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1.
Te-promoted (1%) vanadium phosphate catalyst (VPDTe) was prepared via VOPO4·2H2O by calcining its precursor VOHPO4·0.5H2O in a flow of n-butane/air.VPDTe catalyst has resulted a higher existence of V5+ phase with V5+/V4+ ratio of 0.23.SEM micrographs show that Te addition altered the arrangement of the platelets from "rose-like" clusters to layer with irregular shape.Te addition has also markedly lowered the reduction activation energies of the vanadium phosphate catalyst as revealed by TPR profile.The amount of active oxygen species associated with V4+ phase of the Te promoted catalyst was significantly higher than those of the unpromoted catalyst.These observations suggest that high mobility and availability of reactive oxygen species contributed to the enhancement of n-butane conversion up to 80% at 673 K,while only 47% over unpromoted catalyst (2400 h-1,1.7% n-butane in air). 相似文献
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Experimental data are presented for the mass flow rate and quality of two-phase discharge through a small branch of diameter d (=6.35 mm) attached normally to an inclined flat plane. The flat plane was situated in a large tank containing a stratified mixture of air and water under pressure (316 kPa) and at room temperature. The plane was inclined through various angles (θ) in increments of 30°, from the outlet-branch orientation being vertically upward through the horizontal to vertically downward. The bulk of the data correspond to seven inclination angles and two test-section-to-separator pressure differences (ΔP) of 11.0 and 115.5 kPa, and for each combination of θ and ΔP, the mass flow rate and quality were measured at different values of the interface level (h) between the onsets of gas and liquid entrainment. Four additional data sets were generated for other values of ΔP in order to confirm certain trends. Influences of these independent variables on the mass flow rate and quality are discussed and normalized plots are presented showing that the data can be collapsed for a wide range of conditions. Comparisons are made between the present data and previous correlations/models and new empirical correlations are formulated and shown to be capable of predicting the present data with good accuracy. 相似文献
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First direct observation of the decay of neutral charmed particles produced by neutrinos in emulsion
D. Allasia C. Angelini P. Bagnaia G. Baroni J.H. Bartley G. Bertrand-Coremans V. Bisi A. Breslin E.H.S. Burhop F. Carena R. Casali G. Ciapetti M. Conversi D.H. Davis S. Di Liberto R. Fantechi M.L. Ferrer G. Wilquet 《Physics letters. [Part B]》1979,87(3):287-291
Three examples of the production in emulsion by neutrinos and subsequent decay of neutral short-lived particles are reported. The flight times are ≈ 10?13s, similar in order of magnitude to those previously determined for charged charmed particles in the same experiment. 相似文献
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A screening for thermophilic cellulolytic microbes from the soils of volcanic areas yielded several potentially useful bacteria.
Of these,Microbispora bispora was the most useful. The enzyme complex was stable at 60–65‡C. Analysis of the complex indicated the presence of endoglucanase,
cellobiohydrolase, and Β-glucosidase components. The two former enzymes were secreted, whereas the Β-glucosidase was cell-associated.
The cellobiohydrolase was of particular interest, since this type of enzyme has rarely been reported from bacteria, and therefore
was characterized in greater detail. Its mechanism of action was clarified through its action pattern towards soluble (and
reduced) oligosaccharides. Synergism was observed between the cellobiohydrolase and endoglucanases during attack on crystalline
cellulose (cotton and Avicel). This represents one of the first demonstrations of synergism in a procaryotic cellulase system. 相似文献
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The formulation of organic–inorganic polymer composites can be used to enhance selected properties, such as susceptibility to microbial attack, thermal stability, mechanical strength and water sorption capability. Accordingly, a series of alginic acid–silica hydrogel films was prepared for testing as protective coating materials for PTFE osmotic distillation membranes. Unprotected hydrophobic membranes are subject to wet-out when contacted by surface-active agents, such as oils and detergents. Films containing 5, 10, 15 and 20 wt.% silica, with and without the addition of glycerol for plasticisation, moisturisation and silica dispersion, were characterised using scanning electron microscopy, X-ray diffraction, differential scanning calorimetry, mechanical strength measurements, and water-swelling measurements. Composites prepared with glycerol addition had better thermal stability, mechanical strength and water sorption capability than those prepared without glycerol addition. Uncoated membranes and membranes coated with composites prepared with glycerol addition were tested for OD performance and resistance to surface-active agents using pure water, orange oil (limonene)–water mixtures, and sodium dodecylbenzene sulfonate detergent solutions. Uncoated membranes showed immediate hydrophobicity loss in the presence of orange oil and detergent. For coated membranes, no wet-out occurred over the 15 h duration of three consecutive 5 h OD trials using orange oil–water mixtures. In the case of detergent solutions, the coating afforded protection to the membrane for 4–5 h. In a separate trial, no wet-out occurred when the coated side of the membrane was placed in contact with 1.2 wt.% orange oil for 72 h. 相似文献
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John?Bartley Thomas?Soltau Hereward?Wimborne Sunjun?Kim Angeline?Martin-Studdard David?Hess William?Hill Jennifer?Waller James?CarrollEmail author 《BMC neuroscience》2005,6(1):15
Background
Mechanisms that affect recovery from fetal and neonatal hypoxic-ischemic (H-I) brain injury have not been fully elucidated. The incidence of intrapartum asphyxia is approximately 2.5%, but the occurrence of adverse clinical outcome is much lower. One of the factors which may account for this relatively good outcome is the process of neurogenesis, which has been described in adult animals. We used a neonatal mouse model to assess new cells in the hippocampus after H-I injury. 相似文献9.
The analytical equations for calculating two-phase flow, including local capillary pressures, are developed for the bundle of parallel capillary tubes model. The flow equations that are derived were used to calculate dynamic immiscible displacements of oil by water under the constraint of a constant overall pressure drop across the tube bundle. Expressions for averaged fluid pressure gradients and total flow rates are developed, and relative permeabilities are calculated directly from the two-phase form of Darcy's law. The effects of pressure drop and viscosity ratio on the relative permeabilities are discussed. Capillary pressure as a function of water saturation was delineated for several cases and compared to a steady-state mercury-injection drainage type of capillary pressure profile. The bundle of serial tubes model (a model containing tubes whose diameters change randomly at periodic intervals along the direction of flow), including local Young-Laplace capillary pressures, was analyzed with respect to obtaining relative permeabilities and macroscopic capillary pressures. Relative permeabilities for the bundle of parallel tubes model were seen to be significantly affected by altering the overall pressure drop and the viscosity ratio; relative permeabilities for the bundle of serial tubes were seen to be relatively insensitive to viscosity ratio and pressure, and were consistently X-like in profile. This work also considers the standard Leverett (1941) type of capillary pressure versus saturation profile, where drainage of a wetting phase is completed in a step-wise steady fashion; it was delineated for both tube bundle models. Although the expected increase in capillary pressure at low wetting-phase saturation was produced, comparison of the primary-drainage capillary pressure curves with the pseudo-capillary pressure profiles, that are computed directly using the averaged pressures during the displacements, revealed inconsistencies between the two definitions of capillary pressure. 相似文献
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Mia A. Levy John B. Freymann Justin S. Kirby Andriy Fedorov Fiona M. Fennessy Steven A. Eschrich Anders E. Berglund David A. Fenstermacher Yongqiang Tan Xiaotao Guo Thomas L. Casavant Bartley J. Brown Terry A. Braun Andre Dekker Erik Roelofs James M. Mountz Fernando Boada Charles Laymon Matt Oborski Daniel L. Rubin 《Magnetic resonance imaging》2012