The Maximal Invariance Group of Newtons's Equations for a Free Point Particle

The maximal invariance group of Newton's equations for a free nonrelativistic point particle is shown to be larger than the Galilei group. It is a semi-direct product of the static (nine-parameter) Galilei group and an $SL(2,R)$ group containing time-translations, dilations and a one-parameter group of time-dependent scalings called {\it expansions}. This group was first discovered by Niederer in the context of the free Schr\"odinger equation. We also provide a road map from the free nonrelativistic point particle to the equations of fluid mechanics to which the symmetry carries over. The hitherto unnoticed $SL(2, R)$ part of the symmetry group for fluid mechanics gives a theoretical explanation for an observed similarity between numerical simulations of supernova explosions and numerical simulations of experiments involving laser-induced implosions in inertial confinement plasmas. We also give examples of interacting many body systems of point particles which have this symmetry group.Comment: Plain TeX File: 15 Page

Management Skills for the Contemporary College President: A Critical Review

This review of the literature related to the contemporary college president attempted to describe changes to the presidential role during the past 30 years. In addition to describing changes to the role, the review explores the personal, organizational, interpersonal, and leadership skills required for leading a contemporary university. The findings particularly note that with the changing demands for accountability in higher education, presidents are being forced to spend more of their time and be more focused on issues of finance, law, and public interactions. These issues tend to collide in discussions of public policy and within the framework of state legislative proposals. Continued professional development for college presidents is recommended, especially in terms of aligning work place priorities with the institution’s mission

VAMP3 is associated with endothelial Weibel-Palade bodies and participates in their Ca2+-dependent exocytosis.

AbstractWeibel–Palade bodies (WPBs) are secretory organelles of endothelial cells that store the thrombogenic glycoprotein von Willebrand factor (vWF). Endothelial activation, e.g. by histamine and thrombin, triggers the Ca2+-dependent exocytosis of WPB that releases vWF into the vasculature and thereby initiates platelet capture and thrombus formation. Towards understanding the molecular mechanisms underlying this regulated WPB exocytosis, we here identify components of the soluble N-ethylmaleimide-sensitive factor attachment protein receptor (SNARE) machinery associated with WPB. We show that vesicle-associated membrane protein (VAMP) 3 and VAMP8 are present on WPB and that VAMP3, but not VAMP8 forms a stable complex with syntaxin 4 and SNAP23, two plasma membrane-associated SNAREs in endothelial cells. By introducing mutant SNARE proteins into permeabilized endothelial cells we also show that soluble VAMP3 but not VAMP8 mutants comprising the cytoplasmic domain interfere with efficient vWF secretion. This indicates that endothelial cells specifically select VAMP 3 over VAMP8 to cooperate with syntaxin 4 and SNAP23 in the Ca2+-triggered fusion of WPB with the plasma membrane. This article is part of a Special Issue entitled: 11th European Symposium on Calcium

The Polyakov Loop and its Relation to Static Quark Potentials and Free Energies

It appears well accepted in the literature that the correlator of Polyakov loops in a finite temperature system decays with the "average" free energy of the static quark-antiquark system, and can be decomposed into singlet and adjoint (or octet for QCD) contributions. By fixing a gauge respecting the transfer matrix, attempts have been made to extract those contributions separately. In this paper we point out that the "average" and "adjoint" channels of Polyakov loop correlators are misconceptions. We show analytically that all channels receive contributions from singlet states only, and give a corrected definition of the singlet free energy. We verify this finding by simulations of the 3d SU(2) pure gauge theory in the zero temperature limit, which allows to cleanly extract the ground state exponents and the non-trivial matrix elements. The latter account for the difference between the channels observed in previous simulations.Comment: 14 pages, 3 figures, 1 table; note and reference adde

Continuous Loading of a Conservative Trap from an Atomic Beam

We demonstrate the fast accumulation of Cr atoms in a conservative potential from a magnetically guided atomic beam. Without laser cooling on a cycling transition, a single dissipative step realized by optical pumping allows to load atoms at a rate of 2*10^7 1/s in the trap. Within less than 100 ms we reach the collisionally dense regime, from which we directly produce a Bose-Einstein condensate with subsequent evaporative cooling. This constitutes a new approach to degeneracy where, provided a slow beam of particles can be produced by some means, Bose-Einstein condensation can be reached for species without a cycling transition.Comment: 4 pages, 4 figure

Crossover Between Universality Classes in the Statistics of Rare Events in Disordered Conductors

The crossover from orthogonal to the unitary universality classes in the distribution of the anomalously localized states (ALS) in two-dimensional disordered conductors is traced as a function of magnetic field. We demonstrate that the microscopic origin of the crossover is the change in the symmetry of the underlying disorder configurations, that are responsible for ALS. These disorder configurations are of weak magnitude (compared to the Fermi energy) and of small size (compared to the mean free path). We find their shape explicitly by means of the direct optimal fluctuation method.Comment: 7 pages including 2 figure

Evaporation limited loading of an atom trap

Recently, we have experimentally demonstrated a continuous loading mechanism for an optical dipole trap from a guided atomic beam [1]. The observed evolution of the number of atoms and temperature in the trap are consequences of the unusual trap geometry. In the present paper, we develop a model based on a set of rate equations to describe the loading dynamics of such a mechanism. We consider the collision statistics in the non-uniform trap potential that leads to twodimensional evaporation. The comparison between the resulting computations and experimental data allows to identify the dominant loss process and suggests ways to enhance the achievable steady-state atom number. Concerning subsequent evaporative cooling, we find that the possibility of controlling axial and radial confinement independently allows faster evaporation ramps compared to single beam optical dipole traps.Comment: 10 pages, 7 figure