14,985 research outputs found
Curvature as a Measure of the Thermodynamic Interaction
We present a systematic and consistent construction of geometrothermodynamics
by using Riemannian contact geometry for the phase manifold and harmonic maps
for the equilibrium manifold. We present several metrics for the phase manifold
that are invariant with respect to Legendre transformations and induce
thermodynamic metrics on the equilibrium manifold. We review all the known
examples in which the curvature of the thermodynamic metrics can be used as a
measure of the thermodynamic interaction
The endolysosomal system in neuronal physiology and pathology
Verhage, M. [Promotor]Weering, J.R.T. van [Copromotor
New tests and applications of the worldline path integral in the first order formalism
We present different non-perturbative calculations within the context of
Migdal's representation for the propagator and effective action of quantum
particles. We first calculate the exact propagators and effective actions for
Dirac, scalar and Proca fields in the presence of constant electromagnetic
fields, for an even-dimensional spacetime. Then we derive the propagator for a
charged scalar field in a spacelike vortex (i.e., instanton) background, in a
long-distance expansion, and the exact propagator for a massless Dirac field in
1+1 dimensions in an arbitrary background. Finally, we present an
interpretation of the chiral anomaly in the present context, finding a
condition that the paths must fulfil in order to have a non-vanishing anomaly.Comment: 26 page
Roles of transcriptional and translational control mechanisms in regulation of ribosomal protein synthesis in Escherichia coli
ABSTRACTBacterial ribosome biogenesis is tightly regulated to match nutritional conditions and to prevent formation of defective ribosomal particles. InEscherichia coli, most ribosomal protein (r-protein) synthesis is coordinated with rRNA synthesis by a translational feedback mechanism: when r-proteins exceed rRNAs, specific r-proteins bind to their own mRNAs and inhibit expression of the operon. It was recently discovered that the second messenger nucleotide guanosine tetra and pentaphosphate (ppGpp), which directly regulates rRNA promoters, is also capable of regulating many r-protein promoters. To examine the relative contributions of the translational and transcriptional control mechanisms to the regulation of r-protein synthesis, we devised a reporter system that enabled us to genetically separate thecis-acting sequences responsible for the two mechanisms and to quantify their relative contributions to regulation under the same conditions. We show that the synthesis of r-proteins from the S20 and S10 operons is regulated by ppGpp following shifts in nutritional conditions, but most of the effect of ppGpp required the 5′ region of the r-protein mRNA containing the target site for translational feedback regulation and not the promoter. These results suggest that most regulation of the S20 and S10 operons by ppGpp following nutritional shifts is indirect and occurs in response to changes in rRNA synthesis. In contrast, we found that the promoters for the S20 operon were regulated during outgrowth, likely in response to increasing nucleoside triphosphate (NTP) levels. Thus, r-protein synthesis is dynamic, with different mechanisms acting at different times.IMPORTANCEBacterial cells have evolved complex and seemingly redundant strategies to regulate many high-energy-consuming processes. InE. coli, synthesis of ribosomal components is tightly regulated with respect to nutritional conditions by mechanisms that act at both the transcription and translation steps. In this work, we conclude that NTP and ppGpp concentrations can regulate synthesis of ribosomal proteins, but most of the effect of ppGpp is indirect as a consequence of translational feedback in response to changes in rRNA levels. Our results illustrate how effects of seemingly redundant regulatory mechanisms can be separated in time and that even when multiple mechanisms act concurrently their contributions are not necessarily equivalent.</jats:p
Baryon chemical potential and in-medium properties of BPS skyrmions
We continue the investigation of thermodynamical properties of the BPS Skyrme
model. In particular, we analytically compute the baryon chemical potential
both in the full field theory and in a mean-field approximation. In the full
field theory case, we find that the baryon chemical potential is always exactly
proportional to the baryon density, for arbitrary solutions. We further find
that, in the mean-field approximation, the BPS Skyrme model approaches the
Walecka model in the limit of high density - their thermodynamical functions as
well as the equation of state agree in this limit. This fact allows to read off
some properties of the -meson from the BPS Skyrme action, even though
the latter model is entirely based on the (pionic) Skyrme field. On the
other hand, at low densities, at the order of the usual nuclear matter density,
the equations of state of the two models are no longer universal, such that a
comparison depends on some model details. Still, also the BPS Skyrme model
gives rise to nuclear saturation in this regime, leading, in fact, to an exact
balance between repulsive and attractive forces. The perfect fluid aspects of
the BPS Skyrme model, which, together with its BPS properties, form the base of
our results, are shown to be in close formal analogy with the Eulerian
formulation of relativistic fluid dynamics. Within this analogy, the BPS Skyrme
model, in general, corresponds to a non-barotropic perfect fluid.Comment: Latex, 28 pages, 3 figure
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