4,420 research outputs found
African American and European American Therapistsâ Experiences of Addressing Race in Cross-Racial Psychotherapy Dyads
Using Consensual Qualitative Research, 12 licensed psychologistsâ overall experiences addressing race in psychotherapy were investigated, as were their experiences addressing race in a specific cross-racial therapy dyad. Results indicated that only African American psychologists reported routinely addressing race with clients of color or when race was part of a clientâs presenting concern. European American psychologists indicated that they would address race if clients raised the topic, and some reported that they did not normally address race with racially different clients. When discussing a specific cross-racial dyad, African American therapists more often than European American therapists addressed race because they perceived client discomfort. Only European American therapists reported feeling uncomfortable addressing race, but therapists of both races perceived that such discussions had positive effects
Theory of excitons in cubic III-V semiconductor GaAs, InAs and GaN quantum dots: fine structure and spin relaxation
Exciton fine structures in cubic III-V semiconductor GaAs, InAs and GaN
quantum dots are investigated systematically and the exciton spin relaxation in
GaN quantum dots is calculated by first setting up the effective exciton
Hamiltonian. The electron-hole exchange interaction Hamiltonian, which consists
of the long- and short-range parts, is derived within the effective-mass
approximation by taking into account the conduction, heavy- and light-hole
bands, and especially the split-off band. The scheme applied in this work
allows the description of excitons in both the strong and weak confinement
regimes. The importance of treating the direct electron-hole Coulomb
interaction unperturbatively is demonstrated. We show in our calculation that
the light-hole and split-off bands are negligible when considering the exciton
fine structure, even for GaN quantum dots, and the short-range exchange
interaction is irrelevant when considering the optically active doublet
splitting. We point out that the long-range exchange interaction, which is
neglected in many previous works, contributes to the energy splitting between
the bright and dark states, together with the short-range exchange interaction.
Strong dependence of the optically active doublet splitting on the anisotropy
of dot shape is reported. Large doublet splittings up to 600 eV, and even
up to several meV for small dot size with large anisotropy, is shown in GaN
quantum dots. The spin relaxation between the lowest two optically active
exciton states in GaN quantum dots is calculated, showing a strong dependence
on the dot anisotropy. Long exciton spin relaxation time is reported in GaN
quantum dots. These findings are in good agreement with the experimental
results.Comment: 22+ pages, 16 figures, several typos in the published paper are
corrected in re
Anisotropy in the Cosmic Microwave Background at Degree Angular Scales: Python V Results
Observations of the microwave sky using the Python telescope in its fifth
season of operation at the Amundsen-Scott South Pole Station in Antarctica are
presented. The system consists of a 0.75 m off-axis telescope instrumented with
a HEMT amplifier-based radiometer having continuum sensitivity from 37-45 GHz
in two frequency bands. With a 0.91 deg x 1.02 deg beam the instrument fully
sampled 598 deg^2 of sky, including fields measured during the previous four
seasons of Python observations. Interpreting the observed fluctuations as
anisotropy in the cosmic microwave background, we place constraints on the
angular power spectrum of fluctuations in eight multipole bands up to l ~ 260.
The observed spectrum is consistent with both the COBE experiment and previous
Python results. There is no significant contamination from known foregrounds.
The results show a discernible rise in the angular power spectrum from large (l
~ 40) to small (l ~ 200) angular scales. The shape of the observed power
spectrum is not a simple linear rise but has a sharply increasing slope
starting at l ~ 150.Comment: 5 page
Thermal performance of two heat exchangers for thermoelectric generators
Thermal performance of heat exchanger is important for potential application in integrated solar cell/module and
thermoelectric generator (TEG) system. Usually, thermal performance of a heat exchanger for TEGs is analysed
by using a 1D heat conduction theory which ignores the detailed phenomena associated with thermo-hydraulics.
In this paper, thermal and mass transports in two different exchangers are simulated by means of a steady-state,
3D turbulent flow k -e model with a heat conduction module under various flow rates. In order to simulate an
actual working situation of the heat exchangers, hot block with an electric heater is included in the model. TEG
model is simplified by using a 1D heat conduction theory, so its thermal performance is equivalent to a real TEG.
Natural convection effect on the outside surfaces of the computational model is considered. Computational
models and methods used are validated under transient thermal and electrical experimental conditions of a TEG.
It is turned out that the two heat exchangers designed have a better thermal performance compared with an
existing heat exchanger for TEGs, and more importantly, the fin heat exchanger is more compact and has nearly
half temperature rise compared with the tube heat exchanger
Power Spectrum Estimators For Large CMB Datasets
Forthcoming high-resolution observations of the Cosmic Microwave Background
(CMB) radiation will generate datasets many orders of magnitude larger than
have been obtained to date. The size and complexity of such datasets presents a
very serious challenge to analysing them with existing or anticipated
computers. Here we present an investigation of the currently favored algorithm
for obtaining the power spectrum from a sky-temperature map --- the quadratic
estimator. We show that, whilst improving on direct evaluation of the
likelihood function, current implementations still inherently scale as the
equivalent of the cube of the number of pixels or worse, and demonstrate the
critical importance of choosing the right implementation for a particular
dataset.Comment: 8 pages LATEX, no figures, corrected misaligned columns in table
HAT-P-57b: A Short-Period Giant Planet Transiting A Bright Rapidly Rotating A8V Star Confirmed Via Doppler Tomography
We present the discovery of HAT-P-57b, a P = 2.4653 day transiting planet
around a V = 10.465 +- 0.029 mag, Teff = 7500 +- 250 K main sequence A8V star
with a projected rotation velocity of v sin i = 102.1 +- 1.3 km s^-1. We
measure the radius of the planet to be R = 1.413 +- 0.054 R_J and, based on RV
observations, place a 95% confidence upper limit on its mass of M < 1.85 M_J .
Based on theoretical stellar evolution models, the host star has a mass and
radius of 1.47 +- 0.12 M_sun, and 1.500 +- 0.050 R_sun, respectively.
Spectroscopic observations made with Keck-I/HIRES during a partial transit
event show the Doppler shadow of HAT-P-57b moving across the average spectral
line profile of HAT-P- 57, confirming the object as a planetary system. We use
these observations, together with analytic formulae that we derive for the line
profile distortions, to determine the projected angle between the spin axis of
HAT-P-57 and the orbital axis of HAT-P-57b. The data permit two possible
solutions, with -16.7 deg < lambda < 3.3 deg or 27.6 deg < lambda < 57.4 deg at
95% confidence, and with relative probabilities for the two modes of 26% and
74%, respectively. Adaptive optics imaging with MMT/Clio2 reveals an object
located 2.7" from HAT-P-57 consisting of two point sources separated in turn
from each other by 0.22". The H and L -band magnitudes of the companion stars
are consistent with their being physically associated with HAT-P-57, in which
case they are stars of mass 0.61 +- 0.10 M_sun and 0.53 +- 0.08 M_sun. HAT-P-57
is the most rapidly rotating star, and only the fourth main sequence A star,
known to host a transiting planet.Comment: 18 pages, 14 figures, 5 tables, accepted for publication in A
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