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11.
L. A. Novokshonova N. Yu. Kovaleva T. M. Ushakova I. N. Meshkova V. G. Krasheninnikov T. A. Ladygina I. O. Leipunskii A. N. Zhigach M. L. Kuskov 《Kinetics and Catalysis》2005,46(6):853-860
The heterogenized reaction products of the partial hydrolysis of the organoaluminum compounds AlMe3 and Al(i-Bu)3 with water as a constituent of highly hydrated supports, zeolite (ZSM-5-H2O) and montmorillonite (MMT-H2O), have been synthesized. The thermal degradation of the resulting heterogenized methylalumoxane compound and methylalumoxane (MAO) in a solid state is studied by temperature-programmed desorption with the mass-spectrometric analysis of liberated gaseous products, and the structural identity of the above compounds is found. Alkylalumoxanes prepared immediately on the surface of a support form heterogenized complexes with the metallocenes Cp2ZrCl2 and Et(Ind)2ZrCl2. These heterogenized complexes exhibit high activity in the reactions of ethylene and propylene polymerization. For this reason, MAO can be replaced by AlMe3 or Al(i-Bu)3 and the additional introduction of MAO or another alkylaluminum for zirconocene activation is unnecessary. It has been found that, upon the immobilization of commercial MAO on dehydrated SiO2, the MAO molecule loses a portion of its most reactive methyl groups and, as a result of this, becomes incapable of activating metallocenes. 相似文献
12.
A. L. Buyanov I. V. Gofman A. K. Khripunov A. A. Tkachenko E. E. Ushakova 《Polymer Science Series A》2013,55(5):302-312
New composite hydrogels based on cellulose and poly(acrylamide) have been synthesized via radical polymerization of acrylamide in cellulose swollen in a reaction solution. In this study, both a plant form of cellulose and a bacterial form—that cultivated by Acetobacter xylinum bacteria—were used. The behavior of synthesized hydrogels during swelling in water, as well as the behavior of the samples swollen at equilibrium during deformation under uniaxial compression under various test conditions, have been studied. A comparative analysis of the main mechanical characteristics of hydrogels and the appropriate data for various types of articular cartilage, one of which—rabbit knee meniscus—has been tested in this study, has been performed. An average-strength hydrogel is very close to articular cartilage in all mechanical characteristics. The degrees of loading at the highest compression deformations observed during the function of joint cartilage (30–50%) is in the range 4–12 MPa for this hydrogel, and the average values of the compression modulus in the deformation ranges of 10–15 and 25–30% are 8.8 and 23.7 MPa, respectively. The behavior of hydrogels and rabbit meniscus under cyclic compression with the amplitude of 50% has been studied. Hydrogels and meniscus under this test conditions demonstrate clear viscoelastic behavior, evidenced by noticeable hysteresis for the first cycle and a decrease in the value of the maximum load with an increase in the number of cycles. Structural features of hydrogels, which can affect the behavior of the hydrogels under study, have been considered. On the whole, the results demonstrate the possibility of modeling the mechanical behavior of cartilage with the use of hydrogels of this type. 相似文献
13.
WILLIAM T. SLAVEN IV CHAO-JUN LI YI-PING CHEN VIJAY T. JOHN SUGUNA H. RACHAKONDA 《高分子科学杂志,A辑:纯化学与应用化学》2013,50(7-8):971-980
ABSTRACT A high molecular weight poly(aryleneethynylene) (Mw ~ 60,000) is prepared by the palladium catalyzed copolymerization of 3,5-diiodobenzoic acid and acetylene gas in a basic aqueous medium. The polymer has a “zig-zag”, fully conjugated backbone. The polymer has been characterized by a variety of methods and exhibits high thermal stability. Furthermore, the polymer is readily soluble in aqueous base and is reversibly switchable from the solution state to a hydrogel state, in water, by changing the pH of the solvent. 相似文献
14.
I. N. Flerov M. V. Gorev M. L. Afanas’ev T. V. Ushakova 《Physics of the Solid State》2002,44(10):1961-1966
The heat capacity of partially deuterated crystals with a cryolite structure, namely, (NH4)3ScF6 and (NH4)3GaF6, is measured in the temperature range from 80 to 370 K. The p-T phase diagrams of these compounds are investigated at pressures up to p=0.6 GPa. It is revealed that the deuteration does not affect the sequences of phase transitions observed in the proton-containing ammonium cryolites studied earlier. The isotope effect most clearly manifests itself in significant changes in the thermodynamic parameters of the $I12/m1 - P\bar 1$ low-temperature transformation in scandium cryolite. 相似文献
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17.
V. Z. Kasimov O. V. Ushakova Yu. P. Khomenko 《Journal of Applied Mechanics and Technical Physics》2003,44(5):612-619
An improved procedure for modeling the operation of a light-gas gun is proposed. The motion of working bodies in both the firing chamber and the light-gas chamber is studied within the framework of the mechanics of heterogeneous media. The problem of barrel heating taking into account its melting and removal of thermal ablation products into the medium inside the bore is solved in a coupled formulation. Heat and mass transfer and friction on the barrel surface are calculated using empirical dependences. The deformable piston is considered compressible and elastoviscoplastic. Allowance is made for the presence of a clearance between the lateral surface of the piston and the barrel bore walls and the associated gas flow between the firing and the light-gas chamber. Calculation results are given. 相似文献
18.
V. B. Krylov N. E. Ustyuzhanina A. A. Grachev N. A. Ushakova M. E. Preobrazhenskaya Yu. A. Shchipunov J. Wang M. H. Kim I. Kim N. E. Nifantieva 《Russian Chemical Bulletin》2011,60(12):2572-2578
Three hyperbranched dendrimers (polyglycidols) and the corresponding sulfated derivatives, differing in the average molecular weight, were synthesized. The compounds obtained were characterized in detail by mass spectrometry and 1H and 13C NMR spectroscopy, enabling estimation of the sizes of the corresponding molecules. Assignment of signals and identification of key structural blocks were performed using 2D homo- and heteronuclear spectroscopy (COSY, HSQC). The spectra of the sulfated derivatives showed the absence of the signals for the glycerol moiety with the free OH groups, that confirms exhaustive sulfation. The studies of antiinflammatory and anticoagulant activities of the polyanionic samples showed that all the compounds manifest weak antiinflammatory activity, however, their anticoagulant activity displayed in preliminary trials seems to be considerable. The results obtained indicate that it is reasonable to study in more detail biological activity of sulfated dendrimers of this type in terms of their anticoagulant properties. 相似文献
19.
A. S. Filippov I. A. Korotkin A. A. Kanaev V. V. Kondakov I. O. Urazov O. A. Ushakova P. G. Yakovlev 《Journal of Engineering Thermophysics》2008,17(4):320-327
The results of numerical modeling of two-phase electrolyte thermo-and hydrodynamics in the working space of a separate electrolyzer
cell with vertical electrode arrangement are presented. The problem is solved in a self-consistent formulation taking into
account the electric current, Joule heat evolution, gas evolution, gas and liquid flows, and electric conductivity of the
disperse phase. Within the framework of the proposed two-liquid approach, near-wall bubbly flow is calculated using a model
of expanding gas plume, which is based on the introduction of an effective force acting upon the gas phase. The results of
several variants of such calculations are compared. The numerical solution is also compared to approximate analytical solutions
of the problem. The results of this study can be used to calculate estimations of the electrical and thermal regimes of vertical
electrolyzers. 相似文献
20.
Richard P. Kent IV 《Geometriae Dedicata》2004,106(1):145-159
We answer a question of J. Anderson's by producing infinitely many commensurability classes of fibered hyperbolic 3-manifolds whose fundamental groups contain subgroups that are locally free and not free. These manifolds are obtained by performing 0–surgery on a collection of knots with the same properties. 相似文献