Home About us Contact
|
Home About us Contact | ||
|
|
||
Trial Structures (trial + structure)
Selected AbstractsState, Citizen, and Character in French Criminal ProcessJOURNAL OF LAW AND SOCIETY, Issue 4 2006Stewart Field This paper charts some major differences in the way in which evidence of the defendant's character is treated in France when compared with practice in England and Wales. Such evidence is more pervasive and visible (especially in the most serious cases) and its relevance is more broadly defined. Further, its presentation is shaped by a developed and positive conception of the French citizen. In part, these differences may be explained by differences in procedural tradition: the unitary trial structure in France, the dominance of fact,finding by the professional judiciary, and the rejection of general exclusionary rules of evidence. But a full explanation requires French legal culture to be understood in the context of French political culture. This reveals a very different conception of relations between state and citizen to that of Anglo-Saxon liberalism. As a result the legitimacy of trial is seen in terms of the rehabilitation of the accused as a citizen of the state rather than simply the punishment of a particular infraction. [source] SnB version 2.2: an example of crystallographic multiprocessingJOURNAL OF APPLIED CRYSTALLOGRAPHY, Issue 3 2002Jason Rappleye The computer program SnB implements a direct-methods algorithm, known as Shake-and-Bake, which optimizes trial structures consisting of randomly positioned atoms. Although large Shake-and-Bake applications require significant amounts of computing time, the algorithm can be easily implemented in parallel in order to decrease the real time required to achieve a solution. By using a master,worker model, SnB version 2.2 is amenable to all of the prevalent modern parallel-computing platforms, including (i) shared-memory multiprocessor machines, such as the SGI Origin2000, (ii) distributed-memory multiprocessor machines, such as the IBM SP, and (iii) collections of workstations, including Beowulf clusters. A linear speedup in the processing of a fixed number of trial structures can be obtained on each of these platforms. [source] Systematic conformational search analysis of the SRR and RRR epimers of 7-hydroxymatairesinolJOURNAL OF PHYSICAL ORGANIC CHEMISTRY, Issue 2 2010Giovanni Li Manni Abstract An extensive and systematic conformational search was performed on the two epimers of the natural lignan 7-hydroxymatairesinol (HMR), by means of a home-made Systematic Conformational Search Analysis (SCSA) code, designed to select more and more stable conformers through sequential geometry optimization of trial structures at increasing levels of calculation theory. In the present case, the starting molecular structures were selected by the semi-empirical AM1 method and filtered , i.e. decreased in number by choosing the more stable species , on the basis of their energy calculated by the HF method and the 6-31G(d) basis set. The geometries obtained were further refined by performing density functional theory (DFT) optimizations, using the B3LYP functional and the 6-31G(d,p) basis set, both in vacuo and in ethanol solution. This procedure allowed us to isolate, at a high level of theory, three groups of epimer conformers characterized by open, semi-folded, and folded conformations. Moreover, the SCSA allowed us to describe a conformational space made-up by about 20 species for each of the two epimers. The corresponding energy content of these species was within 27,kJ,mol,1 from the absolute minimum found, both in vacuo and in ethanol solution. The conformational analysis, followed by the inspection of the stereochemistry of the two most stable conformers of both epimers, provides support in rationalizing the proposed reaction mechanism of the catalytic hydrogenolysis of the HMR to matairesinol (MAT). Copyright © 2009 John Wiley & Sons, Ltd. [source] Ill-conditioned Shake-and-Bake: the trap of the false minimumACTA CRYSTALLOGRAPHICA SECTION A, Issue 2 2000Hongliang Xu The alternation of phase refinement with the imposition of real-space constraints is the essence of the Shake-and-Bake procedure. Typically, these constraints prevent trial structures from falling into local minima. Nevertheless, structures appear to migrate to false minima with significant frequency. These false minima are characterized by the presence of a large `uranium' peak on the corresponding Fourier map. Fortunately, they can be recognized and avoided by considering the values of the minimal function both before and after the application of constraints. However, it appears that finding solutions for large structures is likely also to require parameter-shift conditions different from those that have been found to work well in other space groups. In fact, these conditions often yield an unusually high percentage of solutions. [source] ACORN2: new developments of the ACORN conceptACTA CRYSTALLOGRAPHICA SECTION D, Issue 9 2009E. J. Dodson The density-modification procedures incorporated in ACORN, available in the CCP4 package, have proved to be very successful in solving and refining high-resolution crystal structures from very poor starting sets. These can be calculated from a correctly positioned initial fragment containing between 1 and 8% of the scattering power of the total structure. Improvements of ACORN, reported here and incorporated in the program ACORN2, have lowered the size of the fragment required and examples are given of structures solved with only 0.25% of the scattering power in the fragment, which may be a single atom. Applications of ACORN2 to structures with space group P1 have shown the remarkable property that when the starting point is a pair of equal atoms, or even a single atom placed at the origin, the refinement process breaks the centric nature of the initial phases and converges to phases corresponding to one of the two possible enantiomorphs. Examples are given of the application of ACORN2 to the solution and/or refinement of a number of known trial structures and to the refinement of structures when phases are available either from MAD or from a molecular-replacement model. [source] Map self-validation: a useful discriminator of phase correctness at low resolutionACTA CRYSTALLOGRAPHICA SECTION D, Issue 4 2001David A. Langs A new map-validation procedure is based on the correlation-coefficient agreement between the observed structure-factor magnitudes and their extrapolated values from suitably modified electron-density maps from which they have been each in turn systematically excluded. The correlation coefficient tends to a maximum as the phase errors in a map are reduced. This principle was used to resolve the single-wavelength anomalous scattering (SAS) and single-derivative isomorphous replacement (SIR) phase ambiguity for a number of error-free trial structures. Applications employing real data sets tend to be more difficult owing to data incompleteness and errors affecting the construction of the Argand diagram. [source] Low-resolution phase extension using wavelet analysisACTA CRYSTALLOGRAPHICA SECTION D, Issue 10 2000Peter Main A method to extend low-resolution phases is presented which uses histogram matching not only of the electron density, but also of histograms obtained from the different levels of detail provided by the wavelet transform of the electron density. Statistical values for the wavelet coefficients can be predicted and depend only on the resolution and solvent content. Therefore, new details can be added to an electron-density map by matching the values of the wavelet coefficients to those predicted for an increased resolution. The positions of the new details are also guided by the diffraction pattern. In this way, the resolution can be increased gradually; on a number of trial structures of different size, solvent percentage and space group, it has been possible to extend the phasing from 10,Å to around 6,7,Å. [source] P1 Shake-and-Bake: can success be guaranteed?ACTA CRYSTALLOGRAPHICA SECTION D, Issue 2 2000Hongliang Xu The multi-trial direct-methods procedure known as Shake-and-Bake has been applied to three small proteins (alpha-1 peptide, vancomycin and lysozyme) that crystallize in space group P1. Phase refinement was accomplished through parameter-shift optimization using both the cosine and exponential forms of the minimal function. By extending error-free data to sufficiently high resolution, 100% convergence of trial structures to solution could be achieved in all three cases by using the exponential minimal function and a shift angle in the range 130,150°. These results suggest optimum parameters for other P1 structures and emphasize the importance of collecting data to the highest possible resolution. [source] | ||||||||||