Neutral-ionic phase transition : a thorough ab-initio study of TTF-CA

The prototype compound for the neutral-ionic phase transition, namely TTF-CA, is theoretically investigated by first-principles density functional theory calculations. The study is based on three neutron diffraction structures collected at 40, 90 and 300 K (Le Cointe et al., Phys. Rev. B 51, 3374 (1995)). By means of a topological analysis of the total charge densities, we provide a very precise picture of intra and inter-chain interactions. Moreover, our calculations reveal that the thermal lattice contraction reduces the indirect band gap of this organic semi-conductor in the neutral phase, and nearly closes it in the vicinity of the transition temperature. A possible mechanism of the neutral-ionic phase transition is discussed. The charge transfer from TTF to CA is also derived by using three different technics.Comment: 11 pages, 9 figures, 7 table

A close examination of the structure and dynamics of HC(NH2)2PbI3 by MD simulations and group theory

International audienceThe formamidinium lead iodide hybrid perovskite is studied using first principles molecular dynamics simulations and further analyzed using group theory. The simulations are performed on large supercells containing 768 atoms under isothermal and fully anisotropic isobaric conditions. Two trajectories, one at 300 K and another at 450 K, were extended for over 50 ps in order to perform a detailed assessment of the rotational dynamic of the organic cations. The characteristic rotations of the cation are analyzed by defining two rotation axes. It is found that the formamidinium molecules rotate preferentially around the direction parallel to the line connecting the two nitrogen atoms. The rotational dynamics shows some characteristics already observed in methylammonium lead iodide, like a heterogeneous dynamic at room temperature that disappears at 450 K. The orientational probability of the molecules is explored in terms of an expansion in cubic harmonics up to the 12 th order. It reveals a strong directionality at room temperature that relaxes when increasing the temperature. These findings are further rationalized using Landau and group theories suggesting a mixed displacive/order-disorder structural instability at lower temperatures

Vibrational properties of 2H-PbI2 semiconductors studied via Density Functional Theory calculations

International audienceDensity Functional Theory is used to study the vibrational properties of 2H-PbI2 semiconductor. The Born charge tensors are determined. Calculated phonon frequencies at the Brillouin zone center are compared to Raman scattering and IR absorption measurements. The computed Raman spectra show a good agreement with available experimental data. The simulated phonon dispersion curves are compared with triple-axis neutron scattering measurements

Teaching Intercultural Competence in Translator Training

In this position paper we define an interculturally competent translator as one that demonstrates a high level of intercultural knowledge, skills, attitude and flexibility throughout his or her professional engagements. We argue that to attain this goal in translator training intercultural competence needs to be introduced into the curriculum explicitly and in a conceptually clear manner. In this article we provide an overview of earlier attempts at discussing the role of intercultural communication in translator training curricula and we discuss the various pedagogical and practical challenges involved. We also look at some future challenges, identifying increasing societal diversity as both a source of added urgency into intercultural training and a challenge for traditional biculturally based notions of translators’ intercultural competence and we argue for the central role of empathy. Finally, and importantly, we introduce the contributions to the special issue

Computational design of high performance hybrid perovskite on silicon tandem solar cells

In this study, the optoelectronic properties of a monolithically integrated series-connected tandem solar cell are simulated. Following the large success of hybrid organic-inorganic perovskites, which have recently demonstrated large efficiencies with low production costs, we examine the possibility of using the same perovskites as absorbers in a tandem solar cell. The cell consists in a methylammonium mixed bromide-iodide lead perovskite, CH3NH3PbI3(1-x)Br3x (0 < x < 1), top sub-cell and a single-crystalline silicon bottom sub-cell. A Si-based tunnel junction connects the two sub-cells. Numerical simulations are based on a one-dimensional numerical drift-diffusion model. It is shown that a top cell absorbing material with 20% of bromide and a thickness in the 300-400 nm range affords current matching with the silicon bottom cell. Good interconnection between single cells is ensured by standard n and p doping of the silicon at 5.10^19cm-3 in the tunnel junction. A maximum efficiency of 27% is predicted for the tandem cell, exceeding the efficiencies of stand-alone silicon (17.3%) and perovskite cells (17.9%) taken for our simulations, and more importantly, that of the record crystalline Si cells.Comment: 17 pages, 7 figure

Conformational transition of FGFR kinase activation revealed by site-­specific unnatural amino acid reporter and single molecule FRET

Protein kinases share significant structural similarity; however, structural features alone are insufficient to explain their diverse functions. Thus, bridging the gap between static structure and function requires a more detailed understanding of their dynamic properties. For example, kinase activation may occur via a switch-like mechanism or by shifting a dynamic equilibrium between inactive and active states. Here, we utilize a combination of FRET and molecular dynamics (MD) simulations to probe the activation mechanism of the kinase domain of Fibroblast Growth Factor Receptor (FGFR). Using genetically-encoded, site-specific incorporation of unnatural amino acids in regions essential for activation, followed by specific labeling with fluorescent moieties, we generated a novel class of FRET-based reporter to monitor conformational differences corresponding to states sampled by non phosphorylated/inactive and phosphorylated/active forms of the kinase. Single molecule FRET analysis in vitro, combined with MD simulations, shows that for FGFR kinase, there are populations of inactive and active states separated by a high free energy barrier resulting in switch-like activation. Compared to recent studies, these findings support diversity in features of kinases that impact on their activation mechanisms. The properties of these FRET-based constructs will also allow further studies of kinase dynamics as well as applications in vivo

Produção da cenoura e efeito na fertilidade do solo e nutrição decorrente da solarização do solo para controle da tiririca.

Dentre os desafios do cultivo orgânico de hortaliças destaca-se o controle de plantas daninhas, devido à proibição do uso de herbicidas. Entre as invasoras, a tiririca (Cyperus rotundus L.) é de difícil controle pela sua alta competitividade. A solarização é uma alternativa para desinfestação do solo, a qual consiste em cobri-lo com plástico transparente, com bons resultados no controle da tiririca. A fim de avaliar a influência do preparo e do revolvimento do solo sobre a eficiência da solarização no controle da tiririca, bem como seu posterior efeito sobre o cultivo da cenoura, foi realizado um experimento na Fazendinha Agroecológica, em Seropédica (RJ). O experimento foi disposto em blocos ao acaso com três repetições, em arranjo fatorial 2 x 3 mais uma testemunha adicional, sendo: 1) solo solarizado, preparado (com grade aradora) e revolvido 30 dias após a solarização (manualmente com auxílio de uma enxada); 2) solo solarizado, preparado e revolvido aos 60 dias; 3) solo solarizado, preparado e não revolvido; 4) solo solarizado, não preparado e revolvido aos 30 dias; 5) solo solarizado, não preparado e revolvido aos 60 dias; 6) solo solarizado, não preparado e não revolvido; solo não solarizado, não preparado e não revolvido (testemunha). A solarização iniciou-se em 29/1/2002, e durou cem dias. A solarização reduziu em 86% a infestação de tiririca no cultivo da cenoura. Até 10 cm de profundidade, a temperatura do solo foi superior nas parcelas solarizadas, porém a 5 cm, a solarização foi mais eficiente quando associada ao preparo do solo, não havendo efeito do revolvimento. A solarização aumentou os valores da biomassa microbiana e dos teores de Ca, Mg e P do solo. O desenvolvimento da cenoura foi influenciado pela solarização que resultou em maior produtividade

Conformational transition of FGFR kinase activation revealed by site-specific unnatural amino acid reporter and single molecule FRET

Protein kinases share significant structural similarity; however, structural features alone are insufficient to explain their diverse functions. Thus, bridging the gap between static structure and function requires a more detailed understanding of their dynamic properties. For example, kinase activation may occur via a switch-like mechanism or by shifting a dynamic equilibrium between inactive and active states. Here, we utilize a combination of FRET and molecular dynamics (MD) simulations to probe the activation mechanism of the kinase domain of Fibroblast Growth Factor Receptor (FGFR). Using genetically-encoded, site-specific incorporation of unnatural amino acids in regions essential for activation, followed by specific labeling with fluorescent moieties, we generated a novel class of FRET-based reporter to monitor conformational differences corresponding to states sampled by non phosphorylated/inactive and phosphorylated/active forms of the kinase. Single molecule FRET analysis in vitro, combined with MD simulations, shows that for FGFR kinase, there are populations of inactive and active states separated by a high free energy barrier resulting in switch-like activation. Compared to recent studies, these findings support diversity in features of kinases that impact on their activation mechanisms. The properties of these FRET-based constructs will also allow further studies of kinase dynamics as well as applications in vivo

Preventing Recurrent Cardioembolic Stroke: Right Approach, Right Patient (PRECISE) Study Protocol

Cardiac rhythm monitoring is performed to search for atrial fibrillation (AF) after ischaemic stroke or transient ischaemic attack (TIA). Prolonged cardiac rhythm monitoring increases AF detection but is challenging to implement in many healthcare settings and is not needed for all people after ischaemic stroke/TIA. We aimed to develop and validate a model that includes clinical, electrocardiogram (ECG), blood-based, and genetic biomarkers to identify people with a low probability of AF detection after ischaemic stroke or TIA. We will recruit 675 consenting participants who are aged over 18 years, who were admitted with ischaemic stroke or TIA in the 5 days prior, who are not known to have AF, and who would be suitable for anticoagulation if AF is found. We will collect baseline demographic and clinical data, a 12-lead ECG, and a venous blood sample for blood biomarkers (including midregional pro-atrial natriuretic peptide, MRproANP) and genetic data. We will perform up to 28 days of cardiac rhythm monitoring using an R-test or patch device to search for AF in all participants. The sample size of 675 participants is based on true sensitivity of 92.5%, null hypothesis sensitivity of 80%, 80% power, and 5% significance. The primary outcome is AF detection ≥30 s duration during 28 days of cardiac rhythm monitoring. Secondary outcomes are AF detection at 1-year, recurrent cardiovascular events, and mortality and will be identified by electronic linkage and telephone follow-up. The results will guide the development of a more personalized care pathway to search for AF after ischaemic stroke or TIA. This could help to reduce cardiac rhythm monitoring for people with a low probability of AF detection and allow more intensive cardiac monitoring to be focused on people who are more likely to have AF and benefit. Participants will be consented for their data to be used in future research studies, providing a rich resource for stroke and cardiovascular research communities