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Extreme helium star
An extreme helium star (abbreviated EHe), or a PV Telescopii Variable, is a low-mass supergiant that is almost devoid of hydrogen, the most common chemical element of the Universe. Since there are no known conditions where stars devoid of hydrogen can be formed from molecular clouds, it is theorized that they are the product of the mergers of helium-core and carbon-oxygen core white dwarfs.
Extreme helium stars form a sub-group within the broader category of hydrogen-deficient stars. The latter includes cool carbon stars like R Coronae Borealis, helium-rich spectral class O or B stars, population I Wolf–Rayet stars, AM CVn stars, white dwarfs of spectral type WC, and transition stars like PG 1159.[1]
The first known extreme helium star, HD 124448, was discovered in 1942 by Daniel M. Popper at the McDonald Observatory in Austin, Texas, USA. This star displayed no lines of hydrogen in its spectrum, but strong helium lines as well as the presence of carbon and oxygen.[2] The second, PV Telescopii, was discovered in 1952, and by 1996 a total of 25 candidates had been found. (This list was narrowed to 21 by 2006.)[3] A common characteristic of these stars is that the abundance ratio of carbon to helium is always in the range of 0.3 to 1%. This is despite wide variation of other abundance ratios in EHe stars.[4]
The known extreme helium stars are supergiants where hydrogen is underabundant by a factor of 10,000 or more. The surface temperatures of these stars range from 9,000–35,000 K. They are primarily composed of helium, with the second most abundant element, carbon, forming about one atom per 100 atoms of helium. The chemical composition of these stars implies that they have undergone both hydrogen and helium burning at some stage of their evolution.[3]
Theoretical models
Two possible scenarios were proposed to explain the composition of extreme helium stars.[3]
1. The double-degenerate (DD) model explained the stars as forming in a binary system consisting of a smaller helium white dwarf and a more massive carbon-oxygen white dwarf. Both stars had ceased to produce energy through nuclear fusion and were now compact objects. The emission of gravitational radiation caused their orbit to decay until they merged. If the combined mass does not exceed the Chandrasekhar limit, the helium will accrete onto the C-O dwarf and ignite to form a supergiant. Later this will become an EHe star before cooling to become a white dwarf.[3]
2. The final-flash (FF) model suggested that an EHe star could form as a late evolutionary stage of a star after if had left the asymptotic giant branch. As the star is cooling to form a white dwarf, helium ignites in a shell around the core, causing the outer layers to expand rapidly. If the hydrogen in this envelope is consumed, the star becomes hydrogen deficient and it contracts to form an EHe.[3]
Examination of element abundances from seven EHe stars agreed with those predicted by the DD model.[3]
1. ^ Jeffery, C. S.; Heber, U.; Hill, P. W.; Dreizler, S.; Drilling, J. S.; Lawson, W. A.; Leuenhagen, U.; Werner, K. (August 28 – September 1, 1995). "A catalogue of hydrogen-deficient stars". In Jeffery, C. S.; Heber, U. (eds.). Hydrogen deficient stars, Proceedings. 96. Bamberg, Germany: Astronomical Society of the Pacific Conference Series (published 1996). Bibcode:1996ASPC...96..471J.
2. ^ Popper, Daniel M. (June 1942). "A Peculiar B-Type Spectrum". Publications of the Astronomical Society of the Pacific. 54 (319): 160–161. Bibcode:1942PASP...54..160P. doi:10.1086/125431.
3. ^ a b c d e f Pandey, Gajendra; Lambert, David L.; Jeffery, C. Simon; Rao, N. Kameswara (February 2006). "An Analysis of Ultraviolet Spectra of Extreme Helium Stars and New Clues to Their Origins". The Astrophysical Journal. 638 (1): 454–471. arXiv:astro-ph/0510161. Bibcode:2006ApJ...638..454P. doi:10.1086/498674.
4. ^ Pandey, Gajendra; Kameswara Rao, N.; Lambert, David L.; Jeffery, C. Simon; Asplund, Martin (July 2001). "Abundance analyses of cool extreme helium stars". Monthly Notices of the Royal Astronomical Society. 324 (4): 937–959. arXiv:astro-ph/0101518. Bibcode:2001MNRAS.324..937P. doi:10.1046/j.1365-8711.2001.04371.x.
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BX Circini
BX Circini is a star in the constellation Circinus. Its variability was discovered in 1995, with its apparent magnitude ranging from 12.57 to 12.62 over a period of 2 hours 33 minutes. It is currently classified as a PV Telescopii variable star, but has been put forward as the prototype of a new class of pulsating star—the BX Circini variables—along with the only other known example, V652 Herculis. This class of star is rare, possibly because this is a brief stage of stellar evolution. Its mass has been calculated to be around 40 percent that of the Sun and the average surface temperature has been measured at 23,390 ±90 K using optical spectra, but 1750 K cooler if analysing it in both the visual and ultraviolet. The temperature appears to vary by 3450 K. It has an extremely low proportion of hydrogen, which was first noticed in 1980. In fact, over 99% of its composition appears to be helium, qualifying it as an extreme helium star. Its origin is unclear, but thought to be a result of the merger of a helium white dwarf with a carbon/oxygen one. The two merge violently, with material from the lighter helium white dwarf forming the outer envelope. The resulting star expands and shines as a yellow giant, its outer helium shell igniting and undergoing fusion as material continues to be accreted from the lighter star. The size of the star is maintained by the weight upon the helium shell, and once that has become light enough and the helium is exhausted, the star begins heating and shrinking, becoming the smaller blue star now observed.
Circinus is a small, faint constellation in the southern sky, first defined in 1756 by the French astronomer Nicolas-Louis de Lacaille. Its name is Latin for compass, referring to the drafting tool used for drawing circles (it should not be confused with Pyxis, a constellation that represents a mariner's compass which points north). Its brightest star is Alpha Circini, with an apparent magnitude of 3.19. Slightly variable, it is the brightest rapidly oscillating Ap star in the night sky. AX Circini is a Cepheid variable visible with the unaided eye, and BX Circini is a faint star thought to have been formed from the merger of two white dwarfs. Two sun-like stars have planetary systems: HD 134060 has two small planets, and HD 129445 has a Jupiter-like planet. Supernova SN 185 appeared in Circinus in 185 AD and was recorded by Chinese observers. Two novae have been observed more recently, in the 20th century.
The Milky Way runs through the constellation, featuring prominent objects such as the open cluster NGC 5823 and the planetary nebula NGC 5315. Circinus hosts a spiral galaxy, the Circinus Galaxy, which was discovered in 1977 and is the closest Seyfert galaxy to the Milky Way. The Alpha Circinids (ACI), a meteor shower also discovered in 1977, radiate from this constellation.
Compact star
In astronomy, the term compact star (or compact object) refers collectively to white dwarfs, neutron stars, and black holes. It would grow to include exotic stars if such hypothetical, dense bodies are confirmed to exist. All compact objects have a high mass relative to their radius, giving them a very high density, compared to ordinary atomic matter.
Compact stars are often the endpoints of stellar evolution, and are in this respect also called stellar remnants. The state and type of a stellar remnant depends primarily on the mass of the star that it formed from. The ambiguous term compact star is often used when the exact nature of the star is not known, but evidence suggests that it has a very small radius compared to ordinary stars. A compact star that is not a black hole may be called a degenerate star.
DY Centauri
DY Centauri is a variable star in the constellation Centaurus. From its brightness, it is estimated to be 7000 parsecs (23000 light-years) away from Earth.DY Centauri is classified as a R Coronae Borealis variable (RCB), a rare class of supergiant stars which show rapid and irregular decreases in brightness due to the formation of dust clouds on the stellar surface. However, DY Centauri is not an active RCB star anymore, and the last registered obscuration event was in 1934. This seems to be related to evolutionary changes in the star, represented by a very fast horizontal movement across the top of the HR diagram. Spectroscopic and photometric evidence show DY Centuari has increased its effective temperature from 5800 K in 1906 to 24800 K in 2010, while maintaining constant luminosity. As consequence, its visual apparent magnitude has faded from about 11.75 in the beginning of the 20th century to 13.2 in 2010 (due to changes in the bolometric correction), while its radius is calculated to have decreased from 100 R☉ to 8 R☉. There are only three other known stars with this behavior, called hot RCB stars.Periodic changes in the radial velocity of DY Centauri have been detected, indicating that the star in a single-lined spectroscopic binary in an eccentric orbit (e = 0.44) with a period of 39.67 days. The companion star has an estimated minimum mass of 0.2 M☉, so it can be a low mass white dwarf or main sequence star. With an estimated separation of only 10 R☉ at periastron, the system must have interacted in the past when the primary had larger dimensions, forming a common envelope.DY Centauri has a peculiar chemical composition and is poor in hydrogen and rich in helium and carbon, being identified as an extreme helium star (EHe). In comparison to other RCB and EHe stars, however, its hydrogen content is relatively high. Stars of this type are believed to be the product of the merger of two white dwarfs, therefore being single stars, which is inconsistent with the identification of DY Centauri as a close binary. Thus, the origin and evolutionary state of the DY Centauri system remain uncertain. In the future, it is likely that the primary will evolve to a B subdwarf, a class of stars frequently found in binary systems.The spectrum of DY Centauri indicates the presence of a low density expanding nebula around it, formed by gas ionized by ultraviolet radiation from the star. The nebula has an estimated dimension of 1.2 arcseconds and, from its expansion velocity, was probably created about a thousand years ago.
EHE may refer to:
Epithelioid hemangioendothelioma
Extreme helium star
Marriage (1929 film) (German: Die Ehe)
Helium-weak star
Helium-weak stars are chemically peculiar stars which have a weak helium lines for their spectral type. Their helium lines place them in a later (ie. cooler) spectral type then their hydrogen lines.
Outline of astronomy
PV Telescopii
PV Telescopii (also known as HD 168476) is a class B-type (blue) supergiant extreme helium star in the constellation Telescopium. It is also the prototype of variable stars called PV Telescopii variables.
PV Telescopii variable
PV Telescopii variable is a type of variable star that is established in the General Catalogue of Variable Stars with the acronym PVTEL. This class of variables are defined as "helium supergiant Bp stars with weak hydrogen lines and enhanced lines of He and C". That is, the hydrogen spectral lines of these stars are weaker than normal for a star of stellar class B, while the lines of helium and carbon are stronger. The prototype for this category is HD 168476, also known as PV Telescopii, which undergoes small but complex luminosity variations and radial velocity fluctuations. The PV Tel stars are extremely hydrogen-deficient compared to other B-class stars and vary in luminosity on time scales ranging from a few hours to several years. As of 2008, there are twelve confirmed PV Tel variables in the General Catalogue of Variable Stars.PV Telescopii variables are subdivided into three distinct types on the basis of spectral type: type I represents late B and A stars, type II represents O and early B, and type III represents F and G stars. The type III stars are always carbon-rich and hydrogen-deficient, while the type I and II stars do not necessarily have an excess of carbon. The hotter types pulsate more quickly than the cooler types.
R Coronae Borealis
R Coronae Borealis is a peculiar low-mass yellow supergiant star in the constellation of Corona Borealis. It is the prototype of the rare RCB class of variable stars, which fade by several magnitudes at irregular intervals. R Coronae Borealis itself normally shines at approximately magnitude 6, just about visible to the naked eye, but at intervals of several months to many years fades to as faint as 15th magnitude. Over successive months it then gradually returns to its normal brightness, giving it the nickname "reverse nova".
Telescopium is a minor constellation in the southern celestial hemisphere, one of twelve named in the 18th century by French astronomer Nicolas-Louis de Lacaille and one of several depicting scientific instruments. Its name is a Latinized form of the Greek word for telescope. Telescopium was later much reduced in size by Francis Baily and Benjamin Gould.
The brightest star in the constellation is Alpha Telescopii, a blue-white subgiant with an apparent magnitude of 3.5, followed by the orange giant star Zeta Telescopii at magnitude 4.1. Eta and PZ Telescopii are two young star systems with debris disks and brown dwarf companions. Telescopium hosts two unusual stars with very little hydrogen that are likely to be the result of two merged white dwarfs: PV Telescopii, also known as HD 168476, is a hot blue extreme helium star, while RS Telescopii is an R Coronae Borealis variable. RR Telescopii is a cataclysmic variable that brightened as a nova to magnitude 6 in 1948.
Variable star
Extrinsic variables, whose apparent changes in brightness are due to changes in the amount of their light that can reach Earth; for example, because the star has an orbiting companion that sometimes eclipses it.Many, possibly most, stars have at least some variation in luminosity: the energy output of our Sun, for example, varies by about 0.1% over an 11-year solar cycle.
Luminosity class
Star systems
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In binary
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You Are On Multi Choice Question Bank SET 1253
62651. A loss less line is terminated in a circular lines are E lines
62652. Which of the following terminations makes the input impedance of a line equal to characteristic impedance Z0?
62653. In microwave system the function of mode filter is
62654. The total field developed by an antenna array at a distant point is
62655. High speed logic circuits use
62656. To couple a coaxial line to a parallel wire line it is best to use
62657. Assertion (A): A quarter wave transformer is used to match a resistive load to a transmission line.Reason (R): A quarter wave transformer is a transmission line of quarter wave length.
62658. Assertion (A): Magnetron is generally used in n mode.Reason (R): Frequency for p mode can be easily separated from adjacent modes.
62659. A balun should have
62660. Assertion (A): The velocity factor of a line is the ratio of wave velocity on the line to speed of light.Reason (R): If the conductors of a line are immersed in a non magnetic insulating liquid, the wave velocity increases.
62661. In mode filter of the given figure which of the following modes is unaffected
62662. The directive gain of a transmitting antenna is
62663. A duplexer is used to
62664. A branched duplexer requires
62665. In a backward wave oscillator the wave
62666. A coaxial line has L = 500 nH/m and C = 50 pF/m. The characteristic impedance is
62667. The main feature of a parametric amplifier is
62668. Assertion (A): PIN diode is commonly used for microwave control.Reason (R): A PIN diode uses heavily doped p and n materials.
62669. In a vacuum tube, the transit time of electron between cathode and anode is important at
62670. Assertion (A): A line of length and short circuited at far end has an input impedance of infinity.Reason (R): A line of length and short circuited at far end behaves as a parallel resonant circuit.
62671. A cavity resonator is
62672. If antenna diameter is increased four times, the maximum range is increased by a factor of
62673. Assertion (A): Gunn diode is a transferred electron device.Reason (R): A Gunn oscillator uses the phenomenon of transferred electron effect.
62674. Atomic and molecular resonance is observed in many substances
62675. The component in the given figure is
62676. The semiconductor diode which can be used in switching circuit in microwave range is
62677. In the given figure the reflected current wave after first reflection is
62678. A line has an attenuation of 0.054 Np/m. The attenuation in decibels is
62679. If a line is open circuited Zin = Z0 tanh (gl).
62680. A reflex klystron oscillator uses
62681. A coaxial RF cable has a characteristic impedance of 50 Ω and C equal to 40 pF/m. The inductance is
62682. To estimate the water quantity which one of the following is most important?
62683. In a multicavity klystron amplifier the signal to be amplified develops an ac voltage of signal frequency across the gap in buncher cavity
62684. If VSWR is infinite, the transmission line is terminated in
62685. In a circular waveguide TE21 mode has lowest cutoff frequency
62686. The number of TV channels which can be accommodated in a spectrum of 300 MHz is about
62687. The noise figure of multicavity klystron amplifier is very low
62688. Assertion (A): The velocity of electromagnetic waves on overhead lines and coaxial cables is the same.Reason (R): Free space has an intrinsic impedance of 377 ohms.
62689. In the given figure the E and H lines in a coaxial cable
62690. Roughly the time required for microwave cooking as compared to conventional cooking is
62691. If the minimum range of a radar is to be doubled, the peak power has to be increased by a factor of
62692. Which mode has the lowest cut off frequency in circular wave guides?
62693. Assertion (A): Klystron amplifiers use one or more intermediate cavities in addition to buncher and catcher cavity.Reason (R): When one or more intermediate cavities are used the bandwidth can be increased.
62694. A wave Em cos (bx - ωt) is a backward wave.
62695. A reflex klystron oscillator is a
62696. Consider the following applications TV tuningActive filterMicrowave frequency multiplication In which of above can a varactor diode be used?
62697. Consider the following statements Dissipative attenuator has a fixed value of attenuation.Reflective attenuator has a fixed value of attenuation.Both dissipative and reflective attenuators are available only with fixed attenuation.Both dissipative and reflective attenuators are available with either fixed or variable attenuation. Which of the above are correct?
62698. The quantity of water requirement for domestic purpose is:
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Tennis ball can relay
This Tennis ball can relay lesson plan also includes:
Students pull directions out of a tennis ball can and read and perform that task. For this reading and physical education lesson plan, students have to read each task inside a tennis ball can and perform a physical task.
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5 of the Most Inspirational Nelson Mandela Quotes
This year marks 100 years since Nelson Mandela’s birth. His humanity and commitment to education continues to inspire. By celebrating Mandela Day, World Bicycle Relief honors his legacy of positive change and perseverance.
Who was Nelson Mandela?
Nelson Mandela influenced great change in South Africa that resonated around the world. He pioneered the end of white minority rule and fostered post-apartheid reconciliation in the early 1990s. In 1994, he became South Africa’s first democratically elected president and its first black leader. Unlike his predecessors, Mandela stepped down at the conclusion of his term.
Before becoming president, Mandela was imprisoned for 27 years for standing up to the human rights abuses committed by the apartheid government against black South Africans. After being released from prison in 1990, Mandela addressed the crowds from Cape Town’s City Hall, saying:
As a sign of gratitude for his selflessness, many South Africans refer to Mandela as Madiba, the African name of his tribe. When Mandela was a child, it was customary for a South African student to be assigned an English name. In school, he came to be known as Nelson. Many South Africans still refer to Mandela as Madiba as a sign of respect and endearment, paying tribute to his African roots.
After his presidency, Mandela became a philanthropist with a special focus on education. Through the Nelson Mandela Foundation in 1999, he pursued noble work such as rural development, school construction and combating HIV/AIDS.
Nelson Mandela’s legacy of humility and service lives on not only in South Africa, but also around the world.
In honor of International Nelson Mandela Day on July 18, we share some of our favorite Madiba quotes:
mandela quote
At World Bicycle Relief, we believe that education is the gateway to a world of opportunity. We provide bicycles to students to help them travel to school because, armed with an education, they can work hard and pursue their dreams.
WBR strives to improve access to education. Facing challenges such as long distances and unsafe passage, students in rural Africa who walk to school are often late to class – or don’t make it at all. Students with bicycles have fewer absences, more time in class, and more time to study. Education not only improves the life of the individual but it also greatly benefits the entire community, building a better future for all.
mandela quote
We always tell our supporters that The Power of Bicycles isn’t enough to make our work possible. It’s the power of YOU. Each individual can make a world of difference. Any act of kindness or justice, big or small, matters. At World Bicycle Relief, we strive to leave the world a better place.
mandela quote
Many of the communities we serve are made up of individuals who overcome adversity every day. At bicycle distribution ceremonies, Co-Founder Leah Missbach Day often asks students what they want to be when they grow up. In the beginnings of our work, sometimes, they didn’t have answers. Returning to visit these students after a year of using the bicycle, she is met with enthusiasm about becoming a doctor, lawyer, nurse, teacher…With bicycles, students are able to see a better path ahead, work hard, and reach their dreams.
We are dedicated to continuous learning and improvement, as well. We monitor and evaluate our programs so we improve upon them. We see every obstacle as a learning opportunity and a chance to expand our commitment to creating access to resources.
In the rural communities we serve, many people struggle to meet their most basic human needs: shelter, clothing, food and water. With a bicycle, individuals can fight poverty through simple, sustainable measures. We are not in the business of providing charity through bicycles. With a bicycle, recipients are empowered to find new ways to fill those basic needs and pursue a brighter future.
mandela quote
With your help, we can impact lives by providing a tool that allows individuals in developing nations to drive their own positive change. With the bicycle you can help provide students, healthcare workers and entrepreneurs in rural communities the opportunity to change their world.
Will you help us provide The Power of Bicycles?
Donate today, and your contribution will be matched 1:1!
Molly Loftus is a World Bicycle Relief volunteer blogger. She holds a bachelor’s degree in International Relations from Claremont McKenna College. She is passionate about educational equity, West African politics and adventuring on her bike in pursuit of food.
References: Lee, J. (2013). Why Nelson Mandela is Called Madiba. USA Today Network. Retrieved from http://www.usatoday.com/story/news/nation-now/2013/12/06/nelson-mandela-madiba-meaning/3889469/
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One video shoot and two edits leverage their investment and provide both an orientation/recruitment video and a marketing video
CHALLENGE: JEA Senior Living needed two videos with similar messages: one for building culture and recruiting employees, and one to introduce prospective residents and their families to their way of caring for residents.
SOLUTION: Develop two versions of their video with different emphases to maximize their investment. Both videos introduce their audiences to the people, passion, and purpose behind their work, but in different ways.
RESULT: JEA Senior Living personalizes and brings heart to their work, which allays fears families may have about finding a home for their loved one. This is the foundation for building trust and preference for their organization.
You can grow your business.
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Practical Geometry - NCERT Class 7 Maths
Go back to 'Class 7th Maths Solutions'
The chapter 10 begins with an introduction to Practical Geometry by explaining the stepwise procedure for Construction of a line parallel to the given line through a point not on the line.After this, the Construction of a Triangle and various categories under it such as construction of a triangle using SSS Criterion [the length of three sides are known], SAS Criterion [the measure of two sides and an angle is known ], and ASA Criterion [the measure of two angles and a side is known ] is described in detail. Constructing a right-angled triangle when the length of one leg and its hypotenuse are given [RHS Criterion] is the last topic discussed in this chapter.
Download Cuemath's NCERT Math solutions complete with reasoning
Practical Geometry | Solved Examples
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Recipe: studysilverbook
Label: Read 'The Silver Book'
Start Description: Members of the Ordo took an oath, the Silver Chain, that forbade men to lie with woman, or women with men: 'for what may come is not always the Crime of the Sky, yet that is a furious danger.' It was apparently permissible for men to lie with men, and women with women - in fact, Burzghash suggests that should be encouraged, to distract from other temptations.
Description: The manual prescribes potential countermeasures to protect those who might be tempted to go against the oath: masks, disfigurement, severe poetic disciplines. Those who do break it are to be punished with death, although there are lesser punishments prescribed for various acts that don't involve actual coitus. An invocation is included which was used to incorporate these punishments into summoning rites.
Action: study
Requirements: 1
Table Requirements: None
Extant Requirements: None
Effects: -11
Aspects: None
Mutation Effects: None
Alternative Recipes: Nothing
Linked Recipes: Nothing
From Recipes: Nothing
Slots: None
Warmup: 60
Maximum Executions: 0
Deck Effect: None
Internal Deck: None
Ending Flag: None
Signal Ending Flavour: None
Portal Effect: none
Craftable? Yes
Hint Only? No
Signal Important Loop? No
Comments: None
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Women have been the heart of the Christian right for decades
Alabama’s new abortion restrictions were signed into law by Gov. Kay Ivey. But more has been said recently about the fact that the bill was passed by 25 white men in the state Senate. Media reports have pointed to how this law will disproportionately affect black and poor women.
Only four women currently serve in Alabama’s state Senate. Three voted against the bill, while one abstained.
In response to the Alabama vote, Democratic State Sen. Linda Coleman-Madison compared men’s votes on abortion legislation to “a dentist making a decision about heart surgery.”
“That’s why we need more women in office,” Coleman-Madison said.
Across the country, women are underrepresented in legislatures. But the question is: Would voting more women into office necessarily shift the politics of abortion?
Conservative women’s activism
My book, “This Is Our Message,” examines the history of women’s leadership in the modern religious right. When this movement emerged in the late 1970s, women were at the forefront. They helped shape the rhetoric of “family values,” which has included opposition to abortion, feminism and same-sex marriage.
These women’s contributions, however, are often overlooked.
My research shows that in the 1980s, news reports almost always credited conservative men with leading the Christian right. Prominent voices included televangelist Pat Robertson and Jerry Falwell, who helped found the Moral Majority, a conservative Christian political lobbying group, in 1979.
But women also led the movement. Phyllis Schlafly is best known among these women for her fight against the Equal Rights Amendment, which would have outlawed gender discrimination in any law at the local, state or national level. In the early 1970s, the amendment passed through Congress with bipartisan support. Ratification by the states seemed all but certain.
Opponents of the Equal Rights Amendment, led by Phyllis Schlafly, center, white coat, march in front of the White House in Washington, D.C., Feb. 5, 1977. AP Photo/Charles Tasnadi
Then Schlafly mobilized hundreds of thousands of women against the amendment. They argued that it would make women subject to the military draft and that it would eliminate laws designed to protect women in the workplace and in divorce proceedings. They also raised the possibility of consequences that seemed alarming at the time but are familiar today, including same-sex marriage and gender-neutral public bathrooms.
These women lobbied their representatives, protested in state legislatures and wrote letters to the editors of local and national newspapers. In 1982, the amendment failed, lacking sufficient support from the states.
Schlafly was not the only female leader of the religious right in this era. In the late 1970s, pop singer Anita Bryant galvanized a sweeping backlash against the gay rights movement. When her local Miami-Dade County passed anti-discrimination protections for gay residents in 1977, Bryant led a successful repeal effort. She then lent her celebrity status and experience to similar fights nationwide.
Two years later, Beverly LaHaye founded Concerned Women for America, which is now the largest lobbying group in the country representing conservative women. Since its founding, the group has organized millions of women across the country to lobby for socially conservative legislation at the local, state and national levels.
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Have you ever wondered how to make the transition from lazy summer days playing at the pool to a full day of learning a bit easier for your child?
Administrators, principals and teachers spent the summer cleaning, organizing, digging into academic data, learning and preparing for the school year. We are excited and looking forward to another great year.
Here are five tips to help parents get their kids ready to go back to school.
1. Schedule. Schools and classrooms run on schedules. A routine provides students with security and predictability for their day. At home, start with a consistent wake-up and bedtime. Serve meals at the same time each day. Limit snacks to specific times. Set a schedule for activities — like going outside at 9 a.m. each day and having a quiet reading time at 1 p.m. each afternoon.
2. Routines and procedures. Routines and procedures are what make classrooms and schools run effectively. There are routines for lining up, sharpening a pencil, going through the lunch line and more. Help your student prepare for routines and procedures at school by performing the same task the same way on a daily basis. This can be done with a simple chore such as making a bed. Give your child two to four steps to make his or her bed, and ask your child to complete this task every day.
3. Academic mindset. During the school day, every minute of class time has an academic focus. We have a lot to teach. You can help your child prepare for this. Read and discuss a newspaper article, book or story. When you’re cooking, ask your child how much of an ingredient would be needed if you doubled the recipe or cut the recipe in half. At the store, ask your child to count out the correct amount of money or figure out how much change you will get back. Start a journal with your child. You and your child can write back and forth about any topic. This will get your student writing, and you will model good writing skills for him or her.
4. Movement. Movement is good for learning. In “Teaching with the Brain in Mind,” author Eric Jensen writes that movement can strengthen learning, improve memory and enhance learner motivation and morale. Go for a walk, stop and observe a bug, stretch when you wake up or turn on some music and dance.
5. Talk about kindness. Kindness matters. Take some time to review your behavior expectations with your child. Remind them to always show kindness to others. Also, ask your student if they know how to solve a problem at school. They can always talk to a teacher, principal or parent.
There are many pieces to a school day and educating students. By incorporating these tips, you will prepare your student for some of the expectations teachers and schools will have on the first day. Our students’ best achievements happen when school staff and parents work together with the students.
Aimee Kasper is principal of Kishwaukee Elementary School in Rockford. She recently was named the 2016-17 Elementary School Principal of the Year by the Illinois Principals Association.
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What is fallout?
What is fallout? What exactly is fallout? Everyone should know it occurs after a nuclear bomb is detonated, plus you’re supposed to board yourself up in your shelter and hide away from it, so we know we should be scared of it, by why should we be exactly?
Nuclear fallout is simply debris and particles which are lifted, or suspended, by a bomb’s detonation and become radioactive and harmful to living matter. The term comes from the fact that this newly radioactive material, usually in the form of dust, literally falls out of the upper atmosphere, hence ‘fallout’ – as opposed to simply falling out with the explosion because it exploded during your dinner.
It is split into two types: Global and Local. Global fallout occurs when a bomb is detonated far above the ground and all the nuclear material (fissioned and un-fissioned) is vaporized into tiny particles to be swept away into the stratosphere, being dropped on the whole world in the process. Local fallout occurs when a nuclear device is detonated much closer to the ground, with ground material forced up into the radioactive cloud by the surface bust (like when dirt is thrown in the air when a grenade explodes) before it is swept away by the MACH Wave, becomes radioactive and falls back to the earth’s surface.
Many of the radioactive isotopes produced in fallout have a short half-life, which is the time it takes for half of the isotope to decay, meaning that a resulting fallout’s radioactivity tends to decrease fairly quickly. However, some radioisotopes like strontium-90 have a very long half-life meaning an area can still maintain a high level of radioactivity for long periods afterwards.
It is a pretty good idea to cover up when you think about it. Short range Alpha and Beta particles struggle to penetrate skin and heavy clothing, however, long range Gamma Rays do the most damage. Gamma Rays are a lot stronger and seek out calcium – meaning your bones are in danger. But all of these struggle to break through the barriers you create between the particles and your skin, so wrap up for Alpha and Beta particles and stay in doors for the stronger Gamma Rays.
There are a range of potentially dangerous effects posed by fallout radiation. These are broken into three phases: the first is a mixture of nausea and vomiting for 2-3 days. The second phase sees an absence of the original symptoms and the longer this lasts for, the less severe the original exposure. Finally, the third phase, if the exposure is severe enough to induce, involves incapacitation and severe illness, brought on by bone marrow damage, which can occur as long as 20 days after the end of phase 1. Still, there are long term worries to, well, worry about, like decreased fertility, genetic mutations and cancers which can take decades to develop.
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3-5 The cell wall
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Learning Objectives
After reading this section, students will...
1. Be able to describe the function and location of the periplasm.
2. Be able to describe the function of the cell wall and the two common cell wall structures.
The periplasm is between the cytoplasmic and outer membranes in Gram-negative bacteria
The periplasm is found in Gram-negative bacteria and is the space in between the cytoplasmic and outer membranes. (Many feel a periplasm is also present in Gram-positive bacteria in between the cytoplasmic membrane and the peptidoglycan.) The periplasm is filled with water and proteins and is therefore somewhat reminiscent of the cytoplasm. However, pools of small molecules in the periplasm are not like those in the cytoplasm because the membrane prevents the free exchange between these two compartments. Also, the proteins found in the periplasm are distinct from those in the cytoplasm and are specifically guided to this site during translation through specific signal sequences typically near their N-termini. Table 3.2 lists some examples of these proteins.
The peptidoglycan shell that provides the strength to prokaryotic membranes is also found in the periplasmic space of Gram-negative bacteria, while in Gram-positive bacteria it provides the outside border to the periplasm.
Table 3.2 Different types of periplasmic enzymes and their role in the cell
Enzyme Type Examples Function
Hydrolytic enzymes phophatases Degrading phosphate-containing compounds.
proteases Degrading proteins and peptides.
endonucleases Degrading nucleic acids.
Binding proteins sugars, amino acids, norganic ions, vitamins Binding substrates and docking with transport protein in membrane.
Chemoreceptors Chemotaxis, ermination Sensing the environment and changing cell behavior in response.
Detoxifying enzymes β-lactamase Degrading penicillin and related compounds before they get into the cell.
Periplasmic enzymes have several main functions, detecting nutrients in the environment, degradation of polymers, and protection from harmful compounds.
The cell wall surrounds and holds in the microbe
This section will restrict itself to the bacterial cell wall, but at the end of the chapter we will compare this to archaeal cell walls. The cell wall is essential to the survival of most microorganisms. Many microbes live in environments that are relatively dilute and the wall's most important function is to prevent the cell from bursting due to osmotic stress. The cell wall also determines the shape of the cell. Any cell that has lost its cell wall, either artificially or naturally, becomes roughly spherical and lyses due to osmotic pressure, unless placed in certain concentrated solutions. Finally, the cell wall helps to support any structure that penetrates from the cell out into the environment.
A gram-positive bacterium
Figure 3.19. A gram-positive bacterium. Gram stain of the gram-positive bacterium Bacillus cereus
The structure and synthesis of prokaryotic cell walls is unique and many compounds found in the bacterial cell wall are found nowhere else in nature. It is true that plants also make cell walls, but they are chemically and structurally different. There are two basic types of bacterial cell wall structures that have been studied in detail: Gram-positive and Gram-negative. These two classes of bacterial cells look very different following staining with the Gram stain and this has been a standard test for for identification of bacterial species. Figures 2-19 and 2-20 show Gram stains of Gram-positive and Gram-negative bacteria, respectively.
A gram-negative bacterium
Figure 3.20. A gram-negative bacterium. A Gram stain of the gram-negative bacterium Serratia marcescens
When the Gram stain was developed by Hans Christian Gram in 1884 the molecular basis of the stain was unknown. In fact very little was understood about bacteria in general. He just determined empirically that when bacterial smears were run through a four-step staining procedure using two different dyes, some cells retained the first dye and stained purple, while other only retained the second dye and stained pink. Years later it was discovered that the basis for this differential reaction relates to the cell wall as shown in Figure 3.21.
A comparison of the ultrastructure of gram-positive and gram-negative cells
Figure 3.21. A comparison of the ultrastructure of gram-positive and gram-negative cells. The different Gram reactions occur because of structural differences between the bacterial cell walls. Gram-positive cells (Group B streptococci) appear smooth in a scanning electron micrograph (A) and are composed of a single layer of peptidoglycan (B). Gram-negative cells (E. coli) have an undulating surface and have three layers (C and D). (Sources: S. H. Pincus, et al.1992. J. Bacteriol 174:3739-3749 [panels A and B]; M. E. Bayer and C. C. Remsen. 1970. J. Bacteriol. 101:304-313 [panel C]; T. J. Beveridge. 1999. J. Bacteriol. 181:4725-4733 [panel D])
As shown in Figure 3.21, the Gram-negative cell has an additional layer and the outside of the cell appears convoluted when compared to the Gram-positive cell. The Gram-positive wall is much thicker than is the Gram-negative wall and its external appearance is smoother. Gram-positive and Gram-negative cells do share one thing in common that is unique to bacteria - peptidoglycan. We will talk about the structure of this and then move on to examine the various structures found in each cell wall type.
Peptidoglycan is a thick rigid layer composed of an overlapping lattice of two sugars, N-acetyl glucosamine (NAG) and N-acetyl muramic acid (NAM), that are cross-linked by amino acid bridges as shown in Figure 3.22. The exact molecular makeup of these cross-bridges is species-specific. NAM is only found in the cell walls of bacteria and nowhere else. Attached to NAM is a side chain generally composed of four amino acids. In the best-studied bacterial cell walls (E. coli) the cross-bridge is most commonly composed of L-alanine, D-alanine, D-glutamic acid and diaminopimelic acid (DPA).
The chemical structure of peptidoglycan
Figure 3.22. The chemical structure of peptidoglycan. The generalized peptidoglycan monomer showing the two sugars that make up the backbone. The R group consists of four amino acids, with the best-studied cell walls containing L-alanine, D-alanine, D-glutamic acid and diaminopimelic acid.
Note that peptidoglycan contains D-amino acids, which are different than the L-amino acids found in proteins. D-amino acids have the identical composition as L-amino acids, but are their mirror images. The use of D-amino acids is unusual in biology and bacteria have enzymes called racemases to convert between D and L forms specifically for this use.
The NAM, NAG and amino acid side chain form a single peptidoglycan unit that can link with other units via covalent bonds to form a repeating polymer. The polymer is further strengthened by covalent bonds between cross-bridges and the degree of cross-linking determines the degree of rigidity. Figure 3.23 shows an artist's rendering of what the structure might look like. In E. coli, the penultimate D-alanine of one unit is linked to DPA of the next cross-bridge. In some Gram-positive microbes there is a peptide composed of various amino acids that serves as a link between the cross-bridges. For example, in Staphylococcus aureus strains, five glycines make up the linker between peptidoglycan monomers. The sequence of these linkers varies considerably between species. The completed peptidoglycan layer forms a strong mesh that can be thought of as a chain link fence. The complete cell wall contains one or more layers of peptidoglycan one atop the other, providing much of the strength of the cell wall.
A cartoon of the peptiodglycan mesh
Figure 3.23. A cartoon of the peptiodglycan mesh. The peptidoglycan polymers then crosslink with other peptidoglycan chains to form a complex mesh that wraps the cell in a structure a kin to chicken wire.
While both Gram-negative and Gram-positive bacteria have peptidoglycan, its physical arrangement in the cell wall is different. In Gram-positive cells the peptidoglycan is a heavily cross-linked woven structure that encircles the cell in many layers. It is very thick with peptidoglycan accounting for 50% of weight of cell and 90% of the weight of the cell wall. Electron micrographs show the peptidoglycan to be 20-80 nm thick. In Gram-negative bacteria the peptidoglycan is much thinner with only 15-20% of the cell wall being peptidoglycan. In both cases, peptidoglycan is not a barrier to solutes, as the openings in the mesh are large enough for most molecules including proteins to pass through. Figure 3.24 shows a depiction of the Gram-positive cell wall.
The Gram-positive cell wall
Figure 3.24. The Gram-positive cell wall. The cell wall is made mostly of peptidoglycan, interspersed with teichoic acid which knits the different layers together. The amount of crosslinking is higher and the wall is thicker than in gram-negative cell walls.
The Gram-positive cell wall
Gram-positive cells consist almost entirely peptidoglycan, but an important structure found in Gram-positive cell walls is teichoic acid. It is a phosphodiester polymer of glycerol or ribitol joined by phosphate groups. Amino acids such as D-alanine are attached. Teichoic acid is covalently linked to muramic acid and stitches various layers of the peptidoglycan mesh together. Teichoic acid stabilizes the cell wall and makes it stronger. The chemical formula of teichoic acid is shown in Figure 3.25
Teichoic acid
Figure 3.25. Teichoic acid. Teichoic acid is a long, thin molecule that weaves through the peptidoglycan.
Gram-negative cell structure
Gram-negative cell walls have a more complicated structure than do those of Gram-positive organisms. Outside the cytoplasmic membrane is the periplasm, which contains the thin layer of peptidoglycan. The peptidoglycan in Gram-negative cells contains less cross-linking than in Gram-positive cells with no peptide linker. Covalently bound to the peptidoglycan is Braun's lipoprotein, which has a hydrophobic anchor that helps to strongly bind the peptidoglycan to the outer membrane. Figure 3.26 shows the arrangement of the Gram-negative cell wall.
The Gram-negative cell wall
Figure 3.26. The Gram-negative cell wall. The cell wall in Gram-negative bacteria contains much less peptidoglycan and is surrounded by an outer membrane. There is much less crosslinking between the peptidoglycan. LPS is also present in the outer membrane and penetrates into the surrounding environment.
The outer membrane
The outer membrane of Gram-negative bacteria is another lipid bilayer similar to the cytoplasmic membrane, and contains lipids, proteins, and also lipopolysaccharides(LPS). It is a barrier to proteins and prevents enzymes secreted into the periplasm from floating away. The membrane has distinctive sides, with the side that faces the outside containing all the LPS. LPS is composed of two parts: Lipid A and the polysaccharide chain that reaches out into the environment. Lipid A is a derivative of two NAG units with up to 7 hydrophobic fatty acids connected to it that anchor the LPS in the membrane as shown in Figure 3.27. Attached to Lipid A is a conserved core polysaccharide that contains KDO, heptose, glucose and glucosamine sugars. The rest of the polysaccharide consists of repeating sugar units and this is called the O-antigen. The O-antigen varies among bacterial species and even among various isolates of the same species. Many bacterial pathogens vary the make-up of the O-antigen in an effort to avoid recognition by the host's immune system.
The structure of LPS
Figure 3.27. The structure of LPS. LPS is composed of three sections: the lipid A region, a conserved core polysaccharide, and a highly variable O-polysaccharide. (A) The chemical structure of LPS. (B) A molecular model of the outer membrane from Pseudomonas aeruginosa. Source (T. P. Straatsma, Pacific Northwest National Laboratory)
LPS confers a negative charge and also repels hydrophobic compounds including certain drugs and disinfectants that would otherwise kill the cell. Some Gram-negative species live in the gut of mammals and LPS repels fat-solubilizing molecules such as bile that the gal bladder secretes. This repulsion enables these bacteria to survive in this environment. The O-antigen and other molecules on the outer membrane are also used by certain viruses that infect bacteria, as a means to identify the correct hosts for infection.
LPS is medically important because when LPS is released from bacterial cells it is toxic to mammals and is therefore called endotoxin. It creates a wide spectrum of physiological reactions including the induction of a fever (endotoxins are said to be pyrogenic), changes in white blood cell counts, leakage from blood vessels, tumor necrosis and lowered blood pressure leading to vascular collapse and eventually shock. At high enough concentrations the LPS endotoxin is lethal.
There are fewer total proteins and fewer unique types of proteins in the outer membrane than in the cytoplasmic membrane. Porins are particularly important components because of their role in the permeability of the outer membrane to small molecules. Porins are proteins that form pores in the outer membrane large enough to allow passage of most small hydrophilic molecules. Figure 3.28 shows the structure of a porin at the molecular scale. All known porins have a similar structure, with the protein containing a central channel that allows the passage of molecules. This allows migration of these molecules into the periplasmic space for possible transport across the cytoplasmic membrane. Some porins in the outer membrane are general, doing simple discrimination on size and charge, but having little substrate specificity. Examples include OmpF that is selective for positively charged molecules and PhoE that is permeable to negatively charged molecules. Other porins are more specific. The best studied is LamB, which recognizes the sugar polymer maltooligosaccharide and transports it through the outer membrane. Very large or hydrophobic molecules cannot penetrate the outer membrane, so the outer membrane serves as a permeability barrier to at least some molecules.
The molecular structure of a porin
Figure 3.28. The molecular structure of a porin. The view in (A) is from the outside of the cell looking at the membrane surface. The view in (B) is the perspective from the side (i.e. from the membrane). The porin has three protein subunits and the actual pore is the central triangular area in the top panel formed by the three subunits.
There are also other types of outer membrane proteins that are involved in various functions. OmpA in E. coli seems to connect the outer membrane to the peptidoglycan. Some pathogens contain outer membrane proteins that help them neutralize host defenses. Finally all Gram-negative bacteria contain high molecular weight proteins involved in the uptake of large substrates such as iron-complexes and vitamin B12.
The differences between the cell walls of Gram-positive and Gram-negative bacteria greatly influence the success of the microbes in their environments. The thick cell wall of Gram-positive cells allows them to do better in dry conditions because it reduces water loss. The outer membrane and its LPS helps Gram-negative cells excel in the intestines and other host environments. Table 3.3 summarizes the difference between Gram-negative and Gram-positive cell walls.
Table 3.3 Properties of cell walls
Property Gram-positive Gram-negative
Thickness of wall 20-80 nm 10 nm
Number of layers in wall 1 2
Peptidoglycan content >50% 10-20%
Teichoic acid in wall + -
Lipid and lipoprotein content 0-3% 58%
Protein content 0% 9%
Lipopolysaccharide 0 13%
Sensitive to penicillin Yes Less sensitive
Digested by lysozyme Yes Weakly
A summary of the differences between Gram-positive and Gram-negative cell walls.
Some bacteria lack cell walls
For most bacterial cells, the cell wall is critical to cell survival, yet there are some bacteria that do not have cell walls. Mycoplasma species are widespread examples and some can be intracellular pathogens that grow inside their hosts. Cell walls are unnecessary here because the cells only live in the controlled osmotic environment of other cells. It is likely they had the ability to form a cell wall at some point in the past, but as their lifestyle became one of existence inside other cells, they lost the ability to form walls. Consistent with this very limited lifestyle within other cells, these microbes also have very small genomes. They have no need for the genes for all sorts of biosynthetic enzymes, as they can steal the final components of these pathways from the host. Similarly, they have no need for genes encoding many different pathways for various carbon, nitrogen and energy sources, since their intracellular environment is completely predictable. Because of the absence of cell walls, Mycoplasma have a spherical shape and are quickly killed if placed in an environment with very high or very low salt concentrations. However, Mycoplasma do have unusually tough membranes that are more resistant to rupture than other bacteria since this cellular membrane has to contend with the host cell factors. The presence of sterols in the membrane contributes to their durability by helping to increase the forces that hold the membrane together.
Key Takeaways
• Outside the cell membrane is the periplasm, where enzymes often accumulate that perform degradative and transport functions.
• Outside the periplasm in most microbes is the cell wall. The cell wall is important in giving the cell its shape and preventing the cell membrane from rupturing due to the high osmotic pressure it is under.
• Two general types of cell wall structure are found in bacteria, Gram positive and Gram negative.
• Gram-positive cells have a thick peptidoglycan layer surrounding the cell membrane.
• Gram-negative cells have a thin peptidoglycan layer that is surrounded by a second membrane structure, the outer membrane.
• Finally, there are bacteria that have no cell walls.
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Quickcheck 3-5
Answer the questions below and then hit the Grade Exam button
1. Flagella cause movement by their concerted rotation.
1. True
2. False
2. Bacteria can use Type IV pili for motility in an aqueous solution?
1. True
2. False
3. Flagella are assembled by the addition of protein to the tip away from the cell and migrate through the interior of the growing flagella
1. True
2. False
4. Which of the following are possible roles for glycocalyx?
1. Helping cells metabolize sucrose.
2. Allowing cells to attach to specific surfaces
3. Protecting cells from host defense systems in animals.
4. Preventing the bacteria from excessive infectivity.
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Filter by Type Article Q & A Video
Q & A
Can we read “Knight Of Cups” like a poem
Looking to "Knight of Cups" for plot or traditional three act structure is an exercise in futility. So how can a viewer unpack such a deconstructed narrative? The answer could lie not in the language of film but the language of poetry.
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Explain that animals, including humans, cannot make their own food and that when animals eat plants or other animals, the energy stored in the food source is passed to them.
Subject Area: Science
Grade: 4
Body of Knowledge: Life Science
Idea: Level 2: Basic Application of Skills & Concepts
Big Idea: Interdependence -
A. Plants and animals, including humans, interact with and depend upon each other and their environment to satisfy their basic needs.
B. Both human activities and natural events can have major impacts on the environment.
C. Energy flows from the sun through producers to consumers.
Date Adopted or Revised: 02/08
Date of Last Rating: 05/08
Status: State Board Approved
Assessed: Yes
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Learn, hack!
I Control Your Code
Mathias Payer
Chaos Communication Congress 27th (27C3) 2010
Indexed on
Mar 27, 2013
File name
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206.8 KB
Unsafe languages and an arms race for new bugs calls for an additional line of defense in software systems. User-space virtualization uses dynamic instrumentation to detect different attack vectors and protects from the execution of malicious code. An additional advantage of these virtualization systems is that they can be used to analyze different exploits step by step and to extract the exploit code from a running program. This talk explains the concept of different attack vectors (stack buffer overflows, format string attacks, return to libc attacks, race attacks / TOCTTOU, integer overflows, heap buffer overflows, and code anomalies). For each of these attack vectors we show possible exploits and explain how the virtualization system is able to detect and prevent the exploit. User-space virtualization uses a binary translation framework to instrument all running code. The instrumentation works like an additional virtualization layer and makes it possible to observe any changes to the runtime datastructures (code and data) of a running program. We use fastBT to instrument and analyze different exploitable programs. The added instrumentation detects changes in runtime layout and stops the program whenever exploit code is about to be executed. This talk presents different classes of exploits that can be observed in a dynamic instrumentation system. The exploits are analyzed and different security strategies are discussed. We then show how the instrumentation framework can implement an online protection mechanism against each class of attack vectors. Observable Attack Vectors Stack Overflow A limited buffer is (over) flown with user-data and over writes data on the stack (e.g., the return instruction pointer). Format String Attack An attack can write to an arbitrary address (e.g., the return instruction pointer or the address of a library function) if unvalidated user input is passed directly to the printf function. Return to libc Attack This attack prepares multiple stack frames that execute code sequences in libraries. The stack frame can be constructed so that (almost) arbitrary code is executed. Race Attacks / TOCTTOU Time-of-check-to-time-of-use race conditions exploit the fact that they can change values on the stack after they are checked but before they are used in the program or kernel. Integer Overflow Overflows can be triggered by using a negative integer value instead of an unsigned value. Heap Overflow A heap buffer overflow is used to overwrite function pointers or data from the memory allocator to trigger execution of arbitrary code. Code Anomalies x86_64 code is backward compatible to ia32 and in modern operating systems x86_64 and ia32 code can be mixed. The mix of different system calls makes it possible to break out of sand boxes that are not aware of all possible combinations of system calls. The exploits are detected generally whenever the program branches to the injected code or to the constructed code fragments. The program is interrupted and a debugger can be attached to analyze the state of the program. TOCTTOU attacks can be detected by observing the threads and using a specific system call architecture. Conclusion Dynamic instrumentation is an important tool to prohibit, detect, and analyze different attack vectors to running programs. Additional instrumentation guards can be used to better understand exploits. The additional layer of virtualization implemented through dynamic instrumentation can be used to detect and log bugs and is an additional line of defense against new exploits. Related Work A detailed discussion of related work is in the paper. These references here are for informational purposes only (to show how this talk was inspired) and not complete.
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Why did the German authorities use gas chambers?
Photographs documenting the arrival process of Hungarian Jews from the Tet Ghetto in Auschwitz-Birkenau extermination camp (1944). Photo Credit: Wikimedia Commons (Yad Vashem)
After the German invasion of the Soviet Union in 1941, Nazi SS Einsatzgruppen, or mobile killing squads, began the systematic execution of Jews in conquered territories of the U.S.S.R. These mass-killings were carried out by firing squad, but it was soon determined that this technique was inefficient.
The SS then determined that gassing, which had previously been used to kill the physically and mentally handicapped, was a more efficient means of killing large numbers of people in a short period of time. While the Operation Reinhard camps (Treblinka, Belzec, Sobibor and Chelmno) used carbon monoxide as developed in the Euthanasia program. Auschwitz and Majdanek used Zyklon B, a commercially available pesticide, after experiments on Soviet POWs and Polish prisoners had proved its efficiency.
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Quick, clean, and to the point
This video comes from our online video training for Excel.
How to rank values with the RANK function
The RANK function gives you a way to rank values with a simple function that will dynamically calculate rank. If any value changes, you'll get a new rank automatically.
Video Transcript
In this video, we'll look at how to rank values in ascending or descending order using the RANK function.
Here we have a table that contains 5 test scores for a group of students and an average score in Column I.
How can we rank these students from highest to lowest scores?
Well, one option is to sort the students by average score in descending order. Next, you can enter 1 for the rank of the first student in the list, 2 for the second, in then just drag down with the fill handle to fill in the rest of the ranks.
This works fine, but it's not dynamic. If the test scores will be changing over time, or if you don't want to sort the list first, a better approach is to use the RANK function to calculate a rank.
Let me undo these last changes and let's try it out.
The RANK function takes 3 arguments: number, reference, and and optional argument called order. Number is the number being ranked, ref represents the numbers to rank against, and order specifies if rank should be calculated in ascending or descending order.
If order is 0 or omitted, number is ranked by position against the numbers in array sorted in descending order. The highest number will get a rank of 1.
Test scores are normally ranked high to low, so in this case we just need to provide the average for number, and the range that contains averages for ref. Ref needs to be absolute so that it won't change as the formula is copied down.
Now each student has a rank. If I temporarily sort the list by average, you can see that the ranking is correct. And if I manually adjust the test scores, you can see that rank is also dynamic.
Now let's look at a ranking of race results.
As before, number is the number we are ranking and array is the full set of numbers, D6 to D38 in this case.
Again we need to change the reference to absolute format so that it won't change when copied.
This time we need to specify order. The default is zero which calculates a rank in descending order.
For race results, we need to provide 1, which will calculate rank in ascending order - the shortest time will get a rank of 1.
If I sort the list from shortest to longest times, you can see that rank has been correctly calculated.
Dave Bruns
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Stow is a thriving and vibrant city within Massachusetts. Stow offers a favorable environment for relocation considering it's access to housing, various industries and job opportunities.
If you are looking to establish legal residency within the state, you should become familiar with the process of receiving citizenship in Stow MA.
Stow Massachusetts Immigration Lawyers Can Assist
There are various ways to become a legal United States resident in
If you fail to provide complete information regarding your immigration status, the USCIS may decline your request for United States Immigration.
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Yuuko Outfits
Casual outfits
In her home, she wears a short-sleeved V-neck white T-shirt with a hot pink T-shirt with short sleeves which are slightly longer. Yuuko's outfits are typically tomboyish in nature, though she will rarely wear a skirt or dress.
School outfits
Her school uniform consists a pale beige sailor top-like blazer with thin white stripes in the middle and at the end of the blazer with a curved white sailor collar that has a thick pale red stripe nearly around the edges and short pale red bow with a chest pocket at the right side. In the warmer months, Yuuko's school uniform consists of a white top with a blue tie and blue skirt.
In a bedtime, Yuuko wears a yellow pajama.
Yuuko's reaction faces
Yuuko's normal images
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The diffuser uses an ultrasonic (sound waves) mechanism that produces high frequencies. This turns the water and essential oils into small particles producing a micro-mist that is circulated into the air. As of result of this action, negative ions are released that give you a sense of well-being, mood is uplifted, and stress is lessened. This ionization process does not produce ozone.
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Himalayan Art Resources
Item: Mandala of Hevajra (Buddhist Deity)
ཀྱེ་རྡོ་རྗེ། ནང་ལྷ། 喜金刚（佛教本尊）
(item no. 87225)
Origin Location Central Tibet
Date Range 1400 - 1499
Lineages Sakya
Size 63x56cm (24.80x22.05in)
Material Ground Mineral Pigment on Cotton
Collection Museum of Fine Arts, Boston
Catalogue # acc.# 67.823, Gift of John Goelet
Notes about the Central Figure
Classification: Deity
Interpretation / Description
Shri Hevajra Nine Deity Mandala (Tibetan: pal gye pa dor je lha gu'i khyil kor). This painting is dated by inscription to 1461 (Nepal Samvat 581). (See a quick reference chart for understanding the visual and geometric elements of the Hevajra Mandala).
Sanskrit: Hevajra Tibetan: Gye pa dor je
Within the center of the two dimensional circular diagram (mandala) representing the top view of a three dimensional celestial palace and surroundings is the deity Shri Hevajra, dark blue in colour, with eight faces and sixteen hands holding skullcups, standing with four legs in a dancing posture. The first pair of hands embrace the consort Vajra Nairatmya (Selfless One), blue, with one face and two hands holding a curved knife and skullcup, standing on the left leg with the right embracing Hevajra. They are both adorned with bone ornaments and stand atop four corpses within the flames of pristine awareness.
Surrounding the two central figures are eight goddesses of various colours, each with one face and two hands, standing in a dancing posture on the left leg above a corpse seat. Beginning at the top and placed in a clockwise direction is yellow Vetali, multi-coloured Dombini, green Ghasmari, blue Pukkasi, black Gauri, white Shavari, red Chauri, and purple Chandali. They are adorned with various ornaments and each hold their own distinct hand objects.
The floor of the celestial palace is divided into four colours ornately patterned with floral designs: red, blue, white and yellow. On the red veranda outside of the palace walls (barely discernible), on each side of the four doors ('T' shaped), are two dancing offering goddesses, sixteen in total. The outer red and white lines forming a square enclosure represent the stylized decorative facade on the four sides of the palace roof; adorned with upright spears, arrows and banners. The elaborate lintels above each of the four doors are constructed of tiered steps topped with a Dharma wheel, two reclining deer, and gold spires with a silk canopy above.
Surrounding the palace is a circle of multi-coloured (rectangular) petals representing the enormous lotus upon which the entire palace structure rests. The outer circle, divided into eight sections, containing small figures and objects is the ring of the eight great charnel grounds filled with corpses, fires, chaityas (stupas), yogis, nagas, and wrathful worldly deities.
Eight Great Charnel Grounds: according to Tantric literature and the descriptions of wrathful deities and their environments, the eight charnel grounds surround the central palace and deity. There are several different sets of eight names and descriptions for the eight great charnel grounds depending on the Buddhist and Hindu Tantric literature consulted. These charnel grounds also have physical locations in India such as the Laughing charnel ground at Bodhgaya and the Cool Grove charnel ground close by, along with the Frightening charnel ground in the Black Hills of Bihar.
From the Hevajra Tantra literature: "In the east is the Gruesome charnel ground (chandograkatasi); south Frightful with Skulls (bhairavakapalika); west Adorned with a Blazing Garland (jvalamalalankara); north Dense Jungle (girigahvaronnati); north-east Fiercely Resounding (ugropanyasa); south-east Forest of the Lord (ishvaravana); south-west Dark and Terrible (bhairavandhakara); north-west Resounding with the Cries Kili Kili (Kilikilaghoshanadita). Furthermore, there are headless corpses, hanging corpses, lying corpses, stake-impaled corpses, heads, skeletons, jackals, crows, owls, vultures, and zombies making the sound, "phaim". There are also siddha with clear understanding, yaksha, raksha, preta, flesh eaters, lunatics, bhairava, daka, dakini, ponds, fires, stupa, and sadhaka. All of these fill the charnel grounds." (Konchog Lhundrub 1497-1557, written in 1551).
The final ring is composed of the multi-coloured fires of pristine awareness completely enveloping the entire Hevajra Mandala.
Along the top are the lineage gurus for this particular mandala of Shri Hevajra. Starting from the middle and alternating to each side are the primordial buddha Vajradhara, Nairatmya, Virupa, Krishnapa, Damarupa, Avadhutipa, Gayadhara, Drogmi Lotsawa (992-1072), Seton Kunrig (1025-1113), Shangton Chobar (1053-1136), Sachen Kunga Nyingpo (1092-1158), Sonam Tsemo (1142-1182) and Dragpa Gyaltsen (1147-1216).
On the outside of the mandala circle starting at the upper left is yellow Ratnasambhava-Hevajra. On the right is red Amitabha-Hevajra. At the Bottom left is white Vairochana-Hevajra and on the right green Amoghasiddhi-Hevajra. Each of these is in the same general appearance as the central deity.
Shri Hevajra is a meditational deity of the Anuttarayoga Non-dual classification. From the many Hevajra Tantras and forms of the deity, this representation of Hevajra arises from the root Hevajra Tantra of 'two sections' and was popularized by the Indian mahasiddha (the one of great accomplishment) Virupa. The style of the painting is from Ngor Monastery in south western Tibet evidenced by the strong use of red colours and the intricate circular floral patterns used for the background and flame designs.
Mapping a Mandala: Reading a mandala is often very difficult without insider knowledge and the benefit of the explanatory literature. Painted mandala compositions are generally read from the center out and then all of the figures immediately outside of the mandala circle, followed by the top register, and then finishing with the bottom register. The important sections of the MFA Hevajra painting have been divided into colours; blue for the essential deities, red for the Eight Great Charnal Grounds, yellow for the lineage teachers and green for the miscellaneous deities added by the donor or artist.
Jeff Watt 4-2001
Numbered & Coloured Image List:
Blue - Deities:
1. Hevajra & Nairatmya
--- [The Eight Goddesses] ---
2. East - Gauri (black)
3. South - Chauri (red)
4. West - Vetali (yellow)
5. North - Ghashmari (green)
6. North-east - Pukkashi (blue)
7. South-east - Shavari (white)
8. South-west - Chandali (purple)
9. North-west - Dombini (multi-coloured)
--- [The Five Hevajras of the Five Buddha Families] ---
10. Vairochana Hevajra
11. Ratnasambhava Hevajra
12. Amitabha Hevajra
13. Amoghasiddhi Hevajra
--- [The Great Wrathful Ones] ---
14. Ushnisha Chakravartin (yellow)
15. Yamantaka (blue)
16. Humkara (blue)
17. Prajnantaka (white)
18. Padmantaka (red)
19. Vighnantaka (blue)
20. Achala (blue)
21. Takkiraja (blue)
22. Niladanda (Blue)
23. Mahabala (blue)
24. Shumbharaja (blue)
Red - Cemeteries (Charnal Grounds):
1. East - Gruesome charnal ground (Chandograkatasi)
2. South - Frightful with Skulls (Bhairavakapalika)
3. West - Adorned with a Blazing Garland (Jvalamalalankara)
4. North - Dense Jungle (Girigahvaronnati)
5. North-east - Fiercely Resounding (Ugropanyasa)
6. South-east - Forest of the Lord (Ishvaravana)
7. South-west - Dark and Terrible (Bhairavandhakara)
8. North-west - Resounding with the Cries Kili Kili (Kilikilaghoshanadita)
Yellow - Lineage of Teachers:
1. Vajradhara
2. Nairatmya
3. Virupa
4. Kanha
5. Damarupa
6. Avadhutipa
7. Gayadhara
8. Drogmi Lotsawa
9. Seton Kunrig
10. Shangton Chobar
11. Sachen Kunga Nyingpo
12. Sonam Tsemo
13. Dragpa Gyaltsen
14. Sakya Pandita
15. Chogyal Pagpa
16. Konchog Pal
17. Sonam Pal
18. Sonam Gyaltsen
19. Palden Tsultrim
Green - Miscellaneous Deities:
1. Panjarnata Mahakala
2. Shri Devi
3. Yellow Jambhala
4. Legden Mahakala
Secondary Images
Related Items
Subject: Masterworks Main Page (大师之作主页, ཕུལ་བྱུང་གི་སྒྱུ་རྩལ་ཁག།)
Thematic Sets
Buddhist Deity: Hevajra Main Page
Mandalas: Sakya Tradition
Subject: Himalayan Art Number Sets
Buddhist Deity: Hevajra Mandalas
Subject: Greyscale - Figurative & General Composition
Collection of Museum of Fine Arts, Boston
Subject: Lineage Paintings - Alternating
Buddhist Deity: Hevajra & Ten Wrathful Ones
Buddhist Deity: Hevajra Forms
Buddhist Deity: Hevajra Mandalas (Masterworks)
Mandala: Main Page
Tradition: Sakya Deity Paintings
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返回列表 回復 發帖
Players were introduced by the order of their jersey numbers and ended with No. 3,Stitched NFL Jerseys, quarterback Russell Wilson, who walked onto the field pumping the Lombardi Trophy in the air to thunderous applause.
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Discover the most talked about and latest scientific content & concepts.
Journal: Nature
Concepts: Psychology, Memory, Hippocampus, Dentate gyrus, Neurogenesis, Granule cell, Entorhinal cortex, Channelrhodopsin
Concepts: Bacteria, Gut flora, Metabolism, Nutrition, Organism, Feces, Food additive, Sugar substitute
Concepts: DNA, Gene, Genetics, Bioinformatics, Molecular biology, Genomics, Chromosome, Personal genomics
Evolutionary novelties have been important in the history of life, but their origins are usually difficult to examine in detail. We previously described the evolution of a novel trait, aerobic citrate utilization (Cit(+)), in an experimental population of Escherichia coli. Here we analyse genome sequences to investigate the history and genetic basis of this trait. At least three distinct clades coexisted for more than 10,000 generations before its emergence. The Cit(+) trait originated in one clade by a tandem duplication that captured an aerobically expressed promoter for the expression of a previously silent citrate transporter. The clades varied in their propensity to evolve this novel trait, although genotypes able to do so existed in all three clades, implying that multiple potentiating mutations arose during the population’s history. Our findings illustrate the importance of promoter capture and altered gene regulation in mediating the exaptation events that often underlie evolutionary innovations.
Concepts: DNA, Gene, Genetics, Gene expression, Evolution, Biology, Genome, Escherichia coli
Concepts: DNA, Gene, Gene expression, Histone, Epigenetics, DNA methylation, Methylation, Nucleosome
The human X and Y chromosomes evolved from an ordinary pair of autosomes during the past 200-300 million years. The human MSY (male-specific region of Y chromosome) retains only three percent of the ancestral autosomes' genes owing to genetic decay. This evolutionary decay was driven by a series of five ‘stratification’ events. Each event suppressed X-Y crossing over within a chromosome segment or ‘stratum’, incorporated that segment into the MSY and subjected its genes to the erosive forces that attend the absence of crossing over. The last of these events occurred 30 million years ago, 5 million years before the human and Old World monkey lineages diverged. Although speculation abounds regarding ongoing decay and looming extinction of the human Y chromosome, remarkably little is known about how many MSY genes were lost in the human lineage in the 25 million years that have followed its separation from the Old World monkey lineage. To investigate this question, we sequenced the MSY of the rhesus macaque, an Old World monkey, and compared it to the human MSY. We discovered that during the last 25 million years MSY gene loss in the human lineage was limited to the youngest stratum (stratum 5), which comprises three percent of the human MSY. In the older strata, which collectively comprise the bulk of the human MSY, gene loss evidently ceased more than 25 million years ago. Likewise, the rhesus MSY has not lost any older genes (from strata 1-4) during the past 25 million years, despite its major structural differences to the human MSY. The rhesus MSY is simpler, with few amplified gene families or palindromes that might enable intrachromosomal recombination and repair. We present an empirical reconstruction of human MSY evolution in which each stratum transitioned from rapid, exponential loss of ancestral genes to strict conservation through purifying selection.
Concepts: DNA, Gene, Cell, Evolution, Species, Chromosome, Primate, Y chromosome
Genome editing has potential for the targeted correction of germline mutations. Here we describe the correction of the heterozygous MYBPC3 mutation in human preimplantation embryos with precise CRISPR-Cas9-based targeting accuracy and high homology-directed repair efficiency by activating an endogenous, germline-specific DNA repair response. Induced double-strand breaks (DSBs) at the mutant paternal allele were predominantly repaired using the homologous wild-type maternal gene instead of a synthetic DNA template. By modulating the cell cycle stage at which the DSB was induced, we were able to avoid mosaicism in cleaving embryos and achieve a high yield of homozygous embryos carrying the wild-type MYBPC3 gene without evidence of off-target mutations. The efficiency, accuracy and safety of the approach presented suggest that it has potential to be used for the correction of heritable mutations in human embryos by complementing preimplantation genetic diagnosis. However, much remains to be considered before clinical applications, including the reproducibility of the technique with other heterozygous mutations.
Concepts: DNA, Gene, Genetics, Cell, Mutation, Evolution, DNA repair, DNA replication
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Perl: Sort List, Matrix, Object
By Xah Lee. Date: . Last updated: .
This page shows you how to sort in Perl
here's a example of sort (Perl 5.14):
#-*- coding: utf-8 -*-
# perl
# sort a list
@li = (1,9,2,3);
Another form of sort is sort orderFunctionName @list, which uses a function name in place of the comparison block. The function should have 2 parameters, and return one of {-1, 0, 1}.
Compare as Number or as String
Perl has 2 comparison operators.
# -*- coding: utf-8 -*-
# perl
print "\n";
print "3" cmp "20"; # prints 1
Sort Matrix
# -*- coding: utf-8 -*-
# perl
# sort a matrix
use Data::Dumper;
use strict;
my @li1 = ([2,6],[1,3],[5,4]);
my @li2 = sort { $a->[1] <=> $b->[1] } @li1;
print Dumper(\@li2); # [[1, 3], [5, 4], [2, 6]]
The ([2,6],[1,3],[5,4]) is the syntax for nested list. The square brackets inside creates array references.
The $a->[1] is the syntax to get the element of a array reference.
The \@li2 in Dumper(\@li2) gets the reference to the array @li2.
Reverse Sort Order
To reverse sort order, all you have to do is to reverse the placement of $a and $b in your comparison. Example: sort {$b <=> $a} @li
Or, you can use the reverse function afterward, if you don't mind doing extra computation.
# -*- coding: utf-8 -*-
# perl
use Data::Dumper;
@aa = (3, 4, 5);
@bb = reverse(@aa);
print Dumper(\@bb);
Sort Complex Objects
Here's a more complex example of sort.
Suppose you have a list of strings.
You want to sort them by the number embedded in them.
#-*- coding: utf-8 -*-
# perl
@li = (
# sorts a list of strings by their embedded number
decorate-sort-dedecorate, Schwartzian transform
Normally, the key for comparison is computed 2 or more times for each element.
Here's a more efficient way, called decorate-sort-dedecorate (aka Schwartzian transform).
# -*- coding: utf-8 -*-
# perl
# sort a array of string, by comparing the number part inside the string
@li = ('my283.jpg','my23i.jpg','web7-s.jpg','fris88large.jpg');
# this is “decorate-sort-dedecorate”, aka Schwartzian transform
# ↑ take item ↑ sort ↑ create list of pairs [item,key]
use Data::Dumper;
print Dumper(\@li2); # ('web7-s.jpg', 'my23i.jpg', 'fris88large.jpg', 'my283.jpg')
In the above Perl code:
In this way, the cost to compute the same key multiple times is avoided. This method is good when computing the key is expensive.
perldoc -f sort
General Function to Sort Matrix
Perl: Sort Matrix
1. Perl Overview
2. Version String
3. Help System
1. Quoting String
2. Format String
3. String Operations
4. True, False
5. if then else
6. Loop
7. List / Array
8. Loop Thru List
9. Map f to List
10. List Comprehension
11. Hash Table
12. Function Optional Param
13. regex
Text Processing
1. Unicode 🐪
2. Convert File Encoding
3. Read Write File
4. Traverse Dir
5. Find Replace
6. Validate Local Links
7. Split Line by Regex
1. Sort List, Matrix, Object
2. Sort Matrix
3. Sort Unstable
4. Sort Misc
5. List Modules, Search Paths
6. Write a Module
7. Complex Numbers
8. System Call
9. gzip
10. Get Env Var
11. GET Web Content
12. Email
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San Carlos Auto Repair
Call Us: (650) 595-2277
Winter Car Maintenance Tips
Whether it's a vehicle's first winter or fifteenth, it's important to properly prepare it to handle dropping temperatures and inclement weather. Here's a maintenance checklist to make sure cars are ready for winter.
Test the Battery A wet, foggy road
Batteries expend more energy in cold, winter weather than they do during warmer months. A weak battery may die more quickly when temperatures drop. Before it gets too cold, drivers should consider testing the voltage of their car's battery and replacing it if necessary.
Check Lighting Conditions
When winter comes, most car owners take lower temperatures and other conditions into account. However, it's easy to forget that winter also means fewer daylight hours. Before the days begin to shorten, it's important to make sure that a vehicle's lights are in good shape, which means clearing up foggy or yellow lights and making any necessary repairs or replacements.
Top Off Antifreeze
Antifreeze keeps the engine from reaching dangerously low temperatures and can help prevent the need for engine repair. In addition to making sure the car is properly filled with antifreeze, it's also important to ensure there aren't any leaks.
Check Defroster and Climate Control
Having a working heater keeps long car rides in the winter from becoming uncomfortable. Also, a fully functional defroster helps drivers navigate safely because a foggy windshield can obscure a driver's vision in a matter of minutes. Once temperatures start to drop, drivers should check if their heaters and defrosters are working.
Winterize Tires
Finally, it's important to make sure that tires are prepared for winter conditions. It's important to regularly check tire pressure in cold temperatures. A temperature drop of 10 degrees can cause tires to lose an entire pound of pressure per square inch (PSI). In addition to unpredictable handling, this can also create premature tire wear or tread separation if left unchecked, requiring tire repairs.
Although winter maintenance can make a difference, drivers should keep up with car maintenance throughout the year. A+ Japanese Auto Repair Inc. has helped clients from San Mateo and nearby cities since 1997. If your Japanese car is overdue for a winter tune-up or has other repair needs, call us at (650) 595-2277 to schedule a winter service special today!
Car Maintenance
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While all livings learn during their life time, humans are still the most advanced from this perspective as we acquire skills and knowledge in large areas. Therefore, we learn as a population through probability rather than statistics.
Lately, learning happens through the social interactions that are made possible using electronic devises, internet etc.
There is also social interaction, therefore learning exist in an environment where learning is encouraged, supported and nurtured. However, there are as many uphills, as there are downhills. We already know from past that when the environment functions as an operant extinction response, learning declines because it is no longer followed by reward. Yet at the time when we learn something, we rarely know whether what we are going to learn will be useful, therefore the theory of Bayesian experimental design that is to a certain extent based on the theory for making optimal decisions under uncertainty is the closest to human learning.
If we are to scale and assign values to different types of learning, the highest value will be assigned to active learning since the student takes control over what he/she needs to learn, therefore becomes the center of knowledge.
If we now compare learning to the machine learning, there is a process named active learning, but is a special case of semi-supervised machine learning, when the learning algorithm can interactively query the user. In statistics this type of learning is named optimal experimental design which leads us directly to Six Sigma and its Design of Experiments. In optimal designs the parameters can be estimated without bias and with minimum variance.
As many people already know, machine-learning uses in some cases the Bayesian model which is a probability based model.
Bayesian experimental design provides a general probability-theoretical framework from which other theories on experimental design can be derived. It is based on Bayesian inference to interpret the observations/data acquired during the experiment. This allows accounting for prior knowledge on the parameters to be determined, as well as uncertainties present in observations.
Since learning belongs to probability rather than to statistics, the problem in probability would start with us knowing everything about the composition of a population, and then would ask, “What is the likelihood that a selection, or sample, from the population, has certain characteristics?” So, what is the probability that all people will gain knowledge in critical thinking, Lean Six Sigma, math, arts etc.
Obviously, the answer resides within each individual, but as a population, at some point in time all people will gain such knowledge because they exist.
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You are on page 1of 13
Division of words based on phonological level:
1.syllables or segments
2.segments into their constituent phonological feature
Based on morphological level, words may contain more than one unit
that we may call pieces that are not divided into morphological
Stem is a word with its inflectional affixes
Macchin-a machine
Macchin-e machines
Macchin-ista machinist
Root is a word without its inflectional affixes.
Root can be a stem by adding morpheme
Butelk-a bottle Butelk-owa-d to bottle
Filtr filter filtr-owa-d to filter
Bial-y white Biel-i-d to whiten
Gluch-y deaf Gluch-n-d to become deaf
Thematic Vowel
Its not a part of a root, but its part of a word. It
has an important function to many Indo-
European languages.
Larg- o wide
Al-larg-a-re to widen
Al-larg-a-ment-o widening
Bound Morpheme
1. Prefix It appears before the root/stem
a) Al-
2. Suffix It appears after root/stem
a) -a
b) -ment
c) -o
3. Infix within a root
4. Circumfix combination of prefix and suffix
Allomorphy is the phenomenon that a morpheme has more that one
A morph is a particular phonological form of a morpheme.
Plural suffix has three pronounciation:
/s/ after nouns ending in voiceless consonant (cats /kats/)
/z/ after nouns ending in voiced consonant (dogs /dogz/)
/iz/ after nouns ending in a coronal sibilant (horses /horsiz/)
It happens when there is no phonlogical similarity between the
different forms of a lexeme.
Good better
Go went
Morphological Operation
Two types of Morphological operations are:
1. Compounding
2. Affixation
It is a process in which the stem and root of a
word are repeated
1. Full reduplication
2. Partial reduplication
Tonal Morpheme (suprafix)
It is the process in which we differ a word that has different class of
word by listening the tone
Singular Plural English
ba-du Ab-du My father (s)
Morphlogical Typology
It helps us to classify the language of the world that group language
based on their morphological structure.
Synthetic Language
It form words by giving affix of dependant morpheme to a root
Two types of it are:
1. Agglutinative languages: It contains several morpheme that can be
differ easily from one another.
2. Fusional language: It doesnt contain several morpheme that can be
differ easily from one another.
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The PB1014 is a unique product for the protection of ships or floating platforms from sea level attacks. Properly anchored it can prevent even high speed floating attacks.
The protection barrier consists of two main components: the big diameter water filled chamber and the above sea level heavy duty fence webbing net.
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Product-based Neural Networks for User Response Prediction over Multi-field Categorical Data
1 Jul 2018Yanru QuBohui FangWeinan ZhangRuiming TangMinzhe NiuHuifeng GuoYong YuXiuqiang He
User response prediction is a crucial component for personalized information retrieval and filtering scenarios, such as recommender system and web search. The data in user response prediction is mostly in a multi-field categorical format and transformed into sparse representations via one-hot encoding... (read more)
PDF Abstract
Evaluation results from the paper
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• Views:
• Stepping Out Of Eden
Stepping Out Of Eden takes the concept of human origin to a whole new level. In its exploration of this ancient mystery, it delves into our foundational beliefs, thoughts, actions, and deeds. It asks the question why do humans act human. What caused us to transition from ape to man? Did we evolve, as contemporary science says, or did a group of extraterrestrial visitors mold us into who we are today?
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Him, her, and thon?
There used to be a singular gender-neutral pronoun in the English language That’s right, you heard correctly. A big problem in the English language is the need to use ‘he’ and ‘she’. If something is referring to both genders, why can’t we make our lives easier and have a word for that? Also, in this century, gender identity is evolving. Sometimes people would not … Continue reading Him, her, and thon?
New words and slang in the dictionary?
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Calculus 8th Edition
Published by Cengage
ISBN 10: 1285740629
ISBN 13: 978-1-28574-062-1
Chapter 6 - Inverse Functions - 6.3* The Natural Exponential Function - 6.3* Exercises - Page 453: 71
This answer hasn’t been written yet!
Write this answer
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Civil War Essay examples
Submitted By Lizacutie1
Words: 922
Pages: 4
The Civil war era was a time of great change and great revolution. While the Union did have many advantages against the Confederacy, the Confederacy could hold its own very well against the Union, causing the war to be drawn out and almost evenly matched. One of the major reasons the North won was because of blacks, both free and enslaved, who helped their cause. They joined the armed forces to fight for their country and for their freedom, however, after the war, their country limited this hard earned “freedom”. From there, African Americans started to fight for their rights through protest and education. Other member of society such as Radical Republicans helped them. African Americans succeeded in shaping the course and consequences of the war to a certain extent, but even that wasn’t enough for things to go their way.
In the Emancipation Proclamation, Abraham Lincoln used language to describe freeing slaves as a tactical advantage for the Union. This kind of thought is seen throughout the Union, as seen in Major General Butlers report to the secretary of war. General Butler had found many black people, mostly women and children, who had fled the South to go behind Union lines. Butler wanted to know whether these people were to be treated as human beings, or whether they should be treated as war contraband. (Document A). African Americans were given a chance by Abraham Lincoln, who believed that African Americans would fight with a motive, like any other person. Lincoln put it perfectly when he said “Why should they do anything for us, if we do nothing for them?”(Document C). However, this was being asked by both sides, and this culminated in the New York Draft Riots, which essentially became what they were out of the question of “why should we fight for them, if they do not fight for themselves?” Eventually, black freemen and former slaves became an important asset to the Union, as seen in the New York Times article on March 7, 1864. This article describes how the city of New York cheers on African American soldiers marching down the street, when several months before, during the Draft Riots, it hunted down African Americans like animals. (Document F). This shows that New Yorkers did realize the sacrifice these men were making for their freedom and for keeping the Union together. They did no longer feel like they were fighting for those that would not fight for themselves.
Eventually, the Civil War was won, and African Americans went about trying to shape their own destiny. As a result of Reconstruction and the lax leadership of Andrew Johnson, the question of how blacks were to be treated was largely ignored. In the South, people participated in Constitutional Conventions to be readmitted in the Union; however in most of these blacks were a minority. (Document J).This shows that they either were excluded from these conventions, or simply fled in droves to the North. After the war, many blacks tried to establish their rights as citizens, as seen in the Conventions of Colored people’s attempt to get suffrage in Virginia. As citizens they believed that they deserved equal protection and rights, no matter their race. (Document H). Blacks also tried to change their position using education, which they eagerly sought out. Charlotte Forten was a teacher who taught African Americans, and according to her, she never saw people as eager to learn as African Americans after Emancipation. (Document E). Clearly, those freed by the Civil War were trying very hard to advance themselves in society.
They were not alone in this fight, as there were people who…
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Blurring the line between real and virtual motorsports.
Share this video with your friends
Just a brief look/review and thoughts on the recently released Gravel on PC FOLLOW ME Twitter: https://twitter.com/kinduci Facebook: https://www.facebook.com/kinduci Twitch: https://www.twitch.tv/theworldofkinduci DISCORD CHAT: https://discordapp.com/invite/ZJfgVeb Patreon: https://www.patreon.com/kinduci Shirts!: https://shop.spreadshirt.co.uk/kinduci Games: https://www.g2a.com/r/user-5636561084c21 Amazon: https://www.amazon.co.uk/b?_encoding=UTF8&camp=1634&creative=6738&linkCode=ur2&node=560798&site-redirect=&tag=induci-21
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Your Universe site is made up of "blocks" on a grid. There are 3 squares across and 6 down to get you started. To start adding new things to your site:
1. Press any + icon to edit that square.
2. A "tray" will pop up at the bottom of the screen. Here you can choose what you want to add to the block. You can add:
- images
- video
- text
- links
- social media
- contact information
- shapes
- maps
- code
3. Each block type you choose will open a new tray. They each have their own options for things like style (colors, fonts, and more), links, etc.
4. When you like what you see press the green check icon. Or you can delete a block by pressing the red trash can.
You can scroll down in the editor to add or remove rows of blocks, add background images or colors, and change or hide the Universe sticker.
Now let's learn more about making blocks! Press the button...
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Teratomyrmex species by Country
AntWiki - Where Ant Biologists Share Their Knowledge
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Species Richness
Richness of Teratomyrmex species (countries with darker colours are more species-rich). For a list of species and subspecies see the Checklist of Teratomyrmex species or for valid names only see Teratomyrmex species.
Teratomyrmex Species Richness.png
Species of Teratomyrmex are known from the following countries.
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Viral strains that cause 'stomach flu' don't all look alike
Viral strains that cause “stomach flu” don’t all look alike
Stomach bugs come in different sizes.
Norovirus, best known for sweeping through daycares and cruise ships, can form small, medium, and depending on the .
"Everyone thought that all the strains would look about the same—like the one that was solved 20 years ago," says Howard Hughes Medical Institute Investigator Leemor Joshua-Tor. "It turns out that they don't!"
Those structural details will be crucial for scientists working on vaccines or antiviral therapies to treat , says Joshua-Tor, a structural biologist at Cold Spring Harbor Laboratory (CSHL). Though norovirus causes about 21 million cases of foodborne illness in the United States every year, there are currently no approved therapies.
At least one vaccine candidate is working its way through clinical trials now. But CSHL study coauthor James Jung says scientists will need to take the virus's newfound variation into account—so any new vaccine protects against a broad array of strains.
HHMI talked with Jung and Joshua-Tor to find out more about the "stomach flu," the virus that causes it, and how they finally solved the structure of outbreak strains' shells.
What is norovirus?
Joshua-Tor: It's a virus that causes gastroenteritis. It makes you throw up, causes diarrhea, and is extremely infectious.
Jung: It's been reported that it takes as little 10 to 18 virus particles to start an infection.
Viral strains that cause “stomach flu” don’t all look alike
How many particles are in vomit?
Jung: I'm not sure, but it's been estimated for a less-prevalent norovirus strain that a typical diarrheal sample contains approximately five billion viral particles per gram.
That's a lot!
Joshua-Tor and Jung: Yes.
How does norovirus spread?
Joshua-Tor: It's aerosolized when people vomit. Surfaces and food and water supplies can get contaminated. That's why it can spread so quickly among people in close proximity, like in daycare centers, nursing homes, and cruise ships.
What does norovirus look like?
Jung: It belongs to a family called Calciviridae. The name comes from the Latin word "calyx," which means cup-like cavity. The surface of the virus has these spikes with depressions that look a bit like cups. So it's basically a sphere with spikes sticking out. And those spikes bind to human cells.
How many strains of norovirus exist?
Jung: 30 or more. A strain called GII.4 is responsible for the majority of all . But GII.4's structure was completely unknown.
Why has no one focused on outbreak strains' structure until now?
Viral strains that cause “stomach flu” don’t all look alike
How does cryo-EM work?
Joshua-Tor: You place your sample on a small copper grid and put it in this contraption that leaves a thin layer of the sample on the grid. Then, you very quickly plunge it into liquid ethane, which freezes the sample and causes the water inside to become glass (we call it vitreous ice). That means it doesn't form crystals, which could interfere with the image. It also helps protect biological samples from radiation damage from the microscope's electrons.
Cryo-EM has been around for a while. What's new?
When you hit a sample with electrons, it moves a little bit, so you can get a blurring effect. But [study coauthor] Nikolaus Grigorieff [of HHMI's Janelia Research Campus] developed a technique that lets you collect movies instead of images and then computationally align the moving particles. All these things let us get much higher-resolution data than what we were getting before.
How did the norovirus outbreak strain differ from the known strain?
Jung: It turns out that the shell dimensions are different—a lot larger. It's also made of a larger number of components.
Joshua-Tor: James calls it the shape-shifting virus. The organization of the spikes that talk to the cells in the body are positioned differently. You know how babies have toy balls with knobs on them to grip? That's what the virus looks like, but the knobs all look a little different—so that's important.
Joshua-Tor: We think how the knobs interact with human cells can affect virulence. And James discovered that there's a zinc ion that helps the knobs organize in a particular way to promote binding to human cells.
Is it common for viral strains to differ in appearance?
Joshua-Tor: It's not common, but it's not unheard of. It wasn't expected for norovirus.
How can knowing about these shells help us?
Jung: Current vaccine candidates have been made with the assumption that there's only minor variation between . Actually, the dimensions are completely different. Our findings could help people formulate a better vaccine.
Explore further
Asymptomatic infection helps norovirus to spread in Indonesia
Citation: Viral strains that cause 'stomach flu' don't all look alike (2019, June 12) retrieved 16 June 2019 from https://medicalxpress.com/news/2019-06-viral-strains-stomach-flu-dont.html
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Species with data from:
Pepekin, V.I.; Erlikh, R.D.; Matyushin, Yu.N.; Lebedev, Yu.A., Dissociation energy of the C - N3 bond in triphenylazidomethane and benzyl and phenyl azides. Enghalpy of formation of triphenylmethyl radical, Dokl. Phys. Chem. (Engl. Transl.), 1974, 214, 123-125.
4 matching species were found.
For each matching species the following will be displayed:
Click on the name to see more data.
1. Triphenylmethane (C19H16)
2. Benzene, (azidomethyl)- (C7H7N3)
3. Benzene, azido- (C6H5N3)
4. Tritylazide (C19H15N3)
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Walt Whitman: Poems
Reread lines 16-25 of “Song of Myself.” What metaphors does the speaker use to describe what grass means to him? What ideas does each metaphor suggest?
Song of Myself by Walt Whitman.
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Last updated by Aslan
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Can you quote the lines for me so I know exactly the ones you mean?
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Scientists Find Evidence To Support Moon Creation Hypothesis
Posted: Sep 27 2016, 12:32pm CDT | by , Updated: Sep 27 2016, 7:44pm CDT, in Latest Science News
This story may contain affiliate links.
Scientists Find Evidence to Support Moon Creation Hypothesis
Photo Credit: Getty Images
A layer of iron and other elements deep underground is the evidence scientists have long been looking for to support the giant-impact hypothesis.
Scientists say they have finally found evidence to support the giant-impact hypothesis. The hypothesis suggests that the moon was formed by a massive collision between Earth and a planet about the size of Mars, approximately 4.5 billion years ago. Now, researchers believe that the layer of iron and other elements buried deep inside the Earth also support this explanation.
Researchers from John Hopkins University simulated the giant impact in the lab and showed that the impact occuring billions of years ago not only sent a huge mass of debris into the space that created the moon, but also formed a stratified layer beneath the Earth’s surface. The layer is evident in seismic data.
The giant impact hypothesis has been a widely accepted theory for how the Earth’s moon was formed. But it is extremely difficult to prove because some 4 billion years ago Earth was very different from what we see today. Researchers think there are still some clues hidden in the chemical composition of our planet, which could be used to support the claim.
“Our experiments bring additional evidence in favor of the giant impact hypothesis," said lead author Maylis Landeau. “They demonstrate that the giant impact scenario also explains the stratification inferred by seismology at the top of the present-day Earth’s core. This result ties the present-day structure of Earth’s core to its formation.”
The stratified layer consists of a mix of iron and lighter elements, including oxygen, sulfur and silicon and clearly points to a massive collision between earth and forming planet. The stratification was possibly the result of the turbulence caused by the giant impact. If Earth was not struck by another cosmic body, it should logically have a homogenous composition not the mix of materials in the layers.
“We're saying this stratified layer might be the smoking gun," said co-author Peter Olson. "Its properties are consistent with it being a vestige of that impact."
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Hallvard Jensen
Research Scientist
(+47) 406 30 796
Visiting address
Holtveien 66, 9269 Tromsø
To document
Arctic charr and European whitefish are considered to be strong competitors in lakes, with the latter usually being the superior species. However, high niche plasticity and lake morphometry may suggestively facilitate resource partitioning and coexistence between charr and whitefish. Here, we explore the trophic niche utilization (diet and habitat use) of charr and whitefish co-occurring with brown trout in the deep and oligotrophic Lake Fyresvatnet, southern Norway (59°05’N, 8°10’E). Using CPUE, stomach contents and stable isotope analyses, a distinct resource partitioning was revealed between brown trout and the other two species. Brown trout typically occupied the littoral zone, feeding on benthic invertebrates, surface insects and small-sized whitefish. In contrast, charr and whitefish were predominantly zooplanktivorous, but diverged somewhat in habitat utilization as charr shifted seasonally between the profundal and the littoral zone, whereas whitefish were found in the upper water layers (littoral and pelagic habitats). Accordingly, the stable isotope values of carbon (δ13C) reflected a pelagic orientated prey resource use for both charr and whitefish, whereas brown trout had elevated carbon and nitrogen (δ15N) signatures that reflected their benthivore and piscivore diet, respectively. The findings suggest that charr may not rely upon the profundal zone as a feeding habitat but as a refuge area, and may coexist with whitefish if a third competitive and predatory species like brown trout co-occur in the lake. The study indicates that a general high habitat plasticity of Arctic charr may be essential in the presently observed coexistence with a competitively superior fish species like whitefish, and that a third fish species like brown trout may facilitate this particular fish community structure.
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A Distant Mirror: The Calamitous 14th Century Test | Mid-Book Test - Hard
Buy the A Distant Mirror: The Calamitous 14th Century Lesson Plans
Name: _________________________ Period: ___________________
Short Answer Questions
1. What technology was revolutionizing warfare in the 14th century?
2. How are the wealthy different from the poor in size of their families?
3. What was Enguerrange III known for?
4. How long did it take to build the castle of Coucy?
5. What happened to the leader who accepted an invitation to parley with Charles of Navarre?
Short Essay Questions
1. How are taxes collected in Coucy?
2. Describe the castle at Coucy.
3. How do people try to protect themselves from the plague?
4. Who are the Pastoreaux?
5. Describe the 14th-century French entertainment that involved cats.
6. Describe Jean II's captivity in England.
7. What is the state of trade in 14th-century France?
8. Describe education in 14th-century France.
9. What is the relationship between the classes like in 14th-century France?
10. How do people explain the presence of the Black Plague?
Essay Topics
Write an essay for ONE of the following topics:
Essay Topic 1
Italy was hardly ever at war with England or France, but the Italian region was often in turmoil and affected French politics. What was the role of Italy in French and English politics, and how was Italy act its role? What marriage, battles, uprising and policies in Italy affected France and England? Analyze and describe the role of Italian and Vatican politics in France and England.
Essay Topic 2
What was Clisson's role in the French monarchy? Describe his temperament and his effect on French society and military policy. What does Clisson show us about the people who interacted with him?
Essay Topic 3
Religious figures like Catherine of Siena and Pierre de Luxembourg acquired great renown and some power in their religiousness. Mystics sought the same influence by spreading their teachings. Analyze these figures and describe the role of the exceptionally-religious person in society. What was their role? What was their power? How did they influence the people around them?
(see the answer keys)
This section contains 828 words
(approx. 3 pages at 300 words per page)
Buy the A Distant Mirror: The Calamitous 14th Century Lesson Plans
A Distant Mirror: The Calamitous 14th Century from BookRags. (c)2019 BookRags, Inc. All rights reserved.
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Many topologies have an advantage because they operate with a relatively small voltage step compared to older NPC topologies and have an input transformer that avoids any common-mode voltage.
by Mark Harshman (Siemens)
March 9, 2015
Motors and variable frequency drives (VFDs) have been used for upstream oil and gas artificial lift applications (with electric submersible pumps and injection compressors) for many years. VFDs provide energy savings, process control and improvement in older well development. When VFDs were first manufacture, operators discovered that their high harmonic content and voltage characteristics shortened the motor's life by damaging the insulation system. Motor companies designed inverter-grade motors that had increased insulation systems and larger housings to dissipate the additional heat. Eventually, VFD manufacturers found new topologies and methods to mitigate the harmonics and voltage transients so that their products were compatible with standard motors. This development led to the ability to retrofit an existing motor (designed for an across-the-line start) with a VFD. Originally, VFDs had only two or three output levels, and each one had voltage output characteristics that could severely damage the motor insulation system. The addition of output filters and many changes in control and internal VFD design helped these drives handle standard motors. Some types of VFDs were eliminated after providing particularly unfavorable performance with motors. Current-source inverters (CSI) were manufactured by most early VFD designers because the semiconductor devices offered good failure mode performance at a low cost. The output waveform was difficult for the motor to handle, and these topologies have been abandoned—with the exception of very high power ranges above 15 megawatts. They retain some popularity as a transformerless design, which has caused new problems with bearing currents. Operators face three major difficulties with motor insulation when a motor is controlled by a VFD:
• The peak differential voltage on the windings with respect to ground, phase to phase and turn to turn
• Voltage on all the windings with respect to ground, which is the common-mode voltage
• The rate of change of voltage with respect to time (dV/dt)
A motor's windings are not intentionally grounded, but considerable capacitance exists from the winding to the stator frame through which alternating currents will flow. These currents are much larger when the motor is controlled by a VFD because of the high frequency components of the voltage. The conductors in the motor windings are insulated from each other and from the stator. The magnet wire has a heavy varnish overcoat and is usually also wrapped with insulating tape. The insulation in the slots is commonly known as groundwall insulation.
Destructive Effects of Voltage Stress
When voltage is present on the motor windings, an electric field is generated between all conductors, which are at different potentials. This electric field passes through the insulation materials, including air. Each material has a limit regarding the electric field it can withstand before breaking down. The electric field rarely becomes large enough to cause a breakdown of the insulation and create an arc. However, if the electric field becomes too large in the air, it can ionize the air and create ozone. Ozone is an extremely reactive gas that attacks all the organic molecules in the insulation and degrades them, eventually leading to failure. This phenomenon is called partial discharge. It may take days, months or years to destroy an insulation system. Low-voltage and medium-voltage motors typically have different coil constructions, even though the shape and location of the coils is similar. A typical stator coil orientation is shown in Figure 1.
Figure 1. A standard stator coil winding configuration<br />
<em>(Graphics courtesy of Siemens)</em>Figure 1. A standard stator coil winding configuration (Graphics courtesy of Siemens)
Because the voltage stress is less, low-voltage motors (below 1,000 volts alternating current) have random-wound coils with only varnish as the insulation. Random-wound means that no defined location exists for a given turn. This means that the start turn may lie in contact with the finish turn so that the entire coil voltage occurs between those turns. Medium-voltage motors, in contrast, have insulating tape wrapped over the varnish between the turns. Each turn has a defined location with respect to the other turns, so the start turn does not lie next to the finish turn.
Equation 1 and 2
These coils are much better at withstanding voltage than the random-wound, low-voltage motor coils. After the introduction of insulated gate bipolar transistor pulse width modulation (PWM) drives for low-voltage motors, an increase of low-voltage motor insulation failures occurred because of the unexpected harmful effects of the fast-rising pulses on the coil insulation.
Motor Insulation Design
If the motor designer does not know that the motor may be driven by a VFD, the insulation will be designed as follows:
• The motor neutral will be assumed to lie near ground potential, which is the same voltage as the stator frame.
• The terminal voltages will be assumed to be symmetrical with respect to ground with no common-mode voltage. This is the best situation for the groundwall insulation.
• The phase-to-neutral voltage will be assumed to be sinusoidal with a maximum value of the source voltage plus 10 percent. The peak will be calculated using Equation 1. This will determine the groundwall insulation.
• The phase-to-phase voltage will be assumed to be sinusoidal with a maximum value of the source voltage plus 10 percent. The peak will be calculated with Equation 2. This will determine the phase-to-phase insulation at which the coils of different phases that are in the same slot are touching.
• The turns in the stator coils will each have the same voltage impressed on them that is the root mean square (rms) line-neutral voltage divided by the number of turns.
• The dV/dt will be no more than the 50 to 60 hertz utility frequency that the sine wave creates.
Figure 2. Insulation areas of concernFigure 2. Insulation areas of concern
The listed concern areas are shown in Figure 2. Since the motor windings consist of coils embedded in slots in the stator, they have inductance as well as turn-to-turn capacitance and turn-to-ground capacitance. At high frequencies, they behave like transmission lines with wave propagation phenomenon. This means that, for fast-rising voltages, the applied voltage will not be uniformly distributed among the turns. The result is excessively high dV/dt and some turns being more stressed than others. VFDs do not produce sinusoidal voltages. Voltage source drives produce a series of pulses of different widths and amplitudes to approximate a sine wave. Power conversion circuits (more than a few kilowatts) cannot generate a smoothly changing voltage like the utility sine wave. The pulses have very high dV/dt values (1,000 volts/microsecond) on the leading edge compared to the utility sine wave. Because of the PWM process, the waveform has a higher peak value than the utility voltage. Also, for drives that have a thyristor bridge for a line-side converter, the output voltages have a displacement from ground that is referred to as common-mode voltage.
Types of VFDs
VFDs can be divided into voltage-fed and current-fed categories. Voltage-fed drives create a defined voltage at the output. The motor leakage inductance blocks the high-frequency components so only fundamental current flows. Current-fed drives create a defined current at the output. In these CSI drives and the line commutated inverter (LCI), a large capacitive (0.2 to 0.3 per unit) filter absorbs the high-frequency components of the current. The current-fed drive has low dV/dt and low peak voltage but can have a common-mode voltage issue, often necessitating a specially insulated motor. The voltage-fed PWM drives have different pulse patterns but generally fall into a few categories:
• Neutral-point-clamped (NPC) VFDs have three levels of voltage at the output and five levels line-to-line. The voltage step is half the direct-current link voltage (about 3,300 volts for a 4,160-volt alternating-current drive)
• In three-cell, multilevel VFDs, the cell is an NPC inverter. Here, the step is half the direct-current link voltage of a cell, or about 1,000 volts.
• In multi-cell, multilevel VFDs, the voltage step is the value of the direct-current link voltage of a cell, about 900 to 1,000 volts.
Figure 3. Relative stress values caused by VFD output levels Figure 3. Relative stress values caused by VFD output levels
The amplitude of the step and the rise time are the key factors in determining how a VFD waveform will affect the motor insulation after the waveform has propagated along the cable. The relative stress caused by the VFDs output levels is illustrated in Figure 3. As the number of levels increase, the voltage step decreases, resulting in lower dV/dt values and reduced stress on the motor insulation system.
The use of VFDs created some motor insulation issues because the motor insulation was designed for the benign sine waves of the utility. The insulation vulnerabilities occurred because of the presence of fast-rising voltage pulses in the VFD output and the use of power conversion circuits without a transformer, which creates common-mode voltage on the motor windings. Many topologies have an advantage because they operate with a relatively small voltage step compared to older NPC topologies and have an input transformer that avoids any common-mode voltage. When applying a VFD to a motor, operators should consider any potential risks. Most VFD manufacturers can evaluate a motor based on its topology. Manufacturers that produce drives and motors can ensure compatibility and often offer increased warranties because of this relationship.
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提醒你潛在的或即將發生的硬盤故障，監測的參數和內核日誌的任何相關的驅動器事件的歷史 免費麥金塔電腦應用程式 推廌app
Mac OS X 系統版本
原App Store內容轉載:
DiskFailure has a single purpose, to warn you about a potential or imminent hard disk failure before the disk is rendered nonfunctional/data is lost.
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BBC: A new species of dinosaur has been found in an Australia, 30 years after a man had collected them thinking they were just animal fossils.
He didn’t realise they were so special but now scientists have analysed them and found they are from a newly discovered type of dinosaur.
The species has been given the extremely catchy name of Fostoria dhimbangunmal. They got the first part of their name from the man who discovered the fossils in the first place – Bob Foster!
Bob and his wife Jenny with their amazing find
Bob eventually took the fossils to a museum because he thought that there could be something interesting about them.
He was right! After many years of research it’s believed that they belonged to a herd of plant eating dinosaurs.
The dinosaur stood on its back legs and is from a group of dinosaurs called Iguanodontian, this group also includes Dryosaurus and Iguanadon.
But these fossils are not your average dinosaur find.
What makes these dinosaur fossils slightly different is that they are opalised. This means that they have a shimmering crystal look to them because they are made of opal, a type of rock which is really colourful.
It’s pretty common to find opalised fossils in Australia but extremely rare to find a whole new dinosaur species which no one has ever discovered before.
The fossils included many different bones belonging to the same species so it’s likely that they belonged to both adult dinosaurs and baby dinosaurs.
Bob Foster and his family donated the fossils to the Australian Opal Centre so that the incredible discovery can be shared with the world.
Source: Published by BBC
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Vinyasa yoga is a moving meditation where breath and movement are linked together through a series of sun salutations and asanas (postures). Rooted in the Ashtanga yoga tradition this challenging, physical practice will help you create a strong body, increase your physiological balance, and develop a clear, peaceful mind. Classes taught by Natasha Teran
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