8,405 research outputs found
Virial series for inhomogeneous fluids applied to the Lennard-Jones wall-fluid surface tension at planar and curved walls
We formulate a straightforward scheme of statistical mechanics for
inhomogeneous systems that includes the virial series in powers of the activity
for the grand free energy and density distributions. There, cluster integrals
formulated for inhomogeneous systems play a main role. We center on second
order terms that were analyzed in the case of hard-wall confinement, focusing
in planar, spherical and cylindrical walls. Further analysis was devoted to the
Lennard-Jones system and its generalization the 2k-k potential. For this
interaction potentials the second cluster integral was evaluated analytically.
We obtained the fluid-substrate surface tension at second order for the planar,
spherical and cylindrical confinement. Spherical and cylindrical cases were
analyzed using a series expansion in the radius including higher order terms.
We detected a dependence of the surface tension for the
standard Lennard-Jones system confined by spherical and cylindrical walls, no
matter if particles are inside or outside of the hard-walls. The analysis was
extended to bending and Gaussian curvatures, where exact expressions were also
obtained.Comment: 15 pages, 6 figure
A Measurement of Water Vapour amid a Largely Quiescent Environment on Europa
Previous investigations proved the existence of local density enhancements in Europas atmosphere, advancing the idea of a possible origination from water plumes. These measurement strategies, however, were sensitive either to total absorption or atomic emissions, which limited the ability to assess the water content. Here we present direct searches for water vapour on Europa spanning dates from February 2016 to May 2017 with the Keck Observatory. Our global survey at infrared wavelengths resulted in non-detections on 16 out of 17 dates, with upper limits below the water abundances inferred from previous estimates. On one date (26 April 2016) we measured 2,095 658 tonnes of water vapour at Europas leading hemisphere. We suggest that the outgassing ls than previously estimated, with only rare localized events of stronger activity
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Chronic Kidney Disease Increases Cerebral Microbleeds in Mouse and Man.
Brain microbleeds are increased in chronic kidney disease (CKD) and their presence increases risk of cognitive decline and stroke. We examined the interaction between CKD and brain microhemorrhages (the neuropathological substrate of microbleeds) in mouse and cell culture models and studied progression of microbleed burden on serial brain imaging from humans. Mouse studies: Two CKD models were investigated: adenine-induced tubulointerstitial nephritis and surgical 5/6 nephrectomy. Cell culture studies: bEnd.3 mouse brain endothelial cells were grown to confluence, and monolayer integrity was measured after exposure to 5-15% human uremic serum or increasing concentrations of urea. Human studies: Progression of brain microbleeds was evaluated on serial MRI from control, pre-dialysis CKD, and dialysis patients. Microhemorrhages were increased 2-2.5-fold in mice with CKD independent of higher blood pressure in the 5/6 nephrectomy model. IgG staining was increased in CKD animals, consistent with increased blood-brain barrier permeability. Incubation of bEnd.3 cells with uremic serum or elevated urea produced a dose-dependent drop in trans-endothelial electrical resistance. Elevated urea induced actin cytoskeleton derangements and decreased claudin-5 expression. In human subjects, prevalence of microbleeds was 50% in both CKD cohorts compared with 10% in age-matched controls. More patients in the dialysis cohort had increased microbleeds on follow-up MRI after 1.5 years. CKD disrupts the blood-brain barrier and increases brain microhemorrhages in mice and microbleeds in humans. Elevated urea alters the actin cytoskeleton and tight junction proteins in cultured endothelial cells, suggesting that these mechanisms explain (at least in part) the microhemorrhages and microbleeds observed in the animal and human studies
FAST TCP: From Theory to Experiments
We describe a variant of TCP, called FAST, that can sustain high throughput and utilization at multi-Gbps over large distance. We present the motivation, review the background theory, summarize key features of FAST TCP, and report our first experimental results
Novel CP-violating Effects in B decays from Charged-Higgs in a Two-Higgs Doublet Model for the Top Quark
We explore charged-Higgs cp-violating effects in a specific type III
two-Higgs doublet model which is theoretically attractive as it accommodates
the large mass of the top quark in a natural fashion. Two new CP-violating
phases arise from the right-handed up quark sector. We consider CP violation in
both neutral and charged B decays. Some of the important findings are as
follows. 1) Large direct-CP asymmetry is found to be possible for B+- to psi/J
K+-. 2) Sizable D-anti-D mixing effect at the percent level is found to be
admissible despite the stringent constraints from the data on K-anti-K mixing,
b to s gamma and B to tau nu decays. 3) A simple but distinctive CP asymmetry
pattern emerges in decays of B_d and B_s mesons, including B_d to psi/J K_S, D+
D-, and B_s to D_s+ D_s-, psi eta/eta^prime, psi/J K_S. 4) The effect of
D-anti-D mixing on the CP asymmetry in B+- to D/anti-D K+- and on the
extraction of the angle gamma of the unitarity triangle from such decays can be
significant.Comment: 32 pages, 5 figures, section V.A revised, version to appear in PR
An updated analysis of eps'/eps in the standard model with hadronic matrix elements from the chiral quark model
We discuss the theoretical and experimental status of the CP violating ratio
eps'/eps. We revise our 1997 standard-model estimate-based on hadronic matrix
elements computed in the chiral quark model up to O(p^4) in the chiral
expansion-by including an improved statistical analysis of the uncertainties
and updated determination of the Cabibbo-Kobayashi-Maskawa elements and other
short-distance parameters. Using normal distributions for the experimental
input data we find Re eps'/eps = (2.2 \pm 0.8) x 10^{-3}, whereas a flat
scanning gives 0.9 x 10^{-3} < Re eps'/eps < 4.8 x 10^{-3}. Both results are in
agreement with the current experimental data. The key element in our estimate
is, as before, the fit of the Delta I=1/2 rule, which allows us to absorb most
of the theoretical uncertainties in the determination of the model-dependent
parameters in the hadronic matrix elements. Our semi-phenomenological approach
leads to numerical stability against variations of the renormalization scale
and scheme dependence of the short- and long-distance components. The same
dynamical mechanism at work in the selection rule also explains the larger
value obtained for \ratio with respect to other estimates. A coherent picture
of K -> pi pi decays is thus provided.Comment: 15 pages, 11 figures, RevTeX, discussion updated, refs adde
Radiation hardness qualification of PbWO4 scintillation crystals for the CMS Electromagnetic Calorimeter
This is the Pre-print version of the Article. The official published version can be accessed from the link below - Copyright @ 2010 IOPEnsuring the radiation hardness of PbWO4 crystals was one of the main priorities during the construction of the electromagnetic calorimeter of the CMS experiment at CERN. The production on an industrial scale of radiation hard crystals and their certification over a period of several years represented a difficult challenge both for CMS and for the crystal suppliers. The present article reviews the related scientific and technological problems encountered
The composition of the protosolar disk and the formation conditions for comets
Conditions in the protosolar nebula have left their mark in the composition
of cometary volatiles, thought to be some of the most pristine material in the
solar system. Cometary compositions represent the end point of processing that
began in the parent molecular cloud core and continued through the collapse of
that core to form the protosun and the solar nebula, and finally during the
evolution of the solar nebula itself as the cometary bodies were accreting.
Disentangling the effects of the various epochs on the final composition of a
comet is complicated. But comets are not the only source of information about
the solar nebula. Protostellar disks around young stars similar to the protosun
provide a way of investigating the evolution of disks similar to the solar
nebula while they are in the process of evolving to form their own solar
systems. In this way we can learn about the physical and chemical conditions
under which comets formed, and about the types of dynamical processing that
shaped the solar system we see today.
This paper summarizes some recent contributions to our understanding of both
cometary volatiles and the composition, structure and evolution of protostellar
disks.Comment: To appear in Space Science Reviews. The final publication is
available at Springer via http://dx.doi.org/10.1007/s11214-015-0167-
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