1,120 research outputs found
Inelastic Photoproduction at HERA: a Second Charmonium Crisis?
The measurement of the inelastic photoproduction of charmonium at HERA seems
to have ignited a new charmonium crisis. The (already discredited) color
singlet model fits the data for large charmonium energy fraction z, where the
NRQCD model qualitatively fails. We here point out that by the straightforward
inclusion of color singlet and octet processes in the soft color (color
evaporation) scheme, the HERA data can be accommodated for all z. We anticipate
that the color singlet model will fail at low z, as it does in hadroproduction.Comment: 10 pages, Revtex, uses epsfig.sty to include 4 postscript figures.
Also available from the UW-Madison Phenomenology preprint archives at
http://pheno.physics.wisc.edu/pub/preprints/1998/madph-98-1045.ps.Z or at
ftp://pheno.physics.wisc.edu/pub/preprints/1998/madph-98-1045.ps.
On the spherical-axial transition in supernova remnants
A new law of motion for supernova remnant (SNR) which introduces the quantity
of swept matter in the thin layer approximation is introduced. This new law of
motion is tested on 10 years observations of SN1993J. The introduction of an
exponential gradient in the surrounding medium allows to model an aspherical
expansion. A weakly asymmetric SNR, SN1006, and a strongly asymmetric SNR,
SN1987a, are modeled. In the case of SN1987a the three observed rings are
simulated.Comment: 19 figures and 14 pages Accepted for publication in Astrophysics &
Space Science in the year 201
Explaining the Higgs Decays at the LHC with an Extended Electroweak Model
We show that the recent discovery of a new boson at the LHC, which we assume
to be a Higgs boson, and the observed enhancement in its diphoton decays
compared to the SM prediction, can be explained by a new doublet of charged
vector bosons from an extended electroweak gauge sector model with
SU(3)_C\otimesSU(3)_L\otimesU(1)_X symmetry. Our results show a good
agreement between our theoretical expected sensitivity to a 126--125 GeV Higgs
boson and the experimental significance observed in the diphoton channel at the
8 TeV LHC. Effects of an invisible decay channel for the Higgs boson are also
taken into account, in order to anticipate a possible confirmation of deficits
in the branching ratios into , , bottom quarks, and tau leptons.Comment: 16 pages, 5 figure
Violation of the Nernst heat theorem in the theory of thermal Casimir force between Drude metals
We give a rigorous analytical derivation of low-temperature behavior of the
Casimir entropy in the framework of the Lifshitz formula combined with the
Drude dielectric function. An earlier result that the Casimir entropy at zero
temperature is not equal to zero and depends on the parameters of the system is
confirmed, i.e. the third law of thermodynamics (the Nernst heat theorem) is
violated. We illustrate the resolution of this thermodynamical puzzle in the
context of the surface impedance approach by several calculations of the
thermal Casimir force and entropy for both real metals and dielectrics.
Different representations for the impedances, which are equivalent for real
photons, are discussed. Finally, we argue in favor of the Leontovich boundary
condition which leads to results for the thermal Casimir force that are
consistent with thermodynamics.Comment: 24 pages, 3 figures, accepted for publication in Phys. Rev.
The Casimir force and the quantum theory of lossy optical cavities
We present a new derivation of the Casimir force between two parallel plane
mirrors at zero temperature. The two mirrors and the cavity they enclose are
treated as quantum optical networks. They are in general lossy and
characterized by frequency dependent reflection amplitudes. The additional
fluctuations accompanying losses are deduced from expressions of the optical
theorem. A general proof is given for the theorem relating the spectral density
inside the cavity to the reflection amplitudes seen by the inner fields. This
density determines the vacuum radiation pressure and, therefore, the Casimir
force. The force is obtained as an integral over the real frequencies,
including the contribution of evanescent waves besides that of ordinary waves,
and, then, as an integral over imaginary frequencies. The demonstration relies
only on general properties obeyed by real mirrors which also enforce general
constraints for the variation of the Casimir force.Comment: 18 pages, 6 figures, minor amendment
Improved tests of extra-dimensional physics and thermal quantum field theory from new Casimir force measurements
We report new constraints on extra-dimensional models and other physics
beyond the Standard Model based on measurements of the Casimir force between
two dissimilar metals for separations in the range 0.2--1.2 m. The Casimir
force between an Au-coated sphere and a Cu-coated plate of a
microelectromechanical torsional oscillator was measured statically with an
absolute error of 0.3 pN. In addition, the Casimir pressure between two
parallel plates was determined dynamically with an absolute error of mPa. Within the limits of experimental and theoretical errors, the results
are in agreement with a theory that takes into account the finite conductivity
and roughness of the two metals. The level of agreement between experiment and
theory was then used to set limits on the predictions of extra-dimensional
physics and thermal quantum field theory. It is shown that two theoretical
approaches to the thermal Casimir force which predict effects linear in
temperture are ruled out by these experiments. Finally, constraints on Yukawa
corrections to Newton's law of gravity are strengthened by more than an order
of magnitude in the range 56 nm to 330 nm.Comment: Revtex 4, 35 pages, 14 figures in .gif format, accepted for
publication in Phys. Rev.
The Relation Between the Surface Brightness and the Diameter for Galactic Supernova Remnants
In this work, we have constructed a relation between the surface brightness
() and diameter (D) of Galactic C- and S-type supernova remnants
(SNRs). In order to calibrate the -D dependence, we have carefully
examined some intrinsic (e.g. explosion energy) and extrinsic (e.g. density of
the ambient medium) properties of the remnants and, taking into account also
the distance values given in the literature, we have adopted distances for some
of the SNRs which have relatively more reliable distance values. These
calibrator SNRs are all C- and S-type SNRs, i.e. F-type SNRs (and S-type SNR
Cas A which has an exceptionally high surface brightness) are excluded. The
Sigma-D relation has 2 slopes with a turning point at D=36.5 pc: (at 1
GHz)=8.4 D
WmHzster (for
WmHzster and D36.5 pc) and (at 1
GHz)=2.7 10 D
WmHzster (for
WmHzster and D36.5 pc). We discussed the theoretical
basis for the -D dependence and particularly the reasons for the change
in slope of the relation were stated. Added to this, we have shown the
dependence between the radio luminosity and the diameter which seems to have a
slope close to zero up to about D=36.5 pc. We have also adopted distance and
diameter values for all of the observed Galactic SNRs by examining all the
available distance values presented in the literature together with the
distances found from our -D relation.Comment: 45 pages, 2 figures, accepted for publication in Astronomical and
Astrophysical Transaction
Reactivation of ancestral strains of HIV-1 in the gp120 V3 env region in patients failing antiretroviral therapy and subjected to structured treatment interruption
We analyzed gp120V3 HIV-1 env region genetic diversity of 27 patients failing antiretrovirals and subjected to 12-week structured treatment interruption (STI). Based on heteroduplex mobility assays, eight patients presented low pre- and post-STI genetic diversity (G1); five presented high pre-STI but low post-STI diversity (G2); five presented low pre-STI and high post-STI diversity (G3); and nine, high pre- and post-STI diversity (G4). One patient from G1, two from G2 and two from G3 were subjected to proviral DNA end-point PCR and sequencing. in three patients, the dramatic disturbance caused by STI resulted in ancestral viral progeny activation, which repopulated the cell reservoir. in two patients presenting highly homogeneous sequences and low immune selective pressure (dN/dS ratio < 1), this phenomenon was not observed. the mechanisms involved in viral evolution, in which antiretroviral therapy also applies selective pressure, sometimes affects coreceptor usage of circulating viruses, leading to the suppression of x4 strains. (c) 2006 Published by Elsevier Inc.Universidade Federal de São Paulo, Escola Paulista Med, Lab Retrovirol, BR-04039032 São Paulo, BrazilFundacao Pro Sangue, BR-05403000 São Paulo, BrazilUniversidade Federal de São Paulo, Escola Paulista Med, Lab Retrovirol, BR-04039032 São Paulo, BrazilWeb of Scienc
Total harmonic distortion based method for linearity assessment in electrochemical systems in the context of EIS
Electrochemical Impedance Spectroscopy (EIS) is a widely used electrochemical measurement technique
that has been used in a great spectrum of
fields since it allows deconvolving the individual physic-
chemical processes that take place in a given system. Ohm s generalized law, and thus the impedance
concept, are only valid if 4 conditions are fulfilled: causality,
finiteness, stationarity and linearity. In the
case that any of these conditions is not achieved, the obtained impedance spectra will present distortions
that may lead to biased or even erroneous results and conclusions. For this reason it is crucial to verify if
the 4 conditions are fulfilled, before accepting the results extracted from impedance spectra. In this work,
a linearity assessment quantitative method based in the total harmonic distortion (THD) parameter is
presented and verified experimentally. The experimental validation of the implemented method showed
that the implemented method is able to assess quantitatively the linearity of the system. In addition, it is
also able to determine the threshold frequency above which the system will not present significant
nonlinear effects even for large perturbation amplitudes. It was observed that the THD method is more
sensitive to nonlinear effects than the spectra themselves.The authors are very grateful to the Generalitat Valenciana for its economic support in form of Vali+d grant (Ref: ACIF-2013-268).Giner Sanz, JJ.; Ortega Navarro, EM.; Pérez-Herranz, V. (2015). Total harmonic distortion based method for linearity assessment in electrochemical systems in the context of EIS. Electrochimica Acta. 186:598-612. https://doi.org/10.1016/j.electacta.2015.10.152S59861218
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