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Open Access Publications from the University of California

Scholarly Works (5 results)

  • Article
Energy Use in Buildings / Enabling Technologies (2005)
    Cover page: Energy Scavenging From Vibrations
    • Thesis
    • Peer Reviewed
    UC Berkeley Electronic Theses and Dissertations (2009)

    Light emitting diodes are robust and high efficiency light sources that have the potential to replace all lighting applications in the future. Some hindrances to ubiquitous adoption of LEDs though are cost per lumen and lack of high quality materials for green emission or tunable emission. Innovations are needed to continue improving overall efficiency of light emitting diodes as well as finding suitable materials to achieve complete visible tunability. Novel light emitting diodes are made from nanoscale materials to explore potential advantages over conventional thin film approaches. These atomic-scale structures have unique electrical and optical properties that could potentially lead to increased efficiencies.

    Three platforms for improved light emitting diodes were designed, fabricated, and characterized. The first consisted of an n-type ZnO vertical nanowire array grown epitaxially from a p-type GaN thin film. The resulting device showed an increase of 13% in light output in the vertical direction as compared to a thin film LED due to waveguiding of light in the vertically oriented nanowires. The second device took advantage of the ability to synthesize InxGa1-xN materials in nanowire form with x greater than 30%, which would otherwise be unstable in thin film form due to phase segregation. Nanowire arrays were grown on top of conventional InGaN QW LEDs. Resulting light emission was a combination of transmitted QW blue electroluminescence and color converted photoluminescence from the array. Colors achieved ranged from blue, to blue-green, and red-orange. The final platform explored enhancement of electroluminescence by metal coating of nanopillar LEDs. The metal layer is proposed to confine light along the nanopillar and enhance radiative emission due to surface plasmons. Preliminary results suggest some extent of enhanced electroluminescence. However, fidelity of these results needs to be further explored due to concerns of light leakage through cracks in the metal layer.

    Nanowire based light emitting diodes were fabricated and shown to offer advantages over thin film LEDs due to waveguiding of light in the nanowire, full-spectrum tunability, and surface plasmon electroluminescent enhancement.

      Cover page: Zinc Oxide and Nitride Nanowire Based Light Emitting Diodes
      • Article
      • Peer Reviewed
      UCLA Previously Published Works (2019)
      INTRODUCTION:Despite numerous federal investments, chronic disease continues to disproportionately affect certain communities across the United States. Understanding the regional distribution (including any overlaps) of factors that extend beyond built and food environments, especially factors that may adversely affect chronic disease-related behaviors, is important. This case study of Los Angeles County's geospatial landscape sought to address these gaps in research and practice. METHODS:We examined the distributions and geographic overlaps between economic hardship, psychological distress, soda consumption, and availability of publicly funded mental health facilities in 8 Service Planning Areas in Los Angeles County. We categorized the geospatial presence of each variable as low, intermediate, or high. We imported all data, collected during 2014-2018, into ArcGIS Pro version 2.3.3 to create 5 bivariate choropleth maps. RESULTS:Levels of economic hardship were not equally distributed across communities; the county was characterized by intermediate levels of soda consumption and psychological distress. Most areas had low or intermediate availability of publicly funded mental health facilities. We also found some discordance between psychological distress and availability of publicly funded mental health facilities, and between economic hardship and availability of these facilities. CONCLUSION:The need exists to address disparities in economic hardship and to increase access to publicly funded mental health supports and providers in Los Angeles County. The information collected in this case study has policy implications for health, public health, and mental health services planning at the local level.
        Cover page: A Geospatial Analysis of Health, Mental Health, and Stressful Community Contexts in Los Angeles County
        • Article
        • Peer Reviewed
        UCLA Previously Published Works (2016)

        Objective

        This study sought to examine the impact of two Teen Courts operating in Los Angeles County, a juvenile justice system diversion program in which youth are judged by their peers and given restorative sentences to complete during a period of supervision.

        Methods

        A quasi-experimental design was used to compare youth who participated in Teen Court (n=112) to youth who participated in another diversion program administered by the Probation Department (the 654 Contract program) (n=194). Administrative data were abstracted from Probation records for all youth who participated in these programs between January 1, 2012 and June 20, 2014. Logistic and survival models were used to examine differences in recidivism - measured as whether the minor had any subsequent arrest or arrests for which the charge was filed.

        Results

        Comparison group participants had higher rates of recidivism than Teen Court participants, after controlling for age, gender, race/ethnicity, and risk level. While the magnitude of the program effects were fairly consistent across model specifications (odd ratios comparing Teen Court [referent] to school-based 654 Contract ranging from 1.95 to 3.07, hazard ratios ranging from 1.62 to 2.27), differences were not statistically significant in all scenarios.

        Conclusions

        While this study provides modest support for the positive impact of Teen Court, additional research is needed to better understand how juvenile diversion programs can improve youth outcomes.
          Cover page: The Impact of Two Los Angeles County Teen Courts on Youth Recidivism: Comparing Two Informal Probation Programs.
          • Article
          • Peer Reviewed
          UCLA Previously Published Works (2019)
          This analysis describes the socioeconomic attributes of neighborhoods adjacent to low-income neighborhoods with ≥50% of households that are Supplemental Nutrition Assistance Program Education (SNAP-Ed) eligible. It compares the pricing, availability, and quality of fresh produce between these neighborhoods in Los Angeles County. The Los Angeles County Department of Public Health utilized 2013-2014 community-level data from the Communities of Excellence in Nutrition, Physical Activity and Obesity Prevention (CX3) Project to examine the geographic patterns of fresh produce purchases and accessibility in SNAP-Ed eligible census tracts. Community indicators collected by CX3 included information on pricing, availability, and quality of fruits and vegetables from grocery stores (n = 108) in these eligible neighborhoods (n = 21). Correlation statistics were generated to explore the effects of adjacent neighborhoods' socioeconomic status on fruit and vegetable pricing, availability, and quality in the selected neighborhoods ("CX3 neighborhoods"). Poverty data were obtained from the United States Census' American Community Survey. Residents of CX3 neighborhoods that were surrounded by mixed income neighborhoods paid 43% more for fresh produce than CX3 neighborhoods surrounded by other similarly low-income neighborhoods (median produce price, $1.50 versus $1.05). Study results suggest that while quality of produce remains an issue, it is the higher pricing of fresh produce in CX3 neighborhoods - i.e., in the presence of other surrounding mixed income neighborhoods (those with relatively higher income) - that appeared to potentiate food access barriers. Future SNAP-Ed efforts should take this pricing pattern under consideration when designing, planning, and/or implementing nutrition-related programs in these neighborhoods.
            Cover page: Higher pricing of fresh produce is more likely in SNAP-Ed eligible neighborhoods when adjacent non-program eligible neighborhoods are mixed income
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