Enhanced acoustic mode coupling resulting from an internal solitary wave approaching the shelfbreak in the South China Sea.

Internal waves and bathymetric variation create time- and space-dependent alterations in the ocean acoustic waveguide, and cause subsequent coupling of acoustic energy between propagating normal modes. In this paper, the criterion for adiabatic invariance is extended to the case of an internal solitary wave (ISW) encountering a sloping bathymetry (i.e., continental shelfbreak). Predictions based on the extended criterion for adiabatic invariance are compared to experimental observations from the Asian Seas International Acoustics Experiment. Using a mode 1 starter field, results demonstrate time-dependent coupling of mode 1 energy to higher adjacent modes, followed by abrupt coupling of mode 5-7 energy to nonadjacent modes 8-20, produces enhanced mode coupling and higher received levels downrange of the oceanographic and bathymetric features. Numerical simulations demonstrate that increasing ISW amplitude and seafloor slope enhance the coupling of energy to adjacent and nonadjacent modes. This enhanced coupling is the direct result of the simultaneous influence of the ISW and its proximity to the shelfbreak, and, compared to the individual effect of the ISW or shelfbreak, has the capacity to scatter 2-4 times the amount of acoustic energy from below the thermocline into the upper water column beyond the shelfbreak in realistic environments.

Prevalence of human immunodeficiency virus and its association with hepatitis B, C, and D virus infections among incarcerated male substance abusers in Taiwan.

Taiwan has been facing a rising epidemic of human immunodeficiency virus (HIV) infection since 2004. Injection drug users comprised 38.5% of accumulated HIV cases by 2007. This cross-sectional study investigated the seroprevalence of hepatitis B virus (HBV), hepatitis C virus (HCV), hepatitis D virus (HDV), and HIV infection in 753 male substance users who were detained in a detoxification center in Taoyuan, Taiwan. The subjects were enrolled into the study consecutively between February and October, 2005. The seroprevalence rates of HIV antibodies, HCV antibodies, and HBV surface antigens among all subjects, and HDV antibodies among HBV carriers were 6.9% (95% confidence interval [CI]: 5.19-8.95), 30.5% (95% CI: 27.23-33.93), 16.9% (95% CI: 14.24-19.71) and 13.7% (95% CI: 8.19-21.04), respectively. Subjects in the heroin injection group had significantly higher rates of HIV infection, HCV infection and HDV superinfection (25.5%, 89.6%, and 38.7%) than those in the heroin non-injection group (0.9%, 24.5%, and 6.25%), the methamphetamine group (0.3%, 8.1%, and 6.7%), and the club drug group (1%, 3%, and 0%; P < 0.001). The odds of HCV, HIV, or HDV infection were 74.7, 63.8, and 11.1 higher, respectively, for heroin injection drug users than for non-injection drug users (P < 0.0001). Compared to HIV-negative individuals, the odds of being a heroin injector and the odds of HCV co-infections were 64-fold and 149-fold higher, respectively, in HIV-positive individuals. The impact of HBV, HCV, and HDV infection on the HIV epidemic in Taiwan should be monitored closely.

Prevalence of heroin and methamphetamine male users in the northern Taiwan, 1999-2002: capture-recapture estimates.

BACKGROUND: Illegal drug use and related problems have been emerging as an important public health issue in Taiwan. Via the capture-recapture approach, the present study aimed to offer insights into the size of heroin and methamphetamine male user population in the northern Taiwan during the period from 1999 to 2002. METHODS: Annual lists of male subjects were collated from both judiciary and medical systems in Taoyuan County, Taiwan. A total of 2809, 2486, 1661, and 1440 local male illegal drug users aged 15 to 54 years were identified in Taoyuan County from 1999 to 2002, respectively. RESULTS: An estimated number of 16192, 14532, 16844, and 11783 local male methamphetamine or heroin users were found in each of the four consecutive years in the region. From 1999 to 2002, the annual prevalence rate for heroin use was 0.27% (95% CI = 0.20%, 0.38%), 0.33% (95% CI = 0.25%, 0.44%), 0.63% (95% CI = 0.44%, 0.92%), and 0.72% (95% CI = 0.54%, 0.97%), respectively, suggesting a trend of significant increase (chi-square for linear trend = 1677.76, d.f. = 3, p < 0.0001). In contrast, a decreasing trend was found for methamphetamine (2.38%, 1.91%, 2.47%, and 1.24%), with a modest rebound in 2001. The prevalence rates of illegal drug use for male residents in Taoyuan County were approximately 2-3% during this period, and the scale of problem shows no sign of diminution. CONCLUSION: By taking advantage of existing datasets that were incomplete by each alone, the approach of capture-recapture model may be ultimately considered as a tool to estimate the scale of illegal drug use problems. The population of heroin-using males apparently is stably expanding in the northern part of Taiwan in the first years of 21st century.

Gender difference in the clinical and behavioral characteristics of human immunodeficiency virus-infected injection drug users in Taiwan.

BACKGROUND/PURPOSE: Injection drug users (IDUs) have become the major contributors to the human immunodeficiency virus (HIV)/acquired immunodeficiency syndrome epidemic in Taiwan, accounting for more than 60% of new cases in 2005. In Taiwan, gender difference in risk factors for HIV among IDUs has not been reported before. We studied the clinical and sociodemographic characteristics, sexual behaviors, drug use histories and criminal records of male and female HIV-infected IDUs. METHODS: A total of 100 male and 25 female HIV-infected inmates from two prisons were included. An individually structured interview was conducted with each inmate. Serostatus of hepatitis B virus (HBV) and hepatitis C virus (HCV) were tested. CD4+ T cell count and HIV viral load were also evaluated. RESULTS: The mean age of the HIV-infected inmates was 31.7 +/- 6.4 years. All inmates were co-infected with HCV and 20% were HBV carriers. The mean CD4+ T cell count was 498 cells/microL, and the mean viral load was 20,119 copies/mL. Heroin use history averaged 6.3 +/- 5.1 years, and 84.8% of patients had a previous criminal offense prior to current conviction. Female inmates were significantly younger, had more sexual partners, had more drug-using family members or sexual partners, shared injection paraphernalia more frequently, and started using methamphetamine and heroin at younger ages (p < 0.05). Male inmates tended to be single, had less parental support, had been more frequently convicted of non drug-related crimes, started using non-illicit substances more frequently at younger ages and had sex with prostitutes more frequently (p < 0.05). CONCLUSION: The results of this study suggest that drug injection risks and sexual behavior related risks are equally important in determining the risk of HIV infection among IDUs. Gender-specific approaches to prevention which reflect differences in gender-related patterns of risk are also needed.

Psychiatric comorbidity and gender difference among treatment-seeking heroin abusers in Taiwan.

The objectives of the present study were to estimate the psychiatric comorbidity of Taiwanese heroin users seeking treatment and to identify the gender differences in psychiatric comorbidity and drug use behavior. Subjects were interviewed using a structured questionnaire on drug use behavior and the Mini International Neuropsychiatric Interview for psychiatric disorders. Of the subjects, 58.5% of the male and 62.5% of the female subjects had at least one non-substance-use axis I psychiatric disorder or antisocial personality disorder. Compared to male subjects, female subjects were younger, were less educated, had higher rates of unemployment and had earlier onset of illicit drug use. Female subjects were 11-fold more likely than male subjects to exhibit suicidal behavior. Among heroin abusers in the present study, female subjects were more widely exposed to unfavorable social factors and had substantially higher incidence of suicidal behavior than male subjects. Drug treatment centers should be aware of these gender differences and pay particular attention to comorbid depressive disorders and suicidal behavior of female heroin abusers.