Synthesis and characterization of polyaniline doped with organic acids

Spectroscopic [UV–visible and Fourier transform IR (FTIR)] and thermal properties of chemically synthesized polyanilines are found to be affected by varying the protonation media (acetic, citric, oxalic, and tartaric acid). The optical spectra show the presence of a greater fraction of fully oxidized insulating pernigraniline phase in polyaniline doped with acetic acid. In contrast, the selectivity in the formation of the conducting phase is higher in oxalic acid as a protonic acid media. The FTIR spectra of these polymers reveal a higher ratio of the relative intensities of the quinoid to benzenoid ring modes in acetic acid doped polyaniline. Scanning electron micrographs revealed a sponge‐like structure derived from the aggregation of the small granules in acetic acid and oxalic acid doped polyaniline. A three‐step decomposition pattern is observed in all the polymers, regardless of the protonic acid used for the doping. The second step loss related to the loss of dopant is found to be higher in the oxalic acid doped polymer. In accordance with these results the conductivity is also found to be higher in oxalic acid doped material. The temperature dependent conductivity measurements show the thermal activated behavior in all the polymers. © 2004 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 42: 2043–2049, 2004     

Banach spaces which are somewhat uniformly noncreasy

We consider a family of spaces wider than r-UNC spaces and we give some fixed point results in the setting of these spaces.     

Nonlinear resistor based on a polymer-ceramic composition

The resistivity of composite nonlinear resistors (varistors) consisting of zinc oxide ceramic and high-density polyethylene, as well as IR spectra and X-ray diffraction patterns taken of the samples, are studied. The component composition of the resistor is shown to influence its resistivity and IR and X-ray spectra.     

Speed of adaptation in structured populations

Adaptation of populations takes place with the occurrence and subsequent fixation of mutations that confer some selective advantage to the individuals which acquire it. For this reason, the study of the process of fixation of advantageous mutations has a long history in the population genetics literature. Particularly, the previous investigations aimed to find out the main evolutionary forces affecting the strength of natural selection in the populations. In the current work, we investigate the dynamics of fixation of beneficial mutations in a subdivided population. The subpopulations (demes) can exchange migrants among their neighbors, in a migration network which is assumed to have either a random graph or a scale-free topology. We have observed that the migration rate drastically affects the dynamics of mutation fixation, despite of the fact that the probability of fixation is invariant on the migration rate, accordingly to Maruyama's conjecture. In addition, we have noticed a topological dependence of the adaptive evolution of the population when clonal interference becomes effective.     

Studies on Rare-Earth/Iron and Actinide/Iron Multilayers

Hyperfine Interactions - Multilayers of Ce/Fe and U/Fe were fabricated by sputtering and studied by X-ray diffraction and reflectivity, Mössbauer spectroscopy and polarised neutron...     

Recent Developments in Synchrotron Mössbauer Reflectometry

Hyperfine Interactions - Synchrotron Mössbauer Reflectometry (SMR), the grazing incidence nuclear resonant scattering of synchrotron radiation, can be applied to perform depth-selective phase...     

Molecular flow and wall collision age distributions

The use of storage cells has become a standard technique for internal gas targets in conjunction with high energy storage rings. In case of spin-polarized hydrogen and deuterium gas targets the interaction of the injected atoms with the walls of the storage cell can lead to depolarization and recombination. Thus the number of wall collisions of the atoms in the target gas is important for modeling the processes of spin relaxation and recombination. It is shown in this article that the diffusion process of rarefied gases in long tubes or storage cells can be described with the help of the one-dimensional diffusion equation. Mathematical methods are presented that allow one to calculate collision age distributions (CAD) and their moments analytically. These methods provide a better understanding of the different aspects of diffusion than Monte Carlo calculations. Additionally it is shown that measurements of the atomic density or polarization of a gas sample taken from the center of the tube allow one to determine the possible range of the corresponding density weighted average values along the tube. The calculations are applied to the storage cell geometry of the HERMES internal polarized hydrogen and deuterium gas target. Received 9 July 2001 and Received in final form 18 September 2001     

A rapid and sensitive extractive spectrophotometric determination of copper(II) in pharmaceutical and environmental samples using benzildithiosemicarbazone.

Benzildithiosemicarbazone (BDTSC) is proposed as a sensitive and selective analytical reagent for the extractive spectrophotometric determination of copper(II). BDTSC reacts with copper(II) in the pH range 1.0-7.0 to form a yellowish complex. Beer's law is obeyed in the concentration range 0.5-0.4 microg cm(-3). The yellowish Cu(II)-BDTSC complex in chloroform shows a maximum absorbance at 380 nm, with molar absorptivity and Sandell's sensitivity values of 1.63 x 10(4) dm3 mol(-1) cm(-1) and 0.00389 microg cm(-2), respectively. A repetition of the method is checked by finding the relative standard deviation (RSD) (n = 10), which is 0.6%. The composition of the Cu(II)-BDTSC complex is established as 1:1 by slope analysis, molar ratio and Asmus' methods. An excellent linearity with a correlation coefficient value of 0.98 is obtained for the Cu(II)-BDTSC complex. The instability constant of the complex calculated from Edmond and Birnbaum's method is 7.70 x 10(-4) and that of Asmus' method is 7.66 x 10(-4), at room temperature. The method is successfully employed for the determination copper(II) in pharmaceutical and environmental samples. The reliability of the method is assured by analyzing the standard alloys (BCS 5g, 10g, 19e, 78, 32a, 207 and 179) and by inter-comparison of experimental values, using an atomic absorption spectrometer.     

Antioxidant and Prooxidant Effects of Tocopherol

A computer simulation of the kinetics of free-radical oxidation of lipids in the presence of tocopherol was performed. The induction periods and initial rates of oxidation as functions of initial tocopherol concentrations were found to exhibit extremums. The extended kinetic scheme used in this study describes all types of observed relationships and eliminates illusory contradictions between two groups of experiments in which the antioxidant and prooxidant effects of tocopherol were found. The model can form a basis for the prediction of the effects of tocopherol and its analogs under real conditions.