Influence of an electric field on the rheological behavior of a dilute suspension of dipolar dumbbells in a viscoelastic oldroyd liquid

Conclusions 1. Rheological equations of state of a dilute suspension of dipolar dumbbels in a viscoelastic Oldroyd liquid have been obtained for a stationary orientation of suspended particles in steady flows and electric fields.2. Study of the rheological properties of such a medium in simple shear flow in the presence of an electric field, the intensity vector of which lies in the shear plane and is perpendicular to the velocity vector, has shown that the medium examined conducts itself as a viscoelastic liquid. This is the result of both the viscoelastic properties of the dispersion medium and the orientation of the suspended particles under the action of frictional forces and the electric field. The effective viscosity of the suspension and difference in normal stresses resulting from the presence of the suspended particles are greater if one does not take the elastic properties of the dispersion medium into account.T. G. Shevchenko Kiev State University. Translated from Mekhanika Polimerov, No. 3, pp. 519–524, May–June, 1978.     

Acceleration by Double Activation Catalysis and its Negation with Rising Temperature in Hydrolysis of Cellobiose with Phthalic and Hydrochloric Acids

Double activation catalysis was experimentally observed in hydrolysis of cellobiose catalyzed simultaneously with phthalic and hydrochloric acids, confirming earlier theoretical prediction known from literature. Both acids can catalyze the reaction individually, and contribution of the double-activation pathway to the total reaction rate declines as temperature increases. In fact, above a certain temperature, the hydrolysis rate in presence of both acids becomes lower than the sum of the rates for the two acids acting individually. A kinetic model is proposed to explain this transition between double-activated catalysis and inhibition. The trend of declining contribution of cooperative catalytic pathway with rising temperature is theorized to be generally applicable for any reaction with a pathway involving simultaneous action of two catalysts when either of them can individually catalyze the reaction.     

Nonlinear friction characteristics between silica surfaces in high pH solution

Molecular-scale characteristics of friction forces between silica particles and silica wafers in aqueous solutions of the normal (pH 5.6) and high pH (pH 10.6) are investigated, using the lateral force measuring procedure of the atomic force microscope (AFM). Various significant differences of friction characteristics between solutions of normal and high pH's are found. In the case of solutions of normal pH, the friction force increases linearly with increasing loading force, as the Amonton's law for solid bodies indicates. However, in the case of high pH solutions, the increasing rate with the loading force is considerably reduced in the low loading region, but the value increases abruptly above a critical loading force to overcome the magnitude of friction force of normal pH above the region of very high loading. It is very interesting to know that this nonlinear force curve at high pH is independent of the atomic-scale roughness of surfaces, although the magnitude of friction is greatly influenced by the roughness in the case of normal pH. The reason why the friction at high pH is independent of the surface roughness is postulated to be due to the hairy-like layer formed on the silica surface. The existence of hairy-like layers at high pH is proven directly by the dynamic method of normal force measurements with AFM and the thickness is estimated to be at least ca. 1.3 nm.     

Ma?analytische Methoden

Ohne Zusammenfassung     

The temperatures of protons andπ − mesons in central nucleus-nucleus interactions at a momentum of 4.5 GeV/c per incident nucleon

An estimate of the temperature of protons and ^– mesons in central He–Li, He–C, C–C, C–Ne, C–Cu, C–Pb, O–Pb, Mg–Mg interactions is presented. The results indicate an increase of the proton temperature with increasing mass numbers of projectile and target nuclei (A _p ,A _T ) fromT _p =(118±3) MeV for He–Li toT _p =(141±2) MeV for C–Pb. The temperature of ^– mesons does not depend onA _P ,A _T andT 95 MeV. A satisfactory fit for ^– mesons in C–Cu, C–Pb, O–Pb, Mg–Mg collisions can be achieved by using a form involving two temperatures,T ₁ andT ₂. The relative yield of the high temperature component (T ₂) is 24% for C–Cu, C–Pb, and Mg–Mg interactions. The observed results forT _P in C–Ne, C–Cu and C–Pb collisions are consistent with the prediction of the thermodynamic hagedorn model.     

4-Hydroxy-2-quinolones. 38. Synthesis, structure, and anticonvulsant activity of optically active 1-phenylethylamides of 1-R-4-hydroxy-2-oxo-3-quinolinecarboxylic acids

A synthesis is reported for optically pure antipodes of 1-phenylethylamides of 1-R-4-hydroxy-2-oxo-3-quinolinecarboxylic acids. An attempt was made to establish the absolute configuration of these products by X-ray diffraction crystallographic analysis. The anticonvulsant activity of the S-enantiomers was studied.For Communication 37, see ref. [1].Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 1, pp. 55–63, January, 2000.