The nucleon-nucleon interaction and properties of the nucleon in a πρω\pi\rho\omega soliton model including a dilaton field with anomalous dimension

We investigate an extended chiral soliton model which includes $\pi, \rho, \omega$ and $\sigma$ mesons as explicit degrees of freedom. The Lagrangian incorporates chiral symmetry and broken scale invariance. A scalar-isoscalar meson $\sigma$ is associated with a quarkonium dilaton field with a mass \msig\approx 550 MeV. We show that the scalar field with anomalous dimension slightly changes the static and electromagnetic properties of the nucleon. In contrast, it plays a significant role in nucleon-nucleon dynamics and gives an opportunity to describe well the two-nucleon interaction.Comment: 14 pages, REVTeX, 3 figures (Ps), 83 k

Local and global spatial effects in hierarchical models

Hierarchical models have a long history in empirical applications; recognition of the fact that many datasets of interest to applied econometricians are nested; counties within states, pupils within school, regions within countries, etc. Just as many datasets are characterized by nesting, many are also characterized by the presence of spatial dependence or spatial heterogeneity. Significant advances have been made in developing econometric techniques and models to allow applied econometricians to address this spatial dimension to their data. This paper fuses these two literatures together and combines a hierarchical model with the two general spatial econometric models

Is Turing's Thesis the Consequence of a More General Physical Principle?

We discuss historical attempts to formulate a physical hypothesis from which Turing's thesis may be derived, and also discuss some related attempts to establish the computability of mathematical models in physics. We show that these attempts are all related to a single, unified hypothesis.Comment: 10 pages, 0 figures; section 1 revised, other minor change

Comment on Neutron-Proton Spin-Correlation Parameter A_{ZZ} at 68 Mev

We present two arguments indicating that the large value for the $\epsilon_1$ mixing parameter at 50 MeV, which the Basel group extracted from their recent $A_{zz}$ measurement, may be incorrect. First, there are nucleon-nucleon (NN) potentials which predict the $\epsilon_1$ at 50 MeV substantially below the Basel value and reproduce the Basel $A_{zz}$ data accurately. Second, the large value for $\epsilon_1$ at 50 MeV proposed by the Basel group can only be explained by a model for the NN interaction which is very unrealistic (no $\rho$-meson and essentially a point-like $\pi NN$ vertex) and overpredicts the $\epsilon_1$ in the energy range where it is well determined (150--500 MeV) by a factor of two.Comment: 6 pages text (LaTex) and 2 figures (paper, will be faxed upon request), UI-NTH-930

Pour l'introduction de l'histoire des sciences dans l'enseignement du second cycle

Si la place officielle de l'histoire de la biologie dans l'enseignement du second cycle est dérisoire, il est toujours possible, lorsqu'on est convaincu de son intérêt, de saisir les occasions de l'introduire, fût-ce de façon furtive. Les quelques exemples présentés ici correspondent à des essais échelonnés dans le temps conduits par des professeurs de plusieurs disciplines du lycée de Saint-Gaudens| le plus souvent lancés sur un coup de coeur, ils ont permis de " dévorer " des documents, de partager les connaissances, de confronter les points de vue. Lieu d'interdisciplinarité, l'histoire des sciences est pour chacun de nous source de culture. Sans doute, la pratique de l'A., inscrite dans les contraintes de l'institution n'est-elle qu'un patchwork de tentatives partielles et parfois ridiculement ambitieuses. Conscients de privilégier une seule facette de l'histoire de la biologie, il pense avoir toutefois aidé ses élèves (en particulier les " littéraires ") à mieux comprendre et à mieux aimer la biologi

Strange vector currents and the OZI-rule

We investigate the role of correlated $\pi\rho$ exchange in the extraction of matrix elements of the strange vector current in the proton. We show that a realistic isoscalar spectral function including this effect leads to sizeably reduced strange vector form factors based on the dispersion--theoretical analysis of the nucleons' electromagnetic form factors.Comment: 8 pp, plain LaTeX, uses epsf, 3 figure

Cross section and analyzing power of pol{p}p -> pn pi+ near threshold

The cross section and analyzing power of the pol{p}p -> pn pi+ reaction near threshold are estimated in terms of data obtained from the pol{p}p -> d pi+ and pp -> pp pi0 reactions. A simple final state interaction theory is developed which depends weakly upon the form of the pion-production operator and includes some Coulomb corrections. Within the uncertainties of the model and the input data, the approach reproduces well the measured energy dependence of the total cross section and the proton analyzing power at a fixed pion c.m. angle of 90deg, from threshold to T_p = 330 MeV. The variation of the differential cross section with pion angle is also very encouraging.Comment: 20 pages, Latex including 4 eps figure

" Prendre le bâton de l'expérience... "

Le statut de l'expérience au XVIIIe siècle peut-il nous aider à relativiser l'image que nous en donnent les Instructions Officielles inspirées de Claude Bernard? Comment peut-on faire, en biologie, dans le second cycle, l'expérience de l'expérimentation

Using Amino Acid Derivatives to Inhibit Pseudomonas aeruginosa Biofilm Formation on Cystic Fibrosis Bronchial Epithelia Cells

poster abstractCystic Fibrosis is a genetic disease caused by a mutation which inhibits the proper transport of sodium and chloride ions across epithelium. Improper ion transport results in the accumulation of thick mucus in critical organs such as the lungs, pancreas, liver, and intestines. The genetic mutation is incurable, but treating the symptoms can vastly increase life expectancy. CF patients are often afflicted with bacterial infections which colonize the excess mucus within the lungs. The most prevalent pathogen associated with CF lung infection is Pseudomonas aeruginosa, a Gram-negative bacterium found in soil and water. Pseudomonas aeruginosa exists in two forms: planktonic (free-swimming) and sessile (immobile within a biofilm community). The planktonic form is about 1,000x more susceptible to antibiotics and immune cells than the sessile form. Biofilm communities of sessile bacteria are protected by an exopolysaccharide layer outside of the cell wall. Small molecules which inhibit biofilm formation or initiate biofilm disassembly can dramatically increase the effectiveness of drugs and the immune system. In order to identify novel biofilm-inhibitory molecules, we assessed the activity of a library of small molecules in biofilm assays. Active compounds were then screened for activity on living Cystic Fibrosis bronchial epithelial cells infected with Pseudomonas aeruginosa. Compounds which successfully inhibit biofilm formation without affecting the Cystic Fibrosis bronchial epithelium cells can potentially be a new drug for treating Cystic Fibrosis infections