes this computation of b - band magnitude ( from radius ) questionable for these systems . since the publication of ps06 , de mink et al .
( 2007 ) have proposed alternate semidetached solutions for two of the systems originally listed as detached . in order to obtain a direct contrast to the results of ps06
, we will use the original solutions found in hhh03 and hhh05 .
for 48 detached and semidetached binaries in ps06 .
although the two populations show very different distributions of @xmath2 , the distributions of brightness ratio are similar : a k - s test comparing the two distributions of brightness ratio finds that they could be drawn from the same distribution with probability @xmath11 .
this consistency indicates the possibility of a bias which favors similar - brightness binaries throughout the ps06 dataset .
[ fig1 ] ] fig .
1 shows that the detached and semidetached samples of ps06 have similar b - band brightness ratios , despite their different distributions of @xmath2 . this impression is confirmed by kolmogorov - smirnov ( k - s ) tests : a k - s test comparing the detached and semidetached distributions of @xmath2 gives @xmath12 , whereas a k - s test comparing the two populations brightness ratios gives @xmath11 .
ps06 states that the inconsistent distributions of @xmath2 rule out the possibility of a single bias explaining both populations
. however , the consistent distributions of @xmath13 actually support the existence of a single bias , favoring similar - brightness binaries consistently in both samples . to understand the relationship between the distributions of mass ratio and brightness ratio , we show in fig .
2 the relationship between absolute b - band magnitude ( m@xmath14 ) and mass ( @xmath15 ) for the individual stars in the detached and semidetached binaries of ps06 . as one would expect , the detached systems generally feature unevolved stars , for which mass and radius are strongly correlated .
the semidetached systems , by contrast , feature many evolved components , for which mass and radius are weakly correlated .
equal - brightness binaries in the detached sample will therefore have similar masses , but this is not necessarily the case for the semidetached systems .
the presence of twins in the detached sample and the lack of twins in the semidetached sample can therefore be explained by a consistent bias and the differing evolutionary status of the two samples . for 96 stars ( primaries and secondaries ) in the detached and semidetached binaries of ps06 .
most of the stars in detached systems ( solid circles ) lie on the main sequence and show a strong correlation between mass and m@xmath14 .
only four stars in two detached systems ( asterisks ) show clear evolution ; these are classified as evolved in this paper .
the stars in semidetached systems ( open circles ) are more evolved and thus have a weaker relationship between mass and m@xmath14 .
a bias favoring equal - brightness systems will have different effects on the observed distribution of @xmath2 , depending on the relationship between mass and brightness ; this is consistent with the discrepant distributions of @xmath2 shown in fig 1 .
[ fig2 ] ] if the abundance of similar - brightness binaries in ps06 is not due to a bias , then their sample must be representative of the actual population in the smc . in this case
, binaries in the smc must consistently maintain high brightness ratios at various stages of evolution .
in general , the low-@xmath2 semidetached systems of ps06 have a secondary ( lower - mass ) star which is more evolved than the primary : this is necessary in order to have binaries in which the secondary is as bright as the higher - mass primary .
for example , ogle 09064499 has 2.7 and 8.4 m@xmath16 components , but the 2.7 m@xmath16 star has evolved to the point that the components are nearly equal in brightness ( @xmath17 ) .
it is difficult to explain how this system will maintain a brightness ratio as high as those studied by ps06 : does such a binary form only when both stars are at an appropriate stage of evolution , then disband when either component evolves to outshine the other ? or does mass transfer between the two stars occur in a way that maintains high luminosity ratios at all stages of evolution , transferring just enough to counteract evolution at every stage ?
a detailed physical model would be necessary to make either of these explanations credible ; absent such a model , the abundance of high brightness - ratio systems is best understood as the result of observational bias .
we now use a monte carlo model to explore how a brightness ratio bias could affect evolved and unevolved populations of binaries differently . in comparing our model to the mass ratios of ps06 , we divide the observed sample into a group of binaries in which both components are unevolved , and a group in which at least one star is evolved .
there are two detached systems with evolved components ( asterisks in fig .
2 ) ; other than these two systems , our unevolved and evolved samples are the same as the detached and semidetached samples studied by ps06 . we will show that a relatively simple model can explain the inconsistent mass ratio distributions of the evolved and unevolved samples .
our monte carlo model begins with two populations of 100 million binaries each . in both populations ,
single stars are given masses drawn from a salpeter initial mass function ( imf ) between 0.3 m@xmath16 ( low enough that our simulated selection effects eliminate all stars of this mass ) and 30 m@xmath16 ( the highest mass present in ps06 ) .
the brightness of each single star is then computed either according to a fixed relationship ( unevolved sample ) or with some variation added to this relationship ( evolved sample ) . finally , single stars are paired at random into binaries , and both populations are subjected to identical cuts simulating the observational biases present in ps06 . the only difference between the two samples is the relationship between the simulated masses and brightnesses of the single stars being observed . for stars in the simulated unevolved sample ,
we compute b - band magnitude directly from each star s mass . applying a linear regression to the unevolved stars ( closed circles ) in fig .
2 gives m@xmath18 ; we use this formula to compute b - band magnitudes for the individual stars in the simulated unevolved sample .
since our goal is specifically to model the stars observed by ps06 and the biases which may affect them , we derive our mass - brightness relationship from their sample rather than using a more theoretical model . for stars in the simulated evolved sample
, each star s b - band magnitude is computed as the main sequence brightness given above ( @xmath19 ) plus a randomly chosen offset representing the star s evolutionary status .
we start by assigning each star a random offset from the main sequence ( @xmath20 ) , drawn from the distribution of @xmath20 in the observed evolved sample of ps06 . after applying our selection effects ( described below )
, we adjust the intrinsic distribution of @xmath20 so that the observed distribution more closely resembles that of the ps06 evolved systems . by an iterative procedure
, we find a distribution of @xmath20 ( dependent on the observational bias ) which perfectly matches the observed brightness offsets from the main sequence .
we have modeled our stars on the sample of ps06 only in determining the brightness of _ single _ stars : these single stars , whose masses came from a salpeter distribution , are paired randomly into binaries .
our model stars are rather simplistic , but our goal is not to present a fully realistic model and to unambiguously detemine the unbiased population .
rather , we wish to show that a bias based on brightness ratio can have different effects on evolved and unevolved samples of binaries , and that this bias gives a simple explanation for both populations of ps06 . to simulate observational bias , the evolved and unevolved samples are both subjected to a cutoff on total brightness and a cutoff on b - band brightness ratio ( modeling the difficulty of detecting a system as an sb2 ) .
hhh05 applied an explicit brightness limit , @xmath21 . for the distance and reddening to the smc , this is roughly equivalent to m@xmath22 ( see fig .
12 of hhh05 ) . to implement our cut on total brightness
, we use bessell & brett ( 1988 ) to compute m@xmath23 from m@xmath14 , then eliminate systems with m@xmath24 .
we model the cutoff on brightness ratio not as a sharp cut , but rather as an increasing function of brightness ratio . whether a binary is observed as an sb2 probably depends on many things aside from brightness ratio , e.g. orbital velocity and inclination .
perhaps a binary with brightness ratio @xmath25 will be an sb2 only if these other factors are ideally favorable , while systems with higher brightness ratios have more leeway . since 0.27 is the lowest brightness ratio present in ps06
, we eliminate all simulated binaries with brightness ratio ( @xmath26 ) less than 0.27 .
we then assume that the probability of observing a given binary is a linear function of brightness ratio between 0.27 and 1 .
we will explore nonlinear models in section 3 , but the linear model is sufficient to demonstrate the essential properties of our bias .
the results of our monte carlo model are shown in fig .
3 . for the evolved and unevolved samples ,
we show the simulated distribution of brightness ratio and @xmath2 before selection effects , and the distribution of @xmath2 after each selection is applied . before selection effects are applied , the evolved and unevolved distributions of @xmath2 are identical ( random draws from a salpeter distribution ) .
the cut on total brightness favors low-@xmath2 systems in both the evolved and unevolved samples . after the brightness ratio cut ,
the evolved and unevolved populations become distinct in just the way apparent in ps06 : the unevolved sample is peaked at @xmath27 , while the evolved sample is peaked at @xmath28 .
the distribution of @xmath2 given by random draws from a salpeter mass function is @xmath29 ( tout 1991 ) , shown in the second column of fig .
the cut on total brightness strongly favors low-@xmath2 systems ; when mass and radius are correlated , this produces the salpeter relative mass function used by ps06 , @xmath30 .
however , in the evolved sample the distribution of observed mass ratios is less peaked than @xmath30 , due to the presence of luminous , low - mass stars . despite the strong effect of the cutoff on total brightness
, the brightness ratio cutoff eliminates the peak at @xmath31 and dominates the shape of the observed distribution .
the model presented in section 2 qualitatively reproduces the discrepant populations found by ps06 .
to quantitatively compare the observed and simulated populations , we must account for observational error . when ps06 modeled the data , they convolved the simulated mass ratios with observational error ( @xmath32 ) .
however , this gives numerous binaries in which the mass ratio ( with error ) is greater than 1 , i.e. the secondary appears more massive than the primary ; ps06 does not say how they handled these systems . rather than taking this approach , we add error to the individual simulated masses ( @xmath33 , from hhh05 ) and define the mass ratio ( with error ) as the smaller mass ( with error ) divided by the larger mass ( with error ) giving @xmath34 . in fig .
4 , we make a direct comparison between the data of ps06 and our simulated populations including error . the simulated unevolved sample is a good match for the sample of ps06 : a k - s test comparing the two distributions gives @xmath35 .
for the evolved systems , our simulation actually overpredicts the observed number of low-@xmath2 systems .
a k - s test comparing the simulated evolved systems to those in ps06 gives @xmath36 , a difference which could easily be due to our simplified model of binary evolution .
our bias assumes that the probability of detecting a system is a linear function of brightness ratio .
although this is a simplification , our results are not strongly dependent on this assumption : the evolved and unevolved samples of ps06 can be well - modeled using a wide range of nonlinear selections on brightness ratio .
for example , the evolved and unevolved systems of ps06 can be equally well modeled by ( 1 ) the linear cutoff described above , ( 2 ) a probability of detection which is 0 for brightness ratios below 0.5 and 1 above 0.5 , and ( 3 ) a model in which the probability of detection has no lower cutoff and goes as the brightness ratio to the 3.3 .
models 1 , 2 , and 3 match the unevolved population with k - s tests @xmath35 , @xmath37 , and @xmath38 , respectively , and the evolved population with @xmath36 , @xmath39 , and @xmath40 , respectively .
these models are also plotted in fig .
4 . determining the true nature of the brightness ratio cut would require simulating binary spectra and determining which could be observed .
however , such details are not essential to our result : the evolved and unevolved samples of ps06 can be successfully modeled by a variety of cuts on brightness ratio .
after convolving with observational error , a k - s test comparing the detached binaries to the ` twin ' model of ps06 ( and assuming no observational bias ) gives @xmath41 , , which results in many mass ratios greater than 1 .
we suspect that ps06 simply discarded these systems ; doing so gives a much better k - s test ( @xmath42 ) . however , doing so artificially removes many high-@xmath2 systems from the model and therefore inflates the apparent size of the twin population . ] compared to @xmath35 for our model .
modeling the twin population as a bias therefore reproduces the data better than the model proposed by ps06 , despite having one free parameter ( the lower cutoff ) rather than three ( twin fraction and the lower cutoffs of two flat distributions ) .
in addition , our model provides a natural explanation for the lack of twins among evolved systems ; this feature is not explained by ps06 .
finally , our model studies the consequences of a brightness ratio bias which is generally expected : ps06 acknowledged such a bias , but rejected the possibility that it could affect evolved and unevolved binaries differently .
we conclude that the mass ratios studied by ps06 are best understood as the result of an observational bias . for the 48 unevovled and evolved systems of ps06 ( solid lines ) , compared to the results of our monte carlo models of observational biases ( dashed lines ; three in each panel , corresponding to the models described in the text ) . for reference ,
the salpeter mass ratio distribution , the intrinsic distribution of @xmath2 for the simulated samples ( dotted line ) is also provided .
the dashed lines include convolution with observational error , as described in the text .
our model produces a good fit to the unevolved systems : a k - s test comparing our model to the data gives @xmath35 .
our model qualitatively reproduces difference between the evolved and unevolved systems , but significantly overestimates the size of this difference : it predicts even more low-@xmath2 evolved systems ( and fewer evolved twins ) than are observed . [ fig4 ] ] s12 found that ob binaries come from a flat distribution ( @xmath43 , @xmath44 ) , in contrast with the @xmath45 distribution predicted by a salpeter mass function . adopting a flat distribution of ob binaries and applying our simulated bias produces a distribution of detached systems consistent with the data of ps06 :
a k - s test comparing them gives @xmath46 .
the simulated evolved systems also give similar results whether one starts with a salpeter distribution or a flat distribution : @xmath36 and @xmath47 respectively .
the flat and salpeter distributions are quite different , yet after modeling the bias both produce samples consistent with the unevolved systems of ps06 and qualitatively consistent with the evolved systems of ps06 .
the bias we model here is so strong that a range of intrinsic distributions give observed samples similar to those found by ps06 .
as long as the initial distribution is roughly flat for @xmath48 , the observed distribution will be consistent with the data of ps06 .
a significant over- or under - abundance of twins is the only sort of intrinsic distribution for which which the simulated observations will be inconsistent with the data of ps06 . in particular , adopting the ps06 twin population as the intrinsic distribution of @xmath2 ( and applying our simulated bias ) results in an observed sample which is a poor match for the data : a k - s test comparing them gives @xmath49 .
if our bias is realistic , then a wide range of intrinsic distributions should result in similar observed distributions , in which case observed samples of sb2s should have very similar distributions of @xmath2 even if the underlying populations are different .
indeed , the unevolved sb2s in hmua03 ( table 4 of their paper ) have a @xmath2 distribution consistent with the unevolved systems of ps06 : a k - s test comparing them gives @xmath46 . these two populations ( other than being sb2s )
were selected in very different ways . whereas the binaries of ps06 were selected based on a brightness cut ( effectively a minimum primary mass ) , hmua03 selected systems with f7-k primaries ( a narrow range of primary mass ) .
these two procedures should result in different intrinsic distributions of @xmath2 .
the agreement between the two observed samples therefore reinforces the idea that the observed distributions are dominated by a consistent bias affecting samples of sb2s .
although we conclude that the data of ps06 are best explained as the result of a bias , we caution against any effort to reverse this bias and thereby determine the underlying distribution .
the bias we propose is strong enough that it is impossible to reliably determine the underlying distribution given an observed sample of sb2s .
rather , to study the true distribution of @xmath2 , we recommend a study similar to s12 or raghavan ( 2010 ) , in which sb2s are part of a larger sample .
ps06 claims that their large twin population is supported by lucy & ricco ( 1979 ) and tokovinin ( 2000 ) .
however , both these papers considered unevolved sb2s ( like the detached systems in ps06 ) and are therefore subject to the same biases .
we have analyzed the dataset of ps06 and come to a conclusion strongly inconsistent with theirs .
we find that the true twin population may be negligible , whereas ps06 found @xmath50% of systems have @xmath1 .
we now summarize the ways in which our analysis differs from theirs , and the contribution of these differences to the size of the twin population .
\(1 ) when we convolve our model with observational error , we add error to individual stars rather than to @xmath2 .
as discussed in the introduction to section 3 , convolving error directly with @xmath2 may cause some systems to be discarded and thereby inflate the implied size of the twin population .
we redid the fit of ps06 , modeling the detached systems as a flat distribution ( @xmath51 ) and a twin population ( @xmath1 ) but adding error to individual stars rather than to @xmath2 .
the resulting best - fit twin fraction is then @xmath52% .
our method of convolution reduces the twin population by a third even before observational biases are considered .
\(2 ) ps06 noted that if the lack of systems with @xmath53 is due to a bias , then this would effectively cut the number of twins in half .
indeed , we believe that these systems are missed because of observational bias : the lowest brightness ratio observed in any system in ps06 ( detached or semidetached ) is 0.27 .
for unevolved binaries ( using our fit to fig 2 ) this corresponds to @xmath54 . attributing these missing systems to a bias reduces the 29% twin fraction down to @xmath55% .
\(3 ) the remaining difference between our twin fraction and that claimed by ps06 , comes from modeling the brightness ratio bias not as a sharp cut but as graduated over a range of brightness ratio .
this graduated cutoff results in removing some systems with brightness ratio @xmath56 ; it systematically removes relatively low-@xmath2 systems and ( in our model ) reduces the twin fraction to be consistent with the @xmath57% resulting from random draws from a salpeter distribution . of the three differences described above , ( 1 ) and ( 2 ) are quite robust .
these two issues by themselves reduce the twin population from @xmath58% to @xmath55% .
our graduated model of the bias ( 3 ) may be wrong in its details , but it is very likely right in its essence . even if the linear model is flawed , it is likely that the probability of detecting a binary as an sb2 increases over some range of brightness ratio , and that the true twin population is therefore below 16% .
we find that ps06 significantly overestimated the size of the twin population by employing a flawed method of error convolution and by neglecting the important role of observational bias . after correcting for these two effects ,
the data of ps06 are consistent with either a salpeter distribution of mass ratios , or with the flat distribution of s12 ; they do not provide a compelling case for a significant population of twins .
in addition , we find that all binaries observed by ps06 have high brightness ratios , suggesting a consistent bias favoring these binaries .
we present a monte carlo model of this bias , which naturally explains both the abundance of twins in detached ( unevolved ) systems and the lack of twins in semidetached ( evolved ) systems .
since this bias affects the distribution of @xmath2 differently in these two samples , the semidetached sample is not an ` ideal control ' sample as was claimed by ps06 .
compared to the model of ps06 , modeling the twin population as the result of an observational bias has various advantages : ( 1 ) this bias is generally expected , and was acknowledged but not modeled by ps06 , ( 2 ) our model gives a better fit to the mass ratios of the detached ( unevolved ) systems with fewer free parameters , and ( 3 ) our model qualitatively explains the semidetached ( evolved ) systems which are not addressed by ps06 .
the smaller twin population implied by our analysis has various astrophysical implications .
neutron star - black hole systems may be more abundant than neutron star - neutron star systems as gravitational wave sources , consistent with the non - twin population discussed by ps06 but contrary to their conclusion based on a large twin population .
in addition , binary mergers are likely to account for a relatively small fraction of blue stragglers , as coalescence is more likely in twin binaries ( ps06 ) .
a relatively small twin population also helps explain the abundance of black hole x - ray binaries , whose formation requires a relatively low - mass secondary ( e.g. kalogera & webbink 1998 ) .
ps06 additionally discusses the important role of twins in forming type ia supernovae and binary white dwarf systems .
the bias we propose is strong enough that the underlying distribution can not be reliably recovered by correcting for the bias : a range of intrinsic distributions is consistent with the sample of ps06 .
this bias likely affects all samples of sb2s similarly .
although we can not make a precise determination of the true size of the twin population , we find that the twin population ( @xmath1 ) implied by the sample of ps06 is under 16% .
the least certain aspects of our model may affect how far below 16% the twin fraction is , but we strongly rule out a twin population of the size identified by ps06 .
we conclude that a bias similar to the one discussed here has likely affected all observed samples of sb2s , calling into question the large twin populations found by ps06 and other papers based exclusively on sb2s , including t00 , l06 and lr79 .
we would like to thank steve kaback , rand harrington and the blake school for their support of this work .
we thank j.l .
halbwachs , t. maccarone and an anonymous referee for their comments on this paper . 99 bessell , m. s. & brett , j. m. 1988 , pasp , 100 , 1134 de mink , s. e. , pols , o. r. , & hilditch , r. w. 2007 , a&a , 467 , 1181 ferrario , l. 2012 , mnras , 426 , 2500 halbwachs , j. l. , mayor , m. , udry , s. , & arenou , f. 2003 , a&a , 397 , 159 harries , t. j. , hilditch , r. w. , & howarth , i. d. 2003 , mnras , 339 , 157 hilditch , r. w. , harries , t. j. , & howarth , i. d. 2005 , mnras , 357 , 304 kalogera , v. & webbink , r. e. 1988 , apj , 493 , 351 lucy , l.b . 2006 , a&a , 457 , 629 lucy , l.b . and ricco , e. 1979 , aj , 84 , 401 matteucci , f. , panagia , n. , pipino , a. , et al . 2006 , mnras , 372 , 265 pinsonneault , m. h. & stanek , k. z. 2006 , apjl , 639 , l67 popper , d. m. 1980 , ara&a , 18 , 115 salpeter , e. e. 1955 , apj , 121 , 161 sana , h. , de mink , s. e. , de koter , a. , et al . 2012 , science , 337 , 444 tokovinin , a.a . 2000 , a&a , 360 , 997 tout , c. a. 1991 , mnras , 250 , 701
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massive binary stars undergo qualitatively different evolution when the two components are similar in mass ( ` twins ' ) , and the abundance of twin binaries is therefore important to understanding a wide range of astrophysical phenomena . we reconsider the results of pinsonneault & stanek ( 2006 ) , who argue that a large proportion of binary stars have nearly equal - mass components ; we find that their data imply a relatively small number of such ` twins . '
we argue that samples of double - lined spectroscopic binaries are biased towards systems with nearly equal - brightness components .
we present a monte - carlo model of this bias , which simultaneously explains the abundance of twins in the unevolved binaries of pinsonneault & stanek ( 2006 ) , and the lack of twins in their evolved systems .
after accounting for the bias , we find that their observed mass ratios may be consistent with a variety of intrinsic distributions , including either a flat distribution or a salpeter distribution .
we conclude that the observed overabundance of twins in pinsonneault & stanek ( 2006 ) does not reflect the true population of binaries , and we briefly discuss the astrophysical implications of the lack of twins .
[ firstpage ] binaries : spectroscopic stars : luminosity function , mass function methods : observational
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concept of quantum computation by adiabatic evolution , i.e. adiabatic quantum computation ( aqc ) , was introduced by farhi and coauthors @xcite .
it is an alternative to the `` standard '' concept of quantum computation where one has to construct a universal set of gates with long coherence times . as the latter requirement is not easy to achieve in superconducting quantum bits ( qubits ) ,
presently the longest times achieved are of the order of several @xmath0 and only achieved at an optimal point @xcite , aqc seems to be better as the system is only required to stay in the ground state . this led kaminsky and co - authors to propose a scalable superconducting architecture for adiabatic quantum computation @xcite , where they make use of 3 josephson junction persistent current qubits @xcite . in the aqc concept
the solution of some non - polynomially ( np ) hard problem is encoded into the ground state of a complex multi - qubit hamiltonian @xmath1 .
the parameters of such a hamiltonian can be controlled continuously so in this sense this method is similar to _ analog _ computation .
the computation itself contains three majors steps : ( a ) preparation of the system in a well - known state with hamiltonian @xmath2 at time @xmath3 , ( b ) adiabatic evolution during the time interval @xmath4 towards the problem hamiltonian @xmath1 and ( c ) readout of the ground state of the problem hamiltonian , which gives the answer .
therefore , in order to build a quantum computer based on aqc one has to be able to construct a qubit system with a controllable hamiltonian and one has to be able to read out this system once the problem hamiltonian @xmath1 is encoded into it . .
the qubits are coupled to a resonant tank circuit for the readout .
the flux bias to the qubits is provided by a dc current @xmath5 applied to the coil @xmath6 and bias currents @xmath7 applied to additional bias wires , allowing full control over the individual qubits fluxes @xmath8 . in the case of more qubits ,
more current sources would be used.,title="fig:",width=302 ] + there has been an experimental implementation of an aqc algorithm in an nmr three - qubit quantum computer by steffen _ et al .
by using their computer they solve the so - called maxcut problem .
this problem is one of the non - polynomially hard problems of graph theory where the object of the problem is to find the maximal `` cut '' of a graph @xcite and is mathematically equivalent to finding the ground state of some ising - type hamiltonian .
some of the authors have proposed how to implement and readout such an algorithm making use of flux qubits in a setup like the one shown in fig.[setup ] @xcite . in this paper
we review our recently obtained results from coupled flux qubits using our and implemented method for their characterization .
also we will show some of our results on multi qubit systems .
in order to implement any protocol for quantum information processing , qubits should be coupled .
three josephson junction persistent current flux qubits @xcite can be coupled inductively just by placing them next to each other , however the achievable coupling strength is rather weak @xcite .
a larger coupling strength can be achieved by making use of the kinetic inductance of a common leg between them @xcite .
even stronger coupling can be achieved by inserting a josephson junction in this common leg @xcite .
the latter also provides the possibility of ferromagnetic coupling , whereas the other methods only provide anti - ferromagnetic coupling @xcite . by insertion of an additional coupler loop between the qubits
, one could realize controllable / switchable coupling between them @xcite .
this is particulary important for the realization of scalable superconducting architecture for aqc .
controllable coupling enables one to construct a hamiltonian where both the energy bias @xmath9 and the coupling terms @xmath10 can be set _ in - situ_. a coupled @xmath11-flux - qubit system can be described by the hamiltonian : @xmath12 + \sum_{i < j}j_{ij}\sigma_{z}^{(i)}\sigma_{z}^{(j)}.\ ] ] here @xmath13 is the tunneling amplitude , or half energy splitting , of qubit @xmath14 at @xmath15 and @xmath16 gives the energy bias applied to qubit @xmath14 in terms of its persistent current @xmath17 and the normalized flux bias @xmath18 ( @xmath19 is the flux quantum ) .
the symbols @xmath20 denote the pauli matrices of the _ i_-th qubit .
the coupling energy is given by : @xmath21 where @xmath22 represents both the magnetic inductance between qubits @xmath14 and @xmath23 , as well as the kinetic inductance of a common leg .
the second term describes the coupling due to an additional junction with critical current @xmath24 inserted in the common leg between both qubits .
the many - qubit system described by eq .
[ eq_h_q ] can be characterized by the set of eigenstates @xmath25 and eigenenergies @xmath26 which can be obtained from the solution of the equation : @xmath27 as an example the first two levels @xmath28 and @xmath29 are shown in fig .
[ energyafm ] for a two qubit system with anti - ferromagnetic coupling ( @xmath30 ) .
for the readout of the qubit system we use a high - quality lc resonator ( tank - circuit ) consisting of a superconducting coil with inductance @xmath6 in parallel with a capacitance @xmath31 @xcite . in order to analyze the response of such a tank to the qubits we have to consider the complete hamiltonian of the qubits system and readout resonator : @xmath32 , where @xmath33 is the hamiltonian of the driven tank circuit and @xmath34 the interaction term between tank and qubits . in principle , one should also add a term containing the dissipative interaction with the environment , which would result in line broadening , @xmath35 , of the many - qubit spectrum .
however , the measurements are performed at a resonator frequency @xmath36 which is much less than the energy spacings , @xmath37 , of the coupled qubits . under such non - resonant conditions
the effects of dissipation on the measurements are proportional to the small ratio @xmath38 , and can be neglected . the driven tank - circuit hamiltonian can be written in terms of the non - commuting current , @xmath39 and voltage , @xmath40 operators .
( here @xmath41_-= -i \hbar \omega_t^{~2 } , $ ] with @xmath42 the resonance frequency ) as : @xmath43 where @xmath44 is the driving current of the tank . the interaction term is given by @xmath45 with @xmath46 the magnetic flux through the tank loop created by all qubits , @xmath47 .
@xmath48 is the coupling parameter between the @xmath14-th qubit and the tank , which is proportional to the mutual inductance between qubit and the coil of the tank - cirquit @xmath49 and to the magnitude of the persistent current of the qubit . by using the heisenberg equations @xmath50_-$ ] and @xmath51_-$ ] we obtain the following equation for the averaged current and voltage in the lc - circuit : @xmath52 @xmath53 where the damping of the tank @xmath54 was added on an _ ad - hoc _ basis . the flux @xmath55 incorporates not only the flux @xmath46 which the qubits would apply without their interaction with the tank , but also includes the response due to the tank according to:@xmath56 _ - i_t(t_1).\ ] ] here we have used the following notations for the ( anti)commutator of two operators a and b : @xmath57_{\pm } = ab \pm ba,$ ] and the interaction picture .
eq . [ eq1_v_t ] has the solution @xmath58 with @xmath59 the phase shift of the voltage relative to the driving current . for the case of resonant driving , @xmath60 , the voltage - current phase shift
is determined by the sum , over all qubit combinations , of the real part of the qubit susceptibility @xmath61 : @xmath62 the many - qubit susceptibility at the frequency of the tank @xmath63 is calculated in the appendix [ suceptibility ] and results in : @xmath64 here @xmath65 denote the equilibrium occupation of the qubit energy eigenstates : @xmath66 .
a numerical calculation of the predicted response for a 2 qubit system is shown in fig .
[ afresponse ] . by comparing this with the energy diagram in fig .
[ energyafm ] it is seen that the predicted signal is largest close to the anticrossings where the ground state @xmath28 has the largest curvature due to the superposition of flux states . , @xmath67 , @xmath68 and j=300 mk.,title="fig:",width=226 ] + for an afm - coupled two qubit system .
the tank response is calculated for the same qubit parameters as used in fig .
[ energyafm ] .
the read - out parameters are @xmath69 nh , @xmath70 ph and @xmath71 with an effective temperature @xmath72 mk . , title="fig:",width=226 ] +
for our experiments we fabricate the qubit - system of interest inside a prefabricated superconducting planar coil made out of niobium on a si chip . this coil forms the tank - circuit together with an external capacitor @xcite . on the coil chip
there are also nb lines which allow the application of an asymmetric flux bias to the qubits . by applying a dc bias current @xmath5 through the tank and currents @xmath73 and @xmath74 ( in the 3 qubit example shown in fig . [ setup ] ,
[ aqcreadout]a ) through the lines we can separately change the magnetic flux in the qubits . for
more qubits one should add additional lines . as shown above
, measuring the shift of the resonance frequency allows one to read - out the total susceptibility of the qubit system .
therefore , the tank - circuit is driven with a current @xmath44 at a frequency @xmath75 close to the resonance frequency @xmath36 of the tank circuit .
the variation of the resonance frequency , due to the change in the susceptibility of the qubit system according to ( [ eq1_shift ] ) , can be measured by detecting the phase shift @xmath76 between the @xmath77-current @xmath78 applied through the coil and @xmath77voltage over the tank circuit .
this is realized by using the setup shown in fig .
[ setup ] .
the voltage across the tank circuit is amplified by a cold hemt - based amplifier followed by a room temperature amplifier .
the phase shift @xmath59 is measured using a lock - in amplifier with part of the signal which is used to bias the qubit used as a reference . in the simplest case - one qubit at low temperature @xmath79
, @xmath80 is proportional ( through the mutual inductance ) to the persistent current @xmath81 flowing in the qubit system . since a qubit is in the ground state @xmath28 the current @xmath81 is proportional to @xmath82 . by taking into account eq .
[ eq1_v_t ] it can be easily shown that a shift of the tank resonant frequency due the tank - qubit interaction ( and , therefore , @xmath83 or @xmath84 ) is proportional to the ground state curvature @xmath85 . because the ground state curvature is maximal near the anticrossing , the output signal as a function of the applied magnetic flux undergoes a narrow dip @xcite at @xmath86 . from the shape of the dip
the one - qubit hamiltonian can be reconstructed by making use of the following equations @xcite : @xmath87 @xmath88 at higher temperatures one can fit the dip directly to the theory as given by eqs .
( [ eq1_shift ] ) and ( [ eq2_shift ] ) . by properly biasing a multi qubit system one can use this single qubit reconstruction procedure for a multi qubit system .
the bias to such an @xmath11 qubit system is applied as follows : for @xmath89 qubits @xmath90 and @xmath91 for any @xmath23 .
then the @xmath13 in eq .
( [ eq_h_q ] ) for @xmath89 qubits and also the interaction between all qubits can be neglected .
doing so reduces eq .
( [ eq_h_q ] ) to the hamiltonian of a single qubit .
the @xmath89 qubits far from their degeneracy points can be considered as conventional classical magnetic moments and their influence on the nth qubit provides an additional bias @xmath92 only .
the resulting hamiltonian is @xmath93 therefore , from measurements described above , and by making use of eqs .
( [ dip1 ] ) , ( [ dip2 ] ) , the persistent current @xmath94 as well as @xmath95 can be determined . by repeating this procedure for the other qubits
we can find their parameters . in order to complete the determination of the parameters of @xmath96
the coupling energies @xmath10 must be obtained .
they can be obtained from the shift of the qubit dips relative to the common degeneracy point .
this can be seen in the numerically calculated energy levels and qubit response in figs .
[ energyafm ] and [ afresponse ] . for low @xmath97 and small @xmath13 , the locations of the dips in @xmath98 , due to anti - crossings , simply follow the separation lines between the different classical states in the classical stability diagram . due to this
the state of the two - qubit system can be easily reconstructed . moreover
, the coupling energy follows directly from this stability diagram .
for instance , the transition @xmath99 occurs at @xmath100 .
therefore , one can easily show that the coupling energy follows from @xmath101 . in fig .
[ 2q30mk ] we show some quite recent results from a 2 qubit system measured with an improved setup .
the qubits in this sample are coupled by a common josephson junction as in ref .
this allows one to design the coupling strength over a wider range and than with inductive coupling only . by using the procedure described above all parameters of the hamiltonian , eq .
[ eq_h_q ] , were found from the experimental data .
the mutual inductances @xmath102 between the coil and qubits were determined from the periodicity of the qubit signal from a scan over multiple @xmath19 .
the mutual inductances between the bias lines and qubits followed from the slope of the qubit lines in fig .
[ 2q30mk]a .
these mutual inductances can be used to calculate the energy biases @xmath9 and , therefore , for the prediction of the response of the tank from the theory of sec .
[ sec : theory ] .
this prediction is shown shown in fig .
[ 2q30mk]b .
the good agreement between experimental data and the theoretical prediction confirms the systems effective temperature of about 30 mk which also followed from the fit . for afm - coupled qubits measured at the mixing chamber temperature of 10 mk .
( b ) theoretical fit for an effective temperature @xmath103 mk and for the sample parameters @xmath104 ( all in mk ) and @xmath105 na , @xmath106 na.,title="fig:",width=226 ] for afm - coupled qubits measured at the mixing chamber temperature of 10 mk .
( b ) theoretical fit for an effective temperature @xmath103 mk and for the sample parameters @xmath104 ( all in mk ) and @xmath105 na , @xmath106 na.,title="fig:",width=226 ] +
k. @xmath107 k , @xmath108 k , and @xmath109 k. @xmath110 is a global minimum , while @xmath111 is a local one.,title="fig:",width=226 ] + at @xmath112 . the tank s response is calculated for @xmath113 mk , @xmath114 mk , @xmath115 na , @xmath116 na , and @xmath117 mk .
the white dashed lines denote the cross - overs between the different classical states . at the white dot
@xmath118 the maxcut problem with the solution @xmath110 is encoded , see fig .
[ aqchyst ] .
the solid arrows show the directions in which the read - out should be carried out in order to reconstruct this state.,title="fig:",width=226 ] + in this section we review the aqc - algorithm for the solution of the maxcut problem .
in particular we discuss a possible demonstration of aqc by making use of a system composed of three coupled flux - qubits using a resonant tank circuit for the readout . since the hamiltonian of eq .
( [ eq_h_q ] ) is similar to an ising hamiltonian at @xmath119 it encodes the maxcut of a 3 vertex graph if @xmath120 @xcite .
the simplest non - trivial case is a three - qubit system as shown in fig .
[ setup ] , for example with the following qubit parameters : @xmath113 mk , @xmath114 mk , @xmath115 na and @xmath116 na .
if this system is allowed to adiabatically evolve to the qubit energy biases @xmath121 k , @xmath122 k , and @xmath123 k , it will encode a maxcut problem with a solution given by the state @xmath110 .
this can be seen in fig .
[ aqchyst ] where the energies of all flux - states for the hamiltonian of eq.([eq_h_q ] ) with all @xmath119 , @xmath10 and @xmath124 as given above have been depicted .
this system also exhibits a local minimum @xmath111 , two spin - flips away from the global minimum , this makes it an interesting test system for aqc .
if a violation of the adiabatic evolution criterium occurs , the system can be found in this local minimum instead of the global one .
this can be due to either thermal excitations during the readout or landau - zener transitions caused by a too high readout speed
. therefore one should optimize this readout speed depending on the energy gap in order to obtain optimal results .
the tank circuit response @xmath125 predicted by eqs .
( [ eq1_shift ] ) and ( [ eq2_shift ] ) for a fixed value @xmath112 is shown in fig .
[ aqcreadoutth ] .
the white dashed lines denote the cross - overs between the different classical ( @xmath119 ) states , which are marked in the figure by the state vectors @xmath111 , @xmath126 , @xmath127 and @xmath110 .
the main feature of the tank s response is that it restores the classical cross - overs .
this fact can be used for reading out the state of the qubits at any flux point . in the case of fig .
[ aqcreadoutth ] we want to know the qubits configuration at @xmath128 , because this point encodes the solution of the maxcut problem that we are interested in .
therefore , if we perform the measurement of the qubits susceptibility in the directions marked by solid arrows in fig . [ aqcreadoutth ] , a _
peak _ structure will appear either to the left , or the right side of @xmath128 in each flux direction .
this allows the establishment of the following criterium : if the peak appears to the right(left ) side of the starting point when we scan the flux @xmath129 through the qubit @xmath14 , the starting point corresponds to the classical state @xmath130 .
therefore , one can easily check that @xmath131 corresponds to the @xmath110 state if all @xmath119 ( for finding @xmath132 one would need another figure _ e.g. _ the @xmath133 plane at a fixed value of @xmath134 ) . at @xmath135 , measured at @xmath136 mk .
( c ) predicted response for @xmath137 mk , @xmath138 mk , @xmath139 na , @xmath140 na , and @xmath141 mk .
( d ) difference between the ground and first excited states . for ( c ) and
( d ) the black dashed lines denote the cross - overs between the different classical states.,title="fig:",width=188 ] + at @xmath135 , measured at @xmath136 mk .
( c ) predicted response for @xmath137 mk , @xmath138 mk , @xmath139 na , @xmath140 na , and @xmath141 mk .
( d ) difference between the ground and first excited states .
for ( c ) and ( d ) the black dashed lines denote the cross - overs between the different classical states.,title="fig:",width=226 ] + as a first step towards the demonstration of aqc we measured the full three - dimensional susceptibility of three anti - ferromagnetically coupled qubits @xcite . for this purpose
we fabricated a sample with the layout of fig .
[ setup ] and measured it in our setup at a base temperature of 10 mk .
figure [ aqcreadout]a shows a micrograph of the sample : three al persistent current qubits are fabricated inside a nb pancake coil .
two junctions in each qubit are nominally @xmath142 nm@xmath143 , while a third one is @xmath14435% smaller .
each qubit is coupled to the other two both magnetically and via shared @xmath145 nm@xmath143 junctions .
the flux through the qubits is controlled by direct currents through the coil @xmath146 , and two additional lines @xmath147 and @xmath148 ( the third line was not used during the experiment ) . the nb coil has an inductance @xmath149 nh , and together with an external capacitance @xmath150 pf forms a parallel tank circuit with @xmath151 mhz and quality @xmath152 .
the qubit - coil mutual inductances were extracted from the @xmath19 periodicity of the @xmath153-susceptibility of the individual qubits as @xmath154 ph and @xmath155 ph , @xmath156 ph . the mutual inductances between all qubits and biasing wires were found from two scans @xmath157 , see ref .
@xcite . fig .
[ aqcreadout]b shows @xmath125 at @xmath135 , while fig .
[ aqcreadout]c is the theoretical prediction for @xmath137 mk , @xmath138 mk , @xmath139 na , @xmath140 na , and @xmath72 mk .
the experimental and theoretical data are found to be in good agreement in the full three - dimensional flux space ( other data for @xmath158 can be found in @xcite ) .
however , for this sample not all classical cross - overs could be reconstructed .
the narrow lines in the upper right quadrant of fig .
[ aqcreadout]bc are absent .
there are two main reasons for this : firstly the difference between the ground and first excited state ( @xmath159 mk ) along these measured lines is small ( see fig.[aqcreadout]d ) in comparison with the effective temperature @xmath72 mk for this measurements .
secondly all qubits persistent currents ( or magnetic moments ) are similar , therefore there is no significant _ magnetization _ change along the transitions @xmath160 and @xmath111 @xmath161 , thus there is no susceptibility change and no phase shift . in order to observe these lines
, one could make a sample with different persistent currents , increase the gap between the ground and first excited states , or decrease the system s effective temperature . for the latter approach we already made some progress because for our improved experimental setup , see fig.[2q30mk ]
, we have reached an effective temperature @xmath162 mk .
the next steps for aqc will be a improving the readout speed , the demonstration of the real adiabatic evolution / computation and demonstration of its efficiency in comparison with the classical simulated annealing .
this review is concluded by answering some general questions that we have been often asked .
the first question is whether it is possible to realize aqc with coupled classical magnetic moments ? or in other words : do we need quantum mechanics for an aqc implementation ?
in the quantum system there is an energy gap between the ground and the first exited states , thus the qubit system can evolve always staying in the ground state .
a system without level- anticrossings exhibits many metastable states , so that evolution in the ground state is not possible . as the qubits stability diagrams , shown in figs .
[ afresponse ] , [ aqcreadoutth ] are the same as would be is expected for coupled classical magnetic moments , where is the proof that the system described above behaves quantum mechanically ? in the classical limit the persistent current `` qubits '' have a magnetic hysteresis for any finite qubit s inductance .
this hysteresis was observed by making use of our method @xcite . in this work instead of hysteresis we observed a narrow dip , which reflects the level anticrossing due to quantum tunneling .
therefore , there is a nonzero gap between the ground and the first exited state which allows aqc .
the stability of aqc against external noise , to our knowledge , is not known .
on one hand , since we do not use any coherent oscillations , aqc should not be very sensitive to the environment .
on the other hand , external noise can change the hamiltonian itself and , therefore , its ground state .
this issue requires further study . in the present work we discussed our approach for demonstrating an adiabatic quantum algorithm by making use of a coupled flux - qubit system . by making use of a low - frequency resonator inductively
coupled to the qubits we can completely reconstruct the parameters of a multi - qubit system .
this multi - qubit ground state anticrossings read - out can be currently performed at an effective temperature of 30 mk .
the experimental data are found to be in complete agreement with quantum mechanical predictions .
we have reconstructed the susceptibility of three coupled flux qubits in full parameter space .
the next steps towards aqc will be improvement of the read - out speed and the demonstration of adiabatic quantum computation and its efficiency .
[ suceptibility ] starting from the first order approximation of the total flux given in the main text ( eq . [ eq2_phi_tot ] ) we can write out the commutator as a sum of the qubit response functions @xmath163 : @xmath164_-\rangle \theta(t - t_1 ) = \sum_{ij } \lambda_i \lambda_j \varphi_{ij}(t , t_1).\ ] ] with @xmath165_-\rangle \theta(t - t_1),\ ] ] where we introduced the heaviside step function : @xmath166 if @xmath167 and @xmath168 when @xmath169 for small values of the tank current and voltage the derivative of the total qubit flux is given by the expression @xmath170 putting this into eq .
( [ eq1_v_t ] ) results in a shift of the resonant frequency of the tank which is proportional to the susceptibility and is just the fourier transform of the response function : @xmath171 this shift in the resonance frequency causes the phase shift when the tank is driven with its unloaded resonance frequency @xmath36 according to eq .
( [ eq1_shift ] ) . in order to calculate the linear response functions @xmath172 ( eq . ( [ eq2_resp_qub ] ) ) we have to find the product of two projections of pauli matrices taken at times @xmath173 and @xmath174 @xmath175 and the equilibrium distribution @xmath176 . as a result
we obtain the expression @xmath177 for the linear response functions @xmath172 ( [ eq1_resp ] ) . which give after fourier transformation : @xmath178 by taking into account that the resonant frequency of the tank is much smaller than the level spacing and , therefore ,
can be neglected eq .
( [ eq2_shift ] ) of the main text is generated .
we thank d. v. averin , a. blais , a. shnirman , e. goldobin , ya .
s. greenberg , r. gross , h. e. hoenig , yu .
a. pashkin , m. j. storcz , f. k. wilhelm and a. zeilinger for fruitful discussions .
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controllable adiabatic evolution of a multi - qubit system can be used for adiabatic quantum computation ( aqc ) .
this evolution ends at a configuration where the hamiltonian of the system encodes the solution of the problem to be solved . as a first steps towards realization of aqc we have investigated two , three and four flux qubit systems .
these systems were characterized by making use of a radio - frequency method .
we designed two - qubit systems with coupling energies up to several kelvins .
for the three - flux - qubit systems we determined the complete ground - state flux diagram in the three dimensional flux space around the qubits common degeneracy point . we show that the systems hamiltonian can be completely reconstructed from our measurements .
our concept for the implementation of aqc , by making use of flux qubits , is discussed .
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the physics phenomena of nuclei are largely understood by considering the interaction between their building blocks , the nucleons . in 1935 , yukawa described the nucleon - nucleon ( nn ) force by the exchange of massive mesons @xcite in analogy to the electromagnetic interaction which can be represented by the exchange of a massless photon .
several phenomenological nucleon - nucleon potentials have been derived based on yukawa s theory and are able to reproduce data points in neutron - proton and proton - proton scattering with extremely high precision .
these so - called high - quality nn potentials are used in faddeev equations @xcite to give an exact solution of the scattering problem for the three - nucleon system .
already , for the simplest three - nucleon system , the triton , an exact solution of the three - nucleon faddeev equations employing two - nucleon forces ( 2nfs ) underestimates the experimental binding energy @xcite , showing that 2nfs are not sufficient to describe the three - nucleon system accurately .
the existence of an additional force , the three - nucleon ( 3n ) interaction , was predicted a long time ago by primakov @xcite and confirmed by a comparison between precision data and state - of - the - art calculations @xcite .
many high - precision measurements of nucleon - deuteron scattering processes at intermediate energies were carried out in the past decades with the aim to study 3nf effects and to compare the experimental observations with the predictions from rigorous faddeev calculations . in general , adding 3nf effects to the modern nn potentials gives a better agreement between the cross section data for the proton - deuteron scattering processes and the corresponding calculations @xcite , whereas a similar comparison for the spin observables yields various discrepancies @xcite .
the overall conclusion is that the spin - dependent parts of the 3nfs are poorly understood and that more studies in this field are needed .
the 3nf effects are in general small in the three - nucleon system .
a complementary approach is to examine heavier systems for which the 3nf effects are significantly enhanced in magnitude .
naively , one might expect that the 3nf effects increase by the argument that the number of three - nucleon combinations with respect to two - nucleon combinations gets larger with increasing number of nucleons .
we , however , note that the saturation of 3nf effects sets in very quickly for large nuclei as well .
this simple counting rule is supported by a comparison between predictions and data for the binding energies of light nuclei @xcite .
the predictions of a green s function monte - carlo calculation based on the argonne v18 @xcite nn interaction ( av18 ) and the illinois-2 ( il2 ) 3nf @xcite are compared to experimental data . while a calculation which only includes the av18 nn potential deviates significantly from the experimental results , the predictions of calculations which include as well a 3nf come much closer to the data , especially for the first few light nuclei .
note that the effect of the 3nf on the binding energy for the triton is 0.5 - 0.8 mev , whereas the effect increases significantly for the four - nucleon system , @xmath0he , to @xmath14 mev .
for this , it was proposed to study the four - nucleon system at intermediate energies since the experimental database for this is presently poor in comparison with that of three - nucleon systems @xcite .
most of the available data have been measured at very low energies , in particular below the three - body break - up threshold of 2.2 mev .
also , theoretical developments are evolving rapidly at low energies @xcite , but lag behind at higher energies .
this situation calls for extensive four - nucleon studies at intermediate energies .
this paper addresses the feasibility of measuring polarization observables in the three - body break - up channel in deuteron - deuteron scattering , @xmath2 , for an incident beam energy of 65 mev / nucleon .
this work is part of a more extensive experimental program which was carried out at kvi and that aims to provide precision data in various four - nucleon scattering processes at intermediate energies . with these data
, we will significantly enrich the four - nucleon scattering database at intermediate energies and , thereby , provide a basis to test future calculations with the long - term aim to understand the details of 3nf effects .
e , followed by a wall of thick segmented scintillators ( e ) .
the backward ball is not shown in this picture , since it was not used in the analysis presented in this paper . ]
deuteron - deuteron scattering below the pion - production threshold leads to 5 possible final states with a pure hadronic signature , namely : + 1 .
elastic channel : @xmath3 ; 2 .
neutron - transfer channel : @xmath4 ; 3 .
proton - transfer channel : @xmath5 ; 4 .
three - body final - state break - up : @xmath6 ; 5 .
four - body final - state break - up : @xmath7 .
the study and identification of these final states require an experimental setup with specific features , namely , a large phase space coverage , a good energy and angular resolution , and the ability for particle identification .
the experiment presented in this paper was carried out at kvi using the big instrument for nuclear - polarization analysis , bina , which meets all these requirements @xcite .
this work is devoted to the three - body final state .
bina is a setup with a nearly @xmath8 geometrical acceptance and has been used in various few - nucleon scattering experiments to measure the scattering angles and energies of protons and deuterons with the possibility for particle identification .
the detector is composed of a forward part ( forward wall ) and a backward part .
figure [ bina1 ] shows a side view of the forward part of bina which consists of a multi - wire proportional chamber ( mwpc ) , and an array of thin plastic scintillators ( @xmath9e ) with a thickness of 1 mm , followed by a wall of thick segmented scintillators ( e ) with a thickness of 12 cm each .
all scintillators were read out by photo - multiplier tubes ( pmts ) on both ends . the signals from these pmts are integrated using a qdc to measure their energy loss in the scintillator .
the discriminated signals from the constant fraction discriminators ( cfds ) are fed into time - to - digital converters ( tdcs ) .
the time difference between the signals from both ends of the scintillators allows to determine the position of the incoming particle .
in addition , information about the time - of - flight ( tof ) of the particles can be extracted .
the thick scintillators were mounted in a cylindrical shape , thereby , facing the target .
the thickness of these scintillators is sufficient to stop all the protons and deuterons originating from the processes described in this work .
the forward wall has a complete azimuthal coverage for scattering angles from 10@xmath10 to 32@xmath10 , which is advantageous for the determination of the beam polarization and spin observables . with the wire spacing of 2 mm and for a distance of 29.7 cm between mwpc and target
, we obtain an overall accuracy of 0.4@xmath11 for the polar angle and between 0.6@xmath11 and 2.0@xmath11 for the azimuthal angle .
the detection efficiency of the mwpc was obtained by using an unbiased and nearly background - free data sample of elastically - scattered deuterons and was found to be typically 98% with an absolute uncertainty of 1% .
a polarized beam of deuterons originating from the polarized ion source ( polis ) @xcite was accelerated by agor ( acclrateur groningen orsay ) to a kinetic energy of 65 mev / nucleon and bombarded on a liquid - deuterium target @xcite .
the polarization of the deuteron beam was measured in the low - energy beam line with a lamb - shift polarimeter ( lsp ) @xcite as well as in the high - energy beam line with bina @xcite . for the polarization measurements using the lsp ,
the low - energy beam was decelerated and focused on to the lsp detection system . the number of deuterons in the spin - up state , n@xmath12 , spin - zero state , n@xmath13 , and spin - down state , n@xmath14 , were counted to measure directly the vector and tensor polarizations of the beam .
in addition , the polarization of the beam of deuterons was obtained at the high - energy beam line employing bina via @xmath15-asymmetry measurements of the @xmath16 reaction based on its well - known analyzing power .
note that the same detector was used as well for the measurement of the polarization observables of the deuteron - deuteron break - up reaction . with the self - calibrating bina setup ,
regular asymmetry measurements of the elastic deuteron - proton scattering process were performed during the actual experiment by switching rapidly the liquid target to a solid ch@xmath17 target .
the polarization of the beam of deuterons was studied as a function of time to check the stability of polarization during the measurement .
also , the polarization values by bina were compared with those measured with the lsp .
the results for the vector ( top panel ) and tensor ( bottom panel ) polarizations of the deuteron beam from bina and lsp are shown in fig .
[ resultpol ] as a function of time .
each filled circle represents the average value of the measured polarizations deduced from different scattering angles with bina in a range from 55@xmath10 to 140@xmath10 in the center - of - mass frame .
the corresponding analyzing powers were taken from an angle - dependent fit of literature values @xcite .
polarization values obtained for different scattering angles were found to be in good agreement within uncertainties .
the values of the polarization obtained with lsp are depicted as filled squares .
the shaded bands represent the results of a constant - value fit through the data including the results obtained with bina and lsp .
the width of the band corresponds to a 2@xmath18 error of the fit .
the polarization values were found to be @xmath19 and @xmath20 .
the total uncertainties of the polarizations was estimated by adding quadratically the statistical error and the systematic error .
the systematic uncertainty stems from the uncertainty in the analyzing powers , and was found to be 6% and 5% for the vector and tensor polarizations , respectively .
a comparison between the results demonstrates that the beam polarization was stable during the experiments and that there is a good agreement between the measured values obtained at the low - energy beam line with the lsp and those measured at the high - energy beam line with bina .
the beam current was monitored during the experiments via a faraday cup at the end of the beam line .
the faraday cup is made of a copper block containing a heavy alloy metal as the actual beam stopper .
the current meter was connected to the faraday cup with a short cable to avoid the voltage drop and pickup effect .
the current meter was calibrated using a precision current source with an uncertainty of 2% .
the beam current was typically 4 pa during the experiment .
an offset of [email protected] pa in the beam current was observed in the @xmath22 experiment through a comparison of @xmath23 in elastic scattering , measured with bina and the one measured with another experimental setup ( bbs ) @xcite .
the elastic channel , neutron transfer channel , and break - up channels leading to three- and four - body final states were uniquely identified using the information on the energies of the outgoing particles , their scattering angles , and their tof . in this work ,
the deuteron - deuteron break - up into the three - body final - state ( four - body final - state ) is further referred to as the three - body break - up ( four - body break - up ) .
this is the first time that spin observables in the three - body break - up reaction in @xmath24 scattering process at intermediate energies have been measured in a background - free experiment .
the analysis procedure and a part of the results of the three - body break - up channel are presented in this paper .
the kinematics of the three - body break - up reaction are determined unambiguously by exploiting the scattering angles of the proton and the deuteron ( @xmath25 ) and the relation between their energies presented by the kinematical curve which is referred to as the @xmath26-curve . the angles @xmath27 and @xmath28 are the polar angles of the proton and the deuteron , respectively , and @xmath29 is the difference between their azimuthal angles .
the energies of the proton , @xmath30 , and deuteron , @xmath31 , were transferred into two new variables , @xmath32 and @xmath26 .
the variable @xmath26 is the arc - length along the @xmath26-curve with the starting point chosen arbitrarily at the point where e@xmath33 is minimum and @xmath32 is the distance of the ( @xmath30 , @xmath31 ) point from the kinematical curve .
scattering is shown as @xmath26-curves for several kinematical configurations .
the kinematics are defined by ( @xmath34 ) , the polar scattering angles of the deuteron and proton , respectively , and their relative azimuthal angle . ]
the @xmath26-curves for several kinematical configurations are shown in fig .
[ kinema ] .
each @xmath26-curve is labeled by three numbers .
for example , the label ( @xmath35 ) shows a kinematical relation of energies of a deuteron that scatters to @xmath36 and a proton that scatters to @xmath37 , and the azimuthal opening angle , @xmath29 , between them is equal to @xmath38 . for the analysis of the three - body break - up data we measured the kinetic energies and the polar and azimuthal angles of the two coincident charged particles .
we performed the analysis of the three - body break - up reaction for that part of the phase - space in which the deuteron and the proton were detected in coincidence in the forward part of bina .
for some parts of the @xmath9e detector , the yield of scintillation light reaching the photomultipliers was not sufficient to obtain a good particle identification .
we , therefore , decided to make use of the time - of - flight to perform a particle identification instead .
we note that the procedure was checked by a successful comparison with an analysis using those @xmath9e detectors which were operating according to specifications . for the particle identification
, we measured the tof of each registered particle and compared its result with the expectation from the kinematics of the three - body break - up reaction .
the tof was determined by discriminating the signals from the two pmts from each scintillator .
the output of the constant - fraction discriminators were fed into time - to - digital converters ( tdcs ) which were used in a common - stop mode .
the common stop signal was derived from the radio frequency of the cyclotron . for the analysis of the break - up data
, the tdc output corresponding to the left- and right - hand side pmts , @xmath39 and @xmath40 , were added together for each event .
the sum of @xmath41 and @xmath40 is independent of hit position along the scintillator slab .
we call this sum tof@xmath42 with @xmath43 referring to the different particles that hit the forward wall . for particle identification
, we compared these results with the expected tof that was calculated from the energy of a particle , calculating a path length from a scattering angle and assuming a certain particle type .
more precisely , the difference between the measured tof of particles 1 and 2 from the information of the tdcs , @xmath44 , and that extracted from the energies and the scattering angles , @xmath45 , has been used to define the variable @xmath9tof .
we note that @xmath9tof is a difference of differences , and that it compares data with a kinematics calculations , both of which yield a difference .
the identification of the break - up channels proceeds by analyzing @xmath9tof .
figure [ tof_tdc_e ] shows the value of @xmath9tof for two particles that are detected in coincidence in the forward wall .
the scattering angle of both particles is fixed to be @xmath46 and the difference between the azimuthal angles of the two particles is @xmath47 .
we note that @xmath9tof does not depend upon @xmath26 and that the detected particle in each hit can be a proton or a deuteron .
three clear peaks can be recognized corresponding to proton - deuteron , proton - proton , and deuteron - proton coincidences .
the identification of the peaks were confirmed using the @xmath9e responses . for this spectrum , we assumed in the calculation of @xmath45 that the first particle is a deuteron and the second one a proton
. if our assumption is correct , events which correspond to a deuteron - proton combination will give a peak around zero in the @xmath9tof spectrum .
note that a clear signal ( peak on the left - hand side of fig .
[ tof_tdc_e ] ) of the three - body break - up events can be observed corresponding to a final - state consisting of a deuteron - proton combination .
the peak on the most right - hand side corresponds to three - body break - up events , but with a proton - deuteron combination in the final state .
the peak in the middle of the spectrum has been identified as two protons that stem from the four - body break - up reaction .
tof for two particles that are detected in coincidence in the forward wall .
the scattering angle of both particles is fixed to be @xmath48 and the difference between the azimuthal angles of the two particles is @xmath47 . ] the top - left panel of fig .
[ chanid_tdc ] represents the correlation between the energy of two particles that are detected in coincidence in the forward wall .
the scattering angle of both particles is fixed to be @xmath48 and the difference between the azimuthal angles of the two particles is @xmath47 .
the energies were obtained by a charge - integration of the signals from the pmts of the forward scintillators .
this spectrum contains events from two different reactions , namely three- and four - body break - up reactions .
the proton - deuteron or deuteron - proton coincidences from the three - body break - up reaction can be separated by choosing events corresponding to the peak of interest as shown in fig [ tof_tdc_e ] .
the results are shown in the top - right and bottom - right panels .
the bottom - left panel contains events which correspond to the peak in the middle of fig [ tof_tdc_e ] .
they originate from the four - body break - up channel .
figures [ tof_tdc_e ] and [ chanid_tdc ] demonstrate the particle identification capabilities of the detection system .
the identification of the proton and deuteron enables us to measure the missing particle in the three - body break - up reaction in deuteron - deuteron scattering .
the missing particle in this reaction is neutron as well .
this particle can be identified using the missing mass technique .
we used the energy and scattering angles of the identified particles to calculate the rest mass of the undetected particle .
figure [ missmass ] shows a typical result of the calculated mass of the undetected particle using the energy , polar and azimuthal angles of the detected proton and deuteron .
the scattering angle of both detected particles is fixed to be @xmath49 and the difference between the azimuthal angles of the two detected particles is @xmath47 .
the dashed ( solid ) curve represents the results of the calculated missing particle mass before ( after ) applying the identification cut on fig .
[ tof_tdc_e ] .
after applying the identification cut the mass spectra show a clear peak corresponding to the mass of neurons with a fwhm of 6.38 mev which confirms the accuracy of pid procedure .
the events on the right - hand side of the peak correspond to break - up events that undergo a hadronic interaction in the scintillator .
these are discarded in the analysis and properly accounted for in the final analysis of cross sections with the help of simulations . .
the scattering angle of both detected particles is fixed to be @xmath48 and the difference between the azimuthal angles of the two detected particles is @xmath47 . ] the next step in the event selection for the three - body break - up channel is to find the energy correlation between the final - state protons and deuterons for a particular kinematical configuration ( @xmath50 ) .
the number of break - up events in an interval @xmath51 , and @xmath52 was obtained by projecting the events on a line perpendicular to the @xmath26-curve ( @xmath32-axis ) .
the value of @xmath53 was @xmath54 mev for the forward wall data .
-bin onto the @xmath32-axis is shown in the inset . ]
figure [ 25 - 25 - 180 ] depicts the correlation between the energy of protons and deuterons in coincidence for the kinematical configuration , ( @xmath55 . the solid curve is the expected correlation for this configuration .
one of the many @xmath26-intervals and the corresponding @xmath32-axis are also shown .
the result of the projection of events on the @xmath32-axis for a particular @xmath26-bin is presented in the inset of fig . [ 25 - 25 - 180 ] .
this spectrum consists of mainly break - up events with a negligible amount of accidental background .
most of the particles of the break - up events deposit all their energy in the scintillator , which gives rise to a peak around zero in the variable @xmath32 .
the events on the left - hand side of the peak at zero correspond to break - up events that undergo a hadronic interaction in the scintillator ( same as those on the right side of the peak in fig . [ missmass ] ) .
the interaction of a polarized beam with an unpolarized target produces an azimuthal asymmetry or an azimuthally uniform change in the scattering cross section .
the magnitude of this effect is proportional to the product of the polarization of the beam and an observable that is called the analyzing power .
the expression for the cross section of any reaction induced by a polarized spin-1 projectile is @xcite : @xmath56 where @xmath18 and @xmath57 are the polarized and unpolarized cross sections , respectively , and @xmath58 represents the configuration @xmath59 . note that eq .
[ ddbreakcrosfurmola ] does not contain terms with @xmath60 , @xmath61 , @xmath62 , @xmath63 and @xmath64 .
these contributions vanish because we took explicitly @xmath65 and @xmath29 is the absolute value of the difference between the azimuthal angles of the two outgoing particles .
the angle @xmath66 is the angle between the polarization axis and the momentum of the incoming beam . in this work , the variables @xmath67 , @xmath68 and @xmath69 will be referred to as @xmath70 , @xmath23 and @xmath71 , respectively .
the quantities @xmath70 and @xmath72 are the vector - analyzing power and the vector beam polarization , respectively .
the observables @xmath23 and @xmath71 are the tensor - analyzing powers , @xmath73 is the tensor polarization of the beam , and @xmath15 is the azimuthal scattering angle of the deuteron .
mev ) . ] for a deuteron beam with a pure vector polarization , the ratio @xmath74 should show a @xmath75 distribution where @xmath18 and @xmath57 are the polarized and unpolarized cross sections , respectively .
when a pure tensor - polarized deuteron beam is used , the ratio @xmath76 should show a @xmath77 distribution .
these asymmetries are exploited to extract the vector - analyzing power , @xmath70 and the tensor - analyzing powers , @xmath23 and @xmath71 , for every kinematical configuration , @xmath78 .
for a measurement of the analyzing powers , we compare the distribution of the scattered particles at different azimuthal angles for each polarization state with that obtained with the unpolarized beam . the @xmath15-distribution obtained with the polarized beam is normalized to that obtained with an unpolarized beam to obtain the ratio @xmath74 .
this ratio depends on the the number of counts under the peak after background subtraction and the total integrated charge collected in the faraday cup . with this normalization
other parameters like the geometrical asymmetries , inefficiencies , and target thickness are eliminated .
figure [ ddbasy ] shows the ratio @xmath76 for a pure vector - polarized deuteron beam ( top panel ) and a pure tensor - polarized deuteron beam ( bottom panel ) for ( @xmath79 , @xmath80 , @xmath81 , @xmath82 mev ) .
the curves in the top and bottom panels are the results of a fit based on eq .
[ ddbreakcrosfurmola ] through the obtained asymmetry distribution for a beam with a pure vector and tensor polarization , respectively .
the amplitude of the @xmath83 modulation in the top panel equals to @xmath84 and that of the @xmath85 modulation in the lower panel equals to @xmath86 .
the offset from 1 in the lower panel is @xmath87 .
the vector- and tensor - analyzing powers for a few kinematical configurations of the three - body break - up reaction were extracted .
figure [ dd1 ] represents the vector- and tensor - analyzing powers at @xmath88 ( open squares ) and @xmath89 ( filled circles ) as a function of @xmath26 for different azimuthal opening angles .
the gray lines in all panels show the zero level of the analyzing powers .
only statistical uncertainties are indicated . the total systematic uncertainty for the analyzing power is estimated to be @xmath90 which mainly stems from the uncertainty in the measurement of the beam polarization via elastic scattering and to a much lesser extent from the error of the beam - current correction in the analysis of the t20 in the elastic d + d channel .
this paper demonstrates for the first time the feasibility of obtaining precision data of the three - body break - up channel in deuteron - deuteron scattering at the energy of 65 mev / nucleon .
the three - body break - up reaction has been clearly identified using the measured scattering angles , energies , and tof of the final - state protons and deuterons . in this work
, we analyzed a part of the data in which the protons and deuterons were scattered into the forward wall of bina .
we have provided precision data for the vector and tensor analyzing powers of the three - body break - up reaction for an incident deuteron beam of 65 mev / nucleon @xcite .
these four - body scattering experiments at kvi will provide in the near future a complete database in deuteron - deuteron scattering at intermediate energies including the elastic , transfer , three - body break - up , and four - body break - up channels .
together with the upcoming state - of - the - art ab - initio calculations @xcite , these data will provide the basis to understand the mechanisms behind many - body force effects .
the authors acknowledge the work by the cyclotron and ion - source groups at kvi for delivering a high - quality beam used in these measurements .
this work was performed as part of the research program of the `` stichting voor fundamenteel onderzoek der materie '' ( fom ) .
furthermore , the present work has been performed with financial support from the university of groningen ( rug ) , the helmholtzzentrum fr schwerionenforschung gmbh ( gsi ) , darmstadt , the nederlandse organisatie voor wetenschappelijk onderzoek ( nwo ) , the polish 2008 - 2011 science founds as a research project no .
n n202 078135 and iran ministry of science , research , and technology , kashan university .
cdb and ejs acknowledge support from the us national science foundation through grant phy 04 - 57219 .
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|
in an experiment with a 65 mev / nucleon polarized deuteron beam on a liquid - deuterium target at kvi , several multi - body final states in deuteron - deuteron scattering were identified . for these measurements , a unique and advanced detection system , called bina ,
was utilized .
we demonstrate the feasibility of measuring vector and tensor polarization observables of the deuteron break - up reaction leading to a three - body final - state .
the polarization observables were determined with high precision in a nearly background - free experiment . the analysis procedure and some results are presented .
|
SECTION 1. SHORT TITLE.
This Act may be cited as the ``Preventing Homeowners from
Foreclosure Act of 2010''.
SEC. 2. FORECLOSURE MEDIATION GRANT PROGRAM.
(a) Establishment.--The Secretary of Housing and Urban Development
(in this section referred to as the ``Secretary'') shall carry out a
program to make competitive grants to States and units of local
government to establish mediation programs that assist mortgagors under
home mortgages facing foreclosure on such mortgages.
(b) Foreclosure Mediation Program Requirements.--Amounts from a
grant under this section may be used only for costs of a foreclosure
mediation program that provides as follows:
(1) Scope.--
(A) State grantees.--In the case of a grant under
this section to a State, the program shall be carried
out in at least one unit of local government within
such State.
(B) Local government grantees.--In the case of a
grant made to a unit of local government, the program
shall be carried out in such unit of local government.
(2) Applicability.--The program shall apply to--
(A) any mortgagee that, after the expiration of the
90-day period beginning upon receipt, by the grant
recipient, of amounts from a grant under this section,
initiates a foreclosure proceeding on a home mortgage
for a mortgaged home that is located in the
jurisdiction within which such program is being carried
out, pursuant to paragraph (1); and
(B) any mortgagor under such a home mortgage who is
subject to a foreclosure proceeding.
(3) Referral to attorney or housing counselor.--The program
shall provide the mortgagor with a referral and contact
information for a paid or pro bono attorney, or a housing
counselor certified by the Secretary.
(4) Required meeting and mediation.--The program shall
require that, as soon as is practicable after the initiation of
a foreclosure proceeding on a home mortgage or a mortgagee has
provided the required foreclosure notice on a home mortgage to
the mortgagor in accordance with applicable State or local law,
as applicable, and, in any event, before entry of any
foreclosure judgment on or foreclosure sale for, as applicable,
the home mortgage--
(A) any representative obtained by the mortgagor
(including a representative obtained pursuant to a
referral under paragraph (3)) shall meet with the
mortgagor; and
(B) the mortgagee shall conduct, consistent with
any applicable State or local law, a mediation
conference that--
(i) is held to resolve issues relating to
the foreclosure, with the aim of avoiding the
foreclosure, through mediation;
(ii) is held in an appropriate court in the
jurisdiction of the grant recipient or, in the
case of jurisdiction that does not provide for
judicial foreclosure, such other appropriate
venue;
(iii) involves the participation of a
neutral, third party mediator selected by the
court or the administrator of the foreclosure
mediation program; and
(iv) is attended by--
(I) the mortgagee or, if the
mortgagee or an agent of the mortgagee
having authority to execute a
settlement of all matters relating to
the mortgage is immediately accessible
by telephone, by a representative of
the mortgagee; and
(II) the mortgagor, or any
representative obtained by the
mortgagor (including a representative
obtained pursuant to a referral under
paragraph (3)), or both.
If the mortgagor fails to attend the conference, the
requirement under this paragraph for a mediation conference
shall be deemed to be satisfied upon verification by the
administrator of the mediation program that the required
foreclosure notice has been provided and issuance by such
administrator of an order authorizing initiation of such
foreclosure proceeding.
(5) Outreach.--The grant recipient shall establish an
outreach program to raise homeowner awareness of the existence
of the foreclosure mediation program. Such outreach program
shall include providing access to information regarding the
foreclosure mediation program through a telephone hotline or a
World Wide Web site, or both.
(c) Selection of Grant Recipients.--The Secretary shall select
applicants to receive grants under this section under a competition
based on selection criteria that the Secretary shall establish by
regulation.
(d) Recordkeeping.--Each grant recipient shall maintain a record of
the outcome of each mediation conference carried out under the
mediation program assisted with the grant amounts, including the nature
of any loan modification made as a result of participation in the
mediation program.
(e) Definitions.--For purposes of this Act, the following
definitions shall apply:
(1) Foreclosure proceeding.--The term ``foreclosure
proceeding'' means any proceeding or procedure under applicable
law, including judicial and non-judicial procedures, including
a sheriff sale, to foreclose on a home mortgage.
(2) Home mortgage.--The term ``home mortgage'' means a
mortgage loan, repayment of which is secured by an interest in
a one- to four-family residence that is the principal residence
of the mortgagor.
(3) Grant recipient.--The term ``grant recipient'' means a
State or unit of local government that receives grant amounts
under this section.
(4) Mortgaged home.--The term ``mortgaged home'' means,
with respect to a home mortgage, the residence that is subject
to the interest that secures repayment of the home mortgage.
(5) Required foreclosure notice.--The term ``required
foreclosure notice'' means any initial notice that is required
under the law of a State to be submitted to the mortgagor under
a residential mortgage as a condition precedent to foreclosure
on such mortgage.
(6) State.--The term ``State'' means the States of the
United States, the District of Columbia, the Commonwealth of
Puerto Rico, the Commonwealth of the Northern Mariana Islands,
Guam, the Virgin Islands, American Samoa, the Trust Territory
of the Pacific Islands, and any other territory or possession
of the United States.
(f) Authorization of Appropriations.--There is authorized to be
appropriated for grants under this section such sums as may be
necessary for each of fiscal years 2011 through 2015.
(g) Regulations.--The Secretary of Housing and Urban Development
shall issue any regulations necessary to carry out this section.
|
Preventing Homeowners from Foreclosure Act of 2010 - Directs the Secretary of Housing and Urban Development (HUD) to implement a competitive grants program for states and local governmental entities to establish mediation programs to assist mortgagors under home mortgages facing foreclosure on such mortgages.
Requires the program to provide the mortgagor with a referral and contact information for a paid or pro bono attorney or a HUD-certified housing counselor.
Requires grant recipients to establish an outreach program to raise homeowner awareness of the existence of the foreclosure mediation program, including a telephone hotline, a World Wide Web site, or both.
|
The U.S. housing sector is gradually returning to pre-crisis levels. Home prices rose for four consecutive years to a median of $222,400 at the end of 2015, the highest since 2007. Prices rose further in the second quarter — by 4.9% from the same time a year ago. With increased home values as well as continued job and income growth there are plenty of reasons for optimism in the U.S. economy.
Not all U.S. housing markets, however, have returned to pre-crisis levels. According to data released in August by the National Association of Realtors, housing prices increased the most in the Western and Southern United States, while in the Northeast prices grew slowly, or declined.
Based on median single-family home price changes over the year through the second quarter from the NAR, 24/7 Wall St. reviewed the fastest growing (and shrinking) housing markets. The Boulder, Colorado area leads the nation with home prices rising 18.5% over the year. Home prices are down 13.1% in the Atlantic City-Hammonton, New Jersey region, the largest decline.
Click here to see the 25 fastest growing housing markets.
Click here to see the 25 fastest shrinking housing markets.
In an interview with 24/7 Wall St., Danielle Hale, managing director of housing research at the NAR, said, “It’s good to think of [real estate] as being a life cycle product.” Young people with relatively unestablished careers and unsettled families typically rent to remain mobile. Once they become more established, they tend to transition into homeownership. “And they don’t often transition back into renting,” Hale noted.
Rising home prices are obviously a good thing for current owners, and also stimulate the economy. According to the “The State of the Nation’s Housing 2016,” a report by the Joint Center for Housing Studies of Harvard University, when home equity grows, owners spend more on home improvement projects and consumer spending increases in households.
One measure of the economy, the unemployment rate, appears to be tied to home prices. The percentage of the labor force looking for work fell over the year in June across the nation, particularly in growing housing markets. The jobless rate fell in all but one of the 25 fastest growing markets, while in nine of the 25 shrinking markets, the jobless rate actually increased.
To encourage the economic effects of a healthy housing sector, the Federal Reserve has kept interest rates low. The resulting low mortgage rates have helped encourage home purchases and boosted housing prices. However, home prices have risen about twice as fast as incomes over the past 12 months. For this and many other reasons, Hale explained that, while additional equity is great news for homeowners, the rising prices (and stagnant wages) make purchasing a home far more challenging for potential buyers.
The two largest hallmarks of fast-growing — and fast shrinking — markets are inventory levels and location, according to Hale. The NAR has tracked year-over-year inventory declines in each of the past 13 months. This means that there may be multiple offers on a single property, further driving up the original listing price. High demand, coupled with low new home construction rates, are the main drivers of the low inventory.
Demand for homes in particular locations is also a major factor in home price increases. More than half of the 25 fastest growing housing markets are located either in California or Florida. Hale noted that favorable climate in California and the West has always drawn Americans looking to relocate. The enormous success of California’s tech industry has further enhanced the appeal. In Florida, she added, lifestyle factors can be even more important than labor market factors, especially for retirees.
While California is home to some of the nation’s most expensive homes, Florida’s median home prices are fairly low even after nation-leading growths in a number of the state’s housing markets.
To identify the 25 fastest growing (and 25 fastest shrinking) housing markets, 24/7 Wall St. reviewed the largest and smallest home price changes over the 12 months through the second quarter of this year. Single-family home price data for the 180 metropolitan areas reviewed came from the NAR. Unemployment rates for metropolitan areas are for June 2016 from the Bureau of Labor Statistics.
These are the fastest growing (and shrinking) housing markets. ||||| Starting in 1996, Alexa Internet has been donating their crawl data to the Internet Archive. Flowing in every day, these data are added to the Wayback Machine after an embargo period. ||||| Starting in 1996, Alexa Internet has been donating their crawl data to the Internet Archive. Flowing in every day, these data are added to the Wayback Machine after an embargo period.
|
– Looking to invest in real estate? Be careful where you buy. Here are the five cities where house prices are growing and shrinking the fastest, based on average price changes for a single family home over 12 months ending this June, per 24/7 Wall St.: Growing: Boulder, Colo.: 18.5% Elmira, NY: 17.6% Springfield, Ill.: 17.1% Port St. Lucie, Fla.: 16.1% Cumberland, Md.: 15.2% Shrinking: Atlantic City, NJ: -13.1% Binghamton, NY: -10.2% Erie, Pa.: -7.9% New York City/White Plains/Jersey City: -5.9% Bridgeport, Conn.: -5.7% Click for the full lists, or see the 10 US cities losing the most jobs.
|
A space startup says nearby asteroids can be mined for water, platinum, and other natural resources to enable space exploration and bring those valuable materials to Earth.
The first step in Planetary Resources space missions: prospecting by telescope to determine resources available on near-Earth asteroids. (Credit: Planetary Resources)
Space startup Planetary Resources today launched an ambitious plan to capture water and precious metals from near-Earth asteroids, a feat founders say would enrich earthbound society and enable further space exploration
The two-year-old company announced its plans at the Museum of Flight in Seattle, where its founders said that technology has advanced to the point that space-mining valuable natural resources is now economically feasible.
Some asteroids that pass near the Earth may hold water -- a vital commodity for making spacecraft fuel and supporting the lives of astronauts. And that's just the beginning. A single 500-meter-wide asteroid could contain more platinum than has ever been mined on Earth, the company claims.
Planetary Resources' plan to mine asteroids
"Everything we hold of value on Earth -- energy, minerals, metals, real estate, water -- is literally available in near infinite quantities in space," said co-founder Peter Diamandis, a futurist and CEO of the X Prize Foundation. "We're going to change the way the world thinks about natural resources."
Technology and business changes give Planetary Resources a better chance at succeeding on its asteroid mining vision than the people who have failed over the past decades, Diamandis said.
Cheaper electronics, robotics, and artificial intelligence allow for machines that can operate autonomous mining missions in space. Also, commercial space travel from companies such as Space X gives Planetary Resources a route to reach space.
Finally, there are many well-heeled investors willing to invest in a small group of people who have access to these powerful technologies, he said. The company's advisers and investors include Google CEO Larry Page, former CEO Eric Schmidt, and former Microsoft chief software architect and space tourist Charles Simonyi.
Broadly speaking, the company's plan is to identify the most valuable near-Earth asteroids, extract valuable materials, and then deliver them to a specific location. That material could be brought back to Earth or delivered to an orbiting fuel depot in space, said co-founder and space engineer Eric Anderson.
"This will be a seminal event in entrepreneurial space and moving off the planet," he said.
Lower-cost designs
The company's intention is to send its first telescope, the Arkyd 100 series, into low-Earth orbit by the end of next year. Using optical spectroscopy, it will seek to determine the chemical makeup of asteroids approaching the Earth. Its second telescope will gain the ability to propel itself using solar panels to get closer to its targets.
Its third-generation robotic spacecraft will be deployed in "swarms" of half a dozen to approach an asteroid and land on it for mining, explained company president and chief engineer Peter Lewicki, who is a veteran of NASA's Mars programs. By deploying multiple spacecraft, the company hopes to improve the redundancy of the system and improve the chances of success.
The third-generation spacecraft design would launch a "swarm" of about five or ten craft to actually extract resources. This would happen next decade at the earliest. (Credit: Planetary Resources)
The company's goal is to identify those asteroids suitable for mining by the end of the decade, executives said. There are millions of asteroids of different sizes which come close to Earth, but their chemical makeup can be very different.
The most valuable ones appear to be the carbonaceous condrite asteroids which have water and loose rock which would not be difficult to collect. Water would be extracted by heating up mud and separating the water, said Thomas Jones, a NASA veteran and one of the company's advisers, which also includes film director James Cameron, the former chief technology officer of Microsoft David Vaskevitch, and the CEO of the Planetary Science Institute.
The value of natural resources in a single asteroid can be hundreds of millions of dollars, executives said. The company estimates that extracting 20 percent of the hydrogen and oxygen from a single carbonaceous chondrite asteroid about 50 meters across is enough propellant for all of the Space Shuttle flights.
"You don't have to run through detailed calculations to realize that a smallish asteroid has extraordinary value if you find the right kind," said Anderson.
The core challenge for the audacious venture, which is taking on a number of risky tasks, is to keep its costs low. Lewicki said the spacecraft designs will be an order of magnitude cheaper than existing spacecraft. It intends to launch its spacecraft into space by attaching itself on existing missions, a "ride share" approach to keep its costs under control.
"There's a rising tide going on in commercial space exploration. There are extraordinary investors willing to invest in launch technologies, lunar missions, asteroid missions," said Diamandis. "Capital has always been the scarcest part of space exploration and this changes the equation and allows us to go much faster and much farther than before."
Updated at 12:55 p.m. PT with additional details. ||||| Space-faring robots could be extracting gold and platinum from asteroids within 10 years if a new venture backed by two Silicon Valley titans and filmmaker James Cameron goes as planned.
Outside experts are skeptical about the project, announced Tuesday at a news conference in Seattle, because it would likely require untold millions or perhaps billions of dollars and huge advances in technology. But the same entrepreneurs pioneered the selling of space rides to tourists _ a notion that seemed fanciful not long ago, too.
"Since my early teenage years, I've wanted to be an asteroid miner. I always viewed it as a glamorous vision of where we could go," Peter Diamandis, one of the founders of Planetary Resources, told reporters at the Museum of Flight in Seattle. The company's vision "is to make the resources of space available to humanity."
The inaugural step, to be achieved in the next 18 to 24 months, would be launching the first in a series of private telescopes that would search for the right type of asteroids.
The plan is to use commercially built robotic ships to squeeze rocket fuel and valuable minerals out of the rocks that routinely whiz by Earth. Company leaders predict they could have their version of a space-based gas station up and running by 2020.
Several scientists not involved in the project said they were simultaneously thrilled and wary, calling the plan daring, difficult _ and very pricey. They don't see how it could be cost-effective, even with platinum and gold worth nearly $1,600 an ounce. An upcoming NASA mission to return just 2 ounces (60 grams) of an asteroid to Earth will cost about $1 billion.
But the entrepreneurs behind Planetary Resources Inc. have a track record of profiting off space ventures. Diamandis and co-founder Eric Anderson pioneered the idea of selling rides into space to tourists, and Diamandis' company offers "weightless" airplane flights.
Investors and advisers to the new company include Google CEO Larry Page and Executive Chairman Eric Schmidt and Cameron, the man behind the blockbusters "Titanic" and "Avatar."
Anderson says the group will prove naysayers wrong. "Before we started launching people into space as private citizens, people thought that was a pie-in-the-sky idea," Anderson said. "We're in this for decades. But it's not a charity. And we'll make money from the beginning."
The mining, fuel processing and later refueling would all be done without humans, Anderson said.
"It is the stuff of science fiction, but like in so many other areas of science fiction, it's possible to begin the process of making them reality," said former astronaut Thomas Jones, an adviser to the company.
The target-hunting telescopes would be tubes only a couple of feet long, weighing only a few dozen pounds and small enough to be held in your hand. They should cost less than $10 million, company officials said.
The idea that asteroids could be mined for resources has been around for years. Asteroids are the leftovers of a failed attempt to form a planet billions of years ago. Most of the remnants became the asteroid belt between Mars and Jupiter, but some pieces were pushed out to roam the solar system.
Asteroids are made mostly of rock and metal and range from a couple of dozen feet wide to nearly 10 miles long. The new venture targets the free-flying asteroids, seeking to extract from them the rare Earth platinum metals that are used in batteries, electronics and medical devices, Diamandis said.
Water can be broken down in space to liquid oxygen and liquid hydrogen for rocket fuel. Water is very expensive to get off the ground so the plan is to take it from an asteroid to a spot in space where it can be converted into fuel. From there, it can easily and cheaply be shipped to Earth orbit for refueling commercial satellites or spaceships from NASA and other countries.
In the past couple of years, NASA and other space agencies have shifted their attention from the moon and other planets toward asteroids. Because asteroids don't have any substantial gravity, targeting them costs less fuel and money than going to the moon, Anderson said in a phone interview.
There are probably 1,500 asteroids that pass near Earth that would be good initial targets. They are at least 160 feet (50 meters) wide, and Anderson figures 10 percent of them have water and other valuable minerals.
"A depot within a decade seems incredible. I hope there will be someone to use it," said Andrew Cheng at John Hopkins University's Applied Physics Lab, who was the chief scientist for a NASA mission to an asteroid a decade ago. "And I have high hopes that commercial uses of space will become profitable beyond Earth orbit. Maybe the time has come."
Diamandis and Anderson would not disclose how much the project will cost overall. By building and launching quickly, their company hopes to operate much more cheaply than NASA.
Harvard's Tim Spahr, director of the Minor Planet Center, said getting drilling equipment into space and operating safely sounds "expensive and difficult."
"It would be awfully hard to make money on it," Spahr said.
Richard Binzel, professor of planetary science at the Massachusetts Institute of Technology, said the effort "may be many decades ahead of its time. But you have to start somewhere."
___
Borenstein reported from Washington.
___
Online:
Planetary Resources Inc.: http://www.planetaryresources.com/
NASA's 2016 asteroid sampling mission: http://osiris-rex.lpl.arizona.edu/
___
Seth Borenstein, who reported from Washington, can be followed at http://twitter.com/borenbears
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– It's official, earthlings: The world's first asteroid-mining company has launched. Planetary Resources had its official coming out party today, the AP reports, with its co-founders laying out their plan to mine outer space for precious metal. The company, which is backed by such big-name investors as James Cameron and the Google Guys, says that in just 18 to 24 months it will start launching private space telescopes to identify asteroids rich in raw materials. "Everything we hold of value on Earth—energy, minerals, metals, real estate, water—is literally available in near infinite quantities in space," said co-founder Peter Diamandis, who, CNET points out, also is CEO of the X Prize Foundation. Some experts doubt that mining near-earth asteroids can possibly be cost-effective, but co-founder Eric Anderson pointed out that skeptics said the same thing about space tourism, which he and Diamandis pioneered. "We're in this for decades," he said. "But it's not a charity. And we'll make money from the beginning."
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prostate cancer has historically been considered a chemotherapy - resistant disease.1,2 however , over the past few decades , with the development of better cytotoxic agents and improved trial designs focused on clinically relevant endpoints , an important role for chemotherapy in the treatment of castration resistant prostate cancer ( crpc ) has emerged .
initially , estramustine phosphate was approved by the food and drug administration ( fda ) for the treatment of crpc . however , as a single agent , this drug had limited activity and notable treatment - related toxicities .
the combination of mitoxantrone and prednisone was approved by the fda in the 1990s based on clinical trials demonstrating improvements in palliation with this regimen compared with steroids alone.3 subsequently , in 2004 , docetaxel plus prednisone was shown to improve survival compared to mitoxantrone and prednisone , in men with crpc , leading to regulatory approval of this regimen.4 in 2010 , cabazitaxel became the fourth cytotoxic agent approved by the fda for the treatment of crpc .
herein , we will review the preclinical and clinical data supporting the development of cabazitaxel for the treatment of prostate cancer .
we will also discuss the rationale for ongoing clinical trials exploring cabazitaxel in prostate cancer and other malignancies .
the taxanes act by binding to microtubules , cytoskeletal polymers composed of -tubulin and -tubulin heterodimers .
the binding of taxanes to tubulin promotes the stabilization of gdp - bound tubulin in the microtubule resulting in inhibition of disassembly and prevention of subsequent mitosis and cell division . 5 derived from the bark of yew trees , in 1992 , paclitaxel was the first taxane approved by the food and drug administration ( fda ) as an anti - neoplastic agent .
docetaxel , a semisynthetic analog with increased potency , was approved by the fda in 1996 for the treatment advanced breast cancer and later in 2004 for the treatment of metastatic crpc .
these earlier generation taxanes have high substrate affinity for the atp - dependent drug efflux pump p - glycoprotein 1 ( p - gp1).6 therefore , p - gp1 is thought to account for , at least in part , both inherent and acquired resistance to these agents .
cabazitaxel , also known as xrp6258 , is a semi - synthetic taxane from a single diastereoisomer of 10-deacetyl baccatin iii , and derived from the needles of various taxus species . by binding to tubulin
this compound was selected for clinical testing due to its poor affinity for atp - dependent drug efflux pump p - gp16,7 and its greater blood - brain barrier penetration8 compared to paclitaxel and docetaxel .
cabazitaxel has also demonstrated superior in vitro cytotoxicity compared to docetaxel in several murine and human cancer cell lines.6
a phase i trial evaluated the phamacokinetics and safety of administering cabazitaxel at escalating doses starting at 10 mg / m intravenously every three weeks.9 patients enrolled on this trial were allowed up to two prior treatments ( 88% with prior chemotherapy , and 32% with prior taxane therapy ) .
twenty - five patients with advanced solid tumors were enrolled , eight of whom had crpc .
pharmacokinetic parameters , including exposure and maximum concentration , were dose proportional ( table 1 ) .
the decline in plasma concentrations was best described by a triphasic model ; an initial phase with a mean half - life ( t1/2 ) of 2.6 minutes , followed by an intermediate phase with a mean t1/2 of 1.3 hours , and a prolonged terminal phase with a mean t1/2 of 77.3 hours .
cabazitaxel was well tolerated at the studied dose levels up to 25 mg / m,10 but due to incidence of grade 4 neutropenia observed , the recommended phase ii dose was 20 mg / m .
cabazitaxel is metabolized by the liver , mainly by cyp3a4/5 ( 80%90% ) and to some extent cyp2c8 . though formal renal impairment - pharmacokinetic studies have not been performed , the presence of mild ( crcl 5080 ml / min ) or moderate ( crcl 3050 ml / min ) renal impairment in the published phase i study did not have a meaningful impact on exposure or clearance .
likewise , no formal hepatic impairment - pharmacokinetic studies have been performed , though given the hepatic metabolism of cabazitaxel , altered exposure and clearance would be expected . in the phase
i evaluation , the dose limiting toxicity of cabazitaxel observed at 25 mg / m every 3 weeks was grade 4 neutropenia .
common non - hematologic adverse events included low grade diarrhea ( 52% ) , nausea ( 40% ) , and vomiting ( 16% ) . preliminary evidence of antitumor activity was observed .
three patients achieved partial responses including two patients with crpc , one of whom had previously received docetaxel .
given the broad spectrum of activity of the taxanes , there is significant interest in exploring cabazitaxel for the treatment of a variety of malignancies .
preclinical studies have demonstrated the antitumor activity of cabazitaxel in head and neck squamous cell carcinoma .
11 furthermore , early results from breast cancer clinical trials have yielded promising results . in a phase ii multi - center open label trial ,
patients with breast cancer were treated with cabazitaxel 20 mg / m intravenously every three weeks ( subsequently titrated up to 25 mg / m in patients not experiencing adverse events during cycle # 1).12 despite the low overall response rate ( 14% ) , the median response duration was 7.6 months in this heavily pretreated population and 2 patients achieved complete responses .
treatment was generally well tolerated ; grade 3/4 anemia and thrombocytopenia were uncommon , and despite high rates of neutropenia , neutropenic fevers were rare ( 3% of patients ) .
villanueva and colleagues reported a phase i / ii dose - escalating study of cabazitaxel with capecitabine in patients with metastatic breast cancer progressing after anthracycline and taxane treatment.13 using a 3 + 3 dose escalation design , cabazitaxel was given intravenously at 20 mg / m on day 1 , and capecitabine orally at 825 mg / m twice daily from days 114 , in 21 day cycles .
the pk analysis did not reveal any drug - drug interaction . the maximal tolerated dose ( mtd ) determined was cabazitaxel at 20 mg / m , and capecitabine 1000 mg / m .
an additional 18 patients , with a total of 21 patients , were treated at the mtd for the phase ii evaluation . in the phase ii evaluation ,
planned therapy was generally delivered , with the median relative dose intensity ( actual / planned dose intensity ) at 0.97 for cabazitaxel and 0.89 for capecitabine .
antitumor activity was observed , with an overall response rate was 23.8% ( 1 cr , 4 pr ) .
rates of hematologic toxicity were similar to cabazitaxel monotherapy , with 57.1% of the patients experienced grade 34 neutropenia , and one reported case of grade 34 anemia .
given the promising results in the small cohort of patients with crpc in the phase i trial of cabazitaxel , rather than proceeding with a phase ii study , a strategic decision was made to initiate a randomized , multicenter , multinational , phase 3 trial ( efc6193 ; tropic ) to compare cabazitaxel with mitoxantrone in patients with crpc who had progressed despite docetaxel - based chemotherapy.14 patients were randomly assigned to receive either cabazitaxel 25 mg / m intravenously over 1 hour or mitoxantrone 12 mg / m intravenously over 1530 minutes on day 1 of each 21-day cycle , with prednisone 10 mg daily .
premedication , consisting of single intravenous doses of an antihistamine , corticosteroid ( dexamethasone 8 mg or equivalent ) , and histamine h2-antagonist , was administered 30 minutes prior to cabazitaxel administration , while anti - emetic prophylaxis was given at physicians discretion .
a maximum of 10 cycles of treatment were allowed , mainly due to the risk of mitoxantrone - induced cardiotoxicity .
patients did not receive prophylactic first - cycle granulocyte colony stimulating factor , but could receive growth factors with subsequent cycles if prolonged neutropenia was encountered .
while 371 of the patients in each arm received the intended treatment , more patients receiving cabazitaxel completed the full treatment course compared to patients receiving mitoxantrone .
of note , during the conduct of the trial , the protocol was amended to exclude patients previously treated with a cumulative docetaxel dose lower than 225 mg / m to increase the likelihood of enrolling a true
the adverse events observed in the tropic trial are detailed in figures 1 and 2 .
adverse events with cabazitaxel included neutropenia ( 94% ) , anemia ( 97% ) and thrombocytopenia ( 47% ) .
notably , grade 3 neutropenia occurred in 81.7% of patients and 8% experienced neutropenic fever .
the most common non - hematologic toxicities observed in the cabazitaxel arm included diarrhea ( 47% ) and fatigue ( 37% ) .
only 14% of patients treated with cabazitaxel experience any grade peripheral neuropathy . at median follow - up of 12.8 months ,
an improvement in overall survival was demonstrated for patients receiving cabazitaxel compared with mitoxantrone ( 15.1 month vs. 12.7 months , hr0.70 , p < 0.0001 ) .
secondary outcomes that also favored treatment with cabazitaxel over mitoxantrane included progression - free survival ( 2.8 vs. 1.4 months ) , tumor response ( 14.4 vs. 4.4% , p = 0.0005 ) , psa response ( 39.2% vs. 17.8% , p = 0.0002 ) , time to tumor progression ( 8.8 vs. 5.4 months , p < 0.0001 ) , and time to psa progression ( 6.4 vs. 3.1 months , p = 0.001 ) .
however , pain control and time to pain progression were similar among the two treatment arms .
on june , 17th 2010 , cabazitaxel , co - administered with prednisone , was approved by the fda for the treatment of patients with metastatic crpc previously treated with a docetaxel - containing treatment regimen .
cabazitaxel is the first cytotoxic agent to demonstrate a survival benefit in patients with crpc previously treated with docetaxel .
given the risk of severe neutropenia and febrile neutropenia with this agent , prophylactic growth factors are generally administered in clinical practice .
two studies will further investigate the pharmacology of cabazitaxel : nct01140607 will explore the feasibility of cabazitaxel use in liver impairment , while nct01087021 will assess the impact of cabazitaxel on the qtc interval in cancer patients .
given the hematologic toxicities demonstrated in tropic , a non - inferiority study comparing cabazitaxel at 20 mg / m vs. 25 mg / m is currently under clinical testing ( nct01308567 ) . based on the demonstrated activity of cabazitaxel in patients with docetaxel - refractory disease ,
the value of moving this agent earlier in the course of therapy warrants further investigation , and a randomized phase iii trial of docetaxel compared with two doses of cabazitaxel is being planned ( nct01308567 ) . to assess the efficacy and feasibility of combining cabazitaxel with other cytotoxic agents , two phase i trials
in addition , preclinical studies to evaluate potential synergy with existing and novel hormonal therapies are planned . with the fda approval of additional novel agents for the treatment of crpc (
eg , abiraterone , provenge ) , questions regarding optimal sequencing of drugs , and potential non - cross resistance , have emerged which are ripe for clinical investigation .
the armamentarium for the treatment of patients with crpc is rapidly expanding . in the past year , three novel agents with distinct mechanisms of action including cabazitaxel , abiraterone , and sipuleucel - t , have demonstrated improvements in survival in randomized trials .
additional agents in late stage clinical trials have already demonstrated promising results and additional therapeutic options are expected in the near future .
the next challenge in the management of men with crpc will be to determine the optimal sequence of administration of these agents , as well as explore rationale combinations .
|
castration resistant prostate cancer has historically been considered chemotherapy insensitive . however , the approval of estramustine phosphate , mitoxantrone , and docetaxel , over the past few decades , has challenged this notion . despite these advances , until recently , only docetaxel had been shown to improve survival in patients with castration - resistant disease , and there has been no standard treatment options available for men with disease progression on docetaxel . in the last year , cabazitaxel , a novel taxane with decreased affinity for atp - dependent drug efflux pump p - glycoprotein , became the first cytotoxic agent to demonstrate an improvement in survival in men with docetaxel - refractory disease , and has received regulatory approval for treatment in this setting . in this review ,
we examine the clinical development of cabazitaxel for the treatment of castration - resistant prostate cancer , as well as rationale and direction of future therapeutic investigation .
|
SECTION 1. SHORT TITLE.
This Act may be cited as the ``Small Business Enhancement Act of
1995''.
SEC. 2. URBAN UNIVERSITY BUSINESS INITIATIVE GRANTS.
(a) Urban University Business Initiative Grants.--
(1) Authorization.--The Administrator of the Small Business
Administration (hereafter in this section referred to as the
``Administrator'') may make grants to eligible institutions in
accordance with this section.
(2) Application.--
(A) In general.--An eligible institution seeking
assistance under this section shall submit to the
Administrator an application at such time, in such
form, and containing or accompanied by such information
and assurances as the Administrator may require by
regulation.
(B) Contents.--Except as provided in subparagraph
(C), each application submitted pursuant to
subparagraph (A) shall include--
(i) a description of the activities and
services for which assistance is sought;
(ii) evidence of coordination with any
small business development center in existence
in the community; and
(iii) documentation of the formation of a
consortium that includes, in addition to
eligible institutions, one or more of the
following entities:
(I) A nonprofit organization.
(II) A business or other employer.
(C) Waiver.--The Administrator may waive the
requirements of subparagraph (B)(iii) for any applicant
who can demonstrate to the satisfaction of the
Administrator that the applicant has devised an
integrated and coordinated plan that otherwise meets
the requirements of this section.
(3) Selection procedures.--Not later than 120 days after
the date of enactment of this Act, the Administrator shall by
regulation develop a formal procedure for the submission of
applications under this section and shall publish in the
Federal Register an announcement of that procedure and the
availability of funds under this section.
(b) Authorized Activities.--
(1) In general.--Funds provided under this section shall be
used to design and implement programs to assist businesses,
especially those in lower income urban communities, to become
more productive and able to compete in the global marketplace.
(2) Specific authorized activities.--Activities conducted
with funds made available under this section may include
research on, or planning and implementation of technology
transfer, technical training, the delivery of services, or
technical assistance in--
(A) business development;
(B) business creation;
(C) business expansion; and
(D) human resource management.
(c) Peer Review Panel.--
(1) Establishment.--Not later than 90 days after the date
on which the Administrator publishes the announcement in the
Federal Register in accordance with subsection (a)(3), the
Administrator shall appoint a peer review panel (hereafter in
this section referred to as the ``panel'').
(2) Membership.--In appointing the panel under paragraph
(1), the Administrator shall consult with officials of other
Federal agencies and with non-Federal organizations in order to
ensure that--
(A) the panel membership is geographically
balanced; and
(B) the panel is composed of representatives from
public and private institutions of higher education,
labor, business, and nonprofit organizations having
expertise in business development in lower income urban
communities.
(3) Duties.--The panel shall--
(A) review applications submitted under this
section; and
(B) make recommendations to the Administrator
concerning the selection of grant recipients.
(d) Disbursement of Funds.--
(1) Limitation on amount.--The Administrator shall not
provide assistance under this section to any recipient in an
amount that exceeds $400,000 during any 1-year period.
(2) Equitable geographic distribution.--The Administrator
shall award grants under this section in a manner that achieves
equitable geographic distribution of such grants.
(e) Definitions.--For purposes of this section, the following
definitions shall apply:
(1) Lower income urban community.--The term ``lower income
urban community'' means an urban area in which the percent of
residents living below the Federal poverty level is not less
than 115 percent of the statewide average.
(2) Urban area.--
(A) In general.--Except as provided in subparagraph
(B), the term ``urban area'' means a primary
metropolitan statistical area of the Bureau of the
Census, Department of Commerce.
(B) Exception.--With respect to a State that does
not contain an urban area, as defined in subparagraph
(A), the Administrator shall designate 1 area in the
State as an urban area for purposes of this section.
(3) Eligible institution.--
(A) Institution or consortium.--The term ``eligible
institution'' means a nonprofit institution of higher
education that meets the requirements of subparagraph
(b), or a consortium of such institutions, any 1 of
which meets the requirements of subparagraph (B).
(B) Requirements.--An institution meets the
requirements of this subparagraph if the institution--
(i) is located in an urban area;
(ii) draws a substantial portion of its
undergraduate students from the urban area in
which such institution is located, or from
contiguous areas;
(iii) carries out programs to make
postsecondary educational opportunities more
accessible to residents of such urban area, or
contiguous areas;
(iv) has the present capacity to provide
resources responsive to the needs and
priorities of such urban area and contiguous
areas;
(v) offers a range of professional,
technical, or graduate programs sufficient to
sustain the capacity of such institution to
provided such resources;
(vi) has demonstrated and sustained a sense
of responsibility to such urban area and
contiguous areas and the people of such areas;
and
(vii) has a school of business accredited
by the American Assembly of Collegiate Schools
of Business (or similar organization) with
faculty experienced in conducting research on
issues of immediate concern to small and
emerging businesses.
(f) Authorization of Appropriations.--There are authorized to be
appropriated to carry out this section--
(1) $10,000,000 for fiscal year 1996; and
(2) such sums as may be necessary for fiscal years 1997,
1998, 1999, and 2000.
|
Small Business Enhancement Act of 1995 - Authorizes the Administrator of the Small Business Administration (SBA) to make grants to eligible institutions to design and implement programs to assist businesses, especially those in lower income urban communities, to become more productive and able to compete in the global marketplace. Directs the SBA Administrator to establish a peer review panel to review grant applications and make recommendations to the Administrator concerning the selection of grant recipients. Limits to $400,000 the assistance provided to any single recipient during any one-year period. Requires the SBA Administrator to achieve equitable geographic distribution in the awarding of such grants. Defines an eligible institution as a nonprofit institution of higher education that is located in an urban area, has an accredited school of business, draws a substantial amount of its enrollment from urban areas, and carries out programs to make postsecondary educational opportunities more accessible to residents of such urban or contiguous areas. Authorizes appropriations for the grant program for FY 1996 through 2000.
|
'Spider-Man' May Go Dark for Julie Taymor
Mat Devine Talks to PopEater About 'Spider-Man'
Filed under: Highbrow
According to anonymous sources, the negotiations, which took place on Monday, involved expanding Taymor's team so she has more creative support. There was also talk of rewriting the script and score and, once again, setting a new date for its release. But the most drastic piece of information to emerge from the talks was the possibility of Taymor walking away.Taymor, who was initially recruited by Bono and The Edge when the duo first came up with the idea for the superhero musical, has been their creative partner from the get-go. Despite admitting that the production is flawed, she has asserted that it's headed in the right direction. But if the producers' ideas, or, more likely, demands, for improvements don't align with Taymor's ambitious vision, they have no qualms about showing her the door. ||||| 'Spider-Man' director Julie Taymor to be replaced by Philip William McKinley of 'The Boy from Oz'
Platt/Getty A sign for 'Spider-Man: Turn off the Dark' is seen along 42nd St.
Bedder/Getty Julie Taymor Take our Poll Turn off the show? Do you believe the 'Spider-Man' musical can be saved? Yes. Shutting down the show for a few weeks should help. No. Too much has gone wrong - the show will never open. Not sure - it depends on the new director. Related News Articles
Five easy steps to fix the mess that is 'Spider-Man'
The fate of "Spider-Man" is now in the hands of "The Boy from Oz."
Producers of the problem-plagued musical announced Wednesday night that Philip William McKinley, the former director of the Broadway hit "The Boy from Oz" will be taking the reins from star director Julie Taymor.
"Phil is hugely experienced with productions of this scale and is exactly what 'Spider-Man: Turn off the Dark' needs right now," lead producers Michael Cohl and Jeremiah Harris said in a joint statement.
The creative team shakeup came a day after the Daily News reported Taymor was giving up control of the show she cowrote and worked for years to bring to Broadway.
The producers insisted Taymor has not been banished from the production, but her role will be greatly diminished.
"Julie's previous commitments mean that past March 15, she cannot work the 24/7 necessary to make the changes in the production in order to be ready for our opening," Cohl and Harris said in a joint statement.
"We cannot exaggerate how technically difficult it is to make such changes to a show of this complexity, so it's with great pride that we announce that Phil McKinley is joining the creative team," Cohl and Harris said.
They confirmed the show's scheduled opening night will be pushed back from Tuesday to early summer, the sixth time it's been delayed.
The producers also said playwright Roberto Aguirre-Sacasa, who has written "Spider-Man" comic books, has been hired to help rewrite the book.
Taymor may have doomed herself by trying to unravel the musical web that Irish rocker Bono weaved for the show, sources said.
Bono and his U2 bandmate, The Edge, wrote the score for "Spider-Man: Turn Off the Dark," and Taymor recently brought aboard Broadway musical consultant Paul Bogaev to tune up the music.
"If Bono had wanted Taymor to stay, she'd still be here," one source told The News a day after the Tony-winning Taymor gave up control of the the $65 million Broadway boondoggle. "He's a huge part of the decision-making that goes on."
Bono and The Edge were at the Foxwoods Theatre Wednesday night when the cast and crew were briefed on the changes. They only had glowing things to say about Taymor.
"Julie is a truly gifted and imaginative director," he and The Edge said in a joint statement, adding they have "absolute faith in the project."
Show spokesman Rick Miramontez said the rockers gave the cast and crew a rousing pep talk.
"Nobody is going to be able to give a pep talk better than Bono and the Edge," Miramontez said.
Bogaev will stay on a musical consultant, the producers said. Sound designer Peter Hylenski, who Taymor also brought in, will also be sticking around.
Stopped outside the theater, Cohl sounded upbeat. "Here's the scoop: The scoop is Cohl says the show will get better," he told The News.
Meanwhile, Wednesday night's performance, the show's 101st preview, proved Cohl and his reshuffled creative team have their work cut out for them.
An aerial fight scene between Spider-Man and his nemesis the Green Goblin had to be stopped because of technical snafus. Instead of redoing the scene, the audience was told it was going to be skipped.
Jon Perez, 28, and his wife, Ellie Atwood, 26, of Queens, at the show for their sixth wedding anniversary, were so put off by the performance they left at intermission.
"It's something you could see at a high school in the Midwest, not on Broadway," Atwood said.
Cast members said they'll miss Taymor's daily involvement in the show, but vowed to work out the kinks and make her proud.
"I love Julie tremendously," said Patrick Page, who plays the Green Goblin. "Any day she's not in the building, I miss her."
Reeve Carney, who was hand picked by Taymor to play Spidey, sat out Wednesday night's performance after doing the earlier matinee.
"I don't want to talk about this tonight," Carney said plaintively when asked about the changes.
Miramontez said the cast members remain dedicated to the show in spite of the changes.
"The cast is devoted to Julie. So, I'm sure there's a melancholy mood," he said. "But they're giving a robust performance." ||||| Starting in 1996, Alexa Internet has been donating their crawl data to the Internet Archive. Flowing in every day, these data are added to the Wayback Machine after an embargo period.
|
– After days of rumors, the producers of Spider-Man: Turn Off the Dark made the official announcement last night: Director Julie Taymor is out. The problem-plagued musical has also been delayed yet again, this time until “early summer 2011,” according to the show’s blog. Taymor has been replaced with Philip William McKinley, who directed The Boy From Oz, and the script will be revised by Roberto Aguirre-Sacasa, who has written for the Spider-Man comic books. Despite the official party line (Taymor’s “previous commitments” make her unable to stay with the show now that it’s been delayed for the sixth time), friends and colleagues tell the New York Times she was actually pushed out after all the negative reviews came out last month, and because she refused to make changes to the show. Another source tells the New York Daily News that Bono himself, who wrote the score along with U2 bandmate The Edge, wanted Taymor out, presumably because she hired a non-U2 musical consultant to help with the score.
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the high mass x - ray binary ( hmxb ) system smc x-1/sk 160 consists of a neutron star with a mass of @xmath4 ( van der meer et al .
2007 ) and a spin period of 0.71s ( lucke et al.1976 ) , accreting from the b0i star sk 160 with a mass of @xmath5 ( reynolds et al . 1993 ) .
orbital period of the system is @xmath6 days ( schreier et al . 1972 ) .
the system has been observed with several observatories since it was discovered during a rocket flight ( price et al .
it is the only discovered hmxb with a supergiant companion in smc so far ( galache et al .
2008 ) . from the pulse timing studies , the source was observed to be spinning up since it was discovered ( wojdowski et al .
levine et al .
( 1993 ) and wojdowski et al ( 1998 ) found an orbital period decay in the system with @xmath7 of @xmath8yr@xmath2 .
smc x-1 also exhibits super - orbital x - ray flux variations like the 35 day cycle of her x-1 ( gruber @xmath9 rothschild , 1984 ) .
average super - orbital period of the source is @xmath10 55 days ( wojdowski et al . 1998 ; trowbridge et al . 2007 ) .
the super - orbital x - ray flux variations of smc x-1 are thought to be due to the precession of a warped accretion disk ( wojdowski et al .
1998 ) . in this paper
, we present timing and spectral analysis of rxte ( rossi x - ray timing explorer ) observations of smc x-1 between january 1996 and december 2003 . in the next section
, we give brief information about instruments and observations . in section 3
, we present the results of timing analysis , including pulse period history and timing solution of the source . in section 4 ,
x - ray spectral analysis of the source is presented .
we analyzed data from proportional counter array ( pca ) onboard rxte ( jahoda et al 1996 ) of smc x-1 between january 1996 and december 2003 ( mjd 50093 - 52988 ) .
the rxte - pca consists of an array of 5 proportional counters ( pcu ) operating in the 2 - 60 kev energy range , with a total effective area of approximately 7000 @xmath11 and a field of view of @xmath101@xmath12 fwhm .
data obtained from top xenon layers ( l1 and r1 ) of pcus were used to maximize s / n in the 3 - 20 kev energy band . for the observations after may 2000 , for which the propane layer for pcu0 was lost , data obtained from pcu0 was not used in the spectral analysis . out of 167 total pointings ,
we excluded x - ray eclipses ( due to low count statistics ) and used data obtained from @xmath13 pointings with a total exposure of @xmath14 ksec for the timing analysis .
other than the public observations , the principal investigators of these observations are s. eikenberry , w. heindl , d. chakrabarty , g.w .
clark and j. deeter . during the observations between 1998
october 16 and 1998
november 24 , with an exposure of @xmath10 23 ks , the data were contaminated due to the outburst of the nearby transient x - ray pulsar xtej0111.2 - 7317 ( chakrabarty et al 1998 ) .
we did not use these observations in the x - ray spectral analysis . in order to obtain the timing solution of the source , we used observations with the proposal number 10139 covering a time span of about 6 days .
these observations are more suitable than other observations to obtain the timing solution , since they are the only set of observations that continously cover near two orbital periods .
for the timing analysis , we generated lightcurves ( 3 - 20 kev ) with 0.035s timing resolution using good xenon data .
these lightcurves were background corrected with a 16s binned background lightcurve constructed using background estimator models from the rxte team ( url : ftp://legacy.gsfc.nasa.gov/xte /calib_data / pca_bkgd/ ) .
the resulting lightcurves were corrected to the barycenter of the solar system . a template pulse profile from each rxte observation
was constructed by folding the data on the period which had the greatest power in the periodogram .
pulse arrival times were found by cross - correlating the pulse profiles obtained from @xmath15s long segments with the template pulse profile . both the template and cross - correlated pulse profiles consisted of 20 phase bins .
crosscorrelation was performed by using the harmonic representation of pulse profiles ( deeter @xmath9 boynton 1985 ) . in order to obtain pulse arrival times ,
the pulse profiles were expressed in terms of harmonic series and cross - correlated with the template pulse profile . initially , we found pulse arrival times obtained from a series of observations with a time span of @xmath0 days around mjd 50324.7 .
these pulse arrival times can be fitted to an expression to obtain timing solution ( deeter , boynton , @xmath9 pravdo 1981 ) .
we firstly assumed a circular orbit ( e=0 ) and therefore this expression became , @xmath16 here t@xmath17 is the mid - time of the observation ; @xmath18 is the deviation from mean pulse period ; @xmath19 is the time derivative of the pulse period ; @xmath20 is the light traveltime for projected semimajor axis ( where i is the inclination angle between the line of sight and the orbital angular momentum vector ) ; @xmath21 is the mean orbital longitude at t ; @xmath22 is the epoch when the mean orbital longitude is equal to 90 @xmath12 ; @xmath23 is the orbital period of the system . in order to improve the fit
, we used the whole expression containing terms corresponding to an eccentric orbit as @xmath24 in equation 2 , e is the eccentricity and w is the longitude of periastron . the periodic trend of the pulse arrival times yields an eccentric orbit ( e=0.00089(6 ) ) with an orbital period of 3.89220909(4 ) days ( numbers in paranthesis denote @xmath25 uncertainties in the least significant figures hereafter ) .
table 1 presents the timing solution of smc x-1 .
figure 1 presents the pulse arrival times after the removal of the quadratic trend ( or intrinsic -@xmath19 ) together with the residuals of circular ( e=0 ) and eccentric orbit models respectively . in table 2
, we present the orbital epoch ( @xmath22 ) measurements from different observatories and orbital cycle number ( n ) . in figure 2 , we present observed minus calculated values of orbital epochs ( @xmath26 ) relative to the constant orbital period ( @xmath27 days ) .
it should be noted that the rightmost point indicated as `` rxte point '' is our result and other points were already published before ( see figure 7 in wojdowski et al .
a quadratic fit to the epochs from all experiments yielded an estimate of the rate of period change @xmath1 yr@xmath2 .
.timing solution of smc x-1 [ cols="<,<",options="header " , ] [ table 4 example two data ] table 5 shows best fit parameters of the spectral model for two sample observations . in general , we found that power law index , high energy cut - off and e - fold energy does not show variations with time , orbital phase and x - ray flux within the errors .
we found that hydrogen column density gets higher when x - ray flux is lower ( see figure 4 ) .
in this paper , we presented timing and spectral analysis of rxte - pca observations of smc x-1 with a time span of about 8 years . from timing analysis , we revised timing solution of the source and resolved an eccentricity value .
we also confirmed the orbital decay reported before .
our timing analysis helped us to construct a @xmath3 year long pulse period history of the source ( see figure 3 ) . from the spectral analysis
, we found that all spectral parameters except hydrogen column density showed no significant variation with time and x - ray flux .
figure 1 demonstrates that the eccentric orbit model is a better fit compared to the circular orbital model .
the timing solution of the source revealed that the binary orbit has an eccentricity of 0.00089(6 ) .
wojdowski et al .
( 1998 ) had found a circular orbit solution and levine et al .
( 1993 ) had only found an upper limit of 0.00004 for eccentricity . our present value is more than 20 times greater than the upper limit found by levine et al .
this significant eccentricity value should be verified using future monitoring observations . from timing analysis
, we obtained a new orbital epoch of smc x-1 from rxte observations . using this new epoch and previous results ( wojdowski et al .
1998 ) , we found that there is an orbital decay with @xmath28 of @xmath29 yr@xmath2 .
this value is similar to the values found by wojdowski et al .
( 1998 ) and levine et al .
levine et al . ( 1993 ) proposed that the major cause of change in the orbital period is tidal interactions as for the case in cen x-3 ( kelley et al .
1983 ) , and lmc x-4 ( levine et al . 2000 ) .
smc x-1 is unlike her x-1 for which the mass accretion were thought to be primarily related to the orbital period decay ( deeter et al . 1991 ) . from figure 3
, it is seen that smc x-1 spins up continuosly for @xmath3 years .
we found that average long term spin - up rate of the source between mjd 50093.048 and mjd 52987.640 ( whole time span of our analysis ) is @xmath30 hz s@xmath2 .
spin - up rate of a source with a persistent accretion disk can be expressed as @xmath31 where @xmath32 is first time derivative of the spin frequency , @xmath33 is the magnetic moment of the neutron star in units of @xmath34 gauss @xmath35 , @xmath36 is the mass of the neutron star in units of solar mass , @xmath37 is the radius of the neutron star in units of cm , @xmath38 is the moment of inertia of the neutron star in terms of @xmath39 g @xmath11 , and @xmath40 is the luminosity of the neutron star in units of @xmath41 erg s@xmath2 ( ghosh & lamb , 1979 ) . using a distance value of 61kpc ( keller & wood 2006 ) and a flux of @xmath42 ergs @xmath43 s@xmath2 ( see figure 4 ) , luminosity of smc x-1 is @xmath44 erg s@xmath2 . assuming magnetic moment of @xmath34 gauss @xmath45 , mass of @xmath46 , radius of @xmath47 cm , moment of inertia of @xmath39 g @xmath48
, we find @xmath32 to be @xmath49 hz s@xmath2 .
this value is of the order of the observed spin - up rate value of the source . from figure 3 and table 4 ,
it is evident that the long term spin - up rate of smc x-1 varies within a factor of 2 . from equation 3 , this variation may -in principle- be related to a change in x - ray luminosity of the source .
however , previous x - ray observations of the source were performed by different x - ray observatories and/or in different energy bands .
these observations are sparsely distributed and average x - ray flux of these observations are not likely to represent an average x - ray flux for the intervals for which the pulse frequency derivatives were found . moreover ,
x - ray flux variations are also affected by the super - orbital cycle , period of which is not as stable as that of her x-1 ( clarkson et al .
therefore , it is not possible to test whether variation in long term spin - up rate is related to a change in x - ray luminosity or not . from table 1 ,
spin - up rate obtained from @xmath0days long observation around mjd 50324.7 is @xmath50 hz s@xmath2 .
this is about 20@xmath51 greater than the long term spin - up rate between mjd 50093 and 52988 . assuming that the pulse frequency variations can be explained in terms of random walk model in pulse frequency ( baykal & ogelman 1993 )
, one can express the pulse frequency derivative variations as @xmath52 where s is the noise strength and t is the time interval at which the pulse frequency derivatives are observed .
therefore it is natural to observe high pulse frequency derivative fluctuations at shorter time scales .
it is important to note that we refined pulse period values fitting arrival times each obtained from @xmath15s long intervals , therefore we had to have at least a few arrival times to obtain spin period accurately .
so , our shortest timescale to obtain pulse periods is of the order of a single rxte observation which is @xmath53ksec long . from the spectral analysis
, we found that all of the spectral parameters except hydrogen column density did not vary significantly .
hydrogen column density was found to be higher as x - ray flux gets lower .
increase in hydrogen column density with a decrease in x - ray flux is also observed in her x-1 ( inam & baykal , 2005 ) and may be due the fact that soft absorption becomes stronger whenever there is a partial obscuration of the neutron star due to the x - ray eclipses and warping of the accretion disk . the increase in hydrogen column density
may also be an artifact of the simple absorbed power law model .
paul et al . ( 2002 ) showed that smc x-1 has soft excess especially for energies @xmath54 kev .
although we used photon energies greater than 3kev in our analysis , tail of a soft spectral compenent may affect low energies in our analysis and as a result we might have misidentified corresponding changes in energy spectrum as variations in hydrogen column density parameter .
we acknowledge support from eu fp6 transfer of knowledge project `` astrophysics of neutron stars '' ( mtkd - ct-2006 - 042722 ) .
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|
we present timing and spectral analysis of rxte - pca observations of smc x-1 between january 1996 and december 2003 . from observations around 30 august 1996 with a time span of @xmath0 days
, we obtain a precise timing solution for the source and resolve the eccentricity as 0.00089(6 ) .
we find an orbital decay rate of @xmath1 yr@xmath2 which is close to the previous results .
using our timing analysis and the previous studies , we construct a @xmath3 year long pulse period history of the source .
we show that frequency derivative shows long ( i.e. more than a few years ) and short ( i.e. order of days ) term fluctuations . from the spectral analysis
, we found that all spectral parameters except hydrogen column density showed no significant variation with time and x - ray flux .
hydrogen column density is found to be higher as x - ray flux gets lower .
this may be due to the increase in soft absorption when the pulsar is partially obscured as in her x-1 or may just be an artifact of the tail of a soft excess in energy spectrum . *
keywords : * x - rays : binaries , pulsars , individual : smc x-1 , stars : neutron , accretion , accretion discs
|
solving the problem of hot big - bang theory , and providing a natural mechanism for generating primordial density perturbations , make the elegant scenario of inflation as one of the best candidate of very early universe .
the scenario has opend a new and unique window on physics at inaccessible energy scales@xcite-@xcite . during inflation
, quantum vacuum fluctuations are redshifted far outside the hubble radius , imprinting spectrum of classical density perturbations @xcite , @xcite .
+ inflation can be well - defined by a quasi de sitter expansion in which the de sitter expansion is not accurate . because of this , statistic of cosmic microwave background ( cmb ) fluctuation is nearly gaussian , also the power spectrum of fluctuations is almost scale invariant and almost statistically isotropic .
therefore , we have to look at fine structures of the cmb fluctuation , such as non - gaussianity which is a result of violation of translational symmetry and does nt appear in the simplest single field inflaton with a canonical action @xcite-@xcite , spectral tilt as a result of violation of the temporal part of the de sitter symmetry which is characterized by a slow - roll parameter , and statistical anisotropy which means spatial part of the de sitter symmetry is not exact @xcite .
although deviation from gaussianity , scale invariance and statistical isotropy are quite small , they are observationally corroborated by planck and wmap @xcite-@xcite .
+ some anomalies in the cmb are of great importance @xcite , @xcite .
they have been noted since the early wmap releases @xcite . they have been studied extensively by independent groups , and remains unresolved to the present day @xcite , @xcite . among them
, there is hemispherical power asymmetry ( dipolar or quadrupole power asymmetry ) .
despite the fact that the statistical significance of hemispherical power asymmetry is hard to quantify ( especially for the case quadrupole ) , researchers has been prompting to give variety of models , which have been put forward to explain this phenomenon @xcite-@xcite .
+ the first attempt to put constraints on a preferred direction during inflation , and to make robust predictions for its observable consequence and its magnitude , was done by ackerman _
they considered the most general form of the power spectrum ( in which rotational invariance has violated ) as follows , @xmath1 here @xmath2 is the power spectrum for the primordial density perturbations @xmath3 and depends only on the magnitude of the vector * k*. also , @xmath4 is the privileged direction by which rotational invariance is broken .
moreover , @xmath5 characterizes the deviation from the isotropy .
the obtained bound using wmap data is @xmath6 @xcite . a later analysis based on planck data gave the best constraint i.e. @xmath7 so far @xcite .
the planck team got very similar constraints @xcite . + an inflationary theory can accommodate models that produce hemispherical power asymmetry .
anisotropic inflation is categorized as multifield inflation models .
it contains a vector field led to a breaking of statistical isotropy .
so the power spectrum for the primordial density perturbations becomes statistically anisotropic . in this model
the inflaton field @xmath8 is coupled to the gauge kinetic term in the form @xmath9 in the bianchi type i ( bi ) space .
there exists an attractor behavior for the solution and the vector field survives during inflation .
also , it is free from the ghost @xcite .
this model has been studied extensively in the literature @xcite-@xcite . breaking the rotational invariance during inflation , in which we call it anisotropy ,
is characterized by the background shear divided by the hubble rate .
it is shown in @xcite that for the bound from planck , anisotropy is less than @xmath10 .
however , they have shown that for reasonable values of parameters of the model , which they are consistent with observation , it is hard to reach the attractor solution during inflation .
nevertheless , one can assume that the duration of inflation exceeds @xmath11 e - fold , the model settles down to its attractor solution before perturbations exit the horizon .
+ the prototype of an alternative to einstein s general relativity was done by brans and dicke .
the primary motivation for their theory comes from mach s principle , that the phenomenon of inertia ought to arise from accelerations with respect to the general mass distribution of the universe @xcite .
brans - dicke ( bd ) theory is an important branch of the extended theories of gravity in the scalar - tensor theories . in bd theory , however , the gravitational coupling is variable .
it is determined by all matter in the universe , accordingly , a scalar field is considered to couple to the ricci curvature nonminimally .
in spite of declining of interest in bd gravity in the 70s , a surge interest has raised owing to the new importance of scalar fields in unified theories , in particular string theory .
another reason for this interest is discovering plausible mechanisms that allow the parameter @xmath0 ( a variable in the bd gravity ) to get values of order unity in the early universe and diverge later @xcite .
finally the using of scalar tensor gravity theories in inflationary scenarios of the universe , has renewed interest in bd gravity @xcite-@xcite . + this paper
is organized as follows . in section [ s:2 ] ,
the general action of anisotropic inflation in scalar tensor gravity is provided .
then , the most general equations of motion is obtained . in section [ s:3 ] ,
anisotropic brans - dicke inflation is considered , and anisotropy is obtained in the terms of the slow roll parameters .
also , a relation for the phase transition is obtained . in section [ s:4 ] , numerical calculation is obtained for a specific potential .
it shows that , there is an attractor solution , phase transition occurs and anisotropy grows in this model .
conclusion remarks are given in section [ conclusion ] .
in order to generate anisotropic effect during inflation we add an abelian massless gauge kinetic term .
it is coupled to the inflaton field through a gauge coupling function @xmath12 , to the general action of scalar tensor models .
so the action is given by @xmath13,\ ] ] where @xmath14 is a general function of the ricci scalar @xmath15 and the scalar field @xmath8 .
moreover , @xmath16 and @xmath17 are functions of @xmath8 , and @xmath18 is the field strength tensor of the gauge field @xmath19 . also , @xmath20 is the coupling function between @xmath8 and @xmath19 .
it will be specified later .
we have also set the planck scale @xmath21 for convenience .
we focus on the bi metric , given by @xmath22 where @xmath23 is the isotropic scale factor and @xmath24 is spatial shear which represents deviation from the isotropy .
we choose the gauge @xmath25 .
moreover , x - axis provides direction of the gauge field , without loss of generality .
hence we have the homogeneous gauge field of the form @xmath26 .
we take the scalar field to be homogeneous of the form @xmath27 too .
tacking variation of action with respect to the dynamical variable leads to the following equations @xmath28
\frac{\partial\mathcal{f}(r,\phi)}{\partial r}- g_{\mu\nu}u(\phi)+\\ \omega(\phi)\left [ \bigtriangledown_{\mu}\phi\bigtriangledown_{\nu}\phi-\frac{1}{2}g_{\mu\nu}\bigtriangledown_{\lambda}\phi\bigtriangledown^{\lambda}\phi \right ] + \frac{1}{2}f^{2}(\phi)\frac{\partial(f_{\lambda\rho}f^{\lambda\rho})}{\partial g_{\mu\nu}}-\frac{1}{4}g_{\mu\nu}f^{2}f_{\lambda\rho}f^{\lambda\rho}=0 \end{aligned } \label{1}\ ] ] @xmath29 @xmath30 where @xmath31 represents a covariant derivative with respect to the metric @xmath32 and a prime denotes a derivative with respect to @xmath8 . using the metric , equation of motion of the gauge field can be easily solved as @xmath33 where an overdot denotes the derivative with respect to the cosmic time @xmath34 and @xmath35 denotes constant of integration . from equations , and using equation , we obtain constraint , evolution and inflaton field equations in the bi space as @xmath36 @xmath37 @xmath38 @xmath39 where @xmath40 is defined as @xmath41 and the hubble parameter can be expressed as @xmath42 .
- are the most general equations for the anisotropic scalar tensor inflationary model .
when the abelian gauge field goes to zero , i.e. @xmath43 , and @xmath44 ( i.e. spatially flat friedmann - robertson - walker ( frw ) universe ) , the model is reduced to that of the @xcite , @xcite . moreover , in the limit @xmath45 and @xmath46 it is reduced to @xcite . + the slow - roll parameters which has been introduced for this model are @xcite , @xcite @xmath47 where the parameter @xmath48 is defined as @xmath49.\ ] ]
so far we have discussed the anisotropic scalar tensor inflationary model . in this section ,
we consider anisotropic bd inflation as a special case of the anisotropic scalar tensor inflationary model .
the action in the so - called jordan frame is @xmath50 , \label{bransdicke}\ ] ] where this action is obtained from the action by considering @xmath51 where @xmath52 is the bd parameter which is a constant , and hereafter we drop out its subscript , `` bd '' and write it as @xmath0 . using eqs . - for the action , constraint , evolution and inflaton field equations are obtained in the bi universe , as @xmath53 @xmath54 @xmath55 @xmath56 where the last equation can be written in the form @xmath57 using equations , and , the equation for acceleration of the universe is given by @xmath58 the necessary condition for inflation is @xmath59 , and it will be satisfied if the @xmath60 term overcomes shear @xmath61 , energy density of the gauge field @xmath62 and kinetic energy of the inflaton @xmath63 . from equation , it is clear that anisotropy will grow only when the last term i.e. @xmath64 is a dominant term .
therefore if we consider @xmath65 , anisotropy starts to grow at least for @xmath66 .
a generalized form for @xmath20 is @xmath67 where @xmath68 is a constant .
then , the energy density of the gauge filed , ignoring @xmath69 , is @xmath70 . considering the slow roll conditions @xmath71 and
@xmath72 , and additionally @xmath65 , @xmath73 hold , so and reduce to @xmath74 @xmath75 . \end{split } \label{sr1}\ ] ] substituting above equation into eq .
, one arrives at the following expression for slow - roll parameters @xmath76 @xmath77 @xmath78 number e - fold which measure the amount of inflation is given by @xmath79 from the coupling function @xmath20 is @xmath80 we are interested in the configuration where inflation take place with small anisotropies such that @xmath81 but not zero . from equation in the slow - roll approximation
we have @xmath82 where @xmath83 is @xmath84 it can be obtained from in the slow - roll approximation as @xmath85 where @xmath86 in the limit of @xmath87 the first term of equation dominated and @xmath83 diverges to infinity .
consequently anisotropy goes to zero , i.e. @xmath88 . on the other hand , in the limit @xmath89 , second term is dominated , and @xmath90 . therefore @xmath91 it is clear that there is a `` phase transition '' when the anisotropy @xmath92 has a transient from zero to the above equation .
if @xmath93 gose to zero , then @xmath88 .
in order to make the analysis more precise , we consider displaced quadratic inflationary potential as follows @xmath94 where @xmath95 and @xmath96 is a shift in the potential .
this potential is a generalized version of the starobinsky @xmath97 inflation in the einstein frame .
consistency of this potential with the planck @xmath98 data in bd gravity has been investigated by @xcite using jordan frame and with planck @xmath99 data by @xcite in the einstein fram .
the slow - roll parameters for this potential will become @xmath100 @xmath101 @xmath102 therefore from equation , as @xmath103 , the parameter @xmath93 approaches zero and from @xmath104 . solving eqs . -
numerically for the potential with different value of @xmath0 and @xmath105 , phase - plane in @xmath106 is obtained ( fig .
[ phase ] ) .
obviously , there are two slow - roll inflationary phases and the anisotropy grows in this model .
it is clear that , as we increase @xmath0 the phase of anisotropic inflation starts later near the end of inflation . moreover , by decreasing @xmath0 anisotropic inflation starts sooner and it lasts more time until the end of inflation . the same plot for @xmath107 has been shown in fig .
[ phasephi01r3w3to15 ] . clearly , by increasing @xmath0
, we have to decrease @xmath108 to have attractor solution . from equation , if @xmath109 ( i.e. @xmath110 ) , then anisotropy , @xmath92 goes to zero .
this fact is consistent with fig .
[ phasephi01r3w3to15 ] . phase flow for @xmath8
is depicted , @xmath111 , @xmath112 to @xmath113 , initial conditions @xmath114 and @xmath105 is considered .
there is two slow - roll phases . ] , but for @xmath107 , constant value of @xmath115 and different values of @xmath0 .
] evolution of the anisotropy parameter @xmath116 with respect to the e - folding number @xmath117 , for @xmath118 to @xmath119 , @xmath115 and @xmath105 is presented in fig .
[ 2anisotropyomega0to7r3 ] .
obviously , by increasing @xmath0 we have to increase @xmath120 in order to have attractor solution .
thus , anisotropy is shifted out of the @xmath11 e - folds number .
if we assume that duration of inflation exceeds @xmath11 e - fold , the model has attractor solution there , and anisotropy has time to exit the horizon .
it should be noticed that the value of bd parameter @xmath0 is small and it is not compatible with local gravity tests in the solar system ( i.e. @xmath121 ) .
of course , during the slow roll inflation , kinetic energy of the inflaton is smaller than the potential energy .
it seems that @xmath0 is small during this era and , the bd scalar field decays after inflation .
thus , the subsequent cosmology coincides with einstein s general relativity and todays bond is invalid during inflation . with respect to the e - folding number @xmath117 , for different values of @xmath122 and @xmath115
other initial values are the same as fig .
[ phase ] . ] , but for a constant value of @xmath123 and variable value of @xmath124 .
the red line is anisotropy in the einstein gravity for the same potential . ] but for a constant value of @xmath125 and different values of @xmath124 . ] , but for @xmath107 , constant value of @xmath115 and different values of @xmath0 .
anisotropy in the einstein gravity for the same potential and the same value for @xmath124 and @xmath126 is plotted in red . ]
+ the case @xmath127 and @xmath123 is shown in fig .
[ anisotropyomega4r2to45phi100to130 ] .
it shows that there is just one anisotropic phase and anisotropy decreases to the order @xmath10 , which is closer to the bound found by @xcite ( they found a bound for anisotropy of order @xmath128 ) . in this case increasing @xmath108 causes anisotropy reduction . moreover , increasing @xmath124 enhance the anisotropy .
anisotropy in the einstein gravity for the same potential is plotted in red for comparison . clearly , the anisotropy in the bd gravity is smaller than the einstein gravity .
+ the case @xmath125 is considered in fig .
[ 3anisotropyomega0r25to6 ] . for this case
the kinetic term in eq .
this is a way to recover @xmath129 gravity ( which can be regarded as a special case of bd theory with @xmath130)@xcite . hence the potential changes into the potential corresponding to starobinsky @xmath97 inflation in the einstein frame .
therefore the potential in the bd gravity is a generalized version of starobinsky @xmath97 inflation .
[ anisotropyphi01w3t020r2phi105to7 ] we choose @xmath107 . therefore anisotropy starts from a nonzero value . in this case
, increasing @xmath124 for a constant value of @xmath0 leads to elevation of the anisotropy and shifts the anisotropy to smaller e - folds .
thus , the area in which @xmath92 is constant decreases , until this area disappears .
in the present work , we studied anisotropic inflation in the brans - dicke gravity where the quadrupole power asymmetry is modeled by the kinetic part of an abelian gauge field coupled to the inflaton field .
we obtained a relation for the anisotropy @xmath92 which is proportional to the slow - roll parameter , namely @xmath93 .
as an example we carried out the numerical calculation for the displaced quadratic potential and we saw that there is a phase transition in this model , anisotropy grows and it can exit the horizon . also , anisotropy depends on the value of @xmath0 . as we increase @xmath0 , depending on @xmath96 in the inflation potential , attractor solution may occur in larger @xmath108 or in smaller values .
for the case that , attractor solution occurs in smaller @xmath108 , anisotropy is shifted to smaller e - folds until it is disappeared .
this is because @xmath120 converges to @xmath96 , and consequently @xmath131 goes to zero .
thus , @xmath92 is disappeared for larger values of @xmath0 . in the other case , by increasing @xmath0 , we should increase @xmath120 to have attractor solution . increasing @xmath120
shifts the anisotropy to larger e - fold until it leaves @xmath11 e - fold .
we also considered the case @xmath125 , where the displaced quadratic inflationary potential is changed to the potential corresponding to starobinsky @xmath97 inflation in the einstein frame .
moreover , increasing @xmath124 does nt have a significant effect on the anisotropy .
as a special case , @xmath127 was considered . in this case , anisotropy is decreased significantly depending on @xmath0 . for @xmath123 , anisotropy
is decreased to the order @xmath10 .
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we study anisotropic inflation in the brans - dicke gravity in the presence of an abelian gauge field where the gauge field is non - minimally coupled to the inflaton .
we show that the degree of anisotropy , under slow - roll approximations , is proportional to slow - roll parameter of the theory . as a demonstration , we consider the displaced quadratic potential for the inflation .
we do the numerical calculation of the model to investigate the behavior of anisotropy by changing the parameter in the brans - dicke model .
we find out that , the solution is an attractor in the phase space , and anisotropy grows before the end of inflation .
anisotropy depends on the brans - dicke parameter , @xmath0 and initial values of the scalar field .
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periodontitis is a destructive inflammatory disease of the supporting tissues of the teeth and is caused by specific microorganisms or group of specific microorganisms [ table 1 ] resulting in a progressive destruction of the periodontal ligament and alveolar bone with periodontal pocket formation , gingival recession , or both .
periodontal diseases are recognized as infectious processes that require bacterial presence and a host response and are further affected and modified by other local , environmental , and genetic factors .
the association of periodontal infection with organ systems like cardiovascular system , endocrine system , reproductive system , and respiratory system makes periodontal infection a complex multiphase disease .
bacteria are the primary etiological agents in periodontal disease , and it is estimated that more than 500 different bacterial species are capable of colonizing the adult mouth . inflamed periodontal tissues produce significant amounts of proinflammatory cytokines , mainly interleukin 1-beta ( il-1 ) , il-6 , prostaglandin e2 , and tumor necrosis factor - alpha ( tnf- ) , which may have systemic effects on the host .
periodontitis initiates systemic inflammation and can be monitored by inflammatory markers like c - reactive protein or fibrinogen levels .
the continuous production of cytokines in inflamed periodontal tissues is responsible for the progress of periodontitis and periodontal tissue destruction .
particularly , inflammatory cytokines , such as il - l , il-1 , il-6 , and il-8 , are present in the diseased periodontal tissues , and their unrestricted production seems to play a role in chronic leukocyte recruitment and tissue destruction .
acute periodontal disease primarily involves a local innate immune response to the microflora of the oral biofilm .
gingival epithelial cells recognize bacterial cell components via toll - like receptors and respond by producing il-1 and tnf-. bacteria and bacterial products also penetrate into the underlying tissues .
endothelial cells express cellular adhesion molecules ( icam and vcam ) that recruit circulating immune cells .
vascular permeability is also increased allowing the influx of phagocyte cells and serum into the gingival tissue .
neutrophils and macrophages are attracted to the site of infection by chemotaxis following gradients of complement proteins , cytokines , and bacterial products .
overall , these processes result in gingival inflammation , and are responsible for the clinical manifestations of gingivitis further leading to periodontitis .
it is possible that monitoring cytokine production or its profile may allow us to diagnose an individual 's periodontal disease status and/or susceptibility to the disease .
low birth weight , defined as birth weight less than 2,500 g , continues to be a significant public health issue in both developed and developing countries .
preterm delivery , or ptd , is the major cause of neonatal mortality and of nearly one - half of all serious long - term neurological morbidity .
premature and low - birth - weight ( plbw ) infants are still 40 times more likely to die during the neonatal period .
plbw infants who survive the neonatal period face a higher risk of several neurodevelopment disturbances , health problems ( such as asthma , upper and lower respiratory infections , and ear infections ) , and congenital anomalies .
some risk factors that have been associated with a plbw include a high ( > 34 years ) and low ( < 17 years ) maternal age , a low socioeconomic status , inadequate prenatal care , drug abuse , alcohol and tobacco use , hypertension , diabetes , and multiple pregnancies . despite increasing efforts to diminish the effects of these risk factors through preventive interventions during prenatal care ,
there is a reason to believe that other unrecognized risk factors may contribute to the continuing prevalence of plbw infants .
one possible contributing factor to this phenomenon is the effect of an infection on plbw .
it is possible that subclinical genitourinary and periodontal infections can adversely affect the pregnancy outcomes .
women with preterm labor do not invariably present with positive amniotic fluid culture , suggesting that subclinical infections , resulting in the translocation of bacteria , bacterial metabolites , and lipopolysaccharide ( lps ) , may account for some of the inflammatory processes associated with plbw .
miller originally published his focal infection theory in 1891 suggesting that microorganisms or their waste products obtain entrance to parts of the body adjacent to or remote from the mouth .
infection is now considered one of the major causes of plbw deliveries , responsible for somewhere between 30% and 50% of all cases , and periodontitis and periodontal diseases are true infections of the oral cavity .
the oral cavity works as a continuous source of infectious agents , and its condition often reflects progression of systemic pathologies .
research suggests that the bacteria that cause inflammation in the gums can actually get into the bloodstream and target the fetus , potentially leading to plbw babies .
one possible mechanism begins with endotoxins resulting from gram - negative bacterial infections ( such as periodontal disease ) .
these endotoxins stimulate the production of cytokines and prostaglandins ( il-1 , il-6 , and tnf- ) and in appropriate quantities stimulate labor , and proinflammatory mediators may cross the placenta barrier and cause fetal toxicity resulting in preterm delivery and low - birth - weight babies .
high concentrations of these cytokines , in pregnant women , are responsible for rupture of the uterine membranes causing premature birth and retardation . as periodontal medicine
is still in its infancy here in asia , there is a compelling need to determine the possible association between adverse pregnancy outcomes and periodontal infections .
it has been well documented that periodontal disease is a treatable and preventable condition . in the event of a positive association of periodontal infection with plbw ,
this would have potential applications in preventive oral health programs as an integral component of prenatal care for pregnant mothers .
indeed , as healthcare professionals working as a team , an understanding of the role of periodontal and systemic relationship and its implications will further enhance the quality of medical and dental care being provided to our patients in the community .
several animal and clinical studies clearly indicate an association between periodontal infection and adverse pregnancy outcomes . although no definitive causal relationship has been established , and other explanations for the correlation might be offered , a model can nevertheless be envisaged wherein chronic periodontal infection could mediate this systemic effect through one or more of the following mechanisms :
translocation of periodontal pathogens to the fetoplacental unitaction of a periodontal reservoir of lps on the fetoplacental unitaction of a periodontal reservoir of inflammatory mediators ( il-1 , il-6 , tnf- , pge2 ) on the fetoplacental unit .
translocation of periodontal pathogens to the fetoplacental unit action of a periodontal reservoir of lps on the fetoplacental unit action of a periodontal reservoir of inflammatory mediators ( il-1 , il-6 , tnf- , pge2 ) on the fetoplacental unit .
oral health guidelines for pregnant women were accomplished to assist them in maintaining healthy teeth and gums during their pregnancy and into the early stages of motherhood .
the american academy of pediatric dentistry ( aap ) announced new oral health guidelines for pregnant women in 2009 , modified and illustrated in table 2 .
thus it can be concluded that periodontal disease appears to be an independent risk factor for plbw and there is a need to expand preventive measures for pregnant women in harmonization with the gynecological and dental professions , and to provide professional oral hygiene measurements during pregnancy .
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periodontitis is a destructive inflammatory disease of the supporting tissues of the teeth and is caused by specific microorganisms or group of specific microorganisms .
the association of periodontal infection with organ systems like cardiovascular system , endocrine system , reproductive system , and respiratory system makes periodontal infection a complex multiphase disease .
inflamed periodontal tissues produce significant amounts of proinflammatory cytokines , mainly interleukin 1-beta ( il-1 ) , il-6 , prostaglandin e2 , and tumor necrosis factor - alpha ( tnf- ) , which may have systemic effects on the host .
low birth weight , defined as birth weight less than 2,500 g , continues to be a significant public health issue in both developed and developing countries .
research suggests that the bacteria that cause inflammation in the gums can actually get into the bloodstream and target the fetus , potentially leading to premature labor and low - birth - weight ( plbw ) babies .
one reasonable mechanism begins with deleterious effects of endotoxins released from gram - negative bacteria responsible for periodontal disease .
hence periodontal disease appears to be an independent risk factor for plbw and there is a need to expand preventive measures for pregnant women in harmonization with the gynecological and dental professions .
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SECTION 1. SHORT TITLE.
This Act may be cited as the ``Postal Innovation Act''.
SEC. 2. EXPANDED SERVICES.
(a) Pilot Program for Provision of Nonpostal Services.--
(1) In general.--Not later than 90 days after the date of
enactment of this Act, and notwithstanding the provisions of
title 39, United States Code, the Postmaster General shall
establish a pilot program to provide nonpostal services through
public-private partnerships in 5 postal districts or regions,
as determined by the Postmaster General, of which at least 1
district or region contains a post office located in a rural
area.
(2) Services.--The nonpostal services described in
paragraph (1) may include--
(A) financial services;
(B) warehousing;
(C) experimental postal products market testing;
(D) community support services;
(E) Internet voting;
(F) municipal broadband Internet service;
(G) public wireless Internet service;
(H) emergency broadband Internet service; and
(I) passport services.
(3) Report.--Not later than 1 year after the date of the
establishment of the pilot program under subsection (a), the
Postmaster General shall submit to Congress a report
containing--
(A) an analysis of the pilot program conducted
under paragraph (1); and
(B) an assessment of the most cost-effective
implementation of nonpostal services under the pilot
program.
(b) Governmental Services.--Section 411 of title 39, United States
Code, is amended--
(1) in the second sentence, by striking ``this section''
and inserting ``this subsection'';
(2) in the heading of such section, by striking
``Government'' and inserting ``government'';
(3) by striking ``Executive agencies'' and inserting ``(a)
Federal Government.--Executive agencies''; and
(4) by adding at the end the following:
``(b) State, Local, and Tribal Governments.--
``(1) Authority of postal service.--The Postal Service is
authorized to furnish property and services to a State, local
government, or tribal government under such terms and
conditions, including the possibility for reimbursement, as the
Postal Service and the applicable State, local government, or
tribal government shall determine appropriate.
``(2) Definitions.--In this subsection--
``(A) the term `State' means each of the several
States, the District of Columbia, American Samoa, Guam,
the Commonwealth of the Northern Mariana Islands, the
Commonwealth of Puerto Rico, the Virgin Islands of the
United States, and any other territory or possession of
the United States.
``(B) the term `tribal government' means the
government of an Indian tribe (as defined in section
4(e) of the Indian Self-Determination Act (25 U.S.C.
450b(e))).''.
(c) Clerical Amendment.--The item related to section 411 in the
analysis of chapter 4 of title 39, United States Code, is amended to
read as follows:
``411. Cooperation with other government agencies.''.
SEC. 3. SHIPPING OF ALCOHOLIC BEVERAGES.
(a) Mailability.--
(1) Nonmailable articles.--Section 1716(f) of title 18,
United States Code, is amended by striking ``mails'' and
inserting ``mails, except to the extent that the mailing is
allowable under section 3001(p) of title 39''.
(2) Mailable alcoholic beverages.--Section 1154(a) of title
18, United States Code, is amended, by inserting ``or, with
respect to the mailing of alcoholic beverages to the extent
allowed under section 3001(p) of title 39'' after ``mechanical
purposes''.
(b) Regulations.--Section 3001 of title 39, United States Code, is
amended by adding at the end the following:
``(p)(1) Alcoholic beverages shall be considered mailable if
mailed--
``(A) by a covered shipper in accordance with applicable
regulations under paragraph (2); and
``(B) in accordance with the delivery requirements
otherwise applicable to privately carried shipments of
alcoholic beverages.
``(2) The Postal Service shall prescribe such regulations as may be
necessary to carry out this subsection, including regulations providing
that--
``(A) the mailing shall be by a means established by the
Postal Service to ensure direct delivery to the addressee or a
duly authorized agent at a postal facility;
``(B) the addressee (and any duly authorized agent) shall
be an individual at least 21 years of age, and shall present a
valid, government-issued photo identification at the time of
delivery;
``(C) the alcoholic beverage may not be for resale or other
commercial purpose; and
``(D) the covered shipper involved shall--
``(i) certify in writing to the satisfaction of the
Postal Service, through a registration process
administered by the Postal Service, that the mailing is
not in violation of any provision of this subsection or
regulation prescribed under this subsection; and
``(ii) provide any other information or affirmation
that the Postal Service may require, including with
respect to the prepayment of State alcohol beverage
taxes.
``(3) For purposes of this subsection--
``(A) the term `alcoholic beverage' has the meaning given
such term in section 203 of the Federal Alcohol Administration
Act (27 U.S.C. 214); and
``(B) the term `covered shipper' means a winery, brewery,
or beverage distilled spirits plant, or other wholesaler,
distributer, or retailer of alcoholic beverages that--
``(i) possesses a notice of registration or permit
approved by the Alcohol and Tobacco Tax and Trade
Bureau of the Department of the Treasury pursuant to
the Federal Alcohol Administration Act (27 U.S.C. 201
et seq.); or
``(ii) has registered with, obtained a permit from,
or obtained approval of a notice or an application
from, the Secretary of the Treasury pursuant to Chapter
51 of the Internal Revenue Code of 1986 (26 U.S.C. 5001
et seq.).''.
(c) Effective Date.--The amendments made by this section shall take
effect on the earlier of--
(1) the date on which the Postal Service issues regulations
under section 3001(p) of title 39, United States Code, as
amended by this section; or
(2) 120 days after the date of enactment of this Act.
SEC. 4. UPGRADING THE FLEET OF THE POSTAL SERVICE.
(a) Contracting.--
(1) In general.--The Postmaster General may enter into
contracts to upgrade the postal fleet to increase long-term
savings by reducing collision, maintenance, fuel, or other
costs.
(2) Review.--In determining whether to enter into contracts
under paragraph (1), the Postal Service shall review and
identify routes for which the Postal Service provides delivery
to determine if motor vehicles used on such routes can be
replaced or retrofitted with commercially available
technologies that--
(A) increase average fuel economy;
(B) reduce collisions with other motorized
vehicles, nonmotorized vehicles, and pedestrians; or
(C) reduce emissions of carbon dioxide.
(b) Guidelines.--The Postmaster General shall develop guidelines
for contracted vehicles and vehicles purchased or leased for use by the
Postal Service, that, at a minimum, require that--
(1) in the case of a passenger car, the car meets--
(A) with respect to emissions of carbon dioxide,
the more stringent of--
(i) the applicable standards developed by
the Environmental Protection Agency under title
II of the Clean Air Act (42 U.S.C. 7521 et
seq.); or
(ii) on average, less than 235 grams per
mile; and
(B) with respect to average fuel economy, the more
stringent of--
(i) the applicable average fuel economy
standards developed by the National Highway
Traffic Safety Administration under chapter 329
of title 49, United States Code; or
(ii) 37.8 miles per gallon;
(2) in the case of a light-duty truck, the truck meets--
(A) with respect to emissions of carbon dioxide,
the more stringent of--
(i) the applicable standards developed by
the Environmental Protection Agency under title
II of the Clean Air Act (42 U.S.C. 7521 et
seq.); or
(ii) on average, less than 310 grams per
mile; and
(B) with respect to average fuel economy, the more
stringent of--
(i) the applicable average fuel economy
standards developed by the National Highway
Traffic Safety Administration under chapter 329
of title 49, United States Code; or
(ii) 28.8 miles per gallon;
(3) medium-duty and heavy-duty vehicles comply with
applicable standards--
(A) for emissions of carbon dioxide developed by
the Administrator of the Environmental Protection
Agency under title II of the Clean Air Act (42 U.S.C.
7521 et seq.); and
(B) for average fuel economy developed by the
Secretary of Transportation under chapter 329 of title
49, United States Code; and
(4) for safety, the vehicles described in paragraphs (1)
through (3) are equipped with commercially available crash
avoidance solutions, including--
(A) camera-based sensors; and
(B) automatic emergency braking for new vehicles.
(c) Applicability of Guidelines.--The standards described in
subsection (b) shall apply to contracted vehicles and vehicles
purchased or leased for use by the Postal Service after the date that
is 1 year after the date of enactment of this Act.
(d) Reduction of Consumption of Petroleum Products.--The Postmaster
General shall reduce the total consumption of petroleum products by
vehicles in the postal fleet by not less than 2 percent annually
through the end of fiscal year 2025, relative to the baseline
established for fiscal year 2005.
SEC. 5. INVESTING IN THE FUTURE OF THE POSTAL SERVICE.
The Postmaster General may use cost savings from section 2 to
reinvest in innovation, research and development, and operations of the
Postal Service.
SEC. 6. GAO REPORT.
Not later than 180 days after the date of enactment of this Act,
the Comptroller General of the United States shall submit to Congress a
report on the feasibility of the Postal Service providing Internet
services to the public, including access to broadband Internet and
Internet voting services. Such study shall include--
(1) cost-effective strategies for using the infrastructure,
technology, and processes of existing networks that the Postal
Service uses for transportation, delivery, and retail to
provide the Internet services;
(2) recommendations for providing such services in a manner
that is consistent with the public interest; and
(3) an analysis of whether providing such services has the
potential to improve the financial position of the Postal
Service.
SEC. 7. DEFINITION.
In this Act, the term ``Postal Service'' means the United States
Postal Service.
|
Postal Innovation Act This bill directs the U.S. Postal Service (USPS) to establish a pilot program to provide nonpostal services through public-private partnerships in five postal districts or regions, including at least one rural area. Such nonpostal services may include financial services, warehousing, experimental postal products market testing, community support services, Internet voting, municipal broadband and public wireless Internet service, emergency broadband Internet service, and passport services. The bill also authorizes the USPS to furnish property and services to a state, local, or tribal government. USPS may use cost savings from providing such services to reinvest in innovation, research and development, and operations. The bill sets forth conditions under which alcoholic beverages shall be considered mailable. They must be mailed: (1) by a covered shipper, (2) in accordance with delivery requirements otherwise applicable to privately carried shipments, and (3) by a means that ensures direct delivery to a duly authorized agent at a postal facility or to the addressee, who must be at least 21 years of age and must present a valid, government-issued photo identification at the time of delivery. The alcoholic beverage may not be for resale or other commercial purpose. The bill authorizes USPS to enter into contracts to upgrade its fleet of vehicles to increase long-term savings by reducing collision, maintenance, fuel, or other costs. USPS must: (1) develop guidelines for carbon dioxide emissions, fuel economy, and safety for its vehicles; and (2) reduce the petroleum consumption of its vehicles by not less than 2% annually through the end of FY2025. The Government Accountability Office must conduct a study on the feasibility of USPS providing Internet services to the public.
|
Canadians tweet support for Turks and Caicos becoming 11th province
The Premier of Turks and Caicos Islands, Rufus Ewing, met with Prime Minister Stephen Harper today in Ottawa and said the two leaders spoke about exploring a more formal relationship.
Storified by KevinNewmanLive· Mon, May 26 2014 21:16:53
Turks and Caicos premier leaves door open on tropical islands becoming Canada's 11th province: http://t.co/eWl7BtKwgR http://t.co/tTYV8rkdZKCTV Kitchener
The weather is finally warming up across most of Canada now, but we aren't far removed from a time when snow covered our streets and we had to bundle up just to walk out the door. During those days it's easy to think about getting away to a tropical destination. But what if you didn't even need to show your passport to get there.
The premier of Turks and Caicos, Rufus Ewing, met with Prime Minister Stephen Harper today in Ottawa and said they spoke about exploring a more formal relationship. Ewing is leaving the door open to the prospect of joining Canada. He described the meeting as a "courtship", but said they didn't discuss the possibility of the islands becoming the 11th province.
Had a courtesy meeting with Premier of the Turks and Caicos Islands @docrewing today. #cdnpoli http://t.co/2J9JI2kSO8Stephen Harper
Foreign Affairs Minister John Baird was quick to shoot down the idea saying Canada is "not in the business of annexing islands...so that's not something we're exploring."
But a quick look to Twitter shows many Canadians are in favour of the idea. Saskatchewan Premier Brad Wall even tweeted that if the islands can't join Canada, he'd be happy to have them join his province.
If you don't want another prov/territory @pmharper , Turks/Caicos can join Canada as a part of Sask. http://t.co/BYp04F5UhVBrad Wall
@PremierBradWall off to the printers for my lawn signs #mayor #turkscaicosBevra Fee
@PremierBradWall @pmharper right on...direct flights out of Stoon and Regina...I can see it now...James B. Smith
I love Turks and Caicos. I love Canada. Make it happen. #11thProvince http://t.co/KVAf8sI9KeMDS
Making Turks and Caicos the 11th province is the best idea that the current Conservative government has had. http://t.co/WZxCBSUfWsStephen Marche
O Turks and Caicos, be our home and native tropical escape http://t.co/uRdMr8RtFvFrank Kuin
Let's bring Turks and Caicos into confederation! Just think how mutually beneficial it'd be.#MakeItHappen #turksandcaicos #11thProvinceBelluardo
Instead of annexing Turks and Caicos, why don't we offer PEI to the Brits in a trade?Aaron Wherry
Let's bring hockey to the Turks and Caicos Islands and make an 11th province! :DPat Sue-Chan
How cool would it be to have Turks and Caicos as Canada's 11th province? Would be nice to get some real estate... http://t.co/CNre9bpttNLeanne Giles
I want to stay in Canada when I retire. Therefore, I will retire in the Canadian province of Turks and Caicos. #retirement #paradise #nosnowRoberto V
I'm moving. Bye guys. - Canada’s eleventh province: Turks and Caicos? http://t.co/5xZQ3DrhzK via @torontostarAmira de Vera ||||| The head of the Turks and Caicos Islands says the country remains open to the long-simmering notion of joining Canada, which is backed by one Canadian premier but dismissed by the federal government.
Turks and Caicos Premier Rufus Ewing led a delegation to Ottawa on Monday, meeting with Prime Minister Stephen Harper and other officials during a trip aimed at boosting ties between the countries.
However, the Caribbean nation – a collection of 40 mostly uninhabited islands and roughly 35,000 people – has been the subject of annexation talk, a possible 11th province or fourth territory, for nearly a century. The subject came up again on Monday.
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Saskatchewan Premier Brad Wall offered to welcome Turks and Caicos to his province. He later said the offer was partially tongue-in-cheek – "Saskatchewarm," he coined it.
"I think we want to be constructive in Saskatchewan. If the Prime Minister's looking for a way to make this happen and doesn't want to go through the challenge of creating a province or territory, and Turks and Caicos want to make this happen, just, you know, we'd like a tropical island," Mr. Wall said in an interview. Asked how that could legally work, he replied: "I don't know, but if there was a hope we'd put a great group on it and find out."
The notion of the island nation somehow joining Canada dates back at least as far as 1917 and has the backing of one Conservative backbencher, Peter Goldring. He bristles at the notion of annexation but favours boosted economic ties and, if both countries' populations agree, a union of some kind.
The island leader's trip was focused on trade, however. While not ruling out a place in Canada, he said it was not imminent.
"I'm not closing the door completely. It is not of my mandate to close the door … What I'll say is on the radar is some kind of relationship. I can't say what kind of relationship it will be," Dr. Ewing, a surgeon by trade who now serves as his country's premier and tourism minister, told reporters.
Canadians pining for tropical turf can take some solace, however – his trip was aimed at further greasing the wheels for Canadians to travel to and do business in Turks and Caicos, with Dr. Ewing saying he was seeking "relaxation of immigration issues" to the point of "seamless" borders.
The Conservative government, however, was firmly rejecting any suggestion of welcoming Turks and Caicos into the Canadian fold. "We're not in the business of annexing islands in the Caribbean to be part of Canada. So that's not something that we're exploring. We're not looking at any sort of formal association with the islands," Foreign Affairs Minister John Baird said.
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That will come as little surprise to Mr. Wall. He has never been to Turks and Caicos, and Dr. Ewing has never been to Saskatchewan. Mr. Wall said he recalls hearing talk about the Turks and Caicos joining Canada as long as he's been in politics.
"I think people smile when they talk about it," he said, "and probably think it'll never happen."
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– Canadians who want to get away from brutal winters are still going to have to leave the country. After a meeting that Turks and Caicos Premier Rufus Ewing described as a "courtship," a Canadian government spokesman quashed talk that Canada would annex the nation as an 11th province, CTV reports. "We're not in the business of annexing islands in the Caribbean to be part of Canada," the country's foreign minister said. "So that’s not something that we’re exploring." But Ewing refused to rule out the possibility of the nation someday joining Canada, reports the Globe and Mail, which notes that the idea first surfaced almost a century ago. "I'm not closing the door completely. It is not of my mandate to close the door," Ewing said. "What I'll say is on the radar is some kind of relationship. I can't say what kind of relationship it will be." Saskatchewan Premier Brad Wall, meanwhile, says he'd be happy to welcome the island group to his landlocked province to create "Saskatchewarm." He says he's not sure how it would work legally, but if "Turks and Caicos want to make this happen ... you know, we'd like a tropical island."
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The actress and activist is being touted as a potential Senate candidate in Kentucky.
Actress Ashley Judd in Iowa urging early voting. (Photo: Bryon Houlgrave AP) Story Highlights U.S. Senator Ashley Judd?
Actress/activist being touted for office in Kentucky
She's busy celebrating Obama win
U.S. Sen. Ashley Judd? Some Democrats are wondering.
In all the pundit chatter leading up to and in the aftermath of Tuesday's re-election of President Obama, the most intriguing talk was about actress and Obama activist Judd as a potential U.S. Senate candidate in her former home, Kentucky, or even her current home of Tennessee.
Judd, who campaigned vigorously for Obama, has hinted before she might run for public office but never said anything about the U.S. Senate. But that hasn't stopped wishful Dems from dreaming.
On MSNBC Wednesday evening, NBC's political honcho Chuck Todd reported "serious speculation" about Judd being recruited to run in Kentucky against Senate Minority Leader Mitch McConnell, who's up for re-election in 2014 and might be in trouble with his own party thanks to the GOP's sorry showing Tuesday, especially the failure to re-take the Senate.
Meanwhile, the Louisville Courier-Journal interviewed U.S. Rep. John Yarmuth, D-Ky., who said a Judd-McConnell match-up would be a "premier race" and the money would "pour in" for her.
Even before the election, Huffington Post political analyst Howard Fineman said on MSNBC that Democrats in Kentucky would love to draft the 44-year-old TV/movie star, the sister and daughter to best-selling country stars Wynonna Judd and Naomi Judd.
"They want her. I know they want her," Fineman said. "The money people in Kentucky want Ashley Judd."
Judd grew up in Kentucky and went to college there but lives in Tennessee with her husband, race car driver and three-time Indianapolis 500 winner Dario Franchitti. She attended the Democratic National Convention this summer as a delegate from the Volunteer State.
Judd told The Tennessean in August that Democrats had not approached her about running against Tennessee's U.S. Sen. Bob Corker in Tuesday's election and she wouldn't have said yes even if they had.
"The way I'm doing my service right now is the best use of me," she said.
Read or Share this story: http://usat.ly/QpvRIR ||||| Next week’s episode of Parks and Recreation is going to have a VIP: the VP.
Joe Biden — yes, the very guy who was re-elected Vice President of the United States less than 24 hours ago — will guest-star in the Nov. 15 installment of Parks and Recreation, EW has learned. His cameo occurs at the beginning of the episode, in which former Congressional campaign manager Ben Wyatt (Adam Scott) takes fiancée/City Councilwoman Leslie Knope (Amy Poehler), to the White House to meet America’s No. 2, who has long been her No. 1 crush. (As Leslie once noted, her ideal man has “the brains of George Clooney and the body of Joe Biden.”)
Parks scored camera time with Biden in July when the show traveled to Washington, D.C. to film its season 5 premiere, which featured appearances by Senators Barbara Boxer, Olympia Snowe, and John McCain. How big of a casting coup was Biden for NBC’s small-town government comedy? “Given that Eleanor Roosevelt and Bella Abzug are no longer with us, this is probably no. 1,” quips executive producer Michael Schur. “[Leslie] has a lot of female heroes that cross party lines. She has a lot of social figures that she considers heroes, but the funniest hero is Joe Biden. There’s an episode last season where she says, ‘Joe Biden is on my celebrity sex list — well, he is my celebrity sex list’… It was amazing to have her meet Olympia Snowe and Barbara Boxer because that meant something to her politically. But this transcends that. She’s meeting the man that she’s in love with on some deep level. It was a bigger deal to us in some ways that she meet Joe Biden than it was that she meet Barack Obama.” (Obama, by the way, has revealed that he watches Parks with his family, by the way. “It’s a very amazing and weird thing to find out that the President watches your show,” marvels Schur.)
Once the producers committed to shooting an episode in D.C., the process of landing Biden was “so much less difficult than we ever possibly imagined,” says Schur, noting: “His staff really loves the show, and he apparently had watched the show with his family and his family liked it… The hardest part was keeping it secret for so long because there’s all these FEC rules and equal-time rules. We couldn’t air it before the election because it was the equivalent of a campaign contribution to advertise for one candidate.”
The Biden-Knope summit, a surprise “engagement present” from Ben, lasts less than a minute and was written in a manner that would work regardless of the election’s outcome. “We did not in any way want the moment to be a political issue — we treated it in the writing and the execution like our main character was meeting her hero,” says Schur. (He notes that the writers did pen an addendum to the scene in the event of an Obama-Biden loss or a “weird Florida disaster tie.”) The meeting takes place in the Vice President’s Ceremonial Office in the White House-adjacent Eisenhower Executive Office Building, with Biden flanked by his real-life staff. “They have a conversation where she does what you would imagine Leslie Knope would do when meeting Joe Biden, which is she loses control of herself a little bit,” hints Schur. “She gets really giggly and goofy around him.”
When the Parks crew set up in his office to shoot the scene, Biden happened to be tied up in a meeting with… President Barack Obama. Then “Obama got on Marine One and flew away, and Biden walked across the executive building and we shot the scene,” says Schur. “It was really cool: You go this way and get on a helicopter that will take you to some incredibly important thing, and you come this way and shoot a scene with Amy Poehler.”
The Veep handled his scene like a pro, even ad-libbing a response to a crazy Leslie retort that wound up in the final cut of the episode. “He was very nice and charming,” reports Schur. “He was clearly a big fan of Amy. It was the day the Emmy nominations came out and when he walked through the door he congratulated her on her Emmy nomination… He said some very nice things about the show and talked about how the pro-public service message was meaningful.”
While Schur & co. were thrilled to venture onto hallowed Washington ground, they aren’t plotting the next great political cameo right now: “Since the beginning of the show, Joe Biden has been the No. 1 guy, so in terms of her achievements or personal milestones we’ll have to go in a different direction,” he says. “She’ll have to get her thrills elsewhere.”
You can see a tease of Leslie’s historic meeting with the Veep in the following video. Also, check out a montage of her dreamy-eyed mentions of Joe from previous episodes in the second video.
Read more:
‘Parks and Recreation’: Christie Brinkley to play Jerry’s wife — EXCLUSIVE
‘Parks and Recreation’: Pawnee, literally, has the best newsletter ever
‘Parks and Recreation’: Megan Mullally to return
|
– Joe Biden is probably relieved that President Obama won re-election Tuesday—because it means the VP won't have to be embarrassed when his guest stint on Parks and Recreation airs one week from today. Biden filmed the guest appearance back in July, but it was kept strictly under wraps because if it had been leaked, the producers may have had to allow Paul Ryan to film a similar cameo. There are "all these FEC rules and equal-time rules," the executive producer tells Entertainment Weekly. Biden will play himself—the show's smitten main character, Amy Poehler's Leslie Knope, has said her dream man boasts "the brains of George Clooney and the body of Joe Biden"—in a scene that's supposed to occur in real time. "The vice president was amazing," the executive producer tells the New York Times. "He improvised a couple of things that we ended up using." In a statement, Biden says he and his entire family love the show and he had "a great time," although he isn't sure "how Leslie Knope got my home phone number, but that really just shows how committed she is." In more celebrity-political news, now that the election is over, attention is turning to the 2014 midterms—and some are speculating that Ashley Judd, a longtime political activist and Obama supporter, will run for Senate in Kentucky or Tennessee, USA Today reports.
|
short title
Section 1. This Act may be cited as the ``Senior Citizens Health
Insurance Standards Act of 1993''.
findings and purpose
Sec. 2. The Congress finds that--
(1) health care costs are a major expense and source of
concern for the elderly;
(2) Medicare covers less than half of the health care costs
for the elderly;
(3) because of their condition and needs, many elderly have
to purchase private health insurance;
(4) the paucity of consumer information in the field of
health insurance for the elderly makes it almost impossible for
those seeking such insurance to make reasoned choices;
(5) many of the policies sold to supplement Medicare
coverage provide inadequate coverage and low return to
consumers;
(6) the many instances of abuse and deception in the
marketing of health insurance for the elderly, which have been
documented by recent congressional hearings, constitute a
national disgrace; and
(7) these instances of abuse, deception, inadequate
coverage, and low return are now a national problem and the
Federal Government has a responsibility to assist in the
remedy.
(b) It is, therefore, the purpose of this Act to direct the
Secretary to require Federal minimum standards for the sale of health
insurance for the elderly and to take other action designed to provide
future benefits to the elderly who need assistance in meeting their
health insurance needs.
minimum standards
Sec. 3. (a) Each State shall, no later than two years after the
date of enactment of this Act, submit a plan to the Secretary of Health
and Human Services for the purpose of specifying the minimum standards
applicable to health insurance for the elderly in such State. Such plan
shall specify minimum standards which--
(1) provide that at least 75 per centum of the premiums
collected from the sale of such health insurance be returned in
the form of benefits provided under such health insurance, as
specified by the Secretary in regulations;
(2) limit the exclusions of preexisting conditions in
accordance with regulations prescribed by the Secretary;
(3) provide that policies of such health insurance be
written in simplified language which can be understood by
purchasers, as specified in regulations prescribed by the
Secretary;
(4) prohibit the sale of such health insurance if such
health insurance duplicates the coverage provided under the
Medicare Program, except that such a sale may be made if the
purchaser signs a written statement expressing his knowledge of
the duplicative coverage, as specified in regulations
prescribed by the Secretary; and
(5) are in accordance with disclosure provisions, specified
in regulations, which the Secretary determines necessary to
protect purchasers of such insurance, including, but not
limited to, provisions which require a simplified written
statement, to all prospective purchasers, of--
(A) the percentage of premiums collected for such
health insurance which is returned in the form of
benefits;
(B) the name and address of the agent who sold the
policy and a toll free telephone number of the
insurance company;
(C) general information which briefly, simply, and
adequately explains the premiums, benefits,
renewability, coverage, deductibles, coinsurance
charges, and other matters; and
(D) general information which briefly, simply, and
adequately explains the specific matters covered by the
insurance which are not covered under the Medicare
Program.
(b) The Secretary shall issue final regulations referred to in
subsection (a) no later than one hundred and eighty days after the date
of enactment of this Act.
(c) The Secretary shall approve or disapprove any plan submitted
pursuant to subsection (a) no later than ninety days after such
submission.
(d)(1) In the case of any State whose plan is disapproved under
subsection (c), the Secretary shall return such plan to the State with
a detailed explanation of the reasons for such disapproval. The State
may submit a new plan within thirty days after receiving such
explanation, and the Secretary shall approve or disapprove such plan no
later than thirty days after such submission.
(2) If the Secretary disapproves a new plan submitted in accordance
with the second sentence of paragraph (1) of this subsection, such
disapproval shall be subject to judicial review in the United States
court of appeals for the circuit in which the State is located or in
the United States Court of Appeals for the District of Columbia
Circuit. Any such review shall be instituted only by the State involved
and shall be commenced within sixty days after the date on which the
disapproval was issued. The provisions of subsection (f) shall apply
and shall not be stayed pending any such review.
(e)(1) The Secretary shall conduct oversight activities in each
State in which a plan is approved for the purpose of assuring that such
plan is carried out in each such State. Each State shall submit an
annual report to the Secretary containing a detailed account of the
operation of the plan in the State during the previous year. Such
report shall be in such form and contain such information as is
specified by the Secretary in regulations.
(2) No change may be made in a plan by any State unless approved by
the Secretary before the effective date of such change.
(3) In any case in which the Secretary finds that a State, which
has an approved plan, is not carrying out such plan, the Secretary
shall notify the State of such finding and provide the State with
detailed information about the basis of such finding. The Secretary
shall provide the State with an opportunity to correct any problems
specified by the Secretary or to present evidence that such problems do
not exist. After a reasonable time for allowing for corrections of the
problems or for submission of evidence that such problems do not exist,
the Secretary shall make a final determination that an approved plan is
or is not being carried out in the State. If the Secretary determines
that such a plan is not being carried out in the State, the provisions
of subsection (f) shall apply with respect to the State. A final
determination by the Secretary that a State plan is not being carried
out in any State shall be subject to judicial review under the
conditions described in subsection (d)(2).
(f) In any case in which--
(1) a State does not submit a plan under subsection (a);
(2) the Secretary fails to approve a plan submitted by a
State after giving such State an opportunity to submit a new
plan under subsection (d); or
(3) the Secretary makes a final determination under
paragraph (3) of subsection (e) that an approved plan is not
being carried out in such State;
the Secretary shall implement, as soon as practicable, a plan in such
State which carries out the minimum standards described in subsection
(a) with respect to the sale of health insurance for the elderly. The
Secretary shall implement such plan in such State until the Secretary
determines that such State will carry out the plan. The Secretary may
prescribe any regulations that are necessary to implement and
administer such plan in any State.
(g) Any provision of State law which would prevent the
establishment and implementation in that State of a plan implementing
the minimum standards described in subsection (a) is preempted by the
provisions of this Act.
definitions
Sec. 4. For purposes of section 3--
(1) the term ``health insurance for the elderly'' means
health insurance (as specified in regulations prescribed by the
Secretary) sold to persons who, at the time of such sale, are
(A) aged sixty-five or older, or (B) receiving benefits under
the Medicare Program;
(2) the term ``Medicare Program'' means the health
insurance program for the aged and disabled established by
title XVIII of the Social Security Act;
(3) the term ``Secretary'' means the Secretary of Health
and Human Services; and
(4) the term ``State'' means each of the fifty States of
the United States and the District of Columbia.
studies
Sec. 5. Section 1875 of the Social Security Act is amended by
adding the following new subsections at the end thereof:
``(c) The Secretary shall conduct a study for the purpose of making
recommendations to the Congress with respect to a uniform approach to
the regulation of all private health insurance which is offered for
sale to the aged and disabled. Such study shall include, but not be
limited to, an examination of the following matters--
``(1) minimum loss ratios;
``(2) uniform exclusions of pre-existing conditions;
``(3) the various means of differentiating categories of
coverage for purchasers of such health insurance;
``(4) the effectiveness of labels, numerical ratings, or
disclosure information in assisting the aged and disabled to
compare policies;
``(5) whether the sale of dread disease and other indemnity
policies should be banned or limited;
``(6) whether agents' commissions for selling such health
insurance should be limited;
``(7) methods of eliminating misconduct by agents in
selling policies;
``(8) the need for and costs of individualized health
insurance counseling for the aged and disabled;
``(9) whether claims handling requirements should be
imposed;
``(10) whether the sale of overlapping and/or duplicative
coverage should be banned; and
``(11) whether policy standardization is necessary to
promote competition.
The Secretary shall, no later than two years after the date of
enactment of this subsection, transmit a report to the Congress
containing the findings and recommendations of such study and proposed
legislation concerning a comprehensive approach to the regulation of
such health insurance.
``(d) The Secretary shall conduct a study for the purpose of making
recommendations to the Congress with respect to the feasibility of
health insurance coverage under this title in addition to the coverage
provided under parts A and B. Such study shall include, but not be
limited to, an examination of the following matters--
``(1) the need for such additional coverage;
``(2) eligibility requirements;
``(3) alternative approaches to providing such additional
coverage;
``(4) cost estimates of the alternative approaches, taking
into consideration the different coinsurance and deductible
requirements, coverage provisions, and eligibility standards of
each approach; and
``(5) alternative methods of financing such additional
coverage.
The Secretary shall, no later than two years after the date of
enactment of this subsection, transmit a report to the Congress
containing the findings and recommendations of such study.''.
|
Senior Citizens Health Insurance Standards Act of 1993 - Directs each State to submit to the Secretary of Health and Human Services a plan specifying certain minimum standards applicable to the sale of health insurance to the elderly.
Amends title XVIII (Medicare) of the Social Security Act to direct the Secretary to conduct studies for the purposes of making recommendations to the Congress concerning: (1) a uniform approach for regulating all private health insurance sold to the aged and disabled; and (2) the feasibility of additional health insurance coverage under Medicare.
|
Tweet with a location
You can add location information to your Tweets, such as your city or precise location, from the web and via third-party applications. You always have the option to delete your Tweet location history. Learn more ||||| The Justice Department’s internal watchdog is probing James Comey's handling of classified information as part of the memos he gave to a friend documenting discussions with President Trump.
A source familiar with the probe confirmed to Fox News the inspector general is looking at whether classified information was given to unauthorized sources as part of a broader review of Comey's communications outside the bureau -- including media contact.
The developments put the ex-FBI boss in the crosshairs of an investigation just as his former deputy, Andrew McCabe, faces a criminal referral over a separate leak.
The Wall Street Journal reported that at least two of those Comey memos have been to found to contain material now deemed classified, prompting the inspector general investigation.
A broader set of memos detailing Comey’s conversations with Trump were handed over to Congress Thursday evening.
Comey has maintained he didn’t release any memos containing classified material. In his testimony last year before the Senate Intelligence Committee, Comey said he made the decision to document the interactions in a way that would not trigger security classification.
GRASSLEY SAYS COMEY LEAKED CLASSIFIED INFORMATION
But the newly released memos could cause problems for Comey.
The Journal noted that Comey himself redacted classified elements in one of those memos, and another memo had material later upgraded by the FBI to “confidential” (a low classification level).
They apparently were among the four memos Comey gave to friend Daniel Richman, a professor at Columbia Law School.
In the seven total memos handed over to congressional committees, eight of the 15 pages have redactions under classified exceptions. They include classified information at one of the most sensitive levels -- SECRET -- as well as the lower level of confidential.
In one memo documenting his January 2017 Trump Tower meeting, Comey wrote that the material should be classified at the SECRET level unless the intelligence agencies thought otherwise.
“I am not sure of the proper classification here,” Comey writes, “so have chosen SECRET. Please let me know if it should be higher or lower than that.”
This, too, could be at odds with Comey’s June 2017 Senate testimony that he avoided classified material in the memos so that they could be widely shared.
The scrutiny of Comey comes as his former deputy McCabe faces potential legal complications from another IG probe that found he lied about a leak to The Wall Street Journal. The IG referred the findings to the U.S. attorney for Washington, D.C., to determine whether to seek charges.
Comey has backed the IG’s findings and said Thursday that he "could well be a witness" in a criminal case against McCabe.
McCabe attorney Michael Bromwich on Friday said McCabe is “upset and disappointed” about Comey's comments.
|
– When James Comey gave four memos to a friend detailing his interactions with President Trump, he took pains to make sure they contained no classified information, the former FBI chief told Congress last year. However, the Justice Department is now investigating whether he was wrong about that, reports the Wall Street Journal. The department's inspector general is looking at two memos in particular. In one of them, Comey blacked out information of his own accord that he deemed to be confidential, according to the Journal. The other three he considered safe. One of those three, however, apparently contained information that was upgraded to classified status after Comey left the FBI. The situation is similar to one that occurred with Hillary Clinton and her infamous email server—some emails that she circulated were OK at the time she did so but were later upgraded to classified. No charges were brought against her (by Comey), and it's unclear whether Comey himself would face any charges in this new investigation. Fox News confirms that the inspector general is investigating the possible mishandling of classified info. One person who needs no convincing: President Trump. Comey "leaked classified information," the president tweeted Thursday night, continuing a familiar theme of his. "WOW! Will the Witch Hunt continue?"
|
assume @xmath0 is an algebraically closed field and @xmath1 is a projective subscheme of @xmath2 defined by some homogeneous equations @xmath3 in @xmath4 $ ] .
we want to realize @xmath1 as a moduli space of quiver representations and as a quiver grassmannian in a natural way .
moreover , we also like to have a construction making the quiver as small as possible .
let @xmath5 be a bounded path algebra @xmath6 , where @xmath7 is a finite quiver and @xmath8 is an ideal of admissible relations in the path algebra @xmath9 .
moduli spaces for quiver representations have been defined by king in @xcite , a quiver grassmannian is just the variety of all submodules of a given module @xmath10 of a fixed dimension vector .
we note that we can consider moduli spaces and also quiver grassmannians with its natural scheme structure .
moreover , any quiver grassmannian is a moduli space ( just a moduli space of submodules of a given module ) , and there are natural morphisms between quiver grassmannians and moduli spaces . under certain additional conditions
these morphisms are even isomorphisms .
those isomorphisms are always hidden in our construction . since these morphisms can be seen explicitely in our construction we do not need any general result for those morphisms .
this is the main reason why we use line bundles in our construction , for arbitrary vector bundles all constructions become much more technical .
the other advantage of using line bundles is that we can always use modules of dimension vector @xmath11 ( also called thin sincere ) .
[ thm1 ] let @xmath1 be any projective scheme defined by equations @xmath12 in a projective @xmath13-space @xmath2 .
then there exists a quiver @xmath7 , an ideal @xmath8 in the path algebra @xmath9 and a @xmath9module @xmath10 so that 1 . @xmath1 is isomorphic to the moduli space of all indecomposable @xmath6modules of dimension vector @xmath14 , and + 2 .
@xmath1 is isomorphic to the quiver grassmannian of all submodules of @xmath10 of dimension vector @xmath15 for the quiver @xmath7 .
note that @xmath7 can be chosen to be the beilinson quiver , @xmath8 is an ideal just defined by the @xmath16 and @xmath10 is the unique sincere injective cover of one simple module , in particular @xmath10 is indecomposable . for more details
we refer to section [ sect2 ] .
the result on quiver grassmannians recently attracted attention in connection with cluster algebras ( see @xcite ) and in connection with auslanders theory on morphisms determined by objects .
ringel has already pointed out that the result above has been studied by several authors ( @xcite ) , however can be traced back to beilinson ( @xcite ) .
the principal aim of this note is to show how , we can use beilinson , and even better , how we can even improve it .
eventually , we show that all the constructions at the end can be traced back to a tautological construction in algebraic geometry .
any scheme @xmath1 is its own hilbert scheme of sheaves of lenght one : @xmath17 .
we note that the second result , for a variety @xmath1 , was already stated in @xcite and proven again with different methods in @xcite .
it can certainly be traced back to the work in @xcite .
an affine version was already proven in @xcite . however , the first published result in this direction was just an example in @xcite
. we will give a common frame for all those examples , in fact all are variants of the hilbert scheme construction in algebraic geometry and a variant of beilinsons equvivalence .
ringel already noticed that we can even work with the kronecker quiver , thus , two vertices are sufficient for @xmath7 . improving this construction slightly
, we can even realize any projective subscheme of the @xmath13dimensional projective space as a quiver grassmannian for the @xmath18kronecker quiver .
this construction is again explicit .
we denote the the @xmath19th homogenous component of the ideal @xmath20 generated by the polynomials @xmath16 by @xmath21 .
thus the homogeneous coordinate ring of @xmath1 is just @xmath22 for some @xmath18dimensional vector space @xmath23 .
we also denote by @xmath24 a natural number greater or equal to the maximal degree of the the polynomials @xmath16 .
[ thmkronecker ] let @xmath1 be any projective subscheme of the @xmath13dimensional projective space @xmath2 .
there is a module @xmath25 over the kronecker algebra defined by the natural map @xmath26
. then @xmath1 is isomorphic to the quiver grassmannian of submodules of @xmath10 of dimension vector @xmath27 .
the principal part of the note consists of a five step construction that we will use to get a realisation of @xmath1 as such a moduli space .
in addition we also add some modifications of these steps allowing to simplify the quiver or the relations .
we explain these five steps briefly . first note , that any scheme @xmath1 is its own hilbert scheme of sheaves of length one .
so any projective scheme is a moduli space of sheaves ( in a rather trivial way ) . in a second step
we use beilinson s equivalence to construct for @xmath1 an algebra @xmath28 .
roughly , we can take any tilting bundle @xmath29 on @xmath30 , extend it by any other vector bundle @xmath31 to @xmath32 and apply @xmath33 to the universal family of the hilbert scheme @xmath1 . in the particular case when @xmath29 is the direct sum of the line bundles @xmath34 , for @xmath35
, we can just extend it by the line bundles @xmath34 for @xmath36 . in this way
, we get a family of modules over the beilinson algebra for @xmath29 and a family of modules over the enlarged beilinson algebra for @xmath37 .
if @xmath1 is given by polynomials as above , all modules of the family also satisfy the equations @xmath16 , however now in the beilinson algebra .
thus we define @xmath8 to be the ideal generated by the @xmath16 in the enlarged beilinson algebra .
note that we have several choices for such realization , depending on where the relation starts .
however , one can check directly , that family of all modules of dimension vector @xmath14 over @xmath5 , the enlarged beilinson algebra with relations @xmath8 , coincides with @xmath1 , independent of the this realization . consequently
, the moduli space of all modules of dimension vector @xmath15 over @xmath5 is @xmath1 as a scheme . in a final step ,
we realize @xmath1 as a quiver grassmannian by using an injectice hull in @xmath5 .
we already mentioned that this construction is more general in the way that we can take any tilting bundle @xmath29 and any vector bundle @xmath31 , however the direct computation seems to be more sophisticated .
so we use line bundles just for simplicity .
even stronger , in general we do not need @xmath29 to be a tilting bundle . for example , the construction also would work if we only take @xmath38 where @xmath24 is at least the maximal degree of the @xmath16 .
then we get a realization similar to reinekes construction , that is in fact a variant of the realization for the kronecker quiver .
the paper is organized as follows . in the second section we present the five steps of our construction together with a final note on framed moduli spaces . in the third section we reprove the already known results using the construction in section [ sect2 ] .
we conclude in the last section with some open problems and a proof of the second theorem .
we construct , using some elementary results from algebraic geometry , for any algebraic variety a moduli space of quiver representations , a quiver grassmannian and also further examples in five steps .
we also note , that this even holds for any scheme that is quasi - projective .
so we obtain the authors example from 1996 @xcite , huisgen - zimmermann s examples in her work on uniserial modules ( see for example @xcite , and her work with bongartz @xcite on grassmannians , we apologize for being not complete ) , a variant of reineke s result for quiver - grassmannians from 2012 @xcite and last not least michel van den bergh s example , that appeared in a blog of lieven le bruyn .
in fact , all the results at the end of this note can be proven using the following constructions .
( @xcite ) we take an algebraic variety @xmath1 and consider sheaves of length one on @xmath1 .
there is a bijection between those sheaves and points of @xmath1 . in a more sophisticated way we can say @xmath39 the hilbert scheme of length one sheaves on @xmath1 . or
, we can consider any line bundle @xmath40 on @xmath1 as a fine moduli space of skyscraper sheaves by taking the push forward to the diagonal in @xmath41 .
each fiber of some point @xmath42 for the first projection is just the skyscraper sheaf in @xmath42 .
( @xcite ) in the second step we transform the construction above to the representation theoretic side using tilting . to keep the construction easy
, we consider the beilinson tilting bundle @xmath43 on the @xmath13dimensional projective space @xmath2 .
we denote by @xmath5 the beilinson algebra , it is the opposite of @xmath44 . take @xmath45 to be a skyscraper sheaf and let us compute @xmath46 .
note that @xmath47 , thus we get thin sincere representations of @xmath5 , that is each simple occurs with multiplicity one .
now we can see by direct computations that the moduli space of thin sincere representations of @xmath5 is just the projective space @xmath2 .
this example can be easily generalized to any tilting bundle @xmath29 , however , using sheaves ( that are not vector bundles ) we do not get a flat family ( the dimension above jumps at certain points ) .
( @xcite ) now we consider @xmath48 , any subvariety defined by equations @xmath49 in a projective @xmath13space @xmath2 .
assume first @xmath50 for all @xmath51 .
note that the quiver of the beilinson algebra above has @xmath52 arrows from @xmath51 to @xmath53 , we denote by @xmath54 , and paths the monomials @xmath55 of degree @xmath56 at most @xmath13 .
we define an algebra @xmath57 as the quotient of @xmath5 by the ideal @xmath58 , where @xmath59 is any linear combination of path representing @xmath60 in @xmath5 .
note that any representative works , since the arrows in @xmath5 commute , whenever this makes sense : @xmath61 .
this solves the problem we address to the next step already , since @xmath62 for any @xmath63 .
moreover , we could also use the fact , that any projective algebraic variety is already defined by quadratic relations .
however , using serre s theorem we can handle also relations of any degree in @xmath2 . to obtain @xmath48 , as in the previous step , where @xmath64 for any @xmath65 , we consider the sequence of line bundles @xmath66 .
the direct sum of these line bundles is no longer a tilting bundle , however the same computation as above shows that the moduli space of all thin sincere representations of @xmath5 is still a projective @xmath13space .
now the representatives @xmath67 of the polynomials @xmath16 live in @xmath68 and the moduli space of thin sincere representations of @xmath69 is @xmath48 ( even scheme theoretic ) .
the reader familiar with serre s construction will notice that this step is just inspired by this construction ( @xcite ) .
in a final step , we use the embedding of the thin sincere representations of @xmath57 in its minimal injective hull @xmath10 . note that @xmath20 is the indecomposable injective module with the unique simple socle , that is the socle of any thin sincere representation of @xmath57 . in case @xmath70 ( all @xmath16 are zero ) we obtain the projective space as quiver grassmannian of thin sincere subrepresentations of @xmath20 . in a similar way , also @xmath48 coincides with the quiver grassmannian of thin sincere subrepresentations of the large indecomposable injective @xmath57module @xmath10 .
this final step goes back to schofield @xcite and was mentioned later also by van den bergh and ringel ( @xcite ) .
we note that quiver grassmannians can be obtained also directly from a corresponding construction in algebraic geometry .
any skyscraper sheaf is the quotient of a line bundle @xmath71 .
if we consider the moduli space of all those quotients of @xmath40 with fixed hilbert series of the quotient sheaf , we get the ( framed ) hilbert scheme , that coincides with the original one .
if we apply beilinson s tilting again , we get for @xmath72 a projective @xmath5module .
thus @xmath2 is the quotient grassmannian for the large ( that is sincere ) indecomposable projective @xmath5module . the same construction works with @xmath48 instead of @xmath2 . note that any vector bundle @xmath73 for any @xmath74 with at least two elements on @xmath2 defines a morphism from @xmath2 to the moduli space of modules of dimension vector @xmath11 over @xmath75 ( or even over the path algebra of @xmath5 ) and also to the corresponding quiver grassmannian for the injective hull @xmath10 of an indecomposable of dimension vector @xmath11 .
thus , for the projective @xmath13space even two line bundles are sufficient . in the last section
we modify this construction slightly and consider @xmath74 consisting of three , repectively even two , elements so that we still get an isomorphism for any subscheme @xmath1 in @xmath2 .
we prove the theorem [ thm1 ] using the five steps above . in explicit terms
the module @xmath10 is just defined by vector spaces @xmath76 the @xmath19th graded part of the homogeneous coordinate ring .
this becomes a module over the beilinson quiver using the natural map @xmath77 as a multiplication map as follows .
take a basis @xmath78 of @xmath23 and define the linear map of the @xmath51th arrow just by tensoring with @xmath79 : @xmath80 .
the commutative relations force that the moduli space ( or the corresponding quiver grassmannian in @xmath10 ) of thin sincere modules is just a subscheme in @xmath2 defined by some of the polynomials @xmath16 .
if we consider sufficiently many degrees @xmath19 , then any @xmath16 is realized in some homogeneous part @xmath21 of the ideal @xmath20 .
for example the two degrees @xmath81 are sufficient to see any @xmath16 .
thus , if we take the beilinson quiver with vertices @xmath82 we can certainly realize the variety @xmath1 . conversely , we may ask how many degrees we need to realize @xmath1 in the module @xmath10 . a similar consideration as above shows that the three degrees @xmath83 are sufficient , provided @xmath24 is at least the maximum of all degrees of the polynomials @xmath16 , and @xmath84 can be any natural number with @xmath85 .
in particular , we can take @xmath86 or @xmath87 .
this leads to the proof of the second theorem proven in the last section .
the lemma below reduces than even to the kronecker quiver .
now we can use the construction above to get many variations , we can not list all , however we should collect some .
first we construct affine examples .
one way is to take open subvarieties , however we would like to characterize open subsets module theoretic .
huisgen - zimmermann started to consider uniserial modules in @xcite . to obtain affine varieties as moduli spaces of uniserial modules ,
we consider a variant of the beilinson quiver , we replace the first arrow @xmath88 just by a path @xmath89 of length two
. then a thin sincere module is uniserial precisely when its map @xmath89 is not zero .
thus it is the open subvariety ( subscheme ) defined by @xmath90 , that is an affine chart . in our opinion
there are two kind of consequences .
first one might think that we can now obtain results in algebraic geometry using representation theory .
this seems to be impossible , as far we consider any algebraic variety .
however , restricting to some subclasses this might be fruitful , we mention some open problems at the end of this note . moreover , for our construction
, using the beilinson algebra , the relations are directly given by the defining polynomials .
thus we do not get any deeper insight by considering an algebraic variety as a moduli space of quiver representations .
the second consequence concerns the realisation of a variety as a particular moduli space , that is more restrictive .
this is often very useful and is already used quite often .
the main open problem here seems to be to construct all moduli spaces of quiver representations for a particular quiver . in general , for all dimension vectors , this is even open for the @xmath91arrow kronecker quiver .
we use the construction in the previous section to prove some of the already known results just by applying the five steps .
we start with any projective algebraic variety and proceed with affine ones .
as we already explained , we consider @xmath1 as the scheme of length one sheaves on itself and apply the beilinson tilting bundle .
@xcite any projective algebraic scheme of finite type is a fine moduli space of modules over some finite dimensional algebra ( a bounded path algebra ) .
moreover , we can obtain it already for the thin sincere representations , that is the jordan - hlder series contains each simple module just once in its composition series up to isomorphism .
taking open parts we recover the result of huisgen - zimmermann , that was obtained using uniserial modules ( theorem g in @xcite ) .
note , the result was stated in @xcite in a different language , the notion of a moduli space was adapted by her only later .
then grassmannians also appeared in huisgen - zimmermann s work , however the idea was already introduced by schofield @xcite and then intensively used by nakajima @xcite . however
, a similar result could be read of from the work of bongartz and huisgen - zimmermann and was later explicitely stated in @xcite . here
again we can use thin sincere submodules of a module @xmath10 or just uniserial modules . using the beilinson construction with a rather small vector bundle
we can reduce the quiver even to the kronecker quiver .
this is almost the same construction as in reinekes work and based on the following geometric construction .
consider @xmath92 embedded into @xmath93 with the @xmath19uple embedding .
assume @xmath1 is a subscheme in @xmath94 and consider its image in @xmath93 .
if @xmath19 is larger than the maximal degree of the polynomials @xmath16 defining @xmath1 , the equations of @xmath1 in @xmath93 are just linear and the defining equations of the embedding @xmath95 ( that are quadratic ) . just modilfying the beilinson construction we can use the bundle @xmath96 .
this reduces the construction to a quiver with three vertices . for @xmath97 and @xmath24 sufficiently large
, this corresponds to realizing @xmath1 using quadratic equations .
the corresponding module @xmath10 considered as a representation of a three vertex quiver @xmath98 has a simple socle @xmath99 with @xmath100 and @xmath101 .
now we use ringels idea to reduce to the kronecker quiver @xmath102 . with notation above and
any @xmath103 we have an isomorphism of quiver grassmannians as follows .
the quiver grassmannian of submodules of @xmath104 of dimension vector @xmath105 is isomorphic to the quiver grassmannian of submodules of @xmath106 of dimension vector @xmath27 . proof .
note that the restriction of @xmath10 to @xmath107 defines a morphism of quiver grassmannians .
since @xmath108 is just one dimensional , any submodule @xmath107 over the kronecker algebra of dimension vector @xmath27 extends uniquely to a submodule of @xmath10 of dimension vector @xmath105 .
thus , this morphism is a bijection . in the particular case of @xmath1 being the projective space ,
this morphism is an isomorphism .
going back to @xmath10 we just restrict this isomorphism to the subscheme defined by the polynomials @xmath16 , consequently , both quiver grassmannians are also isomorphic .
@xmath109 taking @xmath24 at least the degree of the defining equations @xmath16 and @xmath110 we realize @xmath1 as a quiver grassmannian over the kronecker algebra with @xmath18 vertices .
this proves theorem [ thmkronecker ] .
note that reineke realized the linear subspace using an additional arrow , however , this is not necessary .
obviously , we can not reduce to just one vertex , thus two vertices is the minimum we can achieve .
however , it is not clear whether we can still reduce the number of arrows .
such a reduction would be more complicated and certainly independent of beilinsons result . at the end
we discuss the problem how to obtain projective examples from affine ones and vice versa . as we have mentioned above , one can take a projective variety , that is a moduli space , and obtain an affine cover as moduli spaces of uniserials by modifying the beilinson quiver slightly .
the converse , to obtain complete examples by glueing , is an open problem . in particular , let @xmath1 be a complete variety that is not projective ( see hartshorne for an example @xcite , ex 3.4.1 in appendix b ) then to our knowledge there is no way so far , to get @xmath1 as a moduli space of representations .
moreover , it is clear that @xmath1 can not be a quiver grassmannian , since the latter one is projective by definition .
one might think that also moduli spaces are always projective , however , we should mention that moduli spaces as constructed in king s paper @xcite are , but there might be other constructions as well .
since already kronecker quivers are very complicated with respect to the geometry of quiver grassmannians it would be natural to restrict to particular classes of modules or quivers . as far we know , the problem to describe all quiver grassmannians is open for dynkin quivers and also tame quivers .
it also would be desirable to understand quiver grassmannians for the @xmath91arrow kronecker quiver .
moreover , inspired by cluster algebras , the main open problem seems to be to understand quiver grassmannians for exceptional modules over path algebras .
if we use the explicit construction of the module @xmath10 with @xmath76 one can see , that everything is even defined over any base field . for polynomials over the integers
everything is defined even over @xmath111 .
thus the construction also works in the same fashion over an commutative ring .
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it is a well established fact , that any projective algebraic variety is a moduli space of representations over some finite dimensional algebra .
this algebra can be chosen in several ways .
the counterpart in algebraic geometry is tautological : every variety is its own hilber scheme of sheaves of length one .
this holds even scheme theoretic .
we use beilinson s equivalence to get similar results for finite dimensional algebras , including moduli spaces and quiver grassmannians .
moreover , we show that several already known results can be traced back to the hilbert scheme construction and beilinson s equivalence .
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the hera accelerator , located at desy in hamburg , is an electron - proton collider .
it is @xmath0 in circumference and collides positrons ( or electrons ) at @xmath1 with protons at @xmath2 there are four interaction regions : two containing general purpose , hermetic detectors ( h1 and zeus ) ; another experiment ( hermes ) investigating the spin distributions of the quarks in protons and neutrons ; and another ( hera - b ) planning to measure cp violation in the b - system .
the h1 and zeus detectors took first data in 1992 .
the zeus detector is shown in figure [ fig : zeus ] . the asymmetric design of the detector reflects the proton energy being significantly higher than that of the electron beam .
the tracking system consists of a vertex detector ( vxd ) @xcite and a central tracking chamber ( ctd ) @xcite enclosed in a 1.43 t solenoidal magnetic field . immediately surrounding
the beampipe is the vxd which consists of 120 radial cells , each with 12 sense wires .
the ctd , which encloses the vxd , is a drift chamber consisting of 72 cylindrical layers , arranged in 9 superlayers .
superlayers with wires parallel to the beam axis alternate with those inclined at a small angle to give a stereo view .
a forward tracking detector is employed in the forward region to detect tracks in the proton direction and consists of three 12-layer planar drift chambers sandwiched with pairs of transition radiation detectors . in the rear direction
there is an additional 12-layer planar drift chamber known as the rear tracking detector ( rtd ) . outside
the solenoid is the uranium - scintillator calorimeter ( cal ) @xcite , which is divided into three parts : forward , barrel and rear covering the polar regions @xmath3 to @xmath4 , @xmath4 to @xmath5 and @xmath5 to @xmath6 , respectively .
the cal covers 99.7@xmath7 of the solid angle , with holes of @xmath8 @xmath9 in the centres of the forward and rear calorimeters to accommodate the hera beam pipe .
each of the calorimeter parts is subdivided into towers which are segmented longitudinally into electromagnetic ( emc ) and hadronic ( hac ) sections .
the small angle rear tracking detector ( srtd ) @xcite , which is attached to the front face of the rear calorimeter , measures the impact point of charged particles at small angles with respect to the positron beam direction .
the iron return yoke for the magnet is instrumented with proportional counters .
this backing calorimeter ( bac ) measures any hadronic energy which ` leaks out ' out of the main calorimeter . beyond that and in the forward direction
there are further detectors for muon detection .
downstream of the main detector in the proton direction , six measuring stations are installed in the proton ring for detecting forward scattered protons . beyond the final station , further downstream ,
is a forward neutron calorimeter . in the electron direction
, two lead scintillator calorimeters placed @xmath10 and @xmath11 from the interaction point measure the luminosity and tag events with a small momentum transfer @xcite .
a fuller description of the zeus detector can be found in reference @xcite .
the h1 detector is of a very similar layout as zeus and a description can be found in reference @xcite .
the event kinematics of deep inelastic scattering , dis , are determined by the negative square of the four - momentum transfer at the positron vertex , @xmath12 , and the bjorken scaling variable , @xmath13 , where @xmath14 is the four - momentum of the proton . in the quark parton model ( qpm ) ,
the interacting quark from the proton carries the four - momentum @xmath15 .
the variable @xmath16 , the fractional energy transfer to the proton in its rest frame , is related to @xmath17 and @xmath18 by @xmath19 , where @xmath20 is the positron - proton centre of mass energy . because the h1 and zeus detectors are almost hermetic the kinematic variables @xmath17 and @xmath18 can be reconstructed in a variety of ways using combinations of electron and hadronic system energies and angles @xcite . in qpm
there is a 1 + 1 parton configuration , fig .
[ fig : feyn_alphas]a , which consists of a single struck quark and the proton remnant , denoted by `` + 1 '' . at hera energies
there are significant higher - order quantum chromodynamic ( qcd ) corrections : to leading order in the strong coupling constant , @xmath21 these are qcd - compton scattering ( qcdc ) , where a gluon is radiated by the scattered quark and boson - gluon - fusion ( bgf ) , where the virtual boson and a gluon fuse to form a quark - antiquark pair .
both processes have 2 + 1 partons in the final state , as shown in fig . [
fig : feyn_alphas ] .
there also exists calculations for the higher , next - to - leading ( nlo ) processes .
perturbative qcd does not predict the absolute value of the parton densities within the proton but determines how they vary from a given input . for a given initial distribution at a particular scale altarelli - parisi ( dglap ) evolution
@xcite enables the distributions at higher @xmath18 to be determined .
dglap evolution resums the leading @xmath22 contributions associated with a chain of gluon emissions . at large enough electron - proton centre - of - mass energies
there is a second large variable @xmath23 and , therefore , it is also necessary to resum the @xmath24 contributions .
this is acheived by using the bfkl equation @xcite .
to relate the hadronic final state to the underlying hard partonic behaviour it is generally necessary to apply a jet algorithm .
the jade algorithm @xcite has been used in the following analyses as it was , at the time , the only algorithm which allowed comparison to the nlo calculations ( projet @xcite and disjet @xcite ) .
the jade algorithm is a cluster algorithm based on the scaled invariant mass - squared @xmath25 for any two objects @xmath26 and @xmath27 assuming that these objects are massless .
@xmath28 is the squared invariant mass of the hadronic final state and @xmath29 is the angle between the two objects of energies @xmath30 and @xmath31 .
the minimum @xmath32 of all possible combinations is found .
if the value of this minimum @xmath32 is less than the variable cut - off parameter @xmath33 , the two objects @xmath26 and @xmath27 are merged into a new object by adding their four - momenta and the process is repeated until all @xmath34 .
the surviving objects are called jets which represent the underlying partonic structure that is dependent on @xmath35 . figures [ fig : jet_rates]a d show the zeus jet rates using data taken in 1994 , @xmath36 and @xmath37 as a function of for data compared with the disjet and projet nlo qcd calculations for three @xmath18 intervals
@xmath38 gev@xmath39 , @xmath40 gev@xmath39 , @xmath41 gev@xmath39 , and the combined region @xmath42 gev@xmath39 .
there is good agreement between the corrected @xmath43 and @xmath44 jet rates and the nlo qcd calculation over most of the range in shown .
both programs agree well in their prediction of the jet - rate dependence as a function of .
the values of @xmath35(@xmath45 ) extracted by the h1 @xcite and zeus @xcite collaboration as a function of @xmath45 are shown in fig .
[ fig : alphas ] .
the value of was determined by varying the @xmath46 scale parameter in the qcd calculation until the best fit to the ratio @xmath47 was obtained at a particular value of .
the measured decreases with increasing @xmath45 , consistent with the running of the strong coupling constant , with @xmath18 taken as the scale .
in addition the figure shows the curves for @xmath48 = 100 , 200 , and 300 mev .
an extrapolation to @xmath35(@xmath49 ) yields : @xmath50 which are consistent with other values obtained from a large variety of different processes as shown fig .
[ fig : alphas ] ( see @xcite for references ) .
even with the current statistics the hera measurements are already competitive with those made elsewhere . recently two new , more flexible nlo calculations ( mepjet @xcite and disent @xcite ) have become available allowing the experiments to analyze the data using any particular jet algorithm .
the @xmath51 algorithm @xcite is particularly suited for dis as it allows factorization between the beam fragmentation and the hard process @xcite .
the zeus collaboration has reanalyzed @xcite their 1994 data using this algorithm .
the preliminary values of @xmath35(@xmath45 ) obtained in the three bins of @xmath45 are shown ( with statistical errors only ) in fig .
[ fig : alphas ] and are consistent with the results obtained with the jade algorithm .
a natural frame in which to study the dynamics of the hadronic final state in dis is the breit frame @xcite . in this frame
the exchanged virtual boson is purely space - like with 3-momentum @xmath52 , the incident quark carries momentum @xmath53 in the positive @xmath54 direction , and the outgoing struck quark carries q/2 in the negative @xmath54 direction .
a final state particle has a 4-momentum @xmath55 in this frame , and is assigned to the current region if @xmath56 is negative , and to the target frame if @xmath56 is positive .
the advantage of this frame lies in the maximal separation of the outgoing parton from radiation associated with the incoming parton and the proton remnant , thus providing the optimal environment for the study of the fragmentation of the outgoing parton .
event shape variables have been investigated in @xmath57 experiments and used to extract the strong coupling constant @xmath58 independent of any jet algorithm , see _ eg _ ref .
h1 have recently performed a similar analysis @xcite in deep inelastic scattering in the current fragmentation region of the breit frame .
the event shape dependence on @xmath45 ( or energy dependence ) can be due to the logarithmic change of the strong coupling constant @xmath59 , and/or power corrections ( hadronisation effects ) which are expected to behave like @xmath60 .
recent theoretical developments suggest that @xmath60 corrections are not necessarily related to hadronisation , but may instead be a universal soft gluon phenomenon associated with the behaviour of the running coupling at small momentum scales @xcite .
h1 have analysed a number of infrared safe ( ie independent of the number of partons produced ) event shape variables .
their definitions are given below , where the sums extend over all hadrons @xmath61 ( being a calorimetric cluster in the detector or a parton in the qcd calculations ) with four - momentum @xmath62 the current hemisphere axis @xmath63 coincides with the virtual boson direction . * * thrust @xmath64 * @xmath65 * * thrust @xmath66 * @xmath67 * * jet broadening @xmath68 * @xmath69 * * scaled jet mass @xmath70 * @xmath71 a common characteristic of the mean event shape values @xmath72 and @xmath73 is the fact that they exhibit a clear decrease with rising @xmath45 , fig .
[ meandata ] .
this is due to fact that the energy flow becomes more collimated along the event shape axis as @xmath45 increases , a phenomenon also observed in annihilation experiments .
h1 showed by fitting to the data in fig .
[ meandata ] all the event shape variables can be well described by just the first order power corrections @xmath74 without the need for any higher order corrections .
the second order perturbative qcd parton predictions are also shown and their discrepancies with the data show that the power corrections are substantial at low values of @xmath45 , but become less important with increasing energy .
the analysis of the event shapes give results consistent with each other for @xmath75 the power correction parameter thus supporting the prediction of universality @xcite , and also gives consistent values of @xmath76 the results of the fit are @xmath77 for the power correction parameter and @xmath78 for the strong coupling constant in the @xmath79 scheme .
these values are compatible with those extracted by experiments @xcite
fragmentation functions represent the probability for a parton to fragment into a particular hadron carrying a certain fraction of the parton s energy .
fragmentation functions incorporate the long distance , non - perturbative physics of the hadronization process in which the observed hadrons are formed from final state partons of the hard scattering process and , like structure functions , can not be calculated in perturbative qcd , but can be evolved from a starting distribution at a defined energy scale . if the fragmentation functions are combined with the cross sections for the inclusive production of each parton type in the given physical process , predictions can be made for the scaled momentum , @xmath80 spectra of final state hadrons .
small @xmath81 fragmentation is significantly affected by the coherence ( destructive interference ) of soft gluons @xcite , whilst scaling violation of the fragmentation function at large @xmath81 allows a measurement of @xmath35 @xcite . in annihilation
the two quarks are produced with equal and opposite momenta , @xmath82 this can be compared with a quark struck from within the proton with outgoing momentum @xmath83 in the breit frame . in the direction of the struck quark ( the current fragmentation region ) the particle momentum spectra ,
@xmath84 are expected to have a dependence on @xmath45 similar to those observed in annihilation @xcite at energy @xmath85 the inclusive charged particle distributions @xcite , @xmath86 are shown in figure [ nlo ] plotted in bins of fixed @xmath81 as a function of @xmath87 for @xmath88 the distributions rise with @xmath18 at low @xmath81 and fall - off at high @xmath81 and high @xmath18 . by measuring the amount of scaling violation one can ultimately measure the amount of parton radiation and thus determine @xmath89 below @xmath90 the fall off is due to depopulation of the current region . the results can be compared to the next - to - leading order ( nlo ) qcd calculations , as implemented in cyclops @xcite , of the charged particle inclusive distributions in the restricted region @xmath91 and @xmath92 where the theoretical uncertainties are small , unaffected by the hadron mass effects which are not included in the fragmentation function .
this comparison is shown in figure [ nlo ] .
the nlo calculation combines a full next - to - leading order matrix element with the @xmath93 parton densities ( with a @xmath94 and nlo fragmentation functions derived by binnewies et al . from fits to @xmath57 data @xcite . the data and the nlo calculations are in good agreement , supporting the idea of universality of quark fragmentation .
the peak position of the distributions , , was evaluated .
figure [ figure : slope ] shows the distribution of as a function of @xmath45 for the hera data @xcite and of @xmath95 for the @xmath57 data . over the range
shown the peak moves from @xmath96 1.5 to 3.0 , equivalent to the position of the maximum of the corresponding momentum spectrum increasing from @xmath96 400 to 900 mev .
the hera data points are consistent with those from tasso @xcite data and a clear agreement in the rate of growth of the hera points with the @xmath57 data @xcite is observed .
the increase of can be approximated phenomenologically by the straight line fit @xmath97 also shown in figure [ figure : slope ] .
also shown is the statistical fit to the data when @xmath98 which would be the case if the qcd cascade was of an incoherent nature , dominated by cylindrical phase space .
( a discussion of phase space effects is given in @xcite . ) in such a case , the logarithmic particle momentum spectrum would be peaked at a constant value of momentum , independent of @xmath45 .
the observed gradient is clearly inconsistent with @xmath98 and therefore inconsistent with cylindrical phase space thus supporting the coherent nature of gluon radiation .
in the dglap parton evolution scheme @xcite the parton cascade follows a strong ordering in transverse momentum @xmath99 , while there is only a soft ( kinematical ) ordering for the fractional momentum @xmath100 .
however for low-@xmath17 at hera the bfkl scheme @xcite could well be the dominant scheme . in this scheme
the cascade follows a strong ordering in fractional momentum @xmath101 , while there is no ordering in transverse momentum .
bfkl evolution can be enhanced by studying dis events which contain an identified jet of longitudinal momentum fraction @xmath102 ( in the proton direction ) which is large compared to bjorken @xmath17 @xcite . by tagging a forward jet with @xmath103
this allows minimal phase space for dglap evolution while the condition @xmath104 leaves bfkl evolution active .
this leads to the forward jet production cross section in bfkl dynamics being larger than that of the @xmath105 qcd calculation with dglap evolution @xcite . in fig .
[ fig : h1comp ] , recent data from h1 @xcite and zeus @xcite are compared with bfkl predictions @xcite and fixed order qcd predictions as calculated with the mepjet @xcite program at nlo . the conditions @xmath103 and @xmath104 are satisfied in the two experiments by slightly different selection cuts .
h1 selects events with a forward jet of @xmath106 gev ( in the angular region @xmath107 ) with @xmath108 while zeus triggers on somewhat harder jets of @xmath109 gev and @xmath110 with @xmath111 fig .
[ fig : h1comp ] shows that both experiments observe substantially more forward jet events than expected from nlo qcd .
a very rough estimate of the uncertainty of the nlo calculation is provided by the two dotted lines , which correspond to variations by a factor 10 of the renormalisation and factorisation scales @xmath112 and @xmath113 . a recent bfkl calculation ( dashed lines )
gives a better agreement with the data .
the overall normalisation in this calculation is uncertain and the agreement may be fortuitous , indeed it should also be noted that both experiments observe more centrally produced dijet events than predicted by the nlo qcd calculations . further careful investigation is necessary before claiming that bfkl is the mechanism for this enhanced forward jet production .
to understand the underlying qcd processes in dis it is necessary to study the hadronic final state . at the current level of understanding ,
qcd works well and describes the hera data .
as the precision of the hera data improves and the nlo qcd calculations become available the framework of qcd is being tested more thoroughly .
as yet it is not possible to say conclusively whether the effects of bfkl dynamics are being observed in the hera data , much theoretical and experimental work is in progress to define and measure variables that will allow a definitive statement .
4.mm i would like to thank the organising committee for inviting me to the school and providing such a pleasant and enjoyable environment .
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this lecture contains a brief introduction to hera and deep inelastic scattering ( dis ) , before going on to highlight some of the measurements of the hadronic final state in dis performed by the h1 and zeus collaborations .
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# 1b ( 19#3 ) # 2 # 1#2#3nuovo cimento # 1a ( 19#3 ) # 2 # 1#2#3z .
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c#1 ( 19#3 ) # 2 # 1#2#3jetp lett.#1 ( 19#3 ) # 2 # 1#2#3j .
phys .
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instr .
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# 2 2 m_z^0 glas - ppe/9708october 1997
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Police have "solved" a decades-old missing person case — but the woman who vanished so long ago now has dementia and can't explain her own disappearance.
New York authorities never thought they would solve the 42-year-old missing person case of Flora Stevens, but then a state police investigator contacted the Sullivan County Sheriff's Office last month about some skeletal remains that might fit the vanished woman’s profile.
Sheriff's Detectives Ed Clouse, left, and Rich Morgan pose with Flora Harris. Sullivan County Sheriff's Office
Those skeletal remains pushed Sheriff’s Detective Rich Morgan to look into whether Stevens — who was 36 when she disappeared — had any living relatives. By hunting through federal, state and local databases, he discovered someone was using Stevens' social security number in Massachusetts.
After a short drive up to Lowell, Massachusetts, Morgan and partner Detective Ed Clouse met Flora Harris, 78, in a local nursing home.
Related: Husband Confesses to Wife's Murder, Body Location in Suicide Note
Harris recognized an old employee photograph of Stevens from the Concord Hotel, and the two police officers soon realized Stevens and Harris were the same woman — but much had changed.
"She doesn’t speak in more than one or two words at a time," Sullivan County Undersheriff Eric Chaboty explained, noting that Stevens suffers from dementia. "But she looked at the ID and said, 'Me!'"
The struggle to communicate indicates a late middle stage or end stage form of dementia, according to the Alzheimer's Association.
But Chaboty said when investigators showed her old pictures of the Concord Hotel, Stevens lit up immediately.
Flora Stevens appears in an employee photo from the Concord Hotel circa 1975. Courtesy of Sullivan County Sheriff's Office
"One of the things we talk about for late stage care is to find alternative ways to connect with them," said Beth Kallmyer, vice president of constituent services at the Alzheimer's Association. "They’re still alive, they’re still living here, so that helps make their quality of life better when you can find ways to connect with them. One way to do that is to look through old photos or to tell them about old memories or past events."
Stevens had spent time at nursing homes in New Hampshire and New York City, but the mental health records are relatively vague and no one is quite sure what caused her to leave the small New York town of Monticello 42 years ago, officials said. She has no living relatives who could fill police in, either, they said.
“The main thing is that we know that Flora is safe," said Sullivan County Sheriff Mike Schiff. ||||| MONTICELLO, N.Y. (AP) — A woman who disappeared from upstate New York after being dropped off for a doctor's appointment 42 years ago has been found suffering from dementia and living in an assisted-living facility in Massachusetts, authorities said.
The sheriff's office in Sullivan County, New York, said Flora Stevens, 78, was using the last name Harris when detectives tracked her down this week at the residence in Lowell, near Boston. Officials said they've been unable to figure out details of what happened to her between the time she disappeared in August 1975 and when she was finally found.
"It's not too often we get to solve a 42-year-old missing-person case," Sheriff Mike Schiff said in a press release. "The main thing is we know Flora is safe."
Police said Stevens was a 36-year-old employee of a Catskills resort when her husband dropped her off for a doctor's appointment at a hospital in Monticello, 75 miles (121 kilometers) northwest of New York City. When he returned to pick her up, she wasn't there.
Police periodically reviewed her missing person case but kept hitting dead ends. They got a break in September, thanks to a query from a New York State Police investigator working on a different cold case. The unidentified remains of a woman had been found in neighboring Orange County, and the investigator said they roughly matched Stevens' general characteristics.
The state police investigators asked Sullivan County for help tracking down any relatives who could provide a DNA sample for possible identification. During a records search, Detective Rich Morgan discovered someone was using Stevens' Social Security number in Massachusetts.
Deputies tracked the number to the Lowell assisted-living residence, where staff confirmed the number belonged to a resident named Flora Harris, who has lived there since 2001. Morgan and another detective went there Tuesday and confirmed Harris was actually the Flora Stevens who had disappeared in 1975.
Because of her condition, she couldn't provide details of her life since them, police said. But the detectives brought along Stevens' employee photo identification card from the now-defunct Concord Resort, and she recognized herself, officials said.
Her medical records under her new name show she lived in nursing homes in New Hampshire and New York City before arriving in Lowell, police said. Stevens apparently has no living relatives, officials said.
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– A woman who disappeared from upstate New York 42 years ago has been found suffering from dementia and living in a Massachusetts assisted-living facility, authorities say. The sheriff's office in Sullivan County, NY, says Flora Stevens, 78, was using the last name Harris when detectives tracked her down this week at the residence in Lowell, near Boston, per the AP. Officials say they've been unable to figure out what happened to her between her August 1975 disappearance and when she was found. Police say Stevens was a 36-year-old Catskills resort worker when her husband dropped her off for a doctor's appointment in Monticello. When he returned to get her, she wasn't there. Police periodically reviewed her case but hit dead ends. Thanks to a query from New York State Police working on a different cold case, they got a break in September. Remains had been found in a neighboring county; police thought it might be Stevens. During a records search, a detective found someone was using Stevens' Social Security number in Massachusetts. Deputies tracked it to the Lowell residence, where staff said it belonged to Flora Harris, there since 2001. Detectives confirmed Harris was Stevens. Cops say due to her condition, she couldn't offer details of her life, but she recognized herself in a photo ID card from the now-defunct resort. "She looked at the ID and said, 'Me!'" one of the detectives says, per the New York Daily News. Medical records under "Harris" show she previously lived in New Hampshire and NYC nursing homes. Stevens apparently has no living relatives. "It's not too often we get to solve a 42-year-old missing person case," Sheriff Mike Schiff says in a press release. "The main thing is we know Flora is safe."
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since the report of buonocore in 1955 , phosphoric acid etching has been a standard protocol to treat tooth enamel for bonding resins and orthodontic attachments . however , decalcification is the one potential disadvantage , which leaves the enamel susceptible to caries attack , especially under orthodontic attachments .
consequently , alternative methods that decrease the decalcification risk and provide clinically acceptable bonding strength have been sought .
, after maiman introduced the ruby laser , several types of laser have been applied in dentistry , such as carbon dioxide , neodymium - doped : yttrium aluminum garnet ( nd : yag ) and diode lasers .
the first - generation lasers were suitable for soft - tissue treatment , especially in periodontology .
when these lasers were used in dental hard - tissue , they resulted an inflammatory pulpal response . recently the development of mid - infrared lasers ( erbium - doped yttrium aluminum garnet [ er : yag ] and erbium , chromium : yttrium , scandium , gallium , garnet [ er , cr : ysgg ] ) allow ablation of both soft and hard - tissues with minimal thermal side - effects .
the er : yag laser with a wavelength of 2940 nm can ablate enamel and dentin effectively , because its light is highly and efficiently absorbed by water and hydroxyapatite .
it has been suggested that er : yag laser was able to decrease acid dissolution and increase fluoride uptake ; thus , produce a surface , which is less susceptible to caries .
the result of the studies in the past two decades on the application of laser etching for increasing bond strength of restorative material have been controversial .
some studies indicate that acid - etched teeth had significantly more bond strength than laser - etched teeth . on the other hand
, others suggested that laser etching could result in bond strength comparable with or even stronger than acid etching .
these differences could be attributed to the various types of lasers or various irradiation parameters used , because the laser - hard tissue interaction is dependent on wavelength and irradiation energy . according to the controversial findings regarding the use of erbium lasers for enamel etching ,
the aim of this study is to evaluate the shear bond strength ( sbs ) between the acid etched enamel and laser irradiated enamel and to investigate the fracture mode of the bond .
in this experimental in vitro study , 15 caries - free , intact human upper premolars extracted for orthodontic purposes in the oral surgery department of isfahan university of medical sciences were used .
then , they were stored in hanks balanced salt solution ( hank 's balanced salt solution [ hbss ] , sigma - aldrich , st .
antibiotics ( penicillin 100 , metronidazole 100 , gentamycin 100 , amphotericin 100 ) with 1% volume ratio was added to hbss to prevent bacterial and fungal growth . the teeth were mounted in self - cure acrylic resin ( rapid repair , detrey dentsply ltd , surrey , u.k ) up to the cementoenamel junction .
the buccal enamel surface was cleaned and polished with non - fluoridated pumice and rubber cup , then washed with an oil free air spray .
the buccal enamel surfaces of the premolars were divided into mesial and distal regions with masking tape ( approximately 1 mm width ) .
one region was randomly etched with er : yag laser with a wavelength of 2940 nm ( fotona , fidelis plus , ljubljana , slovenia ) .
laser energy is delivered through a r14 handpiece with fiber optic system with 900 m diameter [ figure 1 ] .
it operates at 2 w power with 100 mj energy output , 20 hz of frequency and short pulse mode .
the beam was directed perpendicular to enamel at 1 mm distance ( contact mode ) and was moved in a sweeping fashion by hand over an approximately 3 3 mm during an exposure time of 20 s , which was enough to scan this area .
the irradiated teeth were dried with an oil free air spray for 15 s. the r14 handpiece used in this study the other region was etched with conventional 37% phosphoric acid gel ( american orthodontics , sheboygan , usa ) for 15 s , then washed for 20 s and dried with an oil - free source for 20 s. the frosty white appearance of enamel was visible in both regions for all specimens . transbond xt primer ( 3 m unitek , monrovia , ca , usa ) was then applied to both etched surfaces ; afterward an air jet was lightly applied to the enamel .
then , transbond xt composite ( 3 m unitek , monrovia , ca , usa ) was applied onto the base of the two metal mandibular incisors brackets ( american orthodontic , standard edgewise.018 , 380 - 0008 , sheboygan , usa ) . according to the manufacturer 's instruction these brackets had a surface bonding area of 8.78 mm .
the brackets were placed onto mesial and distal regions of the buccal tooth surface immediately and adjusted to final position and pressed firmly .
excessive adhesives were removed from the periphery of the bracket base to keep the bond area of each tooth uniform and light - cured with a light - emitting diode ( starlight pro , mectron , carasco , italy ) for 20 s ( 10 s from each proximal side ) . then the masking tape was removed [ figure 2 ] .
one of the samples which , the right side was etched by 37% phosphoric acid and the left side etched by erbiumdoped yttrium aluminum garnet laser after storing the specimens in distilled water at 37c for 24 h , they were thermocycled for a total of 500 cycles at 5 - 55c with a dwell time of 30 s and a 10 s transfer time between baths , to simulate the heat and humidity conditions of the oral cavity .
the shear bond test was accomplished with a chisel edge , mounted on the crosshead of a universal testing machine ( walter + bai ag , lhningen , switzerland ) .
the edge was aimed at the bracket - enamel interface with a crosshead speed of 1 mm / min and the debonding forces were recorded for each specimen in newtons and then converted to megapascals .
the shear bond test was performed by a technician who was blinded about the preparation procedures undertaken for the groups .
the debonded buccal surface of each tooth was evaluated under 10 magnification and the adhesive remnant index ( ari ) was quantified according to the criteria established by artun and bergland , i.e. , 0 = no adhesive left on tooth , 1 = less than half of the adhesive left on tooth , 2 = more than half of the adhesive left on tooth , 3 = all the adhesive left on tooth .
statistical comparisons were performed with software statistical package for the social sciences for windows ( version 19.0 , chicago , il , usa ) .
the frosty white appearance of enamel was visible in both regions for all specimens . transbond xt primer ( 3 m unitek , monrovia , ca , usa ) was then applied to both etched surfaces ; afterward an air jet was lightly applied to the enamel .
then , transbond xt composite ( 3 m unitek , monrovia , ca , usa ) was applied onto the base of the two metal mandibular incisors brackets ( american orthodontic , standard edgewise.018 , 380 - 0008 , sheboygan , usa ) . according to the manufacturer 's instruction these brackets had a surface bonding area of 8.78 mm .
the brackets were placed onto mesial and distal regions of the buccal tooth surface immediately and adjusted to final position and pressed firmly .
excessive adhesives were removed from the periphery of the bracket base to keep the bond area of each tooth uniform and light - cured with a light - emitting diode ( starlight pro , mectron , carasco , italy ) for 20 s ( 10 s from each proximal side ) . then the masking tape was removed [ figure 2 ] .
one of the samples which , the right side was etched by 37% phosphoric acid and the left side etched by erbiumdoped yttrium aluminum garnet laser after storing the specimens in distilled water at 37c for 24 h , they were thermocycled for a total of 500 cycles at 5 - 55c with a dwell time of 30 s and a 10 s transfer time between baths , to simulate the heat and humidity conditions of the oral cavity .
the shear bond test was accomplished with a chisel edge , mounted on the crosshead of a universal testing machine ( walter + bai ag , lhningen , switzerland ) .
the edge was aimed at the bracket - enamel interface with a crosshead speed of 1 mm / min and the debonding forces were recorded for each specimen in newtons and then converted to megapascals .
the shear bond test was performed by a technician who was blinded about the preparation procedures undertaken for the groups .
the debonded buccal surface of each tooth was evaluated under 10 magnification and the adhesive remnant index ( ari ) was quantified according to the criteria established by artun and bergland , i.e. , 0 = no adhesive left on tooth , 1 = less than half of the adhesive left on tooth , 2 = more than half of the adhesive left on tooth , 3 = all the adhesive left on tooth .
statistical comparisons were performed with software statistical package for the social sciences for windows ( version 19.0 , chicago , il , usa ) .
descriptive statistics for the comparison of sbs for the two groups are given in table 1 .
descriptive statistics of shear bond strength ( in mpa ) for the phosphoric acid and laser etching groups the acid - etched group had higher sbs means ( 18.86 6.09 mpa ) than laser - etched group ( 16.61 7.70 mpa ) , but no significant difference was found between both groups ( p = 0.41 ) .
the location of the fracture for each group was evaluated with the ari index [ table 2 ] .
three possible types of fractures may be observed : cohesive fracture ( within the body of the composite ) , adhesive fracture ( at the composite - bracket base or enamel - composite interface ) and mixed fracture .
residual adhesive rating according to ari for laser - etched and acid - etched groups in the acid - etched group , 40% of fractures were located at the bracket - adhesive interface ( ari 3 ) , 20% at enamel - adhesive interface ( ari 0 ) and 40% were mixed fractures ( ari 1 and 2 ) . in the laser
etched group , 47% of bond failures were located at the enamel - adhesive interface ( ari 0 ) , 13% at bracket - adhesive interface ( ari 3 ) and 40% were mixed fractures ( ari 1 and 2 ) .
no cohesive failures within the body of the resin and no enamel tooth fractures were found . the mann - whitney u test showed no significant differences ( p = 0.08 ) between two groups according to the ari evaluation .
in the present study , the laser - etched group had similar loading strengths with the acid - etched group ( p = 0.41 ) .
maijer and smith reported that 8 mpa of bonding strength is adequate for orthodontic brackets .
therefore , bond forces range in both group were within acceptable limit and laser etching at these setting seems acceptable for clinical use .
on the other hand , our results are not in agreement with those of umez et al .
. these controversies could be due to different tooth structures , type of laser and different laser setting such as power output , wavelength , emission mode , contact or non - contact mode , irradiation time , water cooling and irradiation distance .
the ari values indicated no significant difference in the bond failure site among the two groups .
although in the laser group more adhesive remained on the brackets , which is not suitable for orthodontic purposes .
less chair time would be needed with less adhesive left on the enamel after debonding , but some authors state that bond failure at the bracket - adhesive interface or within the adhesive is more acceptable ( safe ) than failure at the adhesive - enamel interface , because enamel fracture and cracking have been reported at bracket debonding , especially with ceramic brackets .
the ability of er : yag laser to ablate dental hard tissue is ascribed to its 2940 nm wavelength , which is coincident with the absorption band of water and hydroxyapatite of enamel .
the irradiation is highly absorbed by the water molecules in the enamel , causing sudden heating and water evaporation .
consequence is high stream pressure that leads to the micro - explosions with ejection of tissue particles , which are characteristic of the ablation process and determine the micro - crater like appearance of lased surface .
the majority of irradiation is consumed in the ablation process and leaving very little residual energy for adverse thermal interactions with the pulp tissue and peripheral soft- and hard - tissues . moreover , er : yag laser can be applied in wet conditions and the clinician has more control of the area to be etched .
although , gel acids are more stable than liquid acids , there is always a shift of gel acid on the enamel surface . often , laser etching leaves the tooth with a rough surface , so time saved with laser etching might be used performing additional polishing after debonding .
furthermore , laser radiation can lead to the micro - crack formation in the enamel surface , which acts as starting points for fracture , acid attack and demineralization .
consequently , the possible positive effect of erbium laser irradiation in preventing enamel demineralization around the brackets is reduced or eliminated . in this study ,
the irradiation was performed manually in order to simulate the clinical condition . to ensure identical conditions for both groups , the buccal surface of each sample was divided into mesial and distal regions using a masking tape then ; one region was etched with acid and the other with laser .
the results show that laser etching procedure produce clinically acceptable bond strengths , but this was an in vitro study and the result may be different when the procedures are performed on the patients .
further investigation to evaluate structure and mechanical properties of the enamel after bonding with laser is suggested .
according to the results of this study , the mean bond strength and bond failure mode of 37% phosphoric acid - etched group and er : yag laser - etched group were not significantly different .
therefore , er : yag laser may be an alternative method for conventional acid - etching .
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background : laser ablation has been suggested as an alternative method to acid etching ; however , previous studies have obtained contrasting results .
the purpose of this study was to compare the shear bond strength ( sbs ) and fracture mode of orthodontic brackets that are bonded to enamel etched with acid and erbium - doped yttrium aluminum garnet ( er : yag ) laser.materials and methods : in this experimental in vitro study , buccal surfaces of 15 non - carious human premolars were divided into mesial and distal regions .
randomly , one of the regions was etched with 37% phosphoric acid for 15 s and another region irradiated with er : yag laser at 100 mj energy and 20 hz frequency for 20 s. stainless steel brackets were then bonded using transbond xt , following which all the samples were stored in distilled water for 24 h and then subjected to 500 thermal cycles .
sbs was tested by a chisel edge , mounted on the crosshead of universal testing machine .
after debonding , the teeth were examined under 10 magnification and adhesive remnant index ( ari ) score determined .
sbs and ari scores of the two groups were then compared using t - test and mann - whitney u test . significant level was set at p < 0.05.results:the mean sbs of the laser group ( 16.61 7.7 mpa ) was not significantly different from that of the acid - etched group ( 18.86 6.09 mpa ) ( p = 0.41 ) . there was no significant difference in the ari scores between two groups ( p = 0.08 ) . however , in the laser group , more adhesive remained on the brackets , which is not suitable for orthodontic purposes.conclusion:laser etching at 100 mj energy produced bond strength similar to acid etching .
therefore , er : yag laser may be an alternative method for conventional acid - etching .
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FILE - This Wednesday, Feb. 21,1996 file photo shows John Lotter, center, being escorted from the Richardson County Courthouse in Falls City, Neb., after being sentenced to death for the December 1993... (Associated Press)
FILE - This Wednesday, Feb. 21,1996 file photo shows John Lotter, center, being escorted from the Richardson County Courthouse in Falls City, Neb., after being sentenced to death for the December 1993 murders of Teena Brandon, Phillip DeVine and Lisa Lambert, a crime that inspired the movie "Boys Don't... (Associated Press)
FILE - This Wednesday, Feb. 21,1996 file photo shows John Lotter, center, being escorted from the Richardson County Courthouse in Falls City, Neb., after being sentenced to death for the December 1993 murders of Teena Brandon, Phillip DeVine and Lisa Lambert, a crime that inspired the movie "Boys Don't... (Associated Press) FILE - This Wednesday, Feb. 21,1996 file photo shows John Lotter, center, being escorted from the Richardson County Courthouse in Falls City, Neb., after being sentenced to death for the December 1993... (Associated Press)
LINCOLN, Neb. (AP) — Attorneys for a Nebraska death row inmate whose case inspired the 1999 movie "Boys Don't Cry" say he should be ruled ineligible for execution because he has the intellect of a young child.
John Lotter was sentenced to death for his role in the 1993 killings of Brandon Teena, a 21-year-old transgender man, and two witnesses, Lisa Lambert and Philip DeVine, at a rural farmhouse in Humboldt, about 75 miles south of Omaha. Lotter has spent the last 22 years on death row.
Lotter's lawyers filed a motion last week stating that recent IQ testing showed that the 46-year-old is intellectually disabled and therefore can't be put to death under a 2002 U.S. Supreme Court ruling forbidding the execution of the intellectually disabled, the Lincoln Journal Star reported .
Under Nebraska law, an IQ of 70 or below is presumptive evidence of an intellectual disability. Court records show that Lotter scored a 67 last year, which would be the equivalent IQ of an 8-year-old.
Neuropsychologist Ricardo Weinstein determined that Lotter qualifies for an intellectual developmental disability diagnosis after reviewing trial and school records, and interviewing Lotter's mother, foster mother and a psychiatrist who worked with him as a child. Lotter scored an IQ of about 73 when he was 10 years old, according to Weinstein.
Lotter's attorneys also cited a 2014 decision by the U.S. Supreme Court that rejected a strict IQ cutoff rule in Florida. They said the court found a consensus among medical experts that IQ test scores shouldn't be read as a single number, but rather as a range that can fluctuate for many reasons.
Richardson County District Judge Vicky Johnson will need to grant an evidentiary hearing in order to consider the issue. If granted, the state can seek its own experts.
Lotter and another man, Marvin Thomas Nissen, raped Teena after finding out he was transgender and then killed him, Lambert and DeVine to silence the rape allegations, according to prosecutors. Nissen is serving life sentences for his role in the crimes.
Teena's death is remembered as an important date in the history of U.S. transgender rights, and Hillary Swank's film portrayal of him won her an Oscar for best actress. ||||| Close Get email notifications on Lori Pilger daily!
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– Attorneys for a Nebraska death row inmate whose case inspired the 1999 movie Boys Don't Cry say he should be ruled ineligible for execution because he has the intellect of a young child. John Lotter was sentenced to death for his role in the 1993 killings of Brandon Teena, a 21-year-old transgender man played by Hillary Swank in the film, and two witnesses, Lisa Lambert and Philip DeVine, at a rural farmhouse in Humboldt, about 75 miles south of Omaha. Lotter has spent the last 22 years on death row. Lotter's lawyers filed a motion last week stating that recent IQ testing showed that the 46-year-old is intellectually disabled and therefore can't be put to death under a 2002 US Supreme Court ruling forbidding the execution of the intellectually disabled, the Lincoln Journal Star reported. Under Nebraska law, an IQ of 70 or below is presumptive evidence of an intellectual disability. Court records show that Lotter scored a 67 last year, which would be the equivalent IQ of an 8-year-old, reports the AP. Neuropsychologist Ricardo Weinstein determined that Lotter qualifies for an intellectual developmental disability diagnosis after reviewing trial and school records, and interviewing Lotter's mother, foster mother and a psychiatrist who worked with him as a child. Lotter scored an IQ of about 73 when he was 10 years old, according to Weinstein. Richardson County District Judge Vicky Johnson will need to grant an evidentiary hearing in order to consider the issue. If granted, the state can seek its own experts.
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the recent experimental confirmation of two- ( 2d ) and three - dimensional ( 3d ) topological insulators @xcite ( tis ) , such as hgte/(hg , cd)te quantum wells @xcite of certain width and compounds involving bismuth , @xcite respectively , has attracted considerable attention from both basic and applied research communities .
the tis introduce an exotic quantum state of matter brought by spin - orbit ( so ) coupling effects in solids which is characterized by a topological invariant that is insensitive to microscopic details and robust with respect to weak disorder .
@xcite thus , although tis have energy gap in the bulk , their topological order leads to quantized physical observables in the form of the number of gapless edge ( in 2d ) or surface ( in 3d ) states modulo two tis have an odd number of edge ( surface ) states in contrast to trivial band insulators with even ( i.e. , typically zero ) number of such states .
as regards applications , the channeling of spin transport @xcite through one - dimensional ( 1d ) counter - propagating spin - filtered ( i.e. , `` helical '' ) edge states of 2d tis , where the time - reversal invariance forces electrons of opposite spin to flow in opposite directions , opens new avenues to realize semiconductor spintronic devices based on manipulation of coherent spin states .
@xcite for example , fabrication of spin - field - effect transistor @xcite ( spin - fet ) , where spin precession in the presence of so coupling is used to switch between on and off current state , requires to prevent entanglement of spin and orbital electronic degrees of freedom in wires with many conducting channels or different amounts of spin precession along different trajectories , @xcite both of which make it impossible to achieve the perfect off state of spin - fet . ) under the fmr conditions induces via the proximity effect a time - dependent exchange field @xmath0 in the ti region underneath .
in the absence of any applied bias voltage , these devices pump pure spin current into the nm electrodes in setup ( a ) or both charge and spin current in setup ( b ) . ]
some of the key questions posed by these rapid developments are : how can the ti phase be detected by conventional measurements of _ quantized _ charge @xcite transport quantities ?
how can spintronic _ heterostructures _
@xcite exploit ti edge or surface states in the presence of interfaces with other materials @xcite or internal and external magnetic fields @xcite used to manipulate spins while breaking the time - reversal invariance ? for example , the 2d ti is operationally defined as a system which exhibits the quantum spin hall effect ( qshe ) with quantized spin conductance ( ratio of transverse pure spin current to longitudinally applied bias voltage ) .
however , this quantity is difficult to observe , and reported measurements @xcite of electrical quantities probing the edge state transport in hgte - based multiterminal devices have exhibited poor precision of quantization when contrasted with the integer quantum hall effect a close cousin of qshe used in metrology . here
we propose two ferromagnet - ti ( ) heterostructures , illustrated in fig .
[ fig : setup ] , where an island of a ferromagnetic insulator ( fi ) is deposited over the surface of 2d ti modeled either as graphene nanoribbon ( gnr ) @xcite with intrinsic so coupling @xcite or hgte - based strip .
@xcite the precessing magnetization of fi under the ferromagnetic resonance conditions @xcite ( fmr ) will induce a time - dependent exchange field in the ti region underneath via the magnetic proximity effect .
@xcite using the nonequilibrium green function ( negf ) approach @xcite to pumping by precessing magnetization in the frame rotating with it , we demonstrate that setup in fig .
[ fig : setup](a ) makes possible efficient conversion of microwave radiation into _ pure _ spin current ( fig .
[ fig : singlefm ] ) whose magnitude can reach a quantized value @xmath1 even at small increase of the precession cone angle ( i.e. , microwave power input @xcite ) away from zero . on the other hand , the device in fig .
[ fig : setup](b ) generates charge current @xmath2 ( in addition to spin current ) which is quantized @xmath3 for a wide range of precession cone angles ( fig .
[ fig : dualfm ] ) .
this offers an alternative operational definition of the 2d ti in terms of electrical measurements or a microwave detector which is more sensitive than conventional spin pumping devices .
@xcite we also analyze the effect of disorder and device size on the quantization of pumped currents .
the paper is organized as follows . in sec .
[ sec : negf ] , we discuss how to compute pumped currents due to precessing magnetization by mapping such time - dependent quantum transport problem to an equivalent four - terminal dc circuit in the frame rotating with magnetization where steady - state spin and charge currents are evaluated using negfs in that frame .
section [ sec : spin ] covers pure spin current pumping in the heterostructure of fig .
[ fig : setup](a ) , while sec .
[ sec : charge ] shows how charge current is pumped in the second type of proposed heterostructure in fig .
[ fig : setup](b ) .
we explain the origin and the corresponding requirements for these pumped currents to be quantized in sec .
[ sec : origin ] .
we conclude in sec .
[ sec : conclusions ] .
the simplest model for the 2d ti central region of the device in fig . [ fig : setup ] is gnr with intrinsic so coupling , as described by the effective single @xmath4-orbital tight - binding hamiltonian : @xmath5 here @xmath6 is the vector of spin - dependent operators ( @xmath7 , @xmath8 denotes electron spin ) which annihilate electron at site @xmath9 of the honeycomb lattice , and @xmath10 is the vector of the pauli matrices . the nearest - neighbor hopping @xmath11 is assumed to be the same on the honeycomb lattice of gnr and square lattice of semi - infinite nm leads .
the third sum in eq .
( [ eq : hlab1 ] ) is non - zero only in the gnr regions where it introduces the intrinsic so coupling compatible with the symmetries of the honeycomb lattice .
@xcite the so coupling , which is responsible for the band gap @xcite @xmath12 , acts as spin - dependent next - nearest neighbor hopping where @xmath13 and @xmath14 are two next - nearest neighbor sites , @xmath15 is the only common nearest neighbor of @xmath13 and @xmath14 , and @xmath16 is a vector pointing from @xmath15 to @xmath13 . for simplicity ,
@xcite we assume unrealistically @xcite large value for @xmath17 .
we use the on - site potential @xmath18 $ ] as a uniform random variable to model the isotropic short - range spin - independent static impurities . in both gnr and hgte models ,
the coupling of itinerant electrons to collective magnetic dynamics is described through the exchange potential @xmath19 .
this is assumed to be non - zero only within the region of the ti which is covered by the fi island with precessing magnetization where the proximity effect @xcite generates the time - dependent zeeman term adiabatically .
the magnitude of the effective exchange potential is selected to be in gnr model and in hgte model for 2d ti .
the components of the rotating exchange field in the plane of the 2d ti , and , generate energy gap by removing the edge states from the @xmath20 gap of the ti region below the fi island ( in both models we assume @xmath21 ) .
the effective tight - binding hamiltonian @xcite for the hgte / cdte quantum wells ( applicable for small momenta around the @xmath22 point ) is defined on the square lattice with four orbitals per site : @xmath23 \hat{c}_{\mathbf{i } } \nonumber \\ & + & \sum_{\mathbf{i } } \hat{c}_{\mathbf{i}}^{\dagger } \left ( \begin{array}{cccc } v_{ss } & v_{sp } & 0 & 0 \\ -v_{sp}^{\ast } & v_{pp } & 0 & 0 \\ 0 & 0 & v_{ss } & v_{sp}^{\ast } \\ 0 & 0 & -v_{sp}^ { { } } & v_{pp } \\
\end{array } \right ) \hat{c}_{\mathbf{i } + \mathbf{e}_x } + \mathrm{h.c . }
\nonumber \\ & + & \sum_{\mathbf{i } } \hat{c}_{\mathbf{i}}^{\dagger } \left ( \begin{array}{cccc } v_{ss } & iv_{sp } & 0 & 0 \\ iv_{sp}^{\ast } & v_{pp } & 0 & 0 \\ 0 & 0 & v_{ss } & -iv_{sp}^{\ast } \\ 0 & 0 & -iv_{sp } & v_{pp } \\ \end{array}% \right ) \hat{c}_{\mathbf{i}+ \mathbf{e}_y } + \mathrm{h.c . }
\nonumber \\\end{aligned}\]]here vector contains four operators which annihilate an electron on site @xmath24 in quantum states @xmath25,@xmath26 , @xmath27 , @xmath28 , while the on - site matrix elements , @xmath29 and @xmath30 , are tuned by the gate potential to ensure that ti regions are insulating and the nm electrodes described by the same hamiltonian ( [ eq : hlab2 ] ) are in the metallic regime .
the unit vectors @xmath31 and @xmath32 are along the @xmath33 and @xmath34 directions , respectively .
the parameters @xmath35 characterizing the clean hgte / cdte quantum wells are defined as @xmath36 , @xmath37 , @xmath38 , @xmath39 , and @xmath40 ( @xmath41 is the lattice constant ) where @xmath42 and @xmath43 are controlled experimentally .
@xcite the width of gnr regions with zigzag edges is measured in terms of the number of zigzag chains @xmath44 comprising it , while its length is measured using the number of carbon atoms @xmath45 in the longitudinal direction .
@xcite the gnr - based devices studied in figs .
[ fig : singlefm ] and [ fig : disorder ] are of the size @xmath46 , @xmath47 where fi island of length @xmath48 covers middle part of the ti , while in figs .
[ fig : dualfm][fig : totallocalspin ] the device is smaller , @xmath46 , @xmath49 and @xmath50 , to allow for transparent images of local current profiles .
the fermi energy @xmath51 is within the ti gap .
the size of hgte - based heterostructures is measured using the number of transverse lattice sites @xmath44 and the number of sites @xmath45 in the longitudinal direction . the devices studied bellow have @xmath52 , @xmath53 with fi island of length covering middle part of the ti region ( fig .
[ fig : singlefm ] also shows result for a larger device , @xmath54 , @xmath55 and ) .
hamiltonians ( [ eq : hlab1 ] ) and ( [ eq : hlab2 ] ) are time - dependent since the spatially uniform unit vector @xmath56 along the local magnetization direction is precessing steadily around the @xmath57-axis with a constant precession cone angle @xmath58 and frequency @xmath59 .
this complicated time - dependent transport problem can be transformed into a simpler time - independent one via the unitary transformation of hamiltonians ( [ eq : hlab1 ] ) or ( [ eq : hlab2 ] ) using @xmath60 [ for @xmath56 precessing counterclockwise ] : @xmath61 the zeeman term @xmath62 , which emerges uniformly in the sample and nm electrodes , will spin - split the bands of the nm electrodes , thereby providing a rotating frame picture of pumping based on the four - terminal dc device .
@xcite in the equivalent dc device , pumping by precessing magnetization can be understood @xcite as a flow of spin - resolved charge currents between four spin - selective ( i.e. , effectively half - metallic fm ) electrodes @xmath63 , @xmath64 , @xmath65 @xmath66 ( @xmath67-left , @xmath68-right ) biased by the electrochemical potential difference @xmath69 .
the basic transport quantity for the dc circuit in the rotating frame is the spin - resolved bond charge current carrying spin-@xmath70 electrons from site @xmath24 to site @xmath71 @xmath72.\ ] ] this is computed in terms of the lesser green function in the rotating frame @xcite @xmath73 . unlike @xmath74 in the lab frame , @xmath75 depends on only one time variable @xmath76 ( or energy @xmath77 after the time difference @xmath78 is fourier transformed ) .
this finally yields local spin @xmath79 and local charge @xmath80 currents flowing between nearest neighbor or next - nearest neighbor sites @xmath24 and @xmath71 connected by hopping @xmath81 .
they can be computed within the device or within the nm electrodes .
the summation of all @xmath82 or @xmath83 at selected transverse cross section , ( assuming the @xmath57-axis for the spin quantization axis ) and , yields total spin or charge current , respectively .
the charge current @xmath2 has to be the same at each cross section due to charge conservation , but the spin current @xmath84 can vary in different regions of the device since spin does not have to be conserved .
the magnitude of total currents pumped into , e.g. , the left nm electrode ( i.e. , computed at any cross section within the left nm electrode ) can also be expressed in terms of the transmission coefficients for the four - terminal dc device in the rotating frame @xcite @xmath85 , \\
\label{eq : totalccurrent } i & = & \frac{1}{4\pi } \int de\ , \left(t_{rl}^{\uparrow \downarrow}- t_{lr}^{\uparrow \downarrow}\right ) \left[f^\downarrow(e)-f^\uparrow(e)\right],\end{aligned}\ ] ] here the transmission coefficients @xmath86 determine the probability for @xmath87 electrons injected through lead @xmath88 to emerge in electrode @xmath89 as spin-@xmath70 electrons , and can be expressed in terms of the spin - resolved negfs .
@xcite the distribution function of electrons in the four electrodes of the dc device is given by where @xmath90 for spin-@xmath7 and @xmath91 for spin-@xmath92 .
since the device is not biased in the laboratory frame ( where all nm electrodes are at the same electrochemical potential @xmath93 ) , this shifted fermi function is uniquely specified by the polarization @xmath7 or @xmath92 of the electrode .
the precessing magnetization of fm island in the device setup of fig .
[ fig : setup](a ) pumps pure ( i.e. , with no accompanying net charge flux ) spin current symmetrically into the left and right nm electrodes in the absence of any bias voltage [ if the device is asymmetric , charge current is also pumped but only as the second order @xmath94 effect @xcite ] . in the case of conventional nm in contact with precessing fm ,
different approaches predict @xcite that pumped spin current by the fm@xmath95 nm interface behaves as @xmath96 . to understand the effect of the ti surrounding the precessing island
, we first reproduce this feature in fig . [
fig : singlefm ] for gnr with no so coupling ( @xmath97 ) . when the intrinsic so coupling @xcite is `` turned on '' ( @xmath98 ) , the pumped pure spin current in fig .
[ fig : singlefm ] is substantially enhanced ( by up to two orders of magnitude at small precession cone angles ) .
in fact , pumping into helical edge states _ profoundly modifies _
@xmath84 vs @xmath58 characteristics which becomes constant quantized quantity @xmath1 for large enough @xmath58 . figure [ fig : singlefm ] also confirms the same behavior for hgte model of 2d ti .
moreover , it shows that interval of cone angles within which pumped current is quantized can be manipulated by using longer fi region .
exploiting this feature would enable giant spin battery effect where large pure spin current is induced by even very small microwave power input which experimentally @xcite controls the precession cone angle .
the ti region is modeled as gnr with zigzag edges and non - zero intrinsic so coupling @xmath98 or hgte - based strip .
for comparison , we also plot pumped spin current when ti is replaced by a zigzag gnr with zero intrinsic so coupling @xmath97 . in the case of hgte - based heterostructure
, we show that increasing the size of the proximity induced magnetic region within ti widens the interval of cone angles within which pumped current is quantized . ] note that since @xmath99 , we can use at low temperatures for the difference of the fermi functions in eqs .
( [ eq : totalscurrent ] ) and ( [ eq : totalccurrent ] ) .
this `` adiabatic approximation '' @xcite is analogous to linear response calculations for biased devices , allowing us to define the pumping spin conductance @xmath100 .
its quantization in fig .
[ fig : singlefm ] is an alternative characterization of the 2d ti phase when compared to qshe in four - terminal bridges @xcite where longitudinal charge current driven by the bias voltage @xmath101 generates transverse spin current @xmath102 and corresponding quantized spin hall conductance @xmath103 .
thus , the spin battery in fig .
[ fig : setup](a ) would produce much larger pure spin currents than currently achieved through , e.g. , conventional she in low - dimensional semiconductors while offering tunability that has been difficult to demonstrate for she - based devices .
@xcite we recall that the original proposal @xcite for spin battery operated by fmr was based on heterostructures .
however , experiments @xcite performed on ni@xmath104fe@xmath105cu bilayers have found that spin pumping by fm@xmath95 nm interfaces is not an efficient scheme to drive spin accumulation in nonmagnetic materials ( e.g. , estimated @xcite spin polarization is only @xmath106 in 10-nm - thick cu layer ) because of the backflow of accumulated spins into the fm and the diffusion of polarized spins inside the nm .
no such spin accumulation or spin dephasing exists in the device in fig .
[ fig : setup](a ) where bulk transport within the ti regions is completely suppressed ( see fig . [
fig : localspin ] ) while 1d spin transport is guided by helical edge states .
the ti region is modeled as gnr with zigzag edges and intrinsic so coupling @xmath17 or hgte - based strip .
in addition to charge current , these heterostructures pump spin current plotted explicitly for the gnr - based ti , while for hgte - based device the two curves are virtually identical ( due to larger device size ) . ]
while the most direct confirmation of the 2d ti phase would be achieved by measuring quantized @xmath107 , this is very difficult to perform experimentally .
thus , several recent studies @xcite have proposed experiments that would detect edge state transport in 2d tis via simpler measurement of conventional electrical quantities in response to external probing fields .
in particular , ref .
has conjectured that a setup with two disconnected fm islands covering two lateral edges of 2d ti , where the magnetization of one of them is precessing while the other one is static , could pump quantized charge current counting the number of helical edge states .
this proposal , based on intuitive arguments @xcite rather than full quantum transport analysis of adiabatic pumping , concludes that charge pumping conductance @xmath108 would be ` universally ' quantized for arbitrary device parameters or precession cone angle . in order to induce quantized
charge current response from the 2d ti phase , we propose an alternative heterostructure in fig .
[ fig : setup](b ) where fi island with precessing magnetization is covering portion of a _ single _ lateral edge of the ti . figure [ fig : dualfm ] demonstrates that this device pumps both charge and spin currents into the nm electrodes .
the pumping conductances @xmath109 plotted in fig .
[ fig : dualfm ] are quantized in a wide interval of precession cone angles , which can also be expanded by using longer fi island similarly to hgte curves in fig .
[ fig : singlefm ] . at @xmath110 for gnr model of ti with @xmath111 .
the corresponding total pumped currents are plotted in figs .
[ fig : singlefm ] and [ fig : totallocalspin ] . ]
to explain the origin of quantized spin and charge pumping in the proposed heterostructures , we compute spatial profiles of local pure spin current in fig .
[ fig : localspin ] and local charge and spin currents in fig .
[ fig : localcharge ] for devices in fig .
[ fig : setup](a ) and fig .
[ fig : setup](b ) , respectively . in the four - terminal dc device picture of pumping , @xcite these local _ nonequilibrium _ currents are generated by the spin flow from electrode @xmath112 at higher @xmath113 into electrode @xmath114 at lower @xmath115 .
the role of the central island with static ( in the rotating frame ) noncollinear magnetization , for which the incoming spins are not the eigenstates of the corresponding zeeman term , is to allow for transmission with spin precession or reflection accompanied by spin rotation ( for transport between @xmath112 and @xmath116 electrodes ) .
the spin precession or rotation is necessary for spin to be able to enter electrode at a lower electrochemical potential ( accepting spins opposite to the originally injected ones ) while flowing through the edge state moving in proper direction compatible with their chirality .
( b ) at @xmath110 .
the corresponding total pumped currents are plotted in fig .
[ fig : dualfm ] . ] the quantization of the pumped pure spin current in fig .
[ fig : singlefm ] is ensured by the absence of flow through the bulk of the magnetic island within ti underneath fi in fig .
[ fig : localspin](a ) . in this case , only perfect reflection with spin rotation at the interface between ti region with proximity induced @xmath0 and ti itself takes place redirecting spins from one helical edge state to the other one at the same edge .
thus , the transmission coefficient @xcite @xmath117 in eq .
( [ eq : totalscurrent ] ) becomes quantized since it is governed by local ballistic transport through edge states on the top right lateral edge in fig .
[ fig : localspin](a ) , while the other two coefficients are zero @xmath118 .
this also explains why the range of precession cone angles within which @xmath119 in fig .
[ fig : singlefm ] or @xmath109 in fig .
[ fig : dualfm ] is quantized can be expanded by increasing the length of the magnetic island within ti ( i.e. , the corresponding fi island on the top ) or the proximity induced exchange potential @xmath120both tunings diminish overlap of evanescent modes from the two ti@xmath95magnetic - island interfaces .
this is further clarified by fig .
[ fig : totallocalspin ] where spin current emerges also in the bulk of the magnetic island in the non - quantized case for small @xmath121 . as
discussed in sec .
[ sec : negf ] , spin current is in general not conserved , which is exemplified in fig .
[ fig : totallocalspin ] by different values of the total pumped spin current at different cross sections ( including zero in the middle of the magnetic island at large precession cone angle @xmath110 ; the non - zero current around interfaces is due to evanescent modes ) .
analogously , quantized charge current in fig .
[ fig : dualfm ] is driven by the same reflection process discussed above which then generates flow of rotated spin along the right ti@xmath95 nm interface and the bottom lateral edge in fig .
[ fig : localcharge](b ) while utilizing only one of the two helical edge states . in the lab frame picture of pumping
, the emission of currents in the absence of bias voltage can be viewed as a flow of spins , driven by absorption of microwave photons , from the region around the interface between the magnetic island and ti where edge states penetrate as evanescent modes into the island .
however , this framework does not offer simple explanation of why pumped currents can become quantized . figures [ fig : localspin ] and [ fig : localcharge ] also provide answer to the following question : what happens to current , which is confined to a narrow region of space along the samples edges within ti , as it exists from the ti region into the nm electrodes ?
the local charge or spin fluxes remain confined to a narrow `` flux tube '' even within the nm electrodes which is refracted at the ti@xmath95 nm interface by an angle @xmath122 .
this feature is explained by the fact that at the ti@xmath95 nm interface the helical edge state in the , e.g. , upper right corner changes direction ( to flow downward along the ti@xmath95 nm interface ) so that at this region of space at which current penetrates from ti into nm the quantum state carrying it has wavevector @xmath123 . by continuity of wavefunctions ,
this relation is preserved within the nm electrodes leading to the observed refraction of the guiding center for electron quantum - mechanical propagation .
( a ) for two different precession cone angles .
the total spin current for cone angle @xmath110 is obtained by summing local currents shown in fig .
[ fig : localspin ] . ] for gnr - based ti , where pure spin current curve labeled with ( a ) is generated by the spin battery device in fig .
[ fig : setup](a ) while curves labeled with ( b ) are for the device in fig .
[ fig : setup](b ) . ] figure [ fig : disorder ] shows that pumped currents remain precisely quantized in the presence of weak static ( spin - independent ) disorder simulating short - range impurity scattering .
further increasing of the disorder strength diminishes pumped charge current much faster than the spin current .
finally , our analysis shows that the second fm island with static magnetization covering the opposite edge of the device in the proposal of ref . for quantized charge pump
is redundant .
moreover , in the case of fm island with precessing magnetization deposited directly on the top of ti to generate proximity effect and pumping , quantization would be lost @xcite if electrons can penetrate into the metallic region provided by such islands so that transport ceases to be governed purely by the helical edge states .
in conclusion , we have proposed two types of heterostructures shown in fig . [
fig : setup ] which can pump quantized spin or charge current in the absence of any applied bias voltage .
the device in fig .
[ fig : setup](a ) emits pure spin current @xmath84 toward both the left and the right nm electrodes .
its quantized value @xmath124 can be attained even at very small microwave power input ( determining the precession cone angle @xcite ) driving the magnetization precession , thereby offering a very efficient spin battery device that would surpass any battery @xcite based on pumping by conventional fm@xmath95 nm interfaces . on the other hand , the device in fig .
[ fig : setup](b ) generates quantized charge current @xmath125 in response to absorbed microwaves , which can be utilized either for electrical detection of the 2d ti phase via measurement of precisely quantized quantity ( that survives weak disorder ) directly related to the number of helical edge states or as a sensitive detector of microwave radiation .
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we study heterostructures where a two - dimensional topological insulator ( ti ) is attached to two normal metal ( nm ) electrodes while an island of a ferromagnetic insulator ( fi ) with precessing magnetization covers a portion of its lateral edges to induce time - dependent exchange field underneath via the magnetic proximity effect .
when the fi island covers both lateral edges , such device pumps _ pure _ spin current in the absence of any bias voltage , thereby acting as an efficient spin battery with giant output current even at very small microwave power input driving the precession . when only one lateral edge is covered by the fi island , both charge and spin current are pumped into the nm electrodes .
we delineate conditions for the corresponding conductances ( current - to - microwave - frequency ratio ) to be quantized in a wide interval of precession cone angles , which is robust with respect to weak disorder and can be further extended by changes in device geometry .
= 1
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One of the rarest and priciest violins in the world was hidden away in a closet for decades, but it is now up for auction at Christie's, with bidding starting Friday.
"Our pre-sale estimate on this is $7.5 million to $10 million," said Kerry Keane, head musical instrument specialist at Christie's, who is hosting the sealed-bid auction. Bidding will go on until June 12.
Part of why this violin is so valuable is its provenance. The violin was made in 1731 by Antonio, who is considered to be the greatest violin maker ever. His 600 surviving violins are highly sought after by collectors, giving them multimillion-dollar price tags.
The violin up for auction is known as the Kreutzer Stradivari, named for its first-known owner, Rodolphe Kreutzer.
If you learned to play the violin, you can likely thank Kreutzer, a French violinist and teacher, who penned the 42 Études, a commonly used foundation for teaching students to play the instrument.
Eventually, the violin came to be owned by Huguette Clark, a wealthy reclusive heiress. She received this pricey Stradivari from her parents, who were American royalty during the Gilded Age.
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"There is a spectacular telegram that her parents sent her in Paris in 1920 that told her...when they were sailing and when they would be arriving in New York, and that her mother had just bought her, quote unquote, the most fabulous violin in the world," Keane said.
The violin is one of more than 400 items from the family collection that Christie's is auctioning. It was found in Clark's closet after collecting dust for decades, according to Keane.
This Stradivari is from his late period. "What's important about his later works is that they're the ones that are consistently the most powerful for players tonally. It has this warm gutsy sound that they produce, and with great color and complexity for the musician," Keane said.
To ensure that the violin is the real deal, Christie's analyzed the ring growths in its wood, a process known as dendrochronology.
"We did a dendrochronology of it. It matches four Stradivaris from 1730 to 1734 made from the same tree. That is a great find. It's like a fingerprint," Keane said.
-- Jennifer Schlesinger ||||| The 300-year-old Stradivarius violin that was taken from the Milwaukee Symphony Orchestra's concertmaster in an armed robbery is pictured in Milwaukee, Wisconsin in this February 6, 2014 handout photo at a news conference after it was recovered.
A detail is seen inside the Kreutzer Stradivarius violin in London May 9, 2014. .
Kerry Keane, Christie's Musical Instruments specialist, poses for a photograph with the Kreutzer Stradivarius violin in London May 9, 2014.
NEW YORK A Stradivarius violin forgotten in a closet for decades and formerly owned by a reclusive U.S. heiress to a copper fortune could sell for as much as $10 million in a sealed bid auction next month, according to Christie's.
If the 1731 violin, known as "The Kreutzer" after the French concert violinist Rodolphe Kreutzer who once owned it, reaches the top end of its pre-sale estimate it would be one of most expensive musical instruments ever sold.
The violin is one of the highlights of the sale from the estate of Huguette Clark, a reclusive, eccentric heiress who owned sprawling Manhattan apartments and palatial homes but chose to spend her final decades living in a New York hospital where she died in 2011 at the age of 104.
After she died, the violin was found in a closet, where it had been for 25 years.
The highest price paid for a Stradivarius violin is $16 million. A rare viola made by the Italian artisan Antonio Stradivari in 1719 that will be sold by Sotheby's in a sealed bid auction in June is valued at $45 million.
"Kreutzer owned and played his namesake Stradivari from about 1795 until his death in 1831," Christie's said in a statement.
The instrument was a present from her parents, copper magnate and politician William A. Clark and his wife Anna, to the then-teenaged Huguette.
The violin will be sold in a special auction with bidding starting on June 6 and will coincide with the New York sale of more than 350 lots from the Clark estate on June 18.
(Reporting by Patricia Reaney; Editing by Mary Milliken and Cynthia Osterman)
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– Funny what turns up in the closet of reclusive, deceased heiress: In this case, one of the world's most expensive musical instruments. Christie's has begun accepting sealed bids for a 1731 Stradivarius violin that had been in a closet of Huguette Clark for about 25 years, reports NBC News. The auction house estimates its worth to be $7.5 million to $10 million, which would be below the Stradivarius record of $16 million but still not too shabby for a longtime dust-collector, notes Reuters. This particular Stradivarius is so pricey in part because it was first owned by renowned concert violinist Rodolphe Kreutzer, both stories explain. Clark's parents bought it in 1920, with her mom sending the teenaged Huguette a telegram from Paris to say she had just bought her "the most fabulous violin in the world," says a Christie's musical expert. Analysis of the wood's ring growths confirms that the violin is legit. (Click to read about how Stradivari may not match up to modern violins.)
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SECTION 1. SHORT TITLE.
This Act may be cited as the ``Fathers Count Act of 1998''.
SEC. 2. GRANTS TO STATES TO ENCOURAGE FATHERS TO BECOME BETTER PARENTS.
Title IV of the Social Security Act (42 U.S.C. 601-679b) is amended
by inserting after part B the following:
``PART C--GRANTS TO STATES TO ENCOURAGE FATHERS TO BECOME BETTER
PARENTS
``SEC. 441. STATE PLAN.
``A State desiring to receive a grant under this part shall submit
to the Secretary a plan which describes how the State will--
``(1) review applications from governmental and private
(nonprofit and for profit) organizations for funds provided to
the State under this part, including the criteria that will be
used to award such funds; and
``(2) administer the funds provided to the State under this
part.
``SEC. 442. GRANTS TO STATES.
``(a) Grant Authority.--Subject to the availability of funds, the
Secretary shall make a grant to a State that complies with section 441,
for each fiscal year beginning with fiscal year 2000 that begins after
the date the Secretary receives the State plan submitted pursuant to
section 441, in the amount described in subsection (b).
``(b) Grant Amount.--
``(1) In general.--The amount of the grant to be made to a
State under this part for a fiscal year shall be the amount
that bears the same relation to the amount specified in
paragraph (2) for the fiscal year as the population of the
State (as determined by the Bureau of the Census for the most
recent fiscal year for which information is available) bears to
the population of the United States (as so determined), subject
to section 447.
``(2) Amount specified.--The amount specified in this
paragraph is--
``(A) $200,000,000 for fiscal year 2000;
``(B) $300,000,000 for fiscal year 2001;
``(C) $400,000,000 for fiscal year 2002;
``(D) $500,000,000 for fiscal year 2003; and
``(E) $500,000,000 for fiscal year 2004.
``SEC. 443. USE OF FUNDS.
``(a) In General.--A State to which a grant is made under this
section--
``(1) shall use the grant to fund projects which--
``(A) encourage unmarried or prospective fathers to
get married, and encourage better parenting by fathers
who are living with 1 or more of their children; or
``(B) include activities that help fathers obtain
gainful employment, or help fathers increase their
skills in order to qualify for higher-paying jobs; and
``(2) may use the grant funds to support projects which
emphasize ways for fathers who do not live with 1 or more of
their children to become better parents.
``(b) Targeting of Nongovernmental Organizations.--A State to which
a grant is made under this section shall provide not less than 75
percent of the grant funds to nongovernmental organizations.
``(c) Targeting of Fathers With Annual Income Below State Average
Income of Male Earners.--A State to which a grant is made under this
section shall ensure that not less than 80 percent of the grant funds
are used to provide services for fathers whose income is less than the
State or local average income level for male earners.
``(d) Availability of Funds.--A State to which a grant is made
under this section for a fiscal year shall remit to the Secretary any
funds remaining from the grant that have not been expended by the end
of the next fiscal year.
``SEC. 444. COORDINATION WITH OTHER PROGRAMS.
``(a) Authority To Use Welfare-to-Work and Title XX Funds for
Activities Under This Part.--A State to which a grant is made under
section 441 may use funds provided under section 403(a)(5) or title XX
in any manner described in section 443.
``(b) Administration of Welfare-to-Work Funds.--A State that uses
funds provided under section 403(a)(5) for activities under this part
may administer the funds so used through the State agency responsible
for administering the funds provided under the other provisions of
section 403(a).
``(c) Coordination With TANF Program.--The State shall coordinate
the State program funded under this part with the State program funded
under part A.
``SEC. 445. DISBURSEMENT OF FUNDS BY STATES.
``(a) Appropriation by State Legislature.--Any funds received by a
State under this part shall be subject to appropriation by the State
legislature, consistent with this part.
``(b) Disbursement by Governor.--The Governor of a State to which
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``SEC. 446. SERVICES PROVIDED BY CHARITABLE, RELIGIOUS, OR PRIVATE
ORGANIZATIONS.
``(a) State Option.--A State may--
``(1) administer and provide services under the program
under this part through contracts with charitable, religious,
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with certificates, vouchers, or other forms of disbursement
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``(b) Religious Organizations.--The purpose of this section is to
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religious character of such organizations, and without diminishing the
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program.
``(c) Nondiscrimination Against Religious Organizations.--In the
event a State exercises its authority under subsection (a), religious
organizations are eligible, on the same basis as any other private
organization, as contractors to provide assistance, or to accept
certificates, vouchers, or other forms of disbursement, under any
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``(d) Religious Character and Freedom.--
``(1) Religious organizations.--A religious organization
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organization's control over the definition, development,
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``(2) Additional safeguards.--Neither the Federal
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of such objection with assistance from an alternative provider
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``(2) Individual described.--An individual described in
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``(f) Employment Practices.--A religious organization's exemption
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against an individual in regard to rendering assistance funded under
any program under this part on the basis of religion, a religious
belief, or refusal to actively participate in a religious practice.
``(h) Fiscal Accountability.--
``(1) In general.--Except as provided in paragraph (2), any
religious organization contracting to provide assistance funded
under any program under this part shall be subject to the same
regulations as other contractors to account in accord with
generally accepted auditing principles for the use of such
funds provided under such programs.
``(2) Limited audit.--If such organization segregates
Federal funds provided under such programs into separate
accounts, then only the financial assistance provided with such
funds shall be subject to audit.
``(i) Compliance.--Any party which seeks to enforce its rights
under this section may assert a civil action for injunctive relief
exclusively in an appropriate State court against the entity or agency
that allegedly commits such violation.
``(j) Limitations on Use of Funds for Certain Purposes.--No funds
provided directly to institutions or organizations to provide services
and administer programs under subsection (a)(1) shall be expended for
sectarian worship, instruction, or proselytization.
``(k) Preemption.--Nothing in this section shall be construed to
preempt any provision of a State constitution or State statute that
prohibits or restricts the expenditure of State funds in or by
religious organizations.
``SEC. 447. ENFORCEMENT PROVISIONS.
``(a) In General.--If the Secretary finds that a State has used
funds provided under this part in violation of this part or of any
provision of the State plan submitted under section 441, the Secretary
shall reduce the amount otherwise payable under section 442 to the
State by the amount so misused as the Secretary considers appropriate.
``(b) Limitation on Amount of Penalties.--
``(1) In general.--In imposing penalties under subsection
(a), the Secretary shall not reduce any payment to a State by
more than 10 percent.
``(2) Carryforward of unrecovered penalties.--To the extent
that paragraph (1) of this subsection prevents the Secretary
from recovering during a fiscal year the full amount of
penalties imposed on a State under subsection (a) of this
section for a prior fiscal year, the Secretary shall apply any
remaining amount of such penalties to the grant payable to the
State under this part for the succeeding fiscal year.
``(c) Appeal of Adverse Decisions.--Section 410 shall apply to an
adverse action taken under this part in the same manner in which the
section applies to an adverse action taken under part A.
``SEC. 448. RESEARCH, EVALUATIONS, AND TECHNICAL ASSISTANCE.
``(a) Research.--The Secretary, directly or through grants,
contracts, or interagency agreements, shall conduct research on the
State programs funded under this part.
``(b) Evaluations.--
``(1) In general.--Beginning in fiscal year 2000, the
Secretary, directly or through grants, contracts, or
interagency agreements, shall annually evaluate how grants made
under this part are used, and a State to which a grant is so
made shall cooperate with the Secretary in the conduct of the
evaluations.
``(2) Reports to the congress.--Beginning with fiscal year
2003, and every 2 fiscal years thereafter, the Secretary shall
submit to the Congress a report on the evaluations conducted
under paragraph (1) before the fiscal year.
``(c) Technical Assistance.--The Secretary, directly or through
grants, contracts, or interagency agreements, shall provide States with
technical assistance for the purpose of disseminating information about
successful programs and program components to entities potentially
eligible to receive funds provided under this part.
``(d) Limitations on Authorization of Appropriations.--
``(1) Research and evaluations.--For research and
evaluations under this section, there are authorized to be
appropriated to the Secretary not more than $10,000,000 for
each of fiscal years 2000 through 2004.
``(2) Technical assistance.--For technical assistance under
this section, there are authorized to be appropriated to the
Secretary not more than $10,000,000 for each of fiscal years
2000 through 2004.
``(e) Limited Reprogramming Authority.--During a fiscal year, the
Secretary may use not more than 20 percent of any amount appropriated
under a paragraph of subsection (d) for the fiscal year for the purpose
described in the other subparagraph of subsection (d).
``SEC. 449. DEFINITIONS.
``In this part:
``(1) Fiscal year.--The term `fiscal year' means any 12-
month period ending on September 30 of a calendar year.
``(2) State.--The term `State' means the 50 States of the
United States, the District of Columbia, the Commonwealth of
Puerto Rico, the United States Virgin Islands, Guam, and
American Samoa.''.
|
Fathers Count Act of 1998 - Amends title IV of the Social Security Act to replace part C (Work Incentive Program) with a new part C (Grants to States to Encourage Fathers to Become Better Parents) instructing the Secretary of Health and Human Services, beginning FY 2000, to award grants to States for projects designed to encourage fathers to become better parents. Prescribes grant amounts for FY 2000 through 2004, and State uses for such funds.
Permits States to contract with religious, charitable, or private organizations to provide and administer services under such grants.
Declares religious organizations eligible as contractors to provide assistance or to accept disbursements on the same basis as any other private organization, so long as program implementation complies with the Establishment Clause of the Constitution.
Prohibits discrimination against religious organizations that apply as contractors or accept disbursements under this Act. Delineates safeguards against certain Federal and State requirements with respect to such religious organizations, including an organization's control over the definition, development, practice, and expression of religious beliefs.
Proscribes the use of funds under this Act for sectarian worship, instruction, or proselytization.
Declares that this Act does not preempt any State constitution or statute that prohibits or restricts the expenditure of State funds in or by religious organizations.
Authorizes appropriations.
|
SECTION 1. SHORT TITLE.
This Act may be cited as the ``Protecting Victims on Campus Act of
2012''.
SEC. 2. DISCLOSURE OF CAMPUS SECURITY POLICY AND CAMPUS CRIME
STATISTICS.
Section 485(f) of the Higher Education Act of 1965 (20 U.S.C.
1092(f)) is amended--
(1) in paragraph (1)--
(A) in subparagraph (A), by inserting before the
semicolon the following: ``, and making available to
students and employees a list of the titles, in each
department of the institution, of each individual who
is a campus security authority to whom students and
employees should report the criminal offenses described
in subparagraph (F)''; and
(B) in subparagraph (F)(i)--
(i) by striking ``and'' at the end of
subclause (VIII); and
(ii) by adding the following at the end:
``(X) criminal offenses involving
minors; and'';
(2) by repealing paragraph (2);
(3) in paragraph (3)--
(A) by striking ``Each'' and inserting ``(A)
Each'';
(B) by inserting ``, that keeps confidential the
personally identifiable information of victims,'' after
``that is timely''; and
(C) by adding at the end the following:
``(B) In carrying out the requirements of
subparagraph (A), an institution shall--
``(i) designate an individual who is
familiar with the requirements of this
subsection to serve as a campus security
authority coordinator to--
``(I) oversee campus security
authorities;
``(II) solicit and compile the
crimes described in subparagraph (F) of
paragraph (1) reported to such
authorities for the purpose of
including such information in the
timely reports required under this
paragraph; and
``(III) ensure that when a crime of
violence (as defined in section 16 of
title 18, United States Code) is
reported to a campus security
authority, the authority reports the
crime to local law police agencies;
``(ii) establish policies or procedures for
training campus security authorities and the
campus security authority coordinator; and
``(iii) employ or designate an individual
or other entity to conduct such training using
the policies or procedures established under
clause (ii), upon receiving approval from the
Secretary for such individual or other entity
to conduct such training.'';
(4) in paragraph (13)--
(A) by striking ``Upon'' and inserting ``(A)
Upon'';
(B) by inserting ``which distinguishes between
institutional neglect and intentional misrepresentation
or withholding of information,'' after ``this
subsection,'';
(C) by inserting ``, except that the Secretary
shall impose a larger civil penalty in the case of an
institution of higher education determined to have
intentionally violated this subsection, as compared to
an institution of higher education that violated this
subsection as a result of institutional neglect. An
intentional violation of this subsection by an
institution of higher education shall be subject to
criminal prosecution'' after ``under section
487(c)(3)(B)''; and
(D) by adding at the end the following:
``(B) Prior to making a determination described in
subparagraph (A) with respect to an institution of
higher education, the Secretary shall--
``(i) conduct an investigation with respect
to the institution; and
``(ii) provide the institution with a
timeline of the investigation and a preliminary
report that includes the reasons for conducting
such investigation.''; and
(5) in paragraph (17), before the period insert the
following: ``or any individual because such individual provided
information or made a complaint to a law enforcement agency
relating to the implementation of any provision of this
subsection, provided that the individual acted in good faith
when providing such information or making such complaint''.
|
Protecting Victims on Campus Act of 2012 - Amends the Higher Education Act of 1965 to revise provisions that require each institution of higher education (IHE) participating in a title IV (Student Assistance) program to comply with certain crime reporting requirements.
Requires IHEs to provide students and employees with a list of the titles, in each department of the IHE, of each individual who is a campus security authority to whom they should report specified criminal offenses.
Includes criminal offenses involving minors that are reported to campus security authorities or the local police among the criminal offenses that are to be included in: (1) the annual campus security report provided to current and prospective students and employees, and (2) the timely reports to the campus community on crimes considered to be a threat to the community.
Requires the personally identifiable information of victims to be kept confidential when IHEs are making timely reports to the campus community on crimes considered to be a threat to the community.
Requires IHEs, in carrying out their obligation to make such timely reports, to: (1) designate an individual to serve as campus security authority coordinator, and (2) provide for the training of that coordinator and the campus security authorities.
Directs the Secretary of Education, when imposing civil penalties on IHEs for substantial violations of the crime reporting requirements, to distinguish between IHEs that intentionally violated those requirements and those whose violations are attributable to institutional neglect.
Requires the Secretary to provide each IHE that is to be investigated for violating such reporting requirements with a timeline of the investigation and a preliminary report that includes the reasons for the investigation.
|
the renormalization group ( rg ) approach , in its most enlightening formulation due to wilson @xcite , is the theory designed to handle fields ( quantum or classical ) fluctuating over range of momentum ( energy ) scales . in the momentum - space formulation ,
this range of scales where fluctuations matter is bounded by some initial ultraviolet ( uv ) cutoff @xmath0 ( not necessarily finite ) provided by the problem under consideration , and @xmath0 is the scale where the rg procedure of the successive mode integration starts . for the most problems where rg was successfully applied ( e.g.
, phase transition , field theories ) the low - energy sector of interest resides near one point of the momentum space which can always be mapped to the origin of that space . in practical loopwise calculations , the original wk infinitesimal scheme seems however to appear too involved beyond one - loop level , and , e.g. , for the wilson s original problem of phase transition in higher orders various field - theoretic rg approaches were applied @xcite . in field theory the cutoff @xmath0 is essentially considered as a `` troublesome '' parameter to get rid of , either by eventually taking the limit @xmath1 , or , e.g , by using another regularization scheme , like the dimensional one where the cutoff is set to infinity from the start .
contrary to the wk scheme , which specifically stipulates that at each rg step the momenta to be integrated out lie within infinitesimally narrow shell in the momentum space , in the field - theoretic rg only overall momentum conservation is taken care of , while separate momenta may lie outside of the ( hyper)sphere of radius @xmath2 ( centered at the origin ) .
this situation is well known , and contributions from the states lying outside of the action s phase space at the distance of several radii @xmath2 or , in other terms , violating phase space constraints by @xmath3 do not affect the leading terms of the rg flow .
however , in condensed matter problems the wilsonian _ effective action s scale _
@xmath0 must be taken seriously . _
a priori _ it can not be set to infinity or even to the largest scale provided by the underlying microscopics , i.e. , inverse lattice , interatomic , etc , spacing . even for a problem
with the low - energy sector localized near the origin of the momentum space , aforementioned violations of the phase space constraints result in double counting of the degrees of freedom lying outside of the wilsonian phase space ( i.e. , the degrees of freedom which are already `` integrated out '' in some way before we reached the wilsonian scale from the microscopic scale ) .
this can affect the next - to - leading terms , as well as finite renormalizations of the action s parameters .
for the important problem of fermions having a fermi surface that is a low - energy sector residing near a manifold in the momentum space accounting for the modes within the phase space _ only _ during the rg procedure becomes a rather non - trivial task , as was explained by shankar @xcite .
moreover , the error of violating the phase space constraints can be of order @xmath4 , where @xmath5 is some characteristic size of the fermi surface , even if the low - energy modes we are integrating out reside within a narrow shell @xmath6 .
note that the answers for many of the most interesting problems of the condensed - matter fermions lie in calculating the abovementioned `` next - to - leading terms '' , where the differences between various rg approaches matter .
for instance , the problem of the fermi - liquid vs non - fermi - liquid regimes of the normal state of the cuprates , from an rg point of view is the difference in the behavior of the irrelevant ( self - energy ) terms in both regimes .
so the choice of the optimal rg scheme and the control over the subleading terms are the issues far from being academical .
the main claim we want to make from the considerations of this paper is that for a condensed - matter problem cast in terms of the wilsonian effective action with a physically meaningful uv cutoff @xmath0 , the wk rg provides the only scheme definitely reliable in all orders of the loopwise expansions , where all modes from the phase space are integrated once and only once .
( strictly speaking , there are no new results in the rg equations we derive below , since for the @xmath7-ology model they have been known for a long time , either from field - theoretical rg scheme @xcite or more recent wk rg formulations @xcite ) .
we address the issues of how to practically employ the wk rg in higher orders , to which technically simpler scheme the wk rg can be reduced and to what extend , by studying the @xmath7-ology model of 1d fermions .
the model we consider is the simplest case of the condensed - matter fermions where the fermi surface manifold is just a set of two points . by going deeper into a recent suggestion to this problem @xcite
, we apply a wk rg transformation assuring that at each step of the procedure all momenta lie within the infinitesimal shell of integration and satisfy the conservation laws , so there are no contributions from the extra states nor double counting .
we show how the higher order renormalizations of the effective action s parameters appear from the summation of the cascades of contractions generated at each step of the wk procedure .
we do nt go beyond the two - loop level , which is apparently the optimal one for feasible calculations . at this level , we show that the summations over the cascades in the wk scheme is equivalent ( in the fixed - point limit of the decreasing cutoff @xmath8 ) to applying the cutoff regularization for the field - theoretic rg _ with the extra states excluded from the phase space_. this result , to the best of our knowledge , was not explicitly shown before .
considerable simplifications for our analysis came from introducing the chiral matrix formalism .
this is a nave ( for the simple 1d case ) first attempt to build into the technique the disentanglement of geometry ( characterized by the `` large '' rigid scale @xmath5 ) and the low - energy sector _ per se _ ( characterized by the decreasing scale @xmath2 ) , and to map the latter to the same origin .
this mapping makes the exclusion of the extra states particularly simple .
the rest of this paper is organized as follows .
sections [ model]-[kwrg ] are introductory
. section [ model ] defines the effective action . in section [ 1dcea ]
the chiral matrix formalism is introduced . in section [ kwrg ]
we explain the terms and notations of the wilson - kadanoff rg as it is applied in this paper . in sections
[ cas]-[2lc ] we explain the procedure and give the results for the two - loop self - energy calculations , and in sections [ wkft ] we establish the relationship between the field - theoretic rg and the present approach . section [ coupl ] contains the two - loop results for the couplings flow equations .
the conclusions and generalizations for other models and/or higher dimensions are presented in the final section [ concl ] .
we treat @xmath10-dimensional interacting fermions at finite temperature in the standard path integral grassmannian formalism @xcite .
the @xmath9-invariant fermionic @xmath11-action along with the related quantities and notations of this subsection have been introduced earlier @xcite , and we recall these here in order to make the paper self - contained .
the partition function is @xmath12 the free part of the action is @xmath13\psi_{\alpha}({\textbf 1})\ ] ] and @xmath14-dimensional vectors and integrals mean [ notation ] @xmath15 where @xmath16 is the inverse temperature , @xmath17 the chemical potential , @xmath18 the fermion matsubara frequencies and @xmath19 a @xmath20-component grassmann field with a spin ( flavor , if @xmath21 ) index @xmath22 .
summation over repeated indices is implicit throughout this paper .
we set @xmath23 and @xmath24 .
the @xmath9-invariant quartic interaction is @xmath25 here the conservation of energy and momentum is enforced by the symbolic delta function @xmath26 note that for the lattice fermions the delta - function above conserves momenta up to an inverse lattice vector .
the physical case of the spin-@xmath27 electrons is recovered by setting @xmath28 .
we decompose the interaction by factorizing its symmetric and antisymmetric frequency - momentum- and spin- dependent parts as @xmath29 where the functions
@xmath30 are symmetric / antisymmetric under exchange of the left or right pairs of their variables .
two operators @xmath31 and @xmath32 , which are respectively symmetric and antisymmetric in the spin space , are defined as follows : [ base ] @xmath33 the one - particle - irreducible ( 1pi ) four - point vertex @xmath34 , defined in the standard way , comprises two components ( @xmath35 , @xmath36 ) and can be written in the same manner as ( [ pots ] ) . along with such representation showing explicitly its antisymmetry , there is another one which separates the vertex into charge and spin components via @xmath37 the latter representation is often more convenient since charge and spin components decouple in many practical calculations .
@xmath38 ( @xmath39 ) in eq.([vrep ] ) are hermitian traceless generators of the @xmath9 group , coinciding with the pauli matrices for @xmath28 , and normalized such that @xmath40 they also satisfy the following fierz identity : @xmath41 the components of the vertex in different representations are related as [ abdef ] @xmath42 the construction of the low - energy effective fermionic action as a simplified form of the generic @xmath11-action ( [ s0],[sint ] ) reduces in 1d essentially to the three key steps : extraction of a finite set of ( marginal ) couplings ; decomposition of the physical electron @xmath43-field into two chiral fields `` near '' left and right fermi points ; linearization of the one - particle spectrum @xmath44 around these points .
there exists an extensive literature on the derivation of the 1d effective action models ( tomonaga - luttinger , @xmath7-ology ) , and on many subtleties it involves ( see , e.g. , ref . [ ] and more references therein ) . so below we simply present notations , approximations and highlight the main points .
the chiral matrix representation we derive here is in fact only a way to re - write the well - known @xmath7-ology model .
( for details see the next subsection . )
however this matrix formalism and related to it diagrammatics help to facilitate bookkeeping of diagrams and handling their contributions to different couplings , and , eventually , to generalize the @xmath7-ology results for other cases .
we decompose 1d momenta as @xmath45 where @xmath46 corresponds to the right ( r ) /left
( l ) fermi points . in the quartic interaction function @xmath47 ( [ pots ] )
we retain only its dependence on the momenta at the fermi points , neglecting that on @xmath48-s and frequencies @xcite .
the @xmath9 and exchange symmetry constraints leave us with four independent marginal couplings : [ 4coupl ] @xmath49 note that the umklapp coupling @xmath50 is operative only in the half - filled case when @xmath51 ( we set the lattice constant @xmath52 ) . for the formalism we develop below this case
is considered as the most general one , while the non - commensurate filling can be recovered by setting @xmath53 .
let us now introduce four @xmath59 matrices @xmath60 such that @xmath61 is the unit matrix , and @xmath60 for @xmath62 correspond to the pauli matrices .
such distinct notation helps to avoid confusion , since @xmath60 operates in the chiral , and not in the spin space .
we attribute an extra chiral index to the grassmannian field as @xmath63 , @xmath64 . then
four terms in the last two lines of eq.([lint ] ) can be written as : @xmath65~ \bar\psi_{\alpha}^{\alpha'}(1)\bar\psi_{\beta}^{\beta'}(2 ) \psi_{\gamma}^{\gamma'}(3)\psi_{\varepsilon}^{\varepsilon'}(4)\ ] ] while the first two lines in that equation give @xmath66~ \bar\psi_{\alpha}^{\alpha'}(1)\bar\psi_{\beta}^{\beta'}(2 ) \psi_{\gamma}^{\gamma'}(3)\psi_{\varepsilon}^{\varepsilon'}(4)\ ] ] where @xmath67 thus @xmath68 the one - particle green s function is spin - independent in the model we consider , but it depends on the chiral index : @xmath69 the linearized bare green s function is given by @xmath70 where @xmath71 now we can define the 1pi four - point vertex @xmath34 in this formalism
. we will be interested in a particular limiting form of this vertex when its dependence on the external momenta lying at the fermi points ( parametrized by the chiral indices ) is retained only , while ( @xmath72 ) are discarded . in the lowest order @xmath73
can be read off from @xmath74 ( [ lfb],[luc],[lsum ] ) .
as follows from the group - theory arguments , this structure of the vertex is preserved by interaction @xmath74 : the latter results in only the renormalization of couplings , but no new couplings are generated .
thus , the following operator expansion with four couplings holds non - perturbatively : @xmath75\ ] ] in order to keep the notations compact , we do not change them in ( [ gamg ] ) , however couplings are renormalized by interaction comparatively to their bare values ( [ 4coupl ] ) . to the same end
we will not indicate explicitly the chiral and spin indices from now on ( unless there is a possibility of confusion ) , incorporating them into the `` thin variables '' .
so we imply @xmath76}~ \mapsto \gamma^{(0)}(12;34)\bar\psi(1)\bar\psi(2)\psi(3)\psi(4)\ ] ] comparison of eqs.([lfb],[luc],[compact ] ) with the operator form ( [ gamg ] ) clarifies how we attribute the chiral and spin indices for the matrix elements of @xmath34 .
note the explicit antisymmetry of the vertex @xmath77 under exchange of the left or right pairs of variables in the representation ( [ gamg ] ) .
we can recover couplings from the vertex by appropriate convolutions , i.e. , [ cps ] @xmath78 and other two couplings are obtained from eq.([cps]b ) by obvious substitutions , namely , @xmath79 ; @xmath80 . here
we want to make a contact between the chiral matrix formalism and more commonly used @xmath7-ology language ( see , e.g. , ref . [ ] ) .
no surprise that this subsection s formal manipulations with the fully ( anti)symmetrized `` chiral '' action amount essentially to reducing it to the non - symmetrized form .
the latter is usually used as a departure point of various @xmath7-ology models .
let us show first how the charge- and spin - operator interaction action , involving forward and backscattering couplings called @xmath81 , @xmath82 respectively in the @xmath7-ology nomenclature , can be recovered from the part @xmath83 ( [ lfb ] ) of the effective quartic interaction ( [ lsum ] ) .
@xmath83 can be split in two terms by the following projection in the chiral space : @xmath84 + t^0_{\alpha \gamma } t^0_{\beta \varepsilon } \big ) ( -g^a \hat i ~t^2_{\alpha \beta } t^2_{\gamma \varepsilon } + g^s \hat t ~t^1_{\alpha \beta } t^1_{\gamma
\varepsilon})[\psi^4]_n \nonumber \\ & \equiv & { \mathcal l}_{\text{cs1}}+{\mathcal l}_{\text{cs2}}\end{aligned}\ ] ] above we indicate explicitly the chiral indices only , and @xmath85_n$ ] stands for the product of four @xmath43-fields `` normally - ordered '' as on the r.h.s . of eq.([lfb ] ) . using the fierz identity ( [ fierz ] ) for the @xmath86 chiral operators @xmath87
, one can prove that @xmath88_n \nonumber \\ & = & \frac12 ( t^1_{\alpha \beta } t^1_{\gamma \varepsilon}+ t^2_{\alpha \beta } t^2_{\gamma \varepsilon } ) ( -g^a \hat
i+g^s \hat t)[\psi^4]_n\end{aligned}\ ] ] it can be also shown that the above expression reduces to @xmath89 in the same manner we find @xmath90 using the symmetry properties of the spin operators and changing the dummy variables , it is easy to see that the term @xmath91 results in the same expression for the action [ cf . eq.([seffint ] ) ] as @xmath92 , so @xmath93 . applying then the fierz identity ( [ fierz ] ) [ cf . also definitions ( [ base ] ) ] for the operators @xmath94 in case of @xmath86 , and using the conservation law for momentum - frequency such that @xmath95 , @xmath96 , we get @xmath97 where we introduced the operators of the chiral ( i.e. , left / right ) charge and of the chiral @xmath98-component of spin as [ scop ] @xmath99 note that in the above formulas there are no sums over @xmath22
we have also defined the charge and spin couplings : [ gsc ] @xmath100 it is worth noting that although there is no one - to - one correspondence between 1d couplings ( [ 4coupl]a , b ) and the vertex components @xmath101 [ the latter in 1d are rather products of corresponding couplings and operators in the chiral space , as can be seen from comparison of eqs.([vrep],[gamg ] ) ] , the definitions for the components which couple separated charge or spin modes ( [ abdef ] ) hold for the chiral ones ( [ gsc ] ) .
it is also useful to give the relationship between our constants and the standard ( dimensionful ) @xmath7-ology couplings : @xmath102 , @xmath103 .
the term @xmath104 of the total quatric interaction generated by the contact coupling at the same fermi point ( @xmath105 ) and the umklapp coupling ( @xmath50 ) can be written as @xmath106 the way we write the umklapp contribution is to reinstate the known fact that since @xmath50 couples fields with different chiralities , it can not be represented in terms of the local chiral charge or spin operators . in this study
we apply the original wilson - kadanoff momentum - space renormalization group scheme @xcite to the effective action with the quartic interaction containing four coupling constants .
this interaction in the chiral formalism is given by eqs .
( [ gamg],[compact ] ) . in that formalism
all the constraints coming from the original two - point geometry of the fermi surface , and consequently , occurrence of the two types ( left / right ) of fermion fields and of green s functions , are taken care of by the appropriate summations over chiral indices . in applying the rg procedure we successively integrate out the grassmannian fields in the phase space of the small momenta @xmath48 ( [ 1dk ] ) .
the latter , like in the quantum or classical @xmath107-theories , can be seen now as having common origin towards which we eliminate modes in the @xmath108-space .
we start with the effective action ( [ gamg],[compact ] ) having momenta restricted by the initial ( bare ) ultra - violet ( uv ) cutoff @xmath0 ( [ ksm ] ) .
after @xmath20 steps of the mode elimination ( @xmath109 ) , we end up with the cutoff @xmath2 chosen such that : @xmath110 ( we choose the rg scheme without rescaling of the cutoff . ) each step consists of mode integration within the infinitesimal shell @xmath111 in the @xmath108-space , where @xmath112 ( the equidistant step is chosen for simplicity only ) such that after n steps the uv cutoff @xmath113 is @xmath114 we define the @xmath115-th shell in the momentum space @xmath116 as @xmath117 \cup [ \lambda_n , \lambda_{n-1 } ] \equiv { \mathcal s}_n^- \cup { \mathcal s}_n^+\ ] ] in the final results given in the following sections we will smoothly take continuous limit @xmath118 ( @xmath119 ) such that relationship ( [ deltad ] ) holds
. then the lowering cutoff @xmath2 will be determined by the continuous rg flow parameter @xmath120 defined as : @xmath121 as it was discussed in the closely related earlier study of the @xmath7-ology model @xcite , the straightforward application of the wilson - kadanoff rg beyond one - loop level encounters some difficulties .
they stem from the constraint on the momenta to be integrated out at the @xmath115-th step to lie within the shell @xmath116 , and on the total momentum flowing through a given graph to conserve .
it was shown in ref .
[ ] that the solution of this problem consistent with the logic of the wk rg can be found when multi - loop graphs ( the standard ones for the field - theoretical rg ) renormalizing action s vertices are obtained through cascades of contractions at different steps of the rg procedure . in this study
we refine the `` cascade scheme '' of the rg calculations put forward in ref .
[ ] for the @xmath7-ology model .
we show that the aforementioned constraints on the momenta can be cast in terms of the `` selection rules '' for the numbers of steps entering a given cascade of contractions .
summations over all allowed types of cascades provides the results particularly illuminating for understanding the origin of the ( logarithmic ) equivalence of the wk and field - theoretic rg versions .
we use the standard definition for the field renormalization constant relating it to the self - energy ( assuming that the analytical continuation from matsubara frequencies is done ) : @xmath122 it is easy to show that in our model @xmath123 does not dependent on the chirality index .
the first correction to @xmath123 comes from the two - loop `` sunrise '' self - energy diagram .
however , in the wk rg scheme such a diagram if obtained in the second order by a contraction of three legs of the four - leg interaction ( [ seffint ] ) with itself , gives a vanishingly small contribution .
this is due to the momentum constraints discussed above .
( see also ref .
[ ] for more details . )
the graphs we are looking for can come only from two types of cascades of contractions generated by the mode elimination of the original action ( [ seffint ] ) : 3-step and 2-step cascades depicted in fig . 1 .
_ 3-step cascade _
1a ) is generated ( in the second order over interaction ) as follows : ( i ) at the @xmath115-th step of the mode elimination the four - point vertex is contracted with itself to generate the six - leg vertex ; ( ii ) @xmath124 steps after [ i.e. at the ( @xmath125)-th step ] two legs of this vertex are contracted ; ( iii ) at the ( @xmath126)-th step two other legs are contracted resulting in the final correction to the two - leg vertex ( i.e. , one - particle green s function ) .
_ 2-step cascade _
1b ) is generated as follows : ( i ) at the @xmath115-th step two pairs of legs of the four - point vertices are contracted ; ( ii ) at the ( @xmath125)-th step two more legs are contracted .
the above description of the cascades was very schematic and illustrative .
we did not take care of the kinematics of diagrams ( that is why we did not indicate the momentum directions in the graphs of fig . 1 ) , and the integers numerating the steps are unrelated and free to take any values restricted only by the total number of steps of the rg procedure , i.e. , @xmath127 . to take zero values .
] [ nm ] to proceed with the further analysis of the pertinent cascades let us consider the renormalization of the one - particle green s function at @xmath128 .
as the rg flows towards the fixed point ( @xmath8 ) this quantity will provide us with the field renormalization constant @xmath123 ( [ zf ] ) .
for this purpose we consider the terms generated by the two types of cascades described above renormalizing the coefficient of the action s grassmannian binomial @xmath129 .
diagrammatically they are shown in fig . 2 .
analysis reveals that there are three kinematically non - equivalent graphs ( @xmath130 in that figure ) generated by the 3-step cascades and two graphs ( @xmath131 ) from 2-step cascades .
we choose the external momentum @xmath132 and the other external variables ( chirality , spin , frequency ) are not specified at this point . for the further applications we approximate @xmath133 where l is an integer ( @xmath134 ) .
the error @xmath135 of the representation ( [ laml ] ) disappears when we eventually take the limit @xmath118 .
let us start with the kinematics of the first three graphs .
we find that for each of these graphs there are two solutions compatible with the constraints imposed by the wk procedure and the momentum conservation law .
they are given in table i. + table i : _
solutions for the momenta of the three graphs in fig . 2 compatible with the kinematic constraints .
_ + [ cols="^,^,^,^,^,^,^ " , ] + the ranges for the integers @xmath136 satisfying the solutions i , ii are : [ nmranges ] @xmath137 thus in order to obtain the total contribution of these cascade - generated graphs to the self - energy we have to integrate two independent momenta in each graph over available range ( i.e. two possible configurations i , ii for each graph ) and to sum over all allowed types of cascades parameterized by ( @xmath136 ) within the ranges ( [ nmranges ] ) .
( and of course , there are always straightforward summations over other variables , i.e. , chirality , spin , frequency which take all available values . )
we have not shown in table 1 available kinematic solutions for the 2-step cascade graphs d , e , since their contribution is negligible in comparison to that of a - c .
indeed , as can be shown from the results below , the graphs d , e as well as a - c _ at a fixed m _ give the contributions @xmath138 to the constant @xmath123 .
however the extra sum over @xmath124 renders the latter logarithmic @xmath139 , while the former do not have this extra sum and thus strictly disappear in the limit @xmath118 . for the same reason we drop some extra solutions for the graphs a - c which occur only under special relationships between @xmath115 and @xmath124 ( i.e.
, there is no double sum over @xmath136 ) : they give vanishing contributions . as some points or lines ,
i.e. , manifolds of inferior measure . ]
now we can proceed with the rg calculations via a straightforward evaluation of the graphs from fig . 2 .
for certainty we fix the external chiral index of those graphs to be 2 , i.e. corresponding to the right component of the grassmannian field .
since graph s contributions in the spin space are diagonal and spin - independent , the external spin can be `` up '' or `` down '' .
after summation over chiral and spin indices we obtain for the sunrise graph contribution @xmath140 ( here plus stands to indicate our choice of the external chiral index ) : @xmath141 ~\delta^{(1 + 1 ) } ( { 1}+ { 2}- { 3}- { 4})\ ] ] where thin variables signify momenta and frequencies ,
i.e. , the only ones left , and [ fs ] @xmath142 \\ { \mathcal f}_+^u~&\equiv&~ g_+(2 ) g_-(3 ) g_-(4 ) \\ { \mathcal f}_+^4~&\equiv&~ g_+(2 )
g_+(3 ) g_+(4)\end{aligned}\ ] ] note that until the integration ranges for the momenta @xmath143 are specified , the same analytical expression @xmath140 ( [ fplus ] ) corresponds to the _ each of graphs _ depicted in fig .
the following summation of matsubara frequencies in ( [ fplus ] ) is straightforward . due to conditions ( [ cutoffs ] ) we approximate the occurring hyperbolic functions up to exponentially small terms @xmath144 . with this accuracy
we drop all contributions from the term @xmath145 .
analysis of the available kinematic configurations from table 1 for other terms shows that some of them are also exponentially small , so we put [ fszero ] @xmath146 our calculations show that the term @xmath147 evaluated for the configurations of the graph a ( solutions i , ii ) and c ( i , ii ) gives four equal contributions to the self - energy .
analogously , two contributions of @xmath148 from b ( i , ii ) are equal to each other . in order to demonstrate how these calculations are done ,
let us consider as an example @xmath147 for the configuration ( a , i ) . to obtain its total contribution to the self - energy , we have to to integrate two independent momenta within the ranges indicated in table i for fixed @xmath136 and then to sum over all available cascades ( a , i ) according to ( [ nmranges]a ) .
this gives : ) .
this approximation ( called `` local '' in ref . [ ] ) is common for all rg schemes , and in any case possible corrections to it lie beyond the two - loop level . ]
[ notegn ] @xmath149 where @xmath150 in eq .
( [ siga1dis ] ) and in the following we use dimensionless couplings absorbing the density of states factor in their definition , i.e. , @xmath151 in the limit @xmath118 the sums above neatly combine into a simple double integral @xmath152 which gives @xmath153 where the omitted terms @xmath154 are irrelevant for the rg flow equations . combining evaluated in the same way other contributions and using the definitions ( [ lpar],[zf ] )
, we obtain the two - loop rg equation @xmath155 this equation was first obtained in ref . [ ] . in order to get more insights from the obtained results ,
let us first rewrite some of the previous formulas . using the transfer momentum vector @xmath156 in eq.([siga1int ] )
, we get @xmath157 in the above equation we dropped the index of the vector @xmath158 and neglected terms @xmath159 in the limits of integrals , since we are eventually interested only in the @xmath8 limit . other three non - zero contributions [ cf .
eq.([fszero]a ) ] to the @xmath160-term of the self - energy after analogous variable changes can be reduced to the form ( [ sigtr ] ) but with different integration ranges . combined together , these contributions can be written as : @xmath161 where @xmath162 is the event ( heaviside ) function .
thus , by applying the canonical wilson - kadanoff scheme where all momenta in the diagrams lie strictly within an infinitesimal shell at each step of the rg procedure , and by summing all pertinent infinitesimal contributions through singling out kinematically - allowed cascades , we end up with results which could have been obtained in the field - theoretic scheme .
as one can see , formula ( [ sigs ] ) for the self - energy resembles the one derived in the rg scheme where momenta are let to run freely within a whole band restricted only by the ir and uv cutoffs . to sharpen the last statement ,
let us derive now the self - energy in the field - theoretic rg scheme with the cutoff regularization .
( thorough description of various field - theoretic rg approaches can be found , e.g. , in ref .
let us assume that we have the same bare effective action as we used before . since the theory is logarithmical , we regularize divergent integrals by introducing ir and uv cutoffs .
we assume that they satisfy the same conditions as those for the wk effective action ( [ cutoffs ] ) .
since _ a priori _ the cutoffs in the field - theoretic and wk approaches are not the same , we will mark the former with tildes . to be the smallest scale of the problem we will work with the theory in the zero - temperature limit . for the following comparisons
note that the second condition ( [ cutoffs ] ) effectively brings the wk rg results to the zero - temperature limit as well . ]
contrary to the wk scheme , in the field - theoretic approach the self - energy contribution we are looking for : _
( i ) _ comes from the _ only one _ sunrise graph as those depicted in fig . 2 ; _ ( ii ) _ independent momenta in the graph
are restricted by the model cutoffs only ; _
( iii ) _ the graph has a combinatorial factor @xmath163 .
all the summations before the final momentum integrations in this graph lead to the same formulas as in the previous subsection ( except the overall factor @xmath163 ) .
we choose a couple of independent momenta @xmath48 restricted by the cutoffs @xmath164 .
it can be shown that the term of the self - energy involving charge and spin couplings can be brought to the form ( [ sigs ] ) with @xmath165 , @xmath166 up to @xmath167 . with the same accuracy
the self - energy umklapp terms coincide in the wk and field - theoretic approaches .
thus both schemes result in the same leading @xmath168 term in the derivative of the self - energy with respect to the frequency , and therefore to the same rg equation ( [ zrg ] ) .
the relationship between the two rg schemes can be seen even in a simpler way in the limit @xmath8 , i.e. , the fixed point limit we are always interested in .
let us draw the regions of momenta integrations corresponding to the solutions from table i summed over available @xmath115 and @xmath124 .
as a couple of independent momenta we choose @xmath169 .
these regions are shown in fig .
let us remind also that while showing kinematically non - equivalent cascades ( a - c ) in fig . 2 we have used the ( anti)symmetry of the vertex , and , correspondingly , that of graph s contributions under the exchange ( @xmath170 ) . so the sum of these three graphs can also be written as @xmath171 , where the primed graphs correspond to the above exchange .
as one can see from fig .
3 the regions for unprimed and primed solutions ( the primed solutions are obtained from their unprimed counterparts by the reflection over the main diagonal ) , fill completely the hexagon shown in bold .
the latter is nothing but the whole phase space of the sunrise graph @xmath172 now assuming that the summations and integrations commute we can write the total sunrise self - energy correction @xmath173 resulting from the sum of three kinematically distinct graphs 2a - c over two solutions for each graph and over all available cascades as a single term @xmath174 here we came back to the original thin variables comprising chiral and spin indices , matsubara frequencies , and momenta ( @xmath175 ) . thus the self - energy correction has the same analytical form as the one written in the cutoff field - theoretic approach . in the latter however , after removing one momentum by the delta - function ( e.g. , @xmath158 ) only two independent momenta are explicitly restricted by @xmath0 .
this results in the contributions from the extra states forbidden by the whole phase space constraints .
these extra states lie in the triangles in the first and third quadrants of the @xmath169-plane ( cf .
fig . 3 ) . in the logarithmic theory as the one we are dealing with , integration over these forbidden states may result in only the finite terms to the self - energy correction , thus leaving the rg equation ( [ zrg ] ) unaffected . )
that summation over frequencies bringing the fermi functions into play , suppresses completely the differences between two schemes coming from the extra states . for @xmath176 the contributions from the first and third quadrants
are completely eliminated by the fermi functions [ cf .
eq.([fszero]a ) ] . but generically there are no reasons for that , and the umklapp contribution provides a counterexample for @xmath176 .
eqs.([fszero]b , c ) . ] the phase space mapping of fig .
3 holds in the fixed - point limit @xmath8 at non - zero temperature as well .
thus the temperature effects can be calculated from the uv cutoff rg scheme upon integration of the all phase space restricted by the hexagon in fig .
3 . , are modified at @xmath177 when decreasing cutoff @xmath178 reaches the scale provided by the temperature . ]
as it should be clear , this is not equivalent either to calculation within wk rg stopped at some @xmath179 when @xmath180 , or within the two - cutoffs rg with the ir cutoff provided by @xmath181 : such two ways of calculations give , strictly speaking , approximations only .
after explaining most of technicalities in the previous section , we will be brief in presenting the results for the rg coupling equations .
let us first write the two - loop perturbative expansion for the four - point 1pi vertex .
it is depicted graphically in fig .
( the tadpole self - energy corrections are absorbed in the one - particle green s functions renormalizations . )
we calculate the couplings from @xmath182 at @xmath183 where @xmath184 is the minimal matsubara fermionic frequency .
the latter is set to zero after appropriate analytical continuation .
the couplings are extracted from @xmath185 by convolutions [ cf .
eqs.([cps ] ) and below ] .
the limits ( [ gamlim ] ) considerably reduce the number of cascades to take into account while calculating the renormalized couplings .
one - loop corrections are generated by a simple contraction shown in the first line of fig .
after summations over the shell number these contributions reduce to three one - loop graphs with the signs and factors as in the pertubrative expansion in fig . 4 and the loop momentum @xmath186 .
pertinent double - loop graphs are generated by the 2-step cascade as follows : at the @xmath115-th step a simple one loop is generated ( cf .
first line of fig .
1b ) and at the @xmath124-th step the left ( or right ) pair of legs of this graph is contracted with the four - leg vertex .
the shell numbers @xmath115 and @xmath124 are independent and can take any value from 1 to @xmath20 .
the sums of these cascades result in the three double - loop graphs ( dl ) as they stand in the second line in fig . 4 with the loop momenta restricted by @xmath187 .
the two - loop graphs combined in the groups ( zz , zc , cz ) in fig .
4 are generated by the 3-step cascades .
for concreteness let us take the first graph from the group zz .
for each type of this loop configuration with a fixed position of external variables ( top left in fig .
5 ) there are six graphs corresponding to all possible types of the 3-step contractions shown in this figure .
direct inspection shows that the sign and combinatorial factor of all these six graphs are the same and coincide with those of their counterpart in the perturbative expansion in fig .
4 . due to conditions ( [ gamlim ] )
we retain only such cascades that the legs of the vertex @xmath22 are contracted at the same step . from the conservation law
the momenta @xmath188 are equal ( opposite for the cz graphs ) , so the phase space constraints near the vertex @xmath22 are satisfied trivially . to find the allowed kinematic solutions from the second independent momentum conservation ( e.g. , at the vertex @xmath16 of this graph ) we can use directly the results of the previous section . indeed , if we identify @xmath189 of the graphs in fig . 5 with @xmath190 of fig . 2 ,
respectively , we recover the situation analysed previously for the self - energy graphs .
the kinematic solutions for the graphs of fig .
5 can be taken from table i ( in the limit @xmath191 ) as follows : @xmath192 , @xmath193 , @xmath194 , @xmath195 , @xmath196 , @xmath197 . then contributions @xmath198 ( cf
. footnote on p. ) can be combined into a single graph ( top left in fig .
5 ) with two independent momenta lying in the phase space shown in fig . 3 .
analogous conclusions can be reached for other graphs of the groups zz , zc , cz .
thus , provided the stipulated above phase space of each graph , the renormalization of the vertex after mode elimination between @xmath2 and @xmath0 ( @xmath8 ) is given by fig .
the rest of the calculations is straightforward .
we introduce the renormalized ( dimensionless ) couplings as follows : @xmath199 the vertex renormalization constants @xmath200 in terms of @xmath201 are found to be : [ zsharp ] @xmath202 combining the equations @xmath203 with eqs.([zrg],[zsharp ] ) we obtain the rg flow equations for couplings : [ grg ] @xmath204 these equations were obtained earlier within the field - theoretic rg analysis @xcite .
note that in the above equations we dropped all the contributions from @xmath105 assuming that they can be absorbed in the renormalization of fermi velocities .
( see , e.g. , ref .
[ ] and more references therein . )
the equivalence of the rg flow equations in the wk and field - theoretic schemes at the two - loop level is proven explicitly for the 1d @xmath7-ology model . to obtain the higher - order rg equations within the canonical wk approach ,
it is crucial to sum over all available cascades of contaractions occurring at the infinitesimal steps of the wk procedure .
moreover , in the fixed - point limit @xmath8 the diagrammatics of the wk rg summed over all cascades is shown to be the same as that of the field - theoretic rg with the cutoff regularization and restricted phase space .
generalizations for the cases of classical or quantum bosonic and fermionic fields and higher dimensions are straightforward within the developed technique , resulting in the same conclusion about the diagrammatics , provided that the relevant phase space of those fields ( i.e. , the low - energy sector ) can be brought to the same origin .
if the latter condition can not be satisfied easily , like , e.g , for the low - energy sector of higher dimensional condensed - matter fermions possessing a fermi surface , the proof of equivalence is not a straightforward extension within the proposed approach , and more explicit work is needed to demonstrate it .
however we conjecture that even in that case the summation over cascades within the wk rg tantamount to applying the field - theoretic rg with a ( bare ) uv cutoff for the low - energy sector and locally - imposed phase - space constraints of the integrated momenta .
( for the examples of how these constraints may be realized , see the review by shankar [ ] . ) at the level of three loops and higher , different rg schemes may result in different flow equations . within the present approach
, it follows from the necessity to take into account the dependence of running couplings on the shell number in higher orders ( cf .
footnote on p. ) .
so various cascade contributions could not be `` compactified '' in a single `` field - theoretic '' graph as it occurs at the two - loop level .
the latter conclusion is hardly surprising , since the differences in the gell - mann low functions in higher orders are known to occur even within different versions of the field - theoretic rg .
( see , e.g , ref .
[ ] . in the context of the 1d @xmath7-ology , see also ref . [ ] for the discussion of the bandwidth- and transfer - cutoff regularizations in higher orders of rg . ) in condensed - matter problems , where the bare uv cutoff @xmath0 might be a meaningful scale and other scales ( e.g. , @xmath181 , @xmath5 ) may be present as well , the wk rg scheme should be applied , as the one which is just an exact way to to integrate the partition function @xcite .
the wk rg does not rely on any assumptions of the scales involved , scaling / logarithmicity of theory , etc , and includes contributions only from the states lying within the phase space of the problem .
this allows to control the results ( at least in principle ) in all orders . in practical terms , after summations over all cascades the wk scheme asymptotically maps to the much easier to handle field - theoretic rg ( up to three loops ) with forbidden states excluded .
we did not verify whether possible simplifications of the wk scheme can be done in even higher orders , but going beyond two - loop level is a formidable problem in any case .
g.y.c . is grateful to m.e .
fisher and a.m. tsvelik for helpful discussions , and to mcgill university for hospitality .
c.b . thanks r. wortis for important remarks at the early stage of this work .
this work is supported by nserc ( canada ) , fcar ( qbec ) , and german science foundation .
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le guillou , and j. zinn - justin , in _ phase transitions and critical phenomena _ , v. 6 , eds . c. domb and m.s .
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b * 5 * , 1033 ( 1991 ) ; c. bourbonnais , in _ les houches , session lvi ( 1991 ) , strongly interacting fermions and high - t@xmath205 superconductivity _ , edited by b. doucot and j. zinn - justin ( elsevier science , amsterdam , 1995 ) , p. 307 . c. bourbonnais , b. guay , and r. wortis , in _ theoretical methods for strongly correlated electrons _ , edited by a. m. tremblay , d. snchal , a. ruckenstein , and c. bourbonnais ( springer , heidelberg , 2003 ) ; cond - mat/0204163 .
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we apply the standard wilson - kadanoff ( wk ) momentum - space renormalization group ( rg ) scheme for the g - ology model of one - dimensional fermions . by explicitly carrying out calculations at the two - loop level ,
we show how the rg flow equations can be derived from the summation of the cascades of contractions generated by the effective action s mode elimination at each infinitesimal step of the wk procedure .
the rules for selecting these series of cascades appear naturally as a consequence of the wk scheme `` on - shell '' kinematic constraints and conservation laws .
the relation between the present rg approach and the field - theoretic schemes used in earlier related studies is analysed .
generalizations for other models and/or higher dimensions are formulated .
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SECTION 1. SHORT TITLE.
This act may be cited as the ``American Travel Industry
Stabilization Act''.
SEC. 2. TRAVEL INDUSTRY DISASTER RELIEF.
(a) In General.--Notwithstanding any other provision of law, the
President shall take the actions described in subsection (b) to
compensate eligible travel-related businesses.
(b) Actions Described.--
(1) In general.--Subject to such terms and conditions as
the President deems necessary, and upon application, the
President is authorized to issue Federal credit instruments to
eligible travel-related businesses described in subsection (c)
that do not, in the aggregate, exceed $5,000,000,000 and
provide the subsidy amounts necessary for such instruments in
accordance with the provisions of the Federal Credit Reform Act
of 1990 (2 U.S.C. 661 et seq.).
(2) Time for application.--An application for a Federal
credit instrument shall be filed by an eligible travel-related
business not later then 60 days after the promulgation of
regulations.
(3) Terms of credit instruments.--A loan guaranteed under
this Act may be used exclusively for the purpose of meeting
obligations and expenses to the extent that an applicant
demonstrates--
(A) business operations were directly and adversely
affected by the events of September 11, 2001;
(B) the loan guarantee is necessary to meet such
obligations;
(C) the inability of the applicant to meet such
obligations or expenses is directly attributable to the
impact of September 11, 2001; and
(D) the applicant has the ability to repay the
loan.
(c) Definitions.--In this Act:
(1) Eligible travel-related business.--The term ``eligible
travel-related business'' means a business that was injured by
the Government shutdown of the airline industry following the
terrorist attacks on the United States that occurred on
September 11, 2001, and that on such date--
(A) had a contractual arrangement with an air
carrier to provide goods or services, including those
with a contractual relationship with the Airline
Reporting Corporation; or
(B) was a non-aeronautical for-profit business
operating at an airport engaged in the sale of consumer
goods or services to the public under an arrangement
with the airport or the airport's governing body.
(2) Federal credit instrument.--The term ``Federal credit
instrument'' means any guarantee or other pledge by the Board
issued under section 2(b) to pledge the full faith and credit
of the United States to pay all or part of any of the principal
of and interest on a loan or other debt obligation issued by an
obligor and funded by a lender.
(d) Emergency Designation.--Congress designates the amount of new
budget authority and outlays in all fiscal years resulting from this
Act as an emergency requirement pursuant to section 252(e) of the
Balanced Budget and Emergency Deficit Control Act of 1985 (2 U.S.C.
901(e)). Such amount shall be available only to the extent that a
request, that includes designation of such amount as an emergency
requirement as defined in such Act, is transmitted by the President to
Congress.
SEC. 3. ADDITIONAL FUNCTIONS FOR THE AIRLINE STABILIZATION BOARD.
(a) Definitions.--In this section:
(1) Board.--The term ``Board'' means the Air Transportation
Stabilization Board established under Public Law 107-42.
(2) Financial obligation.--The term ``financial
obligation'' means any note, bond, debenture, or other debt
obligation issued by an obligor in connection with financing
under this section and section 2(b).
(3) Lender.--The term ``lender'' means any non-Federal
qualified institutional buyer (as defined by section
230.144A(a) of title 17, Code of Federal Regulations (or any
successor regulatory) known as Rule 144A(a) of the Securities
and Exchange Commission and issued under the Securities Act of
1933), including--
(A) a qualified retirement plan (as defined in
section 4974(c) of the Internal Revenue Code of 1986
(26 U.S.C. 4974(c))) that is a qualified institutional
buyer; and
(B) a governmental plan (as defined in section
414(d) of the Internal Revenue Code of 1986 (26 U.S.C.
414(d))) that is a qualified institutional buyer.
(4) Obligor.--The term ``obligor'' means a party primarily
liable for payment of the principal of, or interest on, a
Federal credit instrument, which party may be a corporation,
partnership, joint venture, trust, or governmental entity,
agency, or instrumentality.
(b) Additional Functions To Stabilize the Travel Industry.--The
Board shall review and make recommendations to the President with
respect to applications for Federal credit instruments submitted under
section 2(b).
(c) Federal Credit Instruments.--
(1) In general.--The Board may enter into agreements with 1
or more obligors to issue Federal credit instruments under
section 2(b) if the Board determines, in its discretion, that--
(A) the obligor is an entity in a travel-related
business for which credit is not reasonably available
at the time of the transaction;
(B) the intended obligation by the obligor is
prudently incurred; and
(C) such agreement is a necessary part of
maintaining a safe, efficient, and viable travel
industry in the United States.
(2) Terms and limitations.--
(A) Forms, terms, and conditions.--A Federal credit
instrument shall be issued under section 2(b) in such
form and such terms and conditions and contain such
covenants, representatives, warranties, and
requirements (including requirements for audits) as the
Board determines appropriate, provided that--
(i) a loan shall be repaid over a period
not to exceed 5 years from the date that the
loan is guaranteed under this Act;
(ii) the government guarantee shall cover
not less than 80 percent of the value of the
loan;
(iii) loan guarantees under this Act shall
be extended based upon the ability of the
eligible travel-related business to repay the
loan without regard to collateral;
(iv) any loan origination fee may not
exceed one percent of the loan value.
(B) Procedures.--Not later than 14 days after the
date of enactment of this Act, the Director of the
Office of Management and Budget, in consultation with
the Board, shall issue regulations setting forth
procedures for application and minimum requirements.
(d) Financial Protection of Government.--
(1) In general.--To the extent feasible and practicable, as
provided in paragraphs (2) and (3), the Board shall ensure that
the Government is compensated for the risk assumed in making
guarantees under this Act.
(2) Government participation in gains.--To the extent to
which any participating corporation accepts financial
assistance, in the form of accepting the proceeds of any loans
guaranteed by the Government under this Act, the Board is
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contingent on the financial success of the participating
corporation, would participate in the gains of the
participating corporation or its security holders through the
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(3) Deposit in treasury.--All amounts collected by the
Secretary of the Treasury under this subsection shall be
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(e) Authorization of Funds.--Congress authorizes and hereby
appropriates such sums as are necessary to carry out the purposes of
this Act.
|
American Travel Industry Stabilization Act - Directs the President to issue Federal credit instruments, amounting in the aggregate up to $5 billion, to compensate eligible travel-related businesses that were injured by the Government shutdown of the airline industry following the terrorist attacks on the United States that occurred on September 11, 2001.Requires the Air Transportation Stabilization Board to review and make recommendations to the President with respect to applications for such instruments. Sets forth certain Board and instrument requirements.
|
ring galaxies represent a class of colliding galaxies in which nearly symmetrical density waves are driven into a disk as a result of an almost bulls - eye collision with a compact galaxy @xcite .
hydrodynamical simulations reproduce some of the basic features observed in ring galaxies , such as rings or crescent - shaped structures @xcite .
expanding density waves trigger star formation ( sf ) , and hence a star - forming ring is expected to form in ring galaxies .
the star - forming ring propagates outward with time , leaving behind an evolved stellar population in its wake .
tracers of massive short - lived stars ( e.g. h@xmath0 emission ) are expected to delineate the present position of the wave , while tracers of the remnants of massive stars ( e.g. nonthermal radio continuum ) are expected to illuminate the regions in the wake of the expanding wave .
initial gas density distribution , and the velocity of the wave , would determine the shapes of the radial intensity profiles in the tracers of the young and old components @xcite .
the cartwheel is among the biggest known ring galaxies , in both angular and linear size , and is considered to be the prototype of a ring galaxy . at a distance of 137 mpc ( @xmath2 = 65 kms@xmath3mpc@xmath3 ) , its angular size of 72 corresponds to a linear diameter of 48 kpc .
the entire population of bright hii regions lies in the outer ring , with more than 80% of the current sf occurring in a few hii complexes in the southern sector of the ring ( higdon 1995 , hereafter h95 ) .
there are , however , a few faint regions inside @xcite .
h95 derived a star formation rate ( sfr ) of 67 @xmath1(159 @xmath1for the h@xmath4 adopted in this work ) , based on h@xmath0 flux , which is almost an order of magnitude higher than that derived from far infrared ( fir ) flux .
some of this discrepancy is probably due to problems in the h95 calibration of h@xmath0 fluxes ( j. l. higdon 2000 , private communication ) .
we have carried out sensitive 20 cm radio continuum ( rc ) observations using the very large array ( vla ) with the goal of detecting nonthermal emission in the wake of the wave .
we also carried out new h@xmath0 observations in order to resolve the discrepancy between the sfrs derived from h@xmath0 , and fir luminosity .
we present details of the new observations in section 2 . in section 3
, we describe the observed radio structures and also discuss the sfrs derived from h@xmath0 , fir and rc fluxes . in section 4 , we discuss the results obtained from these new observations from the context of expanding wave models .
rc observations at 20 cm were carried out with the bna configuration of the vla during 2002 may and june , spread over seven runs totaling 35 hr of integration time .
the flux scale , antenna gain , and phase constants were calibrated using observations of standards 0137 + 331 ( 16.32 jy at 1.38 ghz ) and 0025@xmath5260 ( 8.70 jy at 1.38 ghz ) .
data for each run were calibrated before combining them to produce the final map . the final cleaned and self - calibrated maps have almost a circular beam of fwhm of @xmath6 ( p.a.=@xmath7 ) .
several maps with different weight parameters and de - convolved beam sizes were obtained .
some maps were only cleaned and others were the result of several iterations of self - calibration with different restoring beam sizes .
the rms or @xmath8 noise of our final image is 30@xmath9jybeam@xmath3 , which is an improvement by around a factor of 4 over previous observations ( higdon 1996 , hereafter h96 ) .
although some of the radio structures that we discuss here are at the nominal 3@xmath8 limit or just below it , we believe that these structures are true because of their presence in various trial maps we had produced during the reduction process .
new h@xmath0 ccd imaging observations were carried out during one photometric night ( 2003 , september 30 ) at the mcdonald observatory ( texas ) with a 30@xmath10 telescope .
we used three interference filters : 6700/123 , 6560/100 , and 6670/82 , designated so for their central wavelengths and widths , both in units of .
the first one intercepts the redshifted h@xmath0 line from the galaxy ( 6761 ) , and the other two filters facilitate subtraction of the continuum flux entering the h@xmath0 filter .
we took two exposures of the galaxy ( totaling 35 minutes ) as well as the standard stars in each filter .
the exposures of the galaxy were bracketed in time and zenith distance by the calibration stars ltt377 and ltt1020 @xcite .
the measured total rc and h@xmath0 fluxes , along with errors on our measurements are given in table 1 .
our 20 cm flux is in good agreement with the value published by h96 ( 11.5 mjy ) .
fluxes in this table have been corrected for 10% contribution from [ nii ] lines @xcite and galactic extinction ( 2.6% ) .
our value is around 4 times lower than that given by h95 .
we used our new total flux to calibrate an excellent quality h@xmath0 image ( seeing fwhm=0.8 ) that is available at the canada france hawaii telescope data archive .
1 shows the 20 cm contours superposed on gray - scale representation of an h@xmath0 image that is smoothed to the resolution of the radio image , and full resolution _ hubble space telescope _ ( @xmath11 ) @xmath12-band image in panels ( @xmath13 ) and ( @xmath14 ) respectively . in the following section we give a description of the different observed features .
lccc flux & @xmath513.23 @xmath150.12 & @xmath512.40@xmath16 & 12.8 @xmath150.5 + & @xmath17 wm@xmath18 & @xmath17 ergss@xmath3cm@xmath18 & mjy + log luminosity & 10.50 & 41.95 & 29.46 + & l@xmath20 & ergs@xmath3 & whz@xmath3 + sfr ( @xmath1 ) & & & + a@xmath21 & 17.71 & 7.91 & 29.13 + a@xmath22 & 17.71 & 18.13 & 27.67 + a@xmath23 & 17.71 & 25.60 & 26.61 +
it can be seen in figure 1 that the rc morphology of the cartwheel resembles very much the morphology of the ring in h@xmath0 emission .
radio emission is detected from at least 13 hii complexes .
these complexes are among the brightest 15 in h@xmath0 emission ( brighter than @xmath24 ergscm@xmath18s@xmath3 ) .
the two non - detected sources ( cw-6 and cw-29 of h95 ) are among the regions with the highest h@xmath0 equivalent widths , suggesting that they are most likely too young to turn - on nonthermal rc emission .
faint emission is also detected at the nuclear position ( fig . 1
, _ cross _ ) . in the bright southern part of the ring ,
the rc image shows at least seven finger - like structures that seem to originate from parts of the ring near bright hii regions , and point radially inward to the geometrical center of the ring , giving the appearance of spokes of the wheel .
the most prominent spoke originates from close to cw-17 , the brightest hii region in the cartwheel .
this is the only spoke that had been detected in previous rc images ( h96 ) .
the spoke originating near cw-20 crosses the ring , although with a slight change in the direction .
interestingly , the hyperluminous x - ray source reported by @xcite coincides with this region .
are the rc spokes related to their optical counterparts ?
the first impression from figure 1(b ) , is that the relation between the two , if any , is weak .
the rc spokes are short and straight , whereas the stellar spokes connect the two rings of the cartwheel by a curved path .
the brightest rc spoke has no correspondence to any optical spoke even when extrapolated inward .
of the other six rc spokes , only one ( corresponding to cw-10 ) , when extrapolated inward meets an optical spoke . on the other hand ,
some of the weak rc emission interior to the main ring seems to coincide with the brightest points of the stellar spokes .
so it is possible that the rc spokes are also longer and curved like their optical counterparts , but we have detected only the bright part of that .
clearly , deeper rc images are required to address this question . the azimuthal distribution of nonthermal rc intensities , and the thermal fraction , in three successive radial zones , one corresponding to the position of the ring ( radius=36 ) , and the other two positioned 6 on either side of the ring , are plotted in figures 2(a c ) .
each zone has a width of 6 .
the thermal rc flux is calculated from extinction corrected h@xmath0 flux using the relation given by @xcite for an electron temperature of 15000 k @xcite , and visual extinction [email protected] mag .
the azimuthal rc intensity profile of the ring illustrates a well - known fact : regions in the southern part of the ring ( pa = 120240@xmath26 ) are several times brighter than elsewhere in the ring .
the spokes stand out in the azimuthal profile of the annular zone in the wake of the ring .
the rc emission from the spokes is predominantly nonthermal .
the azimuthal profile exterior to the ring resembles that of the ring .
however , unlike in the ring where 820% of the observed rc flux of hii complexes is of thermal origin , it is less than 2% in the external zone except for the region just outside cw-12 .
fir , h@xmath0 and 20 cm rc fluxes have been extensively used as tracers of sfr in galaxies @xcite .
the fir flux , as defined in @xcite , is calculated for the cartwheel using the iras 60 and 100@xmath9 m fluxes from @xcite .
the resulting value is given in table 1 , along with the h@xmath0 and 20 cm rc flux measured in this work .
sfrs are derived from the luminosities in fir , h@xmath0 and 20 cm rc bands using the relations given by @xcite , @xcite , and @xcite , respectively .
additive constants that convert log(luminosity ) of row 2 to log(sfr ) are @xmath59.27 , @xmath541.05 , and @xmath520.98 for fir , h@xmath0 and 20 cm rc bands , respectively .
the rc conversion factor depends on the nonthermal power - law index @xmath0 .
a value of @xmath27 is used in this work , which is based on the measurement for two of the brightest hii regions in the cartwheel ( h96 ) . in all these relations the initial mass function ( imf ) from @xcite
use of salpeter imf would decrease the sfrs by 16% @xcite . in order to calculate the sfr from h@xmath0 fluxes
, we need to correct for the internal extinction in hii regions
. maximum value of a@xmath28 allowed by the observed mean colors of the ring is 1.3 mag @xcite , as compared to a@xmath29 mag measured for the brightest hii region . in the last three rows of table 1 ,
sfrs are tabulated for a@xmath250 , 1.2 and 1.7 mag respectively .
fir - derived sfr is independent of extinction , where as the sfr derived from nonthermal rc flux is weakly dependent on extinction , which is due to the fact that it is obtained by subtracting the thermal component from the total , and that the thermal component is calculated from the extinction - corrected h@xmath0flux . for [email protected]
, sfr derived from h@xmath0 agrees with that from fir , whereas the rc gives around 30% more sfr . the thermal contribution to the global rc flux
is 10% , which is in good agreement with the value found for star - forming galaxies @xcite .
an sfr of 18@xmath1 for the cartwheel compares well with the sfrs of other collisionally formed ring galaxies and interacting galaxies @xcite .
rc emission of star - forming galaxies is correlated with the fir emission .
hence 30% excess sfr derived from rc implies that 30% of the detected rc emission is not related to sf .
what is the reason for this excess rc emission in the cartwheel ?
a comparison of the rc and h@xmath0 morphologies suggests that the regions with excess rc emission are cw-20 , cw-24 and the outer boundaries of these regions .
non - thermal radio emission not associated with sf has been discovered in shocked regions in a number of interacting galaxies , including in the intersection of the two merging galaxies forming antennae @xcite .
considering that the ring in the cartwheel is expanding at high velocities , it is reasonable to think that the shocked gas contributes to a part of the observed nonthermal rc emission .
however , published hi data of the cartwheel , do not show evidence of high velocities suggestive of shocks in these regions .
this implies that the neutral gas is not coming from the same region as the shocked ionized gas .
the expanding density wave is expected to leave in its wake old stars and remnants of massive stars .
non - thermal rc emission originates in supernova remnants , which trace stars that are formed @xmath301050 myr ago ( lifetime of stars more massive than 9 @xmath31 at z = z@xmath32/10 ) .
hence nonthermal rc emission from spokes represent the trajectory of the star - forming wave over the past @xmath3050 myr .
intensity distribution along the spokes has valuable information on the past sf process , and can be used to constrain the models of sf in an expanding density wave . in figure 3(a ) , we plot the radial profiles of rc and h@xmath0 intensities expected from models of sf in an expanding density wave . in particular , we used the @xcite model , in which the density wave is assumed to be of gaussian shape @xmath33 kpc , propagating at 90 km s@xmath3 in an exponential gas disk of scale - length of 20 kpc . a schmidt law with power law index n=1.5 is used to scale gas density to sfr .
the rc emission , which traces stars formed @xmath3050 myr ago , lags behind the h@xmath0 peak , which marks the current location of the wave , by about 2 .
we have carried out a series of tests , and confirmed that the predicted displacements in the peak positions of the profiles should be seen even at the spatial resolution of our rc image .
we obtained radial intensity cuts on the h@xmath0 and rc images , passing through the ring center ( marked by a small circle in figure 1 ) and the rc detected parts of the ring .
all the resulting profiles resemble one of the three representative profiles of figure 3(b - d ) .
the majority of the rc profiles are skewed inward as compared to the h@xmath0 profile , with the peaks of the two profiles coinciding as in ( b ) . in some directions , the rc emission peaks outside the h@xmath0 profile ( c ) .
rc and h@xmath0 profiles of the brightest hii complex ( cw-17 ) are identical except that the former is broader .
surprisingly , none of the regions show the expected inward shift of the rc profile with respect to h@xmath0 profile .
the profiles skewed inward correspond to the zones where spokes are detected in the wake of the wave , where as profiles skewed outward are basically zones where radio emission extends outside the h@xmath0 ring . as discussed in the previous section ,
shocks ahead of the wave are responsible for the rc emission in these zones . in the cartwheel , the @xmath34-band intensity profile , which traces the red supergiant stars that are formed about 1020
myr ago , is found to peak marginally inside the h@xmath0 profile @xcite .
the displacements , are consistent with a wave velocity of @xmath35 km s@xmath3 .
the displacements were not noted along the minor axis cuts , which @xcite explained as due to orientation effects .
hii regions cw-6 and cw-28 are along the major axis , both of which contain radially directed rc spokes , but the expected 2 shift in the position of peak of the rc emission can not be noted .
the lack of radial separation between the rc and h@xmath0 profiles calls for a revision of the physical ingredients that go into the models , especially in the treatment of sf and feedback effects .
the observed profile shapes imply that the sfr increased to the currently observed values abruptly a few tens of myr ago . a possible reason for the lack of sf in the past could be that the pre - collisional gas disk was well below criticality and the density enhancements caused by the passing wave were not sufficient to drive the densities above the critical value required for collapse .
even if the disk was critical before the interaction , the passing wave can heat the disk , making it subcritical .
hence realistic ring models should include heating and cooling of the disk .
observations of more ring galaxies in the rc would be invaluable in working out the details of the physics of sf in an expanding density wave .
we thank the staff at nrao , especially barry clark , for liberal allotment of vla time .
we also thank the staff at mcdonald observatory , and personally david doss .
this work has gained from discussions with alessandro bressan and vladimir korchagin at various stages of the project .
we thank the anonymous referee whose comments helped to improve the presentation of the manuscript .
this work was supported by research grants 39714-f ( conacyt , mexico ) , 99 - 04-oss-058 , and 04 - 02 - 16518 ( jpl / nasa and rfbr ) .
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p. n. 1995 , , 109 , 1002 mazzarella , j. m. , gaume , r. a .. aller , h. d. , & hughes , p. a. 1988 , , 333 , 168 punuzzu , p. , bressan , a. , granato , g. l. , silva , l. , & danese , l. 2004 , , 409 , 99 theys , j. c. , & spiegel , e. a. 1977 , , 212 , 616 thronson , h. a. , & telesco , c. m. 1986 , , 311 , 98 vorobyov , e. i. , & bizyaev , d. 2001 , , 377 , 835 vorobyov , e. i. , & bizyaev , d. 2003 , , 400 , 81
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new sensitive very large array 20 cm continuum observations of the cartwheel , the prototypical collisional ring galaxy , were carried out with the principal aim of tracing supernova remnants that are expected to lie in the wake of the expanding ring and in the ring itself .
we detect predominantly nonthermal radio continuum emission from regions associated with 13 ring hii complexes . the emission interior to the ring
is confined to structures that resemble spokes of the wheel .
the spokes start near bright hii complexes , and extend to around 6(4kpc ) inward in the direction of the geometrical center of the ring .
there is no apparent positional coincidence between the radio continuum and optical spokes .
radial distribution of intensity along the spokes suggests that the past star formation rate ( sfr ) in the cartwheel was much lower than the current sfr .
new h@xmath0 observations were used to revise the current sfr in the cartwheel .
the revised value is 18@xmath1 , which is a factor of 4 lower than the value reported previously , but is in good agreement with the sfr estimated from far infrared luminosity .
about 30% of the observed 20 cm continuum nonthermal emission seems to originate in processes that are not related to star formation .
revised sfr in the cartwheel is comparable to that in the rest of the ring galaxies .
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in this paper we consider the situation of a single chain polymer confined within a space smaller than its radius of gyration .
such a situation is encountered within the nucleus of a cell where one or more chromosomes with a radius of gyration on the order of 10 @xmath0 are confined by the nuclear membrane to a space of order 1 @xmath1 . even in the case of organisms where the genome is composed of many chromosomes ,
the situation is distinct from that of a polymer melt as each chromosome is effectively confined to a separate sub - volume of the nucleus @xcite . since many biological processes such as
gene suppression and activation require a rearrangement of the dna polymer , understanding the dynamics of confined polymers may yield insight to the dynamics of these cellular activities .
strongly confined polymers may also be encountered in the `` lab on a chip '' applications promised by microfluidic technology @xcite . in these applications
the reaction vessels are @xmath2 microdroplets .
while the equilibrium properties of confined polymers may be understood based on scaling arguments @xcite , the dynamics of confined polymers are less well understood , and there has been growing interest in the problem .
for instance , the transport of polymers in confined geometries has been studied in a variety of contexts , including translocation through pores @xcite , diffusion through networks @xcite and tubes @xcite , and the packing of dna within viral capsids @xcite . for these highly confined polymers
the density profile strongly resembles that of a polymer melt . we might naively expect that since a given section of the polymer interacts primarily with segments that are greatly separated along the chain , each segment may be treated as a sub - chain embedded within a melt
however , this picture is troublesome for dynamical quantities as reptation theory says that the dynamics is governed by the time it takes for a given chain to vacate the tube defined by its immediate neighbors . with a system consisting of a single polymer
, this would imply that the tube occupies the entire box .
therefore , we would be forced to conclude that the chain is completely immobile .
we show here that reptation - like motion is , in fact , the dominant mode of deformation of confined polymers .
in contrast to the situation in melts , however , reptational diffusion is not necessarily initiated by the chain ends , and therefore , can not be always thought of as diffusion along a fixed tube .
polymers confined to thin films have been experimentally shown to have glassy characteristics @xcite .
while this phenomenon has attracted considerable theoretical attention , it is not well understood @xcite .
it is also not known whether glassy behavior occurs in other confined geometries . here
we point out a connection between lattice polymer models and kinetically constrained models ( kcm ) with the chain connectivity as the analog of the kinetic constraint .
since many kcms display glassy behavior at high density it is plausible that polymers do as well . in this paper
we numerically explore the dynamics of confined polymers using a kinetically constrained lattice gas model .
we find that monomer diffusion exhibits power law behavior up to densities very close to the close - packing limit .
however , the overall shape of the chain , as quantified by a tangent - tangent correlation function , shows a broad plateau at high densities .
this apparent paradox is due to the reptation - like nature of the chain movement . because the monomer diffusion is primarily in the direction of the chain backbone , only relatively
small rearrangements of the backbone are required for the monomers to move distances comparable to the system size .
the outline of the paper is as follows . in section [ sec : particle model ]
we define our model and employ monte carlo simulations to show that this model reproduces known results for the dynamic and static properties of unconfined polymers in two dimensions . in section [ sec : msd ] we show that the individual monomers diffuse with a power law in time behavior up to the close - packing density . in section [ sec : tantan ] we define the tangent - tangent correlation function and use it to show that the overall shape of the chain is essentially frozen within the time scale required by a monomer to diffuse across distances much larger than the inter - particle seperation . in section [ sec : tan_dis ] we use a tangent - displacement correlation function to show that the discrepancy between the monomer diffusion and reshaping time scales is due to reptation - like diffusion of the polymer along the chain backbone .
finally , in section [ sec : conclusions ] we summarize our conclusions .
inspired by the bond fluctuation model @xcite of polymer dynamics and kinetically constrained models ( kcm ) @xcite such as the kob - andersen model @xcite , we propose a kcm for the dynamics of a self - avoiding polymer .
the fact that the monomers constitute a polymer requires the connectivity to be preserved .
namely , connected ( unconnected ) monomers must remain connected ( unconnected ) during the polymer motion .
we begin by introducing the model in two dimensions with monomers living on the sites of a square lattice for simplicity .
let us define the polymer connectivity in the following way .
consider a square box of linear size @xmath3 whose center lies on a given monomer .
any other monomer that lies inside or on the boundary of this box is defined as a box - neighbor of the monomer at the center .
clearly , if monomer a is a box - neighbor of monomer b , then monomer b is also a box - neighbor of monomer a. we define two monomers as being connected by a bond if and only if they are box - neighbors .
a monomer with no box neighbors is an isolated polymer of length one .
a monomer with only one box - neighbor is the end - point of a polymer .
a monomer with two box neighbors is a point in the middle of a polymer and a monomer with more than two box neighbors corresponds to a branching point along a polymer .
depending on the initial monomer positions , multiple open or closed chains can be modeled . also by using a d - dimensional hyper - cube instead of a square
, the model can be immediately generalized to higher dimensions .
the dynamics is defined as follows .
a monomer can hop to a nearest neighbor unoccupied site if it has exactly the same box - neighbors before and after the move , as in fig .
[ fig : hard particle example ] .
if no monomer enters the box associated with the moving monomer and no monomer falls out of it during the move , the box will contain the exact same monomers before and after the move .
in other words , all the @xmath4 sites ( @xmath5 in @xmath6 dimensions ) that enter or exit the box as it is moved to the new position , must be unoccupied , as shown in fig .
[ fig : dynamics ] . in our model as in many kinetically constrained lattice gas models @xcite , we take the energy to be independent of the configuration , resulting in constant hopping rates .
we assume that the allowed moves take place at unit rate .
so if @xmath7 is defined to assume the value @xmath8 for occupied sites and @xmath9 for empty sites , and @xmath10 , the rate of hopping to the right out of site @xmath11 is given by @xmath12 and by similar expressions for the other directions .
the dynamics forbids monomers that are unconnected from getting too close to each other and therefore ensures self - avoidance .
notice that all the moves are reversible because , as seen in fig .
[ fig : dynamics ] , any particle that was allowed to hop to a nearest neighbor empty site is allowed to hop back to its original position .
an example of a configuration that satisfies the initial conditions discussed in the text to have a single closed polymer .
this is illustrated explicitly for the particle in red : the box of size @xmath3 ( @xmath13 ) is indicated by the dashed purple square , and the two other particles inside the box are colored in blue .
the same condition holds for all the particles in the system .
all the ( nearest - neighbor ) particle moves allowed by the kinetic constraint are shown for each particle with arrows along the corresponding lattice edge .
one particle in this configuration is temporarily frozen ( circled blue particle ) , and its move is subordinated to the move of one of the two particles in its box of size @xmath3 .
notice that the initial sequence of particles , represented by the wiggly green line , is clearly preserved by the allowed moves . ] for a model with an @xmath13 box , a monomer can hop in a given direction if the destination site , as well as the ten sites which the old and new box differ by , are empty . ]
we choose the smallest value of @xmath14 for which the model behaves like a polymer while allowing for shorter simulation times .
the @xmath15 case is too restrictive to model different modes of motion .
for example a polymer lying along a straight line is forbidden in the @xmath15 model to undergo one - dimensional translation .
we choose @xmath13 as it is found to adequately describe the free polymer dynamics , as shown by our numerical simulations .
monte carlo ( mc ) simulations are used to study the model .
a particularly time - efficient algorithm is achieved by storing two representations of the system at each mc step .
one consists of the position vector of all the monomers , and the other is the configuration matrix of the lattice , with unoccupied sites having value zero and occupied sites value one .
this allows us to chose a monomer at random from the position vector ( rather than a site at random from the whole lattice ) and quickly determine if the monomer is allowed to move in a randomly chosen direction by checking the values of at most eleven elements ( the nearest neighbor site plus the sites by which the old and new box differ ) in the configuration matrix .
note that it is possible to define an alternative model by using a circle of radius @xmath13 instead of a square box of side @xmath16 , which would require the same amount of computational effort because the same number of sites , namely ten sites , would enter or leave the circle drawn around the moving monomer .
the @xmath13 model with a square box proved to give consistent results with the ones available in the literature .
namely , the time - averaged radius of gyration squared of the polymer computed for our model in an infinite box scales as @xmath17 , which is consistent with flory s theoretical result of @xmath18 @xcite .
the dynamics of the polymer in unconfined environments is also compatible with the rouse model to a good approximation . as shown in fig .
[ fig : rouse ] , the mean square displacement of the center of mass is diffusive with a diffusion constant that scales as @xmath19 compared to the @xmath20 theoretical value . throughout the paper , time and length
are measured in units of monte - carlo steps and lattice spacings respectively .
only four values of @xmath21 were used for these consistency checks but the fits were very close to the theoretical predictions .
the individual monomer mean square displacement is diffusive at very short times followed by an intermediate - time subdiffusive behavior and a cross - over to a final diffusive behavior at long times as each monomer begins to move with the center of mass .
the subdiffusive msd can be fit with an exponent of @xmath22 over the two - decade interval of @xmath23 which is consistent with the theoretical value of @xmath24 and the bond fluctuation results @xcite . because of the cross - over to diffusive behavior at long times the curve fits well to a higher exponent of @xmath25 over the longer interval of @xmath26 .
center of mass and individual monomer mean square displacement of a free polymer .
the results are shown for @xmath27 . ] in the present paper we focus on open and closed polymers without any branching .
the close - packing density of such polymers clearly has an upper limit .
for a single open chain for example , each monomer except for the two end - points has exactly two box - neighbors .
the maximally packed configuration is achieved once the distance along the chain between the consecutive monomers alternates between one and two lattice spacings , and the distance between parallel segments of the folded polymer equals @xmath28 lattice spacings , as depicted in fig .
[ fig : fully packed ] .
if we have @xmath29 monomers on an @xmath30 lattice with @xmath31 sites , the fully - packed configuration attains a thermodynamic - limit density @xmath32 ( @xmath33 in @xmath6 dimensions ) .
note that except for fluctuations at the u - turns , the polymer is completely frozen at close - packing . a fully packed configuration of the model described in the text .
notice that only the shaded monomers are allowed to move at any given time . ]
the question of whether or not placing a self - avoiding polymer in a highly confining environment can freeze its motion can be addressed by measuring the statistical average of the mean square displacement as a function of time @xmath34 ^ 2 \rangle,\ ] ] where @xmath35 is the position of the @xmath36-th monomer and @xmath37 is the waiting time between the preparation of the sample and the measurement . throughout the paper ,
we denote the ensemble average by @xmath38 .
we prepare random samples with different densities by placing the polymer in a large box and gradually reducing the size of the box .
this is achieved by forbidding the monomers to move to the edges of the box , which corresponds to an infinite repulsive potential at the boundary , and removing one vertical and one horizontal edge line once they have become completely empty . after each shrinking process
, the system is confined to a smaller square box .
shrinking and measurements are done in series . specifically , we start from a very low density of @xmath39 and after each shrinking step we let the system run for @xmath40 monte - carlo steps before trying to shrink further . for measurements involving a long waiting time ( @xmath41 steps ) , i.e. , for densities @xmath42 and @xmath43 , subsequent shrinking steps are preformed starting from the post - measurement configurations . with this method
we are able to reach densities of approximately @xmath44 , compared to the limiting theoretical value of @xmath45 . at high densities , as shown in fig .
[ fig : shrink ] , the overall geometry of the polymer resembles that of a compact polymer described by a hamiltonian path , i.e. , a path which visits all sites exactly once , exploring a lattice with lattice spacing three times larger than in the original one . at these high densities
our model resembles a semi - flexible polymer because the chain is able to attain a higher packing density in the direction parallel to the backbone ( average monomer spacing equal to @xmath46 lattice spacings ) than in the direction perpendicular to the backbone ( average monomer spacing equal to @xmath28 lattice spacings ) ( see fig .
[ fig : fully packed ] ) .
snapshots of a polymer with @xmath47 monomers .
as the box shrinks , the polymer gets more and more confined . at densities close to full - packing , a geometry resembling that of a compact ( hamiltonian walk ) polymer is formed . ]
measurements are done with two values of waiting time , @xmath41 and @xmath48 monte - carlo steps over a period of @xmath49 steps .
( for the highest density we used @xmath50 instead . )
the mean square displacement shows time translation invariance up to the highest densities achieved .
we study the behavior of @xmath51 for @xmath21 at the densities listed above .
the root mean square displacement @xmath52 is a measure of how much the monomers have moved . as shown in fig .
[ fig : msd_tau ] , @xmath51 increases with power law behavior and finally saturates with a limiting root mean square displacement of the order of the box size .
for very large box sizes ( lowest density ) as well as very small box sizes ( very high densities ) , the saturation plateau is not always reached within the measurement time . however , the maximum value of @xmath52 is still of the same order of the box dimensions .
although the dynamics slows down at high confinement , each monomer manages to move an average distance comparable to the box size over our measurement time @xmath53 .
visually observing the polymer motion , however , clearly shows a more complex scenario where at high densities the overall geometry of the polymer is largely preserved ( see fig .
[ fig : shrink ] ) .
indeed , we will see that the tangent - tangent correlation function , although time - translation invariant at low and intermediate densities , exhibits signs of aging at higher densities . in the following sections we discuss in detail the shape persistence as well as the mechanisms by which the polymer shape changes as the box size is reduced .
mean square displacement for @xmath27 and different box sizes ( i.e. , different densities ) as a function of time .
the @xmath54 curve can be fit with a @xmath55 exponent which is close to the intermediate - time regime of the rouse model .
the results for other values of n are qualitatively very similar . ]
the large values reached by @xmath52 within our simulation times even for very high densities indicate that confinement does not freeze the motion of the monomers .
the overall shape or geometry of the polymer , however , exhibits global persistence at high densities as observed via direct visualization of the dynamics . in order to systematically study shape persistence and reshaping ,
we introduce the concept of a tangent field , a vector field defined on the entire lattice which captures the overall shape of the polymer .
we define the instantaneous tangent field as @xmath56 @xmath57 being the position of monomer @xmath36 at time @xmath53 .
the tangent field is defined in a symmetric way so that labeling the monomers in reverse order only changes the direction of the field . in an open chain
, the definition needs to be modified at the end points .
note that the tangent field is indexed by a position in space and not by a monomer number ; this allows us to compare the shapes at different times , independently of the monomer motion . since local vibrations of the polymer do not change the overall geometry , we seek a quantity that is insensitive to these vibrations . coarse - graining the field by time averaging over a carefully chosen interval removes the local vibrations and results in a smeared field @xmath58 which captures the overall geometry , as shown in fig .
[ fig : tang_ex ] .
we have chosen the time interval to be @xmath59 monte carlo steps ( or @xmath60 single monomer attempts ) which is sufficient to allow for several vibrations .
since the success rate of the monte carlo attempts at high density is found to be around @xmath61 , this interval corresponds to roughly @xmath62 moves per monomer .
an example of the coarse - grained tangent field @xmath58 ] in terms of the coarse - grained tangent field defined above , we define the tangent - tangent correlation function @xmath63 \rangle\ ] ] as a measure of the overlap of the tangent field at times @xmath64 and @xmath37 . as shown in fig .
[ fig : tantan_tau ] , @xmath65 decays as a power low in @xmath53 for very low densities . as the density increases , a second time scale emerges and at the highest densities we clearly see an initial decay followed by a broad plateau and a secondary decay .
( notice the use of a logarithmic scale on both axes . )
the time - averaging of the tangent field hides the fast mode responsible for the initial decay and causes the correlation to have a smaller initial value at lower densities .
the correlation function ( [ eq : tantan ] ) does not depend on the value of @xmath29 at low densities , as seen in fig .
[ fig : tantan_size ] , while at higher densities we observe broader plateaux and longer decorrelation times as the number of monomers @xmath29 is increased .
tangent - tangent correlation function for @xmath66 monomers and different box sizes .
the @xmath54 curve fits well to a power law of exponent @xmath67 .
note that the correlation functions are not normalized . ]
the tangent - tangent correlation function for four different polymer sizes .
top : at low density @xmath68 , the curves are independent of @xmath29 .
bottom : at the highest achieved density @xmath69 , the width of the emergent plateau increases with @xmath29 , title="fig : " ] the tangent - tangent correlation function for four different polymer sizes .
top : at low density @xmath68 , the curves are independent of @xmath29 .
bottom : at the highest achieved density @xmath69 , the width of the emergent plateau increases with @xmath29 , title="fig : " ] to check for time - translation invariance , we ran the simulations two more times after increasing the waiting time @xmath37 by an order of magnitude each time .
the mean square displacement exhibits time - translation invariance at all densities . for the tangent - tangent correlation function , however , time - translation invariance is respected at low densities but violated at the highest densities where a broad plateau emerges .
it appears that at high densities the average distance between monomers slowly evolves with time , so that the initial value of the tangent - tangent correlation function @xmath70 depends on @xmath37 .
if we normalize the correlation function using its value at the beginning of the measurement and plot @xmath71 as a function of time , the violation of time - translation invariance suggests the existence of aging effects , a comprehensive study of which is beyond the scope of the present paper .
for @xmath72 , the system has almost equilibrated but there is still a systematic shift toward longer times compared with the @xmath48 correlation function .
[ fig : aging ] summarizes the above observations .
moreover , fig .
[ fig : tantan_size ] suggests longer equilibration times for larger systems and in the thermodynamic limit ( @xmath73 ) the aging effects are expected to survive for arbitrarily large @xmath37 . the normalized tangent - tangent correlation function @xmath71 vs. time for different waiting times shown in log - log plots .
top : up to intermediate densities , before the appearance of a clear plateau , time translation invariance is not broken .
bottom : at higher densities , where a broad plateau has emerged , we observe that the second decay occurs at a longer time scale
. with increasing the waiting times the correlation function approaches equilibrium but there is still a systematic shift between @xmath74 and @xmath75 curves indicating slower decay for the older system .
, title="fig : " ] the normalized tangent - tangent correlation function @xmath71 vs. time for different waiting times shown in log - log plots .
top : up to intermediate densities , before the appearance of a clear plateau , time translation invariance is not broken .
bottom : at higher densities , where a broad plateau has emerged , we observe that the second decay occurs at a longer time scale
. with increasing the waiting times the correlation function approaches equilibrium but there is still a systematic shift between @xmath74 and @xmath75 curves indicating slower decay for the older system .
, title="fig : " ]
as seen in the previous sections , confinement slows down the motion of individual monomers in a polymer chain , but it does not fundamentally change the characteristics of their mean square displacement .
it does , however , have a profound effect on reshaping . without any reshaping
, the only possible motion can happen via reptation , i.e. , when the monomers move back and forth along a fixed path . with the exception of the unlikely event of the two end - points finding each other , reptation without reshaping
is not possible in open chains .
indeed , by studying closed loops in detail we do find that longitudinal diffusion is the main mechanism for motion at high densities .
the existence of large root mean square displacements in strongly confined open chains and in the absence of major reshaping can be explained by noting that local reshaping events with only a minor contribution to the tangent - tangent decorrelation allow for global monomer motion through a reptation - like process .
[ fig : reptation ] shows one instance of such behavior in a particularly mobile realization .
the mechanisms shown in fig . [ fig : reptation ] , namely end - point initiated reptation and `` fingering '' events , are observed in other realizations as well .
a finger is formed when the chain makes a 180-degree bend resulting in two adjacent segments of the polymer running antiparallel to each other .
a fingering event occurs when a finger retracts making room for the extension of another finger . even in the case of closed loops where pure reptation is possible ,
reptation is usually accompanied by local fingering events as shown in fig .
[ fig : reptation_loop ] . to explicitly quantify the contribution of reptation to highly confined motion
, we define tangent - displacement and normal - displacement correlation functions as follows : snapshots of a particularly mobile realization of a @xmath66-monomer chain at density @xmath76 . fingering events
are observed as well of end - point reptation accompanied by local rearrangements .
an end - point initiated reptation is highlighted with a dashed ellipse at the moving end - point .
the dashed rectangle shows the tip of a finger which participates in a fingering event during which the tagged monomer shown with a solid circle , for example , moves through reptation . ]
snapshots of a realization with @xmath66 monomers arranged in a single closed polymer chain , at density @xmath76 .
pure reptation and fingering events are visibly responsible for monomer motion .
the dashed rectangle highlights the tip of a finger taking part in a fingering event .
the dashed ellipse shows the reptational motion of a tagged monomer . ]
@xmath77 \right\}^2 \rangle \\ \label{eq : nordis } c_n(t ) & = & \langle \frac{1}{n } \sum_{i=1}^{n } \left\{\vphantom{\sum } \frac{\vec{n}_{\vec{x}_i}(t_w)}{|\vec{n}_{\vec{x}_i}(t_w)| } \cdot \left[\vphantom{\sum } \vec{x}_{i}(t_w+t ) - \vec{x}_{i}(t_w ) \right ] \right\}^2 \rangle,\end{aligned}\ ] ] where @xmath78 is the normal field defined as @xmath79 and the polymer and therefore @xmath58 belongs to the @xmath80 plane . by comparison with eq .
( [ eq : mean_square - displacement ] ) , one can show that @xmath81 therefore , the correlation functions ( [ eq : nordis ] ) and ( [ eq : tandis ] ) are the contributions to the mean square displacement due to the transverse and longitudinal motion relative to the initial polymer orientation . at very high densities and up to time scales smaller than the beginning of the secondary decay in the tangent - tangent correlation function eq .
( [ eq : tantan ] ) , @xmath82 is a good measure of the reptational contribution to the confined motion .
this is due to the fact that over such time scales the polymer shape is largely preserved .
additionally , over the same time scales the mean square displacement is smaller than the average chain length between major bends , which as seen in fig .
[ fig : reptation ] is a large fraction of the box size .
if the polymer undergoes major reshaping or the monomers move through the bends of the folded polymer , reptation would no longer be equivalent to the motion along the original orientation .
let us define @xmath83 as a measure of the anisotropy of the motion with respect to the longitudinal and transverse directions , @xmath84 we have @xmath85 and @xmath86 , where @xmath83 ranges from @xmath87 to @xmath88 .
a large value of @xmath83 clearly indicates a motion primarily due to reptation . as shown in semi - logarithmic scale in fig .
[ fig : f ] , @xmath83 reaches a maximum value of @xmath89 at short time scales , demonstrating that reptation - like motion is the primary contributor to monomer displacement .
we also observe that the maximum of @xmath83 increases as the number of monomers @xmath29 is increased , consistent with the fact that the width of the plateau becomes monotonically larger and larger with @xmath29 .
top : at the lowest density studied @xmath90 , the function @xmath83 is independent of the number of monomers and approaches zero monotonically ( i.e. , the motion is isotropic at intermediate and large time scales ) .
bottom : at the highest densities achieved @xmath69 , the function @xmath83 reaches very large positive values before decreasing again towards zero . for short polymers
@xmath91 goes down to negative values at large times . here
we ignore the causes of this observation because as explained in the text , @xmath91 is a good measure of the anisotropy of the motion only up to certain time scales.,title="fig : " ] top : at the lowest density studied @xmath90 , the function @xmath83 is independent of the number of monomers and approaches zero monotonically ( i.e. , the motion is isotropic at intermediate and large time scales ) .
bottom : at the highest densities achieved @xmath69 , the function @xmath83 reaches very large positive values before decreasing again towards zero . for short polymers
@xmath91 goes down to negative values at large times . here
we ignore the causes of this observation because as explained in the text , @xmath91 is a good measure of the anisotropy of the motion only up to certain time scales.,title="fig : " ]
as the size of the confining box around a polymer is reduced , the monomer density makes it increasingly difficult for the polymer to move . however , the effect on the polymer movement is not isotropic .
the transverse fluctuations are strongly suppressed due to the proximity of monomers that may be greatly separated along the chain backbone .
this is in contrast to motion parallel to the chain backbone where , due to the connectivity constraint , the monomer density is very similar for the confined and unconfined chains .
while longitudinal motion is sub - dominant in the free chain , it is the primary mode of monomer diffusion when the density becomes high enough to suppress the transverse fluctuations .
the emergence of motion parallel to the chain backbone as the dominant mode of diffusion is similar to what occurs in a polymer solution when the density is increased to form a melt . however , the longitudinal diffusion observed here differs from the classic reptation picture in that the motion is not necessarily initiated at the chain ends but it can also be triggered by fingering events .
the prevalence of fingering reptation over end - initiated reptation is due to three factors .
first , the two - dimensional nature of our system imposes topological constraints that severely limit the mobility of the chain ends .
second , a single confined chain has only two end - points , while the number of fingers it can have grows with the system size .
third , the compact configuration due to the confinement forces the creation of more fingering structures relative to the extended polymer structures found in melts .
the peculiarities of the dynamics of a single chain in extreme confinement ( high density limit ) leads to an interesting effect : monomers can diffuse through large distances comparable to the box size within time scales for which the overall shape of the polymer is , nevertheless , largely preserved . while monomer displacement exhibits a smooth power law behavior in time at all densities , the tangent - tangent correlation function develops a secondary decay at high densities .
this decay takes place at longer time scales for older systems , suggestive of aging phenomena .
we thus find glass - like behavior in the overall geometry concurrently with non - glassy monomer motion . despite significant persistence of geometry
, monomer displacement can reach large values relative to its saturation value over the same time scales because local rearrangements cause monomers to flow even in parts of the system where no reshaping is taking place .
the two dimensional lattice model presented here is a largely simplified one .
however , we believe that this model yields considerable insight into the generic properties of confined polymers .
namely , reptational or longitudinal motion is identified as the primary mechanism for motion at high densities and extreme confinement is found to primarily suppress changes in the overall geometry of the polymer rather than the monomer motion .
the simulations were carried out on boston university supercomputer facilities ( scv ) . we thank b. chakraborty , j. kondev , d. reichman and f. ritort for useful discussions . this work is supported in part by the nsf grant dmr-0403997 ( ar , cc , cc , and js ) and by epsrc grant no . gr / r83712/01 ( c. castelnovo ) .
closed chains can be studied using the same correlation functions .
the only subtlety with closed chains is the existence of a non - trivial background in finite systems .
the background has to do with the topology of closed loops and must be subtracted from the tangent - tangent correlation function .
suppose that the monomers in the chain are initially indexed clockwise or anti - clockwise .
the dynamics can not change the chirality of the loop in two dimensions .
therefore , all the outer segments of the polymer running parallel to the walls of the box have correlated tangent fields . using an ensemble with random chirality
does not remove the problem because each realization , whether clockwise or anti - clockwise , would contribute a positive value to the correlation function . the background tangent field for @xmath27 monomers in a box of size @xmath92 .
the relative scale between the field vectors reflects the actual values of the tangent - tangent field ( an overall scale factor has been introduced to enhance visibility ) . notice that the average field at the boundary does not vanish . ]
the mean square displacements of closed polymers ( cp ) and open polymers ( op ) are identical at low and intermediate densities . at high densities
closed polymers seem to reach the saturation value faster . ] one can correct for this effect as follows . for
an ensemble with a given chirality , let us call the equilibrium tangent - field background @xmath93 .
we can then modify the tangent - tangent correlation function by subtracting this background field . @xmath94
\cdot \left[\vphantom{\sum } \vec{s}_{\vec{x}}(t_w ) - \vec{s}_{\textrm{ave}}(\vec{x } ) \right ] \rangle.\ ] ] the equilibrium background can be obtained at low densities via monte carlo simulations , using realizations with the same chirality and averaging over time and ensemble .
this approach becomes less and less reliable as the density increases and glassy behavior arises , because each realization is essentially stuck in a small region of configuration space over the measurement time scales .
[ fig : background ] shows the background tangent field at an intermediate density @xmath95 .
the modified tangent - tangent correlation function ( [ eq : tantanloop ] ) and the mean square displacement were measured for a closed loop of @xmath27 monomers and no qualitative difference was observed in comparison to open chains .
also @xmath91 behaves similarly in the two cases , reaching high values at high densities for closed chains as well as open chains . as shown in fig .
[ fig : msdloop ] , the mean square displacement for closed chains at high densities reaches its saturation value faster than for open chains , whereas at low and intermediate densities they are identical .
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we study the dynamics of a single chain polymer confined to a two dimensional cell .
we introduce a kinetically constrained lattice gas model that preserves the connectivity of the chain , and we use this kinetically constrained model to study the dynamics of the polymer at varying densities through monte carlo simulations . even at densities close to the fully - packed configuration , we find that the monomers comprising the chain manage to diffuse around the box with a root mean square displacement of the order of the box dimensions over time scales for which the overall geometry of the polymer is , nevertheless , largely preserved . to capture this shape persistence , we define the local tangent field and study the two - time tangent - tangent correlation function , which exhibits a glass - like behavior . in both closed and open chains ,
we observe reptational motion and reshaping through local fingering events which entail global monomer displacement .
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LOS ANGELES (AP) — A scorpion stung a woman on the hand just before her flight from Los Angeles to Portland took off.
Alaska Airlines spokesman Cole Cosgrove says Flight 567 was taxing on the runway Saturday night when the passenger was stung. He says the plane returned to the gate and the woman was checked by medics. She refused additional medical treatment but didn't get back on the plane.
Meanwhile, flight attendants killed the scorpion and checked overhead compartments for any additional unwanted arachnids. The flight then took off at 8:40 p.m., about an hour late. Members of Oregon State University's men's basketball team were on the flight, Cosgrove said.
He says it's unclear how the scorpion got on the plane, but the flight originated in Los Cabos, Mexico. ||||| A plane carrying the Oregon State men's basketball team -- and, coincidentally, Oregonian/OregonLive reporter Tyson Alger -- from Los Angeles to Portland on Saturday had to return to the gate at LAX when a woman was stung by a scorpion.
Passengers were told the scorpion hitched a ride in the carry-on bag of a passenger who had been to Mexico.
The Alaska Airlines flight landed at PDX about 11 p.m. after a 30-minute delay in Los Angeles. The University of Portland women's basketball team was on board as well.
No word yet on the condition of the woman, who remained in California for medical treatment. But the fate of the scorpion is clear: someone stomped it.
Earlier Saturday, the Beavers lost 68-55 to USC.
So this is a new one "We've been pushed back to the gate because a passenger was bit by something poisonous" soooo can we all get off? -- Tyson Alger (@tysonalger) February 15, 2015
Scorpion is the bug de jour -- Tyson Alger (@tysonalger) February 15, 2015
Coach Tinkle was just two rows behind the woman that was stung. Paramedics have just come aboard. pic.twitter.com/BPWQjkoxVi -- Mike Parker (@MEPOSU) February 15, 2015
I swear I just heard someone say "Don't worry Tinkle is taking care of it." So apparently the legend grows. -- Tyson Alger (@tysonalger) February 15, 2015
Guy saw scorpion on his shoulder flicked it off and it landed on lady and stung her. Chivalry is dead. -- Tyson Alger (@tysonalger) February 15, 2015
Tough week for Beavs just got tougher. A scorpion just bit woman two rows in front of @waynetinkle. Plane had to go back to LAX. True story. -- Oregon State Hoops (@OregonStateMBB) February 15, 2015
Landed. No more scorpions. No snakes, lizards or bears either. -- Tyson Alger (@tysonalger) February 15, 2015
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– Right up there with snakes on planes are scorpions, and the presence of one on an Alaska Airlines flight yesterday caused a bit of a stir: As the Oregonian reports, Flight 567 was taxiing on the runway at LAX when a scorpion—apparently having hitched a ride from Mexico in the bag of a returning tourist—stung a female passenger, causing the plane to return to the gate so the woman could be checked by medics. She refused additional medical treatment, notes the AP, and the flight later continued to Portland. Oregon State University's men's basketball team was aboard. As for the scorpion, an uphappy ending: Flight attendants killed it. (Meanwhile, a toddler treated for a scorpion sting had actually ingested meth.)
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Updated: Michael Wolff To Head E5 Global’s Adweek Group
Updated: Several more sources have confirmed that Michael Wolff will be joining E5 Global Media as the editorial director of the Adweek Group of magazines. While all acknowledge that major change is needed in terms of the group’s strategic direction, many are uncertain if Wolff is the person to provide it. As one source put it, “How does [E5 Global Media CEO Richard] Beckman go from Peter Kaplan to [Wolff]? Does he have a plan or is he flailing for a big name?” We will probably find out as soon as this afternoon, according to additional sources. Other sources also said that the announcement had been delayed on Friday due to Beckman being out of town. The expectation is for a formal announcement on Monday, or Wednesday at the latest. SEE ALSO: Wolff On Times: Liddle, AA Gill, Lawson And I Are Fundamentally Useless Original post: We’re hearing a great deal of rumbling about dramatic changes coming Friday to E5 Global Media’s Adweek Group, including the strong possibility that professional media provocateur Michael Wolff could be announced as the group’s editorial director. And with that, comes the expectation that after years of hanging together separately, Adweek, Brandweek and Mediaweek could eventually be combined into one single publication. Repeated emails to Wolff, who currently sits on the board of Newser.com, the aggregation site he founded three years ago, and E5 Global CEO Richard Beckman, were not returned.
At the publications, lower-level staffers are concerned and senior execs are staying mum. One exception: an elliptical evening tweet from Adweek Digital Editor Brian Morrissey predicting “tmrw should be an interesting day at the office.
Newser CEO Patrick Spain told us Thursday that he hadn’t been informed of Wolff taking the job, but said that it shouldn’t affect the company. “He blogs for us, he’s founder and a director but not actively involved in operations.” He added, “I’ve never been too focused on Michael’s outside activities.” Those include his column for Vanity Fair and a new gig as contributing editor to Wired.
Rumors that Wolff is joining E5 Global began after ex-Daily Finance media reporter Jeff Bercovici wrote that Wolff had been sighted three times at the E5 Global’s offices late last month. Both E5 Global and Daily Finance’s parent, AOL (NYSE: AOL), have offices in the same building.
E5 Global, which bought eight of Nielsen’s media-entertainment related trade mags, including The Hollywood Reporter, Billboard, Adweek, Brandweek and Mediaweek at the end of last year, has been trying to find an editorial director since the start of the summer.
More as we know it. ||||| Save E-mail Print Most Popular RSS Reprints
Wolff Named AWM Editorial Director -By Lucia Moses
Photo by Mark Schaefer Michael Wolff
Wolff brings a long history of making waves in media, as a columnist for New York magazine and Vanity Fair, founder of news aggregator Newser and author of Rupert Murdoch bio The Man Who Owns the News. He is the winner of two National Magazine Awards.
“There is no editor and writer that has more passion and edge about the media business than Michael Wolff,” said Richard Beckman, CEO of AdweekMedia parent e5 Global Media, in announcing Wolff’s hire. Beckman said e5 would be making a significant investment in its print and digital businesses to make them “the absolute cutting edge” industry voice.
Wolff, well known for taking provocative stances in his media coverage, said he saw an opportunity to use the publications to tell the story of how the media industry is undergoing what he called “one of the greatest examples of modern industrial transformation.”
“This is the opportunity we have—to not only be great for the media business, [but also] put ourselves in the sweet spot of what we’re covering,” he said. “But most of all I want to have a lot of fun covering it. I want to make some trouble.”
Wolff is the latest high-level hire by e5, which formed with the purchase of Adweek, along with The Hollywood Reporter and Billboard, from Nielsen at the beginning of the year. In May, Beckman, formerly the top ad salesman at Condé Nast, brought in celebrity newsweekly vet Janice Min to head up a relaunch of The Hollywood Reporter.
Michael Wolff, the award-winning journalist and entrepreneur, has been named editorial director of AdweekMedia, the umbrella brand of Adweek, Mediaweek and Brandweek, effective Monday, Oct. 4.Wolff brings a long history of making waves in media, as a columnist for New York magazine and Vanity Fair, founder of news aggregator Newser and author of Rupert Murdoch bio The Man Who Owns the News. He is the winner of two National Magazine Awards.“There is no editor and writer that has more passion and edge about the media business than Michael Wolff,” said Richard Beckman, CEO of AdweekMedia parent e5 Global Media, in announcing Wolff’s hire. Beckman said e5 would be making a significant investment in its print and digital businesses to make them “the absolute cutting edge” industry voice.Wolff, well known for taking provocative stances in his media coverage, said he saw an opportunity to use the publications to tell the story of how the media industry is undergoing what he called “one of the greatest examples of modern industrial transformation.”“This is the opportunity we have—to not only be great for the media business, [but also] put ourselves in the sweet spot of what we’re covering,” he said. “But most of all I want to have a lot of fun covering it. I want to make some trouble.”Wolff is the latest high-level hire by e5, which formed with the purchase of Adweek, along with The Hollywood Reporter and Billboard, from Nielsen at the beginning of the year. In May, Beckman, formerly the top ad salesman at Condé Nast, brought in celebrity newsweekly vet Janice Min to head up a relaunch of The Hollywood Reporter.
Share on LinkedIn Save E-mail Print Most Popular RSS Reprints Wolff Named AWM Editorial Director -By Lucia Moses
Michael Wolff
Wolff brings a long history of making waves in media, as a columnist for New York magazine and Vanity Fair, founder of news aggregator Newser and author of Rupert Murdoch bio The Man Who Owns the News. He is the winner of two National Magazine Awards.
“There is no editor and writer that has more passion and edge about the media business than Michael Wolff,” said Richard Beckman, CEO of AdweekMedia parent e5 Global Media, in announcing Wolff’s hire. Beckman said e5 would be making a significant investment in its print and digital businesses to make them “the absolute cutting edge” industry voice.
Wolff, well known for taking provocative stances in his media coverage, said he saw an opportunity to use the publications to tell the story of how the media industry is undergoing what he called “one of the greatest examples of modern industrial transformation.”
“This is the opportunity we have—to not only be great for the media business, [but also] put ourselves in the sweet spot of what we’re covering,” he said. “But most of all I want to have a lot of fun covering it. I want to make some trouble.”
Wolff is the latest high-level hire by e5, which formed with the purchase of Adweek, along with The Hollywood Reporter and Billboard, from Nielsen at the beginning of the year. In May, Beckman, formerly the top ad salesman at Condé Nast, brought in celebrity newsweekly vet Janice Min to head up a relaunch of The Hollywood Reporter.
Michael Wolff, the award-winning journalist and entrepreneur, has been named editorial director of AdweekMedia, the umbrella brand of Adweek, Mediaweek and Brandweek, effective Monday, Oct. 4.Wolff brings a long history of making waves in media, as a columnist for New York magazine and Vanity Fair, founder of news aggregator Newser and author of Rupert Murdoch bio The Man Who Owns the News. He is the winner of two National Magazine Awards.“There is no editor and writer that has more passion and edge about the media business than Michael Wolff,” said Richard Beckman, CEO of AdweekMedia parent e5 Global Media, in announcing Wolff’s hire. Beckman said e5 would be making a significant investment in its print and digital businesses to make them “the absolute cutting edge” industry voice.Wolff, well known for taking provocative stances in his media coverage, said he saw an opportunity to use the publications to tell the story of how the media industry is undergoing what he called “one of the greatest examples of modern industrial transformation.”“This is the opportunity we have—to not only be great for the media business, [but also] put ourselves in the sweet spot of what we’re covering,” he said. “But most of all I want to have a lot of fun covering it. I want to make some trouble.”Wolff is the latest high-level hire by e5, which formed with the purchase of Adweek, along with The Hollywood Reporter and Billboard, from Nielsen at the beginning of the year. In May, Beckman, formerly the top ad salesman at Condé Nast, brought in celebrity newsweekly vet Janice Min to head up a relaunch of The Hollywood Reporter. Subscribe to Mediaweek
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– Michael Wolff has accepted a new job as editorial director of e5's AdweekMedia, whose trade publications include Adweek, Brandweek, and Mediaweek. The Vanity Fair columnist and Newser co-founder says he plans to bring his signature iconoclastic streak to the gig. "This is the opportunity we have—to not only be great for the media business, [but also] put ourselves in the sweet spot of what we’re covering,” he tells Mediaweek. “But most of all I want to have a lot of fun covering it. I want to make some trouble." Don’t worry Off the Grid fans, Wolff’s role here at Newser will remain unchanged. “He blogs for us, he’s founder and a director but not actively involved in operations,” CEO Patrick Spain told PaidContent. “I’ve never been too focused on Michael’s outside activities.” Wolff will, however, stop writing his regular media column for Vanity Fair, instead turning in longer-form features as a contributing editor. He’ll also do plenty of writing in his new gig. “I will be the dominant voice in the Adweek constellation,” he promises.
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A rotten tooth John Lennon gave to his housekeeper may be the key to bringing the slayed former Beatle back to life. At least, that’s the hope of Michael Zuk, an Edmonton dentist who purchased the tooth back in November in the hopes of creating a clone from the rotten molar.
In a release put out to media, Zuk announced that he has sent the tooth, purchased in auction for just over $31,000, to an Penn State University where “scientists [are] considering ways to extract the genetic code from the fragile specimen.”
“I am nervous and excited at the possibility that we will be able to fully sequence John Lennon’s DNA, very soon I hope.” Zuk said in the press release. “With researchers working on ways to clone mammoths, the same technology certainly could make human cloning a reality.”
Zuk won the tooth back in November as part of an action of items belonging to former Creation Records boss Alan McGee. McGee had obtained it from family of 90-year-old Dorothy “Dot” Jarlett. According to her son, Barry, Jarlett was Lennon’s housekeeper at his Kenwood home in Weybridge from 1964 until 1968. It was during this employ that Lennon allegedly gave the tooth to Dot.
“She was very close with John, and one day whilst chatting in the kitchen, John gave my mother the tooth (he had been to the dentist to have it removed that day) and suggested giving it to my sister as a souvenir, as she was a huge Beatles fan,” he told CNN. “It has been in the family ever since.”
The tooth has spent the majority of its afterlife in Canada, coming over 42 years ago when Jartlett’s daughter married a Canadian. Once the family decided to sell it, it was moved back to Britain where it was sold to McGee. It then returned to Canada when Dr. Zuk — also the proud owner of Elvis Presley’s dental crown — purchased it.
“Many Beatles fans remember where they were when they heard John Lennon was shot.” Zuk says of his grand designs for the famous chomper. “I hope they also live to hear the day he was given another chance,”
Unfortunately for Zuck, Canada banned human cloning in 2004. In the United States, however, he might have more luck.
Fans and curious onlookers will be able to follow the progress of possibly the first human clone via the website JohnLennonTooth.com, ||||| May 2018 - Interviews with Media discussing future John Lennon Paternity Tests:
https://www.thesun.co.uk/news/6403562/dentist-john-lennon-beatles-tooth-love-children-estate/
Michael Zuk DDS announces search for John Lennon's Unknown Children
"I was recently contacted by an individual who believes John Lennon may be the person's father...there is a high chance someone is a rightful heir to some of the Beatle's estate. We will be reviewing further applications and television opportunities and discussing the legal steps that would be necessary if any of the individuals are a match."
Assorted Notes
John Lennon's Molar becomes an Inspiration for a Character in an Award Winning Novel? Amazing!!! http://www.amazon.com/The-Story-Teeth-Valeria-Luiselli/dp/1566894093
Valeria Luiselli Interview (author)
From Mexico and New York, and many places in between, a conversation with the virtuoso young writer, Valeria Luiselli. The National Book Foundation named her one of its “5 Under 35” award. An exciting new voice and original sensibility.
Who are you calling a lunatic Ms. Luiselli?' - mz
----
* "Interesting to read that Yoko actually bought celebrity body parts herself way back in 1978, buying an actual Egyptian mummy in a gold sarcophagus"- Michael Zuk (quoting from the book John Lennon, The Life by Philip Norman- p.775)
* "Song- 'Homepage of RollingStone.com' entered into the John Lennon Songwriting Contest - "Didn't win but it was worth a try!"- mz
*Statement- "John Lennon Paternity Tests may be the near term business plan that comes out of the tooth's exploration. There may be several people walking around in their early fifties with a legitimate claim to a share of the Beatle's fortune." - Michael Zuk
*Beatle DNA goldmine discussed in recent News Story
* John Lennon's Tooth featured on UK Channel 4 FAMOUS DEAD DNA
*Guinness Record Granted for JL Tooth - 'Most Expensive'
* Tooth heads to Manchester UK & sees an article in the United Airlines magazine
Celebrity Tooth Collector predicts John Lennon Clone by 2040 - Story
John Lennon Clone's Legacy Sold Off - "Why did you sell Love Me Do?!!" -Link
Quote:
"Can Lennon (or anyone else for that matter) be cloned? The answer is yes."
-Nobel Prize winning scientist Sir John Gurdon (Link)
TIME MAGAZINE : (LINK)
Quote:
"De-extinction has gone very much further, very much more rapidly than anyone ever would've imagined. " - Ross MacPhee, paleontologist
The first round of press was a snicker about the listing of a Beatle tooth at auction, then an explosion with the sale of the tooth for a record-breaking amount. This second blitz of mega-publicity is NOTHING compared to the attention this story will get when the John Lennon DNA project reaches the ultimate goal of bringing back an actual genetic replica of the late Rock Legend. Many will say the creation of a living clone of John Lennon is immoral or insane, but it can be argued otherwise. JL would have prefered to have lived a full life and continue with his efforts for PEACE. If things are left to natural progression, as seen with Elvis's massive estate, JL INC will eventually fall into the hands of people who have no genetic link to the Beatle. Perhaps the time is right to look into this venture as the Beatle's will.
Quote:
"The thing that I always say is, if you don't try, how would you know it's not possible?" - Insung Hwang, cloning expert
RELATED STORY IN THE HEADLINES:
Human cells have already been cloned and replicated for over 50 years. The story of Henrietta's Cells will shock you. It is a true story about a poor Black woman who had her cells cultured for science and they are still alive today (long after her death) in many of the labs around the world. Rich, poor, famous or unknown the issues related to genetic sciences are complex. Few will be able to make intelligent comments about these topics unless they take the time to learn more about what has already occurred behind the scenes.
Quote:
"If you don't think cloning is possible, you need to read BRINGING THEM BACK TO LIFE, National Geographic April, 2013." - Dr. Michael Zuk
HUMAN CLONING may already be happening. As mentioned in the article above, while you are reading this we know at least one species in Australia is being brought back to life with advanced cloning techniques. If man drove something into extinction, doesn't it seem right to try to bring it/him/her back?
The John Lennon DNA investigation may provide the essentials needed to allow the possibility of an exact genetic clone in the not too distant future. Hank Greely, who is a leading bioethicist at Sanford, commented on bringing back extinct animals as 'really cool'...we wonder what he would say about a Beatle? Groovy?
In a recent interview Harvard synthetic biologist George Church said:
"...reading and writing DNA is now about a million times faster than seven or eight years ago. Another technology that the de-extinction of a Neanderthal would require is human cloning. We can clone all kinds of mammals, so it's very likely that we could clone a human. Why shouldn't we be able to do so?"
"The Tooth gets into Rolling Stone again?"
---------------------------------------------------------------------------------
The John Lennon Tooth recently visited New York City. It participated in the filming of an episode of 'Oddities', visited the Sirius Radio Studio for an interview, dropped off a photo for Anderson Cooper and visited the Dakota on the anniversary of John Lennon's passing. A following trip brought the famous tooth to London, Liverpool and Leeds with a visit to the Beatles Museum.
Dr. Michael Zuk with some of the cast of Oddities and a few pieces of his celebrity dental collection (JLT may appear in an episode). Zuk later purchased some teeth oddities from Ryan (not shown).
The Tooth's Story
The tooth of the matter is John Lennon was such a massive star in the world of music, that a crazy dentist was willing look like an idiot and invest over $30,000 US to buy it. Within 36 hours literally hundreds of millions of people discovered the fate of a small rotten molar and experts in marketing began to applaud the idea. A Kardashian quickie divorce, the Justin Bieber scandal and the Michael Jackson murder trial were surpassed by the news of the John Lennon Tooth auction. One error in the news relates to the chain of ownership - Alan McGee did not own the tooth - he simply was selling items at the same auction at which the tooth was sold.
The obsessed dentist went into overdrive and immediately pumped the press for more exposure, dreamed up a number of charity ideas, wrote a song parody, arranged a photo shoot, designed a DNA sculpture and worked behind the scenes on the DNA mystery. This was not just a rotten stinky tooth...it was an actual physical specimen of a historical figure worth more by weight and size than any other element on earth. (Read more in his book "john Lennon Tooth" - on blurb.com)
"I think it's pretty clear now that John Lennon has a magical power down to the dust of his rotten molar. He gave it to a fan, and I'm thrilled to be able to chosen to share his influence for charity, entertainment and science," says Zuk.
ABOUT Dr. Michael Zuk
As a practising dentist, Dr. Zuk is kept busy with a general practice that provides a new style of extreme smile makeover treatment which you never see on TV. He is an advocate against the reckless use of porcelain veneers and has used some of the notoriety from buying a few celebrity teeth to raise his platform on this issue. As a marketing expert who has competed in high level competitions within the GKIC organization he rubs elbows with many of the most innovative people in the world. His interests include cartooning, songwriting, and marketing development. Dr. Zuk is a marketing consultant to several dental programs and is auditioning for a position with a 1-800 -(Confidential) company. He has a number of books on Blurb.com and made headlines with his first best selling book 'Confessions of a Former Cosmetic Dentist' which was mentioned in the New York Times and reviewed favourably by this critic
Did you know?
'Zuk' translates into the word 'beetle' in Russian/Ukrainian and Dr. Zuk lived the first few years of his life in NYC only a few blocks away from where John Lennon lived the last of his. While the two never met Dr. Zuk has met many people who have shared stories about their experiences with JL.
-----------------------------------------------------------------------------------------------------------------------------------------------------------
SONG: Love Me Tooth -parody written by Michael Zuk & performed by Curtis Phagoo- as played on Sirius radio with Jay Thomas
(click at your own risk)
|
– Remember when a Canadian dentist bought one of John Lennon's teeth for $31,000 in November 2011? Turns out Michael Zuk wanted to do more with the molar than display it on a shelf. Zuk hopes he can use the decaying tooth to clone the dead Beatle. Seriously. Zuk explains in a press release that he has shipped the tooth to Penn State University, where scientists will hopefully "extract the genetic code." Next steps: first, scientists figure how to clone mammoths; then Zuk simply applies that technology to Lennon's DNA. No problem! One bummer for Zuk (who also own Elvis Presley's dental crown), per Canada.com: His country banned human cloning in 2004, so he'll have to continue to chase his dream outside its boundaries. Keep up with his effort at JohnLennonTooth.com.
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Celebrity Photos: February 2014 Hilary Duff was all smiles in LA on Feb. 21.
Celebrity Photos: February 2014 Sofia Vergara filmed scenes on the beach in Sydney, Australia on Feb. 21.
Celebrity Photos: February 2014 Taylor Swift was seen leaving the gym in West Hollywood, Calif. after a workout on Feb. 21.
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Celebrity Photos: February 2014 AnnaSophia Robb attended Ringling Bros. and Barnum & Bailey presents "Legends" at Barclays Center in Brooklyn, NY, on Feb. 20.
Celebrity Photos: February 2014 "American Idol" judges Keith Urban, Jennifer Lopez, Harry Connick, Jr., host Ryan Seacrest and former judge Randy Jackson attended the show's after-party in West Hollywood on Feb. 20.
Celebrity Photos: February 2014 Sofia Vergara and Sarah Hyland filmed a scene for "Modern Family" in Sydney, Australia, on Feb. 20.
Celebrity Photos: February 2014 Kanye West protected himself from the cold in NYC on Feb. 20.
Celebrity Photos: February 2014 Padma Lakshmi stepped out in SoHo, NYC, on Feb. 20.
Celebrity Photos: February 2014 Beyonce performed her hit song "XO" at the 2014 Brit Awards at the 02 Arena in London, England on Feb. 19.
Celebrity Photos: February 2014 Swimsuit model Anne V rocked a black bikini at the beach in Miami Feb. 19.
Celebrity Photos: February 2014 Ashley Greene worked on her fitness at Tracy Anderson Studios in Studio City, Calif. on Feb. 19.
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Celebrity Photos: February 2014 Selena Gomez grabbed coffee with a friend in Studio City, Calif. on Feb. 19.
Celebrity Photos: February 2014 Jesse Tyler Ferguson and Eric Stonestreet filmed scenes for "Modern Family" in Sydney, Australia on Feb. 18.
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Celebrity Photos: February 2014 Reese Witherspoon looked lovely at lunch in Brentwood, Calif., Feb. 18.
Celebrity Photos: February 2014 Ellen Page, who came out as gay last week to much support from her Hollywood peers, was seen heading out of LAX on Feb. 18.
Celebrity Photos: February 2014 Debra Messing arrived at the "Today" show studio in NYC on Feb. 18.
Celebrity Photos: February 2014 "The Tonight Show Starring Jimmy Fallon" premiered Feb. 17 with guest Will Smith.
Celebrity Photos: February 2014 Amber Heard made an appearance on "Late Show with David Letterman" in NYC, Feb. 17.
Celebrity Photos: February 2014 Kourtney and Khloe Kardashian touched down at LAX on Feb. 17.
Celebrity Photos: February 2014 Angelina Jolie and Brad Pitt attended the BAFTA Awards held at The Royal Opera House on Feb. 16 in London, England.
Celebrity Photos: February 2014 Lupita Nyong'o attended the BAFTA Awards held at The Royal Opera House on Feb. 16 in London, England.
Celebrity Photos: February 2014 Leonardo DiCaprio attended the BAFTA Awards held at The Royal Opera House on Feb. 16 in London, England.
Celebrity Photos: February 2014 Dakota Johnson went on a run on the set of "Fifty Shades of Grey" in Vancouver, Feb. 14.
Celebrity Photos: February 2014 Taylor Swift headed to dance class in LA on Feb. 14.
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Celebrity Photos: February 2014 Vogue Editor-in-Chief Anna Wintour, and actresses Lupita Nyong'o and Naomi Watts attended the Calvin Klein Collection fashion show during Mercedes-Benz Fashion Week Fall 2014 at Spring Studios on Feb. 13.
Celebrity Photos: February 2014 Anna Kendrick attended the J. Mendel fashion show during Mercedes-Benz Fashion Week Fall 2014 at The Theatre at Lincoln Center in NYC on Feb. 13.
Celebrity Photos: February 2014 Kristen Stewart was spotted en route to a meeting in Hollywood on Feb. 13.
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Celebrity Photos: February 2014 Taylor Swift went shopping in Hollywood on Feb. 13.
Celebrity Photos: February 2014 Johnny Depp and his fiancee Amber Heard arrived at the premiere of "3 Days To Kill" at the Arclight Theatre on Feb. 12 in LA.
Celebrity Photos: February 2014 Kanye West attended the "River Of Fundament" world premiere at BAM Harvey Theater on Feb. 12 in NYC.
Celebrity Photos: February 2014 Jennifer Lopez took part in a photo shoot on a yacht in Miami, Florida on Feb. 12.
Celebrity Photos: February 2014 Selena Gomez grabbed slurpees with some friends in LA on Feb. 12.
Celebrity Photos: February 2014 Blake Lively posed backstage at the Michael Kors fashion show during Mercedes-Benz Fashion Week Fall 2014 at Spring Studios on Feb. 12.
Celebrity Photos: February 2014 Malin Akerman stopped to refuel her car in West Hollywood, Calif. on Feb. 12.
Celebrity Photos: February 2014 Anna Faris was all smiles as she left a nail salon in West Hollywood, Calif. on Feb. 12.
Celebrity Photos: February 2014 Chrissy Teigen arrived at the Badgley Mischka show during New York Fashion Week on Feb. 11.
Celebrity News: February 2014 <a href="http://www.huffingtonpost.com/2014/02/11/shirley-temple-dead-child-star-ambassador-dies_n_4765333.html?utm_hp_ref=celebrity" target="_blank">Shirley Temple Black</a>, iconic child star and former U.S. ambassador to Ghana and Czechoslovakia, died on Feb. 10 in California. Cause of death was not released. She was 85.
Celebrity Photos: February 2014 Olivia Munn attended the premiere of "Robocop" on Feb. 10 in Hollywood, Calif.
Celebrity Photos: February 2014 Katie Holmes, Rita Ora, Trudie Styler, Deborra-Lee Furness and Hugh Jackman attended the Donna Karan New York 30th Anniversary fashion show during Mercedes-Benz Fashion Week Fall 2014, on Feb. 10.
Celebrity Photos: February 2014 Academy Award nominees, including Sandra Bullock, Amy Adams, Philippe Le Sourd, Alfonso Cuaron, Karen O, and Leonardo DiCaprio, attended the 86th Academy Awards nominee luncheon at The Beverly Hilton Hotel on Feb. 10.
Celebrity Photos: February 2014 Jeremy Piven got ready for a ride on the Can-Am Spyder in Los Angeles, Calif. on Feb. 10. ||||| Happy 70th, Keith Richards!
Since the band was founded in 1962, Richards has been rocking as the Rolling Stones' guitarist. He is credited as one of the best guitarists of all time by Rolling Stone magazine and has penned some of the most famous songs -- including the Stones' famous "Satisfaction." He doesn't seem to be slowing down anytime soon, as the band has tour dates set for 2014.
CORRECTION: In a previous version of this article, it was stated that Keith Richards founded the Rolling Stones. Brian Jones, who left the band about a month prior to his death in 1969, actually started the group.
Also on HuffPost:
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– Not many would think of Brad Pitt as a card-carrying member of AARP, but the actor turns 50 today, which makes him eligible to join—and the organization isn't exactly letting him forget it. It put out a mock cover of its magazine featuring a picture of Pitt, People reports, along with the message: "Acclaimed Actor, Producer, Humanitarian, and Family Man, Mr. Pitt Joins the Club." See it here. More senior celebrity birthdays today: Keith Richards is 70 and Steven Spielberg is 67.
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the strong coupling between condensed matter and quantum light is a core issue of present day quantum optics . realized by exposing the matter with intense quantum field
, it can manifest itself in different quantum systems such as single atoms and ultracold atomic beams @xcite , semiconductor heterostructures @xcite , bose
einstein condensates @xcite , _ etc .
_ albeit these systems are of different physical nature , their interaction with quantum light is governed by common rules . in the strong coupling regime
, these systems enable the generation of different states of quantum light single photons @xcite , fock states @xcite , fock qubits , quantum states with arbitrary photon number distribution @xcite .
that constitutes a basis for the quantum information processing @xcite and quantum metrology @xcite . in practice , the strong light
matter coupling regime can be realized in two ways : by combining the matter with a high - q microcavity or by exposing the matter to a ultrashort intense pump pulse . to describe the strong coupling between an arbitrary two level system and quantum light , the jaynes cummings ( jc ) model is conventionally used @xcite .
one of the most fundamental phenomenon predicted within the jc model is the oscillation of the population between levels with the rabi frequency ( rabi oscillations ) .
however , the standard jc model does not account for a number of physical factors , which , under certain conditions , may significantly influence the rabi effect .
domain modulation of the field
matter coupling constant @xcite and interplay between classical driving field and quantized cavity field @xcite can serve as examples .
more advanced jc models involve additional interaction mechanisms and effects , such as dipole
dipole ( d d ) interaction @xcite , exction phonon coupuling @xcite , and self induced transparency @xcite .
d interaction between two quantum oscillators leads to radiative coupling of them and , as a result , to exchange by the excited state .
that is , rabi oscillations between these two oscillators occur ; see ref .
for a theory and ref .
for the experimental observation in a double quantum dot ( qd ) system . as a whole , the observation and intensive studying of excitonic rabi oscillations @xcite motivates the extension of the jc model to incorporate specific interactions inherent to confined exciton in a host . in the given paper we present a microscopic theory of the interaction of an isolated qd with quantum light for both weak and strong coupling regimes .
we incorporate the local field correction into the jc model as an additional physical mechanism influencing the rabi effect in a qd exposed to quantum light .
in particular , the rabi oscillations are shown to exist even in the limit of a weak incident field . in the weak coupling regime ,
the local field effects in optical properties of qds have been theoretically investigated in refs . for classical exposing light and in ref . for quantum light . in the latter case
it has been shown that for a qd interacting with fock qubits the local fields induce a fine structure of the absorption ( emission ) spectrum : instead of a single line with the frequency corresponding to the exciton transition , a doublet appears with one component shifted to the blue ( red ) .
the intensities of components are completely determined by the quantum light statistics . in the limiting cases of classical light and fock
states the doublet is reduced to a singlet shifted in the former case and unshifted in the latter one .
the role of local fields in the excitonic rabi oscillations in an isolated qd driven by classical excitation was investigated in ref . .
two different oscillatory regimes separated by the bifurcation have been predicted to exist .
the rabi oscillations were predicted to be non - isochronous and arising in the weak excitation regime .
both peculiarities have been experimentally observed by mitsumori _
_ in ref . where the rabi oscillations of excitons localized to quantum islands in a single quantum well were investigated
there exist several different physical interpretations of local field in qds and , correspondingly , different ways of its theoretical description . the first model ( scheme a in the terminology of ref . ) exploits the standard electrodynamical picture : by virtue of external field screening by charges induced on the qd surface ( the quasistatic coulomb electron
hole interactions ) a depolarization field is formed differentiating the local ( acting ) field in the qd and external incident field . in this model
the total electromagnetic field is not pure transverse .
alternatively , only transverse component is attributed to the electromagnetic field , while the longitudinal component is accounted for through the exchange electron
hole interactions ( scheme b accordingly ref . ) .
both approaches are physically equivalent and lead to identical results . in the present paper
we build the analysis on the general microscopic quantum electrodynamical ( qed ) approach where the local field correction originates from the exchange by virtual vacuum photons between electrons and holes forming the exciton and thus is a manifestation of the dipole
dipole ( d d ) interaction between electrons and holes ( the dynamical coulomb interaction ) @xcite .
the approach allows us to overcome a number of principal difficulties related to the field quantization in qds @xcite . in the analysis , approximate solution of the many
body problem is built on the hartree
bogoliubov self consistent field concept @xcite .
the self - consistent technique leads to a separate term in the effective hamiltonian responsible for the interaction of operators and average values of physical quantities .
due to this term the quantum mechanical equations of motion become nonlinear and require numerical integration .
the paper is arranged as follows . in sect .
[ sec : theory ] we develop theoretical model describing the qd quantum light interaction .
we formulate a model hamiltonian with the separate term accounting for the local field correction and corresponding equations of motion . in sect .
[ sec : free_mot ] we analyze the manifestation of local fields in the motion of the qd exciton in the absence of external field . in sec .
[ sec : weak_f_lim ] we investigate the qd interaction with arbitrary state of quantum light in the weak driving field regime .
[ sec : rabioscillations ] is devoted to the theoretical analysis of local field influence on the rabi oscillations in the qd exposed to coherent states of light and fock qubits .
a discussion of the results obtained is presented in sect .
[ sec : discussion ] and concluding remarks are given in sect .
[ sec : conclusion ] .
in this section we formulate the interaction hamiltonian for a qd exposed to quantized field accounting for the local field correction . later on we exploit the hamiltonian for the derivation of equations of motions describing dynamical properties of this system . as aforementioned ,
the local field in qd differs from the incident one due to the d
d electrons holes interaction . a general formalism accounting for the d
d interactions in atomic many body systems exposed to photons has been developed in refs . as applied to nonlinear optics of bose
einstein condensates @xcite .
we extend this formalism to the case of the qd exciton driven by quantized light .
consider an isolated qd exposed to quantized electromagnetic field .
the electron
hole pairs in qd are assumed to be strongly confined ; thus we neglect the static coulomb interaction between electrons and holes .
we decompose the operator of the total electromagnetic field into two components . the first one , @xmath0 , represents a set of modes that do not contain real photons .
the second component , @xmath1 , represents the set of modes emitted by the external source of light ( real photons ) .
such a decomposition as well as the subsequent separate consideration of the field components is analogous to the heisenberg
langvein approach in the quantum theory of damping , see ref . .
the total hamiltonian of the system
qd+electromagnetic field
is then represented as @xmath2 where @xmath3 are the hamiltonians of the qd free charge carriers , the incident photons and the virtual vacuum photons , respectively .
the terms @xmath4 describe the interaction of electron hole pair with incident quantum field @xmath1 and with vacuum field @xmath0 , respectively . in the dipole approximation
these hamiltonians are given by @xmath5 where @xmath6 is the qd volume and @xmath7 is the qd polarization operator .
the hamiltonian @xmath8 is as follows @xmath9 where @xmath10 and @xmath11 are the creation and annihilation operators of vacuum photons , @xmath12 is the mode index , indexes @xmath13 denote the field polarization .
the operator of vacuum electromagnetic field @xmath0 is determined as @xmath14 where @xmath15 is the normalization volume and @xmath16 is the polarization unit vector . as a first step in the development of our theory we eliminate from the consideration the exchange interactions and
proceed to the direct interactions . for that purpose
, we exclude the vacuum photon operators @xmath11 and @xmath10 expressing them ( and corresponding hamiltonians @xmath17 and @xmath18 ) in terms of the polarization operator @xmath19 . recalling the heisenberg equation @xmath20 $ ] ,
the expression as follows can be obtained , @xmath21 where @xmath22 .
solution of eq .
( [ dif_eq_operator_b ] ) is given by @xmath23 with the first term describing the free evolution of the reservoir modes ( quantum noise ) and the second one responsible for the exchange interactions .
further we neglect the first term in ( [ eq_operator_b ] ) leaving the quantum noise beyond the consideration . inserting then this equation into ( [ field_operator_ev ] ) and the resulting expression into hamiltonian ( [ hamil_hamiv ] ) , after some algebra we arrive at @xmath24 where indexes @xmath25 , @xmath26 mark cartesian projections of vectors .
the summation over repetitive indexes is assumed . using the relationship @xcite @xmath27 we proceed to the limit @xmath28 in ( [ hamil ] ) .
that corresponds to the replacement @xmath29\rightarrow\frac{\omega}{(2\pi)^3}\int{[\cdot]}d^3\textbf{k}\ , .
\nonumber\end{aligned}\ ] ] then , utilizing the markov property of the polarization operator , @xmath30 [ ] , the hamiltonian ( [ hamil ] ) is reduced to @xmath31 where @xmath32\,,\label{green_funct}\end{aligned}\ ] ] is the free - space green function @xcite and @xmath33 is the dirac delta function .
evaluation of @xmath34 in ( [ ham_hv ] ) is carried out analogously and gives @xmath35 . as the next step
, we adopt the quasi static approximation , which utilizes the property of qd to be electrically small .
the approximation implies the limit transition @xmath36 and the neglect the terms @xmath37 in hamiltonian ( [ ham_hil_final ] ) .
then , the hamiltonians @xmath38 and @xmath39 are represented by the sum as follows @xmath40 where @xmath41 is the free space green tensor ; @xmath42 is the operator dyadic acting on variables @xmath43 . in the quasi
static approximation we neglect the line broadening due to the dephasing and the spontaneous emission .
the latter effect can be introduced in the model by retaining terms @xmath44 in the the quasi static approximation . in the preceding analysis
we have suggested that the exchange by virtual photons of all modes occurs between all allowed dipole transitions .
that is , on that stage the problem was stated as a quantum
mechanical many body problem .
the analysis can be significantly simplified if we restrict ourselves to the two level approximation assuming the exciton transition frequency to be resonant with the acting field carrier frequency and utilize the self consistent field model .
the self consistent field is introduced by means of the hartree fock
bogoliubov approximation @xcite , which implies the linearization of hamiltonian ( [ deltah ] ) by the substitution @xmath45 the polarization operator of two - level system is given by @xcite @xmath46 where @xmath47 are the pauli pseudospin operators and @xmath48 is the wavefunction of the electron
hole pair . in the strong confinement regime
this function is assumed to be turns out to be the same both in excited and ground states @xcite .
in the two level approximation , the hamiltonian of the carriers motion is represented as @xmath49 where @xmath50 and @xmath51/@xmath52 are the energy eigenvalues and creation / annihilation operators of the exciton ; indices @xmath53 and @xmath54 correspond to the excitonic excited and ground states , respectively .
the acting field operator is expressed by the relation ( [ field_operator_ev ] ) after the substitutions @xmath55 and @xmath56 ; @xmath57 are the creation / annihilation operators of the incident ( real ) photons ( the polarization index @xmath58 is included in the mode number @xmath59 ) .
formally , the relation ( [ eq_operator_b ] ) is fulfilled for operators @xmath60 and @xmath61 too , and the first term describes the evolution of real photons . however , since the exchange interaction is included into the vacuum field component , in the case of real photons the second term in relation ( [ eq_operator_b ] ) disappears .
then , the hamiltonian @xmath62 is given by the relation ( [ ham_hv ] ) after the substitution @xmath63 and @xmath64 . for shortness ,
we denote @xmath65 and @xmath66 .
note that nonresonant transitions can be approximately accounted through a real valued frequency
independent background dielectric function @xmath67 . assuming @xmath67 to be equal to dielectric function of surrounding medium , we put further @xmath68 without loss of generality .
substitutions in final expressions @xmath69 and @xmath70 for the speed of light and the electron - hole pair dipole moment , respectively , will restore the case @xmath71 . as a next step
we introduce the rotating wave approximation @xcite , i.e. , we neglect in ( [ ham_hil_final ] ) the terms that are responsible for the simultaneous creation / annihilation of exciton - exciton and exciton - photon pairs . then , using expressions ( [ hamil_hamiv ] ) , ( [ ham_hv ] ) and ( [ ham_hil_final])([polarization_operator ] ) , after some algebra we derive the effective two particle hamiltonian @xmath72 where @xmath73 is the coupling factor for photons and carriers in the qd and @xmath74 is the radius vector of the qd geometrical center .
the depolarization tensor is given by @xmath75 noted that the resulting hamiltonian ( [ two_body_ham ] ) coincides with that obtained in ref .
in independent way .
let @xmath76 be a wavefunction of a qd interacting with quantum light . in the interaction representation
the system is described by the schrdinger equation @xmath77 with @xmath78|\widetilde\psi(t)\rangle$ ] and @xmath79(\widehat{{\cal h}}_\mathrm{i0}+\delta\widehat{{\cal h } } ) \exp[-(i\widehat{{\cal h}}_0+\widehat{{\cal h}}_{\rm{ph}})t/\hbar]$ ] .
we represent the wavefunction @xmath80 by the sum as follows @xmath81|\{n_{k}\}\rangle\ , , \label{wavefunct}\ ] ] where @xmath82 and @xmath83 are coefficients to be found , @xmath84 denotes the multimode field state with @xmath85 photons in @xmath12 mode ; @xmath86 is the wavefunction of the vacuum state of electromagnetic field ; @xmath87 and @xmath88 are the wavefunctions of the qd ground and excited states , respectively . by inserting the relation ( [ wavefunct ] ) into the schrdinger equation ( [ schrod ] ) , after some manipulations we arrive at the system of equations of motion @xmath89 with @xmath90 as the local field induced depolarization shift @xcite . here
@xmath91 is exciton transition frequency .
it can easily be shown that system ( [ eq_mot_bas0 ] ) satisfies the conservation law @xmath92 the system ( [ eq_mot_bas0 ] ) allows analyzing the interaction between qd and electromagnetic field of an arbitrary spatial configuration and arbitrary polarization . letting the coefficients @xmath93 to be adiabatically slow varying functions we can apply ( [ eq_mot_bas0 ] ) to qds exposed to electromagnetic pulse . among different physical situations described by eqs .
( [ eq_mot_bas0 ] ) the single - mode excitation is of special interest .
indeed , such a case corresponds , for instance , to the light qd interaction in a microcavity with a particular mode resonant with the qd exciton .
owing to the high q - factor , the strong light
qd coupling regime is feasible in microcavity providing numerous potential applications of such systems @xcite . for the case of a spherical qd interacting with single
mode light , only the components @xmath94 with @xmath59 as the number of interacting mode are accounted for in the wavefunction ( [ wavefunct ] ) . then , omitting for shortness the mode number , the system ( [ bas0 ] ) is reduced to @xmath95 note that the conservation law ( [ conserv_law ] ) holds true for eqs .
( [ bas1 ] ) with the substitution @xmath96 .
equations ( [ eq_mot_bas0 ] ) and ( [ bas1 ] ) govern the time evolution of the qd driven by quantum light .
the free motion regime implies neglect the qd electromagnetic field interaction and thus imposes the condition @xmath97 on eqs .
( [ eq_mot_bas ] ) .
wavefunction of the noninteracting qd and electromagnetic field is factorized thus allowing analytical solution of ( [ eq_mot_bas ] ) in the form of @xmath98 where @xmath99 are arbitrary constants satisfying the normalization condition @xmath100 . in that case
the system ( [ eq_mot_bas ] ) is reduced to the exactly integrable form @xmath101 and its solution is given by @xmath102 here @xmath103 and @xmath104 are arbitrary constants satisfying the condition @xmath105 . this solution describes a _ correlated _ motion of the electron - hole pair resulted from the local field induced self - polarization of the qd .
thus , a quasi particle with the wavefunction @xmath106 appears in the qd .
it can easily be shown that the state ( [ wavefunct_fm ] ) satisfies the energy and probability conservation laws .
the inversion , which is defined as the difference between the excited state and the ground - state populations of the qd exciton , for the wavefunction ( [ wavefunct_fm ] ) remains constant in time : @xmath107 , whereas this state is generally non - stationary .
the quasi particle lifetime , which is not included in our model , can be estimated by @xmath108 , where @xmath109 is the qd
exciton spontaneous decay rate . for realistic qds @xmath110 [ ] .
consequently , the state @xmath76 can be treated as stationary within the range @xmath111 .
the macroscopic polarization of the qd is described by @xmath112 where the parameter @xmath113 plays the role of the self induced detuning , which depends on the state occupied by the exciton and on the depolarization shift .
thus , as follows from ( [ polarization_fm ] ) , the local field induced depolarization shift ( @xmath114 ) dictates the _ non - isochronism _ of the polarization oscillations , i.e. the dependence of the oscillations frequency on its amplitude .
this mechanism also influences the rabi oscillations in the system : the smaller @xmath115 the larger rabi oscillations amplitude ; such a behavior was observed experimentally in ref . .
since the inversion @xmath116 lies within the range @xmath117 , the frequency @xmath118 of polarization oscillations in ( [ polarization_fm ] ) may vary in the limits @xmath119 . on the contrary , when @xmath120 the polarization oscillates with the fixed frequency @xmath121 . at first glance
, it seems that the discrete level is transformed into @xmath122 band .
however this is not the case .
indeed , the concept of the band structure corresponds to linear systems where any arbitrary state is a superposition of eigenmodes with different frequencies . as different from that , the electron
hole correlation arises from the nonlinear motion of the particles in a self - consistent field .
consequently , in the presence of light qd interaction ( @xmath123 ) , the exciton motion can not be described by a simple superposition of different partial solutions like ( [ sol_eqs_fm ] ) , but has significantly more complicate behavior . in particular ,
in the strong coupling regime there exist two oscillatory regimes with drastically different characteristics separated by the bifurcation , see sec .
[ sec : rabioscillations ] .
consider a ground state qd be exposed to an arbitrary state of quantum light @xmath124 , where @xmath125 are arbitrary complex valued coefficients satisfying the condition @xmath126 .
then , the initial conditions for eqs .
( [ eq_mot_bas0 ] ) are given by @xmath127 in the linear regime with respect to the electromagnetic field which realized when @xmath128 we can assume @xmath129 , i.e. the analysis is restricted to the time interval much less than the relaxation time of the given exciton state .
then , the system ( [ bas0 ] ) is reduced to @xmath130 for further analysis we rewrite ( [ eq_mot_weak_field ] ) in more convenient matrix notation : @xmath131 where @xmath132 , @xmath133 and @xmath134 are the columnar matrices ( vectors ) and @xmath135 .
vectors @xmath136 and @xmath134 are defined analogously through the elements @xmath137 and @xmath138 , respectively ; @xmath139 is the kroneker symbol .
the quantity @xmath140 is the density matrix of quantum light interacting with the qd .
this matrix corresponds to the pure state of electromagnetic field and satisfies the conditions @xmath141 ( @xmath142 ) and @xmath143 ( where @xmath144 is the unit matrix ) .
integration of ( [ eq_mot_weak_field_matrix_form ] ) imposed by initial conditions ( [ init_cond_arb_field ] ) allows us to find the analytical solution @xmath145 using the truncated taylor expansion @xcite @xmath146 after some standard manipulations we obtain @xmath147\ , .
\label{sol_full}\end{aligned}\ ] ] this expression describes the interaction between the qd and an arbitrary state of quantum field in the weak field limit .
now let us calculate the qd effective scattering cross - section defined by @xmath148 substituting ( [ sol_full ] ) into ( [ cross_section ] ) , after some algebra we arrive at @xmath149 where @xmath150 and @xmath151 , @xmath152 .
the equation obtained demonstrates a fine structure of the absorption in a qd exposed to quantum light with arbitrary statistics . instead of a single line with the exciton transition frequency @xmath152
, a doublet appears with one component shifted to the blue : @xmath153 .
the intensities of components are completely determined by the quantum light statistics .
the same peculiarity has been revealed in ref . in a particular case of a qd exposed to the single
mode fock qubit .
obviously , this result directly follows from ( [ cross_section_final ] ) if we retain in this equation only terms corresponding the mode considered .
the single
mode fock qubit is a superposition of two arbitrary fock states with fixed number of photons and is described by the wavefunction ( the mode index @xmath59 is omitted ) @xmath154 consequently , at @xmath155 the nonzero components of the vector @xmath156 are @xmath157 and @xmath158 .
it can easily be found that in that case eq . ( [ cross_section_final ] )
is reduced to eq .
( 61 ) from ref . .
in the case @xmath159 the only nonzero component @xmath160 survives in ( [ cross_section_final ] ) thus reducing this equation to eq .
( 67 ) from ref . .
for the single fock state @xmath161 and we obtain @xmath162 , i.e. , in agreement with ref .
, only shifted spectral line is presented in the effective cross section . for the qd exposed to coherent states the recurrent formula @xmath163
can easily be obtained , where @xmath164 stands for the photon number mean value . using this formula
the relation @xmath165 can be obtained , which gives @xmath166 .
thus , for this case only shifted line in the effective cross section is manifested .
analogous result has been reported in for a qd driven by classical electromagnetic field .
such a coincidence can be treated as the manifestation of well known concept : among a variety of quantum states of light the coherent states are most close to classical electromagnetic field .
in the case when the coupling constant is comparable in value with the exciton decay rate , the linearization with respect to electromagnetic field utilized in the previous section is no longer admissible . the strong coupling regime can be realized by combining the qd with a high - q microcavity and one of its manifestation is the rabi oscillations of the levels population in a two level system exposed to a strong electromagnetic wave . in this section
we utilize the system of equations ( [ eq_mot_bas ] ) for investigation of the interaction between qd and single
mode quantum light .
the incident field statistics is exemplified by coherent states and fock qubits . in the standard jc model
the rabi oscillations picture is characterized by the following parameters@xcite : ( i ) the coupling constant @xmath167 ; ( ii ) the frequency detuning @xmath168 ; ( iii ) the initial distribution of photonic states in quantum light and ( iv ) the average photon number @xmath164 .
accounting for the local field correction supplements this set with the new parameter , the depolarization shift @xmath169 . for convenience ,
we introduce the depolarization shift by means of the parameter@xcite @xmath170 which compares the shift with the rabi frequency @xmath171 . to understand the dynamical property of the rabi effect we have investigated the following four physical characteristics : the qd
exciton inversion @xmath172 the time evolution of the distribution of photonic states @xmath173 and the normally ordered normalized time
zero second order correlation function of the driving field : @xmath174 ^ 2}\ , .
\label{corr_funct_shrod}\end{aligned}\ ] ] the temporal evolution of the inversion can be detected in pump probe experiments @xcite , while the photonic state distribution ( [ population_distribution ] ) is measurable in quantum nondemolition experiments with atoms @xcite . and
@xmath175 ( a ) , @xmath176 ( b ) , @xmath177 ( c ) , @xmath178 ( d ) , @xmath179 ( e ) , @xmath180 ( f ) .
, width=316 ] and @xmath177 ( a ) , @xmath178 ( b ) , @xmath180 ( c).,width=288 ] let a ground state qd be exposed to the elementary coherent state of light @xmath181
, where@xcite @xmath182}\langle{n(0)}\rangle^{{n}/{2}}/{\sqrt{n!}}$ ] . then , initial conditions for eqs .
( [ bas1 ] ) are given by @xmath183 figures [ fig_cs1_inv ] and [ fig_cs2_inv ] show calculations of the inversion in a lossless qd as a function of the dimensionless time @xmath184 at the exact synchronism ( @xmath185 ) for two different initial photon mean numbers @xmath186 and for several values of parameter @xmath187 .
our calculations demonstrate the appearance of two completely different oscillatory regimes in the rabi oscillations .
the first one manifests itself at @xmath188 and is characterized by periodic oscillations of the inversion within the range @xmath189 ( see figs .
[ fig_cs1_inv]a , [ fig_cs1_inv]b ) .
thus , in this regime the inverted population is unreachable . on the contrary , in the second regime
, at @xmath190 , the inversion oscillates in the range @xmath191 ( figs .
[ fig_cs1_inv]c[fig_cs1_inv]f and fig . [ fig_cs2_inv ] ) .
these two regimes of the rabi effect are separated by the bifurcation which occurs at @xmath192 for both types of incident coherent states ( compare figs .
[ fig_cs1_inv]b and [ fig_cs1_inv]c ) . in the limit @xmath193 ( @xmath194 )
the contribution of terms @xmath195 in eqs .
( [ bas1 ] ) is small .
the neglect these terms corresponds to the elimination of the local field effect . in this case
the system ( [ bas1 ] ) is reduced to that follows from the standard jc model @xcite , allowing thus the analytical solution : @xmath196 \cr \rule{0in}{5ex } & -&|b_{0}(0)|^2\ , , \label{jc_sol}\end{aligned}\ ] ] where @xmath197 . the fundamental effect predicted by this solution
is the collapse
revivals phenomenon in the time evolution of the inversion @xcite .
we have found that at @xmath198 the numerical simulation by eqs .
( [ bas1 ] ) leads to the same result as analytics ( [ jc_sol ] ) , see fig .
[ fig_cs1_inv]f . in the case
@xmath199 the amplitude of rabi oscillations tends to zero and @xmath200 . of qd exposed to the coherent state of light with @xmath201 and
@xmath180 ( _ 1 _ ) , @xmath202 ( _ 2 _ ) , @xmath178 ( _ 3 _ ) , width=288 ] for a single qd imposed to classical light the appearance of two oscillatory regimes in rabi oscillations separated by the bifurcation at @xmath203 has been predicted in ref . .
accordingly to [ ] , the region @xmath190 corresponds to periodic anharmonic oscillations of the inversion . as different from that , in a qd exposed to quantum light the collapse
revivals phenomenon takes place in this region , see figs .
[ fig_cs1_inv]c f and [ fig_cs2_inv ] . as figs .
[ fig_cs1_inv]f and [ fig_cs2_inv]c demonstrate , the collapse and the revivals in the vicinity of the bifurcation are deformed and turn out to be drastically different from those predicted by the solution ( [ jc_sol ] ) . for @xmath178 and @xmath204 ( a ) , @xmath205 ( b ) , @xmath206 ( c ) , @xmath207 ( d ) , @xmath208 ( e).,width=288 ] the collapse
revivals effect in the time evolution of the inversion disappears completely in the range @xmath209 ( see figs .
[ fig_cs1_inv]a b ) , where the rabi effect picture turns out to be identical to the case of qd excited by classical light @xcite .
let us estimate material parameters which provide observability of the effects predicted .
for a spherical ingaas qd with 6 nm radius the dipole moment can be estimated@xcite as @xmath210 debye . for this
qd we obtain @xmath211 mev .
then , for the range of @xmath187 presented in fig
. [ fig_cs1_inv ] , from @xmath175 to @xmath212 , we obtain @xmath213 and @xmath214 mev , respectively .
these values are of the same order as the excitonic rabi splitting measured in recent single qd spectroscopy experiments , see refs . .
on the other hand , refs .
report the qd exciton linewidth @xmath215 of the order of 1 @xmath216ev below the temperature 10 k and laying in the range 4 to 10 @xmath216ev at @xmath217 k. thus , the precondition to observe the strong coupling regime , @xmath218 , is fulfilled for the given range of @xmath187 .
an important feature of the rabi effect in quantum light is the variation of the light statistics during the interaction with a quantum oscillator ( qd ) .
we shall characterize the variation by the second order time
zero correlation function and the photonic state distribution defined by eqs .
( [ corr_funct_shrod ] ) and ( [ population_distribution ] ) , respectively .
these characteristics at different @xmath187 are depicted in figs .
[ fig_cs1_cf ] and [ fig_cs1_pd ] .
one can see that at large @xmath219 the function @xmath220 oscillates around unit in agreement with the standard jc model@xcite , see curve _ 1 _ in fig .
[ fig_cs1_cf ] .
the situation is changed in the vicinity of the bifurcation as it is presented by curves _ 2 _ and _ 3 _ in that figure .
as one can see , at @xmath178 the light statistics becomes super poisonnian .
the correlation function @xmath220 demonstrates the increase in time imposed to small - amplitude oscillations .
these oscillations correspond to regions of revivals in the time evolution of the inversion ( compare curve _ 3 _ in fig .
[ fig_cs1_cf ] and fig .
[ fig_cs1_inv]d ) .
it should be noted that below the bifurcation threshold , at @xmath221 , @xmath220 oscillates in the vicinity of unity too .
[ fig_cs1_pd ] presents the photonic state distribution @xmath222 for different time points at the given @xmath178 .
the figure illustrates consecutive transformation of the initially poissonian distribution ( fig .
[ fig_cs1_pd]a ) into the super
poisonnian one in the course of time , see figs .
[ fig_cs1_pd]c d .
the transformation corresponds to the increase in @xmath220 illustrated by curve _ 3 _ in fig .
[ fig_cs1_cf ] .
let us stress that the standard jc model predicts the photon statistics remaining poisson as it takes place in our case only at large @xmath187 ( curve _ 1 _ in fig .
[ fig_cs1_cf ] ) .
our calculation also show that in the region @xmath188 the photon distribution @xmath222 does not depend on time and remains poissonian .
the invariability of the coherent light statistics in the limit @xmath199 corresponds to the absence of the component @xmath223 in eq .
( [ cross_section_final ] ) .
( a ) , @xmath224 ( b ) , @xmath225 ( c).,width=288 ] let a ground - state qd interacts with electromagnetic field given by the fock qubit ( [ fock_qubit ] ) . then the initial conditions for eqs .
( [ bas1 ] ) are given by @xmath226 further we restrict ourselves to the fock qubit with @xmath227 assuming @xmath228 .
of the qd exposed to the fock qubit with @xmath227 and @xmath225 @xmath229 , @xmath224 @xmath230 , @xmath178 @xmath231.,width=288 ] and @xmath204 ( a ) , @xmath232 ( b ) , @xmath206 ( c ) , @xmath233 ( d ) , @xmath234 ( e).,width=307 ] calculations of time evolution of the inversion for different values of @xmath187 are shown in fig .
[ fig_fq_inv ] . at large @xmath187 ( fig .
[ fig_fq_inv]c ) the local field effect is eliminated : in agreement with the solution ( [ jc_sol ] ) the inversion exhibits harmonic modulation of the oscillation amplitude within the range @xmath235 $ ] .
the oscillation frequency is equal to @xmath236 while the frequency of the modulation is given by @xmath237 . with the parameter
@xmath187 decrease the modulation becomes non harmonic .
the next two figures , [ fig_fq_cf ] and [ fig_fq_pd ] , illustrate the change of the light statistics due to interaction with qds .
the time evolution of the correlation function @xmath220 is depicted in fiq .
[ fig_fq_cf ] for different values of @xmath187 .
curve @xmath238 demonstrates that , same as in fig .
[ fig_cs1_cf ] and in agreement with the standard jc model , at large @xmath187 ( @xmath239 ) the correlation function oscillates in the vicinity of its initial value .
curve @xmath240 shows transformation of the sub - poissonian statistics ( @xmath241 ) into the super - poissonian one ( @xmath242 ) with a pronounced maximum followed by irregular oscillations .
analogous but essentially smoothed behavior is observed at larger @xmath187 ( curve @xmath243 )
. figure [ fig_fq_pd ] presents calculations of the photonic state distribution @xmath222 for @xmath178 ( curve @xmath244 in fig .
[ fig_fq_cf ] ) in different points of time .
the standard jc model when describes the interaction of fock qubit with two level system , predicts variation of those probabilities @xmath222 ( [ population_distribution ] ) that correspond to fock states with @xmath245 numbers of photons . as different from that
, the incorporation of the local field effect leads to the appearance in the distribution of states @xmath246 with photon numbers both smaller and larger than present in the initial fock qubit ( fig.[fig_fq_pd]a ) .
probabilities of these states are redistributed ( figs .
[ fig_fq_pd]b , c ) with time , and light statistics became irregular which signifies the transformation of the photonic state distribution ( figs .
[ fig_fq_pd]d , e ) . in turn
this affects the rabi oscillations picture and the second order correlation function @xmath220 ( compare figs .
[ fig_fq_inv]a and [ fig_fq_cf ] , curve _ 3 _ ) .
the vacuum rabi oscillations characterize interaction of an excited state qd with electromagnetic vacuum .
the initial conditions for eqs .
( [ bas1 ] ) in that case are given by @xmath247 .
numerical solution of this system leads to the time
harmonic oscillations of the inversion .
this agrees with the analytical solution of the system at @xmath120 given by the standard sinusoidal law@xcite : @xmath248 the result can easily be understood from that the vacuum states , like a single fock state , have zero observable electric field .
therefore , such states do not induce in qds observable polarization and , consequently , frequency shift .
for the same reason , zero frequency shift is inherent to single photon states , as it has been revealed under some simplifying assumptions in ref . .
the standard jc model describing the interaction between single mode quantum electromagnetic field and two level system predicts the collapse revivals picture of the time evolution of the level population .
the basic physical result of the analysis presented in our paper is a significant modification of the rabi effect due to the local field induced depolarization of a qd imposed to quantum light .
two oscillatory regimes with drastically different characteristics arise . in the first regime
the time modulation of the population ( the collapse and revivals ) is suppressed and the qd population inversion is found negative .
this indicates that trajectories of charge carriers confined by the qd occupy a finite volume in the phase space . in the second oscillatory regime
the revivals appear , however they are found deformed and significantly different from that predicted by the standard jc model .
the trajectories of charge carriers occupy the entire phase space .
both regimes of oscillations demonstrate the non isochronous dependence on the coherent field strength .
two regimes of the rabi oscillations indicate the appearance of two types of motion of the qd exciton .
the first one is a superposition of time - harmonic oscillations with the rabi frequencies @xmath249 , while the second type is presented by the frequency band @xmath250 .
the resulting exciton motion is thus determined by a nonlinear superposition of these two types of motion .
the first mechanism of the motion is conventional for the rabi effect ; physically it originates from dressing of the qd exciton by the incident field photons .
this type of motion dominates at large strengths of the incident field , when @xmath251 . with the light
qd coupling constant ( and correspondingly @xmath252 ) decrease , the role of the second type of motion grows in importance .
the reason for this is the electron
hole correlations resulting from the exchange interaction .
it can be interpreted as the qd exciton dressing by virtual photons .
this regime becomes dominating in the comparatively weak fields , when @xmath253 .
thus , the reduction of the threshold of the acting field strength needed for the rabi oscillations appearance , recently observed experimentally@xcite , can be attributed as a local field effect .
the experiment@xcite has also elucidated the non - isochronism of excitonic rabi oscillations that can be treated as the local
field effect as well ; see the relation ( [ polarization_fm ] ) and numerical calculations reported in ref .
it should be noted that two oscillatory regimes in the rabi effect may appear in other quantum systems where additional interaction mechanisms exist . as an example , consider a two component bose
einstein condensate with radio - frequency coupling of two separate hyperfine states@xcite .
temporal evolution of this system is governed by the coupled gross
pitaevskii equations , which are similar to those derived in sec .
[ sec : mot_eq ] .
the equations combine both linear and nonlinear couplings .
the linear coupling constant characterizes the interaction between the system and the electric field , while the nonlinear one accounts for the interaction between intra- and inter- species of the condensate@xcite .
dependently on ratio of the coupling parameters , the rabi oscillations between the condensate components may exhibit both well ordered and chaotic behavior @xcite , similar to that depicted in fig .
[ fig_cs1_inv]a , b . the formation of the bardeen
schrieffer state in the fermionic alkali gases cooled bellow degeneracy [ ] can serve as another example . in that system ,
the time modulation of coupling constant leads to the rabi oscillations of the energy gap@xcite with two oscillatory regimes .
the trajectories of individual cooper pairs occupy a finite volume in the phase space in the first regime and the entire phase space in the second one
. now , let us turn to the weak field case .
the the depolarization induced local field is predicted to entail in a qd exposed to an arbitrary photonic state a fine structure of the effective scattering cross section . instead of a single line of the frequency @xmath121 , a duplet is appeared with one component shifted by a value @xmath169 .
the shifted component is due to electron
hole correlations , see eq .
( [ sol_eqs_fm ] ) .
the correlations change the qd state and , consequently , provide the inelastic channel of the light scattering .
the elastic scattering channel is formed by light states inducing zero observable polarization and , consequently , zero frequency shift , such as fock states , vacuum states , etc .
now we take into account the relation @xmath254 , which couples observable polarization and mean value of the incident field ; the quantity @xmath255 is defined through the relation @xmath256 .
the scalar coefficient @xmath25 is the qd polarizability of a spherical qd .
therefore , we conclude that the elastic scattering channel is formed by incident field with zero mean value ( incoherent component of the electromagnetic field ) . correspondingly , the coherent field component is scattered through inelastic channel . as follows from the solution ( [ cross_section_final ] ) ,
the elastic channel is not manifested for pure coherent light ( the glauber state ) .
let us discuss now the local field induced alteration of the quantum light statistics .
as an example we consider the fock qubit ( [ fock_qubit ] ) as the incident field state .
for the case @xmath120 the photonic state distribution is given by @xmath257 where @xmath258 and @xmath259 are the exact solutions of eqs .
( [ bas1 ] ) at @xmath120 , see , e.g. ref . .
it is seen that the fock states with photon numbers @xmath245 are only presented in the distribution .
the probability amplitudes of these states oscillate with the corresponding rabi frequencies , @xmath260 .
in addition to this set , extra fock states with both smaller and larger photon numbers are appeared in the photonic state distribution @xmath222 as the local
field effect , see fig .
[ fig_fq_pd ] .
therefore , a bigger number of fock states than presented in the initial fock qubit , broaden the frequency spectrum of rabi oscillations , providing thus the chaotic time evolution of the inversion .
it should be noted that the variation in the quantum light statistics occurs even in the weak field limit @xmath261 . to illustrate that
, consider the observable polarization of the qd exciton defined in the time domain as @xmath262 using eq .
( [ sol_full ] ) we couple the polarization in the frequency domain with the complex valued amplitude of the mean incident field : @xmath263 then , after some simple manipulations we express the quantum fluctuations of the qd polarization by @xmath264 from eqs .
( [ discussions : pol2 ] ) and ( [ discussions : pol3 ] ) follows that the qd electromagnetic responses to the mean electric field and to its quantum fluctuation are different : the response resonant frequency is shifted by the value @xmath169 in the former case [ relation ( [ discussions : pol2 ] ) ] and remains unshifted in the later one , as given by relation ( [ discussions : pol3 ] ) .
this indicates that the effective polarizability of a qd is an operator in the space of quantum states of light .
it should be pointed out that this property is responsible for the alteration of the photonic state distribution in the weak field regime and is entirely a local field effect .
note that the notions
strong ( weak ) coupling regime and strong ( weak ) field regime are not identical as applied to qds . to illustrate this statement
, we express from eqs .
( [ discussions : pol2 ] ) and ( [ discussions : pol3 ] ) the polarization operator in the weak field limit : @xmath265 this equation is linear in the incident field but includes a term quadratic in the oscillator strength , @xmath266
. nonlinearity of that type violates the weak coupling regime .
the splitting of the qd - exciton spectral line dictated by eq .
( [ discussions : pol3 ] ) is a manifestation of the strong light - matter coupling in the weak incident field regime .
thus , the light
qd interaction is characterized by two coupling parameters , the standard rabi frequency and a new one , the depolarization shift @xmath169 .
in the paper we have developed a theory of the electromagnetic response of a single qd exposed to quantum light , corrected to the local field effects .
the theory exploits the two - level model of qd with both linear and nonlinear coupling of excited and ground states .
the nonlinear coupling is provided by the local field influence .
based on the microscopic hamiltonian accounting for the electron
hole exchange interaction , an effective two body hamiltonian has been derived and expressed in terms of the incident electric field , with a separate term responsible for the local field impact .
the quantum equations of motion have been formulated and solved with this hamiltonian for different types of the qd excitation , such as fock qubit , coherent state , vacuum state and arbitrary state of quantum light . for a qd exposed to coherent
light we predict two oscillatory regimes in the rabi oscillations separated by the bifurcation . in the first regime , the standard collapse
revivals phenomenon do not reveal itself and the qd inversion is found negative . in the second regime , the collapse
revivals picture is found to be strongly distorted as compared with that predicted by the standard jc model .
the model developed can easily be extended to systems of other physical nature exposed to a strong electromagnetic excitation . in particular , we expect manifestation of the local field effects in bose einstein condensates @xcite and fermionic alkai gases cooled below the degeneracy @xcite .
we have also demonstrated that the local field correction alters the light statistics even in the weak field limit .
this is because the local fields give rise to the inelastic scattering channel for the coherent light component . as a result ,
coherent and incoherent light components interact with qd on different frequencies separated by the depolarization shift @xmath169 .
in other words , the local fields eliminate the frequency degeneracy between these components of the incident light .
note that our model does not account for the dephasing .
accordingly to recent experimental measurements @xcite and theoretical estimates @xcite , the electron phonon interaction is the dominant mechanism of the dephasing in qds .
thus , the further development of the theory presented requires this dephasing mechanism incorporation .
a next step is generalization of our model to multi level systems . among them ,
the systems with dark excitons interacting with weak probe pulse in the self
consistent transparency regime @xcite are of special interest .
in the paper we have considered an isolated qd .
the generalization of the theory developed to the case of qd ensembles ( excitonic composites ) , such as self
organized lattices of ordered qd molecules @xcite and 1d ordered ( in , ga)as qd arrays @xcite , is of special interest .
one can expect that dipole
dipole interactions between qds will manifest itself in a periodic transfer of excited state between qds resulting thus in the collective rabi oscillations rabi waves .
the work was partially supported through the intas under project 05 - 1000008 - 7801 and the belarus republican foundation for fundamental research under project f05 - 127 .
the work of s. a. m. was partially carried out during the stay at the institute for solid state physics , tu berlin , and supported by the deutsche forschungsgemeinschaft ( dfg ) .
andrei magyarov acknowledges the support from the intas ys fellowship under the project 04 - 83 - 3607 .
for a spherical qd , the formulae ( [ dep_shift ] ) is reduced to @xmath267 using the expression ( [ deltah ] ) we obtain @xmath268 consider the 1s state .
the normalized wavefunction in this case is given by @xcite @xmath269 where @xmath270 is the bessel function , @xmath271 is the spherical coordinate and @xmath272 is the qd radius . inserting ( [ a3 ] ) into ( [ a2 ] ) and integrating the resulting expression
, we derive the correction to the depolarization shift ( [ a1 ] ) @xmath273 the dipole moment in the expression for the depolarization shift ( [ a1 ] ) for ingaas spherical qd can be estimated using the experimental data of ref .
silverman , r.p .
mirin , s.t .
cundiff , a.g .
normann , appl .
. lett . * 82 * , 25 , ( 2003 ) ] where the value from 25 to 33 debye were measured for the qds with average lateral dimensions from 30 to 40 nm . taking into account the theretical results concerning the dependence of the transition dipole moment on the qd surface area and shape [ a. thnharrdt , c. ell , g. khitrova , h.m .
gibbs * 65 * , 035327 , ( 2002 ) ] , we can roughly estimate the dipole moment @xmath276 debye for spherical qd with radius 6 nm .
|
a theory of both linear and nonlinear electromagnetic response of a single qd exposed to quantum light , accounting the depolarization induced local
field has been developed .
based on the microscopic hamiltonian accounting for the electron
hole exchange interaction , an effective two body hamiltonian has been derived and expressed in terms of the incident electric field , with a separate term describing the qd depolarization . the quantum equations of motion have been formulated and solved with the hamiltonian for various types of the qd excitation , such as fock qubit , coherent fields , vacuum state of electromagnetic field and light with arbitrary photonic state distribution . for a qd exposed to coherent light
, we predict the appearance of two oscillatory regimes in the rabi effect separated by the bifurcation . in the first regime , the standard collapse
revivals phenomenon do not reveal itself and the qd population inversion is found to be negative , while in the second one , the collapse
revivals picture is found to be strongly distorted as compared with that predicted by the standard jaynes - cummings model .
for the case of qd interaction with arbitrary quantum light state in the linear regime , it has been shown that the local field induce a fine structure of the absorbtion spectrum . instead of a single line with frequency corresponding
to which the exciton transition frequency , a duplet is appeared with one component shifted by the amount of the local field coupling parameter .
it has been demonstrated the strong light
mater coupling regime arises in the weak - field limit . a physical interpretation of the predicted effects has been proposed .
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social media networking websites like twitter and facebook have fundamentally changed how people communicate and socialize in the 21st century . with over 200 million users on the popular microblogging site twitter in 2011 @xcite , exploring the social impact of using such a service becomes ever more important .
although twitter has been considered by critics as a site where people tweet ( i.e. update statuses ) about mundane things such as what they are having for dinner , researchers have recently taken an interest in twitter to study social - behavioral attitudes @xcite , positive and negative influences of popular users @xcite , and even temporal patterns of happiness using ideas from linguistics @xcite . in this emerging culture of tweeters ( i.e. one who tweets ) that connect from places all over the world
, there also comes the bigger problem of cyberbullying @xcite .
twitter connects people by allowing them to send short bursts of information , called tweets , consisting of up to 140 characters in length , to other users .
what makes twitter different from other social networking sites is the character limit imposed on tweets , along with its asymmetrical nature : you may follow someone , but they do not have to follow you .
a user has three different types of relationships with fellow tweeters : you can have followers ( i.e. friends ) , which are people who follow you and can see your tweets ; you can also have people who you are following ; and finally there are bi - directional friends , which are people who are mutually following each other . despite the different relationships that occur on twitter ,
when a user tweets to the twitter community , a response is not necessary .
user s friends can see all the tweets sent by the user .
to involve a particular person in a tweet or a conversation , common practice is to use ` @ ' followed by a unique identifier address . to join a conversation , one can reply to a tweet , which uses ` @ ' .
one can also retweet , which allows a user to tweet the same message to all his / her friends while giving credit to the original tweeter , allowing the message to reach a wider range of twitter users @xcite . for simplicity of presentation in this analysis
, we use the term retweet " to describe both types of message repetition . in their retweets
, users can use a hashtag , denoted by ` # , ' which declares a tweet as being a part of a larger conversation whose topic is related to the phrase which comes after the hashtag @xcite .
we differentiate between keywords and hashtags : hashtags are used to identify the topic of a tweet , while keywords are found in the actual tweet .
since the advent of social media sites like twitter , there has been research on cyberbullying @xcite .
some research into methods for stopping cyberbullying on twitter can be found in xu _
_ @xcite . in their report , the authors used natural processing techniques to recognize traces of bullying tweets @xcite , and gorzig and frumkin suggested raising awareness for adolescents , especially with regard to privacy settings @xcite . while a user can block another person specifically on twitter , no current method exists to block offensive or hurtful tweets from the twitter community . per the terms of services , twitter does not currently suspend accounts for cyberbullying ( available at http://twitter.com/tos ) . in this study , we employ a concept refered to as quarantine " that would enable twitter to temporarily separate offenders from the twitter community , therefore protecting users from the spread of offensive messages . in this analysis , we extended the deterministic compartmental model developed by zhao _
et al . _ for rumor spreading in the new media age @xcite . in the model
, they built on the pioneering work of daley and kendall @xcite , who in 1965 introduced a model that looks at the spread of rumors as a non - standard contagion process .
the daley - kendall model was the first rumor spreading model developed , it used the terms ignorants , spreaders and stiflers analogous to the disease model classes of susceptible , infected and recovered , respectively .
et al . _ also looked at the maki - thompson rumor model @xcite , which showed the spreading of rumors through direct contact between spreaders and others , and the model developed by nekovee _
et al . _ which combined the sir epidemic model and the maki - thompson model on complex social networks @xcite . by drawing inferences from these models , zhao _
_ developed their own model which included a hibernator " class where the members of this class become disinterested in spreading the rumor but could become interested in spreading the same rumor again .
we considered instead a model where users are quarantined , " i.e. users are limited in their ability to spread the rumor through the enforced limitation on their contact with other members of the population . to do this
, we developed a discrete - time compartmental model that simulates the dynamics of rumor spreading in social networks , and examined how user s degree of quarantine hinders the spread of offensive messages .
we estimated model parameters by comparing the model predictions to patterns observed in twitter data related to a topic that communities would find offensive . in the following sections we describe the sources of data used in this analysis and give a description of the discrete - time compartmental model used to simulate spread of tweets , followed by a presentation and discussion of results .
= [ rectangle , draw , fill = blue!20 , text width=5em , text centered , rounded corners , minimum height=4em ] = [ rectangle , draw , fill = red!20 , text width=5em , text centered , rounded corners , minimum height=4em ] = [ rectangle , draw , fill = green!20 , text width=5em , text centered , rounded corners , minimum height=4em ] = [ rectangle , draw , fill = violet!20 , text width=5em , text centered , rounded corners , minimum height=4em ]
twitter uses application programming interface ( api ) version 1.1 which allows us to scrape " public data off the website ( https://twitter.com ) . to be able to access the api
, we use the r programming language package twitter " ( http://cran.r-project.org/web/packages/twitter/ ) .
this package acquires the information about a tweet such as the time created , the screen name of the person who tweeted or retweeted , and their follower and friend counts . in order to decide which keywords to use
, we conducted a search on the twitter website and searched for trending hashtags which contained offensive language .
we noticed that anti - gay sentiment is prevalent on twitter so we chose words that expressed disgust towards the gay community to use as an example .
there is no doubt that these tweets are offensive to most people .
we used the searchtwitter " function to search within the days of july 6 - 10 , 2013 for offensive tweets or retweets containing the keywords disgusting " and gay " yielding a total of 884 tweets .
the data showed that there were 100 tweets from this sample of 478 original tweets that had been retweeted at least once .
this is in qualitative concordance with kwak _
_ where they found the fraction of not retweeting to be 79% @xcite , and grabowicz _ et al .
_ who found that 85% of tweets were not retweeted @xcite .
the average duplication of a tweet in our sample was 1.85 times .
in addition , we estimated the probability of a message being retweeted by using @xmath8 ( number of retweets)/(number of friends of offensive tweeters ) , yielding @xmath9 = @xmath10 . thus @xmath11 @xmath12 0.999 , which will be included as a parameter in our model below .
_ found that 99% of twitter users have fewer than 20 followers @xcite .
furthermore , the degree of social networks has been found to follow a power law functional relationship , with exponent @xmath13 @xcite .
the probability of having @xmath14 twitter followers is thus @xmath15 @xcite . with the power law relationship
, most users have few followers and a very few users have many followers .
the average degree of the network , @xmath16 , is @xmath17 $ ] , which has a value of 1.5 to 10 for @xmath18 $ ] . for our model analysis below , we assume @xmath16 = 10 .
we developed a discrete - time model to simulate the dynamics of the spread of messages on twitter , because tweets occur at discrete times , whereas a continuous - time model includes a variable window of times between the tweets . in the following subsections ,
we describe a basic model of twitter message spreading dynamics that does not include a quarantine class .
we determined an expressions for the threshold value of this model , then we extended the model to include a quarantined class and discuss the implications that the addition of this class has for the threshold values of the system .
a simple discrete - time rumor model for describing the spread of a message in a social network is : @xmath19 which was proposed by zhao _
@xcite , where @xmath20 , @xmath21 , @xmath22 are the uninformed , offender , and stifler classes at time @xmath23 , respectively , where the constant population size is @xmath24 , and @xmath11 is the probability that an uninformed user becomes a stifler after seeing an offensive tweet ( which we estimated from twitter data in the previous section ) .
the parameter @xmath25 is the probability of seeing an offensive tweet , and @xmath26 is the probability of an offender becoming a stifler . to ensure that these two probabilities lie between 0 and 1 , we use the form @xcite : @xmath27 where @xmath16 is the degree of the network , which is estimated from studies of twitter data in the published literature , as described in the previous section .
the parameters of the model are shown in table [ tab : params ] and the compartmental diagram is shown in figure [ model : basiccomp ] .
in lemma [ lem : gt0 ] in appendix a we show that if the initial values of @xmath28 , @xmath29 , and @xmath30 are non - negative , then all future populations in those classes will be non - negative . taken in conjunction with the fact that the system is bounded such that the populations in each of the classes sums to @xmath31 ( see lemma [ lem : bound ] in appendix a )
, we see that the population within each class can be at most @xmath31 .
we note that as a result , the population in the uninformed class monotonically decreases asymptotically to zero , because @xmath32 when @xmath33 and @xmath34 ( for a formal proof , see lemma [ lem : decu ] in appendix a ) .
additionally , the population in the stifler class monotonically increases , because the last two terms in @xmath35 are both at least zero for all @xmath36 , @xmath37 , @xmath38 and @xmath33 .
further , when the population in the stifler class is @xmath31 we note that @xmath39 and @xmath40 , and that from system [ eqn : basic ] we see that @xmath41 .
thus , @xmath42 asymptotically monotonically increases to @xmath31 . in theorem [ thm : thresh ] in appendix
a we show that if @xmath43 then @xmath44 .
since @xmath45 monotonically decreases to zero , and @xmath46 monotonically increases because @xmath42 monotonically increases , we see that @xmath47 montonically decreases to zero .
thus there will always exist a point at which @xmath48 , and @xmath49 .
we thus conclude that even without quarantine , the offender class will eventually begin to die out . in the next section
, we will discuss how the implementation of a quarantine class ensures that the offender class will begin to die out more quickly .
= [ rectangle , draw , fill = blue!20 , text width=5em , text centered , rounded corners , minimum height=4em ] = [ rectangle , draw , fill = green!20 , text width=5em , text centered , rounded corners , minimum height=4em ] = [ rectangle , draw , fill = violet!20 , text width=5em , text centered , rounded corners , minimum height=4em ] compartmental model structure for basic twitter model , height=240 ] before we move on to the quarantine model , we examine the equilibrium points for this basic model .
there are two equilibrium points : @xmath50 the first equilibrium point represents the case where there are only offenders , because the only way for an offender to leave the class is to come in contact with a stifler , of which there are none .
the second equilibrium point is analogous to the disease - free equilibrium because there is no one in the offender class .
we refer to this point as the offender - free equilibrium ( ofe ) .
the jacobian for this basic model is : @xmath51 the eigenvalues of the jacobian corresponding to the first equilibrium point , ( @xmath52 ) , which we refer to the offender - only equilibrium , are : @xmath53 we note that @xmath33 and thus the third eigenvalue is always greater than 1 . we thus conclude that the first equilibrium point is not stable .
evaluating the jacobian at the offender - free equilibrium , ( @xmath28 , @xmath54 , @xmath30 ) , we obtain @xmath55 with eigenvalues @xmath56 note that if @xmath57 and @xmath58 the first eigenvalue is @xmath59 which is always greater than zero and less than 1 since @xmath33 .
thus there always exists at least one value of @xmath60 such that the first eigenvalue is less than 1 .
however , the other two eigenvalues , @xmath61 are equal to 1 , which does not _ a priori _ indicate that the equilibrium point is unstable , but neither does it imply stability .
eigenvalues equal to one can result from system constraints not being applied .
we note that one of the equations in system [ eqn : basic ] can be removed if we apply the constraint @xmath62 . evaluating the eigenvalues of the jacobian of this reduced system about the offender - free equilibrium yields @xmath63 the jury criterion is an algorithmic method based upon the characteristic equation of the jacobian that is used to assess the stability of discrete systems@xcite .
a prior condition for use of the method is that the characteristic equation @xmath64 , must be greater than zero when @xmath65 .
this condition is not met for this model , thus we can not apply the jury criterion . thus , in order to assess the stability of this equilibrium point , we would have to resort to higher - order methods , rather than just linearization of the system about the offender - free equilibrium @xcite .
this is beyond the scope of this paper , and we thus conclude that that the stability of the offender - free equilibrium in this model is currently indeterminate .
to calculate the next generation matrix of the model , we use the methods of allen and van den driessche , 2008 @xcite , and we reorder the columns and rows of the offender - free jacobian in equation such that the offender ( infected ) class comes first , and the uninformed and stifler ( uninfected ) classes follow .
then , as in @xcite , we identify the components of this jacobian with the following form : @xmath66 then the matrix @xmath67 is given by @xmath68 the matrix @xmath69 is @xmath70 and the matrix @xmath71 is @xmath72 the next generation matrix ( ngm ) is defined by @xmath73 .
the spectral radius of this matrix is @xmath74 we note that the spectral radius of the matrix @xmath71 , @xmath75 , is exactly equal to one ; in order for the spectral radius of the ngm to be identified with the reproduction number of the system , @xmath75 must be less than one @xcite .
we thus do not identify @xmath76 with the reproduction number , but note with interest that it matches the expression in equation that we had shown could be used as a threshold expression for @xmath49 . to examine how isolation of offending users would hinder the spread of offensive tweets , we extend the basic model in equation by adding a quarantine class where the parameter @xmath77 is the probability that an offender becomes quarantined .
we also include a parameter @xmath78 that describes the probability that a person in the quarantine class becomes a stifler . when @xmath79 is close to one the offenders spend longer in the quarantine class then when @xmath79 is close to zero .
the discrete - time equations of this extended model are : @xmath80 where @xmath81 and @xmath82 are as in the basic model , @xmath83 the parameters of the model are shown in table [ tab : params ] and the compartmental diagram is shown in figure [ flow_chart2 ] .
compartmental model structure , height=240 ] as before in the basic model , the sum of the populations in each of the classes adds to a constant , @xmath31 .
we also note that the population in the uninformed class monotonically asymptotically decreases to zero , and that the population in the stifler class monotonically asymptocally increases to @xmath31 . in theorem [ thm : thresh_quar ] in appendix
a , we show that if @xmath84 then @xmath44 .
since @xmath45 monotonically decreases to zero , and @xmath85 monotonically increases because @xmath42 monotonically increases , we see that @xmath47 montonically decreases to zero .
thus , just as in the basic model , there will always exist a point at which @xmath48 , and @xmath49 .
however , we note that the smaller the @xmath86 ( ie ; the higher the quarantine fraction @xmath87 ) , the faster @xmath47 will decrease to 0 . in theorem [ thm : threshb ] in appendix
a , we show additionally show that if @xmath88 then @xmath89 regardless of the values of @xmath90 further , we show in theorem [ thm : threshc ] in appendix a that if @xmath91 and @xmath92 , then @xmath93 , regardless of the current values of @xmath90 .
we note that @xmath94 and @xmath95 for twitter data , thus @xmath91 .
thus for twitter data there exists a quarantine fraction @xmath86 such that the spread of offensive messages will be guaranteed to decline at the next time step .
there are two equilibrium points for the model with the quarantine class : @xmath96 the first equilibrium point is biologically irrelevant because it implies that the stifler class will have a negative population since @xmath97 .
therefore we disregard this equilibrium point .
the second equilibrium point is analogous to the offender - free equilibrium of equation .
the jacobian of the system is : @xmath98 + the eigenvalues of the jacobian evaluated at the offender - free equilibrium are @xmath99 , @xmath100 , and @xmath101 . as in section [ section : basic ]
, we note that the constraint @xmath102 can be used to reduce the number of equations by one .
the eigenvalues of the reduced system are @xmath103 , @xmath104 , and @xmath105 .
we note that if @xmath91 ( which it is for twitter data , which has @xmath95 and @xmath94 , as seen in the previous section ) then @xmath79 and @xmath86 can always be chosen to ensure that the second and third eigenvalues are less than 1 .
however the first eigenvalue is exactly equal to one .
as before , we find that the jury criterion can not be applied to assess the stability of this equilibrium point , so we conclude that we find the stability to be currently indeterminate . as in section [ section : basic ] , we begin computation of the next generation matrix for this system by reordering the equations such that the infected classes ( offender and quarantine ) classes come first , and the uninfected ( uninformed and stifler ) classes follow@xcite .
the jacobian of the rearranged equations , evaluated at the disease - free equilibrium is thus : @xmath106 as before , we identify the components of this matrix with @xcite @xmath66 then the matrix @xmath67 is given by @xmath107 matrix @xmath69 is @xmath108 and the matrix @xmath71 is @xmath109 the next generation matrix is defined by @xmath73 .
the spectral radius of this matrix is @xmath110 we again note that the spectral radius of the matrix @xmath71 , @xmath75 , is exactly equal to one and thus we do not identify @xmath47 with the reproduction number , but again note with interest that it matches the expression in equation that we have shown could be used as a threshold condition for @xmath49 in the quarantine model .
.[tab : params ] parameter values for the discrete - time models .
[ cols="^,^,^",options="header " , ]
we determined the parameters of equation using current twitter data : * @xmath11 , the probability that the user becomes a stifler * @xmath111 the fraction of the population that is initally in the stifler class .
* @xmath16 , the degree of the network .
we assumed based on our data and information from the literature that @xmath112 and @xmath113 as described in section [ sec : data ] .
we examined values of @xmath111 between @xmath114 to 1 in steps of @xmath114 and determined the model prediction for the number of retweets , and compared this to the number of retweets we observed in the data ( namely approximately one retweet per tweet ) .
this can be seen in table [ tab : params ] .
we found the value of @xmath115 best fit the data .
we let @xmath116 but we found our results were not sensitive to the value of @xmath31 , for large @xmath31 .
figures [ fg : basic_model_output ] and [ fg : quarantined_model_output ] are numerical simulations of our basic and quarantined models respectively .
these figures visually show the dynamics of the systems .
, @xmath113 .
the uninformed and offender classes tend to zero while the stifler class tends to @xmath31 which is the total population .
[ fg : basic_model_output ] ] , @xmath113 , @xmath117 , @xmath118 .
the uninformed , offender , and quarantined classes tend to zero while the stifler class tends to @xmath31 which is the total population .
[ fg : quarantined_model_output ] ] we used the parameter values in table [ tab : params ] to find solutions to equation . in our computations
, we assume the probability a quarantined user becomes a stifler , @xmath119 is zero . to do this we examined values of @xmath87 , the quarantine fraction , between zero and one and obtained the model prediction for the number of retweets
the results are seen in figure [ fg : lambdavsthreshold ] . .
for @xmath120 , @xmath94 , @xmath121 .
we assume that quarantined users are fully isolated from the rest of the community .
as the probability of quarantine increases , the number of retweets decreases .
[ fg : lambdavsthreshold ] ] by looking at the number of offenders over time , while varying @xmath86 we can see how the quarantine fraction , @xmath87 , affects the life - time of the tweet . as @xmath87 increases , the model predicts a decrease in the average life - time of the tweet , see in figure [ fg : offendersvstimelambda ] , i.e. the tweet on average dies out more quickly
. varies .
the parameters @xmath112 , @xmath117 , and @xmath113 . for a low probability of being quarantined
, there is a high number of offenders over time . as the probability of the quarantined increases ,
the offenders deceases ]
in this paper we presented a discrete - time non - linear compartmental model to simulate the dynamics of the spread of offensive messages on twitter .
we developed the model to gain insight into reducing the number of offensive tweets seen by twitter users .
we then extended the model to include a quarantine class whereby offending users were isolated from contact with the rest of the twitter community .
we found that the implementation of quarantine was an effective way to quickly reduce the spread of offensive messages .
further , we proved that if @xmath91 , where @xmath16 is the degree of the network , and @xmath9 is the probability of retweeting , then if @xmath122 the number of offenders at the next time step will always be less than the number of offenders the time step before .
we showed that this was independent of the the number of uninformed , offenders , quarantined , and stiflers at that time step . from data we obtained from twitter , and the published literature , we determined that @xmath94 and @xmath123 , thus for twitter @xmath91 and there thus exists a @xmath86 such that offensive tweets will be effectively suppressed .
we performed numerical simulations to examine the effect of quarantine .
as shown in figure 3 , the quarantine of a certain fraction of offending twitter users led to a disproportionately larger reduction in the number of new offenders .
previous studies in this area have used a wide variety of statistical , computational , and mathematical methods to understand the spread of information in social networks ( see @xcite , for instance ) . the use of a quarantine class to hinder the spread of messages has not been previously considered .
there are some limitations of the model we have developed . for instance , we assume that once offenders leave the quarantine class , they have learned their lesson and do not offend again .
this is not realistic in all cases . also , while we find that the quarantine of offenders is effective , we have not determined how such a quarantine can be implemented .
one way to potentially implement the quarantine is to have twitter use an algorithm that flags tweets as being potentially offensive based on keywords @xcite .
another way to implement a quarantine is to have users give negative rating to tweets they find offensive , for instance , a rating system that goes from zero to minus ten by integer values and lets each user choose the value that fits the type of tweets they want to see . with this basic and quarantine model ,
there are other routes that could be taken to further this research . for instance , performing an analysis of a markov chain model .
we can also examine how quarantined users or stiflers stop the spread of a tweet through a network graph . performing a network analysis on such a model
would provide insight into which users should be quarantined first , or which groups to isolate from the overall population , to reduce the spread of these tweets . in conclusion
, our model indicates that quarantine of users that spread offensive message would likely be effective .
our use of a discrete - time non - linear model highlights the usefulness of mathematical models in understanding the underlying dynamics of social networks , and opens up many interesting possibilities for future research .
we would like to thank dr .
carlos castillo - chavez , executive director of the mathematical and theoretical biology institute ( mtbi ) , for giving us the opportunity to participate in this research program .
we would also like to thank co - executive summer directors dr .
erika t. camacho and dr .
stephen wirkus for their efforts in planning and executing the day to day activities of mtbi .
we also want to give special thanks to daniel burkow for helping us redefine our topic , kamal barley for his graphic enhancements , dr . luis melara , dr . leon arriola , xiaoguang zhang , and oyita udiani for their invaluable help and feedback in writing this paper .
this research was conducted in mtbi at the mathematical , computational and modeling sciences center ( mcmsc ) at arizona state university ( asu ) . this project has been partially supported by grants from the national science foundation ( nsf - grant dmps-1263374 ) , the national security agency ( nsa - grant h98230 - 13 - 1 - 0261 ) , the office of the president of asu , and the office of the provost of asu .
[ lem : gt0 ] if @xmath124 , @xmath125 , @xmath126 in the basic model in system [ eqn : basic ] , then @xmath127 , @xmath128 , @xmath129 let @xmath124 , @xmath125 , @xmath126 @xmath130 since @xmath131 , we can see that @xmath132 for all @xmath23 . therefore , as @xmath133 , we can use a similar argument to show that for @xmath134 @xmath135 lastly to show that @xmath129 for all @xmath23 we notice that @xmath136 since @xmath127 and @xmath128 are always non - negative . therefore since @xmath137 , and @xmath136 then @xmath129 let @xmath140 , @xmath141 . from ( 7),(8 ) we know @xmath143 notice that if @xmath144 then @xmath145 . since @xmath146
, we can see that @xmath147 for all @xmath23 and consequently @xmath148 therefore since @xmath149 , we can say @xmath144 and @xmath150 .
now , we wish to show that when @xmath157 then @xmath158 note that equation implies that @xmath159 substituting this into equation yields @xmath160 from equation we know that @xmath161 , thus @xmath162 the lhs is equal to @xmath163 .
thus @xmath164 now , we wish to show that when @xmath167 then @xmath158 note that equation implies that @xmath168 substituting this into equation yields @xmath169 from equation we know that @xmath161 , thus @xmath170 the lhs is equal to @xmath163 . thus @xmath164 note that the numerator of the lhs is always less than or equal to @xmath173 because @xmath174 , and the denominator of the lhs is always greater than or equal to @xmath87 , because @xmath175 and @xmath33 thus @xmath176 .
thus we have shown that the lhs is at most the rhs .
and thus when @xmath171 , then @xmath93 in the quarantine model .
we have @xmath179 , and we also have that @xmath91 , which ensures that @xmath180 . we thus have that @xmath181)}}$ ] .
the rhs is equal to 1 , thus we have shown that when @xmath91 and @xmath179 , then @xmath182 .
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the 21st century has redefined the way we communicate , our concept of individual and group privacy , and the dynamics of acceptable behavioral norms .
the messaging dynamics on twitter , an internet social network , has opened new ways / modes of spreading information . as a result cyberbullying or in general , the spread of offensive messages , is a prevalent problem .
the aim of this report is to identify and evaluate conditions that would dampen the role of cyberbullying dynamics on twitter .
we present a discrete - time non - linear compartmental model to explore how the introduction of a quarantine class may help to hinder the spread of offensive messages .
we based the parameters of this model on recent twitter data related to a topic that communities would deem most offensive , and found that for twitter a level of quarantine can always be achieved that will immediately suppress the spread of offensive messages , and that this level of quarantine is independent of the number of offenders spreading the message .
we hope that the analysis of this dynamic model will shed some insights into the viability of new models of methods for reducing cyberbullying in public social networks .
@xmath0 department of mathematics , boston university , boston , ma + @xmath1 department of mathematics and computing , columbia college , columbia , sc + @xmath2 department of biology , medgar evers college ( cuny ) , brooklyn , ny + @xmath3 department of mathematics , st .
mary s university , san antonio , tx + @xmath4 department of applied mathematics for the life and social sciences , arizona state university , tempe , az + @xmath5 department of physics , purdue university , west lafayette , in + @xmath6 mathematical , computational & modeling sciences center , arizona state university , tempe , az + @xmath7 school of mathematical & statistical science , arizona state university , tempe , az
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SECTION 1. CONSUMER RENEWABLE CREDIT.
(a) Business Credit.--
(1) In general.--Subpart D of part IV of subchapter A of
chapter 1 of the Internal Revenue Code of 1986 is amended by
adding at the end the following new section:
``SEC. 45S. CONSUMER RENEWABLE CREDIT.
``(a) General Rule.--For purposes of section 38, in the case of an
eligible taxpayer, the consumer renewable credit for any taxable year
is an amount equal to the product of--
``(1) the renewable portfolio factor of such eligible
taxpayer, and
``(2) subject to subsection (e), the number of kilowatt
hours of renewable electricity--
``(A) purchased or produced by such taxpayer, and
``(B) sold by such taxpayer to a retail customer
during the taxable year.
``(b) Renewable Portfolio Factor.--In the case of taxable years
beginning before January 1, 2019, the renewable portfolio factor for an
eligible taxpayer shall be determined as follows:
------------------------------------------------------------------------
Renewable
``Renewable electricity percentage: portfolio factor:
------------------------------------------------------------------------
Less than 6 percent................................ zero cents
At least 6 percent but less than 8 percent......... 0.1 cents
At least 8 percent but less than 12 percent........ 0.2 cents
At least 12 percent but less than 16 percent....... 0.3 cents
At least 16 percent but less than 20 percent....... 0.4 cents
At least 20 percent but less than 24 percent....... 0.5 cents
Equal to or greater than 24 percent................ 0.6 cents.
------------------------------------------------------------------------
``(c) Definitions and Special Rules.--For purposes of this
section--
``(1) Eligible taxpayer.--The term `eligible taxpayer'
means an electric utility, as defined in section 3(22) of the
Federal Power Act (16 U.S.C. 796(22)).
``(2) Renewable electricity.--The term `renewable
electricity' means electricity generated by any facility using
wind or solar energy to generate such electricity.
``(3) Renewable electricity percentage.--The term
`renewable electricity percentage' means the percentage of an
eligible taxpayer's total sales of electricity to retail
customers which is derived from renewable electricity
(determined without regard to whether such electricity was
produced by the taxpayer).
``(4) Application of other rules.--For purposes of this
section, rules similar to the rules of paragraphs (1), (3), and
(5) of section 45(e) shall apply.
``(5) Credit allowed only with respect to one eligible
entity.--No credit shall be allowed under subsection (a) with
respect to renewable electricity purchased from another
eligible entity if a credit has been allowed under this section
to such other eligible entity.
``(d) Coordination With Payments.--The amount of the credit
determined under this section with respect to any electricity shall be
reduced to take into account any payment provided with respect to such
electricity solely by reason of the application of section 6433.
``(e) Renewable Electricity Enhancement.--
``(1) Native american wind and solar.--In the case of
renewable electricity generated by a wind or solar energy
facility which is located on an Indian reservation (as defined
in section 168(j)(6)), the number of kilowatt hours of such
renewable electricity shall, for purposes of subsection (a)(2),
be equal to 200 percent of the kilowatt hours of such renewable
electricity actually purchased or produced and sold during the
taxable year.
``(2) Electric cooperative wind and solar.--In the case of
renewable electricity generated by a wind or solar energy
facility which is wholly owned by a mutual or cooperative
electric company (as described in section 501(c)(12) or
1381(a)(2)(C)), the number of kilowatt hours of such renewable
electricity shall, for purposes of subsection (a)(2), be equal
to 150 percent of the kilowatt hours of such renewable
electricity actually purchased or produced and sold during the
taxable year.''.
(2) Credit made part of general business credit.--
Subsection (b) of section 38 of the Internal Revenue Code of
1986 is amended by striking ``plus'' at the end of paragraph
(35), by striking the period at the end of paragraph (36) and
inserting ``, plus'', and by adding at the end the following
new paragraph:
``(37) the consumer renewable credit determined under
section 45S(a).''.
(3) Specified credit.--Subparagraph (B) of section 38(c)(4)
of the Internal Revenue Code of 1986 is amended by
redesignating clauses (vii) through (ix) as clauses (viii)
through (x), respectively, and by inserting after clause (v)
the following new clause:
``(vi) the credit determined under section
45S.''.
(4) Clerical amendment.--The table of sections for subpart
D of part IV of subchapter A of chapter 1 of the Internal
Revenue Code of 1986 is amended by adding at the end the
following new item:
``Sec. 45S. Consumer renewable credit.''.
(b) Payments in Lieu of Credit.--
(1) In general.--Subchapter B of chapter 65 of the Internal
Revenue Code of 1986 is amended by adding at the end the
following new section:
``SEC. 6433. CONSUMER RENEWABLE CREDIT PAYMENTS.
``(a) In General.--If any eligible person sells renewable
electricity to a retail customer, the Secretary shall pay (without
interest) to any such person who elects to receive a payment an amount
equal to the product of--
``(1) the intermittent renewable portfolio factor of such
eligible person, and
``(2) the number of kilowatt hours of renewable
electricity--
``(A) purchased or produced by such person, and
``(B) sold by such person in the trade or business
of such person to a retail customer.
``(b) Timing of Payments.--
``(1) In general.--Except as provided in paragraph (2),
rules similar to the rules of section 6427(i)(1) shall apply
for purposes of this section.
``(2) Quarterly payments.--
``(A) In general.--If, at the close of any quarter
of the taxable year of any person (or, in the case of
an eligible person that does not have a taxable year,
the close of any quarter of the fiscal year), at least
$750 is payable in the aggregate under subsection (a),
to such person with respect to electricity purchased or
produced during--
``(i) such quarter, or
``(ii) any prior quarter (for which no
other claim has been filed) during such year,
a claim may be filed under this section with respect to
such electricity.
``(B) Time for filing claim.--No claim filed under
this paragraph shall be allowed unless filed on or
before the last day of the first quarter following the
earliest quarter included in the claim.
``(c) Definitions and Special Rules.--For purposes of this
section--
``(1) Eligible person.--The term `eligible person' means--
``(A) an electric utility, as defined in section
3(22) of the Federal Power Act (16 U.S.C. 796(22)), or
``(B) a Federal power marketing agency, as defined
in section 3(19) of such Act (16 U.S.C. 796(19)).
``(2) Other definitions.--Any term used in this section
which is also used in section 45S shall have the meaning given
such term under section 45S.
``(3) Application of other rules.--For purposes of this
section, rules similar to the rules of paragraphs (1) and (3)
of section 45(e) shall apply.
``(d) Payment Disallowed Unless Amount Passed to Third-Party
Generators Charged for Integration Costs.--
``(1) In general.--In the case of renewable electricity
eligible for the payment under subsection (a) that is purchased
and not produced by an eligible person, no payment shall be
made under this section unless any charge the eligible person
has assessed the seller to recover the integration costs
associated with such electricity has been reduced (but not
below zero) to the extent of the payment received under
subsection (a) associated with such electricity.
``(2) Definitions.--For purposes of paragraph (1), charges
intended to recover integration costs do not include amounts
paid by the producer of the electricity for interconnection
facilities, distribution upgrades, network upgrades, or stand
alone network upgrades as those terms have been defined by the
Federal Energy Regulatory Commission in its Standard
Interconnection Procedures.
``(e) Payment Allowed for Special Generating and Transmitting
Entities.--
``(1) In general.--Notwithstanding subsection (a)(2), a
special generating and transmitting entity shall be eligible
for payment under subsection (a) based on the number of
kilowatt hours of renewable electricity transmitted, regardless
of whether such entity purchased or sold such electricity to
retail customers.
``(2) Definition.--For purposes of this subsection, the
term `special generating and transmitting entity' means--
``(A) an entity which is--
``(i) primarily engaged in marketing
electricity,
``(ii) provides transmissions services for
greater than 4,000 megawatts of renewable
electricity generating facilities, as
determined by reference to the machine or
nameplate capacity thereof, and
``(iii) transmits the majority of such
renewable electricity to customers located
outside of the region that it serves, or
``(B) a generation and transmission cooperative
which engages primarily in providing wholesale electric
services to its members (generally consisting of
distribution cooperatives).''.
(2) Clerical amendment.--The table of sections for subpart
B of chapter 65 of the Internal Revenue Code of 1986 is amended
by adding at the end the following new item:
``Sec. 6433. Consumer renewable credit payments.''.
(c) Effective Date.--The amendments made by this section shall
apply to electricity produced or purchased and sold after December 31,
2013, and before January 1, 2019.
SEC. 2. DELAY IN APPLICATION OF WORLDWIDE INTEREST.
(a) In General.--Paragraphs (5)(D) and (6) of section 864(f) of the
Internal Revenue Code of 1986 are each amended by striking ``December
31, 2020'' and inserting ``December 31, 2022''.
(b) Effective Date.--The amendments made by this section shall take
effect on the date of the enactment of this Act.
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Amends the Internal Revenue Code to allow, through December 31, 2018: (1) a new business-related tax credit for sales by an electric utility of renewable electricity generated by a facility using wind or solar energy to a retail customer; and (2) payments to such utilities, in lieu of such tax credit, for sales of renewable electricity to retail customers. Delays, until 2023, the application of rules relating to the allocation and apportionment of the interest expense of domestic corporations that are members of a worldwide affiliated group.
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during 20082013 , a total of 68 satellite or global positioning system radio collars were deployed on african buffalo captured in southern gonarezhou np ; in northern kruger np , south of the limpopo river ; and in zimbabwe , north of limpopo river ( on sengwe communal land ) .
of the 68 buffalo , 47 were adult females , selected because their behavior is representative of core herd movements .
two adult males were also equipped with global positioning system devices because males are believed to move between herds ( 7 ) ; however , these devices failed after a few weeks because the collars fell off .
nineteen subadult female buffalo 2.54.5 years of age ( age determined by teeth eruption ) were also selected because individuals from this group are believed to disperse from their native herds ( 8 ; r. bengis , pers .
blood samples were taken and stored appropriately for disease screening , and individually numbered ear - tags were applied . during the study ,
extraordinarily long - distance movements for 3 subadult females were plotted by satellite telemetry readings ( figure 1 ) . in january 2014 , a 2.5-year - old female buffalo collared in south africa walked a maximum direct distance of 95 km . in 6 days , she crossed into zimbabwe , then into mozambique , and into zimbabwe again to enter gonarezhou np , with localizations within the home range of the buffalo herd in which btb was first diagnosed in a female buffalo in 2008 ( 6 ) .
this subadult buffalo later left the park and visited a commercial farm area before reentering gonarezhou np . in february 2014
, another 4-year - old female buffalo walked a direct distance of 64 km in 8 days .
finally , in march 2013 , a 4.5-year - old female captured in july 2011 was sighted in a location deep into communal land at a distance of 96 km from her capture site .
in contrast to these young female buffalo , no adult females collared in this study moved such long distances outside their home range during 20082014 .
the long - distance travel of these 3 subadult females occurred over a few days during the rainy season ( figure 2 ) and included movements outside the gltfca boundary .
cumulative home - range area of 15 buffalo collared with global positioning system devices in kruger national park , south africa , in november 2013 . only buffalo with collars that functioned for an entire year are displayed .
data for 2 subadult female buffalo ( paths displayed in figure 1 ) are shown ( id65 and id68 ) separately from data for the 13 other buffalo ( subadult and adult females ) .
our findings strengthen the hypothesis that btb was spread from kruger np to gonarezhou np through buffalo - to - buffalo transmission by subadult females that dispersed from their native herds .
buffalo populations in kruger and gonarezhou nps are connected through long - distance movements of individuals , specifically prebreeding heifers .
although this movement is important for buffalo conservation in tfcas , it could also facilitate the spread of animal diseases , including zoonoses , across borders . in 2010 and 2011 ,
btb , rift valley fever , and brucellosis were detected in kruger np buffaloes , although a previous study failed to detect brucellosis in the gonarezhou np population ( 9 ) ( table ) .
buffalo id65 , which was initially captured in kruger np , was seen among a breeding herd in gonarezhou np , indicating the possibility of direct , buffalo - to - buffalo transmission of btb by dispersing infected individuals , without the need for bridge hosts ( e.g. , other wild or domestic ungulate species ) ( 10 ) .
* individuals and herds belong to the same population ( see figure 1 , adult female home range ) .
calf , < 2.5 y of age ; subadult , 2.54.5 y ; adult , > 4.5 y. laboratory tests used : for bovine tuberculosis , gamma - interferon test and isolation ; for brucellosis , rose bengal and complement fixation tests ; for rift valley fever , indirect elisa test .
published results ( 9 ) for the same diseases tested in the gonarezhou national park buffalo population in zimbabwe are shown in parentheses .
difference between kruger and gonarezhou population results for brucellosis was significant by fisher exact test for equality of proportion for small samples ( p<0.02 ) .
additional ecological information on buffalo dispersion is needed : frequency of dispersion events ; size , age , and sex composition of the dispersing groups ; and information about whether dispersed individuals later return to their home ranges .
subadult females appear to be particularly prone to dispersing behavior , unlike adult females , and we speculate that they may do so in small groups of individuals that are approximately the same age ( 8) .
no record exists of subadult female buffalo mixing with male bachelor groups , which are also known to connect to adjacent herds ( 7 ) .
. one possible explanation may be an out - breeding mechanism ( 11 ) that occurs before the start of reproduction ; subadult females may leave their native herd to begin their reproduction in a distant herd to minimize in - breeding . furthermore , abundant resources ( i.e. , water and grazing areas ) available during the rainy season maximize the probability of success of such behavior .
we found that subadult females were infected with btb , brucellosis , and rift valley fever ( table ) , diseases with different mechanisms of transmission .
age and social position in the herd may influence individuals rate of exposure to pathogenic infections and consequently may affect the dynamics of infection within and between herds .
our results indicate that subadult female buffalo could play a role in the spread of diseases among distant populations , across protected areas and international borders , and during the rainy season .
this seasonal pattern contrasts with the timing of most wildlife and livestock contact between adult females , which has been observed to occur predominantly during the dry season in the study area ( 4 ) .
buffalo have been observed far outside the boundaries of protected areas , even outside the gltfca , in communal land where livestock farming is the main livelihood ; these observations considerably widen the wildlife livestock interface area where disease spread can occur ( 12 ) .
livestock interfaces can encompass large areas , rather than being a fence or strip of land at the edge of protected areas .
these data should assist in refining disease modeling by showing the importance of temporal and spatial considerations and by redefining variables ( e.g. , age and sex ) involved in risk for pathogen spillover or emergence ( i.e. , identifying super - spreaders ) ( 13 ) .
our results suggest that the spillover of btb and other zoonoses at the wildlife livestock human interface constitutes a risk to animal and human health in the gltfca ( 9,14 ) .
the health issue in tfcas can not be overlooked and must be part of any management decision . combining ecological and epidemiologic knowledge is necessary to understand disease dynamics in these complex agro - ecosystems .
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we report on the long - distance movements of subadult female buffalo within a transfrontier conservation area in africa .
our observations confirm that bovine tuberculosis and other diseases can spread between buffalo populations across national parks , community land , and countries , thus posing a risk to animal and human health in surrounding wildlife areas .
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slx4 is a scaffold protein that binds to three dna repair endonucleases , mus81-eme1 , xpf - ercc1 , and slx1 ( andersen et al . , 2009 ,
, 2009 , muoz et al . , 2009 , saito et al . , 2009 ,
the slx4 complex is required for the efficient repair of dna interstrand crosslinks ( icls ) , ( fekairi et al . , 2009 ,
2009 ) , and the available evidence strongly suggests a role in processing dna recombination intermediates during icl repair .
the importance of slx4 for icl repair was underscored by the findings that biallelic mutations in slx4 in humans causes fanconi anemia ( fa ) ( kim et al .
many dna repair proteins form subnuclear foci at sites of dna damage , but slx4 overexpressed in epitope - tagged form localizes to subnuclear foci even without dna damage ( svendsen et al . , 2009 ) .
it was suggested that these foci correspond to telomeres , regions of repetitive dna at chromosome ends , which protect the ends from degradation ( svendsen et al . , 2009 ) .
telomeres terminate in an overhang that is thought to invade adjacent duplex telomeric repeats to form a telomeric ( t ) loop so that the chromosome ends are not perceived as dna breaks .
an additional layer of telomere protection is afforded by a multiprotein complex called shelterin , that binds to telomeric dna ( palm and de lange , 2008 ) . in normal somatic cells , telomeres shorten with every cell division , and telomere shortening contributes to organismal aging by limiting the proliferative capacity of adult stem cells ( blasco , 2007 ) . in immortalized cells and in cancers , telomere length is maintained by telomerase , a reverse transcriptase that can add telomere repeats with the aid of an associated rna template ( greider and blackburn , 1989 , mocellin et al . , 2013 ) .
some other immortalized cells , cancer cells , and even normal somatic cells can lengthen telomeres in a telomerase - independent manner using the alt ( alternative lengthening of telomeres ) pathway , which probably involves recombination ( bryan et al .
first , when overexpressed in a special clone of hela cells with abnormally long telomeres slx4 forms subnuclear foci that colocalize with shelterin ( svendsen et al . , 2009 ) .
second , slx4 was identified in a global screen for proteins that bind telomeres ( djardin and kingston , 2009 ) .
also , slx4 promotes telomere cleavage in cells lacking the rtel1 helicase ( vannier et al . , 2012 ) . in rtel1 cells , replisomes stall in telomeres leading to cleavage of t loops and the production of extrachromosomal t circles , which is mediated by the slx4 complex ( vannier et al . , 2012 ) .
although these observations link the slx4 complex to telomeres , it is not known whether endogenous slx4 localizes at telomeres , if this is applicable in cells that differ in the mechanisms used to maintain telomere length , or how slx4 is recruited to chromosome ends .
furthermore , in rtel1-proficient cells it remains to be determined if slx4 has a physiological role to play in telomere homeostasis . here
we first tested if endogenous slx4 localizes at telomeres . using antibodies raised in - house
, we found that endogenous slx4 forms subnuclear foci in u2os cells without addition of genotoxins ( figure 1a ) .
these foci are specific for slx4 because they disappeared when cells were transfected with slx4-specific small interfering rnas ( sirnas ) ( figure s1a ) .
endogenous slx4 foci did not appear to be restricted to any particular cell - cycle stage , and they did not increase in number or intensity after exposure of cells to genotoxins ( data not shown ) . to investigate if endogenous slx4 foci correspond to telomeres , we tested colocalization with subunits of shelterin .
most ( around 80% ) , but not all , endogenous slx4 foci colocalized with trf2 in u2os cells ( figure 1a ) , and also with trf1 and with a peptide - nucleic acid ( pna ) probe specific for telomeric dna ( figure 1b ) . when signal intensity was measured along a straight line in a single z - section through the nucleus , the peaks corresponding to slx4 overlap with trf2 ( figure 1c ) .
it is important to note that , whereas all trf2 foci in u2os cells contained slx4 , a proportion of slx4 foci did not overlap with trf2 ( figure 1a ) .
these observations indicate that slx4 is found at all telomeres in u2os cells , but a proportion of the slx4 foci do not correspond to telomeres .
slx4 associates with three separate structure - specific nucleases , xpf - ercc1 , mus81-eme1 , and slx1 .
xpf - ercc1 was previously shown to localize at telomeres ( zhu et al . , 2003 ) , and in this light we found that all of the xpf - ercc1 foci in cells colocalize with slx4 ( figures s1b and s1d ) .
mus81-eme1 was also shown to localize at telomeres ( zeng et al . , 2009 ) , but only around 5% of u2os cells show mus81 foci colocalizing with slx4 ( figures s1c and s1d ) .
endogenous slx1 foci were only barely detectable with our anti - slx1 antibodies ( data not shown ) .
slx4 controls the stability of slx1 ( muoz et al . , 2009 ) , and
overexpression of a gfp - tagged form of slx4 increased the levels of endogenous slx1 ( data not shown ) . under these conditions ,
endogenous slx1 foci could be detected with anti - slx1 antibodies ( figure 1d ) , and most of these foci colocalize with trf2 ( data not shown ) . in contrast , slx1 foci could not be detected when we overexpressed a mutant form of slx4 ( c1805r ) that is incapable of interacting with slx1 ( figure 1d ) ( d.c .
we also found that a gfp - tagged form of slx1 formed foci that colocalized with trf2 ( figure 1e ) .
taken together , these data show that the endogenous slx4 complex localizes at telomeres . to confirm the association of slx4 with telomeres
telomeric dna , but not alu repeat dna , was detected in slx4 immunoprecipitates of u2os cells using two separate anti - slx4 antibodies raised in sheep , but not when nonspecific sheep immunoglobulin ( ig ) g or anti - cenpa antibodies were used .
the chip signal in slx4 precipitates was comparable to the signal in trf2 precipitates ( figure 2a ) .
we also detected telomeric dna , but not alu dna , in anti - slx1 immunoprecipitates in u2os cells ( figure 2b ) .
telomere length is maintained by the alt pathway in u2os cells , whereas in other cell lines telomere length can be maintained by telomerase ( cesare and reddel , 2010 ) .
chip experiments showed that slx4 associates with telomeric dna , but not alu dna , in a549 and hela epithelial cells , two non - alt cell lines that are telomerase positive ( figures 2c and 2d , left panels ) .
the chip signal in anti - slx4 immunoprecipitates from these cells was weaker than in u2os cells , probably because a549 and hela cell telomeres are shorter than in u2os cells ( lee et al . , 2008 ) .
nonetheless , the chip signal in slx4 precipitates from a549 and hela cells was comparable to the signal in trf2 precipitates ( figures 2c and 2d , left panels ) .
furthermore , slx4 foci in a549 cells and hela cells are considerably less intense than in u2os cells , but a significant proportion of the foci still colocalized with trf2 ( figures 2c and 2d , middle panels ) .
when signal intensity along an arbitrary track in a single z - section of the nucleus was quantitated , the peaks corresponding to slx4 and trf2 in a549 and hela cells demonstrated good overlap ( figures 2c and 2d , right panels ) .
we also observed slx4 foci in ccl-211 primary lung fibroblasts , and some of these colocalize with trf1 similar to hela cells ( figure s1e ) .
although a significant proportion of telomeric foci in these cells do not contain slx4 , when signal intensity along an arbitrary track in a single z - section of the nucleus was quantitated , the peaks corresponding to slx4 demonstrated reasonably good overlap with trf1 ( figure s1e ) .
taken together , these data show that the slx4 complex localizes at telomeres in a range of human cell lines that differ in the mechanisms used to maintain telomere length .
both subunits of the trf2-rap1 shelterin subcomplex were found previously in slx4 immunoprecipitates ( muoz et al . , 2009 , svendsen et al . , 2009 ) .
we next sought to determine whether slx4 is recruited to telomeres by either of these two proteins .
yeast two - hybrid analysis , using xpf as a positive control , revealed that slx4 binds to trf2 , not rap1 ( figure 3a ) , and it seemed likely therefore that slx4 is recruited to telomeres by trf2 .
to investigate this possibility , we sought mutations in slx4 that abolish the interaction with trf2 , and our search was aided by a previous report describing a motif found in a range of proteins that interact with trf2 ( f / y - x - l - x - p ; figure 3b ) ( chen et al . , 2008 ) .
inspection of the primary amino acid sequence of human slx4 failed to identify a classical trf2-binding motif ( tbm ) , but we found a tbm - like motif ( h - x - l - x - p ) in which the first residue ( f / y ) is replaced by a histidine residue , which like f and y contains a planar aromatic ring structure ( figure 3b ) .
this motif in slx4 lies after the btb domain in an unstructured region of the protein ( figure 3b , data not shown ) .
we next tested the effect of mutating the key residues in the putative tbm in human slx4 on its interaction with trf2 .
to this end , u2os cells were cotransfected with rfp - tagged trf2 and ha - tagged slx4 wild - type or ha - slx4 in which h1020 , l1022 , or p1024 were mutated to alanine .
whereas wild - type ha - slx4 coprecipitated with rfp - trf2 , mutation of h1020 , l1022 , or p1024 caused a major reduction in the amount of ha - slx4 coprecipitating with rfp - trf2 ( figure 3c ) .
similar results were obtained when gfp - tagged slx4 was immunoprecipitated from cells coexpressing rfp - trf2 ( figure 3d ) .
importantly , mutating h1020 , l1022 , or p1024 had no effect on the ability of slx4 to interact with xpf - ercc1 , mus81 , or slx1 ( figure s2a )
. taken together , these data show that a tbm in human slx4 mediates interaction with trf2 .
intriguingly , a clear tbm is found in slx4 in primates but not in mammals lower down the evolutionary tree ( figure s2b ) .
slx4 orthologs in some mammals have a motif that is vaguely similar to the tbm in primates ( figure s2b ) , but none of the mammalian motifs would be expected to interact with trf2 based on previous work ( chen et al . , 2008 ) .
we next tested if mutating the tbm in slx4 affects its localization at telomeres . to this end ,
gfp - tagged wild - type slx4 , or gfp - slx4-l1022a , was stably expressed in u2os cells and foci were analyzed .
surprisingly , the overall number of foci formed by the slx4 l1022a mutant was similar to wild - type slx4 ( figures 3e and 3f ) .
however , whereas almost 65% of wild - type gfp - tagged slx4 foci colocalized with trf2 , only around 10% of foci formed by the slx4 l1022a mutant coincided with trf2 , and more than 40% of the foci clearly did not ( figures 3e and 3f ) .
the remaining 40% of slx4l1022a foci did not colocalize with trf2 , but were found adjacent to , but distinct from trf2 foci ( figures 3e and 3f ) . to further test the impact of mutating the slx4 tbm on telomere binding , we used chip analysis , which revealed that mutating slx4 l1022 to alanine caused an almost 80% reduction in the amount of telomeric dna associated with slx4 ( figures 3 g and 3h ) .
we tested this idea further using a dominant - negative form of trf2 ( trf2bm ) that heterodimerizes with endogenous trf2 blocking its binding to dna ( van steensel et al . , 1998 ) .
as shown in figure s2c , overexpression of an rfp - tagged form of trf2bm , but not wild - type trf2 , caused a substantial reduction in the number of slx4 foci in u2os cells ( figure s2c ) .
some of the cells transfected with trf2bm did not express this protein , and slx4 foci were normal in these cells ( figure s2c ) .
taken together , these data indicate that trf2 recruits slx4 to telomeres in human cells .
we also tested if the slx4-trf2 interaction is required for association of slx1 with telomeres .
we showed earlier that endogenous slx1 forms trf2-coincident foci in cells overexpressing wild - type slx4 ( figure 1d ) .
slx1 also forms foci in cells overexpressing slx4-l1022a , but , although these foci colocalize with slx4-l1022a , they do not colocalize with trf2 ( figure s3a ) .
slx4 is required for efficient dna repair . because trf2 has been shown to localize at sites of dna damage ( huda et al . ,
2012 ) , and to promote dna repair ( huda et al . , 2009 ) , we tested the possibility that trf2 might recruit slx4 to dna damage sites as well as to telomeres . to this end , we induced dna damage using local laser microirradiation and then checked by confocal microscopy for the ability of slx4 to form laser stripes .
time - lapse experiments revealed that gfp - tagged slx4 formed subnuclear stripes along the track of dna damage induced by laser irradiation visible within 12 min of irradiation , reaching a maximum intensity after 1 hr ( figure s3b ) .
the slx4-l1022a mutant localized at tracks of laser - induced dna damage with similar kinetics and intensity to wild - type slx4 ( figure s3b ) . we conclude from these data that trf2
we also tested if the association of slx4 with trf2 is required for dna repair using genotoxin hypersensitivity as readout . to this end , we stably expressed untagged forms of slx4 and slx4-l1022a in cells from fanconi anemia patient eufa-1354 that express abnormally low levels of an n - terminally truncated form of slx4 ( stoepker et al .
wild - type slx4 and slx4-l1022a are indistinguishable in their ability to rescue the mitomycin - c hypersensitivity of eufa-1354 cells . taken together , the data above indicate that neither the localization of slx4 at dna damage sites , nor the ability of slx4 to promote dna repair , requires binding to trf2 .
because the l1022a slx4 mutant interacts with xpf - ercc1 , mus81-eme1 , and slx1 ( figure s2a ) but does not localize at telomeres ( figures 3e3h ) , we reasoned that it might function as a dominant negative by sequestering the associated nucleases away from telomeres .
in this light , we made u2os cells that stably express gfp - tagged slx4 , or gfp - slx4-l1022a in a tetracycline - inducible manner .
upon induction of slx4-l1022a , we noticed an increase in the proportion of cells with tifs ( telomere dysfunction - induced foci ) ( takai et al . ,
2003 ) , defined as 53bp1 foci that colocalize with trf1 , compared with cells expressing wild - type slx4 ( figure 4a ) . in contrast , there was little difference between wild - type slx4 and the slx4-l1022a mutant in terms of the induction of 53bp1 foci that did not colocalize with trf1 ( figure 4a ) .
consistent with these data , sirna - mediated depletion of slx4 from u2os cells increased the proportion of cells with tifs ( figures s4a and s4b ) .
slx4-specific sirnas 3 and 4 resulted in more efficient depletion of slx4 than sirnas 1 and 2 , and consequently they were more potent at inducing tifs .
intriguingly , the lack of an obvious trf2 binding motif in nonprimate mammalian orthologs of slx4 suggests that slx4 should not localize at telomeres in mouse cells , for example , and we next investigated this possibility .
as shown in figure s4c , whereas human slx4 forms foci that colocalize with trf2 when ectopically expressed in mouse embryonic fibroblasts ( mefs ) , mouse slx4 forms foci but they do not colocalize with trf2 .
this is reminiscent of the human slx4-l1022a mutant that forms foci that do not colocalize with telomeres ( figure 3e3h ) .
these observations indicate that slx4 does not associate stably with telomeres in mouse cells , at least in fibroblasts .
nonetheless , we reasoned that slx4 might have roles at telomeres that do not require stable association with chromosome ends . with this in mind , we analyzed telomeres in slx4 mice generated in this laboratory , which will be described in detail elsewhere ( d.c .
first , we observed increased incidence of tifs in mouse embryonic fibroblasts ( mefs ) from slx4 mice ( figure s4d ) .
second , telomeres in livers from slx4 mice were longer than in slx4 mice or wild - type mice ( figure 4b ) .
telomeres were also longer in mefs from slx4 mice , but lengthening was reversed by expression of mouse slx4 in these cells so that telomeres were similar in length to wild - type mefs ( figure 4c ) .
these data suggest that slx4 might play a role in trimming telomeres to prevent overlengthening .
we also found that telomeres from slx4 mefs show increased fragility assessed by the frequency of multitelomeric signals ( mtss ) compared with slx4 mefs and wild - type cells ( figure 4d ) .
the data above indicate that targeting of slx4 to telomeres prevents dna damage in human cells , and that slx4 also plays a role in telomere homeostasis in mice in a manner that does not appear to require the stable retention of the slx4 complex at telomeres .
in this study , we showed slx4 is recruited to telomeres in human cells by trf2 .
we identified a motif in human slx4 required for direct interaction with trf2 that is similar but not identical to the trf2-binding motif ( tbm ; f / y - x - l - x - p ) identified in proteins such as apollo ( chen et al . , 2008 ) .
in the slx4 motif , however , the f / y residue is replaced by a histidine residue .
this observation extends the consensus trf2-binding motif and raises the possibility that other proteins might interact with trf2 through tbms similar to that of slx4 .
although slx4 is a rapidly evolving protein , it is somewhat surprising that the slx4 tbm - like motif is conserved in primates but not in mammals lower down the evolutionary tree ( figure s2b ) .
the absence of a tbm , however , does not exclude the possibility that slx4 ( or an slx4-associated protein ) in nonprimate species associates with trf2 and/or telomeres by alternative mechanisms .
however , we have been unable to detect endogenous slx4 at telomeres in mouse embryonic fibroblasts , and , whereas human slx4 overexpressed in mefs forms telomeric foci , mouse slx4 does not ( figure s4c ) .
therefore , slx4 associates with trf2 and telomeres in primates but not in other mammals . in human cells , preventing localization of slx4 at telomeres caused signs of dna damage ( figure 4a ) . the precise nature of this damage is not yet clear , but it might result from difficulties in one of the many processing steps during and after dna replication necessary for establishing the correct structure at telomeres .
it appears that not all of the telomere - related functions of the slx4 complex require stable association with telomeres , because telomeres are longer and more fragile in organs and cells from slx4 mice and telomere lengthening in slx4 mefs can be reversed by expression of wild - type slx4 ( figures 4b and 4c ) . from this perspective
telomere trimming , a mechanism that has been proposed to prevent overlengthening of telomeres ( pickett and reddel , 2012 ) .
it is not yet clear which of the slx4-associated nucleases are required to prevent telomere lengthening .
it is unlikely that xpf - ercc1 is the relevant nuclease because telomere length is not affected in ercc1 mice ( zhu et al . , 2003 ) .
the nuclease that promotes slx4-dependent telomere shortening could be mus81-eme1 and/or slx1 ; it will be interesting to test the relevant knockout mice for abnormally long telomeres .
slx1 is a good candidate considering the boulton lab has shown that it is required for the production of t circles in cells lacking rtel1 ( vannier et al . , 2012 ) .
the consequences of overlong telomeres for cell function and organism function are not clear , but this will be interesting to study .
u2os cells expressing gfp - slx4 were preextracted in csk buffer : 10 mm pipes ( ph 6.8 ) containing 100 mm nacl , 300 mm sucrose , 3 mm magnesium chloride , 1 mm egta , and 0.5% [ v / v ] triton x-100 , fixed with 2% paraformaldehyde ( pfa ) ( ph 7.0 ) , permeabilized with pbs containing 0.5% ( v / v ) triton x-100 , blocked with bsa ( 3% w / v ) in pbs , and probed with primary antibodies for 1 hr at room temperature . after extensive washing
, cells were incubated with secondary alexa antibodies for 2 hr at room temperature .
wide - field image stacks of cells were acquired using a deltavision microscope ( applied precision ) and subjected to iterative deconvolution to remove out - of - focus light and were further processed in omero ( allan et al . , 2012 ) . for endogenous slx4 immunofluorescence , cells grown on poly - l - lysine - coated coverslips were preextracted in csk buffer or pbs containing 0.5% triton x-100 prior to fixation in 3% pfa in csk ( ph 7.0 ) .
cells were permeabilized in pbs - containing 0.5% ( v / v ) triton x-100 and then blocked in antibody dilution buffer ( abdil ) : pbs containing 5% normal donkey serum , 0.1% fish skin gelatin , 0.1% triton x-100 , 0.05% tween-20 , and 0.05% sodium azide , before incubation with primary antibodies in abdil for 1 hr at room temperature or overnight at 4c .
after washing , cells were incubated with the relevant secondary antibodies for 2 hr at room temperature , stained with dapi , and mounted on glass slides .
cells grown to subconfluency on 15 cm plates were crosslinked with 1% ( v / v ) formaldehyde for 15 min , with 0.125 m glycine for 5 min , and then washed twice with pbs .
cells ( 4 10 cells per ip ) were lysed in chromatin immunoprecipitation ( chip ) lysis buffer ( 1% sds , 10 mm edta , 50 mm tris - hcl [ ph 8.0 ] plus protease inhibitors ) , followed by sonication for 15 s at 50% amplitude and 30 s rest ; this was repeated eight times at 4c before cells were centrifuged at 12,000 rpm at 4c for 10 min .
cell supernatants were diluted 1:10 in chip dilution buffer ( 1% [ v / v ] triton x-100 , 2 mm edta , 150 mm nacl , and 20 mm tris - hcl [ ph 8.0 ] ) and precleared with 2 g of sheared salmon sperm dna ( invitrogen ) and 20 l protein g - sepharose beads per equivalent ip volume ( 2 ml ) .
the supernatant was incubated with the relevant antibodies overnight , before the addition of protein g - sepharose beads for 1 hr .
after extensive washes , immune complexes were eluted with elution buffer ( 100 mm nahco3 and 1% sds ) and incubated overnight at 65c to reverse crosslinks .
protein and rna were removed by incubation with proteinase k and rnase a at 37c for 1 hr .
dna was purified by extraction with phenol / chloroform / isoamyl alcohol ( 25:24:1 ) , followed by centrifugation and retrieval of the aqueous supernatant .
dna was precipitated with ice - cold ethanol ( 96% v / v ) , washed with 70% ethanol , and resuspended in 100 l of water .
extended experimental procedurescell culture , fractionation , and lysisu2os cells were cultured in dmem growth medium ( gibco ) supplemented with 10% ( v / v ) fetal bovine serum , 100 units / ml penicillin , 100 g / ml streptomycin and 1% l - glutamate ( gibco , invitrogen ) .
u2os cells stably expressing gfp - slx4 were generated using the flp - in t - rex system ( invitrogen ) as described previously ( muoz et al . , 2009 ) .
cells were maintained in selective media containing 100 g / ml hygromycin and 15 g / ml blasticidin .
protein expression was induced by adding tetracycline to 0.1 g / ml for 24 hr . for immunoprecipitations and western blotting ,
cells were lysed in 50 mm tris - hcl ph 7.4 containing 150 mm nacl , 1 mm edta ph 8 , 1 mm egta ph 8 , 1% ( v / v ) triton x-100 , 270 mm sucrose supplemented with -mercaptoethanol ( 0.1%v / v ) , benzonase ( 50mu/l ) and 1 roche protease inhibitor tablet per 50 ml of buffer.slx4 micethe generation of slx4 mice will be described elsewhere ( d.c . and j.r , unpublished data ) .
animals were housed under specific pathogen free conditions in accordance with uk and eu regulations .
all procedures were carried out in accordance with university of dundee and united kingdom home office regulations.isolation and immortalization of mefsday 13.5 embryos were derived from timed matings between heterozygous parents . after decapitation ,
the red organs were removed , the embryo was minced and resuspended in 1 ml trypsin and incubated at 37c for 15 min before the addition of 10 ml growth medium .
cells were plated and allowed to attach over night before cells were washed with fresh medium to remove debris .
when cells reached confluency they were split and re - plated and this was considered passage 1 .
mefs were 3t3-immortalized.sirnacells were transfected with the relevant sirna duplex ( 30 nm ) using the calcium phosphate precipitation method or hiperfect ( qiagen ) according to the manufacturer s protocol .
the slx4 mrna target sequences used in figures s4a and s4b were : slx4 - 1 gagaagaaccctaatgaaa dtdtslx4 - 2 gcacaagggcccagaacaa dtdtslx4 - 3 ggagaaggaagcagagaat dtdtslx4 - 4 aaacgtgaatgaagcagaa dtdtslx4 - 4 was used in figure s1a .
the final concentration of sirna added to cells was 20 nm.antibodiesthe following primary antibodies were used in this study.western blottingmouse anti - human xpf diluted 1:5000 ( thermoscientific ms1381 ) ; rabbit anti - trf2 diluted 1:1000 ( cst # 2645 ) .
sheep polyclonal slx4 antibodies were raised against a bacterially expressed protein fragment corresponding to anti - human slx4 ( amino acids 1535 - 1834 ) fused to gst .
the antibodies were purified from sheep serum by affinity chromatography on ch - sepharose to which the peptide immunogen had been covalently coupled .
sheep polyclonal slx1 antibodies were raised against bacterially expressed human slx1 ( full - length ) fused to gst .
the antibodies were purified from sheep serum by affinity chromatography on ch - sepharose to which the peptide immunogen had been covalently coupled.immunoprecipitationsheep anti - human slx4 ( 1535 - 1834 ) as above ; sheep anti - gfp ( as sheep igg control , raised in the dstt ) ; mouse anti - trf2 ( millipore 41794 ) ; rabbit anti - rap1 ( bethyl a300 - 306a ) ; normal mouse igg ( cst # 5415 ) ; normal rabbit igg ( cst # 2729 ) .
all antibodies were used at 4 g antibody per 2 mg of cell lysate.immunofluorescencemouse anti - trf1 diluted 1:200 ( abcam ab10579 ) ; rabbit anti-53bp1 diluted 1:500 ( a300 - 272a ) ; mouse anti - human xpf diluted 1:500 ( thermoscientific ms1381 ) ; mouse anti - trf2 diluted 1:400 ( millipore 4a794 ) ; anti - slx1 diluted 1:100 .
all secondary antibodies were from invitrogen : donkey anti - mouse alexa 594 ( diluted 1:800 ) ; donkey anti - sheep alexa 594 ( diluted 1:800 ) ; donkey anti - mouse alexa 647 ( diluted 1:500 ) ; donkey anti - rabbit alexa 647 diluted 1:500 .
sheep polyclonal slx4 antibodies for immunofluorescence were raised against a bacterially expressed protein fragment corresponding to anti - human slx4 ( amino acids 381 - 680 ) fused to gst .
the antibodies were purified from sheep serum by affinity chromatography on ch - sepharose to which the peptide immunogen had been covalently - coupled .
these antibodies were diluted 1:200.chipsheep anti - human slx4 ( 381 - 680 ) as above ; sheep anti - human slx4 ( 1535 - 1834 ) as above ; mouse anti - trf2 ( imgenex img124a ) ; mouse anti - cenpa ( abcam ab13939 ) ; sheep anti - gfp ; rabbit anti - gfp ( abcam ab290 ) ; normal mouse igg ( cst # 5415 ) ; normal rabbit igg ( cst # 2729 ) .
all antibodies used at 3 g per chip.dot blotting and hybridizationchip dna was blotted onto hybond h membrane ( ge healthcare ) and cross - linked with 1200 j / m of uv - c light .
membranes were pre - hybridized by incubation in church buffer ( 0.5 m sodium phosphate buffer ph7.2 , 1 mm edta , 1% bsa ) for 1 hr .
membranes were then incubated with 800bp ( ttagggn ) telomere repeat probe radio - labeled with [ p]-dctp using klenow fragment , boiled before incubation in church buffer .
alternatively , membranes were incubated with a poly - nucleotide kinase ( pnk ) gamma 32p end labeled alu repeat probe ( cggagtctcgctctgtcgcccaggctggagtgcagtggcgcga ) in church buffer .
membranes were washed in 2 x ssc ( 300 mm nacl , 15 mm sodium citrate ) four times for 5 min each at 65c , and exposed to photographic film overnight at 80c.coupled immunofluorescence - fishin coupled immunofluorescence ( if)-fish experiments , immunofluorescence was carried out as normal with cells grown on coverslips .
cells were then washed twice in pbs and fixed again with 3% formaldehyde ( 5 min ) before further washing .
cells were then serially dehydrated in 70% , 95% and then 100% ethanol before drying in air for 2 min .
cells were incubated with fitc labeled telomeric fish probe ( dako ) and dishes were gently covered with saranwrap to aid distribution of the probe .
after 10 min at 80c , the coverslips were transferred to 4c and incubated overnight .
after two 15 min washes in buffer ( 10 mm tris - hcl , ph7.4 ) containing 70% ( v / v ) formamide at 50c , coverslips were washed three times for 5 min each with pbs ; the second pbs wash included dapi at 1 g / ml .
cells were then mounted for microscopic analysis.telomere fluorescence analyses of liver sectionsparaffin - embedded liver sections were hybridized with a pna - telomeric probe , and fluorescence intensity of telomeres was determined as previously described ( zijlmans et al . , 1997 ) .
quantitative image analysis was performed on images obtained using a confocal microscope ( leica tcs - sp5 dobs ) and the definiens developer cell software ( version xd 1.2 ; definiens ag).telomere length and cytogenetic analysis using telomere q - fish on metaphase spreadsq - fish on metaphases from primary mef was performed as described previously ( herrera et al . , 1999 ) . where indicated , mefs were treated with aphidicolin at 0.5 m for 18 hr followed by 6 hr recovery .
images were captured at 100x magnification using a cohu ccd camera on a leica dmra ( leica , heidelberg , germany ) microscope .
telomere fluorescence signals were quantified by using the tfl - telo program ( gift from peter lansdorp , vancouver , canada ) ( zijlmans et al .
, 1997).laser microirradiationcells were plated on glass - bottomed dishes and pre - sensitized with 10 mm 5-bromo-2-deoxyuridine ( brdu , sigma - aldrich ) for 24 h at 37c .
dna damaged was induced using a 405 nm cw 30 mw diode laser scanned 50x at 100% power over the selected roi ( region of interest ) in one optical section corresponding to the middle of the nucleus .
live cell imaging was carried out on a zeiss 710 confocal microscope equipped with a 37c environmental chamber and supplied with humidified 5% co2 .
cells were imaged with a zeiss plan - apochromat 63x 1.4na oil immersion objective lens .
u2os cells were cultured in dmem growth medium ( gibco ) supplemented with 10% ( v / v ) fetal bovine serum , 100 units / ml penicillin , 100 g / ml streptomycin and 1% l - glutamate ( gibco , invitrogen ) .
u2os cells stably expressing gfp - slx4 were generated using the flp - in t - rex system ( invitrogen ) as described previously ( muoz et al .
cells were maintained in selective media containing 100 g / ml hygromycin and 15 g / ml blasticidin .
protein expression was induced by adding tetracycline to 0.1 g / ml for 24 hr . for immunoprecipitations and western blotting
, cells were lysed in 50 mm tris - hcl ph 7.4 containing 150 mm nacl , 1 mm edta ph 8 , 1 mm egta ph 8 , 1% ( v / v ) triton x-100 , 270 mm sucrose supplemented with -mercaptoethanol ( 0.1%v / v ) , benzonase ( 50mu/l ) and 1 roche protease inhibitor tablet per 50 ml of buffer . the generation of slx4 mice will be described elsewhere ( d.c . and
animals were housed under specific pathogen free conditions in accordance with uk and eu regulations .
all procedures were carried out in accordance with university of dundee and united kingdom home office regulations .
the red organs were removed , the embryo was minced and resuspended in 1 ml trypsin and incubated at 37c for 15 min before the addition of 10 ml growth medium .
cells were plated and allowed to attach over night before cells were washed with fresh medium to remove debris .
when cells reached confluency they were split and re - plated and this was considered passage 1 .
cells were transfected with the relevant sirna duplex ( 30 nm ) using the calcium phosphate precipitation method or hiperfect ( qiagen ) according to the manufacturer s protocol .
the slx4 mrna target sequences used in figures s4a and s4b were : slx4 - 1 gagaagaaccctaatgaaa dtdtslx4 - 2 gcacaagggcccagaacaa dtdtslx4 - 3 ggagaaggaagcagagaat dtdtslx4 - 4 aaacgtgaatgaagcagaa dtdtslx4 - 4 was used in figure s1a .
slx4 - 1 gagaagaaccctaatgaaa dtdt slx4 - 2 gcacaagggcccagaacaa dtdt slx4 - 3 ggagaaggaagcagagaat dtdt slx4 - 4 aaacgtgaatgaagcagaa dtdt slx4 - 4 was used in figure s1a .
the final concentration of sirna added to cells was 20 nm . the following primary antibodies were used in this study .
mouse anti - human xpf diluted 1:5000 ( thermoscientific ms1381 ) ; rabbit anti - trf2 diluted 1:1000 ( cst # 2645 ) .
sheep polyclonal slx4 antibodies were raised against a bacterially expressed protein fragment corresponding to anti - human slx4 ( amino acids 1535 - 1834 ) fused to gst .
the antibodies were purified from sheep serum by affinity chromatography on ch - sepharose to which the peptide immunogen had been covalently coupled .
sheep polyclonal slx1 antibodies were raised against bacterially expressed human slx1 ( full - length ) fused to gst .
the antibodies were purified from sheep serum by affinity chromatography on ch - sepharose to which the peptide immunogen had been covalently coupled .
sheep anti - human slx4 ( 1535 - 1834 ) as above ; sheep anti - gfp ( as sheep igg control , raised in the dstt ) ; mouse anti - trf2 ( millipore 41794 ) ; rabbit anti - rap1 ( bethyl a300 - 306a ) ; normal mouse igg ( cst # 5415 ) ; normal rabbit igg ( cst # 2729 ) .
all antibodies were used at 4 g antibody per 2 mg of cell lysate .
mouse anti - trf1 diluted 1:200 ( abcam ab10579 ) ; rabbit anti-53bp1 diluted 1:500 ( a300 - 272a ) ; mouse anti - human xpf diluted 1:500 ( thermoscientific ms1381 ) ; mouse anti - trf2 diluted 1:400 ( millipore 4a794 ) ; anti - slx1 diluted 1:100 .
all secondary antibodies were from invitrogen : donkey anti - mouse alexa 594 ( diluted 1:800 ) ; donkey anti - sheep alexa 594 ( diluted 1:800 ) ; donkey anti - mouse alexa 647 ( diluted 1:500 ) ; donkey anti - rabbit alexa 647 diluted 1:500 . sheep polyclonal slx4 antibodies for immunofluorescence were raised against a bacterially expressed protein fragment corresponding to anti - human slx4 ( amino acids 381 - 680 ) fused to gst .
the antibodies were purified from sheep serum by affinity chromatography on ch - sepharose to which the peptide immunogen had been covalently - coupled .
sheep anti - human slx4 ( 381 - 680 ) as above ; sheep anti - human slx4 ( 1535 - 1834 ) as above ; mouse anti - trf2 ( imgenex img124a ) ; mouse anti - cenpa ( abcam ab13939 ) ; sheep anti - gfp ; rabbit anti - gfp ( abcam ab290 ) ; normal mouse igg ( cst # 5415 ) ; normal rabbit igg ( cst # 2729 ) .
chip dna was blotted onto hybond h membrane ( ge healthcare ) and cross - linked with 1200 j / m of uv - c light .
membranes were pre - hybridized by incubation in church buffer ( 0.5 m sodium phosphate buffer ph7.2 , 1 mm edta , 1% bsa ) for 1 hr .
membranes were then incubated with 800bp ( ttagggn ) telomere repeat probe radio - labeled with [ p]-dctp using klenow fragment , boiled before incubation in church buffer .
alternatively , membranes were incubated with a poly - nucleotide kinase ( pnk ) gamma 32p end labeled alu repeat probe ( cggagtctcgctctgtcgcccaggctggagtgcagtggcgcga ) in church buffer .
membranes were washed in 2 x ssc ( 300 mm nacl , 15 mm sodium citrate ) four times for 5 min each at 65c , and exposed to photographic film overnight at 80c . in coupled immunofluorescence ( if)-fish experiments ,
cells were then washed twice in pbs and fixed again with 3% formaldehyde ( 5 min ) before further washing .
cells were then serially dehydrated in 70% , 95% and then 100% ethanol before drying in air for 2 min .
cells were incubated with fitc labeled telomeric fish probe ( dako ) and dishes were gently covered with saranwrap to aid distribution of the probe .
after 10 min at 80c , the coverslips were transferred to 4c and incubated overnight .
after two 15 min washes in buffer ( 10 mm tris - hcl , ph7.4 ) containing 70% ( v / v ) formamide at 50c , coverslips were washed three times for 5 min each with pbs ; the second pbs wash included dapi at 1 g / ml .
paraffin - embedded liver sections were hybridized with a pna - telomeric probe , and fluorescence intensity of telomeres was determined as previously described ( zijlmans et al . , 1997 ) .
quantitative image analysis was performed on images obtained using a confocal microscope ( leica tcs - sp5 dobs ) and the definiens developer cell software ( version xd 1.2 ; definiens ag ) .
q - fish on metaphases from primary mef was performed as described previously ( herrera et al .
, 1999 ) . where indicated , mefs were treated with aphidicolin at 0.5 m for 18 hr followed by 6 hr recovery .
images were captured at 100x magnification using a cohu ccd camera on a leica dmra ( leica , heidelberg , germany ) microscope .
telomere fluorescence signals were quantified by using the tfl - telo program ( gift from peter lansdorp , vancouver , canada ) ( zijlmans et al . , 1997 ) .
cells were plated on glass - bottomed dishes and pre - sensitized with 10 mm 5-bromo-2-deoxyuridine ( brdu , sigma - aldrich ) for 24 h at 37c .
dna damaged was induced using a 405 nm cw 30 mw diode laser scanned 50x at 100% power over the selected roi ( region of interest ) in one optical section corresponding to the middle of the nucleus .
live cell imaging was carried out on a zeiss 710 confocal microscope equipped with a 37c environmental chamber and supplied with humidified 5% co2 .
cells were imaged with a zeiss plan - apochromat 63x 1.4na oil immersion objective lens .
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summaryslx4 , a scaffold for structure - specific dna repair nucleases , is important for several types of dna repair .
many repair proteins bind to sites of dna damage , resulting in subnuclear
foci ,
but slx4 forms foci in human cells even without dna damage . using several approaches ,
we show that most , but not all , slx4 foci localize to telomeres in a range of human cell lines irrespective of the mechanisms used to maintain telomere length .
the slx1 holliday - junction - processing enzyme is recruited to telomeres by slx4 , and slx4 , in turn , is recruited by a motif that binds to the shelterin subunit trf2 directly .
we also show that trf2-dependent recruitment of slx4 prevents telomere damage .
furthermore , slx4 prevents telomere lengthening and fragility in a manner that appears to be independent of telomere association .
these findings reveal that slx4 plays multiple roles in regulating telomere homeostasis .
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einstein , podolsky and rosen ( epr ) @xcite put forth the question of whether the quantum mechanical description of physical reality is complete , giving the example of a two - particle quantum state showing peculiar correlations ( dubbed `` entanglement '' or `` verschrnkung '' by schrdinger @xcite ) : if one measures the position or momentum of one particle , one can predict with certainty the outcome of measuring their counterpart for the other particle .
thus , depending on which measurement is chosen for the first particle , the value of either the position or momentum can be predicted with arbitrary precision for the second particle .
the ensuing controversy has revolved around the interpretation of the epr problem and its implications on quantum theory @xcite .
later , bohm considered @xcite two entangled spin-1/2 particles , which have become the focus of attention on this epr issue : their _ discrete - variable _ entangled states have served to demonstrate the incompatibility of quantum mechanics with local realism , by the violation of bell s inequality @xcite . in recent years , there has been revival of interest in _ continuous - variable _ entanglement , in the spirit of the original epr problem @xcite .
the original _ ideal _ epr @xcite state of two particles1 and 2 , is , respectively , represented as follows in their coordinates or momenta ( in one dimension ) , @xmath0 if two particles are prepared in such a state , and one measures the value of @xmath1 ( or @xmath2 ) of particle 1 , one can predict the result of measuring @xmath3 ( or @xmath4 , respectively ) with perfect precision . the state of eq .
( [ eprstatedelta ] ) would , however , occupy infinite space and have infinite kinetic energy .
one can consider more realistic variants of this state , e.g. , a gaussian state given by @xmath5 where @xmath6 ( see fig . [ figepr ] ) .
the original epr state corresponds to the limit @xmath7 .
after measuring the position of particle 1 , the position of particle 2 is centered at @xmath8 with the uncertainty @xmath9^{-1/2}$ ] . in the limit of @xmath10 , the position of particle 2
is centered at @xmath1 , and its uncertainty is @xmath11 .
similar relations hold also for the momentum of particle 2 after the momentum of particle 1 is measured .
thus , either of the two conjugate quantities of particle 2 can be predicted with arbitrarily high precision .
of course , the heisenberg uncertainty relation is not violated , since for a single system one can measure only one of the two conjugate quantities .
approximate versions of the translational epr state , wherein the @xmath12-function correlations are replaced by finite - width distributions , have been shown to characterize the quadratures of the two optical - field outputs of parametric downconversion @xcite , or of a fiber interferometer with kerr nonlinearity @xcite .
such states allow for various schemes of continuous - variable quantum information processing such as quantum teleportation @xcite or quantum cryptography @xcite .
a similar state has also been predicted and realized using collective spins of large atomic samples @xcite .
it has been shown that if suitable interaction schemes can be realized , continuous - variable quantum states of the original epr type could even serve for quantum computation @xcite .
notwithstanding its applications to quantum information processing , the translational epr state of eq .
( [ eprstategauss ] ) does not entail a violation of local realism : such a state has a _ non - negative _ wigner function , controlling the position and momentum distribution of each particle .
nevertheless , there exist measurement schemes in which an analog of bell s inequality is violated @xcite for such a state as for any pure entangled state .
the realization and measurement of the epr translational correlations of _ material particles _ appears to be very difficult .
there have been suggestions to start with entangled light fields and to transfer their quantum state into the state of trapped ions in optical cavities @xcite or of vibrating mirrors @xcite .
we have proposed to realize translational epr states by taking advantage of interatom correlations in a dissociating diatom @xcite .
more recently , we have considered dipole - dipole coupled cold atoms in an optical lattice as a source of translational epr states @xcite . in order to generate the translational epr entanglement between interacting material particles , one must be able to accomplish several challenging tasks : ( a ) switch on and off the entangling interaction ; ( b ) confine their motion to single dimension , and ( c ) infer and verify the dynamical variables of particle 2 _ at the time of measurement _ of particle 1 .
the latter requirement is particularly hard for free particles , since by the time we complete the prediction for particle 2 , its position will have changed . in @xcite
we suggested to overcome these hurdles by transforming the wavefunction of flying ( ionized ) atoms emerging from diatom dissociation by an electrostatic / magnetic lens onto the image plane , where its position corresponds to what it was at the time of the diatom dissociation .
in @xcite we have proposed a solution based on the following steps : ( i ) controlling the diatom formation and dissociation in an optical lattice by switching on and off a laser - induced dipole - dipole interaction ; ( ii ) controlling the motion and effective masses of the atoms and the diatom by changing the intensities of the lattice fields . in this article
we discuss our proposal in more detail and elaborate on its principles .
our aim here is to demonstrate the feasibility of preparing a momentum- and position - entangled state of atom pairs in optical lattices , which would be a variant of the original epr state , owing to lattice diffraction . in sec .
[ sec - specif ] we specify the physical system under study . in sec .
[ sec - singles ] the basic properties of single - atom states in optical lattices are discussed . in sec .
[ sec - binding ] we discuss the binding effect of the dipole - dipole interaction .
[ sec - prep ] deals with the preparation of epr states by manipulation of the effective masses of the atoms . in sec .
[ sec - measur ] we discuss experimental demonstration possibilities of measuring the epr sec .
[ sec - conclusion ] is devoted to conclusions .
let us assume two overlapping optical lattices with the same lattice constant @xmath13 , as in fig .
[ fig - lattice ] .
the lattices are very sparsely occupied by two kinds of atoms , each kind interacting with only one of the two lattices .
this can be realized , e.g. , by assuming two different internal ( say , hyperfine ) states of the atoms @xcite . in both lattices
, the potentials are strongly confining in the @xmath14 and @xmath15 directions ( realized by strong laser fields ) , whereas in the @xmath16 direction the lattice potential is only moderately to weakly confining .
thus , the motion of each particle is restricted to the @xmath16 direction . in each direction
we assume that only the lowest vibrational energy band is occupied .
initially , the potential minima of the lattices are displaced from each other by an amount @xmath17 in the @xmath14 direction .
an auxiliary laser produces a laser - induced dipole - dipole interaction ( liddi ) between the atom pairs .
it is linearly polarized in the @xmath14 direction , traveling in the @xmath16 direction and has a wavelength @xmath18 , moderately detuned from an atomic transition that _ differs _ from the transition used to trap the atoms in the lattice . in the case of two atoms with identical polarizabilities in the geometry of fig .
[ f - lattice3 ] , the interatomic lddi potential induced by a linearly polarized laser is of the form @xcite @xmath19 where @xmath20\ ! + \ !
\cos^2 \theta \frac{\cos k r}{k r } \right\ } , \end{aligned}\ ] ] and @xmath21 here the wavenumber is @xmath22 , @xmath23 is the coupling laser intensity , and the atomic dynamic polarizability @xmath24 is @xmath25 @xmath26 being the dipole moment element , @xmath27 the atomic transition frequency , and @xmath28 .
the position - dependent part @xmath29 is a function of @xmath30 , the distance between the atoms , and @xmath31 , the angle between the interatomic axis and the wavevector of the coupling laser .
since @xmath32 , @xmath33 has a pronounced minimum for atoms located at the nearest sites , @xmath34 , where @xmath35 the liddi energy as a function of @xmath36 and the relative position of the atoms is shown in figs . [ f - ddint ] and [ f - potent1 ] . under the above assumptions , we can treat the system as consisting of pairs of `` tubes '' , either empty or occupied , that are oriented along @xmath16 .
only atoms within adjacent tubes are appreciably attracted to each other along @xmath14 , due to the liddi .
let us focus on the subensemble of tube - pairs in which each tube is occupied by exactly one atom .
in the 1d optical lattice , the single - atom hamiltonian is @xmath37 here @xmath38 is the atomic mass , @xmath39 is the momentum operator , @xmath40 is the maximum potential energy due to the interaction of the atomic dipole with the laser field , @xmath41 where @xmath42 is the dipole matrix element of the lattice transition , @xmath43 is the detuning of the lattice field from this transition , and @xmath44 is the intensity of the lattice field .
the hamiltonian ( [ eq - hlat2 ] ) describes a quantum pendulum .
the eigenfunctions of the corresponding schrdinger equation are the mathieu functions @xcite .
the eigenvalues form bands , whose spectrum depends on the ratio of @xmath40 to the recoil energy , @xmath45 so that one can distinguish between strongly binding ( @xmath46 ) and weakly binding ( @xmath47 ) potentials .
we assume that the atoms are cooled down to the lowest energy band of the lattice , in the absence of liddi .
the state of each atom is then conveniently described in terms of wannier functions @xmath48 @xcite that are localized at lattice sites labeled by index @xmath49 .
the wannier functions are superpositions of the delocalized bloch eigenfunctions @xmath50 of the same band , @xmath51 where @xmath52 is the number of lattice sites , and @xmath53 is the position of the @xmath49th site .
since the wannier functions are not eigenfunctions of the single - particle hamiltonian , an atom initially prepared in a wannier state that is localized at one site , will subsequently tunnel to the neighboring sites .
nevertheless , if the tunneling rate is sufficiently slow , the single - particle hamiltonian in the wannier basis has a relatively simple form : @xmath54 here the diagonal elements @xmath55 are equal to the energy at the center of the band , and only two sets of off - diagonal elements , expressing hopping between the neighboring sites , are non - negligible : @xmath56 the hopping rate is related to the energy bandwidth of the lowest lattice band @xmath57 by @xmath58 ) , the quantum - pendulum schrdinger equation yields the approximate formulae for @xmath59 and the single - atom effective mass : @xmath60 the wannier functions of the lowest band can be approximated by gaussians : @xmath61 where @xmath62 this approximation is relatively accurate for @xmath63 ( see the inset in fig .
[ figconprobx ] ) with fidelity @xmath64% .
note , however , that the gaussian approximation is not suitable for calculating the hopping potential ( [ eq - vhop ] ) since this quantity is very sensitive to the non - gaussian tails of the wannier wavefunctions .
let us now assume that two neighboring tubes in fig .
[ f - lattice3 ] are occupied by one atom each and the liddi is turned on .
if the tubes are close to each other ( @xmath65 , as in fig . [ f - ddint ] ) , the interaction hamiltonian in the wannier basis has nonzero elements only for atoms residing at the nearest sites , @xmath66 and the total two - atom hamiltonian is @xmath67 this hamiltonian has been diagonalized numerically , and its eigenvalues are shown in fig .
[ f - envdd ] as a function of the hopping and binding potential strength .
one can see that for a sufficiently large ratio @xmath68 a band of diatomic states is split off the band of independent atoms , towards lower energies . for a strong liddi binding
, @xmath69 , the ground state of the hamiltonian corresponds to a tightly bound diatom which can be approximated by @xmath70 this is a highly correlated state : when particle 1 is found at the @xmath49th site of lattice 1 , then particle 2 is found at the @xmath49th site of lattice 2 , with position dispersion given by the half - width @xmath71 of the atomic wannier function in the lowest band , @xmath72 ( fig .
[ fig - xx]a ) .
the fourier transform of this wave function yields its momentum representation . the corresponding momentum probability distribution exhibits anti - correlation similarly to the epr states ( [ eprstatedelta ] ) or ( [ eprstategauss ] ) , but it reflects the lattice periodicity ( fig . [ fig - pp]a ) . in momentum space ,
the state occupies a region of half - width @xmath73 , and the probability distribution has narrow ridges along @xmath74 .
the width of the ridges is inversely proportional to the lattice size , @xmath75 , and they are shifted by @xmath76 from each other . the probability of atoms to escape their epr partners `` over the next '' sites increases with the ratio @xmath77 .
this leads to an increase of the position dispersion which can be estimated by first - order perturbation theory : let atoms 1 and 2 occupy the @xmath49th site in the absence of @xmath59 . with the perturbation @xmath59 on , atom 2 can occupy also sites @xmath78 , which have energies @xmath79 above the unperturbed state , with the probability @xmath80 .
this contributes to an increase in the diatomic separation dispersion , @xmath81 resulting in the joint probability distribution of the atomic positions and momenta as a function of @xmath77 , shown in fig .
[ fig - xx]b and fig .
[ fig - pp]b , respectively . the states of the tightly bound diatom form a separate band whose bandwidth is @xmath82 below the lowest atomic vibrational band .
the _ diatomic _ hopping potential @xmath83 can be estimated by assuming that the two atoms consecutively hop to their neighboring sites , i.e. , the change @xmath84 is realized either via @xmath85 or via @xmath86 by adiabatic elimination of the higher - energy intermediate states , one obtains @xmath87 all the states of the diatomic band have correlated positions .
however , the momenta are not anti - correlated in all these states in the same way as in the diatomic ground state . to realize strong momentum anti - correlations
, we have to prepare a state that predominantly originates from the bottom of the diatomic band .
if we work with thermal states this means that the temperature of the system must satisfy @xmath88 near the bottom of the band , the diatomic dynamics can be described by means of the 2-atom effective mass given by @xmath89 the thermal ( kinetic ) energy of the diatom is then related to the degree of momentum anti - correlation through the sum - momentum spread @xmath90 , @xmath91 to determine how `` strong '' the epr effect is , we compare the product of the half - widths of the position and momentum peaks in the tightly bound diatom state with the heisenberg uncertainty limit through the parameter @xcite : @xmath92 a value of @xmath93 higher than 1 indicates the occurrence of the epr effect ; the higher the value of @xmath93 , the stronger the effect . strictly speaking , for the multi - peak momentum distribution , one should use a more general uncertainty relation , as discussed , e.g. , in @xcite , that distinguishes the uncertainty of multiple narrow peaks from that of a single broad peak .
however , even the simple half - width of the peaks is a useful measure of the epr effect . in order to maximize @xmath93
, we must adhere to the trade - off between reducing either @xmath94 , by decreasing @xmath95 , or @xmath96 , by increasing @xmath95 .
the optimum value of @xmath93 generally depends on the temperature of the diatom , as detailed below .
cooling down the diatomic system to prepare the epr state is a non - trivial task .
we suggest a `` cooling '' procedure which takes advantage of the difference between the single - atom and the diatom bandwidths , and of the possibility to change the light - induced potentials . the key is first to cool down individual atoms and then separate the unpaired atoms from the diatoms .
the scheme consists of three steps : \(i ) we first switch on only an external , shallow , harmonic potential in the @xmath16 direction ( all other potentials being off ) , and cool the @xmath16-motion of the atoms down to its ground state .
the width @xmath97 of the ground state should be several times the lattice constant ; it is related to the desired momentum anti - correlation by @xmath98 . the temperature necessary to achieve this must be @xmath99 \(ii )
a weak lattice potential in the @xmath16-direction is then slowly switched on , so that the state becomes @xmath100 where the coefficients @xmath101 \end{aligned}\ ] ] are gaussians localized around the minimum of the external potential .
\(iii ) we switch on the liddi and change the external potential , from an attractive well to a repulsive linear potential , acting to remove the particles from the lattice .
the two parts of the wavefunction will respond differently : the motion of the paired atoms ( corresponding to @xmath102 ) will remain in the vicinity of the initial position because of their narrow energy band ( fig .
[ pasy ] ) .
single ( unpaired ) atoms , whose bandwidth is substantially larger , will travel a much longer distance before hitting the top of the energy band .
thus , after a properly chosen time , the unpaired atoms could be removed from the @xmath16-region of interest , which is @xmath103 longer for single atoms than for diatoms [ see eq .
( [ bandwidthdiat ] ) ] . provided the time @xmath104 is short enough for the system to remain near the bottom of these two bands , the dynamics can be interpreted in terms of the appropriate effective masses : the `` heavy '' diatoms with mass move much slower than the `` light '' single atoms with mass ( [ 15 ] ) .
thus , after changing the sign of the external potential , the unpaired atoms will be ejected out of the lattice and separated from the diatoms as glumes from grains .
this effect is illustrated by the numerical simulation in fig .
[ celek ] for two lithium atoms in two lattices with @xmath105 323 nm ( corresponding to the transition 2s3p ) and a dipole - dipole coupling field of @xmath106 670.8 nm ( transition 2s2p ) .
the dipole moment element of the lattice transition is @xmath107 cm , while the liddi coupling dipole element is @xmath108 cm . from these values
we get the recoil energy @xmath109j .
the lattice and liddi field intensities are @xmath110 0.186 w/@xmath111 and @xmath112 0.023 w/@xmath111 .
the corresponding field detunings are @xmath113 , @xmath114 , the respective decay rates being @xmath115 s@xmath116 , and @xmath117 s@xmath116 .
the two lattices are displaced by @xmath118 40 nm . from these values
we get the lattice potential @xmath119 , the liddi potential of the nearest atoms @xmath120 , and the hopping potential @xmath121 .
the two - particle hopping potential is then @xmath122 .
the correlated pairs are prepared by first cooling independent atoms in an external harmonic potential with the ground - state half - width of @xmath123 ( frequency of 1 khz @xmath124 nk ) . when the linear external potential is switched on ,
the atoms start moving in the direction of decreasing potential energy . figure [ celek ] , which captures the situation at three consecutive times , shows that unpaired atoms ( off - diagonal peaks ) are displaced by a much longer distance than the diatoms ( diagonal peaks ) .
the paired atoms remaining in the lattice are then in the state @xmath125 |\chi_{j}^{(1)}\rangle with the uncertainties @xmath126 and @xmath127 , respectively . at higher temperatures the atoms
are not cooled to the ground state of the external potential and the momentum anti - correlation has the spread @xmath128\}. \end{aligned}\ ] ] the parameter @xmath93 of eq .
( [ sparameter ] ) can then be estimated as @xmath129 .
\end{aligned}\ ] ] this relation enables us to select the optimal external harmonic potential ( specified here by @xmath97 ) such that the parameter @xmath93 is maximized , for a given temperature @xmath130 .
the small effective mass of unpaired atoms allows us to cool them to temperatures higher than that corresponding to the bottom of the diatomic band .
the price is , however , that most of the atoms are discarded and only a small fraction of @xmath131 will remain in the bound diatom state .
the different behavior of the paired and unpaired atoms in a periodic potential is a sparse - lattice analogy of the transition from mott - insulator to a superfluid state in the fully occupied lattice , recently observed in ref .
@xcite .
the two - particle joint position distribution of the ground state is a chain of peaks of half - width @xmath71 separated by @xmath13 that are located along the line @xmath132 ( fig .
[ figconprobx ] ) .
the corresponding joint momentum distribution spreads over an area of half - width @xmath133 and consists of ridges in the direction @xmath134 , that are separated by @xmath135 , and have the half - width @xmath136 for a lattice of @xmath52 sites ( fig .
[ figconprobp ] ) .
after preparing the system in the epr state , how can one can test its properties experimentally ? to this end we may increase the lattice potential @xmath137 , switch off the field inducing the liddi , and separate the two lattices by changing the laser - beam angles . by increasing @xmath40 ,
the atoms lose their hopping ability and their quantum state is `` frozen '' with a large effective mass : the bandwidth @xmath138 decreases exponentially with @xmath40 and the effective mass increases exponentially , so that the atoms become too `` heavy '' to move .
one has then enough time to perform measurements on each atom : \a ) the atomic position can be measured by detecting its resonance fluorescence . after finding the site occupied by atom 1
, one can infer the position of atom 2 .
if this inference is confirmed in a large ensemble of measurements , it would suggest that there is an `` element of reality '' @xcite corresponding to the position of particle 2 .
an example of the conditional probability of position of particle 2 after measuring the position of particle 1 is given in fig .
[ figconprobx ] .
\b ) the momentum can be measured by switching off the @xmath16-lattice potential of the atom ( thus bringing it back to its `` normal '' mass @xmath38 ) .
the distance traversed by the atom during a fixed time is proportional to its momentum .
an example of the conditional probability of the momentum of particle 2 given the momentum of particle 1 is shown in fig .
[ figconprobp ] .
\c ) one can test the epr correlations between the atomic _ ensembles _ occupying the two lattices , testing large number of pairs in a single run .
the correlations in @xmath16 and anti - correlations in @xmath139 would be observed by matching the _ distribution histograms _ measured on atoms from the two lattices .
we have discussed a scheme which can be used to prepare a translationally entangled pair of massive particles in a state analogous to the original epr state @xcite .
a novel element of the present scheme is the extension of the epr correlations to account for lattice - diffraction effects .
their momentum and position correlations principally differ from those of free particles [ eqs . , ] : due to the lattice periodicity , the _ position and momentum distributions have generally a multi - peak structure_. the realization of the proposed scheme is expected to be based on the adaptation of existing techniques ( optical trapping , cooling , controlled dipole - dipole interaction ) . to the requirements spelled out in sec .
[ sec - prep ] and [ sec - measur ] the most important ingredient of the scheme is the manipulation of the effective mass , for epr - pairs preparation ( by separating the `` light '' unpaired atoms from the `` heavy '' diatoms ) and for their detection ( by `` freezing '' the atoms in their initial state so that their epr correlations are preserved long enough ) .
one may envision extensions of the present approach to matter teleportation @xcite and quantum computation based on continuous variables @xcite .
such extensions may involve the coupling of entangled atomic ensembles in optical lattices by photons carrying quantum information .
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we study a possible realization of the position- and momentum - correlated atomic pairs that are confined to adjacent sites of two mutually shifted optical lattices and are entangled via laser - induced dipole - dipole interactions .
the einstein - podolsky - rosen ( epr ) `` paradox '' [ phys . rev .
* 47 , * 777 ( 1935 ) ] with translational variables is then modified by lattice - diffraction effects .
this `` paradox '' can be verified to a high degree of accuracy in this scheme .
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SECTION 1. SHORT TITLE.
This Act may be cited as the ``National Research Investment Act of
1997''.
SEC. 2. FINDINGS; PURPOSES.
(a) Findings.--Congress finds that--
(1) for fiscal year 1965, 5.7 percent of the Federal budget
was expended for nondefense research and development
activities;
(2) for fiscal year 1997, the percentage of the Federal
budget allocated for nondefense research and development
activities is 1.9 percent, which is 67 percent less than the
percentage in fiscal year 1965;
(3) for the first time in 25 years during the period
beginning with fiscal year 1992 and ending with fiscal year
1995, the amount of funds expended by the Federal Government on
research (expressed in real dollars) declined each year;
(4) during the period beginning with fiscal year 1970, and
ending with fiscal year 1995, the United States had not, during
any fiscal year, expended an amount for nondefense research and
development activities, that, expressed as a percentage of the
Gross Domestic Product, was greater than or equal to the
percentage expended by Japan or Germany for that fiscal year;
and
(5) an increased level of investment in basic science and
medical research by the Federal Government is essential to
maintaining the position of the United States as the
technological leader of the world.
(b) Purposes.--The purposes of this Act are as follows:
(1) To double the annual authorized amount of Federal
funding for basic science and medical research over the 10-year
period following the date of enactment of this Act, so that the
amount of Federal funding for fiscal year 2007 is equal to
$65,000,000,000.
(2) To restore the high priority that science and
technology had previously been afforded in the Federal budget.
(3) To invest in the future of the United States and the
people of the United States by expanding the research
activities referred to in paragraph (1).
(4) To enhance the quality of life for all the people of
the United States.
(5) To guarantee the leadership of the United States in
science and medicine.
SEC. 3. AUTHORIZATIONS OF APPROPRIATIONS.
(a) Funds for Covered Research and Development Defined.--For
purposes of this section, the term ``funds for covered research and
development'' means--
(1) any funds made available by appropriations for--
(A) the National Science Foundation;
(B) the National Aeronautics and Space
Administration;
(C) the National Oceanic and Atmospheric
Administration of the Department of Commerce;
(D) the National Institute for Standards and
Technology of the Department of Commerce; and
(E) the National Institutes of Health of the
Department of Health and Human Services;
(2) any funds made available by appropriations for use for
research and development activities (as that term is used in
the most recent applicable appropriations Act with respect to a
Federal Agency) for basic science or medical research--
(A) by the Centers for Disease Control of the
Department of Health and Human Services;
(B) by the Department of Energy (to the extent that
the activities are not defense-related activities);
(C) by the Department of Agriculture;
(D) by the Department of Veterans Affairs;
(E) by the Smithsonian Institution; and
(F) by the Department of Education; and
(3) any funds made available by appropriations to the
Environmental Protection Agency for science and technology
activities for basic science or medical research.
(b) Authorization of Appropriations.--
(1) In general.--Subject to the limitations under paragraph
(2), there are authorized to be appropriated as funds for
covered research and development--
(A) for fiscal year 1998, $35,750,000,000, of which
$14,025,000,000 shall be used by the National
Institutes of Health of the Department of Health and
Human Services;
(B) for fiscal year 1999, $39,000,000,000, of which
$15,300,000,000 shall be used by the National
Institutes of Health of the Department of Health and
Human Services;
(C) for fiscal year 2000, $42,250,000,000, of which
$16,575,000,000 shall be used by the National
Institutes of Health of the Department of Health and
Human Services;
(D) for fiscal year 2001, $45,500,000,000, of which
$17,850,000,000 shall be used by the National
Institutes of Health of the Department of Health and
Human Services;
(E) for fiscal year 2002, $48,750,000,000, of which
$19,125,000,000 shall be used by the National
Institutes of Health of the Department of Health and
Human Services;
(F) for fiscal year 2003, $52,000,000,000, of which
$20,400,000,000 shall be used by the National
Institutes of Health of the Department of Health and
Human Services;
(G) for fiscal year 2004, $55,250,000,000, of which
$21,675,000,000 shall be used by the National
Institutes of Health of the Department of Health and
Human Services;
(H) for fiscal year 2005, $58,500,000,000, of which
$22,950,000,000 shall be used by the National
Institutes of Health of the Department of Health and
Human Services;
(I) for fiscal year 2006, $61,750,000,000, of which
$24,225,000,000 shall be used by the National
Institutes of Health of the Department of Health and
Human Services; and
(J) for fiscal year 2007, $65,000,000,000, of which
$25,500,000,000 shall be used by the National
Institutes of Health of the Department of Health and
Human Services.
(2) Limitations.--
(A) Development of public information.--In using
funds made available under this section, the
appropriate officials shall take such action as may be
necessary to ensure that priority is given to basic
scientific research that has the purpose of developing
scientific information to be available to the general
public.
(B) Use of funds.--No funds made available pursuant
to the authorization under this subsection may be used
for commercial purposes, except that such funds may
only be used for precompetitive research and
development for technology.
(C) Peer review.--In allocating funds made
available under this section, the appropriate officials
shall take such action as may be necessary to ensure
that a peer review system is used.
SEC. 4. COMPLIANCE WITH DISCRETIONARY CAPS.
Notwithstanding any other provision of law, no funds may be made
available under this Act in a manner that does not conform with the
discretionary spending caps provided in the most recently adopted
concurrent resolution on the budget.
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National Research Investment Act of 1997 - States purposes of this Act, including to double the annual authorized amount of Federal funding for basic science and medical research over the ten-year period following enactment of this Act.
Authorizes appropriations for covered research and development for FY 1998 through 2007 to be used by the National Institutes of Health of the Department of Health and Human Services. Sets forth limitations on the use of such funds.
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complete oncological surgical resection whenever possible is the cornerstone of treatment . in cases of locally advanced tumors with invasion of adjacent structures ( t4 ) , en bloc resection of all involved tissues is essential so as not to increase local failure and decrease survival .
adjuvant chemotherapy is used in order to eliminate any possibility of developing metastasis from cancer cell dissemination . in cases of perforated colon cancer , a dismal prognosis
is anticipated due to the burden of the septic episode , in addition to the hazardous effect from the cancer .
we present a case of perforated sigmoidal cancer with abscess formation to the ventral abdominal wall , which was , however , first misdiagnosed as strangulating ventral hernia .
a 74-year - old female patient was admitted to our surgical department complaining of a painful palpable mass of the hypogastrium and high fever , which developed over a period of a few hours .
the patient reported changes in bowel habits , anorexia and weight loss during the last 2 months prior to admission .
physical examination revealed a temperature of 38c and a palpable , protruding , and erythematous mass over a midline lower abdominal wall incision .
her past medical history was unremarkable except for an appendectomy 40 years earlier through the aforementioned incision .
routine laboratory data on admission showed leukocytosis ( white blood cells 16,550/l , polymorphonuclears 77.9% ) .
1 ) revealed the presence of an intestinal loop without peristalsis within the abdominal mass , and the diagnosis of a strangulated ventral hernia was set .
3 ) demonstrated a large subcutaneous abscess and a perforated sigmoidal cancer adherent to the abdominal wall , invading it along with the urinary bladder .
the surgical team decided that the sigmoidal cancer was operable and proceeded with an oncological surgical operation .
the abscess was drained , and an en bloc resection of the invaded abdominal wall and urinary bladder was carried out , followed by a hartmann procedure ( resection of the sigmoid colon with a diverting colostomy and rectal stump closure ) .
histopathology of the specimens revealed that none of the 15 lymph nodes harvested was invaded by the tumor .
immunohistochemistry showed positive reactivity to ki67 and p53 in 90 and 80% of the neoplastic nuclei , respectively .
in addition , there was no reactivity for bcl2 , and identification of egfr with kit dako egfr pharm dx was negative . according to tnm classification ,
the patient was staged as t4n0m0 ( stage iib ) . in the immediate postoperative period ,
the patient developed deep vein thrombosis of the left femoral and left common iliac veins and was treated accordingly .
computed tomography of the abdomen and thorax showed no pathology related to the malignancy other than the thrombosis . following an oncological consultation ,
written informed consent was obtained from the patient for publication of this case report and any accompanying images .
a copy of the written consent is available for review by the editor - in - chief of this journal .
screening protocols for colon cancer have failed so far to recruit all patients at risk , mostly due to low socioeconomic conditions and poor education .
therefore , it is not uncommon for colon cancer patients to present with perforation , which might be free , contained or result in a fistula formation .
free perforation leads to secondary peritonitis , while contained or fistulous perforation has a variable outcome .
surgical options for perforated colon cancer include diverting colostomies , partial or subtotal colectomies in a single - stage operation or multiple - stages procedures , and various interventional endoscopic techniques .
many institutions have reported outcomes following surgery for perforation of the colon . in a retrospective study of 129 patients , tan et al
. showed that surgery after colonic perforation is associated with higher morbidity and mortality rates , while short - term outcome is associated with the severity of peritonitis and asa score . in another retrospective study including 45 patients with perforated colorectal cancer , the same authors showed similar results and stated that long - term outcome in these patients is determined by cancer stage .
there are many studies in the literature reporting on unusual presentations of colonic cancer , including incarcerated inguinal hernia , gluteal abscess , and necrotizing fascitis of the thigh . in our case ,
the sigmoid was adherent to the abdominal wall due to adhesion formation from the previous operation .
soon after the tumor mass had ruptured , a fistulous tract formed between the bowel and the abdominal wall .
regardless of the clinical manifestations of colon cancer , the same oncological principles apply to all patients . even in preoperatively undiagnosed colon cancer cases
, surgeons must exhaust all possible means to perform a sound oncological operation . in our case ,
the surgical team managed to resect the invaded abdominal wall and the invaded part of the urinary bladder , and subsequently performed a hartmann procedure .
an issue of importance is the fact that our patient had a contained perforation , which has a more favorable outcome than a free perforation . in a retrospective study , patients with free perforated colon cancer had a 5-year disease - free survival of 15% , while patients with a contained perforation had a disease - free survival of 53% ( p < 0.001 ) .
furthermore , free perforated colon cancer patients had a postoperative mortality rate of 19% compared with 0% in contained perforated patients .
it is quite difficult to recognize a perforated sigmoid tumor resulting in an abdominal wall abscess preoperatively .
the abscess formation may further be misdiagnosed as a ventral hernia , especially if located over a previous abdominal incision .
a high level of suspicion is required in order to make a correct diagnosis of perforated colon cancer to the abdominal wall , especially in older patients .
regardless of the clinical manifestation of bowel cancer , the appropriate surgical therapy is warranted .
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colorectal cancer remains the second leading cause of death from malignant disease . despite improvements in the treatment modalities offered to patients ,
more than half of the operated patients die from the disease .
the most common presenting symptoms of colonic carcinoma are changes in bowel habits , bleeding , abdominal pain , abdominal mass , stools mixed with mucus or not , weight loss , anorexia , and other characteristics related to metastasis . here , the case of a 74-year - old female patient with colon cancer perforation presenting as a strangulating ventral hernia and a mini - review of the current literature are presented .
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How to dance Gangnam Style: free download
Subversive satire of Seoul, Korea's Gangnam district
Top of Australia's ARIAS, UK's Top 40 and 30 other charts
ON track to become the most viewed video in You Tube history, PSY's insanely catchy K-Pop smash has been watched 330m times, and is number one in Australia and the UK.
FREE DOWNLOAD: how to dance G-Style (PDF)
Unless you have been living in Meekatharra, remote north west WA (and surely even there), you must have heard the wonderfully uplifting Gangnam Style, by K-Pop superstar PSY over the last few weeks.
A brilliant satire on the excesses of Korean's version of credit card touting cashed-up bogans, the song has exploded on to the world's consciousness to such an extent that it has become the most-watched video of 2012.
Since being posted on You Tube on July 15, Gangnam Style has bounced its way past Carly Rae Jepsen's hitherto chart topping Call Me Maybe, passing her 277m views more than a week ago.
Gangnam Style
Now, with 330m views on You Tube in less than three months, Gangnam Style is closing in on Justin Bieber's Baby, which has amassed 783m views since February 2010.
Gangnam Style
Interestingly, Bieber, Rae Jepsen and PSY are all You Tube hits discovered by the now-legendary American talent manager Scooter Braun (yes, that is his real name).
Can PSY catch the Biebmeister? At this explosive rate of growth it's a no-brainer: K-Pop is ruling the world.
As Africa, Europe and South America wake-up to G-Style, not only will PSY by number one by Christmas, he'll break the internet at the same time.
FREE DOWNLOAD: how to dance G-Style (PDF) ||||| Step aside Carly Rae Jepsen , the time of the ' Call Me Maybe ' parodies is over. Enter the endless lampoons of ' Gangnam Style .' And what better way to achieve maximum viral impact than to get Trekkies into the mix?
Not too long ago America was introduced to the South Korean singer/rapper Psy. His massive hit 'Gangnam Style' took us all by storm when it went up on YouTube; ever since, he's become a smash here in the States, performing for anyone from the cast of the 'Today Show' to Ellen Degeneres to 'Saturday Night Live,' dancing along to his signature tune. Psy himself claims the famed dance is based on a "Dress classy but dance cheesy" motto.
In this video, we're given 'Klingon Style.' For those who don't know (how dare you!), Klingons are a fictional warrior race in the 'Star Trek' series. So just what does this video have in common with 'Gangnam Style?' Well, aside from the dance — which does vary at times — the other similarity would have to be that we're completely clueless as to what anybody is actually saying. Any Klingon speakers out there? If so, do tell! ||||| YouTuber Moto2h spent the better part of several hours putting together this rather remarkable music-less version of the "Gangnam Style" music video, replacing the audio with the song's official a capella version and sprinkling in everyday sound effects to make up for the missing madness.
Suffice it to say, if you thought the video couldn't get any sillier, you haven't seen it without the music.
Bonus: If you like the music, but not the video, here's an acoustic cover by UC Berkeley's own Ra-On to help you reach a new level of appreciation for the song's many layers.
[Mefi/Reddit] ||||| Psy - the South Korean rapper behind the most "liked" YouTube video of all time - has topped the UK singles chart with Gangnam Style.
The pop track broke into the Top 40 two weeks ago at number 37, four weeks after its release, and has been climbing steadily since ending up at number three in last week's chart.
Irish band The Script were down to number two with Hall Of Fame, featuring will.i.am from the Black Eyed Peas, while US rapper Flo Rida rounds off the top three with I Cry.
The video that accompanies Gangnam Style had amassed more than 334 million views on YouTube as of October 1.
The 34-year-old, whose real name is Park Jae-sang, is popular in his native South Korea - and now worldwide - for his humorous videos and stage performances.
Psy's got style - Gangnam Style
Psy, who has already released six albums in his homeland, taught Britney Spears his dance moves on The Ellen DeGeneres Show last month.
His Gangnam Style video has been shared on the web by celebrities including Spears, T-Pain, Katy Perry and Tom Cruise.
The song is inspired by Gangnam-gu, one of the 25 local government districts, or gu, which make up the city of Seoul.
It has prompted a series of spoof videos - one of which saw a group of US lifeguards lose their jobs.
More than a dozen guards in the Californian city of El Monte were sacked after producing Lifeguard Style.
Lifeguard Style (Gangnam Style Remake) got the guards in hot water
A Facebook page saw hundreds of comments being left in their defence - with Psy himself among their supporters.
The rapper told MTV: "What did they do? They weren't wrong? I think it was off duty - that's what I heard. They can be more flexible to each other."
WKRC-TV said supervisors in the Parks & Recreation Division called in the lifeguards and asked them to review pages from a staff manual about violations of city property before firing them.
Since then, more than 17,000 people have signed up to support the performers via their Facebook page Bring Back The 14 El Monte Lifeguards.
Mayor Andre Quintero admitted Lifeguard Style was a "very good parody".
But he added: "If these employees wanted to produce a video for their own enjoyment and memories they could have asked for permission and shared the video with their family and friends using a medium that is less public."
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– "Gangnam Style," the wildly popular hit from South Korean rapper PSY, has made it to No. 1 on the UK charts, Sky News reports. It could also become the most-viewed YouTube video of all time, with more than 336 million views as of today. For some perspective, Australia's News Network reports that the current most-viewed video is Justin Bieber's "Baby," which has racked up 783 million views since February 2010. "Gangnam Style" has only been up three months. Not surprisingly, the catchy viral hit has spawned a series of spin-off videos, including a kinda creepy one spotted by Gawker in which the music has been removed, and of course, a version entirely in Klingon.
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SECTION 1. SHORT TITLE.
This Act may be cited as the ``Emergency Medical Services Support
Act''.
SEC. 2. DEFINITION.
In this Act, the term ``community-based emergency medical
services'' means any regional, State, or local emergency medical
services system.
SEC. 3. FEDERAL INTERAGENCY COMMITTEE ON EMERGENCY MEDICAL SERVICES.
(a) In General.--There is established a Federal Interagency
Committee on Emergency Medical Services (in this Act referred to as the
``Interagency Committee on EMS'') which shall--
(1) assure coordination between the Federal agencies
involved with State, local, and community-based emergency
medical services;
(2) identify community-based emergency medical services'
needs;
(3) create, or recommend, new or expanded grant programs
for the purposes of improving community-based emergency medical
services;
(4) identify other ways to streamline the process through
which Federal agencies support community-based emergency
medical services; and
(5) assist in priority setting based on discovered needs.
(b) Membership.--The membership of the Interagency Committee on EMS
shall consist of--
(1) a representative from the National Highway
Transportation Administration of the Department of
Transportation;
(2) a representative of the Health Resources and Services
Administration of the Department of Health and Human Services;
(3) a representative of the Centers for Disease Control and
Prevention of the Department of Health and Human Services;
(4) a representative of the United States Fire
Administration of the Federal Emergency Management Agency;
(5) a representative of the Center for Medicare and
Medicaid Services;
(6) a representative of the Department of Defense;
(7) a representative of the Office of Emergency
Preparedness of the Department of Health and Human Services;
(8) a representative from the Wireless Telecom Bureau of
the Federal Communications Commission; and
(9) representatives of any other Federal agencies
identified by the President as having a significant role in the
purposes of the Interagency Committee on EMS.
(c) Administration.--The National Highway Traffic Safety
Administration shall provide administrative support to the Interagency
Committee on EMS and the Advisory Council which shall include the
scheduling of meetings, construction of an agenda, maintenance of
minutes and records, report production, and reimbursement of advisory
council members.
(d) Leadership.--A chairperson of the Interagency Committee on EMS
shall be selected annually by the members of the Interagency Committee
on EMS.
(e) Meetings.--The Interagency Committee on EMS shall meet as
frequently as is determined by the Administrator of the National
Highway Transportation Administration or on a quarter annual basis with
the Advisory Council.
SEC. 4. FEDERAL INTERAGENCY COMMITTEE ON EMERGENCY MEDICAL SERVICES
ADVISORY COUNCIL.
(a) Establishment.--There is established a Federal Interagency
Committee on Emergency Medical Services Advisory Council (in this Act
referred to as the ``Advisory Council'') which shall consist of not
more than 13 individuals with an interest or expertise in emergency
medical services selected by the Interagency Committee on EMS.
(b) Membership.--The Interagency Committee on EMS shall assure
representation from both urban and rural settings, and assure diverse
representation from all sectors of the emergency medical services
community on the panel.
(c) Leadership.--A chairperson of the Advisory Council shall be
selected annually by the Advisory Council members.
(d) Compensation and Reimbursement.--The members of the Advisory
Council shall serve without compensation except for the reimbursement
of necessary expenses.
(e) Meetings.--The Advisory Council shall meet on a quarter annual
basis with the Interagency Committee on EMS.
SEC. 5. ANNUAL REPORTS.
The Interagency Committee on EMS and the Advisory Council shall
each prepare an annual report to each House of Congress which shall
include--
(1) a description of support currently being provided by
the Committee or Council to community-based emergency medical
services providers;
(2) a description of how emergency medical services
programs are being coordinated between the Federal agencies;
(3) a needs assessment for improving community-based
emergency medical services systems at State and local levels;
(4) recommendations to Congress regarding the creation of
new or the expansion of existing grants or other programs for
improving community-based emergency medical services; and
(5) recommendations about other measures that Congress can
take to support community-based emergency medical services.
|
Emergency Medical Services Support Act - Establishes a Federal Interagency Committee on Emergency Medical Services to provide intergovernmental coordination of emergency medical services. Requires the Committee to: (1) identify community-based emergency medical services' needs; (2) make grant program and streamlining recommendations; and (3) set priorities.Establishes a Federal Interagency Committee on Emergency Medical Services Advisory Council. Requires the Committee and the Council to each report annually to Congress on the state of community-abased emergency medical services, including recommendations.
|
nitrate and nitrite when ingested by human beings may have a negative impact on health .
nitrate is transformed to nitrite by the action of certain microorganisms present in the intestine .
then it may transform hemoglobin to methemoglobin by oxidizing fe ( ii ) present in the former substance to fe ( iii ) .
methemoglobin is unable to carry oxygen thus originating a condition called methemoglobinemia , characterized by hypoxia .
young children are more prone to this condition , thus it is important to control the levels of nitrate and nitrite in milk and infant formulas consumed by the children and infants during lactation period , especially those without breast - feeding .
nitrate may appear in dried milk and infant formulas as a consequence of the industrial process , as a contaminant of the salts added in the manufacture of fortified milks and infant formulas .
nitrite , on the other hand , is a consequence of microbial contamination or may be added during the manufacturing process .
powdered infant formulas are not commercially sterile products , they are heat treated during processing , but unlike liquid products , they are not exposed to high temperatures for sufficient time to make the final packaged product commercially sterile .
a search in the scientific literature has shown few papers dealing with methods for the determination of nitrate and nitrite in infant formula or milk powder samples .
gas chromatography and spectrophotometry have been proposed for this purpose in papers published long time ago . on the other hand , the iso - idf standard method consists of a colorimetric determination for nitrite , based on the classical reaction with n-(1-naphthyl)ethylenediamine and sulfanilamide .
. currently , analytical laboratories experience an increasing demand for a large number of analytical determinations which are expected to be carried out in a fast and accurate way .
procedures such as those mentioned before rely heavily on the use of hand labor and are inherently slow and thus may hinder the required laboratory productivity .
on the other hand , the demand for high productivity can be satisfied by resorting to laboratory automation , which can be implemented in an easy and inexpensive way by means of flow - based techniques such as flow injection analysis ( fia ) or sequential injection analysis ( sia ) .
the current iso - idf standard method is primarily carried out as a conventional manual procedure , but the standard allows for the possibility of automation by segmented flow analysis ( sfa ) , or flow injection analysis ( fia ) . despite being very useful automation tools and presenting lower reagent consumption when compared to traditional batch methods , both sfa and fia still resort to the use of a continuous flow of reagent , this being wasted in the periods between sample injections . also , the use of peristaltic pumps requires preventive maintenance with frequent replacement of the pump tubing in order to avoid degradation in the quality of the results .
despite having been developed primarily as a tool for process control , sia also has found a place in the analytical laboratory , because of its inherent advantages such as robustness , reliability , and low consumption of sample and reagents .
it is also based on the use of a syringe pump , which is highly dependable , requiring less maintenance than peristaltic pumps and having excellent repeatability when used to measure small volumes .
it has been used successfully in the determination of nitrate and nitrite in matrixes such as water samples [ 1012 ] .
reis lima et al . developed an sia system for determining nitrate and nitrite in dairy products ; however , the system uses two peristaltic pumps which results in a complicated system and has the disadvantages of using this type of pumps . in this work ,
a simple sia system that uses only one syringe pump was developed for the determination of nitrate and nitrite in infant formula and milk powder for quality control purposes .
this automated system was more precise and faster than the antecedent mentioned with less effluent generation for these kinds of determinations .
total control from a pc was achieved using modern programming languages and with user - friendly graphical interfaces .
the following reagents used were of analytical - reagent grade : potassium hexacyanoferrate ( ii ) trihydrate , zinc sulfate heptahydrate , n-(1-naphtyl)ethylenediamine dihydrochloride ( ned ) , sulfanilamide , phosphoric acid 85% , ammonium chloride , ammonium hydroxide , disodium ethylenediamine tetraacetate ( edta ) , potassium nitrate , and potassium nitrite .
glass - distilled water , further purified in a millipore ( so paulo , brazil ) simplicity 185 water purifier , was used throughout .
standard nitrate and nitrite solutions were prepared daily by dilution of stock solutions of nitrate and nitrite ( 100 mg l no3-n and no2-n , resp . ) prepared from the respective sodium salts .
a buffer solution was prepared by dissolving in distilled water 13 g of nh4cl , 1.7 g of edta per liter .
the ph was adjusted to 8.5 with nh4oh . as it is described in iso standard 14673 - 1:2004/idf standard 189 - 1:2004
, sample preparation consists of a precipitation step where fat and proteins are separated from the bulk solution . for that purpose ,
an exact amount of approximately 10 g of homogenized sample ( dried milk or infant formula ) was prepared as described in the official iso - idf procedure .
progressively 164 ml of purified water at 5055c was added with continuous stirring ; then 6 ml of a solution of zinc sulfate heptahydrate 53.5% ( w / v ) , 6 ml of a solution of potassium hexacyanoferrate ( ii ) trihydrate 17.2% ( w / v ) , and 20 ml of an ammoniacal buffer solution ( ph 9.6 - 9.7 ) were added . after stirring for three minutes
, the protein and fat precipitate was filtered by means of nitrate - free filter paper .
the procedure for preparation of the samples was basically the same described in iso - idf method .
the filtrate was divided into two parts , one for determining nitrate and nitrite by the reference method and the other for determination by the proposed sia method .
the sia system ( figure 1 ) consisted of a microprocessor - controlled syringe pump ( cavro , sunnyvale , calif , usa , model xp-3000 ) featuring a two - position valve , and a 2.5 ml barrel , a valco ( houston , tex , usa ) cheminert 10-port selector valve with microelectric actuator , and a spectrophotometer fitted with a 200 l ( internal volume ) flow cell as detector .
pfa tubing ( 0.8 mm i d ) was used for connections , coiled mixing reactors , and holding coil . a minicolumn made of glass tubing ( length 50 mm , internal diameter 2.1 mm ) packed with cadmium granules
; particle size 0.31.6 mm ( fluka , buchs , switzerland ) was used as reducing agent for nitrate determinations .
control of the system and data acquisition were carried out by means of an ibm - compatible pc ( pentium iii-600 mhz ) with 2 serial ports , fitted with a 12-bit analog to - digital ( a / d ) interface card ( measurement computing cio - das08jr ) and a program compiled in visual basic 6.0 .
the program allowed control of the syringe pump and selector valve via the rs-232 serial ports and capture of analog data from the spectrophotometer which were scaled , transformed into absorbance , displayed on screen in real time , and saved to file on hard disk for later processing .
since the spectrophotometer used only provides an analog signal proportional to light intensity , it is necessary to carry out the definition of the photometric scale before beginning operation . for this purpose ,
the dark signal ( sd ) is measured and memorized with the shutter closed , then the 100% t or reference signal ( sref ) is measured and memorized with the shutter open and the flow cell filled with water . afterwards , each time the a / d interface is triggered and the signal ( sx ) measured , absorbance is calculated by the software using the equation a = ( sx sd)/(sref sd ) and used for all operations .
nitrite was determined by reaction with n-(1-naphthyl)ethylenediamine and sulfanilamide and measurement of absorption at 540 nm .
nitrate was reduced online to nitrite in the cd minicolumn and the total nitrite ( nitrate plus nitrite ) determined colorimetrically .
likewise , the program for the determination of nitrate presented steps for the reduction of nitrate present in the sample by passing it back and forth through the cadmium minicolumn , followed by color development steps as in the determination of total nitrite .
the column end is connected to a reservoir containing buffer solution via hc2 , thus when the excess of water from the column is aspirated to the waste , the end portion of the column is filled with buffer solution ( ph 8.5 ) , and the sample completes its forward and backward passage through the reducing agent packed in the minicolumn .
the short length and the low diameter of the column avoid an excessive dilution of the sample in this reduction step .
the routine described in table 2 corresponds to a sampling frequency of approximately 30 hour for the determination of total nitrogen
if the program is executed for the simultaneous determination of nitrite and nitrate in one sample , the sampling frequency is approximately 20 hour . in order to preserve column lifetime ,
a sequence for washing the column online with buffer was programmed in the routine after each determination .
auxiliary routines were provided in the program for the regeneration and for the copperization of the minicolumn .
this was implemented by using spare ports in valve v1 for the introduction of the appropriate reagents .
the reagents for these operations were prepared according to the iso - idf method , and the operations were carried out within the sia system . a different routine
was provided for purging the sample intake line with fresh sample and the analytical path with water .
this routine was used when changing samples . in order to check the reducing capacity of the column , a nitrite standard solution of the same concentration ( no2-n ) that the most concentrated nitrate ( no3-n ) standard of the calibration plot was run through the sia system in the same conditions as samples and standards .
the comparison of the signal of both solutions of identical concentration ( expressed as nitrogen ) allowed the verification of the reduction column efficiency .
if the reduction capacity was less than 90% , the column had to be regenerated .
signals ( absorbance versus time ) were presented on screen and saved to file on hard disk as ascii files ( first a temporal file.txt is generated and converted to ascii by a subroutine of the main program ) .
torrance , calif , usa ) which was used for establishing the baseline and measuring peak heights of the analytical signals .
the analytical methods developed were assessed for linearity , precision ( repeatability ) , detection ( 3 ) and quantification ( 10 ) limits , and accuracy .
linearity was studied for the two analytes by means of a 9-point calibration curve , in the range of 0.5515.0 mg l ( no3-n ) and 0.0841.01 mg
l ( no2-n ) which was evaluated by visual inspection of the graphical representation and by means of the regression coefficient .
linearity was found to be satisfactory for the two analytes ( r > 0.999 ) .
under these conditions , the sampling frequency was 30 hour(nitrate ) and 80 hour ( nitrite ) .
six different commercial samples were used for validation , four of them representative of infant formulas found in markets in uruguay , respectively , for infants from 0 to 6 months , 6 to 12 months and two generic infant formulas , all milk based .
accuracy was evaluated by analyzing commercial samples for nitrate and nitrite by the proposed methods and by the iso - idf method and comparing the results obtained .
since the levels obtained from the samples were below the quantification limits , it was necessary to spike the samples with the two analytes previous to the deproteinization stage .
the level of this spiking is noted as c1 , and the corresponding found value as s1 . for recovery studies ,
a second standard addition , noted as c2 , was carried out , the corresponding found value being s2 .
the values for the standard additions were chosen to cover the range of nitrate and nitrite content that could present a risk to the health of infants and children .
detection ( 3 ) and quantification ( 10 ) limits calculated were expressed based on the analysis of real samples . in the analysis of commercials samples , analytical precision ( sr(% ) , n = 5 ) ranged from 1.5 to 3.0% for nitrate and from 0.8 to 1.6% for nitrite .
the agreement between the results provided by the proposed and the reference method ranged from 0.2% to 3.4% ( nitrate ) and from 2.4 to 7.8% ( nitrite ) . submitted to student 's t - test for the differences ,
the differences were found to be statistically nonsignificant , as shown on table 4 .
accuracy was also evaluated through the standard additions method , calculating the recovery for the addition level c2 .
percent recovery was calculated as [ ( s2 s1)/(c2 c1 ) ] 100 , where s1 and s2 are the concentrations found after spiking with concentrations c1 and c2 , respectively .
results were statistically equal to 100% as shown in table 4 . during the development of the analytical methods ,
it has been reported that the determination of nitrite and nitrate by methods based on the chemistries chosen for this work can be interfered by a number of ions , especially copper .
milk is a matrix where most of the ions reported as potential interferants are not present at significant levels ( e.g. , copper 0.07 mg l in fluid milk , or 0.9 mg kg in milk powder ) , and the iso - idf standard methods based on the same chemistries do not foresee any of those interferences . in the case of infant formulas
, however , fortification with minerals makes necessary to consider the possibility of interference from copper , which is present in these samples at levels of 3 to 5 mg kg . in order to evaluate this potential interference , solutions of nitrite containing 0.1 and 0.2 mg
l of no2-n were spiked with cu at the 1 and 2 mg l levels .
the difference in absorbance between the spiked and unspiked solutions was below 2% in all cases , thus the interference of copper was considered negligible at those levels , which are much higher than those expected in fluid milk , milk powder , and infant formulas .
figure 3 shows the screen with the peak presentation obtained for a calibration curve using the commercial program peak simple for windows .
the sia system performed satisfactorily in the determination of low levels of nitrate and nitrite in commercial samples .
the specially written program consists of a pure code part and other parts associated with the objects that form the graphical interface . only with a simple click on a button ,
the programmed routines were triggered , and the operator could write specific commands in text boxes .
the routines also allowed the regeneration and copperization of the cadmium reducing minicolumn using the same system and by feeding the appropriate solutions through the minicolumn .
this was achieved by means of the syringe pump and valve , under control of specific software routines . in the official iso - idf method [ 79 ] , it is necessary to regenerate the column frequently by circulating an edta / hcl solution .
also , after a number of samples , the copperization of the cd filling is necessary . in the sia method , the minicolumn could perform efficiently for over 50 injections , with efficiency above 90% .
the sample consumption per determination was 123 l , and the reagent consumption was 4.3 mg of sulfanilamide , 0.4 mg of ned , 63 mg of h3po4 , 9 mg of nh4cl , and 1.2 mg of edta .
this is much lower than the consumption in the batch and fia methods and also slightly lower than other sia methods .
the carrier was purified water , while the iso - idf flow systems [ 8 , 9 ] as well as other sia proposed methods use a buffer solution .
the proposed sia method presents multiple benefits as opposed to the tedious traditional methods of dairy product analysis .
the figures of merit obtained suggest that the method proposed could be used advantageously for the quality control of milk powder and infant formula when compared to others reported in the literature . as an additional advantage , the system is fast , efficient , and environmentally friendly for monitoring nitrate and nitrite of these samples .
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a fast and efficient automated method using a sequential injection analysis ( sia ) system , based on the griess , reaction was developed for the determination of nitrate and nitrite in infant formulas and milk powder .
the system enables to mix a measured amount of sample ( previously constituted in the liquid form and deproteinized ) with the chromogenic reagent to produce a colored substance whose absorbance was recorded . for nitrate determination
, an on - line prereduction step was added by passing the sample through a cd minicolumn .
the system was controlled from a pc by means of a user - friendly program .
figures of merit include linearity ( r2 > 0.999 for both analytes ) , limits of detection ( 0.32 mg kg1 no3-n , and 0.05 mg kg1 no2-n ) , and precision ( sr% ) 0.83.0 .
results were statistically in good agreement with those obtained with the reference iso - idf method .
the sampling frequency was 30 hour1 ( nitrate ) and 80 hour1 ( nitrite ) when performed separately .
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the dynamics of the electrons at the hierarchical hall plateaus @xcite has been described by several theoretical methods , like the jain theory of the composite fermion @xcite , the effective conformal field theories @xcite and the chern - simons gauge theories @xcite .
the filling fractions of these plateaus are nicely given by the jain formula @xcite : = mmp1 , m=2,3,
,p=2,4,6 , , [ filfrac]which generalizes the laughlin series @xcite , @xmath1 , corresponding to @xmath2 . in this paper
we would like to discuss the approach of conformal field theory ( cft ) @xcite ; this describes the low - energy edge excitations , which are one - dimensional ( chiral ) waves propagating on the boundary of the sample .
the conformal field theory for the simpler laughlin plateaus has been clearly identified as that of the abelian chiral boson @xcite , which is also called the chiral luttinger liquid .
this theory describes the edge waves as well as the universal properties of the quasi - particle excitations : in particular , the latter possess fractional electric charge @xmath3 and fractional statistics @xmath4 , in agreement with the laughlin theory @xcite . some of these properties have been recently measured @xcite and have been found to agree with the conformal theory . on the other hand ,
the edge excitations of the hierarchical plateaus ( [ filfrac ] ) are less understood at present .
two classes of cfts have been proposed : the first is the multi - component bosonic theory , which is characterized by the abelian current algebra @xmath5 ( more precisely , @xmath6 ) @xcite ; these theories generalize the well - established one - component theory describing the laughlin plateaus @xcite .
the other proposed theories are given by the minimal models of the @xmath0 algebra @xcite .
according to the laughlin physical picture @xcite , the electrons form a quantum incompressible fluid at the hall plateaus .
this fluid can be characterized by the @xmath7 symmetry of area - preserving diffeomorphisms of the plane @xcite@xcite ; moreover , the corresponding low - energy edge excitations are described by the conformal theories with @xmath0 symmetry @xcite , which include the specific class of the @xmath0 minimal models @xcite .
the two proposed theories are identical for the laughlin hall states ; however , they describe the hierarchical plateaus according to different generalizations of the laughlin theory .
they possess the same spectrum of quasi - particles , but differ in their specific properties .
so far , the experiments have measured the quasi - particle charges and the two - point correlation functions , which are not enough for distinguishing between the two classes of theories .
let us recall here the main features of the @xmath0 minimal models : * they exist for the hierarchical plateaus ( [ filfrac ] ) only .
* they exhibit a smaller number of edge excitations than the corresponding multi - component abelian theories . *
they possess a single abelian charge for the quasi - particles , rather than the @xmath8 charges of the multi - component theories ; this unique charge is clearly identified with @xmath3 .
* they have neutral quasi - particles which are labelled by the weights of the @xmath9 lie algebra , rather than by the @xmath10 abelian charges in the multi - component theories . as a consequence ,
the quasi - particles of the minimal theories have non - abelian statistics .
the @xmath0 minimal models have been introduced in the previous work @xcite : they were obtained by the typical algebraic construction of cft , which builds their hilbert space from a consistent collection of representations of the symmetry algebra .
actually , the minimal models are made by the degenerate @xmath0 @xcite , which possess virasoro central charge @xmath11 , and are equivalent to the of the @xmath12 algebra @xcite .
this construction showed that the minimal theories are obtained from the multi - component abelian ones by performing a reduction of degrees of freedom , which keeps the incompressibility of the electron fluid ; specifically , the reduction of the @xmath13 symmetry down to the @xmath14 one . afterwards , the exact energy spectrum was numerically computed for the hall states of a system of ten electrons @xcite ; this study clearly indicated that the previous reduction of degrees of freedom is realized in the spectrum , and that the @xmath0 minimal models may have a chance to be the correct conformal theories of the hierarchical hall plateaus .
therefore , it is important to describe this reduction in great detail and to understand its dynamical origin . in this paper
, we explicitly formulate the @xmath0 minimal models by quantizing a hamiltonian of the multi - component bosonic fields . in section @xmath15 , this hamiltonian is shown to be relevant in the renormalization - group sense : the corresponding flow interpolates between the multi - component abelian and the minimal theories , and performs the reduction of degrees of freedom for the latter theory in the infrared fixed point .
this infrared limit can also be obtained by imposing a set of constraints on the states of the abelian fock space ; this procedure defines the @xmath14 algebra by the so - called hamiltonian reduction of @xmath13 @xcite .
this rather simple description of the @xmath0 minimal models is completely equivalent to the previous algebraic construction @xcite : moreover , the hamiltonian formulation may be useful for understanding the microscopic dynamics of the reduction and for comparing with other approaches and the experimental results .
in section @xmath16 , we present a simple physical picture for the electron ground state of the @xmath0 minimal models : this is a `` minimal '' incompressible hall fluid , which can be described as a chiral fermi sea , as done earlier for the laughlin fluids @xcite@xcite ; in this picture , the minimal - model constraints can be interpreted as further conditions for incompressibility . in this section
, we also describe the @xmath0 minimal models in terms of spinon excitations , another basis for the @xmath17 states introduced in ref.@xcite . in section @xmath18 ,
we compute the four - point correlation functions of the @xmath0 minimal models by using the coulomb gas method @xcite .
we show that the quasi - particles possess the non - abelian statistics ; this has a rather simple form , which is analogous to that of the [ 331 ] double - layer hall state @xcite .
all results are shown in the simplest case of @xmath19 in ( [ filfrac ] ) , which is relevant for the plateaus @xmath20 the generalization of this analysis to @xmath21 is described in the appendix .
let us finally stress that this hamiltonian formulation makes it clear that the @xmath0 minimal models are fully consistent theories , although they are not rational cfts @xcite ; namely , their partition function is not modular invariant @xcite ( see the discussion in section @xmath15 ) .
we first describe the hilbert spaces of the two classes of theories by recalling the results of the algebraic constructions in ref.@xcite ( see section @xmath23 ) .
next , we discuss the equivalent hamiltonian description of the minimal models .
the two - component abelian theories are built out of two chiral bosonic fields @xmath25 , @xmath26 , which are defined on the edge of the hall sample @xcite : here it is chosen to be a disk , parametrized by an angle @xmath27 and a radius @xmath28 .
the conformal field theory is defined on the space - time cylinder made by the disk boundary and time @xmath29 . as usual , the cft operators are defined on the complex plane @xmath30 , where @xmath31 is the euclidean time . the fermi velocities @xmath32 as well as the chiralities of the two bosonic fields are taken positive in section @xmath15 of ref.@xcite ; the case of mixed chiralities ( some @xmath33 ) are analogous . ] : this case is relevant for the filling fractions , = 22p+1=2 5 , 29 , [ twojain]the edge excitations are described by the chiral currents : j^(i)= - 12 ^(i ) = 12 _ n=-^
^(i)_n e ^in ( -v_i t / r ) , i=1,2 , whose fourier modes @xmath34 satisfy the two - component abelian current algebra , = ^ij n _
[ curralg ] the corresponding generators of the virasoro algebra are obtained by the usual sugawara construction @xmath35 , and read : l_n^(i ) = 12 ^(i)_0 + _
n^(i ) , i=1,2 .
[ ln]they satisfy = ^ij \ { ( n - m ) l_n+m^(i ) + c12 n(n^2 - 1 ) _ n+m,0 } , c=1 .
[ viralg ] the generators of conformal transformations are thus given by @xmath36 , and obey the same algebra with @xmath22 .
the highest weight representations of the abelian algebra ( [ curralg ] ) are characterized by the eigenvalues of @xmath37 and @xmath38 ; the eigenvalue of @xmath39 is proportional to the quasi - particle charge @xmath3 and @xmath40 is their fractional statistics @xmath4 .
the hilbert space of the two - component abelian conformal theory is made of a consistent set of these representations , which is complete with respect to the fusion rules : these are the selection rules for the composition of quasi - particle excitations in the theory ( the so - called bootstrap self - consistent conditions ) @xcite . in the abelian theory
, these rules simply require the addition of the two - component charges of the quasi - particles ; as a consequence , the allowed charge values should fill the points of a two - dimensional lattice .
each lattice specifies a theory : the adjacency matrix of the lattice contains some parameters which are partially determined by the physical conditions , like the matching of the filling fraction .
special lattices allow for an extended symmetry @xcite : the extension from @xmath41 to @xmath42 has been chosen because it reproduces the filling fractions ( [ twojain ] ) uniquely ( the parameter @xmath43 is related to the compactification radius of the field @xmath44 representing the @xmath45 part ) .
the corresponding spectrum of quasi - particles was found to be @xcite : : \
{ l l q & = 22p+1 , + 12 & = 12p+1 ^2 + n^2 , . : \
{ l l q & = 2 2p+1 ( + 12 ) , + 12 & = 12p+1 ( + 12 ) ^2 + ( 2n+1)^2 4 , .
, n . [ splitsp]in the literature , one often finds a unique formula for the two cases ( i ) and ( ii ) above , which can be obtained by substituting @xmath46 , with @xmath47 and @xmath48 , respectively ( see section @xmath49 of ref .
the spectrum ( [ splitsp ] ) is clearly factorized in charged and neutral excitations , with @xmath50 counting the units of fractional charge , and @xmath51 labelling the neutral quasi - particles of the two - component fluids ; the latter are a new feature of the two - component fluids with respect to the laughlin ones .
note that the neutral spectrum is independent of the filling fraction , i.e. of the value of @xmath52 .
let us also introduce the current and virasoro generators in the basis corresponding to the factorization into charged and neutral sectors of the spectrum ( [ splitsp ] ) ( case ( i ) ) : llcl j = j^(1 ) + j^(2 ) , & j_0 & & q = 22p+1 ; + j^3 = 12 ( j^(1 ) - j^(2 ) ) , & j^3_0 & & n ; + l = l^(1 ) + l^(2 ) = l^q + l^s , & l_0 & & ^2 2p+1 + n^2 ; + l^q = 14 : ( j)^2 : , l^s = : ( j^3 ) ^2 : .
& & [ coeq](the eigenvalues of case ( ii ) are found for @xmath53 and @xmath54 ) .
each value in the spectrum ( [ splitsp ] ) is the highest weight of a pair of representations of the abelian current algebra ; as is well known @xcite , these representations describe an infinite tower of edge excitations , generated by the bosonic fock - space operators @xmath55 , @xmath56 , @xmath26 , which correspond to fermionic particle - hole transitions , or to their anyonic generalizations @xcite@xcite@xcite .
these excitations are characterized by their angular momentum value , given by the total virasoro operator @xmath57 ; moreover , the multiplicities of excitations are counted by the characters of the representations : ^11_l_0 _ rep(11 ) ( q^l_0 -1/12 ) = ^1_^2/(2p+1 ) ^1_n^2 , e.g. in the case ( i ) above ; the characters of the abelian representations are @xcite : _
l_0=h^1=q^h ( q ) , ( q)=q^1/24 _ k=1^ ( 1-q^k ) .
[ abecha ] finally , the hamiltonian of the abelian theory which assigns a linear spectrum to the edge excitations can be written in terms of the currents , as follows : h= _ 0 ^ 2r dx : ( v_1 j^(1 ) j^(1 ) + v_2 j^(2 ) j^(2 ) ): = 1r .
let us now discuss the extended symmetry @xmath17 of the neutral sector of the spectrum ( [ splitsp ] ) .
first , we observe that there are two highest weights with dimension one , i.e. @xmath58 , which correspond to the additional chiral currents : j^= : ( i ): , = ( ^(1 ) -^(2 ) ) .
[ jpm]the two fields @xmath59 , together with @xmath60 in ( [ coeq ] ) , form the @xmath17 current algebra of level @xmath61 ; their fourier modes satisfy : & = & i^abc j^c_n+m + ^ab _
n+m,0 , k=1 , a , b , c = 1,2,3 , + & = & -m j^a_n+m ; [ naca ] of course , the @xmath62 commute with the generators of the charged sector @xmath63 .
as is well known , there are two highest - weight representations of the @xmath17 algebra , which are labelled by the `` spin '' @xmath64 .
their ( specialized ) characters are @xcite@xcite : ^2_=0 & = & 1(q)^3 _ k ( 6k+1)q^(6k+1)^2/12 = 1(q ) _ k q^k^2 , + ^2_=1/2 & = & 1(q)^3 _ k ( 6k+2)q^(6k+2)^2/12 = 1(q ) _ k q^(2k+1)^2/4 .
[ char2]the second expression for these characters shows that the two @xmath17 sum up the neutral spectrum of the theory ( [ splitsp ] ) in the two sectors ( i ) and ( ii ) , respectively .
note also that the partition function of the complete theory @xmath24 can be found in ref .
@xcite ( for the annulus geometry ) : it includes all the states in the spectrum ( [ splitsp ] ) with multiplicity one and it is invariant under the modular transformations .
therefore , the @xmath24 theory is a rational cft @xcite .
the @xmath17 can be further decomposed into the @xmath65 virasoro of weight @xmath66 , @xmath67 .
these are characterized by the property of being _ degenerate _ : they contain null - states , i.e. zero - norm states in their tower of excitations , which should be removed from the hilbert space .
this degeneracy is displayed by the corresponding characters @xcite , ^vir_l_0^s = n^2/4 = q^n^2/4 ( 1-q^n+1 ) ( q ) = q^n^2/4 - q^(n+2)^2/4 ( q ) ; [ chiva]their numerator contains a negative term which cancels part of the power expansion of @xmath68 , and reduces the multiplicities of states with respect to the corresponding abelian representation ( [ abecha ] ) .
actually , the last part of equation ( [ chiva ] ) shows that each @xmath69 in the neutral spectrum decomposes into an infinity of virasoro , ^1_j^3_0=n/2 = _
= 0^ ^vir_l_0^s = ( n + 2)^2/4 .
[ inver]in summary , the decomposition of is given by : \{=0}_2 & = & _ k even \{j^3_0=k2 } _ 1 = _ s=0^ ( 2s+1 ) \{l_0^s = s^2 } _ vir , + \{=12}_2 & = & _ k odd \{j^3_0=k2 } _ 1 = _
s=1/2 , s ^+ + 1/2^ ( 2s+1 ) \{l_0^s = s^2 } _ vir . + & &
[ deco]these correspond to the following inclusions of @xmath65 algebras : 2 1 vir .
[ inclu ] next , we observe that the decompositions ( [ deco ] ) show the familiar multiplicities @xmath70 of the @xmath71 lie - algebra with @xmath72 being related to the virasoro dimension . actually , @xmath73 is a true isospin , because the fusion rules of the degenerate virasoro are equivalent to the addition of spins : @xmath74 .
therefore , the @xmath17 `` spin '' @xmath75 is only the parity of @xmath73 ( which is additive modulo two ) ; moreover , the @xmath69 charge @xmath76 is also additive and corresponds to the projection of the isospin on one axis , i.e. to @xmath8 .
the generators of this @xmath71 algebra inside the @xmath17 are the zero modes of the currents @xmath77 ; actually , these commute with the @xmath78 ( see eq.([naca ] ) ) , and thus act within the @xmath70 virasoro of same weight . the decomposition of the two @xmath17 is drawn schematically in fig .
( [ fig1 ] ) : each dash in the @xmath79 plane correspond to a virasoro with @xmath80 ; the @xmath69 are horizontal arrays of dashes corresponding to a given @xmath8 value ( see eq .
( [ inver ] ) ) . according to the laughlin theory @xcite
, the ground state at the hall plateaus can be described as a two - dimensional incompressible fluid , which is characterized by constant electron density @xmath81 and number @xmath82 . its low - energy excitations are deformations of the fluid which have the same area @xmath83 : n = d^2x ( * x*,t ) _ o a .
[ keyeq]these configurations can be mapped into each other by area - preserving transformations of the coordinates of the plane , whose infinitesimal generators obey the @xmath7 algebra .
therefore , the ( semiclassical ) chiral incompressible fluids possess the @xmath7 _ dynamical _ symmetry @xcite @xcite .
the edge excitations are identified with the infinitesimal area - preserving deformations of a droplet of fluid ; their quantization @xcite leads to a conformal field theory with the symmetry of the @xmath0 algebra , which is the quantum analog of @xmath7 .
note that the @xmath0 algebra contains the @xmath69 and virasoro algebras .
we refer to our previous works for the description of the incompressible fluids by the @xmath7 transformations @xcite and for the definition of the @xmath0 algebra @xcite ; here , we recall the main properties of the @xmath0 conformal theories . in ref .
@xcite , the @xmath0 theories have been constructed by the algebraic method of assembling the of the @xmath0 algebra and checking the closure under their fusion rules . for @xmath22 , the @xmath0 unitary
are of two types : _ generic _ or _ degenerate _ @xcite .
the generic are one - to - one equivalent to those of the abelian algebra @xmath41 with charges @xmath84 ( eigenvalues of @xmath85 and @xmath86 ) satisfying @xmath87 . clearly , the @xmath0 theories made of generic representations correspond to the generic two - component abelian theories . on the other hand ,
the degenerate @xmath0 are not equivalent to the abelian ones , but are contained into them ; their charges satisfy the condition @xmath88 .
the conformal theories made of the degenerate ( only ) have been called the _ @xmath0 minimal models _ @xcite .
the main result is that these models are in one - to - one relation with the hierarchical filling fractions ( [ filfrac ] ) and yield the same spectrum of charge and fractional statistics of the @xmath24 theories ( [ splitsp ] ) ; however , the detailed properties of the two spectra are different , as anticipated in the introduction .
the @xmath71 `` symmetry '' present in the @xmath22 degenerate representations of @xmath0 is a consequence of some properties discussed in ref.@xcite : in general , the @xmath89 degenerate @xmath0 representations are equivalent to the representations of the @xmath90 algebra , where @xmath14 is the zamolodchikov - fateev - lukyanov algebra at @xmath91 @xcite .
the @xmath9 lie algebra is used in the construction of the @xmath14 algebra , and its fusion rules are isomorphic to the tensor product of @xmath9 representations . in the case of interest here , @xmath22 , we have : reps = 1 reps , ( c=2 ) , where the abelian algebra describes the charged sector , as usual , and @xmath92 accounts for the neutral sector .
after establishing the nature of the degenerate @xmath0 representations , in ref .
@xcite the spectrum of the corresponding minimal models was obtained by checking the fusion rules : these are again satisfied by a two - dimensional lattice of representations .
their charge and virasoro weights are still given by the abelian spectrum ( [ splitsp ] ) , but the integer @xmath51 is restricted to @xmath93 ( a wedge of the lattice ) , and the meaning of each point in the lattice is different : in the @xmath0 minimal models , it represents one @xmath94 representation , while in the @xmath24 theories this is a @xmath41 representation of the same virasoro weight . our next task is to obtain the minimal models as explicit projections of the @xmath24 theories .
of course , this discussion concerns the neutral sector only . according to the previous discussion
, the minimal model contains each @xmath80 virasoro with multiplicity one , while the @xmath17 theories contain @xmath70 copies of it ( see eq.([deco ] ) ) .
therefore , we should choose one state per @xmath71 multiplet in a consistent way ; this is achieved by imposing a constraint on the states of the form : minimal state = 0 , [ vinc ] for some operator @xmath95 .
this constraint is satisfied by the states of the @xmath24 theory which also belong to the minimal model ; the other states are projected out .
there are two natural choices for the operator @xmath95 , namely @xmath96 and @xmath97 ; these select the highest ( resp .
lowest ) state in each @xmath71 multiplet .
the previous decomposition of the @xmath17 into virasoro ones shows that there are no other choices for @xmath95 in ( [ vinc ] ) ( see fig.([fig1 ] ) , a more formal derivation will be given in section @xmath18 ) .
therefore , the @xmath0 minimal models can be defined by the @xmath24 theory plus the constraint : j^-_0 minimal state = 0 .
[ minvin ] this condition can be completely solved in the basis @xmath98 already discussed at length : the @xmath71 symmetry is clearly killed , because it does not commute with the constraint ( [ minvin ] ) ; the @xmath99 quantum number @xmath8 , is also fixed to @xmath100 ; the remaining good quantum number is the virasoro weight @xmath80 .
we can say that @xmath101 , i.e. virasoro , is the casimir sub - algebra of @xmath17 ; in general , we have that @xmath102 ( see also the appendix ) .
note that the total isospin @xmath73 continues to compose as before in the fusion of two virasoro representations : namely , in the minimal models , the composite quasi - particles form @xmath71 tensor products , but there is no @xmath71 symmetry .
some examples of the minimal states satisfying ( [ minvin ] ) will be given in section 3 .
the projection ( [ minvin ] ) relating the abelian and minimal models is a simple case of the general mechanism of hamiltonian reduction of @xmath103 , which is discussed in the refs .
@xcite .
a first physical interpretation of the constraint ( [ minvin ] ) is that of a strong polarization of the isospin in the @xmath0 minimal models as opposed to the unpolarized @xmath17 system .
note , however , that a zeeman term would give lower energy to the larger @xmath73 values , which is not true in the present case . in order to be more precise , we should introduce the hamiltonian which enforces this constraint .
this is given by the following expression ( @xmath22 ) : h= ( v l^q_0 + v^ l^s_0- ) + j^+_0 j^-_0 , [ 0 , ) .
[ hamin ] the first term is the standard hamiltonian for the @xmath24 theory ; the second term is diagonal in the @xmath104 basis , and its eigenvalues are @xmath105 : for @xmath106 , it selects the lowest weight in each @xmath71 multiplet , i.e. it implements the constraint ( [ minvin ] ) .
note that the new term in the hamiltonian is a non - local interaction :
j^+_0 j^-_0 = _ c_t d _ c_t - d^ * : * e^i ( ) * : * * : * e^-i ( ^ ) * : * ; actually , this expression can not be reduced to a single contour integral . moreover ,
this term is relevant in the renormalization - group sense , because @xmath107 has the dimension of a mass .
therefore , as long as @xmath107 is switched on , the infra - red limit of the theory defined by @xmath108 in ( [ hamin ] ) is the @xmath22 @xmath0 minimal model ( @xmath109 ) .
this infra - red fixed point is known exactly because the @xmath107 term is diagonal in the considered basis , and , moreover , it is conformally invariant because @xmath110=0 $ ] .
therefore , the hamiltonian ( [ hamin ] ) defines a renormalization - group trajectory @xmath111 which interpolates between the two - component abelian theory and the corresponding @xmath0 minimal model .
this renormalization - group flow takes place in the same phase of the system , because the two conformal theories share the same ground - state ( which obviously satisfies the constraint ( [ minvin ] ) ) .
let us remark that this hamiltonian naturally suggests the physical relevance of the minimal models : since the conformal field theories are effective low - energy , long - distance descriptions of the edge excitations , the farthest infra - red fixed - point is physically relevant ; in other words , @xmath106 is naturally reached without fine - tuning . in ref.@xcite
, the exact low - lying spectrum has been computed numerically for ten electrons with repulsive short - range interactions on the disk geometry .
two new criteria have been introduced for the analysis of the low - lying exact states , which allow for their interpretation as cft states and for their identification as either edge or bulk excitations .
a clear pattern is observed : the edge excitations match the states of the @xmath0 minimal models , which satisfy ( [ minvin ] ) ; the remaining abelian states correspond to bulk excitations .
an energy splitting is found between these two set of states , as suggested by the hamiltonian ( [ hamin ] ) , but is rather weak : @xmath112 rather than @xmath106 . in conclusion
, the infrared limit can not be reached in this finite - size system , but the correct edges excitations are nevertheless identified with the states of the minimal models described before .
another virtue of the hamiltonian ( [ hamin ] ) is that it shows that the @xmath0 minimal models are completely consistent conformal field theories .
it had previously been found @xcite that they are not rational cfts @xcite , i.e. their partition function can not by modular invariant models . ] . this is a rather uncommon feature in the literature of cft , which remained unexplained : here ,
we can trace it back to the non - locality of the @xmath107 term , which violates one of the hypothesis for modular invariance @xcite .
note also that generalized modular transformations have been defined for the @xmath65 ( non - minimal ) @xmath0 theories @xcite , for hamiltonians which contain all possible _ local _ operators @xmath113 , @xmath114 , in the cartan subalgebra of @xmath0 @xcite : h = j_0 + vr l_0 + r^2 v^2_0 + r^3 v^3_0 + ,
( here , @xmath115 and @xmath116 ) . however , the proposed hamiltonian ( [ hamin ] ) does not belong to this class .
let us finally remark that the generalization of the constraint ( [ minvin ] ) and of the hamiltonian ( [ hamin ] ) to the @xmath0 minimal models with higher central charges @xmath117 is slightly more technical ; the case @xmath118 is presented in the appendix .
in this section , we discuss the fermionic fock space realization of the @xmath119 minimal models ; this leads to the physical picture of the minimal incompressible hall fluids as chiral fermi seas .
moreover , it allows for a direct comparison with the jain composite - fermion theory @xcite , which has been used in the numerical analysis of ref.@xcite .
we first consider the case of two filled landau levels ( @xmath120 ) ( see fig.([fig2 ] ) ) ; this is not one of the hierarchical plateaus ; thus , this should not be literally taken as a physical realization of the minimal models . however , its hilbert space is isomorphic to those of the hierarchical states @xmath121 , and , in particular , the neutral sector is identical because it is @xmath52-independent ( see eq.([splitsp ] ) ) .
the edge excitations of two filled landau levels are described by two complex chiral ( weyl ) fields @xmath122 and @xmath123 ; their mode expansion in the neveu - schwarz sector is ( for @xmath124 ) : _ 1 & = & _ r e^i r u_r , _ 1 = _
r e^-i(r-1 ) u^_r , + _ 2 & = & _ r e^i r d_r , _ 2 = _
r e^-i(r-1 ) d^_r , [ weypl ] where @xmath125 and @xmath126 denote the fermionic fock space operators , which satisfy @xmath127 .
this system defines a @xmath22 conformal field theory with current algebra @xmath24 .
the ground state of the system @xmath128 is the tensor product of two dirac vacua , with corresponding fermi surfaces ( see fig.([fig2 ] ) ) .
one refers to these two vacua as an `` upper '' and `` lower '' components of @xmath128 , which satisfies the conditions : u_l |&= & d_l |= 0 , l > 0 , + u^_l
|&= & d^_l |= 0 , l 0 .
[ gscond]in the landau level picture , @xmath129 measures the single - particle angular momentum with respect to the ground state .
the @xmath24 currents of section @xmath15 ( see eq.([coeq ] ) ) can be written in terms of the fermionic bilinears , @xmath130 , as follows : j & = & j^(1 ) + j^(2 ) , j^3 = ( j^(1 ) - j^(2 ) ) , + j^+ & = & _ 1 _ 2 , j^- = _ 2 _ 1 . [ curbas ]
their fourier modes are given by ) .
] : j_n & = & _ k ( u^_k - n u_k + d^_k - n d_k ) , + j^3_n & = & _ k ( u^_k - n u_k -d^_k - n d_k ) , + j^+_n & = & _ k u^_k - n d_k , + j^-_n & = & _ k d^_k - n u_k . [ fomcu ] using the sugawara construction , one defines the two @xmath65 stress - energy tensors of section 2.1 , which are associated to the charged and neutral sectors , @xmath131 and @xmath132 , respectively .
their virasoro modes can be written in the fermionic basis as follows : l^q_n & = & _ l ( l - ) ( u^_l - nu_l + d^_l - n d_l ) + _ l ( _ i u^_i - n+lu_i _ j d^_j - ld_j ) , + l^s_n & = & _ l ( l - ) ( u^_l - nu_l + d^_l - n d_l ) - _ l ( _ i u^_i - n+lu_i _ j d^_j - ld_j ) . + & & [ virsq ] let us now discuss the excitations of the @xmath24 theory in the fermionic basis : these are labelled by their angular momentum with respect to the ground state @xmath133 , and by the two abelian charges @xmath134 and @xmath76 , which are symmetric and anti - symmetric with respect to the two layers , respectively . as explained in section 2.2 , the @xmath22 @xmath0 minimal model is obtained from this theory by imposing the constraint ( [ minvin ] ) : j^-_0 = _ k d^_k u_k = 0 . [ hamr ] in this basis , we can interpret the constraint as follows : the operator @xmath97 moves electrons down and holes up between the two layers ( with a minus sign in the latter case ) , without changing their angular momentum value ; it relates the edge excitations in the two layers and actually vanishes on their symmetric linear combinations .
therefore , the condition ( [ hamr ] ) projects out the edge excitations which are antisymmetric with respect to the two levels : this distinguishes the minimal @xmath0 cfts from the abelian ones .
note that the ground state is unique and symmetric , then it satisfies the constraint : namely , the two cfts share the same ground state .
let us see some examples of the allowed edge excitations in the minimal theory .
there are two abelian edge excitations at the first excited level @xmath135 , which can be written : 1 ; = ( d_1^d_0 u_1^u_0 ) .
[ delta1]we find that the symmetric combination @xmath136 satisfies the constraint ( [ hamr ] ) and the antisymmetric does not . at the next level @xmath137
, there are five abelian edge states : 2 ; a & = & d_1^d_0 u_1^u_0 , + 2 ; b&= & ( d_2^d_0 u_2^u_0 ) , + 2 ; c&= & ( d_1^d_-1 u_1^u_-1 ) .
[ deltwo]again , the antisymmetric combinations @xmath138 and @xmath139 do not satisfy the constraint ( [ hamr ] ) . therefore , the @xmath0 minimal models only contains the symmetric excitations , as we anticipated . in general
, the number of edge excitations with given @xmath133 can be obtained by expanding the character of the vacuum in powers of @xmath140 ( see section @xmath141 ) ; this counting of states for the abelian and minimal theories is reported in table ( [ tab1 ] ) .
.the number of edge excitations for the laughlin hall fluids @xmath142 and its quasi - particles ( first row ) and for the hierarchical fluids @xmath143 ( second and third rows ) , according to the two relevant conformal field theories . [ cols="^,<,>,>,>,>,>,>",options="header " , ] in ref .
@xcite , a physical picture has been developed for the ground state of the laughlin plateaus @xmath1 , which is based on the laughlin incompressible fluid idea . at the semiclassical level , we said that the deformation of the incompressible fluids are described by the area - preserving transformations obeying the @xmath144 algebra . in the ( @xmath145 ) quantum theory , the incompressible fluid
can be identified as the filled chiral fermi sea , which occurs in coordinate space rather than in momentum space ( see fig.([fig2 ] ) ) ; moreover , the low - lying edge excitations are identified with the particle - hole transitions across the fermi surface . the effective quantum theory for these excitations
is given by a single weyl fermion , which naturally possesses the @xmath0 quantum symmetry .
actually , the generators @xmath146 of this algebra produce all possible particle - hole transitions with @xmath147 : those with negative @xmath133 are not allowed by the pauli exclusion principle ; thus the ground state is annihilated by all the generators with positive mode index @xcite , v^i_n = 0 , i=0,1,2 , , n > 0 .
[ whwc ] these are the @xmath0 highest - weight conditions , which can be physically interpreted as the incompressibility of the ground state at the quantum level .
the same incompressibility conditions are satisfied by the laughlin ground states @xcite@xcite ; their edge excitations are described by more general @xmath65 @xmath0 conformal theories chiral - boson theories . ] .
actually , the hilbert space of the bosonic ( @xmath148 ) and fermionic ( @xmath145 ) theories are isomorphic and only differ for the quantum numbers of quasi - particles @xcite . in the case of the hierarchical plateaus , there are , correspondingly , the present fermionic basis of two weyl fermions ( @xmath120 ) and the bosonic basis ( @xmath149 ) of the previous section , which are again isomorphic , and actually identical for the ground state and the neutral sector . the @xmath0 highest - weight conditions ( [ whwc ] ) on the two - layer fermi sea can be interpreted as before as incompressibility conditions .
however , the edge excitations possess an additional sector of up - down antisymmetric particle - hole transitions ; these excitations are tangential to the fermi surface and can not be interpreted as deformations of the incompressible fluid as a whole . in this picture , the minimal - model constraint ( [ hamr ] ) can be regarded as an additional incompressibility condition : it removes the antisymmetric excitations , which are not necessary for the `` minimal '' incompressible fluids .
note that the symmetric excitations can be divided into two classes : those generated by the symmetric current @xmath150 in ( [ fomcu ] ) , which are the same as in the laughlin fluids ( corresponding to the @xmath45 part ) ; in addition , there are those generated by the virasoro modes @xmath151 of the neutral sector , which are specific of the ( @xmath22 ) minimal incompressible fluid ; the first example is @xmath152 in ( [ deltwo ] ) , which occurs at level @xmath137 ( in agreement with the multiplicities of the respective theories in tab.([tab1 ] ) ) .
this @xmath120 description of the minimal models can be pictorially extended to the hierarchical states @xmath153 .
the charged sector @xmath45 is bosonized : it remains isomorphic to the fermionic one , but the charge eigenvalues change .
on the other hand , the @xmath52-independent neutral sector remains the same and can still be described in the fermionic basis , provided one pays attention to distinguishing the two types of symmetric excitations discussed in the previous paragraph .
this description of the hierarchical plateaus is analog to the composite - fermion transformation in the jain theory of wave functions @xcite and has been throughoutfully discussed in ref.@xcite .
another possible basis for the states in the @xmath17 cft is given by the spinon excitations @xcite : the spinon fields , ^(z ) = * :* , = 1 , are the @xmath17 primary fields of conformal dimension @xmath154 and isospin @xmath155 .
the exchange of two spinons yields the fractional statistics @xmath156 , which is half of that of the fermions ; moreover , these fields are not charged , since they belong to the neutral sector of @xmath24 .
they are also called semions , i.e. `` half - fermion '' anyons , which carry ( iso)-spin @xmath157 and no charge .
the fourier modes of the spinon fields are obtained from the expansion @xcite : ^(z ) _ ( 0 ) = _ n z^n+ ^_-n--_(0 ) , [ spimo ] where @xmath158 is a generic state containing an even ( resp . odd ) number of spinons for @xmath159 ( resp .
@xmath160 ) .
the @xmath17 hilbert space can be generated by applying these modes to the vacuum ; this is an alternative to the standard basis using the @xmath62 modes discussed in section @xmath161 ( actually , the latter are spinon bilinears ) .
the spinon fields satisfy generalized ( non - local ) commutation relations which imply relations among the states freely generated by the multinomials of their modes .
these relations can be casted into the form of a generalized pauli exclusion principle : therefore , the modes ( [ spimo ] ) build a pseudo - fock space which is neither bosonic ( @xmath162 ) nor fermionic ( @xmath163 ) . this basis has been discussed in the literature in relation to the solution of the @xmath71 haldane - shastry spin chain , whose spectrum breaks the @xmath17 symmetry down to those of the yangian @xmath164 hopf algebra , which contains @xmath71 .
this decomposition is rather different from the one relevant for the @xmath0 minimal models .
indeed , the corresponding interaction term of section @xmath165 , h^(2 ) = j^+_0 j^-_0 , breaks the @xmath17 symmetry down to virasoro , @xmath166=0 $ ] ; moreover , the @xmath71 symmetry @xmath167 is also broken . in the case of the haldane - shastry chain , the interaction is given by : h_2 = _ k > 0 k j^a_-kj^a_k ; this term breaks virasoro , @xmath168 \neq 0 $ ] for @xmath169 , but keeps scale invariance ; moreover , it preserves the @xmath71 symmetry @xmath170=0 $ ] and the yangian symmetry @xmath171=0 $ ] generated by the corresponding @xmath172 operators ( for their definition , see ref .
@xcite@xcite ) . nevertheless , the two breakings of @xmath17 are compatible , because the interactions in the two problems commute , @xmath173=0 $ ] .
actually , we are going to show that the constraint @xmath174 defining the minimal models can be solved in the spinon basis .
first , we remark that the spinon modes @xmath175 have isospin projection @xmath176 ; this follows from analyzing the @xmath17 operator product expansion : j^a(z ) ^(w ) = ( t^a)^ _ + regular terms , where @xmath177 are the pauli matrices divided by @xmath15 .
next , the states of minimal isospin projection @xmath178 , selected by the constraint @xmath179 , are simply generated by multilinears of the @xmath180 modes , because @xmath8 is additive .
therefore , the fully polarized @xmath82-spinon states ( see ref .
@xcite ) , ^-_--n_n ^-_--n_3 ^
-_--n_2 ^-_--n_1 , [ spba ] are explicit solutions of the constraint @xmath179 .
the virasoro weight of these states is given by : h = + _ i=1^n n_i ; [ hdim ] clearly , an even ( resp . odd ) number of spinons gives a state in the @xmath159 ( resp .
@xmath160 ) @xmath17 representation ( see fig.([fig1 ] ) ) .
it remains to be established a basis of independent states among all possible @xmath181-plet @xmath182 in ( [ spba ] ) .
this is a rather difficult task , because the `` commutation relations '' among the modes contain infinite terms ; therefore , we shall use an indirect argument .
we start from the basis of independent states made by @xmath183 up and @xmath184 down spinons , which has been introduced in ref .
@xcite ( basis ii ) : & & ^-_--n^-_n^-^-_--n^-_1 ^+_--n^+_n^+ ^+_--n^+_1 , + & & n^+_n^+ n^+_2 n^+_10 , n^-_n^- n^-_2 n^-_10 . [ bastwo ] the virasoro dimension is again given by ( [ hdim ] ) with @xmath185 and @xmath186
. it has been shown @xcite , that this basis reproduces the @xmath17 representations @xmath159 for @xmath187 even ( resp .
, @xmath160 for @xmath187 odd ) ; this can be checked by computing the corresponding characters , using the following identity for the sum of partitions : _ k_1
k_n0 q^_i=1^n k_i = _ = 1^n _
m_=0^ q^ m _ = .
one obtains : ^2_=0 = _ n^+ , n^- = 0 , n^+ + n^- even^ , and similarly the sum extended to @xmath188 odd for @xmath189 . these are actually equivalent expressions for the characters of the @xmath17 ( [ char2 ] ) , owing to the identities discussed in ref .
@xcite .
next , we remark that the states ( [ bastwo ] ) have isospin projection @xmath190 and isospin @xmath191
. consider the subspace of states with @xmath192 , i.e. @xmath193 : their sum reproduces the @xmath69 vacuum representation , as is clear from fig .
( [ fig1 ] ) .
one can check the corresponding character : _
^ 1 = _ n^+ = 0^ = .
similarly , the @xmath194 subspace , @xmath195 , yields : _ h=1/4 ^ 1 = _ n^+ = 0^ = . from fig.([fig1 ] ) and the discussion in section @xmath161 , it follows that the @xmath196 subspace is isomorphic to the hilbert space of the minimal model , in the sector @xmath159 ( the @xmath194 one matches the @xmath160 sector , respectively ) .
the mapping can be obtained by multiple application of @xmath97 , as it follows : given that @xmath197 for the states with @xmath193 ( [ bastwo ] ) , the action of @xmath198 yields the states of minimal projection @xmath199 which are required for the minimal models ; otherwise , it vanishes . moreover
, this action replaces all the @xmath183 modes @xmath200 with @xmath201 in eq .
( [ bastwo ] ) .
therefore , the basis ( [ bastwo ] ) is mapped into the one of fully polarized spinons ( [ spba ] ) , which satisfy the constraint @xmath179 . in conclusion , the ( neutral part of ) hilbert space of the @xmath22 @xmath0 minimal models can be described by the fully - polarized spinon states ( [ spba ] ) with the following choices of @xmath202 : = 0 : & n & even , \ { n_n n_n-1
n _ + 1 0 , ; .
+ = : & n & odd , \ { n_nn_n-1
n _ 0 , . .
note that this basis is larger than the one introduced in ref .
@xcite ( basis i ) for building the yangian highest - weight states ( as it should ) .
let us finally remark that the physical interpretation of this basis for the ( @xmath22 ) minimal models remains to be understood , possibly by extending the picture of the fermi sea discussed in the previous paragraph .
in this section , we derive the correlation functions of the quasi - particles in the @xmath22 @xmath0 minimal models , i.e. the @xmath94 cfts .
these correlators factorize into charged and neutral parts ; the charged @xmath82-point functions are given by the well - known vertex operator expectation values @xcite : & & v_q_1(z_1)
v_q_n(z_n ) = _ i < j^n ( z_i - z_j ) ^q_i q_j ( p+ ) , + & & v_q ( z ) = * :* , [ verco ] where the @xmath203 are given by the spectrum ( [ splitsp ] )
. the correlators of the neutral part can be obtained by taking the @xmath204 limit of the dotsenko - fateev coulomb gas construction @xcite , which applies to the @xmath205 virasoro minimal models . in this approach ,
the @xmath82-point functions are written in terms of the @xmath69 vertex operators plus screening charges @xmath206 , which project the virasoro null states out of the @xmath65 bosonic fock space .
the properties of the screening charges have been investigated by felder and other authors
@xcite : we first recall some relevant formulae of these works , then we properly take the @xmath207 limit , and compare the result with the formulation of section @xmath15 .
next , we compute some examples for the correlators and discuss the non - abelian statistics .
let us start from the @xmath69 theory of the neutral bosonic field @xmath208 ( section @xmath15 ) ; the screening charges are defined by : q _
= dz * :* e^i _ ( z ) * :* , with _
+ = , _ - = - , c = c(p , p ) = 1 - 6 1 , p , p > 0 .
[ vimi ] these operators have vanishing conformal dimension in the @xmath209 cfts , and satisfy @xmath210=0 $ ] .
their action in the bosonic fock space is to relate states of same conformal dimension which belong to different @xmath69 representations : f__m,m q_+ f__m,m-2 , f__m,m q_- f__m-2,m , where we denote with @xmath211 the representation with `` charge '' @xmath212 .
its relevant values are : _
m,m & = & _ 0 - m _ + - m _ - , 2 _ 0 = _ + + _ - , + h_m,m & = & _ m,m ( _ m,m -2_0 ) = ; [ kactab]actually , they reproduce the dimensions @xmath213 of the @xmath214 degenerate virasoro representations ( the kac table ) @xcite . the screening charges are useful because they can map @xmath69 highest - weight states into virasoro null states , and thus describe their structure . the two lowest null states in the virasoro representation @xmath215 have dimensions @xcite : h_m,m + mm , h_m,m + ( p-m)(p - m ) .
[ nullvec]we are interested in the @xmath65 degenerate virasoro representations , which can be obtained by the controlled limit @xmath216 within the virasoro minimal models .
this limit can be achieved by letting , p , p , 1 , which implies : _ 1 , _ 00 , _
m,m , h_m,m .
the screening charges go into the @xmath71 operators , @xmath217 , and the @xmath214 degenerate representations are mapped into the @xmath65 ones , @xmath218 , with infinite degeneracy .
it can be shown that all the @xmath214 null states but the lowest one decouple ( their dimensions go to infinity ) . in felder
s notation @xcite , @xmath219 denotes the remaining null state in the @xmath65 representation with @xmath66 ; this state has the dimension @xmath220 , e.g. @xmath221 , @xmath222 in ( [ nullvec ] ) ; moreover , it can be obtained from the @xmath69 highest - weight @xmath223 with charge @xmath224 by the action of @xmath225 : ( w_0 ) _
j^3_0= -n/2 = j^+_0 ( v_0 ) _ j^3_0=
-(n-2)/2 . [ felc ] this result matches the description of section @xmath15 : from fig.([fig1 ] ) and the characters ( [ char2 ] ) , it is apparent that the @xmath66 virasoro with @xmath226 ( the @xmath71 lowest - weight state ) can be obtained from the @xmath69 with @xmath227 ( horizontal line in fig.([fig1 ] ) ) by subtracting the @xmath69 of the null - vector with @xmath228 ( adjacent horizontal line ) . in conclusion ,
the @xmath65 virasoro theory is described in the felder approach @xcite as the @xmath69 fock space with all the null - vectors removed ; according to eq.([felc ] ) , this condition can be written : physical state ( j^3_0 = -m ) j^+_0 any state ( j^3_0 = -m-1 ) ( m 0 ) .
this is clearly equivalent to the constraint @xmath229 introduced in section @xmath15 ; therefore , the felder ( coulomb gas ) approach yields another description of the hilbert space of the @xmath0 minimal models , which is equivalent to the previous ones . in the dotsenko - fateev coulomb gas approach @xcite,@xcite , the @xmath82-point function of virasoro primary fields @xmath230 is obtained by the vertex operators with appropriate insertion of a number of screening charges
; for example , the four - point functions have the form : [ fpf ] & & _ s_1
^ 2(z_1)_s_2 ^ 2(z_2 ) _
s_3 ^ 2(z_3 ) _
s_4 ^ 2(z_4 ) _ vir = + & & ( _ i=1^n_+ q_+ ) * : * e^-im_1 ( z_1 ) : * : * e^-im_2 ( z_2 ) : * : * e^-im_3 ( z_3 ) : * : * e^-im_4 ( z_4 ) : ; [ fourp]in this expression , the number of screening charges is determined by the condition of charge neutrality : j^3_0 = n_+ - m_1 - m_2 - m_3 - m_4 = 2_0 = 0 , ( c=1 ) , [ tocha ] with @xmath231 , @xmath232 . in the @xmath214 minimal models , both screening charges @xmath233 and @xmath234 ( see eq.([vimi ] ) ) must be used in the correlator ( [ fpf ] ) , in order to satisfy the charge neutrality condition ( see eq.([kactab ] ) ) ; in the @xmath65 case , there are several possibilities , because the two @xmath206 charges are equivalent by the @xmath235 symmetry ( absent for @xmath214 ) ; moreover , in some correlators the charge neutrality condition can also be satisfied without screening charges , provided that certain permutation rules are employed ( see later ) .
let us first consider the example of the three - point function of the fields @xmath236 and @xmath237 : ( _ i=1^k - n q_+ ) * : * e^-ik ( z_1 ) : * : * e^-ik ( z_2 ) : * : * e^in ( z_3 ) : . using the reflection symmetry @xmath238 for each field , one can choose the simplest case of minimal number of screening charges .
moreover , we can take @xmath239 by using the @xmath240 invariance of the ground state .
a number of properties can be derived from this correlator : as an example , we check the @xmath71 fusion rules @xmath241 ; these imply that the correlator should not vanish for @xmath242 . for @xmath243
, it obviously does not ; for @xmath244 , we find the expression : _
c_u_0 du u^-k ( 1-u)^-k , [ tpc ] where the contour @xmath245 has to be taken around any of the singularities @xmath246 .
this integral is found to vanish for @xmath247 and to take opposite non - vanishing values for @xmath248 and @xmath249 .
next , for @xmath250 , the charge neutrality condition requires the use of one @xmath233 , leading to the same expression ( [ tpc ] ) with @xmath251 ; this vanishes for any choice of @xmath245 and verifies again the fusion rules .
other cases for @xmath51 can be worked out along the same lines @xcite .
the non - abelian statistics of quasi - particles manifests itself in the four ( and higher ) point functions , as we shall now discuss . in the coulomb gas form of the correlator ( [ fpf ] ) ,
the choices of contour @xmath245 yield several independent expressions , which are called the conformal block @xmath252 @xcite : each one corresponds to an intermediate state with a given isospin value , obtained by the fusion of the isospins involved .
for example , the correlation of four electron excitations ( @xmath253 and @xmath254 in ( [ fourp ] ) ) can be written : [ cbc ] g(z_i)&= & q_+ * : * e^-i ( z_1 ) : * : * e^-i ( z_2 ) : * : * e^-i ( z_3 ) : * : * e^i ( z_4 ) : + & = & ( ( 1-))^1/2(z_13 z_24)^1/2 _
c_i du u^-1 ( u-1)^-1 ( u-)^-1 + & = & 1 ( z_13 z_24)^1/2 .in this expression , we have used the @xmath240 invariance to map the four points @xmath255 , with @xmath256 , and @xmath257 .
the correlator ( [ cbc ] ) contains two independent blocks for the isospin channels @xmath258 , which are added with coefficients @xmath259 and @xmath260 ; the third term in the last line of ( [ cbc ] ) is actually a linear combination of the first two .
note also that the full correlator also contains the factor @xmath261 arising from the charged part .
the presence of two independent terms in the correlator ( [ cbc ] ) should be interpreted as a `` dynamical '' degeneracy of the four - electron state . under the exchange of two electrons ,
those two terms transform linearly into themselves .
this is the notion of non - abelian statistics : the exchange operation does not simply map each state into itself up to a phase , but acts on the set of degenerate states by a multi - dimensional unitary transformation .
let us compute it explicitly : putting all terms together , the four - point function becomes , g(z_i)_i < j z_ij^p+1/2 & = & _ i < j z_ij^p+1 , + f_1(z_i ) & = & , _
2(z_i ) = .
[ elco ] for example , the exchange of the @xmath262 and @xmath263 electrons , @xmath264 leads to the following transformation : the prefactor yields the usual minus sign for fermi statistics ( @xmath265 is odd ) , while the two blocks transform as follows , ( ) ( ) ( ) .
[ naexp ] the hierarchical hall states have been commonly considered to posses electrons and quasi - particles with abelian statistics @xcite ; this is in fact true if one adopts the description by the multi - component abelian cfts @xcite , where the quasi - particles are associated to @xmath69 representations and have the usual vertex - operator correlations . on the other hand ,
the @xmath119 @xmath0 minimal models associate the quasi - particles to the virasoro representations , which have assigned an @xmath71 isospin quantum number , leading to non - abelian statistics ( and , correspondingly , an @xmath9 weight for @xmath266 ) .
these two different descriptions of the quasi - particles can be tested in future experiments involving interference and scattering processes , which measure the three and higher point functions .
next , we remark that the non - abelian statistics ( [ naexp ] ) occurring in the @xmath0 minimal models is rather `` mild '' , i.e. it is not due to strong singularities of the correlators ; actually , it has a simple _ a - posteriori _ explanation . in the two - component abelian cft , there are two electron fields , one for each component , which are represented by the vertex operators with @xmath267 and @xmath194 , respectively . on the contrary , in the minimal models
there is a single electron excitation represented by the @xmath155 virasoro primary field : in the coulomb gas approach , this field can be written as either vertex operators with @xmath268 , due to the reflection symmetry @xmath269 . moreover , in the electron correlators the charge neutrality can be satisfied without adding any screening charge : for example , the two conformal blocks in ( [ elco ] ) can also be written as follows : _ 1 & & * : * e^-i ( z_1 ) : * : * e^i ( z_2 ) : * : * e^i ( z_3 ) : * : * e^-i ( z_4 ) : , + f_2 & & * : * e^-i ( z_1 ) : * : * e^-i ( z_2 ) : * : * e^i ( z_3 ) : * : * e^i ( z_4 ) : .
this alternative construction is obtained by taking all possible sign choices for @xmath270 having vanishing sum .
therefore , the electrons are represented as in the two - component abelian theory , but their components , i.e. signs , are not distinguishable and should be summed up .
the occurrence of non - abelian statistics , i.e. of more than one block , can be traced back to this ambiguity .
note that this degeneracy of the electron states is the type of `` non - abelian '' statistics also occurring in the so - called @xmath271 $ ] double - layer hall state @xcite .
clearly , this fact deserves further investigations before it can be physically observed : most notably , one should propose a probe which couples to the non - trivial neutral excitations .
the non - abelian statistics has been also investigated in the pfaffian and haldane - rezayi @xmath272 hall states of paired electrons @xcite .
their quasi - particles are non - abelian , but their electrons are still abelian : actually , for these states there is a clear relation between the ( bulk ) wave - functions and the cft correlators on the edge , which forces the electrons to obey the usual fermionic abelian statistics . on the contrary , in the @xmath0 models , the electrons are also non - abelian ( @xmath155 ) ; actually , the relation with wave functions is not immediate : we have compared the correlator ( [ elco ] ) with the jain composite - fermion wave functions , which have been recently written in the first landau level @xcite .
we have found that these wave functions do not match any conformal correlator , because they are not @xmath240 covariant and then can not be written as correlators of virasoro primary fields .
presumably , the electrons are described by different fields in the bulk and in the edge .
therefore , the result ( [ naexp ] ) for the non - abelian statistics of the electron excitations at the edge is consistent with the experimental and theoretical results known at present .
in this work , we have pursued the investigation of the @xmath0 minimal models , which were previously proposed as the conformal theories of the hierarchical hall states @xcite .
we have explicitly formulated these theories in a bosonic fock space with either a set of constraints or a relevant hamiltonian .
we have presented a detailed analysis of their physical properties and we have compared them with the other , multi - component abelian theories @xcite .
we have relied upon several known methods in conformal field theory , like the hamiltonian reduction , the coulomb gas approach and the spinon excitations .
this explicit formulation of the @xmath0 minimal models has already been useful for interpreting the numerical analysis of the low - lying electron spectrum on a disk geometry of ref.@xcite .
moreover , the hamiltonian formulation of section @xmath15 suggests the possibility of further investigations : for example , it would be interesting to describe the @xmath0 minimal models by means of the chern - simons field theory , along the lines of the well - known relation between edge degrees of freedom and bulk gauge fields @xcite ; this description may reveal interesting properties of the bulk states which support minimal edge excitations .
another interesting result is the computation of correlation functions in section @xmath16 : this will turn out to be important for searching characteristic signals of the @xmath0 minimal models in two recently proposed experiments : the multi - point interferometer of ref.@xcite and the detection of the andreev reflection @xcite .
* acknowledgements * we would like to thank the c.e.r.n .
theory division and the theory group at l.a.p.p .
, annecy , for hospitality .
a. c. also thanks the theory group of the centro atmico bariloche for hospitality and acknowledges the partial support of the european community program fmrx - ct96 - 0012 .
g. r. z. is grateful to i.n.f.n .
, sezione di firenze , and i.c.t.p . , trieste , for hospitality ; his work is supported by a grant of the antorchas foundation ( argentina ) .
in this appendix , we describe the @xmath118 @xmath0 minimal models appropriate for filling fractions @xmath273 ( @xmath43 ) following closely the presentation of sections @xmath15 and @xmath16 .
our aim is to describe the reduction in the number of degrees of freedom from the @xmath274 conformal theories @xcite to the @xmath118 @xmath0 minimal models with symmetry algebra @xmath275 @xcite .
we first rewrite the spectrum of quasi - particle charge @xmath3 and quantum statistics @xmath276 of the @xmath274 theories in a basis which factorizes the @xmath69 part .
next , we analyze the neutral spectrum according to the of the nested algebras @xmath277 . the @xmath274 spectrum in the basis of ref .
@xcite is : q & = & n_1+n_2+n_3 3p+1 , n_1,n_2,n_3 , + h & = & 12 ( n_1 ^ 2 + n_2 ^ 2 + n_3 ^ 2 ) - p2 ( 3p+1 ) ( n_1+n_2+n_3 ) ^2 . [ su3sp]the integers @xmath278 span the three - dimensional lattice @xmath279 , those vectors have norm @xmath280 , the total virasoro dimension ; each point of the lattice identifies a @xmath281 highest - weight in this theory . a two - dimensional sub - lattice is the @xmath282 weight lattice @xmath283 ; this can be generated by the fundamental weights @xmath284 , @xmath26 , which are dual to the simple positive roots @xmath285 .
a standard basis is @xcite : & = & _ 1 ^(1 ) + _ 2 ^(2 ) , + ^(1 ) & = & ( , ) , ^(2 ) = ( 0 , ) , + _ ( 1 ) & = & ( , 0 ) , _ ( 2 ) = ( - , ) ; [ su3latt]they satisfy @xmath286 , @xmath287 and @xmath288 , with @xmath289 , we recall that each @xmath282 lie - algebra can be characterized by a positive highest weight @xmath290 , i.e. by the pair @xmath291 with @xmath292 .
other copies of the have @xmath293 and can be obtained by acting on @xmath294 with the weyl group .
the triality of the @xmath291 is given by : = _ 1 -_2 mod 3 , = 0 , 1 .
[ trial]we denote with @xmath295 the three sub - lattices of @xmath283 with given triality ( each one is equivalent to the root lattice up to a translation ) .
form the construction of the lattice @xmath279 in ref .
@xcite@xcite , it is apparent that its factorization into @xmath283 and the one - dimensional charge lattice can only be done within each @xmath296-sector ; moreover , the integers in the two lattices are related by @xmath297 and @xmath298 . therefore , we consider the @xmath296-dependent change of basis : l l l = 0 : & & + 3=n_1+n_2+n_3 , & _ 1 = n_1 -n_2 = 2k_1 - k_2 , & _ 2 = n_2 -n_3 = 2k_2 - k_1 ; + = 1 : & & + 3 + 1 = n_1+n_2+n_3 , & _ 1 = n_1 -n_2 = 2k_1 - k_2 + 1 , & _ 2 = n_2 -n_3 = 2k_2 - k_1 ; + = -1 : & & + 3 - 1 = n_1+n_2+n_3 , & _ 1 = n_1 -n_2 = 2k_1 - k_2 , & _ 2 = n_2 -n_3 = 2k_2 - k_1 + 1 . [ magtra]this rewrites the spectrum ( [ su3sp ] ) in the form : q & = & , + h & = & + h _ , [ spsu3]where @xmath299 is the dimension of the neutral @xmath300 in the lattice @xmath283 : h _ = 12 ^2 = ( ^2_1 + ^2_2 + _ 1 _ 2 ) = \ { .
[ su3wei]the factorization of @xmath279 into charged and neutral orthogonal sub - lattices is achieved in ( [ spsu3 ] ) : the former is parametrized by @xmath301 ; the latter by @xmath302 ( lattice @xmath283 ) , or alternatively by @xmath303 in each sector @xmath295 .
form now on , we discuss the neutral spectrum only .
we want to analyze the decompositions of its with respect to the algebras @xmath304 .
the @xmath305 algebra has three ( integrable ) labelled by @xmath306 @xcite ; each of these decomposes : ( i ) into the sum of the @xmath300 of the lattice @xmath295 , eqs.([spsu3]),([su3dim ] ) , each with multiplicity one ; ( ii ) into the sum of the @xmath307 of weights @xmath308 , each with multiplicity given by the dimension of the corresponding @xmath282 .
the latter decomposition can be written @xmath309 : actually , the @xmath282 generators @xmath310 , @xmath311 , commute with the @xmath307 ones , @xmath312 and @xmath313 , which are the modes of the virasoro and spin - three currents , respectively ; this factorization is completely analogous to the @xmath17 case of section @xmath15
. these decompositions of can be checked by computing the corresponding characters .
the @xmath305 characters are found in ref .
@xcite : they involve the sum over the sub - lattice @xmath314 , with @xmath315 , for @xmath316 , respectively , and @xmath317 a vector of the root lattice .
their explicit form is : ^ _ = 1 _ ( a , b)= ( i_1,i_2 ) + 4 ( 2k_1-k_2 , 2k_2 - k_1 ) d(a-1,b-1 ) q^(a^2 + b^2+a b)/12 , [ su3cha]with ( i_1,i_2 ) & = & \ { ( 1,1 ) , ( 2,1 ) , ( 1,2 ) } , = \{0,1,-1 } , k_1,k_2 ; + d _ & & d ( _ 1,_2 ) = 12 ( 1 + _ 1 ) ( 1 + _ 2 ) ( 2 + _ 1 + _ 2 ) .
[ su3dim]in the last equation , @xmath318 is the dimension of the @xmath282 @xmath319 ( here extended to all @xmath283 ) . in order to verify the first of the decompositions above
, these characters are compared with those obtained by summing the @xmath300 in each sector @xmath295 of the quasi - particle spectrum ( [ spsu3 ] ) , ( [ su3wei ] ) . using the form ( [ abecha ] ) of the @xmath69 character , we obtain the expressions : ^_=0 & = & 1 _
k_1,k_2 q^k^2_1 + k^2_2 - k_1 k_2 , + ^_=1 & = & 1 _
k_1,k_2 q^k^2_1 + k^2_2 - k_1 k_2 + k_1 + 1/3 .
[ u12cha]the expressions ( [ su3cha ] ) and ( [ u12cha ] ) are actually equivalent , due to non - trivial jacobi - like identities ; these can be checked by expanding both expressions in series of @xmath140 with the help of mathematica @xcite .
this completes the analysis of the content of the @xmath118 abelian cft with symmetry @xmath274 .
the second , more relevant , decomposition is @xmath320 : we need the @xmath22 @xmath307 characters , which are obtained from ref.@xcite .
they read : ^w_3 _ * * = ^w_3__1,_2 = 1 q^(^2_1 + ^2_2 + _ 1 _ 2)/3 ( 1 - q^_1 + 1 ) ( 1 - q^_2 + 1 ) ( 1 - q^_1 + _ 2 + 2 ) .
[ wudue ] actually , the @xmath118 degenerate @xmath0 @xcite of weights @xmath321 , with @xmath322 and @xmath323 , are equivalent to the @xmath324 with @xmath297 and @xmath298 @xcite .
note that these @xmath307 characters are similar to the degenerate virasoro ones ( [ chiva ] ) , in the sense that they are again linear combinations , with alternating signs , of the corresponding abelian characters . in eq .
( [ wudue ] ) , there are six of them , which sit at the points of an hexagon of the root lattice : actually , we can rewrite this character , e.g. for @xmath325 , ^3_2k_1-k_2,2k_2-k_1 = ^1 ^ 2_k_1,k_2 - ^1 ^ 2_k_1 + 1,k_2 + ^1 ^ 2_k_1 + 2,k_2 + 1 - ^1 ^ 2_k_1 + 2,k_2 + 2 + ^1 ^ 2_k_1 +
1,k_2 + 2 - ^1 ^ 2_k_1,k_2 + 1 .
this describes the decomposition of for @xmath326 and shows the existence of @xmath307 null vectors .
according to the equivalence @xmath327 , the character @xmath328 ( [ su3cha ] ) should be reproduced by summing over the @xmath307 ones with weights @xmath329 and multiplicities equal to the dimensions of the corresponding @xmath282 multiplets ( [ su3dim ] ) .
these sums are written : ^_=0 & = & _ k_1=0^ _
2k_1 k_2 k_1/2 d(2k_1 -k_2 , 2k_2 -k_1 ) ^w_3_2k_1 -k_2 , 2k_2 -k_1 , + ^_=1 & = & _ k_1=0^ _ 2k_1 + 1k_2 k_1/2 d(2k_1 -k_2 + 1 , 2k_2 -k_1 ) ^w_3_2k_1 -k_2 + 1 , 2k_2 -k_1 , + ^_=-1 & = & _ k_1=0^ _ 2k_1 k_2 ( k_1 - 1)/2 d(2k_1 -k_2 , 2k_2 -k_1 + 1 ) ^w_3_2k_1 -k_2 ,
2k_2 -k_1 + 1 , [ invsu3]where the ranges for @xmath330 are obtained from @xmath331 . the identities ( [ invsu3 ] ) are again checked by power expansion in @xmath140 .
therefore , we have proven the expected decomposition of @xmath305 into @xmath307 : note the complete analogy with the @xmath17 case ( [ deco ] ) illustrated in fig .
( [ fig1 ] ) .
the hamiltonian reduction from the @xmath274 abelian theory to the @xmath118 @xmath0 minimal model is then obtained by keeping one state per @xmath282 multiplet ; this is the @xmath282 lowest - weight state , which is annihilated by the @xmath282 shift operators @xcite : e^-_(1)_0 & = & 0 , + e^-_(2)_0 & = & 0 .
[ su3cst]these two constraints define the @xmath118 @xmath0 minimal models in the abelian fock space , in analogy with ( [ minvin ] ) .
note that the third negative root @xmath332 does not give an independent condition because @xmath333 = - e^{-\vec{{\alpha}}_{(1)}-\vec{{\alpha}}_{(2)}}_0 $ ] .
the equivalent hamiltonian formulation of the @xmath118 @xmath0 minimal models is obtained by adding the following relevant term to the hamiltonian : h^(2 ) = ( e^_(1)_0 e^-_(1)_0 + e^_(2)_0 e^-_(2)_0 ) , and by considering the infrared limit @xmath106 of the corresponding renormalization - group trajectory . finally , we present the fermionic realization of the @xmath118 @xmath0 minimal models that parallels that of section @xmath16
. consider three weyl chiral fields @xmath334 , @xmath335 .
we can realize the @xmath274 theory in terms of fermion bilinears @xmath336 , where the matrices @xmath337 represent the fundamental of @xmath282 .
the cartan sub - algebra contain the charge current , j =( _ 1 _ 1 + _ 2 _ 2 + _ 3 _ 3 ) , and the neutral currents , h_1 = 1 ( _ 1 _ 1 - _ 2 _ 2 ) , h_2 = 1 ( _ 1 _ 1 + _ 2 _ 2 -2 _ 3 _ 3 ) .
the shift currents are : e^_(1 ) = _ 1 _ 2 , e^_(2)= _ 2 _ 3 , e^_(1)+_(2 ) = _ 1 _ 2 , [ curasu]together with their hermitian conjugates . by construction ,
the zero - modes of these currents satisfy the standard commutation relations of the @xmath282 lie algebra in the cartan basis @xcite . as in section @xmath16
, the constraints ( [ su3cst ] ) can be written in the three - component fermionic fock space , and they imply that the states of the minimal - model are made by particle - hole excitations which are completely symmetric with respect to the three components
. the constraints can be interpreted as further incompressibility conditions which eliminate the anti - symmetric excitations tangential to the fermi surface .
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the @xmath0 minimal models are conformal field theories which can describe the edge excitations of the hierarchical plateaus in the quantum hall effect . in this paper
, these models are described in very explicit terms by using a bosonic fock space with constraints , or , equivalently , with a non - trivial hamiltonian .
the fock space is that of the multi - component abelian conformal theories , which provide another possible description of the hierarchical plateaus ; in this space , the minimal models are shown to correspond to the sub - set of states which satisfy the constraints .
this reduction of degrees of freedom can also be implemented by adding a relevant interaction to the hamiltonian , leading to a renormalization - group flow between the two theories .
next , a physical interpretation of the constraints is obtained by representing the quantum incompressible hall fluids as generalized fermi seas .
finally , the non - abelian statistics of the quasi - particles in the @xmath0 minimal models is described by computing their correlation functions in the coulomb gas approach .
-.5 in 6.in = 11 1 2_1 3w_3 dff 318/8/98 + hep - th/9808179 + .5 in hamiltonian formulation of the @xmath0 minimal models 0.2 in andrea cappelli + _ i.n.f.n . and dipartimento di fisica , largo e. fermi 2 , i-50125 firenze , italy _ + 0.1 in _ and _ + 0.1 in guillermo r. zemba + _ centro atmico bariloche and instituto balseiro , c. n. e. a. and universidad nacional de cuyo , 8400 - san carlos de bariloche , ro negro , argentina _
.1 in 1.cm august 1998
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the circular restricted three body problem is modification of the three body problem where the third body is assumed to have very small mass which is infinitesimal in comparison to other two finite masses are called primaries .
the restricted three body problem is generalized to include radiation pressure , oblateness of the second primary and influence of the belt .
further the primary bodies are moving in circular orbits about their center of mass .
the well - known five equilibrium points(lagrangian points ) that appear in the planar restricted three - body problem are very important for astronautical applications .
the collinear points are unstable and the triangular points are stable @xcite . in the sun - jupiter system
several thousand asteroids , collectively referred to as trojan asteroids , are in orbits of triangular equilibrium points .
but collinear equilibrium points are also made linearly stable by continuous corrections of their orbits(halo orbits ) .
in other words the collinear equilibrium points are metastable points in the sense that , like a ball sitting on top of a hill . however , in practice these lagrange points have proven to be very useful indeed since a spacecraft can be made to execute a small orbit about one of these lagrange points with a very small expenditure of energy @xcite . because of the its unobstructed view of the sun , the sun - earth @xmath0 is a good place to put instruments for doing solar science .
nasa s genesis discovery mission has been there , designed completely using invariant manifolds and other tools form dynamical systems theory . in 1972 , the international sun - earth explorer ( isee ) was established , joint project of nasa and the european space agency(esa ) .
the isee-3 was launched into a halo orbit around the sun - earth @xmath0 point in 1978 , allowing it to collect data on solar wind conditions upstream from the earth @xcite . in the mid-1980s the solar and heliospheric observatory ( soho )
@xcite is places in a halo orbit around the sun - earth @xmath0 position , about a million miles the sun ward from the earth .
they have provided useful places to parka spacecraft for observations .
the chermnykh s problem is a new kind of restricted three body problem which was first time studied by @xcite .
this problem generalizes two classical problems of celestial mechanics : the two fixed center problem and the restricted three body problem .
this gives wide perspectives for applications of the problem in celestial mechanics and astronomy .
the importance of the problem in astronomy has been addressed by @xcite .
some planetary systems are claimed to have discs of dust and they are regarded to be young analogues of the kuiper belt in our solar system .
if these discs are massive enough , they should play important roles in the origin of planetsorbital elements .
since the belt of planetesimal often exists within a planetary system and provides the possible mechanism of orbital circularization , it is important to understand the solutions of dynamical systems with the planet - belt interaction . chermnykh s problem has been studied by many scientists such as , , and reference their in .
the goal of present paper is to investigate the nature of collinear equilibrium point @xmath0 because of the interested point to the mission design .
although there are two new equilibrium points due to mass of the belt(larger than 0.15 ) but they are left to examine .
all the results are computed numerically with the help of computer because pure analytical methods are not suitable .
the actual trajectories and the stability regions of @xmath0 however is more complicated than the discussed here .
but for specific the time intervals , and initial values , these results provide new information on the behavior of trajectories around the lagrangian point @xmath0 for different possible set values of the parameters .
it is supposed that the motion of an infinitesimal mass particle is influenced by the gravitational force from primaries and a belt of mass @xmath2 .
the units of the mass , the distance and the time are taken such that sum of the masses and the distance between primaries are unities , the unit of the time i.e. the time period of @xmath3 about @xmath4 consists of @xmath5 units such that the gaussian constant of gravitational @xmath6 . then perturbed mean motion @xmath7 of the primaries
is given by @xmath8 , where @xmath9 , @xmath10 are flatness and core parameters respectively which determine the density profile of the belt , @xmath11 , @xmath12 is the oblateness coefficient of @xmath13 ; @xmath14 , @xmath15 are the equatorial and polar radii of @xmath13 respectively , @xmath16 is the distance between primaries and @xmath17 are the functions of the time @xmath1 i.e. @xmath1 is only independent variable .
the mass parameter is @xmath18(@xmath19 for the sun - jupiter and @xmath20 for the sun - earth mass distributions respectively ) , @xmath21 is a mass reduction factor and @xmath22 is the solar radiation pressure force which is exactly apposite to the gravitational attraction force @xmath23 .
the coordinates of @xmath3 , @xmath4 are @xmath24 , @xmath25 respectively . in
the above mentioned reference system and @xcite model , the equations of motion of the infinitesimal mass particle in the @xmath26-plane formulated as[please see ] : @xmath27 where @xmath28 @xmath29 from equations ( [ eq : omegax ] ) and ( [ eq : omegay ] ) , the jacobian integral is given by : @xmath30 which is related to the jacobian constant @xmath31 .
the location of three collinear equilibrium points and two triangular equilibrium points is computed by dividing the orbital plane into three parts @xmath32 : @xmath33 , @xmath34 : @xmath35 and @xmath36 : @xmath37 . for the collinear points , an algebraic equation of the fifth degree
is solved numerically with initial approximations to the taylor - series as : @xmath38 the solution of differential equations ( [ eq : omegax ] ) and ( [ eq : omegay ] ) is presented as interpolation function which is plotted for various integration intervals by substituting specific values of the time @xmath1 and initial conditions i.e. @xmath39 where @xmath40 and @xmath41 for the triangular equilibrium points .
, @xmath42 and @xmath43 , panel ( i):red doted curves and blue points for sun - jupiter mass distribution , blue curves and black points for sun - earth mass distribution , ( ii ) : position of @xmath44 with respect to jupiter s and earth s is shown in zoom ] the equilibrium points are shown in figure [ fig : lpoints ] in which two panels i.e. ( i ) red solid curves and blue points correspond to the sun - jupiter mass distribution and blue dashed curves and black points correspond to the sun - earth mass distribution .
panel ( ii ) show the zoom of the neighborhood of @xmath45 .
the numerical values of these points are presented in table [ tab : lpts ] .
one can see that the positions of @xmath46 appeared rightward and the positions of @xmath47 ( @xmath48 is shifted downward also ) are shifted leftward in the sun - earth system with respect to the position in the sun - jupiter system .
the nature of the @xmath49 is similar to the @xmath48 .
the detail behavior of the @xmath0 with stability regions is discussed in sections .
[ sec : trjl1 ] & [ sec : stbl1 ] .
.location of equilibrium points when t=0.01 , @xmath50 , @xmath51 and @xmath43 [ cols="^ , < , < , < , < " , ] [ tab : trajectoryl1 ]
suppose the coordinates @xmath52 of @xmath0 are initially perturbed by changing @xmath53 where @xmath54 .
the @xmath55 indicates the direction of the initial position vector in the local frame .
if the @xmath56 means there is no perturbation .
it is supposed that the @xmath57 and the @xmath58 to examine the stability of @xmath0 .
figure [ fig : stb ] show the path of test particle and its energy with four panels i.e. the panels ( i&iii):@xmath59 , in ( i ) trajectory of perturbed @xmath0 moves in chaotic - circular path around initial position without deviating far from it , then steadily move out of the region . in ( iii ) the test particle move in stability region and returns repeatedly on its initial position .
the blue solid curves represent @xmath60 and dashed curves represent @xmath61 .
it is clear form panel ( iii ) that bounded region for @xmath60 is @xmath62 and for @xmath63 . with panels ( i - ii):@xmath64 and ( iii - iv):@xmath65 in which blue solid curves for @xmath66 , red curves for @xmath67,title="fig : " ] + with panels ( i - ii):@xmath64 and ( iii - iv):@xmath65 in which blue solid curves for @xmath66 , red curves for @xmath67,title="fig : " ] the effect of oblateness of the second primary is shown in figure [ fig : stboblt ] when @xmath68 .
the panel ( i ) shows the trajectory of perturbed point @xmath0 and ( ii ) shows the energy of that point .
the blue doted lines correspond to @xmath69 and red lines for @xmath70 .
one can see that the oblate effect is very powerful on the trajectory and stability of @xmath0 . when @xmath71 the @xmath0 is asymptotically stable for the value of @xmath1 which lies within a certain interval .
but if oblate effect of second primary is present(@xmath72 ) , the stability region of @xmath0 disappears when this effect is increases .
further all the results presented in the manuscripts are similar to the results obtained by @xcite , @xcite . on the stability of @xmath0 panel ( i ) trajectory ( ii ) energy of perturbed point @xmath0 in which blue solid curves for @xmath73 , red curves for @xmath70,title="fig : " ] +
the numerical computation presented in the manuscript provides remarkable results to design trajectories of lagrangian point @xmath0 which helps us to make comments on the stability(asymptotically ) of the point .
we obtained the intervals of the time where trajectory continuously moves around the @xmath0 , does not deviate far from the point but tend to approach ( for some cases ) it , the energy of perturbed point is negative for these intervals , so we conclude that the point is asymptotical stable .
more over we have seen that after the specific time intervals the trajectory of perturbed point depart from the neighborhood and goes away from it , in this case the energy also becomes positive , so the lagrangian point @xmath0 is unstable .
further the trajectories and the stability regions are affected by the radiation pressure , the oblateness of the second primary and mass of the belt .
i wish to express my sincere thanks to the director , indian school of mines dhanbad , the head of the department of applied mathematics for providing all accessary research facilities in the department .
i also thanks to professor b. ishwar , b.r.a .
bihar university muzaffarpur , all my colleagues and special thanks to dr .
rao for the valuable comments and suggestions during the preparation of this article .
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the lagrange point @xmath0 for the sun - earth system is considered due to its special importance for the scientific community for the design of space missions .
the location of the lagrangian points with the trajectories and stability regions of @xmath0 are computed numerically for the initial conditions very close to the point . the influence of belt , effect of radiation pressure due to sun and oblateness effect of second primary(finite body earth )
is presented for various values of parameters .
the collinear point @xmath0 is asymptotically stable within a specific interval of time @xmath1 correspond to the values of parameters and initial conditions .
trajectory , stability , equilibrium points , radiation pressure , oblateness , rtbp .
code , 70f15
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the study of spectroscopy and the decay properties of the heavy flavour mesonic states provides us useful information about the dynamics of quarks and gluons at the hadronic scale . the remarkable progress at the experimental side , with various high energy machines such as lhc , b - factories , tevatron , argus collaborations , cleo etc for the study of hadrons has opened up new challenges in the theoretical understanding of heavy flavour hadrons . in order to understand the structure of the newly observed zoo of open flavour meson resonances@xcite in the energy range of 2 - 5 @xmath3 , it is necessary to analyze their spectroscopic properties and decay modes based on theoretical models . many of these states could be the excited charmed mesonic states while for many other states the possibility of multi - quark or molecular like structures are being proposed .
thus , the main objective of the present talk includes the study of spectroscopy and the decay properties of the open flavour charm mesons .
we study these open charm states as the excited states of the conventional quark - antiquark systems within the frame work of a potential model @xcite .
we also study , following the molecular interpretation of some of the recently observed meson states , the binding energy and the ground state masses of di - hadronic molecules@xcite . for the binding energy of the di - hadronic state
, we consider a large r ( @xmath4 ) limit of the confined gluon propagator employed in our earlier study on n - n integrations.@xcite
for the light - heavy flavour bound system of @xmath5 or @xmath6 we treat the heavy - quark ( q = c , b ) non - relativistically and the light - quark ( q = u , d , s ) relativistically within the mesonic system .
the hamiltonian for the case be written as @xcite@xmath7 where m is the heavy quark mass , m is the light quark mass , p is the relative momentum of each quark , v(r ) is the confined part of the quark- antiquark potential , @xmath8 and @xmath9 are the spin - spin and spin orbital part of the interaction . here
we consider @xmath10 where @xmath11 , @xmath12 being the strong running coupling constant , a and @xmath13 are the potential parameters . for computing the hyperfine and spin - orbit splitting
, we consider the spin dependent part of the usual ogep given by @xcite @xmath14 we employ the harmonic oscillator wave function and use the virial theorem , to get the energy expression from the hamiltonian defined by eqn.([eq : hamiltonian ] ) . here
@xmath15 is the wave function parameter determined using the variational method .
the parameters used here are @xmath16,@xmath17 , @xmath18 , @xmath19 , @xmath20 ( for open charm meson ) and @xmath21 ( for open beauty - charm meson ) .
the computed s and p wave mass spectrum of @xmath22 , @xmath0 and @xmath1 mesons are tabulated in table [ tab:1 ] alongwith the experimental and other theoretical results .
the decay constant of the mesons is an important parameter in the determination of the leptonic , non - leptonic weak decay processes .
it is related to the wave function at the origin through van - royen - weisskoff formula . incorporating a first order qcd correction factor ,
we compute them using the relation @xcite @xmath23\ ] ] where @xmath24 is the ground state mass of the pseudoscalar states . + in the spectator approximation@xcite
the inclusive widths of b and c quarks decay are given by @xmath25 and width of the annihilation channel is computed using the expression given by @xcite @xmath26 where @xmath27 for the @xmath28 channel and @xmath29 for @xmath30 , and @xmath31 is the mass of the heaviest fermions . here@xmath32 and @xmath33 are the respective ckm matrix , where numerical values are obtained from @xcite .
the total width of the @xmath34 meson decay is the addition of partial widths _
@xmath35 @xmath36 @xmath37 . in the case of the @xmath1 meson , both the heavy quark
, b and c under go the decay and the total width is obtained as @xmath38 .
the computed pseudoscalar decay constants with and without the correction factor @xmath39 , the total width and lifetime of @xmath22 , @xmath0 and @xmath1 mesons are listed in table [ tab:2 ] along with other model predictions and experimental values . + & @xmath13&@xmath40&@xmath41&1 @xmath42&1@xmath43&@xmath44&1 @xmath45&@xmath46&2 @xmath47 + d&0.5&1922&1992&2195&2203&2210&2218&2286&2294 + & 1.0&1912&1993&2347&2367&2390&2414&2580&2639 + & 1.5&1905&2003&2388&2435&2481&2527&2599&2709 + & expt.&1864&2006&@xmath48&@xmath48&@xmath48&@xmath48&@xmath48&@xmath48 + & ebert&1875&2009&2414&2438&2459&2501&2579&2629 + & pandya&1815&1909&2385&2417&2449&2481&2653&2690 + @xmath0&0.5&2042&2089&2353&2364&2375&2386&2466&2476 + & 1.0&2003&2104&2512&2544&2576&2608&2813&2847 + & 1.5&1937&2135&2607&2678&2750&2821&3149&3228 + & expt.&1969&2112&@xmath48&@xmath48&2535&2574&@xmath48&@xmath48 + & ebert&1981&2111&2508&2515&2560&2569&2670&2716 + & pandya&2009&2110&2385&2417&2449&2481&2778&2280 + @xmath1&1.0&6349&6373&6715&6726&6738&6749&6821&6855 + & lattice&6280&6321&6727&6743&6765&6783&6960&6990 + & alv&6356&6397&6673&@xmath48&@xmath48&6751&6888&6910 + & efg&6270&6332&6699&6734&6749&6762&6835&7072 + + expt.@xcite , alv@xcite , efg@xcite , pandya@xcite , lattice@xcite , ebert@xcite .__decay constants ( @xmath49 ) and lifetime of meson . _ _ [ cols="^,^,^,^,^ , < " , ]
the low - lying di - hadronic molecular system consisting of di - meson tetra quark states are treated here by assuming non - relativistic .
hamiltonian given by @xmath50 where @xmath51 , @xmath52 and @xmath53 are masses of the hadrons , @xmath15 is the reduced mass , @xmath54 is the relative momentum of the two hadrons and @xmath55 is the residual ( molecular ) interaction potential between the two hadrons given by the asymptotic expression ( @xmath56 ) of the confined one gluon exchange interaction ( cogep ) given by @xcite @xmath57 where @xmath58 is the residual strength of the strong interaction coupling and @xmath59 is the effective colour screening parameter of the confined gluons . using a trial wave function given by @xmath60 by minimizing the expectation value of h ,
the ground state molecule energy is obtained as @xmath61 here , we have added the spin - hyperfine contribution separately .
the binding energy of the di - mesons as @xmath62 and the parameters @xmath63 . and
c=1.25 @xmath3 are employed to compute the binding energy ( be ) at the charmed sector .
the computed masses and binding energies of the di - meson systems are tabulated in table [ tab:3 ] .
the properties of open charm mesons _ vis a vis _ @xmath22 , @xmath0 and @xmath1 are investigated by us using an effective static quark - antiquark interaction potential of the form @xmath64 .
we found that the potential form with @xmath65 is consistent with the experimental results of the light - heavy flavour mesons .
the relativistic treatment of light flavour and non relativistic treatment of heavy flavour seem to be justifiable in light of the successful prediction of the various properties of light - heavy flavour mesons . in the case of @xmath1-meson study , the non - relativistic treatment for both the heavy quarks yields better result .
the @xmath66-wave and @xmath54-wave masses , decay constants @xmath49,the decay widths and life time of @xmath22 , @xmath0 and @xmath1 mesons are studied within the potential scheme with @xmath67 .
the recently observed @xmath68 and @xmath69 are found to be the @xmath70 and @xmath71 states predicted in our model with @xmath65 other predicted excited states are expected to be identified and observed in future experiments .
+ the pseudoscalar decay constant@xmath49 predicted without the correction terms @xmath72 of eqn.([eqn:4 ] ) in our model with potential indeax @xmath73 is found to be in better agreement with the experimental values of @xmath74 of cleo collaboration @xciteand the predicted value of 321@xmath75 for @xmath76 is within the error bar of the experimental result of @xmath77 @xmath75 by babar collaboration@xcite .
however , the pdg average value for @xmath76 is @xmath78 @xmath75 @xcite .
the ratio of @xmath79 in our case is @xmath80 with the correction factor , while that with out correction factor is @xmath81 which is in accordance with the lattice results of @xmath82@xcite .
the lifetime predictions of @xmath83 @xmath84 for @xmath22 and @xmath85 @xmath84 for @xmath0 mesons are in good agreement with the respective experimental result of @xmath86 ps of @xmath87 and @xmath88 @xmath84 with @xmath65 .
+ the exotic states such as @xmath89(2317 , 2460 , 2632 , 2700 and @xmath90 , @xmath91 etc are identified as the low lying di - mesonic molecular states at the charm sector as shown in table [ tab:3 ] .
though there exist many attempts , the zoo of open flavour mesonic states continues to pose challenges to both experimental analysis and theoretical predictions .
+ * acknowledgement : * part of this work is done with a financial support from dst , government of india , under a major research project * sr / s2/hep-20/2006*. 99 aubert b et al .
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a. heister et al.,aleph collaboration phys.lett.*b 528*,1(2002 ) .
l. maiani , et al . ,
phuys . rev . *
d 71 * , 014028 ( 2005 ) .
d. jane and m. rosina , few - body systems * 35 * , 175 ( 2004 ) .
d. ebert , r. n. faustov and v. o. galkin , phys .
* b 634 * , 21 ( 2006 ) .
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1.0 cm 1.0 cm we present here recent results on the investigations of the mass spectrum ( s - states and p - states ) , decay constants , decay widths and life time of the d , @xmath0,and @xmath1mesons within the framework of phenomenological potential models.we also present the binding energy and the masses of the di - meson molecular systems with one or more charm meson combinations .
many of the newly found experimental open charm states are identified with the orbital excitations of the conventional open charm mesons while others like x(3872 ) , y(3930 ) , @xmath2(2632 , 2700 ) _ etc .
_ , are identified as molecular like states .
= 11.6pt
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periodontal disease is common in adult dentition . as inflammatory phenomena that are multifactorial in origin
can destroy periodontal tissue , some sequelae may occur , including elongation , tipping , and pathologic tooth migration.1 as a result of pathologic tooth migration , occlusal trauma and periodontitis are aggravated , resulting in greater losses of attachment , extrusion , and mobility of the displaced teeth.23 these problems are particularly likely to occur in the maxillary anterior region , because these teeth are not protected by occlusal forces and have no anterior - posterior contacts to inhibit tooth migration . to solve these problems , orthodontic treatments for the intrusion of anterior teeth are necessary in most cases.4 miniscrews , which serve as effective temporary anchorage devices ,
have recently acquired an important role in the facilitation of various tooth movements , because anchorage control and patient cooperation are very critical in the field of orthodontics .
many authors have described methods involving miniscrews for the intrusion of incisors , and have reported significant amounts of incisor intrusion.567 direct intrusion methods using miniscrews have the advantage of being able to move the teeth effectively , because they form a force vector in the desired direction without the loss of anchorage .
however , the orthodontic force applied by the miniscrew is an external force in the context of the entire force system . in other words ,
the direction of the force strongly influences the movement pattern of the teeth.8 to move the teeth into a desired pattern , the appropriate force direction must be selected .
therefore , the relationship between the force direction and the movement pattern must be accurately clarified .
orthodontists dealing with periodontally compromised dentitions need to understand how altered biomechanics due to reduced periodontal tissue affect their treatments.910 for example , the center of resistance ( cr ) in a periodontally compromised tooth moves to a more apical position , which requires that the moment / force ratio be adjusted.11 when periodontally compromised patients undergo orthodontic treatments , tooth movements should be as well - targeted and well - controlled as possible , and involve the application of light forces .
the aim of this study was to determine the optimal loading condition for pure intrusion of the six maxillary anterior teeth with miniscrews according to the amount of alveolar bone loss .
for this purpose , three - dimensional ( 3d ) finite element analysis was performed to investigate initial displacement and stress distribution in individual teeth according to various loading conditions with miniscrews and hooks , after setting the alveolar bone loss .
to calculate the tooth elements , the tooth morphologies were based on 3d scans of a dental model produced based on a sample survey of adults with normal occlusion in japan ( model - i21d-400 g ; nissin dental products , kyoto , japan ) .
the positions and axial inclinations of the teeth were determined based on the ideal occlusion of andrews , and the arch form was fabricated according to the broad arch form ( tru arch , ormco , glendora , ca , usa ) .
the thickness of the periodontal ligament ( pdl ) was considered to be 0.25 mm , and this thickness was constant around the root surface.1213 the average alveolar bone thicknesses on the labial and lingual sides were determined from the 3d scans of the same dental model .
the morphology of the alveolar bone was modeled 1 mm above the cemento - enamel junction ( cej ) following the curvature of the cej in the case of normal bone level ( i.e. , bone loss = 0 ) .
alveolar bone loss was assumed to be even in the bucco - lingual and antero - posterior directions . in the 2-mm and 4-mm loss models ,
the brackets were made based on a microarch ( tomy co. , tokyo , japan ) , and the bracket slots were located on the facial axes of the clinical crowns of the individual teeth based on the andrews plane .
the arch wire was made from 0.017 0.025-inch stainless steel wire , and the brackets for all teeth were ligated firmly to the arch wire .
as previously described,14 a finite element model was created for a segment of the six maxillary anterior teeth in order that it could be interpreted as an independent model , that was not affected by the posterior teeth , and the boundary condition between the arch wire and the bracket was set to " no play " .
the teeth , alveolar bone , pdl , and brackets were all generated with 3d tetrahedral elements .
as each tooth was an independent model , it was contacted with the adjacent teeth at the contact points and was connected with the arch wire through the bracket . in order to simulate free sliding of the arch wire , the friction resistance in the interface between the arch wire and the brackets was ignored.1516 the miniscrews were assumed to be located 12 mm gingivally to the arch wire at the midpoints between the adjacent roots of the teeth antero - posteriorly , and just below the arch wire bucco - lingually .
the bracket - tooth , bracket - arch wire , and bone - miniscrew interfaces were defined as fully bonded surfaces .
the x axis was set in the medial - lateral direction , the y axis was set in the anterior - posterior direction , and the z axis was set in the superior - inferior direction .
a + x value was defined as the lateral direction , y as the posterior direction , and + z as the superior direction , to analyze the displacement of the individual teeth under intrusive force ( figure 1 ) .
these properties were selected based on previous studies.1718 although the young 's modulus and poisson 's ratio for the pdl are broad in range according to the literature , those utilized in the current study for the pdl followed those of previous studies on the intrusion or en - masse retraction of the segment of the six maxillary or mandibular anterior teeth using miniscrews.141920 of course , this does not perfectly reflect the complex structure and behavior of the pdl . however , this assumption was sufficient to describe initial tooth displacement in the six - tooth anterior segment under orthodontic loading . for each segment of six anterior teeth ,
the points and directions of the intrusive force were applied by varying the locations of the hooks and miniscrews ( table 2 , figure 2 ) .
the magnitude of the intrusive force applied to the four maxillary incisors was initially suggested to be approximately 100 g.21 on the other hand , ricketts22 proposed a magnitude of 125160 g. in the present study , for the single force of the inter - central incisors , 100 g was applied to the six - tooth anterior segment . in the bilateral force conditions , 50 g of intrusive force per side was applied to the six - tooth anterior segment .
the analyses were performed with ansys software ( version 12.0 ; ansys inc . , canonsburg , pa , usa ) . using the finite element method , the initial displacement of the anterior teeth and the von mises stresses along the root surface were evaluated . in order to measure the displacement of the tooth under the intrusive force , the nodes were selected to be at the midpoints of the incisal edges and root apices of individual teeth , and the movements of the nodes were considered to be tooth displacement .
the displacements of the nodes that appeared in the three directions ( i.e. , the x , y , and z axes ) were calculated by obtaining the coordinates . in order to measure the degree of labial tilting of the individual teeth according to bone loss
, it was calculated via the angles between the longitudinal axes of each tooth before and after loading of the intrusive force , on the sagittal view .
to calculate the tooth elements , the tooth morphologies were based on 3d scans of a dental model produced based on a sample survey of adults with normal occlusion in japan ( model - i21d-400 g ; nissin dental products , kyoto , japan ) .
the positions and axial inclinations of the teeth were determined based on the ideal occlusion of andrews , and the arch form was fabricated according to the broad arch form ( tru arch , ormco , glendora , ca , usa ) .
the thickness of the periodontal ligament ( pdl ) was considered to be 0.25 mm , and this thickness was constant around the root surface.1213 the average alveolar bone thicknesses on the labial and lingual sides were determined from the 3d scans of the same dental model .
the morphology of the alveolar bone was modeled 1 mm above the cemento - enamel junction ( cej ) following the curvature of the cej in the case of normal bone level ( i.e. , bone loss = 0 ) .
alveolar bone loss was assumed to be even in the bucco - lingual and antero - posterior directions . in the 2-mm and 4-mm loss models ,
the brackets were made based on a microarch ( tomy co. , tokyo , japan ) , and the bracket slots were located on the facial axes of the clinical crowns of the individual teeth based on the andrews plane .
the arch wire was made from 0.017 0.025-inch stainless steel wire , and the brackets for all teeth were ligated firmly to the arch wire .
as previously described,14 a finite element model was created for a segment of the six maxillary anterior teeth in order that it could be interpreted as an independent model , that was not affected by the posterior teeth , and the boundary condition between the arch wire and the bracket was set to " no play " .
the teeth , alveolar bone , pdl , and brackets were all generated with 3d tetrahedral elements .
as each tooth was an independent model , it was contacted with the adjacent teeth at the contact points and was connected with the arch wire through the bracket . in order to simulate free sliding of the arch wire , the friction resistance in the interface between the arch wire and the brackets was ignored.1516 the miniscrews were assumed to be located 12 mm gingivally to the arch wire at the midpoints between the adjacent roots of the teeth antero - posteriorly , and just below the arch wire bucco - lingually .
the bracket - tooth , bracket - arch wire , and bone - miniscrew interfaces were defined as fully bonded surfaces .
the x axis was set in the medial - lateral direction , the y axis was set in the anterior - posterior direction , and the z axis was set in the superior - inferior direction .
a + x value was defined as the lateral direction , y as the posterior direction , and + z as the superior direction , to analyze the displacement of the individual teeth under intrusive force ( figure 1 ) .
these properties were selected based on previous studies.1718 although the young 's modulus and poisson 's ratio for the pdl are broad in range according to the literature , those utilized in the current study for the pdl followed those of previous studies on the intrusion or en - masse retraction of the segment of the six maxillary or mandibular anterior teeth using miniscrews.141920 of course , this does not perfectly reflect the complex structure and behavior of the pdl . however , this assumption was sufficient to describe initial tooth displacement in the six - tooth anterior segment under orthodontic loading .
for each segment of six anterior teeth , the points and directions of the intrusive force were applied by varying the locations of the hooks and miniscrews ( table 2 , figure 2 ) .
the magnitude of the intrusive force applied to the four maxillary incisors was initially suggested to be approximately 100 g.21 on the other hand , ricketts22 proposed a magnitude of 125160 g. in the present study , for the single force of the inter - central incisors , 100 g was applied to the six - tooth anterior segment . in the bilateral force conditions , 50 g of intrusive force per side was applied to the six - tooth anterior segment .
the analyses were performed with ansys software ( version 12.0 ; ansys inc . , canonsburg , pa , usa ) . using the finite element method , the initial displacement of the anterior teeth and the von mises stresses along the root surface were evaluated . in order to measure the displacement of the tooth under the intrusive force , the nodes were selected to be at the midpoints of the incisal edges and root apices of individual teeth , and the movements of the nodes were considered to be tooth displacement .
the displacements of the nodes that appeared in the three directions ( i.e. , the x , y , and z axes ) were calculated by obtaining the coordinates . in order to measure the degree of labial tilting of the individual teeth according to bone loss
, it was calculated via the angles between the longitudinal axes of each tooth before and after loading of the intrusive force , on the sagittal view .
without bone loss , intrusion occurred in all of the central incisor , lateral incisor , and canine cases and was accompanied by labial tipping in six of the conditions in which the applied force directions were set differently ( figure 3 , table 3 ) . in case a , the central incisor was labially inclined 32.9 millidegrees under the intrusive force .
the midpoint of the incisor edge of the central incisor moved medially 3.9 m , anteriorly 8.6 m , and superiorly 5.7 m ( table 4 ) .
the apex of the central incisor moved laterally 3.0 m , posteriorly 4.2 m , and superiorly 5.6 m in case a. the amounts of medial - lateral , anterior - posterior , and vertical displacement of the central incisor tip and root apex were the largest in case a. the degree of uncontrolled tipping of the central incisor decreased in the order of cases b , c , d , e , and f. in case f , the midpoint of the incisor edge of the central incisor moved laterally 0.3 m , anteriorly 1.2 m , and superiorly 1.4 m .
the amount of anterior - posterior displacement of the central incisor was negligible , and the lowest vertical displacement of the central incisor tip and root apex was observed in case f. with regard to the lateral incisor , the midpoint of the incisor edge of the lateral incisor moved medially 2.2 m , anteriorly 2.9 m , and superiorly 2.9 m in case b ( table 4 ) .
cases b , c , and d exhibited uncontrolled labial tipping with significant amounts of vertical displacement . in case d , the midpoint of the incisor edge of the canine moved medially 1.0 m , anteriorly 2.7 m , and superiorly 2.1 m .
the anterior - posterior and vertical displacements of the canine were the greatest in case d. in case a , the minimum amount of horizontal displacement of the canine was observed . with 2 mm of bone loss , in all six conditions of varying applied force directions , the degree of labial tilting and the amounts of anterior - posterior and vertical displacement were larger than when there was no bone loss ( tables 3 and 4 ) .
cases a , b , and c , all exhibited uncontrolled tipping of the central and lateral incisors ( figure 4 ) . with 4 mm of bone loss ,
the overall pattern of tooth movement was similar to that of the 0- and 2-mm bone loss conditions , but the degree of labial tilting movement was more severe ( table 3 , figure 5 ) .
the case f showed relatively lower values in the degree of labial tilting and the amounts of medial - lateral and anterior - posterior displacements of the six anterior teeth than the other cases , which was similar in pattern with 0- and 2-mm bone loss conditions . in all cases ,
more von mises stress was applied to the apex than the cervical area of the pdl ( table 5 ) . in case a , the maximum von mises stresses on the central incisor apical and cervical areas were 2.8 g / mm and 1.1 g / mm respectively . in case b , the stresses on the lateral incisor apical and cervical areas were 1.3 g / mm and 0.5 g / mm respectively .
the stress on the central incisor was greatest in case a , and that on the lateral incisor was greatest in case b. the maximum von mises stress on the canine was relatively lower than it was on other types of tooth . in case
f , the maximum von mises stresses were relatively evenly distributed across the central incisor , lateral incisor , and canine . when bone loss was increased to 2 mm , the amount of stress increased further . in case a ,
the stress that was concentrated on the central incisor was noticeable , and with regard to the lateral incisor , case b exhibited the highest stress value . in case
f , the stress was relatively evenly distributed . when bone loss was increased to 4 mm , in case
a the maximum von mises stresses on the central incisor apical and cervical areas were 3.9 g / mm and 1.2 g / mm respectively . in case b ,
the stresses on the lateral incisor apical and cervical areas were 2.0 g / mm and 0.7 g / mm respectively .
the stress distribution pattern was the same as those observed at bone loss levels of 0 and 2 mm , but the stress was markedly increased ( figure 6 ) .
without bone loss , intrusion occurred in all of the central incisor , lateral incisor , and canine cases and was accompanied by labial tipping in six of the conditions in which the applied force directions were set differently ( figure 3 , table 3 ) . in case a , the central incisor was labially inclined 32.9 millidegrees under the intrusive force .
the midpoint of the incisor edge of the central incisor moved medially 3.9 m , anteriorly 8.6 m , and superiorly 5.7 m ( table 4 ) .
the apex of the central incisor moved laterally 3.0 m , posteriorly 4.2 m , and superiorly 5.6 m in case a. the amounts of medial - lateral , anterior - posterior , and vertical displacement of the central incisor tip and root apex were the largest in case a. the degree of uncontrolled tipping of the central incisor decreased in the order of cases b , c , d , e , and f. in case f , the midpoint of the incisor edge of the central incisor moved laterally 0.3 m , anteriorly 1.2 m , and superiorly 1.4 m .
the amount of anterior - posterior displacement of the central incisor was negligible , and the lowest vertical displacement of the central incisor tip and root apex was observed in case f. with regard to the lateral incisor , the midpoint of the incisor edge of the lateral incisor moved medially 2.2 m , anteriorly 2.9 m , and superiorly 2.9 m in case b ( table 4 ) .
cases b , c , and d exhibited uncontrolled labial tipping with significant amounts of vertical displacement . in case d , the midpoint of the incisor edge of the canine moved medially 1.0 m , anteriorly 2.7 m , and superiorly 2.1 m .
the anterior - posterior and vertical displacements of the canine were the greatest in case d. in case a , the minimum amount of horizontal displacement of the canine was observed . with 2 mm of bone loss , in all six conditions of varying applied force directions , the degree of labial tilting and the amounts of anterior - posterior and vertical displacement were larger than when there was no bone loss ( tables 3 and 4 ) .
cases a , b , and c , all exhibited uncontrolled tipping of the central and lateral incisors ( figure 4 ) . with 4 mm of bone loss ,
the overall pattern of tooth movement was similar to that of the 0- and 2-mm bone loss conditions , but the degree of labial tilting movement was more severe ( table 3 , figure 5 ) .
the case f showed relatively lower values in the degree of labial tilting and the amounts of medial - lateral and anterior - posterior displacements of the six anterior teeth than the other cases , which was similar in pattern with 0- and 2-mm bone loss conditions .
in all cases , more von mises stress was applied to the apex than the cervical area of the pdl ( table 5 ) . in case a , the maximum von mises stresses on the central incisor apical and cervical areas were 2.8 g / mm and 1.1 g / mm respectively . in case b , the stresses on the lateral incisor apical and cervical areas were 1.3 g / mm and 0.5 g / mm respectively .
the stress on the central incisor was greatest in case a , and that on the lateral incisor was greatest in case b. the maximum von mises stress on the canine was relatively lower than it was on other types of tooth . in case
f , the maximum von mises stresses were relatively evenly distributed across the central incisor , lateral incisor , and canine . when bone loss was increased to 2 mm , the amount of stress increased further . in case a ,
the stress that was concentrated on the central incisor was noticeable , and with regard to the lateral incisor , case b exhibited the highest stress value . in case
f , the stress was relatively evenly distributed . when bone loss was increased to 4 mm , in case a the maximum von mises stresses on the central incisor apical and cervical areas were 3.9 g / mm and 1.2 g / mm respectively . in case b , the stresses on the lateral incisor apical and cervical areas were 2.0 g / mm and 0.7 g / mm respectively .
the stress distribution pattern was the same as those observed at bone loss levels of 0 and 2 mm , but the stress was markedly increased ( figure 6 ) .
when intrusive force was applied to the six maxillary anterior teeth with miniscrews and hooks in different positions , the central incisor , lateral incisor , and canine all underwent intrusion accompanied by labial tilting movement .
the degree of labial tilting varied depending on the locations of the miniscrews and hooks , because force control involves not only force magnitude but also the points of force application and direction ( line of action).23 the movement of a segment can be determined by the net effect of all forces on it , thus it is necessary to combine applied forces to determine a resultant force.23 in case a , the central incisor exhibited pseudo - intrusion due to a significant amount of labial tilting of the tooth ( table 3 ) .
as the horizontal force component ( a retraction force ) increased and the vertical intrusive force component decreased , the amount of anterior - posterior displacement of the central incisor gradually decreased in the order of cases a , b , c , e , d , and f ( table 4 ) . in the lateral incisor , cases
b , c , and d exhibited the greatest amounts of labial tilting . in the canine , case d exhibited a noticeably greater amount of labial tilting compared with the other conditions , because at the distal part of the canine , a retraction force was not added as only a vertical force was applied onto the arch . in case f , the hook location was mesial to the canine and a considerable amount of labial tilting occurred , but this amount was smaller than that observed in case d. therefore , within the limitations of this study , minimal labial displacement of the six anterior teeth was observed when the hook was positioned distal to the lateral incisor , and the miniscrews were inserted between the canine and the first premolar ( case f ) . in this condition , relatively pure intrusion was observed .
this pattern was likely observed because the force was applied closest to the cr among the six anterior teeth.24 in other words , these findings imply that the intrusion method involving the miniscrew on the posterior side of the canine and the hook on the distal side of the lateral incisor is effective for achieving relatively pure intrusion of the six anterior teeth .
this result is encouraging , because treatment will be much more effective if the six anterior teeth can be simultaneously intruded by a predictable method .
however , in order to intrude only a single tooth such as the central or lateral incisor , the application of this method may not be effective .
particularly when the maxillary anterior teeth are flared and extruded due to periodontal problems , intrusive movements should be attempted with bodily movements or slight linguoversion . in the view of the authors of this study ,
additional retraction horizontal force is necessary in addition to intrusion force passing by the cr , to achieve pure intrusion of the six maxillary anterior teeth .
when the same force was applied with the six anterior teeth being intruded as a segment , the degree of labial tilting of the anterior teeth increased in all cases as bone loss increased ( table 3 ) . moreover ,
the difference in tooth displacement was greater when bone loss was increased from 2 to 4 mm than when it was increased from 0 to 2 mm in the anterior tooth segment ( table 4 ) .
furthermore , the difference in labial tilting was much larger than the difference in intrusion .
a number of studies have investigated the location of the cr of maxillary anterior teeth.1825 with regard to the horizontal location of the cr of the anterior teeth , it has been reported that the cr moves posteriorly as alveolar bone loss occurs , and that the posterior movement of the cr increases as alveolar bone loss increases.26 it is likely that because the posterior movement of the cr was greater as bone loss was increased from 2 to 4 mm than when it was increased from 0 to 2 mm , the anterior - posterior displacement of teeth would be greater going from 2 to 4 mm under the same force vector .
this result was likely caused by a decrease in the alveolar bone support of the anterior part due to the reduction in alveolar bone , because the teeth and alveolar bone of the anterior part were tilted anteriorly .
more von mises stress was concentrated on the tooth apex area than on the cervical area of the pdl in all cases . as the displacement of the tooth became larger , the maximum von mises stress also exhibited a greater tendency to increase ( table 5 ) ; as in case a when the movement of the central incisor was sufficiently large , the maximum von mises stress was also concentrated on the central incisor rather than the other teeth .
the stress level was lowest , and the stress was evenly distributed when the miniscrew was installed on the distal part of the canine , and the intrusion force was applied on the distal part of the lateral incisor .
when there is bone loss , the pdl naturally diminishes , so smaller pdl surfaces should be able to withstand the stress caused by tooth movement .
therefore , it is physiologically desirable that lower levels of stress be distributed evenly along the pdl , to prevent external apical root resorption.2728 the design of this study has some limitations . the study intended to mathematically visualize the initial displacement and stress distribution of the pdl during intrusion using finite element analysis
; thus , the results may not exactly reflect clinical outcomes , which are influenced by the cumulative effects of continuous bone reactions and rebounding of the arch wire due to secondary displacement of the teeth .
in other words , the prediction of ultimate clinical outcomes based on arithmetic calculations of the initial response should be avoided . additionally , due to technical difficulties
, it did not measure the change in the location of the cr of individual teeth according to the amount of alveolar bone loss .
if the change in the location of the cr was quantitatively analyzed , the effect of bone loss on the tooth displacement pattern under intrusive force could be more clearly described .
additional limitations of this study include the constant values that were used for the physical properties of the tissues ( these values would normally vary clinically due to the histologic process ) , and the assumptions that the periodontal membrane was homogeneous , isotropic , and uniform in thickness .
moreover , due to individual variation , it is impossible to create a mathematical model that exactly simulates each case .
recently , the use of 3d computed tomography ( ct ) has increased , and this method could be used to create individual tooth models that would enable simulations of the orthodontic tooth movements of each patient . furthermore , the combination of 3d ct - assisted individual models with finite element analysis software would aid clinical treatment planning .
when the same force was applied with the six maxillary anterior teeth being intruded as a segment , the degree of labial tilting of the anterior teeth increased in all cases as bone loss increased .
it is likely possible to induce initial tooth displacement that is similar to pure intrusion when miniscrews are inserted distal to the maxillary canines and intrusion forces are applied distal to the lateral incisors . in this condition ,
the maximum von mises stress is relatively evenly distributed across the central incisor , lateral incisor , and canine regardless of the amount of alveolar bone loss .
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objectivethe aim of this study was to determine the optimal loading conditions for pure intrusion of the six maxillary anterior teeth with miniscrews according to alveolar bone loss.methodsa three - dimensional finite element model was created for a segment of the six anterior teeth , and the positions of the miniscrews and hooks were varied after setting the alveolar bone loss to 0 , 2 , or 4 mm . under 100 g of intrusive force , initial displacement of the individual teeth in three directions and the degree of labial tilting
were measured.resultsthe degree of labial tilting increased with reduced alveolar bone height under the same load . when a miniscrew was inserted between the two central incisors , the amounts of medial - lateral and anterior - posterior displacement of the central incisor
were significantly greater than in the other conditions . when the miniscrews were inserted distally to the canines and an intrusion force was applied distal to the lateral incisors , the degree of labial tilting and the amounts of displacement of the six anterior teeth were the lowest , and the maximum von mises stress was distributed evenly across all the teeth , regardless of the bone loss.conclusionsinitial tooth displacement similar to pure intrusion of the six maxillary anterior teeth was induced when miniscrews were inserted distal to the maxillary canines and an intrusion force was applied distal to the lateral incisors . in this condition ,
the maximum von mises stresses were relatively evenly distributed across all the teeth , regardless of the bone loss .
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SECTION 1. SHORT TITLE.
This Act may be cited as the ``Improving the Nation's Visitors'
International Travel Experience Act of 2014'' or the ``INVITE Act of
2014''.
SEC. 2. PURPOSES.
The purposes of this Act are--
(1) to create a welcoming experience at United States ports
of entry;
(2) to encourage international travelers to visit the
United States; and
(3) to support jobs and economic prosperity for the Nation.
SEC. 3. DEFINITIONS.
In this Act:
(1) Appropriate congressional committees.--The term
``appropriate congressional committees'' means--
(A) the Committee on Commerce, Science, and
Transportation of the Senate;
(B) the Committee on Foreign Relations of the
Senate;
(C) the Committee on Homeland Security and
Governmental Affairs of the Senate;
(D) the Committee on Appropriations of the Senate;
(E) the Committee on Energy and Commerce of the
House of Representatives;
(F) the Committee on Foreign Affairs of the House
of Representatives;
(G) the Committee on Homeland Security of the House
of Representatives; and
(H) the Committee on Appropriations of the House of
Representatives.
(2) Commissioner.--The term ``Commissioner'' means the
Commissioner of U.S. Customs and Border Protection.
(3) Global entry program.--The term ``Global Entry
Program'' means the program described in section 235.12 of
title 8, Code of Federal Regulations.
(4) Model ports of entry program.--The term ``Model Ports
of Entry Program'' means the program established by the
Secretary of Homeland Security under section 725 of the
Implementing Recommendations of the 9/11 Commission Act of 2007
(8 U.S.C. 1752a).
SEC. 4. GLOBAL ENTRY PROGRAM EXPANSION.
(a) Coordination.--The Secretary of State and the Secretary of
Homeland Security shall explore the feasibility of--
(1)(A) coordinating the enrollment and interview processes
for individuals who--
(i) are nationals of countries with which the
United States has a reciprocal trusted traveler program
agreement; and
(ii) simultaneously apply for a United States visa
and enroll in the Global Entry Program; and
(B) collecting a single application fee from such
applicants; and
(2) coordinating the passport application and Global Entry
Program enrollment processes for eligible United States
citizens.
(b) Report.--Not later than 6 months after the date of the
enactment of this Act, the Secretary of State and the Secretary of
Homeland Security shall jointly submit, to the appropriate
congressional committees, a report that describes--
(1) the status of bilateral negotiations to expand
reciprocal trusted traveler programs such as the Global Entry
Program;
(2) barriers to the expansion of the Global Entry Program;
(3) the number of United States citizens and nationals of
other countries who are enrolled in the Global Entry Program,
the NEXUS Program, or the SENTRI Program;
(4) the feasibility of coordinating Global Entry Program
enrollment with the visa and passport application processes;
(5) if the Secretaries determine that such coordination is
infeasible, the specific reasons for such determination; and
(6) the resources needed and the next steps that the
Department of State and the Department of Homeland Security
would need to take to implement the coordinated Global Entry
and visa and passport application process described in
subsection (a).
SEC. 5. STRENGTHENING THE MODEL PORTS OF ENTRY PROGRAM.
(a) In General.--Section 725 of the Implementing Recommendations of
the 9/11 Commission Act of 2007 (8 U.S.C. 1752a) is amended--
(1) in subsection (a)--
(A) in paragraph (1), by striking ``and'' at the
end;
(B) in paragraph (2), by striking the period at the
end and inserting ``; and''; and
(C) by adding at the end the following:
``(3) modify the program, to the extent determined to be
necessary by the Commissioner of U.S. Customs and Border
Protection, including by expanding the program beyond the 20
airports at which the program was initially implemented.'';
(2) by redesignating subsection (c) as subsection (e); and
(3) by inserting after subsection (b) the following:
``(c) Program Metrics.--
``(1) Development.--To ensure the effectiveness of the
Model Ports of Entry Program (referred to in this subsection as
the `program'), the Commissioner of U.S. Customs and Border
Protection shall develop metrics to measure the performance of
the program, including metrics to measure customer satisfaction
among passengers using the ports of entry at the Model Ports of
Entry airports.
``(2) Report.--Not later than 1 year after the date of the
enactment of the INVITE Act of 2014, the Commissioner of U.S.
Customs and Border Protection shall submit a report to the
appropriate congressional committees that includes--
``(A) a list of the program airports;
``(B) an explanation of how the program has been
implemented at each program airport;
``(C) an analysis of the program's performance
against the metrics established under paragraph (1) to
measure customer satisfaction;
``(D) recommendations for improving public-private
collaboration between U.S. Customs and Border
Protection, airports, and other industry stakeholders
to improve the user experience at United States ports
of entry; and
``(E) recommendations on whether the program should
be expanded to more airports.
``(d) Model Ports of Entry Grant Program.--
``(1) Establishment.--Not later than 1 year after the date
of the enactment of the INVITE Act of 2014, the Secretary of
Homeland Security shall establish the Model Ports of Entry
Grant Program to award, on a competitive basis, up to 10 grants
of an amount deemed appropriate by the Commissioner to airports
designated by the Commissioner of U.S. Customs and Border
Protection to establish public-private sector collaboration to
improve the international arrival process at United States
airports.
``(2) Source of funding.--The funding for the grant program
established under this subsection shall come from the operating
budget of U.S. Customs and Border Protection.
``(3) Matching grant.--The Secretary may not make a grant
to an airport under this subsection unless the airport agrees
to match the grant funding with an equal amount of non-Federal
funds.
``(4) Use of funds.--Grants received under the subsection--
``(A) shall be used to improve the grantee's
international passenger processing facility in
accordance with the objectives of the Model Ports of
Entry Program through activities such as--
``(i) the installation of informational
television monitors;
``(ii) improvements to queue management;
and
``(iii) the use of technology that will
improve the entry process;
``(B) shall be used to provide a more efficient and
welcoming international arrival process to facilitate
and promote business and tourist travel to the United
States; and
``(C) may not be used to replace funding for
airport improvement projects paid for with--
``(i) passenger facility charges authorized
under section 40117 of title 49, United States
Code; or
``(ii) grants received through the Airport
Improvement Program under subchapter I of
chapter 471 of such title 49.
``(5) Working groups.--
``(A) Establishment.--Grantees shall establish
public-private partnership working groups with U.S.
Customs and Border Protection.
``(B) Other members.--Working groups established
under this paragraph may include representatives of the
travel and tourism industry, including--
``(i) the air passenger sector;
``(ii) the hotel sector;
``(iii) the theme park sector;
``(iv) the rental car sector
``(v) the tour operator sector;
``(vi) the travel distribution sector;
``(vii) the retail sector;
``(viii) the State tourism authority;
``(ix) the local convention and visitors
authority;
``(x) local cultural interest groups; and
``(xi) the event management sector.
``(C) Collaboration.--The working groups
established under this paragraph shall--
``(i) support ongoing collaborative efforts
to share best practices for improving the
international arrivals process; and
``(ii) provide recommendations for overall
facility design enhancements and the
integration of public and cultural art into
port of entry facilities at United States
airports.
``(D) Federal advisory committee act.--The
provisions of the Federal Advisory Committee Act (5
U.S.C. App.) shall not apply to working groups
established under this paragraph.
``(6) Administration and selection criteria.--The
Commissioner of U.S. Customs and Border Protection shall--
``(A) administer the Model Ports of Entry Grant
Program; and
``(B) establish the criteria for selecting
grantees.
``(7) Metrics.--The Commissioner of U.S. Customs and Border
Protection shall establish metrics to determine the
effectiveness of the Model Ports of Entry Grant Program.''.
(b) Report.--Not later than 2 years after the date of the enactment
of this Act, the Commissioner shall submit a report to the appropriate
congressional committees that includes--
(1) a description of the status of the Model Ports of Entry
Grant Program;
(2) a description of the metrics U.S. Customs and Border
Protection will use to measure the effectiveness of the Model
Ports of Entry Grant Program;
(3) an analysis comparing the results of the Model Ports of
Entry Grant Program with the metrics established pursuant to
section 725(d)(6) of the Implementing Recommendations of the 9/
11 Commission Act of 2007, as added by subsection (a)(3);
(4) recommendations on whether the Model Ports of Entry
Grant Program should be made available on a competitive basis
to additional airports; and
(5) a description of the improvements the Commissioner
intends to make to the Model Ports of Entry Grant Program.
SEC. 6. U.S. CUSTOMS AND BORDER PROTECTION WAIT TIME METRICS.
(a) Annual Report.--Not later than 1 year after the date of the
enactment of this Act, and annually thereafter, the Commissioner shall
submit a report to the appropriate congressional committees that--
(1) includes data on average passenger wait times and peak
wait times for each month at each port of entry;
(2) provides an analysis of the performance of U.S. Customs
and Border Protection against the metrics developed pursuant to
section 571(a) of the Department of Homeland Security
Appropriations Act, 2014 (division F of Public Law 113-76); and
(3) provides an update on the development and
implementation of operational work plans that support the goal
of reducing passenger processing times at air, land, and sea
ports of entry in accordance with section 571(b) of such Act.
(b) Public Dissemination of Wait Times.--The Commissioner shall--
(1) prominently post the latest information on wait times
for processing arriving international passengers at United
States airports and land ports of entry on the U.S. Customs and
Border Protection website so that such information is easily
accessible to website visitors; and
(2) continuously update the information described in
paragraph (1) during the hours in which the air and land ports
are open and receiving customers.
SEC. 7. REPORT ON EFFORTS TO LEVERAGE TECHNOLOGY IN THE INTERNATIONAL
ARRIVALS PROCESS.
Not later than 1 year after date of the enactment of this Act, the
Commissioner shall submit a report to Congress that--
(1) describes efforts to develop new technologies and
procedures to improve the passenger screening process at United
States ports of entry;
(2) lists the Department of Homeland Security components
for which each technology is being developed; and
(3) identifies methods for more effectively processing
inbound international travelers to the United States while
strengthening security.
SEC. 8. INCREASING THE TRANSPARENCY OF DEPARTMENT OF HOMELAND SECURITY
CUSTOMER SERVICE ENHANCEMENTS.
(a) In General.--The Secretary of Homeland Security shall collect
and analyze traveler feedback--
(1) to develop customer service best practices across all
relevant component agencies;
(2) to ensure a welcoming environment; and
(3) to improve the image of the United States around the
world.
(b) Use of Traveler Feedback.--The Secretary of Homeland Security
shall--
(1) coordinate the collection of all traveler feedback
across all relevant component agencies to improve the
transparency of customer service enhancements;
(2) publicly report the feedback described in paragraph (1)
on a quarterly basis; and
(3) analyze and utilize such feedback to develop customer
service best practices throughout the Department of Homeland
Security, which shall include cultural sensitivity and
diversity training.
(c) Monthly Report.--The Secretary of Homeland Security shall
report all U.S. Customs and Border Protection traveler feedback to the
Department of Transportation for publication in its monthly Air Travel
Consumer Report.
(d) INFO Center Staffing.--The Commissioner shall ensure that the
U.S. Customs and Border Protection INFO Center is adequately staffed in
order to limit caller wait times to shorter than 10 minutes.
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Improving the Nation's Visitors' International Travel Experience Act of 2014 or INVITE Act of 2014 - Directs the Secretary of State and the Secretary of Homeland Security (DHS) to explore the feasibility of: (1) coordinating the enrollment and interview processes for individuals who are nationals of countries with which the United States has a reciprocal trusted traveler program agreement, applying simultaneously for a U.S. visa and global entry program enrollment, and collecting a single application fee from such applicants; and (2) coordinating the passport application and global entry program enrollment processes for eligible U.S. citizens. Amends the Implementing Recommendations of the 9/11 Commission Act of 2007 to: (1) modify the model ports of entry program, including by increasing the number of program airports; and (2) direct U.S. Customs and Border Protection (CBP) to develop metrics to measure the program's performance. Directs the DHS Secretary to establish the model ports of entry grant program to award up to 10 grants to CBP-designated airports to improve the international arrival process at U.S. airports. Directs CBP to report to Congress each year: (1) regarding average passenger wait times and peak wait times for each month at each port of entry, and (2) describing efforts to develop new technologies and procedures to improve the passenger screening process at U.S. ports of entry. Directs the Secretary to collect and analyze traveler feedback to develop customer service best practices, ensure a welcoming environment, and improve the U.S. image.
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It was not Jeopardy‘s finest moment.
During Wednesday night’s game, the categories were challenging and the answers were killer. By the time the dust settled, two of the three contestants had negative scores – a very rare occurrence for the long-running game show.
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So for Final Jeopardy, only one contestant was able to compete: Kristin Sausville, a 34-year-old stay-at-home mom and school volunteer from Delaware.
“This was not one of our greatest days,” host Alex Trebek said dryly. “Kristin, I think you’re going to win.”
Predictably, Twitter went crazy.
“The vibe in the studio was shock,” Sausville tells PEOPLE. “I hadn’t realized that both of the other contestants were in the negative. My husband Justin was in the audience and later told me that there had been a lot of questions as to whether it had happened before.”
As it turned out, it had happened before – including once to a player who ended up competing in the Tournament of Champions against Sausville’s husband.
Yes, the Sausvilles are a husband and wife who have both won big on Jeopardy. We don’t recommend playing Trivial Pursuit at their dinner parties.
When Sausville found herself alone on stage, the butterflies began. “It was more nerve-racking to be the only person on stage,” she says. “On the one hand, it was nice not to have to worry about what anyone else was wagering, but at the same time, it meant that all of the contestant coordinators, compliance people and stage crew were standing around me.”
She didn’t respond to the final answer correctly, but it hardly mattered. She won $6,800 in the game and a two-day total of $31,601. ||||| Answer: This game show had only one contestant make it to the final round because two other competitors ended in the red.
Question: What is the most bizarre episode of Jeopardy! ever?
On Thursday night’s episode of Jeopardy!, Kristin Sausville, a mom of two from Delaware, made it to the final Jeopardy! round after her competition was in the negative figures by the end of Double Jeopardy.
Sausville was forced to play alone and host Alex Trebek had some fun with her. He said, “Kristin, we’re going to start with you. You were in third place and the lead.”
Even though she is a returning Jeopardy! champion, Sausville lost $1,600 during the final question, but upped her two day total to more than $31,000. She was a good sport about the whole situation and tweeted: "Always sad when someone can't play Final. Even when I benefit. Seriously. #Jeopardy."
Always sad when someone can't play Final. Even when I benefit. Seriously. #Jeopardy — Kristin Sausville (@ksausville) March 13, 2015
Watch A Man Solve the Wheel of Fortune Puzzle with One Letter ||||| Tweet with a location
You can add location information to your Tweets, such as your city or precise location, from the web and via third-party applications. You always have the option to delete your Tweet location history. Learn more ||||| Tweet with a location
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– Alex Trebek handled one of the weirder Jeopardy! episodes ever with typical Alex Trebek aplomb. During the game that aired last night, the "categories were challenging and the answers were killer," People notes. So challenging that two of the three contestants ended up with negative scores by the end of Double Jeopardy, disqualifying them from the Final Jeopardy round. That left Delaware's Kristin Sausville to take on herself in the last part of the competition, allowing Trebek to charm the viewing audience with such witticisms as "Kristin, I think you're going to win" and "Kristin, we're going to start with you. You were in third place, and in the lead." Sausville ended up not answering the final question correctly, but she did walk away with a two-day total of more than $31,000, Inside Edition notes. Oddly, the only other time this had happened on the show was to a player who once ended up playing against Sausville's husband, per People. Sausville took to Twitter to defend her utterly crushed competitors, posting: "Always sad when someone can't play Final. Even when I benefit. Seriously." And to second that motion, this: "To anyone snarking Stephanie and Brad: you had better ace the #JeopardyOnlineTest soon. Put up or shut up. It wasn't a good game for anyone." (Maybe ripe for a Will Ferrell parody, if he's not too busy playing baseball.)
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gastrointestinal stromal tumor ( gist ) is the most common mesenchymal tumor of the gastrointestinal tract and it is most frequently found in the stomach
. fifty to sixty percent of gists are found as a localized disease at presentation , and 95% can be completely resected .
surgical resection with a 1~2 cm negative resection margin is the standard treatment for a non - metastatic gist .
the most important oncologic principle while resectioning is to avoid rupturing the tumor during manipulation in order to circumvent peritoneal dissemination of the tumor which can result in poor prognosis of the patient , because the characteristic of the mass is soft and fragile .
the tumor commonly metastasizes to the liver or the peritoneum but it rarely metastasizes to the lymph nodes .
( 1 - 4 ) while minimally invasive surgery has recently been gaining popularity in the resection of gists , it lacks evidence - based recommendation , especially in the resection of a gist larger than 5 cm .
herein , we report a case of a large gist of the stomach which was successfully treated by the laparoscopic approach in order to investigate the technical feasibility and the oncologic safety of laparoscopic resection for large gists .
an esophagogastroduodenoscopy ( egd ) and abdominal computed tomography ( ct ) scan were performed .
on egd finding , a submucosal tumor was found at the posterior wall of the gastric antrum ( fig .
1 ) , and it was revealed by ct scan to be a 10 8 cm sized heterogeneously enhanced , well circumscribed solid mass arising from the posterior wall of the gastric antrum ( fig .
the operator was positioned on the right side , and the first assistant was positioned on the left side of the patient .
a 5 mm trocar and a 12 mm trocar on the right upper abdomen were used as working channels for the operator .
another 5 mm trocar and a 12 mm trocar on left upper abdomen were used for the first assistant .
3 ) . the right gastroepiploic vessels were identified and doubly ligated with clips and the duodenum was resected with a laparoscopic linear stapler .
the right gastric vessels and descending branches of the left gastric artery were identified and doubly ligated .
the stomach was transected at 4 cm proximal from the upper border of the mass with a laparoscopic linear stapler .
the specimen was placed into a plastic bag and retrieved through the umbilical port site which was extended to a 4 cm length ( fig .
as the consistency of the mass was soft , even a 10 cm sized mass could be extracted through a 4 cm length incision without any breakage ( fig .
oral feeding was started from the second postoperative day and the patient was discharged on the 7th postoperative day without any complication .
the pathologic result was cd 117 and cd 34 positive gastrointestinal stromal tumor with 1 mitosis per 50 high power field ( intermediate risk ) .
gastric wedge resection with a proper safety margin is the preferred type of surgery in treating gastric gist .
however , the type of surgery can differ according to the size and location of the tumor . in some cases
in which the tumor is located at the prepyloric area or around the esophagogastric junction , more extended surgery such as a partial gastrectomy or even a total gastrectomy can be necessary.(4 - 6 ) as the laparoscopic approach is gaining popularity in the treatment of gastric gist , many debates on its oncologic safety and relevance have arisen .
the reported early postoperative outcomes of laparoscpic approaches have been comparable to or even better than those of the conventional open approach.(7 ) several reports have been presented about the comparable longterm oncologic outcomes of the laparoscopic approach for gist .
however , most of these reports focus on the oncologic outcomes of small or medium sized ( less than 5 cm ) gists.(8 ) according to the national cancer care network guideline which was revised in 2010 , gastric gists 5 cm or smaller may be removed through laparoscopic wedge resection and the tumor should be removed in a protective plastic bag . however , in the case of a gist of more than 5 cm in size , the laparoscopic or hand - assisted approach was recommended because of the benefit of tactile feedback.(9 ) the reason for this recommendation is that if the size of the tumor is larger , the risk of rupture of the pseudocapsule by laparoscopic manipulation would be greater.(2 ) recently , an increasing number of reports have been presented for safe laparoscopic resection for larger gists due to the advancement of the laparoscpic technique
. however , many reports still recommend open conventional resection for tumors which are more than 7~10 cm in size.(2,5 ) in our case , the authors successfully resected a large gastric gist of 10 cm in size without any breakage of the tumor using a meticulous laparoscopic surgical technique . to avoid tumor rupture ,
an attached fibrosis band was left on the tumor when resecting around the tumor , and if traction was needed , the fibrous tissue or normal gastric wall around the mass was used . as a result , there was no direct manipulation of the tumor during the operation .
moreover , the size of the minilaparotomy incision could be minimized to 4 cm in extracting the 10 cm sized mass .
the laparoscopic approach is feasible for a large gist of the stomach when proper laparoscopic techniques are used by an experienced surgeon .
however , further study will be needed on the limitation of the size of the tumor in laparoscopic resection of gist .
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a debate is currently ongoing about whether a large gastrointestinal stromal tumor ( gist ) should be treated by the laparoscopic approach because of the increased risk of tumor rupture during manipulation of the tumor with laparoscopic instruments and the resultant peritoneal tumor dissemination .
herein , we report a case of a large gist of the stomach which was successfully treated by the laparoscopic approach .
a 57 year old female patient visited our institution complaining of postprandial epigastric discomfort .
an esophagogastroduodenoscopy and an abdominal computed tomography scan revealed a 108 cm sized submucosal tumor at the greater curvature side of the gastric antrum .
the patient underwent laparoscopic distal gastrectomy with intracorporeal billroth - ii reconstruction without any breakage of the tumor .
her postoperative course was uneventful and she was discharged on the 7th postoperative day .
even a large gist of the stomach can safely be treated by the laparoscopic approach when it is performed with proper techniques by an experienced surgeon .
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trained research assistants obtained consent and enrolled participants as part of an ongoing prospective study measuring quality of care for hospitalized general medicine patients at the university of chicago medicine and mercy hospital and medical center ( meltzer et al . ,
the university of chicago medicine and mercy hospital and medical center institutional review boards approved the protocol .
research assistants administered the bvsq , which consisted of the questions , how confident are you filling out medical forms by yourself ? , how often do you have someone help you read hospital materials ? , and how often do you have problems learning about your medical condition because of difficulty understanding written information ? , scored on a likert scale from 0 to 4 .
participants had low health literacy if they had a score of 2 or less on at least one question ( chew et al . , 2004 ; chew et al . , 2008 ) .
the realm - revised ( realm - r ) was administered to participants with at least 20/50 acuity in at least one eye ( snellen eye chart ) .
the realm - r ( bass et al . , 2003 ) is a list of eight medical terms and was used as the comparator to the bvsq due to its brevity and feasibility for implementation .
descriptive statistics were calculated to summarize data using means , standard deviations , and proportions .
mcnemar 's test was utilized for matched pair testing to compare the health literacy tools . a two - tailed p value of less than .05 defined statistical significance .
areas under the receiver operating characteristic curve ( auroc ) allowed comparison between the bvsq items , in individual and composite form , and the realm - r tool .
the auroc , sensitivity , and specificity were therefore calculated for each individual question and as a composite to review tradeoffs with respect to improving sensitivity versus specificity ( chew et al .
, 2008 ; morris , maclean , chew , & littenberg , 2006 ; wallace et al . , 2006 ) .
research assistants administered the bvsq , which consisted of the questions , how confident are you filling out medical forms by yourself ? , how often do you have someone help you read hospital materials ? , and how often do you have problems learning about your medical condition because of difficulty understanding written information ? ,
participants had low health literacy if they had a score of 2 or less on at least one question ( chew et al . , 2004 ; chew et al . , 2008 ) .
the realm - revised ( realm - r ) was administered to participants with at least 20/50 acuity in at least one eye ( snellen eye chart ) .
the realm - r ( bass et al . , 2003 ) is a list of eight medical terms and was used as the comparator to the bvsq due to its brevity and feasibility for implementation .
descriptive statistics were calculated to summarize data using means , standard deviations , and proportions .
mcnemar 's test was utilized for matched pair testing to compare the health literacy tools . a two - tailed p value of less than .05 defined statistical significance .
areas under the receiver operating characteristic curve ( auroc ) allowed comparison between the bvsq items , in individual and composite form , and the realm - r tool .
the auroc , sensitivity , and specificity were therefore calculated for each individual question and as a composite to review tradeoffs with respect to improving sensitivity versus specificity ( chew et al .
, 2008 ; morris , maclean , chew , & littenberg , 2006 ; wallace et al . ,
from june 20 , 2011 , through august 20 , 2012 , 2,776 patients were screened ; 1,061 were discharged before approach , 19 did not complete the bvsq , 63 did not provide consent for participating in the vision screen and/or realm - r , 35 were repeat participants , 4 required a proxy , and 701 did not complete vision testing .
more than three fourths of participants ( 680/893 ) had sufficient vision , and 12 participants did not complete the realm - r for other reasons , including refusing to complete the realm - r or being discharged or otherwise unavailable ( e.g. , taken away for a test ) ; 668 participants completed both the bvsq and the realm - r .
of the 893 participants , 79% were african american , 57% were female , and 29% were age 65 years or older . of those reporting , 20% ( 173/874 ) had less than a high school education , 33% ( 221/678 ) did not have insurance or had medicaid , and 51% ( 163/319 ) had an annual household income less than $ 25,000 .
when comparing participants with poor vision ( completed bvsq only , n = 213 ) to those with sufficient vision ( completed both bvsq and realm - r , n = 668 ) , significant differences emerged between the groups with respect to race ( 91% vs. 81% non - white race , p = .001 ) , income ( 68% vs. 46% low income , p = .003 ) , educational level ( 30% vs. 16% without high school diploma , p < .001 ) , and age ( 40% vs. 26% age 65 years or older , p <
.001 ) , but not with gender ( 59% vs. 56% female , p = .44 ) or insurance type ( 26% vs. 34% without insurance or on medicaid , p = .11 ; see table 1 ) .
bsvq = brief verbal screening questions ; realm - r = rapid estimate of adult learning in medicine revised .
data were missing for 1 participant in the sufficient vision group ( completed both bvsq and realm - r ) ; 375 of 667 participants in the sufficient vision group were female ( 56% ) , 292 of 667 participants were male ( 44% ) .
data were missing for one participant in the insufficient vision group ( completed bvsq only ) ; 125 of 212 participants in the insufficient vision group ( completed bvsq only ) were female ( 59% ) , 87 of 212 participants were male ( 41% ) .
data were missing for nine participants in the sufficient vision group ( completed both bvsq and realm - r ) .
race was dichotomized into white and non - white ; 124 of 659 participants in the sufficient vision group ( 19% ) were white , and all other responses were defined as non - white .
african americans made up the majority of the non - white category with 506 of 659 participants ( 77% ) , 6 of 659 participants ( 0.9% ) were american indian / alaskan native , 2 of 659 participants ( 0.3% ) were asian / pacific islander , and 21 of 659 participants ( 3% ) chose the other category .
data were missing for one participant in the insufficient vision group ( completed bvsq only ) .
race was dichotomized into white and non - white ; 20 of 212 participants in the insufficient vision group ( 9% ) were white , and all other responses were defined as non - white .
african americans made up the majority of the non - white category with 186 of 212 participants ( 88% ) , 3 of 212 participants ( 1% ) were american indian / alaskan native , 0 of 212 participants ( 0% ) were asian / pacific islander , and 3 of 212 participants ( 1% ) chose the other category .
data were missing for 16 participants in the sufficient vision group ( completed both bvsq and realm - r ) ; education categories for this group include junior high school or less ( 17/652 , 3% ) , some high school ( 90/652 , 14% ) , high school graduate ( 188/652 , 29% ) , some college / junior college ( 219/652 , 34% ) , college graduate ( 87/652 , 13% ) , and postgraduate ( 51/652 , 8% ) .
data were missing for four participants in the insufficient vision group ( completed bvsq only ) ; education categories for this group include junior high school or less ( 16/209 , 8% ) , some high school ( 46/209 , 22% ) , high school graduate ( 64/209 , 31% ) , some college / junior college ( 54/209 , 26% ) , college graduate ( 16/209 , 8% ) , and postgraduate ( 13/209 , 6% ) .
data were missing for 102 participants in the sufficient vision group ( completed both bvsq and realm - r ) ; insurance categories for this group include medicare ( 230/566 , 41% ) , medicaid ( 169/566 , 30% ) , private ( 145/566 , 26% ) , no payer ( 21/566 , 4% ) , and grants ( 1/566 , 0.2% ) .
data were missing for 112 participants in the insufficient vision group ( completed bvsq only ) ; insurance categories for this group include medicare ( 63/101 , 62% ) , medicaid ( 20/101 , 20% ) , no payer ( 6/101 , 6% ) , and private ( 12/101 , 12% ) .
data were missing for 411 participants in the sufficient vision group ( completed both bvsq and realm - r ) ; income categories for this group include $ 2,500 or less ( 26/257 , 10% ) , $ 2,501 to $ 5,000 ( 10/257 , 4% ) , $ 5,001 to $ 10,000 ( 26/257 , 10% ) , $ 10,001 to $ 15,000 ( 31/257 , 12% ) , $ 15,001 to $ 25,000 ( 26/257 , 10% ) , $ 25,001 to $ 35,000 ( 33/257 , 13% ) , $ 35,001 to $ 50,000 ( 29/257 , 11% ) , $ 50,001 to $ 100,000 ( 52/257 , 19% ) , $ 100,001 to $ 200,000 ( 18/257 , 4% ) , and over $ 200,000 ( 6/257 , 2% ) .
data were missing for 156 participants in the insufficient vision group ( completed bvsq only ) ; income categories for this group include $ 2,500 or less ( 6/57 , 11% ) , $ 2,501 to $ 5,000 ( 4/57 , 7% ) , $ 5,001 to $ 10,000 ( 7/57 , 12% ) , $ 10,001 to $ 15,000 ( 8/57 , 14% ) , $ 15,001 to $ 25,000 ( 14/57 , 25% ) , $ 25,001 to $ 35,000 ( 7/57 , 12% ) , $ 35,001 to $ 50,000 ( 4/57 , 7% ) , $ 50,001 to $ 100,000 ( 3/57 , 5% ) , $ 100,001 to $ 200,000 ( 3/57 , 5% ) , and over $ 200,000 ( 1/57 , 2% ) . among participants completing the bvsq , 43% ( 384/893 )
of participants completing the realm - r , 47% ( 311/668 ) had low health literacy . among participants who completed both tools ,
the prevalence of low health literacy was greater with the realm - r ( 311/668 , 47% ) than with the bvsq ( 251/668 , 38% ; p = .0001 ) .
the sensitivity of each bvsq item ( 24%34% ) was less than the sensitivity of the combination of all three items ( 51% ) .
the auroc for the combination of the three items was 0.65 ( see table 2 ) .
performance of health literacy screening questions for detecting inadequate health literacy ( n = 668 ) note .
questions adapted from the brief questions to identify patients with inadequate health literacy , by chew , bradley , and boyko ( 2004 ) . confident with forms = how confident are you filling out medical forms by yourself ? help read = how often do you have someone help you read hospital materials ? problems learning = how often do you have problems learning about your medical condition because of difficulty understanding written information ? nearly one fourth of participants had insufficient vision ( 213/893 ) .
approximately one third of the cases of inadequate vision were due to each of the following : participants not having corrective lenses ( 35% ) , participants having inadequate corrective lenses ( 33% ) , or participants not having their lenses with them in the hospital ( 32% ) .
among participants with low health literacy on the bvsq ( n = 213 ) , those with insufficient vision were at greater risk of low health literacy ( 126/213 , 59% ) than those with sufficient vision ( 258/680 , 38% ; p < .001 ) .
of the 893 participants , 79% were african american , 57% were female , and 29% were age 65 years or older . of those reporting , 20% ( 173/874 ) had less than a high school education , 33% ( 221/678 ) did not have insurance or had medicaid , and 51% ( 163/319 ) had an annual household income less than $ 25,000 .
when comparing participants with poor vision ( completed bvsq only , n = 213 ) to those with sufficient vision ( completed both bvsq and realm - r , n = 668 ) , significant differences emerged between the groups with respect to race ( 91% vs. 81% non - white race , p = .001 ) , income ( 68% vs. 46% low income , p = .003 ) , educational level ( 30% vs. 16% without high school diploma , p < .001 ) , and age ( 40% vs. 26% age 65 years or older , p < .001 ) , but not with gender ( 59% vs. 56% female , p = .44 ) or insurance type
( 26% vs. 34% without insurance or on medicaid , p = .11 ; see table 1 ) . characteristics of study population note .
bsvq = brief verbal screening questions ; realm - r = rapid estimate of adult learning in medicine revised .
data were missing for 1 participant in the sufficient vision group ( completed both bvsq and realm - r ) ; 375 of 667 participants in the sufficient vision group were female ( 56% ) , 292 of 667 participants were male ( 44% ) .
data were missing for one participant in the insufficient vision group ( completed bvsq only ) ; 125 of 212 participants in the insufficient vision group ( completed bvsq only ) were female ( 59% ) , 87 of 212 participants were male ( 41% ) .
data were missing for nine participants in the sufficient vision group ( completed both bvsq and realm - r ) .
race was dichotomized into white and non - white ; 124 of 659 participants in the sufficient vision group ( 19% ) were white , and all other responses were defined as non - white .
african americans made up the majority of the non - white category with 506 of 659 participants ( 77% ) , 6 of 659 participants ( 0.9% ) were american indian / alaskan native , 2 of 659 participants ( 0.3% ) were asian / pacific islander , and 21 of 659 participants ( 3% ) chose the other category .
data were missing for one participant in the insufficient vision group ( completed bvsq only ) .
race was dichotomized into white and non - white ; 20 of 212 participants in the insufficient vision group ( 9% ) were white , and all other responses were defined as non - white .
african americans made up the majority of the non - white category with 186 of 212 participants ( 88% ) , 3 of 212 participants ( 1% ) were american indian / alaskan native , 0 of 212 participants ( 0% ) were asian / pacific islander , and 3 of 212 participants ( 1% ) chose the other category .
data were missing for 16 participants in the sufficient vision group ( completed both bvsq and realm - r ) ; education categories for this group include junior high school or less ( 17/652 , 3% ) , some high school ( 90/652 , 14% ) , high school graduate ( 188/652 , 29% ) , some college / junior college ( 219/652 , 34% ) , college graduate ( 87/652 , 13% ) , and postgraduate ( 51/652 , 8% ) .
data were missing for four participants in the insufficient vision group ( completed bvsq only ) ; education categories for this group include junior high school or less ( 16/209 , 8% ) , some high school ( 46/209 , 22% ) , high school graduate ( 64/209 , 31% ) , some college / junior college ( 54/209 , 26% ) , college graduate ( 16/209 , 8% ) , and postgraduate ( 13/209 , 6% ) .
data were missing for 102 participants in the sufficient vision group ( completed both bvsq and realm - r ) ; insurance categories for this group include medicare ( 230/566 , 41% ) , medicaid ( 169/566 , 30% ) , private ( 145/566 , 26% ) , no payer ( 21/566 , 4% ) , and grants ( 1/566 , 0.2% ) .
data were missing for 112 participants in the insufficient vision group ( completed bvsq only ) ; insurance categories for this group include medicare ( 63/101 , 62% ) , medicaid ( 20/101 , 20% ) , no payer ( 6/101 , 6% ) , and private ( 12/101 , 12% ) .
data were missing for 411 participants in the sufficient vision group ( completed both bvsq and realm - r ) ; income categories for this group include $ 2,500 or less ( 26/257 , 10% ) , $ 2,501 to $ 5,000 ( 10/257 , 4% ) , $ 5,001 to $ 10,000 ( 26/257 , 10% ) , $ 10,001 to $ 15,000 ( 31/257 , 12% ) , $ 15,001 to $ 25,000 ( 26/257 , 10% ) , $ 25,001 to $ 35,000 ( 33/257 , 13% ) , $ 35,001 to $ 50,000 ( 29/257 , 11% ) , $ 50,001 to $ 100,000 ( 52/257 , 19% ) , $ 100,001 to $ 200,000 ( 18/257 , 4% ) , and over $ 200,000 ( 6/257 , 2% ) .
data were missing for 156 participants in the insufficient vision group ( completed bvsq only ) ; income categories for this group include $ 2,500 or less ( 6/57 , 11% ) , $ 2,501 to $ 5,000 ( 4/57 , 7% ) , $ 5,001 to $ 10,000 ( 7/57 , 12% ) , $ 10,001 to $ 15,000 ( 8/57 , 14% ) , $ 15,001 to $ 25,000 ( 14/57 , 25% ) , $ 25,001 to $ 35,000 ( 7/57 , 12% ) , $ 35,001 to $ 50,000 ( 4/57 , 7% ) , $ 50,001 to $ 100,000 ( 3/57 , 5% ) , $ 100,001 to $ 200,000 ( 3/57 , 5% ) , and over $ 200,000 ( 1/57 , 2% ) .
. of participants completing the realm - r , 47% ( 311/668 ) had low health literacy . among participants who completed both tools , the prevalence of low health literacy was greater with the realm - r ( 311/668 , 47% ) than with the bvsq ( 251/668 , 38% ; p = .0001 ) .
the sensitivity of each bvsq item ( 24%34% ) was less than the sensitivity of the combination of all three items ( 51% ) .
the auroc for the combination of the three items was 0.65 ( see table 2 ) .
performance of health literacy screening questions for detecting inadequate health literacy ( n = 668 ) note .
questions adapted from the brief questions to identify patients with inadequate health literacy , by chew , bradley , and boyko ( 2004 ) .
confident with forms = how confident are you filling out medical forms by yourself ?
help read = how often do you have someone help you read hospital materials ? problems learning = how often do you have problems learning about your medical condition because of difficulty understanding written information ?
approximately one third of the cases of inadequate vision were due to each of the following : participants not having corrective lenses ( 35% ) , participants having inadequate corrective lenses ( 33% ) , or participants not having their lenses with them in the hospital ( 32% ) . among participants with low health literacy on the bvsq ( n = 213 ) , those with insufficient vision were at greater risk of low health literacy ( 126/213 , 59% ) than those with sufficient vision ( 258/680 , 38% ; p < .001 ) .
we found that within the same population , the realm - r identified a greater proportion of patients with low health literacy than the bvsq .
further , a nontrivial proportion of participants failed a vision screen , which may explain some of the divergent results .
our study demonstrates less concordance , compared to previous studies , between the bvsq and frequently used tools to measure health literacy .
responses to the bvsq self - report items may differ because our inpatient population differs substantially from prior study populations of generally healthier ambulatory patients ( chew et al .
health literacy can also be context specific , varying by the setting or the problem being treated ( baker , parker , williams , & clark , 1998 ; koh et al .
, 2013 ; morris , grant , repp , maclean , & littenberg , 2011 ; six - means et al . , 2012 ) .
for example , inpatients may be facing new challenges based on their current sick state , which may influence how much help they need navigating the health care system compared to their usual well state . although the bvsq may have less utility among inpatients , the tool does not rely on patients ' vision level .
our findings highlight that participants may have a dual risk of low health literacy and poor vision ; those with vision limitations were more likely to have low health literacy .
participants with poor vision were more likely to be african american , older , and have lower income .
our findings have implications for interventions and practice by addressing barriers related to poor vision . because one third of the study population did not have their corrective lenses available , hospital - based interventions to increase access to corrective lenses
similarly , inpatient vision screening may identify access barriers that could prompt vision care referrals following discharge .
one limitation of this study is the generalizability of the findings because the majority of this inpatient population was african american .
although it is important to begin to obtain data on the utility of the bvsq tool for this largely understudied population ( shea et al . , 2004 ) , future multicenter studies can build on this work to further evaluate the utility of the bvsq among diverse hospitalized patients .
the bvsq should be tested against other research tools such as the short - tofhla or the full realm for robust validation ( chew et al . , 2004 ; chew et al . , 2008 ;
haun et al . , 2012 ; powers , trinh , & bosworth , 2010 ) .
lastly , vision may play a role in delirium , falls , or other inpatient hazards ( inouye , 1998 ) .
future research should explicitly evaluate the extent to which poor vision is a proxy for low health literacy versus a unique risk factor that may have implications for self - care .
the implications of poor vision on assessing health literacy and self - care also warrant further study .
|
patient - centered care includes involving patients and their families in self - management of chronic diseases . identifying and addressing barriers to self - management , including those related to health literacy and vision limitations , may enhance one 's ability to self - manage .
a set of brief verbal screening questions ( bv sq ) that does not rely on sufficient vision to assess health literacy was developed by chew and colleagues in the outpatient setting .
the authors aimed to evaluate the usefulness of this tool for hospitalized patients and to determine the prevalence of poor vision among inpatients . in a prospective study , the bvsq and the rapid estimate of adult learning in medicine - revised ( realm - r ; among participants with sufficient vision , 20/50 snellen ) were administered to general medicine inpatients . of 893 participants ,
79% were african american , and 57% were female ; the mean age was 53 years . among 668 participants who completed both tools , the proportion with low health literacy was 38% with the bvsq versus 47% with the realm - r
( p = .0001 ) .
almost one fourth of participants had insufficient vision ; participants with insufficient vision were more likely to be identified as having low health literacy by the bvsq , compared with those with sufficient vision ( 59% vs. 38% , p < .001 ) .
|
The French military base in Djibouti | Carl de Souza/AFP via Getty Images The Coming Wars The most valuable military real estate in the world Strategically placed at the entrance to the Red Sea, Djibouti is home to more foreign bases than any other country.
DJIBOUTI — “World War III will start here.”
We had been driving around the streets of this African city for more than an hour, and my companion — an agent from the national intelligence service whom I will call Mohammed — was excited by the implications of what he had been showing me.
Strategically placed at the entrance to the Red Sea, commanding a large percentage of the trade and energy flows between Europe and Asia, Djibouti is home to more foreign bases than any other country. We drove by one of the four surviving French bases. The perimeter was wide, but the building immediately reminded you of an old Foreign Legion fort, with its run-down walls and picturesque watch towers.
What a contrast to the dark and menacing Chinese naval base I had visited the day before or the autonomous city in the desert that is Camp Lemonnier, the American base.
Mohammed — who asked that an alias be used to protect his identity — must have sensed my bemusement and pointed out that another French base, on Cape Heron, is today more of a tourist resort for quiet swimming and barbecues than an armed camp.
“The French will never leave that one,” he said. “And if they do, it will be immediately taken up by the wealthiest families.”
Welcome to “The Coming Wars,” where over the next few months we’ll examine a world where borders are becoming increasingly meaningless, but where rivalry and the potential for conflict remain undiminished.
As new powers rise and the formerly hegemonic West loses relative power, we are entering the first period in human history in which modern technology will be combined with a chaotic international arena, in which no single actor or group of actor is capable of imposing order.
The coming wars may be armed conflicts, but they could also take radically different forms: struggles to control infrastructure, propaganda battles, tech races in artificial intelligence and robotics, cyberwar, and trade and economic warfare.
Only one thing is certain: They will be contested by nations with deeply integrated economies and infrastructure across borders that are diluted, permeable and sometimes supple.
This column will take us to the most important hot spots, where we’ll talk to the decision-makers and reveal stories taking place behind the curtain. If the world is heading toward a major conflict or war, we need to think about what shape it will take and where it could plausibly start.
And what better place to begin than Djibouti?
As France — the first to maintain a military presence in the country — slowly abandons its bases due to budgetary constraints, others have been moving in. The United States recently opened a second base on Chabelley Airfield — unmentioned in its public list of overseas bases — after its drones interfered with air traffic at Camp Lemonnier.
The country hosts China and Japan’s only foreign military bases. There’s an Italian base too and Saudi Arabia is building one as well. Djibouti has made overtures to Turkey. And, according to Mohammed, (and later an second independent source) Russia has made inquiries.
India too is rumored to be considering the possibility of acquiring a block of the most prized military real estate in the world. If it does, every major global power will have a Djibouti footprint and the country will resemble a live model of state conflict in the 21st century.
During my stay in the city, I witnessed French and Japanese soldiers competing for the attention of the local prostitutes in the center nightclubs, and the Chinese and Americans using every opportunity to try to take pictures of each other’s equipment and logistics. Colonel Bogoreh — the top commander of the Djibouti Coast Guard — told me a revealing story: After Chinese sailors kept taking unauthorized photos of an American destroyer, he was asked to step in and provide some order.
But what happens in case of war between countries with adjacent military bases in Djibouti?
The answer is not clear, and much would depend on the nature of the conflict. If India does indeed open a military base in Djibouti, any future conflict with China would immediately spread there, because Djibouti is so central to China’s ability to encircle India. In a scenario of conflict between the U.S. and China in the South China Sea, their bases in Djibouti would be put on high alert, but they could very well remain uninvolved.
Another possibility is that warring states would choose Djibouti as the scenario for a limited conflict. Every territorial dispute between China and Japan is so fraught with danger that the two countries might prefer to have a show of force far away in Africa.
A recent episode seems to confirm this interpretation: As revealed by an indiscreet piece in the official newspaper of China’s Supreme Prosecutor, last year a Japanese naval ship sent frogmen to approach and spy on a Chinese warship as both ships were docking at Djibouti.
In the last century, conflict was carefully organized along clear borders and spheres of influence, but today, globalization has left rivals all jumbled together — and Djibouti is the perfect image of this new world, where major powers are forced to share the same space.
“Around us you can draw a circle with eight military bases. We are completely surrounded. Most countries would find this strange, but for us …” Mohammed stopped for a moment. “I guess it is quite normal.”
Bruno Maçães, a former Europe minister for Portugal, is a senior adviser at Flint Global in London and a nonresident senior fellow at the Hudson Institute in Washington. His book “The Dawn of Eurasia” will be published on January 25. ||||| In early August, China became the latest country to open a military base in the Horn of Africa nation of Djibouti, the third smallest country on the continent’s mainland.
Chinese officials said the facility had nothing to do with military expansion and will be a supply center for their peacekeeping and humanitarian missions in the region. For many, the decision signified China’s growing role in Africa and its determination to secure its expanding interests across the continent.
But the move was also indicative of Djibouti’s growing role as an attractive spot for global military superpowers. Located at the southern entrance to the Red Sea, Djibouti is a tiny, barren country, with a population less than one million. Yet since the turn of the century, it has become a base for various European, Asian, and American forces, who have all camped in the region for one reason or another.
Djibouti’s location is key for international military and geostrategic operations (Quartz)
As the former colonial power, France still has one of its largest concentration of its overseas forces stationed in Djibouti. After the terrorist attacks of 9/11, the United States also established Camp Lemonnier—its only permanent military installation in Africa—in order to combat terrorist threats in Yemen and the Horn of Africa. Japan’s only foreign military base is also based in the capital Djibouti and is now set for expansion as a counterweight to China’s increasing influence. The Italians also have their own base, while troops from Germany and Spain are hosted by the French.
Djibouti’s geostrategic location and its stability in a volatile region has made it an important playground for world powers. Analysts say Djibouti’s geostrategic location and its stability in a volatile region has made it an important playground for world powers. Located between Somalia, Eritrea, and Yemen, Djibouti occupies a strategic location adjacent to the Bab el Mandab Strait, which is a critical corridor for international shipping.
Over the years, military powers have sent their forces to Djibouti either to carry out surveillance and counterterrorism strikes or to deter the threat of piracy to international shipping lines. More recently, Sunni Arab states like Saudi Arabia and the United Arab Emirates, who are concerned about the expanding influence of the Shiite-led Iran, have been taking an interest in Djibouti as a base to prosecute the war in Yemen and tighten the noose of Houthi rebels.
Ports of call
Djibouti handles an estimated 90% of landlocked Ethiopia’s maritime trade, an important deal given the latter’s 100 million population and exponential economic growth. Ethiopia had to increasingly start using the port of Djibouti after becoming landlocked when Eritrea broke off as an independent nation in 1991.
With very little in the way of natural resources or human capital, Djibouti’s government “has spared no effort to translate geopolitical fortune into commercial and political advantage,” says Matthew Bryden, the director of the think tank Sahan Research.
US defense secretary James Mattis (R) welcomed by Djibouti’s minister of defense Ali Hasan Bahdon. (Reuters/Jonathan Ernst)
Bryden says that president Ismael Omar Guelleh has been the fulcrum in opening the country to international powers and renting some of its territory to foreign military bases. Since ascending to power in 1999, Guelleh has been re-elected four times, with his party holding the majority of the seats in parliament. The 70-year-old’s rule over Djibouti has been labeled autocratic, with his government cracking down on opposition members and approving a constitutional amendment that removed presidential term limits.
Djibouti could be walking a fine line between neutrality and opportunism. In 2001, barely two years into power, and as the US-led War on Terror was unfolding, Guelleh started communicating to foreign powers that the microstate was friendly and was ready to punch above its weight.
As a poor country with high unemployment rates and susceptible to spikes in food and fuel prices, the rents from foreign countries’ military bases would essentially prove crucial for economic growth. For instance, the United States pays $63 million annually to lease its base, while the Chinese will be paying $20 million a year besides the billions they are investing in building a railway, a port, an industrial park, and banks.
For Guelleh the situation proved to be a positive sum. “In addition to developing Djibouti’s ports and infrastructure, Guelleh has attracted foreign bases that both provide income and a degree of protection from external aggression,” Bryden said.
Yet Djibouti could be walking a fine line between neutrality and opportunism, says analysts. For instance, a recent spat with the Dubai-based DP World pushed the UAE to fund ports and military bases in both Eritrea and Somaliland. After Djibouti reduced its diplomatic status with Qatar, the latter removed its peacekeeping forces from the Djibouti-Eritrea border, raising tensions of a renewed border dispute. And with the arrival of the Chinese, any friction with Western powers who are just a few miles away from each other might test the limits of Djiboutian diplomacy.
Djibouti might also risk being drawn into other countries’ wars. As Bryden says: “The Horn of Africa and the Middle East are currently rough neighborhoods, and Djibouti may find itself making enemies, not through any action of its own, but as a consequence of the actions of its military guests.”
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– The US has a single full-scale military base in all of Africa: It's in Djibouti, and we have more than a few neighbors there. Politico takes a look at the small country in the Horn of Africa (it's the size of New Hampshire) and the continually expanding military presence there. It hosts more foreign bases than anywhere else in world, a fact Politico attributes to its strategic location at the mouth of the Red Sea, where it sees "a large percentage of the trade and energy flows between Europe and Asia." France set up shop there first; Italy and Britain have a presence, per the New York Times; China and Japan have but one foreign base each, and it's there. Saudi Arabia is coming, and there are whispers that Turkey, Russia, and India could, too. If we get to that point, Bruno Maçães writes that every big global power will have a presence there, and that raises some big questions for him. Here's one: What happens if two major players—say, China and India—go to war, and just happen to have bases near one another? Here's another: Would a country ever decide to avoid full-scale war but launch an attack on a rival's Djibouti base? As a member of Djibouti's intelligence service tells Maçães, "World War III will start here." Quartz also floats the idea that the situation could imperil Djibouti itself. It has increasingly welcomed foreign militaries under current President Ismael Omar Guelleh, who flung open the country's doors post-9/11 in exchange for hefty fees (the US pays $63 million a year). But the head of a think tank that's focused on the region warns that "the Horn of Africa and the Middle East are currently rough neighborhoods, and Djibouti may find itself making enemies, not through any action of its own, but as a consequence of the actions of its military guests."
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recently , a great advance was achieved in the understanding of pathogenesis of autoimmune diabetes , particularly regarding the molecular mechanism of pancreatic -cell apoptosis and immunological significance of -cell apoptosis .
hence , it has been shown that pancreatic -cell death is important not only in the final effector phase of autoimmune type 1 diabetes ( 1,2 ) but also in the initiation of -cell autoimmunity ( 3,4 ) .
such progress was mostly achieved by employing murine models of autoimmune diabetes because application of most essential genetic manipulation or immunological intervention is possible only in animal models .
murine autoimmune diabetes models and human type 1 diabetes have many common characteristics such as the presence of insulitis , requirement for specific mhc haplotypes and autoimmune responses to autoantigens including glutamic acid decarboxylase ( gad ) .
thus , many recent progress obtained employing murine autoimmune diabetes models would be applicable to human type 1 diabetes , implying important therapeutic potential .
autoreactive t lymphocytes are the most important effector cells in murine autoimmune diabetes ( 5 - 7 ) , and probably in human type 1 diabetes .
they will ultimately induce apoptosis of -islet cells in murine autoimmune diabetes ( 8,9 ) , while apoptosis of pancreatic -cells in human type 1 diabetes has not been demonstrated because of the difficulty in procuring human pancreatic tissue and inability to synchronize disease process in human type 1 diabetes .
we have shown that ifn/tnf synergism is responsible for murine pancreatic -cell apoptosis both in vitro and in vivo ( 2 ) , which was critically dependent on stat1 activation by ifn ( 1 ) . in vivo role of stat1 activation by ifn
other death effector molecules such as fas ligand ( fasl ) might be an effector molecule for a small number of autoreactive lymphocytes ( 10 ) but not for the majority of final death effector cells ( 9,11 ) .
ifn appears to sensitize otherwise resistant pancreatic islet cells or insulinoma cells to tnf -mediated apoptosis by activating stat1/irf-1 signal pathway ( 2 ) .
most such pancreatic -cell death and signal pathways were studied in murine autoimmune diabetes models .
such findings might also be relevant in human type 1 diabetes also . in an effort to elucidate the possible mechanism of human pancreatic islet cell apoptosis leading to human type 1 diabetes
, we investigated if similar cytokine synergism could induce apoptosis of human pancreatic islet cells and similar signal molecules are induced in them .
human pancreatic islets were obtained from brain - dead patients between 1998 and 2002 at samsung medical center , using a modification of the automated method for human islet isolation ( 12 ) .
briefly , 350 ml of hank 's buffered salt solution ( hbss ) containing 9.1mol / l collagenase solution ( liberase , boehringer - mannheim , mannheim , germany ) was injected through the pancreatic duct after cannulation .
the pancreas was loaded into a stainless steel digestion chamber , and islets were separated during a continuous digestion process for 30~45 min . during the recirculation phase ( flow rate , 85 ml / min ) , intrachamber temperature was increased at a rate of 2/min by the passage of the solution through a stainless steel coil immersed in a water bath ( 50 ) .
the chamber containing the distended pancreas was gently agitated and samples were taken every 2 min to monitor digestion .
after 20~30 min of recirculation , digestion was stopped by dilution in 400 ml / min ice - cold hbss . in this phase , the digested tissue was rapidly collected in sterile bottles containing 200 ml fcs .
purification of the islets was carried out over discontinuous euro - ficoll gradients ( 1.108 , 1.096 , 1.037 and hbss ) .
purified islets were then washed twice , evaluated for purity , and counted after dithizone ( sigma , st .
the pellet was resuspended in 3 ml warm 53.7mol / l trypsin-3 mmol / l edta .
after incubation at 37 for 5 min and pipetting for 2~3 min , islets became invisible .
then , cells were washed with warm rpmi-10% fcs at 1,500 rpm for 5 min .
single islet cells were frozen in liquid nitrogen until use . at the time of assays ,
single islet cells were thawed and 1.410 cells were plated per single well of 96-well plates .
viability of the islet cells after thawing was above 90% , as judged by trypan blue staining and acridine orange / propidium iodide staining .
isolated human pancreatic islet cells were grown in dmem containing 15% fbs , 2 mm glutamine , and penicillin - streptomycin ( gibco - brl , gaithersburg , md ) .
recombinant human tnf and recombinant human il-1 were purchased from r&d systems ( minneapolis , mn ) .
louis , mo ) unless stated otherwise . cells ( 210/well for human single islet cells ) were seeded in 96-well microtiter plates and treated with various combinations of cytokines for the indicated time periods .
the optimal concentrations of cytokines for the cytotoxic action were 1,000 u / ml for ifn , 10 ng / ml for tnf , and 17.5 ng / ml for il-1. after cytokine treatment , the medium was removed and 3-[4,5-dimethylthiazol-2-yl]-2,5-diphenyltetrazolium bromide ( mtt , 0.5 mg / ml ) was added followed by incubation at 37 for 2 hr in co2 incubator . after a brief centrifugation , supernatant was carefully removed and dmso was added . after insoluble crystals were completely dissolved , absorbance at 540 nm was measured using thermomax microplate reader ( molecular devices , sunny vale , ca ) .
morphological changes in the nuclear chromatin of cells undergoing apoptosis were detected by staining with 2.5g / ml of dna - binding bisbenzimide hoe33342 fluorochrome ( calbiochem , san diego , ca ) , followed by an examination on a fluorescence microscope . for transmission electron microscopy ,
cells were fixed in 4% glutaraldehyde/1% paraformaldehyde/0.2 m phosphate ( ph 7.2 ) at 4 for 2 hr .
after two washes in 0.2 m phosphate , the cell pellets were postfixed with 2% oso4 in the same buffer for 30 min .
the pellets were dehydrated in ethanol and then in 100% propylene oxide , followed by embedding at 37 overnight and 60 for another 3 days .
ultrafine sections were cut and examined on an electron microscope ( hitachi h7100 , 75 kv ) .
cells were lysed in triple - detergent lysis buffer ( 50 mm tris - cl , ph 8.0 , 150 mm nacl , 0.02% sodium azide , 0.1% sds , 1% np-40 , 0.5% sodium deoxycholate , 1 mm pmsf ) .
an equal amount of protein for each sample was separated by 10% or 12% sds - page and transferred to hybond ecl nitrocellulose membrane ( ge healthcare life sciences , buckinghamshire , uk ) . after blocking with 5% skim milk
, the membranes were sequentially incubated with one of the primary antibodies ( rabbit anti - mouse irf-1 , santa cruz ; rabbit anti - phospho - stat1 , new england biolabs , ipswich , ma ) and then hrp - conjugated secondary antibodies ( anti - rabbit igg , ge healthcare life sciences , buckinghamshire , uk ) , followed by ecl detection ( ge healthcare life sciences , buckinghamshire , uk ) .
human pancreatic islets were obtained from brain - dead patients between 1998 and 2002 at samsung medical center , using a modification of the automated method for human islet isolation ( 12 ) .
briefly , 350 ml of hank 's buffered salt solution ( hbss ) containing 9.1mol / l collagenase solution ( liberase , boehringer - mannheim , mannheim , germany ) was injected through the pancreatic duct after cannulation .
the pancreas was loaded into a stainless steel digestion chamber , and islets were separated during a continuous digestion process for 30~45 min . during the recirculation phase ( flow rate , 85 ml / min ) , intrachamber temperature was increased at a rate of 2/min by the passage of the solution through a stainless steel coil immersed in a water bath ( 50 ) .
the chamber containing the distended pancreas was gently agitated and samples were taken every 2 min to monitor digestion .
after 20~30 min of recirculation , digestion was stopped by dilution in 400 ml / min ice - cold hbss . in this phase , the digested tissue was rapidly collected in sterile bottles containing 200 ml fcs .
purification of the islets was carried out over discontinuous euro - ficoll gradients ( 1.108 , 1.096 , 1.037 and hbss ) .
purified islets were then washed twice , evaluated for purity , and counted after dithizone ( sigma , st .
the pellet was resuspended in 3 ml warm 53.7mol / l trypsin-3 mmol / l edta .
after incubation at 37 for 5 min and pipetting for 2~3 min , islets became invisible .
then , cells were washed with warm rpmi-10% fcs at 1,500 rpm for 5 min .
single islet cells were frozen in liquid nitrogen until use . at the time of assays ,
single islet cells were thawed and 1.410 cells were plated per single well of 96-well plates .
viability of the islet cells after thawing was above 90% , as judged by trypan blue staining and acridine orange / propidium iodide staining .
isolated human pancreatic islet cells were grown in dmem containing 15% fbs , 2 mm glutamine , and penicillin - streptomycin ( gibco - brl , gaithersburg , md ) .
recombinant human tnf and recombinant human il-1 were purchased from r&d systems ( minneapolis , mn ) .
cells ( 210/well for human single islet cells ) were seeded in 96-well microtiter plates and treated with various combinations of cytokines for the indicated time periods .
the optimal concentrations of cytokines for the cytotoxic action were 1,000 u / ml for ifn , 10 ng / ml for tnf , and 17.5 ng / ml for il-1. after cytokine treatment , the medium was removed and 3-[4,5-dimethylthiazol-2-yl]-2,5-diphenyltetrazolium bromide ( mtt , 0.5 mg / ml ) was added followed by incubation at 37 for 2 hr in co2 incubator . after a brief centrifugation , supernatant was carefully removed and dmso was added .
after insoluble crystals were completely dissolved , absorbance at 540 nm was measured using thermomax microplate reader ( molecular devices , sunny vale , ca ) .
morphological changes in the nuclear chromatin of cells undergoing apoptosis were detected by staining with 2.5g / ml of dna - binding bisbenzimide hoe33342 fluorochrome ( calbiochem , san diego , ca ) , followed by an examination on a fluorescence microscope . for transmission electron microscopy ,
cells were fixed in 4% glutaraldehyde/1% paraformaldehyde/0.2 m phosphate ( ph 7.2 ) at 4 for 2 hr .
after two washes in 0.2 m phosphate , the cell pellets were postfixed with 2% oso4 in the same buffer for 30 min .
the pellets were dehydrated in ethanol and then in 100% propylene oxide , followed by embedding at 37 overnight and 60 for another 3 days .
ultrafine sections were cut and examined on an electron microscope ( hitachi h7100 , 75 kv ) .
cells were lysed in triple - detergent lysis buffer ( 50 mm tris - cl , ph 8.0 , 150 mm nacl , 0.02% sodium azide , 0.1% sds , 1% np-40 , 0.5% sodium deoxycholate , 1 mm pmsf ) .
an equal amount of protein for each sample was separated by 10% or 12% sds - page and transferred to hybond ecl nitrocellulose membrane ( ge healthcare life sciences , buckinghamshire , uk ) . after blocking with 5% skim milk
, the membranes were sequentially incubated with one of the primary antibodies ( rabbit anti - mouse irf-1 , santa cruz ; rabbit anti - phospho - stat1 , new england biolabs , ipswich , ma ) and then hrp - conjugated secondary antibodies ( anti - rabbit igg , ge healthcare life sciences , buckinghamshire , uk ) , followed by ecl detection ( ge healthcare life sciences , buckinghamshire , uk ) .
treatment of single human islet cells with cytokines disclosed that combination of ifn , tnf and il-1 induced significant death after 5 days of incubation . when the effect of individual cytokine was studied , a combination of ifn and tnf induced death of human islet cells while single cytokine did not exert significant cytotoxicity on human islet cells ( fig .
the addition of il-1 to the ifn/tnf combination had only a minor effect on islet cell viability .
our results showing death of human islet cells by the triple combination of ifn , tnf and il-1 is similar to previous reports by others employing human islet cells ( 13 - 16 ) .
percent death of human islet cells by the cytokine combination in this investigation was similar to a previous report ( 13 ) , and was smaller than that of murine islet cells by the similar cytokine combination even after prolonged incubation for 5 days ( 2 ) .
most of the death of human islet cells by the triple combination could be explained by ifn/tnf combination because the addition of il-1 to the ifn/tnf combination increased human islet cell death only to a small degree , consistent with a previous paper ( 13 ) .
hoechst 33342 staining and electron microscopic examination showed that the death of human islet cells by ifn/tnf combination was a typical apoptosis characterized by nuclear condensation and fragmentation with preserved plasma membrane integrity ( fig .
these results are similar to previous reports showing nuclear condensation or tunel nuclei after cytokine treatment of human islet cells ( 15,16 ) . next we asked if ifn activates stat1 and induces irf-1 which has been reported to be important for induction of tnf susceptibility in otherwise resistant murine islet cells or cancer cells ( 2,17 ) .
immunoblot analysis using antibody to phosphorylated stat1 showed that stat1 became activated 30 min after ifn treatment , similar to murine insulinoma cells ( 2 ) ( fig .
irf-1 was also induced by ifn treatment of human islet cells for 48 hrs again similar to murine insulinoma cells suggesting that stat1 activation and irf-1 induction by ifn may sensitize human islet cells to tnf-induced apoptosis , similar to the case of murine islet cell death by ifn/tnf synergism ( 2 ) ( fig .
these results were similar to our previous study using murine islet / insulinoma cells and suggests the possibility that intracellular signal activated by ifn may sensitize otherwise resistant human pancreatic islet cells to tnf-induced apoptosis , which could not be proved because of shortage of human islet cells , the absence of immortalized human islet cells and unavailability of genetic manipulation system .
a recent paper has shown that bim , a bh3-only proapoptotic bcl-2 family member , is induced in human islets or rat islet cells after treatment with ifn+tnf which plays an important role in -cell death by ifn+tnf synergism ( 18 ) . in that model ,
bim induction was attributed to ifn-induced activation of stat1 which was bound to bim promoter ( 18 ) .
while detailed biochemical and cellular mechanism of human islet cell death by cytokines could not be investigated further because of limited availability of human islets for diabetes research , our results suggest that the death of human islet cells is basically similar to that of murine islet cells .
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fasl , perforin , tnf , il-1 and no have been considered as effector molecule(s ) leading to -cell death in autoimmune diabetes .
however , the real culprit(s ) of -cell destruction have long been elusive despite intense investigation .
previously we have suggested ifn/tnf synergism as the final effector molecules in autoimmune diabetes of nod mice . a combination of ifn and tnf but neither cytokine alone , induced classical caspase - dependent apoptosis in murine insulinoma and pancreatic islet cells .
ifn treatment conferred susceptibility to tnf-induced apoptosis on otherwise resistant murine insulinoma cells by stat1 activation followed by irf-1 induction . here
we report that ifn/tnf synergism induces apoptosis of human pancreatic islet cells .
we also observed stat1 activation followed by irf-1 induction by ifn treatment in human islet cells . taken together , we suggest that ifn/tnf synergism could be involved in human islet cell death in type 1 diabetes , similar to murine type 1 diabetes .
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Driver, 19-month-old girl, bear all died in crash on Highway 4 in Calaveras County
Baby, mother killed when car crashes into bear near Angels Camp
A mother and her baby were killed Thanksgiving night when their vehicle hit a bear on Highway 4 near Angels Camp, according to the Calaveras County coroner.
Sarah Rohde, 27, was driving east of Angels Camp just after 6 p.m. Thursday when the crash happened.
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Rohde and her 19-month-old daughter, Ariana, were killed in the crash, family members told KCRA.
Rhode’s 4-year-old son, Julian, was also in the car. He survived the crash and was taken to UC Medical Center.
The bear also died.
Rohde’s family was at the crash scene Friday looking for answers.
“She was the best mom any child could ever ask for, and she was the best daughter,” Rohde’s mother, Tracy Browning, said. “She was my rock, and I was her rock too.”
Rohde worked for Tuolumne County as a extreme tour guide at Mercer Caverns in Murphys, her family said.
“I’m having a hard time, questioning God about this. I really am,” Browning said.
Family members hope to erect a roadside memorial to the lives lost.
Those who keep track of bears in Calaveras County said that there are more incidents than ever involving bears on the roadways.
“The bear population is growing and I don’t see it stopping. There are going to be more wrecks,” Calaveras Fish and Game Commissioner Ron Severud said.
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A black bear got on Highway 4 after sundown Thursday and a westbound car crashed into the animal, killing the 27-year-old woman driver, a 19-month-old girl and the bear.
A 4-year-old boy in the car, also a resident of Copperopolis, sustained minor injuries and was flown by helicopter to the University of Davis, California, Medical Center, California Highway Patrol Officer John Fernandez said in a statement.
Names of the three people involved in the crash were not released by law enforcement. Authorities were still trying to contact family of the deceased victims, Kevin Raggio, Calaveras County coroner, said Friday afternoon.
The bear got on Highway 4 between Parrotts Ferry Road and Murphys about 6 p.m. Thanksgiving Day, west of Holiday Mine Road, Fernandez said.
The woman was driving a 2002 Subaru Impreza west on Highway 4 at 55 to 60 miles per hour. The bear entered the road directly in the path of the Subaru, and the car struck the bear and killed it, Fernandez said.
At the same time, “force of the impact with the bear caused major intrusion into the passenger compartment of the vehicle,” Fernandez said. “The driver and her 19-month-old passenger sustained fatal injuries as a result of the collisio
Alcohol and drugs were not believed to be factors in the crash. Fernandez described conditions at the time of the crash as cloudy and dry. Sundown before the crash occurred was about 4:45 p.m.
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– A mother and baby were tragically killed Thanksgiving night when their car hit a bear in northern California. KCRA 3 reports that Sarah Rohde, 27, was driving with her two children in Calaveras County after 6pm when her car struck the wild animal. Rohde and her 19-month-old daughter Ariana died. The bear was also killed in the accident. Per the Union Democrat, Rohde’s four-year-old son Julian survived the crash and was flown to University of Davis Medical Center by helicopter to treat minor injuries. “She was the best mom any child could ever ask for, and she was the best daughter,” said Rohde’s mother, Tracy Browning. “She was my rock, and I was her rock too.” An uptick in car accidents involving bears in the area has officials growing concerned. Calaveras Fish and Game Commissioner Ron Severud told KCRA 3, “The bear population is growing and I don’t see it stopping. There are going to be more wrecks.” (An Alaskan boy lived to tell the tale of a bear crashing through his bedroom window.)
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the development of
a more complete understanding of polymorphism
is an important goal for the solid - state chemist or process engineer ,
and is especially relevant to pharmaceuticals since each polymorphic
form of a given compound can lead to different bioavailabilities .
characterization of polymorphs is often difficult , especially when
single crystals suitable for x - ray diffraction ( xrd ) can not be isolated .
consequently , a broad range of techniques , including ab initio
crystal structure prediction ( csp ) , infrared spectroscopy , and powder x - ray diffraction
( pxrd ) , are currently used to characterize organic powders in this context .
however , these techniques often only provide partial details on atomic
and molecular structure .
consequently , there is much interest in developing
improved methods to characterize polymorphs . among these methods ,
magic angle spinning ( mas ) solid - state nmr
is an extremely powerful method for characterizing polymorphs .
this
is because h , c , and n chemical
shifts are often diagnostic , both for fingerprinting
polymorphs and/or for directly probing atomic structure .
recently , the combination of measured experimental nmr chemical
shifts , csp , and gauge - including projector augmented - wave ( gipaw )
dft calculations of chemical shifts has been very successful both
for validation of polymorph trial structures and for complete structure
determination .
however , the main limitation of nmr methods is poor sensitivity .
indeed , n and many 2d solid - state nmr experiments at
natural abundance often require very long experimental times , except
for compounds with very favorable relaxation characteristics . even in favorable cases , two - dimensional c
c correlation experiments on samples at natural isotopic
abundance typically require times on the order of days .
dynamic
nuclear polarization ( dnp ) is a technique that can increase
the sensitivity of solid - state nmr by up to roughly 2 orders of magnitude
at high fields . in a dnp experiment ,
microwave
irradiation is used to drive the transfer of polarization from unpaired
electrons to nuclei .
dnp can theoretically
provide a signal gain of up to a factor of 658 for h nmr
and cross - polarization ( cp ) nmr experiments which involve h nuclei , although enhancements of 10200 are typically obtained .
we have recently shown how powdered organic solids can be efficiently
polarized using dnp . in our approach ,
the organic solid is finely ground to reduce the particle sizes , and
the powder is impregnated with a nonsolvent liquid that contains the
dnp polarizing agents , usually a stable dinitroxide biradical .
the dnp enhanced nmr experiments are typically
carried out at around 105 k. proton spin diffusion ( exchange of h magnetization ) then distributes the polarization throughout
the sample , and the enhanced h polarization may be transferred
to other desired nuclei via cp . with
this impregnation dnp approach , we have shown that dnp enhancements
between 5 and 200 can be obtained for fine powders of organic solids
such as glucose , sulfathiazole , paracetamol , cetirizine dihydrochloride ,
histidine hydrochloride , polymers , etc .
c / h n heteronuclear correlation ( hetcor ) and c c homonuclear scalar correlation ( inadequate ) experiments
in a few hours for a variety of organic solids .
dnp also allows challenging multinuclear
magnetic resonance experiments such as natural abundance h and o solid - state nmr and n overtone
mas nmr , including o solid - state nmr
for surface - supported species .
the sensitivity
enhancement from dnp can also be used to overcome low loadings of
active pharmaceutical ingredients ( api ) within formulated pharmaceuticals .
additionally , by analyzing the dnp enhanced
nmr signal buildup rates with a numerical spin diffusion model it
is possible to estimate macroscopic api particle sizes .
this technique obviously has great potential for the rapid
characterization
of polymorphs and formulated pharmaceuticals , but there are open questions
related to sample formulation for dnp experiments and how this may
impact species which may display polymorphism or other changes such
as ( de)solvation . before performing a dnp enhanced solid - state nmr
experiment ,
the three main steps in sample preparation involve ( i )
grinding the sample into a very fine powder ( note , this step may not
be necessary for formulated pharmaceuticals ) , ( ii ) impregnation with
an appropriate solution containing the electron polarization source ,
and ( iii ) rapidly cooling the sample to ca .
105 k within the nmr probe
that will be used to acquire the nmr data .
it is obvious that all
three of these steps could potentially induce polymorphic transitions .
here we show how protocols can be developed to prepare samples for
impregnation dnp while maintaining the desired polymorphic form of
the sample . while we focus on the effects of grinding and impregnation
on phase transitions
, it is also well - known that a polymorphic transition
can be induced by a reduction in temperature .
however , we note that
many crystal structures of polymorphs determined by single - crystal
xrd are acquired at reduced temperatures .
interestingly , recent results
indicate that dnp experiments at ambient temperatures could become
feasible . here , we present sample
preparation protocols for impregnation
dnp enhanced nmr of polymorphs .
the protocols are demonstrated with
theophylline as a model system ( scheme 1 ) for this study since it possesses several well - characterized
polymorphs , as well as a hydrated form , and they interconvert quite easily .
we note that viel and co - workers have recently applied impregnation
dnp techniques to a single polymorphic form of theophylline and showed
the rapid acquisition of dipolar c c correlation spectra .
we study three anhydrous polymorphs of theophylline ( figure 1 ) , along with theophylline - monohydrate
( form m ) .
the kinetically stable form
of theophylline under typical lab conditions is often referred to
as form ii in the chemical literature , and is usually the form obtained from commercial suppliers . to obtain
form
i , form ii was heated at 270 c , close to its melting point
( 273 c ) for 2 h , and slowly cooled to room temperature , as outlined
in the literature .
it is obtained
by stirring a methanol solution containing powdered form ii for 15
days .
theophylline monohydrate ( form
m ) is obtained by the recrystallization of theophylline form ii in
distilled water .
schemes for the preparation
and interconversion of the different
theophylline - containing crystal structures considered herein .
form iv is
an anhydrous polymorph of theophylline obtained by stirring form ii
in methanol for 15 days .
form i is an anhydrous polymorph of theophylline
obtained by heating form ii at 270 c for 2 h. form m is a theophylline - containing
hydrate obtained by recrystallizing form ii in water . dashed arrows
illustrate the conversions that are induced by grinding or impregnation .
the four theophylline - containing
systems were synthesized ( or in
the case of form ii , used as received from the supplier ) , and c cpmas nmr spectra were recorded at 105 k on the pristine
powdered polymorphs ( i.e. , no grinding of the sample , and no impregnation
with solvent ) , as shown in figure 2 . as expected , the c chemical shifts vary significantly between the forms .
comparison
between 300 k spectra and 105 k spectra is presented in figure s1 . in all cases ,
the multiplicity of
the carbon peaks is the same at both 105 and 300 k and the only difference
is slight shifts in some of the peaks ( less than a 2 ppm shift difference ) .
previously determined crystal structures for all polymorphs used diffraction
data acquired at temperatures of less than 120 k , suggesting that there is no polymorphic phase transition at low
temperature for all forms of theophylline considered herein .
we note
that form iv possesses twice as many c peaks in its nmr
spectrum as the other forms , which is consistent with the previously
determined crystal structure , as it has two molecules in the asymmetric
unit ( z = 2).h mas and n cpmas nmr spectra of each form
are also shown in figures s2 and s3 .
c solid - state nmr spectra recorded at 105 k and b0 = 9.4 t without microwave irradiation and
with 64 scans for all nonimpregnated polymorphic forms of theophylline
studied here : form ii ( red ) , form i ( blue ) , form iv ( green ) , and form
m ( purple ) .
c , h , and n solid - state
nmr spectra can be found in figures s1s3 .
additionally , comparison between 298 and 105 k c solid - state
nmr spectra is presented in figure s1 .
for dnp enhanced solid - state nmr experiments ,
a powder sample of
each system was finely ground by hand in a mortar and pestle .
the
powder was then impregnated with a tce : methanol - d4 ( 95:5 ) solution containing the biradical tekpol as a
polarization source .
tce was chosen as
a solvent since theophylline was found to be insoluble in tce , and
it has previously been shown that this is a good impregnating medium
for dnp .
5% methanol was found to improve
glass formation for tce . for experiments on form
ii , a high proton
dnp enhancement ( h = solv ) of
220 was obtained for the solvent ( figure 3 ) . c dnp enhanced solid - state nmr
spectra of form ii
of theophylline obtained at 105 k and b0 = 9.4 t ( i.e. , h resonance frequency of 400 mhz ) with
16 scans for microwave on , 64 scans for microwave off , and 20 s recycle
delay .
the powder was finely ground in a mortar and pestle and impregnated
with a solution of tce : methanol - d4 ( 95:5 )
containing tekpol as biradical .
the proton dnp enhancement for form ii of microcrystalline
theophylline ,
as measured with c cpmas experiments ( c , cp ) , was 11 .
the dnp enhanced proton signal buildup rate ( tdnp ) was measured with a dnp enhanced cp saturation recovery
experiment .
usually , tdnp and the proton
longitudinal relaxation time t1 are similar
in magnitude . for the sake of convenience , we only measure in this
study tdnp . for form
105 k ( we speculate
this to be due to the presence of rotating methyl groups ) .
note however
that a signal enhancement by a factor of 11 corresponds to an acceleration
in acquisition times of a factor 121 ( as the signal - to - noise ratio
( s / n ) scales with the square root of the number of transients acquired ) .
the short tdnp is not critically limiting
in the present case since , although it leads to lower enhancements ,
it also allows a relatively short recycle delay of ca .
n hetcor
and c c inadequate nmr spectra were
recorded for form ii in 3 , 5 , and 2 days respectively , shown in figures s4 , s5 , and s6 .
to obtain the inadequate
spectrum with similar conditions of compounds like this using conventional
methods would typically take on the order of a week .
form i was obtained by heating form ii to 270 c ,
just below
its melting point of 273 c ( see experimental
section for details ) . a sample of powdered form i was characterized
by solid - state nmr at room temperature
. the c cpmas nmr
spectrum showed 6 resolvable c peaks ( in accord with
the accepted crystal structure , as z = 1 ) .
we observed different chemical shifts than those
of form ii , as shown in figures 2 , s1 , and s7.figure 4 shows c cpmas nmr spectra of form i before and
after grinding .
grinding is known to supply mechanical energy to the
sample , which can be sufficient to induce a polymorphic conversion
or a desolvation if solvent is present in the lattice . when the powder of form i was manually ground in a mortar and pestle
at room temperature , solid - state c cpmas nmr experiments
confirmed that the sample partially transformed back to form ii . c cpmas nmr spectra recorded at 105 k and b0 = 9.4 t of what was initially powdered theophylline ,
form i , subjected to different preparation procedures . from top
to
bottom : ( a ) pure powdered form i before any procedure , ( b ) a mixture
of forms i and ii obtained after manual grinding of pure form i in
air at room temperature , ( c ) form i manually ground cold at 55
c in a glovebox , ( d ) mixture of forms ii and i after impregnation
with a 16 mm tce : methanol - d4 ( 95:5 ) solution ,
( e ) form i manually ground cold at 55 c in a glovebox
and impregnated with a toluene - d8:decalin
( i.e. , tol : dec ) ( 90:10 ) solution , ( f ) pure form ii .
we found that the polymorphic transition back to
form ii could
be avoided by grinding the sample at reduced temperatures in the absence
of atmospheric moisture .
two procedures were attempted : the first
one was to use an automatic cryogrinder . to use an automatic cryogrinder ,
the powder was put into a water - tight tube immersed in liquid nitrogen
and shaken in order to grind the powder .
this procedure yielded a
powder which , after appropriate sample preparation , did not lead to
dnp nmr enhancements that were encouraging ( i.e. , c , cp = 2 ) , when one considers the eventual goal of efficient acquisition
of 2d solid - state nmr data .
this would suggest that the particles
were not ground finely enough using this technique .
sem images were
recorded before and after this procedure ( see figures s8 and s9 ) and allow us to conclude that the powder
still contained some relatively big particles ( dimensions of around
50 m ) .
another possible simple way to cryogrind the sample
was to cool the sample in a freezer and grind it while it was cold .
this was performed by placing powdered form i on a mortar and pestle
in a 55 c freezer inside a glovebox ( argon atmosphere ) .
the glovebox was used in order to avoid absorption of moisture on
the cold sample .
the powder and the mortar and pestle were allowed
to rest in the freezer for 30 min to reduce their respective system
temperatures .
the form i powder was then quickly ground into a fine
powder while the powder ( and mortar ) were still cold .
this procedure
prevented the i ii transformation , as shown in figure 4c .
however , the c cpmas nmr spectra of the cold ground samples show additional broadening
of the c peaks . this could be explained by some disorder
introduced in the lattice during grinding at cold temperature .
once the problem of grinding was solved by grinding
the cold sample
in a glovebox , the powder was impregnated with a solution of tekpol
in tce : methanol - d4 ( 95:5 ) .
however , impregnation
with tce : methanol - d4 solution also caused
partial transformation of form i to form ii .
figure 4d shows the c cpmas nmr spectrum
after impregnation with a 16 mm tekpol tce : methanol - d4 ( 95:5 ) solution .
the polymorphic transformation could
be due to the polarity of the solvent , which fosters the phase transition
from form i to ii .
less polar
solvents that are compatible with dnp were used for the impregnation
step .
such solvents still were needed to dissolve the radical , while
not dissolving the powdered theophylline - containing organic solid .
we tried impregnation with ortho - terphenyl ( otp ) , 1,3-dibromobutane
( dbb ) , and a mixed solution of toluene - d8:decalin ( 90:10 ) , all of which are nonsolvents for theophylline and
which have been demonstrated to be suitable for dnp .
figure 4e
shows that the toluene - d8:decalin mixture
turns out to completely avoid any form i to form ii transition . in summary , for form i , a protocol was developed involving grinding
a cooled sample in a glovebox followed by impregnation with a toluene - d8:decalin mixture ready for dnp enhanced solid - state
nmr spectra to be recorded without a change in the polymorphic form .
in this case
the h dnp enhancement of the solvent was
around 16 , and the c enhancement was measured to be approximately
4 for form i , as shown in figure 5 . here , the low dnp enhancement results from the poor
performance of toluene - d8:decalin as a
solvent for dnp . we are currently working on identifying additional
solvents / mixtures for dnp on this system .
dnp enhanced c cpmas nmr spectrum recorded at 105
k and b0 = 9.4 t of form i of theophylline
impregnated with a toluene - d8:decalin
( 90:10 ) solution containing 14 mm tekpol with 4 scans for microwave
on , 64 scans for microwave off , and 20 s recycle delay .
it was obtained by stirring a solution of form
ii in methanol for 15 days .
for dnp enhanced nmr experiments , the
powder isolated was ground and then impregnated with a tce : methanol - d4 ( 95:5 ) solution containing the biradical tekpol . a poor solvent enhancement ( compared to usual
enhancement obtained for a bulk solution )
was obtained , c , cp = 40 , and the c enhancement for form iv was even lower , c , cp =
2 ( figure 6 ) .
the low
enhancements are likely due to the very short tdnp ( and by extension proton t1 s ) measured for form i , which were around only 1.5 s. dnp enhanced c cpmas nmr spectra recorded at 105 k
and b0 = 9.4 t of form iv of theophylline
impregnated with a tce : methanol - d4 ( 95:5 )
solution containing 16 mm tekpol , with 4 scans for microwave on , 16
scans for microwave off , and 20 s recycle delay .
the
monohydrated form of theophylline is obtained by a simple recrystallization
of form ii in water . grinding form m at room temperature causes dehydration
of the sample and partial reconversion to form ii , as shown in figure 7 .
comparison of c cpmas solid - state nmr spectra as a
function of the grinding procedure and the solvent used for impregnation
of form m. all spectra were recorded with a 16.4 t spectrometer at
ca .
( b ) mixture of forms
m and ii obtained after grinding at room temperature .
( d ) mixture of forms m and ii after
grinding with a drop of water and impregnation with tce : methanol - d4 ( 95:5 ) solution .
( e ) form m after grinding
with a drop of water and impregnated with a glycerol - d8:d2o : h2o ( 60:30:10 ) solution . ( f )
40 mg of powder was ground in the
presence of several drops of distilled water , to prevent dehydration .
this technique worked well , as shown in the resulting c cpmas nmr spectrum in figure 7c .
an alternative is to grind the powder of form m
while it is completely immersed in liquid nitrogen , and let it warm
under atmospheric air so that the cold powder absorbs the moisture
of the air and prevents form m from dehydrating .
when the ground powder
of form m was impregnated with tce : methanol - d4 ( 95:5 ) ( as done with some of the polymorphs of anhydrous
theophylline ) , partial conversion of form m to form ii was observed .
however , impregnation with a glycerol - d8:d2o : h2o ( 60:30:10 ) solution did not cause
any measurable transformation to form ii , as shown in figure 7e . unfortunately , relatively
low dnp enhancements of c , cp = 2 were obtained from
form m , even though the enhancement of the solvent was , c , cp , was 170 ( figure 8) . the low enhancement for the crystalline phase could be
due to aggregation of particles during grinding with water , which
would explain the high ratio between the solvent and the crystal enhancement .
n nmr spectra have also been recorded in order to confirm
the structure and the presence of hydrogen bonding between the 2 molecules
of theophylline and a water molecule , as predicted by the crystal
structure ( figures s10 and s11 ) .
dnp enhanced c cpmas nmr spectra of theophylline / water
form m ground with a drop of water , and impregnated with a glycerol - d8:d2o : h2o ( 60:30:10 ) solution
containing amupol .
spectra were recorded
at 105 k and b0 = 9.4 t with 4 scans for
microwave on , 16 scans for microwave off , and 20 s recycle delay .
we
investigated the formulation for dnp enhanced nmr experiments
of powdered samples of three polymorphs of theophylline and the monohydrate
form .
we observed that the grinding and impregnation procedures may
cause polymorphic transitions or dehydration in certain situations .
for each form
we were able to determine a procedure for grinding ,
and an appropriate solvent for impregnation that prevented the conversion
to form ii .
dnp enhanced nmr was then applied to these polymorphs .
however , dnp enhancements were relatively low in most theophylline
polymorphs , which is speculated as being due to the presence of methyl
group rotation inducing short tdnp times .
c hetcor or c c inadequate were acquired in reasonable times ,
with a factor over 100 reduction in acquisition times in the best
case ( i.e. , form ii ) .
this will have a direct impact on the efficiency
of nmr crystallography protocols for polymorphs .
finally , we note
that the methods outlined here can most probably also be adapted to
other approaches to formulating samples for dnp experiments in organic
solids , such as recrystallization with polarizing agents , or swelling ( polymers ) with radical - containing
solutions .
geometry optimizations
and
magnetic shielding calculations were
performed using the cambridge serial total energy package ( castep )
density functional theory ( dft ) program , which uses a plane wave basis set to describe the valence electrons ,
and pseudopotentials to describe the core electrons .
the gipaw method provides an efficient method to calculate magnetic
shielding values in crystalline solids .
geometry optimizations , starting
from the xrd reference structures , were carried out using the generalized
gradient approximation ( gga ) functional of perdew , burke , and ernzerhof
( pbe ) .
a maximum plane wave energy cutoff
for the valence electrons of 700 ev was applied . a monkhorst
pack
grid of k - points was
used and corresponded to a maximum spacing of 0.05 in reciprocal space . during the geometry optimizations
, only the
hydrogen positions were relaxed , since the unit cell and all heavy
atoms ( c , n , o ) were fixed .
the magnetic shielding values were calculated
using the same functional and parameters as those used for the geometry
optimization .
the magnetic shielding values were then converted into
calculated chemical shifts using standard procedures . for the chemical shielding calculation
the rotational dynamics
of the methyl group was taken into account by averaging over the three
shifts .
geometry optimization and magnetic shielding calculations
were performed at the ple scientifique de modlisaiton
numrique ( psmn ) at the ens lyon . commercially available
theophylline form ii was obtained from sigma - aldrich
and was used without further purification .
form i was obtained by
heating form ii in a tube furnace . form
ii was loaded into a quartz tube and was then heated to 373 k with
a 753 k / h ramp , stabilized for 5 min , then heated to 523 k with a
753 k / h ramp , then stabilized for 30 min , and heated to 543 k ( 270
c ) with a 373 k / h ramp .
the sample was then left at 543 k for
2 h and then cooled down to room temperature with a 373 k / h ramp .
form iv was obtained by stirring a methanol solution containing
theophylline powder for 15 days .
theophylline
monohydrate , called form m , was obtained
by recrystallization of theophylline in distilled water .
a scanning
electron microscope mse-636 was used to capture images
of the automatically cryoground form ii . in a typical procedure ,
the powder was then put
under vacuum and covered with a 12 nm gold layer using a cressington
sputter coater based on a plasma vapor deposition technique .
the covered
powder was then subjected to a 10 bar vacuum for
analysis .
for dnp enhanced nmr experiments , the powder was finely
ground
by hand in a mortar and pestle for several minutes .
other system - dependent
conditions are specified as part of the results and
discussion .
incipient wetness impregnation ( iwi ) was used to
uniformly wet the surface of particles with radical - containing solution . in a typical preparation
, 1020 l of 16 mm biradical
solution in a suitable solvent was added to ca .
the powder and solvent were then mixed
with a glass stirring rod , transferred to a sapphire rotor , and capped
with a polyfluoroethylene insert . for theophylline form iv , a 16 mm
solution of tekpol in 1,1,2,2-tetrachloroethane
( tce):methanol - d4 ( 95:5 ) solution was
used . for form
i , different radical - containing solutions were tested ,
as detailed in the results and discussion .
for form m
, a 16 mm amupol solution in
glycerol - d8:d2o : h2o ( 60:30:10 ) was used .
dnp solid - state nmr experiments were
performed on wide bore 400
mhz ( i.e. , b0 = 9.4 t ) bruker avance i
( epfl , lausanne ) and avance iiihd ( ens - lyon ) spectrometers equipped
with a 263 ghz gyrotron , a low temperature cooling cabinet , and a
triple resonance 3.2 mm low temperature probe .
the sample temperature
for dnp experiments was approximately 105 k. the field sweep coil
of the main magnetic fields was set so that microwave irradiation
occurred at the same position as the positive enhancement maximum
for 1-(tempo-4-oxy)-3-(tempo-4-amino)propan-2-ol ( totapol ) .
additional
solid - state nmr experiments were performed on a 700 mhz bruker avance
iii solid - state nmr spectrometer ( b0 =
16.4 t ) .
room temperature experiments using the 700 mhz spectrometer
employed a 3.2 mm triple resonance hcn probe and 3.2 mm zirconia rotors .
cpmas nmr experiments were performed with a contact pulse on h which was linearly ramped from 1 = 66
to 93 khz and from 58 to 82 khz for c and n experiments , respectively ; c and n
cp
spin lock rf field amplitudes of 57 and 42 khz were used , respectively .
the spinal-64 heteronuclear decoupling scheme was applied during acquisition
with h rf fields of ca .
e - dumbo-122 homonuclear h decoupling was applied with an rf field strength of approximately
100 khz to improve the resolution in the h dimension ,
followed by cross - polarization to the heteronucleus transition and
signal detection .
the 2d refocused c c inadequate nmr spectra was recorded
with a triple resonance 3.2 mm low temperature probe at 12500 khz
mas .
the sample temperature for dnp experiments was approximately
105 k. the spinal-64 sequence at a proton nutation frequency 1 of 80 khz was used for heteronuclear decoupling .
128 increments
of 64 transients each were acquired with a repetition delay of 20
s , resulting in a total experimental time of 2 days .
|
we
show how dynamic nuclear polarization ( dnp ) enhanced solid - state
nmr spectroscopy can be used to characterize polymorphs and solvates
of organic solids .
we applied dnp to three polymorphs and one hydrated
form of the asthma drug molecule theophylline .
for some forms of theophylline ,
sample grinding and impregnation with the radical - containing solution ,
which are necessary to prepare the samples for dnp , were found to
induce polymorphic transitions or desolvation between some forms .
we present protocols for sample preparation for solid - state magic - angle
spinning ( mas ) dnp experiments that avoid the polymorphic phase transitions
in theophylline .
these protocols include cryogrinding , grinding under
inert atmosphere , and the appropriate choice of the impregnating liquid .
by applying these procedures
, we subsequently demonstrate that two - dimensional
correlation experiments , such as 1h13c and 1h15n hetcor or 13c13c inadequate , can be obtained at natural isotopic
abundance in reasonable times , thus enabling more advanced structural
characterization of polymorphs .
|
renal scintigraphy using technetium-99 m dimercaptosuccinic acid ( dmsa ) has become reference diagnostic test for renal cortical damage .
dmsa is taken up into proximal and distal renal tubular cells actively , and then approximately 2 h after injection , 40 - 65% of injected activity is concentrated in the cortex for a sufficiently long time to enable detailed scintigraphic evaluation and is considered to be the agent of choice for diagnosis of cortical scarring , information regarding relative renal size because of high kidney - to - background ratio , lack of activity in the collecting system , and lack of liver and bowel activity . although technetium-99 m mercaptoacetyltriglycine ( mag3 ) is a renal plasma flow agent secreting in the proximal tubules used mainly for assessment of renal drainage .
initial part of the study , the parenchymal phase , reflects the distribution of functional parenchyma and can give similar information to dmsa with regard to parenchymal damage , with sensitivity and specificity calculated as 88 - 89% and 88 - 100% , respectively . due to its high extraction rate
, mag3 accumulates rapidly in the cortex during the first few minutes after injection ( 40 - 60% per pass ) , while the background activity is also rapidly decreasing .
therefore , mag3 provides sufficient image quality with a high kidney - to - background ratio and acceptable resolution at 2 - 4 min after injection and so , mag3 has been also considered in the evaluation of renal parenchymal disorders .
it is clear that , the value of a diagnostic test essentially depends on good intra- and interobserver reproducibility .
investigations aiming specifically at the evaluation of agreement in the interpretation of renal scans , usually confirm the existence of interobserver variability .
nevertheless , while some authors point to sufficiently good agreement between observers , others advocate that the agreement is poor .
our current study was designed to determine possible sources of variability in the interpretation of degree , extent of parenchymal abnormality and to assess the differences in interpretation of routine renal scintigraphic findings by two nuclear medicine specialists .
posterior view of dmsa cortical ( pvdmsa ) scans and parenchymal phase of mag3 ( ppmag3 ) scans were evaluated using standard criterions .
two experienced nuclear medicine physicians independently interpreted pvdmsa scans of 204 ( seven patients with single kidney ) and ppmag3 scans of 102 ( four patients with single kidney ) pediatric patients ( mean age of 7 years ; range 1 - 16 years ) who had undergone as part of their clinical workup retrospectively .
the nuclear medicine physicians were blind to the laboratory results , other diagnostic tests , and patients ' clinical diagnosis prior to the evaluation .
cortical scan with dmsa was performed approximately 2 - 4 h after the patients had been injected intravenously ( iv ) by an activity of adult dose ( mbq ) body weight ( kg)/70 .
posterior , anterior , left , and right posterior oblique static images ( approximately 400k counts ) were taken , using a gamma camera equipped with parallel hole low energy high resolution collimator ( siemens ecam ; siemens medical systems , hoffman estates , il , usa , 1999 ) . after sufficient hydration , mag3 ( 2 mbq / kg )
simultaneous dynamic images were taken with the same gamma camera for 30 min . during the acquisition period ,
comparisons were made by visual inspection of pvdmsa scans and ppmag3 scans by using a grading system modified from itoh et al . according to this , anatomical damage of
the renal parenchyma was classified into six types : normal ( grade 0 ) , one or two focal / relative decreased activity sides and/or single renal contour defect ( grade i ) , two renal contour defects but remnant areas of normal renal parenchyma and normal sized kidney ( grade ii ) , diffuse reduction in uptake throughout the whole kidney with or without multiple renal contour defects ( grade iii ) , small or shrunken kidney ( grade iv ) , indistinct margins of kidney ( grade v ) .
the results of all evaluations were entered in statistical package for social sciences ( spss ) 21.0 .
the degree of agreement between the readers was measured with the kendall 's tau - b correlation coefficient as for ordinal - level variables .
values less than 0.2 are associated with very poor agreement , 0.2 - 0.40 slight agreement , 0.4 - 0.6 moderate agreement , 0.6 - 0.8 substantial ( good , high ) agreement , and values greater than 0.8 are associated with excellent ( almost perfect ) agreement .
according to our findings , excellent agreement was found for dmsa grade readings ( dmsa - gr ) ( tau - b = 0.827 ) and good agreement for mag3 grade readings ( mag3-gr ) ( tau - b = 0.790 ) between two observers .
agreement between dmsa - gr for left kidneys ( tau - b = 0.851 ) and for right kidneys ( tau - b = 0.803 ) were almost perfect .
mag3-gr for left and right kidneys among two observers were good ( left : tau - b = 0.795 ; right : tau - b = 0.778 ) . also given these findings , interobserver reproducibility was better for dmsa - gr than mag3-gr and was better for left kidneys than right among two observers .
the results showed that most of clear parenchymal lesions ( grade iii - v ) detected on pvdmsa scans and ppmag3 scans identified by observers equally .
studies with negative or minimal lesions reduced correlation degrees for both dmsa - gr and mag3-gr [ tables 1 and 2 ] .
comparison of mag3-gr among two observers comparison of dmsa - gr among two observers an analysis of grade readings by two observers , as shown in tables 1 and 2 , led to the conclusion that observer i had an obvious tendency to see abnormality or scars that were not perceived by remaining colleague .
figure 1a and 2a show perfect agreement on grade of severity , but figure 1b and 2b show those for which interpretations differed .
( a ) ppmag3 scan of a 1-year - old girl with left grade v vesicoureteral reflux . according to our grading system , left kidney 's mag3-gr was iii and right kidney 's mag3-gr was i for both observers .
( b ) ppmag3 scan of a 2-year - old boy with posterior ureteral valve and vesicoureteral reflux .
, right kidney as grade i for first observer and as grade 0 for second observer ( a ) pvdmsa scan of a 8-year - old girl with left grade v vesicoureteral reflux . according to our grading system , left kidney 's dmsa - gr was iii and right kidney 's dmsa - gr was iii for both observers .
( b ) pvdmsa scan of a 6-year - old girl with urinary tract infection .
in clinical practice , dmsa scan considered the standard reference method in the assessment of renal cortical lesions . interpretation is usually only qualitative and differences in reproducibility have been reported previously .
mag3 is mainly a tubular renal imaging agent and used for planar dynamic studies to assess renal parenchymal flow and function and to determine drainage adequacy of the kidneys .
however , due to its high extraction efficiency , mag3 provides high resolution parenchymal images 1 - 4 min after injection and may be suitable for renal cortical scintigraphy .
some investigators have evaluated the use of planar dynamic mag3 scan for investigating the renal parenchymal lesions and variable results were reported in different studies .
the diagnostic value and usability of a method beside accuracy , sensitivity , specificity , and positive and negative predictive values of the method is repeatability and is also associated with high degrees of intra- and interobserver agreements .
dmsa and mag3 scan results affect dramatically diagnosis , treatment type , duration , and follow - up of patients .
correct identification of the scintigraphic results will play an important role in determining the next step .
one of the important indicators of the reliability of a test is intra- and interobserver agreement . for this purpose , there are many studies which investigate intra- and interobserver agreement with evaluation of planar images of dmsa scans , but there are not enough reliable references in the literature on scintigraphic reports in terms of objectivity and standardization . in studies researching agreement between observers by evaluating planar images of dmsa scan have presented different results . while some authors represented good agreement between observers and others suggest that the agreement is poor .
investigations aiming specifically at the evaluation of agreement in the interpretation of renal scintigraphies usually verify the presence of interobserver variability .
the use of standard evaluation criteria is known to increase compliance , therefore , in our study which investigated interobserver agreement , standardized criteria used for assessment of dmsa scan and the results for each parameter was evaluated independently .
, there was no comparative study of inter- and intraobserver agreements of mag3 scan evaluating the renal parenchyma with standard criteria .
good reproducibility was reported when two to four observers had to choose two or three different parameters between normal , abnormal , or equivocal .
in contrast , poor correlation was found when six to seven observers had to quantify the number of scars or to analyze seven different parameters . in a study designed by craig et al . , the kidneys divided into three regions and these regions were evaluated according to goldraich 's grading system and for dmsa planar images high level of agreement was found similar to our study .
goldraich 's graduation displayed a bimodal score distribution which also confirms observations made by craig et al .
the scale , as proposed by goldraich bases the grading on the sum of two separate features : radiopharmaceutical uptake characteristics and the number of renal defects . in a previous study assessing intra- and interobserver variability in the interpretation of dmsa scan using standard criteria by patel et al .
, high levels of intra- ( 95.9% ) and interobserver agreement ( 84.4% ) were demonstrated and there were minor differences in inconsistencies between two kidneys or different kidney zones . in our study , excellent agreement was found among two observers for dmsa - gr and high level for mag3-gr .
the reason for why agreement was better among dmsa - gr than mag3-gr ( tau - b = 0.827 and tau - b = 0.790 , respectively ) will be associated with higher background activity and a little excretion of mag3 through the liver because agreement level was higher in the left kidney than the right .
interobserver variability , especially between grades 0 and i was more than the other grades .
presence of normal variants of the evaluated images may act as an important factor in the differentiation of normal to abnormal .
so , interobserver differentiation of assessments may result from high anatomic variability of kidneys , from persisting fetal lobulation , evident structures of linking parenchyma , the doubling of the pyelocalyceal system , etc .
, differences in the levels of experience among the observers will be an another factor that may reduce the degree of agreement .
it was obvious that the less experienced observer tended to see more renal scars than those with more experienced .
with addition of oblique views will provide a firm basis for clinical decision - making , particularly in kidneys which have photon deficient areas due to dilated calices or unclear contours and with only posterior views , amount of abnormal scans will be overestimated .
the shape , severity , and extent of the renal lesions in the patient groups are also the factors that may affect the level of the concordance of assessment .
while severity of lesion increases and becomes significant , agreement also increases . in our study , with increasing grades , agreement moved towards complete agreement .
the number of criteria used for evaluation in a study affects the statistical correlation , correlation decreases with increasing numbers of criteria as can be seen in our study . in a study with dmsa , iv urography and ultrasonography in 27 children at risk for renal scarring , the percentages of agreement in dmsa scan interpretation for three observers were 90 and 95% for interobserver and intraobserver comparisons , respectively .
in a recent survey reported by de sadeleer et al . , the overall reproducibility was excellent among a large number of nuclear medicine physicians .
the effect of being from the same or different centers was investigated , despite the relatively high agreement among those with the same center , but there was no statistically significant difference between them .
current study provides data about the reproducibility only for a single center and both observers trained in the same center .
further studies are needed to assess for evaluating reproducibility of different centers with the standard criteria . in evaluation of scintigrams , routine application of standard criteria like grading systems , for patients especially who need follow - up , the difference between a previous or subsequent scans can be clearly shown semiquantitatively and can reduce the dependence on the reader . also standardization can be achieved in interpretations between different centers and observers . to minimize differences and to obtain sufficient image quality ,
because final reports will severely affect the patient 's treatment protocol , images should be evaluated systematically and in appropriate time and to act in conjunction with clinicians will be useful . for a better assessment of the differences in interpretation between observers , such studies with larger series of patients should be performed .
although poor correlation was found in the literature when the observers had to quantify the number of scars and parenchymal lesions or to analyze more different parameters , in our study interobserver reproducibility was excellent for pvdmsa scans and good for ppmag3 scans among two observers .
our modified grading system can be used for standardization of reports . such as normal variants ,
some congenital abnormalities and small defects probably constitute the main cause of disagreement among observers in this study .
we conclude that standardization of criteria and terminology in interpretations may result in higher interobserver consistency , improve low interobserver reproducibility and objectivity of renal scintigraphy reports , and improve the quality of reporting of studies .
we propose quantitative measures that reflect some common parameters observed by specialists in the renal scintigraphic studies , attributing numerical values to these parameters , and potentially reducing the subjectivity in the interpretation of visual findings .
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objective : the aim of this study was to investigate the variability in the interpretation of parenchymal abnormalities and to assess the differences in interpretation of routine renal scintigraphic findings on posterior view of technetium-99 m dimercaptosuccinic acid ( pvdmsa ) scans and parenchymal phase of technetium-99 m mercaptoacetyltriglycine ( ppmag3 ) scans by using standard criterions to make standardization and semiquantitative evaluation and to have more accurately correlation.materials and methods : two experienced nuclear medicine physicians independently interpreted pvdmsa scans of 204 and ppmag3 scans of 102 pediatric patients , retrospectively .
comparisons were made by visual inspection of pvdmsa scans , and ppmag3 scans by using a grading system modified from itoh et al . according to this , anatomical damage of
the renal parenchyma was classified into six types : grade 0-v . in the calculation of the agreement rates , kendall correlation ( tau - b ) analysis was used.results:according to our findings , excellent agreement was found for dmsa grade readings ( dmsa - gr ) ( tau - b = 0.827 ) and good agreement for mag3 grade readings ( mag3-gr ) ( tau - b = 0.790 ) between two observers .
most of clear parenchymal lesions detected on pvdmsa scans and ppmag3 scans identified by observers equally .
studies with negative or minimal lesions reduced correlation degrees for both dmsa - gr and mag3-gr.conclusion:our grading system can be used for standardization of the reports .
we conclude that standardization of criteria and terminology in the interpretations may result in higher interobserver consistency , also improve low interobserver reproducibility and objectivity of renal scintigraphy reports .
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stroke is a neurological disease caused by the cutoff of normal blood supply due to vessel
rupture or thrombosis , and it causes brain tissue damage .
motor , sense , recognition ,
language , and perception deficits are typical symptoms of the disease , depending on the
affected areas , size , and the cause of damage1 .
stroke patients mainly experience motor disorders and degeneration
of balancing ability due to unbalanced posture ; this is caused by asymmetric arrangement and
hemiplegia , and this disrupts independent activities of daily living ( adl)2 . the ability to balance is an individual s ability to maintain the center of gravity within
a base region , keeping the body in a balanced state3 .
stroke patients lack balancing ability and show degeneration of
physical function due to a reduction in walking and activity caused by an inappropriate
posture , proprioception malfunction , and abnormal muscle tension4 . to resolve balance problems caused by stroke , the
brunnstrom approach , bobath approach , or proprioceptive neuromuscular facilitation ( pnf ) is
used ; such methods focus on enhancing physical functions and balance by improving active
motor control5 .
pnf utilizes a typical helical or diagonal pattern to stimulate proprioceptive sensation
promote a nerve root response , enhancing functional movement5 , 6 .
it improves muscle
strength , flexibility , and balance ; by applying it on the non - paretic side , force is
transferred to the paretic side , effectively promoting muscle activity6 .
davis7 suggested aquatic pnf lower
extremity patterns for reinforcing muscular strength and enhancing muscle reeducation .
song
and kim8 applied aquatic pnf lower
extremity patterns to patients who had a stroke , which stimulated proprioceptors , thus
improving control and function of the nerve roots while enhancing balance . in an aquatic environment
, the buoyancy allows limbs to be moved more easily with little
strength , enhancing coordination of motion9 .
water resistance also enables the body to move , helping increase
muscle strength , joint movement , and balance10 .
multiple studies had reported pnf lower extremity patterns during
ground - based exercise for stroke patients , but few had reported aquatic pnf .
this study aimed to investigate the effects of aquatic pnf lower extremity patterns on
balance and adl of stroke patients .
six months after receiving a stroke diagnosis via either computed tomography or magnetic
resonance imaging , 20 patients were randomly assigned to a control group ( n = 10 ; 5 males
and 5 females ) or an experimental group ( n = 10 ; 5 males and 5 females ) ; the control group
was assigned to conduct pnf lower extremity patterns on the ground , and the experimental
group was assigned to conduct pnf lower extremity patterns in water .
all participants scored
> 24 points on the mini - mental status examination ( mmse ) , could perform assignments , were
capable of walking 10 m independently , and were classified as > 4 on the brunnstrom scale .
the
protocol was approved by the institutional review board of nambu university and was
conducted in accordance with the ethical standards of the declaration of helsinki .
the
general features of the participants are listed in table 1table 1.general characteristics of subjectseg ( n=10)cg ( n=10)gender ( male / female)5 / 55 / 5age ( years)69.1 3.268.0 3.1height ( cm)167.6 8.2165.9 6.9weight ( kg)67.9 5.966.7 6.7paretic side ( right / left)5 / 55 / 5onset ( months)9.8 1.310.3 1.4meansd , eg : experimental group , cg : control group .
the age of the experimental group was 69.1 3.2 years , height was 167.6
8.2 cm , weight was 67.9 5.9 kg , and time since stroke onset was 9.8 1.3 months .
the age
of the control group was 68.0 3.1 years , height was 165.9 6.9 cm , weight was 66.7
6.7 kg , and time since stroke onset was 10.3 1.4 months .
meansd , eg : experimental group , cg : control group the experimental group conducted pnf lower extremity patterns using the rhythmic initiation
( ri ) method 110 cm below the water surface ; the water temperature was 3133 c .
exercises
were performed in a supine posture after simple stretching ; subjects wore a body ring
between l5 and s1 and a neck collar .
the control group conducted pnf
lower extremity patterns on the ground in a supine posture after simple stretching .
the ri
method starts from passive exercise , proceeds to active resistance exercise , and helps
increase coordination , motor sensation , and balance . the pnf lower extremity patterns
consisted of patterns d1 and d2 .
the d1 pattern ends at
either flexion - adduction - external rotation knee flexion or extension - adduction external
rotation knee extension .
the d2 pattern ends at either flexion - adduction external
rotation knee flexion or extension - adduction - external rotation knee extension .
pnf lower
extremity patterns were conducted 30 minutes / day , 5 days / week for 6 weeks .
balance was measured with the berg balance scale ( bbs ) , timed up and go test ( tugt ) ,
functional reach test ( frt ) , and one leg stand test ( olst ) .
the bbs consists of 14 items and
can be categorized into sitting , standing , and postural changes .
scores in each category
range from 04 , with 56 possible total points ; higher scores indicate better balance .
the
tugt measures the time required to stand up from a chair and shuttle back and forth between
the chair and a spot in front of the subject three times .
the frt measures the distance one
can reach with an arm from a standing posture .
the olst measures how long one can stand on
one foot with the eyes open without placing the other foot on the ground .
adl were measured with the functional independence measure ( fim ) , which consists of 13
items related to mobility and 5 related to recognition .
the items were scored on a scale of
17 with 126 possible total points ; higher scores indicate better independence .
data were analyzed using spss 12.0 ( spss , chicago , il , usa ) for windows .
descriptive
statistics were used for the general features of the participants . a paired t - test was used
to determine pre- and post - experiment differences , and an independent t - test was used to
determine between - group differences .
the changes in the result of the bbs , tug , frt , olst , and fim are listed in table 2table 2.comparison of the results of the bbs , tug , frt , olst , and fim between the
experimental and control groupsgroupprepostd - valuebbseg42.8 1.644.9 1.7 * 2.1 1.7*cg39.9 2.040.6 1.7 * 0.7 0.8tugteg21.9 1.320.1 1.9*1.8 1.3*cg20.4 1.019.7 1.0*0.7 0.6frteg17.7 0.919.0 1.4 * 1.3 0.9*cg16.7 0.617.2 0.4 * 0.5 0.6olsteg4.3 0.85.7 1.1 * 1.4 0.9*cg3.4 0.54.1 0.7 * 0.6 0.7fimeg82.3 2.587.5 3.7 * 5.2 5.3*cg80.1 1.281.4 1.4 * 1.3 1.3meansd , * p<0.05 , d - value : difference value , eg : experimental group ,
cg : control group , bbs : berg balance scale , tugt : timed up and go test , frt :
functional reach test , olst : one leg stand test , fim : functional independence
measure .
the experimental and control groups showed significant differences for all
pre- and post - experiment variables ( p < 0.05 ) . in the between - group comparison ,
the
experimental group was significantly different from the control group ( p < 0.05 ) .
meansd , * p<0.05 , d - value : difference value , eg : experimental group ,
cg : control group , bbs : berg balance scale , tugt : timed up and go test , frt :
functional reach test , olst : one leg stand test , fim : functional independence
measure
the purpose of this study was to investigate the effects of aquatic pnf lower extremity
patterns on balance and adl of stroke patients .
the experimental group showed a significant
improvement in balance and adl after the aquatic pnf ( p < 0.05 ) and had significantly
better balance and adl relative to the control group ( p < 0.05 ) .
for example , performance of 10 weeks of aquatic proprioception exercise by
seniors enhanced their motor abilities11 .
in addition , kim and lee12 pnf reported
that aquatic lower extremity patterns enhanced balance in healthy adults .
moreover , song and
kim8 reported that aquatic pnf
effectively affected the balance of stroke patients .
these results indicate that aquatic pnf
lower extremity patterns help enhance the balance of stroke patients .
pnf , used as a gradual
resistance exercise that employs a helical pattern , maximizes motor unit recruitment through
proprioceptive stimulation5 , 13 .
aquatic pnf promotes the maximum usage of muscle fibers
due to the intense circumstances caused by buoyancy and turbulence ; moreover , the water acts
as a form of resistance , stimulating proprioception and thus helping to improve postural
control and balance8 , 13 , 14 .
the most common method for examining the adl of stroke patients is to use the fim . in the
present study ,
the experimental group showed significant enhancement of adl after the
aquatic pnf ( p < 0.05 ) .
suomi and collier15 reported that the adl of arthritis patients were enhanced after
conducting aquatic exercise , and sato et al.16 reported that the adl of abnormal adults were enhanced after
conducting water exercise .
similar to other studies , enhancement of adl was observed after
conducting aquatic exercise in the present study .
the enhancement of adl was the result of
enabling movement with even a small amount of force .
this was due to the assistance of the
water buoyancy and decreased gravity , reducing the burden on muscles and joints10 , 15 . to promote functional recovery , the paretic side was spontaneously
enabled , thus enhancing the adl and improving functional independence15 , 16 .
the movements
also stimulate shortened muscles , promoting a training effect and enhancing adl17 .
a limitation of this study was that it utilized a small number of participants , and it was
not confirmed that the positive effects persisted .
future research should address these
things when investigating the effect of aquatic pnf lower extremity patterns in stroke
patients .
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[ purpose ] this study investigated the effect of aquatic proprioceptive neuromuscular
facilitation ( pnf ) patterns in the lower extremity on balance and activities of daily
living ( adl ) in stroke patients . [ subjects ] twenty poststroke participants were randomly
assigned to an experimental group ( n = 10 ) or a control group ( n = 10 ) .
the experimental
group performed lower extremity patterns in an aquatic environment , and the control group
performed lower extremity patterns on the ground .
both exercises were conducted for 30
minutes / day , 5 days / week for 6 weeks .
balance was measured with the berg balance scale
( bbs ) , timed up and go test ( tugt ) , functional reach test ( frt ) , and one leg stand test
( olst ) .
activities of daily living were measured with the functional independence measure
( fim ) .
a paired t - test was used to measure pre- and post - experiment differences , and an
independent t - test was used to measure between - group differences .
[ results ] the
experimental and control groups showed significant differences for all pre- and
post - experiment variables . in the between - group comparison , the experimental group was
significantly difference from the control group . [ conclusion ] these results indicate that
performing aquatic proprioceptive neuromuscular facilitation patterns in the lower
extremity enhances balance and adl in stroke patients .
|
white light and extreme ultra violet ( euv ) emission from the polar region of the solar corona shows distinct bright ray like structures known as polar plumes @xcite .
quasi - periodic propagating intensity perturbations are frequently observed in the polar plumes and inter - plume regions with period ranging from 530 minutes .
the measured speed of these propagating disturbances ( pds ) is around 150 km s@xmath0 .
these outward pds are generally interpreted as slow magneto - acoustic waves propagating through the plumes and inter - plumes region because their speeds are similar to the sound speed .
euv observations from solar terrestrial relations observatory ( stereo ) , observed high speed jets of plasma traveling along the plume structures with a mean velocity around 135 km s@xmath0 .
those jets were quasi - periodic with the periodicity of 525 minutes .
@xcite also showed that high - speed repetitive outflows originate near magnetic network elements both in the quiet - sun ( qs ) and coronal holes ( chs ) propagate along plume structures with an average speed @xmath1 120 km s@xmath0 . suggested that the pds are nothing but these jets originating from the upper chromosphere propagate to higher corona and contribute to the solar wind
they further conjectured that these jets will supply adequate energy to the fast solar wind .
@xcite found radially moving radiance variations both in the plume and inter - plume regions .
comparing the apparent outflow speeds at different temperature passbands they concluded that the observed radiance variations represent the material outflows . the quasi - periodic intensity enhancement , the doppler shift and the line width enhancements in coronal structures are also recently interpreted as due to high - speed upflows from spectroscopic observations in magnetic regions of the solar atmosphere @xcite .
@xcite have studied an on - disk plume as seen in aia and their connection to transition region jets seen in iris .
they found that small scale chromospheric jet - like features are linked with the generation of pds within the plume .
@xcite found that spicules seen in aia 304 channels propagate upward and fall back following parabolic paths whereas at the same time they also found that enhanced emissions seen in 171 propagate upward into the corona with speeds of @xmath1 100 km s@xmath0 .
if similar behavior can been seen in the off - limb corona is yet to be explored and is the subject of the present analysis .
recently @xcite claimed that the spicular activities in the solar transition region , as seen in the aia 304 passband , are responsible for the generation of the pds in the polar regions of the corona as observed in the aia 171 images .
however , the exact connection between spicule and pds and on the nature of the pds still remains a mystery .
furthermore for the solar wind studies it is important to have a better understanding on the nature of these pds and their origin .
to find out the spicular connection to the coronal pds , we use simultaneous iris data along with coronal data from aia .
the data was obtained from a coordinated observations using the interface region imaging spectrograph ( iris ) satellite @xcite and the atmospheric imaging assembly ( aia ) instruments @xcite on board the solar dynamics observatory ( sdo ) .
observation was performed from 11:25 ut to 12:55 ut on 21 february 2014 .
slit - jaw images ( sji ) from iris filtergrams centered at 2796 and 1400 , dominated by and emission line , respectively , were analyzed .
aia filtergram images centered at 304 , 171 , and 193 , dominated by , and emission respectively , were also selected for the analysis .
iris 2796 passband is sensitive to emission from plasma at temperatures @xmath110,000 to 15,000 k and iris 1400 is sensitive to temperatures @xmath1 60,000 to 80,000 k. the aia 304 , aia 171 and aia 193 filters response function peaks at 0.05 mk , 0.8 mk and 1.25 mk respectively .
iris observed south pole of the sun in sit - and - stare mode .
we used iris level 2 processed data which is corrected for dark current , flat field and geometrical corrections etc .
all the iris sji were taken with 8 sec exposure time and a cadence of 19 sec .
the pixel size of sji s and aia are @xmath2 and @xmath3 respectively .
the aia images were taken with a 12 sec cadence .
pixel size of aia is interpolated to the match with iris for easier comparison .
all the aia channels were co - aligned and de - rotated to compensate for solar rotation .
the iris sjis and aia images were co - aligned using iris 1400 and aia 1600 images ( as described in @xcite ) .
figures [ aia_iris ] ( a)(e ) show the south polar region of the sun as seen from iris and aia channels .
we should point out here that coronal hole was not seen clearly on the south pole during the observation , hence the the region can be characterized as quiet sun . furthermore , distinct extended plume structures were not so clearly visible from original images .
usually when there is a underlying deep coronal hole present , plume structures are clearly visible .
pds in the corona often repeat with a time scale of 1030 minutes . to find the global behavior of pds , we constructed power maps in the period band of 1030 minutes .
we performed wavelet analysis in time series at each pixel location to estimate the distribution of power .
a background trend is removed by subtracting a 30 minutes running average of the original time series to remove periods longer than 30 minutes .
figure [ aia_iris ] ( f)(j ) show the distribution of power ( referred to as powermaps ) within the 1030 minutes period band of iris 2796 , iris 1400 , aia 304 , aia 171 and aia 193 channels .
the powermaps of iris 2796 , iris 1400 and aia 304 show the power in this period band is limited to lower heights ( within @xmath120@xmath4 from the solar limb ) .
these channels are sensitive to the chromospheric and transition region temperature which is dominated by spicular activity and probably due to this the power is limited to lower heights . at some places we note that the strong power is seen up to higher heights . in aia 171 and aia 193
powermaps , we observed two kinds of features , one reaching to larger distances ( see the location of s1 slit ) and other which have comparatively higher power but confined to shorter distances ( see the location of s2 slit ) . in the next subsection we will study in details the behaviour of pds in these regions ( within s1 and s2 ) . in this subsection , we focus on the plume like structure marked by the s1 slit in figure [ aia_iris ] for a detailed time evolution of pds .
we constructed x - t map to study the temporal evolution of the region inside the s1 slit .
the signal in the aia channels is low for off - disk features , hence to improve the signal to noise , we have used a thick slit of width of 3.32@xmath4 .
the average intensity along the width of the slit was used to construct the x - t maps of different channels .
the x - t map of aia 171 and 193 were processed by removing a smoothed background trend along time axis to enhance the visibility of the alternating ridges .
the results are shown the figure [ xt_s1 ] .
the x - t maps of the iris 2796 , iris 1400 and aia 304 which are sensitive to chromospheric and transition region temperatures show evolution of several spicules . on the other hand
the dark and bright ridges extended over longer distances are seen in the aia 171 and 193 channels .
the zoomed view of a portion of the x - t map is shown in the bottom panels of the same figure .
the temporal evolution of spicules are seen in iris 2796 , iris 1400 and aia 304 appears to have sub - structures rising and falling in all passbands .
it appears that they roughly follow parabolic path as seen in many spicules .
contours are over - plotted by choosing some intensity threshold on the iris 2796 , iris 1400 and aia 304 channels which are shown in black , orange and green contours respectively .
it covers the envelope of the spicular temporal evolution .
these three contours are also overplotted in the aia 171 and 193 x - t maps .
the trajectory of the pds are marked with red dashed curve as shown in zoomed aia 171 and 193 panels of figures [ xt_s1 ] and [ xt_s2 ] .
similar procedure was adopted for slit s2 analysis .
the slit width of the slit s2 is same as s1 .
the x - t maps for different channels are shown in figure [ xt_s2 ] . in the lower panels of figures [ xt_s1 ] and [ xt_s2 ] ,
we note that the start of trajectory of pds is almost co - temporal with the time of the rise of the spicular envelope .
we also note that the falling of the spicular envelope is followed by brightenings and generation of another pd in aia 171 and 193 .
it is worth noting that pds in figure [ xt_s1 ] ( following a plume like structure ) are propagating to higher heights ( 65 mm ) as compared to pds in figure [ xt_s2 ] which seems to propagate roughly about 30 mm .
thus , power was confined to lower heights at slit s2 location . to follow the pds and its connection with rapidly evolving spicular activities we produce composite x - t plot ( figure [ vel2 ] ) .
the iris channels corresponding to the bottom part of the maps ( as marked ) allows to identify the spicules and its temporal evolution whereas the aia channels corresponding to the upper part of the maps allow us to identify the pds quite clearly . in order to see the alternating ridges
clearly we enhance the contrast by subtracting the smooth background in x - t maps .
this procedure is followed for aia channels ( i.e , upper part of the maps in figure [ vel2 ] ) . for iris channel ( lower part of the maps ) no background subtraction is performed because no enhancement in lower part of x - t maps is needed .
it further demonstrates that when a spicule is observed by the chromospheric channel of iris a pd seems to be generated and/or amplified in the aia coronal channels .
this also confirms that the pds seems to be quasi - periodic with a periodicity which is governed by the repetition time scale of occurrence of the spicules . from this figure
we also fit the ridges manually using eye estimation and found the range of velocities from 98 - 148 km s@xmath0 in aia 171 and 103 191 km s@xmath0 in aia 193 .
since there is a large uncertainty in the measured speed thus we can not confirm if we observe different speeds in the two different channels .
we find the speeds of spicules from 22 91 km s@xmath0 corresponding to iris 1400 images and 16 57 km s@xmath0 for iris 2796 images .
since the speeds are higher than sound speed at chromospheric levels these spicules could be generated by reconnection at lower heights .
pds are ubiquitous in the solar atmosphere and recently it has been suggested by @xcite that spicules can trigger coronal pds . from their study using the aia data alone
they provided a possible link of spicular activities with the generation of pds .
they used the aia 304 channel to identify the spicules .
they did not comment on the nature of the pds as well .
we extended that work using the higher cadence and higher resolution iris spectral images to study the dynamical behaviour of the spicular activity and while combining aia channels we are able to confirm the link with a better confidence .
we feel a combination of chromospheric and transition region channels of iris and transition region and coronal channels of aia is better suited for this kind of study .
we also point out a possible connection between the small scale , short lived cool spicular structures with the very large scale long lived hot plume structures . we find that the start of trajectory of pds is almost co - temporal with the time of the rise of the spicular envelope and the spicular material fall is co - temporal with brightenings followed by the generation of another pd in aia 171 and 193 .
co - temporal generation of spicules and pds suggest that they might have a common origin .
we should point out here that there could be a projection effect and we can not rule out the possibility that the spicules and pds may not be in the same position but statistically we find co - temporal and co - spatial match in most of the cases studied .
figure [ vel2 ] illustrates the quasi - periodic nature of the spicular activity as revealed by the iris spectral image sequences and its relation to coronal pds as recorded by the coronal aia channels .
we propose that reconnection like processes generate the spicules and waves simultaneously .
the waves escape while the cool spicular material falls back .
the pds as seen have a mixed signature of waves and flows at lower heights while at the extended coronal heights the wave signature is dominant .
there is also a signature of acceleration of these pds as represented by the curved red dashed lines in the lower panels of figures [ xt_s1 ] & [ xt_s2 ] .
the nature of pds in our case is not always confirmatory but , presence of alternating bright and dark ridges and reaching of accelerating pds to higher heights in slit position s1 ( see figures [ xt_s1 ] , [ vel2 ] ) suggest more wave like nature while manual fitting of pds to derive speeds is not accurate enough to confirm wave like behaviour .
we should also point out that we did not have any coronal holes in the polar regions and thus the presence of plume like structures were also not very clear at all locations .
at slit position s2 we find that pds are not going to higher heights .
thus , power is confined to lower heights close to the limb .
the enhancement in power is due to repeated generation of cool spicular material seen as dark features in hot aia channels . due to almost straight ridges , poor signal to noise
, we could not measure the speeds of these pds convincingly and thus can not comment on their nature .
it is also possible that at the time of the generation of spicules ( due to heating together with reconnection and/or driven by p - modes ) the hot material can escape following the open magnetic field lines and thus cause intensity enhancements in the aia 171 and 193 channels while spicular material falls back because it is denser and cooler than escaping hot material . with the existing spectral imaging data the connection of spicules and pds are subject to line of sight uncertainties . for further confirmation and better understanding on the nature of the pds
, we need simultaneous chromospheric and coronal long spectral time sequences .
+ we thank the iris team for proving the data in the public domain .
we also thank the referee for valuable comments .
iris is a nasa small explorer mission developed and operated by lmsal with mission operations executed at nasa ames research center and major contributions to downlink communications funded by the norwegian space center ( nsc , norway ) through an esa prodex contract .
|
spicules are small hairy like structures seen at the solar limb mainly at chromospheric and transition region lines .
they generally live for 3 - 10 minutes .
we observe these spicules in a south polar region of the sun with a coordinated observations using the interface region imaging spectrograph ( iris ) and the atmospheric imaging assembly ( aia ) instruments on board the solar dynamics observatory .
propagating disturbances ( pds ) are observed everywhere in the polar off - limb regions of the sun at coronal heights . from this simultaneous observations
we show that the spicules and the pds may be originated by a common process . from space - time maps we find that the start of the trajectory of pds is almost co - temporal with the time of the rise of the spicular envelope as seen by iris slit - jaw images at 2796 and 1400 . during the return of spicular material ,
brightenings are seen in aia 171 and 193 images .
the quasi - periodic nature of the spicular activity as revealed by the iris spectral image sequences and its relation to coronal pds as recorded by the coronal aia channels suggest that they have a common origin .
we propose that reconnection like processes generate the spicules and waves simultaneously .
the waves escape while the cool spicular material falls back .
|
SECTION 1. FINDINGS.
Congress makes the following findings:
(1) According to the National Science Board's 2008 Science
and Engineering Indicators, only 5 percent of American college
graduates major in engineering, compared with 13 percent of
European students and 20 percent of students in Asia.
(2) Although United States fourth graders score well
against international competition, United States students fall
near the bottom or dead last by 12th grade in mathematics and
science, respectively.
(3) Admissions requirements for undergraduate engineering
schools include a solid background in mathematics (algebra,
geometry, trigonometry, and calculus) and science (biology,
chemistry, and physics), in addition to courses in English,
social studies, and humanities.
(4) According to the Bureau of Labor Statistics, overall
engineering employment is expected to grow by 11 percent over
the 2008 through 2018 decade, and, as a group, engineers earn
some of the highest average starting salaries among individuals
holding bachelor's degrees.
(5) According to the Department of Labor, engineers should
be creative, inquisitive, analytical, and detail oriented.
Engineers should be able to work as part of a team and to
communicate well, both orally and in writing. Communication
abilities are becoming increasingly important as engineers
interact more frequently with specialists in a wide range of
fields outside engineering.
(6) Exposure to project- and problem-based learning, in a
competitive team environment, gives 9th through 12th graders
the skills the students need to be successful in engineering
programs of study and engineering careers.
(7) According to Brandeis University's Center for Youth and
Communities, participants in FIRST Robotics (a nonprofit
organization that inspires young people to be science and
technology leaders by engaging the young people in mentor-based
programs)--
(A) are more likely to attend college full-time
than nonparticipants (88 percent versus 53 percent);
(B) are nearly 2 times as likely to major in a
science or engineering field; and
(C) are more than 3 times as likely to have majored
specifically in engineering.
SEC. 2. DEFINITIONS.
In this Act:
(1) Eligible entity.--The term ``eligible entity'' means--
(A) a local educational agency; or
(B) if a local educational agency chooses not to
apply for a grant under this Act, a secondary school
served by the nonapplying local educational agency.
(2) Local educational agency.--The term ``local educational
agency'' has the meaning given the term in section 9101 of the
Elementary and Secondary Education Act of 1965 (20 U.S.C.
7801).
(3) Poverty line.--The term ``poverty line'' has the
meaning given the term in section 9101 of the Elementary and
Secondary Education Act of 1965.
(4) Secondary school.--The term ``secondary school'' has
the meaning given the term in section 9101 of the Elementary
and Secondary Education Act of 1965.
(5) Secretary.--The term ``Secretary'' means the Secretary
of Education.
(6) STEM.--The term ``STEM'' means science, technology,
engineering, or mathematics.
SEC. 3. INNOVATIVE INSPIRATION SCHOOL GRANT PROGRAM.
(a) Goals of Program.--The goals of the Innovation Inspiration
grant program are--
(1) to provide opportunities for eligible entities to
support non-traditional STEM education teaching methods;
(2) to support the participation of students in nonprofit
robotics or STEM competitions;
(3) to foster innovation and broaden interest in and access
to careers in the STEM fields by investing in programs
supported by teachers and professional mentors who receive
hands-on training and ongoing communications that strengthen
the interactions of the teachers and mentors with--
(A) students on competitive robotics or STEM teams;
and
(B) other students in the STEM classrooms and
communities of the teachers and mentors; and
(4) to encourage the collaboration among students,
engineers, and professional mentors to design, build, program,
and compete in challenges with sophisticated robots.
(b) Program Authorized.--
(1) In general.--The Secretary is authorized to award
grants, on a competitive basis, to eligible entities to enable
the eligible entities--
(A) to promote STEM in secondary schools;
(B) to support the participation of secondary
school students in robotics or STEM competitions; and
(C) to broaden secondary school students' access to
careers in STEM.
(2) Duration.--The Secretary shall award each grant under
this Act for a period of not more than 5 years.
(3) Amounts.--The Secretary shall award a grant under this
Act in an amount that is sufficient to carry out the goals of
this Act.
(c) Application.--
(1) In general.--Each eligible entity desiring a grant
under this Act shall submit an application to the Secretary at
such time, in such manner, and containing such information as
the Secretary may reasonably require.
(2) Contents.--The application shall, at a minimum, include
a description of how the eligible entity will--
(A) carry out each of the elements of a robotics or
STEM competition described in subparagraphs (B) through
(F) of subsection (d)(1);
(B) establish robotics or STEM competition programs
to inspire students in grades 9 through 12 to become
innovators in STEM;
(C) identify and recruit mentors for the programs
described in subparagraph (B) and the participants in
the programs;
(D) support teachers who lead the programs and
participants in the programs through stipends or other
incentives;
(E) recruit young women and individuals from
populations traditionally underrepresented in the STEM
fields to participate in the programs;
(F) identify public and private partners that can
support the programs with cash or in-kind
contributions;
(G) plan for sustaining the programs financially
beyond the grant period; and
(H) evaluate the grant project and the results of
the grant project among participating students,
including--
(i) comparing students who participate in
the grant project to similar students who do
not so participate; and
(ii) evaluating--
(I) secondary school graduation
rates;
(II) college-going rates;
(III) the number of students taking
advanced STEM related secondary school
classes; and
(IV) the ability of students
participating in the grant project to
partner with professional mentors.
(3) Preference.--In developing the criteria for grant
awards under this Act, the Secretary shall give preference to
an application that addresses the needs of--
(A) a rural or urban school;
(B) a low-performing school or school district; or
(C) a local educational agency or school that
serves--
(i) not fewer than 10,000 children from
families with incomes below the poverty line;
or
(ii) a student population not less than 20
percent of whom are from families with incomes
below the poverty line.
(d) Uses of Funds.--
(1) In general.--Each eligible entity that receives a grant
under this Act may use the grant funds for the following:
(A) STEM education and career activities.--
Promotion of STEM education and career activities.
(B) Purchase of parts.--The purchase of parts
required to support participation in team robotics or
STEM competitions.
(C) Teacher incentives and stipends.--Incentives
and stipends for teachers involved in robotics or STEM
competitions.
(D) Support and expenses.--Support and expenses for
participation in regional and national robotics or STEM
competitions.
(E) Additional materials and support.--Additional
materials and support, such as equipment, facility use,
and other expenses, directly associated with robotics
or STEM competitions.
(F) Evaluation.--Carrying out the evaluation
described in subsection (c)(2)(H).
(2) Nonprofit competitions.--Grant funds made available
under this Act for robotics or STEM competitions shall only be
used to support participation in nonprofit robotics or STEM
competitions.
(3) Administrative costs.--Each eligible entity that
receives a grant under this Act may use not more than 2 percent
of the grant funds for administrative costs related to the
administration of the project supported by the grant.
(e) Matching Requirement.--
(1) In general.--Subject to paragraph (2) each eligible
entity that receives a grant under this Act shall secure,
toward the cost of the activities assisted under the grant,
from non-Federal sources, an amount equal to 50 percent of the
grant. The non-Federal contribution may be provided in cash or
in kind.
(2) Waiver.--The Secretary may waive all or part of the
matching requirement described in paragraph (1) for an eligible
entity if the Secretary determines that applying the matching
requirement would result in a serious financial hardship or a
financial inability to carry out the goals of the grant
project.
(f) Supplement, Not Supplant.--Grant funds provided to an eligible
entity under this Act shall be used to supplement, and not supplant,
funds that would otherwise be used for activities authorized under this
Act.
(g) Secretary's Activities.--
(1) Communications and outreach program.--From amounts
appropriated under subsection (h) for a fiscal year, the
Secretary shall establish a communications and outreach program
to publicize--
(A) non-traditional teaching methods applicable to
STEM; and
(B) the availability and application procedure for
the grant program established by this Act.
(2) Evaluation program.--The Secretary shall establish an
evaluation program to determine the efficacy of the grant
program established by this Act, which shall include assessing
the impact, of student participation in the grant project
assisted under this Act, on future course-taking and
postsecondary study, by comparing students so participating to
similar students who do not so participate.
(h) Authorization of Appropriations.--
(1) In general.--There are authorized to be appropriated to
the Secretary to carry out this Act such sums as may be
necessary for each of the fiscal years 2011 through 2015.
(2) Limitations.--Of the amounts appropriated under
paragraph (1) for a fiscal year--
(A) not more than 1 percent shall be used for the
communications and outreach program under subsection
(g)(1); and
(B) not more than 1 percent shall be used for the
evaluation program under subsection (g)(2).
|
Authorizes the Secretary of Education to award competitive matching grants to local educational agencies (LEAs) to: (1) promote science, technology, engineering, and mathematics (STEM) in secondary schools; (2) support the participation of secondary school students in nonprofit robotics or STEM competitions; and (3) broaden secondary school students' access to STEM careers.
Allows secondary schools to apply for such grants if their LEA does not.
Gives priority to grant applications that address the needs of: (1) rural or urban schools; (2) low-performing schools or school districts; or (3) LEAs or schools that serve at least 10,000 poor children or a student population at least 20% of which is poor.
Authorizes the Secretary to waive all or part of the matching requirement for financially-strapped LEAs or schools.
Directs the Secretary to: (1) publicize the grant program and nontraditional STEM teaching methods; and (2) evaluate the efficacy of the grant program.
|
one of the most active areas in the condensed matter physics is the search for new methods which could capture essential features of electron correlations and disorder in a controllable manner .
perhaps the most successful and widely used methods are the dynamical mean field theory ( dmft)@xcite and the coherent potential approximation ( cpa).@xcite both these methods are exact in infinite dimensions . however , at finite dimensions they neglect nonlocal correlations .
this limitation has raised interests in developing of quantum cluster methods which could capture nonlocal correlations .
the most successful of self consistent quantum cluster methods are the molecular coherent potential approximation ( mcpa ) for disorder systems,@xcite and the cellular dynamical mean field theory ( cdmft)@xcite and the dynamical cluster approximation ( dca)@xcite for correlated electron systems . in these quantum cluster theories
the system lattice is split into a series of clusters .
both local and nonlocal correlations within the clusters are treated exactly , whereas the nonlocal correlations between different clusters are treated in a mean - field approximation .
the mean field is taken into account by mapping the lattice problem onto a self - consistent effective cluster problem .
the mcpa and cdmft are formulated on the real space , and share a common microscopic definition . within the cdmft ( or the mcpa ) the cluster green function
is calculated with open boundary conditions .
the dca is traditionally formulated in the reciprocal space .
it is based on the idea of discretizing irreducible quantities on the reciprocal space . within the dca the cluster green function
is calculated with periodic boundary conditions . due to the difference of boundary conditions it seems that the dca and the cdmft ( or the mcpa ) have different microscopic definitions .
for instance , the cdmft can be formulated within the self - energy functional approach , whereas it seems that the dca can not be.@xcite there is also a view of the dca in the real space representation which shows a relation between the dca and cdmft.@xcite the view is based on an unitary transformation of the hopping matrix .
however , the interaction part still remains unchanged . in this paper
we show that the dca and the cdmft share a common microscopic definition through a canonical transformation .
the canonical transformation is similar to the unitary transformation which was used to view the dca in the real space .
it periodizes the fermions in the cluster space , that the cluster green function has periodic boundary conditions .
we apply the canonical transformation to the whole hamiltonian , and in the presence of a constrain which prevents the umklapp momentum transfer from the superlattice to the cluster space we obtain a periodized hamiltonian .
the umklapp momentum transfer appears when the sum of two momenta of the superlattice is beyond the first brillouin zone , and is solely due to the imaginary superlattice construction of clusters with periodic boundary conditions . within the periodized hamiltonian
the dca can be derived from the cdmft . in the such way
, the dca and the cdmft can be unified into a common microscopic background .
the derivation also gives the microscopic background of the discretization of irreducible quantities on the reciprocal space , and clarifies the approximation nature of the dca .
the present paper consists of two parts . in the first part
a derivation of the dca from the cdmft through the canonical transformation for fermions is presented .
the second part is concerned with the cluster perturbation theory ( cpt).@xcite the cpt is also a quantum cluster approach . however , in difference with the cdmft or the dca , the cpt does not have the self consistency .
the cpt can be viewed as the first term of a systematic expansion around strong coupling . however , within the cpt the cluster green function is calculated with open boundary conditions , that the wave vector within a cluster is no longer a conserved quantum number .
there are also several approaches which generate periodic boundary conditions for the cpt .
one is to add appropriate hopping terms and then subtract them within strong coupling perturbation theory.@xcite however , this approach give results which are less accurate than the ones from open boundary conditions.@xcite the other approach adapts the periodicity of the clusters from the dca .
it was used to study the ising model.@xcite in this paper we present the periodic cluster perturbation theory for fermion systems . the periodic cluster perturbation theory ( pcpt )
is the cpt formulated for the periodized fermions which are obtained after making the canonical transformation .
the pcpt has truly the small parameter @xmath3 , where @xmath1 is the cluster linear size .
it turns out that the pcpt converges quadratically in @xmath3 , whereas the cpt converges linearly in @xmath3 .
this is also tested on the study of an exact solvable model .
the plan of the present paper is as follows . in sec .
ii we present the canonical transformation which transforms the original fermions onto periodized ones . in sec .
iii we derive the dca from the cdmft after making the canonical transformation .
the pcpt is presented in sec .
iv . in this section
we also study an exact solvable model in both the direct and periodized forms .
finally , the conclusion and remarks are presented in sec .
we present a periodization for fermions through a canonical transformation of fermionic operators . for an illustration a fairly general model of correlated electron systems
is considered .
the hamiltonian of the model reads @xmath4 where @xmath5 .
@xmath6 ( @xmath7 ) is the creation ( annihilation ) operator for fermion with spin @xmath8 at lattice site @xmath9 .
@xmath10 is the hopping integral , and @xmath11 is the interaction strength .
we will consider a hypercubic lattice of linear size @xmath12 with the lattice constant @xmath13 on @xmath14 dimensions .
the number of lattice sites thus is @xmath15 .
the lattice is divided into a set of identical clusters of linear size @xmath1 .
the number of lattice sites inside a cluster thus is @xmath16 .
the set of the clusters form a superlattice .
we use letters @xmath9 , @xmath17 , ... to label the lattice site of the original lattice , and use @xmath18 to denote the position of site @xmath9 .
letters @xmath19 , @xmath20 , ... are used to denote the wave vectors of the reciprocal space of the original lattice .
capital letters @xmath21 , @xmath22 , ... are used to label the origin of the clusters .
the origin coordinate of clusters are denoted by @xmath23 , and the wave vectors of the reciprocal space of the superlattice are denoted by @xmath24 , @xmath25 , ... the lattice sites inside a cluster are labeled by @xmath26 , @xmath27 , ... their position is denoted by @xmath28 , @xmath29 , ... and the wave vectors of the reciprocal space of the cluster are denoted by @xmath30 , @xmath31 , ...
thus @xmath32 , @xmath33 , ... note that @xmath34 , since @xmath35 , and @xmath36 , where @xmath37 , @xmath38 are integer .
we use the greek letter @xmath8 to denote the spin ( or other quantum ) variables . with these notations
we rewrite the operators and model parameters as @xmath39 , @xmath40 , @xmath41 , ... denoting @xmath42 , @xmath43 the fourier transform of @xmath6 , @xmath7 , the hamiltonian ( [ h ] ) can be rewritten in the reciprocal space representation @xmath44 where @xmath45 and @xmath46 are the fourier transformation of @xmath10 and @xmath11 , respectively , i.e. , @xmath47 we introduce operators @xmath48 one can check that these operators satisfy the anticommutation relations @xmath49 where @xmath50 . since the anticommutation relations are preserved , the transformation ( [ t1a])-([t1b ] ) is canonical .
the inverse transformation reads @xmath51 we also introduce other operators in the real superlattice space @xmath52 one can check that these operators ( [ t3a])-([t3b ] ) also satisfy the fermionic anticommutation relations .
they annihilate or create a fermion at site @xmath53 .
the transformation ( [ t3a])-([t3b ] ) can be viewed as the fourier transformation for the fermion operators @xmath54 , @xmath55 in the superlattice space . from eqs .
( [ t3a])-([t3b ] ) and ( [ t1a])-([t1b ] ) , one can show that @xmath56 in deriving eqs .
( [ t4a])-([t4b ] ) we have used @xmath57 . since @xmath58 , one can see that the fermionic operators @xmath59 , @xmath60 are periodic in the indexes @xmath26 , whereas the original ones @xmath61 , @xmath62 are not .
the fermion created by @xmath60 is periodic in both the superlattice and cluster spaces . due to the periodic property
we call @xmath59 , @xmath60 the periodized fermion operators .
the periodicity allows to perform the fourier transformation of @xmath59 , @xmath60 in the superlattice and cluster spaces @xmath63 we want to emphasise here that both @xmath24 and @xmath30 should be restricted to the first brillouin zones of the superlattice and cluster spaces . from eqs .
( [ t4a])-([t4b ] ) we obtain immediately @xmath64 , @xmath65 .
however , these relations are valid only for momenta in the first brillouin zones .
thus , from the hamiltonian ( [ hp ] ) we obtain @xmath66 note that in hamiltonian ( [ hpn ] ) all sums over momenta are restricted to the first brillouin zones .
moreover , when @xmath67 and @xmath68 are beyond the first brillouin zone , one has to translate them back to the first brillouin zone , thus the momentum sums still are over the full first brillouin zone .
equivalently , the momenta of the periodized fermion operators take values @xmath69 . in deriving the hamiltonian ( [ hpn ] )
we have used the following restriction @xmath70 where @xmath71 , @xmath72 are arbitrary momenta which are either zero or a vector of the reciprocal superlattice space .
@xmath71 , @xmath72 are also the momenta of the reciprocal cluster space .
@xmath73 just means an umklapp process on the superlattice , and @xmath72 can be interpreted as a momentum transfered by the umklapp process from the superlattice to the cluster space .
the first line of eq .
( [ const ] ) is exact , while the second line is a particular restriction .
this restriction prevents the momentum transfer in the umklapp processes of the superlattice .
the umklapp processes appear when the sum of two momenta of the superlattice is beyond the first brillouin zone , and they transfer a momentum modulo a vector of the reciprocal superlattice to the reciprocal cluster space that generate a momentum nonconservation .
however , the such momentum transfer is unphysical , it is solely due to the imaginary discretization of the original lattice into superlattice of clusters with periodic boundary conditions . in order to maintain the correct physics
, one has to impose a constrain which forbids the umklapp momentum transfer on the superlattice . the restriction ( [ const ] )
is the constrain of the superlattice construction .
as we will see later on an example of exact solvable model , the constrain indeed leads the periodized hamiltonian ( [ hpn ] ) to the exact solution . performing the fourier transformation ( [ t4ia])-([t4ib ] ) , from the hamiltonian ( [ hpn ] ) we obtain @xmath74 where the hopping integral and interaction of the periodized fermions now are @xmath75 one can notice that @xmath76 , @xmath77 are cyclic in the indexes @xmath26 , @xmath27 , whereas @xmath78 , @xmath79 are not .
this means that the fourier transformation of @xmath76 and @xmath77 are diagonal in the reciprocal space .
denoting @xmath80 , @xmath81 the fourier transformation of @xmath76 , @xmath77 , one can see immediately from eqs .
( [ hop])-([int ] ) that @xmath82 , @xmath83 .
note that the hopping term ( [ hop ] ) was also obtained previously by employing an unitary transformation.@xcite the unitary transformation is similar to the canonical transformation for fermion operators . beside the periodicity , the periodized hopping ( [ hop ] ) and interaction ( [ int ] )
are quite different from the original hopping and interaction , respectively .
they may connect those lattice sites that the original ones do not .
for instance , if the original hopping is nearest neighbor then the hopping only couples the nearest neighbor sites either within the clusters , or on the cluster boundaries of the nearest neighbor clusters .
however , in the same case the periodized hopping can couple a lattice site with any other lattice site .
the hamiltonian ( [ h1 ] ) is adequate to quantum cluster methods with periodic boundary conditions .
next , we consider the one - particle green function of the periodized fermions @xmath84 without difficulty one can show that @xmath85 where @xmath86 is the green function of the original fermions .
equation ( [ g1 ] ) shows that the green function of the periodized fermions is diagonal in the reciprocal cluster space .
we immediately obtain @xmath87 equation ( [ gg1 ] ) expresses the identity of the green functions of the original fermions and of the periodized fermions .
the dyson equation of the green function @xmath88 reads @xmath89^{-1 } = z\hat{i } -\hat{\bar{t}}(\mathbf{k } ) - \hat{\sigma}(\mathbf{k},z ) , \end{aligned}\ ] ] where the hat symbol denotes the matrix notation in the cluster space .
@xmath90 is the self energy .
since the green function @xmath91 and the hopping @xmath92 are diagonal in the reciprocal cluster space , the self energy @xmath90 must diagonal in the reciprocal cluster space too .
this is consistent with the hamiltonian ( [ h1 ] ) , where both the hopping and interaction terms are diagonal .
with the periodized hamiltonian ( [ h1 ] ) we can derive the dca from the cdmft ( or from the mcpa ) . applying the cdmft to the periodized fermions we obtain @xmath93^{-1 } .
\label{s1 } \end{aligned}\ ] ] the hopping matrix @xmath92 is the fourier transformation of the periodized hopping ( [ hop ] ) in the superlattice space , i.e. , @xmath94 the self energy @xmath95 is determined from an effective single cluster problem .
the action of the effective single cluster is @xmath96 where @xmath97 plays the role of the effective mean field acting on the cluster .
the interaction in the effective single cluster is obtained from eq .
( [ int ] ) @xmath98 the self consistency requires the identity of the cluster green function obtained from the effective single cluster problem ( [ seff ] ) and the cluster green function of the original cluster , i.e. , @xmath99^{-1 } .
\label{s2}\end{aligned}\ ] ] since in the reciprocal cluster space the lattice green function @xmath100 and the self energy @xmath95 are diagonal , the green function of the effective medium @xmath101 must be diagonal too .
after making the fourier transformation , we obtain from eqs .
( [ s1 ] ) , ( [ s2 ] ) @xmath102 since @xmath103 , @xmath104 , and @xmath105 we recover the dca equations
. equations ( [ s1])-([s2 ] ) can be viewed as the dca equations formulated in the real cluster space .
originally , the dca is formulated in the reciprocal space.@xcite it is based on the idea of discretizing irreducible quantities on the reciprocal space . later , the dca was also viewed in the real space by introducing an unitary transformation for the hopping matrix.@xcite however , in this view only the hopping term is transformed , whereas the interaction term remains unchanged . as a consequence ,
the hopping and interaction terms are not treated on an equal footing .
it correctly recovers the dca only for a local single - site interaction . in the presented approach both the hopping and interaction terms
are treated on an equal footing .
it also clarifies why within the dca the lattice quantities , for instance the hopping term in the lattice green function ( eq . ( [ hopdca ] ) ) , are unchanged , whereas the cluster quantities , for instance the cluster interactions ( eq . ( [ ueff ] ) ) , are discretized or coarse grained .
thus , the dca can be used in both the reciprocal and real spaces . in the real space
the dca is just the cdmft applied to the periodized hamiltonian ( [ h1 ] ) . due to this formulation
the dca has the properties of the cdmft .
for instance , the dca can also be formulated within the self - energy functional approach in the real space by the same way as of the cdmft.@xcite so far we have shown that both the dca and cdmft share a common microscopic definition .
they are related each other through the canonical periodization transformation .
an extensive discussion about the two methods is already given in the recent review.@xcite
the cpt is also a quantum cluster approach , although it does not have the self consistency.@xcite in this section we present a cpt with periodic boundary conditions .
we refer it as pcpt .
basically , the pcpt is the cpt applied to the periodized fermions .
a similar pcpt which employs the formulation of the dca for spin systems was used previously to study the ising model.@xcite we will consider the system with the nearest neighbor hopping . in the periodization version
the hopping ( [ hop ] ) is no longer only nearest neighbor .
it may couple a lattice site with any other lattice site .
as the cpt , the pcpt splits the intra- and inter - cluster parts of the hopping term .
the intra - cluster part of the hamiltonian is @xmath106 where @xmath107 , and @xmath108 .
the inter - cluster part is @xmath109 where @xmath110 .
here we have neglected the inter - cluster interactions .
originally , the cpt is formulated for local single - site interactions , thus the inter - cluster interactions are absent .
often quantum cluster approaches either neglect the inter - cluster interactions or treat them in a static mean - field approximation
. however the inter - cluster interactions can be incorporated beyond the static mean - field approximation by employing a self consistent approach.@xcite note that the cluster hopping @xmath111 may couple any sites within the cluster . at a finite cluster
it is reduced by a factor of @xmath0.@xcite the inter - cluster hopping @xmath112 for large linear cluster size @xmath1 compared to its counterpart @xmath113 of the original cpt.@xcite the nature of the approximation of the cpt is a strong coupling expansion in which the small parameter is the inter - cluster hopping.@xcite therefore in the pcpt the small parameter is truly @xmath3 . within the pcpt
the cluster hamiltonian ( [ hc ] ) is solved exactly .
we obtain the dyson equation for the cluster green function @xmath114 where @xmath115 , and @xmath116 is the cluster self energy . here the dyson equation is written in the reciprocal space representation .
we can make the fourier transformation in the cluster space because the fermions are periodized in the cluster space , thus the cluster green function and self energy are diagonal in the reciprocal space . as the cpt , within the pcpt
the self energy of the lattice green function is approximated by the cluster self energy .
thus we obtain @xmath117 since @xmath118 and @xmath82 we finally obtain the green function of the original fermions @xmath119 equations ( [ cpt1])-([cpt3 ] ) are the principal equations of the pcpt . as the cpt ,
the pcpt is exact in the limits @xmath120 , @xmath121 , and @xmath122 for local interactions .
the pcpt is formulated in the reciprocal space , hence it avoids the diagonalizations of the green function in both real and reciprocal spaces , that significantly reduces the computational time compared to the cpt .
note that the present pcpt is different to the ordinary periodic cpt,@xcite where the periodicity is taken into account by including additional hoppings . in the ordinary periodic cpt
the hopping is still nearest neighbor , while in the present pcpt it is no longer only nearest neighbor .
moreover , in the present pcpt all hoppings within a cluster are treated exactly , whereas in the ordinary periodic cpt the adding and subtracting hoppings are treated on different footings . for an illustration we study the one dimensional large-@xmath123 model , originally introduced by affleck and marston in two dimensions.@xcite the model was also used for comparison between the dca and cdmft schemes.@xcite we will compare the pcpt and cpt schemes to its exact solution .
the hamiltonian of the model reads @xmath124 where @xmath125 denotes the nearest neighbor sites , and @xmath126 . as usually ,
@xmath113 is the hopping integral , @xmath22 is the exchange strength , and @xmath127 is the chemical potential .
we will consider the large @xmath123 limit . in this limit the model can be solved exactly . indeed ,
the quantity @xmath128 does not fluctuate , that the static mean field theory is exact .
we obtain the exact solution @xmath129 where @xmath130 is the inverse temperature , and @xmath131 is the fermi function , and @xmath132 . within the cpt ,
the cluster of size @xmath1 has the following hamiltonian @xmath133 the cluster hamiltonian ( [ hamcpt ] ) can be solved exactly , for instance by the exact diagonalization .
however , at the large-@xmath123 limit it can simply be solved exactly .
indeed , the cluster quantity @xmath134 does not fluctuate , and the cluster hamiltonian ( [ hamcpt ] ) becomes quadratic and can simply be diagonalized .
however , in this case @xmath135 may depends on the cluster index .
the cluster green function is @xmath136^{-1 } , \label{gcpt } \end{aligned}\ ] ] where @xmath137 is the cluster hopping matrix , and @xmath138 is the cluster self energy @xmath139 the cluster quantity @xmath135 can be calculated from the cluster green function @xmath140 equations ( [ gcpt])-([ccpt ] ) give the exact solution of the cluster hamiltonian ( [ hamcpt ] ) at the large-@xmath123 limit .
once the exact cluster solution is obtained , the lattice green function within the cpt is computed by@xcite @xmath141 where @xmath142 .
the lattice quantity @xmath128 within the cpt is calculated from this lattice green function @xmath143 next , we consider the one dimensional large-@xmath123 model ( [ ham ] ) in the periodization form .
the periodized hamiltonian reads @xmath144 where @xmath76 and @xmath145 are determined by the periodization transformation ( [ hop ] ) and ( [ int ] ) , respectively .
the hamiltonian ( [ pham ] ) can be solved exactly in the large-@xmath123 limit . introducing quantity
@xmath146 we obtain @xmath147 when eqs .
( [ ec1])-([ec2 ] ) are solved , the quantity @xmath128 of the original fermions can be calculated too @xmath148 numerically , we alway obtain @xmath149 independently on the cluster size @xmath1 . moreover , since the green function @xmath150 , one must have the identity of the dispersions of periodized and original fermions @xmath151 . in fig . [ figa ]
we plot the dispersions for the cluster size @xmath152 .
it confirms the identity of the dispersions of periodized and original fermions . in fig .
[ figb ] we plot the dispersions at fixed @xmath153 for various cluster sizes @xmath1 .
it shows the identity of the dispersions of periodized and original fermions is independent on the cluster size .
these results confirm the equivalent of the periodized and original hamiltonians .
next , we consider the umklapp case where the constrain ( [ const ] ) is relaxed by its exact relation
. then we obtain @xmath154 where @xmath71 is the umklapp transfer momentum .
since @xmath155 , in the large @xmath1 limit this umklapp case approaches to the normal one .
the lattice quantity @xmath156 of the original fermions can be calculated by @xmath157 in numerical calculations we take @xmath158 .
it turns out numerically that @xmath159 is never equal to @xmath160 , although it approaches to the exact value as @xmath161 , as shown in the inset of fig .
[ figb ] . in fig .
[ figa ] and [ figb ] we plot also the dispersion @xmath162 .
these figures show that the dispersion of the periodized fermions in the presence of the umklapp momentum transfer is not exact .
these results confirm that the constrain is important in order to maintain the correct physics .
now we apply the pcpt to the one dimensional large-@xmath123 model ( [ ham ] )
. the cluster periodized hamiltonian is obtained from ( [ pham ] ) @xmath163 at the large-@xmath123 limit the cluster hamiltonian ( [ cpham ] ) can simply be solved exactly . introducing the cluster quantity @xmath164
we obtain the cluster self energy @xmath165 where @xmath166 .
the cluster quantity @xmath167 can be calculated from the cluster green function .
we obtain @xmath168 finally , once the cluster equations ( [ c1])-([c2 ] ) are solved , we obtain the lattice green function of the original fermions @xmath169 the lattice quantity @xmath170 is calculated from this lattice green function . we obtain @xmath171
so far we have obtained the quantity @xmath172 in both the cpt and pcpt , as well as its exact value .
we use it to compare the error and the convergence of the cpt and pcpt schemes . in fig .
[ fig1 ] we plot the lattice quantity @xmath172 as a function of inverse temperature calculated within the cpt and the pcpt .
it is clear that both the cpt and pcpt results converge well to the exact solution .
the cpt results converge consistently , whereas for small cluster sizes the pcpt results fluctuate around the exact solution .
however , the pcpt results converge faster than the cpt ones .
even at small cluster sizes the pcpt results are closer to the exact solution than the cpt ones . in fig .
[ fig2 ] we plot @xmath172 as a function of @xmath3 at fixed temperature .
it shows that the cpt results converge linearly in @xmath3 , whereas the pcpt results converge quadratically in @xmath3 .
the convergence features of the cpt and pcpt are quite similar to the ones of the cdmft and dca.@xcite the convergence can be understood in the term of the hybridization in the locator expansion.@xcite indeed , the convergence of @xmath172 depends mostly on the convergence of the coarse grained green function ( see eq .
( [ cptchi ] ) ) @xmath173 where the green function @xmath91 can be rewritten as @xmath174^{-1 } - \delta\hat{t}(\mathbf{k } ) \big]^{-1 } .\end{aligned}\ ] ] this is also valid for the pcpt just by replacing the coarse grained green function of the original fermions by its counterpart of the periodized fermions . the coarse grained green function can be rewritten in the locator expansion as@xcite @xmath175^{-1 } - \hat{\gamma}(z ) \big]^{-1 } , \label{cg}\end{aligned}\ ] ] where @xmath176 is the hybridization function @xmath177^{-1 } \nonumber \\ & & \frac{l_c}{l } \sum_{\mathbf{k } } \delta\hat{t}(\mathbf{k } ) \hat{g}(\mathbf{k},z ) \delta\hat{t}(\mathbf{k } ) .
\label{hyb}\end{aligned}\ ] ] the hybridization is an amplitude for fermion hopping from a cluster into the surrounding and back again into the cluster .
it acts as the small parameter in the expansion of the coarse grained green function ( [ cg ] ) . as in the dca , the inter - cluster hopping @xmath178 in the pcpt scales like @xmath3 for large cluster sizes , whereas in the cpt and the cdmft it is of order @xmath179 .
the average hybridization per cluster site scales like @xmath161 in the pcpt , and like @xmath3 in the cpt.@xcite therefore the pcpt converges like @xmath161 , whereas the cpt converges like @xmath3 .
note that these convergences are valid for the coarse grained green function in any dimensions .
the convergence feature is an advantage of the pcpt in comparison with the cpt .
we have introduced a canonical transformation which periodizes fermions in the cluster space . by applying the canonical transformation to the hamiltonian , the periodized hamiltonian is obtained in the presence of a constrain which prevents the umklapp momentum transfer from the superlattice to the cluster space . within the periodized hamiltonian
, the dca can be derived from the cdmft . in the such way
, the dca and the cdmft can be unified into a single microscopic definition .
it also gives an alternative microscopic background of the discretization of irreducible quantities on the reciprocal space , and clarifies the approximation nature of the dca .
we also develop the pcpt in which the wave vector within a cluster is a conserved quantum number .
this allows to avoid the matrix inversion of the green function that reduces significantly the computation time when the cluster size is large .
the pcpt can work on both the direct and reciprocal spaces .
as the cpt , the pcpt is exact in the limits @xmath120 , @xmath121 , and @xmath122 .
it is also clarified that the small parameter of the pcpt is @xmath3 . as a benchmark
the exact one dimension @xmath180 model is studied .
it turns out that the pcpt converges rapidly with corrections @xmath0 , whereas the standard cpt converges with corrections @xmath2 .
the author would like to thank professor s.w .
kim and the asia pacific center for theoretical physics for the hospitality .
he also acknowledges the department of physics , postech for sharing cpu s time .
this work was supported by the asia pacific center for theoretical physics .
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quantum periodic cluster methods for strongly correlated electron systems are reformulated and developed . the reformulation and development
are based on a canonical transformation which periodizes the fermions in the cluster space .
the dynamical cluster approximation and the cellular dynamical mean field theory are related each other through the canonical transformation .
a cluster perturbation theory with periodic boundary conditions is developed .
it is found that the periodic cluster perturbation theory converges rapidly with corrections @xmath0 , where @xmath1 is the linear size of the clusters , whereas the ordinary cluster perturbation theory converges with corrections @xmath2 .
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treatment of iron - deficiency anemia in pregnancy with oral iron therapy and blood transfusion has significant drawbacks .
high dose of oral iron causes significant side effects ; non - compliance is common.intravenous iron produces a better hematological response than oral iron , including a faster increase in hemoglobin and faster replenishment of body iron stores and can provide an alternative to transfusion in profound iron deficiency anemia .
all available iron preparations for parenteral use can cause short - term side - effects , including anaphylactic reaction .
we report here a fatal anaphylactic reaction to iron sucrose in a pregnant woman with severe iron - deficiency anemia .
a 20 years - old primigravida with seven months amenorrhea presented to the emergency department with giddiness and difficulty in breathing .
the history of presenting complaints revealed that she had developed these complaints within few minutes of receiving first infusion of iron sucrose usp 5 ml injection ( ferise 5 brand of intas pharma company ) diluted in 100 ml normal saline for severe iron deficiency anemia in a primary health care centre.parenteral iron therapy was initiated to her because she was noncompliant to oral iron and folic acid supplements.she had no history of allergies or significant past medical illness . on presentation , she was conscious , alert(glasgow coma scale 15/15 ) and afebrile .
her pulse rate was 140/min , respiratory rate 28/min , oxygen saturation of 90% at room air and systolic blood pressure 70 mm of hg . on physical examination ,
chest examination revealed bilateral diminished breath sounds ; rest of the systemic examination was unremarkable .
her hemoglobin was 6.0 gm / dl , total leucocyte count 27900/l , red blood cell count 2.86 million / cmm , platelet count 570000/l , international normalized ratio ( inr ) 1.13 and aptt 34.4 seconds .
arterial blood gas analysis was suggestive of hypoxia ( ph 7.37 , po2 66 , pco2 44,hco3 20 and po2/fio2 0.66 on 100% fio2 ) .
she had normal urine analysis , serum electrolytes , renal , liver and thyroid function tests .
she was treated with intravenous adrenaline , hydrocortisone , antihistaminics and h2 blockers and transferred to the intensive care unit for ventilatory and inotropic support . despite intensive resuscitation attempts in the intensive care unit , the patient expired due to cardiac arrest within 24 hrs .
anemia in pregnant women is estimated to be between 39.9 to 43.8% globally and 43.9 to 52.5%in south - east asia .
it is generally estimated that half of the anemia cases in pregnancy are related to iron deficiency .
the prevalence of iron - deficiency anemia in pregnant women is estimated to be between 35 and 75% in developing countries whereas in industrialized countries , the average prevalence is 18% . parenteral iron therapy in iron - deficiency anemia is recommended in patients where oral iron therapy is ineffective due to mal - absorption states and noncompliance . compared to oral iron therapy ,
intravenous iron results in much more rapid resolution of iron - deficiency anemia with minimal adverse reactions . three commercial formulations ; iron dextran , ,
all available iron preparations for parenteral use can cause short - term side - effects , such as metallic taste , back pain , nausea , vomiting , diarrhea , abdominal pain , hypotension and allergic or even anaphylactic reactions .
symptoms of anaphylaxis include dyspnea , chest pain , angioedema , urticaria with hypotension , and are generally immediate , sudden , and severe , typically occurring in conjunction with the first dose of parenteral iron . the systemic reaction observed in response to the first dose of intravenous iron preparations
have not been found consistently to be ige mediated and are therefore described as anaphylactic or anaphylactoid reaction .
iron dextran induced toxicity is believed to be due to hypersensitivity related to the dextran moiety , since iron dextran is associated with a higher risk for anaphylaxis or anaphylactoid reactions than newer iv iron products .
iron dextran had the highest reports of anaphylaxis , anaphylactoid reaction , urticaria , upper airway angioedema , while iron sucrose carried the lowest risk for these hypersensitivity reactions .
the all - event reporting rates for iron dextran , sodium ferric gluconate , and iron sucrose were 29.2 , 10.5 , and 4.2 reports per million 100 mg dose equivalents , respectively , while the all - fatal - event reporting rates were 1.4 , 0.6 , and 0.0 reports per million 100 mg dose equivalents , respectively .
iron sucrose appears to have a favorable safety profile and is an alternative to other forms of parenteral iron therapy in correction of depletion of iron stores .
rare anaphylactic reactions with iron sucrose have been reported in 0.002% of cases . in our patient ,
an adverse drug reaction occurring few minutes after infusion of first dose of iron sucrose suggests hypersensitivity reaction rather than an immediate dose related toxicity .
use of naranjo probability scale indicated a probable relationship between the hypersensitivity reaction and iron sucrose as the causal drug .
since serum ige or tryptase levels were not obtained , we are not able to establish whether this reaction was an anaphylaxis or an anaphylactoid reaction . in conclusion , clinicians should be alert to the possibility of this fatal adverse effect in patients receiving parenteral iron sucrose . a public health initiative aimed at reducing the number of severe adverse reactions to parenteral iron
would require a rational use of this drug and a mandatory test dose before the first infusion .
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iron - deficiency anemia in pregnancy can have serious deleterious effects for both mother and fetus . parenteral iron therapy in iron - deficiency anemia
is recommended in patients where oral iron therapy is ineffective due to malabsorption states and non - compliance .
compared to oral iron therapy , intravenous iron results in much more rapid resolution of iron - deficiency anemia with minimal adverse reactions .
iron sucrose has a favorable safety profile and is an alternative to other forms of parenteral iron therapy in correction of iron stores depletion .
immune mechanisms and iron agent releasing bioactive , partially unbound iron into the circulation , resulting in oxidative stress appears to cause severe adverse reactions .
although iron sucrose has a favorable safety profile in comparison to other parenteral iron preparations , this report highlights a fatal anaphylactic shock to iron sucrose in a pregnant woman with severe iron deficiency non - compliant to oral iron therapy .
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The apple doesn’t fall far from the tree in the Jackson family.
Paris Jackson, the daughter of the late Michael Jackson, is taking the fashion world by storm; and this photoshoot in Paris, France is just the beginning.
Jackson has been sharing her Paris getaway with fans since she touched down in the City of Lights earlier this week, but on Wednesday, she shared that her trip is not all fun and games. She’s there to work!
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According to E! News, Jackson posed in a WWII themed photoshoot in front of the Eiffel Tower this week at the Esplanade du Trocadero for her fashion debut.
Jackson stunned and gave us serious Marilyn Monroe vibes in these sneak peeks from the set.
J'aime les français, ils sont très amusants pour passer du temps avec. A photo posted by Paris-Michael K. Jackson (@parisjackson) on Jan 18, 2017 at 10:32am PST
A photo posted by Paris-Michael K. Jackson (@parisjackson) on Jan 18, 2017 at 10:34am PST
The label Jackson is posing for has not been confirmed just yet, but “Shahs of Sunset” star and friend of the aspiring model, Asa Soltan Rahmati might have spilled the beans on Instagram.
RELATED: This British actor faced serious backlash after he compared his workout routine to 9/11 first responders’ efforts
“Omg how EPICCCCCCC and gorgeous are these pictures of my beautiful baby @parisjackson for Chanel on location in Paris? SO proud of you baby girl. You’re doing it and I see your courage. You are strong, kind, genuine, and absolutely beautiful. Love you very much,” Rahmati gushed.
Rahmati is close with the Jackson family as she has been dating Paris Jackson’s cousin, Jermaine Jackson II for six years. The couple is also expecting their first child together this month.
Chanel isn’t the only high fashion label Jackson is rumored to have met with during her trip to Paris. According to sources, she also attended a meeting with Christian Dior after doing some sightseeing with boyfriend Michael Snoddy.
It looks like she is already taking this year by storm! ||||| In her first-ever in-depth interview, Michael Jackson's daughter discusses her father's pain and finding peace after addiction and heartache
Paris-Michael Katherine Jackson is staring at a famous corpse. "That's Marilyn Monroe," she whispers, facing a wall covered with gruesome autopsy photos. "And that's JFK. You can't even find these online." On a Thursday afternoon in late November, Paris is making her way through the Museum of Death, a cramped maze of formaldehyde-scented horrors on Hollywood Boulevard. It's not uncommon for visitors, confronted with decapitation photos, snuff films and serial-killer memorabilia, to faint, vomit or both. But Paris, not far removed from the emo and goth phases of her earlier teens, seems to find it all somehow soothing. This is her ninth visit. "It's awesome," she had said on the way over. "They have a real electric chair and a real head!"
Paris Jackson turned 18 last April, and moment by moment, can come across as much older or much younger, having lived a life that's veered between sheltered and agonizingly exposed. She is a pure child of the 21st century, with her mashed-up hippie-punk fashion sense (today she's wearing a tie-dye button-down, jeggings and Converse high-tops) and boundary-free musical tastes (she's decorated her sneakers with lyrics by Mötley Crüe and Arctic Monkeys; is obsessed with Alice Cooper – she calls him "bae" – and the singer-songwriter Butch Walker; loves Nirvana and Justin Bieber too). But she is, even more so, her father's child. "Basically, as a person, she is who my dad is," says her older brother, Prince Michael Jackson. "The only thing that's different would be her age and her gender." Paris is similar to Michael, he adds, "in all of her strengths, and almost all of her weaknesses as well. She's very passionate. She is very emotional to the point where she can let emotion cloud her judgment."
Paris has, with impressive speed, acquired more than 50 tattoos, sneaking in the first few while underage. Nine of them are devoted to Michael Jackson, who died when she was 11 years old, sending her, Prince and their youngest brother, Blanket, spiraling out of what had been – as they perceived it – a cloistered, near-idyllic little world. "They always say, 'Time heals,'" she says. "But it really doesn't. You just get used to it. I live life with the mentality of 'OK, I lost the only thing that has ever been important to me.' So going forward, anything bad that happens can't be nearly as bad as what happened before. So I can handle it." Michael still visits her in her dreams, she says: "I feel him with me all the time."
Related Paris Jackson Speaks out Against Cyberbullying, Defends Justin Bieber Jackson takes a stand against Internet hatred, which she says once caused her to attempt suicide
Michael, who saw himself as Peter Pan, liked to call his only daughter Tinker Bell. She has FAITH, TRUST AND PIXIE DUST inked near her clavicle. She has an image from the cover of Dangerous on her forearm, the Bad logo on her hand, and the words QUEEN OF MY HEART – in her dad's handwriting, from a letter he wrote her – on her inner left wrist. "He's brought me nothing but joy," she says. "So why not have constant reminders of joy?"
She also has tattoos honoring John Lennon, David Bowie and her dad's sometime rival Prince – plus Van Halen and, on her inner lip, the word MÖTLEY (her boyfriend has CRÜE in the same spot). On her right wrist is a rope-and-jade bracelet that Michael bought in Africa. He was wearing it when he died, and Paris' nanny retrieved it for her. "It still smells like him," Paris says.
She fixes her huge blue-green eyes on each of the museum's attractions without flinching, until she comes to a section of taxidermied pets. "I don't really like this room," she says, wrinkling her nose. "I draw the line with animals. I can't do it. This breaks my heart." She recently rescued a hyperactive pit-bull-mix puppy, Koa, who has an uneasy coexistence with Kenya, a snuggly Labrador her dad brought home a decade ago.
Paris describes herself as "desensitized" to even the most graphic reminders of human mortality. In June 2013, drowning in depression and a drug addiction, she tried to kill herself at age 15, slashing her wrist and downing 20 Motrin pills. "It was just self-hatred," she says, "low self-esteem, thinking that I couldn't do anything right, not thinking I was worthy of living anymore." She had been self-harming, cutting herself, managing to conceal it from her family. Some of her tattoos now cover the scars, as well as what she says are track marks from drug use. Before that, she had already attempted suicide "multiple times," she says, with an incongruous laugh. "It was just once that it became public." The hospital had a "three-strike rule," she recalls, and, after that last attempt, insisted she attend a residential therapy program.
Vince Pugliese/ZUMA
Home-schooled before her father's death, Paris had agreed to attend a private school starting in seventh grade. She didn't fit in – at all – and started hanging out with the only kids who accepted her, "a lot of older people doing a lot of crazy things," she says. "I was doing a lot of things that 13-, 14-, 15-year-olds shouldn't do. I tried to grow up too fast, and I wasn't really that nice of a person." She also faced cyberbullying, and still struggles with cruel online comments. "The whole freedom-of-speech thing is great," she says. "But I don't think that our Founding Fathers predicted social media when they created all of these amendments and stuff."
There was another trauma that she's never mentioned in public. When she was 14, a much older "complete stranger" sexually assaulted her, she says. "I don't wanna give too many details. But it was not a good experience at all, and it was really hard for me, and, at the time, I didn't tell anybody."
After her last suicide attempt, she spent sophomore year and half of junior year at a therapeutic school in Utah. "It was great for me," she says. "I'm a completely different person." Before, she says with a small smile, "I was crazy. I was actually crazy. I was going through a lot of, like, teen angst. And I was also dealing with my depression and my anxiety without any help." Her father, she says, also struggled with depression, and she was prescribed the same antidepressants he once took, though she's no longer on any psych meds.
Now sober and happier than she's ever been, with menthol cigarettes her main remaining vice, Paris moved out of her grandma Katherine's house shortly after her 18th birthday, heading to the old Jackson family estate. She spends nearly every minute of each day with her boyfriend, Michael Snoddy, a 26-year-old drummer – he plays with the percussion ensemble Street Drum Corps – and Virginia native whose dyed mohawk, tattoos and perpetually sagging pants don't obscure boy-band looks and a puppy-dog sweetness. "I never met anyone before who made me feel the way music makes me feel," says Paris. When they met, he had an ill-considered, now-covered Confederate flag tattoo that raised understandable doubts among the Jacksons. "But the more I actually got to know him," says Prince, "he's a really cool guy."
Paris took a quick stab at community college after graduating high school – a year early – in 2015, but wasn't feeling it. She is an heir to a mammoth fortune – the Michael Jackson Family Trust is likely worth more than $1 billion, with disbursements to the kids in stages. But she wants to earn her own money, and now that she's a legal adult, to embrace her other inheritance: celebrity.
And in the end, as the charismatic, beautiful daughter of one of the most famous men who ever lived, what choice did she have? She is, for now, a model, an actress, a work in progress. She can, when she feels like it, exhibit a regal poise that's almost intimidating, while remaining chill enough to become pals with her giant-goateed tattoo artist. She has impeccable manners – you might guess that she was raised well. She so charmed producer-director Lee Daniels in a recent meeting that he's begun talking to her manager about a role for her on his Fox show, Star. She plays a few instruments, writes and sings songs (she performs a couple for me on acoustic guitar, and they show promise, though they're more Laura Marling than MJ), but isn't sure if she'll ever pursue a recording contract.
Modeling, in particular, comes naturally, and she finds it therapeutic. "I've had self-esteem issues for a really, really long time," says Paris, who understands her dad's plastic-surgery choices after watching online trolls dissect her appearance since she was 12. "Plenty of people think I'm ugly, and plenty of people don't. But there's a moment when I'm modeling where I forget about my self-esteem issues and focus on what the photographer's telling me – and I feel pretty. And in that sense, it's selfish."
But mostly, she shares her father's heal-the-world impulses ("I'm really scared for the Great Barrier Reef," she says. "It's, like, dying. This whole planet is. Poor Earth, man"), and sees fame as a means to draw attention to favored causes. "I was born with this platform," she says. "Am I gonna waste it and hide away? Or am I going to make it bigger and use it for more important things?"
Her dad wouldn't have minded. "If you wanna be bigger than me, you can," he'd tell her. "If you don't want to be at all, you can. But I just want you to be happy."
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At the moment, Paris lives in the private studio where her dad demoed "Beat It." The Tudor-style main house in the now-empty Jackson family compound in the L.A. neighborhood of Encino – purchased by Joe Jackson in 1971 with some of the Jackson 5's first Motown royalties, and rebuilt by Michael in the Eighties – is under renovation. But the studio, built by Michael in a brick building across the courtyard, happens to be roughly the size of a decent Manhattan apartment, with its own kitchen and bathroom. Paris has turned it into a vibe-y, cozy dorm room.
Traces of her father are everywhere, most unmistakably in the artwork he commissioned. Outside the studio is a framed picture, done in a Disney-like style, of a cartoon castle on a hilltop with a caricatured Michael in the foreground, a small blond boy embracing him. It's captioned "Of Children, Castles & Kings." Inside is a mural taking up an entire wall, with another cartoon Michael in the corner, holding a green book titled The Secret of Life and looking down from a window at blooming flowers – at the center of each bloom is a cartoon face of a red-cheeked little girl.
Paris' chosen decor is somewhat different. There is a picture of Kurt Cobain in the bathroom, a Smashing Pumpkins poster on the wall, a laptop with Against Me! and NeverEnding Story stickers, psychedelic paisley wall hangings, lots of fake candles. Vinyl records (Alice Cooper, the Rolling Stones) serve as wall decorations. In the kitchen, sitting casually on a counter, is a framed platinum record, inscribed to Michael by Quincy Jones ("I found it in the attic," Paris shrugs).
Above an adjacent garage is a mini-museum Michael created as a surprise gift for his family, with the walls and even ceilings covered with photos from their history. Michael used to rehearse dance moves in that room; now Paris' boyfriend has his drum kit set up there.
We head out to a nearby sushi restaurant, and Paris starts to describe life in Neverland. She spent her first seven years in her dad's 2,700-acre fantasy world, with its own amusement park, zoo and movie theater. ("Everything I never got to do as a kid," Michael called it.) During that time, she didn't know that her father's name was Michael, let alone have any grasp of his fame. "I just thought his name was Dad, Daddy," she says. "We didn't really know who he was. But he was our world. And we were his world." (Paris declared last year's Captain Fantastic, where Viggo Mortensen plays an eccentric dad who tries to create a utopian hideaway for his kids, her "favorite movie ever.")
Courtesy of Paris Jackson
"We couldn't just go on the rides whenever we wanted to," she recalls, walking on a dark roadside near the Encino compound. She likes to stride along the lane divider, too close to the cars – it drives her boyfriend crazy, and I don't much like it either. "We actually had a pretty normal life. Like, we had school every single day, and we had to be good. And if we were good, every other weekend or so, we could choose whether we were gonna go to the movie theater or see the animals or whatever. But if you were on bad behavior, then you wouldn't get to go do all those things."
In his 2011 memoir, Michael's brother Jermaine called him "an example of what fatherhood should be. He instilled in them the love Mother gave us, and he provided the kind of emotional fathering that our father, through no fault of his own, could not. Michael was father and mother rolled into one."
Michael gave the kids the option of going to regular school. They declined. "When you're at home," says Paris, "your dad, who you love more than anything, will occasionally come in, in the middle of class, and it's like, 'Cool, no more class for the day. We're gonna go hang out with Dad.' We were like, 'We don't need friends. We've got you and Disney Channel!'" She was, she acknowledges, "a really weird kid."
Her dad taught her how to cook, soul food, mostly. "He was a kick-ass cook," she says. "His fried chicken is the best in the world. He taught me how to make sweet potato pie." Paris is baking four pies, plus gumbo, for grandma Katherine's Thanksgiving – which actually takes place the day before the holiday, in deference to Katherine's Jehovah's Witness beliefs.
Michael schooled Paris on every conceivable genre of music. "My dad worked with Van Halen, so I got into Van Halen," she says. "He worked with Slash, so I got into Guns N' Roses. He introduced me to Tchaikovsky and Debussy, Earth, Wind and Fire, the Temptations, Tupac, Run-DMC."
She says Michael emphasized tolerance. "My dad raised me in a very open-minded house," she says. "I was eight years old, in love with this female on the cover of a magazine. Instead of yelling at me, like most homophobic parents, he was making fun of me, like, 'Oh, you got yourself a girlfriend.'
"His number-one focus for us," says Paris, "besides loving us, was education. And he wasn't like, 'Oh, yeah, mighty Columbus came to this land!' He was like, 'No. He fucking slaughtered the natives.'" Would he really phrase it that way? "He did have kind of a potty mouth. He cussed like a sailor." But he was also "very shy."
Paris and Prince are quite aware of public doubts about their parentage (the youngest brother, Blanket, with his darker skin, is the subject of less speculation). Paris' mom is Debbie Rowe, a nurse Michael met while she was working for his dermatologist, the late Arnold Klein. They had what sounds like an unconventional three-year marriage, during which, Rowe once testified, they never shared a home. Michael said that Rowe wanted to have his children "as a present" to him. (Rowe said that Paris got her name from the location of her conception.) Klein, her employer, was one of several men – including the actor Mark Lester, who played the title role in the 1968 movie Oliver! – who suggested that they could be Paris' actual biological father.
Over popcorn shrimp and a Clean Mean Salmon Roll, Paris agrees to address this issue for what she says will be the only time. She could opt for an easy, logical answer, could point out that it doesn't matter, that either way, Michael Jackson was her father. That's what her brother – who describes himself as "more objective" than Paris – seems to suggest. "Every time someone asks me that," Prince says, "I ask, 'What's the point? What difference does it make?' Specifically to someone who's not involved in my life. How does that affect your life? It doesn't change mine."
But Paris is certain that Michael Jackson was her biological dad. She believes it with a fervency that is both touching and, in the moment, utterly convincing. "He is my father," she says, making fierce eye contact. "He will always be my father. He never wasn't, and he never will not be. People that knew him really well say they see him in me, that it's almost scary.
"I consider myself black," she says, adding later that her dad "would look me in the eyes and he'd point his finger at me and he'd be like, 'You're black. Be proud of your roots.' And I'd be like, 'OK, he's my dad, why would he lie to me?' So I just believe what he told me. 'Cause, to my knowledge, he's never lied to me.
"Most people that don't know me call me white," Paris concedes. "I've got light skin and, especially since I've had my hair blond, I look like I was born in Finland or something." She points out that it's far from unheard of for mixed-race kids to look like her – accurately noting that her complexion and eye color are similar to the TV actor Wentworth Miller's, who has a black dad and a white mom.
At first, she had no relationship with Rowe. "When I was really, really young, my mom didn't exist," Paris recalls. Eventually, she realized "a man can't birth a child" – and when she was 10 or so, she asked Prince, "We gotta have a mom, right?" So she asked her dad. "And he's like, 'Yeah.' And I was like, 'What's her name?' And he's just like, 'Debbie.' And I was like, 'OK, well, I know the name.'" After her father's death, she started researching her mom online, and they got together when Paris was 13.
In the wake of her treatment in Utah, Paris decided to reach out again to Rowe. "She needed a mother figure," says Prince, who declines to comment on his own relationship, or lack thereof, with Rowe. (Paris' manager declined to make Rowe available for an interview, and Rowe did not respond to our request for comment.) "I've had a lot of mother figures," Paris counters, citing her grandmother and nannies, among others, "but by the time my mom came into my life, it wasn't a 'mommy' thing. It's more of an adult relationship." Paris sees herself in Rowe, who just completed a course of chemo in a fight against breast cancer: "We're both very stubborn."
Paris isn't sure how Michael felt about Rowe, but says Rowe was "in love" with her dad. She's also sure that Michael loved Lisa Marie Presley, whom he divorced two years before Paris' birth: "In the music video 'You Are Not Alone,' I can see how he looked at her, and he was totally whipped," she says with a fond laugh.
Blue Wasp/Splash News
Paris Jackson was around nine years old when she realized that much of the world didn't see her father the way she did. "My dad would cry to me at night," she says, sitting at the counter of a New York coffee shop in mid-December, cradling a tiny spoon in her hand. She starts to cry too. "Picture your parent crying to you about the world hating him for something he didn't do. And for me, he was the only thing that mattered. To see my entire world in pain, I started to hate the world because of what they were doing to him. I'm like, 'How can people be so mean?'" She pauses. "Sorry, I'm getting emotional."
Paris and Prince have no doubts that their father was innocent of the multiple child-molestation allegations against him, that the man they knew was the real Michael. Again, they are persuasive – if they could go door-to-door talking about it, they could sway the world. "Nobody but my brothers and I experienced him reading A Light in the Attic to us at night before we went to bed," says Paris. "Nobody experienced him being a father to them. And if they did, the entire perception of him would be completely and forever changed." I gently suggest that what Michael said to her on those nights was a lot to put on a nine-year-old. "He did not bullshit us," she replies. "You try to give kids the best childhood possible. But you also have to prepare them for the shitty world."
Michael's 2005 molestation trial ended in an acquittal, but it shattered his reputation and altered the course of his family's lives. He decided to leave Neverland for good. They spent the next four years traveling the world, spending long stretches of time in the Irish countryside, in Bahrain, in Las Vegas. Paris didn't mind – it was exciting, and home was where her dad was.
By 2009, Michael was preparing for an ambitious slate of comeback performances at London's O2 Arena. "He kind of hyped it up to us," recalls Paris. "He was like, 'Yeah, we're gonna live in London for a year.' We were super-excited – we already had a house out there we were gonna live in." But Paris remembers his "exhaustion" as rehearsals began. "I'd tell him, 'Let's take a nap,'" she says. "Because he looked tired. We'd be in school, meaning downstairs in the living room, and we'd see dust falling from the ceiling and hear stomping sounds because he was rehearsing upstairs."
Paris has a lingering distaste for AEG Live, the promoters behind the planned This Is It tour – her family lost a wrongful-death suit against them, with the jury accepting AEG's argument that Michael was responsible for his own death. "AEG Live does not treat their performers right," she alleges. "They drain them dry and work them to death." (A rep for AEG declined comment.) She describes seeing Justin Bieber on a recent tour and being "scared" for him. "He was tired, going through the motions. I looked at my ticket, saw AEG Live, and I thought back to how my dad was exhausted all the time but couldn't sleep."
Paris blames Dr. Conrad Murray – who was convicted of involuntary manslaughter in her father's death – for the dependency on the anesthetic drug propofol that led to it. She calls him "the 'doctor,'" with satirical air quotes. But she has darker suspicions about her father's death. "He would drop hints about people being out to get him," she says. "And at some point he was like, 'They're gonna kill me one day.'" (Lisa Marie Presley told Oprah Winfrey of a similar conversation with Michael, who expressed fears that unnamed parties were targeting him to get at his half of the Sony/ATV music-publishing catalog, worth hundreds of millions.)
Paris is convinced that her dad was, somehow, murdered. "Absolutely," she says. "Because it's obvious. All arrows point to that. It sounds like a total conspiracy theory and it sounds like bullshit, but all real fans and everybody in the family knows it. It was a setup. It was bullshit."
But who would have wanted Michael Jackson dead? Paris pauses for several seconds, maybe considering a specific answer, but just says, "A lot of people." Paris wants revenge, or at least justice. "Of course," she says, eyes glowing. "I definitely do, but it's a chess game. And I am trying to play the chess game the right way. And that's all I can say about that right now."
Michael had his kids wear masks in public, a protective move Paris considered "stupid" but later came to understand. So it made all the more of an impression when a brave little girl spontaneously stepped to the microphone at her dad's televised memorial service, on July 7th, 2009. "Ever since I was born," she said, "Daddy has been the best father you could ever imagine, and I just wanted to say I love him so much."
Kevork Djansezian/Getty
She was 11 years old, but she knew what she was doing. "I knew afterward there was gonna be plenty of shit-talking," Paris says, "plenty of people questioning him and how he raised us. That was the first time I ever publicly defended him, and it definitely won't be the last." For Prince, his younger sister showed in that moment that she had "more strength than any of us."
The day after her trip to the Museum of Death, Paris, Michael Snoddy and Tom Hamilton, her model-handsome, man-bunned 31-year-old manager, head over to Venice Beach. We stroll the boardwalk, and Snoddy recalls a brief stint as a street performer here when he first moved to L.A., drumming on buckets. "It wasn't bad," he says. "I averaged out to a hundred bucks a day."
Paris has her hair extensions in a ponytail. She's wearing sunglasses with circular lenses, a green plaid shirt over leggings, and a Rasta-rainbow backpack. Her mood is darker today. She's not talking much, and clinging tight to Snoddy, who's in a Willie Nelson tee with the sleeves cut off.
We head toward the canals, lined with ultramodern houses that Paris doesn't like. "They're too harsh and bougie," she says. "It doesn't scream, 'Hey, come for dinner!'" She's delighted to spot a group of ducks. "Hello, friends!" she shouts. "Come play with us!" Among them are what appear to be an avian couple in love, paddling through the shallow water in close formation. Paris sighs and squeezes Snoddy's hand. "Goals," she says. "Hashtag 'goals.'"
Her spirits are lifting, and we walk back toward the beach to watch the sunset. Paris and Snoddy hop on a concrete barrier facing the orange-pink spectacle. It's a peaceful moment, until a middle-aged woman in neon jogging clothes and knee-length socks walks over. She grins at the couple as she presses a button on some kind of tiny stereo strapped to her waist, unleashing a dated-sounding trance song. Paris laughs and turns to her boyfriend. As the sun disappears, they start to dance.
From being a kick-ass cook to a strict dad, here are the 5 things we learned about the King of Pop from Paris Jackson.
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– Paris Jackson, now 18, gives an extensive and candid cover interview to Rolling Stone in which she describes what it was like to grow up with Michael Jackson as her father—and what she thinks really happened to him. "It's obvious" that he was murdered, she says. "Absolutely." She says her father would talk about people wanting to kill him, though she won't specifically say who would have wanted him dead: "A lot of people." She admits that the whole thing sounds like "a total conspiracy theory," but "all real fans and everybody in the family knows it." And someday, justice might be done. "It's a chess game," she says. "And I am trying to play the chess game the right way. And that's all I can say about that right now." Jackson was 11 when her father died. In less-dark moments, Jackson recounts an idyllic childhood, during which she and her siblings attended school at Neverland Ranch and, if they got all their work done and behaved, were able to visit the property's amusement park, movie theater, or zoo on the weekends. When she was 7, after her father's child molestation trial ended in an acquittal, the family left Neverland and traveled the world. When Michael Jackson died, they were preparing to set down roots in London for a year for his O2 Arena performances. Jackson recounts her struggles after his death, including drug addiction, multiple suicide attempts, and a relationship forged with her mother, Debbie Rowe. She also says she's absolutely certain Michael Jackson is her biological father: "He's my dad, why would he lie to me?" The full interview, which also includes tidbits from brother Prince, is worth a read. (Or check out pictures from Paris' modeling debut.)
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in many physical systems , the relevant degrees of freedom are discrete degenerate quantum variables such as spins ( electron or nuclear ) that interact weakly with each other . at sufficiently high temperatures ,
the spins are completely disordered and characterized by the trivial thermodynamic correlators
. however , their dynamical properties remain interesting and important for various applications .
the spins generally fluctuate at frequencies of the order of the typical interaction @xmath3 . for some purposes ,
though , one needs to know the asymptotics of the spin correlation function at much higher frequencies . in this regime ,
the fluctuations and dynamical response are due to the simultaneous excitation of many degrees of freedom and inherent nonlinearity of the system .
the goal of this paper is to develop a formalism for the computation of the high - frequency spin correlator and to apply the result to the problem of magnetic ( flux and inductance ) noise at mk temperatures produced by paramagnetic spins located at the surface of superconductor .
specifically , we consider a set of spins described by the heisenberg hamiltonian with random couplings at high temperatures , @xmath4 .
we show that the spin correlator decays exponentially with frequency at @xmath5 , i.e. @xmath6 , and compute the coefficient @xmath7 in this formula .
the smallness of the high frequency fluctuations has an important consequence when the interaction , although of the order of @xmath3 for the typical pairs of spins , is much larger for a small but significant number of pairs .
this happens , for instance , if the spins are positioned randomly while the interaction between them falls off fast with distance .
each strongly coupled pair
has two states , the singlet and the triplet . transitions between those states require the exchange of a large energy quantum , @xmath8 between the pair and the surrounding spins .
the transition rate is proportional to the dynamical spin correlator at frequency @xmath9 , which is exponentially small . as a result ,
the switching events are rare and produce noise with , as we show below , @xmath2 spectrum at very _
low frequencies_. at intermediate frequencies , the @xmath2 noise is due to spin diffusion @xcite .
our arguments rely on two important assumptions .
first , the condition on the temperature is stricter than in the high frequency case : we need that @xmath10 if the noise is measured at frequency @xmath11 .
the right - hand side of this inequality represents the transition energy @xmath9 of the relevant two - level systems ; if it is too large , such systems are frozen .
we also assume that there is no efficient energy exchange mechanism between the two - level systems and an external thermal bath , e.g. electrons or phonons .
one application of our theory is the property of paramagnetic spins on the surface of superconducting aluminum .
these spins , presumably located in the thin al@xmath12o@xmath13 film or just at the metal - insulator interface , are believed to be responsible for the low frequency flux noise that limits the sensitivity of dc squids @xcite and causes decoherence in superconducting flux qubits @xcite .
it is very likely that the coupling between the spins is due to rkky interaction @xcite , so their dynamics is controlled by the heisenberg hamiltonian .
a number of experiments @xcite shows that the @xmath2 noise at very low frequencies is temperature - independent fot @xmath14 mk .
we take these data as evidence that the inter - spin interaction @xmath3 is so small that the spins remain in the high temperature regime in the whole experimental range .
finally , in the superconductor all electronic excitations are gapped , and direct interaction between the spins and phonons at low temperature is negligible .
all these facts combined together indicate that the spins in the oxide layer on the surface of aluminium or similar superconductors are described by the model studied in this paper . a lower bound on @xmath3 can be inferred from the recent measurements of the flux qubit relaxation rate @xcite .
if we assume that the relaxation is mainly due to the interaction with the surface spin , then @xmath15 , where @xmath9 is the energy difference between the two qubit states .
the experimental data indicate the persistence of magnetic relaxation at very high frequencies , at least up to @xmath16 ghz . we conclude that the typical interaction between the surface spins
is @xmath17 .
this is consistent with the observed spin freezing at @xmath18 in some samples @xcite as well as a theoretical estimate of the rkky interaction , see section [ sect : low_frequency ] .
the theory developed in this paper has many other applications , besides the problem of magnetic noise in superconducting circuits .
it can be applied to many problems in which the relaxation of high energy modes is possible only by the simultaneous creation of a very large number of low energy excitations .
some examples are the relaxation of inverted nuclear spin polarization in high magnetic fields and a similar problem of magnetization relaxation of cold atoms following a rapid quench @xcite or @xmath2 magnetic noise observed in a low temperature calorimeter with superconducting particle absorbers @xcite .
the paper is organized as follows : we first study high frequency spin fluctuations at infinite temperature ; then we show how the high frequency noise generates low frequency noise in a model with a broad distribution of coupling parameters .
we finally discuss the application of this model to the problem of flux noise in superconducting qubits .
we consider a set of spins of magnitude @xmath19 described by the heisenberg hamiltonian , @xmath20 with random couplings @xmath21 .
we are primarily interested in the @xmath22 case because it is most relevant for the physical applications .
let us fix @xmath23 and consider the normalized correlation function for the spin @xmath24 ( with components @xmath25 , @xmath26 ) in the time and frequency domains : @xmath27 note that @xmath28 is real and positive .
this follows from its physical interpretation as the quantum transition probability under a small perturbation @xmath29 ( more abstractly , @xmath30 if the averaging is performed over any quantum state that commutes with the hamiltonian . ) in general , the asymptotics of the fourier transform at large @xmath11 are related to analytic properties of the original function .
however , since @xmath31 , it is sufficient to consider @xmath32 on the imaginary axis : @xmath33 . if the integral converges for @xmath34 , then @xmath28 should decay sufficiently fast , and the real - time correlator has an analytic continuation to the strip @xmath35 . if , in addition , the integral diverges for @xmath36 , then @xmath37 for @xmath38 .
( strictly speaking , this expression is valid if we smooth out some unimportant features , such as peaks at discrete frequencies . ) at infinite temperature , the operator average in ( [ eq : f ] ) is taken over the maximally mixed state , i.e. @xmath39 .
the cyclic property of the trace implies that both variants of the correlation function are even and real .
therefore , the taylor expansion of the real - time spin correlator contains only even terms : @xmath40 d_{2n } = \frac{(-1)^n}{s(s+1)}\lim_{t\rightarrow 0 } \left\langle\frac{d^{2n}}{dt^{2n } } s_{j}^{c}(t ) s_{j}^{c}(0)\right\rangle = \int_{-\infty}^{+\infty}\tilde{f}(\omega)\omega^{2n}\frac{d\omega}{2\pi}. \label{eq : d_2n}\end{gathered}\ ] ] we are interested in the asymptotic behavior of the moments @xmath41 for @xmath42 .
let us assume that the power series ( [ eq : taylor ] ) has a finite convergence radius @xmath43 .
then @xmath32 has singularities at @xmath44 , and the frequency representation of the correlation function decays as @xmath45 for large @xmath11 . our main goal is to show that @xmath43 is nonzero and finite , and to compute its value .
physically , the spin correlation function does not completely vanish at high frequencies only due to nonlinearities that allow for combining the precession frequencies of a large number of spins . to understand it qualitatively ,
consider an infinite system in which each spin is coupled to @xmath46 neighbors with interaction strength @xmath3 .
if an energy quantum @xmath5 is exchanged between a single spin and some external object , it has to be distributed between other spins and divided into portions of the order of @xmath3 .
the most efficient processes of this kind are cascades that correspond to tree - like diagrams and do not involve any back reaction .
summing over such diagrams is equivalent to the mean - field approximation .
it is generally applicable for @xmath47 , but will also produce qualitatively correct results if the energy has many paths to escape , for example , on a tree with @xmath48 .
thus , we assume that each spin @xmath23 precesses in the local exchange field @xmath49 produced by the spins surrounding it . the fluctuating field @xmath50 is characterized by the correlation function @xmath51 where @xmath52 , @xmath53 are spatial indices ( @xmath54 ) and @xmath55 .
using the mean - field approach , we assume that @xmath56 is gaussian . the relevant energy scale in this model ( corresponding to @xmath3 in the qualitative discussion above ) is given by @xmath57 . in this approximation , the time evolution of each spin simplifies to @xmath58 , or , in a matrix form , @xmath59_{ca}s^{a}. \label{eq : ds / dt}\ ] ] here @xmath60 is the matrix corresponding to the cross - product with @xmath61 , and @xmath62_{ca}$ ] are its elements : @xmath63_{ca}=\epsilon_{cab}h^{b}. \label{eq : matr}\ ] ] we solve equation ( [ eq : ds / dt ] ) in a symbolic form , @xmath64_{ca}s^{a}(0)$ ] and average over the thermal state of the spin : @xmath65 .
thus , the spin correlator is expressed as an average over the fluctuating fields : @xmath66 using equations ( [ adjrep ] ) and ( [ hh ] ) , we recursively compute the first few moments @xmath41 : @xmath67 it is unfortunately difficult to pursue this computation much further and find the asymptotic behavior of the moments .
nevertheless , these recursive formulas give an exact expansion of the spin correlation function in lower orders : @xmath68 let us describe a general method for the calculation of the moments .
it can be used to derive equations ( [ rr ] ) and continue to higher orders , though we could not obtain a closed - form expression for @xmath41 .
we first use the equation of motion ( [ eq : ds / dt ] ) to express the @xmath69-th derivative in eq .
( [ eq : d_2n ] ) : @xmath70_{ca } \frac{d^{2n - k}s^{a}}{dt^{2n - k } } , \label{2nthderiv}\ ] ] where @xmath71 . by applying eq .
( [ 2nthderiv ] ) repeatedly , we obtain an expansion @xmath72_{ca_{1}}\dotsm [ \hat{h}^{(k_{m}-1)}]_{a_{m-1},a_{m}}\ , s^{a_{m } } s^{c } \label{eq : derivck}\ ] ] with the coefficients @xmath73 recall that the spin operators in ( [ eq : derivck ] ) pertain to site @xmath23 , and the fields @xmath60 are linear combinations of adjacent spins .
the field derivatives @xmath74 can be expressed in terms of further neighbors .
so far all the calculations have been exact .
now we employ the mean - field approximation and average over the thermal state of the spin , and then over the gaussian fields .
thus , @xmath75 the gaussian average in this formula can be evaluated using wick s theorem and the explicit form of the second - order correlator : @xmath76_{ab}\,[h^{(l)}]_{cd } \bigr\rangle = g^{2}\ , ( -1)^{\frac{k - l}{2}}d_{k+l}\ , \bigl(\delta_{ac}\delta_{bd}-\delta_{ad}\delta_{bc}\bigr ) .
\label{gaussav}\ ] ]
the difficulty in carrying out the above calculation lies in the matrix nature of the fields @xmath60 .
we now introduce two different approximations , which are expected to shift the answer in opposite directions by overestimating or underestimating the moments @xmath41 , thus giving a lower and an upper bound for @xmath43 .
remarkably , we find that the two bounds are quite close in value . in our first approximation , we ignore the noncommutativity of the matrices @xmath74 , or equivalently , @xmath77 for different values of @xmath78 .
more exactly , we symmetrize over all permutations of those matrices .
let us briefly explain how to use this recipe for equation ( [ ex ] ) , although it is easier to start almost from scratch as we will do later . by symmetrizing the combinatorial coefficients ( [ eq : ck ] )
, we obtain the expression @xmath79 .
then we consider an individual wick pairing for the product @xmath80 and relate it to the corresponding paring for the @xmath81-th power of @xmath60 .
the ratio is given by the scalar coefficient @xmath82 in eq .
( [ gaussav ] ) ; there is one such factor for each pair .
summing over all wick pairings , we get @xmath83 times a certain number .
it is easy to show that @xmath84 for @xmath85 .
eventually , eq . ( [ ex ] ) becomes : @xmath86 the solution to this recurrence yields the following expansion of @xmath32 in lower orders : @xmath87 notice the subtle difference from the exact solution ( [ firstord ] ) .
we believe that also in higher orders , the noncommutativity of the field matrices results in smaller values of @xmath41 than the ones obtained by the present method .
the same approximation can be applied directly to eq .
( [ adjrep ] ) if we replace the time ordered exponential with an ordinary exponential : @xmath88 where @xmath89 is the matrix associated with vector @xmath90 .
the vector components @xmath91 ( @xmath26 ) are gaussian fields with the following second moment : @xmath92 higher moments @xmath93 ( for a given @xmath78 ) are calculated directly by integrating over @xmath90 . using the notation @xmath94 , we find that @xmath95 now we calculate the average in eq .
( [ eq : f(t)cos ] ) by expanding @xmath96 in powers of @xmath97 .
the result is : @xmath98 this equation needs to be solved in conjunction with eq .
( [ eq : g ] ) . to compute @xmath99
, we formally replace @xmath78 with @xmath100 and @xmath101 with @xmath102 .
the numerical solution exhibits singularities at @xmath103 for @xmath104 . since the moments @xmath41 have been overestimated
, this gives a lower bound for the true value of @xmath43 .
we now make a different approximation to matrix products , exaggerating the noncommutativity .
specifically , we replace the physical @xmath22 spin for the @xmath105 group with an @xmath106 spin and consider the limit @xmath107 .
let us first introduce the generators of @xmath108 : these are @xmath109 matrices @xmath110 ( @xmath111 ) with the elements @xmath112_{\mu\nu}=\delta_{\alpha\mu}\delta_{\beta\nu}$ ] .
the @xmath106 spin is defined by the traceless matrices @xmath113 the generalized heisenberg interaction is given by the operator @xmath114 with the matrix elements @xmath115_{\gamma\delta } \bigl[\tilde{\sigma}^{\beta\alpha}\bigr]_{\mu\nu } = \frac{1}{n}\bigl(\delta_{\gamma\nu}\delta_{\delta\mu } -\frac{1}{n}\delta_{\gamma\delta}\delta_{\mu\nu}\bigr)$ ] .
note that if we let @xmath116 and @xmath117 act on the same spin ( by contracting over a pair of indices , @xmath118 ) , we get @xmath119 times the identity matrix . for @xmath120 ,
this matches the value of @xmath121 .
thus , the full hamiltonian has the form @xmath122 each spin @xmath23 experiences the effective field @xmath123 . in the mean - field approximation
, we have : @xmath124 where @xmath125 , and the spin correlator is normalized so that @xmath126 .
note that the last term in ( [ gaussn ] ) has no effect when we consider the action of the field on the spin , because @xmath127 .
( for an arbitrary @xmath128 ) using equations ( [ gaussn ] ) and ( [ evoln ] ) .
the arrows indicate @xmath129 ( the propagation from @xmath130 to @xmath78 ) and @xmath131 ( moving backward in time ) ; the shaded ribbons correspond to field correlators .
( b ) the exact definition of lines and ribbons .
note that that they do not depend on time : the factors @xmath132 are coefficients in front of the diagram .
( c ) a planar diagram : one of the leading terms in the @xmath107 limit . ( d ) a diagram for the function @xmath133 defined in ( [ eq : f]).,width=384 ] the calculation of @xmath134 can be performed using the standard diagrammatic technique for matrix models , see fig .
[ fig : diaggen]a , b . the ribbons in the diagrams
may actually be changed to double lines . to justify this step ,
let us express @xmath116 in terms of @xmath110 using ( [ generators ] ) .
the result is : @xmath135 , which shows that the ribbon between @xmath130 and @xmath78 can be changed as stated ( up to the @xmath136 term ) .
we can likewise replace the @xmath117 that enter the expressions for @xmath129 , @xmath131 .
the contributions of the unit operator in ( [ generators ] ) to @xmath129 and to @xmath131 cancel each other , therefore the remaining ribbons are also equivalent to double lines .
a great further simplification occurs in the limit of large @xmath128 @xcite .
the leading contribution to @xmath137 comes from diagrams that maximize the number of loops for a given expansion order in @xmath138 .
such diagrams are planar , and the time evolution factors @xmath129 , @xmath131 separate ; an example is shown in fig .
[ fig : diaggen]c .
thus , in the limit @xmath107 equations ( [ gaussn ] ) and ( [ evoln ] ) become : @xmath139 f_{\infty}(t)=f^{2}(t),\qquad f(t)\openone = \left\langle \operatorname{t\,exp}\int_{0}^{t}{\mathrm{i}}\ , h^{\alpha\beta}(\tau)\sigma^{\beta\alpha}\ , d\tau\right\rangle .
\label{eq : f}\end{gathered}\ ] ] the `` spin propagator '' @xmath133 can be computed by summing up planar diagrams .
specifically , @xmath133 is represented by a single line going from @xmath130 to @xmath78 and dressed with double lines ( the field correlators ) attached on one side ; these lines do not intersect , see fig .
[ fig : diaggen]d .
this diagrammatic expression leads to the dyson equation : @xmath140 curiously , the taylor expansion for @xmath141 coincides with the result ( [ firstord ] ) for @xmath142 up to the sixth order . the numerical solution of eq .
( [ sid ] ) exhibits singularities at @xmath44 for @xmath143 .
thus , the exact value of @xmath43 for the original problem should be between @xmath144 and @xmath145 . recall that this number is the exponent in the expression for the high frequency noise spectrum : @xmath146 .
the high frequency fluctuations of local effective fields drive the switching dynamics of strongly coupled spin pairs , and thus determine the noise at low frequencies ( provided the number of such pairs is significant ) .
we will find the spectrum of the low frequency noise in a specific model , which has been previously discussed in @xcite .
let us consider randomly distributed spins with the two - dimensional density @xmath147 on the surface of a superconductor .
the coupling of each spin to the conduction electrons is described by the kondo term in the hamiltonian : @xmath148 , where @xmath149_{\mu\nu } \hat{\psi}_{\mu}^{\dag}(\vec{r})\hat{\psi}_{\nu}(\vec{r})}$ ] .
the relative coupling strength can be characterized by the dimensionless parameter @xmath150 where @xmath151 is the electron density of states per spin projection and @xmath152 is the kondo temperature .
the rkky interaction between two spins can be expressed as follows : @xmath153 where @xmath154 is random , and @xmath155 is assumed to be much smaller than the coherence length .
the surface is usually covered by an insulator and thus can carry spins with arbitrary coupling to the conduction electrons , ranging from @xmath156 down to @xmath130 .
however , only the spins with @xmath157 are active , the other being quenched by the kondo effect .
this imposes the constraint @xmath158 .
the typical distance between the spins is @xmath159 , which defines the main parameter of our model : @xmath160 .
spins coupled with this strength form an infinite cluster , whereas more strongly coupled pairs are rare .
if we use the values @xmath161 ( the dos in aluminum ) and @xmath162 ( the typical spin density measured in several types of films @xcite ) , we get the estimate @xmath163 .
the upper bound corresponds to the spins with the largest value of @xmath164 .
there are some indications , both experimental @xcite and theoretical @xcite , suggesting that most localized spins arise from surface bound state
. therefore we can expect the actual value of @xmath57 to be close to the upper bound .
the density of pairs with interaction @xmath165 can be found by calculating the probability that a given spin has a neighbor at the corresponding distance .
such pairs constantly switch between the singlet and the triplet states at a characteristic rate @xmath166 , where @xmath7 is a numerical constant .
we estimate the density of pairs in terms of @xmath167 : @xmath168 each pair generates a random telegraph noise in any quantity @xmath169 that is proportional to the number of pairs in the triplet state ; for example , @xmath169 can be the magnetic susceptibility .
this noise has a lorentzian spectrum with width @xmath167 , but , for the purpose of a crude estimate , we may assume that it is concentrated at frequency @xmath170 .
therefore , the total noise spectrum is proportional to the previously calculated distribution of @xmath167 : @xmath171 thus , the magnetic susceptibility noise has a roughly @xmath2 spectrum at low frequencies . in the presence of a constant magnetic field
, it translates to a @xmath2 flux noise .
some experimental data indicate a spontaneous breaking of the time reversal symmetry in spin systems at low temperatures @xcite . although the exact nature of the symmetry - breaking order parameter is unclear , it is most likely to exert local fields on the pairs of spins that undergo the slow fluctuations . in this case
, the triplet state is split in energy and produce a net magnetization , observed as a flux noise .
we are grateful to r. mcdermott for the discussion of the experimental situation .
this work was supported , in part , by triangle de la physique 2007 - 36 , anr-06-blan-0218 , ecs-0608842 , aro w911 - 09 - 1 - 0395 , darpa hr0011 - 09 - 1 - 0009 .
a.k . acknowledges funding by the institute of quantum information under nsf grant no .
phy-0803371 .
t. lanting , a. j. berkley , b. bumble , p. bunyk , a. fung , j. johansson , a. kaul , a. kleinsasser , e. ladizinsky , f. maibaum , r. harris , m. w. johnson , e. tolkacheva , and m. h. s. amin phys .
b * 79 * , 060509 ( 2009 )
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we develop a technique to compute the high - frequency asymptotics of spin correlators in weakly interacting disordered spin systems .
we show that the dynamical spin correlator decreases exponentially at high frequencies , @xmath0 and compute the characteristic time @xmath1 of this dependence . in a typical random configuration ,
some fraction of spins form strongly coupled pairs , which behave as two - level systems .
their switching dynamics is driven by the high - frequency noise from the surrounding spins , resulting in low - frequency @xmath2 noise in the magnetic susceptibility and other physical quantities .
we discuss application of these results to the problem of susceptibility and flux noise in superconducting circuits at mk temperatures .
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SECTION 1. SHORT TITLE.
This Act may be cited as the ``Sugar Reform Act of 2015''.
SEC. 2. SUGAR PROGRAM.
(a) Sugarcane.--Section 156(a) of the Federal Agriculture
Improvement and Reform Act of 1996 (7 U.S.C. 7272(a)) is amended--
(1) in paragraph (3), by striking ``and'' after the
semicolon at the end;
(2) in paragraph (4)--
(A) by striking ``2018'' and inserting ``2014'';
and
(B) by striking the period at the end and inserting
``; and''; and
(3) by adding at the end the following:
``(6) 18 cents per pound for raw cane sugar for each of the
2015 through 2018 crop years.''.
(b) Sugar Beets.--Section 156(b)(2) of the Federal Agriculture
Improvement and Reform Act of 1996 (7 U.S.C. 7272(b)(2)) is amended by
striking ``2009'' and inserting ``2015''.
(c) Effective Period.--Section 156(i) of the Federal Agriculture
Improvement and Reform Act of 1996 (7 U.S.C. 7272(i)) is amended by
striking ``2008'' and inserting ``2015''.
SEC. 3. FLEXIBLE MARKETING ALLOTMENTS FOR SUGAR.
(a) In General.--Section 359b of the Agricultural Adjustment Act of
1938 (7 U.S.C. 1359bb) is amended--
(1) in subsection (a)(1)--
(A) in the matter before subparagraph (A), by
striking ``2008'' and inserting ``2017''; and
(B) in subparagraph (B), by inserting ``at
reasonable prices'' after ``stocks''; and
(2) in subsection (b)(1)--
(A) in subparagraph (A), by striking ``but'' after
the semicolon at the end and inserting ``and''; and
(B) by striking subparagraph (B) and inserting the
following:
``(B) appropriate to maintain adequate domestic
supplies at reasonable prices, taking into account all
sources of domestic supply, including imports.''.
(b) Establishment of Flexible Marketing Allotments.--Section 359c
of the Agricultural Adjustment Act of 1938 (7 U.S.C. 1359cc) is
amended--
(1) in subsection (b)--
(A) in paragraph (1)--
(i) in subparagraph (A), by striking
``but'' after the semicolon at the end and
inserting ``and''; and
(ii) by striking subparagraph (B) and
inserting the following:
``(B) appropriate to maintain adequate supplies at
reasonable prices, taking into account all sources of
domestic supply, including imports.''; and
(B) in paragraph (2)(B), by inserting ``at
reasonable prices'' after ``market''; and
(2) in subsection (g)(1)--
(A) by striking ``Adjustments.--'' and all that
follows through ``Subject to subparagraph (B), the''
and inserting ``Adjustments.--The''; and
(B) by striking subparagraph (B).
(c) Suspension or Modification of Provisions.--Section 359j of the
Agricultural Adjustment Act of 1938 (7 U.S.C. 1359jj) is amended by
adding at the end the following:
``(c) Suspension or Modification of Provisions.--Notwithstanding
any other provision of this part, the Secretary may suspend or modify,
in whole or in part, the application of any provision of this part if
the Secretary determines that the action is appropriate, taking into
account--
``(1) the interests of consumers, workers in the food
industry, businesses (including small businesses), and
agricultural producers; and
``(2) the relative competitiveness of domestically produced
and imported foods containing sugar.''.
(d) Administration of Tariff Rate Quotas.--Section 359k of the
Agricultural Adjustment Act of 1938 (7 U.S.C. 1359kk) is amended to
read as follows:
``SEC. 359K. ADMINISTRATION OF TARIFF RATE QUOTAS.
``(a) Establishment.--Notwithstanding any other provision of law,
at the beginning of the quota year, the Secretary shall establish the
tariff-rate quotas for raw cane sugar and refined sugar at no less than
the minimum level necessary to comply with obligations under
international trade agreements that have been approved by Congress.
``(b) Adjustment.--
``(1) In general.--Subject to subsection (a), the Secretary
shall adjust the tariff-rate quotas for raw cane sugar and
refined sugar to provide adequate supplies of sugar at
reasonable prices in the domestic market.
``(2) Ending stocks.--Subject to paragraphs (1) and (3),
the Secretary shall establish and adjust tariff-rate quotas in
such a manner that the ratio of sugar stocks to total sugar use
at the end of the quota year will be approximately 15.5
percent.
``(3) Maintenance of reasonable prices and avoidance of
forfeitures.--
``(A) In general.--The Secretary may establish a
different target for the ratio of ending stocks to
total use if, in the judgment of the Secretary, the
different target is necessary to prevent--
``(i) unreasonably high prices; or
``(ii) forfeitures of sugar pledged as
collateral for a loan under section 156 of the
Federal Agriculture Improvement and Reform Act
of 1996 (7 U.S.C. 7272).
``(B) Announcement.--The Secretary shall publicly
announce any establishment of a target under this
paragraph.
``(4) Considerations.--In establishing tariff-rate quotas
under subsection (a) and making adjustments under this
subsection, the Secretary shall consider the impact of the
quotas on consumers, workers, businesses (including small
businesses), and agricultural producers.
``(c) Temporary Transfer of Quotas.--
``(1) In general.--To promote full use of the tariff-rate
quotas for raw cane sugar and refined sugar, notwithstanding
any other provision of law, the Secretary shall promulgate
regulations that provide that any country that has been
allocated a share of the quotas may temporarily transfer all or
part of the share to any other country that has also been
allocated a share of the quotas.
``(2) Transfers voluntary.--Any transfer under this
subsection shall be valid only on voluntary agreement between
the transferor and the transferee, consistent with procedures
established by the Secretary.
``(3) Transfers temporary.--
``(A) In general.--Any transfer under this
subsection shall be valid only for the duration of the
quota year during which the transfer is made.
``(B) Following quota year.--No transfer under this
subsection shall affect the share of the quota
allocated to the transferor or transferee for the
following quota year.''.
(e) Effective Period.--Section 359l(a) of the Agricultural
Adjustment Act of 1938 (7 U.S.C. 1359ll(a)) is amended by striking
``2008'' and inserting ``2015''.
SEC. 4. REPEAL OF FEEDSTOCK FLEXIBILITY PROGRAM FOR BIOENERGY
PRODUCERS.
(a) In General.--Section 9010 of the Farm Security and Rural
Investment Act of 2002 (7 U.S.C. 8110) is repealed.
(b) Conforming Amendments.--
(1) Section 359a(3)(B) of the Agricultural Adjustment Act
of 1938 (7 U.S.C. 1359aa(3)(B)) is amended--
(A) in clause (i), by inserting ``and'' after the
semicolon at the end;
(B) in clause (ii), by striking ``; and'' at the
end and inserting a period; and
(C) by striking clause (iii).
(2) Section 359b(c)(2)(C) of the Agricultural Adjustment
Act of 1938 (7 U.S.C. 1359bb(c)(2)(C)) is amended by striking
``, except for'' and all that follows through ``of 2002''.
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Sugar Reform Act of 2015 This bill revises the Department of Agriculture (USDA) sugar program to decrease price support levels and make other modifications. The bill amends the Federal Agriculture Improvement and Reform Act of 1996 to decrease the rate for price support loans to processors of domestically grown sugarcane and sugar beets. The loan rate is the price level at which processors can take out loans. The bill amends the Agricultural Adjustment Act of 1938 to require USDA to set the marketing allotments at a level appropriate to maintain adequate domestic supplies at reasonable prices. The allotments limit the amount of sugar that each processor may sell. The allotments may be suspended or modified based on: (1) the interests of consumers, workers, businesses, and agricultural producers; and (2) the relative competitiveness of domestically produced and imported foods containing sugar. In setting import quotas necessary to comply with trade agreements, USDA must: set the quotas at no less than the minimum level necessary for compliance, adjust the quotas to provide adequate domestic supplies at reasonable prices, establish and adjust quotas so that the ratio of sugar stocks to total sugar use at the end of the year will be approximately 15.5% or the target necessary to prevent unreasonably high prices or forfeitures, and permit the temporary transfer of quotas between countries. The bill amends the Farm Security and Rural Investment Act of 2002 to repeal the Feedstock Flexibility Program for Bioenergy Producers, which requires USDA to purchase sugar from domestic processors and sell it to bioenergy producers for biofuel production.
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