Synthesis of Spiro[indole-3,2′-pyrroles] from Pyrrolopyrazinetriones and Aminocyclohexenones

Russian Journal of Organic Chemistry - 8-Benzoyl-2-phenyl-3,4-dihydropyrrolo[1,2-a]pyrazine-1,6,7(2H)-trione reacted with 3-(alkylamino)-5,5-dimethylcyclohex-2-en-1-ones to give...     

Photoreflectance study of plasma-etched semi-insulating GaAs substrates treated

Semi-insulating GaAs(100) substrates subjected to ion plasma etching in different regimes have been investigated by photoreflectance spectroscopy. The photoreflectance spectra of the processed samples exhibit Franz-Keldysh oscillations, which indicate a decrease in the defect density in the surface region. On the basis of the experimental data and the results of simulation of the photoreflectance spectra, optimal regimes of sample etching have been found.     

Study of the effects of size quantization in coupled AlxGa1? x As/GaAs/Alx Ga1? x as quantum wells by means of photoreflectance spectroscopy

Photoreflectance spectra are measured in heterostructures with coupled quantum wells at room temperature. The energies of the optical transitions are determined, and their variation with the well width and barrier thickness is studied. The experimental results are compared with the theoretically calculated electron-hole transition energies. Good agreement is obtained for narrow wells. __________ Translated from Optika i Spektroskopiya, Vol. 93, No. 6, 2002, pp. 929–934. Original Russian Text Copyright ? 2002 by Avakyants, Bokov, Galiev, Kaminskiĭ, Kul’bachinskiĭ, Mokerov, Chervyakov.     

Determination of the carrier concentration in doped <Emphasis Type="Italic">n</Emphasis>-GaAs layers by Raman and light reflection spectroscopies

The carrier concentrations in Si-doped n-GaAs films have been determined by Raman and light reflection spectroscopies. The data obtained are in good agreement with the results of Hall measurements. It is shown that the light reflection and Raman spectroscopies supplement each other in determination of carrier concentrations in the range 10¹⁷?10¹⁹ cm^?3.     

General solutions of nonlinear equations in the geometric theory of the relativistic string

General solutions for the system of nonlinear equations in the second order partial derivatives with two independent variables are obtained. They determine the basic differential forms of the two-dimensional minimal surface embedded inton-dimensional pseudo-Euclidean space.     

Study of the structure of aqueous solutions of ionic macromolecules by low-frequency Raman spectroscopy

Using low-frequency Raman spectroscopy, the structure of aqueous solutions of polyacrylic acid as a function of polyelectrolyte concentration and chain length was studied. The fractal dimension of structures in aqueous solutions of polyacrylic acid with different acid concentrations and polyion chain lengths was determined. The size of fractal regions in systems with different structures was estimated.     

Reduction in the model of a relativistic string for arbitrary dimension of Minkowski space

Conclusions At the first glance, the investigation of the relativistic string model in d-dimensional space-time might appear to be a purely mathematical problem. However, this is not so. Bearing in mind that as yet there is no satisfactory quantum theory of strings, it would be interesting by analogy with nonlinear string models to develop an expansion with respect to 1/d as d in string theory as well. Further, the geometrical theory of a string in d-dimensional space-time generated an entire series of nonlinear equations for which a general solution can be constructed explicitly. For the lower dimensions this was done in [5]. The method used there can probably by also generalized to the case of arbitrary d.It should be noted that our Eqs. (1.22) and (2.28) are not identical to the so-called string type equations constructed and solved explicitly in [14, 15] by means of group methods.Joint Institute for Nuclear Research, Dubna. Translated from Teoreticheskaya i Matematicheskaya Fizika, Vol. 59, No. 2, pp. 209–219, May, 1984.