2,696 research outputs found
Effects of Strong Magnetic Fields in Strange Baryonic Matter
We investigate the effects of very strong magnetic fields upon the equation
of state of dense bayonic matter in which hyperons are present. In the presence
of a magnetic field, the equation of state above nuclear density is
significantly affected both by Landau quantization and magnetic moment
interactions, but only for field strengths G. The former
tends to soften the EOS and increase proton and lepton abundances, while the
latter produces an overall stiffening of the EOS. Each results in a supression
of hyperons relative to the field-free case. The structure of a neutron star
is, however, primarily determined by the magnetic field stress. We utilize
existing general relativistic magneto-hydrostatic calculations to demonstrate
that maximum average fields within a stable neutron are limited to values G. This is not large enough to significantly influence
particle compositions or the matter pressure, unless fluctuations dominate the
average field strengths in the interior or configurations with significantly
larger field gradients are considered.Comment: 12 pages, 3 figures. To be submitted to Phys. Lett.
Induced four fold anisotropy and bias in compensated NiFe/FeMn double layers
A vector spin model is used to show how frustrations within a multisublattice
antiferromagnet such as FeMn can lead to four-fold magnetic anisotropies acting
on an exchange coupled ferromagnetic film. Possibilities for the existence of
exchange bias are examined and shown to exist for the case of weak chemical
disorder at the interface in an otherwise perfect structure. A sensitive
dependence on interlayer exchange is found for anisotropies acting on the
ferromagnet through the exchange coupling, and we show that a wide range of
anisotropies can appear even for a perfect crystalline structure with an
ideally flat interface.Comment: 7 pages, 7 figure
Electrochemical behaviour of gamma hydroxybutyric acid at a platinum electrode in acidic medium
The electrooxidation of Gamma Hydroxybutyric Acid (GHB) on a polycrystalline platinum electrode is studied by cyclic voltammetry in acidic medium. Two oxidation peaks, A and B, are obtained in the positive scan within the potential range of the double layer region and of the platinum oxide region, respectively. In the negative going potential sweep an inverted oxidation peak with an onset partially overlapping with the tail of the cathodic peak for the reduction of the platinum oxide formed during the anodic scan is obtained (peak C). This inverted peak can be observed at a potential close to +0.2 V (vs Ag/AgCl at pH 2) and separated 0.4 and 0.8 V from the two other oxidation peaks obtained during the anodic scan and in such conditions that the surface is particularly activated to favour this electrochemical process. The response obtained in the electronic current for the different peaks when GHB concentration and scan rate were changed to allows inferring that these are the result of a potential dependent mechanism. The behaviour observed is according with the oxidation of the alcohol group to the corresponding aldehyde and carboxylic acid (succinic acid) as main products
Droplet actuation induced by coalescence: experimental evidences and phenomenological modeling
This paper considers the interaction between two droplets placed on a
substrate in immediate vicinity. We show here that when the two droplets are of
different fluids and especially when one of the droplet is highly volatile, a
wealth of fascinating phenomena can be observed. In particular, the interaction
may result in the actuation of the droplet system, i.e. its displacement over a
finite length. In order to control this displacement, we consider droplets
confined on a hydrophilic stripe created by plasma-treating a PDMS substrate.
This controlled actuation opens up unexplored opportunities in the field of
microfluidics. In order to explain the observed actuation phenomenon, we
propose a simple phenomenological model based on Newton's second law and a
simple balance between the driving force arising from surface energy gradients
and the viscous resistive force. This simple model is able to reproduce
qualitatively and quantitatively the observed droplet dynamics
Large-scale structural organization of social networks
The characterization of large-scale structural organization of social
networks is an important interdisciplinary problem. We show, by using scaling
analysis and numerical computation, that the following factors are relevant for
models of social networks: the correlation between friendship ties among people
and the position of their social groups, as well as the correlation between the
positions of different social groups to which a person belongs.Comment: 5 pages, 3 figures, Revte
Higgs Boson Production in Association with Three Jets
The scattering amplitudes for Higgs + 5 partons are computed, with the Higgs
boson produced via gluon fusion in the large top-quark mass limit. A
parton-level analysis of Higgs + 3 jet production via gluon fusion and via
weak-boson fusion is presented, and the effectiveness of a central-jet veto is
analysed.Comment: 26 pages, 4 Postscript figures, uses JHEP3.cl
Post-Newtonian SPH calculations of binary neutron star coalescence. I. Method and first results
We present the first results from our Post-Newtonian (PN) Smoothed Particle
Hydrodynamics (SPH) code, which has been used to study the coalescence of
binary neutron star (NS) systems. The Lagrangian particle-based code
incorporates consistently all lowest-order (1PN) relativistic effects, as well
as gravitational radiation reaction, the lowest-order dissipative term in
general relativity. We test our code on sequences of single NS models of
varying compactness, and we discuss ways to make PN simulations more relevant
to realistic NS models. We also present a PN SPH relaxation procedure for
constructing equilibrium models of synchronized binaries, and we use these
equilibrium models as initial conditions for our dynamical calculations of
binary coalescence. Though unphysical, since tidal synchronization is not
expected in NS binaries, these initial conditions allow us to compare our PN
work with previous Newtonian results.
We compare calculations with and without 1PN effects, for NS with stiff
equations of state, modeled as polytropes with . We find that 1PN
effects can play a major role in the coalescence, accelerating the final
inspiral and causing a significant misalignment in the binary just prior to
final merging. In addition, the character of the gravitational wave signal is
altered dramatically, showing strong modulation of the exponentially decaying
waveform near the end of the merger. We also discuss briefly the implications
of our results for models of gamma-ray bursts at cosmological distances.Comment: RevTeX, 37 pages, 17 figures, to appear in Phys. Rev. D, minor
corrections onl
The small x gluon and b\bar{b} production at the LHC
We study open b\bar{b} production at large rapidity at the LHC in an attempt
to pin down the gluon distribution at very low x. For the LHC energy of 7 TeV,
at next-to-leading order (NLO), there is a large factorization scale
uncertainty. We show that the uncertainty can be greatly reduced if events are
selected in which the transverse momenta of the two B-mesons balance each other
to some accuracy, that is |\vec p_{1T}+\vec p_{2T}| < k_0. This will fix the
scale \mu_F \simeq k_0, and will allow the LHCb experiment, in particular, to
study the x-behaviour of gluon distribution down to x ~ 10^{-5}, at rather low
scales, \mu ~ 2 GeV. We evaluate the expected cross sections using, for
illustrative purposes, various recent sets of Parton Distribution Functions.Comment: 13 pages, 5 figure
Irrotational binary neutron stars in quasiequilibrium
We report on numerical results from an independent formalism to describe the
quasi-equilibrium structure of nonsynchronous binary neutron stars in general
relativity. This is an important independent test of controversial numerical
hydrodynamic simulations which suggested that nonsynchronous neutron stars in a
close binary can experience compression prior to the last stable circular
orbit. We show that, for compact enough stars the interior density increases
slightly as irrotational binary neutron stars approach their last orbits. The
magnitude of the effect, however, is much smaller than that reported in
previous hydrodynamic simulations.Comment: 4 pages, 2 figures, revtex, accepted for publication in Phys. Rev.
Selectivity enhancement in molecularly imprinted polymers for binding of bisphenol A
Bisphenol A (BPA) is an estrogen-mimicking chemical that can be selectively detected in water using a chemical sensor based on molecularly imprinted polymers (MIPs). However, the utility of BPA-MIPs in sensor applications is limited by the presence of non-specific binding sites. This study explored a dual approach to eliminating these sites: optimizing the molar ratio of the template (bisphenol A) to functional monomer (methacrylic acid) to cross-linker (ethylene glycol dimethacrylate), and esterifying the carboxylic acid residues outside of specific binding sites by treatment with diazomethane. The binding selectivity of treated MIPs and non-treated MIPs for BPA and several potential interferents was compared by capillary electrophoresis with ultraviolet detection. Baclofen, diclofenac and metformin were demonstrated to be good model interferents to test all MIPs for selective binding of BPA. Treated MIPs demonstrated a significant decrease in binding of the interferents while offering high selectivity toward BPA. These results demonstrate that conventional optimization of the molar ratio, together with advanced esterification of non-specific binding sites, effectively minimizes the residual binding of interferents with MIPs to facilitate BPA sensing
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