Applications of the Covariant Spectator Theory

In this talk I provide a short overview of applications of the so-called Covariant Spectator Theory to two- and three-nucleon systems. It is a quasi-potential formalism based on relativistic quantum field theory, and can be derived from a reorganization of the complete Bethe-Salpeter series. In this framework, we con- structed two one-boson-exchange models, called WJC-1 and WJC-2, for the neutron-proton interaction that fit the 2007 world data base, containing several thousands of neutron-proton scattering data below 350 MeV, with a χ2/Ndata close to 1. The close fit to the observables implies that the phase shifts derived from these models can be interpreted as new phase-shift analyses, which can be used also in nonrelativistic frameworks. Both models have a considerably smaller number of adjustable parameters than are present in realistic nonrel- ativistic potentials, which shows that the inclusion of relativity actually helps to achieve a realistic description of the interaction between nucleons. This became also evident in calculations of the three-nucleon bound state, where the correct binding energy is obtained without additional irreducible three-body forces which are needed in nonrelativistic calculations. In addition, calculations of the electromagnetic form factors of helium- 3 and of the triton in complete impulse approximation also give very reasonable results, demonstrating the Covariant Spectator Theory’s ability to describe the structure of the three-nucleon bound states realistically

Children of Guest Workers in Europe: Social and Cultural Needs in Relation to Library Service

published or submitted for publicatio

Education and innovation as twin-engines of growth

We develop a dynamic general equilibrium model of education, quality and variety innovation, and scale-invariant growth. The early endogenous innovation-based growth models incorporate a scale e?ect predicting that larger economies are characterized by higher per capita growth rates. Recent models of semi-endogenous growth remove this scale e?ect but instead imply that economic growth depends proportionally on population growth. In contrast to the predecessor models, this paper argues that endogenous human-capital accumulation rather than an exogenously given continuing increase of the population is decisive for per capita growth. The consequence of the proposed integration of human capital accumulation into a two-R&D-sector model of quality and variety innovation is that education and innovation appear as twin-engines of growth and that steady state growth rates can be enhanced by subsidizing education. - education ; quality and variety innovation ; scale-invariant growth --

Phase behavior of grafted chain molecules: Influence of head size and chain length

Constant pressure Monte Carlo simulations of a coarse grained off-lattice model for monolayers of amphiphilic molecules at the air/water interface are presented. Our study focusses on phase transitions within a monolayer rather than on self aggregation. We thus model the molecules as stiff chains of Lennard-Jones spheres with one slightly larger repulsive end bead (head) grafted to a planar surface. Depending on the size of the head, the temperature and the pressure, we find a variety of phases, which differ in tilt order (including tilt direction), and in positional order. In particular, we observe a modulated phase with a striped superstructure. The modulation results from the competition between two length scales, the head size and the tail diameter. As this mechanism is fairly general, it may conceivably also be relevant in experimental monolayers. We argue that the superstructure would be very difficult to detect in a scattering experiment, which perhaps accounts for the fact that it has not been reported so far. Finally the effect of varying the chain length on the phase diagram is discussed. Except at high pressures and temperatures, the phase boundaries in systems with longer chains are shifted to higher temperatures.Comment: To appear in J. Chem. Phy

Modes of entry of petroleum distilled spray-oils into insects: a review

Petroleum oils are some of the oldest and safest pesticides in use. In spite of the numerous improvements achieved in oil technology, the mode of entry and the insecticide action mechanism of these products have been the subject of considerable debate and conjecture over many years. The literature reviewed suggests that insecticide oils can penetrate the insect body through the integument as well as through the tracheal system. Suffocation by spiracle blockage was held as the most accepted theory on its mode of action. However, an in depth analysis of the interaction between oils and insects body surface from a physical perspective suggests that suffocation occurs only when insects are over-sprayed or dipped in oil. Based on this analysis, it is more likely that when petroleum oils contact the insect surface, capillary forces and complex physical interactions take place in the cuticular layer, which lead to differences in the melting point and permeability of cuticle waxes. This in turn, alters the waterproofing properties of the cuticle and also leads to penetration of spray oils that can be carried to different lipophilic tissues. The changes in the cuticle caused by oils, which range from changes in melting point of the cuticular wax layer to cuticle dewaxing, strongly suggest cuticular penetration as the foremost mode of entry of insecticide oils.Fil: Stadler, Teodoro. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Mendoza. Instituto de Medicina y Biología Experimental de Cuyo; ArgentinaFil: Buteler, Micaela. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Mendoza. Instituto de Medicina y Biología Experimental de Cuyo; Argentin