889 research outputs found
Poynting vector, energy density and energy velocity in anomalous dispersion medium
The Poynting vector, energy density and energy velocity of light pulses
propagating in anomalous dispersion medium (used in WKD-like experiments) are
calculated. Results show that a negative energy density in the medium
propagates along opposite of incident direction with such a velocity similar to
the negative group velocity while the direction of the Poynting vector is
positive. In other words, one might say that a positive energy density in the
medium would propagate along the positive direction with a speed having
approximately the absolute valueof the group velocity. We further point out
that neither energy velocity nor group velocity is a good concept to describe
the propagation process of light pulse inside the medium in WKD experiment
owing to the strong accumulation and dissipation effects.Comment: 6 page
Polarization and power density trends of a soil-based microbial fuel cell treated with human urine
Inverse Temperature 4-vector in Special Relativity
There exist several prescriptions for identifying the notion of temperature
in special relativity. We argue that the inverse temperature 4-vector is the only viable option from the laws of thermodynamics, and is a future-directed timelike 4-vector. Using a superfluidity thought
experiment, one can show that is not necessarily along the time
direction of the comoving frame of the system, as is usually thought. It is
conjectured that, for an isolated system, the 4-vector is determined from the
entropy-maximum principle.Comment: 11 pages, revised versio
Collisions of Einstein-Conformal Scalar Waves
A large class of solutions of the Einstein-conformal scalar equations in
D=2+1 and D=3+1 is identified. They describe the collisions of asymptotic
conformal scalar waves and are generated from Einstein-minimally coupled scalar
spacetimes via a (generalized) Bekenstein transformation. Particular emphasis
is given to the study of the global properties and the singularity structure of
the obtained solutions. It is shown, that in the case of the absence of pure
gravitational radiation in the initial data, the formation of the final
singularity is not only generic, but is even inevitable.Comment: 17 pages, LaTe
One-step continuous synthesis of biocompatible gold nanorods for optical coherence tomography
We present a novel one-step flow process to synthesize biocompatible gold nanorods with tunable absorption and biocompatible surface ligands. Photothermal optical coherence tomography (OCT) of human breast tissue is successfully demonstrated using tailored gold nanorods designed to have strong absorption in the near-infrared range.National Science Foundation (U.S.) (grant CHE-0714189)National Institutes of Health (U.S.) (R01-CA75289-15)National Institutes of Health (U.S.) (K99-EB010071-01A1)United States. Air Force Office of Scientific Research (FA9550-10-1-0063)Deutsche Forschungsgemeinschaft (DFG-GSC80-SAOT)Spain. Ministerio de Educación y Ciencia (MEC)US-UK Fulbright Commissio
Temperature and entropy of Schwarzschild-de Sitter space-time
In the light of recent interest in quantum gravity in de Sitter space, we
investigate semi-classical aspects of 4-dimensional Schwarzschild-de Sitter
space-time using the method of complex paths. The standard semi-classical
techniques (such as Bogoliubov coefficients and Euclidean field theory) have
been useful to study quantum effects in space-times with single horizons;
however, none of these approaches seem to work for Schwarzschild-de Sitter or,
in general, for space-times with multiple horizons. We extend the method of
complex paths to space-times with multiple horizons and obtain the spectrum of
particles produced in these space-times. We show that the temperature of
radiation in these space-times is proportional to the effective surface gravity
-- inverse harmonic sum of surface gravity of each horizon. For the
Schwarzschild-de Sitter, we apply the method of complex paths to three
different coordinate systems -- spherically symmetric, Painleve and Lemaitre.
We show that the equilibrium temperature in Schwarzschild-de Sitter is the
harmonic mean of cosmological and event horizon temperatures. We obtain
Bogoliubov coefficients for space-times with multiple horizons by analyzing the
mode functions of the quantum fields near the horizons. We propose a new
definition of entropy for space-times with multiple horizons analogous to the
entropic definition for space-times with a single horizon. We define entropy
for these space-times to be inversely proportional to the square of the
effective surface gravity. We show that this definition of entropy for
Schwarzschild-de Sitter satisfies the D-bound conjecture.Comment: Final version; To appear in Phys. Rev. D; 12 pages, 1 figure,
RevTex-4; Typos corrected; References adde
Pairing symmetry and properties of iron-based high temperature superconductors
Pairing symmetry is important to indentify the pairing mechanism. The
analysis becomes particularly timely and important for the newly discovered
iron-based multi-orbital superconductors. From group theory point of view we
classified all pairing matrices (in the orbital space) that carry irreducible
representations of the system. The quasiparticle gap falls into three
categories: full, nodal and gapless. The nodal-gap states show conventional
Volovik effect even for on-site pairing. The gapless states are odd in orbital
space, have a negative superfluid density and are therefore unstable. In
connection to experiments we proposed possible pairing states and implications
for the pairing mechanism.Comment: 4 pages, 1 table, 2 figures, polished versio
G1 Cosmologies with Gravitational and Scalar Waves
I present here a new algorithm to generate families of inhomogeneous massless
scalar field cosmologies. New spacetimes, having a single isometry, are
generated by breaking the homogeneity of massless scalar field models
along one direction. As an illustration of the technique I construct
cosmological models which in their late time limit represent perturbations in
the form of gravitational and scalar waves propagating on a non-static
inhomogeneous background. Several features of the obtained metrics are
discussed, such as their early and late time limits, structure of singularities
and physical interpretation.Comment: 24 pages, 2 figure
Physics at BES-III
This physics book provides detailed discussions on important topics in
-charm physics that will be explored during the next few years at \bes3 .
Both theoretical and experimental issues are covered, including extensive
reviews of recent theoretical developments and experimental techniques. Among
the subjects covered are: innovations in Partial Wave Analysis (PWA),
theoretical and experimental techniques for Dalitz-plot analyses, analysis
tools to extract absolute branching fractions and measurements of decay
constants, form factors, and CP-violation and \DzDzb-oscillation parameters.
Programs of QCD studies and near-threshold tau-lepton physics measurements are
also discussed.Comment: Edited by Kuang-Ta Chao and Yi-Fang Wan
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