Multi-Phase Interleaved AC-DC Step-Down Converter with Power Factor Improvement.

This paper presents the converter design of a single-phase non-isolated step-down controlled rectifier for power factor improvement and output voltage regulation. The converter consists of a full-bridge diode rectifier and a DC-DC interleaved buck converter of two or more switching cells that has an LC filter in its input. It is proposed that the interleaved switching cells operate in discontinuous conduction mode and the current through the input LC filter be continuous, avoiding switching frequency components to be injected into the grid. The controller, which has a simple structure and a small number of sensors, allows the system to achieve a high power factor. It also regulates the output voltage to a constant reference. An experimental prototype is built and tested to validate the analysis and proposed design. The closed-loop converter is evaluated both in a steady state and in transient conditions. At steady state, the converter achieves a power factor above 0.9 with a maximum of 45.4% THD at 110.1W. The main contributions of this paper are guidelines for the design of the converter, open-loop analysis, and converter control.

Hybrid PWM Techniques for a DCM-232 Three-Phase Transformerless Inverter with Reduced Leakage Ground Current.

Pulse Width Modulation (PWM) strategies are crucial for controlling DC-AC power converters. In particular, transformerless inverters require specific PWM techniques to improve efficiency and to deal with leakage ground current issues. In this paper, three hybrid PWM methods are proposed for a DCM-232 three-phase topology. These methods are based on the concepts of carrier-based PWM and space vector modulation. Calculations of time intervals for active and null vectors are performed in a conventional way, and the resulting waveforms are compared with a carrier signal. The digital signals obtained are processed using Boolean functions, generating ten signals to control the DCM-232 three-phase inverter. The performance of the three proposed PWM methods is evaluated considering the reduction in leakage ground current and efficiency. The proposed modulation techniques have relevant performances complying with international standards, which make them suitable for transformerless three-phase photovoltaic (PV) inverter markets. To validate the proposed hybrid PWM strategies, numerical simulations and experimental tests were performed.

HIV-related stigma, isolation, discrimination, and serostatus disclosure: a global survey of 2035 HIV-infected adults.

BACKGROUND: Little is known globally about the perspectives of people living with HIV/AIDS (PLWHA) on perceived HIV-related stigma and its consequences. METHODS: Cross-sectional study (January-March 2010) of perceived HIV-related stigma among PLWHA (N = 2035) using a standardized questionnaire. FINDINGS: Thirty-seven percent of respondents reported loneliness as a result of their HIV status. Depression was reported by 27%. While 96% reported disclosing their HIV status to at least 1 person, 17% of patients who reported being in a long-term sexual relationship had not disclosed their status to their partner. Variables associated with perceived stigma were living in Asia-Pacific versus other regions (odds ratio [OR]: 2.77; 95% confidence interval [CI] 1.96-3.92); having experienced body/face changes; reported depression (OR: 1.25; 95% CI 1.11-1.38); and nondisclosure of HIV status (OR: 1.75; 95% CI 1.28-2.41). CONCLUSION: Thirty years into the HIV pandemic, perceived HIV stigma, isolation, and discrimination persist and are associated with loneliness and depression among PLWHA.

HIV treatment adherence, patient health literacy, and health care provider-patient communication: results from the 2010 AIDS Treatment for Life International Survey.

BACKGROUND: Little is known about patients' health literacy regarding antiretroviral therapy (ART) adherence and drug resistance and patient-provider communication about these topics. DESIGN AND METHODS: The AIDS Treatment for Life International Survey was a multicountry cross-sectional study (January-March 2010) including 2035 HIV-infected adults. A 40-minute interview was conducted using a standardized self-report adherence questionnaire. RESULTS: Overall, 57% of patients reported a 30-day recall of 100% adherence (Latin America: 89%; Africa: 73% vs North America: 45% and Asia Pacific: 47%; P < .01). Overall, 18% identified HIV drug resistance as a "good thing" in North America (35%) and Africa (24%). Only 71% said their health care providers had offered practical recommendations about adherence, 62% of the patients in North America and 80% in Latin America and Africa. CONCLUSIONS: Optimal ART adherence remains a challenge globally. There is a critical need to improve patient-provider communication about the importance of ART adherence and its benefits for patient's health.