Quantum Interference in Single Molecule Electronic Systems

We present a general analytical formula and an ab initio study of quantum interference in multi-branch molecules. Ab initio calculations are used to investigate quantum interference in a benzene-1,2-dithiolate (BDT) molecule sandwiched between gold electrodes and through oligoynes of various lengths. We show that when a point charge is located in the plane of a BDT molecule and its position varied, the electrical conductance exhibits a clear interference effect, whereas when the charge approaches a BDT molecule along a line normal to the plane of the molecule and passing through the centre of the phenyl ring, interference effects are negligible. In the case of olygoynes, quantum interference leads to the appearance of a critical energy $E_c$, at which the electron transmission coefficient $T(E)$ of chains with even or odd numbers of atoms is independent of length. To illustrate the underlying physics, we derive a general analytical formula for electron transport through multi-branch structures and demonstrate the versatility of the formula by comparing it with the above ab-initio simulations. We also employ the analytical formula to investigate the current inside the molecule and demonstrate that large counter currents can occur within a ring-like molecule such as BDT, when the point charge is located in the plane of the molecule. The formula can be used to describe quantum interference and Fano resonances in structures with branches containing arbitrary elastic scattering regions connected to nodal sites.Comment: 12 pages, 11 figure

Symmetry-induced interference effects in metalloporphyrin wires

Organo-metallic molecular structures where a single metallic atom is embedded in the organic backbone are ideal systems to study the effect of strong correlations on their electronic structure. In this work we calculate the electronic and transport properties of a series of metalloporphyrin molecules sandwiched by gold electrodes using a combination of density functional theory and scattering theory. The impact of strong correlations at the central metallic atom is gauged by comparing our results obtained using conventional DFT and DFT+U approaches. The zero bias transport properties may or may not show spin-filtering behavior, depending on the nature of the d state closest to the Fermi energy. The type of d state depends on the metallic atom and gives rise to interference effects that produce different Fano features. The inclusion of the U term opens a gap between the d states and changes qualitatively the conductance and spin-filtering behavior in some of the molecules. We explain the origin of the quantum interference effects found as due to the symmetry-dependent coupling between the d states and other molecular orbitals and propose the use of these systems as nanoscale chemical sensors. We also demonstrate that an adequate treatment of strong correlations is really necessary to correctly describe the transport properties of metalloporphyrins and similar molecular magnets

Effect of an exercise program on musculoskeletal symptoms in primary school teachers

Introducción. Los docentes de nivel primario están expuestos a riesgos físicos que pueden controlar mediante un programa de ejercicios, el cual busca promover mejoras para su salud de manera oportuna. Objetivos. Determinar el efecto de un programa de ejercicios en los síntomas músculo esqueléticos en docentes de nivel primario. Métodos. Se realizó un estudio experimental, donde se aplicó el cuestionario de Cornell. Resultados. Los docentes presentaron una mediana de 52 años de edad. Al inicio se encontró que los síntomas músculo esqueléticos más frecuentes de todos los docentes se encontraban en cuello (50,8%), espalda baja (41,5%), pie izquierdo (35,4%) y pie derecho (33,9%); en la comparación final entre los grupos, se observó que la intensidad obtuvo diferencias significativas de valor de p<0,01 para cuello, hombro derecho/izquierdo, espalda alta, espalda baja, rodilla derecha/izquierda. El grupo intervención obtuvo 25% a más para las zonas de cuello, espalda baja, hombro derecho/izquierdo y pie derecho; mientras que en el grupo control, el 18,2% empeorarían en la zona de la espalda baja. Conclusiones. El programa de ejercicios disminuyó significativamente los síntomas musculo esqueléticos de los docentes del grupo intervención, mientras que en el grupo control se mantuvieron similares o aumentaron.Introduction. Primary-level teachers are exposed to physical risks that they can control through an exercise program, which seeks improved promotions for their health in a timely manner. Objectives. To determine the effect of an exercise program on the musculoskeletal symptoms in primary school teachers. Methods. An experimental study was carried out, where the Cornell questionnaire was applied. Results. The teachers had a median age of 52 years. Initially, it was found that the most frequent musculoskeletal symptoms of all teachers were found in the neck (50,8%), lower back (41,5%), left foot (35,4%) and right foot (33,9%); in the final comparison between the groups, it is observed that the intensity obtained significant differences of p value <0,01 for neck, right/left shoulder, upper back, lower back, right/left knee. It is worth noting in the difference in initial and final data, the intervention group obtained 25% or more for the neck, lower back, right/left shoulder and right foot areas; while in the control group, 18,2% would worsen in the lower back area. Conclusions. The exercise program frequently improves the musculoskeletal symptoms of the teachers in the intervention group, while in the control group similar or are used or increase

GOLLUM: a next-generation simulation tool for electron, thermal and spin transport

We have developed an efficient simulation tool 'GOLLUM' for the computation of electrical, spin and thermal transport characteristics of complex nanostructures. The new multi-scale, multi-terminal tool addresses a number of new challenges and functionalities that have emerged in nanoscale-scale transport over the past few years. To illustrate the flexibility and functionality of GOLLUM, we present a range of demonstrator calculations encompassing charge, spin and thermal transport, corrections to density functional theory such as LDA+U and spectral adjustments, transport in the presence of non-collinear magnetism, the quantum-Hall effect, Kondo and Coulomb blockade effects, finite-voltage transport, multi-terminal transport, quantum pumps, superconducting nanostructures, environmental effects and pulling curves and conductance histograms for mechanically-controlled-break-junction experiments.Comment: 66 journal pages, 57 figure

Bullous pemphigoid and dipeptidyl peptidase-4 inhibitors: The importance of the pharmacotherapeutic history

A 97-year-old man with a history of type II diabetes mellitus was treated with oral antidiabetic agents. He went to the emergency department after the appearance of blister-like itchy lesions on the abdomen and extremities since 2 months. The examination revealed eczematous lesions on the back, abdomen and extremities along with tense blisters on an erythematous base and serous content (figure 1A). In the blood test carried out, 285?mg/dL glucose and 7.1% eosinophilia stood out, with no associated leucocytosis or other relevant findings. Positive glycosuria (+++) was observed in urinalysis without other alterations. A skin biopsy was performed for histological and immunofluorescence studies that confirmed the diagnosis of bullous pemphigoid (figure 1B–D). Given the poor control of autoimmune blistering disease, possible triggers were looked for and linagliptin intake could be associated with the appearance of skin lesions 1?month earlier. ..

Evaluation of some important physicochemical properties of starch free grewia gum

Gums obtained by extraction from the inner bark of stems can be found in association with starch, which must be digested in order to obtain a refined polysaccharide isolate. In the present study, grewia gum obtained from the inner bark of the stems of Grewia mollis was shown to co-exist with starch and the effect of starch digestion on the physicochemical properties of the resultant polysaccharide was evaluated. The gum was extracted by maceration of the inner bark in deionized water and isolated by a combination of filtration, centrifugation and finally precipitation with absolute ethanol to produce the crude grewia gum extract (GG). The presence and content of starch in the gum sample was determined followed by enzymatic digestion of the starch using α-amylase (Termamyl 120L) to give a starch-free extract (GGDS). Physicochemical properties of the extracts such as total carbohydrates, total protein, differential sugar composition, NMR, intrinsic viscosity and rheological behaviour of the samples were evaluated. The GG extract had total carbohydrate content of ∼ 60 % out of which 11.8 % was starch, and a protein content of 2.3 %. Samples also contained galacturonic and glucuronic acid which were highly acetylated. Both samples had a higher proportion of galacturonic acid than glucuronic acid and contained rhamnose, arabinose, galactose, glucose and xylose as neutral sugars in varying proportions. Rheological measurements on 2 %w/w dispersions of the extracts show minor differences between both the original extract and the de-starched material but were influenced by changes in pH

"Detection of Helicobacter pylori in faeces of children of rural human settlements: An exploratory study in Peru"

"Introduction: Helicobacter pylori is one of the major infectious agents in low-income countries, and its clinical characteristics are unknown in many populations. Children are a susceptible population and can contract these pathogens through contaminated food and water. Objectives: To determine the presence of Helicobacter pylori in children under eight years of age of rural human settlements in Peru. Methods: This exploratory study was conducted with 25 child volunteers authorized by the parents for their evaluation, without precedent of any apparent clinical manifestation. Antigen detection of H. pylori in faeces by a rapid assay onsite H. pylori Ag. Rapid test according to the manufacturer’s requirements. Has been evaluated the social determinants related to possible infection. Results: The average age (2±1.8 years) of 14 girls was different from the average age (2.7±2.2 years) of 11 boys included in the study (p=0.010). Of the total we determinate nine (36%) positive tests, which mainly affected boys (five patients 20%) under two years of age (six patients, 24%). In general, ~90% wash their hands with soap and water and ~70% wash fruits and vegetables with water before eating. In addition, >50% ate foods outside of home and ~24% was asymptomatic and did not have a specific meal schedule. Conclusions: Among rural children, Helicobacter pylori antibody was detected in 36% of the participants, unaffected by gender, and presenting specific dietary patterns.