2,542 research outputs found
Nonequilibrium stochastic processes: Time dependence of entropy flux and entropy production
Based on the Fokker-Planck and the entropy balance equations we have studied
the relaxation of a dissipative dynamical system driven by external
Ornstein-Uhlenbeck noise processes in absence and presence of nonequilibrium
constraint in terms of the thermodynamically inspired quantities like entropy
flux and entropy production. The interplay of nonequilibrium constraint,
dissipation and noise reveals some interesting extremal nature in the time
dependence of entropy flux and entropy production.Comment: RevTex, 17 pages, 9 figures. To appear in Phys. Rev.
Upper bound for the time derivative of entropy for nonequilibrium stochastic processes
We have shown how the intrinsic properties of a noise process can set an
upper bound for the time derivative of entropy in a nonequilibrium system. The
interplay of dissipation and the properties of noise processes driving the
dynamical systems in presence and absence of external forcing, reveals some
interesting extremal nature of the upper bound.Comment: RevTex, 13 pages, 6 figure
Statistical properties of multistep enzyme-mediated reactions
Enzyme-mediated reactions may proceed through multiple intermediate
conformational states before creating a final product molecule, and one often
wishes to identify such intermediate structures from observations of the
product creation. In this paper, we address this problem by solving the
chemical master equations for various enzymatic reactions. We devise a
perturbation theory analogous to that used in quantum mechanics that allows us
to determine the first () and the second (variance) cumulants of the
distribution of created product molecules as a function of the substrate
concentration and the kinetic rates of the intermediate processes. The mean
product flux V=d/dt (or "dose-response" curve) and the Fano factor
F=variance/ are both realistically measurable quantities, and while the mean
flux can often appear the same for different reaction types, the Fano factor
can be quite different. This suggests both qualitative and quantitative ways to
discriminate between different reaction schemes, and we explore this
possibility in the context of four sample multistep enzymatic reactions. We
argue that measuring both the mean flux and the Fano factor can not only
discriminate between reaction types, but can also provide some detailed
information about the internal, unobserved kinetic rates, and this can be done
without measuring single-molecule transition events.Comment: 8 pages, 3 figure
Guillain-Barré Syndrome-related campylobacter jejuni in Bangladesh: ganglioside mimicry and cross-reactive antibodies
BACKGROUND:
<br/>
Campylobacter jejuni is the predominant antecedent infection in Guillain-Barré syndrome (GBS). Molecular mimicry and cross-reactive immune responses to C. jejuni lipo-oligosaccharides (LOS) precipitate the development of GBS, although this mechanism has not been established in patients from developing countries. We determined the carbohydrate mimicry between C. jejuni LOS and gangliosides, and the cross-reactive antibody response in patients with GBS in Bangladesh.<br/>
METHODOLOGY:<br/>
Sera from 97 GBS patients, and 120 neurological and family controls were tested for antibody reactivity against LOS from C. jejuni isolates from GBS patients in Bangladesh (BD-07, BD-39, BD-10, BD-67 and BD-94) by enzyme-linked immunosorbent assay (ELISA). Cross-reactivity to LOS was determined by ELISA. The LOS outer core structures of C. jejuni strains associated with GBS/MFS were determined by mass spectrometry.<br/>
PRINCIPLE FINDINGS:<br/>
IgG antibodies to LOS from C. jejuni BD-07, BD-39, BD-10, and BD-67 IgG antibodies were found in serum from 56%, 58%, 14% and 15% of GBS patients respectively, as compared to very low frequency (<3%) in controls (p<0.001). Monoclonal antibodies specific for GM1 and GD1a reacted strongly with LOS from the C. jejuni strains (BD-07 and BD-39). Mass spectrometry analysis confirmed the presence of GM1 and GD1a carbohydrate mimics in the LOS from C. jejuni BD-07 and BD-39. Both BD-10 and BD-67 express the same LOS outer core, which appears to be a novel structure displaying GA2 and GD3 mimicry. Up to 90-100% of serum reactivity to gangliosides in two patients (DK-07 and DK-39) was inhibited by 50 µg/ml of LOS from the autologous C. jejuni isolates. However, patient DK-07 developed an anti-GD1a immune response while patient DK-39 developed an anti-GM1 immune response.<br/>
CONCLUSION:<br/>
Carbohydrate mimicry between C. jejuni LOS and gangliosides, and cross-reactive serum antibody precipitate the majority of GBS cases in Bangladesh
Simulating EGFR-ERK signaling control by scaffold proteins KSR and MP1 reveals differential Ligand-Sensitivity Co-Regulated by CBL-CIN85 and Endophilin
10.1371/journal.pone.0022933PLoS ONE68
Jet angular correlation in vector-boson fusion processes at hadron colliders
Higgs boson and massive-graviton productions in association with two jets via
vector-boson fusion (VBF) processes and their decays into a vector-boson pair
at hadron colliders are studied. They include scalar and tensor boson
production processes via weak-boson fusion in quark-quark collisions, gluon
fusion in quark-quark, quark-gluon and gluon-gluon collisions, as well as their
decays into a pair of weak bosons or virtual gluons which subsequently decay
into , or . We give the helicity amplitudes
explicitly for all the VBF subprocesses, and show that the VBF amplitudes
dominate the exact matrix elements not only for the weak-boson fusion processes
but also for all the gluon fusion processes when appropriate selection cuts are
applied, such as a large rapidity separation between two jets and a slicing cut
for the transverse momenta of the jets. We also show that our off-shell
vector-boson current amplitudes reduce to the standard quark and gluon
splitting amplitudes with appropriate gluon-polarization phases in the
collinear limit. Nontrivial azimuthal angle correlations of the jets in the
production and in the decay of massive spin-0 and -2 bosons are manifestly
expressed as the quantum interference among different helicity states of the
intermediate vector-bosons. Those correlations reflect the spin and the CP
nature of the Higgs bosons and the massive gravitons.Comment: 47 pages, 7 figures, 10 tables; references added, version to appear
in JHE
Mass formulas and thermodynamic treatment in the mass-density-dependent model of strange quark matter
The previous treatments for strange quark matter in the quark
mass-density-dependent model have unreasonable vacuum limits. We provide a
method to obtain the quark mass parametrizations and give a self-consistent
thermodynamic treatment which includes the MIT bag model as an extreme. In this
treatment, strange quark matter in bulk still has the possibility of absolute
stability. However, the lower density behavior of the sound velocity is
opposite to previous findings.Comment: Formatted in REVTeX 3.1, 5 pages, 3 figures, to appear in PRC6
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