2,164 research outputs found
Qualitative study in Loop Quantum Cosmology
This work contains a detailed qualitative analysis, in General Relativity and
in Loop Quantum Cosmology, of the dynamics in the associated phase space of a
scalar field minimally coupled with gravity, whose potential mimics the
dynamics of a perfect fluid with a linear Equation of State (EoS). Dealing with
the orbits (solutions) of the system, we will see that there are analytic ones,
which lead to the same dynamics as the perfect fluid, and our goal is to check
their stability, depending on the value of the EoS parameter, i.e., to show
whether the other orbits converge or diverge to these analytic solutions at
early and late times.Comment: 12 pages, 7 figures. Version accepted for publication in CQ
Radio Astronomy
Contains reports on seven research projects.M. I. T. Sloan Fund for Basic ResearchNational Science Foundation (Grant GP-8415)Joint Services Electronics Programs (U. S. Army, U. S. Navy, and U. S. Air Force) under Contract DA 28-043-AMC-02536(E)National Aeronautics and Space Administration (Grant NGL 22-009-016
Heavy Baryon Specroscopy from the Lattice
The results of an exploratory lattice study of heavy baryon spectroscopy are
presented. We have computed the full spectrum of the eight baryons containing a
single heavy quark, on a lattice at , using an
-improved fermion action. We discuss the lattice baryon operators and
give a method for isolating the contributions of the spin doublets
, and to the correlation
function of the relevant operator. We compare our results with the available
experimental data and find good agreement in both the charm and the beauty
sectors, despite the long extrapolation in the heavy quark mass needed in the
latter case. We also predict the masses of several undiscovered baryons. We
compute the \Lambda-\mbox{pseudoscalar meson} and mass
splittings. Our results, which have errors in the range , are in good
agreement with the experimental numbers. For the mass
splitting, we find results considerably smaller than the experimental values
for both the charm and the beauty baryons, although in the latter case the
experimental results are still preliminary. This is also the case for the
lattice results for the hyperfine splitting for the heavy mesons.Comment: 31 pages LaTex, with postscript figures include
Uptake of oxLDL and IL-10 production by macrophages requires PAFR and CD36 recruitment into the same lipid rafts
Macrophage interaction with oxidized low-density lipoprotein (oxLDL) leads to its differentiation into foam cells and cytokine production, contributing to atherosclerosis development. In a previous study, we showed that CD36 and the receptor for platelet-activating factor (PAFR) are required for oxLDL to activate gene transcription for cytokines and CD36. Here, we investigated the localization and physical interaction of CD36 and PAFR in macrophages stimulated with oxLDL. We found that blocking CD36 or PAFR decreases oxLDL uptake and IL-10 production. OxLDL induces IL-10 mRNA expression only in HEK293T expressing both receptors (PAFR and CD36). OxLDL does not induce IL-12 production. The lipid rafts disruption by treatment with βCD reduces the oxLDL uptake and IL-10 production. OxLDL induces co-immunoprecipitation of PAFR and CD36 with the constitutive raft protein flotillin-1, and colocalization with the lipid raft-marker GM1-ganglioside. Finally, we found colocalization of PAFR and CD36 in macrophages from human atherosclerotic plaques. Our results show that oxLDL induces the recruitment of PAFR and CD36 into the same lipid rafts, which is important for oxLDL uptake and IL-10 production. This study provided new insights into how oxLDL interact with macrophages and contributing to atherosclerosis development
Standard Model Matrix Elements for Neutral B-Meson Mixing and Associated Decay Constants
We present results of quenched lattice calculations of the matrix elements
relevant for B_d-\bar B_d and B_s-\bar B_s mixing in the Standard Model.
Results for the corresponding SU(3)-breaking ratios, which can be used to
constrain or determine |V_{td}|, are also given. The calculations are performed
at two values of the lattice spacing, corresponding to \beta = 6.0 and \beta =
6.2, with quarks described by a mean-field-improved Sheikholeslami-Wohlert
action. As a by-product, we obtain the leptonic decay constants of B and D
mesons. We also present matrix elements relevant for D^0-\bar D^0 mixing. Our
results are summarized in the Introduction.Comment: 27 pages (RevTeX), 26 figures, version published in Phys. Rev. D:
improved estimate of the systematic error associated with the uncertainty on
the strange quark mass and other small improvements to analysis (results
change only slightly); correction of typos and minor changes to text; RevTeX
formattin
Heavy-light Mesons and Baryons with b quarks
We present lattice results for the spectrum of mesons containing one heavy
quark and of baryons containing one or two heavy quarks. The calculation is
done in the quenched approximation using the NRQCD formalism for the heavy
quark. We analyze the dependence of the mass splittings on both the heavy and
the light quark masses. Meson P-state fine structure and baryon hyperfine
splittings are resolved for the first time. We fix the b quark mass using both
M_B and M_{\Lambda_b}, and our best estimate is m_b^\MSbar(m_b^\MSbar) =
4.35(10)({}^{-3}_{+2})(10) GeV. The spectrum, obtained by interpolation to m_b,
is compared with the experimental data.Comment: 34 pages, LaTeX, 13 postscript figures, version as publish in Phys.
Rev.
Recommended from our members
Brief report: a comparison of the preference for viewing social and non-social movies in typical and autistic adolescents
The recently proposed Social Motivation theory (Chevallier et al., Trends in cognitive sciences 16(4):231–239, 2012) suggests that social difficulties in Autism Spectrum Condition (ASC) might be caused by a difference in the motivation to engage with other people. Here we compared adolescents with (N = 31) and without (N = 37) ASC on the Choose-a-Movie paradigm that measures the social seeking. The results showed a preference for viewing objects over smiling faces in ASC, which is in line with the theory of low social motivation. However, typical adolescents did not show any stimuli preferences, raising questions about developmental changes in social motivation. Age was found to play a significant role in moderating the choice behaviour of the participants. We discuss the implications of these findings in detail
Effects of Irradiation Temperature on the Response of CeO2, ThO2, and UO2 to Highly Ionizing Radiation
Microcrystalline CeO2, ThO2, and UO2 were irradiated with 198 MeV 132Xe ions to the same fluence at temperatures ranging from 25 °C to 700 °C then characterized by synchrotron X-ray diffraction and X-ray absorption spectroscopy. All samples retain crystallinity and their nominal fluorite-type phase at a fluence of 1.5 × 1013 ions/cm2. Both CeO2 and ThO2 display defect-induced unit cell expansion after irradiation at room temperature (∼0.15% and ∼0.10%, respectively), yet as irradiation temperature increases, the maximum swelling produced decreases to ∼0.02%. Alternatively, UO2 shows an initial contraction in unit cell parameter (approximately −0.05%) for room temperature irradiation, most likely related to irradiation-enhanced annealing or irradiation-induced oxidation. At higher temperatures (above 200 °C) UO2 begins to swell, surpassing its unit cell parameter prior to irradiation (∼0.05%), an effect which could be attributed to minor reduction in uranium oxidation state in vacuum. However, while CeO2 irradiated at room temperature undergoes partial reduction, both UO2 and ThO2 exhibit no measurable change in cation oxidation state as evidenced by X-ray absorption spectroscopy. All samples display a decrease in irradiation-induced heterogeneous microstrain as a function of increasing irradiation temperature. © 2019 Elsevier B.V.This work was supported by the Energy Frontier Research Center Materials Science of Actinides funded by the US Department of Energy, Office of Science, Office of Basic Energy Sciences (DE-SC0001089). Portions of this work were performed at HPCAT (Sector 16), Advanced Photon Source, Argonne National Laboratory. HPCAT operations are supported by DOE-NNSA under award No. DE-NA0001974 and DOE-BES under award No. DE-FG02-99ER45775, with partial instrumentation funding by NSF. APS is supported by DOE-BES, under contract No. DE-AC02-06CH11357. W.F.C. and R.I.P. gratefully acknowledge support from the U.S. Department of Energy (DOE) National Nuclear Security Administration (NNSA) through the Capital/DOE Alliance Center (DE-NA0003858). HPCAT beamtime was granted by the Capital/DOE Alliance Center
- …