波茨坦砂岩的微观结构和碱活性快速检测方法的适应性

为研究集料微观结构对碱活性快速检测方法中对岩石适应性的影响,采用混凝土棱柱体法、快速砂浆棒法、压蒸法、中国快速砂浆棒法研究了波茨坦砂岩的膨胀行为,并研究了膨胀后试件的微观结构.结果表明:快速砂浆棒法、压蒸法、中国快速砂浆棒法均不能正确判定波茨坦砂岩的碱活性,主要是由于这些方法使用的集料中含大量粒径太小、不能反映该砂岩特殊结构特征的颗粒;对该类岩石,除活性组分的类型、数量外,岩石的微观结构特征能够显著影响碱-集料反应发生的位置和膨胀行为.在快速法中采用能够保持岩石原有结构特征的集料粒径是正确鉴定类似波茨坦砂岩微观结构岩石及其它非均质、多矿物岩石碱活性的关键.     

Two-Chains Tissue Plasminogen Activator Unifies Met and NMDA Receptor Signalling to Control Neuronal Survival

Tissue-type plasminogen activator (tPA) plays roles in the development and the plasticity of the nervous system. Here, we demonstrate in neurons, that by opposition to the single chain form (sc-tPA), the two-chains form of tPA (tc-tPA) activates the MET receptor, leading to the recruitment of N-Methyl-d-Aspartate receptors (NMDARs) and to the endocytosis and proteasome-dependent degradation of NMDARs containing the GluN2B subunit. Accordingly, tc-tPA down-regulated GluN2B-NMDAR-driven signalling, a process prevented by blockers of HGFR/MET and mimicked by its agonists, leading to a modulation of neuronal death. Thus, our present study unmasks a new mechanism of action of tPA, with its two-chains form mediating a crosstalk between MET and the GluN2B subunit of NMDARs to control neuronal survival.     

Modélisation et simulation du séchage en continu des couches minces par rayonnement infrarouge

Basé sur des concepts de transferts simultanés de masse et d'énergie, un modèle différentiel est posé pour le séchage en continu des couches minces par rayonnement infrarouge. Des essais conduits sur le séchage d'une nappe de coton non-mercerisé dans un séchoir semi-industriel d'une capacité maximale de 20 kW ont servi à la calibration du modèle. Les simulations, par intégration numérique des bilans de masse et d'énergie, fournissent les conditions à la sortie du séchoir: température de l'air, température du tissu et degré d'humidité résiduelle dans la nappe. Une étude de sensibilité indique que la température des émetteurs infrarouges est le paramètre qui influence le plus significativement le séchage. Les résultats montrent également que l'air alimenté sert presqu'uniquement à évacuer la vapeur produite, le transfert de chaleur par convection étant faible par rapport au rayonnement.     

Multilayer optics for the EUV and soft X-rays

1Introduction Engineersandscientistsinfieldsasdiverse asmicrolithographyandspaceastronomyhavea commonneedtouse“light”rangingfromEUV tothesoftX rayregion.Theextremeultraviolet andsoftX rayspectralregionliebetweentheul travioletandthehardX rayregionsoftheelec tromagneticspectrum.Inspiteofthesmooth transitionsbetweenthespectralsubdivisionsit’s worthtodefineroughlytheirapproximatebor ders[1]:extremeultravioletEUV～50nmto～5nm～25eVto～250eV,softX rayregion～5nmto～0.2nm～250eVto～6keV.The…     

Evidence for a Substrate-Borne Sex Pheromone in the Parasitoid Wasp Trichogramma brassicae

While the use of chemical cues in host location is well known in parasitoid insects, little is known about their role in sexual communication. Sex pheromones were investigated in the egg parasitoid Trichogramma brassicae, and the evidence for a substrate-borne pheromone was demonstrated. Mated and unmated males concentrated their walking in an area where virgin females (<1 or 5 days old) had walked. Males were tested 15 min after females left the area. Male response decreased over time but was always significant during the 8 min of tracking. This suggests that females deposit chemicals on the substrate for mate finding. The pheromone is soluble in hexane, as shown by two kinds of extracts: female body rinsing and rinsing of the flask where females had walked. Hexane extracts resulted in a positive response by males. The response to different doses showed a saturation above a threshold of 4–8 female equivalents. The results do not exclude the possibility that a volatile part of the pheromone attracts males over long distances. Substrate-borne pheromones may increase mating chances for virgin females searching for oviposition sites, and may also increase mating chances on emergence sites by reducing male dispersion.     

Pure N-Alkylaminopropionic Acid and N-Alkylaminodipropionic Acid Sodium Salts: Synthesis, Characterization, and Physicochemical Properties

Fourteen pure β-aminopropionic acid amphoteric surfactants were synthesized from methyl acrylate using primary amines. The synthesis was done in two steps. First, Michael addition of a primary amine to methyl acrylate gave two separable addition products. Second, because the resulting esters gave, by the classical saponification procedure, undesired retro-Michael products, they were treated with sodium trimethylsilanolate to give the corresponding pure anhydrous acid salt under mild non-aqueous reaction conditions. Two types of amphoteric surfactants were obtained: the monocarboxylate and the dicarboxylate series. The pure surfactants were characterized by IR, ¹H NMR, and ¹³C NMR spectroscopy. The surfactant critical micelle concentrations were evaluated. From these the Gibbs free energy of micellizations [∆G(–CH₂–)_mic] were calculated. These are related to the methylene units that contribute an average of −1.0 (±0.3) kJ mol⁻¹ for both the monocarboxylate and the dicarboxylate series.

Measurement of Whole Soybean Fatty Acids by Near Infrared Spectroscopy

Whole soybean fatty acid contents were measured by near infrared spectroscopy. Three calibration algorithms—partial least squares (PLS), artificial neural networks (ANN), and least squares support vector machines (LS-SVM)—were implemented. Three different validation strategies using independent sets and part of calibration samples as validation sets were created. There was a significant improvement of the prediction precision of all fatty acids measured on relative concentration of oil compared with previous literature using PLS (standard error of prediction of 0.85, 0.42, 1.64, 1.67, and 0.90% for palmitic, stearic, oleic, linoleic and linolenic acids respectively). ANN and LS-SVM methods performed significantly better than PLS for palmitic, oleic and linolenic acids. Calibration models developed on relative concentrations (% of oil) were compared to prediction models created on absolute fatty acid concentration (% of weight) and corrected to relative concentration by multiplying by the predicted oil content. While models were easier to develop in absolute concentration (higher coefficients of determination), the multiplication of errors with the total oil content model resulted in no net precision improvement.     

Estimation of membrane hydration status for standby proton exchange membrane fuel cell systems by complex impedance measurement: Constant temperature stack characterization

Fuel cell-based backup units are characterized by long standby periods but they must be ready to start at any instant in the shortest possible time. In the case of low temperature proton exchange membrane fuel cells, the estimation of the hydration status of the fuel cell's membrane during standby is important for determining the cell's ability to perform a fast and safe startup. In this article, non-conventional electrochemical impedance spectroscopy (EIS) is suggested as a method to estimate the membrane's hydration status. The proposed technique differs from standard EIS in that the current through the fuel cell cannot contain a DC component, since hydrogen is absent. A 56-cell fuel cell stack has been symmetrically fed with air, whose temperature and relative humidity were controlled, and its complex impedance was measured at different frequencies and for different values of relative humidity at constant temperature. Power regression models were applied to the data, and the relationships between complex impedance and relative humidity were found. The results showed that the proposed technique is a viable way for estimating the membrane hydration status of a fuel cell stack during standby. Moreover, the most suitable frequency values at which the measurements should be performed are given.     

Hemiretinal contribution to the timing of the full-field PVEP as determined with the motor reaction time

With the use of the simple motor reaction time (RT), we examined the contribution of the hemiretinas to the timing of the pattern reversal visual evoked potential (PVEP). RTs were obtained to the reversal of a progressively dimmer check falling either on the central, nasal, temporal, superior or inferior retina. Results were correlated with the peak time of the P1 wave evoked to the reversal of the entire checkerboard stimulus to the same luminance conditions as that used to generate the RT measurements. Our results clearly indicate that the time taken to trigger a manual response depends not only on the luminance of the stimulus, but also on where it falls on the retina. Comparing the above data with the peak time of the PVEP obtained to the reversal of the entire screen indicates that at brighter luminance the peak time of the P1 wave correlates with that measured from the most central retina, while at dimmer intensities it correlates with the mathematical average of all the retinal locations tested.