A unified electrostatic and cavitation model for first-principles molecular dynamics in solution

The electrostatic continuum solvent model developed by Fattebert and Gygi is combined with a first-principles formulation of the cavitation energy based on a natural quantum-mechanical definition for the surface of a solute. Despite its simplicity, the cavitation contribution calculated by this approach is found to be in remarkable agreement with that obtained by more complex algorithms relying on a large set of parameters. Our model allows for very efficient Car-Parrinello simulations of finite or extended systems in solution, and demonstrates a level of accuracy as good as that of established quantum-chemistry continuum solvent methods. We apply this approach to the study of tetracyanoethylene dimers in dichloromethane, providing valuable structural and dynamical insights on the dimerization phenomenon

Growth Route Toward III-V Multispectral Solar Cells on Silicon

To date, high efficiency multijunction solar cells have been developed on Ge or GaAs substrates for space applications, and terrestrial applications are hampered by high fabrication costs. In order to reduce this cost, we propose a breakthrough technique of III-V compound heteroepitaxy on Si substrates without generation of defects critical to PV applications. With this technique we expect to achieve perfect integration of heterogeneous Ga1-xInxAs micro-crystals on Si substrates. In this paper, we show that this is the case for x=0. GaAs crystals were grown by Epitaxial Lateral Overgrowth on Si (100) wafers covered with a thin SiO2 nanostructured layer. The cristallographic structure of these crystals is analysed by MEB and TEM imaging. Micro-Raman and Micro-Photomuminescence spectra of GaAs crystals grown with different conditions are compared with those of a reference GaAs wafer in order to have more insight on eventual local strains and their cristallinity. This work aims at developping building blocks to further develop a GaAs/Si tandem demonstrator with a potential conversion efficiency of 29.6% under AM1.5G spectrum without concentration, as inferred from our realistic modeling. This paper shows that Epitaxial Lateral Overgrowth has a very interesting potential to develop multijunction solar cells on silicon approaching the today 30.3% world record of a GaInP/GaAs tandem cell under the same illumination conditions, but on a costlier substrate than silicon.Comment: Preprint of the 28th EUPVSEC proceedings, September 2013, Paris, France. (5 pages

Uncertainty in vernacular religions

WOS:000344691100001 (Nº de Acesso Web of Science

Copper phosphoramidite-catalyzed enantioselective desymmetrization of meso-cyclic allylic bisdiethyl phosphates

A highly regio-, diastereo-, and enantioselective desymmetrization of five-, six-, and seven-membered meso-cyclic allylic bis-diethyl phosphates (2a, 2b, and 2c, respectively) was obtained with diethylzinc, using catalytic amounts of [Cu(OTf)](2).C6H6 and phosphoramidite ligands 5. Enantiomeric excesses of up to 87, 94, and >98% were obtained for the addition of diethylzinc to cyclopentene, cyclohexene, and cycloheptene bis-diethyl phosphates, respectively

A self-consistent perturbative evaluation of ground state energies: application to cohesive energies of spin lattices

The work presents a simple formalism which proposes an estimate of the ground state energy from a single reference function. It is based on a perturbative expansion but leads to non linear coupled equations. It can be viewed as well as a modified coupled cluster formulation. Applied to a series of spin lattices governed by model Hamiltonians the method leads to simple analytic solutions. The so-calculated cohesive energies are surprisingly accurate. Two examples illustrate its applicability to locate phase transition.Comment: Accepted by Phys. Rev.

Field evaluation of rigid and flexible scarifier shanks

Se llevaron a cabo ensayos en campo con el objeto de evaluar parámetros de prestación de arcos de escarificador rígidos y flexibles. Se empleó un tractor de diseño convencional de 73 kW de potencia y un bastidor de tracción libre, registrándose los esfuerzos traccionales mediante una celda de carga interpuesta entre ambos, determinándose el área removida mediante un perfilómetro y obteniéndose los valores de resistencia específica. Los arcos rígidos produjeron un frente de labor significativamente mayor que los arcos flexibles. Los arcos rígidos son energéticamente más eficientes que los arcos flexiblesField tests were carried out with the aim to evaluate both rigid and flexible scarifier shanks performance parameters. A 2WD, 73 kW tractor and a pull type implement were used. The draft force was measured with a force transducer with strain gauges. The loosening area was recorded through a profilometer and, from this data, the specific resistance was calculated. The rigid shanks produced a significantly greather working area than the flexible shanks. The rigid shanks shows higher efficiency than the flexible shanksFacultad de Ciencias Agrarias y Forestale

Field evaluation of rigid and flexible scarifier shanks

Se llevaron a cabo ensayos en campo con el objeto de evaluar parámetros de prestación de arcos de escarificador rígidos y flexibles. Se empleó un tractor de diseño convencional de 73 kW de potencia y un bastidor de tracción libre, registrándose los esfuerzos traccionales mediante una celda de carga interpuesta entre ambos, determinándose el área removida mediante un perfilómetro y obteniéndose los valores de resistencia específica. Los arcos rígidos produjeron un frente de labor significativamente mayor que los arcos flexibles. Los arcos rígidos son energéticamente más eficientes que los arcos flexiblesField tests were carried out with the aim to evaluate both rigid and flexible scarifier shanks performance parameters. A 2WD, 73 kW tractor and a pull type implement were used. The draft force was measured with a force transducer with strain gauges. The loosening area was recorded through a profilometer and, from this data, the specific resistance was calculated. The rigid shanks produced a significantly greather working area than the flexible shanks. The rigid shanks shows higher efficiency than the flexible shanksFacultad de Ciencias Agrarias y Forestale

Multiple technology approach based on stable isotope ratio analysis, Fourier transform infrared spectrometry and thermogravimetric analysis to ensure the fungal origin of the chitosan

Chitosan is a natural polysaccharide which has been authorized for oenological practices for the treatment of musts and wines. This authorization is limited to chitosan of fungal origin while that of crustacean origin is prohibited. To guarantee its origin, a method based on the measurement of the stable isotope ratios (SIR) of carbon δ13C, nitrogen δ15N, oxygen δ18O and hydrogen δ2H of chitosan has been recently proposed without indicating the threshold authenticity limits of these parameters which, for the first time, were estimated in this paper. In addition, on part of the samples analysed through SIR, Fourier transform infrared spectrometry (FTIR) and thermogravimetric analysis (TGA) were performed as simple and rapid discrimination methods due to limited technological resources. Samples having δ13C values above -14.2‱ and below -125.1‱ can be considered as authentic fungal chitosan without needing to analyse other parameters. If the δ13C value falls between -25.1‱ and -24.9‱, it is necessary to proceed further with the evaluation of the parameter δ15N, which must be above +2.7‱. Samples having δ18O values lower than +25.3‱ can be considered as authentic fungal chitosan. The combination of maximum degradation temperatures (obtained using TGA) and peak areas of Amide I and NH2/Amide II (obtained using FTIR) also allows the discrimination between the two origins of the polysaccharide. Hierarchical cluster analysis (HCA) and principal component analysis (PCA) based on TGA, FTIR and SIR data successfully distributed the tested samples into informative clusters. Therefore, we present the technologies described as part of a robust analytical strategy for the correct identification of chitosan samples from crustaceans or fung