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Concentration Difference (concentration + difference)
Selected AbstractsFloating zone growth of CuO under elevated oxygen pressure and its relevance for the crystal growth of cupratesCRYSTAL RESEARCH AND TECHNOLOGY, Issue 1-2 2005G. Behr Abstract CuO single crystals have been grown from the melt by a floating zone method with optical heating at elevated oxygen pressures 3.5 to 5.5 MPa and growth rates as high as 10 mm/h. Melting experiments and recalculated Cu-O phase diagram data show that CuO melts incongruently. The melting temperature increases and the concentration difference between the melt and the CuO phase decreases for rising oxygen partial pressure. Accordingly, increasing the oxygen partial pressure improves the growth process by reducing both the significant oxygen loss during melting as well as the composition difference at the growth interface. The results on CuO provide important information for the crystal growth of more complex cuprates. (© 2005 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] An idealised model of turbulent dispersion: two rectangular pulse initial conditionENVIRONMETRICS, Issue 5 2009Nils Mole Abstract An idealised model of turbulent dispersion was introduced by Zimmerman and Chatwin in 1995 and it was further developed by Mole and Yeun in 2007, for the case of an initial concentration field consisting of one rectangular pulse. Here we extend this model to the case of two initial pulses in order to investigate the effect of varying concentration. We present analytical and numerical results for the dependence of the variance, skewness, kurtosis and probability density function of concentration on time and on the pulse locations and concentrations. For moderately large concentration difference between the pulses, one pulse dominates and the behaviour is close to that for the one pulse case. This suggests that a model incorporating distributions of pulse separations and concentrations can be constructed by averaging over an ensemble of one pulse cases. The distributions used would be those appropriate to the ,strands' of highest concentration. Copyright © 2008 John Wiley & Sons, Ltd. [source] Hole,polar phonon interaction scattering mobility in chain structured TlSe0.75S0.25 crystalsPHYSICA STATUS SOLIDI (A) APPLICATIONS AND MATERIALS SCIENCE, Issue 7 2009A. F. Qasrawi Abstract In this study, the electrical resistivity, charge carriers density and Hall mobility of chain structured TlSe0.75S0.25 crystal have been measured and analyzed to establish the dominant scattering mechanism in crystal. The data analyses have shown that this crystal exhibits an extrinsic p-type conduction. The temperature-dependent dark electrical resistivity analysis reflected the existence of three energy levels located at 280 meV, 68 meV and 48 meV. The temperature dependence of carrier density was analyzed by using the single donor,single acceptor model. The carrier concentration data were best reproduced assuming the existence of an acceptor impurity level being located at 68 meV consistent with that observed from resistivity measurement. The model allowed the determination of the hole effective mass and the acceptor,donor concentration difference as 0.44m0 and 2.2 × 1012 cm,3, respectively. The Hall mobility of the TlSe0.75S0.25 crystal is found to be limited by the scattering of charged carriers over the (chain) boundaries and the scattering of hole,polar phonon interactions above and below 300 K, respectively. The value of the energy barrier height at the chain boundaries was found to be 261 meV. The polar phonon scattering mobility revealed the high-frequency and static dielectric constants of 13.6 and 15.0, respectively. (© 2009 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] Decreased hepatic RBP4 secretion is correlated with reduced hepatic glucose production but is not associated with insulin resistance in patients with liver cirrhosisCLINICAL ENDOCRINOLOGY, Issue 1 2009Matthias J. Bahr Summary Objective, Patients with liver cirrhosis have a high incidence of insulin resistance and diabetes. This study was designed to determine circulating levels and hepatic production of retinol-binding protein 4 (RBP4) in relation to parameters of hepatic and systemic metabolism in patients with liver cirrhosis. Design and method, Circulating RBP4 levels were measured in 19 patients with liver cirrhosis at different clinical stages of the disease and in 20 age-, sex- and body mass index (BMI)-matched controls. Hepatic production rates of RBP4 and glucose were assessed by measuring the arterial hepatic venous concentration difference together with hepatic blood flow. Insulin resistance was determined by the Quantitative Insulin Sensitivity Check Index (QUICKI) and the homeostasis model assessment of insulin resistance (HOMA-IR), energy expenditure by indirect calorimetry and body composition by bioelectrical impedance analysis (BIA). Results, Compared with controls, RBP4 levels in cirrhosis were decreased (8·1 ± 1·8 vs. 22·6 ± 2·4 mg/l, P < 0·001) due to decreased hepatic production (P < 0·05). RBP4 correlated with hepatic protein synthesis capacity (P < 0·01), but not with insulin resistance, energy expenditure, BMI or body fat mass. Plasma RBP4 correlated with hepatic glucose production (P < 0·05). Conclusions, These data demonstrate that RBP4 in cirrhosis (i) is decreased due to reduced hepatic production, (ii) is not associated with insulin resistance, and (iii) might have a beneficial role by decreasing hepatic glucose production and could thus also be regarded as a hepatokine. [source] Cerebral oxygenation decreases during exercise in humans with beta-adrenergic blockadeACTA PHYSIOLOGICA, Issue 3 2009T. Seifert Abstract Aim:, Beta-blockers reduce exercise capacity by attenuated increase in cardiac output, but it remains unknown whether performance also relates to attenuated cerebral oxygenation. Methods:, Acting as their own controls, eight healthy subjects performed a continuous incremental cycle test to exhaustion with or without administration of the non-selective beta-blocker propranolol. Changes in cerebral blood flow velocity were measured with transcranial Doppler ultrasound and those in cerebral oxygenation were evaluated using near-infrared spectroscopy and the calculated cerebral mitochondrial oxygen tension derived from arterial to internal jugular venous concentration differences. Results:, Arterial lactate and cardiac output increased to 15.3 ± 4.2 mm and 20.8 ± 1.5 L min,1 respectively (mean ± SD). Frontal lobe oxygenation remained unaffected but the calculated cerebral mitochondrial oxygen tension decreased by 29 ± 7 mmHg (P < 0.05). Propranolol reduced resting heart rate (58 ± 6 vs. 69 ± 8 beats min,1) and at exercise exhaustion, cardiac output (16.6 ± 3.6 L min,1) and arterial lactate (9.4 ± 3.7 mm) were attenuated with a reduction in exercise capacity from 239 ± 42 to 209 ± 31 W (all P < 0.05). Propranolol also attenuated the increase in cerebral blood flow velocity and frontal lobe oxygenation (P < 0.05) whereas the cerebral mitochondrial oxygen tension decreased to a similar degree as during control exercise (delta 28 ± 10 mmHg; P < 0.05). Conclusion:, Propranolol attenuated the increase in cardiac output of consequence for cerebral perfusion and oxygenation. We suggest that a decrease in cerebral oxygenation limits exercise capacity. [source] Temporal and spatial variability of cation and silica export in an alpine watershed, Emerald Lake, CaliforniaHYDROLOGICAL PROCESSES, Issue 10 2004T. Meixner Abstract A reaction set of possible mineral weathering reactions is proposed to explain observed cation and silica export for the Emerald Lake watershed, a small Sierra Nevada, California catchment. The reaction set was calculated through a stoichiometric mole-balance method, using a multiyear record of stream flow and snowpack chemical analyses and site-specific mineral compositions. Reaction-set calculations were intended to explore how the processes controlling stream cation and silica export depend on differing bedrock mineralogy across the catchment as snowmelt and runoff patterns change over the year. Different regions within the watershed can be differentiated by lake inflow subdrainages, each exhibiting different stream-flow chemistry and calculated weathering stoichiometry, indicating that different silica and cation generation processes are dominant in wet steep portions of the catchment. Short-term differences in stream concentrations were assumed to reflect ion exchange equilibria and rapid biological processes, whereas long-term persistent stream concentration differences in different areas of the catchment were assumed to reflect spatial variability in mineral weathering stoichiometry. Mineralogical analyses of rock samples from the watershed provided site-specific chemical compositions of major mineral species for reaction calculations. Reaction sets were evaluated by linear regression of calculated versus observed differences between snowmelt and stream-flow chemistry and by a combined measure. Initially, single weathering reactions were balanced and evaluated to determine the reactions that best explained observed stream chemical export. Next, reactions were combined, using mineral compositions from different rock types to estimate the dependence of ion fluxes on lithology. The seasonal variability of major solute calculated fluxes is low, approximately one order of magnitude, relative to the observed three orders of magnitude variability in basin discharge. Reaction sets using basin-averaged lithology and Aplite lithologies gave superior explanations of stream chemical composition. Copyright © 2004 John Wiley & Sons, Ltd. [source] Protein EqualizerÔ Technology, : The quest for a "democratic proteome"PROTEINS: STRUCTURE, FUNCTION AND BIOINFORMATICS, Issue 14 2006Pier Giorgio Righetti Professor Abstract No proteome can be considered "democratic", but rather "oligarchic", since a few proteins dominate the landscape and often obliterate the signal of the rare ones. This is the reason why most scientists lament that, in proteome analysis, the same set of abundant proteins is seen again and again. A host of pre-fractionation techniques have been described, but all of them, one way or another, are besieged by problems, in that they are based on a "depletion principle", i.e. getting rid of the unwanted species. Yet "democracy" calls not for killing the enemy, but for giving "equal rights" to all people. One way to achieve that would be the use of "Protein Equalizer Technology" for reducing protein concentration differences. This comprises a diverse library of combinatorial ligands coupled to spherical porous beads. When these beads come into contact with complex proteomes (e.g. human urine and serum, egg white, and any cell lysate, for that matter) of widely differing protein composition and relative abundances, they are able to "equalize" the protein population, by sharply reducing the concentration of the most abundant components, while simultaneously enhancing the concentration of the most dilute species. It is felt that this novel method could offer a strong step forward in bringing the "unseen proteome" (due to either low abundance and/or presence of interference) within the detection capabilities of current proteomics detection methods. Examples are given of equalization of human urine and serum samples, resulting in the discovery of a host of proteins never reported before. Additionally, these beads can be used to remove host cell proteins from purified recombinant proteins or protein purified from natural sources that are intended for human consumption. These proteins typically reach purities of the order of 98%: higher purities often become prohibitively expensive. Yet, if incubated with "equalizer beads", these last impurities can be effectively removed at a small cost and with minute losses of the main, valuable product. [source] Early Renal Ischemia-Reperfusion Injury in Humans Is Dominated by IL-6 Release from the AllograftAMERICAN JOURNAL OF TRANSPLANTATION, Issue 7 2009D. K. De Vries The pathophysiology of ischemia/reperfusion (I/R) injury is complex, and current knowledge of I/R injury in humans is incomplete. In the present study, human living-donor kidney transplantation was used as a highly reproducible model to systematically study various processes potentially involved in early I/R injury. Unique, direct measurements of arteriovenous concentration differences over the kidney revealed massive release of interleukin (IL)-6 in the first 30 minutes of graft reperfusion and a modest release of IL-8. Among the assessed markers of oxidative and nitrosative stress, only 15(S)-8- iso -PGF2, was released. When assessing cell activation, release of prothrombin factor 1 + 2 indicated thrombocyte activation, whereas there was no release of markers for endothelial activation or neutrophil activation. Common complement activation complex sC5b-9 was not released into the bloodstream, but was released into urine rapidly after reperfusion. To investigate whether IL-6 plays a modulating role in I/R injury, a mouse experiment of renal I/R injury was performed. Neutralizing anti-IL-6 antibody treatment considerably worsened kidney function. In conclusion, this study shows that renal I/R in humans is dominated by local IL-6 release. Neutralization of IL-6 in mice resulted in a significant aggravation of renal I/R injury. [source] | |||||||||||||