Some features of hydrolysis of organic and inorganic substrates by Escherichia coli inorganic pyrophosphatase in the presence of various activator cations

The kinetics of hydrolysis of the inorganic (PP_i) and organic (ATP) substrates by Escherichia coli inorganic pyrophosphatase (PPase) and its mutant forms with Asp42 replaced by Ala, Asn, or Glu was studied. The Mn²⁺ or Zn²⁺ ions were used as activators of the enzymatic reaction. The kinetic parameters of hydrolysis were determined. The inhibitory effect of these cations on substrate hydrolysis was investigated. The dissociation constants were calculated for the Mn²⁺- and Zn²⁺-binding activator and inhibitor subsites of E. coli PPase. The observed hydrolysis rate of PP_i increases in the series Zn²⁺ < Mn²⁺ < Mg²⁺, whereas the potential efficiency of these cations decreases in this series. Hydrolysis of ATP by E. coli PPase occurs only in the presence of Mn²⁺. The reasons for the observed differences in the substrate specificity of the enzyme are discussed.     

常见随机数发生器的缺陷及组合随机数发生器的理论与实践

随机数是蒙特卡罗 Monte- Carlo方法的基础 .本文首先指出线性同余法和移位寄存器 (亦称 Tausworthe)序列等常见随机数发生器的一些缺陷 ;在此基础上介绍可产生具有优良品质随机数的组合发生器。本文既介绍理论结果 ,用以证明组合发生器确实可以优于单个发生器 ;也具体构造了几个可供实际使用的组合随机数发生器。严格而全面的统计检验表明 ,它们可以产生具有优良品质的随机数     

Comparison theorem on Cartan-Hartogs domain of the first type

In this paper the holomorphic sectional curvature under invariant Kahler metrics on Cartan-Hartogs domain of the first type are given in explicit forms. In the meantime, we construct an invariant Kahler metric, which is not less than Bergman metric such that its holomorphic sectional curvature is bounded from above by a negative constant. Hence we obtain the comparison theorem for the Bergman metric and Kobayashi metric on Cartan-Hartogs domain of the first type.     

Elliptic operators with infinite-dimensional state spaces

Motivated by applications to problems from physics, we study elliptic operators with operator-valued coefficients acting on Banach-space-valued distributions. After giving a definition of ellipticity, normal ellipticity in particular, generalizing the classical concepts, we show that normally elliptic operators are negative generators of analytic semigroups on for 1 and on and , as well as on all Besov spaces of E-valued distributions on , where E is any Banach space. This is true under minimal regularity assumptions for the coefficients, thanks to a point-wise multiplier theorem for E-valued distributions proven in the appendix. Received August 23, 2000; accepted December 12, 2000.     

On Variance and Covariance for Bounded Linear Operators

In this paper we initiate a study of covariance and variance for two operators on a Hilbert space, proving that the c-v (covariance-variance) inequality holds, which is equivalent to the Cauchy-Schwarz inequality. As for applications of the c-v inequality we prove uniformly the Bernstein-type inequalities and equalities, and show the generalized Heinz-Kato-Furuta-type inequalities and equalities, from which a generalization and sharpening of Reid's inequality is obtained. We show that every operator can be expressed as a p-hyponormal-type, and a hyponormal-type operator. Finally, some new characterizations of the Furuta inequality are given. Received April 9, 2000, Revised July 20, 2000, Accepted August 8, 2000     

Austempering Transformation Kinetics of Compacted Graphite Cast Irons Obtained by Mössbauer Spectroscopy

Mössbauer spectroscopy has been applied systematically to study the processes occurring during the Stage I of the austempering transformation of compacted graphite cast irons at temperatures from 573 to 673 K for two Mn concentrations. The kinetics of transformation (γ→α _Fe +γ _hc ) was followed determining the dependence of the high-carbon austenite percentage on austempering time for different austempering temperatures and Mn contents. The evolution of the C concentration and the total amount of C incorporated into high-carbon austenite were also monitored. The results are compared with those of other morphologies and discussed in the frame of Johnson-Mehl's and diffusion models.     

Mechanochemical Reactions in Fe2O3–M (M: Al, Ti)

The production of metal–ceramic nanodispersion by mechanical milling of powders through the displacement reaction Fe₂O₃+M→Fe+M-oxide (with M: Al, Ti) was studied. The reaction progress with milling time was followed by recording the temperature and pressure during the process. The samples were characterized by X-ray diffraction and Mössbauer spectroscopy at the intermediate and final stages. In both cases self-sustained reactions were observed with different activation times. The results confirm that mechanical work at room temperature yields the reduction of hematite by Ti and Al. The final oxides were identified as Ti₂O₃ and Al₂O₃, respectively. The dependence of the intermediate and final stages on the milling conditions and the starting composition will be discussed.     

具有物理背景的高维Painlevé可积模型

提出了一种求解任意维数非线性模型的“M?bious”变换下不变的渐进展开方法,并可同时获得许多新的与原模型有着相同维数的Painlevé可积模型.取(2+1)维KdV-Burgers(KdVB)方程和Kadomtsev-Petviashvili(KP)方程为具体例子,获得了一些新的具有Painlevé性质的高维“M?bious”变换下不变的方程及原模型的近似解.在某些特殊情况下,某些近似解可以成为精确解 关键词： 高维可积模型 “M?bious”不变 近似方法     

Depopulation of the Jπ = 9- isomer in 180Ta to the Jπ = 1+ ground state by Coulomb excitation

In-beam Coulomb excitation of the exotic odd-odd nucleus ¹⁸⁰Ta has been studied by using a ¹³⁶Xe beam and a setup consisting of five EUROBALL CLUSTER detectors and the Darmstadt-Heidelberg Crystal Ball array. Spectroscopic information on the extremely rare ¹⁸⁰Ta is obtained from the comparison between an enriched (3.6±0.3% ¹⁸⁰Ta) and a natural tantalum target. Possible evidence for a depopulation from the long-lived high-spin J ^π = 9^- isomer to the short-lived J ^π = 1⁺ ground state is searched for by different methods. The decay of low-K bandheads, which are nanosecond isomers, towards the ground-state band can be demonstrated in delayed spectroscopy. A γγ coincidence analysis provides indications of K = 5 in-band transitions. Finally, when the Crystal Ball is used as an energy and γ multiplicity filter, signals of decay into the K = 0 band are observed. Received: 23 January 2001 / Accepted: 8 February 2001     

Rotational bands in the near-drip-line nucleus 128Nd

The even-even nucleus ¹²⁸Nd was studied via in-beam γ-ray spectroscopy using the ⁴⁰Ca + ⁸²Mo reaction at 190 MeV. Two new bands were observed besides the yrast one, that has been extended up to spin 34⁺. Configurations were assigned to the three bands by analysing their rotational properties and by comparison with the neighboring even-even nuclei. Received: 18 July 2001 / Accepted: 25 October 2001