16,748 research outputs found
Capacitance of Gated GaAs/AlGaAs Heterostructures Subject to In-plane Magnetic Fields
A detailed analysis of the capacitance of gated GaAs/AlGaAs heterostructures
is presented. The nonlinear dependence of the capacitance on the gate voltage
and in-plane magnetic field is discussed together with the capacitance quantum
steps connected with a population of higher 2D gas subbands. The results of
full self-consistent numerical calculations are compared to recent experimental
data.Comment: 4 pages, Revtex. 4 PostScript figures in an uuencoded compressed file
available upon request. Phys. Rev.B, in pres
Dual Instantons
We show how to map the Belavin-Polyakov instantons of the O(3)-nonlinear
model to a dual theory where they then appear as nontopological
solitons. They are stationary points of the Euclidean action in the dual
theory, and moreover, the dual action and the O(3)-nonlinear model
action agree on shell.Comment: 13 page
An effective theory of accelerated expansion
We work out an effective theory of accelerated expansion to describe general
phenomena of inflation and acceleration (dark energy) in the Universe. Our aim
is to determine from theoretical grounds, in a physically-motivated and model
independent way, which and how many (free) parameters are needed to broadly
capture the physics of a theory describing cosmic acceleration. Our goal is to
make as much as possible transparent the physical interpretation of the
parameters describing the expansion. We show that, at leading order, there are
five independent parameters, of which one can be constrained via general
relativity tests. The other four parameters need to be determined by observing
and measuring the cosmic expansion rate only, H(z). Therefore we suggest that
future cosmology surveys focus on obtaining an accurate as possible measurement
of to constrain the nature of accelerated expansion (dark energy and/or
inflation).Comment: In press; minor changes, results unchange
Serotonin Syndrome after Concomitant Treatment with Linezolid and Citalopram
Linezolid, a new synthetic antimicrobial, is an important weapon against methicillin-resistant Staphylococcus aureus (MRSA). Although there are reports of serotonin syndrome developing after concomitant use of linezolid and the selective serotonin reuptake inhibitor paroxitene, this report concerns a patient receiving citalopram who developed thrombocytopenia, serotonin syndrome, and lactic acidosis and died following long-term linezolid therap
Two-body linear guidance matrices
Analytical expressions for two-body linear guidance matrices in velocity dependent coordinate system for variant motion equation solution
Inter-layer Hall effect in double quantum wells subject to in-plane magnetic fields
We report on a theoretical study of the transport properties of two coupled
two-dimensional electron systems subject to in-plane magnetic fields. The
charge redistribution in double wells induced by the Lorenz force in crossed
electric and magnetic fields has been studied. We have found that the
redistribution of the charge and the related inter-layer Hall effect originate
in the chirality of diamagnetic currents and give a substantial contribution to
the conductivity.Comment: 7 RevTex pages, 4 figures, appendix added and misprint in Eq. (11)
correcte
Spin dynamics in electrochemically charged CdSe quantum dots
We use time-resolved Faraday rotation to measure coherent spin dynamics in
colloidal CdSe quantum dots charged in an electrochemical cell at room
temperature. Filling of the 1Se electron level is demonstrated by the bleaching
of the 1Se-1S3/2 absorption peak. One of the two Lande g-factors observed in
uncharged quantum dots disappears upon filling of the 1Se electron state. The
transverse spin coherence time, which is over 1 ns and is limited by
inhomogeneous dephasing, also appears to increase with charging voltage. The
amplitude of the spin precession signal peaks near the half-filling potential.
Its evolution at charging potentials without any observable bleaching of the
1Se-1S3/2 transition suggests that the spin dynamics are influenced by
low-energy surface states.Comment: 4 pages, 4 figure
The Spitzer South Pole Telescope Deep Field Survey: Linking galaxies and halos at z=1.5
We present an analysis of the clustering of high-redshift galaxies in the
recently completed 94 deg Spitzer-SPT Deep Field survey. Applying flux and
color cuts to the mid-infrared photometry efficiently selects galaxies at
in the stellar mass range , making this
sample the largest used so far to study such a distant population. We measure
the angular correlation function in different flux-limited samples at scales
(corresponding to physical distances Mpc) and
thereby map the one- and two-halo contributions to the clustering. We fit halo
occupation distributions and determine how the central galaxy's stellar mass
and satellite occupation depend on the halo mass. We measure a prominent peak
in the stellar-to-halo mass ratio at a halo mass of , 4.5 times higher than the value. This supports
the idea of an evolving mass threshold above which star formation is quenched.
We estimate the large-scale bias in the range and the satellite
fraction to be , showing a clear evolution compared to
. We also find that, above a given stellar mass limit, the fraction of
galaxies that are in similar mass pairs is higher at than at . In
addition, we measure that this fraction mildly increases with the stellar mass
limit at , which is the opposite of the behavior seen at low-redshift.Comment: 32 pages, 22 figures. Published in MNRA
The Poisson-Boltzmann model for implicit solvation of electrolyte solutions: Quantum chemical implementation and assessment via Sechenov coefficients.
We present the theory and implementation of a Poisson-Boltzmann implicit solvation model for electrolyte solutions. This model can be combined with arbitrary electronic structure methods that provide an accurate charge density of the solute. A hierarchy of approximations for this model includes a linear approximation for weak electrostatic potentials, finite size of the mobile electrolyte ions, and a Stern-layer correction. Recasting the Poisson-Boltzmann equations into Euler-Lagrange equations then significantly simplifies the derivation of the free energy of solvation for these approximate models. The parameters of the model are either fit directly to experimental observables-e.g., the finite ion size-or optimized for agreement with experimental results. Experimental data for this optimization are available in the form of Sechenov coefficients that describe the linear dependence of the salting-out effect of solutes with respect to the electrolyte concentration. In the final part, we rationalize the qualitative disagreement of the finite ion size modification to the Poisson-Boltzmann model with experimental observations by taking into account the electrolyte concentration dependence of the Stern layer. A route toward a revised model that captures the experimental observations while including the finite ion size effects is then outlined. This implementation paves the way for the study of electrochemical and electrocatalytic processes of molecules and cluster models with accurate electronic structure methods
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