Prevalence and vulnerability of homeless people to HIV infection in Sao Paulo, Brazil

OBJECTIVE: To assess the prevalence and vulnerability of homeless people to HIV infection. METHODS: Cross-sectional study conducted with a non-probabilistic sample of 1,405 homeless users of shelters in the city of Sao Paulo, southeastern Brazil, from 2006 to 2007. They were all tested for HIV and a structured questionnaire was applied. Their vulnerability to HIV was determined by the frequency of condom use: those who reported using condoms only occasionally or never were considered the most vulnerable. Multinomial and logistic regression models were used to estimate effect measures and 95% confidence intervals. RESULTS: There was a predominance of males (85.6%), with a mean age of 40.9 years, 72.0% had complete elementary schooling, and 71.5% were non-white. Of all respondents, 15.7% reported being homosexual or bisexual and 62,0% reported having casual sex. The mean number of sexual partners in the last 12 months was 5.4. More than half (55.7%) of the respondents reported lifetime drug use, while 25.7% reported frequent use. Sexually-transmitted disease was reported by 39.6% of the homeless and 38.3% reported always using condoms. The prevalence of HIV infection was 4.9% (17.4% also tested positive for syphilis) and about half of the respondents (55.4%) had access to prevention programs. Higher HIV prevalence was associated with younger age (18-29 years, OR = 4.0 [95% CI 1.54; 10.46]); past history of sexually-transmitted disease (OR = 3.3 [95% CI 1.87; 5.73]); homosexual sex (OR = 3.0 [95% CI 1.28; 6.92]); and syphilis (OR = 2.4 [95% CI 1.13; 4.93]). Increased vulnerability to HIV infection was associated with being female; young; homosexual sex; having few partners or a steady partner; drug and alcohol use; not having access to prevention programs and social support. CONCLUSIONS: The HIV epidemic has a major impact on homeless people reflecting a cycle of exclusion, social vulnerability, and limited access to prevention.

Models for capacitated lot-sizing problem with backlogging, setup carryover and crossover

Setup operations are significant in some production environments. It is mandatory that their production plans consider some features, as setup state conservation across periods through setup carryover and crossover. The modelling of setup crossover allows more flexible decisions and is essential for problems with long setup times. This paper proposes two models for the capacitated lot-sizing problem with backlogging and setup carryover and crossover. The first is in line with other models from the literature, whereas the second considers a disaggregated setup variable, which tracks the starting and completion times of the setup operation. This innovative approach permits a more compact formulation. Computational results show that the proposed models have outperformed other state-of-the-art formulation.