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排序方式: 共有103条查询结果,搜索用时 15 毫秒
51.
Using RDF to describe networks 总被引:1,自引:0,他引:1
Jeroen J. Freek Franco Hubertus M.A. Cees T.A.M. 《Future Generation Computer Systems》2006,22(8):862-867
52.
Tom H.J.A. Sleutels Hubertus V.M. Hamelers René A. Rozendal Cees J.N. Buisman 《International Journal of Hydrogen Energy》2009,34(9):3612-3620
Previous studies have shown that Microbial Electrolysis Cells (MECs) perform better when an anion exchange membrane (AEM) than when a cation exchange membrane (CEM) separates the electrode chambers. Here, we have further studied this phenomenon by comparing two analysis methods for bio-electrochemical systems, based on potential losses and partial system resistances. Our study reconfirmed the large difference in performance between the AEM configuration (2.1 m3 H2 m?3 d?1) and CEM configuration (0.4 m3 H2 m?3 d?1) at 1 V. This better performance was caused mainly by the much lower internal resistance of the AEM configuration (192 mΩ m2) compared to the CEM configuration (435 mΩ m2). This lower internal resistance could be attributed to the lower transport resistance of ions through the AEM compared to the CEM caused by the properties of both membranes. By analyzing the changes in resistances the limitations in an MEC can be identified which can lead to improved cell design and higher hydrogen production rates. 相似文献
53.
Tom H.J.A. Sleutels Rob Lodder Hubertus V.M. Hamelers Cees J.N. Buisman 《International Journal of Hydrogen Energy》2009
To create an efficient MEC high current densities and high coulombic efficiencies are required. The aim of this study was to increase current densities and coulombic efficiencies by influencing mass and charge transport in porous electrodes by: (i) introduction of a forced flow through the anode to see the effect of enhanced mass transport of substrate, buffer and protons inside the porous anode and (ii) the use of different concentrations of buffer solution to study the effect of enhanced proton transport near the biofilm. A combination of both strategies led to a high current density of 16.4 A m−2 and a hydrogen production rate of 5.6 m3 m−3 d−1 at an applied voltage of 1 V. This current density is 228% higher than the current density without forced flow and high buffer concentration. Furthermore the combination of the anode and transport resistance was reduced from 36 mΩm2 to 20 mΩm2. Because of this reduced resistance the coulombic efficiency reached values of over 60% in this continuous system. 相似文献
54.
K George GG Zafiropoulos Y Murat S Hubertus RJ Nisengard 《Canadian Metallurgical Quarterly》1994,65(8):766-770
Peri-implantitis, an inflammatory response around implants, has a poorly defined etiology and pathogenesis. To better understand the role of specific microorganisms in this disease process, clinical and microbiological parameters were examined in 24 patients with 98 osseointegrated implants. Sites were evaluated for probing depth (PD), plaque/calculus index (PI), gingival bleeding index (GBI), mobility, and crevicular fluid flow rate (CFFR). Actinobacillus actinomycetemcomitans, Porphyromonas gingivalis, and Prevotella intermedia in subgingival plaque were identified by latex agglutination assays. Clinically, a statistically significant correlation (P < 0.001) was observed between probing depth and the length of time an implant was present. Mobility was also significantly greater (P < 0.001) in the maxillary than in the mandibular implants. Subgingival sites harboring one of the three microorganisms had significantly greater PD, GBI, and CFFR than non-colonized sites. Implants in partially edentulous patients more frequently were colonized with P. gingivalis/P. intermedia than edentulous patients. The incidence of these microorganisms also correlated with fixture longevity. Implants present for 3 to 4 years had a significantly greater frequency of test microorganisms than implants present for 1 to 2 years. These findings suggest that microbial pathogens associated with periodontitis occur more commonly around implants exhibiting gingival inflammation (GBI) and may contribute to peri-implantitis. 相似文献
55.
56.
Kool J de Kloe G Denker AD van Altena K Smoluch M van Iperen D Nahar TT Limburg RJ Niessen WM Lingeman H Leurs R de Esch IJ Smit AB Irth H 《Analytical chemistry》2011,83(1):125-132
The development of a contactless postcolumn spotter technology capable of rapidly and accurately depositing LC eluent onto another platform (e.g., 1536-well microtiter plates) is described. Many detection methodologies are suitable for online analysis, such as mass spectrometry, UV-vis, and fluorescence. In some cases, when online analysis is less suitable, off-line postcolumn analysis is the methodology of choice and usually relies on LC-based fractionation prior to detection (e.g., MALDI-MS, Raman spectrsocopy, biochemical assays). As fractionation generally involves loss in resolution, the technology described here allows high-resolution contactless fractionation by tailoring the fractionation frequency to the chromatographic peaks and mixing in of postcolumn reagents. Droplet ejection at frequencies of at least 6 Hz could be performed in the nanoliter to low microliter range with repeatabilities of ~6%. Furthermore, multiple droplets can be ejected at the same position thereby allowing adjustment of fractionation volume and speed. The technology was evaluated, optimized, and validated prior to two proof-of-principle demonstrations comprising off-line chemical detection of injected fluorescein and off-line postcolumn biochemical detection of acetylcholine-binding protein ligands, both based on 1536-well plate reader analysis. 相似文献
57.
58.
Due to the excellent proton conductivity of Nafion membranes in polymer electrolyte membrane fuel cells (PEMFCs), Nafion has been applied also in microbial fuel cells (MFCs). In literature, however, application of Nafion in MFCs has been associated with operational problems. Nafion transports cation species other than protons as well, and in MFCs concentrations of other cation species (Na+, K+, NH4+, Ca2+, and Mg2+) are typically 10(5) times higher than the proton concentration. The objective of this study, therefore, was to quantify membrane cation transport in an operating MFC and to evaluate the consequences of this transport for MFC application on wastewaters. We observed that during operation of an MFC mainly cation species other than protons were responsible for the transport of positive charge through the membrane, which resulted in accumulation of these cations and in increased conductivity in the cathode chamber. Furthermore, protons are consumed in the cathode reaction and, consequently, transport of cation species other than protons resulted in an increased pH in the cathode chamber and a decreased MFC performance. Membrane cation transport, therefore, needs to be considered in the development of future MFC systems. 相似文献
59.
Energy recovery from controlled mixing salt and fresh water with a reverse electrodialysis system 总被引:1,自引:0,他引:1
The global potential to obtain clean energy from mixing river water with seawater is considerable. Reverse electrodialysis is a membrane-based technique for direct production of sustainable electricity from controlled mixing of river water and seawater. It has been investigated generally with a focus on obtained power, without taking care of the energy recovery. Optimizing the technology to power output only, would generally give a low energetic efficiency. In the present work, therefore, we emphasized the aspect of energy recovery. No fundamental obstacle exists to achieve an energy recovery of > 80%. This number was obtained with taking into account no more than the energetic losses for ionic transport. Regarding the feasibility, it was assumed to be a necessary but not sufficient condition that these internal losses are limited. The internal losses could be minimized by reducing the intermembrane distance, especially from the compartments filled with the low-conducting river water. It was found that a reduction from 0.5 to 0.2 mm indeed could be beneficial, although not to the expected extent. From an evaluation of the internal losses, it was supposed that besides the compartment thickness, also the geometry of the spacer affects the internal resistance. 相似文献
60.
Friedrich Kiermeier und Hubertus Graf zu Solms-Baruth 《Zeitschrift für Lebensmitteluntersuchung und -Forschung A》1966,130(5):291-295
Zusammenfassung Die Aktivierungsversuche haben gezeigt, daß die Xanthindehydrase in frisch ermolkener Rohmilch nicht quantitativ erfaßbar ist. Erst durch längeres Lagern bei 0° C, durch Rühren; Homogenisieren oder Wolframatzusatz wird das gesamte in der Probe enthaltene Enzym freigesetzt. Da der Aktivierungseffekt dieser Maßnahmen größenordnungsmäßig der gleiche ist, kann angenommen werden, daß die Aktivitätssteigerung in allen diesen Fällen auf ein und demselben Vorgang beruht. Die wahrscheinlichste Erklärung für die Aktivierungserscheinungen ist die Loslösung des Enzyms von der Fettkügelchenmembran.Dagegen können die Ergebnisse aus den Gefrierversuchen nicht in dieser einfachen Weise gedeutet werden. Wie aus der Zusammenstellung der Ergebnisse aus den Aktivierungsversuchen hervorgeht, wird durch Gefrieren der Milch die Aktivität der Probe auf den doppelten bzw. vierfachen Wert gesteigert. Offenbar wird die Xanthindehydrase bei dieser Behandlung in Untereinheiten aufgespalten.Auszug aus der Dissertation vonHubertus Graf zuSolms-Baruth: Über den Einfluß von Effektoren auf die Xanthindehydrase der Milch. Technische Hochschule München 1965. 相似文献