Response to A. Carpinteri, B. Chiaia, P. Cornetti and S. Puzzi’s Comments on “Is the cause of size effect on structural strength fractal or energetic-statistical?”

Carpinteri et al.’s discussion is very welcome for it gives an opportunity to clarify long-running disagreements on the problem of size effect, important to several engineering fields. However, the discussion misinterprets many points of Ba ant and Yavari’s paper and attempts to raise new issues. This response presents recent experimental results contradicting applicability of Carpinteri’s “multifractal scaling law” (MFSL), and refutes the discussers’ arguments on their proposed concepts of “fractal mechanics”, on the statistical size effect, on the validity of mathematical derivation of MFSL and its asymptotic slope, and on various other aspects of scaling of quasibrittle failure.     

Sensitivity analysis of the stability problems of thin-walled structures

Analysing the system behaviour in relation to the input quantities it is often necessary to find out what quantities have the greatest effect on the studied output. The article shows the essential methods of applied sensitivity analysis. The objective of the paper is to analyse the influence of initial imperfections on the resistance of a member under axial compression. The analysis uses the Latin Hypercube Sampling simulation method (LHS) [Novák D, Teplý B, Shiraishi N. Sensitivity analysis of structures. In: Proc. of the fifth int. conference on civil and structural engineering computing. 1993. p. 201-07; Novák D, Lawanwisut W, Bucher C. Simulation of random fields based on orthogonal transformation of covariance matrix and Latin hypercube sampling. In: Proc. of int. conference on Monte Carlo simulation. 2000. p. 129-36] together with advanced models based on the nonlinear beam finite element method. The histograms of initial imperfections obtained by measurement [Melcher J, Kala Z, Holický M, Fajkus M, Rozlívka L. Design characteristics of structural steels based on statistical analysis of metallurgical products. Journal of Constructional Steel Research 2004;60:795-808] were considered.     

On the former constraints on Eastern European science: A case illustration of the AvH-fellowship accessability to scholars of the former Czechoslovakia

A survey is presented showing an above-average performance by candidates of several Central/Eastern European countries in the world-wide competition for the Alexander von Humboldt fellowships in the period before 1989, in spite of various administrative obstacles imposed by their countries. The success rate can be linked to the traditionally relatively high level of educational standards there. The administrative obstacles are illustrated by taking the former Czechoslovakia as an example, and also by way of a personal case study. Dedicated to the 10th anniversary of the 1988 denunciation of author’s personal letters.     

Quantum-Chemical Calculations of Model Systems of Interest in Fullerene-Based Superconductivity

Quantum-chemical computations can supply molecular details useful in understanding fullerene-based superconductivity. This paper deals with computations of three related systems: C₆₀ & Li, C₆₀ & CHCl₃ and C₆₀ & CHBr₃. Their molecular and electronic structures are discussed, especially charge distributions. Computations are also reported on a model system C^6– ₆₀.     

Black Phosphorus Nanoparticles Potentiate the Anticancer Effect of Oxaliplatin in Ovarian Cancer Cell Line

During the past few years, growing attention has been paid to black phosphorus (BP) and its unique optical, electrical, and catalytic properties. Furthermore, BP has proven to be biocompatible and biodegradable; qualities that present new opportunities for its utilization in the field of life sciences. However, despite all its suitable properties and applicability, its utilization in biomedicine is still in its infancy. This study reports on the synthesis of black phosphorus nanoparticles (BP NPs) and exploration of thier applicability in targeted drug delivery. BP NPs are loaded with platinum agents—cisplatin and oxaliplatin—and subjected to in vitro evaluation of targeted drug delivery. The BP NPs are not only able to load the investigated platinum derivatives on their surfaces, but also to transfer the therapeutic cargo to target specific tissue and to combine their effect with oxaliplatin, which leads to further potentiation of the anticancer effect.     

Continuous dialysis of hydrochloric acid and sodium chloride mixture

Using a two-compartment counter-current dialyzer with single passes, the simultaneous transport of hydrochloric acid and sodium chloride through an anion-exchange membrane Neosepta-AFN was studied at steady state. The diffusion dialysis process was quantified by four membrane mass transfer coefficients, which were correlated with the hydrochloric acid and sodium chloride concentrations in the feed. These characteristics were calculated from the experimental data on dialysis using a two-step procedure combining the numerical integration of the basic differential equations and a multivariable optimization. The second step of this procedure ensured the best agreement between the experimental and calculated data.     

Double-layer effects on the Cs ion transfer kinetics at the water/nitrobenzene interface

Double layer effects on the kinetics of the Cs⁺ ion transfer across the water/nitrobenzene interface were studied by an ac polarographic technique. Apparent kinetic parameters agree well with those reported previously. By applying the Frumkin-type correction based on the Gouy-Chapman theory, the non-linear Tafel plots were inferred indicating some dependence of the charge transfer coefficient on the interfacial potential difference. The latter effect can weaken the contribution of the diffuse-layer potentials to the apparent kinetic parameters, thereby accounting in part for the observed negligible change of these parameters with the aqueous electrolyte concentration. The Frumkin-type correction failure at low electrolyte concentrations and high surface charge densities is due to an overestimation of the diffuse/layer potential by the Gouy-Chapman theory, rather than due to the dynamic (Levich) effect of the diffuse double layer.     

Elastodynamic fields near running cracks by finite elements

A finite element method is developed for the computation of elastodynamic stress intensity factors at a rapidly moving crack tip. The method is restricted to bodies whose surfaces and two-material interfaces are either parallel to the direction of propagation or are sufficiently remote. The crack tip starts to move at the instant that it is struck by an incident wave. The finite element grid moves undeformed with the crack tip. The main result consists in the fact that the method of non-singular calibrated crack tip elements, in which the stress-intensity factor is determined from its statically calibrated ratio to the crack opening displacement in an adjacent node, is extended to dynamic problems with moving cracks, for both in-plane and anti-plane motions. The dependence of the calibration ratio on the crack tip velocity is established from previously developed analytical solutions for the near-tip displacement fields. Numerical results compare favorably with known analytical solutions for cracks moving in an infinite solid. The grid motion causes an apparent asymmetric additional damping matrix.     

Three-dimensional harmonic functions near termination or intersection of gradient singularity lines: A general numerical method

The harmonic function u near point 0 from which a single singularity ray emanates is assumed to be dominated by the term r^λρ^ρU where r = distance from point 0, p = known constant and ρ = chosen function of angular spherical coordinates θ, ?, for which a partial differential equation with boundary conditions, especially those at the singularity rays, and a variational principle, are derived. Because grad U is nonsingular, a 1numerical solution is possible, using, e.g. the finite difference or finite element methods. This reduces the problem to finding λ of the smallest real part satisfying the equation Det (A_ij) = 0 where A_ij is a large matrix whose coefficients depend linearly on μ = λ(λ + 1). In general λ and A_ij are complex. Solutions can be obtained either by reduction to a standard matrix eigenvalue problem for μ, or by successive conversions to nonhomogeneous linear equation systems. Computer studies have confirmed the feasibility of the method and have shown that highly accurate results can be obtained. Solutions for cracks and notches ending at a plane or conical surface, and for cracks ending obliquely at a halfspace surface, are presented. In these cases, λ is real and the singularity is always weaker (λ > p) than on the singularity line and may even disappear (λ > 1). Furthermore, elastic stresses under a wedge-shaped rigid sliding stamp or at a corner of a crack edge, and also harmonic functions at three-sided pyramidal notches, have been analyzed. Here λ < p was found to occur. A simple analytical solution for one class of special cases has also been found and used to check some of the numerical results.     

Shape Recovery Versus Breakup of Deformed Droplets in a Polymer Blend after Uniaxial Extension

The morphology development in a PS/LLDPE 95/5 blend after uniaxial elongation at constant stress is investigated with a special attention on the influence of the temperature on the competition between shape recovery and droplet breakup. The lower the recovery temperature, the finer the morphology obtained, i.e. fibril breakup was preferred against shape recovery. This is due to a stronger retraction of matrix molecules at higher temperatures in early stages of recovery which forces the fibrils to shrink back to less deformed states and thus suppresses the droplet breakup. The elasticity of the blend was found to increase with temperature although the elasticity of pure PS is temperature independent. This is explained as a consequence of the temperature dependence of the morphology development.