Sum rules and dualities for generalized parton distributions: is there a holographic principle?

To leading order approximation, the physical content of generalized parton distributions (GPDs) that is accessible in deep virtual electroproduction of photons or mesons is contained in their value on the cross-over trajectory. This trajectory separates the t-channel and s-channel dominated GPD regions. The underlying Lorentz covariance implies correspondence between these two regions through their relation to GPDs on the cross-over trajectory. This point of view leads to a family of GPD sum rules which are a quark analogue of finite energy sum rules and it guides us to a new phenomenological GPD concept. As an example, we discuss the constraints from the JLab/Hall A data on the dominant u-quark GPD H. The question arises whether GPDs are governed by some kind of holographic principle.Comment: 45 pages, 4 figures, Sect. 2 reorganized for clarity. Typos in Eq. (20) corrected. 4 new refs. Matches published versio

Integral boundary conditions for the time-dependent Schrödinger equation: Atom in a laser field

We formulate exact integral boundary conditions for a solution of the time-dependent Schrödinger equation that describes an atom interacting, in the dipole approximation, with a laser pulse. These conditions are imposed on a surface (boundary) which is usually chosen at a finite (but sufficiently remote) distance from the atom where the motion of electrons can be assumed to be semiclassical. For the numerical integration of the Schrödinger equation, these boundary conditions may be used to replace mask functions and diffuse absorbing potentials applied at the edge of the integration grid. These latter are usually introduced in order to (approximately) compensate for unphysical reflection which occurs at the boundary of a finite region if a zero-value condition is imposed there on the solution. The present method allows one to reduce significantly the size of the space domain needed for numerical integration. Considering the numerical solution for a one-dimensional model, we demonstrate the effectiveness of our approach in comparison with some other numerical methods.SCOPUS: ar.jinfo:eu-repo/semantics/publishe

Evaluation of Changes Induced in the Probiotic Escherichia coli M17 Following Recurrent Exposure to Antimicrobials

Introduction: It is already well known that the exposure of certain bacteria, pathogenic or not, to antimicrobials is likely to increase their virulence and induce the development of direct or cross resistance to antimicrobials, but there is almost no information available regarding probiotics. Aim: To assess the changes induced in susceptibility to antibiotics, biofilm formation, growth rate and relative pathogenicity in the probiotic Escherichia coli M17 (EC-M17) after long exposure to antimicrobials namely ampicillin, kanamycin, cefazolin and silver nanoparticles (AgNPs). Methods: After determining the minimum inhibitory concentrations (MIC) and minimum bactericidal concentrations (MBC) of the 4 antimicrobials above-mentioned by the microdilution method, EC-M17 was exposed to increasing subinhibitory doses ranging from MIC/8 to MIC for 8 days. The susceptibility to antibiotics of the mutants obtained was assessed by the Kirby Bauer disc diffusion method, biofilm formation by the Congo red agar method and with crystal violet bacterial attachment assay, and relative pathogenicity was assessed using a Galleria melonella waxworm model. Results: Exposure to antimicrobials induces noticeable changes in EC-M17. The highest adaptation to antimicrobials was observed on AgNPs with 8-fold increase in MIC and 16-fold increase in MBC of AgNPs. EC-M17 exposed to ampicillin, kanamycin and silver nanoparticles became resistant to ampicillin, ceftazidime, ceftazidime/clavulanate and tetracycline while exposure to cefazolin induced a significant decrease in sensitivity to tetracycline and ampicillin and resistance to ceftazidime/clavulanate and ceftazidime. The strain exposed to ampicillin was the only one to produce more biofilm than the control strain and except the EC-M17 exposed to cefazolin, all other EC-M17 strains were more pathogenic on G. melonella model than the control. Conclusion: Data in this investigation suggest that repeated exposure of the probiotic EC-M17 to antimicrobials may induce changes in antimicrobials susceptibility, biofilm formation, growth rate, and relative pathogenicity. Therefore, as far as possible, the probiotic E. coli M17 should not be used in combination with antibiotics and further investigations are required to expand similar work on more probiotics in order to avoid resistance build-up which might be transmitted by horizontal transfer

Effects of Female Sex Hormones on Adhesion of Candida Albicans Yeast-Like Fungi to the Buccal Epithelium

Hormonal regulation of receptor expression and glycogen concentrations in the epithelial cells of the oral cavity remains poorly studied. Adhesion of microorganisms to the vaginal epithelium correlates with their adhesion to the buccal epithelium. Analysis of the correlation between Candida adhesion to the vaginal and buccal epithelium depending on the hormonal status has demonstrated that activity of Candida albicans strains in the buccal epithelium correlates with their adhesion activity in the vaginal epithelium, with the coeffi cient of correlations (r) reaching 0.76

Surface adhesins of lactobacilli loosely connected to the cell wall and eliminated into the environment during culturing in liquid nutrient media

Six lactobacillus species and 4 clones of one of them were studied in order to clear out the ratio between the adhesion capacities of concanavalin A-reactive glycoprotein adhesins on the surface of the bacterial cell and glycoprotein adhesins released into the broth during culturing in liquid nutrient media. The adhesive activity of cultures is largely determined by the strain rather than species appurtenance. Elimination of glycoprotein adhesins from the bacterial cell and their antagonistic activity towards Candida albicans were demonstrated in specific interactions of glycoprotein adhesins with immune serum and concanavalin A. © Springer Science+Business Media, Inc. 2006

Characterization of surface adhesins of lactobacilli used in production of probiotic preparations

We examined production of the protein-lipoteichoic complex detectable by concanavalin A in six lactobacillus strains. A correlation was found between detection of this complex by both reaction with concanavalin A and agglutination with strain-specific antiserum. The cultures were characterized by expression of different types of adhesins. Among them, strains were differentiated with low adhesion activity and intensive production of the protein-lipoteichoic complex and strains with wide adhesin spectrum not producing the complex. We assume that a combination of lactobacillus variants differing in production of the protein-lipoteichoic complex and adhesion potency can be a basis of efficient probiotic preparation. © Springer Science+Business Media, Inc. 2006

Surface adhesins of lactobacilli loosely connected to the cell wall and eliminated into the environment during culturing in liquid nutrient media

Six lactobacillus species and 4 clones of one of them were studied in order to clear out the ratio between the adhesion capacities of concanavalin A-reactive glycoprotein adhesins on the surface of the bacterial cell and glycoprotein adhesins released into the broth during culturing in liquid nutrient media. The adhesive activity of cultures is largely determined by the strain rather than species appurtenance. Elimination of glycoprotein adhesins from the bacterial cell and their antagonistic activity towards Candida albicans were demonstrated in specific interactions of glycoprotein adhesins with immune serum and concanavalin A. © Springer Science+Business Media, Inc. 2006

Effects of Female Sex Hormones on Adhesion of Candida Albicans Yeast-Like Fungi to the Buccal Epithelium

Hormonal regulation of receptor expression and glycogen concentrations in the epithelial cells of the oral cavity remains poorly studied. Adhesion of microorganisms to the vaginal epithelium correlates with their adhesion to the buccal epithelium. Analysis of the correlation between Candida adhesion to the vaginal and buccal epithelium depending on the hormonal status has demonstrated that activity of Candida albicans strains in the buccal epithelium correlates with their adhesion activity in the vaginal epithelium, with the coeffi cient of correlations (r) reaching 0.76