124 research outputs found
Effect of interdiffusion of quantum well infrared photodetector
The intersubband infrared photodetector performance is theoretically analyzed for various stages of interdiffusion in AlGaAs/GaAs quantum well. The absorption strength and responsivity are enhanced for certain extents of interdiffusion and the peak detection wavelength red shifts continuously with a large tunable range from 7 to 38.4 ”m. The dark current is at an acceptable value for small diffusion extent. ©1996 American Institute of Physics.published_or_final_versio
Diffused quantum well solar cell
An alternative multi-bandgap solar cell made of diffused quantum well (DFQW) as the absorber is proposed here. The modeling of the spectral response and energy conversion efficiency of the solar cell will be shown. Significant enhancement in energy conversion efficiency is demonstrated when compared to that of the single bandgap cells.published_or_final_versio
Thermal interdiffusion in InGaAs/GaAs strained multiple quantum well infrared photodetector
RTA at 850 °C for 5 and 10 s is carried out to study the effect of interdiffusion on the optical and electrical properties of strained InGaAs/GaAs quantum well infrared photodetector. Photoluminescence measurement at 4.5 K shows that no strain relaxation or misfit dislocation formation occurs throughout the annealing process. Absorption and responsivity peak wavelengths are red shifted continuously without appreciable degradation in absorption strength. The normal incident absorption, which is believed to be the result of band-mixing effects induced by the coupling between the conduction and valence and is usually forbidden in conventional polarization selection rule, is preserved after interdiffusion. Responsivity spectra of both 0° and 90° polarization are of compatible amplitude and the shape of the annealed spectra becomes narrower. Dark current of the annealed devices is not very sensitive to temperature variation and is found to be an order of magnitude larger than the as-grown one at 77K.published_or_final_versio
The reasons of dropout of sport in Hong Kong school athletes
domains. The aim of this study was to identify the potential dropout reasons of school athletes and to examine if their perception of dropout was affected by the previous dropout experience. There were 50 subjects who were divided into two groups based on their previous dropout experience (Dropout Group=22, No Dropout Group=28). They filled a questionnaire about potential dropout reasons of the current sport. Coach and teammates were two predominated reasons of dropout; Influence of parent and training seemed to affect the termination of the sport to a lesser extent. Moreover, the perception of social value and lost focus were significantly different between two groups. Character of coach and teammates affect the engagement of training in school athletes. However, the parental influence had less influence than expected. Training intensity played little role as the dropout reason. Previous experience of dropout had an impact of potential dropout reasons on their current sport training
Validity and Reliability of Timed Up and Go Test on Dynamic Balance in 3-5 Years Old Preschool Children
Objective: The purpose of this study was to investigate the validity and reliability of the Timed Up and Go Test (TUG) among normal 3-5 years old preschool children in Hong Kong. Methods: Cross-sectional design was applied to this study. Sixty (30 female, 30 male) preschool children aged from 3 to 5 years old (mean age=4.22 ± 0.85) from local normal preschool was recruited using convenient sampling to perform three dynamic balance tests: Timed Up and Go Test (TUG), Star Excursion Balance Test (SEBT) and the Pediatric Balance Scale Test (PBS). A simple self-administrative questionnaire survey was also conducted with their parents. Results: Positive correlation (r=0.74, p<0.05) was found between TUG results obtained at two time points when assessing the test-retest reliability. Moderated negative correlations were found between TUG and SEBT or PBS, which indicated children with longer reaching distance or higher PBS score tend to use shorter time to complete TUG. Conclusion: TUG was a valid and reliable tool for assessing dynamic balance of preschool children aged between 3 and 5 years old. This can also be used for screening or early detection of developmental coordination disorder (DCD) for children aged 6 years old or younger
Frequent reduced expression of alpha-1B-adrenergic receptor caused by aberrant promoter methylation in gastric cancers
Recent studies have suggested that epigenetic inactivation of tumour-related genes by promoter methylation participates in the development of gastric cancer. We newly identified the frequently aberrant promoter methylation of alpha-1B-adrenergic receptor (ADRA1B) in colorectal cancer by methylation-sensitive representational difference analysis (MS-RDA) and examined the methylation status of the ADRA1B promoter in 34 paired samples of colorectal cancer and surrounding epithelial tissue, and 34 paired samples of gastric cancer and surrounding epithelial tissue. In colorectal cancers, only four of 34 (11.8%) tumours showed ADRA1B promoter methylation. In contrast, ADRA1B promoter methylation was detected in 24 of 34 (70.6%) gastric cancers and in 14 of 34 (41.2%) surrounding epithelial tissues. The frequency of ADRA1B promoter methylation was higher in gastric epithelial tissues with intestinal metaplasia (41.6%) than in those without intestinal metaplasia (25.0%). Reverse transcriptionâPCR detected reduced ADRA1B expression in 12 of 18 (66.7%) gastric cancers, and its promoter methylation was detected in 11 of these 12 (91.7%) gastric cancers with reduced ADRA1B expression. Thus, ADRA1B promoter is frequently methylated in gastric cancer. Our results suggest that the ADRA1B gene is an important tumour-related gene frequently involved in the development and progression of gastric cancer
Test of lepton universality in decays
The first simultaneous test of muon-electron universality using
and decays is performed, in two ranges of the dilepton
invariant-mass squared, . The analysis uses beauty mesons produced in
proton-proton collisions collected with the LHCb detector between 2011 and
2018, corresponding to an integrated luminosity of 9 . Each
of the four lepton universality measurements reported is either the first in
the given interval or supersedes previous LHCb measurements. The
results are compatible with the predictions of the Standard Model.Comment: All figures and tables, along with any supplementary material and
additional information, are available at
https://cern.ch/lhcbproject/Publications/p/LHCb-PAPER-2022-046.html (LHCb
public pages
Precision measurement of violation in the penguin-mediated decay
A flavor-tagged time-dependent angular analysis of the decay
is performed using collision data collected
by the LHCb experiment at % at TeV, the center-of-mass energy of
13 TeV, corresponding to an integrated luminosity of 6 fb^{-1}. The
-violating phase and direct -violation parameter are measured
to be rad and
, respectively, assuming the same values
for all polarization states of the system. In these results, the
first uncertainties are statistical and the second systematic. These parameters
are also determined separately for each polarization state, showing no evidence
for polarization dependence. The results are combined with previous LHCb
measurements using collisions at center-of-mass energies of 7 and 8 TeV,
yielding rad and . This is the most precise study of time-dependent violation
in a penguin-dominated meson decay. The results are consistent with
symmetry and with the Standard Model predictions.Comment: All figures and tables, along with any supplementary material and
additional information, are available at
https://cern.ch/lhcbproject/Publications/p/LHCb-PAPER-2023-001.html (LHCb
public pages
Measurement of the differential branching fraction
The branching fraction of the rare decay is measured for the first time, in the squared dimuon mass
intervals, , excluding the and regions. The data
sample analyzed was collected by the LHCb experiment at center-of-mass energies
of 7, 8, and 13 TeV, corresponding to a total integrated luminosity of $9\
\mathrm{fb}^{-1}q^{2}q^{2} >15.0\
\mathrm{GeV}^2/c^4$, where theoretical predictions have the smallest model
dependence, agrees with the predictions.Comment: All figures and tables, along with any supplementary material and
additional information, are available at
https://cern.ch/lhcbproject/Publications/p/LHCb-PAPER-2022-050.html (LHCb
public pages
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