Browsing by Author "Song, Wei"
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Item Microscopic and thermal characterization studies of heterogeneous biocatalysis: polyurethane film immobilized enzymes and degradation of algal cells.(2011-07) Song, WeiHeterogeneous biocatalysis, associated with either solid-state biocatalyst systems or solid-state substrate systems, has garnered a lot of interest for chemical synthesis, bioseparation, and biosensing. In the pursuit of high efficiency, the characterization of the physical structure of solid-state biocatalysts and solid-state substrates is necessary to provide detailed information and deepen the understanding for the heterogeneous biocatalytic systems. In this study, microscopic and thermal analytical methods were utilized to characterize the physical structure of solid-state biocatalysts and solid-state substrates. Particularly, we chose the versatile polymer polyurethane (PU) to immobilize enzymes as model solid-state biocatalysts. Two important physical properties, enzyme distribution and glass transition temperature (Tg), were analyzed. It was found that several preparation parameters, including hydrophobic/hydrophilic properties of resin and cross-linker for PU film, weight ratio of starting materials, and mixing speed, showed significant influences on enzyme distribution and Tg. Using microscopic and thermal characterization methods, we further studied the integrity of enzyme-containing PU film against water. The enzyme was found prone to leak from the PU film, indicating incompleteness of cross-linking with PU. Several approaches (e.g., increasing the reaction time and using a hydrophilic cross-linker) were explored in this work to promote better cross-linking between the enzyme and PU matrix. The hydrophilic cross-linker (Bayhydur 302) demonstrated 70% improvement in retaining the enzyme against 24 hours of washing compared to a hydrophobic cross-linker (DESMOPHEN N3600). Moreover, algae cells were studied as model solid-state substrates. We report a novel enzymatic method to disrupt the cell wall and release lipids from the algae cells. Microscopic analysis indicated that the cell wall of Chlamydomonas reinhardtii (C.R.) algae was disrupted after being treated by a three-step method, which included one hour of incubation in 4 M of lithium chloride, eight hours of hydrolytic reaction in enzyme solution, and one cycle of freeze/thaw process. Protease Subtilisin Carlsberg was found effective in catalyzing the degradation of C.R. cell wall due to its unspecific activity toward peptide bonds.Item North St Paul City Communications Effort Evaluation Plan(Resilient Communities Project (RCP), University of Minnesota, 2013) Toosi, Kumars; Song, Wei; Vollrath, Bre; Sisser, JohnThis project was completed as part of the 2013-2014 Resilient Communities Project (rcp.umn.edu) partnership with the City of North St. Paul. In 2013, the North St. Paul City Council identified improving communication with residents as a priority. Project lead Laurie Koehnle collaborated with students in OLPD 5501: Principles and Methods of Evaluation, taught by Randi Nelson, to develop an evaluation plan for the city’s existing communication efforts. The students designed a plan, suggested to the City evaluation questions, necessary data, and collection methods. The final report, presentation, and handout are available.Item Social Capital, Self-Control, and Academic Performance in School-Age Children and Adolescents: Patterns Associated with Race/Ethnicity(2018-11) Song, WeiChildren’s abilities to control behaviors and emotions continue to grow from childhood to adolescence. The thesis examined the degree to which the social capital in family and school contexts shaped self-control among four racial/ethnic groups (i.e., Caucasian, African American, Hispanic, Asian American), and whether self-control served as a mediator of the relationship between social capital and academic performance. It consisted of two studies using two major datasets (Early Childhood Longitudinal Study – Kindergarten: 2011 and Minnesota Student Survey). Study 1 analyzed a nationally representative sample of children who entered kindergarten during the school year of 2010-2011, following them through second grade. Study 2 analyzed a statewide sample of adolescents in secondary schools (8th, 9th, and 11th grader) between 12 to 18 years old in 2016. In the investigation of racial/ethnic differences, first the measurement equivalence of family/school social capital, self-control, and academic performance were established in each study. Then multi-group Structural Equation Modeling (SEM) was conducted to assess whether racial/ethnic membership moderates proposed associations for children and adolescence. Study 1 found that family social capital positively predicted self-control and academic achievement for Caucasian and Hispanic children, while school social capital was not significant for any group. Self-control was a partial and positive mediator of the relationship between family social capital and academic achievement for the Caucasian and Hispanic children. Study 2 found positive associations from family and school social capital to self-control, and self-control partially and significantly mediated associations between social capital and academic achievement for adolescents across racial/ethnic groups. Implications for prevention, intervention, and public policy for different populations of interest are provided.