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51.
Dependence of gluconeogenesis on beta-oxidation and ketogenesis from long-chain fatty acids was examined in isolated sheep hepatocytes. Hepatocytes were incubated with a combination of gluconeogenic precursors (2 mM pyruvate, 20 mM lactate, and 5 mM propionate) plus other fatty acids, in the presence and absence of tetradecylglycidic acid, an inhibitor of the carnitine palmitoyltransferase reaction. Palmitate oxidation to total acid-soluble metabolites or beta-hydroxybutyrate was markedly inhibited by the addition of tetradecylglycidic acid. In general, oxidation of palmitate to carbon dioxide was not altered by tetradecylglycidic acid. Glucose production was inhibited 28 to 50% in the presence of tetradecylglycidic acid. Addition of acetate and butyrate inhibited gluconeogenesis, but octanoate addition had a slight stimulatory effect. In the presence of tetradecylglycidic acid, butyrate, but not acetate, addition further reduced gluconeogenesis. In contrast, addition of octanoate in the presence of tetradecylglycidic acid restored gluconeogenic rates to control values. The results are consistent with observations in several nonruminant species and suggest that, as in those species, ruminant gluconeogenesis requires at least a basal rate of beta-oxidation and ketogenesis from long-chain fatty acids to support maximum gluconeogenic rates. 相似文献
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A note on elevated total gaseous mercury concentrations downwind from an agriculture field during tilling 总被引:2,自引:0,他引:2
Elevated mercury concentrations were measured at the University of Connecticut's mercury forest flux tower during spring agricultural field operations on an adjacent corn field. Concentrations at the tower were elevated, a peak of 7.03 ng m(-3) over the background concentration of 1.74+/-0.26 ng m(-3), during times when the prevailing wind was from the direction of the corn field and during periods when the soil was disturbed by tilling. Strong deposition to the forest was recorded at the point of measurement when atmospheric mercury concentrations were elevated. The strongest deposition rate was a 1 hour maximum of -4011 ng m(-2) h(-1) following the initial peak in atmospheric concentrations, Analyses of the meteorological conditions and mercury content in agricultural soil, manure and the diesel consumed in the tilling operation indicate that the source of the mercury was from the agricultural tilling operations and it was advected over the tower enriching the atmospheric concentrations above the forest canopy leading to deposition. These results indicate that agriculture operations resulting in a disturbed soil surface may be a source of atmospheric mercury originating from the pool of mercury bound in the soil. This represents a previously undocumented source of mercury emissions resulting from anthropogenic activities. 相似文献
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Analyzed criteria of performance and adaptation of Peace Corps volunteers in Tonga (N = 52) who had received high overall evaluation, moderate to marginal overall evaluation, or who had terminated early. Ss were rated independently by 3 present or past staff members on a 24-item field-rating form derived from interviews. The items were found to meet criteria of internal consistency, interjudge agreement, and discrimination of the 3 subgroups. Both discriminant and factor analyses revealed that basic character traits were the single most important class of variables, followed by 3 factors labeled General Technical Competence, Cultural Interaction, and Interpersonal Relations. The necessity for pooled judgments by competent people and for basic research to justify professional psychological services in the field is discussed, and implications for the systematic evaluation of selection and training in governmental agencies are examined. (21 ref.) (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
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Henry Hieslmair Jesse Appel Jai Kasthuri Jason Guo Bayard Johnson Jeff Binns 《Progress in Photovoltaics: Research and Applications》2016,24(11):1448-1457
The injection‐level‐dependent (ILD) lifetime of the silicon wafer impacts many characteristics of the final photovoltaic cell. While efficiency is commonly understood to be impacted by the silicon bulk lifetime (at the maximum power point injection level), this work demonstrates the wide ranging impacts of ILD lifetime on the Voc, the fill factor (FF), the diode ideality factor m, and the dim light response. Instead of a two‐diode model, we utilize a boundary + ILD bulk lifetime model to analyze a commercial passivated emitter rear contact (PERC) cell featuring an AlOx dielectric rear passivation. The ILD lifetime is directly measured and used to calculate the bulk recombination current across injection levels. With this boundary + ILD lifetime model, we demonstrate the role of the ILD lifetime on many cell parameters in this PERC cell. For most high efficiency commercial p‐type monocrystalline solar cells, the typically lower bulk lifetime at the maximum power point versus the lifetime at the open circuit point reduces the measured FF and pseudo‐FF. This work illustrates that for a commercial PERC cell with AlOx rear passivation, the ILD lifetime is the primary mechanism behind reduced FF, ideality factors greater than 1, and the source of the J02 term in the two‐diode model. The crucial implications of this work are not only to better understand commercial PERC cell loss mechanisms but also to encourage a focus on different metrics in cell diagnostics. One such metric is the Voc at 0.1 or 0.05 suns. Copyright © 2016 John Wiley & Sons, Ltd. 相似文献
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Surratt JD Kroll JH Kleindienst TE Edney EO Claeys M Sorooshian A Ng NL Offenberg JH Lewandowski M Jaoui M Flagan RC Seinfeld JH 《Environmental science & technology》2007,41(2):517-527
Recent work has shown that particle-phase reactions contribute to the formation of secondary organic aerosol (SOA), with enhancements of SOA yields in the presence of acidic seed aerosol. In this study, the chemical composition of SOA from the photooxidations of alpha-pinene and isoprene, in the presence or absence of sulfate seed aerosol, is investigated through a series of controlled chamber experiments in two separate laboratories. By using electrospray ionization-mass spectrometry, sulfate esters in SOA produced in laboratory photooxidation experiments are identified for the first time. Sulfate esters are found to account for a larger fraction of the SOA mass when the acidity of seed aerosol is increased, a result consistent with aerosol acidity increasing SOA formation. Many of the isoprene and alpha-pinene sulfate esters identified in these chamber experiments are also found in ambient aerosol collected at several locations in the southeastern U.S. It is likely that this pathway is important for other biogenic terpenes, and may be important in the formation of humic-like substances (HULIS) in ambient aerosol. 相似文献
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Many school systems, in both the developed and developing world, are implementing educational technology to assist in student learning. However, there is no clear consensus on how to evaluate these new technologies. This paper proposes a comprehensive methodology for estimating the value of a new educational technology in three steps: benefit analysis, through the administration of a well-designed experiment; cost analysis, which incorporates costs to weigh against the benefits; and feasibility analysis, which introduces real-world concerns that may affect the ability to actually implement the technology. To illustrate the methodology, a case study from Chile is used where portable educational video games were introduced into first and second grade classrooms with the aim of improving learning in mathematics and language. This paper demonstrates the importance of all three steps in the evaluation process and provides a framework for future analyses. 相似文献
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Martyn A. McLachlan David W. McComb Mary P. Ryan Anna N. Morozovska Eugene A. Eliseev E. Andrew Payzant Stephen Jesse Katyayani Seal Arthur P. Baddorf Sergei V. Kalinin 《Advanced functional materials》2011,21(5):802-802
We describe the characterization, ferroelectric phase stability and polarization switching in strain‐free assemblies of PbZr0.3Ti0.7O3 (PZT) nanostructures. The 3‐dimensionally ordered macroporous structures present uniquely large areas and volumes of PZT where the microstructure is spatially modulated and the composition is homogeneous. Variable temperature powder X‐ray diffraction (XRD) studies show that the global structure is crystalline and tetragonal at room temperature and undergoes a reversible tetragonal to cubic phase transition on heating/cooling. The measured phase‐transition temperature is 50–60 °C lower than bulk PZT of the same composition. The local ferroelectric properties were assessed using piezoresponse force spectroscopy that reveal an enhanced piezoresponse from the nanostructured films and demonstrate that the switching polarization can be spatially mapped across these structures. An enhanced piezoresponse is observed in the nanostructured films which we attribute to the formation of strain free films, thus for the first time we are able to assess the effects of crystallite‐size independently of internal stress. Corresponding polarization distributions have been calculated for the bulk and nanostructured materials using a direct variational method and Landau‐Ginzburg‐Devonshire (LGD) theory. By correlating local and global characterization techniques we have for the first time unambiguously demonstrated the formation of tetragonal and ferroelectric PZT in large volume nanostructured architectures. With the wide range of materials available that can be formed into such controlled architectures we conclude that this study opens a pathway for the effective studies of nanoscale ferroelectrics in uniquely large volumes. 相似文献