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

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

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

Adaptive pseudolinear compensators of dynamic characteristics of automatic control systems

Adaptive pseudolinear gain and phase compensators of dynamic characteristics of automatic control systems are suggested. The automatic control system performance with adaptive compensators has been explored. The efficiency of pseudolinear adaptive compensators in the automatic control systems with time-varying parameters has been demonstrated

Conformational transitions of heteropolymers in dilute solutions

In this paper we extend the Gaussian self-consistent method to permit study of the equilibrium and kinetics of conformational transitions for heteropolymers with any given primary sequence. The kinetic equations earlier derived by us are transformed to a form containing only the mean squared distances between pairs of monomers. These equations are further expressed in terms of instantaneous gradients of the variational free energy. The method allowed us to study exhaustively the stability and conformational structure of some periodic and random aperiodic sequences. A typical phase diagram of a fairly long amphiphilic heteropolymer chain is found to contain phases of the extended coil, the homogeneous globule, the micro-phase separated globule, and a large number of frustrated states, which result in conformational phases of the random coil and the frozen globule. We have also found that for a certain class of sequences the frustrated phases are suppressed. The kinetics of folding from the extended coil to the globule proceeds through non-equilibrium states possessing locally compacted, but partially misfolded and frustrated, structure. This results in a rather complicated multistep kinetic process typical of glassy systems.Comment: 15 pages, RevTeX, 20 ps figures, accepted for publication in Phys. Rev.

The development of blockchain technology in Russia : outlook and trends

Purpose: The article addresses the issue of new scientific decisions shaping with respect to the study of problems, current trends and perspectives of blockchain technology usage in the Russian Federation. Design/methodology/approach: To achieve the objectives of this study the increasing interest to blockchain technology in Russia was discussed. Findings: The article determined main problems in blockchain technology which includes gaps in legislative regulation; the existence of a considerable number of projects that are undergoing the development stage and that have not proved own economic feasibility yet; incomplete understanding of the blockchain spheres’ implementation by state officials, society and business representatives as well as expected outcomes according to the amount and time of their receiving; disputes on cryptocurrencies turnover in the country’s territory and their influence in the national economy. Practical implications: The study has demonstrated the interest growth mainly by businesses to the usage of blockchain technology in order to improve own competitiveness and to obtain additional benefits, including the form of their profits. Originality/value: The research has also determined the area of further key studies in blockchain technology usage in Russia and the world.peer-reviewe

The Condition and Prospects of the Development of the Government Securities Market Instruments in Ukraine

The article contains the results of studying instruments of the domestic market for government securities in Ukraine. Due to the fact that the financial market has become a powerful and efficient source for accumulating temporarily free funds, which will satisfy interests of investors themselves, the state is trying to diversify and improve the list of government securities of Ukraine. The main trends in the development of government borrowing in the domestic market of Ukraine are described, the advantages and disadvantages of the subtypes of government debt obligations are considered. Over the past decades the number of instruments in the government debt market of Ukraine has increased. In particular, these are VAT bonds, domestic government bonds in foreign currency, indexed bonds, hryvnia-denominated and US dollar-denominated treasury bills, war bonds. Despite a rather large list of financial instruments, almost all issues of non-standard debt instruments did not have much success. The main factors affecting the issuance and circulation of government securities in Ukraine are identified. Moreover, the relationship of the state and the NBU in the government securities market is highlighted. Financial bills and discussions of scientists about its legal status are considered in the context of financial instruments. There analyzed foreign experience in implementing government debt relief programs in the USA, Japan, and Canada, in which employers participate to financially support their employees. Positive and negative aspects of their functioning are identified, and conclusions are drawn about the possible consequences and prospects for Ukraine. There substantiated proposals for measures to increase the level of investor interest in government debt instruments in the securities market that concern both legal and economic components of qualitative changes and reforms

Adaptive pseudolinear compensators of dynamic characteristics of automatic control systems

Adaptive pseudolinear gain and phase compensators of dynamic characteristics of automatic control systems are suggested. The automatic control system performance with adaptive compensators has been explored. The efficiency of pseudolinear adaptive compensators in the automatic control systems with time-varying parameters has been demonstrated

Dynamic Behavior in Piezoresponse Force Microscopy

Frequency dependent dynamic behavior in Piezoresponse Force Microscopy (PFM) implemented on a beam-deflection atomic force microscope (AFM) is analyzed using a combination of modeling and experimental measurements. The PFM signal comprises contributions from local electrostatic forces acting on the tip, distributed forces acting on the cantilever, and three components of the electromechanical response vector. These interactions result in the bending and torsion of the cantilever, detected as vertical and lateral PFM signals. The relative magnitudes of these contributions depend on geometric parameters of the system, the stiffness and frictional forces of tip-surface junction, and operation frequencies. The dynamic signal formation mechanism in PFM is analyzed and conditions for optimal PFM imaging are formulated. The experimental approach for probing cantilever dynamics using frequency-bias spectroscopy and deconvolution of electromechanical and electrostatic contrast is implemented.Comment: 65 pages, 15 figures, high quality version available upon reques

Torsional-flexural buckling of unevenly battened columns under eccentrical compressive loading

In this paper, an analytical model is developed to determine the torsional-flexural buckling load of a channel column braced by unevenly distributed batten plates. Solutions of the critical-buckling loads were derived for three boundary cases using the energy method in which the rotating angle between the adjacent battens was presented in the form of a piecewise cubic Hermite interpolation (PCHI) for unequally spaced battens. The validity of the PCHI method was numerically verified by the classic analytical approach for evenly battened columns and a finite-element analysis for unevenly battened ones, respectively. Parameter studies were then performed to examine the effects of loading eccentricities on the torsional-flexural buckling capacity of both evenly and unevenly battened columns. Design parameters taken into account were the ratios of pure torsional buckling load to pure flexural–buckling load, the number and position of battens, and the ratio of the relative extent of the eccentricity. Numerical results were summarized into a series of relative curves indicating the combination of the buckling load and corresponding moments for various buckling ratios.National Natural Science Foundation of China (NSFC) under grant number (No.) 51175442 and Sichuan International Cooperation Research Project under grant No. 2014HH002