Formation of fibrillar aggregates in concentrated solutions of rigid-chain amphiphilic macromolecules with fixed torsion and bend angles

The molecular-dynamics method is used to study solutions of amphiphilic macromolecules with a local helical structure. A deterioration in the solvent quality in concentrated solutions of these macromolecules leads to the formation of intermolecular fibrillar helix bundles with approximately the same lengths and aggregation numbers. The number of chains in a bundle is determined by parameters that characterize the local structure and is weakly dependent on the length of the macromolecule and the volume fraction of the polymer in the solution. In racemic mixtures of these macromolecules, a deterioration in the solvent quality leads to effective demixing; that is, the resultant fibrillar bundles generally contain macromolecules of exclusively the same chirality.     

The influence of ZnO-Sensor modification by porphyrins on to the character of sensor response to volatile organic compounds

The influence of modification of semi conductive ZnO and SnO₂ sensors by porphyrins and their metal complexes on the parameters of sensor response to volatile organic compounds, ethanol, acetone and benzene, was analyzed. The concentration of volatile organic compounds (c _i ) varied in the range of 1–200 ppm. The sensor response was characterized by specific sensitivity γ _i = 100ΔR _i /R ₀ c _i , where ΔR _i = R _i − R ₀, R _i and R ₀ are measurable and initial resistance of the sensitive sensor layer correspondingly. It was established that the modification of sensors by porphyrins caused changes in sensor response and first of all decrease of ZnO sensor temperature at which the threshold of sensitivity is achieved (as used at this method c _i ^min = 0.1 ppm) from 300 to 100°C. It also caused a change in sing of the parameter γ, which was of importance for creating “electronic nose” sensor systems. It was shown also, that the modification of ZnO sensor by metal complexes of porphyrin did not change sensor response parameters.     

Drag of Bodies of Revolution in Supersonic Flow with Heat and Mass Addition to the Near Wake

It is shown experimentally that the base drag of bodies of revolution in Mach 1.15 to 3.0 flow can be completely eliminated using special techniques for injecting hydrogen and the products of incomplete combustion of pyrotechnic compounds into the near wake. The experimental data obtained are generalized.     

Possible dibaryon states produced in4He-proton interactions

In the hydrogen bubble chamber study of the⁴Hep→dppn reaction at incident alpha 8.6 GeV/c momentum the structures in the two-proton effective mass distribution are observed at 2,035±15 MeV and 2,137±15 MeV. Possible nature of the effect is discussed.     

Air temperature stabilization in the thermally isolated optical laboratory

For the studies and calibration of optoelectronic components of the high-precision laser based metrology systems the large volume (50 m³) thermoisolated lab based on seismic isolated concrete block is created. The inside lab volume temperature stabilization for the daily observation at 16.5°C is ±0.05°C with ±0.015°C temperature difference between maximal space separated points. This work was initiated by the needs of high-precision alignment of accelerator components of the CLIC, ILC-type colliders.     

Effect of the nature of polymer matrix on the process of cholesterol photooxidation in the presence of immobilized tetraphenylporphyrins

It was shown that carrying out the reaction of cholesterol photosensitized oxidation in the presence of porphyrins immobilized on the hydrolyzed copolymer of tetrafluorethylene and H⁺ form of perfluoro-3,6-dioxo-5-methyl-6-sulfonylfluorideoctene-1 leads to the formation of not previously described new products: 6β-phormyl-B-norcholestan-3β,5β-diol, 6β-chlorocholestan-3β,5α-diol, cholestan-3β,5α,6β-triol, and 5α-chlorocholestan-3β,6β-diol.     

Cross sections of the interactions of4He nuclei with protons at 8·6 and 13·6 GeV/c

⁴He-p collisions at two values of⁴He momenta-8·6 GeV/c and 13·6 GeV/c — have been studied using the one-metre JINR hydrogen bubble chamber. Total, elastic and topological cross sections have been measured. The results are in agreement with other published data. The elastic differential cross section was compared with the predictions of the Glauber model formalism.Dedicated to Academician Václav Votruba on ths occasion of his eightieth birthday.We would like to thank Mrs. M. Stehlíková for drawing the figures.     

Effect of parameters of a crosslinked polyacrylic matrix on the impregnation of photoactive compounds in supercritical fluids

The effect of the network density of spatially crosslinked polyacrylic transparent matrices and the conditions of their impregnation with a photochromic compound via the use of supercritical carbon dioxide on the concentration of the introduced photochromic compound of the spiroxazin family is studied. The concentration of impregnated filler in a matrix is shown to increase with increases in the interjunction distance (below a certain level) and network chain flexibility as well as with increases in the temperature and pressure of the impregnation process. Impregnation in rigid networks occurs only in surface layers, whereas, in an elastic network, impregnation occurs in the entire volume of a sample. Matrices based on oligourethanemethacrylates are characterized by a good thermodynamic affinity toward spiroxazin photochromic compounds, a fact that makes it possible to increase the concentration of photochromic compounds in the matrix up to 3 wt % under conditions of supercritical impregnation. The photochromic characteristics of an impregnated compound are shown to be preserved in samples.     

The photochromic properties of indoline spirooxazine-thermoplastic polymer systems obtained by supercritical fluid impregnation

The impregnation of thermoplastic polymers (polyethylene, polypropylene, polymethyl methacrylate, and polycarbonate) with photochromic compounds from the class of indoline spirooxazines in supercritical carbon dioxide (SC-CO₂) was studied. The concentration of the photochrome and the kinetics of decolorization of its colored form depended strongly on the type of the polymer matrix and the structure of spirooxazine. The introduction of 1,3′,3′-trimethylspiro(indoline-2′,3-3H-anthraceno[2,1-b][1,4]oxazine) (SAO) into polycarbonate caused anomalous stabilization (the prolonged conservation of the excited colored form of SAO in the polymer matrix). In contrast to other photochrome-polymer pairs, after supercritical impregnation into polycarbonate, at least 10% of all SAO molecules were in the colored form, which was highly stable and did not decolorize after 150 days; the rest of the impregnated SAO molecules were localized in the matrix as individual molecules, partially colorized after matrix relaxation, or nanocrystals of characteristic sizes ∼10–20 nm. The mechanisms of the anomalous stabilization of the colored SAO form in the polycarbonate matrix are discussed. Original Russian Text ? N.N. Glagolev, A.B. Solov’eva, A.V. Kotova, V.T. Shashkova, B.I. Zapadinskii, N.L. Zaichenko, L.S. Kol’tsova, A.I. Shienok, P.S. Timashev, V.N. Bagratashvili, 2009, published in Zhurnal Fizicheskoi Khimii, 2009, Vol. 83, No. 5, pp. 985–992.