Showing papers by "Moscow State University published in 1985"

A supersymmetric extension of the Kadomtsev-Petviashvili hierarchy

Abstract: An extension of the Kadomtsev-Petviashvili hierarchy by odd variables is given. Conservation laws and formal integrability are proved.

Theory of the Bloch-wave oscillations in small Josephson junctions

Abstract: A quantum-statistical theory of the low-temperature behavior of Josephson junctions with very small capacitanceC and quasiparticle conductivityG, driven by a small currentI(t), is developed. In such junctions the “secondary” quantum macroscopic effects (tunneling and interference) are significant for all values of the Josephson phase difference ϕ, so that new features in the junction dynamics arise, including quantum “Bloch-wave” oscillations. Here the junction dynamics is analyzed in detail starting from a simple macroscopic Hamiltonian. The simplest way to analyze the Bloch-wave oscillations turns out to be a Langevin-type equation for the operator of the junction “quasicharge”q. In particular, this equation shows that the frequencyf B of these oscillations is related by the fundamental equation $$f_B = (\bar I - G\bar V)/2e$$ to the dc current $$\bar I$$ and voltage $$\bar V$$ . The main effects suppressing or masking the Bloch-wave oscillations can be analyzed using the equation for the density matrix of the system traced over the states of the quasiparticles. This analysis has made it possible to establish the main conditions for the experimental observation of the predicted effects and to present a general picture of the low temperature dynamics of Josephson junctions.

Calculation of shrinkage corrections in harmonic approximation

Abstract: The classical spectral problem is analyzed on the level of the harmonic force field approximation to determine the vector describing the mean atomic displacements from the equilibrium positions, x &> =Σ k x &> =— 1 2 B(O) −1 Σ k ΔB k , where B(O) is the transformation matrix between the internal and Cartesian coordinates defined for the equilibrium configuration, ΔB k is the variation in the transformation matrix caused by molecular motion along the k th eigenvector and the summation is over all molecular modes. A simple procedure for determining the ΔB k quantities without explicitly calculating the ΔB k matrices is described. The vectors x and k enter nto the expressions for the shrinkage corrections and the mean square vibrational amplitudes. The harmonic amplitudes calculated for the C 3 O 2 molecule using the present theory agree well with the observed quantities.

Coexistence of superconductivity and magnetism theoretical predictions and experimental results

Abstract: Superconductivity and ferromagnetic ordering are two antagonistic types of ordering, and their mutual influence leads to many interesting phenomena which have been studied recently in ternary compounds. Theoretical analysis of ferromagnetic materials which are type II superconductors near the superconducting transition point T cl shows that they become type I near the magnetic transition point T M. The proposed theory constructed for the case T M « T cl predicts the formation of a transverse domain-like (DS phase) magnetic structure below T M. The electronic spectrum appears to be gapless in the DS phase of clean compounds with a re-entrant transition. The change from type II to type I behaviour as the sample is cooled to T M has been observed in ErRh4B4. Experimental data for HoMo6S8, HoMo6Se8 and ErRh4B4 give evidence for the coexistence of super-conductivity and non-uniform magnetic ordering below T M. Mutual influence of superconducting and magnetic orderings is also studied.

On the theory of liquid-crystalline ordering of polymer chains with limited flexibility

Abstract: We propose a universal approximate method which enables us to study the statistical mechanics of the liquid-crystalline ordering in the solutions of stiffchain macromolecules with limited flexibility of arbitrary nature at arbitrary solution concentrations and arbitrary temperatures (solvent quality). In the variables temperature and concentration we construct the full phase diagrams for the nematic transition for the cases of long rigid rods and semiflexible macromolecules with freely jointed, persistent, and rotational-isomeric flexibility mechanisms. The method proposed can be easily generalized for the study of thermotropic polymer liquid crystals, as well as more complex polymer chain models (e.g., copolymers containing stiff and flexible fragments in the chain).

Control of locomotion in marine mollusc Clione limacina. I. Efferent activity during actual and fictitious swimming.

Abstract: 1.The marine mollusc Clione limacina swims by making rhythmic movements (with a frequency of 1–5 Hz) of its two wings. Filming demonstrated that the wings perform oscillatory movements in the frontal plane of the animal. During both the upward and downward movements of the wing, its posterior edge lagged behind the anterior one, i.e. the wing plane was inclined in relation to the longitudinal axis of an animal. As a result of this inclination, the wing oscillations in the frontal plane produce a force directed forwards. 2.In restrained animals with the body cavity opened (a whole-animal preparation), the wing position, electrical activity in the wing nerve and activity of two identified efferent neurons (1A and 2A) were recorded during locomotory wing movements. There were two bursts of activity in the wing nerve during the locomotory cycle, the first one corresponding to the excitation of efferent neurons controlling the wing elevation, and the second one, to the excitation of efferent neurons controlling the lowering of the wing. Neurons 1A and 2A fired reciprocally at the beginning of the phase of elevating and lowering the wing, respectively. During excitation of one of the neurons, an IPSP appeared in its antagonist. 3. A pair of isolated pedal ganglia of Clione was capable of generating the locomotory rhythm (“fictitious swimming”). In fictitious swimming, as in actual swimming, there were two bursts of activity in the wing nerve per locomotory cycle, and the 1A and 2A neurons fired reciprocally. Homologous neurons from the left and right ganglia fired inphase. A single pedal ganglion was also capable of generating the locomotory rhythm. 4.Serotonin (10-5–10-6 M) increased the locomotor activity both in the whole-animal preparation and in the isolated pedal ganglia.

Control of locomotion in marine mollusc Clione limacina. III. On the origin of locomotory rhythm.

Abstract: 1. Neurons from the isolated pedal ganglia of the marine mollusc Clione limacina were recorded from intracellularly during generation of the locomotory rhythm. Polarization of single type 7 or type 8 interneurons (which discharge in the D-and V-phases of a swim cycle, respectively) strongly affected activity of the rhythm generator. Injection of depolarizing and hyperpolarizing current usually resulted in shortening and lengthening of a swim cycle, respectively. A short pulse of hyperpolarizing current shifted the phase of the rhythmic generator. The same effect could be evoked by polarization of efferent neurons of types 2, 3 and 4 which are electrically coupled to interneurons. On the contrary, polarization of types 1, 6 and 10 efferent neurons, having no electrical connections with interneurons, did not affect the locomotory rhythm. 2. A number of observations indicate that type 7 and 8 interneurons constitute the main source of postsynaptic potentials that were observed in all the “rhythmic” neurons of the pedal ganglia. Type 7 interneurons excited the D-phase neurons and inhibited the V-phase neurons; type 8 interneurons produced opposite effects. 3. Tetrodotoxin eliminated spike generation in all efferent neurons of the pedal ganglia, while in interneurons spike generation persisted. After blocking the spike discharges in all the efferent neurons, type 7 and 8 interneurons were capable of generating alternating activity. One may conclude that these interneurons determine the main features of the swim pattern, i.e., the rhythmic alternating activity of two (D and V) populations of neurons. 4. Both type 7 and type 8 interneurons were capable of endogenous rhythmic discharges with a period like that in normal swimming. This was demonstrated in experiments in which one of the two populations of “rhythmic” neurons (D or V) was inhibited by means of strong electrical hyperpolarization, as well as in experiments in which interaction between the two populations, mediated by chemical synapses, was blocked by Co2+ ions. 5. Type 7 and 8 interneurons were capable of “rebound”, i.e. they had a tendency to discharge after termination of inhibition. 6. V-phase neurons exerted not only inhibitory but also excitatory action upon D-phase neurons, the excitatory action being longer than the inhibitory one. 7. The main experimental findings correspond well to the model of rhythm generator consisting of two half centres possessing endogenous rhythmic activity. The half-centres exert strong, short duration inhibitory and weak long duration excitatory actions upon one another. The behaviour of such a model is considered and compared with that of the locomotor generator of Clione.

Control of locomotion in marine mollusc Clione limacina II. Rhythmic neurons of pedal ganglia

Abstract: 1.Activity from neurons in isolated pedal ganglia of Clione limacina was recorded intracellularly during generation of rhythmic swimming. To map the distribution of cells in a ganglion, one of two microelectrodes was used to monitor activity of the identified neuron (1A or 2A), while the second electrode was used to penetrate successively all the visible neurons within a definite area of the ganglion. In addition, pairs of neurons of various types were recorded in different combinations with each other. Intracellular staining of neurons was also performed. 2.Each ganglion contained about 400 neurons, of which about 60 neurons exhibited rhythmic activity related to a swim cycle. These rhythmic neurons were divided into 9 groups (types) according to axonal projections, electrical properties and the phase of activity in a swim cycle. Three types of interneurons and six types of efferent neurons were distinguished. 3.Type 7 and 8 interneurons generated only one spike of long (50–150 ms) duration per swim cycle. Type 7 interneurons discharged in the phase of the cycle that corresponded (in actual swimming) to the dorsal movement of wings (D-phase). Type 8 interneurons discharged in the opposite phase corresponding to the ventral movement of wings (V-phase). With excitation of type 7 interneurons, an IPSP appeared in the type 8 interneurons, and vice versa. Neuropilar branching of these neurons was observed in the ipsilateral ganglion. In addition, they sent an axon to the contralateral ganglion across the pedal commissure. 4.Efferent neurons (i.e. the cell sending axons into the wing nerve) generated spikes of 1–5 ms duration. Type 1 and 3 neurons were excited in the D-phase of a swim cycle and were inhibited in the V-phase. Type 2 and 4 neurons were excited in the V-phase and inhibited in the D-phase. Type 10 neurons received only an excitatory input in the V-phase, while type 6 neurons received only an inhibitory input in the D-phase. 5. Type 12 interneurons were non-spiking cells, they generated a stable depolarization (“plateau”) throughout most of the V-phase. 6. Neurons of the same type from one ganglion (except for type 6) were electrically coupled to each other. There were also electrical connections between most neurons firing in the same phase of the cycle, i.e. between types 3 and 7, as well as between types 2, 4 and 8. Type 7 interneurons from the left and right ganglia were electrically coupled, the same was true for type 8 interneurons.

Cooperative interpolyelectrolyte reactions

Abstract: Water-soluble nonstoichiometric polyelectrolyte complexes (NPEC) are formed as a result of interaction of opposite charged polyelectrolytes used in nonequivalent ratios. One of the most important properties of NPEC is their ability to participate in intermacromolecular exchange and substitution reactions in aqueous solutions. The kinetics of exchange and substitution reactions has been studied by the method of luminescence quenching. It has been found that such reactions proceed by the contact mechanism and that addition of low molecular electrolytes to the reaction mixtures results in a dramatic increase in the rates of the reactions. The kinetics of the reactions is well described by the equation q = 1-exp(- kt∝) (here q is the degree of conversion and ∝ < 1), deduced under the assumption that exchange and substitution occur by the nucleation mechanism and the development of nuclei is inhibited in time. The studied reactions represent a new class of interpolymer reactions and they can be very important, in particular, for understanding the mechanism of functioning of biologically important macromolecules and for the interpretation of the physiological activity of polyelectrolytes.

The surface of Venus as revealed by the Venera landings: Part II

Abstract: Observations of the panoramic photographs transmitted by Veneras 13 and 14 indicate that many visible rock units are layered and that at least a portion of the fine material could be the result of in situ geomorphic disintegration. Chemical and material property experiments indicate that the chemical composition of the material at the landing sites is essentially basaltic, that the bearing strength is minimal (a few kilograms per square centimetre, or a few hundred kilopascals), that the density is less than 1.5 g/cm 3 , that the porosity is very high (>50%), and that the electrical resistivity is very low ( The discussion on the possible geological nature of the surface of Venus presented in Part I (Florensky and others, 1977a) is extended in light of these new data. Six possible origins of the rock units were discussed: (1) surface lava extrusion; (2) igneous intrusion, later exposed by erosion; (3) pyroclastic fall; (4) impact ejection and lithification; (5) sedimentary deposits lithified at depth and later exposed by erosion; and (6) surface metamorphism due to unique Venusian surface conditions. It is concluded that, although none of the above hypotheses can be conclusively proven or disproven, hypothesis 6 is to be advanced to the forefront. This is suggested by (1) the low density and low bearing strength, (2) the presence of layering, (3) the possible presence of sedimentary structures in the rock units, such as cross-bedding and ripple marks, (4) the low electrical resistivity, which may indicate chemical alterations of surface material, and (5) the albedo of the loose, fine material, which is lower than the albedo of the rock units. This again suggests chemical alterations. Within the context of this hypothesis, the rock units are sedimentary or sedimentary-volcanic. Lithification occurred in the past due to surface chemical effects. The rock units, analogous with a similar terrestrial phenomenon, can be referred to as “duricrusts” (with the understanding that the Venusian process is completely different from the terrestrial process). Presently, the rock units are undergoing disintegration, indicating that changes have occurred in the surface conditions at the landing sites.

Synchrotron radiation and its applications

Abstract: In this paper, the basic formulas are derived for the theory of synchrotron radiation and some important practical applications of synchrotron radiation are discussed, as well as the prospects for the further development of these investigations.

Control of locomotion in marine mollusc Clione limacina. IV. Role of type 12 interneurons.

Abstract: 1. Type 12 interneurons in pedal ganglia of Clione limacina exerted a strong influence upon the locomotor generator during “intense” swimming. These neurons generated “plateau” potentials, i.e. their membrane potential had two stable states: the “upper” one when a neuron was depolarized, and the “down” one, separated by 30–40 mV. The interneurons could remain in each state for a long time. Short depolarizing and hyperpolarizing current pulses, as well as excitatory and inhibitory postsynaptic potentials, could transfer the interneurons from one state to another. 2. When the pedal ganglia generated the locomotory rhythm, type 12 neurons received an EPSP and passed to the “upper” state in the V2-phase of a locomotor cycle. They remained at this state until the beginning of the D1-phase when they received an IPSP and passed to the “down” state. The EPSP in type 12 neurons was produced by type 8d neurons, and the IPSP by type 7 neurons. 3. Type 12 neurons exerted inhibitory influences upon many neurons active in the V1 and V2 phases, and excitatory influences upon the D-phase interneurons (type 7). 4. The functional role of type 12 neurons was to limit the activity of neurons discharging in the V-phase of a locomotory cycle. In addition, they enhanced the excitation of the D-phase neurons and promoted, thus, the transition from the V-phase to the D-phase.

Reversible conveyer computation in array of parametric quantrons

Abstract: A possibility of physically and logically reversible processing of digital information in Josephson-junction circuits of a reasonable complexity has been considered. As example, a 8-bit 1024-point fast convolver has been designed on the basis of a two-dimentional quasi-uniform array of \sim 250\times30,000 parametric quantrons. This completely reversible conveyer device can operate with the estimated rate of at least \sim10^{9} numbers per second, which corresponds to \sim10^{14} binary logical operations per second. At this rate the power dissipation in the whole device can still be as low as ∼30nW. A new mode of the parametric quantron operation with larger parameter margins is also described.

Single-reagent polarization fluoroimmunoassay for amphetamine in urine.

Abstract: This simple polarization fluoroimmunoassay for detection of amphetamine in urine involves the use of a single reagent: suitably diluted antiserum plus fluorescein-labeled amphetamine as tracer. To this, one adds 10 microL of urine, incubates for a few minutes at room temperature, and measures the fluorescence polarization. By using an antiserum obtained against an immunogen conjugated via the para position of the drug's phenyl ring, we have attained greater specificity than that of most existing immunoassays. As little as 1 mg of amphetamine per liter was easily detected. Results for 266 patients' urines agreed completely with those by gas-liquid chromatography. When a nonseparation enzymoimmunoassay (EMIT-d.a.u., Syva) was applied to 62 specimens chosen without conscious bias, three results were falsely negative, three falsely positive.

Recycle of the cellulase-enzyme complex after hydrolysis of steam-exploded wood

Abstract: Cellulase can be recovered in high yields by contacting fresh substrate with hydrolysis filtrate and by extraction of spent hydrolysis residue with pH 7 buffer. Recycled enzymes give hydrolysis rates about equal to those with fresh enzymes. Steam-exploded wood (SEW) is washed with water to remove sugars and byproducts from breakdown of hemicellulose, and recycle of enzymes proceeds better if lignin is also removed prior to hydrolysis. Oven drying of SEW interferes with recycle, and the recovery of enzymes is only one-half of that with SEW that is kept moist. Effectiveness of enzyme recovery depends on the completeness of hydrolysis, as determined by contact time and enzyme concentration. For cost-effective operation, enzyme should not be recovered until appreciable filter paper activity and carboxylmethylcellulase activity appear in the hydrolysate. 6 references.