23,496 research outputs found
CsCl-type compounds in binary alloys of rare-earth metals with gold and silver
In binary alloys of silver with Sm, Tb, Ho, and Tm, and of gold with Y, Pr, Nd, Sm, Gd, Tb, Dy, Ho, Er, and Tm, intermediate phases containing stoichiometric proportions of the two metals were found to crystallize into the CsCl (B2)-type structure. The lattice parameters of these phases are reported and a correlation has been found between these lattice parameters and the trivalent ionic radii of the rare-earth metals
Units of Evidence for Analyzing Subdisciplinary Difference in Data Practice Studies
Digital libraries (DLs) are adapting to accommodate research data
and related services. The complexities of this new content spans
the elements of DL development, and there are questions
concerning data selection, service development, and how best to
align these with local, institutional initiatives for
cyberinfrastructure, data-intensive research, and data stewardship.
Small science disciplines are of particular relevance due to the
prevalence of this mode of research in the academy, and the
anticipated magnitude of data production. To support data
acquisition into DLs – and subsequent data reuse – there is a need
for new knowledge on the range and complexities inherent in
practice-data-curation arrangements for small science research.
We present a flexible methodological approach crafted to generate
data units to analyze these relationships and facilitate crossdisciplinary
comparisons.Library Services (LG-06-07-0032-07) and National Science Foundation (OCI-0830976).is peer reviewe
Non-equilibrium Transport in the Anderson model of a biased Quantum Dot: Scattering Bethe Ansatz Phenomenology
We derive the transport properties of a quantum dot subject to a source-drain
bias voltage at zero temperature and magnetic field. Using the Scattering Bethe
Anstaz, a generalization of the traditional Thermodynamic Bethe Ansatz to open
systems out of equilibrium, we derive exact results for the quantum dot
occupation out of equilibrium and, by introducing phenomenological spin- and
charge-fluctuation distribution functions in the computation of the current,
obtain the differential conductance for large U/\Gamma. The Hamiltonian to
describe the quantum dot system is the Anderson impurity Hamiltonian and the
current and dot occupation as a function of voltage are obtained numerically.
We also vary the gate voltage and study the transition from the mixed valence
to the Kondo regime in the presence of a non-equilibrium current. We conclude
with the difficulty we encounter in this model and possible way to solve them
without resorting to a phenomenological method.Comment: 20 pages, 20 figures, published versio
Hadronic production of the -wave excited -states ()
Adopting the complete approach of the perturbative QCD (pQCD)
and updated parton distribution functions, we have estimated the hadronic
production of -wave excited -states (). In the estimate,
special care on the relation of the production amplitude to the derivative of
wave function at origin of the potential model is payed. For experimental
references, main uncertainties are discussed, and the total cross sections and
the distributions of the production with reasonable cuts at the energies of
Tevatron and LHC are computed and presented. The results show that -wave
production may contribute to the -meson production indirectly by a factor
about 0.5 of the direct production, and with such a big cross section, it is
worth further to study the possibility to observe the -wave production
itself experimentally.Comment: 23 pages, 9 figures, to replace for revising the misprints ec
Preliminary Evidence of Increased Hippocampal Myelin Content in Veterans with Posttraumatic Stress Disorder.
Recent findings suggest the formation of myelin in the central nervous system by oligodendrocytes is a continuous process that can be modified with experience. For example, a recent study showed that immobilization stress increased oligodendrogensis in the dentate gyrus of adult rat hippocampus. Because changes in myelination represents an adaptive form of brain plasticity that has a greater reach in the adult brain than other forms of plasticity (e.g., neurogenesis), the objective of this "proof of concept" study was to examine whether there are differences in myelination in the hippocampi of humans with and without post-traumatic stress disorder (PTSD). We used the ratio of T1-weighted/T2-weighted magnetic resonance image (MRI) intensity to estimate the degree of hippocampal myelination in 19 male veterans with PTSD and 19 matched trauma-exposed male veterans without PTSD (mean age: 43 ± 12 years). We found that veterans with PTSD had significantly more hippocampal myelin than trauma-exposed controls. There was also found a positive correlation between estimates of hippocampal myelination and PTSD and depressive symptom severity. To our knowledge, this is the first study to examine hippocampal myelination in humans with PTSD. These results provide preliminary evidence for stress-induced hippocampal myelin formation as a potential mechanism underlying the brain abnormalities associated with vulnerability to stress
Molecular evidence of genetic diversity of Borrelia burgdorferi sensu lato detected in Ixodes granulatus ticks removed from rodents in Taiwan
Comparison of acoustic travel-time measurement of solar meridional circulation from SDO/HMI and SOHO/MDI
Time-distance helioseismology is one of the primary tools for studying the
solar meridional circulation. However, travel-time measurements of the
subsurface meridional flow suffer from a variety of systematic errors, such as
a center-to-limb variation and an offset due to the P-angle uncertainty of
solar images. Here we apply the time-distance technique to contemporaneous
medium-degree Dopplergrams produced by SOHO/MDI and SDO/HMI to obtain the
travel-time difference caused by meridional circulation throughout the solar
convection zone. The P-angle offset in MDI images is measured by
cross-correlating MDI and HMI images. The travel-time measurements in the
south-north and east-west directions are averaged over the same observation
period for the two data sets and then compared to examine the consistency of
MDI and HMI travel times after correcting the systematic errors.
The offsets in the south-north travel-time difference from MDI data induced
by the P-angle error gradually diminish with increasing travel distance.
However, these offsets become noisy for travel distances corresponding to waves
that reach the base of the convection zone. This suggests that a careful
treatment of the P-angle problem is required when studying a deep meridional
flow. After correcting the P-angle and the removal of the center-to-limb
effect, the travel-time measurements from MDI and HMI are consistent within the
error bars for meridional circulation covering the entire convection zone. The
fluctuations observed in both data sets are highly correlated and thus indicate
their solar origin rather than an instrumental origin. Although our results
demonstrate that the ad hoc correction is capable of reducing the wide
discrepancy in the travel-time measurements from MDI and HMI, we cannot exclude
the possibility that there exist other systematic effects acting on the two
data sets in the same way.Comment: accepted for publication in A&
The Saccharomyces cerevisiae Mob2p-Cbk1p kinase complex promotes polarized growth and acts with the mitotic exit network to facilitate daughter cell-specific localization of Ace2p transcription factor.
The Saccharomyces cerevisiae mitotic exit network (MEN) is a conserved signaling network that coordinates events associated with the M to G1 transition. We investigated the function of two S. cerevisiae proteins related to the MEN proteins Mob1p and Dbf2p kinase. Previous work indicates that cells lacking the Dbf2p-related protein Cbk1p fail to sustain polarized growth during early bud morphogenesis and mating projection formation (Bidlingmaier, S., E.L. Weiss, C. Seidel, D.G. Drubin, and M. Snyder. 2001. Mol. Cell. Biol. 21:2449-2462). Cbk1p is also required for Ace2p-dependent transcription of genes involved in mother/daughter separation after cytokinesis. Here we show that the Mob1p-related protein Mob2p physically associates with Cbk1p kinase throughout the cell cycle and is required for full Cbk1p kinase activity, which is periodically activated during polarized growth and mitosis. Both Mob2p and Cbk1p localize interdependently to the bud cortex during polarized growth and to the bud neck and daughter cell nucleus during late mitosis. We found that Ace2p is restricted to daughter cell nuclei via a novel mechanism requiring Mob2p, Cbk1p, and a functional nuclear export pathway. Furthermore, nuclear localization of Mob2p and Ace2p does not occur in mob1-77 or cdc14-1 mutants, which are defective in MEN signaling, even when cell cycle arrest is bypassed. Collectively, these data indicate that Mob2p-Cbk1p functions to (a) maintain polarized cell growth, (b) prevent the nuclear export of Ace2p from the daughter cell nucleus after mitotic exit, and (c) coordinate Ace2p-dependent transcription with MEN activation. These findings may implicate related proteins in linking the regulation of cell morphology and cell cycle transitions with cell fate determination and development
Nonclassical photon pairs generated from a room-temperature atomic ensemble
We report experimental generation of non-classically correlated photon pairs
from collective emission in a room-temperature atomic vapor cell. The
nonclassical feature of the emission is demonstrated by observing a violation
of the Cauchy-Schwarz inequality. Each pair of correlated photons are separated
by a controllable time delay up to 2 microseconds. This experiment demonstrates
an important step towards the realization of the Duan-Lukin-Cirac-Zoller scheme
for scalable long-distance quantum communication.Comment: 4 pages, 2 figure
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