Visibility Fringe Reduction Due to Noise-Induced Effects: Microscopic Approach to Interference Experiments

Decoherence is the main process behind the quantum to classical transition. It is a purely quantum mechanical effect by which the system looses its ability to exhibit coherent behavior. The recent experimental observation of diffraction and interference patterns for large molecules raises some interesting questions. In this context, we identify possible agents of decoherence to take into account when modeling these experiments and study theirs visible (or not) effects on the interference pattern. Thereby, we present an analysis of matter wave interferometry in the presence of a dynamic quantum environment and study how much the visibility fringe is reduced and in which timescale the decoherence effects destroy the interference of massive objects. Finally, we apply our results to the experimental data reported on fullerenes and cold neutrons.Comment: 14 pages, 5 figures. Version to appear in Mod. Phys.

Nascent polypeptide chains exit the ribosome in the same relative position in both eucaryotes and procaryotes.

We located the polypeptide nascent chain as it leaves cytoplasmic ribosomes from the plant Lemna gibba by immune electron microscopy using antibodies against the small subunit of the enzyme ribulose-1,5-bisphosphate carboxylase. Similar studies with Escherichia coli ribosomes, using antibodies directed against the enzyme beta-galactosidase, show that the polypeptide nascent chain emerges in the same relative position in plants and bacteria. The eucaryotic ribosomal exit site is on the large subunit, approximately 75 A from the interface between subunits and nearly 160 A from the central protuberance, the presumed site for peptidyl transfer. This is the first functional site on both the eucaryotic and procaryotic ribosomes to be determined

Bose-Einstein Correlations for Mixed Neutral Mesons

Correlations are shown to arise in nonidentical mixed-particle pairs like $K^o \bar K^o$ when observed in identical decay modes like $K_S K_S$ in multiparticle final states containing many partial waves. No enhancement is found in any single partial wave and all partial wave analyses of the s-wave threshold resonance $a_o$ and $f_o$ should give the same results for all decay modes. In CP violation experiments where $B^o - \bar B^o$ pairs are inclusively produced and correlated decays into $\psi K_S$ and leptonic modes are observed, the CP-violating lepton asymmetry is enhanced by a factor of two in the kinematic region where Bose enhancement occurs.Comment: 11 page

Universal extra dimensions and Z->b bar-b

We study, at the one loop level, the dominant contributions from a single universal extra dimension to the process (Z\to b\bar{b}). By resorting to the gaugeless limit of the theory we explain why the result is expected to display a strong dependence on the mass of the top-quark, not identified in the early literature. A detailed calculation corroborates this expectation, giving rise to a lower bound for the compactification scale which is comparable to that obtained from the $\rho$ parameter. An estimate of the subleading corrections is furnished, together with a qualitative discussion on the difference between the present results and those derived previously for the non-universal case.Comment: 16 pages, 4 figures, revtex

Innovación curricular con el aprendizaje basado en problema en estudios universitarios : estudio de caso

Este artículo presenta una investigación cuyo objetivo general ha sido estudiar la cultura de la Escuela Universitaria de Enfermería Vall d'Hebron en la que se ha llevado a cabo una innovación organizativa y curricular fundamentada en el Aprendizaje Basado en Problemas (ABP) como metodología de enseñanza-aprendizaje. Los objetivos específicos han sido: 1) estudiar qué elementos característicos de la cultura innovadora se dan en dicha innovación y 2) contrastar la percepción que tienen los diferentes agentes implicados sobre las fases de la innovación. La metodología de investigación ha sido cualitativa y en el estudio de caso. Se han elaborado dos instrumentos de recogida de información que son las entrevistas en profundidad y el Focus Grup en el que han participado todo el profesorado de la Escuela. Los resultados indican que la autonomía que disponía la Escuela, tanto para la toma de decisiones, como para la gestión económica era una característica fundamental que explica el éxito de la innovación. El liderazgo ejercido por la dirección de la Escuela así como la tradición de trabajo en equipo del profesorado se ha considerado factores imprescindibles. La motivación de todo el equipo para llevar adelante el ABP para erigirse como un centro de referencia también ha sido decisiva así como el continuo asesoramiento de un experto externo durante todo el proceso de cambioThis research has been focused on the curricular innovation within the university framework. The general aim of the research has been the study of the innovation culture in the Escuela Universitaria de Enfermería Vall d'Hebron, using the Problem Based Learning (PBL) methodology. The specific objectives have been: 1) to study those elements of the innovation culture presents in the innovation and 2) to contrast the perception of the different agents implicated in the innovation phases. The research design has been based on the case study. Personal deep interviews and the Focus Group analysis have been used for data collection. The main results of this study have been: 1)the autonomy of the center for making decisions and for economical management 2) the institutional decision favorable to the change supported by the director of the center 3) the work as a team of all the professors of the center, absolutely necessary for make possible the change 4) the interest to be a reference center among other possible competitors 5)to have an external expert during all the process of the change. The teaching experience described in this paper aims to strengthen various aspects of competence of students through a dynamic learning method. The main aim of the experience is none other than making that students learn the basics of the subject, while developing different jurisdictional issues aligned with the student's imminent accession to the labor market. Teaching experience presents a co-assessment system linked to role playing by the student, that make it an appealing and efficient experience from the point of view of learning and skills development of the student. This work provides also a comparison between the results of teaching experience based on peer-assessment and role play with the traditional teaching of the same content during the previous academic year in the same subject but taught with traditional teaching methodolog

Excavaciones en Valentia

Resultados de una de las primeras campañas de excavación en la ciudad de Valenti