1,975 research outputs found
Eulerian Statistically Preserved Structures in Passive Scalar Advection
We analyze numerically the time-dependent linear operators that govern the
dynamics of Eulerian correlation functions of a decaying passive scalar
advected by a stationary, forced 2-dimensional Navier-Stokes turbulence. We
show how to naturally discuss the dynamics in terms of effective compact
operators that display Eulerian Statistically Preserved Structures which
determine the anomalous scaling of the correlation functions. In passing we
point out a bonus of the present approach, in providing analytic predictions
for the time-dependent correlation functions in decaying turbulent transport.Comment: 10 pages, 10 figures. Submitted to Phys. Rev.
Antimicrobial treatment improves mycobacterial survival in nonpermissive growth conditions
Antimicrobials targeting cell wall biosynthesis are generally considered inactive against nonreplicating bacteria. Paradoxically, we found that under nonpermissive growth conditions, exposure of Mycobacterium bovis BCG bacilli to such antimicrobials enhanced their survival. We identified a transcriptional regulator, RaaS (for regulator of antimicrobial-assisted survival), encoded by bcg1279 (rv1219c) as being responsible for the observed phenomenon. Induction of this transcriptional regulator resulted in reduced expression of specific ATP-dependent efflux pumps and promoted long-term survival of mycobacteria, while its deletion accelerated bacterial death under nonpermissive growth conditions in vitro and during macrophage or mouse infection. These findings have implications for the design of antimicrobial drug combination therapies for persistent infectious diseases, such as tuberculosis
The pion photoproduction in the \Delta(1232) region
We investigate the pion photoproduction in the \Delta(1232) region in the
framework of an effective Lagrangian including pions, nulceon and \Delta(1232).
We work to third order in a small scale expansion with both and
treated as light scales. We note that in the region,
straightward power counting breaks as the amplitudes become very large, to deal
with this problem, we suggest that the appropriate way to compare theoretical
calculations with experimental data is via weighted integrals of the amplitudes
through the region.Comment: 34 pages and 5 figures,new counterterms arr adde
J.S. Bell's Concept of Local Causality
John Stewart Bell's famous 1964 theorem is widely regarded as one of the most
important developments in the foundations of physics. It has even been
described as "the most profound discovery of science." Yet even as we approach
the 50th anniversary of Bell's discovery, its meaning and implications remain
controversial. Many textbooks and commentators report that Bell's theorem
refutes the possibility (suggested especially by Einstein, Podolsky, and Rosen
in 1935) of supplementing ordinary quantum theory with additional ("hidden")
variables that might restore determinism and/or some notion of an
observer-independent reality. On this view, Bell's theorem supports the
orthodox Copenhagen interpretation. Bell's own view of his theorem, however,
was quite different. He instead took the theorem as establishing an "essential
conflict" between the now well-tested empirical predictions of quantum theory
and relativistic \emph{local causality}. The goal of the present paper is, in
general, to make Bell's own views more widely known and, in particular, to
explain in detail Bell's little-known mathematical formulation of the concept
of relativistic local causality on which his theorem rests. We thus collect and
organize many of Bell's crucial statements on these topics, which are scattered
throughout his writings, into a self-contained, pedagogical discussion
including elaborations of the concepts "beable", "completeness", and
"causality" which figure in the formulation. We also show how local causality
(as formulated by Bell) can be used to derive an empirically testable Bell-type
inequality, and how it can be used to recapitulate the EPR argument.Comment: 19 pages, 4 figure
Oleoyl Coenzyme A regulates interaction of transcriptional regulator RaaS (Rv1219c) with DNA in Mycobacteria
We have recently shown that RaaS (regulator of antimicrobial-assisted survival), encoded by Rv1219c in Mycobacterium tuberculosis and by bcg_1279c in Mycobacterium bovis bacillus Calmette-Guérin, plays an important role in mycobacterial survival in prolonged stationary phase and during murine infection. Here, we demonstrate that long chain acyl-CoA derivatives (oleoyl-CoA and, to lesser extent, palmitoyl-CoA) modulate RaaS binding to DNA and expression of the downstream genes that encode ATP-dependent efflux pumps. Moreover, exogenously added oleic acid influences RaaS-mediated mycobacterial improvement of survival and expression of the RaaS regulon. Our data suggest that long chain acyl-CoA derivatives serve as biological indicators of the bacterial metabolic state. Dysregulation of efflux pumps can be used to eliminate non-growing mycobacteria
Hot Hypernuclear Matter in the Modified Quark Meson Coupling Model
Hot hypernuclear matter is investigated in an explicit SU(3) quark model
based on a mean field description of nonoverlapping baryon bags bound by the
self-consistent exchange of scalar and vector
mesons. The mean fields are assumed to couple to the
u,d-quarks while the mean fields are coupled to the s-quark. The
coupling constants of the mean fields with the quarks are assumed to satisfy
SU(6) symmetry. The calculations take into account the medium dependence of the
bag parameter on the scalar fields . We consider only the octet
baryons in hypernuclear matter. An ideal gas of the
strange mesons and is introduced to keep zero net strangeness
density. Our results for symmetric hypernuclear matter show that a phase
transition takes place at a critical temperature around 180 MeV in which the
scalar mean fields take nonzero values at zero baryon density.
Furthermore, the bag contants of the baryons decrease significantly at and
above this critical temperature indicating the onset of quark deconfinement.
The present results imply that the onset of quark deconfinement in SU(3)
hypernuclear matter is much stronger than in SU(2) nuclear matter.Comment: LaTeX/TeX 11 pages (dfg3r.tex), 9 figures in eps forma
A Broken Trust: Lessons from the Vaccine–Autism Wars: Researchers long ago rejected the theory that vaccines cause autism, yet many parents don't believe them. Can scientists bridge the gap between evidence and doubt?
Researchers long ago rejected the theory that vaccines cause autism, yet many parents don't believe them. Can scientists bridge the gap between evidence and doubt
Evaluation of the Workplace Environment in the UK, and the Impact on Users’ Levels of Stimulation
The purpose of this study is to evaluate a number of recently completed workplaces in the UK. The first aim is to assess the impact of various aspects of the workplace environment on users’ levels of stimulation. The body of previous research undertaken into the workplace environment, identified the aspects to be investigated. Samples of employees from the sixteen businesses were surveyed to determine their perceptions of the workplaces. The results were entered into a regression analysis, and the most significant predictors of perceived stimulation identified. The data also revealed a dramatic reduction in staff arousal levels from mornings to afternoons. Thus, there is a second aim to determine whether changes to significant aspects of the workplace environment during the day can counteract the reduction in users’ stimulation. Two further workplaces were studied to enable changes to be made over a 12-week period. A sample of employees completed questionnaires, and semi-structured interviews revealed the reasons behind the results. It was found that provision of artwork, personal control of temperature and ventilation and regular breaks were the most significant contributions to increasing stimulation after lunch; while user choice of layout, and design and décor of workspaces and break areas, were the most significant aspects at design stage
The standard model at low energies
The hadronic sector of the standard model at low energies is described by a
non--decoupling effective field theory, chiral perturbation theory. An
introduction is given to the construction of effective chiral Lagrangians, both
in the purely mesonic sector and with inclusion of baryons. The connection
between the relativistic formulation and the heavy baryon approach to chiral
perturbation theory with baryons is reviewed.Comment: Lectures given at the 6th Indian-Summer School on Intermediate Energy
Physics, Prague, Aug. 1993, Latex, 26 pages (with a4.sty), UWThPh-1993-3
A Mean Field Approach To The Instanton-Induced Effect Close To The QCD Phase Transition
In the instanton models the chiral phase transition is driven by a transition
from random instanton-antiinstanton liquid and correlated
instanton-antiinstanton molecules. So far this phenomenon was studied by
numerical simulations, while we develop alternative semi-analytic approach. For
two massless quark flavors, both instantons and ``molecules" generate specific
4-fermion effective interactions. After those are derived, we determine the
temperature dependence of the thermodynamic quantities, the quark condensate
and the fraction of molecules using standard mean field method. Using
Bethe-Salpeter equation, we calculate T-dependence of mesonic correlation
functions.Comment: 26 pages, LaTeX, 6 postscript files of 6 figures in additio
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