Natural motion density of elastic shells under intensive dynamic loading

The question of the natural motion density in dynamics problems of elastic shells is considered. Motions are studied for which an exponential growth in amplitude with time occurs. The number of natural motions incident in a given range of variation of the exponent is computed by using an idea of R. Courant. The governing natural motions and condensation points at which the natural motion density tends to infinity are found. The condensation points and governing motions are compared in specific examples.     

Electric and photoconductivity of polymer composites containing heteropolynuclear M(II)/Cr(III) complexes in the presence of additives with different electron donor-acceptor properties

Electro-and photoconductive properties of polymer composites doped with heteropolynuclear M(II)/Cr(III) (M = Zn, Co, Mn) complexes were studied in the presence of organic additives with different electron donor-acceptor properties: anthracene, fullerene C₆₀, terephthaloyldianthracene, and bis(biphenyl)chromium(I) fulleride (Ph-Ph)₂CrC₆₀. Upon excitation of the d-d transition in Cr(III), the magnitude of inner photoelectric effect in composite films examined is the highest for the Zn(II)/Cr(III) complex and increases in the series of additives anthracene, fullerene C₆₀, terephthaloyldianthracene, (Ph-Ph)₂CrC₆₀. The use of the dopant (Ph-Ph)₂CrC₆₀ increases photocurrent by about two orders of magnitude.     

Synthesis,structure, and properties of the Sc chloride complex coordinated by the tridentate bis(phenolate)-tethered NHC ligand

The scandium chloride complex LScCl(py)₂ (L is bis[(2,4-di-tert-butyl)phenolato]-6,6′-(4,5-dihydroimidazol-2-ylidene)) containing the dianionic bis(phenolate)-tethered N-heterocyclic carbene (NHC) ligand was synthesized. The X-ray diffraction study demonstrated that the complex has a mononuclear structure with intramolecular coordination of the carbene moiety to the Sc³⁺ ion. In the presence of moist air, the NHC moiety is hydrolyzed, resulting in the formation of the chloride complex [L’ScCl(py)]₂ with the dianionic tetradentate bis(phenolate) ligand containing the [NH(CH)₂N(HC=O)] linker. The binuclear complex [L’ScClpy]₂ is formed through the coordination of the oxygen atom of the formylethylenediamine moiety to the second Sc³⁺ ion.

     

Surface-Enhanced Raman Spectroscopy for the Determination of Medical and Narcotic Drugs in Human Biofluids

Journal of Analytical Chemistry - The review is devoted to an analysis of the capabilities, limitations, and special features of the application of surface-enhanced Raman spectroscopy (SERS) to the...     

Thermodynamic characteristics of fullerene-containing poly(methyl methacrylate-<Emphasis Type="Italic">co</Emphasis>-allyl methacrylate) and the C<Subscript>60</Subscript>-free copolymer analog

The heat capacities of fullerene-containing poly(methyl methacrylate-co-allyl methacrylate) and the C₆₀-free copolymer of the same composition are studied in the temperature interval 8 to 350–450 K via the methods of high-accuracy adiabatic and differential scanning calorimetry. Thermodynamic characteristics of glass transition, standard thermodynamic functions, and temperature intervals of the thermal stability of the samples are estimated. The fractal dimension is calculated, and conclusions about the topological structure of the copolymers are proposed. The effect of C₆₀ on the thermodynamic characteristics of the copolymer is studied.     

The steady axisymmetric flow of ideally plastic materials in a conical channel

The problem of the asymmetric flow of an ideally plastic medium is formulated within the framework of the von Mises model and the total plasticity condition, using the invariant condition of compatibility for the deviator component of the stress tensor. Flow in a converging conical channel, on the boundary of which the shear stresses are specified, is considered. First-order differential equations are obtained, describing the shear-stress distribution in the moving medium, one of which corresponds to the von Mises model, and the other to the total plasticity condition. It is established from an analysis of the solution in the neighbourhood of singular points, that the minus sign in front of the radical in these equations corresponds to positive shear stresses and vice versa. The problem of the shear stresses reaching a maximum value on the specified boundary surface of the channel is investigated. The aperture angle of the channel, beginning from which this value is reached, is determined. It is established that the value of the angle, following from the total plasticity condition, somewhat exceeds its value obtained within the framework of the von Mises model.     

Some problems in the classical theory of radiation

The article considers the problem of the complete radiation of the energy of a charged particle moving in constant and homogeneous electric and magnetic fields and in the field of a plane wave. Exact formulas are obtained for these cases. The problem is al so considered of the instantaneous radiation of an arbitrary moving charge. The problems are considered according to classical theory.