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991.
Chung-Yi Tsai Anthony G. Dixon Yi Hua Ma William R. Moser Marina R. Pascucci 《Journal of the American Ceramic Society》1998,81(6):1437-1444
La1- x A' x Fe0.8 Co0.2 O3-δ (A'= Ca, Sr, Ba) perovskite powders were synthesized to attain the desired properties of high O2 flux and stability under reducing conditions. Steady-state oxygen permeation rates for La1- x A' x Fe0.8 -Co0.2 O3-δ perovskite membranes in nonreacting experiments with air on one side and helium on the other side of the membrane were in the order A' x = Ba0.8 > Ba0.6 > Ca0.6 > Sr0.6 . Partial oxidation of methane to syngas (CO + H2 ) was performed in a dense La0.2 Ba0.8 Fe0.8 Co0.2 O3-δ membrane reactor at 850°C in which oxygen was separated from air and simultaneously fed into the methane stream. The reducing atmosphere affected the membrane reaction-side surface while barium enrichment occurred on the air-side surface. Oxygen continuously transported from the air side appeared to stabilize the membrane interior, and the reactor was operated for up to 850 h. 相似文献
992.
Satu Pekkarinen Anu Hopia Marina Heinonen 《European Journal of Lipid Science and Technology》1998,100(3):69-74
The effect of various processing conditions on the composition and the oxidative stability of mechanically pressed (90–95°C) rapeseed oil was investigated. The five different rapeseed oils included crude (nondegummed), superdegummed, steam stripped (at 140°C for 4h, nondegummed), physically refined (degummed, bleached and deodorized at 240°C), and cold pressed (40°C) oils. Oils were autoxidized in the dark at 60°C and under light at 25°C. Oxidation was followed by measuring changes in the peroxide values (PV) and the consumption of tocopherol and carotenoid was measured. In the dark the oils reached PVs of 10 meq/kg in the order: cold pressed > superdegummed > steam stripped ≅ crude > refined. However, under light conditions the order changed as follows: cold pressed > crude ≅ steam stripped > superdegummed > refined. Processing had no effect on fatty acid composition nor α-tocopherol content of the oils. Superdegumming and steam stripping decreased the carotenoid content of the oils while cold pressing and refining reduced also chlorophyll, γ-tocopherol and phosphorus content of the oils. 相似文献
993.
Shells of the freshwater, pulmonate snail Physa (Mollusca, Gasteropoda), ranging from 0.5 to 10 mm in length, were studied using scanning microscopy, x-ray analysis, and infrared spectroscopy. Results obtained suggest that the shell is composed of aragonite, which occurs in several distinct crystalline forms. A selective distribution of crystalline forms (hexagonal plates, prisms, rhombohedra, and spherulites) occurred along specific sites of the shell. A variable distribution of the forms was also detected in adult shells and in protoconchs of developing embryos. Qualitative elemental analysis, using an energy-dispersive spectrometer, corroborates the presence of calcium, phosphorus and sulphur ions. 相似文献
994.
An instrument is described that allows the use of Fourier transform infrared (FTIR) spectroscopy as a detection system for kinetic processes after a pressure jump of up to 100 bars. The pressure is generated using a high performance liquid chromatography (HPLC) pump and water as a pressure transducing medium. A flexible membrane separates the liquid sample in the IR cell from the pressure transducing medium. Two electromagnetic switching valves in the setup enable pressure jumps with a decay time of 4 ms. The FTIR spectrometer is configured to measure time resolved spectra in the millisecond time regime using the rapid scan mode. All components are computer controlled. For a demonstration of the capability of the method first results on the kinetics of a phase transition between two lamellar phases of an aqueous phospholipid dispersion are presented. This combination of FTIR spectroscopy with the pressure jump relaxation technique can also be used for other systems which display cooperative transitions with concomitant volume changes. 相似文献
995.
996.
Georgiy B. Shul’pin Marina V. Kirillova Tawan Sooknoi Armando J. L. Pombeiro 《Catalysis Letters》2008,123(1-2):135-141
Hydrogen peroxide oxidizes alkanes at room temperature to produce the corresponding alkyl hydroperoxides in the presence of titanosilicalite-1, NaOH and acetonitrile. The reaction proceeds with low regio- and bond-selectivity and its mechanism apparently involves the formation of hydroxyl radicals. 相似文献
997.
Adriana Zulema Valencia-Pérez Miriam Hiessu García-Morales José Luis Cárdenas-López José Ronaldo Herrera-Urbina Ofelia Rouzaud-Sández Josafat Marina Ezquerra-Brauer 《Food chemistry》2008
The effect of two thermal treatments (fast freezing at −40 °C and vapor cooking at 100 °C) on connective tissue extract (CTE) from jumbo squid (Dosidicus gigas) was investigated. Samples of CTE frozen at −40 °C were taken at 0, 3, 5 and 12 min. Also CTE was cooked at 100 °C and samples were taken at 0, 1, 2.5 and 5 min. Light microscopic observations of CTE after 12 min of freezing showed rupture of fibres. The CTE fibres showed agglutination during cooking time. The CTE insoluble fraction increased with freezing and cooking time. Maximum zeta potential value of untreated CTE was detected at pH 5.0 at +30 mV, meanwhile in the frozen CTE it was detected at pH 7.0 at +30 mV and two peaks (at pH 5.5 and 9.0) were observed at +20 mV in the cooked CTE. One endothermic peak was found at 105.9 °C in the untreated CTE, while in the frozen and cooked CTE the endothermic peaks were found at lower temperatures and enthalpies. Electrophoresis analysis of untreated CTE showed three bands. In the frozen CTE two bands appeared above 200 kDa, and in the cooked CTE, a 45 kDa band disappeared. These results suggest that during freezing and cooking processes there were modifications to molecular bonds that hold the integrity of the structure of the connective tissue of the jumbo squid mantle. 相似文献
998.
Fulvio ArdenteAuthor Vitae Marco BeccaliAuthor VitaeMaurizio CelluraAuthor Vitae Marina Mistretta 《Energy and Buildings》2008,40(1):1-10
The paper presents a life cycle assessment of a kenaf-fibre insulation board following the international standards of the ISO 14040 series. Each life-cycle step has been checked, from kenaf production and board manufacture by an Italian firm, to use and disposal. 相似文献
999.
Phuong Hoai HaAuthor Vitae Marina PapatriantafilouAuthor VitaePhilippas Tsigas 《Journal of Parallel and Distributed Computing》2007
Reactive diffracting trees are efficient distributed objects that support synchronization, by distributing sets of memory accesses to different memory banks in a coordinated manner. They adjust their size in order to retain their efficiency in the presence of different contention levels. Their adjustment is sensitive to parameters that have to be manually determined after experimentation. Since these parameters depend on the application as well as on the system configuration and load, determining their optimal values is difficult in practice. Moreover, the adjustments are done one level at a time, hence the cost of multi-level adjustments can be high. 相似文献
1000.
SM Gaini EP Sganzerla L Fiori R Marina G Citerio 《Canadian Metallurgical Quarterly》1998,64(4):177-179
The examination of deaths due to electricity may require a comparison between current marks on the body and the electrodes suspected to have caused them. Normally the identification of the responsible electrode is carried out by analysing metal traces on the current marks. We however examined the conductor for traces of biological material after experimentally produced current marks. The surfaces of the conductors were investigated using a low-power macroscope and burnt tissue could always be recognised. Subsequently, all electrodes were carefully swabbed, extracted with chelex and typed for short tandem repeat polymorphisms using PCR. This procedure was successful in all cases. Therefore, DNA analysis can be a powerful tool to supplement conventional scene reconstruction in cases of deaths due to electricity. 相似文献