bluuebunny/crossref_metadata_2025 huggingface dataset:
Developmental effects of early immune stress on aggressive, socially reactive, and inhibited
behaviors
Authors: GRANGER DOUGLAS A. , HOOD KATHRYN E. , DRESCHEL NANCY A. , SERGEANT ERIC , LIKOS ANDREA
Published: July 2002

The origins of individual differences in social development are examined in relation to early
stress (immune challenge) and social milieu (maternal behavior) in a genetic–developmental
analysis using an animal model. Neonatal male mice (5 or 6 days of age) from two lines of mice
selectively bred for high versus low levels of inter-male aggressive behavior received a standard
immune challenge (i.p. injections of 0.05 mg/kg endotoxin or saline). Animals were reared by
their line-specific biological dam or by a foster dam from a line bred without selection. Adult
levels of social behaviors were assessed in a dyadic test (age 45–50 days). Mice from the
high-aggressive line show more developmental sensitivity to immune challenge than mice from the
low-aggressive line, and line differences persist regardless of the early maternal environment. As
adults, endotoxin-treated mice from the high-aggressive line have lower levels of aggressive
behavior, longer latency to attack, and higher rates of socially reactive and inhibited behaviors
compared to saline controls. Developmental effects of endotoxin in the low-aggressive line are
minimal: endotoxin increases socially reactive behaviors, compared to saline controls, but only for
mice reared by their biological dams. Rearing by foster dams increases social exploration in the
low-aggressive line. The findings raise novel questions regarding the openness of behavioral
systems to effects of nonobvious but omnipresent features of the environment, such as antigenic
load, how these effects are integrated to affect social development and psychopathology, and the
nature of intrinsic factors that contribute to individual differences in sensitivity to early stressors.
Using randomization to make recursive matrix algorithms practical
Authors: LÊ DINH , STOTT PARKER D.
Published: July 2002

Recursive block decomposition algorithms (also known as quadtree algorithms when the
blocks are all square) have been proposed to solve well-known problems such as matrix
addition, multiplication, inversion, determinant computation, block LDU decomposition and
Cholesky and QR factorization. Until now, such algorithms have been seen as impractical,
since they require leading submatrices of the input matrix to be invertible (which is rarely
guaranteed). We show how to randomize an input matrix to guarantee that submatrices meet
these requirements, and to make recursive block decomposition methods practical on well-conditioned input matrices. The resulting algorithms are elegant, and we show the recursive
programs can perform well for both dense and sparse matrices, although with randomization
dense computations seem most practical. By ‘homogenizing’ the input, randomization provides
a way to avoid degeneracy in numerical problems that permits simple recursive quadtree
algorithms to solve these problems.
String rewriting and homology of monoids
Authors: COHEN DANIEL E.
Published: July 2002

Results of Anick (1986), Squier (1987), Kobayashi (1990), Brown
(1992b),
and others, show
that a monoid with a finite convergent rewriting system satisfies a homological
condition known as FP∞.

In this paper we give a simplified version of Brown's proof, which
is
conceptual, in
contrast with the other proofs, which are computational.

We also collect together a large number of results and examples of
monoids and groups
that satisfy FP∞ and others that do not. These
may provide techniques for showing that
various monoids do not have finite convergent rewriting systems, as well
as explicit
examples with which methods can be tested.
Biology of human testicular germ cell tumours
Authors: Pera Martin F
Published: July 2002

Testicular germ cell tumours are a rare and bizarre diversion in the life cycle of the male germ line. These neoplasms are thought to originate during embryonic life from primordial germ cells (PGCs) which fail to undergo maturation into prospermatogonia. Maturation arrest and the development of aneuploidy in the PGC give rise to the precursor of germ cell malignancy, the testicular carcinoma in situ (CIS) cell. Thereafter, a complex series of genetic changes, coupled with the onset of puberty, can either convert the CIS cell into a malignant tumour made up of cells resembling primordial germ cells (a seminoma), or drive it down a pathway akin to parthenogenesis, so that it acquires a special property shared with cells of the early embryo – pluripotentiality, or the ability to differentiate into a wide range of somatic cells. The latter form of germ cell tumour, a teratocarcinoma, will contain primitive undifferentiated stem cells and multiple somatic tissues representing derivatives of all three germ layers plus the extraembryonic membranes which support development. Pluripotentiality is a property common to the oocyte, the cells of the early embryo up to the stage just after implantation, primordial germ cells, and the stem cells of germ cell tumours (Figure 1).
Alternative Medicine or Alternatives to Medicine? A Physician's
Perspective
Authors: SCHNEIDERMAN LAWRENCE J.
Published: July 2002

Regina R. is a 12-year-old girl with recently diagnosed
insulin-dependent diabetes. Before discharging her from
the hospital, her family physician and consulting diabetes
specialist try to instruct the girl and her parents in
the appropriate program of treatment, including diet, insulin,
and regular self-monitoring. However, the parents become
upset when they learn what is involved in insulin treatment
and inform the family physician they plan to employ the
services of an alternative healing clinic that promises
to cure their daughter with a combination of herbal potions,
macrobiotics, aroma therapy, therapeutic touch, Ayurveda,
homeopathy, and guided imagery.
Expectations and Outcomes in Organ Transplantation
Authors: McCHESNEY LAWRENCE P. , BRAITHWAITE SUSAN S.
Published: July 2002

The coauthors of this dialogue, a surgeon and
an internist, work together on an institutional patient
selection committee for transplantation of solid organs.
They have observed a spectrum of outcomes of organ transplantation,
mostly favorable, at several institutions.
A Model for Random Random-Walks on Finite Groups
Authors: GREENHALGH ANDREW S.
Published: July 2002

A model for a random random-walk on a finite group is

developed where the group elements that generate the random-walk are

chosen uniformly and with replacement from the group. When the group

is the d-cube Zd2, it is shown

that if the generating set is size k then as d

→ ∞ with k − d → ∞

almost all of the random-walks converge to uniform in

k ln (k/(k −

d))/4+ρk steps, where ρ

is any constant satisfying ρ > −ln (ln 2)/4.
On a Conjecture of Bollobás and Brightwell
Concerning Random Walks on Product Graphs
Authors: HÄGGSTRÖM OLLE
Published: July 2002

We consider continuous time random walks on a product
graph G×H, where G is arbitrary
and H consists of two vertices x and y
linked by an edge. For any t>0 and any
a, b∈V(G),
we show that the random walk starting at (a, x)
is more likely to have hit (b, x) than (b, y)

by time t. This contrasts with the discrete time case and
proves a conjecture of Bollobás
and Brightwell. We also generalize the result to cases where H

is either a complete graph on n vertices or a cycle on n
vertices.
Ambulatory blood pressure monitoring in pregnancy
Authors: Shennan Andrew H , Halligan Aidan WF
Published: July 2002

The hypertensive disorders of pregnancy remain a significant problem in antenatal care. The measurement of blood pressure in pregnancy is fundamental in diagnosing and managing these conditions. The introduction of technology in the form of ambulatory automated blood pressure monitors has allowed multiple, standardised measurements to be made away from the clinical environment, and has addressed many of the errors associated with conventional sphygmomanometry. This article explores the potential role of ambulatory blood pressure monitoring in pregnancy.
Analysing mammalian fertilisation: reservations and potential pitfalls with an in vitro approach
Authors: Hunter R. H. F. , Rodriguez-Martinez H.
Published: July 2002

There can be little doubt that one of the major technical advances in the discipline of mammalian reproductive physiology in recent years has been the development and refinement of procedures of cell maintenance and culture outside the body. Such in vitro systems have been applied, for example, to questions of (1) ovarian follicular physiology, especially the respective hormonal contributions and interactions of granulosa and theca interna cells, (2) oviduct and uterine activity, especially the novel secretions of endosalpinx and endometrium at different stages of the reproductive cycle, and (3) maturation of gametes, especially endocrine support of the resumption of meiosis in artificially liberated oocytes and the requirements for final maturation (capacitation) of epididymal or ejaculated spermatozoa, either fresh or cryopreserved. Establishment of in vitro systems has been assisted and encouraged by the ready availability of chemically-defined culture media, disposable plastic dishes and tubes, and computer-controlled incubators set to predetermined gas phase, humidity and temperature. Laminair flowhoods for tissue preparation and culture laboratories with filtered air and ultraviolet irradiation have together reduced problems of contamination and infection. Overall, the technical standards are impressive and inspection of modern tissue culture facilities invariably generates confidence in the quality of studies being pursued. In a phrase, such aesthetically pleasing and excellent laboratory facilities must surely be producing excellent science.
Partial parsing via finite-state cascades
Authors: ABNEY STEVEN
Published: July 2002

Finite state cascades represent an attractive architecture for
parsing unrestricted text. Deterministic parsers specified by finite state
cascades are fast and reliable. They can be extended at
modest cost to construct parse trees with finite feature structures.
Finally, such deterministic
parsers do not necessarily involve trading off accuracy against speed —
they may in fact be
more accurate than exhaustive search stochastic context free parsers.
Fitness to drive in older drivers with cognitive impairment
Authors: WITHAAR FREDERIEC K. , BROUWER WIEBO H. , VAN ZOMEREN ADRIAAN H.
Published: July 2002

This paper is a literature review on assessment of
fitness to drive in older drivers with cognitive impairment.
Early studies on dementia and driving generally failed
to distinguish between safe and unsafe drivers on the basis
of cognitive test performance. Predictive studies demonstrated
that cognitively impaired persons as a group perform significantly
worse than controls on both neuropsychological and driving
measures. A high prevalence of cognitive impairment was
found in groups of older drivers involved in traffic accidents
and crashes. However, a large range in neuropsychological
test scores has been found. Low to moderate correlations
could be established between neuropsychological test results
and on-road driving performance, making it difficult to
discriminate between cognitively impaired subjects who
are fit or unfit to drive. The review concludes with a
discussion of methodological difficulties in the field
of dementia and driving, including participant selection,
the choice of neuropsychological tests, and the operationalization
of driving performance. (JINS, 2000, 6,
480–490.)
Sustainability criteria and cost–benefit analysis: an analytical framework for environmental–economic decision making at the project level
Authors: TIWARI DIRGHA N.
Published: July 2002

This article develops a framework for environmental–economic decision-making in a single project case that includes the ecological sustainability criteria, environmental costs, natural resource scarcity prices and local peoples’ preferences and presents a case study of the lowland irrigated agriculture system. The geographic information system (GIS) technique has been used for evaluating ecological criteria and integrating information for use in the cost–benefit analysis at different levels of computation process. The environmental costs and economic value of water associated with the lowland irrigated agriculture are estimated using both the direct and indirect economic valuation approaches. Various sets of alternatives were designed for promoting sustainable use of resources, and the net present value is estimated in each of these cases by incorporating environmental costs and economic values of water obtained from different methods. The cost–benefit analysis (CBA) carried out in these different cases indicated that diversification of crops, rather than the conventional monocropping system, would promote sustainable resource use and generate higher benefits to the farmers and society, if external costs, such as environmental costs and scarcity value of irrigation water, and ecological sustainability criteria are also considered in the economic decision-making process. The results of the case study also indicated that sustainability criteria could well be incorporated into the CBA in a single project case by addressing local people's concerns, resource scarcity values and ecological sustainability criteria with the use of spatial analysis techniques such as GIS.
A developmental transition in definitive erythropoiesis: erythropoietin expression is sequentially regulated by retinoic acid receptors and HNF4
Authors: Makita Takako , Hernandez-Hoyos Gabriela , Chen Tim Hung-Po , Wu Hong , Rothenberg Ellen V. , Sucov Henry M.
Published: July 2002

The cytokine erythropoietin (Epo) promotes erythropoietic progenitor cell proliferation and is required for erythropoietic differentiation. We have found that the Epo gene is a direct transcriptional target gene of retinoic acid signaling during early erythropoiesis (prior to embryonic day E12.5) in the fetal liver. Mouse embryos lacking the retinoic acid receptor gene RXRα have a morphological and histological phenotype that is comparable with embryos in which the Epo gene itself has been mutated, and flow cytometric analysis indicates that RXRα-deficient embryos are deficient in erythroid differentiation. Epo mRNA levels are reduced substantially in the fetal livers of RXRα−/−embryos at E10.25 and E11.25, and genetic analysis shows that theRXRα and Epo genes are coupled in the same pathway. We furthermore show that the Epo gene is retinoic acid inducible in embryos, and that the Epo gene enhancer contains a DR2 sequence that represents a retinoic acid receptor-binding site and a retinoic acid receptor transcriptional response element. However, unlike Epo-deficient embryos that die from anemia, the erythropoietic deficiency in RXRα−/− embryos is transient; Epo mRNA is expressed at normal levels by E12.5, and erythropoiesis and liver morphology are normal by E14.5. We show that HNF4, like RXRα a member of the nuclear receptor family, is abundantly expressed in fetal liver hepatocytes, and is competitive with retinoic acid receptors for occupancy of the Epo gene enhancer DR2 element. We propose that Epo expression is regulated during the E9.5–E11.5 phase of fetal liver erythropoiesis by RXRα and retinoic acid, and that expression then becomes dominated by HNF4 activity from E11.5 onward. This transition may be responsible for switching regulation of Epo expression from retinoic acid control to hypoxic control, as is found throughout the remainder of life.
MAGPIE/EGRET Annotation of the 2.9-Mb Drosophila melanogaster Adh Region
Authors: Gaasterland Terry , Sczyrba Alexander , Thomas Elizabeth , Aytekin-Kurban Gulriz , Gordon Paul , Sensen Christoph W.
Published: July 2002

Our challenge in annotating the 2.91-Mb Adh region of theDrosophila melanogaster genome was to identify genetic and genomic features automatically, completely, and precisely within a 6-week period. To do so, we augmented the MAGPIE microbial genome annotation system to handle eukaryotic genomic sequence data. The new configuration required the integration of eukaryotic gene-finding tools and DNA repeat tools into the automatic data collection module. It also required us to define in MAGPIEnew strategies to combine data about eukaryotic exon predictions with functional data to refine the exon predictions. At the heart of the resulting new eukaryotic genome annotation system is a reverse comparison of public protein and complementary DNA sequences against the input genome to identify missing exons and to refine exon boundaries. The software modules that add eukaryotic genome annotation capability to MAGPIE are available as EGRET(Eukaryotic Genome RapidEvaluation Tool).
The Repertoire of Na,K-ATPase α and β Subunit Genes Expressed in the Zebrafish, Danio rerio
Authors: Rajarao S. Johannes R. , Canfield Victor A. , Mohideen Manzoor-Ali P.K. , Yan Yi-Lin , Postlethwait John H. , Cheng Keith C. , Levenson Robert
Published: July 2002

We have identified a cohort of zebrafish expressed sequence tags encoding eight Na,K-ATPase α subunits and five β subunits. Sequence comparisons and phylogenetic analysis indicate that five of the zebrafish α subunit genes comprise an α1-like gene subfamily and two are orthologs of the mammalian α3 subunit gene. The remaining α subunit clone is most similar to the mammalian α2 subunit. Among the five β subunit genes, two are orthologs of the mammalian β1 isoform, one represents a β2 ortholog, and two are orthologous to the mammalian β3 subunit. Using zebrafish radiation hybrid and meiotic mapping panels, we determined linkage assignments for each α and β subunit gene. Na,K-ATPase genes are dispersed in the zebrafish genome with the exception of four of the α1-like genes, which are tightly clustered on linkage group 1. Comparative mapping studies indicate that most of the zebrafish Na,K-ATPase genes localize to regions of conserved synteny between zebrafish and humans. The expression patterns of Na,K-ATPase α and β subunit genes in zebrafish are quite distinctive. No two α or β subunit genes exhibit the same expression profile. Together, our data imply a very high degree of Na,K-ATPase isoenzyme heterogeneity in zebrafish, with the potential for 40 structurally distinct α/β subunit combinations. Differences in expression patterns of α and β subunits suggest that many of the isoenzymes are also likely to exhibit differences in functional properties within specific cell and tissue types. Our studies form a framework for analyzing structure function relationships for sodium pump isoforms using reverse genetic approaches.
A Gene Encoding a Hevein-Like Protein from Elderberry Fruits Is Homologous to PR-4 and Class V Chitinase Genes1
Authors: Van Damme Els J.M. , Charels Diana , Roy Soma , Tierens Koenraad , Barre Annick , Martins José C. , Rougé Pierre , Van Leuven Fred , Does Mirjam , Peumans Willy J.
Published: July 2002

We isolated SN-HLPf (Sambucusnigrahevein-like fruitprotein), a hevein-like chitin-binding protein, from mature elderberry fruits. Cloning of the corresponding gene demonstrated that SN-HLPf is synthesized as a chimeric precursor consisting of an N-terminal chitin-binding domain corresponding to the mature elderberry protein and an unrelated C-terminal domain. Sequence comparisons indicated that the N-terminal domain of this precursor has high sequence similarity with the N-terminal domain of class I PR-4 (pathogenesis-related) proteins, whereas the C terminus is most closely related to that of class V chitinases. On the basis of these sequence homologies the gene encoding SN-HLPf can be considered a hybrid between a PR-4 and a class V chitinase gene.
Heritable Variation in Quinone-Induced Haustorium Development in the Parasitic Plant Triphysaria
Authors: Jamison Denneal S. , Yoder John I.
Published: July 2002

We are using the facultative hemiparasite,Triphysaria, as a model for studying host-parasite signaling in the Scrophulariaceae. Parasitic members of this family form subterranean connections, or haustoria, on neighboring host roots to access host water and nutrients. These parasitic organs develop in response to haustorial-inducing factors contained in host root exudates. A well-characterized inducing factor, 2, 6-dimethoxy-p-benzoquinone (DMBQ), can be used to trigger in vitro haustorium formation in the roots ofTriphysaria. We have assayed three species,Triphysaria eriantha (Benth.) Chuang and Heckard, Triphysaria pusilla (Benth.) Chuang and Heckard, andTriphysaria versicolor Fischer and C. Meyer, for haustorium development in response to DMBQ. There were significant differences between the species in their ability to recognize and respond to this quinone. Ninety percent of T. versicolorindividuals responded, whereas only 40% of T. pusillaand less than 10% of T. eriantha formed haustoria. Within field collections of self-pollinating T. pusilla, differential responsiveness to DMBQ was seen in distinct maternal families. Assaying haustorium development in subsequent generations of self-pollinated T. pusilla showed that DMBQ responsiveness was heritable. Reciprocal crosses between T. eriantha and T. versicolor demonstrated that DMBQ responsiveness was influenced by maternal factors. These results demonstrate heritable, natural variation in the recognition of a haustorial-inducing factor by a parasitic member of the Scrophulariaceae.
OASIS: a computer program for breaking phase ambiguity in one-wavelength anomalous scattering or single isomorphous substitution (replacement) data
Authors: Hao Q. , Gu Y. X. , Zheng C. D. , Fan H. F.
Published: July 2002

The phase problem is reduced to a sign problem once the anomalous-scatterer or the replacing-heavy-atom sites are located.OASISadopts theCCP4 format [Collaborative Computational Project, Number 4 (1994).Acta Cryst.D50, 760–763]. It applies a direct-method procedure to break the phase ambiguity intrinsic to one-wavelength anomalous scattering (OAS) or single isomorphous replacement (SIR) data.
Etude structurale d'un hydrate 10 Å instable de kaolinite
Authors: Jemai S. , Ben Haj Amara A. , Ben Brahim J. , Plançon A.
Published: July 2002

The treatment of KGa-1 kaolinite with dimethyl sulfoxide and ammonium fluoride heated at 383 K provides an unstable hydrated phase characterized by a 10 Å basal distance. When air-dried, this hydrate gives a dehydrated phase at 7.15 Å. The aim of this work is to determine the structural characteristics of this hydrate. The method used to characterize this hydrate is based on the comparison between experimental and calculated X-ray diffraction profiles. This study is achieved in two steps: the study of 00lreflections enabled the determination of the number of intercalated water molecules, their positions and the stacking mode along the normal to the (a,b) plane; and the study of thehklreflections withhand/ork≠ 0 enabled the determination of the stacking mode and the positions of water molecules in the (a,b) plane. The unstable hydrate is characterized by two water molecules per Al2Si2O5(OH)4unit situated atz1=z2= 7.57 Å. Two adjacent layers are translated with respect to each other withTI= −0.155a+ 0.13b+ 10n.
Anisotropic strain in YBa2Cu3O7−δfilms analysed by deconvolution of two-dimensional intensity data
Authors: Brötz J. , Fuess H.
Published: July 2002

The influence of the instrumental resolution on two-dimensional reflection profiles of epitaxic YBa2Cu3O7−δfilms on SrTiO3(001) has been studied in order to investigate the strain in the superconducting films. The X-ray diffraction intensity data were obtained by two-dimensional scans in reciprocal space (q-scan). Since the reflection broadening caused by the apparatus differs for each position in reciprocal space, a highly crystalline substrate was used as a standard. Thus it was possible to measure a standard very close to the YBa2Cu3O7−δreflections in reciprocal space. The two-dimensional deconvolution of reflections by a new computer program revealed an anisotropic strain of the two twinning systems of the film.
Diffuse scattering anisotropy and theP21/a↔A2/aphase transition in titanite, CaTiOSiO4
Authors: Malcherek Thomas , Paulmann Carsten , Domeneghetti M. Chiara , Bismayer Ulrich
Published: July 2002

Diffuse scattering in titanite has been measured at three temperatures, 0.951Tc, 1.053Tcand 1.177Tc, using synchrotron radiation.Tc= 487 K is the temperature of the antiferroelectric paraelectric phase transition. Charge-coupled device (CCD) intensity measurements were centred about the \bar{4}01 reciprocal-lattice position (space-group settingP21/a) and extended beyond the neighbouring \bar{4}11 and \bar{4}\bar{1}1 fundamental positions. Planar diffuse scattering intensity is observed normal to [100] with a lens-shaped maximum centred at \bar{4}01. On approachingTcfrom above, the intensity of the maximum at \bar{4}01 increases, while intensity scattered into the planes decreases at large distances to the critical zone-boundary position. The intensity distribution is interpreted in terms of a two-dimensional spin-1/2 Ising model, in which individual spin states represent the collective displacement of octahedrally coordinated Ti atoms parallel to [100].
Global indicators of X-ray data quality
Authors: Weiss Manfred S.
Published: July 2002

Global indicators of the quality of diffraction data are presented and discussed, and are evaluated in terms of their performance with respect to various tasks. Based on the results obtained, it is suggested that some of the conventional indicators still in use in the crystallographic community should be abandoned, such as the nominal resolutiondminor the mergingRfactorRmerge, and replaced by more objective and more meaningful numbers, such as the effective optical resolutiondeff,optand the redundancy-independent mergingRfactorRr.i.m.. Furthermore, it is recommended that the precision-indicating mergingRfactorRp.i.m.should be reported with every diffraction data set published, because it describes the precision of the averaged measurements, which are the quantities normally used in crystallography as observables.
Droplet interfacial structure studied by SANS contrast variation
Authors: Heenan R.K. , Eastoe J.
Published: July 2002

Details of structure and composition at interfaces may be obtained by Small Angle Neutron Scattering (SANS) contrast variation. At the curved oil/surfactant/water interfaces of microemulsion droplets useful results may be obtained by simultaneous fits of core-shell models to SANS data measured at different scattering contrasts. Results for small ethyl octanoate/dimethyldodecylamineoxide/water droplets, where the oil core penetrates the surfactant layer, will illustrate this method. For block-copolymer micelles with deuterated poly(lactic acid) core, the composition profiles of thicker poly(ethylene glycol) shells were obtained using a model with a vertical step and two diffuse shells. One of the three water contrasts used was close to the "mean contrast" match point for the whole micelle, as opposed to "shell" contrast, providing a peak in the form factor very sensitive to the model used.
Polycapillary optic–source combinations for protein crystallography
Authors: Hofmann F. A. , Gibson W. M. , MacDonald C. A. , Carter D. A. , Ho J. X. , Ruble J. R.
Published: July 2002

The work in this paper is a systematic study of the application of collimating and slightly focusing polycapillary optics to the X-ray crystallographic structure determination of egg-white lysozyme using two different sources: a standard rotating anode source and a low-power table-top microfocusing source. For the rotating anode source, a series of measurements comparing duplicate data sets obtained from the same individual crystal are summarized. Intensity and data quality are discussed for measurements with a pinhole collimator, a collimating polycapillary optic and a focusing polycapillary optic. The collected data were analyzed using conventional analysis software; limitations of the use of conventional analysis software for focused beams are discussed. Two data sets were collected using the low-power source and collimating optics, and three data sets using a lower-power source and focusing optics with three different limiting apertures.
Rietveld texture analysis of Dabie Shan eclogite from TOF neutron diffraction spectra
Authors: Wenk H.-R. , Cont L. , Xie Y. , Lutterotti L. , Ratschbacher L. , Richardson J.
Published: July 2002

Orientation distributions of garnet and omphacite in eclogite from the ultra-high pressure Dabie Shan belt in east-central China were determined from neutron diffraction data by the Rietveld method. Diffraction spectra were recorded in 16 sample orientations with seven detectors, with a kappa-geometry texture goniometer at the time-of-flight (TOF) neutron facility at the Intense Pulsed Neutron Source (IPNS). The textures of the two minerals were extracted simultaneously from 16 × 7 = 112 diffraction spectra, covering a large portion of the pole figure. The texture analysis was performed both with the Williams–Imhof–Matthies–Vinel (WIMV) method and the harmonic method, implemented in the program packageMAUD. The incomplete pole-figure coverage introduced artificial oscillations in the case of the harmonic method. The discrete WIMV method produced better results, which illustrate a more or less random orientation distribution for cubic garnet. Apparently elongated grains turned out to be layers of randomly oriented crystals. Monoclinic omphacite displays a sharp texture, with [001] parallel to the lineation direction. The texture data obtained by neutron diffraction were verified with EBSP (electron backscatter pattern) measurements.
Sagittal focusing of high-energy synchrotron X-rays with asymmetric Laue crystals. I. Theoretical considerations
Authors: Zhong Z. , Kao C. C. , Siddons D. P. , Hastings J. B.
Published: July 2002

The ability of asymmetric Laue crystals to focus X-rays sagittally is demonstrated. The extent of such focusing is similar to that of sagittal focusing by a Bragg crystal, except for a factor related to the asymmetry angle. The anticlastic bending facilitates the use of inverse-Cauchois geometry in the meridional plane to provide better energy resolution and to increase the photon flux by an order of magnitude compared with traditional sagittal focusing with Bragg crystals. Furthermore, for sagittal focusing at X-ray energies above 30 keV, a Laue crystal is preferred to a Bragg crystal because the length of the beam's footprint on a Laue crystal, unlike on a Bragg crystal, is small and insensitive to energy. The conditions imposed on the asymmetry angle of the Laue crystal to achieve simultaneous sagittal focusing and inverse-Cauchois geometry in the meridional plane are derived for both single-crystal and double-crystal fixed-exit sagittally focusing monochromators.
Cross-sectional texture of carbon fibres analysed by scanning microbeam X-ray diffraction
Authors: Paris Oskar , Loidl Dieter , Müller Martin , Lichtenegger Helga , Peterlik Herwig
Published: July 2002

Scanning microbeam X-ray diffraction analysis of single carbon fibres allows the cross-sectional orientation distribution (texture) of the carbon layers to be determined, even when the fibre axis is oriented perpendicular to the X-ray beam (fibre geometry). The fibre is scanned across a microbeam with a diameter significantly smaller than the fibre diameter, and fibre diffraction patterns are recorded for every scanning step. The cross-sectional texture information is obtained from the integrated intensities of two different equatorial reflections as a function of the position on the fibre. As an example, results from two different types of carbon fibres are presented: a polyacrylonitrile-based fibre, with random cross-sectional texture, and a fibre based on mesophase pitch, which exhibits a radially folded cross-sectional texture. Detailed modelling of the diffraction data allows a quantitative description of the radial folded texture.
Radii of gyration and scattering functions of a torus and its derivatives
Authors: Kawaguchi Takeshi
Published: July 2002

A torus is a simple body with cylindrical rotational symmetry. The radius of gyration and scattering function of a torus have been derived in cylindrical coordinates. Some derivatives of a torus (torus with elliptical cross section, tubular torus and two stacked tori) have been treated in the same manner as the torus. The radii of gyration are given by simple formulae and the scattering curves are easily obtained by numerical calculation using a personal computer.
A monolithic monochromator–collimator for high-resolution X-ray diffraction
Authors: Ferrari Claudio , Korytar Dusan
Published: July 2002

The possibility of finding, for a given X-ray wavelength, the conditions for obtaining multiple coplanar reflections in a single block of crystal is investigated. It is found that by introducing a small relative tilt between two parts of the crystal, the conditions for a high-resolution X-ray monochromator for conventional and synchrotron X-ray sources can be obtained. The design of a new high-resolution monochromator–collimator based on a single crystal, which takes advantage of the existence for almost any wavelength ofnandmplanes in the single crystal that lie near the Bragg condition, is presented. A weak link between the two reflecting surfaces is used to align the crystal planes and to obtain efficient reflections in the dispersive configuration. DuMond diagrams are used to evaluate the total diffracted intensity and the resolution of such a monochromator. The experimental results obtained from prototypes made of single crystals of silicon and germanium are in good agreement with theoretical predictions. This new type of monochromator offers the advantages of a compact design and simple alignment.
Matching selenium-atom peak positions with a different hand or origin
Authors: Smith G. David
Published: July 2002

An algorithm is described for matching and correlating two or more sets of peaks or atoms. The procedure is particularly useful for matching putative selenium atoms from a selenium-atom substructure as obtained fromEmaps from two or more random-atom trials. The algorithm will work for any space group exceptP1. For non-polar space groups, the procedure is relatively straightforward. For polar space groups, the calculation is performed in projection along the polar axis in order to identify potential matching peaks, and an iterative procedure is used to eliminate incorrect peaks and to calculate the displacement along the polar axis. The algorithm has been incorporated into a computer program,NANTMRF, written in Fortran 90. Less than 0.5 s are required to match 27 peaks in space groupP21, and the output lists the correct origin, enantiomorph, symmetry operations, and provides the relative displacements between pairs of matching peaks.
Determination of spherical voids in layered structures (void program)
Authors: Langlet G. A. , Figueiredo M. O. , Lima-de-Faria J.
Published: July 2002

An APL program has been written to compute the locations and the radii of spherical voids between two packing layers of atoms, and to obtain plottings which correspond to the various types of standard sheets used for the representation of crystal structures according to the condensed-model technique. Conversational facilities, together with the use of original APL routines, enable the crystallographer to get the results in a few minutes of real time.
Further studies on the dielectric behaviour of cadmium iodide polytypes
Authors: Fernandez A. M. , Srivastava O. N.
Published: July 2002

The dielectric constants (∊
r
) of several cadmium iodide polytypes have been measured and found to be higher than that of the parent 4H structure. The dielectric constants for several long-period polytypes have been found to lie between 60 and 190 whereas the 4H parent structure has a value in the range of about 15 to 30. In particular, both increasing polytype periodicity and increasing disorder increase the dielectric constant, e.g. from 16 for an ordered 4H structure to 114 for a 32H structure and 67 for a highly disordered 4H structure. In the absence of disorder a particular polytype has its own characteristic dielectric constant value, e.g. the two 14H polytypes which have a common ∊
r
value of 63.
A multiple-counter X-ray diffractometer with equatorial geometry
Authors: Banner D. W. , Evans P. R. , Marsh D. J. , Phillips D. C.
Published: July 2002

The design, construction and operation of a multiple-counter diffractometer are described. The instrument is used to measure up to five X-ray reflections from single crystals quasi-simultaneously: rates of data collection from protein crystals of 250 reflections per hour are achieved.
X-ray misorientation contrast for a (lineage) subgrain boundary
Authors: Armstrong R. W.
Published: July 2002

The separation or overlapping of adjacent subgrain images in Berg–Barrett X-ray (reflection) micrographs is described for a reasonably general misorientation between the crystal subgrains. The five crystallographic parameters which describe the diffraction experiment also specify, effectively, the direction of the rotation axis for the misorientation, the amount of the angular misorientation, and the relative orientation of the subgrain boundary interface.
Crystal data for [2.1.2.1]paracyclophan C30H28
Authors: Ghemard G. , Souleau C. , Sergheraert S. , Cuingnet E.
Published: July 2002

The powder data for [2.1.2.1]paracyclophan is reported. This compound is monoclinic with a = 21.44 (4), b = 17.22 (6), c = 9.70 (4) Å, γ = 141.30 (3)°, Z = 4.
The Cambridge Crystallography Subroutine Library
Authors: Matthewman J. C. , Thompson P. , Brown P. J.
Published: July 2002

The Cambridge Crystallography Subroutine Library (CCSL) is a versatile set of subroutines which will have many different applications for non-standard crystallography. At present it is used extensively at the Institut Laue–Langevin for interpreting all polarized neutron measurements, proceeding from the raw flipping-ratio measurements to the final production of spin-density maps. It is also used to analyse simple magnetic and more complicated nuclear structures, and for more general crystallographic applications such as arranging lists of reflections into groups of symmetry equivalents. It finds applications in the analysis of neutron powder diffraction patterns, as well as in more recent developments for the analysis of X-ray powder diffraction photographs.
The f.c.c.+tetragonal two-phase region of the Cu–Ni–Zn system
Authors: Mayall O. S.
Published: July 2002

The f.c.c. + tetragonal two-phase region of the Cu–Ni–Zn system has been delineated, and unit-cell parameters along the boundaries determined. Apparently anomalous parameter measurements prevented the determination of the tie lines. A pattern of diffraction broadening from the tetragonal phase common to both the two-phase and single-phase regions was related to the variation in lattice spacing of the tetragonal phase along the boundary. Reasons for this broadening are discussed.
The structure of Na2UCl6 and Li2UCl6 from multiphase powder neutron profile refinement
Authors: Bendall P. J. , Fitch A. N. , Fender B. E. F.
Published: July 2002

The structures of Na2UCl6 and Li2UCl6 have been determined by powder neutron diffraction at room temperature in the presence of NaCl and LiCl respectively as impurity. Na2UCl6crystallizes in space group P{\bar 3}m1, with a = 11 8062(9), c = 6.3243(2) Å, and Z = 3. The best description of Li2UCl6 was found in space group P63/mmc, a = 11.1915(5), c = 6.0356(1) Å, and Z = 3, with uranium and lithium ions disordered over the available octahedral sites. The results give the first illustration of the relative ease of analysing a two-phase mixture using a Rietveld profile program adapted to refine simultaneously more than one phase.
Difference thermal analysis of crystalline solids by the use of energy-dispersive X-ray diffraction
Authors: Eisenreich N. , Engel W.
Published: July 2002

A method is described to study the structural behavior of solids subjected to various temperature programs. The instrumentation consists of a high- or low-temperature device, a temperature programmer, a system for energy-dispersive X-ray diffraction and a data processing and storing unit and allows the fully automatic acquisition of series of spectra. A strong data reduction is performed by summing up difference diagrams. Plotting the resulting values versus temperature yields curves comparable to those obtained by differential scanning calorimetry (DSC) or thermal gravimetry (TG). A kinetic evaluation as used in the case of DSC or TG curves is possible. The method was applied to study the thermal behavior of a mixture of ammonium nitrate with zinc oxide. The curves indicate the strong anisotropic thermal expansion of the ammonium nitrate phase IV below 323 K, its transition to phase II at 325–329 K and the solid-state reaction with zinc oxide within the temperature interval of 353–383 K.
Crystal data for bis(η5-tert-butylcyclopentadienyl)hafnium(IV) dihydride dimer, [(η5-t-BuC5H4)2HfH(μ-H)]2
Authors: Laarif A. , Theobald F. , Gautheron B. , Tainturier G.
Published: July 2002

The air-sensitive title hydride [Hf(C9H13)2H2]2 was prepared by hydrogenolysis of (t-BuCp)2HfMe2 [Couturier, Tainturier & Gautheron (1980). J. Organomet. Chem.
195, 291–306] and crystallized from a solution in heptane or toluene and hexane. The compound is triclinic with the following cell parameters: a = 7.22(3), b = 10.31(4), c = 12.47(6) Å, α = 80.4(4), β = 74.6(4)°, γ = 72.1(3)°, V = 847 Å3, Z = 1, Dx
= 1.67 Mg m− 3. Powder diffraction data were obtained from Debye–Scherrer photographs. The extended version of the paper examines several examples where Zr or Hf hydrides are monomers or dimers and shows that this structure is very similar to the related [(MeCp)2ZrH2]2 compound [Jones & Petersen (1981). Inorg. Chem.
20, 2889–2894]. This similarity and spectroscopic data show that the molecule probably has a center of symmetry situated between the two Hf atoms and the two bridging H atoms. The JCPDS Diffraction File No. for [Hf(C9H13)2H2]2 is 33-1996.
The small-angle approximation of X-ray and neutron scatter from rigid rods of non-uniform cross section of finite length
Authors: Hjelm R. P.
Published: July 2002

The theory of small-angle neutron or X-ray scattering from a solution consisting of rods that are uncorrelated in position and orientation and its use in determining the mass per unit length and cross-sectional radius of gyration is extended to rods of finite length and non-uniform cross-sectional structure. The case of a rod made up of identical motifs spaced in a regularly repeating axial structure is considered first. Analysis of the small-angle scatter by a modified Guinier plot gives the mean mass per unit length of the motifs. The apparent squared cross-sectional radius of gyration is the weight average. These results are then generalized to the case where variable randomly distributed structural elements are present including variable spacing between the motifs making up the rod. In this way expressions are obtained that describe the scatter from rods with structural contributions from random thermal fluctuations, bound ligands and intrinsic structural heterogeneity. It is shown that, in general, systematic errors are introduced in the analysis of rods of finite length having variable structural components. However, if all the motifs have the same mass, and if the variance in their spacing is small, such errors are not important provided that the rods are of sufficient length.
Resolution of time-of-flight small-angle neutron diffractometers
Authors: Hjelm R. P.
Published: July 2002

A simple method of calculating the resolution of small-angle neutron data from diffractometers which use time-of-flight techniques has been derived in terms of the variances of the time and spatial channels of the measurement. The method is used to calculate the resolution in scattering-vector space of scattering intensity from a simulated isotropic scatterer on the small-angle neutron diffractometer at the Intense Pulsed Neutron Source at Argonne National Laboratory. The effects of the various instrumental geometries, time-of-flight measurement strategies and data reduction methods that can be chosen by the experimenter are considered. It is found that the best resolution is obtained with weighted constant Δt/t time-of-flight data acquisition schemes, with the detector placed in the beam in such a way that the highest possible angular range is accessed.
Matrix formulation of the iterative method of phase analysis
Authors: Čerňanský M.
Published: July 2002

A matrix formulation is given of the numerical procedures for the iterative method of X-ray diffraction phase analysis [Fiala (1980). Anal. Chem.
52, 1300–1304; Fiala (1982). Cryst. Res. Technol.
17, 643–650].
Expressions for first and second derivatives in least-squares refinements including extinction
Authors: Spackman M. A.
Published: July 2002

Compact expressions are given for first and second derivatives necessary for inclusion of the Becker–Coppens isotropic extinction model in a least-squares procedure. Derivatives with respect to a scale factor, a structural parameter, and the two extinction parameters g and ρ are considered, for refinements on |F| and |F|2.
X-ray diffraction evidence for transient composition effects in MOVPE multilayer growth for Ga1−x
Al
x
As alloys
Authors: Bensoussan S. , Malgrange C. , Sauvage-Simkin M. , N'Guessan K. , Gibart P.
Published: July 2002

X-ray rocking-curve analysis is applied to the detection of artifacts in multilayer epitactic growth of III–V ternary compounds by metal–organic vapour-phase epitaxy (MOVPE). Transient spikes in the composition result in unwanted additional thin layers whose presence disturbs the interference pattern expected from the designed heterostructures, thus modifying the oscillating part of the reflection profile. X-ray methods and secondary-ion mass spectroscopy (SIMS) lead to descriptions of the actual layer stacking in good agreement with each other.
A high-pressure single-crystal X-ray diffraction study of V3O5 including the phase transition at 6.2 GPa
Authors: Åsbrink S. , Malinowski M.
Published: July 2002

The unit-cell parameters of the mixed-valence oxide V3O5 have been studied as functions of pressure from 0.3 up to 7.5 GPa in a single-crystal experiment involving measurements at 21 different pressure values. A diamond-anvil high-pressure (h.p.) cell of new construction [Malinowski (1987). Submitted to J. Appl. Cryst.] mounted on a four-circle X-ray diffractometer was used. At Pt
= 6.25(9) GPa a phase transition was observed at room temperature. This is analogous to the semiconductor-metal transition observed at Tt
= 428 K and normal pressure, which implies a change in the ordering of the metal-atom valencies. The linear Eulerian strain tensor for the transition has been calculated. The bulk modulus K has been determined for the low-pressure (l.p.) as well as for the h.p. phase: K
l.p.(0.3–5.5 GPa) = 269(3), K
h.p.(6.3–7.5 GPa) = 175(11) GPa. Certain anomalies in the cell-parameter values in a small pressure interval around the phase transition indicate a preparation in the crystal structure for the transition in both the l.p. and the h.p. phase.
Layer-disordered wurtzite (ZnS-2H): diffuse X-ray scattering recorded by c-axis precession photography
Authors: Fleet M. E.
Published: July 2002

A novel type of X-ray diffraction pattern results when a layer-disordered crystal is photographed by X-ray precession using the stacking direction as the precession axis and no layer-line screen. The 10l, 20l, 21l and symmetry-equivalent rows of diffuse scattering of layer-disordered wurtzite (ZnS-2H) are represented by compound loops superimposed on the zero-level hk0 diffraction pattern. Closed loops result because the reciprocal-lattice rows associated with diffuse scattering remain in contact with the sphere of reflection during the precession cycle. Formulae for dimensional parameters of the compound loops of diffuse scattering are derived from the sphere-of-reflection construction.