Self-assembled three dimensional network designs for soft electronics.

Low modulus, compliant systems of sensors, circuits and radios designed to intimately interface with the soft tissues of the human body are of growing interest, due to their emerging applications in continuous, clinical-quality health monitors and advanced, bioelectronic therapeutics. Although recent research establishes various materials and mechanics concepts for such technologies, all existing approaches involve simple, two-dimensional (2D) layouts in the constituent micro-components and interconnects. Here we introduce concepts in three-dimensional (3D) architectures that bypass important engineering constraints and performance limitations set by traditional, 2D designs. Specifically, open-mesh, 3D interconnect networks of helical microcoils formed by deterministic compressive buckling establish the basis for systems that can offer exceptional low modulus, elastic mechanics, in compact geometries, with active components and sophisticated levels of functionality. Coupled mechanical and electrical design approaches enable layout optimization, assembly processes and encapsulation schemes to yield 3D configurations that satisfy requirements in demanding, complex systems, such as wireless, skin-compatible electronic sensors.

Intergenerational benefits of family-based HIV interventions.

The longitudinal impact of a family-based intervention on grandchildren of parents with HIV (PWH) is evaluated. Because PWH and their daughters demonstrated gains over 6 years when randomized to a coping skills intervention compared with a control condition, the adjustment of the PWH's grandchildren was also compared across conditions. Grandchildren in the intervention condition reported significantly fewer internalizing and externalizing behavioral symptoms compared with grandchildren in the control condition. There is weak evidence that grandchildren in the intervention condition had higher scores on measures of cognitive development and more positive home environments. These results suggest that there are possibly long-term, intergenerational benefits of an intervention for families coping with HIV.

Predictors of intervention adherence among young people living with HIV.

OBJECTIVE: To examine adherence to a 23-session intervention for young people living with HIV. METHODS: Two hundred eight HIV-positive youth were assigned by small cohort to a behavioral intervention. RESULTS: Youth with more personal strengths were more likely to attend the intervention; those with more competing environmental demands (eg, employment, school) were less likely to attend the intervention. Using a social support, spiritual hope, or self-destructive and escape coping style was associated with attendance. Youth who reported many sexual partners attended fewer sessions. Adherence varied by cohort assignment. CONCLUSION: When designing future interventions, high attendance should be considered as a goal.

A comparison of imputation methods in a longitudinal randomized clinical trial.

It is common for longitudinal clinical trials to face problems of item non-response, unit non-response, and drop-out. In this paper, we compare two alternative methods of handling multivariate incomplete data across a baseline assessment and three follow-up time points in a multi-centre randomized controlled trial of a disease management programme for late-life depression. One approach combines hot-deck (HD) multiple imputation using a predictive mean matching method for item non-response and the approximate Bayesian bootstrap for unit non-response. A second method is based on a multivariate normal (MVN) model using PROC MI in SAS software V8.2. These two methods are contrasted with a last observation carried forward (LOCF) technique and available-case (AC) analysis in a simulation study where replicate analyses are performed on subsets of the originally complete cases. Missing-data patterns were simulated to be consistent with missing-data patterns found in the originally incomplete cases, and observed complete data means were taken to be the targets of estimation. Not surprisingly, the LOCF and AC methods had poor coverage properties for many of the variables evaluated. Multiple imputation under the MVN model performed well for most variables but produced less than nominal coverage for variables with highly skewed distributions. The HD method consistently produced close to nominal coverage, with interval widths that were roughly 7 per cent larger on average than those produced from the MVN model.

The influence of partner type and risk status on the sexual behavior of young men who have sex with men living with HIV/AIDS.

OBJECTIVES: The influence of partner type and risk status on the unprotected sexual behavior of young men living with HIV (YMLH) who have sex with men is examined. METHODS: Sexual behavior and sexual partner characteristics of 217 YMLH recruited from adolescent care clinics in 4 AIDS epicenters (Los Angeles, San Francisco, New York, and Miami) were assessed. YMLH were categorized by sexual behavior pattern, and sexual partners were classified by type and risk status. Generalized linear modeling employing overdispersed Poisson distribution was used to analyze the effect of partner type and partner risk status on unprotected sex acts. RESULTS: Most YMLH (62%) reported multiple partners, 26% reported 1 sexual partner, and 12% reported abstinence in the past 3 months. Approximately 34% of polygamous and 28% of monogamous youth engaged in unprotected sex. Monogamous youth were most likely to have unprotected sex with HIV-positive partners. Polygamous youth were most likely to have unprotected sex with HIV-positive partners, irrespective of whether the partner was regular or casual. For polygamous YMLH, unprotected sex did not differ among single-time/new partners with different risk levels. CONCLUSIONS: Partner characteristics influence the condom use behavior of YMLH. YMLH make decisions regarding condom use based on perception of their partner's risk. Preventive interventions must include skills for acquiring accurate information about partner risk status and education regarding the health risks of unprotected sex with HIV seroconcordant partners.

Imputation for incomplete high-dimensional multivariate normal data using a common factor model.

It is common in applied research to have large numbers of variables measured on a modest number of cases. Even with low rates of missingness on individual variables, such data sets can have a large number of incomplete cases. Here we present a new method for handling missing continuously scaled items in multivariate data, based on extracting common factors to reduce the number of covariance parameters to be estimated in a multivariate normal model. The technique is compared in several simulation settings to available-case analysis and to a multivariate normal model with a ridge prior. The method is also illustrated on a study with over 100 variables evaluating an emergency room intervention for adolescents who attempted suicide.

Reductions in HIV risk among runaway youth.

Runaway youth are 6-12 times more likely to become infected with HIV than other youth. Using a quasi-experimental design, the efficacy of an HIV prevention program was evaluated over 2 years among 2 groups of runaways: (1) those at 2 shelters who received Street Smart, an intensive HIV intervention program, and (2) youth at 2 control shelters. Street Smart provided youth with access to health care and condoms and delivered a 10-session skill-focused prevention program based on social learning theory to youth. Prior to analysis of the intervention's outcomes, propensity scores were used to identify comparable subgroups of youth in the intervention (n = 101) and control conditions (n = 86). Compared to females in the control condition, females in the intervention condition significantly reduced their unprotected sexual acts at 2 years and alcohol use, marijuana use, and the number of drugs used over 12 months. Male adolescents in the intervention condition showed significant reductions in marijuana use over 6 months compared to control youth. Adolescent HIV prevention programs must proactively identify mechanisms for maintaining behavior change over the long-term, and innovative research designs are needed to allow examination of agency-level interventions.