bluuebunny/crossref_metadata_2025 huggingface dataset:
Special Issue: Evolutionary Design
Authors: BENTLEY PETER
Published: July 2002

Throughout the natural world and our human-designed
world, design and evolution seem to go hand-in-hand. Some
of the most astonishing and complex designs known to humankind—the
embryogeny process, the immune system, the brain, the very
structure of DNA—are products of natural evolution,
not human endeavor. In addition, the progress of our own
designs seems evolutionary, as the best concepts from existing
designs are combined with some small variation to produce
the next generation of cars, computers, and indeed, most
types of human design. And now, as the papers in this and
subsequent special issues will show, our computers are
allowing us to harness the power of evolution directly,
to aid the design process.
Compilation of a specialized functional language for massively parallel computers
Authors: FRADET PASCAL , MALLET JULIEN
Published: July 2002

We propose a parallel specialized language that ensures portable and cost-predictable
implementations on parallel computers. The language is basically a first-order, recursion-less,
strict functional language equipped with a collection of higher-order functions or skeletons.
These skeletons apply on (nested) vectors and can be grouped into four classes: computation,
reorganization, communication and mask skeletons. The compilation process is described as
a series of transformations and analyses leading to SPMD-like functional programs which can
be directly translated into real parallel code. The language restrictions enforce a programming
discipline whose benefit is to allow a static, symbolic and accurate cost analysis. The parallel
cost takes into account both load balancing and communications, and can be statically
evaluated even when the actual size of vectors or the number of processors are unknown. It is
used to automatically select the best data distribution among a set of standard distributions.
Interestingly, this work can be seen as a cross-fertilization between techniques developed
within the FORTRAN parallelization, skeleton and functional programming communities.
Identification and treatment of anaemia in older patients
Authors: Casey MC , Murphy PT
Published: July 2002

Anaemia is the most common haematological problem of older patients. Given the
heterogenous nature of this group, with an age span of over 30 years, the reported
prevalence of anaemia is, not surprisingly, quite variable. However, a large survey
from the UK has reported an overall prevalence of anaemia of 20.1% in elderly
men and 13.7% in elderly women.

The types and causes of anaemia differ between elderly and younger patients. Anaemia of chronic disease becomes the commonest cause of anaemia in the older age group and reflects the increased incidence of chronic inflammation and malignancy in later years. Iron deficiency anaemia is commonly seen and due to gastrointestinal blood loss. Furthermore dietary deficiencies not only of iron, but also of folate, protein and ascorbic acid can all precipitate anaemia in the many elderly subjects who live in poor socio-economic conditions. Pernicious anaemia, as with other autoimmune conditions, is also encountered more commonly in the elderly than in the younger population. Malignant blood disorders with associated anaemia, such as myelodysplasia and leukaemia, become more frequent with advancing age.
The status of seabird colonies on the Cook Islands atoll of Suwarrow
Authors: Jones Rhys J.
Published: July 2002

Suwarrow (Suvorov) atoll is an important seabird breeding site in the central Pacific Ocean. However, it is not protected and is attractive to developers of potentially damaging aquaculture industries. In this paper I report the results of a survey conducted to establish the present status of Suwarrow's seabird colonies and to generate base-line data for measuring the effect of a proposed pearl-farm development. Between late July and early September 2000 the reef islets were surveyed for seabird chick numbers and age-states using a simple sampling method. In addition to Sooty Tern Sterna fuscata, populations of boobies Sula spp., noddies Anous spp., frigatebirds Fregata spp. and tropicbirds Phaethon spp. were assessed. Results showed that bird populations were maintaining levels similar to those from findings of surveys in 1992. Of particular note were globally significant numbers of Lesser Frigatebird Fregata ariel and Red-tailed Tropicbird Phaethon rubricauda. Migratory birds were observed with Bristle-thighed Curlew Numenius tahitiensis regularly seen. The well-being of bird-life on the islets appears to be indirectly proportional to the proximity of human activity, with birds not observed breeding on Anchorage Island – the islet most often visited by people.
‘Cultural Bosses’ as Patrons and Clients: the Functioning of the Soviet Creative Unions in the Postwar Period
Authors: Tolz Vera
Published: July 2002

The article argues that the postwar years rather than the 1930s, as hitherto has been assumed, was the period when top administrators of the Soviet creative Unions acquired their super-elite status. It shows how in this period the Union leaders finalised their control over the production and distribution of, as well as the reward for, literary and artistic work. The article looks at the reasons behind the government's conscious decision to allow a small group from the intelligentsia to become part of the state elite. It also assesses the consequences of postwar government policies towards the intelligentsia for the long-term stability of the regime.
Autonomy, Power, and Control in Palliative Care
Authors: SCOTT P. ANNE
Published: July 2002

A review of the literature on palliative care in the United
Kingdom over the last fifteen years suggests that elements such
as the development of the modern hospice, on the model developed
by Cicely Saunders (at St. Christopher's Hospice, London),
have led to major improvements in the lot of the terminally ill.
CAPITALISM, CHARITY, AND JUDAISM: THE TRIUMVIRATE OF BENJAMIN FARJEON
Authors: Persell Michelle
Published: July 2002

BENJAMIN LEOPOLD FARJEON (1838–1903) was a novelist of, at best, middling abilities who achieved a modicum of popular success working in the sentimental realist tradition. He was also Jewish, a fact that he neither avoided nor obsessed over. It is just Farjeon’s laissez-faire approach towards ethnic identity that spurs our interest today. He assumed an attitude that was only beginning to be possible in the British Empire in the middle to late Victorian period. Over the years, Farjeon has made perfunctory appearances in such familiar survey and reference materials as Richard Altick’s The English Common Reader (1957), John Sutherland’s The Stanford Companion to Victorian Fiction (1989), and Linda Gertner Zatlin’s Nineteenth Century Anglo-Jewish Novel (1981), but the only substantial piece of scholarship devoted solely to his work is Lillian Faderman’s dissertation “B. L. Farjeon: Victorian Novelist” (1967). Where Faderman provides a broad-based chronicle of Farjeon’s publications, I focus here on one aspect of his legacy — i.e., how he partook of an incipient opportunity to construct a position for Jews as Englishmen in economic terms.
Semantic interpretation of deverbal nominalizations
Authors: HULL RICHARD D. , GOMEZ FERNANDO
Published: July 2002

An algorithmic approach to the semantic interpretation of deverbal nominalizations found
in encyclopedic texts, such as support, publication and control, is described. Interpreting these
nominalizations is crucial because they are quite common in encyclopedic texts, hence a great
deal of information is represented within them. Interpretation involves three tasks: deciding
whether the nominalization is being used in a verbal or non-verbal sense; disambiguating the
nominalized verb when a verbal sense is used; and determining the fillers of the thematic roles
of the verbal concept or predicate of the nominalization. A verbal sense can be recognized
by the presence of modifiers that represent the arguments of the verbal concept. It is these
same modifiers which provide the semantic clues to disambiguate the nominalized verb. In
the absence of explicit modifiers, heuristics are used to discriminate between verbal and
non-verbal senses. A correspondence between verbs and their nominalizations is exploited so
that only a small amount of additional knowledge is needed to handle the nominal form.
These methods are tested in the domain of encyclopedic texts and the results are shown.
Jonathan Harvey's Quest of Spirit through music
Authors: DE GROOT ROKUS
Published: July 2002

In this review of Jonathan Harvey's In Quest of Spirit: Thoughts on Music,
special attention is given to the question of how the musical domain may be
related to the spiritual one, e.g. by representation (‘giving a
picture’, ‘portrayal’), symbolism, parallelism, mediation
and ‘overlap’. Harvey's sources and personal experiences are
discussed, and the relationships between the different parts the author
plays in his book assessed: the spiritual seeker, the thinker about music,
and the composer. A possible conflict between spiritual search and
professional music composition is pointed out, given an implicit tendency
in the former to surrender, and in the latter to mastery and control. One of
the questions looked into is how music, especially by articulating contrasts,
may convey insight into ‘unity’. Other issues discussed are the
possible addiction to music as a spiritual means at the expense of the
spiritual quest itself; the alleged special role of electronics and
spectrality in the composition of spiritual music; the possibility of
developing spiritual listening; and possible modernist overtones in the
notion of making progress as a composer while mediating spiritual insights
and experiences.
The Framework for the Assessment of Children in Need and Their Families
Authors: Gray Jenny
Published: July 2002

The Framework for the assessment of children in need and their families
(Department of Health et al., 2000) has been developed to provide a
systematic way of analysing, understanding and recording what is
happening to children and young people within their families and the
wider context of the community in which they live. From such an
understanding of what are inevitably complex issues and inter-relationships, clear professional judgements can be made. These
judgements include whether the child being assessed is in need, whether
the child is suffering or likely to suffer significant harm, what actions must
be taken, and which services would best meet the needs of this particular
child and family. The Assessment Framework was issued jointly by the
Department of Health, Department for Education and Employment and
Home Office. It was issued as Section 7 Guidance under the Local
Authority Social Services Act 1970, which means it must be complied with
unless local authorities can justify why not.
An SH2-domain-containing kinase negatively regulates the phosphatidylinositol-3 kinase pathway
Authors: Moniakis John , Funamoto Satoru , Fukuzawa Masashi , Meisenhelder Jill , Araki Tsuyoshi , Abe Tomoaki , Meili Ruedi , Hunter Tony , Williams Jeffrey , Firtel Richard A.
Published: July 2002

SHK1 is a novel dual-specificity kinase that contains an SH2 domain in its C-terminal region. We demonstrate that SHK1 is required for proper chemotaxis and phagocytosis. Mutant shk1 null cells lack polarity, move very slowly, and exhibit an elevated and temporally extended chemoattractant-mediated activation of the kinase Akt/PKB. GFP fusions of the PH domain of Akt/PKB or the PH-domain-containing protein CRAC, which become transiently associated with the plasma membrane after a global stimulation with a chemoattractant, remain associated with the plasma membrane for an extended period of time in shk1null cells. These results suggest that SHK1 is a negative regulator of the PI3K (phosphatidylinositol-3kinase) pathway. Furthermore, when a chemoattractant gradient is applied to a wild-type cell, these PH-domain-containing proteins and the F-actin-binding protein coronin localize to its leading edge, but in an shk1 null cell they become randomly associated with the plasma membrane and cortex, irrespective of the direction of the chemoattractant gradient, suggesting that SHK1 is required for the proper spatiotemporal control of F-actin levels in chemotaxing cells. Consistent with such functions, SHK1 is localized at the plasma membrane/cortex, and we show that its SH2 domain is required for this localization and the proper function of SHK1.
Ionization chambers for monitoring the position and tilt of X-ray beams
Authors: Arndt U. W. , Kyte M. P.
Published: July 2002

An air-filled ionization chamber with a three-way split anode can be used to measure the tilt and the translation of a collimated X-ray beam with respect to the chamber axis.
An introductory exercise in Fourier synthesis and structure-factor calculation for undergraduates, using anEXCELworkbook
Authors: Taylor Max R.
Published: July 2002

AnEXCEL(Microsoft Corp.) workbook has been configured to enable spreadsheet calculation of two-dimensional structure factors and Fourier syntheses. An exercise in which it can be used by undergraduate students to solve the structure of potassium bicarbonate in projection is described. The package is available from the internet.
Resonant X-ray diffraction using high-resolution image-plate data
Authors: Ehrenberg H. , Knapp M. , Hartmann T. , Fuess H. , Wroblewski T.
Published: July 2002

The experimental setup for the collection of synchrotron X-ray powder diffraction data from samples with high absorption (μR> 10) is described. It consists of a combination of a vacuum chamber with an image-plate system. A numerical absorption correction for the applied geometry has been derived and the data were corrected accordingly. Values forf ′(Er) andf ′′(Er) were refined from eight measurements on Er5Re2O12above and below the ErLIIIabsorption edge. Successful refinement of the crystallographic data has verified the high quality of the collected intensities.
An imaging-plate detector for small-angle neutron scattering
Authors: Cheng Y. T. , Mildner D. F. R. , Chen-Mayer H. H. , Sharov V. A. , Glinka C. J.
Published: July 2002

Small-angle neutron scattering (SANS) measurements have been performed on long-flight-path pinhole-collimation SANS instruments using, as a two-dimensional position-sensitive detector, both a neutron imaging plate, incorporating gadolinium, and a two-step transfer method, with dysprosium foil as the image transfer medium. The measurements are compared with corresponding data taken using conventional position-sensitive gas proportional counters on the SANS instruments in order to assess the viability of the imaging techniques. The imaging plates have pixel sizes of about two orders of magnitude smaller than those of the gas proportional counter. The reduced pixel size provides definite advantages over the gas counter in certain specific situations, namely when limited space necessitates a short sample-to-detector distance, when only small samples (comparable in size to the detector pixels) are available, or when used in conjunction with focusing beam optics.
Analysis of the asymptotic properties of X-ray line broadening caused by dislocations
Authors: Groma I. , Székely F.
Published: July 2002

A new evaluation method and its application are discussed in detail for the determination of some important statistical parameters of a dislocation assembly, namely the average dislocation density, the average fluctuation of the dislocation density and the average polarization, from the X-ray diffraction line profile. The method is based only on the analytical properties of the strain field of dislocations, regardless of the actual form of the dislocation distribution, so it can also be applied to inhomogeneous dislocation structures. The applicability of the evaluation procedure is demonstrated for broadened Bragg peaks of deformed Cu single crystals and of nanocrystalline Cu produced by inert-gas condensation.
Small-angle X-ray scattering by PVP–water mixtures
Authors: van der Elsken Jan , Bras Wim , Michielsen Jan
Published: July 2002

Small-angle X-ray scattering experiments reveal the formation of large-scale structures when a 60 wt% poly(vinylpyrrolidone) (PVP)–water mixture is cooled to 260 K. The formation of these structures leads to an enhancement of continuous small-angle scattering with decreasing temperature. This is accompanied by the appearance of sharp Bragg peaks that have a very short lifetime. The scattering angles of these peaks are in accordance with a hexagonal columnar structure. It appears that such structures occasionally live long enough to undergo rotational Brownian motion.
Asymmetries of the Voigt line shape
Authors: Flores-Llamas H.
Published: July 2002

Two cases of asymmetric Voigt line shape are analysed, from which two power series expansions are obtained. In the first case, the line shape is built as a linear combination of the Voigt line shape (VLS) and its derivatives. This is valid for small asymmetries. The second line shape is built as the sum of the VLS and an odd-parity line shape; this second case is valid for intermediate asymmetries. An improved line shape, defined as a linear combination of the traditional VLS with the odd-parity line shape, is also presented. The improved procedure and intermediate case are particularly useful for dealing with X-ray line shapes at lower diffraction angles, as is demonstrated by a practical example.
Peak profile function for synchrotron X-ray diffractometry
Authors: Ida T. , Hibino H. , Toraya H.
Published: July 2002

A formula of the instrumental function for a high-resolution synchrotron X-ray diffractometer, equipped with a flat crystal analyser and a set of Soller slits for limiting the axial divergence of the diffracted beam, has been derived. The formula incorporates the effects of (i) the axial divergence of the diffracted beam limited by the Soller slits, (ii) the Bragg angle of the flat crystal analyser, and (iii) the tilt angle defined as the deviation of the normal direction of the analyser face from the goniometer plane. The model profile function given by the convolution of a Lorentzian function with the instrumental function has been applied to fit the experimental diffraction peak profiles of standard Si powder (NIST SRM640b) measured with a high-resolution synchrotron X-ray diffractometer, MDS, on beamline BL4B2 at the Photon Factory in Tsukuba. The convolution has been calculated by applying an efficient algorithm for numerical integration. The profile function reproduces not only the experimental profiles measured with a well aligned crystal analyser, but also significantly distorted profiles arising from misalignment of the analyser, withRpvalues within 1.4%, by varying only the instrumental parameter for the tilt angle. It is suggested that further convolution with a Gaussian distribution is practically not necessary for the model instrumental function to fit the data collected with MDS. More rapid computation can be achieved by applying an analytical formula of the profile function, when the tilt angle of the crystal analyser is within about 0.2°.
Solution structure of a biological bimolecular electron transfer complex: characterization of the photosynthetic reaction center-cytochrome c2 protein complex by small angle neutron scattering
Authors: Tiede D. M. , Littrell K. , Marone P. A. , Zhang R. , Thiyagarajan P.
Published: July 2002

The structures of kinetically distinct electron transfer complexes formed between the photosynthetic reaction center from Rhodobacter sphaeroides R-26, and a water-soluble cytochrome c2 were characterized using small angle neutron scattering, SANS. Reaction center-cytochrome c2 complexes, RC-C, exhibiting predominately single exponential electron transfer kinetics were found to be 1:1 molar complexes, consistent with a low resolution, co-crystal, x-ray structure (Adir et al., 1996), provided that the cofactor separation was adjusted to 14 ± 3 Å. Other RC-C configurations are consistent with SANS data, but are distinguishable by cofactor separation. RC-C preparations exhibiting more complex kinetics were found to have a particle volume markedly greater than that of a 1:1 complex. These results suggest that RC aggregation is associated with the variation in kinetics reported in the literature, and provide evidence that the model for the 1:1 complex in co-crystals is relevant to the solution environment.
The diameter of the DNA superhelix decreases with salt concentration: SANS measurements and Monte Carlo simulations
Authors: Hammermann M. , Brun N. , Klenin K.V. , May R. P. , Tóth K. , Langowski Jorg
Published: July 2002

We have measured the static form factor of superhelical DNA by SANS in dilute aqueous solution as a function of salt concentration. Theoretical static form factors were calculated by Monte Carlo simulations. Simulated and measured form factors are in very good agreement and can be interpreted in terms of the superhelix diameter, which decreases from (16.0±0.9) nm at 10 mM to (9.0±0.7) nm at 100 mM Na+ concentration. This result contradicts a lateral collapse of the DNA superhelix in physiological salt concentrations as recently found by cryo-electron microscopy.
Modelling of small-angle X-ray scattering data using Hermite polynomials
Authors: Swain A. K. , Parida J. K. , Bisoyi D. K. , Mazumder S. , Mohanty A. K.
Published: July 2002

A new algorithm, called the term-selection algorithm (TSA), is derived to treat small-angle X-ray scattering (SAXS) data by fitting models to the scattering intensity using weighted Hermite polynomials. This algorithm exploits the orthogonal property of the Hermite polynomials and introduces an error-reduction ratio test to select the correct model terms or to determine which polynomials are to be included in the model and to estimate the associated unknown coefficients. With noa prioriinformation about particle sizes, it is possible to evaluate the real-space distribution function as well as three- and one-dimensional correlation functions directly from the models fitted to raw experimental data. The success of this algorithm depends on the choice of a scale factor and the accuracy of orthogonality of the Hermite polynomials over a finite range of SAXS data. An algorithm to select a weighted orthogonal term is therefore derived to overcome the disadvantages of the TSA. This algorithm combines the properties and advantages of both weighted and orthogonal least-squares algorithms and is numerically more robust for the estimation of the parameters of the Hermite polynomial models. The weighting feature of the algorithm provides an additional degree of freedom to control the effects of noise and the orthogonal feature enables the reorthogonalization of the Hermite polynomials with respect to the weighting matrix. This considerably reduces the error in orthogonality of the Hermite polynomials. The performance of the algorithm has been demonstrated considering both simulated data and experimental data from SAXS measurements of dewaxed cotton fibre at different temperatures.
Geometrical equatorial aberrations in a Bragg–Brentano powder diffractometer with a linear position-sensitive detector
Authors: Słowik Jacek , Zięba Andrzej
Published: July 2002

The use of a position-sensitive detector with a Bragg–Brentano diffractometer implies the registration of the diffracted beam at a finite distance from the true focusing point. This gives rise to an aberration which is characterized by the peak intensity profileI(y) and its parameters, the shift of the centre of gravity 〈y〉 and the profile variationW. These are calculated in terms of exact expressions and approximate results. The obtained closed formulae for 〈y〉 andWaugment analogous calculations for other aberrations, tabulated by Parrish and Wilson in theInternational Tables for X-ray Crystallography(Vol. III, 1995). Calculation of the peak profiles is verified by experiment.
A furnace forin situX-ray diffraction studies of insertion processes in electrode materials at elevated temperatures
Authors: Eriksson T. , Andersson A. M. , Bergström Ö. , Edström K. , Gustafsson T. , Thomas J. O.
Published: July 2002

A furnace is described forin situX-ray diffraction studies, in transmission mode, of structural changes in electrode materials for Li-ion (polymer) batteries in the ambient to 300°C temperature range. The method exploits the thin flat-cell geometry of the lithium-polymer battery concept. The flat sample is able to oscillate about a horizontal axis in its own plane in the X-ray beam, to provide better averaging during the diffraction experiment. The use of the device is demonstrated in a study of lithium intercalation in graphite (a commonly used anode material in lithium-ion batteries) during electrochemical cycling and storage at 70°C.
Optical monitoring of freeze-trapped reaction intermediates in protein crystals: a microspectrophotometer for cryogenic protein crystallography
Authors: Sakai Keisuke , Matsui Yasuhiro , Kouyama Tsutomu , Shiro Yoshitsugu , Adachi Shin-ichi
Published: July 2002

A microspectrophotometer for cryogenic protein crystallography is described. It is capable of measuring visible absorption spectra (350–800 nm) of a single crystal during X-ray data collection. The microspectrophotometer is designed to minimize the level of stray light by using a double monochromator and an optical microscope equipped with two field diaphragms and a pinhole. In this system, a thick crystal with an optical density of ∼5 is measurable. In order to demonstrate the performance of the system, the absorption spectra of the unphotolyzed state and the primary photoreaction intermediate of bacteriorhodopsin in the P622 crystal have been measured under a flow of cold nitrogen gas at 100 K.
Temperature-dependent gyration tensor of LiIO3single crystal using the high-accuracy universal polarimeter
Authors: Herreros-Cedrés J. , Hernández-Rodríguez C. , Guerrero-Lemus R.
Published: July 2002

The gyration tensor of LiIO3has been measured in the temperature range between 293 and 493 K at a wavelength of 632.8 nm. Optical activity and birefringence for the (010) plane were determined by using a high-accuracy universal polarimeter (HAUP). Likewise, optical activity for the (001) plane was studied by using a conventional polarimeter in the same temperature range at 632.8 nm wavelength. In the latter case, a modulation of the optical activity was observed. This effect can be explained by multiple reflections within the slab with a high degree of plane parallelism.
Illustration of the anisotropic Porod law
Authors: Ciccariello S. , Schneider J.-M. , Schönfeld B. , Kostorz G.
Published: July 2002

A simple derivation of the leading asymptotic term of small-angle scattering intensities relevant to anisotropic particulate samples is reported. The result is illustrated for the case of ellipsoidal particles. It is discussed under what circumstances the anisotropic Porod law can be applied to scattering intensities collected by a two-dimensional detector.
A precise and accurate method of measuring Kendrew model coordinates
Authors: Frentrup M. A. , Tulinsky A.
Published: July 2002

Polar coordinates of a Kendrew model of α-chymotrypsin (α-CHT) have been measured with a surveyor's transit and a cathetometer to a high degree of accuracy and precision. Bond distances calculated independently for more than 200 independent amino-acid residues have standard deviations of 0.10 Å or less, the torsion angle ω has a standard error of 7°, and the τ angle is precise to 3°. The measured coordinates of about 1800 non-hydrogen atoms of one molecule of the α-CHT dimer fit a set of idealized polypeptide coordinates with a r.m.s. deviation of 0.17 Å, while the average deviation is 0.15 Å.
Studies on triple orthovanadates: synthesis and crystallographic data on triple orthovanadates, CdLnTh(VO4)3
Authors: Nabar M. A. , Mhatre B. G. , Vasaikar A. P.
Published: July 2002

The results of crystallographic studies of the thermally preparable orthovanadates, CdLnTh(VO4)3 are communicated. The data suggest that all these compounds are isomorphous, possessing zircon (ZrSiO4) structure with space group I41/amd and four molecules per unit cell.
A uniaxial stress apparatus for single-crystal X-ray diffraction on a four-circle diffractometer: application to silicon and diamond
Authors: d'Armour H. , Denner W. , Schulz H. , Cardona M.
Published: July 2002

An apparatus for applying uniaxial stress to a single-crystal has been constructed. The stress is produced by turning a differential screw and is measured by a strain gauge. The device fits on a goniometer of a four-circle diffractometer and can rotate around all three axes of the goniometer without restrictions. The lattice constants of Si stressed along [111] were measured and compared with ultrasonically measured elastic constants. The internal stress parameter ξ was calculated from changes of the intensity of the 600 reflection: ξ = 0.74 ± 0.04, larger than the value generally accepted (ξ = 0.64 ± 0.04). The implications of this unexpected result are discussed.
Information retrieval from X-ray small-angle scattering with polychromatic (`white') synchrotron radiation
Authors: Glatter O. , Laggner P.
Published: July 2002

The possibilities of obtaining structural information from X-ray small-angle scattering experiments with `white' polychromatic synchrotron radiation using line collimation are investigated by numerical simulation. Theoretical scattering curves of geometrical models were smeared with the appropriate wavelength distributions and slit-length functions, afflicted by statistical noise, and then evaluated by identical methods as normally used for experimental data, as described previously [program ITP; Glatter (1977). J. Appl. Cryst.
10, 415–421]. It is shown that even for a wavelength distribution of 50% half width, the information content is not limited to the parameters derived from the central part of the scattering curves, i.e. the radius of gyration and the zero-angle intensity, but also allows qualitative information on particle shape via the distance distribution function p(r). By a `hinge-bending model' consisting of two cylinders linked together at different angles it is demonstrated that changes in the radius of gyration amounting to less than 5% can be detected and quantified, and the qualitative changes in particle shape be reproduced.
Detwinning cell for high-transition-temperature atmosphere-sensitive ferroelastic crystals
Authors: Abrahams S. C. , Bernstein J. L. , Chaminade J. P. , Ravez J.
Published: July 2002

A universal cell is reported for detwinning ferroelastic crystals, with transition temperatures that range from 300 to 1300 K, in a controlled atmosphere. A carefully oriented compressive stress on the order of 0.1–1 MN m−2 is applied to the twinned crystal at room temperature. The crystal temperature is raised from 300 K through the phase transition and is slowly lowered again under stress. The cell has been used to detwin crystals of Na5W3O9F5 with a Curie temperature of 800 K in an atmosphere of flowing high-purity oxygen, and crystals of Rb2KMoO3F3 with a Curie temperature of 328 K in air. Successful detwinning is demonstrable by the complete conversion of high-angle multiple-component line profiles diffracted by the as-grown crystal to single-component reflection profiles.
Protein model building by the use of a constrained–restrained least-squares procedure
Authors: Herzberg O. , Sussman J. L.
Published: July 2002

The use of a macromolecular model building program, CORELS, which fits a series of constrained groups to a set of approximate guide coordinates, while simultaneously restraining the stereochemistry between groups, is described for protein molecules. The results of an application of this program to hen egg white lysozyme are discussed.
Microdiffraction from stacking faults and twin boundaries in F.c.c. crystals
Authors: Zhu J. , Cowley J. M.
Published: July 2002

Electron microdiffraction patterns have been obtained from regions of diameter about 15 Å in thin crystals of stainless steel containing twin boundaries and stacking faults. The diffraction spots show splittings which are characteristic of the type of defect present as a result of interference effects in the coherent convergent electron beam. The observations of spot splitting are in good agreement with calculations based on simple theoretical models. In conjunction with previous work on antiphase domain boundaries [Zhu & Cowley (1982). Acta Cryst. A38, 718–724] these results suggest that the observation of spot splitting is of general relevance for the study of all planar faults in thin crystals.
The many-beam moiré effect in electron micrographs of epitaxic Sn/SnTe layers
Authors: Kranjc K. , Kunstelj D. , Pećina P. , Marinković V.
Published: July 2002

The many-beam dynamical theory of moiré fringes of Gevers [Phys. Status Solidi (1963). 3, 2289–2297] has been applied to the parallel moiré case and the results have been verified on epitaxically grown Sn/SnTe specimens showing the sensitivity of moiré patterns to the presence of systematic reflections. The Fourier analysis of the calculated intensity profiles showed that each additional diffracted beam gives rise to a new term in the Fourier series so that the profile can be sinusoidal only in the two-beam approximation. The same result has been obtained recently by Pardo, Pariset & Renard [Phys. Status Solidi A. (1981). 64, 283–295], who applied a slightly different theoretical approach to Sb/Bi specimens. It is shown that the corrections to scattering factors for temperature effects are not important since they do not affect the general character of the moiré profiles. Some experiments were performed showing the dependence of the moiré pattern on the number of beams that are transmitted through the objective aperture. The effect of the gradual thinning of one layer on the moiré pattern could be reproduced by computer simulation.
Generalization of the parallel position in diffraction using elastically curved crystals
Authors: Arrott A. S. , Templeton T. L.
Published: July 2002

A theoretical and experimental study of double-crystal rocking curves with elastically deformed silicon wafers yields the result that rotating one of the crystals through 180° can change the peak intensity by a large factor, limited only by the sharpness of the intrinsic mosaic spread. The conventional double-crystal rocking curve with equivalent scattering vectors in what is called the parallel position has its counterpart for two crystals with different scattering vectors if each crystal is bent to its proper radius of curvature. Like the parallel-position case, the collimation does not enter into the width of the rocking curve. The rocking curve can be sharper than the usual parallel-position convolution of the two mosaic spreads. The often observed lack of agreement between rocking curves in what seem to be identical geometries is explained as a rotation of the mean of the mosaic spread across a crystal, which is equivalent to a bent crystal.
Absolute energy calibration of X-ray radiation from synchrotron sources
Authors: Pettifer R. F. , Hermes C.
Published: July 2002

A new apparatus and technique to determine the absolute energy of X-rays from a synchrotron source were used to establish the absolute energy of the zinc metal K absorption edge [9661.1(2) eV] and to measure systematic errors in the angular settings of a typical rotation table used for X-ray spectroscopy. These errors have a period of 1° associated with the worm gear of the rotation table and should provide a warning to other synchrotron radiation spectroscopists that systematic errors exist in experimental data. The technique relies on determining the orientation of a static silicon crystal with respect to the incoming beam by establishing degenerate reflections with differing Miller indices. Absolute energies can be determined for X-rays with energies greater than 6 keV. An analysis of the system shows that the technique is also useful for the accurate characterization of the monochromator resolution.
Observations of growth defects in berlinite by high-temperature X-ray topography
Authors: Zarka A. , Capelle B.
Published: July 2002

Growth defects in a synthetic berlinite sample were studied at high temperature (300–500 K) by X-ray topography. Preliminary observations of contrast changes with temperature are reported.
Crystal data for 1.3-dibromo-5-methylbenzene at 293 K
Authors: Belaaraj A. , Chanh N. B. , Haget Y. , Tauler E.
Published: July 2002

The title compound C7H6Br2 (also called 3,5-dibromotoluene) is orthorhombic, space group P212121 with a = 14.426(2), b = 13.636(2), c = 4.076(1) Å, V = 801.8(3) Å3, Z = 4, Dx
= 2.071 Mg m−3. The space group and preliminary cell parameters have been determined by single-crystal diffraction methods (Bragg, Weissenberg and precession patterns). The cell dimensions have been refined by least squares from accurate powder diffractometer data recorded at T = 293(1) K (quartz as internal standard, Cu Kα
1−Kα
2 correction so that λ = 1.54056 Å). The indexed powder data are given. No phase transition is detected between 123 K and the melting point 311.1(2) K (differential scanning calorimetry and Guinier–Lenné analysis). The results show that 1,3-dibromo-5-methylbenzene is isomorphous with 1,3,5-trichlorobenzene and 1,3,5-tribromobenzene. The JCPDS Diffraction File No. For C7H6Br2 is 36-1991.
Oscillatory deviations from Porod's law in the intensities scattered by some glasses
Authors: Ciccariello S. , Benedetti A.
Published: July 2002

The oscillatory deviations with respect to the Porod asymptote, observed in the small-angle X-ray intensities scattered by some selenium ruby glasses, are explained in terms of a finite discontinuity of the second-order derivative of the correlation function. The best fit of the intensity allows the value of the discontinuity to be determined as well as the point at which it occurs. The physical implications of these results are discussed.
Evidence of a single-q incommensurate phase in quartz by synchrotron X-ray diffraction
Authors: Zarka A. , Capelle B. , Petit M. , Dolino G. , Bastie P. , Berge B.
Published: July 2002

X-ray scattering is used to demonstrate the existence in quartz of an incommensurate phase with a single modulation when a uniaxial stress is applied in the X Y plane. Good agreement with earlier neutron scattering experiments is found.
Mirror and Bragg reflections of neutrons at a nuclear resonance
Authors: Batigun C. M. , Brugger R. M.
Published: July 2002

A set of experiments has observed the mirror reflection and Bragg diffraction of neutrons at the energy of a low-lying nuclear resonance of 115In. The reflector was a mirror of In metal with the resonance at 1.457 eV. The mirror reflection for different angles of incidence was measured and sets of data showing the relative reflectivities were obtained. For the Bragg diffraction experiment the crystal was a wafer of InP and several examples of Bragg reflections near 1.456 eV were measured.
X-ray diffraction with a four-reflection monochromator
Authors: Slusky S. E. G. , Macrander A. T.
Published: July 2002

A formula is derived for simulating rocking-curve measurements made with an X-ray diffractometer fitted with a four-reflection monochromator. The derivation is carried out both graphically and algebraically. Results of a simulation using this formula are then compared with experimentally obtained rocking curves. The rocking curves were obtained using a diffractometer with a four-reflection monochromator that uses 440 reflections from two channel-cut germanium crystals. The experimental data comprise 200, 400, 600, 511, 711, 622, 422 and 444 reflections from thick single-crystal indium phosphide grown by the vertical-gradient freeze technique. The simulated data correlate well with the experimental data, although the simulations consistently show somewhat higher reflectivities and narrower linewidths than the experiment, indicating the existence of broadening mechanisms not included in the simulation that are affecting the experiment.
Rapid small-angle X-ray diffraction of a tonically contracting molluscan smooth muscle recorded with imaging plates
Authors: Tajima Y. , Okada K. , Yoshida O. , Seto T. , Amemiya Y.
Published: July 2002

Small-angle X-ray diffraction patterns from the anterior byssus retractor muscles of Mytilus edulis contracting tonically in response to stimulation with acetylcholine were recorded in a 30 s exposure with synchrotron radiation and a high-sensitivity X-ray area detector called an imaging plate. The 190 Å layer line from the thin filaments increased in intensity with increase in tonic tension up to 6 x 104 kg m−2. Above this value, the layer-line intensity remained almost constant and comparable to that for a contracting skeletal muscle, indicating that the same structural changes of the thin filaments occur in both muscles.
A high-resolution multiple-crystal multiple-reflection diffractometer
Authors: Fewster P. F.
Published: July 2002

A high-resolution multiple-reflection diffractometer has been built to study crystals distorted by epitaxy and defects in nearly perfect crystals. The diffractometer combines the merits of the two-crystal four-reflection monochromator (to define a narrow wavelength range with a tailless reflectivity profile) and an analyser crystal to select the angular range diffracted from the sample crystal. The diffractometer is operated in two modes. In the first the sample and analyser rotations are coupled to obtain near-perfect rocking curves from distorted crystals, and in the second mode the two axes are uncoupled to obtain a diffraction space map for studying the diffuse scattering. The simulation of these profiles and maps based on dynamical theory is presented. The former allows complex structures to be analysed and the latter case, by deconvolving the dynamical scattering in these maps, permits a complete interpretation of the kinematic scattering.
Absolute configuration, polarity, morphology and optical activity of α-LiIO3
Authors: Yang H.-g. , Zhang D.-f. , Chen W.-c. , Li Y.-y.
Published: July 2002

The absolute configuration of α-LiIO3 crystals has been reinvestigated. The redetermination of the absolute configuration is in agreement with a report by Stadnicka, Glazer & Moxon [J. Appl. Cryst. (1985), 18, 237–240]. Special attention should be paid to the selection of Bijvoet pairs in these and similar crystals. The signs of the piezoelectric and pyroelectric coefficients have been verified and correlated with the spontaneous polarization. The pyroelectric coefficient p
3 was −4.4 × 10−5 C m−2 K−1 at 180 K. The correlation between the optical activity and the morphology of the crystals is discussed.
Effect of stress from the glue on single-crystal X-ray intensities at high or low temperatures
Authors: Argoud R. , Muller J.
Published: July 2002

For high- or low-temperature single-crystal X-ray data collection, the glues used to bind crystals to silica rods may induce strong modifications of the intensities. When an yttrium iron garnet (YIG) crystal was cooled, reflections which were equivalent at room temperature became different. This is explained by strong stresses of the glue on the crystal which lead to an anisotropic modification of the secondary extinction. At low temperatures, `glues' such as beeswax or paraffin do not exert stresses.
Permanent cooling of protein crystals by a collinear air flow
Authors: Rossi F. A.
Published: July 2002

In order to cool protein crystals a commercially available airstream cooling apparatus was remodeled to fit the Enraf–Nonius precession camera and the Arndt–Wonacott rotation camera for simultaneous use. The device is mechanically refrigerated. The operating temperatures are in the range of 242 to 335 K. Permanent operation for many months causes no freezing problems.
X-ray diffuse scattering of a decomposing hexagonal alloy
Authors: Barabash R. I. , Demin S. A. , Krivoglaz M. A. , Chuistov K. V.
Published: July 2002

A new type of X-ray diffuse scattering has been found in the early stages of decomposition of the hexagonal phase of Mn–44at.% Al. The diffuse scattering is observed mainly within the basal plane of the reciprocal lattice and differs for the 10{\bar 1}l and 11{\bar 2}l points. Theoretical calculations of the X-ray diffuse scattering according to the kinematic scattering theory have been performed for the elastically isotropic and anisotropic cases and for precipitates of various forms and orientations with and without a depleted layer surrounding them. In the latter case, a zero-intensity region near the reciprocal-lattice points occurs. There are cases of good agreement between the experimental results and calculations for the precipitates with a depleted layer.
The pressure-induced transformation B1 to B2 in actinide compounds
Authors: Gerward L. , Olsen J. S. , Steenstrup S. , Benedict U. , Dabos-Seignon S.
Published: July 2002

The phase transformation from NaCl structure (B 1) to CsCl structure (B2) in actinide compounds has been studied using X-ray powder diffraction in the pressure range up to about 60 GPa. It is shown that the transition is sluggish, has a strong hysteresis and is accompanied by a volume change in the range 8–12%. These features are similar to those of the corresponding transition in the alkali halides and other B1 compounds, indicating a common mechanism for the transformation as concerns the lattice geometry.
Automatic searching of an asymmetric unit from the space-group symbol
Authors: Cascarano G. , Giacovazzo C. , Spagna R.
Published: July 2002

A program for the automatic definition of an asymmetric unit is described. Starting from the space-group symbol, an asymmetric unit is automatically calculated by means of a simple algorithm in the case of space groups up to the orthorhombic system. For higher symmetry a tabulation is used.
Using CPS120 (curved position-sensitive detector covering 120°) powder diffraction data in Rietveld analysis. The dehydration process in the zeolite thomsonite
Authors: Ståhl K. , Thomasson R.
Published: July 2002

A powder diffractometer (CPS120 by INEL) equipped with a position-sensitive detector covering 120° in 2θ has been tested and the data have been successfully used with the Rietveld method. The detector was found to have a characteristic variation in linearity of ±1.5%. A calibration compound with well known 2θ values was used to determine a cubic spline calibration function to describe the 2θ
versus channel-number function, which was then incorporated in the Rietveld analysis program. A procedure is also described to correct for air and capillary scattering, taking sample absorption into account. The methods have been applied to a structure refinement of quartz and to a study of the dehydration process of the zeolite thomsonite. Quartz: Rp
= 11.0%, Rw
= 14.0% and RB
= 7.9%, based on 10 < 2θ < 116.3° in 3470 steps, λ = 1.540598 Å. Space group P312, Z = 3, a = 4.91201 (7), c = 5.40301 (5) Å, x(Si) = 0.4702 (3), B
ave(Si) = 0.77 (6) Å2, x(O) = 0.4112 (6), y(O) = 0.2712 (5), z(O) = −0.2811 (4) and B
ave(O) = 1.0 (1) Å2. Thomsonite: Rp
= 8.18%, Rw
= 11.04% and RB
= 3.33%, based on 10 < 2θ < 110° in 3270 steps. Space group Pncn, Z = 4, a = 13.0778 (3), b = 13.0398 (3) and c = 13.1970 (3) Å. The unit cell changes continuously with increasing dehydration temperatures up to 523 K, at which a = 12.9725 (3), b = 12.9537 (3) and c = 13.2288 (3) Å. In this first dehydration step, the W3 and W4 molecules coordinated to the Ca/Na site are lost and the Ca/Na and W1 sites are shifted approximately 0.3 Å from their original positions towards the framework O atoms. After dehydration at 573 K, the mode of unit-cell variations is changed: a = 12.908 (3), b = 13.039 (3) and c = 13.034 (3) Å. In this dehydration step, W1 is lost. The W2 site appears unaffected by the dehydration below 573 K. On dehydration above 573 K, the diffraction intensities decrease as the compound becomes amorphous.