bluuebunny/crossref_metadata_2025 huggingface dataset:
PANTHER: A Library of Protein Families and Subfamilies Indexed by Function
Authors: Thomas Paul D. , Campbell Michael J. , Kejariwal Anish , Mi Huaiyu , Karlak Brian , Daverman Robin , Diemer Karen , Muruganujan Anushya , Narechania Apurva
Published: September 2003

In the genomic era, one of the fundamental goals is to characterize the function of proteins on a large scale. We describe a method, PANTHER, for relating protein sequence relationships to function relationships in a robust and accurate way. PANTHER is composed of two main components: the PANTHER library (PANTHER/LIB) and the PANTHER index (PANTHER/X). PANTHER/LIB is a collection of “books,” each representing a protein family as a multiple sequence alignment, a Hidden Markov Model (HMM), and a family tree. Functional divergence within the family is represented by dividing the tree into subtrees based on shared function, and by subtree HMMs. PANTHER/X is an abbreviated ontology for summarizing and navigating molecular functions and biological processes associated with the families and subfamilies. We apply PANTHER to three areas of active research. First, we report the size and sequence diversity of the families and subfamilies, characterizing the relationship between sequence divergence and functional divergence across a wide range of protein families. Second, we use the PANTHER/X ontology to give a high-level representation of gene function across the human and mouse genomes. Third, we use the family HMMs to rank missense single nucleotide polymorphisms (SNPs), on a database-wide scale, according to their likelihood of affecting protein function.
Global Haplotype Diversity in the Human Insulin Gene Region
Authors: Stead John D.H. , Hurles Matthew E. , Jeffreys Alec J.
Published: September 2003

The insulin minisatellite (INS VNTR) has been intensively analyzed due to its associations with diseases including diabetes. We have previously used patterns of variant repeat distribution in the minisatellite to demonstrate that genetic diversity is unusually great in Africans compared to non-Africans. Here we analyzed variation at 56 single nucleotide polymorphisms (SNPs) flanking the minisatellite in individuals from six populations, and we show that over 40% of the total genetic variance near the minisatellite is due to differences between Africans and non-Africans, far higher than seen in most genomic regions and consistent with differential selection acting on the insulin gene region, most likely in the non-African ancestral population. Linkage disequilibrium was lower in African populations, with evidence of clustering of historical recombination events. Analysis of haplotypes from the relatively nonrecombining region around the minisatellite revealed a star-shaped phylogeny with lineages radiating from an ancestral African-specific haplotype. These haplotypes confirmed that minisatellite lineages defined by variant repeat distributions are monophyletic in origin. These analyses provide a framework for a cladistic approach to future disease association studies of the insulin region within both African and non-African populations, and they identify SNPs which can be rapidly analyzed as surrogate markers for minisatellite lineage.
Diffraction peak profiles from spherical crystallites with lognormal size distribution
Authors: Ida T. , Shimazaki S. , Hibino H. , Toraya H.
Published: September 2003

An efficient and accurate method to evaluate the theoretical diffraction peak profiles from spherical crystallites with lognormal size distribution (SLN profile) is presented. Precise results can be obtained typically by an eight-term numerical integral for any values of the parameters, by applying an appropriate substitution of the variable to the integral formula. The calculated SLN profiles have been verified by comparison with those calculated by inverse Fourier transform from the exact analytical solution of the Fourier-transformed SLN profile. It has been found that the shape of the SLN profile strongly depends on the variance of size distribution. When the logarithmic standard deviation ω of the size distribution is close to 0.76, the SLN profile becomes close to a Lorentzian profile, and `super-Lorentzian' profiles are predicted for larger values of ω, as has been concluded by Popa & Balzar [J. Appl. Cryst.(2002),35, 338–346]. The intrinsic diffraction peak profiles of an SiC powder sample obtained by deconvolution of the instrumental function have certainly shown `super-Lorentzian' line profiles, and they are well reproduced by the SLN profile for the value ω = 0.93.
Automatic inference of protein quaternary structure from crystals
Authors: Ponstingl Hannes , Kabir Thomas , Thornton Janet M.
Published: September 2003

The arrangement of the subunits in an oligomeric protein often cannot be inferred without ambiguity from crystallographic studies. The annotation of the functional assembly of protein structures in the Protein Data Bank (PDB) is incomplete and frequently inconsistent. Instructions for the reconstruction, by symmetry, of the functional assembly from the deposited coordinates are often absent. An automatic procedure is proposed for the inference of assembly structures that are likely to be physiologically relevant. The method scores crystal contacts by their contact size and chemical complementarity. The subunit assembly is then inferred from these scored contacts by a clustering procedure involving a single adjustable parameter. When predicting the oligomeric state for a non-redundant set of 55 monomeric and 163 oligomeric proteins from dimers up to hexamers, a classification error rate of 16% was observed.
A full-pattern fitting algorithm for energy-dispersive X-ray diffraction
Authors: Dong Yu-Hui , Liu Jing , Li Yan-Chun , Li Xiao-Dong
Published: September 2003

A full-pattern fitting algorithm for energy-dispersive X-ray diffraction is proposed, especially for high-pressure X-ray diffraction studies. The algorithm takes into account the errors in measuring the energy and the diffraction angle. A lognormal function is introduced to represent the background. All the peaks that are detectable in the diffraction spectra, including fluorescence and diffraction peaks, are considered together. Because all the data points in the spectra are used, the accuracy of the cell parameters obtained by this method is very high. This is very helpful in the analysis of the equation of state and the identification of new phases under high pressure.
Monte Carlo simulation of models for biological systems: thermodynamic properties and small-angle scattering from collections of interacting binary mixtures of spheres
Authors: Sjöberg Bo
Published: September 2003

As models for highly concentrated biological and other colloidal systems, computer simulations using Monte Carlo (MC) methods are used to study two bidisperse systems of spheres, one system consisting of mixtures of hard spheres and the other consisting of mixtures of hard spheres and spheres having an additional repulsive potential. First, the nonideal parts of the chemical potentials \beta \mu _{ i}^{\rm ni} (i= 1, 2) are obtained by using Widom's test particle method. From the chemical potentials the osmotic compression factorZis obtained by Gibbs–Duhem integration of \beta \mu _{ i}^{\rm ni}. For the hard-particle model, comparison is also made withZvalues calculated from the pair correlation functionspijat contact, and withZvalues obtained using an analytical expression based on Percus–Yevick theory. Next, the normalized isothermal compressibility ρkTχTis obtained from \beta \mu _{ i}^{\rm ni},viathe Gibbs–Duhem values ofZ. During the MC simulations the partial structure factorsSijare also calculated by Debye double summation and by averaging over the cubic MC cell. The latter parameters are used to calculate the corresponding small-angle X-ray and neutron intensitiesI(Q), which are compared with intensities obtained by Percus–Yevick theory. Comparison is also made between the structural values of \mathop {\lim }_{Q \to 0}I(Q) obtained by Debye double summation and the thermodynamic ρkTχTvalues obtained from \beta \mu _{ i}^{\rm ni}. As already seen,e.g.from measurements of osmotic pressure, the MC simulations show that, for a typical biological system, activity factors can deviate from the value one by several powers of ten, already at fairly low concentrations.
Residual stresses in tool steel due to hard-turning
Authors: Ordás Nerea , Penalva Mari Luz , Fernández Justino , García-Rosales Carmen
Published: September 2003

Residual stresses induced by hard-turning are the result of a combination of mechanical and thermal effects, leading to a compressive or tensile stress state at the surface, depending on the machining parameters and the tool wear state. In this work, the residual stress depth profiles generated on steel grade F-521 (AISI D2) by hard-turning with tools of different wear states were measured by X-ray diffraction. An integral method was applied to determine the full stress tensor and the stress gradient tensors in the tangential, radial and depth directions. Both macroscopic and microscopic residual stresses were investigated. Compressive residual stresses were measured below the surface in all machined specimens. The magnitude of the compressive stress was much lower and the depth was much shallower when using new cutting tools than when using worn tools. However, the sample that has been hard-turned with a worn tool suffered strong microstructural changes in a layer more than 150 µm thick, especially at the surface, where the presence of a hard and very brittle layer of untempered martensite was evidenced.
PRIMUS: a Windows PC-based system for small-angle scattering data analysis
Authors: Konarev Petr V. , Volkov Vladimir V. , Sokolova Anna V. , Koch Michel H. J. , Svergun Dmitri I.
Published: September 2003

A program suite for one-dimensional small-angle scattering data processing running on IBM-compatible PCs under Windows 9x/NT/2000/XP is presented. The main program,PRIMUS, has a menu-driven graphical user interface calling computational modules to perform data manipulation and analysis. Experimental data in binary OTOKO format can be reduced by calling the programSAPOKO, which includes statistical analysis of time frames, averaging and scaling. Tools to generate the angular axis and detector response files from diffraction patterns of calibration samples, as well as binary to ASCII transformation programs, are available. Several types of ASCII files can be directly imported intoPRIMUS, in particular, sasCIF or ILL-type files are read without modification.PRIMUSprovides basic data manipulation functions (averaging, background subtraction, merging of data measured in different angular ranges, extrapolation to zero sample concentration,etc.) and computes invariants from Guinier and Porod plots. Several external modules coupled withPRIMUSviapop-up menus enable the user to evaluate the characteristic functions by indirect Fourier transformation, to perform peak analysis for partially ordered systems and to find shape approximations in terms of three-parametric geometrical bodies. For the analysis of mixtures,PRIMUSenables model-independent singular value decomposition or linear fitting if the scattering from the components is known. An interface is also provided to the general non-linear fitting programMIXTURE, which is designed for quantitative analysis of multicomponent systems represented by simple geometrical bodies, taking shape and size polydispersity as well as interparticle interference effects into account.
Thick-mode resonance of a PZT/Si wafer stack investigated by X-ray diffraction in Bragg geometry
Authors: de Souza Paulo Eduardo Narcizo , Cusatis César , Saul Cyro Ketzer , Rodrigues Antônio Ricardo Drohler , de Camargo Paulo César
Published: September 2003

X-ray diffraction in Bragg geometry was used to investigate the effects of standing longitudinal acoustic waves on an Si(111) wafer. A PZT/Si(111) stack with a resonant frequency of 2.34 MHz was constructed. In addition to the ultrasonic vibration, a thermal effect is evident. The thermal contribution causes an angular displacement of the Bragg profile and was mapped without time resolution. The actual ultrasonic oscillation of the surface was measured using a stroboscopic system. Bulging of the Si(111) surface was mapped out and the maximum deformation near the centre of the Si wafer was determined for a given ultrasonic power. Simple modelling using finite differences was helpful in determining the acoustic and thermal contributions.
Determination of nanoparticle structure type, size and strain distribution from X-ray data for monatomic f.c.c.-derived non-crystallographic nanoclusters
Authors: Cervellino Antonio , Giannini Cinzia , Guagliardi Antonietta
Published: September 2003

Whole-profile-fitting least-squares techniques are applied to simulated and experimental X-ray diffraction patterns of monatomic face-centred cubic (f.c.c.)-derived non-crystallographic nanoclusters to extract structure and size information. Three main structure types have been considered (cuboctahedral, icosahedral and decahedral). Nanocluster structure models have been generated within an original mathematical approach so as to be independent of a specific material. For each structure type, a log-normal size distribution is assumed and a phenomenological function is introduced to model possible additional size-related strain effects. The Debye function method (modified to increase computational efficiency) has been used to obtain the diffracted intensities of the nanocluster. Tests revealed the effectiveness of the method to recognize the structure types correctly and to estimate with good accuracy structure concentrations and size distributions. Application to a thiol-passivated gold nanoparticle sample is presented.
Microscope detection options for colorless protein crystals grown in lipidic cubic phases
Authors: Nollert Peter
Published: September 2003

The use of lipidic cubic phases as crystal nucleation and growth matrices is becoming popular and has yielded crystals of soluble and membrane proteins. So far, all of the membrane proteins crystallized by this method have been colored. This feature has facilitated the detection of the often encountered microcrystals in initial screening rounds. Indeed, small colorless protein crystals have poor optical contrast as a result of the small differences in refractive index of the protein crystal and the surrounding lipidic cubic phase. While a perfect preparation of a lipidic cubic phase is transparent and optically isotropic, in a crystallization setup it frequently disguises crystals due to cracks, inclusions, surface distortions and phase boundaries. Here, several specialized microscopic techniques and illumination conditions are compared and it is found that sufficient contrast is generated by cross polarization microscopy and by Hoffman modulation contrast microscopy for the detection of colorless protein crystals.
General-case data interpretation of spin-echo small-angle neutron scattering
Authors: Zhao Jinkui
Published: September 2003

Following previous works on data interpretation in the case of a one-dimensionally encoded spin-echo small-angle neutron scattering instrument when the scattering data are collected along a single direction, further studies for the more general case of data collection in two dimensions are presented. A mathematical relationship between the correlation function measured in two dimensions and the pair-distance distribution function of the scattering sample is established. The relationship between the correlation function measured in one and two dimensions is also examined.
In situdetermination of stresses from time-of-flight neutron transmission spectra
Authors: Steuwer Axel , Santisteban Javier Roberto , Withers Philip J. , Edwards Lyndon , Fitzpatrick Mike E.
Published: September 2003

The pulsed neutron transmission diffraction technique exploits the sharp steps in intensity (Bragg edges) appearing in the transmitted spectra of thermal neutrons through polycrystalline materials. In this paper the positions of these edges acquired by the time-of-flight (TOF) technique are used to measure accurately the interplanar lattice distances to a resolution of Δd/d≃ 10−4of specimens subjected toin situuniaxial tensile loading. The sensitivity of the method is assessed for elastically isotropic (b.c.c. ferritic) and anisotropic (f.c.c. austenitic) polycrystalline specimens of negligible and moderately textured steels. For the more anisotropic austenitic steel, the elastic anisotropy is studied with regard to a Pawley refinement, and compared with previous results from conventional neutron diffraction experiments on the same material. It is shown that the method can be used to determine anisotropic strains, diffraction elastic constants, the residual and applied stress state as well as the unstrained lattice parameter by recording transmission spectra at different specimen inclinations, by complete analogy with the sin2ψ technique frequently used in X-ray diffraction. The technique is shown to deliver reliable measures of strain even in the case of moderate texture and elastic anisotropy.
Accuracy in Rietveld quantitative phase analysis of Portland cements
Authors: De la Torre A. G. , Aranda M. A. G.
Published: September 2003

The polymorphs that constitute most Portland cements have been synthesized: tricalcium silicate, dicalcium silicate, aluminate, ferrite, gypsum, bassanite and calcite. They have been used to prepare artificial mixtures,i.e.white Portland clinker, grey Portland clinker and two types of grey Portland cements. Quantitative mineralogical analyses of these mixtures have been obtained by laboratory X-ray powder diffraction (λ = 1.54 Å) and the Rietveld method. To assess the accuracy of these analyses, high-energy synchrotron X-ray powder data (λ = 0.40 Å) for the same mixtures have also been studied. Furthermore, synchrotron X-ray powder data were collected for binary mixtures of the polymorphs and a corundum standard. This was done to determine the presence of impurity crystalline phases in the synthesized samples and to check the presence of non-negligible amorphous phase contents. The errors in the synchrotron X-ray analyses are quite low (usually smaller than 1 wt%). The relative errors in the laboratory X-ray analyses are of the order of 2% for the main phases and increase to approximately 5–10% for the low-content components. These errors are acceptable in the factory environment and the routine application of this methodology in the cement industry is being implemented.
Strategies for solving neighboring-element problems: a case study using resonant X-ray diffraction and pulsed neutron diffraction to examine Sr8Ga16Ge30
Authors: Zhang Yuegang , Wilkinson Angus P. , Nolas George S. , Lee Peter L. , Hodges Jason P.
Published: September 2003

The distribution of gallium and germanium over the available framework sites in the type-I clathrate Sr8Ga16Ge30(Pm\bar{3}n) has been determined by powder diffraction using several different combinations of resonant scattering data sets, collected at energies close to both the Ga and GeK-edges, and time-of-flight (TOF) neutron diffraction data. Based on a combined refinement using three X-ray data sets and a composition restraint, the fractional occupancies of the 6c, 16iand 24ksites by gallium are estimated to be 0.705 (5), 0.181 (3) and 0.376 (2), respectively. The required resonant scattering factors were determined by Kramers–Kronig transformation from X-ray absorption spectra. The results from refinements using single data sets and various combinations of data sets are compared. The high degree of scattering contrast that resonant diffraction can provide leads to very precise site occupancies. However, systematic errors in the resonant diffraction intensity data can considerably degrade the accuracy of the results. The use of a carefully chosen multiple-data-set strategy can minimize bias in the refinement results by reducing the correlations between site occupancies, atomic displacement parameters and histogram scale factors. The effect of errors in the resonant scattering factors on the refinement results was also examined.
A quick and gentle method for mounting crystals in capillaries
Authors: Basavappa Ravi , Petri Edward T. , Tolbert Blanton S.
Published: September 2003

The capillary mounting of protein crystals is still necessary under some circumstances, despite its being supplanted by loop mounting/flash freezing as the favored method for crystal mounting prior to data collection. Traditional capillary mounting methods require a degree of dexterity and finesse that causes apprehension among many crystallographers. Here a simple method for capillary mounting that uses a loop for depositing the crystal in the capillary is described.
SAPI: a direct-methods program for finding heavy-atom sites with SAD or SIR data
Authors: Hao Q. , Gu Y. X. , Yao J. X. , Zheng C. D. , Fan H. F.
Published: September 2003

SAPIis aCCP4-format program that applies a direct-methods procedure to find heavy-atom sites using single-wavelength anomalous dispersion (SAD) or single-isomorphous replacement (SIR) data. The program is designed to run in a fast (typical CPU time consumed is less than 1 min) and simple way. User input is kept to a minimum and the default parameter values are adequate in most cases. It can also be used to solve general small-molecule structures.
Estimation of chord length distributions from small-angle scattering using indirect Fourier transformation
Authors: Hansen Steen
Published: September 2003

It is shown that it is possible to estimate the chord length distribution from small-angle scattering data by indirect Fourier transformation. This is done for several examples of scatterers varying in structure from globular to elongated as well as scatterers consisting of separated parts. The presented examples suggest that the chord length distribution may give additional information about the scatterer. Therefore it may be relevant to consider estimation of the chord length distribution as an additional tool for analysis of small-angle scattering data.
Twinning in La0.95Sr0.05Ga0.9Mg0.1O2.92crystal studied by white-beam (Laue) X-ray microdiffraction
Authors: Savytskii D. I. , Trots D. M. , Vasylechko L. O. , Tamura N. , Berkowski M.
Published: September 2003

The investigation of twin structure in La0.95Sr0.05Ga0.9Mg0.1O2.92perovskite-type crystals has been undertaken using the technique of white-beam X-ray microdiffraction. The sample shows definite twinning which is reflected in the Laue patterns as apparent splitting of the peaks. Reflections from the different domains were indexed separately. Positional shifts of twin domain spots with respect to the reference matrix spot, arising from the mutual misorientation of diffraction vectors, were measured on Laue patterns and compared with calculated values in order to solve the twin laws in this system. The dominant twin operations were found to be (12\bar{1}) and (10\bar{1}) mirror reflections.
Scan profiles for neutron spectrometers. II. Rectangular-profile elements by acceptance-diagram methods
Authors: Cussen L. D.
Published: September 2003

The recent development of neutron collimators with rectangular transmission profiles (intensityversusangular divergence) extends hope of improved count rates on neutron scattering instruments. It is usually assumed that a more effective use of beam angular spread in these devices should increase count rates by about a factor of two. However, real beams have both angular and wavevector spread and both these spreads are governed by the allowed collimation. In this extended view, the gains from ideal rectangular-profile elements (angle filters) are shown to be much larger (about a factor of four). The mirror reflections used to achieve the rectangular profiles in real devices complicate the resolution effects. Specifically, the reflections disturb the wavevector–angular divergence correlation in the beams, leading to unusual peak shapes characterized by triple peaks on powder diffractometers. Thus, these reflecting collimators are likely to be universally useful only before the monochromator and immediately preceding the detector, where wavevector–angle correlations have no effect. This reduces the potential gains to a factor of two or so. Note that the gains are as previously expected but for quite different reasons than imagined. This remains a very significant gain in a field where most work is intensity-limited.
Scan profiles for neutron spectrometers. I. Gaussian-profile elements by acceptance-diagram methods
Authors: Cussen L. D.
Published: September 2003

`Acceptance diagrams' are a powerful graphical method of describing beam characteristics on neutron scattering instruments. Recent examples of the technique have used hypothetical rectangular-profile beam elements, not the conventional Gaussian profiles, to clarify the description. This article develops the method for Gaussian-profile beam elements and shows that it gives identical results to accepted techniques. Direct expressions are presented for scan profiles, their widths and intensities for both powder diffractometers and three-axis spectrometers. This work gives some necessary background and therefore forms the first part of a discussion of the resolution effects of the new reflecting Soller collimators for neutrons.
Scan profiles for neutron spectrometers. III. Rectangular-profile elements by numerical methods
Authors: Cussen L. D. , Wildes A. R.
Published: September 2003

Newly developed reflecting neutron collimators promise increased detector count rates in a field where most work is intensity-limited. The effects of such elements on instrument resolution are complicated and appear to be even more subtle than previously imagined. Numerical tests using theMcSTASray-tracing program (http://neutron.risoe.dk/mcstas) are reported which support and extend the recent analysis of these effects. If reflecting collimators are used in all instrument positions they give unusual scan profiles. Using reflecting collimators only before the monochromator and immediately before the detector has no deleterious resolution effects and increases count rates by a factor of more than two on powder diffractometers.
Habit modification of nearly perfect single crystals of potassium dihydrogen phosphate (KDP) by trivalent manganese ions studied using synchrotron radiation X-ray multiple diffraction in Renninger scanning mode
Authors: Lai X. , Roberts K. J. , Avanci L. H. , Cardoso L. P. , Sasaki J. M.
Published: September 2003

The X-ray multiple diffraction technique using synchrotron radiation is applied in the preliminary study of the habit modification of KDP samples as induced by incorporation of the trivalent transition metal cation Mn3+. High-resolution Renninger scans of pure and doped KDP were carried out using 400 as the primary reflection, echoing the fact that these impurity species were segregated in the {100} growth sector. The analysis of the Renninger scans of the doped KDP crystals is consistent with the presence of the impurity species chemically bound within the KDP crystal structure, as confirmed through the suppression of the huge observed peak asymmetry, characteristic of perfect crystals. In addition, an extra Renninger-scan peak measured for the doped material is indicative of the impurity atoms occupying interstitial crystallographic sites in the lattice, a result consistent with X-ray standing-wave measurements. Renninger-scan reflection curve widths and lattice parameter measurements reveal the decrease in crystalline perfection (increased mosaic spread, η) and lattice contraction ofca0.4% in theaandclattice directions at the surface plane for the Mn3+-doped KDP samples in comparison with the undoped crystals.
Note on Bravais–Miller indices
Authors: Schwarzenbach D.
Published: September 2003

In the trigonal and hexagonal crystal systems, four-membered Bravais–Miller indiceshkilare commonly used. Corresponding four-membered direction indices may be found in the literature, but their use is not straightforward. This note reminds readers of the meaning and the applicability of such indices.
Investigation of distorted subsurface layers of thick perfect crystals
Authors: Aboyan A. O. , Drmeyan H. R.
Published: September 2003

The effect of crystal surface defects on the intensity of X-ray scattering has been investigated. It was found that in the presence of distorted subsurface layers, the occurrence of reflection structures (fine lines) depended on the divergence and monochromaticity of the incident beam, as well as on the absorption and character of X-ray scattering on distorted layers and in the main bulk (perfect part) of the crystal.
In situX-ray diffraction studies of aluminium-induced crystallization of hydrogenated amorphous silicon
Authors: Kishore Ram , Hotz Chris , Naseem H. A. , Brown W. D.
Published: September 2003

Thin intrinsic hydrogenated amorphous silicon (α-Si:H) films (5000 Å thickness) were deposited on (111)-orientedn-type silicon substrates by plasma-enhanced chemical vapor deposition. A 4000 Å thick Al film was then deposited on the α-Si:H film by vacuum evaporation.In situannealing of these films was carried out in an evacuated temperature-controlled (Model TTK) camera of an X-ray diffractometer at a glancing angle of 5° using a thin-film optics attachment. The crystallization behavior of aluminium-capped α-Si:H was monitored using the 111 silicon peak as a function of annealing temperature between 273–523 K. The results show that aluminium-induced crystallization of α-Si:H initiates at a temperature between 413 and 423 K. The crystallization rate increases with increasing temperature, and saturates for an anneal of 30 min at a temperature of 523 K.
Texture and microstructure imaging in six dimensions with high-energy synchrotron radiation
Authors: Bunge Hans Joachim , Wcislak Leszek , Klein Helmut , Garbe Ulf , Schneider Jochen Richard
Published: September 2003

The texture of a material can be calculated from several pole figures, which, in turn, are usually measured by one of several `step-scan' techniques. In these techniques, the finite step width limits the attainable orientation resolving power. In the present paper, the discontinuous step-scan technique is replaced by a continuous `sweeping' technique based on the continuous movement of an area detector during exposure. In this way, continuous two-dimensional `images' of pole figures are obtained, without the necessity of interpolation. Similar sweeping techniques are also being used to obtain continuous images of other sections and projections of the six-dimensional `orientation–location' space which characterizes a polycrystalline structure completely. The high potential orientation and/or location resolving power of these imaging techniques can only be reached with synchrotron radiation. In the present paper, the measurements were made at the high-energy (short-wavelength) beamline BW5 at HASYLAB/DESY in Hamburg. The high orientation and location resolving power implies the necessity to distinguish `grain-resolved' textures and microstructures (mainly in recrystallized materials) from `continuous' ones (mainly in deformed materials). Under certain conditions, it is thus possible to obtain the complete six-dimensional `orientation stereology' of grain-resolved microstructures. The new methods are illustrated with several examples, including technological applications.
Intensity and resolution effects in converging multichannel collimators for SANS by Monte Carlo simulation
Authors: Falcão A. N. , Margaça F. M. A. , Carvalho F. G.
Published: September 2003

A study of the contribution of the individual channels of a converging multichannel collimator to the operation of the device is carried out by means of a Monte Carlo computer simulation. The simulation shows that the coupling between the divergence of the incident neutron beam and the inclination of the individual CMC channel axis relative to the beam direction modulates the channel performance as far as intensity and resolution of the transmitted neutrons are concerned. While this does not impair in any significant way the usefulness of the device, the results are helpful to the designer.
A contribution to the practical implementation of a variable-geometry converging multichannel collimator for SANS
Authors: Falcão A. N. , Margaça F. M. A. , Carvalho F. G.
Published: September 2003

The feasibility of constructing a variable-geometry converging multichannel collimator consisting of interlaced planes of thin neutron-absorbing strips is discussed. A process is reported for producing strips of a composite material incorporating gadolinium oxide as the neutron absorber with the required mechanical and neutron-absorbing properties.
OLEX: new software for visualization and analysis of extended crystal structures
Authors: Dolomanov Oleg V. , Blake Alexander J. , Champness Neil R. , Schröder Martin
Published: September 2003

We have developed new software (OLEX) for the visualization and analysis of extended crystal structures. This software has a Windows-compatible mouse-driven graphical interface which gives full control over all structural elements.OLEXprovides the user with tools to construct topological networks, visualize interpenetrating or overlapping fragments, and analyse networks constructed fully or partially by exploiting short interactions. It is also easy to generate conventional ellipsoid, ball-and-stick or packing plots.
CIF applications. XII. Inspecting Rietveld fits from pdCIF:pdCIFplot
Authors: Toby Brian H.
Published: September 2003

A description is given of thepdCIFplotprogram. This program is used to inspect the quality of fits obtained from Rietveld refinements where the results are communicated in pdCIF files. The program runs on almost all contemporary operating systems.
CIF applications. XIII.CIFEDIT, a program for viewing and editing CIFs
Authors: Toby Brian H.
Published: September 2003

TheCIFEDITprogram displays the contents of single- or multi-block crystallographic information files (CIF). The program can also be used to edit the data values for CIF items, including adding or deleting sets of entries in a loop. CIF dictionaries are used to display definitions for data names and units. In the case of DDL 1.4 dictionaries, validation information is used to check numerical values. The program is written using the cross-platform scripting language Tcl/Tk and thus is largely platform-independent. It has been tested under Windows, Mac OS X and Unix.
CIF applications. XIV. Reporting of Rietveld results using pdCIF:GSAS2CIF
Authors: Toby Brian H. , Von Dreele Robert B. , Larson Allen C.
Published: September 2003

A discussion of the process of creating powder diffraction CIF documents (pdCIF) from Rietveld results is presented, with particular focus on the computer programGSAS2CIF. The data structures used withinGSAS2CIFare described, as well as how the program implements template files for descriptive information. Two graphical user interface utilities are also discussed.
MgCl2.2.5C2H5OH–NaCl mixed crystals
Authors: Jiang Xue , Fan Zhiqiang
Published: September 2003

This paper describes the formation of two kinds of mixed crystals of MgCl2and NaCl by ball milling magnesium chloride–ethanol adducts together with sodium chloride. X-ray diffraction analysis of the ball-milled MgCl2.2.5C2H5OH–NaCl powder shows that the two mixed crystals are NaMgCl3and Na2MgCl4.
Digital libraries: barriers or gateways to scholarly information?
Authors: Byrne Alex
Published: September 2003

Unprecedented desktop access to scholarly information has been made possible by the introduction of digital libraries. The powerful combination of digital publications, specialist and generalist databases, sophisticated search systems and portals enables scholars and students to rapidly examine a great variety of the literature in their own disciplines and those new to them. Access is available globally 24 hours a day without geographical limitation. But that access is not without limitations. It is limited by the availability of reliable and affordable information and communication technologies. It is limited to those scholars and students who are affiliated with organisations which have the money and skills to provide access. It is limited to those who are literate, information‐literate and have a command of the major languages of commerce and scholarship (English in particular). In addition, contractual and other bounds imposed by vendors exclude many potential users. In combination, these limitations inhibit many scholars and students from using digital scholarly information and can increase the marginalisation of the already marginalised including, especially, indigenous peoples. This contradiction between access for some and marginalisation for many poses many challenges for libraries.
Perspectives on tribal archives
Authors: Roy Loriene , Alonzo Daniel L.
Published: September 2003

Tribal archives are an essential resource for documenting cultural history. This article explores the essential archival functions of a tribal repository and addresses special concerns tribal archivists may face in managing these unique institutions. Tribal archives are growing in number, sparking new initiatives for training and collaboration among those tribes that house archives. As more and more documentation becomes available in electronic form, more repositories feel the pressure to contribute material. Electronic media and the Internet pose a number of concerns and possibilities for tribal archives and tribes as a whole. Funding is perhaps the most important factor in supporting digitization projects. There are a number of ways that archives, libraries and museums of tribes can obtain financial support. Funding agencies such as the Institute of Museum and Library Services (IMLS), the National Park Service, and the National Historical Publications and Records Commission all administer both competitive and non‐competitive grants in support of museums, libraries and archives.
Native American technology access: the Gates Foundation in Four Corners
Authors: Gordon Andrew C. , Gordon Margaret , Dorr Jessica
Published: September 2003

The Bill & Melinda Gates Foundation’s Native American Access to Technology Program (NAATP) was designed to provide computer and Internet access to Native peoples in the Four Corners area of the USA. Through this multi‐year effort, complex packages of hardware, software, installation and training have been made available to 43 tribes in 161 settings. An intensive, collaborative process resulted in a package carefully designed to fit tribal interests, circumstances and political arrangements, including multimedia (graphics‐intensive) equipment, language preservation software, and satellite connections to the Internet as necessary. This interim assessment concludes that the program has substantially increased tribal access to computing and information and has often fostered creative use of the technologies. Deeply embedded economic and political realities and their legacies remain, however, with substantial immediate and long‐term consequences.
School‐museum partnerships for culturally responsive teaching
Authors: Christal Mark
Published: September 2003

A dissertation study combined four case studies that examined school‐museum partnerships for virtual museum projects in which students did virtual reality imaging of museum objects related to their cultures. Students also researched their selected objects with the help of museum professionals, anthropologists, and community members. Project plans also specified that students would write essays to accompany the virtual museum exhibits, but that was not always accomplished. Each case is discussed, giving a brief sampling of some of the themes that emerged from them. A composite picture of the cases provided a more comprehensive description of the innovation through nine theme categories derived from the four cases. Three of the theme categories are discussed. The four cases were also examined to see what they revealed about culturally responsive teaching. Four of the ten culturally responsive elements identified in the study are discussed.
Indians on the Internet – selected Native American Web sites
Authors: Mitten Lisa
Published: September 2003

Native Americans made an early appearance on the Internet in 1994. The number of Indian‐run Web sites about Native American issues, histories and cultures continues to expand. Web sites are created and maintained by Indian tribes, organizations and individuals, and may be directed at tribal members, the non‐Indian public, or both. Major categories of Indian Web sites include tribes, organizations, education, media, businesses, music and languages. This article looks at 120 selected Web sites on these topics.
American Indian tribal Web sites: a review and comparison
Authors: Gaston Anderson Cokie
Published: September 2003

Many Native American tribes have Web sites, but the content of these sites varies depending on a number of factors, including the audience, purpose and context of the site, geographic distribution of tribal members, economic factors, tribal policies, and the digital divide. Some sites are geared primarily to non‐Native tourists and the general public, while others are designed to reach out to those tribal members who live far from Indian lands. Economic factors impact both the type of Web site the tribe can afford and the ability of tribal members to access the Internet. Tribal policies and cultural traditions determine what kind of information can be included. There are also a number of attributes that are common to most tribal Web sites. This article looks at both the similarities and the differences among American Indian tribal Web sites.
Maori access to information technology
Authors: Parker Brett
Published: September 2003

The extent of Internet access is a key indicator of the Maori people’s ability to use information technologies for social, e‐commerce and e‐government communication. The key findings from national surveys of Internet use during 2000 and 2001, together with census data, provide an indication of Internet access amongst Maori. The results show there is a substantial “digital divide” between Maori and other New Zealanders, in terms of access to the Internet and employment in information technology industries. This “divide” is likely to be due to the lower household incomes and educational outcomes of Maori adults. While Maori currently do not have the same level of access to information technology as non‐Maori, the growth in their participation has nonetheless been rapid.
Iwi archivists as recordmakers?
Authors: Falconer Sandra
Published: September 2003

This paper is a brief summary of a presentation and the ensuing discussion that was part of a workshop on recent developments in iwi (tribal) archives at the LIANZA Conference, held in Wellington, New Zealand, in November 2002. The presentation was made to an audience of Maori librarians and those who work with Maori information, who may not be accustomed to working with information from a record‐keeping perspective. The paper introduces some core issues in electronic record keeping and then looks at ways in which the lessons of electronic records management may be applied to other aspects of record keeping.
Te Mata o te Tai – the edge of the tide: rising capacity in information technology of Maori in Aotearoa‐New Zealand
Authors: Kamira Robyn
Published: September 2003

This paper argues that one can extract relevant lessons in the information technology era from one’s colonial past. One such lesson is to understand how information technologies might further impact on one’s knowledge. While there are many recent information technology projects, they are often ad hoc and in “pilot” or “trial” mode, reducing any chance of sustainability or “proof of concept”. However, experience has taught people some of the pitfalls, management and effectiveness of information technology, and the capacity to understand, select and critique is increasing. Thus, the edge of the tide creeps slowly forward.
Impact of ICT‐based distance learning: the African story
Authors: van Brakel Pieter A. , Chisenga Justin
Published: September 2003

Neither distance learning courses nor utilising information and communication technologies (ICT) to enhance these courses are new to sub‐Saharan Africa. “Long‐distance” training by correspondence has been practised here for decades. ICT as basic as e‐mail has the potential to enable the remotely situated student to interactively take part in a particular programme. Additional equipment can simulate the lecture environment by allowing the student to watch a video of a presentation while communicating via telephone. This article is an investigation of the status quo of ICT‐based distance learning in sub‐Saharan Africa. Broad trends were derived from the multitude of sources on the topic, depicting just as many examples of programmes currently being maintained. ICT inroads in Africa are addressed; the problems to acquire and maintain these are discussed, as well as ICT’s potential role in future distance learning programmes. Examples of public‐private partnerships are highlighted. It is emphasised that only through these partnerships will African tertiary institutions succeed in increasing the output of their much needed graduates.
The impact of IT on indigenous peoples
Authors: Roy Loriene , Raitt David
Published: September 2003

This Special Issue of The Electronic Library on the “Impact of information technology on indigenous peoples” gathers articles from several different countries and cultures in an effort not only to highlight the difficulties faced by indigenous peoples with accessing the Internet or using computers, but also to show how they are aiming at self‐determination and supporting their goals as sovereign nations, as well as preserving their heritage. The articles, in most cases specially written for this Issue, illustrate how tribal nations are using information technology to explore their culture, document these efforts, and share elements of their perspectives with the larger world.
Process development for PWB compatible embedded capacitors
Authors: Bhattacharya Swapan K. , Markondeya Raj P. , Balaraman Devarajan , Windlass Hitesh , Tummala Rao R.
Published: September 2003

This paper addresses materials and processes for printed wiring board compatible embedded capacitors using polymer/ceramic nanocomposites and hydrothermal barium titanate. Polymers allow low temperature fabrication appropriate to the board (MCM‐L) technology. The lower dielectric constants of the commercially available polymers can be greatly compensated by incorporating higher permittivity ceramic fillers. Materials requirements for higher capacitance density (>30 nF/cm2) have been addressed through implementation of a novel low‐temperature processable hydrothermal barium titanate film on a patterned titanium foil laminated to the PWB. Application of hydrothermal grown barium titanate is currently being evaluated using a multi‐layer system‐on‐package demonstration.
Evaluating National Capacity for Direct Participation in International Accounting Harmonization: France as a Test Case
Authors: Standish Peter
Published: September 2003

This article evaluates national capacity for direct participation in international accounting harmonization through its principal current formal institutional forum, the International Accounting Standards Board (IASB), with France as a test case. The objective is to derive propositions by which individual nation states, their indigenous accounting professions and other significant elements of their institutional framework might: (a) evaluate their present national capacity to contribute to international accounting harmonization; and (b) address policy issues relevant to development and deployment of capacity for effective engagement. The objective of the framework of analysis employed is to infer essential or desirable attributes for direct participation in international accounting harmonization by reference to the observed attributes of the initial IASB appointments. The likelihood and sustainability of direct French participation in the process is then assessed in relation to those attributes.