3,803 research outputs found
Decay dynamics of quantum dots influenced by the local density of optical states of two-dimensional photonic crystal membranes
We have performed time-resolved spectroscopy on InAs quantum dot ensembles in
photonic crystal membranes. The influence of the photonic crystal is
investigated by varying the lattice constant systematically. We observe a
strong slow down of the quantum dots' spontaneous emission rates as the
two-dimensional bandgap is tuned through their emission frequencies. The
measured band edges are in full agreement with theoretical predictions. We
characterize the multi-exponential decay curves by their mean decay time and
find enhancement of the spontaneous emission at the bandgap edges and strong
inhibition inside the bandgap in good agreement with local density of states
calculations.Comment: 9 pages (preprint), 3 figure
Chronic pain: the importance of a sex and gender-based approach to treatment
Twenty-eight million women in the United States suffer from chronic pain. 70% of patients seeking treatment for chronic pain are women, and are found to return to pain clinics thirty-two times more frequently than men. These findings indicate that women experience insuficient pain relief following intervention. Given that 80% of pain research has been conducted on men, most knowledge of pain pathways in women are extrapolations, shedding light on the ineficiencies of current treatment algorithms, and the importance of a sex and gender-based approach to chronic pain.
The biochemistry and physiology of the pain pathway, as well as the pharmacokinetics and pharmacodynamics of medications used to remedy pain responses, are signifcantly different between men and women. Low-estradiol states result in a reduction in both mu-opioid receptor recruitment and basal activation, leading to significant hyperalgesia and sensitivity to chronic pain in women as compared to men. Further compounding the dichotomy between the chronic pain response is the response to analgesics. Women have lower levels of glucuronidation, higher volumes of distribution, and lower clearance of commonly administered analgesics as compared to men. Psychosocial factors such as gender roles, expectations surrounding pain, and coping strategies also determine how pain is perceived and ultimately influence how pain is treated. These findings are just beginning to shed light on the ways in which women and men respond differently in vivo to pain. However, the decision to treat women and men as separate entities with respect to pain management should not be a binary one. While patients should be treated as individuals, pre-menopausal, post-menopausal and transgender women, should all be met with an approach that takes into account the sex and gender differences that exist. Pain management physicians should take heed of these complex differences and utilize a sex and gender-based approach while managing patients.https://jdc.jefferson.edu/sexandgenderhealth/1025/thumbnail.jp
Women Authors in Medicine: A Gender Based Study on Authorship Opportunities and its Implications in Promotions in Medicine
Obtaining first authorship in research and published papers is widely held as grounds for promotions and advancements in the medical field. However, the opportunities to be involved in research and to have the primary authorship position are not equally divided amongst specialties, including primary care. Women physicians are becoming a greater percentage of the workforce in primary care, including Internal Medicine and the potential lack of opportunity for authorship may disproportionately affect their promotion. This poster presents the preliminary research on an investigation into the Indiana University School of Medicine’s Department of Medicine gender authorship profiles in the last five years. By utilizing the search engine scopus, a database of the papers written by physicians was created, and gender identifications of the first, second, and last author was made to find correlations between gender and authorship positions. These results will be used to make a case for reexamining the qualifications for promotions, and ensuring that genders have equal opportunity for job advancement and leadership in the medical field.https://jdc.jefferson.edu/sexandgenderhealth/1014/thumbnail.jp
Exchange-correlation orbital functionals in current-density-functional theory: Application to a quantum dot in magnetic fields
The description of interacting many-electron systems in external magnetic
fields is considered in the framework of the optimized effective potential
method extended to current-spin-density functional theory. As a case study, a
two-dimensional quantum dot in external magnetic fields is investigated.
Excellent agreement with quantum Monte Carlo results is obtained when
self-interaction corrected correlation energies from the standard local
spin-density approximation are added to exact-exchange results. Full
self-consistency within the complete current-spin-density-functional framework
is found to be of minor importance.Comment: 5 pages, 2 figures, submitted to PR
A method to suppress dielectric breakdowns in liquid argon ionization detectors for cathode to ground distances of several millimeters
We present a method to reach electric field intensity as high as 400 kV/cm in
liquid argon for cathode-ground distances of several millimeters. This can be
achieved by suppressing field emission from the cathode, overcoming limitations
that we reported earlier
A steerable UV laser system for the calibration of liquid argon time projection chambers
A number of liquid argon time projection chambers (LAr TPC's) are being build
or are proposed for neutrino experiments on long- and short baseline beams. For
these detectors a distortion in the drift field due to geometrical or physics
reasons can affect the reconstruction of the events. Depending on the TPC
geometry and electric drift field intensity this distortion could be of the
same magnitude as the drift field itself. Recently, we presented a method to
calibrate the drift field and correct for these possible distortions. While
straight cosmic ray muon tracks could be used for calibration, multiple coulomb
scattering and momentum uncertainties allow only a limited resolution. A UV
laser instead can create straight ionization tracks in liquid argon, and allows
one to map the drift field along different paths in the TPC inner volume. Here
we present a UV laser feed-through design with a steerable UV mirror immersed
in liquid argon that can point the laser beam at many locations through the
TPC. The straight ionization paths are sensitive to drift field distortions, a
fit of these distortion to the linear optical path allows to extract the drift
field, by using these laser tracks along the whole TPC volume one can obtain a
3D drift field map. The UV laser feed-through assembly is a prototype of the
system that will be used for the MicroBooNE experiment at the Fermi National
Accelerator Laboratory (FNAL)
Measurement of the drift field in the ARGONTUBE LAr TPC with 266~nm pulsed laser beams
ARGONTUBE is a liquid argon time projection chamber (LAr TPC) with a drift
field generated in-situ by a Greinacher voltage multiplier circuit. We present
results on the measurement of the drift-field distribution inside ARGONTUBE
using straight ionization tracks generated by an intense UV laser beam. Our
analysis is based on a simplified model of the charging of a multi-stage
Greinacher circuit to describe the voltages on the field cage rings
On the Electric Breakdown in Liquid Argon at Centimeter Scale
We present a study on the dependence of electric breakdown discharge
properties on electrode geometry and the breakdown field in liquid argon near
its boiling point. The measurements were performed with a spherical cathode and
a planar anode at distances ranging from 0.1 mm to 10.0 mm. A detailed study of
the time evolution of the breakdown volt-ampere characteristics was performed
for the first time. It revealed a slow streamer development phase in the
discharge. The results of a spectroscopic study of the visible light emission
of the breakdowns complement the measurements. The light emission from the
initial phase of the discharge is attributed to electro-luminescence of liquid
argon following a current of drifting electrons. These results contribute to
set benchmarks for breakdown-safe design of ionization detectors, such as
Liquid Argon Time Projection Chambers (LAr TPC).Comment: Minor revision according to editor report. 17 pages, 15 figures, 2
tables. Turboencabulato
Ion and polymer dynamics in polymer electrolytes PPO-LiClO4: II. 2H and 7Li NMR stimulated-echo experiment
We use 2H NMR stimulated-echo spectroscopy to measure two-time correlation
functions characterizing the polymer segmental motion in polymer electrolytes
PPO-LiClO4 near the glass transition temperature Tg. To investigate effects of
the salt on the polymer dynamics, we compare results for different ether oxygen
to lithium ratios, namely, 6:1, 15:1, 30:1 and infinity. For all compositions,
we find nonexponential correlation functions, which can be described by a
Kohlrausch function. The mean correlation times show quantitatively that an
increase of the salt concentration results in a strong slowing down of the
segmental motion. Consistently, for the high 6:1 salt concentration, a high
apparent activation energy E_a=4.1eV characterizes the temperature dependence
of the mean correlation times at Tg < T< 1.1T_g, while smaller values E_a=2.5eV
are observed for moderate salt contents. The correlation functions are most
nonexponential for 15:1 PPO-LiClO4, whereas the stretching is reduced for
higher and lower salt concentrations. A similar dependence of the correlation
functions on the evolution time in the presence and in the absence of ions
indicates that addition of salt hardly affects the reorientational mechanism.
For all compositions, mean jump angles of about 15 degree characterize the
segmental reorientation. In addition, comparison of results from 2H and 7Li NMR
stimulated-echo experiments suggests a coupling of ion and polymer dynamics in
15:1 PPO-LiClO4.Comment: 14 pages, 12 figure
Exploring the validity and limitations of the Mott-Gurney law for charge-carrier mobility determination of semiconducting thin-films
Using drift-diffusion simulations, we investigate the voltage dependence of the dark current in single carrier devices, typically used to determine charge-carrier mobilities. For both low and high voltages, the current increases linearly with the applied voltage. Whereas the linear current at low voltages is mainly due to space charge in the middle of the device, the linear current at high voltage is caused by charge-carrier saturation due to a high degree of injection. As a consequence, the current density at these voltages does not follow the classical square law derived by Mott and Gurney, and we show that for trap-free devices, only for intermediate voltages, a space-charge-limited drift current can be observed with a slope that approaches two. We show that, depending on the thickness of the semiconductor layer and the size of the injection barriers, the two linear current-voltage regimes can dominate the whole voltage range, and the intermediate Mott-Gurney regime can shrink or disappear. In this case, which will especially occur for thicknesses and injection barriers typical for single-carrier devices used to probe organic semiconductors, a meaningful analysis using the Mott-Gurney law will become unachievable, because a square-law fit can no longer be achieved, resulting in the mobility being substantially underestimated. General criteria for when to expect deviations from the Mott-Gurney law when used for analysis of intrinsic semiconductors are discussed
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