Sorption of SPADNS azo dye on polystyrene anion exchangers: Equilibrium and kinetic studies

The sorption of SPANDS from aqueous solution onto the macroporous polystyrene anion exchangers of weakly basic Amberlyst A-21 and strongly basic Amberlyst A-29 in a batch method was studied. The effect of initial dye concentration and phase contact time was considered to evaluate the sorption capacity of anion exchangers. Equilibrium data were attempted by various adsorption isotherms including the Langmuir, Freundlich and Dubinin–Radushkevich (D–R) models. A comparison of kinetic models applied to the adsorption rate constants and equilibrium sorption capacities was made for the Lagergren first-order, pseudo second-order and Morris–Weber intraparticle diffusion kinetic models. The results showed that the adsorption isotherm is in the good agreement with the Langmuir equation and that the adsorption kinetics of SPADNS on both anion exchangers can be best described by the pseudo second-order model.     

Self-assembly of perylenediimide based semiconductor on polymer substrate

The continuous bi-layer composites consisting of top, ordered crystalline layer of perylenediimide derivative (2,9-di(pent-3-yl)-anthra[,1,9-def:6,5,10-d′e′f′]diisoquinoline-1,3,8,10-tetrone) - PTCDI-C5(3) and bottom poly(3-hexylthiophene-2,5-diyl) (P3HT) support were obtained from one solution, with a use of so called “two-step reticulate doping” method. Optical, atomic force and scanning electron microscopy images show that the top crystalline layer is made of relatively large, anisotropic domains composed of long, parallel crystals. The crystalline character of the surface layer of PTCDI-C5(3) grown on the P3HT film was confirmed by wide angle X-ray scattering measurements. Furthermore, the grazing-incidence angle X-ray diffraction experiments revealed that the self-assembly of PTCDI-C5(3) molecules on P3HT is dominated by π−π interaction between the conjugated perylene cores, and the stacks are parallel to the long axis of the crystals and to the polymer surface. The surface conductivity, measured along the long axis of the crystals was estimated to be ca. 2.4 10^− 8 Ω^− 1 square^− 1 at 285 K. Temperature dependence of the conductivity in the range 140-285 K reveal semiconductor-like behaviour with activation energy ca. 150 meV.     

Approximations to most powerful invariant tests for multinormality against some irregular alternatives

The problem of testing multinormality against some alternatives invariant with respect to a subgroup of affine transformations is studied. Using the Laplace expansion for integrals, some approximations to the most powerful invariant (MPI) tests are derived. The cases of bivariate exponential and bivariate uniform alternatives are studied in detail, whereas higher-dimensional extensions are only outlined. Those alternatives are irregular and need a special treatment because of the dependence of their supports on the unknown parameters. It is shown that likelihood ratio (LR) tests are asymptotically equivalent to the MPI tests. A Monte Carlo simulation study shows that the powers of the LR tests are very close to the powers of the MPI tests, even in small samples.     

Design of diffractive axicons producing uniform line images in Gaussian Schell-model illumination

We present a design method for diffractive axicons in spatially partially coherent Gaussian Schell-model illumination. The method of stationary phase applied to the Fresnel diffraction integral for on-axis intensity leads, on requiring a uniform axial image profile, to a second-order differential equation for the optimal axicon phase function. The first integral can be formally performed, and the phase function is subsequently obtained numerically. The correctness of the synthesized phase profiles is confirmed by numerical simulations using partially coherent Fresnel diffraction theory. The effects of input-beam spot size and coherence width are assessed, and influences of different forms of apodization, including asymmetric functions for narrow incident beams, in annular-aperture diffractive axicons are examined.     

Coexistence of polar and non-polar phases in ND4DSeO4 crystals

The temperature variation of the dielectric constant has been measured in ND₄DSeO₄ with over 90 mole percent of deuterium content. The grown crystals having P2₁2₁2₁ symmetry at room temperature, after being heated above 367 K, exhibit irreversible phase transition to I2 symmetry. At room temperature the phase I2 is not stable unlike for the crystal with lower degree of deuteration and the crystal returns to P2₁2₁2₁ phase during about 60 hours. A t 275 K occurs the phase transition to I1 but only from I2 phase.     

On symbolic dynamics of a chaotic second-order digital filter

This paper presents a contribution to the symbolic analysis of fractal patterns exhibited by a second-order digital filter with modular adder overflow characteristic. We use symbolic dynamics for the analysis of phenomena encountered in the system. We present several new results concerning the existence of admissible sequences for periodic orbits in the filter. an efficient computational algorithm based on rigorous mathematical results presented in the paper enabled us to calculate sequences with long periods, thus allowing deeper understanding of the underlying mechanisms of complex behaviour encountered in the filter.     

Influence of load-non-uniformity and eccentricity on the stability and load carrying capacity of orthotropic tubular columns of regular hexagonal cross-section

The paper contains an analysis of the influence of non-uniformity and eccentricity of compressive loads on global and local buckling, on interactive buckling, and on the load-carrying capacity of thin-walled columns. Isotropic and orthotropic tubular columns of regular hexagonal cross-section have been examined. Equilibrium equations for the first and the second order non-linear approximation have been solved using the asymptotic Byskov–Hutchinson method. Numerical calculations have been performed for numerous different loading modes of isotropic columns and also for several loading modes of orthotropic columns. The results are presented in diagrams with some conclusions.     

Noninertial particle transfer to the rotating disc under an external force field (laminar flow)

A theoretical analysis of fine particle deposition kinetics on the rotating disc surface is presented, in the case when short-range surface interactions occur (electrical double-layer and London-van der Waals force). The results of the numerical evaluation of the particle transfer Sh number are compared with those obtained by adopting the surface-force boundary layer approximation, in the case when primary and secondary energy minima occur It was shown that this approximation may be used for the Péclet number smaller than about 10^?2 and if the energy barrier is higher than 5 kT (provided that the secondary minimum is absent).     

Ion sputtering and its application to biomaterials

The main purpose of this article is to review the mechanisms of surface morphology and chemistry changes induced by ion sputtering of solids, and in so doing, discuss the influence of ion processing on surface morphology and chemical composition of biological implant materials. The influence of the ion bombardment induced morphological and chemical changes of biomaterials on mechanical properties and tissue response is also presented in the article.     

Calorimetric and emf studies on liquid Li-Sn alloys

By means of high temperature calorimetry the mixing enthalpies ΔH of liquid Li-Sn alloys have been measured; however, due to experimental problems they were determined only forx _Li = 0.01 to 0.5 andx _Li = 0.87 to 0.99. The range of temperatures studied was 691 to 938 K. High compound forming tendency in Li-Sn is reflected by a triangular-shaped relation for ΔH vs x _Li. The extrapolated maximum of this plot is about −40 kJ mol⁻¹ close to Li₄Sn. Using the concentration cell Bi(l)Li₃Bi(s)| LiF-LiCl|Li-Sn(l) the emf was measured as function of temperature (775 to 906 K) atx _Li = 0.1 to 0.603 enabling calculations of partial thermodynamic data for lithium in liquid Li-Sn solutions. Integral enthalpies calculated from partial enthalpies of lithium correspond well to the calorimetrically obtained integral mixing enthalpies in the concentration range where both emf and calorimetric data were obtained. The extrapolated maximum of ΔH from calorimetric studies and minimum of integral excess entropies from emf measurements correlate well with results of structure measurements and of other structure sensitive properties. All this experimental information indicates a maximum chemical short range order close to the composition Li₄Sn.