(Q)SAR modelling of nanomaterial toxicity: A critical review

There is increasing recognition that some nanomaterials may pose a risk to human health and the environment. Moreover, the industrial use of the novel engineered nanomaterials (ENMs) increases at a higher rate than data generation for hazard assessment; consequently, many of them remain untested. The large number of nanomaterials and their variants (e.g., different sizes and coatings) requiring testing and the ethical pressure towards nonanimal testing means that in a first instance, expensive animal bioassays are precluded, and the use of (quantitative) structure–activity relationships ((Q)SARs) models as an alternative source of (screening) hazard information should be explored. (Q)SAR modelling can be applied to contribute towards filling important knowledge gaps by making best use of existing data, prioritizing the physicochemical parameters driving toxicity, and providing practical solutions for the risk assessment problems caused by the diversity of ENMs. This paper covers the core components required for successful application of (Q)SAR methods to ENM toxicity prediction, summarizes the published nano-(Q)SAR studies, and outlines the challenges ahead for nano-(Q)SAR modelling. It provides a critical review of (1) the present availability of ENM characterization/toxicity data, (2) the characterization of nanostructures that meet the requirements for (Q)SAR analysis, (3) published nano-(Q)SAR studies and their limitations, (4) in silico tools for (Q)SAR screening of nanotoxicity, and (5) prospective directions for the development of nano-(Q)SAR models.     

Real-life experiences with flow-induced vibration

A number of occurrences of flow-induced vibration in the power-generating industry are presented, many in nuclear plant where all incidents/problems have to be reported. Specifically, cases of (i) vortex-induced vibration (VIV), (ii) fluidelastic instability in cylinder arrays, (iii) axial and (iv) annular-flow-induced vibration, (v) leakage-flow instability and (vi) shell-type ovalling are discussed. For items (ii), (v) and (vi), a few words on the mechanisms underlying the vibration are provided.     

A review: Acoustic emission,a tool for composite-materials studies

The technique of acoustic emission has two broad applications areas. The first is nondestructive evaluation. The second is as a tool in studies or research which are not fundamentally directed towards acoustic emission. It is this second application with which we are concerned here. Acoustic emission is a very useful tool in this role because of its high sensitivity, real-time capability, volume-monitoring approach, and sensitivity to any process or mechanism which generates sound waves. This paper presents a comprehensive review of areas where acoustic emission (AE) has been used for materials studies on composite materials. The following fields, among others, will be covered: (1) time-dependent composite properties, (2) impact studies, (3) correlation of AE with stress level, (4) application to matrix cure studies, (5) relationship of AE-detected damage to other measures of damage, (6) studies of the effects of matrix material, (7) application to differences in second phase, (8) interface studies, (9) AE and dimensional stability, (10) AE applied to orientation studies, and (11) environmental effects. This review will emphasize the roles that AE can play as a tool for the materials scientist: (1) discovery of damage mechanisms, (2) characterization of damage progression with increasing time or stress, (3) optimization of fabrication variables, and (4) reduction in the numbers of test specimens required in various studies.     

On the boundedness and the stability properties of solution of certain fourth order differential equations

This paper investigates equation(1)in two cases:(i)P≡0,(ii)P(≠O)satisfies|P(t,x,y,z,ω)|≤(A |y| |z| |ω|)q(t),where q(t)is a nonnegative function of t.For case(i)the asymptotic stability in the large of the trivial solution x=0 is investigatedand for case(ii)the boundedness result is obtained for solutions of equation(1).Theseresults improve and include several well-known results.     

Scaling mixing during miscible displacement in heterogeneous porous media

This paper discusses scaling of mixing during miscible flow in heterogeneous porous media. In large field systems dispersivity appears to depend on system length due to heterogeneities. Three types of scaling are discussed to investigate the heterogeneous effects. Dimensional analysis of mixing during flow through geometerically scaled heterogeneous models is illustrated using measured dispersion. Fractal analysis of mixing in statistically scaled heterogeneous porous media is discussed. Analog scaling of pressure transients in heterogeneous porous media is suggested as an in-situ method of estimating dispersion.Notation L Length - M mass - t time, (1) indicates dimensionless - a dispersivity (L) - V local velocity (L/t) - c concentration (l). - v velocity (L/t) - C₁ fluid compressibility (Lt²/M) - v time averaged velocity (LJt) - D dispersion VA) - W width (L) - D fractional dimension (1) - x coordinate (L) - d Euclidean dimension (1) - Y Y=In \-k (l) - \-d average particle size (L) - y coordinate (L) - g acceleration due to gravity (L/t2) - _c fractal cutoff (L) - \-k average permeability (L2) - viscosity (LM/t) - L length (L) - porosity (1) - L correlation scale (1/L) - density (N/L³) - N Number of sites (l) - ² variance (dimension depends on variable) - p pressure (W/t²L) - spectral exponent (l) - [R] randomnumber (1) - r radius (L) - t time (t)     

Synthesis of submicron-sized composite particles with unique morphology by emulsifier-free seeded emulsion copolymerization

Polystyrene （PSt） microspheres with diameter of 375 nm to be used as the seeds for seeded emulsion polymerization were prepared via emulsion polymerization using potassium persulfate （KPS） as initiator in ethanol-water mixed solvents. Emulsifier-free seeded emulsion copolymerization of styrene （St） with acrylonitrile （AN） was carried out in the presence of poly（ethylene glycol） monomethoxymonomethacrylate （PEGm） macromonomer as reactive stabilizer and 2,2＇-azobisisobutyronitrile （AIBN） as initiator to obtain submicron-sized PEGm graft poly（styrene-coacrylonitrile） （PEGm-g-PSAN） composite particles with unique morphology. Scanning electron microscopy （SEM） indicated that St and AN together contributed to forming the unusual morphology. The concentration of St and AN, total monomer concentration, initiator type and the monomer adding method remarkably affected the morphology of the composite polymer particles.     

(Q)SAR modelling of nanomaterial toxicity:A critical review

There is increasing recognition that some nanomaterials may pose a risk to human health and the environment.Moreover,the industrial use of the novel engineered nanomaterials(ENMs) increases at a higher rate than data generation for hazard assessment;consequently,many of them remain untested.The large number of nanomaterials and their variants(e.g.,different sizes and coatings) requiring testing and the ethical pressure towards nonanimal testing means that in a first instance,expensive animal bioassays are precluded,and the use of(quantitative) structure-activity relationships((Q)SARs) models as an alternative source of(screening) hazard information should be explored.(Q)SAR modelling can be applied to contribute towards filling important knowledge gaps by making best use of existing data,prioritizing the physicochemical parameters driving toxicity,and providing practical solutions for the risk assessment problems caused by the diversity of ENMs.This paper covers the core components required for successful application of(Q)SAR methods to ENM toxicity prediction,summarizes the published nano-(Q)SAR studies,and outlines the challenges ahead for nano-(Q)SAR modelling.It provides a critical review of(1) the present availability of ENM characterization/toxicity data,(2) the characterization of nanostructures that meet the requirements for(Q)SAR analysis,(3) published nano-(Q)SAR studies and their limitations,(4)in silico tools for(Q)SAR screening of nanotoxicity,and(5) prospective directions for the development of nano-(Q)SAR models.     

超细氧化铁对TNT炸药爆热的影响

利用均匀沉淀法制备得到纳米级氧化铁,研究了不同粒度的氧化铁颗粒对TNT炸药爆热的影响。结果表明:随着氧化铁颗粒度的减小,它与TNT组成的混合炸药的爆热得到有效的提高。     

流变学研究的若干问题

本文综述了1988年8月第10届国际流变学会议部分大会邀请报告及分组报告的下列几个领域内容:①分子动力学;②光学流变测量;⑧血液的动态测量;④数值仿真;⑤钻探油井;⑥强化采油;⑦减阻;⑧聚合物挤压成形加工;⑨食品流变学.     

Synthesis of submicron-sized composite particles with unique morphology by emulsifier-free seeded emulsion copolymerization

Polystyrene (PSt) microspheres with diameter of 375 nm to be used as the seeds for seeded emulsion polymerization were prepared via emulsion polymerization using potassium persulfate (KPS) as initiator in ethanol-water mixed solvents.Emulsifier-free seeded emulsion copolymerization of styrene (St) with acrylonitrile (AN) was carried out in the presence of poly(ethylene glycol) monomethoxymonomethacrylate (PEGm)macromonomer as reactive stabilizer and 2,2'-azobisisobutyronitrile (AIBN) as initiator to obtain submicron-sized PEGm graft poly(styrene-co-acrylonitrile) (PEGm-g-PSAN) composite particles with unique morphology.Scanning electron microscopy (SEM) indicated that St and AN together contributed to forming the unusual morphology.The concentration of St and AN,total monomer concentration,initiator type and the monomer adding method remarkably affected the morphology of the composite polymer particles.     

Vapour-diffusion assisted growth of oriented or-cobalt hydroxide thin films

Layered ,α-cobalt hydroxides Co(OH) 1.65Cl0.35.0.5H2O (1), Co(OH) 1.75(NO3)0.25.0.1H2O (2) with unique macro- and microscale morphologies have been synthesised by a low temperature, ammonia-controlled vapour-diffusion method. The materials have thin film morphologies and were characterized by X-ray powder diffraction (XRD) and field emission scanning electron microscopy (FESEM).     

国内非牛顿流体力学进展

非牛顿流体;;本构方程;;流变测量;;流动稳定性;;收缩流动;;聚合物加工;;石油工业;;生物流体力学     

An inverse heat conduction problem of estimating boundary fluxes in an irregular domain with conjugate gradient method

A Boundary Element Method (BEM)-based inverse algorithm utilizing the iterative regularization method, i.e. the Conjugate Gradient Method (CGM), is used to solve the Inverse Heat Conduction Problem (IHCP) of estimating the unknown transient boundary heat flux in a multi-dimensional domain with arbitrary geometry. Results show that the advantages of applying the CGM in the inverse calculations lie in that the major difficulties in (i) choosing a suitable quadratic norm, (ii) determining a proper regularization order and (iii) determining the optimal smoothing (or regularization) coefficient in the conventional Regularization Method (RM) are avoided. Received on 27 October 1997     

粘性土(红土)中游离氧化铁含量对其工程地质性质的影响

通过试验, 本文就游离氧化铁在粘性土尤其是红土中富积含量的变化对土体工程地质性质产生的影响及其规律性做了初步研究。     

结构工程科学中若干计算结构力学问题的研究展望

本文概述了计算结构力学的形成过程,评述了结构工程科学中以下７个需要重点研究的计算结构力学问题:数值方法基本理论问题（误差估计理论、网格自适应加密技术、多变量有限元理论和半解析数值方法）、工程结构优化设计、结构施工力学、计算机数值模拟和仿真技术、本构模型、计算机技术新发展的影响、计算机辅助设计。并论述了数值计算、理论和试验这三者之间相互依赖、相互促进、相互交叉又相互制约的辩证关系。      

Computerized Developments in Design,Generation, Simulation of Meshing,and Stress Analysis of Gear Drives

The paper represents new computerized developments in design, generation, simulation of meshing, and stress analysis of gear drives. The main contents of the paper are: (i) application of a predesigned parabolic function of transmission errors for reduction of noise, (ii) computerized simulation of noise caused by transmission errors, (iii) modification of the basic algorithm of tooth contact analysis, and (iv) application of approaches developed for enhanced design and simulation of meshing of the following gear drives: (a) spiral bevel gear drives, (b) face-gear drives (including an approach for grinding), and (c) modified helical gear drives. The developed theory is illustrated with numerical examples.     

欧拉流体力学数值方法中的界面计算

本文所提算法适用于二维和三维多介质流体力学两步欧拉数值方法中输运计算的混合网格(包括自由面网格)界面处理。在一个混合网格中，界面被近似地看作直线(二维)或平面(三维)。整个方法分为三步：(1)第一步，用混合网格周围的八个网格的介质面积份额(二维)或二十六个网格的介质体积份额(三维)确定界面的法线方向；第二步，用混合网格的本身的介质面积份额(二维)或体积份额(三维)确定界面的方程(位置)；第三步，用此直线方程求出通过网格边界的流以及下一时刻网格的面积份额(二维)或体积份额(三维)。最后给出了用此方法所做的一些数值计算及与SLIC算法的比较。     

An analytical model for the critical shell thickness in core/shell nanowires based on crystallographic slip

Employing crystal plasticity theory and micromechanics inclusion theory, we developed a full-strain relaxation model under isotropic assumption of materials properties to predict the dependence of the critical shell thickness (CST) for defect-free core/shell nanowires (NWs) on their growth direction. Unlike prior models, we consider three important factors in the energetic analysis (1) the self-energy of a dislocation loop in a finite domain, (2) the three-dimensional mismatch strains that develop in core/shell NWs (axial, radial and tangential directions) as a result of the finite NW geometry and the lattice mismatch between the core and shell materials, and (3) the three-dimensional plastic strains from misfit dislocations that nucleate to relax the mismatch strains. With these, the full-relaxation model is able to reveal that (i) the variation of the CST with growth direction depends on the core radius, (ii) misfit dislocations will not nucleate when the core radius falls below a critical value, (iii) the CST tends to a constant as the core radius increases, and (iv) the CST predicted by prior uniaxial-strain relaxation models is a lower bound.     

Proper solutions and limit boundary value problems of nonlinear second-order systems of differential equations

For the system of differential equations x=r(t)y,y=-a(t)f(x)g(y) where a(t)>0, r(t)>0 for t≥t; f(x) >0 and is decreasing for x>0 g(y)>0, we give necessary and sufficient condition of the existence of a proper solution, a bounded proper solution or solutions of two kinds of boundary value problems on an infinite interval [c,∞] c≥t_g. Several examples are given to illustrate the conditions of these results.     

Experimental Study of the Bottom Structure Effect on the Damping of Standing Surface Waves in a Rectangular Vessel

The damping coefficient is estimated for standing surface waves in a rectangular vessel: (1) with a smooth horizontal rigid bottom, (2) with developed sandy bottom structures, (3) with a profiled rigid bottom, and with thin bottom layers of (4) fine-grained sand and (5) glass spheres. The results obtained are compared with available theoretical models.