Thesis (M.A.)--York University, 2002. Graduate Programme in Psychology. / Typescript. Includes bibliographical references (leaves 72-82). Also available on the Internet. MODE OF ACCESS via web browser by entering the following URL: http://wwwlib.umi.com/cr/yorku/fullcit?pMQ71569.

Gaits have become an integral part of the design method of robots heading to complex terrains. But research into optimal ways to transition between different gaits is still lacking, and is the primary motivation behind this research. An essential characteristic of gaits is periodicity, and considering that a novel notion of graceful transition is proposed: a graceful transition is one that has maximally persisting periodicity. This particular notion of persistence in the characteristic behavior can be generalized. Therefore, a comprehensive framework for the general problem of connecting any two trajectories of a dynamical system, with an underlying characteristic behavior, over a finite time interval and in a manner that the behavior persists maximally during the transition, is developed and presented. This transition is called the Gluskabi Raccordation, and the characteristic behavior is defined by a kernel representation. Along with establishing this framework, the kernel representations for some interesting characteristic behaviors are also identified. The problem of finding the Gluskabi Raccordations is then solved for different combinations of characteristic behaviors and dynamical systems, and compact widely applicable results are obtained. Lastly, the problem of finding graceful gait transitions is treated within this newly established broader framework, and these graceful gait transitions are obtained for the case of a two-piece worm model.

Increasing women's participation in the fields of science, technology, engineering and mathematics (STEM) can promote a healthy economy by ensuring a diverse and well-qualified STEM workforce, not only in the quantity of females in the workforce, but diversity in thinking and creativity. It will also send a positive message to young women about the breadth of educational opportunities and career choices they have available to them. However, women continue to participate in engineering education in a far lower rate than men. Attracting and retaining female students has become a challenging problem for the academic engineering community. In this study, a classic model of student withdrawal is presented as a theoretical framework for examining the relationships between the environment and the people in undergraduate engineering departments, and how they can influence students' commitment to and persistence in their program. A sample of 1,369 engineering undergraduates enrolled in eight Florida universities participated in a survey assessing the climate of the engineering department, the socialization process, student commitment and withdrawal intentions. The results of a factor analysis reveal that faculty support, a sense of community, and encouraging and valuing diversity are all important elements of a climate for retention. In general, women perceived the academic climate as being less supportive than men did, reported lower levels of commitment, and greater withdrawal intentions. These climate factors, as well as socialization, also played a significant role in predicting the levels of student commitment to their program, and their intentions to withdraw or persist in their academic goals. However, there was little evidence for a moderating role of gender in these relationships. This research suggests the importance of having a supportive faculty and fostering a sense of community among students, both of which aid in the successful socialization of engineering students, and ultimately promote commitment and persistence.

A review of the literature indicates that Latinos lag behind Whites and Blacks in college degree attainment. This educational disparity is of concern because Latinos are currently the largest minority group in the United States, and the Latino population is expected to increase exponentially in the future. College degree attainment for Latinos is imperative because statistics show an undeniable relationship between degree attainment and income level. In order to ensure the economic wellbeing of Latinos, it is important that Latinos persist through college degree programs. This is especially true for Puerto Ricans because they are the second largest Latino subgroup. The majority of college persistence and departure literature applies to students in general and some of the studies focus on Latino College students. However, fewer studies explore the perspectives of Latinos with the process of graduate or doctoral degree attainment. This is especially true of Latinos of specific ethnic backgrounds such as Cuban, Mexican, or Puerto Rican. I conducted this study in order to address this gap in the literature. This study described and explained the perspectives of a purposive sample of Puerto Rican doctoral graduates on their education by exploring those social and cultural factors that influenced their perceptions, and served as educational facilitators or barriers to their doctoral attainment. The questions that guided the study were: 1.What are the components of their perspectives? and; 2. What social-cultural variables influenced their perspectives?  In order to answer the research questions, I interviewed eight Puerto Ricans with doctorates who were affiliated with the GOTHAM educational system in the state of New York. In order to collect the data, I went to New York in February and March 2010 and conducted face to face interviews with the participants, which were recorded. After I recorded the interviews, I transcribed the data, which I analyzed using a software program called Atlas.ti. I analyzed the data by coding the excerpts, which I identified as the subthemes or variables of this study. The subthemes were coalesced into major themes, which were validated by peer review, several iterations of member check, and data triangulation. After coming to a consensus at all levels of validation, I determined that the emergent themes were in fact evidence of the components of the perceptions of the participants‟ experiences with doctoral attainment. Those components are Personal Factors, Social Role Factors, Cultural Factors, and Social Factors. Based on the analysis of the data, the most profound influence to the perception of the participants‟ lived doctoral experiences was that of the interaction of being a doctoral student, or Adult Learner, with at least one other social role. The most commonly reported negative interaction was being an Adult Learner and a Worker at the same time. Having a lack of Finances, No Latino Role Models, experiencing Negative Events by Ethnicity, and struggling with Self-Efficacy served as barriers to most of the participants. Having Peer Networks and Faculty Support served as facilitators to most of the participants. In order to add to the usefulness of this study, I asked the participants for their advice to future or current doctoral students, and for suggestions to faculty and administrators of higher education. I included their responses as part of this study.

Based on a model that considers self-control (SC) to be a limited resource, research suggests that diminished SC resources increase the likelihood of smoking. Yet, no study has evaluated how smoking affects SC resources. This study used a randomized, 2 x 2 crossed factorial (SC depletion manipulation X smoking manipulation), between-subjects design to test the hypothesis that smoking restores depleted SC resources. To manipulate SC depletion, half of the 132 dependent smokers were instructed to suppress their emotional reaction to a brief video depicting environmental damage (i.e., Depletion), whereas the other half were instructed to “act natural” (i.e., No Depletion) during viewing. Half of the participants in each condition then smoked a cigarette, whereas the other half sat patiently, without smoking (i.e., Smoke vs. No Smoke). All participants then completed two behavioral measures of SC (Mirror Tracing Performance Task: MTPT; and breath-holding). As hypothesized, a disordinal interaction occurred between the Depletion and Smoking manipulations for duration of time spent on the MTPT. That is, participants in the depletion condition showed less persistence on the MTPT, unless they were permitted to smoke. There was no evidence for mediation of this effect from the influence of smoking on affect and/or urge. Thus, smoking appeared to restore depleted SC resources, independent of its effects on self-reported affect and urge. Findings suggest that restoration of SC resources may represent another form of negative reinforcement from smoking that may play a role in nicotine dependence, and could inform treatment development.

Student persistence and achievement are areas of significant concern for institutions of higher education. With national college graduation rates hovering in the 50% range, it is important for colleges and universities to understand which student characteristics and campus environments lead to greater success, as well as the expectations students have of the college experience. Research on undeclared students is vast and dates back more than 70 years, and many of the seminal studies and respected research data have led to the perception that they are at higher risk of attrition and have lower levels of academic achievement than their declared peers. Research also shows that the two most important ways to help students connect to institutions is through faculty interactions and involvement in clubs and organizations. A new and growing body of research on student expectations posits that students who have unmet expectations of the college experience are also at higher risk of attrition. This study sought to integrate those three research concepts and analyze the expectations of undeclared students to determine if undeclared students had lower expectations of the college experience than their declared peers, specifically as those expectations relate to interactions with faculty and involvement in clubs and organizations. This study also sought to determine if undeclared students had lower levels of academic achievement or persistence than their declared peers. Using the College Student Expectations Questionnaire (CSXQ), this research analyzed the expectations of 3,219 first time in college (FTIC) students at a large, metropolitan, public university in the South who responded to the CSXQ during summer 2008 orientation. Results indicated that although differences were discovered between undeclared and declared students for expectations of student-faculty interaction and for expectations of involvement in clubs and organizations, the low effect sizes indicated that the differences could not be attributed directly to declaration of major. Results also indicated that undeclared students did not persist at rates statistically significantly different than their declared peers, nor did they achieve lower GPAs or fewer credit hours. While this study did not reveal statistically significant differences for any of the dependent variables, this research is beneficial in that these results contribute to the research findings that undeclared students are not attrition prone or less likely to achieve. More current research is needed on the population of undeclared students to determine if the perceptions are outdated and no longer generalizable to today's generation of students. Additionally, more research is needed on the expectations of students, in general, to determine what impact, if any, those expectations have on student interactions with the college environment and on the outcomes of persistence, achievement, and graduation.

This thesis is divided into two independent parts. The first part concerns the 3D Navier-Stokes equations. The second part deals with regularity issues for a family of integro-differential equations. In the first part of this thesis, we consider weak solutions of the 3D Navier-Stokes equations with L² initial data. We prove that ([Nabla superscript alpha])u is locally integrable in space-time for any real [alpha] such that 1 < [alpha] < 3. Up to now, only the second derivative ([Nabla]²)u was known to be locally integrable by standard parabolic regularization. We also present sharp estimates of those quantities in local weak-L[superscript (4/([alpha]+1))]. These estimates depend only on the L² norm of the initial data and on the domain of integration. Moreover, they are valid even for [alpha] ≥ 3 as long as u is smooth. The proof uses a standard approximation of Navier-Stokes from Leray and blow-up techniques. The local study is based on De Giorgi techniques with a new pressure decomposition. To handle the non-locality of fractional Laplacians, Hardy space and Maximal functions are introduced. In the second part of this thesis, we consider non-local integro-differential equations under certain natural assumptions on the kernel, and obtain persistence of Hölder continuity for their solutions. In other words, we prove that a solution stays in C[superscript beta] for all time if its initial data lies in C[superscript beta]. Also, we prove a C[superscript beta]-regularization effect from [mathematical equation] initial data. It provides an alternative proof to the result of Caffarelli, Chan and Vasseur [10], which was based on De Giorgi techniques. This result has an application for a fully non-linear problem, which is used in the field of image processing. In addition, we show Hölder regularity for solutions of drift diffusion equations with supercritical fractional diffusion under the assumption [mathematical equation]on the divergent-free drift velocity. The proof is in the spirit of Kiselev and Nazarov [48] where they established Hölder continuity of the critical surface quasi-geostrophic (SQG) equation by observing the evolution of a dual class of test functions. / text

Many higher education institutions offer first-year college students the opportunity to participate in second-year retention programs in order to support the persistence of college students who seek assistance in navigating the college experience. Research regarding the traits that characterize second-year students and what the second-year experience entails is still in progress. (Braxton, 2000; Hunter et al. 2009; Schaller, 2000, 2005, 2010; Schreiner & Pattengale, 2000). While the existing research has built the foundation for research around the second-year experience, additional research is required to compose a truly holistic picture of the second-year experience. The purpose of this study is to identify the characteristics of first-year students who choose to apply to second-year retention programs and why they choose to apply to such programs. The study will address three research questions. 1. What are the characteristics of students who apply to participate in a second-year retention program? 2. What student noncognitive variables reflect which students apply to participate in a second-year retention program? 3. What factors do first-year students consider when determining whether or not they will participate in a second-year retention program? A mixed methods explanatory design (Cresswell & Plano-Clark, 2007) was implemented to investigate the research questions. The research population was composed of 337 first-year college students, primarily first generation students and students of color, eligible for participation in a second-year retention program at a large research institution in the western United States. This study hopes to contribute to a greater understanding of the characteristics of first-year students who choose to apply to participate in second-year retention programs and why they choose to apply. The findings can inform universities as to how they can offer more effective support of second-year students in a manner relevant to their needs. / text

The main purpose of this study was to evaluate medication use patterns (i.e., dose escalation, medication adherence, persistence, and switching) of rheumatoid arthritis (RA) patients on etanercept (ETN), infliximab (IFX) or adalimumab (ADA) and the associated healthcare utilization costs using Texas Medicaid data. Study participants were Medicaid beneficiaries (18-63 years) with an RA diagnosis (ICD-9-CM code 714.0x) who had no claim for a biologic agent in the 6-month pre-index period (July 1, 2003 - Dec 31, 2010). The index date was the first date when the patient had the first fill for any of the study TNF inhibitors (ETN, ADA or IFX) within the study identification period (Jan 1, 2004 – Aug 31, 2010). Data were extracted from July 1, 2003 to August 31, 2011. Prescription and medical claims were analyzed over an 18-month study period (i.e., 6-month pre-index and 12-month post-index periods). The primary study outcomes were adherence, persistence, dose escalation, switching and cost (i.e., total healthcare, RA-related and TNF inhibitor therapy cost). The study covariates were demographic factors (age, gender, race/ethnicity), pre-index use of other RA-related medications (pain, glucocorticoids and disease modifying antirheumatic drugs), total number of non-study RA-related medications used at index, pre-index RA and non-RA related visits, pre-index healthcare utilization cost and Charlson Comorbidity Index score. Conditional regression analyses, which accounts for matched samples, were used to address the study objectives. After propensity score matching, 822 patients (n=274/group) comprised the final sample. The mean age (±SD) was 48.9(±9.8) years, and the majority of the subjects were between 45 and 63 years (69.2%), Hispanic (53.7%) and female (88.0%). Compared to patients on ETN, the odds of having a dose escalation were ≈ 5 [Odds Ratio= 4.605 [95% CI= 1.605-12.677], p=0.0031] and ≈ 8 [Odds Ratio=7.520, [95% CI= 2.461-22.983], p=0.0004] times higher for IFX and ADA patients, respectively, while controlling for other variables in the model. Compared to ETN, patients on IFX (p=0.0171) were more adherent while adherence was comparable with patients on ADA (p=0.1144). Compared to patients on ETN, the odds of being adherent (MPR ≥ 80%) to IFX was ≈ 2 times higher [Odds Ratio= 2.437, [95% CI=1.592-3.731], p < 0.0001] while controlling for other variables in the model. Persistence to index TNF inhibitor therapy and likelihood to switch or discontinue index TNF inhibitor therapy were comparable among the 3 study groups. In addition, the duration of medication use (i.e., persistence) prior to switching or discontinuation of index therapy was comparable among the 3 study groups. Furthermore, for each of the cost variables (total healthcare, RA-related and TNF inhibitor therapy cost), costs incurred by patients on ETN were significantly lower (p < 0.01) than those incurred by ADA patients but significantly higher (p < 0.01) than those incurred by IFX patients. Finally, a positive and significant relationship (p < 0.0001) was found between RA-related healthcare cost, adherence and persistence to TNF inhibitor therapies. In conclusion, ETN was associated with lower rates of dose escalation compared to ADA or IFX. However, adherence was better and associated healthcare costs were lower with IFX. Clinicians should endeavor to work with each individual patient to identify patient-specific factors responsible for poor medication use behaviors with TNF-inhibitor therapies. Reducing the impact of these factors and improving adherence should be included as a major part of the treatment plan for each RA patient. RA patients need to be adequately educated on the importance of adhering and persisting to their TNF-inhibitor therapy as poor medication adherence/persistence negatively impacts the RA disease process. / text

In light of drastically escalating costs for today’s medications, pharmacy benefit managers are seeking a constant balance of effectiveness and cost control. Step Therapy helps to address these concerns with a try medication “A” before medication “B” logic. Like all medical interventions, the possibility of unintended consequences exists. The purpose of this study was to determine if non-adherence results from application of Step Therapy for selected medication classes (antihyperlipidemics (specifically the HMG Co-A reductase inhibitors), angiotensin receptor blockers, uro-selective alpha-blockers, and dipeptidyl peptidase-4 inhibitors) in the Department of Defense. Using a retrospective database analysis, this study examined the primary adherence rate of subjects after they have been denied coverage due to Step Therapy intervention. Additionally, this study examined the association of demographic and service-related factors with the likelihood that a patient will be non-adherent after encountering the intervention. Finally, the study measured the time to adherence after intervention for those who were persistent after a Step Therapy claim rejection. STATA version 10.0 was used to conduct logistic regression analyses to meet the study objectives. After examination of 279,508 claims for 27,202 subjects, the estimated primary non-adherence rate following the Step Therapy intervention for all medication classes combined was 15.1%. Additionally, there was inter-class variability in this rate ranging between 13.1% and 19.5%. A statistical and practical difference was also noted in non-adherence rates between subjects who received care at the retail point of service versus those who received care at the mail order point of service. Subjects who received care through retail were nearly twice as likely to be non-adherent as those who received care in the mail order segment. For those subjects who were persistent with therapy, the median time-to-fill was estimated at 7 days. The occurrence of non-adherence following a Step Therapy intervention was clearly demonstrated through this study. Although this study provides good framework for designing interventions after claim rejection, further research would help to determine the health impact of primary non-adherence as well as the economic consequences of the intervention. / text