Anomalous relaxation kinetics of biological lattice-ligand binding models

We discuss theoretical models for the cooperative binding dynamics of ligands to substrates, such as dimeric motor proteins to microtubules or more extended macromolecules like tropomyosin to actin filaments. We study the effects of steric constraints, size of ligands, binding rates and interaction between neighboring proteins on the binding dynamics and binding stoichiometry. Starting from an empty lattice the binding dynamics goes, quite generally, through several stages. The first stage represents fast initial binding closely resembling the physics of random sequential adsorption processes. Typically this initial process leaves the system in a metastable locked state with many small gaps between blocks of bound molecules. In a second stage the gaps annihilate slowly as the ligands detach and reattach. This results in an algebraic decay of the gap concentration and interesting scaling behavior. Upon identifying the gaps with particles we show that the dynamics in this regime can be explained by mapping it onto various reaction-diffusion models. The final approach to equilibrium shows some interesting dynamic scaling properties. We also discuss the effect of cooperativity on the equilibrium stoichiometry, and their consequences for the interpretation of biochemical and image reconstruction results.Comment: REVTeX, 20 pages, 17 figures; review, to appear in Chemical Physics; v2: minor correction

The state of the art in evaluating the performance of assistant and associate deans as seen by deans and assistant and associate deans.

This study explores the little-understood process of evaluating the performance of assistant and associate deans at dental colleges in the United States and Canada. Specifically, this research aimed to identify the methods, processes, and outcomes related to the performance appraisals of assistant/associate deans. Both deans and assistant/associate deans were surveyed. Forty-four of sixty-six deans (66.7 percent) and 227 of 315 assistant/associate deans (72.1 percent) completed surveys with both close-ended and open-ended questions. In addition, ten individuals from each group were interviewed. Results indicate that 75-89 percent of assistant/associate deans are formally evaluated, although as many as 27 percent may lack formal job descriptions. Some recommended best practices for performance appraisal are being used in a majority of colleges. Examples of these best practices are having at least yearly appraisals, holding face-to-face meetings, and setting specific, personal performance objectives/benchmarks for assistant/associate deans. Still, there is much room to improve appraisals by incorporating other recommended practices. Relatively high levels of overall satisfaction were reported by both assistant/associate deans and deans for the process and outcomes of appraisals. Assistant/associate deans rated the value of appraisals to overall development lower than did deans. Qualitative data revealed definite opinions about what constitutes effective and ineffective appraisals, including the use of goal-setting, timeliness, and necessary commitment. Several critical issues related to the results are discussed: differences in perspectives on performance reviews, the importance of informal feedback and job descriptions, the influence of an assistant/associate deans\u27 lack of tenure, and the length of service of deans. Lastly, recommendations for enhancing performance evaluations are offered

Strategic management and organizational behavior in dental education: reflections on key issues in an environment of change.

With issues such as shrinking revenue, access to care, faculty workloads, and graying faculty, dental schools are faced with difficult challenges that fall to dental school deans to manage. Do dental school deans have the organizational skill sets and ethical frameworks necessary to address the challenges now facing dental schools? The purpose of this article is to pose questions and suggestions regarding some of the key issues in dental colleges today and to stimulate discussion in the dental community about needed changes in dental education

The state of the art in evaluating the performance of department chairs and division heads.

This study explores the little understood process of evaluating the performance of department chairs/division heads in dental schools. Specifically, this research aimed to elucidate the methods, processes, and outcomes related to the job performance of department chairs/division heads. Forty-three deans and 306 chairs completed surveys with both close-ended and open-ended questions. In addition, ten deans and ten chairs were interviewed. Results indicate that 80 to 90 percent of department chairs are formally evaluated, although as many as 50 percent may lack job descriptions. Recommended best practices for performance appraisal--such as having at least yearly appraisals, holding face-to-face meetings, and setting specific, personal performance objectives/benchmarks for chairs--are being used in most schools. Still, there is much room to improve appraisals by incorporating other recommended practices. Overall high levels of satisfaction were reported by both chairs and deans for the process and outcomes of appraisals. Qualitative data showed some convergence of opinions about appraisals with the notable exception of informal feedback. We explore some implications of these results, especially as they relate to improving performance appraisals

The benchmark aeroelastic models program: Description and highlights of initial results

An experimental effort was implemented in aeroelasticity called the Benchmark Models Program. The primary purpose of this program is to provide the necessary data to evaluate computational fluid dynamic codes for aeroelastic analysis. It also focuses on increasing the understanding of the physics of unsteady flows and providing data for empirical design. An overview is given of this program and some results obtained in the initial tests are highlighted. The tests that were completed include measurement of unsteady pressures during flutter of rigid wing with a NACA 0012 airfoil section and dynamic response measurements of a flexible rectangular wing with a thick circular arc airfoil undergoing shock boundary layer oscillations

Physical Properties of Trans-Neptunian Object (20000) Varuna

We present new time-resolved photometric observations of the bright trans-Neptunian object (20000) Varuna and use them to study the rotation period, shape, and color. In observations from 2001 February and April, we find a best-fit two-peaked lightcurve with period 6.3442 +-0.0002 hr. The peak-to-peak photometric range in the R-band is 0.42 +-0.02 mag. We find no rotational variation in colors over the 0.45 < lambda < 0.85 micron wavelength range. From the short double-peaked period and large amplitude we suggest that Varuna is an elongated, prolate body perhaps close in shape to one of the Jacobi ellipsoids. If so, the ratio of the axes projected into the plane of the sky is 1.5:1 and the density is near 1000 kg m^(-3). (20000) Varuna may be a rotationally distorted rubble pile, with a weak internal constitution due to fracturing by past impacts. The high specific angular momentum implied by our observations and recent detections of binary Trans-Neptunian Objects both point to an early, intense collisional epoch in which large Trans-Neptunian Objects were about 100 times more abundant than now. In order to maintain a cosmochemically plausible rock:ice mass ratio of about 0.5, Varuna must be internally porous.Comment: 26 pages, 6 figures, 5 tables, accepted to A