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排序方式: 共有275条查询结果,搜索用时 46 毫秒
91.
A simple method for preparing gelled alginate beads with a diameter smaller than 5 μm is described. A 1% alginate solution and a medium chain triglyceride (MCT) oil are used to prepare a water-in-oil (w/o) emulsion, stabilized by polyglycerol polyricinoleate. CaCl2 nanoparticles with dimensions in the nano-range (6–400 nm), dispersed in MCT oil, are then added to the emulsion. Energy-dispersive X-ray spectroscopy (EDX) and Auger electron spectroscopy (AES) show that these nanoparticles migrate to the emulsion droplet interface, where they dissolve into the aqueous alginate phase and cause gelation, forming beads. Gelation of the beads was confirmed with a novel technique using Congo red as an indicator. A color change occurs upon the addition of CaCl2 to a Congo red solution and we believe this is due to formation of a Congo red–calcium complex. Scanning electron microscopy shows that alginate beads are mostly in a size range around 1 μm, but beads as small as 200 nm and smaller were also found. Extending the size range of alginate beads into the submicron range, while maintaining relatively mild pH conditions in the interior of the bead, will significantly extend the range of applications for this type of beads. 相似文献
92.
Hydrogen production with a microbial biocathode 总被引:11,自引:0,他引:11
Rozendal RA Jeremiasse AW Hamelers HV Buisman CJ 《Environmental science & technology》2008,42(2):629-634
This paper, for the first time, describes the development of a microbial biocathode for hydrogen production that is based on a naturally selected mixed culture of electrochemically active micro-organisms. This is achieved through a three-phase biocathode startup procedure that effectively turned an acetate- and hydrogen-oxidizing bioanode into a hydrogen-producing biocathode by reversing the polarity of the electrode. The microbial biocathode that was obtained in this way had a current density of about -1.2 A/Nm2 at a potential of -0.7 V. This was 3.6 times higher than that of a control electrode (-0.3 A/m2). Furthermore, the microbial biocathode produced about 0.63 m3 H2/m3 cathode liquid volume/day at a cathodic hydrogen efficiency of 49% during hydrogen yield tests, whereas the control electrode produced 0.08 m3 H2/m3 cathode liquid volume/day at a cathodic hydrogen efficiency of 25%. The effluent of the biocathode chamber could be used to inoculate another electrochemical cell that subsequently also developed an identical hydrogen-producing biocathode (-1.1 A/m2 at a potential of -0.7 V). Scanning electron micrographs of both microbial biocathodes showed a well-developed biofilm on the electrode surface. 相似文献
93.
Performance of a scaled-up Microbial Fuel Cell with iron reduction as the cathode reaction 总被引:1,自引:0,他引:1
Annemiek Ter Heijne Fei LiuLucas S. van Rijnsoever Michel Saakes Hubertus V.M. Hamelers Cees J.N. Buisman 《Journal of power sources》2011,196(18):7572-7577
Scale-up studies of Microbial Fuel Cells are required before practical application comes into sight. We studied an MFC with a surface area of 0.5 m2 and a volume of 5 L. Ferric iron (Fe3+) was used as the electron acceptor to improve cathode performance. MFC performance increased in time as a combined result of microbial growth at the bio-anode, increase in iron concentration from 1 g L−1 to 6 g L−1, and increased activity of the iron oxidizers to regenerate ferric iron. Finally, a power density of 2.0 W m−2 (200 W m−3) was obtained. Analysis of internal resistances showed that anode resistance decreased from 109 to 7 mΩ m2, while cathode resistance decreased from 939 to 85 mΩ m2. The cathode was the main limiting factor, contributing to 58% of the total internal resistance. Maximum energy efficiency of the MFC was 41%. 相似文献
94.
Marc Schut Annemarie van Paassen Cees Leeuwis Sandra Bos Wilson Leonardo Anna Lerner 《Energy Policy》2011
This paper provides insights and recommendations for policy on the opportunities and constrains that influence the space for innovation for sustainable community-based biofuel production and use. Promoted by the Mozambican government, Nhambita community established jatropha trials in 2005. Initial results were promising, but crop failure and the absence of organized markets led to scepticism amongst farmers. 相似文献
95.
Gas diffusion electrodes improve hydrogen gas mass transfer for a hydrogen oxidizing bioanode 下载免费PDF全文
Pau Rodenas Fangqi Zhu Annemiek ter Heijne Tom Sleutels Michel Saakes Cees Buisman 《Journal of chemical technology and biotechnology (Oxford, Oxfordshire : 1986)》2017,92(12):2963-2968
Background
Bioelectrochemical systems (BESs) are capable of recovery of metals at a cathode through oxidation of organic substrate at an anode. Recently, also hydrogen gas was used as an electron donor for recovery of copper in BESs. Oxidation of hydrogen gas produced a current density of 0.8 A m‐2 and combined with Cu2+ reduction at the cathode, produced 0.25 W m‐2. The main factor limiting current production was the mass transfer of hydrogen to the biofilm due to the low solubility of hydrogen in the anolyte. Here, the mass transfer of hydrogen gas to the bioanode was improved by use of a gas diffusion electrode (GDE).Results
With the GDE, hydrogen was oxidized to produce a current density of 2.9 A m‐2 at an anode potential of –0.2 V. Addition of bicarbonate to the influent led to production of acetate, in addition to current. At a bicarbonate concentration of 50 mmol L‐1, current density increased to 10.7 A m‐2 at an anode potential of –0.2 V. This increase in current density could be due to oxidation of formed acetate in addition to oxidation of hydrogen, or enhanced growth of hydrogen oxidizing bacteria due to the availability of acetate as carbon source. The effect of mass transfer was further assessed through enhanced mixing and in combination with the addition of bicarbonate (50 mmol L‐1) current density increased further to 17.1 A m‐2.Conclusion
Hydrogen gas may offer opportunities as electron donor for bioanodes, with acetate as potential intermediate, at locations where excess hydrogen and no organics are available. © 2017 The Authors. Journal of Chemical Technology & Biotechnology published by John Wiley & Sons Ltd on behalf of Society of Chemical Industry. 相似文献96.
The semantic pathfinder: using an authoring metaphor for generic multimedia indexing 总被引:2,自引:0,他引:2
Snoek CG Worring M Geusebroek JM Koelma DC Seinstra FJ Smeulders AW 《IEEE transactions on pattern analysis and machine intelligence》2006,28(10):1678-1689
This paper presents the semantic pathfinder architecture for generic indexing of multimedia archives. The semantic pathfinder extracts semantic concepts from video by exploring different paths through three consecutive analysis steps, which we derive from the observation that produced video is the result of an authoring-driven process. We exploit this authoring metaphor for machine-driven understanding. The pathfinder starts with the content analysis step. In this analysis step, we follow a data-driven approach of indexing semantics. The style analysis step is the second analysis step. Here, we tackle the indexing problem by viewing a video from the perspective of production. Finally, in the context analysis step, we view semantics in context. The virtue of the semantic pathfinder is its ability to learn the best path of analysis steps on a per-concept basis. To show the generality of this novel indexing approach, we develop detectors for a lexicon of 32 concepts and we evaluate the semantic pathfinder against the 2004 NIST TRECVID video retrieval benchmark, using a news archive of 64 hours. Top ranking performance in the semantic concept detection task indicates the merit of the semantic pathfinder for generic indexing of multimedia archives. 相似文献
97.
98.
Daragh Byrne Aiden R. Doherty Cees G. M. Snoek Gareth J. F. Jones Alan F. Smeaton 《Multimedia Tools and Applications》2010,49(1):119-144
The Microsoft SenseCam is a small lightweight wearable camera used to passively capture photos and other sensor readings from
a user’s day-to-day activities. It captures on average 3,000 images in a typical day, equating to almost 1 million images
per year. It can be used to aid memory by creating a personal multimedia lifelog, or visual recording of the wearer’s life.
However the sheer volume of image data captured within a visual lifelog creates a number of challenges, particularly for locating
relevant content. Within this work, we explore the applicability of semantic concept detection, a method often used within
video retrieval, on the domain of visual lifelogs. Our concept detector models the correspondence between low-level visual
features and high-level semantic concepts (such as indoors, outdoors, people, buildings, etc.) using supervised machine learning.
By doing so it determines the probability of a concept’s presence. We apply detection of 27 everyday semantic concepts on
a lifelog collection composed of 257,518 SenseCam images from 5 users. The results were evaluated on a subset of 95,907 images,
to determine the accuracy for detection of each semantic concept. We conducted further analysis on the temporal consistency,
co-occurance and relationships within the detected concepts to more extensively investigate the robustness of the detectors
within this domain. 相似文献
99.
Peter Nijkamp Pim Klamer Cees Gorter 《Journal of Housing and the Built Environment》2002,17(2):109-125
This exploratory paper examines the localsuccess conditions and the region-specificorientation of real estate investment trusts(REITs). After a concise overview of thehistory of REITs in the USA, the criticalperformance factors of retail REITs areaddressed by investigating the empiricalrelationship between local retail rents and aselected set of local explanatory factors. Asequential regression method is deployed toidentify the most prominent, statisticallysignificant variables and to create a rankingof most promising metropolitan areas from aninvestor's perspective. 相似文献
100.
van der Wiel Bernou Zoë Weijma Jan van Middelaar Corina Everarda Kleinke Matthias Buisman Cees Jan Nico Wichern Florian 《Nutrient Cycling in Agroecosystems》2021,121(2-3):209-226
Nutrient Cycling in Agroecosystems - Regions with intensive agriculture often encounter environmental problems caused by nutrient excess of agro-food-waste systems that have become increasingly... 相似文献