1,511 research outputs found
Origin of the inner ring in photoluminescence patterns of quantum well excitons
In order to explain and model the inner ring in photoluminescence (PL)
patterns of indirect excitons in GaAs/AlGaAs quantum wells (QWs), we develop a
microscopic approach formulated in terms of coupled nonlinear equations for the
diffusion, thermalization and optical decay of the particles. The origin of the
inner ring is unambiguously identified: it is due to cooling of indirect
excitons in their propagation from the excitation spot. We infer that in our
high-quality structures the in-plane diffusion coefficient is about 10-30cm^2/s
and the amplitude of the disorder potential is about 0.45meV.Comment: 4 pages, 3 figure
Trapping of Cold Excitons with Laser Light
Optical trapping and manipulation of neutral particles has led to a variety
of experiments from stretching DNA-molecules to trapping and cooling of neutral
atoms. An exciting recent outgrowth of the technique is an experimental
implementation of atom Bose-Einstein condensation. In this paper, we propose
and demonstrate laser induced trapping for a new system--a gas of excitons in
quantum well structures. We report on the trapping of a highly degenerate Bose
gas of excitons in laser induced traps.Comment: 9 pages, 3 figure
Bound on Lorentz- and CPT-Violating Boost Effects for the Neutron
A search for an annual variation of a daily sidereal modulation of the
frequency difference between co-located Xe and He Zeeman
masers sets a stringent limit on boost-dependent Lorentz and CPT violation
involving the neutron, consistent with no effect at the level of 150 nHz. In
the framework of the general Standard-Model Extension, the present result
provides the first clean test for the fermion sector of the symmetry of
spacetime under boost transformations at a level of GeV.Comment: 4 pages, 1 figur
What makes great physical education teaching? Application of evidence-based research to the training experience of ITE students
What makes great physical education (PE) teaching? If only it were as simple as reading this article! In 2014, The Sutton Trust reviewed over 200 pieces of research to discover what constitutes great teaching. This is just one piece of evidence-informed research that the Secondary PE PGCE and School Direct course at the University of Worcester is informed by. Coe et al. (2014) acknowledge the extreme difficulties in being able to precisely define effective teaching. However, the focus remains on improving pupil achievement and outcomes. The report identified effective practices, as well as practices that were deemed to be less effective; all of which are grounded in evidence and will be discussed within this article
The lights are on but no one’s home: Meta-awareness and the decoupling of attention when the mind wanders
Timing of adjuvant chemotherapy after limb amputation and effect on outcome in dogs with appendicular osteosarcoma without distant metastases
Objective: To determine an optimal time interval between amputation and initiation of adjuvant chemotherapy (TIamp-chemo) in dogs with appendicular osteosarcoma without distant metastases and whether TIamp-chemo was associated with outcome.
Animals: 168 client-owned dogs treated at 9 veterinary oncology centers.
Procedures: Data were collected from the dogs' medical records concerning potential prognostic variables and outcomes. Dogs were grouped as to whether they received chemotherapy within 3, 5, 7, 10, 15, 20, 30, or > 30 days after amputation of the affected limb. Analyses were performed to identify variables associated with time to tumor progression and survival time after limb amputation and to determine an optimal TIamp-chemo.
Results: Median TIamp-chemo was 14 days (range, 1 to 210 days). Median time to tumor progression for dogs with a TIamp-chemo ≤ 5 days (375 days; 95% CI, 162 to 588 days) was significantly longer than that for dogs with a TIamp-chemo > 5 days (202 days; 95% CI, 146 to 257 days). Median overall survival time for dogs with a TIamp-chemo ≤ 5 days (445 days; 95% CI, 345 to 545 days) was significantly longer than that for dogs with a TIamp-chemo > 5 days (239 days; 95% CI, 186 to 291 days).
Conclusions and clinical relevance: Findings indicated that early (within 5 days) initiation of adjuvant chemotherapy after limb amputation was associated with a significant and clinically relevant survival benefit for dogs with appendicular osteosarcoma without distant metastases. These results suggested that the timing of chemotherapy may be an important prognostic variabl
Well dispersed fractal aggregates as filler in polymer-silica nanocomposites: long range effects in rheology
We are presenting a new method of processing polystyrene-silica
nanocomposites, which results in a very well-defined dispersion of small
primary aggregates (assembly of 15 nanoparticles of 10 nm diameter) in the
matrix. The process is based on a high boiling point solvent, in which the
nanoparticles are well dispersed, and controlled evaporation. The filler's fine
network structure is determined over a wide range of sizes, using a combination
of Small Angle Neutron Scattering (SANS) and Transmission Electronic Microscopy
(TEM). The mechanical response of the nanocomposite material is investigated
both for small (ARES oscillatory shear and Dynamical Mechanical Analysis) and
large deformations (uniaxial traction), as a function of the concentration of
the particles. We can investigate the structure-property correlations for the
two main reinforcement effects: the filler network contribution, and a
filler-polymer matrix effect. Above a silica volume fraction threshold, we see
a divergence of the modulus correlated to the build up of a connected network.
Below the threshold, we obtain a new additional elastic contribution of much
longer terminal time than the matrix. Since aggregates are separated by at
least 60 nm, this new filler-matrix contribution cannot be described solely
with the concept of glassy layer (2nm)
Rapid generation of endogenously driven transcriptional reporters in cells through CRISPR/Cas9
CRISPR/Cas9 technologies have been employed for genome editing to achieve gene knockouts and knock-ins in somatic cells. Similarly, certain endogenous genes have been tagged with fluorescent proteins. Often, the detection of tagged proteins requires high expression and sophisticated tools such as confocal microscopy and flow cytometry. Therefore, a simple, sensitive and robust transcriptional reporter system driven by endogenous promoter for studies into transcriptional regulation is desirable. We report a CRISPR/Cas9-based methodology for rapidly integrating a firefly luciferase gene in somatic cells under the control of endogenous promoter, using the TGFβ-responsive gene PAI-1. Our strategy employed a polycistronic cassette containing a non-fused GFP protein to ensure the detection of transgene delivery and rapid isolation of positive clones. We demonstrate that firefly luciferase cDNA can be efficiently delivered downstream of the promoter of the TGFβ-responsive gene PAI-1. Using chemical and genetic regulators of TGFβ signalling, we show that it mimics the transcriptional regulation of endogenous PAI-1 expression. Our unique approach has the potential to expedite studies on transcription of any gene in the context of its native chromatin landscape in somatic cells, allowing for robust high-throughput chemical and genetic screens
Hidden Silicon-Vacancy Centers in Diamond
We characterize a high-density sample of negatively charged silicon-vacancy
(SiV) centers in diamond using collinear optical multidimensional coherent
spectroscopy. By comparing the results of complementary signal detection
schemes, we identify a hidden population of \ce{SiV^-} centers that is not
typically observed in photoluminescence, and which exhibits significant
spectral inhomogeneity and extended electronic times. The phenomenon is
likely caused by strain, indicating a potential mechanism for controlling
electric coherence in color-center-based quantum devices
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