Silane Deuteration Catalyzed by Ruthenium Bis(dihydrogen) Complexes or Simple Metal Salts

The deuteration of a diverse group of silanes: alkyl‐, aryl‐, alkoxy‐ and chlorosilanes, siloxane and silazane, under an atmosphere of dideuterium (D₂) was explored with ruthenium bis(dihydrogen) dihydride complexes and hydrated metal salts. Deuterium incorporation of greater than 97% for the silanes O(SiMe₂H)₂, Et₃SiH, (EtO)₃SiH and Me₂ClSiH was possible with 0.1 mol% of the ruthenium complex [RuH₂(η²‐H₂)₂(PCyp₃)₂] [0.05 mol% for O(SiMe₂H)₂] when catalysis was conducted in the neat silane at 30 °C under 1 bar of D₂ for 3.5 h. The air‐stable ruthenium trichloride salt RuCl₃⋅x H₂O was also an efficient catalyst for the deuteration of O(SiMe₂H)₂ and Et₃SiH; deuterium incorporations for the two silanes of 93% and 90%, respectively, were possible under the same conditions as for [RuH₂(η²‐H₂)₂(PCyp₃)₂] with 0.1% catalyst loading. Hydrogen–deuterium exchange of O(SiMe₂H)₂ catalyzed by the rhodium trichloride (RhCl₃⋅x H₂O) and iridium trichloride (IrCl₃⋅x H₂O) was similarly efficient as with RuCl₃⋅x H₂O although catalytic alacrity dropped for Et₃SiH.

     

Four permeases import proline and the toxic proline analogue azetidine-2-carboxylate into yeast

We have found that proline and the toxic proline analogue azetidine-2-carboxylate (AzC) are efficiently imported into Saccharomyces cerevisiae cells by four amino acid permeases, including two nitrogen-regulated permeases (PUT4 and GAP1) and two permeases that are regulated by the SPS sensor of extracellular amino acids (AGP1 and GNP1). In contrast to Agp1p, Gnp1p is not functionally expressed when cells are grown on media containing proline as sole nitrogen source. These findings have implications for the interpretation of studies using AzC to characterize nitrogen source-dependent regulation of amino acid uptake and of post-Golgi targeting and localization of amino acid permeases in yeast.     

Removal of pesticide mixtures in a stormwater wetland collecting runoff from a vineyard catchment

Wetlands can collect contaminated runoff from agricultural catchments and retain dissolved and particle-laden pesticides. However, knowledge about the capacity and functioning of wetland systems with respect to the removal of pesticides is very limited. Here we show that stormwater wetlands can efficiently remove pesticides in runoff from vineyard catchments during the period of pesticide application, although flow and hydrochemical conditions of the wetland largely vary over time. During the entire agricultural season, the inflowing load of nine fungicides, six herbicides, one insecticide and four degradation products was 8.039 g whereas the outflowing load was 2.181 g. Removal rates of dissolved loads by the wetland ranged from 39% (simazine) to 100% (cymoxanil, gluphosinate, kresoxim methyl and terbuthylazine). Dimethomorph, diuron, glyphosate, metalaxyl and tetraconazole were more efficiently removed in spring than in summer. More than 88% of the input mass of suspended solids was retained, underscoring the capability of the wetland to trap pesticide-laden particles via sedimentation. Only the insecticide flufenoxuron was frequently detected in the wetland sediments. Our results demonstrate that stormwater wetlands can efficiently remove pesticide mixtures in agricultural runoff during critical periods of pesticide application, although fluctuations in the runoff regime and hydrochemical characteristics can affect the removal rates of individual pesticides.     

Exhaustive analysis and simulation for distributed systems,both sides of the same coin

This paper presents exhaustive analysis and simulation for distributed systems validation. Exhaustive analysis makes possible to detect quickly several types of errors, for instance, unspecified reception of signals, errors in timer management, deadlock, errors in precedence, etc. But, in general, exhaustive analysis can only be applied to a simplified model of the distributed system due to the state explosion problem. On the other hand, simulation permits accurate tests and confronts the distributed system to complex situations. We think both forms of validation are complementary. Validation was done on systems specified in the SDL language, using OVAL, a tool for specification validation developed at CNET, Paris A. This tool allows exhaustive analysis and simulation of SDL specified systems. We illustrate our results with several examples. Ana R. Cavalli received the Doctorat d'Etat ès Sciences Mathematiques in 1984, from the University of Paris VII, France. From 1975 to 1981 she was associate professor in the Computer Science Department, at the Universidad Central de Venezuela, Caracas. In 1981, she joined the Laboratoire d'Informatique Theorique et Programmation of the C.N.R.S., Paris, where she worked on automatic proofs methods for temperal logics and their applications to the specification and verification of protocols. She is now involved in the Concurrency Communication and Cooperation Project. (C.N.R.S.). In 1985, she joined the Department of Langages et Systèmes de Commutation, at the CNET (Centre National d'Etudes des Telecommunications), Paris, where she works on software engineering and formal specification techniques. His research interests are in formal specification techniques.and verification of distributed systems, including logics and models for parallel systems. Etienne Paul received the ingenieer degree in 1974, from the Ecole Polytechnique, France, and the telecommunications ingenieer degree in 1976 from the Ecole Nationale Superieure des Telecommunications, France. He joined the Department of Langages et Systèmes de Commutation, at the CNET (Centre National d'Etudes des Telecommunications), in 1977. From 1977 to 1981, he worked on the development of telecommunications systems, and since 1982, on software engineering and formal specification techniques. His first interest in formal specification techniques has been in the field of algebraic data types and logic programming. Now he is mainly working on SDL language and is responsible for the OVAL project. During the RACE definition phase, he has also worked on the SPECS project.     

Modeling of soil nutrient balances,flows and stocks revealed effects of management on soil fertility in south Ecuadorian smallholder farming systems

Nutrient Cycling in Agroecosystems - Linking nutrient balances and flows to soil nutrient stocks creates a valuable indicator for sustainability assessment in agricultural land-use systems....     

Purely numerical compensation for microscope objective phase curvature in digital holographic microscopy: influence of digital phase mask position

Introducing a microscope objective in an interferometric setup induces a phase curvature on the resulting wavefront. In digital holography, the compensation of this curvature is often done by introducing an identical curvature in the reference arm and the hologram is then processed using a plane wave in the reconstruction. This physical compensation can be avoided, and several numerical methods exist to retrieve phase contrast images in which the microscope curvature is compensated. Usually, a digital array of complex numbers is introduced in the reconstruction process to perform this curvature correction. Different corrections are discussed in terms of their influence on the reconstructed image size and location in space. The results are presented according to two different expressions of the Fresnel transform, the single Fourier transform and convolution approaches, used to propagate the reconstructed wavefront from the hologram plane to the final image plane.     

FLAVOUR AND HAZE STABILITY DIFFERENCES DUE TO HOP TANNINS IN ALL-MALT PILSNER BEERS BREWED WITH PROANTHOCYANIDIN-FREE MALT

All-malt Pilsner beers were brewed with proanthocyanidin-free malt (ant 13 × 13 × Rupal). Hopping was with n-hexane tannin-free hop extract with or without n-hexane extracted hop residue or with whole leaf hops. The different beers were analysed chemically and presented to an expert panel to detect possible preferences and differences in bitterness and astringency. The impact of hop proantho-cyanidins on haze formation is comparable to that of malt proanthocyanidins. No differences between the beers were found in triangular tests. Statistical analysis of the paired comparison tests showed that hop proanthocyanidins do not contribute to the bitterness of beer since beer brewed with tannin-free hop extract is slightly more bitter than beer brewed with whole leaf hops. No differences in astringency were noted between beers brewed with or without hop proanthocyanidins and it was found that the panel expressed a very slight preference for beer brewed with n-hexane hop extract over beer brewed with both n-hexane hop extract and extracted hop residue.     

Refining the Dynamic Network of T2SS Endopilus Tip Heterocomplex Combining cw-EPR and Nitroxide–GdIII Distance Measurements

The type 2 secretion system (T2SS) is a bacterial nanomachine composed of an inner membrane assembly platform, an outer membrane pore and a dynamic endopilus. T2SS endopili are organized into a homo-multimeric body formed by the major pilin capped by a heterocomplex of four minor pilins. The first model of the T2SS endopilus was recently released, even if structural dynamics insights are still required to decipher the role of each protein in the full tetrameric complex. Here, we applied continuous-wave and pulse EPR spectroscopy using nitroxide-gadolinium orthogonal labelling strategies to investigate the hetero-oligomeric assembly of the minor pilins. Overall, our data are in line with the endopilus model even if they evidenced conformational flexibility and alternative orientations at local scale of specific regions of minor pilins. The integration of different labelling strategies and EPR experiments demonstrates the pertinence of this approach to investigate protein–protein interactions in such multiprotein heterocomplexes.     

Modeling the thermal decomposition and residual mass of a carbon fiber epoxy matrix composite with a phenomenological approach: Effect of the reaction scheme

The thermal decomposition of polymer matrix composites is a complex process involving hundreds of reactions and species, which are often modeled with simplified one-step schemes. These schemes can be improved by adding intermediate reactions of different nature (competitive, parallel, and consecutive). However, the optimal number and nature of intermediate reactions are rarely discussed. In this paper, several reaction schemes of increasing complexity have been developed to model the decomposition of a carbon/epoxy composite. The kinetic parameters describing each reaction have been extracted from thermogravimetric analysis (TGA) by means of isoconversional methods. The composite mass loss rate and residual mass have been modeled and compared to TGA and tube furnace data. This research shows that adding parallel or consecutive intermediate reactions improves the agreement against TGA data compared to a single-step model, but only competitive reactions can account for the variation of the residual mass observed in the tube furnace when the heating rate is varied.