Spectral transformation of the energy in Fröhlich systems

Spectral energy transformation is one of the general properties of nonlinear systems. We examined the Fröhlich vibration system as a model nonlinear system. Energy is transferred down towards low frequency vibration modes with considerable damping.     

Polyaniline-coated silica gel

Silica gel microspheres 7 and 15 μm in diameter were coated with an overlayer of polyaniline camphorsulfonate or hydrochloride during the oxidative polymerization of aniline. Coated silica gel and polyaniline precipitate were separated using a difference in sedimentation rate. In an alternative approach, the microspheres were modified with polyaniline in the presence of 35 nm colloidal silica. This technique prevented the macroscopic precipitation of polyaniline. Coatings of neat, 3-aminopropyl- and octadecyl-modified silica gel with polyaniline hydrochloride were compared. The surface composition of coated microspheres was characterized by X-ray photoelectron spectroscopy. Potential applications of particles in electrorheology, organic catalysis, and in modeling of conductivity behavior in composites are demonstrated.     

A microcomputer-controlled titrator for automated individual analysis

A titration unit for automatic analysis systems is described. The titrator performs different titrations specified by strings of digital parameters. It has 4 independent titration stations with individual electrode systems. A multiburette with 20 cylinders provides all stations with the necessary reagents. End-point titrations, and incremental and equilibrium titrations are controlled by a microcomputer. In combination with a sample transport and a desk calculator, the titrator can be used to process automatically samples of different natures which require different treatment.     

Qualitative analysis of ten-dimensional lovelock cosmological models

The Einstein-like field equations obtained from the variation of a Lagrangian containing linear, quadratic (Gauss-Bonnet) and quartic terms for a ten-dimensional cosmological model cannot be solved analytically. However, we can reduce them to a system of dynamical equations for the Hubble parameters. The study of the mathematical properties of the fixed points of this system gives a qualitative picture of the behaviour of a class of possible solutions. The inclusion of a quartic term generates an extremely rich structure for the corresponding dynamical system. Some solutions are shown to exhibit the interesting property of dimensional reduction, which has been proposed as a possible explanation of the three-dimensional character of our universe.     

AC susceptibility of thin Pb films in intermediate and mixed state

Thin films of type I superconductors of a thickness comparable or less than a flux penetration length behave like type II superconductors in a mixed state. With decreasing film thickness normal domains carrying a magnetic flux get smaller with smaller number of flux quanta per domain and finally transform into single quantum flux lines, i.e. quantum vortices similar to those found in type II superconductors. We give an evidence of this behavior from the measurements of the nonlinear response of a total magnetic moment to an applied AC magnetic field, directly from the temperature dependence of an AC susceptibility.     

Determination of amineptine and its main metabolite in plasma by high-performance liquid chromatography after solid-phase extraction

Amineptine and its main metabolite were determined simultaneously in plasma by high-performance liquid chromatography using quinupramine as internal standard. The method comprised adsorption on Extrelut column from alkaline plasma, elution with diethyl ether-methylene chloride, evaporation in the presence of 0.01 M hydrochloric acid and injection of the acid solution onto a mu Bondapak C18 column, using acetonitrile-0.025 M potassium dihydrogenphosphate as mobile phase and ultraviolet detection at 210 nm. Average steady-state concentrations of the two compounds were determined in four patients under treatment regimen (two 100-mg doses of amineptine per day, at 8.00 and 12.00 h). The concentrations determined 20 h after the last dose were undetectable in all cases, whereas the concentrations determined 1 h after the second dose were found to be 780 +/- 96 ng ml-1 for amineptine and 690 +/- 137 ng ml-1 for its metabolite. The technique can also be applied to whole blood with, if necessary, identification on the basis of the ultraviolet spectrum obtained by photodiode-array detection.     

Evolution of high-frequency gravitational waves in some cosmological models

We investigate Isaacson’s high-frequency gravitational waves which propagate in some relevant cosmological models, in particular the FRW spacetimes. Their time evolution in Fourier space is explicitly obtained for various metric forms of (anti-)de Sitter universe. Behaviour of high-frequency waves in the anisotropic Kasner spacetime is also described.     

Coefficients for the determination of one-sided tolerance limits of normal distribution

A table of such coefficientsk is given that the interval (?∞, ¯x+ks) or (¯x?ks, +∞) covers with the probabilityP at least the ratioα of the normal population with unknown parameters.