Thesis (M.D.)--Boston University

Cartas al editor

The literature suggests that body kinematics and musculoskeletal differences are major factors contributing to the high disparity in non-contact Anterior Cruciate Ligament (ACL) injury rate between genders. The literature also indicates that the incidence of non-contact ACL injury predominates during single-leg landing sports such as basketball, soccer, and handball. Despite this, there are few studies investigating kinematics or musculoskeletal differences between genders during single-leg landing from increasing vertical heights and horizontal distances. The objectives of this study are threefold: first, conduct a gap study identifying the barriers to predicting mechanisms and risk factors for non-contact ACL injury. Second, propose a new approach that can address some of the challenges encountered in some existing non-contact ACL injury study approaches. Finally, whilst determining whether or not gender differences explain the higher rate of ACL injuries among females, identify and correlate the biomechanical and musculoskeletal variables significantly impacted by gender, vertical landing height, and/or horizontal landing distance and their interactions to various ACL injury risk predictor variables during single-leg landing. Experiments using male and female subjects, inverse dynamics analysis using Visual3D, and musculoskeletal modeling simulation using AnyBody Modeling System were approaches used to explore these objectives. Salient findings from this dissertation includes but are not limited to, non-contact ACL injury that occurs during single-leg landing is mutifaceted entailing many factors that cannot be captured in any one existing ACL injury study approach. Non-contact ACL injury during single-leg landing may not be gender specific. Both vertical height and horizontal distance of landing increase the risk of non-contact ACL injury during single-leg landing. Body kinematics during single-leg landing may not be the sole determinant in attenuating ground reaction forces and consequently risk of ACL injury. The hamstring and gastrocnemius muscles were determined to strain shield the ACL while the quadriceps were found to have no significant effect on risk of ACL injury during single-leg landing. Within the findings and limitations of this study the knowledge garnered from this research may aid in tailoring future studies so as to enable more robust non-contact ACL injury prevention protocols.

Many scholars examining desistance from crime have emphasized the importance of social factors in triggering the desistance process. Most notably, the work of Sampson and Laub (1993) focuses on the role of social bonds (e.g., marriage and employment), which serve as turning points in offenders’ lives, while other scholars have emphasized other important social factors, such as antisocial peer influence (Stouthamer-Loeber, Wei, Loeber, Masten, 2004; Warr, 1998, 2002). However, missing from such works is the role of subjective factors (e.g., thinking patterns, expectations, self-identity) in the desistance process, despite evidence that changes in identity and other cognitive transformations promote desistance from criminal offending (Giordano, Cernkovich, & Rudolph, 2002; Maruna, 2001). Examining the combined role of subjective and social factors is important, because it may lead to a more comprehensive understanding of the desistance process. Desistance researchers typically focus on one set of factors, while downplaying the other set of factors. Rarely have researchers examined the effects of social and subjective factors simultaneously (for exceptions, see Healy, 2010; Laub & Sampson, 2003; Morizot & Le Blanc, 2007). And even fewer attempts have been made to examine the interplay between social and subjective factors (for exceptions, see LeBel, Burnett, Maruna, & Bushway, 2008; Simons & Barr, 2012). Further, there is a special need to examine the impact of change in subjective and social factors on the desistance process using within-individual analyses (Farrington, 2007; Horney, Osgood, & Marshall, 1995; Kazemian, 2007). Thus, research on desistance is advanced in the current study in the following three ways. First, the influence of both subjective and social factors on desistance are considered, within the same statistical model. Second, this study is based on within-individual analyses. Third, the interplay between subjective and social factors is explored in this study, including mediation and moderation (interaction) effects. Data used in the current study are drawn from the Pathways to Desistance study (see Mulvey, 2004), following serious adolescent offenders for seven years – from mid-adolescence through early adulthood. The theoretical, policy, and research implications of the findings are discussed.

Thesis (Ph. D.)--University of Göteborg, 1994. / Published dissertation.

Although previous studies have considered the factors affecting other certification exam outcomes, they have not examined those that are related to performance on the Professional in Human Resources (PHR) exam. In response to that need, this study specifically investigates technology and training factors that affect self-efficacy and self-set goals, and through them, influence PHR certification exam results. The target population for the study consisted of recent examinees who had taken a formal PHR examination preparation class or used another form of exam preparation training. The survey results were analyzed using partial least squares modeling techniques, and mediation effects were then tested. The results demonstrated that PHR training self-efficacy affected PHR exam self-efficacy and self-set goals. These factors then had an impact on PHR exam scores. Also, the results of task-technology fit were indirectly related to PHR training self-efficacy through a multiple mediation model that included the instructional factor of time on task and the technology factor of perceived usefulness. Surprisingly, time spent on practice exam questions was found to be negatively related to PHR certification exam scores. Finally, instructional feedback indirectly affected outcomes through its positive relationship to self-set goals. The results of the research should help training professionals and examinees in structuring PHR exam training and preparation activities. They also suggest avenues for improving outcomes in other similar types of training.

Low back pain (LBP) is the most prevalent work-related musculoskeletal disorder. Occupational risk factors have been studied for current ergonomic prevention strategies; however, other underlying mechanisms may exist since not all workers performing the same task develop the same severity. Previous research has identified personal and psychosocial risk factors that also contribute to LBP. Research quantifying the interactive effects of the various personal, psychosocial and occupational factors is limited, along with research on the effect of risk factor combinations on LBP severity. The objectives of this study were to: 1) study the various factors that are known to be involved in low back pain and analyze interactions, and 2) develop a model to predict low back pain and validate it. In order to address these objectives, 2 studies were conducted. The first study investigated the effects of various personal, genetic, occupational and psychosocial factors on two subjective LBP severity ratings: Oswestry Disability Index (ODI) and a Visual Analog Scale (VAS), and three physician-based ratings: MRI severity, canal stenosis and nerve impingement. Personal and psychosocial factors, in addition to occupational factors, were found to significantly affect the severity ratings. The second study involved building predictive models of LBP severity for each risk factor category as well as a combined risk factor model. Results showed that the combined risk factor models considering interaction effects both within and across risk factor categories were significantly better in predicting severity ratings than the individual models. However, validation conducted using 5 random samples showed inconsistent accuracies. Results obtained may help to develop a more reliable way to predict and, hence, prevent chronic LBP.

Extra-Cytoplasmic Function (ECF) σ factors are a subset of σ factors many organisms use to transcribe specific genes in response to environmental cues. In the absence of an inducing signal, ECF σ factors are inhibited by an anti-σ factor that prevents the ECF σ factor from interacting with RNA polymerase. The ECF σ factor σV from Bacillus subtilis is activated in response to lysozyme stress. Lysozyme damages bacterial peptidoglycan by cleaving at the 1,4-ß-linkage between N-acetylmuramic acid and N-acetylglucosamine. In the absence of lysozyme, the activity of σV is inhibited by the anti-σ factor RsiV, a single pass transmembrane protein. The two main components of this project have been to elucidate the mechanism of σV activation and examine how this system senses lysozyme stress. In chapter 2 we show that the activation of σV is specific to lysozyme, and the anti-σ factor RsiV is degraded by a step wise proteolytic cascade known as Regulated Intramembrane Proteolysis (RIP). In the presence of lysozyme, the extracellular domain of RsiV is removed by cleavage at site-1. Upon removal of the extracellular domain, the site-2 protease, RasP, cleaves RsiV within the membrane. The remainder of RsiV is degraded by cytosolic proteases allowing σV to interact with RNA polymerase. In response to lysozyme stress σV activates an O-actyltransferase, OatA, which modifies the peptidoglycan to prevent further lysozyme damage. Our studies in chapter 3 identifed the protease(s) responsible for site-1 cleavage of RsiV and revealed RsiV directly interacts with lysozyme. We determined the cleavage site of the site-1 protease using N-terminal sequencing, and demonstrate that disruption of site-1 cleavage blocks σV activation. Site-1 cleavage occurs at what appears to be a signal peptide cleavage site. We demonstrate that four out of the five signal peptidases from B. subtilis are able to cleave RsiV at site-1 in vitro only in the presence of lysozyme. Additionally, we show that the extracellular domain of RsiV directly binds the inducing substrate lysozyme. In chapter 4 we focus on determining if the interaction between RsiV and lysozyme is necessary for σV activation. Based on the co-crystal structure of RsiV and lysozyme we mutated sveral residues predicted to be involved in binding. One combination of RsiV mutations (S169W, P259A, Y261A) was unable to activate σV and subsequently was unable to bind lysozyme. We propose a RIP dependent mechanism of σV activation that is contingent upon the anti-σ factor (RsiV) directly binding the inducing signal (lysozyme) to present the site-1 cleavage site to signal peptidase. The co-crystal structure of RsiV and lysozyme also revealed that RsiV interacts with the active site of lysozyme. We demonstrate that purified RsiV inhibits lysozyme activity suggesting RsiV provides an additional lysozyme response mechanism. Thus, the anti-σ factor RsiV senses the presence of lysozyme, activates σV, and protects against further lysozyme damage.

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The objective of this dissertation is to evaluate how regulatory and market factors affect title insurance charges in different states. As substantial components of home purchase closing costs, title insurance charges have been controversial for decades, and both practitioners and analysts have pointed out apparent variations in title insurance charges among states. Although existing studies have suggested a set of regulatory and market factors as explanations for these among-state variations, empirical evaluations are limited. To fill in this gap, this dissertation empirically assesses whether these factors influence title insurance charges. The research outcomes of these dissertation indicate that after taking into account market factors such as services included in title insurance charges, title-related losses, property values, state populations, home sale volumes, housing prices, and income levels, regulation styles can still partially explain the title insurance charge variations in different states. In particular, states with promulgation regulation can have a higher average title insurance charge than states allowing free competition. This dissertation also tests whether regulation affects title insurance charges by influencing competition in the market and whether regulators' characteristics are related to the effect of regulation on charges. The test results imply that appointed commissioners can be associated with a higher average title insurance charge than elected commissioners. This dissertation provides insights into the title insurance regulatory reform in different states. More broadly, one methodology (multiple model for change) used in this dissertation simultaneously assesses regulation's over-time and state-by-state effects on title insurance charges, which contributes to the development of regulation evaluation methods. The outcomes of this dissertation can also provide empirical evidence to the theoretical debate of regulation versus competition. / text