Showing papers by "Moscow Institute of Physics and Technology published in 2002"
TL;DR: The use of an intense collimated beam of protons produced by a high-intensity laser pulse interacting with a plasma for the proton treatment of oncological diseases is discussed and the generation of high quality proton beams is proved with particle in cell simulations.
446 citations
TL;DR: It is shown that the proposed CA models can be very transparent and still reproduce the two main types of congested patterns as well as their dependence on the flows near an on-ramp, in qualitative agreement with the recently developed continuum version of the three-phase traffic theory.
Abstract: The cellular automata (CA) approach to traffic modelling is extended to allow for spatially homogeneous steady state solutions that cover a two-dimensional region in the flow–density plane. Hence these models fulfil a basic postulate of a three-phase traffic theory proposed by Kerner. This is achieved by a synchronization distance, within which a vehicle always tries to adjust its speed to that of the vehicle in front. In the CA models presented, the modelling of the free and safe speeds, the slow-to-start rules as well as some contributions to noise are based on the ideas of the Nagel–Schreckenberg-type modelling. It is shown that the proposed CA models can be very transparent and still reproduce the two main types of congested patterns (the general pattern and the synchronized flow pattern) as well as their dependence on the flows near an on-ramp, in qualitative agreement with the recently developed continuum version of the three-phase traffic theory (Kerner B S and Klenov S L 2002 J. Phys. A: Math. Gen. 35 L31 ). These features are qualitatively different from those in previously considered CA traffic models. The probability of the breakdown phenomenon (i.e. of the phase transition from free flow to synchronized flow) as function of the flow rate to the on-ramp and of the flow rate on the road upstream of the on-ramp is investigated. The capacity drops at the on-ramp which occur due to the formation of different congested patterns are calculated.
398 citations
TL;DR: The X-ray structure of the complex between N. pharaonis SRII and the receptor-binding domain of HtrII at 1.94 Å resolution provides an atomic picture of the first signal transduction step, providing evidence for a common mechanism for this process in phototaxis and chemotaxis.
Abstract: Microbial rhodopsins, which constitute a family of seven-helix membrane proteins with retinal as a prosthetic group, are distributed throughout the Bacteria, Archaea and Eukaryota1,2,3. This family of photoactive proteins uses a common structural design for two distinct functions: light-driven ion transport and phototaxis. The sensors activate a signal transduction chain similar to that of the two-component system of eubacterial chemotaxis4. The link between the photoreceptor and the following cytoplasmic signal cascade is formed by a transducer molecule that binds tightly and specifically5 to its cognate receptor by means of two transmembrane helices (TM1 and TM2). It is thought that light excitation of sensory rhodopsin II from Natronobacterium pharaonis (SRII) in complex with its transducer (HtrII) induces an outward movement of its helix F (ref. 6), which in turn triggers a rotation of TM2 (ref. 7). It is unclear how this TM2 transition is converted into a cellular signal. Here we present the X-ray structure of the complex between N. pharaonis SRII and the receptor-binding domain of HtrII at 1.94 A resolution, which provides an atomic picture of the first signal transduction step. Our results provide evidence for a common mechanism for this process in phototaxis and chemotaxis.
389 citations
TL;DR: In this article, the evolution of large atomic clusters exposed to a super-intense ultrashort laser pulse is considered, and the optimal conditions are analyzed for efficient absorption of laser radiation by large clusters.
360 citations
TL;DR: In this paper, a microscopic model for phase transitions in traffic flow is presented, where the basic assumption of the model is that hypothetical homogeneous and stationary, i.e., vehicles cover a two-dimensional region in the flow-density plane.
Abstract: A microscopic model for phase transitions in traffic flow is presented. The basic assumption of the model is that hypothetical homogeneous and stationary, i.e. `equilibrium' states of the model cover a two-dimensional region in the flow-density plane. As in empirical observations, in the model moving jams do not spontaneously occur in free flow. Instead, the first-order phase transition to synchronized flow beginning at some density in free flow is realized. The moving jams emerge only in synchronized flow. As a result, the diagrams of patterns (states) both for a homogeneous road without bottlenecks and at on-ramps are qualitatively different from those found in other approaches at present. In particular, only one type of pattern occurs at on-ramps, if the flow rates to the on-ramp and on the road are high enough: in this general pattern synchronized flow occurs upstream of the on-ramp and wide moving jams spontaneously emerge in this synchronized flow.
217 citations
TL;DR: In this paper, a macroscopic bubble-like structure has been detected through the deflection that the associated electric charge separation causes in a proton probe beam, interpreted as the remnants of a cloud of relativistic solitons generated in the plasma by the ultraintense laser pulse.
Abstract: A novel physical phenomenon has been observed following the interaction of an intense $({10}^{19}\mathrm{W}/{\mathrm{cm}}^{2})$ laser pulse with an underdense plasma. Long-lived, macroscopic bubblelike structures have been detected through the deflection that the associated electric charge separation causes in a proton probe beam. These structures are interpreted as the remnants of a cloud of relativistic solitons generated in the plasma by the ultraintense laser pulse. This interpretation is supported by an analytical study of the soliton cloud evolution, by particle-in-cell simulations, and by a reconstruction of the proton-beam deflection.
189 citations
TL;DR: In this paper, boundary-layer transition experiments were performed on a sharp 5.06-deg half-angle round cone at zero angle of attack in the T5 Hypervelocity Shock Tunnel to test the effects of the porous surface.
Abstract: Recently performed linear stability analyses suggested that transition could be delayed in hypersonic boundary layers by using an ultrasonically absorptive surface to damp the second mode (Mack mode). Boundary-layer transition experiments were performed on a sharp 5.06-deg half-angle round cone at zero angle of attack in the T5 Hypervelocity Shock Tunnel to test this concept. The cone was constructed with a smooth surface around half the cone circumference (to serve as a control) and an acoustically absorptive porous surface on the other half. Test gases investigated included nitrogen and carbon dioxide at M∞ ≃ 5 with specific reservoir enthalpy ranging from 1.3 to 13.0 MJ/kg and reservoir pressure ranging from 9.0 to 50.0 MPa. Comparisons were performed to ensure that previous results obtained in similar experiments (on a regular smooth surface) were reproduced, and the results were extended to examine the effects of the porous surface. These experiments indicated that the porous surface was highly effective in delaying transition provided that the pore size was significantly smaller than the viscous length scale.
170 citations
TL;DR: Theoretical analysis of hypersonic boundary-layer receptivity to wall disturbances was conducted using a combination of asymptotic and numerical methods in this paper. But the results of the analysis were limited to a flat-plate surface.
Abstract: Theoretical analysis of hypersonic boundary-layer receptivity to wall disturbances is conducted using a combination of asymptotic and numerical methods. Excitation of the second mode by distributed and local forcing on a flat-plate surface is studied under adiabatic and cooled wall conditions. Analysis addresses receptivity to wall vibrations, periodic suction/blowing, and temperature disturbances. A strong excitation occurs in local regions where forcing is in resonance with normal waves. It is shown that the receptivity function tends to infinity as the resonance point tends to the branch point of the discrete spectrum that is typical for boundary layers on cool surfaces. Asymptotic analysis resolves this singularity and provides the receptivity coefficient in the branch-point vicinity. Numerical results indicate extremely high receptivity to vibrations and suction/blowing in the vicinity of the branch point located near the lower neutral branch of the Mack second mode.
90 citations
TL;DR: In this paper, a retarding structure that allows the effective admittance of a tube wall to increase smoothly along the tube axis is considered, where the sound velocity gradually decreases along a finite segment of the tube and finally vanishes at some cross section.
Abstract: A retarding structure that allows the effective admittance of a tube wall to increase smoothly along the tube axis is considered. The sound velocity gradually decreases along a finite segment of the tube and finally vanishes at some cross section. The time of the sound propagation along this segment is infinitely long. A wave incident on the input cross section cannot reach the other end of the tube within a finite time, and, hence, it is not reflected from it. The wave is completely absorbed, the absorption being caused by the energy accumulation in the cross section where the velocity of sound vanishes, rather than by the energy transformation to heat, as in common sound absorbers. A differential equation is obtained to describe the sound propagation in a one-dimensional waveguide with a varying cross section and varying acoustic admittance of the walls. The solutions to this equation are analyzed in the WKB approximation. An exact solution is determined for the case of some specific functions describing the variations of the cross section and admittance. Calculated results for the input admittance of the waveguide are presented. A possible similarity to the problem of shear waves in sea sediments is pointed out.
76 citations
TL;DR: This work presents the first quantitative determination of tunneling in atomic ions in the relativistic regime, as obtained from a semiclassical solution of the three-dimensional Dirac equation, which opens the possibility to study strong laser field processes with highly charged ions, where relativity plays a dominant role.
Abstract: We present analytic tunnel ionization rates for hydrogenlike ions in ultrahigh intensity laser fields, as obtained from a semiclassical solution of the three-dimensional Dirac equation. This presents the first quantitative determination of tunneling in atomic ions in the relativistic regime. Our theory opens the possibility to study strong laser field processes with highly charged ions, where relativistic ionization plays a dominant role.
68 citations
TL;DR: In this article, the authors proposed to use two-layer targets in which the first layer consists of heavy multicharged ions and the second layer (thin and narrow in the transverse direction) consists of protons.
Abstract: Numerous applications of protons and ions accelerated by laser radiation require charged particle beams of high quality (i.e., such that the ratio of the energy width of the beam to its mean energy is small). In order to produce beams with controlled quality, it is proposed to use two-layer targets in which the first layer consists of heavy multicharged ions and the second layer (thin and narrow in the transverse direction) consists of protons. The possibility of generating a high-quality proton beam in the interaction of ultraintense laser radiation with such a two-layer target is demonstrated by two-and three-dimensional particle-in-cell computer simulations.
TL;DR: In this article, the characteristics of a positive transient corona discharge near the tip of a tall solitary grounded object in the electric field of a thundercloud are studied analytically and numerically.
Abstract: Characteristics of a positive transient corona discharge near the tip of a tall solitary grounded object in the electric field of a thundercloud are studied analytically and numerically. The time evolution of the discharge current and the space distribution of the total electric field are simulated for different growth rates of the external field and the dimensions and geometry of the stressed electrode. The effect of aerosol ions is shown to be negligible at a short duration of the corona. The developed simplified analytical approach agrees with numerical simulations.
TL;DR: In this paper, it was shown that a formulation in terms of the minimum (or extremum) of wave travel time between two points is not correct in general, and the correct formulation involves the extremum of the total optical length, with the optical length for the wave propagation through left-handed materials taken to be negative.
Abstract: The formulation of Fermat's principle for electromagnetic waves traveling in materials with a negative refractive index is refined. It is shown that a formulation in terms of the minimum (or extremum) of wave travel time between two points is not correct in general. The correct formulation involves the extremum of the total optical length, with the optical length for the wave propagation through left-handed materials taken to be negative.
TL;DR: A mathematical model of clotting is constructed, which is based on a current view of the molecular pathways of blood coagulation, and describes well all spatio-temporal aspects of clotts, as well as data obtained in the homogeneous systems.
Abstract: We constructed a mathematical model of clotting, which is based on a current view of the molecular pathways of blood coagulation. Several hypothetical reactions are introduced to allow accurate description of the spatio-temporal dynamics of blood clotting. The resulting model describes well all spatio-temporal aspects of clotting, as well as data obtained in the homogeneous systems.
TL;DR: In this article, the asymmetric nature of the boson "destruction" operator and its "creation" partner is made apparent by applying them to a quantum state different from the Fock state, and it is shown that it is possible to increase (by many times or by any quantity) the mean number of quanta in the new "photonsubtracted" state.
Abstract: The asymmetric nature of the boson ‘destruction’ operator ˆ a and its ‘creation’ partner ˆ a † is made apparent by applying them to a quantum state |ψ� different from the Fock state |n� .W e show that it is possible to increase (by many times or by any quantity) the mean number of quanta in the new ‘photonsubtracted’ state ˆ a|ψ� .M oreover, for certain ‘hyper-Poissonian’ states |ψ� the mean number of quanta in the (normalized) state ˆ a|ψ� can be much greater than in the ‘photon-added’ state ˆ a † |ψ� .T he explanation of this ‘paradox’ is given and some examples elucidating the meaning of Mandel’s q-parameter and the exponential phase operators are considered.
TL;DR: In this paper, the interaction of the solar wind with weak comets, leading to the formation of the cometary magnetosphere with different types of structures in solar wind and heavy ion plasmas, is simulated using a three-dimensional hybrid code.
TL;DR: In this article, a single-electron-response theory of tunnel ionization of atomic ions in relativistic laser fields, as described by the three-dimensional Klein-Gordon and Dirac equations, is presented.
Abstract: We present a single-electron-response theory of tunnel ionization of atomic ions in relativistic laser fields, as described by the three-dimensional Klein–Gordon and Dirac equations. The ionization rates are derived analytically for hydrogen-like ions taking into account the presence of the Coulomb potential and are then generalized to arbitrary atomic ions by using quantum defect theory. The resulting ionization rates allow for the first time a quantitative prediction of tunnel ionization of atomic ions in relativistic laser fields.
TL;DR: The history of development and the current status of the Soviet and Russian early-warning system are presented, which was built to provide the Soviet strategic forces with information about a missile attack in an event of a nuclear conflict with the United States.
Abstract: This article presents an overview of the history of development and the current status of the Soviet and Russian early-warning system, which was built to provide the Soviet strategic forces with information about a missile attack in an event of a nuclear conflict with the United States. Two main components of this system are considered--the network of early-warning radars, and the space-based early-warning system, which includes satellites on highly-elliptical and geosynchronous orbits. The system appears to be capable of detecting a massive attack, but cannot be relied upon to detect individual missile launches.
TL;DR: In this paper, the dependence of the decay width on the T-odd kinematical variable on the tree and one-loop levels of the standard model (SM) is studied at the tree level.
Abstract: The dependence of the ${K}^{+}\ensuremath{\rightarrow}{\ensuremath{\pi}}^{0}{l}^{+}{\ensuremath{
u}}_{l}\ensuremath{\gamma}$ decay width on the T-odd kinematical variable $\ensuremath{\xi}=\stackrel{\ensuremath{\rightarrow}}{q}\ensuremath{\cdot}[{p}_{l}\ifmmode\times\else\texttimes\fi{}{p}_{\ensuremath{\pi}}]{/M}^{3}$ is studied at the tree and one-loop levels of the standard model (SM). It is shown that at the tree level this decay width is an even function of $\ensuremath{\xi},$ while the odd contribution arises due to the electromagnetic final state interaction. This contribution is determined by the imaginary parts of the one-loop diagrams. The calculations performed show that the \ensuremath{\xi}-odd contribution to the ${K}^{+}\ensuremath{\rightarrow}{\ensuremath{\pi}}^{0}{e}^{+}{\ensuremath{
u}}_{e}\ensuremath{\gamma}$ and ${K}^{+}\ensuremath{\rightarrow}{\ensuremath{\pi}}^{0}{\ensuremath{\mu}}^{+}{\ensuremath{
u}}_{\ensuremath{\mu}}\ensuremath{\gamma}$ decay widths is four orders of magnitude smaller than the even contribution coming from the tree level of the SM.
01 Jan 2002
TL;DR: In this article, basic properties of materials that can be characterized by having simultaneously negative permittivity and permeability are discussed, including Poynting vector, Doppler effect, Cherenkov radiation, Snellius law, Fermat principle and possible devices.
Abstract: This chapter concentrates on basic properties of materials that can be characterised by having simultaneously negative permittivity and permeability. Poynting vector, Doppler effect, Cherenkov radiation, Snellius law, Fermat principle, possible devices, and experimental work on such materials are discussed.
TL;DR: In this paper, a theory for the transfer function of an electrochemical cell under conditions of convective diffusion is constructed, and a variational principle for the integration of the convective-diffusion equation is developed, which reduces the problem solution to selecting adequate trial functions.
Abstract: A theory for the transfer function of an electrochemical cell under conditions of convective diffusion is constructed. The variational principle for the integration of the convective-diffusion equation is developed, which reduces the problem solution to selecting adequate trial functions. With the diffusion frequency exceeded, the decay in the frequency dependence of the transfer function is defined by the system geometry. At a certain balance between parameters of the electrode system the frequency dependence of the transfer function can be strictly analytical, i.e. of the ω–1 type.
TL;DR: In this article, the vertical and pitching motions of a thin body of revolution separating from a rectangular cavity in a subsonic stream are investigated using combined asymptotic and numerical methods.
Abstract: Vertical and pitching motions (two degrees of freedom) of a thin body of revolution separating from a rectangular cavity in a subsonic stream are investigated using combined asymptotic and numerical methods. The analysis is based on explicit analytical solutions for the lift force and pitching moment obtained in our previous studies. Body trajectory dependencies on initial conditions, body parameters, and freestream velocity are studied. The problem is divided into three phases of the motion. In phase 1, the body is inside the cavity. In phase 2, the body crosses the shear layer, and in phase 3, the body is outside the cavity. For phases 1 and 3, analytical solutions of the body dynamics are obtained for typical cases. This analysis provides insight into the separation process and identifies governing lumped nondimensional parameters relevant to the body dynamics as well providing a model that can provide quick, computationally non-intensive estimates of store separation with a personal computer. The role of the nondimensional parameters in the dynamic stability eigenvalues is identified and found particularly useful in this connection. These parameters implicitly contain the effect of the shear layer
TL;DR: In this paper, a simple derivation of the Galitskii-Yakimets distribution function over momentum is presented, which contains the law ∼ p −8 as a quantum correction to the classical Maxwellian distribution function at large momenta.
Abstract: A simple derivation of the Galitskii–Yakimets distribution function over momentum is presented. For dense plasmas it contains the law ∼ p −8 as a quantum correction to the classical Maxwellian distribution function at large momenta. The integral equation for the width of the spectral distribution of kinetic Green functions is analyzed. The asymptotic behavior of the quantum corrections to the distribution function of particles is expressed via the Fourier transform of the wave function in the external potential. It is shown that the asymptotic power law for the distribution function over momentum is also correct for a non-equilibrium at the external electrical and laser fields.
TL;DR: In this article, the Ginzburg-Landau equations are solved based on trial functions for the order parameter for vortex-free, single-vortex, multivortex, and giant vortex phases.
Abstract: Vortex structures in a mesoscopic cylinder placed in external magnetic field are studied under the general de Gennes boundary condition for the order parameter corresponding to the suppression of surface superconductivity. The Ginzburg-Landau equations are solved based on trial functions for the order parameter for vortex-free, single-vortex, multivortex, and giant vortex phases. The equilibrium vortex diagrams in the plane of external field and cylinder radius and magnetization curves are calculated at different values of the de Gennes ``extrapolation length'' characterizing the boundary condition for the order parameter. The comparison of the obtained variational results with some available exact solutions shows the good accuracy of our approach.
TL;DR: More than 200 mW of a single-transverse mode cw output power is produced from a semiconductor heterolaser by optimising the waveguide properties of its ridge structure as mentioned in this paper.
Abstract: More than 200 mW of a single-transverse-mode cw output power is produced from a semiconductor heterolaser by optimising the waveguide properties of its ridge structure. The laser-beam divergence is close to the diffraction limit and its brightness exceeds 5 × 107 W cm-2 sr-1. The calculated and experimental parameters of the laser beam are coincident with a high accuracy, which allows their reliable simulation.
TL;DR: The relativistic self-focusing of high-intensity laser pulses in underdense plasmas is investigated with three-dimensional particle in cell simulations to interpret the different behavior of a linearly polarized pulse in the two transverse directions.
Abstract: The relativistic self-focusing of high-intensity laser pulses in underdense plasmas is investigated with three-dimensional particle in cell simulations. The different behavior of a linearly polarized pulse in the two transverse directions is interpreted as a combination of two two-dimensional responses with different polarizations. In the polarization plane a high density sheet is formed, which separates the two regions of oppositely directed quasistatic magnetic field.
21 Mar 2002
TL;DR: In this article, emission optical spectroscopy is applied to kinetic description of pulse-periodic discharges at high overvoltages in the pressure range 0.1-30 Torr and at atmospheric pressure.
Abstract: Spectroscopy of pulsed nonequilibrium plasma allows to control behaviour of active particles in situ, that is with subnanosecond temporal and high spatial resolution. Present work demonstrates advantages of emission optical spectroscopy as applied to kinetic description of pulse-periodic discharges at high overvoltages in the pressure range 0.1-30 Torr and at atmospheric pressure. Features in common and distinction in experimental observation of such discharges are discussed. Measurements of velocity of the discharge propagation, reduced electric field behaviour and number density of excited particles are represented for a wide range of experimental conditions.
TL;DR: It is shown that the Darrieus-Landau instability influences the flamelet velocity considerably, and the obtained results are in agreement with experimental data on the turbulent burning of moderate values of the Reynolds number.
Abstract: The propagation of turbulent premixed flames influenced by the intrinsic hydrodynamic flame instability (the Darrieus-Landau instability) is considered in a two-dimensional case using the model nonlinear equation proposed recently by Bychkov [Phys. Rev. Lett. 84, 6122 (2000)]. The nonlinear equation takes into account both the influence of external turbulence and the intrinsic properties of a flame front, such as small but finite flame thickness and realistically large density variations across the flame front. Dependence of the flame velocity on the turbulent length scale, turbulent intensity, and density variations is investigated in the case of weak nonlinearity and weak external turbulence. It is shown that the Darrieus-Landau instability influences the flamelet velocity considerably. The obtained results are in agreement with experimental data on the turbulent burning of moderate values of the Reynolds number.
TL;DR: A peptide antibiotic with cyanolytic activity was isolated from the IGM52 strain of the Brevibacillus laterosporus Gram-positive spore-forming bacteria by 1H NMR spectroscopy, and the spatial structure of loloatin A in solution was determined.
Abstract: A peptide antibiotic with cyanolytic activity was isolated from the IGM52 strain of the Brevibacillus laterosporus Gram-positive spore-forming bacteria. By 1H NMR spectroscopy, this antibiotic was identified as loloatin A, a cyclic decapeptide cyclo(-Asn-Asp-Tyr-Val-Orn-Leu-D-Tyr-Pro-Phe-D-Phe-). The spatial structure of loloatin A in solution was determined.
TL;DR: In this paper, a review of various types of atomic core polarization effects in the free-free, free-bound and bound-bound transitions of charged particles in the field of a multielectron atom is presented.
Abstract: In this review an attempt is made to provide a unified description of various types of atomic core polarization effects in the free–free, free–bound and bound–bound transitions of charged particles in the field of a multielectron atom — effects that have generally been treated independently in various contexts for over 40 years. For all types of transitions, both classical and quantum models are used for describing the scattering and energy reemission of a particle interacting with the atomic core. Experimental and theoretical results are given for the oscillator strengths of atoms and multiply charged ions; polarization phenomena associated with the photoeffect; a new polarization recombination channel, and the bremsstrahlung of electrons, relativistic and heavy particles on complex atoms and ions.