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Water Pools (water + pool)
Selected AbstractsExciplex-type Behavior and Partition of 3-Substituted Indole Derivatives in Reverse Micelles Made with Benzylhexadecyldimethylammonium Chloride, Water and Benzene,PHOTOCHEMISTRY & PHOTOBIOLOGY, Issue 2 2001Claudio D. Borsarelli ABSTRACT The fluorescence properties of 3-methylindole (MI), 3-indoleacetic acid (IAA), 3-indoleethyltrimethylammonium bromide (IETA), l -tryptophan (Trp) and tryptamine hydrochloride (TA) were studied in reverse micelles solutions made with the cationic surfactant benzylhexadecyldimethylammonium chloride (BHDC) in benzene as a function of the molar ratio water/surfactant R (=[H2O]/[BHDC]). The fluorescence quenching of the model compound MI by benzene in cyclohexane solutions and by BHDC in benzene solutions were also studied in detail. The fluorescence of MI in benzene is characteristic of a charge-transfer exciplex. The exciplex is quenched by the presence of BHDC, due to the interactions of the surfactant ion pairs with the polar exciplex. In reverse micelle solutions at low R values, all the indoles show exciplex-type fluorescence. As R increases, the fluorescence behavior strongly depends on the nature of the indole derivative. The anionic IAA remains anchored to the cationic interface and its fluorescence is quenched upon water addition due to the increases of interface's micropolarity. For IETA, TA and Trp an initial fluorescence quenching is observed at increasing R, but a fluorescence recovery is observed at R > 5, indicating a probe partition between the micellar interface and the water pool. For the neutral MI, the fluorescence changes with R indicate the partition of the probe between the micellar interface and the bulk benzene pseudophase. A simple two-site model is proposed for the calculation of the partition constants K as a function of R. In all cases, the calculation showed that even at the highest R value, about 90% of the indole molecules remain associated at the micellar interface. [source] Influence of the equatorial warm water pool on the tropical cyclogenesis: an aqua planet experimentATMOSPHERIC SCIENCE LETTERS, Issue 4 2008Mayumi K. Yoshioka Abstract Aqua planet experiments were performed to investigate any favorable environmental conditions for tropical cyclogenesis with a high-resolution atmospheric general circulation model. Zonally localized enhanced sea surface temperature distributions on the equator modify atmospheric circulation east,west asymmetrically. Tropical cyclogenesis is observed in the off-equatorial western half of the warm water pool where an enhanced distribution of absolute vorticity is produced. The region associated with the equatorward planetary vorticity transport contributes to make the western half of the pool notably favorable for generating tropical cyclones. Copyright © 2008 Royal Meteorological Society [source] Strong seasonal disequilibrium measured between the oxygen isotope signals of leaf and soil CO2 exchangeGLOBAL CHANGE BIOLOGY, Issue 11 2010LISA WINGATE Abstract The oxygen isotope composition (,18O) of atmospheric CO2 is among a very limited number of tools available to constrain estimates of the biospheric gross CO2 fluxes, photosynthesis and respiration at large scales. However, the accuracy of the partitioning strongly depends on the extent of isotopic disequilibrium between the signals carried by these two gross fluxes. Chamber-based field measurements of total CO2 and CO18O fluxes from foliage and soil can help evaluate and refine our models of isotopic fractionation by plants and soils and validate the extent and pattern of isotopic disequilibrium within terrestrial ecosystems. Owing to sampling limitations in the past, such measurements have been very rare and covered only a few days. In this study, we coupled automated branch and soil chambers with tuneable diode laser absorption spectroscopy techniques to continuously capture the ,18O signals of foliage and soil CO2 exchange in a Pinus pinaster Aït forest in France. Over the growing season, we observed a seasonally persistent isotopic disequilibrium between the ,18O signatures of net CO2 fluxes from leaves and soils, except during rain events when the isotopic imbalance became temporarily weaker. Variations in the ,18O of CO2 exchanged between leaves, soil and the atmosphere were well explained by theory describing changes in the oxygen isotope composition of ecosystem water pools in response to changes in leaf transpiration and soil evaporation. [source] Parameters related to lipid metabolism as markers of myelination in mouse brainJOURNAL OF NEUROCHEMISTRY, Issue 1 2001Evan D. Muse Myelination, during both normal development and with respect to disorders of myelination, is commonly studied by morphological and/or biochemical techniques that assay as their end-points the extent of myelination. The rate of myelination is potentially a more useful parameter, but it is difficult and time-consuming to establish, requiring a complete developmental study with labor-intensive methodology. We report herein development of methodology to assay the absolute rate of myelination at any desired time during development. This involves intraperitoneal injection of 3H2O to label body water pools, followed by determination of label in the myelin-specific lipid, cerebroside. The absolute amount of cerebroside synthesized can then be calculated from the specific radioactivity of body water and knowledge of the number of hydrogens from water incorporated into cerebroside. During development, the rate of cerebroside synthesis correlated well with the rate of accumulation of the myelin-specific components, myelin basic protein and cerebroside. For purposes of control, we also tested other putative, albeit less quantitative, indices of the rate of myelination. Levels of mRNA for ceramide galactosyltransferase (rate-limiting enzyme in cerebroside synthesis) and for myelin basic protein did not closely correlate with myelination at all times. Cholesterol synthesis closely matched the rate of cholesterol accumulation but did not track well with myelination. Synthesis of fatty acids did not correlate well with accumulation of either fatty acids (phospholipids) or myelin markers. We conclude that measurement of cerebroside synthesis rates provides a good measure of the rate of myelination. This approach may be useful as an additional parameter for examining the effects of environmental or genetic alterations on the rate of myelination. [source] Fluorescence saturation of dye molecules in water pools of reversed micellesLASER PHYSICS LETTERS, Issue 10 2005A. V. Potapov Abstract Rhodamine 6G has been used as a fluorescence probe in AOT reversed micelles systems with the different amounts of solubilized water (hydratation power ,). The saturation of fluorescence and the lifetime of dye molecules were measured. The absorption cross section values were calculated from the saturation curves. We showed the differences in values of the absorption cross section, lifetime and velocity of fluorescence saturation in micellar phase with different , and in comparison to bulk phase. Additionally, the structure of hydrated reversed micelles has been studied by the method of correlation spectroscopy. The influence of , on size and shape of micelles was detected. (© 2005 by Astro, Ltd. Published exclusively by WILEY-VCH Verlag GmbH & Co. KGaA) [source] Diffusion-weighted MRI measurements on stroke patients reveal water-exchange mechanisms in sub-acute ischaemic lesionsNMR IN BIOMEDICINE, Issue 6 2009J. Lätt Abstract The aim of this study was to investigate the diffusion time dependence of signal- versus - b curves obtained from diffusion-weighted magnetic resonance imaging (DW-MRI) of sub-acute ischaemic lesions in stroke patients. In this case series study, 16 patients with sub-acute ischaemic stroke were examined with DW-MRI using two different diffusion times (60 and 260,ms). Nine of these patients showed sufficiently large lesions without artefacts to merit further analysis. The signal- versus - b curves from the lesions were plotted and analysed using a two-compartment model including compartmental exchange. To validate the model and to aid the interpretation of the estimated model parameters, Monte Carlo simulations were performed. In eight cases, the plotted signal- versus - b curves, obtained from the lesions, showed a signal,curve split-up when data for the two diffusion times were compared, revealing effects of compartmental water exchange. For one of the patients, parametric maps were generated based on the extracted model parameters. These novel observations suggest that water exchange between different water pools is measurable and thus potentially useful for clinical assessment. The information can improve the understanding of the relationship between the DW-MRI signal intensity and the microstructural properties of the lesions. Copyright © 2009 John Wiley & Sons, Ltd. [source] | ||||||||||