Photooxidation of Hg(0) in artificial and natural waters

The oxidation of volatile aqueous Hg(0) in aquatic systems may be important in reducing fluxes of Hg out of aquatic systems. Here we report the results of laboratory and field experiments designed to identify the parameters that control the photooxidation of Hg(0)(aq) and to assess the possible importance of this process in aquatic systems. The concentrations of elemental and total Hg were measured as a function of time in both artificial and natural waters irradiated with a UV-B lamp. No change in Hg speciation was observed in dark controls, while a significant decrease in Hg(0) was observed in UV-B irradiated artificial solutions containing both chloride ions and benzoquinone. Significant photooxidation rates were also measured in natural samples spiked with Hg(0)(aq); the photooxidation of Hg(0) then follows pseudo first-order kinetics (k = 0.6 h(-1)). These results indicate that the previously observed Hg(II) photoreduction rates in natural waters could represent a net balance between Hg(0) photoreduction and Hg(0) photooxidation. As calculated from Hg(0) photooxidation rates, the dominant Hg(0) sink is likely to be photooxidation rather than volatilization from the water column during summer days.     

Oxidative catabolism of α-tocopherol in rat liver microsomes

The goal of this study was to clarify the mechanism responsible for the catabolism of α-tocopherol. The vitamin, bound to albumin, was incubated with rat liver microsomes and appeared to be broken down. Optimal production of the metabolite was obtained when 1 mg of microsomal protein was incubated with 36 μM of α-tocopherol in the presence of 1.5 mM of NADPH. Chromatographic and mass spectrometric analyses of the metabolite led to the conclusion that it consists of an ω-acid with an opened chroman ring, although we could not perform nuclear magnetic resonance analysis to confirm this. Our data show that α-tocopherol is ω-oxidized to a carboxylic acid and that this process can occur in rat liver microsomes in the presence of NADPH and O₂. The oxidation to the quinone structure appears to be a subsequent event that may be artifactual and/or catalyzed by a microsomal enzyme(s).     

Experimental Analysis of Punch-Through Conditions in Power P-I- N Diodes

Commercial power diodes are optimized to feature punch-through behavior. However, a tradeoff between the width and the doping level of the diode epitaxial layer leads to various levels of optimization. For a given breakdown voltage, a shorter epitaxial layer width leads to better transient performances. Device datasheets do not cover this issue and a simple experimental setup is presented to assess the optimization conditions inside the diode epitaxial layer. Three commercial devices are tested and experimental results are confronted to device simulations. A good agreement is found     

Photoluminescence studies of CdTe films and junctions

Device quality CdTe films and junctions have been studied using low-temperature photoluminescence (PL) measurements. The behavior of the PL was studied as a function of the measurement temperature and excitation intensity. The CdTe films and junctions were prepared under various deposition conditions to determine the effect of film deposition and solar cell fabrication parameters, such as the effect of oxygen, and chloride treatment. A PL band located at 1.232 eV has been attributed to the presence of oxygen. This band is present only in as-deposited samples excited at the CdTe surface. Samples annealed in the presence of CdCl₂ exhibit a single PL band located at 1.42 eV. A model explaining the behavior of these bands is presented.     

Examining the consistency of products derived from various ocean color sensors in open ocean (Case 1) waters in the perspective of a multi-sensor approach

During its lifetime, a space-borne ocean color sensor provides world-wide information about important biogeochemical properties of the upper ocean every 2 to 4 days in cloudless regions. Merging simultaneous or complementary data from such sensors to obtain better spatial and temporal coverage is a recurring objective, but it can only be reached if the consistency of the sensor-specific products, as delivered by the various Space Agencies, has first been carefully examined. The goal of the present study is to provide a procedure for establishing a coherency of open ocean (Case-1 waters) data products, for which the various data processing methods are sufficiently similar. The development of the procedure includes a detailed comparison of the marine algorithms used (after atmospheric corrections) by space agencies for the production of standard products, such as the chlorophyll concentration, [Chl], and the diffuse attenuation coefficient, K_d. The MODIS-Aqua, SeaWiFS and MERIS [Chl] products agree over a wide range, between ∼ 0.1 and 3 mg m^− 3, whereas increasing divergences occur for oligotrophic waters ([Chl] (from 0.02 to 0.09 mg m^− 3). For the K_d(490) coefficient, different algorithms are in use, with differing results. Based on a semi-analytical reflectance model and hyperspectral approach, the present work proposes a harmonization of the algorithms allowing the products of the various sensors to be comparable, and ultimately, meaningfully merged (the merging procedures themselves are not examined). Additional potential products, obtained by using [Chl] as an intermediate tool, are also examined and proposed. These products include the thickness of the layer heated by the sun, the depth of the euphotic zone, and the Secchi disk depth. The physical limitations in the predictive skill of such downward extrapolations, made from information concerning only the upper layer, are stressed.     

Simulated Microgravity Subtlety Changes Monoamine Function across the Rat Brain

Microgravity, one of the conditions faced by astronauts during spaceflights, triggers brain adaptive responses that could have noxious consequences on behaviors. Although monoaminergic systems, which include noradrenaline (NA), dopamine (DA), and serotonin (5-HT), are widespread neuromodulatory systems involved in adaptive behaviors, the influence of microgravity on these systems is poorly documented. Using a model of simulated microgravity (SMG) during a short period in Long Evans male rats, we studied the distribution of monoamines in thirty brain regions belonging to vegetative, mood, motor, and cognitive networks. SMG modified NA and/or DA tissue contents along some brain regions belonging to the vestibular/motor systems (inferior olive, red nucleus, cerebellum, somatosensorily cortex, substantia nigra, and shell of the nucleus accumbens). DA and 5-HT contents were reduced in the prelimbic cortex, the only brain area exhibiting changes for 5-HT content. However, the number of correlations of one index of the 5-HT metabolism (ratio of metabolite and 5-HT) alone or in interaction with the DA metabolism was dramatically increased between brain regions. It is suggested that SMG, by mobilizing vestibular/motor systems, promotes in these systems early, restricted changes of NA and DA functions that are associated with a high reorganization of monoaminergic systems, notably 5-HT.     

Analysis of residual stress and work-hardened profiles on Inconel 718 when face turning with large-nose radius tools

Surface integrity (SI) and, particularly, the residual stress profile, has a great influence on the fatigue life of machined aeronautical critical parts. Among the different cutting parameters that affect the final SI, tool geometry is one of the most important factors. In particular, tool nose radius determines the surface roughness, as well as the thermoplastic deformation of the workpiece. Indeed, the use of large tool nose radius in the industry enables (1) increasing the feed rate while keeping the roughness values below specifications and (2) reducing the influence of the tool wear in the surface roughness. Therefore, in this study, the influence of tool nose radius in the induced residual stress profile and work-hardened layer when face turning Inconel 718 is analysed for a cutting speed range between (30–70 m/min) and a feed rate range of (0.15–0.25 mm/rev). For this purpose, residual stress profiles and work-hardened layer were measured by x-ray diffraction method after machining with a 4 mm nose radius. Then, results have been compared against different tool nose radius studies carried out by other authors for the specified working conditions. Results revealed that residual stress profiles varied when machining with different nose radius for the studied range. In particular, the increase of the nose radius brought to a higher difference between surface tensile stress and subsurface compressive peak stress, which is attributed to an increase of the thermal effect. Moreover, thicker work-hardened layer (around 100 μm) was observed when machining with large-nose radius for the studied working conditions.     

Quantitative luminescence mapping of Cu(In,Ga)Se2 thin‐film solar cells

We investigate photoluminescence and electroluminescence (PL and EL) emission images from Cu(In,Ga)Se₂‐based solar cells by means of a Hyperspectral Imager. Using the generalized Planck's law, maps of the effective quasi‐Fermi level splitting Δμ_eff in absolute values are obtained. A good agreement is found between the spatially averaged splitting in PL and the global open‐circuit voltage. However, from a local carrier transport discussion, we conclude that the equality does not hold locally. The spatial variations are rather attributed to local depth variations of the quasi‐Fermi level splitting due to material properties spatial fluctuations. By comparing PL and EL emissions, we discuss qualitatively the local effective lifetimes and collection efficiencies. Copyright © 2014 John Wiley & Sons, Ltd.     

A physically based diode model for circuit simulation

A physically based power PiN diode model is presented. Eigen value internal approximation method is used to solve the ambipolar diffusion equation. This model is implemented in SIMPLORER circuit simulator using VHDL‐AMS language. The proposed model can be used in both circuit simulators and the optimization of a given power PiN diode. Good agreement is obtained by comparing the results of the suggested model with experimental data. Copyright © 2013 John Wiley & Sons, Ltd.     

Conceptualizing and Measuring Personality Vulnerability to Depression: Comment on Coyne and Whiffen (1995).

J. C. Coyne and V. E. Whiffen (1995) reviewed research on personality vulnerability to depression, focusing on S. J. Blatt's (1974, 1990) concepts of dependency and self-criticism and A. T. Beck's (1983) concepts of sociotropy and autonomy. The authors discuss 6 issues raised in that review: (a) the typological or dimensional nature of vulnerability, (b) the theoretical implications of "mixed" vulnerability, (c) the relations of vulnerability to Neuroticism. (d) the potential confounding of vulnerability with concurrent depression, (e) the potential confounding of vulnerability with social context, and (f) the differentiation of dependency from relatedness. The authors conclude that Blatt's and Beck's concepts are continuous, nearly orthogonal dimensions that can be identified and measured independently from Neuroticism, depression, and social context. (PsycINFO Database Record (c) 2010 APA, all rights reserved)