Astrophysical and Astrobiological Implications of Gamma-Ray Burst Properties

Combining results for the local cosmic rate and mean peak luminosity of GRBs with the cosmic history of the star formation rate, we provide estimates for the local GRB rate per unit blue luminosity in galaxies. We find a typical GRB rate per unit B luminosity of 2.4x10^-17 h_{70}^2/Lsun/yr. The corresponding mean rate in the Milky Way is 5.5x10^-7 h_{70}^2/yr. We conclude: 1) the ratio of supernova rate to isotropic equivalent GRB rate is large: more than 6000 SNIbc per GRB or 30,000 SNII per GRB. GRBs could arise in a large fraction of black hole-forming events only with collimation in the range 0.01 - 0.001 and a steep enough slope of the IMF; 2) GRBs cannot account for the majority of large HI holes observed in galaxies; 3) the probability that the solar system was exposed to a fluence large enough to melt the chondrules during the first 10^7 yr of solar system history is negligibly small; 4) Even for very opaque atmospheres, a significant fraction of the GRB energy is transmitted as UV lines due to excitation by secondary electrons. For eukaryotic-like organisms in thin atmospheres (e.g. contemporary Mars), or for UV line exposure in thick atmospheres (e.g. Earth), biologically significant events occur at a rate of about 100--500 /Gyr. The direct contribution of these "jolts" to mutational evolution may, however, be negligible because of the short duration of the GRBs. Evolutionary effects due to partial sterilizations and to longer-lived disruptions of atmospheric chemistry should be more important. (Abridged)Comment: 36 pages, no figures Accepted by Astrophysical Journal Oct. 2001. First submitted December,1999. Substantially rewritten discussion of burst source count distributions and of biological implication

Project proposal on funding for parks

This study will look at state and county level parks and see what and if there are alternative funding solutions for these parks. We will interview officials and administrators of two parks, while using surveys to gather information about visitors of the parks. The interviews that we will use for the park officials and administrators will be semi-structured. When it comes to analyzing the data we receive from the interviews, we will use three techniques: member checking, qualitative coding, and developing themes. The second method we plan on using is surveys of park visitors. We want to conduct exit surveys with visitors of two different parks, one local and one state. Approximately 200 surveys will be collected from those visiting Table Rock State Park and Nettles Park in Clemson. This will give us a good summary of what people would like and not like. From these results we would be able to make inferences about the population of park visitors, and would we be able to advise parks which funding alternatives would be successful and unsuccessful

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

Effect of macromolecular crowding on the rate of diffusion-limited enzymatic reaction

The cytoplasm of a living cell is crowded with several macromolecules of different shapes and sizes. Molecular diffusion in such a medium becomes anomalous due to the presence of macromolecules and diffusivity is expected to decrease with increase in macromolecular crowding. Moreover, many cellular processes are dependent on molecular diffusion in the cell cytosol. The enzymatic reaction rate has been shown to be affected by the presence of such macromolecules. A simple numerical model is proposed here based on percolation and diffusion in disordered systems to study the effect of macromolecular crowding on the enzymatic reaction rates. The model explains qualitatively some of the experimental observations.Comment: 6 pages, 4 figure

Hard Spheres in Vesicles: Curvature-Induced Forces and Particle-Induced Curvature

We explore the interplay of membrane curvature and nonspecific binding due to excluded-volume effects among colloidal particles inside lipid bilayer vesicles. We trapped submicron spheres of two different sizes inside a pear-shaped, multilamellar vesicle and found the larger spheres to be pinned to the vesicle's surface and pushed in the direction of increasing curvature. A simple model predicts that hard spheres can induce shape changes in flexible vesicles. The results demonstrate an important relationship between the shape of a vesicle or pore and the arrangement of particles within it.Comment: LaTeX with epsfig; ps available at http://dept.physics.upenn.edu/~nelson/index.shtml Phys Rev Lett in press (1997

An Assessment of Computer Use, Knowledge, and Attitudes of Diabetes Educators

A questionnaire to survey attitudes, use, and knowledge of computers was sent to 816 randomly selected members of AADE to determine the degree to which currently available computer resources are used in diabetes education and to investigate the need for future computing resources designed to support diabetes education. Analysis of the data showed that even diabetes educators who use computers infrequently have a generally favorable attitude toward them. Highest use of computers is in noneducational applications, mostly for word processing and record keeping. Most respondents believe that computers have yet to make a major contribution to the teaching and learning process in diabetes education, and few felt adequately prepared for creative use or development of computer applications. Increasing the role of computers in support of patient education will require encouragement and demonstrations of computer efficacy from health care institutions and professional organizations.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/68469/2/10.1177_014572179201800107.pd

Very rapid long-distance sea crossing by a migratory bird

Landbirds undertaking within-continent migrations have the possibility to stop en route, but most long-distance migrants must also undertake large non-stop sea crossings, the length of which can vary greatly. For shorebirds migrating from Iceland to West Africa, the shortest route would involve one of the longest continuous sea crossings while alternative, mostly overland, routes are available. Using geolocators to track the migration of Icelandic whimbrels (Numenius phaeopus), we show that they can complete a round-trip of 11,000 km making two non-stop sea crossings and flying at speeds of up to 24 m s-1; the fastest recorded for shorebirds flying over the ocean. Although wind support could reduce flight energetic costs, whimbrels faced headwinds up to twice their ground speed, indicating that unfavourable and potentially fatal weather conditions are not uncommon. Such apparently high risk migrations might be more common than previously thought, with potential fitness gains outweighing the costs

Hydrophobic and ionic-interactions in bulk and confined water with implications for collapse and folding of proteins

Water and water-mediated interactions determine thermodynamic and kinetics of protein folding, protein aggregation and self-assembly in confined spaces. To obtain insights into the role of water in the context of folding problems, we describe computer simulations of a few related model systems. The dynamics of collapse of eicosane shows that upon expulsion of water the linear hydrocarbon chain adopts an ordered helical hairpin structure with 1.5 turns. The structure of dimer of eicosane molecules has two well ordered helical hairpins that are stacked perpendicular to each other. As a prelude to studying folding in confined spaces we used simulations to understand changes in hydrophobic and ionic interactions in nano droplets. Solvation of hydrophobic and charged species change drastically in nano water droplets. Hydrophobic species are localized at the boundary. The tendency of ions to be at the boundary where water density is low increases as the charge density decreases. Interaction between hydrophobic, polar, and charged residue are also profoundly altered in confined spaces. Using the results of computer simulations and accounting for loss of chain entropy upon confinement we argue and then demonstrate, using simulations in explicit water, that ordered states of generic amphiphilic peptide sequences should be stabilized in cylindrical nanopores

Professionalism, Golf Coaching and a Master of Science Degree: A commentary

As a point of reference I congratulate Simon Jenkins on tackling the issue of professionalism in coaching. As he points out coaching is not a profession, but this does not mean that coaching would not benefit from going through a professionalization process. As things stand I find that the stimulus article unpacks some critically important issues of professionalism, broadly within the context of golf coaching. However, I am not sure enough is made of understanding what professional (golf) coaching actually is nor how the development of a professional golf coach can be facilitated by a Master of Science Degree (M.Sc.). I will focus my commentary on these two issues