NASA Astrophysics Data System (ADS)
Tay, B. A.
2017-07-01
We obtain the solutions of the generic bilinear master equation for a quantum oscillator with constant coefficients in the Gaussian form. The well-behavedness and positive semidefiniteness of the stationary states could be characterized by a three-dimensional Minkowski vector. By requiring the stationary states to satisfy a factorized condition, we obtain a generic class of master equations that includes the well-known ones and their generalizations, some of which are completely positive. A further subset of the master equations with the Gibbs states as stationary states is also obtained. For master equations with not completely positive generators, an analysis on the stationary states for a given initial state suggests conditions on the coefficients of the master equations that generate positive evolution.
NASA Technical Reports Server (NTRS)
Kleinman, D. L.
1976-01-01
A numerical technique is given for solving the matrix quadratic equation that arises in the optimal stationary control of linear systems with state (and/or control) dependent noise. The technique exploits fully existing, efficient algorithms for the matrix Lyapunov and Ricatti equations. The computational requirements are discussed, with an associated example.
Nonequilibrium stationary states and entropy.
Gallavotti, G; Cohen, E G D
2004-03-01
In transformations between nonequilibrium stationary states, entropy might not be a well defined concept. It might be analogous to the "heat content" in transformations in equilibrium which is not well defined either, if they are not isochoric (i.e., do involve mechanical work). Hence we conjecture that in a nonequilibrium stationary state the entropy is just a quantity that can be transferred or created, such as heat in equilibrium, but has no physical meaning as "entropy content" as a property of the system.
Multiple stationary solutions of an irradiated slab
NASA Astrophysics Data System (ADS)
Taylor, P. D.; Feltham, D. L.
2005-04-01
A mathematical model describing the heat budget of an irradiated medium is introduced. The one-dimensional form of the equations and boundary conditions are presented and analysed. Heat transport at one face of the slab occurs by absorption (and reflection) of an incoming beam of short-wave radiation with a fraction of this radiation penetrating into the body of the slab, a diffusive heat flux in the slab and a prescribed incoming heat flux term. The other face of the slab is immersed in its own melt and is considered to be a free surface. Here, temperature continuity is prescribed and evolution of the surface is determined by a Stefan condition. These boundary conditions are flexible enough to describe a range of situations such as a laser shining on an opaque medium, or the natural environment of polar sea ice or lake ice. A two-stream radiation model is used which replaces the simple Beer's law of radiation attenuation frequently used for semi-infinite domains. The stationary solutions of the governing equations are sought and it is found that there exists two possible stationary solutions for a given set of boundary conditions and a range of parameter choices. It is found that the existence of two stationary solutions is a direct result of the model of radiation absorption, due to its effect on the albedo of the medium. A linear stability analysis and numerical calculations indicate that where two stationary solutions exist, the solution corresponding to a larger thickness is always stable and the solution corresponding to a smaller thickness is unstable. Numerical simulations reveal that when there are two solutions, if the slab is thinner than the smaller stationary thickness it will melt completely, whereas if the slab is thicker than the smaller stationary thickness it will evolve toward the larger stationary thickness. These results indicate that other mechanisms (e.g. wave-induced agglomeration of crystals) are necessary to grow a slab from zero initial
Poissonian steady states: from stationary densities to stationary intensities.
Eliazar, Iddo
2012-10-01
Markov dynamics are the most elemental and omnipresent form of stochastic dynamics in the sciences, with applications ranging from physics to chemistry, from biology to evolution, and from economics to finance. Markov dynamics can be either stationary or nonstationary. Stationary Markov dynamics represent statistical steady states and are quantified by stationary densities. In this paper, we generalize the notion of steady state to the case of general Markov dynamics. Considering an ensemble of independent motions governed by common Markov dynamics, we establish that the entire ensemble attains Poissonian steady states which are quantified by stationary Poissonian intensities and which hold valid also in the case of nonstationary Markov dynamics. The methodology is applied to a host of Markov dynamics, including Brownian motion, birth-death processes, random walks, geometric random walks, renewal processes, growth-collapse dynamics, decay-surge dynamics, Ito diffusions, and Langevin dynamics.
Stability of Stationary Solutions of the Multifrequency Radiation Diffusion Equations
Hald, O H; Shestakov, A I
2004-01-20
A nondimensional model of the multifrequency radiation diffusion equation is derived. A single material, ideal gas, equation of state is assumed. Opacities are proportional to the inverse of the cube of the frequency. Inclusion of stimulated emission implies a Wien spectrum for the radiation source function. It is shown that the solutions are uniformly bounded in time and that stationary solutions are stable. The spatially independent solutions are asymptotically stable, while the spatially dependent solutions of the linearized equations approach zero.
The problem on stationary states in self gravitational field
NASA Astrophysics Data System (ADS)
Fisenko, Stanislav
2017-01-01
To follow is the problem on stationary states of an electron in its own gravitational field where the boundary conditions earlier described by are made specific. The simplest approximation provides an assessment of the energy spectrum of stationary states only. Nevertheless, this is enough to confirm the existence of such stationary states and to further elaborate a detailed solution of the problem on stationary states including determination of all the quantum numbers' spectra and corresponding wave functions. No other matters are discussed here. The case in hand is a purely mathematical problem, further physical interpretation of which is of a fundamental value.
Universal BPS structure of stationary supergravity solutions
NASA Astrophysics Data System (ADS)
Bossard, Guillaume; Nicolai, Hermann; Stelle, K. S.
2009-07-01
We study asymptotically flat stationary solutions of four-dimensional supergravity theories via the associated fraktur G/fraktur H* pseudo-Riemannian non-linear sigma models in three spatial dimensions. The Noether charge Script C associated to fraktur G is shown to satisfy a characteristic equation that determines it as a function of the four-dimensional conserved charges. The matrix Script C is nilpotent for non-rotating extremal solutions. The nilpotency degree of Script C is directly related to the BPS degree of the corresponding solution when they are BPS. Equivalently, the charges can be described in terms of a Weyl spinor |Script Crangle of Spin*(2Script N), and then the characteristic equation becomes equivalent to a generalisation of the Cartan pure spinor constraint on |Script Crangle. The invariance of a given solution with respect to supersymmetry is determined by an algebraic `Dirac equation' on the Weyl spinor |Script Crangle. We explicitly solve this equation for all pure supergravity theories and we characterise the stratified structure of the moduli space of asymptotically Taub-NUT black holes with respect to their BPS degree. The analysis is valid for any asymptotically flat stationary solutions for which the singularities are protected by horizons. The fraktur H*-orbits of extremal solutions are identified as Lagrangian submanifolds of nilpotent orbits of fraktur G, and so the moduli space of extremal spherically symmetric black holes is identified as a Lagrangian subvariety of the variety of nilpotent elements of fraktur g. We also generalise the notion of active duality transformations to an `almost action' of the three-dimensional duality group fraktur G on asymptotically flat stationary solutions.
On Stationary States in the Double Phosphorylation-dephosphorylation Cycle
NASA Astrophysics Data System (ADS)
Bersani, Alberto Maria; Dell'Acqua, Guido; Tomassetti, Giovanna
2011-09-01
In this paper we study the double phosphorylation-dephosphorylation cycle, which is a special case of multiple futile cycle. We study the stationary states, finding some classes of explicit solutions.
Numerical methods for finding stationary gravitational solutions
NASA Astrophysics Data System (ADS)
Dias, Óscar J. C.; Santos, Jorge E.; Way, Benson
2016-07-01
The wide applications of higher dimensional gravity and gauge/gravity duality have fuelled the search for new stationary solutions of the Einstein equation (possibly coupled to matter). In this topical review, we explain the mathematical foundations and give a practical guide for the numerical solution of gravitational boundary value problems. We present these methods by way of example: resolving asymptotically flat black rings, singly spinning lumpy black holes in anti-de Sitter (AdS), and the Gregory-Laflamme zero modes of small rotating black holes in AdS{}5× {S}5. We also include several tools and tricks that have been useful throughout the literature.
Stationary states in quantum walk search
NASA Astrophysics Data System (ADS)
PrÅ«sis, Krišjānis; Vihrovs, Jevgěnijs; Wong, Thomas G.
2016-09-01
When classically searching a database, having additional correct answers makes the search easier. For a discrete-time quantum walk searching a graph for a marked vertex, however, additional marked vertices can make the search harder by causing the system to approximately begin in a stationary state, so the system fails to evolve. In this paper, we completely characterize the stationary states, or 1-eigenvectors, of the quantum walk search operator for general graphs and configurations of marked vertices by decomposing their amplitudes into uniform and flip states. This infinitely expands the number of known stationary states and gives an optimization procedure to find the stationary state closest to the initial uniform state of the walk. We further prove theorems on the existence of stationary states, with them conditionally existing if the marked vertices form a bipartite connected component and always existing if nonbipartite. These results utilize the standard oracle in Grover's algorithm, but we show that a different type of oracle prevents stationary states from interfering with the search algorithm.
Self-Organized Stationary States of Tokamaks
Jardin, S. C.; Ferraro, N.; Krebs, I.
2015-11-01
We demonstrate that in a 3D resistive magnetohydrodynamic simulation, for some parameters it is possible to form a stationary state in a tokamak where a saturated interchange mode in the center of the discharge drives a near helical flow pattern that acts to nonlinearly sustain the configuration by adjusting the central loop voltage through a dynamo action. This could explain the physical mechanism for maintaining stationary nonsawtoothing "hybrid" discharges, often referred to as "flux pumping."
Self-Organized Stationary States of Tokamaks.
Jardin, S C; Ferraro, N; Krebs, I
2015-11-20
We demonstrate that in a 3D resistive magnetohydrodynamic simulation, for some parameters it is possible to form a stationary state in a tokamak where a saturated interchange mode in the center of the discharge drives a near helical flow pattern that acts to nonlinearly sustain the configuration by adjusting the central loop voltage through a dynamo action. This could explain the physical mechanism for maintaining stationary nonsawtoothing "hybrid" discharges, often referred to as "flux pumping."
Exact Stationary and Non-stationary Solutions to Inelastic Maxwell Model with Infinite Energy
NASA Astrophysics Data System (ADS)
Ilyin, Oleg
2016-11-01
The one-dimensional inelastic Boltzmann equation with a constant collision rate (the Maxwell model) is considered. It is shown that for special values of restitution parameter there exists a stationary solution with the characteristic function in the form e^{-P(log (z))z}, where P is a periodic function. The corresponding distribution function belongs to a one special class of stochastic processes termed as a generalized stable in the probability theory. The Fourier transform of the non-stationary equation has the solution bigl (1+P(log (z))zbigr )e^{-Q(log (z))z}. It is proved that this solution is a characteristic function if periodic functions P, Q satisfy some not very restrictive conditions. The stationary and non-stationary solutions correspond to a gas with infinite temperature.
Self-Organized Stationary States of Tokamaks
Jardin, S. C.; Ferraro, N.; Krebs, I.
2015-11-17
We demonstrate that in a 3D resistive magnetohydrodynamic (MHD) simulation, for some parameters it is possible to form a stationary state in a tokamak where a saturated interchange mode in the center of the discharge drives a near helical flow pattern that acts to non-linearly sustain the configuration by adjusting the central loop voltage through a dynamo action. This could explain the physical mechanism for maintaining stationary non-sawtoothing “hybrid” discharges, often referred to as “flux-pumping”.
Self-Organized Stationary States of Tokamaks
Jardin, S. C.; Ferraro, N.; Krebs, I.
2015-11-17
We demonstrate that in a 3D resistive magnetohydrodynamic (MHD) simulation, for some parameters it is possible to form a stationary state in a tokamak where a saturated interchange mode in the center of the discharge drives a near helical flow pattern that acts to non-linearly sustain the configuration by adjusting the central loop voltage through a dynamo action. This could explain the physical mechanism for maintaining stationary non-sawtoothing “hybrid” discharges, often referred to as “flux-pumping”.
Stationary solutions and asymptotic flatness I
NASA Astrophysics Data System (ADS)
Reiris, Martin
2014-08-01
In general relativity, a stationary isolated system is defined as an asymptotically flat (AF) stationary spacetime with compact material sources. Other definitions that are less restrictive on the type of asymptotic could in principle be possible. Between this article and its sequel, we show that under basic assumptions, asymptotic flatness indeed follows as a consequence of Einstein's theory. In particular, it is proved that any vacuum stationary spacetime-end whose (quotient) manifold is diffeomorphic to {{{R}}^{3}} minus a ball and whose Killing field has its norm bounded away from zero, is necessarily AF with Schwarzschildian fall off. The ‘excised’ ball would contain (if any) the actual material body, but this information is unnecessary to reach the conclusion. In this first article, we work with weakly asymptotically flat (WAF) stationary ends, a notion that generalizes as much as possible that of the AF end, and prove that WAF ends are AF with Schwarzschildian fall off. Physical and mathematical implications are also discussed.
Stationary solutions of the Dirac equation in the gravitational field of a charged black hole
Dokuchaev, V. I. Eroshenko, Yu. N.
2013-07-15
A stationary solution of the Dirac equation in the metric of a Reissner-Nordstroem black hole has been found. Only one stationary regular state outside the black hole event horizon and only one stationary regular state below the Cauchy horizon are shown to exist. The normalization integral of the wave functions diverges on both horizons if the black hole is non-extremal. This means that the solution found can be only the asymptotic limit of a nonstationary solution. In contrast, in the case of an extremal black hole, the normalization integral is finite and the stationary regular solution is physically self-consistent. The existence of quantum levels below the Cauchy horizon can affect the final stage of Hawking black hole evaporation and opens up the fundamental possibility of investigating the internal structure of black holes using quantum tunneling between external and internal states.
Stationary solutions for conservation laws with singular nonlocal sources
NASA Astrophysics Data System (ADS)
Coclite, Giuseppe Maria; Coclite, Mario Michele
The existence of an a.e. positive stationary solution with bounded variation in [0,1] for an integro-differential conservation law with source depending on a function singular in the origin is proved.
Static and stationary multiple soliton solutions to the Einstein equations
Letelier, P.S.
1985-03-01
The application of the Belinsky--Zakharov solution-generating technique, i.e., the inverse scattering method, to generate stationary axially symmetric solutions to the vacuum Einstein equations is reduced to a single quadrature when the seed solution is diagonal. The possibility of having real odd-number soliton solutions is investigated. These solutions represent solitonic perturbations of Euclidean metrics. The possibility of using instantons as seed solutions is also investigated. The one- and two-soliton solutions generated from a diagonal seed solution are studied. As an application, a unified derivation of some well-known static solutions, like the Schwarzschild metric and the Chazy--Curzon metric, as well as other new metrics is presented. By using these metrics as seed solutions, some known stationary solutions, like the Kerr-NUT metric, the double Kerr metric, and the rotating Weyl C-metric, as well as other new metrics are also derived in a unified way.
Nucleoid restructuring in stationary-state bacteria.
Frenkiel-Krispin, Daphna; Ben-Avraham, Irit; Englander, Joseph; Shimoni, Eyal; Wolf, Sharon G; Minsky, Abraham
2004-01-01
The textbook view of the bacterial cytoplasm as an unstructured environment has been overturned recently by studies that highlighted the extent to which non-random organization and coherent motion of intracellular components are central for bacterial life-sustaining activities. Because such a dynamic order critically depends on continuous consumption of energy, it cannot be perpetuated in starved, and hence energy-depleted, stationary-state bacteria. Here, we show that, at the onset of the stationary state, bacterial chromatin undergoes a massive reorganization into ordered toroidal structures through a process that is dictated by the intrinsic properties of DNA and by the ubiquitous starvation-induced DNA-binding protein Dps. As starvation proceeds, the toroidal morphology acts as a structural template that promotes the formation of DNA-Dps crystalline assemblies through epitaxial growth. Within the resulting condensed assemblies, DNA is effectively protected by means of structural sequestration. We thus conclude that the transition from bacterial active growth to stationary phase entails a co-ordinated process, in which the energy-dependent dynamic order of the chromatin is sequentially substituted with an equilibrium crystalline order.
Existence of stationary states for nonlinear Dirac equations
NASA Astrophysics Data System (ADS)
Merle, F.
We generalize the previous result of Cazenave and Vasquez on the existence of stationary states for nonlinear Dirac equations of the form i∑ μ3 = 0 γμ∂μΨ - mΨ + L( ΨΨ) Ψ = 0. We seek solutions which are separable in spherical coordinates and we then make use of a shooting method to solve the associated problem for ordinary differential equations.
NASA Astrophysics Data System (ADS)
Horvath, I.; Lukacs, B.
The stationary vacuum solutions of the Einstein equations of general relativity give the external space-time around stationary mass distributions, as e.g. final states of stellar evolution. The Kerr solution has shear-free geodesic eigenrays and describes all black hole configurations with good asymptotic behaviour at infinity. Other solutions of this class are unphysical. Classes with shearing geodesic or shearfree nongeodesic eigenrays do not contain physical solutions at all, so for other physical configurations one must turn to the generic case of shearing nongeodesic eigenrays. For the stationary axisymmetric case Ansaetze for solutions can be formulated in form of a specific functional dependence between the parameters of shear and nongeodesicity, unless they both are constants. Here the authors investigate the second subcase. Their result is that there is no solution of the vacuum Einstein equations in this subclass, except when both parameters vanish.
Landau superfluids as nonequilibrium stationary states
Wreszinski, Walter F.
2015-01-15
We define a superfluid state to be a nonequilibrium stationary state (NESS), which, at zero temperature, satisfies certain metastability conditions, which physically express that there should be a sufficiently small energy-momentum transfer between the particles of the fluid and the surroundings (e.g., pipe). It is shown that two models, the Girardeau model and the Huang-Yang-Luttinger (HYL) model, describe superfluids in this sense and, moreover, that, in the case of the HYL model, the metastability condition is directly related to Nozières’ conjecture that, due to the repulsive interaction, the condensate does not suffer fragmentation into two (or more) parts, thereby assuring its quantum coherence. The models are rigorous examples of NESS in which the system is not finite, but rather a many-body system.
Gibbsian Stationary Non-equilibrium States
NASA Astrophysics Data System (ADS)
De Carlo, Leonardo; Gabrielli, Davide
2017-09-01
We study the structure of stationary non-equilibrium states for interacting particle systems from a microscopic viewpoint. In particular we discuss two different discrete geometric constructions. We apply both of them to determine non reversible transition rates corresponding to a fixed invariant measure. The first one uses the equivalence of this problem with the construction of divergence free flows on the transition graph. Since divergence free flows are characterized by cyclic decompositions we can generate families of models from elementary cycles on the configuration space. The second construction is a functional discrete Hodge decomposition for translational covariant discrete vector fields. According to this, for example, the instantaneous current of any interacting particle system on a finite torus can be canonically decomposed in a gradient part, a circulation term and an harmonic component. All the three components are associated with functions on the configuration space. This decomposition is unique and constructive. The stationary condition can be interpreted as an orthogonality condition with respect to an harmonic discrete vector field and we use this decomposition to construct models having a fixed invariant measure.
Analyzing stationary states of gene regulatory network using petri nets.
Gambin, Anna; Lasota, Sławomir; Rutkowski, Michał
2006-01-01
We introduce and formally define the notion of a stationary state for Petri nets. We also propose a fully automatic method for finding such states. The procedure makes use of the Presburger arithmetic to describe all the stationary states. Finally we apply this novel approach to find stationary states of a gene regulatory network describing the flower morphogenesis of A. thaliana. This shows that the proposed method can be successfully applied in the study of biological systems.
Analyzing stationary States of gene regulatory network using petri nets.
Gambin, Anna; Lasota, Sławomir; Rutkowski, Michał
2011-01-01
We introduce and formally define the notion of a stationary state for Petri nets. We also propose a fully automatic method for finding such states. The procedure makes use of the Presburger arithmetic to describe all the stationary states. Finally we apply this novel approach to find stationary states of a gene regulatory network describing the flower morphogenesis of A. thaliana. This shows that the proposed method can be successfully applied in the study of biological systems.
Self-organized stationary states of tokamaks
NASA Astrophysics Data System (ADS)
Jardin, Stephen
2015-11-01
We report here on a nonlinear mechanism that forms and maintains a self-organized stationary (sawtooth free) state in tokamaks. This process was discovered by way of extensive long-time simulations using the M3D-C1 3D extended MHD code in which new physics diagnostics have been added. It is well known that most high-performance modes of tokamak operation undergo ``sawtooth'' cycles, in which the peaking of the toroidal current density triggers a periodic core instability which redistributes the current density. However, certain modes of operation are known, such as the ``hybrid'' mode in DIII-D, ASDEX-U, JT-60U and JET, and the long-lived modes in NSTX and MAST, which do not experience this cycle of instability. Empirically, it is observed that these modes maintain a non-axisymmetric equilibrium which somehow limits the peaking of the toroidal current density. The physical mechanism responsible for this has not previously been understood, but is often referred to as ``flux-pumping,'' in which poloidal flux is redistributed in order to maintain q0 >1. In this talk, we show that in long-time simulations of inductively driven plasmas, a steady-state magnetic equilibrium may be obtained in which the condition q0 >1 is maintained by a dynamo driven by a stationary marginal core interchange mode. This interchange mode, unstable because of the pressure gradient in the ultra-low shear region in the center region, causes a (1,1) perturbation in both the electrostatic potential and the magnetic field, which nonlinearly cause a (0,0) component in the loop voltage that acts to sustain the configuration. This hybrid mode may be a preferred mode of operation for ITER. We present parameter scans that indicate when this sawtooth-free operation can be expected.
Fundamental solutions for stationary Stokes systems with measurable coefficients
NASA Astrophysics Data System (ADS)
Choi, Jongkeun; Yang, Minsuk
2017-10-01
We establish the existence and the pointwise bound of the fundamental solution for the stationary Stokes system with measurable coefficients in the whole space Rd, d ≥ 3, under the assumption that weak solutions of the system are locally Hölder continuous. We also discuss the existence and the pointwise bound of the Green function for the Stokes system with measurable coefficients on Ω, where Ω is an unbounded domain such that the divergence equation is solvable. Such a domain includes, for example, half space and an exterior domain.
Exchangeable, stationary, and entangled chains of Gaussian states
NASA Astrophysics Data System (ADS)
Parthasarathy, K. R.; Sengupta, Ritabrata
2015-10-01
We explore conditions on the covariance matrices of a consistent chain of mean zero finite mode Gaussian states in order that the chain may be exchangeable or stationary. For an exchangeable chain, our conditions are necessary and sufficient. Every stationary Gaussian chain admits an asymptotic entropy rate. Whereas an exchangeable chain admits a simple expression for its entropy rate, in our examples of stationary chains, the same admits an integral formula based on the asymptotic eigenvalue distribution for Toeplitz matrices. An example of a stationary entangled Gaussian chain is given.
Stationary solutions in a model three-body problem
NASA Astrophysics Data System (ADS)
Zlenko, A. A.
2016-12-01
Two visco-elastic bodies (deformable spheres) are considered which interact with each other and move in quasi-circular orbits in the attractive force field of a fixed centre - a heavy point mass. Their axes of rotation are perpendicular to their orbital plane. Stationary solutions of the evolutionary equations of motion are found. In one particular case, they extend solutions of the restricted circular three-body problem corresponding to two collinear libration points. All three bodies are located along a straight line. This implies synchronization of motion of the barycentre of the two visco-elastic bodies relative to the attracting centre with their orbital motion relative to the barycentre in a 1:1 resonance. The rotation of the two bodies relative to their own centres of mass takes place in such a way that the bodies "view" the attracting centre and each other from the same side, i.e., they are synchronized in a 1:1 resonance with their orbital motion. Instability of stationary solutions is analytically proven.
On the Gross-Pitaevskii Equation with Pumping and Decay: Stationary States and Their Stability
NASA Astrophysics Data System (ADS)
Sierra, Jesús; Kasimov, Aslan; Markowich, Peter; Weishäupl, Rada-Maria
2015-06-01
We investigate the behavior of solutions of the complex Gross-Pitaevskii equation, a model that describes the dynamics of pumped decaying Bose-Einstein condensates. The stationary radially symmetric solutions of the equation are studied, and their linear stability with respect to two-dimensional perturbations is analyzed. Using numerical continuation, we calculate not only the ground state of the system, but also a number of excited states. Accurate numerical integration is employed to study the general nonlinear evolution of the system from the unstable stationary solutions to the formation of stable vortex patterns.
Thermodynamical description of stationary, asymptotically flat solutions with conical singularities
Herdeiro, Carlos; Rebelo, Carmen; Radu, Eugen
2010-05-15
We examine the thermodynamical properties of a number of asymptotically flat, stationary (but not static) solutions having conical singularities, with both connected and nonconnected event horizons, using the thermodynamical description recently proposed in [C. Herdeiro, B. Kleihaus, J. Kunz, and E. Radu, Phys. Rev. D 81, 064013 (2010).]. The examples considered are the double-Kerr solution, the black ring rotating in either S{sup 2} or S{sup 1}, and the black Saturn, where the balance condition is not imposed for the latter two solutions. We show that not only the Bekenstein-Hawking area law is recovered from the thermodynamical description, but also the thermodynamical angular momentum is the Arnowitt-Deser-Misner angular momentum. We also analyze the thermodynamical stability and show that, for all these solutions, either the isothermal moment of inertia or the specific heat at constant angular momentum is negative, at any point in parameter space. Therefore, all these solutions are thermodynamically unstable in the grand canonical ensemble.
Thermodynamical description of stationary, asymptotically flat solutions with conical singularities
NASA Astrophysics Data System (ADS)
Herdeiro, Carlos; Radu, Eugen; Rebelo, Carmen
2010-05-01
We examine the thermodynamical properties of a number of asymptotically flat, stationary (but not static) solutions having conical singularities, with both connected and nonconnected event horizons, using the thermodynamical description recently proposed in [C. Herdeiro, B. Kleihaus, J. Kunz, and E. Radu, Phys. Rev. DPRVDAQ1550-7998 81, 064013 (2010).10.1103/PhysRevD.81.064013]. The examples considered are the double-Kerr solution, the black ring rotating in either S2 or S1, and the black Saturn, where the balance condition is not imposed for the latter two solutions. We show that not only the Bekenstein-Hawking area law is recovered from the thermodynamical description, but also the thermodynamical angular momentum is the Arnowitt-Deser-Misner angular momentum. We also analyze the thermodynamical stability and show that, for all these solutions, either the isothermal moment of inertia or the specific heat at constant angular momentum is negative, at any point in parameter space. Therefore, all these solutions are thermodynamically unstable in the grand canonical ensemble.
NASA Astrophysics Data System (ADS)
Elgindi, Tarek M.
2017-08-01
We study the stability of stationary solutions of the two dimensional inviscid incompressible porous medium equation (IPM). We show that solutions which are near certain stable stationary solutions must converge as t → ∞ to a stationary solution of the IPM equation. It turns out that linearizing the IPM equation about certain stable stationary solutions gives a non-local partial damping mechanism. On the torus, the linearized problem has a very large set of stationary (undamped) modes. This makes the problem of long-time behavior more difficult since there is the possibility of a cascading non-linear growth along the stationary modes of the linearized problem. We solve this by, more or less, doing a second linearization around the undamped modes, exploiting a special non-linear structure, and showing that the stationary modes can be controlled.
Exact solutions for discs around stationary black holes
NASA Astrophysics Data System (ADS)
Požár, N.; Semerák, O.; Šácha, J.; Žáček, M.; Zellerin, T.
2007-04-01
Linking together technology, observations, Einstein's theory and pure mathematics, black holes surrounded by disc-like structures prosper in some of the most interesting and violent sources in the universe - in galactic nuclei and X-ray binaries. However, a consistent exact description of the gravitational field of these systems is still lacking. In static axisymmetric case, the task reduces to Laplace equation and the fields of multiple sources follow by mere superposition, but in a rotating case, so relevant under the above astrophysical conditions, non-linearity of the field equations resists full grasp. Recently, mathematical methods developed in the theory of completely integrable systems seem to verge on explicit and satisfactory solutions to the Ernst version of the stationary axisymmetric Einstein's equations. Today referred to as methods of algebraic geometry, they seek them in terms of theta-functions on special manifolds which are - symptomatically - connected with the names of Riemann and Hilbert.
Exponentially Stable Stationary Solutions for Stochastic Evolution Equations and Their Perturbation
Caraballo, Tomas Kloeden, Peter E. Schmalfuss, Bjoern
2004-10-15
We consider the exponential stability of stochastic evolution equations with Lipschitz continuous non-linearities when zero is not a solution for these equations. We prove the existence of anon-trivial stationary solution which is exponentially stable, where the stationary solution is generated by the composition of a random variable and the Wiener shift. We also construct stationary solutions with the stronger property of attracting bounded sets uniformly. The existence of these stationary solutions follows from the theory of random dynamical systems and their attractors. In addition, we prove some perturbation results and formulate conditions for the existence of stationary solutions for semilinear stochastic partial differential equations with Lipschitz continuous non-linearities.
Macroscopic Fluctuation Theory for Stationary Non-Equilibrium States
NASA Astrophysics Data System (ADS)
Bertini, L.; de Sole, A.; Gabrielli, D.; Jona-Lasinio, G.; Landim, C.
2002-05-01
We formulate a dynamical fluctuation theory for stationary non-equilibrium states (SNS) which is tested explicitly in stochastic models of interacting particles. In our theory a crucial role is played by the time reversed dynamics. Within this theory we derive the following results: the modification of the Onsager-Machlup theory in the SNS; a general Hamilton-Jacobi equation for the macroscopic entropy; a non-equilibrium, nonlinear fluctuation dissipation relation valid for a wide class of systems; an H theorem for the entropy. We discuss in detail two models of stochastic boundary driven lattice gases: the zero range and the simple exclusion processes. In the first model the invariant measure is explicitly known and we verify the predictions of the general theory. For the one dimensional simple exclusion process, as recently shown by Derrida, Lebowitz, and Speer, it is possible to express the macroscopic entropy in terms of the solution of a nonlinear ordinary differential equation; by using the Hamilton-Jacobi equation, we obtain a logically independent derivation of this result.
Discretization of Stationary Solutions of Stochastic Systems Driven by Fractional Brownian Motion
Garrido-Atienza, Maria J. Kloeden, Peter E. Neuenkirch, Andreas
2009-10-15
In this article we study the behavior of dissipative systems with additive fractional noise of any Hurst parameter. Under a one-sided dissipative Lipschitz condition on the drift the continuous stochastic system is shown to have a unique stationary solution, which pathwise attracts all other solutions. The same holds for the discretized stochastic system, if the drift-implicit Euler method is used for the discretization. Moreover, the unique stationary solution of the drift-implicit Euler scheme converges to the unique stationary solution of the original system as the stepsize of the discretization decreases.
On axisymmetric and stationary solutions of the self-gravitating Vlasov system
NASA Astrophysics Data System (ADS)
Ames, Ellery; Andréasson, Håkan; Logg, Anders
2016-08-01
Axisymmetric and stationary solutions are constructed to the Einstein-Vlasov and Vlasov-Poisson systems. These solutions are constructed numerically, using finite element methods and a fixed-point iteration in which the total mass is fixed at each step. A variety of axisymmetric stationary solutions are exhibited, including solutions with toroidal, disk-like, spindle-like, and composite spatial density configurations, as are solutions with non-vanishing net angular momentum. In the case of toroidal solutions, we show for the first time, solutions of the Einstein-Vlasov system which contain ergoregions.
Caraballo, T. Kloeden, P.E.
2006-11-15
Under a one-sided dissipative Lipschitz condition on its drift, a stochastic evolution equation with additive noise of the reaction-diffusion type is shown to have a unique stochastic stationary solution which pathwise attracts all other solutions. A similar situation holds for each Galerkin approximation and each implicit Euler scheme applied to these Galerkin approximations. Moreover, the stationary solution of the Euler scheme converges pathwise to that of the Galerkin system as the stepsize tends to zero and the stationary solutions of the Galerkin systems converge pathwise to that of the evolution equation as the dimension increases. The analysis is carried out on random partial and ordinary differential equations obtained from their stochastic counterparts by subtraction of appropriate Ornstein-Uhlenbeck stationary solutions.
Maximum entropy principle for stationary states underpinned by stochastic thermodynamics
NASA Astrophysics Data System (ADS)
Ford, Ian J.
2015-11-01
The selection of an equilibrium state by maximizing the entropy of a system, subject to certain constraints, is often powerfully motivated as an exercise in logical inference, a procedure where conclusions are reached on the basis of incomplete information. But such a framework can be more compelling if it is underpinned by dynamical arguments, and we show how this can be provided by stochastic thermodynamics, where an explicit link is made between the production of entropy and the stochastic dynamics of a system coupled to an environment. The separation of entropy production into three components allows us to select a stationary state by maximizing the change, averaged over all realizations of the motion, in the principal relaxational or nonadiabatic component, equivalent to requiring that this contribution to the entropy production should become time independent for all realizations. We show that this recovers the usual equilibrium probability density function (pdf) for a conservative system in an isothermal environment, as well as the stationary nonequilibrium pdf for a particle confined to a potential under nonisothermal conditions, and a particle subject to a constant nonconservative force under isothermal conditions. The two remaining components of entropy production account for a recently discussed thermodynamic anomaly between over- and underdamped treatments of the dynamics in the nonisothermal stationary state.
Relaxation dynamics near nonequilibrium stationary states in Brownian ratchets
NASA Astrophysics Data System (ADS)
Woo, Hyung-June
2009-02-01
A comprehensive study of the static and dynamical properties of a representative stochastic model of Brownian ratchet effects for molecular motors is reported. The model describes Brownian motions on two periodic potentials under static and time-dependent forces, where there are two distinct locations of chemical reactions coupling the levels with reversible rates within a period. Complete stationary properties have been obtained analytically for arbitrary potentials under external force. Dynamical relaxation properties near nonequilibrium stationary states were examined by considering the response function of velocity upon time-dependent external force, expressed in terms of the conditional probability density of the model. The latter is fully calculated using a systematic numerical method using matrix diagonalization, which is easily generalized to more complicated models for studying both static and dynamical properties. The behavior of the time-dependent response examined for model potentials suggests that the characteristic relaxation time near stationary states generally decreases linearly with respect to increasing velocity as one goes away from equilibrium via an increase in chemical potential of fuel species, a prediction testable in single molecule experiments.
All the stationary vacuum states of de Sitter space
NASA Astrophysics Data System (ADS)
Parikh, Maulik; Samantray, Prasant
2013-06-01
We obtain all the stationary vacua of de Sitter space by classifying the inequivalent timelike isometries of the de Sitter group. Besides the static vacuum, de Sitter space also admits a family of rotating vacua, which we use to obtain Kerr-de Sitter solutions in three, four, and five dimensions. By writing the metric in a coordinate system adapted to the rotating Hamiltonian, we show that empty de Sitter space admits not only an observer-dependent horizon but also an observer-dependent ergosphere.
All stationary vacuum solutions with geodesic shearfree eigenrays.
NASA Astrophysics Data System (ADS)
Horvath, I.; Lukacs, B.; Szello, L.
1997-12-01
The Kerr solution, which is the general vacuum black hole solution in general relativity, belongs to the class of geodesic shearfree eigenrays, but it is somehow isolated within the class. For better orientation in future Kerr generalisation one would like to map completely the σ = κ = 0 class. Therefore in this paper the authors methodically look for all possible subclasses of solutions in the said class, and explicitly treat their connections with each other.
Stationary states and spatial patterning in an SIS epidemiology model with implicit mobility
NASA Astrophysics Data System (ADS)
Ilnytskyi, Jaroslav; Kozitsky, Yuri; Ilnytskyi, Hryhoriy; Haiduchok, Olena
2016-11-01
By means of the asynchronous cellular automata algorithm we study stationary states and spatial patterning in an SIS model, in which the individuals are attached to the vertices of a graph and their mobility is mimicked by varying the neighbourhood size q. Here we consider the following cases: q is fixed at certain value; and q is taken at random at each step and for each individual. The obtained numerical data are then mapped onto the solution of its version, corresponding to the limit q → ∞. This allows for deducing an explicit form of the dependence of the fraction of infected individuals on the curing rate γ. A detailed analysis of the appearance of spatial patterns of infected individuals in the stationary state is performed.
NASA Astrophysics Data System (ADS)
Chruściel, Piotr T.; Delay, Erwann; Klinger, Paul
2017-05-01
We construct infinite-dimensional families of nonsingular stationary space-times, solutions of Yang-Mills-Higgs-Einstein-Maxwell-Chern-Simons-dilaton-scalar field equations with a negative cosmological constant. The families include an infinite-dimensional family of solutions with the usual anti-de Sitter conformal structure at conformal infinity.
Stationary solutions in five-dimensional gravity with a magnetic field
Becerril, R. ); Matos, T. )
1992-08-15
Using the potential formalism, six new stationary axisymmetric solutions of the five-dimensional Kaluza-Klein field equations are constructed. It is supposed that each potential depends only on one parameter which satisfies the Laplace equation. All the solutions have a scalar potential and some of them possess magnetic fields which represent a magnetic monopole, dipole, and quadrupole.
Stationary solutions of SPDEs and infinite horizon BDSDEs with non-Lipschitz coefficients
NASA Astrophysics Data System (ADS)
Zhang, Qi; Zhao, Huaizhong
We prove a general theorem that the Lρ2(R;R)⊗Lρ2(R;R)-valued solution of an infinite horizon backward doubly stochastic differential equation, if exists, gives the stationary solution of the corresponding stochastic partial differential equation. We prove the existence and uniqueness of the Lρ2(R;R)⊗Lρ2(R;R)-valued solutions for backward doubly stochastic differential equations on finite and infinite horizon with linear growth without assuming Lipschitz conditions, but under the monotonicity condition. Therefore the solution of finite horizon problem gives the solution of the initial value problem of the corresponding stochastic partial differential equations, and the solution of the infinite horizon problem gives the stationary solution of the SPDEs according to our general result.
NASA Astrophysics Data System (ADS)
Barré, Julien; Yamaguchi, Yoshiyuki Y.
2015-08-01
We consider the one-dimensional Vlasov equation with an attractive cosine potential, and its non-homogeneous stable stationary states that are decreasing functions of the energy. We show that in the Sobolev space W1,p (p > 2) neighborhood of such a state, all stationary states that are decreasing functions of the energy are stable. This is in sharp contrast with the situation for homogeneous stationary states of a Vlasov equation, where a control over strictly more than one derivative is needed to ensure the absence of unstable stationary states in a neighborhood of a reference stationary state [Z. Lin and C. Zeng, Commun. Math. Phys. 306, 291-331 (2011)].
Deterministic creation of stationary entangled states by dissipation
Alharbi, A. F.; Ficek, Z.
2010-11-15
We propose a practical physical system for creation of stationary entanglement by dissipation without employing environmental engineering techniques. The system proposed is composed of two perfectly distinguishable atoms, through their significantly different transition frequencies, with only one atom addressed by an external laser field. We show that the arrangement would easily be realized in practice by trapping the atoms at a distance equal to the quarter-wavelength of a standing-wave laser field and locating one of the atoms at a node and the other at the successive antinode of the wave. The undesirable dipole-dipole interaction between the atoms, which could be large at this small distance, is adjusted to zero by a specific initial preparation of the atoms or by a specific polarization of the atomic dipole moments. Following this arrangement, we show that the dissipative relaxation can create a stationary entanglement on demand by tuning the Rabi frequency of the laser field to the difference between the atomic transition frequencies. The laser field dresses the atom and we identify that the entangled state occurs when the frequency of one of the Rabi sidebands of the driven atom tunes to the frequency of the undriven atom. It is also found that this system behaves as a cascade open system where the fluorescence from the dressed atom drives the other atom with no feedback.
Stationary states of extended nonlinear Schrödinger equation with a source
NASA Astrophysics Data System (ADS)
Borich, M. A.; Smagin, V. V.; Tankeev, A. P.
2007-02-01
Structure of nonlinear stationary states of the extended nonlinear Schrödinger equation (ENSE) with a source has been analyzed with allowance for both third-order and nonlinearity dispersion. A new class of particular solutions (solitary waves) of the ENSe has been obtained. The scenario of the destruction of these states under the effect of an external perturbation has been investigated analytically and numerically. The results obtained can be used to interpret experimental data on the weakly nonlinear dynamics of the magnetostatic envelope in heterophase ferromagnet-insulator-metal, metal-insulator-ferromagnet-insulator-metal, and other similar structures and upon the simulation of nonlinear processes in optical systems.
Free energy for non-equilibrium quasi-stationary states
NASA Astrophysics Data System (ADS)
Allahverdyan, A. E.; Martirosyan, N. H.
2017-03-01
We study a class of non-equilibrium quasi-stationary states for a Markov system interacting with two different thermal baths. We show that the work done under a slow, external change of parameters admits a potential, i.e., the free energy. Three conditions are needed for the existence of free energy in this non-equilibrium system: time-scale separation between variables of the system, partial controllability (external fields couple only with the slow variable), and an effective detailed balance. These conditions are facilitated in the continuous limit for the slow variable. In contrast to its equilibrium counterpart, the non-equilibrium free energy can increase with temperature. One example of this is that entropy reduction by means of external fields (cooling) can be easier (in the sense of the work cost) if it starts from a higher temperature.
NASA Astrophysics Data System (ADS)
Liu, Qun; Jiang, Daqing; Hayat, Tasawar; Ahmad, Bashir
2017-09-01
In this paper, we investigate two stochastic SIR epidemic models with higher order perturbation. For the nonautonomous periodic case of the model, by using Has'minskii's theory of periodic solution, we show that the system has at least one nontrivial positive T-periodic solution. For the system disturbed by both the white noise and telephone noise, we establish sufficient conditions for positive recurrence and the existence of ergodic stationary distribution of the positive solution.
NASA Astrophysics Data System (ADS)
Gariel, J.; Marcilhacy, G.; Santos, N. O.
2008-02-01
We extend the method of separation of variables, studied by Léauté and Marcilhacy [Ann. Inst. Henri Poincare, Sect. A 331, 363 (1979)], to obtain transcendent solutions of the field equations for stationary axisymmetric systems. These solutions depend on transcendent functions satisfying a third order differential equation. For some solutions this equation satisfies the necessary conditions, but not sufficient, to have fixed critical points.
Time and 'angular' dependent backgrounds from stationary axisymmetric solutions
Obregon, Octavio; Quevedo, Hernando; Ryan, Michael P.
2004-09-15
Backgrounds depending on time and on angular variable, namely, polarized and unpolarized S{sup 1}xS{sup 2} Gowdy models, are generated as the sector inside the horizons of the manifold corresponding to axisymmetric solutions. As is known, an analytical continuation of ordinary D-branes, iD-branes allow one to find S-brane solutions. Simple models have been constructed by means of analytic continuation of the Schwarzschild and the Kerr metrics. The possibility of studying the i-Gowdy models obtained here is outlined with an eye toward seeing if they could represent some kind of generalized S-branes depending not only on time but also on an angular variable.
GPELab, a Matlab toolbox to solve Gross-Pitaevskii equations I: Computation of stationary solutions
NASA Astrophysics Data System (ADS)
Antoine, Xavier; Duboscq, Romain
2014-11-01
This paper presents GPELab (Gross-Pitaevskii Equation Laboratory), an advanced easy-to-use and flexible Matlab toolbox for numerically simulating many complex physics situations related to Bose-Einstein condensation. The model equation that GPELab solves is the Gross-Pitaevskii equation. The aim of this first part is to present the physical problems and the robust and accurate numerical schemes that are implemented for computing stationary solutions, to show a few computational examples and to explain how the basic GPELab functions work. Problems that can be solved include: 1d, 2d and 3d situations, general potentials, large classes of local and nonlocal nonlinearities, multi-components problems, and fast rotating gases. The toolbox is developed in such a way that other physics applications that require the numerical solution of general Schrödinger-type equations can be considered. Catalogue identifier: AETU_v1_0 Program summary URL:http://cpc.cs.qub.ac.uk/summaries/AETU_v1_0.html Program obtainable from: CPC Program Library, Queen’s University, Belfast, N. Ireland Licensing provisions: Standard CPC licence, http://cpc.cs.qub.ac.uk/licence/licence.html No. of lines in distributed program, including test data, etc.: 26 552 No. of bytes in distributed program, including test data, etc.: 611 289 Distribution format: tar.gz Programming language: Matlab. Computer: PC, Mac. Operating system: Windows, Mac OS, Linux. Has the code been vectorized or parallelized?: Yes RAM: 4000 Megabytes Classification: 2.7, 4.6, 7.7. Nature of problem: Computing stationary solutions for a class of systems (multi-components) of Gross-Pitaevskii equations in 1d, 2d and 3d. This program is particularly well designed for the computation of ground states of Bose-Einstein condensates as well as dynamics. Solution method: We use the imaginary-time method with a Semi-Implicit Backward Euler scheme, a pseudo-spectral approximation and a Krylov subspace method. Running time: From a few minutes
NASA Astrophysics Data System (ADS)
Grach, V. S.; Garasev, M. A.
2015-07-01
We consider the interaction of a isolated conducting sphere with a collisional weakly ionized plasma in an external field. We assume that the plasma consists of two species of ions neglecting of electrons. We take into account charging of the sphere due to sedimentation of plasma ions on it, the field of the sphere charge and the space charge, as well as recombination and molecular diffusion. The nonstationary problem of interaction of the sphere with the surrounding plasma is solved numerically. The temporal dynamics of the sphere charge and plasma perturbations is analyzed, as well as the properties of the stationary state. It is shown that the duration of transient period is determined by the recombination time and by the reverse conductivity of ions. The temporal dynamics of the sphere charge and plasma perturbations is determined by the intensity of recombination processes relative to the influence of the space charge field and diffusion. The stationary absolute value of the sphere charge increases linearly with the external electric field, decreases with the relative intensity of recombination processes and increases in the presence of substantial diffusion. The scales of the perturbed region in the plasma are determined by the radius of the sphere, the external field, the effect of diffusion, and the relative intensity of recombination processes. In the limiting case of the absence of molecular diffusion and a strong external field, the properties of the stationary state coincide with those obtained earlier as a result of approximate solution.
Grach, V. S. Garasev, M. A.
2015-07-15
We consider the interaction of a isolated conducting sphere with a collisional weakly ionized plasma in an external field. We assume that the plasma consists of two species of ions neglecting of electrons. We take into account charging of the sphere due to sedimentation of plasma ions on it, the field of the sphere charge and the space charge, as well as recombination and molecular diffusion. The nonstationary problem of interaction of the sphere with the surrounding plasma is solved numerically. The temporal dynamics of the sphere charge and plasma perturbations is analyzed, as well as the properties of the stationary state. It is shown that the duration of transient period is determined by the recombination time and by the reverse conductivity of ions. The temporal dynamics of the sphere charge and plasma perturbations is determined by the intensity of recombination processes relative to the influence of the space charge field and diffusion. The stationary absolute value of the sphere charge increases linearly with the external electric field, decreases with the relative intensity of recombination processes and increases in the presence of substantial diffusion. The scales of the perturbed region in the plasma are determined by the radius of the sphere, the external field, the effect of diffusion, and the relative intensity of recombination processes. In the limiting case of the absence of molecular diffusion and a strong external field, the properties of the stationary state coincide with those obtained earlier as a result of approximate solution.
Determining stationary-state quantum properties directly from system-environment interactions
NASA Astrophysics Data System (ADS)
Nicacio, F.; Paternostro, M.; Ferraro, A.
2016-11-01
Considering stationary states of continuous-variable systems undergoing an open dynamics, we unveil the connection between properties and symmetries of the latter and the dynamical parameters. In particular, we explore the relation between the Lyapunov equation for dynamical systems and the steady-state solutions of a time-independent Lindblad master equation for bosonic modes. Exploiting bona fide relations that characterize some genuine quantum properties (entanglement, classicality, and steerability), we obtain conditions on the dynamical parameters for which the system is driven to a steady state possessing such properties. We also develop a method to capture the symmetries of a steady state based on symmetries of the Lyapunov equation. All the results and examples can be useful for steady-state engineering processes.
NASA Astrophysics Data System (ADS)
Garcia-Diaz, Alberto A.; Gutierrez-Cano, Gustavo
It is established that the conformal type D electrovacuum stationary axisymmetric Carter class of metrics splits into three families of solutions: the Plebański-Demiański family, the Carter-Plebański spacetimes, and the trigonometric-hyperbolic conformal class. This last class, via coordinate transformations, can be brought to the C-P form. These metrics admit an Abelian group of motions G2 with commuting stationary and angular Killing vectors, are of Petrov type D; the null eigenvectors of the general electromagnetic field coincide with the directions of the Debever null vectors of Weyl curvature tensor. These solutions exhibit, for certain ranges of the coordinate variables, a black hole behavior; a "ring" singularity similar to the one of the Kerr metric is present. The limiting transition of these solutions leads to the Kerr-Newman black hole solution as a subbranch.
Mixed addenda polyoxometalate "solutions" for stationary energy storage.
Pratt, Harry D; Anderson, Travis M
2013-11-28
A series of redox flow batteries utilizing mixed addenda (vanadium and tungsten), phosphorus-based polyoxometalates (A-α-PV3W9O40(6-), B-α-PV3W9O40(6-), and P2V3W15O62(9-)) were prepared and tested. Cyclic voltammetry and bulk electrolysis experiments on the Keggin compounds (A-α-PV3W9O40(6-) and B-α-PV3W9O40(6-)) established that the vanadium centers of these compounds could be used as the positive electrode (PV(IV)3W(VI)9O40(9-)/PV(V)3W(VI)9O40(6-)), and the tungsten centers could be used as the negative electrode (PV(IV)3W(VI)9O40(9-)/PV(IV)3W(V)3W(VI)6O40(12-)) since these electrochemical processes are separated by about 1 V. The results showed that A-α-PV3W9O40(6-) (where A indicates adjacent, corner-sharing vanadium atoms) had coulombic efficiencies (charge in divided by charge out) above 80%, while the coulombic efficiency of B-α-PV3W9O40(6-) (where B indicates adjacent edge-sharing vanadium atoms) fluctuated between 50% and 70% during cycling. The electrochemical yield, a measurement of the actual charge or discharge observed in comparison with the theoretical charge, was between 40% and 50% for A-α-PV3W9O40(6-), and (31)P NMR showed small amounts of PV2W10O40(5-) and PVW11O40(4-) formed with cycling. The electrochemical yield for B-α-PV3W9O40(6-) decreased from 90% to around 60% due to precipitation of the compound on the electrode, but there were no decomposition products detected in the solution by (31)P NMR, and infrared data on the electrode suggested that the cluster remained intact. Testing of P2V3W15O62(9-) (Wells-Dawson structure) suggested higher charge density clusters were not as suitable as the Keggin structures for a redox flow battery due to the poor stability and inaccessibility of the highly reduced materials.
On the asymptotic behaviour of 2D stationary Navier–Stokes solutions with symmetry conditions
NASA Astrophysics Data System (ADS)
Decaster, Agathe; Iftimie, Dragoş
2017-10-01
We consider the 2D stationary incompressible Navier-Stokes equations in ℝ2. Under suitable symmetry, smallness and decay at infinity conditions on the forcing we determine the behaviour at infinity of the solutions. Moreover, when the forcing is small, satisfies suitable symmetry conditions and decays at infinity like a vector field homogeneous of degree -3, we show that there exists a unique small solution whose asymptotic behaviour at infinity is homogeneous of degree -1.
Periodic solutions and stationary distribution of mutualism models in random environments
NASA Astrophysics Data System (ADS)
Zhang, Xinhong; Jiang, Daqing; Alsaedi, Ahmed; Hayat, Tasawar
2016-10-01
This paper is concerned with mutualism models in random environments. For the periodic mutualism model disturbed by white noise, using Has'minskii theory of periodic solution, we show that this model admits a nontrivial positive periodic solution. Then sufficient conditions for the existence and global attractivity of the boundary periodic solutions are established. For the mutualism model disturbed by both white noise and telephone noise, sufficient conditions for positive recurrence and the existence of ergodic stationary distribution of the solution are established. Finally, examples are introduced to illustrate the results developed.
NASA Astrophysics Data System (ADS)
Pástor, P.
2016-07-01
The equations of secular evolution for dust grains in mean motion resonances with a planet are solved for stationary points. Non-gravitational effects caused by stellar radiation (the Poynting-Robertson effect and the stellar wind) are taken into account. The solutions are stationary in the semimajor axis, eccentricity and resonant angle, but allow the pericentre to advance. The semimajor axis of stationary solutions can be slightly shifted from the exact resonant value. The periodicity of the stationary solutions in a reference frame orbiting with the planet is proved analytically. The existence of periodic solutions in mean motion resonances means that analytical theory enables infinitely long capture times for dust particles. The stationary solutions are periodic motions to which the eccentricity asymptotically approaches and around which the libration occurs. Initial conditions corresponding to the stationary solutions are successfully found by numerically integrating the equation of motion. Numerically and analytically determined shifts of the semimajor axis from the exact resonance for the stationary solutions are in excellent agreement. The stationary solutions can be plotted by the locations of pericentres in the reference frame orbiting with the planet. The pericentres are distributed in space according to the properties of the dust particles.
Modified Navier-Stokes model for nonequilibrium stationary states
NASA Astrophysics Data System (ADS)
Garcia-Colin, L. S.; Velasco, R. M.
1982-10-01
A hydrodynamic model is developed in order to study the features of the behavior of a fluid which is brought to a stationary state by the action of an external gradient in the cases of the action of a thermal gradient and of a constant shear rate. An examination of the sound absorption of the fluid shows that the Stokes-Kirchhoff formula is modified by the presence of the gradients, which suggests an experimental verification of the model which is independent of the magnitude of the real wave vector. In addition, the light scattering of the fluid is examined by computing the Brillouin-Rayleigh spectra which yields in both cases the same shift in the Brillouin peaks previously predicted. However, a small change in the intensity of the peaks due to the modification of the sound-absorption coefficient is predicted by this model. Calculations show a shift of the Rayleigh peak arising from the entropy flow in the case of the thermal gradient and an entropy-production term in the case of the constant rate of shear, while in both cases the order of magnitude of this correction in terms of the wave vector is the same as the terms responsible for the shift in the Brillouin peaks.
Linear Augmentation for Stabilizing Stationary Solutions: Potential Pitfalls and Their Application.
Karnatak, Rajat
2015-01-01
Linear augmentation has recently been shown to be effective in targeting desired stationary solutions, suppressing bistablity, in regulating the dynamics of drive response systems and in controlling the dynamics of hidden attractors. The simplicity of the procedure is the main highlight of this scheme but questions related to its general applicability still need to be addressed. Focusing on the issue of targeting stationary solutions, this work demonstrates instances where the scheme fails to stabilize the required solutions and leads to other complicated dynamical scenarios. Examples from conservative as well as dissipative systems are presented in this regard and important applications in dissipative predator-prey systems are discussed, which include preventative measures to avoid potentially catastrophic dynamical transitions in these systems.
Linear Augmentation for Stabilizing Stationary Solutions: Potential Pitfalls and Their Application
Karnatak, Rajat
2015-01-01
Linear augmentation has recently been shown to be effective in targeting desired stationary solutions, suppressing bistablity, in regulating the dynamics of drive response systems and in controlling the dynamics of hidden attractors. The simplicity of the procedure is the main highlight of this scheme but questions related to its general applicability still need to be addressed. Focusing on the issue of targeting stationary solutions, this work demonstrates instances where the scheme fails to stabilize the required solutions and leads to other complicated dynamical scenarios. Examples from conservative as well as dissipative systems are presented in this regard and important applications in dissipative predator—prey systems are discussed, which include preventative measures to avoid potentially catastrophic dynamical transitions in these systems. PMID:26544879
NASA Astrophysics Data System (ADS)
Boshkayev, Kuantay; Quevedo, Hernando; Toktarbay, Saken; Zhami, Bakytzhan; Abishev, Medeu
2016-10-01
We study stationary axially symmetric solutions of the Einstein vacuum field equations that can be used to describe the gravitational field of astrophysical compact objects in the limiting case of slow rotation and slight deformation. We derive explicitly the exterior Sedrakyan-Chubaryan approximate solution, and express it in analytical form, which makes it practical in the context of astrophysical applications. In the limiting case of vanishing angular momentum, the solution reduces to the well-known Schwarzschild solution in vacuum. We demonstrate that the new solution is equivalent to the exterior Hartle-Thorne solution. We establish the mathematical equivalence between the Sedrakyan-Chubaryan, Fock-Abdildin and Hartle-Thorne formalisms.
The sensitivity of stationary waves to variations in the basic state zonal flow
NASA Technical Reports Server (NTRS)
Nigam, Sumant; Lindzen, Richard S.
1989-01-01
A linear, primitive equation stationary wave model having high vertical and meridional resolution is used to examine the sensitivity of orographically forced (primarily by Himalayas) stationary waves at middle and high latitudes to variations in the basic state zonal wind distribution. We find relatively little sensitivity to the winds in high latitudes, but remarkable sensitivity to small variations in the subtropical jet. Fluctuations well within the range of observed variability in the jet can lead to large variations in the stationary waves of the high latitude stratosphere, and to large changes even in tropospheric stationary waves. Implications for both sudden warmings and large-scale weather are discussed.
Multi-hump solutions with small oscillations at infinity for stationary Swift-Hohenberg equation
NASA Astrophysics Data System (ADS)
Deng, Shengfu; Sun, Shu-Ming
2017-02-01
The paper considers the stationary Swift-Hohenberg equation cw-(∂x2+k02)2w-w3=0, where c > 0 is a constant, k02=\\sqrt{c}-μ , and μ >0 is a small parameter. In this case, the linear operator has a pair of real eigenvalues and a pair of purely imaginary eigenvalues. It can be proved that the equation has homoclinic (or single hump) solutions approaching to periodic solutions as |x|\\to +∞ (called single-hump generalized homoclinic solutions). This paper provides the first rigorous proof of existence of homoclinic solutions with two humps which tend to periodic solutions at infinity (or two-hump generalized homoclinic solutions) by pasting two appropriate single-hump generalized homoclinic solutions together. The dynamical system approach is used to reformulate the problem into a classical dynamical system problem and then the solution is decomposed into a decaying part and an oscillatory part at positive infinity. By adjusting some free constants and modifying the single-hump generalized homoclinic solution near negative infinity, it is shown that the solution is reversible with respect to a point near negative infinity. Therefore, the translational invariant and reversibility properties of the system yield a two-hump generalized homoclinic solution. The method may be applied to prove the existence of 2 k -hump solutions for any positive integer k.
Stability of stationary solutions for inflow problem on the micropolar fluid model
NASA Astrophysics Data System (ADS)
Yin, Haiyan
2017-04-01
In this paper, we study the asymptotic behavior of solutions to the initial boundary value problem for the micropolar fluid model in a half-line R+:=(0,∞). We prove that the corresponding stationary solutions of the small amplitude to the inflow problem for the micropolar fluid model are time asymptotically stable under small H1 perturbations in both the subsonic and degenerate cases. The microrotation velocity brings us some additional troubles compared with Navier-Stokes equations in the absence of the microrotation velocity. The proof of asymptotic stability is based on the basic energy method.
Method for Numerical Solution of the Stationary Schrödinger Equation
NASA Astrophysics Data System (ADS)
Knyazev, S. Yu.; Shcherbakova, E. E.
2017-02-01
The aim of this work is to describe a method of numerical solution of the stationary Schrödinger equation based on the integral equation that is identical to the Schrödinger equation. The method considered here allows one to find the eigenvalues and eigensolutions for quantum-mechanical problems of different dimensionality. The method is tested by solving problems for one-dimensional and two-dimensional quantum oscillators, and results of these tests are presented. Satisfactory agreement of the results obtained using this numerical method with well-known analytical solutions is demonstrated.
Theory of periodic solutions of the stationary Landau-Lifshitz equation
Bar'yakhtar, V.G.; Leonov, I.A.; Soboleva, T.K.
1987-04-01
In the phenomenological approach, quasi-one-dimensional structures in a magnet of a definite symmetry are described by solutions of the stationary Landau-Lifshitz equation or, equivalently, by the solutions of a variational problem with Lagrangian L whose actual form is determined by the requirement of invariance with respect to the symmetry group of the paramagnetic phase of the given magnet. In the present note, the methods of the variational calculus in the large are used to estimate the number of possible magnetic phases with periodic superstructure corresponding to a given free energy functional of the magnet.
Quasi-stationary states in the Southern Hemisphere
NASA Technical Reports Server (NTRS)
Mo, K. C.
1986-01-01
Pattern correlations between daily anomalies have been used to study the persistence of the Southern Hemisphere circulations. The dataset consists of daily Australian analyses of 500 mb heights and sea level pressure for the period from 1972 to 1983. Compared to the Northern Hemisphere, the pattern correlations are much lower and more variable in the Southern Hemisphere. The mean one-day lag autocorrelation is only 0.57, compared to 0.81 in the Northern Hemisphere. The correlations increase significantly for the filtered anomalies, which consist of the planetary wavenumbers from 0 to 4. Subjective criteria based on the pattern correlations are used to select quasi-stationary events. A series of 5 or more daily maps is defined to be quasi-stationary if the pattern correlations between all pairs of five consecutive maps in this time series are larger than or equal to 0.5. In winter, quasi-stationary events can be classified in terms of wavenumbers. Waves 3 and 4 are by far the dominant waves. More than half of the events have large wave 3 amplitude with geographically fixed orientations.
NASA Astrophysics Data System (ADS)
Li, Yeping; Yang, Xiongfeng
2017-02-01
In this paper, we consider the 3-D compressible viscous magnetohydrodynamic (MHD) equations with some large potential force in bounded rigid vessel. We firstly construct the non-constant stationary solutions of the compressible viscous MHD equations under suitable constitutive assumptions. Next, a critical energy identity is established to achieve a universal stability criterion of the stationary solution. In this case, the stationary solution is exponential stable for any large external potential force. Finally, we show the well-posedness of the initial boundary value problem for the compressible viscous MHD equations with the large potential force, provided that the prescribed initial data is close to the stationary solution. It implies that the set satisfying the stability criterion is not empty.
NASA Astrophysics Data System (ADS)
Uzunov, Ivan M.; Arabadzhiev, Todor N.; Georgiev, Zhivko D.
2015-08-01
We have studied the impact of the higher-order effects: intrapulse Raman scattering (IRS), third-order of dispersion (TOD) and self-steepening (SS) on pulsating solutions, moving fronts and stationary solutions of the complex cubic-quintic Ginzburg-Landau equation (CCQGLE) found in Tsoy and Akhmediev (2005) as well as on the solutions presented in Uzunov et al. (2014). The applied basic equation generalizes the CCQGLE with the IRS, TOD and SS effects. A finite-dimensional dynamical system has been derived using the method of moments. Applying the derived dynamical system alongside with the numerical solution of the generalized CCQGLE performed by means of the fourth-order Runge-Kutta interaction picture method we have found that the influence of IRS and SS is stronger than the impact of TOD for the solutions of Tsoy and Akhmediev (2005). Perturbed pulsating solutions, moving fronts and stationary solutions in the presence of IRS, SS and TOD have been numerically observed. They exist up to some critical values of the parameters of perturbations. For the values of parameters larger than the critical ones the pulsating solutions are transformed into stable stationary solutions or unstable solutions. New localized fluctuating and stationary solutions have been obtained for fairly large values of parameters of IRS and TOD, respectively. The transformation of the stable stationary solution of Uzunov et al. (2014) under the influence of SS into pulsating solution has been numerically observed.
Convergence rates to stationary solutions of a gas-liquid model with external forces
NASA Astrophysics Data System (ADS)
Fan, Long; Liu, Qingqing; Zhu, Changjiang
2012-10-01
In this paper, we study the asymptotic behaviour of solutions to a gas-liquid model with external forces. Under some suitable assumptions on the initial data, if γ > 1 and \\theta\\in(0,\\frac{\\gamma}{2}]\\cap(0,\\gamma-1]\\cap(0,1-\\alpha\\gamma] , we prove the weak solution (cQ (x, t), u(x, t)) behaviour asymptotically to the stationary one by adapting and modifying the technique of weighted estimates. In addition, if \\theta\\in(0,\\frac{\\gamma}{2}]\\cap(0,\\gamma-1)\\cap(0,1-\\alpha\\gamma] , following the same idea used in Zhang and Fang (2006 Arch. Ration. Mech. Anal. 182 223-53), we estimate the stabilization rate of the solution as time tends to infinity in the sense of L∞ norm.
Time-periodic and stationary solutions to the compressible Hall-magnetohydrodynamic system
NASA Astrophysics Data System (ADS)
Cheng, Ming
2017-04-01
We are concerned with the 3-D compressible Hall-magnetohydrodynamic system with a time-periodic external force in a periodic domain, and establish the existence of a strong time-periodic solution under some smallness and symmetry assumptions by adapting a new approach. The basic idea of the proof is the following. First, we prove the existence of a time-periodic solution to the linearized system by applying the Tychonoff fixed point theorem combined with the energy method and the decay estimates. From the details of the proof, we see that the initial data of the time-periodic solution to the linearized system lies in some convex hull. Then, we construct a set-value function, such that the fixed point of this function is a time-periodic solution of the compressible Hall-magnetohydrodynamic system. The existence of the fixed point is obtained by the Kakutani fixed point theorem. Moreover, we establish the uniqueness of the time-periodic solution and the existence of the stationary solution.
NASA Astrophysics Data System (ADS)
Siettos, C. I.; Gear, C. W.; Kevrekidis, I. G.
2012-08-01
We show how the equation-free approach can be exploited to enable agent-based simulators to perform system-level computations such as bifurcation, stability analysis and controller design. We illustrate these tasks through an event-driven agent-based model describing the dynamic behaviour of many interacting investors in the presence of mimesis. Using short bursts of appropriately initialized runs of the detailed, agent-based simulator, we construct the coarse-grained bifurcation diagram of the (expected) density of agents and investigate the stability of its multiple solution branches. When the mimetic coupling between agents becomes strong enough, the stable stationary state loses its stability at a coarse turning point bifurcation. We also demonstrate how the framework can be used to design a wash-out dynamic controller that stabilizes open-loop unstable stationary states even under model uncertainty.
NASA Astrophysics Data System (ADS)
Zuo, Wenjie; Jiang, Daqing
2016-07-01
In this paper, we investigate the dynamics of the stochastic autonomous and non-autonomous predator-prey systems with nonlinear predator harvesting respectively. For the autonomous system, we first give the existence of the global positive solution. Then, in the case of persistence, we prove that there exists a unique stationary distribution and it has ergodicity by constructing a suitable Lyapunov function. The result shows that, the relatively weaker white noise will strengthen the stability of the system, but the stronger white noise will result in the extinction of one or two species. Particularly, for the non-autonomous periodic system, we show that there exists at least one nontrivial positive periodic solution according to the theory of Khasminskii. Finally, numerical simulations illustrate our theoretical results.
Ferrofluid patterns in Hele-Shaw cells: Exact, stable, stationary shape solutions
NASA Astrophysics Data System (ADS)
Lira, Sérgio A.; Miranda, José A.
2016-01-01
We investigate a quasi-two-dimensional system composed of an initially circular ferrofluid droplet surrounded by a nonmagnetic fluid of higher density. These immiscible fluids flow in a rotating Hele-Shaw cell, under the influence of an in-plane radial magnetic field. We focus on the situation in which destabilizing bulk magnetic field effects are balanced by stabilizing centrifugal forces. In this framing, we consider the interplay of capillary and magnetic normal traction effects in determining the fluid-fluid interface morphology. By employing a vortex-sheet formalism, we have been able to find a family of exact stationary N -fold polygonal shape solutions for the interface. A weakly nonlinear theory is then used to verify that such exact interfacial solutions are in fact stable.
Ferrofluid patterns in Hele-Shaw cells: Exact, stable, stationary shape solutions.
Lira, Sérgio A; Miranda, José A
2016-01-01
We investigate a quasi-two-dimensional system composed of an initially circular ferrofluid droplet surrounded by a nonmagnetic fluid of higher density. These immiscible fluids flow in a rotating Hele-Shaw cell, under the influence of an in-plane radial magnetic field. We focus on the situation in which destabilizing bulk magnetic field effects are balanced by stabilizing centrifugal forces. In this framing, we consider the interplay of capillary and magnetic normal traction effects in determining the fluid-fluid interface morphology. By employing a vortex-sheet formalism, we have been able to find a family of exact stationary N-fold polygonal shape solutions for the interface. A weakly nonlinear theory is then used to verify that such exact interfacial solutions are in fact stable.
Ferrofluid patterns in Hele-Shaw cells: Exact, stable, stationary shape solutions
NASA Astrophysics Data System (ADS)
Lira, Sergio; Miranda, Jose
2016-11-01
We investigate a quasi-two-dimensional system composed by an initially circular ferrofluid droplet surrounded by a nonmagnetic fluid of higher density. These immiscible fluids flow in a rotating Hele-Shaw cell, under the influence of an in-plane radial magnetic field. We focus on the situation in which destabilizing bulk magnetic field effects are balanced by stabilizing centrifugal forces. In this framing, we consider the interplay of capillary and magnetic normal traction effects in determining the fluid-fluid interface morphology. By employing a vortex-sheet formalism we have been able to find a family of exact stationary N-fold polygonal shape solutions for the interface. A weakly nonlinear theory is then used to verify that such exact interfacial solutions are in fact stable. We thank CNPq (Brazilian Research Council) for financial support.
Dynamics of order parameters near stationary states in superconductors with a charge-density wave
NASA Astrophysics Data System (ADS)
Moor, Andreas; Volkov, Pavel A.; Volkov, Anatoly F.; Efetov, Konstantin B.
2014-07-01
We consider a simple model of a quasi-one-dimensional conductor in which two order parameters (OP) may coexist, i.e., the superconducting OP Δ and the OP W that characterize the amplitude of a charge-density wave (CDW). In the mean field approximation, we present equations for the matrix Green's functions Gik, where the first subscript i relates to the one of the two Fermi sheets and the other, k, operates in the Gor'kov-Nambu space. Using the solutions of these equations, we find stationary states for different values of the parameter describing the curvature of the Fermi surface μ, which can be varied, e.g., by doping. It is established, in particular, that in the interval μ1<μ <μ2, the self-consistency equations have a solution for coexisting OPs Δ and W. However, this solution corresponds to a saddle point in the energy functional Φ (Δ,W), i.e., it is unstable. Stable states are (1) the W state, i.e., the state with the CDW (W ≠0, Δ =0) at μ <μ2 and (2) the S state, i.e., the purely superconducting state (Δ ≠0, W =0) at μ1<μ. These states correspond to minima of Φ. At μ <μ0=(μ1+μ2)/2, the state (1) corresponds to a global minimum, and at μ0<μ, the state (2) has a lower energy, i.e., only the superconducting state survives at large μ. We study the dynamics of the variations δΔ and δW from these states in the collisionless limit. It is characterized by two modes of oscillations, the fast and the slow one. The fast mode is analogous to damped oscillations in conventional superconductors. The frequency of slow modes depends on the curvature μ and is much smaller than 2Δ /ℏ if the coupling constants for superconductivity and CDW are close to each other. The considered model can be applied to high-Tc superconductors where the parts of the Fermi surface near the "hot" spots may be regarded as the considered two Fermi sheets. We also discuss relation of the considered model to the simplest model for Fe-based pnictides.
Stationary Source Related Documents for State and Local Transportation
State and Local Transporation Resources is an EPA/OTAQ web page for state and local air quality regulators and transportation planners that offers guidance on how to reduce air pollution from cars, diesel trucks, city and school buses
NASA Astrophysics Data System (ADS)
Génois, Mathieu; Hersen, Pascal; Bertin, Eric; Courrech du Pont, Sylvain; Grégoire, Guillaume
2016-10-01
The exploration of the phase diagram of a minimal model for barchan fields leads to the description of three distinct phases for the system: stationary, percolable, and unstable. In the stationary phase the system always reaches an out-of-equilibrium, fluctuating, stationary state, independent of its initial conditions. This state has a large and continuous range of dynamics, from dilute—where dunes do not interact—to dense, where the system exhibits both spatial structuring and collective behavior leading to the selection of a particular size for the dunes. In the percolable phase, the system presents a percolation threshold when the initial density increases. This percolation is unusual, as it happens on a continuous space for moving, interacting, finite lifetime dunes. For extreme parameters, the system exhibits a subcritical instability, where some of the dunes in the field grow without bound. We discuss the nature of the asymptotic states and their relations to well-known models of statistical physics.
Génois, Mathieu; Hersen, Pascal; Bertin, Eric; Courrech du Pont, Sylvain; Grégoire, Guillaume
2016-10-01
The exploration of the phase diagram of a minimal model for barchan fields leads to the description of three distinct phases for the system: stationary, percolable, and unstable. In the stationary phase the system always reaches an out-of-equilibrium, fluctuating, stationary state, independent of its initial conditions. This state has a large and continuous range of dynamics, from dilute-where dunes do not interact-to dense, where the system exhibits both spatial structuring and collective behavior leading to the selection of a particular size for the dunes. In the percolable phase, the system presents a percolation threshold when the initial density increases. This percolation is unusual, as it happens on a continuous space for moving, interacting, finite lifetime dunes. For extreme parameters, the system exhibits a subcritical instability, where some of the dunes in the field grow without bound. We discuss the nature of the asymptotic states and their relations to well-known models of statistical physics.
Hermite-Gaussian stationary solutions in strongly nonlocal nonlinear optical media
NASA Astrophysics Data System (ADS)
Zhong, Lanhua; Yang, Jing; Ren, Zhanmei; Guo, Qi
2017-01-01
Approximate analytical stationary solutions (SSs) of a cluster of Hermite-Gaussian (HG) shape is obtained in strongly nonlocal nonlinear media by the variational approach. The evolution of the HG SSs shows that when the order n ⩽ 3, they propagate stably and form solitons; otherwise, when n ⩾ 4, they always propagate unstably and evolve into self-trapped speckle-like beams. However, all these SSs maintain nearly invariant statistic beam-width during their propagation. Furthermore, when the input power deviates from the so-called critical power, the unstable HG beam will adjust its beam-width to form a new self-trapped beam, unlike the soliton which will turn to be a breather. But the average beam-widths are independent of the stability of the propagation of the HG SSs.
NASA Astrophysics Data System (ADS)
Hong, Xinguo; Hao, Quan
2009-01-01
In this paper, we report a method of precise in situ x-ray scattering measurements on protein solutions using small stationary sample cells. Although reduction in the radiation damage induced by intense synchrotron radiation sources is indispensable for the correct interpretation of scattering data, there is still a lack of effective methods to overcome radiation-induced aggregation and extract scattering profiles free from chemical or structural damage. It is found that radiation-induced aggregation mainly begins on the surface of the sample cell and grows along the beam path; the diameter of the damaged region is comparable to the x-ray beam size. Radiation-induced aggregation can be effectively avoided by using a two-dimensional scan (2D mode), with an interval as small as 1.5 times the beam size, at low temperature (e.g., 4 °C). A radiation sensitive protein, bovine hemoglobin, was used to test the method. A standard deviation of less than 5% in the small angle region was observed from a series of nine spectra recorded in 2D mode, in contrast to the intensity variation seen using the conventional stationary technique, which can exceed 100%. Wide-angle x-ray scattering data were collected at a standard macromolecular diffraction station using the same data collection protocol and showed a good signal/noise ratio (better than the reported data on the same protein using a flow cell). The results indicate that this method is an effective approach for obtaining precise measurements of protein solution scattering.
Hong Xinguo; Hao Quan
2009-01-15
In this paper, we report a method of precise in situ x-ray scattering measurements on protein solutions using small stationary sample cells. Although reduction in the radiation damage induced by intense synchrotron radiation sources is indispensable for the correct interpretation of scattering data, there is still a lack of effective methods to overcome radiation-induced aggregation and extract scattering profiles free from chemical or structural damage. It is found that radiation-induced aggregation mainly begins on the surface of the sample cell and grows along the beam path; the diameter of the damaged region is comparable to the x-ray beam size. Radiation-induced aggregation can be effectively avoided by using a two-dimensional scan (2D mode), with an interval as small as 1.5 times the beam size, at low temperature (e.g., 4 deg. C). A radiation sensitive protein, bovine hemoglobin, was used to test the method. A standard deviation of less than 5% in the small angle region was observed from a series of nine spectra recorded in 2D mode, in contrast to the intensity variation seen using the conventional stationary technique, which can exceed 100%. Wide-angle x-ray scattering data were collected at a standard macromolecular diffraction station using the same data collection protocol and showed a good signal/noise ratio (better than the reported data on the same protein using a flow cell). The results indicate that this method is an effective approach for obtaining precise measurements of protein solution scattering.
Hong, Xinguo; Hao, Quan
2009-01-01
In this paper, we report a method of precise in situ x-ray scattering measurements on protein solutions using small stationary sample cells. Although reduction in the radiation damage induced by intense synchrotron radiation sources is indispensable for the correct interpretation of scattering data, there is still a lack of effective methods to overcome radiation-induced aggregation and extract scattering profiles free from chemical or structural damage. It is found that radiation-induced aggregation mainly begins on the surface of the sample cell and grows along the beam path; the diameter of the damaged region is comparable to the x-ray beam size. Radiation-induced aggregation can be effectively avoided by using a two-dimensional scan (2D mode), with an interval as small as 1.5 times the beam size, at low temperature (e.g., 4 °C). A radiation sensitive protein, bovine hemoglobin, was used to test the method. A standard deviation of less than 5% in the small angle region was observed from a series of nine spectra recorded in 2D mode, in contrast to the intensity variation seen using the conventional stationary technique, which can exceed 100%. Wide-angle x-ray scattering data were collected at a standard macromolecular diffraction station using the same data collection protocol and showed a good signal∕noise ratio (better than the reported data on the same protein using a flow cell). The results indicate that this method is an effective approach for obtaining precise measurements of protein solution scattering. PMID:19191451
Irreducible Decompositions and Stationary States of Quantum Channels
NASA Astrophysics Data System (ADS)
Carbone, Raffaella; Pautrat, Yan
2016-06-01
For a quantum channel (completely positive, trace-preserving map), we prove a generalization to the infinite-dimensional case of a result by Baumgartner and Narnhofer [3]: this result is, in a probabilistic language, a decomposition of a general quantum channel into its irreducible recurrent components. More precisely, we prove that the positive recurrent subspace (i.e. the space supporting the invariant states) can be decomposed as the direct sum of supports of extremal invariant states; this decomposition is not unique, in general, but we can determine all the possible decompositions. This allows us to describe the full structure of invariant states.
Entropy production and thermodynamics of nonequilibrium stationary states: a point of view.
Gallavotti, Giovanni
2004-09-01
Entropy might be a not well defined concept if the system can undergo transformations involving stationary nonequilibria. It might be analogous to the heat content (once called "caloric") in transformations that are not isochoric (i.e., which involve mechanical work): it could be just a quantity that can be transferred or created, like heat in equilibrium. The text first reviews the philosophy behind a recently proposed definition of entropy production in nonequilibrium stationary systems. A detailed technical attempt at defining the entropy of a stationary states via their variational properties follows: the unsatisfactory aspects of the results add arguments in favor of the nonexistence of a function of state to be identified with entropy; at the same time new aspects and properties of the phase space contraction emerge.
Dadinova, Liubov A; Shtykova, Eleonora V; Konarev, Petr V; Rodina, Elena V; Snalina, Natalia E; Vorobyeva, Natalia N; Kurilova, Svetlana A; Nazarova, Tatyana I; Jeffries, Cy M; Svergun, Dmitri I
2016-01-01
The structural analyses of four metabolic enzymes that maintain and regulate the stationary growth phase of Escherichia coli have been performed primarily drawing on the results obtained from solution small angle X-ray scattering (SAXS) and other structural techniques. The proteins are (i) class I fructose-1,6-bisphosphate aldolase (FbaB); (ii) inorganic pyrophosphatase (PPase); (iii) 5-keto-4-deoxyuronate isomerase (KduI); and (iv) glutamate decarboxylase (GadA). The enzyme FbaB, that until now had an unknown structure, is predicted to fold into a TIM-barrel motif that form globular protomers which SAXS experiments show associate into decameric assemblies. In agreement with previously reported crystal structures, PPase forms hexamers in solution that are similar to the previously reported X-ray crystal structure. Both KduI and GadA that are responsible for carbohydrate (pectin) metabolism and acid stress responses, respectively, form polydisperse mixtures consisting of different oligomeric states. Overall the SAXS experiments yield additional insights into shape and organization of these metabolic enzymes and further demonstrate the utility of hybrid methods, i.e., solution SAXS combined with X-ray crystallography, bioinformatics and predictive 3D-structural modeling, as tools to enrich structural studies. The results highlight the structural complexity that the protein components of metabolic networks may adopt which cannot be fully captured using individual structural biology techniques.
Dadinova, Liubov A.; Shtykova, Eleonora V.; Konarev, Petr V.; Rodina, Elena V.; Snalina, Natalia E.; Vorobyeva, Natalia N.; Kurilova, Svetlana A.; Nazarova, Tatyana I.; Jeffries, Cy M.; Svergun, Dmitri I.
2016-01-01
The structural analyses of four metabolic enzymes that maintain and regulate the stationary growth phase of Escherichia coli have been performed primarily drawing on the results obtained from solution small angle X-ray scattering (SAXS) and other structural techniques. The proteins are (i) class I fructose-1,6-bisphosphate aldolase (FbaB); (ii) inorganic pyrophosphatase (PPase); (iii) 5-keto-4-deoxyuronate isomerase (KduI); and (iv) glutamate decarboxylase (GadA). The enzyme FbaB, that until now had an unknown structure, is predicted to fold into a TIM-barrel motif that form globular protomers which SAXS experiments show associate into decameric assemblies. In agreement with previously reported crystal structures, PPase forms hexamers in solution that are similar to the previously reported X-ray crystal structure. Both KduI and GadA that are responsible for carbohydrate (pectin) metabolism and acid stress responses, respectively, form polydisperse mixtures consisting of different oligomeric states. Overall the SAXS experiments yield additional insights into shape and organization of these metabolic enzymes and further demonstrate the utility of hybrid methods, i.e., solution SAXS combined with X-ray crystallography, bioinformatics and predictive 3D-structural modeling, as tools to enrich structural studies. The results highlight the structural complexity that the protein components of metabolic networks may adopt which cannot be fully captured using individual structural biology techniques. PMID:27227414
Immune network behavior: Oscillations, chaos and stationary states
De Boer, R.J.; Perelson, A.S.; Kevrekidis, I.G.
1994-04-01
The authors report two types of behavior in models of immune networks. The typical behavior of simple models, which involve B cells only, consists of several coexisting steady states. Finite amplitude perturbations may cause the model to switch between different equilibria. The typical behavior of more realistic models, which involve both B cells and antibody, consists of autonomous oscillations and/or chaos. While steady-state behavior leads to easy interpretations in terms of immune memory, oscillatory behavior seems to be in better agreement with experimental data obtained in unimmunized animals. The stability of the steady states, and the structure and interactions of the stable and unstable manifolds of the saddle-type equilibria turn out to be factors influencing the model`s behavior. Whether or not the model is able to attain any form of sustained oscillatory behavior, i.e., limit cycles or chaos, seems to be determined by (global) bifurcations involving the stable and unstable manifolds of the steady states.
Self-organized critical system with no stationary attractor state
NASA Astrophysics Data System (ADS)
Nørrelykke, Simon F.; Bak, Per
2002-03-01
A simple model economy with interacting producers and consumers is introduced. When driven by extremal dynamics, the model self-organizes not to an attractor state, but to an asymptote, on which the economy has a constant rate of deflation, is critical, and exhibits avalanches of activity with power-law distributed sizes. This example demonstrates that self-organized critical behavior occurs in a larger class of systems than so far considered: systems not driven to an attractive fixed point, but, e.g., an asymptote, may also display self-organized criticality.
Quasi-stationary states in nonlocal stochastic growth models with infinitely many absorbing states
NASA Astrophysics Data System (ADS)
Jara, D. A. C.; Alcaraz, F. C.
2017-04-01
We study a two parameter (u, p) extension of the conformally invariant raise and peel model. The model also represents a nonlocal and biased-asymmetric exclusion process with local and nonlocal jumps of excluded volume particles in the lattice. The model exhibits an unusual and interesting critical phase where, in the bulk limit, there are an infinite number of absorbing states. In spite of these absorbing states the system stays, during a time that increases exponentially with the lattice size, in a critical quasi-stationary state. In this critical phase the critical exponents depend only on one of the parameters defining the model (u). The endpoint of this critical phase, where the system changes from an active to an inactive frozen phase, belongs to a distinct universality class. This new behavior, we believe, is due to the appearance of Jordan cells in the Hamiltonian describing the time evolution. The dimensions of these cells increase with the lattice size. In a special case (u = 0) where the model has no adsorptions we are able to calculate analytically the time evolution of some observables. A polynomial time dependence is obtained thanks to the appearance of Jordan cells structures in the Hamiltonian.
Sandin, Patrik; Ögren, Magnus; Gulliksson, Mårten
2016-03-01
We formulate a damped oscillating particle method to solve the stationary nonlinear Schrödinger equation (NLSE). The ground-state solutions are found by a converging damped oscillating evolution equation that can be discretized with symplectic numerical techniques. The method is demonstrated for three different cases: for the single-component NLSE with an attractive self-interaction, for the single-component NLSE with a repulsive self-interaction and a constraint on the angular momentum, and for the two-component NLSE with a constraint on the total angular momentum. We reproduce the so-called yrast curve for the single-component case, described in [A. D. Jackson et al., Europhys. Lett. 95, 30002 (2011)], and produce for the first time an analogous curve for the two-component NLSE. The numerical results are compared with analytic solutions and competing numerical methods. Our method is well suited to handle a large class of equations and can easily be adapted to further constraints and components.
NASA Astrophysics Data System (ADS)
Sandin, Patrik; Ögren, Magnus; Gulliksson, Mârten
2016-03-01
We formulate a damped oscillating particle method to solve the stationary nonlinear Schrödinger equation (NLSE). The ground-state solutions are found by a converging damped oscillating evolution equation that can be discretized with symplectic numerical techniques. The method is demonstrated for three different cases: for the single-component NLSE with an attractive self-interaction, for the single-component NLSE with a repulsive self-interaction and a constraint on the angular momentum, and for the two-component NLSE with a constraint on the total angular momentum. We reproduce the so-called yrast curve for the single-component case, described in [A. D. Jackson et al., Europhys. Lett. 95, 30002 (2011), 10.1209/0295-5075/95/30002], and produce for the first time an analogous curve for the two-component NLSE. The numerical results are compared with analytic solutions and competing numerical methods. Our method is well suited to handle a large class of equations and can easily be adapted to further constraints and components.
Diagnostics of many-particle electronic states: non-stationary currents and residual charge dynamics
NASA Astrophysics Data System (ADS)
Maslova, N. S.; Mantsevich, V. N.; Arseyev, P. I.
2017-01-01
We propose the method for identifying many particle electronic states in the system of coupled quantum dots (impurities) with Coulomb correlations. We demonstrate that different electronic states can be distinguished by the complex analysis of localized charge dynamics and non-stationary characteristics. We show that localized charge time evolution strongly depends on the properties of initial state and analyze different time scales in charge kinetics for initially prepared singlet and triplet states. We reveal the conditions for existence of charge trapping effects governed by the selection rules for electron transitions between the states with different occupation numbers.
Diagnostics of many-particle electronic states: Non-stationary currents and residual charge dynamics
NASA Astrophysics Data System (ADS)
Maslova, N. S.; Mantsevich, V. N.; Arseyev, P. I.
2017-01-01
We propose the method for identifying many particle electronic states in the system of coupled quantum dots (impurities) with Coulomb correlations. We demonstrate that different electronic states can be distinguished by the complex analysis of localized charge dynamics and non-stationary characteristics. We show that localized charge time evolution strongly depends on the properties of initial state and analyze different time scales in charge kinetics for initially prepared singlet and triplet states. We reveal the conditions for existence of charge trapping effects governed by the selection rules for electron transitions between the states with different occupation numbers.
Not Available
1993-01-01
Objective is to understand the surface science underlying liquid chromatographic separations, enabling improvements in design of chromatographic stationary phases. Progress was made both in use of laser spectroscopy to probe chromatographic surfaces and in developing new stationary phases based on self-assembled monolayers.
Jump Markov models and transition state theory: the quasi-stationary distribution approach.
Di Gesù, Giacomo; Lelièvre, Tony; Le Peutrec, Dorian; Nectoux, Boris
2016-12-22
We are interested in the connection between a metastable continuous state space Markov process (satisfying e.g. the Langevin or overdamped Langevin equation) and a jump Markov process in a discrete state space. More precisely, we use the notion of quasi-stationary distribution within a metastable state for the continuous state space Markov process to parametrize the exit event from the state. This approach is useful to analyze and justify methods which use the jump Markov process underlying a metastable dynamics as a support to efficiently sample the state-to-state dynamics (accelerated dynamics techniques). Moreover, it is possible by this approach to quantify the error on the exit event when the parametrization of the jump Markov model is based on the Eyring-Kramers formula. This therefore provides a mathematical framework to justify the use of transition state theory and the Eyring-Kramers formula to build kinetic Monte Carlo or Markov state models.
Lévy flights and nonhomogenous memory effects: Relaxation to a stationary state
NASA Astrophysics Data System (ADS)
Srokowski, Tomasz
2015-07-01
The non-Markovian stochastic dynamics involving Lévy flights and a potential in the form of a harmonic and nonlinear oscillator is discussed. The subordination technique is applied and the memory effects, which are nonhomogeneous, are taken into account by a position-dependent subordinator. In the nonlinear case, the asymptotic stationary states are found. The relaxation pattern to the stationary state is derived for the quadratic potential: the density decays like a linear combination of the Mittag-Leffler functions. It is demonstrated that in the latter case the density distribution satisfies a fractional Fokker-Planck equation. The densities for the nonlinear oscillator reveal a complex picture, qualitatively dependent on the potential strength, and the relaxation pattern is exponential at large time.
Bertini, L; Gabrielli, D; Jona-Lasinio, G; Landim, C
2013-01-11
Nonequilibrium stationary states of thermodynamic systems dissipate a positive amount of energy per unit of time. If we consider transformations of such states that are realized by letting the driving depend on time, the amount of energy dissipated in an unbounded time window then becomes infinite. Following the general proposal by Oono and Paniconi and using results of the macroscopic fluctuation theory, we give a natural definition of a renormalized work performed along any given transformation. We then show that the renormalized work satisfies a Clausius inequality and prove that equality is achieved for very slow transformations, that is, in the quasistatic limit. We finally connect the renormalized work to the quasipotential of the macroscopic fluctuation theory, which gives the probability of fluctuations in the stationary nonequilibrium ensemble.
NASA Technical Reports Server (NTRS)
Mitchell, K. E.; Dutton, J. A.
1981-01-01
The considered investigation is concerned with periodic solutions in the context of a forced, dissipative, barotropic spectral model truncated to three complex coefficients with constant forcing on only the intermediate scale. It is found that determining a periodic solution of this three-coefficient model also reduces to finding the algebraic roots of a real polynomial. In the derivation of this polynomial, a class of hydrodynamic spectral systems is described for which a periodic solution might be similarly specified. The existence of periodic solutions of the three-coefficient model is controlled by the roots of the stability polynomial of the basic stationary solution, which represents the simplest response to the constant forcing. When the forcing exceeds a critical value, the basic solution becomes unstable. Owing to the nature of the roots of the stability polynomial at critical forcing, bifurcation theory guarantees the existence of a periodic solution.
NASA Astrophysics Data System (ADS)
Broutman, Dave; Eckermann, Stephen D.; Knight, Harold; Ma, Jun
2017-01-01
A relatively general stationary phase solution is derived for mountain waves from localized topography. It applies to hydrostatic, nonhydrostatic, or anelastic dispersion relations, to arbitrary localized topography, and to arbitrary smooth vertically varying background temperature and vector wind profiles. A simple method is introduced to compute the ray Jacobian that quantifies the effects of horizontal geometrical spreading in the stationary phase solution. The stationary phase solution is applied to mesospheric mountain waves generated by Auckland Island during the Deep Propagating Gravity Wave Experiment. The results are compared to a Fourier solution. The emphasis is on interpretations involving horizontal geometrical spreading. The results show larger horizontal geometrical spreading for nonhydrostatic waves than for hydrostatic waves in the region directly above the island; the dominant effect of horizontal geometrical spreading in the lower ˜30 km of the atmosphere, compared to the effects of refraction and background density variation; and the enhanced geometrical spreading due to directional wind in the approach to a critical layer in the mesosphere.
Aljhni, Rania; Andre, Claire; Lethier, Lydie; Guillaume, Yves Claude
2015-11-01
A carbon nanotube (CNT) stationary phase was used for the first time to study the β-cyclodextrin (β-CD) solute complexation mechanism using high performance liquid chromatography (HPLC). For this, the β-CD was added at various concentrations in the mobile phase and the effect of column temperature was studied on both the retention of a series of aniline and benzoic acid derivatives with the CNT stationary phase and their complexation mechanism with β-CD. A decrease in the solute retention factor was observed for all the studied molecules without change in the retention order. The apparent formation constant KF of the inclusion complex β-CD/solute was determined at various temperatures. Our results showed that the interaction of β-CD with both the mobile phase and the stationary phase interfered in the complex formation. The enthalpy and entropy of the complex formation (ΔHF and ΔSF) between the solute molecule and CD were determined using a thermodynamic approach. Negative enthalpies and entropies indicated that the inclusion process of the studied molecule in the CD cavity was enthalpically driven and that the hydrogen bonds between carboxylic or aniline groups and the functional groups on the β-CD rim play an important role in the complex formation. Copyright © 2015 Elsevier B.V. All rights reserved.
The stationary resonance fluorescence of a two-level atom in a cat-state field
NASA Astrophysics Data System (ADS)
Tomilin, V. A.; Il'ichov, L. V.
2016-09-01
We investigate the resonance fluorescence of a two-level atom placed in non-classical field which is a superposition of Glauber coherent states. The source of this superposition known under the common name of 'Schrödinger cat'-states is explicitly incorporated into the model. This let us to explore the stationary regime. In the strong (multiphoton) field limit the steady-state of the atom+photons system is found. We evaluated the spectrum of the resonance fluorescence. It appears to be one-component in contrast to the case with the classical external field.
The quasilinear theory in the approach of long-range systems to quasi-stationary states
NASA Astrophysics Data System (ADS)
Campa, Alessandro; Chavanis, Pierre-Henri
2017-05-01
We develop a quasilinear theory of the Vlasov equation in order to describe the approach of systems with long-range interactions to quasi-stationary states. The quasilinear theory is based on the assumption that, although the initial distribution is not Vlasov stable, nevertheless its evolution towards a Vlasov stable stationary state is such that it is always only slightly inhomogeneous. We derive a diffusion equation governing the evolution of the velocity distribution of the system towards a steady state. This steady state is expected to correspond to the space-averaged quasi-stationary distribution function reached by the Vlasov equation as a result of a collisionless relaxation. We compare the prediction of the quasilinear theory to direct numerical simulations of the Hamiltonian mean field model, starting from an unstable spatially homogeneous distribution, either Gaussian or semi-elliptical. In the Gaussian case, we find that the quasilinear theory works reasonably well for weakly unstable initial conditions (i.e. close to the critical energy ε_c=3/4=0.75 ) and that it is able to predict the energy ε_t≃ 0.735 marking the effective out-of-equilibrium phase transition between unmagnetized and magnetized quasi-stationary states found in the numerical simulations. Similarly, the quasilinear theory works well for energies close to the instability threshold of the semi-elliptical case ε^*c =5/8=0.625 , and it predicts an effective out-of-equilibrium transition at εt≃ 0.619 . In both situations, the quasilinear theory works less well at energies lower than the out-of-equilibrium transition, the disagreement with the numerical simulations increasing with decreasing energy. In that case, we observe, in agreement with our previous numerical study (Campa and Chavanis 2013 Eur. Phys. J. B 86 170), that the quasi-stationary states are remarkably well fitted by polytropic distributions (Tsallis distributions) with index n = 2 (Gaussian case) or n
Bruckman, W.
1986-11-15
The inverse scattering method of Belinsky and Zakharov is used to investigate axially symmetric stationary vacuum soliton solutions in the five-dimensional representation of the Brans-Dicke-Jordan theory of gravitation, where the scalar field of the theory is an element of a five-dimensional metric. The resulting equations for the spacetime metric are similar to those of solitons in general relativity, while the scalar field generated is the product of a simple function of the coordinates and an already known scalar field solution. A family of solutions is considered that reduce, in the absence of rotation, to the five-dimensional form of a well-known Weyl-Levi Civita axially symmetric static vacuum solution. With a suitable choice of parameters, this static limit becomes equivalent to the spherically symmetric solution of the Brans-Dicke theory. An exact metric, in which the Kerr-scalar McIntosh solution is a special case, is given explicitly.
2002-06-24
UNCLASSIFIED Defense Technical Information Center Compilation Part Notice ADP012554 TITLE: Non-Collisional Kinetic Model for Non-Neutral Plasmas in a...following report: TITLE: Non-Neutral Plasma Physics 4. Workshop on Non-Neutral Plasmas [2001] Held in San Diego, California on 30 July-2 August 2001...Kinetic Model for Non-Neutral Plasmas in a Penning Trap: General Properties and Stationary Solutions Gianni G.M. Coppa, Paolo Ricci Istituto
Stationary bound-state scalar configurations supported by rapidly-spinning exotic compact objects
NASA Astrophysics Data System (ADS)
Hod, Shahar
2017-07-01
Some quantum-gravity theories suggest that the absorbing horizon of a classical black hole should be replaced by a reflective surface which is located a microscopic distance above the would-be classical horizon. Instead of an absorbing black hole, the resulting horizonless spacetime describes a reflective exotic compact object. Motivated by this intriguing prediction, in the present paper we explore the physical properties of exotic compact objects which are linearly coupled to stationary bound-state massive scalar field configurations. In particular, solving the Klein-Gordon wave equation for a stationary scalar field of proper mass μ and spheroidal harmonic indices (l , m) in the background of a rapidly-rotating exotic compact object of mass M and angular momentum J = Ma, we derive a compact analytical formula for the discrete radii {rc (μ , l , m , M , a ; n) } of the exotic compact objects which can support the stationary bound-state massive scalar field configurations. We confirm our analytical results by direct numerical computations.
NASA Astrophysics Data System (ADS)
Korennoy, Ya. A.; Man'ko, V. I.
2017-04-01
Symplectic and optical joint probability representations of quantum mechanics are considered, in which the functions describing the states are the probability distributions with all random arguments (except the argument of time). The general formalism of quantizers and dequantizers determining the star product quantization scheme in these representations is given. Taking the Gaussian functions as the distributions of the tomographic parameters the correspondence rules for most interesting physical operators are found and the expressions of the dual symbols of operators in the form of singular and regular generalized functions are derived. Evolution equations and stationary states equations for symplectic and optical joint probability distributions are obtained.
NASA Astrophysics Data System (ADS)
Korennoy, Ya. A.; Man'ko, V. I.
2016-12-01
Symplectic and optical joint probability representations of quantum mechanics are considered, in which the functions describing the states are the probability distributions with all random arguments (except the argument of time). The general formalism of quantizers and dequantizers determining the star product quantization scheme in these representations is given. Taking the Gaussian functions as the distributions of the tomographic parameters the correspondence rules for most interesting physical operators are found and the expressions of the dual symbols of operators in the form of singular and regular generalized functions are derived. Evolution equations and stationary states equations for symplectic and optical joint probability distributions are obtained.
NASA Astrophysics Data System (ADS)
Ribeiro, M. S.; Nobre, F. D.; Curado, E. M. F.
2012-12-01
By comparing numerical and analytical results, it is shown that a system of interacting particles under overdamped motion is very well described by a nonlinear Fokker-Planck equation, which can be associated with nonextensive statistical mechanics. The particle-particle interactions considered are repulsive, motivated by three different physical situations: (i) modified Bessel function, commonly used in vortex-vortex interactions, relevant for the flux-front penetration in disordered type-II superconductors; (ii) Yukawa-like forces, useful for charged particles in plasma, or colloidal suspensions; (iii) derived from a Gaussian potential, common in complex fluids, like polymer chains dispersed in a solvent. Moreover, the system is subjected to a general confining potential, φ( x) = ( α| x| z )/ z ( α > 0 , z > 1), so that a stationary state is reached after a sufficiently long time. Recent numerical and analytical investigations, considering interactions of type (i) and a harmonic confining potential ( z = 2), have shown strong evidence that a q-Gaussian distribution, P( x,t), with q = 0, describes appropriately the particle positions during their time evolution, as well as in their stationary state. Herein we reinforce further the connection with nonextensive statistical mechanics, by presenting numerical evidence showing that: (a) in the case z = 2, different particle-particle interactions only modify the diffusion parameter D of the nonlinear Fokker-Planck equation; (b) for z ≠ 2, all cases investigated fit well the analytical stationary solution P st( x), given in terms of a q-exponential (with the same index q = 0) of the general external potential φ( x). In this later case, we propose an approximate time-dependent P( x,t) (not known analytically for z ≠ 2), which is in very good agreement with the simulations for a large range of times, including the approach to the stationary state. The present work suggests that a wide variety of physical phenomena
Stationary distribution and periodic solutions for stochastic Holling-Leslie predator-prey systems
NASA Astrophysics Data System (ADS)
Jiang, Daqing; Zuo, Wenjie; Hayat, Tasawar; Alsaedi, Ahmed
2016-10-01
The stochastic autonomous and periodic predator-prey systems with Holling and Leslie type functional response are investigated. For the autonomous system, we prove that there exists a unique stationary distribution, which is ergodic by constructing a suitable Lyapunov function under relatively small white noise. The result shows that, stationary distribution doesn't rely on the existence and the stability of the positive equilibrium in the undisturbed system. Furthermore, for the corresponding non-autonomous system, we show that there exists a positive periodic Markov process under relatively weaker condition. Finally, numerical simulations illustrate our theoretical results.
Fullerene triplet states in solution
NASA Astrophysics Data System (ADS)
Ausman, Kevin Douglas
Triplet state pre-equilibration by reversible energy transfer has been observed by transient-absorption spectroscopy in mixed toluene solutions of C70 and C60 and of C70 and C60(CH 3)2. The equilibrium constants governing the asymptotic partitioning of triplet energy in these mixtures were determined as a function of temperature. The enthalpies of these excited states were found from van't Hoff plots of the equilibrium constant data to be -0.1 +/- 0.2 and -3.4 +/- 0.3 kJ mol-1 for C60 and C60 (CH3)2 respectively relative to a C70 triplet energy exchange partner. The corresponding relative entropies are 5.8 +/- 0.5 and -4.0 +/- 1.0 kJ mol-1 K-1 respectively. Transient spectra from high temperature C70/C60(CH3)2 mixed samples revealed evidence of a third, unidentified transient absorber that exhibited different kinetics from the pre-equilibrated triplet pool. Triplet state transient difference spectra and intrinsic decay kinetics were measured and compared for C60 and several derivatives of C 60. These derivatives were C60H2, C60(CH 3)2, ortho-xylyl-C60, N,N'-dimethyl-1,2-ethylenediamine- C 60, C60C(COOCH2CH3)2, and C60O. The spectral locations of the main triplet-triplet absorption peak for these compounds correlates linearly with the observed intrinsic intersystem crossing rate constant. The triplet state persistence of C60 was measured in toluene solution as a function of both ground state concentration and solution temperature. The unimolecular intersystem crossing deactivation channel shows very little thermal activation, whereas the observed bimolecular self-quenching decay channel is found to be highly activated. At room temperature, the deduced exponential lifetime of the solvent-caged encounter complex between triplet and ground state molecules is three orders of magnitude shorter than that of the isolated monomer triplet state. This suggests that the self-quenching process is not a simple perturbation of an isolated molecule's intersystem crossing, but
NASA Astrophysics Data System (ADS)
Wang, Deng-Shan; Han, Wei; Shi, Yuren; Li, Zaidong; Liu, Wu-Ming
2016-07-01
The spin-1 Bose-Einstein condensates trapped in a standing light wave can be described by three coupled Gross-Pitaevskii equations with a periodic potential. In this paper, nine families of stationary solutions without phase structures in the form of Jacobi elliptic functions are proposed, and their stabilities are analyzed by both linear stability analysis and dynamical evolutions. Taking the ferromagnetic 87Rb atoms and antiferromagnetic (polar) 23Na atoms as examples, we investigate the stability regions of the nine stationary solutions, which are given in term of elliptic modulus k. It is shown that for the same stationary solution the stability regions of condensates with antiferromagnetic (polar) spin-dependent interactions are larger than that of the condensates with ferromagnetic ones. The dn-dn-dn stationary solution is the most stable solution among the nine families of stationary solutions. Moreover, in the same standing light wave, the spin-1 Bose-Einstein condensates are more stable than the scalar Bose-Einstein condensate.
Transition state structures in solution
Bertran, J.; Lluch, J. M.; Gonzalez-Lafont, A.; Dillet, V.; Perez, V.
1995-04-05
In the present paper the location of transition state structures for reactions in solution has been studied. Continuum model calculations have been carried out on the Friedel-Crafts alkylation reaction and a proton transfer through a water molecule between two oxygen atoms in formic acid. In this model the separation between the chemical system and the solvent has been introduced. On the other hand, the discrete Monte Carlo methodology has also been used to simulate the solvent effect on dissociative electron transfer processes. In this model, the hypothesis of separability is not assumed. Finally, the validity of both approaches is discussed.
Transition state structures in solution
NASA Astrophysics Data System (ADS)
Bertrán, J.; Lluch, J. M.; Gonzàlez-Lafont, A.; Dillet, V.; Pérez, V.
1995-04-01
In the present paper the location of transition state structures for reactions in solution has been studied. Continuum model calculations have been carried out on the Friedel-Crafts alkylation reaction and a proton transfer through a water molecule between two oxygen atoms in formic acid. In this model the separation between the chemical system and the solvent has been introduced. On the other hand, the discrete Monte Carlo methodology has also been used to simulate the solvent effect on dissociative electron transfer processes. In this model, the hypothesis of separability is not assumed. Finally, the validity of both approaches is discussed.
Heat conduction and the nonequilibrium stationary states of stochastic energy exchange processes
NASA Astrophysics Data System (ADS)
Gilbert, Thomas
2017-08-01
I revisit the exactly solvable Kipnis-Marchioro-Presutti model of heat conduction (Kipnis et al 1982 J. Stat. Phys. 27 65) and describe, for one-dimensional systems of arbitrary sizes whose ends are in contact with thermal baths at different temperatures, a systematic characterisation of their non-equilibrium stationary states. These arguments avoid resorting to the analysis of a dual process and yield a straightforward derivation of Fourier’s law, as well as higher-order static correlations, such as the covariant matrix. The transposition of these results to families of gradient models generalising the KMP model is established and specific cases are examined.
The Electron Relaxation to Stationary States in Collision Dominated Plasmas in Molecular Gases
NASA Astrophysics Data System (ADS)
Capitelli, M.; Gorse, C.; Wilhelm, J.; Winkler, R.
The temporal collision dominated relaxation of electrons to new stationary states, starting from initial stationary states and due to jump-like changes of the electric field, was studied in the plasmas of the molecular gases N2 and CO. Numerical solving of the time dependent Boltzmann equation for the electrons yields the temporal evolution of their energy distribution function and of resulting macroscopic quantities. The varying relaxation due to different values of the field strength in the final stationary state has been investigated considering the molecules of the plasma only as vibrationally non-excited and, in another case, including the additional impact of collisions with vibrationally excited molecules. The results obtained are discussed and, in particular, the relaxation times found for the transitions to the new stationary states are analysed on the basis of the energy transfer effectiveness by the collision processes. An approximative microphysical basis for the understanding of the main features of the relaxation in such complex molecular gas plasmas could be obtained.Translated AbstractDie Relaxation der Elektronen zu stationären Zuständen in stoßbestimmten Plasmen in molekularen GasenAusgehend von stationären Anfangszuständen und verursacht durch sprungartige Veränderung des elektrischen Feldes wurde die zeitliche stoßbestimmte Relaxation von Elektronen zu neuen stationären Zuständen in Plasmen der molekularen Gase N2 und CO2 untersucht. Die numerische Lösung der zeitabhängigen Boltzmann-Gleichung für die Elektronen liefert die zeitliche Entwicklung ihrer Energieverteilungsfunktion und hieraus folgender makroskopischer Größen. Das verschiedenartige Relaxationsverhalten infolge unterschiedlicher Werte der Feldstärke im stationären Endzustand wurde untersucht, indem die Moleküle des Plasmas einmal nur als nicht schwingungsangeregt betrachtet werden und zum anderen der zusätzliche Einfluß von Stößen mit schwingungsangeregten Molek
NASA Astrophysics Data System (ADS)
de Oliveira, Mário J.
2017-08-01
We analyze a microscopic model for heat transport consisting of two interacting harmonic chains in contact with reservoirs at different temperatures. The chains are mechanically uncoupled but exchange energy randomly through a stochastic noise that affects nearest neighbor particles belonging to distinct chains. We show numerically that the deviations of the correlations from their equilibrium values are proportional to the inverse of the system size and that they decay exponentially with distance. From these results we show Fourier’s law and that the nonequilibrium stationary state is a multivariate Gaussian distribution, for large enough system sizes.
Stability and hierarchy of quasi-stationary states: financial markets as an example
NASA Astrophysics Data System (ADS)
Stepanov, Yuriy; Rinn, Philip; Guhr, Thomas; Peinke, Joachim; Schäfer, Rudi
2015-08-01
We combine geometric data analysis and stochastic modeling to describe the collective dynamics of complex systems. As an example we apply this approach to financial data and focus on the non-stationarity of the market correlation structure. We identify the dominating variable and extract its explicit stochastic model. This allows us to establish a connection between its time evolution and known historical events on the market. We discuss the dynamics, the stability and the hierarchy of the recently proposed quasi-stationary market states.
On metastability and Markov state models for non-stationary molecular dynamics.
Koltai, Péter; Ciccotti, Giovanni; Schütte, Christof
2016-11-07
Unlike for systems in equilibrium, a straightforward definition of a metastable set in the non-stationary, non-equilibrium case may only be given case-by-case-and therefore it is not directly useful any more, in particular in cases where the slowest relaxation time scales are comparable to the time scales at which the external field driving the system varies. We generalize the concept of metastability by relying on the theory of coherent sets. A pair of sets A and B is called coherent with respect to the time interval [t1, t2] if (a) most of the trajectories starting in A at t1 end up in B at t2 and (b) most of the trajectories arriving in B at t2 actually started from A at t1. Based on this definition, we can show how to compute coherent sets and then derive finite-time non-stationary Markov state models. We illustrate this concept and its main differences to equilibrium Markov state modeling on simple, one-dimensional examples.
On metastability and Markov state models for non-stationary molecular dynamics
NASA Astrophysics Data System (ADS)
Koltai, Péter; Ciccotti, Giovanni; Schütte, Christof
2016-11-01
Unlike for systems in equilibrium, a straightforward definition of a metastable set in the non-stationary, non-equilibrium case may only be given case-by-case—and therefore it is not directly useful any more, in particular in cases where the slowest relaxation time scales are comparable to the time scales at which the external field driving the system varies. We generalize the concept of metastability by relying on the theory of coherent sets. A pair of sets A and B is called coherent with respect to the time interval [t1, t2] if (a) most of the trajectories starting in A at t1 end up in B at t2 and (b) most of the trajectories arriving in B at t2 actually started from A at t1. Based on this definition, we can show how to compute coherent sets and then derive finite-time non-stationary Markov state models. We illustrate this concept and its main differences to equilibrium Markov state modeling on simple, one-dimensional examples.
NASA Astrophysics Data System (ADS)
Carter, Brandon
2010-03-01
This is a reprinting of Part 2 of Brandon Carter’s lectures given at the 1972 Les Houches school on black holes, first published in a book of proceedings of that school in 1973, in which the author presents a general theory of stationary black holes. The paper has been selected by the Editors of General Relativity and Gravitation for re-publication in the Golden Oldies series of the journal. Several errors of the original text were corrected for this reprinting by the author. The reprinted article is accompanied by an editorial note written by Marek Abramowicz.
Stationary State After a Quench to the Lieb-Liniger from Rotating BECs
NASA Astrophysics Data System (ADS)
Bucciantini, Leda
2016-08-01
We study long-time dynamics of a bosonic system after suddenly switching on repulsive delta-like interactions. As initial states, we consider two experimentally relevant configurations: a rotating BEC and two counter-propagating BECs with opposite momentum, both on a ring. In the first case, the rapidity distribution function for the stationary state is derived analytically and it is given by the distribution obtained for the same quench starting from a BEC, shifted by the momentum of each boson. In the second case, the rapidity distribution function is obtained numerically for generic values of repulsive interaction and initial momentum. The significant differences for the case of large versus small quenches are discussed.
Stationary distribution of self-organized states and biological information generation
NASA Astrophysics Data System (ADS)
Woo, Hyung Jun
2013-11-01
Self-organization, where spontaneous orderings occur under driven conditions, is one of the hallmarks of biological systems. We consider a statistical mechanical treatment of the biased distribution of such organized states, which become favored as a result of their catalytic activity under chemical driving forces. A generalization of the equilibrium canonical distribution describes the stationary state, which can be used to model shifts in conformational ensembles sampled by an enzyme in working conditions. The basic idea is applied to the process of biological information generation from random sequences of heteropolymers, where unfavorable Shannon entropy is overcome by the catalytic activities of selected genes. The ordering process is demonstrated with the genetic distance to a genotype with high catalytic activity as an order parameter. The resulting free energy can have multiple minima, corresponding to disordered and organized phases with first-order transitions between them.
Stationary spectroscopy of biotissues in vivo: Fluorescent studies of some pathological states
NASA Astrophysics Data System (ADS)
Giraev, K. M.; Ashurbekov, N. A.; Medzhidov, R. T.
2003-11-01
The stationary spectra of autofluorescence, along with the reflection coefficient at the wavelength of excitation, are measured in vivo for some stomach tissues in the case of different pathological states (dysplasia, superficial gastritis, and cancer) using a nitrogen laser as the source of excitation (λrad=337.1 nm). The fluorescence spectra obtained are decomposed into Gaussian-Lorentzian components. It is found that, in development of dysplasia and tumor processes, at least seven groups of fluorophores can be distinguished that form the entire emission spectrum. The ratio between the fluorescence intensities of flavins and NAD(P)H is determined and the degree of respiratory activity of cells estimated for the states considered. The quantum yields of fluorescence of the biotissues under investigation are estimated.
Barra, Felipe; Gaspard, Pierre; Gilbert, Thomas
2009-08-01
Galton boards are models of deterministic diffusion in a uniform external field, akin to driven periodic Lorentz gases, here considered in the absence of dissipation mechanism. Assuming a cylindrical geometry with axis along the direction of the external field, the two-dimensional board becomes a model for one-dimensional mass transport along the direction of the external field. This is a purely diffusive process which admits fractal nonequilibrium stationary states under flux boundary conditions. Analytical results are obtained for the statistics of multibaker maps modeling such a nonuniform diffusion process. A correspondence is established between the local phase-space statistics and their macroscopic counterparts. The fractality of the invariant state is shown to be responsible for the positiveness of the entropy production rate.
Kinetic insights over a PEMFC operating on stationary and oscillatory states.
Mota, Andressa; Gonzalez, Ernesto R; Eiswirth, Markus
2011-12-01
Kinetic investigations in the oscillatory state have been carried out in order to shed light on the interplay between the complex kinetics exhibited by a proton exchange membrane fuel cell fed with poisoned H(2) (108 ppm of CO) and the other in serie process. The apparent activation energy (E(a)) in the stationary state was investigated in order to clarify the E(a) observed in the oscillatory state. The apparent activation energy in the stationary state, under potentiostatic control, rendered (a) E(a) ≈ 50-60 kJ mol(-1) over 0.8 V < E < 0.6 V and (b) E(a) ≈ 10 kJ mol(-1) at E = 0.3 V. The former is related to the H(2) adsorption in the vacancies of the surface poisoned by CO and the latter is correlated to the process of proton conductivity in the membrane. The dependence of the period-one oscillations on the temperature yielded a genuine Arrhenius dependence with two E(a) values: (a) E(a) around 70 kJ mol(-1), at high temperatures, and (b) E(a) around 10-15 kJ mol(-1), at lower temperatures. The latter E(a) indicates the presence of protonic mass transport coupled to the essential oscillatory mechanism. These insights point in the right direction to predict spatial couplings between anode and cathode as having the highest strength as well as to speculate the most likely candidates to promote spatial inhomogeneities. © 2011 American Chemical Society
Corticospinal beta-range coherence is highly dependent on the pre-stationary motor state.
Omlor, Wolfgang; Patino, Luis; Mendez-Balbuena, Ignacio; Schulte-Mönting, Jürgen; Kristeva, Rumyana
2011-06-01
During steady muscle contractions, the human sensorimotor cortex generates oscillations in the beta-frequency range (15-30 Hz) that are coherent with the activity of contralateral spinal motoneurons. This corticospinal coherence is thought to favor stationary motor states, but its mode of operation remains elusive. We hypothesized that corticospinal beta-range coherence depends on the sensorimotor processing state before a steady force task and may thus increase after sensorimotor tuning to dynamic force generation. To test this hypothesis we instructed 16 human subjects to compensate static force after rest as well as after compensating predictable or unpredictable dynamic force with their right index finger. We calculated EEG-EMG coherence, cortical motor spectral power, and the motor performance during the force conditions. Corticospinal beta-coherence during stationary force was excessively elevated if the steady-state contraction was preceded by predictable dynamic force instead of rest, and was highest after unpredictable dynamic force. The beta-power decreased from rest to predictable dynamic force, and was lowest during unpredictable dynamic force. The increase in corticospinal beta-coherence showed a significant negative correlation with the preceding change in beta-power. The tuning to dynamic force did not entail an inferior motor performance during static force. The results imply a correlation between corticospinal beta-range coherence and the computational load of the preceding isometric motor engagement. We suggest beta-range coherence provides a functional corticospinal gateway for steady force-related processing that can override cortical states tuned to dynamic force. The modulation of corticospinal beta-range coherence might thus ensure comparable precision of static force in various motor contexts.
Finite current stationary states of random walks on one-dimensional lattices with aperiodic disorder
NASA Astrophysics Data System (ADS)
Miki, Hiroshi
2016-11-01
Stationary states of random walks with finite induced drift velocity on one-dimensional lattices with aperiodic disorder are investigated by scaling analysis. Three aperiodic sequences, the Thue-Morse (TM), the paperfolding (PF), and the Rudin-Shapiro (RS) sequences, are used to construct the aperiodic disorder. These are binary sequences, composed of two symbols A and B, and the ratio of the number of As to that of Bs converges to unity in the infinite sequence length limit, but their effects on diffusional behavior are different. For the TM model, the stationary distribution is extended, as in the case without current, and the drift velocity is independent of the system size. For the PF model and the RS model, as the system size increases, the hierarchical and fractal structure and the localized structure, respectively, are broken by a finite current and changed to an extended distribution if the system size becomes larger than a certain threshold value. Correspondingly, the drift velocity is saturated in a large system while in a small system it decreases as the system size increases.
Schnell, Santiago
2014-01-01
The Michaelis-Menten equation is generally used to estimate the kinetic parameters, V and K(M), when the steady-state assumption is valid. Following a brief overview of the derivation of the Michaelis-Menten equation for the single-enzyme, single-substrate reaction, a critical review of the criteria for validity of the steady-state assumption is presented. The application of the steady-state assumption makes the implicit assumption that there is an initial transient during which the substrate concentration remains approximately constant, equal to the initial substrate concentration, while the enzyme-substrate complex concentration builds up. This implicit assumption is known as the reactant stationary assumption. This review presents evidence showing that the reactant stationary assumption is distinct from and independent of the steady-state assumption. Contrary to the widely believed notion that the Michaelis-Menten equation can always be applied under the steady-state assumption, the reactant stationary assumption is truly the necessary condition for validity of the Michaelis-Menten equation to estimate kinetic parameters. Therefore, the application of the Michaelis-Menten equation only leads to accurate estimation of kinetic parameters when it is used under experimental conditions meeting the reactant stationary assumption. The criterion for validity of the reactant stationary assumption does not require the restrictive condition of choosing a substrate concentration that is much higher than the enzyme concentration in initial rate experiments.
Mikhaltsevitch, V T; Rudakov, T N
2004-01-01
Experimental and theoretical study of quasistationary and stationary states that are established in the quadrupolar spin system subjected to the steady-state sequences which consist of a chain of identical pulses and can be preceded by a preparatory pulse. We have obtained theoretical expressions for the magnetisation of the spin system that take into account off-resonance conditions during the effect of the pulses. Frequency dependencies of the NQR signal in the quasistationary and stationary states are shown for C3H6N6O6 (RDX) and NaNO2, and compared with theoretical results.
NASA Astrophysics Data System (ADS)
Dunne, J. F.; Ghanbari, M.
1997-10-01
The accuracy of two well-established numerical methods is demonstrated, and the importance of “bandwidth” examined, for computationally efficient Markov based extreme-value predictions associated with finite duration stationary sample paths of a non-linear oscillator driven by Gaussian white noise. By making the Poisson assumption of independent upcrossings, extreme exceedance probabilities are predicted via the mean threshold crossing rate, using numerical solutions of the stationary Fokker-Planck (FPK) equation. With bandwidth initially ignored, predicted exceedances using the Weighted Residual methods of Bhandari and Sherrer, Soize and Kunert, and the Finite Element method of Langley, are compared with nominally “exact” predictions for a heavily damped Duffing-type model obtained by using an explicit FPK solution—the FE method being established as superior. Predictions via FE solutions are then compared with very long Monte Carlo simulations, in which bandwidth effects are included. Two lightly damped non-linear oscillator models are examined, both with cubic stiffness, but different damping mechanisms—one model again being of simple Duffing-type with linear damping, the other being appropriate to single co-ordinate random vibration of a clamped-clamped beam, with wholly non-linear damping. The realistic damping parameter values assigned to the beam model are statistically equivalent to the linear damping level chosen for the simple model, at just above 1%. At this overall damping level, results clearly demonstrate that, for the probability levels and durations considered, bandwidth is only important for the linearly damped model—for the beam model with non-linear damping, bandwidth can be ignored, allowing accurate extreme exceedance predictions by using only the stationary FPK equation. The paper also demonstrates that the “limiting decay rate of the first-passage probability”—advocated by Crandall, Roberts and others, as a criterion for
Equilibrium and stationary nonequilibrium states in a chain of colliding harmonic oscillators
Sano
2000-02-01
Equilibrium and nonequilibrium properties of a chain of colliding harmonic oscillators (ding-dong model) are investigated. Our chain is modeled as harmonically bounded particles that can only interact with neighboring particles by hard-core interaction. Between the collisions, particles are just independent harmonic oscillators. We are especially interested in the stationary nonequilibrium state of the ding-dong model coupled with two stochastic heat reservoirs (not thermostated) at the ends, whose temperature is different. We check the Gallavotti-Cohen fluctuation theorem [G. Gallavoti and E. G. D. Cohen, Phys. Rev. Lett. 74, 2694 (1995)] and also the Evans-Searles identity [D. Evans and D. Searles, Phys. Rev. E. 50, 1994 (1994)] numerically. It is verified that the former theorem is satisfied for this system, although the system is not a thermostated system.
Boundary integral method for stationary states of two-dimensional quantum systems
Kosztin, I.; Schulten, K.
1997-04-01
The boundary integral method for calculating the stationary states of a quantum particle in nano-devices and quantum billiards is presented in detail at an elementary level. According to the method, wave functions inside the domain of the device or billiard are expressed in terms of line integrals of the wavefunction and its normal derivative along the domain`s boundary; the respective energy eigenvalues are obtained as the roots of Fredholm determinants. Numerical implementations of the method are described and applied to determine the energy level statistics of billiards with circular and stadium shapes and demonstrate the quantum mechanical characteristics of chaotic motion. The treatment of other examples as well as the advantages and limitations of the boundary integral method are discussed.
Cuevas, Carlos; Martinez, Raquel; Berjon, Daniel; Garcia, Narciso
2017-03-01
There is a huge proliferation of surveillance systems that require strategies for detecting different kinds of stationary foreground objects (e.g., unattended packages or illegally parked vehicles). As these strategies must be able to detect foreground objects remaining static in crowd scenarios, regardless of how long they have not been moving, several algorithms for detecting different kinds of such foreground objects have been developed over the last decades. This paper presents an efficient and high-quality strategy to detect stationary foreground objects, which is able to detect not only completely static objects but also partially static ones. Three parallel nonparametric detectors with different absorption rates are used to detect currently moving foreground objects, short-term stationary foreground objects, and long-term stationary foreground objects. The results of the detectors are fed into a novel finite state machine that classifies the pixels among background, moving foreground objects, stationary foreground objects, occluded stationary foreground objects, and uncovered background. Results show that the proposed detection strategy is not only able to achieve high quality in several challenging situations but it also improves upon previous strategies.
An integrodifferential model for phase transitions: stationary solutions in higher dimensions
NASA Astrophysics Data System (ADS)
Cortazar, Carmen; Elgueta, Manuel; Rossi, Julio D.; Wolanski, Noemi
2008-01-01
We present a model for nonlocal diffusion with Neumann boundary conditions in a bounded smooth domain prescribing the flux through the boundary. We study the limit of this family of nonlocal diffusion operators when a rescaling parameter related to the kernel of the nonlocal operator goes to zero. We prove that the solutions of this family of problems converge to a solution of the heat equation with Neumann boundary conditions.
NASA Technical Reports Server (NTRS)
Morozov, S. K.; Krasitskiy, O. P.
1978-01-01
A computational scheme and a standard program is proposed for solving systems of nonstationary spatially one-dimensional nonlinear differential equations using Newton's method. The proposed scheme is universal in its applicability and its reduces to a minimum the work of programming. The program is written in the FORTRAN language and can be used without change on electronic computers of type YeS and BESM-6. The standard program described permits the identification of nonstationary (or stationary) solutions to systems of spatially one-dimensional nonlinear (or linear) partial differential equations. The proposed method may be used to solve a series of geophysical problems which take chemical reactions, diffusion, and heat conductivity into account, to evaluate nonstationary thermal fields in two-dimensional structures when in one of the geometrical directions it can take a small number of discrete levels, and to solve problems in nonstationary gas dynamics.
Stochastic analysis of non-stationary subsurface solute transport, 2. Conditional moments
NASA Astrophysics Data System (ADS)
Graham, Wendy; McLaughlin, Dennis
1989-11-01
Stochastic analyses of subsurface transport indicate that the concentration distributions of individual solute plumes may deviate significantly from those predicted by unconditional ensemble statistics, particularly in near-source regions. This paper presents a method for developing improved concentration predictions which are tailored to site-specific conditions. The improved predictions are obtained by conditioning ensemble moments on field observations of log hydraulic conductivity, head, and solute concentration. The conditional moments are obtained from a distributed parameter Kaiman filter which is recursively linearized about the most recent estimates of solute concentration and velocity. The conditioning procedure is illustrated for two synthetic random solute plumes. Reasonably good estimates of the solute concentration distributions are obtained by conditioning the ensemble moments on a small number of measurements located in regions of high concentration uncertainty. The sampling networks adapt to the unique characteristics of each plume as they evolve over time. The example indicates that it is important to capture the dominant trends of the velocity field at as early a time as possible. As more measurements become available, advection accounts for a greater portion of small-scale velocity variability, and the magnitude of the macrodispersion term diminishes. This is reflected in the behavior of the conditional ensemble moments.
NASA Astrophysics Data System (ADS)
Sourie, Aurélien; Oertel, Micaela; Novak, Jérôme
2016-04-01
We present a numerical model for uniformly rotating superfluid neutron stars in a fully general relativistic framework with, for the first time, realistic microphysics including entrainment. We compute stationary and axisymmetric configurations of neutron stars composed of two fluids, namely superfluid neutrons and charged particles (protons and electrons), rotating with different rates around a common axis. Both fluids are coupled by entrainment, a nondissipative interaction which in the case of a nonvanishing relative velocity between the fluids causes the fluid momenta to be not aligned with the respective fluid velocities. We extend the formalism put forth by Comer and Joynt in order to calculate the equation of state (EOS) and entrainment parameters for an arbitrary relative velocity as far as superfluidity is maintained. The resulting entrainment matrix fulfills all necessary sum rules, and in the limit of small relative velocity our results agree with Fermi liquid theory ones derived to lowest order in the velocity. This formalism is applied to two new nuclear equations of state which are implemented in the numerical model, which enables us to obtain precise equilibrium configurations. The resulting density profiles and moments of inertia are discussed employing both EOSs, showing the impact of entrainment and the dependence on the EOS.
Lantz, Andrew W; Pino, Verónica; Anderson, Jared L; Armstrong, Daniel W
2006-05-19
The use of micelles in ionic liquid based gas-chromatography stationary phases was evaluated using equations derived for a "three-phase" model. This model allows the determination of all three partition coefficients involved in the system, and elucidates the micellar contribution to retention and selectivity. Four types of micellar-ionic liquid columns were examined in this study: 1-butyl-3-methylimidazolium chloride with sodium dodecylsulfate or dioctyl sulfosuccinate, and 1-butyl-3-methylimidazolium hexafluorophosphate with polyoxyethylene-100-stearyl ether or polyoxyethylene-23-lauryl ether. The partition coefficients were measured for a wide range of probe molecules capable of a variety of types and magnitudes of interactions. In general, most probe molecules preferentially partitioned to the micellar pseudophase over the bulk ionic liquid component of the stationary phase. Therefore, addition of surfactant to the stationary phase usually resulted in greater solute retention. It is also shown that the selectivity of the stationary phase is significantly altered by the presence of micelles, either by enhancing or lessening the separation. The effects of surfactant on the interaction parameters of the stationary phase are determined using the Abraham solvation parameter model. The addition of sodium dodecylsulfate and dioctyl sulfosuccinate to 1-butyl-3-methylimidazolium chloride stationary phases generally increased the phase's hydrogen bond basicity and increased the level of dispersion interaction. Polyoxyethylene-100-stearyl ether and polyoxyethylene-23-lauryl ether surfactants, however, enhanced the pi-pi/n-pi, polarizability/dipolarity, and hydrogen bond basicity interactions of 1-butyl-3-methylimidazolium hexafluorophosphate to a greater degree than the ionic surfactants with 1-butyl-3-methylimidazolium chloride. However, these nonionic surfactants appeared to hinder the ability of the stationary phase to interact with solutes via dispersion forces
Asymptotics of the solution of parabolic problems with multipoint stationary phase
NASA Astrophysics Data System (ADS)
Omuraliev, Asan; Abylaeva, Ella
2017-09-01
The aim of this paper is to construct regularized asymptotics of the solution of a singularly perturbed parabolic problem when the limit operator has not range and with rapidly oscillating free term, its derivative of the phase vanishes at finite points. The vanishing of the first derivative of the phase of the free term induces transition layers. It is shown that the asymptotic solution of the problem contains parabolic, inner, corner and rapidly oscillating boundary-layer functions. Corner boundary-layer functions have two components: the first component is described by the product of parabolic boundary layer and boundary layer functions, which have a rapidly oscillating nature of the change, and the second component is described by the product of the inner and parabolic boundary layer functions.
Stationary states of fermions in a sign potential with a mixed vector–scalar coupling
Castilho, W.M. Castro, A.S. de
2014-01-15
The scattering of a fermion in the background of a sign potential is considered with a general mixing of vector and scalar Lorentz structures with the scalar coupling stronger than or equal to the vector coupling under the Sturm–Liouville perspective. When the vector coupling and the scalar coupling have different magnitudes, an isolated solution shows that the fermion under a strong potential can be trapped in a highly localized region without manifestation of Klein’s paradox. It is also shown that the lonely bound-state solution disappears asymptotically as one approaches the conditions for the realization of spin and pseudospin symmetries. -- Highlights: •Scattering of fermions in a sign potential assessed under a Sturm–Liouville perspective. •An isolated bounded solution. •No pair production despite the high localization. •No bounded solution under exact spin and pseudospin symmetries.
Stationary charged scalar clouds around black holes in string theory
NASA Astrophysics Data System (ADS)
Bernard, Canisius
2016-10-01
It was reported that Kerr-Newman black holes can support linear charged scalar fields in their exterior regions. These stationary massive charged scalar fields can form bound states, which are called stationary scalar clouds. In this paper, we show that Kerr-Sen black holes can also support stationary massive charged scalar clouds by matching the near- and far-region solutions of the radial part of the Klein-Gordon wave equation. We also review stationary scalar clouds within the background of static electrically charged black hole solutions in the low-energy limit of heterotic string field theory, namely, the Gibbons-Maeda-Garfinkle-Horowitz-Strominger black holes.
1981-06-26
T IC APPLIED RESEARCH LABORATORY Post Office Box 30 ^C State College, PA 16801 SEP 1 1981 Approved for Public Release Distribution Unlimited A NAVY ...CONTROLLING OFFICE NAME AND ADDRESS 12. REPORT DATE Naval Sea Systems Command 26 June 1981 Department of the Navy 13. NUMBER OF PAGES Washington, DC...128 C.3 a. Schematic of a Circular Cascade Showing the Orientation of the Airfoil Coordinate System in the Global System. b. A Schematic Showing
Yu, Huapeng; Zhu, Hai; Gao, Dayuan; Yu, Meng; Wu, Wenqi
2015-02-13
The Kalman filter (KF) has always been used to improve north-finding performance under practical conditions. By analyzing the characteristics of the azimuth rotational inertial measurement unit (ARIMU) on a stationary base, a linear state equality constraint for the conventional KF used in the fine north-finding filtering phase is derived. Then, a constrained KF using the state equality constraint is proposed and studied in depth. Estimation behaviors of the concerned navigation errors when implementing the conventional KF scheme and the constrained KF scheme during stationary north-finding are investigated analytically by the stochastic observability approach, which can provide explicit formulations of the navigation errors with influencing variables. Finally, multiple practical experimental tests at a fixed position are done on a postulate system to compare the stationary north-finding performance of the two filtering schemes. In conclusion, this study has successfully extended the utilization of the stochastic observability approach for analytic descriptions of estimation behaviors of the concerned navigation errors, and the constrained KF scheme has demonstrated its superiority over the conventional KF scheme for ARIMU stationary north-finding both theoretically and practically.
Yu, Huapeng; Zhu, Hai; Gao, Dayuan; Yu, Meng; Wu, Wenqi
2015-01-01
The Kalman filter (KF) has always been used to improve north-finding performance under practical conditions. By analyzing the characteristics of the azimuth rotational inertial measurement unit (ARIMU) on a stationary base, a linear state equality constraint for the conventional KF used in the fine north-finding filtering phase is derived. Then, a constrained KF using the state equality constraint is proposed and studied in depth. Estimation behaviors of the concerned navigation errors when implementing the conventional KF scheme and the constrained KF scheme during stationary north-finding are investigated analytically by the stochastic observability approach, which can provide explicit formulations of the navigation errors with influencing variables. Finally, multiple practical experimental tests at a fixed position are done on a postulate system to compare the stationary north-finding performance of the two filtering schemes. In conclusion, this study has successfully extended the utilization of the stochastic observability approach for analytic descriptions of estimation behaviors of the concerned navigation errors, and the constrained KF scheme has demonstrated its superiority over the conventional KF scheme for ARIMU stationary north-finding both theoretically and practically. PMID:25688588
Cerri, S. S.; Pegoraro, F.; Califano, F.; Jenko, F.
2014-11-15
Observations and numerical simulations of laboratory and space plasmas in almost collisionless regimes reveal anisotropic and non-gyrotropic particle distribution functions. We investigate how such states can persist in the presence of a sheared flow. We focus our attention on the pressure tensor equation in a magnetized plasma and derive analytical self-consistent plasma equilibria which exhibit a novel asymmetry with respect to the magnetic field direction. These results are relevant for investigating, within fluid models that retain the full pressure tensor dynamics, plasma configurations where a background shear flow is present.
Stationary convection in dilute solutions of 3He in superfluid 4He
Warkentin, P. A.; Haucke, H. J.; Lucas, P.; Wheatley, J. C.
1980-01-01
Two symmetric, convecting steady states have been observed in a novel cell of unity aspect ratio and studied over a range of temperature for two concentrations of 3He in superfluid 4He. An existing theory due to Parshin has been related to the conditions necessary for convection in this system, defining a Rayleigh number closely analogous to that of a classical one-component Bénard system. Values of this Rayleigh number at the onset of convection calculated from experimental data are found to have little temperature dependence, with an average value near that for a classical one-component fluid in this geometry. The Prandtl number is small and temperature dependent, with a smallest calculated value of 0.05. PMID:16592932
Ibrahim, R. S.; El-Kalaawy, O. H.
2006-10-15
The relativistic nonlinear self-consistent equations for a collisionless cold plasma with stationary ions [R. S. Ibrahim, IMA J. Appl. Math. 68, 523 (2003)] are extended to 3 and 3+1 dimensions. The resulting system of equations is reduced to the sine-Poisson equation. The truncated Painleve expansion and reduction of the partial differential equation to a quadrature problem (RQ method) are described and applied to obtain the traveling wave solutions of the sine-Poisson equation for stationary and nonstationary equations in 3 and 3+1 dimensions describing the charge-density equilibrium configuration model.
Coppa, G G M; Ricci, Paolo
2002-10-01
This work deals with a noncollisional kinetic model for non-neutral plasmas in a Penning trap. Using the spatial coordinates r, theta, z and the axial velocity v(z) as phase-space variables, a kinetic model is developed starting from the kinetic equation for the distribution function f(r,theta,z,v(z),t). In order to reduce the complexity of the model, the kinetic equations are integrated along the axial direction by assuming an ergodic distribution in the phase space (z,v(z)) for particles of the same axial energy epsilon and the same planar position. In this way, a kinetic equation for the z-integrated electron distribution F(r,theta,epsilon,t) is obtained taking into account implicitly the three-dimensionality of the problem. The general properties of the model are discussed, in particular the conservation laws. The model is also related to the fluid model that was introduced by Finn et al. [Phys. Plasmas 6, 3744 (1999); Phys. Rev. Lett. 84, 2401 (2000)] and developed by Coppa et al. [Phys. Plasmas 8, 1133 (2001)]. Finally, numerical investigations are presented regarding the stationary solutions of the model.
NASA Technical Reports Server (NTRS)
Skarda, J. Raymond Lee; McCaughan, Frances E.
1998-01-01
Stationary onset of convection due to surface tension variation in an unbounded multicomponent fluid layer is considered. Surface deformation is included and general flux boundary conditions are imposed on the stratifying agencies (temperature/composition) disturbance equations. Exact solutions are obtained to the general N-component problem for both finite and infinitesimal wavenumbers. Long wavelength instability may coexist with a finite wavelength instability for certain sets of parameter values, often referred to as frontier points. For an impermeable/insulated upper boundary and a permeable/conductive lower boundary, frontier boundaries are computed in the space of Bond number, Bo, versus Crispation number, Cr, over the range 5 x 10(exp -7) less than or equal to Bo less than or equal to 1. The loci of frontier points in (Bo, Cr) space for different values of N, diffusivity ratios, and, Marangoni numbers, collapsed to a single curve in (Bo, D(dimensional variable)Cr) space, where D(dimensional variable) is a Marangoni number weighted diffusivity ratio.
NASA Astrophysics Data System (ADS)
Arndt, Peter F.; Rittenberg, Vladimir
2002-06-01
We further study the stochastic model discussed in ref. 2 in which positive and negative particles diffuse in an asymmetric, CP invariant way on a ring. The positive particles hop clockwise, the negative counter-clockwise and oppositely-charged adjacent particles may swap positions. We extend the analysis of this model to the case when the densities of the charged particles are not the same. The mean-field equations describing the model are coupled nonlinear differential equations that we call the two-component Burgers equations. We find roundabout weak solutions of these equations. These solutions are used to describe the properties of the stationary states of the stochastic model. The values of the currents and of various two-point correlation functions obtained from Monte-Carlo simulations are compared with the mean-field results. Like in the case of equal densities, one finds a pure phase, a mixed phase and a disordered phase.
NASA Astrophysics Data System (ADS)
Jasinski, Jerzy
2015-05-01
In the paper propagation of axially-symmetric (1+2)D beam in nonlinear medium with dual-power nonlinearity is analyzed. The ordinary differential equation for transverse stationary profile of the propagating field is derived and solved using a perturbation technique. The simple analytical formulas for the three lowest order solutions are obtained. They describe fields of algebraic profiles. The zero order solution satisfies exactly the nonlinear Schrödinger equation in (1+2)D case. Higher order solutions are determined by propagation constant and describe fields of different initial amplitude. The accuracy of approximation and stability of the obtained solutions are discussed.
NASA Astrophysics Data System (ADS)
Casana, Rodolfo; Ferreira, Manoel M.; Gomes, A. R.; Pinheiro, Paulo R. D.
2009-08-01
In this work, we focus on some properties of the parity-even sector of the CPT-even electrodynamics of the standard model extension. We analyze how the six non-birefringent terms belonging to this sector modify the static and stationary classical solutions of the usual Maxwell theory. We observe that the parity-even terms do not couple the electric and magnetic sectors (at least in the stationary regime). The Green’s method is used to obtain solutions for the field strengths E and B at first order in the Lorentz-covariance-violating parameters. Explicit solutions are attained for point-like and spatially extended sources, for which a dipolar expansion is achieved. Finally, an Earth-based experiment is presented that can lead (in principle) to an upper bound on the anisotropic coefficients as stringent as left(widetilde{kappa}_{e-}right)^{ij}<2.9×10^{-20}.
Reversible State Transition in Nanoconfined Aqueous Solutions
NASA Astrophysics Data System (ADS)
Zhao, Liang; Wang, Chunlei; Liu, Jian; Wen, Binghai; Tu, Yusong; Wang, Zuowei; Fang, Haiping
2014-02-01
Using molecular dynamics simulations, we find a reversible transition between the dispersion and aggregation states of solute molecules in aqueous solutions confined in nanoscale geometry, which is not observed in macroscopic systems. The nanoscale confinement also leads to a significant increase of the critical aggregation concentration (CAC). A theoretical model based on Gibbs free energy calculation is developed to describe the simulation results. It indicates that the reversible state transition is attributed to the low free energy barrier (of order kBT) in between two energy minima corresponding to the dispersion and aggregation states, and the enhancement of the CAC results from the fact that at lower concentrations the number of solute molecules is not large enough to allow the formation of a stable cluster in the confined systems.
Stationary to nonstationary transition in crossed-field devices
Marini, Samuel; Rizzato, Felipe B.; Pakter, Renato
2016-03-15
The previous results based on numerical simulations showed that a cold electron beam injected in a crossed field gap does not reach a time independent stationary state in the space charge limited regime [P. J. Christenson and Y. Y. Lau, Phys. Plasmas 1, 3725 (1994)]. In this work, the effect of finite injection temperature in the transition from stationary to nonstationary states is investigated. A fully kinetic model for the electron flow is derived and used to determine the possible stationary states of the system. It is found that although there is always a stationary solution for any set of parameters, depending on the injection temperature the electron flow becomes very sensitive to fluctuations and the stationary state is never reached. By investigating the nonlinear dynamics of a characteristic electron, a theory based on a single free parameter is constructed to predict when the transition between stationary and nonstationary states occurs. In agreement with the previous numerical results, the theory indicates that for vanishing temperatures the system never reaches the time independent stationary state in the space charge limited regime. Nevertheless, as the injection temperature is raised it is found a broad range of system parameters for which the stationary state is indeed attained. By properly adjusting the free parameter in the theory, one can be able to describe, to a very good accuracy, when the transition occurs.
Extraction of shear viscosity in stationary states of relativistic particle systems.
Reining, F; Bouras, I; El, A; Wesp, C; Xu, Z; Greiner, C
2012-02-01
Starting from a classical picture of shear viscosity we construct a stationary velocity gradient in a microscopic parton cascade. Employing the Navier-Stokes ansatz we extract the shear viscosity coefficient η. For elastic isotropic scatterings we find an excellent agreement with the analytic values. This confirms the applicability of this method. Furthermore, for both elastic and inelastic scatterings with pQCD based cross sections we extract the shear viscosity coefficient η for a pure gluonic system and find a good agreement with already published calculations.
NASA Astrophysics Data System (ADS)
Antoine, Xavier; Besse, Christophe; Duboscq, Romain; Rispoli, Vittorio
2017-10-01
The aim of this paper is to propose a simple accelerated spectral gradient flow formulation for solving the Gross-Pitaevskii Equation (GPE) when computing the stationary states of Bose-Einstein Condensates. The new algorithm, based on the recent iPiano minimization algorithm (Ochs et al., 2014), converges three to four times faster than the standard implicit gradient scheme. To support the method, we provide a complete numerical study for 1d-2d-3d GPEs, including rotation and dipolar terms.
NASA Astrophysics Data System (ADS)
Chen, Sheng; Täuber, Uwe C.
2015-03-01
Spatially extended stochastic models for predator-prey competition and coexistence display complex, correlated spatio-temporal structures and are governed by remarkably large fluctuations. Both populations are characterized by damped erratic oscillations whose properties are governed by the reaction rates. Here, we specifically study a stochastic lattice Lotka-Volterra model by means of Monte Carlo simulations that impose spatial restrictions on the number of occupants per site. The system tends to relax into a quasi-stationary state, independent of the imposed initial conditions. We investigate the non-equilibrium relaxation between two such quasi-stationary states, following an instantaneous change of the predation rate. The ensuing relaxation times are measured via the peak width of the population density Fourier transforms. As expected, we find that the initial state only influences the oscillations for the duration of this relaxation time, implying that the system quickly loses any memory of the initial configuration. Research supported by the U.S. Department of Energy, Office of Basic Energy Sciences, Division of Materials Sciences and Engineering under Award DE-FG02-09ER46613.
Hydrogen Storage Materials for Mobile and Stationary Applications: Current State of the Art.
Lai, Qiwen; Paskevicius, Mark; Sheppard, Drew A; Buckley, Craig E; Thornton, Aaron W; Hill, Matthew R; Gu, Qinfen; Mao, Jianfeng; Huang, Zhenguo; Liu, Hua Kun; Guo, Zaiping; Banerjee, Amitava; Chakraborty, Sudip; Ahuja, Rajeev; Aguey-Zinsou, Kondo-Francois
2015-09-07
One of the limitations to the widespread use of hydrogen as an energy carrier is its storage in a safe and compact form. Herein, recent developments in effective high-capacity hydrogen storage materials are reviewed, with a special emphasis on light compounds, including those based on organic porous structures, boron, nitrogen, and aluminum. These elements and their related compounds hold the promise of high, reversible, and practical hydrogen storage capacity for mobile applications, including vehicles and portable power equipment, but also for the large scale and distributed storage of energy for stationary applications. Current understanding of the fundamental principles that govern the interaction of hydrogen with these light compounds is summarized, as well as basic strategies to meet practical targets of hydrogen uptake and release. The limitation of these strategies and current understanding is also discussed and new directions proposed. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.
Mallory, Kristina; Van Gorder, Robert A
2015-07-01
Stationary solutions for the cubic nonlinear Schrödinger equation modeling Bose-Einstein condensates (BECs) confined in three spatial dimensions by general forms of a potential are studied through a perturbation method and also numerically. Note that we study both repulsive and attractive BECs under similar frameworks in order to deduce the effects of the potentials in each case. After outlining the general framework, solutions for a collection of specific confining potentials of physical relevance to experiments on BECs are provided in order to demonstrate the approach. We make several observations regarding the influence of the particular potentials on the behavior of the BECs in these cases, comparing and contrasting the qualitative behavior of the attractive and repulsive BECs for potentials of various strengths and forms. Finally, we consider the nonperturbative where the potential or the amplitude of the solutions is large, obtaining various qualitative results. When the kinetic energy term is small (relative to the nonlinearity and the confining potential), we recover the expected Thomas-Fermi approximation for the stationary solutions. Naturally, this also occurs in the large mass limit. Through all of these results, we are able to understand the qualitative behavior of spherical three-dimensional BECs in weak, intermediate, or strong confining potentials.
NASA Astrophysics Data System (ADS)
Brian Walton, D.; Visscher, Koen
2004-05-01
It recently has been shown that the observed noise amplitude of an intrinsically noisy system may be reduced by causing the underlying state to fluctuate [
The phase delay and its complex time: From stationary states up to wave packets
Grossel, Ph.
2013-03-15
Complex time is often invoked about tunneling effect where the classical phase delay is completed with a crucial filter effect. Usually the complex times are obtained by considering the flux-flux correlation function, but this can be obtained by a very simple approach using the search of the maximum of the generalized complex phase function, including the amplitude of the wave function. Various aspects of the phase delay are presented in the case of wave packets impinging on simple or resonant quantum barriers. Formal links with the classical mechanics give birth to quasi-trajectories of the quantum particle, totally compatible with the quantum mechanics. - Highlights: Black-Right-Pointing-Pointer The stationary phase method is extended in including the variations of the spectra. Black-Right-Pointing-Pointer The complex phase delay leads to a complex trajectory inside and out-side the barrier. Black-Right-Pointing-Pointer Examples of quasi-trajectories are given in case of different quantum barriers. Black-Right-Pointing-Pointer Phase delays are specified for resonant tunneling or above-barrier wave-packets. Black-Right-Pointing-Pointer The coherence between the quasi-trajectories and quantum mechanics is shown.
Corresponding-states laws for protein solutions.
Katsonis, Panagiotis; Brandon, Simon; Vekilov, Peter G
2006-09-07
The solvent around protein molecules in solutions is structured and this structuring introduces a repulsion in the intermolecular interaction potential at intermediate separations. We use Monte Carlo simulations with isotropic, pair-additive systems interacting with such potentials. We test if the liquid-liquid and liquid-solid phase lines in model protein solutions can be predicted from universal curves and a pair of experimentally determined parameters, as done for atomic and colloid materials using several laws of corresponding states. As predictors, we test three properties at the critical point for liquid-liquid separation: temperature, as in the original van der Waals law, the second virial coefficient, and a modified second virial coefficient, all paired with the critical volume fraction. We find that the van der Waals law is best obeyed and appears more general than its original formulation: A single universal curve describes all tested nonconformal isotropic pair-additive systems. Published experimental data for the liquid-liquid equilibrium for several proteins at various conditions follow a single van der Waals curve. For the solid-liquid equilibrium, we find that no single system property serves as its predictor. We go beyond corresponding-states correlations and put forth semiempirical laws, which allow prediction of the critical temperature and volume fraction solely based on the range of attraction of the intermolecular interaction potential.
Khokhlova, Svetlana S; Burshtein, Anatoly I
2011-01-21
The Stern-Volmer constants for either pulse-induced or stationary fluorescence being quenched by a contact charge transfer are calculated and their free energy dependencies (the free energy gap laws) are specified. The reversibility of charge transfer is taken into account as well as spin conversion in radical ion pairs, followed by their recombination in either singlet or triplet neutral products. The natural decay of triplets as well as their impurity quenching by ionization are accounted for when estimating the fluorescence quantum yield and its free energy dependence.
Silva, Felipe O; Hemerly, Elder M; Leite Filho, Waldemar C
2017-02-23
This paper presents the second part of a study aiming at the error state selection in Kalman filters applied to the stationary self-alignment and calibration (SSAC) problem of strapdown inertial navigation systems (SINS). The observability properties of the system are systematically investigated, and the number of unobservable modes is established. Through the analytical manipulation of the full SINS error model, the unobservable modes of the system are determined, and the SSAC error states (except the velocity errors) are proven to be individually unobservable. The estimability of the system is determined through the examination of the major diagonal terms of the covariance matrix and their eigenvalues/eigenvectors. Filter order reduction based on observability analysis is shown to be inadequate, and several misconceptions regarding SSAC observability and estimability deficiencies are removed. As the main contributions of this paper, we demonstrate that, except for the position errors, all error states can be minimally estimated in the SSAC problem and, hence, should not be removed from the filter. Corroborating the conclusions of the first part of this study, a 12-state Kalman filter is found to be the optimal error state selection for SSAC purposes. Results from simulated and experimental tests support the outlined conclusions.
Silva, Felipe O.; Hemerly, Elder M.; Leite Filho, Waldemar C.
2017-01-01
This paper presents the second part of a study aiming at the error state selection in Kalman filters applied to the stationary self-alignment and calibration (SSAC) problem of strapdown inertial navigation systems (SINS). The observability properties of the system are systematically investigated, and the number of unobservable modes is established. Through the analytical manipulation of the full SINS error model, the unobservable modes of the system are determined, and the SSAC error states (except the velocity errors) are proven to be individually unobservable. The estimability of the system is determined through the examination of the major diagonal terms of the covariance matrix and their eigenvalues/eigenvectors. Filter order reduction based on observability analysis is shown to be inadequate, and several misconceptions regarding SSAC observability and estimability deficiencies are removed. As the main contributions of this paper, we demonstrate that, except for the position errors, all error states can be minimally estimated in the SSAC problem and, hence, should not be removed from the filter. Corroborating the conclusions of the first part of this study, a 12-state Kalman filter is found to be the optimal error state selection for SSAC purposes. Results from simulated and experimental tests support the outlined conclusions. PMID:28241494
Theory of stationary ultarshort pulses in solid-state laserswith passive mode locking
Komarov, K.P.
1986-02-01
The formation of steady-state pulses in solid-state lasers with passive mode locking is investigated under conditions when the refractive index is frequency dispersive and nonlinear. The case of a noninertial absorber is considered as well as that of an inertial one. It is shown that when the nonlinearity of the refractive index exceeds a certain critical level phase modulation of the pulse leads to instability of the steady-state regime. The possibility is discussed of forming extremely short pulses in wide-band amplifying media such as alexandrite.
Noguera, Norman; Rózga, Krzysztof
2015-07-15
In this work, one provides a justification of the condition that is usually imposed on the parameters of the hypergeometric equation, related to the solutions of the stationary Schrödinger equation for the harmonic oscillator in two-dimensional constant curvature spaces, in order to determine the solutions which are square-integrable. One proves that in case of negative curvature, it is a necessary condition of square integrability and in case of positive curvature, a necessary condition of regularity. The proof is based on the analytic continuation formulas for the hypergeometric function. It is observed also that the same is true in case of a slightly more general potential than the one for harmonic oscillator.
NASA Astrophysics Data System (ADS)
Zhan, Y. M.; Jardine, A. K. S.
2005-09-01
Parametric time-frequency representation based on parametric models is more desirable for presenting highly precise time-frequency domain information due to its high-resolution property. However, the sensitivity and robustness of parametric models, in particular the parametric models on the basis of advanced adaptive filtering algorithms, has never been investigated for on-line condition monitoring of rotating machinery. Part 1 of this study proposed three adaptive parametric models based on three advanced adaptive filtering algorithms. Part 2 of this study is concerned with the effectiveness of the proposed models under distinct gear states, especially the highly non-stationary conditions accrued from advanced gear faults. Four gear states are considered: healthy state, adjacent gear tooth failure, non-adjacent gear tooth failure and distributed gear tooth failure. The vibration signals used in this study include the time-domain synchronous averaging signal and gear motion residual signal for each considered gear state. The test results demonstrate that the optimum filter behavior can readily be attained and the white Gaussian assumption of innovations can relatively be easily guaranteed for the NAKF-based model under distinct gear states and a wide variety of model initializations. On the other hand, the EKF- and MEKF-based models are capable of generating more accurate time-frequency representations than the NAKF-based model, but in general the optimality condition for white Gaussian assumption cannot be guaranteed for these two advanced models. Therefore, the NAKF-based model is preferred for automatic condition monitoring due to its appealing robustness to distinct gear states and arbitrary model initializations, whereas the EKF- and MEKF-based models are desirable when accurate time-frequency representation is concerned.
Solute retention and the states of water in polyethylene glycol and poly(vinyl alcohol) gels.
Baba, Takayuki; Sakamoto, Ryosaku; Shibukawa, Masami; Oguma, Koichi
2004-06-18
The states of water sorbed in a cross-linked polyethylene glycol (PEG) gel, TSKgel Ether-250, and cross-linked poly(vinyl alcohol) (PVA) gels of different pore sizes, TSKgel Toyopearl HW-40S, 50S, 55S and 75S, were investigated by means of differential scanning calorimetry (DSC). It was found that there were three types of water in these hydrogels, non-freezing water, freezable bound water and free water. The amount of water that functions as the stationary phase in the column packed with the each gel was also estimated by a liquid chromatographic method. The estimated amount of the stationary phase water is in good agreement with the sum of the amount of non-freezing water and that of freezable bound water for HW-40S, 50S and 55S, while it agrees with the amount of only non-freezing water for HW-75S and Ether-250. This means that the stationary phase water consists of non-freezing water and freezable bound water for HW-40S, 50S and 55S, while only non-freezing water functions as the stationary phase in HW-75S and Ether-250 gels. This result can be attributed to the difference in the structure of the gels; the PVA gels containing PVA at relatively high concentrations, HW-40S, 50S and 55S, have a homogeneous gel phase, whereas HW-75S and Ether-250 have a heterogeneous gel phase consisting hydrated polymer domains and macropores with relatively hydrophobic surface. The freezable bound water in Toyopearl HW-40S, 50S and 55S can be regarded as a component of a homogeneous PVA solution phase, while that in HW-75S and Ether-250 may be water isolated in small pores of the hydrophobic domains. The results obtained by the investigation on the retention selectivity of these hydrogels in aqueous solutions supported our postulated view on the structures of the hydrogels.
Effect of interference between two colored noises on the stationary states of a Brownian particle
NASA Astrophysics Data System (ADS)
Mondal, Shrabani; Bag, Bidhan Chandra
2015-04-01
In this paper we present properties of an external colored cross-correlated noise-driven Brownian system which is coupled to a thermal bath. Multiplicative cross-correlated noises can stabilize the transition state. Thus by monitoring the interference between the noises one can understand the mechanism of a chemical reaction. At the same time, we have investigated how the interference affects the barrier-crossing dynamics. In its presence breakdown of the Arrhenius result occurs. The breakdown becomes prominent if the multiplicative noises become additive in nature. We have also investigated how the power law behavior of the rate constant as a function of damping strength is affected by the properties of external colored noises. Furthermore, we have observed that multiplicative colored cross-correlated noises can induce the resonant activation phenomenon.
Shekhtman, V.L.
1995-12-01
A theoretical investigation of the correlation between the resonance scattering from a quasi-stationary state and the Einstein relations in the quantum theory of radiation was carried out. On the basis of the Einstein relations, the mode-averaged value of the total scattering cross section at the frequency of the resonance maximum was obtained in the general form. With allowance for radiative, vibronic, transverse, and inhomogeneous widths of a zero-phonon line, relations were obtained that permit the oscillator strength of a resonance electronic transition to be found from measurements of the absorption cross section at the resonance frequency and the half-width of the absorption spectral line. The relations depend on the shape of the absorption spectrum. The cases of the Lorentzian, Gaussian, and Voigt line shapes were considered. Using the E-2A transitions in an optically excited ruby as an example, the cross section of the phonon resonance scattering from impurity centers in crystals with a sufficiently large value of the Debye-Waller factor, e{sup {minus}2M}{ge} 0.5, was considered. The results can be applied in phonon spectroscopy. The main results are interpreted in detail in terms of the Bohr spectroscopic correspondence principle. A new derivation is given of the Ladenburg formula relating the transition probabilities and the dispersion constants. 23 refs., 1 fig.
Jiménez, Rolando Placeres; Pupo, Ana Elisa Bergues; Cabrales, Jesús Manuel Bergues; Joa, Javier Antonio González; Cabrales, Luis Enrique Bergues; Nava, Juan José Godina; Aguilera, Andrés Ramírez; Mateus, Miguel Angel O'Farril; Jarque, Manuel Verdecia; Brooks, Soraida Candida Acosta
2011-02-01
Electrotherapy with direct current delivered through implanted electrodes is used for local control of solid tumors in both preclinical and clinical studies. The aim of this research is to develop a solution method for obtaining a three-dimensional analytical expression for potential and electric current density as functions of direct electric current intensity, differences in conductivities between the tumor and the surrounding healthy tissue, and length, number and polarity of electrodes. The influence of these parameters on electric current density in both media is analyzed. The results show that the electric current density in the tumor is higher than that in the surrounding healthy tissue for any value of these parameters. The conclusion is that the solution method presented in this study is of practical interest because it provides, in a few minutes, a convenient way to visualize in 3D the electric current densities generated by a radial electrode array by means of the adequate selection of direct current intensity, length, number, and polarity of electrodes, and the difference in conductivity between the solid tumor and its surrounding healthy tissue.
Decay of stationary light pulses in ultracold atoms
Wu Jinhui; Artoni, M.; La Rocca, G. C.
2010-03-15
We develop a general scheme for studying the optical response of ultracold atoms driven into a regime of standing-wave electromagnetically induced transparency. We rely on full numerical solutions of the Maxwell-Liouville equations without invoking secular and adiabatic approximations and arbitrary initial state assumptions. These approximations and assumptions can conceal, e.g., significant loss and diffusion responsible for the decay of stationary light pulses in cold atomic samples. The complex decay dynamics of a stationary light pulse is here analyzed in terms of higher-order spin and optical coherences that arise from nonlinear interactions of the stationary light pulse with the two counterpropagating components of a standing-wave driving field. Specific results for stationary light pulses in cold {sup 87}Rb atoms have been discussed for temperature regimes where the residual Doppler broadening is negligible.
NASA Astrophysics Data System (ADS)
Pantellini, Filippo; Griton, Léa
2016-10-01
The spatial structure of a steady state plasma flow is shaped by the standing modes with local phase velocity exactly opposite to the flow velocity. The general procedure of finding the wave vectors of all possible standing MHD modes in any given point of a stationary flow requires numerically solving an algebraic equation. We present the graphical procedure (already mentioned by some authors in the 1960's) along with the exact solution for the Alfvén mode and approximate analytic solutions for both fast and slow modes. The technique can be used to identify MHD modes in space and laboratory plasmas as well as in numerical simulations.
NASA Astrophysics Data System (ADS)
Palma, A.; Semprini, E.; Stefani, F.; Talamo, A.
1996-09-01
We found many stationary points (minima and transition states) for the title reaction on the 2A' surface at unrestricted Hartree-Fock self-consistent field (UHF-SCF) level with two different basis sets. Stable adducts, as suggested by previous experimental works, have been ascertained and several reaction paths are obtained through intrinsic reaction coordinate (IRC) calculations. A link to the HNC+OH reaction is possible. Multiconfiguration SCF (MC-SCF) calculations have been carried out for the addition reaction with the lowest energy barrier in order to eliminate the spin contamination error on these geometries. Correlation energy at the stationary points was estimated via a perturbative scheme, Møller-Plesset at fourth order (MP4) which does not seem adequate for such a system, and via multireference double configuration interaction (MR-DCI) with extrapolation to full CI values for ground and first excited states. Electronic excitations may open some reaction channels.
Sun, Xiang; Ladanyi, Branka M; Stratt, Richard M
2015-07-23
Experimental studies of solvation dynamics in liquids invariably ask how changing a solute from its electronic ground state to an electronically excited state affects a solution's dynamics. With traditional time-dependent-fluorescence experiments, that means looking for the dynamical consequences of the concomitant change in solute-solvent potential energy. But if one follows the shift in the dynamics through its effects on the macroscopic polarizability, as recent solute-pump/solvent-probe spectra do, there is another effect of the electronic excitation that should be considered: the jump in the solute's own polarizability. We examine the spectroscopic consequences of this solute polarizability change in the classic example of the solvation dye coumarin 153 dissolved in acetonitrile. After demonstrating that standard quantum chemical methods can be used to construct accurate multisite models for the polarizabilities of ground- and excited-state solvation dyes, we show via simulation that this polarizability change acts as a contrast agent, significantly enhancing the observable differences in optical-Kerr spectra between ground- and excited-state solutions. A comparison of our results with experimental solute-pump/solvent-probe spectra supports our interpretation and modeling of this spectroscopy. We predict, in particular, that solute-pump/solvent-probe spectra should be sensitive to changes in both the solvent dynamics near the solute and the electronic-state-dependence of the solute's own rotational dynamics.
NASA Astrophysics Data System (ADS)
Manko, V. S.; Rabadán, R. I.; Sanabria-Gómez, J. D.
2014-03-01
In this paper, we present and analyze the simplest physically meaningful model for stationary black diholes—a binary configuration of counterrotating Kerr-Newman black holes endowed with opposite electric charges—elaborated in a physical parametrization on the basis of one of the Ernst-Manko-Ruiz equatorially antisymmetric solutions of the Einstein-Maxwell equations. The model saturates the Gabach-Clement inequality for interacting black holes with struts, and in the absence of rotation, it reduces to the Emparan-Teo electric dihole solution. The physical characteristics of each dihole constituent satisfy identically the well-known Smarr's mass formula.
Sharada, Shaama Mallikarjun; Bell, Alexis T. E-mail: bell@cchem.berkeley.edu; Head-Gordon, Martin E-mail: bell@cchem.berkeley.edu
2014-04-28
The cost of calculating nuclear hessians, either analytically or by finite difference methods, during the course of quantum chemical analyses can be prohibitive for systems containing hundreds of atoms. In many applications, though, only a few eigenvalues and eigenvectors, and not the full hessian, are required. For instance, the lowest one or two eigenvalues of the full hessian are sufficient to characterize a stationary point as a minimum or a transition state (TS), respectively. We describe here a method that can eliminate the need for hessian calculations for both the characterization of stationary points as well as searches for saddle points. A finite differences implementation of the Davidson method that uses only first derivatives of the energy to calculate the lowest eigenvalues and eigenvectors of the hessian is discussed. This method can be implemented in conjunction with geometry optimization methods such as partitioned-rational function optimization (P-RFO) to characterize stationary points on the potential energy surface. With equal ease, it can be combined with interpolation methods that determine TS guess structures, such as the freezing string method, to generate approximate hessian matrices in lieu of full hessians as input to P-RFO for TS optimization. This approach is shown to achieve significant cost savings relative to exact hessian calculation when applied to both stationary point characterization as well as TS optimization. The basic reason is that the present approach scales one power of system size lower since the rate of convergence is approximately independent of the size of the system. Therefore, the finite-difference Davidson method is a viable alternative to full hessian calculation for stationary point characterization and TS search particularly when analytical hessians are not available or require substantial computational effort.
Plurality of inherent states in equiatomic solid solutions
NASA Astrophysics Data System (ADS)
Demkowicz, M. J.
2017-03-01
We show that single-crystal, equiatomic solid solutions of Lennard-Jones particles have a plurality of inherent states: mechanically stable configurations with identical lattice site occupancies, yet distinct potential-energy minima. External loading triggers transitions between inherent states via localized shear transformations. A plurality of inherent states and mechanically activated transitions between them make equiatomic solid solutions an unusual form of matter: one that is crystalline like single-component metals, yet exhibits localized shear transformations like metallic glasses.
Díaz, J. I.; Hidalgo, A.; Tello, L.
2014-01-01
We study a climatologically important interaction of two of the main components of the geophysical system by adding an energy balance model for the averaged atmospheric temperature as dynamic boundary condition to a diagnostic ocean model having an additional spatial dimension. In this work, we give deeper insight than previous papers in the literature, mainly with respect to the 1990 pioneering model by Watts and Morantine. We are taking into consideration the latent heat for the two phase ocean as well as a possible delayed term. Non-uniqueness for the initial boundary value problem, uniqueness under a non-degeneracy condition and the existence of multiple stationary solutions are proved here. These multiplicity results suggest that an S-shaped bifurcation diagram should be expected to occur in this class of models generalizing previous energy balance models. The numerical method applied to the model is based on a finite volume scheme with nonlinear weighted essentially non-oscillatory reconstruction and Runge–Kutta total variation diminishing for time integration. PMID:25294969
Lin, Cheng-Lan; Singco, Brenda; Wu, Ching-Yi; Liang, Pei-Zhu; Cheng, Yi-Jie; Huang, Hsi-Ya
2013-01-11
This study describes the ability of triallyl isocyanurate (TAIC)-co-methacrylate ester polymer monoliths as stationary phases for the separation of hydrophilic compounds (phenolic acids, amino acids and catecholamines) in capillary electrochromatography (CEC) and ultra high pressure liquid chromatography (UHPLC). Several TAIC-co-methacrylate ester polymer monoliths prepared by single-step in situ copolymerization of TAIC, ethylene dimethacrylate (EDMA) and 2-acrylamido-2-methylpropane sulfonic acid (AMPS), with or without alkyl methacrylates were characterized by examining the SEM image, surface area, contact angle, and the thermal decomposition temperature. Compared to the conventional methacrylate ester-based monoliths, these proposed monoliths possessed hydrophilic character thus increased wettability which improved chromatographic separation selectivity of polar phenolic acids. Among the proposed TAIC-co-methacrylate monoliths, poly(TAIC-co-EDMA-AMPS-co-stearyl methacrylate (SMA)) showed separation selectivity with an increased analyte resolution from 0.0 to 0.92 for 4-hydroxybenzoic acid and vanillic acid, which were consistently difficult to resolve in the reversed-phase chromatographic mechanism of these monoliths in aqueous mobile phases. Moreover, stable ionization efficiencies were observed when this monolith was combined with ESI-MS detector possibly because an organic solvent-rich sheath liquid was used in the CEC-MS. This study demonstrates the potentiality of novel TAIC-co-methacrylate polymer monoliths in hydrophilic solute separation either in CEC or UHPLC mode.
Díaz, J I; Hidalgo, A; Tello, L
2014-10-08
We study a climatologically important interaction of two of the main components of the geophysical system by adding an energy balance model for the averaged atmospheric temperature as dynamic boundary condition to a diagnostic ocean model having an additional spatial dimension. In this work, we give deeper insight than previous papers in the literature, mainly with respect to the 1990 pioneering model by Watts and Morantine. We are taking into consideration the latent heat for the two phase ocean as well as a possible delayed term. Non-uniqueness for the initial boundary value problem, uniqueness under a non-degeneracy condition and the existence of multiple stationary solutions are proved here. These multiplicity results suggest that an S-shaped bifurcation diagram should be expected to occur in this class of models generalizing previous energy balance models. The numerical method applied to the model is based on a finite volume scheme with nonlinear weighted essentially non-oscillatory reconstruction and Runge-Kutta total variation diminishing for time integration.
Saum, Stephan H; Müller, Volker
2008-03-01
The moderately halophilic, chloride-dependent bacterium Halobacillus halophilus switches its osmolyte strategy with the salinity in its environment by the production of different compatible solutes. Ectoine is produced predominantly at very high salinities, along with proline. Interestingly, ectoine production is growth phase dependent which led to a more than 1000-fold change in the ectoine : proline ratio from 0.04 in exponential to 27.4 in late stationary phase cultures. The genes encoding the ectoine biosynthesis pathway were identified on the chromosome in the order ectABC. They form an operon that is expressed in a salinity-dependent manner with low-level expression below 1.5 M NaCl but 10-fold and 23-fold increased expression at 2.5 and 3.0 M NaCl respectively. The temporal expression of genes involved in osmoresponse is different with gdh/gln and pro genes being first, followed by ect genes. Chloride had no effect on expression of ect genes, but stimulated cellular EctC synthesis as well as ectoine production. These data demonstrate, for the first time, a growth-phase dependent switch in osmolyte strategy in a moderate halophile and, additionally, represent another piece of the chloride regulon of H. halophilus.
NASA Astrophysics Data System (ADS)
Tagawa, S.; Washio, M.; Tabata, Y.; Kobayashi, H.
Transient absorption spectra of the solute anion, cation and triplet state and the solute fluorescence in the pulse radiolysis of 0.1 mole 1 -1 biphenyl in cyclohexane were observed on a nanosecond timescale longer than 1 ns after a 20 ps pulse. The formation of the solute excited singlet state is mainly due to the geminate ion recombination reaction even in the high concentrated solutions. The decay of the solute ions obeys the reciprocal square root dependence on time longer than 10 ns from the end of a 10 ps pulse. The slope of this reciprocal square root plots agrees with the literature value on a longer timescale obtained by microwave absorption. The yield of free ions obtained from the intercept of the slope agrees also with the literature values obtained by the field clearing method. Ratio of the formation rate of the solute excited triplet state to the decay rate of the solute anion changes in a time range between 5 and 20 ns. It is very well correlated with a theoretical calculation of spin correlation decay of the germinate ion pairs by Brocklehurst, although the formation of the solute triplet state was observed even on a timescale shorter than 5 ns from the end of a 20 ps pulse, where loss of spin correlation is negligibly small.
NASA Astrophysics Data System (ADS)
Kravtsov, Nikolai V.; Chekina, S. N.
2007-02-01
The effect of a constant magnetic field on the nonlinear radiation dynamics of a monolithic chip ring Nd:YAG laser pumped by modulated radiation is studied experimentally. It is found that the application of a constant magnetic field to the active element of the solid-state ring laser operating in the non-stationary regime results in the displacement of the regions of existence of quasi-periodic and chaotic lasing regimes to the low-frequency region of pump power modulation. In addition, the application of a magnetic field to the active element of the laser gives rise to the spectral nonreciprocity.
NASA Technical Reports Server (NTRS)
Lobashov, A. A.; Mostepanenko, V. M.
1993-01-01
The theory of quantum effects in nonlinear dielectric media is developed. The nonlinear dielectric media is influenced by an external pumping field. The diagonalization of the Hamiltonian of a quantized field is obtained by the canonical Bogoliubov transformations. The transformations allow us to obtain the general expressions for the number of created photons and for the degree of squeezing. In the case of a plane pumping wave, for example, the results are calculated by using the zero order of the secular perturbation theory, with small parameters characterizing the medium nonlinearity. The Heisenberg equations of motion are obtained for non-stationary case and a commonly used Hamiltonian is derived from the first principles of quantum electrodynamics.
Stationary rotating strings as relativistic particle mechanics
Ogawa, Kouji; Ishihara, Hideki; Saito, Shinya; Kozaki, Hiroshi; Nakano, Hiroyuki
2008-07-15
Stationary rotating strings can be viewed as geodesic motions in appropriate metrics in two-dimensional space. We obtain all solutions describing stationary rotating strings in flat spacetime as an application. These rotating strings have infinite length with various wiggly shapes. Averaged value of the string energy, the angular momentum, and the linear momentum along the string are discussed.
NASA Astrophysics Data System (ADS)
Haslauer, Claus; Heißerer, Theresia; Bárdossy, András
2014-05-01
Using Information on Land-use and Capture Zones for non-Stationary State-Wide Interpolation of Groundwater Quality Parameters A novel approach for spatial non-stationary interpolation is presented. This approach takes censored measurements, secondary information in physically based neighbourhoods, and non-Gaussian spatial dependence structures into account. The impact of the improvements of the geostatistical model are evaluated using regional groundwater quality data. Secondary information has an influence on the distribution of the concentration at each interpolation location. In this study, land-use and hydrogeological units are used as two types of secondary information. The influence of the land-use composition of local neighbourhoods at an interpolation location is modelled by mixed distributions of concentrations. The mixture is derived from the distributions of concentrations within groups of similar land-uses. These pure distributions are jointly optimized for all groups of secondary information.Different geometries and sizes of the neighbourhood are used. Additionally, physically-based delineated capture zones are taken into account for evaluating the influence of the neighbourhood on the measurement distribution. Censored measurements, such as measurements below some detection limit, are commonly ignored, but are incorporated in the presented approach both in the marginal distributions and the multivariate distributions via probabilities of non-exceedance. This is an important feature for emerging contaminants, which typically have a large portion of censored measurements. Spatial copulas are multidimensional dependence models that are capable of incorporating not censored and censored measurements. The dependence can deviate from Gaussian dependence and is independent of the marginal distribution. The proposed model is used for estimation based on the measured parameters and for spatial interpolation purposes. The improved quality of the interpolation
NASA Astrophysics Data System (ADS)
Toktarbay, S.; Quevedo, H.
2014-10-01
We present a stationary generalization of the static $q-$metric, the simplest generalization of the Schwarzschild solution that contains a quadrupole parameter. It possesses three independent parameters that are related to the mass, quadrupole moment and angular momentum. We investigate the geometric and physical properties of this exact solution of Einstein's vacuum equations, and show that it can be used to describe the exterior gravitational field of rotating, axially symmetric, compact objects.
Exact Solutions of Relativistic Bound State Problem for Spinless Bosons
NASA Astrophysics Data System (ADS)
Aslanzadeh, M.; Rajabi, A. A.
2017-01-01
We investigated in detail the relativistic bound states of spin-zero bosons under the influence of Coulomb-plus-linear potentials with an arbitrary combination of scalar and vector couplings. Through an exact analytical solution of three-dimensional Klein-Gordon equation, closed form expressions were derived for energy eigenvalues and wave functions and some correlations between potential parameters were found. We also presented the relativistic description of bound states and nonrelativistic limit of the problem in some special cases.
Steady-state axisymmetric nonlinear magnetohydrodynamic solutions with various boundary conditions
NASA Astrophysics Data System (ADS)
Wang, Lile; Lou, Yu-Qing
2014-04-01
Axisymmetric magnetohydrodynamics (MHD) can be invoked for describing astrophysical magnetized flows and formulated to model stellar magnetospheres including main-sequence stars (e.g. the Sun), compact stellar objects [e.g. magnetic white dwarfs (MWDs), radio pulsars, anomalous X-ray pulsars, magnetars, isolated neutron stars, etc.] and planets as a major step forward towards a full three-dimensional model construction. Using powerful and reliable numerical solvers based on two distinct finite-difference method and finite-element method schemes of algorithm, we examine axisymmetric steady-state or stationary MHD models in Throumoulopoulos & Tasso, finding that their separable semi-analytic non-linear solutions are actually not unique given their specific selection of several free functionals and chosen boundary conditions. Similar situations of multiple non-linear solutions with the same boundary conditions actually also happen to force-free magnetic field models of Low & Lou. The multiplicity of non-linear steady MHD solutions gives rise to differences in the total energies contained in the magnetic fields and flow velocity fields as well as in the asymptotic behaviours approaching infinity, which may in turn explain why numerical solvers tend to converge to a non-linear solution with a lower energy than the corresponding separable semi-analytic one. By properly adjusting model parameters, we invoke semi-analytic and numerical solutions to describe different kinds of scenarios, including nearly parallel case and the situation in which the misalignment between the plasma flow and magnetic field is considerable. We propose that these MHD models are capable of describing the magnetospheres of MWDs as examples of applications with moderate conditions (including magnetic field) where the typical values of several important parameters are consistent with observations. Physical parameters can also be estimated based on such MHD models directly. We discuss the challenges
HDG schemes for stationary convection-diffusion problems
NASA Astrophysics Data System (ADS)
Dautov, R. Z.; Fedotov, E. M.
2016-11-01
For stationary linear convection-diffusion problems, we construct and study a hybridized scheme of the discontinuous Galerkin method on the basis of an extended mixed statement of the problem. Discrete schemes can be used for the solution of equations degenerating in the leading part and are stated via approximations to the solution of the problem, its gradient, the flow, and the restriction of the solution to the boundaries of elements. For the spaces of finite elements, we represent minimal conditions responsible for the solvability, stability and accuracy of the schemes.
Full analytical solution of Adapted Polarisation State Contrast Imaging.
Upadhyay, Debajyoti; Mondal, Sugata; Lacot, Eric; Orlik, Xavier
2011-12-05
We have earlier proposed a 2-channel imaging technique: Adapted Polarisation State Contrast Imaging (APSCI), which noticeably enhances the polarimetric contrast between an object and its background using fully polarised incident state adapted to the scene, such that the polarimetric responses of those regions are located as far as possible on the Poincaré sphere. We address here the full analytical and graphical analysis of the ensemble of solutions of specific incident states, by introducing 3-Distance Eigen Space and explain the underlying physical structure of APSCI and the effect of noise over the measurements.
Yeman, Helen; Nicholson, Tim; Matyska, Maria T; Pesek, Joseph J; Albert, Klaus
2013-01-01
The interactions of different analytes with monomeric and hydride-modified stationary phases have been investigated employing suspended-state NMR spectroscopy. The suspended-state high-resolution/magic-angle-spinning (1)H-NMR spectrum of an analyte in the presence of C(18) SP material shows a splitting into two sets of signals for the analyte molecule. One state reflects a closer interaction between analyte and C(18) -modified surface that results in an upfield shift and broader signal half-widths. This phenomenon suggests that the analyte exists in two environments. We report a systematic approach upon the investigation on the interaction in the interface of analyte, mobile phase, and modified silica through synthesis of differently modified silica with a gradual increase in surface coverage. The determination of the signal half-widths and chemical shifts revealed a relationship between the modification technique of the C(18) SPs and the chromatographic and NMR spectroscopic behavior. Increasing ligand density results in higher shielding of the NMR signals for the analyte in the "adsorbed" state. The measurement of spin-lattice relaxation times T(1) of the analyte molecule correlate NMR parameter together with separation behavior in HPLC. Furthermore, suspended-state and solid-state NMR measurements revealed different alkyl chain mobilities for the monomeric and hydride-modified SPs. © 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.
WEST,WP; BURRELL,KH; deGRASSIE,JS; DOYLE,EJ; GREENFIELD,CM; LASNIER,CJ; SNYDER,PB; ZENG,L
2003-08-01
OAK-B135 The quiescent H-mode (QH-mode) is an ELM-free and stationary state mode of operation discovered on DIII-D. This mode achieves H-mode levels of confinement and pedestal pressure while maintaining constant density and radiated power. The elimination of edge localized modes (ELMs) and their large divertor loads while maintaining good confinement and good density control is of interest to next generation tokamaks. This paper reports on the correlations found between selected parameters in a QH-mode database developed from several hundred DIII-D counter injected discharges. Time traces of key plasma parameters from a QH-mode discharge are shown. On DIII-D the negative going plasma current (a) indicates that the beam injection direction is counter to the plasma current direction, a common feature of all QH-modes. The D{sub {alpha}} time behavior (c) shows that soon after high powered beam heating (b) is applied, the discharge makes a transition to ELMing H-mode, then the ELMs disappear, indicating the start of the QH period that lasts for the remainder of the high power beam heating (3.5 s). Previously published work showing density and temperature profiles indicates that long-pulse, high-triangularity QH discharges develop an internal transport barrier in combination with the QH edge barrier. These discharges are known as quiescent, double-barrier discharges (QDB). The H-factor (d) and stored energy (c) rise then saturate at a constant level and the measured axial and minimum safety factors remain above 1.0 for the entire QH duration. During QDB operation the performance of the plasma can be very good, with {beta}{sub N}*H{sub 89L} product reaching 7 for > 10 energy confinement times. These discharges show promise that a stationary state can be achieved.
Khandokhin, P A; Mamaev, Yu A
2015-02-28
The Jones matrix method is used to study the optimal conditions for steady-state generation through intracavity frequency conversion in a solid-state laser under type-II phase matching based on a weakly anisotropic model of an active medium (amplitude and phase anisotropy) and a nonlinear element. The optimal rotation angles of the nonlinear element are found. (nonlinear optical phenomena)
Tau Aggregation Propensity Engrained in Its Solution State.
Eschmann, Neil A; Do, Thanh D; LaPointe, Nichole E; Shea, Joan-Emma; Feinstein, Stuart C; Bowers, Michael T; Han, Songi
2015-11-12
A peptide fragment of the human tau protein which stacks to form neat cross β-sheet fibrils, resembling that found in pathological aggregation, (273)GKVQIINKKLDL(284) (here "R2/WT"), was modified with a spin-label at the N-terminus. With the resulting peptide, R2/G273C-SL, we probed events at time scales spanning seconds to hours after aggregation is initiated using transmission electron microscopy (TEM), thioflavin T (THT) fluorescence, ion mobility mass spectrometry (IMMS), electron paramagnetic resonance (EPR), and Overhauser dynamic nuclear polarization (ODNP) to determine if deliberate changes to its conformational states and population in solution influence downstream propensity to form fibrillar aggregates. We find varying solution conditions by adding the osmolyte urea or TMAO, or simply using different buffers (acetate buffer, phosphate buffer, or water), produces significant differences in early monomer/dimer populations and conformations. Crucially, these characteristics of the peptide in solution state before aggregation is initiated dictate the fibril formation propensity after aggregation. We conclude the driving forces that accelerate aggregation, when heparin is added, do not override the subtle intra- or interprotein interactions induced by the initial solvent conditions. In other words, the balance of protein-protein vs protein-solvent interactions present in the initial solution conditions is a critical driving force for fibril formation.
Tau Aggregation Propensity Engrained in Its Solution State
2016-01-01
A peptide fragment of the human tau protein which stacks to form neat cross β-sheet fibrils, resembling that found in pathological aggregation, 273GKVQIINKKLDL284 (here “R2/WT”), was modified with a spin-label at the N-terminus. With the resulting peptide, R2/G273C-SL, we probed events at time scales spanning seconds to hours after aggregation is initiated using transmission electron microscopy (TEM), thioflavin T (THT) fluorescence, ion mobility mass spectrometry (IMMS), electron paramagnetic resonance (EPR), and Overhauser dynamic nuclear polarization (ODNP) to determine if deliberate changes to its conformational states and population in solution influence downstream propensity to form fibrillar aggregates. We find varying solution conditions by adding the osmolyte urea or TMAO, or simply using different buffers (acetate buffer, phosphate buffer, or water), produces significant differences in early monomer/dimer populations and conformations. Crucially, these characteristics of the peptide in solution state before aggregation is initiated dictate the fibril formation propensity after aggregation. We conclude the driving forces that accelerate aggregation, when heparin is added, do not override the subtle intra- or interprotein interactions induced by the initial solvent conditions. In other words, the balance of protein–protein vs protein–solvent interactions present in the initial solution conditions is a critical driving force for fibril formation. PMID:26484390
Excited State Absorption Measurements In Some Scintillator Dye Solutions
NASA Astrophysics Data System (ADS)
Dharamsi, A., N.; Jong, Shawpin; Hassam, A. B.
1986-11-01
Time-resolved excited state triplet-triplet absorption spectra were measured for solutions of 2,5 diphenyloxazole (PPO) and 2,1 napthyl, 5 phenyloxazole (aNPO) in several solvents. Concentration quenching effects due to excimer formation in nonaromatic solvents were observed. A numerical analysis of the experimental results yielded the rate constants for intersystem crossing, triplet quenching by 02, triplet self quenching and the formation of excimers.
Solid-State and Solution Characterization of Myricetin.
Franklin, Stephen J; Myrdal, Paul B
2015-12-01
Myricetin (MYR) is a natural compound that has been investigated as a chemopreventative agent. MYR has been shown to suppresses ultraviolet B (UVB)-induced cyclooxygenase-2 (COX-2) protein expression and reduce the incidence of UVB-induced skin tumors in mice. Despite MYR's promise as a therapeutic agent, minimal information is available to guide the progression of formulations designed for future drug development. Here, data is presented describing the solid-state and solution characterization of MYR. Investigation into the solid-state properties of MYR identified four different crystal forms, two hydrates (MYR I and MYR II) and two metastable forms (MYR IA and MYR IIA). From solubility studies, it was evident that all forms are very insoluble (<5 μg/ml) in pure water. MYR I was found to be the most stable form at 23, 35, and 56°C. Stability determination indicated that MYR undergoes rapid apparent first-order degradation under basic pH conditions, and that degradation was influenced by buffer species. Apparent first-order degradation was also seen when MYR was introduced to an oxidizing solution. Improved stability was achieved after introducing 0.1% antioxidants to the solution. MYR was found to have good stability following exposure to ultraviolet radiation (UVR), which is a consideration for topical applications. Finally, a partitioning study indicated that MYR possess a log P of 2.94 which, along with its solid-state properties, contributes to its poor aqueous solubility. Both the solid-state properties and solution stability of MYR are important to consider when developing future formulations.
NASA Astrophysics Data System (ADS)
Kang, Xiaoyan; He, Anqi; Guo, Ran; Chen, Jing; Zhai, Yanjun; Xu, Yizhuang; Noda, Isao; Wu, Jinguang
2016-11-01
The spectral behavior of a pair of 2D asynchronous spectra generated by using the double asynchronous orthogonal sample design (DAOSD) approach on a chemical system is investigated. Two solutes (P and Q) are dissolved in the solution and intermolecular interaction between P and Q is characterized. In this particular system, P occurs in two exchangeable states when it is dissolved in the solutions. Results on mathematical analysis and computer simulation demonstrated that interference unrelated to the intermolecular interaction can be completely removed. Hence the resultant 2D asynchronous spectra generated by using the DAOSD approach can reflect intermolecular interaction reliably. Moreover, properties of cross peaks in different regions of the pair of asynchronous spectra are discussed. In our previous works, cross peaks generated by using the DAOSD and relevant techniques reflect variations on peak position, bandwidth or absorptivity of the characteristic peaks of solutes caused by intermolecular interaction. However, we find that cross peak can still be produced even if intermolecular interaction do not bring about any changes on the characteristic peaks of solutes. Mathematical analysis demonstrates that cross peaks are related to the variations of chemical systems caused by intermolecular interaction at a network level.
Anharmonic densities of states: A general dynamics-based solution
Jellinek, Julius; Aleinikava, Darya
2016-06-07
Density of states is a fundamental physical characteristic that lies at the foundation of statistical mechanics and theoretical constructs that derive from them (e.g., kinetic rate theories, phase diagrams, and others). Even though most real physical systems are anharmonic, the vibrational density of states is customarily treated within the harmonic approximation, or with some partial, often limited, account for anharmonicity. The reason for this is that the problem of anharmonic densities of states stubbornly resisted a general and exact, yet convenient and straightforward in applications, solution. Here we formulate such a solution within both classical and quantum mechanics. It is based on actual dynamical behavior of systems as a function of energy and as observed, or monitored, on a chosen time scale, short or long. As a consequence, the resulting anharmonic densities of states are fully dynamically informed and, in general, time-dependent. As such, they lay the ground for formulation of new statistical mechanical frameworks that incorporate time and are ergodic, by construction, with respect to actual dynamical behavior of systems.
Stationary discrete solitons in a driven dissipative Bose-Hubbard chain
NASA Astrophysics Data System (ADS)
Naether, Uta; Quijandría, Fernando; García-Ripoll, Juan José; Zueco, David
2015-03-01
We demonstrate that stationary localized solutions (discrete solitons) exist in one-dimensional Bose-Hubbard lattices with gain and loss in a semiclassical regime. Stationary solutions, by definition, are robust and do not demand state preparation. Losses, unavoidable in experiments, are not a drawback, but a necessary ingredient for these modes to exist. The semiclassical calculations are complemented with their classical limit and dynamics based on a Gutzwiller ansatz. We argue that circuit quantum electrodynamic architectures are ideal platforms for realizing the physics developed here. Finally, within the input-output formalism, we explain how to experimentally access the different phases, including the solitons, of the chain.
NASA Astrophysics Data System (ADS)
Gabovich, Alexander M.; Li, Mai Suan; Szymczak, Henryk; Voitenko, Alexander I.
2014-05-01
Stationary Josephson current I c in symmetric and non-symmetric junctions involving d-wave superconductors with charge density waves (CDWs) was calculated. It was found that, if CDWs are weak or absent, there exists an approximate proportionality between I c and the product of superconducting order parameters in the electrodes (the law of corresponding states) for several factors affecting those quantities, such as the temperature, T, or one of the parameters characterizing the combined CDW superconducting phase (the degree of the Fermi surface dielectric gapping and the ratio between the parent superconducting and CDW order parameters). Otherwise, the dependences I c ( T) were shown to deviate from those in the absence of CDWs, and the relevant corresponding-state dependences from linearity, the deviations being especially strong at certain rotation angles of crystalline electodes with respect to the junction plane. Hence, making use of specially designed experimental setups and analyzing the I c ( T) and corresponding-state dependences, the existence of CDWs in cuprates and other non-conventional superconductors can be detected.
Peculiarities of state diagrams of aqueous solutions of cryoprotective agents.
Osetsky, Alexander I
2009-10-01
The phase transitions in aqueous solutions of glycerol and PEO-1500 within the temperature range of +30 to -150 degrees C have been studied using the methods of thermoplastic analysis and volumetric scanning tensodilatometry. We present the revealed phenomenon of cluster cyrystallization of these solutions as well as principles of describing this phenomenon using state diagrams, containing the intervals of concentration corresponding to the existence of amorphous and cryocolloid fractions. We note that for the cryocolloid fraction, a low temperature association of molecules of cryoprotective agents leads the formation of ice nanocrystals either close to or directly inside the aggregations. These fractions exist in cooled cryoprotective solutions near the vitrification temperatures of the liquid phase and may contribute to the initiation of damaging events in cryopreserved biological systems. Our data may be helpful in explaining the peculiarities observed during crystallization of cryoprotective solutions and may further contribute to a broader understanding of the principles of protection and protocol optimization of biological materials at temperatures approaching vitrification.
NASA Astrophysics Data System (ADS)
Yankovskii, A. P.
2017-03-01
The nonlinear problem of non-stationary heat conductivity of the layered anisotropic heat-sensitive shells was formulated taking into account the linear dependence of thermal-physical characteristics of the materials of phase compositions on the temperature. The initial-boundary-value problem is formulated in the dimensionless form, and four small parameters are identified: thermal-physical, characterizing the degree of heat sensitivity of the layer material; geometric, characterizing the relative thickness of the thin-walled structure, and two small Biot numbers on the front surfaces of shells. A sequential recursion of dimensionless equations is carried out, at first, using the thermalphysical small parameter, then, small Biot numbers and, finally, geometrical small parameter. The first type of recursion allowed us to linearize the problem of heat conductivity, and on the basis of two latter types of recursion, the outer asymptotic expansion of solution to the problem of non-stationary heat conductivity of the layered anisotropic non-uniform shells and plates under boundary conditions of the II and III kind and small Biot numbers on the facial surfaces was built, taking into account heat sensitivity of the layer materials. The resulting two-dimensional boundary problems were analyzed, and asymptotic properties of solutions to the heat conductivity problem were studied. The physical explanation was given to some aspects of asymptotic temperature decomposition.
Gravastar solutions with continuous pressures and equation of state
NASA Astrophysics Data System (ADS)
DeBenedictis, A.; Horvat, D.; Ilijić, S.; Kloster, S.; Viswanathan, K. S.
2006-04-01
We study the gravitational vacuum star (gravastar) configuration as proposed by Cattoen et al (2005 Class. Quantum Grav. 22 4189) in a model where the interior de Sitter spacetime segment is continuously extended to the exterior Schwarzschild spacetime. The multilayered structure of Mazur and Mottola (2001 Preprint gr-qc/0109035, 2003 Proc. 6th Workshop on Quantum Field Theory Under the Influence of External Conditions (Oklahoma) (Princeton, NJ: Rinton), Preprint gr-qc/0405111 (2004 Proc. Natl Acad. Sci. 111 9545) is replaced by a continuous stress-energy tensor at the price of introducing anisotropy in the (fluid) model of the gravastar. Either with an ansatz for the equation of state connecting the radial pr and tangential pt pressure or with a calculated equation of state with non-homogeneous energy/fluid density, solutions are obtained which in all aspects satisfy the conditions expected for an anisotropic gravastar (Cattoen et al 2005 Class. Quantum Grav. 22 4189). Certain energy conditions have been shown to be obeyed and a polytropic equation of state has been derived. Stability of the solution with respect to possible axial perturbation is shown to hold.
Steady-State Solution of a Flexible Wing
NASA Technical Reports Server (NTRS)
Karkehabadi, Reza; Chandra, Suresh; Krishnamurthy, Ramesh
1997-01-01
A fluid-structure interaction code, ENSAERO, has been used to compute the aerodynamic loads on a swept-tapered wing. The code has the capability of using Euler or Navier-Stokes equations. Both options have been used and compared in the present paper. In the calculation of the steady-state solution, we are interested in knowing how the flexibility of the wing influences the lift coefficients. If the results of a flexible wing are not affected by the flexibility of the wing significantly, one could consider the wing to be rigid and reduce the problem from fluid-structure interaction to a fluid problem.
Schauff, Siri; Friebolin, Volker; Grynbaum, Marc David; Meyer, Christoph; Albert, Klaus
2007-11-01
The separation process in reversed-phase high-performance liquid chromatography employing C18 phases is mainly due to hydrophobic interactions. The separation of tocopherol isomers, exhibited by the C30 phases, however, is additionally driven by shape selectivity. This phenomenon is investigated by suspended-state nuclear magnetic resonance spectroscopy using the saturation transfer difference technique, which was originally introduced to study protein-ligand interactions. The interaction strength between beta-/gamma-tocopherol and three different stationary phases was estimated qualitatively. The nuclear magnetic resonance data are compared to chromatographic data, and a similar mode of interaction between the analytes and the stationary phases is elucidated.
Moulds, Rebecca J; Buntine, Mark A; Lawrance, Warren D
2004-09-08
The potential energy surfaces of the van der Waals complexes benzene-Ar and p-difluorobenzene-Ar have been investigated at the second-order Møller-Plesset (MP2) level of theory with the aug-cc-pVDZ basis set. Calculations were performed with unconstrained geometry optimization for all stationary points. This study has been performed to elucidate the nature of a conflict between experimental results from dispersed fluorescence and velocity map imaging (VMI). The inconsistency is that spectra for levels of p-difluorobenzene-Ar and -Kr below the dissociation thresholds determined by VMI show bands where free p-difluorobenzene emits, suggesting that dissociation is occurring. We proposed that the bands observed in the dispersed fluorescence spectra are due to emission from states in which the rare gas atom orbits the aromatic chromophore; these states are populated by intramolecular vibrational redistribution from the initially excited level [S. M. Bellm, R. J. Moulds, and W. D. Lawrance, J. Chem. Phys. 115, 10709 (2001)]. To test this proposition, stationary points have been located on both the benzene-Ar and p-difluorobenzene-Ar potential energy surfaces (PESs) to determine the barriers to this orbiting motion. Comparison with previous single point CCSD(T) calculations of the benzene-Ar PES has been used to determine the amount by which the barriers are overestimated at the MP2 level. As there is little difference in the comparable regions of the benzene-Ar and p-difluorobenzene-Ar PESs, the overestimation is expected to be similar for p-difluorobenzene-Ar. Allowing for this overestimation gives the barrier to movement of the Ar atom around the pDFB ring via the valley between the H atoms as < or = 204 cm(-1) in S0 (including zero point energy). From the estimated change upon electronic excitation, the corresponding barrier in S1 is estimated to be < or = 225 cm(-1). This barrier is less than the 240 cm(-1) energy of 30(2), the vibrational level for which the
Wikberg, Erika; Sparrman, Tobias; Viklund, Camilla; Jonsson, Tobias; Irgum, Knut
2011-09-23
2H NMR has been used as a tool for probing the state of water in hydrophilic stationary phases for liquid chromatography at temperatures between -80 and +4 °C. The fraction of water that remained unfrozen in four different neat silicas with nominal pore sizes between 60 and 300 Å, and in silicas with polymeric sulfobetaine zwitterionic functionalities prepared in different ways, could be determined by measurements of the line widths and temperature-corrected integrals of the 2H signals. The phase transitions detected during thawing made it possible to estimate the amount of non-freezable water in each phase. A distinct difference was seen between the neat and modified silicas tested. For the neat silicas, the relationship between the freezing point depression and their pore size followed the expected Gibbs-Thomson relationship. The polymeric stationary phases were found to contain considerably higher amounts of non-freezable water compared to the neat silica, which is attributed to the structural effect that the sulfobetaine polymers have on the water layer close to the stationary phase surface. The sulfobetaine stationary phases were used alongside the 100 Å silica to separate a number of polar compounds in hydrophilic interaction (HILIC) mode, and the retention characteristics could be explained in terms of the surface water structure, as well as by the porous properties of the stationary phases. This provides solid evidence supporting a partitioning mechanism, or at least of the existence of an immobilized layer of water into which partitioning could be occurring.
NASA Astrophysics Data System (ADS)
Rassi, Erik M.; Codd, Sarah L.; Seymour, Joseph D.
2011-01-01
Flow in porous media and the resultant hydrodynamics are important in fields including but not limited to the hydrology, chemical, medical and petroleum industries. The observation and understanding of the hydrodynamics in porous media are critical to the design and optimal utilization of porous media, such as those seen in trickle-bed reactors, medical filters, subsurface flows and carbon sequestration. Magnetic resonance (MR) provides for a non-invasive technique that can probe the hydrodynamics on pore and bulk scale lengths; many previous works have characterized fully saturated porous media, while rapid MR imaging (MRI) methods in particular have previously been applied to partially saturated flows. We present time- and ensemble-averaged MR measurements to observe the effects on a bead pack partially saturated with air under flowing water conditions. The 10 mm internal diameter bead pack was filled with 100 μm borosilicate glass beads. Air was injected into the bead pack as water flowed simultaneously through the sample at 25 ml h-1. The initial partially saturated state was characterized with MRI density maps, free induction decay (FID) experiments, propagators and velocity maps before the water flow rate was increased incrementally from 25 to 500 ml h-1. After the maximum flow rate of 500 ml h-1, the MRI density maps, FID experiments, propagators and velocity maps were repeated and compared to the data taken before the maximum flow rate. This work shows that a partially saturated single-phase flow has global flow dynamics that return to characteristic flow statistics once a steady-state high flow rate has been reached. This high flow rate pushed out a significant amount of the air in the bead pack and caused the return of a preferential flow pattern. Velocity maps indicated that local flow statistics were not the same for the before and after blow out conditions. It has been suggested and shown previously that a flow pattern can return to
NASA Astrophysics Data System (ADS)
Antoine, Xavier; Levitt, Antoine; Tang, Qinglin
2017-08-01
We propose a preconditioned nonlinear conjugate gradient method coupled with a spectral spatial discretization scheme for computing the ground states (GS) of rotating Bose-Einstein condensates (BEC), modeled by the Gross-Pitaevskii Equation (GPE). We first start by reviewing the classical gradient flow (also known as imaginary time (IMT)) method which considers the problem from the PDE standpoint, leading to numerically solve a dissipative equation. Based on this IMT equation, we analyze the forward Euler (FE), Crank-Nicolson (CN) and the classical backward Euler (BE) schemes for linear problems and recognize classical power iterations, allowing us to derive convergence rates. By considering the alternative point of view of minimization problems, we propose the preconditioned steepest descent (PSD) and conjugate gradient (PCG) methods for the GS computation of the GPE. We investigate the choice of the preconditioner, which plays a key role in the acceleration of the convergence process. The performance of the new algorithms is tested in 1D, 2D and 3D. We conclude that the PCG method outperforms all the previous methods, most particularly for 2D and 3D fast rotating BECs, while being simple to implement.
Stationary shapes of deformable particles moving at low Reynolds numbers
NASA Astrophysics Data System (ADS)
Boltz, Horst-Holger; Kierfeld, Jan
2016-11-01
We introduce an iterative solution scheme in order to calculate stationary shapes of deformable elastic capsules which are steadily moving through a viscous fluid at low Reynolds numbers. The iterative solution scheme couples hydrodynamic boundary integral methods and elastic shape equations to find the stationary axisymmetric shape and the velocity of an elastic capsule moving in a viscous fluid governed by the Stokes equation. We use this approach to systematically study dynamical shape transitions of capsules with Hookean stretching and bending energies and spherical resting shape sedimenting under the influence of gravity or centrifugal forces. We find three types of possible axisymmetric stationary shapes for sedimenting capsules with fixed volume: a pseudospherical state, a pear-shaped state, and buckled shapes. Capsule shapes are controlled by two dimensionless parameters, the Föppl-von-Kármán number characterizing the elastic properties and a Bond number characterizing the driving force. For increasing gravitational force the spherical shape transforms into a pear shape. For very large bending rigidity (very small Föppl-von-Kármán number) this transition is discontinuous with shape hysteresis. The corresponding transition line terminates, however, in a critical point, such that the discontinuous transition is not present at typical Föppl-von-Kármán numbers of synthetic capsules. In an additional bifurcation, buckled shapes occur upon increasing the gravitational force.
Electronic states of graphene nanoribbons and analytical solutions
Wakabayashi, Katsunori; Sasaki, Ken-ichi; Nakanishi, Takeshi; Enoki, Toshiaki
2010-01-01
Graphene is a one-atom-thick layer of graphite, where low-energy electronic states are described by the massless Dirac fermion. The orientation of the graphene edge determines the energy spectrum of π-electrons. For example, zigzag edges possess localized edge states with energies close to the Fermi level. In this review, we investigate nanoscale effects on the physical properties of graphene nanoribbons and clarify the role of edge boundaries. We also provide analytical solutions for electronic dispersion and the corresponding wavefunction in graphene nanoribbons with their detailed derivation using wave mechanics based on the tight-binding model. The energy band structures of armchair nanoribbons can be obtained by making the transverse wavenumber discrete, in accordance with the edge boundary condition, as in the case of carbon nanotubes. However, zigzag nanoribbons are not analogous to carbon nanotubes, because in zigzag nanoribbons the transverse wavenumber depends not only on the ribbon width but also on the longitudinal wavenumber. The quantization rule of electronic conductance as well as the magnetic instability of edge states due to the electron–electron interaction are briefly discussed. PMID:27877361
TOPICAL REVIEW Electronic states of graphene nanoribbons and analytical solutions
NASA Astrophysics Data System (ADS)
Wakabayashi, Katsunori; Sasaki, Ken-ichi; Nakanishi, Takeshi; Enoki, Toshiaki
2010-10-01
Graphene is a one-atom-thick layer of graphite, where low-energy electronic states are described by the massless Dirac fermion. The orientation of the graphene edge determines the energy spectrum of π-electrons. For example, zigzag edges possess localized edge states with energies close to the Fermi level. In this review, we investigate nanoscale effects on the physical properties of graphene nanoribbons and clarify the role of edge boundaries. We also provide analytical solutions for electronic dispersion and the corresponding wavefunction in graphene nanoribbons with their detailed derivation using wave mechanics based on the tight-binding model. The energy band structures of armchair nanoribbons can be obtained by making the transverse wavenumber discrete, in accordance with the edge boundary condition, as in the case of carbon nanotubes. However, zigzag nanoribbons are not analogous to carbon nanotubes, because in zigzag nanoribbons the transverse wavenumber depends not only on the ribbon width but also on the longitudinal wavenumber. The quantization rule of electronic conductance as well as the magnetic instability of edge states due to the electron-electron interaction are briefly discussed.
NASA Astrophysics Data System (ADS)
Manard, Benjamin T.; Marcus, R. Kenneth
2012-08-01
Capillary-channeled polymer (C-CP) fibers are employed in a micropipette tip format to affect a stationary phase for the solid phase extraction (SPE) of proteins from buffer solutions prior to MALDI-MS analysis. Proteins readily adsorb to the polypropylene (PP) C-CP fibers while buffer species are easily washed off the tips using DI-H2O. Elution of the solutes is achieved with an aliquot of 50:50 ACN:H2O, which is compatible with the subsequent spotting on the MALDI target with the matrix solution. Lysozyme and cytochrome c are used as test species, with a primary buffer composition of 100 mM Tris-HCl. In this case, direct MALDI-MS produces no discernible protein signals. SPE on the C-CP fibers yields high fidelity mass spectra for 1 μL sample volumes. Limits of detection for cytochrome c in 100 mM Tris-HCl are on the order of 40 nM. Extraction of cytochrome c from buffer concentrations of up to 1 M Tris-HCl, provides signal recoveries that are suppressed by only ~50 % versus neat protein solutions. Finally, extraction of 3.1 μM cytochrome c from a synthetic urine matrix exhibits excellent recovery.
Ground state solutions for semilinear time-harmonic Maxwell equations
NASA Astrophysics Data System (ADS)
Tang, Xianhua; Qin, Dongdong
2016-04-01
This paper is concerned with the time-harmonic semilinear Maxwell equation: ∇ × (∇ × u) + λu = f(x, u) in Ω with the boundary condition ν × u = 0 on ∂Ω, where Ω ⊂ ℝ3 is a simply connected, smooth, bounded domain with connected boundary and ν : ∂Ω → ℝ3 is the exterior normal. Here ∇ × denotes the curl operator in ℝ3 and the boundary condition holds when Ω is surrounded by a perfect conductor. By using the generalized Nehari manifold method due to Szulkin and Weth [Handbook of Nonconvex Analysis and Applications (International Press, Somerville, 2010), pp. 597-632] and some new techniques, existence of ground state solutions for above equation is established under some generic conditions on f.
Extended law of corresponding states for protein solutions
NASA Astrophysics Data System (ADS)
Platten, Florian; Valadez-Pérez, Néstor E.; Castañeda-Priego, Ramón; Egelhaaf, Stefan U.
2015-05-01
The so-called extended law of corresponding states, as proposed by Noro and Frenkel [J. Chem. Phys. 113, 2941 (2000)], involves a mapping of the phase behaviors of systems with short-range attractive interactions. While it has already extensively been applied to various model potentials, here we test its applicability to protein solutions with their complex interactions. We successfully map their experimentally determined metastable gas-liquid binodals, as available in the literature, to the binodals of short-range square-well fluids, as determined by previous as well as new Monte Carlo simulations. This is achieved by representing the binodals as a function of the temperature scaled with the critical temperature (or as a function of the reduced second virial coefficient) and the concentration scaled by the cube of an effective particle diameter, where the scalings take into account the attractive and repulsive contributions to the interaction potential, respectively. The scaled binodals of the protein solutions coincide with simulation data of the adhesive hard-sphere fluid. Furthermore, once the repulsive contributions are taken into account by the effective particle diameter, the temperature dependence of the reduced second virial coefficients follows a master curve that corresponds to a linear temperature dependence of the depth of the square-well potential. We moreover demonstrate that, based on this approach and cloud-point measurements only, second virial coefficients can be estimated, which we show to agree with values determined by light scattering or by Derjaguin-Landau-Verwey-Overbeek (DLVO)-based calculations.
Steady state solutions to dynamically loaded periodic structures
NASA Technical Reports Server (NTRS)
Kalinowski, A. J.
1980-01-01
The general problem of solving for the steady state (time domain) dynamic response (i.e., NASTRAN rigid format-8) of a general elastic periodic structure subject to a phase difference loading of the type encountered in traveling wave propagation problems was studied. Two types of structural configurations were considered; in the first type, the structure has a repeating pattern over a span that is long enough to be considered, for all practical purposes, as infinite; in the second type, the structure has structural rotational symmetry in the circumferential direction. The theory and a corresponding set of DMAP instructions which permits the NASTRAN user to automatically alter the rigid format-8 sequence to solve the intended class of problems are presented. Final results are recovered as with any ordinary rigid format-8 solution, except that the results are only printed for the typical periodic segment of the structure. A simple demonstration problem having a known exact solution is used to illustrate the implementation of the procedure.
Crystallization of probucol from solution and the glassy state.
Kawakami, Kohsaku; Ohba, Chie
2017-01-30
Crystallization of probucol (PBL) from both solution and glassy solid state was investigated. In the crystallization study from solution, six solvents and three methods, i.e., evaporation, addition of a poor solvent, and cooling on ice, were used to obtain various crystal forms. In addition to common two crystal forms (forms I and II), two further forms (forms III and cyclohexane-solvate) were found in this study, and their thermodynamic relationships were determined. Forms I and II are likely to be enantiotropically related with thermodynamic transition temperature below 5°C. Isothermal crystallization studies revealed that PBL glass initially crystallized into form III between 25 and 50°C, and then transformed to form I. The isothermal crystallization appears to be a powerful option to find uncommon crystal forms. The crystallization of PBL was identified to be pressure controlled, thus the physical stability of PBL glass is higher than that of typical compounds. Copyright © 2016 Elsevier B.V. All rights reserved.
NEXAFS Chemical State and Bond Lengths of p-Aminobenzoic Acid in Solution and Solid State
NASA Astrophysics Data System (ADS)
Stevens, J. S.; Gainar, A.; Suljoti, E.; Xiao, J.; Golnak, R.; Aziz, E. F.; Schroeder, S. L. M.
2016-05-01
Solid-state and solution pH-dependent NEXAFS studies allow direct observation of the electronic state of para-aminobenzoic acid (PABA) as a function of its chemical environment, revealing the chemical state and bonding of the chemical species. Variations in the ionization potential (IP) and 1s→π* resonances unequivocally identify the chemical species (neutral, cationic, or anionic) present and the varying local environment. Shifts in σ* shape resonances relative to the IP in the NEXAFS spectra vary with C-N bond length, and the important effect of minor alterations in bond length is confirmed with nitrogen FEFF calculations, leading to the possibility of bond length determination in solution.
Van Gorder, Robert A
2013-04-01
We provide a formulation of the local induction approximation (LIA) for the motion of a vortex filament in the Cartesian reference frame (the extrinsic coordinate system) which allows for scaling of the reference coordinate. For general monotone scalings of the reference coordinate, we derive an equation for the planar solution to the derivative nonlinear Schrödinger equation governing the LIA. We proceed to solve this equation perturbatively in small amplitude through an application of multiple-scales analysis, which allows for accurate computation of the period of the planar vortex filament. The perturbation result is shown to agree strongly with numerical simulations, and we also relate this solution back to the solution obtained in the arclength reference frame (the intrinsic coordinate system). Finally, we discuss nonmonotone coordinate scalings and their application for finding self-intersections of vortex filaments. These self-intersecting vortex filaments are likely unstable and collapse into other structures or dissipate completely.
States leverage telepsychiatry solutions to ease ED crowding, accelerate care.
2015-02-01
Many states are having success turning to telepsychiatry-based solutions to connect mental health patients with needed care while also decompressing crowded EDs. Just one year into a statewide telepsychiatry initiative in North Carolina (NC-STeP), administrators say the approach has saved as much as $7 million, and hospital demand for the service is higher than anticipated. In Texas, mental health emergency centers (MHEC) that use telepsychiatry to connect patients in rural areas with needed psychiatric care are freeing up EDs to focus on medical care. In just 11 months, 91 North Carolina hospitals have at least started the process to engage in NC-STeP. Much of the savings from NC-STeP come from involuntary commitment orders being overturned as a result of the telepsychiatry consults, reducing the need for expensive inpatient care. Implementing NC-STeP has involved multiple hurdles including credentialing difficulties and technical/firewall challenges. The Texas model provides 24/7 availability of psychiatrists via telemedicine through a network of MHECs. In-person staff at the MHECs perform basic screening tests and blood draws so that medical clearance can be achieved without the need for an ED visit in most cases. Funding for the MHECs comes from the state, hospitals in the region, and local governmental authorities that reap savings or benefits from the initiative.
Marenich, Aleksandr V; Cramer, Christopher J; Truhlar, Donald G
2013-08-13
We present a new kind of treatment of the solute-solvent dispersion contribution to the free energy of solvation using a solvation model with state-specific polarizability (SMSSP). To evaluate the solute-solvent dispersion contribution, the SMSSP model utilizes only two descriptors, namely, the spherically averaged dipole polarizability of the solute molecule (either in its ground or excited electronic state) and the refractive index of the solvent. The model was parametrized over 643 ground-state solvation free energy data for 231 solutes in 14 nonpolar, non-hydrogen-bonding solvents. We show that the SMSSP model is applicable to solutes in both the ground and the excited electronic state. For example, in comparison to available experimental data, the model yields qualitatively accurate predictions of the solvatochromic shifts for a number of systems where solute-solvent dispersion is the dominant contributor to the shift.
NASA Astrophysics Data System (ADS)
Masalov, Vladimir M.; Vasilyeva, Natalia A.; Manomenova, Vera L.; Zhokhov, Andrei A.; Rudneva, Elena B.; Voloshin, Alexey E.; Emelchenko, Gennadi A.
2017-10-01
The technique and the scheme of the system for growing single crystals, including complex mixed composition, under stationary conditions of supercooling and forced convection of aqueous solution were described. Solubility in water of various compositions of K2CoxNi1-x(SO4)2·6H2O (KCNSH) and the dependence of Co content in the KCNSH crystal of Co concentration in the saline part of aqueous solutions of KCNSH have been measured in the temperature range of 30-70 °C. It was found that the growth sectors {0 0 1} and {1 1 0} differ in Ni and Co contents. The Ni/Co ratio is dependent on the value of solution supersaturation. The optical transmission spectra of crystals grown showed high transmittance in the UV region of the spectrum and the almost complete absorption of light in the visible spectrum. It is concluded that the crystals grown can be used as efficient UV filters.
Dynamical and stationary properties of on-line learning from finite training sets.
Luo, Peixun; Wong, K Y Michael
2003-01-01
The dynamical and stationary properties of on-line learning from finite training sets are analyzed by using the cavity method. For large input dimensions, we derive equations for the macroscopic parameters, namely, the student-teacher correlation, the student-student autocorrelation and the learning force fluctuation. This enables us to provide analytical solutions to Adaline learning as a benchmark. Theoretical predictions of training errors in transient and stationary states are obtained by a Monte Carlo sampling procedure. Generalization and training errors are found to agree with simulations. The physical origin of the critical learning rate is presented. Comparison with batch learning is discussed throughout the paper.
Dynamical and stationary properties of on-line learning from finite training sets
NASA Astrophysics Data System (ADS)
Luo, Peixun; Michael Wong, K. Y.
2003-01-01
The dynamical and stationary properties of on-line learning from finite training sets are analyzed by using the cavity method. For large input dimensions, we derive equations for the macroscopic parameters, namely, the student-teacher correlation, the student-student autocorrelation and the learning force fluctuation. This enables us to provide analytical solutions to Adaline learning as a benchmark. Theoretical predictions of training errors in transient and stationary states are obtained by a Monte Carlo sampling procedure. Generalization and training errors are found to agree with simulations. The physical origin of the critical learning rate is presented. Comparison with batch learning is discussed throughout the paper.
Mitavskiy, Boris; Cannings, Chris
2009-01-01
The evolutionary algorithm stochastic process is well-known to be Markovian. These have been under investigation in much of the theoretical evolutionary computing research. When the mutation rate is positive, the Markov chain modeling of an evolutionary algorithm is irreducible and, therefore, has a unique stationary distribution. Rather little is known about the stationary distribution. In fact, the only quantitative facts established so far tell us that the stationary distributions of Markov chains modeling evolutionary algorithms concentrate on uniform populations (i.e., those populations consisting of a repeated copy of the same individual). At the same time, knowing the stationary distribution may provide some information about the expected time it takes for the algorithm to reach a certain solution, assessment of the biases due to recombination and selection, and is of importance in population genetics to assess what is called a "genetic load" (see the introduction for more details). In the recent joint works of the first author, some bounds have been established on the rates at which the stationary distribution concentrates on the uniform populations. The primary tool used in these papers is the "quotient construction" method. It turns out that the quotient construction method can be exploited to derive much more informative bounds on ratios of the stationary distribution values of various subsets of the state space. In fact, some of the bounds obtained in the current work are expressed in terms of the parameters involved in all the three main stages of an evolutionary algorithm: namely, selection, recombination, and mutation.
NASA Astrophysics Data System (ADS)
Vasil'eva, V. I.; Vorob'eva, E. A.
2012-11-01
The conjugated diffusion transport of amino acid and mineral salt through a profiled sulfo group cation exchange membrane that simulates the extraction of amino acid from wash waters of microbiological production containing mineral components not used in synthesis is studied. The competitive nature of the conjugation of flows resulting in a decrease in the rate of the mass transfer of components and their separation factor is established from a comparative analysis of experimental data on the diffusion transfer of phenylalanine and sodium chloride in the form of hydrogen from individual and mixed solutions through a profiled sulfo group cation exchange membrane. The range of concentrations and the ratio of components in solution corresponding to the effective separation of phenylalanine and sodium chloride are determined.
NASA Astrophysics Data System (ADS)
Kuznetsov, V. I.; Pramanik, Sourav; Gerasimenko, A. B.; Chakrabarti, Nikhil
2017-02-01
The stability properties of a non-neutral plasma diode [Pramanik et al., Phys. Plasmas 23, 103105 (2016)] have been investigated for the stationary states taking arbitrary value of the neutralization parameter. A constant magnetic field is also assumed to be applied externally along the transverse direction. The (η, ɛ)-diagram technique is used to study the stability features of all types of solutions with respect to small aperiodic perturbations. Employing the first order perturbation theory, a relevant dispersion relation has been derived and analyzed for the regimes when electrons are not turned around by the magnetic field. These regimes of solutions belong to the "Normal C branch" and "C-overlap branch" of the "emitter field strength vs. diode gap"-diagrams. With the help of this dispersion relation, both aperiodic and oscillatory stability properties of such solutions have been presented.
NASA Astrophysics Data System (ADS)
Yen, C. T.; Tiller, W. A.
1992-03-01
A one-dimensional mathematical analysis is made of the redistribution of solute which occurs during crystal growth from a convected melt. In this analysis, the important contribution from lateral melt convection to one-dimensional solute redistribution analysis is taken into consideration via an annihilation/creation term in the one-dimensional solute transport equation. Calculations of solute redistribution under steady-state conditions have been carried out analytically. It is found that this new solute redistribution model overcomes several weaknesses that occur when applying the Burton, Prim and Slichter solute segregation equation (1953) in real melt growth situations. It is also found that, with this correction, the diffusion coefficients for solute's in liquid silicon are now found to be in the same range as other liquid metal diffusion coefficients.
Solid state lighting for the developing world: the only solution
NASA Astrophysics Data System (ADS)
Peon, Rudolfo; Doluweera, Ganesh; Platonova, Inna; Irvine-Halliday, Dave; Irvine-Halliday, Gregor
2005-09-01
Approximately two billion people, one third of humanity still has no access to electricity, and thus relies on fuel-based lighting, a dangerous alternative of last resort that is unhealthy, expensive, and offers very poor levels of illumination. This lack of light makes it difficult to perform most evening activities including studies by children and adults alike and therefore represents a significant barrier to human development. Over the past five years The Light Up The World Foundation (LUTW) has pioneered the use of the white light emitting diode (WLED) as an alternative home lighting solution, bringing clean, affordable light to thousands of non-electrified homes around the world. The information presented herein is intended to increase awareness of the enormous potential possessed by this emergent technology, "Solid State Lighting" (SSL), to improve the quality of life of millions of people around the world. The feasibility of its implementation is demonstrated with results from comprehensive field experience and laboratory research work. The mutual economic, social and environmental benefits for both stakeholders and SSL suppliers are discussed. Strategies conducive to the dissemination of this technology throughout the developing world are also presented.
Burdette, Carolyn Q; Marcus, R Kenneth
2013-02-21
Polypropylene (PP) capillary-channeled polymer (C-CP) fibers are applied for solid phase extraction (SPE) of proteins from aqueous buffer solutions using a micropipette tip-based format. A process was developed in which centrifugation is used as the moving force for solution passage in the loading/washing steps instead of the previously employed manual aspiration. The complete procedure requires ~15 minutes, with the number of samples run in parallel limited only by the capacity of the centrifuge. The method performance was evaluated based on adsorption and elution characteristics of several proteins (cytochrome c, lysozyme, myoglobin, and glucose oxidase) from 150 mM phosphate buffered saline (PBS) solutions. Protein concentration ranges of ~2 to 100 μg mL(-1) were employed and the recovery characteristics determined through UV-Vis absorbance spectrophotometry for protein quantification. The protein loading capacities across the range of proteins was ~1.5 μg for the 5 mg fiber tips. Average recoveries from PBS were determined for each protein sample; cytochrome c ~86%, lysozyme ~80%, myoglobin ~86%, and glucose oxidase ~89%. Recoveries from more complex matrices, synthetic urine and synthetic saliva, were determined to be ~90%. A 10× dilution study for a fixed 1 μg protein application yielded 94 ± 3.2% recoveries. The C-CP tips provided significantly higher recoveries for myoglobin in a 150 mM PBS matrix in comparison to a commercially available protein SPE product, with the added advantages of low cost, rapid processing, and reusability.
Gas fluidization of solids in a stationary liquid
Gabor, J.D.; Cassulo, J.C.; Fountain, D.; Bingle, J.D.
1984-11-01
Critical gas flow rates were measured for fluidizing initially static beds of particles and for settling of fluidized beds in a stationary pool of liquid. Experiments were conducted with beds of glass, nickel and UO/sub 2/ particles ranging in size from 11 to 548 ..mu..m in pools of water, ethanol, Freon-113 and water-glycerine solutions. Beds of particles smaller than 328 ..mu..m were fluidized by a mechanism of individual particles being carried off of walls of channels in the bed, and beds of particles larger than 328 ..mu..m slugged before breaking up to a fluidized state. The data were empirically correlated.
Asymptotic Steady-state Solution to a Bow Shock with an Infinite Mach Number
NASA Astrophysics Data System (ADS)
Yalinewich, Almog; Sari, Re'em
2016-08-01
The problem of a cold gas flowing past a stationary obstacle is considered. We study the bow shock that forms around the obstacle and show that at large distances from the obstacle the shock front forms a parabolic solid of revolution. The profiles of the hydrodynamic variables in the interior of the shock are obtained by solution of the hydrodynamic equations in parabolic coordinates. The results are verified with a hydrodynamic simulation. The drag force on the obstacle is also calculated. Finally, we use these results to model the bow shock around an isolated neutron star.
2011-10-01
covariance matrix, for example, is out of the question. Usually, the method of choice for computing statistics is Markov chain Monte Carlo (MCMC) [28...normalized constant (which is not required by Markov chain Monte Carlo methods), d (m) = πlike × πprior. Denote J = − log d (m), then we have J = 1...23] Montserrat Fuentes and Richard L. Smith, A new class of nonstationary spatial models, tech. report, North Carolina state University, 2001. [24] D
Ayano, Eri; Okada, Yuji; Sakamoto, Chikako; Kanazawa, Hideko; Kikuchi, Akihiko; Okano, Teruo
2006-06-30
We investigated a thermo-sensitive polymer, poly(N-isopropylacrylamide) (PNIPAAm), which is the basis of an HPLC stationary phase. We prepared a PNIPAAm terminally-modified surface. In this study, we investigated the effect of PNIPAAm on the surface of a stationary phase on separation based on changes of the retention time with the temperature step gradient. As the temperature changed the surface property of the stationary phase switched from hydrophilic to hydrophobic. The retention on the polymer-modified stationary phase remarkably changed upon changing the temperature. Using a column packed with PNIPAAm-modified silica, the separation of steroids was carried out by changing the temperature. With increasing temperature, an increased interaction between solutes and PNIPAAm-grafted surfaces of the stationary phases was observed. A temperature-dependent resolution of steroids was achieved using only water as a mobile phase. The PNIPAAm-modified surface of the stationary phase exhibited temperature-controlled hydrophilic-hydrophobic changes. The drastic and reversible surface hydrophilic-hydrophobic property alteration for PNIPAAm terminally-grafted surfaces should be due to rapid changes in the polymer hydration state around the polymer's transition temperature. A solvent gradient elution-like effect could be achieved with a single mobile phase by programmed temperature changes during chromatographic runs. This system should be highly useful to control the function and property of the stationary phase for HPLC only by changing the temperature with an aqueous solvent.
Effect of solution saturation state and temperature on diopside dissolution
Dixit, Suvasis; Carroll, Susan A
2007-01-01
Steady-state dissolution rates of diopside are measured as a function of solution saturation state using a titanium flow-through reactor at pH 7.5 and temperature ranging from 125 to 175°C. Diopside dissolved stoichiometrically under all experimental conditions and rates were not dependent on sample history. At each temperature, rates continuously decreased by two orders of magnitude as equilibrium was approached and did not exhibit a dissolution plateau of constant rates at high degrees of undersaturation. The variation of diopside dissolution rates with solution saturation can be described equally well with a ion exchange model based on transition state theory or pit nucleation model based on crystal growth/dissolution theory from 125 to 175°C. At 175°C, both models over predict dissolution rates by two orders of magnitude indicating that a secondary phase precipitated in the experiments. The ion exchange model assumes the formation of a Si-rich, Mg-deficient precursor complex. Lack of dependence of rates on steady-state aqueous calcium concentration supports the formation of such a complex, which is formed by exchange of protons for magnesium ions at the surface. Fit to the experimental data yields R a t e ( m o l d i o p s i d e c m − 2 s − 1 ) = k × 10 − E a / 2.303 R T ( a H + 2 a M g 2 + ) n MathType@MTEF@5@5@+=feaafiart1ev1aaatCvAUfKttLearuWrP9MDH5MBPbIqV92AaeXatLxBI9gBaebbnrfifHhDYfgasaacH8akY=wiFfYdH8Gipec8Eeeu0xXdbba9frFj0=OqFfea0dXdd9vqai=hGuQ8kuc9pgc9s8qqaq=dirpe0xb9q8qiLsFr0=vr0=vr0dc8meaabaqaciaacaGaaeqabaqabeGadaaakeaaieaacqWFsbGucqWFHbqycqWF0baDcqWFLbqzcqqGGaaicqGGOaakcqWFTbqBcqWFVbWBcqWFSbaBcqWFGaaicqWFKbazcqWFPbqAcqWFVbWBcqWFWbaCcqWFZbWCcqWFPbqAcqWFKbazcqWFLbqzcqWFGaaicqWFJbWycqWFTbqBdaahaaWcbeqaaiabgkHiTiabikdaYaaakiab=bcaGiab=nhaZnaaCaaaleqabaGaeyOeI0IaeGymaedaaOGaeiykaKIaeyypa0Jaem4AaSMaey41aqRaeeymaeJaeeimaaZaaWbaaSqabeaacqGHsislcqWGfbqrdaWgaaadbaGaemyyaegabeaaliabc+caViabikdaYiabc6caUiabioda
Evidence for Two New Solution States of Ubiquitin by IMS–MS Analysis
2015-01-01
Ion mobility spectrometry coupled with mass spectrometry (IMS–MS) is used to investigate the populations of different states for ubiquitin in water:methanol solutions. In these experiments, ubiquitin is electrosprayed from 20 water:methanol (100:0 to 5:95, pH = 2) solutions, ranging from native to denaturing conditions. With an increased percentage of methanol in solution, ubiquitin ions ([M + 7H]7+ to [M + 12H]12+) show substantial variations in both charge state distributions and ion mobility distributions. Analysis of these data provides evidence for the existence of five ubiquitin states in solution: the native N state, favored in solutions of 100:0 to 70:30 water:methanol for the +7 and +8 charge states; the more helical A state and a new closely related A′ state, favored in solutions of 70:30 to 5:95 water:methanol for the +9 to +12 charge states; the unfolded U state, populated in 40:60 to 5:95 water:methanol solutions for the +8 to +10 and +12 charge states; and a new low-abundance state termed the B state, observed for 100:0 to 70:30 water:methanol solutions in the +8 to +10 and +12 charge states. The relative abundances for different states in different solutions are determined. The analysis presented here provides insight into how solution structures evolve into anhydrous conformations and demonstrates the utility of IMS–MS methods as a means of characterizing populations of conformers for proteins in solution. PMID:24625065
Chiang, Chao-Ching; Su, Chien-You; Yang, An-Chih; Wang, Ting-Yu; Lee, Wen-Ya; Hua, Chi-Chung; Kang, Dun-Yen
2016-07-27
This paper reports on the fabrication of low-k (amorphous) silica thin films cast from solutions without and with two different types of surfactants (TWEEN® 80 and Triton™ X-100) to elucidate the relationships between the structural/morphological features of the casting solutions and the physical properties of the resulting thin films. Cryogenic transmission microscopy (cryo-TEM), static/dynamic light scattering (SLS/DLS), and small-angle X-ray scattering (SAXS) revealed contrasting colloidal dispersion states and phase behavior among the three casting solutions. Casting solution with the Triton™ X-100 surfactant produced stable (>90 days) nanoparticles with good dispersion in solution (mean particle size ∼10 nm) as well as good mesopore volume (characterized by nitrogen physisorption) in powder and thin films of high mechanical strength (characterized by the nanoindentation test). The longer main chain and bulkier side units of the TWEEN® 80 surfactant led to stable micelle-nanoparticle coexisting dispersion, which resulted in the highest mesopore volume in powder and thin films with the lowest dielectric constant (∼3) among the samples in this study. The casting solution without the surfactant failed to produce a stabilized solution or thin films of acceptable uniformity. These findings demonstrate the possibility of fine-tuning low-k silica film properties by controlling the colloidal state of casting solutions.
Stationary phase in the yeast Saccharomyces cerevisiae.
Werner-Washburne, M; Braun, E; Johnston, G C; Singer, R A
1993-01-01
Growth and proliferation of microorganisms such as the yeast Saccharomyces cerevisiae are controlled in part by the availability of nutrients. When proliferating yeast cells exhaust available nutrients, they enter a stationary phase characterized by cell cycle arrest and specific physiological, biochemical, and morphological changes. These changes include thickening of the cell wall, accumulation of reserve carbohydrates, and acquisition of thermotolerance. Recent characterization of mutant cells that are conditionally defective only for the resumption of proliferation from stationary phase provides evidence that stationary phase is a unique developmental state. Strains with mutations affecting entry into and survival during stationary phase have also been isolated, and the mutations have been shown to affect at least seven different cellular processes: (i) signal transduction, (ii) protein synthesis, (iii) protein N-terminal acetylation, (iv) protein turnover, (v) protein secretion, (vi) membrane biosynthesis, and (vii) cell polarity. The exact nature of the relationship between these processes and survival during stationary phase remains to be elucidated. We propose that cell cycle arrest coordinated with the ability to remain viable in the absence of additional nutrients provides a good operational definition of starvation-induced stationary phase. PMID:8393130
Controlling Molecular Ordering in Solution-State Conjugated Polymers
Zhu, Jiahua; Han, Youngkyu; Kumar, Rajeev; Hong, Kunlun; Bonnesen, Peter V.; Sumpter, Bobby G.; Smith, Gregory Scott; Ivanov, Ilia N.; Do, Changwoo
2015-07-17
Rationally encoding molecular interactions that can control the assembly structure and functional expression in solution of conjugated polymers holds great potential for enabling optimal organic optoelectronic and sensory materials. In this work, we show that thermally-controlled and surfactant-guided assembly of water-soluble conjugated polymers in aqueous solution is a simple and effective strategy to generate optoelectronic materials with desired molecular ordering. We have studied a conjugated polymer consisting of a hydrophobic thiophene backbone and hydrophilic, thermo-responsive ethylene oxide side groups, which shows a step-wise, multi-dimensional assembly in water. By incorporating the polymer into phase-segregated domains of an amphiphilic surfactant in solution, we demonstrate that both chain conformation and degree of molecular ordering of the conjugated polymer can be tuned in hexagonal, micellar and lamellar phases of the surfactant solution. The controlled molecular ordering in conjugated polymer assembly is demonstrated as a key factor determining the electronic interaction and optical function.
1980-03-01
The first portion of the Conceptual Design Study of Stirling Engines for Stationary Power Application in the 500 to 3000 hp range which was aimed at state-of-the-art stationary Stirling engines for a 1985 hardware demonstration is summarized. The main goals of this effort were to obtain reliable cost data for a stationary Stirling engine capable of meeting future needs for total energy/cogeneration sysems and to establish a pragmatic and conservative base design for a first generation hardware. Starting with an extensive screening effort, 4 engine types, i.e., V-type crank engine, radial engine, swashplate engine, and rhombic drive engine, and 3 heat transport systems, i.e., heat pipe, pressurized gas heat transport loop, and direct gas fired system, were selected. After a preliminary layout cycle, the rhombic drive engine was eliminated due to intolerable maintenance difficulties on the push rod seals. V, radial and swashplate engines were taken through a detailed design/layout cycle, to establish all important design features and reliable engine weights. After comparing engine layouts and analyzing qualitative and quantitative evaluation criteria, the V-crank engine was chosen as the candidate for a 1985 hardware demonstration.
Solid state and solution nitrate photochemistry: photochemical evolution of the solid state lattice.
Asher, Sanford A; Tuschel, David D; Vargson, Todd A; Wang, Luling; Geib, Steven J
2011-05-05
We examined the deep UV 229 nm photochemistry of NaNO(3) in solution and in the solid state. In aqueous solution excitation within the deep UV NO(3)¯ strong π → π* transition causes the photochemical reaction NO(3)¯ → NO(2)¯ + O·. We used UV resonance Raman spectroscopy to examine the photon dose dependence of the NO(2)¯ band intensities and measure a photochemical quantum yield of 0.04 at pH 6.5. We also examined the response of solid NaNO(3) samples to 229 nm excitation and also observe formation of NO(2)¯. The quantum yield is much smaller at ∼10(-8). The solid state NaNO(3) photochemistry phenomena appear complex by showing a significant dependence on the UV excitation flux and dose. At low flux/dose conditions NO(2)¯ resonance Raman bands appear, accompanied by perturbed NO(3)¯ bands, indicating stress in the NaNO(3) lattice. Higher flux/dose conditions show less lattice perturbation but SEM shows surface eruptions that alleviate the stress induced by the photochemistry. Higher flux/dose measurements cause cratering and destruction of the NaNO(3) surface as the surface layers are converted to NO(2)¯. Modest laser excitation UV beams excavate surface layers in the solid NaNO(3) samples. At the lowest incident fluxes a pressure buildup competes with effusion to reach a steady state giving rise to perturbed NO(3)¯ bands. Increased fluxes result in pressures that cause the sample to erupt, relieving the pressure.
NASA Astrophysics Data System (ADS)
Bondarev, S. L.; Tikhomirov, S. A.; Buganov, O. V.; Knyukshto, V. N.; Raichenok, T. F.
2017-03-01
The spectroscopic and photophysical properties of the biologically important plant antioxidant quercetin in organic solvents, polymer films of polyvinyl alcohol, and a buffer solution at pH 7.0 are studied by stationary luminescence and femtosecond laser spectroscopy at room temperature and 77 K. The large magnitude of the dipole moment of the quercetin molecule in the excited Franck-Condon state μ e FC = 52.8 C m indicates the dipolar nature of quercetin in this excited state. The transient induced absorption spectra S 1→ S n in all solvents are characterized by a short-wave band at λ abs max = 460 nm with exponential decay times in the range of 10.0-20.0 ps. In the entire spectral range at times of >100 ps, no residual induced absorption was observed that could be attributed to the triplet-triplet transitions T 1 → T k in quercetin. In polar solvents, two-band fluorescence was also recorded at room temperature, which is due to the luminescence of the initial enol form of quercetin ( 415 nm) and its keto form with a transferred proton (550 nm). The short-wave band is absent in nonpolar 2-methyltetrahydrofuran (2-MTHF). The spectra of fluorescence and fluorescence excitation exhibit a low dependence on the wavelength of excitation and detection, which may be related to the solvation and conformational changes in the quercetin molecule. Decreasing the temperature of a glassy-like freezing quercetin solution in ethanol and 2-MTHF to 77 K leads to a strong increase in the intensity (by a factor of 100) of both bands. The energy circuits for the proton transfer process are proposed depending on the polarity of the medium. The main channel for the exchange of electronic excitation energy in the quercetin molecule at room temperature is the internal conversion S 1 ⇝ S 0, induced by the state with a proton transfer.
Osmotic Second Virial Coefficients of Aqueous Solutions from Two-Component Equations of State.
Cerdeiriña, Claudio A; Widom, B
2016-12-29
Osmotic second virial coefficients in dilute aqueous solutions of small nonpolar solutes are calculated from three different two-component equations of state. The solutes are five noble gases, four diatomics, and six hydrocarbons in the range C1-C4. The equations of state are modified versions of the van der Waals, Redlich-Kwong, and Peng-Robinson equations, with an added hydrogen-bonding term for the solvent water. The parameters in the resulting equations of state are assigned so as to reproduce the experimental values and temperature dependence of the density, vapor pressure, and compressibility of the solvent, the gas-phase second virial coefficient of the pure solute, the solubility and partial molecular volume of the solute, and earlier estimates of the solutes' molecular radii. For all 15 solutes, the calculations are done for 298.15 K, whereas for CH4, C2H6, and C3H8 in particular, they are also done as functions of temperature over the full range 278.15-348.15 K. The calculated osmotic virial coefficients are compared with earlier calculations of these coefficients for these solutes and also with the results derived from earlier computer simulations of model aqueous solutions of methane. They are also compared with the experimental gas-phase second virial coefficients of the pure gaseous solutes to determine the effect the mediation of the solvent has on the resulting solute-solute interactions in the solution.
Controlling Molecular Ordering in Solution-State Conjugated Polymers
Zhu, Jiahua; Han, Youngkyu; Kumar, Rajeev; ...
2015-07-17
Rationally encoding molecular interactions that can control the assembly structure and functional expression in solution of conjugated polymers holds great potential for enabling optimal organic optoelectronic and sensory materials. In this work, we show that thermally-controlled and surfactant-guided assembly of water-soluble conjugated polymers in aqueous solution is a simple and effective strategy to generate optoelectronic materials with desired molecular ordering. We have studied a conjugated polymer consisting of a hydrophobic thiophene backbone and hydrophilic, thermo-responsive ethylene oxide side groups, which shows a step-wise, multi-dimensional assembly in water. By incorporating the polymer into phase-segregated domains of an amphiphilic surfactant in solution,more » we demonstrate that both chain conformation and degree of molecular ordering of the conjugated polymer can be tuned in hexagonal, micellar and lamellar phases of the surfactant solution. The controlled molecular ordering in conjugated polymer assembly is demonstrated as a key factor determining the electronic interaction and optical function.« less
Kvitko, Alexander
2016-06-08
By constructing a Luenberger-type asymptotic observer, a method of finding the control function, that ensures the translation of a class of nonlinear stationary control systems of ordinary differential equations from the initial state to a given final state taking into account the actual measured values, was developed. A constructive criterion guaranteeing the existence of solution of this problem was found. An algorithm is proposed for constructing a control function that transfer wide class of nonlinear systems of ordinary differential equations from an initial state to an fixed state. The algorithm is convenient for numerical implementation. A constructive condition is obtained for which this transfer is possible.
Is State-Mandated Redesign an Effective and Sustainable Solution?
ERIC Educational Resources Information Center
Young, Michelle D.
2013-01-01
There is a pervasive and ongoing perception that leadership preparation is a problem. Important questions remain about the intentions, capacity, and impact of state departments of education engaged in leadership preparation program redesign. In this essay, I take up several issues concerning this state policy work, including whether a one size…
Is State-Mandated Redesign an Effective and Sustainable Solution?
ERIC Educational Resources Information Center
Young, Michelle D.
2013-01-01
There is a pervasive and ongoing perception that leadership preparation is a problem. Important questions remain about the intentions, capacity, and impact of state departments of education engaged in leadership preparation program redesign. In this essay, I take up several issues concerning this state policy work, including whether a one size…
Quan, Guo-Bo; Han, Ying; Liu, Xiu-Zhen; Liu, An; Jin, Peng; Cao, Wei
2003-06-01
To study effect of vitrification state of protective solutions on recovery of red blood cells after lyophilization, four protective solutions composed of isotonic buffers containing 7% DMSO (v/v) and 20%, 30%, 40% or 50% polyvinylpyrrolidone (PVP) (w/v) were adopted. Vitrification state of protective solutions was examined first when white ice crystal appeared in any protective solution during freezing or thawing, if the used solution was not a vitrification solution. Red blood cells were lyophilized in MINILYO45 freeze-dryer after washing, mixing with protective solutions and prefreezing. After lyophilization, the samples were quickly rehydrated by 37 degrees C rehydration solution. The results showed that in vitrification and devitrification experiments, white ice crystal appeared in solution of 20% PVP + 7% DMSO and 30% PVP + 7% DMSO during freezing and thawing; vitrification appeared in solution of 40% PVP + 7% DMSO during freezing, but devitrification appeared during thawing; vitrification appeared in solution of 50% PVP + 7% DMSO during freezing and thawing. After rehydration, the recoveries of red blood cells and hemoglobin in 40% PVP + 7% DMSO group were (81.36 +/- 14.94)% and (77.54 +/- 12.86)%, which were significantly higher than that in 20% PVP + 7% DMSO, 30% PVP + 7% DMSO and 50% PVP + 7% DMSO groups (P < 0.01). The concentration of free hemoglobin in 40% PVP + 7% DMSO group was also significantly lower than that in other three groups (P < 0.01). With increase of PVP concentration in protective solutions, vitrification state and protective effect of these solutions also increased; when concentration of PVP in protective solution was 40% though it was not a vitrification solution, the effect of lyophilization was the best; but when concentration of PVP further increased to 50%, though it was a vitrification solution, the effect decreased. It is concluded that excessive vitrification state could not benefit lyophilization of red blood cells.
Generalization of Carey's equality and a theorem on stationary population.
Srinivasa Rao, Arni S R; Carey, James R
2015-09-01
Carey's Equality pertaining to stationary models is well known. In this paper, we have stated and proved a fundamental theorem related to the formation of this Equality. This theorem will provide an in-depth understanding of the role of each captive subject, and their corresponding follow-up duration in a stationary population. We have demonstrated a numerical example of a captive cohort and the survival pattern of medfly populations. These results can be adopted to understand age-structure and aging process in stationary and non-stationary population models.
Back to the future: stationary source testing for fine PM
Ron Myers
2006-04-15
Decisions will be necessary concerning the most appropriate stationary source test methodologies for continuing our efforts to clean up the atmosphere. In many regions of the United States, existing methods to measure stationary source pollutant emissions may be acceptable for the foreseeable future. However, other regions will require more comprehensive source measurement methods that expand the measured pollutants to include the full range of the atmospheric burden. Decisions about which path(s) to follow will depend on existing ambient air quality levels an the need to better quantify atmospheric emissions of primary PM from stationary sources, control stationary source primary PM to achieve the ambient air quality standard, and better understand the components of stationary source primary PM emissions. This article focuses on quantifying fine PM emissions from stationary sources, including Method 5B for utility plants. 24 refs., 1 tab.
Stationary Flux in Mesoscopic Noisy Cylinders
NASA Astrophysics Data System (ADS)
Dajka, J.; Łuczka, J.; Szopa, M.
2003-07-01
The aim of this paper is to investigate the existence of the stationary states of current in the mesoscopic cylinder. The dynamics of the flux is governed by a stochastic differential equation. We discuss both the influence of equilibrium (thermal) and non-equilibrium noise sources.
Stationary convection in a cylindrical plasma
Gomberoff, L.; Hernandez, M.
1983-02-01
It is shown that viscosity and thermal conductivity leads to large-scale steady convection in a cylindrical current-carrying plasma, under the influence of a magnetic field satisfying (B/sub theta//B/sub z/)>>1. This state is the analog in a plasma of stationary convection in ordinary hydrodynamics.
Stationary light in cold-atomic gases
Nikoghosyan, Gor; Fleischhauer, Michael
2009-07-15
We discuss stationary light created by a pair of counterpropagating control fields in {lambda}-type atomic gases with electromagnetically induced transparency for the case of negligible Doppler broadening. In this case, the secular approximation used in the discussion of stationary light in hot vapors is no longer valid. We discuss the quality of the effective light-trapping system and show that in contrast to previous claims it is finite even for vanishing ground-state dephasing. The dynamics of the photon loss is in general nonexponential and can be faster or slower than in hot gases.
Normalization of bound-state solutions to the Breit equation
Malenfant, J.
1989-03-15
We derive the spin-(1/2), two-particle Breit equation from the Bethe-Salpeter equation with instantaneous interaction kernel, and solve for the relative time dependence of the resulting Bethe-Salpeter amplitude psi(x). As t..-->.. +- infinity, psi(x) increases exponentially in Dirac hole theory, but goes to zero in single-electron theory. Assuming single-electron theory, a normalization condition is derived for psi(r,0), the solution to the Breit equation, from the normalization for the Bethe-Salpeter amplitude.
On D = 4 Stationary Black Holes
NASA Astrophysics Data System (ADS)
Andrianopoli, L.; D'Auria, R.; Gallerati, A.; Trigiante, M.
2013-11-01
We review some recent results concerning non-extremal and extremal stationary, asymptotically flat black hole solutions in extended D = 4 supergravities, and their properties with respect to the global symmetries of the theory. More specifically we refer to the effective three-dimensional description of these solutions and their classification within orbits with respect to the action of the global symmetry group, illustrating, for single-center solutions, the general mathematical relation between the orbits of non-extremal and extremal black holes.
Effect of cross-diffusion on the stationary problem of a prey-predator model with a protection zone
NASA Astrophysics Data System (ADS)
Oeda, Kazuhiro
This paper is concerned with the stationary problem of a prey-predator cross-diffusion system with a protection zone for the prey. We discuss the existence and non-existence of coexistence states of the two species by using the bifurcation theory. As a result, it is shown that the cross-diffusion for the prey has beneficial effects on the survival of the prey when the intrinsic growth rate of the predator is positive. We also study the asymptotic behavior of positive stationary solutions as the cross-diffusion coefficient of the prey tends to infinity.
Qualitative analysis of stationary Keller-Segel chemotaxis models with logistic growth
NASA Astrophysics Data System (ADS)
Wang, Qi; Yan, Jingda; Gai, Chunyi
2016-06-01
We study the stationary Keller-Segel chemotaxis models with logistic cellular growth over a one-dimensional region subject to the Neumann boundary condition. We show that nonconstant solutions emerge in the sense of Turing's instability as the chemotaxis rate {χ} surpasses a threshold number. By taking the chemotaxis rate as the bifurcation parameter, we carry out bifurcation analysis on the system to obtain the explicit formulas of bifurcation values and small amplitude nonconstant positive solutions. Moreover, we show that solutions stay strictly positive in the continuum of each branch. The stabilities of these steady-state solutions are well studied when the creation and degradation rate of the chemical is assumed to be a linear function. Finally, we investigate the asymptotic behaviors of the monotone steady states. We construct solutions with interesting patterns such as a boundary spike when the chemotaxis rate is large enough and/or the cell motility is small.
Arbitrary Steady-State Solutions with the K-epsilon Model
NASA Technical Reports Server (NTRS)
Rumsey, Christopher L.; Pettersson Reif, B. A.; Gatski, Thomas B.
2006-01-01
Widely-used forms of the K-epsilon turbulence model are shown to yield arbitrary steady-state converged solutions that are highly dependent on numerical considerations such as initial conditions and solution procedure. These solutions contain pseudo-laminar regions of varying size. By applying a nullcline analysis to the equation set, it is possible to clearly demonstrate the reasons for the anomalous behavior. In summary, the degenerate solution acts as a stable fixed point under certain conditions, causing the numerical method to converge there. The analysis also suggests a methodology for preventing the anomalous behavior in steady-state computations.
Counterterrorism in African Failed States: Challenges and Potential Solutions
2006-04-01
and generally accepted in the literature on state failure.4 For purposes of this anal - ysis, loss of government legitimacy, loss of public sector...the . . . fundamental problems—economic distress, ethnic and religious fissures , fragile governance, weak democracy, and rampant human rights abuses
2015-06-01
This fact sheet describes opportunities for interested stationary fuel cell developers and end users to participate in an objective and credible analysis of stationary fuel cell systems to benchmark the current state of the technology and support industry growth.
NASA Astrophysics Data System (ADS)
Leuenberger, Daiana; Pascale, Céline; Guillevic, Myriam; Ackermann, Andreas; Niederhauser, Bernhard
2017-04-01
Ammonia (NH3) in the atmosphere is the major precursor for neutralising atmospheric acids and is thus affecting not only the long-range transport of sulphur dioxide and nitrogen oxides but also stabilises secondary particulate matter. These aerosols have negative impacts on air quality and human health. Moreover, they negatively affect terrestrial ecosystems after deposition. NH3 has been included in the air quality monitoring networks and emission reduction directives of European nations. Atmospheric concentrations are in the order of 0.5-500 nmol/mol. However, the lowest substance amount fraction of available certified reference material (CRM) is 10 μmol/mol. This due to the fact that adsorption on the walls of aluminium cylinders and desorption as pressure in the cylinder decreases cause substantial instabilities in the amount fractions of the gas mixtures. Moreover, analytical techniques to be calibrated are very diverse and cause challenges for the production and application of CRM. The Federal Institute of Metrology METAS has developed, partially in the framework of EMRP JRP ENV55 MetNH3, an infrastructure to meet with the different requirements in order to generate SI-traceable NH3 reference gas mixtures dynamically in the amount fraction range 0.5-500 nmol/mol and with uncertainties UNH3 <3%. The infrastructure consists of a stationary as well as a mobile device for full flexibility in the application: In the stationary system, a magnetic suspension balance monitors the specific temperature and pressure dependent mass loss over time of the pure substance in a permeation tube (here NH3) by permeation through a membrane into a constant flow of carrier gas. Subsequently, this mixture is diluted with a system of thermal mass flow controllers in one or two consecutive steps to desired amount fractions. The permeation tube with calibrated permeation rate (mass loss over time previously determined in the magnetic suspension balance) can be transferred into the
Ceramic stationary gas turbine
Roode, M. van
1995-10-01
The performance of current industrial gas turbines is limited by the temperature and strength capabilities of the metallic structural materials in the engine hot section. Because of their superior high-temperature strength and durability, ceramics can be used as structural materials for hot section components (blades, nozzles, combustor liners) in innovative designs at increased turbine firing temperatures. The benefits include the ability to increase the turbine inlet temperature (TIT) to about 1200{degrees}C ({approx}2200{degrees}F) or more with uncooled ceramics. It has been projected that fully optimized stationary gas turbines would have a {approx}20 percent gain in thermal efficiency and {approx}40 percent gain in output power in simple cycle compared to all metal-engines with air-cooled components. Annual fuel savings in cogeneration in the U.S. would be on the order of 0.2 Quad by 2010. Emissions reductions to under 10 ppmv NO{sub x} are also forecast. This paper describes the progress on a three-phase, 6-year program sponsored by the U.S. Department of Energy, Office of Industrial Technologies, to achieve significant performance improvements and emissions reductions in stationary gas turbines by replacing metallic hot section components with ceramic parts. Progress is being reported for the period September 1, 1994, through September 30, 1995.
Ceramic stationary gas turbine
Roode, M. van
1995-12-31
The performance of current industrial gas turbines is limited by the temperature and strength capabilities of the metallic structural materials in the engine hot section. Because of their superior high-temperature strength and durability, ceramics can be used as structural materials for hot section components (blades, nozzles, combustor liners) in innovative designs at increased turbine firing temperatures. The benefits include the ability to increase the turbine inlet temperature (TIT) to about 1200{degrees}C ({approx}2200{degrees}F) or more with uncooled ceramics. It has been projected that fully optimized stationary gas turbines would have a {approx}20 percent gain in thermal efficiency and {approx}40 percent gain in output power in simple cycle compared to all metal-engines with air-cooled components. Annual fuel savings in cogeneration in the U.S. would be on the order of 0.2 Quad by 2010. Emissions reductions to under 10 ppmv NO{sub x} are also forecast. This paper describes the progress on a three-phase, 6-year program sponsored by the U.S. Department of Energy, Office of Industrial Technologies, to achieve significant performance improvements and emissions reductions in stationary gas turbines by replacing metallic hot section components with ceramic parts. Progress is being reported for the period September 1, 1994, through September 30, 1995.
Stationary black holes: large D analysis
NASA Astrophysics Data System (ADS)
Suzuki, Ryotaku; Tanabe, Kentaro
2015-09-01
We consider the effective theory of large D stationary black holes. By solving the Einstein equations with a cosmological constant using the 1 /D expansion in near zone of the black hole we obtain the effective equation for the stationary black hole. The effective equation describes the Myers-Perry black hole, bumpy black holes and, possibly, the black ring solution as its solutions. In this effective theory the black hole is represented as an embedded membrane in the background, e.g., Minkowski or Anti-de Sitter spacetime and its mean curvature is given by the surface gravity redshifted by the background gravitational field and the local Lorentz boost. The local Lorentz boost property of the effective equation is observed also in the metric itself. In fact we show that the leading order metric of the Einstein equation in the 1 /D expansion is generically regarded as a Lorentz boosted Schwarzschild black hole. We apply this Lorentz boost property of the stationary black hole solution to solve perturbation equations. As a result we obtain an analytic formula for quasinormal modes of the singly rotating Myers-Perry black hole in the 1 /D expansion.
Stationary stability for evolutionary dynamics in finite populations
Harper, Marc; Fryer, Dashiell
2016-08-25
Here, we demonstrate a vast expansion of the theory of evolutionary stability to finite populations with mutation, connecting the theory of the stationary distribution of the Moran process with the Lyapunov theory of evolutionary stability. We define the notion of stationary stability for the Moran process with mutation and generalizations, as well as a generalized notion of evolutionary stability that includes mutation called an incentive stable state (ISS) candidate. For sufficiently large populations, extrema of the stationary distribution are ISS candidates and we give a family of Lyapunov quantities that are locally minimized at the stationary extrema and at ISS candidates. In various examples, including for the Moran andWright–Fisher processes, we show that the local maxima of the stationary distribution capture the traditionally-defined evolutionarily stable states. The classical stability theory of the replicator dynamic is recovered in the large population limit. Finally we include descriptions of possible extensions to populations of variable size and populations evolving on graphs.
Spurious States-Free Solution of the k dot p Hamiltonian for Heterostructures
NASA Technical Reports Server (NTRS)
Kolokolov, Konstantin I.; Li, Jian-Zhong; Ning, Cun-Zheng
2003-01-01
A method for eliminating spurious solution in the k dot p Hamiltonian has been proposed. Introduction of additional off-diagonal alpha k(exp 2) term converts spurious solution with large real wave vector to evanescent solution with large imaginary wave vector. This modification keeps the same effective masses at Gamma point and introduces negligible deviation from original nonparabolicity. A set of unphysical fast oscillation eigenfunctions in confined states of heterostructures are removed.
Finite element solution of optimal control problems with state-control inequality constraints
NASA Technical Reports Server (NTRS)
Bless, Robert R.; Hodges, Dewey H.
1992-01-01
It is demonstrated that the weak Hamiltonian finite-element formulation is amenable to the solution of optimal control problems with inequality constraints which are functions of both state and control variables. Difficult problems can be treated on account of the ease with which algebraic equations can be generated before having to specify the problem. These equations yield very accurate solutions. Owing to the sparse structure of the resulting Jacobian, computer solutions can be obtained quickly when the sparsity is exploited.
Finite element solution of optimal control problems with state-control inequality constraints
NASA Technical Reports Server (NTRS)
Bless, Robert R.; Hodges, Dewey H.
1992-01-01
It is demonstrated that the weak Hamiltonian finite-element formulation is amenable to the solution of optimal control problems with inequality constraints which are functions of both state and control variables. Difficult problems can be treated on account of the ease with which algebraic equations can be generated before having to specify the problem. These equations yield very accurate solutions. Owing to the sparse structure of the resulting Jacobian, computer solutions can be obtained quickly when the sparsity is exploited.
Mechanism of connective drying of solutions of fish hydrolyzates in a foamed state
NASA Astrophysics Data System (ADS)
Buinov, A. A.; Ginzburg, A. S.; Syroedov, V. I.
1982-07-01
The results of experimental investigations of the kinetics of foam drying of fish hydrolyzates are presented. The dehydration mechanism is analyzed and the enhancement of the process with dehydration of solutions in a foamed state is explained.
Nonexistence of nonconstant steady-state solutions in a triangular cross-diffusion model
NASA Astrophysics Data System (ADS)
Lou, Yuan; Tao, Youshan; Winkler, Michael
2017-05-01
In this paper we study the Shigesada-Kawasaki-Teramoto model for two competing species with triangular cross-diffusion. We determine explicit parameter ranges within which the model exclusively possesses constant steady state solutions.
Zaidel, Jacob
2013-01-01
Known analytical solutions of groundwater flow equations are routinely used for verification of computer codes. However, these analytical solutions (e.g., the Dupuit solution for the steady-state unconfined unidirectional flow in a uniform aquifer with a flat bottom) represent smooth and continuous water table configurations, simulating which does not pose any significant problems for the numerical groundwater flow models, like MODFLOW. One of the most challenging numerical cases for MODFLOW arises from drying-rewetting problems often associated with abrupt changes in the elevations of impervious base of a thin unconfined aquifer. Numerical solutions of groundwater flow equations cannot be rigorously verified for such cases due to the lack of corresponding exact analytical solutions. Analytical solutions of the steady-state Boussinesq equation, associated with the discontinuous water table configurations over a stairway impervious base, are presented in this article. Conditions resulting in such configurations are analyzed and discussed. These solutions appear to be well suited for testing and verification of computer codes. Numerical solutions, obtained by the latest versions of MODFLOW (MODFLOW-2005 and MODFLOW-NWT), are compared with the presented discontinuous analytical solutions. It is shown that standard MODFLOW-2005 code (as well as MODFLOW-2000 and older versions) has significant convergence problems simulating such cases. The problems manifest themselves either in a total convergence failure or erroneous results. Alternatively, MODFLOW-NWT, providing a good match to the presented discontinuous analytical solutions, appears to be a more reliable and appropriate code for simulating abrupt changes in water table elevations.
Wu, Chin H.; Das, Bibhuti B.; Opella, Stanley J.
2010-01-01
13C NMR of isotopically labeled methyl groups has the potential to combine spectroscopic simplicity with ease of labeling for protein NMR studies. However, in most high resolution separated local field experiments, such as polarization inversion spin exchange at the magic angle (PISEMA), that are used to measure 1H–13C hetero-nuclear dipolar couplings, the four-spin system of the methyl group presents complications. In this study, the properties of the 1H–13C hetero-nuclear dipolar interactions of 13C-labeled methyl groups are revealed through solid-state NMR experiments on a range of samples, including single crystals, stationary powders, and magic angle spinning of powders, of 13C3 labeled alanine alone and incorporated into a protein. The spectral simplifications resulting from proton detected local field (PDLF) experiments are shown to enhance resolution and simplify the interpretation of results on single crystals, magnetically aligned samples, and powders. The complementarity of stationary sample and magic angle spinning (MAS) measurements of dipolar couplings is demonstrated by applying polarization inversion spin exchange at the magic angle and magic angle spinning (PISEMAMAS) to unoriented samples. PMID:19896874
Wu, Chin H; Das, Bibhuti B; Opella, Stanley J
2010-02-01
(13)C NMR of isotopically labeled methyl groups has the potential to combine spectroscopic simplicity with ease of labeling for protein NMR studies. However, in most high resolution separated local field experiments, such as polarization inversion spin exchange at the magic angle (PISEMA), that are used to measure (1)H-(13)C hetero-nuclear dipolar couplings, the four-spin system of the methyl group presents complications. In this study, the properties of the (1)H-(13)C hetero-nuclear dipolar interactions of (13)C-labeled methyl groups are revealed through solid-state NMR experiments on a range of samples, including single crystals, stationary powders, and magic angle spinning of powders, of (13)C(3) labeled alanine alone and incorporated into a protein. The spectral simplifications resulting from proton detected local field (PDLF) experiments are shown to enhance resolution and simplify the interpretation of results on single crystals, magnetically aligned samples, and powders. The complementarity of stationary sample and magic angle spinning (MAS) measurements of dipolar couplings is demonstrated by applying polarization inversion spin exchange at the magic angle and magic angle spinning (PISEMAMAS) to unoriented samples. Copyright 2009 Elsevier Inc. All rights reserved.
Thermocapillary Convection Due to a Stationary Bubble - A Paradox
NASA Technical Reports Server (NTRS)
Balasubramaniam, R.; Subramanian, R. S.
2003-01-01
We analyze the velocity and temperature fields at steady state due to thermocapillary convection around a gas bubble that is stationary in a liquid. A linear temperature field is imposed in the undisturbed liquid. Our interest is in investigating the effect of convective transport of momentum and energy on the velocity and temperature fields. We assume the pertinent physical properties to be constant, and that buoyant convection is negligible. Suitably defined Reynolds and Marangoni numbers are assumed to be small compared with unity. When both the Reynolds and Marangoni numbers are set equal to zero, a solution can be found. In this solution, far from the bubble, the velocity field decays as the inverse of the distance from the bubble, and the disturbance temperature field decays as the inverse of the square of this distance. We now attempt to obtain a solution when the Reynolds number is zero, but the Marangoni number is small, but non-zero, by a perturbation expansion in the Marangoni number. When the temperature field is expanded in a regular perturbation series in the Marangoni number, we show that the problem for the first correction field is ill-posed. The governing equation for this perturbation field contains an inhomogeneity, and the corresponding particular solution neither decays far from the bubble, nor can be canceled by a homogeneous solution. Additional information is included in the original extended abstract.
NASA Astrophysics Data System (ADS)
Millett, Stephen; Mahadevan, Kathya
Battelle is identifying the most likely markets and economic impacts of stationary polymer electrolyte membrane (PEM) fuel cells in the range of 1-250 kW in the U.S. by the year 2015. For this task, Battelle is using the Interactive Future Simulations (IFS™), an analytical modeling and forecasting tool that uses expert judgment, trend analysis, and cross-impact analysis methods to generate most likely future conditions for PEM fuel cell applications, market acceptance, commercial viability, and economic impacts. The cross-impact model contains 28 descriptors including commercial and technological advances in both polymer electrolyte membrane (PEM) fuel cells and fossil fuel technologies, sources of hydrogen, investments, public policy, environmental regulation, value to consumers, commercialization leadership, modes of generation, and the reliability and prices of grid electricity. One likely scenario to the year 2015 is that the PEM fuel cells will be limited to commercial and industrial customers in the range of 50-200 kW with a market size less than US$ 5 billion a year.
Stationary Phonon Squeezing by Optical Polaron Excitation
NASA Astrophysics Data System (ADS)
Papenkort, T.; Axt, V. M.; Kuhn, T.
2017-03-01
We demonstrate that a stationary squeezed phonon state can be prepared by a pulsed optical excitation of a semiconductor quantum well. Unlike previously discussed scenarios for generating squeezed phonons, the corresponding uncertainties become stationary after the excitation and do not oscillate in time. The effect is caused by two-phonon correlations within the excited polaron. We demonstrate by quantum kinetic simulations and by a perturbation analysis that the energetically lowest polaron state comprises two-phonon correlations which, after the pulse, result in an uncertainty of the lattice momentum that is continuously lower than in the ground state of the semiconductor. The simulations show the dynamics of the polaron formation process and the resulting time-dependent lattice uncertainties.
State-constrained booster trajectory solutions via finite elements and shooting
NASA Technical Reports Server (NTRS)
Bless, Robert R.; Hodges, Dewey H.; Seywald, Hans
1993-01-01
This paper presents an extension of a FEM formulation based on variational principles. A general formulation for handling internal boundary conditions and discontinuities in the state equations is presented, and the general formulation is modified for optimal control problems subject to state-variable inequality constraints. Solutions which only touch the state constraint and solutions which have a boundary arc of finite length are considered. Suitable shape and test functions are chosen for a FEM discretization. All element quadrature (equivalent to one-point Gaussian quadrature over each element) may be done in closed form. The final form of the algebraic equations is then derived. A simple state-constrained problem is solved. Then, for a practical application of the use of the FEM formulation, a launch vehicle subject to a dynamic pressure constraint (a first-order state inequality constraint) is solved. The results presented for the launch-vehicle trajectory have some interesting features, including a touch-point solution.
State-constrained booster trajectory solutions via finite elements and shooting
NASA Technical Reports Server (NTRS)
Bless, Robert R.; Hodges, Dewey H.; Seywald, Hans
1993-01-01
This paper presents an extension of a FEM formulation based on variational principles. A general formulation for handling internal boundary conditions and discontinuities in the state equations is presented, and the general formulation is modified for optimal control problems subject to state-variable inequality constraints. Solutions which only touch the state constraint and solutions which have a boundary arc of finite length are considered. Suitable shape and test functions are chosen for a FEM discretization. All element quadrature (equivalent to one-point Gaussian quadrature over each element) may be done in closed form. The final form of the algebraic equations is then derived. A simple state-constrained problem is solved. Then, for a practical application of the use of the FEM formulation, a launch vehicle subject to a dynamic pressure constraint (a first-order state inequality constraint) is solved. The results presented for the launch-vehicle trajectory have some interesting features, including a touch-point solution.
Stationary engineering handbook
Petrocelly, K.L.
1989-01-01
Years ago, the only qualifications you needed to become to become an operating engineer were the ability to shovel large chunks of coal through small furnace doors and the fortitude to sweat profusely for hours without fainting. As a consequence of technological evolution, the engineer's coal shovels have been replaced with computers and now perspiration is more the result of job stress than exposure to high temperatures. The domain of the operator has been extended far beyond the smoke-filled caverns that once encased him, out into the physical plant, and his responsibilities have been expanded accordingly. Unlike his less sophisticated predecessor, today's technician must be well versed in all aspects of the operation. The field of power plant operations has become a full-fledged profession and its principals are called Stationary Engineers. This book addresses the areas of responsibility and the education and skills needed for successful operation of building services equipment.
Protolytic dissociation of cyanophenols in ground and excited states in alcohol and water solutions
NASA Astrophysics Data System (ADS)
Szczepanik, Beata; Styrcz, Stanisław
2011-08-01
The effect of cyano substituents on acidity in ground and excited states of mono- and dicyanophenols was investigated. The equilibrium dissociation constants of 3,4-dicyanophenol in ground and lowest excited states in water solution and the change of these constants in the excited state during the transfer to the ground state for o-, m-, p-cyanophenol and 3,4-dicyanophenol in alcohol and water solutions were determined. It was shown that the cyano substitution increases the acidity of ortho-, meta- and dicyano-derivative in ground state in comparison to the phenol, which makes the anions of these derivatives appear in solutions from methanol to 1-butanol. In the excited state the acidity of investigated compounds changes significantly in comparison to the ground state. 3,4-Dicyanophenol is the strongest acid in the lowest excited singlet state, while p-cyanophenol is the weakest one in both alcohol and water solutions. The distribution of the electronic charge and dipole moments of all investigated cyanophenols in ground and excited states were determined on the basis of ab initio calculations using the GAMESS program.
PROCESS OF SECURING PLUTONIUM IN NITRIC ACID SOLUTIONS IN ITS TRIVALENT OXIDATION STATE
Thomas, J.R.
1958-08-26
>Various processes for the recovery of plutonium require that the plutonium be obtalned and maintained in the reduced or trivalent state in solution. Ferrous ions are commonly used as the reducing agent for this purpose, but it is difficult to maintain the plutonium in a reduced state in nitric acid solutions due to the oxidizing effects of the acid. It has been found that the addition of a stabilizing or holding reductant to such solution prevents reoxidation of the plutonium. Sulfamate ions have been found to be ideally suitable as such a stabilizer even in the presence of nitric acid.
Efficient Steady-State Solution Techniques for Variably Saturated Groundwater Flow
NASA Astrophysics Data System (ADS)
Farthing, M. W.; Kees, C. E.; Coffey, T. S.; Kelley, C. T.; Miller, C. T.
2002-12-01
We consider the simulation of steady-state variably saturated groundwater flow using Richards' equation. The difficulties associated with solving Richards' equation numerically are well known. Most discretization approaches for Richards' equation lead to nonlinear systems that are large and difficult to solve. The solution of nonlinear systems for steady-state problems can be particularly challenging, since a good initial guess for the steady-state solution is often hard to obtain, and the resulting linear systems may be poorly scaled. Common approaches like modified Picard iteration or variations of Newton's method have their advantages but perform poorly with standard globalization techniques under certain conditions. Pseudo-transient continuation has been used in computational fluid dynamics for some time to obtain steady-state solutions for problems in which Newton's method with standard line-search strategies fails. It combines aspects of backward Euler time integration and Newton's method to select intermediate estimates of the steady-state solution. In this work, we examine the use of pseudo-transient continuation methods for Richards' equation. We evaluate their performance for steady-state problems in heterogeneous domains by comparing them with Newton's method using standard globalization techniques. We investigate the methods' performance with both direct and preconditioned Krylov iterative linear solvers. We then make recommendations for robust and efficient approaches to obtain steady-state solutions for Richards' equation under a variety of conditions.
Solution of steady-state one-dimensional conservation laws by mathematical programming
NASA Technical Reports Server (NTRS)
Lavery, J. E.
1989-01-01
Solution techniques for a class of steady-state scalar conservation laws are developed analytically. Discretization by finite-volume formulas is employed to obtain an overdetermined system of algebraic equations, which are then perturbed nonsingularly (with perturbation coefficient = epsilon) and solved using the l(1) mathematical-programming algorithm of Seneta and Steiger (1984); this approach limits the matrix bandwidth to two, so that an explicit solution can be found efficiently. It is shown that, for small values of epsilon, the l(1) solutions exhibit sharp correctly located shocks and are nonoscillatory O(epsilon) approximations of the physically relevant solutions.
Integrating matrix solution of the hybrid state vector equations for beam vibration
NASA Technical Reports Server (NTRS)
Lehman, L. L.
1982-01-01
A simple, versatile, and efficient computational technique has been developed for dynamic analysis of linear elastic beam and rod type of structures. Moreover, the method provides a rather general solution approach for two-point boundary value problems that are described by a single independent spatial variable. For structural problems, the method is implemented by a mixed state vector formulation of the differential equations, combined with an integrating matrix solution procedure. Highly accurate solutions are easily achieved with this approach. Example solutions are given for beam vibration problems including discontinuous stiffness and mass parameters, elastic restraint boundary conditions, concentrated inertia loading, and rigid body modes
Almost-stationary motions and gauge conditions in general relativity
Bona, C.; Carot, J.; Palenzuela-Luque, C.
2005-12-15
An almost-stationary gauge condition is proposed with a view to numerical relativity applications. The time lines are defined as the integral curves of the timelike solutions of the harmonic almost-Killing equation. This vector equation is derived from a variational principle, by minimizing the deviations from isometry. The corresponding almost-stationary gauge condition allows us to put the field equations in hyperbolic form, both in the free-evolution ADM and in the Z4 formalisms.
Stability of erythrocyte suspensions layered on stationary and flowing liquids
NASA Technical Reports Server (NTRS)
Omenyi, S. N.; Rhodes, P. H.; Snyder, R. S.
1982-01-01
The apparent stability of erythrocyte suspensions layered on stationary and flowing Ficoll solutions was studied considering the effects of particle concentration, type and size, and the different flow rates of the particle suspensions and chamber liquid. The data from the flowing system were empirically fitted and, when extrapolated to zero chamber liquid flow rate, gave values comparable to the data from the stationary system, thus confirming the validity of the data and our approach to obtain that data.
Stability of Riccati's Equation with Random Stationary Coefficients
Fakhfakh, S.
1999-09-15
The purpose of this paper is to study under weak conditions of stabilizability and detectability, the asymptotic behavior of the matrix Riccati equation which arises in stochastic control and filtering with random stationary coefficients. We prove the existence of a stationary solution (P-bar{sub t}) of this Riccati equation. This solution is attracting, in the sense that if P{sub t} is another solution, then P{sub t}-P-bar{sub t} converges to 0 exponentially fast as t tends to +{infinity} , at a rate given by the smallest positive Lyapunov exponent of the associated Hamiltonian matrices.
Quasi-stationary distributions for models of heterogeneous catalysis
NASA Astrophysics Data System (ADS)
de Oliveira, Marcelo M.; Dickman, Ronald
2004-11-01
We construct the quasi-stationary (QS) distribution for two models of heterogeneous catalysis having two absorbing states: the ZGB model for the oxidation of CO, and a version with noninstantaneous reactions. Using a mean-field-like approximation, we study the quasi-stationary surface coverages, moment ratios and the lifetime of the QS state. We also derive an improved, consistent one-site mean-field theory for the ZGB model.
Stationary Engineering Laboratory Manual--2.
ERIC Educational Resources Information Center
Steingress, Frederick M.; Frost, Harold J.
The Stationary Engineering Laboratory Manual 2 was designed for vocational/technical high school students who have received instruction in the basics of stationary engineering. It was developed for students who will be operating a live plant and who will be responsible for supplying steam for heating, cooking, and baking. Each lesson in the manual…
Stationary Engineering. Science Manual--2.
ERIC Educational Resources Information Center
Frost, Harold J.; Steingress, Frederick M.
This second-year student manual contains 140 brief related science lessons applying science and math to trade activities in the field of stationary engineering. The lessons are organized into 16 units: (1) Introduction to Stationary Engineering, (2) Engineering Fundamentals, (3) Steam Boilers, (4) Boiler Fittings, (5) Boilerroom System, (6)…
Trumpet solution from spherical gravitational collapse with puncture gauges
Thierfelder, Marcus; Bernuzzi, Sebastiano; Hilditch, David; Bruegmann, Bernd; Rezzolla, Luciano
2011-03-15
We investigate the stationary end state obtained by evolving a collapsing spherical star with the gauges routinely adopted to study puncture black holes. We compare the end state of the collapse with the trumpet solution found in the evolution of a single wormhole slice and show that the two solutions closely agree. We demonstrate that the agreement is caused by the use of the Gamma-driver shift condition, which allows the matter to fall inwards into a region of spacetime that is not resolved by the numerical grid, and which simultaneously finds the stationary coordinates of the trumpet outside the matter.
Test profiles for stationary energy storage applications
Butler, P.C.; Cole, J.F.; Taylor, P.A.
1998-09-01
Evaluation of battery and other energy storage technologies for stationary uses is progressing rapidly toward application-specific testing that uses computer-based data acquisition and control equipment, active electronic loads and power supplies, and customized software, to enable sophisticated test regimes that simulate actual use conditions. These simulated-use tests provide more accurate performance and life evaluations than simple constant resistance or current testing regimes. Some of the tests use stepped constant-power charge and discharge regimes to simulate conditions created by electric utility applications such as frequency regulation and spinning reserve. Other test profiles under development simulate conditions for the energy storage component of Remote Area Power Supplies (RAPS) that include renewable and/or fossil-fueled generators. Various RAPS applications have unique sets of service conditions that require specialized test profiles. However, almost all RAPS tests and many tests that represent other stationary applications need to simulate significant time periods during which storage devices operate at low-to-medium states-of-charge without full recharge. Consideration of these and similar issues in simulated-use test regimes is necessary to effectively predict the responses of the various types of batteries in specific stationary applications. This paper describes existing and evolving stationary applications for energy storage technologies and test regimes that are designed to simulate them. The paper also discusses efforts to develop international testing standards.
Stationary Waves of the Ice Age Climate.
NASA Astrophysics Data System (ADS)
Cook, Kerry H.; Held, Isaac M.
1988-08-01
A linearized, steady state, primitive equation model is used to simulate the climatological zonal asymmetries (stationary eddies) in the wind and temperature fields of the 18 000 YBP climate during winter. We compare these results with the eddies simulated in the ice age experiments of Broccoli and Manabe, who used CLIMAP boundary conditions and reduced atmospheric CO2 in an atmospheric general circulation model (GCM) coupled with a static mixed layer ocean model. The agreement between the models is good, indicating that the linear model can be used to evaluate the relative influences of orography, diabatic heating, and transient eddy heat and momentum transports in generating stationary waves. We find that orographic forcing dominates in the ice age climate. The mechanical influence of the continental ice sheets on the atmosphere is responsible for most of the changes between the present day and ice age stationary eddies. This concept of the ice age climate is complicated by the sensitivity of the stationary eddies to the large increase in the magnitude of the zonal mean meridional temperature gradient simulated in the ice age GCM.
Asymptotic behavior for the viscous Burgers equation with a stationary source
NASA Astrophysics Data System (ADS)
Chung, Jaywan; Kwon, Ohsang
2016-10-01
Long-time asymptotic behavior for the viscous Burgers equation on the real line is considered. When there is a non-negative and compactly supported Radon measure as a stationary source, we prove that solutions of the viscous Burgers equation converge to a positive, bounded, and nondecreasing steady state by finding an almost optimal convergence order. The non-integrability of the steady state only allows local convergence on compact subsets, hence a Véron-type argument must be modified by adopting a proper weight function.
Bifurcation analysis of interacting stationary modes in thermohaline convection
Neveling, M.; Dangelmayr, G.
1988-09-01
The Boussinesq equations for thermohaline convection in a finite two-dimensional box and with stress-free boundaries are considered. There are critical values of the aspect ratio at which the conduction state becomes unstable to two different roll patterns simultaneously. Near such a critical value a center manifold reduction allows us to reduce the dynamical behavior of the Boussinesq equations to a standard normal form equation that describes the interaction of two stationary modes. We present explicit analytical expressions for the linear and nonlinear coefficients on which the normal form depends. A numerical investigation of these coefficients leads to a division of the space of parameters (Prandtl number, solute Rayleigh number, Lewis number) into various regions that give rise to qualitatively different bifurcation behavior. Besides those encountered in ordinary convection, a variety of further phenomena is found, in particular in a vicinity of double tricritical points.
Singular perturbation solutions of steady-state Poisson-Nernst-Planck systems.
Wang, Xiang-Sheng; He, Dongdong; Wylie, Jonathan J; Huang, Huaxiong
2014-02-01
We study the Poisson-Nernst-Planck (PNP) system with an arbitrary number of ion species with arbitrary valences in the absence of fixed charges. Assuming point charges and that the Debye length is small relative to the domain size, we derive an asymptotic formula for the steady-state solution by matching outer and boundary layer solutions. The case of two ionic species has been extensively studied, the uniqueness of the solution has been proved, and an explicit expression for the solution has been obtained. However, the case of three or more ions has received significantly less attention. Previous work has indicated that the solution may be nonunique and that even obtaining numerical solutions is a difficult task since one must solve complicated systems of nonlinear equations. By adopting a methodology that preserves the symmetries of the PNP system, we show that determining the outer solution effectively reduces to solving a single scalar transcendental equation. Due to the simple form of the transcendental equation, it can be solved numerically in a straightforward manner. Our methodology thus provides a standard procedure for solving the PNP system and we illustrate this by solving some practical examples. Despite the fact that for three ions, previous studies have indicated that multiple solutions may exist, we show that all except for one of these solutions are unphysical and thereby prove the existence and uniqueness for the three-ion case.
Efficient steady-state solution techniques for variably saturated groundwater flow
NASA Astrophysics Data System (ADS)
Farthing, Matthew W.; Kees, Christopher E.; Coffey, Todd S.; Kelley, C. T.; Miller, Cass T.
We consider the simulation of steady-state variably saturated groundwater flow using Richards' equation (RE). The difficulties associated with solving RE numerically are well known. Most discretization approaches for RE lead to nonlinear systems that are large and difficult to solve. The solution of nonlinear systems for steady-state problems can be particularly challenging, since a good initial guess for the steady-state solution is often hard to obtain, and the resulting linear systems may be poorly scaled. Common approaches like Picard iteration or variations of Newton's method have their advantages but perform poorly with standard globalization techniques under certain conditions. Pseudo-transient continuation has been used in computational fluid dynamics for some time to obtain steady-state solutions for problems in which Newton's method with standard line-search strategies fails. Here, we examine the use of pseudo-transient continuation as well as Newton's method combined with standard globalization techniques for steady-state problems in heterogeneous domains. We investigate the methods' performance with direct and preconditioned Krylov iterative linear solvers. We then make recommendations for robust and efficient approaches to obtain steady-state solutions for RE under a range of conditions.
Infinite product expansion of the Fokker–Planck equation with steady-state solution
Martin, R. J.; Craster, R. V.; Kearney, M. J.
2015-01-01
We present an analytical technique for solving Fokker–Planck equations that have a steady-state solution by representing the solution as an infinite product rather than, as usual, an infinite sum. This method has many advantages: automatically ensuring positivity of the resulting approximation, and by design exactly matching both the short- and long-term behaviour. The efficacy of the technique is demonstrated via comparisons with computations of typical examples. PMID:26346100
Anti-periodic solutions of Liénard equations with state dependent impulses
NASA Astrophysics Data System (ADS)
Belley, J.-M.; Bondo, É.
2016-10-01
Subject to a priori bounds, Liénard equations with state dependent impulsive forcing are shown to admit a unique absolutely continuous anti-periodic solution with first derivative of bounded variation on finite intervals. The point-wise convergence of a sequence of iterates to the solution is obtained, along with a bound for the rate of convergence. The results are applied to Josephson's and van der Pol's equations.
Approximate semi-analytical solutions for the steady-state expansion of a contactor plasma
NASA Astrophysics Data System (ADS)
Camporeale, E.; Hogan, E. A.; MacDonald, E. A.
2015-04-01
We study the steady-state expansion of a collisionless, electrostatic, quasi-neutral plasma plume into vacuum, with a fluid model. We analyze approximate semi-analytical solutions, that can be used in lieu of much more expensive numerical solutions. In particular, we focus on the earlier studies presented in Parks and Katz (1979 American Institute of Aeronautics, Astronautics Conf. vol 1), Korsun and Tverdokhlebova (1997 33rd Joint Prop. Conf. (Seattle, WA) AIAA-97-3065), and Ashkenazy and Fruchtman (2001 27th Int. Electric Propulsion Conf. (Pasadena, CA)). By calculating the error with respect to the numerical solution, we can judge the range of validity for each solution. Moreover, we introduce a generalization of earlier models that has a wider range of applicability, in terms of plasma injection profiles. We conclude by showing a straightforward way to extend the discussed solutions to the case of a plasma plume injected with non-null azimuthal velocity.
f-state luminescence of lanthanide and actinide ions in solution
Beitz, J.V.
1993-09-01
Detailed studies of the luminescence of aquated Am{sup 3+} are presented in the context of prior lanthanide and actinide ion work. The luminescing state of aquated Am{sup 3+} is confirmed to be {sup 5}D{sub l} based on observed emission and excitation spectra. The luminescence lifetime of Am{sup 3+} in H{sub 2}O solution is (22 {plus_minus} 3) ns and (155 {plus_minus} 4) ns in D{sub 2}O solution at 295 K. Judd-Ofelt transition intensity theory qualitatively describes the observed Am{sup 3+} relative integrated fluorescence intensities. Recent luminescence studies on complexed trivalent f-element ions in solution are reviewed as to the similarities and differences between lanthanide ion 4f state and actinide ion 5f state properties.
Isotope Labeling for Solution and Solid-State NMR Spectroscopy of Membrane Proteins
Verardi, Raffaello; Traaseth, Nathaniel J.; Masterson, Larry R.; Vostrikov, Vitaly V.; Veglia, Gianluigi
2013-01-01
In this chapter, we summarize the isotopic labeling strategies used to obtain high-quality solution and solid-state NMR spectra of biological samples, with emphasis on integral membrane proteins (IMPs). While solution NMR is used to study IMPs under fast tumbling conditions, such as in the presence of detergent micelles or isotropic bicelles, solid-state NMR is used to study the structure and orientation of IMPs in lipid vesicles and bilayers. In spite of the tremendous progress in biomolecular NMR spectroscopy, the homogeneity and overall quality of the sample is still a substantial obstacle to overcome. Isotopic labeling is a major avenue to simplify overlapped spectra by either diluting the NMR active nuclei or allowing the resonances to be separated in multiple dimensions. In the following we will discuss isotopic labeling approaches that have been successfully used in the study of IMPs by solution and solid-state NMR spectroscopy. PMID:23076578
Zeron, E S; Santillán, M
2011-01-01
In this work, we introduce a couple of algorithms to compute the stationary probability distribution for the chemical master equation (CME) of arbitrary chemical networks. We further find the conditions guaranteeing the algorithms' convergence and the unity and stability of the stationary distribution. Next, we employ these algorithms to study the mRNA and protein probability distributions in a gene regulatory network subject to negative feedback regulation. In particular, we analyze the influence of the promoter activation/deactivation speed on the shape of such distributions. We find that a reduction of the promoter activation/deactivation speed modifies the shape of those distributions in a way consistent with the phenomenon known as mRNA (or transcription) bursting.
Regularity of the 3 D Stationary Hall Magnetohydrodynamic Equations on the Plane
NASA Astrophysics Data System (ADS)
Chae, Dongho; Wolf, Jörg
2017-08-01
We study the regularity of weak solutions to the 3D valued stationary Hall magnetohydrodynamic equations on R^2. We prove that every weak solution is smooth. Furthermore, we prove a Liouville type theorem for the Hall equations.
Analytical steady-state solutions for water-limited cropping systems using saline irrigation water
NASA Astrophysics Data System (ADS)
Skaggs, T. H.; Anderson, R. G.; Corwin, D. L.; Suarez, D. L.
2014-12-01
Due to the diminishing availability of good quality water for irrigation, it is increasingly important that irrigation and salinity management tools be able to target submaximal crop yields and support the use of marginal quality waters. In this work, we present a steady-state irrigated systems modeling framework that accounts for reduced plant water uptake due to root zone salinity. Two explicit, closed-form analytical solutions for the root zone solute concentration profile are obtained, corresponding to two alternative functional forms of the uptake reduction function. The solutions express a general relationship between irrigation water salinity, irrigation rate, crop salt tolerance, crop transpiration, and (using standard approximations) crop yield. Example applications are illustrated, including the calculation of irrigation requirements for obtaining targeted submaximal yields, and the generation of crop-water production functions for varying irrigation waters, irrigation rates, and crops. Model predictions are shown to be mostly consistent with existing models and available experimental data. Yet the new solutions possess advantages over available alternatives, including: (i) the solutions were derived from a complete physical-mathematical description of the system, rather than based on an ad hoc formulation; (ii) the analytical solutions are explicit and can be evaluated without iterative techniques; (iii) the solutions permit consideration of two common functional forms of salinity induced reductions in crop water uptake, rather than being tied to one particular representation; and (iv) the utilized modeling framework is compatible with leading transient-state numerical models.
Bound state solutions of the Schrödinger equation for modified Kratzer's molecular potential
NASA Astrophysics Data System (ADS)
Berkdemir, Cüneyt; Berkdemir, Ayşe; Han, Jiaguang
2006-01-01
We present the arbitrary angular momentum solutions of the Schrödinger equation for a diatomic molecule with the modified Kratzer potential De[( r - re)/ r] 2. The bound state energy eigenvalues and the corresponding eigenfunctions are obtained by the use of the Nikiforov-Uvarov (NU) method which is related to the solutions in terms of Jacobi polynomials. The bound states are calculated for various values of ℓ with n ⩽ 5 and applied to several diatomic molecules. All of these calculations present an effective and methodological procedure under the NU method to investigate the Kratzer's molecular systems.
Periodic solution for state-dependent impulsive shunting inhibitory CNNs with time-varying delays.
Şaylı, Mustafa; Yılmaz, Enes
2015-08-01
In this paper, we consider existence and global exponential stability of periodic solution for state-dependent impulsive shunting inhibitory cellular neural networks with time-varying delays. By means of B-equivalence method, we reduce these state-dependent impulsive neural networks system to an equivalent fix time impulsive neural networks system. Further, by using Mawhin's continuation theorem of coincide degree theory and employing a suitable Lyapunov function some new sufficient conditions for existence and global exponential stability of periodic solution are obtained. Previous results are improved and extended. Finally, we give an illustrative example with numerical simulations to demonstrate the effectiveness of our theoretical results.
State of ions in electrolyte solutions in the ionic-plasma approximation
Baldanov, M.M.; Mokhosoev, M.V.
1986-04-01
This paper examines the state of ions in the framework of the concept of an ionic plasma. Results are presented of the evaluations of the equivalent conductivity of lithium chloride in aqueous solutions at 18 C. The Debye-Falkenhagne effect and the Wien effect are discussed. The proposed interpretation of the state of ions in electrolyte solutions gives a more natural and more systematic explanation for such factors as the Debye-Falkenhagen dispersion of the electrical conductivity, the Wien effect, and the activity coefficients of electrolytes.
A solid state and solution NMR study of the tautomerism in hydroxyquinoline carboxylic acids.
Gudat, Dietrich; Nycz, Jacek E; Polanski, Jaroslaw
2008-01-01
Some hydroxyquinoline carboxylic acids and their conjugate acids and bases were characterized by 13C and 15N NMR spectroscopy in solution and in the solid state. Differences in 13C and, in particular, 15N chemical shift patterns allow to distinguish between individual tautomers and confirm the presence of zwitterionic species in the solid state. Solution NMR spectra in dimethyl sulfoxide (DMSO) show effects resulting as a consequence of dynamic exchange and suggest the presence of an equilibrium mixture of hydroxyquinoline carboxylic acid and zwitterionic hydroxyquinolinium carboxylate tautomers.
R. Haggerty
2013-01-01
In this technical note, a steady-state analytical solution of concentrations of a parent solute reacting to a daughter solute, both of which are undergoing transport and multirate mass transfer, is presented. Although the governing equations are complicated, the resulting solution can be expressed in simple terms. A function of the ratio of concentrations, In (daughter...
Quantum stability of nonlinear wave type solutions with intrinsic mass parameter in QCD
NASA Astrophysics Data System (ADS)
Kim, Youngman; Lee, Bum-Hoon; Pak, D. G.; Park, Chanyong; Tsukioka, Takuya
2017-09-01
The problem of the existence of a stable vacuum field in pure QCD is revised. Our approach is based on using classical stationary nonlinear wave type solutions with an intrinsic mass scale parameter. Such solutions can be treated as quantum-mechanical wave functions describing massive spinless states in quantum theory. We verify whether nonlinear wave type solutions can form a stable vacuum field background within the framework of the effective action formalism. We demonstrate that there is a special class of stationary generalized Wu-Yang monopole solutions that are stable against quantum gluon fluctuations.
Uniqueness of Positive Ground State Solutions of the Logarithmic Schrödinger Equation
NASA Astrophysics Data System (ADS)
Troy, William C.
2016-12-01
We prove the uniqueness of positive ground state solutions of the problem { {{d2u}/{dr2}} + {{n-1}/{r}}{du/dr}} + u ln(|u|) = 0}, {u(r) > 0 forall r ≥ 0}, and {(u(r),u'(r)) to (0, 0)} as {r to ∞}. This equation is derived from the logarithmic Schrödinger equation {iψt = {Δ} ψ + u ln (|u|2)}, and also from the classical equation {{{partial u}/{partial t}} = {Δ} u +u (|u|^{p-1}) -u}. For each {n ≥ 1}, a positive ground state solution is { u0(r) = exp (-{r^2/4} + {n/2}), 0 ≤ r < ∞}. We combine {u0(r)} with energy estimates and associated Ricatti equation estimates to prove that, for each {n in [1, 9 ]}, {u0(r)} is the only positive ground state. We also investigate the stability of {u0(r)}. Several open problems are stated.
Generalized stationary phase approximations for mountain waves
NASA Astrophysics Data System (ADS)
Knight, H.; Broutman, D.; Eckermann, S. D.
2016-04-01
Large altitude asymptotic approximations are derived for vertical displacements due to mountain waves generated by hydrostatic wind flow over arbitrary topography. This leads to new asymptotic analytic expressions for wave-induced vertical displacement for mountains with an elliptical Gaussian shape and with the major axis oriented at any angle relative to the background wind. The motivation is to understand local maxima in vertical displacement amplitude at a given height for elliptical mountains aligned at oblique angles to the wind direction, as identified in Eckermann et al. ["Effects of horizontal geometrical spreading on the parameterization of orographic gravity-wave drag. Part 1: Numerical transform solutions," J. Atmos. Sci. 72, 2330-2347 (2015)]. The standard stationary phase method reproduces one type of local amplitude maximum that migrates downwind with increasing altitude. Another type of local amplitude maximum stays close to the vertical axis over the center of the mountain, and a new generalized stationary phase method is developed to describe this other type of local amplitude maximum and the horizontal variation of wave-induced vertical displacement near the vertical axis of the mountain in the large altitude limit. The new generalized stationary phase method describes the asymptotic behavior of integrals where the asymptotic parameter is raised to two different powers (1/2 and 1) rather than just one power as in the standard stationary phase method. The vertical displacement formulas are initially derived assuming a uniform background wind but are extended to accommodate both vertical shear with a fixed wind direction and vertical variations in the buoyancy frequency.
Stationary Black Holes: Uniqueness and Beyond.
Chruściel, Piotr T; Costa, João Lopes; Heusler, Markus
2012-01-01
The spectrum of known black-hole solutions to the stationary Einstein equations has been steadily increasing, sometimes in unexpected ways. In particular, it has turned out that not all black-hole-equilibrium configurations are characterized by their mass, angular momentum and global charges. Moreover, the high degree of symmetry displayed by vacuum and electro-vacuum black-hole spacetimes ceases to exist in self-gravitating non-linear field theories. This text aims to review some developments in the subject and to discuss them in light of the uniqueness theorem for the Einstein-Maxwell system.
Size evolution and surface characterization of solid-state nanopores in different aqueous solutions.
Li, Qingtao; Zhao, Qing; Lu, Bo; Zhang, Hengbin; Liu, Song; Tang, Zhipeng; Qu, Lijia; Zhu, Rui; Zhang, Jingmin; You, Liping; Yang, Fuhua; Yu, Dapeng
2012-03-07
The stability and surface evolution of solid-state nanopores in aqueous solutions are extremely important since they would get immersed in solutions during DNA translocation experiment for DNA analyses. In this work, we systematically studied the size evolution of SiN nanopores in ethanol, deionized water and potassium chloride (KCl) solutions by careful surface characterization and composition analyses using a transmission electron microscope. Surprisingly, we found that nanopores closed up completely in ethanol in an hour and showed a 30% and 20% size decrease in deionized water and KCl solutions, respectively. Strong evidence of surface oxidation was found by composition analyses in the nanopore area. Nanopore size evolution was strongly dependent on initial pore size and solution pH value. In pH = 13 KCl solution, SiN nanopores were observed to increase in size instead of decrease. The results not only provide useful information for DNA detection based on solid-state nanopores, but can also guide design and application of other nanodevices exposed to electrolyte-solvent systems such as cell-on-a-chip devices and biosensors.
NASA Astrophysics Data System (ADS)
Gorbatenko, M. V.; Neznamov, V. P.; Popov, E. Yu; Safronov, I. I.
2016-02-01
The paper explores quantum mechanics of half-spin particle motion in the field of Reissner-Nordström (RN) naked singularity. It is shown that for any quantum mechanical Dirac particle, irrespective of availability and sign of its electrical charge, the RN naked singularity is separated by an infinitely high positive potential barrier. With like charges of a particle and the source of the RN naked singularity, near the origin there exists the second completely impenetrable potential barrier. It has been proved that in the field of the RN naked singularity, bound states of half-spin particles can exist. The conditions for appearance of such states were revealed and computations were performed to find energy eigenvalues and eigenfunctions.
A solution state diode using semiconductor polymer nanorods with nanogap electrodes.
Mutlu, Senol; Sonmez, Bedri Gurkan
2012-06-22
A solution state polymer diode, which uses regioregular poly(3-hexylthiophene-2,5-diyl) (P3HT):dichlorobenzene solution as the semiconductor between highly doped p-type silicon and aluminum electrodes has been built. Electrodes separated by a 40 nm gap enable intra-chain charge carrier transfer through the lengths of single polymer chains. This prevents chain to chain hopping and chain entanglements, increasing carrier mobility. The degradation with time and hysteresis effects of the diodes are measured. An optimal P3HT solution concentration of 6 mg ml(-1) is found. A current density of at least 300 mA cm(-2) is achieved, indicating at least a six-fold improvement in carrier mobility compared to previously fabricated solid state P3HT diodes.
On the existence of sign changing bound state solutions of a quasilinear equation
NASA Astrophysics Data System (ADS)
Cortázar, Carmen; García-Huidobro, Marta; Yarur, Cecilia S.
In this paper we establish the existence of bound state solutions having a prescribed number of sign changes for (P) Δmu+f(u)=0, x∈RN, N⩾m>1, where Δmu=∇ṡ(|∇u). Our result is new even for the case of the Laplacian (m=2).
USING HIGH-RESOLUTION SOLUTION-STATE NMR SPECTROSCOPY TO INVESTIGATE PMDI REACTIONS WITH WOOD
USDA-ARS?s Scientific Manuscript database
Solution-state NMR spectroscopy provides a powerful tool for understanding the formation of chemical bonds between wood components and adhesives. Finely ground cell wall (CW) material fully dissolves in a solvent system containing dimethylsulfoxide (DMSO-d6) and N-methyl¬imidazole (NMI-d6), keeping ...
NASA Astrophysics Data System (ADS)
Hernandez, Eduardo; Pierri, Michelle; Wu, Jianhong
2016-12-01
We study the existence and uniqueness of C 1 + α-strict solutions for a general class of abstract differential equations with state dependent delay. We also study the local well-posedness of this type of problems on subspaces of C 1 + α ([ - p , 0 ] ; X). Some examples involving partial differential equations are presented.
High-resolution solution-state NMR of unfractionated plant cell walls
John Ralph; Fachuang Lu; Hoon Kim; Dino Ress; Daniel J. Yelle; Kenneth E. Hammel; Sally A. Ralph; Bernadette Nanayakkara; Armin Wagner; Takuya Akiyama; Paul F. Schatz; Shawn D. Mansfield; Noritsugu Terashima; Wout Boerjan; Bjorn Sundberg; Mattias Hedenstrom
2009-01-01
Detailed structural studies on the plant cell wall have traditionally been difficult. NMR is one of the preeminent structural tools, but obtaining high-resolution solution-state spectra has typically required fractionation and isolation of components of interest. With recent methods for dissolution of, admittedly, finely divided plant cell wall material, the wall can...
Efficient and Color-Tunable Oxyfluoride Solid Solution Phosphors for Solid-State White Lighting
Im, Won Bin; George, Nathan; Kurzman, Joshua; Brinkley, Stuart; Mikhailovsky, Alexander; Hu, Jerry; Chmelka, Bradley F.; DenBaars, Steven P.; Seshadri, Ram
2012-09-06
A solid solution strategy helps increase the efficiency of Ce{sup 3+} oxyfluoride phosphors for solid-state white lighting. The use of a phosphor-capping architecture provides additional light extraction. The accompanying image displays electroluminescence spectra from a 434-nm InGaN LED phosphor that has been capped with the oxyfluoride phosphor.
Existence of ground state solutions to Dirac equations with vanishing potentials at infinity
NASA Astrophysics Data System (ADS)
Figueiredo, Giovany M.; Pimenta, Marcos T. O.
2017-01-01
In this work we study the existence of ground-state solutions of Dirac equations with potentials which are allowed to vanish at infinity. The approach is based on minimization of the energy functional over a generalized Nehari set. Some conditions on the potentials are given in order to overcome the lack of compactness.
Investigation of the oxidation states of Pu isotopes in a hydrochloric acid solution.
Lee, M H; Kim, J Y; Kim, W H; Jung, E C; Jee, K Y
2008-12-01
The characteristics of the oxidation states of Pu in a hydrochloric acid solution were investigated and the results were applied to a separating of Pu isotopes from IAEA reference soils. The oxidation states of Pu(III) and Pu(IV) were prepared by adding hydroxylamine hydrochloride and sodium nitrite to a Pu stock solution, respectively. Also, the oxidation state of Pu(VI) was adjusted with concentrated HNO(3) and HClO(4). The stability of the various oxidation states of plutonium in a HCl solution with elapsed time after preparation were found to be in the following order: Pu(III) approximately Pu(VI)>Pu(IV)>Pu(V). The chemical recoveries of Pu(IV) in a 9M HCl solution with an anion exchange resin were similar to those of Pu(VI). This method for the determination of Pu isotopes with an anion exchange resin in a 9M HCl medium was applied to IAEA reference soils where the activity concentrations of (239,240)Pu and (238)Pu in IAEA-375 and IAEA-326 were consistent with the reference values reported by the IAEA.
The equation of state for solutions of the sunflower oil+isomerhexane system
NASA Astrophysics Data System (ADS)
Safarov, M. M.; Abdukhamidova, Z.
1995-11-01
The article presents the results of an experimental investigation into the density of solutions of the sunflower oil+isomerhexane system (from 23 to 75%) at temperatures of from 293 to 450 K and pressures of from 0.101 to 98.1 MPa. An equation of state is obtained.
Jehle, Stefan; van Rossum, Barth; Stout, Joseph R; Noguchi, Satoshi M; Falber, Katja; Rehbein, Kristina; Oschkinat, Hartmut; Klevit, Rachel E; Rajagopal, Ponni
2009-02-06
Atomic-level structural information on alphaB-Crystallin (alphaB), a prominent member of the small heat-shock protein family, has been a challenge to obtain due its polydisperse oligomeric nature. We show that magic-angle spinning solid-state NMR can be used to obtain high-resolution information on an approximately 580-kDa human alphaB assembled from 175-residue 20-kDa subunits. An approximately 100-residue alpha-crystallin domain is common to all small heat-shock proteins, and solution-state NMR was performed on two different alpha-crystallin domain constructs isolated from alphaB. In vitro, the chaperone-like activities of full-length alphaB and the isolated alpha-crystallin domain are identical. Chemical shifts of the backbone and C(beta) resonances have been obtained for residues 64-162 (alpha-crystallin domain plus part of the C-terminus) in alphaB and the isolated alpha-crystallin domain by solid-state and solution-state NMR, respectively. Both sets of data strongly predict six beta-strands in the alpha-crystallin domain. A majority of residues in the alpha-crystallin domain have similar chemical shifts in both solid-state and solution-state, indicating similar structures for the domain in its isolated and oligomeric forms. Sites of intersubunit interaction are identified from chemical shift differences that cluster to specific regions of the alpha-crystallin domain. Multiple signals are observed for the resonances of M68 in the oligomer, identifying the region containing this residue as existing in heterogeneous environments within alphaB. Evidence for a novel dimerization motif in the human alpha-crystallin domain is obtained by a comparison of (i) solid-state and solution-state chemical shift data and (ii) (1)H-(15)N heteronuclear single quantum coherence spectra as a function of pH. The isolated alpha-crystallin domain undergoes a dimer-monomer transition over the pH range 7.5-6.8. This steep pH-dependent switch may be important for alphaB to function
Jehle, Stefan; van Rossum, Barth; Stout, Joseph R.; Noguchi, Satoshi M.; Falber, Katja; Rehbein, Kristina; Oschkinat, Hartmut; Klevit, Rachel E.; Rajagopal, Ponni
2008-11-14
Atomic-level structural information on αB-Crystallin (αB), a prominent member of the small heat-shock protein family, has been a challenge to obtain due its polydisperse oligomeric nature. We show that magic-angle spinning solid-state NMR can be used to obtain high-resolution information on an ~580-kDa human αB assembled from 175-residue 20-kDa subunits. An ~100-residue α-crystallin domain is common to all small heat-shock proteins, and solution-state NMR was performed on two different α- crystallin domain constructs isolated from αB. In vitro, the chaperone-like activities of full-length αB and the isolated α-crystallin domain are identical. Chemical shifts of the backbone and C^{β }resonances have been obtained for residues 64–162 (α-crystallin domain plus part of the C-terminus) in αB and the isolated α-crystallin domain by solid-state and solution-state NMR, respectively. Both sets of data strongly predict six β-strands in the α-crystallin domain. A majority of residues in the α-crystallin domain have similar chemical shifts in both solid-state and solution-state, indicating similar structures for the domain in its isolated and oligomeric forms. Sites of intersubunit interaction are identified from chemical shift differences that cluster to specific regions of the α-crystallin domain. Multiple signals are observed for the resonances of M68 in the oligomer, identifying the region containing this residue as existing in heterogeneous environments within αB. Evidence for a novel dimerization motif in the human α-crystallin domain is obtained by a comparison of (i) solid-state and solution-state chemical shift data and (ii) ^{1}H–^{15}N heteronuclear single quantum coherence spectra as a function of pH. The isolated α-crystallin domain undergoes a dimer–monomer transition over the pH range 7.5–6.8. This steep pHdependent switch may be important for αB to function optimally (e.g., to preserve the filament integrity
A fluorescent chemosensor for Zn(II). Exciplex formation in solution and the solid state.
Bencini, Andrea; Berni, Emanuela; Bianchi, Antonio; Fornasari, Patrizia; Giorgi, Claudia; Lima, Joao C; Lodeiro, Carlos; Melo, Maria J; de Melo, J Seixas; Parola, Antonio Jorge; Pina, Fernando; Pina, Joao; Valtancoli, Barbara
2004-07-21
The macrocyclic phenanthrolinophane 2,9-[2,5,8-triaza-5-(N-anthracene-9-methylamino)ethyl]-[9]-1,10-phenanthrolinophane (L) bearing a pendant arm containing a coordinating amine and an anthracene group forms stable complexes with Zn(II), Cd(II) and Hg(II) in solution. Stability constants of these complexes were determined in 0.10 mol dm(-3) NMe(4)Cl H(2)O-MeCN (1:1, v/v) solution at 298.1 +/- 0.1 K by means of potentiometric (pH metric) titration. The fluorescence emission properties of these complexes were studied in this solvent. For the Zn(II) complex, steady-state and time-resolved fluorescence studies were performed in ethanol solution and in the solid state. In solution, intramolecular pi-stacking interaction between phenanthroline and anthracene in the ground state and exciplex emission in the excited state were observed. From the temperature dependence of the photostationary ratio (I(Exc)/I(M)), the activation energy for the exciplex formation (E(a)) and the binding energy of the exciplex (-DeltaH) were determined. The crystal structure of the [ZnLBr](ClO(4)).H(2)O compound was resolved, showing that in the solid state both intra- and inter-molecular pi-stacking interactions are present. Such interactions were also evidenced by UV-vis absorption and emission spectra in the solid state. The absorption spectrum of a thin film of the solid complex is red-shifted compared with the solution spectra, whereas its emission spectrum reveals the unique featureless exciplex band, blue shifted compared with the solution. In conjunction with X-ray data the solid-state data was interpreted as being due to a new exciplex where no pi-stacking (full overlap of the pi-electron cloud of the two chromophores - anthracene and phenanthroline) is observed. L is a fluorescent chemosensor able to signal Zn(II) in presence of Cd(II) and Hg(II), since the last two metal ions do not give rise either to the formation of pi-stacking complexes or to exciplex emission in solution.
Raynal, Philippe; Luetkenhaus, Norbert
2005-08-15
Recently the problem of unambiguous state discrimination of mixed quantum states has attracted much attention. So far, bounds on the optimum success probability have been derived [T. Rudolph, R. W. Spekkens, and P. S. Turner, Phys. Rev. A 68, 010301(R) (2003)]. For two mixed states they are given in terms of the fidelity. Here we give tighter bounds as well as necessary and sufficient conditions for two mixed states to reach these bounds. Moreover we construct the corresponding optimal measurement strategies. With this result, we provide analytical solutions for unambiguous discrimination of a class of generic mixed states. This goes beyond known results which are all reducible to some pure state case. Additionally, we show that examples exist where the bounds cannot be reached.
Deremigio, Hilary; Kemper, Peter; Lamar, M Drew; Smith, Gregory D
2008-01-01
Mathematical models of calcium release sites derived from Markov chain models of intracellular calcium channels exhibit collective gating reminiscent of the experimentally observed phenomenon of stochastic calcium excitability (i.e., calcium puffs and sparks). We present a Kronecker structured representation for calcium release site models and perform benchmark stationary distribution calculations using numerical iterative solution techniques that leverage this structure. In this context we find multi-level methods and certain preconditioned projection methods superior to simple Gauss-Seidel type iterations. Response measures such as the number of channels in a particular state converge more quickly using these numerical iterative methods than occupation measures calculated via Monte Carlo simulation.
Theory of a stationary microwave discharge with multiply charged ions in an expanding gas jet
NASA Astrophysics Data System (ADS)
Shalashov, A. G.; Abramov, I. S.; Golubev, S. V.; Gospodchikov, E. D.
2016-08-01
The formation of a jet of a nonequilibrium multiply charged ion plasma is studied in the inhomogeneous gas jet. It is shown that the geometrical divergence of the jet restricts the maximum ion charge state and results in the spatial localization of the discharge. Stationary solutions corresponding to such regimes are constructed. The model proposed can be used to optimize modern experiments on generation of hard UV radiation due to the line emission of multiply ionized atoms in a gas jet heated by high-power millimeter and submillimeter radiation.
Theory of a stationary microwave discharge with multiply charged ions in an expanding gas jet
Shalashov, A. G. Abramov, I. S.; Golubev, S. V.; Gospodchikov, E. D.
2016-08-15
The formation of a jet of a nonequilibrium multiply charged ion plasma is studied in the inhomogeneous gas jet. It is shown that the geometrical divergence of the jet restricts the maximum ion charge state and results in the spatial localization of the discharge. Stationary solutions corresponding to such regimes are constructed. The model proposed can be used to optimize modern experiments on generation of hard UV radiation due to the line emission of multiply ionized atoms in a gas jet heated by high-power millimeter and submillimeter radiation.
Shim, Jaesool; Yoo, Kisoo; Dutta, Prashanta
2017-03-01
The determination of an analytical solution to find the steady-state protein concentration distribution in IEF is very challenging due to the nonlinear coupling between mass and charge conservation equations. In this study, approximate analytical solutions are obtained for steady-state protein distribution in carrier ampholyte based IEF. Similar to the work of Svensson, the final concentration profile for proteins is assumed to be Gaussian, but appropriate expressions are presented in order to obtain the effective electric field and pH gradient in the focused protein band region. Analytical results are found from iterative solutions of a system of coupled algebraic equations using only several iterations for IEF separation of three plasma proteins: albumin, cardiac troponin I, and hemoglobin. The analytical results are compared with numerically predicted results for IEF, showing excellent agreement. Analytically obtained electric field and ionic conductivity distributions show significant deviation from their nominal values, which is essential in finding the protein focusing behavior at isoelectric points. These analytical solutions can be used to determine steady-state protein concentration distribution for experiment design of IEF considering any number of proteins and ampholytes. Moreover, the model presented herein can be used to find the conductivity, electric field, and pH field. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.
Combining solid-state and solution-state 31P NMR to study in vivo phosphorus metabolism.
Cholli, A L; Yamane, T; Jelinski, L W
1985-01-01
Otherwise unavailable information concerning the distribution of phosphorylated compounds in biological systems is obtained by a combined solid-state/solution-state NMR approach, illustrated here for oocytes from Rana pipiens. General methodology is developed, and further extensions are proposed. The following conclusions pertain to the specific system under examination. (i) Nucleoside phosphates can be observed by magic-angle sample spinning of the lyophilized material. (ii) The solid-state NMR technique of dipolar decoupling provides no additional resolution of the phospholipid and phosphoprotein components of the yolk. However, cellular death produces sufficient pH changes to cause the phospholipid and protein phosphate peaks to become resolvable. The concentration of nucleoside phosphates also decreases. (iii) The phospholipid and phosphoprotein components are shown by computer simulation to be present in a ratio of 40:60, respectively. (iv) The amounts of inorganic phosphate, nucleoside phosphates, and sugar phosphates are determined by solution-state NMR observation of the perchloric acid extract of the oocytes. PMID:3871524
Gillet, Sébastien; Aguedo, Mario; Petrut, Raul; Olive, Gilles; Anastas, Paul; Blecker, Christophe; Richel, Aurore
2017-03-01
Two fractions of carob galactomannans (GM25 and GM80) were extracted at respectively 25°C and 80°C from crude locust bean gum. Those fractions having slightly different chemical structures, previously characterized, were studied for their viscosity properties over a wide range of concentrations: diluted solution, unperturbed state and gel state. For each of the physical properties, links to the chemical fine structure could be established, expanding knowledge on the topic: in dilute solution, GM25 is more soluble in water while GM80 seems to tend to self-association due to its structure as highlighted by intrinsic viscosity measurements ([η]GM25=9.96dLg(-1) and [η]GM80=4.04dLg(-1)). In unperturbed state, initial viscosities η0 were more important for GM80 fractions at 1% and 2% due to greater hyperentanglements (η0(GM80,1%)=9.9Pas; η0(GM80,2%)=832.0; Pa.s η0(GM25,1%)=3.1Pas; η0(GM25,2%)=45.1Pas). In gel state, hydrogels obtained from GM80 were also stronger (hardness GM80 (2%)=0.51N and hardness GM25 (2%)=0.11N), suggesting a much more important number of junction areas within the gel network. The findings discussed herein demonstrate the potential for new applications.
Multiplicity results for sign changing bound state solutions of a semilinear equation
NASA Astrophysics Data System (ADS)
Cortázar, Carmen; García-Huidobro, Marta; Herreros, Pilar
2015-12-01
In this paper we give conditions on $f$ so that problem $$ \\Delta u +f(u)=0,\\quad x\\in \\mathbb{R}^N, N\\ge 2, $$ has at least two radial bound state solutions with any prescribed number of zeros, and such that $u(0)$ belongs to a specific subinterval of $(0,\\infty)$. This property will allow us to give conditions on $f$ so that this problem has at least any given number of radial solutions having a prescribed number of zeros.
On the steady-state solutions of a nonlinear photonic lattice model
Liu, Chungen E-mail: tjftp@mail.nankai.edu.cn; Ren, Qiang E-mail: tjftp@mail.nankai.edu.cn
2015-03-15
In this paper, we consider the steady-state solutions of the following equation related with nonlinear photonic lattice model Δu=(Pu)/(1+|u|{sup 2}+|v|{sup 2}) +λu, Δv=(Qv)/(1+|u|{sup 2}+|v|{sup 2}) +λv, where u, v are real-value function defined on R/(τ{sub 1}Z) × R/(τ{sub 2}Z). The existence and non-existence of non-constant semi-trivial (with only one component zero) solutions are considered.
A multi-level solution algorithm for steady-state Markov chains
NASA Technical Reports Server (NTRS)
Horton, Graham; Leutenegger, Scott T.
1993-01-01
A new iterative algorithm, the multi-level algorithm, for the numerical solution of steady state Markov chains is presented. The method utilizes a set of recursively coarsened representations of the original system to achieve accelerated convergence. It is motivated by multigrid methods, which are widely used for fast solution of partial differential equations. Initial results of numerical experiments are reported, showing significant reductions in computation time, often an order of magnitude or more, relative to the Gauss-Seidel and optimal SOR algorithms for a variety of test problems. The multi-level method is compared and contrasted with the iterative aggregation-disaggregation algorithm of Takahashi.
Influence of Stationary Crossflow Modulation on Secondary Instability
NASA Technical Reports Server (NTRS)
Choudhari, Meelan M.; Li, Fei; Paredes, Pedro
2016-01-01
A likely scenario for swept wing transition on subsonic aircraft with natural laminar flow involves the breakdown of stationary crossflow vortices via high frequency secondary instability. A majority of the prior research on this secondary instability has focused on crossflow vortices with a single dominant spanwise wavelength. This paper investigates the effects of the spanwise modulation of stationary crossflow vortices at a specified wavelength by a subharmonic stationary mode. Secondary instability of the modulated crossflow pattern is studied using planar, partial-differential-equation based eigenvalue analysis. Computations reveal that weak modulation by the first subharmonic of the input stationary mode leads to mode splitting that is particularly obvious for Y-type secondary modes that are driven by the wall-normal shear of the basic state. Thus, for each Y mode corresponding to the fundamental wavelength of results in unmodulated train of crossflow vortices, the modulated flow supports a pair of secondary modes with somewhat different amplification rates. The mode splitting phenomenon suggests that a more complex stationary modulation such as that induced by natural surface roughness would yield a considerably richer spectrum of secondary instability modes. Even modest levels of subharmonic modulation are shown to have a strong effect on the overall amplification of secondary disturbances, particularly the Z-modes driven by the spanwise shear of the basic state. Preliminary computations related to the nonlinear breakdown of these secondary disturbances provide interesting insights into the process of crossflow transition in the presence of the first subharmonic of the dominant stationary vortex.
A hybrid multigrid technique for computing steady-state solutions to supersonic flows
NASA Technical Reports Server (NTRS)
Sanders, Richard
1992-01-01
Recently, Li and Sanders have introduced a class of finite difference schemes to approximate generally discontinuous solutions to hyperbolic systems of conservation laws. These equations have the form together with relevant boundary conditions. When modelling hypersonic spacecraft reentry, the differential equations above are frequently given by the compressible Euler equations coupled with a nonequilibrium chemistry model. For these applications, steady state solutions are often sought. Many tens (to hundreds) of super computer hours can be devoted to a single three space dimensional simulation. The primary difficulty is the inability to rapidly and reliably capture the steady state. In these notes, we demonstrate that a particular variant from the schemes presented can be combined with a particular multigrid approach to capture steady state solutions to the compressible Euler equations in one space dimension. We show that the rate of convergence to steady state coming from this multigrid implementation is vastly superior to the traditional approach of artificial time relaxation. Moreover, we demonstrate virtual grid independence. That is, the rate of convergence does not depend on the degree of spatial grid refinement.
West, C; Lesellier, E
2006-03-31
In this third paper, varied types of polar stationary phases, namely silica gel (SI), cyano (CN)- and amino-propyl (NH2)-bonded silica, propanediol-bonded silica (DIOL), poly(ethylene glycol) (PEG) and poly(vinyl alcohol) (PVA), were investigated in subcritical fluid mobile phase. This study was performed to provide a greater knowledge of the properties of these phases in SFC, and to allow a more rapid and efficient choice of polar stationary phase in regard of the chemical nature of the solutes to be separated. The effect of the nature of the stationary phase on interactions between solute and stationary phases and between solute and carbon dioxide-modifier mobile phases was studied by the use of a linear solvation energy relationship (LSER), the solvation parameter model. The retention behaviour observed with sub/supercritical fluid with carbon dioxide-methanol is close to the one reported in normal-phase liquid chromatography with hexane. The hydrogen bond acidity and basicity, and the polarity/polarizability favour the solute retention when the molar volume of the solute reduces it. As with non-polar phases, the absence of water in the subcritical fluid allows the solute/stationary phase interactions to play a greater part in the retention behaviour. As expected, the DIOL phase and the bare silica display a similar behaviour towards acidic and basic solutes, when interactions with basic compounds are lower with the NH2 phase. On the CN phase, all interactions (hydrogen bonding, dipole-dipole and charge transfer) have a nearly equivalent weight on the retention. The polymeric phases, PEG and PVA, provide the most accurate models, possibly due to their better surface homogeneity.
Co‐existence of Distinct Supramolecular Assemblies in Solution and in the Solid State
Reddy, G. N. Manjunatha; Huqi, Aida; Iuga, Dinu; Sakurai, Satoshi; Marsh, Andrew; Davis, Jeffery T.; Masiero, Stefano
2016-01-01
Abstract The formation of distinct supramolecular assemblies, including a metastable species, is revealed for a lipophilic guanosine (G) derivative in solution and in the solid state. Structurally different G‐quartet‐based assemblies are formed in chloroform depending on the nature of the cation, anion and the salt concentration, as characterized by circular dichroism and time course diffusion‐ordered NMR spectroscopy data. Intriguingly, even the presence of potassium ions that stabilize G‐quartets in chloroform was insufficient to exclusively retain such assemblies in the solid state, leading to the formation of mixed quartet and ribbon‐like assemblies as revealed by fast magic‐angle spinning (MAS) NMR spectroscopy. Distinct N−H⋅⋅⋅N and N−H⋅⋅⋅O intermolecular hydrogen bonding interactions drive quartet and ribbon‐like self‐assembly resulting in markedly different 2D 1H solid‐state NMR spectra, thus facilitating a direct identification of mixed assemblies. A dissolution NMR experiment confirmed that the quartet and ribbon interconversion is reversible–further demonstrating the changes that occur in the self‐assembly process of a lipophilic nucleoside upon a solid‐state to solution‐state transition and vice versa. A systematic study for complexation with different cations (K+, Sr2+) and anions (picrate, ethanoate and iodide) emphasizes that the existence of a stable solution or solid‐state structure may not reflect the stability of the same supramolecular entity in another phase. PMID:27897351
Active Control of Stationary Vortices
NASA Astrophysics Data System (ADS)
Nino, Giovanni; Breidenthal, Robert; Bhide, Aditi; Sridhar, Aditya
2016-11-01
A system for active stationary vortex control is presented. The system uses a combination of plasma actuators, pressure sensors and electrical circuits deposited on aerodynamic surfaces using printing electronics methods. Once the pressure sensors sense a change on the intensity or on the position of the stationary vortices, its associated controller activates a set of plasma actuator to return the vortices to their original or intended positions. The forces produced by the actuators act on the secondary flow in the transverse plane, where velocities are much less than in the streamwise direction. As a demonstration case, the active vortex control system is mounted on a flat plate under low speed wind tunnel testing. Here, a set of vortex generators are used to generate the stationary vortices and the plasma actuators are used to move them. Preliminary results from the experiments are presented and compared with theoretical values. Thanks to the USAF AFOSR STTR support under contract # FA9550-15-C-0007.
On the Oxidation State of Manganese Ions in Li-Ion Battery Electrolyte Solutions.
Banerjee, Anjan; Shilina, Yuliya; Ziv, Baruch; Ziegelbauer, Joseph M; Luski, Shalom; Aurbach, Doron; Halalay, Ion C
2017-02-08
We demonstrate herein that Mn(3+) and not Mn(2+), as commonly accepted, is the dominant dissolved manganese cation in LiPF6-based electrolyte solutions of Li-ion batteries with lithium manganate spinel positive and graphite negative electrodes chemistry. The Mn(3+) fractions in solution, derived from a combined analysis of electron paramagnetic resonance and inductively coupled plasma spectroscopy data, are ∼80% for either fully discharged (3.0 V hold) or fully charged (4.2 V hold) cells, and ∼60% for galvanostatically cycled cells. These findings agree with the average oxidation state of dissolved Mn ions determined from X-ray absorption near-edge spectroscopy data, as verified through a speciation diagram analysis. We also show that the fractions of Mn(3+) in the aprotic nonaqueous electrolyte solution are constant over the duration of our experiments and that disproportionation of Mn(3+) occurs at a very slow rate.
Protein Crystal Growth in Gels and Stationary Magnetic Fields
Moreno,A.; Quiroz-Garcia, B.; Yokaichiya, F.; Stojanoff, V.; Rudolph, P.
2007-01-01
Thaumatin, lysozyme, and ferritin single crystals were grown in solutions and gels without and with surrounding strong stationary magnetic fields. The crystal size, number and alignment in dependence on the induction force were analyzed. The crystal quality, like mosaicity, as function of the magnetic force is discussed by using synchrotron X-ray diffraction analysis.
Cao, Youfang; Terebus, Anna; Liang, Jie
2016-01-01
The discrete chemical master equation (dCME) provides a general framework for studying stochasticity in mesoscopic reaction networks. Since its direct solution rapidly becomes intractable due to the increasing size of the state space, truncation of the state space is necessary for solving most dCMEs. It is therefore important to assess the consequences of state space truncations so errors can be quantified and minimized. Here we describe a novel method for state space truncation. By partitioning a reaction network into multiple molecular equivalence groups (MEG), we truncate the state space by limiting the total molecular copy numbers in each MEG. We further describe a theoretical framework for analysis of the truncation error in the steady state probability landscape using reflecting boundaries. By aggregating the state space based on the usage of a MEG and constructing an aggregated Markov process, we show that the truncation error of a MEG can be asymptotically bounded by the probability of states on the reflecting boundary of the MEG. Furthermore, truncating states of an arbitrary MEG will not undermine the estimated error of truncating any other MEGs. We then provide an overall error estimate for networks with multiple MEGs. To rapidly determine the appropriate size of an arbitrary MEG, we also introduce an a priori method to estimate the upper bound of its truncation error. This a priori estimate can be rapidly computed from reaction rates of the network, without the need of costly trial solutions of the dCME. As examples, we show results of applying our methods to the four stochastic networks of 1) the birth and death model, 2) the single gene expression model, 3) the genetic toggle switch model, and 4) the phage lambda bistable epigenetic switch model. We demonstrate how truncation errors and steady state probability landscapes can be computed using different sizes of the MEG(s) and how the results validate out theories. Overall, the novel state space
Cao, Youfang; Terebus, Anna; Liang, Jie
2016-04-01
The discrete chemical master equation (dCME) provides a general framework for studying stochasticity in mesoscopic reaction networks. Since its direct solution rapidly becomes intractable due to the increasing size of the state space, truncation of the state space is necessary for solving most dCMEs. It is therefore important to assess the consequences of state space truncations so errors can be quantified and minimized. Here we describe a novel method for state space truncation. By partitioning a reaction network into multiple molecular equivalence groups (MEGs), we truncate the state space by limiting the total molecular copy numbers in each MEG. We further describe a theoretical framework for analysis of the truncation error in the steady-state probability landscape using reflecting boundaries. By aggregating the state space based on the usage of a MEG and constructing an aggregated Markov process, we show that the truncation error of a MEG can be asymptotically bounded by the probability of states on the reflecting boundary of the MEG. Furthermore, truncating states of an arbitrary MEG will not undermine the estimated error of truncating any other MEGs. We then provide an overall error estimate for networks with multiple MEGs. To rapidly determine the appropriate size of an arbitrary MEG, we also introduce an a priori method to estimate the upper bound of its truncation error. This a priori estimate can be rapidly computed from reaction rates of the network, without the need of costly trial solutions of the dCME. As examples, we show results of applying our methods to the four stochastic networks of (1) the birth and death model, (2) the single gene expression model, (3) the genetic toggle switch model, and (4) the phage lambda bistable epigenetic switch model. We demonstrate how truncation errors and steady-state probability landscapes can be computed using different sizes of the MEG(s) and how the results validate our theories. Overall, the novel state space
Wingfield, Cai; Su, Li; Liu, Xunying; Zhang, Chao; Woodland, Phil; Thwaites, Andrew; Fonteneau, Elisabeth; Marslen-Wilson, William D
2017-09-01
There is widespread interest in the relationship between the neurobiological systems supporting human cognition and emerging computational systems capable of emulating these capacities. Human speech comprehension, poorly understood as a neurobiological process, is an important case in point. Automatic Speech Recognition (ASR) systems with near-human levels of performance are now available, which provide a computationally explicit solution for the recognition of words in continuous speech. This research aims to bridge the gap between speech recognition processes in humans and machines, using novel multivariate techniques to compare incremental 'machine states', generated as the ASR analysis progresses over time, to the incremental 'brain states', measured using combined electro- and magneto-encephalography (EMEG), generated as the same inputs are heard by human listeners. This direct comparison of dynamic human and machine internal states, as they respond to the same incrementally delivered sensory input, revealed a significant correspondence between neural response patterns in human superior temporal cortex and the structural properties of ASR-derived phonetic models. Spatially coherent patches in human temporal cortex responded selectively to individual phonetic features defined on the basis of machine-extracted regularities in the speech to lexicon mapping process. These results demonstrate the feasibility of relating human and ASR solutions to the problem of speech recognition, and suggest the potential for further studies relating complex neural computations in human speech comprehension to the rapidly evolving ASR systems that address the same problem domain.
NASA Astrophysics Data System (ADS)
Leray, Sarah; Engdahl, Nicholas B.; Massoudieh, Arash; Bresciani, Etienne; McCallum, James
2016-12-01
This review presents the physical mechanisms generating residence time distributions (RTDs) in hydrologic systems with a focus on steady-state analytical solutions. Steady-state approximations of the RTD in hydrologic systems have seen widespread use over the last half-century because they provide a convenient, simplified modeling framework for a wide range of problems. The concept of an RTD is useful anytime that characterization of the timescales of flow and transport in hydrologic systems is important, which includes topics like water quality, water resource management, contaminant transport, and ecosystem preservation. Analytical solutions are often adopted as a model of the RTD and a broad spectrum of models from many disciplines has been applied. Although these solutions are typically reduced in dimensionality and limited in complexity, their ease of use makes them preferred tools, specifically for the interpretation of tracer data. Our review begins with the mechanistic basis for the governing equations, highlighting the physics for generating a RTD, and a catalog of analytical solutions follows. This catalog explains the geometry, boundary conditions and physical aspects of the hydrologic systems, as well as the sampling conditions, that altogether give rise to specific RTDs. The similarities between models are noted, as are the appropriate conditions for their applicability. The presentation of simple solutions is followed by a presentation of more complicated analytical models for RTDs, including serial and parallel combinations, lagged systems, and non-Fickian models. The conditions for the appropriate use of analytical solutions are discussed, and we close with some thoughts on potential applications, alternative approaches, and future directions for modeling hydrologic residence time.
Co-existence of Distinct Supramolecular Assemblies in Solution and in the Solid State.
Reddy, G N Manjunatha; Huqi, Aida; Iuga, Dinu; Sakurai, Satoshi; Marsh, Andrew; Davis, Jeffery T; Masiero, Stefano; Brown, Steven P
2017-02-16
The formation of distinct supramolecular assemblies, including a metastable species, is revealed for a lipophilic guanosine (G) derivative in solution and in the solid state. Structurally different G-quartet-based assemblies are formed in chloroform depending on the nature of the cation, anion and the salt concentration, as characterized by circular dichroism and time course diffusion-ordered NMR spectroscopy data. Intriguingly, even the presence of potassium ions that stabilize G-quartets in chloroform was insufficient to exclusively retain such assemblies in the solid state, leading to the formation of mixed quartet and ribbon-like assemblies as revealed by fast magic-angle spinning (MAS) NMR spectroscopy. Distinct N-H⋅⋅⋅N and N-H⋅⋅⋅O intermolecular hydrogen bonding interactions drive quartet and ribbon-like self-assembly resulting in markedly different 2D (1) H solid-state NMR spectra, thus facilitating a direct identification of mixed assemblies. A dissolution NMR experiment confirmed that the quartet and ribbon interconversion is reversible-further demonstrating the changes that occur in the self-assembly process of a lipophilic nucleoside upon a solid-state to solution-state transition and vice versa. A systematic study for complexation with different cations (K(+) , Sr(2+) ) and anions (picrate, ethanoate and iodide) emphasizes that the existence of a stable solution or solid-state structure may not reflect the stability of the same supramolecular entity in another phase. © 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.
Alarcón, Tomás
2014-05-14
In this paper, we propose two methods to carry out the quasi-steady state approximation in stochastic models of enzyme catalytic regulation, based on WKB asymptotics of the chemical master equation or of the corresponding partial differential equation for the generating function. The first of the methods we propose involves the development of multiscale generalisation of a WKB approximation of the solution of the master equation, where the separation of time scales is made explicit which allows us to apply the quasi-steady state approximation in a straightforward manner. To the lowest order, the multi-scale WKB method provides a quasi-steady state, Gaussian approximation of the probability distribution. The second method is based on the Hamilton-Jacobi representation of the stochastic process where, as predicted by large deviation theory, the solution of the partial differential equation for the corresponding characteristic function is given in terms of an effective action functional. The optimal transition paths between two states are then given by those paths that maximise the effective action. Such paths are the solutions of the Hamilton equations for the Hamiltonian associated to the effective action functional. The quasi-steady state approximation is applied to the Hamilton equations thus providing an approximation to the optimal transition paths and the transition time between two states. Using this approximation we predict that, unlike the mean-field quasi-steady approximation result, the rate of enzyme catalysis depends explicitly on the initial number of enzyme molecules. The accuracy and validity of our approximated results as well as that of our predictions regarding the behaviour of the stochastic enzyme catalytic models are verified by direct simulation of the stochastic model using Gillespie stochastic simulation algorithm.
Alarcón, Tomás
2014-05-14
In this paper, we propose two methods to carry out the quasi-steady state approximation in stochastic models of enzyme catalytic regulation, based on WKB asymptotics of the chemical master equation or of the corresponding partial differential equation for the generating function. The first of the methods we propose involves the development of multiscale generalisation of a WKB approximation of the solution of the master equation, where the separation of time scales is made explicit which allows us to apply the quasi-steady state approximation in a straightforward manner. To the lowest order, the multi-scale WKB method provides a quasi-steady state, Gaussian approximation of the probability distribution. The second method is based on the Hamilton-Jacobi representation of the stochastic process where, as predicted by large deviation theory, the solution of the partial differential equation for the corresponding characteristic function is given in terms of an effective action functional. The optimal transition paths between two states are then given by those paths that maximise the effective action. Such paths are the solutions of the Hamilton equations for the Hamiltonian associated to the effective action functional. The quasi-steady state approximation is applied to the Hamilton equations thus providing an approximation to the optimal transition paths and the transition time between two states. Using this approximation we predict that, unlike the mean-field quasi-steady approximation result, the rate of enzyme catalysis depends explicitly on the initial number of enzyme molecules. The accuracy and validity of our approximated results as well as that of our predictions regarding the behaviour of the stochastic enzyme catalytic models are verified by direct simulation of the stochastic model using Gillespie stochastic simulation algorithm.
Optical limiting and excited-state absorption in fullerene solutions and doped glasses
McBranch, D.; Smilowitz, L.; Klimov, V.
1995-09-01
We report the ground state and excited state optical absorption spectra in the visible and near infrared for several substituted fullerenes and higher fullerenes in toluene solutions. Based on these measurements, broadband predictions of the optical limiting performance of these molecules can be deduced. These predictions are then tested at 532 to 700 nm in intensity-dependent transmission measurements. We observe optical limiting in all fullerenes measured; higher fullerenes show the greatest potential for limiting in the near infrared (650-1000 nm), while substituted C{sub 60} shows optimal limiting in the visible (450-700 nm). We observe dramatically reduced limiting for solid forms of C{sub 60} (thin films and C{sub 60}-doped porous glasses), indicating that efficient optical limiting in fullerenes requires true molecular solutions.
Stability of periodic steady-state solutions to a non-isentropic Euler-Maxwell system
NASA Astrophysics Data System (ADS)
Liu, Cunming; Peng, Yue-Jun
2017-10-01
This paper is concerned with a stability problem in a periodic domain for a non-isentropic Euler-Maxwell system without temperature diffusion term. This system is used to describe the dynamics of electrons in magnetized plasmas when the ion density is a given smooth function which can be large. When the initial data are close to the steady states of the system, we show the global existence of smooth solutions which converge toward the steady states as the time tends to infinity. We make a change of unknown variables and choose a non-diagonal symmetrizer of the full Euler equations to get the dissipation estimates. We also adopt an induction argument on the order of derivatives of solutions in energy estimates to get the stability result.
NASA Astrophysics Data System (ADS)
Li, Shuang; Zhang, Huiyu; Lu, Rong; Yu, Anchi
2017-09-01
Triethanolamine (TEOA) has been often used as a hole-scavenger in dye-sensitized semiconductor photocatalytic systems. However, the femtosecond time-resolved kinetics of the interaction between a sensitized dye and TEOA has not been reported in literatures. Herein, we selected four commonly used xanthene dyes, such as fluorescein, dibromofluorescein, eosin Y, and erythrosine B, and studied their ultrafast fluorescence quenching dynamics in the presence of TEOA in aqueous solution, respectively, by using both femtosecond transient absorption and time-resolved fluorescence measurements. We obtained the electron transfer rate from TEOA to each photoexcited xanthene dye in 2.0 M TEOA solution. We also obtained the intersystem crossing rate of each xanthene dye in aqueous solution with fluorescence quantum yield and lifetime measurements. Finally we found that TEOA mainly interacts with the singlet excited-state of fluorescein, dibromofluorescein, and eosin Y, and that TEOA can interact with both the singlet and triplet excited-states of erythrosine B in high concentration of TEOA aqueous solution.
NASA Astrophysics Data System (ADS)
Zlatanov, Kaloyan N.; Vitanov, Nikolay V.
2017-07-01
The common objective of the application of adiabatic techniques in the field of quantum control is to transfer a quantum system from one discrete energy state to another. These techniques feature both high efficiency and insensitivity to variations in the experimental parameters, e.g., variations in the driving field amplitude, duration, frequency, and shape, as well as fluctuations in the environment. Here we explore the potential of adiabatic techniques for creating arbitrary predefined coherent superpositions of two quantum states. We show that an equally weighted coherent superposition can be created by temporal variation of the ratio between the Rabi frequency Ω (t ) and the detuning Δ (t ) from 0 to ∞ (case 1) or vice versa (case 2), as it is readily deduced from the explicit adiabatic solution for the Bloch vector. We infer important differences between cases 1 and 2 in the composition of the created coherent superposition: The latter depends on the dynamical phase of the process in case 2, while it does not depend on this phase in case 1. Furthermore, an arbitrary coherent superposition of unequal weights can be created by using asymptotic ratios of Ω (t )/Δ (t ) different from 0 and ∞ . We supplement the general adiabatic solution with analytic solutions for three exactly soluble models: two trigonometric models and the hyperbolic Demkov-Kunike model. They allow us not only to demonstrate the general predictions in specific cases but also to derive the nonadiabatic corrections to the adiabatic solutions.
The optimal solution of a non-convex state-dependent LQR problem and its applications.
Xu, Xudan; Zhu, J Jim; Zhang, Ping
2014-01-01
This paper studies a Non-convex State-dependent Linear Quadratic Regulator (NSLQR) problem, in which the control penalty weighting matrix [Formula: see text] in the performance index is state-dependent. A necessary and sufficient condition for the optimal solution is established with a rigorous proof by Euler-Lagrange Equation. It is found that the optimal solution of the NSLQR problem can be obtained by solving a Pseudo-Differential-Riccati-Equation (PDRE) simultaneously with the closed-loop system equation. A Comparison Theorem for the PDRE is given to facilitate solution methods for the PDRE. A linear time-variant system is employed as an example in simulation to verify the proposed optimal solution. As a non-trivial application, a goal pursuit process in psychology is modeled as a NSLQR problem and two typical goal pursuit behaviors found in human and animals are reproduced using different control weighting [Formula: see text]. It is found that these two behaviors save control energy and cause less stress over Conventional Control Behavior typified by the LQR control with a constant control weighting [Formula: see text], in situations where only the goal discrepancy at the terminal time is of concern, such as in Marathon races and target hitting missions.
The Optimal Solution of a Non-Convex State-Dependent LQR Problem and Its Applications
Xu, Xudan; Zhu, J. Jim; Zhang, Ping
2014-01-01
This paper studies a Non-convex State-dependent Linear Quadratic Regulator (NSLQR) problem, in which the control penalty weighting matrix in the performance index is state-dependent. A necessary and sufficient condition for the optimal solution is established with a rigorous proof by Euler-Lagrange Equation. It is found that the optimal solution of the NSLQR problem can be obtained by solving a Pseudo-Differential-Riccati-Equation (PDRE) simultaneously with the closed-loop system equation. A Comparison Theorem for the PDRE is given to facilitate solution methods for the PDRE. A linear time-variant system is employed as an example in simulation to verify the proposed optimal solution. As a non-trivial application, a goal pursuit process in psychology is modeled as a NSLQR problem and two typical goal pursuit behaviors found in human and animals are reproduced using different control weighting . It is found that these two behaviors save control energy and cause less stress over Conventional Control Behavior typified by the LQR control with a constant control weighting , in situations where only the goal discrepancy at the terminal time is of concern, such as in Marathon races and target hitting missions. PMID:24747417
Fisher, Harvey F
2016-08-01
The transient-state kinetic approach has failed to reach its full potential despite its advantage over the steady-state approach in its ability to observe mechanistic events directly and in real time. This failure has been due in part to the lack of any rigorously derived and readily applicable body of theory corresponding to that which currently characterizes the steady-state approach. In order to clarify the causes of this discrepancy and to suggest a route to its solution we examine the capabilities and limitations of the various forms of transient-state kinetic approaches to the mathematical resolution of enzymatic reaction mechanisms currently available. We document a lack of validity inherent in their basic assumptions and suggest the need for a potentially more rigorous analytic approach.
On the efficient and reliable numerical solution of rate-and-state friction problems
NASA Astrophysics Data System (ADS)
Pipping, Elias; Kornhuber, Ralf; Rosenau, Matthias; Oncken, Onno
2016-03-01
We present a mathematically consistent numerical algorithm for the simulation of earthquake rupture with rate-and-state friction. Its main features are adaptive time stepping, a novel algebraic solution algorithm involving nonlinear multigrid and a fixed point iteration for the rate-and-state decoupling. The algorithm is applied to a laboratory scale subduction zone which allows us to compare our simulations with experimental results. Using physical parameters from the experiment, we find a good fit of recurrence time of slip events as well as their rupture width and peak slip. Computations in 3-D confirm efficiency and robustness of our algorithm.
NASA Astrophysics Data System (ADS)
Chen, Zhi-Min
2016-10-01
It is shown that the non-homogeneous dissipative quasi-geostrophic equation ∂θ∂t+uṡ∇θ+κ(-Δ)αθ=sinx2, u=(-∂x2, ∂x1)(-Δ)-β/2θ with α =0 and β >1 losses stability at a critical value {κc}>0 and this instability gives rise to a circle of steady-state solutions.
Daniel J. Yelle; John Ralph; Charles R. Frihart
2008-01-01
A recently described plant cell wall dissolution system has been modified to use perdeuterated solvents to allow direct in-NMR-tube dissolution and high-resolution solution-state NMR of the whole cell wall without derivatization. Finely ground cell wall material dissolves in a solvent system containing dimethylsulfoxide-d6 and 1-methylimidazole-d6 in a ratio of 4:1 (v/...
The solution and solid state stability and excipient compatibility of parthenolide in feverfew.
Jin, Ping; Madieh, Shadi; Augsburger, Larry L
2007-12-14
The objectives of this research were to evaluate the stability of parthenolide in feverfew solution state and powdered feverfew (solid state), and explore the compatibility between commonly used excipients and parthenolide in feverfew. Feverfew extract solution was diluted with different pH buffers to study the solution stability of parthenolide in feverfew. Powdered feverfew extract was stored under 40 degrees C/0% approximately 75% relative humidities (RH) or 31% RH/5~50 degrees C to study the influence of temperature and relative humidity on the stability of parthenolide in feverfew solid state. Binary mixtures of feverfew powered extract and different excipients were stored at 50 degrees C/ 75% RH for excipient compatibility evaluation. The degradation of parthenolide in feverfew solution appears to fit a typical first-order reaction. Parthenolide is comparatively stable when the environmental pH is in the range of 5 to 7, becoming unstable when pH is less than 3 or more than 7. Parthenolide degradation in feverfew in the solid state does not fit any obvious reaction model. Moisture content and temperature both play important roles affecting the degradation rate. After 6 months of storage, parthenolide in feverfew remains constant at 5 degrees C/31% RH. However, approximately 40% parthenolide in feverfew can be degraded if stored at 50 degrees C/31% RH. When the moisture changed from 0% to 75% RH, the degradation of parthenolide in feverfew increased from 18% to 32% after 6-month storage under 40 degrees C. Parthenolide in feverfew exhibits good compatibility with commonly used excipients under stressed conditions in a 3-week screening study.
Dalsin, Molly C; Tale, Swapnil; Reineke, Theresa M
2014-02-10
Spray dried dispersions (SDDs), solid dispersions of polymer excipients and active pharmaceuticals, are important to the field of oral drug delivery for improving active stability, bioavailability, and efficacy. Herein, we examine the influence of solution-state polymer assemblies on amorphous spray-dried dispersion (SDD) performance with two BCS II model drugs, phenytoin and probucol. These drugs were spray dried with 4 model polymer excipients consisting of poly(ethylene-alt-propylene) (PEP), N,N,-dimethylacrylamide (DMA), or 2-methacrylamido glucopyranose (MAG): amphiphilic diblock ter- and copolymers, PEP-P(DMA-grad-MAG) and PEP-PDMA, and their respective hydrophilic analogues, P(DMA-grad-MAG) and PDMA. Selective and nonselective solvents for the hydrophilic block of the diblock ter- and copolymers were used to induce or repress solution-state assemblies prior to spray drying. Prespray dried solution-state assemblies of these four polymers were probed with dynamic light scattering (DLS) and showed differences in solution assembly size and structure (free polymer versus aggregates versus micelles). Solid-state structures of spray dried dispersions (SDDs) showed a single glass transition event implying a homogeneous mixture of drug/polymer. Crystallization temperatures and enthalpies indicated that the drugs interact mostly with the DMA-containing portions of the polymers. Scanning electron microscopy was used to determine SDD particle size and morphology for the various polymer-drug pairings. In vitro dissolution tests showed excellent performance for one system, spray-dried PEP-PDMA micelles with probucol. Dissolution structures were investigated through DLS to determine drug-polymer aggregates that lead to enhanced SDD performance. Forced aggregation of the polymer into regular micelle structures was found to be a critical factor to increase the dissolution rate and supersaturation maintenance of SDDs, and may be an attractive platform to exploit in excipient
Analytical Solution of Steady State Equations for Chemical Reaction Networks with Bilinear Rate Laws
Halász, Ádám M.; Lai, Hong-Jian; McCabe, Meghan M.; Radhakrishnan, Krishnan; Edwards, Jeremy S.
2014-01-01
True steady states are a rare occurrence in living organisms, yet their knowledge is essential for quasi-steady state approximations, multistability analysis, and other important tools in the investigation of chemical reaction networks (CRN) used to describe molecular processes on the cellular level. Here we present an approach that can provide closed form steady-state solutions to complex systems, resulting from CRN with binary reactions and mass-action rate laws. We map the nonlinear algebraic problem of finding steady states onto a linear problem in a higher dimensional space. We show that the linearized version of the steady state equations obeys the linear conservation laws of the original CRN. We identify two classes of problems for which complete, minimally parameterized solutions may be obtained using only the machinery of linear systems and a judicious choice of the variables used as free parameters. We exemplify our method, providing explicit formulae, on CRN describing signal initiation of two important types of RTK receptor-ligand systems, VEGF and EGF-ErbB1. PMID:24334389
Optimal unambiguous state discrimination of two density matrices: A second class of exact solutions
Raynal, Philippe; Luetkenhaus, Norbert
2007-11-15
We consider the unambiguous state discrimination (USD) of two mixed quantum states. We study the rank and the spectrum of the elements of an optimal USD measurement. This naturally leads to a partial fourth reduction theorem. This theorem shows that either the failure probability equals its overall lower bound given in terms of the fidelity or a two-dimensional subspace can be split off from the original Hilbert space. We then use this partial reduction theorem to derive the optimal solution for any two equally probable geometrically uniform states {rho}{sub 0} and {rho}{sub 1}=U{rho}{sub 0}U{sup {dagger}}, U{sup 2}=1, in a four-dimensional Hilbert space. This represents a second class of analytical solutions for USD problems that cannot be reduced to some pure state cases. We apply our result to answer two questions that are relevant in implementations of the Bennett and Brassard 1984 quantum key distribution protocol using weak coherent states.
Halász, Adám M; Lai, Hong-Jian; McCabe Pryor, Meghan; Radhakrishnan, Krishnan; Edwards, Jeremy S
2013-01-01
True steady states are a rare occurrence in living organisms, yet their knowledge is essential for quasi-steady-state approximations, multistability analysis, and other important tools in the investigation of chemical reaction networks (CRN) used to describe molecular processes on the cellular level. Here, we present an approach that can provide closed form steady-state solutions to complex systems, resulting from CRN with binary reactions and mass-action rate laws. We map the nonlinear algebraic problem of finding steady states onto a linear problem in a higher-dimensional space. We show that the linearized version of the steady-state equations obeys the linear conservation laws of the original CRN. We identify two classes of problems for which complete, minimally parameterized solutions may be obtained using only the machinery of linear systems and a judicious choice of the variables used as free parameters. We exemplify our method, providing explicit formulae, on CRN describing signal initiation of two important types of RTK receptor-ligand systems, VEGF and EGF-ErbB1.
Karunakaran, Venugopal; Prabhu, Deepak D; Das, Suresh; Varughese, Sunil
2015-07-28
Detailed photophysical properties of cyano and mono (MA)/bis alkoxy (DA) substituted diphenylacetylene moieties with different alkyl chain lengths (methyl (1), octyl (8) and dodecyl (12)) were investigated in solution and the solid state in an effort to determine the effect of self-aggregation on these properties. The solvated molecules showed a minimal bathochromic shift with an increase of solvent polarity in their absorption spectra, whereas a significant shift was observed in the emission spectra. This could be attributed to the relatively low change in dipole moment between ground and Franck-Condon excited states and luminescence arising from the intramolecular charge transfer state with a dipole moment significantly higher than that of the ground state. In solid state the emission quantum yields of these materials were significantly higher than in solution. For DA1, polymorphic materials with distinct photophysical properties were obtained. The DA1 materials obtained by fast precipitation (DA1) showed broad fluorescence with peaks at 398, 467 and 535 nm upon excitation at different wavelengths. Detailed analysis of absorption, emission and excitation spectra and lifetime experiments indicated that these peaks could be attributed to the monomer, J- and H-type aggregates respectively. Whereas the crystals obtained by slow crystallization (DA1C) showed only one emission peak at around 396 nm attributed to the monomer. This is supported by the single crystal X-ray structure which consists of a monomer molecule having minimal interaction with nearest neighbour molecules.
Two-Photon Excitation of Conjugated Molecules in Solution: Spectroscopy and Excited-State Dynamics
NASA Astrophysics Data System (ADS)
Elles, Christopher G.; Houk, Amanda L.; de Wergifosse, Marc; Krylov, Anna
2017-06-01
We examine the two-photon absorption (2PA) spectroscopy and ultrafast excited-state dynamics of several conjugated molecules in solution. By controlling the relative wavelength and polarization of the two photons, the 2PA measurements provide a more sensitive means of probing the electronic structure of a molecule compared with traditional linear absorption spectra. We compare experimental spectra of trans-stilbene, cis-stilbene, and phenanthrene in solution with the calculated spectra of the isolated molecules using EOM-EE-CCSD. The calculated spectra show good agreement with the low-energy region of the experimental spectra (below 6 eV) after suppressing transitions with strong Rydberg character and accounting for solvent and method-dependent shifts of the valence transitions. We also monitor the excited state dynamics following two-photon excitation to high-lying valence states of trans-stilbene up to 6.5 eV. The initially excited states rapidly relax to the lowest singlet excited state and then follow the same reaction path as observed following direct one-photon excitation to the lowest absorption band at 4.0 eV.
Probing the excited state relaxation dynamics of pyrimidine nucleosides in chloroform solution.
Röttger, Katharina; Marroux, Hugo J B; Böhnke, Hendrik; Morris, David T J; Voice, Angus T; Temps, Friedrich; Roberts, Gareth M; Orr-Ewing, Andrew J
2016-12-16
Ultrafast transient electronic and vibrational absorption spectroscopy (TEAS and TVAS) of 2'-deoxy-cytidine (dC) and 2'-deoxy-thymidine (dT) dissolved in chloroform examines their excited-state dynamics and the recovery of ground electronic state molecules following absorption of ultraviolet light. The chloroform serves as a weakly interacting solvent, allowing comparisons to be drawn with prior experimental studies of the photodynamics of these nucleosides in the gas phase and in polar solvents such as water. The pyrimidine base nucleosides have some propensity to dimerize in aprotic solvents, but the monomer photochemistry can be resolved clearly and is the focus of this study. UV absorption at a wavelength of 260 nm excites a (1)ππ* ← S0 transition, but prompt crossing of a significant fraction (50% in dC, 17% in dT) of the (1)ππ* population into a nearby (1)nπ* state is too fast for the experiments to resolve. The remaining flux on the (1)ππ* state leaves the vertical Franck-Condon region and encounters a conical intersection with the ground electronic state of ethylenic twist character. In dC, the (1)ππ* state decays to the ground state with a time constant of 1.1 ± 0.1 ps. The lifetime of the (1)nπ* state is much longer in the canonical forms of both molecules: recovery of the ground state population from these states occurs with time constants of 18.6 ± 1.1 ps in amino-oxo dC and ∼114 ps in dT, indicating potential energy barriers to the (1)nπ*/S0 conical intersections. The small fraction of the imino-oxo tautomer of dC present in solution has a longer-lived (1)nπ* state with a lifetime for ground state recovery of 193 ± 55 ps. No evidence is found for photo-induced tautomerization of amino-oxo dC to the imino-oxo form, or for population of low lying triplet states of this nucleoside. In contrast, ∼8% of the UV-excited dT molecules access the long-lived T1 ((3)ππ*) state through the (1)nπ* state. The primary influence of the solvent
Steady-state electrodiffusion. Scaling, exact solution for ions of one charge, and the phase plane.
Leuchtag, H R; Swihart, J C
1977-01-01
This is the first of two papers dealing with electrodiffusion theory (the Nernst-Planck equation coupled with Gauss's law) and its application to the current-voltage behavior of squid axon. New developments in the exact analysis of the steady-state electrodiffusion problem presented here include (a) a scale transformation that connects a given solution to an infinity of other solutions, suggesting the po-sibility of direct comparison of electrical data for membranes with different thicknesses and other properties; (b) a first-integral relation between the electric field and ion densities more general than analogous relations previously reported, and (c) an exact solution for the homovalent system, i.e., a membrane system permeated by various ion species of the same charge. The latter is a generalization of the known one-ion solution. The properties of the homovalent solution are investigated analytically and graphically. In particular we study the phase-plane curves, which reduce to the parabolas discussed by K. S. Cole in the special case in which the current-density parameter (a linear combination of the ionic current densities) is zero. PMID:831855
Li, Jianguo; Hu, Zhongqiao; Beuerman, Roger; Verma, Chandra
2017-04-06
Human β-defensin 2 is a cysteine-rich antimicrobial peptide. In the crystal state, the N-terminal segment (residues 1-11) exhibits a helical conformation. However, a truncated form, with four amino acids removed from the N-terminus, adopts nonhelical conformations in solution, as shown by NMR. To explore the molecular origins of these different conformations, we performed Hamiltonian replica exchange molecular dynamics simulations of the peptide in solution and in the crystal state. It is found that backbone hydration and specific protein-protein interactions are key parameters that determine the peptide conformation. The helical conformation in the crystal state mainly arises from reduced hydration as well as a salt bridge between the peptide and a symmetry-related neighboring monomer in the crystal. When the extent of hydration is reduced and the salt bridge is reintroduced artificially, the peptide is successfully folded back to the helical conformation in solution. The findings not only shed light on the development of accurate force field parameters for protein molecules but also provide practical guidance in the design of functional proteins and peptides.
Multiple solutions of steady-state Poisson-Nernst-Planck equations with steric effects
NASA Astrophysics Data System (ADS)
Lin, Tai-Chia; Eisenberg, Bob
2015-07-01
Experiments measuring currents through single protein channels show unstable currents. Channels switch between ‘open’ or ‘closed’ states in a spontaneous stochastic process called gating. Currents are either (nearly) zero or at a definite level, characteristic of each type of protein, independent of time, once the channel is open. The steady state Poisson-Nernst-Planck equations with steric effects (PNP-steric equations) describe steady current through the open channel quite well, in a wide variety of conditions. Here we study the existence of multiple solutions of steady state PNP-steric equations to see if they themselves, without modification or augmentation, can describe two levels of current. We prove that there are two steady state solutions of PNP-steric equations for (a) three types of ion species (two types of cations and one type of anion) with a positive constant permanent charge, and (b) four types of ion species (two types of cations and their counter-ions) with a constant permanent charge but no sign condition. The excess currents (due to steric effects) associated with these two steady state solutions are derived and expressed as two distinct formulas. Our results indicate that PNP-steric equations may become a useful model to study spontaneous gating of ion channels. Spontaneous gating is thought to involve small structural changes in the channel protein that perhaps produce large changes in the profiles of free energy that determine ion flow. Gating is known to be modulated by external structures. Both can be included in future extensions of our present analysis.
NASA Astrophysics Data System (ADS)
Bernardin, Cédric; Landim, Claudio
2010-12-01
We examine the entropy of stationary nonequilibrium measures of boundary driven symmetric simple exclusion processes. In contrast with the Gibbs-Shannon entropy (Bahadoran in J. Stat. Phys. 126(4-5):1069-1082, 2007; Derrida et al. in J. Stat. Phys. 126(4-5):1083-1108, 2007), the entropy of nonequilibrium stationary states differs from the entropy of local equilibrium states.
2011-05-01
Successfully Demonstrating an Integrated Roofing and BIPV Solution for an Historic Building Renovation at the United States Air Force Academy...COVERED 00-00-2011 to 00-00-2011 4. TITLE AND SUBTITLE Successfully Demonstrating an Integrated Roofing and BIPV Solution for an Historic...ANSI Std Z39-18 Successfully Demonstrating an Integrated Roofing and BIPV Solution for an Historic Building Renovation at the United States Air Force
Stationary measure in the multiverse
Linde, Andrei; Vanchurin, Vitaly; Winitzki, Sergei E-mail: vitaly@cosmos2.phy.tufts.edu
2009-01-15
We study the recently proposed ''stationary measure'' in the context of the string landscape scenario. We show that it suffers neither from the ''Boltzmann brain'' problem nor from the ''youngness'' paradox that makes some other measures predict a high CMB temperature at present. We also demonstrate a good performance of this measure in predicting the results of local experiments, such as proton decay.
Wave-Mechanical Properties of Stationary States.
ERIC Educational Resources Information Center
Holden, Alan
This monograph is a review of the quantum mechanical concepts presented in two other monographs, "The Nature of Atoms" and "Bonds Between Atoms," by the same author. It is assumed the reader is familiar with these ideas. The monograph sketches only those aspects of quantum mechanics that are of most direct use in picturing and calculating the…
SedNMR: on the edge between solution and solid-state NMR.
Bertini, Ivano; Luchinat, Claudio; Parigi, Giacomo; Ravera, Enrico
2013-09-17
Solid-state NMR (SS-NMR) of proteins requires that those molecules be immobilized, usually by crystallization, freezing, or lyophilization. However, self-crowding can also slow molecular rotation sufficiently to prevent the nuclear interactions from averaging. To achieve self-crowding, researchers can use a centrifugal field to create a concentration gradient or use regular ultracentrifugation to produce highly concentrated, gel-like solutions. Thus sedimented solute NMR (SedNMR) provides a simple method to prepare biological samples for SS-NMR experiments with minimal perturbation. This method may also give researchers a way to investigate species that are not otherwise accessible by NMR. We induce the sedimentation in one of two ways: (1) by the extreme centrifugal force exerted during magic angle spinning (MAS-induced sedimentation or in situ) or (2) by an ultracentrifuge (UC-induced sedimentation or ex situ). Sedimentation is particularly useful in situations where it is difficult to obtain protein crystals. Furthermore, because the proteins remain in a largely hydrated state, the sedimented samples may provide SS-NMR spectra that have better resolution than the spectra from frozen solutions or lyophilized powders. If sedimentation is induced in situ, the same protein sample can be used for both solution and SS-NMR studies. Finally, we show that in situ SedNMR can be used to detect the NMR signals of large molecular adducts that have binding constants that are too weak to allow for the selective isolation and crystallization of the complexed species. We can selectively induce sedimentation for the heaviest molecular species. Because the complexed molecules are subtracted from the bulk solution, the reaction proceeds further toward the formation of complexes.
Shi, Huilin; Pierson, Nicholas A.; Valentine, Stephen J.; Clemmer, David E.
2012-01-01
Ion mobility and mass spectrometry measurements are used to examine the gas-phase populations of [M+8H]8+ ubiquitin ions formed upon electrospraying 20 different solutions: from 100:0 to 5:95 water:methanol that are maintained at pH = 2.0. Over this range of solution conditions, mobility distributions for the +8 charge state show substantial variations. Here we develop a model that treats the combined measurements as one data set. By varying the relative abundances of a discrete set of conformation types, it is possible to represent distributions obtained from any solution. For solutions that favor the well-known A-state ubiquitin, it is possible to represent the gas-phase distributions with seven conformation types. Aqueous conditions that favor the native structure require four more structural types to represent the distribution. This analysis provides the first direct evidence for trace amounts of the A state under native conditions. The method of analysis presented here should help illuminate how solution populations evolve into new gas-phase structures as solvent is removed. Evidence for trace quantities of previously unknown states under native solution conditions may provide insight about the relationship of dynamics to protein function as well as misfolding and aggregation phenomena. PMID:22315998
Steady-state solutions of a diffusive energy-balance climate model and their stability
NASA Technical Reports Server (NTRS)
Ghil, M.
1975-01-01
A diffusive energy-balance climate model, governed by a nonlinear parabolic partial differential equation, was studied. Three positive steady-state solutions of this equation are found; they correspond to three possible climates of our planet: an interglacial (nearly identical to the present climate), a glacial, and a completely ice-covered earth. Models similar to the main one are considered, and the number of their steady states was determined. All the models have albedo continuously varying with latitude and temperature, and entirely diffusive horizontal heat transfer. The stability under small perturbations of the main model's climates was investigated. A stability criterion is derived, and its application shows that the present climate and the deep freeze are stable, whereas the model's glacial is unstable. The dependence was examined of the number of steady states and of their stability on the average solar radiation.
A modified two-state empirical valence bond model for proton transport in aqueous solutions
Mabuchi, Takuya; Fukushima, Akinori; Tokumasu, Takashi
2015-07-07
A detailed analysis of the proton solvation structure and transport properties in aqueous solutions is performed using classical molecular dynamics simulations. A refined two-state empirical valence bond (aTS-EVB) method, which is based on the EVB model of Walbran and Kornyshev and the anharmonic water force field, is developed in order to describe efficiently excess proton transport via the Grotthuss mechanism. The new aTS-EVB model clearly satisfies the requirement for simpler and faster calculation, because of the simplicity of the two-state EVB algorithm, while providing a better description of diffusive dynamics of the excess proton and water in comparison with the previous two-state EVB models, which significantly improves agreement with the available experimental data. The results of activation energies for the excess proton and water calculated between 300 and 340 K (the temperature range used in this study) are also found to be in good agreement with the corresponding experimental data.
Silver, Mark A; Cary, Samantha K; Johnson, Jason A; Baumbach, Ryan E; Arico, Alexandra A; Luckey, Morgan; Urban, Matthew; Wang, Jamie C; Polinski, Matthew J; Chemey, Alexander; Liu, Guokui; Chen, Kuan-Wen; Van Cleve, Shelley M; Marsh, Matthew L; Eaton, Teresa M; van de Burgt, Lambertus J; Gray, Ashley L; Hobart, David E; Hanson, Kenneth; Maron, Laurent; Gendron, Frédéric; Autschbach, Jochen; Speldrich, Manfred; Kögerler, Paul; Yang, Ping; Braley, Jenifer; Albrecht-Schmitt, Thomas E
2016-08-26
Berkelium is positioned at a crucial location in the actinide series between the inherently stable half-filled 5f(7) configuration of curium and the abrupt transition in chemical behavior created by the onset of a metastable divalent state that starts at californium. However, the mere 320-day half-life of berkelium's only available isotope, (249)Bk, has hindered in-depth studies of the element's coordination chemistry. Herein, we report the synthesis and detailed solid-state and solution-phase characterization of a berkelium coordination complex, Bk(III)tris(dipicolinate), as well as a chemically distinct Bk(III) borate material for comparison. We demonstrate that berkelium's complexation is analogous to that of californium. However, from a range of spectroscopic techniques and quantum mechanical calculations, it is clear that spin-orbit coupling contributes significantly to berkelium's multiconfigurational ground state.
NASA Astrophysics Data System (ADS)
Queloz, P.; Rao, P. C.; Rinaldo, A.
2012-12-01
Travel and residence times are well-known descriptors of hydrologic and solute transport in the vadose zone. It has been observed that their probability density functions are stationary only under specific conditions, rarely encountered in natural catchments. This study aims at demonstrating the emergence of non-stationary solute transport in a highly monitored system, and identifying the factors controlling the variations of the observed solute travel-times. 2-meters deep weighing lysimeters are exposed to stochastic rainfall sequences. Multiple derivatives of difluorobenzoate compounds are sequentially injected at different times in the system, and are analyzed in the drainage flux at the bottom outlet and at different depth within the soil profiles. Willow trees planted in the systems create a stochastic soil water deficit by evapotranspiration. As each tracer injected is analytically differentiable from the others, the computation of the tracer breakthrough curves at the lysimeter outlet allows measuring the solute travel-time distributions conditional on the injection time. The observed breakthrough curves display a large variability, emphasizing the effects of the initial conditions at the injection time and the subsequent states encountered in the system on solute transport. Two types of climate have been simulated on the lysimeters. With the precision load cells installed under each lysimeter and the water content probes deployed in the soil profiles, a detailed comparison of the water balance and storage dynamics and their influence on solute transport timing can be done.
NASA Astrophysics Data System (ADS)
Pei, Yongquan; Sun, Jitao
2016-11-01
This paper investigates the stationary average consensus problem for second-order discrete-time multi-agent systems (SDMAS). A stationary consensus problem is to find a control algorithm that brings the state of a group of agents to a common constant value which is called the collective decision. We introduce the concept of stationary average consensus of SDMAS and propose a consensus algorithm. Based on the polynomial stability and the graph theory, we obtain two necessary and sufficient conditions of stationary average consensus of SDMAS. The last theorem provides an algebraic criterion of stationary average consensus, and can help us to determine the parameters in the consensus algorithm. Furthermore, in this consensus algorithm, only the states of the agents are transferred among the agents. Therefore, this algorithm can not only solve the stationary average consensus problem but also reduce the amount of transferred data. A numerical example is provided to illustrate the efficiency of our results.
Sivchik, Vasily V; Grachova, Elena V; Melnikov, Alexei S; Smirnov, Sergey N; Ivanov, Alexander Yu; Hirva, Pipsa; Tunik, Sergey P; Koshevoy, Igor O
2016-04-04
The noncovalent intermolecular interactions (π-π stacking, metallophilic bonding) of the cyclometalated complexes [Pt(NCN)L](+)X(-) (NCN = dipyridylbenzene, L = pyridine (1), acetonitrile (2)) are determined by the steric properties of the ancillary ligands L in the solid state and in solution, while the nature of the counterion X(-) (X(-) = PF6(-), ClO4(-), CF3SO3(-)) affects the molecular arrangement of 2·X in the crystal medium. According to the variable-temperature X-ray diffraction measurements, the extensive Pt···Pt interactions and π-stacking in 2·X are significantly temperature-dependent. The variable concentration (1)H and diffusion coefficients NMR measurements reveal that 2·X exists in the monomeric form in dilute solutions at 298 K, while upon increase in concentration [Pt(NCN)(NCMe)](+) cations undergo the formation of the ground-state oligomeric aggregates with an average aggregation number of ∼3. The photoluminescent characteristics of 1 and 2·X are largely determined by the intermolecular aggregation. For the discrete molecules the emission properties are assigned to metal perturbed IL charge transfer mixed with some MLCT contribution. In the case of oligomers 2·X the luminescence is significantly red-shifted with respect to 1 and originates mainly from the (3)MMLCT excited states. The emission energies depend on the structural arrangement in the crystal and on the complex concentration in solution, variation of which allows for the modulation of the emission color from greenish to deep red. In the solid state the lability of the ligands L leads to vapor-induced reversible transformation 1 ↔ 2 that is accompanied by the molecular reorganization and, consequently, dramatic change of the photophysical properties. Time-dependent density functional theory calculations adequately support the models proposed for the rationalization of the experimental observations.
Cosmic ray heating in cool core clusters I: diversity of steady state solutions
NASA Astrophysics Data System (ADS)
Jacob, Svenja; Pfrommer, Christoph
2017-01-01
The absence of large cooling flows in cool core clusters appears to require self-regulated energy feedback by active galactic nuclei (AGNs) but the exact heating mechanism has not yet been identified. Here, we analyse whether a combination of cosmic ray (CR) heating and thermal conduction can offset radiative cooling. To this end, we compile a large sample of 39 cool core clusters and determine steady state solutions of the hydrodynamic equations that are coupled to the CR energy equation. We find solutions that match the observed density and temperature profiles for all our clusters well. Radiative cooling is balanced by CR heating in the cluster centres and by thermal conduction on larger scales, thus demonstrating the relevance of both heating mechanisms. Our mass deposition rates vary by three orders of magnitude and are linearly correlated to the observed star formation rates. Clusters with large mass deposition rates show larger cooling radii and require a larger radial extent of the CR injection function. Interestingly, our sample shows a continuous sequence in cooling properties: clusters hosting radio mini halos are characterised by the largest cooling radii, star formation and mass deposition rates in our sample and thus signal the presence of a higher cooling activity. The steady state solutions support the structural differences between clusters hosting a radio mini halo and those that do not.
Unsteady-state transfer of impurities during crystal growth of sucrose in sugarcane solutions
NASA Astrophysics Data System (ADS)
Martins, P. M.; Ferreira, A.; Polanco, S.; Rocha, F.; Damas, A. M.; Rein, P.
2009-07-01
In this work, we present growth rate data of sucrose crystals in the presence of impurities that can be used by both sugar technologists and crystal growth scientists. Growth rate curves measured in a pilot-scale evaporative crystallizer suggest a period of slow growth that follows the seeding of crystals into supersaturated technical solutions. The observed trend was enhanced by adding typical sugarcane impurities such as starch, fructose or dextran to the industrial syrups. Maximum growth rates of sucrose resulted at intermediate rather than high supersaturation levels in the presence of the additives. The effects of the additives on the sucrose solubility and sucrose mass transfer in solution were taken into account to explain the observed crystal growth kinetics. A novel mechanism was identified of unsteady-state adsorption of impurities at the crystal surface and their gradual replacement by the crystallizing solute towards the equilibrium occupation of the active sites for growth. Specifically designed crystallization experiments at controlled supersaturation confirmed this mechanism by showing increasing crystal growth rates with time until reaching a steady-state value for a given supersaturation level and impurity content.
The finite state projection algorithm for the solution of the chemical master equation
NASA Astrophysics Data System (ADS)
Munsky, Brian; Khammash, Mustafa
2006-01-01
This article introduces the finite state projection (FSP) method for use in the stochastic analysis of chemically reacting systems. One can describe the chemical populations of such systems with probability density vectors that evolve according to a set of linear ordinary differential equations known as the chemical master equation (CME). Unlike Monte Carlo methods such as the stochastic simulation algorithm (SSA) or τ leaping, the FSP directly solves or approximates the solution of the CME. If the CME describes a system that has a finite number of distinct population vectors, the FSP method provides an exact analytical solution. When an infinite or extremely large number of population variations is possible, the state space can be truncated, and the FSP method provides a certificate of accuracy for how closely the truncated space approximation matches the true solution. The proposed FSP algorithm systematically increases the projection space in order to meet prespecified tolerance in the total probability density error. For any system in which a sufficiently accurate FSP exists, the FSP algorithm is shown to converge in a finite number of steps. The FSP is utilized to solve two examples taken from the field of systems biology, and comparisons are made between the FSP, the SSA, and τ leaping algorithms. In both examples, the FSP outperforms the SSA in terms of accuracy as well as computational efficiency. Furthermore, due to very small molecular counts in these particular examples, the FSP also performs far more effectively than τ leaping methods.
Cosmic ray heating in cool core clusters - I. Diversity of steady state solutions
NASA Astrophysics Data System (ADS)
Jacob, Svenja; Pfrommer, Christoph
2017-05-01
The absence of large cooling flows in cool core clusters appears to require self-regulated energy feedback by active galactic nuclei but the exact heating mechanism has not yet been identified. Here, we analyse whether a combination of cosmic ray (CR) heating and thermal conduction can offset radiative cooling. To this end, we compile a large sample of 39 cool core clusters and determine steady state solutions of the hydrodynamic equations that are coupled to the CR energy equation. We find solutions that match the observed density and temperature profiles for all our clusters well. Radiative cooling is balanced by CR heating in the cluster centres and by thermal conduction on larger scales, thus demonstrating the relevance of both heating mechanisms. Our mass deposition rates vary by three orders of magnitude and are linearly correlated to the observed star formation rates. Clusters with large mass deposition rates show larger cooling radii and require a larger radial extent of the CR injection function. Interestingly, our sample shows a continuous sequence in cooling properties: clusters hosting radio mini haloes are characterized by the largest cooling radii, star formation and mass deposition rates in our sample and thus signal the presence of a higher cooling activity. The steady state solutions support the structural differences between clusters hosting a radio mini halo and those that do not.
Ruthenium complexes of substituted hydrazine: new solution- and solid-state binding modes.
Dabb, Serin L; Messerle, Barbara A; Otting, Gottfried; Wagler, Jörg; Willis, Anthony
2008-01-01
The methylhydrazine complex [Ru(NH(2)NHMe)(PyP)(2)]Cl(BPh(4)) (PyP=1-[2-(diphenylphosphino)ethyl]pyrazole) was synthesised by addition of methylhydrazine to the bimetallic complex [Ru(mu-Cl)(PyP)(2)](2)(BPh(4))(2). The methylhydrazine ligand of the ruthenium complex has two different binding modes: side-on (eta(2)-) when the complex is in the solid state and end-on (eta(1)-) when the complex is in solution. The solid-state structure of [Ru(PyP)(2)(NH(2)NHMe)]Cl(BPh(4)) was determined by X-ray crystallography. 2D NMR spectroscopic experiments with (15)N at natural abundance confirmed that in solution the methylhydrazine is bound to the metal centre by only the -NH(2) group and the ruthenium complex retains an octahedral conformation. Hydrazine complexes [RuCl(PyP)(2)(eta(1)-NH(2)NRR')]OSO(2)CF(3) (in which R=H, R'=Ph, R=R'=Me and NRR'=NC(5)H(10)) were formed in situ by the addition of phenylhydrazine, 1,1-dimethylhydrazine and N-aminopiperidine, respectively, to a solution of the bimetallic complex [Ru(mu-Cl)(PyP)(2)](2)(OSO(2)CF(3))(2) in dichloromethane. These substituted hydrazine complexes of ruthenium were shown to exist in an equilibrium mixture with the bimetallic starting material.
NASA Astrophysics Data System (ADS)
Pazderka, Tomáš; Kopecký, Vladimír
2017-10-01
The Raman spectra of 20 proteinogenic amino acids were recorded in the solution, glass phase (as drop coating deposition Raman (DCDR) samples) and crystalline forms in the wide spectral range of 200-3200 cm- 1. The most apparent spectral differences between the Raman spectra of the crystalline forms, glass phases and aqueous solutions of amino acids were briefly discussed and described in the frame of published works. The possible density dependencies of spectral bands were noted. In some cases, a strong influence of the sample density, as well as of the organization of the water envelope, was observed. The most apparent changes were observed for Ser and Thr. Nevertheless, for the majority of amino acids, the DCDR sample form is an intermediate between the solution and crystalline forms. In contrast, aromatic amino acids have only a small sensitivity to the form of the sample. Our reference set of Raman spectra is useful for revealing discrepancies between the SERS and solid/solution spectra of amino acids. We also found that some previously published Raman spectra of polycrystalline samples resemble glassy state rather than crystalline spectra. Therefore, this reference set of spectra will find application in every branch of Raman spectroscopy where the spectra of biomolecules are collected from coatings.
Pazderka, Tomáš; Kopecký, Vladimír
2017-10-05
The Raman spectra of 20 proteinogenic amino acids were recorded in the solution, glass phase (as drop coating deposition Raman (DCDR) samples) and crystalline forms in the wide spectral range of 200-3200cm(-1). The most apparent spectral differences between the Raman spectra of the crystalline forms, glass phases and aqueous solutions of amino acids were briefly discussed and described in the frame of published works. The possible density dependencies of spectral bands were noted. In some cases, a strong influence of the sample density, as well as of the organization of the water envelope, was observed. The most apparent changes were observed for Ser and Thr. Nevertheless, for the majority of amino acids, the DCDR sample form is an intermediate between the solution and crystalline forms. In contrast, aromatic amino acids have only a small sensitivity to the form of the sample. Our reference set of Raman spectra is useful for revealing discrepancies between the SERS and solid/solution spectra of amino acids. We also found that some previously published Raman spectra of polycrystalline samples resemble glassy state rather than crystalline spectra. Therefore, this reference set of spectra will find application in every branch of Raman spectroscopy where the spectra of biomolecules are collected from coatings. Copyright © 2017 Elsevier B.V. All rights reserved.
Hydrodynamics of steady state phloem transport with radial leakage of solute
Cabrita, Paulo; Thorpe, Michael; Huber, Gregor
2013-01-01
Long-distance phloem transport occurs under a pressure gradient generated by the osmotic exchange of water associated with solute exchange in source and sink regions. But these exchanges also occur along the pathway, and yet their physiological role has almost been ignored in mathematical models of phloem transport. Here we present a steady state model for transport phloem which allows solute leakage, based on the Navier-Stokes and convection-diffusion equations which describe fluid motion rigorously. Sieve tube membrane permeability Ps for passive solute exchange (and correspondingly, membrane reflection coefficient) influenced model results strongly, and had to lie in the bottom range of the values reported for plant cells for the results to be realistic. This smaller permeability reflects the efficient specialization of sieve tube elements, minimizing any diffusive solute loss favored by the large concentration difference across the sieve tube membrane. We also found there can be a specific reflection coefficient for which pressure profiles and sap velocities can both be similar to those predicted by the Hagen-Poiseuille equation for a completely impermeable tube. PMID:24409189
Tracer breakthrough curves in a complex lysimeter system: evidence of non-stationary transport
NASA Astrophysics Data System (ADS)
Queloz, P.; Bertuzzo, E.; Botter, G.; Rao, P.; Rinaldo, A.
2013-12-01
We report on the outcomes of a lysimeter experiment aimed at the measurement of travel time distributions of water and certain nonreactive solutes under non-stationary conditions to examine the kinematics of age mixing. In order to simulate the release of a compound in a receiving water body, it is common in hydrology to attribute a travel time probability distribution to each particle, which reflects the response of a catchment unit to a solute input. Hence, the concentration measured at a control section becomes the convolution between the travel time distribution and the concentration of the inputs throughout the past. This study aims at experimentally demonstrating that the tracer travel time probability distribution is, in fact, strongly dependent on the antecedent conditions at the time of tracer injection and the subsequent states experienced in the system. It is therefore a function of numerous transient processes such as hydrologic filtering in soils, climatic forcing or evapotranspiration patterns. A 2-meter deep weighing lysimeter was equipped with a discharge measurement system coupled with a sample collector, an array of water content sensors and an array of porous cups for soil water sampling at three different depths. Controlled random rainfall following a Poisson process was generated, and evapotranspiration losses from two willow trees planted in the lysimeter created an important soil-water storage deficit. Five species of fluorobenzoic acids were used as tracers, and sequentially injected through rainfall at different times. The measurement system installed allowed a precise and accurate monitoring of every input and output flux and water storage, which is crucial to determine the conditions influencing the travel time distribution and to calculate the mass loads and recovery rates. Breakthrough curves for multiple tracers measured at several depths within the lysimeter and at the lysimeter outlet provide support for non-stationary tracer travel
ATUS-PRO: A FEM-based solver for the time-dependent and stationary Gross-Pitaevskii equation
NASA Astrophysics Data System (ADS)
Marojević, Želimir; Göklü, Ertan; Lämmerzahl, Claus
2016-05-01
ATUS-PRO is a solver-package written in C++ designed for the calculation of numerical solutions of the stationary- and the time dependent Gross-Pitaevskii equation for local two-particle contact interaction utilising finite element methods. These are implemented by means of the deal.II library (Bangerth et al., 0000) [1], (Bangerth et al., 2007) [2]. The code can be used in order to perform simulations of Bose-Einstein condensates in gravito-optical surface traps, isotropic and full anisotropic harmonic traps, as well as for arbitrary trap geometries. A special feature of this package is the possibility to calculate non-ground state solutions (topological modes, excited states) (Marojević et al., 2013), (Yukalov et al., 1997, 2004) [3,4] for an arbitrarily high non-linearity term. The solver-package is designed to run on parallel distributed machines and can be applied to problems in one, two, or three spatial dimensions with axial symmetry or in Cartesian coordinates. The time dependent Gross-Pitaevskii equation is solved by means of the fully implicit Crank-Nicolson method, whereas stationary states are obtained with a modified version based on our own constrained Newton method (Marojević et al., 2013). The latter method enables to find the excited state solutions.
Soil and soil solution chemistry under red spruce stands across the northeastern united states
David, M.B.; Lawrence, G.B.
1996-01-01
Red spruce ecosystems in the northeastern United States are of interest because this species is undergoing regional decline. Their underlying soils have been examined closely at only a few sites, and information available on red spruce soils throughout this region is limited.This study was conducted to examine soil and soil solution chemistry at red spruce sites in the northeastern US that encompass the range of soil conditions in which red spruce grow. Soils and soil solutions from Oa and B horizons were obtained over a 2-year period from 12 undisturbed red spruce forests (elevations of 80-975 m) in New York, Vermont, New Hampshire, and Maine. All sites had extremely acid Spodosols (Oa soil pH range 2.56 to 3.11 in 0.01 M CaCl2), with generally low concentrations of base cations and high concentrations of Al on soil exchange sites. There was considerable range in exchange chemistry across the sites, however, with exchangeable Ca in Oa horizons ranging from 2.1 to 21.6 cmolckg-1 and exchangeable Al from 3.6 to 18.3 cmolckg-1. Solution chemistry had high concentrations of DOC in the Oa horizons (1160-15200 ??mol L-1), with higher concentrations in the fall than in the spring, which was probably a reflection of fresh litter inputs. Despite high concentrations of DOC in all solutions, inorganic Al was found in some Oa solutions at concentrations as high as 26 ??mol L-1. Ratios of Ca2+ to inorganic Al concentraturns were less than 1.0 in the Oa horizon of one site, and were well below 1.0 in B horizons of all sites. That soil chemistry was related to soil solution chemistry was demonstrated by solution Al concentrations in the forest floor having significant relationships with pyrophosphate extractable Al, although it was not related in the B horizon. Soil exchangeable Ca/Al ratios in the Oa horizon explained 75% of the variation in solution Ca2+/inorganic Al ratios when mean values were used for each site. Our studies have expanded the range of soil chemical
NASA Astrophysics Data System (ADS)
Kobayashi, Motoyasu; Mitamura, Koji; Terada, Masami; Yamada, Norifumi L.; Takahara, Atsushi
2011-01-01
Cationic and zwitterionic polyelectrolyte brushes on quartz substrate were synthesized by surface-initiated atom transfer radical polymerization of 2-(methacryloyloxy)-ethyltrimethylammonium chloride (MTAC) and 2-(methacryloyloxy)ethyl phosphorylcholine (MPC). The effects of ionic strength on brush structure are investigated by neutron reflectivity (NR) in NaCl deuterium oxide (D2O) solutions. We observed that poly(MTAC) chains were drastically shrunk at concentrations above 0.1 M NaCl/D2O, which may be the change in charge-screening effect against ions on poly(MTAC). On the other hand, effect of salt concentration on a swollen state of poly(MPC) brush was negligible, even at the high concentration (5.0 M) close to saturation. The behaviour of poly(MPC) in salt aqueous solution is completely different from that of poly(MTAC), which may arise from the unique interaction properties, neutral nature, and hydrated water structure of phosphorylcholine units.
Refractive index and equation of state of a shock-compressed aqueous solution of zinc chloride
NASA Astrophysics Data System (ADS)
Wise, J. L.
1983-06-01
Velocity interferometers measurements have yielded refractive index and Hugoniot equation-of-state data for a 9.1-molar aqueous solution of zinc chloride which was shock-compressed to initial stresses ranging from 2.2 to 24.1 GPa in a series of plate-impact experiments. The Hugoniot data are accurately described by a linear variation of shock velocity with particle velocity. The optical data verify sustained solution transparency over the investigated range of shock stresses, and provide a calibration of the correction which must be applied to interferometer measurements to account for the stress-induced change in refractive index of the material. Refractive index data derived from the measured particle velocity corrections exhibit a departure from predictions based on the Gladstone-Dale relation.
The transverse magnetic field effect on steady-state solutions of the Bursian diode
Pramanik, Sourav; Chakrabarti, Nikhil
2015-04-15
A study of steady-states of a planar vacuum diode driven by a cold electron beam (the Bursian diode) under an external transverse magnetic field is presented. The regime of no electrons turned around by a magnetic field only is under the consideration. The emitter electric field is evaluated as a characteristic function for the existence of solutions depending on the diode length, the applied voltage, and the magnetic field strength. At certain conditions, it is shown that a region of non-unique solutions exists in the Bursian diode when the magnetic field is absent. An expression for the maximum current transmitted through the diode is derived. The external magnetic field is put forth to control fast electronic switches based on the Bursian diode.
Santa María, Dolores; Claramunt, Rosa M; Alkorta, Ibon; Elguero, José
2009-06-01
The structure of the hypoglycemic agent Gliclazide has been studied by (1)H, (13)C, and (15)N NMR in solution (CDCl(3) and DMSO-d(6)) and in the solid state. In the solid state, the compound crystallizes as an EZ isomer without dynamic properties. In CDCl(3) solution, the structure is still EZ but with a slow nitrogen inversion about the pyrrolidine nitrogen: two invertomers have been observed and characterized. In DMSO-d(6), the rate is faster and only averaged signals were observed. GIAO calculated absolute shieldings were used to confirm the nature of the observed species. In the solid state, Gliclazide presents the phenomenon of solid-solution with two disordered conformations present in the crystal at a 90:10 ratio.
Unified semiclassical theory for the two-state system: Analytical solutions for scattering matrices
NASA Astrophysics Data System (ADS)
Zhu, Chaoyuan
1996-09-01
Unified semiclassical theory is established for general two-state system by employing an exactly analytical quantum solution [C. Zhu, J. Phys. A29, 1293 (1996)] for the Nikitin exponential-potential model which contains the two-state curve crossing and noncrossing cases as a whole. Analytical solutions for scattering matrices are found for both three- and two-channel cases within the time-independent treatment. This is made possible by introducing a very important parameter d(R0)=√)/[V22(R0)-V11(R0)]2 (V11(R), V22(R) and V12(R) are diabatic potentials and coupling, R0 is real part of complex crossing point between two adiabatic potentials) which represents a type of nonadiabatic transition for the two-state system. For instance, d=∞ represents the Landau-Zener type and d=√ represents Rosen-Zener type. Since d(R0) runs from unity to infinity, this parameter provides a quantitative description of nonadiabatic transition. The idea used here is the parameter comparison method which makes a unique link between the model and general potential system at the complex crossing point. This method is testified not only by numerical examples, but also by agreement of the present semiclassical formulas with all existing semiclassical formulas.
Wen, Jia-Long; Sun, Shao-Long; Xue, Bai-Liang; Sun, Run-Cang
2013-01-01
The demand for efficient utilization of biomass induces a detailed analysis of the fundamental chemical structures of biomass, especially the complex structures of lignin polymers, which have long been recognized for their negative impact on biorefinery. Traditionally, it has been attempted to reveal the complicated and heterogeneous structure of lignin by a series of chemical analyses, such as thioacidolysis (TA), nitrobenzene oxidation (NBO), and derivatization followed by reductive cleavage (DFRC). Recent advances in nuclear magnetic resonance (NMR) technology undoubtedly have made solution-state NMR become the most widely used technique in structural characterization of lignin due to its versatility in illustrating structural features and structural transformations of lignin polymers. As one of the most promising diagnostic tools, NMR provides unambiguous evidence for specific structures as well as quantitative structural information. The recent advances in two-dimensional solution-state NMR techniques for structural analysis of lignin in isolated and whole cell wall states (in situ), as well as their applications are reviewed. PMID:28809313
Acid-base state of the preterm infant and the formulation of intravenous feeding solutions.
MacMahon, P; Mayne, P D; Blair, M; Pope, C; Kovar, I Z
1990-04-01
An acidic intravenous source of phosphorus (Addiphos) was compared with dipotassium hydrogen phosphate in 25 preterm infants to study acid-base state. Eight infants were given either Addiphos or dipotassium hydrogen phosphate alternately for 48 hour periods and similar amounts of calcium and phosphorus were delivered. There were no significant differences in calcium and phosphorus intake, calcium and phosphate plasma concentrations, or acid-base state between study periods on the two solutions. Seventeen infants were given the two solutions alternately for 72 hour periods; Addiphos was used to increase the amounts of calcium and phosphorus being delivered. Calcium and phosphorus intake was decreased on dipotassium hydrogen phosphate, but Addiphos significantly increased calcium and phosphorus intake and plasma calcium and phosphate concentrations. It also lowered the pH of the urine and raised the titratable acidity. Acid-base state, however, was not significantly different. It is therefore possible to increase intake of calcium and phosphorus in preterm infants without causing a significant metabolic acidosis.
Acid-base state of the preterm infant and the formulation of intravenous feeding solutions.
MacMahon, P; Mayne, P D; Blair, M; Pope, C; Kovar, I Z
1990-01-01
An acidic intravenous source of phosphorus (Addiphos) was compared with dipotassium hydrogen phosphate in 25 preterm infants to study acid-base state. Eight infants were given either Addiphos or dipotassium hydrogen phosphate alternately for 48 hour periods and similar amounts of calcium and phosphorus were delivered. There were no significant differences in calcium and phosphorus intake, calcium and phosphate plasma concentrations, or acid-base state between study periods on the two solutions. Seventeen infants were given the two solutions alternately for 72 hour periods; Addiphos was used to increase the amounts of calcium and phosphorus being delivered. Calcium and phosphorus intake was decreased on dipotassium hydrogen phosphate, but Addiphos significantly increased calcium and phosphorus intake and plasma calcium and phosphate concentrations. It also lowered the pH of the urine and raised the titratable acidity. Acid-base state, however, was not significantly different. It is therefore possible to increase intake of calcium and phosphorus in preterm infants without causing a significant metabolic acidosis. PMID:2110804
NASA Astrophysics Data System (ADS)
Nagy, M. I.; Csörgő, T.
2016-12-01
We present a class of analytic solutions of nonrelativistic fireball hydrodynamics for a fairly general class of equation of state. The presented solution describes the expansion of a triaxial ellipsoid that rotates around one of its principal axes. We calculate the hadronic final state observables such as single-particle spectra, directed, elliptic, and third flows, as well as two-particle Bose-Einstein (also named HBT) correlations and corresponding radius parameters, utilizing simple analytic formulas. The final tilt angle of the fireball, an important observable quantity, is shown to be not independent of its exact definition: one gets different tilt angles from the geometrical anisotropies, from the single-particle spectra, and from HBT measurements. Taken together, the tilt angle in the momentum space and in the relative momentum or HBT variable may be sufficient for the determination of the magnitude of the rotation of the fireball. We argue that observing this rotation and its dependence on collision energy could characterize the softest point of the equation of state. Thus determining the rotation may be a powerful tool for the experimental search for the critical point in the phase diagram of strongly interacting matter.
Stationary stability for evolutionary dynamics in finite populations
Harper, Marc; Fryer, Dashiell
2016-08-25
Here, we demonstrate a vast expansion of the theory of evolutionary stability to finite populations with mutation, connecting the theory of the stationary distribution of the Moran process with the Lyapunov theory of evolutionary stability. We define the notion of stationary stability for the Moran process with mutation and generalizations, as well as a generalized notion of evolutionary stability that includes mutation called an incentive stable state (ISS) candidate. For sufficiently large populations, extrema of the stationary distribution are ISS candidates and we give a family of Lyapunov quantities that are locally minimized at the stationary extrema and at ISSmore » candidates. In various examples, including for the Moran andWright–Fisher processes, we show that the local maxima of the stationary distribution capture the traditionally-defined evolutionarily stable states. The classical stability theory of the replicator dynamic is recovered in the large population limit. Finally we include descriptions of possible extensions to populations of variable size and populations evolving on graphs.« less
The physical state of nafcillin sodium in frozen aqueous solutions and freeze-dried powders.
Milton, N; Nail, S L
1996-10-01
The purpose of this study was to develop a better understanding of the physical chemistry of freeze drying of lyotropic liquid crystals using nafcillin sodium as a model solute. Solutions and freeze-dried powders of nafcillin sodium were studied by polarized light microscopy, differential scanning calorimetry, x-ray powder diffraction, and water vapor adsorption. Differential scanning calorimetry thermograms of nafcillin sodium solutions contain a melting endotherm at approximately -5.5 degrees C and, depending on the concentration and heating rate, a crystallization exotherm immediately after this endotherm followed by the melting endotherm of ice. When the sample is annealed at -4 degrees C, both the endotherm and exotherm are eliminated, and a new endotherm appears at approximately -1 degree C on the shoulder of the ice-melting endotherm. The data are interpreted as melting of a liquid crystalline phase, followed by crystallization. X-ray powder diffractograms of unannealed freeze-dried nafcillin sodium are consistent with a lamellar liquid crystal. Diffractograms of annealed freeze-dried nafcillin sodium indicate crystalline material which is a different crystal form than the monohydrate starting material. Moisture adsorption isotherms of the freeze-dried annealed (crystalline) and unannealed (liquid crystalline) nafcillin sodium show different affinities for moisture compared to the crystalline starting material. Solid-state stability data demonstrate that the freeze-dried liquid crystalline form of nafcillin sodium is much less stable than the freeze-dried crystal-line material. The literature recognizes two types of solute behavior on freezing, where the solute either crystallizes from the freeze concentrate or remains amorphous. Lyotropic liquid crystal formation during freezing represents a separate category of freezing behavior, the physical chemistry of which is worthy of further investigation.
NASA Astrophysics Data System (ADS)
Kunst, Flore K.; Trescher, Maximilian; Bergholtz, Emil J.
2017-08-01
The hallmark of topological phases is their robust boundary signature whose intriguing properties—such as the one-way transport on the chiral edge of a Chern insulator and the sudden disappearance of surface states forming open Fermi arcs on the surfaces of Weyl semimetals—are impossible to realize on the surface alone. Yet, despite the glaring simplicity of noninteracting topological bulk Hamiltonians and their concomitant energy spectrum, the detailed study of the corresponding surface states has essentially been restricted to numerical simulation. In this work, however, we show that exact analytical solutions of both topological and trivial surface states can be obtained for generic tight-binding models on a large class of geometrically frustrated lattices in any dimension without the need for fine-tuning of hopping amplitudes. Our solutions derive from local constraints tantamount to destructive interference between neighboring layer lattices perpendicular to the surface and provide microscopic insights into the structure of the surface states that enable analytical calculation of many desired properties including correlation functions, surface dispersion, Berry curvature, and the system size dependent gap closing, which necessarily occurs when the spatial localization switches surface. This further provides a deepened understanding of the bulk-boundary correspondence. We illustrate our general findings on a large number of examples in two and three spatial dimensions. Notably, we derive exact chiral Chern insulator edge states on the spin-orbit-coupled kagome lattice, and Fermi arcs relevant for recently synthesized slabs of pyrochlore-based Eu2Ir2O7 and Nd2Ir2O7 , which realize an all-in-all-out spin configuration, as well as for spin-ice-like two-in-two-out and one-in-three-out configurations, which are both relevant for Pr2Ir2O7 . Remarkably, each of the pyrochlore examples exhibit clearly resolved Fermi arcs although only the one
NASA Astrophysics Data System (ADS)
Galić, Nives; Brođanac, Ivan; Kontrec, Darko; Miljanić, Snežana
2013-04-01
Structural forms of aroylhydrazones derived from nicotinic acid hydrazide have been studied in the solid state by FT-IR spectroscopy and in solution by NMR, UV-Vis and ATR spectroscopy. The studied compounds were N'-benzylidene-3-pyridinecarbohydrazide (1), N'-(2,4-dihydroxyphenylmethylidene)-3-pyridinecarbohydrazide (2), N'-(5-chloro-2-hydroxyphenylmethylidene)-3-pyridinecarbohydrazide (3), and N'-(3,5-dichloro-2-hydroxymethoxyphenylmethylidene)-3-pyridinecarbohydrazide (4). The compound 1 adopted the most stable ketoamine form (form I, sbnd COsbnd NHsbnd Ndbnd Csbnd ) in the solid state as well as in various organic solvents. In mixtures of organic solvents with water the UV-Vis and ATR spectra implied intermolecular hydrogen bonding of 1 with water molecules. The presence of both tautomeric forms I and II (form II, sbnd COHdbnd Nsbnd Ndbnd Csbnd ) was proposed for the solid substance and highly concentrated solutions of 2, whereas form I was detected as the predominant one in diluted solutions. For compounds 3 and 4 a coexistence of forms I and III (form III, sbnd COsbnd NHsbnd NHsbnd Cdbnd Csbnd COsbnd ) was noticed in the solid state and in polar protic organic solvents. The conversion to form III was induced by increasing the water content in the solvent mixtures. This process was the most pronounced for compound 4. When exposed to daylight, an appearance of a new band was observed during time in the UV-Vis spectrum of 4 in organic solvent/water 1/1 mixtures, which implied that tautomeric interconversion was most likely followed by E/Z isomerisation.
NASA Astrophysics Data System (ADS)
Urayama, Kenji; Kawamura, Takanobu; Kohjiya, Shinzo
1996-09-01
We have investigated the degree of equilibrium swelling and the elastic modulus of networks prepared by end-linking oligo(dimethylsiloxane)s (ODMS) in solution as a function of polymer concentration at crosslinking. The molecular weight of ODMS is so low that entanglement couplings are not formed in uncrosslinked state. It has been found from the preparation concentration dependence of elastic modulus in preparation state that trapped entanglements are formed by the introduction of crosslinks, and those considerably contribute to elastic modulus, even if the prepolymers are not entangled in uncrosslinked state. The experimental results for preparation concentration dependence of the degree of equilibrium swelling and the elastic modulus of equilibrium swollen networks are compared with the theoretical predictions by the two theories, i.e., the affine model and the c* theorem. It has been clearly shown that the affine model describes well the experimental results, while the discrepancies between the experimental results and the predictions by the c* theorem are considerable. These results strongly suggest that preparation concentration should be regarded as a reference state, and the displacement of crosslinks moves affinely on swelling, while the complete disinterpenetration of network chains in equilibrium swollen state, which is a postulate of the c* theorem, does not occur.
On the uniqueness of sign changing bound state solutions of a semilinear equation
NASA Astrophysics Data System (ADS)
Cortázar, Carmen; García-Huidobro, Marta; Yarur, Cecilia S.
2011-07-01
We establish the uniqueness of the higher radial bound state solutions of $$ \\Delta u +f(u)=0,\\quad x\\in \\RR^n. \\leqno(P) $$ We assume that the nonlinearity $f\\in C(-\\infty,\\infty)$ is an odd function satisfying some convexity and growth conditions, and either has one zero at $b>0$, is non positive and not identically 0 in $(0,b)$, and is differentiable and positive $[b,\\infty)$, or is positive and differentiable in $[0,\\infty)$.
Existence of ground state solutions to a generalized quasilinear Schrödinger-Maxwell system
NASA Astrophysics Data System (ADS)
Zhu, Xiaoli; Li, Fuyi; Liang, Zhanping
2016-10-01
In this paper, a class of generalized quasilinear Schrödinger-Maxwell systems is considered. Via the mountain pass theorem, we conclude the existence of positive ground state solutions when the potential may vanish at infinity and the nonlinear term has a quasicritical growth. During this process, we use the Coulomb energy studied by Ruiz [Arch. Ration. Mech. Anal. 198(1), 349-368 (2010)] and establish a convergency theorem to overcome the lack of compactness caused by the potential which may vanish at infinity.
Self-regulating genes. Exact steady state solution by using Poisson representation
NASA Astrophysics Data System (ADS)
Sugár, István; Simon, István
2014-09-01
Systems biology studies the structure and behavior of complex gene regulatory networks. One of its aims is to develop a quantitative understanding of the modular components that constitute such networks. The self-regulating gene is a type of auto regulatory genetic modules which appears in over 40% of known transcription factors in E. coli. In this work, using the technique of Poisson Representation, we are able to provide exact steady state solutions for this feedback model. By using the methods of synthetic biology (P.E.M. Purnick and Weiss, R., Nature Reviews, Molecular Cell Biology, 2009, 10: 410-422) one can build the system itself from modules like this.
Lunin, A.; Yakovlev, V.; Grudiev, A.; /CERN
2011-05-02
Analytical solutions are derived for both transient and steady state gradient distributions in the traveling wave (TW) accelerating structures with arbitrary variation of parameters over the structure length. The results of the unloaded and beam loaded cases are presented. Finally, the exact analytical shape of the rf pulse waveform was found in order to apply the transient beam loading compensation scheme during the structure filling time. The obtained theoretical formulas were cross-checked by direct numerical simulations on the CLIC main linac accelerating structure and demonstrated a good agreement. The proposed methods provide a fast and reliable tool for the initial stage of the TW structure analysis.
Synthesis of dental enamel-like hydroxyapatite through solution mediated solid-state conversion.
Zhang, Junling; Jiang, Dongliang; Zhang, Jingxian; Lin, Qingling; Huang, Zhengren
2010-03-02
An ordered dental enamel-like structure of hydroxyapatite (HAp) was achieved through a solution mediated solid-state conversion process with organic phosphate surfactant and gelatin as the mediating agent. Transmission electron microscopy (TEM) tests demonstrated uniform sizes in the obtained apatite nanorods which arranged in parallel to each other along the c-axis and formed organized microarchitectural units over 10 microm in size. The sizes of the synthetic hydroxyapatite nanorods were similar to that observed in enamel from human teeth. The formation and regulation of the orientation and size of HAp nanorods might lead to a better understanding of the biomineralization process for the preparation of high performance biomaterials.
Characterizing RNA Dynamics at Atomic Resolution Using Solution-state NMR Spectroscopy
Bothe, Jameson R.; Nikolova, Evgenia N.; Eichhorn, Catherine D.; Chugh, Jeetender; Hansen, Alexandar L.; Al-Hashimi, Hashim M.
2012-01-01
Many recently discovered non-coding RNAs do not fold into a single native conformation, but rather, sample many different conformations along their free energy landscape to carry out their biological function. Unprecedented insights into the RNA dynamic structure landscape are provided by solution-state NMR techniques that measure the structural, kinetic, and thermodynamic characteristics of motions spanning picosecond to second timescales at atomic resolution. From these studies a basic description of the RNA dynamic structure landscape is emerging, bringing new insights into how RNA structures change to carry out their function as well as applications in RNA-targeted drug discovery and RNA bioengineering. PMID:22036746
NASA Technical Reports Server (NTRS)
Yao, M.-S.
1980-01-01
A study of the maintenance of the quasistationary waves forced by topography using a truncated two-level quasigeostrophic spectral model in a zonal channel on a beta-plane is presented. The model's motion contains wavenumbers 0, n, and 2n in the zonal direction, where n is the lowest eddy wavenumber and also the wavenumber of the topography. The study covered the two cases defined by n=2 and n=3; the spectral mode was integrated by initially perturbing the stationary solution of the equations governing the spectral coefficients, and a detailed energetics study was made of the quasiequilibrium state to study the maintenance of the quasistationary waves. The energy conversions required for maintaining these waves when n=3 imply that they are generated mainly by baroclinic stability of the forced waves; this type of baroclinic wave tends to become stationary to draw efficiently on the available energy of the forced wave.
Time scale of stationary decoherence
NASA Astrophysics Data System (ADS)
Polonyi, Janos
2017-07-01
The decoherence of a test particle interacting with an ideal gas is studied by the help of the effective Lagrangian, derived in the leading order of the perturbation expansion and in order O (∂t2) . The stationary decoherence time is found to be comparable to or longer than the diffusion time. The decoherence time reaches its minimal value for classical, completely decohered environment, suggesting that physical decoherence is slowed down as compared with diffusion by the quantum coherence of the environment.
A Solution Space for a System of Null-State Partial Differential Equations: Part 3
NASA Astrophysics Data System (ADS)
Flores, Steven M.; Kleban, Peter
2015-01-01
This article is the third of four that completely and rigorously characterize a solution space for a homogeneous system of 2 N + 3 linear partial differential equations (PDEs) in 2 N variables that arises in conformal field theory (CFT) and multiple Schramm-Löwner evolution (SLE κ ). The system comprises 2 N null-state equations and three conformal Ward identities that govern CFT correlation functions of 2 N one-leg boundary operators. In the first two articles (Flores and Kleban, in Commun Math Phys, arXiv:1212.2301, 2012; Commun Math Phys, arXiv:1404.0035, 2014), we use methods of analysis and linear algebra to prove that dim , with C N the Nth Catalan number. Extending these results, we prove in this article that dim and entirely consists of (real-valued) solutions constructed with the CFT Coulomb gas (contour integral) formalism. In order to prove this claim, we show that a certain set of C N such solutions is linearly independent. Because the formulas for these solutions are complicated, we prove linear independence indirectly. We use the linear injective map of Lemma 15 in Flores and Kleban (Commun Math Phys, arXiv:1212.2301, 2012) to send each solution of the mentioned set to a vector in , whose components we find as inner products of elements in a Temperley-Lieb algebra. We gather these vectors together as columns of a symmetric matrix, with the form of a meander matrix. If the determinant of this matrix does not vanish, then the set of C N Coulomb gas solutions is linearly independent. And if this determinant does vanish, then we construct an alternative set of C N Coulomb gas solutions and follow a similar procedure to show that this set is linearly independent. The latter situation is closely related to CFT minimal models. We emphasize that, although the system of PDEs arises in CFT in away that is typically non-rigorous, our treatment of this system here and in Flores and Kleban (Commun Math Phys, arXiv:1212.2301, 2012; Commun Math Phys, arXiv:1404
Hartree-Fock solutions for spin polarized states in low dimensional
NASA Astrophysics Data System (ADS)
Giuliani, G. F.; Marinescu, D. C.
2000-03-01
In the Hartree-Fock (HF) approximation, a two dimensional electron gas is known to exhibit a number of magnetic instabilities both in the absence as well as in the presence of a quantizing magnetic field. The situation is even more interesting in layered structures (e.g. bilayers and semiconducting superlattices) where the HF phase diagram is richer. Here HF states with non uniform magnetization have been predicted to occur and be actually physically realized under suitable conditions.(D.C. Marinescu, G. F. Giuliani, and J.J. Quinn, submitted) Although the HF approximation for the electron gas problem has been known for quite some time, there have been no detailed studies of the self-consistent solutions corresponding to non uniform states in these systems. Results of such a study are discussed in the present paper for a number of electronic systems in this class.
NASA Astrophysics Data System (ADS)
Agnesi, Antoniangelo; Reali, Giancarlo C.
1998-07-01
Referring to the work carried out in our laboratory, we review low-medium power diode pumped all solid state laser systems for scientific, bio-medical and industrial applications. Side- and end-pumping are discussed and compared for such a laser systems. End-pumped scheme is mainly exploited in this report. Coupling solutions and cavity design are described emphasizing energy deposition and extraction optimization, thermal lens effects, beam quality control and longitudinal mode control. Both cw- and quasi-cw-pumped lasers are considered, operating either in continuous wave, passive Q-switching, and mode-locking regimes. Intracavity and extracavity harmonic generation, optical parametric generation and short pulse generation are among the aims of these all-solid-state sources: some result of these applications are reported.
Adiabatic triplet state tautomerization of p-hydroxyacetophenone in aqueous solution.
Klíčová, Ĺubica; Šebej, Peter; Šolomek, Tomáš; Hellrung, Bruno; Slavíček, Petr; Klán, Petr; Heger, Dominik; Wirz, Jakob
2012-03-22
The primary photophysical processes of p-hydroxyacetophenone (HA) and the ensuing proton transfer reactions in aqueous solution were investigated by picosecond pump-probe spectroscopy and nanosecond laser flash photolysis. Previous studies have led to mutually inconsistent conclusions. The combined data allow us to rationalize the excited-state proton transfer processes of HA in terms of a comprehensive, well-established reaction scheme. Following fast and quantitative ISC to the triplet state, (3)HA*, adiabatic proton transfer through solvent water simultaneously forms both the anion, (3)A(-)*, and the quinoid triplet enol tautomer, (3)Q*. The latter subsequently equilibrates with its anion (3)A(-)*. Ionization and tautomerization are likely to compete with the desired release reactions of p-hydroxyphenacyl photoremovable protecting groups. © 2012 American Chemical Society
Hawking radiation of stationary and non-stationary Kerr-de Sitter black holes
NASA Astrophysics Data System (ADS)
Singh, T. Ibungochouba
2015-07-01
Hawking radiation of the stationary Kerr-de Sitter black hole is investigated using the relativistic Hamilton-Jacobi method. Meanwhile, extending this work to a non-stationary black hole using Dirac equations and generalized tortoise coordinate transformation, we derived the locations, the temperature of the thermal radiation as well as the maximum energy of the non-thermal radiation. It is found that the surface gravity and the Hawking temperature depend on both time and different angles. An extra coupling effect is obtained in the thermal radiation spectrum of Dirac particles which is absent from thermal radiation of scalar particles. Further, the chemical potential derived from the thermal radiation spectrum of scalar particle has been found to be equal to the highest energy of the negative energy state of the scalar particle in the non-thermal radiation for the Kerr-de Sitter black hole. It is also shown that for stationary black hole space time, these two different methods give the same Hawking radiation temperature.
All-Solution-Based Aggregation Control in Solid-State Photon Upconverting Organic Model Composites.
Goudarzi, Hossein; Keivanidis, Panagiotis E
2017-01-11
Hitherto, great strides have been made in the development of organic systems that exhibit triplet-triplet annihilation-induced photon-energy upconversion (TTA-UC). Yet, the exact role of intermolecular states in solid-state TTA-UC composites remains elusive. Here we perform a comprehensive spectroscopic study in a series of solution-processable solid-state TTA-UC organic composites with increasing segregated phase content for elucidating the impact of aggregate formation in their TTA-UC properties. Six different states of aggregation are reached in composites of the 9,10-diphenylanthracene (DPA) blue emitter mixed with the (2,3,7,8,12,13,17,18-octaethylporphyrinato)platinum(II) sensitizer (PtOEP) in a fixed nominal ratio (2 wt % PtOEP). Fine-tuning of the PtOEP and DPA phase segregation in these composites is achieved with a low-temperature solution-processing protocol when three different solvents of increasing boiling point are alternatively used and when the binary DPA:PtOEP system is dispersed in the optically inert polystyrene (PS) matrix (PS:DPA:PtOEP). Time-gated (in the nanosecond and microsecond time scales) photoluminescence measurements identify the upper level of PtOEP segregation at which the PtOEP aggregate-based networks favor PtOEP triplet exciton migration toward the PtOEP:DPA interfaces and triplet energy transfer to the DPA triplet manifold. The maximum DPA TTA-UC luminescence intensity is ensured when the bimolecular annihilation constant of PtOEP remains close to γTTA-PtOEP = 1.1 × 10(-13) cm(3) s(-1). Beyond this PtOEP segregation level, the DPA TTA-UC luminescence intensity decreases because of losses caused by the generation of PtOEP delayed fluorescence and DPA phosphorescence in the nanosecond and microsecond time scales, respectively.
Implicit unified gas-kinetic scheme for steady state solutions in all flow regimes
NASA Astrophysics Data System (ADS)
Zhu, Yajun; Zhong, Chengwen; Xu, Kun
2016-06-01
This paper presents an implicit unified gas-kinetic scheme (UGKS) for non-equilibrium steady state flow computation. The UGKS is a direct modeling method for flow simulation in all regimes with the updates of both macroscopic flow variables and microscopic gas distribution function. By solving the macroscopic equations implicitly, a predicted equilibrium state can be obtained first through iterations. With the newly predicted equilibrium state, the evolution equation of the gas distribution function and the corresponding collision term can be discretized in a fully implicit way for fast convergence through iterations as well. The lower-upper symmetric Gauss-Seidel (LU-SGS) factorization method is implemented to solve both macroscopic and microscopic equations, which improves the efficiency of the scheme. Since the UGKS is a direct modeling method and its physical solution depends on the mesh resolution and the local time step, a physical time step needs to be fixed before using an implicit iterative technique with a pseudo-time marching step. Therefore, the physical time step in the current implicit scheme is determined by the same way as that in the explicit UGKS for capturing the physical solution in all flow regimes, but the convergence to a steady state speeds up through the adoption of a numerical time step with large CFL number. Many numerical test cases in different flow regimes from low speed to hypersonic ones, such as the Couette flow, cavity flow, and the flow passing over a cylinder, are computed to validate the current implicit method. The overall efficiency of the implicit UGKS can be improved by one or two orders of magnitude in comparison with the explicit one.
High efficiency stationary hydrogen storage
Hynek, S.; Fuller, W.; Truslow, S.
1995-09-01
Stationary storage of hydrogen permits one to make hydrogen now and use it later. With stationary hydrogen storage, one can use excess electrical generation capacity to power an electrolyzer, and store the resultant hydrogen for later use or transshipment. One can also use stationary hydrogen as a buffer at fueling stations to accommodate non-steady fueling demand, thus permitting the hydrogen supply system (e.g., methane reformer or electrolyzer) to be sized to meet the average, rather than the peak, demand. We at ADL designed, built, and tested a stationary hydrogen storage device that thermally couples a high-temperature metal hydride to a phase change material (PCM). The PCM captures and stores the heat of the hydriding reaction as its own heat of fusion (that is, it melts), and subsequently returns that heat of fusion (by freezing) to facilitate the dehydriding reaction. A key component of this stationary hydrogen storage device is the metal hydride itself. We used nickel-coated magnesium powder (NCMP) - magnesium particles coated with a thin layer of nickel by means of chemical vapor deposition (CVD). Magnesium hydride can store a higher weight fraction of hydrogen than any other practical metal hydride, and it is less expensive than any other metal hydride. We designed and constructed an experimental NCM/PCM reactor out of 310 stainless steel in the form of a shell-and-tube heat exchanger, with the tube side packed with NCMP and the shell side filled with a eutectic mixture of NaCL, KCl, and MgCl{sub 2}. Our experimental results indicate that with proper attention to limiting thermal losses, our overall efficiency will exceed 90% (DOE goal: >75%) and our overall system cost will be only 33% (DOE goal: <50%) of the value of the delivered hydrogen. It appears that NCMP can be used to purify hydrogen streams and store hydrogen at the same time. These prospects make the NCMP/PCM reactor an attractive component in a reformer-based hydrogen fueling station.
Steady state analytical solutions for pumping in a fully bounded rectangular aquifer
NASA Astrophysics Data System (ADS)
Lu, Chunhui; Xin, Pei; Li, Ling; Luo, Jian
2015-10-01
Using the Schwartz-Christoffel conformal mapping method together with the complex variable techniques, we derive steady state analytical solutions for pumping in a rectangular aquifer with four different combinations of impermeable and constant-head boundaries. These four scenarios include: (1) one constant-head boundary and three impermeable boundaries, (2) two pairs of orthogonal impermeable and constant-head boundaries, (3) three constant-head boundaries and one impermeable boundary, and (4) four constant-head boundaries. For these scenarios, the impermeable and constant-head boundaries can be combined after applying the mapping functions, and hence only three image wells exist in the transformed plane, despite an infinite number of image wells in the real plane. The closed-form solutions reflect the advantage of the conformal mapping method, though the method is applicable for the aspect ratio of the rectangle between 1/10.9 and 10.9/1 due to the limitation in the numerical computation of the conformal transformation from a half plane onto an elongated region (i.e., so-called "crowding" phenomenon). By contrast, for an additional scenario with two parallel constant-head boundaries and two parallel impermeable boundaries, an infinite series of image wells is necessary to express the solution, since it is impossible to combine these two kinds of boundaries through the conformal transformation. The usefulness of the results derived is demonstrated by an application to pumping in a finite coastal aquifer.
Carbon-dot organic surface modifier analysis by solution-state NMR spectroscopy
NASA Astrophysics Data System (ADS)
Philippidis, Aggelos; Spyros, Apostolos; Anglos, Demetrios; Bourlinos, Athanasios B.; Zbořil, Radek; Giannelis, Emmanuel P.
2013-07-01
Carbon dots (C-dots) represent a new class of carbon-based materials that were discovered recently and have drawn the interest of the scientific community, particularly because of their attractive optical properties and their potential as fluorescent sensors. Investigation of the chemical structure of C-dots is extremely important for correlating the surface modifier composition with C-dot optical properties and allow for structure-properties fine tuning. In this article, we report the structural analysis of the surface modifiers of three different types of C-dot nanoparticles (Cwax, Cws, and Csalt) by use of 1D- and 2D-high-resolution NMR spectroscopy in solution. We unambiguously verify that the structure of the modifier chains remains chemically unchanged during the passivation procedure, and confirm the covalent attachment of the modifiers to the nanoparticle core, which contributes no signal to the solution-state NMR spectra. To our knowledge, this is the first study confirming the full structural assignment of C-dot organic surface modifiers by use of solution NMR spectroscopy.
Immobilized strychnine as a new chiral stationary phase for HPLC.
Sýkora, David; Vozka, Jiří; Tesařová, Eva; Kalíková, Květa; Havlík, Martin; Matějka, Pavel; Král, Vladimír
2017-08-01
A new ion-exchanger type chiral stationary phase for high-performance liquid chromatography was prepared. The synthetic protocol is based on derivatization of silica with (3-iodopropyl)trimethoxysilane in the first step followed by immobilization of strychnine via quaternization of nitrogen atom of the alkaloid strychnine. The synthesized chiral stationary phase was chromatographically characterized. The main effort was headed towards the evaluation of the enantioselectivity of the novel sorbent. For that purpose a set of suitable chiral probes, specifically, binaphthyl derivatives, was employed. The influence of methanol content, concentration of aqueous ammonium acetate buffer, and its pH on retention factors, separation selectivity, and resolution of the atropoisomers of the mentioned chiral solutes was studied in detail. It was demonstrated that the new chiral stationary phase was capable to separate atropoisomers of four out of seven testing compounds. Despite the strong influence of the above mentioned variables on retention, their impact on selectivity and resolution was rather moderate. Concerning retention mechanism, it seems that electrostatic interaction between the positively charged quaternary nitrogen of the chiral stationary phase and anionic solute participates significantly in the retention process. © 2017 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.
2013-01-01
Background Several papers described the structure of curcumin and some other derivatives in solid and in solution. In the crystal structure of curcumin, the enol H atom is located symmetrically between both oxygen atoms of the enolone fragment with an O···O distance of 2.455 Å, which is characteristic for symmetrical H-bonds. In the solution, the geometry of the enolone fragment is attributed to the inherent disorder of the local environment, which solvates one of the basic sites better than the other, stabilizing one tautomer over the other. In this paper, how the position of methoxy groups in dimethoxy curcuminoids influence the conformation of molecules and how the halogen atoms change it when they are bonded at α-position in keto-enol part of molecules is described. Results Six isomers of dimethoxy curcuminoids were prepared. Conformations in solid state, which were determined by X-ray single crystallography and 1H MAS and 13C CPMAS NMR measurements, depend on the position of methoxy groups in curcuminoid molecules. In solution, a fast equilibrium between both keto-enol forms exists. A theoretical calculation finding shows that the position of methoxy groups changes the energy of HOMO and LUMO. An efficient protocol for the highly regioselective bromination and chlorination leading to α-halogenated product has been developed. All α-halogenated compounds are present mainly in cis keto-enol form. Conclusions The structures in solid state of dimethoxy curcuminoids depend on the position of methoxy groups. The NMR data of crystalline solid samples of 3,4-diOCH3 derivative, XRD measurements and X-ray structures lead us to the conclusion that polymorphism exists in solids. The same conclusion can be done for 3,5-diOCH3 derivative. In solution, dimethoxy curcuminoids are present in the forms that can be described as the coexistence of two equivalent tautomers being in fast equilibrium. The position of methoxy groups has a small influence on the enolic hydrogen
Jungbauer, Stefan H; Schindler, Severin; Herdtweck, Eberhardt; Keller, Sandro; Huber, Stefan M
2015-09-21
The binding properties of neutral halogen-bond donors (XB donors) bearing two multidentate Lewis acidic motifs toward halides were investigated. Employing polyfluorinated and polyiodinated terphenyl and quaterphenyl derivatives as anion receptors, we obtained X-ray crystallographic data of the adducts of three structurally related XB donors with tetraalkylammonium chloride, bromide, and iodide. The stability of these XB complexes in solution was determined by isothermal titration calorimetry (ITC), and the results were compared to X-ray analyses as well as to calculated binding patterns in the gas phase. Density functional theory (DFT) calculations on the gas-phase complexes indicated that the experimentally observed distortion of the XB donors during multiple multidentate binding can be reproduced in 1:1 complexes with halides, whereas adducts with two halides show a symmetric binding pattern in the gas phase that is markedly different from the solid state structures. Overall, this study demonstrates the limitations in the transferability of binding data between solid state, solution, and gas phase in the study of complex multidentate XB donors.
Bound state solutions of Dirac equation with radial exponential-type potentials
NASA Astrophysics Data System (ADS)
Peña, J. J.; Morales, J.; García-Ravelo, J.
2017-04-01
In this work, a direct approach for obtaining analytical bound state solutions of the Dirac equation for radial exponential-type potentials with spin and pseudospin symmetry conditions within the frame of the Green and Aldrich approximation to the centrifugal term is presented. The proposal is based on the relation existing between the Dirac equation and the exactly solvable Schrödinger equation for a class of multi-parameter exponential-type potential. The usefulness of the present approach is exemplified by considering some known specific exponential-type potentials which are obtained as particular cases from our proposal. That is, instead of solving the Dirac equation for a special exponential potential, by means of a specialized method, the energy spectra and wave functions are derived directly from the proposed approach. Beyond the applications considered in this work, our proposition could be used as an alternative way in the search of bound state solutions of the Dirac equation for other potentials as well as it can be easily adapted to other approximations to the centrifugal term.
Ultraviolet resonance Raman spectroscopy of explosives in solution and the solid state.
Emmons, Erik D; Tripathi, Ashish; Guicheteau, Jason A; Fountain, Augustus W; Christesen, Steven D
2013-05-23
Resonance Raman cross sections of common explosives have been measured by use of excitation wavelengths in the deep-UV from 229 to 262 nm. These measurements were performed both in solution and in the native solid state for comparison. While measurements of UV Raman cross sections in solution with an internal standard are straightforward and commonly found in the literature, measurements on the solid phase are rare. This is due to the difficulty in preparing a solid sample in which the molecules of the internal standard and absorbing analyte/explosive experience the same laser intensity. This requires producing solid samples that are mixtures of strongly absorbing explosives and an internal standard transparent at the UV wavelengths used. For the solid-state measurements, it is necessary to use nanostructured mixtures of the explosive and the internal standard in order to avoid this bias due to the strong UV absorption of the explosive. In this study we used a facile spray-drying technique where the analyte of interest was codeposited with the nonresonant standard onto an aluminum-coated microscope slide. The generated resonance enhancement profiles and quantitative UV-vis absorption spectra were then used to plot the relative Raman return as a function of excitation wavelength and particle size.
Kim, Myoung-Ho; Choi, Suk-Jung
2015-04-15
In this study, we devised a stationary liquid-phase lab-on-a-chip (SLP LOC), which was operated by moving solid-phase magnetic particles in the stationary liquid phase. The SLP LOC consisted of a sample chamber to which a sample and reactants were added, a detection chamber containing enzyme substrate solution, and a narrow channel connecting the two chambers and filled with buffer. As a model system, competitive immunoassays of saxitoxin (STX), a paralytic shellfish toxin, were conducted in the SLP LOC using protein G-coupled magnetic particles (G-MPs) as the solid phase. Anti-STX antibodies, STX-horseradish peroxidase conjugate, G-MPs, and a STX sample were added to the sample chamber and reacted by shaking. While liquids were in the stationary state, G-MPs were transported from the sample chamber to the detection chamber by moving a magnet below the LOC. After incubation to allow the enzymatic reaction to occur, the absorbance of the detection chamber solution was found to be reciprocally related to the STX concentration of the sample. Thus, the SLP LOC may represent a novel, simple format for point-of-care testing applications of enzyme-linked immunosorbent assays by eliminating complicated liquid handling steps.
NASA Astrophysics Data System (ADS)
Janiš, Václav; Pokorný, Vladislav; Žonda, Martin
2016-09-01
Behavior of Andreev gap states in a quantum dot with Coulomb repulsion symmetrically attached to superconducting leads is studied via the perturbation expansion in the interaction strength. We find the exact asymptotic form of the spin-symmetric solution for the Andreev states continuously approaching the Fermi level. We thereby derive a critical interaction at which the Andreev states at zero temperature merge at the Fermi energy, being the upper bound for the 0-π transition. We show that the spin-symmetric solution becomes degenerate beyond this interaction, in the π phase, and the Andreev states do not split unless the degeneracy is lifted. We further demonstrate that the degeneracy of the spin-symmetric state extends also into the 0 phase in which the solutions with zero and non-zero frequencies of the Andreev states may coexist.
Seidel, Robert; Atak, Kaan; Thürmer, Stephan; Aziz, Emad F; Winter, Bernd
2015-08-20
The electronic structure of a Ti(3+) aqueous solution is studied by liquid-jet soft X-ray photoelectron (PE) spectroscopy. Measured valence and Ti 2p core-level binding energies, together with the Ti 2p resonant photoelectron (RPE) spectra and the derived partial electron-yield L-edge X-ray absorption (PEY-XA) spectra, reveal mixing between metal 3d and water orbitals. Specifically, ligand states with metal character are identified through the enhancement of signal intensities in the RPE spectra. An observed satellite 3d peak structure is assigned to several different metal-ligand states. Experimental energies and the delocalized nature of the respective orbitals are supported by ground-state electronic structure calculations. We also show that by choice of the detected Auger-electron-decay channel, from which different PEY-XA spectra are obtained, the experimental sensitivity to the interactions of the metal 3d electrons with the solvent can be varied. The effect of such a state-dependent electronic relaxation on the shape of the PEY-XA spectra is discussed in terms of different degrees of electron delocalization.
Realization of quantum SWAP gate between flying and stationary qubits
Liang Linmei; Li Chengzu
2005-08-15
This paper presents a scheme to realize the SWAP gate between flying and stationary qubits through cavity QED, which is a necessary condition for networkability of quantum computation. As application, the storage of quantum information and teleportation of atomic and ionic states are present.
Advances in numerical solutions to integral equations in liquid state theory
NASA Astrophysics Data System (ADS)
Howard, Jesse J.
Solvent effects play a vital role in the accurate description of the free energy profile for solution phase chemical and structural processes. The inclusion of solvent effects in any meaningful theoretical model however, has proven to be a formidable task. Generally, methods involving Poisson-Boltzmann (PB) theory and molecular dynamic (MD) simulations are used, but they either fail to accurately describe the solvent effects or require an exhaustive computation effort to overcome sampling problems. An alternative to these methods are the integral equations (IEs) of liquid state theory which have become more widely applicable due to recent advancements in the theory of interaction site fluids and the numerical methods to solve the equations. In this work a new numerical method is developed based on a Newton-type scheme coupled with Picard/MDIIS routines. To extend the range of these numerical methods to large-scale data systems, the size of the Jacobian is reduced using basis functions, and the Newton steps are calculated using a GMRes solver. The method is then applied to calculate solutions to the 3D reference interaction site model (RISM) IEs of statistical mechanics, which are derived from first principles, for a solute model of a pair of parallel graphene plates at various separations in pure water. The 3D IEs are then extended to electrostatic models using an exact treatment of the long-range Coulomb interactions for negatively charged walls and DNA duplexes in aqueous electrolyte solutions to calculate the density profiles and solution thermodynamics. It is found that the 3D-IEs provide a qualitative description of the density distributions of the solvent species when compared to MD results, but at a much reduced computational effort in comparison to MD simulations. The thermodynamics of the solvated systems are also qualitatively reproduced by the IE results. The findings of this work show the IEs to be a valuable tool for the study and prediction of
Suparmi, A. Cari, C.; Angraini, L. M.
2014-09-30
The bound state solutions of Dirac equation for Hulthen and trigonometric Rosen Morse non-central potential are obtained using finite Romanovski polynomials. The approximate relativistic energy spectrum and the radial wave functions which are given in terms of Romanovski polynomials are obtained from solution of radial Dirac equation. The angular wave functions and the orbital quantum number are found from angular Dirac equation solution. In non-relativistic limit, the relativistic energy spectrum reduces into non-relativistic energy.
Long, Christopher J; Purdon, Patrick L; Temereanca, Simona; Desai, Neil U; Hämäläinen, Matti S; Brown, Emery N
2011-06-01
Determining the magnitude and location of neural sources within the brain that are responsible for generating magnetoencephalography (MEG) signals measured on the surface of the head is a challenging problem in functional neuroimaging. The number of potential sources within the brain exceeds by an order of magnitude the number of recording sites. As a consequence, the estimates for the magnitude and location of the neural sources will be ill-conditioned because of the underdetermined nature of the problem. One well-known technique designed to address this imbalance is the minimum norm estimator (MNE). This approach imposes an L(2) regularization constraint that serves to stabilize and condition the source parameter estimates. However, these classes of regularizer are static in time and do not consider the temporal constraints inherent to the biophysics of the MEG experiment. In this paper we propose a dynamic state-space model that accounts for both spatial and temporal correlations within and across candidate intra-cortical sources. In our model, the observation model is derived from the steady-state solution to Maxwell's equations while the latent model representing neural dynamics is given by a random walk process. We show that the Kalman filter (KF) and the Kalman smoother [also known as the fixed-interval smoother (FIS)] may be used to solve the ensuing high-dimensional state-estimation problem. Using a well-known relationship between Bayesian estimation and Kalman filtering, we show that the MNE estimates carry a significant zero bias. Calculating these high-dimensional state estimates is a computationally challenging task that requires High Performance Computing (HPC) resources. To this end, we employ the NSF Teragrid Supercomputing Network to compute the source estimates. We demonstrate improvement in performance of the state-space algorithm relative to MNE in analyses of simulated and actual somatosensory MEG experiments. Our findings establish the
Stationary and transient leakage current in the Pauli spin blockade.
Qassemi, F; Coish, W A; Wilhelm, F K
2009-05-01
We study the effects of cotunneling and a nonuniform Zeeman splitting on the stationary and transient leakage current through a double quantum dot in the Pauli spin blockade regime. We find that the stationary current due to cotunneling vanishes at low temperature and large applied magnetic field, allowing for the dynamical (rapid) preparation of a pure spin ground state, even at large voltage bias. Additionally, we analyze current that flows between blocking events, characterized, in general, by a fractional effective charge e*. This charge can be used as a sensitive probe of spin-relaxation mechanisms and can be used to determine the visibility of Rabi oscillations.
Two-soliton stationary axisymmetric sprouts from Weyl seeds
NASA Astrophysics Data System (ADS)
Zellerin, T.; Semerák, O.; Zellerin, T.
2000-12-01
The Belinskii-Zakharov inverse-scattering method is employed in its two-soliton version with a general Weyl seed, to obtain a stationary axisymmetric metric which in spheroidal coordinates of the Boyer-Lindquist type appears as a generalization of the Kerr-NUT solution. It contains several constants and two functions which can be found by integration from the seed potential (they can also be written as Legendre series). With a natural choice of parameters, the solution describes a reflectionally symmetric, asymptotically flat spacetime of a rotating black hole surrounded by a stationary axisymmetric source inherited from the seed. In a static limit, it goes over to a nonlinear superposition of the seed with a Schwarzschild black hole. A number of properties of the obtained class of solutions is given, in particular the characteristics of the horizon. For moderate angular momenta there seem to be no singularities on and outside the horizon. For a thin annular disc as the seed, the solution can represent a stationary thin annular disc around a rotating black hole.
Mach, Patryk; Pietka, Małgorzata
2010-04-01
We give a solution of the Riemann problem in relativistic hydrodynamics in the case of ultrarelativistic equation of state and nonvanishing components of the velocity tangent to the initial discontinuity. Simplicity of the ultrarelativistic equation of state (the pressure being directly proportional to the energy density) allows us to express this solution in analytical terms. The result can be used both to construct and test numerical schemes for relativistic Euler equations in (3+1) dimensions.
Gomberoff, L.; Palma, G.
1984-08-01
The stability of a current-carrying cylindrical plasma is studied by using the nonideal magnetohydrodynamic equations in a shearless magnetic field. It is shown that for each m mode there are four marginal stationary states which, under some conditions, give rise to large scale stationary convection when nonlinear effects are taken into account.
Analytical Reduced Models for the Non-stationary Diabatic Atmospheric Boundary Layer
NASA Astrophysics Data System (ADS)
Momen, Mostafa; Bou-Zeid, Elie
2017-09-01
Geophysical boundary-layer flows feature complex dynamics that often evolve with time; however, most current knowledge centres on the steady-state problem. In these atmospheric and oceanic boundary layers, the pressure gradient, buoyancy, Coriolis, and frictional forces interact to determine the statistical moments of the flow. The resulting equations for the non-stationary mean variables, even when succinctly closed, remain challenging to handle mathematically. Here, we derive a simpler physical model that reduces these governing unsteady Reynolds-averaged Navier-Stokes partial differential equations into a single first-order ordinary differential equation with non-constant coefficients. The reduced model is straightforward to solve under arbitrary forcing, even when the statistical moments are non-stationary and the viscosity varies in time and space. The model is successfully validated against large-eddy simulation for, (1) time-variable pressure gradients, and (2) linearly time-variable buoyancy. The new model is shown to have a superior performance compared to the classic Blackadar solutions (and later improvements on these solutions), and it covers a much wider range of conditions.
Stationary through-flows in a Bose-Einstein condensate with a PT -symmetric impurity
NASA Astrophysics Data System (ADS)
Zezyulin, Dmitry A.; Barashenkov, I. V.; Konotop, Vladimir V.
2016-12-01
Superfluid currents in the boson condensate with a source and sink of particles are modeled by the PT -symmetric Gross-Pitaevskii equation with a complex potential. We demonstrate the existence of through-flows of the condensate—stationary states with the asymptotically nonvanishing flux. The through-flows come in two broad varieties determined by the form of their number density distribution. One variety is described by diplike solutions featuring a localized density depression; the other one comprises humplike structures with a density spike in their core. We exemplify each class by exact closed-form solutions. For a fixed set of parameters of the PT -symmetric potential, stationary through-flows form continuous families parametrized by the strength of the background flux. All humplike and some diplike members of the family are found to be stable. We show that the through-flows can be controlled by varying the gain-and-loss amplitude of the complex potential and that these amplitude variations may produce an anomalous response of the flux across the gain-loss interface.
Analytical Reduced Models for the Non-stationary Diabatic Atmospheric Boundary Layer
NASA Astrophysics Data System (ADS)
Momen, Mostafa; Bou-Zeid, Elie
2017-04-01
Geophysical boundary-layer flows feature complex dynamics that often evolve with time; however, most current knowledge centres on the steady-state problem. In these atmospheric and oceanic boundary layers, the pressure gradient, buoyancy, Coriolis, and frictional forces interact to determine the statistical moments of the flow. The resulting equations for the non-stationary mean variables, even when succinctly closed, remain challenging to handle mathematically. Here, we derive a simpler physical model that reduces these governing unsteady Reynolds-averaged Navier-Stokes partial differential equations into a single first-order ordinary differential equation with non-constant coefficients. The reduced model is straightforward to solve under arbitrary forcing, even when the statistical moments are non-stationary and the viscosity varies in time and space. The model is successfully validated against large-eddy simulation for, (1) time-variable pressure gradients, and (2) linearly time-variable buoyancy. The new model is shown to have a superior performance compared to the classic Blackadar solutions (and later improvements on these solutions), and it covers a much wider range of conditions.
Passive tracking scheme for a single stationary observer
NASA Astrophysics Data System (ADS)
Chan, Y. T.; Rea, Terry
2001-08-01
While there are many techniques for Bearings-Only Tracking (BOT) in the ocean environment, they do not apply directly to the land situation. Generally, for tactical reasons, the land observer platform is stationary; but, it has two sensors, visual and infrared, for measuring bearings and a laser range finder (LRF) for measuring range. There is a requirement to develop a new BOT data fusion scheme that fuses the two sets of bearing readings, and together with a single LRF measurement, produces a unique track. This paper first develops a parameterized solution for the target speeds, prior to the occurrence of the LRF measurement, when the problem is unobservable. At, and after, the LRF measurement, a BOT formulated as a least squares (LS) estimator then produces a unique LS estimate of the target states. Bearing readings from the other sensor serve as instrumental variables in a data fusion setting to eliminate the bias in the BOT estimator. The result is recursive, unbiased and decentralized data fusion scheme. Results from two simulation experiments have corroborated the theoretical development and show that the scheme is optimal.
A Solution Space for a System of Null-State Partial Differential Equations: Part 1
NASA Astrophysics Data System (ADS)
Flores, Steven M.; Kleban, Peter
2015-01-01
This article is the first of four that completely and rigorously characterize a solution space for a homogeneous system of 2 N + 3 linear partial differential equations (PDEs) in 2 N variables that arises in conformal field theory (CFT) and multiple Schramm-Löwner evolution (SLE). In CFT, these are null-state equations and conformal Ward identities. They govern partition functions for the continuum limit of a statistical cluster or loop-gas model, such as percolation, or more generally the Potts models and O( n) models, at the statistical mechanical critical point. (SLE partition functions also satisfy these equations.) For such a lattice model in a polygon with its 2 N sides exhibiting a free/fixed side-alternating boundary condition , this partition function is proportional to the CFT correlation function where the w i are the vertices of and where is a one-leg corner operator. (Partition functions for "crossing events" in which clusters join the fixed sides of in some specified connectivity are linear combinations of such correlation functions.) When conformally mapped onto the upper half-plane, methods of CFT show that this correlation function satisfies the system of PDEs that we consider. In this first article, we use methods of analysis to prove that the dimension of this solution space is no more than C N , the Nth Catalan number. While our motivations are based in CFT, our proofs are completely rigorous. This proof is contained entirely within this article, except for the proof of Lemma 14, which constitutes the second article (Flores and Kleban, in Commun Math Phys, arXiv:1404.0035, 2014). In the third article (Flores and Kleban, in Commun Math Phys, arXiv:1303.7182, 2013), we use the results of this article to prove that the solution space of this system of PDEs has dimension C N and is spanned by solutions constructed with the CFT Coulomb gas (contour integral) formalism. In the fourth article (Flores and Kleban, in Commun Math Phys, arXiv:1405
INCA: a computational platform for isotopically non-stationary metabolic flux analysis.
Young, Jamey D
2014-05-01
13C flux analysis studies have become an essential component of metabolic engineering research. The scope of these studies has gradually expanded to include both isotopically steady-state and transient labeling experiments, the latter of which are uniquely applicable to photosynthetic organisms and slow-to-label mammalian cell cultures. Isotopomer network compartmental analysis (INCA) is the first publicly available software package that can perform both steady-state metabolic flux analysis and isotopically non-stationary metabolic flux analysis. The software provides a framework for comprehensive analysis of metabolic networks using mass balances and elementary metabolite unit balances. The generation of balance equations and their computational solution is completely automated and can be performed on networks of arbitrary complexity.
NASA Technical Reports Server (NTRS)
Poe, C. H.; Owocki, S. P.; Castor, J. I.
1990-01-01
The steady state solution topology for absorption line-driven flows is investigated for the condition that the Sobolev approximation is not used to compute the line force. The solution topology near the sonic point is of the nodal type with two positive slope solutions. The shallower of these slopes applies to reasonable lower boundary conditions and realistic ion thermal speed v(th) and to the Sobolev limit of zero of the usual Castor, Abbott, and Klein model. At finite v(th), this solution consists of a family of very similar solutions converging on the sonic point. It is concluded that a non-Sobolev, absorption line-driven flow with a realistic values of v(th) has no uniquely defined steady state. To the extent that a pure absorption model of the outflow of stellar winds is applicable, radiatively driven winds should be intrinsically variable.
GEL-STATE NMR OF BALL-MILLED WHOLE CELL WALLS IN DMSO-d6 USING 2D SOLUTION-STATE NMR SPECTROSCOPY
USDA-ARS?s Scientific Manuscript database
Plant cell walls were used for obtaining 2D solution-state NMR spectra without actual solubilization or structural modification. Ball-milled whole cell walls were swelled directly in the NMR tube with DMSO-d6 where they formed a gel. There are relatively few gel-state NMR studies. Most have involved...
Solution of steady-state, two-dimensional conservation laws by mathematical programming
NASA Technical Reports Server (NTRS)
Lavery, John E.
1991-01-01
A truly two-dimensional algorithm is created for solving the steady-state two-dimensional conservation-law problem. An overdetermined system of algebraic equations is obtained through discretization by finite-volume formulas. These equations are perturbed nonsingularly and are solved by an efficient geometrically oriented l(1) procedure. The basic algorithm and the theory for the linear case f(u) = u are presented, and computational results for the nonlinear case f(u) = sq u are also analyzed. It is noted that the l(1) procedure captures boundary shocks as well as oblige and zigzag interior shocks in bands that are one cell wide, and the solution values are accurate up to the edge of the shock.
Analysis of lasers as a solution to efficiency droop in solid-state lighting
Chow, Weng W.; Crawford, Mary H.
2015-10-06
This letter analyzes the proposal to mitigate the efficiency droop in solid-state light emitters by replacing InGaN light-emitting diodes (LEDs) with lasers. The argument in favor of this approach is that carrier-population clamping after the onset of lasing limits carrier loss to that at threshold, while stimulated emission continues to grow with injection current. A fully quantized (carriers and light) theory that is applicable to LEDs and lasers (above and below threshold) is used to obtain a quantitative evaluation. The results confirm the potential advantage of higher laser output power and efficiency above lasing threshold, while also indicating disadvantages including low efficiency prior to lasing onset, sensitivity of lasing threshold to temperature, and the effects of catastrophic laser failure. As a result, a solution to some of these concerns is suggested that takes advantage of recent developments in nanolasers.
Analysis of lasers as a solution to efficiency droop in solid-state lighting
Chow, Weng W.; Crawford, Mary H.
2015-10-06
This letter analyzes the proposal to mitigate the efficiency droop in solid-state light emitters by replacing InGaN light-emitting diodes (LEDs) with lasers. The argument in favor of this approach is that carrier-population clamping after the onset of lasing limits carrier loss to that at threshold, while stimulated emission continues to grow with injection current. A fully quantized (carriers and light) theory that is applicable to LEDs and lasers (above and below threshold) is used to obtain a quantitative evaluation. The results confirm the potential advantage of higher laser output power and efficiency above lasing threshold, while also indicating disadvantages includingmore » low efficiency prior to lasing onset, sensitivity of lasing threshold to temperature, and the effects of catastrophic laser failure. As a result, a solution to some of these concerns is suggested that takes advantage of recent developments in nanolasers.« less
Greaves, Stuart J; Rose, Rebecca A; Oliver, Thomas A A; Glowacki, David R; Ashfold, Michael N R; Harvey, Jeremy N; Clark, Ian P; Greetham, Gregory M; Parker, Anthony W; Towrie, Michael; Orr-Ewing, Andrew J
2011-03-18
Solvent collisions can often mask initial disposition of energy to the products of solution-phase chemical reactions. Here, we show with transient infrared absorption spectra obtained with picosecond time resolution that the nascent HCN products of reaction of CN radicals with cyclohexane in chlorinated organic solvents exhibit preferential excitation of one quantum of the C-H stretching mode and up to two quanta of the bending mode. On time scales of approximately 100 to 300 picoseconds, the HCN products undergo relaxation to the vibrational ground state by coupling to the solvent bath. Comparison with reactions of CN radicals with alkanes in the gas phase, known to produce HCN with greater C-H stretch and bending mode excitation (up to two and approximately six quanta, respectively), indicates partial damping of the nascent product vibrational motion by the solvent. The transient infrared spectra therefore probe solvent-induced modifications to the reaction free energy surface and chemical dynamics.
Investigating the Mechanisms of Amylolysis of Starch Granules by Solution-State NMR
2015-01-01
Starch is a prominent component of the human diet and is hydrolyzed by α-amylase post-ingestion. Probing the mechanism of this process has proven challenging, due to the intrinsic heterogeneity of individual starch granules. By means of solution-state NMR, we demonstrate that flexible polysaccharide chains protruding from the solvent-exposed surfaces of waxy rice starch granules are highly mobile and that during hydrothermal treatment, when the granules swell, the number of flexible residues on the exposed surfaces increases by a factor of 15. Moreover, we show that these flexible chains are the primary substrates for α-amylase, being cleaved in the initial stages of hydrolysis. These findings allow us to conclude that the quantity of flexible α-glucan chains protruding from the granule surface will greatly influence the rate of energy acquisition from digestion of starch. PMID:25815624
Stranius, K.; Börjesson, K.
2017-01-01
Photoswitchable molecules are able to isomerize between two metastable forms through light stimuli. Originally being studied by photochemists, this type of molecule has now found a wide range of applications within physics, chemistry and biology. The extensive usage of photochromic molecules is due to the two isomers having fundamentally different physical and chemical properties. The most important attribute of a photoswitch is the photoisomerization quantum yield, which defines the efficiency of the photoisomerization event. Here we show how to determine the photoisomerization quantum yield in the solid state and in solution when taking thermal processes into account. The described method together with provided software allows for rapid and accurate determination of the isomerization process for this important class of molecules. PMID:28117426
NASA Astrophysics Data System (ADS)
Stranius, K.; Börjesson, K.
2017-01-01
Photoswitchable molecules are able to isomerize between two metastable forms through light stimuli. Originally being studied by photochemists, this type of molecule has now found a wide range of applications within physics, chemistry and biology. The extensive usage of photochromic molecules is due to the two isomers having fundamentally different physical and chemical properties. The most important attribute of a photoswitch is the photoisomerization quantum yield, which defines the efficiency of the photoisomerization event. Here we show how to determine the photoisomerization quantum yield in the solid state and in solution when taking thermal processes into account. The described method together with provided software allows for rapid and accurate determination of the isomerization process for this important class of molecules.
Photon emission via surface state at the gold/acetonitrile solution interface
Uosaki, Kohei; Murakoshi, Kei; Kita, Hideaki )
1991-01-24
The emission of light caused by an electron-transfer reaction at a gold electrode in acetonitrile solution containing one of three redox species (benzophenone, trans-stilbene, and benzonitrile) with different redox potentials was studied. The high-energy threshold of the spectrum decreases linearly as the potential of the gold electrode becomes more negative. The peak position with respect to the high-energy threshold of the spectrum varies with electrode potential and is not affected by the redox potential of the electron injection species at the same electrode potential. The emission efficiency also depends on the potential. From these results, the authors proposed that the emission is due to a charge-transfer reaction inverse photoemission (CTRIP) process that takes place via a surface state.
Analysis of lasers as a solution to efficiency droop in solid-state lighting
NASA Astrophysics Data System (ADS)
Chow, W. W.; Crawford, M. H.
2015-10-01
This letter analyzes the proposal to mitigate the efficiency droop in solid-state light emitters by replacing InGaN light-emitting diodes (LEDs) with lasers. The argument in favor of this approach is that carrier-population clamping after the onset of lasing limits carrier loss to that at threshold, while stimulated emission continues to grow with injection current. A fully quantized (carriers and light) theory that is applicable to LEDs and lasers (above and below threshold) is used to obtain a quantitative evaluation. The results confirm the potential advantage of higher laser output power and efficiency above lasing threshold, while also indicating disadvantages including low efficiency prior to lasing onset, sensitivity of lasing threshold to temperature, and the effects of catastrophic laser failure. A solution to some of these concerns is suggested that takes advantage of recent developments in nanolasers.
Exact solution to the steady-state dynamics of a periodically modulated resonator
NASA Astrophysics Data System (ADS)
Minkov, Momchil; Shi, Yu; Fan, Shanhui
2017-07-01
We provide an analytic solution to the coupled-mode equations describing the steady-state of a single periodically modulated optical resonator driven by a monochromatic input. The phenomenology of this system was qualitatively understood only in the adiabatic limit, i.e., for low modulation speed. However, both in and out of this regime, we find highly non-trivial effects for specific parameters of the modulation. For example, we show complete suppression of the transmission even with zero detuning between the input and the static resonator frequency. We also demonstrate the possibility for complete, lossless frequency conversion of the input into the sideband frequencies, as well as for optimizing the transmitted signal towards a given target temporal waveform. The analytic results are validated by first-principle simulations.
Structure-forming properties of 3-furylpropenoic acid derivatives in solution and in the solid state
NASA Astrophysics Data System (ADS)
Kiss, J. T.; Felföldi, K.; Paksi, Z.; Pálinkó, I.
2003-06-01
Measurements by infrared (FT-IR) spectroscopy in the solid state as well as in solution and molecular modeling calculations revealed that the major structure forming force (short range ordering) between 2-phenyl-3(2'-furyl)propenoic acid stereoisomers was the CO⋯H-O intermolecular hydrogen bonding between the carboxylic groups. For the E isomer no other secondary intermolecular interaction could be measured nor calculated. Molecular modeling showed that long-range ordering was possible between the hydrogen-bonded dimers of the Z isomer via (phenyl)C-H⋯(furyl)O close contacts. The methyl esters also had short-range ordering through (phenyl)C-H⋯(carbonyl)O interaction, while only the Z isomer offered the possibility of long-range order. Chain-like structures were formed via (phenyl)C-H⋯(furyl)O hydrogen bonds.
Cho, Herman; Felmy, Andrew R; Craciun, Raluca; Keenum, J Patrick; Shah, Neil; Dixon, David A
2006-02-22
Evidence for nine new solution state silicate oligomers has been discovered by (29)Si NMR homonuclear correlation experiments of (29)Si-enriched samples. In addition to enhancing signal sensitivity, the isotopic enrichment increases the probability of the (29)Si-(29)Si two-bond scalar couplings that are necessary for the observation of internuclear correlations in 2-D experiments. The proposed assignments are validated by comparisons of experimental and simulated cross-peaks obtained with high digital resolution. The internuclear connectivity indicated by the NMR data suggests that several of these oligomers can have multiple stereoisomers, including conformers and/or diastereomers. The stabilities of these oligomers and their possible stereoisomers have been investigated by electronic structure calculations.
Kinetic properties of tetrameric glycogen phosphorylase b in solution and in the crystalline state.
Leonidas, D. D.; Oikonomakos, N. G.; Papageorgiou, A. C.; Sotiroudis, T. G.
1992-01-01
R-state monoclinic P2(1) crystals of phosphorylase have been shown to be catalytically active in the presence of an oligosaccharide primer and glucose-1-phosphate in 0.9 M ammonium sulfate, 10 mM beta-glycerophosphate, 0.5 mM EDTA, and 1 mM dithiothreitol, the medium in which the crystals are grown or equilibrated for crystallographic studies (Barford, D. & Johnson, L.N., 1989, Nature 360, 609-616; Barford, D., Hu, S.-H., & Johnson, L.N., 1991, J. Mol. Biol. 218, 233-260). Kinetic data suggest that the activity of crystalline tetrameric phosphorylase is similar to that determined in solution for the enzyme tetramer. However, large differences were found in the maximal velocities for both oligosaccharide or glucose-1-phosphate substrates between the soluble dimeric and crystalline tetrameric enzyme. PMID:1304391
Cho, Herman M.; Felmy, Andrew R.; Craciun, Raluca; Keenum, Johnathan P.; Shah, Neil K.; Dixon, David A.
2006-02-22
Evidence for nine new solution state silicate oligomers has been discovered by 29Si NMR homonuclear correlation experiments of 29Si-enriched samples. In addition to enhancing signal sensitivity, the isotopic enrichment increases the probability of the 29Si–29Si two-bond scalar couplings that are necessary for the observation of internuclear correlations in 2-D experiments. The proposed assignments are validated by comparisons of experimental and simulated crosspeaks obtained with high digital resolution. The internuclear connectivity indicated by the NMR data suggests that several of these oligomers can have multiple stereoisomers, including conformers and/or diastereomers. The stability of these oligomers and their possible stereoisomers have been investigated by electronic structure calculations.
NASA Astrophysics Data System (ADS)
Brooks, C. L., III; Balk, M. W.; Adelman, S. A.
1983-07-01
The dynamics of vibrational energy relaxation of highly excited molecular iodine in three monatomic solvents is studied via stochastic classical trajectory simulations based on the molecular timescale generalized Langevin equation (MTGLE) of motion for liquid state chemical reactions [S. A. Adelman, J. Chem. Phys. 73, 3145 (1980)]. Also presented for comparison purposes are parallel studies based on a matrix Langevin equation of motion characterized by friction coefficients which depend on the instantaneous I2 internuclear separation R. The qualitative features of the energy relaxation may be interpreted as effects arising from modifications of the solute dynamics due to molecular timescale correlations between its motion and that of its solvation shells. Such dynamical solvent effects are realistically described by the MTGLE equation of motion but not by the Langevin equation. Thus, for example, the marked slowdown of the rate of I2 energy relaxtion in simple solvents when the I2 vibrational quantum number drops below a solvent-dependent critical value, earlier predicted by Nesbitt and Hynes, is predicted by MTGLE dynamics but not by Langevin dynamics. Finally, practical algorithms for numerically constructing the MTGLE and Langevin equations for specific solute-solvent systems are presented.
FTIR assessment of poly(ethylene oxide) irradiated in solid state, melt and aqeuous solution
NASA Astrophysics Data System (ADS)
Pucić, Irina; Jurkin, Tanja
2012-09-01
FTIR spectroscopy was used to study poly(ethylene oxide), PEO, irradiated in solid and molten aggregate states and as aqueous solutions of various concentrations. The changes in shape and width of -C-O-C- complex absorption intensities at around 1112 cm-1 were the most prominent. On irradiation of solid samples in contact with air shrinking of -C-O-C- complex and increase in its absorption intensities indicated predominant degradation. Crosslinking prevailed on irradiation of molten PEO and of its aqueous solutions in nitrogen atmosphere and manifested itself as widening of -C-O-C- absorption and decrease of corresponding intensities. Partial or complete merging of CH2 wagging vibrations at 1342 cm-1 and 1360 cm-1 that are characteristic of crystalline PEO into a single absorption at around 1350 cm-1 indicated amorphization what was observed for samples that had reduced degree of crystallinity determined by differential scanning calorimetry. DSC could not discriminate between degradation and crosslinking while the changes in width and shape of -C-O-C- complex were independent of the changes in crystallinity. Comparison of FTIR spectra of the same PEO samples obtained as thin film and as KBr pellets revealed that pellet preparation results in a number of spectral artefacts.
A globally convergent algorithm for the solution of the steady-state semiconductor device equations
NASA Astrophysics Data System (ADS)
Korman, Can E.; Mayergoyz, Isaak D.
1990-08-01
An iterative method for solving the discretized steady-state semiconductor device equations is presented. This method uses Gummel's block iteration technique to decouple the nonlinear Poisson and electron-hole current continuity equations. However, the main feature of this method is that it takes advantage of the diagonal nonlinearity of the discretized equations, and solves each equation iteratively by using the nonlinear Jacobi method. Using the fact that the diagonal nonlinearities are monotonically increasing functions, it is shown that this method has two important advantages. First, it has global convergence, i.e., convergence is guaranteed for any initial guess. Second, the solution of simultaneous algebraic equations is avoided by updating the value of the electrostatic and quasi-Fermi potentials at each mesh point by means of explicit formulae. This allows the implementation of this method on computers with small random access memories, such as personal computers, and also makes it very attractive to use on parallel processor machines. Furthermore, for serial computations, this method is generalized to the faster nonlinear successive overrelaxation method which has global convergence as well. The iterative solution of the nonlinear Poisson equation is formulated with energy- and position-dependent interface traps. It is shown that the iterative method is globally convergent for arbitrary distributions of interface traps. This is an important step in analyzing hot-electron effects in metal-oxide-silicon field-effect transistors (MOSFETs). Various numerical results on two- and three-dimensional MOSFET geometries are presented as well.
State of the Art in LP-WAN Solutions for Industrial IoT Services
Sanchez-Iborra, Ramon; Cano, Maria-Dolores
2016-01-01
The emergence of low-cost connected devices is enabling a new wave of sensorization services. These services can be highly leveraged in industrial applications. However, the technologies employed so far for managing this kind of system do not fully cover the strict requirements of industrial networks, especially those regarding energy efficiency. In this article a novel paradigm, called Low-Power Wide Area Networking (LP-WAN), is explored. By means of a cellular-type architecture, LP-WAN–based solutions aim at fulfilling the reliability and efficiency challenges posed by long-term industrial networks. Thus, the most prominent LP-WAN solutions are reviewed, identifying and discussing the pros and cons of each of them. The focus is also on examining the current deployment state of these platforms in Spain. Although LP-WAN systems are at early stages of development, they represent a promising alternative for boosting future industrial IIoT (Industrial Internet of Things) networks and services. PMID:27196909
State of the Art in LP-WAN Solutions for Industrial IoT Services.
Sanchez-Iborra, Ramon; Cano, Maria-Dolores
2016-05-17
The emergence of low-cost connected devices is enabling a new wave of sensorization services. These services can be highly leveraged in industrial applications. However, the technologies employed so far for managing this kind of system do not fully cover the strict requirements of industrial networks, especially those regarding energy efficiency. In this article a novel paradigm, called Low-Power Wide Area Networking (LP-WAN), is explored. By means of a cellular-type architecture, LP-WAN-based solutions aim at fulfilling the reliability and efficiency challenges posed by long-term industrial networks. Thus, the most prominent LP-WAN solutions are reviewed, identifying and discussing the pros and cons of each of them. The focus is also on examining the current deployment state of these platforms in Spain. Although LP-WAN systems are at early stages of development, they represent a promising alternative for boosting future industrial IIoT (Industrial Internet of Things) networks and services.
Fabrication and Performance of All-Solid-State Chloride Sensors in Synthetic Concrete Pore Solutions
Gao, Xiaojian; Zhang, Jian; Yang, Yingzi; Deng, Hongwei
2010-01-01
One type of all-solid-state chloride sensor was fabricated using a MnO2 electrode and a Ag/AgCl electrode. The potentiometric response of the sensor to chloride in synthetic concrete pore solutions was systematically studied, and the polarization performance was also evaluated. The results show a good linear relationship between the potential reading of the sensor and the logarithm of chloride activity (concentration ranges from 0.05 to 5.0 M), and the potential value remains stable with increasing immersion time. The existence of K+, Ca2+, Na+ and SO42− ions have little influence on the potentiometric response of the sensor to chloride, but the pH has a significant influence on the potential value of the sensor at low chloride concentration. The potential reading of the sensor increases linearly with the solution temperature over the range from 5 to 45 °C. Meanwhile, an excellent polarization behavior is proven by galvanostatic and potentiodynamic tests. All of the results reveal that the developed sensor has a great potential for monitoring chloride ions in concrete environments. PMID:22163467
State of the art and recent development of embedded network solutions research
NASA Astrophysics Data System (ADS)
Gillet, Michel; Balandin, Sergey
2008-04-01
Recently we could observe a huge change in the mobile industry when the original idea of mobile phone was transformed into the new concept of mobile multimedia devices capable to perform multiple complex tasks and integrating a number of functionalities. As a consequence it resulted in significant increase of the device integration time and cost and complicated deployment of the new technologies. The device integrators are forced to favor modularity everywhere where it is possible in design of new devices, which results in a new trend towards networked architectures for the mobile devices. However, moving towards networked architectures specifically designed to overcome limitations brought by the mobile devices is a time consuming task. It requires fresh mind analysis of many solutions applied in other contexts, since some of the constraints and requirements are unique in comparison with e.g. SoC, NoC, which are the most known embedded network solutions, and of course they are significantly different comparing to the wide area networks. The main differentiating factors are: strongly constrained power consumption by the battery life time; and a need for modular architecture to allow reuse of the existing components or modules. The paper provides an overview of the state of art in the embedded networks research and describes general background for our studies, key assumptions, restrictions and limitations that we faced at the beginning of development of the embedded networks architecture for mobile devices.
Enhanced Conformational Sampling of N-glycans in Solution with Replica State Exchange Metadynamics.
Galvelis, Raimondas; Re, Suyong; Sugita, Yuji
2017-04-11
Molecular dynamics (MD) simulation of a N-glycan in solution is challenging due to high- energy barriers of the glycosidic linkages, functional group rotational barriers, and numerous intra- and inter-molecular hydrogen bonds. In this study, we apply different enhanced conformational sampling approaches, namely, metadynamics (MTD), the replica-exchange MD (REMD), and the recently proposed replica state exchange MTD (RSE-MTD), to a N-glycan in solution and compare their conformational sampling efficiencies. MTD helps to cross the high- energy barrier along the ω angle by utilizing a bias potential, but it cannot enhance sampling of the other degrees of freedom. REMD ensures moderate-energy barrier crossings by exchanging temperatures between replicas, while it hardly crosses the barriers along ω. In contrast, RSE- MTD succeeds to cross the high-energy barrier along ω as well as to enhance sampling of the other degrees of freedom. We tested two RSE-MTD schemes: in one scheme, 64 replicas were simulated with the bias potential along ω at different temperatures, while simulations of 4 replicas were performed with the bias potentials for different CVs at 300 K. In both schemes, one unbiased replica at 300 K was included to compute conformational properties of the glycan. The conformational sampling of the former is better than the other enhanced sampling methods, while the latter shows reasonable performance without spending large computational resources. The latter scheme is likely to be useful when a N-glycan-attached protein is simulated.
Austin, Jane E.
2012-01-01
The main conflicts between Sandhill Cranes (Grus canadensis) and farmers in western United States occur in the Rocky Mountain region during migration and wintering periods. Most crop damage by cranes occurs in mature wheat (Triticum aestivum) and barley (Hordeum vulgare), young shoots of alfalfa (Medicago sativa) and cereal grains, chilies (Capsicum annuum), and silage corn (Zea mays). Damage is related to proximity of crop fields to roost sites and timing of crane concentrations relative to crop maturity or vulnerability. The evolution of conflicts between farmers and cranes and current solutions are described for two areas of the Rocky Mountains used by staging, migrating, or wintering cranes: Grays Lake, Idaho, and the Middle Rio Grande Valley, New Mexico. In both areas, conflicts with growing crane populations were aggravated by losses of wetlands and cropland, proximity of crops to roosts and other wetland areas, changing crop types and practices, and increasing urbanization. At Grays Lake, fall-staging cranes damaged barley fields near an important breeding refuge as well as fields 15-50 km away. In the Middle Rio Grande Valley, migrating and wintering cranes damaged young alfalfa fields, chilies, and silage corn. Solutions in both areas have been addressed through cooperative efforts among federal and state agencies, that manage wetlands and croplands to increase food availability and carrying capacity on public lands, provide hazing programs for private landowners, and strategically target crane hunting to problem areas. Sustaining the success of these programs will be challenging. Areas important to Sandhill Cranes in the western United Sates experience continued loss of habitat and food resources due to urbanization, changes in agricultural crops and practices, and water-use conflicts, which threaten the abilities of both public and private landowners to manage wetlands and croplands for cranes. Conservation of habitats and water resources are important
NASA Astrophysics Data System (ADS)
Pradhan, Tuhin; Gazi, Harun Al Rasid; Biswas, Ranjit
2009-08-01
Temperature dependence of the excited state intramolecular charge transfer reaction of 4-(1-azetidinyl)benzonitrile (P4C) in ethyl acetate (EA), acetonitrile (ACN), and ethanol at several concentrations of lithium perchlorate (LiClO4) has been investigated by using the steady state and time resolved fluorescence spectroscopic techniques. The temperature range considered is 267-343 K. The temperature dependent spectral peak shifts and reaction driving force (-ΔGr) in electrolyte solutions of these solvents can be explained qualitatively in terms of interaction between the reactant molecule and ion-atmosphere. Time resolved studies indicate that the decay kinetics of P4C is biexponential, regardless of solvents, LiClO4 concentrations, and temperatures considered. Except at higher electrolyte concentrations in EA, reaction rates in solutions follow the Arrhenius-type temperature dependence where the estimated activation energy exhibits substantial electrolyte concentration dependence. The average of the experimentally measured activation energies in these three neat solvents is found to be in very good agreement with the predicted value based on data in room temperature solvents. While the rate constant in EA shows a electrolyte concentration induced parabolic dependence on reaction driving force (-ΔGr), the former in ethanol and ACN increases only linearly with the increase in driving force (-ΔGr). The data presented here also indicate that the step-wise increase in solvent reorganization energy via sequential addition of electrolyte induces the ICT reaction in weakly polar solvents to crossover from the Marcus inverted region to the normal region.
Pradhan, Tuhin; Gazi, Harun Al Rasid; Biswas, Ranjit
2009-08-07
Temperature dependence of the excited state intramolecular charge transfer reaction of 4-(1-azetidinyl)benzonitrile (P4C) in ethyl acetate (EA), acetonitrile (ACN), and ethanol at several concentrations of lithium perchlorate (LiClO(4)) has been investigated by using the steady state and time resolved fluorescence spectroscopic techniques. The temperature range considered is 267-343 K. The temperature dependent spectral peak shifts and reaction driving force (-DeltaG(r)) in electrolyte solutions of these solvents can be explained qualitatively in terms of interaction between the reactant molecule and ion-atmosphere. Time resolved studies indicate that the decay kinetics of P4C is biexponential, regardless of solvents, LiClO(4) concentrations, and temperatures considered. Except at higher electrolyte concentrations in EA, reaction rates in solutions follow the Arrhenius-type temperature dependence where the estimated activation energy exhibits substantial electrolyte concentration dependence. The average of the experimentally measured activation energies in these three neat solvents is found to be in very good agreement with the predicted value based on data in room temperature solvents. While the rate constant in EA shows a electrolyte concentration induced parabolic dependence on reaction driving force (-DeltaG(r)), the former in ethanol and ACN increases only linearly with the increase in driving force (-DeltaG(r)). The data presented here also indicate that the step-wise increase in solvent reorganization energy via sequential addition of electrolyte induces the ICT reaction in weakly polar solvents to crossover from the Marcus inverted region to the normal region.
Stationary and transient Soret separation in a binary mixture with a consolute critical point.
Ryzhkov, Ilya I; Kozlova, Sofia V
2016-12-01
The stationary and transient Soret separation in a binary mixture with a consolute critical point is studied theoretically. The mixture is placed between two parallel plates kept at different temperatures. A polymer blend is used as a model system. Analytical solutions are constructed to describe the stationary separation in a binary mixture with variable Soret coefficient. The latter strongly depends on temperature and concentration and enhances near a consolute critical point due to reduced diffusion. As a result, a large concentration gradient is observed locally, while much smaller concentration variations are found in the rest of the layer. It is shown that complete separation can be obtained by applying a small temperature difference first, waiting for the establishment of stationary state, and then increasing this difference again. In this case, the critical temperature lies between hot and cold wall temperatures, while the mixture still remains in the one-phase region. When the initial (mean) temperature or concentration are shifted away from the near-critical values, the separation decreases. The analysis of transient behavior shows that the Soret separation occurs much faster than diffusion to the homogeneous state when the initial concentration is close to the critical one. It happens due to the decrease (increase) of the local relaxation time during the Soret (Diffusion) steps. The transient times of these steps become comparable for small temperature differences or off-critical initial concentrations. An unusual (non-exponential) separation dynamics is observed when the separation starts in the off-critical domain, and then enhances greatly when the system enters into the near-critical region. It is also found that the transient time decreases with increasing the applied temperature difference.
Schneider, Hans-Jörg
2015-01-01
The lock-and-key concept is discussed with respect to necessary extensions. Formation of supramolecular complexes depends not only, and often not even primarily on an optimal geometric fit between host and guest. Induced fit and allosteric interactions have long been known as important modifications. Different binding mechanisms, the medium used and pH effects can exert a major influence on the affinity. Stereoelectronic effects due to lone pair orientation can lead to variation of binding constants by orders of magnitude. Hydrophobic interactions due to high-energy water inside cavities modify the mechanical lock-and-key picture. That optimal affinities are observed if the cavity is only partially filled by the ligand can be in conflict with the lock-and-key principle. In crystals other forces than those between host and guest often dominate, leading to differences between solid state and solution structures. This is exemplified in particular with calixarene complexes, which by X-ray analysis more often than other hosts show guest molecules outside their cavity. In view of this the particular problems with the identification of weak interactions in crystals is discussed. PMID:25815592
Aggregation for Computing Multi-Modal Stationary Distributions in 1-D Gene Regulatory Networks.
Avcu, Neslihan; Pekergin, Nihal; Pekergin, Ferhan; Guzelis, Cuneyt
2017-04-27
This paper proposes aggregation-based, three-stage algorithms to overcome the numerical problems encountered in computing stationary distributions and mean first passage times for multi-modal birth-death processes of large state space sizes. The considered birth-death processes which are defined by Chemical Master Equations are used in modeling stochastic behavior of gene regulatory networks. Computing stationary probabilities for a multi-modal distribution from Chemical Master Equations is subject to have numerical problems due to the probability values running out of the representation range of the standard programming languages with the increasing size of the state space. The aggregation is shown to provide a solution to this problem by analyzing first reduced size subsystems in isolation and then considering the transitions between these subsystems. The proposed algorithms are applied to study the bimodal behavior of the lac operon of E. coli described with a one-dimensional birth-death model. Thus the determination of the entire parameter range of bimodality for the stochastic model of lac operon is achieved.
About local controllability of a nonlinear stationary system
NASA Astrophysics Data System (ADS)
Kvitko, Alexander
2017-07-01
The paper presents an algorithm for constructing of synthesizing control function. This algorithm is sufficiently convenient for numerical implementation and a wide class of nonlinear stationary systems of ordinary differential equations, provide the passage from initial state into to origin coordinates. We obtain a constructive condition for the choice of initial state for which the passage is possible with regard of the constraints imposed on the control. We consider an interorbital flight problem, for which we carry numerical simulation.
Unprecedented synthesis of 1,3-dimethylcyclobutadiene in the solid state and aqueous solution.
Legrand, Yves-Marie; Gilles, Arnaud; Petit, Eddy; van der Lee, Arie; Barboiu, Mihail
2011-08-29
Cyclobutadiene (CBD), the smallest cyclic hydrocarbon bearing conjugated double bonds, has long intrigued chemists because of its chemical characteristics. The question of whether the molecule could be prepared at all has been answered, but the parent compound and its unperturbed derivatives have eluded crystallographic characterization or synthesis "in water". Different approaches have been used to generate and to trap cyclobutadiene in a variety of confined environments: a) an Ar matrix at cryogenic temperatures, b) a hemicarcerand cage enabling the characterization by NMR spectroscopy in solution, and c) a crystalline guanidinium-sulfonate-calixarene G(4)C matrix that is stable enough to allow photoreactions in the solid state. In the latter case, the 4,6-dimethyl-α-pyrone precursor, Me(2)1, has been immobilized in a guanidinium-sulfonate-calixarene G(4)C crystalline network through a combination of non-covalent interactions. UV irradiation of the crystals transforms the entrapped Me(2)1 into a 4,6-dimethyl-Dewar-β-lactone intermediate, Me(2)2, and rectangular-bent 1,3-dimethylcyclobutadiene, Me(2)CBD(R), which are sufficiently stable under the confined conditions at 175 K to allow a conventional structure determination by X-ray diffraction. Further irradiation drives the reaction towards Me(2)3&Me(2)CBD(S)/CO(2) (63.7 %) and Me(2)CBD(R) (37.3 %) superposed crystalline architectures and the amplification of Me(2)CBD(R). The crystallographic models are supported by additional FTIR and Raman experiments in the solid state and by (1)H NMR spectroscopy and ESI mass spectrometry experiments in aqueous solution. Amazingly, the 4,6-dimethyl-Dewar-β-lactone, Me(2)2, the cyclobutadiene-carboxyl zwitterion, Me(2)3, and 1,3-dimethylcyclobutadiene, Me(2)CBD, were obtained by ultraviolet irradiation of an aqueous solution of G(4)C{Me(2)1}. 1,3-Dimethylcyclobutadiene is stable in water at room temperature for several weeks and even up to 50 °C as demonstrated by
Solution and Solid-State Studies of DNA-Programmable Nanoparticle Single Crystals
NASA Astrophysics Data System (ADS)
Auyeung, Evelyn
This thesis lays the foundation for three main areas that have significantly advanced the field of DNA-programmable nanoparticle assembly: (1) the synthesis of nanoparticle superlattices with novel lattice symmetries (2) post-assembly characterization and applications of superlattices that have been transferred from solution to the solid state and (3) the realization of a slow-cooling strategy for synthesizing faceted nanoparticle single crystals. Together, these advances mark a turning point in the evolution of DNA-programmable assembly from a simple proof-of-concept demonstrated in 1996 to a powerful materials development strategy that has inspired many ongoing investigations in fields including catalysis, plasmonics, and electronics. Chapter 1 begins with an overview of controlled crystallization and its importance across fields including chemistry and materials science. This followed by a description of DNA-programmable assembly and a discussion on its advantages as an assembly strategy. Chapter 2 describes a powerful strategy for synthesizing nanoparticle superlattices using a coreless nanoparticle consisting purely of spherically-oriented oligonucleotides. This "three dimensional spacer approach" allows for the synthesis of nanoparticle superlattices with exotic structures, including one with no mineral equivalent. While DNA is a versatile ligand for nanoparticle assembly, the resulting superlattices are only stable in solution. Chapter 3 addresses these limitations and presents a method for transitioning these materials from solution to the solid state through silica encapsulation. This encapsulation process has transformed the ability to interrogate these materials using electron microscopy, and it has enabled all the studies in subsequent chapters of this thesis. In Chapter 4, a slow-cooling crystallization technique is described that allows for the synthesis of single crystalline microcrystals with well-defined facets from DNA-nanoparticle building blocks
Talygin, E A; Zazybo, N A; Zhorzholiany, S T; Krestinich, I M; Mironov, A A; Kiknadze, G I; Bokerya, L A; Gorodkov, A Y; Makarenko, V N; Alexandrova, S A
2016-01-01
New approach to intracardiac blood flow condition analysis based on geometric parameters of left ventricle flow channel has been suggested. Parameters, that used in this method, follow from exact solutions of nonstationary Navier-Stocks equations for selforganized tornado-like flows of viscous incompressible fluid. The main advantage of this method is considering dynamic anatomy of intracardiac cavity and trabeculae relief of left ventricle streamlined surface, both registered in a common mri-process, as flow condition indicator. Calculated quantity options that characterizes blood flow condition can be use as diagnostic criterias for estimation of violation in blood circulation function which entails heart ejection reduction. Developed approach allows to clarify heart jet organization mechanism and estimate the share of the tornado-like flow self-organization in heart ejection structure.
A Solution Space for a System of Null-State Partial Differential Equations: Part 4
NASA Astrophysics Data System (ADS)
Flores, Steven M.; Kleban, Peter
2015-01-01
This article is the last of four that completely and rigorously characterize a solution space for a homogeneous system of 2 N + 3 linear partial differential equations in 2 N variables that arises in conformal field theory (CFT) and multiple Schramm-Löwner evolution (SLE). The system comprises 2 N null-state equations and three conformal Ward identities that govern CFT correlation functions of 2 N one-leg boundary operators. In the first two articles (Flores and Kleban in Commun Math Phys, 2012; Flores and Kleban, in Commun Math Phys, 2014), we use methods of analysis and linear algebra to prove that dim , with C N the Nth Catalan number. Using these results in the third article (Flores and Kleban, in Commun Math Phys, 2013), we prove that dim and is spanned by (real-valued) solutions constructed with the Coulomb gas (contour integral) formalism of CFT. In this article, we use these results to prove some facts concerning the solution space . First, we show that each of its elements equals a sum of at most two distinct Frobenius series in powers of the difference between two adjacent points (unless is odd, in which case a logarithmic term may appear). This establishes an important element in the operator product expansion for one-leg boundary operators, assumed in CFT. We also identify particular elements of , which we call connectivity weights, and exploit their special properties to conjecture a formula for the probability that the curves of a multiple-SLE process join in a particular connectivity. This leads to new formulas for crossing probabilities of critical lattice models inside polygons with a free/fixed side-alternating boundary condition, which we derive in Flores et al. (Partition functions and crossing probabilities for critical systems inside polygons, in preparation). Finally, we propose a reason for why the exceptional speeds [certain values that appeared in the analysis of the Coulomb gas solutions in Flores and Kleban (Commun Math Phys, 2013)] and
NASA Astrophysics Data System (ADS)
Trendafilova, N.; Kellner, R.
The IR spectra of zinc(II) bis-(N,N'-diethyldithiocarbamate) in the solid state (at 20, 80 and 120°C) as well as in solution (20°C) have been recorded and discussed as to the changes in the zinc coordination sphere that may occur upon heating and dissolution. The decreased number of bands in the high-temperature and in the solution specta as compared with the room temperature solid state spectra has been explained by removal of the intermolecular contacts upon dissolution or thermal averaging in the high temperature solid state.