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Microbial fuel cells: methodology and technology   总被引:46,自引:0,他引:46  
Microbial fuel cell (MFC) research is a rapidly evolving field that lacks established terminology and methods for the analysis of system performance. This makes it difficult for researchers to compare devices on an equivalent basis. The construction and analysis of MFCs requires knowledge of different scientific and engineering fields, ranging from microbiology and electrochemistry to materials and environmental engineering. Describing MFC systems therefore involves an understanding of these different scientific and engineering principles. In this paper, we provide a review of the different materials and methods used to construct MFCs, techniques used to analyze system performance, and recommendations on what information to include in MFC studies and the most useful ways to present results.  相似文献
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Microbial fuel cells (MFCs) are emerging as a novel technology with a great potential to reduce the costs of wastewater treatment. Their most studied application is organic carbon removal. One of the parameters commonly used to quantify the performance of these cells is the Coulombic efficiency, i.e., the electron recovery as electricity from the removed substrate. However, the "inefficiencies" of the process have never been fully identified. This study presents a method that uses the combination of electrochemical monitoring, chemical analysis, and a titration and off-gas analysis (TOGA) sensor to identify and quantify the sources of electron loss. The method was used successfully to close electron, carbon, and proton balances in acetate and glucose fed microbial fuel cells. The method revealed that in the case that a substrate is loaded as pulses carbon is stored inside the cells during initial high substrate conditions and consumed during starvation, with up to 57% of the current being generated after depletion of the external carbon source. Nile blue staining of biomass samples revealed lipophilic inclusions during high substrate conditions, thus confirming the storage of polymeric material in the bacterial cells. The method also allows for indirect measurement of growth yields, which ranged from 0 to 0.54 g biomass-C formed per g substrate-C used, depending on the type of substrate and the external resistance of the circuit.  相似文献
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This study was performed to investigate changes in expression level of genes involved in hepatic cholesterol metabolism in the transition from pregnancy to lactation and during different stages of lactation in dairy cows. Therefore, relative mRNA abundances of several genes involved in various pathways of cholesterol homeostasis in liver biopsy samples of 20 dairy cows, taken in late pregnancy (3 wk prepartum) and early lactation (1, 5, and 14 wk postpartum), were determined. At 1 wk postpartum, hepatic mRNA abundances of genes involved in cholesterol synthesis (3-hydroxy-3-methylglutaryl-coenzyme A reductase, mevalonate kinase, and farnesyl diphosphate synthase), cholesterol uptake from blood (low-density lipoprotein receptor), bile acid synthesis (cholesterol-7α-hydroxylase), cholesterol efflux [ATP-binding cassette (ABC) transporter A1 and ABCG1], esterification of cholesterol (acyl-coenzyme A:cholesterol acyltransferase), and proteins involved in assembly and secretion of very low-density lipoproteins (microsomal triglyceride transfer protein, ApoB100) were increased compared with 3 wk prepartum. The mRNA abundances of most of these genes decreased after 1 wk of lactation and reached levels in 5 and 14 wk of lactation similar to those at 3 wk prepartum. Only mRNA abundances of cholesterol-7α-hydroxylase, ABC transporters, and ApoB100 remained at 5 and 14 wk postpartum at levels higher than those at 3 wk prepartum. Hepatic cholesterol abundance was highest at 1 wk postpartum and was, thereafter, decreasing to values similar to that at 3 wk prepartum. Overall, this study shows that the onset of lactation is associated with an increased expression of various genes involved in cholesterol metabolism in the liver of dairy cows, suggesting that pronounced changes in hepatic cholesterol metabolism take place in the periparturient phase.  相似文献
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Iodinated X-ray contrast media (ICM) are only to a limited extent removed from conventional wastewater treatment plants, due to their high recalcitrance. This work reports on the cathodic dehalogenation of the ICM iopromide in a bioelectrochemical system (BES), fed with acetate at the anode and iopromide at the cathode. When the granular graphite cathode potential was decreased from -500 to -850 mV vs standard hydrogen electrode (SHE), the iopromide removal and the iodide release rates increased from 0 to 4.62 ± 0.01 mmol m(-3) TCC d(-1) and 0 to 13.4 ± 0.16 mmol m(-3) TCC d(-1) (Total Cathodic Compartment, TCC) respectively. Correspondingly, the power consumption increased from 0.4 ± 1 to 20.5 ± 3.3 W m(-3) TCC. The Coulombic efficiency of the iopromide dehalogenation at the cathode was less than 1%, while the Coulombic efficiency of the acetate oxidation at the anode was lower than 50% at various granular graphite cathode potentials. The results suggest that iopromide could be completely dehalogenated in BESs when the granular graphite cathode potential was controlled at -800 mV vs SHE or lower. This finding was further confirmed using mass spectrometry to identify the dehalogenated intermediates and products of iopromide in BESs. Kinetic analysis indicates that iopromide dehalogenation in batch experiments can be described by a first-order model at various cathode potentials. This work demonstrates that the BESs have a potential for efficient dehalogenation of ICM from wastewater or environmental streams.  相似文献
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