Wavelength-tunable short-pulse diode-laser fiber-amplifier system around 1.06 /spl mu/m

We report the first actively mode-locked diode-laser fiber-amplifier system with wide wavelength tuning around 1.06 /spl mu/m. Tuning is achieved over 45 nm via a feedback grating. Pulses with a repetition rate of 1.4 GHz and a pulse duration of 30 ps are generated with up to 9.5 W of average output power.     

Cloning and disruption of a gene required for growth on acetate but not on ethanol: the acetyl-coenzyme A synthetase gene of Saccharomyces cerevisiae.

A DNA fragment of Saccharomyces cerevisiae with high homology to the acetyl-coenzyme A (acetyl-CoA) synthetase genes of Aspergillus nidulans and Neurospora crassa has been cloned, sequenced and mapped to chromosome I. It contains an open reading frame of 2139 nucleotides, encoding a predicted gene product of 79.2 kDa. In contrast to its ascomycete homologs, there are no introns in the coding sequence. The first ATG codon of the open reading frame is in an unusual context for a translational start site, while the next ATG, 24 codons downstream, is in a more conventional context. Possible implications of two alternative translational start sites for the cellular localization of the enzyme are discussed. A stable mutant of this gene, obtained by the gene disruption technique, had the same low basal activity of acetyl-CoA synthetase as wild-type cells when grown on glucose but completely lacked the strong increase in activity upon entering the stationary phase, providing direct proof that the gene encodes an inducible acetyl-CoA synthetase (ACS1) of yeast. As expected, the mutant was unable to grow on acetate as sole carbon source. Nevertheless, it showed normal induction of isocitrate lyase on acetate media, indicating that activity of acetyl-CoA synthetase is dispensable for induction of the glyoxylate cycle in S. cerevisiae. Surprisingly, disruption of the ACS1 gene did not affect growth on media containing ethanol as the sole carbon source, demonstrating that there are alternative pathways leading to acetyl-CoA under these conditions.     

Mechanism of carbon–nitrogen bond scission in the presence of H2S on Pt Supported catalysts

The reactivity of a series of amines with various structures and different numbers of hydrogen atoms on the carbon atoms in the and position was used to evidence the C–N bond scission mechanism in the presence of H₂S on Pt based catalysts (deposited on alumina, zirconia and silica–alumina) and compare it with the mechanism on a NiMoP on alumina sulfide catalyst. The effect of the H₂S partial pressure was also checked. Catalytic activities (amine overall conversion, C₅ hydrocarbon formation, and amine disproportionation) deeply depend on the structure of the N-containing molecule. Tert-pentylamine is the most reactive molecule for sulfide catalysts whereas, in the case of n-pentylamine, Pt on zirconia was found to be the most efficient for C–N bond breaking. Such properties cannot be related to the acidic properties of the support but to a unique support–metal interaction, since alumina or silica–alumina supported platinum catalysts do not present this behaviour.     

New nanostructured carbons based on porous cellulose: Elaboration,pyrolysis and use as platinum nanoparticles substrate for oxygen reduction electrocatalysis

New nanostructured carbons have been prepared from pyrolysis of recently developed highly porous cellulose, aerocellulose (AC). Aerocellulose is an ultra-light and highly porous pure cellulose material prepared from cellulose gels followed by drying in carbon dioxide supercritical conditions. The carbonized aerocellulose (CAC) materials were obtained after pyrolysis of the aerocellulose under nitrogen flow at 830 °C, and subsequently doped by platinum nanoparticles. The platinum insertion process consisted of (i) thermal activation at various temperatures in CO₂ atmosphere, (ii) impregnation by PtCl₆²⁻ and (iii) platinum salt chemical reduction. The aerocellulose materials and their carbonized counterparts were investigated by scanning and transmission electron microscopy (SEM and TEM), mercury porosimetry and thermogravimetric analysis. The morphology of the platinum particles deposited on the carbonized aerocellulose materials (Pt/CAC) was investigated by transmission electron microscopy (TEM) and X-ray diffraction (XRD): the Pt particles are of 4–5 nm size, mainly agglomerated, as a result of the complex surface chemistry of the CAC. Their electrocatalytic activity was investigated by quasi-steady-state voltammetry in the rotating disk electrode (RDE) setup, regarding the oxygen reduction reaction (ORR). The Pt/CAC materials exhibit ORR specific activities comparable with those of commercial Pt/Vulcan XC72R. Their mass activity is lower, as a result of the ca. 10 times smaller specific area of platinum as compared with the commercial electrocatalyst. We nevertheless believe that provided an appropriate pyrolysis temperature is chosen, such green carbonized aerocellulose could be a promising electrocatalyst support for PEM application.     

Thermography in high cycle fatigue short‐term evaluation procedures applied to a medium carbon steel

This paper focuses on the fatigue life calculation for an unalloyed medium carbon steel SAE1045 (German DIN‐standard: C45E), by applying an energy dissipation‐based approach quantified through thermographic measurements. The purpose of this approach is to establish an intrinsic dissipation model and to predict characteristics derived from the cyclic deformation behavior of stress‐controlled fatigue tests, eg, the fatigue limit and the S‐N data by using simplified (zero‐dimensional, 0D) thermodynamic equations. In order to investigate the possibilities for a rapid evaluation while simultaneously reducing the experimental effort, one load increase test (LIT) and two constant amplitude tests (CATs) were carried out. The S‐N data evaluated on such a basis is competitive to conventionally determined S‐N data as will be shown.     

Characterization of ALBA Family Expression and Localization in Arabidopsis thaliana Generative Organs

ALBA DNA/RNA-binding proteins form an ancient family, which in eukaryotes diversified into two Rpp25-like and Rpp20-like subfamilies. In most studied model organisms, their function remains unclear, but they are usually associated with RNA metabolism, mRNA translatability and stress response. In plants, the enriched number of ALBA family members remains poorly understood. Here, we studied ALBA dynamics during reproductive development in Arabidopsis at the levels of gene expression and protein localization, both under standard conditions and following heat stress. In generative tissues, ALBA proteins showed the strongest signal in mature pollen where they localized predominantly in cytoplasmic foci, particularly in regions surrounding the vegetative nucleus and sperm cells. Finally, we demonstrated the involvement of two Rpp25-like subfamily members ALBA4 and ALBA6 in RNA metabolism in mature pollen supported by their co-localization with poly(A)-binding protein 3 (PABP3). Collectively, we demonstrated the engagement of ALBA proteins in male reproductive development and the heat stress response, highlighting the involvement of ALBA4 and ALBA6 in RNA metabolism, storage and/or translational control in pollen upon heat stress. Such dynamic re-localization of ALBA proteins in a controlled, developmentally and environmentally regulated manner, likely reflects not only their redundancy but also their possible functional diversification in plants.     

Three-dimensional rigid multiphase networks providing high-temperature strength to cast AlSi10Cu5Ni1-2 piston alloys

The three-dimensional (3-D) architecture of rigid multiphase networks present in AlSi10Cu5Ni1 and AlSi10Cu5Ni2 piston alloys in as-cast condition and after 4?h spheroidization treatment is characterized by synchrotron tomography in terms of the volume fraction of rigid phases, interconnectivity, contiguity and morphology. The architecture of both alloys consists of α-Al matrix and a rigid long-range 3-D network of Al(7)Cu(4)Ni, Al(4)Cu(2)Mg(8)Si(7), Al(2)Cu, Al(15)Si(2)(FeMn)(3) and AlSiFeNiCu aluminides and Si. The investigated architectural parameters of both alloys studied are correlated with room-temperature and high-temperature (300?°C) strengths as a function of solution treatment time. The AlSi10Cu5Ni1 and AlSi10Cu5Ni2 alloys behave like metal matrix composites with 16 and 20?vol.% reinforcement, respectively. Both alloys have similar strengths in the as-cast condition, but the AlSi10Cu5Ni2 is able to retain ～15% higher high temperature strength than the AlSi10Cu5Ni1 alloy after more than 4?h of spheroidization treatment. This is due to the preservation of the 3-D interconnectivity and the morphology of the rigid network, which is governed by the higher degree of contiguity between aluminides and Si.     

Simulation of synthetic climate at local scale as a mean to assess the impact of climate change on infrastructures

A global modelling approach for estimating the climate influence on corrosion activity in reinforced concrete is developed. It combines: (a) the identification of statistical properties of climates in various temperate regions, and the development of a synthetic simulator able to reproduce its dominant patterns, (b) the identification of an empirical corrosion activity model, based on the analysis of experimental data, highlighting the respective influence of temperature and humidity. Synthetic simulations combining these two models are carried out. They show the complexity of the interactions, since the influence of temperature and humidity may be adverse, and the interest to describe both random fluctuations at daily scale and at seasonal scale. They confirm that monitoring of corrosion must account for this time variability and propose a way to estimate average corrosion even with measurements which would remain limited to a short period. Synthetic simulations are also used for estimating the influence of a global warming scenario on the corrosion activity. A global increase of about 38% of corrosion activity has been estimated in response to an average temperature elevation of 3°C.