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排序方式: 共有614条查询结果,搜索用时 218 毫秒
101.
Laurens LM Dempster TA Jones HD Wolfrum EJ Van Wychen S McAllister JS Rencenberger M Parchert KJ Gloe LM 《Analytical chemistry》2012,84(4):1879-1887
Algal biomass compositional analysis data form the basis of a large number of techno-economic process analysis models that are used to investigate and compare different processes in algal biofuels production. However, the analytical methods used to generate these data are far from standardized. This work investigated the applicability of common methods for rapid chemical analysis of biomass samples with respect to accuracy and precision. This study measured lipids, protein, carbohydrates, ash, and moisture of a single algal biomass sample at 3 institutions by 8 independent researchers over 12 separate workdays. Results show statistically significant differences in the results from a given analytical method among laboratories but not between analysts at individual laboratories, suggesting consistent training is a critical issue for empirical analytical methods. Significantly different results from multiple lipid and protein measurements were found to be due to different measurement chemistries. We identified a set of compositional analysis procedures that are in best agreement with data obtained by more advanced analytical procedures. The methods described here and used for the round robin experiment do not require specialized instrumentation, and with detailed analytical documentation, the differences between laboratories can be markedly reduced. 相似文献
102.
103.
Simon A. Cotton Victoria M.A. Fisher Paul R. Raithby Stefanie Schiffers Simon J. Teat 《Inorganic chemistry communications》2008,11(7):822-824
Reaction of hydrated scandium nitrate with 1,10-phenanthroline (phen) in methanol leads to formation of the unusual dimeric complex [(phen)(NO3)2Sc(μ-OMe)2Sc(NO3)2(phen)], in which the scandium centres are eight co-ordinate. The complex features two bridging methoxy ligands, as well as bidentate nitrates and chelating 1,10-phenanthroline ligands. 相似文献
104.
Conrad F Massue C Kühl S Kunkes E Girgsdies F Kasatkin I Zhang B Friedrich M Luo Y Armbrüster M Patzke GR Behrens M 《Nanoscale》2012,4(6):2018-2028
Nanostructured Cu(x)Zn(1-x)Al(2)O(4) with a Cu:Zn ratio of ?:? has been prepared by a microwave-assisted hydrothermal synthesis at 150 °C and used as a precursor for Cu/ZnO/Al(2)O(3)-based catalysts. The spinel nanoparticles exhibit an average size of approximately 5 nm and a high specific surface area (above 250 m(2) g(-1)). Cu nanoparticles of an average size of 3.3 nm can be formed by reduction of the spinel precursor in hydrogen and the accessible metallic Cu(0) surface area of the reduced catalyst was 8 m(2) g(-1). The catalytic performance of the material in CO(2) hydrogenation and methanol steam reforming was compared with conventionally prepared Cu/ZnO/Al(2)O(3) reference catalysts. The observed lower performance of the spinel-based samples is attributed to a lack of synergetic interaction of the Cu nanoparticles with ZnO due to the incorporation of Zn(2+) in the stable spinel lattice. Despite its lower performance, however, the nanostructured nature of the spinel catalyst was stable after thermal treatment up to 500 °C in contrast to other Cu-based catalysts. Furthermore, a large fraction of the re-oxidized copper migrates back into the spinel upon calcination of the reduced catalyst, thereby enabling a regeneration of sintered catalysts after prolonged usage at high temperatures. Similarly prepared samples with Ga instead of Al exhibit a more crystalline catalyst with a spinel particle size around 20 nm. The slightly decreased Cu(0) surface area of 3.2 m(2) g(-1) due to less copper incorporation is not a significant drawback for the methanol steam reforming. 相似文献
105.
Stefanie Baum Fred van Rantwijk Andreas Stolz 《Advanced Synthesis \u0026amp; Catalysis》2012,354(1):113-122
The conversion of benzaldehyde and cyanide into mandelic acid and mandeloamide by a recombinant Escherichia coli strain which simultaneously expressed an (S)‐hydroxynitrile lyase (oxynitrilase) from cassava (Manihot esculenta) and an arylacetonitrilase from Pseudomonas fluorescens EBC191 was studied. Benzaldehyde exhibited a pronounced inhibitory effect on the nitrilase activity in concentrations ≥25 mM. Therefore, it was tested if two‐phase systems consisting of a buffered aqueous phase and the ionic liquid 1‐butyl‐1‐pyrrolidinium bis(trifluoromethanesulfonyl)imide (BMpl NTf2) or 1‐butyl‐3‐methylimidazolium hexafluorophosphate (BMim PF6) could be used for the intended biotransformation. The distribution coefficients of the substrates, intermediates and products of the reaction were determined and it was found that BMpl NTf2 and BMim PF6 were highly efficient as substrate reservoirs for benzaldehyde. The recombinant E. coli strain was active in the presence of BMpl NTf2 or BMim PF6 phases and converted benzaldehyde and cyanide into mandelic acid and mandeloamide. The two‐phase systems allowed the conversion of benzaldehyde dissolved in the ionic liquids to a concentration of 700 mM with product yields (=sum of mandelic acid and mandeloamide) of 87–100%. The cells were slightly more effective in the presence of BMpl NTf2 than in the presence of BMim PF6. In both two‐phase systems benzaldehyde and cyanide were converted into (S)‐mandeloamide and (S)‐mandelic acid with enantiomeric excesses ≥94%. The recombinant E. coli cells formed, in the two‐phase systems with ionic liquids and increased substrate concentrations, higher relative amounts of mandeloamide than in a purely aqueous system with lower substrate concentrations. 相似文献
106.
107.
Mohamed?S.?A.?DarwishEmail author Stefanie?Machunsky Urs?Peuker Ulrich?Kunz Thomas?Turek 《Journal of Polymer Research》2011,18(1):79-88
Magnetic composite particles with a magnetic core consisting of superparamagnetic iron oxide and a cover layer of hydrophobic
polyvinylbenzylchloride are described. The magnetite was prepared by precipitation starting with mixed iron II and iron III
salts and coating of the solid with oleic acid. The coating is conducted via the liquid–liquid phase transfer. Thereby oleic
acid adsorbed on the magnetite surface. In a second step the oleic acid treated magnetite was coated with polyvinylbenzylchloride
in a miniemulsion polymerization to get a protective layer. The obtained magnetite core-shell nano-composites with chlorine
functionality were characterized by different methods: particle size measurement, acid treatment, iron content, morphology
and elemental profiles across the composite particles diameter. The test result reveals the binding of the iron oxide inside
the composites which can be also recognize in TEM pictures. 相似文献
108.
Johannes Krantz Tobias Stubhan Moses Richter Stefanie Spallek Ivan Litzov Gebhard J. Matt Erdmann Spiecker Christoph J. Brabec 《Advanced functional materials》2013,23(13):1711-1717
Silver nanowire (Ag NW) thin films are investigated as top electrodes in semitransparent inverted organic solar cells. The performance of semitransparent poly(3‐hexylthiophene‐2,5‐diyl):[6,6]‐phenyl‐C61‐butyric acid methyl ester (P3HT:PCBM) organic solar cells with Ag NW top electrode layers is found to match very closely the performance of reference devices based on thermally evaporated, highly reflective metal silver top electrodes. The optical losses of the semitransparent electrodes are investigated in detail and analyzed in terms of transmission, scattering, and reflection losses. The impact on an external back reflector is shown to increase the light harvesting efficiency of optically thin devices. Further analysis of transparent devices under illumination from the indium tin oxide (ITO) backside and through the Ag NW front electrode open the possibility to gain deep insight into the vertical microstructure related devices performance. Overall, Ag NW top electrodes are established as a serious alternative to TCO based electrodes. Semitransparent devices with efficiencies of over η = 2.0% are realized. 相似文献
109.
Josef Lohr Olaf Georg Treusch Gernot Standfest Alexander Petutschnigg Stefanie Wieland Gerd Wegener 《Holz als Roh- und Werkstoff》2013,71(4):417-428
The possibility of fabricating SiC ceramics using special wood-based materials has been shown in previous research. To form accurate SiC bodies from wood-based green templates, special shaping techniques are necessary to fulfill the requirements on the finished ceramic products. Due to the fact that wood-based green templates undergo shrinkage during carbonization, no suitable forming processes for the wood-based green templates have been presented so far. In this publication different raw materials and 3D shaping production processes and their influence on green body properties are described. It was possible to produce green bodies with a MOR higher than 15 N/mm² and a density in the range above 0.82 g/cm³. It is shown that reduction of resin content decreases the strength significantly and a reduction to 30 mass % resin content reduces the MOR of flat pressed panels to the defined limit. The extruded samples showed a significantly lower strength (mean 18.1 N/mm², standard deviation 8.6 N/mm²). Injection molding was not applied successfully. The findings show that shape pressing and extrusion were applied successfully, but the green body properties differed significantly from the results achieved by flat pressing. 相似文献
110.
Dominik Saner Ronnie Juraske Markus Kübert Philipp Blum Stefanie Hellweg Peter Bayer 《Renewable & Sustainable Energy Reviews》2010,14(7):1798-1813
Shallow geothermal systems such as open and closed geothermal heat pump (GHP) systems are considered to be an efficient and renewable energy technology for cooling and heating of buildings and other facilities. The numbers of installed ground source heat pump (GSHP) systems, for example, is continuously increasing worldwide. The objective of the current study is not only to discuss the net energy consumption and greenhouse gas (GHG) emissions or savings by GHP operation, but also to fully examine environmental burdens and benefits related to applications of such shallow geothermal systems by employing a state-of the-art life cycle assessment (LCA). The latter enables us to assess the entire energy flows and resources use for any product or service that is involved in the life cycle of such a technology. The applied life cycle impact assessment methodology (ReCiPe 2008) shows the relative contributions of resources depletion (34%), human health (43%) and ecosystem quality (23%) of such GSHP systems to the overall environmental damage. Climate change, as one impact category among 18 others, contributes 55.4% to the total environmental impacts. The life cycle impact assessment also demonstrates that the supplied electricity for the operation of the heat pump is the primary contributor to the environmental impact of GSHP systems, followed by the heat pump refrigerant, production of the heat pump, transport, heat carrier liquid, borehole and borehole heat exchanger (BHE). GHG emissions related to the use of such GSHP systems are carefully reviewed; an average of 63 t CO2 equivalent emissions is calculated for a life cycle of 20 years using the Continental European electricity mix with 0.599 kg CO2 eq/kWh. However, resulting CO2 eq savings for Europe, which are between ?31% and 88% in comparison to conventional heating systems such as oil fired boilers and gas furnaces, largely depend on the primary resource of the supplied electricity for the heat pump, the climatic conditions and the inclusion of passive cooling capabilities. Factors such as degradation of coefficient of performance, as well as total leakage of the heat carrier fluid into the soil and aquifer are also carefully assessed, but show only minor environmental impacts. 相似文献