1,663 research outputs found
Affinity and Fluctuations in a Mesoscopic Noria
We exhibit the invariance of cycle affinities in finite state Markov
processes under various natural probabilistic constructions, for instance under
conditioning and under a new combinatorial construction that we call ``drag and
drop''. We show that cycle affinities have a natural probabilistic meaning
related to first passage non-equilibrium fluctuation relations that we
establish.Comment: 30 pages, 1 figur
The two-dimensional two-component plasma plus background on a sphere : Exact results
An exact solution is given for a two-dimensional model of a Coulomb gas, more
general than the previously solved ones. The system is made of a uniformly
charged background, positive particles, and negative particles, on the surface
of a sphere. At the special value of the reduced inverse
temperature, the classical equilibrium statistical mechanics is worked out~:
the correlations and the grand potential are calculated. The thermodynamic
limit is taken, and as it is approached the grand potential exhibits a
finite-size correction of the expected universal form.Comment: 23 pages, Plain Te
A modern Fizeau experiment for education and outreach purposes
On the occasion of the laser's 50th anniversary, we performed a modern Fizeau
experiment, measuring the speed of light with a laser beam passing over the
city centre of Marseille. For a round trip distance of almost five kilometers,
the measurement has reached an uncertainty of about 10, mainly due to
atmospheric fluctuations. We present the experimental and pedagogical
challenges of this brilliant outreach experiment.Comment: accepted by Eur J Phys in november 201
New duality relation for the Discrete Gaussian SOS model on a torus
We construct a new duality for two-dimensional Discrete Gaussian models. It
is based on a known one-dimensional duality and on a mapping, implied by the
Chinese remainder theorem, between the sites of an torus and those
of a ring of sites. The duality holds for an arbitrary translation
invariant interaction potential between the height variables on
the torus. It leads to pairs of mutually dual potentials
and to a temperature inversion according to .
When is isotropic, duality renders an anisotropic
. This is the case, in particular, for the potential that is
dual to an isotropic nearest-neighbor potential. In the thermodynamic limit
this dual potential is shown to decay with distance according to an inverse
square law with a quadrupolar angular dependence. There is a single pair of
self-dual potentials . At the self-dual
temperature the height-height
correlation can be calculated explicitly; it is anisotropic and diverges
logarithmically with distance.Comment: 26 pages, 2 figure
Genetic dissection of NK cell responses
The association of Natural Killer (NK) cell deficiencies with disease susceptibility has established a central role for NK cells in host defence. In this context, genetic approaches have been pivotal in elucidating and characterizing the molecular mechanisms underlying NK cell function. To this end, homozygosity mapping and linkage analysis in humans have identified mutations that impact NK cell function and cause life-threatening diseases. However, several critical restrictions accompany genetic studies in humans. Studying NK cell pathophysiology in a mouse model has therefore proven a useful tool. The relevance of the mouse model is underscored by the similarities that exist between cell-structure-sensing receptors and the downstream signaling that leads to NK cell activation. In this review, we provide an overview of how human and mouse quantitative trait locis (QTLs) have facilitated the identification of genes that modulate NK cell development, recognition, and killing of target cells
NK Cell Receptor/H2-Dk–Dependent Host Resistance to Viral Infection Is Quantitatively Modulated by H2q Inhibitory Signals
The cytomegalovirus resistance locus Cmv3 has been linked to an
epistatic interaction between two loci: a Natural Killer (NK) cell receptor gene
and the major histocompatibility complex class I (MHC-I) locus. To demonstrate
the interaction between Cmv3 and
H2k, we generated double congenic mice between
MA/My and BALB.K mice and an F2 cross between FVB/N
(H-2q) and BALB.K
(H2k) mice, two strains susceptible to mouse
cytomegalovirus (MCMV). Only mice expressing H2k in
conjunction with Cmv3MA/My or
Cmv3FVB were resistant to MCMV infection.
Subsequently, an F3 cross was carried out between transgenic
FVB/H2-Dk and MHC-I deficient mice in which
only the progeny expressing Cmv3FVB and a single
H2-Dk class-I molecule completely controlled
MCMV viral loads. This phenotype was shown to be NK cell–dependent and
associated with subsequent NK cell proliferation. Finally, we demonstrated that
a number of H2q alleles influence the expression
level of H2q molecules, but not intrinsic functional
properties of NK cells; viral loads, however, were quantitatively proportional
to the number of H2q alleles. Our results support a
model in which H-2q molecules convey Ly49-dependent
inhibitory signals that interfere with the action of
H2-Dk on NK cell activation against MCMV
infection. Thus, the integration of activating and inhibitory signals emanating
from various MHC-I/NK cell receptor interactions regulates NK
cell–mediated control of viral load
The Ideal Conductor Limit
This paper compares two methods of statistical mechanics used to study a
classical Coulomb system S near an ideal conductor C. The first method consists
in neglecting the thermal fluctuations in the conductor C and constrains the
electric potential to be constant on it. In the second method the conductor C
is considered as a conducting Coulomb system the charge correlation length of
which goes to zero. It has been noticed in the past, in particular cases, that
the two methods yield the same results for the particle densities and
correlations in S. It is shown that this is true in general for the quantities
which depend only on the degrees of freedom of S, but that some other
quantities, especially the electric potential correlations and the stress
tensor, are different in the two approaches. In spite of this the two methods
give the same electric forces exerted on S.Comment: 19 pages, plain TeX. Submited to J. Phys. A: Math. Ge
Statistical properties of charged interfaces
We consider the equilibrium statistical properties of interfaces submitted to
competing interactions; a long-range repulsive Coulomb interaction inherent to
the charged interface and a short-range, anisotropic, attractive one due to
either elasticity or confinement. We focus on one-dimensional interfaces such
as strings. Model systems considered for applications are mainly aggregates of
solitons in polyacetylene and other charge density wave systems, domain lines
in uniaxial ferroelectrics and the stripe phase of oxides. At zero temperature,
we find a shape instability which lead, via phase transitions, to tilted
phases. Depending on the regime, elastic or confinement, the order of the
zero-temperature transition changes. Thermal fluctuations lead to a pure
Coulomb roughening of the string, in addition to the usual one, and to the
presence of angular kinks. We suggest that such instabilities might explain the
tilting of stripes in cuprate oxides. The 3D problem of the charged wall is
also analyzed. The latter experiences instabilities towards various tilted
phases separated by a tricritical point in the elastic regime. In the
confinement regime, the increase of dimensionality favors either the melting of
the wall into a Wigner crystal of its constituent charges or a strongly
inclined wall which might have been observed in nickelate oxides.Comment: 17 pages, 11 figure
The effects of choice on the reading comprehension and enjoyment of children with severe inattention and no attentional difficulties
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