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Open Access Publications from the University of California

Scholarly Works (6 results)

  • Thesis
  • Peer Reviewed
UC San Diego Electronic Theses and Dissertations (2018)

Atmospheric longwave irradiance (LW, with wavenumbers ranging from 0 to 2,500 cm-1) and solar shortwave irradiance (SW, wavenumbers ranging from 2,500 to 40,000 cm-1) determine the radiative balance in the atmosphere. The balance between these radiative flux contributions is also essential in the design and operation of cooling systems, including evaporative cooling towers, passive dry fans, and optically selective materials, among many other natural and engineered surfaces exposed to solar and atmospheric radiation. Large scale solar farms interact with the local atmosphere through greenhouse gases emission offset and by replacing surface albedo with materials that respond to radiation very differently than soil or vegetation. Solar photovoltaic (PV) farms are highly absorbing (lower albedo) while concentrated solar power (CSP) farms are highly reflective (higher albedo) when compared to the ground where they are usually deployed. This work employs detailed and comprehensive spectral radiative models to calculate LW and SW through the atmosphere for different ground surfaces in order to quantify local interactions caused by the different boundary conditions for a model of the atmosphere.

First, existing data-driven empirical models for determination of the surface downwelling longwave irradiance (DLW) are reviewed and recalibrated, and a more accurate comprehensive empirical model is proposed.

The broadband empirical model then serves as a benchmark to validate a Line-by-Line (LBL) spectral radiative model that is able to capture details of the highly wavenumber-dependent nature of the irradiance fluxes. For the atmospheric longwave spectrum that is emitted and absorbed by gases, aerosols, clouds and the ground, a high-resolution two-flux model with a recursive scattering method is developed. For the shortwave (solar) part of the spectrum, which includes scattering from atmospheric constituents and the ground, comprehensive Monte-Carlo LBL simulations are used.

The LW spectral model is then used to quantify the contribution of each atmospheric constituent to DLW as well as the spectral and vertical distribution of LW irradiance. The SW spectral model is used to quantify the albedo replacement effects of PV and CSP farms on local SW irradiance field. A thermal balance accounting for both longwave and shortwave irradiance is then performed for both PV and CSP surfaces. In general, CSP farms reduce while PV farms increase ground temperatures with respective changes in relative humidity. The change in temperature is a function of solar zenith angle, column water vapor content, aerosol optical depth, cloud optical depth and cloud fraction. This work then quantifies the temperature anomaly due to albedo replacement as function of these parameters. A hybrid solar farm design to minimize both local thermal effects and operational variability is proposed.

    Cover page: Spectral Modeling of Solar and Atmospheric Radiation for Solar Power Integration
    • Article
    • Peer Reviewed
    UC San Diego Previously Published Works (2021)
    The ever-growing installation of solar power systems imposes severe challenges on the operations of local and regional power grids due to the inherent intermittency and variability of ground-level solar irradiance. In recent decades, solar forecasting methodologies for intra-hour, intra-day and day-ahead energy markets have been extensively explored as cost-effective technologies to mitigate the negative effects on the power grids caused by solar power instability. In this work, the progress in intra-hour solar forecasting methodologies are comprehensively reviewed and concisely summarized. The theories behind the forecasting methodologies and how these theories are applied in various forecasting models are presented. The reviewed mathematical tools include regressive methods, stochastic learning methods, deep learning methods, and genetic algorithm. The reviewed forecasting methodologies include data-driven methods, local-sensing methods, hybrid forecasting methods, and application orientated methods that generate probabilistic forecasts and spatial forecasts. Furthermore, suggestions to accelerate the development of future intra-hour forecasting methods are provided.
      Cover page: Intra-hour irradiance forecasting techniques for solar power integration: a review.
      • Article
      • Peer Reviewed
      UC Irvine Previously Published Works (2017)

      Objective

      Self-regulation (SR) is a core aspect of child development with enduring effects on health and wellbeing across the lifespan. Early childhood poverty may shape SR development. This study examined the cross-sectional relationship among family income, family context, and SR in 5-year-old children.

      Methods

      A total of 140 five-year-old children and their mothers participated in the study. Children completed a battery of SR tasks; mothers completed questionnaires. Cognitive and emotional SR composite scores were generated based on a principal component analysis of the SR tasks. The SR scores were first regressed on family income (in 10 levels ranging from <5000 to 150,000+) adjusting for age, sex, and race of the child; family context variables were subsequently added to the models.

      Results

      Controlling for age, sex, and race, each level increase in family income was associated with 0.04 SD increase in emotional SR (p = .32) and 0.08 SD increase in cognitive SR (p = .01). In fully adjusted models, exposure to household instability and experiencing 10 or more negative life events was associated with worse emotional SR; exposure to mother's depressive symptoms was associated with worse cognitive SR. Higher income buffered children's SR from some contextual risk factors. Family contextual variables explained 62% of the correlation between higher income and better cognitive SR scores.

      Conclusion

      Income-based cognitive SR disparities were associated with family contextual factors. Screening for family adversity in pediatric care and linking families to needed resources may protect children's developing SR capacities, with benefits to health and well-being.
        Cover page: Income, Family Context, and Self-Regulation in 5-Year-Old Children
        • Article
        • Peer Reviewed
        UC Riverside Previously Published Works (2020)
        Maternal plasma phospholipid polyunsaturated fatty acids (PUFAs) play critical roles in maternal health and fetal development. Beyond dietary factors, maternal moderate-to-vigorous physical activity (MVPA) has been linked to multiple health benefits for both the mother and offspring, but studies investigating the influence of maternal MVPA on maternal PUFA profile are scarce. The objective of present study was to examine the time-specific and prospective associations of MVPA with plasma PUFA profile among pregnant women. This study included 321 participants from the National Institute of Child Health and Human Development (NICHD) Fetal Growth Studies-Singletons cohort. Maternal plasma phospholipid PUFAs and MPVA were measured at four visits during pregnancy (10-14, 15-26, 23-31, and 33-39 gestational weeks (GW)). Associations of maternal MVPA with individual plasma PUFAs and desaturase activity were examined using generalized linear models. Maternal MVPA was associated inversely with plasma phospholipid linoleic acid, gamma-linolenic acid, and Δ6-desaturase in late pregnancy (23-31 or 33-39 GW), independent of maternal age, race, education, parity, pre-pregnancy body mass index, and dietary factors. Findings from this longitudinal study indicate that maternal habitual MVPA may play a role on PUFAs metabolism, particular by alerting plasma n-6 subclass and desaturase activity in late pregnancy. These associations are novel and merit confirmation in future studies.
          Cover page: Plasma Phospholipid n-3/n-6 Polyunsaturated Fatty Acids and Desaturase Activities in Relation to Moderate-to-Vigorous Physical Activity through Pregnancy: A Longitudinal Study within the NICHD Fetal Growth Studies.
          • Article
          • Peer Reviewed
          UCLA Previously Published Works (2020)

          Objective

          Nut intake has been associated with reduced cardiometabolic risk, but few studies have examined its association with renal function. We examined associations between nut intake and renal function among women with previous gestational diabetes mellitus (GDM), a population with an increased risk for renal dysfunction.

          Design and methods

          This study included 607 women with a history of GDM who participated in the Diabetes & Women's Health Study (2012-2014) follow-up clinical examination in Denmark. At the clinic, biospecimens were collected, and habitual intake of nuts (9 types) in the past year was assessed using a food frequency questionnaire. A total of 330 women free of major chronic diseases were included in the analysis. Total nut intake was classified as none (≤1 serving/month), monthly (2-3 servings/month), weekly (1-6 servings/week), and daily (≥1 serving/day). One serving was defined as 28 g. Renal function markers included estimated glomerular rate (eGFR) and urinary albumin-to-creatinine ratio (UACR), calculated based on plasma creatinine (mg/dL), and urinary albumin (mg/L), and creatinine (mg/dL) measurements, respectively. We estimated percent differences with 95% confidence intervals for each outcome by nut intake, adjusted for current body mass index, age, physical activity, energy intake, alcohol consumption, and vegetables intake.

          Results

          We observed a nonlinear association between total nut intake and UACR with lowest UACR values among women with weekly intake. Compared to women with weekly intake (n = 222), the adjusted UACR values were higher by 86% [95% confidence interval: 15%, 202%], 24% [-1%, 54%], and 117% [22%, 288%] among women with no (n = 13), monthly (n = 86), and daily (n = 9) intake, respectively. Compared to weekly consumers, daily nut consumers also had 9% [0%, 19%] significantly higher eGFR values, but eGFR values were similar among women with no and monthly intake.

          Conclusion

          Moderate nut consumption may be beneficial to kidney health among women with prior GDM.
            Cover page: Nut Consumption and Renal Function Among Women With a History of Gestational Diabetes
            • Article
            • Peer Reviewed
            UCLA Previously Published Works (2019)

            Background

            Artificially sweetened beverages (ASBs) are commonly consumed and recommended for individuals at high risk for cardiometabolic diseases; however, the health effects of ASBs remain contradictory. Given that cross-sectional analyses are subject to reverse causation, prospective studies with long-term follow-up are needed to evaluate associations between ASBs and cardiometabolic health, especially among high-risk individuals.

            Objective

            The aim of this study was to examine associations of ASB intake and cardiometabolic health among high-risk women with prior gestational diabetes mellitus (GDM).

            Methods

            We included 607 women with GDM from the Danish National Birth Cohort (DNBC; 1996-2002) who completed a clinical exam 9-16 y after the DNBC pregnancy for the Diabetes & Women's Health (DWH) Study (2012-2014). We assessed ASB intake using FFQs completed during the DNBC pregnancy and at the DWH Study clinical exam. We examined cardiometabolic outcomes at the DWH clinical exam. We estimated percentage differences in continuous cardiometabolic markers and RRs for clinical endpoints in association with ASB intake both during pregnancy and at follow-up adjusted for prepregnancy BMI, diet, and lifestyle factors. Sensitivity analyses to account for reverse causation were performed.

            Results

            In pregnancy and at follow-up, 30.4% and 36.4% of women regularly (≥2 servings/wk) consumed ASB, respectively. Consumption of ASBs, both during pregnancy and at follow-up, was associated with higher glycated hemoglobin (HbA1c), insulin, HOMA-IR, triglycerides, liver fat, and adiposity and with lower HDL at follow-up. After adjustment for covariates, particularly prepregnancy BMI, the majority of associations between ASB intake in pregnancy and outcomes at follow-up became null with the exception of HbA1c. ASB intake at follow-up (≥1 serving/d compared with <1 serving/mo) was associated with higher HbA1c (6.5%; 95% CI: 1.9, 11.3; P-trend = 0.007); however, associations were not upheld in sensitivity analyses for reverse causation.

            Conclusions

            Among Danish women with a history of GDM, ASB intake was not significantly associated with cardiometabolic profiles.
              Cover page: A prospective study of artificially sweetened beverage intake and cardiometabolic health among women at high risk
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