ICP-MS测定饮用水源中的钼、钴、铍、锑、镍、钡、钒、钛和铊等9种特定项目

采用电感耦合等离子体-质谱法（ICP-M S）测定水中的钼、钴、铍、锑、镍、钡、钒、钛、铊等9种元素。结果表明,各元素检出限0.005—0.07μg.L^-1,满足饮用水源分析要求;空白加标回收率94.2%—106.0%,相对标准偏差RSD〈4.0%,n=9）。样品加标回收率93.8%—110.0%,该方法高效、简便、线性范围宽,适用于饮用水源水质分析。     

微波萃取技术

微波萃取技术在有机污染物和有害金属分离的研究和应用方面出现了令人鼓舞的进展。微波萃取方法具有方便、快速、试剂消耗低、回收率高和可用水作萃取溶剂的优点。本综述介绍了微波萃取技术的原理、方法、设备和应用研究现状。     

Reacting polymers with highly correlated initial conditions

We propose and theoretically study an experiment designed to measure short-time polymer reaction kinetics in melts or dilute solutions. The photolysis of groups centrally located along chain backbones, one group per chain, creates pairs of spatially highly correlated macroradicals. We calculate time-dependent rate coefficients κ(t) governing their first-order recombination kinetics, which are novel on account of the far-from-equilibrium initial conditions. In dilute solutions (good solvents) reaction kinetics are intrinsically weak, despite the highly reactive radical groups involved. This leads to a generalised mean-field kinetics in which the rate of radical density decay - ∼S(t), where S(t) ∼t ^{- (1 + g/3)} is the equilibrium return probability for 2 reactive groups, given initial contact. Here g≈ 0.27 is the correlation hole exponent for self-avoiding chain ends. For times beyond the longest coil relaxation time τ, - ∼S(t) remains true, but center of gravity coil diffusion takes over with rms displacement of reactive groups x(t) ∼t ^1/2 and S(t) ∼ 1/x ³(t). At the shortest times ( t 10^-6s), recombination is inhibited due to spin selection rules and we find ∼tS(t). In melts, kinetics are intrinsically diffusion-controlled, leading to entirely different rate laws. During the regime limited by spin selection rules, the density of radicals decays linearly, n(0) - n(t) ∼t. At longer times the standard result - ∼d ³(t)/d (for randomly distributed ends) is replaced by ∼d2x ³(t)/d ² for these correlated initial conditions. The long-time behavior, t > τ, has the same scaling form in time as for dilute solutions. Received 18 May 2000     

The spatially one-dimensional relativistic Ornstein-Uhlenbeck process in an arbitrary inertial frame

The spatially one-dimensional relativistic Ornstein-Uhlenbeck process is studied in an arbitrary inertial reference frame. In particular, we derive directly from the stochastic equations of motion in an arbitrary inertial frame the transport equation for the distribution function of the diffusing particles in phase-space. We explain why this result is not trivial and has, at the very least, methodological interest. We also show that this result offers a conceptually new proof of the well-known fact that the relativistic one-particle distribution function in phase-space is a Lorentz scalar. Received 28 March 2000     

A mathematical model of external electrostatic field of a special collector for electrospinning of nanofibers

This article focuses on the analysis of electrostatic field generated by a special collector consisting of two parallel cylindrical conductors used for electrospinning. Computed values of critical electrical potential obtained by an analytical model are compared with measurements. Here we show that the gap distance between the special collector and a spinning electrode, i.e., a syringe needle, has not substantial effect on the critical potential if the special collector distance from the syringe needle is higher than the gap distance between cylindrical conductors. The presented model is a good analytical approximation of electric field created by the used special collector.     

Covariant Kolmogorov equation and entropy current for the relativistic Ornstein-Uhlenbeck process

The relativistic Ornstein-Uhlenbeck Process (ROUP), which is a toy-model of relativistic irreversible phenomena, is studied statistically in an explicitly covariant manner. An 8-dimensional phase space is introduced (four dimensions for space-time coordinates, and four dimensions for the 4-momentum coordinates), on which `extended' probability distributions are defined (the usual probability distribution is recovered as their restriction to the mass shell). An explicitly covariant Kolmogorov equation is derived for these `extended' probability distributions. The whole formalism is used to introduce a 4-current of conditional entropy and prove that the 4-divergence of this 4-current is always positive. This constitutes an H-theorem for the ROUP. Received 30 May 2001     

Network economics and optimal replacement of age-structured IT capital

The constructed hierarchical optimization model of vintage capital replacement takes into account network effects and the age-dependent technological structure of capital equipment. It involves the control of a network coalition choice, endogenous investments, capital structure, and capital lifetime. The qualitative analysis of the model shows how the lifetime and financial structure of the IT capital depends on technological change. These results are relevant for strategic management on a firm level. Provided numeric examples simulate the optimal lifetime of personal computers. This research is partially supported by the NATO grant CLG 982209.     

Hyper-symplectic structures on integrable systems

We prove that an integrable system over a symplectic manifold whose symplectic form is covariantly constant carries a natural hyper-symplectic structure. Moreover, a special Kähler structure is induced on the base manifold.     

The Sufficient and Necessary Conditions for the Space X in －Space（X，）to be a Cohomology Sphere

ＴｈｅＳｕｆｆｉｃｉｅｎｔａｎｄＮｅｃｅｓｓａｒｙＣｏｎｄｉｔｉｏｎｓｆｏｒｔｈｅＳｐａｃｅＸｉｎ－Ｓｐａｃｅ（Ｘ，）ｔｏｂｅａＣｏｈｏｍｏｌｏｇｙＳｐｈｅｒｅＺｈａｎｇＺｅｎｇｘｉ（张增喜）（ＤｅｐａｒｔｍｅｎｔｏｆＭａｔｈｅｍａｔｉｃｓ，Ｃａ...