Transport properties of a two impurity system: a theoretical approach

A system of two interacting cobalt atoms, at varying distances, was studied in a recent scanning tunneling microscope experiment by Bork et. al.[Nature Phys. 7, 901 (2011)]. We propose a microscopic model that explains, for all experimentally analyzed interatomic distances, the physics observed in these experiments. Our proposal is based on the two-impurity Anderson model, with the inclusion of a two-path geometry for charge transport. This many-body system is treated in the finite-U slave boson mean-field approximation and the logarithmic-discretization embedded-cluster approximation. We physically characterize the different charge transport regimes of this system at various interatomic distances and show that, as in the experiments, the features observed in the transport properties depend on the presence of two impurities but also on the existence of two conducting channels for electron transport. We interpret the splitting observed in the conductance as the result of the hybridization of the two Kondo resonances associated with each impurity.Comment: 5 pages, 5 figure

K X-Ray Energies and Transition Probabilities for He-, Li- and Be-like Praseodymium ions

Theoretical transition energies and probabilities for He-, Li- and Be-like Praseodymium ions are calculated in the framework of the multi-configuration Dirac-Fock method (MCDF), including QED corrections. These calculated values are compared to recent experimental data obtained in the Livermore SuperEBIT electron beam ion trap facility

Narratives of adolescents with an active and sedentary lifestyle

Nuestra investigación trata de analizar las narraciones de adolescentes que han adoptado diferentes estilos de vida e identificar las variables psicológicas, comportamentales, sociales y ambientales relacionadas con un estilo de vida activo y una vida sedentaria. Se aplicaron entrevistas de carácter narrativo a 2 niñas (1 activa y 1 sedentaria) y 2 niños (1 activo y 1 sedentario). El análisis temático ha identificado las categorías que distinguen a los dos grupos de estudiantes, a lo largo de su infancia y adolescencia, específicamente: historia de la actividad física (AF); valor de los comportamientos sedentarios; apoyo social de la familia y amigos a la AF; seguridad física y las instalaciones en el barrio; participación en AF extracurricular en la escuela; la escuela primaria y secundaria y experiencias en Educación Física (EF); profesores y compañeros de EF; conocimiento de la AF y la salud; y actitudes hacia la EF y la escuelaThis study sought to analyse the narratives of adolescents who have adopted an active or a sedentary lifestyle, and to identify psychological, behavioural, social and environmental variables related to an active and a sedentary lifestyle among adolescents. Narrative interviews were conducted with 2 girls (1active and 1 sedentary) and 2 boys (1 active and 1sedentary). Thematic analysis identified a number of key personal, social and environmental influences on physical activity (PA) that distinguished the two groups of students, through their childhood and adolescence. These included PA history, the value of sedentary behaviours, social support from family and friends for PA, safety and PA facilities in the local neighbourhood, PA participation in school besides Physical Education (PE), primary and secondary school and experiences in PE, PE teachers and PE peers, PA and health knowledge and perception of PE goals, and attitudes toward school and PE

Differential mesenteric fat deposition in bovines fed on silage or concentrate is independent of glycerol membrane permeability

© The Animal Consortium 2011In the meat industry, the manipulation of fat deposition in cattle is of pivotal importance to improve production efficiency, carcass composition and ultimately meat quality. There is an increasing interest in the identification of key factors and molecular mechanisms responsible for the development of specific fat depots. This study aimed at elucidating the influence of breed and diet on adipose tissue membrane permeability and fluidity and their interplay on fat deposition in bovines. Two Portuguese autochthonous breeds, Alentejana and Barrosã, recognized as late- and early-maturing breeds, respectively, were chosen to examine the effects of breed and diet on fat deposition and on adipose membrane composition and permeability. Twenty-four male bovines from these breeds were fed on silage-based or concentrate-based diets for 11 months. Animals were slaughtered to determine their live slaughter and hot carcass weights, as well as weights of subcutaneous and visceral adipose depots. Mesenteric fat depots were excised and used to isolate adipocyte membrane vesicles where cholesterol content, fatty acid profile as well as permeability and fluidity were determined. Total accumulation of neither subcutaneous nor visceral fat was influenced by breed. In contrast, mesenteric and omental fat depots weights were higher in concentrate-fed bulls relative to silage-fed animals. Membrane fluidity and permeability to water and glycerol in mesenteric adipose tissue were found to be independent of breed and diet. Moreover, the deposition of cholesterol and unsaturated fatty acids, which may influence membrane properties, were unchanged among experimental groups. Adipose membrane lipids from the mesenteric fat depot of ruminants were rich in saturated fatty acids, and unaffected by polyunsaturated fatty acids dietary levels. Our results provide evidence against the involvement of cellular membrane permeability to glycerol on fat accumulation in mesenteric fat tissue of concentrate-fed bovines, which is consistent with the unchanged membrane lipid profile found among experimental groups.This study was supported by Fundação para a Ciência e a Tecnologia (FCT) through grant PTDC/CVT/2006/66114 and individual fellowships to Ana P. Martins (SFRH/BD/2009/65046), Ana S. H. Costa (SFRH/BD/2009/61068) and Susana V. Martins (SFRH/BPD/2009/63019). Paula A. Lopes is a researcher from the program ‘‘Ciência 2008’’ from FC

Interactional response during infants’ aquatic sessions

The aim of study was to assess infants’ behaviour during routine swimming sessions using a naturalistic observation method. The study sample included 14 infants (13.7 ± 7.5 months old) with previous aquatic experience. The frequency of occurrences per unit of time (session) in the different dimensions – infant’s motor behaviour and social-affective interaction – was registered over the course of two sessions by two independent experts. The behaviours most frequently observed were accompanied displacement (61.1 %) and interaction with others (41.6 %). Submersions or jumps represented only 8.4 % of the session. Implementing a child-centred methodology leads to positive behaviours during this type of sessions, contributing to the child’s healthy development.info:eu-repo/semantics/publishedVersio

Classroom teachers’ perception about physical education and physical activity: A typology

Introduction: According to the socioecological model teachers may act as facilitators or barriers in a school physical activity (PA) program. Objectives: The purpose of this study was to characterize classroom teachers’ perceptions about Physical Education (PE). Methods: 297 teachers answered a questionnaire about PE past experience, status, aims, and academic benefits of PA. The Multiple Correspondence Analysis was used aiming to identify teachers’ profiles. Results: Dimension 1 combines the view that the PA affects academic achievement (AA) with the idea that PE must be optional or compulsory, but non-examinable. In dimension 2 the biggest difference is between a standard that refers to a relatively neutral position in relation to PA (PE as important for promotion of healthy lifestyles associated with the idea that PA does not affect AA, and PE should be compulsory but non-examinable), as opposed to positions, either in favour (PA benefits AA and PE should be compulsory and examinable) or against PA (PE should be optional). The joint analysis of the two dimensions allowed to identify three distinct patterns of teacher’s perceptions which made possible to build a typology, regardless the cluster they belong to. Considering their personal experience teachers make a misjudgment of PE in schools they attended specially in cluster 3. As for the relation between PA and AA, most teachers say that the PA benefits AA (65% in cluster 1; 96% in cluster 2). In cluster 3, 70% of the teachers say that PA impairs AA. Conclusions: These results support the importance of the earliest good experiences in PE, in generating positive attitudes towards PE. PE teachers should explain to other teachers that PA does not affect academic performance, and that PA prevents deviant behaviours.info:eu-repo/semantics/publishedVersio

Efeitos de Anestésico Local no Tempo Entre Bólus e na Duração do Trabalho de Parto em Patient-Controlled Epidural Analgesia: Estudo Prospectivo de Dois Regimes de Doses Ultra-Baixas com Ropivacaina e Sufentanil

BACKGROUND: Patient-controlled epidural analgesia with low concentrations of anesthetics is effective in reducing labor pain. The aim of this study was to assess and compare two ultra-low dose regimens of ropivacaine and sufentanil (0.1% ropivacaine plus 0.5 μg.ml-1 sufentanil vs. 0.06% ropivacaine plus 0.5 μg.ml-1 sufentanil) on the intervals between boluses and the duration of labor. MATERIAL AND METHODS: In this non-randomized prospective study, conducted between January and July 2010, two groups of parturients received patient-controlled epidural analgesia: Group I (n = 58; 1 mg.ml-1 ropivacaine + 0.5 μg.ml-1 sufentanil) and Group II (n = 57; 0.6 mg.ml-1 ropivacaine + 0.5 μg.ml-1 sufentanil). Rescue doses of ropivacaine at the concentration of the assigned group without sufentanil were administered as necessary. Pain, local anesthetic requirements, neuraxial blockade characteristics, labor and neonatal outcomes, and maternal satisfaction were recorded. RESULTS: The ropivacaine dose was greater in Group I (9.5 [7.7-12.7] mg.h-1 vs. 6.1 [5.1-9.8 mg.h-1], p < 0.001). A time increase between each bolus was observed in Group I (beta = 32.61 min, 95% CI [25.39; 39.82], p < 0.001), whereas a time decrease was observed in Group II (beta = -1.40 min, 95% CI [-2.44; -0.36], p = 0.009). The duration of the second stage of labor in Group I was significantly longer than that in Group II (78 min vs. 65 min, p < 0.001). CONCLUSIONS: Parturients receiving 0.06% ropivacaine exhibited less evidence of cumulative effects and exhibited faster second stage progression than those who received 0.1% ropivacaine

Knowledge Acquisition by Networks of Interacting Agents in the Presence of Observation Errors

In this work we investigate knowledge acquisition as performed by multiple agents interacting as they infer, under the presence of observation errors, respective models of a complex system. We focus the specific case in which, at each time step, each agent takes into account its current observation as well as the average of the models of its neighbors. The agents are connected by a network of interaction of Erd\H{o}s-Renyi or Barabasi-Albert type. First we investigate situations in which one of the agents has a different probability of observation error (higher or lower). It is shown that the influence of this special agent over the quality of the models inferred by the rest of the network can be substantial, varying linearly with the respective degree of the agent with different estimation error. In case the degree of this agent is taken as a respective fitness parameter, the effect of the different estimation error is even more pronounced, becoming superlinear. To complement our analysis, we provide the analytical solution of the overall behavior of the system. We also investigate the knowledge acquisition dynamic when the agents are grouped into communities. We verify that the inclusion of edges between agents (within a community) having higher probability of observation error promotes the loss of quality in the estimation of the agents in the other communities.Comment: 10 pages, 7 figures. A working manuscrip