13,330 research outputs found
Development of dispersion-strengthened Ni-Cr-ThOz alloys for the space shuttle thermal protection system
Manufacturing processes were developed for TD-NiCr providing small sheet (45 x 90 cm), and larger sheet (60 x 150 cm) and foil. The alternate alloy, DS-NiCr, was produced by pack-chromizing Ni-ThO2 sheet. Formability criteria are being established for basic sheet forming processes, which are brake forming, corrugation forming, joggling, dimpling, and beading. Resistance spot welding (fusion and solid state), resistance seam welding, solid state diffusion welding, and brazing are included in the joining programs. Major emphasis is centered on an Al-modified Ni-Cr-ThO2 alloy development. These alloys, containing 3 to 5% Al, form the protective Al2O3 scale. This enhances oxidation resistance under reentry conditions. Both TD-NiCrAl and DS-NiCrAl alloys are included. A tentative composition of Ni-16Cr-3.5Al-2ThO2 was selected based on oxidation resistance and fabricability
Spin Freezing in Geometrically Frustrated Antiferromagnets with Weak Disorder
We investigate the consequences for geometrically frustrated antiferromagnets
of weak disorder in the strength of exchange interactions. Taking as a model
the classical Heisenberg antiferromagnet with nearest neighbour exchange on the
pyrochlore lattice, we examine low-temperature behaviour. We show that random
exchange generates long-range effective interactions within the extensively
degenerate ground states of the clean system. Using Monte Carlo simulations, we
find a spin glass transition at a temperature set by the disorder strength.
Disorder of this type, which is generated by random strains in the presence of
magnetoelastic coupling, may account for the spin freezing observed in many
geometrically frustrated magnets.Comment: 4 pages, 5 figure
Construction and evaluation of classifiers for forensic document analysis
In this study we illustrate a statistical approach to questioned document
examination. Specifically, we consider the construction of three classifiers
that predict the writer of a sample document based on categorical data. To
evaluate these classifiers, we use a data set with a large number of writers
and a small number of writing samples per writer. Since the resulting
classifiers were found to have near perfect accuracy using leave-one-out
cross-validation, we propose a novel Bayesian-based cross-validation method for
evaluating the classifiers.Comment: Published in at http://dx.doi.org/10.1214/10-AOAS379 the Annals of
Applied Statistics (http://www.imstat.org/aoas/) by the Institute of
Mathematical Statistics (http://www.imstat.org
Displaying desire and distinction in housing
The article discusses the significance of cultural capital for the understanding of the field of housing in contemporary Britain. It explores the relationship between housing and the position of individuals in social space mapped out by means of a multiple correspondence analysis. It considers the material aspects of housing and the changing contexts that are linked to the creation and display of desire for social position and distinction expressed in talk about home decoration as personal expression and individuals' ideas of a `dream house'. It is based on an empirical investigation of taste and lifestyle using nationally representative survey data and qualitative interviews. The article shows both that personal resources and the imagination of home are linked to levels of cultural capital, and that rich methods of investigation are required to grasp the significance of these normally invisible assets to broaden the academic understanding of the field of housing in contemporary culture
Efficient extraction of a collimated ultra-cold neutron beam using diffusive channels
We present a first experimental demonstration of a new method to extract a
well-collimated beam of ultra-cold neutrons (UCN) from a storage vessel.
Neutrons with too large divergence are not removed from the beam by an
absorbing collimation, but a diffuse or semidiffuse channel with high Fermi
potential reflects them back into the vessel. This avoids unnecessary losses
and keeps the storage time high, which may be beneficial when the vessel is
part of a UCN source with long buildup time of a high UCN density
Reply: Expression of oestrogen receptor beta proteins in human breast cancer biopsies
British Journal of Cancer (2002) 87, 688â689. doi:10.1038/sj.bjc.6600535 www.bjcancer.co
When it Pays to Rush: Interpreting Morphogen Gradients Prior to Steady-State
During development, morphogen gradients precisely determine the position of
gene expression boundaries despite the inevitable presence of fluctuations.
Recent experiments suggest that some morphogen gradients may be interpreted
prior to reaching steady-state. Theoretical work has predicted that such
systems will be more robust to embryo-to-embryo fluctuations. By analysing two
experimentally motivated models of morphogen gradient formation, we investigate
the positional precision of gene expression boundaries determined by
pre-steady-state morphogen gradients in the presence of embryo-to-embryo
fluctuations, internal biochemical noise and variations in the timing of
morphogen measurement. Morphogens that are direct transcription factors are
found to be particularly sensitive to internal noise when interpreted prior to
steady-state, disadvantaging early measurement, even in the presence of large
embryo-to-embryo fluctuations. Morphogens interpreted by cell-surface receptors
can be measured prior to steady-state without significant decrease in
positional precision provided fluctuations in the timing of measurement are
small. Applying our results to experiment, we predict that Bicoid, a
transcription factor morphogen in Drosophila, is unlikely to be interpreted
prior to reaching steady-state. We also predict that Activin in Xenopus and
Nodal in zebrafish, morphogens interpreted by cell-surface receptors, can be
decoded in pre-steady-state.Comment: 18 pages, 3 figure
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Inequalities in Health and Service Use among People with Borderline Intellectual Impairment
This report, produced in collaboration with Professor Angela Hassiotis and others, sets out the extent to which people with borderline intellectual impairment face inequalities in health and use of services compared with the rest of the population, and seeks to improve awareness of these inequalities.
Findings
- Borderline intellectual impairment is common, affecting at least one adult in ten in England. The term is used here to refer to people with good verbal skills and living in private households, but who may experience cognitive impairments.
- The findings in this report are consistent with previous research: people with borderline intellectual impairment are a disadvantaged group and their needs are not well understood.
- Such adults face high levels of poor mental health, poorer general health, and many limitations in their daily lives.
- Their level of use of mental health treatment and services does not appear to be commensurate with their higher level of need. This indicates that they are underserved compared with the rest of the population.
- This may be due to a lack of professional awareness of their needs, to services not adapting enough to meet those needs, or to difficulties the individual faces in seeking treatment and support.
- Adults with borderline intellectual impairment constitute key users of primary and secondary health care, and employment, education and welfare support. Improving awareness of the needs of this group should form part of wider plans to reduce inequalities in health and service use in England.
Methods
Secondary analysis of data from the Adult Psychiatric Morbidity Survey (APMS) was conducted to profile the circumstances of people with borderline intellectual impairment. APMS is one of the most authoritative and comprehensive national household surveys to assess both intellectual functioning and mental health in adults in England
Large-scale structure in a new deep IRAS galaxy redshift survey
We present here the first results from two recently completed, fully sampled redshift surveys comprising 3703 IRAS Faint Source Survey (FSS) galaxies. An unbiased counts-in-cells analysis finds a clustering strength in broad agreement with other recent redshift surveys and at odds with the standard cold dark matter model. We combine our data with those from the QDOT and 1.2 Jy surveys, producing a single estimate of the IRAS galaxy clustering strength. We compare the data with the power spectrum derived from a mixed dark matter universe. Direct comparison of the clustering strength seen in the IRAS samples with that seen in the APM-Stromlo survey suggests b_O/b_I=1.20+/-0.05 assuming a linear, scale independent biasing. We also perform a cell by cell comparison of our FSS-z sample with galaxies from the first CfA slice, testing the viability of a linear-biasing scheme linking the two. We are able to rule out models in which the FSS-z galaxies identically trace the CfA galaxies on scales 5-20h^{-1}Mpc. On scales of 5 and 10h^{-1}Mpc no linear-biasing model can be found relating the two samples. We argue that this result is expected since the CfA sample includes more elliptical galaxies which have different clustering properties from spirals. On scales of 20h^{-1}Mpc no linear-biasing model with b_O/b_I < 1.70 is acceptable. When comparing the FSS-z galaxies to the CfA spirals, however, the two populations trace the same structures within our uncertaintie
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