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      • The influence of fetal and early growth on adult mental distress: Evidence from the Johns Hopkins collaborative perinatal study birth cohort

        Alford, Aaron A The Johns Hopkins University 2009 해외박사(DDOD)

        RANK : 233326

        Objectives. Early childhood physical growth may have an impact on the development of adult mental distress. The primary objectives were to (2) assess the association of early growth in weight adjusted for height with adult mental distress, and (2) determine if there are patterns of early growth that increase or decrease the likelihood of adult mental distress. Methods. Subjects were all Johns Hopkins Collaborative Perinatal Study cohort subjects with complete birth size information that successfully completed the Pathways to Adulthood follow-up in early adulthood. Variability in the timing of growth in weight adjusted for height from birth to age 7.5 years was taken into account using a nonhierarchical linear model. Two critical periods of growth were considered as tertiles of change in weight adjusted for height from birth to age seven and birth to age 1 year. Mental distress in adulthood (ages 29-32) was measured using the General Health Questionnaire (GHQ-28). Results. Small for gestational age subjects were at increased risk of later mental distress, but not uniformly so. Those born with low weight and length for gestational age were a distinct subgroup of those born small for gestational age, and had unique patterns of risk for adult mental distress when early growth was considered. Conclusions. Acceleration and deceleration in weight for height change is associated with mental distress over multiple periods of early life and acts differentially between those periods. Furthermore, the association of early childhood growth on the likelihood of adult mental distress is dependent on prenatal growth.

      • Topics in high-energy physics: The standard model and beyond

        Blechman, Andrew Eric The Johns Hopkins University 2006 해외박사(DDOD)

        RANK : 233326

        This thesis is compiled from the various projects I completed as a graduate student at the Johns Hopkins University Physics Department. The first project studied threshold effects in excited charmed baryon decays. The strong decays of the L+c (2593) are sensitive to finite width effects. This distorts the shape of the invariant mass spectrum in L+c1 → L+c pi+pi- from a simple Breit-Wigner resonance, which has implications for the experimental extraction of the L+c (2593) mass and couplings. A fit is performed to unpublished CLEO data which gives M( L+c (2593))---M( L+c ) = 305.6 +/- 0.3 MeV and h22=0.24+0.23 -0.11 , with h2 the L+c → Sigmacpi strong coupling in the chiral Lagrangian. In the second project, by shining a hypermultiplet from one side of the bulk of a flat five-dimensional orbifold, supersymmetry is broken. The extra dimension is stabilized in a supersymmetric way, and supersymmetry breaking does not damage the radius stabilization mechanism. The low energy theory contains the radion and two complex scalars that are massless in the global supersymmetric limit and are stabilized by tree level supergravity effects. It is shown that radion mediation can play the dominant role in communicating supersymmetry breaking to the visible sector and contact terms are exponentially suppressed at tree level. The third project studied lepton flavor violation in flavor anarchic Randall-Sundrum models. All Yukawa couplings and mixing matrices are generated at the TeV-scale by wavefunction overlaps in the five-dimensional Anti-deSitter geometry present in this theory, without introducing any additional structure. This leads to a TeV-scale solution to both the flavor and electroweak hierarchy problems. A thorough scan of the available parameter space is performed, including the effects of allowing the Higgs boson to propagate in the full five-dimensional space-time. These models give constraints at the few TeV level throughout the natural range of parameters. Near-future experiments will definitively test this model.

      • The link between children's anxiety and aggression: A longitudinal study

        Chen, Yi-Hua The Johns Hopkins University 2001 해외박사(DDOD)

        RANK : 233326

        This longitudinal project was designed to examine the impact of children's anxious/aggressive status on the long-term trajectories of aggressive behaviors over time, with the aim to further clarify the conflicting and contradictory link between anxiety and later aggression in children and adolescents identified in past literature. In addition to four overall (or combined) anxiety/aggression status (i.e., neither anxious nor aggressive, anxious only, aggressive only, and both anxious and aggressive), two subtypes of anxiety, anxiety from social evaluation concerns and anxiety from hostile environment, were additionally specified. In examining the pathway, the effects of individual (i.e., sex, age, race/ethnicity, intervention status) and social factors (i.e., income, parental monitoring, neighborhood characteristics, family structure, household size, and parental marital, educational, and employment status) that were suspected to associate with the relationship investigated were also considered. Employed data from an ongoing prospective approach of the Prevention Program of the Johns Hopkins University Prevention Research Center from 1985 to 1992, this project sample comprised two consecutive first grade cohorts in 43 classrooms of 19 elementary schools in five eastern Baltimore districts. Specifically, due to the modification of the annual assessment instruments, overall (or combined) anxious levels measured in the fall of 1987 for Cohort 1 and the fall of 1988 for Cohort 2 were available for 1,352 students (Sample 1), whereas initial anxiety status assessed in the fall of 1985 was only available for 1,062 first-graders in Cohort 1 (Sample 2). Two primary outcomes, teacher's report of aggressive/disruptive behaviors and child's self-reported overt antisocial behaviors, were specified in this study. For each outcome, three sets of models were outlined, including logistic regression models, population-averaged approaches, and random effects methods; however, approximately similar trends of results were observed. Children's various aggression comorbid with anxiety status (i.e., both overall and initial anxiety/aggression status) indeed presented diverse developmental outcomes of aggressive behaviors over time. The estimates reported below were from models adjusted for an array of covariates of individual and social factors mentioned above. (Abstract shortened by UMI.).

      • Flow problems in hyperbolic space

        Xiao, Ling The Johns Hopkins University 2013 해외박사(DDOD)

        RANK : 233326

        The aim of this dissertation is threefold and it records three distinct results that the author along with her collaborators proved, during her time as a graduate student at The Johns Hopkins University. Firstly, with L. Lin, in [33] we defined a new modified mean curvature flow (MMCF) in hyperbolic space Hn+1 . We showed the existence, uniqueness and convergence of the MMCF of complete embedded star-shaped hypersurfaces with prescribed asymptotic boundary at infinity. The proofs of our main theorems closely follow the work of Guan and Spruck [16], and may be thought of as a parabolic analogue. Secondly, in [37] the author investigated the existence, convergence and uniqueness of the modified curvature flow of convex hypersurfaces (MCFC) in hyperbolic space with a prescribed asymptotic boundary. Finally, the author extended her result in [37] to the case of finding the general curvature flow of complete hypersurfaces (MGCF) in hyperbolic space with a prescribed asymptotic boundary at infinity. This is part of the project of generalizing Guan and Spruck's result in [20].

      • Child and adolescent predictors of youth alcohol use to intoxication

        Anderson, Karyn Lynn The Johns Hopkins University 2004 해외박사(DDOD)

        RANK : 233326

        While youthful experimentation with alcohol is often tolerated and even condoned by many segments of society, there may be serious implications when the onset of drinking occurs at a young age. There is evidence that the earlier in life youth drink alcohol for the first time, the greater their risk is for impeding their brain's healthy development, being implicated in a serious injury, having a traumatic experience, or eventually suffering from a diagnosable alcohol or drug use disorder. The risk of these adversities is even greater when alcohol is consumed to the point of intoxication. In spite of this well recognized fact, however, very few studies of youth drinking have focused specifically on intoxication as a study outcome. Furthermore, while the association between peer-affiliation and youthful alcohol and drug use is well established in the literature, very few alcohol-use studies have investigated the role of peers or other contextual factors in adolescence with adjustment for early childhood markers of increased susceptibility. The overarching purpose of this dissertation research was therefore to estimate the extent to which intoxicated drinking in adolescence is a function of characteristics in early childhood and the evolving risk factors in adolescents' more immediate social worlds. In fact while the literature supports both routes to substance use and abuse, no studies have prospectively investigated drinking to intoxication as a function of both childhood and adolescent characteristics that are known or suspected to increase risk. This research project drew upon data from the second generation of the ongoing and longitudinal Johns Hopkins University Prevention Intervention Research Center (JHU-PIRC) randomized field trial of two first-grade preventive interventions. Study participants in this second generation consisted of one cohort of first graders representing nine different schools in Baltimore Maryland. These young study participants were randomly assigned to one of three first grade classroom conditions within each school and tracked annually up through the end of the ninth grade school year, their first year of high school. In addition to a range of appropriate univariate and bivariate descriptive statistics, the data were analyzed using the generalized estimating equations (GEE) extension of logistic regression analysis for binary response data collected at multiple time points. (Abstract shortened by UMI.).

      • Changing cervical cancer screening guidelines: Patient attitudes and clinical practice

        Silver, Michelle I The Johns Hopkins University 2015 해외박사(DDOD)

        RANK : 233326

        Objectives: Cervical cancer screening guidelines have been revised, and now emphasize evidence-based medicine, resulting in recommendations for less frequent screening; however, these changes have been met with concern by both patients and providers. Understanding the patterns of acceptance versus reticence to accept these guidelines by health systems, providers, and patients is critical to developing successful strategies for translating policy change into routine practice. Here we fill some of these knowledge gaps by incorporating both actual cervical cancer screening practice data and patient perspectives towards HPV testing and screening interval changes through the following specific aims: 1a) describe the uptake of co-testing and examine the correlates of receiving an HPV co-test, 1b) estimate the length of time until the next screening test following either a negative Pap smear alone or a dual negative co-test, and 2) investigate the correlates of reluctance to adhere to revised guidelines, which recommend the addition of HPV testing along with less frequent cervical cancer screening. Methods: Using cervical cancer screening records from the Pathology Data Systems (PDS) at Johns Hopkins Hospital, we estimate temporal trends in choice of screening strategy (cytology alone or with HPV DNA testing) and the interval between successive screening tests in routine clinical practice. We then incorporate the patient perspective by using data collected in the HPV in Perimenopause (HIP) natural history study of women age 35-60 years, we will compare women who indicate willingness versus reluctance to accept alternative screening strategies such as HPV testing and a longer interval between cervical cancer screening tests. Results: In clinical practice, we saw a significant increase in use of HPV co-testing over the last 10 years, reaching almost 80% of screening tests. We also saw a significant increase in time between screening tests following a dual-negative co-test to almost 3 years, but essentially no change in time to next screening test following a normal Pap smear, remaining near 1.5 years. Among patients, we found a majority of study participants indicated a willingness to adopt a cervical cancer screening strategy of cytology alone or Pap-HPV co-testing every 3 years if recommended by their physician, but remain concerned about primary HPV testing and co-testing with 5-year screening intervals. Conclusion: HPV testing was incorporated into screening with an assumption of less frequent screening due to its greater sensitivity and negative predictive value. While intervals have increased following a co-test, more time will be needed to see whether they reach 5 years as recommended. We also found evidence of continued reticence to accepting newer HPV-based screening algorithms among routinely screened women over age 35, highlighting a need for more patient education regarding the use and meaning of HPV testing.

      • Genetic epidemiology of pancreatic cancer

        Klein, Alison Patricia The Johns Hopkins University 2002 해외박사(DDOD)

        RANK : 233326

        <italic>Background</italic>. Pancreatic cancer is the 5<super>th</super> leading cause of cancer death in the United States. The only risk factor that has been consistently associated with pancreatic cancer is cigarette smoking. Recently, studies have shown that family history of cancer or family history of pancreatic cancer are risk factors for pancreatic cancer, suggesting genetic factors may be involved in pancreatic cancer susceptibility. The <italic> primary objective</italic> of this study was to determine if there is evidence for a major gene involved in susceptibility to pancreatic cancer. <italic>Methods</italic>. Segregation analysis was performed using family data from 287 patients treated at The Johns Hopkins Hospital and The Johns Hopkins Bayview Medical Center (collectively referred to as JHMI) between January 1, 1994 and December 30, 1999. Cigarette smoking exposure was included in the analysis to determine if it modifies putative genetic risk. An additional segregation analysis on 320 families enrolled in The National Familial Pancreatic Tumor Registry at The Johns Hopkins Hospital was performed. Analyses were performed using the REGTL program in the Statistical Analysis for Genetic Epidemiology (S.A.G.E.) software package under both Model 1, where age-at-onset is allowed to be type-dependent and under Model 2 where susceptibility is type dependent. <italic>Results</italic>. In our segregation analysis of 287 JHMI families, we were able to reject all non-genetic transmission models (p < 0.0001). The Mendelian models did provide an adequate fit to the data, both under Model 1 and Model 2. In our analysis of the 320 referral families enrolled in the NFPTR, all restricted models, including Mendelian and non-genetic models, were rejected under Model 1. However, in the analysis under Model 2, non-genetic models were rejected, while the Mendelian models could not be rejected. <italic>Conclusions</italic>. These results support the hypothesis that a major gene may be involved in increased susceptibility to pancreatic cancer. Based upon the results of our hospital-based segregation analysis, we estimate that approximate 4 in every 1,000 individuals carry this high-risk allele. While cigarette smoking has been shown to be an important risk factor for pancreatic cancer in other studies, it was not a statistically significant predictor of developing pancreatic cancer in these data.

      • Advances in dynamical modeling and control of underwater robotic vehicles

        Smallwood, David Andrew The Johns Hopkins University 2003 해외박사(DDOD)

        RANK : 233326

        This Thesis addresses problems in the dynamical modeling, identification, and control of underwater vehicles. First we report the design, construction, and testing by the Author of the Johns Hopkins University Remotely Operated underwater robotic Vehicle (JHUROV), a experimental test platform for research in underwater robotic vehicle navigation, dynamics, and control. Second we report a complete derivation of a general, six-degree-of-freedom finite-dimensional approximate dynamical plant model for rigid body underwater robotic vehicles, and an empirically justified simplification resulting in a single-degree-of-freedom finite-dimensional approximate dynamical plant model. Third, we report the novel use of and a stability proof for a scalar adaptive identification technique for identifying plant model parameters from experimental vehicle dynamics data. This technique is shown to produce superior experimentally identified dynamical plant model parameters in comparison to those obtained via a conventional least-squares technique. Fourth, we report a detailed comparative experimental evaluation of a family of model-based controllers designed for the task of trajectory tracking. Numerical simulation and extensive experimental results are reported, examining the comparative performance of five model-based controllers and a conventional linear controller.

      • Data management in environmental monitoring sensor networks

        Gupchup, Jayant The Johns Hopkins University 2012 해외박사(DDOD)

        RANK : 233326

        Data gathered from multi-month to multi-year battery-powered environmental monitoring sensor networks present numerous challenges. This thesis explores three problems. First, design issues related to loading, storing and data integrity are studied in detail. An end-to-end system addressing these tasks by decoupling deployment-specific and deployment-independent phases is presented. This solution places a strong emphasis on the ability to trace the origins of every collected measurement for provenance and scientific reproducibility. Second, we explore the problem of assigning accurate global timestamps to the measurements collected using the motes' local clocks. In deployments lacking a persistent gateway, a data-driven approach is employed to assign timestamps to within 10 parts per million. Building on these experiences, we developed a novel low-power approach to accurately timestamp measurements in the presence of random, frequent mote reboots. The system is tested in simulation and on a real deployment in a Brazilian rain forest. It is able to achieve an accuracy in the order of seconds for more than 99% of measurements even when a global clock source is missing for days to months. Lastly, this thesis explores a generic data-driven approach to reduce communication costs in order to increase network lifetime. In particular, spatial correlation among sampling stations is leveraged to adaptively retrieve data from a small subset of informative sensors rather than all instrumented locations. Soil temperature data collected every half hour for four months from 50 locations is used to evaluate this system. The method achieves a factor of two reduction in collected data with a median error of 0.06°C and 95th percentile error of 0.325°C. This work is part of the Life Under Your Feet project developed at the Hopkins Inter-Networking Research (HiNRG) and eScience Labs at the Johns Hopkins University. At the time of writing, the data collected for this project is available at http://www.lifeunderyourfeet.org.

      • Optimizing treatment outcomes in HIV-infected drug users: An epidemiological assessment and interventional model

        Lucas, Gregory M The Johns Hopkins University 2004 해외박사(DDOD)

        RANK : 233310

        Individuals with a history of injection drug use account for 31% of AIDS cases in the United States and up to half of those treated in many urban settings. This dissertation comprises a series of epidemiologic studies on the relationship between drug use and HIV treatment outcomes in the Johns Hopkins Clinical Cohort, and the development and pilot assessment of an interventional strategy, directly administered antiretroviral therapy (DAART). First, in a cross-sectional analysis of 764 treatment-eligible HIV-infected participants who completed a confidential survey, we found that active drug users were less likely to have used combination antiretroviral therapy, had lower self-reported adherence, smaller decreases in HIV RNA levels, and smaller increases in CD4+ cell counts than non-drug users. Conversely, former drug users and non-drug users were quite similar in utilization of and adherence with therapy, and in measures of treatment effectiveness. Second, in a longitudinal analysis of 695 treatment-eligible participants, who completed at least two confidential surveys at 6-month intervals, transitions from non-use to use of drugs were associated with worsening utilization of antiretroviral therapy, virologic status, and immunologic status, compared to those who remained non-users in consecutive surveys. In contrast, transitions from use to non-use of drugs were associated with improvements in all HIV treatment outcomes, compared to those who remained users in consecutive surveys. Finally, 50 participants were enrolled in a pilot study of DAART in a methadone treatment facility, located near the Johns Hopkins HIV Clinic. In a non-randomized cohort comparison study, the proportion of DAART participants who achieved viral suppression at 6 months was significantly higher than the proportions achieving viral suppression in two frequency-matched randomly-selected comparison groups from the Johns Hopkins HIV Clinical Cohort: drug users currently in methadone treatment, and non-drug users. This research highlights the close temporal relationship between changes in drug user status and HIV treatment outcomes, and provides the rationale for the further development and assessment of treatment models that integrate HIV care and substance abuse treatment.

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