6,289 research outputs found
Spin dynamics of electrons in the first excited subband of a high-mobility low-density 2D electron system
We report on time-resolved Kerr rotation measurements of spin coherence of
electrons in the first excited subband of a high-mobility low-density
two-dimensional electron system in a GaAs/Al0.35Ga0.65As heterostructure. While
the transverse spin lifetime (T2*) of electrons decreases monotonically with
increasing magnetic field, it has a non-monotonic dependence on the
temperature, with a peak value of 596 ps at 36 K, indicating the effect of
inter-subband electron-electron scattering on the electron spin relaxation. The
spin lifetime may be long enough for potential device application with
electrons in excited subbands
Injection drug use and HIV/AIDS in China: Review of current situation, prevention and policy implications
Illicit drug abuse and HIV/AIDS have increased rapidly in the past 10 to 20 years in China. This paper reviews drug abuse in China, the HIV/AIDS epidemic and its association with injection drug use (IDU), and Chinese policies on illicit drug abuse and prevention of HIV/AIDS based on published literature and unpublished official data. As a major drug trans-shipment country with source drugs from the "Golden Triangle" and "Gold Crescent" areas in Asia, China has also become an increasingly important drug consuming market. About half of China's 1.14 million documented drug users inject, and many share needles. IDU has contributed to 42% of cumulatively reported HIV/AIDS cases thus far. Drug trafficking is illegal in China and can lead to the death penalty. The public security departments adopt "zero tolerance" approach to drug use, which conflict with harm reduction policies of the public health departments. Past experience in China suggests that cracking down on drug smuggling and prohibiting drug use alone can not prevent or solve all illicit drug related problems in the era of globalization. In recent years, the central government has outlined a series of pragmatic policies to encourage harm reduction programs; meanwhile, some local governments have not fully mobilized to deal with drug abuse and HIV/AIDS problems seriously. Strengthening government leadership at both central and local levels; scaling up methadone substitution and needle exchange programs; making HIV voluntary counseling and testing available and affordable to both urban and rural drug users; and increasing utilization of outreach and nongovernmental organizations are offered as additional strategies to help cope with China's HIV and drug abuse problem
Learning Robust Visual-Semantic Embedding for Generalizable Person Re-identification
Generalizable person re-identification (Re-ID) is a very hot research topic
in machine learning and computer vision, which plays a significant role in
realistic scenarios due to its various applications in public security and
video surveillance. However, previous methods mainly focus on the visual
representation learning, while neglect to explore the potential of semantic
features during training, which easily leads to poor generalization capability
when adapted to the new domain. In this paper, we propose a Multi-Modal
Equivalent Transformer called MMET for more robust visual-semantic embedding
learning on visual, textual and visual-textual tasks respectively. To further
enhance the robust feature learning in the context of transformer, a dynamic
masking mechanism called Masked Multimodal Modeling strategy (MMM) is
introduced to mask both the image patches and the text tokens, which can
jointly works on multimodal or unimodal data and significantly boost the
performance of generalizable person Re-ID. Extensive experiments on benchmark
datasets demonstrate the competitive performance of our method over previous
approaches. We hope this method could advance the research towards
visual-semantic representation learning. Our source code is also publicly
available at https://github.com/JeremyXSC/MMET
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