Experiences with Problem-Based Learning: Virginia Initiative for Science Teaching and Achievement

The Virginia Initiative for Science Teaching and Achievement (VISTA) provides high-quality professional development for teachers and administrators to enhance the quality of their science instructional programs. One emphasis of this program is helping teachers learn to implement Problem-Based Learning in the elementary science classroom. Problem-Based Learning (PBL) has the potential to produce significant positive outcomes for students, such as increased student engagement, and opportunities for in-depth critical thinking [1]. Teachers find PBL challenging because it does take additional time for planning and material acquisition, but experience has shown that the benefits outweigh these challenges. Setting clear goals, identifying specific learning objectives, and developing big questions that tie these together help increase the success of the unit. Additionally, administrators can help teachers succeed in implementing a Problem-Based Learning unit by understanding the dynamic nature of the PBL environment, providing flexibility with unit pacing, and setting aside time for refining, reflection, and revision of the unit

Phylogenetic and Genomic Characterization of the Host-Pathogen Arms Race Between Bacterial Pathogens and Gossypium hirsutum

Hosts and pathogens are eternally intertwined in an evolutionary arms race. When a pathogen causes a disease outbreak, scientists must identify resistance strategies that can durably tilt the arms race in favor of the host. This requires a deep understanding of both the genetic and environmental contexts in which the outbreak occurs. In this thesis I investigate the bacterial pathogens Xanthomonas citri pv. malvacearum (Xcm) and Pseudomonas syringae that caused disease outbreaks on Gossypium hirsutum from 2011-2017. I use pathogen genomics and host transcriptomics to develop hypotheses for how these pathogens emerged and how they cause disease. Phylogenetics and virulence factor analysis reveal few differences between contemporary and historical isolates. Data on agricultural practices point to changing germplasm dynamics as a reason for disease re-emergence. These data led to a RNA-Seq experiment that identified several new candidate susceptibility genes including four SWEET sugar transporters and two Mildew Locus-O homologs that have been used to confer resistance to bacterial pathogens in other systems. As an alternative approach, a diversity panel of 52 cotton varieties was screened to reveal seven sources of resistance that can be used to prevent Xcm outbreaks in the future. While no resistance strategies have been identified for P. syringae, several virulence factors such as the type IV pilus and filamentous hemagglutinin were identified, which show evolutionary markers of a function in the host-pathogen arms race. These data are pivotal for determining the best strategies for developing durable host resistance strategies. Future work will focus on developing resistant varieties of cotton and performing reverse genetics to confirm the identities of virulence factors that contribute to pathogen fitness

Evaluation of the Wellspring Model for Improving Nursing Home Quality

Examines how successfully the Wellspring model improved the quality of care for residents of eleven nonprofit nursing homes in Wisconsin. Looks at staff turnover, and evaluates the impact on facilities, employees, residents, and cost

Isolation of the ALG6 locus of Saccharomyces cerevisiae required for glucosylation in the N-linked glycosylation pathway

N-Linked protein glycosylation in most eukaryotic cells initiates with the transfer of the oligosaccharide Glc3Man9GlcNAc2 from the lipid carrier dolichyl pyrophosphate to selected asparagine residues. In the yeast Saccharomyces cerevisiae, alg mutations which affect the assembly of the lipid-linked oligosaccharide at the membrane of the endoplasmic reticulum result in the accumulation of lipid-linked oligosaccharide intermediates and a hypoglycosylation of proteins. Exploiting the synthetic growth defect of alg mutations in combination with mutations affecting oligosaccharyl transferase activity (Stagljar et al., 1994), we have isolated the ALG6 locus. alg6 mutants accumulate lipid-linked Man9GlcNAc2, suggesting that this locus encodes an endoplasmic glucosyltransferase. Alg6p has sequence similarity to Alg8p, a protein required for glucosylation of Glc1Man9GlcNAc

Psychological Empowerment Among Urban Youth: Measurement Model and Associations with Youth Outcomes

Empowermentâ based strategies have become widely used method to address health inequities and promote social change. Few researchers, however, have tested theoretical models of empowerment, including multidimensional, higherâ order models. We test empirically a multidimensional, higherâ order model of psychological empowerment (PE), guided by Zimmerman’s conceptual framework including three components of PE: intrapersonal, interactional, and behavioral. We also investigate if PE is associated with positive and negative outcomes among youth. The sample included 367 middle school youth aged 11â 16 (M = 12.71; SD = 0.91); 60% female, 32% (n = 117) white youth, 46% (n = 170) Africanâ American youth, and 22% (n = 80) identifying as mixed race, Asianâ American, Latino, Native American, or other ethnic/racial group; schools reported 61â 75% free/reduced lunch students. Our results indicated that each of the latent factors for the three PE components demonstrate a good fit with the data. Our results also indicated that these components loaded on to a higherâ order PE factor (X2 = 32.68; df: 22; p = .07; RMSEA: 0.04; 95% CI: .00, .06; CFI: 0.99). We found that the secondâ order PE factor was negatively associated with aggressive behavior and positively associated with prosocial engagement. Our results suggest that empowermentâ focused programs would benefit from incorporating components addressing how youth think about themselves in relation to their social contexts (intrapersonal), understanding social and material resources needed to achieve specific goals (interactional), and actions taken to influence outcomes (behavioral). Our results also suggest that integrating the three components and promoting PE may help increase likelihood of positive behaviors (e.g., prosocial involvement); we did not find an association between PE and aggressive behavior. Implications and future directions for empowerment research are discussed.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/135336/1/ajcp12094_am.pdfhttp://deepblue.lib.umich.edu/bitstream/2027.42/135336/2/ajcp12094.pd

Modeling metallic island coalescence stress via adhesive contact between surfaces

Tensile stress generation associated with island coalescence is almost universally observed in thin films that grow via the Volmer-Weber mode. The commonly accepted mechanism for the origin of this tensile stress is a process driven by the reduction in surface energy at the expense of the strain energy associated with the deformation of coalescing islands during grain boundary formation. In the present work, we have performed molecular statics calculations using an embedded atom interatomic potential to obtain a functional form of the interfacial energy vs distance between two closely spaced free surfaces. The sum of interfacial energy plus strain energy provides a measure of the total system energy as a function of island separation. Depending on the initial separation between islands, we find that in cases where coalescence is thermodynamically favored, gap closure can occur either spontaneously or be kinetically limited due to an energetic barrier. Atomistic simulations of island coalescence using conjugate gradient energy minimization calculations agree well with the predicted stress as a function of island size from our model of spontaneous coalescence. Molecular dynamics simulations of island coalescence demonstrate that only modest barriers to coalescence can be overcome at room temperature. A comparison with thermally activated coalescence results at room temperature reveals that existing coalescence models significantly overestimate the magnitude of the stress resulting from island coalescence.Comment: 20 pages, 8 figures, 2 tables, submitted to PR

Dynamics of DNA Ejection From Bacteriophage

The ejection of DNA from a bacterial virus (``phage'') into its host cell is a biologically important example of the translocation of a macromolecular chain along its length through a membrane. The simplest mechanism for this motion is diffusion, but in the case of phage ejection a significant driving force derives from the high degree of stress to which the DNA is subjected in the viral capsid. The translocation is further sped up by the ratcheting and entropic forces associated with proteins that bind to the viral DNA in the host cell cytoplasm. We formulate a generalized diffusion equation that includes these various pushing and pulling effects and make estimates of the corresponding speed-ups in the overall translocation process. Stress in the capsid is the dominant factor throughout early ejection, with the pull due to binding particles taking over at later stages. Confinement effects are also investigated, in the case where the phage injects its DNA into a volume comparable to the capsid size. Our results suggest a series of in vitro experiments involving the ejection of DNA into vesicles filled with varying amounts of binding proteins from phage whose state of stress is controlled by ambient salt conditions or by tuning genome length.Comment: 17 pages, 5 figure

Entropic Tension in Crowded Membranes

Unlike their model membrane counterparts, biological membranes are richly decorated with a heterogeneous assembly of membrane proteins. These proteins are so tightly packed that their excluded area interactions can alter the free energy landscape controlling the conformational transitions suffered by such proteins. For membrane channels, this effect can alter the critical membrane tension at which they undergo a transition from a closed to an open state, and therefore influence protein function \emph{in vivo}. Despite their obvious importance, crowding phenomena in membranes are much less well studied than in the cytoplasm. Using statistical mechanics results for hard disk liquids, we show that crowding induces an entropic tension in the membrane, which influences transitions that alter the projected area and circumference of a membrane protein. As a specific case study in this effect, we consider the impact of crowding on the gating properties of bacterial mechanosensitive membrane channels, which are thought to confer osmoprotection when these cells are subjected to osmotic shock. We find that crowding can alter the gating energies by more than $2\;k_BT$ in physiological conditions, a substantial fraction of the total gating energies in some cases. Given the ubiquity of membrane crowding, the nonspecific nature of excluded volume interactions, and the fact that the function of many membrane proteins involve significant conformational changes, this specific case study highlights a general aspect in the function of membrane proteins.Comment: 20 pages (inclduing supporting information), 4 figures, to appear in PLoS Comp. Bio

Zero-bias anomalies of point contact resistance due to adiabatic electron renormalization of dynamical defects

We study effect of the adiabatic electron renormalization on the parameters of the dynamical defects in the ballistic metallic point contact. The upper energy states of the ``dressed'' defect are shown to give a smaller contribution to a resistance of the contact than the lower energy ones. This holds both for the "classical" renormalization related to defect coupling with average local electron density and for the "mesoscopic" renormalization caused by the mesoscopic fluctuations of electronic density the dynamical defects are coupled with. In the case of mesoscopic renormalization one may treat the dynamical defect as coupled with Friedel oscillations originated by the other defects, both static and mobile. Such coupling lifts the energy degeneracy of the states of the dynamical defects giving different mesoscopic contribution to resistance, and provides a new model for the fluctuator as for the object originated by the electronic mesoscopic disorder rather than by the structural one. The correlation between the defect energy and the defect contribution to the resistance leads to zero-temperature and zero-bias anomalies of the point contact resistance. A comparison of these anomalies with those predicted by the Two Channel Kondo Model (TCKM) is made. It is shown, that although the proposed model is based on a completely different from TCKM physical background, it leads to a zero-bias anomalies of the point contact resistance, which are qualitatively similar to TCKM predictions.Comment: 6 pages, to be published in Phys. Rev.