Chemical markers’ fishing and knockout for holistic activity and interaction evaluation of the components in herbal medicines

A strategy based on chemical markers’ fishing and knockout has been proposed for holistic activity and interaction evaluation of the bioactive components in herbal medicines (HMs). It was devised to screen bioactive-compound group that represents the efficacy of HM, estimate the bioactivity contribution of each component and elucidate the interactions of multi-components. This strategy was accomplished through the following steps: (1) screen out the chemical markers (target peaks) in a HM fingerprint using online two-dimensional turbulent flow chromatography/liquid chromatography–mass spectrometry technique, (2) fish target peaks and knockout any interested peak, and (3) evaluate the bioactivities of fishing and knockout portions. After comparison of the bioactivities of samples containing different target peaks, the efficacy of target-peak group, bioactivity contribution of each compound, and the interactions of multi-components are elucidated. Using Acetylcholinesterase (AChE) and Bulbs of Lycoris radiata (L. Herit.) Herb. (BLR) as the experimental materials, four target peaks were screened out as the AChE binders. By target peaks’ fishing and knockout, combined with activity evaluation, we observed that the bioactivity of the four-peak mixture is similar with the global bioactivity of BLR extract, and there are significant suppressive actions among these four target peaks. These results indicate that this proposed strategy is a useful approach for holistic screening of bioactive-compound group and elucidation of the multi-component interactions in HM.     

反相流动注射化学发光法测定黄芩苷

在碱性介质中,K3Fe(CN)6氧化鲁米诺产生化学发光,黄芩苷对该体系化学发光具有强烈的抑制作用。利用该化学发光的抑制体系,结合反相流动注射技术,建立了测定黄酮类药物黄芩苷含量的新方法。在优化的条件下,黄芩苷浓度在1.0×10-8～1.0×10-7和3.0×10-7～4.0×10-6mol/L范围内与化学发光抑制强度ΔI呈良好的线性关系,检出限为1.0×10-9mol/L,对3.0×10-7mol/L的黄芩苷进行平行测定10次,得相对标准偏差(RSD)为1.7%。该方法可应用于银黄口服液中黄芩提取物(黄芩苷计)的含量测定。     

空气污染组分H2O和CO2对乙烯燃烧性能的影响(II)——反应机理和动力学模拟

超燃冲压发动机在高空工作时, 以高温高速纯净空气作氧化剂使燃料燃烧. 但在地面实验中, 高温空气往往通过燃烧加热方式获得, 会使空气中含有H2O和CO2等污染组分. 本文用活塞流反应器进行动力学模拟, 研究在不同初温、压强和燃气比的条件下, H2O和CO2污染组分对乙烯燃烧的温度、压强和点火延迟时间等特性的影响. 模拟结果表明: 乙烯在含有H2O/CO2污染物的空气中燃烧, 相比纯净的空气而言, H2O对乙烯的点火有一定的促进作用, 而CO2有一定的抑制作用; 空气中含H2O和CO2污染物使乙烯燃烧的平衡温度和压强降低, 在污染物浓度相同时, CO2引起的下降幅度比H2O的大. 模拟结果能较好地解释现有的实验现象.     

Heterogeneous versus bulk nucleation of lysozyme crystals

Heterogeneous (on‐glass) protein crystal nucleation was separated from the bulk one in systems of thin protein solution layers, confined between two glass plates of custom made quasi two‐dimensional all‐glass cells, as well as by applying forced protein solution flow. Two commercial samples of hen‐egg‐white lysozyme, Seikagaku and Sigma were used as model proteins. Applying the classical technique of separation in time of nucleation and growth stages with protein solution layers of thickness 0.05 cm we found that the on‐glass crystal nucleation prevailed highly with Seikagaku HEWL, while on the opposite, bulk nucleated crystals represented the main crystal fraction in Sigma solution. Also using 0.05 cm solution layers nucleation rates were measured separately for the on‐glass and bulk protein crystals. The process was investigated by varying solution layer thicknesses as well, from 0.05 down to 0.01, 0.0065 and 0.002 cm. Studying the influence of the forced protein solution flow on HEWL crystal nucleation the classical double‐pulse technique was modified by separating the nucleation and growth stages not only in time, but simultaneously also in place. In this case we found that the ratio of on‐glass formed crystal nuclei to bulk nuclei depended on the flow velocity, but in different manner with Seikagaku HEWL and Sigma HEWL. A plausible explanation of our experimental results is that the bulk crystal nucleation occurs on foreign surfaces as well, e.g. on rests of source biomaterial, which are always present in the protein solutions. Moreover, biomaterial seems to be more active nucleant than glass. (© 2010 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

气流对水面的冲击效果

通过实验研究了在气流冲击下水面的凹陷情况,并通过理论计算予以解释.结果表明凹陷的体积和深度主要与气流速度、玻璃管内径和玻璃管底部到水面上的距离有关的结论.     

On the Bergman representative coordinates

We study the set where the so-called Bergman representative coordinates (or Bergman functions) form an immersion. We provide an estimate of the size of a maximal geodesic ball with respect to the Bergman metric contained in this set. By concrete examples we show that these estimates are the best possible.     

共形平坦的Randers度量

本文研究共形平坦的Randers 度量的性质. 证明了具有数量旗曲率的共形平坦的Randers 度量都是局部射影平坦的, 并且给出了这类度量的分类结果. 本文还证明了不存在非平凡的共形平坦且具有近迷向S 曲率的Randers 度量.     

非紧L-凸度量空间中的一个新的不动点定理及其对极大极小不等式和鞍点的应用

In this paper,a new fixed point theorem is established in noncompact complete Lconvex metric spaces.As applications,a maximal element theorem,a minimax inequality and a saddle point theorem are obtained.     

Time-dependent and outflow boundary conditions for Dissipative Particle Dynamics

We propose a simple method to impose both no-slip boundary conditions at fluid-wall interfaces and at outflow boundaries in fully developed regions for Dissipative Particle Dynamics (DPD) fluid systems. The procedure to enforce the no-slip condition is based on a velocity-dependent shear force, which is a generalized force to represent the presence of the solid-wall particles and to maintain locally thermodynamic consistency. We show that this method can be implemented in both steady and time-dependent fluid systems and compare the DPD results with the continuum limit (Navier-Stokes) results. We also develop a force-adaptive method to impose the outflow boundary conditions for fully developed flow with unspecified outflow velocity profile or pressure value. We study flows over the backward-facing step and in idealized arterial bifurcations using a combination of the two new boundary methods with different flow rates. Finally, we explore the applicability of the outflow method in time-dependent flow systems. The outflow boundary method works well for systems with Womersley number of O(1), i.e., when the pressure and flowrate at the outflow are approximately in-phase.     

Sub-iteration leads to accuracy and stability enhancements of semi-implicit schemes for the Navier–Stokes equations

We present an iterative semi-implicit scheme for the incompressible Navier–Stokes equations, which is stable at CFL numbers well above the nominal limit. We have implemented this scheme in conjunction with spectral discretizations, which suffer from serious time step limitations at very high resolution. However, the approach we present is general and can be adopted with finite element and finite difference discretizations as well. Specifically, at each time level, the nonlinear convective term and the pressure boundary condition – both of which are treated explicitly in time – are updated using fixed-point iteration and Aitken relaxation. Eigenvalue analysis shows that this scheme is unconditionally stable for Stokes flows while numerical results suggest that the same is true for steady Navier–Stokes flows as well. This finding is also supported by error analysis that leads to the proper value of the relaxation parameter as a function of the flow parameters. In unsteady flows, second- and third-order temporal accuracy is obtained for the velocity field at CFL number 5–14 using analytical solutions. Systematic accuracy, stability, and cost comparisons are presented against the standard semi-implicit method and a recently proposed fully-implicit scheme that does not require Newton’s iterations. In addition to its enhanced accuracy and stability, the proposed method requires the solution of symmetric only linear systems for which very effective preconditioners exist unlike the fully-implicit schemes.