Non-Linear Approximation of Bayesian Update
Litvinenko, Alexander
2016-01-01
We develop a non-linear approximation of expensive Bayesian formula. This non-linear approximation is applied directly to Polynomial Chaos Coefficients. In this way, we avoid Monte Carlo sampling and sampling error. We can show that the famous Kalman Update formula is a particular case of this update.
Non-Linear Approximation of Bayesian Update
Litvinenko, Alexander
2016-06-23
We develop a non-linear approximation of expensive Bayesian formula. This non-linear approximation is applied directly to Polynomial Chaos Coefficients. In this way, we avoid Monte Carlo sampling and sampling error. We can show that the famous Kalman Update formula is a particular case of this update.
Electron diffraction study of {alpha}-AlMnSi crystals including non-crystallographic axes
Energy Technology Data Exchange (ETDEWEB)
Song, G.L.; Bursill, L.A.
1997-06-01
The structure of crystalline {alpha}-AlMnSi is examined by electron diffraction. Six distinct zone axes are examined, including both normal crystallographic and non-crystallographic zones axes, allowing the space group symmetry to be studied. Electron diffraction patterns characteristic of Pm3-bar were obtained for thicker specimens. However, for very thin specimens, as used for HRTEM imaging, the electron diffraction patterns were characteristic of Im3-bar space group symmetry. The structural basis of the Pm3-bar to Im3-bar transformation may be understood in terms of an analysis of the icosahedral structural elements located at the corners and body-centers of the cubic unit cell. A method for indexing the non-crystallographic zone axis diffraction patterns is described. An electron diffraction pattern of the 5-fold axis of the quasicrystalline phase i-AlMnSi is also included; this is compared with the experimental results and calculations for the [0{tau}1] axis of Pm3-bar and Im3-bar crystalline phases. 26 refs., 4 tabs., 7 figs.
Effect of crystallographic texture on the bulk magnetic properties of non-oriented electrical steels
Energy Technology Data Exchange (ETDEWEB)
Ghosh, Pampa, E-mail: pampaghosh@gmail.com [Department of Mining and Materials Engineering, McGill University, 3610 University Street, Montreal, Quebec, Canada H3A 0C5 (Canada); Chromik, Richard R., E-mail: richard.chromik@mcgill.ca [Department of Mining and Materials Engineering, McGill University, 3610 University Street, Montreal, Quebec, Canada H3A 0C5 (Canada); Vashegi, Babak; Knight, Andrew M. [Department of Electrical and Computer Engineering, University of Alberta, Edmonton, Alberta, Canada T6G 2V4 (Canada)
2014-09-01
Quantitative physical models for non-oriented electrical steels require precise knowledge of chemical and microstructural parameters for the material, with crystallographic texture being one of the most important. Describing the structure–property relationships in these materials is made difficult in that all of the parameters have an effect on magnetic properties. In the present study, a set of non-oriented electrical steel specimens are examined, where chemistry and grain size are kept similar from sample to sample, but texture is varied. A new texture parameter called Magnetic Texture Factor is introduced which is defined as the ratio of the volume fractions of 〈100〉 direction to 〈111〉 direction along magnetization vector. It was found that this Magnetic Texture Factor was a better parameter for identifying trends of magnetic properties with crystallographic texture than the often used Texture Factor, which is described as the ratio of the volume fractions of {100} planes to {111} planes. - Highlights: • Magnetic properties of a set of electrical steels were measured. • The effect of crystallographic texture was isolated from other material parameters. • A new texture factor is introduced called the Magnetic Texture Factor.
HRTEM study of α-AlMnSi crystals including non-crystallographic projection axes
International Nuclear Information System (INIS)
Song, G.L.; Bursill, L.A.
1997-01-01
The structure of α-AlMnSi is examined by atomic resolution high-resolution transmission electron microscopy (HRTEM) and computer-based image matching techniques. Six distinct zone axes are examined; including both normal crystallographic and non-crystallographic zones axes of the structural motifs, which have m3-bar 5 icosahedral symmetry. The results provide a sound basis for understanding HRTEM images of the quasicrystalline alloy i-AlMnSi; thus it was examined to what extent the requirements for obtaining so-called structure images of complex alloy structures may be met experimentally and define when the images may be reliably interpreted on the basis of computer simulation and image-matching at about 0.17nm resolution. Most difficulty was experienced in obtaining the experimental images, especially for the non-crystallographic zones, which are very sensitive to slight changes in orientation off the desired zone axis or projection, the rate at which the crystal thickness is increasing (wedge-angle) and the orientation of the surfaces of the specimen. Surface amorphous layers due to oxidation and/or electron-induced irradiation damage also limit the efficiency of the HRTEM analysis. For the thin specimens used for HRTEM, both the electron diffraction patterns and the HRTEM images are characteristic of Im3-bar space group symmetry. It is suggested that this Im3-bar symmetry may be an example of a statistical symmetry, where the local symmetry is close to Pm3-bar but the average symmetry is Im3-bar. The transition from Pm3-bar to Im3-bar may be understood in terms of an analysis of small changes in the outer shells of the large icosahedral structural elements which are located at the corners and body-centers of the cubic unit cell. 21 refs., 3 tabs., 10 figs
HRTEM study of {alpha}-AlMnSi crystals including non-crystallographic projection axes
Energy Technology Data Exchange (ETDEWEB)
Song, G.L.; Bursill, L.A.
1997-06-01
The structure of {alpha}-AlMnSi is examined by atomic resolution high-resolution transmission electron microscopy (HRTEM) and computer-based image matching techniques. Six distinct zone axes are examined; including both normal crystallographic and non-crystallographic zones axes of the structural motifs, which have m3-bar 5 icosahedral symmetry. The results provide a sound basis for understanding HRTEM images of the quasicrystalline alloy i-AlMnSi; thus it was examined to what extent the requirements for obtaining so-called structure images of complex alloy structures may be met experimentally and define when the images may be reliably interpreted on the basis of computer simulation and image-matching at about 0.17nm resolution. Most difficulty was experienced in obtaining the experimental images, especially for the non-crystallographic zones, which are very sensitive to slight changes in orientation off the desired zone axis or projection, the rate at which the crystal thickness is increasing (wedge-angle) and the orientation of the surfaces of the specimen. Surface amorphous layers due to oxidation and/or electron-induced irradiation damage also limit the efficiency of the HRTEM analysis. For the thin specimens used for HRTEM, both the electron diffraction patterns and the HRTEM images are characteristic of Im3-bar space group symmetry. It is suggested that this Im3-bar symmetry may be an example of a statistical symmetry, where the local symmetry is close to Pm3-bar but the average symmetry is Im3-bar. The transition from Pm3-bar to Im3-bar may be understood in terms of an analysis of small changes in the outer shells of the large icosahedral structural elements which are located at the corners and body-centers of the cubic unit cell. 21 refs., 3 tabs., 10 figs.
Some non-linear physics in crystallographic structures
International Nuclear Information System (INIS)
Aubry, S.
1977-10-01
A summary of studies on simple but strongly nonlinear crystallographic models that make use of some methods in stochasticity is presented. Two one-dimensional models are described; one has been studied to understand some aspects of the nonlinear dynamics in crystals when close to the transition temperature, the other is for commensurability and incommensurability problems. Periodic orbits and the dynamics of a one-dimensional coupled double-well chain are considered, along with lattice locking and stochasticity
Crystallographic changes in lead zirconate titanate due to neutron irradiation
Directory of Open Access Journals (Sweden)
Alexandra Henriques
2014-11-01
Full Text Available Piezoelectric and ferroelectric materials are useful as the active element in non-destructive monitoring devices for high-radiation areas. Here, crystallographic structural refinement (i.e., the Rietveld method is used to quantify the type and extent of structural changes in PbZr0.5Ti0.5O3 after exposure to a 1 MeV equivalent neutron fluence of 1.7 × 1015 neutrons/cm2. The results show a measurable decrease in the occupancy of Pb and O due to irradiation, with O vacancies in the tetragonal phase being created preferentially on one of the two O sites. The results demonstrate a method by which the effects of radiation on crystallographic structure may be investigated.
International Nuclear Information System (INIS)
Santos, Hamilta de Oliveira
1999-01-01
The aim of the present study is the microstructural and crystallographic orientation of Fe-3%Si steel. The silicon steel shows good electrical properties and it is used in the nuclear and electrical power fields. The studied steel was supplied by Cia. Acos Especiais Itabira S/A - ACESITA. The material was received in the hot compressed condition, in one or two passes. The hot compressing temperatures used were 900, 1000 and 1100 deg C with soaking times ranging from 32 to 470 s. The material preferential crystallographic orientation was evaluated in every grain of the samples. The characterization techniques used were: scanning electron microscopy (SEM) using the etch pit method; X ray diffraction using the Laue back-reflection method; orientation imaging microscopy (OIM). Microstructural characterization in terms of grain size measurement and mean number of grains in the sample were also undertaken. The Laue method was found an easy technique to access crystallographic orientation of this work polycrystalline samples 2.5 mm average grain size. This was due to the inability to focus the X-rays on a single grain of the material. The scanning electron microscopy showed microcavities left by the etch pit method, which allowed the observation of the crystallographic orientation of each grain from the samples. No conclusive grain crystallographic orientation was possible to obtain by the OIM technique due to the non-existing rolling direction. A more extensive work with the OIM technique must be undertaken on the Fe-3%Si with oriented grains and non oriented grains. (author)
Crystallographic theory of the martensitic transformation
Directory of Open Access Journals (Sweden)
Edwar A. Torres-López
2014-08-01
Full Text Available The martensitic transformation is one of the most researched topics in the materials science during the 20th century. The second half of this century was mainly remembered by the development of several theories related with the kinetics of phase transformation, the mechanisms involved in the nucleation phenomenon, and the way as the crystallographic change is produced. In this paper are described the fundamental concepts that are defined in the crystallographic framework of the martensitic transformation. The study is focused on the application of the most outstanding crystallographic models: the Bain; the Wechsler, Lieberman & Read; and the Bowles & Mackenzie. The topic is presented based upon the particular features of the martensitic transformation, such as its non-diffusional character, type of interface between parent (austenite and product (martensite phases, the formation of substructural defects, and the shape change; all of these features are mathematically described by equations aimed to predict how the transformation will take place rather than to explain the actual movement of the atoms within the structure. This mathematical development is known as the Phenomenological Theory of Martensite Crystallography (PTMC.
Non-Gaussianity in two-field inflation beyond the slow-roll approximation
Energy Technology Data Exchange (ETDEWEB)
Jung, Gabriel; Tent, Bartjan van, E-mail: gabriel.jung@th.u-psud.fr, E-mail: bartjan.van-tent@th.u-psud.fr [Laboratoire de Physique Théorique (UMR 8627), CNRS, Univ. Paris-Sud, Université Paris-Saclay, Bâtiment 210, 91405 Orsay Cedex (France)
2017-05-01
We use the long-wavelength formalism to investigate the level of bispectral non-Gaussianity produced in two-field inflation models with standard kinetic terms. Even though the Planck satellite has so far not detected any primordial non-Gaussianity, it has tightened the constraints significantly, and it is important to better understand what regions of inflation model space have been ruled out, as well as prepare for the next generation of experiments that might reach the important milestone of Δ f {sub NL}{sup local}=1. We derive an alternative formulation of the previously derived integral expression for f {sub NL}, which makes it easier to physically interpret the result and see which types of potentials can produce large non-Gaussianity. We apply this to the case of a sum potential and show that it is very difficult to satisfy simultaneously the conditions for a large f {sub NL} and the observational constraints on the spectral index n {sub s} . In the case of the sum of two monomial potentials and a constant we explicitly show in which small region of parameter space this is possible, and we show how to construct such a model. Finally, the new general expression for f {sub NL} also allows us to prove that for the sum potential the explicit expressions derived within the slow-roll approximation remain valid even when the slow-roll approximation is broken during the turn of the field trajectory (as long as only the ε slow-roll parameter remains small).
Hu, Jinyan; Li, Li; Yang, Yunfeng
2017-06-01
The hierarchical and successive approximate registration method of non-rigid medical image based on the thin-plate splines is proposed in the paper. There are two major novelties in the proposed method. First, the hierarchical registration based on Wavelet transform is used. The approximate image of Wavelet transform is selected as the registered object. Second, the successive approximation registration method is used to accomplish the non-rigid medical images registration, i.e. the local regions of the couple images are registered roughly based on the thin-plate splines, then, the current rough registration result is selected as the object to be registered in the following registration procedure. Experiments show that the proposed method is effective in the registration process of the non-rigid medical images.
The use of Fourier reverse transforms in crystallographic phase refinement
Energy Technology Data Exchange (ETDEWEB)
Ringrose, Sharon [Iowa State Univ., Ames, IA (United States)
1997-10-08
Often a crystallographer obtains an electron density map which shows only part of the structure. In such cases, the phasing of the trial model is poor enough that the electron density map may show peaks in some of the atomic positions, but other atomic positions are not visible. There may also be extraneous peaks present which are not due to atomic positions. A method for determination of crystal structures that have resisted solution through normal crystallographic methods has been developed. PHASER is a series of FORTRAN programs which aids in the structure solution of poorly phased electron density maps by refining the crystallographic phases. It facilitates the refinement of such poorly phased electron density maps for difficult structures which might otherwise not be solvable. The trial model, which serves as the starting point for the phase refinement, may be acquired by several routes such as direct methods or Patterson methods. Modifications are made to the reverse transform process based on several assumptions. First, the starting electron density map is modified based on the fact that physically the electron density map must be non-negative at all points. In practice a small positive cutoff is used. A reverse Fourier transform is computed based on the modified electron density map. Secondly, the authors assume that a better electron density map will result by using the observed magnitudes of the structure factors combined with the phases calculated in the reverse transform. After convergence has been reached, more atomic positions and less extraneous peaks are observed in the refined electron density map. The starting model need not be very large to achieve success with PHASER; successful phase refinement has been achieved with a starting model that consists of only 5% of the total scattering power of the full molecule. The second part of the thesis discusses three crystal structure determinations.
World directory of crystallographers and of other scientists employing crystallographic methods
Filippini, G; Hashizume, H; Torriani, I; Duax, W
1995-01-01
The 9th edition of the World Directory of Crystallographers and of Other Scientists Employing Crystallographic Methods, which contains 7907 entries embracing 72 countries, differs considerably from the 8th edition, published in 1990. The content has been updated, and the methods used to acquire the information presented and to produce this new edition of the Directory have involved the latest advances in technology. The Directory is now also available as a regularly updated electronic database, accessible via e-mail, Telnet, Gopher, World-Wide Web, and Mosaic. Full details are given in an Appendix to the printed edition.
Crystallographically uniform arrays of ordered (In)GaN nanocolumns
Energy Technology Data Exchange (ETDEWEB)
Gačević, Ž., E-mail: gacevic@isom.upm.es; Bengoechea-Encabo, A.; Albert, S.; Calleja, E. [ETSIT-ISOM, Universidad Politécnica de Madrid, Avda. Complutense s/n, 28040 Madrid (Spain); Torres-Pardo, A.; González-Calbet, J. M. [Dept. Química Inorgánica, Universidad Complutense, 28040 Madrid (Spain); CEI Campus Moncloa, UCM-UPM, Madrid (Spain)
2015-01-21
In this work, through a comparative study of self-assembled (SA) and selective area grown (SAG) (In)GaN nanocolumn (NC) ensembles, we first give a detailed insight into improved crystallographic uniformity (homogeneity of crystallographic tilts and twists) of the latter ones. The study, performed making use of: reflective high energy electron diffraction, X-ray diffraction and scanning electron microscopy, reveals that unlike their SA counterparts, the ensembles of SAG NCs show single epitaxial relationship to both sapphire(0001) and Si(111) underlying substrates. In the second part of the article, making use of X-ray diffraction, we directly show that the selective area growth leads to improved compositional uniformity of InGaN NC ensembles. This further leads to improved spectral purity of their luminescence, as confirmed by comparative macro-photoluminescence measurements performed on SA and SAG InGaN NC ensembles. An improved crystallographic uniformity of NC ensembles facilitates their integration into optoelectronic devices, whereas their improved compositional uniformity allows for their employment in single-color optoelectronic applications.
Crystallographic Mapping of Guided Nanowires by Second Harmonic Generation Polarimetry.
Neeman, Lior; Ben-Zvi, Regev; Rechav, Katya; Popovitz-Biro, Ronit; Oron, Dan; Joselevich, Ernesto
2017-02-08
The growth of horizontal nanowires (NWs) guided by epitaxial and graphoepitaxial relations with the substrate is becoming increasingly attractive owing to the possibility of controlling their position, direction, and crystallographic orientation. In guided NWs, as opposed to the extensively characterized vertically grown NWs, there is an increasing need for understanding the relation between structure and properties, specifically the role of the epitaxial relation with the substrate. Furthermore, the uniformity of crystallographic orientation along guided NWs and over the substrate has yet to be checked. Here we perform highly sensitive second harmonic generation (SHG) polarimetry of polar and nonpolar guided ZnO NWs grown on R-plane and M-plane sapphire. We optically map large areas on the substrate in a nondestructive way and find that the crystallographic orientations of the guided NWs are highly selective and specific for each growth direction with respect to the substrate lattice. In addition, we perform SHG polarimetry along individual NWs and find that the crystallographic orientation is preserved along the NW in both polar and nonpolar NWs. While polar NWs show highly uniform SHG along their axis, nonpolar NWs show a significant change in the local nonlinear susceptibility along a few micrometers, reflected in a reduction of 40% in the ratio of the SHG along different crystal axes. We suggest that these differences may be related to strain accumulation along the nonpolar wires. We find SHG polarimetry to be a powerful tool to study both selectivity and uniformity of crystallographic orientations of guided NWs with different epitaxial relations.
approximate controllability of a non-autonomous differential equation
Indian Academy of Sciences (India)
53
for a non-autonomous functional differential equation using the theory of linear ... approximate controllability of various functional differential equations in abstract ...... the operator A(t) and into the requirement that x(t) ∈ D(A) for all t ≥ 0.
Recovery of crystallographic texture in remineralized dental enamel.
Siddiqui, Samera; Anderson, Paul; Al-Jawad, Maisoon
2014-01-01
Dental caries is the most prevalent disease encountered by people of all ages around the world. Chemical changes occurring in the oral environment during the caries process alter the crystallography and microstructure of dental enamel resulting in loss of mechanical function. Little is known about the crystallographic effects of demineralization and remineralization. The motivation for this study was to develop understanding of the caries process at the crystallographic level in order to contribute towards a long term solution. In this study synchrotron X-ray diffraction combined with scanning electron microscopy and scanning microradiography have been used to correlate enamel crystallography, microstructure and mineral concentration respectively in enamel affected by natural caries and following artificial demineralization and remineralization regimes. In particular, the extent of destruction and re-formation of this complex structure has been measured. 2D diffraction patterns collected at the European Synchrotron Radiation Facility were used to quantify changes in the preferred orientation (crystallographic texture) and position of the (002) Bragg reflection within selected regions of interest in each tooth slice, and then correlated with the microstructure and local mineral mass. The results revealed that caries and artificial demineralization cause a large reduction in crystallographic texture which is coupled with the loss of mineral mass. Remineralization restores the texture to the original level seen in healthy enamel and restores mineral density. The results also showed that remineralization promotes ordered formation of new crystallites and growth of pre-existing crystallites which match the preferred orientation of healthy enamel. Combining microstructural and crystallographic characterization aids the understanding of caries and erosion processes and assists in the progress towards developing therapeutic treatments to allow affected enamel to regain
Recovery of crystallographic texture in remineralized dental enamel.
Directory of Open Access Journals (Sweden)
Samera Siddiqui
Full Text Available Dental caries is the most prevalent disease encountered by people of all ages around the world. Chemical changes occurring in the oral environment during the caries process alter the crystallography and microstructure of dental enamel resulting in loss of mechanical function. Little is known about the crystallographic effects of demineralization and remineralization. The motivation for this study was to develop understanding of the caries process at the crystallographic level in order to contribute towards a long term solution. In this study synchrotron X-ray diffraction combined with scanning electron microscopy and scanning microradiography have been used to correlate enamel crystallography, microstructure and mineral concentration respectively in enamel affected by natural caries and following artificial demineralization and remineralization regimes. In particular, the extent of destruction and re-formation of this complex structure has been measured. 2D diffraction patterns collected at the European Synchrotron Radiation Facility were used to quantify changes in the preferred orientation (crystallographic texture and position of the (002 Bragg reflection within selected regions of interest in each tooth slice, and then correlated with the microstructure and local mineral mass. The results revealed that caries and artificial demineralization cause a large reduction in crystallographic texture which is coupled with the loss of mineral mass. Remineralization restores the texture to the original level seen in healthy enamel and restores mineral density. The results also showed that remineralization promotes ordered formation of new crystallites and growth of pre-existing crystallites which match the preferred orientation of healthy enamel. Combining microstructural and crystallographic characterization aids the understanding of caries and erosion processes and assists in the progress towards developing therapeutic treatments to allow affected
Crystallographic features of lath martensite in low-carbon steel
International Nuclear Information System (INIS)
Kitahara, Hiromoto; Ueji, Rintaro; Tsuji, Nobuhiro; Minamino, Yoritoshi
2006-01-01
Electron backscattering diffraction with field-emission scanning electron microscopy was used to analyze crystallographically the lath martensite structure in a 0.20% carbon steel. The crystallographic features of the lath martensite structure, of the order of the prior austenite grain size or larger, were clarified. Although the orientations of the martensite crystals were scattered around the ideal variant orientations, the martensite in this steel maintained the Kurdjumov-Sachs (K-S) orientation relationship. The procedures of the crystallographic analysis of the martensite (ferrite) phase with the K-S orientation relationship were explained in detail. Variant analysis showed that all 24 possible variants did not necessarily appear within a single prior austenite grain and that all six variants did not necessarily appear within each packet. Specific combinations of two variants appeared within local regions (sub-blocks), indicating a strict rule for variant selection. Prior austenite grain boundaries and most of the packet boundaries were clearly recognized. However, it was difficult to determine the block boundaries within the sub-blocks
Dependence of Crystallographic Orientation on Pitting Corrosion Behavior of Ni-Fe-Cr Alloy 028
Zhang, LiNa; Szpunar, Jerzy A.; Dong, JianXin; Ojo, Olanrewaju A.; Wang, Xu
2018-03-01
The influence of crystallographic orientation on the pitting corrosion behavior of Ni-Fe-Cr alloy 028 was studied using a combination of X-ray diffraction (XRD), electron backscatter diffraction (EBSD), potentiodynamic polarization technique, and atomic force microscopy (AFM). The results show that there is anisotropy of pitting corrosion that strongly depends on crystallographic orientation of the surface plane. The distribution of pit density in a standard stereographic triangle indicates that the crystallographic planes close to {100} are more prone to pitting corrosion compared to planes {110} and {111}. The surface energy calculation of (001) and (111) shows that the plane with a high atomic packing density has a low surface energy with concomitant strong resistance to pitting corrosion. A correlation function between crystallographic orientation and pitting corrosion susceptibility suggests a method that not only predicts the pitting resistance of known textured materials, but also could help to improve corrosion resistance by controlling material texture.
Non-linear adjustment to purchasing power parity: an analysis using Fourier approximations
Juan-Ángel Jiménez-Martín; M. Dolores Robles Fernández
2005-01-01
This paper estimates the dynamics of adjustment to long run purchasing power parity (PPP) using data for 18 mayor bilateral US dollar exchange rates, over the post-Bretton Woods period, in a non-linear framework. We use new unit root and cointegration tests that do not assume a specific non-linear adjustment process. Using a first-order Fourier approximation, we find evidence of non-linear mean reversion in deviations from both absolute and relative PPP. This first-order Fourier approximation...
Applicability of refined Born approximation to non-linear equations
International Nuclear Information System (INIS)
Rayski, J.
1990-01-01
A computational method called ''Refined Born Approximation'', formerly applied exclusively to linear problems, is shown to be successfully applicable also to non-linear problems enabling me to compute bifurcations and other irregular solutions which cannot be obtained by the standard perturbation procedures. (author)
Correlation between Crystallographic and Magnetic Domains at Co/NiO(001) Interfaces
Energy Technology Data Exchange (ETDEWEB)
Ohldag, H.; van der Laan, G.; Arenholz, E.
2008-12-18
Using soft x-ray spectromicroscopy we show that NiO(001) exhibits a crystallographic and magnetic domain structure near the surface identical to that of the bulk. Upon Co deposition a perpendicular coupling between the Ni and Co moments is observed that persists even after formation of uncompensated Ni spins at the interface through annealing. The chemical composition at the interface alters its crystallographic structure and leads to a reorientation of the Ni moments from the <112> to the <110> direction. We show that this reorientation is driven by changes in the magnetocrystalline anisotropy rather than exchange coupling mediated by residual uncompensated spins.
Energy Technology Data Exchange (ETDEWEB)
Krinsky, Jamin L.; Arnold, John; Bergman, Robert G.
2006-10-03
Monomeric thiosalicylaldiminate complexes of rhodium(I) and iridium(I) were prepared by ligand transfer from the homoleptic zinc(II) species. In the presence of strongly donating ligands, the iridium complexes undergo insertion of the metal into the imine carbon-hydrogen bond. Thiophenoxyketimines were prepared by non-templated reaction of o-mercaptoacetophenone with anilines, and were complexed with rhodium(I), iridium(I), nickel(II) and platinum(II). X-ray crystallographic studies showed that while the thiosalicylaldiminate complexes display planar ligand conformations, those of the thiophenoxyketiminates are strongly distorted. Results of a computational study were consistent with a steric-strain interpretation of the difference in preferred ligand geometries.
Non-uniform approximations for sums of discrete m-dependent random variables
Vellaisamy, P.; Cekanavicius, V.
2013-01-01
Non-uniform estimates are obtained for Poisson, compound Poisson, translated Poisson, negative binomial and binomial approximations to sums of of m-dependent integer-valued random variables. Estimates for Wasserstein metric also follow easily from our results. The results are then exemplified by the approximation of Poisson binomial distribution, 2-runs and $m$-dependent $(k_1,k_2)$-events.
Application of a non-integer Bessel uniform approximation to inelastic molecular collisions
International Nuclear Information System (INIS)
Connor, J.N.L.; Mayne, H.R.
1979-01-01
A non-integer Bessel uniform approximation has been used to calculate transition probabilities for collinear atom-oscillator collisions. The collision systems used are a harmonic oscillator interacting via a Lennard-Jones potential and a Morse oscillator interacting via an exponential potential. Both classically allowed and classically forbidden transitions have been treated. The order of the Bessel function is chosen by a physical argument that makes use of information contained in the final-action initial-angle plot. Limitations of this procedure are discussed. It is shown that the non-integer Bessel approximation is accurate for elastic 0 → 0 collisions at high collision energies, where the integer Bessel approximation is inaccurate or inapplicable. (author)
Approximations to the non-adiabatic particle response in toroidal geometry
International Nuclear Information System (INIS)
Schep, T.J.; Braams, B.J.
1981-08-01
The non-adiabatic part of the particle response to low-frequency electromagnetic modes with long parallel wavelengths is discussed. Analytic approximations to the kernels of the integrals that relate the amplitudes of the perturbed potentials to the non-adiabatic part of the perturbed density in an axisymmetric toroidal configuration are presented and the results are compared with numerical calculations. It is shown that both in the plane slab and in toroidal geometry the kernel contains a logarithmic singularity. This singularity is associated with particles with vanishing parallel velocity so that, in toroidal geometry, it is related with the behaviour of trapped particles near their turning points. In contrast to the plane slab, in toroidal geometry this logarithmic singularity is mainly real and associated with non-resonant particles. Apart from this logarithmic term, the kernel contains a complex regular part arising from resonant as well as from non-resonant particles. The analytic approximations that will be presented make the dispersion relation of drift-type modes in toroidal geometry amenable to analytic as well as to simpler numerical calculation of the growth rate and of the spatial mode structure
Bridge density functional approximation for non-uniform hard core repulsive Yukawa fluid
International Nuclear Information System (INIS)
Zhou Shiqi
2008-01-01
In this work, a bridge density functional approximation (BDFA) (J. Chem. Phys. 112, 8079 (2000)) for a non-uniform hard-sphere fluid is extended to a non-uniform hard-core repulsive Yukawa (HCRY) fluid. It is found that the choice of a bulk bridge functional approximation is crucial for both a uniform HCRY fluid and a non-uniform HCRY fluid. A new bridge functional approximation is proposed, which can accurately predict the radial distribution function of the bulk HCRY fluid. With the new bridge functional approximation and its associated bulk second order direct correlation function as input, the BDFA can be used to well calculate the density profile of the HCRY fluid subjected to the influence of varying external fields, and the theoretical predictions are in good agreement with the corresponding simulation data. The calculated results indicate that the present BDFA captures quantitatively the phenomena such as the coexistence of solid-like high density phase and low density gas phase, and the adsorption properties of the HCRY fluid, which qualitatively differ from those of the fluids combining both hard-core repulsion and an attractive tail. (condensed matter: structure, thermal and mechanical properties)
Crystallographic Analysis of a Japanese Sword by using Bragg Edge Transmission Spectroscopy
Shiota, Yoshinori; Hasemi, Hiroyuki; Kiyanagi, Yoshiaki
Neutron imaging using a pulsed neutron source can give crystallographic information over wide area of a sample by analysing position dependent transmission spectra. With the use of a Bragg edge imaging method we non-destructively obtained crystallographic information of a Japanese sword, signed by Bishu Osafune Norimitsu, in order to know position dependent crystallographic characteristics and to check usefulness of the method for the Japanese sword investigation. Strong texture appeared on the back side. On the other hand in the middle area almost isotropic feature appeared and edge side showed feature between them. Rather isotropic area in the centre area gradually reduced from the grip side to the tip side. The crystallite size was smaller near the edge and became larger towards the back side. The smaller crystallite size will be due to quenching around the edge and this trend disappeared in the grip (nakago) area. The larger crystallite size will be due to strong hammering. Coarse grains were also observed directly as transmission images with the use of a high spatial resolution detector. The spatial distribution of the grains was not uniform but the reason have not been understood. Furthermore, a white area around a tip area was proved to be a void by looking at the Brag edge transmission spectra. This void may be formed during forging process of two kinds of steel. It is suggested that consideration on differences in the texture and the crystallite size depending on position will give information to clarify the manufacturing process, and Bragg edge analysis will be a profitable tool for research of Japanese sword.
International Nuclear Information System (INIS)
Deane, Janet E.; Cordes, Frank S.; Roversi, Pietro; Johnson, Steven; Kenjale, Roma; Picking, William D.; Picking, Wendy L.; Lea, Susan M.; Blocker, Ariel
2006-01-01
A monodisperse truncation mutant of MxiH, the subunit of the S. flexneri type III secretion system needle, has been crystallized. SeMet derivatives and a uranyl derivative have undergone preliminary crystallographic analysis. A monodisperse truncation mutant of MxiH, the subunit of the needle from the Shigella flexneri type III secretion system (TTSS), has been overexpressed and purified. Crystals were grown of native and selenomethionine-labelled MxiH CΔ5 and diffraction data were collected to 1.9 Å resolution. The crystals belong to space group C2, with unit-cell parameters a = 183.4, b = 28.1, c = 27.8 Å, β = 96.5°. An anomalous difference Patterson map calculated with the data from the SeMet-labelled crystals revealed a single peak on the Harker section v = 0. Inspection of a uranyl derivative also revealed one peak in the isomorphous difference Patterson map on the Harker section v = 0. Analysis of the self-rotation function indicates the presence of a twofold non-crystallographic symmetry axis approximately along a. The calculated Matthews coefficient is 1.9 Å 3 Da −1 for two molecules per asymmetric unit, corresponding to a solvent content of 33%
The Crystallographic Information File (CIF
Directory of Open Access Journals (Sweden)
I D Brown
2006-11-01
Full Text Available The Crystallographic Information File (CIF, owned by the International Union of Crystallography, is a file structure based on tag-value ASCII pairs with tags defined in machine-readable dictionaries. The crystallographic community publishes and archives large quantities of numeric information generated by crystal structure determinations, and CIF's acceptance was assured by its adoption as the submission format for Acta Crystallographica and by the obvious needs of the community. CIF's strength lies in its dictionaries, which define most of the concepts of crystallography; its weakness is the difficulty of writing software that exploits its full potential.
Non-Equilibrium Liouville and Wigner Equations: Moment Methods and Long-Time Approximations
Directory of Open Access Journals (Sweden)
Ramon F. Álvarez-Estrada
2014-03-01
Full Text Available We treat the non-equilibrium evolution of an open one-particle statistical system, subject to a potential and to an external “heat bath” (hb with negligible dissipation. For the classical equilibrium Boltzmann distribution, Wc,eq, a non-equilibrium three-term hierarchy for moments fulfills Hermiticity, which allows one to justify an approximate long-time thermalization. That gives partial dynamical support to Boltzmann’s Wc,eq, out of the set of classical stationary distributions, Wc;st, also investigated here, for which neither Hermiticity nor that thermalization hold, in general. For closed classical many-particle systems without hb (by using Wc,eq, the long-time approximate thermalization for three-term hierarchies is justified and yields an approximate Lyapunov function and an arrow of time. The largest part of the work treats an open quantum one-particle system through the non-equilibrium Wigner function, W. Weq for a repulsive finite square well is reported. W’s (< 0 in various cases are assumed to be quasi-definite functionals regarding their dependences on momentum (q. That yields orthogonal polynomials, HQ,n(q, for Weq (and for stationary Wst, non-equilibrium moments, Wn, of W and hierarchies. For the first excited state of the harmonic oscillator, its stationary Wst is a quasi-definite functional, and the orthogonal polynomials and three-term hierarchy are studied. In general, the non-equilibrium quantum hierarchies (associated with Weq for the Wn’s are not three-term ones. As an illustration, we outline a non-equilibrium four-term hierarchy and its solution in terms of generalized operator continued fractions. Such structures also allow one to formulate long-time approximations, but make it more difficult to justify thermalization. For large thermal and de Broglie wavelengths, the dominant Weq and a non-equilibrium equation for W are reported: the non-equilibrium hierarchy could plausibly be a three-term one and possibly not
Directory of Open Access Journals (Sweden)
Rossiza I. Kabakchieva
2014-10-01
Full Text Available Aim: To apply and follow up in clinical conditions the success rate of microinvasive technique of infiltration with low viscosity resin ICON® (DMG of non cavitated approximal caries lesions of permanent children's teeth for a period of one year. Material and methods: The study included 18 children aged 7-16 years. They were divided into two groups - children with medium and high caries risk. The survey include 20 teeth with approximal non-cavitated enamel lesions up to the outer third of dentin (E1, E2, D1 – according to the manufacturer’s instructions of ICON®. The size of the lesions was determined using bitewing radiographs and the activity - by Papilla Bleeding Index. The clinical application of the infiltr+ant (ICON® Caries Infiltrant Proximal, DMG was conducted according to the manufacturer's instructions. Bitewing radiographs were made at 6 and 12 months after infiltration in order to evaluate the success of the method. A test of the difference between two relative proportions and alternative test for analysis of the results were used. Results: Our study confirm the hypothesis that this method of infiltration is equally successful for permanent teeth in patients with moderate caries risk as well as those at high caries risk. Conclusion: This study is the first survey regarding the success of the application of ICON® for treatment of non-cavitated approximal carious lesions in permanent dentition of children in the country. Research in this direction should continue in order to increase the conviction that caries can be controlled and arrested in its earliest stages.
Polynomial approximation of non-Gaussian unitaries by counting one photon at a time
Arzani, Francesco; Treps, Nicolas; Ferrini, Giulia
2017-05-01
In quantum computation with continuous-variable systems, quantum advantage can only be achieved if some non-Gaussian resource is available. Yet, non-Gaussian unitary evolutions and measurements suited for computation are challenging to realize in the laboratory. We propose and analyze two methods to apply a polynomial approximation of any unitary operator diagonal in the amplitude quadrature representation, including non-Gaussian operators, to an unknown input state. Our protocols use as a primary non-Gaussian resource a single-photon counter. We use the fidelity of the transformation with the target one on Fock and coherent states to assess the quality of the approximate gate.
Navruz, N.
2008-06-01
The various requirements for effective transformation toughening cannot be predicted without a detailed understanding of the crystallography of the martensitic transformation. In this connection, a comparative crystallographic analysis for four pairs of lattice-correspondence variants in the yttria-zirconia system has been performed on the basis of infinitesimal-deformation (ID) approach and Wechsler-Lieberman-Read (WLR) crystallographic theory. A comparison of the crystallographic features obtained from these two theories was made. In order to verify the applicability of the two theories to this transformation, the calculated results were also compared with the experimental data available. The present study shows that the predictions of both the ID approach and the WLR crystallographic theory can provide data necessary for the model of transformation toughening and act as a guideline for the experimental work in the yttria-zirconia system.
Crystallographic data processing for free-electron laser sources
International Nuclear Information System (INIS)
White, Thomas A.; Barty, Anton; Stellato, Francesco; Holton, James M.; Kirian, Richard A.; Zatsepin, Nadia A.; Chapman, Henry N.
2013-01-01
A processing pipeline for diffraction data acquired using the ‘serial crystallography’ methodology with a free-electron laser source is described with reference to the crystallographic analysis suite CrystFEL and the pre-processing program Cheetah. A processing pipeline for diffraction data acquired using the ‘serial crystallography’ methodology with a free-electron laser source is described with reference to the crystallographic analysis suite CrystFEL and the pre-processing program Cheetah. A detailed analysis of the nature and impact of indexing ambiguities is presented. Simulations of the Monte Carlo integration scheme, which accounts for the partially recorded nature of the diffraction intensities, are presented and show that the integration of partial reflections could be made to converge more quickly if the bandwidth of the X-rays were to be increased by a small amount or if a slight convergence angle were introduced into the incident beam
Crystallographic data processing for free-electron laser sources
Energy Technology Data Exchange (ETDEWEB)
White, Thomas A., E-mail: taw@physics.org; Barty, Anton; Stellato, Francesco [DESY, Notkestrasse 85, 22607 Hamburg (Germany); Holton, James M. [University of California, San Francisco, CA 94158 (United States); Lawrence Berkeley National Laboratory, Berkeley, CA 94720 (United States); Kirian, Richard A. [DESY, Notkestrasse 85, 22607 Hamburg (Germany); Arizona State University, Tempe, AZ 85287 (United States); Zatsepin, Nadia A. [Arizona State University, Tempe, AZ 85287 (United States); Chapman, Henry N. [DESY, Notkestrasse 85, 22607 Hamburg (Germany); University of Hamburg, Luruper Chaussee 149, 22761 Hamburg (Germany)
2013-07-01
A processing pipeline for diffraction data acquired using the ‘serial crystallography’ methodology with a free-electron laser source is described with reference to the crystallographic analysis suite CrystFEL and the pre-processing program Cheetah. A processing pipeline for diffraction data acquired using the ‘serial crystallography’ methodology with a free-electron laser source is described with reference to the crystallographic analysis suite CrystFEL and the pre-processing program Cheetah. A detailed analysis of the nature and impact of indexing ambiguities is presented. Simulations of the Monte Carlo integration scheme, which accounts for the partially recorded nature of the diffraction intensities, are presented and show that the integration of partial reflections could be made to converge more quickly if the bandwidth of the X-rays were to be increased by a small amount or if a slight convergence angle were introduced into the incident beam.
Crystallographic properties of fertilizer compounds
Energy Technology Data Exchange (ETDEWEB)
Frazier, A.W.; Dillard, E.F.; Thrasher, R.D.; Waerstad, K.R.; Hunter, S.R.; Kohler, J.J.; Scheib, R.M.
1991-02-01
This bulletin is a compilation of crystallographic data collected at NFERC on 450 fertilizer-related compounds. In TVA's fertilizer R and D program, petrographic examination, XRD, and infrared spectroscopy are combined with conventional chemical analysis methods in identifying the individual compounds that occur in fertilizer materials. This handbook brings together the results of these characterization studies and supplemental crystallographic data from the literature. It is in one-compound-per-page, loose-leaf format, ordered alphabetically by IUPAC name. Indexes provided include IUPAC name, formula, group, alternate formula, synonyms, x-ray data, optical data. Tables are given for solids, compounds in commercial MAP and DAP, and matrix materials in phosphate rock.
Energy Technology Data Exchange (ETDEWEB)
Deane, Janet E.; Cordes, Frank S.; Roversi, Pietro [Laboratory of Molecular Biophysics, Department of Biochemistry, University of Oxford (United Kingdom); Johnson, Steven [Laboratory of Molecular Biophysics, Department of Biochemistry, University of Oxford (United Kingdom); Sir William Dunn School of Pathology, University of Oxford (United Kingdom); Kenjale, Roma; Picking, William D.; Picking, Wendy L. [Department of Molecular Biosciences, University of Kansas (United States); Lea, Susan M., E-mail: susan.lea@biop.ox.ac.uk [Laboratory of Molecular Biophysics, Department of Biochemistry, University of Oxford (United Kingdom); Sir William Dunn School of Pathology, University of Oxford (United Kingdom); Blocker, Ariel [Sir William Dunn School of Pathology, University of Oxford (United Kingdom); Laboratory of Molecular Biophysics, Department of Biochemistry, University of Oxford (United Kingdom)
2006-03-01
A monodisperse truncation mutant of MxiH, the subunit of the S. flexneri type III secretion system needle, has been crystallized. SeMet derivatives and a uranyl derivative have undergone preliminary crystallographic analysis. A monodisperse truncation mutant of MxiH, the subunit of the needle from the Shigella flexneri type III secretion system (TTSS), has been overexpressed and purified. Crystals were grown of native and selenomethionine-labelled MxiH{sub CΔ5} and diffraction data were collected to 1.9 Å resolution. The crystals belong to space group C2, with unit-cell parameters a = 183.4, b = 28.1, c = 27.8 Å, β = 96.5°. An anomalous difference Patterson map calculated with the data from the SeMet-labelled crystals revealed a single peak on the Harker section v = 0. Inspection of a uranyl derivative also revealed one peak in the isomorphous difference Patterson map on the Harker section v = 0. Analysis of the self-rotation function indicates the presence of a twofold non-crystallographic symmetry axis approximately along a. The calculated Matthews coefficient is 1.9 Å{sup 3} Da{sup −1} for two molecules per asymmetric unit, corresponding to a solvent content of 33%.
Hydrogen-induced crack interaction and coalescence: the role of local crystallographic texture
Energy Technology Data Exchange (ETDEWEB)
Caleyo, F.; Hallen, J. M.; Venegas, V. [ESIQIE, Instituto Politecnico Nacional, Mexico, (Mexico); Baudin, T. [Universite de Paris Sud, Orsay, (France)
2010-07-01
Hydrogen induced cracking (HIC) is a big concern in pipeline industry specialized in sour service. The strategies to improve HIC resistance of pipeline steel have not been completely efficient. This study investigated the role of grain orientation in the interaction and coalescence of non-coplanar HIC cracks through experimental analysis. HIC samples of pipeline steels (API 5L X46 and ASME-A106) were studied using automated electron backscatter diffraction (EBSD) and orientation imaging microscopy (OIM). The results showed that the microtexture can play a significant role in the coalescence of closely spaced non-coplanar HIC cracks. It was also found that the presence of cleavage planes and slip systems correctly oriented to the mixed-mode stresses can activate low-resistance transgranular paths along in which cracks can merge. It is demonstrated that crystallographic texture must be considered in developing predictive models for the study of the stepwise propagation of HIC cracking in pipeline steels.
Watanabe, Yukio
2018-05-01
In the calculations of tetragonal BaTiO3, some exchange-correlation (XC) energy functionals such as local density approximation (LDA) have shown good agreement with experiments at room temperature (RT), e.g., spontaneous polarization (PS), and superiority compared with other XC functionals. This is due to the error compensation of the RT effect and, hence, will be ineffective in the heavily strained case such as domain boundaries. Here, ferroelectrics under large strain at RT are approximated as those at 0 K because the strain effect surpasses the RT effects. To find effective XC energy functionals for strained BaTiO3, we propose a new comparison, i.e., a criterion. This criterion is the properties at 0 K given by the Ginzburg-Landau (GL) theory because GL theory is a thermodynamic description of experiments working under the same symmetry-constraints as ab initio calculations. With this criterion, we examine LDA, generalized gradient approximations (GGA), meta-GGA, meta-GGA + local correlation potential (U), and hybrid functionals, which reveals the high accuracy of some XC functionals superior to XC functionals that have been regarded as accurate. This result is examined directly by the calculations of homogenously strained tetragonal BaTiO3, confirming the validity of the new criterion. In addition, the data points of theoretical PS vs. certain crystallographic parameters calculated with different XC functionals are found to lie on a single curve, despite their wide variations. Regarding these theoretical data points as corresponding to the experimental results, analytical expressions of the local PS using crystallographic parameters are uncovered. These expressions show the primary origin of BaTiO3 ferroelectricity as oxygen displacements. Elastic compliance and electrostrictive coefficients are estimated. For the comparison of strained results, we show that the effective critical temperature TC under strain 1000 K from an approximate method combining ab initio
Global crystallographic textures obtained by neutron and synchrotron radiation
International Nuclear Information System (INIS)
Brokmeier, Heinz-Guenter
2006-01-01
Global crystallographic textures belong to the main characteristic parameters of engineering materials. The global crystallographic texture is always the average texture of a well-defined sample volume which is representative to solve practical engineering problems. Thus a beam having a high penetration power is needed available as neutron or high energetic X-ray radiation. Texture type and texture sharpness are of great importance for materials properties such as the deep drawing behaviour, one of the basic techniques in many industries. Advantages and disadvantages of both radiations make them complementary for measuring crystallographic textures in a wide range of materials
Transuranic Hybrid Materials: Crystallographic and Computational Metrics of Supramolecular Assembly
Energy Technology Data Exchange (ETDEWEB)
Surbella, Robert G. [Department; Ducati, Lucas C. [Department; Pellegrini, Kristi L. [Pacific Northwest National Laboratory, 902 Battelle Boulevard, Richland, Washington 99354, United States; McNamara, Bruce K. [Pacific Northwest National Laboratory, 902 Battelle Boulevard, Richland, Washington 99354, United States; Autschbach, Jochen [Department; Schwantes, Jon M. [Pacific Northwest National Laboratory, 902 Battelle Boulevard, Richland, Washington 99354, United States; Cahill, Christopher L. [Department
2017-07-26
A family of twelve supramolecular [AnO2Cl4]2- (An = U, Np, Pu) containing compounds assembled via hydrogen and halogen bonds donated by substituted 4-X-pyridinium cations (X = H, Cl, Br, I) is reported. These materials were prepared from a room-temperature synthesis wherein crystallization of unhydrolyzed and valence pure [An(VI)O2Cl4]2- (An = U, Np, Pu) tectons are the norm. We present a hierarchy of assembly criteria based on crystallographic observations, and subsequently quantify the strengths of the non-covalent interactions using Kohn-Sham density functional calculations. We provide, for the first time, a detailed description of the electrostatic potentials (ESPs) of the actinyl tetrahalide dianions and reconcile crystallographically observed structural motifs and non-covalent interaction (NCI) acceptor-donor pairings. Our findings indicate that the average electrostatic potential across the halogen ligands (the acceptors) changes by only ~2 kJ mol-1 across the AnO22+ series, indicating the magnitude of the potential is independent of the metal center. The role of the cation is therefore critical in directing structural motifs and dictating the resulting hydrogen and halogen bond strengths, the former being stronger due to the positive charge centralized on the pyridyl nitrogen N-H+. Subsequent analyses using the Quantum theory of atoms in molecules (QTAIM) and natural bond orbital (NBO) approaches support this conclusion and highlight the structure directing role of the cations. Whereas one can infer that the 2 Columbic attraction is the driver for assembly, the contribution of the non-covalent interaction is to direct the molecular-level arrangement (or disposition) of the tectons.
A Journey into Reciprocal Space; A crystallographer's perspective
Glazer, A. M.
2017-10-01
This book introduces undergraduate and graduate students to a crystallographer's view of real and reciprocal space, a concept that has been of particular use by crystallographers to understand the patterns of spots when x-rays are diffracted by crystals. It then proceeds to develop the concept in a form suitable for physics applications; such as how solid-state physicists use reciprocal space to explain various solid-state properties such as thermal and electrical phenomena.
A rational approximation to Reich-Moore collision matrix of non-fissile nuclides
International Nuclear Information System (INIS)
Devan, K.; Keshavamurthy, R.S.
1999-01-01
The cross sections of many important nuclides are represented in Reich-Moore (RM) formalism in the recent American Evaluated Nuclear Data file, ENDF/B-VI. Processing of cross sections with RM resonance parameters is much more difficult than the other multilevel formalisms such as MLBW and Adler-Adler. In this paper, we derive a rational approximation to the RM collision matrix in the vicinity of a resonance. This simplifies the cross section processing. The energy range of the validity of this approximation in the vicinity of a resonance is also derived. Choosing Ni 58 as an example, results of our approximation for a non-fissile nuclide are given for two typical s-wave resonances. Our rational approximation method is found to work with good accuracies in the vicinity of resonances
A preliminary neutron crystallographic study of thaumatin
Energy Technology Data Exchange (ETDEWEB)
Teixeira, Susana C. M. [ILL-EMBL Deuteration Laboratory, Partnership for Structural Biology, 6 Rue Jules Horowitz, 38042 Grenoble (France); Institut Laue Langevin, 6 Rue Jules Horowitz, 38042 Grenoble (France); EPSAM and ISTM, Keele University, Staffordshire ST5 5BG (United Kingdom); Blakeley, Matthew P. [Institut Laue Langevin, 6 Rue Jules Horowitz, 38042 Grenoble (France); Leal, Ricardo M. F. [ILL-EMBL Deuteration Laboratory, Partnership for Structural Biology, 6 Rue Jules Horowitz, 38042 Grenoble (France); Institut Laue Langevin, 6 Rue Jules Horowitz, 38042 Grenoble (France); EPSAM and ISTM, Keele University, Staffordshire ST5 5BG (United Kingdom); ESRF, 6 Rue Jules Horowitz, BP-220, 38043 Grenoble (France); Mitchell, Edward P. [EPSAM and ISTM, Keele University, Staffordshire ST5 5BG (United Kingdom); ESRF, 6 Rue Jules Horowitz, BP-220, 38043 Grenoble (France); Forsyth, V. Trevor, E-mail: tforsyth@ill.fr [ILL-EMBL Deuteration Laboratory, Partnership for Structural Biology, 6 Rue Jules Horowitz, 38042 Grenoble (France); Institut Laue Langevin, 6 Rue Jules Horowitz, 38042 Grenoble (France); EPSAM and ISTM, Keele University, Staffordshire ST5 5BG (United Kingdom)
2008-05-01
Preliminary neutron crystallographic data from the sweet protein thaumatin have been recorded using the LADI-III diffractometer at the Institut Laue Langevin (ILL). The results illustrate the feasibility of a full neutron structural analysis aimed at further understanding the molecular basis of the perception of sweet taste. Such an analysis will exploit the use of perdeuterated thaumatin. A preliminary neutron crystallographic study of the sweet protein thaumatin is presented. Large hydrogenated crystals were prepared in deuterated crystallization buffer using the gel-acupuncture method. Data were collected to a resolution of 2 Å on the LADI-III diffractometer at the Institut Laue Langevin (ILL). The results demonstrate the feasibility of a full neutron crystallographic analysis of this structure aimed at providing relevant information on the location of H atoms, the distribution of charge on the protein surface and localized water in the structure. This information will be of interest for understanding the specificity of thaumatin–receptor interactions and will contribute to further understanding of the molecular mechanisms underlying the perception of taste.
[Crystallographic evaluation of structural changes in water].
Farashchuk, N F; Rakhmanin, Yu A; Savostikova, O N; Telenkova, O G
2014-01-01
The study of the structural state of tap water that has been stored for two days in the packaging materials of various type and in different conditions, was performed with the use of crystallographic method for the investigation of liquids based on a special approach for dehydration of the drop, which is a fixed thin "slice" of the examines liquid. Most organized crystallographic pattern was shown to observe in a drop of water after treatment Bioptron lamp (content of liquid-crystal associates (LCA)--6.90 ± 0.23), and stored in a silver vessel (content LCA--6.28 ± 0.17), and the least organized, almost amorphous precipitate is formed in a drop of water stored in plastic containers (content LCA--2.92 ± 0.15%). Basing on the obtained results, it can be concluded that the crystallographic method can be used for the identification of qualitative changes occurring in liquid water under the influence of various physical factors, for the identification of the rationality of the use of hereafter sophisticated quantitative techniques.
Crystallographic Topology 2: Overview and Work in Progress
Energy Technology Data Exchange (ETDEWEB)
Johnson, C.K.
1999-08-01
This overview describes an application of contemporary geometric topology and stochastic process concepts to structural crystallography. In this application, crystallographic groups become orbifolds, crystal structures become Morse functions on orbifolds, and vibrating atoms in a crystal become vector valued Gaussian measures with the Radon-Nikodym property. Intended crystallographic benefits include new methods for visualization of space groups and crystal structures, analysis of the thermal motion patterns seen in ORTEP drawings, and a classification scheme for crystal structures based on their Heegaard splitting properties.
Analysis of the dynamical cluster approximation for the Hubbard model
Aryanpour, K.; Hettler, M. H.; Jarrell, M.
2002-01-01
We examine a central approximation of the recently introduced Dynamical Cluster Approximation (DCA) by example of the Hubbard model. By both analytical and numerical means we study non-compact and compact contributions to the thermodynamic potential. We show that approximating non-compact diagrams by their cluster analogs results in a larger systematic error as compared to the compact diagrams. Consequently, only the compact contributions should be taken from the cluster, whereas non-compact ...
Automatic rebuilding and optimization of crystallographic structures in the Protein Data Bank.
Joosten, Robbie P; Joosten, Krista; Cohen, Serge X; Vriend, Gert; Perrakis, Anastassis
2011-12-15
Macromolecular crystal structures in the Protein Data Bank (PDB) are a key source of structural insight into biological processes. These structures, some >30 years old, were constructed with methods of their era. With PDB_REDO, we aim to automatically optimize these structures to better fit their corresponding experimental data, passing the benefits of new methods in crystallography on to a wide base of non-crystallographer structure users. We developed new algorithms to allow automatic rebuilding and remodeling of main chain peptide bonds and side chains in crystallographic electron density maps, and incorporated these and further enhancements in the PDB_REDO procedure. Applying the updated PDB_REDO to the oldest, but also to some of the newest models in the PDB, corrects existing modeling errors and brings these models to a higher quality, as judged by standard validation methods. The PDB_REDO database and links to all software are available at http://www.cmbi.ru.nl/pdb_redo. r.joosten@nki.nl; a.perrakis@nki.nl Supplementary data are available at Bioinformatics online.
Toufik, Mekkaoui; Atangana, Abdon
2017-10-01
Recently a new concept of fractional differentiation with non-local and non-singular kernel was introduced in order to extend the limitations of the conventional Riemann-Liouville and Caputo fractional derivatives. A new numerical scheme has been developed, in this paper, for the newly established fractional differentiation. We present in general the error analysis. The new numerical scheme was applied to solve linear and non-linear fractional differential equations. We do not need a predictor-corrector to have an efficient algorithm, in this method. The comparison of approximate and exact solutions leaves no doubt believing that, the new numerical scheme is very efficient and converges toward exact solution very rapidly.
International Nuclear Information System (INIS)
Ngoc Tam, Nguyen; Nakamura, Yasunori; Terao, Toshihiro; Kuramae, Hiroyuki; Nakamachi, Eiji; Sakamoto, Hidetoshi; Morimoto, Hideo
2007-01-01
Recently, the asymmetric rolling (ASR) has been applied to the material processing of aluminum alloy sheet to control micro-crystal structure and texture in order to improve the mechanical properties. Previously, several studies aimed at high formability sheet generation have been carried out experimentally, but finite element simulations to predict the deformation induced texture evolution of the asymmetrically rolled sheet metals have not been investigated rigorously. In this study, crystallographic homogenized finite element (FE) codes are developed and applied to analyze the asymmetrical rolling processes. The textures of sheet metals were measured by electron back scattering diffraction (EBSD), and compared with FE simulations. The results from the dynamic explicit type Crystallographic homogenization FEM code shows that this type of simulation is a comprehensive tool to predict the plastic induced texture evolution
An approximate method to calculate ionization of LTE and non-LTE plasma
International Nuclear Information System (INIS)
Zhang Jun; Gu Peijun
1987-01-01
When matter, especially high Z element, is heated to high temperature, it will be ionized many times. The degree of ionization has a strong effect on many plasma properties. So an approximate method to calculate the mean ionization degree is needed for solving many practical problems. An analytical expression which is convenient for the approximate numerical calculation is given by fitting it to the scaling law and numerical results of the ionization potential of Thomas-Fermi statistical model. In LTE case, the ionization degree of Au calculated by using the approximate method is in agreement with that of the average ion model. By extending the approximate method to non-LTE case, the ionization degree of Au is similarly calculated according to Corona model and Collision-Radiatoin model(C-R). The results of Corona model agree with the published data quite well, while the results of C-R approach those of Corona model as the density is reduced and approach those of LTE as the density is increased. Finally, all approximately calculated results of ionization degree of Au and the comparision of them are given in figures and tables
HQET at order 1/m. Pt. 1. Non-perturbative parameters in the quenched approximation
International Nuclear Information System (INIS)
Blossier, Benoit; Della Morte, Michele; Garron, Nicolas; Edinburgh Univ.; Sommer, Rainer
2010-01-01
We determine non-perturbatively the parameters of the lattice HQET Lagrangian and those of heavy-light axial-vector and vector currents in the quenched approximation. The HQET expansion includes terms of order 1/m b . Our results allow to compute, for example, the heavy-light spectrum and B-meson decay constants in the static approximation and to order 1/m b in HQET. The determination of the parameters is separated into universal and non-universal parts. The universal results can be used to determine the parameters for various discretizations. The computation reported in this paper uses the plaquette gauge action and the ''HYP1/2'' action for the b-quark described by HQET. The parameters of the currents also depend on the light-quark action, for which we choose non-perturbatively O(a)-improved Wilson fermions. (orig.)
HQET at order 1/m. Pt. 1. Non-perturbative parameters in the quenched approximation
Energy Technology Data Exchange (ETDEWEB)
Blossier, Benoit [Paris XI Univ., 91 - Orsay (France). Lab. de Physique Theorique; Della Morte, Michele [Mainz Univ. (Germany). Inst. fuer Kernphysik; Garron, Nicolas [Universidad Autonoma de Madrid (Spain). Dept. Fisica Teorica y Inst. de Fisica Teorica UAM/CSIC; Edinburgh Univ. (United Kingdom). School of Physics and Astronomy - SUPA; Sommer, Rainer [Deutsches Elektronen-Synchrotron (DESY), Zeuthen (Germany). John von Neumann-Inst. fuer Computing NIC
2010-01-15
We determine non-perturbatively the parameters of the lattice HQET Lagrangian and those of heavy-light axial-vector and vector currents in the quenched approximation. The HQET expansion includes terms of order 1/m{sub b}. Our results allow to compute, for example, the heavy-light spectrum and B-meson decay constants in the static approximation and to order 1/m{sub b} in HQET. The determination of the parameters is separated into universal and non-universal parts. The universal results can be used to determine the parameters for various discretizations. The computation reported in this paper uses the plaquette gauge action and the ''HYP1/2'' action for the b-quark described by HQET. The parameters of the currents also depend on the light-quark action, for which we choose non-perturbatively O(a)-improved Wilson fermions. (orig.)
International Nuclear Information System (INIS)
Tarvainen, Tanja; Vauhkonen, Marko; Kolehmainen, Ville; Arridge, Simon R; Kaipio, Jari P
2005-01-01
In this paper, a coupled radiative transfer equation and diffusion approximation model is extended for light propagation in turbid medium with low-scattering and non-scattering regions. The light propagation is modelled with the radiative transfer equation in sub-domains in which the assumptions of the diffusion approximation are not valid. The diffusion approximation is used elsewhere in the domain. The two equations are coupled through their boundary conditions and they are solved simultaneously using the finite element method. The streamline diffusion modification is used to avoid the ray-effect problem in the finite element solution of the radiative transfer equation. The proposed method is tested with simulations. The results of the coupled model are compared with the finite element solutions of the radiative transfer equation and the diffusion approximation and with results of Monte Carlo simulation. The results show that the coupled model can be used to describe photon migration in turbid medium with low-scattering and non-scattering regions more accurately than the conventional diffusion model
Silva, J. M.; Baêta Júnior, E. S.; Moraes, N. R. D. C.; Botelho, R. A.; Felix, R. A. C.; Brandao, L.
2017-01-01
The purpose of this work was to study the influence of different kinds of rolling on the magnetic properties of NOG steel, an electric steel widely used in electrical motors. These properties are highly correlated with the crystallographic texture of the material, which can be changed by rolling. Three kinds of rolling were examined: conventional rolling, cross-rolling and asymmetrical rolling. The crystallographic texture was determined by X-ray diffraction and the magnetic properties were calculated from a theoretical model that related the magnetic induction to crystallographic texture through the anisotropy energy. The results show that cross-rolling yields higher values of magnetic induction than the other processes.
Approximate Stream Function wavemaker theory for highly non-linear waves in wave flumes
DEFF Research Database (Denmark)
Zhang, H.W.; Schäffer, Hemming Andreas
2007-01-01
An approximate Stream Function wavemaker theory for highly non-linear regular waves in flumes is presented. This theory is based on an ad hoe unified wave-generation method that combines linear fully dispersive wavemaker theory and wave generation for non-linear shallow water waves. This is done...... by applying a dispersion correction to the paddle position obtained for non-linear long waves. The method is validated by a number of wave flume experiments while comparing with results of linear wavemaker theory, second-order wavemaker theory and Cnoidal wavemaker theory within its range of application....
Crystallographic deterioration of MOVPE InN during the growth
International Nuclear Information System (INIS)
Sugita, K.; Nagai, Y.; Houchin, Y.; Hashimoto, A.; Yamamoto, A.
2007-01-01
This paper reports the crystallographic degradation of MOVPE InN during the growth. Using FWHMs of X-ray rocking curve, tilt ((0002)) and twist ((10-10)) angle distributions are evaluated and effects of the major growth parameters, such as growth temperature, growth time and with/without GaN buffer in the degradation, are revealed. With increasing either thickness of grown InN or growth temperature up to 600 C, the tilt angle distribution is markedly increased, indicating the crystallographic degradation of grown films. The use of a GaN buffer reduces such degradation. Since the twist angle distribution is scarcely changed by such growth parameters, the destruction of InN crystals during growth and annealing is concluded to be anisotropic. The trends of the crystallographic degradation revealed here are in good agreement with those for the electrical and optical degradation previously reported. (copyright 2007 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (orig.)
DEFF Research Database (Denmark)
Köylüoglu, H. U.; Nielsen, Søren R. K.; Cakmak, A. S.
Geometrically non-linear multi-degree-of-freedom (MDOF) systems subject to random excitation are considered. New semi-analytical approximate forward difference equations for the lower order non-stationary statistical moments of the response are derived from the stochastic differential equations...... of motion, and, the accuracy of these equations is numerically investigated. For stationary excitations, the proposed method computes the stationary statistical moments of the response from the solution of non-linear algebraic equations....
Markov Jump Processes Approximating a Non-Symmetric Generalized Diffusion
International Nuclear Information System (INIS)
Limić, Nedžad
2011-01-01
Consider a non-symmetric generalized diffusion X(⋅) in ℝ d determined by the differential operator A(x) = -Σ ij ∂ i a ij (x)∂ j + Σ i b i (x)∂ i . In this paper the diffusion process is approximated by Markov jump processes X n (⋅), in homogeneous and isotropic grids G n ⊂ℝ d , which converge in distribution in the Skorokhod space D([0,∞),ℝ d ) to the diffusion X(⋅). The generators of X n (⋅) are constructed explicitly. Due to the homogeneity and isotropy of grids, the proposed method for d≥3 can be applied to processes for which the diffusion tensor {a ij (x)} 11 dd fulfills an additional condition. The proposed construction offers a simple method for simulation of sample paths of non-symmetric generalized diffusion. Simulations are carried out in terms of jump processes X n (⋅). For piece-wise constant functions a ij on ℝ d and piece-wise continuous functions a ij on ℝ 2 the construction and principal algorithm are described enabling an easy implementation into a computer code.
Crystallographic cut that maximizes of the birefringence in photorefractive crystals
Rueda-Parada, Jorge Enrique
2017-01-01
The electro-optical birefringence effect depends on the crystal type, cut crystal, applied electric field and the incidence direction of light on the principal crystal faces. It is presented a study of maximizing the birefringence in photorefractive crystals of cubic crystallographic symmetry, in terms of these three parameters. General analytical expressions for the birefringence were obtained, from which birefringence can be established for any type of cut. A new crystallographic cut was en...
The crystallographic growth directions of Sn whiskers
International Nuclear Information System (INIS)
Stein, J.; Welzel, U.; Leineweber, A.; Huegel, W.; Mittemeijer, E.J.
2015-01-01
The growth directions of 55 Sn whiskers, i.e. the crystallographic orientation parallel to the whisker-growth axes, were determined using (i) a focused ion beam microscope for the determination of the physical growth angles of the whiskers with respect to a specimen (reference) coordinate system and (ii) an electron backscatter detector in a scanning electron microscope for the determination of the crystallographic orientation of the whiskers. The Sn whiskers were found to grow preferentially along low-index directions of the β-Sn crystal structure. The experimental findings of this study (and most of the results presented in the literature as well) were explained by applying, in a modified way, the Hartman–Perdok concept of periodic bond chains, i.e. chains of strong bonds running uninterruptedly through the structure, to the Sn whisker-growth phenomenon
Multi-variate joint PDF for non-Gaussianities: exact formulation and generic approximations
Verde, Licia; Heavens, Alan F; Jimenez, Raul; Matarrese, Sabino
2013-01-01
We provide an exact expression for the multi-variate joint probability distribution function of non-Gaussian fields primordially arising from local transformations of a Gaussian field. This kind of non-Gaussianity is generated in many models of inflation. We apply our expression to the non- Gaussianity estimation from Cosmic Microwave Background maps and the halo mass function where we obtain analytical expressions. We also provide analytic approximations and their range of validity. For the Cosmic Microwave Background we give a fast way to compute the PDF which is valid up to 7{\\sigma} for fNL values (both true and sampled) not ruled out by current observations, which consists of expressing the PDF as a combination of bispectrum and trispectrum of the temperature maps. The resulting expression is valid for any kind of non-Gaussianity and is not limited to the local type. The above results may serve as the basis for a fully Bayesian analysis of the non-Gaussianity parameter.
On approximation of non-Newtonian fluid flow by the finite element method
Svácek, Petr
2008-08-01
In this paper the problem of numerical approximation of non-Newtonian fluid flow with free surface is considered. Namely, the flow of fresh concrete is addressed. Industrial mixtures often behaves like non-Newtonian fluids exhibiting a yield stress that needs to be overcome for the flow to take place, cf. [R.B. Bird, R.C. Armstrong, O. Hassager, Dynamics of Polymeric Liquids, vol. 1, Fluid Mechanics, Wiley, New York, 1987; R.P. Chhabra, J.F. Richardson, Non-Newtonian Flow in the Process Industries, Butterworth-Heinemann, London, 1999]. The main interest is paid to the mathematical formulation of the problem and to discretization with the aid of finite element method. The described numerical procedure is applied onto the solution of several problems.
Approximate L0 constrained Non-negative Matrix and Tensor Factorization
DEFF Research Database (Denmark)
Mørup, Morten; Madsen, Kristoffer Hougaard; Hansen, Lars Kai
2008-01-01
Non-negative matrix factorization (NMF), i.e. V = WH where both V, W and H are non-negative has become a widely used blind source separation technique due to its part based representation. The NMF decomposition is not in general unique and a part based representation not guaranteed. However...... constraint. In general, solving for a given L0 norm is an NP hard problem thus convex relaxatin to regularization by the L1 norm is often considered, i.e., minimizing ( 1/2 ||V-WHk||^2+lambda|H|_1). An open problem is to control the degree of sparsity imposed. We here demonstrate that a full regularization......, the L1 regularization strength lambda that best approximates a given L0 can be directly accessed and in effect used to control the sparsity of H. The MATLAB code for the NLARS algorithm is available for download....
International Nuclear Information System (INIS)
Coppola, R.; Rodriguez-Carvajal, J.; Wang, M.; Zhang, G.; Zhou, Z.
2014-01-01
High resolution neutron diffraction measurements have been carried out to characterize the crystallographic phases present in different Oxide Dispersion Strengthened (ODS) steels of interest for fusion technology. The different lattice structures, Im3m for the ferritic ODS and Fm3m for the austenitic ODS, are resolved showing line anisotropy effects possibly correlated with differences in dislocation densities and texture. Many contributions from minority phases are detected well above the background noise; none of the expected crystallographic phases, such as M 23 C 6 and including Y 2 O 3 , fits them, but the TiN phase is identified in accordance with results of other microstructural techniques
Energy Technology Data Exchange (ETDEWEB)
Caleyo, F; Hallen, J M; Herrera, O; Venegas, V [ESIQIE, Instituto Politecnico Nacional, Mexico, (Mexico); Baudin, T [Universite de Paris Sud, Orsay, (France)
2010-07-01
The resistance to HIC of sour service pipeline steels has been improved through several strategies but none have proven to be totally efficient in the preservation of HIC in difficult operating conditions. The crystallographic texture plays a significant role in determining the behavior of HIC in pipeline steels. The present study tried to prove that crystallographic texture control, through warm rolling schedules, helps improve pipeline steel resistance to HIC. Several samples of an API 5L X52 grade pipeline steel were produced using different thermomechanical processes (austenization, controlled rolling and recrystallization). These samples were subjected to cathodic charging. Scanning electron microscopy and automated FEG/EBSD were used to perform metallographic inspections and to collect microstructure data. The results showed that the strong y fiber texture significantly reduces or even prevents the HIC damage. It is possible to improve the HIC resistance of pipeline steels using crystallography texture control and grain boundary engineering.
International Nuclear Information System (INIS)
Kumar, Lokesh; Bansal, Arvind K.
2011-01-01
Highlights: → Utility of TGA to differentiate between unbound and bound water was demonstrated. → Nature of the lattice arrangement in prazosin hydrochloride polyhydrate was confirmed to be expanded (non-stoichiometric) type hydrate. → Correlation of the DSC, TGA, PXRD and DVS for dehydration of prazosin hydrochloride polyhydrate was delineated. - Abstract: In this study, hydration behaviour of prazosin hydrochloride polyhydrate was assessed using differential scanning calorimetry, thermogravimetric analysis, powder X-ray diffraction and dynamic vapour sorption techniques. Differential scanning calorimetry and thermogravimetric analysis at faster heating rate (20 o C/min) showed single step water loss, attributed to both dihydrate and unbound water. In contrast, thermogravimetric analysis at slower heating rate (1 o C/min) showed unbound and dihydrate lattice water separately, with unbound water being lost initially, followed by loss of dihydrate water. Variable vacuum and variable humidity PXRD study revealed shift in diffraction peaks to higher values on removal of unbound water. Initial PXRD patterns were regained when kept again at ambient conditions. Dynamic vapour sorption depicted type I sorption isotherm with interstitial water, indicating that polyhydrate form show reversible behaviour with change in humidity. Correlation between thermal, sorption and crystallographic data established hydration behaviour to be characteristic of expanded channel type (non-stoichiometric) hydrate.
International Nuclear Information System (INIS)
Abesi, F.; Mirshekar, A.; Moudi, E.; Seyedmajidi, M.; Haghanifar, S.; Haghighat, N.; Bijani, A.
2012-01-01
Radiography plays an important role in the detection of interproximal caries. The aim of the present study was to determine diagnostic accuracy of charge coupled devices, Photo Stimulable Phosphor and film radiography in detecting non-cavitated caries. Seventy-two non-cavitated approximal surfaces of extracted human posterior teeth were radiographed under standardized conditions using three intraoral modalities: charge coupled devices Dixi3 (Planmeca, Finland), PSP Digora PCT (Soredex, Finland), and E-speed film (Kodak, USA). Radiographs were interpreted by four observers and caries lesions were classified as sound (R0), restricted to enamel (R1), reaching the dentinoenamel junction and the outer half of the dentin (R2) and the inner half of the dentin (R3). The teeth were subsequently sectioned for histological analysis which served as the gold standard for radiographic examination. Microscopic examinations showed that the distribution of caries were 63.9% sound, 18.1% enamel, 9.7% dentinoenamel junction and outer half of the dentin and 8.3% into the inner half of the dentin. The sensitivity and specificity of film, charge coupled devices and Photo Stimulable Phosphor for the detection of enamel caries were 38% and 98%; 15% and 96%; and 23% and 98%, respectively. The sensitivity and specificity of film, charge coupled devices and Photo Stimulable Phosphor for the detection of both dentin and enamel caries were 55% and 100%; 45% and 100% ; and 55% and 100%, respectively. The results demonstrated that the diagnostic accuracy of digital images is similar to that of conventional film radiography in the detection of non-cavitated approximal caries.
Directory of Open Access Journals (Sweden)
Meina Sun
2016-05-01
Full Text Available We study the Riemann problem for a non-strictly hyperbolic system of conservation laws under the linear approximations of flux functions with three parameters. The approximated system also belongs to the type of triangular systems of conservation laws and this approximation does not change the structure of Riemann solutions to the original system. Furthermore, it is proven that the Riemann solutions to the approximated system converge to the corresponding ones to the original system as the perturbation parameter tends to zero.
Non-declarative sequence learning does not show savings in relearning.
Keisler, Aysha; Willingham, Daniel T
2007-04-01
Researchers have utilized the savings in relearning paradigm in a variety of settings since Ebbinghaus developed the tool over a century ago. In spite of its widespread use, we do not yet understand what type(s) of memory are measurable by savings. Specifically, can savings measure both declarative and non-declarative memories? The lack of conscious recollection of the encoded material in some studies indicates that non-declarative memories may show savings effects, but as all studies to date have used declarative tasks, we cannot be certain. Here, we administer a non-declarative task and then measure savings in relearning the material declaratively. Our results show that while material outside of awareness may show savings effects, non-declarative sequence memory does not. These data highlight the important distinction between memory without awareness and non-declarative memory.
Approximating distributions from moments
Pawula, R. F.
1987-11-01
A method based upon Pearson-type approximations from statistics is developed for approximating a symmetric probability density function from its moments. The extended Fokker-Planck equation for non-Markov processes is shown to be the underlying foundation for the approximations. The approximation is shown to be exact for the beta probability density function. The applicability of the general method is illustrated by numerous pithy examples from linear and nonlinear filtering of both Markov and non-Markov dichotomous noise. New approximations are given for the probability density function in two cases in which exact solutions are unavailable, those of (i) the filter-limiter-filter problem and (ii) second-order Butterworth filtering of the random telegraph signal. The approximate results are compared with previously published Monte Carlo simulations in these two cases.
International Nuclear Information System (INIS)
Michiuchi, M.; Nambu, S.; Ishimoto, Y.; Inoue, J.; Koseki, T.
2009-01-01
Electron backscattering diffraction patterns were used to investigate the relationship between local deformation behavior and the crystallographic features of as-quenched lath martensite of low-carbon steel during uniform elongation in tensile tests. The slip system operating during the deformation up to a strain of 20% was estimated by comparing the crystal rotation of each martensite block after deformation of 20% strain with predictions by the Taylor and Sachs models. The results indicate that the in-lath-plane slip system was preferentially activated compared to the out-of-lath-plane system up to this strain level. Further detailed analysis of crystal rotation at intervals of approximately 5% strain confirmed that the constraint on the operative slip system by the lath structure begins at a strain of 8% and that the local strain hardening of the primary slip systems occurred at approximately 15% strain.
Three sets of crystallographic sub-planar structures in quartz formed by tectonic deformation
Derez, Tine; Pennock, Gill; Drury, Martyn; Sintubin, Manuel
2016-05-01
In quartz, multiple sets of fine planar deformation microstructures that have specific crystallographic orientations parallel to planes with low Miller-Bravais indices are commonly considered as shock-induced planar deformation features (PDFs) diagnostic of shock metamorphism. Using polarized light microscopy, we demonstrate that up to three sets of tectonically induced sub-planar fine extinction bands (FEBs), sub-parallel to the basal, γ, ω, and π crystallographic planes, are common in vein quartz in low-grade tectonometamorphic settings. We conclude that the observation of multiple (2-3) sets of fine scale, closely spaced, crystallographically controlled, sub-planar microstructures is not sufficient to unambiguously distinguish PDFs from tectonic FEBs.
A crystallographic perspective on sharing data and knowledge
Bruno, Ian J.; Groom, Colin R.
2014-10-01
The crystallographic community is in many ways an exemplar of the benefits and practices of sharing data. Since the inception of the technique, virtually every published crystal structure has been made available to others. This has been achieved through the establishment of several specialist data centres, including the Cambridge Crystallographic Data Centre, which produces the Cambridge Structural Database. Containing curated structures of small organic molecules, some containing a metal, the database has been produced for almost 50 years. This has required the development of complex informatics tools and an environment allowing expert human curation. As importantly, a financial model has evolved which has, to date, ensured the sustainability of the resource. However, the opportunities afforded by technological changes and changing attitudes to sharing data make it an opportune moment to review current practices.
Hydrophilic Pt nanoflowers: synthesis, crystallographic analysis and catalytic performance.
Mourdikoudis, Stefanos; Altantzis, Thomas; Liz-Marzán, Luis M; Bals, Sara; Pastoriza-Santos, Isabel; Pérez-Juste, Jorge
2016-05-21
Water-soluble Pt nanoflowers (NFs) were prepared by diethylene glycol-mediated reduction of Pt acetylacetonate (Pt(acac) 2 ) in the presence of polyethylenimine. Advanced electron microscopy analysis showed that the NFs consist of multiple branches with a truncated cubic morphology and different crystallographic orientations. We demonstrate that the nature of the solvent strongly influences the resulting morphology. The catalytic performance of the Pt NFs in 4-nitrophenol reduction was found to be superior to that of other nanoparticle-based catalysts. Additionally, the Pt NFs display good catalytic reusability with no loss of activity after five consecutive cycles.
Rights, Jason D; Sterba, Sonya K
2016-11-01
Multilevel data structures are common in the social sciences. Often, such nested data are analysed with multilevel models (MLMs) in which heterogeneity between clusters is modelled by continuously distributed random intercepts and/or slopes. Alternatively, the non-parametric multilevel regression mixture model (NPMM) can accommodate the same nested data structures through discrete latent class variation. The purpose of this article is to delineate analytic relationships between NPMM and MLM parameters that are useful for understanding the indirect interpretation of the NPMM as a non-parametric approximation of the MLM, with relaxed distributional assumptions. We define how seven standard and non-standard MLM specifications can be indirectly approximated by particular NPMM specifications. We provide formulas showing how the NPMM can serve as an approximation of the MLM in terms of intraclass correlation, random coefficient means and (co)variances, heteroscedasticity of residuals at level 1, and heteroscedasticity of residuals at level 2. Further, we discuss how these relationships can be useful in practice. The specific relationships are illustrated with simulated graphical demonstrations, and direct and indirect interpretations of NPMM classes are contrasted. We provide an R function to aid in implementing and visualizing an indirect interpretation of NPMM classes. An empirical example is presented and future directions are discussed. © 2016 The British Psychological Society.
Energy Technology Data Exchange (ETDEWEB)
Jacquier, Sandra [Ecole Nationale Superieure des Mines de Saint-Etienne, 158 Cours Fauriel, 42023 F-St. Etienne (France); Gruy, Frederic [Ecole Nationale Superieure des Mines de Saint-Etienne, 158 Cours Fauriel, 42023 F-St. Etienne (France)], E-mail: fgruy@emse.fr
2008-11-15
We previously [Jacquier S, Gruy F. Approximation of the light scattering cross-section for aggregated spherical non-absorbent particles. JQSRT 2008;109:789-810] reformulated the anomalous diffraction (AD) approximation to calculate the light scattering cross section of aggregates by introducing their chord length distribution (CLD). It was applied to several ordered aggregates. This new method is entitled ADr, with the r for rapid because this one is at least 100 times faster than the standard AD method. In this article, we are searching for an approximated expression for CLD suitable all at once for ordered and disordered aggregates. The corresponding scattering cross-section values are compared to the ones coming from the standard AD approximation.
International Nuclear Information System (INIS)
Jacquier, Sandra; Gruy, Frederic
2008-01-01
We previously [Jacquier S, Gruy F. Approximation of the light scattering cross-section for aggregated spherical non-absorbent particles. JQSRT 2008;109:789-810] reformulated the anomalous diffraction (AD) approximation to calculate the light scattering cross section of aggregates by introducing their chord length distribution (CLD). It was applied to several ordered aggregates. This new method is entitled ADr, with the r for rapid because this one is at least 100 times faster than the standard AD method. In this article, we are searching for an approximated expression for CLD suitable all at once for ordered and disordered aggregates. The corresponding scattering cross-section values are compared to the ones coming from the standard AD approximation
Crystallographic orientations in one-directional gray cast solidification
International Nuclear Information System (INIS)
Roviglione, A.; Hermida, J.D.
1991-01-01
The aim of this work is to determine the crystallographic orientations of austenite and the A laminar graphite and the compact, in one-directionally grown samples to decide upon the validity of the mentioned theory. (Author) [es
Algebraic K-theory of crystallographic groups the three-dimensional splitting case
Farley, Daniel Scott
2014-01-01
The Farrell-Jones isomorphism conjecture in algebraic K-theory offers a description of the algebraic K-theory of a group using a generalized homology theory. In cases where the conjecture is known to be a theorem, it gives a powerful method for computing the lower algebraic K-theory of a group. This book contains a computation of the lower algebraic K-theory of the split three-dimensional crystallographic groups, a geometrically important class of three-dimensional crystallographic group, representing a third of the total number. The book leads the reader through all aspects of the calculation. The first chapters describe the split crystallographic groups and their classifying spaces. Later chapters assemble the techniques that are needed to apply the isomorphism theorem. The result is a useful starting point for researchers who are interested in the computational side of the Farrell-Jones isomorphism conjecture, and a contribution to the growing literature in the field.
Drozd, Marek; Daszkiewicz, Marek
2018-06-01
According to literature data the two crystals are known: guanidinium m-nitrobenzoate and guanidinium p-nitrobenzoate. Both compounds belong to noncetrosymmetric crystallographic systems are consider as second order generators in nonlinear optic (NLO). For each of these crystals the detailed crystallographic, theoretical calculations and vibrational studies were performed. It is interesting that nitrobenzoic acid create tree variety of compounds ((2) ortho-, (3) meta- and (4) para-) what any data for third member of guanidinium nitrobenzoate crystal were not known. The guanidinium o-nitrobenzoate hydrate crystal was synthesized first time. The performed X-ray crystallographic study shown that crystal belongs to space group without macroscopic symmetry center. Additionally, the vibrational spectra (intensities, frequencies and PED analysis) of investigated compound are presented. These results are compared with theoretical calculations for equilibrium geometry and vibrational properties. Furthermore, the results of the theoretical approach include HOMO and LUMO energies and first order hyperpolarizability were obtained, also. On the basis of these data the crystal was classified as second order generator. All obtained results are compared with previous literature data of guanidinium m-nitrobenzoate and guanidinium p-nitrobenzoate compounds. Surprisingly, each of examined crystal belongs to different crystallographic system and shows different vibrational properties.
Discovery of novel inhibitors for DHODH via virtual screening and X-ray crystallographic structures
Energy Technology Data Exchange (ETDEWEB)
McLean, Larry R.; Zhang, Ying; Degnen, William; Peppard, Jane; Cabel, Dasha; Zou, Chao; Tsay, Joseph T.; Subramaniam, Arun; Vaz, Roy J.; Li, Yi (Sanofi)
2010-10-28
Amino-benzoic acid derivatives 1-4 were found to be inhibitors for DHODH by virtual screening, biochemical, and X-ray crystallographic studies. X-ray structures showed that 1 and 2 bind to DHODH as predicted by virtual screening, but 3 and 4 were found to be structurally different from the corresponding compounds initially identified by virtual screening.
Directory of Open Access Journals (Sweden)
Gian Song
2017-12-01
Full Text Available Over the past decade, wavelength-dependent neutron radiography, also known as Bragg-edge imaging, has been employed as a non-destructive bulk characterization method due to its sensitivity to coherent elastic neutron scattering that is associated with crystalline structures. Several analysis approaches have been developed to quantitatively determine crystalline orientation, lattice strain, and phase distribution. In this study, we report a systematic investigation of the crystal structures of metallic materials (such as selected textureless powder samples and additively manufactured (AM Inconel 718 samples, using Bragg-edge imaging at the Oak Ridge National Laboratory (ORNL Spallation Neutron Source (SNS. Firstly, we have implemented a phenomenological Gaussian-based fitting in a Python-based computer called iBeatles. Secondly, we have developed a model-based approach to analyze Bragg-edge transmission spectra, which allows quantitative determination of the crystallographic attributes. Moreover, neutron diffraction measurements were carried out to validate the Bragg-edge analytical methods. These results demonstrate that the microstructural complexity (in this case, texture plays a key role in determining the crystallographic parameters (lattice constant or interplanar spacing, which implies that the Bragg-edge image analysis methods must be carefully selected based on the material structures.
Resolution of a protein sequence ambiguity by X-ray crystallographic and mass spectrometric methods
International Nuclear Information System (INIS)
Keefe, L.J.; Lattman, E.E.; Wolkow, C.; Woods, A.; Chevrier, M.; Cotter, R.J.
1992-01-01
Ambiguities in amino acid sequences are a potential problem in X-ray crystallographic studies of proteins. Amino acid side chains often cannot be reliably identified from the electron density. Many protein crystal structures that are now being solved are simple variants of a known wild-type structure. Thus, cloning artifacts or other untoward events can readily lead to cases in which the proposed sequence is not correct. An example is presented showing that mass spectrometry provides an excellent tool for analyzing suspected errors. The X-ray crystal structure of an insertion mutant of Staphylococcal nuclease has been solved to 1.67 A resolution and refined to a crystallographic R value of 0.170. A single residue has been inserted in the C-terminal α helix. The inserted amino acid was believed to be an alanine residue, but the final electron density maps strongly indicated that a glycine had been inserted instead. To confirm the observations from the X-ray data, matrix-assisted laser desorption mass spectrometry was employed to verify the glycine insertion. This mass spectrometric technique has sufficient mass accuracy to detect the methyl group that distinguishes glycine from alanine and can be extended to the more common situation in which crystallographic measurements suggest a problem with the sequence, but cannot pinpoint its location or nature. (orig.)
Resolution of a protein sequence ambiguity by X-ray crystallographic and mass spectrometric methods
Energy Technology Data Exchange (ETDEWEB)
Keefe, L.J.; Lattman, E.E. (Dept. of Biophysics and Biophysical Chemistry, Johns Hopkins Univ. School of Medicine, Baltimore, MD (United States)); Wolkow, C.; Woods, A.; Chevrier, M.; Cotter, R.J. (Middle Atlantic Mass Spectrometry Lab., Johns Hopkins Univ. School of Medicine, Baltimore, MD (United States))
1992-04-01
Ambiguities in amino acid sequences are a potential problem in X-ray crystallographic studies of proteins. Amino acid side chains often cannot be reliably identified from the electron density. Many protein crystal structures that are now being solved are simple variants of a known wild-type structure. Thus, cloning artifacts or other untoward events can readily lead to cases in which the proposed sequence is not correct. An example is presented showing that mass spectrometry provides an excellent tool for analyzing suspected errors. The X-ray crystal structure of an insertion mutant of Staphylococcal nuclease has been solved to 1.67 A resolution and refined to a crystallographic R value of 0.170. A single residue has been inserted in the C-terminal {alpha} helix. The inserted amino acid was believed to be an alanine residue, but the final electron density maps strongly indicated that a glycine had been inserted instead. To confirm the observations from the X-ray data, matrix-assisted laser desorption mass spectrometry was employed to verify the glycine insertion. This mass spectrometric technique has sufficient mass accuracy to detect the methyl group that distinguishes glycine from alanine and can be extended to the more common situation in which crystallographic measurements suggest a problem with the sequence, but cannot pinpoint its location or nature. (orig.).
The effect of crystallographic orientation on the active corrosion of pure magnesium
International Nuclear Information System (INIS)
Liu Ming; Qiu Dong; Zhao Mingchun; Song, Guangling; Atrens, Andrej
2008-01-01
An improved method was used to investigate the influence of crystallographic orientation on the corrosion of pure magnesium in 0.1 N HCl. The corrosion depth and orientation of surface features were mapped against crystallographic orientation (obtained by electron backscatter diffraction) for many off-principal magnesium crystals. The grains near (0 0 0 1) orientation are the most corrosion resistant. Most grains exhibited a striated structure of long and narrow hillocks with a unique direction
Energy Technology Data Exchange (ETDEWEB)
Ansanay-Alex, G.
2009-06-17
The development of simulation codes aimed at a precise simulation of fires requires a precise approach of flame front phenomena by using very fine grids. The need to take different spatial scale into consideration leads to a local grid refinement and to a discretization with homogeneous grid for computing time and memory purposes. The author reports the approximation of the non-linear convection term, the scalar advection-diffusion in finite volumes, numerical simulations of a flow in a bent tube, of a three-dimensional laminar flame and of a low Mach number an-isotherm flow. Non conformal finite elements are also presented (Rannacher-Turek and Crouzeix-Raviart elements)
Crystallographic Analysis of Nucleation at Hardness Indentations in High-Purity Aluminum
DEFF Research Database (Denmark)
Xu, Chaoling; Zhang, Yubin; Lin, Fengxiang
2016-01-01
Nucleation at Vickers hardness indentations has been studied in high-purity aluminum cold-rolled 12 pct. Electron channeling contrast was used to measure the size of the indentations and to detect nuclei, while electron backscattering diffraction was used to determine crystallographic orientations....... It is found that indentations are preferential nucleation sites. The crystallographic orientations of the deformed grains affect the hardness and the nucleation potentials at the indentations. Higher hardness gives increased nucleation probabilities. Orientation relationships between nuclei developed...... they form. Finally, possible nucleation mechanisms are briefly discussed....
Identification of some crystallographic features of martensite in steels by microdiffraction
International Nuclear Information System (INIS)
Sarikaya, M.; Rao, B.V.N.; Thomas, G.
1980-03-01
Considerable attention should be paid to the interpretation of electron diffraction, such as the understanding of the extra reflections and other effects in an SAD pattern obtained from lath martensite by making allowances for spatial resolution limitations in the SAD patterns. These difficulties can be overcome by utilizing the convergent beam electron diffraction (CBED) method which permits the use of different probe sizes to obtain crystallographic information from very small regions. Some crystallographic features of lath martensite in low and medium C steels have been identified and some others verified by using CBED
Determination of crystallographic and macroscopic orientation of planar structures in TEM
DEFF Research Database (Denmark)
Huang, X.; Liu, Q.
1998-01-01
With the aid of a double-tilt holder in a transmission electron microscope (TEM), simple methods are described for determination of the crystallographic orientation of a planar structure and for calculation of the macroscopic orientation of the planar structure. The correlation between a planar...... structure and a crystallographic plane can be found by comparing the differences in their trace directions on the projection plane and inclination angles with respect to that plane. The angles between the traces of planar structures and the sample axis measured from the TEM micrographs, which have been...
International Nuclear Information System (INIS)
Larin, S.A.; Ritbergen, T. van; Vermaseren, J.A.M.
1993-12-01
We obtain the analytic next-next-to-leading perturbative QCD corrections in the leading twist approximation for the moments N = 2, 4, 6, 8 of the non-singlet deep inelastic structure functions F 2 and F L . We calculate the three-loop anomalous dimensions of the corresponding non-singlet operators and the three-loop coefficient functions of the structure function F L . (orig.)
Ryu, S O; Lee, W J
2003-01-01
We report on the crystallization and electrical properties of Bi sub 3 sub . sub 4 sub 7 La sub 0 sub . sub 8 sub 5 Ti sub 3 O sub 1 sub 2 (BLT) thin films for possible ferroelectric non-volatile memory applications. The film properties were found to be strongly dependent on process conditions especially on the intermediate heat treatment conditions. The crystallographic orientation of the films showed sharp changes at the intermediate rapid thermal annealing (RTA) temperature of 450degC. Below 450degC, BLT thin films have (117) orientation while they have preffered c-axis orientation above 450degC. We found that RTA conditions of the first coating layer play a major role in determining the entire crystallographic orientation of the films. The films also showed of ferroelectric hysterisis behavior strongly dependent on RTA treatment. In fact, the remanent polarization of Bi sub 3 sub . sub 4 sub 6 sub 5 La sub 0 sub . sub 8 sub 5 Ti sub 3 O sub 1 sub 2 thin films having (001) preferred crystallographic orient...
Directory of Open Access Journals (Sweden)
Ramon F. Alvarez-Estrada
2012-02-01
Full Text Available We consider non-equilibrium open statistical systems, subject to potentials and to external “heat baths” (hb at thermal equilibrium at temperature T (either with ab initio dissipation or without it. Boltzmann’s classical equilibrium distributions generate, as Gaussian weight functions in momenta, orthogonal polynomials in momenta (the position-independent Hermite polynomialsHn’s. The moments of non-equilibrium classical distributions, implied by the Hn’s, fulfill a hierarchy: for long times, the lowest moment dominates the evolution towards thermal equilibrium, either with dissipation or without it (but under certain approximation. We revisit that hierarchy, whose solution depends on operator continued fractions. We review our generalization of that moment method to classical closed many-particle interacting systems with neither a hb nor ab initio dissipation: with initial states describing thermal equilibrium at T at large distances but non-equilibrium at finite distances, the moment method yields, approximately, irreversible thermalization of the whole system at T, for long times. Generalizations to non-equilibrium quantum interacting systems meet additional difficulties. Three of them are: (i equilibrium distributions (represented through Wigner functions are neither Gaussian in momenta nor known in closed form; (ii they may depend on dissipation; and (iii the orthogonal polynomials in momenta generated by them depend also on positions. We generalize the moment method, dealing with (i, (ii and (iii, to some non-equilibrium one-particle quantum interacting systems. Open problems are discussed briefly.
Shape effect related to crystallographic orientation of deformation behavior in copper crystals
International Nuclear Information System (INIS)
Kim, K.H.; Chang, C.H.; Koo, Y.M.; MacDowell, A.A.
1999-01-01
The deformation behavior of pure copper single crystals has been investigated by scanning electron microscopy and synchrotron radiation using the in situ reflection Laue method. Two types of samples with the same orientation of tensile axes, but with different crystallographic orientations in the directions of the width and thickness of the samples, have been studied. They showed different characteristics of deformation behavior, such as the activated slip systems, the movement of the tensile axis, and the mode of fracture
Crystallographic contribution to the formation of the columnar grain structure in cobalt films
International Nuclear Information System (INIS)
Hara, K.; Itoh, K.; Okamoto, K.; Hashimoto, T.
1996-01-01
In order to clarify the crystallographic contribution to the formation of the columnar grain structure, the geometric and crystallographic alignments of columnar grains in cobalt films were investigated on the basis of magnetic and optical measurements. The films were deposited by sputtering at an incidence angle of 45 on glass substrates heated at 332 K. The film thickness ranged from 20 to 850 nm. Above 50 nm the columnar grains align in the direction parallel to the incidence plane and form a two-degree crystallographic orientation. The packing density of columnar grains decreases with increasing thickness when the thickness exceeds 50 nm. From these results we conclude that the crystal habit appearing on column tops induces the two-degree orientation through geometric selection and aligns the selected columnar grains in the parallel direction. (orig.)
Energy Technology Data Exchange (ETDEWEB)
Larin, S.A.; Ritbergen, T. van; Vermaseren, J.A.M.
1993-12-01
We obtain the analytic next-next-to-leading perturbative QCD corrections in the leading twist approximation for the moments N = 2, 4, 6, 8 of the non-singlet deep inelastic structure functions F{sub 2} and F{sub L}. We calculate the three-loop anomalous dimensions of the corresponding non-singlet operators and the three-loop coefficient functions of the structure function F{sub L}. (orig.).
International Nuclear Information System (INIS)
Delfosse, Vanessa; Hugonnet, Jean-Emmanuel; Sougakoff, Wladimir; Mayer, Claudine
2005-01-01
The crystallization of a hypothetical penicillin-binding protein from the archaeon P. abyssi in space group C2 by hanging-drop vapour diffusion is reported. The genome of the hyperthermophilic archaeon Pyrococcus abyssi contains a gene (pab0087) encoding a penicillin-binding protein (PBP) homologue. This sequence consists of 447 residues and shows significant sequence similarity to low-molecular-weight PBPs and class C β-lactamases. The Pab0087 protein was overexpressed, purified and crystallized. Diffraction data from two different crystal forms were collected to 2.7 and 2.0 Å resolution. Both crystals belong to space group C2, with unit-cell parameters a = 160.59, b = 135.74, c = 113.02 Å, β = 117.36° and a = 166.97, b = 131.25, c = 189.39 Å, β = 113.81°, respectively. The asymmetric unit contains four and eight molecules, respectively, with fourfold non-crystallographic symmetry
X-Ray powder diffractometry, crystallographic phase analysis and ...
African Journals Online (AJOL)
Computerized X-Ray diffraction system has been used to determine the composition and lattice parameters of raw and activated kaolinite. The universal diffractometry URD 63 was interfaced with computer via an APX 63 software package for rapid capturing of data on reflected intensity and other crystallographic ...
An alternative to the crystallographic reconstruction of austenite in steels
International Nuclear Information System (INIS)
Bernier, Nicolas; Bracke, Lieven; Malet, Loïc; Godet, Stéphane
2014-01-01
An alternative crystallographic austenite reconstruction programme written in Matlab is developed by combining the best features of the existing models: the orientation relationship refinement, the local pixel-by-pixel analysis and the nuclei identification and spreading strategy. This programme can be directly applied to experimental electron backscatter diffraction mappings. Its applicability is demonstrated on both quenching and partitioning and as-quenched lath-martensite steels. - Highlights: • An alternative crystallographic austenite reconstruction program is developed. • The method combines a local analysis and a nuclei identification/spreading strategy. • The validity of the calculated orientation relationship is verified on a Q and P steel. • The accuracy of the reconstructed microtexture is investigated on a martensite steel
International Nuclear Information System (INIS)
Suram, Santosh K.; Rajan, Krishna
2013-01-01
The purpose of this work is to develop a methodology to estimate the APT reconstruction parameters when limited crystallographic information is available. Reliable spatial scaling of APT data currently requires identification of multiple crystallographic poles from the field desorption image for estimating the reconstruction parameters. This requirement limits the capacity of accurately reconstructing APT data for certain complex systems, such as highly alloyed systems and nanostructured materials wherein more than one pole is usually not observed within one grain. To overcome this limitation, we develop a quantitative methodology for calibrating the reconstruction parameters in an APT dataset by ensuring accurate inter-planar spacing and optimizing the curvature correction for the atomic planes corresponding to a single crystallographic orientation. We validate our approach on an aluminum dataset and further illustrate its capabilities by computing geometric reconstruction parameters for W and Al–Mg–Sc datasets. - Highlights: ► Quantitative approach is developed to accurately reconstruct APT data. ► Curvature of atomic planes in APT data is used to calibrate the reconstruction. ► APT reconstruction parameters are determined from a single crystallographic axis. ► Quantitative approach is demonstrated on W, Al and Al–Mg–Sc systems. ► Accurate APT reconstruction of complex materials is now possible
Energy Technology Data Exchange (ETDEWEB)
Lou, Chang-Sheng [School of Materials Science and Engineering, Shenyang Ligong University, Shenyang 110159 (China); Key Laboratory of Electromagnetic Processing of Materials (Ministry of Education), Northeastern University, Shenyang 110819 (China); Liu, Tie, E-mail: liutie@epm.neu.edu.cn [Key Laboratory of Electromagnetic Processing of Materials (Ministry of Education), Northeastern University, Shenyang 110819 (China); Dong, Meng; Wu, Chun; Shao, Jian-Guo; Wang, Qiang [Key Laboratory of Electromagnetic Processing of Materials (Ministry of Education), Northeastern University, Shenyang 110819 (China)
2017-02-15
The influences of the crystallographic orientation and morphological alignment upon the magnetic anisotropic behavior of polycrystalline materials were investigated. Microstructures obtained in eutectic Mn-Sb alloys via directional solidification simultaneously displayed crystallographic orientation and morphological alignment. Both the crystallographic orientation and the morphological alignment were able to induce magnetic anisotropy in the alloys, wherein the influence of the crystallographic orientation and the morphological alignment upon the magnetic anisotropic behavior of the alloys strongly depended upon their directions and exhibited either mutual promotion or competition. These findings may provide useful guidance for the fabrication design of functional magnetic materials. - Highlights: • We study effects of orientation in crystal and morphology on magnetic anisotropy. • Both orientation in crystal and morphology can induce magnetic anisotropy. • Their effects depend on direction and exhibit either mutual promotion or competition.
Using function approximation to determine neural network accuracy
International Nuclear Information System (INIS)
Wichman, R.F.; Alexander, J.
2013-01-01
Many, if not most, control processes demonstrate nonlinear behavior in some portion of their operating range and the ability of neural networks to model non-linear dynamics makes them very appealing for control. Control of high reliability safety systems, and autonomous control in process or robotic applications, however, require accurate and consistent control and neural networks are only approximators of various functions so their degree of approximation becomes important. In this paper, the factors affecting the ability of a feed-forward back-propagation neural network to accurately approximate a non-linear function are explored. Compared to pattern recognition using a neural network for function approximation provides an easy and accurate method for determining the network's accuracy. In contrast to other techniques, we show that errors arising in function approximation or curve fitting are caused by the neural network itself rather than scatter in the data. A method is proposed that provides improvements in the accuracy achieved during training and resulting ability of the network to generalize after training. Binary input vectors provided a more accurate model than with scalar inputs and retraining using a small number of the outlier x,y pairs improved generalization. (author)
Automated identification of crystallographic ligands using sparse-density representations
International Nuclear Information System (INIS)
Carolan, C. G.; Lamzin, V. S.
2014-01-01
A novel procedure for identifying ligands in macromolecular crystallographic electron-density maps is introduced. Density clusters in such maps can be rapidly attributed to one of 82 different ligands in an automated manner. A novel procedure for the automatic identification of ligands in macromolecular crystallographic electron-density maps is introduced. It is based on the sparse parameterization of density clusters and the matching of the pseudo-atomic grids thus created to conformationally variant ligands using mathematical descriptors of molecular shape, size and topology. In large-scale tests on experimental data derived from the Protein Data Bank, the procedure could quickly identify the deposited ligand within the top-ranked compounds from a database of candidates. This indicates the suitability of the method for the identification of binding entities in fragment-based drug screening and in model completion in macromolecular structure determination
Crystallographic computing system JANA2006: General features
Czech Academy of Sciences Publication Activity Database
Petříček, Václav; Dušek, Michal; Palatinus, Lukáš
2014-01-01
Roč. 229, č. 5 (2014), s. 345-352 ISSN 0044-2968 R&D Projects: GA ČR(CZ) GAP204/11/0809; GA ČR(CZ) GA14-03276S Grant - others:AV ČR(CZ) Praemium Academiae Institutional support: RVO:68378271 Keywords : JANA2006 * aperiodic structures * magnetic structures * crystallographic computing Subject RIV: BM - Solid Matter Physics ; Magnetism Impact factor: 1.310, year: 2014
International Nuclear Information System (INIS)
Sentis, R.
1984-07-01
The radiative transfer equations may be approximated by a non linear diffusion equation (called Rosseland equation) when the mean free paths of the photons are small with respect to the size of the medium. Some technical assomptions are made, namely about the initial conditions, to avoid any problem of initial layer terms
International Nuclear Information System (INIS)
Ansanay-Alex, G.
2009-01-01
The development of simulation codes aimed at a precise simulation of fires requires a precise approach of flame front phenomena by using very fine grids. The need to take different spatial scale into consideration leads to a local grid refinement and to a discretization with homogeneous grid for computing time and memory purposes. The author reports the approximation of the non-linear convection term, the scalar advection-diffusion in finite volumes, numerical simulations of a flow in a bent tube, of a three-dimensional laminar flame and of a low Mach number an-isotherm flow. Non conformal finite elements are also presented (Rannacher-Turek and Crouzeix-Raviart elements)
On Nash-Equilibria of Approximation-Stable Games
Awasthi, Pranjal; Balcan, Maria-Florina; Blum, Avrim; Sheffet, Or; Vempala, Santosh
One reason for wanting to compute an (approximate) Nash equilibrium of a game is to predict how players will play. However, if the game has multiple equilibria that are far apart, or ɛ-equilibria that are far in variation distance from the true Nash equilibrium strategies, then this prediction may not be possible even in principle. Motivated by this consideration, in this paper we define the notion of games that are approximation stable, meaning that all ɛ-approximate equilibria are contained inside a small ball of radius Δ around a true equilibrium, and investigate a number of their properties. Many natural small games such as matching pennies and rock-paper-scissors are indeed approximation stable. We show furthermore there exist 2-player n-by-n approximation-stable games in which the Nash equilibrium and all approximate equilibria have support Ω(log n). On the other hand, we show all (ɛ,Δ) approximation-stable games must have an ɛ-equilibrium of support O(Δ^{2-o(1)}/ɛ2{log n}), yielding an immediate n^{O(Δ^{2-o(1)}/ɛ^2log n)}-time algorithm, improving over the bound of [11] for games satisfying this condition. We in addition give a polynomial-time algorithm for the case that Δ and ɛ are sufficiently close together. We also consider an inverse property, namely that all non-approximate equilibria are far from some true equilibrium, and give an efficient algorithm for games satisfying that condition.
Carlberg, Kevin
2010-10-28
A Petrov-Galerkin projection method is proposed for reducing the dimension of a discrete non-linear static or dynamic computational model in view of enabling its processing in real time. The right reduced-order basis is chosen to be invariant and is constructed using the Proper Orthogonal Decomposition method. The left reduced-order basis is selected to minimize the two-norm of the residual arising at each Newton iteration. Thus, this basis is iteration-dependent, enables capturing of non-linearities, and leads to the globally convergent Gauss-Newton method. To avoid the significant computational cost of assembling the reduced-order operators, the residual and action of the Jacobian on the right reduced-order basis are each approximated by the product of an invariant, large-scale matrix, and an iteration-dependent, smaller one. The invariant matrix is computed using a data compression procedure that meets proposed consistency requirements. The iteration-dependent matrix is computed to enable the least-squares reconstruction of some entries of the approximated quantities. The results obtained for the solution of a turbulent flow problem and several non-linear structural dynamics problems highlight the merit of the proposed consistency requirements. They also demonstrate the potential of this method to significantly reduce the computational cost associated with high-dimensional non-linear models while retaining their accuracy. © 2010 John Wiley & Sons, Ltd.
Carlberg, Kevin; Bou-Mosleh, Charbel; Farhat, Charbel
2010-01-01
A Petrov-Galerkin projection method is proposed for reducing the dimension of a discrete non-linear static or dynamic computational model in view of enabling its processing in real time. The right reduced-order basis is chosen to be invariant and is constructed using the Proper Orthogonal Decomposition method. The left reduced-order basis is selected to minimize the two-norm of the residual arising at each Newton iteration. Thus, this basis is iteration-dependent, enables capturing of non-linearities, and leads to the globally convergent Gauss-Newton method. To avoid the significant computational cost of assembling the reduced-order operators, the residual and action of the Jacobian on the right reduced-order basis are each approximated by the product of an invariant, large-scale matrix, and an iteration-dependent, smaller one. The invariant matrix is computed using a data compression procedure that meets proposed consistency requirements. The iteration-dependent matrix is computed to enable the least-squares reconstruction of some entries of the approximated quantities. The results obtained for the solution of a turbulent flow problem and several non-linear structural dynamics problems highlight the merit of the proposed consistency requirements. They also demonstrate the potential of this method to significantly reduce the computational cost associated with high-dimensional non-linear models while retaining their accuracy. © 2010 John Wiley & Sons, Ltd.
International Nuclear Information System (INIS)
Zhou, Le; Schneider, Matthew M.; Giri, Anit; Cho, Kyu; Sohn, Yongho
2017-01-01
A combinatorial approach using diffusion couples and TEM analyses was carried out to investigate the composition-dependent martensitic transformation in NiMnGa alloys. The compositions cover a large portion of the off-stoichiometric Ni 2 MnGa compositions and some Mn-rich compositions. Crystallographic variations of the martensitic phase, including non-modulated (NM) martensite, modulated (5M or 7M) martensite, and austenitic phase were identified in the diffusion couples and investigated with respect to their microstructure and crystallography. The 5M and 7M martensitic structures were only found near the interphase boundary between austenite and martensite, while the NM martensitic structures were found mostly away from the interphase boundary. The tetragonality ratio (c/a) for NM martensite generally increases with e/a ratio, but was also dependent on the composition. The habit plane and martensitic microstructure that consists of twinned variants with differing orientations were documented using electron diffraction. The pre-martensitic state was observed in the austenitic phase that was located near the interphase boundary between austenite and martensite, with distinctive tweed microstructure and a strain field originating from the local lattice distortions. The combinatorial approach proves to be efficient and systematic in studying the composition-dependent martensitic transformation in NiMnGa alloys and can be potentially applied to other shape memory alloys.
International Nuclear Information System (INIS)
Maurente, André; França, Francis H.R.; Miki, Kenji; Howell, John R.
2012-01-01
Approximations for joint cumulative k-distribution for mixtures are efficient for full spectrum k-distribution (FSK) computations. These approximations provide reduction of the database that is necessary to perform FSK computation when compared to the direct approach, which uses cumulative k-distributions computed from the spectrum of the mixture, and also less computational expensive when compared to techniques in which RTE's are required to be solved for each component of the mixture. The aim of the present paper is to extend the approximations for joint cumulative k-distributions for non-LTE media. For doing that, a FSK to non-LTE media formulation well-suited to be applied along with approximations for joint cumulative k-distributions is presented. The application of the proposed methodology is demonstrated by solving the radiation heat transfer in non-LTE high temperature plasmas composed of N, O, N 2 , NO, N 2 + and mixtures of these species. The two more efficient approximations, that is, the superposition and multiplication are employed and analyzed.
Energy Technology Data Exchange (ETDEWEB)
Silva, J.M.; Baêta Júnior, E.S.; Moraes, N.R.D.C.; Botelho, R.A. [Department of Mechanical and Materials Engineering, Military Institute of Engineering (IME), Praça General Tibúrcio, 80,Urca, Rio de Janeiro/RJ (Brazil); Felix, R.A.C. [Scientific Instrumentation and Mechanical Technology Laboratory, Brazilian Center for Physics Research (CBPF), Rua Dr. Xavier Sigaud, 150-Urca, Rio de Janeiro-RJ (Brazil); Brandao, L., E-mail: brandao@ime.eb.br [Department of Mechanical and Materials Engineering, Military Institute of Engineering (IME), Praça General Tibúrcio, 80,Urca, Rio de Janeiro/RJ (Brazil)
2017-01-01
The purpose of this work was to study the influence of different kinds of rolling on the magnetic properties of NOG steel, an electric steel widely used in electrical motors. These properties are highly correlated with the crystallographic texture of the material, which can be changed by rolling. Three kinds of rolling were examined: conventional rolling, cross-rolling and asymmetrical rolling. The crystallographic texture was determined by X-ray diffraction and the magnetic properties were calculated from a theoretical model that related the magnetic induction to crystallographic texture through the anisotropy energy. The results show that cross-rolling yields higher values of magnetic induction than the other processes. - Highlights: • The B{sub 50} of NOG steels was evaluated via texture for different rolling processes. • On comparison to all processes used, the cross-rolling led to highest average B{sub 50}. • Cross-rolling enhances Goss and γ-fiber after annealing. • The better B{sub 50} values were obtained for symmetrical and cross-rolling processes. • For asymmetric rolling process, cylinder diameter ratio changed slightly the texture.
Non-Hermitian wave packet approximation for coupled two-level systems in weak and intense fields
Energy Technology Data Exchange (ETDEWEB)
Puthumpally-Joseph, Raiju; Charron, Eric [Institut des Sciences Moléculaires d’Orsay (ISMO), CNRS, Univ. Paris-Sud, Université Paris-Saclay, F-91405 Orsay (France); Sukharev, Maxim [Science and Mathematics Faculty, College of Letters and Sciences, Arizona State University, Mesa, Arizona 85212 (United States)
2016-04-21
We introduce a non-Hermitian Schrödinger-type approximation of optical Bloch equations for two-level systems. This approximation provides a complete and accurate description of the coherence and decoherence dynamics in both weak and strong laser fields at the cost of losing accuracy in the description of populations. In this approach, it is sufficient to propagate the wave function of the quantum system instead of the density matrix, providing that relaxation and dephasing are taken into account via automatically adjusted time-dependent gain and decay rates. The developed formalism is applied to the problem of scattering and absorption of electromagnetic radiation by a thin layer comprised of interacting two-level emitters.
Stamnes, S.; Ou, S. C.; Lin, Z.; Takano, Y.; Tsay, S. C.; Liou, K.N.; Stamnes, K.
2016-01-01
The reflection and transmission of polarized light for a cirrus cloud consisting of randomly oriented hexagonal columns were calculated by two very different vector radiative transfer models. The forward peak of the phase function for the ensemble-averaged ice crystals has a value of order 6 x 10(exp 3) so a truncation procedure was used to help produce numerically efficient yet accurate results. One of these models, the Vectorized Line-by-Line Equivalent model (VLBLE), is based on the doubling- adding principle, while the other is based on a vector discrete ordinates method (VDISORT). A comparison shows that the two models provide very close although not entirely identical results, which can be explained by differences in treatment of single scattering and the representation of the scattering phase matrix. The relative differences in the reflected I and Q Stokes parameters are within 0.5 for I and within 1.5 for Q for all viewing angles. In 1971 Hansen showed that for scattering by spherical particles the 3 x 3 approximation is sufficient to produce accurate results for the reflected radiance I and the degree of polarization (DOP), and he conjectured that these results would hold also for non-spherical particles. Simulations were conducted to test Hansen's conjecture for the cirrus cloud particles considered in this study. It was found that the 3 x 3 approximation also gives accurate results for the transmitted light, and for Q and U in addition to I and DOP. For these non-spherical ice particles the 3 x 3 approximation leads to an absolute error 2 x 10(exp -6) for the reflected and transmitted I, Q and U Stokes parameters. Hence, it appears to be an excellent approximation, which significantly reduces the computational complexity and burden required for multiple scattering calculations.
Crystallographically-based analysis of the NMR spectra of maghemite
International Nuclear Information System (INIS)
Spiers, K.M.; Cashion, J.D.
2012-01-01
All possible iron environments with respect to nearest neighbour vacancies in vacancy-ordered and vacancy-disordered maghemite have been evaluated and used as the foundation for a crystallographically-based analysis of the published NMR spectra of maghemite. The spectral components have been assigned to particular configurations and excellent agreement obtained in comparing predicted spectra with published spectra taken in applied magnetic fields. The broadness of the published NMR lines has been explained by calculations of the magnetic dipole fields at the various iron sites and consideration of the supertransferred hyperfine fields. - Highlights: ► Analysis of 57 Fe NMR of maghemite based on vacancy ordering and nearest neighbour vacancies. ► Assignment of NMR spectral components based on crystallographic analysis of unique iron sites. ► Strong agreement between predicted spectra and published spectra taken in applied magnetic fields. ► Maghemite NMR spectral broadening due to various iron sites and supertransferred hyperfine field.
Effects of crystallographic texture on stress-migration resistance in copper thin films
International Nuclear Information System (INIS)
Koike, J.; Wada, M.; Sanada, M.; Maruyama, K.
2002-01-01
The crystallographic texture of heat-treated Cu thin films and its effects on stress-migration resistance were studied as a function of film thickness within a range of 50-900 nm. All as-deposited films had (111) texture. After heat treatment at 723 K, texture transition from (111) to (100) was observed in films of thickness greater than 300 nm. The (111) texture films after heat treatment showed severe stress migration; in contrast, the (100) texture films showed no noticeable stress migration. The observed stress-migration resistance in the (100) texture films can be attributed to the absence of twins and to lower thermal stress as compared with the (111) texture films
Macromolecular crystallographic results obtained using a 2048x2048 CCD detector at CHESS
International Nuclear Information System (INIS)
Thiel, D.J.; Ealick, S.E.; Tate, M.W.; Gruner, S.M.; Eikenberry, E.F.
1996-01-01
We present results of macromolecular crystallographic experiments performed at the Cornell High Energy Synchrotron Source (CHESS) with a new CCD-based detector. This detector, installed in January 1995, complements a 1024x1024 CCD detector that has been in continuous operation at CHESS since December 1993. The new detector is based on a 4-port, 2048x2048 pixel CCD that is directly coupled to a Gd 2 O 2 S:Tb phosphor by a 3:1 tapered fiber optic. The active area of the phosphor is a square 82 mm on an edge. The readout time is 7 seconds. In the standard mode of operation, the pixel size at the active area is 41 μm on the edge leading to the capability of resolving approximately 200 orders of diffraction across the detector face. The detector also operates in a 1024x1024 mode in which the pixel size is electronically increased by a factor of 4 in area resulting in smaller data files and faster detector readout but at the expense of spatial resolution. Most of the data that has been collected by this detector has been collected in this mode. Dozens of data sets have been collected by many experimenters using this detector at CHESS during the four month period from its installation until the start of the six-month down period of the storage ring. The capabilities of the detector will be illustrated with results from various crystallographic measurements including experiments in which the recorded diffraction patterns extend in resolution as far as 1 A. The results demonstrate that this detector is capable of collecting data of quality at least equal to that of imaging plates but, in many circumstances, with much greater beamline efficiency. copyright 1996 American Institute of Physics
International Nuclear Information System (INIS)
Mikhin, V.I.; Matukhin, N.M.
2000-01-01
The approach to generalization of the non-stationary heat exchange data for the central zones of the nuclear reactor fuel assemblies and the approximate thermal-model-testing criteria are proposed. The fuel assemblies of fast and water-cooled reactors with different fuel compositions have been investigated. The reason of the non-stationary heat exchange is the fuel-energy-release time dependence. (author)
Rahimi, S.; Wynne, B. P.; Baker, T. N.
2017-01-01
The evolution of microstructure and crystallographic texture has been investigated in double-sided friction stir welded microalloyed steel, using electron backscatter diffraction (EBSD). The microstructure analyses show that the center of stirred zone reached a temperature between Ac1 and Ac3 during FSW, resulting in a dual-phase austenitic/ ferritic microstructure. The temperatures in the thermo-mechanically affected zone and the overlapped area between the first and second weld pass did not exceed the Ac1. The shear generated by the rotation probe occurs in austenitic/ferritic phase field where the austenite portion of the microstructure is transformed to a bainitic ferrite, on cooling. Analysis of crystallographic textures with regard to shear flow lines generated by the probe tool shows the dominance of simple shear components across the whole weld. The austenite texture at Ac1 - Ac3 is dominated by the B { {1bar{1}2} }D2 { {11bar{2}} }< 111rangle simple shear texture components. The formation of ultrafine equiaxed ferrite with submicron grain size has been observed in the overlapped area between the first and second weld pass. This is due to continuous dynamic strain-induced recrystallization as a result of simultaneous severe shear deformation and drastic undercooling.
Exact constants in approximation theory
Korneichuk, N
1991-01-01
This book is intended as a self-contained introduction for non-specialists, or as a reference work for experts, to the particular area of approximation theory that is concerned with exact constants. The results apply mainly to extremal problems in approximation theory, which in turn are closely related to numerical analysis and optimization. The book encompasses a wide range of questions and problems: best approximation by polynomials and splines; linear approximation methods, such as spline-approximation; optimal reconstruction of functions and linear functionals. Many of the results are base
Exact and approximate formulas for neutrino mixing and oscillations with non-standard interactions
International Nuclear Information System (INIS)
Meloni, Davide; Ohlsson, Tommy; Zhang, He
2009-01-01
We present, both exactly and approximately, a complete set of mappings between the vacuum (or fundamental) leptonic mixing parameters and the effective ones in matter with non-standard neutrino interaction (NSI) effects included. Within the three-flavor neutrino framework and a constant matter density profile, a full set of sum rules is established, which enables us to reconstruct the moduli of the effective leptonic mixing matrix elements, in terms of the vacuum mixing parameters in order to reproduce the neutrino oscillation probabilities for future long-baseline experiments. Very compact, but quite accurate, approximate mappings are obtained based on series expansions in the neutrino mass hierarchy parameter η ≡ Δm 2 21 /Δm 2 31 , the vacuum leptonic mixing parameter s 13 ≡ sin θ 13 , and the NSI parameters ε αβ . A detailed numerical analysis about how the NSIs affect the smallest leptonic mixing angle θ 13 , the deviation of the leptonic mixing angle θ 23 from its maximal mixing value, and the transition probabilities useful for future experiments are performed using our analytical results.
Y-TZP zirconia regeneration firing: Microstructural and crystallographic changes after grinding.
Ryan, Daniel Patrick Obelenis; Fais, Laiza Maria Grassi; Antonio, Selma Gutierrez; Hatanaka, Gabriel Rodrigues; Candido, Lucas Miguel; Pinelli, Ligia Antunes Pereira
2017-07-26
This study evaluated microstructural and crystallographic phase changes after grinding (G) and regeneration firing/anneling (R) of Y-TZP ceramics. Thirty five bars (Lava TM and Ice Zirkon) were divided: Y-TZP pre-sintered, control (C), regeneration firing (R), dry grinding (DG), dry grinding+regeneration firing (DGR), wet grinding (WG) and wet grinding+regeneration firing (WGR). Grinding was conducted using a diamond bur and annealing at 1,000°C. The microstructure was analyzed by SEM and the crystalline phases by X-ray diffraction (XRD). XRD showed that pre-sintered specimens contained tetragonal and monoclinic phases, while groups C and R showed tetragonal, cubic and monoclinic phases. After grinding, the cubic phase was eliminated in all groups. Annealing (DGR and WGR) resulted in only tetragonal phase. SEM showed semi-circular cracks after grinding and homogenization of particles after annealing. After grinding, surfaces show tetragonal and monoclinic phases and R can be assumed to be necessary prior to porcelain layering when grinding is performed.
Non-intrusive low-rank separated approximation of high-dimensional stochastic models
Doostan, Alireza; Validi, AbdoulAhad; Iaccarino, Gianluca
2013-01-01
This work proposes a sampling-based (non-intrusive) approach within the context of low-. rank separated representations to tackle the issue of curse-of-dimensionality associated with the solution of models, e.g., PDEs/ODEs, with high-dimensional random inputs. Under some conditions discussed in details, the number of random realizations of the solution, required for a successful approximation, grows linearly with respect to the number of random inputs. The construction of the separated representation is achieved via a regularized alternating least-squares regression, together with an error indicator to estimate model parameters. The computational complexity of such a construction is quadratic in the number of random inputs. The performance of the method is investigated through its application to three numerical examples including two ODE problems with high-dimensional random inputs. © 2013 Elsevier B.V.
Non-intrusive low-rank separated approximation of high-dimensional stochastic models
Doostan, Alireza
2013-08-01
This work proposes a sampling-based (non-intrusive) approach within the context of low-. rank separated representations to tackle the issue of curse-of-dimensionality associated with the solution of models, e.g., PDEs/ODEs, with high-dimensional random inputs. Under some conditions discussed in details, the number of random realizations of the solution, required for a successful approximation, grows linearly with respect to the number of random inputs. The construction of the separated representation is achieved via a regularized alternating least-squares regression, together with an error indicator to estimate model parameters. The computational complexity of such a construction is quadratic in the number of random inputs. The performance of the method is investigated through its application to three numerical examples including two ODE problems with high-dimensional random inputs. © 2013 Elsevier B.V.
Microstructure, crystallographic texture and mechanical properties of friction stir welded AA2017A
Energy Technology Data Exchange (ETDEWEB)
Ahmed, M.M.Z., E-mail: mohamed_ahmed4@s-petrol.suez.edu.eg [Institute for Microstructural and Mechanical Processing Engineering, University of Sheffield (IMMPETUS), Mappin Street, Sheffield S1 3JD (United Kingdom); Department of Metallurgical and Materials Engineering, Suez Canal University, Suez 43721 (Egypt); Wynne, B.P.; Rainforth, W.M. [Institute for Microstructural and Mechanical Processing Engineering, University of Sheffield (IMMPETUS), Mappin Street, Sheffield S1 3JD (United Kingdom); Threadgill, P.L. [TWI LTD, Granta Park, Great Abington, Cambridge CB21 6AL (United Kingdom)
2012-02-15
In this study a thick section (20 mm) friction stir welded AA2017A-T451 has been characterized in terms of microstructure, crystallographic texture and mechanical properties. For microstructural analysis both optical and scanning electron microscopes have been used. A detailed crystallographic texture analysis has been carried out using the electron back scattering diffraction technique. Crystallographic texture has been examined in both shoulder and probe affected regions of the weld NG. An entirely weak texture is observed at the shoulder affected region which is mainly explained by the effect of the sequential multi pass deformation experienced by both tool probe and tool shoulder. The texture in the probe dominated region at the AS side of the weld is relatively weak but still assembles the simple shear texture of FCC metals with B/B{sup Macron} and C components existing across the whole map. However, the texture is stronger at the RS than at the AS of the weld, mainly dominated byB/B{sup Macron} components and with C component almost absent across the map. An alternating bands between (B) components and (B{sup Macron }) component are observed only at the AS side of the weld. - Highlights: Black-Right-Pointing-Pointer Detailed investigation of microstructure and crystallographic texture. Black-Right-Pointing-Pointer The grain size is varied from the top to the bottom of the NG. Black-Right-Pointing-Pointer An entirely weak texture is observed at the shoulder affected region. Black-Right-Pointing-Pointer The texture in the probe affected region is dominated by simple shear texture.
Approximate and renormgroup symmetries
International Nuclear Information System (INIS)
Ibragimov, Nail H.; Kovalev, Vladimir F.
2009-01-01
''Approximate and Renormgroup Symmetries'' deals with approximate transformation groups, symmetries of integro-differential equations and renormgroup symmetries. It includes a concise and self-contained introduction to basic concepts and methods of Lie group analysis, and provides an easy-to-follow introduction to the theory of approximate transformation groups and symmetries of integro-differential equations. The book is designed for specialists in nonlinear physics - mathematicians and non-mathematicians - interested in methods of applied group analysis for investigating nonlinear problems in physical science and engineering. (orig.)
Statistical convergence of a non-positive approximation process
International Nuclear Information System (INIS)
Agratini, Octavian
2011-01-01
Highlights: → A general class of approximation processes is introduced. → The A-statistical convergence is studied. → Applications in quantum calculus are delivered. - Abstract: Starting from a general sequence of linear and positive operators of discrete type, we associate its r-th order generalization. This construction involves high order derivatives of a signal and it looses the positivity property. Considering that the initial approximation process is A-statistically uniform convergent, we prove that the property is inherited by the new sequence. Also, our result includes information about the uniform convergence. Two applications in q-Calculus are presented. We study q-analogues both of Meyer-Koenig and Zeller operators and Stancu operators.
International Nuclear Information System (INIS)
Lublinsky, M.
2004-01-01
A simple analytic expression for the non-singlet structure function fns is given. The expression is derived from the result of B. I. Ermolaev et al. (1996) obtained by low x resummation of the quark ladder diagrams in the double logarithmic approximation of perturbative QCD. (orig.)
International Nuclear Information System (INIS)
Teixeira, S.R.
1981-01-01
The structural behavior of UO 2 sintered plates was studied as a function of temperature by X-ray diffractometry. All the experiments were carried out under an inert atmosphere with low oxygen content (approximated 140 ppm). The thermal expansion coefficient of UO 2 05 was found to be 10,5 x 10 - 6 0 C - 1 for temperatures above 165 0 C. Structural transformations during oxidation were observed at 170,235 and 275 0 C. The isothermal oxidation of UO 2 to U 3 O 7 follows a parabolic form and the diffusion of oxygen through the product layer U 4 O 9 is the mechanism controlling the oxidation rate. The phases observed were UO 2 (cubic) - U 4 O 9 (cubic) - U 3 O 7 (tetragonal). Activation energies of oxidation were found for different crystallographic planes (hkl). From this one can conclude that there is a preferential occupation of interstitial oxygen within the UO 2 structure. (Author) [pt
Huschmann, Franziska U; Linnik, Janina; Sparta, Karine; Ühlein, Monika; Wang, Xiaojie; Metz, Alexander; Schiebel, Johannes; Heine, Andreas; Klebe, Gerhard; Weiss, Manfred S; Mueller, Uwe
2016-05-01
Crystallographic screening of the binding of small organic compounds (termed fragments) to proteins is increasingly important for medicinal chemistry-oriented drug discovery. To enable such experiments in a widespread manner, an affordable 96-compound library has been assembled for fragment screening in both academia and industry. The library is selected from already existing protein-ligand structures and is characterized by a broad ligand diversity, including buffer ingredients, carbohydrates, nucleotides, amino acids, peptide-like fragments and various drug-like organic compounds. When applied to the model protease endothiapepsin in a crystallographic screening experiment, a hit rate of nearly 10% was obtained. In comparison to other fragment libraries and considering that no pre-screening was performed, this hit rate is remarkably high. This demonstrates the general suitability of the selected compounds for an initial fragment-screening campaign. The library composition, experimental considerations and time requirements for a complete crystallographic fragment-screening campaign are discussed as well as the nine fully refined obtained endothiapepsin-fragment structures. While most of the fragments bind close to the catalytic centre of endothiapepsin in poses that have been observed previously, two fragments address new sites on the protein surface. ITC measurements show that the fragments bind to endothiapepsin with millimolar affinity.
Huschmann, Franziska U.; Linnik, Janina; Sparta, Karine; Ühlein, Monika; Wang, Xiaojie; Metz, Alexander; Schiebel, Johannes; Heine, Andreas; Klebe, Gerhard; Weiss, Manfred S.; Mueller, Uwe
2016-01-01
Crystallographic screening of the binding of small organic compounds (termed fragments) to proteins is increasingly important for medicinal chemistry-oriented drug discovery. To enable such experiments in a widespread manner, an affordable 96-compound library has been assembled for fragment screening in both academia and industry. The library is selected from already existing protein–ligand structures and is characterized by a broad ligand diversity, including buffer ingredients, carbohydrates, nucleotides, amino acids, peptide-like fragments and various drug-like organic compounds. When applied to the model protease endothiapepsin in a crystallographic screening experiment, a hit rate of nearly 10% was obtained. In comparison to other fragment libraries and considering that no pre-screening was performed, this hit rate is remarkably high. This demonstrates the general suitability of the selected compounds for an initial fragment-screening campaign. The library composition, experimental considerations and time requirements for a complete crystallographic fragment-screening campaign are discussed as well as the nine fully refined obtained endothiapepsin–fragment structures. While most of the fragments bind close to the catalytic centre of endothiapepsin in poses that have been observed previously, two fragments address new sites on the protein surface. ITC measurements show that the fragments bind to endothiapepsin with millimolar affinity. PMID:27139825
Origin of intragranular crystallographic misorientations in hot-dip Al-Zn-Si coatings
International Nuclear Information System (INIS)
Niederberger, Ch.; Michler, J.; Jacot, A.
2008-01-01
The origin of intragranular variations of the crystallographic orientation in hot-dip Al-Zn-Si coatings is discussed based on new experimental results and modelling. The solidification microstructure in as-received 55Al-43.4Zn-1.6Si (in wt.%) coatings deposited on steel plates in an industrial production line was analyzed by electron backscattered diffraction, glow-discharge optical emission spectroscopy and atomic force microscopy (AFM). The results were compared with those obtained in coatings re-solidified under different cooling and mechanical loading conditions. Continuous variations of the crystallographic orientation as large as 35 deg. were observed within individual grains of Al-Zn-Si, consistent with previous studies. However, the mechanisms previously proposed for the origin of intragranular crystallographic misorientations had to be revisited. The new experimental data acquired during this study indicate that the solidification shrinkage accumulating in the area of the grain envelope is the driving force for the formation of intragranular misorientations. The solidification shrinkage leads to the development of tensile stresses in the oxide film covering the coating while it solidifies. Estimations based on AFM profiles and phase field simulations of the dendritic structure indicate that the stresses applied on the dendrite network are sufficient to deform plastically the dendrite arms during solidification
Approximate and renormgroup symmetries
Energy Technology Data Exchange (ETDEWEB)
Ibragimov, Nail H. [Blekinge Institute of Technology, Karlskrona (Sweden). Dept. of Mathematics Science; Kovalev, Vladimir F. [Russian Academy of Sciences, Moscow (Russian Federation). Inst. of Mathematical Modeling
2009-07-01
''Approximate and Renormgroup Symmetries'' deals with approximate transformation groups, symmetries of integro-differential equations and renormgroup symmetries. It includes a concise and self-contained introduction to basic concepts and methods of Lie group analysis, and provides an easy-to-follow introduction to the theory of approximate transformation groups and symmetries of integro-differential equations. The book is designed for specialists in nonlinear physics - mathematicians and non-mathematicians - interested in methods of applied group analysis for investigating nonlinear problems in physical science and engineering. (orig.)
Non-Declarative Sequence Learning does not Show Savings in Relearning
Keisler, Aysha; Willingham, Daniel T.
2007-01-01
Researchers have utilized the savings in relearning paradigm in a variety of settings since Ebbinghaus developed the tool over a century ago. In spite of its widespread use, we do not yet understand what type(s) of memory are measurable by savings. Specifically, can savings measure both declarative and non-declarative memories? The lack of conscious recollection of the encoded material in some studies indicates that non-declarative memories may show savings effects, but as all studies to date...
International Nuclear Information System (INIS)
Zhang Yongde.
1987-03-01
In this paper, the neutron Dirac-equation is presented. After decoupling it into two equations of the simple spinors, the rigorous solution of this equation is obtained in the case of slab-like uniform magnetic fields at perpendicular incidence. At non-relativistic approximation and first order approximation of weak field (NRWFA), our results have included all results that have been obtained in references for this case up to now. The corresponding transformations of the neutron's spin vectors are given. The single particle spectrum and its approximate expression are obtained. The characteristics of quantum statistics with the approximate expression of energy spectrum are studied. (author). 15 refs
Synthesis, structure and magnetic properties of crystallographically aligned CuCr_2Se_4 thin films
International Nuclear Information System (INIS)
Esters, Marco; Liebig, Andreas; Ditto, Jeffrey J.; Falmbigl, Matthias; Albrecht, Manfred; Johnson, David C.
2016-01-01
We report the low temperature synthesis of highly textured CuCr_2Se_4 thin films using the modulated elemental reactant (MER) method. The structure of CuCr_2Se_4 is determined for the first time in its thin film form and exhibits cell parameters that are smaller than found in bulk CuCr_2Se_4. X-ray diffraction and precession electron diffraction show a strong degree of crystallographic alignment of the crystallites, where the axis is oriented perpendicular to the substrate surface, while being rotationally disordered within the plane. Temperature and field dependent in-plane and out-of-plane magnetization measurements show that the film is ferromagnetic with a Curie temperature of 406 K CuCr_2Se_4 synthesized utilizing the MER method shows stronger magnetic anisotropy (effective anisotropy: 1.82 × 10"6 erg cm"−"3; shape anisotropy: 1.07 × 10"6 erg cm"−"3), with the easy axis lying out of plane, and a larger magnetic moment (6 μ_B/f.u.) than bulk CuCr_2Se_4. - Highlights: • Crystallographically aligned, phase pure CuCr_2Se_4 were synthesized. • The degree of alignment decreases with annealing time. • The films are ferromagnetic with the easy axis along the direction. • The magnetization is larger than bulk CuCr_2Se_4 or other CuCr_2Se_4 films made to date.
Haghdadi, N.; Cizek, P.; Hodgson, P. D.; Tari, V.; Rohrer, G. S.; Beladi, H.
2018-05-01
The crystallography of interfaces in a duplex stainless steel having an equiaxed microstructure produced through the ferrite to austenite diffusive phase transformation has been studied. The five-parameter interface character distribution revealed a high anisotropy in habit planes for the austenite-ferrite and austenite-austenite interfaces for different lattice misorientations. The austenite and ferrite habit planes largely terminated on (1 1 1) and (1 1 0) planes, respectively, for the austenite-ferrite interfaces associated with Kurdjumov-Sachs (K-S) and Nishiyama-Wasserman (N-W) orientation relationships. This was mostly attributed to the crystallographic preference associated with the phase transformation. For the austenite-ferrite interfaces with orientation relationships which are neither K-S nor N-W, both austenite and ferrite habit planes had (1 1 1) orientations. Σ3 twin boundaries comprised the majority of austenite-austenite interfaces, mostly showing a pure twist character and terminating on (1 1 1) planes due to the minimum energy configuration. The second highest populated austenite-austenite boundary was Σ9, which tended to have grain boundary planes in the tilt zone due to the geometrical constraints. Furthermore, the intervariant crystallographic plane distribution associated with the K-S orientation relationship displayed a general tendency for the austenite habit planes to terminate with the (1 1 1) orientation, mainly due to the crystallographic preference associated with the phase transformation.
Potvin, Guy
2015-10-01
We examine how the Rytov approximation describing log-amplitude and phase fluctuations of a wave propagating through weak uniform turbulence can be generalized to the case of turbulence with a large-scale nonuniform component. We show how the large-scale refractive index field creates Fermat rays using the path integral formulation for paraxial propagation. We then show how the second-order derivatives of the Fermat ray action affect the Rytov approximation, and we discuss how a numerical algorithm would model the general Rytov approximation.
International Nuclear Information System (INIS)
Nakamura, Yasunori; Tam, Nguyen Ngoc; Ohata, Tomiso; Morita, Kiminori; Nakamachi, Eiji
2004-01-01
The crystallographic texture evolution induced by plastic deformation in the sheet metal forming process has a great influence on its formability. In the present study, a dynamic explicit finite element (FE) analysis code is newly developed by introducing a crystallographic homogenization method to estimate the polycrystalline sheet metal formability, such as the extreme thinning and 'earing'. This code can predict the plastic deformation induced texture evolution at the micro scale and the plastic anisotropy at the macro scale, simultaneously. This multi-scale analysis can couple the microscopic crystal plasticity inhomogeneous deformation with the macroscopic continuum deformation. In this homogenization process, the stress at the macro scale is defined by the volume average of those of the corresponding microscopic crystal aggregations in satisfying the equation of motion and compatibility condition in the micro scale 'unit cell', where the periodicity of deformation is satisfied. This homogenization algorithm is implemented in the conventional dynamic explicit finite element code by employing the updated Lagrangian formulation and the rate type elastic/viscoplastic constitutive equation.At first, it has been confirmed through a texture evolution analyses in cases of typical deformation modes that Taylor's 'constant strain homogenization algorithm' yields extreme concentration toward the preferred crystal orientations compared with our homogenization one. Second, we study the plastic anisotropy effects on 'earing' in the hemispherical cup deep drawing process of pure ferrite phase sheet metal. By the comparison of analytical results with those of Taylor's assumption, conclusions are drawn that the present newly developed dynamic explicit crystallographic homogenization FEM shows more reasonable prediction of plastic deformation induced texture evolution and plastic anisotropy at the macro scale
Crystallographic investigation of grain selection during initial solidification
International Nuclear Information System (INIS)
Esaka, H; Shinozuka, K; Kataoka, Y
2016-01-01
Normally, macroscopic solidified structure consists of chill, columnar and equiaxed zones. In a chill zone, many fine grains nucleate on the mold surface and grow their own preferred growth direction. Only a few of them continue to grow because of grain selection. In order to understand the grain selection process, crystallographic investigation has been carried out in the zone of initial solidification in this study. 10 g of Al-6 wt%Si alloy was melted at 850 °C and poured on the thick copper plate. Longitudinal cross section of the solidified shell was observed by a SEM and analyzed by EBSD. The result of EBSD mapping reveals that crystallographic orientation was random in the range of initial solidification. Further, some grains are elongated along their <100> direction. Columnar grains, whose growth directions are almost parallel to the heat flow direction, develop via grain selection. Here, a dendrite whose growth direction is close to the heat flow direction overgrows the other dendrite whose growth direction is far from the heat flow direction. However, sometimes we observed that dendrite, whose zenith angle is large, overgrew the other dendrite. It can be deduced that the time of nucleation on the mold surface is not constant. (paper)
Auxeticity of Yukawa Systems with Nanolayers in the (111 Crystallographic Plane
Directory of Open Access Journals (Sweden)
Paweł M. Pigłowski
2017-11-01
Full Text Available Elastic properties of model crystalline systems, in which the particles interact via the hard potential (infinite when any particles overlap and zero otherwise and the hard-core repulsive Yukawa interaction, were determined by Monte Carlo simulations. The influence of structural modifications, in the form of periodic nanolayers being perpendicular to the crystallographic axis [111], on auxetic properties of the crystal was investigated. It has been shown that the hard sphere nanolayers introduced into Yukawa crystals allow one to control the elastic properties of the system. It has been also found that the introduction of the Yukawa monolayers to the hard sphere crystal induces auxeticity in the [ 11 1 ¯ ] [ 112 ] -direction, while maintaining the negative Poisson’s ratio in the [ 110 ] [ 1 1 ¯ 0 ] -direction, thus expanding the partial auxeticity of the system to an additional important crystallographic direction.
Surface crystallographic structures of cellulose nanofiber films and overlayers of pentacene
Nakayama, Yasuo; Mori, Toshiaki; Tsuruta, Ryohei; Yamanaka, Soichiro; Yoshida, Koki; Imai, Kento; Koganezawa, Tomoyuki; Hosokai, Takuya
2018-03-01
Cellulose nanofibers or nanocellulose is a promising recently developed biomass and biodegradable material used for various applications. In order to utilize this material as a substrate in organic electronic devices, thorough understanding of the crystallographic structures of the surfaces of the nanocellulose composites and of their interfaces with organic semiconductor molecules is essential. In this work, surface crystallographic structures of nanocellulose films (NCFs) and overlayers of pentacene were investigated by two-dimensional grazing-incidence X-ray diffraction. The NCFs are found to crystallize on solid surfaces with the crystal lattice preserving the same structure of the known bulk phase, whereas distortion of interchain packing toward the surface normal direction is suggested. The pentacene overlayers on the NCFs are found to form the thin-film phase with an in-plane mean crystallite size of over 10 nm.
International Conference Approximation Theory XIV
Schumaker, Larry
2014-01-01
This volume developed from papers presented at the international conference Approximation Theory XIV, held April 7–10, 2013 in San Antonio, Texas. The proceedings contains surveys by invited speakers, covering topics such as splines on non-tensor-product meshes, Wachspress and mean value coordinates, curvelets and shearlets, barycentric interpolation, and polynomial approximation on spheres and balls. Other contributed papers address a variety of current topics in approximation theory, including eigenvalue sequences of positive integral operators, image registration, and support vector machines. This book will be of interest to mathematicians, engineers, and computer scientists working in approximation theory, computer-aided geometric design, numerical analysis, and related approximation areas.
The crystallographic space groups and Heterotic string theory
International Nuclear Information System (INIS)
El Naschie, M.S.
2009-01-01
While the 17 planar crystallographic groups were shown to correspond to 17 two and three Stein spaces with a total dimension equal to DimE12=5α-bar o ≅685, the present work reveals that the corresponding 219 three dimensional groups leads to a total dimensionality equal to N o ≅8872 which happens to be the exact total number of massless states of the transfinite version of Heterotic super string spectrum.
Towards automated crystallographic structure refinement with phenix.refine
Afonine, Pavel V.; Grosse-Kunstleve, Ralf W.; Echols, Nathaniel; Headd, Jeffrey J.; Moriarty, Nigel W.; Mustyakimov, Marat; Terwilliger, Thomas C.; Urzhumtsev, Alexandre; Zwart, Peter H.; Adams, Paul D.
2012-01-01
phenix.refine is a program within the PHENIX package that supports crystallographic structure refinement against experimental data with a wide range of upper resolution limits using a large repertoire of model parameterizations. It has several automation features and is also highly flexible. Several hundred parameters enable extensive customizations for complex use cases. Multiple user-defined refinement strategies can be applied to specific parts of the model in a single refinement run. An i...
Zeng, Lang; He, Yu; Povolotskyi, Michael; Liu, XiaoYan; Klimeck, Gerhard; Kubis, Tillmann
2013-06-01
In this work, the low rank approximation concept is extended to the non-equilibrium Green's function (NEGF) method to achieve a very efficient approximated algorithm for coherent and incoherent electron transport. This new method is applied to inelastic transport in various semiconductor nanodevices. Detailed benchmarks with exact NEGF solutions show (1) a very good agreement between approximated and exact NEGF results, (2) a significant reduction of the required memory, and (3) a large reduction of the computational time (a factor of speed up as high as 150 times is observed). A non-recursive solution of the inelastic NEGF transport equations of a 1000 nm long resistor on standard hardware illustrates nicely the capability of this new method.
Spectroscopic and crystallographic studies of YAG:Pr4+ single crystals
International Nuclear Information System (INIS)
Pawlak, D.; Frukacz, Z.; Mierczyk, Z.; Suchocki, A.; Zachara, J.
1998-01-01
Y 3 Al 5 O 12 single crystals doped with praseodymium and magnesium ions have been prepared. The reversible color change of this crystal is observed when annealing in oxidizing or reducing atmospheres. The change is ascribed to the formation of Pr 4+ in the as-grown crystal, caused by the second dopant, Mg 2+ . The absorption spectra of YAG:Pr,Mg in the range 200-1100 nm, as grown and annealed in air and H 2 /N 2 atmosphere, are presented and discussed. Additional broad absorption bands are observed for the as-grown crystals and those annealed in oxidizing atmosphere. Crystallographic investigations of the original crystal and after annealing in a reducing atmosphere as described above, show no distinct structural differences. A redox mechanism is proposed to explain the color change during annealing. (orig.)
International Nuclear Information System (INIS)
Klüser, Lars; Di Biagio, Claudia; Kleiber, Paul D.; Formenti, Paola; Grassian, Vicki H.
2016-01-01
Optical properties (extinction efficiency, single scattering albedo, asymmetry parameter and scattering phase function) of five different desert dust minerals have been calculated with an asymptotic approximation approach (AAA) for non-spherical particles. The AAA method combines Rayleigh-limit approximations with an asymptotic geometric optics solution in a simple and straightforward formulation. The simulated extinction spectra have been compared with classical Lorenz–Mie calculations as well as with laboratory measurements of dust extinction. This comparison has been done for single minerals and with bulk dust samples collected from desert environments. It is shown that the non-spherical asymptotic approximation improves the spectral extinction pattern, including position of the extinction peaks, compared to the Lorenz–Mie calculations for spherical particles. Squared correlation coefficients from the asymptotic approach range from 0.84 to 0.96 for the mineral components whereas the corresponding numbers for Lorenz–Mie simulations range from 0.54 to 0.85. Moreover the blue shift typically found in Lorenz–Mie results is not present in the AAA simulations. The comparison of spectra simulated with the AAA for different shape assumptions suggests that the differences mainly stem from the assumption of the particle shape and not from the formulation of the method itself. It has been shown that the choice of particle shape strongly impacts the quality of the simulations. Additionally, the comparison of simulated extinction spectra with bulk dust measurements indicates that within airborne dust the composition may be inhomogeneous over the range of dust particle sizes, making the calculation of reliable radiative properties of desert dust even more complex. - Highlights: • A fast and simple method for estimating optical properties of dust. • Can be used with non-spherical particles of arbitrary size distributions. • Comparison with Mie simulations and
DEFF Research Database (Denmark)
Patrick, Christopher; Thygesen, Kristian Sommer
2016-01-01
In non-self-consistent calculations of the total energy within the random-phase approximation (RPA) for electronic correlation, it is necessary to choose a single-particle Hamiltonian whose solutions are used to construct the electronic density and noninteracting response function. Here we...... investigate the effect of including a Hubbard-U term in this single-particle Hamiltonian, to better describe the on-site correlation of 3d electrons in the transitionmetal compounds ZnS, TiO2, and NiO.We find that the RPA lattice constants are essentially independent of U, despite large changes...... in the underlying electronic structure. We further demonstrate that the non-selfconsistent RPA total energies of these materials have minima at nonzero U. Our RPA calculations find the rutile phase of TiO2 to be more stable than anatase independent of U, a result which is consistent with experiments...
A preliminary neutron crystallographic study of proteinase K at pD 6.5
Energy Technology Data Exchange (ETDEWEB)
Gardberg, Anna S [ORNL; Blakeley, Matthew P. [Institut Laue-Langevin (ILL); Myles, Dean A A [ORNL
2009-01-01
AbstractA preliminary neutron crystallographic study of the proteolytic enzyme proteinase K is presented. Large hydrogenated crystals were prepared in deuterated crystallization buffer using the vapour-diffusion method. Data were collected to a resolution of 2.3 on the LADI-III diffractometer at the Institut Laue Langevin (ILL) in 2.5 days. The results demonstrate the feasibility of a full neutron crystallographic analysis of this structure aimed at providing relevant information on the location of H atoms, particularly at the active site. This information will contribute to further understanding of the molecular mechanisms underlying proteinase K's catalytic activity and to an enriched understanding of the subtilisin clan of serine proteases.
Towards automated crystallographic structure refinement with phenix.refine
Energy Technology Data Exchange (ETDEWEB)
Afonine, Pavel V., E-mail: pafonine@lbl.gov; Grosse-Kunstleve, Ralf W.; Echols, Nathaniel; Headd, Jeffrey J.; Moriarty, Nigel W. [Lawrence Berkeley National Laboratory, One Cyclotron Road, MS64R0121, Berkeley, CA 94720 (United States); Mustyakimov, Marat; Terwilliger, Thomas C. [Los Alamos National Laboratory, M888, Los Alamos, NM 87545 (United States); Urzhumtsev, Alexandre [CNRS–INSERM–UdS, 1 Rue Laurent Fries, BP 10142, 67404 Illkirch (France); Université Henri Poincaré, Nancy 1, BP 239, 54506 Vandoeuvre-lès-Nancy (France); Zwart, Peter H. [Lawrence Berkeley National Laboratory, One Cyclotron Road, MS64R0121, Berkeley, CA 94720 (United States); Adams, Paul D. [Lawrence Berkeley National Laboratory, One Cyclotron Road, MS64R0121, Berkeley, CA 94720 (United States); University of California Berkeley, Berkeley, CA 94720 (United States)
2012-04-01
phenix.refine is a program within the PHENIX package that supports crystallographic structure refinement against experimental data with a wide range of upper resolution limits using a large repertoire of model parameterizations. This paper presents an overview of the major phenix.refine features, with extensive literature references for readers interested in more detailed discussions of the methods. phenix.refine is a program within the PHENIX package that supports crystallographic structure refinement against experimental data with a wide range of upper resolution limits using a large repertoire of model parameterizations. It has several automation features and is also highly flexible. Several hundred parameters enable extensive customizations for complex use cases. Multiple user-defined refinement strategies can be applied to specific parts of the model in a single refinement run. An intuitive graphical user interface is available to guide novice users and to assist advanced users in managing refinement projects. X-ray or neutron diffraction data can be used separately or jointly in refinement. phenix.refine is tightly integrated into the PHENIX suite, where it serves as a critical component in automated model building, final structure refinement, structure validation and deposition to the wwPDB. This paper presents an overview of the major phenix.refine features, with extensive literature references for readers interested in more detailed discussions of the methods.
Non-specific Inflammatory Disease Showed Abnormal FDG Uptake in Lower Extremities
International Nuclear Information System (INIS)
Chun, Kyung Ah; Kong, Eun Jung; Cho, Ihn Ho; Hong, Young Hoon; Lee, Choong Ki
2008-01-01
Including malignancy, various disease can show abnormal uptake in bone marrow. 1,2) We report a case of non-specific inflammatory FDG uptake in bone marrow mimicking malignancy. A 35-year old woman with fever of unknown origin (FUO) underwent 18 F-FDG PET/CT to find out fever focus and unknown malignancy. 18 F-FDG was injected and imaged 1hr after injection with Discovery ST (GE, USA). 18 F-FDG PET/CT whole body image showed abnormal uptake in lower extremities. MRI and biopsy was also done in the sites of abnormal uptake. PET and MRI suspect malignancy, but biopsy result was non-specific inflammatory process. The patient was improved her clinical condition after antibiotics therapy
CRYSTMET—The NRCC Metals Crystallographic Data File
Wood, Gordon H.; Rodgers, John R.; Gough, S. Roger; Villars, Pierre
1996-01-01
CRYSTMET is a computer-readable database of critically evaluated crystallographic data for metals (including alloys, intermetallics and minerals) accompanied by pertinent chemical, physical and bibliographic information. It currently contains about 60 000 entries and covers the literature exhaustively from 1913. Scientific editing of the abstracted entries, consisting of numerous automated and manual checks, is done to ensure consistency with related, previously published studies, to assign structure types where necessary and to help guarantee the accuracy of the data and related information. Analyses of the entries and their distribution across key journals as a function of time show interesting trends in the complexity of the compounds studied as well as in the elements they contain. Two applications of CRYSTMET are the identification of unknowns and the prediction of properties of materials. CRYSTMET is available either online or via license of a private copy from the Canadian Scientific Numeric Database Service (CAN/SND). The indexed online search and analysis system is easy and economical to use yet fast and powerful. Development of a new system is under way combining the capabilities of ORACLE with the flexibility of a modern interface based on the Netscape browsing tool. PMID:27805157
Approximate symmetries of Hamiltonians
Chubb, Christopher T.; Flammia, Steven T.
2017-08-01
We explore the relationship between approximate symmetries of a gapped Hamiltonian and the structure of its ground space. We start by considering approximate symmetry operators, defined as unitary operators whose commutators with the Hamiltonian have norms that are sufficiently small. We show that when approximate symmetry operators can be restricted to the ground space while approximately preserving certain mutual commutation relations. We generalize the Stone-von Neumann theorem to matrices that approximately satisfy the canonical (Heisenberg-Weyl-type) commutation relations and use this to show that approximate symmetry operators can certify the degeneracy of the ground space even though they only approximately form a group. Importantly, the notions of "approximate" and "small" are all independent of the dimension of the ambient Hilbert space and depend only on the degeneracy in the ground space. Our analysis additionally holds for any gapped band of sufficiently small width in the excited spectrum of the Hamiltonian, and we discuss applications of these ideas to topological quantum phases of matter and topological quantum error correcting codes. Finally, in our analysis, we also provide an exponential improvement upon bounds concerning the existence of shared approximate eigenvectors of approximately commuting operators under an added normality constraint, which may be of independent interest.
International Nuclear Information System (INIS)
Hermida, J.D.; Pochettino, A.A.
1982-01-01
The theoretical fundaments of the Distribution Function of Crystalline Orientations (DFCO) are described and this method is compared with the usual description of the crystallographic texture by direct pole figures. Such function is applied to the study of a Zry-4 sample obtained from a tube belonging to a CANDU type fuel element. The DFCO is obtained from the pole figures (0002), (101-bar0) and (101-bar1). The results show the existence of six fundamental components of texture, which are enunciated below, in decreasing order of importance: (2-bar115) ; (3-bar128) ; (1-bar013) ; (2-bar114) ; (0001) ; (0001) . A much more complete view of the crystals' orientation state of such sample can be obtained by analyzing the weight and the distribution of the different components. (M.E.L.) [es
Dai, Gaole
2015-01-01
Two soluble and stable dianthraceno[a,e]pentalenes with two (DAP1) and six (DAP2) phenyl substituents were synthesized. Both compounds possess a small energy band gap and show amphoteric redox behaviour due to intramolecular donor-accepter interactions. X-ray crystallographic analysis revealed that DAP2 has a closely packed structure with multi-dimensional [C-H⋯π] interactions although there are no π-π interactions between the dianthraceno[a,e]pentalene cores. As a result, solution-processed field effect transistors based on DAP2 exhibited an average hole mobility of 0.65 cm2 V-1 s-1. Under similar conditions, DAP1 showed an average field effect hole mobility of 0.001 cm2 V-1 s-1. This journal is
Crystallographic study of grain refinement in aluminum alloys using the edge-to-edge matching model
International Nuclear Information System (INIS)
Zhang, M.-X.; Kelly, P.M.; Easton, M.A.; Taylor, J.A.
2005-01-01
The edge-to-edge matching model for describing the interfacial crystallographic characteristics between two phases that are related by reproducible orientation relationships has been applied to the typical grain refiners in aluminum alloys. Excellent atomic matching between Al 3 Ti nucleating substrates, known to be effective nucleation sites for primary Al, and the Al matrix in both close packed directions and close packed planes containing these directions have been identified. The crystallographic features of the grain refiner and the Al matrix are very consistent with the edge-to-edge matching model. For three other typical grain refiners for Al alloys, TiC (when a = 0.4328 nm), TiB 2 and AlB 2 , the matching only occurs between the close packed directions in both phases and between the second close packed plane of the Al matrix and the second close packed plane of the refiners. According to the model, it is predicted that Al 3 Ti is a more powerful nucleating substrate for Al alloy than TiC, TiB 2 and AlB 2 . This agrees with the previous experimental results. The present work shows that the edge-to-edge matching model has the potential to be a powerful tool in discovering new and more powerful grain refiners for Al alloys
International Nuclear Information System (INIS)
Huynh, Frederick; Tan, Tien-Chye; Swaminathan, Kunchithapadam; Patel, Bharat K. C.
2004-01-01
The first crystallographic study of a sucrose phosphate synthase from H. orenii, an organism that is both thermophilic and halophilic, is reported. The protein crystal diffracts X-rays to 3.01 Å. This is the first report of the crystallization of a sucrose phosphate synthase (SPS; EC 2.4.1.14). It also constitutes the first study of a sucrose phosphate synthase from a non-photosynthetic thermohalophilic anaerobic bacterium, Halothermothrix orenii. The purified recombinant spsA protein has been crystallized in the monoclinic space group C2, with unit-cell parameters a = 154.2, b = 47.9, c = 72.3 Å, β = 103.16°, using the hanging-drop vapour-diffusion method. The crystal diffracts X-rays to a resolution limit of 3.01 Å. Heavy-metal and halide-soaking trials are currently in progress to solve the structure
International Nuclear Information System (INIS)
Costa, M.A.F.; Magalhaes, R.D.; Nagem, R.A.P.; Ferreira-Junior, J.R.; Barros, M.H.
2012-01-01
Full text: Ubiquinone is a molecule that functions as an electron carrier in the respiratory chain in living organisms. Some clinical phenotypes, including, encephalomyopathy, has been associated with ubiquinone deficiency, raising the interest in the biosynthetic pathway of this molecule. This pathway was proposed mainly from the results of the genetic analysis of mutants of E. coli. UbiG is a methyltransferase involved in ubiquinone biosynthesis in E. coli. In this work we have cloned, expressed, purified and made initial crystallographic assessments of UbiG for later determination of its three-dimensional structure. The gene encoding UbiG was amplified from E. coli genomic DNA by polymerase chain reaction. The 753 bases pairs amplicon was inserted into the expression plasmid pMCSG7 by ligation independent cloning system and transformed into BL21(DE3) E. coli strain. The expression of UbiG, verified by SDS polyacrylamide gel, showed a protein of approximately 29kDa after IPTG induction. The recombinant UbiG, in the soluble fraction of the cellular lysate, was purified by affinity chromatography and the molecular weight of recombinant UbiG of approximately 29 kDa was confirmed by mass spectrometry. After removal of His-tag by TEV protease, another affinity chromatography was performed and UbiG, without His-tag, was observed in flow-through fraction. In Size-Exclusion Chromatography (SEC), the recombinant UbiG showed a unique peak with correct molecular weight of a monomer. Analysis of CD indicated that recombinant UbiG has 31,80% of alpha helix at 20 deg C and DLS showed that 70.9% of the sample is still monomeric in solution even five days after purification. Initial crystallization studies were performed with Crystal Screen 1 and Crystal Screen 2 from Hampton Research. Needle-shaped microcrystals of UbiG were obtained using a precipitant solution consisting of 0,1M lithium sulfate, 0,1M Tris pH 7,5 and 30% w/v polyethylene glycol 4,000. (author)
Energy Technology Data Exchange (ETDEWEB)
Costa, M.A.F.; Magalhaes, R.D.; Nagem, R.A.P. [Universidade Federal de Minas Gerais (UFMG), Belo Horizonte, MG (Brazil); Ferreira-Junior, J.R.; Barros, M.H. [Universidade de Sao Paulo (USP), SP (Brazil)
2012-07-01
Full text: Ubiquinone is a molecule that functions as an electron carrier in the respiratory chain in living organisms. Some clinical phenotypes, including, encephalomyopathy, has been associated with ubiquinone deficiency, raising the interest in the biosynthetic pathway of this molecule. This pathway was proposed mainly from the results of the genetic analysis of mutants of E. coli. UbiG is a methyltransferase involved in ubiquinone biosynthesis in E. coli. In this work we have cloned, expressed, purified and made initial crystallographic assessments of UbiG for later determination of its three-dimensional structure. The gene encoding UbiG was amplified from E. coli genomic DNA by polymerase chain reaction. The 753 bases pairs amplicon was inserted into the expression plasmid pMCSG7 by ligation independent cloning system and transformed into BL21(DE3) E. coli strain. The expression of UbiG, verified by SDS polyacrylamide gel, showed a protein of approximately 29kDa after IPTG induction. The recombinant UbiG, in the soluble fraction of the cellular lysate, was purified by affinity chromatography and the molecular weight of recombinant UbiG of approximately 29 kDa was confirmed by mass spectrometry. After removal of His-tag by TEV protease, another affinity chromatography was performed and UbiG, without His-tag, was observed in flow-through fraction. In Size-Exclusion Chromatography (SEC), the recombinant UbiG showed a unique peak with correct molecular weight of a monomer. Analysis of CD indicated that recombinant UbiG has 31,80% of alpha helix at 20 deg C and DLS showed that 70.9% of the sample is still monomeric in solution even five days after purification. Initial crystallization studies were performed with Crystal Screen 1 and Crystal Screen 2 from Hampton Research. Needle-shaped microcrystals of UbiG were obtained using a precipitant solution consisting of 0,1M lithium sulfate, 0,1M Tris pH 7,5 and 30% w/v polyethylene glycol 4,000. (author)
International Nuclear Information System (INIS)
Zhang, Yanfei; Cherney, Maia M.; Solomonson, Matthew; Liu, Jianshe; James, Michael N. G.; Weiner, Joel H.
2009-01-01
The sulfide:quinone oxidoreductase from A. ferrooxidans ATCC 23270 was overexpressed in E. coli and purified. Crystallization and preliminarily X-ray crystallographic analysis were performed for the recombinant enzyme. The gene product of open reading frame AFE-1293 from Acidithiobacillus ferrooxidans ATCC 23270 is annotated as encoding a sulfide:quinone oxidoreductase, an enzyme that catalyses electron transfer from sulfide to quinone. Following overexpression in Escherichia coli, the enzyme was purified and crystallized using the hanging-drop vapour-diffusion method. The native crystals belonged to the tetragonal space group P4 2 2 1 2, with unit-cell parameters a = b = 131.7, c = 208.8 Å, and diffracted to 2.3 Å resolution. Preliminary crystallographic analysis indicated the presence of a dimer in the asymmetric unit, with an extreme value of the Matthews coefficient (V M ) of 4.53 Å 3 Da −1 and a solvent content of 72.9%
Elasto-plastic stress/strain at notches, comparison of test and approximative computations
International Nuclear Information System (INIS)
Beste, A.; Seeger, T.
1979-01-01
The lifetime of cyclically loaded components is decisively determined by the value of the local load in the notch root. The determination of the elasto-plastic notch-stress and-strain is therefore an important element of recent methods of lifetime determination. These local loads are normally calculated with the help of approximation formulas. Yet there are no details about their accuracy. The basic construction of the approximation formulas is presented, along with some particulars. The use of approximations within the fully plastic range and for material laws which show a non-linear stress-strain (sigma-epsilon-)-behaviour from the beginning is explained. The use of approximation for cyclic loads is particularly discussed. Finally, the approximations are evaluated in terms of their exactness. The test results are compared with the results of the approximation calculations. (orig.) 891 RW/orig. 892 RKD [de
Chigvintsev, A. Yu; Zorina, I. G.; Noginova, L. Yu; Iosilevskiy, I. L.
2018-01-01
Impressive appearance of discontinuities in equilibrium spatial charge profiles in non-uniform Coulomb systems is under discussions in wide number of thermoelectrostatics problems. Such discontinuities are considered as peculiar micro-level manifestation of phase transitions and intrinsic macro-level non-ideality effects in local equation of state (EOS), which should be used for description of non-ideal ionic subsystem in frames of local-density (or “pseudofluid”, or “jellium” etc) approximation. Such discontinuities were discussed already by the authors for electronic subsystems. Special emphasis is made in present paper on the mentioned above non-ideality effects in non-uniform ionic subsystems, such as micro-ions profile within screening “cloud” around macro-ion in complex (dusty, colloid etc) plasmas, equilibrium charge profile in ionic traps or (and) in the neighborhood vicinity of “charged wall” etc). Multiphase EOS for simplified ionic model of classical charged hard spheres on uniformly compressible electrostatic compensating background was constructed and several illustrative examples of discussed discontinuous ionic profiles were calculated.
Directory of Open Access Journals (Sweden)
Dhaundiyal Alok
2017-12-01
Full Text Available This paper describes the influence of some parameters significant to biomass pyrolysis on the numerical solutions of the non-isothermal nth order distributed activation energy model (DAEM using the Gamma distribution and discusses the special case for the positive integer value of the scale parameter (λ, i.e. the Erlang distribution. Investigated parameters are the integral upper limit, the frequency factor, the heating rate, the reaction order, and the shape and rate parameters of the Gamma distribution. Influence of these parameters has been considered for the determination of the kinetic parameters of the non-isothermal nth order Gamma distribution from the experimentally derived thermoanalytical data of biomass pyrolysis. Mathematically, the effect of parameters on numerical solution is also used for predicting the behaviour of the unpyrolysized fraction of biomass with respect to temperature. Analysis of the mathematical model is based upon asymptotic expansions, which leads to the systematic methods for efficient way to determine the accurate approximations. The proposed method, therefore, provides a rapid and highly effective way for estimating the kinetic parameters and the distribution of activation energies.
Operator approximant problems arising from quantum theory
Maher, Philip J
2017-01-01
This book offers an account of a number of aspects of operator theory, mainly developed since the 1980s, whose problems have their roots in quantum theory. The research presented is in non-commutative operator approximation theory or, to use Halmos' terminology, in operator approximants. Focusing on the concept of approximants, this self-contained book is suitable for graduate courses.
Wallace, Nathan D; Ceguerra, Anna V; Breen, Andrew J; Ringer, Simon P
2018-06-01
Atom probe tomography is a powerful microscopy technique capable of reconstructing the 3D position and chemical identity of millions of atoms within engineering materials, at the atomic level. Crystallographic information contained within the data is particularly valuable for the purposes of reconstruction calibration and grain boundary analysis. Typically, analysing this data is a manual, time-consuming and error prone process. In many cases, the crystallographic signal is so weak that it is difficult to detect at all. In this study, a new automated signal processing methodology is demonstrated. We use the affine properties of the detector coordinate space, or the 'detector stack', as the basis for our calculations. The methodological framework and the visualisation tools are shown to be superior to the standard method of crystallographic pole visualisation directly from field evaporation images and there is no requirement for iterations between a full real-space initial tomographic reconstruction and the detector stack. The mapping approaches are demonstrated for aluminium, tungsten, magnesium and molybdenum. Implications for reconstruction calibration, accuracy of crystallographic measurements, reliability and repeatability are discussed. Copyright © 2018 Elsevier B.V. All rights reserved.
Arias-González, Felipe; del Val, Jesús; Comesaña, Rafael; Penide, Joaquín; Lusquiños, Fernando; Quintero, Félix; Riveiro, Antonio; Boutinguiza, Mohamed; Gil, Francisco Javier; Pou, Juan
2018-01-01
In this paper, the microstructure and crystallographic texture of pure Ti thin walls generated by Additive Manufacturing based on Laser Cladding (AMLC) are analyzed in depth. From the results obtained, it is possible to better understand the AMLC process of pure titanium. The microstructure observed in the samples consists of large elongated columnar prior β grains which have grown epitaxially from the substrate to the top, in parallel to the building direction. Within the prior β grains, α-Ti lamellae and lamellar colonies are the result of cooling from above the β-transus temperature. This transformation follows the Burgers relationship and the result is a basket-weave microstructure with a strong crystallographic texture. Finally, a thermal treatment is proposed to transform the microstructure of the as-deposited samples into an equiaxed microstructure of α-Ti grains.
Mice lacking hippocampal left-right asymmetry show non-spatial learning deficits.
Shimbo, Akihiro; Kosaki, Yutaka; Ito, Isao; Watanabe, Shigeru
2018-01-15
Left-right asymmetry is known to exist at several anatomical levels in the brain and recent studies have provided further evidence to show that it also exists at a molecular level in the hippocampal CA3-CA1 circuit. The distribution of N-methyl-d-aspartate (NMDA) receptor NR2B subunits in the apical and basal synapses of CA1 pyramidal neurons is asymmetrical if the input arrives from the left or right CA3 pyramidal neurons. In the present study, we examined the role of hippocampal asymmetry in cognitive function using β2-microglobulin knock-out (β2m KO) mice, which lack hippocampal asymmetry. We tested β2m KO mice in a series of spatial and non-spatial learning tasks and compared the performances of β2m KO and C57BL6/J wild-type (WT) mice. The β2m KO mice appeared normal in both spatial reference memory and spatial working memory tasks but they took more time than WT mice in learning the two non-spatial learning tasks (i.e., a differential reinforcement of lower rates of behavior (DRL) task and a straight runway task). The β2m KO mice also showed less precision in their response timing in the DRL task and showed weaker spontaneous recovery during extinction in the straight runway task. These results indicate that hippocampal asymmetry is important for certain characteristics of non-spatial learning. Copyright © 2017 Elsevier B.V. All rights reserved.
International Nuclear Information System (INIS)
Timokhov, D. F.; Timokhov, F. P.
2009-01-01
Possible ways for increasing the photoluminescence quantum yield of porous silicon layers have been investigated. The effect of the anodization parameters on the photoluminescence properties for porous silicon layers formed on silicon substrates with different crystallographic orientations was studied. The average diameters for silicon nanoclusters are calculated from the photoluminescence spectra of porous silicon. The influence of the substrate crystallographic orientation on the photoluminescence quantum yield of porous silicon is revealed. A model explaining the effect of the substrate orientation on the photoluminescence properties for the porous silicon layers formed by anode electrochemical etching is proposed.
The Almost Periodic Rigidity of Crystallographic Bar-Joint Frameworks
Directory of Open Access Journals (Sweden)
Ghada Badri
2014-04-01
Full Text Available A crystallographic bar-joint framework, C in Rd, is shown to be almost periodically infinitesimally rigid if and only if it is strictly periodically infinitesimally rigid and the rigid unit mode (RUM spectrum, Ω (C, is a singleton. Moreover, the almost periodic infinitesimal flexes of C are characterised in terms of a matrix-valued function, ΦC(z, on the d-torus, Td, determined by a full rank translation symmetry group and an associated motif of joints and bars.
Directory of Open Access Journals (Sweden)
David Heimann
2007-08-01
Full Text Available In supply chains, domestic and global, a producer must decide on an optimal quantity of items to order from suppliers and at what inventory level to place this order (the EOQ problem. We discuss how to modify the EOQ in the face of failures and recoveries by the supplier. This is the EOQ with disruption problem (EOQD. The supplier makes transitions between being capable and not being capable of filling an order in a Markov failure and recovery process. The producer adjusts the reorder point and the inventories to provide a margin of safety. Numerical solutions to the EOQD problem have been developed. In addition, a closed-form approximate solution has been developed for the zero inventory option (ZIO, where the inventory level on reordering is set to be zero. This paper develops a closed-form approximate solution for the EOQD problem when the reorder point can be non-zero, obtaining for that situation an optimal reorder quantity and optimal reorder point that represents an improvement on the optimal ZIO solution. The paper also supplies numerical examples demonstrating the cost savings against the ZIO situation, as well as the accuracy of the approximation technique.
Energy Technology Data Exchange (ETDEWEB)
Esters, Marco [Department of Chemistry, University of Oregon, Eugene, OR 97403 (United States); Liebig, Andreas [Institut für Physik, Universität Augsburg, 86159 Augsburg (Germany); Ditto, Jeffrey J.; Falmbigl, Matthias [Department of Chemistry, University of Oregon, Eugene, OR 97403 (United States); Albrecht, Manfred [Institut für Physik, Universität Augsburg, 86159 Augsburg (Germany); Johnson, David C., E-mail: davej@uoregon.edu [Department of Chemistry, University of Oregon, Eugene, OR 97403 (United States)
2016-06-25
We report the low temperature synthesis of highly textured CuCr{sub 2}Se{sub 4} thin films using the modulated elemental reactant (MER) method. The structure of CuCr{sub 2}Se{sub 4} is determined for the first time in its thin film form and exhibits cell parameters that are smaller than found in bulk CuCr{sub 2}Se{sub 4}. X-ray diffraction and precession electron diffraction show a strong degree of crystallographic alignment of the crystallites, where the <111> axis is oriented perpendicular to the substrate surface, while being rotationally disordered within the plane. Temperature and field dependent in-plane and out-of-plane magnetization measurements show that the film is ferromagnetic with a Curie temperature of 406 K CuCr{sub 2}Se{sub 4} synthesized utilizing the MER method shows stronger magnetic anisotropy (effective anisotropy: 1.82 × 10{sup 6} erg cm{sup −3}; shape anisotropy: 1.07 × 10{sup 6} erg cm{sup −3}), with the easy axis lying out of plane, and a larger magnetic moment (6 μ{sub B}/f.u.) than bulk CuCr{sub 2}Se{sub 4}. - Highlights: • Crystallographically aligned, phase pure CuCr{sub 2}Se{sub 4} were synthesized. • The degree of alignment decreases with annealing time. • The films are ferromagnetic with the easy axis along the <111> direction. • The magnetization is larger than bulk CuCr{sub 2}Se{sub 4} or other CuCr{sub 2}Se{sub 4} films made to date.
Effect of pre-existing crystallographic preferred orientation on the rheology of Carrara marble
de Raadt, W.S.; Burlini, L.; Kunze, K.; Spiers, C.J.
2014-01-01
Abstract Localized deformation during high temperature plastic flow is frequently attributed to mechanical weakening caused by grain size reduction and, in some cases, by the development of a crystallographic preferred orientation (CPO). This study aims to investigate experimentally the contribution
Approximate cohomology in Banach algebras | Pourabbas ...
African Journals Online (AJOL)
We introduce the notions of approximate cohomology and approximate homotopy in Banach algebras and we study the relation between them. We show that the approximate homotopically equivalent cochain complexes give the same approximate cohomologies. As a special case, approximate Hochschild cohomology is ...
Bhowmick, Amiya Ranjan; Bandyopadhyay, Subhadip; Rana, Sourav; Bhattacharya, Sabyasachi
2016-01-01
The stochastic versions of the logistic and extended logistic growth models are applied successfully to explain many real-life population dynamics and share a central body of literature in stochastic modeling of ecological systems. To understand the randomness in the population dynamics of the underlying processes completely, it is important to have a clear idea about the quasi-equilibrium distribution and its moments. Bartlett et al. (1960) took a pioneering attempt for estimating the moments of the quasi-equilibrium distribution of the stochastic logistic model. Matis and Kiffe (1996) obtain a set of more accurate and elegant approximations for the mean, variance and skewness of the quasi-equilibrium distribution of the same model using cumulant truncation method. The method is extended for stochastic power law logistic family by the same and several other authors (Nasell, 2003; Singh and Hespanha, 2007). Cumulant truncation and some alternative methods e.g. saddle point approximation, derivative matching approach can be applied if the powers involved in the extended logistic set up are integers, although plenty of evidence is available for non-integer powers in many practical situations (Sibly et al., 2005). In this paper, we develop a set of new approximations for mean, variance and skewness of the quasi-equilibrium distribution under more general family of growth curves, which is applicable for both integer and non-integer powers. The deterministic counterpart of this family of models captures both monotonic and non-monotonic behavior of the per capita growth rate, of which theta-logistic is a special case. The approximations accurately estimate the first three order moments of the quasi-equilibrium distribution. The proposed method is illustrated with simulated data and real data from global population dynamics database. Copyright © 2015 Elsevier Inc. All rights reserved.
Self-similar factor approximants
International Nuclear Information System (INIS)
Gluzman, S.; Yukalov, V.I.; Sornette, D.
2003-01-01
The problem of reconstructing functions from their asymptotic expansions in powers of a small variable is addressed by deriving an improved type of approximants. The derivation is based on the self-similar approximation theory, which presents the passage from one approximant to another as the motion realized by a dynamical system with the property of group self-similarity. The derived approximants, because of their form, are called self-similar factor approximants. These complement the obtained earlier self-similar exponential approximants and self-similar root approximants. The specific feature of self-similar factor approximants is that their control functions, providing convergence of the computational algorithm, are completely defined from the accuracy-through-order conditions. These approximants contain the Pade approximants as a particular case, and in some limit they can be reduced to the self-similar exponential approximants previously introduced by two of us. It is proved that the self-similar factor approximants are able to reproduce exactly a wide class of functions, which include a variety of nonalgebraic functions. For other functions, not pertaining to this exactly reproducible class, the factor approximants provide very accurate approximations, whose accuracy surpasses significantly that of the most accurate Pade approximants. This is illustrated by a number of examples showing the generality and accuracy of the factor approximants even when conventional techniques meet serious difficulties
Ting, Tan Yee; Idrus, Nor'ashiqin Mohd.; Masri, Rohaidah; Sarmin, Nor Haniza; Hassim, Hazzirah Izzati Mat
2014-06-01
Torsion free crystallographic groups, called Bieberbach groups, appear as fundamental groups of compact, connected, flat Riemannian manifolds and have many interesting properties. New properties of the group can be obtained by, not limited to, exploring the groups and by computing their homological functors such as nonabelian tensor squares, the central subgroup of nonabelian tensor squares, the kernel of the mapping of nonabelian tensor squares of a group to the group and many more. In this paper, the homological functor, J(G) of a centerless torsion free crystallographic group of dimension five with a nonabelian point group which is a dihedral point group is computed using commutator calculus.
Effect of metallurgical factors on the bulk magnetic properties of non-oriented electrical steels
Energy Technology Data Exchange (ETDEWEB)
Ghosh, Pampa, E-mail: pampaghosh@gmail.com [Department of Mining and Materials Engineering, McGill University, 3610 University Street, Montreal, Que., Canada H3A 0C5 (Canada); Chromik, Richard R., E-mail: richard.chromik@mcgill.ca [Department of Mining and Materials Engineering, McGill University, 3610 University Street, Montreal, Que., Canada H3A 0C5 (Canada); Knight, Andrew M. [Department of Electrical and Computer Engineering, University of Alberta, Edmonton, Alta., Canada T6G 2V4 (Canada); Wakade, Shekhar G. [GM Powertrain, General Motors Company, 823 Joslyn Avenue, Building B, 4AJ35, Pontiac, MI 48340-2920 (United States)
2014-04-01
Non-oriented electrical steel (NOES) is one of the most common material used in electrical motors. Core loss and permeability are the most important properties that the motor manufacturers look for. Both these properties are structure sensitive and depend on several metallurgical factors; such as chemistry, grain size, crystallographic texture, cleanliness and stress states in non-oriented electrical steels. It has been observed in this course of the study that the grain size and Si content of NOES are the primary controlling factors to core loss, especially at higher frequencies. On the contrary, crystallographic texture plays an important role at lower frequencies. At higher frequency, core loss increases with increasing grain size and decreasing Si content of the steels. Small difference in grain size (∼50 μm) at lower frequency range has little influence on the magnetic properties but has significant adverse effect as frequency reaches high enough. - Highlights: • Magnetic properties of a set of electrical steels were measured. • Crystallographic texture, chemistry and grain size were studied for their effects on core loss and permeability. • Structure–magnetic property relationships were identified for the electrical steels.
International Nuclear Information System (INIS)
Effenberg, Guenter; Ilyenko, Svitlana; Aldinger, Fritz; Bochvar, Nataliya; Cacciamani, Gabriele
2007-01-01
The present volume in the New Series of Landolt-Boernstein provides critically evaluated data on phase diagrams, crystallographic and thermodynamic data of ternary alloy systems. Reliable phase diagrams provide materials scientists and engineers with basic information important for fundamental research, development and optimization of materials. The often conflicting literature data have been critically evaluated by Materials Science International Team, MSIT registered , a team working together since many years, and with expertise in a broad range of methods, materials and applications. All evaluation reports published here have undergone a thorough review process in which the reviewers had access to all the original data. The data for each ternary system are provided in a standard format which includes text, tables and diagrams. The topics presented are literature data, binary systems, solid phases, pseudobinary systems, invariant equilibria, liquidus, solidus, and solvus surfaces, isothermal sections, temperature-composition sections, thermodynamics, materials properties and applications, and miscellanea. Finally, a detailed bibliography of all cited references is provided. In the present volume IV/11C selected non-ferrous-metal systems are considered, especially selected nuclear materials and engineering systems in this Part 4. (orig.)
Fano-Agarwal couplings and non-rotating wave approximation in single-photon timed Dicke subradiance
Mirza, Imran M.; Begzjav, Tuguldur
2016-04-01
Recently a new class of single-photon timed Dicke (TD) subradiant states has been introduced with possible applications in single-photon-based quantum information storage and on demand ultrafast retrieval (Scully M. O., Phys. Rev. Lett., 115 (2015) 243602). However, the influence of any kind of virtual processes on the decay of these new kind of subradiant states has been left as an open question. In the present paper, we focus on this problem in detail. In particular, we investigate how pure Fano-Agarwal couplings and other virtual processes arising from non-rotating wave approximation impact the decay of otherwise sub- and superradiant states. In addition to the overall virtual couplings among all TD states, we also focus on the dominant role played by the couplings between specific TD states.
Determination of lower bound crystallographic yield loci of zircaloy-4 tubes
International Nuclear Information System (INIS)
Costa Viana, C.S. da
1980-01-01
The use of zircaloy-4 tubing in fuel elements of water cooled reactors is discussed with respect to its mechanisms of deformation and also its resulting anisotropic plastic behaviour. A method for obtaining lower bound crystallographic yield loci of α-Zr is presented and applied to individual crystal orientations and to a real texture described by the main components observed on a direct pole figure. (Author) [pt
Subquadratic medial-axis approximation in $\\mathbb{R}^3$
Directory of Open Access Journals (Sweden)
Christian Scheffer
2015-09-01
Full Text Available We present an algorithm that approximates the medial axis of a smooth manifold in $\\mathbb{R}^3$ which is given by a sufficiently dense point sample. The resulting, non-discrete approximation is shown to converge to the medial axis as the sampling density approaches infinity. While all previous algorithms guaranteeing convergence have a running time quadratic in the size $n$ of the point sample, we achieve a running time of at most $\\mathcal{O}(n\\log^3 n$. While there is no subquadratic upper bound on the output complexity of previous algorithms for non-discrete medial axis approximation, the output of our algorithm is guaranteed to be of linear size.
International Nuclear Information System (INIS)
El-Deab, Mohamed S.
2009-01-01
The crystallographic orientation of Au nanoparticles electrodeposited at glassy carbon (nano-Au/GC) electrodes (prepared by potential step electrolysis) is markedly influenced by the width of the potential step. The oxygen reduction reaction (ORR) and the reductive desorption of cysteine have been studied on nano-Au/GC electrodes. Furthermore, electron backscatter diffraction (EBSD) technique has been used to probe the crystallographic orientation of the electrodeposited Au nanoparticles. That is, Au nanoparticles prepared in short time (5-60 s) have been found rich in the Au(1 1 1) facet orientation and are characterized by a relatively small particle size (ca. 10-50 nm) as well as high particle density (number of particles per unit area) as revealed by SEM images. Whereas Au nanoparticles prepared by longer electrolysis time (>60 s) are found to be much enriched in the Au(1 0 0) and Au(1 1 0) facets and are characterized by a relatively large particle size (>100 nm). EBSD patterns provided definitive information about the crystal orientations mapping of Au nanoparticles prepared at various deposition times.
International Nuclear Information System (INIS)
Liu, Qingbo; Li, Defeng; Hu, Yonglin; Wang, Da-Cheng
2013-01-01
GluB, a substrate-binding protein from C. glutamicum, was expressed, purified and crystallized, followed by X-ray diffraction data collection and preliminary crystallographic analysis. GluB is a substrate-binding protein (SBP) which participates in the uptake of glutamic acid in Corynebacterium glutamicum, a Gram-positive bacterium. It is part of an ATP-binding cassette (ABC) transporter system. Together with the transmembrane proteins GluC and GluD and the cytoplasmic protein GluA, which couples the hydrolysis of ATP to the translocation of glutamate, they form a highly active glutamate-uptake system. As part of efforts to study the amino-acid metabolism, especially the metabolism of glutamic acid by C. glutamicum, a bacterium that is widely used in the industrial production of glutamic acid, the GluB protein was expressed, purified and crystallized, an X-ray diffraction data set was collected to a resolution of 1.9 Å and preliminary crystallographic analysis was performed. The crystal belonged to space group P3 1 21 or P3 2 21, with unit-cell parameters a = b = 82.50, c = 72.69 Å
International Nuclear Information System (INIS)
Kowalinski, Eva; Bange, Gert; Wild, Klemens; Sinning, Irmgard
2007-01-01
Preliminary X-ray analysis of the proliferation-associated protein Ebp1 from Homo sapiens is provided. ErbB-3-binding protein 1 (Ebp1) is a member of the family of proliferation-associated 2G4 proteins (PA2G4s) and plays a role in cellular growth and differentiation. Ligand-induced activation of the transmembrane receptor ErbB3 leads to dissociation of Ebp1 from the receptor in a phosphorylation-dependent manner. The non-associated protein is involved in transcriptional and translational regulation in the cell. Here, the overexpression, purification, crystallization and preliminary crystallographic studies of Ebp1 from Homo sapiens are reported. Initially observed crystals were improved by serial seeding to single crystals suitable for data collection. The optimized crystals belong to the tetragonal space group P4 1 2 1 2 or P4 3 2 1 2 and diffracted to a resolution of 1.6 Å
Energy Technology Data Exchange (ETDEWEB)
Kowalinski, Eva; Bange, Gert; Wild, Klemens; Sinning, Irmgard, E-mail: irmi.sinning@bzh.uni-heidelberg.de [Heidelberg University Biochemistry Center, INF 328, D-69120 Heidelberg (Germany)
2007-09-01
Preliminary X-ray analysis of the proliferation-associated protein Ebp1 from Homo sapiens is provided. ErbB-3-binding protein 1 (Ebp1) is a member of the family of proliferation-associated 2G4 proteins (PA2G4s) and plays a role in cellular growth and differentiation. Ligand-induced activation of the transmembrane receptor ErbB3 leads to dissociation of Ebp1 from the receptor in a phosphorylation-dependent manner. The non-associated protein is involved in transcriptional and translational regulation in the cell. Here, the overexpression, purification, crystallization and preliminary crystallographic studies of Ebp1 from Homo sapiens are reported. Initially observed crystals were improved by serial seeding to single crystals suitable for data collection. The optimized crystals belong to the tetragonal space group P4{sub 1}2{sub 1}2 or P4{sub 3}2{sub 1}2 and diffracted to a resolution of 1.6 Å.
Messica, A.
2016-10-01
The probability distribution function of a weighted sum of non-identical lognormal random variables is required in various fields of science and engineering and specifically in finance for portfolio management as well as exotic options valuation. Unfortunately, it has no known closed form and therefore has to be approximated. Most of the approximations presented to date are complex as well as complicated for implementation. This paper presents a simple, and easy to implement, approximation method via modified moments matching and a polynomial asymptotic series expansion correction for a central limit theorem of a finite sum. The method results in an intuitively-appealing and computation-efficient approximation for a finite sum of lognormals of at least ten summands and naturally improves as the number of summands increases. The accuracy of the method is tested against the results of Monte Carlo simulationsand also compared against the standard central limit theorem andthe commonly practiced Markowitz' portfolio equations.
International Nuclear Information System (INIS)
Wang, Xiaoying; Akasaka, Ryogo; Takemoto, Chie; Morita, Satoshi; Yamaguchi, Machiko; Terada, Takaho; Shirozu, Mikako; Yokoyama, Shigeyuki; Chen, Shilin; Si, Shuyi; Xie, Yong
2011-01-01
A hyperthermophilic adenylosuccinate synthetase from P. horikoshii OT3, which is 90–120 amino acids shorter than those from the vast majority of organisms, was expressed, purified and crystallized and X-ray diffraction data were collected to 2.5 Å resolution. Adenylosuccinate synthetase (AdSS) is a ubiquitous enzyme that catalyzes the first committed step in the conversion of inosine monophosphate (IMP) to adenosine monophosphate (AMP) in the purine-biosynthetic pathway. Although AdSS from the vast majority of organisms is 430–457 amino acids in length, AdSS sequences isolated from thermophilic archaea are 90–120 amino acids shorter. In this study, crystallographic studies of a short AdSS sequence from Pyrococcus horikoshii OT3 (PhAdSS) were performed in order to reveal the unusual structure of AdSS from thermophilic archaea. Crystals of PhAdSS were obtained by the microbatch-under-oil method and X-ray diffraction data were collected to 2.50 Å resolution. The crystal belonged to the trigonal space group P3 2 12, with unit-cell parameters a = b = 57.2, c = 107.9 Å. There was one molecule per asymmetric unit, giving a Matthews coefficient of 2.17 Å 3 Da −1 and an approximate solvent content of 43%. In contrast, the results of native polyacrylamide gel electrophoresis and analytical ultracentrifugation showed that the recombinant PhAdSS formed a dimer in solution
International Nuclear Information System (INIS)
Peng, Degao; Yang, Yang; Zhang, Peng; Yang, Weitao
2014-01-01
In this article, we develop systematically second random phase approximations (RPA) and Tamm-Dancoff approximations (TDA) of particle-hole and particle-particle channels for calculating molecular excitation energies. The second particle-hole RPA/TDA can capture double excitations missed by the particle-hole RPA/TDA and time-dependent density-functional theory (TDDFT), while the second particle-particle RPA/TDA recovers non-highest-occupied-molecular-orbital excitations missed by the particle-particle RPA/TDA. With proper orbital restrictions, these restricted second RPAs and TDAs have a formal scaling of only O(N 4 ). The restricted versions of second RPAs and TDAs are tested with various small molecules to show some positive results. Data suggest that the restricted second particle-hole TDA (r2ph-TDA) has the best overall performance with a correlation coefficient similar to TDDFT, but with a larger negative bias. The negative bias of the r2ph-TDA may be induced by the unaccounted ground state correlation energy to be investigated further. Overall, the r2ph-TDA is recommended to study systems with both single and some low-lying double excitations with a moderate accuracy. Some expressions on excited state property evaluations, such as 〈S ^2 〉 are also developed and tested
Energy Technology Data Exchange (ETDEWEB)
Peng, Degao; Yang, Yang; Zhang, Peng [Department of Chemistry, Duke University, Durham, North Carolina 27708 (United States); Yang, Weitao, E-mail: weitao.yang@duke.edu [Department of Chemistry and Department of Physics, Duke University, Durham, North Carolina 27708 (United States)
2014-12-07
In this article, we develop systematically second random phase approximations (RPA) and Tamm-Dancoff approximations (TDA) of particle-hole and particle-particle channels for calculating molecular excitation energies. The second particle-hole RPA/TDA can capture double excitations missed by the particle-hole RPA/TDA and time-dependent density-functional theory (TDDFT), while the second particle-particle RPA/TDA recovers non-highest-occupied-molecular-orbital excitations missed by the particle-particle RPA/TDA. With proper orbital restrictions, these restricted second RPAs and TDAs have a formal scaling of only O(N{sup 4}). The restricted versions of second RPAs and TDAs are tested with various small molecules to show some positive results. Data suggest that the restricted second particle-hole TDA (r2ph-TDA) has the best overall performance with a correlation coefficient similar to TDDFT, but with a larger negative bias. The negative bias of the r2ph-TDA may be induced by the unaccounted ground state correlation energy to be investigated further. Overall, the r2ph-TDA is recommended to study systems with both single and some low-lying double excitations with a moderate accuracy. Some expressions on excited state property evaluations, such as 〈S{sup ^2}〉 are also developed and tested.
Directory of Open Access Journals (Sweden)
Hirotaka Sato
2017-12-01
Full Text Available Current status of Bragg-edge/dip neutron transmission analysis/imaging methods is presented. The method can visualize real-space distributions of bulk crystallographic information in a crystalline material over a large area (~10 cm with high spatial resolution (~100 μm. Furthermore, by using suitable spectrum analysis methods for wavelength-dependent neutron transmission data, quantitative visualization of the crystallographic information can be achieved. For example, crystallographic texture imaging, crystallite size imaging and crystalline phase imaging with texture/extinction corrections are carried out by the Rietveld-type (wide wavelength bandwidth profile fitting analysis code, RITS (Rietveld Imaging of Transmission Spectra. By using the single Bragg-edge analysis mode of RITS, evaluations of crystal lattice plane spacing (d-spacing relating to macro-strain and d-spacing distribution’s FWHM (full width at half maximum relating to micro-strain can be achieved. Macro-strain tomography is performed by a new conceptual CT (computed tomography image reconstruction algorithm, the tensor CT method. Crystalline grains and their orientations are visualized by a fast determination method of grain orientation for Bragg-dip neutron transmission spectrum. In this paper, these imaging examples with the spectrum analysis methods and the reliabilities evaluated by optical/electron microscope and X-ray/neutron diffraction, are presented. In addition, the status at compact accelerator driven pulsed neutron sources is also presented.
Approximate kernel competitive learning.
Wu, Jian-Sheng; Zheng, Wei-Shi; Lai, Jian-Huang
2015-03-01
Kernel competitive learning has been successfully used to achieve robust clustering. However, kernel competitive learning (KCL) is not scalable for large scale data processing, because (1) it has to calculate and store the full kernel matrix that is too large to be calculated and kept in the memory and (2) it cannot be computed in parallel. In this paper we develop a framework of approximate kernel competitive learning for processing large scale dataset. The proposed framework consists of two parts. First, it derives an approximate kernel competitive learning (AKCL), which learns kernel competitive learning in a subspace via sampling. We provide solid theoretical analysis on why the proposed approximation modelling would work for kernel competitive learning, and furthermore, we show that the computational complexity of AKCL is largely reduced. Second, we propose a pseudo-parallelled approximate kernel competitive learning (PAKCL) based on a set-based kernel competitive learning strategy, which overcomes the obstacle of using parallel programming in kernel competitive learning and significantly accelerates the approximate kernel competitive learning for large scale clustering. The empirical evaluation on publicly available datasets shows that the proposed AKCL and PAKCL can perform comparably as KCL, with a large reduction on computational cost. Also, the proposed methods achieve more effective clustering performance in terms of clustering precision against related approximate clustering approaches. Copyright © 2014 Elsevier Ltd. All rights reserved.
Non-additive non-interacting kinetic energy of rare gas dimers
Jiang, Kaili; Nafziger, Jonathan; Wasserman, Adam
2018-03-01
Approximations of the non-additive non-interacting kinetic energy (NAKE) as an explicit functional of the density are the basis of several electronic structure methods that provide improved computational efficiency over standard Kohn-Sham calculations. However, within most fragment-based formalisms, there is no unique exact NAKE, making it difficult to develop general, robust approximations for it. When adjustments are made to the embedding formalisms to guarantee uniqueness, approximate functionals may be more meaningfully compared to the exact unique NAKE. We use numerically accurate inversions to study the exact NAKE of several rare-gas dimers within partition density functional theory, a method that provides the uniqueness for the exact NAKE. We find that the NAKE decreases nearly exponentially with atomic separation for the rare-gas dimers. We compute the logarithmic derivative of the NAKE with respect to the bond length for our numerically accurate inversions as well as for several approximate NAKE functionals. We show that standard approximate NAKE functionals do not reproduce the correct behavior for this logarithmic derivative and propose two new NAKE functionals that do. The first of these is based on a re-parametrization of a conjoint Perdew-Burke-Ernzerhof (PBE) functional. The second is a simple, physically motivated non-decomposable NAKE functional that matches the asymptotic decay constant without fitting.
Energy Technology Data Exchange (ETDEWEB)
Palombi, F. [Deutsches Elektronen-Synchrotron (DESY), Hamburg (Germany). Gruppe Theorie; Papinutto, M. [Istituto Nazionale di Fisica Nucleare, Rome (Italy); Pena, C. [European Organization for Nuclear Research, Geneva (Switzerland). Theoretical Physics Div.; Wittig, H. [Mainz Univ. (Germany). Inst. fuer Kernphysik
2006-04-15
We discuss the renormalisation properties of the complete set of {delta}B=2 four-quark operators with the heavy quark treated in the static approximation. We elucidate the role of heavy quark symmetry and other symmetry transformations in constraining their mixing under renormalisation. By employing the Schroedinger functional, a set of non-perturbative renormalisation conditions can be defined in terms of suitable correlation functions. As a first step in a fully non-perturbative determination of the scale-dependent renormalisation factors, we evaluate these conditions in lattice perturbation theory at one loop. Thereby we verify the expected mixing patterns and determine the anomalous dimensions of the operators at NLO in the Schroedinger functional scheme. Finally, by employing twisted-mass QCD it is shown how finite subtractions arising from explicit chiral symmetry breaking can be avoided completely. (Orig.)
International Nuclear Information System (INIS)
Palombi, F.; Pena, C.; Wittig, H.
2006-04-01
We discuss the renormalisation properties of the complete set of ΔB=2 four-quark operators with the heavy quark treated in the static approximation. We elucidate the role of heavy quark symmetry and other symmetry transformations in constraining their mixing under renormalisation. By employing the Schroedinger functional, a set of non-perturbative renormalisation conditions can be defined in terms of suitable correlation functions. As a first step in a fully non-perturbative determination of the scale-dependent renormalisation factors, we evaluate these conditions in lattice perturbation theory at one loop. Thereby we verify the expected mixing patterns and determine the anomalous dimensions of the operators at NLO in the Schroedinger functional scheme. Finally, by employing twisted-mass QCD it is shown how finite subtractions arising from explicit chiral symmetry breaking can be avoided completely. (Orig.)
Truthful approximations to range voting
DEFF Research Database (Denmark)
Filos-Ratsika, Aris; Miltersen, Peter Bro
We consider the fundamental mechanism design problem of approximate social welfare maximization under general cardinal preferences on a finite number of alternatives and without money. The well-known range voting scheme can be thought of as a non-truthful mechanism for exact social welfare...
APPROXIMATIONS TO PERFORMANCE MEASURES IN QUEUING SYSTEMS
Directory of Open Access Journals (Sweden)
Kambo, N. S.
2012-11-01
Full Text Available Approximations to various performance measures in queuing systems have received considerable attention because these measures have wide applicability. In this paper we propose two methods to approximate the queuing characteristics of a GI/M/1 system. The first method is non-parametric in nature, using only the first three moments of the arrival distribution. The second method treads the known path of approximating the arrival distribution by a mixture of two exponential distributions by matching the first three moments. Numerical examples and optimal analysis of performance measures of GI/M/1 queues are provided to illustrate the efficacy of the methods, and are compared with benchmark approximations.
Crystallographic Investigation of Ag (4 mol%) Doped ZnO (SZO) Thin Films by XRD
International Nuclear Information System (INIS)
Lwin Lwin Nwe; Sandar Dwe; Khant Khant Lin; Khin Thuzar; Than Than Win; Ko Ko Kyaw Soe
2008-03-01
Silver doped ZnO(SZO) thin films are prepared by sol-based method. The silver dopant concentration is 4 mol % in this case. XRD analysis carried out to determine, crystallographic properties such as lattice parameters and crystallite size of SZO thin films.
Chatzaras, V.; Kruckenberg, Seth C.; Cohen, Shaina M.; Medaris Jr., L. Gordon; Withers, Anthony C.; Bagley, Brian
The effect of finite strain geometry on crystallographic preferred orientation (CPO) is poorly constrained in the upper mantle. Specifically, the relationship between shape preferred orientation (SPO) and CPO in the mantle rocks remains unclear. We analyzed a suite of 40 spinel peridotite xenoliths
Diophantine approximation and badly approximable sets
DEFF Research Database (Denmark)
Kristensen, S.; Thorn, R.; Velani, S.
2006-01-01
. The classical set Bad of `badly approximable' numbers in the theory of Diophantine approximation falls within our framework as do the sets Bad(i,j) of simultaneously badly approximable numbers. Under various natural conditions we prove that the badly approximable subsets of Omega have full Hausdorff dimension...
Comparison of the free volume sizes and shapes determined from crystallographic and PALS data
Directory of Open Access Journals (Sweden)
Tydda Maciej
2015-12-01
Full Text Available Two different classes of molecular crystals were investigated. The first group was benzenediols, which are characterized by the same chemical composition but a different organization of their crystallographic structures; all of the compounds from this group have only one kind of free volumes. The second class was represented by olanzapine, which has more complex chemical composition and two kinds of free volumes in the structure. The o-Ps lifetime values determined from positron annihilation lifetime spectroscopy (PALS measurements agree quite well with those calculated for sizes found from crystallographic data for benzenediols (agreement within 10% of the lifetime values. For olanzapine, a good agreement is observed in the case of cuboidal free volumes, while for the other kind of void, the agreement is less satisfactory. Positronium diffusion coefficient determined from o-Ps redistribution in olanzapine agrees with these found for polymers.
Broken symmetry within crystallographic super-spaces: structural and dynamical aspects
International Nuclear Information System (INIS)
Mariette, Celine
2013-01-01
Aperiodic crystals have the property to possess long range order without translational symmetry. These crystals are described within the formalism of super-space crystallography. In this manuscript, we will focus on symmetry breaking which take place in such crystallographic super-space groups, considering the prototype family of n-alkane/urea. Studies performed by X-ray diffraction using synchrotron sources reveal multiple structural solutions implying or not changes of the dimension of the super-space. Once the characterization of the order parameter and of the symmetry breaking is done, we present the critical pre-transitional phenomena associated to phase transitions of group/subgroup types. Coherent neutron scattering and inelastic X-ray scattering allow a dynamical analysis of different kind of excitations in these materials (phonons, phasons). The inclusion compounds with short guest molecules (alkane C n H 2n+2 , n varying from 7 to 13) show at room temperature unidimensional 'liquid-like' phases. The dynamical disorder along the incommensurate direction of these materials generates new structural solutions at low temperature (inter-modulated monoclinic composite, commensurate lock-in). (author) [fr
Experimental studies on the crystallographic and plastic anisotropies of zircaloy-4 tubes
International Nuclear Information System (INIS)
Costa Viana, C.S. da
1982-01-01
The crystallographic and plastic anisotropies of a zircaloy-4 tubing using direct pole figures and experimental yield loci are analyzed. Tensile and plane-strain compression tests were used to assess the mecahnical behaviour. The results are discussed with respect to the dimensional stability and mechanical behaviour expected for the tube in its use in the core of pressurized water cooled reactors. (Author) [pt
Conditional Density Approximations with Mixtures of Polynomials
DEFF Research Database (Denmark)
Varando, Gherardo; López-Cruz, Pedro L.; Nielsen, Thomas Dyhre
2015-01-01
Mixtures of polynomials (MoPs) are a non-parametric density estimation technique especially designed for hybrid Bayesian networks with continuous and discrete variables. Algorithms to learn one- and multi-dimensional (marginal) MoPs from data have recently been proposed. In this paper we introduce...... two methods for learning MoP approximations of conditional densities from data. Both approaches are based on learning MoP approximations of the joint density and the marginal density of the conditioning variables, but they differ as to how the MoP approximation of the quotient of the two densities...
The crystallographic information file (CIF): A new standard archive file for crystallography
International Nuclear Information System (INIS)
Hall, S.R.; Allen, F.H.; Brown, I.D.
1991-01-01
The specification of a new standard Crystallographic Information File (CIF) is described. Its development is based on the Self-Defining Text Archieve and Retrieval (STAR) procedure. The CIF is a general, flexible and easily extensible free-format archive file; it is human and machine readable and can be edited by a simple editor. The CIF is designed for the electronic transmission of crystallographic data between individual laboratories, journals and databases: It has been adopted by the International Union of Crystallography as the recommended medium for this purpose. The file consists of data names and data items, together with a loop facility for repeated items. The data names, constructed hierarchically so as to form data categories, are self-descriptive within a 32-character limit. The sorted list of data names, together with their precise definitions, constitutes the CIF dictionary (core version 1991). The CIF core dictionary is presented in full and covers the fundamental and most commonly used data items relevant to crystal structure analysis. The dictionary is also available as an electronic file suitable for CIF computer applications. Future extensions to the dictionary will include data items used in more specialized areas of crystallography. (orig.)
Higher Order Improvements for Approximate Estimators
DEFF Research Database (Denmark)
Kristensen, Dennis; Salanié, Bernard
Many modern estimation methods in econometrics approximate an objective function, through simulation or discretization for instance. The resulting "approximate" estimator is often biased; and it always incurs an efficiency loss. We here propose three methods to improve the properties of such appr......Many modern estimation methods in econometrics approximate an objective function, through simulation or discretization for instance. The resulting "approximate" estimator is often biased; and it always incurs an efficiency loss. We here propose three methods to improve the properties...... of such approximate estimators at a low computational cost. The first two methods correct the objective function so as to remove the leading term of the bias due to the approximation. One variant provides an analytical bias adjustment, but it only works for estimators based on stochastic approximators......, such as simulation-based estimators. Our second bias correction is based on ideas from the resampling literature; it eliminates the leading bias term for non-stochastic as well as stochastic approximators. Finally, we propose an iterative procedure where we use Newton-Raphson (NR) iterations based on a much finer...
Crystallization and preliminary X-ray crystallographic studies of DnaJ from Streptococcus pneumoniae
International Nuclear Information System (INIS)
Zhao, Shasha; Jin, Li; Niu, Siqiang; Yang, Wei; Zhang, Shaocheng; Guo, Zhen; Zhang, Hongpeng; Huang, Ailong; Yin, Yibing; Wang, Deqiang
2013-01-01
DnaJ from Streptococcus pneumoniae (SpDnaJ) is involved in the infectious disease process and is being developed as a potential vaccine to prevent bacterial infection. Here the expression, purification, crystallization and preliminary crystallographic analysis of SpDnaJ are reported. DnaJ, cooperating with DnaK and GrpE, promotes the folding of unfolded hydrophobic polypeptides, dissociates protein complexes and translocates protein across membranes. Additionally, DnaJ from Streptococcus pneumoniae (SpDnaJ) is involved in the infectious disease process and is being developed as a potential vaccine to prevent bacterial infection. Here the expression, purification, crystallization and preliminary crystallographic analysis of SpDnaJ are reported. The crystals belong to space groups I222 or I2 1 2 1 2 1 and the diffraction resolution is 3.0 Å with unit-cell parameters a = 47.68, b = 104.45, c = 234.57 Å. The crystal most likely contains one molecule in the asymmetric unit, with a V M value of 3.24 Å 3 Da −1 and a solvent content of 62.1%
International Nuclear Information System (INIS)
Moradian, Rostam
2006-01-01
We develop a generalized real-space effective medium super-cell approximation (EMSCA) method to treat the electronic states of interacting disordered systems. This method is general and allows randomness both in the on-site energies and in the hopping integrals. For a non-interacting disordered system, in the special case of randomness in the on-site energies, this method is equivalent to the non-local coherent potential approximation (NLCPA) derived previously. Also, for an interacting system the EMSCA method leads to the real-space derivation of the generalized dynamical cluster approximation (DCA) for a general lattice structure. We found that the original DCA and the NLCPA are two simple cases of this technique, so the EMSCA is equivalent to the generalized DCA where there is included interaction and randomness in the on-site energies and in the hopping integrals. All of the equations of this formalism are derived by using the effective medium theory in real space
International Nuclear Information System (INIS)
Beladi, Hossein; Rohrer, Gregory S.; Rollett, Anthony D.; Tari, Vahid; Hodgson, Peter D.
2014-01-01
Electron backscatter diffraction analysis was employed to compute the closest orientation relationship and the distribution of intervariant boundary character in a lath martensitic microstructure. The misorientations were close to the Kurdjumov–Sachs orientation relationship. The intervariant crystallographic plane distribution exhibited a relatively high anisotropy with a tendency for the lath interfaces to terminate on (1 1 0) planes. This results from the crystallographic constraints associated with the shear transformation rather than a low energy interface configuration. The lath martensite habit plane was determined to be mostly (1 1 0) or near (1 1 0). The relative populations of boundaries with [1 1 1] and [1 1 0] misorientations were greater than other high index misorientations, mostly characterized as (1 1 0) symmetric tilt and (1 1 0) twist boundary types, respectively. Analysis with homology metrics of the connectivity in the lath martensitic microstructure revealed the connectivity dominated by population of misorientation angle and boundary plane type
XTAL system of crystallographic programs: programmer's manual
International Nuclear Information System (INIS)
Hall, S.R.; Stewart, J.M.; Norden, A.P.; Munn, R.J.; Freer, S.T.
1980-02-01
This document establishes the basis for collaborative writing of transportable computer programs for x-ray crystallography. The concepts and general-purpose utility subroutines described here can be readily adapted to other scientific calculations. The complete system of crystallographic programs and subroutines is called XTAL and replaces the XRAY (6,7,8) system of programs. The coding language for the XTAL system is RATMAC (5). The XTAL system of programs contains routines for controlling execution of application programs. In this sense it forms a suboperating system that presents the same computational environment to the user and programmer irrespective of the operating system in use at a particular installation. These control routines replace all FORTRAN I/O code, supply character reading and writing, supply binary file reading and writing, serve as a support library for applications programs, and provide for interprogram communication
Gauge-invariant intense-field approximations to all orders
International Nuclear Information System (INIS)
Faisal, F H M
2007-01-01
We present a gauge-invariant formulation of the so-called strong-field KFR approximations in the 'velocity' and 'length' gauges and demonstrate their equivalence in all orders. The theory thus overcomes a longstanding discrepancy between the strong-field velocity and the length-gauge approximations for non-perturbative processes in intense laser fields. (fast track communication)
Low-cost synthesis of pure ZnO nanowalls showing three-fold symmetry
Scuderi, Mario; Strano, Vincenzina; Spinella, Corrado; Nicotra, Giuseppe; Mirabella, Salvo
2018-04-01
ZnO nanowalls (NWLs) represent a non-toxic, Earth abundant, high surface-to-volume ratio, semiconducting nanostructure which has already showed potential applications in biosensing, environmental monitoring and energy. Low-cost synthesis of these nanostructures is extremely appealing for large scale upgrading of laboratory results, and its implementation has to be tested at the nanoscale, at least in terms of chemical purity and crystallographic orientation. Here, we have produced pure and texturized ZnO NWLs by using chemical bath deposition (CBD) synthesis followed by a thermal treatment at 300 °C. We examined the NWL formation process and the new obtained structure at the nanoscale, by means of scanning and transmission electron microscopy in combination with x-ray diffraction and Rutherford backscattering spectrometry. We have shown that only after annealing at 300 °C in nitrogen does the as-grown material, composed of a mixture of Zn compounds NWLs, show its peculiar crystal arrangement. The resulting ZnO sheets are in fact made by ZnO wurtzite domains (4-5 nm) that show a particular kind of texturization; indeed, they are aligned with their own c-axis always perpendicular to the sheets forming the wall and rotated (around the c-axis) by multiples of 20° from each other. The presented data show that low-cost CBD, followed by an annealing process, gives pure ZnO with a peculiarly ordered nanostructure that shows three-fold symmetry. Such evidence at the nanoscale will have significant implications for realizing sensing or catalyst devices based on ZnO NWLs.
International Nuclear Information System (INIS)
Li, Kun-Dar
2014-01-01
Highlights: •We model the faceted precipitates formation by post-implantation annealing. •The anisotropic interfacial energy and diffusion kinetics play crucial roles. •The evolutions of faceted precipitates, including Ostwald ripening, are revealed. •The mechanism of the nucleation and growth is based on the atomic diffusion. •The effects of ion dose and crystallographic symmetry are also investigated. -- Abstract: Thermal annealing is one of the most common techniques to synthesize embedded precipitates by ion implantation process. In this study, an anisotropic phase field model is presented to investigate the effects of ion dose and crystallographic symmetry on the morphological formation and evolution of embedded precipitates during post-implantation thermal annealing process. This theoretical model provides an efficient numerical approach to understand the phenomenon of faceted precipitates formation by ion implantation. As a theoretical analysis, the interfacial energy and diffusion kinetics play prominent roles in the mechanism of atomic diffusion for the precipitates formation. With a low ion dose, faceted precipitates are developed by virtue of the anisotropic interfacial energy. As an increase of ion dose, connected precipitates with crystallographic characters on the edge are appeared. For a high ion dose, labyrinth-like nanostructures of precipitates are produced and the characteristic morphology of crystallographic symmetry becomes faint. These simulation results for the morphological evolutions of embedded precipitates by ion implantation are corresponded with many experimental observations in the literatures. The quantitative analyses of the simulations are also well described the consequence of precipitates formation under different conditions
evaluation of approximate design procedures for biaxially loaded
African Journals Online (AJOL)
The approximation according to the ACI is based on the work by Parme [9] who chose to approximate a as a logarithmic function 9f a parameter /3 representing an actual point on· the non-dimensional load contour, where the two moment components, . related to the respective uniaxial capacities are equal,. i.e. f3=;: my lmuy ...
CRYSNET manual. Informal report. [Hardware and software of crystallographic computing network
Energy Technology Data Exchange (ETDEWEB)
None,
1976-07-01
This manual describes the hardware and software which together make up the crystallographic computing network (CRYSNET). The manual is intended as a users' guide and also provides general information for persons without any experience with the system. CRYSNET is a network of intelligent remote graphics terminals that are used to communicate with the CDC Cyber 70/76 computing system at the Brookhaven National Laboratory (BNL) Central Scientific Computing Facility. Terminals are in active use by four research groups in the field of crystallography. A protein data bank has been established at BNL to store in machine-readable form atomic coordinates and other crystallographic data for macromolecules. The bank currently includes data for more than 20 proteins. This structural information can be accessed at BNL directly by the CRYSNET graphics terminals. More than two years of experience has been accumulated with CRYSNET. During this period, it has been demonstrated that the terminals, which provide access to a large, fast third-generation computer, plus stand-alone interactive graphics capability, are useful for computations in crystallography, and in a variety of other applications as well. The terminal hardware, the actual operations of the terminals, and the operations of the BNL Central Facility are described in some detail, and documentation of the terminal and central-site software is given. (RWR)
Boughariou, A; Damamme, G; Kallel, A
2015-04-01
This paper focuses on the effect of sample annealing temperature and crystallographic orientation on the secondary electron yield of MgO during charging by a defocused electron beam irradiation. The experimental results show that there are two regimes during the charging process that are better identified by plotting the logarithm of the secondary electron emission yield, lnσ, as function of the total trapped charge in the material QT. The impact of the annealing temperature and crystallographic orientation on the evolution of lnσ is presented here. The slope of the asymptotic regime of the curve lnσ as function of QT, expressed in cm(2) per trapped charge, is probably linked to the elementary cross section of electron-hole recombination, σhole, which controls the trapping evolution in the reach of the stationary flow regime. © 2014 The Authors Journal of Microscopy © 2014 Royal Microscopical Society.
Odic, Darko; Lisboa, Juan Valle; Eisinger, Robert; Olivera, Magdalena Gonzalez; Maiche, Alejandro; Halberda, Justin
2016-01-01
What is the relationship between our intuitive sense of number (e.g., when estimating how many marbles are in a jar), and our intuitive sense of other quantities, including time (e.g., when estimating how long it has been since we last ate breakfast)? Recent work in cognitive, developmental, comparative psychology, and computational neuroscience has suggested that our representations of approximate number, time, and spatial extent are fundamentally linked and constitute a "generalized magnitude system". But, the shared behavioral and neural signatures between number, time, and space may alternatively be due to similar encoding and decision-making processes, rather than due to shared domain-general representations. In this study, we investigate the relationship between approximate number and time in a large sample of 6-8 year-old children in Uruguay by examining how individual differences in the precision of number and time estimation correlate with school mathematics performance. Over four testing days, each child completed an approximate number discrimination task, an approximate time discrimination task, a digit span task, and a large battery of symbolic math tests. We replicate previous reports showing that symbolic math abilities correlate with approximate number precision and extend those findings by showing that math abilities also correlate with approximate time precision. But, contrary to approximate number and time sharing common representations, we find that each of these dimensions uniquely correlates with formal math: approximate number correlates more strongly with formal math compared to time and continues to correlate with math even when precision in time and individual differences in working memory are controlled for. These results suggest that there are important differences in the mental representations of approximate number and approximate time and further clarify the relationship between quantity representations and mathematics. Copyright
Limitations of shallow nets approximation.
Lin, Shao-Bo
2017-10-01
In this paper, we aim at analyzing the approximation abilities of shallow networks in reproducing kernel Hilbert spaces (RKHSs). We prove that there is a probability measure such that the achievable lower bound for approximating by shallow nets can be realized for all functions in balls of reproducing kernel Hilbert space with high probability, which is different with the classical minimax approximation error estimates. This result together with the existing approximation results for deep nets shows the limitations for shallow nets and provides a theoretical explanation on why deep nets perform better than shallow nets. Copyright © 2017 Elsevier Ltd. All rights reserved.
Montalto, L.; Natali, P. P.; Daví, F.; Mengucci., P.; Paone, N.; Rinaldi, D.
2017-12-01
Among scintillators, the PWO is one of the most widely used, for instance in CMS calorimeter at CERN and PANDA project. Crystallographic structure and chemical composition as well as residual stress condition, are indicators of homogeneity and good quality of the crystal. In this paper, structural characterization of a defective PbWO4 (PWO) crystal has been performed by X-ray Diffraction (XRD), Energy Dispersive Spectroscopy (EDS) and Photoelasticity in the unusual (a, c) crystallographic plane. XRD and EDS analysis have been used to investigate crystallographic orientation and chemical composition, while stress distribution, which indicates macroscopic inhomogeneities and defects, has been obtained by photoelastic approaches, in Conoscopic and Sphenoscopic configuration. Since the sample is cut along the (a, c) crystallographic plane, a new method is proposed for the interpretation of the fringe pattern. The structural analysis has detected odds from the nominal lattice dimension, which can be attributed to the strong presence of Pb and W. A strong inhomogeneity over the crystal sample has been revealed by the photoelastic inspection. The results give reliability to the proposed procedure which is exploitable in crystals with other structures.
Kostov, Konstantin S.; Moffat, Keith
2011-01-01
The initial output of a time-resolved macromolecular crystallography experiment is a time-dependent series of difference electron density maps that displays the time-dependent changes in underlying structure as a reaction progresses. The goal is to interpret such data in terms of a small number of crystallographically refinable, time-independent structures, each associated with a reaction intermediate; to establish the pathways and rate coefficients by which these intermediates interconvert; and thereby to elucidate a chemical kinetic mechanism. One strategy toward achieving this goal is to use cluster analysis, a statistical method that groups objects based on their similarity. If the difference electron density at a particular voxel in the time-dependent difference electron density (TDED) maps is sensitive to the presence of one and only one intermediate, then its temporal evolution will exactly parallel the concentration profile of that intermediate with time. The rationale is therefore to cluster voxels with respect to the shapes of their TDEDs, so that each group or cluster of voxels corresponds to one structural intermediate. Clusters of voxels whose TDEDs reflect the presence of two or more specific intermediates can also be identified. From such groupings one can then infer the number of intermediates, obtain their time-independent difference density characteristics, and refine the structure of each intermediate. We review the principles of cluster analysis and clustering algorithms in a crystallographic context, and describe the application of the method to simulated and experimental time-resolved crystallographic data for the photocycle of photoactive yellow protein. PMID:21244840
Crystallographic Study of U-Th bearing minerals in Tranomaro, Anosy Region-Madagascar
International Nuclear Information System (INIS)
Sahoa, F.E.; Rabesiranana, N.; Raoelina Andriambololona; Geckeis, H.; Marquardt, C.; Finck, K.
2011-01-01
As an alternative to conventional fossil fuel, there is a renewed interest in the nuclear fuel to support increasing energy demand. New studies are then undertaken to characterize Madagascar U-Th bearing minerals. This is the case for the urano-thorianite bearing pyroxenites in the south East of Madagascar. In this region, several quarries were abandoned, after being mined by the French Atomic Energy Commission (C.E.A) in the fifties and sixties and are now explored by new mining companies. For this purpose, seven U-Th bearing mineral samples from old abandoned uranium quarries in Tranomaro, Amboasary Sud, Madagascar, have been collected. To determine the mineral microstructure, they were investigated for qualitative and quantitative identification of crystalline compounds using X-ray powder diffraction analytical method (XRD). Results showed that the U and Th compounds, as minor elements, are present in various crystalline structures. This is important to understand their environmental behaviours, in terms of crystallographic dispersion of U-Th minerals and their impacts on human health.
Analysis of elastic strain and crystallographic texture in poled rhombohedral PZT ceramics
International Nuclear Information System (INIS)
Hall, D.A.; Steuwer, A.; Cherdhirunkorn, B.; Mori, T.; Withers, P.J.
2006-01-01
The elastic strain and crystallographic texture of a rhombohedral lead zirconate titanate ceramic have been characterised in the remanent state, after poling, using high-energy synchrotron X-ray diffraction as a function of the grain orientation ψ relative to the poling direction. It is observed that the (2 0 0) diffraction peak exhibits pronounced shifts as a function of ψ, indicating an elastic lattice strain, while others ({1 1 1}, {1 1 2} and {2 2 0}) show marked changes in intensity as a result of preferred ferroelectric domain orientation. It is shown that the (2 0 0) peak is not affected by the domain switching itself but rather acts like an elastic macrostrain sensor. A simple Eshelby analysis is used to demonstrate that both the elastic strain and texture vary systematically with ψ according to the factor (3cos 2 ψ - 1). This angular dependence is evaluated through micromechanics modelling. The physical meaning of the texture variations with ψ is also discussed
Non-asthmatic patients show increased exhaled nitric oxide concentrations
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Beatriz M. Saraiva-Romanholo
2009-01-01
Full Text Available OBJECTIVE: Evaluate whether exhaled nitric oxide may serve as a marker of intraoperative bronchospasm. INTRODUCTION: Intraoperative bronchospasm remains a challenging event during anesthesia. Previous studies in asthmatic patients suggest that exhaled nitric oxide may represent a noninvasive measure of airway inflammation. METHODS: A total of 146,358 anesthesia information forms, which were received during the period from 1999 to 2004, were reviewed. Bronchospasm was registered on 863 forms. From those, three groups were identified: 9 non-asthmatic patients (Bronchospasm group, 12 asthmatics (Asthma group and 10 subjects with no previous airway disease or symptoms (Control group. All subjects were submitted to exhaled nitric oxide measurements (parts/billion, spirometry and the induced sputum test. The data was compared by ANOVA followed by the Tukey test and Kruskal-Wallis followed by Dunn's test. RESULTS: The normal lung function test results for the Bronchospasm group were different from those of the asthma group (p <0.05. The median percentage of eosinophils in induced sputum was higher for the Asthma [2.46 (0.45-6.83] compared with either the Bronchospasm [0.55 (0-1.26] or the Control group [0.0 (0] (p <0.05; exhaled nitric oxide followed a similar pattern for the Asthma [81.55 (57.6-86.85], Bronchospasm [46.2 (42.0 -62.6] and Control group [18.7 (16.0-24.7] (p< 0.05. CONCLUSIONS: Non-asthmatic patients with intraoperative bronchospasm detected during anesthesia and endotracheal intubation showed increased expired nitric oxide.
Influence of crystallographic orientation on the fracture toughness of strongly textured Ti--6Al--4V
International Nuclear Information System (INIS)
Bowen, A.W.
1978-01-01
Fracture toughness values for six test piece orientations in a strongly textured 57-mm thick rolled and annealed Ti--6Al--4V bar have been related to their crystallographic orientations. The K/sub Ic/ values, ranging from 46.3 to 93.3 MPa/m, could be divided into two groups. High values (74.7 to 93.3 MPa/m) were obtained when a crystallographic deformation mode ([1010] or [1122] slip) was parallel to the planes of maximum shear stress for plane strain conditions, and the significant fractographic feature for this group was a clearly defined stretch zone. In the second group, where crystallographic deformation modes were not aligned with the planes of maximum shear stress, much lower K/sub Ic/ values were recorded (46.3 to 50.7 MPa/m). In this case there was no stretch zone and, in addition, some test pieces appeared, in effect, to have delaminated in the immediate vicinity of the crack tip. Similar trends were also indicated by the results of Charpy impact tests. The influence of in-plane elastic anisotropy on fracture toughness is discussed, and the importance of test piece geometry highlighted. From the results it could be inferred that high toughness in anisotropic materials is possible only in certain orientations; stretch zone formation and fatigue striation formation are by the same mechanical process; and there will be significantly different critical crack sizes in textured titanium alloy components
Purwar, Namrta
crystal. Time-resolved X-ray data collected at pH's of 4, 7 and 9 demonstrate that pH alters the kinetics of the PYP photocycle dramatically. At pH 4 the photocycle lasts almost one order of magnitude longer in time compared to pH 7. The final intermediate that accumulates at both pH 7 and pH 4 is absent at pH 9. Results from the dose- and the pH-dependent time-resolved crystallographic experiments show that it is imperative to carefully control the conditions under which time-resolved data are collected. With these considerations we collected a comprehensive time-series from nanoseconds to seconds at 14 different temperature settings from -40 °C to 70 °C. Results from time-resolved crystallography are corroborated by employing time-resolved absorption spectroscopy. For this, absorption spectra on crystals and solution are collected by a fast micro-spectrophotometer custom-designed in our lab. We identify kinetic phases of the PYP photocycle at all 14 temperature settings. Relaxation times associated with these phases are temperature-dependent and can be fit by the Van't Hoff-Arrhenius equation. Kinetic modeling yields entropy and enthalpy values at the barriers of the activation solely from the time-resolved crystallographic data. With this, we advance crystallography to a new frontier: the determination of free energy surfaces. Investigating enzymatic reactions can be challenging, because they are non-cyclic. After one turnover product must be washed away and substrate must be reloaded. A promising approach for routine application can be envisioned at the new 4th generation X-ray sources, such as X-ray free electron lasers (XFELs). With our results we set the scene to comprehensively investigate all kinds of enzymatic reactions with these instruments.
Diophantine approximation and Dirichlet series
Queffélec, Hervé
2013-01-01
This self-contained book will benefit beginners as well as researchers. It is devoted to Diophantine approximation, the analytic theory of Dirichlet series, and some connections between these two domains, which often occur through the Kronecker approximation theorem. Accordingly, the book is divided into seven chapters, the first three of which present tools from commutative harmonic analysis, including a sharp form of the uncertainty principle, ergodic theory and Diophantine approximation to be used in the sequel. A presentation of continued fraction expansions, including the mixing property of the Gauss map, is given. Chapters four and five present the general theory of Dirichlet series, with classes of examples connected to continued fractions, the famous Bohr point of view, and then the use of random Dirichlet series to produce non-trivial extremal examples, including sharp forms of the Bohnenblust-Hille theorem. Chapter six deals with Hardy-Dirichlet spaces, which are new and useful Banach spaces of anal...
Hutzenthaler, Martin
2015-01-01
Many stochastic differential equations (SDEs) in the literature have a superlinearly growing nonlinearity in their drift or diffusion coefficient. Unfortunately, moments of the computationally efficient Euler-Maruyama approximation method diverge for these SDEs in finite time. This article develops a general theory based on rare events for studying integrability properties such as moment bounds for discrete-time stochastic processes. Using this approach, the authors establish moment bounds for fully and partially drift-implicit Euler methods and for a class of new explicit approximation method
Directory of Open Access Journals (Sweden)
Kun-Dar Li
2018-02-01
Full Text Available To improve the advanced manufacturing technology for functional materials, a sophisticated control of chemical etching process is highly demanded, especially in the fields of environment and energy related applications. In this study, a phase-field-based model is utilized to investigate the etch morphologies influenced by the crystallographic characters during anisotropic chemical etching. Three types of etching modes are inspected theoretically, including the isotropic, and preferred oriented etchings. Owing to the specific etching behavior along the crystallographic directions, different characteristic surface structures are presented in the simulations, such as the pimple-like, pyramidal hillock and ridge-like morphologies. In addition, the processing parameters affecting the surface morphological formation and evolution are also examined systematically. According to the numerical results, the growth mechanism of surface morphology in a chemical etching is revealed distinctly. While the etching dynamics plays a dominant role on the surface formation, the characteristic surface morphologies corresponding to the preferred etching direction become more apparent. As the atomic diffusion turned into a determinative factor, a smoothened surface would appear, even under the anisotropic etching conditions. These simulation results provide fundamental information to enhance the development and application of anisotropic chemical etching techniques.
Li, Kun-Dar; Miao, Jin-Ru
2018-02-01
To improve the advanced manufacturing technology for functional materials, a sophisticated control of chemical etching process is highly demanded, especially in the fields of environment and energy related applications. In this study, a phase-field-based model is utilized to investigate the etch morphologies influenced by the crystallographic characters during anisotropic chemical etching. Three types of etching modes are inspected theoretically, including the isotropic, and preferred oriented etchings. Owing to the specific etching behavior along the crystallographic directions, different characteristic surface structures are presented in the simulations, such as the pimple-like, pyramidal hillock and ridge-like morphologies. In addition, the processing parameters affecting the surface morphological formation and evolution are also examined systematically. According to the numerical results, the growth mechanism of surface morphology in a chemical etching is revealed distinctly. While the etching dynamics plays a dominant role on the surface formation, the characteristic surface morphologies corresponding to the preferred etching direction become more apparent. As the atomic diffusion turned into a determinative factor, a smoothened surface would appear, even under the anisotropic etching conditions. These simulation results provide fundamental information to enhance the development and application of anisotropic chemical etching techniques.
Improved Dutch Roll Approximation for Hypersonic Vehicle
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Liang-Liang Yin
2014-06-01
Full Text Available An improved dutch roll approximation for hypersonic vehicle is presented. From the new approximations, the dutch roll frequency is shown to be a function of the stability axis yaw stability and the dutch roll damping is mainly effected by the roll damping ratio. In additional, an important parameter called roll-to-yaw ratio is obtained to describe the dutch roll mode. Solution shows that large-roll-to-yaw ratio is the generate character of hypersonic vehicle, which results the large error for the practical approximation. Predictions from the literal approximations derived in this paper are compared with actual numerical values for s example hypersonic vehicle, results show the approximations work well and the error is below 10 %.
International Nuclear Information System (INIS)
Nakamachi, Eiji
2005-01-01
A crystallographic homogenization procedure is introduced to the conventional static-explicit and dynamic-explicit finite element formulation to develop a multi scale - double scale - analysis code to predict the plastic strain induced texture evolution, yield loci and formability of sheet metal. The double-scale structure consists of a crystal aggregation - micro-structure - and a macroscopic elastic plastic continuum. At first, we measure crystal morphologies by using SEM-EBSD apparatus, and define a unit cell of micro structure, which satisfy the periodicity condition in the real scale of polycrystal. Next, this crystallographic homogenization FE code is applied to 3N pure-iron and 'Benchmark' aluminum A6022 polycrystal sheets. It reveals that the initial crystal orientation distribution - the texture - affects very much to a plastic strain induced texture and anisotropic hardening evolutions and sheet deformation. Since, the multi-scale finite element analysis requires a large computation time, a parallel computing technique by using PC cluster is developed for a quick calculation. In this parallelization scheme, a dynamic workload balancing technique is introduced for quick and efficient calculations
Directory of Open Access Journals (Sweden)
Chi-Chang Wang
2013-09-01
Full Text Available This paper seeks to use the proposed residual correction method in coordination with the monotone iterative technique to obtain upper and lower approximate solutions of singularly perturbed non-linear boundary value problems. First, the monotonicity of a non-linear differential equation is reinforced using the monotone iterative technique, then the cubic-spline method is applied to discretize and convert the differential equation into the mathematical programming problems of an inequation, and finally based on the residual correction concept, complex constraint solution problems are transformed into simpler questions of equational iteration. As verified by the four examples given in this paper, the method proposed hereof can be utilized to fast obtain the upper and lower solutions of questions of this kind, and to easily identify the error range between mean approximate solutions and exact solutions.
Efficient approximation of random fields for numerical applications
Harbrecht, Helmut; Peters, Michael; Siebenmorgen, Markus
2015-01-01
We consider the rapid computation of separable expansions for the approximation of random fields. We compare approaches based on techniques from the approximation of non-local operators on the one hand and based on the pivoted Cholesky decomposition on the other hand. We provide an a-posteriori error estimate for the pivoted Cholesky decomposition in terms of the trace. Numerical examples validate and quantify the considered methods.
Efficient approximation of random fields for numerical applications
Harbrecht, Helmut
2015-01-07
We consider the rapid computation of separable expansions for the approximation of random fields. We compare approaches based on techniques from the approximation of non-local operators on the one hand and based on the pivoted Cholesky decomposition on the other hand. We provide an a-posteriori error estimate for the pivoted Cholesky decomposition in terms of the trace. Numerical examples validate and quantify the considered methods.
Ohaeri, Enyinnaya; Omale, Joseph; Eduok, Ubong; Szpunar, Jerzy
2018-04-01
This work presents the electrochemical response of X70 pipeline steel substrates thermomechanically processed at different conditions. The WE sample was hot rolled at a temperature range of 850 °C to 805 °C and cooled at a rate of 42.75 °C/s. Another sample WD was hot rolled from 880 °C to 815 °C and cooled at a faster rate of 51.5 °C/s. Corrosion tests were conducted electrochemically by potentiodynamic polarization in hydrogen-charged and non-hydrogen-charged environments. A lower corrosion rate was measured with hydrogen charging due to the rapid formation of corrosion product film on pipeline substrate, but WE specimen emerged as the most susceptible to corrosion with and without hydrogen charging. Variations in thermomechanical rolling conditions influenced grain orientation, protective film properties, corrosion, and cracking behavior on both specimens. Cracks were seen in both specimens after hydrogen charging, but specimen WE experienced a more intense deterioration of protective corrosion product film and subsequent cracking. A large part of specimen WD retained its protective corrosion product film after the polarization test, and sites where spalling occurred resulted in pitting with less cracking. Despite weak crystallographic texture noticed in both specimens, WD showed a higher intensity of corrosion-resistant 111||ND-oriented grains, while WE showed a more random distribution of 111||ND-, 011||ND-, and 001||ND-oriented grains with a lower intensity.
Ohaeri, Enyinnaya; Omale, Joseph; Eduok, Ubong; Szpunar, Jerzy
2018-06-01
This work presents the electrochemical response of X70 pipeline steel substrates thermomechanically processed at different conditions. The WE sample was hot rolled at a temperature range of 850 °C to 805 °C and cooled at a rate of 42.75 °C/s. Another sample WD was hot rolled from 880 °C to 815 °C and cooled at a faster rate of 51.5 °C/s. Corrosion tests were conducted electrochemically by potentiodynamic polarization in hydrogen-charged and non-hydrogen-charged environments. A lower corrosion rate was measured with hydrogen charging due to the rapid formation of corrosion product film on pipeline substrate, but WE specimen emerged as the most susceptible to corrosion with and without hydrogen charging. Variations in thermomechanical rolling conditions influenced grain orientation, protective film properties, corrosion, and cracking behavior on both specimens. Cracks were seen in both specimens after hydrogen charging, but specimen WE experienced a more intense deterioration of protective corrosion product film and subsequent cracking. A large part of specimen WD retained its protective corrosion product film after the polarization test, and sites where spalling occurred resulted in pitting with less cracking. Despite weak crystallographic texture noticed in both specimens, WD showed a higher intensity of corrosion-resistant 111|| ND-oriented grains, while WE showed a more random distribution of 111|| ND-, 011|| ND-, and 001|| ND-oriented grains with a lower intensity.
On the description of exclusive processes beyond the leading twist approximation
International Nuclear Information System (INIS)
Anikin, I.V.; Ivanov, D.Yu.; Pire, B.; Szymanowski, L.; Wallon, S.
2010-01-01
We describe hard exclusive processes beyond the leading twist approximation in a framework based on the Taylor expansion of the amplitude around the dominant light-cone directions. This naturally introduces an appropriate set of non-perturbative correlators whose number is minimalized after taking into account QCD equations of motion and the invariance under rotation on the light-cone. We exemplify this method at the twist 3 level and show that the coordinate and momentum space descriptions are fully equivalent.
On the description of exclusive processes beyond the leading twist approximation
Energy Technology Data Exchange (ETDEWEB)
Anikin, I.V. [Bogoliubov Laboratory of Theoretical Physics, JINR, 141980 Dubna (Russian Federation); Ivanov, D.Yu. [Institute of Mathematics, 630090 Novosibirsk (Russian Federation); Pire, B., E-mail: pire@cpht.polytechnique.f [CPhT, Ecole Polytechnique, CNRS, F-91128 Palaiseau (France); Szymanowski, L. [Soltan Institute for Nuclear Studies, Hoza 69, 00-681 Warsaw (Poland); Wallon, S. [LPT, Universite d' Orsay, CNRS, 91404 Orsay (France); UPMC Univ. Paris 6, Faculte de Physique, 4 place Jussieu, 75252 Paris Cedex 05 (France)
2010-01-04
We describe hard exclusive processes beyond the leading twist approximation in a framework based on the Taylor expansion of the amplitude around the dominant light-cone directions. This naturally introduces an appropriate set of non-perturbative correlators whose number is minimalized after taking into account QCD equations of motion and the invariance under rotation on the light-cone. We exemplify this method at the twist 3 level and show that the coordinate and momentum space descriptions are fully equivalent.
Crystallization and preliminary crystallographic analysis of l-asparaginase from Erwinia carotovora
International Nuclear Information System (INIS)
Wikman, Linnea E. K.; Krasotkina, Julya; Kuchumova, Anastasia; Sokolov, Nikolay N.; Papageorgiou, Anastassios C.
2005-01-01
Er. carotovoral-asparaginase, a potential antileukaemic agent, has been crystallized. Crystals diffract to 2.6 Å using a rotating-anode source and belong to space group P2 1 , with unit-cell parameters a = 78.0, b = 112.3, c = 78.7 Å, β = 101.9° and a homotetramer in the crystallographic asymmetric unit. Bacterial l-asparaginases have been used as therapeutic agents in the treatment of acute childhood lymphoblastic leukaemia for over 30 y. However, their use is limited owing to the glutaminase activity of the administered enzymes, which results in serious side effects. In contrast, l-asparaginase from Erwinia carotovora exhibits low glutaminase activity at physiological concentrations of l-asparagine and l-glutamine in the blood. Recombinant Er. carotovoral-asparaginase was crystallized in the presence of l-glutamate by the hanging-drop vapour-diffusion method using 10 mg ml −1 purified enzyme, 16–18%(w/v) PEG 3350 and 0.2 M NaF. X-ray diffraction data were collected to 2.6 Å at 293 K using an in-house rotating-anode generator. The crystals belong to the monoclinic P2 1 space group, with unit-cell parameters a = 78.0, b = 112.3, c = 78.7 Å, β = 101.9° and a homotetramer in the crystallographic asymmetric unit. A molecular-replacement solution has been found and refinement is currently in progress. The crystal structure may provide leads towards protein-engineering efforts aimed at safer asparaginase administration in leukaemia treatment
Exact and approximate multiple diffraction calculations
International Nuclear Information System (INIS)
Alexander, Y.; Wallace, S.J.; Sparrow, D.A.
1976-08-01
A three-body potential scattering problem is solved in the fixed scatterer model exactly and approximately to test the validity of commonly used assumptions of multiple scattering calculations. The model problem involves two-body amplitudes that show diffraction-like differential scattering similar to high energy hadron-nucleon amplitudes. The exact fixed scatterer calculations are compared to Glauber approximation, eikonal-expansion results and a noneikonal approximation
Ordering, symbols and finite-dimensional approximations of path integrals
International Nuclear Information System (INIS)
Kashiwa, Taro; Sakoda, Seiji; Zenkin, S.V.
1994-01-01
We derive general form of finite-dimensional approximations of path integrals for both bosonic and fermionic canonical systems in terms of symbols of operators determined by operator ordering. We argue that for a system with a given quantum Hamiltonian such approximations are independent of the type of symbols up to terms of O(ε), where ε of is infinitesimal time interval determining the accuracy of the approximations. A new class of such approximations is found for both c-number and Grassmannian dynamical variables. The actions determined by the approximations are non-local and have no classical continuum limit except the cases of pq- and qp-ordering. As an explicit example the fermionic oscillator is considered in detail. (author)
Cranswick, Lachlan Michael David
2008-01-01
The history of crystallographic computing and use of crystallographic software is one which traces the escape from the drudgery of manual human calculations to a world where the user delegates most of the travail to electronic computers. In practice, this involves practising crystallographers communicating their thoughts to the crystallographic program authors, in the hope that new procedures will be implemented within their software. Against this background, the development of small-molecule single-crystal and powder diffraction software is traced. Starting with the analogue machines and the use of Hollerith tabulators of the late 1930's, it is shown that computing developments have been science led, with new technologies being harnessed to solve pressing crystallographic problems. The development of software is also traced, with a final caution that few of the computations now performed daily are really understood by the program users. Unless a sufficient body of people continues to dismantle and re-build programs, the knowledge encoded in the old programs will become as inaccessible as the knowledge of how to build the Great Pyramid at Giza.
Study of some approximation schemes in the spin-boson problem
International Nuclear Information System (INIS)
Kenkre, V.M.; Giuggioli, L.
2004-01-01
Some approximation schemes used in the description of the evolution of the spin-boson system are studied through numerical and analytic methods. Among the procedures investigated are semiclassical approximations and the memory function approach. An infinitely large number of semiclassical approximations are discussed. Their two extreme limits are shown to be characterized, respectively, by effective energy mismatch and effective intersite transfer. The validity of the two limits is explored by explicit numerical calculations for important regions in parameter space, and it is shown that they can provide good descriptions in the so-called adiabatic and anti-adiabatic regimes, respectively. The memory function approach, which provides an excellent approximation scheme for a certain range of parameters, is shown to be connected to other approaches such as the non-interacting blip approximation. New results are derived from the memory approach in semiclassical contexts. Comments are made on thermal effects in the spin-boson problem, the discrete non-linear Schroedinger equation, and connections to the areas of dynamic localization, and quantum control
Electrical properties of NiAs-type MnTe films with preferred crystallographic plane of (110)
Energy Technology Data Exchange (ETDEWEB)
Yang, L.; Wang, Z. H., E-mail: zhwang@imr.ac.cn; Zhang, Z. D. [Shenyang National Laboratory for Materials Science, Institute of Metal Research, Chinese Academy of Sciences, 72 Wenhua Road, Shenyang 110016 (China)
2016-01-28
NiAs-type manganese telluride (MnTe) films with preferred crystallographic plane of (110) were prepared on Si/SiO{sub 2} substrates by pulsed laser deposition. X-ray diffraction (XRD) of the films was studied at different temperatures. The XRD peak of MnTe (110) films shifts to higher angle with decreasing temperature, showing the decrease of the lattice parameter. Resistivity of the films was studied in the temperature range of 2–350 K. The bump between 150 and 250 K was observed in the films, which may be related to the special s-d and p-d overlaps induced by the compressed lattice. The magnon drag effect near its Néel temperature T{sub N} and enlarged magnetic-elastic coupling below 100 K were observed and analyzed in details.
Cosmological applications of Padé approximant
International Nuclear Information System (INIS)
Wei, Hao; Yan, Xiao-Peng; Zhou, Ya-Nan
2014-01-01
As is well known, in mathematics, any function could be approximated by the Padé approximant. The Padé approximant is the best approximation of a function by a rational function of given order. In fact, the Padé approximant often gives better approximation of the function than truncating its Taylor series, and it may still work where the Taylor series does not converge. In the present work, we consider the Padé approximant in two issues. First, we obtain the analytical approximation of the luminosity distance for the flat XCDM model, and find that the relative error is fairly small. Second, we propose several parameterizations for the equation-of-state parameter (EoS) of dark energy based on the Padé approximant. They are well motivated from the mathematical and physical points of view. We confront these EoS parameterizations with the latest observational data, and find that they can work well. In these practices, we show that the Padé approximant could be an useful tool in cosmology, and it deserves further investigation
Cosmological applications of Padé approximant
Wei, Hao; Yan, Xiao-Peng; Zhou, Ya-Nan
2014-01-01
As is well known, in mathematics, any function could be approximated by the Padé approximant. The Padé approximant is the best approximation of a function by a rational function of given order. In fact, the Padé approximant often gives better approximation of the function than truncating its Taylor series, and it may still work where the Taylor series does not converge. In the present work, we consider the Padé approximant in two issues. First, we obtain the analytical approximation of the luminosity distance for the flat XCDM model, and find that the relative error is fairly small. Second, we propose several parameterizations for the equation-of-state parameter (EoS) of dark energy based on the Padé approximant. They are well motivated from the mathematical and physical points of view. We confront these EoS parameterizations with the latest observational data, and find that they can work well. In these practices, we show that the Padé approximant could be an useful tool in cosmology, and it deserves further investigation.
Energy Technology Data Exchange (ETDEWEB)
Johnson, Steven [Laboratory of Molecular Biophysics, Department of Biochemistry, University of Oxford (United Kingdom); Sir William Dunn School of Pathology, University of Oxford (United Kingdom); Roversi, Pietro [Laboratory of Molecular Biophysics, Department of Biochemistry, University of Oxford (United Kingdom); Espina, Marianela [Department of Molecular Biosciences, University of Kansas (United States); Deane, Janet E. [Laboratory of Molecular Biophysics, Department of Biochemistry, University of Oxford (United Kingdom); Birket, Susan; Picking, William D. [Department of Molecular Biosciences, University of Kansas (United States); Blocker, Ariel [Sir William Dunn School of Pathology, University of Oxford (United Kingdom); Picking, Wendy L. [Department of Molecular Biosciences, University of Kansas (United States); Lea, Susan M., E-mail: susan.lea@path.ox.ac.uk [Laboratory of Molecular Biophysics, Department of Biochemistry, University of Oxford (United Kingdom); Sir William Dunn School of Pathology, University of Oxford (United Kingdom)
2006-09-01
IpaD, the putative needle-tip protein of the S. flexneri type III secretion system, has been crystallized in a variety of crystal forms using in-drop proteolysis. Native and selenomethionine-labelled data collection and preliminary analyses are reported. IpaD, the putative needle-tip protein of the Shigella flexneri type III secretion system, has been overexpressed and purified. Crystals were grown of the native protein in space group P2{sub 1}2{sub 1}2{sub 1}, with unit-cell parameters a = 55.9, b = 100.7, c = 112.0 Å, and data were collected to 2.9 Å resolution. Analysis of the native Patterson map revealed a peak at 50% of the origin on the Harker section v = 0.5, suggesting twofold non-crystallographic symmetry parallel to the b crystallographic axis. As attempts to derivatize or grow selenomethionine-labelled protein crystals failed, in-drop proteolysis was used to produce new crystal forms. A trace amount of subtilisin Carlsberg was added to IpaD before sparse-matrix screening, resulting in the production of several new crystal forms. This approach produced SeMet-labelled crystals and diffraction data were collected to 3.2 Å resolution. The SeMet crystals belong to space group C2, with unit-cell parameters a = 139.4, b = 45.0, c = 99.5 Å, β = 107.9°. An anomalous difference Patterson map revealed peaks on the Harker section v = 0, while the self-rotation function indicates the presence of a twofold noncrystallographic symmetry axis, which is consistent with two molecules per asymmetric unit.
International Nuclear Information System (INIS)
Johnson, Steven; Roversi, Pietro; Espina, Marianela; Deane, Janet E.; Birket, Susan; Picking, William D.; Blocker, Ariel; Picking, Wendy L.; Lea, Susan M.
2006-01-01
IpaD, the putative needle-tip protein of the S. flexneri type III secretion system, has been crystallized in a variety of crystal forms using in-drop proteolysis. Native and selenomethionine-labelled data collection and preliminary analyses are reported. IpaD, the putative needle-tip protein of the Shigella flexneri type III secretion system, has been overexpressed and purified. Crystals were grown of the native protein in space group P2 1 2 1 2 1 , with unit-cell parameters a = 55.9, b = 100.7, c = 112.0 Å, and data were collected to 2.9 Å resolution. Analysis of the native Patterson map revealed a peak at 50% of the origin on the Harker section v = 0.5, suggesting twofold non-crystallographic symmetry parallel to the b crystallographic axis. As attempts to derivatize or grow selenomethionine-labelled protein crystals failed, in-drop proteolysis was used to produce new crystal forms. A trace amount of subtilisin Carlsberg was added to IpaD before sparse-matrix screening, resulting in the production of several new crystal forms. This approach produced SeMet-labelled crystals and diffraction data were collected to 3.2 Å resolution. The SeMet crystals belong to space group C2, with unit-cell parameters a = 139.4, b = 45.0, c = 99.5 Å, β = 107.9°. An anomalous difference Patterson map revealed peaks on the Harker section v = 0, while the self-rotation function indicates the presence of a twofold noncrystallographic symmetry axis, which is consistent with two molecules per asymmetric unit
Ocean acidification reduces the crystallographic control in juvenile mussel shells.
Fitzer, Susan C; Cusack, Maggie; Phoenix, Vernon R; Kamenos, Nicholas A
2014-10-01
Global climate change threatens the oceans as anthropogenic carbon dioxide causes ocean acidification and reduced carbonate saturation. Future projections indicate under saturation of aragonite, and potentially calcite, in the oceans by 2100. Calcifying organisms are those most at risk from such ocean acidification, as carbonate is vital in the biomineralisation of their calcium carbonate protective shells. This study highlights the importance of multi-generational studies to investigate how marine organisms can potentially adapt to future projected global climate change. Mytilus edulis is an economically important marine calcifier vulnerable to decreasing carbonate saturation as their shells comprise two calcium carbonate polymorphs: aragonite and calcite. M. edulis specimens were cultured under current and projected pCO2 (380, 550, 750 and 1000μatm), following 6months of experimental culture, adults produced second generation juvenile mussels. Juvenile mussel shells were examined for structural and crystallographic orientation of aragonite and calcite. At 1000μatm pCO2, juvenile mussels spawned and grown under this high pCO2 do not produce aragonite which is more vulnerable to carbonate under-saturation than calcite. Calcite and aragonite were produced at 380, 550 and 750μatm pCO2. Electron back scatter diffraction analyses reveal less constraint in crystallographic orientation with increased pCO2. Shell formation is maintained, although the nacre crystals appear corroded and crystals are not so closely layered together. The differences in ultrastructure and crystallography in shells formed by juveniles spawned from adults in high pCO2 conditions may prove instrumental in their ability to survive ocean acidification. Copyright © 2014 Elsevier Inc. All rights reserved.
Mapping moveout approximations in TI media
Stovas, Alexey; Alkhalifah, Tariq Ali
2013-01-01
Moveout approximations play a very important role in seismic modeling, inversion, and scanning for parameters in complex media. We developed a scheme to map one-way moveout approximations for transversely isotropic media with a vertical axis of symmetry (VTI), which is widely available, to the tilted case (TTI) by introducing the effective tilt angle. As a result, we obtained highly accurate TTI moveout equations analogous with their VTI counterparts. Our analysis showed that the most accurate approximation is obtained from the mapping of generalized approximation. The new moveout approximations allow for, as the examples demonstrate, accurate description of moveout in the TTI case even for vertical heterogeneity. The proposed moveout approximations can be easily used for inversion in a layered TTI medium because the parameters of these approximations explicitly depend on corresponding effective parameters in a layered VTI medium.
Mapping moveout approximations in TI media
Stovas, Alexey
2013-11-21
Moveout approximations play a very important role in seismic modeling, inversion, and scanning for parameters in complex media. We developed a scheme to map one-way moveout approximations for transversely isotropic media with a vertical axis of symmetry (VTI), which is widely available, to the tilted case (TTI) by introducing the effective tilt angle. As a result, we obtained highly accurate TTI moveout equations analogous with their VTI counterparts. Our analysis showed that the most accurate approximation is obtained from the mapping of generalized approximation. The new moveout approximations allow for, as the examples demonstrate, accurate description of moveout in the TTI case even for vertical heterogeneity. The proposed moveout approximations can be easily used for inversion in a layered TTI medium because the parameters of these approximations explicitly depend on corresponding effective parameters in a layered VTI medium.
Approximate Integrals of rf-driven Particle Motion in Magnetic Field
International Nuclear Information System (INIS)
Dodin, I.Y.; Fisch, N.J.
2004-01-01
For a particle moving in nonuniform magnetic field under the action of an rf wave, ponderomotive effects result from rf-driven oscillations nonlinearly coupled with Larmor rotation. Using Lagrangian and Hamiltonian formalism, we show how, despite this coupling, two independent integrals of the particle motion are approximately conserved. Those are the magnetic moment of free Larmor rotation and the quasi-energy of the guiding center motion parallel to the magnetic field. Under the assumption of non-resonant interaction of the particle with the rf field, these integrals represent adiabatic invariants of the particle motion
Energy Technology Data Exchange (ETDEWEB)
Son, Hyo-Soo; Choi, Nak-Jung [Department of Nano-Optical Engineering, Korea Polytechnic University, Siheung 429-793 (Korea, Republic of); Kim, Kyoung-Bo [Department of Metallurgical and Materials Engineering, Inha Technical College, Incheon 402-752 (Korea, Republic of); Kim, Moojin [Department of Renewable Energy, Jungwon University, Goesan-gun, Chungbuk 367-805 (Korea, Republic of); Lee, Sung-Nam, E-mail: snlee@kpu.ac.kr [Department of Nano-Optical Engineering, Korea Polytechnic University, Siheung 429-793 (Korea, Republic of)
2016-10-15
Highlights: • Polar and semipolar ZnO NRs were successfully achieved by hydrothermal synthesis. • Semipolar and polar ZnO NRs were grown on ZnO and AZO/m-sapphire, respectively. • Al % of AZO/m-sapphire enhanced the lateral growth rate of polar ZnO NRs. - Abstract: We investigated the effect of an Al-doped ZnO film on the crystallographic direction of ZnO nanorods (NRs) using electrochemical deposition. From high-solution X-ray diffraction measurements, the crystallographic plane of ZnO NRs grown on (1 0 0) ZnO/m-plane sapphire was (1 0 1). The surface grain size of the (100) Al-doped ZnO (AZO) film decreased with increasing Al content in the ZnO seed layer, implying that the Al dopant accelerated the three-dimensional (3D) growth of the AZO film. In addition, it was found that with increasing Al doping concentration of the AZO seed layer, the crystal orientation of the ZnO NRs grown on the AZO seed layer changed from [1 0 1] to [0 0 1]. With increasing Al content of the nonpolar (1 0 0) AZO seed layer, the small surface grains with a few crystallographic planes of the AZO film changed from semipolar (1 0 1) ZnO NRs to polar (0 0 1) ZnO NRs due to the increase of the vertical [0 0 1] growth rate of the ZnO NRs owing to excellent electrical properties.
Coefficients Calculation in Pascal Approximation for Passive Filter Design
Directory of Open Access Journals (Sweden)
George B. Kasapoglu
2018-02-01
Full Text Available The recently modified Pascal function is further exploited in this paper in the design of passive analog filters. The Pascal approximation has non-equiripple magnitude, in contrast of the most well-known approximations, such as the Chebyshev approximation. A novelty of this work is the introduction of a precise method that calculates the coefficients of the Pascal function. Two examples are presented for the passive design to illustrate the advantages and the disadvantages of the Pascal approximation. Moreover, the values of the passive elements can be taken from tables, which are created to define the normalized values of these elements for the Pascal approximation, as Zverev had done for the Chebyshev, Elliptic, and other approximations. Although Pascal approximation can be implemented to both passive and active filter designs, a passive filter design is addressed in this paper, and the benefits and shortcomings of Pascal approximation are presented and discussed.
Dissociation between exact and approximate addition in developmental dyslexia.
Yang, Xiujie; Meng, Xiangzhi
2016-09-01
Previous research has suggested that number sense and language are involved in number representation and calculation, in which number sense supports approximate arithmetic, and language permits exact enumeration and calculation. Meanwhile, individuals with dyslexia have a core deficit in phonological processing. Based on these findings, we thus hypothesized that children with dyslexia may exhibit exact calculation impairment while doing mental arithmetic. The reaction time and accuracy while doing exact and approximate addition with symbolic Arabic digits and non-symbolic visual arrays of dots were compared between typically developing children and children with dyslexia. Reaction time analyses did not reveal any differences across two groups of children, the accuracies, interestingly, revealed a distinction of approximation and exact addition across two groups of children. Specifically, two groups of children had no differences in approximation. Children with dyslexia, however, had significantly lower accuracy in exact addition in both symbolic and non-symbolic tasks than that of typically developing children. Moreover, linguistic performances were selectively associated with exact calculation across individuals. These results suggested that children with dyslexia have a mental arithmetic deficit specifically in the realm of exact calculation, while their approximation ability is relatively intact. Copyright © 2016 Elsevier Ltd. All rights reserved.
Energy Technology Data Exchange (ETDEWEB)
Abdulmalik, Osheiza [The Children’s Hospital of Philadelphia, Philadelphia, PA 19104 (United States); Ghatge, Mohini S.; Musayev, Faik N.; Parikh, Apurvasena [Virginia Commonwealth University, Richmond, VA 23298 (United States); Chen, Qiukan; Yang, Jisheng [The Children’s Hospital of Philadelphia, Philadelphia, PA 19104 (United States); Nnamani, Ijeoma [Duke University Medical Center, Durham, NC 27710 (United States); Danso-Danquah, Richmond [Virginia Commonwealth University, Richmond, VA 23298 (United States); Eseonu, Dorothy N. [Virginia Union University, Richmond, VA 23220 (United States); Asakura, Toshio [Duke University Medical Center, Durham, NC 27710 (United States); Abraham, Donald J.; Venitz, Jurgen; Safo, Martin K., E-mail: msafo@vcu.edu [Virginia Commonwealth University, Richmond, VA 23298 (United States); The Children’s Hospital of Philadelphia, Philadelphia, PA 19104 (United States)
2011-11-01
Pyridyl derivatives of vanillin increase the fraction of the more soluble oxygenated sickle hemoglobin and/or directly increase the solubility of deoxygenated sickle hemoglobin. Crystallographic analysis reveals the structural basis of the potent and dual antisickling activity of these derivatives. Vanillin has previously been studied clinically as an antisickling agent to treat sickle-cell disease. In vitro investigations with pyridyl derivatives of vanillin, including INN-312 and INN-298, showed as much as a 90-fold increase in antisickling activity compared with vanillin. The compounds preferentially bind to and modify sickle hemoglobin (Hb S) to increase the affinity of Hb for oxygen. INN-312 also led to a considerable increase in the solubility of deoxygenated Hb S under completely deoxygenated conditions. Crystallographic studies of normal human Hb with INN-312 and INN-298 showed that the compounds form Schiff-base adducts with the N-terminus of the α-subunits to constrain the liganded (or relaxed-state) Hb conformation relative to the unliganded (or tense-state) Hb conformation. Interestingly, while INN-298 binds and directs its meta-positioned pyridine-methoxy moiety (relative to the aldehyde moiety) further down the central water cavity of the protein, that of INN-312, which is ortho to the aldehyde, extends towards the surface of the protein. These studies suggest that these compounds may act to prevent sickling of SS cells by increasing the fraction of the soluble high-affinity Hb S and/or by stereospecific inhibition of deoxygenated Hb S polymerization.
International Nuclear Information System (INIS)
Abdulmalik, Osheiza; Ghatge, Mohini S.; Musayev, Faik N.; Parikh, Apurvasena; Chen, Qiukan; Yang, Jisheng; Nnamani, Ijeoma; Danso-Danquah, Richmond; Eseonu, Dorothy N.; Asakura, Toshio; Abraham, Donald J.; Venitz, Jurgen; Safo, Martin K.
2011-01-01
Pyridyl derivatives of vanillin increase the fraction of the more soluble oxygenated sickle hemoglobin and/or directly increase the solubility of deoxygenated sickle hemoglobin. Crystallographic analysis reveals the structural basis of the potent and dual antisickling activity of these derivatives. Vanillin has previously been studied clinically as an antisickling agent to treat sickle-cell disease. In vitro investigations with pyridyl derivatives of vanillin, including INN-312 and INN-298, showed as much as a 90-fold increase in antisickling activity compared with vanillin. The compounds preferentially bind to and modify sickle hemoglobin (Hb S) to increase the affinity of Hb for oxygen. INN-312 also led to a considerable increase in the solubility of deoxygenated Hb S under completely deoxygenated conditions. Crystallographic studies of normal human Hb with INN-312 and INN-298 showed that the compounds form Schiff-base adducts with the N-terminus of the α-subunits to constrain the liganded (or relaxed-state) Hb conformation relative to the unliganded (or tense-state) Hb conformation. Interestingly, while INN-298 binds and directs its meta-positioned pyridine-methoxy moiety (relative to the aldehyde moiety) further down the central water cavity of the protein, that of INN-312, which is ortho to the aldehyde, extends towards the surface of the protein. These studies suggest that these compounds may act to prevent sickling of SS cells by increasing the fraction of the soluble high-affinity Hb S and/or by stereospecific inhibition of deoxygenated Hb S polymerization
Connection of crystallographic texture with anisotropy of yield strength of titanium alloy sheets
International Nuclear Information System (INIS)
Serebryannyj, V.N.; Koknaev, R.G.
1983-01-01
Using the programs developed in FORTRAN-4 algorithmic language for the ES-1022 computer the contribution of crystallographic texture to the anisotropy of yield strength in the sheet plane for warm-rolled sheets of α-titanium alloys VT1 and VT5-1, is evaluated. It is established, that experimental and calculation data for the sheet of VT1-0 agree satisfactorily in the angle range phi 40 deg the value anti M (phi) exceeds the experimental values σsub(0.2)(phi./σsub(0.2)(0). The results obtained for the sheet of the VT5-1 alloy show, that calculation and experimental data agree well for narrow angles (phi <= 60 deg) and at wider angles the values anti M(phi) exceed the values σsub(0.2)(phi)/σsub(0.2)(0). Calculation and experimental curves for the VT5-1 alloy on the whole agree better than for the VT1-0 one
Challenges in quantitative crystallographic characterization of 3D thin films by ACOM-TEM.
Kobler, A; Kübel, C
2017-02-01
Automated crystal orientation mapping for transmission electron microscopy (ACOM-TEM) has become an easy to use method for the investigation of crystalline materials and complements other TEM methods by adding local crystallographic information over large areas. It fills the gap between high resolution electron microscopy and electron back scatter diffraction in terms of spatial resolution. Recent investigations showed that spot diffraction ACOM-TEM is a quantitative method with respect to sample parameters like grain size, twin density, orientation density and others. It can even be used in combination with in-situ tensile or thermal testing. However, there are limitations of the current method. In this paper we discuss some of the challenges and discuss solutions, e.g. we present an ambiguity filter that reduces the number of pixels with a '180° ambiguity problem'. For that an ACOM-TEM tilt series of nanocrystalline Pd thin films with overlapping crystallites was acquired and analyzed. Copyright © 2017. Published by Elsevier B.V.
Magdziarz, M.; Mista, P.; Weron, A.
2007-05-01
We introduce an approximation of the risk processes by anomalous diffusion. In the paper we consider the case, where the waiting times between successive occurrences of the claims belong to the domain of attraction of alpha -stable distribution. The relationship between the obtained approximation and the celebrated fractional diffusion equation is emphasised. We also establish upper bounds for the ruin probability in the considered model and give some numerical examples.
Crystallographic disorder and magnetism in UPd2-xSn
International Nuclear Information System (INIS)
Suellow, S.; Mattheus, C.C.; Becker, B.; Snel, C.E.; Nieuwenhuys, G.J.; Mydosh, J.A.; Schenck, A.
1997-01-01
The intermetallic compound UPd 2 Sn has been shown in previous investigations to crystallize in an orthorhombic structure (space group Pnma). No indications for magnetic or superconducting transitions were found. However, if the Pd content is reduced, then, similar to UNi 2 Sn, a structural transition occurs. We prepared UPd 1.85 Sn and found it to crystallize as a Heusler compound in the MnCu 2 Al-structure (space group Fm anti 3m). Now the system undergoes a transition into a disordered magnetic state at T mag ≅ 28 K. Here, we present our measurements of the specific heat, susceptibility and muon relaxation of UPd 1.85 Sn, and discuss the nature of the magnetic state in relation to the crystallographic structure. (orig.)
Phormidium phycoerythrin forms hexamers in crystals: a crystallographic study
Sonani, Ravi Raghav; Sharma, Mahima; Gupta, Gagan Deep; Kumar, Vinay; Madamwar, Datta
2015-01-01
The crystallographic analysis of a marine cyanobacterium (Phormidium sp. A09DM) phycoerythrin (PE) that shows distinct sequence features compared with known PE structures from cyanobacteria and red algae is reported. Phormidium PE was crystallized using the sitting-drop vapour-diffusion method with ammonium sulfate as a precipitant. Diffraction data were collected on the protein crystallography beamline at the Indus-2 synchrotron. The crystals diffracted to about 2.1 Å resolution at 100 K. The crystals, with an apparent hexagonal morphology, belonged to space group P1, with unit-cell parameters a = 108.3, b = 108.4 Å, c = 116.6 Å, α = 78.94, β = 82.50, γ = 60.34°. The molecular-replacement solution confirmed the presence of 12 αβ monomers in the P1 cell. The Phormidium PE elutes as an (αβ)3 trimer of αβ monomers from a molecular-sieve column and exists as [(αβ)3]2 hexamers in the crystal lattice. Unlike red algal PE proteins, the hexamers of Phormidium PE do not form higher-order structures in the crystals. The existence of only one characteristic visual absorption band at 564 nm suggests the presence of phycoerythrobilin chromophores, and the absence of any other types of bilins, in the Phormidium PE assembly. PMID:26249689
Fox, Austin J; Drawl, Bill; Fox, Glen R; Gibbons, Brady J; Trolier-McKinstry, Susan
2015-01-01
Optimized processing conditions for Pt/TiO2/SiO2/Si templating electrodes were investigated. These electrodes are used to obtain [111] textured thin film lead zirconate titanate (Pb[ZrxTi1-x ]O3 0 ≤ x ≤ 1) (PZT). Titanium deposited by dc magnetron sputtering yields [0001] texture on a thermally oxidized Si wafer. It was found that by optimizing deposition time, pressure, power, and the chamber pre-conditioning, the Ti texture could be maximized while maintaining low surface roughness. When oxidized, titanium yields [100]-oriented rutile. This seed layer has as low as a 4.6% lattice mismatch with [111] Pt; thus, it is possible to achieve strongly oriented [111] Pt. The quality of the orientation and surface roughness of the TiO2 and the Ti directly affect the achievable Pt texture and surface morphology. A transition between optimal crystallographic texture and the smoothest templating surface occurs at approximately 30 nm of original Ti thickness (45 nm TiO2). This corresponds to 0.5 nm (2 nm for TiO2) rms roughness as determined by atomic force microscopy and a full-width at half-maximum (FWHM) of the rocking curve 0002 (200) peak of 5.5/spl degrees/ (3.1/spl degrees/ for TiO2). A Pb[Zr0.52Ti 0.48]O3 layer was deposited and shown to template from the textured Pt electrode, with a maximum [111] Lotgering factor of 87% and a minimum 111 FWHM of 2.4/spl degrees/ at approximately 30 nm of original Ti.
Real space method of powder diffraction for non-periodic and nearly periodic materials
International Nuclear Information System (INIS)
Egami, T.; Toby, B.H.; Dmowski, W.; Janot, C.; Jorgensen, J.D.
1990-01-01
The use of high-energy neutrons from pulsed or hot sources allows the method of atomic pair distribution analysis to be applied to the structural determination of crystalline as well as amorphous solids. This method complements the standard crystallographic methods in studying non-periodic aspects of solids with or without long range order
International Nuclear Information System (INIS)
Alguero, M.; Bushby, A.J.; Reece, M.J.; Seifert, A.
2002-01-01
Lead zirconate titanate Pb(Zr,Ti)O 3 ferroelectric thin films show significant anelastic deformation when indented with spherical tipped indenters. Experiments on films with different Zr/Ti ratio and a mixed , preferred crystallographic orientation have shown that there is a good agreement between the anelastic deformation and the maximum strain achievable by non-180 deg. domain wall movement. An expected increase of the indentation stiffness of the films also accompanies the anelastic deformation because of the single crystal elastic anisotropy. All these observations seem to indicate that non-180 deg. ferroelectric domain wall movements occur under indentation stresses and cause anelasticity. Stresses for maximum anelastic deformation are compared with those for recently reported stress-induced depolarization
On Covering Approximation Subspaces
Directory of Open Access Journals (Sweden)
Xun Ge
2009-06-01
Full Text Available Let (U';C' be a subspace of a covering approximation space (U;C and X⊂U'. In this paper, we show that and B'(X⊂B(X∩U'. Also, iff (U;C has Property Multiplication. Furthermore, some connections between outer (resp. inner definable subsets in (U;C and outer (resp. inner definable subsets in (U';C' are established. These results answer a question on covering approximation subspace posed by J. Li, and are helpful to obtain further applications of Pawlak rough set theory in pattern recognition and artificial intelligence.
5,7,12,14-Tetrahydro-5,14:7,12-bis([1,2]benzenopentacene-6,13-diol dimethylformamide disolvate
Directory of Open Access Journals (Sweden)
Mohammad Nozari
2016-07-01
Full Text Available The crystal lattice of the title compound, C34H22O2·2C3H7NO, at 173 K has monoclinic (P21/n symmetry. Molecules are located on crystallographic centers of symmetry and have approximate non-crystallographic mmm symmetry, indicating that in solution the chemical and spectroscopic behavior would be that of a D2h molecule. The compound has applications in gas-separation membranes fabricated from polymers of intrinsic microporosity (PIM. The compound is the product of reduction of the corresponding quinone by Na2S2O4 in DMF/NaHCO3.
International Nuclear Information System (INIS)
Bennett, Joseph W.; Rabe, Karin M.
2012-01-01
In this concept paper, the development of strategies for the integration of first-principles methods with crystallographic database mining for the discovery and design of novel ferroelectric materials is discussed, drawing on the results and experience derived from exploratory investigations on three different systems: (1) the double perovskite Sr(Sb 1/2 Mn 1/2 )O 3 as a candidate semiconducting ferroelectric; (2) polar derivatives of schafarzikite MSb 2 O 4 ; and (3) ferroelectric semiconductors with formula M 2 P 2 (S,Se) 6 . A variety of avenues for further research and investigation are suggested, including automated structure type classification, low-symmetry improper ferroelectrics, and high-throughput first-principles searches for additional representatives of structural families with desirable functional properties. - Graphical abstract: Integration of first-principles methods with crystallographic database mining, for the discovery and design of novel ferroelectric materials, could potentially lead to new classes of multifunctional materials. Highlights: ► Integration of first-principles methods and database mining. ► Minor structural families with desirable functional properties. ► Survey of polar entries in the Inorganic Crystal Structural Database.
International Nuclear Information System (INIS)
Petrareanu, Georgiana; Balasu, Mihaela C.; Zander, Ulrich; Scheidig, Axel J.; Szedlacsek, Stefan E.
2010-01-01
The expression, purification, preliminary crystallization and crystallographic analysis of phosphoketolase from L. lactis ssp. lactis (strain IL 1403) are reported. Phosphoketolases are thiamine diphosphate-dependent enzymes which play a central role in the pentose-phosphate pathway of heterofermentative lactic acid bacteria. They belong to the family of aldehyde-lyases and in the presence of phosphate ion cleave the carbon–carbon bond of the specific substrate d-xylulose 5-phosphate (or d-fructose 6-phosphate) to give acetyl phosphate and d-glyceraldehyde 3-phosphate (or d-erythrose 4-phosphate). Structural information about phosphoketolases is particularly important in order to fully understand their mechanism as well as the steric course of phosphoketolase-catalyzed reactions. Here, the purification, preliminary crystallization and crystallographic characterization of d-xylulose 5-phosphate phosphoketolase from Lactococcus lactis are reported. The presence of thiamine diphosphate during purification was essential for the enzymatic activity of the purified protein. The crystals belonged to the monoclinic space group P2 1 . Diffraction data were obtained to a resolution of 2.2 Å
Fenn, Timothy D.; Schnieders, Michael J.; Mustyakimov, Marat; Wu, Chuanjie; Langan, Paul; Pande, Vijay S.; Brunger, Axel T.
2011-01-01
Most current crystallographic structure refinements augment the diffraction data with a priori information consisting of bond, angle, dihedral, planarity restraints and atomic repulsion based on the Pauli exclusion principle. Yet, electrostatics and van der Waals attraction are physical forces that provide additional a priori information. Here we assess the inclusion of electrostatics for the force field used for all-atom (including hydrogen) joint neutron/X-ray refinement. Two DNA and a prot...
International Nuclear Information System (INIS)
Oyenarte, Iker; Majtan, Tomas; Ereño, June; Corral-Rodríguez, María Angeles; Kraus, Jan P.; Martínez-Cruz, Luis Alfonso
2012-01-01
This article describes the crystallization and preliminary crystallographic analysis of a protein construct (hCBS 516–525 ) that contains the full-length cystathionine β-synthase from Homo sapiens (hCBS) and just lacks amino-acid residues 516–525. Human cystathionine β-synthase (CBS) is a pyridoxal-5′-phosphate-dependent hemeprotein, whose catalytic activity is regulated by S-adenosylmethionine. CBS catalyzes the β-replacement reaction of homocysteine (Hcy) with serine to yield cystathionine. CBS is a key regulator of plasma levels of the thrombogenic Hcy and deficiency in CBS is the single most common cause of homocystinuria, an inherited metabolic disorder of sulfur amino acids. The properties of CBS enzymes, such as domain organization, oligomerization degree or regulatory mechanisms, are not conserved across the eukaryotes. The current body of knowledge is insufficient to understand these differences and their impact on CBS function and physiology. To overcome this deficiency, we have addressed the crystallization and preliminary crystallographic analysis of a protein construct (hCBS 516–525 ) that contains the full-length CBS from Homo sapiens (hCBS) and just lacks amino-acid residues 516–525, which are located in a disordered loop. The human enzyme yielded crystals belonging to space group I222, with unit-cell parameters a = 124.98, b = 136.33, c = 169.83 Å and diffracting X-rays to a resolution of 3.0 Å. The crystal structure appears to contain two molecules in the asymmetric unit which presumably correspond to a dimeric form of the enzyme
Crystallization and preliminary crystallographic analysis of l-asparaginase from Erwinia carotovora
Energy Technology Data Exchange (ETDEWEB)
Wikman, Linnea E. K. [Turku Centre for Biotechnology, University of Turku and Åbo Akademi University, Turku 20521 (Finland); Krasotkina, Julya; Kuchumova, Anastasia; Sokolov, Nikolay N. [Institute for Biomedical Chemistry, Russian Academy of Medical Sciences, 559-B, 10 Pogodinskay St, Moscow 119121 (Russian Federation); Papageorgiou, Anastassios C., E-mail: tassos.papageorgiou@btk.fi [Turku Centre for Biotechnology, University of Turku and Åbo Akademi University, Turku 20521 (Finland)
2005-04-01
Er. carotovoral-asparaginase, a potential antileukaemic agent, has been crystallized. Crystals diffract to 2.6 Å using a rotating-anode source and belong to space group P2{sub 1}, with unit-cell parameters a = 78.0, b = 112.3, c = 78.7 Å, β = 101.9° and a homotetramer in the crystallographic asymmetric unit. Bacterial l-asparaginases have been used as therapeutic agents in the treatment of acute childhood lymphoblastic leukaemia for over 30 y. However, their use is limited owing to the glutaminase activity of the administered enzymes, which results in serious side effects. In contrast, l-asparaginase from Erwinia carotovora exhibits low glutaminase activity at physiological concentrations of l-asparagine and l-glutamine in the blood. Recombinant Er. carotovoral-asparaginase was crystallized in the presence of l-glutamate by the hanging-drop vapour-diffusion method using 10 mg ml{sup −1} purified enzyme, 16–18%(w/v) PEG 3350 and 0.2 M NaF. X-ray diffraction data were collected to 2.6 Å at 293 K using an in-house rotating-anode generator. The crystals belong to the monoclinic P2{sub 1} space group, with unit-cell parameters a = 78.0, b = 112.3, c = 78.7 Å, β = 101.9° and a homotetramer in the crystallographic asymmetric unit. A molecular-replacement solution has been found and refinement is currently in progress. The crystal structure may provide leads towards protein-engineering efforts aimed at safer asparaginase administration in leukaemia treatment.
International Nuclear Information System (INIS)
Brett, Tobias; Galla, Tobias
2014-01-01
We present a heuristic derivation of Gaussian approximations for stochastic chemical reaction systems with distributed delay. In particular, we derive the corresponding chemical Langevin equation. Due to the non-Markovian character of the underlying dynamics, these equations are integro-differential equations, and the noise in the Gaussian approximation is coloured. Following on from the chemical Langevin equation, a further reduction leads to the linear-noise approximation. We apply the formalism to a delay variant of the celebrated Brusselator model, and show how it can be used to characterise noise-driven quasi-cycles, as well as noise-triggered spiking. We find surprisingly intricate dependence of the typical frequency of quasi-cycles on the delay period
Brett, Tobias; Galla, Tobias
2014-03-28
We present a heuristic derivation of Gaussian approximations for stochastic chemical reaction systems with distributed delay. In particular, we derive the corresponding chemical Langevin equation. Due to the non-Markovian character of the underlying dynamics, these equations are integro-differential equations, and the noise in the Gaussian approximation is coloured. Following on from the chemical Langevin equation, a further reduction leads to the linear-noise approximation. We apply the formalism to a delay variant of the celebrated Brusselator model, and show how it can be used to characterise noise-driven quasi-cycles, as well as noise-triggered spiking. We find surprisingly intricate dependence of the typical frequency of quasi-cycles on the delay period.
A Bayesian non-inferiority test for two independent binomial proportions.
Kawasaki, Yohei; Miyaoka, Etsuo
2013-01-01
In drug development, non-inferiority tests are often employed to determine the difference between two independent binomial proportions. Many test statistics for non-inferiority are based on the frequentist framework. However, research on non-inferiority in the Bayesian framework is limited. In this paper, we suggest a new Bayesian index τ = P(π₁ > π₂-Δ₀|X₁, X₂), where X₁ and X₂ denote binomial random variables for trials n1 and n₂, and parameters π₁ and π₂ , respectively, and the non-inferiority margin is Δ₀> 0. We show two calculation methods for τ, an approximate method that uses normal approximation and an exact method that uses an exact posterior PDF. We compare the approximate probability with the exact probability for τ. Finally, we present the results of actual clinical trials to show the utility of index τ. Copyright © 2013 John Wiley & Sons, Ltd.
Study of the crystallographic and magnetic properties of cubic manganite spinels NiMn2O4
International Nuclear Information System (INIS)
Boucher, B.
1969-01-01
We study the variation of the crystallographic properties (inversion degree, position parameters and short range order) of the cubic spinel Mn ν Ni 1-ν [Mn 2ν Ni ν ]O 4 , as a function of the thermal treatment applied to the sample. ν lies between 0. 74 and 0. 93; the slower the sample is cooled the more inverse it is. We show, in a molecular field theory, that a system of three magnetic sublattices can afford a 'star' configuration. We establish the conditions of stability of such a structure and its evolution as a function of temperature is foreseen. Neutron diffraction measurements show that the magnetic structure of NiMn 2 O 4 at 4.2 K is a 'star' configuration and that with increasing temperature it becomes a collinear structure in agreement with the theory. Furthermore, we find an anomaly in the value of specific heat at the transition temperature between 'star' and collinear structures. (author) [fr
Square well approximation to the optical potential
International Nuclear Information System (INIS)
Jain, A.K.; Gupta, M.C.; Marwadi, P.R.
1976-01-01
Approximations for obtaining T-matrix elements for a sum of several potentials in terms of T-matrices for individual potentials are studied. Based on model calculations for S-wave for a sum of two separable non-local potentials of Yukawa type form factors and a sum of two delta function potentials, it is shown that the T-matrix for a sum of several potentials can be approximated satisfactorily over all the energy regions by the sum of T-matrices for individual potentials. Based on this, an approximate method for finding T-matrix for any local potential by approximating it by a sum of suitable number of square wells is presented. This provides an interesting way to calculate the T-matrix for any arbitary potential in terms of Bessel functions to a good degree of accuracy. The method is applied to the Saxon-Wood potentials and good agreement with exact results is found. (author)
Hierarchical low-rank approximation for high dimensional approximation
Nouy, Anthony
2016-01-07
Tensor methods are among the most prominent tools for the numerical solution of high-dimensional problems where functions of multiple variables have to be approximated. Such high-dimensional approximation problems naturally arise in stochastic analysis and uncertainty quantification. In many practical situations, the approximation of high-dimensional functions is made computationally tractable by using rank-structured approximations. In this talk, we present algorithms for the approximation in hierarchical tensor format using statistical methods. Sparse representations in a given tensor format are obtained with adaptive or convex relaxation methods, with a selection of parameters using crossvalidation methods.
Hierarchical low-rank approximation for high dimensional approximation
Nouy, Anthony
2016-01-01
Tensor methods are among the most prominent tools for the numerical solution of high-dimensional problems where functions of multiple variables have to be approximated. Such high-dimensional approximation problems naturally arise in stochastic analysis and uncertainty quantification. In many practical situations, the approximation of high-dimensional functions is made computationally tractable by using rank-structured approximations. In this talk, we present algorithms for the approximation in hierarchical tensor format using statistical methods. Sparse representations in a given tensor format are obtained with adaptive or convex relaxation methods, with a selection of parameters using crossvalidation methods.
Pade approximant calculations for neutron escape probability
International Nuclear Information System (INIS)
El Wakil, S.A.; Saad, E.A.; Hendi, A.A.
1984-07-01
The neutron escape probability from a non-multiplying slab containing internal source is defined in terms of a functional relation for the scattering function for the diffuse reflection problem. The Pade approximant technique is used to get numerical results which compare with exact results. (author)
Detection accuracy of in vitro approximal caries by cone beam computed tomography images
Energy Technology Data Exchange (ETDEWEB)
Qu Xingmin, E-mail: quxingmin@bjmu.edu.cn [Department of Oral and Maxillofacial Radiology, Peking University School and Hospital of Stomatology, 22 Zhongguancun Nandajie, Hai Dian District, Beijing 100081 (China); Li Gang, E-mail: kqgang@bjmu.edu.cn [Department of Oral and Maxillofacial Radiology, Peking University School and Hospital of Stomatology, 22 Zhongguancun Nandajie, Hai Dian District, Beijing 100081 (China); Zhang Zuyan, E-mail: zhangzy-bj@vip.sina.com [Department of Oral and Maxillofacial Radiology, Peking University School and Hospital of Stomatology, 22 Zhongguancun Nandajie, Hai Dian District, Beijing 100081 (China); Ma Xuchen, E-mail: kqxcma@bjmu.edu.cn [Department of Oral and Maxillofacial Radiology, Peking University School and Hospital of Stomatology, 22 Zhongguancun Nandajie, Hai Dian District, Beijing 100081 (China)
2011-08-15
Aims: To evaluate the diagnostic accuracy of approximal carious lesions among five CBCT systems and to assess the effect of detector types employed by different CBCT systems on the accuracy of approximal caries diagnosis. Materials and methods: Thirty-nine extracted non-cavitated human permanent teeth were employed in the study. Seven observers evaluated 78 approximal surfaces of the teeth with respect to caries by the images from the following five CBCT systems: (1) NewTom 9000; (2) Accuitomo 3DX; (3) Kodak 9000 3D; (4) ProMax 3D; and (5) DCT PRO, respectively. The lesions were validated by histological examination. The area under receiver operating characteristic (ROC) curve (A{sub z}) was used to evaluate the diagnostic accuracy. Results: Microscopy of approximal surfaces found 47.4% sound, 39.8% enamel and 12.8% dentin lesions. The differences of A{sub z} values among the five CBCT systems were not statistically significant (p = 0.348). No significant difference was found between the two detector types of CBCT systems (p = 0.47). Conclusions: The five CBCT systems employed in the study showed no significant difference in the in vitro approximal caries detection. Neither the detector nor the FOV employed by the CBCT systems has an impact on the detection accuracy of approximal caries.
Detection accuracy of in vitro approximal caries by cone beam computed tomography images
International Nuclear Information System (INIS)
Qu Xingmin; Li Gang; Zhang Zuyan; Ma Xuchen
2011-01-01
Aims: To evaluate the diagnostic accuracy of approximal carious lesions among five CBCT systems and to assess the effect of detector types employed by different CBCT systems on the accuracy of approximal caries diagnosis. Materials and methods: Thirty-nine extracted non-cavitated human permanent teeth were employed in the study. Seven observers evaluated 78 approximal surfaces of the teeth with respect to caries by the images from the following five CBCT systems: (1) NewTom 9000; (2) Accuitomo 3DX; (3) Kodak 9000 3D; (4) ProMax 3D; and (5) DCT PRO, respectively. The lesions were validated by histological examination. The area under receiver operating characteristic (ROC) curve (A z ) was used to evaluate the diagnostic accuracy. Results: Microscopy of approximal surfaces found 47.4% sound, 39.8% enamel and 12.8% dentin lesions. The differences of A z values among the five CBCT systems were not statistically significant (p = 0.348). No significant difference was found between the two detector types of CBCT systems (p = 0.47). Conclusions: The five CBCT systems employed in the study showed no significant difference in the in vitro approximal caries detection. Neither the detector nor the FOV employed by the CBCT systems has an impact on the detection accuracy of approximal caries.
DEFF Research Database (Denmark)
Zhang, Zhenbo; Pantleon, Wolfgang
2017-01-01
Oxide nanoparticles are quintessential for ensuring the extraordinary properties of oxide dispersion strengthened (ODS) steels. In this study, the crystallographic structure of oxide nanoparticles, and their interface with the ferritic steel matrix in an Al-alloyed ODS steel, i.e. PM2000, were...
Chan, Kok Lim; Lee, Andreas Astuti; Yuan, Xiaojun; Krishna, Kotlanka R; Je, Minkyu
2010-01-01
A successive approximation analog-to-digital converter (SAR ADC) with a split-capacitor switching scheme implementing the generalized non-binary redundant SAR algorithm and an energy efficient level shifter is proposed for bio-implanted applications. The generalized non-binary redundant SAR algorithm removes the radix constraint in conventional non-binary redundant SAR algorithm, and the energy efficient level shifter allows optimal power supplies to be chosen independently for the analog and digital blocks. A FOM of 34.7fJ/step has been achieved.
International Nuclear Information System (INIS)
Zhou Xianju; Wong, W.-T.; Faucher, Michele D.; Tanner, Peter A.
2008-01-01
Along with crystallographic data of Ln[Fe(CN) 6 ].4H 2 O (Ln=lanthanide), the infrared spectra are reassigned to examine bond length trends across the series of Ln. The changes in mean Ln-O, Ln-N, C≡N and Fe-C distances are discussed and the bond natures of Ln-N and Ln-O are studied by bond length linear or quadratic fitting and comparisons with relevant ionic radii. The two different C≡N bond distances have been simulated by the covalo-electrostatic model. - Graphical abstract: Crystallographic and FTIR data for Ln[Fe(CN) 6 ].4H 2 O enable the changes in Ln-O, Ln-N, C≡N and Fe-C distances to be determined and modeled across the lanthanide series
Energy Technology Data Exchange (ETDEWEB)
Sharma, A.D., E-mail: ads.hpu@gmail.com [Department of Physics, Himachal Pradesh University, Shimla 171005 (India); Sharma, A.K. [Terminal Ballistics Research Laboratory, Chandigarh 160030 (India); Thakur, N. [Department of Physics, Himachal Pradesh University, Shimla 171005 (India)
2014-06-01
Highlights: • Measurement of detonation velocity and compaction of powder are achieved together. • A plastic explosive detonation results into dense compacts without grain-growth. • We have studied crystallographic, micromechanical and microstructural features. • The results show no segregation within the compacts. • Density (98%), microhardness (470 ± 3)H{sub v}, microstrain (0.3%), UTS (806 MPa) are obtained. - Abstract: Dynamic consolidation of IN718 superalloy powder without grain-growth and negligible density gradient is accomplished through explosively generated shock wave loading. The compaction of powder and measurement of detonation velocity are achieved successfully in a single-shot experiment by employing instrumented detonics. A plastic explosive having a detonation velocity of the order of 7.1 km/s in a direct proximity with superalloy powder is used for the consolidation process. The compacted specimens are examined for structural, microstructure and mechanical characteristics. X-ray diffraction (XRD) study suggests intact crystalline structure of the compacts. A small micro-strain (0.26%) is observed by using Williamson–Hall method. Wavelength dispersive spectroscopy indicates no segregation within the shock processed superalloy compacted specimens. The monoliths investigated for fractography by using field emission scanning electron microscopy (FE-SEM) show original dendritic structure accompanied by re-solidified molten regions across the interparticle boundaries. Depth-sensing indentations (at 1.96 N) on compacted specimens show excellent micro-hardness of the order of (470 ± 3)H{sub v}. Tensile and compressive strengths of the superalloy monolith are observed to be 806 and 822 MPa, respectively.
Benmansour, Fatiha; Trist, Iuni; Coutard, Bruno; Decroly, Etienne; Querat, Gilles; Brancale, Andrea; Barral, Karine
2017-01-05
With the aim to help drug discovery against dengue virus (DENV), a fragment-based drug design approach was applied to identify ligands targeting a main component of DENV replication complex: the NS5 AdoMet-dependent mRNA methyltransferase (MTase) domain, playing an essential role in the RNA capping process. Herein, we describe the identification of new inhibitors developed using fragment-based, structure-guided linking and optimization techniques. Thermal-shift assay followed by a fragment-based X-ray crystallographic screening lead to the identification of three fragment hits binding DENV MTase. We considered linking two of them, which bind to proximal sites of the AdoMet binding pocket, in order to improve their potency. X-ray crystallographic structures and computational docking were used to guide the fragment linking, ultimately leading to novel series of non-nucleoside inhibitors of flavivirus MTase, respectively N-phenyl-[(phenylcarbamoyl)amino]benzene-1-sulfonamide and phenyl [(phenylcarbamoyl)amino]benzene-1-sulfonate derivatives, that show a 10-100-fold stronger inhibition of 2'-O-MTase activity compared to the initial fragments. Copyright Â© 2016 Elsevier Masson SAS. All rights reserved.
Adachi, Tetsuya; Pezzotti, Giuseppe; Yamamoto, Toshiro; Ichioka, Hiroaki; Boffelli, Marco; Zhu, Wenliang; Kanamura, Narisato
2015-05-01
A systematic investigation, based on highly spectrally resolved Raman spectroscopy, was undertaken to research the efficacy of vibrational assessments in locating chemical and crystallographic fingerprints for the characterization of dental caries and the early detection of non-cavitated carious lesions. Raman results published by other authors have indicated possible approaches for this method. However, they conspicuously lacked physical insight at the molecular scale and, thus, the rigor necessary to prove the efficacy of this spectroscopy method. After solving basic physical challenges in a companion paper, we apply them here in the form of newly developed Raman algorithms for practical dental research. Relevant differences in mineral crystallite (average) orientation and texture distribution were revealed for diseased enamel at different stages compared with healthy mineralized enamel. Clear spectroscopy features could be directly translated in terms of a rigorous and quantitative classification of crystallography and chemical characteristics of diseased enamel structures. The Raman procedure enabled us to trace back otherwise invisible characteristics in early caries, in the translucent zone (i.e., the advancing front of the disease) and in the body of lesion of cavitated caries.
Relative Stabilities of Conserved and Non-Conserved Structures in the OB-Fold Superfamily
Directory of Open Access Journals (Sweden)
Andrei T. Alexandrescu
2009-05-01
Full Text Available The OB-fold is a diverse structure superfamily based on a β-barrel motif that is often supplemented with additional non-conserved secondary structures. Previous deletion mutagenesis and NMR hydrogen exchange studies of three OB-fold proteins showed that the structural stabilities of sites within the conserved β-barrels were larger than sites in non-conserved segments. In this work we examined a database of 80 representative domain structures currently classified as OB-folds, to establish the basis of this effect. Residue-specific values were obtained for the number of Cα-Cα distance contacts, sequence hydrophobicities, crystallographic B-factors, and theoretical B-factors calculated from a Gaussian Network Model. All four parameters point to a larger average flexibility for the non-conserved structures compared to the conserved β-barrels. The theoretical B-factors and contact densities show the highest sensitivity.Our results suggest a model of protein structure evolution in which novel structural features develop at the periphery of conserved motifs. Core residues are more resistant to structural changes during evolution since their substitution would disrupt a larger number of interactions. Similar factors are likely to account for the differences in stability to unfolding between conserved and non-conserved structures.
Reduction of Linear Programming to Linear Approximation
Vaserstein, Leonid N.
2006-01-01
It is well known that every Chebyshev linear approximation problem can be reduced to a linear program. In this paper we show that conversely every linear program can be reduced to a Chebyshev linear approximation problem.
Time-dependent Hartree approximation and time-dependent harmonic oscillator model
International Nuclear Information System (INIS)
Blaizot, J.P.
1982-01-01
We present an analytically soluble model for studying nuclear collective motion within the framework of the time-dependent Hartree (TDH) approximation. The model reduces the TDH equations to the Schroedinger equation of a time-dependent harmonic oscillator. Using canonical transformations and coherent states we derive a few properties of the time-dependent harmonic oscillator which are relevant for applications. We analyse the role of the normal modes in the time evolution of a system governed by TDH equations. We show how these modes couple together due to the anharmonic terms generated by the non-linearity of the theory. (orig.)
Approximate number word knowledge before the cardinal principle.
Gunderson, Elizabeth A; Spaepen, Elizabet; Levine, Susan C
2015-02-01
Approximate number word knowledge-understanding the relation between the count words and the approximate magnitudes of sets-is a critical piece of knowledge that predicts later math achievement. However, researchers disagree about when children first show evidence of approximate number word knowledge-before, or only after, they have learned the cardinal principle. In two studies, children who had not yet learned the cardinal principle (subset-knowers) produced sets in response to number words (verbal comprehension task) and produced number words in response to set sizes (verbal production task). As evidence of approximate number word knowledge, we examined whether children's numerical responses increased with increasing numerosity of the stimulus. In Study 1, subset-knowers (ages 3.0-4.2 years) showed approximate number word knowledge above their knower-level on both tasks, but this effect did not extend to numbers above 4. In Study 2, we collected data from a broader age range of subset-knowers (ages 3.1-5.6 years). In this sample, children showed approximate number word knowledge on the verbal production task even when only examining set sizes above 4. Across studies, children's age predicted approximate number word knowledge (above 4) on the verbal production task when controlling for their knower-level, study (1 or 2), and parents' education, none of which predicted approximation ability. Thus, children can develop approximate knowledge of number words up to 10 before learning the cardinal principle. Furthermore, approximate number word knowledge increases with age and might not be closely related to the development of exact number word knowledge. Copyright © 2014 Elsevier Inc. All rights reserved.
International Nuclear Information System (INIS)
Terai, Tomoyuki; Yasui, Motoyoshi; Yamamoto, Masataka; Kakeshita, Tomoyuki
2009-01-01
We have investigated the rearrangement of crystallographic domains (martensite variants) in Ni 2 MnGa ferromagnetic shape memory alloy and CoO antiferromagnetic oxide by applying magnetic field up to 8.0 MA/m. From the result of optical microscope observation of Ni 2 MnGa single crystal, when a magnetic field is applied along [001] p (p represents a parent phase), the rearrangement of crystallographic domains occurs and the single domain state is obtained below T Ms = 202 K. The same rearrangement occurs but partially when a magnetic field is applied along [110] p . On the other hand, when a magnetic field is applied along [111] p , the rearrangement does not occur. In case of the CoO single crystal, when a magnetic field is applied along [001] p below T Ms = 293 K, the rearrangement occurs at 170 K ≤ T ≤ 293 K, but does not occur at T p and [111] p , the rearrangement does not occur below T Ms . In order to explain the rearrangement in the alloy and the oxide, we have evaluated the magnetic shear stress, τ mag , which is derived from the difference in magnetic energy among crystallographic domains and have compared it with the shear stress required for the twinning plane movement, τ req . As a result, we have found that the rearrangement occurs when the value of τ mag is larger than or equal to the value of τ req for the present alloy and oxide.
Real-time method of powder diffraction for non-periodic and nearly periodic materials
International Nuclear Information System (INIS)
Egami, T.; Toby, B.H.; Dmowski, T.W.; Jorgensen, J.D.
1989-12-01
The use of high-energy neutrons from pulsed or hot sources allows the method of atomic pair distribution analysis to be applied to the structural determination of crystalline as well as amorphous solids. This method complements the standard crystallographic methods in studying non-periodic aspects of solids with or without long range order. 14 refs., 3 figs
International Nuclear Information System (INIS)
Marmodoro, A; Staunton, J B
2011-01-01
Over the last few years the Non-Local Coherent Potential Approximation (NL-CPA) has been shown to provide an effective way to describe the electronic structure and related properties of disordered systems, where short-range order (SRO) and other local environment effects are important. Here we present its generalization to materials with multi-atom per unit cell lattices. The method is described using a Green function formalism and illustrated by an implementation for a simplified one-dimensional tight-binding model with substitutional disorder. This development paves the way for a natural reimplementation of the Korringa-Kohn-Rostoker (KKR) multiple scattering solution of Kohn-Sham equations for ab-initio calculations of real materials.
International Nuclear Information System (INIS)
Ye, Dong; Li, Shaohong; Li, Jun; Jiang, Wen; Su, Jie; Zhao, Kunyu
2015-01-01
Effect of carbides and crystallographic orientation relationship on the formation mechanism of reversed austenite of economical Cr12 super martensitic stainless steel (SMSS) has been investigated mainly by transmission electron microscopy (TEM) and electron backscatter diffraction (EBSD). The results indicate that the M_2_3C_6 precipitation and the formation of the reversed austenite have the interaction effect during tempering process in SMSS. The reversed austenite forms intensively at the sub-block boundary and the lath boundary within a misorientation range of 0–60°. M_2_3C_6 has the same crystallographic orientation relationship with reversed austenite. There are two different kinds of formation modes for reversed austenite. One is a nondiffusional shear reversion; the other is a diffusion transformation. Both are strictly limited by crystallographic orientation relationship. The austenite variants are limited to two kinds within one packet and five kinds within one prior austenite grain. - Highlights: • Reversed austenite forms at martensite boundaries with misorientation of 0–60° • M_2_3C_6 precipitation and reversed austenite formation have the interaction effect. • Two austenite variants with different orientations can be formed inside a packet. • Two reversed austenite formation modes: shear reversion; diffusion transformation
Energy Technology Data Exchange (ETDEWEB)
Ye, Dong; Li, Shaohong; Li, Jun; Jiang, Wen [Faculty of Materials Science and Engineering, Kunming University of Science and Technology, Kunming 650093 (China); Su, Jie [Institute for Structural Materials, Central Iron and Steel Research Institute, Beijing 100081 (China); Zhao, Kunyu, E-mail: kyzhaoy@sina.com [Faculty of Materials Science and Engineering, Kunming University of Science and Technology, Kunming 650093 (China)
2015-11-15
Effect of carbides and crystallographic orientation relationship on the formation mechanism of reversed austenite of economical Cr12 super martensitic stainless steel (SMSS) has been investigated mainly by transmission electron microscopy (TEM) and electron backscatter diffraction (EBSD). The results indicate that the M{sub 23}C{sub 6} precipitation and the formation of the reversed austenite have the interaction effect during tempering process in SMSS. The reversed austenite forms intensively at the sub-block boundary and the lath boundary within a misorientation range of 0–60°. M{sub 23}C{sub 6} has the same crystallographic orientation relationship with reversed austenite. There are two different kinds of formation modes for reversed austenite. One is a nondiffusional shear reversion; the other is a diffusion transformation. Both are strictly limited by crystallographic orientation relationship. The austenite variants are limited to two kinds within one packet and five kinds within one prior austenite grain. - Highlights: • Reversed austenite forms at martensite boundaries with misorientation of 0–60° • M{sub 23}C{sub 6} precipitation and reversed austenite formation have the interaction effect. • Two austenite variants with different orientations can be formed inside a packet. • Two reversed austenite formation modes: shear reversion; diffusion transformation.
Photoelectron spectroscopy and the dipole approximation
Energy Technology Data Exchange (ETDEWEB)
Hemmers, O.; Hansen, D.L.; Wang, H. [Univ. of Nevada, Las Vegas, NV (United States)] [and others
1997-04-01
Photoelectron spectroscopy is a powerful technique because it directly probes, via the measurement of photoelectron kinetic energies, orbital and band structure in valence and core levels in a wide variety of samples. The technique becomes even more powerful when it is performed in an angle-resolved mode, where photoelectrons are distinguished not only by their kinetic energy, but by their direction of emission as well. Determining the probability of electron ejection as a function of angle probes the different quantum-mechanical channels available to a photoemission process, because it is sensitive to phase differences among the channels. As a result, angle-resolved photoemission has been used successfully for many years to provide stringent tests of the understanding of basic physical processes underlying gas-phase and solid-state interactions with radiation. One mainstay in the application of angle-resolved photoelectron spectroscopy is the well-known electric-dipole approximation for photon interactions. In this simplification, all higher-order terms, such as those due to electric-quadrupole and magnetic-dipole interactions, are neglected. As the photon energy increases, however, effects beyond the dipole approximation become important. To best determine the range of validity of the dipole approximation, photoemission measurements on a simple atomic system, neon, where extra-atomic effects cannot play a role, were performed at BL 8.0. The measurements show that deviations from {open_quotes}dipole{close_quotes} expectations in angle-resolved valence photoemission are observable for photon energies down to at least 0.25 keV, and are quite significant at energies around 1 keV. From these results, it is clear that non-dipole angular-distribution effects may need to be considered in any application of angle-resolved photoelectron spectroscopy that uses x-ray photons of energies as low as a few hundred eV.
Non Debye approximation on specific heat of solids
Bhattacharjee, Ruma; Das, Anamika; Sarkar, A.
2018-05-01
A simple non Debye frequency spectrum is proposed. The normalized frequency spectrum is compared to that of Debye spectrum. The proposed spectrum, provides a good account of low frequency phonon density of states, which gives a linear temperature variation at low temperature in contrast to Debye T3 law. It has been analyzed that the proposed model provides a good account of excess specific heat for nanostructure solid.
An Approximate Approach to Automatic Kernel Selection.
Ding, Lizhong; Liao, Shizhong
2016-02-02
Kernel selection is a fundamental problem of kernel-based learning algorithms. In this paper, we propose an approximate approach to automatic kernel selection for regression from the perspective of kernel matrix approximation. We first introduce multilevel circulant matrices into automatic kernel selection, and develop two approximate kernel selection algorithms by exploiting the computational virtues of multilevel circulant matrices. The complexity of the proposed algorithms is quasi-linear in the number of data points. Then, we prove an approximation error bound to measure the effect of the approximation in kernel matrices by multilevel circulant matrices on the hypothesis and further show that the approximate hypothesis produced with multilevel circulant matrices converges to the accurate hypothesis produced with kernel matrices. Experimental evaluations on benchmark datasets demonstrate the effectiveness of approximate kernel selection.
International Nuclear Information System (INIS)
Nicolas, G.; Voltz, M.
2001-01-01
Quite often the W-Ni-Fe-Co heavy alloys are subjected to a thermomechanical processing of swaging and aging in order to obtain the highest possible level of resistance. Within the framework of this plastic deformation on cylindrical parts, the swaging leads to the distribution of morphological and crystallographic texture as well as specific internal stresses. The resulting mechanical characteristics are correlated to structural and sub-structural variations. (author)
Double ionization in Helium. Ab initio calculations beyond the one dimensional approximation
International Nuclear Information System (INIS)
Camilo Ruiz; Luis Plaja; Luis Roso; Andreas Becker
2006-01-01
Complete test of publication follows. We present ab-initio computations of the ionization of two-electron atoms by short pulses of coherent radiation beyond the one-dimensional approximation. In the model the electron correlation is included in its full dimensionality, while the center-of-mass motion is restricted along the polarization axis. We show some result for Non Sequential Double Ionization (NSDI) as well as for SDI for high intensity low IR frequency. Some recent applications for this correlated system is also presented.
New finite volume methods for approximating partial differential equations on arbitrary meshes
International Nuclear Information System (INIS)
Hermeline, F.
2008-12-01
This dissertation presents some new methods of finite volume type for approximating partial differential equations on arbitrary meshes. The main idea lies in solving twice the problem to be dealt with. One addresses the elliptic equations with variable (anisotropic, antisymmetric, discontinuous) coefficients, the parabolic linear or non linear equations (heat equation, radiative diffusion, magnetic diffusion with Hall effect), the wave type equations (Maxwell, acoustics), the elasticity and Stokes'equations. Numerous numerical experiments show the good behaviour of this type of method. (author)
Directory of Open Access Journals (Sweden)
Molčanov, K.
2006-06-01
Full Text Available The article is dedicated to 40th anniversary of The Cambridge Crystallographic Data Centre (CCDC, the world-known centre (http://www.ccdc.cam.ac.uk responsible for deposition and control of crystallographic data, including atomic coordinates that define the three-dimensional structures of organic molecules and metal complexes containing organic ligands. Cambride Structural Database (CSD, one among the first established electronic databases, nowadays is the most significant crystallographic database in the world. CSD has about 400,000 deposited structures. The use of the extensive database, which is growing rapidly, needs support of efficient and sophisticated software for searching, analysing and visualising structural data. The seminal role of CSD in the research related to crystallography, chemistry, material sciences, solid state physics and chemistry, life sciences, pharmacology, and in particular in drug design, has been documented in more than 1300 scientific papers. The important issues of CCDC are the accuracy of deposited data and development of software that enables a wide variety of applications. Such demanding project requires higly competent team of experts; thus the article brings into focus the scientific approach of the team based on the long tradition in crystallography, modelling and informatics. The article is not dedicated to 40th anniversary of the centre only, but it also reveals how Cambridge Structural Database can be used in the research and teaching. The use of electronic media and computer graphics makes data mining" very efficient and useful but also esthetically appealing due to the molecular architecture. At the Rudjer Bošković Institute, Zagreb, Croatia there is The National Affiliated Centre of Cambridge Crystallographic Data Centre responsible for communication and dissemination of CSD in Croatia, Slovenia and Macedonia. The use of CSD is illustrated by two examples performed and published by the presenting
Nonperturbative dynamics of hot non-Abelian gauge fields: Beyond the leading log approximation
International Nuclear Information System (INIS)
Arnold, Peter; Yaffe, Laurence G.
2000-01-01
Many aspects of high-temperature gauge theories, such as the electroweak baryon number violation rate, color conductivity, and the hard gluon damping rate, have previously been understood only at leading logarithmic order (that is, neglecting effects suppressed only by an inverse logarithm of the gauge coupling). We discuss how to systematically go beyond leading logarithmic order in the analysis of physical quantities. Specifically, we extend to next-to-leading-log order (NLLO) the simple leading-log effective theory due to Bo''deker that describes non-perturbative color physics in hot non-Abelian plasmas. A suitable scaling analysis is used to show that no new operators enter the effective theory at next-to-leading-log order. However, a NLLO calculation of the color conductivity is required, and we report the resulting value. Our NLLO result for the color conductivity can be trivially combined with previous numerical work by Moore to yield a NLLO result for the hot electroweak baryon number violation rate
Brillouin-zone database on the Bilbao Crystallographic Server.
Aroyo, Mois I; Orobengoa, Danel; de la Flor, Gemma; Tasci, Emre S; Perez-Mato, J Manuel; Wondratschek, Hans
2014-03-01
The Brillouin-zone database of the Bilbao Crystallographic Server (http://www.cryst.ehu.es) offers k-vector tables and figures which form the background of a classification of the irreducible representations of all 230 space groups. The symmetry properties of the wavevectors are described by the so-called reciprocal-space groups and this classification scheme is compared with the classification of Cracknell et al. [Kronecker Product Tables, Vol. 1, General Introduction and Tables of Irreducible Representations of Space Groups (1979). New York: IFI/Plenum]. The compilation provides a solution to the problems of uniqueness and completeness of space-group representations by specifying the independent parameter ranges of general and special k vectors. Guides to the k-vector tables and figures explain the content and arrangement of the data. Recent improvements and modifications of the Brillouin-zone database, including new tables and figures for the trigonal, hexagonal and monoclinic space groups, are discussed in detail and illustrated by several examples.
Directory of Open Access Journals (Sweden)
Dong-Kyu Kim
Full Text Available Non-eosinophilic nasal polyps (NPs show less inflammatory changes and are less commonly associated with lower airway inflammatory disorders such as asthma, compared with eosinophilic NPs. However, the development of non-eosinophilic NPs which is a predominant subtype in Asian population still remains unclear.A total of 81 patients (45 with non-eosinophilic NPs and 36 with eosinophilic NPs were enrolled. Clinical information and computed tomography (CT, endoscopic, and histological findings were investigated. Tissue samples were analyzed for total IgE levels and for mRNA expression levels of interleukin (IL-4, IL-5, IL-13, interferon (IFN-γ, tumor necrosis factor (TNF-α, IL-17A, IL-22, IL-23p19, transforming growth factor (TGF-β1, TGF-β2, TGF-β3, and periostin. Immunostaining assessment of Ki-67 as a proliferation marker was performed.We found that epithelial in-growing patterns such as pseudocysts were more frequently observed in histological and endoscopic evaluations of non-eosinophilic NPs, which was linked to increase epithelial staining of Ki-67, a proliferating marker. Eosinophilic NPs were characterized by high infiltration of inflammatory cells, compared with non-eosinophilic NPs. To investigate the developmental course of each subtype, CT was analyzed according to CT scores and subtypes. Non-eosinophilic NPs showed more localized pattern and maxillary sinus involvement, but lesser olfactory involvement in early stage whereas eosinophilic NPs were characterized by diffuse ethmoidal and olfactory involvement. In addition, high ethmoidal/maxillary (E/M CT scores, indicating ethmoidal dominant involvement, were one of surrogate markers for eosinophilic NP. E/M CT scores was positively correlated with levels of TH2 inflammatory markers, including IL-4, IL-5, periostin mRNA expression and total IgE levels in NPs, whereas levels of the TH1 cytokine, IFN- γ were inversely correlated. Moreover, if the combinatorial algorithm meet the three
Regression with Sparse Approximations of Data
DEFF Research Database (Denmark)
Noorzad, Pardis; Sturm, Bob L.
2012-01-01
We propose sparse approximation weighted regression (SPARROW), a method for local estimation of the regression function that uses sparse approximation with a dictionary of measurements. SPARROW estimates the regression function at a point with a linear combination of a few regressands selected...... by a sparse approximation of the point in terms of the regressors. We show SPARROW can be considered a variant of \\(k\\)-nearest neighbors regression (\\(k\\)-NNR), and more generally, local polynomial kernel regression. Unlike \\(k\\)-NNR, however, SPARROW can adapt the number of regressors to use based...
A test of the adhesion approximation for gravitational clustering
Melott, Adrian L.; Shandarin, Sergei; Weinberg, David H.
1993-01-01
We quantitatively compare a particle implementation of the adhesion approximation to fully non-linear, numerical 'N-body' simulations. Our primary tool, cross-correlation of N-body simulations with the adhesion approximation, indicates good agreement, better than that found by the same test performed with the Zel-dovich approximation (hereafter ZA). However, the cross-correlation is not as good as that of the truncated Zel-dovich approximation (TZA), obtained by applying the Zel'dovich approximation after smoothing the initial density field with a Gaussian filter. We confirm that the adhesion approximation produces an excessively filamentary distribution. Relative to the N-body results, we also find that: (a) the power spectrum obtained from the adhesion approximation is more accurate than that from ZA or TZA, (b) the error in the phase angle of Fourier components is worse than that from TZA, and (c) the mass distribution function is more accurate than that from ZA or TZA. It appears that adhesion performs well statistically, but that TZA is more accurate dynamically, in the sense of moving mass to the right place.
Long wavelength approximation of transport processes in a single-band crystal
International Nuclear Information System (INIS)
Ferrari, Loris
2014-01-01
The single band, long wavelength approximation (SBA–LWA) is currently used in textbooks as a quasi-free-particle picture of the motion in a quantum crystal. The resulting transport process might thereby look a trivial issue. In contrast, we shall show that the SBA–LWA hides some controversial aspects that should be clarified at the level of an advanced course of condensed matter physics, and refer to the incompleteness of the SBA representation. In particular, it will be shown that the single-band velocity v 1B , expressed in terms of the projectors on the Bloch states, cannot be a transport velocity in a full sense, since the resulting current violates the continuity equation. The drawback manifests itself as a ‘lost’ current J lost , which provides a non conventional estimate of the limits of accuracy of SBA–LWA. The vanishing of J lost corresponds to the effective mass approximation in which the dispersion relation can be reduced to a quadratic form in the (pseudo) momentum components. In practice, the quantity transported by v 1B is not the bare mass, but the effective mass, until this notion does make sense. Recalling that the non-quadratic expression of the relativistic kinetic energy leads to a difference between the rest and moving mass, the notion of the lost current is finally used as a non-conventional approach to relativistic quantum mechanics, with special reference to Dirac’s theory. (paper)
International Nuclear Information System (INIS)
Converse, Matthew I.; Fullwood, David T.
2013-01-01
Current methods of image segmentation and reconstructions from scanning electron micrographs can be inadequate for resolving nanoscale gaps in composite materials (1–20 nm). Such information is critical to both accurate material characterizations and models of piezoresistive response. The current work proposes the use of crystallographic orientation data and machine learning for enhancing this process. It is first shown how a machine learning algorithm can be used to predict the connectivity of nanoscale grains in a Nickel nanostrand/epoxy composite. This results in 71.9% accuracy for a 2D algorithm and 62.4% accuracy in 3D. Finally, it is demonstrated how these algorithms can be used to predict the location of gaps between distinct nanostrands — gaps which would otherwise not be detected with the sole use of a scanning electron microscope. - Highlights: • A method is proposed for enhancing the segmentation/reconstruction of SEM images. • 3D crystallographic orientation data from a nickel nanocomposite is collected. • A machine learning algorithm is used to detect trends in adjacent grains. • This algorithm is then applied to predict likely regions of nanoscale gaps. • These gaps would otherwise be unresolved with the sole use of an SEM
Monte-Carlo simulation of crystallographical pore growth in III-V-semiconductors
International Nuclear Information System (INIS)
Leisner, Malte; Carstensen, Juergen; Foell, Helmut
2011-01-01
The growth of crystallographical pores in III-V-semiconductors can be understood in the framework of a simple model, which is based on the assumption that the branching of pores is proportional to the current density at the pore tips. The stochastic nature of this model allows its implementation into a three-dimensional Monte-Carlo-simulation of pore growth. The simulation is able to reproduce the experimentally observed crysto pore structures in III-V-semiconductors in full quantitative detail. The different branching probabilities for different semiconductors, as well as doping levels, can be deduced from the specific passivation behavior of the semiconductor-electrolyte-interface at the pore tips.
Mazzocco, Michèle M M; Feigenson, Lisa; Halberda, Justin
2011-01-01
The Approximate Number System (ANS) is a primitive mental system of nonverbal representations that supports an intuitive sense of number in human adults, children, infants, and other animal species. The numerical approximations produced by the ANS are characteristically imprecise and, in humans, this precision gradually improves from infancy to adulthood. Throughout development, wide ranging individual differences in ANS precision are evident within age groups. These individual differences have been linked to formal mathematics outcomes, based on concurrent, retrospective, or short-term longitudinal correlations observed during the school age years. However, it remains unknown whether this approximate number sense actually serves as a foundation for these school mathematics abilities. Here we show that ANS precision measured at preschool, prior to formal instruction in mathematics, selectively predicts performance on school mathematics at 6 years of age. In contrast, ANS precision does not predict non-numerical cognitive abilities. To our knowledge, these results provide the first evidence for early ANS precision, measured before the onset of formal education, predicting later mathematical abilities.
X-ray diffraction study of A- plane non-polar InN epilayer grown by MOCVD
Moret, Matthieu; Briot, Olivier; Gil, Bernard
2015-03-01
Strong polarisation-induced electric fields in C-plane oriented nitrides semiconductor layers reduce the performance of devices. Eliminating the polarization fields can be achieved by growing nitrides along non polar direction. We have grown non polar A-plane oriented InN on R-plane (1‾102) nitridated sapphire substrate by MOCVD. We have studied the structural anisotropy observed in these layers by analyzing High Resolution XRay Diffraction rocking curve (RC) experiments as a function of the in-plane beam orientation. A-plane InN epilayer have a unique epitaxial relationship on R-Plane sapphire and show a strong structural anisotropy. Full width at half maximum (FWHM) of the InN(11‾20) XRD RC values are contained between 44 and 81 Arcmin. FWHM is smaller when the diffraction occurs along the [0001] and the largest FWHM values, of the (11‾20) RC, are obtained when the diffraction occurs along the [1‾100] in-plane direction. Atomic Force Microscopy imaging revealed morphologies with well organized crystallites. The grains are structured along a unique crystallographic orientation of InN, leading to larger domains in this direction. This structural anisotropy can be, in first approximation, attributed to the difference in the domain sizes observed. XRD reciprocal space mappings (RSM) were performed in asymmetrical configuration on (13‾40) and (2‾202) diffraction plane. RSM are measured with a beam orientation corresponding to a maximal and a minimal width of the (11‾20) Rocking curves, respectively. A simple theoretical model is exposed to interpret the RSM. We concluded that the dominant contribution to the anisotropy is due to the scattering coherence length anisotropy present in our samples.
Space-efficient path-reporting approximate distance oracles
DEFF Research Database (Denmark)
Elkin, Michael; Neiman, Ofer; Wulff-Nilsen, Christian
2016-01-01
We consider approximate path-reporting distance oracles, distance labeling and labeled routing with extremely low space requirements, for general undirected graphs. For distance oracles, we show how to break the nlogn space bound of Thorup and Zwick if approximate paths rather than distances need...
Unambiguous results from variational matrix Pade approximants
International Nuclear Information System (INIS)
Pindor, Maciej.
1979-10-01
Variational Matrix Pade Approximants are studied as a nonlinear variational problem. It is shown that although a stationary value of the Schwinger functional is a stationary value of VMPA, the latter has also another stationary value. It is therefore proposed that instead of looking for a stationary point of VMPA, one minimizes some non-negative functional and then one calculates VMPA at the point where the former has the absolute minimum. This approach, which we call the Method of the Variational Gradient (MVG) gives unambiguous results and is also shown to minimize a distance between the approximate and the exact stationary values of the Schwinger functional
International Nuclear Information System (INIS)
Gupta, Pankaj; Gaur, Vineet; Salunke, Dinakar M.
2008-01-01
A 2S albumin from L. culinaris was purified and crystallized and preliminary crystallographic studies were carried out. Lens culinaris (lentil) is a widely consumed high-protein-content leguminous crop. A 2S albumin protein (26.5 kDa) has been identified using NH 2 -terminal sequencing from a 90% ammonium sulfate saturation fraction of total L. culinaris seed protein extract. The NH 2 -terminal sequence shows very high homology to PA2, an allergy-related protein from Pisum sativum. The 2S albumin protein was purified using a combination of size-exclusion and ion-exchange chromatography. Crystals of the 2S seed albumin obtained using the hanging-drop vapour-diffusion method diffracted to 2.5 Å resolution and were indexed in space group P4 1 (or P4 3 ), with unit-cell parameters a = b = 78.6, c = 135.2 Å
Transfer of olivine crystallographic orientation through a cycle of serpentinisation and dehydration
Dunkel, Kristina G.; Austrheim, Håkon; Ildefonse, Benoit; Jamtveit, Bjørn
2017-08-01
Our ability to decipher the mechanisms behind metamorphic transformation processes depends in a major way on the extent to which crystallographic and microstructural information is transferred from one stage to another. Within the Leka Ophiolite Complex in the Central Norwegian Caledonides, prograde olivine veins that formed by dehydration of serpentinite veins in dunites exhibit a characteristic distribution of microstructures: The outer part of the veins comprises coarse-grained olivine that forms an unusual, brick-like microstructure. The inner part of the veins, surrounding a central fault, is composed of fine-grained olivine. Where the fault movement included a dilational component, optically clear, equant olivine occurs in the centre. Electron backscatter diffraction mapping reveals that the vein olivine has inherited its crystallographic preferred orientation (CPO) from the olivine in the porphyroclastic host rock; however, misorientation is weaker and associated to different rotation axes. We propose that prograde olivine grew epitaxially on relics of mantle olivine and thereby acquired its CPO. Growth towards pre-existing microfractures along which serpentinisation had occurred led to straight grain boundaries and a brick-like microstructure in the veins. When dehydration embrittlement induced slip, a strong strain localisation on discrete fault planes prevented distortion of the CPO due to cataclastic deformation; grain size reduction did not significantly modify the olivine CPO. This illustrates how a CPO can be preserved though an entire metamorphic cycle, including hydration, dehydration, and deformation processes, and that the CPO and the microstructures (e.g. grain shape) of one phase do not necessarily record the same event.
Manzano, Veronica E; Baggio, Ricardo; Cukiernik, Fabio D
2015-11-01
The synthesis of 3,3'-diacetoxy-4,4'-bis(hexyloxy)biphenyl following the nickel-modified Ullmann reaction yielded a by-product which was identified successfully by crystallographic analysis as 1-(4-hexyloxy-3-hydroxyphenyl)ethanone, C14H20O3. This unexpected nonbiphenyl by-product exhibited IR, (1)H NMR, (13)C NMR and COSY (correlation spectroscopy) spectra fully consistent with the proposed structure. The compound crystallized in the orthorombic Pbca space group, with two independent formula units in the asymmetric unit (one of which was slightly disordered), and showed a supramolecular architecture in which molecules linked by hydroxy-ethanone O-H···O interactions are organized in columns separated by the aliphatic tails.
Approximation of the semi-infinite interval
Directory of Open Access Journals (Sweden)
A. McD. Mercer
1980-01-01
Full Text Available The approximation of a function f∈C[a,b] by Bernstein polynomials is well-known. It is based on the binomial distribution. O. Szasz has shown that there are analogous approximations on the interval [0,∞ based on the Poisson distribution. Recently R. Mohapatra has generalized Szasz' result to the case in which the approximating function is αe−ux∑k=N∞(uxkα+β−1Γ(kα+βf(kαuThe present note shows that these results are special cases of a Tauberian theorem for certain infinite series having positive coefficients.
Two systems of non-symbolic numerical cognition
Directory of Open Access Journals (Sweden)
Daniel C. Hyde
2011-11-01
Full Text Available Studies of human adults, infants, and non-human animals demonstrate that non-symbolic numerical cognition is supported by at least two distinct cognitive systems: a ‘parallel individuation system’ that encodes the numerical identity of individual items and an ‘approximate number system’ that encodes the approximate numerical magnitude, or numerosity, of a set. The exact nature of these systems, however, have been debated for over a hundred years. Some argue that the non-symbolic representation of small numbers (< 4 is carried out solely by the parallel individuation system and the non-symbolic representation of large numbers (> 4 is carried out solely by the approximate number system. Others argue that all numbers are represented by the approximate number system. This debate has been fueled largely by some studies showing dissociations in processing and other studies showing similar processing of small and large numbers. Recent work has addressed this debate by showing that the two systems are present and distinct from early infancy, persist despite the acquisition of a symbolic number system, activate distinct cortical networks, and engage differentially based attentional constraints. Based on the recent discoveries, I provide a hypothesis that may explain the puzzling findings and makes testable predictions as to when each system will be engaged. In particular, when items are presented under conditions that allow selection of individuals, they will be represented as distinct mental items through parallel individuation and not as a numerical magnitude. In contrast, when items are presented outside attentional limits (e.g. too many, too close together, under high attentional load, they will be represented as a single mental numerical magnitude and not as distinct mental items. These predictions provide a basis on which researchers can further investigate the role of each system in the development of uniquely human numerical thought.
Single image super-resolution based on approximated Heaviside functions and iterative refinement
Wang, Xin-Yu; Huang, Ting-Zhu; Deng, Liang-Jian
2018-01-01
One method of solving the single-image super-resolution problem is to use Heaviside functions. This has been done previously by making a binary classification of image components as “smooth” and “non-smooth”, describing these with approximated Heaviside functions (AHFs), and iteration including l1 regularization. We now introduce a new method in which the binary classification of image components is extended to different degrees of smoothness and non-smoothness, these components being represented by various classes of AHFs. Taking into account the sparsity of the non-smooth components, their coefficients are l1 regularized. In addition, to pick up more image details, the new method uses an iterative refinement for the residuals between the original low-resolution input and the downsampled resulting image. Experimental results showed that the new method is superior to the original AHF method and to four other published methods. PMID:29329298
Chen, Zhenhua; Hoffmann, Mark R
2012-07-07
A unitary wave operator, exp (G), G(+) = -G, is considered to transform a multiconfigurational reference wave function Φ to the potentially exact, within basis set limit, wave function Ψ = exp (G)Φ. To obtain a useful approximation, the Hausdorff expansion of the similarity transformed effective Hamiltonian, exp (-G)Hexp (G), is truncated at second order and the excitation manifold is limited; an additional separate perturbation approximation can also be made. In the perturbation approximation, which we refer to as multireference unitary second-order perturbation theory (MRUPT2), the Hamiltonian operator in the highest order commutator is approximated by a Mo̸ller-Plesset-type one-body zero-order Hamiltonian. If a complete active space self-consistent field wave function is used as reference, then the energy is invariant under orbital rotations within the inactive, active, and virtual orbital subspaces for both the second-order unitary coupled cluster method and its perturbative approximation. Furthermore, the redundancies of the excitation operators are addressed in a novel way, which is potentially more efficient compared to the usual full diagonalization of the metric of the excited configurations. Despite the loss of rigorous size-extensivity possibly due to the use of a variational approach rather than a projective one in the solution of the amplitudes, test calculations show that the size-extensivity errors are very small. Compared to other internally contracted multireference perturbation theories, MRUPT2 only needs reduced density matrices up to three-body even with a non-complete active space reference wave function when two-body excitations within the active orbital subspace are involved in the wave operator, exp (G). Both the coupled cluster and perturbation theory variants are amenable to large, incomplete model spaces. Applications to some widely studied model systems that can be problematic because of geometry dependent quasidegeneracy, H4, P4
Hierarchical matrix approximation of large covariance matrices
Litvinenko, Alexander; Genton, Marc G.; Sun, Ying
2015-01-01
We approximate large non-structured Matérn covariance matrices of size n×n in the H-matrix format with a log-linear computational cost and storage O(kn log n), where rank k ≪ n is a small integer. Applications are: spatial statistics, machine learning and image analysis, kriging and optimal design.
Hierarchical matrix approximation of large covariance matrices
Litvinenko, Alexander
2015-11-30
We approximate large non-structured Matérn covariance matrices of size n×n in the H-matrix format with a log-linear computational cost and storage O(kn log n), where rank k ≪ n is a small integer. Applications are: spatial statistics, machine learning and image analysis, kriging and optimal design.
An inhomogeneous wave equation and non-linear Diophantine approximation
DEFF Research Database (Denmark)
Beresnevich, V.; Dodson, M. M.; Kristensen, S.
2008-01-01
A non-linear Diophantine condition involving perfect squares and arising from an inhomogeneous wave equation on the torus guarantees the existence of a smooth solution. The exceptional set associated with the failure of the Diophantine condition and hence of the existence of a smooth solution...
Intensity approximation of random fluctuation in complex systems
Yulmetyev, R. M.; Gafarov, F. M.; Yulmetyeva, D. G.; Emeljanova, N. A.
2002-01-01
The Markov and non-Markov processes in complex systems are examined with the help of dynamical information Shannon entropy method. Here we consider the essential role of two mutually independent channels of entropy involving creation of correlation and annihilation of correlation. The developed method has been used to analyze the intensity fluctuation of the complex systems of various nature: in psychology (to analyze numerical and pattern short-time human memory, to study the effect of stress on the parameters of the dynamical taping-test) and in cardiology (to analyze the random dynamics of RR-intervals in human ECG's and to diagnose various diseases of human cardiovascular systems). The received results show that the application of intensity approximation allows to improve essentially the diagnostics of parameters in the evolution of human dynamic states.
International Nuclear Information System (INIS)
Roversi, Pietro; Johnson, Steven; Field, Terry; Deane, Janet E.; Galyov, Edouard E.; Lea, Susan M.
2006-01-01
A construct consisting of residues 10–310 of mature BipD, a component of the B. pseudomallei type III secretion system, has been crystallized. Native BipD crystals and SeMet and K 2 PtCl 4 derivative crystals have undergone preliminary crystallographic analysis. A construct consisting of residues 10–310 of BipD, a component of the Burkholderia pseudomallei type III secretion system (T3SS), has been overexpressed as a GST fusion, cleaved from the GST tag and purified. Crystals were grown of native and selenomethionine-labelled BipD. The crystals grow in two different polymorphs from the same condition. The first polymorph belongs to space group C222, with unit-cell parameters a = 103.98, b = 122.79, c = 49.17 Å, a calculated Matthews coefficient of 2.4 Å 3 Da −1 (47% solvent content) and one molecule per asymmetric unit. The second polymorph belongs to space group P2 1 2 1 2, with unit-cell parameters a = 136.47, b = 89.84, c = 50.15 Å, and a calculated Matthews coefficient of 2.3 Å 3 Da −1 (45% solvent content) for two molecules per asymmetric unit (analysis of the self-rotation function indicates the presence of a weak twofold non-crystallographic symmetry axis in this P2 1 2 1 2 form). The native crystals of both forms give diffraction data to 2.7 Å resolution, while the SeMet-labelled P2 1 2 1 2 crystals diffract to 3.3 Å resolution. A K 2 PtCl 4 derivative of the P2 1 2 1 2 form was also obtained and data were collected to 2.7 Å with radiation of wavelength λ = 0.933 Å. The Pt-derivative anomalous difference Patterson map revealed two self-peaks on the Harker sections
Non-uniform tube representation of proteins
DEFF Research Database (Denmark)
Hansen, Mikael Sonne
Treating the full protein structure is often neither computationally nor physically possible. Instead one is forced to consider various reduced models capturing the properties of interest. Previous work have used tubular neighborhoods of the C-alpha backbone. However, assigning a unique radius...... might not correctly capture volume exclusion - of crucial importance when trying to understand a proteins $3$d-structure. We propose a new reduced model treating the protein as a non-uniform tube with a radius reflecting the positions of atoms. The tube representation is well suited considering X......-ray crystallographic resolution ~ 3Å while a varying radius accounts for the different sizes of side chains. Such a non-uniform tube better capture the protein geometry and has numerous applications in structural/computational biology from the classification of protein structures to sequence-structure prediction....
Bounded fractional diffusion in geological media: Definition and Lagrangian approximation
Zhang, Yong; Green, Christopher T.; LaBolle, Eric M.; Neupauer, Roseanna M.; Sun, HongGuang
2016-01-01
Spatiotemporal Fractional-Derivative Models (FDMs) have been increasingly used to simulate non-Fickian diffusion, but methods have not been available to define boundary conditions for FDMs in bounded domains. This study defines boundary conditions and then develops a Lagrangian solver to approximate bounded, one-dimensional fractional diffusion. Both the zero-value and non-zero-value Dirichlet, Neumann, and mixed Robin boundary conditions are defined, where the sign of Riemann-Liouville fractional derivative (capturing non-zero-value spatial-nonlocal boundary conditions with directional super-diffusion) remains consistent with the sign of the fractional-diffusive flux term in the FDMs. New Lagrangian schemes are then proposed to track solute particles moving in bounded domains, where the solutions are checked against analytical or Eularian solutions available for simplified FDMs. Numerical experiments show that the particle-tracking algorithm for non-Fickian diffusion differs from Fickian diffusion in relocating the particle position around the reflective boundary, likely due to the non-local and non-symmetric fractional diffusion. For a non-zero-value Neumann or Robin boundary, a source cell with a reflective face can be applied to define the release rate of random-walking particles at the specified flux boundary. Mathematical definitions of physically meaningful nonlocal boundaries combined with bounded Lagrangian solvers in this study may provide the only viable techniques at present to quantify the impact of boundaries on anomalous diffusion, expanding the applicability of FDMs from infinite do mains to those with any size and boundary conditions.
Absorption Efficiencies of Forsterite. I: DDA Explorations in Grain Shape and Size
Lindsay, Sean S.; Wooden, Diane; Harker, David E.; Kelley, Michael S.; Woodward, Charles E.; Murphy, Jim R.
2013-01-01
We compute the absorption efficiency (Q(sub abs)) of forsterite using the discrete dipole approximation (DDA) in order to identify and describe what characteristics of crystal grain shape and size are important to the shape, peak location, and relative strength of spectral features in the 8 - 40 micron wavelength range. Using the DDSCAT code, we compute Q(sub abs) for non-spherical polyhedral grain shapes with a(sub eff) = 0.1 micron. The shape characteristics identified are: 1) elongation/reduction along one of three crystallographic axes; 2) asymmetry, such that all three crystallographic axes are of different lengths; and 3) the presence of crystalline faces that are not parallel to a specific crystallographic axis, e.g., non-rectangular prisms and (di)pyramids. Elongation/reduction dominates the locations and shapes of spectral features near 10, 11, 16, 23.5, 27, and 33.5 micron, while asymmetry and tips are secondary shape effects. Increasing grain sizes (0.1 - 1.0 micron) shifts the 10, 11 micron features systematically towards longer wavelengths and relative to the 11 micron feature increases the strengths and slightly broadens the longer wavelength features. Seven spectral shape classes are established for crystallographic a-, b-, and c-axes and include columnar and platelet shapes plus non-elongated or equant grain shapes. The spectral shape classes and the effects of grain size have practical application in identifying or excluding columnar, platelet or equant forsterite grain shapes in astrophysical environs. Identification of the shape characteristics of forsterite from 8 - 40 micron spectra provides a potential means to probe the temperatures at which forsterite formed.
Symmetric approximations of the Navier-Stokes equations
International Nuclear Information System (INIS)
Kobel'kov, G M
2002-01-01
A new method for the symmetric approximation of the non-stationary Navier-Stokes equations by a Cauchy-Kovalevskaya-type system is proposed. Properties of the modified problem are studied. In particular, the convergence as ε→0 of the solutions of the modified problem to the solutions of the original problem on an infinite interval is established
Optical bistability without the rotating wave approximation
Energy Technology Data Exchange (ETDEWEB)
Sharaby, Yasser A., E-mail: Yasser_Sharaby@hotmail.co [Physics Department, Faculty of Applied Sciences, Suez Canal University, Suez (Egypt); Joshi, Amitabh, E-mail: ajoshi@eiu.ed [Department of Physics, Eastern Illinois University, Charleston, IL 61920 (United States); Hassan, Shoukry S., E-mail: Shoukryhassan@hotmail.co [Mathematics Department, College of Science, University of Bahrain, P.O. Box 32038 (Bahrain)
2010-04-26
Optical bistability for two-level atomic system in a ring cavity is investigated outside the rotating wave approximation (RWA) using non-autonomous Maxwell-Bloch equations with Fourier decomposition up to first harmonic. The first harmonic output field component exhibits reversed or closed loop bistability simultaneously with the usual (anti-clockwise) bistability in the fundamental field component.
Optical bistability without the rotating wave approximation
International Nuclear Information System (INIS)
Sharaby, Yasser A.; Joshi, Amitabh; Hassan, Shoukry S.
2010-01-01
Optical bistability for two-level atomic system in a ring cavity is investigated outside the rotating wave approximation (RWA) using non-autonomous Maxwell-Bloch equations with Fourier decomposition up to first harmonic. The first harmonic output field component exhibits reversed or closed loop bistability simultaneously with the usual (anti-clockwise) bistability in the fundamental field component.
International Nuclear Information System (INIS)
Das, Shyamal K.; Bhattacharyya, Aninda J.
2011-01-01
Highlights: → Carbon wired TiO 2 nanotubes as anode for lithium ion batteries. → Mixed phase nanotubes show higher energy and power density than titania nanosheets. → Lithium storage and phase stabilization influenced by morphology of carbon coating. - Abstract: The role of homogeneity in ex situ grown conductive coatings and dimensionality in the lithium storage properties of TiO 2 is discussed here. TiO 2 nanotube and nanosheet comprising of mixed crystallographic phases of anatase and TiO 2 (B) have been synthesized by an optimized hydrothermal method. Surface modifications of TiO 2 nanotube are realized via coating the nanotube with Ag nanoparticles and amorphous carbon. The first discharge cycle capacity (at current rate = 10 mA g -1 ) for TiO 2 nanotube and nanosheet were 355 mAh g -1 and 225 mAh g -1 , respectively. The conductive surface coating stabilized the titania crystallographic structure during lithium insertion-deinsertion processes via reduction in the accessibility of lithium ions to the trapping sites. The irreversible capacity is beneficially minimized from 110 mAh g -1 for TiO 2 nanotubes to 96 mAh g -1 and 57 mAh g -1 respectively for Ag and carbon modified TiO 2 nanotubes. The homogeneously coated amorphous carbon over TiO 2 renders better lithium battery performance than randomly distributed Ag nanoparticles coated TiO 2 due to efficient hopping of electrons.
Estimating the approximation error when fixing unessential factors in global sensitivity analysis
Energy Technology Data Exchange (ETDEWEB)
Sobol' , I.M. [Institute for Mathematical Modelling of the Russian Academy of Sciences, Moscow (Russian Federation); Tarantola, S. [Joint Research Centre of the European Commission, TP361, Institute of the Protection and Security of the Citizen, Via E. Fermi 1, 21020 Ispra (Italy)]. E-mail: stefano.tarantola@jrc.it; Gatelli, D. [Joint Research Centre of the European Commission, TP361, Institute of the Protection and Security of the Citizen, Via E. Fermi 1, 21020 Ispra (Italy)]. E-mail: debora.gatelli@jrc.it; Kucherenko, S.S. [Imperial College London (United Kingdom); Mauntz, W. [Department of Biochemical and Chemical Engineering, Dortmund University (Germany)
2007-07-15
One of the major settings of global sensitivity analysis is that of fixing non-influential factors, in order to reduce the dimensionality of a model. However, this is often done without knowing the magnitude of the approximation error being produced. This paper presents a new theorem for the estimation of the average approximation error generated when fixing a group of non-influential factors. A simple function where analytical solutions are available is used to illustrate the theorem. The numerical estimation of small sensitivity indices is discussed.
Approximation of the inverse G-frame operator
Indian Academy of Sciences (India)
... projection method for -frames which works for all conditional -Riesz frames. We also derive a method for approximation of the inverse -frame operator which is efficient for all -frames. We show how the inverse of -frame operator can be approximated as close as we like using finite-dimensional linear algebra.
Cummings, Patrick
We consider the approximation of solutions of two complicated, physical systems via the nonlinear Schrodinger equation (NLS). In particular, we discuss the evolution of wave packets and long waves in two physical models. Due to the complicated nature of the equations governing many physical systems and the in-depth knowledge we have for solutions of the nonlinear Schrodinger equation, it is advantageous to use approximation results of this kind to model these physical systems. The approximations are simple enough that we can use them to understand the qualitative and quantitative behavior of the solutions, and by justifying them we can show that the behavior of the approximation captures the behavior of solutions to the original equation, at least for long, but finite time. We first consider a model of the water wave equations which can be approximated by wave packets using the NLS equation. We discuss a new proof that both simplifies and strengthens previous justification results of Schneider and Wayne. Rather than using analytic norms, as was done by Schneider and Wayne, we construct a modified energy functional so that the approximation holds for the full interval of existence of the approximate NLS solution as opposed to a subinterval (as is seen in the analytic case). Furthermore, the proof avoids problems associated with inverting the normal form transform by working with a modified energy functional motivated by Craig and Hunter et al. We then consider the Klein-Gordon-Zakharov system and prove a long wave approximation result. In this case there is a non-trivial resonance that cannot be eliminated via a normal form transform. By combining the normal form transform for small Fourier modes and using analytic norms elsewhere, we can get a justification result on the order 1 over epsilon squared time scale.
Hardness and Approximation for Network Flow Interdiction
Chestnut, Stephen R.; Zenklusen, Rico
2015-01-01
In the Network Flow Interdiction problem an adversary attacks a network in order to minimize the maximum s-t-flow. Very little is known about the approximatibility of this problem despite decades of interest in it. We present the first approximation hardness, showing that Network Flow Interdiction and several of its variants cannot be much easier to approximate than Densest k-Subgraph. In particular, any $n^{o(1)}$-approximation algorithm for Network Flow Interdiction would imply an $n^{o(1)}...
Energy Technology Data Exchange (ETDEWEB)
Avelino, P.P., E-mail: ppavelin@fc.up.pt [Centro de Astrofísica da Universidade do Porto, Rua das Estrelas, 4150-762 Porto (Portugal)
2012-11-01
In this paper we investigate the classical non-relativistic limit of the Eddington-inspired Born-Infeld theory of gravity. We show that strong bounds on the value of the only additional parameter of the theory κ, with respect to general relativity, may be obtained by requiring that gravity plays a subdominant role compared to electromagnetic interactions inside atomic nuclei. We also discuss the validity of the continuous fluid approximation used in this and other astrophysical and cosmological studies. We argue that although the continuous fluid approximation is expected to be valid in the case of sufficiently smooth density distributions, its use should eventually be validated at a quantum level.
International Nuclear Information System (INIS)
Avelino, P.P.
2012-01-01
In this paper we investigate the classical non-relativistic limit of the Eddington-inspired Born-Infeld theory of gravity. We show that strong bounds on the value of the only additional parameter of the theory κ, with respect to general relativity, may be obtained by requiring that gravity plays a subdominant role compared to electromagnetic interactions inside atomic nuclei. We also discuss the validity of the continuous fluid approximation used in this and other astrophysical and cosmological studies. We argue that although the continuous fluid approximation is expected to be valid in the case of sufficiently smooth density distributions, its use should eventually be validated at a quantum level
Patel, Disha; Bauman, Joseph D; Arnold, Eddy
2014-01-01
X-ray crystallography has been an under-appreciated screening tool for fragment-based drug discovery due to the perception of low throughput and technical difficulty. Investigators in industry and academia have overcome these challenges by taking advantage of key factors that contribute to a successful crystallographic screening campaign. Efficient cocktail design and soaking methodologies have evolved to maximize throughput while minimizing false positives/negatives. In addition, technical improvements at synchrotron beamlines have dramatically increased data collection rates thus enabling screening on a timescale comparable to other techniques. The combination of available resources and efficient experimental design has resulted in many successful crystallographic screening campaigns. The three-dimensional crystal structure of the bound fragment complexed to its target, a direct result of the screening effort, enables structure-based drug design while revealing insights regarding protein dynamics and function not readily obtained through other experimental approaches. Furthermore, this "chemical interrogation" of the target protein crystals can lead to the identification of useful reagents for improving diffraction resolution or compound solubility. Copyright © 2014. Published by Elsevier Ltd.
Patel, Disha; Bauman, Joseph D.; Arnold, Eddy
2015-01-01
X-ray crystallography has been an under-appreciated screening tool for fragment-based drug discovery due to the perception of low throughput and technical difficulty. Investigators in industry and academia have overcome these challenges by taking advantage of key factors that contribute to a successful crystallographic screening campaign. Efficient cocktail design and soaking methodologies have evolved to maximize throughput while minimizing false positives/negatives. In addition, technical improvements at synchrotron beamlines have dramatically increased data collection rates thus enabling screening on a timescale comparable to other techniques. The combination of available resources and efficient experimental design has resulted in many successful crystallographic screening campaigns. The three-dimensional crystal structure of the bound fragment complexed to its target, a direct result of the screening effort, enables structure-based drug design while revealing insights regarding protein dynamics and function not readily obtained through other experimental approaches. Furthermore, this “chemical interrogation” of the target protein crystals can lead to the identification of useful reagents for improving diffraction resolution or compound solubility. PMID:25117499
Qamar, Afzaal; Dao, Dzung Viet; Phan, Hoang-Phuong; Dinh, Toan; Dimitrijev, Sima
2016-08-01
Piezo-Hall effect in a single crystal p-type 3C-SiC, grown by LPCVD process, has been characterized for various crystallographic orientations. The quantified values of the piezo-Hall effect in heavily doped p-type 3C-SiC(100) and 3C-SiC(111) for different crystallographic orientations were used to obtain the fundamental piezo-Hall coefficients, P 12 = ( 5.3 ± 0.4 ) × 10 - 11 Pa - 1 , P 11 = ( - 2.6 ± 0.6 ) × 10 - 11 Pa - 1 , and P 44 = ( 11.42 ± 0.6 ) × 10 - 11 Pa - 1 . Unlike the piezoresistive effect, the piezo-Hall effect for (100) and (111) planes is found to be independent of the angle of rotation of the device within the crystal plane. The values of fundamental piezo-Hall coefficients obtained in this study can be used to predict the piezo-Hall coefficients in any crystal orientation which is very important for designing of 3C-SiC Hall sensors to minimize the piezo-Hall effect for stable magnetic field sensitivity.
Fast wavelet based sparse approximate inverse preconditioner
Energy Technology Data Exchange (ETDEWEB)
Wan, W.L. [Univ. of California, Los Angeles, CA (United States)
1996-12-31
Incomplete LU factorization is a robust preconditioner for both general and PDE problems but unfortunately not easy to parallelize. Recent study of Huckle and Grote and Chow and Saad showed that sparse approximate inverse could be a potential alternative while readily parallelizable. However, for special class of matrix A that comes from elliptic PDE problems, their preconditioners are not optimal in the sense that independent of mesh size. A reason may be that no good sparse approximate inverse exists for the dense inverse matrix. Our observation is that for this kind of matrices, its inverse entries typically have piecewise smooth changes. We can take advantage of this fact and use wavelet compression techniques to construct a better sparse approximate inverse preconditioner. We shall show numerically that our approach is effective for this kind of matrices.
Thin-wall approximation in vacuum decay: A lemma
Brown, Adam R.
2018-05-01
The "thin-wall approximation" gives a simple estimate of the decay rate of an unstable quantum field. Unfortunately, the approximation is uncontrolled. In this paper I show that there are actually two different thin-wall approximations and that they bracket the true decay rate: I prove that one is an upper bound and the other a lower bound. In the thin-wall limit, the two approximations converge. In the presence of gravity, a generalization of this lemma provides a simple sufficient condition for nonperturbative vacuum instability.
Hierarchical matrix approximation of large covariance matrices
Litvinenko, Alexander
2015-01-05
We approximate large non-structured covariance matrices in the H-matrix format with a log-linear computational cost and storage O(nlogn). We compute inverse, Cholesky decomposition and determinant in H-format. As an example we consider the class of Matern covariance functions, which are very popular in spatial statistics, geostatistics, machine learning and image analysis. Applications are: kriging and op- timal design.
Hierarchical matrix approximation of large covariance matrices
Litvinenko, Alexander; Genton, Marc G.; Sun, Ying; Tempone, Raul
2015-01-01
We approximate large non-structured covariance matrices in the H-matrix format with a log-linear computational cost and storage O(nlogn). We compute inverse, Cholesky decomposition and determinant in H-format. As an example we consider the class of Matern covariance functions, which are very popular in spatial statistics, geostatistics, machine learning and image analysis. Applications are: kriging and op- timal design.
Śmiga, Szymon; Fabiano, Eduardo; Laricchia, Savio; Constantin, Lucian A; Della Sala, Fabio
2015-04-21
We analyze the methodology and the performance of subsystem density functional theory (DFT) with meta-generalized gradient approximation (meta-GGA) exchange-correlation functionals for non-bonded molecular systems. Meta-GGA functionals depend on the Kohn-Sham kinetic energy density (KED), which is not known as an explicit functional of the density. Therefore, they cannot be directly applied in subsystem DFT calculations. We propose a Laplacian-level approximation to the KED which overcomes this limitation and provides a simple and accurate way to apply meta-GGA exchange-correlation functionals in subsystem DFT calculations. The so obtained density and energy errors, with respect to the corresponding supermolecular calculations, are comparable with conventional approaches, depending almost exclusively on the approximations in the non-additive kinetic embedding term. An embedding energy error decomposition explains the accuracy of our method.
A new way of obtaining analytic approximations of Chandrasekhar's H function
International Nuclear Information System (INIS)
Vukanic, J.; Arsenovic, D.; Davidovic, D.
2007-01-01
Applying the mean value theorem for definite integrals in the non-linear integral equation for Chandrasekhar's H function describing conservative isotropic scattering, we have derived a new, simple analytic approximation for it, with a maximal relative error below 2.5%. With this new function as a starting-point, after a single iteration in the corresponding integral equation, we have obtained a new, highly accurate analytic approximation for the H function. As its maximal relative error is below 0.07%, it significantly surpasses the accuracy of other analytic approximations
Crystallographic study of one turn of G/C-rich B-DNA.
Heinemann, U; Alings, C
1989-11-20
The DNA decamer d(CCAGGCCTGG) has been studied by X-ray crystallography. At a nominal resolution of 1.6 A, the structure was refined to R = 16.9% using stereochemical restraints. The oligodeoxyribonucleotide forms a straight B-DNA double helix with crystallographic dyad symmetry and ten base-pairs per turn. In the crystal lattice, DNA fragments stack end-to-end along the c-axis to form continuous double helices. The overall helical structure and, notably, the groove dimensions of the decamer are more similar to standard, fiber diffraction-determined B-DNA than A-tract DNA. A unique stacking geometry is observed at the CA/TG base-pair step, where an increased rotation about the helix axis and a sliding motion of the base-pairs along their long axes leads to a superposition of the base rings with neighboring carbonyl and amino functions. Three-center (bifurcated) hydrogen bonds are possible at the CC/GG base-pair steps of the decamer. In their common sequence elements, d(CCAGGCCTGG) and the related G.A mismatch decamer d(CCAAGATTGG) show very similar three-dimensional structures, except that d(CCAGGCCTGG) appears to have a less regularly hydrated minor groove. The paucity of minor groove hydration in the center of the decamer may be a general feature of G/C-rich DNA and explain its relative instability in the B-form of DNA.
Challenges in quantitative crystallographic characterization of 3D thin films by ACOM-TEM
Energy Technology Data Exchange (ETDEWEB)
Kobler, A. [Institute of Nanotechnology (INT), Karlsruhe Institute of Technology (KIT), Hermann-von-Helmholtz-Platz 1, 76344, Eggenstein-Leopoldshafen (Germany); Karlsruhe Nano Micro Facility (KNMF), Karlsruhe Institute of Technology (KIT), Hermann-von-Helmholtz-Platz 1, 76344, Eggenstein-Leopoldshafen (Germany); Kübel, C., E-mail: christian.kuebel@kit.edu [Institute of Nanotechnology (INT), Karlsruhe Institute of Technology (KIT), Hermann-von-Helmholtz-Platz 1, 76344, Eggenstein-Leopoldshafen (Germany); Karlsruhe Nano Micro Facility (KNMF), Karlsruhe Institute of Technology (KIT), Hermann-von-Helmholtz-Platz 1, 76344, Eggenstein-Leopoldshafen (Germany)
2017-02-15
Automated crystal orientation mapping for transmission electron microscopy (ACOM-TEM) has become an easy to use method for the investigation of crystalline materials and complements other TEM methods by adding local crystallographic information over large areas. It fills the gap between high resolution electron microscopy and electron back scatter diffraction in terms of spatial resolution. Recent investigations showed that spot diffraction ACOM-TEM is a quantitative method with respect to sample parameters like grain size, twin density, orientation density and others. It can even be used in combination with in-situ tensile or thermal testing. However, there are limitations of the current method. In this paper we discuss some of the challenges and discuss solutions, e.g. we present an ambiguity filter that reduces the number of pixels with a ‘180° ambiguity problem’. For that an ACOM-TEM tilt series of nanocrystalline Pd thin films with overlapping crystallites was acquired and analyzed. - Highlights: • Tilt series of nanocrystalline Pd thin films. • Quantitative ACOM-TEM data processing, including a rotation map of crystallites. • Noise filter for orientation data: Ambiguity Filter and min. distance filter.
Automating crystallographic structure solution and refinement of protein–ligand complexes
International Nuclear Information System (INIS)
Echols, Nathaniel; Moriarty, Nigel W.; Klei, Herbert E.; Afonine, Pavel V.; Bunkóczi, Gábor; Headd, Jeffrey J.; McCoy, Airlie J.; Oeffner, Robert D.; Read, Randy J.; Terwilliger, Thomas C.; Adams, Paul D.
2013-01-01
A software system for automated protein–ligand crystallography has been implemented in the Phenix suite. This significantly reduces the manual effort required in high-throughput crystallographic studies. High-throughput drug-discovery and mechanistic studies often require the determination of multiple related crystal structures that only differ in the bound ligands, point mutations in the protein sequence and minor conformational changes. If performed manually, solution and refinement requires extensive repetition of the same tasks for each structure. To accelerate this process and minimize manual effort, a pipeline encompassing all stages of ligand building and refinement, starting from integrated and scaled diffraction intensities, has been implemented in Phenix. The resulting system is able to successfully solve and refine large collections of structures in parallel without extensive user intervention prior to the final stages of model completion and validation
Energy Technology Data Exchange (ETDEWEB)
Wencka, Magdalena [Polish Academy of Sciences, Poznan (Poland). Inst. of Molecular Physics; Vrtnik, Stanislav; Kozelj, Primoz; Dolinsek, Janez [Ljubljana Univ. (Slovenia). Faculty of Mathematics and Physics; Jozef Stefan Institute, Ljubljana (Slovenia); Jaglicic, Zvonko [Ljubljana Univ. (Slovenia). Inst. of Mathematics, Physics and Mechanics; Gille, Peter [Muenchen Univ. (Germany). Crystallography Section
2017-09-01
We present measurements of the anisotropic electrical and thermal transport coefficients (the electrical resistivity, the thermoelectric power, the thermal conductivity), the magnetization and the specific heat of the Al{sub 13}Ru{sub 4} monoclinic approximant to the decagonal quasicrystal, in comparison to the isostructural Al{sub 13}Fe{sub 4}. The electrical and thermal transport parameters of Al{sub 13}Ru{sub 4} were found to exhibit significant anisotropy, qualitatively similar to that found previously in the Al{sub 13}Fe{sub 4} (P. Popcevic, et al., Phys. Rev. B 2010, 81, 184203). The crystallographic b direction, corresponding to the stacking direction of the (a,c) atomic planes, is the most conducting direction for the electricity and heat. The thermopower is strongly anisotropic with a complicated temperature dependence, exhibiting maxima, minima, crossovers and sign change. The electronic density of states (DOS) at the Fermi energy is reduced to 35% of the DOS of Al metal. The magnetic susceptibility is diamagnetic and the diamagnetism is by a factor of 2 stronger for the magnetic field along the stacking b direction.
Hierarchical matrix approximation of large covariance matrices
Litvinenko, Alexander
2015-01-07
We approximate large non-structured covariance matrices in the H-matrix format with a log-linear computational cost and storage O(n log n). We compute inverse, Cholesky decomposition and determinant in H-format. As an example we consider the class of Matern covariance functions, which are very popular in spatial statistics, geostatistics, machine learning and image analysis. Applications are: kriging and optimal design
Hierarchical matrix approximation of large covariance matrices
Litvinenko, Alexander; Genton, Marc G.; Sun, Ying; Tempone, Raul
2015-01-01
We approximate large non-structured covariance matrices in the H-matrix format with a log-linear computational cost and storage O(n log n). We compute inverse, Cholesky decomposition and determinant in H-format. As an example we consider the class of Matern covariance functions, which are very popular in spatial statistics, geostatistics, machine learning and image analysis. Applications are: kriging and optimal design
Approximate analysis of high-rise frames with flexible connections
Hoenderkamp, J.C.D.; Snijder, H.H.
2000-01-01
An approximate hand method for estimating horizontal deflections in high-rise steel frames with flexible beam–column connections subjected to horizontal loading is presented. The method is developed from the continuous medium theory for coupled walls which is expressed in non-dimensional structural
Direct non-destructive observation of bulk nucleation in 30% deformed aluminum
DEFF Research Database (Denmark)
West, Stine; Schmidt, Søren; Sørensen, Henning Osholm
2009-01-01
A 30% deformed aluminum sample was mapped non-destructively using three-dimensional X-ray diffraction (3DXRD) before and after annealing to nucleation of recrystallization. Nuclei appeared in the bulk of the sample. Their positions and volumes were determined, and the crystallographic orientations...... were compared with the orientations of the deformed grains. It was found that nuclei with new orientations can form and their orientations have been related to the dislocation structure in the deformed grains....
Capacitor Mismatch Error Cancellation Technique for a Successive Approximation A/D Converter
DEFF Research Database (Denmark)
Zheng, Zhiliang; Moon, Un-Ku; Steensgaard-Madsen, Jesper
1999-01-01
An error cancellation technique is described for suppressing capacitor mismatch in a successive approximation A/D converter. At the cost of a 50% increase in conversion time, the first-order capacitor mismatch error is cancelled. Methods for achieving top-plate parasitic insensitive operation...... are described, and the use of a gain- and offset-compensated opamp is explained. SWITCAP simulation results show that the proposed 16-bit SAR ADC can achieve an SNDR of over 91 dB under non-ideal conditions, including 1% 3 sigma nominal capacitor mismatch, 10-20% randomized parasitic capacitors, 66 dB opamp...
Model-free method for isothermal and non-isothermal decomposition kinetics analysis of PET sample
International Nuclear Information System (INIS)
Saha, B.; Maiti, A.K.; Ghoshal, A.K.
2006-01-01
Pyrolysis, one possible alternative to recover valuable products from waste plastics, has recently been the subject of renewed interest. In the present study, the isoconversion methods, i.e., Vyazovkin model-free approach is applied to study non-isothermal decomposition kinetics of waste PET samples using various temperature integral approximations such as Coats and Redfern, Gorbachev, and Agrawal and Sivasubramanian approximation and direct integration (recursive adaptive Simpson quadrature scheme) to analyze the decomposition kinetics. The results show that activation energy (E α ) is a weak but increasing function of conversion (α) in case of non-isothermal decomposition and strong and decreasing function of conversion in case of isothermal decomposition. This indicates possible existence of nucleation, nuclei growth and gas diffusion mechanism during non-isothermal pyrolysis and nucleation and gas diffusion mechanism during isothermal pyrolysis. Optimum E α dependencies on α obtained for non-isothermal data showed similar nature for all the types of temperature integral approximations
Kokornaczyk, Maria Olga; Dinelli, Giovanni; Betti, Lucietta
2013-01-01
The present paper reports on an observation that dendrite-like polycrystalline structures from evaporating droplets of wheat grain leakages exhibit bilateral symmetry. The exactness of this symmetry, measured by means of fluctuating asymmetry, varies depending on the cultivar and stress factor influence, and seems to correspond to the seed germination rate. In the bodies of plants, animals, and humans, the exactness of bilateral symmetry is known to reflect the environmental conditions of an organism's growth, its health, and its success in sexual selection. In polycrystalline structures, formed under the same conditions, the symmetry exactness depends on the properties of the crystallizing solution such as the composition and viscosity; however, it has never been associated with sample quality. We hypothesize here that, as in living nature, the exactness of approximate bilateral symmetry might be considered a quality indicator also in crystallographic methods applied to food quality analysis.
Erbium-ion implantation into various crystallographic cuts of Al{sub 2}O{sub 3}
Energy Technology Data Exchange (ETDEWEB)
Nekvindova, P. [Department of Inorganic Chemistry, Institute of Chemical Technology, Technicka 5, 166 28 Prague 6 (Czech Republic); Mackova, A.; Malinsky, P. [Nuclear Physics Institute of the Academy of Sciences of the Czech Republic v.v.i., 250 68 Rez (Czech Republic); Department of Physics, Faculty of Science, J.E. Purkinje University, Ceske mladeze 8, 400 96 Usti nad Labem (Czech Republic); Cajzl, J.; Svecova, B. [Department of Inorganic Chemistry, Institute of Chemical Technology, Technicka 5, 166 28 Prague 6 (Czech Republic); Oswald, J. [Institute of Physics, Academy of Sciences of the Czech Republic, v.v.i., Cukrovarnicka 10, 162 53 Prague (Czech Republic); Wilhelm, R.A. [Institute of Ion Beam Physics and Materials Research, Helmholtz-Zentrum Dresden-Rossendorf, 01314 Dresden (Germany); Technische Universität Dresden, 01062 Dresden (Germany)
2015-12-15
This paper reports on the importance of crystallographic cuts with a different orientation on the luminescent properties and structural changes of Al{sub 2}O{sub 3} implanted with Er{sup +} ions at 190 keV and with a fluence of 1.0 × 10{sup 16} cm{sup −2}. Post-implantation annealing at 1000 °C in oxygen atmosphere was also done. The chemical compositions and erbium concentration-depth profiles of implanted layers were studied by Rutherford Backscattering Spectrometry (RBS) and compared to SRIM simulations. The same value of the maximum erbium concentration (up to 2 at.%) was observed at a depth of about 40 nm for all crystallographic cuts. The structural properties of the prepared layers were characterised by RBS/channelling. The relative amount of disordered atoms of 70–80% was observed in the prepared implanted layers and discussed for various cuts. It has been found that erbium is positioned randomly in the Al{sub 2}O{sub 3} crystalline matrix, and no preferential positions appeared even after the annealing procedure. Erbium luminescence properties were measured in the wavelength range of 1440–1650 nm for all samples. As-implanted Al{sub 2}O{sub 3} samples had a significant luminescence band at 1530 nm. The best luminescence was repeatedly observed in the 〈0 0 0 1〉 cut of Al{sub 2}O{sub 3}. The annealing procedure significantly improved the luminescent properties.
A simple approximation for the current-voltage characteristics of high-power, relativistic diodes
Energy Technology Data Exchange (ETDEWEB)
Ekdahl, Carl, E-mail: cekdahl@lanl.gov [Los Alamos National Laboratory, Los Alamos, New Mexico 87545 (United States)
2016-06-15
A simple approximation for the current-voltage characteristics of a relativistic electron diode is presented. The approximation is accurate from non-relativistic through relativistic electron energies. Although it is empirically developed, it has many of the fundamental properties of the exact diode solutions. The approximation is simple enough to be remembered and worked on almost any pocket calculator, so it has proven to be quite useful on the laboratory floor.
An extension of Brosowski-Meinardus theorem on invariant approximation
International Nuclear Information System (INIS)
Liaqat Ali Khan; Abdul Rahim Khan.
1991-07-01
We obtain a generalization of a fixed point theorem of Dotson for non-expansive mappings on star-shaped sets and then use it to prove a unified Brosowski-Meinardus theorem on invariant approximation in the setting of p-normed linear spaces. (author). 13 refs
Yao, Fang; LeGeros, John P; LeGeros, Racquel Z
2009-07-01
The mineral in bone is an impure hydroxyapatite, with carbonate as the chief minor substituent. Fluoride has been shown to stimulate osteoblastic activity and inhibit osteoclastic resorption in vitro. CO(3)- and F-substituted apatite (CFA) has been considered as potential bone graft material for orthopedic and dental applications. The objective of this study was to determine the effects of simultaneously incorporated CO(3) and F on the crystallographic physico-chemical properties of apatite. The results showed that increasing CO(3) and Na content in apatites with relatively constant F concentration caused a decrease in crystallite size and an increase in the extent of calcium release; increasing F content in apatites with relatively constant CO(3) concentration caused an increase in crystallite size and a decrease in the extent of Ca release. These findings suggest that CFAs as bone graft materials of desired solubility can be prepared by manipulating the relative concentrations of CO(3) and F incorporated in the apatite.
International Nuclear Information System (INIS)
Pasic, S.; Uroic, M.; Tocilj, Z.; Majer, M.; Gamulin, O.; Bokulic, T.; Ilakovac, K.
2005-01-01
Double-differential Compton cross sections at two incident photon energies of 68.9 and 70.8 keV (mercury Kα X-rays) at the scattering angle of about 172 deg were measured in germanium using the coincidence technique with a detector as the scatterer. The cross sections were determined by normalization of the Compton spectra to the peaks due to the escape of characteristic Kα and Kβ X-rays from the target detector. This new approach of determination of absolute-scale Compton cross sections can also be applied in widely used single-mode measurements (source-scatterer-detector assembly). Our analysis shows that the new method is especially convenient and accurate at lower incident photon energies above the K-edge in the target atoms. The experimental results are compared with the non-relativistic impulse approximation, the frequently used simplified version of the relativistic impulse approximation and the non-relativistic impulse approximation used with the relativistic expression for the atomic electron momentum in the direction of the photon momentum transfer. Contrary to our expectation, the non-relativistic impulse approximation clearly gives the best agreement with the experimental data in the region of the Compton peak
International Nuclear Information System (INIS)
Thijs, Lore; Montero Sistiaga, Maria Luz; Wauthle, Ruben; Xie, Qingge; Kruth, Jean-Pierre; Van Humbeeck, Jan
2013-01-01
Selective laser melting (SLM) makes use of a high energy density laser beam to melt successive layers of metallic powders in order to create functional parts. The energy density of the laser is high enough to melt refractory metals like Ta and produce mechanically sound parts. Furthermore, the localized heat input causes a strong directional cooling and solidification. Epitaxial growth due to partial remelting of the previous layer, competitive growth mechanism and a specific global direction of heat flow during SLM of Ta result in the formation of long columnar grains with a 〈1 1 1〉 preferential crystal orientation along the building direction. The microstructure was visualized using both optical and scanning electron microscopy equipped with electron backscattered diffraction and the global crystallographic texture was measured using X-ray diffraction. The thermal profile around the melt pool was modeled using a pragmatic model for SLM. Furthermore, rotation of the scanning direction between different layers was seen to promote the competitive growth. As a result, the texture strength increased to as large as 4.7 for rotating the scanning direction 90° every layer. By comparison of the yield strength measured by compression tests in different orientations and the averaged Taylor factor calculated using the viscoplastic self-consistent model, it was found that both the morphological and crystallographic texture observed in SLM Ta contribute to yield strength anisotropy
A monoclinic polymorph of (1E,5E)-1,5-bis-(2-hy-droxy-benzyl-idene)thio-carbono-hydrazide.
Schmitt, Bonell; Gerber, Thomas; Hosten, Eric; Betz, Richard
2011-08-01
The title compound, C(15)H(14)N(4)O(2)S, is a derivative of thio-ureadihydrazide. In contrast to the previously reported polymorph (ortho-rhom-bic, space group Pbca, Z = 8), the current study revealed monoclinic symmetry (space group P2(1)/n, Z = 4). The mol-ecule shows non-crystallographic C(2) as well as approximate C(s) symmetry. Intra-molecular bifurcated O-H⋯(N,S) hydrogen bonds, are present. In the crystal, inter-molecular N-H⋯S hydrogen bonds and C-H⋯π contacts connect the mol-ecules into undulating chains along the b axis. The shortest centroid-centroid distance between two aromatic systems is 4.5285 (12) Å.
Recombinant ACHT1 from Arabidopsis thaliana: crystallization and X-ray crystallographic analysis.
Pan, Weimin; Wang, Junchao; Yang, Ye; Liu, Lin; Zhang, Min
2017-07-01
Thioredoxins (Trxs) play important roles in chloroplasts by linking photosynthetic light reactions to a series of plastid functions. They execute their function by regulating the oxidation and reduction of disulfide bonds. ACHT1 (atypical cysteine/histidine-rich Trx1) is a thylakoid-associated thioredoxin-type protein found in the Arabidopsis thaliana chloroplast. Recombinant ACHT1 protein was overexpressed in Escherichia coli, purified and crystallized by the vapour-diffusion method. The crystal diffracted to 1.7 Å resolution and a complete X-ray data set was collected. Preliminary crystallographic analysis suggested that the crystals belonged to space group C222 1 , with unit-cell parameters a = 102.7, b = 100.6, c = 92.8 Å.
International Nuclear Information System (INIS)
Cafiero, Mauricio; Gonzalez, Carlos
2005-01-01
We show that potentials for exchange-correlation functionals within the Kohn-Sham density-functional-theory framework may be written as potentials for simpler functionals multiplied by a factor close to unity, and in a self-consistent field calculation, these effective potentials find the correct self-consistent solutions. This simple theory is demonstrated with self-consistent exchange-only calculations of the atomization energies of some small molecules using the Perdew-Kurth-Zupan-Blaha (PKZB) meta-generalized-gradient-approximation (meta-GGA) exchange functional. The atomization energies obtained with our method agree with or surpass previous meta-GGA calculations performed in a non-self-consistent manner. The results of this work suggest the utility of this simple theory to approximate exchange-correlation potentials corresponding to energy functionals too complicated to generate closed forms for their potentials. We hope that this method will encourage the development of complex functionals which have correct boundary conditions and are free of self-interaction errors without the worry that the functionals are too complex to differentiate to obtain potentials
Trajectory averaging for stochastic approximation MCMC algorithms
Liang, Faming
2010-10-01
The subject of stochastic approximation was founded by Robbins and Monro [Ann. Math. Statist. 22 (1951) 400-407]. After five decades of continual development, it has developed into an important area in systems control and optimization, and it has also served as a prototype for the development of adaptive algorithms for on-line estimation and control of stochastic systems. Recently, it has been used in statistics with Markov chain Monte Carlo for solving maximum likelihood estimation problems and for general simulation and optimizations. In this paper, we first show that the trajectory averaging estimator is asymptotically efficient for the stochastic approximation MCMC (SAMCMC) algorithm under mild conditions, and then apply this result to the stochastic approximation Monte Carlo algorithm [Liang, Liu and Carroll J. Amer. Statist. Assoc. 102 (2007) 305-320]. The application of the trajectory averaging estimator to other stochastic approximationMCMC algorithms, for example, a stochastic approximation MLE algorithm for missing data problems, is also considered in the paper. © Institute of Mathematical Statistics, 2010.
International Nuclear Information System (INIS)
Ginsburg, C.A.
1980-01-01
In many problems, a desired property A of a function f(x) is determined by the behaviour of f(x) approximately equal to g(x,A) as x→xsup(*). In this letter, a method for resuming the power series in x of f(x) and approximating A (modulated Pade approximant) is presented. This new approximant is an extension of a resumation method for f(x) in terms of rational functions. (author)
Synthesis, crystallographic and magnetic properties of protactinium pnictides
International Nuclear Information System (INIS)
Hery, Yves.
1979-03-01
From a theoretical point of view, protactinium lies in a very important place in the periodic system for it seems to be the first element of the actinide series where the 5f state is occupied. We have studied protactinium pnictides, particularly arsenides and antimonides. PaAs 2 , Pa 3 As 4 , PaSb 2 and Pa 3 Sb 4 were synthetized and their crystallographic properties were determined and discussed. We have measured the magnetic susceptibilities of PaC, PaAs 2 and PaSb 2 . Protactinium exhibits a dual character. In its monocarbide, which is a weakly diamagnet, it behaves as a transition element while in the temperature independent paramagnets PaAs 2 and PaSb 2 , it behaves like a 'f' element. This 'f' element character increases with increasing metal-metal distances. Furthermore the radial expansion of the protactinium 5f orbital seems to be more important than the Uranium one, and consequently the corresponding protactinium 5f electrons are less localized. In addition, some protactinium chalcogenides (βPaS 2 , γPaSe 2 and PaOSe) have been identified [fr
Approximate Dynamic Programming: Combining Regional and Local State Following Approximations.
Deptula, Patryk; Rosenfeld, Joel A; Kamalapurkar, Rushikesh; Dixon, Warren E
2018-06-01
An infinite-horizon optimal regulation problem for a control-affine deterministic system is solved online using a local state following (StaF) kernel and a regional model-based reinforcement learning (R-MBRL) method to approximate the value function. Unlike traditional methods such as R-MBRL that aim to approximate the value function over a large compact set, the StaF kernel approach aims to approximate the value function in a local neighborhood of the state that travels within a compact set. In this paper, the value function is approximated using a state-dependent convex combination of the StaF-based and the R-MBRL-based approximations. As the state enters a neighborhood containing the origin, the value function transitions from being approximated by the StaF approach to the R-MBRL approach. Semiglobal uniformly ultimately bounded (SGUUB) convergence of the system states to the origin is established using a Lyapunov-based analysis. Simulation results are provided for two, three, six, and ten-state dynamical systems to demonstrate the scalability and performance of the developed method.
Zhukova, Yu. S.; Petrzhik, M. I.; Prokoshkin, S. D.
2010-11-01
Three methods are described to calculate the crystallographic strain limit that is determined by the maximum deformation of the crystal lattice in the reversible βbcc ⇄ α″orth martensitic transformation and ensures pseudoelastic deformation accumulation and shape recovery in Ti-Nb-Ta alloys.
On badly approximable complex numbers
DEFF Research Database (Denmark)
Esdahl-Schou, Rune; Kristensen, S.
We show that the set of complex numbers which are badly approximable by ratios of elements of , where has maximal Hausdorff dimension. In addition, the intersection of these sets is shown to have maximal dimension. The results remain true when the sets in question are intersected with a suitably...
High-order above-threshold ionization beyond the electric dipole approximation
Brennecke, Simon; Lein, Manfred
2018-05-01
Photoelectron momentum distributions from strong-field ionization are calculated by numerical solution of the one-electron time-dependent Schrödinger equation for a model atom including effects beyond the electric dipole approximation. We focus on the high-energy electrons from rescattering and analyze their momentum component along the field propagation direction. We show that the boundary of the calculated momentum distribution is deformed in accordance with the classical three-step model including the beyond-dipole Lorentz force. In addition, the momentum distribution exhibits an asymmetry in the signal strengths of electrons emitted in the forward/backward directions. Taken together, the two non-dipole effects give rise to a considerable average forward momentum component of the order of 0.1 a.u. for realistic laser parameters.
Agarwal, Mukul
2018-01-01
It is proved that the limit of the normalized rate-distortion functions of block independent approximations of an irreducible, aperiodic Markoff chain is independent of the initial distribution of the Markoff chain and thus, is also equal to the rate-distortion function of the Markoff chain.
Rational approximation of vertical segments
Salazar Celis, Oliver; Cuyt, Annie; Verdonk, Brigitte
2007-08-01
In many applications, observations are prone to imprecise measurements. When constructing a model based on such data, an approximation rather than an interpolation approach is needed. Very often a least squares approximation is used. Here we follow a different approach. A natural way for dealing with uncertainty in the data is by means of an uncertainty interval. We assume that the uncertainty in the independent variables is negligible and that for each observation an uncertainty interval can be given which contains the (unknown) exact value. To approximate such data we look for functions which intersect all uncertainty intervals. In the past this problem has been studied for polynomials, or more generally for functions which are linear in the unknown coefficients. Here we study the problem for a particular class of functions which are nonlinear in the unknown coefficients, namely rational functions. We show how to reduce the problem to a quadratic programming problem with a strictly convex objective function, yielding a unique rational function which intersects all uncertainty intervals and satisfies some additional properties. Compared to rational least squares approximation which reduces to a nonlinear optimization problem where the objective function may have many local minima, this makes the new approach attractive.
Influence of chemical composition in crystallographic texture Fe-Cr-Mo alloys
International Nuclear Information System (INIS)
Moura, L.B.; Guimaraes, R.F.
2010-01-01
The use of steels with higher contents of Mo in the oil industry has been an alternative to reduce the effect of naphthenic corrosion in refining units. The addition of Mo in Fe-Cr alloys in the same manner that increases resistance to corrosion naphthenic causes some difficulties such as difficulty of forming, welding and embrittlement. In this work, experimental ingots of Fe-Cr-Mo alloys (Cr - 9, 15 and 17%, Mo - 5, 7 and 9%) were melted in vacuum induction furnace and hot and cold rolled in a laboratory rolling mill. The influence of chemical composition on crystallographic texture of samples subjected to the same thermo-mechanical treatment was analyzed by x-ray diffraction. The results indicate that fiber (111) becomes more intense with increasing Mo and/or Cr contents. (author)
Smooth function approximation using neural networks.
Ferrari, Silvia; Stengel, Robert F
2005-01-01
An algebraic approach for representing multidimensional nonlinear functions by feedforward neural networks is presented. In this paper, the approach is implemented for the approximation of smooth batch data containing the function's input, output, and possibly, gradient information. The training set is associated to the network adjustable parameters by nonlinear weight equations. The cascade structure of these equations reveals that they can be treated as sets of linear systems. Hence, the training process and the network approximation properties can be investigated via linear algebra. Four algorithms are developed to achieve exact or approximate matching of input-output and/or gradient-based training sets. Their application to the design of forward and feedback neurocontrollers shows that algebraic training is characterized by faster execution speeds and better generalization properties than contemporary optimization techniques.
International Nuclear Information System (INIS)
Gibert, C.
1999-01-01
The-increasing deterioration of the initially protective zirconia layer is one of the hypotheses which can explain the impairment with time of PWR fuel cladding corrosion. This deterioration could be worsened by irradiation or lithium presence in the oxidizing medium. The aim of this thesis was to underline the influence of those two parameters on zirconia crystallographic nature. We first studied the impact of ionic irradiation on pure, powdery, monoclinic zirconia and oxidation formed zirconia, mainly with X-ray diffraction and Raman microscopy. The high or low energy particles used (Kr n+- , Ar n+ ) respectively favored electronic or atomic defaults production. The crystallographic analyses showed that these irradiation have a significant effect on zirconia by inducing nucleation or growth of tetragonal phase. The extent depends on sample nature and particles energy. In all cases, phase transformation is correlated with crystalline parameters, grain size and especially micro-stress changes. The results are consistent with those obtained with 1 to 5 cycles PWR claddings. Therefore, the corrosion acceleration observed in reactor can partly be explained by the stress fields appearance under irradiation, which is particularly detrimental to zirconia layer cohesion. Last, we have underlined that the presence of considerable amounts of lithium in the oxidizing medium ((> 700 ppm) induces the disappearance of the tetragonal zirconia located at the metal/oxide interface and the appearance of a porosity of the dense under layer, which looses its protectiveness. (author)
Delta-function Approximation SSC Model in 3C 273 S. J. Kang1 ...
Indian Academy of Sciences (India)
Abstract. We obtain an approximate analytical solution using δ approximate calculation on the traditional one-zone synchrotron self-. Compton (SSC) model. In this model, we describe the electron energy distribution by a broken power-law function with a sharp cut-off, and non- thermal photons are produced by both ...
Approximate, analytic solutions of the Bethe equation for charged particle range
Swift, Damian C.; McNaney, James M.
2009-01-01
By either performing a Taylor expansion or making a polynomial approximation, the Bethe equation for charged particle stopping power in matter can be integrated analytically to obtain the range of charged particles in the continuous deceleration approximation. Ranges match reference data to the expected accuracy of the Bethe model. In the non-relativistic limit, the energy deposition rate was also found analytically. The analytic relations can be used to complement and validate numerical solu...
Non-Markovian reservoir-dependent squeezing
International Nuclear Information System (INIS)
Paavola, J
2010-01-01
The squeezing dynamics of a damped harmonic oscillator are studied for different types of environment without making the Markovian approximation. The squeezing dynamics of a coherent state depend on the reservoir spectrum in a unique way that can, in the weak coupling approximation, be analysed analytically. Comparison of squeezing dynamics for ohmic, sub-ohmic and super-ohmic environments is done, showing a clear connection between the squeezing-non-squeezing oscillations and reservoir structure. Understanding the effects occurring due to structured reservoirs is important both from a purely theoretical point of view and in connection with evolving experimental techniques and future quantum computing applications.
An approximate analytical approach to resampling averages
DEFF Research Database (Denmark)
Malzahn, Dorthe; Opper, M.
2004-01-01
Using a novel reformulation, we develop a framework to compute approximate resampling data averages analytically. The method avoids multiple retraining of statistical models on the samples. Our approach uses a combination of the replica "trick" of statistical physics and the TAP approach for appr...... for approximate Bayesian inference. We demonstrate our approach on regression with Gaussian processes. A comparison with averages obtained by Monte-Carlo sampling shows that our method achieves good accuracy....
Energy Technology Data Exchange (ETDEWEB)
Roversi, Pietro; Johnson, Steven [Laboratory of Molecular Biophysics, Department of Biochemistry, University of Oxford, South Parks Road, Oxford OX1 3QU (United Kingdom); Field, Terry [Division of Microbiology, Institute for Animal Health, Compton Laboratory, Berkshire RG20 7NN (United Kingdom); Deane, Janet E. [Laboratory of Molecular Biophysics, Department of Biochemistry, University of Oxford, South Parks Road, Oxford OX1 3QU (United Kingdom); Galyov, Edouard E. [Division of Microbiology, Institute for Animal Health, Compton Laboratory, Berkshire RG20 7NN (United Kingdom); Lea, Susan M., E-mail: susan.lea@biop.ox.ac.uk [Laboratory of Molecular Biophysics, Department of Biochemistry, University of Oxford, South Parks Road, Oxford OX1 3QU (United Kingdom); Sir William Dunn School of Pathology, University of Oxford, South Parks Road, Oxford OX1 3RE (United Kingdom)
2006-09-01
A construct consisting of residues 10–310 of mature BipD, a component of the B. pseudomallei type III secretion system, has been crystallized. Native BipD crystals and SeMet and K{sub 2}PtCl{sub 4} derivative crystals have undergone preliminary crystallographic analysis. A construct consisting of residues 10–310 of BipD, a component of the Burkholderia pseudomallei type III secretion system (T3SS), has been overexpressed as a GST fusion, cleaved from the GST tag and purified. Crystals were grown of native and selenomethionine-labelled BipD. The crystals grow in two different polymorphs from the same condition. The first polymorph belongs to space group C222, with unit-cell parameters a = 103.98, b = 122.79, c = 49.17 Å, a calculated Matthews coefficient of 2.4 Å{sup 3} Da{sup −1} (47% solvent content) and one molecule per asymmetric unit. The second polymorph belongs to space group P2{sub 1}2{sub 1}2, with unit-cell parameters a = 136.47, b = 89.84, c = 50.15 Å, and a calculated Matthews coefficient of 2.3 Å{sup 3} Da{sup −1} (45% solvent content) for two molecules per asymmetric unit (analysis of the self-rotation function indicates the presence of a weak twofold non-crystallographic symmetry axis in this P2{sub 1}2{sub 1}2 form). The native crystals of both forms give diffraction data to 2.7 Å resolution, while the SeMet-labelled P2{sub 1}2{sub 1}2 crystals diffract to 3.3 Å resolution. A K{sub 2}PtCl{sub 4} derivative of the P2{sub 1}2{sub 1}2 form was also obtained and data were collected to 2.7 Å with radiation of wavelength λ = 0.933 Å. The Pt-derivative anomalous difference Patterson map revealed two self-peaks on the Harker sections.
International Nuclear Information System (INIS)
Bazhin, M.A.; Fedosenko, G.Eh.; Shiryaeva, N.M.; Mal'ko, M.V.
1986-01-01
It is shown that adiabatic non-equilibrium chemically reacting gas flow with energy exchange in a variable cross-section channel may be subdivided into five possible types: 1) quasi-equilibrium flow; 2) flow in the linear region of deviation from equilibrium state; 3) quasi-frozen flow; 4) flow in the linear region of deviation from frozen state; 5) non-equilibrium flow. Criteria of quasi-equilibrium and quazi-frozen flows, including factors of external action of chemically reacting gas on flow, allow to obtain simple but sufficiently reliable approximate method of calculation of flow parameters. The considered method for solving the problem of chemically reacting nitrogen tetroxide in the variable cross-section channel with energy exchange can be used for evaluation of chemical reaction kinetics on the flow parameter in the stages of axial-flow and radial-flow turbines and in another practical problems
Plasma Physics Approximations in Ares
International Nuclear Information System (INIS)
Managan, R. A.
2015-01-01
Lee & More derived analytic forms for the transport properties of a plasma. Many hydro-codes use their formulae for electrical and thermal conductivity. The coefficients are complex functions of Fermi-Dirac integrals, Fn( μ/θ ), the chemical potential, μ or ζ = ln(1+e μ/θ ), and the temperature, θ = kT. Since these formulae are expensive to compute, rational function approximations were fit to them. Approximations are also used to find the chemical potential, either μ or ζ . The fits use ζ as the independent variable instead of μ/θ . New fits are provided for A α (ζ ),A β (ζ ), ζ, f(ζ ) = (1 + e -μ/θ )F 1/2 (μ/θ), F 1/2 '/F 1/2 , F c α , and F c β . In each case the relative error of the fit is minimized since the functions can vary by many orders of magnitude. The new fits are designed to exactly preserve the limiting values in the non-degenerate and highly degenerate limits or as ζ→ 0 or ∞. The original fits due to Lee & More and George Zimmerman are presented for comparison.
Energy Technology Data Exchange (ETDEWEB)
Jans, L., E-mail: lennartjans@hotmail.com [Department of Radiology and Medical Imaging, Ghent University Hospital, De Pintelaan 185, 9000 Gent (Belgium); Van Praet, L.; Elewaut, D.; Van den Bosch, F.; Carron, P. [Department of Rheumatology, Ghent University Hospital, De Pintelaan 185, 9000 Gent (Belgium); Jaremko, J.L. [Department of Radiology, University of Alberta Hospital, 8440-112 Street, Edmonton T6G 2B7, Alberta (Canada); Behaeghe, M.; Denis, A.; Huysse, W.; Lambrecht, V.; Verstraete, K. [Department of Radiology and Medical Imaging, Ghent University Hospital, De Pintelaan 185, 9000 Gent (Belgium)
2014-01-15
Purpose: To determine the prevalence of clinically relevant non-inflammatory disease on MRI of the sacroiliac (SI) joints in patients suspected of sacroiliitis. To assess the added value of axial imaging of the pelvis in these patients. Methods: In a retrospective study of 691 patients undergoing MRI of the SI joints from January 2006 to December 2012 for inflammatory back pain the prevalence of sacroiliitis and non-inflammatory disease was recorded. Results: In 285 (41%) patients MRI did not show any abnormal findings. In 36% of patients MRI features of sacroiliitis were present. Spinal degenerative changes were the most common non-inflammatory finding in 305 patients (44.1%) and consisted of disc degeneration in 222 (32%) patients, facet joint arthrosis in 58 (8.4%) patients and disc herniation in 25 (3.6%) patients. Hip joint disease in 44 (6.4%) patients, lumbosacral transitional anomaly in 41 (5.9%) patients, SI joint degenerative changes in 25 (3.6%) patients and diffuse idiopathic skeletal hyperostosis in 24 (3.5%) patients were also common. Osteitis condensans ilii in 17 (2.5%) patients, tumour in 11 (1.6%) patients, fracture in 8 (1.2%) patients, infection in 4 (0.6%) patients and acute spondylolysis in 2 patients (0.3%) were less frequently seen. Conclusion: Our study shows that non-inflammatory disease is more common than true sacroiliitis on MRI of the SI joints in patients with inflammatory type back pain. Axial pulse sequences may demonstrate unexpected findings that remain undetected if only coronal images are obtained. Clinical relevance statement:, MRI of the SI joints may demonstrate conditions that clinically mimic sacroiliitis. Axial imaging of the pelvis may help detect these unexpected findings.
International Nuclear Information System (INIS)
Jans, L.; Van Praet, L.; Elewaut, D.; Van den Bosch, F.; Carron, P.; Jaremko, J.L.; Behaeghe, M.; Denis, A.; Huysse, W.; Lambrecht, V.; Verstraete, K.
2014-01-01
Purpose: To determine the prevalence of clinically relevant non-inflammatory disease on MRI of the sacroiliac (SI) joints in patients suspected of sacroiliitis. To assess the added value of axial imaging of the pelvis in these patients. Methods: In a retrospective study of 691 patients undergoing MRI of the SI joints from January 2006 to December 2012 for inflammatory back pain the prevalence of sacroiliitis and non-inflammatory disease was recorded. Results: In 285 (41%) patients MRI did not show any abnormal findings. In 36% of patients MRI features of sacroiliitis were present. Spinal degenerative changes were the most common non-inflammatory finding in 305 patients (44.1%) and consisted of disc degeneration in 222 (32%) patients, facet joint arthrosis in 58 (8.4%) patients and disc herniation in 25 (3.6%) patients. Hip joint disease in 44 (6.4%) patients, lumbosacral transitional anomaly in 41 (5.9%) patients, SI joint degenerative changes in 25 (3.6%) patients and diffuse idiopathic skeletal hyperostosis in 24 (3.5%) patients were also common. Osteitis condensans ilii in 17 (2.5%) patients, tumour in 11 (1.6%) patients, fracture in 8 (1.2%) patients, infection in 4 (0.6%) patients and acute spondylolysis in 2 patients (0.3%) were less frequently seen. Conclusion: Our study shows that non-inflammatory disease is more common than true sacroiliitis on MRI of the SI joints in patients with inflammatory type back pain. Axial pulse sequences may demonstrate unexpected findings that remain undetected if only coronal images are obtained. Clinical relevance statement:, MRI of the SI joints may demonstrate conditions that clinically mimic sacroiliitis. Axial imaging of the pelvis may help detect these unexpected findings
Big geo data surface approximation using radial basis functions: A comparative study
Majdisova, Zuzana; Skala, Vaclav
2017-12-01
Approximation of scattered data is often a task in many engineering problems. The Radial Basis Function (RBF) approximation is appropriate for big scattered datasets in n-dimensional space. It is a non-separable approximation, as it is based on the distance between two points. This method leads to the solution of an overdetermined linear system of equations. In this paper the RBF approximation methods are briefly described, a new approach to the RBF approximation of big datasets is presented, and a comparison for different Compactly Supported RBFs (CS-RBFs) is made with respect to the accuracy of the computation. The proposed approach uses symmetry of a matrix, partitioning the matrix into blocks and data structures for storage of the sparse matrix. The experiments are performed for synthetic and real datasets.
Perturbative corrections for approximate inference in gaussian latent variable models
DEFF Research Database (Denmark)
Opper, Manfred; Paquet, Ulrich; Winther, Ole
2013-01-01
Expectation Propagation (EP) provides a framework for approximate inference. When the model under consideration is over a latent Gaussian field, with the approximation being Gaussian, we show how these approximations can systematically be corrected. A perturbative expansion is made of the exact b...... illustrate on tree-structured Ising model approximations. Furthermore, they provide a polynomial-time assessment of the approximation error. We also provide both theoretical and practical insights on the exactness of the EP solution. © 2013 Manfred Opper, Ulrich Paquet and Ole Winther....
Influence of crystallographic orientation on the response of copper crystallites to nanoindentation
Energy Technology Data Exchange (ETDEWEB)
Korchuganov, Aleksandr V., E-mail: avkor@ispms.tsc.ru [Institute of Strength Physics and Materials Science SB RAS, Tomsk, 634055 (Russian Federation); Kryzhevich, Dmitrij S., E-mail: kryzhev@ispms.tsc.ru, E-mail: kost@ispms.tsc.ru; Zolnikov, Konstantin P., E-mail: kryzhev@ispms.tsc.ru, E-mail: kost@ispms.tsc.ru [Institute of Strength Physics and Materials Science SB RAS, Tomsk, 634055, Russia and National Research Tomsk State University, Tomsk, 634050 (Russian Federation); Psakhie, Sergey G., E-mail: sp@ispms.tsc.ru [Institute of Strength Physics and Materials Science SB RAS, Tomsk, 634055, Russia and National Research Tomsk Polytechnic University, Tomsk, 634050 (Russian Federation)
2014-11-14
Molecular dynamics simulation was performed to study the features of nucleation and development of plastic deformation in copper crystallites in nanoindentation with different crystallographic orientations of their loaded surface: (011), (001), and (111). Atomic interaction was described by a potential constructed in terms of the embedded atom method. It is shown that behavior of the crystallite reaction force correlates well with a change in the fraction of atoms involved in local structural rearrangements. The generation of local structural changes decreases the slope of the crystallite reaction force curve or results in an extremum due to internal stress relaxation. Analysis of structural changes in the material being indented demonstrates that the orientation of its loaded surface greatly affects the features of nucleation and development of plastic deformation.
International Nuclear Information System (INIS)
Takayama, Y; Watanabe, H; Yoshimura, T
2015-01-01
In order to investigate relationship between stored strain and crystallographic orientation, 99.99% purity aluminum cubes were compressed with uniaxial or with plane strain state up to a nominal strain of 30%. The aluminum cubes were examined on the same surface before and after compression by SEM/EBSD technique. Stored strain was estimated by Kernel Average Misorientation (KAM) derived from the EBSD analysis, and Taylor factor (TF) was measured before the compressive deformation. The analysis revealed that KAM value or the stored strain decreases until a certain value of TF and then increases with increment of TF. (paper)
Direct application of Padé approximant for solving nonlinear differential equations.
Vazquez-Leal, Hector; Benhammouda, Brahim; Filobello-Nino, Uriel; Sarmiento-Reyes, Arturo; Jimenez-Fernandez, Victor Manuel; Garcia-Gervacio, Jose Luis; Huerta-Chua, Jesus; Morales-Mendoza, Luis Javier; Gonzalez-Lee, Mario
2014-01-01
This work presents a direct procedure to apply Padé method to find approximate solutions for nonlinear differential equations. Moreover, we present some cases study showing the strength of the method to generate highly accurate rational approximate solutions compared to other semi-analytical methods. The type of tested nonlinear equations are: a highly nonlinear boundary value problem, a differential-algebraic oscillator problem, and an asymptotic problem. The high accurate handy approximations obtained by the direct application of Padé method shows the high potential if the proposed scheme to approximate a wide variety of problems. What is more, the direct application of the Padé approximant aids to avoid the previous application of an approximative method like Taylor series method, homotopy perturbation method, Adomian Decomposition method, homotopy analysis method, variational iteration method, among others, as tools to obtain a power series solutions to post-treat with the Padé approximant. 34L30.
Study on Crystallographic Orientation Effect on Surface Generation of Aluminum in Nano-cutting.
Xu, Feifei; Fang, Fengzhou; Zhu, Yuanqing; Zhang, Xiaodong
2017-12-01
The material characteristics such as size effect are one of the most important factors that could not be neglected in cutting the material at nanoscale. The effects of anisotropic nature of single crystal materials in nano-cutting are investigated employing the molecular dynamics simulation. Results show that the size effect of the plastic deformation is based on different plastic carriers, such as the twin, stacking faults, and dislocations. The minimum uncut chip thickness is dependent on cutting direction, where even a negative value is obtained when the cutting direction is {110}. It also determines the material deformation and removal mechanism (e.g., shearing, extruding, and rubbing mechanism) with a decrease in uncut chip thickness. When material is deformed by shearing, the primary shearing zone expands from the stagnation point or the tip of stagnation zone. When a material is deformed by extruding and rubbing, the primary deformation zone almost parallels to the cutting direction and expands from the bottom of the cutting edge merging with the tertiary deformation zone. The generated surface quality relates to the crystallographic orientation and the minimum uncut chip thickness. The cutting directions of {110}, {110}, and {111}, whose minimum uncut chip thickness is relatively small, have better surface qualities compared to the other cutting direction.
Approximation properties of haplotype tagging
Directory of Open Access Journals (Sweden)
Dreiseitl Stephan
2006-01-01
Full Text Available Abstract Background Single nucleotide polymorphisms (SNPs are locations at which the genomic sequences of population members differ. Since these differences are known to follow patterns, disease association studies are facilitated by identifying SNPs that allow the unique identification of such patterns. This process, known as haplotype tagging, is formulated as a combinatorial optimization problem and analyzed in terms of complexity and approximation properties. Results It is shown that the tagging problem is NP-hard but approximable within 1 + ln((n2 - n/2 for n haplotypes but not approximable within (1 - ε ln(n/2 for any ε > 0 unless NP ⊂ DTIME(nlog log n. A simple, very easily implementable algorithm that exhibits the above upper bound on solution quality is presented. This algorithm has running time O((2m - p + 1 ≤ O(m(n2 - n/2 where p ≤ min(n, m for n haplotypes of size m. As we show that the approximation bound is asymptotically tight, the algorithm presented is optimal with respect to this asymptotic bound. Conclusion The haplotype tagging problem is hard, but approachable with a fast, practical, and surprisingly simple algorithm that cannot be significantly improved upon on a single processor machine. Hence, significant improvement in computatational efforts expended can only be expected if the computational effort is distributed and done in parallel.
International Nuclear Information System (INIS)
Sahoa, F.E.
2015-01-01
Heavy metal contamination of artificial lakes water has been investigated in the Tranomaro mining sites combining crystallographic and analytical chemistry approaches. On one hand, X-ray diffraction analysis of the samples has shown the presence of thorianite (ThO 2 ) in a simple cubic crystalline system whereas uranium oxides are present in multiphase systems as α-uraninite, β-uraninite and τ-uraninite.Heavy metals concentrations were determined by using ICP-MS technique in mineral and water samples. Results show high level of heavy metals in minerals otherwise low level far beyond the guideline values recommended by international organizations in water samples. This fact can be explained by the adsorption and the coprecipitation phenomena that may take place due to the presence of complexes such as sulfates and carbonates.The accumulation of ETM in minerals in excessive levels represents a potential risk to the aquatic ecosystem by leaching of these elements at the slightest change in the physicochemical conditions of the environment. [fr
Energy Technology Data Exchange (ETDEWEB)
Murayama, Chisato; Okabe, Momoko; Fukuda, Koichiro [Department of Materials Science and Engineering, Nagoya Institute of Technology, Gokiso-cho, Showa-ku Nagoya 466-8555 (Japan); Urushihara, Daisuke; Asaka, Toru, E-mail: asaka.toru@nitech.ac.jp [Department of Materials Science and Engineering, Nagoya Institute of Technology, Gokiso-cho, Showa-ku Nagoya 466-8555 (Japan); Frontier Research Institute for Materials Science, Nagoya Institute of Technology, Gokiso-cho, Showa-ku Nagoya 466-8555 (Japan); Isobe, Masahiko [Max Planck Institute for Solid State Research, Heisenbergstrasse 1, D-70569 Stuttgart (Germany); Yamamoto, Kazuo [Nanostructures Research Laboratory, Japan Fine Ceramics Center, Nagoya 456-8587 (Japan); Matsushita, Yoshitaka [Research Network and Facility Services Division, National Institute for Materials Science, 1-2-1 Sengen, Tsukuba 305-0047 (Japan)
2016-10-14
We investigated the crystallographic structure of FePS{sub 3} with a layered structure using transmission electron microscopy and powder X-ray diffraction. We found that FePS{sub 3} forms a rotational twin structure with the common axis along the c*-axis. The high-resolution transmission electron microscopy images revealed that the twin boundaries were positioned at the van der Waals gaps between the layers. The narrow bands of dark contrast were observed in the bright-field transmission electron microscopy images below the antiferromagnetic transition temperature, T{sub N} ≈ 120 K. Low-temperature X-ray diffraction showed a lattice distortion; the a- and b-axes shortened and lengthened, respectively, as the temperature decreased below T{sub N.} We propose that the narrow bands of dark contrast observed in the bright-field transmission electron microscopy images are caused by the directional lattice distortion with respect to each micro-twin variant in the antiferromagnetic phase.
DEFF Research Database (Denmark)
Kuznetsova, Nadezda; Kulkova, Irina; Semenova, Elizaveta
2014-01-01
Selective area etching and growth in the metalorganic vapor phase epitaxy (MOVPE) reactor on nano-scale structures have been examined. Using different mask orientations, crystallographic dependent etching of InP can be observed when carbon tetrabromide (CBr4) is used as an etchant. Scanning...
Analytical Approximation of Spectrum for Pulse X-ray Tubes
International Nuclear Information System (INIS)
Vavilov, S; Fofanof, O; Koshkin, G; Udod, V
2016-01-01
Among the main characteristics of the pulsed X-ray apparatuses the spectral energy characteristics are the most important ones: the spectral distribution of the photon energy, effective and maximum energy of quanta. Knowing the spectral characteristics of the radiation of pulse sources is very important for the practical use of them in non-destructive testing. We have attempted on the analytical approximation of the pulsed X-ray apparatuses spectra obtained in the different experimental papers. The results of the analytical approximation of energy spectrum for pulse X-ray tube are presented. Obtained formulas are adequate to experimental data and can be used by designing pulsed X-ray apparatuses. (paper)
Group C∗-algebras without the completely bounded approximation property
DEFF Research Database (Denmark)
Haagerup, U.
2016-01-01
It is proved that: (1) The Fourier algebra A(G) of a simple Lie group G of real rank at least 2 with finite center does not have a multiplier bounded approximate unit. (2) The reduced C∗-algebra C∗ r of any lattice in a non-compact simple Lie group of real rank at least 2 with finite center does...... not have the completely bounded approximation property. Hence, the results obtained by de Canniere and the author for SOe (n, 1), n ≥ 2, and by Cowling for SU(n, 1) do not generalize to simple Lie groups of real rank at least 2. © 2016 Heldermann Verlag....
Standard filter approximations for low power Continuous Wavelet Transforms.
Casson, Alexander J; Rodriguez-Villegas, Esther
2010-01-01
Analogue domain implementations of the Continuous Wavelet Transform (CWT) have proved popular in recent years as they can be implemented at very low power consumption levels. This is essential for use in wearable, long term physiological monitoring systems. Present analogue CWT implementations rely on taking mathematical a approximation of the wanted mother wavelet function to give a filter transfer function that is suitable for circuit implementation. This paper investigates the use of standard filter approximations (Butterworth, Chebyshev, Bessel) as an alternative wavelet approximation technique. This extends the number of approximation techniques available for generating analogue CWT filters. An example ECG analysis shows that signal information can be successfully extracted using these CWT approximations.
International Nuclear Information System (INIS)
Ramesh, S.; Liew, Chiam-Wen; Morris, Ezra; Durairaj, R.
2010-01-01
In this paper, temperature dependence of ionic conductivity, crystallographic structural, morphological and thermal characteristics of polymer blends of PMMA and PVC with lithium bis(trifluoromethanesulfonyl) imide (LiTFSI) as a dopant salt are investigated. The study on the temperature dependence of ionic conductivity shows that these polymer blends exhibit Arrhenius behavior. The highest ionic conductivity was achieved when 70 wt% of PMMA was blended with 30 wt% of PVC. X-ray diffraction (XRD) and scanning electron microscopy (SEM) reveal the amorphous nature and surface morphology of polymer electrolytes, respectively. In DSC analysis it was found that the glass transition temperature (T g ) and melting temperature (T m ) decreased, whereas the decomposition temperature (T d ) increased. In contrast, the shift towards higher decomposition temperature and decrease in weight loss of polymer electrolytes, in TGA studies, indicates that the thermal stability of polymer electrolytes improved.
Pythagorean Approximations and Continued Fractions
Peralta, Javier
2008-01-01
In this article, we will show that the Pythagorean approximations of [the square root of] 2 coincide with those achieved in the 16th century by means of continued fractions. Assuming this fact and the known relation that connects the Fibonacci sequence with the golden section, we shall establish a procedure to obtain sequences of rational numbers…
The modified signed likelihood statistic and saddlepoint approximations
DEFF Research Database (Denmark)
Jensen, Jens Ledet
1992-01-01
SUMMARY: For a number of tests in exponential families we show that the use of a normal approximation to the modified signed likelihood ratio statistic r * is equivalent to the use of a saddlepoint approximation. This is also true in a large deviation region where the signed likelihood ratio...... statistic r is of order √ n. © 1992 Biometrika Trust....
Directory of Open Access Journals (Sweden)
V. A. Baturin
2017-03-01
Full Text Available An optimal control problem for discrete systems is considered. A method of successive improvements along with its modernization based on the expansion of the main structures of the core algorithm about the parameter is suggested. The idea of the method is based on local approximation of attainability set, which is described by the zeros of the Bellman function in the special problem of optimal control. The essence of the problem is as follows: from the end point of the phase is required to find a path that minimizes functional deviations of the norm from the initial state. If the initial point belongs to the attainability set of the original controlled system, the value of the Bellman function equal to zero, otherwise the value of the Bellman function is greater than zero. For this special task Bellman equation is considered. The support approximation and Bellman equation are selected. The Bellman function is approximated by quadratic terms. Along the allowable trajectory, this approximation gives nothing, because Bellman function and its expansion coefficients are zero. We used a special trick: an additional variable is introduced, which characterizes the degree of deviation of the system from the initial state, thus it is obtained expanded original chain. For the new variable initial nonzero conditions is selected, thus obtained trajectory is lying outside attainability set and relevant Bellman function is greater than zero, which allows it to hold a non-trivial approximation. As a result of these procedures algorithms of successive improvements is designed. Conditions for relaxation algorithms and conditions for the necessary conditions of optimality are also obtained.
Nonstandard approximation schemes for lower dimensional quantum field theories
International Nuclear Information System (INIS)
Fitzpatrick, D.A.
1981-01-01
The purpose of this thesis has been to apply two different nonstandard approximation schemes to a variety of lower-dimensional schemes. In doing this, we show their applicability where (e.g., Feynman or Rayleigh-Schroedinger) approximation schemes are inapplicable. We have applied the well-known mean-field approximation scheme by Guralnik et al. to general lower dimensional theories - the phi 4 field theory in one dimension, and the massive and massless Thirring models in two dimensions. In each case, we derive a bound-state propagator and then expand the theory in terms of the original and bound-state propagators. The results obtained can be compared with previously known results thereby show, in general, reasonably good convergence. In the second half of the thesis, we develop a self-consistent quantum mechanical approximation scheme. This can be applied to any monotonic polynomial potential. It has been applied in detail to the anharmonic oscillator, and the results in several analytical domains are very good, including extensive tables of numerical results
Nanocrystalline materials: recent advances in crystallographic characterization techniques
Directory of Open Access Journals (Sweden)
Emilie Ringe
2014-11-01
Full Text Available Most properties of nanocrystalline materials are shape-dependent, providing their exquisite tunability in optical, mechanical, electronic and catalytic properties. An example of the former is localized surface plasmon resonance (LSPR, the coherent oscillation of conduction electrons in metals that can be excited by the electric field of light; this resonance frequency is highly dependent on both the size and shape of a nanocrystal. An example of the latter is the marked difference in catalytic activity observed for different Pd nanoparticles. Such examples highlight the importance of particle shape in nanocrystalline materials and their practical applications. However, one may ask `how are nanoshapes created?', `how does the shape relate to the atomic packing and crystallography of the material?', `how can we control and characterize the external shape and crystal structure of such small nanocrystals?'. This feature article aims to give the reader an overview of important techniques, concepts and recent advances related to these questions. Nucleation, growth and how seed crystallography influences the final synthesis product are discussed, followed by shape prediction models based on seed crystallography and thermodynamic or kinetic parameters. The crystallographic implications of epitaxy and orientation in multilayered, core-shell nanoparticles are overviewed, and, finally, the development and implications of novel, spatially resolved analysis tools are discussed.
Non-linear unidimensional Debye screening in plasmas
International Nuclear Information System (INIS)
Clemente, R.A.; Martin, P.
1992-01-01
An exact analytical solution for T e = T i and an approximate solution for T e ≠ T i have been obtained for the unidimensional non-linear Debye potential. The approximate expression is a solution of the Poisson equation obtained by expanding up to third order the Boltzmann's factors. The analysis shows that the effective Debye screening length can be quite different from the usual Debye length, when the potential to thermal energy ratio of the particles is not much smaller than unity. (author)
International Nuclear Information System (INIS)
Liu, Xiuhua; Wang, Zhi; Zhu, Deyu; Wei, Tiandi; Gu, Lichuan; Xu, Sujuan
2011-01-01
This article reports the molecular cloning, protein expression and purification, crystallization and preliminary X-ray crystallographic analysis of the vibriobactin synthetase VibE from V. cholerae. Vibriobactin synthetases (VibABCDEFH) catalyze the biosynthesis of vibriobactin in the pathogenic bacterium Vibrio cholerae. VibE, a vibriobactin-specific 2,3-dihydroxybenzoate-AMP ligase, plays a critical role in the transfer of 2,3-dihydroxybenzoate to the aryl carrier protein domain of holo VibB. Here, the cloning, protein expression and purification, crystallization and preliminary X-ray crystallographic analysis of VibE from V. cholerae are reported. The VibE crystal diffracted to 2.3 Å resolution. The crystal belonged to space group P2 1 , with unit-cell parameters a = 56.471, b = 45.927, c = 77.014 Å, β = 95.895°. There is one protein molecule in the asymmetric unit, with a corresponding Matthews coefficient of 1.63 Å 3 Da −1 and solvent content of 24.41%
Approximate estimation of system reliability via fault trees
International Nuclear Information System (INIS)
Dutuit, Y.; Rauzy, A.
2005-01-01
In this article, we show how fault tree analysis, carried out by means of binary decision diagrams (BDD), is able to approximate reliability of systems made of independent repairable components with a good accuracy and a good efficiency. We consider four algorithms: the Murchland lower bound, the Barlow-Proschan lower bound, the Vesely full approximation and the Vesely asymptotic approximation. For each of these algorithms, we consider an implementation based on the classical minimal cut sets/rare events approach and another one relying on the BDD technology. We present numerical results obtained with both approaches on various examples
Crystallographic and magnetic properties of (C6D11ND3)CuBr3 and (Zn1-xMnx)3As2
International Nuclear Information System (INIS)
Vries, G.C. de.
1989-08-01
The investigations described concern the crystallographic and magnetic properties of the quasi one-dimensional (1d) ferromagnetic system (C 6 D 11 ND 3 )CuBr 3 (or CHAB) and the II-V type diluted magnetic semiconductor (Zn 1 - x Mn x ) 3 As 2 (or ZMA). Both compounds have been studied with various neutron scattering techniques. The crystallographic properties of CHAB and ZMA have been investigated by neutron diffraction. These diffraction experiments were carried out at the High Flux Reactor (HFR) at Petten, Netherlands. For the investigation of the static and dynamic magnetic properties of CHAB neutron scattering experiments were performed in Petten as well as other European reactor institutes. These investigations comprise a study of the 3d long-rate order and the 1d correlations of the magnetic moments, and a study of the behaviour of the linear spin-wave excitations
Geometric approximation algorithms
Har-Peled, Sariel
2011-01-01
Exact algorithms for dealing with geometric objects are complicated, hard to implement in practice, and slow. Over the last 20 years a theory of geometric approximation algorithms has emerged. These algorithms tend to be simple, fast, and more robust than their exact counterparts. This book is the first to cover geometric approximation algorithms in detail. In addition, more traditional computational geometry techniques that are widely used in developing such algorithms, like sampling, linear programming, etc., are also surveyed. Other topics covered include approximate nearest-neighbor search, shape approximation, coresets, dimension reduction, and embeddings. The topics covered are relatively independent and are supplemented by exercises. Close to 200 color figures are included in the text to illustrate proofs and ideas.
Non-Linear Transaction Costs Inclusion in Mean-Variance Optimization
Directory of Open Access Journals (Sweden)
Christian Johannes Zimmer
2005-12-01
Full Text Available In this article we propose a new way to include transaction costs into a mean-variance portfolio optimization. We consider brokerage fees, bid/ask spread and the market impact of the trade. A pragmatic algorithm is proposed, which approximates the optimal portfolio, and we can show that is converges in the absence of restrictions. Using Brazilian financial market data we compare our approximation algorithm with the results of a non-linear optimizer.
Discovery of functional and approximate functional dependencies in relational databases
Directory of Open Access Journals (Sweden)
Ronald S. King
2003-01-01
Full Text Available This study develops the foundation for a simple, yet efficient method for uncovering functional and approximate functional dependencies in relational databases. The technique is based upon the mathematical theory of partitions defined over a relation's row identifiers. Using a levelwise algorithm the minimal non-trivial functional dependencies can be found using computations conducted on integers. Therefore, the required operations on partitions are both simple and fast. Additionally, the row identifiers provide the added advantage of nominally identifying the exceptions to approximate functional dependencies, which can be used effectively in practical data mining applications.
Approximation methods for efficient learning of Bayesian networks
Riggelsen, C
2008-01-01
This publication offers and investigates efficient Monte Carlo simulation methods in order to realize a Bayesian approach to approximate learning of Bayesian networks from both complete and incomplete data. For large amounts of incomplete data when Monte Carlo methods are inefficient, approximations are implemented, such that learning remains feasible, albeit non-Bayesian. The topics discussed are: basic concepts about probabilities, graph theory and conditional independence; Bayesian network learning from data; Monte Carlo simulation techniques; and, the concept of incomplete data. In order to provide a coherent treatment of matters, thereby helping the reader to gain a thorough understanding of the whole concept of learning Bayesian networks from (in)complete data, this publication combines in a clarifying way all the issues presented in the papers with previously unpublished work.
Impact of side-effects of atypical antipsychotics on non-compliance, relapse and cost.
Mortimer, A; Williams, P; Meddis, D
2003-01-01
Atypical antipsychotics generally have milder side-effects than conventional antipsychotics, but also differ among themselves in this respect. This study aimed to compare the impact of different side-effect profiles of individual atypical antipsychotics on non-compliance, relapse and cost in schizophrenia. A state-transition model was built using literature data supplemented by expert opinion. The model found that quetiapine and ziprasidone were similar in estimated non-compliance and relapse rates. Olanzapine and risperidone had higher estimated non-compliance and relapse rates, and incremental, 1-year, per-patient direct costs, using US-based cost data, of approximately $530 (95% confidence interval [CI] approximately $275, $800), and approximately $485 (95% CI approximately $235, $800), respectively, compared with quetiapine. Incremental costs attributable to different side-effect profiles were highly significant. This study shows that differing side-effect profiles of the newer antipsychotic agents are likely to lead to different compliance rates, and consequent variation in relapse rates. The cost implications of these heterogenous clinical outcomes are substantial.
Energy Technology Data Exchange (ETDEWEB)
Galego, E., E-mail: egalego@ipen.br; Serna, M.M.; Ramanathan, L.V.; Faria, R.N.
2017-02-15
Anomalous x-ray synchrotron diffraction was used to determine the crystallographic parameters of PrFeCoB-based magnetic alloys. The effect of cobalt concentration on the crystallographic parameters of the magnetically hard Pr{sub 2}Fe{sub 14−x}Co{sub x}B phase was studied. The results indicate that addition of cobalt has a marked effect on crystal structure. Variation of the c parameter decreased twice as much as the a parameter with increase in Co content. The positions of inequivalent atoms of the magnetically hard matrix phase ϕ in the Pr-based alloys were determined using Rietveld refinement. This permitted determination of the relative distance of each inequivalent atom from its nearest neighbors. Cobalt occupied the 16k{sub 2} site and Fe had a tendency to occupy the 8j{sub 2} sites located between the Kagomé layers. - Highlights: • Good magnetics properties can be achieved with addition of 4% and 8% Co. • Rietveld refinement is proposed for crystallographic parameters studies. • Co has preference to substitute Fe in 16k{sub 2} site and avoid the 8j{sub 2} site.
Finite approximations in fluid mechanics
International Nuclear Information System (INIS)
Hirschel, E.H.
1986-01-01
This book contains twenty papers on work which was conducted between 1983 and 1985 in the Priority Research Program ''Finite Approximations in Fluid Mechanics'' of the German Research Society (Deutsche Forschungsgemeinschaft). Scientists from numerical mathematics, fluid mechanics, and aerodynamics present their research on boundary-element methods, factorization methods, higher-order panel methods, multigrid methods for elliptical and parabolic problems, two-step schemes for the Euler equations, etc. Applications are made to channel flows, gas dynamical problems, large eddy simulation of turbulence, non-Newtonian flow, turbomachine flow, zonal solutions for viscous flow problems, etc. The contents include: multigrid methods for problems from fluid dynamics, development of a 2D-Transonic Potential Flow Solver; a boundary element spectral method for nonstationary viscous flows in 3 dimensions; navier-stokes computations of two-dimensional laminar flows in a channel with a backward facing step; calculations and experimental investigations of the laminar unsteady flow in a pipe expansion; calculation of the flow-field caused by shock wave and deflagration interaction; a multi-level discretization and solution method for potential flow problems in three dimensions; solutions of the conservation equations with the approximate factorization method; inviscid and viscous flow through rotating meridional contours; zonal solutions for viscous flow problems
Problems with the quenched approximation in the chiral limit
International Nuclear Information System (INIS)
Sharpe, S.R.
1992-01-01
In the quenched approximation, loops of the light singlet meson (the η') give rise to a type of chiral logarithm absent in full QCD. These logarithms are singular in the chiral limit, throwing doubt upon the utility of the quenched approximation. In previous work, I summed a class of diagrams, leading to non-analytic power dependencies such as left-angle anti ψψ right-angle ∝ m q -δ /(1+δ) I suggested, however, that these peculiar results could be redefined away. Here I give an alternative derivation of the results, based on the renormalization group, and argue that they cannot be redefined away. I discuss the evidence (or lack thereof) for such effects in numerical data
Large hierarchies from approximate R symmetries
International Nuclear Information System (INIS)
Kappl, Rolf; Ratz, Michael; Vaudrevange, Patrick K.S.
2008-12-01
We show that hierarchically small vacuum expectation values of the superpotential in supersymmetric theories can be a consequence of an approximate R symmetry. We briefly discuss the role of such small constants in moduli stabilization and understanding the huge hierarchy between the Planck and electroweak scales. (orig.)
Variational Multi-Scale method with spectral approximation of the sub-scales.
Dia, Ben Mansour; Chá con-Rebollo, Tomas
2015-01-01
A variational multi-scale method where the sub-grid scales are computed by spectral approximations is presented. It is based upon an extension of the spectral theorem to non necessarily self-adjoint elliptic operators that have an associated base
A surprise in the first Born approximation for electron scattering
International Nuclear Information System (INIS)
Treacy, M.M.J.; Van Dyck, D.
2012-01-01
A standard textbook derivation for the scattering of electrons by a weak potential under the first Born approximation suggests that the far-field scattered wave should be in phase with the incident wave. However, it is well known that waves scattered from a weak phase object should be phase-shifted by π/2 relative to the incident wave. A disturbing consequence of this missing phase is that, according to the Optical Theorem, the total scattering cross section would be zero in the first Born approximation. We resolve this mystery pedagogically by showing that the first Born approximation fails to conserve electrons even to first order. Modifying the derivation to conserve electrons introduces the correct phase without changing the scattering amplitude. We also show that the far-field expansion for the scattered waves used in many texts is inappropriate for computing an exit wave from a sample, and that the near-field expansion also give the appropriately phase-shifted result. -- Highlights: ► The first Born approximation is usually invoked as the theoretical physical basis for kinematical electron scattering theory. ► Although it predicts the correct scattering amplitude, it predicts the wrong phase; the scattered wave is missing a prefactor of i. ► We show that this arises because the standard textbook version of the first Born approximation does not conserve electrons. ► We show how this can be fixed.
Function approximation using combined unsupervised and supervised learning.
Andras, Peter
2014-03-01
Function approximation is one of the core tasks that are solved using neural networks in the context of many engineering problems. However, good approximation results need good sampling of the data space, which usually requires exponentially increasing volume of data as the dimensionality of the data increases. At the same time, often the high-dimensional data is arranged around a much lower dimensional manifold. Here we propose the breaking of the function approximation task for high-dimensional data into two steps: (1) the mapping of the high-dimensional data onto a lower dimensional space corresponding to the manifold on which the data resides and (2) the approximation of the function using the mapped lower dimensional data. We use over-complete self-organizing maps (SOMs) for the mapping through unsupervised learning, and single hidden layer neural networks for the function approximation through supervised learning. We also extend the two-step procedure by considering support vector machines and Bayesian SOMs for the determination of the best parameters for the nonlinear neurons in the hidden layer of the neural networks used for the function approximation. We compare the approximation performance of the proposed neural networks using a set of functions and show that indeed the neural networks using combined unsupervised and supervised learning outperform in most cases the neural networks that learn the function approximation using the original high-dimensional data.
Kanel, G. I.; Nellis, W. J.; Savinykh, A. S.; Razorenov, S. V.; Rajendran, A. M.
2009-01-01
Shock-wave profiles of sapphire (single-crystal Al2O3) with seven crystallographic orientations were measured with time-resolved VISAR interferometry at shock stresses in the range 16 to 86 GPa. Shock propagation was normal to the surface of each cut. The angle between the c-axis of the hexagonal crystal structure and the direction of shock propagation varied from 0 for c-cut up to 90 degrees for m-cut in the basal plane. Based on published shock-induced transparencies, shock-induced optical ...
Redetermination of 3,5-dimethylphenol
Directory of Open Access Journals (Sweden)
Richard Betz
2011-05-01
Full Text Available The previous structure determination [Gillier-Pandraud et al. (1972. C. R. Acad. Sci. Ser. C, 275, 1495] of the title compound, C8H10O, did not report atomic coordinates. There are two molecules in the asymmetric unit, A and B, which both show approximate non-crystallographic Cs symmetry. The intracyclic C—C—C angles cover the range 118.74 (12–121.76 (13°. In the crystal, molecules are linked by O—H...O hydrogen bonds, generating [001] C22(4 chains such that molecules A and B alternate. There is no aromatic π–π stacking in the crystal as the shortest centroid–centroid distance is greater than 4.74 Å.
A monoclinic polymorph of (1E,5E)-1,5-bis(2-hydroxybenzylidene)thiocarbonohydrazide
Schmitt, Bonell; Gerber, Thomas; Hosten, Eric; Betz, Richard
2011-01-01
The title compound, C15H14N4O2S, is a derivative of thioureadihydrazide. In contrast to the previously reported polymorph (orthorhombic, space group Pbca, Z = 8), the current study revealed monoclinic symmetry (space group P21/n, Z = 4). The molecule shows non-crystallographic C 2 as well as approximate C s symmetry. Intramolecular bifurcated O—H⋯(N,S) hydrogen bonds, are present. In the crystal, intermolecular N—H⋯S hydrogen bonds and C—H⋯π contacts connect the molecules into undulating chains along the b axis. The shortest centroid–centroid distance between two aromatic systems is 4.5285 (12) Å. PMID:22091213
Sparse approximation with bases
2015-01-01
This book systematically presents recent fundamental results on greedy approximation with respect to bases. Motivated by numerous applications, the last decade has seen great successes in studying nonlinear sparse approximation. Recent findings have established that greedy-type algorithms are suitable methods of nonlinear approximation in both sparse approximation with respect to bases and sparse approximation with respect to redundant systems. These insights, combined with some previous fundamental results, form the basis for constructing the theory of greedy approximation. Taking into account the theoretical and practical demand for this kind of theory, the book systematically elaborates a theoretical framework for greedy approximation and its applications. The book addresses the needs of researchers working in numerical mathematics, harmonic analysis, and functional analysis. It quickly takes the reader from classical results to the latest frontier, but is written at the level of a graduate course and do...
Neutron crystallographic studies of amino acids and nucleic acids
International Nuclear Information System (INIS)
Kashiwagi, Tatsuki
2014-01-01
Neutron crystallographic studies of two representative umami materials were executed utilizing iBLX at MLF/J-PARC. The results of them will be summarized in this report. At first, structure analysis of the alpha form crystal of L-glutamic acid was performed in order to assess the usefulness of neutron crystallography at iBIX to our company's R and D. Neutron crystal structure of it was successfully determined at 0.6 A resolution. All hydrogen atoms were clearly observed. Next, the mixed crystal of disodium Inosine-5'-phosphate (IMP · 2Na) and disodium Guanosine-5'-phosphate (GMP · 2Na) was analyzed by neutron crystallography. Neutron crystal structure of the mixed crystal of IMP and GMP (IM/GMP rate = 1.7) was successfully determined at 0.8 A resolution. In the neutron crystal structure of the mixed crystal, the hydrogen atom bonded to the C2 atom of purine base in IMP and the nitrogen atom bonded to the C2 atom of purine base in GMP were clearly observed in the nuclear density map, structurally demonstrating that this crystal is the mixed crystal. (author)
International Nuclear Information System (INIS)
Nkemzi, B.
2005-10-01
Three-dimensional time-harmonic Maxwell's problems in axisymmetric domains Ω-circumflex with edges and conical points on the boundary are treated by means of the Fourier-finite-element method. The Fourier-fem combines the approximating Fourier series expansion of the solution with respect to the rotational angle using trigonometric polynomials of degree N (N → ∞), with the finite element approximation of the Fourier coefficients on the plane meridian domain Ω a is a subset of R + 2 of Ω-circumflex with mesh size h (h → 0). The singular behaviors of the Fourier coefficients near angular points of the domain Ω a are fully described by suitable singular functions and treated numerically by means of the singular function method with the finite element method on graded meshes. It is proved that the rate of convergence of the mixed approximations in H 1 (Ω-circumflex) 3 is of the order O (h+N -1 ) as known for the classical Fourier-finite-element approximation of problems with regular solutions. (author)
Individual differences in non-verbal number acuity correlate with maths achievement.
Halberda, Justin; Mazzocco, Michèle M M; Feigenson, Lisa
2008-10-02
Human mathematical competence emerges from two representational systems. Competence in some domains of mathematics, such as calculus, relies on symbolic representations that are unique to humans who have undergone explicit teaching. More basic numerical intuitions are supported by an evolutionarily ancient approximate number system that is shared by adults, infants and non-human animals-these groups can all represent the approximate number of items in visual or auditory arrays without verbally counting, and use this capacity to guide everyday behaviour such as foraging. Despite the widespread nature of the approximate number system both across species and across development, it is not known whether some individuals have a more precise non-verbal 'number sense' than others. Furthermore, the extent to which this system interfaces with the formal, symbolic maths abilities that humans acquire by explicit instruction remains unknown. Here we show that there are large individual differences in the non-verbal approximation abilities of 14-year-old children, and that these individual differences in the present correlate with children's past scores on standardized maths achievement tests, extending all the way back to kindergarten. Moreover, this correlation remains significant when controlling for individual differences in other cognitive and performance factors. Our results show that individual differences in achievement in school mathematics are related to individual differences in the acuity of an evolutionarily ancient, unlearned approximate number sense. Further research will determine whether early differences in number sense acuity affect later maths learning, whether maths education enhances number sense acuity, and the extent to which tertiary factors can affect both.
Designing quantum information processing via structural physical approximation.
Bae, Joonwoo
2017-10-01
In quantum information processing it may be possible to have efficient computation and secure communication beyond the limitations of classical systems. In a fundamental point of view, however, evolution of quantum systems by the laws of quantum mechanics is more restrictive than classical systems, identified to a specific form of dynamics, that is, unitary transformations and, consequently, positive and completely positive maps to subsystems. This also characterizes classes of disallowed transformations on quantum systems, among which positive but not completely maps are of particular interest as they characterize entangled states, a general resource in quantum information processing. Structural physical approximation offers a systematic way of approximating those non-physical maps, positive but not completely positive maps, with quantum channels. Since it has been proposed as a method of detecting entangled states, it has stimulated fundamental problems on classifications of positive maps and the structure of Hermitian operators and quantum states, as well as on quantum measurement such as quantum design in quantum information theory. It has developed efficient and feasible methods of directly detecting entangled states in practice, for which proof-of-principle experimental demonstrations have also been performed with photonic qubit states. Here, we present a comprehensive review on quantum information processing with structural physical approximations and the related progress. The review mainly focuses on properties of structural physical approximations and their applications toward practical information applications.
The Padé approximant in theoretical physics
Baker, George Allen
1970-01-01
In this book, we study theoretical and practical aspects of computing methods for mathematical modelling of nonlinear systems. A number of computing techniques are considered, such as methods of operator approximation with any given accuracy; operator interpolation techniques including a non-Lagrange interpolation; methods of system representation subject to constraints associated with concepts of causality, memory and stationarity; methods of system representation with an accuracy that is the best within a given class of models; methods of covariance matrix estimation;methods for low-rank mat
Improving the Weizsäcker-Williams approximation in electron-proton collisions
Frixione, Stefano; Nason, P; Ridolfi, G
1993-01-01
We critically examine the validity of the Weizs\\"acker-Williams approximation in electron-hadron collisions. We show that in its commonly used form it can lead to large errors, and we show how to improve it in order to get accurate results. In particular, we present an improved form that is valid beyond the leading logarithmic approximation in the case when a small-angle cut is applied to the scattered electron. Furthermore we include comparisons of the approximate expressions with the exact electroproduction calculation in the case of heavy-quark production.
Variational Gaussian approximation for Poisson data
Arridge, Simon R.; Ito, Kazufumi; Jin, Bangti; Zhang, Chen
2018-02-01
The Poisson model is frequently employed to describe count data, but in a Bayesian context it leads to an analytically intractable posterior probability distribution. In this work, we analyze a variational Gaussian approximation to the posterior distribution arising from the Poisson model with a Gaussian prior. This is achieved by seeking an optimal Gaussian distribution minimizing the Kullback-Leibler divergence from the posterior distribution to the approximation, or equivalently maximizing the lower bound for the model evidence. We derive an explicit expression for the lower bound, and show the existence and uniqueness of the optimal Gaussian approximation. The lower bound functional can be viewed as a variant of classical Tikhonov regularization that penalizes also the covariance. Then we develop an efficient alternating direction maximization algorithm for solving the optimization problem, and analyze its convergence. We discuss strategies for reducing the computational complexity via low rank structure of the forward operator and the sparsity of the covariance. Further, as an application of the lower bound, we discuss hierarchical Bayesian modeling for selecting the hyperparameter in the prior distribution, and propose a monotonically convergent algorithm for determining the hyperparameter. We present extensive numerical experiments to illustrate the Gaussian approximation and the algorithms.
Energy Technology Data Exchange (ETDEWEB)
Ramesh, S., E-mail: rameshtsubra@gmail.com [Centre for Ionics University Malaya, Department of Physics, Faculty of Science, University of Malaya, Lembah Pantai, 50603 Kuala Lumpur (Malaysia); Liew, Chiam-Wen; Morris, Ezra; Durairaj, R. [Faculty of Engineering and Science, Universiti Tunku Abdul Rahman, Setapak, 53300 Kuala Lumpur (Malaysia)
2010-11-20
In this paper, temperature dependence of ionic conductivity, crystallographic structural, morphological and thermal characteristics of polymer blends of PMMA and PVC with lithium bis(trifluoromethanesulfonyl) imide (LiTFSI) as a dopant salt are investigated. The study on the temperature dependence of ionic conductivity shows that these polymer blends exhibit Arrhenius behavior. The highest ionic conductivity was achieved when 70 wt% of PMMA was blended with 30 wt% of PVC. X-ray diffraction (XRD) and scanning electron microscopy (SEM) reveal the amorphous nature and surface morphology of polymer electrolytes, respectively. In DSC analysis it was found that the glass transition temperature (T{sub g}) and melting temperature (T{sub m}) decreased, whereas the decomposition temperature (T{sub d}) increased. In contrast, the shift towards higher decomposition temperature and decrease in weight loss of polymer electrolytes, in TGA studies, indicates that the thermal stability of polymer electrolytes improved.
Energy Technology Data Exchange (ETDEWEB)
Silva, Davi J.M.; Nunes, Carlos E.A.; Alves Filho, Hermes; Barros, Ricardo C., E-mail: davijmsilva@yahoo.com.br, E-mail: ceanunes@yahoo.com.br, E-mail: rcbarros@pq.cnpq.br [Secretaria Municipal de Educacao de Itaborai, RJ (Brazil); Universidade Estacio de Sa (UNESA), Rio de Janeiro, RJ (Brazil); Universidade do Estado do Rio de Janeiro (UERJ), Novra Friburgo, RJ (Brazil). Instituto Politecnico. Departamento de Modelagem Computacional
2017-11-01
Discussed here is the accuracy of approximate albedo boundary conditions for energy multigroup discrete ordinates (S{sub N}) eigenvalue problems in two-dimensional rectangular geometry for criticality calculations in neutron fission reacting systems, such as nuclear reactors. The multigroup (S{sub N}) albedo matrix substitutes approximately the non-multiplying media around the core, e.g., baffle and reflector, as we neglect the transverse leakage terms within these non-multiplying regions. Numerical results to a typical model problem are given to illustrate the accuracy versus the computer running time. (author)
Crystallographic information of intermediate phases in binary Mg–X (X=Sn, Y, Sc, Ag alloys
Directory of Open Access Journals (Sweden)
Dongyan Liu
2015-09-01
Full Text Available The compositions and structures of thermodynamically stable or metastable precipitations in binary Mg-X (X=Sn, Y, Sc, Ag alloys are predicted using ab-initio evolutionary algorithm. The geometry optimizations of the predicted intermetallic compounds are carried out in the framework of density functional theory (DFT [1]. A complete list of the optimized crystallographic information (in cif format of the predicted intermetallic phases is presented here. The data is related to “Predictions on the compositions, structures, and mechanical properties of intermediate phases in binary Mg–X (X=Sn, Y, Sc, Ag alloys” by Liu et al. [2].
Amano, Yasushi; Tanabe, Eiki; Yamaguchi, Tomohiko
2015-05-15
Soluble epoxide hydrolase (sEH) is a potential target for the treatment of inflammation and hypertension. X-ray crystallographic fragment screening was used to identify fragment hits and their binding modes. Eight fragment hits were identified via soaking of sEH crystals with fragment cocktails, and the co-crystal structures of these hits were determined via individual soaking. Based on the binding mode, N-ethylmethylamine was identified as a promising scaffold that forms hydrogen bonds with the catalytic residues of sEH, Asp335, Tyr383, and Tyr466. Compounds containing this scaffold were selected from an in-house chemical library and assayed. Although the starting fragment had a weak inhibitory activity (IC50: 800μM), we identified potent inhibitors including 2-({[2-(adamantan-1-yl)ethyl]amino}methyl)phenol exhibiting the highest inhibitory activity (IC50: 0.51μM). This corresponded to a more than 1500-fold increase in inhibitory activity compared to the starting fragment. Co-crystal structures of the hit compounds demonstrate that the binding of N-ethylmethylamine to catalytic residues is similar to that of the starting fragment. We therefore consider crystallographic fragment screening to be appropriate for the identification of weak but promising fragment hits. Copyright © 2015 Elsevier Ltd. All rights reserved.
International Nuclear Information System (INIS)
Gómez García, Inmaculada; Oyenarte, Iker; Martínez-Cruz, Luis Alfonso
2011-01-01
This work describes the purification and preliminary crystallographic analysis of the CBS-pair regulatory domain of the human ancient domain protein 4 (ACDP4), also known as CNNM4. This work describes the purification and preliminary crystallographic analysis of the CBS-pair regulatory domain of the human ancient domain protein 4 (ACDP4), also known as CNNM4. ACDP proteins represent the least-studied members of the eight different types of magnesium transporters that have been identified in mammals to date. In humans the ACDP family includes four members: CNNM1–4. CNNM1 acts as a cytosolic copper chaperone and has been associated with urofacial syndrome, whereas CNNM2 and CNNM4 have been identified as magnesium transporters. Interestingly, mutations in the CNNM4 gene have clinical consequences that are limited to retinal function and biomineralization and are considered to be the cause of Jalili syndrome, which consists of autosomal recessive cone-rod dystrophy and amelogenesis imperfecta. The truncated protein was overexpressed, purified and crystallized in the orthorhombic space group C222. The crystals diffracted X-rays to 3.6 Å resolution using synchrotron radiation. Matthews volume calculations suggested the presence of two molecules in the asymmetric unit, which were likely to correspond to a CBS module of the CBS pair of CNNM4
Al-Jabr, Haytham M.
The effects of microstructure and crystallographic texture in four commercially-produced API X70 pipeline steels and their relation to planar anisotropy of toughness and delamination were evaluated. The experimental steels were processed through either a hot strip mill, a Steckel mill, or a compact strip mill. Different processing routes were selected to obtain plates with potential variations in the microstructure and anisotropic characteristics. Tensile and Charpy impact testing were used to evaluate the mechanical properties in three orientations: longitudinal (L), transverse (T) and diagonal (D) with respect to the rolling direction to evaluate mechanical property anisotropy. The yield and tensile strengths were higher in the T orientation and toughness was lower in the D orientation for all plates. Delamination was observed in some of the ductile fracture surfaces of the impact samples. To further study the splitting behavior and effects on impact toughness, a modified impact test (MCVN) specimen with side grooves was designed to intensify induced stresses parallel to the notch root and thus facilitate evaluation of delamination. Scanning electron microscopy combined with electron backscattered diffraction (EBSD) were used to evaluate the grain size, microstructural constituents, and crystallographic texture to determine the factors leading to delamination and the anisotropy in toughness. The ferrite grain size is mainly responsible for the differences in DBTTs between the L and T orientations. The higher DBTT in the D orientation observed in pipeline steels is attributed to crystallographic texture. The higher DBTT in the D direction is due to the higher volume fraction of grains having their {100} planes parallel or close to the primary fracture plane for the D orientation. An equation based on a new "brittleness parameter," based on an assessment of grain orientations based on EBSD data, was developed to predict the changes in DBTTs with respect to sample
International Nuclear Information System (INIS)
Gong, Liping; Xiao, Yi; Liu, Qiang; Li, Sumei; Zhang, Changsheng; Liu, Jinsong
2010-01-01
The recombinant glycosyltransferase ElaGT from the elaiophylin-producing marine Streptomyces sp. SCSIO 01934 has been overexpressed in E. coli, purified and crystallized. Diffraction data were collected to 2.9 Å resolution. ElaGT is a glycosyltransferase from a marine Streptomyces species that is involved in the biosynthesis of elaiophylin. Here, the molecular cloning, protein expression and purification, preliminary crystallization and crystallographic characterization of ElaGT are reported. The rod-shaped crystals belonged to space group P2 1 22, with unit-cell parameters a = 66.7, b = 131.7, c = 224.6 Å, α = 90, β = 90, γ = 90°. Data were collected to 2.9 Å resolution. A preliminary molecular-replacement solution implied the presence of two ElaGT molecules in the asymmetric unit
Teabpinyok, Nopporn; Samingprai, Sutheerawat; Chareonpanich, Metta
2012-12-01
In this research, nickel metal of three different morphologies including nanostar, icosahedra, and microsphere structures were synthesized. It was found nanostar nickel revealed the Ni(111) crystallographic plane with particle size in the range of 150-200 nm and BET surface area of 13 m2/g. The icosahedra nickel also showed the Ni(111) crystallographic plane with larger particle size (300-400 nm) and BET surface area of 20 m2/g, whereas microsphere nickel exhibited the relatively large cluster size (approximately 3 microm) and BET surface area (114 m2/g) as a result of an aggregation of Ni(101) nanoplates. The obtained nickel catalysts were tested for the activity in carbon dioxide reforming with methane. Based on the similar specific surface area of catalysts, nanostar nickel showed the highest carbon dioxide and methane conversions due to its crystallographic structure. At 700 degrees C, nanostar nickel catalyst exhibited the highest carbon dioxide and methane conversions of 17.6 and 10.5 times higher than those of microsphere nickel catalyst, respectively.
Contribution to the crystallographic study of the uranium-oxygenated system
International Nuclear Information System (INIS)
Perio, P.
1955-04-01
Three uranium oxides, UO 2 , U 3 O 8 and UO 3 are known since a long time. The existence of a fourth, U 2 O 5 , is discussed. The mechanisms of decomposition between UO 3 and U 3 O 8 have even some shadow zones. The aim of this report is the study of the phase relations in an uranium - oxygen system, from the metal until UO 3 . We considered, on the one hand, the equilibrium relations, what should result in a diagram of phases in pressures and temperatures, on the other hand, the transformations bringing one oxide to the other, often by a continuous way and through intermediate of metastable phases. The introduction of the temperature and the consideration of the kinetics effects have permitted to raise the ambiguities. We adopted, to facilitate the presentation of the results, a partition a few arbitrary but convenient, in three chapters,: I - experimental Techniques II - Crystallographic species between U and UO 3 . III - Kinetic of oxidisation of UO 2 . (M.B.) [fr
The mathematical structure of the approximate linear response relation
International Nuclear Information System (INIS)
Yasuda, Muneki; Tanaka, Kazuyuki
2007-01-01
In this paper, we study the mathematical structures of the linear response relation based on Plefka's expansion and the cluster variation method in terms of the perturbation expansion, and we show how this linear response relation approximates the correlation functions of the specified system. Moreover, by comparing the perturbation expansions of the correlation functions estimated by the linear response relation based on these approximation methods with exact perturbative forms of the correlation functions, we are able to explain why the approximate techniques using the linear response relation work well
Upper bounds on minimum cardinality of exact and approximate reducts
Chikalov, Igor
2010-01-01
In the paper, we consider the notions of exact and approximate decision reducts for binary decision tables. We present upper bounds on minimum cardinality of exact and approximate reducts depending on the number of rows (objects) in the decision table. We show that the bound for exact reducts is unimprovable in the general case, and the bound for approximate reducts is almost unimprovable in the general case. © 2010 Springer-Verlag Berlin Heidelberg.
Research on the phenomenon of graphitization. Crystallographic study - Study of bromine sorption
International Nuclear Information System (INIS)
Maire, Jacques
1967-01-01
This research thesis reports the study of the mechanism of graphitization of carbon by using X-ray diffraction analysis and the physical and chemical study of lamellar reactions between carbon and bromine. The author first presents generalities and results of preliminary studies (meaning of graphitization, presentation of the various carbon groups and classes), and then reports the study of the graphitization of compact carbons (soft carbons). More precisely, he reports the crystallographic study of partially graphitized carbons: methods and principles, experimental results and their analysis, discussion of the graphitization mechanism. In the next part, the author reports the study of bromine sorption on carbons: experimental method, isotherms of a natural graphite and of a graphitized carbon, structure of carbon-bromine complexes, isotherms of graphitizable carbons and of all other carbons, distribution of bromine layers in partially graphitized carbons, bromine sorption and Fermi level
Initial crystallographic studies of a small heat-shock protein from Xylella fastidiosa
International Nuclear Information System (INIS)
Tada, Susely F. S.; Saraiva, Antonio Marcos; Lorite, Gabriela S.; Rosselli-Murai, Luciana K.; Pelloso, Alexandre César; Santos, Marcelo Leite dos; Trivella, Daniela B. B.; Cotta, Mônica A.; Souza, Anete Pereira de; Aparicio, Ricardo
2012-01-01
Initial crystallographic studies of the X. fastidiosa small heat-shock protein HSP17.9 are reported. The ORF XF2234 in the Xylella fastidiosa genome was identified as encoding a small heat-shock protein of 17.9 kDa (HSP17.9). HSP17.9 was found as one of the proteins that are induced during X. fastidiosa proliferation and infection in citrus culture. Recombinant HSP17.9 was crystallized and surface atomic force microscopy experiments were conducted with the aim of better characterizing the HSP17.9 crystals. X-ray diffraction data were collected at 2.7 Å resolution. The crystal belonged to space group P4 3 22, with unit-cell parameters a = 68.90, b = 68.90, c = 72.51 Å, and is the first small heat-shock protein to crystallize in this space group
On the approximation of the optically thin layer in plasma spectroscopy
International Nuclear Information System (INIS)
Preobrazhensky, N.G.
1975-01-01
Recent studies are described of criteria for the optically thin approximation relevant to more reliable interpretation of various plasma spectroscopic measurements. Non-equilibrium situations are in the focus of attention. Applicability of well-known criteria suggested by McWhirter and Hearn is outlined. (Auth.)
Evaluation of stochastic differential equation approximation of ion channel gating models.
Bruce, Ian C
2009-04-01
Fox and Lu derived an algorithm based on stochastic differential equations for approximating the kinetics of ion channel gating that is simpler and faster than "exact" algorithms for simulating Markov process models of channel gating. However, the approximation may not be sufficiently accurate to predict statistics of action potential generation in some cases. The objective of this study was to develop a framework for analyzing the inaccuracies and determining their origin. Simulations of a patch of membrane with voltage-gated sodium and potassium channels were performed using an exact algorithm for the kinetics of channel gating and the approximate algorithm of Fox & Lu. The Fox & Lu algorithm assumes that channel gating particle dynamics have a stochastic term that is uncorrelated, zero-mean Gaussian noise, whereas the results of this study demonstrate that in many cases the stochastic term in the Fox & Lu algorithm should be correlated and non-Gaussian noise with a non-zero mean. The results indicate that: (i) the source of the inaccuracy is that the Fox & Lu algorithm does not adequately describe the combined behavior of the multiple activation particles in each sodium and potassium channel, and (ii) the accuracy does not improve with increasing numbers of channels.
Energy Technology Data Exchange (ETDEWEB)
Pharr, M.; Katoh, Y.; Bei, H.
2006-01-01
Along with other desirable properties, the ability of silicon carbide (SiC) to retain high strength after elevated temperature exposures to neutron irradiation renders it potentially applicable in fusion and advanced fission reactors. However, properties of the material such as room temperature fracture toughness must be thoroughly characterized prior to such practical applications. The objective of this work is to investigate the dependence of fracture toughness on crystallographic orientation for single-crystalline β-SiC. X-ray diffraction was first performed on the samples to determine the orientation of the crystal. Nanoindentation was used to determine a hardness of 39.1 and 35.2 GPa and elastic modulus of 474 and 446 GPa for the single-crystalline and polycrystalline samples, respectively. Additionally, crack lengths and indentation diagonals were measured via a Vickers micro-hardness indenter under a load of 100 gf for different crystallographic orientations with indentation diagonals aligned along fundamental cleavage planes. Upon examination of propagation direction of cracks, the cracks usually did not initiate and propagate from the corners of the indentation where the stresses are concentrated but instead from the indentation sides. Such cracks clearly moved along the {1 1 0} family of planes (previously determined to be preferred cleavage plane), demonstrating that the fracture toughness of SiC is comparatively so much lower along this set of planes that the lower energy required to cleave along this plane overpowers the stress-concentration at indentation corners. Additionally, fracture toughness in the <1 1 0> direction was 1.84 MPa·m1/2, lower than the 3.46 MPa·m1/2 measured for polycrystalline SiC (which can serve as an average of a spectrum of orientations), further demonstrating that single-crystalline β-SiC has a strong fracture toughness anisotropy.
Compound Poisson Approximations for Sums of Random Variables
Serfozo, Richard F.
1986-01-01
We show that a sum of dependent random variables is approximately compound Poisson when the variables are rarely nonzero and, given they are nonzero, their conditional distributions are nearly identical. We give several upper bounds on the total-variation distance between the distribution of such a sum and a compound Poisson distribution. Included is an example for Markovian occurrences of a rare event. Our bounds are consistent with those that are known for Poisson approximations for sums of...
A Gaussian Approximation Potential for Silicon
Bernstein, Noam; Bartók, Albert; Kermode, James; Csányi, Gábor
We present an interatomic potential for silicon using the Gaussian Approximation Potential (GAP) approach, which uses the Gaussian process regression method to approximate the reference potential energy surface as a sum of atomic energies. Each atomic energy is approximated as a function of the local environment around the atom, which is described with the smooth overlap of atomic environments (SOAP) descriptor. The potential is fit to a database of energies, forces, and stresses calculated using density functional theory (DFT) on a wide range of configurations from zero and finite temperature simulations. These include crystalline phases, liquid, amorphous, and low coordination structures, and diamond-structure point defects, dislocations, surfaces, and cracks. We compare the results of the potential to DFT calculations, as well as to previously published models including Stillinger-Weber, Tersoff, modified embedded atom method (MEAM), and ReaxFF. We show that it is very accurate as compared to the DFT reference results for a wide range of properties, including low energy bulk phases, liquid structure, as well as point, line, and plane defects in the diamond structure.
Lin, Yezhi; Liu, Yinping; Li, Zhibin
2013-01-01
The Adomian decomposition method (ADM) is one of the most effective methods to construct analytic approximate solutions for nonlinear differential equations. In this paper, based on the new definition of the Adomian polynomials, Rach (2008) [22], the Adomian decomposition method and the Padé approximants technique, a new algorithm is proposed to construct analytic approximate solutions for nonlinear fractional differential equations with initial or boundary conditions. Furthermore, a MAPLE software package is developed to implement this new algorithm, which is user-friendly and efficient. One only needs to input the system equation, initial or boundary conditions and several necessary parameters, then our package will automatically deliver the analytic approximate solutions within a few seconds. Several different types of examples are given to illustrate the scope and demonstrate the validity of our package, especially for non-smooth initial value problems. Our package provides a helpful and easy-to-use tool in science and engineering simulations. Program summaryProgram title: ADMP Catalogue identifier: AENE_v1_0 Program summary URL:http://cpc.cs.qub.ac.uk/summaries/AENE_v1_0.html Program obtainable from: CPC Program Library, Queen's University, Belfast, N. Ireland Licensing provisions: Standard CPC licence, http://cpc.cs.qub.ac.uk/licence/licence.html No. of lines in distributed program, including test data, etc.: 12011 No. of bytes in distributed program, including test data, etc.: 575551 Distribution format: tar.gz Programming language: MAPLE R15. Computer: PCs. Operating system: Windows XP/7. RAM: 2 Gbytes Classification: 4.3. Nature of problem: Constructing analytic approximate solutions of nonlinear fractional differential equations with initial or boundary conditions. Non-smooth initial value problems can be solved by this program. Solution method: Based on the new definition of the Adomian polynomials [1], the Adomian decomposition method and the Pad
International Nuclear Information System (INIS)
Terawaki, Shin-ichi; Kitano, Ken; Aoyama, Miki; Hakoshima, Toshio
2008-01-01
The radixin FERM domain was shown to bind the MT1-MMP cytoplasmic peptide and crystals of the complex were obtained. ERM proteins play a role in the cross-linking found between plasma membranes and actin filaments. The N-terminal FERM domains of ERM proteins are responsible for membrane association through direct interaction with the cytoplasmic tails of integral membrane proteins. During cell migration and movement, membrane-type 1 matrix metalloproteinase (MT1-MMP) on plasma membranes sheds adhesion molecule CD44 in addition to degrading the extracellular matrix. Here, the interaction between the radixin FERM domain and the MT1-MMP cytoplasmic tail is reported and preliminary crystallographic characterization of crystals of the radixin FERM domain bound to the cytoplasmic tail of MT1-MMP is presented. The crystals belong to space group P6 1 22, with unit-cell parameters a = b = 122.7, c = 128.3 Å, and contain one complex in the crystallographic asymmetric unit. The diffraction data were collected to a resolution of 2.4 Å
Distorted-wave Born approximation in the case of an optical scattering potential
International Nuclear Information System (INIS)
Mytnichenko, Sergey V.
2005-01-01
Application of the distorted-wave Born approximation in the conventional form developed for the case of a real scattering potential is shown to cause significant errors in calculating X-ray diffuse scattering from non-ideal crystals, superlattices, multilayers and other objects if energy dissipation (photoabsorption, inelastic scattering, and so on) is not negligible, or in other words, in the case of an optical (complex) scattering potential. We show how a correct expression for the X-ray diffuse-scattering cross-section can be obtained in this case. Generally, the diffuse-scattering cross-section from an optical potential is not T-invariant, i.e. the reciprocity principle is violated. Violations of T-invariance are more evident when the dynamical nature of the diffraction is more critical
Gain scheduling for non-linear time-delay systems using approximated model
Pham, H.T.; Lim, J.T
2012-01-01
The authors investigate a regulation problem of non-linear systems driven by an exogenous signal and time-delay in the input. In order to compensate for the input delay, they propose a reduction transformation containing the past information of the control input. Then, by utilising the Euler
Rational approximations of f(R) cosmography through Pad'e polynomials
Capozziello, Salvatore; D'Agostino, Rocco; Luongo, Orlando
2018-05-01
We consider high-redshift f(R) cosmography adopting the technique of polynomial reconstruction. In lieu of considering Taylor treatments, which turn out to be non-predictive as soon as z>1, we take into account the Pad&apose rational approximations which consist in performing expansions converging at high redshift domains. Particularly, our strategy is to reconstruct f(z) functions first, assuming the Ricci scalar to be invertible with respect to the redshift z. Having the so-obtained f(z) functions, we invert them and we easily obtain the corresponding f(R) terms. We minimize error propagation, assuming no errors upon redshift data. The treatment we follow naturally leads to evaluating curvature pressure, density and equation of state, characterizing the universe evolution at redshift much higher than standard cosmographic approaches. We therefore match these outcomes with small redshift constraints got by framing the f(R) cosmology through Taylor series around 0zsimeq . This gives rise to a calibration procedure with small redshift that enables the definitions of polynomial approximations up to zsimeq 10. Last but not least, we show discrepancies with the standard cosmological model which go towards an extension of the ΛCDM paradigm, indicating an effective dark energy term evolving in time. We finally describe the evolution of our effective dark energy term by means of basic techniques of data mining.
Approximation techniques for engineers
Komzsik, Louis
2006-01-01
Presenting numerous examples, algorithms, and industrial applications, Approximation Techniques for Engineers is your complete guide to the major techniques used in modern engineering practice. Whether you need approximations for discrete data of continuous functions, or you''re looking for approximate solutions to engineering problems, everything you need is nestled between the covers of this book. Now you can benefit from Louis Komzsik''s years of industrial experience to gain a working knowledge of a vast array of approximation techniques through this complete and self-contained resource.
International Conference Approximation Theory XV
Schumaker, Larry
2017-01-01
These proceedings are based on papers presented at the international conference Approximation Theory XV, which was held May 22–25, 2016 in San Antonio, Texas. The conference was the fifteenth in a series of meetings in Approximation Theory held at various locations in the United States, and was attended by 146 participants. The book contains longer survey papers by some of the invited speakers covering topics such as compressive sensing, isogeometric analysis, and scaling limits of polynomials and entire functions of exponential type. The book also includes papers on a variety of current topics in Approximation Theory drawn from areas such as advances in kernel approximation with applications, approximation theory and algebraic geometry, multivariate splines for applications, practical function approximation, approximation of PDEs, wavelets and framelets with applications, approximation theory in signal processing, compressive sensing, rational interpolation, spline approximation in isogeometric analysis, a...
High-Dimensional Function Approximation With Neural Networks for Large Volumes of Data.
Andras, Peter
2018-02-01
Approximation of high-dimensional functions is a challenge for neural networks due to the curse of dimensionality. Often the data for which the approximated function is defined resides on a low-dimensional manifold and in principle the approximation of the function over this manifold should improve the approximation performance. It has been show that projecting the data manifold into a lower dimensional space, followed by the neural network approximation of the function over this space, provides a more precise approximation of the function than the approximation of the function with neural networks in the original data space. However, if the data volume is very large, the projection into the low-dimensional space has to be based on a limited sample of the data. Here, we investigate the nature of the approximation error of neural networks trained over the projection space. We show that such neural networks should have better approximation performance than neural networks trained on high-dimensional data even if the projection is based on a relatively sparse sample of the data manifold. We also find that it is preferable to use a uniformly distributed sparse sample of the data for the purpose of the generation of the low-dimensional projection. We illustrate these results considering the practical neural network approximation of a set of functions defined on high-dimensional data including real world data as well.
Crystallographic features of poly(vinylidene fluoride) film upon an attractive substrate of KBr.
Huang, Rui; Wang, Gang; Guo, Shuo; Wang, Ke; Fu, Qiang
2017-10-18
Among all the polymorphs of poly(vinylidene fluoride) (PVDF), the polar γ-form possesses the highest melting point and electrical breakdown strength as well as the strongest solvent and irradiation resistance, which are beneficial for the durability of PVDF products. Since the γ-form is neither kinetically favorable nor the most thermodynamically stable, it is still difficult to attain the exclusive γ-polymorph, particularly in the case of neat PVDF. In this study, the melt isothermal crystallization of PVDF films was carried out between two KBr wafers. Owing to the characteristics of KBr wafer, including no IR absorbance and high optical transmittance, the crystallographic features originating from the KBr substrate can be conveniently elucidated through the in situ inspected techniques of FTIR and PLM. The KBr wafers significantly accelerated the crystallization kinetics of α-crystals, and then readily triggered the solid-state α- to γ-transformation of the pre-formed α-spherulites, resulting in a 10 μm-thick, neat PVDF film with an absolute crystallinity of 35% and a relative γ fraction as high as 94%. When the film thickness was increased to 40 μm, the crystallization rate of the α-form was still rapid, but the solid-state transformation was not appreciable. These interesting crystallographic phenomena are attributed to the existence of ion-dipole interaction between the -CF 2 or -CH 2 of PVDF chains and the surface of KBr wafer. Unlike most traditional substrate-dominated crystallizations that prevail in a surface epitaxy manner, in which the target films are of ultra-thin thickness (of the order of 10 nm), the ion-dipole interaction promotes the effective thickness to a ten micron level, which enables its production and application at scalable level. Moreover, the triggering of α- to γ-transformation via external fields could be an alternative for achieving the γ-dominant PVDF products, particularly when the introduction of external additives is
Minimum mean square error estimation and approximation of the Bayesian update
Litvinenko, Alexander; Matthies, Hermann G.; Zander, Elmar
2015-01-01
Given: a physical system modeled by a PDE or ODE with uncertain coefficient q(w), a measurement operator Y (u(q); q), where u(q; w) uncertain solution. Aim: to identify q(w). The mapping from parameters to observations is usually not invertible, hence this inverse identification problem is generally ill-posed. To identify q(w) we derived non-linear Bayesian update from the variational problem associated with conditional expectation. To reduce cost of the Bayesian update we offer a functional approximation, e.g. polynomial chaos expansion (PCE). New: We derive linear, quadratic etc approximation of full Bayesian update.
Minimum mean square error estimation and approximation of the Bayesian update
Litvinenko, Alexander
2015-01-07
Given: a physical system modeled by a PDE or ODE with uncertain coefficient q(w), a measurement operator Y (u(q); q), where u(q; w) uncertain solution. Aim: to identify q(w). The mapping from parameters to observations is usually not invertible, hence this inverse identification problem is generally ill-posed. To identify q(w) we derived non-linear Bayesian update from the variational problem associated with conditional expectation. To reduce cost of the Bayesian update we offer a functional approximation, e.g. polynomial chaos expansion (PCE). New: We derive linear, quadratic etc approximation of full Bayesian update.
Approximate quantum Markov chains
Sutter, David
2018-01-01
This book is an introduction to quantum Markov chains and explains how this concept is connected to the question of how well a lost quantum mechanical system can be recovered from a correlated subsystem. To achieve this goal, we strengthen the data-processing inequality such that it reveals a statement about the reconstruction of lost information. The main difficulty in order to understand the behavior of quantum Markov chains arises from the fact that quantum mechanical operators do not commute in general. As a result we start by explaining two techniques of how to deal with non-commuting matrices: the spectral pinching method and complex interpolation theory. Once the reader is familiar with these techniques a novel inequality is presented that extends the celebrated Golden-Thompson inequality to arbitrarily many matrices. This inequality is the key ingredient in understanding approximate quantum Markov chains and it answers a question from matrix analysis that was open since 1973, i.e., if Lieb's triple ma...
Hou, Jin-Le; Luo, Wen; Wu, Yin-Yin; Su, Hu-Chao; Zhang, Guang-Lin; Zhu, Qin-Yu; Dai, Jie
2015-12-14
Two benzene dicarboxylate (BDC) and salicylate (SAL) substituted titanium-oxo-clusters, Ti13O10(o-BDC)4(SAL)4(O(i)Pr)16 (1) and Ti13O10(o-BDC)4(SAL-Cl)4(O(i)Pr)16 (2), are prepared by one step in situ solvothermal synthesis. Single crystal analysis shows that the two Ti13 clusters take a paddle arrangement with an S4 symmetry. The non-compact (non-sphere) structure is stabilized by the coordination of BDC and SAL. Film photoelectrodes are prepared by the wet coating process using the solution of the clusters and the photocurrent response properties of the electrodes are studied. It is found that the photocurrent density and photoresponsiveness of the electrodes are related to the number of coating layers and the annealing temperature. Using ligand coordinated titanium-oxo-clusters as the molecular precursors of TiO2 anatase films is found to be effective due to their high solubility, appropriate stability in solution and hence the easy controllability.
Approximate systems with confluent bonding mappings
Lončar, Ivan
2001-01-01
If X = {Xn, pnm, N} is a usual inverse system with confluent (monotone) bonding mappings, then the projections are confluent (monotone). This is not true for approximate inverse system. The main purpose of this paper is to show that the property of Kelley (smoothness) of the space Xn is a sufficient condition for the confluence (monotonicity) of the projections.
A note on the geometric phase in adiabatic approximation
International Nuclear Information System (INIS)
Tong, D.M.; Singh, K.; Kwek, L.C.; Fan, X.J.; Oh, C.H.
2005-01-01
The adiabatic theorem shows that the instantaneous eigenstate is a good approximation of the exact solution for a quantum system in adiabatic evolution. One may therefore expect that the geometric phase calculated by using the eigenstate should be also a good approximation of exact geometric phase. However, we find that the former phase may differ appreciably from the latter if the evolution time is large enough
Smokers Show Lower Levels of Psychological Well-Being and Mindfulness than Non-Smokers.
Directory of Open Access Journals (Sweden)
Víviam Vargas Barros
Full Text Available Mindfulness is defined as "paying attention in a particular way, on purpose, in the present moment, and nonjudgmentally". Mindfulness is associated with positive affect, life satisfaction, self-esteem, lower negative affect and rumination. Conversely, evidence suggests a relationship between nicotine dependence and psychiatric disorders. This study aimed to compare the levels of Mindfulness and Subjective Well-Being (SWB between smokers and non-smokers. Ninety seven smokers and eighty four non-smokers participated in the study (n = 181. The Five Facet Mindfulness Questionnaire (FFMQ-BR and the Subjective Well-Being Scale (SWBS were used. In all the factors of SWBS, the total scores in the FFMQ-BR and in the facets of Observing and Non-Reactivity, the non-smokers scored higher than the smokers. This study suggests that smokers present lower levels of Mindfulness and SWB than non-smokers. Consequently, we propose that Mindfulness-Based Interventions (MBI may help smokers deal with treatment and abstinence by increasing their level of SWB.
Evaluation of the successive approximations method for acoustic streaming numerical simulations.
Catarino, S O; Minas, G; Miranda, J M
2016-05-01
This work evaluates the successive approximations method commonly used to predict acoustic streaming by comparing it with a direct method. The successive approximations method solves both the acoustic wave propagation and acoustic streaming by solving the first and second order Navier-Stokes equations, ignoring the first order convective effects. This method was applied to acoustic streaming in a 2D domain and the results were compared with results from the direct simulation of the Navier-Stokes equations. The velocity results showed qualitative agreement between both methods, which indicates that the successive approximations method can describe the formation of flows with recirculation. However, a large quantitative deviation was observed between the two methods. Further analysis showed that the successive approximation method solution is sensitive to the initial flow field. The direct method showed that the instantaneous flow field changes significantly due to reflections and wave interference. It was also found that convective effects contribute significantly to the wave propagation pattern. These effects must be taken into account when solving the acoustic streaming problems, since it affects the global flow. By adequately calculating the initial condition for first order step, the acoustic streaming prediction by the successive approximations method can be improved significantly.
International Nuclear Information System (INIS)
Palacios-Lidon, E; Perez-GarcIa, B; Colchero, J; Vennegues, P; Zuniga-Perez, J; Munoz-Sanjose, V
2009-01-01
ZnO thin films grown by metal-organic vapor phase epitaxy along the nonpolar [112-bar] direction and exhibiting semipolar {101-bar 1-bar}/{101-bar +1} facets have been chemically etched with HCl. In order to get an insight into the influence of the ZnO wurtzite structure in the chemical reactivity of the material, Kelvin probe microscopy and convergent beam electron diffraction have been employed to unambiguously determine the absolute polarity of the facets, showing that {101-bar +1} facets are unstable upon etching in an HCl solution and transform into (000+1)/{101-bar 1-bar} planes. In contrast, {101-bar 1-bar} undergo homogeneous chemical etching perpendicular to the initial crystallographic plane. The observed etching behavior has been explained in terms of surface oxygen dangling bond density, suggesting that the macroscopic polarity plays a secondary role in the etching process.
Ordered cones and approximation
Keimel, Klaus
1992-01-01
This book presents a unified approach to Korovkin-type approximation theorems. It includes classical material on the approximation of real-valuedfunctions as well as recent and new results on set-valued functions and stochastic processes, and on weighted approximation. The results are notonly of qualitative nature, but include quantitative bounds on the order of approximation. The book is addressed to researchers in functional analysis and approximation theory as well as to those that want to applythese methods in other fields. It is largely self- contained, but the readershould have a solid background in abstract functional analysis. The unified approach is based on a new notion of locally convex ordered cones that are not embeddable in vector spaces but allow Hahn-Banach type separation and extension theorems. This concept seems to be of independent interest.
International Nuclear Information System (INIS)
Adler, P.H.; Olson, G.B.
1986-01-01
Determination of invariant-plane strain crystallographic solutions for martensitic transformation between the FCC δ and monoclinic α phases in plutonium alloys, using three possible lattice correspondences and 53 possible lattice-invariant shear systems, identifies the most probable δ-α lattice correspondence. The operative lattice-invariant shear systems are predicted by comparison of both shape strain magnitudes and computed interfacial energies. For δ → α transformation twinning on (001) [100]/sub α/ is favored, giving a (.817, .538, .208)/sub δ/ habit and a [.947, .269, .174]/sub δ/ shape strain of magnitude m 1 = .324. The α → δ transformation favors slip on (111) [101]/sub δ/, giving a (.255, .844, .471)/sub α/ habit and [.822, .466, .355]/sub α/ shape strain of magnitude m 1 = .417
Effective mass approximation for tunneling states with dissipation
International Nuclear Information System (INIS)
Chen Hong; Wu Xiang.
1987-08-01
The dissipative tunneling in an asymmetric double-well potential is studied at low temperature. With effective mass approximation, the dissipation can be replaced by a temperature-dependent effective mass. The effective mass increases with decreasing temperature and becomes infinite at T=0. The partition function of the system is derived, which has the same form as that of a non-dissipative tunneling system. Some possible applications in glasses and heavy fermion system are also discussed. (author). 21 refs, 1 fig
Directory of Open Access Journals (Sweden)
Bruno Linclau
2010-06-01
Full Text Available A large-scale synthesis of meso-2,3-difluoro-1,4-butanediol in 5 steps from (Z-but-2-enediol is described. Crystallographic analysis of the diol and the corresponding benzyl ether reveals an anti conformation of the vicinal difluoride moiety. Monosilylation of the diol is high-yielding but all attempts to achieve chain extension through addition of alkyl Grignard and acetylide nucleophiles failed.
CERN. Geneva
2015-01-01
Most physics results at the LHC end in a likelihood ratio test. This includes discovery and exclusion for searches as well as mass, cross-section, and coupling measurements. The use of Machine Learning (multivariate) algorithms in HEP is mainly restricted to searches, which can be reduced to classification between two fixed distributions: signal vs. background. I will show how we can extend the use of ML classifiers to distributions parameterized by physical quantities like masses and couplings as well as nuisance parameters associated to systematic uncertainties. This allows for one to approximate the likelihood ratio while still using a high dimensional feature vector for the data. Both the MEM and ABC approaches mentioned above aim to provide inference on model parameters (like cross-sections, masses, couplings, etc.). ABC is fundamentally tied Bayesian inference and focuses on the “likelihood free” setting where only a simulator is available and one cannot directly compute the likelihood for the dat...
Approximated Function Based Spectral Gradient Algorithm for Sparse Signal Recovery
Directory of Open Access Journals (Sweden)
Weifeng Wang
2014-02-01
Full Text Available Numerical algorithms for the l0-norm regularized non-smooth non-convex minimization problems have recently became a topic of great interest within signal processing, compressive sensing, statistics, and machine learning. Nevertheless, the l0-norm makes the problem combinatorial and generally computationally intractable. In this paper, we construct a new surrogate function to approximate l0-norm regularization, and subsequently make the discrete optimization problem continuous and smooth. Then we use the well-known spectral gradient algorithm to solve the resulting smooth optimization problem. Experiments are provided which illustrate this method is very promising.
Merging Belief Propagation and the Mean Field Approximation: A Free Energy Approach
DEFF Research Database (Denmark)
Riegler, Erwin; Kirkelund, Gunvor Elisabeth; Manchón, Carles Navarro
2013-01-01
We present a joint message passing approach that combines belief propagation and the mean field approximation. Our analysis is based on the region-based free energy approximation method proposed by Yedidia et al. We show that the message passing fixed-point equations obtained with this combination...... correspond to stationary points of a constrained region-based free energy approximation. Moreover, we present a convergent implementation of these message passing fixed-point equations provided that the underlying factor graph fulfills certain technical conditions. In addition, we show how to include hard...
Approximate Arithmetic Training Improves Informal Math Performance in Low Achieving Preschoolers
Directory of Open Access Journals (Sweden)
Emily Szkudlarek
2018-05-01
Full Text Available Recent studies suggest that practice with approximate and non-symbolic arithmetic problems improves the math performance of adults, school aged children, and preschoolers. However, the relative effectiveness of approximate arithmetic training compared to available educational games, and the type of math skills that approximate arithmetic targets are unknown. The present study was designed to (1 compare the effectiveness of approximate arithmetic training to two commercially available numeral and letter identification tablet applications and (2 to examine the specific type of math skills that benefit from approximate arithmetic training. Preschool children (n = 158 were pseudo-randomly assigned to one of three conditions: approximate arithmetic, letter identification, or numeral identification. All children were trained for 10 short sessions and given pre and post tests of informal and formal math, executive function, short term memory, vocabulary, alphabet knowledge, and number word knowledge. We found a significant interaction between initial math performance and training condition, such that children with low pretest math performance benefited from approximate arithmetic training, and children with high pretest math performance benefited from symbol identification training. This effect was restricted to informal, and not formal, math problems. There were also effects of gender, socio-economic status, and age on post-test informal math score after intervention. A median split on pretest math ability indicated that children in the low half of math scores in the approximate arithmetic training condition performed significantly better than children in the letter identification training condition on post-test informal math problems when controlling for pretest, age, gender, and socio-economic status. Our results support the conclusion that approximate arithmetic training may be especially effective for children with low math skills, and that
Approximate Arithmetic Training Improves Informal Math Performance in Low Achieving Preschoolers.
Szkudlarek, Emily; Brannon, Elizabeth M
2018-01-01
Recent studies suggest that practice with approximate and non-symbolic arithmetic problems improves the math performance of adults, school aged children, and preschoolers. However, the relative effectiveness of approximate arithmetic training compared to available educational games, and the type of math skills that approximate arithmetic targets are unknown. The present study was designed to (1) compare the effectiveness of approximate arithmetic training to two commercially available numeral and letter identification tablet applications and (2) to examine the specific type of math skills that benefit from approximate arithmetic training. Preschool children ( n = 158) were pseudo-randomly assigned to one of three conditions: approximate arithmetic, letter identification, or numeral identification. All children were trained for 10 short sessions and given pre and post tests of informal and formal math, executive function, short term memory, vocabulary, alphabet knowledge, and number word knowledge. We found a significant interaction between initial math performance and training condition, such that children with low pretest math performance benefited from approximate arithmetic training, and children with high pretest math performance benefited from symbol identification training. This effect was restricted to informal, and not formal, math problems. There were also effects of gender, socio-economic status, and age on post-test informal math score after intervention. A median split on pretest math ability indicated that children in the low half of math scores in the approximate arithmetic training condition performed significantly better than children in the letter identification training condition on post-test informal math problems when controlling for pretest, age, gender, and socio-economic status. Our results support the conclusion that approximate arithmetic training may be especially effective for children with low math skills, and that approximate arithmetic
The relaxation time approximation
International Nuclear Information System (INIS)
Gairola, R.P.; Indu, B.D.
1991-01-01
A plausible approximation has been made to estimate the relaxation time from a knowledge of the transition probability of phonons from one state (r vector, q vector) to other state (r' vector, q' vector), as a result of collision. The relaxation time, thus obtained, shows a strong dependence on temperature and weak dependence on the wave vector. In view of this dependence, relaxation time has been expressed in terms of a temperature Taylor's series in the first Brillouin zone. Consequently, a simple model for estimating the thermal conductivity is suggested. the calculations become much easier than the Callaway model. (author). 14 refs
Renormalization in self-consistent approximation schemes at finite temperature I: theory
International Nuclear Information System (INIS)
Hees, H. van; Knoll, J.
2001-07-01
Within finite temperature field theory, we show that truncated non-perturbative self-consistent Dyson resummation schemes can be renormalized with local counter-terms defined at the vacuum level. The requirements are that the underlying theory is renormalizable and that the self-consistent scheme follows Baym's Φ-derivable concept. The scheme generates both, the renormalized self-consistent equations of motion and the closed equations for the infinite set of counter terms. At the same time the corresponding 2PI-generating functional and the thermodynamic potential can be renormalized, in consistency with the equations of motion. This guarantees the standard Φ-derivable properties like thermodynamic consistency and exact conservation laws also for the renormalized approximation scheme to hold. The proof uses the techniques of BPHZ-renormalization to cope with the explicit and the hidden overlapping vacuum divergences. (orig.)
Directory of Open Access Journals (Sweden)
Elena D. Koch
2018-03-01
Full Text Available Physical activity is known to preserve both physical and mental health. However, the physical activity levels of a large proportion of adolescents are insufficient. This is critical, since physical activity levels in youth have been shown to translate into adulthood. Whereas in adult populations, mood has been supposed to be one important psychological factor that drives physical activity in everyday life, this issue has been poorly studied in adolescent populations. Ambulatory Assessment is the state-of-the-art approach to investigate how mood and non-exercise activity fluctuate within persons in everyday life. Through assessments in real time and real life, this method provides ecological validity, bypassing several limitations of traditional assessment methods (e.g., recall biases. To investigate whether mood is associated with non-exercise activity in adolescents, we equipped a community-based sample comprising 113 participants, aged 12–17 years, with GPS-triggered e-diaries querying for valence, energetic arousal, and calmness, and with accelerometers continuously measuring physical activity in their everyday lives for 1 week. We excluded all acceleration data due to participants' exercise activities and thereafter we parameterized non-exercise activity as the mean value across 10-min intervals of movement acceleration intensity following each e-diary prompt. We used multilevel analyses to compute the effects of the mood dimensions on non-exercise activity within 10-min intervals directly following each e-diary prompt. Additionally, we conducted explorative analyses of the time course of the effects, i.e., on different timeframes of non-exercise activity up to 300 min following the mood assessment. The results showed that valence (p < 0.001 and energetic arousal (p < 0.001 were positively associated with non-exercise activity within the 10 min interval, whereas calmness (p < 0.001 was negatively associated with non-exercise activity
International Nuclear Information System (INIS)
Kuznetsov, Alexander M.; Medvedev, Igor G.
2006-01-01
Effects of deviation from the Born-Oppenheimer approximation (BOA) on the non-adiabatic transition probability for the transfer of a quantum particle in condensed media are studied within an exactly solvable model. The particle and the medium are modeled by a set of harmonic oscillators. The dynamic interaction of the particle with a single local mode is treated explicitly without the use of BOA. Two particular situations (symmetric and non-symmetric systems) are considered. It is shown that the difference between the exact solution and the true BOA is negligibly small at realistic parameters of the model. However, the exact results differ considerably from those of the crude Condon approximation (CCA) which is usually considered in the literature as a reference point for BOA (Marcus-Hush-Dogonadze formula). It is shown that the exact rate constant can be smaller (symmetric system) or larger (non-symmetric one) than that obtained in CCA. The non-Condon effects are also studied
Improved WKB approximation for quantum tunneling: Application to heavy-ion fusion
Energy Technology Data Exchange (ETDEWEB)
Toubiana, A.J. [Universidade Federal do Rio de Janeiro, Departamento de Engenharia Nuclear, Escola Politecnica, C.P. 68529, Rio de Janeiro, RJ (Brazil); Ecole CentraleSupelec, Gif-sur-Yvette (France); Paris Saclay, Saint-Aubin (France); Canto, L.F. [Universidade Federal do Rio de Janeiro, Instituto de Fisica, C.P. 68528, Rio de Janeiro (Brazil); Universidade Federal Fluminense, Instituto de Fisica, Niteroi, RJ (Brazil); Hussein, M.S. [Universidade de Sao Paulo, Instituto de Estudos Avancados, C.P. 72012, Sao Paulo, SP (Brazil); Universidade de Sao Paulo, Instituto de Fisica, C.P. 66318, Sao Paulo, SP (Brazil); Instituto Tecnologico de Aeronautica, CTA, Departamento de Fisica, Sao Jose dos Campos, Sao Paulo, SP (Brazil)
2017-02-15
In this paper we revisit the one-dimensional tunnelling problem. We consider Kemble's approximation for the transmission coefficient. We show how this approximation can be extended to above-barrier energies by performing the analytical continuation of the radial coordinate to the complex plane. We investigate the validity of this approximation by comparing their predictions for the cross section and for the barrier distribution with the corresponding quantum-mechanical results. We find that the extended Kemble's approximation reproduces the results of quantum mechanics with great accuracy. (orig.)
Analysis of a Cartesian PML approximation to acoustic scattering problems in and
Bramble, James H.
2013-08-01
We consider the application of a perfectly matched layer (PML) technique applied in Cartesian geometry to approximate solutions of the acoustic scattering problem in the frequency domain. The PML is viewed as a complex coordinate shift ("stretching") and leads to a variable complex coefficient equation for the acoustic wave posed on an infinite domain, the complement of the bounded scatterer. The use of Cartesian geometry leads to a PML operator with simple coefficients, although, still complex symmetric (non-Hermitian). The PML reformulation results in a problem whose solution coincides with the original solution inside the PML layer while decaying exponentially outside. The rapid decay of the PML solution suggests truncation to a bounded domain with a convenient outer boundary condition and subsequent finite element approximation (for the truncated problem). This paper provides new stability estimates for the Cartesian PML approximations both on the infinite and the truncated domain. We first investigate the stability of the infinite PML approximation as a function of the PML strength σ0. This is done for PML methods which involve continuous piecewise smooth stretching as well as piecewise constant stretching functions. We next introduce a truncation parameter M which determines the size of the PML layer. Our analysis shows that the truncated PML problem is stable provided that the product of Mσ0 is sufficiently large, in which case the solution of the problem on the truncated domain converges exponentially to that of the original problem in the domain of interest near the scatterer. This justifies the simple computational strategy of selecting a fixed PML layer and increasing σ0 to obtain the desired accuracy. The results of numerical experiments varying M and σ0 are given which illustrate the theoretically predicted behavior. © 2013 Elsevier B.V. All rights reserved.
Approximative calculation of transient short-circuit currents in power-systems
Energy Technology Data Exchange (ETDEWEB)
Heuck, K; Rosenberger, R; Dettmann, K D; Kegel, R
1986-08-01
The paper shows that it is approximatively possible to calculate the transient short-circuit currents for symmetrical and asymmetrical faults in power-systems. For that purpose a simple equivalent network is found. Its error of approximation is small. For the important maximum short-circuit current limits of error are pointed out compared to VDE 0102.
An approximate method for nonlinear diffusion applied to enzyme inactivation during drying
Liou, J.K.
1982-01-01
An approximate model was developed for nonlinear diffusion with a power-function variation of the diffusion coefficient with concentration. This model may serve for the computation of desorption times and concentration profiles in non-shrinking or shrinking slabs, cylinders or spheres, under
Fast approximate convex decomposition using relative concavity
Ghosh, Mukulika; Amato, Nancy M.; Lu, Yanyan; Lien, Jyh-Ming
2013-01-01
Approximate convex decomposition (ACD) is a technique that partitions an input object into approximately convex components. Decomposition into approximately convex pieces is both more efficient to compute than exact convex decomposition and can also generate a more manageable number of components. It can be used as a basis of divide-and-conquer algorithms for applications such as collision detection, skeleton extraction and mesh generation. In this paper, we propose a new method called Fast Approximate Convex Decomposition (FACD) that improves the quality of the decomposition and reduces the cost of computing it for both 2D and 3D models. In particular, we propose a new strategy for evaluating potential cuts that aims to reduce the relative concavity, rather than absolute concavity. As shown in our results, this leads to more natural and smaller decompositions that include components for small but important features such as toes or fingers while not decomposing larger components, such as the torso, that may have concavities due to surface texture. Second, instead of decomposing a component into two pieces at each step, as in the original ACD, we propose a new strategy that uses a dynamic programming approach to select a set of n c non-crossing (independent) cuts that can be simultaneously applied to decompose the component into n c+1 components. This reduces the depth of recursion and, together with a more efficient method for computing the concavity measure, leads to significant gains in efficiency. We provide comparative results for 2D and 3D models illustrating the improvements obtained by FACD over ACD and we compare with the segmentation methods in the Princeton Shape Benchmark by Chen et al. (2009) [31]. © 2012 Elsevier Ltd. All rights reserved.
Fast approximate convex decomposition using relative concavity
Ghosh, Mukulika
2013-02-01
Approximate convex decomposition (ACD) is a technique that partitions an input object into approximately convex components. Decomposition into approximately convex pieces is both more efficient to compute than exact convex decomposition and can also generate a more manageable number of components. It can be used as a basis of divide-and-conquer algorithms for applications such as collision detection, skeleton extraction and mesh generation. In this paper, we propose a new method called Fast Approximate Convex Decomposition (FACD) that improves the quality of the decomposition and reduces the cost of computing it for both 2D and 3D models. In particular, we propose a new strategy for evaluating potential cuts that aims to reduce the relative concavity, rather than absolute concavity. As shown in our results, this leads to more natural and smaller decompositions that include components for small but important features such as toes or fingers while not decomposing larger components, such as the torso, that may have concavities due to surface texture. Second, instead of decomposing a component into two pieces at each step, as in the original ACD, we propose a new strategy that uses a dynamic programming approach to select a set of n c non-crossing (independent) cuts that can be simultaneously applied to decompose the component into n c+1 components. This reduces the depth of recursion and, together with a more efficient method for computing the concavity measure, leads to significant gains in efficiency. We provide comparative results for 2D and 3D models illustrating the improvements obtained by FACD over ACD and we compare with the segmentation methods in the Princeton Shape Benchmark by Chen et al. (2009) [31]. © 2012 Elsevier Ltd. All rights reserved.
The triangular density to approximate the normal density: decision rules-of-thumb
International Nuclear Information System (INIS)
Scherer, William T.; Pomroy, Thomas A.; Fuller, Douglas N.
2003-01-01
In this paper we explore the approximation of the normal density function with the triangular density function, a density function that has extensive use in risk analysis. Such an approximation generates a simple piecewise-linear density function and a piecewise-quadratic distribution function that can be easily manipulated mathematically and that produces surprisingly accurate performance under many instances. This mathematical tractability proves useful when it enables closed-form solutions not otherwise possible, as with problems involving the embedded use of the normal density. For benchmarking purposes we compare the basic triangular approximation with two flared triangular distributions and with two simple uniform approximations; however, throughout the paper our focus is on using the triangular density to approximate the normal for reasons of parsimony. We also investigate the logical extensions of using a non-symmetric triangular density to approximate a lognormal density. Several issues associated with using a triangular density as a substitute for the normal and lognormal densities are discussed, and we explore the resulting numerical approximation errors for the normal case. Finally, we present several examples that highlight simple decision rules-of-thumb that the use of the approximation generates. Such rules-of-thumb, which are useful in risk and reliability analysis and general business analysis, can be difficult or impossible to extract without the use of approximations. These examples include uses of the approximation in generating random deviates, uses in mixture models for risk analysis, and an illustrative decision analysis problem. It is our belief that this exploratory look at the triangular approximation to the normal will provoke other practitioners to explore its possible use in various domains and applications
van Weely, S.F.E.; van Denderen, J.C.; Steultjens, M.P.M.; Nurmohamed, M.T.; Dijkmans, B.A.C.; Dekker, J.; van der Horst-Bruinsma, I.E.
2013-01-01
Objective: A prospective study was conducted in order to establish whether AS patients, who are defined as non-responders after 3 months of anti-TNF therapy, show improvement on performance-based tests of physical functioning. Methods: At baseline and 3 months after the start of anti-TNF therapy, AS
Preliminary crystallographic characterization of an RNA helicase from Kunjin virus
International Nuclear Information System (INIS)
Mastrangelo, Eloise; Bollati, Michela; Milani, Mario; Brisbarre, Nadège; Lamballerie, Xavier de; Coutard, Bruno; Canard, Bruno; Khromykh, Alexander; Bolognesi, Martino
2006-01-01
The C-terminal 440 amino acids of the NS3 protein from Kunjin virus (Flaviviridae) code for a helicase. The protein has been overexpressed and crystallized. Characterization of the isolated monoclinic crystal form and diffraction data (at 3.0 Å resolution) are presented, together with a preliminary molecular-replacement solution. Kunjin virus is a member of the Flavivirus genus and is an Australian variant of West Nile virus. The C-terminal domain of the Kunjin virus NS3 protein displays helicase activity. The protein is thought to separate daughter and template RNA strands, assisting the initiation of replication by unwinding RNA secondary structure in the 3′ nontranslated region. Expression, purification and preliminary crystallographic characterization of the NS3 helicase domain are reported. It is shown that Kunjin virus helicase may adopt a dimeric assembly in absence of nucleic acids, oligomerization being a means to provide the helicases with multiple nucleic acid-binding capability, facilitating translocation along the RNA strands. Kunjin virus NS3 helicase domain is an attractive model for studying the molecular mechanisms of flavivirus replication, while simultaneously providing a new basis for the rational development of anti-flaviviral compounds
Correlating Atom Probe Crystallographic Measurements with Transmission Kikuchi Diffraction Data.
Breen, Andrew J; Babinsky, Katharina; Day, Alec C; Eder, K; Oakman, Connor J; Trimby, Patrick W; Primig, Sophie; Cairney, Julie M; Ringer, Simon P
2017-04-01
Correlative microscopy approaches offer synergistic solutions to many research problems. One such combination, that has been studied in limited detail, is the use of atom probe tomography (APT) and transmission Kikuchi diffraction (TKD) on the same tip specimen. By combining these two powerful microscopy techniques, the microstructure of important engineering alloys can be studied in greater detail. For the first time, the accuracy of crystallographic measurements made using APT will be independently verified using TKD. Experimental data from two atom probe tips, one a nanocrystalline Al-0.5Ag alloy specimen collected on a straight flight-path atom probe and the other a high purity Mo specimen collected on a reflectron-fitted instrument, will be compared. We find that the average minimum misorientation angle, calculated from calibrated atom probe reconstructions with two different pole combinations, deviate 0.7° and 1.4°, respectively, from the TKD results. The type of atom probe and experimental conditions appear to have some impact on this accuracy and the reconstruction and measurement procedures are likely to contribute further to degradation in angular resolution. The challenges and implications of this correlative approach will also be discussed.
Approximating chiral quark models with linear σ-models
International Nuclear Information System (INIS)
Broniowski, Wojciech; Golli, Bojan
2003-01-01
We study the approximation of chiral quark models with simpler models, obtained via gradient expansion. The resulting Lagrangian of the type of the linear σ-model contains, at the lowest level of the gradient-expanded meson action, an additional term of the form ((1)/(2))A(σ∂ μ σ+π∂ μ π) 2 . We investigate the dynamical consequences of this term and its relevance to the phenomenology of the soliton models of the nucleon. It is found that the inclusion of the new term allows for a more efficient approximation of the underlying quark theory, especially in those cases where dynamics allows for a large deviation of the chiral fields from the chiral circle, such as in quark models with non-local regulators. This is of practical importance, since the σ-models with valence quarks only are technically much easier to treat and simpler to solve than the quark models with the full-fledged Dirac sea