Polymer optical fiber detector adapted for low-dose-rate gamma-ray detection.

In this Letter, a polymer optical fiber (POF) detector with a convex spherical aperture microstructure probe is designed for low-energy and low-dose rate gamma-ray detection. Simulation and experimental results demonstrate that this structure has a higher optical coupling efficiency and that the angular coherence of the detector depends strongly on the depth of the probe micro-aperture. By modeling the relationship between angular coherence and micro-aperture depth, the optimal depth of the micro-aperture is determined. The sensitivity of the fabricated POF detector is 701 cps at 59.5-keV gamma-ray of 2.78 µSv/h and the maximum percentage error of the average count rate at different angles is 5.16%.

Prevalence of mild cognitive impairment and its subtypes in community-dwelling residents aged 65 years or older in Guangzhou, China.

BACKGROUND: Prevalence of mild cognitive impairment (MCI) has been reported substantial variations, and mostly in Western countries. Less is known about MCI in the south of China. The study is to estimate the prevalence of MCI and its subtypes in residents aged 65year or older in community-dwelling residents of Guangzhou, China. METHODS: The study was a community-based, cross-sectional study conducted in rural and urban areas of Guangzhou between April and October 2009. Eight communities were randomly selected using a cluster sampling method. Each elderly was interviewed with Montreal Cognitive Assessment, the Mini-Mental state examination, Auditory Verbal Learning Test, the Clinical Dementia Rating scale et al. MCI was classified as amnestic MCI (a-MCI) or nonamnestic MCI (na-MCI). RESULTS: 2427 individuals were contacted, but in-person interviews were conducted with 2111 participants. 299 participants with MCI were identified. The prevalence of MCI, a-MCI and na-MCI was 14.2%, 12.2%, 2.0% respectively. The prevalence of MCI and a-MCI increased with age, decreased with education level, and was higher in rural areas than in urban areas. The difference of prevalence of MCI and a-MCI between women with men wasn't statistically significant(MCIχ2=1.0, OR 0.9, 95%CI=0.6-1.2; a-MCIχ2=1.0, OR 0.9, 95%CI=0.6-1.2), when controlling for education by logistic regression analysis. CONCLUSIONS: The results suggest that 14.2% of elderly individuals are affected by MCI in Guangzhou, China. And MCI was dominated by a-MCI. The prevalence of MCI and a-MCI increased with age, decreased with education level, and was higher in the rural population compared to the urban population.