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61.
62.
Pete E. Benville Jr Thomas G. Yocom Pepsi Nunes Jeffrey M. O'Neill 《Water research》1981,15(10):1197-1204
A continuous flow apparatus, referred to as a solubilizer, was constructed to dissolve the water-soluble fraction (WSF) of crude oil into water for short and long-term experiments with marine organisms. The basic solubilizer system consists of an oil reservoir, oil pump, modified glass bottle, and oil waste reservoir. This system dissolves the water-soluble components of crude oil without the loss of the more volatile compounds and without the formation of emulsions or oil droplets. Four solubilizer systems (two continuous flow and two recirculating) were evaluated for their efficiency in extracting the water-soluble components from Cook Inlet crude oil by analyzing for six monoaromatics over a 96-h period of continuous operation. When a solubilizer system was started, a stable concentration of the monocyclic aromatics in the water-soluble fraction was reached within 24 h. The water quality of the WSF effluent was not altered markedly in the continuous (open) flow systems, but there was a substantial reduction in dissolved oxygen in the recirculated (closed) systems. A single solubilizer system (open flow) with a 3 ml min−1 oil flow and a 1 l min−1 sea-water flow generated approx. 1.4 ppm of the total monoaromatics, which includes benzene, toluene, ethylbenzene and the three xylene isomers. This concentration varied depending on physical parameters and the chemical composition of the crude oil and water. With only slight modifications of the basic continuous flow system, a higher concentration (> 3.4 ppm total monoaromatics) of the water-soluble fraction of crude oil was achieved. By recirculating the water supply, concentrations of 6.7–11 ppm total monoaromatics in the WSF were produced. The stability, reproducibility, and reliability of the four systems were demonstrated in several experiments. Researchers working in aquatic systems with crude oil can well appreciate a simple system that is easily cleaned, relatively maintenance-free, and which produces stable, reproducible concentrations of the WSF over extended periods of time. The increasing demands for ecological studies on aquatic organisms with crude oil, a difficult mixture of chemicals with which to work, precipitated the development of these solubilizer systems. 相似文献
63.
64.
To demonstrate the efficacy of flexible retrograde ureterorenoscopic holmium-YAG intracorporeal laser lithotripsy for the treatment of renal calculi, a total of 86 patients presenting to our hospital with renal calculi underwent flexible retrograde ureterorenoscopic holmium-YAG intracorporeal laser lithotripsy of their stones, and the data were collected prospectively. As extracorporeal shock wave lithotripsy is not available at our institution, all patients with renal calculi in this study were treated in a retrograde fashion using the Richard Wolf 6.0F semirigid ureteroscope, the 7.5F flexible ureterorenoscope, and the holmium-YAG laser by Coherent Inc. Except for inhospital consults or patients requiring admission secondary to infection, all cases were performed on an ambulatory basis. All renal calculi 3 cm or smaller were approached in a retrograde fashion. Where possible, the stones were initially debulked using the semirigid ureteroscope and the 550-microm fiber followed by the flexible ureterorenoscope in combination with the 360- or 200-microm laser fiber depending on stone position. Stones were fragmented until they were small enough to be removed by hydrocleansing. Using this technique, stone-free success rates for calculi 2.5 cm or smaller after a single treatment, regardless of stone composition or location, are superior to those of extracorporeal shock wave lithotripsy. For calculi between 2.5 and 3 cm, the results also are noted to be superior. We conclude that for calculi larger than 3 cm or for partial staghorn calculi, the treatment of choice appears to be a percutaneous approach. 相似文献
65.
The specificity of substrate hydrolysis by bovine brain phospholipase A1 (PLA1) was examined. In the presence of Mg2+, using pH values of 7 to 9, the purified enzyme deacylated 1-palmitoyl-2-[1-14C]arachidonoyl-phosphatidylethanolamine yielding 2-[1-14C]arachidonoyl-lysophosphatidylethanolamine at a rate of 70 mumol/min per mg. In the absence of Mg2+, however, the reaction rate slowed at pH values above 7.25. In contrast, brain PLA1 slowly (3.8 mumol/min per mg) hydrolyzed 1-palmitoyl-2-[1-14C]arachidonoyl-phosphatidylcholine (PAPC) unless phosphatidylserine (PS) was included. Maximal PAPC hydrolyzing activity required a PAPC/PS molar ratio of 2.5:1, Mg2+, and a pH value of 8.5-9.5. Replacing PS with phosphatidylethanolamine (PE) or phosphatidic acid (PA), but not phosphatidylinositol (PI), produced a similar effect. Moreover, hydrolysis of either arachidonoyl-substituted or dipalmitoyl-substituted PC at pH 7.5 was enhanced by increasing the mol fraction of PE. Brain PLA1 also hydrolyzed 1-stearoyl-[1-14C]arachidonoyl-PI with high velocity, but only if the substrate was dispersed in PE vesicles. In contrast, the velocity of PS, 1-palmitoyl-lyso-PC or diacylglycerol hydrolysis was low and unaffected by PE. In summary, PLA1 hydrolyzed PE with high velocity and specificity, whereas a high rate of PC or PI hydrolysis was observed only if PS, PE, or PA was present. In addition, PLA1 activity was greatly influenced by pH and Mg2+, implying that the substrate conformation is important to the catalytic efficiency of PLA1. Finally, the high rate of PE, PC or PI hydrolysis suggests PLA1 significantly contributes to the turnover of these phospholipids in the brain. 相似文献
66.
The Anatomy of a Context-Aware Application 总被引:9,自引:0,他引:9
We describe a sensor-driven, or sentient, platform for context-aware computing that enables applications to follow mobile users as they move around a building. The platform is particularly suitable for richly equipped, networked environments. The only item a user is required to carry is a small sensor tag, which identifies them to the system and locates them accurately in three dimensions. The platform builds a dynamic model of the environment using these location sensors and resource information gathered by telemetry software, and presents it in a form suitable for application programmers. Use of the platform is illustrated through a practical example, which allows a user's current working desktop to follow them as they move around the environment. 相似文献
67.
68.
Tyrone E. Benson Leonard I. Kamlet Pete Klimecky Fred L. Terry 《Journal of Electronic Materials》1996,25(6):955-964
Accurate film thickness monitors are important for the development of real-time feedback control of dry etch processes and
are very useful for run-to-run process control and process diagnostics. Technologically important films such as polycrystalline
Si, which can have process-dependent refractive indices and/or surface roughness, pose significant challenges for low-cost,
high-speed film thickness measurement systems. We have used spectroscopic reflectometry (SR) to make accuratein-situ, high-speed film thickness measurements during plasma etching of polycrystalline Si. The SR system determines the film thickness
using a least squares regression algorithm that fits the theoretical reflectance to the experimental reflectance vs wavelength
data. We have included physically based models for the variation of the polycrystalline Si bulk refractive indices and surface
roughness in the fitting procedure. The parameters of the refractive index models are adjusted at the beginning of each run
to account for wafer-to-wafer variationswithout the use of additional ex-situ measurements. We have usedex-situ spectroscopic ellipsometry to validate the models used and to check the accuracy of our SR measurements. Currently, our SR
system can acquire data in 40 ms and the software can calculate the polycrystalline Si thickness in less than 55 ms per measurement,
so that a new film thickness and etch rate estimate can be obtained in less than 100 ms. The methods used for analysis of
polycrystalline Si are also directly useful for improving the accuracy of microscope-based spectral reflection measurement
systems commonly used for in-line measurements. Using similar optical modeling concepts, the SR technique can also be used
to accurately measure film thicknesses and etch rates of other thin films with process-dependent optical constants, such as
deposited dielectrics and compound semiconductors. 相似文献
69.
There is a need to increase the temperature capability of superalloy turbine disks to allow higher operating temperatures
in advanced aircraft engines. When modifying processing and chemistry of disk alloys to achieve this capability, it is important
to preserve the ability to use rapid cooling during supersolvus heat treatments to achieve coarse grain, fineγ′ microstructures. An important step in this effort is an understanding of the key variables controlling the cracking tendencies
of nickel-base disk alloys during quenching from supersolvus heat treatments. The objective of this study was to investigate
the quench cracking tendencies of several advanced disk superalloys during simulated heat treatments. Miniature disk specimens
were rapidly quenched after solution heat treatments. The responses and failure modes were compared and related to the quench
cracking tendencies of actual disk forgings. Cracking along grain boundaries was generally observed to be operative. For the
alloys examined in this study, the solution temperature, not alloy chemistry, was found to be the primary factor controlling
quench cracking. Alloys with high solvus temperatures show greater tendency for quench cracking. 相似文献
70.
Jess D. Reed Rober T. E. McDowell Peter J. van Soest Pete R. J. Horvath 《Journal of the science of food and agriculture》1982,33(3):213-220
Cassava (Manihot esculenta, Crantz), an important tropical root crop, is considered to have a good potential for use as a forage because leaf blades generally contain <20% crude protein (CP). However, neutral-detergent fibre (NDF) obtained from cassava leaf blades contains condensed tannins (CTs) and high levels of CP. The amount of CP in the NDF that is insoluble when treated with pepsin or protease is highly correlated with the amount of CTs in the NDF. CTs in the NDF are rich in prodelphinidin. CTs may be an important factor limiting the nutritive value of cassava forage. 相似文献