A comparison of HREM and weak beam transmission electron microscopy for the quantitative measurement of the thickness of ferroelectric domain walls

In this paper we present two methods for the quantitative measurement of the thickness of ferroelectric domain walls, one using high-resolution electron microscopy (HREM) and the other weak beam transmission electron microscopy (WBTEM). These techniques can be used to determine the thickness of domain walls at room temperature as well as close to the ferroelectric to paraelectric phase transition. The first method allows a direct visualization of the lattice distortion across the domain wall, by measuring the continuous deviation of a set of planes with respect to the undistorted lattice. The second method consists in a quantitative analysis of the thickness fringes that appear on weak beam images of inclined domain walls. By fitting simulated fringe profiles to experimental ones, we can extract the thickness of the domain walls in a quantitative way. These two complementary techniques lead to a complete characterization of the thickness of ferroelectric domain walls over a wide range of specimen thicknesses at different magnifications. As an example we apply these methods to ferroelectric domain walls in PbTiO3 The domain wall thickness at room temperature is found to be 1.5 ± 0.3 nm using HREM (in very thin samples≈10 nm) and 2.1 ± 0.7 nm using WBTEM (in samples thicker than 30 nm

Evaluation du projet SPAS-PMU REVIAC

Le projet REVIAC: Le projet REVIAC (Réinsertion vie active) est un projet de collaboration entre le Service de prévoyance et d'aides sociales (SPAS) et la Policlinique médicale universitaire (PMU) pour améliorer les possibilités de démarches de réinsertion chez les bénéficiaires du revenu d'insertion (RI) avec certificat d'incapacité de travail. En effet, certains bénéficiaires ont des certificats médicaux d'incapacité récurrents et les assistants sociaux (AS) ne peuvent entreprendre les démarches nécessaires. Le projet développé par le SPAS et la PMU comprend deux axesa : ? La création à la PMU d'une consultation pour les bénéficiaires du RI dont l'état de santé compromet toute démarche d'insertion/d'activation. ? Le développement de l'information et de la formation : a) des médecins, principalement de premier recours, sur les thématiques sociales liées au RI et le réseau socio-sanitaire existant, et b) des assistants sociaux sur les pratiques des médecins traitants. Les objectifs du projet sont : Encourager l'élaboration de projets favorisant l'autonomie des bénéficiaires (autonomie sociale comme professionnelle et financière), compatibles avec leur état de santé, réalistes et réalisables ; Apporter un soutien médical aux bénéficiaires entrant dans une démarche d'insertion ou en cours d'insertion, en collaboration avec leurs médecins traitants ; Fournir aux AS les informations nécessaires leur permettant d'initier, au besoin, une collaboration avec l'AI dans le cadre de mesures de prévention et d'insertion ; Permettre aux AS de diriger et accompagner les bénéficiaires dont l'état de santé est incompatible avec une démarche d'insertion vers d'autres types de mesures ou d'autres prises en charge plus adéquates (rentes AI, etc.) ; Améliorer la collaboration entre les médecins traitants des bénéficiaires et les assistants sociaux en charge de leur dossier ; Proposer, à terme, le développement de nouvelles mesures adaptées aux problématiques de santé des bénéficiaires

Cathodoluminescence in a (S)TEM - Exploring Possibilities and Limits

Extended abstract of a paper presented at Microscopy and Microanalysis 2010 in Portland, Oregon, USA, August 1 - August 5, 201

Magnetization of carbon-coated ferromagnetic nanoclusters determined by electron holography

The magnetic properties of carbon-coated Co and Ni nanoparticles aligned in chains were determined using transmission electron holography. The measurements of the phase change of the electron wave due to the magnetization of the sample were performed. The ratio of remnant magnetization to bulk saturation magnetization Mr/Ms of Co decreased from 53% to 16% and of Ni decreased from 70% to 30% as the particle diameter increased from 25 to 90 nm. It was evident that the inhomogenous magnetic configurations could diminish the stray field of the particles. After being exposed to a 2-Tesla external magnetic field, the Mr/Ms of Co increased by 45% from the original values with the same dependency on the particle size. The Mr/Ms of Ni particles, on the other hand, increased only 10%. The increased magnetization could be attributed to the merging of small domains into larger ones after the exposure to the external magnetic field. The validity of the interpretation of the holograms was established by simulatio

Exploring differences in healthcare utilization of prisoners in the Canton of Vaud, Switzerland.

Prison healthcare is an important public health concern given the increasing healthcare needs of a growing and aging prison population, which accumulates vulnerability factors and suffers from higher disease prevalence than the general population. This study identifies the key factors associated with outpatient general practitioner (GP), nursing or psychiatric healthcare utilization (HCU) within prisons. Cross-sectional data systematically collected by the prison medical staff were obtained for a sample of 1664 adult prisoners of the Canton of Vaud, Switzerland, for the year 2011. They contain detailed information on demographics (predisposing factors), diagnosed chronic somatic and psychiatric disorders (needs factors), as well as prison stay characteristics (contextual factors). For GP, nurse and psychiatric care, two-part regressions are used to model separately the probability and the volume of HCU. Predisposing factors are generally not associated with the probability to use healthcare services after controlling for needs factors. However, female inmates use higher volumes of care, and the volume of GP consultations increases with age. Chronic somatic and psychiatric conditions are the most important predictors of the probability of HCU, but associations with volumes differ in their magnitude and significance across disease groups. Infectious, musculoskeletal, nervous and circulatory diseases actively mobilize GP and nursing staff. Schizophrenia, illicit drug and pharmaceuticals abuse are strongly positively associated with psychiatric and nurse HCU. The occupancy rate displays positive associations among contextual factors. Prison healthcare systems face increasingly complex organizational, budgetary and ethical challenges. This study provides relevant insights into the HCU patterns of a marginalized and understudied population

Médecines complémentaires dans le canton de Vaud : recours et offres actuels, principaux enjeux sanitaires et possibilités de réglementation.

Selon les données de l'Enquête suisse sur la santé (ESS), le canton de Vaud comprend une des plus grandes proportions d'utilisateurs de médecines complémentaires « au cours des 12 derniers mois » en Suisse (30% en 2012). L'homéopathie, la phytothérapie et l'acupuncture sont les thérapies les plus prisées. L'auto-recours dans le domaine des médecines complémentaires est difficile à estimer. Sur la base des quelques études disponibles en Suisse, ce phénomène paraît néanmoins fréquent. Selon une enquête téléphonique conduite auprès d'un échantillon représentatif d'adultes en Suisse, seuls 34% des répondant/es consultant des thérapeutes non-médecins affirment en informer toujours leurs médecins traitants

Osteoclastogenesis can be mechanically-induced in the peri-implant bone

Total joint replacements are highly successful in relieving pain and restoring movement of damaged joints. However, the lifespan of the implants is limited. The implant’s long-term stability depends largely on the preservation of periprosthetic bone. Debris-wear particulates were first identified as the factor inducing periprosthetic bone loss. However, it was later shown that the resorption process starts before the particulates reach the periprosthetic bone. Thus a mechanical factor, interface micromotions, has been suspected to be the initiator of the early bone loss. In this work, we then investigated the response of bone cells to micromotions. Using an ex vivo setup, we applied micromotions on fresh human bone cores and showed that micromotions could indirectly activate osteoclasts after only 1 hour of stimulation. Thus micromotion-related osteoclastic activity could be the initiator of periprosthetic bone loss

Combined effects of zoledronate and mechanical stimulation on bone adaptation in an axially loaded mouse tibia

Background: Local bisphosphonate delivery may be a solution to prevent periprosthetic bone loss and improve orthopedic implants fixation. In load-bearing implants, periprosthetic bone is exposed to high mechanical demands, which in normal conditions induce an adaptation of bone. In this specific mechanical situation, the modulation of the bone response by bisphosphonate remains uncertain. Methods: We assessed the combined effects of zoledronate and mechanical loading on bone adaptation using an in-vivo axial compression model of the mouse tibia and injections of zoledronate. Bone structure was quantified with in-vivo µCT before and after the period of stimulation and the biomechanical properties of the tibias were evaluated with 3 point-bending tests after sacrifice. Findings: Axial loading induced a localized increase of cortical thickness and bone area. Zoledronate increased cortical thickness, bone perimeter, and bone area. At the most loaded site of the tibia, the combined effect of zoledronate and mechanical stimulation was significantly smaller than the effect of zoledronate plus the effect of mechanical loading. Interpretations: The results of this study suggested that a negative interaction between zoledronate and mechanical loading might exist at high level of strain

Molecular Systematics of the Fishing Bat Myotis (Pizonyx) vivesi

Phylogenetic reconstructions based on molecular data have shown recurrent morphological convergence during evolution of the species-rich genus Myotis. Species or groups of species with similar feeding strategies have evolved independently several times to produce remarkable similarities in external morphology. In this context, we investigated the contentious phylogenetic position of 1 of the 2 piscivorous bat species, Myotis vivesi, which was not included in previous molecular studies. This bat, endemic to the coasts and islands of the Gulf of California, Mexico, was long classified in its own genus, Pizonyx, because of its distinctive morphology. To reconstruct its phylogenetic origins relative to other Myotis, we sequenced the mitochondrial cytochrome-b gene of 2 M. vivesi and related vespertilionids. These outgroups included Pipistrellus subflavus, a member of the subgenus Perimyotis, sometimes classified within the genus Myotis. Unexpectedly, all reconstructions placed M. vivesi within a strongly supported clade including all other typical neotropical and Nearctic Myotis. This molecular phylogeny supports an endemic radiation of New World Myotis. Other Myotis species with similar adaptations to gaffing prey from the water surface present no close phylogenetic relationships with M. vivesi, indicating that such adaptations are convergences. On the other hand, P. subflavus is genetically as distant from the genus Myotis as from other Pipistrellus species, suggesting that generic rank to Perimyotis is warrante

Microstimulations at the bone implant interface upregulate osteoclast activation pathway

Peri-implant bone resorption after total joint arthroplasty is a key parameter in aseptic loosening. Implant wear debris and biomechanical aspects have both been demonstrated to be part of the bone resorption process. However, neither of these two parameters has been clearly identified as the primary initiator of peri-implant bone resorption. For the biomechanical parameters, micromotions were measured at the bone implant interface during normal gait cycles. The amplitude of the micromotions was shown to trigger differentiation of bone tissues. So far no data exists directly quantifying the effect of micromotion and compression on human bone. We hypothesize that micromotion and compression at the bone implant interface may induce direct activation of bone resorption around the implant through osteoblasts- osteoclasts cell signaling in human bone. This hypothesis was tested with an ex vivo loading system developed to stimulate trabecular bone cores and mimic the micromotions arising at the bone-implant interface. Gene expression of RANKL, OPG, TGFB2, IFNG and CSF-1 were analyzed after no mechanical stimulation (control), exposure to static compression or exposure to micromotions. We observed an 8-fold upregulation of RANKL after exposure to micromotions, and down regulation of OPG, IFNG and TGFB2. The RANK:OPG ratio was up regulated 24 fold after micromotions. This suggests that the micromotions arising at the bone-implant interface during normal gait cycles induce a bone resorption response after only one hour, which occurs before any wear debris particles enter the system