K-Entropies of Electrons and Ions in Nonideal Plasmas

The Krylov-Kolmogorov entropy (K-entropy) is calculated for electrons and ions in nonideal plasmas by the method of molecular dynamics. Two different time scales are established corresponding to the electron and ion K-entropies.     

The role of linear objective functions in barrier methods

Received December 10, 1994 / Revised version received April 29, 1998 Published online October 21, 1998     

Multifaceted Studies of the DNA Interactions and In Vitro Cytotoxicity of Anticancer Polyaromatic Platinum(II) Complexes

This study reports a detailed biophysical analysis of the DNA binding and cytotoxicity of six platinum complexes (PCs). They are of the type [Pt(P_L)(SS‐dach)]Cl₂, where P_L is a polyaromatic ligand and SS‐dach is 1S,2S‐diaminocyclohexane. The DNA binding of these complexes was investigated using six techniques including ultraviolet and fluorescence spectroscopy, linear dichroism, synchrotron radiation circular dichroism, isothermal titration calorimetry and mass spectrometry. This portfolio of techniques has not been extensively used to study the interactions of such complexes previously; each assay provided unique insight. The in vitro cytotoxicity of these compounds was studied in ten cell lines and compared to the effects of their R,R enantiomers; activity was very high in Du145 and SJ‐G2 cells, with some submicromolar IC₅₀ values. In terms of both DNA affinity and cytotoxicity, complexes of 5,6‐dimethyl‐1,10‐phenanthroline and 2,2′‐bipyridine exhibited the greatest and least activity, respectively, suggesting that there is some correlation between DNA binding and cytotoxicity.     

Synthesis,characterization, preliminary biological screening,and interaction studies of the bis(pyridinium)amine compound, 4,4'-[(2-aminophenyl)azanediyl]bis(1-methylpyridin-1-ium)triflate with biological macromolecules

Russian Journal of General Chemistry - Bis(pyridinium)amine 4,4'-[(2-aminophenyl)azanediyl]bis(1-methylpyridin-1-ium)triflate ([H2L][TfO]2) was synthesized and characterized by elemental...     

Degradation of carboxylated styrene butadiene rubber based water born paints: Part 2 - Models to predict UV stability and water absorption through central composite design

Central composite experimental design methods have been used to examine the simultaneous effects of talc (Viaton Viatalc^® 30), titanium dioxide (modified Rutile, Tioxide^® TR92) and additional hindered phenolic stabiliser (Aquanox^® L, a 50% w/w aqueous dispersion of Winstay^® L) on the water uptake and UV stability of composite films based on a carboxylated styrene butadiene rubber (c-SBR) latex. The talc and TR92 were in situ treated as pre-dispersions with Solsperse^® S27000 and Solplus^® D540 dispersants, respectively. For water uptake related responses, quadratic models were found to provide the most accurate prediction of effects associated with interactions between talc and TR92. It was found that the addition of TR92 to formulations with high talc loading reduced the water uptake, this was attributed a packing effect that arose due to the vast difference in pigment and filler particle size. For responses related to photo-oxidation (Microscal unit/mercury lamp, carboxylic acid carbonyl growth was monitored by IR), linear models gave the best data fit, thus indicating negligible interaction between the three variables. Within the experimental space explored, the level of talc had by far the strongest influence; increasing talc level led to a proportional increase in rate of carbonyl growth. This corroborates previous single variable studies, where the iron impurities present in the talc were suspected to be associated with the pro-degradant effect observed. Interestingly, the addition of dispersants amplified the latter effect and strongly muted the UV stabilising effect of TR92. An optimised formulation based on c-SBR was determined from the response equations and subsequently evaluated; in general the actual response trends matched those predicted. The suitability of experimental design as a tool to discover effects, interactions and responses of the ingredients of a paint system, and to optimise its formulation was thus confirmed.     

An experimental investigation into the kinematics of a concentrated hard-sphere colloidal suspension during Hopkinson bar evaluation at high stresses

The behavior of a concentrated, hard-sphere colloidal suspension is evaluated using the split Hopkinson pressure bar (SHPB) experimental technique. The composition of the suspension is measured using thermograviometric analysis before and after loading. This, combined with recorded pressure distributions, result in the conclusion that the suspension undergoes high rate squeezing flow. Experimental results demonstrate that the suspension exhibits shear thickening consistent with that observed in standard rotational rheometry. At sufficiently high stresses the suspension exhibits a second regime of shear thinning behavior that is consistent with elastohydrodynamic theory that incorporates the shear modulus of the particles themselves. Further increases in stress result in irreversible behavior, i.e., rather than fracturing or crushing, the particles form non-reversible agglomerates during testing. This fact is demonstrated through the use of dynamic light scattering and electron microscopy. This behavior occurs within a regime of viscous material response which is seen to occur at normal strain rates and stresses over 10⁴ s^?1 and 40 MPa, respectively.     

Strategies used to detect auditory signals in small sets of random maskers

Detection performance for a masked auditory signal of fixed frequency can be substantially degraded if there is uncertainty about the frequency content of the masker. A quasimolecular psychophysical approach was used to examine response strategies in masker-uncertainty conditions, and to investigate the influence of uncertainty when the number of different masker samples was limited to ten or fewer. The task of the four listeners was to detect a 1000-Hz signal that was presented simultaneously with one of ten ten-tone masker samples. The masker sample was either fixed throughout a block of two-interval forced-choice trials or was randomized across or within trials. The primary results showed that: (1) When the signal level was low and the masker sample differed between the two intervals of a trial, most listeners based their responses more on the presence of specific masker samples than on the signal. (2) The detrimental effect of masker uncertainty was clearly evident when only four maskers were randomly presented, and grew as the size of the masker set was increased from two to ten. (3) The slopes of psychometric functions measured with the same masker samples differed among the fixed and two random-masker conditions. (4) There were large differences in the influence of masker uncertainty across masker samples and listeners. These data demonstrate the great susceptibility of human listeners to the influence of masker uncertainty and the ability of quasimolecular investigations to reveal important aspects of behavior in uncertainty condition.     

Detection of ultrafast phenomena by use of a modified Sagnac interferometer

We describe a time-division interferometer based on the Sagnac geometry for monitoring ultrafast changes in the real and the imaginary components of the refractive index as well as phase changes that are due to surface displacement. Particular advantages of this interferometer are its simple common-path design and operation at normal incidence with a microscope objective for both pumping and probing. Operation is demonstrated by detection of temperature changes and coherent phonon generation in a gold film.