Photoinduced structure transformations in dichromate-impregnated denatured collagen

X-ray structure analysis shows that irradiating gelatin films containing chromates causes a spiral-coil transition in the denatured collagen molecules. The concentration and type of the chromate have substantial effects, as do the film preparation conditions. The x-ray diffraction and ESR data indicate that chromium(V) compounds formed by photoreduction from chromium(VI) ones are mainly responsible for the conformation transition. In the absence of chromium compounds, light absorbed by the gelatin macromolecules results in macroradicals on account of the photolysis in the denatured protein chains. There is no phase transition.Translated from Teoreticheskaya i Éksperimental'naya Khimiya, Vol. 24, No, 2, pp. 247–251, March–April 1988.     

Photoproduction of homogeneous chromium(V) compounds in pentanol for targets containing polarized hydrogen nuclei

Measurements have been made on photochemical and subsequent dark reactions with an He-Cd laser (44l nm) with ammonium dichromate solutions in pentanol. Exposing the solution directly in the spectrometer cavity leads to an ESR signal having g = 1.973 characteristic of chromium(V) compounds. The compounds have been examined by ESR and optical spectroscopy. A kinetic analysis is presented. It is suggested that homogeneous Cr(V) compounds are formed. No Cr(III) or other paramagnetic products have been detected. These compounds can be used in polarized nuclear targets.Joint Nuclear Research Institute, Dubna. Pisarzhevskii Physical Chemistry Institute, Academy of Sciences of the Ukrainian SSR, Kiev. Translated from Teoreticheskaya i Éksperimental' naya Khimiya, No. 1, pp. 60–65, January–February, 1991. original article submitted November 17, 1987.     

Control of motion of a legged locomotion machine with minimal-power motor

We consider the problem of control of motion of a many-legged statically stable locomotion machine ensuring the choice of a minimal-power motor. We show that the machine frame can be used as a kinetic energy recuperator, thus providing a significant decrease in the reactive power.     

Photoactive intermediates in the photoreduction of bichromates

It was found that labile photoactive intermediates, absorbing in the region of 650 nm, are formed during the photoreduction of bichromates in isopropyl alcohol. They were interpreted as the oxyanions of pentavalent chromium in coordination with the radical products from phototransfer of an electron. L. V. Pisarzhevskii Institute of Physical Chemistry, National Academy of Sciences of Ukraine, 31 Prospekt Nauki, Kiev 252039, Ukraine. Translated from Teoreticheskaya i éksperimental'naya Khimiya, Vol. 35, No. 4, pp. 227–230, July–August, 1999.     

Third-Order Nonlinear Optical Response of a New PVA Composite with PbS Nanocrystals

High third-order nonlinear optical susceptibility (⁽³⁾(;, –,)=3.4·10 ^–16 m²/V²) in the visible spectral range may be achieved in PVA composites with narrow-gap PbS semiconductor nanocrystals with a large exciton diameter.     

Estimates of efficiency of cycle mechanisms

The problem of choosing the program regime of a cycle mechanism motion on the basis of complex estimates of its energy and dynamic parameters is solved. An optimization criterion is formed as a functional consisting of the introduced parameters, which are determined by solving some differential equations describing the mechanism motion. For a specific mechanism, an example of complex estimate of its efficiency is given. An application procedure for the proposed method is discussed.     

Change in the paramagnetic properties of Fe3O4 upon interaction with benzimidazole derivatives

ESR spectroscope was used to study the interaction between magnetite particles and organic molecules in model systems and real luminescent magnetic powder compositions. Ferric compounds localized on the magnetite surface are very labile and the introduction of organic compounds such as 1,2-naphthoylene 1,2-benzimidazole or DMF leads to a change in their electronic structure and the geometry of the environment. The observed changes presumably result from a coordination interaction of Fe(III) sites with organic compounds in the mechanical mixture. The role of vibrational interactions of the dye molecules and the oxygen sublattice in Fe₃O₄ in these processes was discussed.Translated from Teoreticheskaya i Éksperimental'naya Khimiya, Vol. 29, No. 5, pp. 456–461, September–October, 1993.     

Second-order nonlinear-optical response of new polymeric materials based on epoxides

In the example of new nonlinear-optical polymeric materials based on the diglycidyl ether of bisphenol A, bonded covalently to a series of chromophores, it has been demonstrated that an increase of the second-order nonlinear-optical characteristics in the polymers can be achieved by creating a more complex conjugated -electron structure.Translated from Teoreticheskaya i Éksperimental'naya Khimiya, Vol. 31, No. 5, pp. 308–312, September–October, 1995.     

On the energy efficiency of cyclic mechanisms

We consider cyclic mechanisms with one degree of freedom driven by engines of various types such as alternating and direct current motors, internal combustion engines, etc. We pose the problem of modifying the mechanism structure by joining additional links or by varying the parameters or operation mode of the original mechanism so as to minimize the thermal losses in the driving motor. The solution is based on the minimization of the functional determining the irreversible power losses. We show that, for the engines considered, all cyclic mechanisms with one degree of freedom should satisfy a fundamental condition ensuring the minimum of losses. We consider two examples, one of which corresponds to actually existing mechanisms.     

Third-order nonlinear optical response of a new polymeric material based on epoxides containing a nickel(II) complex

A novel polymeric material having nonlinear optical properties has been prepared from the diglycidyl ether of bisphenol A and a macrocyclic complex of nickel(II). It has been shown that relatively high levels of third-order nonlinear susceptibility of polymers can be obtained without the use of highly conjugated systems. L. V. Pisarzhevskii Institute of Physical Chemistry, National Academy of Sciences of Ukraine, 31 Nauka Prospect, Kiev 252039, Ukraine. Translated from Teoreticheskaya i éksperimental’naya Khimiya, Vol. 33, No. 3, pp. 165–169, May–June, 1997.