Showing papers by "Moscow State University published in 1987"

Single-electron transistors: Electrostatic analogs of the DC SQUIDS

Abstract: Dynamics of two simple structures (Fig 2) comprising twin pairs of small tunnel junctions is analyzed If the single-electron conductances R\min{12}\max{-1} and capacitances C 12 of the junctions are small enough (Eq 1), the dynamics is influenced drastically by e-quantization of the electrical charge Q of the central electrode As a result, the structures become close analogs of the dc SQUIDs within the framework of the well-known electro \leftrightarrow magnetic duality ( Q\leftrightarrow\Phi , etc) In particular, the dc I-V curves of the structures can be controlled by the "gate" voltage U, so that the devices can be used as "Single-Electron Transistors" (SETs) with characteristics resembling those of the usual FETs, but at a new quantitative level Analysis shows that the physics of the SETs allows much smaller dimensions, higher cutoff frequencies and much lower power consumption than for their semiconductor counterparts New transistors can be apparently used to achieve extremely large integration scales, possibly opening a way to three-dimensional and molecular-level integration

Gravitational-wave bursts with memory and experimental prospects

Abstract: Experimenters usually divide the gravitational waves which they hope to detect into three classes: 'bursts' in which the wave field hTTij rises from zero, oscillates for only a few cycles and then returns to zero; 'periodic waves', and 'stochastic waves'1. There is, however, a fourth class, 'bursts with memory'2–6 (BWM), in which hTTij rises from zero, oscillates for a few cycles, and then after a burst of duration Δt settles down into a non-zero final value δhTTij. Here we show that for any kind of detector the best way to search for a BWM is to integrate up the signal for an integration time t 1/fopt, where fopt is the frequency at which the detector has optimal amplitude sensitivity to ordinary bursts (bursts without memory). In such a search the sensitivity to BWM with duration Δ <= 1/fopt is independent of the burst duration Δt and is approximately equal to the sensitivity to ordinary bursts one cycle long with frequency fopt (see Fig. 1). It is possible, though not highly probable, that BWM will be among the earliest kinds of gravitational waves detected; therefore experimenters should take them into account when planning their search strategies and data analyses.

Vacuum polarization in the gravitational field of a cosmic string.

Abstract: The contributions of the scalar massless, neutrino, and electromagnetic fields to the vacuum polarization in the gravitational field of a cosmic string are found.

Conformal Field Theories with Additional Z(N) Symmetry

Abstract: In this paper we construct the correlation functions for ZN twists. These correlation functions are connected with partition function of string propagating on orbifold. Using the correlation functions of Z2 twists we reproduce the two-loop amplitude in the bosonic string theory.

Ultimate performance of the RSFQ logic circuits

Abstract: A new family of dc-powered Josephson junction digital devices, the Rapid Single Flux Quantum (RSFQ) logic, is described. The devices use overdamped Josephson junctions and two-junction interferometers to store, pass and process the digital information presented in form of single flux quanta. We have carried out extensive numerical simulation of the dynamics of the RSFQ logic gates and of some more complex circuits including serial full adder and reversible shift register, within the standard microscopic-theory ("Werthamer") description of Josephson junctions. The minimum clock cycles of the basic RSFQ circuits turn out to be as small as 2.5 ps. The most promising ways to use the RSFQ logic circuits at the present stage of development of the Josephson junction digital technology are discussed.

The antioxidative properties of carnosine, a natural histidine containing dipeptide.

Abstract: The experimental results suggest that the antioxidative function of carnosine is one of the most important manifestations of its biological role. The ability of carnosine to interact directly with lipid peroxidation products was demonstrated. The effects of carnosine on partial restoration of lens transparency in dog eyes with senile cataract which is known to be caused by lipid peroxidation were demonstrated "in vitro" and "in vivo".

Bovine cardiac troponin T: amino acid sequences of the two isoforms.

Abstract: Troponin T (TnT) is the tropomyosin-binding subunit of troponin, the thin filament regulatory complex that confers calcium sensitivity to striated muscle contraction and actomyosin ATPase activity. Bovine cardiac muscle contains two isoforms (TnT-1 and TnT-2) of TnT that differ in sequence near their amino termini. Thin filaments containing TnT-2 require less calcium to activate the MgATPase rate of myosin than do thin filaments containing TnT-1. Using whole troponin T purified from adult bovine cardiac muscle, we have determined the complete amino acid sequence of the larger, more abundant isoform TnT-1. We confirmed that sequence differences between TnT-1 and TnT-2 are confined to the amino-terminal regions and found that TnT-1 makes up approximately 75% of the total troponin T isolated. Partial sequencing of the separated isoforms showed that the difference between them is due solely to residues 15-19 (Glu-Ala-Ala-Glu-Glu) of TnT-1 being absent from TnT-2. The deleted segment may correspond to the product of exon 4 of the chicken cardiac TnT gene [Cooper, T.A., & Ordahl, C.P. (1985) J. Biol. Chem. 260, 11140-11148]. Exon 5, which is developmentally regulated in the chicken, is not expressed in either TnT-1 or TnT-2. TnT-1 contains 284 amino acid residues and has a Mr of 33,808, while TnT-2 contains 279 amino acid residues and has a Mr of 33,279. Bovine cardiac TnT contains the only known thiol group in any isolated TnT (Cys-39 of TnT-1, Cys-34 of TnT-2). Comparison of bovine, rabbit, and chicken cardiac TnT sequences shows near identity of the amino-terminal 13 amino acid residues (exons 2 and 3 of the chicken cardiac gene), many differences in the following 60 residues (exons 4-8), and great similarity in the C-terminal 230 residues (exons 9-18).

Association of intermediate filaments with vinculin-containing adhesion plaques of fibroblasts.

Abstract: Double immunofluorescence staining of quail embryo fibroblasts with rabbit antibody to vinculin and mouse monoclonal antibody to vimentin revealed a coincidence between fluorescence patterns for cell-substrate focal contacts and intermediate filaments. Most of the vinculin-containing adhesion plaques coincided with the ends of vimentin-positive fibrils. This association was further corroborated by immunoelection microscopic observations of the cytoskeletons of quail and mouse fibroblasts using a platinum replica technique. The intermediate filaments were identified either by direct treatment with antivimentin IgM or by an indirect immunogold staining method. Colcemid treatment of the cells caused a collapse of intermediate filaments and destroyed their association with focal contacts. During the early stages of the colcemid-induced collapse of the intermediate filaments, single vimentin fibrils appeared to retain their association with focal contacts. The possible role of the intermediate filaments in the formation and maintenance of focal contacts is discussed.

On the Behavior at Infinity of Solutions of Elliptic Systems with a Finite Energy Integral

Abstract: Asymptotic behavior in a neighborhood of infinity is studied in this paper for solutions of an elliptic system of order 2m with constant complex coefficients. It is supposed that the weighted Dirichlet integral is bounded. Our considerations include solutions with finite energy for the system of linear elasticity (see Theorem 3). A class of solutions periodic in some independent variables is also studied in this paper (the E. Sanchez-Palencia problem).

Godel's Incompleteness Theorem

Abstract: There are some topics in mathematics which, although enjoying a certain fame, have traditionally been considered either too complicated or of insufficient importance to be included in the core mathematical curriculum. Customarily, such subjects are relegated to optional units of the syllabus, independent study projects, seminar papers, and math club talks. Among such topics are several which remain in this nebulous status only because of inertia. An example is Godel’s incompleteness theorem.

Dynamics of a polymer chain in an array of obstacles

Abstract: On the basis of the model “polymer chain in an array of obstacles” the influence of the topology effects on the dynamics of concentrated polymer systems is investigated theoretically. The 1/ z -expansion (where z is the coordinational number of the lattice of obstacles) is proposed for this problem. By means of this expansion the diffusion coefficient of a linear unclosed polymer chain is calculated. The equilibrium properties of linear closed chain (i.e. ring) unentangled with either of the edges of the lattice are investigated in detail. In particular, it is shown that the diffusion coefficient D of the center of mass of closed chain consisting of N links is proportional to N −5/2 .

Enzymes Entrapped Into Reversed Micelles Of Surfactants In Organic Solvents: Key Trends In Applied Enzymology (Biotechnology)

Abstract: This paper discusses applications of enzymes solubilized by surfactants in organic solvents to fine organic syntheses, in clinical and chemical analysis, and in therapy, as well as some future trends in biotechnology.

On estimates of the maximum of a solution of a parabolic equation and estimates of the distribution of a semimartingale

Abstract: Estimates are proved for the maximum of a solution of a linear parabolic equation in terms of the -norm of the right-hand side. The coefficients of the first derivatives are assumed to be integrable to a suitable power. Various boundary value problems are considered. Corresponding -estimates are proved also for the distributions of semimartingales.Bibliography: 16 titles.

Actin cortex and microtubular system in morphogenesis: cooperation and competition.

Abstract: SUMMARY Actin cortex and microtubules determine two different types of morphological organization of the cytoplasm. Cooperation and competition between these two organizations may produce a diversity of final forms. Actin cortex alone, without the other cytoskeletal systems, is sufficient for the organization of vectorized pseudopod-forming cytoplasmatic units termed ‘actinoplasts’. Reversible segregation of cytoplasm into actinoplasts and microtubule-rich stable domains (‘tubuloplasts’) is suggested to play an important role in many types of morphogenesis. Segregation of this type can be induced in fibroblasts of certain lines by the tumour promotor, tetradecanoyl phorbol-acetate (TPA). Self-organization of each actinoplast leads to the development of microfilament bundles associated with focal contacts. Analysis of the evolution of these bundle-contact structures during spreading of mouse fibroblasts suggests that their patterns are determined by the degree of centripetal tension within the actin cortex; the microtubular system stabilizes these patterns. Pseudopodial activity of the edges of the actinoplasts can be controlled by environmental factors. One particular type of control, i.e. the effect of cell–cell contact, is discussed. Actin cortex and microtubules seem to have alternative effects on the distribution of vimentin-containing intermediate filaments.

Callus formation in seven species of agarophyte marine algae

Abstract: Callus formation of seven species of the agarophyte marine algae Phyllophora nervosa, Gracilaria verrucosa, Furcellaria fastigiata, ceramium kondoi, Gelidium vagum, Laurencia paniculata, Rhodymenia pertusa was obtained from 1984 to 1986. A new sterile agent, chlorhexidin bigluconate, was used to get axenic explants from the algae thalli. The formation of callus from axenic explants depended on temperature of cultivation. In the case of F. fastigiata and G. vagum it occurred at 12° to 20°C, and with P. nervosa at 18° to 26°C. The exchange of sucrose with mannitol in the culture medium and the addition of some growth regulators stimulated the formation of callus. Mass formation of lumpy and warty extensions was observed in the explants from leaf blades of P. nervosa. The results might be useful for improving the aquaculture of agarophyte marine algae.