化学自催化混沌反应模型中的耦合作用与混沌同步

选用混沌自催化反应作为子系统,构造了耦合自催化反应系统,研究了耦合变量、耦合系数对混沌动力学行为的影响,给出了不同耦合系数下系统的动力学特征,探讨了耦合作用机制.结果表明,耦合作用能明显地改变子系统的动力学行为,强化系统间的相关性.耦合后的混沌运动受到调整与抑制,耦合强度加大时,呈现出混沌运动轨线的周期化,耦合系数大于临界值,两子系统实现了完全的同步.不同变量的耦合时,影响最大的是第二种变量.对于三种物质均有耦合时,更容易出现混沌的抑制、运动状态的锁相与周期化和混沌的完全同步.     

运用系统动力学模型预测稀土战略储备规模

基于全球稀土资源的供需形势和中国稀土资源减少的趋势,运用系统动力学的模型来预测未来17年我国稀土资源储备量。选取了2000~2013的生产和消费数据,通过定量模拟计算中国稀土供需差波动系数,设计了稀土资源供需差波动范围分别为0%,20%的两个方案,模拟计算了两个方案的年储备量、累计储备量和储备量绝对值。方案一范围是(-0%,+0%),仿真预测出稀土未来17年累积储备量为720551 t,即战略储备规模达到720551 t,该方案下不论供需差发生如何波动,国家都会进行储备或释放调节;方案二范围是(-20%,+20%),预测出未来17年战略储备规模为461331 t,国家只需在这个范围外进行收储释放调节,从而调节市场供求,降低价格波动幅度。本文从不同供需差的波动系数来模拟计算储备量,目的是为国家相关部门在进行稀土储备决策时提供参考,可以根据我国经济景气状况和供需形势,以及稀土产业发展状况,进行不同规模的稀土储备。     

Control of stochastic spike motion in an excitable system via recycled noise

The control effect of recycled noise,generated by the superposition of a primary Gaussian noise source and a secondary source with a constant delay,has been studied in an excitable FitzHugh-Nagumo system.We mainly focus on the performance of noise-induced spike and coherence resonance in a parameter region sub-threshold to supercritical Hopf bifurcation.For fixed noise intensity,simulations show that the coherence(quantitatively measured by R,which is defined as the mean value of the spike interval time T n...     

Ordering in linear multipolar colloids driven by an external field

An approach to describe a linear multipolar colloid driven by an external field is developed by considering a colloid which in absence of the field is low structured and its coupling potential is axially symmetric. The equilibrium correlation of one component of the orientation tensor, self and collective, is computed up to linear order in density, which can be measured in an appropriate light scattering experiment. The self-correlation is written in terms of the second and fourth order parameters. All the equilibrium quantities are computed up to two-body level. This is done by assuming that the two-body equilibrium density function is given by the Boltzmann distribution, whereas the one-body density function is computed as solution of the equilibrium N-body Smoluchowski equation in the absence of hydrodynamic interactions. These observables, self and collective, as well as the second and fourth order parameters are able to describe when the colloid would evolve to an orientationally ordered phase. Explicit results for the dipole and quadrupole moments are reported. These results predict a different alignment with the external field for each moment. A relationship is provided between second and fourth order parameters, predicting the critical value of the external field in which the colloid goes into an axially symmetric phase.     

Localization in some discontinuously and randomly driven quantum systems

A charged particle moving in a harmonic, symmetric double well, a square well, or a Morse potential is allowed to interact with a discontinuously reversing spatially homogeneous electric field. Randomly reversing field is seen to cause localization in the quantum system. A critical reversal frequency is seen to exist below which no localization is manifested in the harmonic, double and square well. In the Morse case, there is dissociation if the upper limit of the interval between random kicks exceeds τ_max. © 2009 Wiley Periodicals, Inc. Int J Quantum Chem, 2010     

Quantum two-state dynamics driven by stationary non-Markovian discrete noise: Exact results

We consider the problem of stochastic averaging of a quantum two-state dynamics driven by non-Markovian, discrete noises of the continuous time random walk type (multistate renewal processes). The emphasis is put on the proper averaging over the stationary noise realizations corresponding, e.g., to a stationary environment. A two-state non-Markovian process with an arbitrary non-exponential distribution of residence times (RTDs) in its states with a finite mean residence time provides a paradigm. For the case of a two-state quantum relaxation caused by such a classical stochastic field we obtain the explicit exact, analytical expression for the averaged Laplace-transformed relaxation dynamics. In the limit of Markovian noise (implying an exponential RTD), all previously known results are recovered. We exemplify new more general results for the case of non-Markovian noise with a biexponential RTD. The averaged, real-time relaxation dynamics is obtained in this case by numerically exact solving of a resulting algebraic polynomial problem. Moreover, the case of manifest non-Markovian noise with an infinite range of temporal autocorrelation (which in principle is not accessible to any kind of perturbative treatment) is studied, both analytically (asymptotic long-time dynamics) and numerically (by a precise numerical inversion of the Laplace-transformed averaged quantum relaxation).     

Stochastic bi-resonance induced by external noise for Ca~(2+) signaling in hepatocytes

Noise-induced effects have been widely studied theoretically and experimentally in different fields of science, one of the most interesting phenomena is sto- chastic resonance (SR), and the traditional SR was confined to the single-peak form. However, in …     

The effects of quality-management systems on external quality-assessment performance in Finnish clinical chemistry laboratories

The effects of the implementation of quality-management systems and technological changes on the performance of 23 Finnish clinical chemistry laboratories were studied in external quality-assessment (EQA) schemes organized by Labquality Ltd., Finland, during 1993 to 1999. The investigated serum analytes were sodium, calcium, glucose, cholesterol, and alanine aminotransferase. According to the results, the improvements in analytical quality due to the quality programs were rather small. The effects to the proportions of satisfactory results in terms of precision and deviation from the target value were 5–15% (95% confidence intervals for the proportions ±1–5%). At the same time the laboratories were implementing quality-management systems new technology and characteristics of quality-control materials affected the EQA performance. Both improvements and deteriorations in analytical quality due to these factors were identified. The effects and their total outcomes differed substantially between the five analytes.     

Studies on external peak broadening in open-tubular liquid chromatography systems using the exponentially modified Gaussian model

Summary To optimize performance in Open-Tubular Liquid Chromatography (OTLC) it is necessary to minimize external peak broadening. To see how to reduce the external broadening an insight into its origins is required. This can be obtained by careful evaluation of experimental results with peak deconvolution methods based on the exponentially modified Gaussian model and comparison with theoretical predictions. It is assumed that the column response is Gaussian and that the responses due to the external effects are exponential.For peak deconvolution the algorithm described by Yau was used. Simulations were carried out to check the performance of the algorithm in calculating the standard deviation and the time constant. The effects of the presence of more than one time constant and of the number of data points and their position were investigated. The limits within which reliable results can be obtained are reported.Experimental results were obtained with laser-induced fluorescence and mass spectrometric detection. It is shown that the Yau algorithm can be used to obtain physically realistic estimates of the contribution to peak distortion in the various system components. By suitable design external effects can be reduced to the order of 1 nl and in some cases even lower limits can be reached.Part of this paper was presented at the 3rd Workshop on LC/MS and MS/MS, October, 24–26, 1984 in Montreux, Switzerland.     

New applications of cyclodextrins in electrically driven chromatographic systems: a review

The new achievements in the employment of native and derivatised cyclodextrins in various electrically driven chromatographic systems are compiled. Cyclodextrin-assisted separation techniques are concisely described and critically evaluated with special emphasis on the separation of enantiomer pairs.     

Switching the nature of catalytic centers in Pd/NHC systems by solvent effect driven non-classical R-NHC Coupling

A well-established oxidative addition of organic halides (R-X) to N-heterocyclic carbene (NHC) complexes of palladium(0) leads to formation of (NHC)(R)Pd^II(X)L species, the key intermediates in a large variety of synthetically useful cross-coupling reactions. Typical consideration of the cross-coupling catalytic cycle is based on the assumption of intrinsic stability of these species, where the subsequent steps involve coordination of the second reacting partner. Thus, high stability of the intermediate (NHC)(R)Pd^II(X)L species is usually taken for granted. In the present study it is discussed that such intermediates are prone to non-classical R-NHC intramolecular coupling process (R = Me, Ph, Vinyl, Ethynyl) that results in removal of NHC ligand and generation of another type of Pd catalytic system. DFT calculations (BP86, TPSS, PBE1PBE, B3LYP, M06, wB97X-D) clearly show that outcome of R-NHC coupling process is not only determined by chemical nature of the organic substituent R, but also strongly depends on the type of solvent. The reaction is most favorable in polar solvents, whereas the non-polar solvents render the products less stable. © 2019 Wiley Periodicals, Inc.     

Stochastic bi-resonance induced by external noise for Ca<Superscript>2+</Superscript> signaling in hepatocytes

The influence of external noise on intracellular Ca²⁺ oscillations dynamics in a single cell of rat hepatocytes is studied. The coherence of noise-induced intracellular Ca²⁺ oscillations reached two maxima for multiple external noise intensity, indicating the occurrence of external noise stochastic bi-resonance (SBR). This phenomenon is compared with our previous result that was induced by internal noise. Additionally, the deterministic bifurcation character of the system was also discussed.