The boundary field theory induced by the Chern-Simons theory

The Chern-Simons theory defined on a 3-dimensional manifold with boundary is written as a two-dimensional field theory defined only on the boundary of the three-manifold. The resulting theory is, essentially, the pullback to the boundary of a symplectic structure defined on the space of auxiliary fields in terms of which the connection one-form of the Chern-Simons theory is expressed when solving the condition of vanishing curvature. The counting of the physical degrees of freedom living in the boundary associated to the model is performed using Dirac's canonical analysis for the particular case of the gauge group SU(2). The result is that the specific model has one physical local degree of freedom. Moreover, the role of the boundary conditions on the original Chern- Simons theory is displayed and clarified in an example, which shows how the gauge content as well as the structure of the constraints of the induced boundary theory is affected.Comment: 10 page

Rolling-sliding laboratory tests of friction modifiers in dry and wet wheel-rail contacts

Friction management has been carried out extensively in the majority of railway networks in the last few years. A popular practice is the application of friction modifiers to increase the adhesion level in contaminated wheel-rail contacts. Two friction modifiers have particularly been used or tested on several railway networks as adhesion enhancers to facilitate the traction and braking operation under poor adhesion conditions. However, for assessment of the performance the railway operators and infrastructure managers mostly rely on practical observations that do not elucidate completely the effectiveness and side effects of these adhesion enhancers. In this paper, the constituents of the two friction modifiers are identified and the solid components are analyzed. A twin-disk roller rig has been used to study their performance in dry and wet contacts under closely controlled laboratory conditions. The adhesion characteristics of both friction modifiers are examined for different slip ratios. Furthermore, the wheel and rail disks are examined after a series of dry tests to analyze the mass loss, the surface damage, the change in surface hardness and roughness, and the subsurface deformation caused by the friction modifiers compared to dry clean contacts. (C) 2009 Elsevier B.V. All rights reserved

Biological synthesis of fluorescent nanoparticles by cadmium and tellurite resistant Antarctic bacteria: exploring novel natural nanofactories

Indexación: Web of ScienceBackground: Fluorescent nanoparticles or quantum dots (QDs) have been intensely studied for basic and applied research due to their unique size-dependent properties. There is an increasing interest in developing ecofriendly methods to synthesize these nanoparticles since they improve biocompatibility and avoid the generation of toxic byproducts. The use of biological systems, particularly prokaryotes, has emerged as a promising alternative. Recent studies indicate that QDs biosynthesis is related to factors such as cellular redox status and antioxidant defenses. Based on this, the mixture of extreme conditions of Antarctica would allow the development of natural QDs producing bacteria. Results: In this study we isolated and characterized cadmium and tellurite resistant Antarctic bacteria capable of synthesizing CdS and CdTe QDs when exposed to these oxidizing heavy metals. A time dependent change in fluorescence emission color, moving from green to red, was determined on bacterial cells exposed to metals. Biosynthesis was observed in cells grown at different temperatures and high metal concentrations. Electron microscopy analysis of treated cells revealed nanometric electron-dense elements and structures resembling membrane vesicles mostly associated to periplasmic space. Purified biosynthesized QDs displayed broad absorption and emission spectra characteristic of biogenic Cd nanoparticles. Conclusions: Our work presents a novel and simple biological approach to produce QDs at room temperature by using heavy metal resistant Antarctic bacteria, highlighting the unique properties of these microorganisms as potent natural producers of nano-scale materials and promising candidates for bioremediation purposes.http://microbialcellfactories.biomedcentral.com/articles/10.1186/s12934-016-0477-

Self-other agreement measures of acceptance in predicting academic achievement: A longitudinal analysis

This research focused on sed light to the process that surrounded accuracy perception of acceptance status during adolescence from a non-componential view of social perception. With a longitudinal data of adolescents, mediational models are proposed in order to understand the different types of accuracy measures developed, and how they worked to finally predict academic achievement..

What leads to loneliness?An integrative model of Social, Motivational and Emotional approaches in adolescence

Loneliness has been linked to many physical and mental health problems, especially during adolescence. From evolutionary, social needs, and cognitive approaches, this study examined whether emotional repair, relatedness need, and peer-rated indicators of relations behave in predicting loneliness, considering all approaches together. The sample consisted of 373 adolescents measured longitudinally at three time points. Results of a cross-lagged panel design found that, considering all the influences together, relatedness need showed the highest strength to predict loneliness. Furthermore, adolescents who were accepted by their peers and whose relatedness need was satisfied activated emotional regulation which additionally produced a decrease in prospective feelings of loneliness. In addition, loneliness has been shown to be a consequence of these variables

Screening Ryegrass Cultivars for Aluminium Sensitivity in Nutrient Soluations

The objective of this study was to evaluate Al and H+ tolerance of nine ryegrass (Lolium perenne and L. multiflorum) cultivars by growing plants in a mineral solution (pH 4.8 and 6.0 and 0-200 (M Al). Results showed that Yatsyn-1, with a relative root length of 91 was the cultivar least affected by acidity (H+), and Concord ( RRLpH = 58) was the cultivar with the highest H+ sensitivity. In connection with Al-tolerance, Yatsyn-1 and Concord, were the most tolerant cultivars with 88 and 87 RRLAl, respectively whereas Nui and Marathon, were the most sensitive ones, reaching only a 66, 60 RRLAl, respectively

Weight teasing and eating disorders. A comparative study in adolecent and adult samples

Disordered eating, unhealthy weight-control behaviours and body dissatisfaction are associated with diminished mental health. A key aspect that has been identified for the development of disordered eating behaviours and body dissatisfaction is to be teased. Additionally, the literature suggests that weight may affect the relationship between weight-teasing and disordered eating and body dissatisfaction, although this pattern is unclear. This study presents two cross-sectional studies with an adult and an adolescent sample. The adolescent sample comprised 15,224 participants, and the adult sample comprised 321 participants, all from Spain. Hierarchical regression analyses were conducted. Aims: to assess the relations among disordered eating, body dissatisfaction, weight, and weight-teasing among adolescents and adults; and to examine whether weight-teasing, weight, age, and gender predict disordered eating and body dissatisfaction in adults and adolescents. The results showed that adolescent girls presented greater effects, and all interactions were significant between weight-teasing and eating disorders. Adults also showed greater effects for women, and only eating disorder interactions were significant. Weight-control behaviours did not show any relationship with weight-teasing. Conclusion: Different approaches may be used in the prevention of eating disorders. Our results show that weight-teasing affects adults differently from adolescents