Investigation of the tensile properties of “epoxy resin‐monomer” systems using cationic UV‐crosslinkable blends

The compatibility of cycloaliphatic and aromatic multifunctional epoxides with several epoxide resins allows the development of a wide range of cationic radiation‐curable formulations. The influence of different “epoxide resin‐monomer” systems UV‐cured in the presence of suitable cationic photoinitiators on the resulting physicochemical film properties was studied, and the results are stated. Copyright © 2004 John Wiley & Sons, Ltd.     

Some analytical semigroups occurring in probability theory

One-parameter semigroups occurring in operator-limit distributions are investigated. The topological-algebraic background of the relevant monoids is discussed and Lie semigroup theory is applied to the Urbanik Decomposability Semigroup.     

Heuristic methods for evolutionary computation techniques

Evolutionary computation techniques, which are based on a powerful principle of evolution—survival of the fittest, constitute an interesting category of heuristic search. In other words, evolutionary techniques are stochastic algorithms whose search methods model some natural phenomena: genetic inheritance and Darwinian strife for survival.Any evolutionary algorithm applied to a particular problem must address the issue of genetic representation of solutions to the problem and genetic operators that would alter the genetic composition of offspring during the reproduction process. However, additional heuristics should be incorporated in the algorithm as well; some of these heuristic rules provide guidelines for evaluating (feasible and infeasible) individuals in the population. This paper surveys such heuristics and discusses their merits and drawbacks.An abridged version of this paper appears in the volume entitled META-HEURISTICS: Theory & Application, edited by Ibrahim H. Osman and James P. Kelly, to be published by Kluwer Academic Publishers in March 1996.     

On three-dimensional conformally flat quasi-Sasakian manifolds

LetM be a 3-dimensional quasi-Sasakian manifold. On such a manifold, the so-called structure function is defined. With the help of this function, we find necessary and sufficient conditions forM to be conformally flat. Next it is proved that ifM is additionally conformally flat with = const., then (a)M is locally a product ofR and a 2-dimensional Kählerian space of constant Gauss curvature (the cosymplectic case), or (b)M is of constant positive curvature (the non cosymplectic case; here the quasi-Sasakian structure is homothetic to a Sasakian structure). An example of a 3-dimensional quasi-Sasakian structure being conformally flat with nonconstant structure function is also described. For conformally flat quasi-Sasakian manifolds of higher dimensions see [O₁]     

Jauch-Piron system of imprimitivities for phonons. I. Localizability in discrete space

This paper is devoted to a discussion of the notion of localizability for phonons, i.e., quasiparticles arising from the harmonic vibrations of a system ofn atoms bound to one another by elastic forces. The natural tools for the analysis of localizability are the projection operatorsÊ() acting on the Hilbert space of one-phonon states, where is an arbitrary subset of the set that consists ofn vectors specifying the equilibrium positions ofn atoms. The expectation value ofÊ() is the probability that the phonon belongs to the atoms whose equilibrium positions are characterized by the elements of . For a strongly localizable phonon all of the projection operatorsÊ() commute with one another, whereas in the case of a weakly localizable phonon the operatorsÊ(₁) andÊ(₂) do not commute when ₁ and ₂ overlap. With the aid of the Jauch-Piron quantum theory of localization in space, the present paper describes the method of obtainingÊ() and also shows that if in the system ofn atoms there exist normal modes of zero frequency, then the phonon is only weakly localizable. Given the explicit expression forÊ(), one can define the number-of-phonons operator as well as the quasiparticle analogue (given in a companion paper) of the Wigner distribution function.     

Structure of colloid silica determined by viscosity measurements

The viscosity of nanosized colloid silica suspensions, used as binders in the investment casting, was determined as a function of their weight fraction reaching 52%. A new capillary viscometer was used whose construction eliminated sedimentation effects. The experiments have been carried out at fixed pH 10.0 and controlled ionic strength. It was found that for a low silica concentration range (weight fraction below 5%) the suspension viscosity increased more rapidly than the Einstein theory predicts. This anomalous behavior could not be explained in terms of the primary electroviscous effect predicted to be a few orders of magnitude smaller as observed. This discrepancy was accounted for by postulating a fuzzy, gel-like structure of colloid silicas used in our experiments. Hence, the apparent hydrodynamic radius of silica particles in aqueous suspensions was found to be larger than the primary particle size in accordance with previous observations. Based on this postulate, an apparent density of the silica sols was found to be 1.32-1.37 g/cm(3) instead of 2.2-2.32 g/cm(3) as determined from the suspension dilution method. This behavior was interpreted in terms of the core/shell model with high shell porosity, reaching 85%. Similarly, for higher concentration ranges, silica viscosity increased more rapidly with increased sol concentration than predicted by the Batchelor model derived for hard particles. The deviation was attributed to the secondary electroviscous effect stemming from the electrostatic interactions among silica particles in sheared suspensions. This effect has quantitatively been interpreted in terms of Russel's theory. On the other hand, for the high concentration range the experimental results were well accounted for by the Dougherty-Krieger model. By exploiting our experimental findings a sensitive method of determining the structure and apparent density of silica sols in aqueous media was proposed.     

Quecksilber(II)-Titrationen mit Variaminblau als Redoxindicator

Zusammenfassung Es wird eine volumetrische Methode zur Bestimmung von Cyanid- und Quecksilber(II)-ionen mit titrierter Quecksilber(II)-nitratlösung gegen Variaminblau als Indicator beschrieben. Das Verfahren liefert genaue, wenig streuende Werte.Vorgetragen auf der III. Arbeitstagung für analytische Chemie in Prag am 1. September 1959.     

Structural changes in the monomeric despentapeptide (B30-B26) insulin crystal

Insulin modified by the removal of its 5 B chain C terminal residues is monomeric but remains substantially potent. The crystal structures of the beef and insulin (dpi) with two molecules in the asymmetric unit has been determined by x-ray analysis. The 3-dimensional structure ofdpi proves to be generally similar to that of native molecule in 2Zn insulin. More detailed comparison reveals that the slight differences in the two independent molecules of beefdpi are distributed uniformly throughout the structure in contrast to insulin in 2Zn insulin, where the structural changes are concentrated in specific regions. The loss of symmetry in thedpi crystal appears to be the inability of the A9 serine to pack effectively in the C2 cell. The efficient packing of the sheepdpi molecule whose crystal structure has also been determined and where A9 is glycine supports this conclusion.     

Development in the area of UV-crosslinkable solvent-based pressure-sensitive adhesives with excellent shrinkage resistance

Solvent-based UV-crosslinkable pressure-sensitive adhesives (PSA) present a new class of products that offers the potential to produce a novel generation of ultraviolet cured self-adhesive products with excellent shrinkage resistance. A variety of solvent-based pressure-sensitive adhesives were prepared by synthesis in ethyl acetate with solid content on 50 wt.% with 2-ethylhexyl acrylate, methyl acrylate, acrylic acid, N-vinyl caprolactam and unsaturated photoinitiators: 4-acryloyloxy benzophenone, allyl benzoine and phenyl-(1-acryloyloxy)-cyclohexyl ketone. The main emphasis is given to the influence of viscosity and molecular mass of synthesized adhesive on their shrinkage. Further trials show the effect of the UV-crosslinking process with UV-lamp and comparison with acrylics PSA crosslinked with metal chelates aluminium acetylacetonate and titanium acetylacetonate on shrinkage. Further examinations describe the influence of various factors such as UV exposure time and UV dose on very relevant PSA performance such as shrinkage on coated PVC carrier.