Showing papers by "Moscow Institute of Physics and Technology published in 1998"

Parallel thermodynamic analysis of duplexes on oligodeoxyribonucleotide microchips

Abstract: A microchip method has been developed for massive and parallel thermodynamic analyses of DNA duplexes. Fluorescently labeled oligonucleotides were hybridized with oligonucleotides immobilized in the 100 x 100 x 20 mum gel pads of the microchips. The equilibrium melting curves for all microchip duplexes were measured in real time in parallel for all microchip duplexes. Thermodynamic data for perfect and mismatched duplexes that were obtained using the microchip method directly correlated with data obtained in solution. Fluorescent labels or longer linkers between the gel and the oligonucleotides appeared to have no significant effect on duplex stability. Extending the immobilized oligonucleotides with a four-base mixture from the 3'-end or one or two universal bases (5-nitroindole) from the 3'- and/or 5'-end increased the stabilities of their duplexes. These extensions were applied to increase the stabilities of the duplexes formed with short oligonucleotides in microchips, to significantly lessen the differences in melting curves of the AT- and GC-rich duplexes, and to improve discrimination of perfect duplexes from those containing poorly recognized terminal mismatches. This study explored a way to increase the efficiency of sequencing by hybridization on oligonucleotide microchips.

Tunneling and barrier-suppression ionization of atoms and ions in a laser radiation field

Abstract: Experimental and theoretical data on tunneling and barrier-suppression ionization of atoms and atomic ions in a low-frequency laser radiation field are considered. The yields of single- and multi-charged ions, the energy and angular distributions of photoelectrons, and effects of the laser pulse length and laser polarization are analyzed.

On the MHD effects on the force-free monopole outflow

Abstract: The stationary axisymmetric outflow from a rotating sphere with a (split) monopole magnetic field is considered. The stream equation describing the outflow is linearized in terms of the Michel magnetization parameter σ−1 ≪ 1, which allows a self-consistent analysis of the direct problem. It is shown that for a finite σ the fast magnetosonic surface is located at a finite distance ∼ σ1/3RL (RL = c/ΩF is the light cylinder). We have also found that the particle energy at the fast surface is just equal to the Michel value γ ∼ 1/3σ. The particle acceleration and magnetic field collimation are shown to become ineffective outside the fast magnetosonic surface.

The shape of WC crystals in cemented carbides

Abstract: A study has been made of the shape development of WC crystals in cemented carbides during liquid phase sintering. The relative influence of shape relaxation and carbide crystal growth processes on the shape is discussed. An effect of titanium additions on the shape of WC crystals in WC–Ni cemented carbides was observed. A shape parameter referred to as shape equiaxiality has been defined and calculated theoretically for various triangular prisms. The observed change of shape equiaxiality with titanium concentration in the binder phase of WC–Ni cemented carbides is discussed in terms of titanium segregation at the interphase boundary.

Low-frequency relativistic electromagnetic solitons in collisionless plasmas

Abstract: A relativistic electromagnetic soliton solution in the model of a one-dimensional, unbounded, cold, collisionless plasma is obtained without using the envelope approximation. The breaking of solitons with over-critical amplitudes is observed. The stability of undercritical solitons and the breaking of overcritical solitons are demonstrated by a particle-in-cell computer simulation.

Problems in high speed flow prediction relevant to control

Abstract: Three flow problems are discussed whose solutions suggest flow control schemes. These are 1) unsteady hypersonic flow over bodies in the Newtonian approximation, 2) a mechanism of hypersonic flow stabilization over acoustically semi-transparent walls and 3) store separation from cavities. Simplified systematic approximations based on asymptotic frameworks lead to compact computational models that elucidate the flow structure and opportunities for control. Besides generalizing the steady model of Cole, the Newtonian approximation in the unsteady context shows that unsteady body perturbations can lead to inflectional velocity profiles that can produce instabilities and boundary layer transition to enhance mixing in combustors and inlets. The absorbing wall illustrates a mechanism that can be exploited to damp 2 mode hypersonic instabilities. Simplified flow modeling based on systematic asymptotics for store separation from cavities shows the influence of the cavity shear layer on apparent mass effects that are important to damping in pitch and clearance from the parent body. Comparisons with free drop experiments are used for initial validations of the analytical models. * Senior Scientist, Fellow, AIAA f Principal Researcher, Member, AIAA * Margaret Damn Distinguished Professor, Mathematical Sciences, Fellow, AIAA § Professor ** Professor, Associate Fellow Copyright© 1998, American Institute of Aeronautics and Astronautics, Inc. 1. Unsteady Newtonian thin shock layers and hypersonic flow stability 1.11ntroduction Although the stability of high speed flows has received much attention in the recent literature, major complicating aspects have not been treated in a unified way. These features include the combined effects of the finite shock displacement on the boundary layer, the nonparallelism of the flow and the vorticity introduced by the shock curvature. The relevant structure of the shock and boundary layers has been treated in [1][9]. In [6] and [7], the aforementioned stability issues were discussed within the Hypersonic Small Disturbance approximation for the inviscid deck strongly interacting with the hypersonic boundary layer. Equations of motion for the mean and fluctuating small amplitude flows were analyzed. Because of nonparallelism in this framework, the spatial part of the waves cannot be treated by the usual Fourier decomposition and an initial value rather than eigenproblem for spatial stability is obtained. The initial value problem leads to partial rather than ordinary differential equations that require a numerical marching method for their solution. Results indicate that the specific heat ratio 7 plays a major role in the stability of flow since it controls the reflection of waves from the shock and the radiation of energy in the shock layer whose thickness scales with 7 -1. Early experiments such as those described in [2] showed that for a practically interesting class of flows, the shock layer becomes very thin compared to the boundary layer near the nose of hypersonic flat plates. This feature and the desire to further understand the shock and boundary layer structure encourage the use of the Newtonian approximation 7 —> 1. The connection with flow stability motivates the study of this approximation in an unsteady context. In this chapter, limit process expansions will be discussed relevant to unsteady viscous interactions as a prelude to the analysis of hypersonic stability and transition. The application of these limits is an unsteady extension of the steady state analysis of [3]. Although the focus here is the treatment of viscous interaction, boundary layer stability, receptivity and transition, the results derived are useful in inviscid hypersonic unsteady aerodynamic methodology and load prediction as well. 1.2 Analysis Figure 1 schematically indicates strong interaction flow near the leading edge of a hypersonic body. The viscous boundary layer which is usually thin, occupies an appreciable fraction of the distance between the shock and body that will be considered without undue loss of generality a flat plate in what follows. Accordingly F(x,f} = Q, in the notation of Fig. 1. The results in this chapter will be expressed in terms of the boundary layer thickness function A(3c,r) = 0, which in the interpretation mentioned in the Introduction could be the body shape in an inviscid context. Copyright© 1998, American Institute of Aeronautics and Astronautics, Inc. The unsteady form of the Hypersonic Small Disturbance Theory (HSDT) equations [9] are applicable and are obtained as in [7] from limit process expansions of hatted variables defined as quantities normalized by their freestream counterparts, with p,T,u,v,fJL the density, temperature, horizontal, vertical components of the velocity vector, and viscosity respectively. If the freestream density, pressure and velocity are denoted as U,p^ and p^ respectively, then a pressure coefficient used in these expansions is defined as p = (P-PJ/P-U. Fig. 1 Schematic of hypersonic strong interaction flow. With these definitions and the coordinate system in Fig. 1 as well the normalization of the Cartesian dimensional coordinates x and y to the unit reference length L and the reference time scale L/U for the time t, unbarred dimensionless normalized counterparts of these independent variables are defined. If M^ and R^ are respectively the freestream Mach and Reynolds numbers, and 5 is a characteristic flow deflection angle, then the expansions are p=a(x,y,t;H,y)+--(1.1) T=T+— p = 8p+M = l+v =• §v+• • (1.2) (1.3) (1.4) (1.5) (1.6) where y = y/(L8}. These expansions are valid in the HSDT limit x, y, t, H = M o are fixed as 8 — > 0 ,

Dense plasma diagnostics by fast proton beams

Abstract: Coulomb energy losses by 3-MeV protons in a capillary discharge channel are used as a diagnostics tool to measure the plasma density. By combining the proton energy loss data with the electron temperature measurements,we have been able to diagnose the free electron density ${n}_{\mathrm{fe}}=6.4\ifmmode\times\else\texttimes\fi{}{10}^{19}\phantom{\rule{0ex}{0ex}}{\mathrm{cm}}^{\ensuremath{-}3}$ in a 3.3-eV ${\mathrm{CH}}_{2}$ plasma to an accuracy of $\ifmmode\pm\else\textpm\fi{}17%$. A considerably better accuracy can be expected for higher values of the electron temperature.

Shock compression and thermodynamics of highly nonideal metallic plasma

Abstract: Using experimental data on compression and heating of dense metallic plasma by powerful shock waves, we have analyzed the effect of strong Coulomb interaction on both discrete and continuum bands of energy spectrum, the role of short-range repulsion, and the effect of degeneracy on the equation of state for a dense, nonideal metallic plasma. Explosive devices have been used to produce plasma for which the degree of ionization, nonideal parameter, and degeneracy varied over wide ranges. In order to increase effects of irreversible energy dissipation, metal targets of low densities have been used. Thermodynamic measurements have been compared to theoretical models taking into account Coulomb interaction, short-range repulsion, and degeneracy of electrons. The plasma models have been shown to be applicable to the equilibrium properties of multiply ionized plasma in a wide region of the phase diagram characterized by extremely high parameters [T⩾104 K, P⩾10 GPa, and ρ=(0.1–1)ρ 0], which is beyond the traditional domain of plasma physics.

Properties of Intersecting p-Branes in Various Dimensions

Abstract: General properties of intersecting extremal p-brane solutions of gravity coupled with dilatons and several different d-form fields in arbitrary space-time dimensions are considered. It is shown that heuristically expected properties of the intersecting p-branes follow from the explicit formulae for solutions. In particular, harmonic superposition and S-duality hold for all p-brane solutions. Generalized T-duality takes place under additional restrictions on the initial theory parameters.

Enzyme-mononucleotide interactions: three different folds share common structural elements for ATP recognition.

Abstract: Three ATP-dependent enzymes with different folds, cAMP-dependent protein kinase, D-Ala:D-Ala ligase and the alpha-subunit of the alpha2beta2 ribonucleotide reductase, have a similar organization of their ATP-binding sites. The most meaningful similarity was found over 23 structurally equivalent residues in each protein and includes three strands each from their beta-sheets, in addition to a connecting loop. The equivalent secondary structure elements in each of these enzymes donate four amino acids forming key hydrogen bonds responsible for the common orientation of the "AMP" moieties of their ATP-ligands. One lysine residue conserved throughout the three families binds the alpha-phosphate in each protein. The common fragments of structure also position some, but not all, of the equivalent residues involved in hydrophobic contacts with the adenine ring. These examples of convergent evolution reinforce the view that different proteins can fold in different ways to produce similar structures locally, and nature can take advantage of these features when structure and function demand it, as shown here for the common mode of ATP-binding by three unrelated proteins.

Two "unrelated" families of ATP-dependent enzymes share extensive structural similarities about their cofactor binding sites.

Abstract: Two proteins, D-alanine:D-alanine ligase and cAMP-dependent protein kinase, share a remarkable degree of structural convergence despite having different three-dimensional folds and different enzymatic functions. Here we report that as many as 103 residues from 10 segments form two identical super-secondary structures between which the cofactor ATP is bound. The cofactor, two bound metal cations, and several water molecules form a large network of electrostatic and hydrophobic interactions common to both enzymes, and these are mediated by the similar placement of equivalent amino acids within the common supersecondary structures.

Two-loop renormalization group restrictions on the standard model and the fourth chiral family

Abstract: In the framework of the two-loop renormalization group, the global profile of the Standard Model (SM) in its full parameter space is investigated up to the scale of the gauge singularity. The critical Higgs masses bordering the strong coupling, unstable and the safe regions are explicitly found. Restrictions on the Higgs boson mass as a function of a cutoff scale are obtained from the stability of the electroweak vacuum and from the absence of the strong coupling both in the Higgs and Yukawa sectors. The cutoff being equal to the Plank scale requires the Higgs mass to be M=(161.3+-20.6)+4-10 GeV and M>=140.7+-10 GeV, where the M corridor is the theoretical one and the errors are due to the top mass uncertainty. The SM two-loop beta-functions are generalized to the massive neutrino case. Modification of the two-loop global profile of the SM extended by one new chiral family is studied, and bounds on the masses of the family are found. The requirement of self-consistency of the perturbative SM as an underlying theory up to the Planck or GUT scale excludes the fourth chiral family with the mass up to 250 GeV depending on the Higgs mass and the cutoff scale. Under precision experiment restriction M<=200 GeV, the fourth chiral family, taken alone, is excluded. Nevertheless a pair of the chiral families constituting the vector-like one could still exist.

On the self-consistent model of an axisymmetric radio pulsar magnetosphere

Abstract: We consider a model of axisymmetric neutron star magnetospheres. In our approach, the current density in the region of open field lines is constant and the returning current flows in a narrow layer along the separatrix. In this case, the stream equation describing the magnetic field structure is linear both in the open and closed regions; the main problem is matching the solutions along the separatrix. We demonstrate that it is the stability condition on the separatrix that allows us to obtain a unique solution of the problem. In particular, the zero point of magnetic field is shown to be located near the light cylinder. Moreover, the hypothesis of the existence of the non-linear Ohm’s Law, connecting the potential drop in the pair creation region and the longitudinal electric current flowing in the magnetosphere, is confirmed.

Non-extremal localized branes and vacuum solutions in M-theory

Abstract: Non-extremal overlapping p-brane supergravity solutions localized in their relative transverse coordinates are constructed. The construction uses an algebraic method of solving the bosonic equations of motion. It is shown that these non-extremal solutions can be obtained from the extremal solutions by means of the superposition of two deformation functions defined by vacuum solutions of M-theory. Vacuum solutions of M-theory including irrational powers of harmonic functions are discussed.

The mechanism of re-breakdown within a post-arc channel in long non-uniform air gaps

Abstract: A kinetic model for the ionization processes in high-temperature air in a strong electric field is used to study numerically the mechanism of re-breakdown in a post-arc channel in long non-uniform gaps between a spherical anode and a plane cathode Our simulation shows two distinct phases of the re-breakdown The first phase consists of an ionizing wave traversing the gap After this phase the electrical field in the channel is re-arranged, tending towards being a uniform one The second phase consists of uniform increases in electron density and gas temperature along the whole channel length The re-breakdown reduced field increases from 8 to 60 Td when the initial gas temperature T decreases from 3000 to 700 K The dominant ionization mechanisms in the channel are electron impact ionization of NO at 1000

Soot formation in the pyrolysis of halogenated hydrocarbons. Part I, binary mixtures of carbon tetrachloride with hydrogen and iron pentacarbonyl

Abstract: Measurements on carbon particle growth during CCl4 thermal decomposition were carried out behind both incident and reflected shock waves. Three kind of mixture compositions have been investigated: 4000 ppm CCl4 in argon; 200 to 4000 ppm CCl4 and 200 to 8000 ppm Fe(CO)5 in argon; 4000 ppm CCl4 and 4000 ppm hydrogen in argon. The temperature range 1200

Energy distribution of relativistic electrons in the tunneling ionization of atoms by super-intense laser radiation.

Abstract: We studied theoretically the influence of relativistic effects on the energy distribution of electrons in the tunneling ionization of atoms by a field of linearly polarized super-intense laser radiation. It was shown that the energy distribution of ejected electrons is determined by relativistic law though the electron kinetic energy can be less than its rest energy. The relativistic probability of ionization along the field strength decreases exponentially with the electron kinetic energy, but more quickly than in the non-relativistic case.

Laser Control of Atomic Motion inside Diatomic Molecules

Abstract: Globally optimal solution describing a phase conjugated field of Raman scattering on the resonant B ← X transition of iodine I2 is studied. Maximum optical coherence is found as a top eigenvalue problem. A reversibility theorem has been stated. This provides sufficient conditions for a tightly localized waveform and molecular hologram to exist. A noisy picosecond pulse has been computed to show how femtosecond polarization is regained at target time.

Equation of State of Shock Compressed Plasma of Metals

Abstract: For the example of shock compressed nickel and iron, one can see that the chemical model can provide satisfactory description of strongly coupled plasma of expanded metals. The same agreement with experimental data was achieved for copper and lead [13,14].

Detailed structure of a Pb-doped Bi 2 Sr 2 CuO 6 superconductor

Abstract: The crystal structure of ${(\mathrm{B}\mathrm{i}}_{1.82}{\mathrm{Pb}}_{0.18})$ ${(\mathrm{S}\mathrm{r}}_{1.84}{\mathrm{Pb}}_{0.16})$ ${\mathrm{CuO}}_{6}$ was determined from single-crystal intensity data measured on a four-circle diffractometer. The structure is orthorhombic, space group Cccm (No. 66); the lattice parameters: $a$=5.392(3) \AA{}, $b$=24.603(5) \AA{}, $c$=5.300(3) \AA{}, $V$=703.2 (5) ${\mathrm{\AA{}}}^{3}$ (the space group can be denoted as Amaa by a cyclic transformation of the cell constants). The $R$ value was 0.048 for 418 unique reflections with $Ig3.00$ $\ensuremath{\sigma}(I).$ One of the O atoms bonded to Bi ions is disordered at two sites with a half occupancy and ${B}_{\mathrm{eq}}$=3.6(6) ${\mathrm{\AA{}}}^{2};$ although the thermal parameter is not so large as that reported by Torardi et al. [Phys. Rev. B 38, 225 (1988)], the disorder suggests that the crystal has a lower symmetry. The valence state of the Cu ion in the present compound was evaluated to be trivalent based on the Cu-O distances [Asbrink and Norrby, Acta Crystallogr. B 26, 8 (1970)] and the valence of Bi was estimated in comparison with that in other compounds. The O(3) sublattice dynamics in these types of superconductors is discussed based on the structural investigations.

Raman vertex in cuprates: Role of the extended Van Hove singularity

Abstract: We consider the bare electronic Raman vertex for ${\mathrm{CuO}}_{2}$ planes near an extended Van Hove singularity. It is shown than even for a simple band structure the vertex is rather complicated and contains many Brillouin-zone harmonics. The vertex anisotropy is larger than the anisotropy of the Fermi surface and even in the simplest cases does not follow the effective-mass anisotropy being much smaller than the latter one.

A new PCR-based approach to a fast search of a wide spectrum of cry genes from Bacillus thuringiensis strains

Abstract: Summary A pair of highly degenerated primers was adapted to carry out a single-step PCR-detection of any known and probably unknown cry genes of classes cryl, cry4 and cry9 encoding for 130 kDa protein ~5-endotoxins in the natural Bacillus thuringiensis (BT) strains. The Southern hybridization of the product has demonstrated that essentially remote cry-genes like crylAa and cry9A (crylG) could be represented in the single amplificate if they are simultaneously present in the genome of the analyzed strain. Four genes were detected by the proposed scheme in the BT ssp. galleriae 11-67. One of them, gene crylGal was originally found and cloned using the PCR-amplification product obtained from the genomic DNA of this strain as a probe. The new gene was completely identical to one cloned by B. Lambert (unpublished, EMBL accession number Z22510) and essentially related to crylM (EMBL accession number Y09326), renamed according to the new nomenclature as cryl Ga2.

Rotation and alignment of diatomic molecules and their molecular ions in strong laser fields

Abstract: A theory of classical rotation and alignment of diatomic molecules with and without permanent dipole moments and of their molecular ions in strong laser fields is developed. The actions of both cw and pulsed laser fields is considered. Conditions under which molecular axes are aligned with the field, which is presumed to be linearly polarized, have been determined. The analysis leads to a conclusion that molecules exposed to ultrashort laser pulses continue to rotate even after the end of the laser pulse. The effect of dynamical chaos on the rotational angular velocity in strong laser field is discussed.

Caldirola-Kanai Oscillator in Classical Formulation of Quantum Mechanics

Abstract: The quadrature distribution for the quantum damped oscillator is introduced in the framework of the formulation of quantum mechanics based on the tomography scheme. The probability distribution for the coherent and Fock states of the damped oscillator is expressed explicitly in terms of Gaussian and Hermite polynomials, correspondingly.

Extended Van Hove Singularity in Raman Spectra of High-Tc Superconductors

Abstract: We consider theoretically and experimentally how an extended van Hove singularity manifests itself in electronic and phonon Raman scattering in superconducting cuprates. Our analysis and experimental data shows that in the case of singularity carriers redistribution between different parts of the Brillouin zone and/or electronic bands is a common feature of both the electronic and phonon Raman scattering.