Demonstration of a robust pseudogap in a three-dimensional correlated electronic system

We outline a partial-fractions decomposition method for determining the one-particle spectral function and single-particle density of states of a correlated electronic system on a finite lattice in the non self-consistent T-matrix approximation to arbitrary numerical accuracy, and demonstrate the application of these ideas to the attractive Hubbard model. We then demonstrate the effectiveness of a finite-size scaling ansatz which allows for the extraction of quantities of interest in the thermodynamic limit from this method. In this approximation, in one or two dimensions, for any finite lattice or in the thermodynamic limit, a pseudogap is present and its energy diverges as Tc is approached from above; this is an unphysical manifestation of using an approximation that predicts a spurious phase transition in one or two dimensions. However, in three dimensions one expects the transition predicted by this approximation to represent a true continuous phase transition, and in the thermodynamic limit any pseudogap predicted by this formulation will remain finite. We have applied our method to the attractive Hubbard model on a three-dimensional simple cubic lattice, and find that for intermediate coupling a prominent pseudogap is found in the single-particle density of states, and this gap persists over a large temperature range. In addition, we also show that for weak coupling a pseudogap is also present. The pseudogap energy at the transition temperature is almost a factor of three larger than the T=0 BCS gap for intermediate coupling, whereas for weak coupling the pseudogap and BCS gap energies are essentially equal.Comment: 28 pages, 9 figure

Propuesta metodol?gica para rescatar los valores y mejorar la convivencia escolar

99 p. Recurso Electr?nicoLa presente propuesta metodol?gica est? dirigida aquellos ni?os y ni?as del grado (2-4) para el rescate de los valores y mejorar la convivencia escolar, es una propuesta que favorece a las docentes y padres de familia y a la Instituci?n Educativa Francisco de Paula Santander en tener las alternativas para incentivar en los estudiantes las relaciones interpersonales pacificas con los dem?s en un ambiente de respeto y tolerancia. En consecuencia, esta propuesta cuenta con un itinerario de referentes te?ricos que dan respuesta a la necesidad que tiene la instituci?n educativa para el rescate de los valores y motivar a la participaci?n de todos los miembros de comunidad educativa para que sea posible. Igualmente, para continuar con este proceso se hizo necesario la aplicaci?n de encuestas a los ni?os y ni?as, padres de familia y docentes y conocer las concepciones que tienen cada uno de ellos acerca de los valores para la sana convivencia escolar, por lo tanto, esta propuesta propone una serie de actividades y talleres l?dicos pedag?gicos para fortalecimiento de los valores. Palabras Clave: Resoluci?n de conflictos, convivencia escolar, valores, propuesta, comunidad educativa.This proposal is aimed at those children of grade (2-4) for the rescue of values and improve school coexistence, is a proposal that favors teachers and parents and the Educational Institution Francisco de Paula Santander in having the alternatives to encourage students to have peaceful interpersonal relationships with others in an environment of respect and tolerance. In consecuentica, this proposal has an itinerary of theoretical referents that respond to the need of the educational institution for the rescue of values and motivate the participation of all members of the educational community to make it possible. Likewise, in order to continue with this process, it became necessary to apply surveys to children, parents and teachers and to know the conceptions that each of them has about the values for healthy school coexistence, therefore, this The proposal proposes a series of pedagogical play activities and workshops to strengthen values. Keywords: Conflict resolution, school coexistence, values, proposal, educational community

Electron-phonon renormalization in small Fermi energy systems

The puzzling features of recent photoemission data in cuprates have been object of several analysis in order to identity the nature of the underlying electron-boson interaction. In this paper we point out that many basilar assumptions of the conventional analysis as expected to fail in small Fermi energy systems when, as the cuprates, the Fermi energy $E_{\rm F}$ is comparable with the boson energy scale. We discuss in details the novel features appearing in the self-energy of small Fermi energy systems and the possible implications on the ARPES data in cuprates.Comment: 4 pages, 5 eps figures include

Hamiltonian Dynamics and the Phase Transition of the XY Model

A Hamiltonian dynamics is defined for the XY model by adding a kinetic energy term. Thermodynamical properties (total energy, magnetization, vorticity) derived from microcanonical simulations of this model are found to be in agreement with canonical Monte-Carlo results in the explored temperature region. The behavior of the magnetization and the energy as functions of the temperature are thoroughly investigated, taking into account finite size effects. By representing the spin field as a superposition of random phased waves, we derive a nonlinear dispersion relation whose solutions allow the computation of thermodynamical quantities, which agree quantitatively with those obtained in numerical experiments, up to temperatures close to the transition. At low temperatures the propagation of phonons is the dominant phenomenon, while above the phase transition the system splits into ordered domains separated by interfaces populated by topological defects. In the high temperature phase, spins rotate, and an analogy with an Ising-like system can be established, leading to a theoretical prediction of the critical temperature $T_{KT}\approx 0.855$.Comment: 10 figures, Revte

Is it possible to make a diagnosis of raw, heated and baked egg allergy in children using cut-offs? A systematic review

The diagnosis of IgE-mediated egg allergy lies both on a compatible clinical history and on the results of skin prick tests (SPTs) and IgEs levels. Both tests have good sensitivity but low specificity. For this reason, oral food challenge (OFC) is the ultimate gold standard for the diagnosis. The aim of the present paper is to systematically review the literature in order to identify, analyze and synthesize the predictive value of SPT and specific IgEs both to egg white and main egg allergens and to review the cut-offs suggested in the literature

Endothelial function and serum concentration of toxic metals in frequent consumers of fish

BACKGROUND:Endothelial dysfunction is involved in the pathogenesis of atherosclerosis. Consumption of fish is associated with reduced cardiovascular risk, but there is paucity of data concerning its effect on endothelial function. Furthermore, investigation of the effects of fish consumption on health must take into account the ingestion of contaminants, including transition metals and some metalloids, which may have unfavorable effects on health, including those on the cardiovascular system. We investigated the association between fish consumption, endothelial function (flow mediated dilation of the brachial artery), and serum concentration of some toxic metals in apparently healthy people. METHODS:Twenty-nine high fish consumers (at least 3 portions a week) were compared with 25 low fish consumers (less than 1 portion a week). All participants were free of diabetes, cardiovascular or other systemic diseases. Serum metal (antimonium, arsenic, mercury, lead, cobalt, copper, zinc, selenium, strontium) concentrations were measured in subgroups of 24 high fish consumers and 19 low fish consumers. RESULTS:Both groups exhibited similar habitual dietary patterns, age and anthropometric characteristics. The high fish consumers had higher flow mediated dilation (9.7 ± 1.8 vs. 7.3 ± 1.9%; P<0.001), but also higher serum concentrations of mercury (5.87 ± 2.69 vs. 1.65 ± 1.10 mcg/L; P<0.001) and arsenic (6.04 ± 3.25 vs. 2.30 ± 1.58 mcg/L; P<0.001). The fasting plasma glucose concentrations were significantly correlated with both mercury (r = 0.39; P = 0.01) and arsenic concentrations (r = 0.55; P<0.001). CONCLUSIONS:Habitual consumption of high amounts of fish is associated with better endothelial function despite higher serum concentrations of mercury and arsenic

Acute effects of coffee on endothelial function in healthy subjects

Background/Objectives: Coffee is the most widely consumed beverage in the world, but its effect on the cardiovascular system has not been fully understood. Coffee contains caffeine and antioxidants, which may influence endothelial function, both of which have not yet been investigated. The objective of this study was to investigate the acute effects of coffee on endothelial function measured by brachial artery flow-mediated dilation (FMD). Subjects/Methods: A total of 20 (10 males and 10 females) healthy non-obese subjects underwent a double-blind, crossover study. Subjects ingested one cup of caffeinated (CC) and one cup of decaffeinated (DC) Italian espresso coffee in random order at 5- to 7-day intervals. Results: Following CC ingestion, FMD decreased progressively and significantly (mean±s.e.m.: 0min, 7.7±0.6; 30min, 6.3±0.7; 60 min, 6.0±0.8%; ANOVA (analysis of variance), Po0.05), but it did not significantly increase after DC ingestion (0min, 6.9±0.6; 30min, 8.1±0.9; 60min, 8.5±0.9%; P1⁄40.115). Similarly, CC significantly increased both systolic and diastolic blood pressure; this effect was not observed after DC ingestion. Blood glucose concentrations remained unchanged after ingestion of both CC and DC, but insulin (0min, 15.8±0.9; 60min, 15.0±0.8mU/ml; Po0.05) and C-peptide (0min, 1.25±0.09; 60 min, 1.18±0.09 ng/ml; Po0.01) blood concentrations decreased significantly only after CC ingestion. Conclusions: CC acutely induced unfavorable cardiovascular effects, especially on endothelial function. In the fasting state, insulin secretion is also likely reduced after CC ingestion. Future studies will determine whether CC has detrimental clinically relevant effects, especially in unhealthy subjects

Long-term effects of a multidisciplinary treatment of uncomplicated obesity on carotid intima-media thickness

Obesity is associated with well-known cardiovascular risk factors and a lower life expectancy. This study investigated whether nonoperative nutritional treatment of obesity without comorbidities influenced the carotid intima-media thickness (c-IMT) in the long run. Fifty-four subjects of an original cohort of 251 subjects were re-evaluated 10 years after a medical nutritional treatment (MNT) with cognitive-behavioral approach for uncomplicated obesity. Forty subjects were classified as failure (10-year body weight change >0.5 kg) and 14 (body weight change 640.5 kg) as a success of the MNT. Ten years after MNT, c-IMT significantly increased (0.06 \ub1 0.02 mm; P = 0.004) in the failure group and significantly decreased ( 120.07 \ub1 0.03 mm; P = 0.027) in the success group. Ten-year change in c-IMT correlated significantly with 10-year change in body weight (r = 0.28; P = 0.040). Multiple stepwise linear regression analysis demonstrated that age, final BMI, and group (success or failure) influenced independently the 10-year c-IMT. In conclusion, this study is in agreement with the possibility that the successful MNT of obesity may be an effective choice in the long run and seems to indicate that it may be able to reduce the cardiovascular risk as reflected by the change in c-IMT