bluuebunny/crossref_metadata_2025 huggingface dataset:
Repair strategies and social interaction in spontaneous spoken French: the pragmatic particle enfin
Authors: Beeching Kate
Published: July 2002

The spoken language has traditionally been regarded as being a degenerate version of the written language, marred by backtrackings and repetitions. This paper explores the role of the pragmatic particle enfin when it is used as a corrective, both to introduce a repair and, in its mitigating or hedging capacity, as a mediator of social relations. An attempt is made to account for the pragmatico-syntactic characteristics of a particular manifestation of corrective enfin – the echo/self-mimic corrective. The behaviour of enfin is arguably a microcosm in a much larger universe of rules governing the way speakers produce and hearers interpret the shifting signals of participatory discourse.
Foreword
Authors: Bahsoun J. P. , Fiadeiro J. L. , Galmiche D.
Published: July 2002

There are various logic-based approaches to modelling concurrent programming. The use
of logic for system development concerns both the specification step and the study of
the operational aspects (through proof analysis and construction) of such development.
This means that we have to consider different logical systems for different uses of logic.
Moreover, we can also consider concurrency from both points of view: we want to reason
and to specify systems where some concurrency aspects are involved, but also to have
some operational interpretation of concurrency within logic (focusing on the concept of
proof). For this purpose, it seems clear that we have to identify and to study, on the
one hand, the role and the treatment of objects (representation, inheritance, modularity,
communication, and so on) in this context, and, on the other hand, the interaction of
work on proofs and concurrency with the Object-Oriented Programming paradigm.

The ECOOP’96 workshop on ‘Proof Theory of Concurrent Object-Oriented
Programming’ took place in Linz, Austria, in July 1996. Its objective was to
provide an integrated
forum for the presentation of research and the exchange of ideas and experiences in
the topics concerned with proofs, concurrency and object-oriented programming
(specification, proof development, and so on). The call for papers for this Special Issue of
Mathematical Structures in Computer Science can be considered to have been a natural
scientific continuation of the workshop.

The papers selected for this Special Issue address some of the topics discussed in
the workshop. They present different alternative frameworks that are effectively based
on a proof-theoretic approach. They illustrate, from different points of view, the interest,
potentialities and difficulties of dealing with such an approach in the design of object-based
concurrent systems.
Against Relativism: Cultural Diversity and the Search for
Ethical Universals in Medicine, by Ruth Macklin. New York:
Oxford University Press, 1999. 304 pp.
Authors: Spike Jeffrey
Published: July 2002

Ruth Macklin's new book, Against Relativism,
says in its subtitle that it intends to address cultural
diversity and the search for ethical universals in medicine.
This it does very well. Every chapter includes some discussion
of cultural relativism, cultural anthropology, or postmodernism,
and her analyses are acute and scathing. Macklin is unabashed
in her defense of the principles of medical ethics, and
she gives a strong argument that principles are essential
elements of any ethical system that is to successfully
survive the skeptical doubts of relativism.
Ram Dass on Being a Patient
Authors: HEILIG STEVE
Published: July 2002

Ram Dass is one of America's most renowned
spiritual teachers. Born Richard Alpert, he received his
Ph.D. in psychology from Stanford University and taught
there and at Harvard University before going to India and
receiving the name Ram Dass (“Servant of God”)
from his guru. He has long been involved in many charitable
service organizations, particularly those devoted to providing
healthcare for underserved populations. Among his many
books are Be Here Now (currently in its fortieth
printing), How Can I Help, and Compassion
in Action; his newest book is Still Here: Embracing
Aging, Changing, and Dying (Putnam, 2000).
A Crossroads in Genetic Counseling and Ethics
Authors: McGEE GLENN , ARRUDA MONICA
Published: July 2002

Genetic counselors are on the front lines of the
genetic revolution, presented with tests of varying predictive
values and reliability, unfair testing distribution mechanisms,
tests for conditions where no treatment exists, and companies
that oversell the usefulness of their tests to physicians
and nurses. Many scholars, both genetic testing task forces
as well as the newly formed National Bioethics Advisory
Commission, have all noted that genetic counseling programs
and services are critical for adequate genetic testing.
At the same time, in our own work at the University of
Pennsylvania we have encountered many requests for new
materials for training genetic counselors in ethics and
providing ethics resources for genetic counseling. One
of us has noted elsewhere that it is crucial that resources
from the Human Genome Project, the Centers for Disease
Control, and other public agencies be devoted to providing
better resources for genetic counselors facing difficult
ethical issues. Although the American Board
of Genetic Counseling requires that training programs include
some formal coursework in ethics, many wonder whether enough
is being done to prepare genetic counselors for an ever-tougher
job, and in particular there has been much concern expressed
about whether “nondirectiveness” is an outmoded
ideal that hampers this profession as it attempts to grow
and identify the value of its practice. On the basis of
many comments to us by genetic counselors and on the basis
of our review of the current literature, we hypothesized
that accredited genetic counseling training programs are poised at the
turn of the century to begin planning a new approach to
teaching the philosophy of genetic counseling, one that integrates
philosophical, theoretical, and ethical training throughout the
curriculum in genetic counseling.
Retransplantation and the “Noncompliant” Patient
Authors: KUCZEWSKI MARK G.
Published: July 2002

The patient was a 19-year-old female who was transferred
to this children's hospital from a community hospital
in a neighboring state. She is well known to the hospital
staff because she had a kidney transplanted and retransplanted
several times there. Her first transplant as at age 8 and
she was retransplanted most recently approximately 3 years
ago. She immediately rejected her second kidney and received
a third. She is currently admitted because she is again
rejecting her kidney, probably due to not taking her medication.
The ethics consultant was called because the attending
physician wanted to know if it was ethical to retransplant
a “noncompliant” patient.
Bipartite Coverings of Graphs
Authors: RÖDL VOJTECH , RUCIŃSKI ANDRZEJ
Published: July 2002

In this note we give a probabilistic proof of the existence of
an
n-vertex graph Gn,
n=1, 2, [ctdot ], such that, for some constant c>0,
the
edges of Gn cannot be covered by
n−c log n complete bipartite subgraphs
of
Gn. This result improves a previous bound
due
to F. R. K. Chung and is the best possible up to a constant.
Lower Bounds for the Probability of Intersection of
Several Unions of Events
Authors: CHEN TUHAO , SENETA E.
Published: July 2002

To bound the probability of a union of n events
from a single set of events, Bonferroni
inequalities are sometimes used. There are sharper bounds
which are called Sobel–Uppuluri–Galambos inequalities. When
two (or more)
sets of events are involved, bounds are
considered on the probability of intersection of several such unions, one
union from
each set. We present a method for unified treatment of bivariate lower
and upper bounds
in this note. The lower bounds obtained are new and at least as good as
lower bounds
appearing in the literature so far. The upper bounds coincide with existing
bivariate
Sobel–Uppuluri–Galambos type upper bounds derived by the
method of indicator functions. A
numerical example is given to illustrate that the new lower bounds can
be strictly better
than existing ones.
Placental oxygen transfer and the oxygen supply to the fetus
Authors: Carter Anthony M
Published: July 2002

Some babies are hypoxic at birth, yet suffer no ill effects, whilst others have a poor prognosis. To understand why this is so, we need to consider the factors that determine fetal oxygen supply and how the fetus copes with any decrease in oxygen delivery.
Dithiothreitol induces sperm nuclear decondensation and protects against chromosome damage during male pronuclear formation in hybrid zygotes between Chinese hamster spermatozoa and Syrian hamster oocytes
Authors: Tateno Hiroyuki , Kamiguchi Yujiroh
Published: July 2002

Summary

The present study was undertaken to investigate whether a time lag in sperm nuclear decondensation and male pronuclear formation in the course of development of eggs is associated with any occurrence of structural chromosome aberrations in male genomes of hybrid zygotes between Chinese hamster spermatozoa and zona-free Syrian hamster oocytes. Shortly after insemination, hybrid zygotes were treated with dithiothreitol (DTT) at different concentrations (0.1–10.0 mM) for 30 min to reduce protamine disulphide (S–S) bonds and thereby accelerate sperm nuclear decondensation and male pronuclear formation. The incidence of sperm nuclear decondensation and male pronuclear formation increased with increasing DTT concentrations, indicating that a reduction in S–S bonds effectively induces these cytological events. Chromosomes of male genomes in hybrid zygotes generated by treatment with 1.0 mM, 2.5 mM and 10.0 mM DTT were analysed at the first cleavage metaphase. Incidence of structural chromosome aberrations in each treatment was 34.5%, 27.1% and 24.7%, respectively. There was a significant difference between the incidences with 1.0 mM and 10.0 mM DTT treatment. As the time lag in nuclear decondensation and male pronuclear formation was greatest in the 1.0 mM treatment condition, followed in order by 2.5 mM and 10.0 mM, it is suggested that the lag in sperm nuclear development behind egg development is responsible for structural chromosome aberrations in male genomes of hybrid zygotes.
VICTORIAN MELODRAMA AND THE PERFORMANCE OF POVERTY
Authors: Leaver Kristen
Published: July 2002

QUESTIONSABOUT THE PERFORMATIVE NATURE of Victorian culture have received extended attention in the past decade or so as critics have begun to examine the relationship between representation and subjectivity.1 By and large, such studies have fruitfully problematized our received assumptions about the private character of the Victorians. At the same time, however, they have also implicitly privileged the middle-class frames of reference that shape the distinction, for even as they complicate our understanding of performance by calling into question the distinction between public and private modes, critics who take up such issues tend not to question the stability of the categories of experience under scrutiny. As a result, while we gain important new insights into the cultural formation of identity or genre underwritten by the separation of public and private spheres, we also risk reading all Victorians as if their relationships to such ideological formations were identical with those of the emerging middle class.
Maximising net benefits through biodiversity as a primary land use
Authors: WALKER BRIAN
Published: July 2002

In many developing regions of the world conventional agriculture is failing to meet the needs of people and at the same time is becoming progressively less ecologically sustainable. It is proposed that in a number of these regions, both overall economic development and the welfare of the inhabitants would improve if the primary form of land use was based on multiple use of those regions' natural biological resources, rather than continuing the practice of replacing or displacing them with marginal forms of agriculture. Testing this proposition, and then (if appropriate) effecting it, requires answers to a number of ecological, economic and management questions, in particular to do with:
identifying those regions where biodiversity use has high potential
the appropriate spatial scales for planning and management
compatible combinations of different types of resource use
ecological and economic trade-offs between different resource use enterprises
how to arrive at the most efficient form of resource use
sustainable levels of biodiversity harvest
resource use decisions in relation to ecological drivers (such as climate and fire)
institutional and regulatory structures that dictate current resource use.
These questions, it is proposed, should form the basis of an international 'virtual' institute, composed of three Biodiversity Centres, one each in Latin America, southern Africa and Southeast Asia. Examples of multiple use, such as of wildlife in southern Africa, are used to illustrate the potential, and the management scale and other issues involved. If the development of this form of land use is to succeed, it will require technical and management advice and, in many cases, removal of 'perverse incentives' that prevent a change to the more economically and ecologically sustainable form of land use. From the beginning, the emphasis in the proposed centres would be on collaborative work involving governments, landowners and resource-based industries.
Music as mirror of mind
Authors: Spiegel Laurie
Published: July 2002

Hierarchical and other historically dominant models of perceived musical organisation are increasingly inapplicable to new musical processes and repertoire. The next major paradigm shift for music models, structures and concepts, perhaps comparable in importance to that in which polyphony gave way to homophony, may be a shift of emphasis from means of acoustic production and the nature of sound per se to new musical models based on psychoacoustics, cognitive studies and subjective auditory experience.
The Importance of Play: A Child Psychotherapist's View
Authors: Alvarez Anne , Phillips Asha
Published: July 2002

The authors examine the historical framework within which child

psychotherapists have used play. They discuss developments in theory
and technique influenced by advances in psychoanalytic thinking, child

development studies, and clinical work with severely deprived and
disturbed patients.
Legal Update: New Guidelines for the Conduct of Care Proceedings
Authors: Tufnell Guinevere
Published: July 2002

Re CB and JB (care proceedings: case conduct)[1998]
2
FCR 313 Family Division, Manchester. Wall J.

Care proceedings were brought in respect of twins who
were born in February 1996. It was alleged that one of
them had been the victim of two shaking episodes, whilst
in the care of their parents. In February 1998, a care order
was made and the children were freed for adoption. The
facts of the case were very simple, the only factual issue
being which parent had inflicted the child's injuries. Care
proceedings were commenced in November 1996 and the
substantive hearing took place in February 1998; a large
number of expert opinions had been sought; the legal
advisers had not worked towards clarifying the issues. The
judge, Mr Justice Wall, was highly critical of the conduct
of the case and made a number of recommendations.
PRODUCTIVE GOVERNMENT EXPENDITURE IN A
STOCHASTICALLY GROWING ECONOMY
Authors: Turnovsky Stephen J.
Published: July 2002

This paper analyzes productive government
expenditure in a stochastic
AK growth model. First, a centrally planned economy is characterized,
emphasizing the trade-off between the effects of both deterministic
and stochastic government expenditures on the equilibrium growth rate
and its variance. Both the growth-maximizing and the
welfare-maximizing shares of government expenditure are derived and
shown to depend (differentially) upon the degree of risk in the
economy. Whereas production risk reduces the welfare-maximizing
share of government expenditure, it may either increase or decrease
the growth-maximizing share, depending upon the degree of risk
aversion. Next, the stochastic equilibrium in a decentralized economy
is derived. The first-best optimal tax structure is characterized and
its dependence on risk is determined. The formal analysis is
supplemented by some numerical simulations to assess the quantitative
significance of risk and the divergence that this generates between the
welfare-maximizing and growth-maximizing size of government.
WUSCHEL signaling functions in interregional communication during Arabidopsis ovule development
Authors: Groß-Hardt Rita , Lenhard Michael , Laux Thomas
Published: July 2002

Coordinating the behaviors of different cell populations is essential for multicellular development. One important example for this can be found in ovule development in higher plants. Ovules give rise to the gametophyte in the distal nucellus and form protective sporophytic organs from the underlying chalaza. We show that the WUSCHEL(WUS) homeobox gene provides a mechanism to coordinate these events. WUS is expressed in the nucellus and our loss- and gain-of-function analyses show that WUS is not only necessary but also sufficient for integument formation from the chalaza. WUS protein is retained in the nucellus, indicating that WUS activity in the nucellus generates a downstream signal that non-cell-autonomously regulates integument initiation in the chalaza. This signal appears to act locally, thus determining the position of organ formation from chalazal cells adjacent to the nucellus. Analysis of WUS andAINTEGUMENTA functions indicates that integument initiation requires inputs from different ovule regions. Together with previous findings for shoot and floral meristems, where WUS signaling establishes a stem cell niche, our results indicate that WUSdefines a signaling mechanism that is used repeatedly during plant development in coordinating the behavior of adjacent cell groups.
Cell cycle– and cell growth–regulated proteolysis of mammalian CDC6 is dependent on APC–CDH1
Authors: Petersen Birgit Otzen , Wagener Christian , Marinoni Federica , Kramer Edgar R. , Melixetian Marina , Denchi Eros Lazzerini , Gieffers Christian , Matteucci Cristian , Peters Jan-Michael , Helin Kristian
Published: July 2002

CDC6 is conserved during evolution and is essential and limiting for the initiation of eukaryotic DNA replication. Human CDC6 activity is regulated by periodic transcription and CDK-regulated subcellular localization. Here, we show that, in addition to being absent from nonproliferating cells, CDC6 is targeted for ubiquitin-mediated proteolysis by the anaphase promoting complex (APC)/cyclosome in G1. A combination of point mutations in the destruction box and KEN-box motifs in CDC6 stabilizes the protein in G1 and in quiescent cells. Furthermore, APC, in association with CDH1, ubiquitinates CDC6 in vitro, and both APC and CDH1 are required and limiting for CDC6 proteolysis in vivo. Although a stable mutant of CDC6 is biologically active, overexpression of this mutant or wild-type CDC6 is not sufficient to induce multiple rounds of DNA replication in the same cell cycle. The APC–CDH1-dependent proteolysis of CDC6 in early G1 and in quiescent cells suggests that this process is part of a mechanism that ensures the timely licensing of replication origins during G1.
RHO—Radiation Hybrid Ordering
Authors: Ben-Dor Amir , Chor Benny , Pelleg Dan
Published: July 2002

Radiation hybrid (RH) mapping is a somatic cell technique that is used for ordering markers along a chromosome and estimating the physical distances between them. With the advent of this mapping technique, analyzing the experimental data is becoming a challenging and demanding computational task. In this paper we present the software package RHO (radiationhybridordering). The package implements a number of heuristics that attempt to order genomic markers along a chromosome, given as input the results of an RH experiment. The heuristics are based on reducing an appropriate optimization problem to the traveling salesman problem (TSP). The reduced optimization problem is either the nonparametric obligate chromosome breaks (OCBs) or the parametric maximum likelihood estimation (MLE). We tested our package on both simulated and publicly available RH data. For synthetic RH data, the reconstructed markers' permutation is very close to the original permutation, even with fairly high error rates. For real data we used the framework markers' data from the Whitehead Institute maps. For most of the chromosomes (18 out of 23), there is a perfect agreement or nearly perfect agreement (reversal of chromosome arm or arms) between our maps and the Whitehead framework maps. For the remaining five chromosomes, our maps improve on the Whitehead framework maps with respect to both optimization criteria, having higher likelihood and fewer breakpoints. For three chromosomes, the results differ significantly (lod score >1.75), with chromosome 2 having the largest improvement (lod score 3.776).
Automation for Genomics, Part Two: Sequencers, Microarrays, and Future Trends
Authors: Meldrum Deirdre
Published: July 2002

Automation for genomics has enabled a 43-fold increase in the total finished human genomic sequence in the world in the past four years. This is the second half of a two-part, noncomprehensive review that presents an overview of different types of automation equipment used in genome sequencing. The first part of the review, published in the previous issue, focused on automated procedures used to prepare DNA for sequencing or analysis. This second part of the review presents a look at available DNA sequencers and array technology and concludes with a look at future technologies. Alternate sequencing technologies including mass spectrometry, biochips, and single molecule analysis are included in this review.
The Effect of Elevated Concentrations of Fructose 2,6-Bisphosphate on Carbon Metabolism during Deacidification in the Crassulacean Acid Metabolism Plant Kalanchöe daigremontiana
Authors: Truesdale Mark R. , Toldi Otto , Scott Peter
Published: July 2002

In C3 plants, the metabolite fructose 2,6-bisphosphate (Fru 2,6-P2) has an important role in the regulation of carbon partitioning during photosynthesis. To investigate the impact of Fru 2,6-P2 on carbon metabolism during Crassulacean acid metabolism (CAM), we have developed an Agrobacterium tumefaciens-mediated transformation system in order to alter genetically the obligate CAM plant Kalanchöe daigremontiana. To our knowledge, this is the first report to use genetic manipulation of a CAM species to increase our understanding of this important form of plant metabolism. Transgenic plants were generated containing a modified rat liver 6-phosphofructo-2-kinase gene. In the plants analyzed the activity of 6-phosphofructo-2-kinase ranged from 175% to 198% of that observed in wild-type plants, resulting in Fru 2,6-P2 concentrations that were 228% to 350% of wild-type plants after 2 h of illumination. A range of metabolic measurements were made on these transgenic plants to investigate the possible roles of Fru 2,6-P2 during Suc, starch, and malic acid metabolism across the deacidification period of CAM. The results suggest that Fru 2,6-P2 plays a major role in regulating partitioning between Suc and starch synthesis during photosynthesis. However, alterations in Fru 2,6-P2 levels had little effect on malate mobilization during CAM fluxes.
Intron-Mediated Enhancement of Gene Expression Independent of Unique Intron Sequences and Splicing
Authors: Rose Alan B. , Beliakoff Jason A.
Published: July 2002

Either of the first two introns of the Arabidopsis tryptophan pathway genePAT1 elevates mRNA accumulation from aPAT1:β-glucuronidase (GUS) fusion roughly 5-fold without affecting the rate of PAT1:GUS transcription. To further explore the mechanism of this intron-mediated enhancement of gene expression, we wanted to determine whether splicing or specific intron sequences were necessary. In-frame derivatives ofPAT1 intron 1, whose splicing was prevented by a point mutation or large deletions, were able to increase mRNA accumulation from a PAT1:GUS fusion, demonstrating that splicing per se is not required. Furthermore, each of a series of introns containing overlapping deletions that together span PAT1 intron 1 increased PAT1:GUS mRNA accumulation as much as the full-length intron did, indicating that all intron sequences are individually dispensable for this phenomenon. These results eliminate the simple idea that this intron stimulates mRNA accumulation via a unique RNA-stabilizing sequence or through the completed act of splicing. However, they are consistent with a possible role for redundant intron sequence elements or an association of the pre-mRNA with the spliceosome.
NADPH Supply and Mannitol Biosynthesis. Characterization, Cloning, and Regulation of the Non-Reversible Glyceraldehyde-3-Phosphate Dehydrogenase in Celery Leaves
Authors: Gao Zhifang , Loescher Wayne H.
Published: July 2002

Mannitol, a sugar alcohol, is a major primary photosynthetic product in celery (Apium graveolens L. cv Giant Pascal). We report here on purification, characterization, and cDNA cloning of cytosolic non-reversible glyceraldehyde-3-P dehydrogenase (nr-G3PDH, EC1.2.1.9), the apparent key contributor of the NADPH required for mannitol biosynthesis in celery leaves. As determined by sodium dodecyl sulfate-polyacrylamide gel electrophoresis, purified nr-G3PDH showed a molecular mass of 53 kD. A 1,734-bp full-length cDNA clone (accession no. AF196292) encoding nr-G3PDH was identified using polymerase chain reaction and rapid amplification of cDNA ends techniques. The cDNA clone has an open reading frame of 1,491 bp encoding 496 amino acid residues with a calculated molecular weight of 53,172.K  m values for the celery nr-G3PDH were low (6.8 μm for NADP+ and 29 μm ford-glyceraldehyde-3-P). NADPH, 3-phosphoglycerate, and ATP were competitive inhibitors, and cytosolic levels of these three metabolites (as determined by nonaqueous fractionation) were all above the concentrations necessary to inhibit activity in vitro, suggesting that nr-G3PDH may be regulated through feedback inhibition by one or more metabolites. We also determined a tight association between activities of nr-G3PDH and mannose-6-P reductase and mRNA expression levels in response to both leaf development and salt treatment. Collectively, our data clearly show metabolic, developmental, and environmental regulation of nr-G3PDH, and also suggest that the supply of NADPH necessary for mannitol biosynthesis is under tight metabolic control.
Molecular Characterization of the Abp1 5′-Flanking Region in Maize and the Teosintes
Authors: Elrouby Nabil , Bureau Thomas E.
Published: July 2002

Auxin-binding protein 1 subsp. mays (ABP1) has been suggested as a receptor mediating auxin-induced cell expansion and differentiation. In maize (Zea mays), ABP1 is encoded by a single gene, Abp1. The TATA and CAAT promoter elements as well as the transcriptional start site were previously identified and all were found to be located within a transposable element (TE),Tourist-Zm11. In this study we report the cloning and characterization of the Abp1 5′-flanking region in maize and its wild relatives, the teosintes. We provide evidence for insertion polymorphism corresponding to Tourist-Zm11 and two novel TEs, Batuta and Pilgrim. Despite this polymorphic structure, the Abp1 core promoter in maize and the teosintes is conserved, is located downstream of the TE insertions in the 5′-flanking region, and is TATA-less. We discuss the potential evolutionary impact of these TEs on the regulation of Abp1 gene expression.
An error assessment of single-crystal 2πdata from four-circle diffractometry
Authors: Frevel L. K. , Emge T. J. , Kistenmacher T. J.
Published: July 2002

The criteria developed in the error analysis of 2θ powder data for cubic and uniaxial phases [Frevel (1978). J. Appl. Cryst.
11, 184–189] are extended to biaxial single-crystal data. A methodology is described for applying the focusing matrix method to exhaustive sets of 2θ data for pinacoid and prism reflections measured on a four-circle diffractometer. A spheroidal crystal of hyperpure Si is used to calibrate a Syntex P{\bar 1} automated diffractometer and to establish an effective wavelength for graphite-monochromated Mo Kβ
1
β
3 radiation. A high-quality single-crystal of cis-[bis(7,9-dimethylhypoxanthine) (ethylenediamine)platinum(II)] hexafluorophosphate, [Pt(C2H8N2)(C 7H8N4O)2].(PF6)2, serves as a test case for comparing the normal least-squared analysis with the focusing matrix method. It is concluded that an absolute accuracy greater than one part in 2000 for cell constants of biaxial crystals is difficult to achieve from automated four-circle diffractometer data (2θ ≤ 40°) for non-spheroidal crystals with linear dimensions ca 0.2 mm.
Vibrating crystals as possible neutron monochromators
Authors: Stoica A. D. , Popovici M.
Published: July 2002

The Bragg reflection of neutrons by vibrating perfect crystals is considered. The additional possibilities offered by the Doppler effect for shaping neutron beams in the k space are discussed. A simple model for computing the vibrating crystal reflectivity is proposed.
The true unit cell of ammonium hydrogen sulfate, (NH4)3H(SO4)2
Authors: Davis B. L. , Johnson L. R.
Published: July 2002

A combination of X-ray powder diffraction and single-crystal Laue photography was used to determine the unit-cell parameters for letovicite. μr
= 247.25. The unit cell is triclinic, P1 or P{\bar 1}, and has dimensions a
0 = 5.87(1), b
0 = 10.17(3), c
0 = 8.27(1) Å, α = 101.1(4), β = 111.1(1), γ = 89.9(2)°, V = 450.7 Å3, Z = 2, Dx
= 1.82 Mg m−3. The M(20) cell reliability is 23.8. Many weak powder spectra were observed, which preclude the possibility of monoclinic cell symmetry previously reported. Projection of the letovicite Laue data along [001] reveals the striking pseudo-hexagonal symmetry observed optically. The JCPDS Diffraction File No. for ammonium hydrogen sulfate is 35-1500.
The rotation rate field and geometry of orientation space
Authors: Morawiec A.
Published: July 2002

This paper contains information about the Riemannian structure of orientation space which is necessary for the analysis of the rotation rate field, which in turn describes some aspects of the plastic deformation of textured polycrystalline materials. The components of the metric tensor and the connection coefficients in the coordinates used in quantitative texture analysis are given. The relation between the vector components at symmetrically equivalent points and the relation between the frequently used vectors of infinitesimal rotations are presented. The solution of the continuity equation is given for the case of a constant rotation rate field during the deformation process.
Estimation of d
min, λmin and λmax from the gnomonic projections of Laue patterns
Authors: Cruickshank D. W. J. , Carr P. D. , Harding M. M.
Published: July 2002

The parameters d
min and λmin, needed for the processing of synchrotron X-ray Laue patterns, may be estimated by simple formulae from the sizes of the clear gaps surrounding prominent zone lines in gnomonic projections. The estimation of λmax is similarly considered. Examples are given.
About the primitivity theorem
Authors: Le Page Y.
Published: July 2002

Loosely stated, the primitivity theorem says that a cell based on the three shortest noncoplanar translations of a lattice is primitive. No course on elementary crystallography can omit this basic property of three-dimensional lattices, with everyday applications for selection of cells and for cell reduction. Textbooks have treated this property as obvious for many years now and have not hinted at a proof. The complexity of several apparently little-known proofs published since 1831 and the fact that no similar theorem exists in four dimensions or more show that this property cannot be taken for granted. However, little more than a drawing schematizing the simple proof of Delaunay, Galiulin, Dolbilin, Zalgaller & Stogrin [Dokl. Akad. Nauk SSSR (1973), 209, 25–58] would be needed to clarify this important theorem for average undergraduate students.
Structure-refinement program for disordered carbons
Authors: Shi H. , Reimers J. N. , Dahn J. R.
Published: July 2002

An automated structure-refinement program has been developed for X-ray powder diffraction data collected on disordered carbons. The program minimizes the difference between the observed and calculated diffraction profiles in a least-squares sense by optimizing model parameters analogously to the popular Rietveld refinement method. Unlike the Rietveld method, which is designed for crystalline materials, this program allows the quantification of the finite size, strain and disorder present in disordered carbon fibers and cokes. For example, the structural model used includes the probability of a random translation parallel to adjacent carbon layers as a refinable parameter describing turbostratic disorder. Other parameters are used to describe finite size, fluctuations in the spacing between adjacent layers, average lattice constants, background and other important quantities. The structural model, combined with the refinement program, acceptably describes the diffraction patterns from disordered carbons such as pitch heated near 823 K, cokes, fibers, heat-treated cokes and synthetic graphite.
An improved deviation parameter for the simulation of dynamical X-ray diffraction on epitaxic heterostructures
Authors: Zaus R.
Published: July 2002

X-ray diffraction rocking curves of a strained-layer superlattice structure have been measured at symmetric and asymmetric Bragg reflections and compared with simulated diffraction curves. The calculations are based on dynamical scattering theory. The experimental and theoretical curves exhibit a discrepancy with regard to the angular position of the higher-order satellite reflections, which can be removed by introducing a new expression for the deviation parameter in the dynamical diffraction theory. The improved deviation parameter extends the range of validity of the two-beam approximation, especially for asymmetric reflections with glancing exit geometry. Therefore, if the relaxation of strained-layer heterostructures is to be determined by comparison with simulated rocking curves, only the improved parameter should be used.
The Laue Data Module (LDM) – a software development for Laue X-ray diffraction data processing
Authors: Campbell J. W. , Clifton I. J. , Harding M. M. , Hao Q.
Published: July 2002

The Laue Data Module (LDM) has been defined and implemented in Fortran as the basis for new developments in the processing of Laue X-ray diffraction data. It provides a program-independent way of handling, storing and accessing the parameters required in the initial stages of Laue data processing. The program-independent Laue Reflection List (LRL) and associated functions have also been developed. The way in which these two developments may be used in application programs and as the basis for developing further program-independent Laue-data processing functions is described.
On-line processing of pharmaceutical materials using in situ X-ray diffraction
Authors: MacCalman M. L. , Roberts K. J. , Kerr C. , Hendriksen B.
Published: July 2002

A novel on-line processing cell for examination of the polymorphic forms of pharmaceutical materials using in situ X-ray diffraction is presented. The utility of this technique is demonstrated through an examination of the temperature-dependent polymorphic behaviour of an antibiotic material following recrystallization.
Thermal expansion of caesium halides with the CsCl structure. Erratum
Authors: Wang K. , Reeber R.
Published: July 2002

Corrected units are given for X
1, X
2 and X
3 in Table 1 of the paper by Wang & Reeber [J. Appl. Cryst. (1995). 28, 306–313]. The correct units are (× 10−1 K−1).
Status of the Small-Angle Neutron Scattering Station at the Beijing Synchrotron Radiation Facility
Authors: Dong B. , Sheng W. , Yang H. , Zhang Z.
Published: July 2002

Beamline 4B9A at the Beijing Synchrotron Radiation Facility provides focused monochromatic radiation in an energy range of 3–10 keV. The small-angle X-ray scattering (SAXS) station that is located at the end of the beamline is equipped with a SAXS camera, a position-sensitive detector, an on-line data-acquisition and control system and an alignment carriage. Studies in molecular biology and materials science have been performed at the station. Some results of SAXS studies of biomembranes are described. The experiments confirm that the angular resolution is better than 0.5 mrad with this setting.
Polycapillary X-ray optics for microdiffraction
Authors: MacDonald C. A. , Owens S. M. , Gibson W. M.
Published: July 2002

Polycapillary optics,i.e.shaped arrays consisting of hundreds of thousands of hollow glass capillary tubes, can be used to redirect, collimate or focus X-ray beams. X-rays emitted over a large angular range from conventional laboratory-based sources can be transformed into a beam with a small angular divergence or focused onto a small sample or sample area. Convergent beams of X-rays, with convergence angles as high as 15°, have been produced using polycapillary X-ray optics. Focused-spot sizes as small as 20 µm have been achieved, with flux densities two orders of magnitude larger than that produced by pinhole collimation. This results in a comparable decrease in data collection times because of the increase in direct-beam intensity and reciprocal-space coverage. In addition, the optics can be employed to reduce background and provide more convenient alignment geometries. The inverse dependence of the critical angle for total external reflection on photon energy results in suppression of high-energy photons. This effect can be employed to allow the use of higher tube potentials to increase the characteristic line emission and has also been employed to increase significantly theKα/Kβ ratio in Cu radiation. Measurements of X-ray diffraction data and crystallographic analyses have been performed for systems ranging from elemental crystals to proteins. Data from a lysozyme protein `standard' with a slightly convergent beam, taken in 3 min per frame with 2° oscillation with a 2.8 kW source, refined to an intensity variance of 5% compared to a standard data set. High-quality data were also obtained with a 0.03 kW fixed-anode source and a 2° convergent lens in 5 min per frame.
Morphological characterization of ion-sputtered C–Ag, C/C–Ag and Ag/C films by GISAXS
Authors: Babonneau D. , Naudon A. , Thiaudière D. , Lequien S.
Published: July 2002

A carbon–silver thin film (33 at.% Ag and thickness of 2100 Å) has been synthesized by co-sputtering of a C–Ag target and characterized by grazing-incidence small-angle X-ray scattering (GISAXS), a technique that gives a considerably enhanced surface sensitivity. Experiments have been carried out at or near the critical angle of the layer. It is shown that, because C and Ag show no mutual solubility, a demixing occurs during the co-deposition process and silver clusters form within an amorphous carbon matrix. Using different incident angles of the X-ray beam, it is demonstrated that two populations of clusters are present in the layer: some large and nearly spherical on the surface, others smaller and elongated along the direction of the growth of the thin film in the bulk. In the case of a C/C–Ag bilayer, the surface diffusion is avoided just after the co-deposition process and it is shown that only the small and elongated clusters in the bulk are formed. In the case of a very thin Ag/C layer, there is only surface diffusion and it is shown that large silver islands are formed on the carbon surface. Such experiments demonstrate that the growth mechanism that takes place during the co-deposition process involves mainly a surface diffusion of silver and carbon atoms, as opposed to a volume diffusion.
Quantitative phase analysis of α- and β-silicon nitrides. I. Estimation of errors
Authors: Toraya H.
Published: July 2002

Errors in the quantitative phase analysis (QPA) of α- and β-silicon nitrides (Si3N4) using the mean normalized intensity (MNI) method and the Rietveld method have been estimated by theory and experiments. A total error for a weight fraction (w) in a binary system can be expressed in the formE(w) =w(1 −w)S, whereSis the quadratic sum of statistical and systematic errors. Random errors associated with counting statistics for integrated intensities in the MNI method are below 0.1∼0.2 wt% if the studied reflections have average peak heights of more than ∼1000 counts. Such errors will become approximately twice as large if peak-height intensities are used. The error associated with particle statistics in the studied samples was smaller than the counting-statistics error. Among various sources of systematic errors examined, incorrect choice of constrained/unconstrained full width at half-maximum (FWHM) parameters gave the largest error. The choice of the background function had little influence on the QPA, whereas the choice of the profile function had a large influence. Truncation errors in profile function calculations and the 2θ range of the observed data are below ±0.1 wt% when appropriate criteria are applied. Systematic errors in the measurement of peak-height intensity arise primarily from the overestimation of intensities of weak peaks that overlap the tails of strong peaks, as well as from line broadening of β-phase reflections in the studied samples. Errors caused by ignoring the difference in density between the two phases were negligibly small. Estimated errors of the methods followed the order: the MNI method using peak-height intensities < the MNI method using integrated intensities ≃ the Rietveld method.
Structure of ζ-phase plutonium–uranium
Authors: Lawson A. C. , Goldstone J. A. , Cort B. , Martinez R. J. , Vigil F. A. , Zocco T. G. , Richardson J. W. , Mueller M. H.
Published: July 2002

The structure of the ζ-phase in the Pu—U system has been determined by neutron powder diffraction. The phase crystallizes in space group R{\bar 3}m with 58 atoms in the primitive unit cell and 10 atoms in the asymmetric unit. The structure is characterized by many short bonds and fits the general pattern of the light actinides. Thermal expansion and elastic data were obtained from the diffraction experiments.
Statistical analysis of noncovalent interactions of anion groups in crystal structures. II. Hydrogen bonding of thiocyanate anions
Authors: Tchertanov L. , Pascard C.
Published: July 2002

The hydrogen-bond acceptor function of the thiocyanate anion is analyzed in 52 crystal structures retrieved from the Cambridge Crystallographic Database. All modes of hydrogen-bond coordination are represented: by the sulfur, by the nitrogen and by the π-system of the anion. The preferred areas for the H donors (D = OH and NH groups) were determined: (a) around sulfur, as a torus centered at the S end, the axis of which is the linear anion, and with an average DSON angle of 99°, and (b) around nitrogen, on a spherical cap delimited by the solid angle, SOND (average = 145°), with the linear anion. The anion-acceptor function is characterized by multiple hydrogen bonding and, in most cases (80%), thiocyanate binds through both acceptor centers (S and N). Important backbonding of sulfur in the thiocyanate anion is structurally evidenced.
Hexamethylenetetramine suberate, a strongly anharmonic modulated structure
Authors: Bussien Gaillard V. , Paciorek W. , Schenk K. , Chapuis G.
Published: July 2002

Hexamethylenetetramine suberate is an organic compound presenting a one-dimensional modulation with strong satellite reflections between 123 and 300 K. Single-crystal X-ray intensities of main reflections and satellites up to fourth order have been measured and used for refining a model based on displacive atomic modulation functions. Harmonic terms up to eighth order were necessary to describe the strongly anharmonic modulation. The structure consists of alternating sheets of hexamethylenetetramine and suberic acid connected by hydrogen bonds. Each layer of suberic acid chains consists of alternating areas, each of which is characterized by a common orientation for all chains. These orientations subtend an angle of roughly 60°. At the interfaces, neighbouring chains in adjacent areas adopt intermediate orientations. The two carboxyl groups participate in hydrogen bonds, the character of which depends on the internal coordinate t. In one group and for all values of t, the same oxygen forms a double bond with the α-carbon and the other a single bond, and in the other the carboxylate form is observed for all values of t. The packings of both moieties are incompatible and are conjectured to be responsible for the incommensurability of the structure.
Refinement of Ammonium Perrhenate Structure Using a Pseudo-Spin Model for the Ammonium Ion Orientation
Authors: Swainson I. P. , Brown R. J. C.
Published: July 2002

A new Rietveld refinement of previously reported powder neutron diffraction data on ND4ReO4 taken over a wide range of temperatures [Powell, Brown, Harnden & Reid (1993). Acta Cryst. B49, 463–468] is reported. Rigid-body constraints are applied to the cation geometry and occupation of a second cation orientation at higher temperatures is permitted. The resulting structure at higher temperatures is to be preferred to the previous structure with a single cation orientation and supports the pseudo-spin theory of cooperative disordering without a phase transition.
Zeolite Rho Loaded with Methylamines. I. Monomethylamine Loadings
Authors: Weidenthaler C. , Fischer R. X. , Abrams L. , Hewat A.
Published: July 2002

Samples of two differently prepared zeolite rho loaded with different amounts of monomethylamine (MMA) were studied in their hydrated and dehydrated forms by X-ray and neutron diffraction. Both zeolites are partially dealuminated, as indicated by nonframework alumina, which is assumed to be Al2O3 or AlOOH. Series I was prepared from dry-calcined NH4-rho at 873 K, series II from steam-calcined NH4-rho at 773 K. The samples were loaded with different amounts of deuterated MMA, Rietveld refinements yielded the following results for series I (dry): (1) H3.8(H-MMA)5Cs0.2Al9Si39O2.Al2O3.28H2O, X-ray data collection at room temperature, Im\overline 3m, a = 14.9991 (2) Å, R

wp
= 0.095; (2) composition as in (1), anhydrous and deuterated, neutron data collected at 5 K, disproportionation into two phases in I\overline 43m, with a = 14.8410 (7) and 14.5273 (11) Å, R

wp
= 0.038; (3) (H-MMA)8.8Cs0.2Al9Si39O96.Al2O3.25H2O, X-ray data collection at room temperature, I\overline 43m, a = 14.9771 (2) Å, R

wp
= 0.090. Series II (steam): (4) H0.3(H-MMA)5Cs0.7Al6Si42O96.2.5Al2O3.23H2O, X-ray data collected at room temperature,Im\overline 3m, a = 15.0323 (2) Å, R

wp
= 0.124; (5) composition as in (4), anhydrous and deuterated, neutron data collected at 5 K, disproportionation into two phases in I\overline 43m with a = 14.9151 (2) and 14.6475(8) Å, R

wp
= 0.031. In the hydrated samples MMA resides on the center axis in the α-cage with the N atoms pointing to the single eight-ring; upon dehydration it migrates into the double eight-rings.
Distortion of Crystal Structures of Some CoIII Ammine Complexes. I. Distortion of Crystal Structure of [Co(NH3)5NO2]Cl(NO3) on Cooling
Authors: Boldyreva E. , Kivikoski J. , Howard J. A. K.
Published: July 2002

The anisotropy of the structural distortion of [Co(NH3)5NO2]Cl(NO3), pentaamminenitrocobalt(III) chloride nitrate, on cooling from 290 to 150 K was studied by variable-temperature single-crystal X-ray diffraction. The changes in lattice parameters were used to calculate the strain tensors and to scan linear distortion in various crystallographic directions. The changes of different intra- and intermolecular distances in the structure were followed. Lattice strain induced by low temperature was compared with lattice strain in the same structure under high hydrostatic pressure and with lattice strain induced by homogeneous nitro–nitrito linkage isomerization.