Speeding-up and scaling of domain-wall relaxation nearT c of a uniaxial ferromagnet

The dynamic susceptibility () measured between 10 Hz and 10 MHz on different GdCl₃-ellipsoids (T _c=2.21 K) reveals a completely reversible motion of the domain walls. Taking into account the contribution of the fast adiabatic intradomain magnetization to the nearly Debye-shaped (), we determine for the first time the kinetic Onsager coefficientL _d of the domain wall relaxation of a ferromagnet. Approaching the CurietemperatureL _d speeds up critically, which by a novel simple relaxational model can be related to the increasing width (=correlation length) of linear Bulaevskii-Ginzburg domain-walls and to the shrinking domain period. The reduction ofL _d by an external field can be represented by a universal scaling function, and within the same dynamical model, this effect is ascribed to the increase of the domain period, predicted for a bubble phase. However, the effect of sample size onL _d is much smaller than expected.     

Structure of the products of the cyclization in acetic anhydride of β-(2-carboxy-5-chlorophenylamino) propionic acid and its nitrile

-(2-Carboxy-5-chlorophenylamino)propionic acid cyclizes in acetic anhydride to form 4-chloro-2-(2,4-dioxopiperidino)benzoic acid, which subsequently undergoes conversion into its lactone. Under the same conditions, -[acetyl(2-carboxy-5-chlorophenyl)amino]-propionitrile forms 7-chloro-1--cyanoethyl-1,2,3,4-tetrahydroquinoline-2,4-dione. The structures of the compounds obtained were confirmed by their IR, UV, and PMR spectra. An evaluation of the stability of the ketonic and enolic forms of the compounds obtained on the basis of calculations by Hückel's method has been made.Translated from Khimiya Geterotsiklicheskikh Soedinenii, Vol. 6, No. 7, pp. 879–884, July, 1970.     

Chemical instabilities during oxidation of 1,4-naphthalenediol in a homogeneous medium: II. Thermodynamic analysis and mathematical modeling

A possible mechanism of 1,4-naphthalenediol oxidation in the oscillatory regime has been considered, and a mathematical model describing the kinetics has been developed. Based on a thermodynamic Lyapunov function, it has been shown that the source of chemical instabilities is in the existence of autocatalytic steps and dynamic feedbacks. Qualitative analysis and numerical solution of the set of differential equations that model the reaction kinetics have been performed. The character of the stationary state and the possibility of bifurcations have been determined. The mathematical model satisfactorily describes the processes occurring in the system.     

Formation of Se0 Nanoparticles in an Aqueous Cationic Polyelectrolyte

The nanostructures formed by reduction of Se(IV) in the selenite-ascorbate redox system in an aqueous solution of supermacromolecular polycation, poly[trimethyl(methacryloyloxyethyl)ammonium] methyl sulfate, were studied by static and dynamic optical scattering and flow birefringence.     

Zwei Beispiele zur Anwendung der Polarographie in der pharmazeutischen Industrie

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