19,467 research outputs found
Assimilation via prices or quantities? Sources of immigrant earnings growth in Australia, Canada and the United States
Using 1980/81 and 1990/91 census data from Australia, Canada, and the United States, we
estimate the effects of time in the destination country on male immigrants’ wages,
employment, and earnings. We find that total earnings assimilation is greatest in the United
States and least in Australia. Employment assimilation explains all of the earnings progress
experienced by Australian immigrants, whereas wage assimilation plays the dominant role in
the United States, and Canada falls in-between. We argue that relatively inflexible wages and
generous unemployment insurance in countries like Australia may cause assimilation to occur
along the “quantity” rather than the price dimension
Theory of the time-resolved Kerr rotation on trapped holes
We formulate a model of the time-resolved Kerr rotation experiment on a
single hole in a semiconductor nanostructure (e.g., a quantum dot) or on an
ensemble of trapped holes (e.g., in a quantum well) in a tilted magnetic field.
We use a generic Markovian description of the hole and trion dephasing and
focus on the interpretation of the time-resolved signal in terms of the
microscopic evolution of the spin polarization. We show that the signal in an
off-plane field contains components that reveal both the spin relaxation rate
and the spin coherence dephasing rate. We derive analytical formulas for the
hole spin polarization, which may be used to extract the two relevant rates by
fitting to the measurement data.Comment: 13 pages, 7 figure
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Expression regulation of MAO isoforms in monocytic cells in response to Th2 cytokines
Background: Th2-cytokines, such as interleukins-4 and –13 (IL-4, IL-13), have been identified as alternative stimuli of monocytes/macrophages. We have recently profiled the gene-expression pattern of IL-4-teated human peripheral monocytes and found that 15-lipoxygenase-1 (15-LOX1) and monoamine oxidase A (MAO-A) are among the five most strongly upregulated gene products in IL-4-treated cells. Transfection of monocytic cells (U937) with 15-LOX1 also induced MAO-A expression. These data suggested that 15-LOX1 products might play a role in the IL4-induced signaling cascade leading to expression of MAO-A in human monocytes. Material/Methods: To test this hypothesis we incubated wild-type and 15-LOX1-transfected U937 cells with different concentrations of either IL-4 or 15-LOX-products [13S-H(p)ODE, 15S-H(p)ETE] and quantified the expression of 15-LOX1, MAO-A, and MAO-B by activity assays and real-time RT-PCR. Results: Wild-type U937 cells express neither MAO-A nor MAO-B, but after three days of IL4 treatment, MAO-A mRNA was detected. A similar isoform-specific expression of MAO-A mRNA was observed when U937 cells were transfected with 15-LOX1 or when the cells were incubated with primary 15-LOX1 products (hydroperoxy fatty acids) or H2O2. In contrast, the corresponding hydroxy fatty acids were ineffective. Conclusions: These data indicate that increased intracellular peroxide concentrations (oxidative stress) induce MAO-A expression in monocytes/macrophages, which normally do not express the enzyme. Our findings also suggest that IL-4-induced upregulation of MAO-A expression in human peripheral monocytes may proceed via 15-LOX1-dependent and 15-LOX1-independent pathways. The biological role of MAO-A expression for monocyte function is discussed
Polarization-controlled single photons
Vacuum-stimulated Raman transitions are driven between two magnetic substates
of a rubidium-87 atom strongly coupled to an optical cavity. A magnetic field
lifts the degeneracy of these states, and the atom is alternately exposed to
laser pulses of two different frequencies. This produces a stream of single
photons with alternating circular polarization in a predetermined
spatio-temporal mode. MHz repetition rates are possible as no recycling of the
atom between photon generations is required. Photon indistinguishability is
tested by time-resolved two-photon interference.Comment: 4 pages, 3 figure
Predictors of homelessness among families and single adults after exit from homelessness prevention and rapid re-housing programs: evidence from the Department of Veterans Affairs Supportive Services for Veteran Families Program
This article assesses the extent and predictors of homelessness among Veterans (both Veterans in families with children and single adults Veterans) exiting the Supportive Services for Veteran
Families (SSVF) program, which is
a nationwide
homelessness prevention and rapid re-housing
program geared primarily towards those experiencing crisis homelessness. Among
rapid re-housing participants,
16% and 26% of single adult Veterans experienced an episode of homelessness at one and two years post-SSVF exit; the comparable figures
at those
follow-up
times for Veterans in families were 9.4% and 15.5%, respectively. Relatively fewer single adult
Veterans and Veterans in families receiving homelessness prevention services experienced an
episode of homelessness at one
and two years post-SSVF exit. Veteran-level characteristics,
including age, gender, prior history of homelessness and recent engagement with VA healthcare
were generally more salient predictors of homelessness following SSVF exit than variables
measuring SSVF program factors, or
community-level housing market conditions.U.S. Department of Veterans Affairs, National Center on Homelessness Among Veteran
Calculating the Fine Structure of a Fabry-Perot Resonator using Spheroidal Wave Functions
A new set of vector solutions to Maxwell's equations based on solutions to
the wave equation in spheroidal coordinates allows laser beams to be described
beyond the paraxial approximation. Using these solutions allows us to calculate
the complete first-order corrections in the short-wavelength limit to
eigenmodes and eigenfrequencies in a Fabry-Perot resonator with perfectly
conducting mirrors. Experimentally relevant effects are predicted. Modes which
are degenerate according to the paraxial approximation are split according to
their total angular momentum. This includes a splitting due to coupling between
orbital angular momentum and spin angular momentum
Dynamic rotor mode in antiferromagnetic nanoparticles
We present experimental, numerical, and theoretical evidence for a new mode
of antiferromagnetic dynamics in nanoparticles. Elastic neutron scattering
experiments on 8 nm particles of hematite display a loss of diffraction
intensity with temperature, the intensity vanishing around 150 K. However, the
signal from inelastic neutron scattering remains above that temperature,
indicating a magnetic system in constant motion. In addition, the precession
frequency of the inelastic magnetic signal shows an increase above 100 K.
Numerical Langevin simulations of spin dynamics reproduce all measured neutron
data and reveal that thermally activated spin canting gives rise to a new type
of coherent magnetic precession mode. This "rotor" mode can be seen as a
high-temperature version of superparamagnetism and is driven by exchange
interactions between the two magnetic sublattices. The frequency of the rotor
mode behaves in fair agreement with a simple analytical model, based on a high
temperature approximation of the generally accepted Hamiltonian of the system.
The extracted model parameters, as the magnetic interaction and the axial
anisotropy, are in excellent agreement with results from Mossbauer
spectroscopy
Electroweak Sudakov Logarithms and Real Gauge-Boson Radiation in the TeV Region
Electroweak radiative corrections give rise to large negative,
double-logarithmically enhanced corrections in the TeV region. These are partly
compensated by real radiation and, moreover, affected by selecting
isospin-noninvariant external states. We investigate the impact of real gauge
boson radiation more quantitatively by considering different restricted final
state configurations. We consider successively a massive abelian gauge theory,
a spontaneously broken SU(2) theory and the electroweak Standard Model. We find
that details of the choice of the phase space cuts, in particular whether a
fraction of collinear and soft radiation is included, have a strong impact on
the relative amount of real and virtual corrections.Comment: 20 pages, 4 figure
Resummation of Threshold, Low- and High-Energy Expansions for Heavy-Quark Correlators
With the help of the Mellin-Barnes transform, we show how to simultaneously
resum the expansion of a heavy-quark correlator around q^2=0 (low-energy), q^2=
4 m^2 (threshold, where m is the quark mass) and q^2=-\infty (high-energy) in a
systematic way. We exemplify the method for the perturbative vector correlator
at O(alpha_s^2) and O(alpha_s^3). We show that the coefficients, Omega(n), of
the Taylor expansion of the vacuum polarization function in terms of the
conformal variable \omega admit, for large n, an expansion in powers of 1/n (up
to logarithms of n) that we can calculate exactly. This large-n expansion has a
sign-alternating component given by the logarithms of the OPE, and a fixed-sign
component given by the logarithms of the threshold expansion in the external
momentum q^2.Comment: 27 pages, 8 figures. We fix typos in Eqs. (18), (27), (55) and (56).
Results unchange
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