1,495 research outputs found
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
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
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