chunk_id
stringlengths 5
8
| chunk
stringlengths 1
1k
|
|---|---|
665_7 | Her work tackles difficult subjects such as sex, pregnancy and depression and makes it palatable through irony and humor. Her narrative style uses visual metaphors to communicate how living people feel inside; one example is in her animated short Birth her use of the body as a vessel in her film. Baumane's Teat Beat of Sex, a series of semi fictionalized personal recollections that stem from the artist's firsthand experience and an array of viewpoints on the subject, are uncompromisingly yet refreshingly candid, oftentimes dealing with somewhat taboo areas that can serve as discussion points.
Filmography |
665_8 | Animated Shorts
The Witch And The Cow (1991)
Tiny Shoes (1993)
The Gold Of The Tigers (1995)
Love Story (1998)
The Threatened One (1999)
Natasha (2001)
Five Fucking Fables (2002)
Woman (2002)
Dentist (2005)
Five Infomercials For Dentists (2005)
Teat Beat Of Sex (2007)
Veterinarian (2007)
The Very First Desire Now and Forever (2007)
Teat Beat Of Sex: Episodes 8,9,19,11 (2007)
Birth (2009)
Animated Features
Rocks in My Pockets (2014)
Compilations (DVD)
Avoid Eye Contact Vol. 1
Avoid Eye Contact Vol. 2
Ten Animated Films by Signe Baumane
Teat Beat of Sex
Music Videos
Cousin Joe Twoshacks - "Tarzan" (2014)
References
External links
Signe Baumane's official website
Rocks in My Pockets official website
Teat Beat of Sex website
Online art gallery
Latvian animators
Latvian women animators
1964 births
Living people
People from Auce
Moscow State University alumni
Lielais Kristaps Award winners |
666_0 | The , developed by the Japanese government's initiative "Earth Simulator Project", was a highly parallel vector supercomputer system for running global climate models to evaluate the effects of global warming and problems in solid earth geophysics. The system was developed for Japan Aerospace Exploration Agency, Japan Atomic Energy Research Institute, and Japan Marine Science and Technology Center (JAMSTEC) in 1997. Construction started in October 1999, and the site officially opened on 11 March 2002. The project cost 60 billion yen. |
666_1 | Built by NEC, ES was based on their SX-6 architecture. It consisted of 640 nodes with eight vector processors and 16 gigabytes of computer memory at each node, for a total of 5120 processors and 10 terabytes of memory. Two nodes were installed per 1 metre × 1.4 metre × 2 metre cabinet. Each cabinet consumed 20 kW of power. The system had 700 terabytes of disk storage (450 for the system and 250 for the users) and 1.6 petabytes of mass storage in tape drives. It was able to run holistic simulations of global climate in both the atmosphere and the oceans down to a resolution of 10 km. Its performance on the LINPACK benchmark was 35.86 TFLOPS, which was almost five times faster than the previous fastest supercomputer, ASCI White. As of 2020, comparable performance can be achieved by using 4 Nvidia A100 GPUs, each with 9.746 FP64 TFlops.
ES was the fastest supercomputer in the world from 2002 to 2004. Its capacity was surpassed by IBM's Blue Gene/L prototype on 29 September 2004. |
666_2 | ES was replaced by the Earth Simulator 2 (ES2) in March 2009. ES2 is an NEC SX-9/E system, and has a quarter as many nodes each of 12.8 times the performance (3.2× clock speed, four times the processing resource per node), for a peak performance of 131 TFLOPS. With a delivered LINPACK performance of 122.4 TFLOPS, ES2 was the most efficient supercomputer in the world at that point. In November 2010, NEC announced that ES2 topped the Global FFT, one of the measures of the HPC Challenge Awards, with the performance number of 11.876 TFLOPS.
ES2 was replaced by the Earth Simulator 3 (ES3) in March 2015. ES3 is a NEC SX-ACE system with 5120 nodes, and a performance of 1.3 PFLOPS.
ES3, from 2017 to 2018, ran alongside Gyoukou, a supercomputer with immersion cooling that can achieve up to 19 PFLOPS.
System overview |
666_3 | Hardware
The Earth Simulator (ES for short) was developed as a national project by three governmental agencies: the National Space Development Agency of Japan (NASDA), the Japan Atomic Energy Research Institute (JAERI), and the Japan Marine Science and Technology Center (JAMSTEC). The ES is housed in the Earth Simulator Building (approx; 50m × 65m × 17m). The Earth Simulator 2 (ES2) uses 160 nodes of NEC's SX-9E. The upgrade of the Earth Simulator has been completed in March 2015. The Earth Simulator 3(ES3) system uses 5120 nodes of NEC's SX-ACE. |
666_4 | System configuration
The ES is a highly parallel vector supercomputer system of the distributed-memory type, and consisted of 160 processor nodes connected by Fat-Tree Network. Each Processor nodes is a system with a shared memory, consisting of 8 vector-type arithmetic processors, a 128-GB main memory system. The peak performance of each Arithmetic processors is 102.4Gflops. The ES as a whole thus consists of 1280 arithmetic processors with 20 TB of main memory and the theoretical performance of 131Tflops. |
666_5 | Construction of CPU
Each CPU consists of a 4-way super-scalar unit (SU), a vector unit (VU), and main memory access control unit on a single LSI chip. The CPU operates at a clock frequency of 3.2 GHz. Each VU has 72 vector registers, each of which has 256 vector elements, along with 8 sets of six different types of vector pipelines: addition /shifting, multiplication, division, logical operations, masking, and load/store. The same type of vector pipelines works together by a single vector instruction and pipelines of different types can operate concurrently.
Processor Node (PN)
The processor node is composed of 8 CPU and 10 memory modules.
Interconnection Network (IN)
The RCU is directly connected to the crossbar switches and controls inter-node data communications at 64 GB/s bidirectional transfer rate for both sending and receiving data. Thus the total bandwidth of inter-node network is about 10 TB/s. |
666_6 | Processor Node (PN) Cabinet
The processor node is composed two nodes of one cabinet, and consists of power supply part 8 memory modules and PCI box with 8 CPU modules.
Software
Below is the description of software technologies used in the operating system, Job Scheduling and the programming environment of ES2.
Operating system
The operating system running on ES, "Earth Simulator Operating System", is a custom version of NEC's SUPER-UX used for the NEC SX supercomputers that make up ES.
Mass storage file system
If a large parallel job running on 640 PNs reads from/writes to one disk installed in a PN, each PN accesses to the disk in sequence and performance degrades terribly. Although local I/O in which each PN reads from or writes to its own disk solves the problem, it is a very hard work to manage such a large number of partial files. Then ES adopts Staging and Global File System (GFS) that offers a high-speed I/O performance. |
666_7 | Job scheduling
ES is basically a batch-job system. Network Queuing System II (NQSII) is introduced to manage the batch job.
Queue configuration of the Earth Simulator.
ES has two-type queues. S batch queue is designed for single-node batch jobs and L batch queue is for multi-node batch queue.
There are two-type queues. One is L batch queue and the other is S batch queue. S batch queue is aimed at being used for a pre-run or a post-run for large-scale batch jobs (making initial data, processing results of a simulation and other processes), and L batch queue is for a production run. Users choose the appropriate queue for their job.
The nodes allocated to a batch job are used exclusively for that batch job.
The batch job is scheduled based on elapsed time instead of CPU time. |
666_8 | Strategy (1) enables to estimate the job termination time and to make it easy to allocate nodes for the next batch jobs in advance. Strategy (2) contributes to an efficient job execution. The job can use the nodes exclusively and the processes in each node can be executed simultaneously. As a result, the large-scale parallel program is able to be executed efficiently.
PNs of L-system are prohibited from access to the user disk to ensure enough disk I/O performance. Herefore the files used by the batch job are copied from the user disk to the work disk before the job execution. This process is called "stage-in". It is important to hide this staging time for the job scheduling.
Main steps of the job scheduling are summarized as follows;
Node Allocation
Stage-in (copies files from the user disk to the work disk automatically)
Job Escalation (rescheduling for the earlier estimated start time if possible)
Job Execution |
666_9 | Stage-out (copies files from the work disk to the user disk automatically)
When a new batch job is submitted, the scheduler searches available nodes (Step.1). After the nodes and the estimated start time are allocated to the batch job, stage-in process starts (Step.2). The job waits until the estimated start time after stage-in process is finished. If the scheduler find the earlier start time than the estimated start time, it allocates the new start time to the batch job. This process is called "Job Escalation" (Step.3). When the estimated start time has arrived, the scheduler executes the batch job (Step.4). The scheduler terminates the batch job and starts stage-out process after the job execution is finished or the declared elapsed time is over (Step.5). |
666_10 | To execute the batch job, the user logs into the login-server and submits the batch script to ES. And the user waits until the job execution is done. During that time, the user can see the state of the batch job using the conventional web browser or user commands. The node scheduling, the file staging and other processing are automatically processed by the system according to the batch script. |
666_11 | Programming environment
Programming model in ES |
666_12 | The ES hardware has a 3-level hierarchy of parallelism: vector processing in an AP, parallel processing with shared memory in a PN, and parallel processing among PNs via IN. To bring out high performance of ES fully, you must develop parallel programs that make the most use of such parallelism. the 3-level hierarchy of parallelism of ES can be used in two manners, which are called hybrid and flat parallelization, respectively . In the hybrid parallelization, the inter-node parallelism is expressed by HPF or MPI, and the intra-node by microtasking or OpenMP, and you must, therefore, consider the hierarchical parallelism in writing your programs. In the flat parallelization, the both inter- and intra-node parallelism can be expressed by HPF or MPI, and it is not necessary for you to consider such complicated parallelism. Generally speaking, the hybrid parallelization is superior to the flat in performance and vice versa in ease of programming. Note that the MPI libraries and the HPF |
666_13 | runtimes are optimized to perform as well as possible both in the hybrid and flat parallelization. |
666_14 | Languages
Compilers for Fortran 90, C and C++ are available. All of them have an advanced capability of automatic vectorization and microtasking. Microtasking is a sort of multitasking provided for the Cray's supercomputer at the same time and is also used for intra-node parallelization on ES. Microtasking can be controlled by inserting directives into source programs or using the compiler's automatic parallelization. (Note that OpenMP is also available in Fortran 90 and C++ for intra-node parallelization.)
Parallelization
Message Passing Interface (MPI) |
666_15 | MPI is a message passing library based on the MPI-1 and MPI-2 standards and provides high-speed communication capability that fully exploits the features of IXS and shared memory. It can be used for both intra- and inter-node parallelization. An MPI process is assigned to an AP in the flat parallelization, or to a PN that contains microtasks or OpenMP threads in the hybrid parallelization. MPI libraries are designed and optimizedcarefully to achieve highest performance of communication on the ES architecture in both of the parallelization manner.
High Performance Fortrans (HPF)
Principal users of ES are considered to be natural scientists who are not necessarily familiar with the parallel programming or rather dislike it. Accordingly, a higher-level parallel language is in great demand.
HPF/SX provides easy and efficient parallel programming on ES to supply the demand. It supports the specifications of HPF2.0, its approved extensions, HPF/JA, and some unique extensions for ES |
666_16 | Tools
-Integrated development environment (PSUITE)
Integrated development environment (PSUITE) is integration of various tools to develop the program that operates by SUPER-UX. Because PSUITE assumes that various tools can be used by GUI, and has the coordinated function between tools, it comes to be able to develop the program more efficiently than the method of developing the past the program and easily.
-Debug Support
In SUPER-UX, the following are prepared as strong debug support functions to support the program development.
Facilities
Features of the Earth Simulator building |
666_17 | Protection from natural disasters
The Earth Simulator Center has several special features that help to protect the computer from natural disasters or occurrences. A wire nest hangs over the building which helps to protect from lightning. The nest itself uses high-voltage shielded cables to release lightning current into the ground. A special light propagation system utilizes halogen lamps, installed outside of the shielded machine room walls, to prevent any magnetic interference from reaching the computers. The building is constructed on a seismic isolation system, composed of rubber supports, that protect the building during earthquakes. |
666_18 | Lightning protection system
Three basic features:
Four poles at both sides of the Earth Simulator Building compose wire nest to protect the building from lightning strikes.
Special high-voltage shielded cable is used for inductive wire which releases a lightning current to the earth.
Ground plates are laid by keeping apart from the building about 10 meters.
Illumination
Lighting: Light propagation system inside a tube
(255mm diameter, 44m(49yd) length, 19 tubes)
Light source: halogen lamps of 1 kW
Illumination: 300 lx at the floor in average
The light sources installed out of the shielded machine room walls.
Seismic isolation system
11 isolators
(1 ft height, 3.3 ft. Diameter, 20-layered rubbers supporting the bottom of the ES building)
Performance |
666_19 | LINPACK
The new Earth Simulator system (ES2), which began operation in March 2009, achieved sustained performance of 122.4 TFLOPS and computing efficiency (*2) of 93.38% on the LINPACK Benchmark (*1).
1. LINPACK Benchmark
The LINPACK Benchmark is a measure of a computer's performance and is used as a standard benchmark to rank computer systems in the TOP500 project.
LINPACK is a program for performing numerical linear algebra on computers.
2. Computing efficiency
Computing efficiency is the ratio of sustained performance to a peak computing performance. Here, it is the ratio of 122.4TFLOPS to 131.072TFLOPS.
Computational performance of WRF on Earth Simulator |
666_20 | WRF (Weather Research and Forecasting Model) is a mesoscale meteorological simulation code which has been developed under the collaboration among US institutions, including NCAR (National Center for Atmospheric Research) and NCEP (National Centers for Environmental Prediction). JAMSTEC has optimized WRFV2 on the Earth Simulator (ES2) renewed in 2009 with the measurement of computational performance. As a result, it was successfully demonstrated that WRFV2 can run on the ES2 with outstanding and sustained performance. |
666_21 | The numerical meteorological simulation was conducted by using WRF on the Earth Simulator for the earth's hemisphere with the Nature Run model condition. The model spatial resolution is 4486 by 4486 horizontally with the grid spacing of 5 km and 101 levels vertically. Mostly adiabatic conditions were applied with the time integration step of 6 seconds.
A very high performance on the Earth Simulator was achieved for high-resolution WRF. While the number of CPU cores used is only 1% as compared to the world fastest class system Jaguar (CRAY XT5) at Oak Ridge National Laboratory, the sustained performance obtained on the Earth Simulator is almost 50% of that measured on the Jaguar system. The peak performance ratio on the Earth Simulator is also record-high 22.2%.
See also
Supercomputing in Japan
Attribution of recent climate change
NCAR
HadCM3
EdGCM
References
External links
ES for kids |
666_22 | 2002 in science
Effects of climate change
NEC supercomputers
Numerical climate and weather models
One-of-a-kind computers
Scientific simulation software
Vector supercomputers
64-bit computers
Japan Agency for Marine-Earth Science and Technology |
667_0 | In chemistry, isomers are molecules or polyatomic ions with identical molecular formulae — that is, same number of atoms of each element — but distinct arrangements of atoms in space. Isomerism is existence or possibility of isomers.
Isomers do not necessarily share similar chemical or physical properties. Two main forms of isomerism are structural or constitutional isomerism, in which bonds between the atoms differ; and stereoisomerism or spatial isomerism, in which the bonds are the same but the relative positions of the atoms differ.
Isomeric relationships form a hierarchy. Two chemicals might be the same constitutional isomer, but upon deeper analysis be stereoisomers of each other. Two molecules that are the same stereoisomer as each other might be in different conformational forms or be different isotopologues. The depth of analysis depends on the field of study or the chemical and physical properties of interest. |
667_1 | The English word "isomer" () is a back-formation from "isomeric", which was borrowed through German isomerisch from Swedish ; which in turn was coined from Greek ἰσόμερoς , with roots = "equal", = "part".
Structural isomers
Structural isomers have the same number of atoms of each element (hence the same molecular formula), but the atoms are connected in distinct ways.
Example:
For example, there are three distinct compounds with the molecular formula C3H8O: |
667_2 | The first two isomers shown of C3H8O are propanols, that is, alcohols derived from propane. Both have a chain of three carbon atoms connected by single bonds, with the remaining carbon valences being filled by seven hydrogen atoms and by a hydroxyl group -OH comprising the oxygen atom bound to a hydrogen atom. These two isomers differ on which carbon the hydroxyl is bound to: either to an extremity of the carbon chain propan-1-ol (1-propanol, n-propyl alcohol, n-propanol; I) or to the middle carbon propan-2-ol (2-propanol, isopropyl alcohol, isopropanol; II). These can be described by the condensed structural formulas H3C-CH2-CH2OH and H3C-CH(OH)-CH3.
The third isomer of C3H8O is the ether methoxyethane (ethyl-methyl-ether; III). Unlike the other two, it has the oxygen atom connected to two carbons, and all eight hydrogens bonded directly to carbons. It can be described by the condensed formula H3C-O-CH2-CH3. |
667_3 | The alcohol "3-propanol" is not another isomer, since the difference between it and 1-propanol is not real; it is only the result of an arbitrary choice in the ordering of the carbons along the chain. For the same reason, "ethoxymethane" is not another isomer.
1-Propanol and 2-propanol are examples of positional isomers, which differ by the position at which certain features, such as double bonds or functional groups, occur on a "parent" molecule (propane, in that case).
Example:
There are also three structural isomers of the hydrocarbon C3H4: |
667_4 | In two of the isomers, the three carbon atoms are connected in an open chain, but in one of them (propadiene or allene; I) the carbons are connected by two double bonds, while in the other (propyne or methylacetylene, II) they are connected by a single bond and a triple bond. In the third isomer (cyclopropene; III) the three carbons are connected into a ring by two single bonds and a double bond. In all three, the remaining valences of the carbon atoms are satisfied by the four hydrogens.
Again, note that there is only one structural isomer with a triple bond, because the other possible placement of that bond is just drawing the three carbons in a different order. For the same reason, there is only one cyclopropene, not three.
Tautomers
Tautomers are structural isomers which readily interconvert, so that two or more species co-exist in equilibrium such as
H-X-Y=Z <=> X=Y-Z-H. |
667_5 | Important examples are keto-enol tautomerism and the equilibrium between neutral and zwitterionic forms of an amino acid.
Resonance forms
The structure of some molecules is sometimes described as a resonance between several apparently different structural isomers. The classical example is 1,2-methylbenzene (o-xylene), which is often described as a mix of the two apparently distinct structural isomers:
However, neither of these two structures describes a real compound; they are fictions devised as a way to describe (by their "averaging" or "resonance") the actual delocalized bonding of o-xylene, which is the single isomer of C8H10 with a benzene core and two methyl groups in adjacent positions.
Stereoisomers
Stereoisomers have the same atoms or isotopes connected by bonds of the same type, but differ in their shapes — the relative positions of those atoms in space — apart from rotations and translations. |
667_6 | In theory, one can imagine any arrangement in space of the atoms of a molecule or ion to be gradually changed to any other arrangement in infinitely many ways, by moving each atom along an appropriate path. However, changes in the positions of atoms will generally change the internal energy of a molecule, which is determined by the angles between bonds in each atom and by the distances between atoms (whether they are bonded or not). |
667_7 | A conformational isomer is an arrangement of the atoms of the molecule or ion for which the internal energy is a local minimum; that is, an arrangement such that any small changes in the positions of the atoms will increase the internal energy, and hence result in forces that tend to push the atoms back to the original positions. Changing the shape of the molecule from such an energy minimum A to another energy minimum B will therefore require going through configurations that have higher energy than A and B. That is, a conformation isomer is separated from any other isomer by an energy barrier: the amount that must be temporarily added to the internal energy of the molecule in order to go through all the intermediate conformations along the "easiest" path (the one that minimizes that amount). |
667_8 | A classic example of conformational isomerism is cyclohexane. Alkanes generally have minimum energy when the C-C-C angles are close to 110 degrees. Conformations of the cyclohexane molecule with all six carbon atoms on the same plane have a higher energy, because some or all the C-C-C angles must be far from that value (120 degrees for a regular hexagon). Thus the conformations which are local energy minima have the ring twisted in space, according to one of two patterns known as chair (with the carbons alternately above and below their mean plane) and boat (with two opposite carbons above the plane, and the other four below it). |
667_9 | If the energy barrier between two conformational isomers is low enough, it may be overcome by the random inputs of thermal energy that the molecule gets from interactions with the environment or from its own vibrations. In that case, the two isomers may as well be considered a single isomer, depending on the temperature and the context. For example, the two conformations of cyclohexane convert to each other quite rapidly at room temperature (in the liquid state), so that they are usually treated as a single isomer in chemistry.
In some cases, the barrier can be crossed by quantum tunneling of the atoms themselves. This last phenomenon prevents the separation of stereoisomers of fluorochloroamine NHFCl or hydrogen peroxide H2O2, because the two conformations with minimum energy interconvert in a few picoseconds even at very low temperatures. |
667_10 | Conversely, the energy barrier may be so high that the easiest way to overcome it would require temporarily breaking and then reforming or more bonds of the molecule. In that case, the two isomers usually are stable enough to be isolated and treated as distinct substances. These isomers are then said to be different configurational isomers or "configurations" of the molecule, not just two different conformations. (However, one should be aware that the terms "conformation" and "configuration" are largely synonymous outside of chemistry, and their distinction may be controversial even among chemists.) |
667_11 | Interactions with other molecules of the same or different compounds (for example, through hydrogen bonds) can significantly change the energy of conformations of a molecule. Therefore, the possible isomers of a compound in solution or in its liquid and solid phases many be very different from those of an isolated molecule in vacuum. Even in the gas phase, some compounds like acetic acid will exist mostly in the form of dimers or larger groups of molecules, whose configurations may be different from those of the isolated molecule.
Enantiomers
Two compounds are said to be enantiomers if their molecules are mirror images of each other, that cannot be made to coincide only by rotations or translations — like a left hand and a right hand. The two shapes are said to be chiral. |
667_12 | A classical example is bromochlorofluoromethane (CHFClBr). The two enantiomers can be distinguished, for example, by whether the path F->Cl->Br turns clockwise or counterclockwise as seen from the hydrogen atom. In order to change one conformation to the other, at some point those four atoms would have to lie on the same plane — which would require severely straining or breaking their bonds to the carbon atom. The corresponding energy barrier between the two conformations is so high that there is practically no conversion between them at room temperature, and they can be regarded as different configurations.
The compound chlorofluoromethane CH2ClF, in contrast, is not chiral: the mirror image of its molecule is also obtained by a half-turn about a suitable axis. |
667_13 | Another example of a chiral compound is 2,3-pentadiene H3C-CH=C=CH-CH3 a hydrocarbon that contains two overlapping double bonds. The double bonds are such that the three middle carbons are in a straight line, while the first three and last three lie on perpendicular planes. The molecule and its mirror image are not superimposable, even though the molecule has an axis of symmetry. The two enantiomers can be distinguished, for example, by the right-hand rule. This type of isomerism is called axial isomerism.
Enantiomers behave identically in chemical reactions, except when reacted with chiral compounds or in the presence of chiral catalysts, such as most enzymes. For this latter reason, the two enantiomers of most chiral compounds usually have markedly different effects and roles in living organisms. In biochemistry and food science, the two enantiomers of a chiral molecule — such as glucose — are usually identified, and treated as very different substances. |
667_14 | Each enantiomer of a chiral compound typically rotates the plane of polarized light that passes through it. The rotation has the same magnitude but opposite senses for the two isomers, and can be a useful way of distinguishing and measuring their concentration in a solution. For this reason, enantiomers were formerly called "optical isomers". However, this term is ambiguous and is discouraged by the IUPAC.
Stereoisomers that are not enantiomers are called diastereomers. Some diastereomers may contain chiral center, some not.
Some enantiomer pairs (such as those of trans-cyclooctene) can be interconverted by internal motions that change bond lengths and angles only slightly. Other pairs (such as CHFClBr) cannot be interconverted without breaking bonds, and therefore are different configurations. |
667_15 | Cis-trans isomerism
A double bond between two carbon atoms forces the remaining four bonds (if they are single) to lie on the same plane, perpendicular to the plane of the bond as defined by its π orbital. If the two bonds on each carbon connect to different atoms, two distinct conformations are possible, that differ from each other by a twist of 180 degrees of one of the carbons about the double bond. |
667_16 | The classical example is dichloroethene C2H2Cl2, specifically the structural isomer Cl-HC=CH-Cl that has one chlorine bonded to each carbon. It has two conformational isomers, with the two chlorines on the same side or on opposite sides of the double bond's plane. They are traditionally called cis (from Latin meaning "on this side of") and trans ("on the other side of"), respectively; or Z and E in the IUPAC recommended nomenclature. Conversion between these two forms usually requires temporarily breaking bonds (or turning the double bond into a single bond), so the two are considered different configurations of the molecule.
More generally, cis–trans isomerism (formerly called "geometric isomerism") occurs in molecules where the relative orientation of two distinguishable functional groups is restricted by a somewhat rigid framework of other atoms. |
667_17 | For example, in the cyclic alcohol inositol (CHOH)6 (a six-fold alcohol of cyclohexane), the six-carbon cyclic backbone largely prevents the hydroxyl -OH and the hydrogen -H on each carbon from switching places. Therefore, one has different configurational isomers depending on whether each hydroxyl is on "this side" or "the other side" of the ring's mean plane. Discounting isomers that are equivalent under rotations, there are nine isomers that differ by this criterion, and behave as different stable substances (two of them being enantiomers of each other). The most common one in nature (myo-inositol) has the hydroxyls on carbons 1, 2, 3 and 5 on the same side of that plane, and can therefore be called cis-1,2,3,5-trans-4,6-cyclohexanehexol. And each of these cis-trans isomers can possibly have stable "chair" or "boat" conformations (although the barriers between these are significantly lower than those between different cis-trans isomers). |
667_18 | Cis and trans isomers also occur in inorganic coordination compounds, such as square planar MX2Y2 complexes and octahedral MX4Y2 complexes.
For more complex organic molecules, the cis and trans labels are ambiguous. The IUPAC recommends a more precise labeling scheme, based on the CIP priorities for the bonds at each carbon atom.
Centers with non-equivalent bonds
More generally, atoms or atom groups that can form three or more non-equivalent single bonds (such as the transition metals in coordination compounds) may give rise to multiple stereoisomers when different atoms or groups are attached at those positions. The same is true if a center with six or more equivalent bonds has two or more substituents. |
667_19 | For instance, in the compound PF4Cl, the bonds from the phosphorus atom to the five halogens have approximately trigonal bipyramidal geometry. Thus two stereoisomers with that formula are possible, depending on whether the chlorine atom occupies one of the two "axial" positions, or one of the three "equatorial" positions.
For the compound PF3Cl2, three isomers are possible, with zero, one, or two chlorines in the axial positions.
As another example, a complex with a formula like MX3Y3, where the central atom M forms six bonds with octahedral geometry, has at least two facial–meridional isomers, depending on whether the three X bonds (and thus also the three Y bonds) are directed at the three corners of one face of the octahedron (fac isomer), or lie on the same equatorial or "meridian" plane of it (mer isomer). |
667_20 | Rotamers and atropisomers
Two parts of a molecule that are connected by just one single bond can rotate about that bond. While the bond itself is indifferent to that rotation, attractions and repulsions between the atoms in the two parts normally cause the energy of the whole molecule to vary (and possibly also the two parts to deform) depending on the relative angle of rotation φ between the two parts. Then there will be one or more special values of φ for which the energy is at a local minimum. The corresponding conformations of the molecule are called rotational isomers or rotamers. |
667_21 | Thus, for example, in an ethane molecule H3C-CH3, all the bond angles and length are narrowly constrained, except that the two methyl groups can independently rotate about the C-C axis. Thus, even if those angles and distances are assumed fixed, there are infinitely many conformations for the ethane molecule, that differ by the relative angle φ of rotation between the two groups. The feeble repulsion between the hydrogen atoms in the two methyl groups causes the energy to minimized for three specific values of φ, 120° apart. In those configurations, the six planes H-C-C or C-C-H are 60° apart. Discounting rotations of the whole molecule, that configuration is a single isomer — the so-called staggered conformation. |
667_22 | Rotation between the two halves of the molecule 1,2-dichloroethane (ClH2C-CH2Cl also has three local energy minima, but they have different energies due to differences between the H-H, Cl-Cl, and H-Cl interactions. There are therefore three rotamers: a trans isomer where the two chlorines are on the same plane as the two carbons, but with oppositely directed bonds; and two gauche isomers, mirror images of each other, where the two -CH2Cl groups are rotated about 109° from that position. The computed energy difference between trans and gauche is ~1.5 kcal/mol, the barrier for the ~109° rotation from trans to gauche is ~5 kcal/mol, and that of the ~142° rotation from one gauche to its enantiomer is ~8 kcal/mol. The situation for butane is similar, but with sightly lower gauche energies and barriers. |
667_23 | If the two parts of the molecule connected by a single bond are bulky or charged, the energy barriers may be much higher. For example, in the compound biphenyl — two phenyl groups connected by a single bond — the repulsion between hydrogen atoms closest to the central single bond gives the fully planar conformation, with the two rings on the same plane, a higher energy than conformations where the two rings are skewed. In the gas phase, the molecule has therefore at least two rotamers, with the ring planes twisted by ±47°, which are mirror images of each other. The barrier between them is rather low (~8 kJ/mol). This steric hindrance effect is more pronounced when those four hydrogens are replaced by larger atoms or groups, like chlorines or carboxyls. If the barrier is high enough for the two rotamers to be separated as stable compounds at room temperature, they are called atropisomers. |
667_24 | Topoisomers
Large molecules may have isomers that differ by the topology of their overall arrangement in space, even if there is no specific geometric constraint that separate them. For example, long chains may be twisted to form topologically distinct knots, with interconversion prevented by bulky substituents or cycle closing (as in circular DNA and RNA plasmids). Some knots may come in mirror-image enantiomer pairs. Such forms are called topological isomers or topoisomers.
Also, two or more such molecules may be bound together in a catenane by such topological linkages, even if there is no chemical bond between them. If the molecules are large enough, the linking may occur in multiple topologically distinct ways, constituting different isomers. Cage compounds, such as helium enclosed in dodecahedrane (He@) and carbon peapods, are a similar type of topological isomerism involving molecules with large internal voids with restricted or no openings.
Isotopes and spin |
667_25 | Isotopomers
Different isotopes of the same element can be considered as different kinds of atoms when enumerating isomers of a molecule or ion. The replacement of one or more atoms by their isotopes can create multiple structural isomers and/or stereoisomers from a single isomer.
For example, replacing two atoms of common hydrogen (^1 H ) by deuterium (^2 H , or D) on an ethane molecule yields two distinct structural isomers, depending on whether the substitutions are both on the same carbon (1,1-dideuteroethane, HD2C-CH3) or one on each carbon (1,2-dideuteroethane, DH2C-CDH2); as if the substituent was chlorine instead of deuterium. The two compounds do not interconvert easily and have different properties, such as their microwave spectrum. |
667_26 | Another example would be substituting one atom of deuterium for one of the hydrogens in chlorofluoromethane (CH2ClF). While the original compound is not chiral and has a single isomer, the substitution creates a pair of chiral enantiomers of CHDClF, which could be distinguished (at least in theory) by their optical activity.
When two isomers would be identical if all isotopes of each element were replaced by a single isotope, they are described as isotopomers or isotopic isomers. In the above two examples if all D were replaced by H, the two dideuteroethanes would both become ethane and the two deuterochlorofluoromethanes would both become CH2ClF.
The concept of isotopomers is different from isotopologs or isotopic homologs, which differ in their isotopic composition. For example, C2H5D and C2H4D2 are isotopologues and not isotopomers, and are therefore not isomers of each other. |
667_27 | Spin isomers
Another type of isomerism based on nuclear properties is spin isomerism, where molecules differ only in the relative spins of the constituent atomic nuclei. This phenomenon is significant for molecular hydrogen, which can be partially separated into two spin isomers: parahydrogen, with the spins of the two nuclei pointing in opposite ways, and orthohydrogen, where the spins point the same way.
Ionization and electronic excitation
The same isomer can also be in different excited states, that differ by the quantum state of their electrons. For example, the oxygen molecule can be in the triplet state or one of two singlet states. These are not considered different isomers, since such molecules usually decay spontaneously to their lowest-energy excitation state in a relatively short time scale.
Likewise, polyatomic ions and molecules that differ only by the addition or removal of electrons, like oxygen O2or the peroxide ion O2^2- are not considered isomers.
Isomerization |
667_28 | Isomerization is the process by which one molecule is transformed into another molecule that has exactly the same atoms, but the atoms are rearranged. In some molecules and under some conditions, isomerization occurs spontaneously. Many isomers are equal or roughly equal in bond energy, and so exist in roughly equal amounts, provided that they can interconvert relatively freely, that is the energy barrier between the two isomers is not too high. When the isomerization occurs intramolecularly, it is considered a rearrangement reaction.
An example of an organometallic isomerization is the production of decaphenylferrocene, [(η5-C5Ph5)2Fe] from its linkage isomer.
Synthesis of fumaric acid
Industrial synthesis of fumaric acid proceeds via the cis-trans isomerization of maleic acid:
Topoisomerases are enzymes that can cut and reform circular DNA and thus change its topology. |
667_29 | Medicinal chemistry
Isomers having distinct biological properties are common; for example, the placement of methyl groups. In substituted xanthines, theobromine, found in chocolate, is a vasodilator with some effects in common with caffeine; but, if one of the two methyl groups is moved to a different position on the two-ring core, the isomer is theophylline, which has a variety of effects, including bronchodilation and anti-inflammatory action. Another example of this occurs in the phenethylamine-based stimulant drugs. Phentermine is a non-chiral compound with a weaker effect than that of amphetamine. It is used as an appetite-reducing medication and has mild or no stimulant properties. However, an alternate atomic arrangement gives dextromethamphetamine, which is a stronger stimulant than amphetamine. |
667_30 | In medicinal chemistry and biochemistry, enantiomers are a special concern because they may possess distinct biological activity. Many preparative procedures afford a mixture of equal amounts of both enantiomeric forms. In some cases, the enantiomers are separated by chromatography using chiral stationary phases. They may also be separated through the formation of diastereomeric salts. In other cases, enantioselective synthesis have been developed.
As an inorganic example, cisplatin (see structure above) is an important drug used in cancer chemotherapy, whereas the trans isomer (transplatin) has no useful pharmacological activity. |
667_31 | History
Isomerism was first observed in 1827, when Friedrich Wöhler prepared silver cyanate and discovered that, although its elemental composition of AgCNO was identical to silver fulminate (prepared by Justus von Liebig the previous year), its properties were distinct. This finding challenged the prevailing chemical understanding of the time, which held that chemical compounds could be distinct only when their elemental compositions differ. (We now know that the bonding structures of fulminate and cyanate can be approximately described as O- N+≡C- and O=C=N-, respectively.)
Additional examples were found in succeeding years, such as Wöhler's 1828 discovery that urea has the same atomic composition (CH4N2O) as the chemically distinct ammonium cyanate. (Their structures are now known to be (H2N-)2C=O and [NH+4] [O=C=N^ -] , respectively.) In 1830 Jöns Jacob Berzelius introduced the term isomerism to describe the phenomenon. |
667_32 | In 1848, Louis Pasteur observed that tartaric acid crystals came into two kinds of shapes that were mirror images of each other. Separating the crystals by hand, he obtained two version of tartaric acid, each of which would crystallize in only one of the two shapes, and rotated the plane of polarized light to the same degree but in opposite directions.
See also
Chirality (chemistry)
Cis-trans isomerism
Cyclohexane conformation
Descriptor (chemistry)
Electromerism
Isomery (botany)
Ligand isomerism
Nuclear isomer
Stereocenter
Structural isomerism
Tautomer
Vitamer
References
External links
Organic chemistry
Isomerism
1827 introductions
ga:Isiméir |
668_0 | On 7 March 2015, a steam-hauled charter train passed a signal at danger and subsequently came to a stand across a high-speed mainline junction near Wootton Bassett Junction, Wiltshire, England. Another train, which had right of way, had passed through the junction 44 seconds earlier and no collision occurred nor was any damage done.
As a result of this signal passed at danger (SPAD), Network Rail banned the train's operator, West Coast Railway Company (WCRC), from operating trains anywhere on the British railway network. The Rail Accident Investigation Branch (RAIB) opened an investigation into the incident, which it called a "dangerous occurrence". The incident was rated the most serious SPAD in the United Kingdom since December 2010. Following improvements made by WCRC, the ban was lifted. A subsequent incident led to a further ban, which was later lifted. |
668_1 | In December 2015, the Office of Rail and Road initiated a prosecution against the driver of the train and WCRC for offences under the Health and Safety at Work Act 1974. The case was heard in June 2016. Both WCRC and the driver of the train pleaded guilty. WCRC was fined £200,000 plus costs. The driver received a sentence of four months' imprisonment, suspended for eighteen months.
In May 2016, the RAIB published a report on the incident, which largely blamed the incident on the train crew tampering with a safety system that would otherwise have safely brought the train to a halt.
Incident |
668_2 | At 17:25 GMT on 7 March 2015, a charter train approached Wootton Bassett Junction, where the Great Western Main Line and South Wales Main Line diverge at Royal Wootton Bassett, Wiltshire. In the approach to signal SN43, an Automatic Warning System (AWS) magnet was present in the trackbed, warning of a temporary speed restriction ahead. The line speed was . The temporary restriction of then in force did not apply to the train as steam locomotives are restricted to a maximum of on Network Rail (NR) tracks in any event. An emergency brake application occurred on the train after it had passed over the magnet because the driver failed to press the AWS cancelling button within 2.7 seconds. |
668_3 | The driver should have allowed the train to come to a stand and contacted the signalman, but he did not. Instead the AWS isolating cock was operated, releasing the brake after the train's speed had been reduced from to about . This had the effect of isolating both the AWS and the Train Protection & Warning System (TPWS), rendering them unable to apply the brakes. Although the driver was permitted to operate the isolating cock under certain fault conditions, he did not follow rulebook protocol or inform the signaller that he had done so. |
668_4 | The next signal, SN45, was displaying a red (danger) aspect. By the time the driver saw this, there was insufficient distance available to stop the train, which eventually came to a stand on the junction some past the signal. The service train that was being protected by the red signal had already passed through the junction and no collision occurred. As the points had already moved for the passage of the charter train, no damage was done to the trackwork at Wooton Bassett Jn. The line speed approaching the junction was for the service train. Before he was relieved from driving duties, the driver of the charter train claimed that signal SN43 had displayed a green (proceed) aspect. NR investigations showed that a single yellow (caution) aspect was displayed.
Following the incident, the driver was relieved at . There a new driver was supplied by West Coast Railway Company (WCRC) who drove the train to , where the train was terminated. |
668_5 | The incident was rated the most serious SPAD since December 2010, rating 25 out of 28 on Network Rail's scale. Any SPAD rated at 20 or more leads to a mandatory investigation by the Office of Rail and Road (ORR). The scale is logarithmic, with each increment rated twice as serious as the previous; thus the incident was rated as nominally over thirty times more serious than this threshold. The December 2010 SPAD was rated at 26, and was at Uphill Junction, Somerset, on the Bristol to Exeter line when a passenger train overran a signal by . The month before that incident, a passenger train overran a signal at , Staffordshire, in an incident rated at 25. |
668_6 | RAIB investigation findings |
668_7 | The RAIB investigation into the accident reported that the outward working, reporting number 1Z21, the 07:22 from to , had been fitted with a numbered plastic tie on the handle of the Automatic Warning System (AWS) isolating cock. The train was driven to Bristol without incident, although some misting of the driver's window was reported. The driver of that train was not the driver later involved in the SPAD at Wootton Bassett. During an empty coaching stock movement to St Philip's Marsh depot, the emergency brake applied because the driver did not cancel an AWS warning in the allotted time. The AWS isolating cock was opened, breaking the seal. On leaving St Philip's Marsh, a similar incident occurred, and the AWS isolating cock was opened again. There was a change of traincrew on arrival at Bristol Temple Meads, where the return working was designated 1Z67. According to the rulebook, the driver of the train should have reported the missing seal on the AWS isolating cock. The train |
668_8 | should not have been allowed to depart until the cock had been sealed. The driver did not do this, and set off with an unsealed cock. |
668_9 | Due to misting and exhaust obstructing the driver's view through the window, the driver drove leaning out of the cab for much of the time. This made hearing the AWS sounder and observing the AWS reminder light harder. Approaching signal SN43, there was a temporary speed restriction of , which was warned of by a temporary AWS magnet in advance of the restriction, and indicated by a sign at the start of the temporary speed restriction. The train approached signal SN43 at and passed over the temporary AWS magnet. The driver failed to react to the warning given within the time allowed and the brakes were applied. Because the AWS isolating cock was out of reach of the driver, he instructed the fireman to open it for him. The train's speed had reduced by about when the brakes were released. The rules require that the train is brought to a stand and the signaller contacted in the event of an AWS brake application. Additionally the driver must inform the signaller whenever the AWS is |
668_10 | isolated;"Driver: If it becomes necessary to isolate the AWS, you must: |
668_11 | stop your train immediately
tell the signaller
not move the train until instructed to do so
carry out the instructions given." The train then passed signal SN43, which was displaying a single yellow (caution) aspect. The driver acknowledged the AWS warning, but did not reduce speed. |
668_12 | In the twelve seconds between brake application and brake release, the train passed over the fixed AWS magnet for signal SN43, which was displaying a single yellow (caution) aspect. This warning was cancelled in time. The train then passed over the TPWS+ overspeed sensor for signal SN45, which was displaying a red (danger) aspect. As the train was travelling more slowly than the trigger speed, no brake action was demanded from the train. The train then passed over the second TPWS overspeed sensor for signal SN45, this time at , which was in excess of the trigger speed. Consequently, a TPWS intervention occurred, but as the AWS isolating cock was open the brakes did not apply. When the driver saw that signal SN45 was at danger, he applied the brakes on the train. Due to there being insufficient distance to stop, the train overran the signal by and came to a stand across Wootton Basset Junction. |
668_13 | Then the driver reported to the signaller by radio, claiming that the signals had not sequenced properly (i.e. that SN43 had been green). During the time that he was on the radio, the fireman closed the AWS isolating cock. The signaller initially treated the event as a Technical SPAR (i.e., Signal Passed at Red due to an Irregular Signal Sequence) because there was no SPAD alarm provided for signal SN45 and the driver had claimed that the preceding signal was displaying a green aspect. Because this is not a safety-critical event he authorised the driver to take the train forward to . However, by the time the train arrived at Swindon, it was understood that signal SN45 had been passed at danger without authority and the driver was relieved of his duties. The driver was not tested for the presence of drugs or alcohol in his system, as is required by Railway Group Standards. The investigation found that there was no evidence of alcohol in his system. Prescription drugs that he was taking |
668_14 | were assessed as not having an effect on his ability to drive the train. Fatigue was found not to be a factor. |
668_15 | The investigation found that crewing of the train was insufficient. There was no traction inspector on board. WCRC had discontinued the use of traction inspectors by 2012. A traction inspector's duties include assisting the driver with the sighting of signals. Two members of the train support crew were also on the footplate of Tangmere, but they had no responsibility in respect of the operation of the train. No problems were found with the ability to sight signals SN43 and SN45. The locomotive and carriages from the train were tested separately following the incident; no fault was found with either, although some of the sensors were not being recorded by the On Train Data Recorder (OTDR). The RAIB were able to reconstruct the sequence of events from the data that was recorded by the OTDR. |
668_16 | The investigation found that the fixed AWS magnet for signal SN43 was incorrectly positioned. It was located from the signal, instead of the standard . The actual location of signal SN43 was closer to the junction than shown on signalling diagrams, which was at from London. These errors meant that the placing of the AWS magnet for the temporary speed restriction was also incorrect. Instead of being from the fixed AWS magnet, the temporary AWS magnet for the speed restriction was only from it. The installation of signal SN43 was in 1978, and the errors had remained undetected since then. An emergency speed restriction had been introduced in January 2015 due to the condition of the track, and had subsequently been converted to a temporary speed restriction. These errors were found not to have been contributory factors in the incident. |
668_17 | The safety culture at WCRC was found by the investigation to be weak. This was evidenced by a number of factors, including the lack of traction inspectors, failure to test for drugs and alcohol, failure to download data from OTDRs to analyse individual driver performance, failure to maintain OTDR equipment correctly, failure to report missing seals on safety equipment where they were required to be fitted, failure to keep proper records, and failure to improve following the incident at Bell Busk (detailed below).
Trains
Charter train
The charter train, reporting number 1Z67, was a steam-hauled passenger train, the 16:35 Cathedrals Express charter from to , Essex. The train was hauled by Battle of Britain-class locomotive 34067 Tangmere (TOPS number 98 767). Tangmere was hauling thirteen carriages, which were a mixture of Mk 1s and Mk 2s. The train was operated by WCRC. There were 477 passengers and 39 staff on board the train. |
668_18 | Service train
The service train was the 15:28 to , reporting number 1L76. It was operated by a First Great Western InterCity 125 "High Speed Train", and was carrying about 240 passengers.
Investigations
The Rail Accident Investigation Branch opened an investigation into the incident, which it called a "dangerous occurrence". One aspect of the investigation was whether the seals on the TPWS equipment were already broken before the train departed from Bristol, or were not in place at the time. In March 2016, the RAIB published an update on their investigation. The final report was released in May 2016. Five safety recommendations were made and one learning point was identified. |
668_19 | The Rail Safety and Standards Board opened an investigation into the incident. The ORR opened two investigations; one into WCRC's Safety Management System, with the second a criminal investigation. The ORR subsequently charged WCRC and the driver of the train with various offences under the Health and Safety at Work Act 1974. WCRC also opened an internal investigation into the incident.
Ban
Network Rail |
668_20 | Effective midnight on 3 April, NR banned WCRC from operating trains anywhere on the British railway network, stating in the suspension notice that "the operations of WCR are a threat to the safe operation of the railway". Seven areas of deficiencies were identified. WCRC was required to address five of them and show significant progress towards addressing the other two by 15 May. If this could be achieved, the ban would be lifted. During the period that WCRC was banned from the rail network, it was still required to pay Track Access Charges to Network Rail. This was the first time that a train operating company had been banned in the United Kingdom.
Following improvements made by WCRC, the ban was lifted on 8 May. A review of progress made was scheduled to be made after 3 months. |
668_21 | Office of Rail and Road
On 17 April, the ORR took steps to revoke WCRC's Safety Certificate. A process of representation was started, with parties having until 15 May to comment. The ORR's opinion was that WCRC's Safety Management System "is not able to ensure that services are being operated, designed or maintained safely". On 21 May 2015, the ORR issued WCRC an improvement notice under the Railways and Other Guided Transport Systems (Safety) Regulations 2006. |
668_22 | Previous incident
On 12 July 2014, a charter train operated by WCRC, reporting number 1Z57, caused a lineside fire at , North Yorkshire, The train was headed by Hall-class locomotive 5972 Olton Hall, which was hauling a charter train from , Lancashire to . The fire was caused by a defect in the locomotive's ash pan which allowed a piece of burning coal to fall from the locomotive and land alongside the track. Following the incident, WCRC was served with a Suspension Notice, which had the effect that WCRC was banned from operating steam locomotives on that route. It raised the issue with the Access Disputes Committee (ADC), calling Network Rail's actions "partial and malicious". The Suspension Notice was later partly lifted, allowing operation on routes where there was deemed not to be an enhanced fire risk. |
668_23 | An investigation found that the crew of the train had not been advised that there was a raised fire risk at the time. WCRC was found not to have co-operated fully with the investigation. The ADC found that WCRC's Safety Management System was deficient due to confusion over whether or not the crew of the train had been informed of the increased fire risk. WCRC failed to inform Network Rail of its plans to try to prevent future incidents of a similar nature. The ADC found that this was in breach of WCRC's Safety Management System. WCRC chairman David Smith instructed his staff that no further correspondence would be gone into over the matter. The ADC found that this instruction was prejudicial to the safe operation of WCRC's Safety Management System. The instruction was later rescinded. WCRC was also found to be in breach of its Track Access Contract. |
668_24 | Fallout
At the time of the ban, WCRC operated about 90% of all steam charter operations on Britain's railways. DB Schenker was the only other operator licensed to run steam trains on Network Rail tracks. DB Schenker has a policy of only operating air braked trains, whereas many trains operated by WCRC use vacuum brakes, which meant that DB Schenker was unable to operate those charters in place of WCRC.
Steam Railway editor Howard Johnston said that the aftermath of the SPAD represented "possibly the greatest challenge to our movement". ASLEF General Secretary Mick Whelan called for better regulation of crew driving charter trains. Following the ban, eighteen charters were cancelled and eleven were postponed in the period 4 April – 5 May. DB Schenker and GB Railfreight operated three charters each. Companies affected included Belmond, Compass, NENTA Traintours, PMR Railtours, Railway Touring Company, SRPS Railtours, Statesman Rail, Steam Dreams and Vintage Trains. |
668_25 | On 6 May, it was reported that The Jacobite season was likely to start late due to the suspension. The trains, which run on the West Highland Line in Scotland, were due to start running on 11 May for the start of the 2015 season. Following the lifting of the ban on 8 May, it was announced that The Jacobite trains would run as scheduled from 11 May.
In May 2015, Abellio ScotRail announced that as a result of the ban, it was reconsidering its decision to give WCRC preferred bidder status for a contract to run steam trains on the Waverley Line, which was scheduled to reopen between Edinburgh and in September 2015. |
668_26 | In June 2015, it was reported that the ORR was planning to call a "Safety Summit" involving operators of charter trains on NR tracks. It was reported that one proposal to be put forward by the ORR was that all charter trains be limited to a maximum of eleven carriages. This, if enacted, would mean a loss of revenue of up to £5,000 per train for operators. Part of the reasoning behind the proposal was that steam locomotives have a lower rate of acceleration than modern traction. As they are limited to , they have to be worked harder in order to maintain time. A reduction in train weight would make acceleration rates a little faster and reduce the need to work locomotives so hard. |
668_27 | Despite many requests from Rail, WCRC chairman David Smith refused to comment on the incident. In an interview with Steam Railway, he stated that the company was working to satisfy the seven demands made by Network Rail, and was only cancelling trains about a week in advance, in the hope that WCRC would be able to run trains again in the future. Responding to a comment by Smith that "We are co-operating with the ORR in its enquiries, but from what we can see, all it is doing is keeping a watchful eye on what is going on", Rail editor Nigel Harris expressed astonishment at the "jaw-dropping" comments as criminal charges could lead to imprisonment following a guilty verdict. The reputational damage to WCRC was described as "possibly commercially fatal". Rail contributor Pip Dunn said that WCRC refused to talk to journalists when negative stories concerning the company were being reported, yet was happy to when publicising a charter it was running. On 28 May, WCRC issued a press release |
668_28 | apologising for the distress, disappointment and inconvenience caused by the incident and events arising from it. It also thanked the ORR and others for assistance and support given. It stated that it was giving full assistance to the RAIB in respect of its investigation into the SPAD. |
668_29 | In April 2015, the ORR was considering whether or not to prosecute WCRC, and subsequently decided to prosecute both WCRC and the driver of the train. Although the suspension had been lifted by NR, the ORR could still have revoked WCRC's Safety Certificate at the end of the 28-day consultation period. The lifting of the suspension by NR was subject to a review after three months.
Great Britain VIII |
668_30 | Great Britain VIII was a nine-day railtour, one of an annual series, from London to Cornwall, then to Scotland, and back to London. Various steam locomotives were scheduled to haul the train on each day of the tour, which was to have been entirely steam-hauled. Participants paid between £1,995 and £2,895 per person for the nine-day tour, which ran from 28 April to 6 May 2015. Despite fears that the tour would be cancelled, it was run although with changes to the locomotives hauling it. DB Schenker agreed to operate the first two days of the tour. The tour suffered a number of issues including steam locomotives being replaced by diesels, and a lack of train heating; these resulted in a significant number of passengers leaving the tour early. |
668_31 | Subsequent incident and further ban
On 2 October 2015, Black 5 steam locomotive 45231 Sherwood Forester was working a WCRC special through Doncaster when it was noticed that its TPWS had been isolated by the fireman. As a result, in November 2015 a further prohibition notice was issued to WCRC by the ORR, suspending further steam services operated by them. It was reported that locomotives would need to have their TPWS modified to prevent the crew from being able to isolate it, before this suspension could be lifted. |
668_32 | On 17 February 2016, the ORR served a Prohibition Notice on WCRC, citing a further seven incidents which had occurred since the SPAD at Wootton Bassett. The prohibition was to become effective from 18 February 2016 meaning that WCRC would "no longer be able to operate trains on the mainline network until such a time as [WCRC] can satisfy [the ORR] that its governance and operations meet industry practice and are fit for the scale of its operations". In addition the ORR found that the conditions for the revocation of WCRC's safety certificate had been met, which could have implications for WCRC's European train operator's licence. This second prohibition was lifted on 23 March 2016. |
668_33 | Prosecution
On 9 December 2015, the ORR announced that WCRC and the driver of the train were to be prosecuted for offences contrary to the Health and Safety at Work Act 1974. An initial hearing was scheduled to be heard at Swindon Magistrates Court on 11 January 2016, but postponed until 20 January. When the case opened, neither the driver Melvyn Cox nor WCRC entered pleas. The case was committed to Swindon Crown Court, where it was scheduled to be heard on 19 February; unconditional bail was granted to Cox. The case was subsequently postponed until 18 March, and then further postponed to an undisclosed date in May 2016. In late May, it was announced that the trial would begin on 27 June 2016. |
668_34 | At the trial, both WCRC and Cox pleaded guilty. WCRC were fined £200,000 plus costs of £64,000. The fine imposed was half of the maximum that could have been imposed. This was decided by Judge Peter Blair QC after he took mitigating circumstances into account. Cox was sentenced to four months imprisonment, suspended for eighteen months. He was also ordered to do 80 hours unpaid work. Cox's counsel stated in court that "he would never drive trains again".
References
Further reading
Railway accidents in 2015
Railway accidents and incidents in Wiltshire
History of Wiltshire
2015 in England
Railway accidents involving a signal passed at danger
2015 in British law
Accidents and incidents involving First Great Western
Accidents and incidents involving West Coast Railways
2016 in British law
March 2015 events in the United Kingdom |
669_0 | Fuladu (; ) or Fuladugu (French: Fouladougou) is a historic region in the Upper Casamance, in the south of Senegal, including certain areas in The Gambia near the border with Guinea. It corresponds roughly to the modern Kolda Department.
History
Historically, Fuladu was the last kingdom to be established in Senegal, in the second half of the nineteenth century. This kingdom was established by the Fula chief who belonged to the Fulbe Firdu group. Before the creation of this kingdom, the Mandinka controlled the region. They had established the kingdom of Kaabu as a vassal of the Mali Empire in the fifteenth century.
Nomadic pastoralists, the Fula peoples arrived in the region in a significant way in the fourteenth century, attracted by the pastureland. Other Fula people had migrated through the region before the arrival of the second wave of Fulbe, but they did not remain long; it was this second wave that lead to a permanent presence in the region. |
669_1 | Initially, the Fula and the dominant Mandinka people had a good relationship. The Fula settled near the Mandinka in order to sell them dairy products produced by their cattle, in exchange for the agricultural products of the Mandinka. The Mandinka entrusted their own herds to the Fula, who circulated freely in Kaabu. Intermarriage between the two communities took place. |
669_2 | Later, however, the relationship between the Fula and the Mandinka deteriorated. The once mutually beneficial relationship (in which the Mandinka provided pasturage and protection in exchange for taxes, services, and gifts from the Fula) became more exploitative. Fula became vassals of the Mandinka of Kaabu and they remained so until the middle of the nineteenth century. The Mandinka kings maintained a system similar to servitude with respect to the Fula. Numerous Fula families were required to settle sedentarily in the "fulakunda", established for the Fula by the Mandinka. Many were forced to adopt agriculture, in order to supply the Mandinka, who imposed a very heavy tax on them. The Fula were victims of harassment and humiliation and had to assimilate to the culture and language of the Mandinka. The Mandinka and Fula intermarried extensively. Despite this, many Fula fought to safeguard their language, traditions, and nomadic way of life. They revolted several times, but always |
669_3 | suffered defeat. The Mandinka justified the exactions that they practiced against the Fula as responses to these revolts. |
669_4 | Eventually, Alpha Molo Balde, the future founder of the Fuladu kingdom, revolted against the Mandinka, unified the Fula of Kaabu, and sought the help of the Fula of Fouta Djallon for maintaining the revolt against the kings of Kaabu (who were entitled "Mansa"). After a very difficult revolt, thanks to numerous attacks by Fouta Djallon which led to enormous casualties, Alpha Molo took control of the territory in which the Fula predominated. This marked the creation of Fuladu, stretching from the Upper Casamance up to the land north of Guinea-Bissau. In modern oral tradition, he is referred to as "Alpha the Liberator." |
669_5 | Before Alpha Molo, the Fula had followed the traditional religion, although there were some Fula marabouts. They now converted to Islam in large numbers in order to win the support of Fouta Djalon for the revolt, since the Almami of Fouta Djallon were opposed to followers of traditional religion, whether they were Fula, Mandinka, or others. Without this conversion to Islam, Fouta Djalon would not have agreed to help the Fula. In the course of the nineteenth century, numerous short-lived Fula Muslim states were established in this way: the Sokoto Caliphate, the Massina Empire (Diina), the Adamawa Emirate, and the Toucouleur Empire of El Hadj Umar Tall. Alpha Molo had also profited from this phenomenon to defeat the Mansa of Kaabu. |
669_6 | Alpha Molo Balde died in 1881 at Dandu (now in Guinea-Bissau) and his son attempted to complete what his father had begun. After the death of Alpha Molo, French colonists began to enter the region in a significant way. Moussa Molo maintained a strong resistance against colonisation in the Upper Casamance, but he was defeated and killed in battle at Keserekunda in Gambia in 1931.
Population
As its name suggests, the Fula form a majority of the population of Fuladu (about 55%). Most of the Fula in Fuladu are engaged in agriculture. They belong to the Fulbe Firdu group.
There are also several Madinka groups in the region: , Mandinka, Yalunka and Jakhanke people, as well as Wolofs, Jola, Bainuk, Balanta, and Manjacks. |
Subsets and Splits
No community queries yet
The top public SQL queries from the community will appear here once available.