Background Sexual transmission is the fastest growing route of HIV transmission in China. Methods Cross-sectional study of 737 female sex workers (FSW) in Kaiyuan City, Yunnan Province, China from March-May 2006 to describe risk factors for HIV infection and to determine the commercial sex venues where FSWs were most at risk of being infected with or infecting others with HIV. Results Overall HIV prevalence was 10.3%, but prevalence varied with the sex venue with 25.8% of FSWs working on streets being HIV-positive and none of the FSWs working in night clubs. Adjusted odds ratios (OR) of HIV infection were 9.1 (95% CI: 4.67–17.55) for injection drug use; 3.3 (95% CI: 1.46–7.37) for non-injection illegal drug use; 2.7 (95% CI: 1.25–5.93) for duration of sex work ≥5 years; 2.2 (95% CI: 1.05–4.70) for infection with herpes simplex virus type 2; and 2.0 (95% CI: 1.12–3.47) for working at a higher risk entertainment venue. Although condom use was not a significant risk factor in the overall model, FSWs in lower risk venues who reported consistent use with clients had a 70% reduction in HIV infections (OR: 0.30; 95% CI: 0.12–0.90). Conclusions Illegal drug use, particularly with injection drugs, is the single greatest risk factor for HIV infection among FSWs in Kaiyuan City, China. FSWs working on the street or in temporary sublets, beauty salons or saunas are at particularly high risk for transmitting and being infected with HIV. HIV prevention efforts among FSWs should target illegal drug users and these other subgroups.

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Normal aging is typically characterized by abnormal resting-state functional connectivity (FC), including decreasing connectivity within networks and increasing connectivity between networks, under the assumption that the FC over the scan time was stationary. In fact, the resting-state FC has been shown in recent years to vary over time even within minutes, thus showing the great potential of intrinsic interactions and organization of the brain. In this article, we assumed that the dynamic FC consisted of an intrinsic dynamic balance in the resting brain and was altered with increasing age. Two groups of individuals (N = 36, ages 20–25 for the young group; N = 32, ages 60–85 for the senior group) were recruited from the public data of the Nathan Kline Institute. Phase randomization was first used to examine the reliability of the dynamic FC. Next, the variation in the dynamic FC and the energy ratio of the dynamic FC fluctuations within a higher frequency band were calculated and further checked for differences between groups by non-parametric permutation tests. The results robustly showed modularization of the dynamic FC variation, which declined with aging; moreover, the FC variation of the inter-network connections, which mainly consisted of the frontal-parietal network-associated and occipital-associated connections, decreased. In addition, a higher energy ratio in the higher FC fluctuation frequency band was observed in the senior group, which indicated the frequency interactions in the FC fluctuations. These results highly supported the basis of abnormality and compensation in the aging brain and might provide new insights into both aging and relevant compensatory mechanisms.

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Surface acoustic wave (SAW)-based formaldehyde gas sensor using bi-layer nanofilms of bacterial cellulose (BC) and polyethyleneimine (PEI) was developed on an ST-cut quartz substrate using sol-gel and spin coating processes. BC nanofilms significantly improve the sensitivity of PEI films to formaldehyde gas, and reduces response and recovery times. The BC films have superfine filamentary and fibrous network structures, which provide a large number of attachment sites for the PEI particles. Measurement results obtained using in situ diffuse reflectance Fourier transform infrared spectroscopy showed that the primary amino groups of PEI strongly adsorb formaldehyde molecules through nucleophilic reactions, thus resulting in a negative frequency shift of the SAW sensor due to the mass loading effect. In addition, experimental results showed that the frequency shifts of the SAW devices are determined by thickness of PEI film, concentration of formaldehyde and relative humidity. The PEI/BC sensor coated with three layers of PEI as the sensing layer showed the optimal sensing performance, which had a frequency shift of 35.6 kHz for 10 ppm formaldehyde gas, measured at room temperature and 30% RH. The sensor also showed good selectivity and stability, with a low limit of detection down to 100 ppb.

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