High-visibility multi-photon interference of Hanbury Brown - Twiss type for classical light

Difference-phase (or Hanbury Brown - Twiss type) intensity interference of classical light is considered in higher orders in the intensity. It is shown that, while the visibility of sum-phase (NOON-type) interference for classical sources drops with the order of interference, the visibility of difference-phase interference has opposite behavior. For three-photon and four-photon interference of two coherent sources, the visibility can be as high as 81.8% and 94.4%, respectively. High-visibility three-photon and four-photon interference of space-time and polarization types has been observed in experiment, for both coherent and pseudo-thermal light.Comment: 11 pages, 9 figure

Possibility of local pair existence in optimally doped SmFeAsO(1-x) in pseudogap regime

We report the analysis of pseudogap Delta* derived from resistivity experiments in FeAs-based superconductor SmFeAsO(0.85), having a critical temperature T_c = 55 K. Rather specific dependence Delta*(T) with two representative temperatures followed by a minimum at about 120 K was observed. Below T_s = 147 K, corresponding to the structural transition in SmFeAsO, Delta*(T) decreases linearly down to the temperature T_AFM = 133 K. This last peculiarity can likely be attributed to the antiferromagnetic (AFM) ordering of Fe spins. It is believed that the found behavior can be explained in terms of Machida, Nokura, and Matsubara (MNM) theory developed for the AFM superconductors.Comment: 5 pages, 2 figure

TRANSIENT ELECTROMAGNETIC SOUNDING IN 2D, 3D, AND 4D MODES: SEQUENCE OF GEOLOGICAL EXPLORATION ACTIVITIES

From 1980s, electromagnetic prospecting is an integral component of geophysical techniques for oil and gas exploration in many regions of the Russian Federation. Electromagnetic methods are used at all stages of geological exploration, including reconnaissance, discovery, prospecting and appraisal, and economic mining. In oil and gas exploration, the most commonly used technique is the near-field transient electromagnetic sounding (TEM). On the other hand, for each of these stages, specific tasks of electromagnetic prospecting have not been clearly defined yet. Furthermore, there are no standard requirements to the volume of a priori geological and geophysical information, which is sufficient for solving a geological problem. If such information is lacking or insufficient, a geological problem may be incorrectly stated and/or improperly correlated with the current stage of works. Our study aims to define which geological problems should be addressed by electromagnetic survey at the different stages of geological exploration, and to specify the requirements to the availability of a priori geological and geophysical information. We have analyzed the electromagnetic data from the regions of East and West Siberia, which have different geological settings. The main geological problems that can be solved by the seismic and electromagnetic techniques are determined. We propose a set of geophysical survey operations, which is optimal for oil and gas exploration. An effective sequence of electromagnetic prospecting stages is determined, and preliminary and accompanying surveys are specified. The requirements to the availability of a priori information are proposed, and its volume is defined. Geological problems are defined with respect to the corresponding stages of geological exploration. Special attention is given to approaches to the mineral resource estimation and calculation of hydrocarbon reserves, taking into account electromagnetic survey results. It is proposed to use the electromagnetic data at the stage of prospecting and appraisal, which aims to assess the resources of categories Dl and D0, as well as at the exploration stage for estimating the reserves of category C2 in new and explored fields. Approaches to the economic assessment of using electromagnetic surveys as part of the geological exploration are discussed. Our study shows that a correct sequence of electromagnetic prospecting operations at each stage can ensure obtaining an original geological dataset of the given stage and thus providing a proper basis for the next stage of oil-gas field investigation

Laplace transformations of hydrodynamic type systems in Riemann invariants: periodic sequences

The conserved densities of hydrodynamic type system in Riemann invariants satisfy a system of linear second order partial differential equations. For linear systems of this type Darboux introduced Laplace transformations, generalising the classical transformations in the scalar case. It is demonstrated that Laplace transformations can be pulled back to the transformations of the corresponding hydrodynamic type systems. We discuss periodic Laplace sequences of with the emphasize on the simplest nontrivial case of period 2. For 3-component systems in Riemann invariants a complete discription of closed quadruples is proposed. They turn to be related to a special quadratic reduction of the (2+1)-dimensional 3-wave system which can be reduced to a triple of pairwize commuting Monge-Ampere equations. In terms of the Lame and rotation coefficients Laplace transformations have a natural interpretation as the symmetries of the Dirac operator, associated with the (2+1)-dimensional n-wave system. The 2-component Laplace transformations can be interpreted also as the symmetries of the (2+1)-dimensional integrable equations of Davey-Stewartson type. Laplace transformations of hydrodynamic type systems originate from a canonical geometric correspondence between systems of conservation laws and line congruences in projective space.Comment: 22 pages, Late

Invariant description of solutions of hydrodynamic type systems in hodograph space: hydrodynamic surfaces

Hydrodynamic surfaces are solutions of hydrodynamic type systems viewed as non-parametrized submanifolds of the hodograph space. We propose an invariant differential-geometric characterization of hydrodynamic surfaces by expressing the curvature form of the characteristic web in terms of the reciprocal invariants.Comment: 12 page

Construction of PCR Test-System for Differentiation between Genetically Altered Toxigenic Vibrio cholerae Strains, Biovar El Tor, with Varied Epidemic Potential

Designed is a multi-locus PCR test-system that allows for differentiation between genetically altered Vibrio cholerae strains, biovar El Tor, with high and low epidemic potential respectively, based on identification of genetic marker structure in the agent of the seventh cholera pandemic - pandemicity island VSP-II. In the course of investigations selected have been three target genes allocated in the central region and terminal end of the mobile genetic element. This test-system offers the possibility to identify the strains containing intact VSP-II, the ones containing VSP-II with a short-length deletion, and the strains with VSP-II with extended deletion. The first two are classified as the variants with low epidemic potential, while the last ones - as the variants with high epidemic potential. Specificity and efficacy of the test-system is shown by the experiments with 28 toxigenic genetically altered V. cholerae strains, biovar El Tor, and 6 strains of closely related species and enterobacteria. The results obtained coincide with the data on mono-locus PCR assay and in a number of instances are verified by sequencing

Phenotypic and Molecular-Genetic Analysis of Genetically Modified Toxigenic <I>Vibrio cholerae</I> El Tor Strain 301, Isolated in 2011 in Russia

The phenotypic and molecular-genetic analysis of Vibrio cholerae O1 El Tor Inaba strain 301, isolated in 2011 from sea water in recreation zone in Taganrog, demonstrated this isolate to be a genetic variant of El Tor cholera causative agent. Its genome was shown to carry a hybrid prophage, containing gene ctxB of classical type and gene rstR of El Tor type, as well as altered pathogenicity island VPI-1 and pandemicity island VSP-II. This strain produced much more cholera toxin (0,12 mcg/ml) than typical strains of this causative agent

EFFECT OF THE PROPHAGE CTXΦ DELETION UPON PHENOTYPIC PROPERTIES IN STRAINS OF VIBRIO CHOLERAE BIOVAR EL TOR, ASSOCIATED WITH VIRULENCE AND PERSISTENCE

Objective of the study is to evaluate the influence of CTXφ prophage deletion, which carries ctxAB genes, on phenotypical properties associated with pathogenicity or biofilm formation in non-toxigenic mutants. Materials and methods. Utilized have been the clinical strains of Vibrio cholerae biovar El Tor and their spontaneous non-toxigenic mutants that lost CTXφ prophage. Applied have been microbiological and biochemical methods, inoculation of model animals with cells of the strains under study. Results and conclusions. The results of comparative analysis of phenotypic properties in isogenic toxigenic and non-toxigenic strains of Vibrio cholerae biovar El Tor, which lost CTXφ prophage encoding the cholera toxin, are represented. It is established that the deletion of CTXφ prophage leads to the simultaneous change of several phenotypic properties associated with virulence (colonizing ability, production of soluble hemagglutinin/protease and heat labile hemolysin/cytolysin) and biofilm formation (motility, exopolysaccharide biosynthesis) in spontaneous non-toxigenic mutants. It is suggested that the reason for these phenotypic changes in the mutants might be the changes in activity of the related to each other regulatory genes controlling virulence and biofilm formation process in cholera agent