64 research outputs found
A Mean Field Model for the Quadrupolar Phases of UPd
UPd is known to exhibit four antiferroquadrupolar ordered phases at low
temperatures. We report measurements of the magnetisation and magnetostriction
of single crystal UPd, along the principal symmetry directions, in fields
up to 33 T. These results have been combined with recent inelastic neutron and
x-ray resonant scattering measurements to construct a mean field model of
UPd including up to fourth nearest neighbour interactions. In particular we
find that anisotropic quadrupolar interactions must be included in order to
explain the low temperature structures derived from the scattering data.Comment: 9 pages, 6 figures, 3 table
The Influences of Reproductive Status and Acute Stress on the Levels of Phosphorylated Mu Opioid Receptor Immunoreactivity in Rat Hippocampus
Opioids play a critical role in hippocampally dependent behavior and plasticity. In the hippocampal formation, mu opioid receptors (MOR) are prominent in parvalbumin (PARV) containing interneurons. Previously we found that gonadal hormones modulate the trafficking of MORs in PARV interneurons. Although sex differences in response to stress are well documented, the point at which opioids, sex, and stress interact to influence hippocampal function remains elusive. Thus, we used quantitative immunocytochemistry in combination with light and electron microscopy for the phosphorylated MOR (pMOR) at the SER375 carboxy-terminal residue in male and female rats to assess these interactions. In both sexes, pMOR-immunoreactivity (ir) was prominent in axons and terminals and in a few neuronal somata and dendrites, some of which contained PARV in the mossy fiber pathway region of the dentate gyrus (DG) hilus and CA3 stratum lucidum. In unstressed rats, the levels of pMOR-ir in the DG or CA3 were not affected by sex or estrous cycle stage. However, immediately following 30 min of acute immobilization stress (AIS), males had higher levels of pMOR-ir whereas females at proestrus and estrus (high estrogen stages) had lower levels of pMOR-ir within the DG. In contrast, the number and types of neuronal profiles with pMOR-ir were not altered by AIS in either males or proestrus females. These data demonstrate that although gonadal steroids do not affect pMOR levels at resting conditions, they are differentially activated both pre and postsynaptic MORs following stress. These interactions may contribute to the reported sex differences in hippocampally dependent behaviors in stressed animals
Simulating Bacterial Growth, Competition, and Resistance with Agent-Based Models and Laboratory Experiments
Defects in tRNA Modification Associated with Neurological and Developmental Dysfunctions in Caenorhabditis elegans Elongator Mutants
Elongator is a six subunit protein complex, conserved from yeast to humans. Mutations in the human Elongator homologue, hELP1, are associated with the neurological disease familial dysautonomia. However, how Elongator functions in metazoans, and how the human mutations affect neural functions is incompletely understood. Here we show that in Caenorhabditis elegans, ELPC-1 and ELPC-3, components of the Elongator complex, are required for the formation of the 5-carbamoylmethyl and 5-methylcarboxymethyl side chains of wobble uridines in tRNA. The lack of these modifications leads to defects in translation in C. elegans. ELPC-1::GFP and ELPC-3::GFP reporters are strongly expressed in a subset of chemosensory neurons required for salt chemotaxis learning. elpc-1 or elpc-3 gene inactivation causes a defect in this process, associated with a posttranscriptional reduction of neuropeptide and a decreased accumulation of acetylcholine in the synaptic cleft. elpc-1 and elpc-3 mutations are synthetic lethal together with those in tuc-1, which is required for thiolation of tRNAs having the 5′methylcarboxymethyl side chain. elpc-1; tuc-1 and elpc-3; tuc-1 double mutants display developmental defects. Our results suggest that, by its effect on tRNA modification, Elongator promotes both neural function and development
Valid and reliable instruments for arm-hand assessment at ICF activity level in persons with hemiplegia: a systematic review
Contains fulltext :
110141.pdf (publisher's version ) (Open Access)BACKGROUND: Loss of arm-hand performance due to a hemiparesis as a result of stroke or cerebral palsy (CP), leads to large problems in daily life of these patients. Assessment of arm-hand performance is important in both clinical practice and research. To gain more insight in e.g. effectiveness of common therapies for different patient populations with similar clinical characteristics, consensus regarding the choice and use of outcome measures is paramount. To guide this choice, an overview of available instruments is necessary. The aim of this systematic review is to identify, evaluate and categorize instruments, reported to be valid and reliable, assessing arm-hand performance at the ICF activity level in patients with stroke or cerebral palsy. METHODS: A systematic literature search was performed to identify articles containing instruments assessing arm-hand skilled performance in patients with stroke or cerebral palsy. Instruments were identified and divided into the categories capacity, perceived performance and actual performance. A second search was performed to obtain information on their content and psychometrics. RESULTS: Regarding capacity, perceived performance and actual performance, 18, 9 and 3 instruments were included respectively. Only 3 of all included instruments were used and tested in both patient populations. The content of the instruments differed widely regarding the ICF levels measured, assessment of the amount of use versus the quality of use, the inclusion of unimanual and/or bimanual tasks and the inclusion of basic and/or extended tasks. CONCLUSIONS: Although many instruments assess capacity and perceived performance, a dearth exists of instruments assessing actual performance. In addition, instruments appropriate for more than one patient population are sparse. For actual performance, new instruments have to be developed, with specific focus on the usability in different patient populations and the assessment of quality of use as well as amount of use. Also, consensus about the choice and use of instruments within and across populations is needed
Searching for continuous Gravitational Waves in the second data release of the International Pulsar Timing Array
The International Pulsar Timing Array 2nd data release is the combination of
datasets from worldwide collaborations. In this study, we search for continuous
waves: gravitational wave signals produced by individual supermassive black
hole binaries in the local universe. We consider binaries on circular orbits
and neglect the evolution of orbital frequency over the observational span. We
find no evidence for such signals and set sky averaged 95% upper limits on
their amplitude h 95 . The most sensitive frequency is 10nHz with h 95 = 9.1
10-15 . We achieved the best upper limit to date at low and high frequencies of
the PTA band thanks to improved effective cadence of observations. In our
analysis, we have taken into account the recently discovered common red noise
process, which has an impact at low frequencies. We also find that the peculiar
noise features present in some pulsars data must be taken into account to
reduce the false alarm. We show that using custom noise models is essential in
searching for continuous gravitational wave signals and setting the upper
limit
Comparing Recent Pulsar Timing Array Results on the Nanohertz Stochastic Gravitational-wave Background
The Australian, Chinese, European, Indian, and North American pulsar timing array (PTA) collaborations recently reported, at varying levels, evidence for the presence of a nanohertz gravitational-wave background (GWB). Given that each PTA made different choices in modeling their data, we perform a comparison of the GWB and individual pulsar noise parameters across the results reported from the PTAs that constitute the International Pulsar Timing Array (IPTA). We show that despite making different modeling choices, there is no significant difference in the GWB parameters that are measured by the different PTAs, agreeing within 1σ. The pulsar noise parameters are also consistent between different PTAs for the majority of the pulsars included in these analyses. We bridge the differences in modeling choices by adopting a standardized noise model for all pulsars and PTAs, finding that under this model there is a reduction in the tension in the pulsar noise parameters. As part of this reanalysis, we "extended" each PTA's data set by adding extra pulsars that were not timed by that PTA. Under these extensions, we find better constraints on the GWB amplitude and a higher signal-to-noise ratio for the Hellings–Downs correlations. These extensions serve as a prelude to the benefits offered by a full combination of data across all pulsars in the IPTA, i.e., the IPTA's Data Release 3, which will involve not just adding in additional pulsars but also including data from all three PTAs where any given pulsar is timed by more than a single PTA
Comparing recent PTA results on the nanohertz stochastic gravitational wave background
The Australian, Chinese, European, Indian, and North American pulsar timing
array (PTA) collaborations recently reported, at varying levels, evidence for
the presence of a nanohertz gravitational wave background (GWB). Given that
each PTA made different choices in modeling their data, we perform a comparison
of the GWB and individual pulsar noise parameters across the results reported
from the PTAs that constitute the International Pulsar Timing Array (IPTA). We
show that despite making different modeling choices, there is no significant
difference in the GWB parameters that are measured by the different PTAs,
agreeing within . The pulsar noise parameters are also consistent
between different PTAs for the majority of the pulsars included in these
analyses. We bridge the differences in modeling choices by adopting a
standardized noise model for all pulsars and PTAs, finding that under this
model there is a reduction in the tension in the pulsar noise parameters. As
part of this reanalysis, we "extended" each PTA's data set by adding extra
pulsars that were not timed by that PTA. Under these extensions, we find better
constraints on the GWB amplitude and a higher signal-to-noise ratio for the
Hellings and Downs correlations. These extensions serve as a prelude to the
benefits offered by a full combination of data across all pulsars in the IPTA,
i.e., the IPTA's Data Release 3, which will involve not just adding in
additional pulsars, but also including data from all three PTAs where any given
pulsar is timed by more than as single PTA.Comment: 21 pages, 9 figures, submitted to Ap
The genetic architecture of the human cerebral cortex
The cerebral cortex underlies our complex cognitive capabilities, yet little is known about the specific genetic loci that influence human cortical structure. To identify genetic variants that affect cortical structure, we conducted a genome-wide association meta-analysis of brain magnetic resonance imaging data from 51,665 individuals. We analyzed the surface area and average thickness of the whole cortex and 34 regions with known functional specializations. We identified 199 significant loci and found significant enrichment for loci influencing total surface area within regulatory elements that are active during prenatal cortical development, supporting the radial unit hypothesis. Loci that affect regional surface area cluster near genes in Wnt signaling pathways, which influence progenitor expansion and areal identity. Variation in cortical structure is genetically correlated with cognitive function, Parkinson's disease, insomnia, depression, neuroticism, and attention deficit hyperactivity disorder
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