7,342 research outputs found
Rational solutions of pairs of diagonal equations, one cubic and one quadratic
We obtain an essentially optimal estimate for the moment of order 32/3 of the
exponential sum having argument . Subject to modest local
solubility hypotheses, we thereby establish that pairs of diagonal Diophantine
equations, one cubic and one quadratic, possess non-trivial integral solutions
whenever the number of variables exceeds 10
Physicality and Cooperative Design
CSCW researchers have increasingly come to realize that material work setting and its population of artefacts play a crucial part in coordination of distributed or co-located work. This paper uses the notion of physicality as a basis to understand cooperative work. Using examples from an ongoing fieldwork on cooperative design practices, it provides a conceptual understanding of physicality and shows that material settings and co-worker’s working practices play an important role in understanding physicality of cooperative design
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Epigenetic Inheritance of a Cocaine Resistance Phenotype
A heritable phenotype resulting from the self-administration of cocaine in rats was delineated. We observed delayed acquisition and reduced maintenance of cocaine self-administration in male, but not female, offspring of sires that self-administered cocaine. Brain-derived neurotrophic factor (BDNF) mRNA and protein were increased in the medial prefrontal cortex (mPFC) and there was an increased association of acetylated histone H3 with BDNF promoters only in the male offspring of cocaine-experienced sires. Administration of a BDNF receptor antagonist (the TrkB receptor antagonist ANA-12) reversed the diminished cocaine self-administration in male cocaine-sired rats. In addition, the association of acetylated histone H3 with BDNF promoters was increased in the sperm of sires that self-administered cocaine. Collectively, these findings indicate that voluntary paternal ingestion of cocaine results in epigenetic reprograming of the germline resulting in profound effects on mPFC gene expression and resistance to cocaine reinforcement in male offspring
Near-Infrared and Optical Luminosity Functions from the 6dF Galaxy Survey
Luminosity functions and their integrated luminosity densities are presented
for the 6dF Galaxy Survey (6dFGS). This ongoing survey ultimately aims to
measure around 150,000 redshifts and 15,000 peculiar velocities over almost the
entire southern sky at |b|>10 deg. The main target samples are taken from the
2MASS Extended Source Catalog and the SuperCOSMOS Sky Survey catalogue, and
comprise 138,226 galaxies complete to (K, H, J, rF, bJ) = (12.75, 13.00, 13.75,
15.60, 16.75). These samples are comparable in size to the optically-selected
Sloan Digital Sky Survey and 2dF Galaxy Redshift Survey samples, and improve on
recent near-infrared-selected redshift surveys by more than an order of
magnitude in both number and sky coverage. The partial samples used in this
paper contain a little over half of the total sample in each band and are ~90
percent complete.
Luminosity distributions are derived using the 1/Vmax, STY and SWML
estimators, and probe 1 to 2 absolute magnitudes fainter in the near-infrared
than previous surveys. The effects of magnitude errors, redshift incompleteness
and peculiar velocities have been taken into account and corrected throughout.
Generally, the 6dFGS luminosity functions are in excellent agreement with those
of similarly-sized surveys. Our data are of sufficient quality to demonstrate
that a Schechter function is not an ideal fit to the true luminosity
distribution, due to its inability to simultaneously match the faint end slope
and rapid bright end decline. Integrated luminosity densities from the 6dFGS
are consistent with an old stellar population and moderately declining star
formation rate.Comment: 20 pages, 15 figures. MNRAS published. Replaces earlier version
carrying a typo in Table 6. High resolution versions of the figures can be
obtained from http://www.aao.gov.au/local/www/6df/Publication
Linear spaces on the intersection of cubic hypersurfaces
Upper bounds for the number of variables necessary to imply the existence of an m -dimensional linear variety on the intersection of r cubic hypersurfaces over local and global fields are given.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/41633/1/605_2006_Article_BF02349626.pd
Maintaining Force Control Despite Changes in Emotional Context Engages Dorsomedial Prefrontal and Premotor Cortex
Viewing emotional as compared with neutral images results in an increase in force production. An emotion-driven increase in force production has been associated with increased brain activity in ventrolateral prefrontal cortex and primary motor cortex (M1). In many instances, however, force production must be held constant despite changes in emotional state and the neural circuits underlying this form of control are not well understood. To address this issue, we designed a task in which subjects viewed pleasant, unpleasant, and neutral images during a force production task. We measured brain activity using functional magnetic resonance imaging and examined functional connectivity between emotion and motor circuits. Despite similar force performance across conditions, increased brain activity was evidenced in dorsomedial prefrontal cortex (dmPFC) and left ventral premotor cortex (PMv) when force was produced during emotional as compared with neutral conditions. Connectivity analyses extended these findings by demonstrating a task-dependent functional circuit between dmPFC and ventral and dorsal portions of premotor cortex. Our findings show that when force production has to be consistent despite changes in emotional context, a functional circuit between dmPFC and PMv and dorsal premotor cortex is engaged
Regularity Properties and Pathologies of Position-Space Renormalization-Group Transformations
We reconsider the conceptual foundations of the renormalization-group (RG)
formalism, and prove some rigorous theorems on the regularity properties and
possible pathologies of the RG map. Regarding regularity, we show that the RG
map, defined on a suitable space of interactions (= formal Hamiltonians), is
always single-valued and Lipschitz continuous on its domain of definition. This
rules out a recently proposed scenario for the RG description of first-order
phase transitions. On the pathological side, we make rigorous some arguments of
Griffiths, Pearce and Israel, and prove in several cases that the renormalized
measure is not a Gibbs measure for any reasonable interaction. This means that
the RG map is ill-defined, and that the conventional RG description of
first-order phase transitions is not universally valid. For decimation or
Kadanoff transformations applied to the Ising model in dimension ,
these pathologies occur in a full neighborhood of the low-temperature part of the first-order
phase-transition surface. For block-averaging transformations applied to the
Ising model in dimension , the pathologies occur at low temperatures
for arbitrary magnetic-field strength. Pathologies may also occur in the
critical region for Ising models in dimension . We discuss in detail
the distinction between Gibbsian and non-Gibbsian measures, and give a rather
complete catalogue of the known examples. Finally, we discuss the heuristic and
numerical evidence on RG pathologies in the light of our rigorous theorems.Comment: 273 pages including 14 figures, Postscript, See also
ftp.scri.fsu.edu:hep-lat/papers/9210/9210032.ps.
Metal enrichment processes
There are many processes that can transport gas from the galaxies to their
environment and enrich the environment in this way with metals. These metal
enrichment processes have a large influence on the evolution of both the
galaxies and their environment. Various processes can contribute to the gas
transfer: ram-pressure stripping, galactic winds, AGN outflows, galaxy-galaxy
interactions and others. We review their observational evidence, corresponding
simulations, their efficiencies, and their time scales as far as they are known
to date. It seems that all processes can contribute to the enrichment. There is
not a single process that always dominates the enrichment, because the
efficiencies of the processes vary strongly with galaxy and environmental
properties.Comment: 18 pages, 8 figures, accepted for publication in Space Science
Reviews, special issue "Clusters of galaxies: beyond the thermal view",
Editor J.S. Kaastra, Chapter 17; work done by an international team at the
International Space Science Institute (ISSI), Bern, organised by J.S.
Kaastra, A.M. Bykov, S. Schindler & J.A.M. Bleeke
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Beyond handover: supporting awareness for continuous coverage
Abstract Hospitals are required to operate as a continuous system because patient care cannot be temporarily suspended and handover is seen as a key method for enabling this. This paper reports a study of handover in a medical admissions unit. We draw on the notion of awareness as conceptualised within the Computer Supported Cooperative Work literature to explore the role played by a variety of cognitive artifacts in supporting continuous coverage. While such awareness is typically characterised as being ‘effortless’, our study reveals that maintaining awareness in a context such as the medical admissions unit is effortful due to invisible work. We suggest that the notion of awareness is beneficial for exploring the practices of continuous coverage because it moves attention away from the moment of handover, instead encouraging consideration of the variety of practices through which clinicians display their work to, and monitor the work of, colleagues on different shifts. We argue that efforts to support continuous coverage should focus on improving awareness by increasing the visibility of information
Recurrent mutations in the U2AF1 splicing factor in myelodysplastic syndromes
Myelodysplastic syndromes (MDS) are hematopoietic stem cell disorders that often progress to chemotherapy-resistant secondary acute myeloid leukemia (sAML). We used whole-genome sequencing to perform an unbiased comprehensive screen to discover the somatic mutations in a sample from an individual with sAML and genotyped the loci containing these mutations in the matched MDS sample. Here we show that a missense mutation affecting the serine at codon 34 (Ser34) in U2AF1 was recurrently present in 13 out of 150 (8.7%) subjects with de novo MDS, and we found suggestive evidence of an increased risk of progression to sAML associated with this mutation. U2AF1 is a U2 auxiliary factor protein that recognizes the AG splice acceptor dinucleotide at the 3' end of introns, and the alterations in U2AF1 are located in highly conserved zinc fingers of this protein. Mutant U2AF1 promotes enhanced splicing and exon skipping in reporter assays in vitro. This previously unidentified, recurrent mutation in U2AF1 implicates altered pre-mRNA splicing as a potential mechanism for MDS pathogenesis
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