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991.
J Buc CL Santini F Blasco R Giordani ML Cárdenas M Chippaux A Cornish-Bowden G Giordano 《Canadian Metallurgical Quarterly》1995,234(3):766-772
A soluble alpha beta complex of nitrate reductase can be obtained from a strain of Escherichia coli that lacks the narI gene and expresses only the alpha and beta subunits. The beta subunit contains four Fe-S centres and the alpha subunit contains the molybdenum cofactor, which is the site at which nitrate is reduced. Despite the lack of the gamma subunit of the complete enzyme, this complex can still catalyse the reduction of nitrate with artificial electron donors such as benzyl viologen, so that it is suitable for studying the transfer of electrons between these two types of redox centre. To examine whether the electrons from reduced benzyl viologen are initially delivered to the Fe-S centres, or directly to the molybdenum cofactor, or both, we have studied the steady-state kinetics and the binding of benzyl viologen to the alpha beta complex and mutants alpha beta* with altered beta subunits. Reduction of the enzyme by reduced benzyl viologen in the absence of nitrate showed that all four Fe-S centres and the molybdenum cofactor could be reduced. Two classes of site with different equilibrium constants could be distinguished. The kinetic results suggest that benzyl viologen supplies its electrons directly to the molybdenum cofactor, at a rate showing a hyperbolic dependence on the square of the concentration of the electron donor. A reaction mechanism is proposed for the reduction of nitrate catalysed by the alpha beta complex of nitrate reductase with artificial electron donors. 相似文献
992.
J. J. Quist W. J. A. Dhert W. Visser F. C. Oner A. J. Verbout B. P. Meij H. A. W. Hazewinkel 《Journal of materials science. Materials in medicine》1995,6(12):731-738
In the present study the potential of Polyactive® bilayer sheets in the prevention of scar tissue formation after spinal surgery was investigated. Eight adult beagle dogs underwent 3 laminectomies at three levels (L2, L4 and L6). According to a randomized implantation schedule a Polyactive® sheet or autogenous fat graft was placed in the defect. The third site served as a control without implant. After 4 or 12 weeks (4 dogs per period) the dogs were sacrificed and histological sections were prepared. The Polyactive® treated defects showed partial closure by newly formed bone. The Polyactive® was encapsuled by a thin fibrous tissue layer. Ventral to the defect, dense fibrous tissue was present which was separated from the dura by the Polyactive® sheet in all cases. In some cases fibrous tissue was present between the implant capsule and the dura. In the fat graft group there were no signs of closure of the defect but most sites showed fibrous tissue at the edges of the graft, which was in 4 sites continous with the dura mater. Fibrosis and degeneration of the fat grafts were seen. All control defects showed partial closure by newly formed bone, and ventral to the defect extensive fibrous tissue, which was in 50% continous with the dura mater. Other sections showed loose connective tissue in contact with the dura mater. It is concluded that Polyactive® has a potential as a mechanical barrier in the prevention of adhesions between the dorsal spinal muscles and the dura mater. 相似文献
993.
994.
R. G. Grebenshchikov V. F. Popova A. K. Shirvinskaya 《Glass Physics and Chemistry》2003,29(5):479-483
The phase equilibria in the LnAlO3–CaTiO3 (Ln = Dy, Y, Lu) systems are investigated and their phase diagrams are constructed for the first time. The thermal stability of the prepared solid solutions with a perovskite structure is studied. 相似文献
995.
This paper deals with an economic comparison between costs and incomes in small wastewater treatment plants where the anaerobic co-digestion process of sludge and biowaste with energy recovery is operated. Plants in the size range 1,000-30,000 persons equivalent (pe) were considered in the study: typical costs, comprehensive of capital and operating costs, were in the range euro69-105 per person per year depending on the plant size: the smaller the size the higher the specific cost. The incomes deriving from taxes and fees for wastewater treatment are generally in the range euro36-54 per person per year and can only partially cover costs in small wastewater treatment plants. However, the co-treatment of biowaste and the use of produced energy for extra credits (green certificates) determine a clear improvement in the possible revenues from the plant. These were calculated to be euro23-25 per person per year; as a consequence the costs and incomes can be considered comparable for wastewater treatment plants (WWTPs) with size larger than 10,000 pe. Therefore, anaerobic co-digestion of biowaste and sludge can also be considered a sustainable solution for small wastewater treatment plants in rural areas where several different kinds of biowaste are available to enhance biogas production in anaerobic reactors. 相似文献
996.
997.
This note describes a method for measurement of isokinetic strength for prediction of manual materials handling capacity of individuals. The apparatus used in this methodology and measurement technique are illustrated in detail. 相似文献
998.
Using the data from vendors and open literature, we have constructed a preliminary cost model to predict the cost of liquid hydrogen (LH2) from water electrolysis. The model has been applied to two LH2 plants. Both have a production rate of 10 886 kg day−1. The first plant (Plant 1) consists of a tank-type electrolyzer and a liquefier and runs all day at the base-load (or equivalent base-load) power rate. The second (Plant 2) consists of a tank-type electrolyzer, a liquefier, a compressor, and storage vessels. The electrolyzer and the compressor shall run only during the off-peak hours at the off-peak power rate. However, the liquefier shall run all day at the base-load (or equivalent base-load) power rate. The costs of LH2 from both plants are presented. Unless the base-load power rate is high and the off-peak power rate is substantially low, Plant 1 appears to be economically more feasible than Plant 2. 相似文献
999.
F. Legay-Desesquelles B. Prunet-Foch 《International Journal of Heat and Mass Transfer》1985,28(12):2363-2370
The dynamical behaviour of laminar and turbulent boundary layers inside which a condensation phenomena exists, has been experimentally and numerically studied. The temperature difference between the exchange cold wall and the saturated air-steam flow at atmospheric pressure and moderate temperature (
0–90°C) does not exceed 20°C. Evaluation of the mass flux at the wall in such a case, allows the prediction of the ‘equivalent suction rate’ in a sucked boundary layer for the same external conditions but without any temperature difference. The comparison between the two phenomena reveals interesting similarities and some differences. 相似文献
1000.