Characterizing the University of California's tenure-track teaching position from the faculty and administrator perspectives.

Teaching faculty are a potential mechanism to generate positive change in undergraduate STEM education. One such type of faculty is the Lecturer with Potential Security of Employment (L(P)SOE), a tenure-track faculty line within the University of California (UC) system. As a foundation for future studies, we sought to characterize individuals in the L(P)SOE position in terms of their background training, job expectations, and resources available for their success. Data were collected through an online survey completed by over 80% of STEM L(P)SOEs across the UC system, as well as interviews with over 20 deans and chairs in STEM departments at three UC campuses. From this work, we found that the majority of current L(P)SOEs were formally trained within their disciplines and not in an education field; however, they possessed substantial education experience, such as classroom teaching or participation in professional development opportunities. Expectations for time spent on teaching, research, and service are aligned between individuals within varying ranks of the L(P)SOE faculty and between L(P)SOEs and administrators. L(P)SOEs and administrators are also in agreement about what constitutes acceptable professional development activities. Interestingly, we identified differences that may reflect changes in the position over time, including increased start-up funds for more recently hired L(P)SOE faculty and a differing perspective on the role of discipline-based education research and scholarly activities between non-tenured and more senior L(P)SOEs. Overall, these data provide a snapshot of the L(P)SOE position that will aid in future work to identify the potential institutional impact of these individuals

Applying Graph Theory to Examine the Dynamics of Student Discussions in Small-Group Learning.

Group work in science, technology, engineering, and mathematics courses is an effective means of improving student outcomes, and many different factors can influence the dynamics of student discussions and, ultimately, the success of collaboration. The substance and dynamics of group discussions are commonly examined using qualitative methods such as discourse analysis. To complement existing work in the literature, we developed a quantitative methodology that uses graph theory to map the progression of talk-turns of discussions within a group. We observed groups of students working with peer facilitators to solve problems in biological sciences, with three iterations of data collection and two major refinements of graph theory calculations. Results include general behaviors based on the turns in which different individuals talk and graph theory parameters to quantify group characteristics. To demonstrate the potential utility of the methodology, we present case studies with distinct patterns: a centralized group in which the peer facilitator behaves like an authority figure, a decentralized group in which most students talk their fair share of turns, and a larger group with subgroups that have implications for equity, diversity, and inclusion. Together, these results demonstrate that our adaptation of graph theory is a viable quantitative methodology to examine group discussions

Evolutionary minority game with heterogeneous strategy distribution

We present detailed numerical results for a modified form of the so-called Minority Game, which provides a simplified model of a competitive market. Each agent has a limited set of strategies, and competes to be in a minority. An evolutionary rule for strategy modification is included to mimic simple learning. The results can be understood by considering crowd formation within the population.Comment: Revtex file + 4 figure

Intrinsic tethering activity of endosomal Rab proteins.

Rab small G proteins control membrane trafficking events required for many processes including secretion, lipid metabolism, antigen presentation and growth factor signaling. Rabs recruit effectors that mediate diverse functions including vesicle tethering and fusion. However, many mechanistic questions about Rab-regulated vesicle tethering are unresolved. Using chemically defined reaction systems, we discovered that Vps21, a Saccharomyces cerevisiae ortholog of mammalian endosomal Rab5, functions in trans with itself and with at least two other endosomal Rabs to directly mediate GTP-dependent tethering. Vps21-mediated tethering was stringently and reversibly regulated by an upstream activator, Vps9, and an inhibitor, Gyp1, which were sufficient to drive dynamic cycles of tethering and detethering. These experiments reveal a previously undescribed mode of tethering by endocytic Rabs. In our working model, the intrinsic tethering capacity Vps21 operates in concert with conventional effectors and SNAREs to drive efficient docking and fusion

Chromatin Modification by PSC Occurs at One PSC per Nucleosome and Does Not Require the Acidic Patch of Histone H2A

Chromatin architecture is regulated through both enzymatic and non-enzymatic activities. For example, the Polycomb Group (PcG) proteins maintain developmental gene silencing using an array of chromatin-based mechanisms. The essential Drosophila PcG protein, Posterior Sex Combs (PSC), compacts chromatin and inhibits chromatin remodeling and transcription through a non-enzymatic mechanism involving nucleosome bridging. Nucleosome bridging is achieved through a combination of nucleosome binding and self-interaction. Precisely how PSC interacts with chromatin to bridge nucleosomes is not known and is the subject of this work. We determine the stoichiometry of PSC-chromatin interactions in compact chromatin (in which nucleosomes are bridged) using Scanning Transmission Electron Microscopy (STEM). We find that full compaction occurs with one PSC per nucleosome. In addition to compacting chromatin, we show that PSC oligomerizes nucleosome arrays. PSC-mediated oligomerization of chromatin occurs at similar stoichiometry as compaction suggesting it may also involve nucleosome bridging. Interactions between the tail of histone H4 and the acidic patch of histone H2A are important for chromatin folding and oligomerization, and several chromatin proteins bind the histone H2A acidic patch. However, mutation of the acidic patch of histone H2A does not affect PSC’s ability to inhibit chromatin remodeling or bridge nucleosomes. In fact, PSC does not require nucleosomes for bridging activity but can bridge naked DNA segments. PSC clusters nucleosomes on sparsely assembled templates, suggesting it interacts preferentially with nucleosomes over bare DNA. This may be due to the ability of PSC to bind free histones. Our data are consistent with a model in which each PSC binds a nucleosome and at least one other PSC to directly bridge nucleosomes and compact chromatin, but also suggest that naked DNA can be included in compacted structures. We discuss how our data highlight the diversity of mechanisms used to modify chromatin architecture.Molecular and Cellular Biolog

Defining Understanding: Perspectives from Biology Instructors & Biology Education Researchers

Promoting student understanding of biological concepts is a key part of biology education, and the ability to “understand” a concept forms one of the six categories of the oft-used Bloom’s Taxonomy. Despite this, there remains no consensus as to what it means to understand a concept. While several formal definitions have been offered, we investigated how biology instructors and biology education researchers define the term and how they perceived the skill sets needed for a student to understand a concept in the context of assessments. We found that there was no agreement on the definition of understanding, and that responses differed in the cognitive level required to reach “understanding” of a concept. We discuss these findings in the context of Bloom’s Taxonomy and variation theory and provide directions for future inquiries. We conclude by discussing implications for biology instructors and the importance of explicitly conveying expectations to better align student and instructor expectations