Towards high-power single-cycle THz laser for initiating high-field-sensitive phenomena

Powerful THz radiation confined in one field period or less is an adequate tool for triggering nonlinear actions. We show results towards the realization of a tunable high-power THz source based on a laser-driven frequency conversion scheme in plasma and nonlinear crystals. A powerful THz source in combination with the future X-ray Free Electron Laser facility in Switzerland (SwissFEL) holds promise for exciting experiments in a variety of different research areas.     

Oxidative degradations of oxodegradable LDPE enhanced with thermoplastic pea starch: Thermo‐mechanical properties,morphology, and UV‐ageing studies

The abiotic UV‐degradation behavior of oxodegradable LDPE was investigated in the presence of thermoplastic pea starch (TPPS) in this study. Oxodegradable LDPE was first melt‐blended with thermoplastic pea starch (TPPS) using an internal mixing chamber to enhance the abiotic oxidative degradation of oxodegradable LDPE. Because of their different affinity, maleated polyethylene was added as compatibilizer. Tensile properties, thermal properties, and morphology of resulting melt‐blends were determined at different content in TPPS. High content in TPPS (40 wt %) could be readily added to oxodegradable LDPE without affecting the tensile properties of resulting melt‐blends. UV‐ageing studies on compatibilized TPPS/oxodegradable LDPE melt‐blends were carried out by Attenuated Total Reflectance infrared spectroscopy (ATR‐FTIR), Dynamic Thermomechanical Analyses (DMTA) and Differential Scanning Calorimetry (DSC) under abiotic conditions. These results suggested a synergistic effect on the UV‐ageing of TPPS‐based melt‐blends provided by both components during the first stage of UV‐irradiation. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011.     

Synthesis and Characterization of Cell‐Permeable Caged Phosphates that Can Be Photolyzed by Visible Light or 800 nm Two‐Photon Photolysis

We report the synthesis and photolytic properties of caged inorganic phosphates (Pi compounds) based on the 2‐(4′‐{bis[2‐(2‐methoxyethoxy)ethyl]amino}‐4‐nitro‐[1,1′‐biphenyl]‐3‐yl)propan‐1‐ol (EANBP) and 7‐(diethylamino)coumarin‐4‐yl]methyl (DEACM) protecting groups. The EANBP‐Pi showed unprecedented photolysis efficiency at 405 nm, with 95 % release of free phosphate and a quantum yield of 0.28. Thanks to the high two‐photon sensitivity of the EANBP chromophore, Pi release through two‐photon photolysis is also possible, with an action cross section of 20.5 GM at 800 nm. Two bioactivatable acetoxymethyl protection groups were added to the “caged‐Pi” compounds. The resulting triesters of phosphoric acid were able to diffuse through the cellular membranes of plant cells. Once inside a cell, the cleavage of these biocleavable motifs by intracellular esterases allows intracellular accumulation of EANBP‐Pi. Bis(AM)‐EANBP‐Pi therefore represents a very attractive tool for study of the Pi signal transduction cascade in living cells.     

Aerobic Dehydrogenative Heck Reactions of Heterocycles with Styrenes: A Negative Effect of Metallic Co‐Oxidants

The aerobic dehydrogenative Heck reaction (DHR) of heterocycles with styrenes was found to be more efficient in the absence of metallic co‐oxidants. According to a study of the isotope effect, the C H cleavage was the rate‐determining step of the catalytic cycle. Electrospray ionization mass spectrometry, subsequent MS/MS, and high‐resolution mass spectrometry were used to detect and characterize catalytic intermediates and species formed in the presence of metallic co‐oxidants.     

Effect of Seed Addition on SnO2‐Based Varistors for Low Voltage Application

The effect of seed addition on the microstructure and non‐ohmic properties of the SnO₂ + 1%CoO + 0.05%Nb₂O₅ ceramic‐based system was analyzed. Two classes of seeds were prepared: 99% SnO₂ + 1%CuO and 99% SnO₂ + 1%CoO (mol%); both classes were added to the ceramic‐based system in the amount of 1%, 5%, and 10%. The two systems containing 1% of seeds resulted in a larger grain size and a lower breakdown voltage. The addition of 1% copper seeds produces a breakdown voltage (V_b) of ~ 37 V and a leakage current (f_ic) of 29 μA. On the other hand, the addition of 1% cobalt seeds produced a breakdown voltage of 57 V and a leakage current of 70 μA. Both systems are of great technological interest for low voltage varistor applications, by means of appropriate strategies to reduce the leakage current. Using larger amounts of seeds was not effective since the values of breakdown voltage in both cases are close to a system without seeds. To our knowledge, there are no reports in the literature regarding the use of seeds in the SnO₂ system for low voltage applications. A potential barrier model which illustrates the formation of oxygen species (O′_2(ads), O′_ads, and O″_ads) at the expense of clusters near the interface between grains is proposed.     

In-Silico Calculations as a Helpful Tool for Designing New Extractants in Liquid-Liquid Extraction

Due to new challenges, new extraction solvents based on innovative extractants are needed in hydrometallurgy for specific tasks. Thus, the aim of the present article is to discuss the potential and limits of Quantitative Structure–Properties Relationship (QSPR) and molecular modeling for identifying new extractants. QSPR methods may have useful applications in such a complex problem as the design of ligands for metal separation. Nevertheless, the degree of reliability of the predictions is still limited and, in the present state of the art, these techniques are likely more useful for optimization within a given family of extractants than to build in-silico new reagents. The molecular modeling techniques provide binding energies between target metals and given ligands, as well as optimized chemical structures of the formed complexes. Thus, in principle, the information, which can be deduced from the molecular modeling computations are richer than that provided by QSPR methods. Nevertheless, an effort should be made to establish more tangible links between the calculated binding energies and the physical parameters used by the hydrometallurgists, such as the complexation constants in aqueous phase (β_MAn) or better the extraction constants (K_ex).     

Electro‐optical study of a ×1024 concentrator photovoltaic system

Concentrator photovoltaic (CPV) systems are one of the most promising technologies for future energy supply. Several studies reported the interest of using a Fresnel lens coupled with a secondary optical element in such a system. For high concentration factor, the optimization of the optical configuration plays a key role regarding electrical performances. On the other hand, the thermal management of the solar cell is also critical to ensure a better module efficiency. This paper presents a study of a ×1024 CPV system performances and a methodology for estimating the optical chain efficiency, the cell temperature impact and the alignment requirements. Module efficiencies were then measured as a function of the cell temperature and correlated to optical performances through current‐tension characterizations under real solar illumination conditions and the estimation of the power density received by the solar cell. The system yield was up to 27% for a cell temperature around 30 °C, confirming that high concentration ratio should be of great interest in the near future. A 1D model was also developed in order to quantify the possible improvements of this CPV system. Using a solar cell with an efficiency of 36.7% at ×600, we then demonstrated that the ×1024 CPV system could reach up to 30% in standard test conditions. Copyright © 2012 John Wiley & Sons, Ltd.     

Effects of Probiotic Lactobacillus gasseri Strains of Breast-Fed Infant in a Murine Model

The ingestion of probiotic lactic acid bacteria has been evaluated and noted that it has an effect on the balance of desirable microbiota in the gastrointestinal tract. Lactobacillus gasseri demonstrates good survival in the gastrointestinal tract, and it has been associated with a variety of probiotic activities and roles, including the reduction of fecal mutagenic enzymes, the production of bacteriocins and the stimulation of macrophages immunomodulation. The aim of the study was to evaluate the effects of a pool of L. gasseri strains isolated from the feces of breastfed infants added in the human milk of healthy women. The milk was both pasteurized and unpasteurized, to verify the cell cytotoxicity of macrophages and to quantify the production of immunologic mediators such as IL-4, IL-6, IFN-γ, TNF-α, NO and oxygen intermediary compounds （H2O2）. The administration of raw human milk and pasteurized human milk to infants is a regular, encouraged practice in units of intensive therapy （UITs） and our present investigation verified the beneficial effect of addition of a pool of L. gasseri to pasteurized human milk （PHML）. Our results show that probiotic supplementation helped to maintain cell viability, reduced IL-6 and IFN-γ production and stimulated TNF-α, NO, H2O2, IL-4 production. Nevertheless, the results indicate that the addition of lactobacillus to human milk was not a determinant in the production of TNF-α. L. gasseri added to breast milk did not present a cytotoxic risk, and the addition ofL. gasseri to pasteurized milk of human milk bank would benefit newborns that depend on milk banks for the colonization of more desirable microbiota.     

Molecular cloning, heterologous expression, and characterization of Ornithine decarboxylase from Oenococcus oeni

Ornithine decarboxylase (ODC) is responsible for the production of putrescine, the major biogenic amine found in wine. Oenococcus oeni is the most important lactic acid bacterium in the winemaking process and is involved in malolactic fermentation. We report here the characterization of ODC from an O. oeni strain isolated from wine. Screening of 263 strains isolated from wine and cider from all over the world revealed that the presence of the odc gene appears to be strain specific in O. oeni. After cloning, heterologous expression in Escherichia coli, and characterization, the enzyme was found to have a molecular mass of 85 kDa and a pI of 6.2 and revealed maximal activity at pH 5.5 and an optimum temperature of 35°C. Kinetic studies showed that O. oeni ODC is specific for L-ornithine with a K(m) value of 1 mM and a V(max) of 0.57 U·mg(-1). The hypothesis that cadaverine, which results from lysine decarboxylation, may be linked to putrescine production is not valid since O. oeni ODC cannot decarboxylate L-lysine. As no lysine decarboxylase was detected in any of the O. oeni genomes sequenced, cadaverine synthesis may result from another metabolic pathway. This work is the first characterization of an ODC from a lactic acid bacterium isolated from a fermented product.