Linearized force constants method for lattice dynamics in mixed semiconductors

A simple and accurate method of calculating phonon spectra in mixed semiconductors alloys, on the basis of preliminarily (from first principles) relaxed atomic structure, is proposed and tested for (Zn,Be)Se and (Ga,In)As solid solutions. The method uses an observation that the interatomic force constants, calculated ab initio for a number of microscopic configurations in the systems cited, show a clear linear variation of the main (diagonal) values of the interatomic force constants with the corresponding bond length. We formulate simple rules about how to recover the individual 3x3 subblocks of the force constants matrix in their local (bonds-related) coordinate systems and how to transform them into a global (crystal cell-related) coordinate system. Test calculations done for 64-atom supercells representing different concentrations of (Zn,Be)Se and (Ga,In)As show that the phonon frequencies and compositions of eigenvectors are faithfully reproduced in a linearized force constants calculation, as compared to true ab initio calculations.Comment: to appear in the proceedings of the Phonons2007 conference (Paris, July 2007

Lattice dynamics of mixed semiconductors (Be,Zn)Se from first-principles calculations

Vibration properties of Zn(1-x)Be(x)Se, a mixed II-VI semiconductor haracterized by a high contrast in elastic properties of its pure constituents, ZnSe and BeSe, are simulated by first-principles calculations of electronic structure, lattice relaxation and frozen phonons. The calculations within the local density approximation has been done with the Siesta method, using norm-conserving pseudopotentials and localized basis functions; the benchmark calculations for pure endsystems were moreover done also by all-electron WIEN2k code. An immediate motivation for the study was to analyze, at the microscopic level, the appearance of anomalous phonon modes early detected in Raman spectra in the intermediate region (20 to 80%) of ZnBe concentration. This was early discussed on the basis of a percolation phenomenon, i.e., the result of the formation of wall-to-wall --Be--Se-- chains throughout the crystal. The presence of such chains was explicitly allowed in our simulation and indeed brought about a softening and splitting off of particular modes, in accordance with experimental observation, due to a relative elongation of Be--Se bonds along the chain as compared to those involving isolated Be atoms. The variation of force constants with interatomic distances shows common trends in relative independence on the short-range order.Comment: 11 pages, 10 figures, to be published in Phys. Rev.

Schmallenberg virus detection in Culicoides biting midges in Spain: First laboratory evidence for highly efficient infection of Culicoides of the Obsoletus complex and Culicoides imicola

Since Schmallenberg disease was discovered in 2011, the disease rapidly spread across Europe. Culicoides biting midges have been implicated as putative Schmallenberg vectors in Europe. The detection of Schmallenberg virus (SBV) in field collected Culicoides was evaluated through retrospective (2011–2012) collections and captures performed in 2013. This study represents the first detection of SBV in field collected Culicoides in Spain. Infectious midges were detected at the foothills of Pyrenees, Aramunt, in the summer 2012. All the specimens infected with Schmallenberg were of the species Culicoides obsoletus s.s. confirming its putative vector status in Spain. Experimental infection on field collected Culicoides provided evidence of atypical high efficiency for SBV vector infection and transmission potential in local populations of Culicoides imicola and in Culicoides of the Obsoletus complex. However, captured individuals of C. imicola were more susceptible to SBV infection than C. obsoletus s.l. (p < .001), with an infection ratio of 0.94 and 0.63, respectively. In contrast, a Culicoides nubeculosus colony appeared to be refractory to SBV infection.info:eu-repo/semantics/acceptedVersio

Vascular endothelial growth factor-A and Poly(A) binding protein-interacting protein 2 expression in human head and neck carcinomas: correlation and prognostic significance

Vascular endothelial growth factor-A (VEGF-A) has been demonstrated to play an important role in tumour angiogenesis and to influence prognosis in many cancers. However its prognostic value in head and neck squamous cell carcinomas (HNSCCs) remains controversial. Therefore, we investigated the clinical relevance of VEGF-A expression in HNSCCs and analysed whether its expression was associated with PAIP2 protein levels, a VEGF-A mRNA-binding partner that strongly regulates VEGF-A expression in tissue culture. We determined the correlation of VEGF-A and PAIP2 protein levels, quantitatively evaluated in tumour tissue homogenates from 54 patients with HNSCC, to clinicopathological parameters. We showed that VEGF-A expression in HNSCC is correlated to the stage of tumour differentiation (P=0.050) and is an independent prognostic factor for progression-free survival (P=0.001) and overall survival (P=0.0004). In a pharynx carcinoma cell line, we demonstrated by RNA interference that VEGF-A expression is closely controlled by PAIP2. Moreover, in human HNSCCs, VEGF-A expression is significantly correlated to PAIP2 protein levels (P=0.0018). Nevertheless, PAIP2 expression is associated with neither clinicopathological factors nor patient's survival. Our data suggest that, in contrast to PAIP2 protein levels, which are unrelated to tumour prognosis, VEGF-A expression could serve as a prognostic marker in head and neck cancer and may be helpful for targeted therapies

A multi-approach survey as the most reliable tool to accurately assess biodiversity: an example of thai murine rodents

Wildlife surveys rely on an accurate taxonomic framework. Identification tools used to reach this goal are not equivalent and may depend on several objectives and constraints, including sampling conservation difficulties, the invasiveness of the sampling techniques, sampling capacity, the relevance of the results, materials needed, the cost and the user time required in the field and laboratory. This article presents and discusses the advantages and limits of each identification tool used in the Ceropath (Community ecology of rodents and their pathogens in South East Asia) program to reach a fast and relevant identification of the rodents sampled. It is concluded that there needs to be a combination of the results from different methods, including the most recent ones, to achieve an improvement in taxonomic identification

Urban environment soundscape evaluation: Milan case study of noise events perceptions by citizens

As one of the main urban environmental pollutants, noise is becoming a real public health concern due to its impact on citizen's well-being. Real-operation noise monitoring can help policy makers in improving the quality of urban environments. To this end, Wireless Acoustic Sensor Networks (WASNs) have been deployed in crowded city centers in both America and Europe. The main application of WASNs is to measure the noise levels from road traffic. Yet, other types of sounds can be found in urban areas, which may also affect citizen's health. Here, we aim to evaluate the citizen's perception of different urban sounds considering their psychoacoustic characteristics, namely loudness, sharpness, roughness, fluctuation strength and tonality. To this end, we have conducted an on-line and off-site listening test using a urban acoustic event dataset collected by WASNs in Milan. The dataset includes seven common urban noises such as sirens, horns, people talking, truck, works, among others. Participants have been asked to rate the level of agreement with adjectives such as loud, shrilling, disturbing, sharp or pleasant. The test responses from one hundred volunteers allow us to gather valuable information about people's perceptions of common urban noises

Preliminary morphologic and molecular study of teh Entoloma rusticoides group (Agaricales - Basidiomycota)

Es presenta un estudi sobre el grup rusticoides del gènere Entoloma subgènere Claudopus a la Península Ibérica. L'anàlisi filogenètica, sobre la base de 48 seqüències d'ITS i 45 seqüències de LSU, entre les quals, les dels tipus de 8 dels tàxons analitzats, mostra una marcada diversitat genètica que concorda amb la notable variabilitat observada en aquest grup. D'acord amb aquest fet, es descriuen els següents nous tàxons: E. almeriense, E. graphitipes f. cystidiatum, E. halophilum, E. muscoalpinum i E. phaeocarpum. A més, es tipifiquen E. phaeocyathus i E. rusticoides. S'inclouen claus provisionals d'identificació. S'aporten descripcions macro i microscòpiques, dibuixos i fotografies de la majoria dels tàxons estudiats.A study of the Entoloma rusticoides-group (subgenus Claudopus) in the Iberian peninsula is presented. Phylogenetic inference, based on 48 nrITS and 45 28S nrLSU sequences, including those of 8 type specimens, revealed a high genetic diversity, in accordance with the observed morphological variability in this group. In addition new taxa are proposed to accomodate independent lineages (E. almeriense, E. graphitipes f. cystidiatum, E. halophilum, E. muscoalpinum and E. phaeocarpum) and the typification of E. phaeocyathus and E. rusticoides is proposed. Preliminary taxonomic keys are included to help identification. For most species macro and microscopic descriptions, drawings and photographs are presented

Porins and small-molecule translocation across the outer membrane of Gram-negative bacteria

Gram-negative bacteria and their complex cell envelope, which comprises an outer membrane and an inner membrane, are an important and attractive system for studying the translocation of small molecules across biological membranes. In the outer membrane of Enterobacteriaceae, trimeric porins control the cellular uptake of small molecules, including nutrients and antibacterial agents. The relatively slow porin-mediated passive uptake across the outer membrane and active efflux via efflux pumps in the inner membrane creates a permeability barrier. The synergistic action of outer membrane permeability, efflux pump activities and enzymatic degradation efficiently reduces the intracellular concentrations of small molecules and contributes to the emergence of antibiotic resistance. In this Review, we discuss recent advances in our understanding of the molecular and functional roles of general porins in small-molecule translocation in Enterobacteriaceae and consider the crucial contribution of porins in antibiotic resistance

Habitabilidad, un concepto en crisis. Sobre su redefinición orientada hacia la sostenibilidad

The urgent response to the environmental crisis –produced by our industrial productive system– constitutes the main challenge that the building sector should face, implying profound transformations on its objectives and intervention procedures. In this article, the possibilities to achieve the sustainability of the building sector are considered from a re-definition of the social utility that the sector should supply: habitability. First, the current regulations are analysed in order to identify the barriers against the sustainability conditions. Secondly, alternatives in the same Spanish regulations contexts are explored to identify the possibilities of adapting these ones to the new sustainable paradigm. Finally, the article reveals the changes which the redefinition of the concept habitability brings about in the own dynamic of the sector and, specifically, in the building stock renovation.La inaplazable respuesta a la crisis ambiental provocada por el sistema productivo industrial, supone el primer y mayor reto que debe afrontar el sector de la edificación, pues conllevará transformaciones profundas en sus objetivos y en sus procedimientos de actuación. La consecución de la condición de edificación sostenible se aborda en el presente artículo a partir de la aproximación a una redefinición de la misma utilidad social que debe procurar el sector: la habitabilidad. En primer lugar, se analiza la concepción normativa actual y se detectan las barreras que opone frente a las demandas de sostenibilidad. En segundo lugar se exploran alternativas disponibles en el mismo contexto legislativo español que permiten adecuarlo al nuevo paradigma ambiental. En último término, el artículo también presenta los cambios que la redefinición del concepto de habitabilidad conlleva en la misma dinámica de sector y, concretamente, en la rehabilitación del parque construido