Mutual effect of thermochemical surface decomposition and viscous interaction during hypersonic flow past a sharp cone

Numerical results on the hypersonic gas flow in viscous interaction regime past sharp circular cones with thermally destructible Teflon surface are presented. Characteristics of the mutual influence between the thermochemical decomposition of the surface and the viscous interaction are revealed

The partition function versus boundary conditions and confinement in the Yang-Mills theory

We analyse dependence of the partition function on the boundary condition for the longitudinal component of the electric field strength in gauge field theories. In a physical gauge the Gauss law constraint may be resolved explicitly expressing this component via an integral of the physical transversal variables. In particular, we study quantum electrodynamics with an external charge and SU(2) gluodynamics. We find that only a charge distribution slowly decreasing at spatial infinity can produce a nontrivial dependence in the Abelian theory. However, in gluodynamics for temperatures below some critical value the partition function acquires a delta-function like dependence on the boundary condition, which leads to colour confinement.Comment: 14 pages, RevTeX, submitted to Phys. Rev.

Structure and stability of chiral beta-tapes: a computational coarse-grained approach

We present two coarse-grained models of different levels of detail for the description of beta-sheet tapes obtained from equilibrium self-assembly of short rationally designed oligopeptides in solution. Here we only consider the case of the homopolymer oligopeptides with the identical sidegroups attached, in which the tapes have a helicoid surface with two equivalent sides. The influence of the chirality parameter on the geometrical characteristics, namely the diameter, inter-strand distance and pitch, of the tapes have been investigated. The two models are found to produceequivalent results suggesting a considerable degree of universality in conformations of the tapes.Comment: 24 pages, 5 PS figures. Accepted to J. Chem. Phy

Flexoelectric effect in finite samples

Static flexoelectric effect in a finite sample of a solid is addressed in terms of phenomenological theory for the case of a thin plate subjected to bending. It has been shown that despite an explicit asymmetry inherent to the bulk constitutive electromechanical equations which take into account the flexoelectric coupling, the electromechanical response for a finite sample is "symmetric". "Symmetric" means that if a sensor and an actuator are made of a flexoelectric element, performance of such devices can be characterized by the same effective piezoelectric coefficient. This behavior is consistent with the thermodynamic arguments offered earlier, being in conflict with the current point of view on the matter in literature. This result was obtained using standard mechanical boundary conditions valid for the case where the polarization vanishes at the surface. It was shown that, for the case where there is the polarization is nonzero at the surface, the aforementioned symmetry of electromechanical response may be violated if standard mechanical boundary conditions are used, leading to a conflict with the thermodynamic arguments. It was argued that this conflict may be resolved when using modified mechanical boundary conditions. It was also shown that the contribution of surface piezoelectricity to the flexoelectric response of a finite sample is expected to be comparable to that of the static bulk contribution (including the material with high values of the dielectric constant) and to scale as the bulk value of the dielectric constant (similar to the bulk contribution). This finding implies that if the experimentally measured flexoelectric coefficient scales as the dielectric constant of the material, this does not imply that the measured flexoelectric response is controlled by the static bulk contribution to the flexoelectric effect

Is it possible to assign physical meaning to field theory with higher derivatives?

To overcome the difficulties with the energy indefiniteness in field theories with higher derivatives, it is supposed to use the mechanical analogy, the Timoshenko theory of the transverse flexural vibrations of beams or rods well known in mechanical engineering. It enables one to introduce the notion of a "mechanical" energy in such field models that is wittingly positive definite. This approach can be applied at least to the higher derivative models which effectively describe the extended localized solutions in usual first order field theories (vortex solutions in Higgs models and so on). Any problems with a negative norm ghost states and unitarity violation do not arise here.Comment: 16 pp, LaTeX, JINR E2-93-19

Політичні злочини як елемент політичного життя.

Тимошенко, В.О. Політичні злочини як елемент політичного життя. / В.О.Тимошенко // Актуальні проблеми політики : зб. наук. пр. / редкол. : С. В. Ківалов (голов. ред.), Л. І. Кормич (заст. голов. ред.), Ю. П. Аленін [та ін.] ; МОНмолодьспорт України, НУ ОЮА. – Одеса : Фенікс, 2011. – Вип. 43. С.174 - 179.The institute of political crimes as element of political life is examined in the article. Description of political crimes is given with legal and political science points of view

The Dynamic Characteristics of the Manipulator With Parallel Kinematic Structure Based on Experimental Data

The chapter presents two identification techniques which the authors found most useful in examining the dynamic characteristics of a manipulator with a parallel kinematic structure as an object of control. These techniques emphasize a frequency domain approach. If all input/output signals of an object can be measured, then the first one of such techniques may be used for identification. In the case when all disturbances can’t be measured, the second identification technique may be used

Синтез гідрованих тіофенів реакцією [3+2] циклоприєднання тіокарбоніліліду

Aim. To study the use of chloromethyl trimethylsilylmethyl sulfide as a precursor of thiocarbonyl ylide in [3+2] cycloaddition reaction to a number of α,β-unsaturated compounds and to establish the regularities of the reaction course. To develop an effective method for the synthesis of new dihydro- and tetrahydrothiophene derivatives which are convenient for further modification.Results and discussion. The synthetic approach to tetrahydrothiophenes with substituents in positions 3 and 4 was extended by the [3+2] cycloaddition reaction of thiocarbonyl ylide with a number of compounds containing an activated multiple bond. The stereoselectivity and limitations of this reaction were determined. Further functionalization of the obtained compounds was carried out.Experimental part. Thiocarbonyl ylide was obtained by fluoride ion-promoted 1,3-desilylation of the known chloromethyl trimethylsilylmethyl sulfide. The synthesis of the target compounds involved the [3+2] cycloaddition of such an ylide to a series of compounds with an activated multiple bond. The stereochemistry of the target compounds was determined by 1H NOESY experiments. Synthetic derivatives of thiolancarboxylic acids, in particular aldehydes, alcohols, amines, amidines, were obtained by functionalization of the [3+2] adducts.Conclusions. The synthetic approach to functionalized tetrahydrothiophenes by the [3+2] cycloaddition reaction of thiocarbonyl ylide with a number of compounds containing an activated multiple bond has expanded the limits of application of this reaction and allows obtaining the target compounds in multigram quantities. A high stereoselectivity of this reaction was observed. The reaction products are convenient synthetic precursors to the various classes of organic compounds.Мета. Вивчити використання хлорометилтриметилсилілметил сульфіду як попередника тіокарбоніліліду в реакції [3+2] циклоприєднанні з рядом α,β-ненасичених сполук та виявити закономірності перебігу цієї реакції. Розробити ефективний метод синтезу нових похідних дигідро- та тетрагідротіофенового ряду, які можуть бути зручними для подальшої модифікації.Результати та їх обговорення. Розширено синтетичний підхід до дигідро- та тетрагідротіофенів із замісниками в 3 та 4 положеннях через реакцію [3+2]-циклоприєднання тіокарбоніліліду до ряду сполук з активованим кратним зв’язком. Визначено стереоселективність та межі застосування цієї реакції. Проведено подальшу функціоналізацію отриманих сполук.Експериментальна частина. Тіокарбонілілід було отримано шляхом промотованого флуорид-йоном 1,3-десилілювання відомого хлорометилтриметилсилілметил сульфіду. Синтез цільових сполук передбачав [3+2]-циклоприєднання такого іліду до ряду сполук з активованими кратними зв’язками. Стереохімію цільових сполук визначено за допомогою 1H NOESY експериментів. Функціоналізацією отриманих сполук одержано синтетичні похідні тіоланкарбонових кислот, зокрема альдегіди, спирти, аміни, амідини.Висновки. Синтетичний підхід до функціоналізованих дигідро- та тетрагідротіофенів за допомогою реакції [3+2]-циклоприєднання тіокарбоніліліду з рядом сполук, які містять активований кратний зв’язок, розширив межі застосування цієї реакції і дозволив одержати цільові сполуки у мультиграмових кількостях. Виявлено високу стереоселективність цієї реакції. Продукти реакції є зручними синтетичними попередниками різних класів органічних сполук