42,965 research outputs found
Static potential in scalar QED with non-minimal coupling
Here we compute the static potential in scalar at leading order in
. We show that the addition of a non-minimal coupling of Pauli-type
(\eps j^{\mu}\partial^{\nu}A^{\alpha}), although it breaks parity, it does
not change the analytic structure of the photon propagator and consequently the
static potential remains logarithmic (confining) at large distances. The
non-minimal coupling modifies the potential, however, at small charge
separations giving rise to a repulsive force of short range between opposite
sign charges, which is relevant for the existence of bound states. This effect
is in agreement with a previous calculation based on Mller
scattering, but differently from such calculation we show here that the
repulsion appears independently of the presence of a tree level Chern-Simons
term which rather affects the large distance behavior of the potential turning
it into constant.Comment: 13 pages, 3 figure
The effect of coatings and liners on heat transfer in a dry shaft-bush tribosystem
The temperatures due to frictional heating within a solid lubricated or coated journal bearing were analyzed by using a finite element method. A solid model of the shaft-bush tribocontact was generated with an eight-node, three-dimensional, first-order isoparametric heat-transfer element and the Patran solid modeler software. The Patmar (Patran-Marc) translator was used to help develop the Marc-based finite element program for the system; this software was used on the Cray X-MP supercomputer to perform a finite element analysis of the contact. The analysis was performed for various liner materials, for thin, hard, wear-resistant coated bearings, and for different geometries and thermal cooling boundary conditions. The analyses indicated that thermal conductivity of the liner or coating material is the most vital thermal parameter that controls the interface temperature. In addition to design variations, the proximity of the cooling source to the heat-flux-generating interface is critically important to the temperature control in the system
Deconvolving the Wedge: Maximum-Likelihood Power Spectra via Spherical-Wave Visibility Modeling
Direct detection of the Epoch of Reionization (EoR) via the red-shifted 21-cm
line will have unprecedented implications on the study of structure formation
in the infant Universe. To fulfill this promise, current and future 21-cm
experiments need to detect this weak EoR signal in the presence of foregrounds
that are several orders of magnitude larger. This requires extreme noise
control and improved wide-field high dynamic-range imaging techniques. We
propose a new imaging method based on a maximum likelihood framework which
solves for the interferometric equation directly on the sphere, or equivalently
in the -domain. The method uses the one-to-one relation between spherical
waves and spherical harmonics (SpH). It consistently handles signals from the
entire sky, and does not require a -term correction. The spherical-harmonics
coefficients represent the sky-brightness distribution and the visibilities in
the -domain, and provide a direct estimate of the spatial power spectrum.
Using these spectrally-smooth SpH coefficients, bright foregrounds can be
removed from the signal, including their side-lobe noise, which is one of the
limiting factors in high dynamics range wide-field imaging. Chromatic effects
causing the so-called "wedge" are effectively eliminated (i.e. deconvolved) in
the cylindrical () power spectrum, compared to a
power spectrum computed directly from the images of the foreground visibilities
where the wedge is clearly present. We illustrate our method using simulated
LOFAR observations, finding an excellent reconstruction of the input EoR signal
with minimal bias.Comment: 13 pages, 8 figures. Replaced to match accepted MNRAS version; few
typos corrected & textual clarification added (no changes to results
Slowly Rotating Dilaton Black hole In Anti-de Sitter Spacetime
Rotating dilaton black hole solution for asymptotically anti-de Sitter
spacetime are obtained in the small angular momentum limit with an appropriate
combination of three Liouville-type dilaton potentials. The angular momentum,
magnetic dipole moment and the gyromagnetic ratio of such a black hole are
determined for arbitrary values of the dilaton-electromagnetic coupling
parameter.Comment: 5 pages, Revtex, To appear in Phys.Rev.
Hydrodynamic lubrication of rigid nonconformal contacts in combined rolling and normal motion
A numerical solution to the problem of hydrodynamic lubrication of rigid point contacts with an isoviscous, incompressible lubricant was obtained. The hydrodynamic load-carrying capacity under unsteady (or dynamic) conditions arising from the combined effects of squeeze motion superposed upon the entraining motion was determined for both normal approach and separation. Superposed normal motion considerably increases net load-carrying capacity during normal approach and substantially reduces net load-carrying capacity during separation. Geometry was also found to have a significant influence on the dynamic load-carrying capacity. The ratio of dynamic to steady state load-carrying capacity increases with increasing geometry parameter for normal approach and decreases during separation. The cavitation (film rupture) boundary is also influenced significantly by the normal motion, moving downstream during approach and upstream during separation. For sufficiently high normal separation velocity the rupture boundary may even move upstream of the minimum-film-thickness position. Sixty-three cases were used to derive a functional relationship for the ratio of the dynamic to steady state load-carrying capacity in terms of the dimensionless normal velocity parameter (incorporating normal velocity, entraining velocity, and film thickness) and the geometry parameter
Requirement of the FATC domain of protein kinase Tel1 for localization to DNA ends and target protein recognition
Two large phosphatidylinositol 3-kinase-related protein kinases (PIKKs), ATM and ATR, play a central role in the DNA damage response pathway. PIKKs contain a highly conserved extreme C-terminus called the FRAP-ATM-TRRAP-C-terminal (FATC) domain. In budding yeast, ATM and ATR correspond to Tel1 and Mec1, respectively. In this study, we characterized functions of the FATC domain of Tel1 by introducing substitution or truncation mutations. One substitution mutation, termed tel1-21, and a truncation mutation, called tel1- Î"C, did not significantly affect the expression level. The tel1-21 mutation impaired the cellular response to DNA damage and conferred moderate telomere maintenance defect. In contrast, the tel1-Î"C mutation behaved like a null mutation, conferring defects in both DNA damage response and telomere maintenance. Tel1-21 protein localized to DNA ends as effectively as wild-type Tel1 protein, whereas Tel1-Î"C protein failed. Introduction of a hyperactive TEL1-hy mutation suppressed the tel1-21 mutation but not the tel1-Î"C mutation. In vitro analyses revealed that both Tel1-21 and Tel1-Î"C proteins undergo efficient autophosphorylation but exhibit decreased kinase activities toward the exogenous substrate protein, Rad53. Our results show that the FATC domain of Tel1 mediates localization to DNA ends and contributes to phosphorylation of target proteins. © 2015 Ogi, Goto, Ghosh, et al
Contribution of Kaon component in viscosity and conductivity of hadronic medium
The two-point correlation functions of kaonic viscous stress tensors and
electro-magnetic currents have been calculated respectively to estimate the
contributions of the strange sector in the shear viscosity and electrical
conductivity of hadronic medium. In the one-loop correlators, kaon propagators
contain a non-zero thermal width that leads to non-divergent values of
transport coefficients. With the help of effective Lagrangian densities of
strange hadrons, we have calculated in-medium self-energy of kaon for different
possible mesonic loops, whose imaginary part provide the estimation of kaon
thermal width. It is observed that near the quark-hadron transition
temperature, the contribution of kaons to shear viscosity is larger and
increases faster with temperature than pionic contribution. In case of
electrical conductivity the trend due kaon component appears to be opposite in
nature with respect to pion component
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