Photovoltaic cell efficiency at elevated temperatures

Thesis (S.B.)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering, 2010.Cataloged from PDF version of thesis.Includes bibliographical references (p. 23).In order to determine what type of photovoltaic solar cell could best be used in a thermoelectric photovoltaic hybrid power generator, we tested the change in efficiency due to higher temperatures of three types of solar cells: a polymer cell, an amorphous silicon cell and a CIS cell. Using an AM1.5 G solar simulator at 973 W/m2 we took the I-V curve of each of the three cells at increasing temperatures. We used the I-V curve to find the maximum power and determine the efficiency of each cell with respect to temperature. We found that the CIS cell had an efficiency of 10% and the performance decreased with respect to temperature in a non-linear manner. The efficiency at 83*C was a peak and the same efficiency as at 40"C. We found that the amorphous silicon cell tested had an efficiency of 4% at 450C that decreased with respect to temperature in a linear manner such that an 800C increase in temperature resulted in an efficiency of 3%. We further found that the polymer cell efficiency decreased from 1.1% to 1% with a 60*C increase in temperature, but that the polymer cell is destroyed at temperatures higher than 1 00*C. We determined that CIS or amorphous silicon could be suitable materials for the photovoltaic portion of the hybrid system.by Katherine Leung Ray.S.B

PARENTS’ AWARENESS AND PERSPECTIVE OF SCHOOL CHOICE SCALES: DEVELOPMENT, REVISION, AND VALIDATION USING THE RASCH MODEL

Parents want the best for their children. But for those who also believe in equal educational opportunity, they struggle with the moral dilemmas raised by school choice. To investigate where parents stand in this dilemma, this study is devoted to the creation of the Parents’ Awareness and Perspective of School Choice (PAPSC) scales, a survey instrument capturing a continuum of conversations surrounding parental school choice, from parents’ awareness of school choice policies or programs to debates surrounding parental freedom of school choice. This study also emphasized the use of well-developed, validated survey tools in educational policy and school choice research. This study documented the development process of the PAPSC survey which involved two phases. The first phase included the construction of a conceptual framework and an item matrix for inclusion of theoretical considerations relevant to the items, a pilot study which collected 119 responses from parents with K-12 children living in a small town in Kentucky, and initial Rasch analyses to examine if the scales met the formal requirements of measurements as defined in the Rasch model. The second phase involved a revision and addition of survey items to improve construct validity, a full implementation of the survey which collected 950 responses from Kentucky parents with P-12 children, a second series of Rasch analyses to establish psychometric properties and validation procedures, and subsequently, differential item functioning (DIF) analyses to measure how item endorsabilities varied with different demographic variables. Results confirmed unidimensionality for two of the original scales and one revised scale in the PAPSC survey. All scales exhibited good item and personal reliabilities, and their rating scales were performing as expected. There was one misfit item in the Parents’ Perspective of School Choice scale. The results yielded a new three-scale, 23-item Web-based instrument surveying parents’ awareness and perspectives of school choice policies and programs

Impact of Body Mass Index and Weight Change on Risk of Recurrence in Patients Treated for Endometrial Adenocarcinoma

Background: Obesity is a well-documented risk factor for EAC, but the relationship between obesity and disease recurrence is controversial. Additionally, body weight is an inherently dynamic variable and no studies have examined the relationship between interval weight change and risk of EAC recurrence. Objectives: To identify if there is a relationship between body mass index (BMI) or interval weight change and the risk of disease recurrence among women treated for EAC. Methods: We conducted a retrospective chart review of 337 women diagnosed and treated surgically for EAC at UMass Memorial Medical Center from 2010 to 2015. The effect of BMI on risk of disease recurrence was assessed by Cox proportional hazards model adjusting for age, FIGO stage, myometrial invasion, lymphovascular space involvement and status of adjuvant therapy. The effect of interval weight change on EAC recurrence was assessed using logistic regression, adjusting for BMI and recurrence free interval. Results: Among 337 women diagnosed with EAC, mean BMI at diagnosis was 35.9 pounds (SD: 8.9), mean weight at diagnosis was 201.5 pounds (SD: 52.7) and mean interval weight change was -8.1 pounds (SD: 18.8). At time of data extraction there were 19 patients (5.7%) with disease recurrence. The hazard ratio for recurrence in women with BMI \u3e50 was 11.4 [95%CI: 1.54-84.05] times that of women with BMI(p=0.02). Women who maintained or gained weight following primary surgical resection had no increased risk of recurrence compared to those who lost weight [OR: 1.02, 95%CI: 0.27-3.82] (p=0.97). Conclusion: Women with extreme obesity at diagnosis are more likely to have disease recurrence following primary surgical treatment for endometrial adenocarcinoma. However, women who lose weight following primary surgical treatment of EAC are just as likely to have disease recurrence as those who maintain or gain weight

Racial and Ethnic Disparities in Contraceptive Use in Young Women

Background: Young women have the highest rates of unintended pregnancies among reproductive­ aged women. Black and Latina women are at highest risk. Few studies have examined reasons for these differences. In this study, we examined disparities in contraceptive use and contraceptive counseling by race and ethnicity among young women. Methods: Using the 2011-2013 National Survey of Family Growth (NSFG), a cross-sectional, nationally representative database, our analysis included women aged 15-24 years who had sexual intercourse within the past year, and were not pregnant or seeking pregnancy. The primary outcomes were contraceptive use and receipt of contraceptive services within the past 12 months. Results: Young women who identify as Hispanic (H) or Non-Hispanic Black (NHB) are less likely to report current contraceptive use than their non-Hispanic White (NHW) or Non-Hispanic Other (NHO) counterparts. This finding remains statistically significant among NHB women after controlling for confounders (H: adjusted OR=0.57±0.17, 95% CI [0.32, 1.02]; NHB: adjusted OR=0.51±0.13, 95% CI [0.31-0.82;] NHO: OR=1.91±0.67, 95% CI [0.96, 3.81]). There were no differences in birth control counseling received by race/ethnicity. However, NHW and NHO were more likely to have been issued contraception within the last 12 months (H: 49.6%, NHB: 49.0%, NHW: 60.1%, NHO: 64.8; p=0.047). Conclusions/Implications: Young Black and Latina women are less likely to use contraception than other racial and ethnic groups; this difference persists among young black women after controlling for sociodemographic differences. Future studies should explore reasons for the decreased contraceptive usage rate among young black women

HPV Vaccine Reminders at the Point of Service: Efficacy and Missed Opportunities. A Claims Based Study within One Health Plan

Introduction: Our objective is to assess HPV vaccine series completion rates, whether on-screen Point of Service reminders (POS) make a difference, and missed opportunities for reminders to have an effect. Methods: Retrospective, claims-based study of females aged 9-26 receiving an initial dose of HPV vaccine during 2 periods: before (period 1) and after (period 2) implementation of a POS reminder system in 1(“Change Group”) of 2 physician groups using EHRs for both periods. Completion rates, and missed opportunities during eligible periods were calculated for those with continuous enrollment in the health plan investigated. Results: Completion rates within 1 year of the 1st dose were Period 1: 47% Change Group vs. 46% Control Group (p=0.847). Period 2: 50% Change group vs. 57% Control Group (p=0.158). No significant improvement occurred between the 2 periods in either group. Differences in 1 year completion rates by specialty of initiating provider or age group (≥18) were not significant. During period 2, among those with continuous insurance plan enrollment in the Change Group, 43 patients received 1 dose and 46 received 2 doses. Of those receiving 1 dose, 30 (70%) had a visit to the same group within an eligible time period (median # visits: 2, range 1-20); of those completing 2 doses, 4 (9%) had a visit to the same group within an eligible period (median # visits: 1, range: 1-3). Among those receiving 1 dose, 25 (58%) had a visit to the same group and same specialty as the initial dose (median # visits: 1, range 1-8); for those having received 2 doses, 3 (6%) had a subsequent visit to same group and specialty (median # visits: 1, range 1-3). Conclusion: POS reminder systems was not associated with improved completion rates. POS reminders are limited by infrequent visits among non-completers in an eligible period

Treatment of Rheumatoid Arthritis with Marine and Botanical Oils: Influence on Serum Lipids

The gap in mortality between patients with rheumatoid arthritis (RA) and the general population (1.5–3.0 fold risk) is increasing. This disparity is attributable mainly to cardiovascular disease (CVD), as the CVD risk is comparable to patients with diabetes mellitus. The purpose of this study is to determine whether borage seed oil rich in gamma-linolenic acid, fish oil rich in eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA), or the combination of both oils are useful treatments for dyslipidemia in patients with RA. We randomized patients into a double blind, 18 month trial. Mixed effects models were used to compare trends over time in serum lipids. No significant differences were observed between the three groups: All three treatment groups exhibited similar meaningful improvement in the lipid profile at 9 and 18 months. When all groups were combined, these treatments significantly reduced total and LDL-cholesterol and triglycerides, increased HDL-cholesterol, and improved the atherogenic index. All improvements observed at 9 months persisted at 18 months (P < 0.001 verses baseline). Conclusion. Marine and botanical oils may be useful treatment for rheumatoid arthritis patients who are at increased risk for cardiovascular disease compared to the general population

Treatment of Rheumatoid Arthritis with Marine and Botanical Oils: Influence on Serum Lipids (poster)

Background: Over the past 30 years substantial progress has been made in the medical and surgical management of patients with rheumatoid arthritis (RA). Despite this progress, there is an increasing gap in mortality between patients with RA (1.5-3.0 fold risk) and the general population. This disparity is mainly attributable to cardiovascular disease (CVD) as the CVD risk is comparable in RA patients as to patients with diabetes mellitus. Although the reasons for this gap are not entirely clear, the traditional risk of abnormalities in lipid profiles appears to be enhanced by a chronic increase in inflammatory cytokines, resulting in accelerated atherosclerosis. Study Objective: The object of this study was to determine the effect of marine (fish oil) and botanical oils (borage oil) on lipids (TC, HDL, LDL, TG), a risk factor for cardiovascular disease in patients with RA. The main outcome (to be presented elsewhere) was to determine whether a combination of borage seed oil rich in gammalinolenic acid (GLA) and fish oil rich in eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA) is superior to either oil alone for the treatment of RA. Population and Setting: The study was an 18 month randomized, double-masked comparison of borage seed oil, fish oil, and the combination of both oils in RA patients with active synovitis. Intervention: Patients received 3.5 gm omega-3 fatty acids daily in a 2.1gm EPA/1.4 gm DHA ratio (7 fish oil and 6 sunflower oil capsules daily); or 1.8 gm /d GLA (6 borage oil and 7 sunflower oil capsules /d); or 7 fish oil and 6 borage oil capsules daily (combination therapy). Discussion: Rheumatoid Arthritis (RA) is a chronic systemic inflammatory disease. Mediators of inflammation and prothrombotic factors contribute to endothelial dysfunction and development of cardiovascular disease in RA patients. Marine and botanical oils represent an excellent primary or secondary therapy for improvement of the cardiovascular risk management in RA. Patients taking these oils exhibit significant additional reductions in total and LDL-cholesterol, triglycerides, the TC/HDL ratio, and in the atherogenic index, and experience a significant increase in HDL-cholesterol. All of these improvements in the lipid profile were seen after 9 months of therapy, and increased after 18 months of oils administration. The overall dropout rate was 51%, and was similar across groups: 25 in the borage oil group, 28 in the fish oil group, and 22 in the combination group. Reasons for dropout were mainly gastrointestinal distress (belching, bloating, diarrhea, nausea, cramping), or an inability to swallow the large number of rather sizable capsules. This can be ameliorated by freezing the capsules and reducing their size. Among those evaluated for this study, compliance was 100%, assessed by pill counts. Learning Outcome: All treatments were safe, thus treatment of RA patients with one or a combination of these or similar oils should prove useful for reduction of cardiovascular risk in RA patients