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Long Term Property Prediction of Polyethylene Nanocomposites

Long Term Property Prediction of Polyethylene Nanocomposites

Date: December 2008
Creator: Shaito, Ali Al-Abed
Description: The amorphous fraction of semicrystalline polymers has long been thought to be a significant contributor to creep deformation. In polyethylene (PE) nanocomposites, the semicrystalline nature of the maleated PE compatibilizer leads to a limited ability to separate the role of the PE in the nanocomposite properties. This dissertation investigates blown films of linear low-density polyethylene (LLDPE) and its nanocomposites with montmorillonite-layered silicate (MLS). Addition of an amorphous ethylene propylene copolymer grafted maleic anhydride (amEP) was utilized to enhance the interaction between the PE and the MLS. The amorphous nature of the compatibilizer was used to differentiate the effect of the different components of the nanocomposites; namely the matrix, the filler, and the compatibilizer on the overall properties. Tensile test results of the nanocomposites indicate that the addition of amEP and MLS separately and together produces a synergistic effect on the mechanical properties of the neat PE Thermal transitions were analyzed using differential scanning calorimetry (DSC) to determine if the observed improvement in mechanical properties is related to changes in crystallinity. The effect of dispersion of the MLS in the matrix was investigated by using a combination of X-ray Diffraction (XRD) and Scanning Electron Microscopy (SEM). Mechanical measurements were correlated to ...
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A Longitudinal Examination of Factors Associated with Custodial Grandparenting: A Test of Moderated Mediation

A Longitudinal Examination of Factors Associated with Custodial Grandparenting: A Test of Moderated Mediation

Date: December 2009
Creator: Moske, Amanda Kay
Description: The purpose of this study was to explore the following relationships: (a) how moderating factors (gender, age, ethnicity, social support, marital status, reason for role assumption and number of grandchildren in the home) can influence the mediating role of resiliency, and (b) how resiliency may mediate the negative effects of raising grandchildren (role demands, life disruptions, and difficulties with grandchildren) on grandparent adjustment over time. Resiliency was hypothesized to have the greatest effect on custodial grandparents who experienced the most stress (i.e., older, single, Caucasian males lacking social support and raising more than one grandchild). Mediation was assessed using structural equation modeling. Results indicated resilience mediated the relationship between role assumptions (i.e., role demands and life disruptions) and grandparent adjustment; however, resilience did not mediate the relationship between grandchild characteristics and grandparent adjustment. Due to the small number of custodial grandfathers (n = 14), non-married grandparents (n = 29), non-Caucasian grandparents (n = 10), the small number of grandparents who assumed the custodial role for less ambiguous reasons (n = 24), and the number of custodial grandparents with more than one grandchild residing in the home (n = 29) participating within the study, hierarchical multiple regressions were only conducted to ...
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A Longitudinal Investigation of Different Exercise Modalities on Social Physique Anxiety

A Longitudinal Investigation of Different Exercise Modalities on Social Physique Anxiety

Date: August 1995
Creator: Diehl, Nancy S. (Nancy Sue)
Description: The current study examined if students' levels of social physique anxiety vary depending on the type of exercise setting they select. The study determined the degree to which social physique anxiety changed over the course of semester-long involvements in different exercise settings.
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A Longitudinal Study of Graduation, Retention, and School Dropout for Students in Regular and Special Education

A Longitudinal Study of Graduation, Retention, and School Dropout for Students in Regular and Special Education

Date: May 1998
Creator: Smith, Karen S., 1948-
Description: This study examined differences in retention, graduation, and dropout between students in grades 9-12 in special education and regular education in the state of Texas for school years 1992-93 through 1995-96. The purpose was to gather information regarding the possible adverse effects of increased academic standards and mandatory testing on students with disabilities. The results indicate that when compared to students in regular education, students with disabilities are significantly more likely to be retained and are not experiencing the same decline in dropout rates as regular students. There is no indication that students with disabilities have been adversely affected by school reform but the size of the school district may play a significant role in whether or not students with disabilities dropout of school.
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A Longitudinal Study of Juvenile Facility Directors' Job Satisfaction Levels in the United States

A Longitudinal Study of Juvenile Facility Directors' Job Satisfaction Levels in the United States

Date: August 2006
Creator: Skertich, Jonathan David
Description: This national study, focusing on job satisfaction within juvenile facility directors, was conducted by the means of a survey. The study is longitudinal in nature; the survey was conducted in 1995 and 2000. Other past studies have focused on line level employees, guards, and the juveniles, but few have concentrated on juvenile facility directors. Literature on directors is currently lacking, this continuous study will give a better ongoing perspective of their attitudes and beliefs. Findings from this particular study will help to address current concerns inside of the system, starting at the apex. The survey's goal is to correlate factors that have a direct impact on their job satisfaction. Results indicate that staff issues have a dramatic impact on a director's job satisfaction.
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Longitudinal Study of Loneliness and Depression as Predictors of Health in Mid- to Later Life

Longitudinal Study of Loneliness and Depression as Predictors of Health in Mid- to Later Life

Date: May 2008
Creator: Chlipala, M. Linda
Description: The longitudinal relationship between loneliness and depression as predictors of chronic health conditions in middle-aged to older adults was investigated utilizing data collected by the Health and Retirement Study (HRS), a national representative longitudinal study of health, retirement, and aging, conducted by the Institute for Social Research (ISR) Survey Research Center (SRC) at the University of Michigan, funded by the National Institute on Aging and the Social Security Administration. The correlation between these loneliness and depression was moderate (r = .32 to r = 51). The single-item subjective self-report of loneliness was found to be an adequate measure of loneliness. A cross-lagged panel correlation and regression design was used to examine the longitudinal relationship between loneliness, depression, and chronic health conditions. A temporal precedence was indicated implying a causal relationship with depression leading to subsequent loneliness. The relationship between recurring loneliness and chronic health conditions was weak (r = .13).
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A Longitudinal Study of Rape Attitude Correlates among College Men

A Longitudinal Study of Rape Attitude Correlates among College Men

Date: May 2006
Creator: Howe-Martin, Laura S.
Description: Research has linked rape victim-blaming attitudes (VBAs) with gender role stereotyping, negative peer attitudes towards women, and acceptance of interpersonal violence. The current study analyzed longitudinal questionnaire data of college men (n=166) from White and Smith's (2001) study of college student victimization. Results indicate that VBAs can be conceptualized as either overt or covert, and that the covert VBA was more strongly correlated with alcohol use, sexualized peer attitudes, traditional gender stereotypes, need for sexual dominance, and perpetration of dating aggression. The covert VBA was also correlated with rape proclivity one year later, and partially mediated relationships between earlier variables and later rape proclivity. Additionally, endorsement of chivalry moderated the relationship between traditional gender stereotypes and the covert VBA, casting new perspective on the role of chivalry. Overall, results demonstrate the importance of targeting subtle expressions of VBAs in educational programs, and the need for longitudinal studies on rape attitude development.
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Longitudinal Study of the Impact of Performance Appraisals in Organizations

Longitudinal Study of the Impact of Performance Appraisals in Organizations

Access: Use of this item is restricted to the UNT Community.
Date: May 2006
Creator: Herreid, Cheryl
Description: The purpose of this study was to determine the effectiveness of and the subjects' overall satisfaction with the implementation of an internally created performance appraisal system. The system was implemented at a major technology consulting firm in the US. The subjects of this study were manager level employees of the firm. An employee survey conducted annually at the firm included questions relating to the implementation of the performance appraisal system. Eight years of managers' responses to six key questions in the Career Development category were analyzed. Managers' perceptions of their contribution to the firm, their understanding of what career paths are available to them, their understanding of the requirements for promotion, as well as their overall satisfaction with the implementation of the performance appraisal system were captured by this survey. Trend analysis indicates that managers at the firm perceived their career path knowledge improved and their understanding of promotion criteria improved as a result of the implementation. Overall satisfaction with the implementation did not improve enough to site confidence in managers' perceptions for the period immediately after the implementation; managers' responses to the actual implementation were disagreeable to neutral. Managers did not feel their impact on the organization improved as ...
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Longitudinal Study to Assess the Impact of Instructor-Based Training Versus Computer-Based Training on User Performance: A Field Experiment

Longitudinal Study to Assess the Impact of Instructor-Based Training Versus Computer-Based Training on User Performance: A Field Experiment

Date: August 1996
Creator: Desai, Mayur S.
Description: The purpose of this study is to investigate the relationships between selected end-user training programs corporations provide to their employees and subsequent employee performance based on these opportunities.
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Loose Id for Orchestra

Loose Id for Orchestra

Date: August 1996
Creator: Bryant, Steven 1972-
Description: Loose Id, scored for orchestra (piccolo, 2 flutes, 2 oboes, 2 clarinets in B-flat, B-flat contrabass clarinet, 2 bassoons, contrabassoon, 4 horns in F, 3 trumpets in B-flat, 2 trombones, 1 bass trombone, tuba, timpani, percussion (3 parts), violin I, violin II, viola, violoncello, and contrabass), is an abstract realization in sound of the energy of the Id. Unleashed, without the counterbalance of Ego or Superego, the Id generates unbridled instinctual energy, resulting in an orgiastic frenzy. Distinct from a state of dementia, this piece represents a thoroughly lucid and intentional rampage of self-indulgence. The accompanying essay examines the underlying structural principles of Loose Id, focusing on how they aid the creation of the overall experience of the piece. Particular attention is given to the concepts of linearity and nonlinearity and their roles in different levels of creative and listening processes.
Contributing Partner: UNT Libraries