Effect of the Supporting-Electrolyte Cation on the Chloroplatinite Ion Reduction at a Dropping Mercury Electrode

The effect of nature and concentration of supporting-electrolyte cations (Li⁺, Na⁺, Cs⁺, (CH₃)₄N⁺, Ca²⁺, Ba²⁺) on electroreduction kinetics of PtCl^2- ₄at a dropping mercury electrode is studied. The electroreduction wave for PtCl^2- ₄is complicated by a polarographic maximum of first kind followed by a pronounced plateau of limiting current, after which the current passes through a minimum. The electroreduction occurs probably via two different mechanisms and presumably involves the same species, because the charge z _iof discharging species, determined by the Frumkin–Petrii method, remains virtually constant (z _i –1) on both descending (E= –0.6 to –1.0 V vs. SCE) and ascending (–1.3 to –1.6 V) branches of polarization curves and is independent of the nature of the supporting-electrolyte cation. The mechanism is presumably changed by a changed orientation of discharging species relative to the electrode surface.     

Interaction of biological and nonbiological surfaces. New opportunities for research and technologies using synchrotron radiation

The applicability of synchrotron radiation to implementation of medical ideas associated with introduction of nonbiological objects into a human body—implants, drug nanocapsules, and X-ray therapeutic means (metal nanoparticles and nanocrystalline phosphors and scintillators)—is considered. Synchrotron radiation presents new possibilities of analyzing the surface with a resolution comparable to the sizes of biological nanostructures involved in interactions such as chemical and biochemical modification of implant surfaces in vitro; activation of implant surface integration with biological tissue in a tissue culture (in vitro) and in vivo; biochemical modification of therapeutic nanoparticle surface in vitro; immunocamouflage by host proteins; attachment of “molecular targets”, i.e., antibodies, to target tissue to provide targeted delivery vehicles; and local activation of X-ray therapeutic drugs and drug nanocapsules in biological tissues. A functional block diagram of a medical technological station is given.     

Effect of a fullerene C60 addition on the strength properties of nanocrystalline copper and aluminum under shock-wave loading

The Hugoniot elastic limit and the spall strength of aluminum and copper samples pressed from a mixture of a metallic powder and 2–5 wt % C₆₀ fullerene powder are measured under a shock loading pressure up to 6 GPa and a strain rate of 10⁵ s^?1 by recording and analyzing full wave profiles using a VISAR laser interferometer. It is shown that a 5% C₆₀ fullerene addition to an initial aluminum sample leads to an increase in its Hugoniot elastic limit by an order of magnitude. Mixture copper samples with 2% fullerene also exhibit a multiple increase in the elastic limit as compared to commercial-grade copper. The elastic limits calculated from the wave profiles are 0.82–1.56 GPa for aluminum samples and 1.35–3.46 GPa for copper samples depending on the sample porosity. The spall strength of both aluminum and copper samples with fullerene additions decreases approximately threefold because of the effect of high-hardness fullerene particles, which serve as tensile stress concentrators in a material under dynamic fracture.     

Recovery of parameters of delayed-feedback systems from chaotic time series

Methods for reconstructing a delay differential equation from the time series of an observable quantity are proposed for various classes of time-delay systems. The methods rely on knowledge of the distributions of extrema of the time series of observed oscillations and projection of the infinite-dimensional phase spaces of time-delay systems onto special low-dimensional subspaces. The effectiveness of the proposed methods is demonstrated by reconstructing delay differential equations from their chaotic solutions, including those corrupted by noise, and by constructing models of real time-delay systems from chaotic time series.     

Orientation effect on the parameters of the polymorphic transformation of graphite under shock compression

A large effect of the shock compression direction with respect to the crystallographic planes of graphite on the detected pressure and rate of the transformation of graphite to a diamond or diamond-like high-pressure phase has been revealed. The effect is pronounced in more ordered graphite. The results indicate that shifts in basal planes complicate high-rate graphite-diamond transformation.     

Multistability and isomer classification and evolution in coupled feigenbaum systems

Saratov Affiliate of the Institute of Radio Engineering and Electronics, Academy of Sciences of the USSR. Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Radiofizika, Vol. 34, No. 1, pp. 35–39, January, 1991.     

Estimation of coupling between oscillators from short time series via phase dynamics modeling: limitations and application to EEG data

We demonstrate in numerical experiments that estimators of strength and directionality of coupling between oscillators based on modeling of their phase dynamics [D. A. Smirnov and B. P. Bezruchko, Phys. Rev. E 68, 046209 (2003)] are widely applicable. Namely, although the expressions for the estimators and their confidence bands are derived for linear uncoupled oscillators under the influence of independent sources of Gaussian white noise, they turn out to allow reliable characterization of coupling from relatively short time series for different properties of noise, significant phase nonlinearity of the oscillators, and nonvanishing coupling between them. We apply the estimators to analyze a two-channel human intracranial epileptic electroencephalogram (EEG) recording with the purpose of epileptic focus localization.     

Determination of parameters of elements and coupling architecture in ensembles of coupled time-delay systems from their time series

We propose a method for reconstructing model differential equations with time delay for ensembles of coupled time-delay systems from their time series. The method has made it possible to recover the parameters of elements of the ensemble as well as the architecture and strength of couplings in ensembles of nonidentical systems with delay with an arbitrary number of unidirectional and bidirectional couplings between them. The effectiveness of the method is demonstrated for chaotic and periodic time series of model equations for ensembles of diffusively coupled systems with time delay in the presence of noise, as well as experimental time series for resistively coupled radiotechnical oscillators with delayed feedback.     

On the yield strength of single-crystal zinc under uniaxial compression in a plane shock wave

The shock wave pattern in zinc single crystals compressed in the direction normal to the basal plane of the crystal is traced with a high time resolution. In this geometry of the experiment, plastic deformation of the zinc is found to begin at a shock compression pressure above 15 GPa and is not accompanied by splitting of the shock wave into an elastic precursor and a plastic compression wave.