The Kirchhoff gauge

We discuss the Kirchhoff gauge in classical electrodynamics. In this gauge the scalar potential satisfies an elliptical equation and the vector potential satisfies a wave equation with a nonlocal source. We find the solutions of both equations and show that, despite of the unphysical character of the scalar potential, the electric and magnetic fields obtained from the scalar and vector potentials are given by their well-known retarded expressions. We note that the Kirchhoff gauge pertains to the class of gauges known as the velocity gauge.Comment: 12 page

Syntheses in the Pyridazine Series. XXXII. Some Investigations on Polynuclear Systems Containing a Pyridazine Ring

Some 5,6-dihydrobenzo[f]phthalazines have been aromatized to II and the structures of a number of nitro derivatives prepared from several polynuclear systems (III, IV, V) , have been established

Syntheses in the Pyridazine Series. XXXII. Some Investigations on Polynuclear Systems Containing a Pyridazine Ring

Some 5,6-dihydrobenzo[f]phthalazines have been aromatized to II and the structures of a number of nitro derivatives prepared from several polynuclear systems (III, IV, V) , have been established

Frustration - how it can be measured

A misfit parameter is used to characterize the degree of frustration of ordered and disordered systems. It measures the increase of the ground-state energy due to frustration in comparison with that of a relevant reference state. The misfit parameter is calculated for various spin-glass models. It allows one to compare these models with each other. The extension of this concept to other combinatorial optimization problems with frustration, e.g. p-state Potts glasses, graph-partitioning problems and coloring problems is given.Comment: 10 pages, 1 table, no figures, uses revtex.st

Heterogeneous nucleation is required for crystallization of the ZnuA domain of pneumococcal AdcA

Zn2+ is an essential nutrient for all known forms of life. In the major human pathogen Streptococcus pneumoniae, the acquisition of Zn2+ is facilitated by two Zn2+-specific solute-binding proteins: AdcA and AdcAII. To date, there has been a paucity of structural information on AdcA, which has hindered a deeper understanding of the mechanism underlying pneumococcal Zn2+ acquisition. Native AdcA consists of two domains: an N-terminal ZnuA domain and a C-terminal ZinT domain. In this study, the ZnuA domain of AdcA was crystallized. The initial crystals of the ZnuA-domain protein were obtained using dried seaweed as a heterogeneous nucleating agent. No crystals were obtained in the absence of the heterogeneous nucleating agent. These initial crystals were subsequently used as seeds to produce diffraction-quality crystals. The crystals diffracted to 2.03 angstrom resolution and had the symmetry of space group P1. This study demonstrates the utility of heterogeneous nucleation. The solution of the crystal structures will lead to further understanding of Zn2+ acquisition by S. pneumoniae

How do Customers Alter Their Basket Composition When They Perceive the Retail Store to Be Crowded? An Empirical Study

Using data from a large-scale field study, we show that (perceptions of) crowding change(s) the composition of a consumer's shopping basket. Specifically, as shoppers experience more crowding, their shopping basket contains (a) relatively more affect-rich (“hedonic”) products, and (b) relatively more national brands. We offer a plausible dual-process explanation for this phenomenon: Crowding induced distraction limits cognitive capacity, increasing the relative impact of affective responses in purchase decisions. As we are the first to show that level of crowding relates to what shoppers buy (at both product and brand level), the implications of these effects for retailers are discussed

On the Quasiparticle Description of Lattice QCD Thermodynamics

We propose a novel quasiparticle interpretation of the equation of state of deconfined QCD at finite temperature. Using appropriate thermal masses, we introduce a phenomenological parametrization of the onset of confinement in the vicinity of the predicted phase transition. Lattice results of the energy density, the pressure and the interaction measure of pure SU(3) gauge theory are excellently reproduced. We find a relationship between the thermal energy density of the Yang-Mills vacuum and the chromomagnetic condensate _T. Finally, an extension to QCD with dynamical quarks is discussed. Good agreement with lattice data for 2, 2+1 and 3 flavour QCD is obtained. We also present the QCD equation of state for realistic quark masses.Comment: 20 pages, 10 eps figure

Derivation of Boltzmann Principle

We present a derivation of Boltzmann principle $S_{B}=k_{B}\ln \mathcal{W}$ based on classical mechanical models of thermodynamics. The argument is based on the heat theorem and can be traced back to the second half of the nineteenth century with the works of Helmholtz and Boltzmann. Despite its simplicity, this argument has remained almost unknown. We present it in a modern, self-contained and accessible form. The approach constitutes an important link between classical mechanics and statistical mechanics

Crystallization of the C-terminal domain of the mouse brain cytosolic long-chain acyl-CoA thioesterase

The mammalian long-chain acyl-CoA thioesterase, the enzyme that catalyses the hydrolysis of acyl-CoAs to free fatty acids, contains two fused 4HBT (4-hydroxybenzoyl-CoA thioesterase) motifs. The C-terminal domain of the mouse long-chain acyl-CoA thioesterase (Acot7) has been expressed in bacteria and crystallized. The crystals were obtained by vapour diffusion using PEG 2000 MME as precipitant at pH 7.0 and 290 K. The crystals have the symmetry of space group R32 ( unit-cell parameters a = b = 136.83, c = 99.82 angstrom, gamma = 120 degrees). Two molecules are expected in the asymmetric unit. The crystals diffract to 2.4 angstrom resolution using the laboratory X-ray source and are suitable for crystal structure determination