Regional processes in mangrove ecosystems: spatial scaling relationships, biomass, and turnover rates following catastrophic disturbance

Physiological processes and local-scale structural dynamics of mangroves are relatively well studied. Regional-scale processes, however, are not as well understood. Here we provide long-term data on trends in structure and forest turnover at a large scale, following hurricane damage in mangrove ecosystems of South Florida, U.S.A. Twelve mangrove vegetation plots were monitored at periodic intervals, between October 1992 and March 2005. Mangrove forests of this region are defined by a −1.5 scaling relationship between mean stem diameter and stem density, mirroring self-thinning theory for mono-specific stands. This relationship is reflected in tree size frequency scaling exponents which, through time, have exhibited trends toward a community average that is indicative of full spatial resource utilization. These trends, together with an asymptotic standing biomass accumulation, indicate that coastal mangrove ecosystems do adhere to size-structured organizing principles as described for upland tree communities. Regenerative dynamics are different between areas inside and outside of the primary wind-path of Hurricane Andrew which occurred in 1992. Forest dynamic turnover rates, however, are steady through time. This suggests that ecological, more-so than structural factors, control forest productivity. In agreement, the relative mean rate of biomass growth exhibits an inverse relationship with the seasonal range of porewater salinities. The ecosystem average in forest scaling relationships may provide a useful investigative tool of mangrove community biomass relationships, as well as offer a robust indicator of general ecosystem health for use in mangrove forest ecosystem management and restoration.

Practical dynamic thermal management on Intel desktop computer

Fueled by increasing human appetite for high computing performance, semiconductor technology has now marched into the deep sub-micron era. As transistor size keeps shrinking, more and more transistors are integrated into a single chip. This has increased tremendously the power consumption and heat generation of IC chips. The rapidly growing heat dissipation greatly increases the packaging/cooling costs, and adversely affects the performance and reliability of a computing system. In addition, it also reduces the processor's life span and may even crash the entire computing system. Therefore, dynamic thermal management (DTM) is becoming a critical problem in modern computer system design. Extensive theoretical research has been conducted to study the DTM problem. However, most of them are based on theoretically idealized assumptions or simplified models. While these models and assumptions help to greatly simplify a complex problem and make it theoretically manageable, practical computer systems and applications must deal with many practical factors and details beyond these models or assumptions. The goal of our research was to develop a test platform that can be used to validate theoretical results on DTM under well-controlled conditions, to identify the limitations of existing theoretical results, and also to develop new and practical DTM techniques. This dissertation details the background and our research efforts in this endeavor. Specifically, in our research, we first developed a customized test platform based on an Intel desktop. We then tested a number of related theoretical works and examined their limitations under the practical hardware environment. With these limitations in mind, we developed a new reactive thermal management algorithm for single-core computing systems to optimize the throughput under a peak temperature constraint. We further extended our research to a multicore platform and developed an effective proactive DTM technique for throughput maximization on multicore processor based on task migration and dynamic voltage frequency scaling technique. The significance of our research lies in the fact that our research complements the current extensive theoretical research in dealing with increasingly critical thermal problems and enabling the continuous evolution of high performance computing systems.

Risk factors that predict maladaptive outcomes among sexually abused girls presenting for services at a community agency

The purpose of this study was to determine which factors predicted maladaptive outcomes in sexually abused children. Key factors were aggregated into four categories: abuse characteristics risk factors, individual-level risk factors, family disruption risk factors, and social disruption risk factors. It was hypothesized that (a) individual-level risk factors (e.g., school performance, child alcohol/substance abuse) and (b) abuse characteristics risk factors (e.g., longer duration/frequency of abuse, use of force/threats of force, intrafamilial abuse) would predict higher levels of trauma symptoms. Furthermore, it was hypothesized that (a) family disruption risk factors (e.g., family alcohol/substance use, family psychopathology) and (b) social disruption risk factors (e.g., parental divorce, homelessness, witnessing homicide or violence) would moderate the impact of prior sexual abuse and predict higher levels of trauma symptoms. ^ The participants were 110 female children (5 to 18 years old) presenting for treatment for sexual abuse at a community agency (The Journey Institute) in Miami, Florida. This study conducted a retrospective analysis of an archival data set collected over a three-year period (1998–2001). The measures completed upon intake included The Journey Psychosocial Assessment and The Trauma Symptom Checklist for Children (TSCC; Briere, 1996). Using Pearson correlations and hierarchical multiple regression analysis, this study found that abuse characteristics risk factors and individual-level risk factors were predictive of maladaptive outcomes in this sample of sexually abused girls. However, no moderating effects were found for family disruption risk factors or social disruption risk factors. Therefore, the results of these analyses provided support for the contention that abuse characteristics and individual-level risk factors were appropriate targets for treatment for sexually abused girls. Moreover, limitations of this study, implications for treatment, and directions for future research were discussed. ^

Risk factors of coronary heart disease and correlates of type 2 diabetes among Cuban Americans

Cuban Americans, a minority Hispanic subgroup, have a high prevalence of type 2 diabetes. Persons with diabetes experience a higher rate of coronary heart disease (CHD) compared to those without diabetes. The objectives of the National Institute of Diabetes and Digestive and Kidney Disease (NIDDK) are to investigate the risk factors of CHD and the etiology of diabetes among diabetics of minority ethnic populations. No information is available on the etiology of CHD risks for Cuban Americans. ^ This cross-sectional study compared Cuban Americans with (N = 79) and without (N = 80) type 2 diabetes residing in South Florida. Data on risk factors of CHD and type 2 diabetes were collected using sociodemographics, smoking habit, Rose Angina, Modifiable Activity, and Willet's food frequency questionnaires. Anthropometrics and blood pressure (BP) were recorded. Glucose, glycated hemoglobin, lipid profile, homocysteine, and C-reactive protein were assessed in fasting blood. ^ Diabetics reported a significantly higher rate of angina symptoms than non-diabetics (P = 0.008). After adjusting for age and gender, diabetics had significantly (P < 0.001) larger waist circumference and higher systolic BP than non-diabetics. There was no significant difference in major nutrient intakes between the groups. One quarter of subjects, both diabetics and non-diabetics, exceeded the intake of percent calories from total fat and almost 60% had cholesterol intake >200 mg/d and more than 60% had fiber intake <20 gm/d. The pattern of physical activity did not differ between groups though, it was much below the recommended level. After adjusting for age and gender, diabetics had significantly (P < 0.001) higher levels of blood glucose, glycated hemoglobin, triglycerides, and homocysteine than non-diabetics. In contrast, diabetics had significantly (P < 0.01) lower levels of high-density lipoprotein cholesterol (HDL-C). ^ Multivariate logistic regression analyses showed that increasing age, male gender, large waist circumference, lack of acculturation, and high levels of triglycerides were independent risk factors of type 2 diabetes. In contrast, moderate alcohol consumption conferred protection against diabetes. ^ The study identified several risk factors of CHD and diabetes among Cuban Americans. Health care providers are encouraged to practice ethno-specific preventive measures to lower the burden of CHD and diabetes in Cuban Americans. ^

Hispanic adolescents with severe substance abuse problems: Parental involvement, acculturation-related factors, and attachment

The main objective of the study was to investigate the relationship between parent-related, acculturation-related, and substance use-related variables found within individual, familial/parental, peer and school adolescent ecological domains, in a clinical sample (i.e. adolescents who met criteria for a Diagnostic Statistical Manual-IV [DSMIV] clinical diagnosis of substance abuse/dependence) of Hispanic adolescents from Miami, Florida. ^ The sample for this study consisted of 94 adolescent-mother pairs. The adolescent sample was 65% male, and 35% female, with a mean age of 15 years. More than half of the adolescents were born in the United States (60%) and had resided in the U.S. for an average of 12 years; 80% of the caregivers (primarily mothers) were foreign-born and lived in the U.S. for an average of 21 years. ^ Correlation and hierarchical regression were used to answer the research questions. The findings indicate that the hypothesized model and corresponding anticipated effect of the relationship between parental school and peer involvement on adolescents’ frequency of alcohol, marijuana and cocaine use was not supported by the data. Parental “acculturation-related” variables did not explain any of the variance in adolescent substance use frequency in this sample. Mediation and moderation models were not supported either. However, some interesting relationships were found: ^ The larger the acculturation gap, the lower the parental involvement in school tended to be (r = -.21, p < .05). Adolescents who experienced a greater acculturation gap with their parents (-.81, p >.01) had an earlier onset of marijuana (-.33, p < .01) and cocaine use (r = -.24, p <.01). The less acculturated parents experienced more parenting stress (r = -.31, p = < .01). Attachment was positively associated with parental peer involvement (r = .24, p < .05) and inversely associated with parenting acculturative stress (r = -.24, p < .05). Attachment was also positively associated with marijuana (r = .39, p < .01) and cocaine use (r = .33, p < .01). Adolescent males reported being more attached to their mothers when compared to adolescent females (r = .22, p >.05), they also reported using marijuana more frequently than females (.21, p >.05). ^

Social factors influencing antiretroviral therapy (ART) adherence among Black men living with HIV who use illicit drugs

In the United States 1.2 million persons are HIV infected. Among men, HIV rates in Blacks are seven times higher than Whites. More Black men progress to AIDS because of treatment failure and adherence problems. Antiretroviral therapy (ART), the only treatment effective for long term HIV suppression, requires near perfect adherence. Illicit drug use and homelessness pose further challenges. Suboptimal ART adherence leads to HIV mutations that can render entire classes of medication ineffective and transmission of mutated HIV to others in the community. The purpose of this study was to investigate ART adherence behaviors of Black men living with HIV who use illicit drugs. A sample of 160 Black men living with HIV who use illicit drugs was recruited using flyers and snowball sampling. These men completed study questionnaires that included: demographics, the K-10, PSOM and Social Capital Integrated Questionnaire, among others. One-way ANOVAs, multiple regression, and path analysis were used to address the study's research questions. Most of the Black men in this sample were high school graduates and single, with high rates of being marginally housed and homeless. Unemployment and disability were common, and personal and household income was low. The men reported high numbers of sexual partners both over the past year and during their lifetimes, suggesting continued engagement in high risk behaviors. The majority of the men attributed their HIV to heterosexual sex, with sexual commoditization being common. About half of the 105 men currently taking ART reported the current regimen was their first. Patient-provider relationship was positively associated with tolerability of ART. ART adherence was greater with less psychological distress, lower frequency of current illicit drug use, and greater tolerability of ART. Partner status negatively influenced ART adherence. This study of Black men's ART adherence behaviors has implications for public health. It identified social context factors that influence ART adherence among the men and provides evidence to refine existing, or develop new, ART adherence interventions.

Personal and institutional factors: Relationship to self-efficacy of persistence to the senior year in college among self-identified Black undergraduate students in a Hispanic serving institution

While undergraduate enrollment of all racial groups in United States higher education institutions has increased, 6-year graduation rates of Blacks (39%) remain low compared to other races; Asians (69%), Whites (62%), and Hispanics (50%; NCES, 2010). Women's graduation rate is higher than men's; 58% compared to men's at 53% in public institutions (IPEDS, 2011). Retention literature does not address the perceptions of Black ethnic groups' experiences in college, particularly in Hispanic serving institutions. Informed by Tinto's (1975, 1987, 1993) student academic and social integration model, Guiffrida's (2003, 2004, 2005, 2006) model of relationships while at college, and ex-post facto research design, the study investigated personal and institutional factors that relate to Black students' self-efficacy and persistence to the senior year in college. Data about Black ethnic undergraduate seniors' (N = 236) academic and social experiences in college were collected using the Student Institutional Integration Survey (SIIS), an online questionnaire. Descriptive statistics were used to collect background information about the sample, correlation was calculated to indicate the degree of relationship between the variables, and multiple linear regressions were used to identify variables that are predictors of self-efficacy of persistence. Independent samples t-test and analyses of variance were computed to determine whether differences in perceptions of personal and institutional factors that relate to self-efficacy of persistence to the senior year in college could be identified between gender and ethnicity. Frequency was summarized to identify themes of participants' primary motivation for finishing undergraduate degree programs. These themes were: (a) self-pride/personal goal, (b) professional aspiration/career (c) motivation to support family, (d) desire to have financial independence/better job, (e) to serve community, (f) opportunity to go to college, (g) being first-generation college student, and (h) prove to family the value of higher education. The research findings support the tenets of academic and social integration theories which suggest that students' interaction with peer and faculty, relationships with family and friends, and involvement in institutional activities and organizations influence their persistence in college. Implications based on the findings affect institutional policy, curriculum, and program improvements that relate to Black undergraduate students' academic and social support.

Personal and Institutional Factors: Relationship to Self-Efficacy of Persistence to the Senior Year in College among Self-Identified Black Undergraduate Students in a Hispanic Serving Institution

While undergraduate enrollment of all racial groups in United States higher education institutions has increased, 6-year graduation rates of Blacks (39%) remain low compared to other races; Asians (69%), Whites (62%), and Hispanics (50%; NCES, 2010). Women’s graduation rate is higher than men’s; 58% compared to men’s at 53% in public institutions (IPEDS, 2011). Retention literature does not address the perceptions of Black ethnic groups’ experiences in college, particularly in Hispanic serving institutions. Informed by Tinto’s (1975, 1987, 1993) student academic and social integration model, Guiffrida’s (2003, 2004, 2005, 2006) model of relationships while at college, and ex-post facto research design, the study investigated personal and institutional factors that relate to Black students’ self-efficacy and persistence to the senior year in college. Data about Black ethnic undergraduate seniors’ (N = 236) academic and social experiences in college were collected using the Student Institutional Integration Survey (SIIS), an online questionnaire. Descriptive statistics were used to collect background information about the sample, correlation was calculated to indicate the degree of relationship between the variables, and multiple linear regressions were used to identify variables that are predictors of self-efficacy of persistence. Independent samples t-test and analyses of variance were computed to determine whether differences in perceptions of personal and institutional factors that relate to self-efficacy of persistence to the senior year in college could be identified between gender and ethnicity. Frequency was summarized to identify themes of participants’ primary motivation for finishing undergraduate degree programs. These themes were: (a) self-pride/personal goal, (b) professional aspiration/career (c) motivation to support family, (d) desire to have financial independence/better job, (e) to serve community, (f) opportunity to go to college, (g) being first-generation college student, and (h) prove to family the value of higher education. The research findings support the tenets of academic and social integration theories which suggest that students’ interaction with peer and faculty, relationships with family and friends, and involvement in institutional activities and organizations influence their persistence in college. Implications based on the findings affect institutional policy, curriculum, and program improvements that relate to Black undergraduate students’ academic and social support.

Risk factors and associations for hepatitis C infection among Hispanic/Latino intravenous drug users in Miami-Dade County, Florida

Hepatitis C infection (HCV) continues to disproportionately affect Hispanics/Latinos in the United States. Hispanic/Latino intravenous drug users (IDUs), because of their risky injection and sexual behaviors, are prone to HCV infection and rapid transmission of the virus to others via several routes. With a prevalence rate of approximately 75% among IDUs, it is imperative that transmission of HCV be prevented in this population. This study aims to examine the associations between demographic, injection and sexual risk factors to HCV infection in a group Hispanic/Latino IDUs in Miami-Dade County, Florida. Preliminary unadjusted results in this sample reveal that age (OR=4.592, p=0.004), weekly injection (OR=5.171, p=0.000), daily injection frequency (OR=3.856, p=0.000) and use of a dirty needle (OR=2.320, p= 0.006) were all significantly associated with HCV infection. Being born outside the U.S. was significantly negatively associated with HCV infection (OR=0.349, p=0.004). Additionally, having two or more sex partners in the past three months (OR=0.472, p=0.014) was negatively associated with HCV infection. After adjusting for all other variables, older age (AOR=7.470, p=0.006), weekly injection (AOR=3.238, p=0.007) and daily injection frequency (AOR=2.625, p=0.010) were all significantly associated with HCV infection. Being born outside the U.S. (AOR=0.369, p=0.019) was a significant protective factor for HCV infection, along with having two or more sex partners in the past three months (AOR=0.481, p=0.037). When analyzing the significant variables in a backward regression model, having 2 or more sex partners in the past three months was not significant at the p

Patriarchal ideology and frequency of partner abuse among men in batterer treatment groups

This research examined the relative influence of a number of factors, patriarchal ideology, age, socio-economic status, partner relationship, and problem behaviors on the frequency of partner abuse. Patriarchal ideology as measured by the Attitudes Toward Women Scale (AWS), and the Inventory of Beliefs about Wife Beating (IBWB) among men in batterer treatment programs did not have the strong influence expected on whether men in treatment are more frequent abusers of their partners. Instead, having a criminal record and having been identified as having a substance abuse problem stood out as being the most influential factors associated with frequent partner abuse. Questionnaires were administered to 283 men in batterer treatment programs in Dade County Florida who volunteered to participate in the study. Specifically, men in batterer groups who scored low on the AWS or high on the IBWB indicating an adherence to patriarchal ideology were predicted to report more frequent abuse of their partners. Conversely, men in treatment who scored high on the AWS or low on the IBWB indicating a tendency towards a non-patriarchal ideology were predicted to report less frequent abuse. ^

Hispanic Adolescents With Severe Substance Abuse Issues: Parental Involvement, Acculturation-Related Factors and Attachment

The main objective of the study was to investigate the relationship between parent-related, acculturation-related, and substance use-related variables found within individual, familial/parental, peer and school adolescent ecological domains, in a clinical sample (i.e. adolescents who met criteria for a Diagnostic Statistical Manual-IV [DSM-IV] clinical diagnosis of substance abuse/dependence) of Hispanic adolescents from Miami, Florida. The sample for this study consisted of 94 adolescent-mother pairs. The adolescent sample was 65% male, and 35% female, with a mean age of 15 years. More than half of the adolescents were born in the United States (60%) and had resided in the U.S. for an average of 12 years; 80% of the caregivers (primarily mothers) were foreign-born and lived in the U.S. for an average of 21 years. Correlation and hierarchical regression were used to answer the research questions. The findings indicate that the hypothesized model and corresponding anticipated effect of the relationship between parental school and peer involvement on adolescents’ frequency of alcohol, marijuana and cocaine use was not supported by the data. Parental “acculturation-related” variables did not explain any of the variance in adolescent substance use frequency in this sample. Mediation and moderation models were not supported either. However, some interesting relationships were found: The larger the acculturation gap, the lower the parental involvement in school tended to be (r = -.21, p < .05). Adolescents who experienced a greater acculturation gap with their parents (-.81, p >.01) had an earlier onset of marijuana (-.33, p < .01) and cocaine use (r = -.24, p .05), they also reported using marijuana more frequently than females (.21, p >.05).

Improved Criteria for Estimating Calibration Factors for Highway Safety Manual (HSM) Applications

The Highway Safety Manual (HSM) estimates roadway safety performance based on predictive models that were calibrated using national data. Calibration factors are then used to adjust these predictive models to local conditions for local applications. The HSM recommends that local calibration factors be estimated using 30 to 50 randomly selected sites that experienced at least a total of 100 crashes per year. It also recommends that the factors be updated every two to three years, preferably on an annual basis. However, these recommendations are primarily based on expert opinions rather than data-driven research findings. Furthermore, most agencies do not have data for many of the input variables recommended in the HSM. This dissertation is aimed at determining the best way to meet three major data needs affecting the estimation of calibration factors: (1) the required minimum sample sizes for different roadway facilities, (2) the required frequency for calibration factor updates, and (3) the influential variables affecting calibration factors. In this dissertation, statewide segment and intersection data were first collected for most of the HSM recommended calibration variables using a Google Maps application. In addition, eight years (2005-2012) of traffic and crash data were retrieved from existing databases from the Florida Department of Transportation. With these data, the effect of sample size criterion on calibration factor estimates was first studied using a sensitivity analysis. The results showed that the minimum sample sizes not only vary across different roadway facilities, but they are also significantly higher than those recommended in the HSM. In addition, results from paired sample t-tests showed that calibration factors in Florida need to be updated annually. To identify influential variables affecting the calibration factors for roadway segments, the variables were prioritized by combining the results from three different methods: negative binomial regression, random forests, and boosted regression trees. Only a few variables were found to explain most of the variation in the crash data. Traffic volume was consistently found to be the most influential. In addition, roadside object density, major and minor commercial driveway densities, and minor residential driveway density were also identified as influential variables.

Risk Factors and Associations for Hepatitis C Infection among Hispanic/Latino Intravenous Drug Users in Miami-Dade County, Florida

Hepatitis C infection (HCV) continues to disproportionately affect Hispanics/Latinos in the United States. Hispanic/Latino intravenous drug users (IDUs), because of their risky injection and sexual behaviors, are prone to HCV infection and rapid transmission of the virus to others via several routes. With a prevalence rate of approximately 75% among IDUs, it is imperative that transmission of HCV be prevented in this population. This study aims to examine the associations between demographic, injection and sexual risk factors to HCV infection in a group Hispanic/Latino IDUs in Miami-Dade County, Florida. Preliminary unadjusted results in this sample reveal that age (OR=4.592, p=0.004), weekly injection (OR=5.171, p=0.000), daily injection frequency (OR=3.856, p=0.000) and use of a dirty needle (OR=2.320, p= 0.006) were all significantly associated with HCV infection. Being born outside the U.S. was significantly negatively associated with HCV infection (OR=0.349, p=0.004). Additionally, having two or more sex partners in the past three months (OR=0.472, p=0.014) was negatively associated with HCV infection. After adjusting for all other variables, older age (AOR=7.470, p=0.006), weekly injection (AOR=3.238, p=0.007) and daily injection frequency (AOR=2.625, p=0.010) were all significantly associated with HCV infection. Being born outside the U.S. (AOR=0.369, p=0.019) was a significant protective factor for HCV infection, along with having two or more sex partners in the past three months (AOR=0.481, p=0.037). When analyzing the significant variables in a backward regression model, having 2 or more sex partners in the past three months was not significant at the p