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Pathogenic Cav3.2 channel mutation in a child with primary generalized epilepsy.
Two paternally-inherited missense variants in CACNA1H were identified and characterized in a 6-year-old child with generalized epilepsy. Febrile and unprovoked seizures were present in this child. Both variants were expressed in cis or isolation using human recombinant Cav3.2 calcium channels in tsA-201 cells. Whole-cell patch-clamp recordings indicated that one variant (c.3844C > T; p.R1282W) caused a significant increase in current density consistent with a pathogenic gain-of-function phenotype; while the other cis-related variant (c.5294C > T; p.A1765V) had a benign profile
Chaotic Hypothesis, Fluctuation Theorem and singularities
The chaotic hypothesis has several implications which have generated interest
in the literature because of their generality and because a few exact
predictions are among them. However its application to Physics problems
requires attention and can lead to apparent inconsistencies. In particular
there are several cases that have been considered in the literature in which
singularities are built in the models: for instance when among the forces there
are Lennard-Jones potentials (which are infinite in the origin) and the
constraints imposed on the system do not forbid arbitrarily close approach to
the singularity even though the average kinetic energy is bounded. The
situation is well understood in certain special cases in which the system is
subject to Gaussian noise; here the treatment of rather general singular
systems is considered and the predictions of the chaotic hypothesis for such
situations are derived. The main conclusion is that the chaotic hypothesis is
perfectly adequate to describe the singular physical systems we consider, i.e.
deterministic systems with thermostat forces acting according to Gauss'
principle for the constraint of constant total kinetic energy (``isokinetic
Gaussian thermostats''), close and far from equilibrium. Near equilibrium it
even predicts a fluctuation relation which, in deterministic cases with more
general thermostat forces (i.e. not necessarily of Gaussian isokinetic nature),
extends recent relations obtained in situations in which the thermostatting
forces satisfy Gauss' principle. This relation agrees, where expected, with the
fluctuation theorem for perfectly chaotic systems. The results are compared
with some recent works in the literature.Comment: 7 pages, 1 figure; updated to take into account comments received on
the first versio
Glassy behavior of light
We study the nonlinear dynamics of a multi-mode random laser using the
methods of statistical physics of disordered systems. A replica-symmetry
breaking phase transition is predicted as a function of the pump intensity. We
thus show that light propagating in a random non-linear medium displays glassy
behavior, i.e. the photon gas has a multitude of metastable states and a non
vanishing complexity, corresponding to mode-locking processes in random lasers.
The present work reveals the existence of new physical phenomena, and
demonstrates how nonlinear optics and random lasers can be a benchmark for the
modern theory of complex systems and glasses.Comment: 5 pages, 1 figur
Is it possible to experimentally verify the fluctuation relation? A review of theoretical motivations and numerical evidence
The theoretical motivations to perform experimental tests of the stationary
state fluctuation relation are reviewed. The difficulties involved in such
tests, evidenced by numerical simulations, are also discussed.Comment: 36 pages, 4 figures. Extended version of a presentation to the
discussion "Is it possible to experimentally verify the fluctuation
theorem?", IHP, Paris, December 1, 2006. Comments are very welcom
Mean field theory of hard sphere glasses and jamming
Hard spheres are ubiquitous in condensed matter: they have been used as
models for liquids, crystals, colloidal systems, granular systems, and powders.
Packings of hard spheres are of even wider interest, as they are related to
important problems in information theory, such as digitalization of signals,
error correcting codes, and optimization problems. In three dimensions the
densest packing of identical hard spheres has been proven to be the FCC
lattice, and it is conjectured that the closest packing is ordered (a regular
lattice, e.g, a crystal) in low enough dimension. Still, amorphous packings
have attracted a lot of interest, because for polydisperse colloids and
granular materials the crystalline state is not obtained in experiments for
kinetic reasons. We review here a theory of amorphous packings, and more
generally glassy states, of hard spheres that is based on the replica method:
this theory gives predictions on the structure and thermodynamics of these
states. In dimensions between two and six these predictions can be successfully
compared with numerical simulations. We will also discuss the limit of large
dimension where an exact solution is possible. Some of the results we present
here have been already published, but others are original: in particular we
improved the discussion of the large dimension limit and we obtained new
results on the correlation function and the contact force distribution in three
dimensions. We also try here to clarify the main assumptions that are beyond
our theory and in particular the relation between our static computation and
the dynamical procedures used to construct amorphous packings.Comment: 59 pages, 25 figures. Final version published on Rev.Mod.Phy
Replica analysis of the generalized p-spin interaction glass model
We investigate stability of replica symmetry breaking solutions in
generalized -spin models. It is shown that the kind of the transition to the
one-step replica symmetry breaking state depends not only on the presence or
absence of the reflection symmetry of the generalized "spin"-operators
but on the number of interacting operators and their individual
characteristics.Comment: 14 pages, 1 figur
Scanning mutagenesis of omega-atracotoxin-Hv1a reveals a spatially restricted epitope that confers selective activity against insect calcium channels
We constructed a complete panel of alanine mutants of the insect-specific calcium channel blocker omega-atracotoxin-Hv1a. Lethality assays using these mutant toxins identified three spatially contiguous residues, Pro(10), Asn(27), and Arg(35), that are critical for insecticidal activity against flies (Musca domestica) and crickets (Acheta domestica). Competitive binding assays using radiolabeled omega-atracotoxin-Hv1a and neuronal membranes prepared from the heads of American cockroaches (Periplaneta americana) confirmed the importance of these three residues for binding of the toxin to target calcium channels presumably expressed in the insect membranes. At concentrations up to 10 muM, omega-atracotoxin-Hv1a had no effect on heterologously expressed rat Ca(v)2.1, Ca(v)2.2, and Ca(v)1.2 calcium channels, consistent with the previously reported insect selectivity of the toxin. 30 muM omega-atracotoxin-Hv1a inhibited rat Ca-v currents by 10-34%, depending on the channel subtype, and this low level of inhibition was essentially unchanged when Asn(27) and Arg(35), which appears to be critical for interaction of the toxin with insect Ca-v channels, were both mutated to alanine. We propose that the spatially contiguous epitope formed by Pro(10), Asn(27), and Arg(35) confers specific binding to insect Ca-v channels and is largely responsible for the remarkable phyletic selectivity of omega-atracotoxin-Hv1a. This epitope provides a structural template for rational design of chemical insecticides that selectively target insect Ca-v channels
Glassy behavior of light in random lasers
A theoretical analysis [Angelani et al., Phys. Rev. Lett. 96, 065702 (2006)]
predicts glassy behaviour of light in a nonlinear random medium. This implies
slow dynamics related to the presence of many metastable states. We consider
very general equations (that also apply to other systems, like Bose-Condensed
gases) describing light in a disordered non-linear medium and through some
approximations we relate them to a mean-field spin-glass-like model. The model
is solved by the replica method, and replica-symmetry breaking phase transition
is predicted. The transition describes a mode-locking process in which the
phases of the modes are locked to random (history and sample-dependent) values.
The results are based on very general theory, and embrace a variety of physical
phenomena.Comment: 21 pages, 3 figures. Revised and enlarged version. To be published in
Physical Review
Crossover between Equilibrium and Shear-controlled Dynamics in Sheared Liquids
We present a numerical simulation study of a simple monatomic Lennard-Jones
liquid under shear flow, as a function of both temperature and shear rate. By
investigating different observables we find that i) It exists a line in the
(temperature-shear) plane that sharply marks the boarder between an
``equilibrium'' and a ``shear-controlled'' region for both the dynamic and the
thermodynamic quantities; and ii) Along this line the structural relaxation
time, is proportional to the inverse shear rate, i.e. to the typical time-scale
introduced by the shear flow. Above the line the liquid dynamics is unaffected
by the shear flow, while below it both temperature and shear rate control the
particle motion.Comment: 14 pages, 5 figure
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