Confinement of neutral fermions by a pseudoscalar double-step potential in (1+1) dimensions

The problem of confinement of neutral fermions in two-dimensional space-time is approached with a pseudoscalar double-step potential in the Dirac equation. Bound-state solutions are obtained when the coupling is of sufficient intensity. The confinement is made plausible by arguments based on effective mass and anomalous magnetic interaction.Comment: 8 pages, 1 figur

Trapped ion emulation of electric dipole moment of neutral relativistic particles

The electric dipole moments of various neutral elementary particles, such as neutron, neutrinos, certain hypothetical dark matter particles and others, are predicted to exist by the standard model of high energy physics and various extensions of it. However, the predicted values are beyond the present experimental capabilities. We propose to simulate and emulate the electric dipole moment of neutral relativistic particles and the ensuing effects in the presence of electrostatic field by emulation of an extended Dirac equation in ion traps

Slowly decaying classical fields, unitarity, and gauge invariance

In classical external gauge fields that fall off less fast than the inverse of the evolution parameter (time) of the system the implementability of a unitary perturbative scattering operator ($S$-matrix) is not guaranteed, although the field goes to zero. The importance of this point is exposed for the counter-example of low-dimensionally expanding systems. The issues of gauge invariance and of the interpretation of the evolution at intermediate times are also intricately linked to that point.Comment: 8 pages, no figure

Mapping quantitative trait loci in outcross populations via residual maximum likelihood. II. A simulation study

International audienc

Species diversity, spatial distribution, and virulence associated genes of culturable vibrios in a brackish coastal Mediterranean environment

The Vibrio genus is widespread in marine and brackish environments, and several species are human and animal pathogens of global importance. Vibrios adapt rapidly to many environmental stresses, so that brackish environments can be both a suitable niche and a possible reservoir for them. To test the occurrence of culturable vibrios and their possible correlation with environmental factors in a temperate brackish environment, a 1year sampling study was performed in three brackish ponds located along the Central Thyrrenian coast in the Macchiatonda Nature Reserve (Santa Marinella, district of Rome, Italy). Molecular methods were used to detect Vibrio cholerae, Vibrio arahaemolyticus, and Vibrio vulnificus pathogenicity associated genes among the Vibrio isolates. Out of 130 Vibrio isolates identified by sequencing a recA fragment, 70 harbored virulence associated genes including ctx, ace, tcpA, tdh, trh, vvhA, vllY, and toxRS, so confirming the spread of virulence determinants across the environmental isolates. Ecological analysis showed that, although the water temperature is known to be a strong predictor of abundance and distribution of vibrios, its influence accounts for 27 % of the observed variance in the Macchiatonda samples, increasing to 40 % when combined with salinity

On essential self-adjointness for magnetic Schroedinger and Pauli operators on the unit disc in R^2

We study the question of magnetic confinement of quantum particles on the unit disk \ID in \IR^2, i.e. we wish to achieve confinement solely by means of the growth of the magnetic field $B(\vec x)$ near the boundary of the disk. In the spinless case we show that $B(\vec x)\ge \frac{\sqrt 3}{2}\cdot\frac{1}{(1-r)^2}-\frac{1}{\sqrt 3}\frac{1}{(1-r)^2\ln \frac{1}{1-r}}$, for $|\vec x|$ close to 1, insures the confinement provided we assume that the non-radially symmetric part of the magnetic field is not very singular near the boundary. Both constants $\frac{\sqrt 3}{2}$ and $-\frac{1}{\sqrt 3}$ are optimal. This answers, in this context, an open question from Y. Colin de Verdi\`ere and F. Truc. We also derive growth conditions for radially symmetric magnetic fields which lead to confinement of spin 1/2 particles.Comment: 18 pages; the main theorem has been expanded and generalize

Full transmission within a wide energy range and super-criticality in relativistic barrier scattering

For potential barriers with scalar and vector coupling, we show that a Dirac particle could experience nearly full transmission within a wide sub-barrier energy band. Moreover, for certain potential configurations, including pseudo-spin symmetry where the scalar potential is the negative of the vector, full transmission occurs for arbitrarily small momentum.Comment: 10 pages, 4 figures, 1 table, 1 video animatio

Characterization and sequence of PhoC, the principal phosphate-irrepressible acid phosphatase of Morganella morganii.

Phosphatase activities were investigated in Morganella morganii, which is one of the few enterobacterial species producing high-level phosphateirrepressible acid phosphatase activity (HPAP phenotype), and the gene encoding the major phosphate-irrepressible acid phosphatase was cloned, sequenced, and its product characterized. Using p-nitrophenyl phosphate as substrate, Morganella produced a major phosphate-irrepressible acid phosphatase (named PhoC) which is associated with the HPAP phenotype, a minor phosphate-irrepressible acid phosphatase, and a phosphate-repressible alkaline phosphatase. The presence of the PhoC activity prevented induction of alkaline phosphatase when a PhoC-hydrolysable organic phosphate ester, such as glycerol &phosphate, was the sole phosphate source. PhoC is a secreted nonspecific acid phosphatase apparently composed of four 25 kDa polypeptide subunits. The enzyme is resistant to EDTA, Pi# fluoride and tartrate. The M. morganii PhoC showed 84.6% amino acid sequence identity to the PhoN nonspecific acid phosphatase of Providencia stuartii, 45.3 O/O to the PhoN nonspecific acid phosphatase of Salmonella typhimurium, and 3708% to the principal acid phosphatase (PhoC) of Zymomonas mobilis. Comparison of sequence data and of regulation of these enzymes suggested a different phylogeny of members of this gene family within the Enterobacteriaceae

Perturbation Theory for Metastable States of the Dirac Equation with Quadratic Vector Interaction

The spectral problem of the Dirac equation in an external quadratic vector potential is considered using the methods of the perturbation theory. The problem is singular and the perturbation series is asymptotic, so that the methods for dealing with divergent series must be used. Among these, the Distributional Borel Sum appears to be the most well suited tool to give answers and to describe the spectral properties of the system. A detailed investigation is made in one and in three space dimensions with a central potential. We present numerical results for the Dirac equation in one space dimension: these are obtained by determining the perturbation expansion and using the Pad\'e approximants for calculating the distributional Borel transform. A complete agreement is found with previous non-perturbative results obtained by the numerical solution of the singular boundary value problem and the determination of the density of the states from the continuous spectrum.Comment: 10 pages, 1 figur