Fractal Structure of Random Matrices

A multifractal analysis is performed on the universality classes of random matrices and the transition ones.Our results indicate that the eigenvector probability distribution is a linear sum of two chi-squared distribution throughout the transition between the universality ensembles of random matrix theory and Poisson

Variance of the decay intensity of superdeformed bands

We present analytic formulae for the energy average and variance of the intraband decay intensity of a superdeformed band.Comment: 4 pages, 2 figures, presented at the VIII International Conference on Nucleus-Nucleus Collisions in Moscow (Russia) on June 17-21, 200

Resonances and the thermonuclear reaction rate

We present an approximate analytic expression for thermonuclear reaction rate of charged particles when the cross section contains a single narrow or wide resonance described by a Breit-Wigner shape. The resulting expression is uniformly valid as the effective energy and resonance energy coalesce. We use our expressions to calculate the reaction rate for $^{12}$C(p,$\gamma$)$^{13}$N.Comment: 4 pages, 1 figure, presented at the VIII International Conference on Nucleus-Nucleus in Moscow (Russia) on June 17-21, 200

Spectral properties of a generalized chGUE

We consider a generalized chiral Gaussian Unitary Ensemble (chGUE) based on a weak confining potential. We study the spectral correlations close to the origin in the thermodynamic limit. We show that for eigenvalues separated up to the mean level spacing the spectral correlations coincide with those of chGUE. Beyond this point, the spectrum is described by an oscillating number variance centered around a constant value. We argue that the origin of such a rigid spectrum is due to the breakdown of the translational invariance of the spectral kernel in the bulk of the spectrum. Finally, we compare our results with the ones obtained from a critical chGUE recently reported in the literature. We conclude that our generalized chGUE does not belong to the same class of universality as the above mentioned model.Comment: 12 pages, 3 figure

Neuromuscular synaptic transmission in aged ganglioside-deficient mice

Gangliosides are sialylated glycosphingolipids that are present in high density on neuronal membranes, especially at synapses, where they are assumed to play functional or modulating roles. Mice lacking GM2/GD2-synthase express only the simple gangliosides GD3 and GM3 and develop progressive motor behaviour deficits upon ageing, apparently due to failing complex ganglioside-dependent maintenance and/or repair processes or, alternatively, toxic GM3/GD3 accumulation. We investigated the function of neuromuscular junctions (NMJs) of aged (>9 month-old) GM2/GD2-synthase null-mutant mice, because synaptic dysfunction might develop with age and could potentially contribute to the late-onset motor phenotype. In addition, we studied NMJs of old mice lacking GD3-synthase (expressing only O- and a-series gangliosides), which do not show an overt neurological phenotype but may develop subclinical synaptic deficits. Detailed electrophysiological analyses showed subtle changes in presynaptic neurotransmitter release. Acetylcholine release at 40 Hz nerve stimulation at aged GM2/GD2-synthase null-mutant NMJs ran down slightly more pronounced than at wild-type NMJs, and spontaneous acetylcholine release rate at GD3-synthase null-mutant NMJs was somewhat higher than at wild-type, selectively at 25 degrees C bath temperature. Interestingly, we observed faster kinetics of postsynaptic electrophysiological responses at aged GD3-synthase null-mutant NMJs, not previously seen by us at NMJs of young GD3-synthase null-mutants or other types of (aged or young) ganglioside-deficient mice. These kinetic changes might reflect a change in postsynaptic acetylcholine receptor behaviour. Our data indicate that it is highly unlikely that transmission failure at NMJs contributes to the progressive motor defects of aged GM2/GD2-synthase null-mutants and that, despite some kinetic changes of synaptic signals, neuromuscular transmission remains successful in aged GD3-synthase null-mutant mice. Apparently, mutual redundancy of the different gangliosides in supporting presynaptic function, as observed previously by us in young mice, remains adequate upon ageing or, alternatively, gangliosides have only relatively little direct impact on neuromuscular synaptic function, even in aged mice. (C) 2009 Elsevier Inc. All rights reserve

Contributions of common genetic variants to risk of schizophrenia among individuals of African and Latino ancestry

Schizophrenia is a common, chronic and debilitating neuropsychiatric syndrome affecting tens of millions of individuals worldwide. While rare genetic variants play a role in the etiology of schizophrenia, most of the currently explained liability is within common variation, suggesting that variation predating the human diaspora out of Africa harbors a large fraction of the common variant attributable heritability. However, common variant association studies in schizophrenia have concentrated mainly on cohorts of European descent. We describe genome-wide association studies of 6152 cases and 3918 controls of admixed African ancestry, and of 1234 cases and 3090 controls of Latino ancestry, representing the largest such study in these populations to date. Combining results from the samples with African ancestry with summary statistics from the Psychiatric Genomics Consortium (PGC) study of schizophrenia yielded seven newly genome-wide significant loci, and we identified an additional eight loci by incorporating the results from samples with Latino ancestry. Leveraging population differences in patterns of linkage disequilibrium, we achieve improved fine-mapping resolution at 22 previously reported and 4 newly significant loci. Polygenic risk score profiling revealed improved prediction based on trans-ancestry meta-analysis results for admixed African (Nagelkerke’s R2 = 0.032; liability R2 = 0.017; P < 10−52), Latino (Nagelkerke’s R2 = 0.089; liability R2 = 0.021; P < 10−58), and European individuals (Nagelkerke’s R2 = 0.089; liability R2 = 0.037; P < 10−113), further highlighting the advantages of incorporating data from diverse human populations