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181.
Transglutaminase (TGase) was separated from the culture broth of an isolated strain of Streptoverticillium mobaraense. The crude enzyme was prepared by centrifugation, ultrafiltration, precipitation by alcohol, centrifugation and freeze‐drying. The yield after these processes was 65–70%. Then the enzyme was purified to homogeneity by chromatography on CM‐cellulose and Sephadex G‐75 on which the yields were about 70% and 80%, respectively; the purified folds reached 2.5–4.7 and 1.08–2.06, respectively. The molecular weight of this TGase was 39,500–40,100 Da by gel filtration chromatography. Optimum enzyme activity was observed in the pH range of 5.0–7.0, and it was maintained stable at 20–40C. The optimal temperature and pH was 52C and 6.0, respectively. At 1 mM and 5 mM metal ion or inhibitors concentration, TGase activity was strongly inhibited by Zn2+ and NEM, and not affected obviously by Ba2+, Ca2+, Co2+, Cu2+, Fe2+, Fe3+, Mg2+, Mn2+, Na+ as well as PMSF and EDTA. The effects of these additions on this TGase were compared with those of other microbial TGases. 相似文献
182.
Total simulation model of the thermo-mechanical process in shape rolling of steel rods 总被引:2,自引:0,他引:2
The production of steel reinforcing bars for civil engineering is investigated by means of FEM-simulation. An integrated system for computing appropriate thermo-mechanical parameters of the rolling process is proposed. Generalized plane strain approach and coupled thermal-mechanical solution are applied. The microstructural model combines both the effect of the recrystallization mechanisms (static, dynamic and metadynamic) upon the austenite grain forming in hot rolling and that of phase transformation upon the final microstructure. The phases are created during interrupted below the temperature of martensite transition cooling. Thus a typical industrial process for thermo-mechanical strengthening of reinforcing bars, known as Tempcor-process is considered. Computational results are validated to experimental measured mechanical properties of the steel. By means of computer simulation the system can perform different solutions, giving the possibility to obtain a reasonable choice of different thermo-mechanical rolling conditions. 相似文献
183.
N. S. Postnikov 《Atomic Energy》2006,101(2):555-563
Methods are proposed for controlling temporal and space-time pulsed chaos in nuclear reactors where the control actions are
implemented as a result of external changes in the neutron multiplication coefficient or introducing external neutron sources.
Cases of periodically varying controlling actions and cases where the controlling actions are introduced at the moment the
neutron pulses start are examined. The cases of a singly connected regulation system, introducing control at each point of
a reactor, and multiconnected systems consisting of several regulators, introducing controlling actions in local regions of
the core, are examined. The case where control is introduced in the regions where neutrons bursts start is examined. The proposed
methods of control make it possible to excite or suppress pulsed stochastic regimes in reactors and change the regime characteristics
purposefully.
__________
Translated from Atomnaya énergiya, Vol. 101, No. 2, pp. 103–112, August, 2006. 相似文献
184.
The processes of optical spin orientation and spin relaxation of electrons are treated theoretically for semiconductor quantum wells, in which the spin splitting of the energy spectrum is comparable with the characteristic energy of charge carriers. The density matrix of photoexcited electrons at the instant of optical excitation is obtained in explicit form. A system of kinetic equations describing the behavior of the spin density matrix at an arbitrary relation between the average energy of charge carriers and the spin splitting is derived. It is demonstrated that, upon photoexcitation, a noticeable degree of orientation can be attained only in the pulse mode of operation, when the photoexcitation pulse duration is comparable with the period of spin precession in the field of spin splitting. It is shown that the total spin of the ensemble of electrons exhibits oscillations damping with time; the shape and damping time of the oscillations are sensitive to the parameters of photoexcitation and the spin splitting. 相似文献
185.
Zhiping Lin Xu L. Bose N.K. 《IEEE transactions on circuits and systems. I, Regular papers》2008,55(1):445-461
186.
The photoelectric parameters of silicon solar cells degraded under the action of 60Co gamma-radiation can be partly restored using an ultrasonic treatment (UST). The growth of the maximum output power of solar cells after the UST is related to a redistribution of the radiation defects and an increase in the homogeneity of a semiconductor crystal structure. 相似文献
187.
Mark N. Frolick 《Information Systems Management》2003,20(1):29-34
As more companies develop Web sites to show or sell their products online, there is a corresponding increase in attacks by those who want to maliciously damage a company's reputation or steal its resources. Securing a Web site against savvy hackers can be a daunting task for a firm's Webmaster. This article explores the threat of attack and the measures that a company can take to gain its highest level of defense. 相似文献
188.
S.N. Al-Refaie H.S.B. Elayyan 《Science, Measurement & Technology, IET》2007,1(3):133-137
The dispersion of potassium niobate (KNbO3) ceramics is analysed using the multiple-arc approach. This has revealed a high frequency arc that is unattainable by the Cole-Cole single arc analysis. The temperature dependence of the new arc is derived through the spread parameter of the relaxation distribution and interpreted in terms of the ferroelectric property of the KNbO3 ceramics. It is shown that the overall dispersion behaviour of the ceramics is mainly due to the existence of two distinctly different polarisation mechanisms. The arc approach has also provided an effective tool for network simulation of dispersion whereby the ceramics are modelled by nine parallel R-C branches over the frequency range 102-105 Hz used 相似文献
189.
V. N. Fetisov 《Automation and Remote Control》2004,65(4):594-602
Studies are made of a problem of constructing a robust system according to an averaged performance criterion of a stochastic control system. Cases of the parametric and the structural uncertainty are considered. The relation of the notion of the stochastic robustness to the classical definition of deterministic systems is shown. A comparative analysis of the suggested method of developing a robust system and some other approaches is carried out. 相似文献
190.
In this note, simple symmetric interval bounds on the singular values of a matrix based on its Gershgorin disks are proposed. This allows the Gershgorin theorem to be used not only to provide information about the location of the eigenvalues of a matrix but also its singular values. This is utilized for the proposition of a new design technique for singular value loop shaping based on the diagonal dominance methodology for design of linear multivariable plants. In return, this allows multiple-channel simply structured controllers to be designed with a view to robustness and to meet constraints and specifications on the behavior of its singular values. A design example is given demonstrating the effectiveness of this approach. 相似文献