Nonempirical cluster-model study of the chemisorption of atomic hydrogen on the (111) surface of diamondlike crystals

The interaction of atomic hydrogen with C4H9, Si4H9, and Ge4H9 model clusters has been studied using all-electron and pseudopotential ab initio Hartree-Fock computations with basis sets of increasing flexibility. The results show that the effect of polarization functions is important in order to reproduce the experimental findings, but their inclusion only for the atoms directly involved in the chemisorption bond is usually sufficient. For the systems H-C4H9 and H-Si4H9 all-electron and pseudopotential results are in excellent agreement when basis sets of comparable quality are used. Besides, semiempirical modified-neglect-of-differential-overlap computations provide quite reliable results both for diamond and silicon and have been used to investigate larger model clusters. The results confirm the local nature of chemisorption and further justify the use of minimal X4H9 model clusters.

Ab initio theoretical comparative study of magnetic coupling in KNiF3 and K2NiF4s

The origin of magnetic coupling in KNiF3 and K2 NiF4 is studied by means of an ab initio cluster model approach. By a detailed study of the mapping between eigenstates of the exact nonrelativistic and spin model Hamiltonians it is possible to obtain the magnetic coupling constant J and to compare ab initio cluster-model values with those resulting from ab initio periodic Hartree-Fock calculations. This comparison shows that J is strongly determined by two-body interactions; this is a surprising and unexpected result. The importance of the ligands surrounding the basic metal-ligand-metal interacting unit is reexamined by using two different partitions and the constrained space orbital variation method of analysis. This decomposition enables us to show that this effect is basically environmental. Finally, dynamical electronic correlation effects have found to be critical in determining the final value of the magnetic coupling constant.

Electronic structure and magnetic interactions of the spin-chain compounds Ca2CuO3 and Sr2CuO3

The results are presented of a combined periodic and cluster model approach to the electronic structure and magnetic interactions in the spin-chain compounds Ca2CuO3 and Sr2CuO3. An extended t-J model is presented that includes in-chain and interchain hopping and magnetic interaction processes with parameters extracted from ab initio calculations. For both compounds, the in-chain magnetic interaction is found to be around -240 meV, larger than in any of the other cuprates reported in the literature. The interchain magnetic coupling is found to be weakly antiferromagnetic, -1 meV. The effective in-chain hopping parameters are estimated to be ~650 meV for both compounds, whereas the value of the interchain hopping parameter is 30 meV for Sr2CuO3 and 40 meV for Ca2CuO3, in line with the larger interchain distance in the former compound. These effective parameters are shown to be consistent with expressions recently suggested for the Néel temperature and the magnetic moments, and with relations that emerge from the t-J model Hamiltonian. Next, we investigate the physical nature of the band gap. Periodic calculations indicate that an interpretation in terms of a charge-transfer insulator is the most appropriate one, in contrast to the suggestion of a covalent correlated insulator recently reported in the literature.

National Identity and the Preference for State Opting-Out in the Basque Country

We argue that preferences for secession are the expression of a common unobserved mechanisms determining national identity. This paper examines the hypothesis of independence of both preferences for secession (independent Euskadi) and Basque national identity in the light of Akerloff and Kranton (2000). We deal with psychological determinants of individuals' national identity formation as well as those that influence the propensity of individuals to support the secession of their perceived ¿imagined community¿ or nation.. We undertake econometric survey analysis for the Basque Country using a bivariate probit model and publicly available data from the Spanish Centre for Sociological Research. Our results provide robust evidence of a common determination of national identity and political preferences for the secession of the Basque Country consistently with Akerloff and Kranton model.

Coherency and sharpness measures by using ICA algorithms. An investigation for Alzheimer’s disease discrimination

In this paper, we present a comprehensive study of different Independent Component Analysis (ICA) algorithms for the calculation of coherency and sharpness of electroencephalogram (EEG) signals, in order to investigate the possibility of early detection of Alzheimer’s disease (AD). We found that ICA algorithms can help in the artifact rejection and noise reduction, improving the discriminative property of features in high frequency bands (specially in high alpha and beta ranges). In addition to different ICA algorithms, the optimum number of selected components is investigated, in order to help decision processes for future works.

Some of the challenges and experiences of formal education in a Mobile-Centric Society (MCS) = Algunos retos y experiencias de la educación formal en la Sociedad Móvil-Céntrica (SMC)

The aim of the paper is to describe some of the challenges faced by schools, or by formal education in general, as a consequence of today"s mobilecentric society (henceforth MCS), the term we will use to denote the new, networked learning ecology that has arisen from the massive penetration of digital media in everyday life. After revisiting some of the ideas of McLuhan and Vygotsky in the light of this new technological scenario, we describe five traits of the MCS and the challenges illustrated through educational practices that we believe schools will face if they wish to preserve their function of individualization and socialization. We believe that despite the emergence of the MCS, the main function of the school is still to provide the"box of tools" (a set of psychological instruments, such as reading, writing, mathematical notation, digital literacy, etc.) that enables people to develop their learning skills and life projects and to become part of communities and groups. However, the complexity and mobility of the new learning environments means that the position held by schools needs to be reevaluated in the face of the informal learning paths and experiences both online and offline to which learners now have access. We also need to reevaluate the meaning of the school itself as an institution and the model of learner it should be training

Effect of cattle on Salmonella carriage, diversity and antimicrobial resistance in free-ranging wild boar (Sus scrofa) in northeastern Spain

Salmonella is distributed worldwide and is a pathogen of economic and public health importance. As a multi-host pathogen with a long environmental persistence, it is a suitable model for the study of wildlife-livestock interactions. In this work, we aim to explore the spill-over of Salmonella between free-ranging wild boar and livestock in a protected natural area in NE Spain and the presence of antimicrobial resistance. Salmonella prevalence, serotypes and diversity were compared between wild boars, sympatric cattle and wild boars from cattle-free areas. The effect of age, sex, cattle presence and cattle herd size on Salmonella probability of infection in wild boars was explored by means of Generalized Linear Models and a model selection based on the Akaike’s Information Criterion. Prevalence was higher in wild boars co-habiting with cattle (35.67%, CI 95% 28.19–43.70) than in wild boar from cattle-free areas (17.54%, CI 95% 8.74–29.91). Probability of a wild boar being a Salmonella carrier increased with cattle herd size but decreased with the host age. Serotypes Meleagridis, Anatum and Othmarschen were isolated concurrently from cattle and sympatric wild boars. Apart from serotypes shared with cattle, wild boars appear to have their own serotypes, which are also found in wild boars from cattle-free areas (Enteritidis, Mikawasima, 4:b:- and 35:r:z35). Serotype richness (diversity) was higher in wild boars co-habiting with cattle, but evenness was not altered by the introduction of serotypes from cattle. The finding of a S. Mbandaka strain resistant to sulfamethoxazole, streptomycin and chloramphenicol and a S. Enteritidis strain resistant to ciprofloxacin and nalidixic acid in wild boars is cause for public health concern.

Psychometric properties and dimensional structure of the Spanish version of the Coping Responses Inventory - Adult Form

One of the goals of psychological assessment focuses on the adaptation of its instruments to different populations. The objective of this study is to establish the psychometric properties and dimensional structure of the Spanish version of the Coping Responses Inventory- Adult Form (CRI-Adult, Moos, 1993). The following criteria were analyzed: a) descriptive statistics; b) internal consistency reliability (Cronbach"s alpha, and intercorrelations between scales); c) test-retest reliability (4-week interval); d) dimensionality of CRI-Adult (exploratory factor analysis); e) construct validity (confirmatory factor analysis); f) convergent criterion validity (correlations between CRI-Adult and Coping Strategies Indicator, CSI, Amirkhan, 1990), and g) predictive criterion validity (correlations between CRI-Adult, and SCL-90-R, Derogatis, 1983). The results, obtained with 800 adults from Barcelona and surrounding area (334 men and 466 women, aged between 18 to 76 years) indicate that the Spanish version of CRIAdult has satisfactory psychometric properties that allow using this test with guarantee.

NADPH oxidase NOX4 mediates stellate cell activation and hepatocyte cell death during liver fibrosis development.

A role for the NADPH oxidases NOX1 and NOX2 in liver fibrosis has been proposed, but the implication of NOX4 is poorly understood yet. The aim of this work was to study the functional role of NOX4 in different cell populations implicated in liver fibrosis: hepatic stellate cells (HSC), myofibroblats (MFBs) and hepatocytes. Two different mice models that develop spontaneous fibrosis (Mdr2−/−/p19ARF−/−, Stat3Δhc/Mdr2−/−) and a model of experimental induced fibrosis (CCl4) were used. In addition, gene expression in biopsies from chronic hepatitis C virus (HCV) patients or non-fibrotic liver samples was analyzed. Results have indicated that NOX4 expression was increased in the livers of all animal models, concomitantly with fibrosis development and TGF-β pathway activation. In vitro TGF-β-treated HSC increased NOX4 expression correlating with transdifferentiation to MFBs. Knockdown experiments revealed that NOX4 downstream TGF-β is necessary for HSC activation as well as for the maintenance of the MFB phenotype. NOX4 was not necessary for TGF-β-induced epithelial-mesenchymal transition (EMT), but was required for TGF-β-induced apoptosis in hepatocytes. Finally, NOX4 expression was elevated in patients with hepatitis C virus (HCV)-derived fibrosis, increasing along the fibrosis degree. In summary, fibrosis progression both in vitro and in vivo (animal models and patients) is accompanied by increased NOX4 expression, which mediates acquisition and maintenance of the MFB phenotype, as well as TGF-β-induced death of hepatocytes.

Estimating 750 years of temperature variations and uncertainties in the Pyrenees by tree-ring reconstructions and climate simulations.

Past temperature variations are usually inferred from proxy data or estimated using general circulation models. Comparisons between climate estimations derived from proxy records and from model simulations help to better understand mechanisms driving climate variations, and also offer the possibility to identify deficiencies in both approaches. This paper presents regional temperature reconstructions based on tree-ring maximum density series in the Pyrenees, and compares them with the output of global simulations for this region and with regional climate model simulations conducted for the target region. An ensemble of 24 reconstructions of May-to-September regional mean temperature was derived from 22 maximum density tree-ring site chronologies distributed over the larger Pyrenees area. Four different tree-ring series standardization procedures were applied, combining two detrending methods: 300-yr spline and the regional curve standardization (RCS). Additionally, different methodological variants for the regional chronology were generated by using three different aggregation methods. Calibration verification trials were performed in split periods and using two methods: regression and a simple variance matching. The resulting set of temperature reconstructions was compared with climate simulations performed with global (ECHO-G) and regional (MM5) climate models. The 24 variants of May-to-September temperature reconstructions reveal a generally coherent pattern of inter-annual to multi-centennial temperature variations in the Pyrenees region for the last 750 yr. However, some reconstructions display a marked positive trend for the entire length of the reconstruction, pointing out that the application of the RCS method to a suboptimal set of samples may lead to unreliable results. Climate model simulations agree with the tree-ring based reconstructions at multi-decadal time scales, suggesting solar variability and volcanism as the main factors controlling preindustrial mean temperature variations in the Pyrenees. Nevertheless, the comparison also highlights differences with the reconstructions, mainly in the amplitude of past temperature variations and in the 20th century trends. Neither proxy-based reconstructions nor model simulations are able to perfectly track the temperature variations of the instrumental record, suggesting that both approximations still need further improvements.

Synthesis of highly focused fields with circular polarization at any transverse plane

We develop a method for generating focused vector beams with circular polarization at any transverse plane. Based on the Richards-Wolf vector model, we derive analytical expressions to describe the propagation of these set of beams near the focal area. Since the polarization and the amplitude of the input beam are not uniform, an interferometric system capable of generating spatially-variant polarized beams has to be used. In particular, this wavefront is manipulated by means of spatial light modulators displaying computer generated holograms and subsequently focused using a high numerical aperture objective lens. Experimental results using a NA=0.85 system are provided: irradiance and Stokes images of the focused field at different planes near the focal plane are presented and compared with those obtained by numerical simulation.

Adsorption energy and spin state of first-row transition metals adsorbed on MgO(100)

Slab and cluster model spin-polarized calculations have been carried out to study various properties of isolated first-row transition metal atoms adsorbed on the anionic sites of the regular MgO(100) surface. The calculated adsorption energies follow the trend of the metal cohesive energies, indicating that the changes in the metal-support and metal-metal interactions along the series are dominated by atomic properties. In all cases, except for Ni at the generalized gradient approximation level, the number of unpaired electron is maintained as in the isolated metal atom. The energy required to change the atomic state from high to low spin has been computed using the PW91 and B3LYP density-functional-theory-based methods. PW91 fails to predict the proper ground state of V and Ni, but the results for the isolated and adsorbed atom are consistent within the method. B3LYP properly predicts the ground state of all first-row transition atom the high- to low-spin transition considered is comparable to experiment. In all cases, the interaction with the surface results in a reduced high- to low-spin transition energy.

Com explicar un sistema CLIL: un model dinàmic newtonià

En la implementació del CLIL a l’educació superior, apart d’estudis sobre el nivell de l’estudiantat i la disponibilitat del professorat, i de l’elaboració de material educatiu interdisciplinari, el repte actual és aconseguir que s’involucrin activament en CLIL els professors de contingut d’un ventall ampli de disciplines. En aquesta comunicació es presenten les bases d’un model per un sistema CLIL, utilitzant la dinàmica newtoniana. Pot ser un model interessant i plausible en un context universitari científic i tecnològic, on fins ara el CLIL s’ha implementat només lleugerament.