Spectral properties in supersymmetric matrix models

We formulate a general sufficiency criterion for discreteness of the spectrum of both supersymmmetric and non-su-persymmetric theories with a fermionic contribution. This criterion allows an analysis of Hamiltonians in complete form rather than just their semiclassical limits. In such a framework we examine spectral properties of various (1+0) matrix models. We consider the BMN model of M-theory compactified on a maximally supersymmetric pp-wave background, different regularizations of the supermembrane with central charges and a non-supersymmetric model comprising a bound state of N D2 with m D0. While the first two examples have a purely discrete spectrum, the latter has a continuous spectrum with a lower end given in terms of the monopole charge.Comment: 40 pages, 5 figure

Modélisation géomatique rétrospective des paysages par évaluation multicritères et multiobjectifs

International audienceParmi les fonctions SIG pour la modélisation spatio-temporelle et l'aide à la décision, l'évaluation multicritères et multiobjectifs s'avèrent être particulièrement utile en ce qui concerne la reproductibilité des résultats et le paramétrage de scénarii en termes de prise de risque et de compensation. Ce travail illustre la méthodologie et les résultats obtenus pour la reconstitution probabiliste du paysage historique de la Alta Alpujarra Granadina (Sierra Nevada, Espagne) du 16ème, 18ème et 19ème siècle. L'évaluation multicritères génère des cartes de potentialité - ou d'aptitude - pour chaque usage (objectif), en l'occurrence les différentes catégories d'occupation du sol. Elle se base sur l'hypothèse qu'il existe, pour une date donnée, une série de critères spatialisés pouvant expliquer la variabilité des états de la variable (catégories d'occupation du sol), autrement dit l'aptitude pour un usage. L'évaluation multiobjectifs consiste, en tenant compte des superficies réellement occupées, à intégrer les objectifs concurrents (cartes d'aptitude monothématiques) afin de construire les cartes probabilistes d'occupation du sol historiques pour 1572, 1752 et 1855/61. Les résultats expriment la probabilité de présence d'une occupation du sol à un endroit donné selon les critères inclus dans l'analyse. Leur interprétation permet de se prononcer sur les apports et limites de la méthodologie mise en oeuvre sans pour autant autoriser une validation faute de documents historiques de comparaiso

Variabilidad del ADN cloroplástico y su contribución al conocimiento del estado de conservación de Ulmus glabra en el Sistema Central

En el presente trabajo se ha analizado la diversidad existente en el ADN cloroplástico (ADNcp) de 16 poblaciones distribuidas a lo largo del Sistema Central. Para ello, se ha empleado la técnica de PCR-RFLP (amplificación de fragmentos específicos y posterior digestión con enzimas de restricción) sobre 38 regiones del ADNcp (Grivet et al., 2001)

Reversible Nuclear-Lipid-Droplet Morphology Induced by Oleic Acid: A Link to Cellular-Lipid Metabolism

Neutral lipidsÐinvolved in many cellular processesÐare stored as lipid droplets (LD), thosemainly cytosolic (cLD) along with a small nuclear population (nLD). nLD could be involved innuclear-lipid homeostasis serving as an endonuclear buffering system that would provide orincorporate lipids and proteins involved in signalling pathways as transcription factors andas enzymes of lipid metabolism and nuclear processes. Our aim was to determine if nLDconstituted a dynamic domain. Oleic-acid (OA) added to rat hepatocytes or HepG2 cells inculture produced cellular-phenotypic LD modifications: increases in TAG, CE, C, and PLcontent and in cLD and nLD numbers and sizes. LD increments were reversed on exclusionof OA and were prevented by inhibition of acyl-CoA synthetase (with Triacsin C) and thuslipid biosynthesis. Under all conditions, nLD corresponded to a small population (2±10%) oftotal cellular LD. The anabolism triggered by OA, involving morphologic and size changeswithin the cLD and nLD populations, was reversed by a net balance of catabolism, uponeliminating OA. These catabolic processes included lipolysis and the mobilization of hydrolyzedFA from the LD to cytosolic-oxidation sites. These results would imply that nLD areactively involved in nuclear processes that include lipids. In conclusion, nLD are a dynamicnuclear domain since they are modified by OA through a reversible mechanism in combinationwith cLD; this process involves acyl-CoA-synthetase activity; ongoing TAG, CE, and PLbiosynthesis. Thus, liver nLD and cLD are both dynamic cellular organelles.Fil: Lagrutta, Lucía Carolina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata. Instituto de Investigaciones Bioquímicas de La Plata "Prof. Dr. Rodolfo R. Brenner". Universidad Nacional de la Plata. Facultad de Ciencias Médicas. Instituto de Investigaciones Bioquímicas de La Plata ; ArgentinaFil: Montero Villegas, Sandra. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata. Instituto de Investigaciones Bioquímicas de La Plata "Prof. Dr. Rodolfo R. Brenner". Universidad Nacional de la Plata. Facultad de Ciencias Médicas. Instituto de Investigaciones Bioquímicas de La Plata ; ArgentinaFil: Layerenza, Juan Pablo. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata. Instituto de Investigaciones Bioquímicas de La Plata "Prof. Dr. Rodolfo R. Brenner". Universidad Nacional de la Plata. Facultad de Ciencias Médicas. Instituto de Investigaciones Bioquímicas de La Plata ; ArgentinaFil: Sisti, Martin Sebastian. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata. Instituto de Investigaciones Bioquímicas de La Plata "Prof. Dr. Rodolfo R. Brenner". Universidad Nacional de la Plata. Facultad de Ciencias Médicas. Instituto de Investigaciones Bioquímicas de La Plata ; ArgentinaFil: Garcia, Margarita Maria. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata. Instituto de Investigaciones Bioquímicas de La Plata "Prof. Dr. Rodolfo R. Brenner". Universidad Nacional de la Plata. Facultad de Ciencias Médicas. Instituto de Investigaciones Bioquímicas de La Plata ; ArgentinaFil: Ves Losada, Ana. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata. Instituto de Investigaciones Bioquímicas de La Plata "Prof. Dr. Rodolfo R. Brenner". Universidad Nacional de la Plata. Facultad de Ciencias Médicas. Instituto de Investigaciones Bioquímicas de La Plata ; Argentin

The effect of 'research based learning activities' on students’ intention to do research in graduate courses

Nowadays, universities have a pronounced interest to link teaching and research. Research into this link has developed rapidly over the last decades, and focused on how the teaching-research nexus (TRN) enhances the quality and outcomes of the learning experience for both students and academics. As part of this nexus, Research-Based Learning (RBL) involves a curriculum designed around inquiry activities in which students have the opportunity to conduct their own research. We hypothesize if graduate students involved in a RBL version of a course reflect a higher intention to do research compared to students in a control condition of the same course. We also attempt to determine the impact of course contexts and changes in mediating variables such as autonomous motivation, engagement, perceived behavioural control (self-efficacy), behavioural beliefs, subjective norm and the interaction with age and gender. A quasi-experimental pretest-posttest design was set up involving 52 students from 6 different programs at a public university. We developed scales building on Bandura's guidelines to determine self-efficacy (perceived behavioural control), Ajzen's Theory of Planned Behaviour to test the intention to do research along with behavioural beliefs and subjective norm; and Deci and Ryan's Intrinsic Motivation Inventory to determine autonomous motivation. To measure engagement, we developed a 6-week intervention in which students in the experimental condition worked on RBL assignments whereas students in the control condition worked on TRN activities. All student activities were managed through an online learning management system. Our results show a clear trend, reflecting how students in an RBL version of the course attain slightly higher levels of intention to do research. However these differences are not significant. There are some explanations for the current findings. First of all, the students in the control condition were similarly involved in - though basic - research activities. This might have also boosted their level of intention in doing research considering the rather short term set up of the study (6 weeks). An additional explanation is related to our RBL design and the fact that students from 6 different programs were involved. This resulted in an RBL design that had to comply with the research focus of all 6 programs and as such involved the students in more general research activities. The results of the present study - though promising - push a research programme aiming at more in-depth research. Nevertheless, the RBL approach has invoked in the local university setting an innovative way of thinking about the teaching-research nexus. From a focus on a single-course innovation, a focus at a programme level approach of RBL has been put at the centre. This opens avenues for new and promising research endeavours. Future RBL related research implies setting up qualitative studies to compare the actual experiences of students in both conditions and whether they report differences. In addition, a new study could be set up in a single course setting, while involving a larger number of enrolled students. This is not an easy undertaking given the limited student numbers in advanced engineering courses in the target Ecuadorian University. Building on the limitations as to the quantitative nature of the study, a mixed method design could help developing a richer picture

Adenosine Signaling in Mast Cells and Allergic Diseases.

Adenosine is a nucleoside involved in the pathogenesis of allergic diseases. Its effects are mediated through its binding to G protein-coupled receptors: A1, A2a, A2b and A3. The receptors differ in the type of G protein they recruit, in the effect on adenylyl cyclase (AC) activity and the downstream signaling pathway triggered. Adenosine can produce both an enhancement and an inhibition of mast cell degranulation, indicating that adenosine effects on these receptors is controversial and remains to be clarified. Depending on the study model, A1, A2b, and A3 receptors have shown anti- or pro-inflammatory activity. However, most studies reported an anti-inflammatory activity of A2a receptor. The precise knowledge of the adenosine mechanism of action may allow to develop more efficient therapies for allergic diseases by using selective agonist and antagonist against specific receptor subtypes