Incommensurate instability and lattice dynamics of potassium selenate within a semiempirical rigid-ion model

The lattice dynamics of potassium selenate is analyzed using a rigid-ion model with the selenate groups reduced to rigid bodies. The interatomic forces have been adjusted only using static structural data. The number of adjustable parameters varies from two to five. Such a simple model is already sufficient to reproduce semiquantitatively the phonon dynamics of the real system. In particular, the model exhibits the lattice instability leading to the existence of an incommensurate phase. The characteristics of the resulting soft mode agree with those observed experimentally. The calculated eigenvector, in excellent agreement with the experimental one, is rather insensitive to the details of the interactions. This explains the strong similarities of the incommensurate modulations in most A2BX4 compounds. On the other hand, the form of the soft-phonon branch strongly depends on the force model. It is sufficient to fit the model to the static structure observed at 145 K instead of the one at room temperature, to provoke a conspicuous softening of the branch. The branch minimum is specially sensitive to some potassium-oxygen interactions. The relative size of the cations plays an essential role in the origin of the incommensurate instability. For comparison the results of a similar analysis for Cs2SeO4 are presented. In this case, the unstable or soft character of the lowest 2 branch disappears.Dirección General de Investigación Científica y Técnica PB87-074

Optimized local modes for lattice dynamical applications

We present a new scheme for the construction of highly localized lattice Wannier functions. The approach is based on a heuristic criterion for localization and takes the symmetry constraints into account from the start. We compare the local modes thus obtained with those generated by other schemes and find that they also provide a better description of the relevant vibrational subspace.Comment: 6 pages, ReVTeX, plus four postscript files for figure

Finite strain Landau theory of high pressure phase transformations

The properties of materials near structural phase transitions are often successfully described in the framework of Landau theory. While the focus is usually on phase transitions, which are induced by temperature changes approaching a critical temperature T-c, here we will discuss structural phase transformations driven by high hydrostatic pressure, as they are of major importance for understanding processes in the interior of the earth. Since at very high pressures the deformations of a material are generally very large, one needs to apply a fully nonlinear description taking physical as well as geometrical nonlinearities (finite strains) into account. In particular it is necessary to retune conventional Landau theory to describe such phase transitions. In Troster et al (2002 Phys. Rev. Lett. 88 55503) we constructed a Landau-type free energy based on an order parameter part, an order parameter-(finite) strain coupling and a nonlinear elastic term. This model provides an excellent and efficient framework for the systematic study of phase transformations for a wide range of materials up to ultrahigh pressures

Qualitative and quantitative characterization of exosomes secreted by rat hepatocytes

Comunicaciones a congreso

PREDIRCAM eHealth platform for individualized telemedical assistance for lifestyle modification in the treatment of obesity, diabetes, and cardiometabolic risk prevention: a pilot study (PREDIRCAM 1)

Background: Healthy diet and regular physical activity are powerful tools in reducing diabetes and cardiometabolic risk. Various international scientific and health organizations have advocated the use of new technologies to solve these problems. The PREDIRCAM project explores the contribution that a technological system could offer for the continuous monitoring of lifestyle habits and individualized treatment of obesity as well as cardiometabolic risk prevention. Methods: PREDIRCAM is a technological platform for patients and professionals designed to improve the effectiveness of lifestyle behavior modifications through the intensive use of the latest information and communication technologies. The platform consists of a web-based application providing communication interface with monitoring devices of physiological variables, application for monitoring dietary intake, ad hoc electronic medical records, different communication channels, and an intelligent notification system. A 2-week feasibility study was conducted in 15 volunteers to assess the viability of the platform. Results: The website received 244 visits (average time/session: 17 min 45 s). A total of 435 dietary intakes were recorded (average time for each intake registration, 4 min 42 s ± 2 min 30 s), 59 exercises were recorded in 20 heart rate monitor downloads, 43 topics were discussed through a forum, and 11 of the 15 volunteers expressed a favorable opinion toward the platform. Food intake recording was reported as the most laborious task. Ten of the volunteers considered long-term use of the platform to be feasible. Conclusions: The PREDIRCAM platform is technically ready for clinical evaluation. Training is required to use the platform and, in particular, for registration of dietary food intake

Search for CP Violation in the Decay Z -> b (b bar) g

About three million hadronic decays of the Z collected by ALEPH in the years 1991-1994 are used to search for anomalous CP violation beyond the Standard Model in the decay Z -> b \bar{b} g. The study is performed by analyzing angular correlations between the two quarks and the gluon in three-jet events and by measuring the differential two-jet rate. No signal of CP violation is found. For the combinations of anomalous CP violating couplings, ${\hat{h}}_b = {\hat{h}}_{Ab}g_{Vb}-{\hat{h}}_{Vb}g_{Ab}$ and $h^{\ast}_b = \sqrt{\hat{h}_{Vb}^{2}+\hat{h}_{Ab}^{2}}$, limits of \hat{h}_b < 0.59$and$h^{\ast}_{b} < 3.02$ are given at 95\% CL.Comment: 8 pages, 1 postscript figure, uses here.sty, epsfig.st

Prevalence of Symptomatic Axial Osteoarthritis Phenotypes in Spain and Associated Socio-Demographic, Anthropometric, and Lifestyle Variables

Epidemiology of RMDFinanciado para publicación en acceso aberto: Universidade da Coruña/CISUG[Abstract] Objective. Axial osteoarthritis (OA) is a common cause of back and neck pain, however, few studies have examined its prevalence. The aim was to estimate the prevalence and the characteristics of symptomatic axial OA in Spain. Methods. EPISER2016 is a cross-sectional multicenter population-based study of people aged 40 years or older. Subjects were randomly selected using multistage stratified cluster sampling. Participants were contacted by telephone to complete rheumatic disease screening questionnaires. Two phenotypes were analyzed, patients with Non-exclusive axial OA (NEA-OA) and Exclusive axial OA (EA-OA). To calculate the prevalence and its 95% confidence interval (CI), the sample design was considered and weighting was calculated according to age, sex and geographic origin. Results. Prevalence of NEA-OA by clinical or clinical-radiographic criteria was 19.17% (95% CI: 17.82–20.59). The frequency of NEA-OA increased with age (being 3.6 times more likely in patients aged 80 s or more than in those between 40 and 49 years) and body mass index. It was significantly more frequent in women, as well as in the center of Spain. It was less frequent in those with a higher level of education. Lumbar OA was more frequent than cervical OA. This difference grew with increasing age and was not associated with gender. It was also greater in overweight and obese subjects. Conclusions. This is the first study on the prevalence of axial OA phenotypes in Europe describing the associated socio-demographic, anthropometric, and lifestyle variables.Open Access funding provided thanks to the CRUE-CSIC agreement with Springer Nature. EPISER2016 was supported by Celgene, Gebro Pharma, Merck Sharp & Dohme in Spain, Pfizer, and Sanofi-Aventis, none of whom had any role in the study design, data collection, data analysis, interpretation, or writing of this manuscript. MS was financed via the Rio Hortega Contract—Health Research Fund (CM17/00101), the Sanitary Research Fund integrated in the National Plan of Scientific Program, Technological Development and Innovation 2013–2016 and funded by the ISCIII-Subdirectorate General Evaluation and Promotion of Research-European Regional Development Fund (ERDF) "A way of making Europe

Substrate finishing and niobium content effects on the high temperature corrosion resistance in steam atmosphere of CrN/NbN superlattice coatings deposited by PVD-HIPIMS

The main objective of this work was to evaluate the oxidation resistance of three PVD-HIPIMS CrN/NbN coatings, studying the effect of the surface finishing of the substrate and the role of niobium content into the coating composition. CrN/NbN nano-multilayered films on P92 steel were tested at 650°C in pure steam atmosphere. The mass gain was measured at fixed intervals to study their oxidation kinetics. The morphology and thickness of nanoscales were measured by transmission electron microscopy (TEM). Characterization of coatings before and after the thermal treatment was performed by scanning electron microscopy-energy with facilities of dispersive X-ray spectroscopy (SEM–EDX) and X-ray diffraction (XRD). All coatings improved the oxidation resistance of the substrate material, but the best behaviour was exhibited by the CrN/NbN with the high niobium (Nb) content and deposited on the substrate with the finest surface finishing