College of Agriculture & Natural Resources
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The collections in this community comprise faculty research works, as well as graduate theses and dissertations.
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Item Determinants of Food Insecurity in the League of Arab States(2022) Sheikomar, Olfat Bakur; Sahyoun, Nadine R; Nutrition; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)Background Food insecurity (FI) is widespread in the League of Arab States (LAS) due to factors including gender inequality, conflict, and political turmoil. However, limited data are available on its prevalence and determinants in that region. This dissertation aims to 1) validate the Food Insecurity Experience Scale (FIES), developed by the UN Food and Agriculture Organization, and assess the prevalence of FI in that region; 2) examine the association between FI, physical health, and mental well-being by sex and whether social support modifies this association in women; 3) examine the relationship between Palestinian live-in grandparents (GP) and the health and well-being of their grandchildren.Methods Rasch modeling was applied to the Gallup World Poll data to validate FIES in 19 countries of the region. Descriptive and logistic regression analyses were applied to data from 62,261 respondents aged 19 and over to examine determinants of FI. Logistic regression was also used to analyze the data of 2707 households and 8,034 children ages 0-17 from two surveys of Palestinian refugees. Results FIES met the Rasch assumptions indicating good internal validity. The prevalence of severe FI was 15.7% and women were at highest risk compared to men (17.6% vs. 14.1%, respectively, p<0.0001). Older age, living in rural areas, and high dependency ratio were associated with severe FI in women. High negative experience and low income were associated with severe FI, but good physical health and high positive experience with lower prevalence of severe FI. Having a live-in GP in the household was associated with grandchildren’s lower odds of experiencing an acute disease and higher odds of attending school. Conclusion FIES is a valid tool; however, cognitive testing of some items and omission of correlated ones may improve the scale. FI is highly prevalent and should be monitored to develop multi-sectoral intervention strategies. Mixed method studies are needed to better understand the relationship between grandparents and their grandchildren.Item Development of machine learning and advanced data analytical techniques to incorporate genomic data in predictive modeling for Salmonella enterica(2021) Karanth, Shraddha; Pradhan, Abani K; Food Science; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)The past few decades have seen a renaissance in the field of food safety, with the increasing usage of genomic data (e.g., whole genome sequencing (WGS)) in determining the cause of microbial foodborne illness, particularly for multi-serovar agents such as Salmonella enterica. However, utilizing such data in a preventative framework, specifically in the field of quantitative microbial risk assessment (QMRA) remains in its infancy, because incorporating such large-scale datasets in statistical models is hindered by the sheer number of variables/features introduced. Thus, the goal of this research is to introduce machine learning (ML)-based approaches to potentially incorporate WGS data in various stages of a risk assessment for Salmonella enterica. Specifically, we developed a machine learning-based workflow to obtain an association between gene presence/absence data from microbial whole genome sequences and severity of Salmonella-related health outcomes in host systems. A key contribution of this dissertation is assessing the applicability of Elastic Net model, a recursive feature selection technique, which resolves a well-known issue concerning WGS-based data analysis: variables/features outnumber the count of observations. Building on this finding, we developed a gene weighted Poisson regression method to incorporate genes into a dose-response framework for Salmonella enterica, thereby incorporating genetic variability directly into a risk assessment framework. Finally, we combined machine learning with count-based models to determine how significant genes interact with meteorological factors in impacting the severity of salmonellosis outbreaks. This dissertation uncovers some interesting findings. First, although commonly used classifiers (such as random forest) performed well in predicting disease severity, logistic regression, in conjunction with Elastic Net, performed significantly better. This finding is important, as the result of a logistic regression is generally more interpretable than that of other classifiers, easing its incorporation into predictive microbial modeling. Next, machine learning-supported count-based models, such as Poisson regression also proved to be a good fit for gene-informed dose-response modeling and determination of outbreak severity when combined with extrinsic factors such as atmospheric temperature and precipitation. Overall, this dissertation identified areas within a QMRA framework that could benefit from incorporating genetic information, and introduced ML models to incorporate such information.Item Food Insecurity, Service Awareness, Social Factors, and Quality of Life in Community-Dwelling Older Adults(2021) Vaudin, Anna Margaret; Sahyoun, Nadine R; Nutrition; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)Older adults are at risk for food insecurity due to financial constraints, physical difficulties, social isolation, and the resulting limitations on food access. Social isolation has two components – objective, such as social contacts, and subjective, such as loneliness – and each may have a unique relationship with food insecurity. Unmet needs exist for services that aim to improve food access in older adults, and research is limited on how those who do use the services find out about them. Additionally, these services aim to improve quality of life (QOL), and yet this impact cannot be quantified because current tools do not capture the ways food affect QOL beyond nutritional status. This dissertation uses qualitative methods to understand (1) how food and eating impact QOL in community-dwelling older adults, (2) how individuals become aware of the services they use to address barriers to food and eating, and (3) the interaction between food security, loneliness, and QOL. In-depth interviews were conducted with 25 urban- and suburban-dwelling older adults. Interview scripts were transcribed and themes identified in the data using grounded theory methods. The first study showed that health and vitality, independence, mental and emotional well-being, socialization and support, and activities, both inside and outside the home, affected participants’ QOL. Food and eating affected QOL through access and choice, health and vitality, enjoyment of food, and food preparation. The second study showed that participants primarily found out about the resources they use through encounters in their daily lives, rather than service outreach. The final study showed that, compared with those who were food secure, those who were food insecure were more likely to report a negative effect of loneliness on their QOL, primarily experienced as depressive symptoms. This dissertation shows that food and eating affect older adults through not only the physiological effects of good nutrition, but also through social, psychological, and sensory effects on QOL. Additionally, the results point to the importance of social factors for both service awareness and mental health in those who face barriers to food and eating. Future studies and new tools are needed to quantify these impacts.Item DIET, FOOD SECURITY, SOCIAL RELATIONSHIPS AND DEPRESSIVE SYMPTOMS IN HOMEBOUND OLDER ADULTS IN THE UNITED STATES AND THEIR IMPACT ON HEALTHCARE UTILIZATION(2020) Ashour, Fayrouz A.; Sahyoun, Nadine R; Nutrition; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)Homebound older adults may be at increased risk for malnutrition and social isolation, posing a potential threat to them aging in their communities and increasing healthcare cost. The Nutrition Service Program under Older Americans Act (OAANSP) was established to support older adults aging in place by delivering meals and providing nutrition-related services. Aims: 1) Examine diet quality of home-delivered meal (HDM) recipients; 2) examine direct and indirect associations between social relationships, depressive symptoms, food insecurity (FI) and diet quality; and 3) examine direct and indirect associations between social relationships, FI, diet quality and hospitalization. Methods: Data obtained from OAANSP Outcomes Evaluation study included: 1) client outcomes survey, 2) two 24-hour dietary recalls, and 3) Medicare healthcare utilization data. Dietary recalls examined diet quality by calculating 1) population-level mean HEI scores; and 2) usual vegetable and protein intakes. Diet quantity was compared to Dietary Guidelines for Americans 2010 (DGA), and structural equation modeling was used to examine direct and indirect relationships. Results: HDM recipients and controls have high prevalence of FI, 22.4% and 16.5%, respectively. HDM recipients who did not receive a meal on day of dietary recall (no-meal recipients) had significantly poorer diet quality than HDM recipients who received a meal (meal recipients) that day and control group. Quality of overall diet for meal recipients, no-meal recipients and controls did not meet recommendations for several food groups/nutrients. Compared to DGA, HDM and complementary foods were low in whole grains, dairy, fiber, and surpassed upper limit of consumption for saturated fats, refined grains, sodium and added sugar. High FI was associated with greater depressive symptoms and lower usual vegetable intake in control group. High FI was associated with lower usual protein intake in HDM recipients and controls. Both groups were at high risk for protein insufficiency, which was associated with greater hospitalization in the control group. Conclusions: HDM recipients and controls have high prevalence of FI, poor diet quality, and insufficient protein intake. Increasing funding for OAANSP can allow program expansion and improvement of HDM. Validated tools to examine social relationships and additional contributors to FI are neededItem USE OF RISK ASSESSMENT MODELING TECHNIQUES TO DEVELOP QUANTITATIVE RISK-BASED HAZARD ANALYSIS AND CRITICAL CONTROL POINT (RB-HACCP) PLANS(2017) Williams, Elizabeth Noelia; Buchanan, Robert L; Food Science; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)Hazard Analysis and Critical Control Point (HACCP) is the internationally recognized system to assure the safety of food products and the foundation of food safety programs worldwide. However, its success is limited by its inability to relate stringency to measurable public health impacts and its inherent qualitative nature. The aim of this research was to incorporate quantitative microbiological risk assessment (QMRA) techniques into HACCP to develop risk-based HACCP (RB-HACCP) plans. The research hypothesized that the Critical Control Points (CCPs) are steps in the process that significantly reduce the mean and/or variance of a hazard and that these can be identified and quantified using risk assessment modeling techniques such as sensitivity analysis (SA) and what-if scenario analysis, as well as providing a more objective means in considering Critical Limits (CLs). QMRA models were developed for two distinctly different commercial food products, frankfurters and cold-smoked salmon (CSS). The former has a definitive inactivation step while the latter achieves control through a series of partial control steps. Modular Product Pathogen Pathway risk assessment models were developed to identify potential risk-based CCPs (RB-CCPs) for the control of Listeria monocytogenes. Steps of the processes within modules were evaluated and prioritized using SA to determine the relative contribution of the process steps to control L. monocytogenes. What-if scenario analyses were subsequently used to quantitatively determine the consequences of system deviations, thereby allowing risk-based CLs (RB-CLs) to be set and the most-effective risk mitigation strategies to be identified. This conceptual framework, combined with relevant plant-specific data, was used to identify RB-CCPs and RB-CLs, thereby producing RB-HACCP plans that are linked with public health goals to lower the risk of listeriosis. This allowed a direct comparison between current industry HACCP plans for frankfurters and CSS with RB-HACCP plans derived from the risk assessments. The comparison suggests that the use of RB-HACCP plans may offer advantages in developing the “preventive controls” risk management food safety plans required under the FDA Food Safety Modernization Act of 2011.Item The Marcellus Shale in Maryland and Twitter: A Mixed Methods Analysis of Tweets from November 2016(2017) Breitenother, Allison Gost; Puett, Robin; Environmental Science and Technology; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)Recent research shows about 75% of US adults are on social networking sites. Social media platforms like Twitter, provide potential new modes of networked public participation around contested technologies while affording communities a space for identity development and expression. During 2016, Maryland saw increasing interest in and debate around opening the State to hydraulic fracturing. To understand public perception of hydraulic fracturing, researchers collected tweets associated with relevant hashtags. Data collection occurred during the month of November 2016 which included the 2016 General Election and the release of proposed regulations in Maryland. The final sample of tweets for this period was n=638 stratified across thirteen hashtags. The timing, actors involved and central themes of the discussion around hydraulic fracturing in Maryland were analyzed using qualitative methods. The frequency of tweets by date showed three peaks – November 14, November 18 and November 22. November 14, 2016 was when the Maryland Department of the Environment released the proposed regulations, November 18 was a day of action referred to as #frackfreefriday and the content of tweets from November 22 focused on the regulations. Additional analysis showed individual actors and the hashtag #dontfrackmd contributed the most to the final. Additional stratification by hashtag, content and stance towards fracking further described the Twitter discourse around hydraulic fracturing in Maryland during the study period. Additional analysis is recommended to understand the public perception expressed on Twitter for the entire Marcellus Shale region as it pertains to hydraulic fracturing.Item Formative research regarding social support programs and young adults living with type one diabetes(2015) Brady, Patrick James; Song, Hee-Jung; Nutrition; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)Little research has been conducted regarding social support programs (SSPs) for young adults with Type 1 Diabetes Mellitus (T1DM). Formative research was conducted including: in-depth interviews with individuals who have organized or lead SSPs, a survey of young adults with T1DM, and forming a community advisory board to develop themes and discussion points for a SSP. Eight interviews were conducted. The perceived benefits of and barriers to attending a SSP, the perceived barriers to managing a SSP, and topics important for young adults were described. 38 individuals completed the survey and were included in the analysis. The survey identified ever attended a SSP as significant in the perception of tangible and affectionate support. Two CAB meetings resulted in six themes and discussion points to be used as a framework for a proposed SSP. This study suggests the benefit of SSPs for young adults and provides insight into the role of SSPs in managing T1DM.Item Electronic Interventions to Improve Health Behaviors in College Students(2014) Schweitzer, Amy; Lei, David K.Y.; Nutrition; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)Introduction: In transitioning from adolescence to adulthood, college students are faced with significant challenges to their health habits. Time, independence and stress have been known to result in poor eating and exercise habits which can lead to increased disease risk. Objective: To assess whether an electronic health intervention can improve health habits in college students. Methods: A 24-week diet and physical activity program was delivered by e-mail to 148 college students. The intervention involved weekly tailored, interactive diet and physical activity goals. The control group received non-diet-non-exercise-related health fact sheets. Baseline, 12-week, and 24-week diet and physical activity surveys were completed online. BMI, neck circumference, waist circumference, and percent fat mass (FM%) by bioelectrical impedance analysis were measured at baseline, week 12 and week 24. Results: Students were 18-20 years old 70% female from a diverse college campus (46% Caucasian, 23% Asian, 20% African American, 5% Hispanic, and 6% other). At baseline, 23% were overweight/obese by BMI, 88% reported consuming <5 fruits and vegetables daily, 59% consumed >10% of kcalories from saturated fat, although 91% met or exceeded 150 minutes/week of moderate-vigorous exercise. Seventy-one percent of students completed all study visits. Repeated measures ANOVA showed a significant treatment by linear time interaction for saturated fat. A significant change from baseline saturated fat intake was detected between the treatment groups at week 24 (mean change ± standard error 0.7±0.42% of kcal for control and -0.3±0.30% of kcal for intervention). Differences in saturated fat intake between the two treatment groups were more evident in those whose intake exceeded recommendations. BMI, neck circumference, waist circumference, FM%, weekly minutes of moderate and vigorous physical activity as well as intake of fruit, vegetables, and added sugar were not significantly different between treatment groups. Conclusion: College students enrolled in an interactive electronic health intervention decreased saturated fat intake compared to control. Furthermore, the decrease observed in the intervention group was mainly due to those whose intake of saturated fat intake was above the recommended 10% of total kcalories. Further development of the electronic intervention program is needed to maximize health benefits in college students.Item ASSESSMENT OF PREHARVEST MICROBIAL QUALITY OF CANTALOUPES AND PUBLIC HEALTH RISKS ASSOCIATED WITH CANTALOUPES CONTAMINATED WITH LISTERIA MONOCYTOGENES(2014) Wang, Miao; Pradhan, Abani K; Food Science; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)Cantaloupe has been recognized as a common vehicle for foodborne infections among fresh produce commodities. A severe multistate outbreak of Listeria monocytogenes associated with the consumption of whole cantaloupe resulted in 33 deaths in 2011. Quantitative microbial risk assessment (QMRA) modeling in food safety risk analysis has been acknowledged as an efficient tool to estimate and provide knowledge needed to manage potential public health risks associated with foodborne pathogens. The objectives of this study were to (i) conduct a microbiological survey of pre-harvest cantaloupes from farms in mid-Atlantic region, and (ii) develop a "farm to table" QMRA model for L. monocytogenes in cantaloupe. The results of the regional microbiological survey indicated a 5.3% (2/38) prevalence of generic Escherichia coli and negative for L. monocytogenes and Salmonella on cantaloupe during harvest season. A QMRA model was developed based on a thorough review of data from scientific publications and communications with fresh-cut processing industry. The model was simulated with Monte Carlo technique for 100,000 iterations in @Risk. The model estimated the public health risks associated with the consumption of both fresh-cut and whole cantaloupes in the U.S. The model demonstrated the risk associated with the consumption of a serving of fresh-cut cantaloupe is around 10 times higher than that for whole cantaloupe. Using the baseline model, the estimated median number of listeriosis cases per year associated with the consumption of fresh-cut cantaloupe among susceptible subpopulation and general healthy population are 0.0368 and 0.00134, respectively. Sensitivity analysis suggested temperature control during retail (correlation coefficient: 0.69) and home storage (correlation coefficient: 0.48) are two critical factors in mitigating the risk for fresh-cut cantaloupe consumption while home storage temperature (correlation coefficient: 0.79) after cutting is the most important factor for whole cantaloupe consumption. The QMRA model provided critical information for risk management and identified the critical data gaps including initial contamination and prevalence for future risk assessments of melon.Item Managerial Incentives in Public Service Delivery: Evidence from School-based Nutrition Programs in Rural China(2014) Sylvia, Sean Yuji; Hoffmann, Vivian; Agricultural and Resource Economics; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)Growing evidence indicates that weak or misaligned incentives facing providers pose a significant barrier to service delivery in many developing countries. To address weak supply-side incentives, performance pay and related approaches explicitly linking provider pay and performance have become increasingly common in public service delivery. Despite the growing prominence of these approaches, however, many conceptual issues surrounding the use of performance pay in this context remain unexplored. A fundamental one is the role of performance pay for managers in the organizations commonly tasked with delivering public services. Although a large literature examines performance pay for managers in private firms, much less is known about the use of performance pay for their counterparts in public service organizations. Improving public service delivery may nonetheless depend heavily on aligning the incentives of managers with social objectives. Drawing on a large-scale field experiment involving 300 primary schools in rural China, this dissertation explores how performance incentives for school administrators affect their implementation of new, school-based nutrition programs targeting anemia. School-based nutrition programs are an important function of schools, particularly in settings with less developed public health infrastructures. Weak incentives for schools to effectively implement these programs are compounded as these programs compete with more traditional functions for finite school resources. I report the results of this field experiment which was designed to test three main issues concerning the use of performance incentives for school administrators in this context. First, I study the effect of offering administrators performance pay contracts tied to reductions in school-level anemia prevalence. As part of the experiment, a subset of schools were randomly allocated to receive one of two levels of performance incentives for reductions in student anemia or to a no-incentive comparison group. I find that large incentives led to meaningful reductions while smaller incentives (10% of the size) were ineffective in reducing anemia. Further, I find that an important channel through which large incentives impacted student nutrition was by motivating administrators to engage households and influence feeding at home. I discuss the implications of this finding for the design of performance incentives tied to jointly produced outcomes. Second, I study the impact of providing administrators with more resources to implement a nutrition program and how this interacts with performance incentives. To test this, schools were orthogonally assigned to two levels of block grants within each level of performance incentives. I find that, absent explicit anemia-based incentives, increasing the size of block grants under the control of administrators led to sizable reductions in anemia prevalence but were nearly twice as costly as performance incentives. This impact was not purely the result of additional inputs; larger block grants also caused a more efficient use of inputs and an increase in effort devoted to reducing anemia. I also find that additional resources and incentives are substitutes in this context. I provide evidence that this substitution is due, at least in part, to incentives re-framing the task of implementing the nutrition programs from one that was part of the professional role of administrators to one that was not. Finally, I approach the health promotion and education roles of schools as a multi-tasking problem and use remaining experimental groups to examine how performance incentives for school administrators to reduce anemia and improve test scores each affect anemia prevalence and academic performance. Although the theory of multitasking is well-developed, there are few empirical studies testing this theory directly. I emphasize three main findings. First, incentives in the two dimensions (given in the context of an anemia reduction program) both led to significant reductions in anemia prevalence. Second, anemia-based and test-based incentives serve as substitutes in the direction of anemia reduction: providing administrators with both types of incentives did not lead to significantly larger reductions in anemia. Third, I find that anemia incentives caused an allocation of resources away from education 'inputs' but this did not lead to significantly lower student performance on standardized exams after one year. These results reflect that test-based incentives are well-aligned with improving nutrition, but anemia-based incentives are not well aligned with effort to improve academic performance. Strengthening incentives to improve academic performance while also emphasizing the relationship between good nutrition and academic performance may therefore be sufficient to motivate administrators to effectively implement school-based anemia reduction programs while causing less reallocation of resources away from education.