Strain-controlled ferromagnetism in BiFeO3 nanoparticles.

Multiferroic materials are at the core of voltage-controlled spintronic devices. Therefore, an understanding of the underlying electronic correlations and their effects associated with their complex energy landscape is an important and ongoing task. One key parameter in oxide-based perovskite multiferroics is their sensitivity to strain effects under confinement. Here, we report on the ferromagnetism induced by strain-engineering at the nanoscale on BiFeO3 (BFO) nanoparticles. By controlling synthesis parameters, we were able to modify the BFO lattice parameters up to 0.15% and as a consequence, induce ferromagnetism in otherwise antiferromagnetic bulk BFO. In order to understand the driving mechanisms behind such an effect, we performed density functional theory calculations (DFT) using the BFO parameters obtained from the experiment. We found that small distortions of the structural lattice parameters of the order of 0.01% are sufficient to induce a significant spin imbalance close to the Fermi energy at the Fe sites. This may explain the appearance of weak ferromagnetism in strained BFO thin films reported earlier and offers a new route to novel voltage-controlled spintronic devices based on multiferroic materials.

Terapia ocupacional y paciente crítico / Occupational therapy and critical ill patients

El presente estudio fue realizado en la Unidad de Pacientes Críticos adultos, del Hospital Clínico de la Pontificia Universidad Católica de Chile (UPC-HCPUC), durante el año 2012, donde se exploraron las características del paciente crítico, para obtener un perfil de salud global durante su estadía en la UPC, con el fin de determinar si sería posible realizar una intervención desde la Terapia Ocupacional que fuese un aporte a esta unidad.Se realizó un estudio prospectivo, observacional en la UPC médico quirúrgica durante 25 días. Los resultados obtenidos permitieron caracterizar al paciente crítico de esta unidad, como un sujeto con alta probabilidad de presentar compromiso de conciencia, edema en mano, limitación de rango de movimiento articular (ROM) en muñeca y dedos, y carencia de estímulos que evoquen su realidad previa a la hospitalización. Finalmente, a partir del análisis del perfil del paciente crítico de la UPC HCPUC y del contexto al que se encuentra expuesto, se concluye que la intervención temprana de Terapia Ocupacional podría disminuir y prevenir la aparición de algunos signos asociados al paciente crítico, comprobándose la hipótesis, que dadas las características de este paciente, sería posible realizar una intervención desde la Terapia Ocupacional.

This study was conducted in The Unit Critics adult patients, Clinical Hospital of the Catholic University of Chile (UPC HCPUC), in 2012, where the characteristics of critical patients were explored to obtain a profile of global health while in the UPC, in order to determine whether it would be possible to make an intervention from occupational therapy to be a contribution to this unit.A prospective, observational study in medical UPC-surgery for 25 days. The results allowed to characterize critical patients of this unit, as a subject with high probability of impairment of consciousness, edema in hand, limitation of joint range of motion (ROM) in the wrist and fingers, and lack of stimuli that evoke your reality prior to hospitalization.Finally, from the analysis of the profile of critical patient - HCPUC UPC and the context to which it is exposed, it is concluded that early intervention occupational therapy could reduce and prevent the appearance of certain signs associated with critical patient, checking hypothesized that given the characteristics of this patient, it would be an intervention from Occupational Therapy.

[Clinical and epidemiological study of blood donors seropositive for Trypanosoma cruzi]. / Estudio clínico y epidemiológico en donantes de sangre seropositivos por Trypanosoma cruzi.

BACKGROUND: The prevalence of positive antibodies for Chagas disease in a blood bank of a public hospital in Santiago is 1.2%. These positive individuals should be informed about their condition and further studied. AIM: To perform a serological confirmation, an epidemiological and clinical assessment of blood donors seropositive for Chagas disease in a blood bank of Santiago. SUBJECTS AND METHODS: One hundred eleven seropositive donors, detected between 1994 and 1996, were studied. Serological reactions were confirmed with ELISA and indirect immunofluorescence reactions. Those confirmed as positive were subjected to a clinical-epidemiological questionnaire, physical examination, EKG and barium enema or swallow according to symptoms. RESULTS: Seventy individuals were confirmed as positive for Chagas disease. Most of them lived at least once in an endemic zone for Chagas disease or in a sun-dried clay brick house. Forty-percent of individuals knew reduviid bugs and 14% had been bitten by these insects. Twenty six percent of these subjects had an abnormal EKG (61% with bradycardia). No digestive diseases attributable to Chagas disease were detected. CONCLUSIONS: The high prevalence of problems attributable to Chagas disease among seropositive blood donors underscores the need of an epidemiological follow up of these individuals.