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Head and neck injuries are common in contact sports. Proper function of the cervical spine sensorimotor system is important in limiting these injuries. Repetitive stress incurred during contact sport participation may negatively affect this system and increase injury risk. Currently, there is a paucity of research examining contact sport exposure and cervical spine sensorimotor function. The purpose of this study was to examine the effect of contact sport participation on cervical sensorimotor function. The independent variables were group (rugby, non-contact), sex (male, female), and time (pre-season, post-season). The primary dependent variable was neck position sense error as measured by total neck reposition (TNRE) error and maximum neck reposition error (MaxNRE). Secondary dependent variables included neck disability index, signs and symptom (S/S) number, symptom severity, concussion history, cervical range of motion, and isometric neck strength. This prospective observational study included forty-nine participants (15 male rugby, 11 female rugby, 11 non-contact male control, 12 non-contact female control) from Temple University campus recreation club sport teams. Athletes participated in two testing sessions, one prior to the season (i.e., pre-season) and one following the season. Data were analyzed using descriptive and inferential statistics. Independent-sample t-tests with Bonferroni corrections were used to assess statistically significant differences in dependent variables at pre-season between groups (Aim 1) and sex (Aim 2). Independent-samples t-tests with Bonferroni correction were also used to explore statistically significant differences in dependent variables change scores from pre-season to post-season between groups (Aim 1). Pearson correlations (r > .60) were used to assess potential covariates but none were identified. Pearson correlations were also used to evaluate the relationship between pre-season maximum and total neck reposition sense error and the following dependent variables: years of contact sport participation, concussion S/S number and severity score, global cervical range of motion and global cervical isometric strength (Aim 3). For Aim 1, between group differences were identified for global cervical isometric strength, t (1, 45) = 2.98, p = .005, and total joint reposition error t (1, 45) = 2.78, p = .008, only. There were no significant change score differences between groups across time. For Aim 2, sex differences were identified in years of contact sport exposure (p = .004), height (p < .001) and global isometric strength (p <.001), only. For Aim 3, preseason concussion S/S number and severity scores were significantly correlated (p < .05) with total joint reposition error (r = .352) and maximum joint reposition error (r = .476). The present study findings indicate a difference in cervical spine sensorimotor function between collegiate club rugby athletes and controls. Specifically, rugby athletes exhibited significantly greater neck reposition sense error than controls. Additionally, concussion S/S scores were related to reposition sense error. Differences in position sense error were not identified between males and females, however females did exhibit less neck strength mirroring previous reports. These findings suggest that exposure to contact sport-related impacts may lead to changes in cervical spine sensorimotor function. These changes are important as they could represent an increased risk of injury and can be modified proactively. A comprehensive cervical spine pre-season examination including concussion S/S and position sense assessments could identify individuals needing preventative intervention. Future research should explore the risk associated with these proprioceptive deficits and the benefits of proactive therapeutic intervention designed to mitigate sensorimotor deficits in contact sport athletes. / Kinesiology

The process of reversible growth arrest, otherwise known as cellular quiescence or the G₀ phase denoted by withdrawal from the cell cycle, is a poorly characterized state. Subsets of growth arrest-specific (GAS) genes are upregulated during quiescence, however, these subsets are specific to/dependent on the limiting factor or circumstance inducing growth arrest. Here I characterize the expression and regulation of the lipid trafficking GAS gene Fatty Acid-Binding Protein 4 in the quiescence-inducing conditions of contact inhibition and oxygen limitation (hypoxia). Chicken Embryo Fibroblasts (CEF) were cultured to high density or subjected to hypoxia, in which oxygen is the limiting factor inducing growth arrest, or serum starvation, in which nutrients is the limiting factor inducing growth arrest. Contact inhibition and hypoxia induced FABP4 expression, whereas cycling control CEF and serum depleted CEF did not. At higher, though still hypoxic, oxygen levels that did not robustly induce FABP4, proliferation assays showed a slight reduction in CEF proliferation. The GAS gene p20k lipocalin has been shown to exhibit similar expression patterns to FABP4, with its regulation determined by the presence of the transcription factor C/EBP-β. CEF overexpressing C/EBP-β also showed strong FABP4 induction. Furthermore, chromatin immunoprecipitation (ChIP) assays revealed that C/EBP-β bound directly to the FABP4 promoter in both normoxic and hypoxic cells, although only the latter condition induced FABP4 protein expression. In summary, these results suggest that FABP4 is induced during growth arrest specifically when oxygen is the limiting factor, as induction was not seen during growth arrest mediated by starvation-induced endoplasmic reticulum (ER) stress, where nutrients was the limiting factor. The induction of these hypoxia-responsive genes suggests that oxygen availability regulates the expression of a sub-class of growth arrest specific genes. Additionally, FABP4 was shown to be associated with growth arrest and the promotion of cell survival and proliferation, as depicted by proliferation assays. Lastly, C/EBP-β not only strongly induced FABP4 expression, but directly bound to the FABP4 promoter. This suggests that C/EBP-β is a regulator of FABP4, although there may be other interacting factors acting as activators or repressors as this FABP4-C/EBP-β interaction was observed in conditions permissive and non-permissive to FABP4 expression. / Thesis / Master of Science (MSc) / The process of reversible growth arrest is a poorly characterized state. Subsets of growth arrest-specific (GAS) genes are upregulated during quiescence, however, these subsets are specific to the limiting factor or circumstance inducing growth arrest. Here we characterize the expression and regulation of the lipid trafficking GAS gene Fatty Acid-Binding Protein 4 in the quiescence-inducing conditions of contact inhibition (CI) and hypoxia. Chicken Embryo Fibroblasts (CEF) were cultured to high density or subjected to hypoxia, in which oxygen is the limiting factor inducing growth arrest, or serum starvation, in which nutrients availability is the limiting factor. CI and hypoxia induced FABP4 expression, whereas control and serum depleted CEF did not. At higher, though still hypoxic, oxygen levels that did not robustly induce FABP4, proliferation assays showed a slight reduction in CEF proliferation. When overexpressing C/EBP-β, CEF showed strong FABP4 induction. Additionally, a direct interaction with the FABP4 promoter was observed in both normoxic and hypoxic cells, although only the latter condition induced expression. In summary, the induction of this hypoxia-responsive gene suggests that oxygen availability regulates the expression of a sub-class of growth arrest specific genes and that this induction may be regulated by C/EBP-β.

The radiological hazards from tritium are usually associated with exposure to tritium oxide either by inhalation, ingestion or permeation through skin. However, exposure from skin-contact with tritium gas contaminated surfaces represents a different radiological hazard in tritium removal facilities and future fusion power plants. Previous experiments on humans by Eakins et al. (8), and more recent experiments on hairless rats at Chalk River Laboratories have shown that when a tritium gas-contaminated surface is brought into contact with intact skin, high concentrations of organically-bound tritium in urine and skin are observed which were not seen from single tritiated water (liquid or vapour form) contamination. The results of the rat experiments, which involved measurements of tritium activity in urine and skin, after contact with contaminated stainless steel, are described. These results are also compared to previous data from human experiments. The effect of various exposure conditions and different contaminated surfaces such as brass, aluminum and glass are analysed and related to the results from contaminated stainless steel exposure. Dosimetric models are being developed in order to improve the basis for dose assessment for this mode of tritium uptake. The presently studied model is explained along with the assumptions and methods involved in its derivation. The features of 'STELLA', the software program used to implement the model, are discussed. The methods used to estimate skin and whole body dose from a model are demonstrated. Finally, some experiments for improving the accuracy of the model are proposed. Briefly, this study compares the results from animal and human experiments as well as different exposure conditions, and determine the range of whole body and skin dose that may be involved from skin-contact intake. This information is essential for regulatory purposes particularly in the derivation of doses for skin-contact contamination. / Thesis / Master of Science (MS)

Finite element simulation of contact/impact problems using the penalty method is a well-established capability. The automatic penalty stiffness provides an easy way to implement the contact analysis. However, this way in which the penalty stiffness is associated with the material property and geometry of the master surface can lead to inappropriate distributions of contact pressure at edges or mesh transitions, or even cause much numerical noise. A new method of defining the penalty stiffness, which is associated with geometry of the slave surface, the reference penetration and reference contact pressure, is developed to consistently relate forces on contacting nodes with the contact pressure. This technique is successfully applied to several examples as the clamping simulation during the punch test and the rolling process. The results of such applications of new contact stiffness model demonstrate the effectiveness of such a model in avoiding the stress edge effect and the accompanying numerical noise. As an alternative approach to define the penalty stiffness, this new model provides another option for the contact analysis and gives the users more possibilities to control the contact performance. / Thesis / Master of Engineering (ME)

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yes / The nature of the contact behaviour between a grinding wheel and a workpiece in the grinding process has a great effect on the grinding temperature and the occurrence of thermal induced damage on the ground workpiece. It is found that the measured contact length le in grinding is considerably longer than the geometric contact length lg and the contact length due to wheel-workpiece deflection lf. The orthogonal relationship among the contact lengths, i.e. lc2 = (Rrlf)2 + lg2, reveals how the grinding force and grinding depth of cut affect the overall contact length between a grinding wheel and a workpiece in grinding processes. To make the orthogonal contact length model easy to use, attempts on modification of the model are carried out in the present study, in which the input variable of the model, Fn’, is replaced by a well-established empirical formula and specific grinding power. By applying the modified model in this paper, an analysis on the contributions of the individual factors, i.e. the wheel/workpiece deformation and the grinding depth of cut, on the overall grinding contact length is conducted under a wide range of grinding applications, i.e. from precise/shallow grinding to deep/creep-feed grinding. Finally, using a case study, the criterion of using geometric contact length lg to represent the real contact length lc, in terms of convenience versus accuracy, is discussed.

This dissertation examines how multiple, hybridized literacy practices exist in the "contact zone" of the classroom, a "social space where cultures meet, clash, and grapple, with each other, often in contexts of highly asymmetrical relations of power, such as colonialism, slavery, or their aftermaths as they are lived out in many parts of the world today" (Pratt, 2002, p. 4). The rural high school English class under study here operates as such a "contact zone," as the teacher and students engage in conflicted negotiation, rather than assimilation or acculturation, when multiple literacy practices vie for recognition. Fieldnotes collected during two months of participant observation, collected artifacts in the form of student written texts, teacher syllabi and school documents, i.e., student handbooks, as well as interviews with three male students, one female student, one teacher, one special education aide, and a school principal provided the data for this study. Findings make problematic the beliefs that 1) literacy is a homogenous, static, singular either/or phenomenon, i.e., official school literacy or unofficial, and that 2) classrooms represent homogeneous, unified communities of obedient students who share literacy practices. Rather, classrooms, as "contact zones," can represent heterogeneous groups of students whose literacy practices are hybrid and intercultural, grafting together often reactionary, oppressive sociopolitical intentions with officially sanctioned literacy goals. This inquiry raises questions about literacy as only a local social practice, as well as literacy pedagogical discourses that students do not simply assimilate or acculturate, but contest, appropriate, resist, and use to harass and oppress others, even as they accomplish school literacy assignments. / Ph. D.