Predicting the in-term persistence of community college English-as-a-second-language students

The English-as-a-second-language (ESL) community college student population has increased notably in the past decade, but a decreasing number of these students are completing courses, programs, or degrees (Erisman & Looney, 2008). These students come to college with unique background experiences, and once in college, deal with challenging linguistic, academic, and social integration issues. Though they are not linguistically homogenous, and they do not have a common purpose, ESL students share the common goal of attending community college to learn to speak English (Szelényi & Chang, 2002). Course completion is a primary measure of progress toward that goal, and is therefore an issue of concern for both ESL students and community colleges, which continue to be the access point for language-minority students progressing into higher education (Laden, 2004).^ The purpose of this study was to investigate the factors that predict in-term persistence of community college ESL students. A mixed methods research design consisting of two phases was utilized, and participants in this study were ESL students enrolled in a large community college in south Florida. Phase 1 students completed the Community College ESL Student Questionnaire (CCSEQ), which collected demographic data and data on entry characteristics, academic integration, and social integration. Discriminant and descriptive analyses were used to report the data collected in Phase I. Phase 2 students were a matching cohort of completing and non-completing students who participated in semi-structured interviews at the end of the term. Data collected in the interviews were analyzed thematically, using a constant comparative method as described by Glaser and Strauss (1967).^ Students’ self reported demographic data, background characteristics, goal commitment, and integration factors on the CCSEQ showed no significance between the students who completed the term and the students who did not complete the term. However, several differentiating themes emerged from the interview data, which indicated differences in goal commitment and integration between the two groups. The focus of non-completers on getting good grades rather than completing the course, and the commitment of completers to the goal of finishing the class in order to go forward, both raise questions for future research studies.^

Synthetic Approaches to Flexible Fluorescent Conjugated Polymers

Conjugated polymers (CPs) are intrinsically fluorescent materials that have been used for various biological applications including imaging, sensing, and delivery of biologically active substances. The synthetic control over flexibility and biodegradability of these materials aids the understanding of the structure-function relationships among the photophysical properties, the self-assembly behaviors of the corresponding conjugated polymer nanoparticles (CPNs), and the cellular behaviors of CPNs, such as toxicity, cellular uptake mechanisms, and sub-cellular localization patterns. Synthetic approaches towards two classes of flexible CPs with well-preserved fluorescent properties are described. The synthesis of flexible poly(p-phenylenebutadiynylene)s (PPBs) uses competing Sonogashira and Glaser coupling reactions and the differences in monomer reactivity to incorporate a small amount (~10%) of flexible, non-conjugated linkers into the backbone. The reaction conditions provide limited control over the proportion of flexible monomer incorporation. Improved synthetic control was achieved in a series of flexible poly(p-phenyleneethynylene)s (PPEs) using modified Sonogashira conditions. In addition to controlling the degree of flexibility, the linker provides disruption of backbone conjugation that offers control of the length of conjugated segments within the polymer chain. Therefore, such control also results in the modulation of the photophysical properties of the materials. CPNs fabricated from flexible PPBs are non-toxic to cells, and exhibit subcellular localization patterns clearly different from those observed with non-flexible PPE CPNs. The subcellular localization patterns of the flexible PPEs have not yet been determined, due to the toxicity of the materials, most likely related to the side-chain structure used in this series. The study of the effect of CP flexibility on self-assembly reorganization upon polyanion complexation is presented. Owing to its high rigidity and hydrophobicity, the PPB backbone undergoes reorganization more readily than PPE. The effects are enhanced in the presence of the flexible linker, which enables more efficient π-π stacking of the aromatic backbone segments. Flexibility has minimal effects on the self-assembly of PPEs. Understanding the role of flexibility on the biophysical behaviors of CPNs is key to the successful development of novel efficient fluorescent therapeutic delivery vehicles.

Synthetic approaches to flexible fluorescent conjugated polymers

Conjugated polymers (CPs) are intrinsically fluorescent materials that have been used for various biological applications including imaging, sensing, and delivery of biologically active substances. The synthetic control over flexibility and biodegradability of these materials aids the understanding of the structure-function relationships among the photophysical properties, the self-assembly behaviors of the corresponding conjugated polymer nanoparticles (CPNs), and the cellular behaviors of CPNs, such as toxicity, cellular uptake mechanisms, and sub-cellular localization patterns. ^ Synthetic approaches towards two classes of flexible CPs with well-preserved fluorescent properties are described. The synthesis of flexible poly( p-phenylenebutadiynylene)s (PPBs) uses competing Sonogashira and Glaser coupling reactions and the differences in monomer reactivity to incorporate a small amount (∼10%) of flexible, non-conjugated linkers into the backbone. The reaction conditions provide limited control over the proportion of flexible monomer incorporation. Improved synthetic control was achieved in a series of flexible poly(p-phenyleneethynylene)s (PPEs) using modified Sonogashira conditions. In addition to controlling the degree of flexibility, the linker provides disruption of backbone conjugation that offers control of the length of conjugated segments within the polymer chain. Therefore, such control also results in the modulation of the photophysical properties of the materials. ^ CPNs fabricated from flexible PPBs are non-toxic to cells, and exhibit subcellular localization patterns clearly different from those observed with non-flexible PPE CPNs. The subcellular localization patterns of the flexible PPEs have not yet been determined, due to the toxicity of the materials, most likely related to the side-chain structure used in this series. ^ The study of the effect of CP flexibility on self-assembly reorganization upon polyanion complexation is presented. Owing to its high rigidity and hydrophobicity, the PPB backbone undergoes reorganization more readily than PPE. The effects are enhanced in the presence of the flexible linker, which enables more efficient π-π stacking of the aromatic backbone segments. Flexibility has minimal effects on the self-assembly of PPEs. Understanding the role of flexibility on the biophysical behaviors of CPNs is key to the successful development of novel efficient fluorescent therapeutic delivery vehicles.^