The LSH-study started in 2003 at the department of Health and Society at the University of Linköping. The purpose of the study was to examine the relationship between life condition, stress and health. A total of 1007 people from ten different health centres in Östergötlands län participated. At the follow up, a couple of years later, 795 of the 1007 participated. 127 of the 212 in the attrition turned down the follow up, twelve people were not invited (for example in case of death) and the rest did not respond at all. The purpose of this paper is to find out in what degree the attrition in the follow up can be predicted using the information from the first survey and which variables are important. The differences between different types of attrition have also been examined. Simple and multiple bi- and multinomial logistic regression have been used in the analysis. In total 34 variables were examined and in the final model six variables remained with a significant relation to the attrition. High BMI, regular smoking, high pulse and lack of daily exercise at the first survey were connected to a higher risk for an individual to not participate at the follow up. It is interesting that these factors are considered as risk factors for unhealthy living. Other factors related to a higher attrition were unemployment in the last year before the first survey and if the individual had parents born in another country than Sweden. The risk for attrition increased gradually when more risk factors were shown by the individual. The factors contributing an individual to turn down the follow up instead of not responding at all was if he or she were in the older age segments in the survey or if they were not active in any type of association.

A social network represents the interconnected relations among people. In a knowledge-intensive era as of now, people have less capability to resolve more ill-defined and complicated problems. Several researches indicate that under such a circumstance people are more likely to turn to other people through their social networks than to consult sources like databases and documents. Searching in social networks is therefore an essential issue. In addition, typical social networks are neither regular nor completely random ones, but instead, they are mixtures between these two, which are referred to as small worlds. Consequently, such an issue is also called the small world search. Search mechanism in the small world can be classified into single-attribute approach (e.g. best connected) and multiple-attribute approach (e.g. social distance). Relevant research works, however, are mostly based on acquaintance networks. And one of the problems to search in acquaintance networks is its high attrition rate that hinders further search and results in low success rate. On the other hand, in recent years several researchers focus on the constitution and propagation of trust networks that represent the trustworthy relations among people. Since trust implies much closer to what we mean friends rather than acquaintance, we believe that the attrition rate in trust networks should be lower than in acquaintance networks. Based on this belief, we propose to search in trust networks rather than acquaintance networks to enhance the quality of the search process. We design three experiments to compare the search performance in the trust networks and in the acquaintance networks. Experiment I is to examine the ¡§social-distance¡¨ search strategy we adopt in the search. The second experiment evaluates the performance comparison without considering attrition. Finally, we consider the attrition rate and attrition rate difference for the comparison. The results show that as long as the attrition rate difference is beyond 10%, search in trust networks performs better than in acquaintance networks. It therefore justifies the feasibility of our proposed approach in gaining good search performance.

Genetic studies of lung disease in Cystic Fibrosis are faced with the challenge of identifying a severity measure that accounts for chronic disease progression and mortality attrition. Further, combining analyses across studies requires common phenotypes that are robust to study design and patient ascertainment. This thesis uses data from the North American Cystic Fibrosis Modifier Consortium (Canadian Consortium for CF Genetic Studies (CGS), Johns Hopkins University Twins and Siblings Study (TSS), and University of North Carolina/Case Western Reserve University Gene Modifier Study (GMS)), to calculate two novel phenotypes using age-specific CF percentile values of FEV1 (Forced Expiratory Volume in 1 second), with adjustment for CF age-specific mortality. The normalized residual, mortality adjusted (NoRMA) was designed for population based samples, while KNoRMA, using Kulich percentiles, is robust to sample ascertainment; both account for the effects of age-related disease progression and mortality attrition. NoRMA was computed for 2122 patients representing the Canadian CF population. KNoRMA was computed for these 2122 patients and also 1137 extreme phenotype patients in the GMS study and 1323 patients from multiple CF sib families in the TSS study. Phenotype was distributed in all three samples in a manner consistent with ascertainment differences, reflecting the lung disease severity of each individual in the underlying population. The new phenotype was highly correlated with the previously recommended mixed model phenotype1; 2, but computationally much easier and suited to studies with limited follow up time. As an example of its use, KNoRMA was used to test the association between locus variants in a previously published candidate gene, Transforming Growth Factor β1(TGFβ1), and lung function in CF, in an attempt to provide insight into discrepant results in the literature. A disease progression and mortality adjusted phenotype reduces the need for stratification or additional covariates, increasing statistical power and avoiding possible interpolation distortions.

Teacher shortages are a critical issue for education, and agricultural education has not been exempt from this trend. Many factors possibly contribute to this lack of qualified teachers. Researchers suggest that retention practices, stress factors associated with agricultural education, and job satisfaction may be areas for improvement within the profession. A deeper understanding of the problems beginning teachers experience is a critical first step in raising the retention rate for new teachers. An original researcher-designed instrument based on Moir was composed of 66 items intended to measure induction-year teachers’ attitude toward teaching and was administered at six different points in time to induction-year agriculture teachers in Texas, Oklahoma, and New Mexico during the 2011–2012 school year. Data collection occurred via a mixed mode design following the Tailored Design Method. The overall response rate was 52.5% with 197 responses to the instrument. All 66 scale items from the original questionnaire were included in the principal component analysis (PCA) with varimax rotation; coefficients with an absolute value less than 0.45 were suppressed. The Kaiser–Meyer–Olkin (KMO) of sampling adequacy was 0.787 and Bartlett’s test of sphericity was significant (p < 0.001). Factor analysis yielded a nine factor solution using varimax rotation. Forty-five items composed the Agricultural Education Induction-Year Teacher Attitudinal Scale. Descriptive names for the constructs were the product of 20 experts in the field of agricultural education: “Professional Efficacy,” “Balanced Reflection,” “Professional Commitment,” “Professional Confidence,” “Anticipated Change,” “Work-Life Balance,” “Strategic Renewal,” “Problem Solving,” and “Professional Resolve.” Overall reliability coefficient for the proposed new instrument was 0.88. Overall attitude toward teaching was not statistically significantly different across measures. No significant predictors of attitude toward teaching based on selected demographic variables were generated as a result of forced entry regression. Grand mean scores per round did not statistically differ from one round to another. A model of induction-year agricultural education teacher’s attitudes was proposed along with a scale adjusted model of agricultural education teacher attitude toward teaching. A model of all attitude constructs was presented to illustrate the effect of time on the attitude of the induction-year agricultural education teachers.

In 2007, the National Center for Education Statistics (NCES) reported in their 2004-2005 Teacher Follow-up Survey that nearly 20% of U.S. teachers leave the profession after their first year of teaching and almost 30% leave after the fourth year of teaching. These percentages are even greater for mathematics teachers. Using symbolic interactionism, adult learning, and partnership as a theoretical framework, this ethnographic case study investigated and examined the factors that influenced second-career mathematics teachers to remain in the teaching profession and their experiences with instructional coaching. The following guiding research question and sub-questions were pursued in the study: Why have four second-career mathematics teachers remained in their role for 5 or more years? What are the teachers’ experiences with instructional coaching? How would they describe coaching? Which aspects of coaching do the teachers find least and most beneficial? How would you improve the coaching program? A purposeful sampling was used in the selection of participants. The four participants were African-American mathematics teachers; three women and one man. The participants are second-career teachers, and they all have been coached. The research is based on data collected from teacher narratives, participant observation, photo elicitation, and focus groups. Data were analyzed and categorized as follows: making a difference in a student’s life, teacher resiliency, job satisfaction, and support. Data analysis showed evidence of all four factors of retention for one or more of the participants, although the factors have varying degrees of influence.

Longitudinal substance abuse research has often been compromised by high rates of attrition, thought to be the result of the lifestyle that often accompanies addiction. Several studies have used a standardized follow-up protocol to minimize attrition, however it is unclear whether this protocol is equally effective for participants struggling with varying levels of housing stability, support for sobriety, and substance abuse severity. The current study extends research supporting the effectiveness of this protocol by demonstrating the importance of two central aspects of the follow-up protocol: locator form completion and continual verification contacts. Results indicated that each additional piece of locator form information and verification contact significantly and independently increased the odds for completing a follow-up interview, and that these effects were not moderated by participant characteristics. Practical and theoretical implications for longitudinal substance abuse research are discussed.

This study sought to understand why some students at Eagle University (pseudo.) complete the doctoral program in instructional technology while others do not. The study explores factors and issues affecting doctoral attrition and completion of the Ph.D. in instructional technology (IT) in the College of Education at Eagle University, a major research university with very high research activity. Participants in the study were eleven former doctoral students from Eagle University (pseudo.), six of whom met the requirements for graduation (completers) and five of whom ended the pursuit of the doctoral degree in instructional technology at EU (non-completers). A qualitative study informed by phenomenology, the purpose of the study was to explore these phenomena from the perspective of the students. Postmodernism served as the theoretical framework. Participants were interviewed using the structured interview guide developed by the researcher. Two important findings were that only one of the eleven students knew what to expect from the program; and that completers were more likely to report that their primary motivation for pursuing the Ph.D. was for personal satisfaction. Recommendations were made based on student feedback, and included implications for students as well as implications for the university/program. Examples of advice for students were: 1) contemplate their goal(s) in pursuing the Ph.D. and consider the impact if something happened to alter that goal, and 2) seek out doctoral support groups and begin to establish relationships with current members. Two selected recommendations for the university/program were 1) develop a pre-application seminar or eLearning module to provide potential doctoral students with a realistic understanding of the program, and 2) consider developing a mentoring program that matched more experienced students or non-advisory professors to new students. Results of the study indicated that multiple factors affected both completers and non-completers; and these factors were often similar. However, among the key factors separating completers from non-completers were the determination of the student and the quality of the advisor relationship.

This thesis describes results of a study aimed at developing and evaluating attrition resistant iron catalysts prepared by spray drying technique. These catalysts are intended for Fischer-Tropsch (F-T) synthesis in a slurry bubble column reactor (SBCR). One of the major challenges associated with the use of SBCR for this purpose is the problem of catalyst/wax separation. If the catalyst particles break up into smaller ones during the F-T synthesis, these small particles (>5-10 &#61549;m in diameter) will cause problems with the catalyst/wax separation. Several research groups have worked on development of attrition resistant spray-dried iron catalysts, and methodology to measure and predict their attrition behavior. However, these attrition tests were not conducted under conditions representative of those encountered in a SBCR. In this work, the attrition behavior of six spray-dried catalysts and two precipitated catalysts was evaluated under slurry reaction conditions in a stirred tank slurry reactor (STSR). Spray-dried catalysts used in this study were prepared at Texas A&M University (TAMU) and at Hampton University (HU), employing different preparation procedures and silica sources (potassium silicate, tetraethyl orthosilicate or colloidal silica). The attrition properties of F-T catalysts were determined by measuring particle size distribution (PSD) of catalysts before and after F-T synthesis in the STSR. This provides a direct measure of changes in particle size distribution in the STSR, and accounts for both physical and chemical attrition effects. Also, scanning electron microscopy (SEM) was used to investigate the mechanism of attrition - erosion vs. fracture, and to obtain morphological characteristics of catalysts. Spray dried 100Fe/3Cu/5K/16SiO2 catalyst (WCS3516-1), prepared from wet precursors using colloidal silica as the silica source, was the best in terms of its attrition strength. After 337 hours of F-T synthesis in the STSR, the reduction in the average particle size and generation of particles less than 10 &#61549;m in diameter were found to be very small. This indicates that both particle fracture and erosion were insignificant during testing in the STSR. All other catalysts, except one of the spray dried catalysts synthesized at Hampton University, also had a good attrition resistance and would be suitable for use in slurry reactors for F-T synthesis.

Extensive research has been conducted on college student retention and graduation and many studies have found certain characteristics to be predictive of successful completion of college. However, few studies have focused on a target population which is primarily Hispanic. This study examined the 1990 entering freshmen class of students at Texas A&M University-Kingsville (TAMUK), of which more than 68% were Hispanic. An attempt was made to examine characteristics that would predict success, defined as graduation from TAMUK. Data derived from institutional records and the Texas Higher Education Coordinating Board were examined using descriptive statistics and stepwise multiple logistic regression. Pre-college characteristics studied included age, gender, ethnicity, marital status, high school GPA (Grade Point Average), high school class rank, high school of origin, county of origin, and American College Test (ACT) and the Scholastic Assessment Test (SAT) scores. In-college characteristics studied included residency status, admission status, enrollment status, number of hours enrolled fall 1990, college major, the Texas Academic Skills Program (TASP) scores, developmental courses, semester GPA??s, academic standing, and finally, attrition, transfer or graduation status. The fall 1990 entering students were evenly divided between males (53.4%) and females (46.6%), were young (79% were age 19 or less), single (91.4%), and Hispanic (68.2%). Almost half (46%) of the students came from high schools within 50 miles of Kingsville. The mean college entrance exam scores (ACT=16.76 and SAT=766) were well below the national means of 21 and 999, respectively. Of the 1106 entering freshmen, 307 (27.7%) graduated from TAMUK within the 10 years under study. An additional 490 (44.3%) transferred to other state institutions, and 309 (27.9%) dropped out of TAMUK and did not enroll in any other state college or university. The fall-tospring attrition rate was only 16.5%; however, the fall-to-fall attrition rate was 50.0% at the end of the first year. Stepwise multiple logistic regression (backward) analysis revealed that only high school GPA and the ACT composite score were statistically significant predictors of graduation.

<p>The LSH-study started in 2003 at the department of Health and Society at the University of Linköping. The purpose of the study was to examine the relationship between life condition, stress and health. A total of 1007 people from ten different health centres in Östergötlands län participated. At the follow up, a couple of years later, 795 of the 1007 participated. 127 of the 212 in the attrition turned down the follow up, twelve people were not invited (for example in case of death) and the rest did not respond at all. The purpose of this paper is to find out in what degree the attrition in the follow up can be predicted using the information from the first survey and which variables are important. The differences between different types of attrition have also been examined. Simple and multiple bi- and multinomial logistic regression have been used in the analysis.</p><p>In total 34 variables were examined and in the final model six variables remained with a significant relation to the attrition. High BMI, regular smoking, high pulse and lack of daily exercise at the first survey were connected to a higher risk for an individual to not participate at the follow up. It is interesting that these factors are considered as risk factors for unhealthy living. Other factors related to a higher attrition were unemployment in the last year before the first survey and if the individual had parents born in another country than Sweden. The risk for attrition increased gradually when more risk factors were shown by the individual. The factors contributing an individual to turn down the follow up instead of not responding at all was if he or she were in the older age segments in the survey or if they were not active in any type of association.</p>