Testing the Perey effect

DOE PAGES

Titus, L. J.; Nunes, Filomena M.

2014-03-12

Here, the effects of non-local potentials have historically been approximately included by applying a correction factor to the solution of the corresponding equation for the local equivalent interaction. This is usually referred to as the Perey correction factor. In this work we investigate the validity of the Perey correction factor for single-channel bound and scattering states, as well as in transfer (p, d) cross sections. Method: We solve the scattering and bound state equations for non-local interactions of the Perey-Buck type, through an iterative method. Using the distorted wave Born approximation, we construct the T-matrix for (p,d) on 17O, 41Ca,more » 49Ca, 127Sn, 133Sn, and 209Pb at 20 and 50 MeV. As a result, we found that for bound states, the Perey corrected wave function resulting from the local equation agreed well with that from the non-local equation in the interior region, but discrepancies were found in the surface and peripheral regions. Overall, the Perey correction factor was adequate for scattering states, with the exception of a few partial waves corresponding to the grazing impact parameters. These differences proved to be important for transfer reactions. In conclusion, the Perey correction factor does offer an improvement over taking a direct local equivalent solution. However, if the desired accuracy is to be better than 10%, the exact solution of the non-local equation should be pursued.« less

Conservation laws, bilinear forms and solitons for a fifth-order nonlinear Schrödinger equation for the attosecond pulses in an optical fiber

DOE Office of Scientific and Technical Information (OSTI.GOV)

Chai, Jun; Tian, Bo, E-mail: tian_bupt@163.com; Zhen, Hui-Ling

Under investigation in this paper is a fifth-order nonlinear Schrödinger equation, which describes the propagation of attosecond pulses in an optical fiber. Based on the Lax pair, infinitely-many conservation laws are derived. With the aid of auxiliary functions, bilinear forms, one-, two- and three-soliton solutions in analytic forms are generated via the Hirota method and symbolic computation. Soliton velocity varies linearly with the coefficients of the high-order terms. Head-on interaction between the bidirectional two solitons and overtaking interaction between the unidirectional two solitons as well as the bound state are depicted. For the interactions among the three solitons, two head-onmore » and one overtaking interactions, three overtaking interactions, an interaction between a bound state and a single soliton and the bound state are displayed. Graphical analysis shows that the interactions between the two solitons are elastic, and interactions among the three solitons are pairwise elastic. Stability analysis yields the modulation instability condition for the soliton solutions.« less

Ground state sign-changing solutions for fractional Kirchhoff equations in bounded domains

NASA Astrophysics Data System (ADS)

Luo, Huxiao; Tang, Xianhua; Gao, Zu

2018-03-01

We study the existence of ground state sign-changing solutions for the fractional Kirchhoff problem. Under mild assumptions on the nonlinearity, by using some new analytical skills and the non-Nehari manifold method, we prove that the fractional Kirchhoff problem possesses a ground state sign-changing solution ub. Moreover, we show that the energy of ub is strictly larger than twice that of the ground state solutions of Nehari-type. Finally, we establish the convergence property of ub as the parameter b ↘ 0. Our results generalize some results obtained by Shuai [J. Differ. Equations 259, 1256 (2015)] and Tang and Cheng [J. Differ. Equations 261, 2384 (2016)].

Bound states and interactions of vortex solitons in the discrete Ginzburg-Landau equation

NASA Astrophysics Data System (ADS)

Mejía-Cortés, C.; Soto-Crespo, J. M.; Vicencio, Rodrigo A.; Molina, Mario I.

2012-08-01

By using different continuation methods, we unveil a wide region in the parameter space of the discrete cubic-quintic complex Ginzburg-Landau equation, where several families of stable vortex solitons coexist. All these stationary solutions have a symmetric amplitude profile and two different topological charges. We also observe the dynamical formation of a variety of “bound-state” solutions composed of two or more of these vortex solitons. All of these stable composite structures persist in the conservative cubic limit for high values of their power content.

Existence of global weak solution for a reduced gravity two and a half layer model

DOE Office of Scientific and Technical Information (OSTI.GOV)

Guo, Zhenhua, E-mail: zhenhua.guo.math@gmail.com; Li, Zilai, E-mail: lizilai0917@163.com; Yao, Lei, E-mail: yaolei1056@hotmail.com

2013-12-15

We investigate the existence of global weak solution to a reduced gravity two and a half layer model in one-dimensional bounded spatial domain or periodic domain. Also, we show that any possible vacuum state has to vanish within finite time, then the weak solution becomes a unique strong one.

Expected performance of m-solution backtracking

NASA Technical Reports Server (NTRS)

Nicol, D. M.

1986-01-01

This paper derives upper bounds on the expected number of search tree nodes visited during an m-solution backtracking search, a search which terminates after some preselected number m problem solutions are found. The search behavior is assumed to have a general probabilistic structure. The results are stated in terms of node expansion and contraction. A visited search tree node is said to be expanding if the mean number of its children visited by the search exceeds 1 and is contracting otherwise. It is shown that if every node expands, or if every node contracts, then the number of search tree nodes visited by a search has an upper bound which is linear in the depth of the tree, in the mean number of children a node has, and in the number of solutions sought. Also derived are bounds linear in the depth of the tree in some situations where an upper portion of the tree contracts (expands), while the lower portion expands (contracts). While previous analyses of 1-solution backtracking have concluded that the expected performance is always linear in the tree depth, the model allows superlinear expected performance.

Valence tautomerism in synthetic models of cytochrome P450

PubMed Central

Das, Pradip Kumar; Samanta, Subhra; McQuarters, Ashley B.; Lehnert, Nicolai

2016-01-01

CytP450s have a cysteine-bound heme cofactor that, in its as-isolated resting (oxidized) form, can be conclusively described as a ferric thiolate species. Unlike the native enzyme, most synthetic thiolate-bound ferric porphyrins are unstable in air unless the axial thiolate ligand is sterically protected. Spectroscopic investigations on a series of synthetic mimics of cytP450 indicate that a thiolate-bound ferric porphyrin coexists in organic solutions at room temperature (RT) with a thiyl-radical bound ferrous porphyrin, i.e., its valence tautomer. The ferric thiolate state is favored by greater enthalpy and is air stable. The ferrous thiyl state is favored by entropy, populates at RT, and degrades in air. These ground states can be reversibly interchanged at RT by the addition or removal of water to the apolar medium. It is concluded that hydrogen bonding and local electrostatics protect the resting oxidized cytP450 active site from degradation in air by stabilizing the ferric thiolate ground state in contrast to its synthetic analogs. PMID:27302948

Stochastic analysis of three-dimensional flow in a bounded domain

USGS Publications Warehouse

Naff, R.L.; Vecchia, A.V.

1986-01-01

A commonly accepted first-order approximation of the equation for steady state flow in a fully saturated spatially random medium has the form of Poisson's equation. This form allows for the advantageous use of Green's functions to solve for the random output (hydraulic heads) in terms of a convolution over the random input (the logarithm of hydraulic conductivity). A solution for steady state three- dimensional flow in an aquifer bounded above and below is presented; consideration of these boundaries is made possible by use of Green's functions to solve Poisson's equation. Within the bounded domain the medium hydraulic conductivity is assumed to be a second-order stationary random process as represented by a simple three-dimensional covariance function. Upper and lower boundaries are taken to be no-flow boundaries; the mean flow vector lies entirely in the horizontal dimensions. The resulting hydraulic head covariance function exhibits nonstationary effects resulting from the imposition of boundary conditions. Comparisons are made with existing infinite domain solutions.

Powered Descent Guidance with General Thrust-Pointing Constraints

NASA Technical Reports Server (NTRS)

Carson, John M., III; Acikmese, Behcet; Blackmore, Lars

2013-01-01

The Powered Descent Guidance (PDG) algorithm and software for generating Mars pinpoint or precision landing guidance profiles has been enhanced to incorporate thrust-pointing constraints. Pointing constraints would typically be needed for onboard sensor and navigation systems that have specific field-of-view requirements to generate valid ground proximity and terrain-relative state measurements. The original PDG algorithm was designed to enforce both control and state constraints, including maximum and minimum thrust bounds, avoidance of the ground or descent within a glide slope cone, and maximum speed limits. The thrust-bound and thrust-pointing constraints within PDG are non-convex, which in general requires nonlinear optimization methods to generate solutions. The short duration of Mars powered descent requires guaranteed PDG convergence to a solution within a finite time; however, nonlinear optimization methods have no guarantees of convergence to the global optimal or convergence within finite computation time. A lossless convexification developed for the original PDG algorithm relaxed the non-convex thrust bound constraints. This relaxation was theoretically proven to provide valid and optimal solutions for the original, non-convex problem within a convex framework. As with the thrust bound constraint, a relaxation of the thrust-pointing constraint also provides a lossless convexification that ensures the enhanced relaxed PDG algorithm remains convex and retains validity for the original nonconvex problem. The enhanced PDG algorithm provides guidance profiles for pinpoint and precision landing that minimize fuel usage, minimize landing error to the target, and ensure satisfaction of all position and control constraints, including thrust bounds and now thrust-pointing constraints.

Analytical bound-state solutions of the Schrödinger equation for the Manning-Rosen plus Hulthén potential within SUSY quantum mechanics

NASA Astrophysics Data System (ADS)

Ahmadov, A. I.; Naeem, Maria; Qocayeva, M. V.; Tarverdiyeva, V. A.

2018-01-01

In this paper, the bound-state solution of the modified radial Schrödinger equation is obtained for the Manning-Rosen plus Hulthén potential by using new developed scheme to overcome the centrifugal part. The energy eigenvalues and corresponding radial wave functions are defined for any l≠0 angular momentum case via the Nikiforov-Uvarov (NU) and supersymmetric quantum mechanics (SUSY QM) methods. Thanks to both methods, equivalent expressions are obtained for the energy eigenvalues, and the expression of radial wave functions transformations to each other is presented. The energy levels and the corresponding normalized eigenfunctions are represented in terms of the Jacobi polynomials for arbitrary l states. A closed form of the normalization constant of the wave functions is also found. It is shown that, the energy eigenvalues and eigenfunctions are sensitive to nr radial and l orbital quantum numbers.

Magnetic states at short distances

NASA Astrophysics Data System (ADS)

Crater, Horace W.; Wong, Cheuk-Yin

2012-06-01

The magnetic interactions between a fermion and an antifermion of opposite electric or color charges in the S0-+1 and P0++3 states with J=0 are very attractive and singular near the origin and may allow the formation of new bound and resonance states at short distances. In the two-body Dirac equations formulated in constraint dynamics, the short-distance attraction for these states for point particles leads to a quasipotential that behaves near the origin as -α2/r2, where α is the coupling constant. Representing this quasipotential at short distances as λ(λ+1)/r2 with λ=(-1+1-4α2)/2, both S0-+1 and P0++3 states admit two types of eigenstates with drastically different behaviors for the radial wave function u=rψ. One type of states, with u growing as rλ+1 at small r, will be called usual states. The other type of states with u growing as r-λ will be called peculiar states. Both of the usual and peculiar eigenstates have admissible behaviors at short distances. Remarkably, the solutions for both sets of S01 states can be written out analytically. The usual bound S01 states possess attributes the same as those one usually encounters in QED and QCD, with bound QED state energies explicitly agreeing with the standard perturbative results through order α4. In contrast, the peculiar bound S01 states, yet to be observed, not only have different behaviors at the origin, but also distinctly different bound state properties (and scattering phase shifts). For the peculiar S01 ground state of fermion-antifermion pair with fermion rest mass m, the root-mean-square radius is approximately 1/m, binding energy is approximately (2-2)m, and rest mass approximately 2m. On the other hand, the (n+1)S01 peculiar state with principal quantum number (n+1) is nearly degenerate in energy and approximately equal in size with the nS01 usual states. For the P03 states, the usual solutions lead to the standard bound state energies and no resonance, but resonances have been found for the peculiar states whose energies depend on the description of the internal structure of the charges, the mass of the constituent, and the coupling constant. The existence of both usual and peculiar eigenstates in the same system leads to the non-self-adjoint property of the mass operator and two nonorthogonal complete sets. As both sets of states are physically admissible, the mass operator can be made self-adjoint with a single complete set of admissible states by introducing a new peculiarity quantum number and an enlarged Hilbert space that contains both the usual and peculiar states in different peculiarity sectors. Whether or not these newly-uncovered quantum-mechanically acceptable peculiar S01 bound states and P03 resonances for point fermion-antifermion systems correspond to physical states remains to be further investigated.

Higher-order vector discrete rogue-wave states in the coupled Ablowitz-Ladik equations: Exact solutions and stability.

PubMed

Wen, Xiao-Yong; Yan, Zhenya; Malomed, Boris A

2016-12-01

An integrable system of two-component nonlinear Ablowitz-Ladik equations is used to construct complex rogue-wave (RW) solutions in an explicit form. First, the modulational instability of continuous waves is studied in the system. Then, new higher-order discrete two-component RW solutions of the system are found by means of a newly derived discrete version of a generalized Darboux transformation. Finally, the perturbed evolution of these RW states is explored in terms of systematic simulations, which demonstrates that tightly and loosely bound RWs are, respectively, nearly stable and strongly unstable solutions.

Homoclinic accretion solutions in the Schwarzschild-anti-de Sitter space-time

NASA Astrophysics Data System (ADS)

Mach, Patryk

2015-04-01

The aim of this paper is to clarify the distinction between homoclinic and standard (global) Bondi-type accretion solutions in the Schwarzschild-anti-de Sitter space-time. The homoclinic solutions have recently been discovered numerically for polytropic equations of state. Here I show that they exist also for certain isothermal (linear) equations of state, and an analytic solution of this type is obtained. It is argued that the existence of such solutions is generic, although for sufficiently relativistic matter models (photon gas, ultrahard equation of state) there exist global solutions that can be continued to infinity, similarly to standard Michel's solutions in the Schwarzschild space-time. In contrast to that global solutions should not exist for matter models with a nonvanishing rest-mass component, and this is demonstrated for polytropes. For homoclinic isothermal solutions I derive an upper bound on the mass of the black hole for which stationary transonic accretion is allowed.

Bounding Averages Rigorously Using Semidefinite Programming: Mean Moments of the Lorenz System

NASA Astrophysics Data System (ADS)

Goluskin, David

2018-04-01

We describe methods for proving bounds on infinite-time averages in differential dynamical systems. The methods rely on the construction of nonnegative polynomials with certain properties, similarly to the way nonlinear stability can be proved using Lyapunov functions. Nonnegativity is enforced by requiring the polynomials to be sums of squares, a condition which is then formulated as a semidefinite program (SDP) that can be solved computationally. Although such computations are subject to numerical error, we demonstrate two ways to obtain rigorous results: using interval arithmetic to control the error of an approximate SDP solution, and finding exact analytical solutions to relatively small SDPs. Previous formulations are extended to allow for bounds depending analytically on parametric variables. These methods are illustrated using the Lorenz equations, a system with three state variables ( x, y, z) and three parameters (β ,σ ,r). Bounds are reported for infinite-time averages of all eighteen moments x^ly^mz^n up to quartic degree that are symmetric under (x,y)\\mapsto (-x,-y). These bounds apply to all solutions regardless of stability, including chaotic trajectories, periodic orbits, and equilibrium points. The analytical approach yields two novel bounds that are sharp: the mean of z^3 can be no larger than its value of (r-1)^3 at the nonzero equilibria, and the mean of xy^3 must be nonnegative. The interval arithmetic approach is applied at the standard chaotic parameters to bound eleven average moments that all appear to be maximized on the shortest periodic orbit. Our best upper bound on each such average exceeds its value on the maximizing orbit by less than 1%. Many bounds reported here are much tighter than would be possible without computer assistance.

Eikonal solutions to optical model coupled-channel equations

NASA Technical Reports Server (NTRS)

Cucinotta, Francis A.; Khandelwal, Govind S.; Maung, Khin M.; Townsend, Lawrence W.; Wilson, John W.

1988-01-01

Methods of solution are presented for the Eikonal form of the nucleus-nucleus coupled-channel scattering amplitudes. Analytic solutions are obtained for the second-order optical potential for elastic scattering. A numerical comparison is made between the first and second order optical model solutions for elastic and inelastic scattering of H-1 and He-4 on C-12. The effects of bound-state excitations on total and reaction cross sections are also estimated.

Energies and excited-state dynamics of 1Bu+, 1Bu- and 3Ag- states of carotenoids bound to LH2 antenna complexes from purple photosynthetic bacteria

NASA Astrophysics Data System (ADS)

Christiana, Rebecca; Miki, Takeshi; Kakitani, Yoshinori; Aoyagi, Shiho; Koyama, Yasushi; Limantara, Leenawaty

2009-10-01

Time-resolved pump-probe stimulated-emission and transient-absorption spectra were recorded after excitation with ˜30 fs pulses to the 1Bu+(0) and optically-forbidden diabatic levels of carotenoids, neurosporene, spheroidene and lycopene having n = 9-11 double bonds, bound to LH2 antenna complexes from Rhodobacter sphaeroides G1C, 2.4.1 and Rhodospirillum molischianum. The low-energy shift of stimulated emission from the covalent 1Bu-(0) and 3Ag-(0) levels slightly larger than that from the ionic 1Bu+(0) state suggests the polarization, whereas more efficient triplet generation suggests the twisting of the conjugated chain in Cars bound to the LH2 complexes, when compared to Cars free in solution.

Application of the N-quantum approximation to the proton radius problem

NASA Astrophysics Data System (ADS)

Cowen, Steven

This thesis is organized into three parts: 1. Introduction and bound state calculations of electronic and muonic hydrogen, 2. Bound states in motion, and 3.Treatment of soft photons. In the first part, we apply the N-Quantum Approximation (NQA) to electronic and muonic hydrogen and search for any new corrections to energy levels that could account for the 0.31 meV discrepancy of the proton radius problem. We derive a bound state equation and compare our numerical solutions and wave functions to those of the Dirac equation. We find NQA Lamb shift diagrams and calculate the associated energy shift contributions. We do not find any new corrections large enough to account for the discrepancy. In part 2, we discuss the effects of motion on bound states using the NQA. We find classical Lorentz contraction of the lowest order NQA wave function. Finally, in part 3, we develop a clothing transformation for interacting fields in order to produce the correct asymptotic limits. We find the clothing eliminates a trilinear interacting Hamiltonian term and produces a quadrilinear soft photon interaction term.

A Conditionally Integrable Bi-confluent Heun Potential Involving Inverse Square Root and Centrifugal Barrier Terms

NASA Astrophysics Data System (ADS)

Ishkhanyan, Tigran A.; Krainov, Vladimir P.; Ishkhanyan, Artur M.

2018-05-01

We present a conditionally integrable potential, belonging to the bi-confluent Heun class, for which the Schrödinger equation is solved in terms of the confluent hypergeometric functions. The potential involves an attractive inverse square root term x-1/2 with arbitrary strength and a repulsive centrifugal barrier core x-2 with the strength fixed to a constant. This is a potential well defined on the half-axis. Each of the fundamental solutions composing the general solution of the Schrödinger equation is written as an irreducible linear combination, with non-constant coefficients, of two confluent hypergeometric functions. We present the explicit solution in terms of the non-integer order Hermite functions of scaled and shifted argument and discuss the bound states supported by the potential. We derive the exact equation for the energy spectrum and approximate that by a highly accurate transcendental equation involving trigonometric functions. Finally, we construct an accurate approximation for the bound-state energy levels.

Approximation solution of Schrodinger equation for Q-deformed Rosen-Morse using supersymmetry quantum mechanics (SUSY QM)

DOE Office of Scientific and Technical Information (OSTI.GOV)

Alemgadmi, Khaled I. K., E-mail: azozkied@yahoo.com; Suparmi; Cari

2015-09-30

The approximate analytical solution of Schrodinger equation for Q-Deformed Rosen-Morse potential was investigated using Supersymmetry Quantum Mechanics (SUSY QM) method. The approximate bound state energy is given in the closed form and the corresponding approximate wave function for arbitrary l-state given for ground state wave function. The first excited state obtained using upper operator and ground state wave function. The special case is given for the ground state in various number of q. The existence of Rosen-Morse potential reduce energy spectra of system. The larger value of q, the smaller energy spectra of system.

Making the Impossible Possible: Strategies for Fast POMDP Monitoring

NASA Technical Reports Server (NTRS)

Washington, Richard; Lau, Sonie (Technical Monitor)

1998-01-01

Systems modeled as partially observable Markov decision processes (POMDPs) can be tracked quickly with three restrictions: all actions are grouped together, the out-degree of each system state is bounded by a constant, and the number of non-zero elements in the belief state is bounded by a (different) constant. With these restrictions, the tracking algorithm operates in constant time and linear space. The first restriction assumes that the action itself is unobservable. The second restriction defines a subclass of POMDPs that covers however a wide range of problems. The third restriction is an approximation technique that can lead to a potentially vexing problem: an observation may be received that has probability according to the restricted belief state. This problem of impossibility will cause the belief state to collapse. In this paper we discuss the tradeoffs between the constant bound on the belief state and the quality of the solution. We concentrate on strategies for overcoming the impossibility problem and demonstrate initial experimental results that indicate promising directions.

Sensor selection cost optimisation for tracking structurally cyclic systems: a P-order solution

NASA Astrophysics Data System (ADS)

Doostmohammadian, M.; Zarrabi, H.; Rabiee, H. R.

2017-08-01

Measurements and sensing implementations impose certain cost in sensor networks. The sensor selection cost optimisation is the problem of minimising the sensing cost of monitoring a physical (or cyber-physical) system. Consider a given set of sensors tracking states of a dynamical system for estimation purposes. For each sensor assume different costs to measure different (realisable) states. The idea is to assign sensors to measure states such that the global cost is minimised. The number and selection of sensor measurements need to ensure the observability to track the dynamic state of the system with bounded estimation error. The main question we address is how to select the state measurements to minimise the cost while satisfying the observability conditions. Relaxing the observability condition for structurally cyclic systems, the main contribution is to propose a graph theoretic approach to solve the problem in polynomial time. Note that polynomial time algorithms are suitable for large-scale systems as their running time is upper-bounded by a polynomial expression in the size of input for the algorithm. We frame the problem as a linear sum assignment with solution complexity of ?.

Preparation and preliminary characterization of crystallizing fluorescent derivatives of chicken egg white lysozyme

NASA Astrophysics Data System (ADS)

Sumida, John P.; Forsythe, Elizabeth L.; Pusey, Marc L.

2001-11-01

Fluorescence is one of the most versatile and powerful tools for the study of macromolecules. While most proteins are intrinsically fluorescent, working at crystallization concentrations require the use of covalently prepared derivatives added as tracers. This approach requires derivatives that do not markedly affect the crystal packing. We have prepared fluorescent derivatives of chicken egg white lysozyme with probes bound to one of two different sites on the protein molecule. Lucifer yellow and 5-(2-aminoethyl)aminonapthalene-1-sulfonic acid (EDANS) have been attached to the side chain carboxyl of Asp 101 using a carbodiimide coupling procedure. Asp 101 lies within the active site cleft, and it is believed that the probes are "buried" within that cleft. Lucifer yellow and EDANS probes with iodoacetamide reactive groups have been bound to His 15, located on the "back side" of the molecule relative to the active site. All the derivatives fluoresce in the solution and the crystalline states. Fluorescence characterization has focused on determination of binding effects on the probe quantum yield, lifetime, absorption and emission spectra, and quenching by added solutes. Quenching studies show that, as postulated, the Asp 101-bound probes are partially sheltered from the bulk solution by their location within the active site cleft. Probes bound to His 15 have quenching constants about equal to those for the free probes, indicating that this site is highly exposed to the bulk solution.

Bound states, scattering states, and resonant states in PT -symmetric open quantum systems

NASA Astrophysics Data System (ADS)

Garmon, Savannah; Gianfreda, Mariagiovanna; Hatano, Naomichi

2015-08-01

We study a simple open quantum system with a PT -symmetric defect potential as a prototype in order to illustrate a number of general features of PT -symmetric open quantum systems; however, the potential itself could be mimicked by a number of PT systems that have been experimentally studied quite recently. One key feature is the resonance in continuum (RIC), which appears in both the discrete spectrum and the scattering spectrum of such systems. The RIC wave function forms a standing wave extending throughout the spatial extent of the system and in this sense represents a resonance between the open environment associated with the leads of our model and the central PT -symmetric potential. We also illustrate that as one deforms the system parameters, the RIC may exit the continuum by splitting into a bound state and a virtual bound state at the band edge, a process which should be experimentally observable. We also study the exceptional points appearing in the discrete spectrum at which two eigenvalues coalesce; we categorize these as either EP2As, at which two real-valued solutions coalesce before becoming complex-valued, and EP2Bs, for which the two solutions are complex on either side of the exceptional point. The EP2As are associated with PT -symmetry breaking; we argue that these are more stable against parameter perturbation than the EP2Bs. We also study complex-valued solutions of the discrete spectrum for which the wave function is nevertheless spatially localized, something that is not allowed in traditional open quantum systems; we illustrate that these may form quasibound states in continuum under some circumstances. We also study the scattering properties of the system, including states that support invisible propagation and some general features of perfect transmission states. We finally use our model as a prototype for the construction of scattering states that satisfy PT -symmetric boundary conditions; while these states do not conserve the traditional probability current, we introduce the PT current which is preserved. The perfect transmission states appear as a special case of the PT -symmetric scattering states.

Exact solution to the Schrödinger’s equation with pseudo-Gaussian potential

DOE Office of Scientific and Technical Information (OSTI.GOV)

Iacob, Felix, E-mail: felix@physics.uvt.ro; Lute, Marina, E-mail: marina.lute@upt.ro

2015-12-15

We consider the radial Schrödinger equation with the pseudo-Gaussian potential. By making an ansatz to the solution of the eigenvalue equation for the associate Hamiltonian, we arrive at the general exact eigenfunction. The values of energy levels for the bound states are calculated along with their corresponding normalized wave-functions. The case of positive energy levels, known as meta-stable states, is also discussed and the magnitude of transmission coefficient through the potential barrier is evaluated.

Ground state for a massive scalar field in the BTZ spacetime with Robin boundary conditions

NASA Astrophysics Data System (ADS)

Bussola, Francesco; Dappiaggi, Claudio; Ferreira, Hugo R. C.; Khavkine, Igor

2017-11-01

We consider a real, massive scalar field in Bañados-Teitelboim-Zanelli spacetime, a 2 +1 -dimensional black hole solution of Einstein's field equations with a negative cosmological constant. First, we analyze the space of classical solutions in a mode decomposition, and we characterize the collection of all admissible boundary conditions of Robin type which can be imposed at infinity. Second, we investigate whether, for a given boundary condition, there exists a ground state by constructing explicitly its two-point function. We demonstrate that for a subclass of the boundary conditions it is possible to construct a ground state that locally satisfies the Hadamard property. In all other cases, we show that bound state mode solutions exist and, therefore, such construction is not possible.

Selective Injection of Magnetization by Slow Chemical Exchange in NMR

NASA Astrophysics Data System (ADS)

Boulat, Benoit; Epstein, David M.; Rance, Mark

1999-06-01

In a system in slow dynamic equilibrium two NMR methods are shown to be suitable for injecting magnetization from one resonance to another by means of slow chemical exchange. The combined outputs of the methods may be employed to measure the value of the off-rate constant κoff in the complex. The methods are implemented experimentally using the complex of molecules composed of the enzyme Esherichia coli dihydrofolate reductase (DHFR) and the ligand folate. In an equilibrium solution with DHFR, folate is known to undergo chemical exchange between a free state and a bound state. The modified synchronous nutation method is applied to a spin of the folate molecule in the free and bound states; magnetization transfer occurs between the two sites due to the underlying exchange process. As a preliminary step for the application of the synchronous nutation method, a new one-dimensional 1H NMR technique is proposed which facilitates the assignment of the resonance of a spin in the bound state, provided the resonance of its exchange partner in the free state is known. This experiment is also used to obtain quantitative estimates of the transverse relaxation rate constant of the bound resonance. The numerical procedure necessary to analyze the experimental results of the synchronous nutation experiment is presented.

The use of amphipols for solution NMR studies of membrane proteins: advantages and constraints as compared to other solubilizing media.

PubMed

Planchard, Noelya; Point, Élodie; Dahmane, Tassadite; Giusti, Fabrice; Renault, Marie; Le Bon, Christel; Durand, Grégory; Milon, Alain; Guittet, Éric; Zoonens, Manuela; Popot, Jean-Luc; Catoire, Laurent J

2014-10-01

Solution-state nuclear magnetic resonance studies of membrane proteins are facilitated by the increased stability that trapping with amphipols confers to most of them as compared to detergent solutions. They have yielded information on the state of folding of the proteins, their areas of contact with the polymer, their dynamics, water accessibility, and the structure of protein-bound ligands. They benefit from the diversification of amphipol chemical structures and the availability of deuterated amphipols. The advantages and constraints of working with amphipols are discussed and compared to those associated with other non-conventional environments, such as bicelles and nanodiscs.

Detachment dynamics of colloidal spheres with adhesive interactions

NASA Astrophysics Data System (ADS)

Bergenholtz, J.

2018-04-01

Escape of colloidal-size particles from various kinds of solids, such as aggregates and surfaces, occurs in a wide variety of settings of both fundamental and applied scientific interest. In this paper an exact solution for the detachment of adhesive spheres from each other by means of diffusion is presented. The solution takes into account repeated detachment and reattachment events in the course of time on the way toward the permanently separated state. For strongly adhesive spheres this state is approached in an exponential manner essentially regardless of how the bound state is specified. The analytical solution is shown to capture semiquantitatively the escape from more realistic potential wells using a mapping procedure whereby equality of second virial coefficients is imposed.

Quantum decay model with exact explicit analytical solution

NASA Astrophysics Data System (ADS)

Marchewka, Avi; Granot, Er'El

2009-01-01

A simple decay model is introduced. The model comprises a point potential well, which experiences an abrupt change. Due to the temporal variation, the initial quantum state can either escape from the well or stay localized as a new bound state. The model allows for an exact analytical solution while having the necessary features of a decay process. The results show that the decay is never exponential, as classical dynamics predicts. Moreover, at short times the decay has a fractional power law, which differs from perturbation quantum method predictions. At long times the decay includes oscillations with an envelope that decays algebraically. This is a model where the final state can be either continuous or localized, and that has an exact analytical solution.

Preparation and Preliminary Characterization of Crystallizing Fluorescent Derivatives of Chicken Egg White Lysozyme

NASA Technical Reports Server (NTRS)

Sumida, John; Forsythe, Elizabeth L.; Pusey, Marc L.; Whitaker, Ann F. (Technical Monitor)

2001-01-01

Fluorescence is one of the most versatile and powerful tools for the study of macromolecules. While most proteins are intrinsically fluorescent, working at crystallization concentrations require the use of covalently prepared derivatives added as tracers. This approach requires derivatives that do not markedly affect the crystal packing. We have prepared fluorescent derivatives of chicken egg white lysozyme with probes bound to one of two different sites on the protein molecule. Lucifer yellow and 5-(2-aminoethyl)aminonapthalene-1-sulfonic acid (EDANS) have been attached to the side chain carboxyl of Asp(sup 101) using a carbodiimide coupling procedure. Asp(sup 101) lies within the active site cleft, and it is believed that the probes are "buried" within that cleft. Lucifer yellow and MANS probes with iodoacetamide reactive groups have been bound to His(sup 15), located on the "back side" of the molecule relative to the active site. All the derivatives fluoresce in the solution and the crystalline states. Fluorescence characterization has focused on determination of binding effects on the probe quantum yield, lifetime, absorption and emission spectra, and quenching by added solutes. Quenching studies show that, as postulated, the Asp(sup 101)-bound probes are partially sheltered from the bulk solution by their location within the active site cleft. Probes bound to His(sup 15) have quenching constants about equal to those for the free probes, indicating that this site is highly exposed to the bulk solution.

Preparation and Preliminary Characterization of Crystallizing Fluorescent Derivatives of Chicken Egg White Lysozyme

NASA Technical Reports Server (NTRS)

Sumida, John P.; Forsythe, Elizabeth L.; Pusey, Marc L.

2001-01-01

Fluorescence is one of the most versatile and powerful tools for the study of macromolecules. While most proteins are intrinsically fluorescent, working at crystallization concentrations require the use of covalently prepared derivatives added as tracers. This approach requires derivatives that do not markedly affect the crystal packing. We have prepared fluorescent derivatives of chicken egg white lysozyme with probes bound to one of two different sites on the protein molecule. Lucifer yellow and 5-(2-aminoethyl)aminonapthalene-i-sulfonic acid (EDANS) have been attached to the side chain carboxyl of Asp(sup 101) using a carbodiimide coupling procedure. Asp(sup 101) lies within the active site cleft, and it is believed that the probes are 'buried' within that cleft. Lucifer yellow and MANS probes with iodoacetamide reactive five groups have been bound to His(sup 15), located on the 'back side' of the molecule relative to the active site. All the derivatives fluoresce in the solution and the crystalline states. Fluorescence characterization has focused on determination of binding effects on the probe quantum yield, lifetime, absorption and emission spectra, and quenching by added solutes. Quenching studies show that, as postulated, the Asp(sup 101)-bound probes are partially sheltered from the bulk solution by their location within the active site cleft. Probes bound to His(sup 15) have quenching constants about equal to those for the free probes, indicating that this site is highly exposed to the bulk solution.

Quasi-soliton scattering in quantum spin chains

NASA Astrophysics Data System (ADS)

Vlijm, R.; Ganahl, M.; Fioretto, D.; Brockmann, M.; Haque, M.; Evertz, H. G.; Caux, J.-S.

2015-12-01

The quantum scattering of magnon bound states in the anisotropic Heisenberg spin chain is shown to display features similar to the scattering of solitons in classical exactly solvable models. Localized colliding Gaussian wave packets of bound magnons are constructed from string solutions of the Bethe equations and subsequently evolved in time, relying on an algebraic Bethe ansatz based framework for the computation of local expectation values in real space-time. The local magnetization profile shows the trajectories of colliding wave packets of bound magnons, which obtain a spatial displacement upon scattering. Analytic predictions on the displacements for various values of anisotropy and string lengths are derived from scattering theory and Bethe ansatz phase shifts, matching time-evolution fits on the displacements. The time-evolved block decimation algorithm allows for the study of scattering displacements from spin-block states, showing similar scattering displacement features.

Quasi-soliton scattering in quantum spin chains

NASA Astrophysics Data System (ADS)

Fioretto, Davide; Vljim, Rogier; Ganahl, Martin; Brockmann, Michael; Haque, Masud; Evertz, Hans-Gerd; Caux, Jean-Sébastien

The quantum scattering of magnon bound states in the anisotropic Heisenberg spin chain is shown to display features similar to the scattering of solitons in classical exactly solvable models. Localized colliding Gaussian wave packets of bound magnons are constructed from string solutions of the Bethe equations and subsequently evolved in time, relying on an algebraic Bethe ansatz based framework for the computation of local expectation values in real space-time. The local magnetization profile shows the trajectories of colliding wave packets of bound magnons, which obtain a spatial displacement upon scattering. Analytic predictions on the displacements for various values of anisotropy and string lengths are derived from scattering theory and Bethe ansatz phase shifts, matching time evolution fits on the displacements. The TEBD algorithm allows for the study of scattering displacements from spin-block states, showing similar displacement scattering features.

Bounded energy states in homogeneous turbulent shear flow - An alternative view

NASA Technical Reports Server (NTRS)

Bernard, P. S.; Speziale, C. G.

1992-01-01

The equilibrium structure of homogeneous turbulent shear flow is investigated from a theoretical standpoint. Existing turbulence models, in apparent agreement with physical and numerical experiments, predict an unbounded exponential time growth of the turbulent kinetic energy and dissipation rate; only the anisotropy tensor and turbulent time scale reach a structural equilibrium. It is shown that if a residual vortex stretching term is maintained in the dissipation rate transport equation, then there can exist equilibrium solutions, with bounded energy states, where the turbulence production is balanced by its dissipation. Illustrative calculations are presented for a k-epsilon model modified to account for net vortex stretching.

The interaction of Dirac particles with non-abelian gauge fields and gravity - bound states

NASA Astrophysics Data System (ADS)

Finster, Felix; Smoller, Joel; Yau, Shing-Tung

2000-09-01

We consider a spherically symmetric, static system of a Dirac particle interacting with classical gravity and an SU(2) Yang-Mills field. The corresponding Einstein-Dirac-Yang-Mills equations are derived. Using numerical methods, we find different types of soliton-like solutions of these equations and discuss their properties. Some of these solutions are stable even for arbitrarily weak gravitational coupling.

Momentum fractionation on superstrata

DOE PAGES

Bena, Iosif; Martinec, Emil; Turton, David; ...

2016-05-11

Superstrata are bound states in string theory that carry D1, D5, and momentum charges, and whose supergravity descriptions are parameterized by arbitrary functions of (at least) two variables. In the D1-D5 CFT, typical three-charge states reside in highdegree twisted sectors, and their momentum charge is carried by modes that individually have fractional momentum. Understanding this momentum fractionation holographically is crucial for understanding typical black-hole microstates in this system. We use solution-generating techniques to add momentum to a multi-wound supertube and thereby construct the first examples of asymptotically-flat superstrata. The resulting supergravity solutions are horizonless and smooth up to well-understood orbifoldmore » singularities. Upon taking the AdS3 decoupling limit, our solutions are dual to CFT states with momentum fractionation. We give a precise proposal for these dual CFT states. Lastly, our construction establishes the very nontrivial fact that large classes of CFT states with momentum fractionation can be realized in the bulk as smooth horizonless supergravity solutions.« less

A Transformation Approach to Optimal Control Problems with Bounded State Variables

NASA Technical Reports Server (NTRS)

Hanafy, Lawrence Hanafy

1971-01-01

A technique is described and utilized in the study of the solutions to various general problems in optimal control theory, which are converted in to Lagrange problems in the calculus of variations. This is accomplished by mapping certain properties in Euclidean space onto closed control and state regions. Nonlinear control problems with a unit m cube as control region and unit n cube as state region are considered.

Exact results for the finite time thermodynamic uncertainty relation

NASA Astrophysics Data System (ADS)

Manikandan, Sreekanth K.; Krishnamurthy, Supriya

2018-03-01

We obtain exact results for the recently discovered finite-time thermodynamic uncertainty relation, for the dissipated work W d , in a stochastically driven system with non-Gaussian work statistics, both in the steady state and transient regimes, by obtaining exact expressions for any moment of W d at arbitrary times. The uncertainty function (the Fano factor of W d ) is bounded from below by 2k_BT as expected, for all times τ, in both steady state and transient regimes. The lower bound is reached at τ=0 as well as when certain system parameters vanish (corresponding to an equilibrium state). Surprisingly, we find that the uncertainty function also reaches a constant value at large τ for all the cases we have looked at. For a system starting and remaining in steady state, the uncertainty function increases monotonically, as a function of τ as well as other system parameters, implying that the large τ value is also an upper bound. For the same system in the transient regime, however, we find that the uncertainty function can have a local minimum at an accessible time τm , for a range of parameter values. The large τ value for the uncertainty function is hence not a bound in this case. The non-monotonicity suggests, rather counter-intuitively, that there might be an optimal time for the working of microscopic machines, as well as an optimal configuration in the phase space of parameter values. Our solutions show that the ratios of higher moments of the dissipated work are also bounded from below by 2k_BT . For another model, also solvable by our methods, which never reaches a steady state, the uncertainty function, is in some cases, bounded from below by a value less than 2k_BT .

Intertwining solutions for magnetic relativistic Hartree type equations

NASA Astrophysics Data System (ADS)

Cingolani, Silvia; Secchi, Simone

2018-05-01

We consider the magnetic pseudo-relativistic Schrödinger equation where , m  >  0, is an external continuous scalar potential, is a continuous vector potential and is a convolution kernel, is a constant, , . We assume that A and V are symmetric with respect to a closed subgroup G of the group of orthogonal linear transformations of . If for any , the cardinality of the G-orbit of x is infinite, then we prove the existence of infinitely many intertwining solutions assuming that is either linear in x or uniformly bounded. The results are proved by means of a new local realization of the square root of the magnetic laplacian to a local elliptic operator with Neumann boundary condition on a half-space. Moreover we derive an existence result of a ground state intertwining solution for bounded vector potentials, if G admits a finite orbit.

Conformational Plasticity of the Cell-Penetrating Peptide SAP As Revealed by Solid-State 19F-NMR and Circular Dichroism Spectroscopies.

PubMed

Afonin, Sergii; Kubyshkin, Vladimir; Mykhailiuk, Pavel K; Komarov, Igor V; Ulrich, Anne S

2017-07-13

The cell-penetrating peptide SAP, which was designed as an amphipathic poly-l-proline helix II (PPII), was suggested to self-assemble into regular fibrils that are relevant for its internalization. Herein we have analyzed the structure of SAP in the membrane-bound state by solid-state 19 F-NMR, which revealed other structural states, in addition to the expected surface-aligned PPII. Trifluoromethyl-bicyclopentyl-glycine (CF 3 -Bpg) and two rigid isomers of trifluoromethyl-4,5-methanoprolines (CF 3 -MePro) were used as labels for 19 F-NMR analysis. The equilibria between different conformations of SAP were studied and were found to be shifted by the substituents at Pro-11. Synchrotron-CD results suggested that substituting Pro-11 by CF 3 -MePro governed the coil-to-PPII equilibrium in solution and in the presence of a lipid bilayer. Using CD and 19 F-NMR, we examined the slow kinetics of the association of SAP with membranes and the dependence of the SAP conformational dynamics on the lipid composition. The peptide did not bind to lipids in the solid ordered phase and aggregated only in the liquid ordered "raft"-like bilayers. Self-association could not be detected in solution or in the presence of liquid disordered membranes. Surface-bound amphipathic SAP in a nonaggregated state was structured as a mixture of nonideal extended conformations reflecting the equilibrium already present in solution, i.e., before binding to the membrane.

Position dependent mass Schroedinger equation and isospectral potentials: Intertwining operator approach

DOE Office of Scientific and Technical Information (OSTI.GOV)

Midya, Bikashkali; Roy, B.; Roychoudhury, R.

2010-02-15

Here, we have studied first- and second-order intertwining approaches to generate isospectral partner potentials of position dependent (effective) mass Schroedinger equation. The second-order intertwiner is constructed directly by taking it as second-order linear differential operator with position dependent coefficients, and the system of equations arising from the intertwining relationship is solved for the coefficients by taking an ansatz. A complete scheme for obtaining general solution is obtained, which is valid for any arbitrary potential and mass function. The proposed technique allows us to generate isospectral potentials with the following spectral modifications: (i) to add new bound state(s), (ii) to removemore » bound state(s), and (iii) to leave the spectrum unaffected. To explain our findings with the help of an illustration, we have used point canonical transformation to obtain the general solution of the position dependent mass Schrodinger equation corresponding to a potential and mass function. It is shown that our results are consistent with the formulation of type A N-fold supersymmetry [T. Tanaka, J. Phys. A 39, 219 (2006); A. Gonzalez-Lopez and T. Tanaka, J. Phys. A 39, 3715 (2006)] for the particular cases N=1 and N=2, respectively.« less

On the Duffin-Kemmer-Petiau equation with linear potential in the presence of a minimal length

NASA Astrophysics Data System (ADS)

Chargui, Yassine

2018-04-01

We point out an erroneous handling in the literature regarding solutions of the (1 + 1)-dimensional Duffin-Kemmer-Petiau equation with linear potentials in the context of quantum mechanics with minimal length. Furthermore, using Brau's approach, we present a perturbative treatment of the effect of the minimal length on bound-state solutions when a Lorentz-scalar linear potential is applied.

Error analysis of analytic solutions for self-excited near-symmetric rigid bodies - A numerical study

NASA Technical Reports Server (NTRS)

Kia, T.; Longuski, J. M.

1984-01-01

Analytic error bounds are presented for the solutions of approximate models for self-excited near-symmetric rigid bodies. The error bounds are developed for analytic solutions to Euler's equations of motion. The results are applied to obtain a simplified analytic solution for Eulerian rates and angles. The results of a sample application of the range and error bound expressions for the case of the Galileo spacecraft experiencing transverse torques demonstrate the use of the bounds in analyses of rigid body spin change maneuvers.

A B-spline Galerkin method for the Dirac equation

NASA Astrophysics Data System (ADS)

Froese Fischer, Charlotte; Zatsarinny, Oleg

2009-06-01

The B-spline Galerkin method is first investigated for the simple eigenvalue problem, y=-λy, that can also be written as a pair of first-order equations y=λz, z=-λy. Expanding both y(r) and z(r) in the B basis results in many spurious solutions such as those observed for the Dirac equation. However, when y(r) is expanded in the B basis and z(r) in the dB/dr basis, solutions of the well-behaved second-order differential equation are obtained. From this analysis, we propose a stable method ( B,B) basis for the Dirac equation and evaluate its accuracy by comparing the computed and exact R-matrix for a wide range of nuclear charges Z and angular quantum numbers κ. When splines of the same order are used, many spurious solutions are found whereas none are found for splines of different order. Excellent agreement is obtained for the R-matrix and energies for bound states for low values of Z. For high Z, accuracy requires the use of a grid with many points near the nucleus. We demonstrate the accuracy of the bound-state wavefunctions by comparing integrals arising in hyperfine interaction matrix elements with exact analytic expressions. We also show that the Thomas-Reiche-Kuhn sum rule is not a good measure of the quality of the solutions obtained by the B-spline Galerkin method whereas the R-matrix is very sensitive to the appearance of pseudo-states.

Solutions of the Schrodinger Equation Using Approximate Nucleon-Nucleon and Lambda-Nucleon Potentials.

ERIC Educational Resources Information Center

Banerjee, S. N.; Chakraborty, S. N.

1980-01-01

Presents the outline of an approach related to the teaching of the chapter on bound and scattering states in a short-range potential, which forms a standard part of an undergraduate quantum mechanics course or nuclear physics course. (HM)

Deconfinement as an entropic self-destruction: A solution for the quarkonium suppression puzzle?

DOE PAGES

Kharzeev, Dmitri E.

2014-10-02

The entropic approach to dissociation of bound states immersed in strongly coupled systems is developed. In such systems, the excitations of the bound state are often delocalized and characterized by a large entropy, so that the bound state is strongly entangled with the rest of the statistical system. If this entropy S increases with the separation r between the constituents of the bound state, S=S(r), then the resulting entropic force F=T ∂S/∂r (T is temperature) can drive the dissociation process. As a specific example, we consider the case of heavy quarkonium in strongly coupled quark-gluon plasma, where lattice QCD indicatesmore » a large amount of entropy associated with the heavy quark pair at temperatures 0.9T c ≤ T ≤ 1.5T c (T c is the deconfinement temperature); this entropy S(r) grows with the interquark distance r. We argue that the entropic mechanism results in an anomalously strong quarkonium suppression in the temperature range near T c. This entropic self-destruction may thus explain why the experimentally measured quarkonium nuclear modification factor at RHIC (lower energy density) is smaller than at LHC (higher energy density), possibly resolving the “quarkonium suppression puzzle”—all of the previously known mechanisms of quarkonium dissociation operate more effectively at higher energy densities, and this contradicts the data. As a result, we find that near T c the entropic force leads to delocalization of the bound hadron states; we argue that this delocalization may be the mechanism underlying deconfinement.« less

Mechanistic Insight into Nanoparticle Surface Adsorption by Solution NMR Spectroscopy in an Aqueous Gel

DOE Office of Scientific and Technical Information (OSTI.GOV)

Egner, Timothy K.; Naik, Pranjali; Nelson, Nicholas C.

Engineering nanoparticle (NP) functions at the molecular level requires a detailed understanding of the dynamic processes occurring at the NP surface. Herein we show that a combination of dark-state exchange saturation transfer (DEST) and relaxation dispersion (RD) NMR experiments on gel-stabilized NP samples enables the accurate determination of the kinetics and thermodynamics of adsorption. We used the former approach to describe the interaction of cholic acid (CA) and phenol (PhOH) with ceria NPs with a diameter of approximately 200 nm. Whereas CA formed weak interactions with the NPs, PhOH was tightly bound to the NP surface. Interestingly, we found thatmore » the adsorption of PhOH proceeds via an intermediate, weakly bound state in which the small molecule has residual degrees of rotational diffusion. Here we believe the use of aqueous gels for stabilizing NP samples will increase the applicability of solution NMR methods to the characterization of nanomaterials.« less

Mechanistic Insight into Nanoparticle Surface Adsorption by Solution NMR Spectroscopy in an Aqueous Gel

DOE PAGES

Egner, Timothy K.; Naik, Pranjali; Nelson, Nicholas C.; ...

2017-06-22

Engineering nanoparticle (NP) functions at the molecular level requires a detailed understanding of the dynamic processes occurring at the NP surface. Herein we show that a combination of dark-state exchange saturation transfer (DEST) and relaxation dispersion (RD) NMR experiments on gel-stabilized NP samples enables the accurate determination of the kinetics and thermodynamics of adsorption. We used the former approach to describe the interaction of cholic acid (CA) and phenol (PhOH) with ceria NPs with a diameter of approximately 200 nm. Whereas CA formed weak interactions with the NPs, PhOH was tightly bound to the NP surface. Interestingly, we found thatmore » the adsorption of PhOH proceeds via an intermediate, weakly bound state in which the small molecule has residual degrees of rotational diffusion. Here we believe the use of aqueous gels for stabilizing NP samples will increase the applicability of solution NMR methods to the characterization of nanomaterials.« less

Parametric symmetries in exactly solvable real and PT symmetric complex potentials

DOE Office of Scientific and Technical Information (OSTI.GOV)

Yadav, Rajesh Kumar, E-mail: rajeshastrophysics@gmail.com; Khare, Avinash, E-mail: khare@physics.unipune.ac.in; Bagchi, Bijan, E-mail: bbagchi123@gmail.com

In this paper, we discuss the parametric symmetries in different exactly solvable systems characterized by real or complex PT symmetric potentials. We focus our attention on the conventional potentials such as the generalized Pöschl Teller (GPT), Scarf-I, and PT symmetric Scarf-II which are invariant under certain parametric transformations. The resulting set of potentials is shown to yield a completely different behavior of the bound state solutions. Further, the supersymmetric partner potentials acquire different forms under such parametric transformations leading to new sets of exactly solvable real and PT symmetric complex potentials. These potentials are also observed to be shape invariantmore » (SI) in nature. We subsequently take up a study of the newly discovered rationally extended SI potentials, corresponding to the above mentioned conventional potentials, whose bound state solutions are associated with the exceptional orthogonal polynomials (EOPs). We discuss the transformations of the corresponding Casimir operator employing the properties of the so(2, 1) algebra.« less

Low-density homogeneous symmetric nuclear matter: Disclosing dinucleons in coexisting phases

NASA Astrophysics Data System (ADS)

Arellano, Hugo F.; Delaroche, Jean-Paul

2015-01-01

The effect of in-medium dinucleon bound states on self-consistent single-particle fields in Brueckner, Bethe and Goldstone theory is investigated in symmetric nuclear matter at zero temperature. To this end, dinucleon bound state occurences in the 1 S 0 and 3 SD 1 channels are explicitly accounted for --within the continuous choice for the auxiliary fields-- while imposing self-consistency in Brueckner-Hartree-Fock approximation calculations. Searches are carried out at Fermi momenta in the range fm-1, using the Argonne bare nucleon-nucleon potential without resorting to the effective-mass approximation. As a result, two distinct solutions meeting the self-consistency requirement are found with overlapping domains in the interval 0.130 fm-1 0.285 fm-1, corresponding to mass densities between and g cm-3. Effective masses as high as three times the nucleon mass are found in the coexistence domain. The emergence of superfluidity in relationship with BCS pairing gap solutions is discussed.

New derivation of soliton solutions to the AKNS2 system via dressing transformation methods

NASA Astrophysics Data System (ADS)

Assunção, A. de O.; Blas, H.; da Silva, M. J. B. F.

2012-03-01

We consider certain boundary conditions supporting soliton solutions in the generalized nonlinear Schrödinger equation (AKNSr) (r = 1, 2). Using the dressing transformation (DT) method and the related tau functions, we study the AKNSr system for the vanishing, (constant) non-vanishing and the mixed boundary conditions, and their associated bright, dark and bright-dark N-soliton solutions, respectively. Moreover, we introduce a modified DT related to the dressing group in order to consider the free-field boundary condition and derive generalized N dark-dark solitons. As a reduced submodel of the AKNSr system, we study the properties of the focusing, defocusing and mixed focusing-defocusing versions of the so-called coupled nonlinear Schrödinger equation (r-CNLS), which has recently been considered in many physical applications. We have shown that two-dark-dark-soliton bound states exist in the AKNS2 system, and three- and higher-dark-dark-soliton bound states cannot exist. The AKNSr (r ⩾ 3) extension is briefly discussed in this approach. The properties and calculations of some matrix elements using level-one vertex operators are outlined. Dedicated to the memory of S S Costa

Quantum state discrimination bounds for finite sample size

DOE Office of Scientific and Technical Information (OSTI.GOV)

Audenaert, Koenraad M. R.; Mosonyi, Milan; Mathematical Institute, Budapest University of Technology and Economics, Egry Jozsef u 1., Budapest 1111

2012-12-15

In the problem of quantum state discrimination, one has to determine by measurements the state of a quantum system, based on the a priori side information that the true state is one of the two given and completely known states, {rho} or {sigma}. In general, it is not possible to decide the identity of the true state with certainty, and the optimal measurement strategy depends on whether the two possible errors (mistaking {rho} for {sigma}, or the other way around) are treated as of equal importance or not. Results on the quantum Chernoff and Hoeffding bounds and the quantum Stein'smore » lemma show that, if several copies of the system are available then the optimal error probabilities decay exponentially in the number of copies, and the decay rate is given by a certain statistical distance between {rho} and {sigma} (the Chernoff distance, the Hoeffding distances, and the relative entropy, respectively). While these results provide a complete solution to the asymptotic problem, they are not completely satisfying from a practical point of view. Indeed, in realistic scenarios one has access only to finitely many copies of a system, and therefore it is desirable to have bounds on the error probabilities for finite sample size. In this paper we provide finite-size bounds on the so-called Stein errors, the Chernoff errors, the Hoeffding errors, and the mixed error probabilities related to the Chernoff and the Hoeffding errors.« less

Necessary and sufficient optimality conditions for classical simulations of quantum communication processes

NASA Astrophysics Data System (ADS)

Montina, Alberto; Wolf, Stefan

2014-07-01

We consider the process consisting of preparation, transmission through a quantum channel, and subsequent measurement of quantum states. The communication complexity of the channel is the minimal amount of classical communication required for classically simulating it. Recently, we reduced the computation of this quantity to a convex minimization problem with linear constraints. Every solution of the constraints provides an upper bound on the communication complexity. In this paper, we derive the dual maximization problem of the original one. The feasible points of the dual constraints, which are inequalities, give lower bounds on the communication complexity, as illustrated with an example. The optimal values of the two problems turn out to be equal (zero duality gap). By this property, we provide necessary and sufficient conditions for optimality in terms of a set of equalities and inequalities. We use these conditions and two reasonable but unproven hypotheses to derive the lower bound n ×2n -1 for a noiseless quantum channel with capacity equal to n qubits. This lower bound can have interesting consequences in the context of the recent debate on the reality of the quantum state.

State space truncation with quantified errors for accurate solutions to discrete Chemical Master Equation

PubMed Central

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 truncation and error analysis methods developed here can be used to ensure accurate direct solutions to the dCME for a large number of stochastic networks. PMID:27105653

State Space Truncation with Quantified Errors for Accurate Solutions to Discrete Chemical Master Equation

DOE Office of Scientific and Technical Information (OSTI.GOV)

Cao, Youfang; Terebus, Anna; Liang, Jie

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. Wemore » 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 truncation and error analysis methods developed here can be used to ensure accurate direct solutions to the dCME for a large number of stochastic networks.« less

State Space Truncation with Quantified Errors for Accurate Solutions to Discrete Chemical Master Equation

DOE PAGES

Cao, Youfang; Terebus, Anna; Liang, Jie

2016-04-22

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. Wemore » 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 truncation and error analysis methods developed here can be used to ensure accurate direct solutions to the dCME for a large number of stochastic networks.« less

Selectively increasing the clearance of protein-bound uremic solutes

PubMed Central

Luo, Frank J.-G.; Plummer, Natalie S.; Hostetter, Thomas H.; Meyer, Timothy W.

2012-01-01

Background. The toxicity of bound solutes could be better evaluated if we could adjust the clearance of such solutes independent of unbound solutes. This study assessed whether bound solute clearances can be increased while maintaining urea clearance constant during the extended hours of nocturnal dialysis. Methods. Nine patients on thrice-weekly nocturnal dialysis underwent two experimental dialysis treatments 1 week apart. The experimental treatments were designed to provide the same urea clearance while providing widely different bound solute clearance. One treatment employed a large dialyzer and high dialyzate flow rate (Qd) of 800 mL/min while blood flow (Qb) was 270 mL/min. The other treatment employed a smaller dialyzer and Qd of 300 mL/min while Qb was 350 mL/min. Results. Treatment with the large dialyzer and higher Qd greatly increased the clearances of the bound solutes p-cresol sulfate (PCS: 27 ± 9 versus 14 ± 6 mL/min) and indoxyl sulfate (IS: 26 ± 8 versus 14 ± 5 mL/min) without altering the clearance of urea (204 ± 20 versus 193 ± 16 mL/min). Increasing PCS and IS clearances increased the removal of these solutes (PCS: 375 ± 200 versus 207 ± 86 mg/session; IS: 201 ± 137 versus 153 ± 74 mg/session), while urea removal was not different. Conclusions. The removal of bound solutes can thus be increased by raising the dialyzate flow and dialyzer size above the low levels sufficient to achieve target Kt/Vurea during extended treatment. Selectively increasing the clearance of bound solutes provides a potential means to test their toxicity. PMID:22231033

Accuracy of analytic energy level formulas applied to hadronic spectroscopy of heavy mesons

NASA Technical Reports Server (NTRS)

Badavi, Forooz F.; Norbury, John W.; Wilson, John W.; Townsend, Lawrence W.

1988-01-01

Linear and harmonic potential models are used in the nonrelativistic Schroedinger equation to obtain article mass spectra for mesons as bound states of quarks. The main emphasis is on the linear potential where exact solutions of the S-state eigenvalues and eigenfunctions and the asymptotic solution for the higher order partial wave are obtained. A study of the accuracy of two analytical energy level formulas as applied to heavy mesons is also included. Cornwall's formula is found to be particularly accurate and useful as a predictor of heavy quarkonium states. Exact solution for all partial waves of eigenvalues and eigenfunctions for a harmonic potential is also obtained and compared with the calculated discrete spectra of the linear potential. Detailed derivations of the eigenvalues and eigenfunctions of the linear and harmonic potentials are presented in appendixes.

Nonlinear Thermal Instability in Compressible Viscous Flows Without Heat Conductivity

NASA Astrophysics Data System (ADS)

Jiang, Fei

2018-04-01

We investigate the thermal instability of a smooth equilibrium state, in which the density function satisfies Schwarzschild's (instability) condition, to a compressible heat-conducting viscous flow without heat conductivity in the presence of a uniform gravitational field in a three-dimensional bounded domain. We show that the equilibrium state is linearly unstable by a modified variational method. Then, based on the constructed linearly unstable solutions and a local well-posedness result of classical solutions to the original nonlinear problem, we further construct the initial data of linearly unstable solutions to be the one of the original nonlinear problem, and establish an appropriate energy estimate of Gronwall-type. With the help of the established energy estimate, we finally show that the equilibrium state is nonlinearly unstable in the sense of Hadamard by a careful bootstrap instability argument.

Quadrupolar, Triple [Delta]-Function Potential in One Dimension

ERIC Educational Resources Information Center

Patil, S. H.

2009-01-01

The energy and parity eigenstates for quadrupolar, triple [delta]-function potential are analysed. Using the analytical solutions in specific domains, simple expressions are obtained for even- and odd-parity bound-state energies. The Heisenberg uncertainty product is observed to have a minimum for a specific strength of the potential. The…

Discrete diffraction managed solitons: Threshold phenomena and rapid decay for general nonlinearities

NASA Astrophysics Data System (ADS)

Choi, Mi-Ran; Hundertmark, Dirk; Lee, Young-Ran

2017-10-01

We prove a threshold phenomenon for the existence/non-existence of energy minimizing solitary solutions of the diffraction management equation for strictly positive and zero average diffraction. Our methods allow for a large class of nonlinearities; they are, for example, allowed to change sign, and the weakest possible condition, it only has to be locally integrable, on the local diffraction profile. The solutions are found as minimizers of a nonlinear and nonlocal variational problem which is translation invariant. There exists a critical threshold λcr such that minimizers for this variational problem exist if their power is bigger than λcr and no minimizers exist with power less than the critical threshold. We also give simple criteria for the finiteness and strict positivity of the critical threshold. Our proof of existence of minimizers is rather direct and avoids the use of Lions' concentration compactness argument. Furthermore, we give precise quantitative lower bounds on the exponential decay rate of the diffraction management solitons, which confirm the physical heuristic prediction for the asymptotic decay rate. Moreover, for ground state solutions, these bounds give a quantitative lower bound for the divergence of the exponential decay rate in the limit of vanishing average diffraction. For zero average diffraction, we prove quantitative bounds which show that the solitons decay much faster than exponentially. Our results considerably extend and strengthen the results of Hundertmark and Lee [J. Nonlinear Sci. 22, 1-38 (2012) and Commun. Math. Phys. 309(1), 1-21 (2012)].

Computational modeling of chemical reactions and interstitial growth and remodeling involving charged solutes and solid-bound molecules

PubMed Central

Nims, Robert J.; Maas, Steve; Weiss, Jeffrey A.

2014-01-01

Mechanobiological processes are rooted in mechanics and chemistry, and such processes may be modeled in a framework that couples their governing equations starting from fundamental principles. In many biological applications, the reactants and products of chemical reactions may be electrically charged, and these charge effects may produce driving forces and constraints that significantly influence outcomes. In this study, a novel formulation and computational implementation are presented for modeling chemical reactions in biological tissues that involve charged solutes and solid-bound molecules within a deformable porous hydrated solid matrix, coupling mechanics with chemistry while accounting for electric charges. The deposition or removal of solid-bound molecules contributes to the growth and remodeling of the solid matrix; in particular, volumetric growth may be driven by Donnan osmotic swelling, resulting from charged molecular species fixed to the solid matrix. This formulation incorporates the state of strain as a state variable in the production rate of chemical reactions, explicitly tying chemistry with mechanics for the purpose of modeling mechanobiology. To achieve these objectives, this treatment identifies the specific theoretical and computational challenges faced in modeling complex systems of interacting neutral and charged constituents while accommodating any number of simultaneous reactions where reactants and products may be modeled explicitly or implicitly. Several finite element verification problems are shown to agree with closed-form analytical solutions. An illustrative tissue engineering analysis demonstrates tissue growth and swelling resulting from the deposition of chondroitin sulfate, a charged solid-bound molecular species. This implementation is released in the open-source program FEBio (www.febio.org). The availability of this framework may be particularly beneficial to optimizing tissue engineering culture systems by examining the influence of nutrient availability on the evolution of inhomogeneous tissue composition and mechanical properties, the evolution of construct dimensions with growth, the influence of solute and solid matrix electric charge on the transport of cytokines, the influence of binding kinetics on transport, the influence of loading on binding kinetics, and the differential growth response to dynamically loaded versus free-swelling culture conditions. PMID:24558059

Computational modeling of chemical reactions and interstitial growth and remodeling involving charged solutes and solid-bound molecules.

PubMed

Ateshian, Gerard A; Nims, Robert J; Maas, Steve; Weiss, Jeffrey A

2014-10-01

Mechanobiological processes are rooted in mechanics and chemistry, and such processes may be modeled in a framework that couples their governing equations starting from fundamental principles. In many biological applications, the reactants and products of chemical reactions may be electrically charged, and these charge effects may produce driving forces and constraints that significantly influence outcomes. In this study, a novel formulation and computational implementation are presented for modeling chemical reactions in biological tissues that involve charged solutes and solid-bound molecules within a deformable porous hydrated solid matrix, coupling mechanics with chemistry while accounting for electric charges. The deposition or removal of solid-bound molecules contributes to the growth and remodeling of the solid matrix; in particular, volumetric growth may be driven by Donnan osmotic swelling, resulting from charged molecular species fixed to the solid matrix. This formulation incorporates the state of strain as a state variable in the production rate of chemical reactions, explicitly tying chemistry with mechanics for the purpose of modeling mechanobiology. To achieve these objectives, this treatment identifies the specific theoretical and computational challenges faced in modeling complex systems of interacting neutral and charged constituents while accommodating any number of simultaneous reactions where reactants and products may be modeled explicitly or implicitly. Several finite element verification problems are shown to agree with closed-form analytical solutions. An illustrative tissue engineering analysis demonstrates tissue growth and swelling resulting from the deposition of chondroitin sulfate, a charged solid-bound molecular species. This implementation is released in the open-source program FEBio ( www.febio.org ). The availability of this framework may be particularly beneficial to optimizing tissue engineering culture systems by examining the influence of nutrient availability on the evolution of inhomogeneous tissue composition and mechanical properties, the evolution of construct dimensions with growth, the influence of solute and solid matrix electric charge on the transport of cytokines, the influence of binding kinetics on transport, the influence of loading on binding kinetics, and the differential growth response to dynamically loaded versus free-swelling culture conditions.

Generalization of the Hartree-Fock approach to collision processes

NASA Astrophysics Data System (ADS)

Hahn, Yukap

1997-06-01

The conventional Hartree and Hartree-Fock approaches for bound states are generalized to treat atomic collision processes. All the single-particle orbitals, for both bound and scattering states, are determined simultaneously by requiring full self-consistency. This generalization is achieved by introducing two Ansäauttze: (a) the weak asymptotic boundary condition, which maintains the correct scattering energy and target orbitals with correct number of nodes, and (b) square integrable amputated scattering functions to generate self-consistent field (SCF) potentials for the target orbitals. The exact initial target and final-state asymptotic wave functions are not required and thus need not be specified a priori, as they are determined simultaneously by the SCF iterations. To check the asymptotic behavior of the solution, the theory is applied to elastic electron-hydrogen scattering at low energies. The solution is found to be stable and the weak asymptotic condition is sufficient to produce the correct scattering amplitudes. The SCF potential for the target orbital shows the strong penetration by the projectile electron during the collision, but the exchange term tends to restore the original form. Potential applicabilities of this extension are discussed, including the treatment of ionization and shake-off processes.

Mitochondrial Hsp90 is a ligand-activated molecular chaperone coupling ATP binding to dimer closure through a coiled-coil intermediate

PubMed Central

Sung, Nuri; Lee, Jungsoon; Kim, Ji-Hyun; Chang, Changsoo; Joachimiak, Andrzej; Lee, Sukyeong; Tsai, Francis T. F.

2016-01-01

Heat-shock protein of 90 kDa (Hsp90) is an essential molecular chaperone that adopts different 3D structures associated with distinct nucleotide states: a wide-open, V-shaped dimer in the apo state and a twisted, N-terminally closed dimer with ATP. Although the N domain is known to mediate ATP binding, how Hsp90 senses the bound nucleotide and facilitates dimer closure remains unclear. Here we present atomic structures of human mitochondrial Hsp90N (TRAP1N) and a composite model of intact TRAP1 revealing a previously unobserved coiled-coil dimer conformation that may precede dimer closure and is conserved in intact TRAP1 in solution. Our structure suggests that TRAP1 normally exists in an autoinhibited state with the ATP lid bound to the nucleotide-binding pocket. ATP binding displaces the ATP lid that signals the cis-bound ATP status to the neighboring subunit in a highly cooperative manner compatible with the coiled-coil intermediate state. We propose that TRAP1 is a ligand-activated molecular chaperone, which couples ATP binding to dramatic changes in local structure required for protein folding. PMID:26929380

On the Klein–Gordon oscillator subject to a Coulomb-type potential

DOE Office of Scientific and Technical Information (OSTI.GOV)

Bakke, K., E-mail: kbakke@fisica.ufpb.br; Furtado, C., E-mail: furtado@fisica.ufpb.br

2015-04-15

By introducing the scalar potential as modification in the mass term of the Klein–Gordon equation, the influence of a Coulomb-type potential on the Klein–Gordon oscillator is investigated. Relativistic bound states solutions are achieved to both attractive and repulsive Coulomb-type potentials and the arising of a quantum effect characterized by the dependence of angular frequency of the Klein–Gordon oscillator on the quantum numbers of the system is shown. - Highlights: • Interaction between the Klein–Gordon oscillator and a modified mass term. • Relativistic bound states for both attractive and repulsive Coulomb-type potentials. • Dependence of the Klein–Gordon oscillator frequency on themore » quantum numbers. • Relativistic analogue of a position-dependent mass system.« less

Fast Bound Methods for Large Scale Simulation with Application for Engineering Optimization

NASA Technical Reports Server (NTRS)

Patera, Anthony T.; Peraire, Jaime; Zang, Thomas A. (Technical Monitor)

2002-01-01

In this work, we have focused on fast bound methods for large scale simulation with application for engineering optimization. The emphasis is on the development of techniques that provide both very fast turnaround and a certificate of Fidelity; these attributes ensure that the results are indeed relevant to - and trustworthy within - the engineering context. The bound methodology which underlies this work has many different instantiations: finite element approximation; iterative solution techniques; and reduced-basis (parameter) approximation. In this grant we have, in fact, treated all three, but most of our effort has been concentrated on the first and third. We describe these below briefly - but with a pointer to an Appendix which describes, in some detail, the current "state of the art."

Classification of billiard motions in domains bounded by confocal parabolas

DOE Office of Scientific and Technical Information (OSTI.GOV)

Fokicheva, V V

2014-08-01

We consider the billiard dynamical system in a domain bounded by confocal parabolas. We describe such domains in which the billiard problem can be correctly stated. In each such domain we prove the integrability for the system, analyse the arising Liouville foliation, and calculate the invariant of Liouville equivalence--the so-called marked molecule. It turns out that billiard systems in certain parabolic domains have the same closures of solutions (integral trajectories) as the systems of Goryachev-Chaplygin-Sretenskii and Joukowski at suitable energy levels. We also describe the billiard motion in noncompact domains bounded by confocal parabolas, namely, we describe the topology of themore » Liouville foliation in terms of rough molecules. Bibliography: 16 titles.« less

A linear quadratic regulator approach to the stabilization of uncertain linear systems

NASA Technical Reports Server (NTRS)

Shieh, L. S.; Sunkel, J. W.; Wang, Y. J.

1990-01-01

This paper presents a linear quadratic regulator approach to the stabilization of uncertain linear systems. The uncertain systems under consideration are described by state equations with the presence of time-varying unknown-but-bounded uncertainty matrices. The method is based on linear quadratic regulator (LQR) theory and Liapunov stability theory. The robust stabilizing control law for a given uncertain system can be easily constructed from the symmetric positive-definite solution of the associated augmented Riccati equation. The proposed approach can be applied to matched and/or mismatched systems with uncertainty matrices in which only their matrix norms are bounded by some prescribed values and/or their entries are bounded by some prescribed constraint sets. Several numerical examples are presented to illustrate the results.

A performability solution method for degradable nonrepairable systems

NASA Technical Reports Server (NTRS)

Furchtgott, D. G.; Meyer, J. F.

1984-01-01

The present performability model-solving algorithm identifies performance with 'reward', representing the state behavior of a system S by a finite-state stochastic process and determining reward by means of reward rates that are associated with the states of the base model. A general method is obtained for determining the probability distribution function of the performance (reward) variable, and therefore the performability, of the corresponding system. This is done for bounded utilization periods, and the result is an integral expression which is either analytically or numerically solvable.

A point particle model of lightly bound skyrmions

NASA Astrophysics Data System (ADS)

Gillard, Mike; Harland, Derek; Kirk, Elliot; Maybee, Ben; Speight, Martin

2017-04-01

A simple model of the dynamics of lightly bound skyrmions is developed in which skyrmions are replaced by point particles, each carrying an internal orientation. The model accounts well for the static energy minimizers of baryon number 1 ≤ B ≤ 8 obtained by numerical simulation of the full field theory. For 9 ≤ B ≤ 23, a large number of static solutions of the point particle model are found, all closely resembling size B subsets of a face centred cubic lattice, with the particle orientations dictated by a simple colouring rule. Rigid body quantization of these solutions is performed, and the spin and isospin of the corresponding ground states extracted. As part of the quantization scheme, an algorithm to compute the symmetry group of an oriented point cloud, and to determine its corresponding Finkelstein-Rubinstein constraints, is devised.

Halogen bonding in solution: thermodynamics and applications.

PubMed

Beale, Thomas M; Chudzinski, Michael G; Sarwar, Mohammed G; Taylor, Mark S

2013-02-21

Halogen bonds are noncovalent interactions in which covalently bound halogens act as electrophilic species. The utility of halogen bonding for controlling self-assembly in the solid state is evident from a broad spectrum of applications in crystal engineering and materials science. Until recently, it has been less clear whether, and to what extent, halogen bonding could be employed to influence conformation, binding or reactivity in the solution phase. This tutorial review summarizes and interprets solution-phase thermodynamic data for halogen bonding interactions obtained over the past six decades and highlights emerging applications in molecular recognition, medicinal chemistry and catalysis.

A Self-Stabilizing Hybrid-Fault Tolerant Synchronization Protocol

NASA Technical Reports Server (NTRS)

Malekpour, Mahyar R.

2014-01-01

In this report we present a strategy for solving the Byzantine general problem for self-stabilizing a fully connected network from an arbitrary state and in the presence of any number of faults with various severities including any number of arbitrary (Byzantine) faulty nodes. Our solution applies to realizable systems, while allowing for differences in the network elements, provided that the number of arbitrary faults is not more than a third of the network size. The only constraint on the behavior of a node is that the interactions with other nodes are restricted to defined links and interfaces. Our solution does not rely on assumptions about the initial state of the system and no central clock nor centrally generated signal, pulse, or message is used. Nodes are anonymous, i.e., they do not have unique identities. We also present a mechanical verification of a proposed protocol. A bounded model of the protocol is verified using the Symbolic Model Verifier (SMV). The model checking effort is focused on verifying correctness of the bounded model of the protocol as well as confirming claims of determinism and linear convergence with respect to the self-stabilization period. We believe that our proposed solution solves the general case of the clock synchronization problem.

Confining potential in momentum space

NASA Technical Reports Server (NTRS)

Norbury, John W.; Kahana, David E.; Maung, Khin Maung

1992-01-01

A method is presented for the solution in momentum space of the bound state problem with a linear potential in r space. The potential is unbounded at large r leading to a singularity at small q. The singularity is integrable, when regulated by exponentially screening the r-space potential, and is removed by a subtraction technique. The limit of zero screening is taken analytically, and the numerical solution of the subtracted integral equation gives eigenvalues and wave functions in good agreement with position space calculations.

Theoretical and material studies on thin-film electroluminescent devices

NASA Technical Reports Server (NTRS)

Summers, C. J.; Brennan, K. F.

1986-01-01

A theoretical study of resonant tunneling in multilayered heterostructures is presented based on an exact solution of the Schroedinger equation under the application of a constant electric field. By use of the transfer matrix approach, the transmissivity of the structure is determined as a function of the incident electron energy. The approach presented is easily extended to many layer structures where it is more accurate than other existing transfer matrix or WKB models. The transmission resonances are compared to the bound state energies calculated for a finite square well under bias using either an asymmetric square well model or the exact solution of an infinite square well under the application of an electric field. The results show good agreement with other existing models as well as with the bound state energies. The calculations were then applied to a new superlattice structure, the variablly spaced superlattice energy filter, (VSSEP) which is designed such that under bias the spatial quantization levels fully align. Based on these calculations, a new class of resonant tunneling superlattice devices can be designed.

Bilinear forms and soliton solutions for a fourth-order variable-coefficient nonlinear Schrödinger equation in an inhomogeneous Heisenberg ferromagnetic spin chain or an alpha helical protein

NASA Astrophysics Data System (ADS)

Yang, Jin-Wei; Gao, Yi-Tian; Wang, Qi-Min; Su, Chuan-Qi; Feng, Yu-Jie; Yu, Xin

2016-01-01

In this paper, a fourth-order variable-coefficient nonlinear Schrödinger equation is studied, which might describe a one-dimensional continuum anisotropic Heisenberg ferromagnetic spin chain with the octuple-dipole interaction or an alpha helical protein with higher-order excitations and interactions under continuum approximation. With the aid of auxiliary function, we derive the bilinear forms and corresponding constraints on the variable coefficients. Via the symbolic computation, we obtain the Lax pair, infinitely many conservation laws, one-, two- and three-soliton solutions. We discuss the influence of the variable coefficients on the solitons. With different choices of the variable coefficients, we obtain the parabolic, cubic, and periodic solitons, respectively. We analyse the head-on and overtaking interactions between/among the two and three solitons. Interactions between a bound state and a single soliton are displayed with different choices of variable coefficients. We also derive the quasi-periodic formulae for the three cases of the bound states.

The role of free and bound water in irradiation preservation: Free radical damage as a function of the physical state of water

USGS Publications Warehouse

Wedemeyer, Gary; Dollar, A.M.

1964-01-01

English sole fillets previously equilibrated with aqueous 0.1% cysteine were dehydrated by three methods to moisture levels ranging from 2 to 72%. Model systems using cellulose to replace the fish tissue were also used. The samples were irradiated at 1 Mrad in an air, nitrogen, or oxygen atmosphere. The destruction of −SH groups was measured and related to the amount and physical state of the tissue water. As free water was removed, destruction steadily increased, reaching a maximum at about 20% moisture. Destruction decreased markedly at moisture levels below 10%, and calorimetric measurements confirmed that 10% moisture was about the level of bound water in this species. These data suggest that dehydration favors the reaction of solute molecules with free radicals formed in the free water of muscle cells. At moisture levels greater than about 20%, simple free radical recombination is more likely than reaction with solute molecules, while below 20% moisture the reverse is true. The calculated α values support this conclusion, as do the results from model systems using cellulose.

How fast can a black hole rotate?

NASA Astrophysics Data System (ADS)

Herdeiro, Carlos A. R.; Radu, Eugen

2015-11-01

Kerr black holes (BHs) have their angular momentum, J, bounded by their mass, M: Jc ≤ GM2. There are, however, known BH solutions violating this Kerr bound. We propose a very simple universal bound on the rotation, rather than on the angular momentum, of four-dimensional, stationary and axisymmetric, asymptotically flat BHs, given in terms of an appropriately defined horizon linear velocity, vH. The vH bound is simply that vH cannot exceed the velocity of light. We verify the vH bound for known BH solutions, including some that violate the Kerr bound, and conjecture that only extremal Kerr BHs saturate the vH bound.

Assessment of chemical exchange in tryptophan-albumin solution through (19)F multicomponent transverse relaxation dispersion analysis.

PubMed

Lin, Ping-Chang

2015-06-01

A number of NMR methods possess the capability of probing chemical exchange dynamics in solution. However, certain drawbacks limit the applications of these NMR approaches, particularly, to a complex system. Here, we propose a procedure that integrates the regularized nonnegative least squares (NNLS) analysis of multiexponential T2 relaxation into Carr-Purcell-Meiboom-Gill (CPMG) relaxation dispersion experiments to probe chemical exchange in a multicompartmental system. The proposed procedure was validated through analysis of (19)F T2 relaxation data of 6-fluoro-DL-tryptophan in a two-compartment solution with and without bovine serum albumin. Given the regularized NNLS analysis of a T2 relaxation curve acquired, for example, at the CPMG frequency υ CPMG  = 125, the nature of two distinct peaks in the associated T2 distribution spectrum indicated 6-fluoro-DL-tryptophan either retaining the free state, with geometric mean */multiplicative standard deviation (MSD) = 1851.2 ms */1.51, or undergoing free/albumin-bound interconversion, with geometric mean */MSD = 236.8 ms */1.54, in the two-compartment system. Quantities of the individual tryptophan species were accurately reflected by the associated T2 peak areas, with an interconversion state-to-free state ratio of 0.45 ± 0.11. Furthermore, the CPMG relaxation dispersion analysis estimated the exchange rate between the free and albumin-bound states in this fluorinated tryptophan analog and the corresponding dissociation constant of the fluorinated tryptophan-albumin complex in the chemical-exchanging, two-compartment system.

Optical soliton solutions, periodic wave solutions and complexitons of the cubic Schrödinger equation with a bounded potential

NASA Astrophysics Data System (ADS)

Yan, Xue-Wei; Tian, Shou-Fu; Dong, Min-Jie; Zou, Li

2018-01-01

In this paper, we consider the cubic Schrödinger equation with a bounded potential, which describes the propagation properties of optical soliton solutions. By employing an ansatz method, we precisely derive the bright and dark soliton solutions of the equation. Moreover, we obtain three classes of analytic periodic wave solutions expressed in terms of the Jacobi's elliptic functions including cn ,sn and dn functions. Finally, by using a tanh function method, its complexitons solutions are derived in a very natural way. It is hoped that our results can enrich the nonlinear dynamical behaviors of the cubic Schrödinger equation with a bounded potential.

Lower Bounds for Possible Singular Solutions for the Navier-Stokes and Euler Equations Revisited

NASA Astrophysics Data System (ADS)

Cortissoz, Jean C.; Montero, Julio A.

2018-03-01

In this paper we give optimal lower bounds for the blow-up rate of the \\dot{H}s( T^3) -norm, 1/25/2.

Picosecond absorption studies of photoinduced charge separation in polyelectrolyte bound aromatic chromophores

NASA Astrophysics Data System (ADS)

Shand, M. A.; Rodgers, M. A. J.; Webber, S. E.

1991-02-01

Picosecond absorption studies of photoinduced electron transfer between aromatic chromophores bound to polymethacrylic acid (P) and methylviologen (MV 2+ have been carried out in aqueous solution. The diphenylanthracene copolymer/viologen system at pH 2.8 shows the corresponding redox products DPA + rad and MV + rad arising from the singlet state of DPA with a forward rate constant of electron transfer of 2.6 × 10 9 s -1. At pH 9.0 the quenching of the S 1 state of DPA occurs with no charge separated products being observed. The pyrene copolymer shows no evidence of charge separated products at any pH in the range 2.8-9.0. It is proposed that the differences in the radical pair kinetics arise from differences in the degree of binding of the ground state complexes formed by the donor and acceptor species.

Remarks on High Reynolds Numbers Hydrodynamics and the Inviscid Limit

NASA Astrophysics Data System (ADS)

Constantin, Peter; Vicol, Vlad

2018-04-01

We prove that any weak space-time L^2 vanishing viscosity limit of a sequence of strong solutions of Navier-Stokes equations in a bounded domain of R^2 satisfies the Euler equation if the solutions' local enstrophies are uniformly bounded. We also prove that t-a.e. weak L^2 inviscid limits of solutions of 3D Navier-Stokes equations in bounded domains are weak solutions of the Euler equation if they locally satisfy a scaling property of their second-order structure function. The conditions imposed are far away from boundaries, and wild solutions of Euler equations are not a priori excluded in the limit.

Solution Structure of an Intramembrane Aspartyl Protease via Small Angle Neutron Scattering

DOE Office of Scientific and Technical Information (OSTI.GOV)

Naing, Swe-Htet; Oliver, Ryan C.; Weiss, Kevin L.

Intramembrane aspartyl proteases (IAPs) comprise one of four families of integral membrane proteases that hydrolyze substrates within the hydrophobic lipid bilayer. IAPs include signal peptide peptidase, which processes remnant signal peptides from nascent polypeptides in the endoplasmic reticulum, and presenilin, the catalytic component of the γ-secretase complex that processes Notch and amyloid precursor protein. Despite their broad biomedical reach, basic structure-function relationships of IAPs remain active areas of research. Characterization of membrane-bound proteins is notoriously challenging due to their inherently hydrophobic character. For IAPs, oligomerization state in solution is one outstanding question, with previous proposals for monomer, dimer, tetramer, andmore » octamer. Here we used small angle neutron scattering (SANS) to characterize n-dodecyl-β-D-maltopyranoside (DDM) detergent solutions containing and absent a microbial IAP ortholog. A unique feature of SANS is the ability to modulate the solvent composition to mask all but the enzyme of interest. The signal from the IAP was enhanced by deuteration and, uniquely, scattering from DDM and buffers were matched by the use of both tail-deuterated DDM and D 2O. The radius of gyration calculated for IAP and the corresponding ab initio consensus model are consistent with a monomer. The model is slightly smaller than the crystallographic IAP monomer, suggesting a more compact protein in solution compared with the crystal lattice. In conclusion, our study provides direct insight into the oligomeric state of purified IAP in surfactant solution, and demonstrates the utility of fully contrast-matching the detergent in SANS to characterize other intramembrane proteases and their membrane-bound substrates.« less

Solution Structure of an Intramembrane Aspartyl Protease via Small Angle Neutron Scattering

DOE PAGES

Naing, Swe-Htet; Oliver, Ryan C.; Weiss, Kevin L.; ...

2018-02-06

Intramembrane aspartyl proteases (IAPs) comprise one of four families of integral membrane proteases that hydrolyze substrates within the hydrophobic lipid bilayer. IAPs include signal peptide peptidase, which processes remnant signal peptides from nascent polypeptides in the endoplasmic reticulum, and presenilin, the catalytic component of the γ-secretase complex that processes Notch and amyloid precursor protein. Despite their broad biomedical reach, basic structure-function relationships of IAPs remain active areas of research. Characterization of membrane-bound proteins is notoriously challenging due to their inherently hydrophobic character. For IAPs, oligomerization state in solution is one outstanding question, with previous proposals for monomer, dimer, tetramer, andmore » octamer. Here we used small angle neutron scattering (SANS) to characterize n-dodecyl-β-D-maltopyranoside (DDM) detergent solutions containing and absent a microbial IAP ortholog. A unique feature of SANS is the ability to modulate the solvent composition to mask all but the enzyme of interest. The signal from the IAP was enhanced by deuteration and, uniquely, scattering from DDM and buffers were matched by the use of both tail-deuterated DDM and D 2O. The radius of gyration calculated for IAP and the corresponding ab initio consensus model are consistent with a monomer. The model is slightly smaller than the crystallographic IAP monomer, suggesting a more compact protein in solution compared with the crystal lattice. In conclusion, our study provides direct insight into the oligomeric state of purified IAP in surfactant solution, and demonstrates the utility of fully contrast-matching the detergent in SANS to characterize other intramembrane proteases and their membrane-bound substrates.« less

Improved Pedagogy for Linear Differential Equations by Reconsidering How We Measure the Size of Solutions

ERIC Educational Resources Information Center

Tisdell, Christopher C.

2017-01-01

For over 50 years, the learning of teaching of "a priori" bounds on solutions to linear differential equations has involved a Euclidean approach to measuring the size of a solution. While the Euclidean approach to "a priori" bounds on solutions is somewhat manageable in the learning and teaching of the proofs involving…

Bounded energy states in homogeneous turbulent shear flow: An alternative view

NASA Technical Reports Server (NTRS)

Bernard, Peter S.; Speziale, Charles G.

1990-01-01

The equilibrium structure of homogeneous turbulent shear flow is investigated from a theoretical standpoint. Existing turbulence models, in apparent agreement with physical and numerical experiments, predict an unbounded exponential time growth of the turbulent kinetic energy and dissipation rate; only the anisotropy tensor and turbulent time scale reach a structural equilibrium. It is shown that if vortex stretching is accounted for in the dissipation rate transport equation, then there can exist equilibrium solutions, with bounded energy states, where the turbulence production is balanced by its dissipation. Illustrative calculations are present for a k-epsilon model modified to account for vortex stretching. The calculations indicate an initial exponential time growth of the turbulent kinetic energy and dissipation rate for elapsed times that are as large as those considered in any of the previously conducted physical or numerical experiments on homogeneous shear flow. However, vortex stretching eventually takes over and forces a production-equals-dissipation equilibrium with bounded energy states. The validity of this result is further supported by an independent theoretical argument. It is concluded that the generally accepted structural equilibrium for homogeneous shear flow with unbounded component energies is in need of re-examination.

Archimedes Quadrature of the Parabola: A Mechanical View

ERIC Educational Resources Information Center

Oster, Thomas J.

2006-01-01

In his famous quadrature of the parabola, Archimedes found the area of the region bounded by a parabola and a chord. His method was to fill the region with infinitely many triangles each of whose area he could calculate. In his solution, he stated, without proof, three preliminary propositions about parabolas that were known in his time, but are…

D-Dimensional Dirac Equation for Energy-Dependent Pseudoharmonic and Mie-type Potentials via SUSYQM

NASA Astrophysics Data System (ADS)

A. N., Ikot; Hassanabadi, H.; Maghsoodi, E.; Zarrinkamar, S.

2014-04-01

We investigate the approximate solution of the Dirac equation for energy-dependent pseudoharmonic and Mie-type potentials under the pseudospin and spin symmetries using the supersymmetry quantum mechanics. We obtain the bound-state energy equation in an analytical manner and comment on the system behavior via various figures and tables.

Structural Characterization of the Binding of Myosin*ADP*Pi to Actin in Permeabilized Rabbit Psoas Muscle

DOE Office of Scientific and Technical Information (OSTI.GOV)

Xu,S.; Gu, J.; Belknap, B.

2006-01-01

When myosin is attached to actin in a muscle cell, various structures in the filaments are formed. The two strongly bound states (A{center_dot}M{center_dot}ADP and A{center_dot}M) and the weakly bound A{center_dot}M{center_dot}ATP states are reasonably well understood. The orientation of the strongly bound myosin heads is uniform ('stereospecific' attachment), and the attached heads exhibit little spatial fluctuation. In the prehydrolysis weakly bound A{center_dot}M{center_dot}ATP state, the orientations of the attached myosin heads assume a wide range of azimuthal and axial angles, indicating considerable flexibility in the myosin head. The structure of the other weakly bound state, A{center_dot}M{center_dot}ADP{center_dot}P{sub i}, however, is poorly understood. Thismore » state is thought to be the critical pre-power-stroke state, poised to make the transition to the strongly binding, force-generating states, and hence it is of particular interest for understanding the mechanism of contraction. However, because of the low affinity between myosin and actin in the A{center_dot}M{center_dot}ADP{center_dot}P{sub i} state, the structure of this state has eluded determination both in isolated form and in muscle cells. With the knowledge recently gained in the structures of the weakly binding M{center_dot}ATP, M{center_dot}ADP{center_dot}P{sub i} states and the weakly attached A{center_dot}M{center_dot}ATP state in muscle fibers, it is now feasible to delineate the in vivo structure of the attached state of A{center_dot}M{center_dot}ADP{center_dot}P{sub i}. The series of experiments presented in this article were carried out under relaxing conditions at 25{sup o}C, where {approx}95% of the myosin heads in the skinned rabbit psoas muscle contain the hydrolysis products. The affinity for actin is enhanced by adding polyethylene glycol (PEG) or by lowering the ionic strength in the bathing solution. Solution kinetics and binding constants were determined in the presence and in the absence of PEG. When the binding between actin and myosin was increased, both the myosin layer lines and the actin layer lines increased in intensity, but the intensity profiles did not change. The configuration (mode) of attachment in the A{center_dot}M{center_dot}ADP{center_dot}P{sub i} state is thus unique among the intermediate attached states of the cross-bridge ATP hydrolysis cycle. One of the simplest explanations is that both myosin filaments and actin filaments are stabilized (e.g., undergo reduced spatial fluctuations) by the attachment. The alignment of the myosin heads in the thick filaments and the alignment of the actin monomers in the thin filaments are improved as a result. The compact atomic structure of M{center_dot}ADP{center_dot}P{sub i} with strongly coupled domains may contribute to the unique attachment configuration: the 'primed' myosin heads may function as 'transient struts' when attached to the thin filaments.« less

Rigorous Statistical Bounds in Uncertainty Quantification for One-Layer Turbulent Geophysical Flows

NASA Astrophysics Data System (ADS)

Qi, Di; Majda, Andrew J.

2018-04-01

Statistical bounds controlling the total fluctuations in mean and variance about a basic steady-state solution are developed for the truncated barotropic flow over topography. Statistical ensemble prediction is an important topic in weather and climate research. Here, the evolution of an ensemble of trajectories is considered using statistical instability analysis and is compared and contrasted with the classical deterministic instability for the growth of perturbations in one pointwise trajectory. The maximum growth of the total statistics in fluctuations is derived relying on the statistical conservation principle of the pseudo-energy. The saturation bound of the statistical mean fluctuation and variance in the unstable regimes with non-positive-definite pseudo-energy is achieved by linking with a class of stable reference states and minimizing the stable statistical energy. Two cases with dependence on initial statistical uncertainty and on external forcing and dissipation are compared and unified under a consistent statistical stability framework. The flow structures and statistical stability bounds are illustrated and verified by numerical simulations among a wide range of dynamical regimes, where subtle transient statistical instability exists in general with positive short-time exponential growth in the covariance even when the pseudo-energy is positive-definite. Among the various scenarios in this paper, there exist strong forward and backward energy exchanges between different scales which are estimated by the rigorous statistical bounds.

How hairpin vortices emerge from exact invariant solutions

NASA Astrophysics Data System (ADS)

Schneider, Tobias M.; Farano, Mirko; de Palma, Pietro; Robinet, Jean-Christoph; Cherubini, Stefania

2017-11-01

Hairpin vortices are among the most commonly observed flow structures in wall-bounded shear flows. However, within the dynamical system approach to turbulence, those structures have not yet been described. They are not captured by known exact invariant solutions of the Navier-Stokes equations nor have other state-space structures supporting hairpins been identified. We show that hairpin structures are observed along an optimally growing trajectory leaving a well known exact traveling wave solution of plane Poiseuille flow. The perturbation triggering hairpins does not correspond to an unstable mode of the exact traveling wave but lies in the stable manifold where non-normality causes strong transient amplification.

The Aharonov-Bohm effect and Tonomura et al. experiments: Rigorous results

DOE Office of Scientific and Technical Information (OSTI.GOV)

Ballesteros, Miguel; Weder, Ricardo

The Aharonov-Bohm effect is a fundamental issue in physics. It describes the physically important electromagnetic quantities in quantum mechanics. Its experimental verification constitutes a test of the theory of quantum mechanics itself. The remarkable experiments of Tonomura et al. ['Observation of Aharonov-Bohm effect by electron holography', Phys. Rev. Lett 48, 1443 (1982) and 'Evidence for Aharonov-Bohm effect with magnetic field completely shielded from electron wave', Phys. Rev. Lett 56, 792 (1986)] are widely considered as the only experimental evidence of the physical existence of the Aharonov-Bohm effect. Here we give the first rigorous proof that the classical ansatz of Aharonovmore » and Bohm of 1959 ['Significance of electromagnetic potentials in the quantum theory', Phys. Rev. 115, 485 (1959)], that was tested by Tonomura et al., is a good approximation to the exact solution to the Schroedinger equation. This also proves that the electron, that is, represented by the exact solution, is not accelerated, in agreement with the recent experiment of Caprez et al. in 2007 ['Macroscopic test of the Aharonov-Bohm effect', Phys. Rev. Lett. 99, 210401 (2007)], that shows that the results of the Tonomura et al. experiments can not be explained by the action of a force. Under the assumption that the incoming free electron is a Gaussian wave packet, we estimate the exact solution to the Schroedinger equation for all times. We provide a rigorous, quantitative error bound for the difference in norm between the exact solution and the Aharonov-Bohm Ansatz. Our bound is uniform in time. We also prove that on the Gaussian asymptotic state the scattering operator is given by a constant phase shift, up to a quantitative error bound that we provide. Our results show that for intermediate size electron wave packets, smaller than the ones used in the Tonomura et al. experiments, quantum mechanics predicts the results observed by Tonomura et al. with an error bound smaller than 10{sup -99}. It would be quite interesting to perform experiments with electron wave packets of intermediate size. Furthermore, we provide a physical interpretation of our error bound.« less

Process for separating and recovering an anionic dye from an aqueous solution

DOEpatents

Rogers, Robin; Horwitz, E. Philip; Bond, Andrew H.

1998-01-01

A solid/liquid phase process for the separation and recovery of an anionic dye from an aqueous solution is disclosed. The solid phase comprises separation particles having surface-bonded poly(ethylene glycol) groups, whereas the aqueous solution from which the anionic dye molecules are separated contains a poly(ethylene glycol) liquid/liquid biphase-forming amount of a dissolved lyotropic salt. After contact between the aqueous solution and separation particles, the anionic dye is bound to the particles. The bound anionic dye molecules are freed from the separation particles by contacting the anionic dye-bound particles with an aqueous solution that does not contain a poly(ethylene glycol) liquid/liquid biphase-forming amount of a dissolved lyotropic salt to form an aqueous anionic dye solution whose anionic dye concentration is preferably higher than that of the initial dye-containing solution.

On the arbitrary l-wave solutions of the deformed hyperbolic manning-rosen potential including an improved approximation to the orbital centrifugal term

NASA Astrophysics Data System (ADS)

Xu, Chun-Long; Zhang, Min-Cang

2017-01-01

The arbitrary l-wave solutions to the Schrödinger equation for the deformed hyperbolic Manning-Rosen potential is investigated analytically by using the Nikiforov-Uvarov method, the centrifugal term is treated with an improved Greene and Aldrich's approximation scheme. The wavefunctions depend on the deformation parameter q, which is expressed in terms of the Jocobi polynomial or the hypergeometric function. The bound state energy is obtained, and the discrete spectrum is shown to be independent of the deformation parameter q.

On numerical solution of the Schrödinger equation: the shooting method revisited

NASA Astrophysics Data System (ADS)

Indjin, D.; Todorović, G.; Milanović, V.; Ikonić, Z.

1995-09-01

An alternative formulation of the "shooting" method for a numerical solution of the Schrödinger equation is described for cases of general asymmetric one-dimensional potential (planar geometry), and spherically symmetric potential. The method relies on matching the asymptotic wavefunctions and the potential core region wavefunctions, in course of finding bound states energies. It is demonstrated in the examples of Morse and Kratzer potentials, where a high accuracy of the calculated eigenvalues is found, together with a considerable saving of the computation time.

Two-dimensional description of surface-bounded exospheres with application to the migration of water molecules on the Moon

NASA Astrophysics Data System (ADS)

Schorghofer, Norbert

2015-05-01

On the Moon, water molecules and other volatiles are thought to migrate along ballistic trajectories. Here, this migration process is described in terms of a two-dimensional partial differential equation for the surface concentration, based on the probability distribution of thermal ballistic hops. A random-walk model, a corresponding diffusion coefficient, and a continuum description are provided. In other words, a surface-bounded exosphere is described purely in terms of quantities on the surface, which can provide computational and conceptual advantages. The derived continuum equation can be used to calculate the steady-state distribution of the surface concentration of volatile water molecules. An analytic steady-state solution is obtained for an equatorial ring; it reveals the width and mass of the pileup of molecules at the morning terminator.

The C2'- and C3'-endo equilibrium for AMP molecules bound in the cystathionine-beta-synthase domain.

PubMed

Feng, Na; Qi, Chao; Hou, Yan-Jie; Zhang, Ying; Wang, Da-Cheng; Li, De-Feng

2018-03-04

The equilibrium between C2'- and C3'-endo conformations of nucleotides in solution, as well as their polymers DNA and RNA, has been well studied in previous work. However, this equilibrium of nucleotides in their binding state remains unclear. We observed two AMP molecules, in C3'- and C2'-endo conformations respectively, simultaneously bound to a cystathionine-beta-synthase (CBS) domain dimer of the magnesium and cobalt efflux protein CorC in the crystallographic study. The C2'-endo AMP molecule assumes the higher sugar pucker energy and one more hydrogen bond with the protein than the C3'-endo molecule does. The balance between the high sugar pucker energy and the low binding energy suggests an equilibrium or switch between C2'- and C3'-endo conformations of the bound nucleotides. Our work challenge the previous hypothesis that the ribose of the bound nucleotides would be locked in a fixed conformation. Copyright © 2018 Elsevier Inc. All rights reserved.

Time- and angle-resolved photoemission spectroscopy of hydrated electrons near a liquid water surface.

PubMed

Yamamoto, Yo-ichi; Suzuki, Yoshi-Ichi; Tomasello, Gaia; Horio, Takuya; Karashima, Shutaro; Mitríc, Roland; Suzuki, Toshinori

2014-05-09

We present time- and angle-resolved photoemission spectroscopy of trapped electrons near liquid surfaces. Photoemission from the ground state of a hydrated electron at 260 nm is found to be isotropic, while anisotropic photoemission is observed for the excited states of 1,4-diazabicyclo[2,2,2]octane and I- in aqueous solutions. Our results indicate that surface and subsurface species create hydrated electrons in the bulk side. No signature of a surface-bound electron has been observed.

Preparation and Characterization of Fluorescent Derivatives of Chicken Egg White Lysozyme

NASA Technical Reports Server (NTRS)

Sumida, John; Forsythe, Elizabeth; Pusey, Marc

2000-01-01

Fluorescence is one of the most versatile and powerful tools for the study of macromolecules. While most proteins are intrinsically fluorescent, working at crystallization concentrations require the use of covalently prepared derivatives added as tracers. This approach requires derivatives that do not markedly affect the crystal packing. We have prepared a number of fluorescent derivatives of chicken egg white lysozyme with probes bound to one of two different sites on the protein molecule. Lucifer yellow, cascade blue, and 5-(2-aminoethyl)aminonapthalene-l-sulfonic acid (EDANS) have been attached to the side chain carboxyl of asp101 using a carbodiimide coupling procedure. asp101 lies within the active site cleft, and it is believed that the probes are at least partially "buried" within that cleft. Lucifer yellow and MANS probes with iodoacetamide reactive groups have been bound to hisl5, located on the "back side" of the molecule relative to the active site. The fluorescently labeled protein is readily purified from the starting material by cation exchange chromatography. All the derivatives fluoresce in both the solution and the crystalline states. Fluorescence characterization has focused on determining the bound probe quantum yields, lifetimes, absorption and emission spectra, and quenching by added solutes in comparison to the free probe. No appreciable changes are found in the lifetimes of any of the probes except for cascade blue, where Tau(sub free) = 3.52 ns vrs Tau(sub bound) = 2.8 ns. Spectral shifts are found in most cases. Particularly strong quenching upon binding is found in the case of the cascade blue derivative, likely due to probe interactions with the active site cleft. While none of the asp101 bound probes are well quenched by commonly employed solutes, such as potassium and sodium iodide, acrylamide, primuline, the chloride salts of manganese, cesium, and cobalt, trifluoroacetamide, trichloroethanol, and thallium iodide, in those cases where quenching is observed the bound probe is less efficiently quenched relative to the free probe. This indicates that the bound probes are less accessible to the bulk solution, an expected finding for attachment within the active site cleft. Attempts have been made to bind other molecules to these sites, with varying success. Interestingly, all three probes contain one or more sulfonate ((Ar-S03)-) groups. We have not been successful in binding analogous probes without sulfate groups such as pyrene, or with derivatized sulfonate groups such as dansyl type probes, analogous to MANS but where the sulfonate group is derivatized, Ar-S02-N2C2H7. None of the probes is rigidly bound to the protein, i.e., they all have a probe motion superimposed on that of the protein.

Shift in the equilibrium between on and off states of the allosteric switch in Ras-GppNHp affected by small molecules and bulk solvent composition.

PubMed

Holzapfel, Genevieve; Buhrman, Greg; Mattos, Carla

2012-08-07

Ras GTPase cycles between its active GTP-bound form promoted by GEFs and its inactive GDP-bound form promoted by GAPs to affect the control of various cellular functions. It is becoming increasingly apparent that subtle regulation of the GTP-bound active state may occur through promotion of substates mediated by an allosteric switch mechanism that induces a disorder to order transition in switch II upon ligand binding at an allosteric site. We show with high-resolution structures that calcium acetate and either dithioerythritol (DTE) or dithiothreitol (DTT) soaked into H-Ras-GppNHp crystals in the presence of a moderate amount of poly(ethylene glycol) (PEG) can selectively shift the equilibrium to the "on" state, where the active site appears to be poised for catalysis (calcium acetate), or to what we call the "ordered off" state, which is associated with an anticatalytic conformation (DTE or DTT). We also show that the equilibrium is reversible in our crystals and dependent on the nature of the small molecule present. Calcium acetate binding in the allosteric site stabilizes the conformation observed in the H-Ras-GppNHp/NOR1A complex, and PEG, DTE, and DTT stabilize the anticatalytic conformation observed in the complex between the Ras homologue Ran and Importin-β. The small molecules are therefore selecting biologically relevant conformations in the crystal that are sampled by the disordered switch II in the uncomplexed GTP-bound form of H-Ras. In the presence of a large amount of PEG, the ordered off conformation predominates, whereas in solution, in the absence of PEG, switch regions appear to remain disordered in what we call the off state, unable to bind DTE.

Shift in the Equilibrium between On and Off States of the Allosteric Switch in Ras-GppNHp Affected by Small Molecules and Bulk Solvent Composition

DOE Office of Scientific and Technical Information (OSTI.GOV)

Holzapfel, Genevieve; Buhrman, Greg; Mattos, Carla

2012-08-31

Ras GTPase cycles between its active GTP-bound form promoted by GEFs and its inactive GDP-bound form promoted by GAPs to affect the control of various cellular functions. It is becoming increasingly apparent that subtle regulation of the GTP-bound active state may occur through promotion of substates mediated by an allosteric switch mechanism that induces a disorder to order transition in switch II upon ligand binding at an allosteric site. We show with high-resolution structures that calcium acetate and either dithioerythritol (DTE) or dithiothreitol (DTT) soaked into H-Ras-GppNHp crystals in the presence of a moderate amount of poly(ethylene glycol) (PEG) canmore » selectively shift the equilibrium to the 'on' state, where the active site appears to be poised for catalysis (calcium acetate), or to what we call the 'ordered off' state, which is associated with an anticatalytic conformation (DTE or DTT). We also show that the equilibrium is reversible in our crystals and dependent on the nature of the small molecule present. Calcium acetate binding in the allosteric site stabilizes the conformation observed in the H-Ras-GppNHp/NOR1A complex, and PEG, DTE, and DTT stabilize the anticatalytic conformation observed in the complex between the Ras homologue Ran and Importin-{beta}. The small molecules are therefore selecting biologically relevant conformations in the crystal that are sampled by the disordered switch II in the uncomplexed GTP-bound form of H-Ras. In the presence of a large amount of PEG, the ordered off conformation predominates, whereas in solution, in the absence of PEG, switch regions appear to remain disordered in what we call the off state, unable to bind DTE.« less

Closed-form solutions of performability. [modeling of a degradable buffer/multiprocessor system

NASA Technical Reports Server (NTRS)

Meyer, J. F.

1981-01-01

Methods which yield closed form performability solutions for continuous valued variables are developed. The models are similar to those employed in performance modeling (i.e., Markovian queueing models) but are extended so as to account for variations in structure due to faults. In particular, the modeling of a degradable buffer/multiprocessor system is considered whose performance Y is the (normalized) average throughput rate realized during a bounded interval of time. To avoid known difficulties associated with exact transient solutions, an approximate decomposition of the model is employed permitting certain submodels to be solved in equilibrium. These solutions are then incorporated in a model with fewer transient states and by solving the latter, a closed form solution of the system's performability is obtained. In conclusion, some applications of this solution are discussed and illustrated, including an example of design optimization.

The Biharmonic Oscillator and Asymmetric Linear Potentials: From Classical Trajectories to Momentum-Space Probability Densities in the Extreme Quantum Limit

ERIC Educational Resources Information Center

Ruckle, L. J.; Belloni, M.; Robinett, R. W.

2012-01-01

The biharmonic oscillator and the asymmetric linear well are two confining power-law-type potentials for which complete bound-state solutions are possible in both classical and quantum mechanics. We examine these problems in detail, beginning with studies of their trajectories in position and momentum space, evaluation of the classical probability…

Solving the chemical master equation using sliding windows

PubMed Central

2010-01-01

Background The chemical master equation (CME) is a system of ordinary differential equations that describes the evolution of a network of chemical reactions as a stochastic process. Its solution yields the probability density vector of the system at each point in time. Solving the CME numerically is in many cases computationally expensive or even infeasible as the number of reachable states can be very large or infinite. We introduce the sliding window method, which computes an approximate solution of the CME by performing a sequence of local analysis steps. In each step, only a manageable subset of states is considered, representing a "window" into the state space. In subsequent steps, the window follows the direction in which the probability mass moves, until the time period of interest has elapsed. We construct the window based on a deterministic approximation of the future behavior of the system by estimating upper and lower bounds on the populations of the chemical species. Results In order to show the effectiveness of our approach, we apply it to several examples previously described in the literature. The experimental results show that the proposed method speeds up the analysis considerably, compared to a global analysis, while still providing high accuracy. Conclusions The sliding window method is a novel approach to address the performance problems of numerical algorithms for the solution of the chemical master equation. The method efficiently approximates the probability distributions at the time points of interest for a variety of chemically reacting systems, including systems for which no upper bound on the population sizes of the chemical species is known a priori. PMID:20377904

Large time behavior of entropy solutions to one-dimensional unipolar hydrodynamic model for semiconductor devices

NASA Astrophysics Data System (ADS)

Huang, Feimin; Li, Tianhong; Yu, Huimin; Yuan, Difan

2018-06-01

We are concerned with the global existence and large time behavior of entropy solutions to the one-dimensional unipolar hydrodynamic model for semiconductors in the form of Euler-Poisson equations in a bounded interval. In this paper, we first prove the global existence of entropy solution by vanishing viscosity and compensated compactness framework. In particular, the solutions are uniformly bounded with respect to space and time variables by introducing modified Riemann invariants and the theory of invariant region. Based on the uniform estimates of density, we further show that the entropy solution converges to the corresponding unique stationary solution exponentially in time. No any smallness condition is assumed on the initial data and doping profile. Moreover, the novelty in this paper is about the unform bound with respect to time for the weak solutions of the isentropic Euler-Poisson system.

Process for separating and recovering an anionic dye from an aqueous solution

DOEpatents

Rogers, R.; Horwitz, E.P.; Bond, A.H.

1998-01-13

A solid/liquid phase process for the separation and recovery of an anionic dye from an aqueous solution is disclosed. The solid phase comprises separation particles having surface-bonded poly(ethylene glycol) groups, whereas the aqueous solution from which the anionic dye molecules are separated contains a poly(ethylene glycol) liquid/liquid biphase-forming amount of a dissolved lyotropic salt. After contact between the aqueous solution and separation particles, the anionic dye is bound to the particles. The bound anionic dye molecules are freed from the separation particles by contacting the anionic dye-bound particles with an aqueous solution that does not contain a poly(ethylene glycol) liquid/liquid biphase-forming amount of a dissolved lyotropic salt to form an aqueous anionic dye solution whose anionic dye concentration is preferably higher than that of the initial dye-containing solution. 7 figs.

An ion mobility-mass spectrometry investigation of monocyte chemoattractant protein-1

NASA Astrophysics Data System (ADS)

Schenauer, Matthew R.; Leary, Julie A.

2009-10-01

In the present article we describe the gas-phase dissociation behavior of the dimeric form of monocyte chemoattractant protein-1 (MCP-1) using quadrupole-traveling wave ion mobility spectrometry-time of flight mass spectrometry (q-TWIMS-TOF MS) (Waters Synapt(TM)). Through investigation of the 9+ charge state of the dimer, we were able to monitor dissociation product ion (monomer) formation as a function of activation energy. Using ion mobility, we were able to observe precursor ion structural changes occurring throughout the activation process. Arrival time distributions (ATDs) for the 5+ monomeric MCP-1 product ions, derived from the gas-phase dissociation of the 9+ dimer, were then compared with ATDs obtained for the 5+ MCP-1 monomer isolated directly from solution. The results show that the dissociated monomer is as compact as the monomer arising from solution, regardless of the trap collision energy (CE) used in the dissociation. The solution-derived monomer, when collisionally activated, also resists significant unfolding within measure. Finally, we compared the collisional activation data for the MCP-1 dimer with an MCP-1 dimer non-covalently bound to a single molecule of the semi-synthetic glycosaminoglycan (GAG) analog Arixtra(TM); the latter a therapeutic anti-thrombin III-activating pentasaccharide. We observed that while dimeric MCP-1 dissociated at relatively low trap CEs, the Arixtra-bound dimer required much higher energies, which also induced covalent bond cleavage in the bound Arixtra molecule. Both the free and Arixtra-bound dimers became less compact and exhibited longer arrival times with increasing trap CEs, albeit the Arixtra-bound complex at slightly higher energies. That both dimers shifted to longer arrival times with increasing activation energy, while the dissociated MCP-1 monomers remained compact, suggests that the longer arrival times of the Arixtra-free and Arixtra-bound dimers may represent a partial breach of non-covalent interactions between the associated MCP-1 monomers, rather than extensive unfolding of individual subunits. The fact that Arixtra preferentially binds MCP-1 dimers and prevents dimer dissociation at comparable activation energies to the Arixtra-free dimer, may suggest that the drug interacts across the two monomers, thereby inhibiting their dissociation.

Bounding the solutions of parametric weakly coupled second-order semilinear parabolic partial differential equations

DOE PAGES

Azunre, P.

2016-09-21

Here in this paper, two novel techniques for bounding the solutions of parametric weakly coupled second-order semilinear parabolic partial differential equations are developed. The first provides a theorem to construct interval bounds, while the second provides a theorem to construct lower bounds convex and upper bounds concave in the parameter. The convex/concave bounds can be significantly tighter than the interval bounds because of the wrapping effect suffered by interval analysis in dynamical systems. Both types of bounds are computationally cheap to construct, requiring solving auxiliary systems twice and four times larger than the original system, respectively. An illustrative numerical examplemore » of bound construction and use for deterministic global optimization within a simple serial branch-and-bound algorithm, implemented numerically using interval arithmetic and a generalization of McCormick's relaxation technique, is presented. Finally, problems within the important class of reaction-diffusion systems may be optimized with these tools.« less

Recrystallization of freezable bound water in aqueous solutions of medium concentration

NASA Astrophysics Data System (ADS)

Lishan, Zhao; Liqing, Pan; Ailing, Ji; Zexian, Cao; Qiang, Wang

2016-07-01

For aqueous solutions with freezable bound water, vitrification and recrystallization are mingled, which brings difficulty to application and misleads the interpretation of relevant experiments. Here, we report a quantification scheme for the freezable bound water based on the water-content dependence of glass transition temperature, by which also the concentration range for the solutions that may undergo recrystallization finds a clear definition. Furthermore, we find that depending on the amount of the freezable bound water, different temperature protocols should be devised to achieve a complete recrystallization. Our results may be helpful for understanding the dynamics of supercooled aqueous solutions and for improving their manipulation in various industries. Project supported by the Knowledge Innovation Project of Chinese Academy of Sciences on Water Science Research (Grant No. KJZD-EW-M03) and the National Natural Science Foundation of China (Grant Nos. 11474325 and 11290161).

[Mode of action and inhibition of polygalacturonase covalently bound to polysaccharide and glass carriers].

PubMed

Bock, W; Krause, M; Göbel, H; Anger, H; Schawaller, H J; Flemming, C; Gabert, A

1978-01-01

Endo-polygalacturonase (EC 3.2.1.15.) from Aspergillus spec. is much changed as far as its mode of action and the interaction with vegetable inhibitors of pectinase (from green beans and cucumbers) are concerned when it is covalently bound to insoluble carriers (Sepharose, cellulose powder, macroporous glass and nonporous ballotinis). Whereas a 2% degradation of substrate by the soluble enzyme caused a 50% decrease of viscosity of citrus pectic acid, the comparable degradation of substrate was increased to a level of about 10% with the investigated polygalacturonase carrier complexes apparently independent of the properties of the carriers and the kind of binding of the enzyme. In contrast to this the higher degradation of substrate of 15 and 20% respectively which was further stated at a 50% decrease of viscosity is unambiguously connected with the carriers and is in direct correlation with the specific activity of the polygalacturonase carrier complexes. Contrary to the soluble enzyme the covalently bound enzyme produces more lower oligomerous galacturonic acids by an exo-mechanism or by multiple attack already at the beginning of the hydrolysis of pectic acid. During the final stage there is an enrichment of trigalacturonic acid besides mono- and digalacturonic acids independent of the state of solution of the enzyme. It could further be stated that the strong inhibition of the soluble endo-polygalacturonase by selected pectinase inhibitors which was described earlier is reduced by degrees with the enzyme covalently bound to the insoluble carriers.

An integral equation-based numerical solver for Taylor states in toroidal geometries

NASA Astrophysics Data System (ADS)

O'Neil, Michael; Cerfon, Antoine J.

2018-04-01

We present an algorithm for the numerical calculation of Taylor states in toroidal and toroidal-shell geometries using an analytical framework developed for the solution to the time-harmonic Maxwell equations. Taylor states are a special case of what are known as Beltrami fields, or linear force-free fields. The scheme of this work relies on the generalized Debye source representation of Maxwell fields and an integral representation of Beltrami fields which immediately yields a well-conditioned second-kind integral equation. This integral equation has a unique solution whenever the Beltrami parameter λ is not a member of a discrete, countable set of resonances which physically correspond to spontaneous symmetry breaking. Several numerical examples relevant to magnetohydrodynamic equilibria calculations are provided. Lastly, our approach easily generalizes to arbitrary geometries, both bounded and unbounded, and of varying genus.

Some remarks concerning the centrifugal term approximation

NASA Astrophysics Data System (ADS)

Ferreira, F. J. S.; Bezerra, V. B.

2017-10-01

We generalize the Pekeris approximation for the centrifugal term potential, l/(l +1 ) r2 , and use this to obtain the solutions of the radial Schrödinger equation for the arbitrary angular quantum number, l, of the Hulthén potential. We also obtain the expressions for the bound state energies corresponding to this potential and calculate their values for different states and compare with other results presented in the literature. We also consider some models of physical potentials, namely, the Eckart potential, the Poschl-Teller potentials, the Rosen-Morse potential, the Woods-Saxon potential, and the Manning-Rosen potential. Thus, following straightforward the example corresponding to the Hulthén potential, we show what the radial solutions and the energy spectra for these potentials are.

Determining modes for the 3D Navier-Stokes equations

NASA Astrophysics Data System (ADS)

Cheskidov, Alexey; Dai, Mimi; Kavlie, Landon

2018-07-01

We introduce a determining wavenumber for the forced 3D Navier-Stokes equations (NSE) defined for each individual solution. Even though this wavenumber blows up if the solution blows up, its time average is uniformly bounded for all solutions on the weak global attractor. The bound is compared to Kolmogorov's dissipation wavenumber and the Grashof constant.

Symmetry breaking, Josephson oscillation and self-trapping in a self-bound three-dimensional quantum ball.

PubMed

Adhikari, S K

2017-11-22

We study spontaneous symmetry breaking (SSB), Josephson oscillation, and self-trapping in a stable, mobile, three-dimensional matter-wave spherical quantum ball self-bound by attractive two-body and repulsive three-body interactions. The SSB is realized by a parity-symmetric (a) one-dimensional (1D) double-well potential or (b) a 1D Gaussian potential, both along the z axis and no potential along the x and y axes. In the presence of each of these potentials, the symmetric ground state dynamically evolves into a doubly-degenerate SSB ground state. If the SSB ground state in the double well, predominantly located in the first well (z > 0), is given a small displacement, the quantum ball oscillates with a self-trapping in the first well. For a medium displacement one encounters an asymmetric Josephson oscillation. The asymmetric oscillation is a consequence of SSB. The study is performed by a variational and a numerical solution of a non-linear mean-field model with 1D parity-symmetric perturbations.

Mechanically triggered solute uptake in soft contact lenses.

PubMed

Tavazzi, Silvia; Ferraro, Lorenzo; Fagnola, Matteo; Cozza, Federica; Farris, Stefano; Bonetti, Simone; Simonutti, Roberto; Borghesi, Alessandro

2015-06-01

Molecular arrangement plays a role in the diffusion of water and solutes across soft contact lenses. In particular, the uptake of solutes in hydrated contact lenses can occur as long as free water is available for diffusion. In this work, we investigated the effect of mechanical vibrations of low frequency (200 Hz) on the solute uptake. Hyaluronan, a polysaccharide of ophthalmic use, was taken as example of solute of interest. For a specific water-hydrated hydrogel material, differential scanning calorimetry experiments showed that a large fraction of the hydration water accounted for loosely-bound water, both before and after one week of daily-wear of the lenses. The size (of the order of magnitude of few hundreds of nanometers) of hyaluronan in aqueous solution was found to be less than the size of the pores of the lens observed by scanning electron microscopy. However, solute uptake in already-hydrated lenses was negligible by simple immersion, while a significant increase occurred under mechanical vibrations of 200 Hz, thus providing experimental evidence of mechanically triggered enhanced solute uptake, which is attributed to the release of interfacial loosely-bound water. Also other materials were taken into consideration. However, the effectiveness of mechanical vibrations for hyaluronan uptake is restricted to lenses containing interfacial loosely-bound water. Indeed, loosely-bound water is expected to be bound to the polymer with bonding energies of the order of magnitude of 10-100 J/g, which are compatible with the energy input supplied by the vibrations. Copyright © 2015 Elsevier B.V. All rights reserved.

Comparison of a preQ1 riboswitch aptamer in metabolite-bound and free states with implications for gene regulation.

PubMed

Jenkins, Jermaine L; Krucinska, Jolanta; McCarty, Reid M; Bandarian, Vahe; Wedekind, Joseph E

2011-07-15

Riboswitches are RNA regulatory elements that govern gene expression by recognition of small molecule ligands via a high affinity aptamer domain. Molecular recognition can lead to active or attenuated gene expression states by controlling accessibility to mRNA signals necessary for transcription or translation. Key areas of inquiry focus on how an aptamer attains specificity for its effector, the extent to which the aptamer folds prior to encountering its ligand, and how ligand binding alters expression signal accessibility. Here we present crystal structures of the preQ(1) riboswitch from Thermoanaerobacter tengcongensis in the preQ(1)-bound and free states. Although the mode of preQ(1) recognition is similar to that observed for preQ(0), surface plasmon resonance revealed an apparent K(D) of 2.1 ± 0.3 nm for preQ(1) but a value of 35.1 ± 6.1 nm for preQ(0). This difference can be accounted for by interactions between the preQ(1) methylamine and base G5 of the aptamer. To explore conformational states in the absence of metabolite, the free-state aptamer structure was determined. A14 from the ceiling of the ligand pocket shifts into the preQ(1)-binding site, resulting in "closed" access to the metabolite while simultaneously increasing exposure of the ribosome-binding site. Solution scattering data suggest that the free-state aptamer is compact, but the "closed" free-state crystal structure is inadequate to describe the solution scattering data. These observations are distinct from transcriptional preQ(1) riboswitches of the same class that exhibit strictly ligand-dependent folding. Implications for gene regulation are discussed.

Soliton excitations and interactions for the three-coupled fourth-order nonlinear Schrödinger equations in the alpha helical proteins

NASA Astrophysics Data System (ADS)

Sun, Wen-Rong; Tian, Bo; Wang, Yu-Feng; Zhen, Hui-Ling

2015-06-01

Three-coupled fourth-order nonlinear Schrödinger equations describe the dynamics of alpha helical proteins with the interspine coupling at the higher order. Through symbolic computation and binary Bell-polynomial approach, bilinear forms and N-soliton solutions for such equations are constructed. Key point lies in the introduction of auxiliary functions in the Bell-polynomial expression. Asymptotic analysis is applied to investigate the elastic interaction between the two solitons: two solitons keep their original amplitudes, energies and velocities invariant after the interaction except for the phase shifts. Soliton amplitudes are related to the energy distributed in the solitons of the three spines. Overtaking interaction, head-on interaction and bound-state solitons of two solitons are given. Bound states of three bright solitons arise when all of them propagate in parallel. Elastic interaction between the bound-state solitons and one bright soliton is shown. Increase of the lattice parameter can lead to the increase of the soliton velocity, that is, the interaction period becomes shorter. The solitons propagating along the neighbouring spines are found to interact elastically. Those solitons, exhibited in this paper, might be viewed as a possible carrier of bio-energy transport in the protein molecules.

Control of discrete event systems modeled as hierarchical state machines

NASA Technical Reports Server (NTRS)

Brave, Y.; Heymann, M.

1991-01-01

The authors examine a class of discrete event systems (DESs) modeled as asynchronous hierarchical state machines (AHSMs). For this class of DESs, they provide an efficient method for testing reachability, which is an essential step in many control synthesis procedures. This method utilizes the asynchronous nature and hierarchical structure of AHSMs, thereby illustrating the advantage of the AHSM representation as compared with its equivalent (flat) state machine representation. An application of the method is presented where an online minimally restrictive solution is proposed for the problem of maintaining a controlled AHSM within prescribed legal bounds.

The NMR contribution to protein-protein networking in Fe-S protein maturation.

PubMed

Banci, Lucia; Camponeschi, Francesca; Ciofi-Baffoni, Simone; Piccioli, Mario

2018-03-22

Iron-sulfur proteins were among the first class of metalloproteins that were actively studied using NMR spectroscopy tailored to paramagnetic systems. The hyperfine shifts, their temperature dependencies and the relaxation rates of nuclei of cluster-bound residues are an efficient fingerprint of the nature and the oxidation state of the Fe-S cluster. NMR significantly contributed to the analysis of the magnetic coupling patterns and to the understanding of the electronic structure occurring in [2Fe-2S], [3Fe-4S] and [4Fe-4S] clusters bound to proteins. After the first NMR structure of a paramagnetic protein was obtained for the reduced E. halophila HiPIP I, many NMR structures were determined for several Fe-S proteins in different oxidation states. It was found that differences in chemical shifts, in patterns of unobserved residues, in internal mobility and in thermodynamic stability are suitable data to map subtle changes between the two different oxidation states of the protein. Recently, the interaction networks responsible for maturing human mitochondrial and cytosolic Fe-S proteins have been largely characterized by combining solution NMR standard experiments with those tailored to paramagnetic systems. We show here the contribution of solution NMR in providing a detailed molecular view of "Fe-S interactomics". This contribution was particularly effective when protein-protein interactions are weak and transient, and thus difficult to be characterized at high resolution with other methodologies.

Generator for gallium-68 and compositions obtained therefrom

DOEpatents

Neirinckx, Rudi D.; Davis, Michael A.

1981-01-01

A generator for obtaining radioactive gallium-68 from germanium-68 bound in a resin containing unsubstituted phenolic hydroxyl groups. The germanium-68 is loaded into the resin from an aqueous solution of the germanium-68. A physiologically acceptable solution of gallium-68 having an activity of 0.1 to 50 millicuries per milliliter of gallium-68 solution is obtained. The solution is obtained from the bound germanium-68 which forms gallium-68 in situ by eluting the column with a hydrochloric acid solution to form an acidic solution of gallium-68. The acidic solution of gallium-68 can be neutralized.

A one-layer recurrent neural network for constrained pseudoconvex optimization and its application for dynamic portfolio optimization.

PubMed

Liu, Qingshan; Guo, Zhishan; Wang, Jun

2012-02-01

In this paper, a one-layer recurrent neural network is proposed for solving pseudoconvex optimization problems subject to linear equality and bound constraints. Compared with the existing neural networks for optimization (e.g., the projection neural networks), the proposed neural network is capable of solving more general pseudoconvex optimization problems with equality and bound constraints. Moreover, it is capable of solving constrained fractional programming problems as a special case. The convergence of the state variables of the proposed neural network to achieve solution optimality is guaranteed as long as the designed parameters in the model are larger than the derived lower bounds. Numerical examples with simulation results illustrate the effectiveness and characteristics of the proposed neural network. In addition, an application for dynamic portfolio optimization is discussed. Copyright © 2011 Elsevier Ltd. All rights reserved.

On a relativistic particle and a relativistic position-dependent mass particle subject to the Klein–Gordon oscillator and the Coulomb potential

DOE Office of Scientific and Technical Information (OSTI.GOV)

Vitória, R.L.L.; Furtado, C., E-mail: furtado@fisica.ufpb.br; Bakke, K., E-mail: kbakke@fisica.ufpb.br

2016-07-15

The relativistic quantum dynamics of an electrically charged particle subject to the Klein–Gordon oscillator and the Coulomb potential is investigated. By searching for relativistic bound states, a particular quantum effect can be observed: a dependence of the angular frequency of the Klein–Gordon oscillator on the quantum numbers of the system. The meaning of this behaviour of the angular frequency is that only some specific values of the angular frequency of the Klein–Gordon oscillator are permitted in order to obtain bound state solutions. As an example, we obtain both the angular frequency and the energy level associated with the ground statemore » of the relativistic system. Further, we analyse the behaviour of a relativistic position-dependent mass particle subject to the Klein–Gordon oscillator and the Coulomb potential.« less

Numerical studies of the Bethe-Salpeter equation for a two-fermion bound state

NASA Astrophysics Data System (ADS)

de Paula, W.; Frederico, T.; Salmè, G.; Viviani, M.

2018-03-01

Some recent advances on the solution of the Bethe-Salpeter equation (BSE) for a two-fermion bound system directly in Minkowski space are presented. The calculations are based on the expression of the Bethe-Salpeter amplitude in terms of the so-called Nakanishi integral representation and on the light-front projection (i.e. the integration of the light-front variable k - = k 0 - k 3). The latter technique allows for the analytically exact treatment of the singularities plaguing the two-fermion BSE in Minkowski space. The good agreement observed between our results and those obtained using other existing numerical methods, based on both Minkowski and Euclidean space techniques, fully corroborate our analytical treatment.

A Reduced Basis Method with Exact-Solution Certificates for Symmetric Coercive Equations

DTIC Science & Technology

2013-11-06

the energy associated with the infinite - dimensional weak solution of parametrized symmetric coercive partial differential equations with piecewise...builds bounds with respect to the infinite - dimensional weak solution, aims to entirely remove the issue of the “truth” within the certified reduced basis...framework. We in particular introduce a reduced basis method that provides rigorous upper and lower bounds

Monitoring solute interactions with poly(ethylene oxide)-modified colloidal silica nanoparticles via fluorescence anisotropy decay.

PubMed

Tleugabulova, Dina; Duft, Andy M; Brook, Michael A; Brennan, John D

2004-01-06

The fluorescence-based nanosize metrology approach, proposed recently by Geddes and Birch (Geddes, C. D.; Birch, D. J. S. J. Non-Cryst. Solids 2000, 270, 191), was used to characterize the extent of binding of a fluorescent cationic solute, rhodamine 6G (R6G), to the surface of silica particles after modification of the surface with the hydrophilic polymer poly(ethylene oxide) (PEO) of various molecular weights. The measurement of the rotational dynamics of R6G in PEO solutions showed the absence of strong interactions between R6G and PEO chains in water and the ability of the dye to sense the presence of polymer clusters in 30 wt % solutions. Time-resolved anisotropy decays of polymer-modified Ludox provided direct evidence for distribution of the dye between bound and free states, with the bound dye showing two decay components: a nanosecond decay component that is consistent with local motions of bound probes and a residual anisotropy component due to slow rotation of large silica particles. The data showed that the dye was strongly adsorbed to unmodified silica nanoparticles, to the extent that less than 1% of the dye was present in the surrounding aqueous solution. Addition of PEO blocked the adsorption of the dye to a significant degree, with up to 50% of the probe being present in the aqueous solution for Ludox samples containing 30 wt % of low molecular weight PEO. The addition of such agents also decreased the value and increased the fractional contribution of the nanosecond rotational correlation time, suggesting that polymer adsorption altered the degree of local motion of the bound probe. Atomic force microscopy imaging studies provided no evidence for a change in the particle size upon surface modification but did suggest interparticle aggregation after polymer adsorption. Thus, this redistribution of the probe is interpreted as being due to coverage of particles with the polymer, resulting in lower adsorption of R6G to the silica. The data clearly show the power of time-resolved fluorescence anisotropy decay measurements for probing the modification of silica surfaces and suggest that this method should prove useful in characterization of new chromatographic stationary phases and nanocomposite materials.

Exact Solution of a Two-Species Quantum Dimer Model for Pseudogap Metals

NASA Astrophysics Data System (ADS)

Feldmeier, Johannes; Huber, Sebastian; Punk, Matthias

2018-05-01

We present an exact ground state solution of a quantum dimer model introduced by Punk, Allais, and Sachdev [Quantum dimer model for the pseudogap metal, Proc. Natl. Acad. Sci. U.S.A. 112, 9552 (2015)., 10.1073/pnas.1512206112], which features ordinary bosonic spin-singlet dimers as well as fermionic dimers that can be viewed as bound states of spinons and holons in a hole-doped resonating valence bond liquid. Interestingly, this model captures several essential properties of the metallic pseudogap phase in high-Tc cuprate superconductors. We identify a line in parameter space where the exact ground state wave functions can be constructed at an arbitrary density of fermionic dimers. At this exactly solvable line the ground state has a huge degeneracy, which can be interpreted as a flat band of fermionic excitations. Perturbing around the exactly solvable line, this degeneracy is lifted and the ground state is a fractionalized Fermi liquid with a small pocket Fermi surface in the low doping limit.

Partial branch and bound algorithm for improved data association in multiframe processing

NASA Astrophysics Data System (ADS)

Poore, Aubrey B.; Yan, Xin

1999-07-01

A central problem in multitarget, multisensor, and multiplatform tracking remains that of data association. Lagrangian relaxation methods have shown themselves to yield near optimal answers in real-time. The necessary improvement in the quality of these solutions warrants a continuing interest in these methods. These problems are NP-hard; the only known methods for solving them optimally are enumerative in nature with branch-and-bound being most efficient. Thus, the development of methods less than a full branch-and-bound are needed for improving the quality. Such methods as K-best, local search, and randomized search have been proposed to improve the quality of the relaxation solution. Here, a partial branch-and-bound technique along with adequate branching and ordering rules are developed. Lagrangian relaxation is used as a branching method and as a method to calculate the lower bound for subproblems. The result shows that the branch-and-bound framework greatly improves the resolution quality of the Lagrangian relaxation algorithm and yields better multiple solutions in less time than relaxation alone.

The effect of anions on bound acetylcholine in frog sartorius muscle.

PubMed Central

Ceccarelli, B; Molenaar, P C; Oen, B S; Polak, R L; Torri-Tarelli, F; van Kempen, G T

1989-01-01

1. Frog sartorius muscles were treated with an irreversible cholinesterase inhibitor and then incubated in isotonic potassium propionate solution (isotonic KPr). Total and bound, presumably vesicular, acetylcholine (ACh) in the tissue and ACh in the medium were assayed by mass fragmentography, miniature end-plate potentials (MEPPs) were recorded and the end-plates were investigated by electron microscopy. 2. Incubation in isotonic KPr for 30 min stimulated ACh release and concomitantly decreased total and bound ACh. Nerve stimulation for 30 min by trains of impulses (0.1 s trains of 100 Hz, 1 train s-1) in normal-potassium propionate-containing solution had the same effects. 3. When the tissue was incubated in normal-K+ Ringer solution for 3 h, following chemical or electric stimulation, bound ACh recovered to about 75% of the initial value, provided that Cl- ions were present in the medium. In the presence of propionate instead of Cl- ions almost no recovery of bound ACh took place. There was also recovery of bound ACh in the presence of either NO3- or gluconate ions. In NO3- it was the same as in Cl-, but in gluconate it was less than found in Cl- -containing medium. 4. Recovery of total ACh, in contrast to bound ACh, took place even in the presence of propionate ions, showing that extracellular Cl- is not required for the synthesis of ACh. 5. In terminals recovered in normal Ringer solution, many synaptic vesicles were found, but terminals 'recovered' in propionate solution were depleted of vesicles. 6. From these and other results it is concluded that the recycling of synaptic vesicles normally requires the presence of extracellular chloride. Images Fig. 1 Fig. 2 PMID:2789283

Global solutions to a class of multi-species reaction-diffusion systems with cross-diffusions arising in population dynamics

NASA Astrophysics Data System (ADS)

Wen, Zijuan; Fu, Shengmao

2009-08-01

In this paper, an n-species strongly coupled cooperating diffusive system is considered in a bounded smooth domain, subject to homogeneous Neumann boundary conditions. Employing the method of energy estimates, we obtain some conditions on the diffusion matrix and inter-specific cooperatives to ensure the global existence and uniform boundedness of a nonnegative solution. The globally asymptotical stability of the constant positive steady state is also discussed. As a consequence, all the results hold true for multi-species Lotka-Volterra type competition model and prey-predator model.

The Multidimensional Solitons in a Plasma: Structure Stability and Dynamics

DTIC Science & Technology

2003-07-20

ax(8 H’ / 8u), (2) into GKP (Generalized Kadomtsev - Petviashvili ) class where of equations , and in the case when 13 4nnT / B 2 << 1 1 1 for 6) < OB= eB...that the soliton elastic collisions can lead to formation of complex structures including the multisoliton bound states. 1. Basic equations Eq. (1) with...scribed by equation 2. Stability of 2D and 3D solutions atu + A(t,u)u =f, f= K 0X Ajudx, (1) To study stability of the GKP equation solutions, we =a 2

Stochastic solution to quantum dynamics

NASA Technical Reports Server (NTRS)

John, Sarah; Wilson, John W.

1994-01-01

The quantum Liouville equation in the Wigner representation is solved numerically by using Monte Carlo methods. For incremental time steps, the propagation is implemented as a classical evolution in phase space modified by a quantum correction. The correction, which is a momentum jump function, is simulated in the quasi-classical approximation via a stochastic process. The technique, which is developed and validated in two- and three- dimensional momentum space, extends an earlier one-dimensional work. Also, by developing a new algorithm, the application to bound state motion in an anharmonic quartic potential shows better agreement with exact solutions in two-dimensional phase space.

A Review of Methods for Moving Boundary Problems

DTIC Science & Technology

2009-07-01

the bound- ary value problem for the eikonal equation: ‖∇u‖ = 1 for x ∈ Ω (29) u = 0 for x ∈ Γ (30) ERDC/CHL TR-09-10 8 where ‖ ‖ is the Euclidean norm...Solutions of the eikonal equation can in turn be characterized as steady state solutions of the initial value prob- lem ut + sgn(u0)(‖∇u‖ − 1) = 0...LS using the eikonal equation and use the NCI equation for the LS dynam- ics. The complete system of equations in weak form is ∫ Ω (‖∇u‖ − 1)wdV = 0

Conserved conformational selection mechanism of Hsp70 chaperone-substrate interactions

PubMed Central

Velyvis, Algirdas; Zoltsman, Guy; Rosenzweig, Rina; Bouvignies, Guillaume

2018-01-01

Molecular recognition is integral to biological function and frequently involves preferred binding of a molecule to one of several exchanging ligand conformations in solution. In such a process the bound structure can be selected from the ensemble of interconverting ligands a priori (conformational selection, CS) or may form once the ligand is bound (induced fit, IF). Here we focus on the ubiquitous and conserved Hsp70 chaperone which oversees the integrity of the cellular proteome through its ATP-dependent interaction with client proteins. We directly quantify the flux along CS and IF pathways using solution NMR spectroscopy that exploits a methyl TROSY effect and selective isotope-labeling methodologies. Our measurements establish that both bacterial and human Hsp70 chaperones interact with clients by selecting the unfolded state from a pre-existing array of interconverting structures, suggesting a conserved mode of client recognition among Hsp70s and highlighting the importance of molecular dynamics in this recognition event. PMID:29460778

Towards the Solution of the Many-Electron Problem in Real Materials: Equation of State of the Hydrogen Chain with State-of-the-Art Many-Body Methods

DOE PAGES

Motta, Mario; Ceperley, David M.; Chan, Garnet Kin-Lic; ...

2017-09-28

We present numerical results for the equation of state of an infinite chain of hydrogen atoms. A variety of modern many-body methods are employed, with exhaustive cross-checks and validation. Approaches for reaching the continuous space limit and the thermodynamic limit are investigated, proposed, and tested. The detailed comparisons provide a benchmark for assessing the current state of the art in many-body computation, and for the development of new methods. The ground-state energy per atom in the linear chain is accurately determined versus bond length, with a confidence bound given on all uncertainties.

Towards the Solution of the Many-Electron Problem in Real Materials: Equation of State of the Hydrogen Chain with State-of-the-Art Many-Body Methods

DOE Office of Scientific and Technical Information (OSTI.GOV)

Motta, Mario; Ceperley, David M.; Chan, Garnet Kin-Lic

We present numerical results for the equation of state of an infinite chain of hydrogen atoms. A variety of modern many-body methods are employed, with exhaustive cross-checks and validation. Approaches for reaching the continuous space limit and the thermodynamic limit are investigated, proposed, and tested. The detailed comparisons provide a benchmark for assessing the current state of the art in many-body computation, and for the development of new methods. The ground-state energy per atom in the linear chain is accurately determined versus bond length, with a confidence bound given on all uncertainties.

Bound state and localization of excitation in many-body open systems

NASA Astrophysics Data System (ADS)

Cui, H. T.; Shen, H. Z.; Hou, S. C.; Yi, X. X.

2018-04-01

We study the exact bound state and time evolution for single excitations in one-dimensional X X Z spin chains within a non-Markovian reservoir. For the bound state, a common feature is the localization of single excitations, which means the spontaneous emission of excitations into the reservoir is prohibited. Exceptionally, the pseudo-bound state can be found, for which the single excitation has a finite probability of emission into the reservoir. In addition, a critical energy scale for bound states is also identified, below which only one bound state exists, and it is also the pseudo-bound state. The effect of quasirandom disorder in the spin chain is also discussed; such disorder induces the single excitation to locate at some spin sites. Furthermore, to display the effect of bound state and disorder on the preservation of quantum information, the time evolution of single excitations in spin chains is studied exactly. An interesting observation is that the excitation can stay at its initial location with high probability only when the bound state and disorder coexist. In contrast, when either one of them is absent, the information of the initial state can be erased completely or becomes mixed. This finding shows that the combination of bound state and disorder can provide an ideal mechanism for quantum memory.

Global solutions of restricted open-shell Hartree-Fock theory from semidefinite programming with applications to strongly correlated quantum systems.

PubMed

Veeraraghavan, Srikant; Mazziotti, David A

2014-03-28

We present a density matrix approach for computing global solutions of restricted open-shell Hartree-Fock theory, based on semidefinite programming (SDP), that gives upper and lower bounds on the Hartree-Fock energy of quantum systems. While wave function approaches to Hartree-Fock theory yield an upper bound to the Hartree-Fock energy, we derive a semidefinite relaxation of Hartree-Fock theory that yields a rigorous lower bound on the Hartree-Fock energy. We also develop an upper-bound algorithm in which Hartree-Fock theory is cast as a SDP with a nonconvex constraint on the rank of the matrix variable. Equality of the upper- and lower-bound energies guarantees that the computed solution is the globally optimal solution of Hartree-Fock theory. The work extends a previously presented method for closed-shell systems [S. Veeraraghavan and D. A. Mazziotti, Phys. Rev. A 89, 010502-R (2014)]. For strongly correlated systems the SDP approach provides an alternative to the locally optimized Hartree-Fock energies and densities with a certificate of global optimality. Applications are made to the potential energy curves of C2, CN, Cr2, and NO2.

Coulomb bound states of strongly interacting photons

DOE PAGES

Maghrebi, M. F.; Gullans, Michael J.; Bienias, P.; ...

2015-09-16

We show that two photons coupled to Rydberg states via electromagnetically induced transparency (EIT) can interact via an effective Coulomb potential. The interaction then gives rise to a continuum of two-body bound states. Within the continuum, metastable bound states are distinguished in analogy with quasi-bound states tunneling through a potential barrier. We find multiple branches of metastable bound states whose energy spectrum is governed by the Coulomb problem, thus obtaining a photonic analogue of the hydrogen atom. These states propagate with a negative group velocity in the medium, which allows for a simple preparation and detection scheme, before they slowlymore » decay to pairs of bound Rydberg atoms. As a result, we verify the metastability and backward propagation of these Coulomb bound states with exact numerical simulations.« less

Exact solution of finite parabolic potential disc-like quantum dot with and without electric field R. Djelti, S. Bentata and Z. Aziz: Trimer barrier hight effect oh the nature of the electronic state of the superlatice GaAs/AlxGa1-xAs Bibhas K. Dutta and Prasanta K. Mahapatra: Study of velocity-dependent collision effects on Lamb dip and crossover resonances in three-level system

NASA Astrophysics Data System (ADS)

Hassanien, H. H.; Abdelmoly, S. S.; Elmeshad, N.

The exact series solutions of finite parabolic potential disc-like quantum dot are given in the absence and presence of uniform applied electric field. We define some normalized parameters. From the complex eigenenergy E=E0 - i G/2, due to the electric field, we calculate the resonance width G of a bounded state. The ground and the first excited state of the electron and the hole are obtained with and without the electric field. The corresponding envelope functions are presented as a function of the disc dimensionality, radius R and half-width L.

Acidity and hydrogen exchange dynamics of iron(II)-bound nitroxyl in aqueous solution.

PubMed

Gao, Yin; Toubaei, Abouzar; Kong, Xianqi; Wu, Gang

2014-10-20

Nitroxyl-iron(II) (HNO-Fe(II)) complexes are often unstable in aqueous solution, thus making them very difficult to study. Consequently, many fundamental chemical properties of Fe(II)-bound HNO have remained unknown. Using a comprehensive multinuclear ((1)H, (15)N, (17)O) NMR approach, the acidity of the Fe(II)-bound HNO in [Fe(CN)5(HNO)](3-) was investigated and its pK(a) value was determined to be greater than 11. Additionally, HNO undergoes rapid hydrogen exchange with water in aqueous solution and this exchange process is catalyzed by both acid and base. The hydrogen exchange dynamics for the Fe(II)-bound HNO have been characterized and the obtained benchmark values, when combined with the literature data on proteins, reveal that the rate of hydrogen exchange for the Fe(II)-bound HNO in the interior of globin proteins is reduced by a factor of 10(6). © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Asymptotic expansions of solutions of the heat conduction equation in internally bounded cylindrical geometry

USGS Publications Warehouse

Ritchie, R.H.; Sakakura, A.Y.

1956-01-01

The formal solutions of problems involving transient heat conduction in infinite internally bounded cylindrical solids may be obtained by the Laplace transform method. Asymptotic series representing the solutions for large values of time are given in terms of functions related to the derivatives of the reciprocal gamma function. The results are applied to the case of the internally bounded infinite cylindrical medium with, (a) the boundary held at constant temperature; (b) with constant heat flow over the boundary; and (c) with the "radiation" boundary condition. A problem in the flow of gas through a porous medium is considered in detail.

Analysis of groundwater flow and stream depletion in L-shaped fluvial aquifers

NASA Astrophysics Data System (ADS)

Lin, Chao-Chih; Chang, Ya-Chi; Yeh, Hund-Der

2018-04-01

Understanding the head distribution in aquifers is crucial for the evaluation of groundwater resources. This article develops a model for describing flow induced by pumping in an L-shaped fluvial aquifer bounded by impermeable bedrocks and two nearly fully penetrating streams. A similar scenario for numerical studies was reported in Kihm et al. (2007). The water level of the streams is assumed to be linearly varying with distance. The aquifer is divided into two subregions and the continuity conditions of the hydraulic head and flux are imposed at the interface of the subregions. The steady-state solution describing the head distribution for the model without pumping is first developed by the method of separation of variables. The transient solution for the head distribution induced by pumping is then derived based on the steady-state solution as initial condition and the methods of finite Fourier transform and Laplace transform. Moreover, the solution for stream depletion rate (SDR) from each of the two streams is also developed based on the head solution and Darcy's law. Both head and SDR solutions in the real time domain are obtained by a numerical inversion scheme called the Stehfest algorithm. The software MODFLOW is chosen to compare with the proposed head solution for the L-shaped aquifer. The steady-state and transient head distributions within the L-shaped aquifer predicted by the present solution are compared with the numerical simulations and measurement data presented in Kihm et al. (2007).

Blow-up of solutions to a quasilinear wave equation for high initial energy

NASA Astrophysics Data System (ADS)

Li, Fang; Liu, Fang

2018-05-01

This paper deals with blow-up solutions to a nonlinear hyperbolic equation with variable exponent of nonlinearities. By constructing a new control function and using energy inequalities, the authors obtain the lower bound estimate of the L2 norm of the solution. Furthermore, the concavity arguments are used to prove the nonexistence of solutions; at the same time, an estimate of the upper bound of blow-up time is also obtained. This result extends and improves those of [1,2].

Chemotaxis with logistic source

NASA Astrophysics Data System (ADS)

Winkler, Michael

2008-12-01

We consider the chemotaxis system in a smooth bounded domain , where [chi]>0 and g generalizes the logistic function g(u)=Au-bu[alpha] with [alpha]>1, A[greater-or-equal, slanted]0 and b>0. A concept of very weak solutions is introduced, and global existence of such solutions for any nonnegative initial data u0[set membership, variant]L1([Omega]) is proved under the assumption that . Moreover, boundedness properties of the constructed solutions are studied. Inter alia, it is shown that if b is sufficiently large and u0[set membership, variant]L[infinity]([Omega]) has small norm in L[gamma]([Omega]) for some then the solution is globally bounded. Finally, in the case that additionally holds, a bounded set in L[infinity]([Omega]) can be found which eventually attracts very weak solutions emanating from arbitrary L1 initial data. The paper closes with numerical experiments that illustrate some of the theoretically established results.

Brooker's merocyanine: Comparison of single crystal structures

NASA Astrophysics Data System (ADS)

Hayes, Kathleen L.; Lasher, Emily M.; Choczynski, Jack M.; Crisci, Ralph R.; Wong, Calvin Y.; Dragonette, Joseph; Deschner, Joshua; Cardenas, Allan Jay P.

2018-06-01

Brooker's merocyanine and its derivatives are well-studied molecules due to their very interesting optical properties. Merocyanine dyes exhibit different colors in solution depending on the solvent's polarity, pH, aggregation and intermolecular interactions. The synthesis of 1-methyl-4-[(oxocyclohexadienylidene)ethylidene]-1,4-dihydropyridine (MOED) dye yielded a particularly interesting solid state structure where in one crystal lattice, MOED and its protonated form are bound by hydrogen bonding interactions.

Bound state solution of Dirac equation for 3D harmonics oscillator plus trigonometric scarf noncentral potential using SUSY QM approach

DOE Office of Scientific and Technical Information (OSTI.GOV)

Cari, C., E-mail: carinln@yahoo.com; Suparmi, A., E-mail: carinln@yahoo.com

2014-09-30

Dirac equation of 3D harmonics oscillator plus trigonometric Scarf non-central potential for spin symmetric case is solved using supersymmetric quantum mechanics approach. The Dirac equation for exact spin symmetry reduces to Schrodinger like equation. The relativistic energy and wave function for spin symmetric case are simply obtained using SUSY quantum mechanics method and idea of shape invariance.

A finite state projection algorithm for the stationary solution of the chemical master equation.

PubMed

Gupta, Ankit; Mikelson, Jan; Khammash, Mustafa

2017-10-21

The chemical master equation (CME) is frequently used in systems biology to quantify the effects of stochastic fluctuations that arise due to biomolecular species with low copy numbers. The CME is a system of ordinary differential equations that describes the evolution of probability density for each population vector in the state-space of the stochastic reaction dynamics. For many examples of interest, this state-space is infinite, making it difficult to obtain exact solutions of the CME. To deal with this problem, the Finite State Projection (FSP) algorithm was developed by Munsky and Khammash [J. Chem. Phys. 124(4), 044104 (2006)], to provide approximate solutions to the CME by truncating the state-space. The FSP works well for finite time-periods but it cannot be used for estimating the stationary solutions of CMEs, which are often of interest in systems biology. The aim of this paper is to develop a version of FSP which we refer to as the stationary FSP (sFSP) that allows one to obtain accurate approximations of the stationary solutions of a CME by solving a finite linear-algebraic system that yields the stationary distribution of a continuous-time Markov chain over the truncated state-space. We derive bounds for the approximation error incurred by sFSP and we establish that under certain stability conditions, these errors can be made arbitrarily small by appropriately expanding the truncated state-space. We provide several examples to illustrate our sFSP method and demonstrate its efficiency in estimating the stationary distributions. In particular, we show that using a quantized tensor-train implementation of our sFSP method, problems admitting more than 100 × 10 6 states can be efficiently solved.

A finite state projection algorithm for the stationary solution of the chemical master equation

NASA Astrophysics Data System (ADS)

Gupta, Ankit; Mikelson, Jan; Khammash, Mustafa

2017-10-01

The chemical master equation (CME) is frequently used in systems biology to quantify the effects of stochastic fluctuations that arise due to biomolecular species with low copy numbers. The CME is a system of ordinary differential equations that describes the evolution of probability density for each population vector in the state-space of the stochastic reaction dynamics. For many examples of interest, this state-space is infinite, making it difficult to obtain exact solutions of the CME. To deal with this problem, the Finite State Projection (FSP) algorithm was developed by Munsky and Khammash [J. Chem. Phys. 124(4), 044104 (2006)], to provide approximate solutions to the CME by truncating the state-space. The FSP works well for finite time-periods but it cannot be used for estimating the stationary solutions of CMEs, which are often of interest in systems biology. The aim of this paper is to develop a version of FSP which we refer to as the stationary FSP (sFSP) that allows one to obtain accurate approximations of the stationary solutions of a CME by solving a finite linear-algebraic system that yields the stationary distribution of a continuous-time Markov chain over the truncated state-space. We derive bounds for the approximation error incurred by sFSP and we establish that under certain stability conditions, these errors can be made arbitrarily small by appropriately expanding the truncated state-space. We provide several examples to illustrate our sFSP method and demonstrate its efficiency in estimating the stationary distributions. In particular, we show that using a quantized tensor-train implementation of our sFSP method, problems admitting more than 100 × 106 states can be efficiently solved.

Hierarchical Cluster Formation in Concentrated Monoclonal Antibody Formulations

NASA Astrophysics Data System (ADS)

Godfrin, P. Douglas; Zarzar, Jonathan; Zarraga, Isidro Dan; Porcar, Lionel; Falus, Peter; Wagner, Norman; Liu, Yun

Reversible cluster formation has been identified as an underlying cause of large solution viscosities observed in some concentrated monoclonal antibody (mAb) formulations. As high solution viscosity prevents the use of subcutaneous injection as a delivery method for some mAbs, a fundamental understanding of the interactions responsible for high viscosities in concentrated mAb solutions is of significant relevance to mAb applications in human health care as well as of intellectual interest. Here, we present a detailed investigation of a well-studied IgG1 based mAb to relate the short time dynamics and microstructure to significant viscosity changes over a range of pharmaceutically relevant physiochemical conditions. Using a combination of experimental techniques, it is found that upon adding Na2SO4, these antibodies dimerize in solution. Proteins form strongly bounded reversible dimers at dilute concentrations that, when concentrated, interact with each other to form loosely bounded, large, transient clusters. The combined effect of forming strongly bounded dimers and a large transient network is a significant increase in the solution viscosity. Strongly bounded, reversible dimers may exist in many IgG1 based mAb systems such that these results contribute to a more comprehensive understanding of the physical mechanisms producing high viscosities in concentrated protein solutions.

Performance bounds for nonlinear systems with a nonlinear ℒ2-gain property

NASA Astrophysics Data System (ADS)

Zhang, Huan; Dower, Peter M.

2012-09-01

Nonlinear ℒ2-gain is a finite gain concept that generalises the notion of conventional (linear) finite ℒ2-gain to admit the application of ℒ2-gain analysis tools of a broader class of nonlinear systems. The computation of tight comparison function bounds for this nonlinear ℒ2-gain property is important in applications such as small gain design. This article presents an approximation framework for these comparison function bounds through the formulation and solution of an optimal control problem. Key to the solution of this problem is the lifting of an ℒ2-norm input constraint, which is facilitated via the introduction of an energy saturation operator. This admits the solution of the optimal control problem of interest via dynamic programming and associated numerical methods, leading to the computation of the proposed bounds. Two examples are presented to demonstrate this approach.

On lower bounds for possible blow-up solutions to the periodic Navier-Stokes equation

DOE Office of Scientific and Technical Information (OSTI.GOV)

Cortissoz, Jean C., E-mail: jcortiss@uniandes.edu.co; Montero, Julio A., E-mail: ja.montero907@uniandes.edu.co; Pinilla, Carlos E., E-mail: ce.pinilla108@uniandes.edu.co

2014-03-15

We show a new lower bound on the H{sup .3/2} (T{sup 3}) norm of a possible blow-up solution to the Navier-Stokes equation, and also comment on the extension of this result to the whole space. This estimate can be seen as a natural limiting result for Leray's blow-up estimates in L{sup p}(R{sup 3}), 3 < p < ∞. We also show a lower bound on the blow-up rate of a possible blow-up solution of the Navier-Stokes equation in H{sup .5/2} (T{sup 3}), and give the corresponding extension to the case of the whole space.

On the global well-posedness of BV weak solutions to the Kuramoto-Sakaguchi equation

NASA Astrophysics Data System (ADS)

Amadori, Debora; Ha, Seung-Yeal; Park, Jinyeong

2017-01-01

The Kuramoto model is a prototype phase model describing the synchronous behavior of weakly coupled limit-cycle oscillators. When the number of oscillators is sufficiently large, the dynamics of Kuramoto ensemble can be effectively approximated by the corresponding mean-field equation, namely "the Kuramoto-Sakaguchi (KS) equation". This KS equation is a kind of scalar conservation law with a nonlocal flux function due to the mean-field interactions among oscillators. In this paper, we provide a unique global solvability of bounded variation (BV) weak solutions to the kinetic KS equation for identical oscillators using the method of front-tracking in hyperbolic conservation laws. Moreover, we also show that our BV weak solutions satisfy local-in-time L1-stability with respect to BV-initial data. For the ensemble of identical Kuramoto oscillators, we explicitly construct an exponentially growing BV weak solution generated from BV perturbation of incoherent state for any positive coupling strength. This implies the nonlinear instability of incoherent state in a positive coupling strength regime. We provide several numerical examples and compare them with our analytical results.

Modelling transient temperature distribution for injecting hot water through a well to an aquifer thermal energy storage system

NASA Astrophysics Data System (ADS)

Yang, Shaw-Yang; Yeh, Hund-Der; Li, Kuang-Yi

2010-10-01

Heat storage systems are usually used to store waste heat and solar energy. In this study, a mathematical model is developed to predict both the steady-state and transient temperature distributions of an aquifer thermal energy storage (ATES) system after hot water is injected through a well into a confined aquifer. The ATES has a confined aquifer bounded by aquicludes with different thermomechanical properties and geothermal gradients along the depth. Consider that the heat is transferred by conduction and forced convection within the aquifer and by conduction within the aquicludes. The dimensionless semi-analytical solutions of temperature distributions of the ATES system are developed using Laplace and Fourier transforms and their corresponding time-domain results are evaluated numerically by the modified Crump method. The steady-state solution is obtained from the transient solution through the final-value theorem. The effect of the heat transfer coefficient on aquiclude temperature distribution is appreciable only near the outer boundaries of the aquicludes. The present solutions are useful for estimating the temperature distribution of heat injection and the aquifer thermal capacity of ATES systems.

Microwave Dielectric Constant Dependence on Soil Tension.

DTIC Science & Technology

1983-10-01

water to be only a single monolayer thick .1 (OA) with Ice-like dielectric properties EWS = (3.15, JO). The first approach apportions the soil solution Into...mixing model that accounts explicitly for the presence of a hydrationU layer of bound water adjacent to hydrophilic soil particle surfaces. The soil ... solution is differentiated Into (1) a bound, ice-like component and (2) a bulk solution component, by a physical soil model dependent upon either soil

Some aspects of an induced electric dipole moment in rotating and non-rotating frames.

PubMed

Oliveira, Abinael B; Bakke, Knut

2017-06-01

Quantum effects on a neutral particle (atom or molecule) with an induced electric dipole moment are investigated when it is subject to the Kratzer potential and a scalar potential proportional to the radial distance. In addition, this neutral is placed in a region with electric and magnetic fields. This system is analysed in both non-rotating and rotating reference frames. Then, it is shown that bound state solutions to the Schrödinger equation can be achieved and, in the search for polynomial solutions to the radial wave function, a restriction on the values of the cyclotron frequency is analysed in both reference frames.

Static Einstein-Maxwell Black Holes with No Spatial Isometries in AdS Space.

PubMed

Herdeiro, Carlos A R; Radu, Eugen

2016-11-25

We explicitly construct static black hole solutions to the fully nonlinear, D=4, Einstein-Maxwell-anti-de Sitter (AdS) equations that have no continuous spatial symmetries. These black holes have a smooth, topologically spherical horizon (section), but without isometries, and approach, asymptotically, global AdS spacetime. They are interpreted as bound states of a horizon with the Einstein-Maxwell-AdS solitons recently discovered, for appropriate boundary data. In sharp contrast to the uniqueness results for a Minkowski electrovacuum, the existence of these black holes shows that single, equilibrium, black hole solutions in an AdS electrovacuum admit an arbitrary multipole structure.

Silica-coated gold nanorods as saturable absorber for bound-state pulse generation in a fiber laser with near-zero dispersion

NASA Astrophysics Data System (ADS)

Wang, Xude; Luo, Aiping; Luo, Zhichao; Liu, Meng; Zou, Feng; Zhu, Yanfang; Xue, Jianping; Xu, Wencheng

2017-11-01

We presented a bound-state operation in a fiber laser with near-zero anomalous dispersion based on a silica-coated gold nanorods (GNRs@SiO2) saturable absorber (SA). Using a balanced twin detector measurement technique, the modulation depth and nonsaturable loss of the GNRs@SiO2 SA were measured to be approximately 3.5% and 39.3%, respectively. By virtue of the highly nonlinear effect of the GNRs@SiO2 SA, the bound-state pulses could be easily observed. Besides the lower-order bound-state pulses with two, three, and four solitons, the higher-order bound states with up to 12 solitons were also obtained in the laser cavity. The pulse profiles of the higher-order bound states were further reconstructed theoretically. The experimental results would give further insight towards understanding the complex nonlinear dynamics of bound-state pulses in fiber lasers.

The Cramér-Rao Bounds and Sensor Selection for Nonlinear Systems with Uncertain Observations.

PubMed

Wang, Zhiguo; Shen, Xiaojing; Wang, Ping; Zhu, Yunmin

2018-04-05

This paper considers the problems of the posterior Cramér-Rao bound and sensor selection for multi-sensor nonlinear systems with uncertain observations. In order to effectively overcome the difficulties caused by uncertainty, we investigate two methods to derive the posterior Cramér-Rao bound. The first method is based on the recursive formula of the Cramér-Rao bound and the Gaussian mixture model. Nevertheless, it needs to compute a complex integral based on the joint probability density function of the sensor measurements and the target state. The computation burden of this method is relatively high, especially in large sensor networks. Inspired by the idea of the expectation maximization algorithm, the second method is to introduce some 0-1 latent variables to deal with the Gaussian mixture model. Since the regular condition of the posterior Cramér-Rao bound is unsatisfied for the discrete uncertain system, we use some continuous variables to approximate the discrete latent variables. Then, a new Cramér-Rao bound can be achieved by a limiting process of the Cramér-Rao bound of the continuous system. It avoids the complex integral, which can reduce the computation burden. Based on the new posterior Cramér-Rao bound, the optimal solution of the sensor selection problem can be derived analytically. Thus, it can be used to deal with the sensor selection of a large-scale sensor networks. Two typical numerical examples verify the effectiveness of the proposed methods.

Pseudospin symmetry of the Dirac equation for a Möbius square plus Mie type potential with a Coulomb-like tensor interaction via SUSYQM

NASA Astrophysics Data System (ADS)

Akpan, N. Ikot; Zarrinkamar, S.; Eno, J. Ibanga; Maghsoodi, E.; Hassanabadi, H.

2014-01-01

We investigate the approximate solution of the Dirac equation for a combination of Möbius square and Mie type potentials under the pseudospin symmetry limit by using supersymmetry quantum mechanics. We obtain the bound-state energy equation and the corresponding spinor wave functions in an approximate analytical manner. We comment on the system via various useful figures and tables.

Generalized surface tension bounds in vacuum decay

NASA Astrophysics Data System (ADS)

Masoumi, Ali; Paban, Sonia; Weinberg, Erick J.

2018-02-01

Coleman and De Luccia (CDL) showed that gravitational effects can prevent the decay by bubble nucleation of a Minkowski or AdS false vacuum. In their thin-wall approximation this happens whenever the surface tension in the bubble wall exceeds an upper bound proportional to the difference of the square roots of the true and false vacuum energy densities. Recently it was shown that there is another type of thin-wall regime that differs from that of CDL in that the radius of curvature grows substantially as one moves through the wall. Not only does the CDL derivation of the bound fail in this case, but also its very formulation becomes ambiguous because the surface tension is not well defined. We propose a definition of the surface tension and show that it obeys a bound similar in form to that of the CDL case. We then show that both thin-wall bounds are special cases of a more general bound that is satisfied for all bounce solutions with Minkowski or AdS false vacua. We discuss the limit where the parameters of the theory attain critical values and the bound is saturated. The bounce solution then disappears and a static planar domain wall solution appears in its stead. The scalar field potential then is of the form expected in supergravity, but this is only guaranteed along the trajectory in field space traced out by the bounce.

Theoretical Bounds of Direct Binary Search Halftoning.

PubMed

Liao, Jan-Ray

2015-11-01

Direct binary search (DBS) produces the images of the best quality among half-toning algorithms. The reason is that it minimizes the total squared perceived error instead of using heuristic approaches. The search for the optimal solution involves two operations: (1) toggle and (2) swap. Both operations try to find the binary states for each pixel to minimize the total squared perceived error. This error energy minimization leads to a conjecture that the absolute value of the filtered error after DBS converges is bounded by half of the peak value of the autocorrelation filter. However, a proof of the bound's existence has not yet been found. In this paper, we present a proof that shows the bound existed as conjectured under the condition that at least one swap occurs after toggle converges. The theoretical analysis also indicates that a swap with a pixel further away from the center of the autocorrelation filter results in a tighter bound. Therefore, we propose a new DBS algorithm which considers toggle and swap separately, and the swap operations are considered in the order from the edge to the center of the filter. Experimental results show that the new algorithm is more efficient than the previous algorithm and can produce half-toned images of the same quality as the previous algorithm.

Origin of poor doping efficiency in solution processed organic semiconductors.

PubMed

Jha, Ajay; Duan, Hong-Guang; Tiwari, Vandana; Thorwart, Michael; Miller, R J Dwayne

2018-05-21

Doping is an extremely important process where intentional insertion of impurities in semiconductors controls their electronic properties. In organic semiconductors, one of the convenient, but inefficient, ways of doping is the spin casting of a precursor mixture of components in solution, followed by solvent evaporation. Active control over this process holds the key to significant improvements over current poor doping efficiencies. Yet, an optimized control can only come from a detailed understanding of electronic interactions responsible for the low doping efficiencies. Here, we use two-dimensional nonlinear optical spectroscopy to examine these interactions in the course of the doping process by probing the solution mixture of doped organic semiconductors. A dopant accepts an electron from the semiconductor and the two ions form a duplex of interacting charges known as ion-pair complexes. Well-resolved off-diagonal peaks in the two-dimensional spectra clearly demonstrate the electronic connectivity among the ions in solution. This electronic interaction represents a well resolved electrostatically bound state, as opposed to a random distribution of ions. We developed a theoretical model to recover the experimental data, which reveals an unexpectedly strong electronic coupling of ∼250 cm -1 with an intermolecular distance of ∼4.5 Å between ions in solution, which is approximately the expected distance in processed films. The fact that this relationship persists from solution to the processed film gives direct evidence that Coulomb interactions are retained from the precursor solution to the processed films. This memory effect renders the charge carriers equally bound also in the film and, hence, results in poor doping efficiencies. This new insight will help pave the way towards rational tailoring of the electronic interactions to improve doping efficiencies in processed organic semiconductor thin films.

Indirect consequences of exciplex states on the phosphorescence lifetime of phenazine-based 1,2,3-triazole luminescent probes.

PubMed

Costa, Bárbara B A; Jardim, Guilherme A M; Santos, Paloma L; Calado, Hállen D R; Monkman, Andrew P; Dias, Fernando B; da Silva Júnior, Eufrânio N; Cury, Luiz A

2017-02-01

The optical properties of phenazine derivative probe solutions involving intersystem crossing from singlet to triplet states were investigated by time resolved spectroscopy. The room temperature phosphorescence emission presented different time responses when Cd 2+ ions were bound to the probe chemical structure. The complex exciplex formation observed to occur in this case was not directly responsible for the change in the phosphorescence lifetime. This was more influenced by the new molecular conformation and modified spin-orbit coupling imposed by the binding of the Cd 2+ ions to the phenazine molecules.

Approximate arbitrary κ-state solutions of Dirac equation with Schiöberg and Manning-Rosen potentials within the coulomb-like Yukawa-like and generalized tensor interactions

NASA Astrophysics Data System (ADS)

Ikot, Akpan N.; Hassanabadi, Hassan; Obong, Hillary Patrick; Mehraban, H.; Yazarloo, Bentol Hoda

2015-07-01

The effects of Coulomb-like tensor (CLT), Yukawa-like tensor (YLT) and generalized tensor (GLT) interactions are investigated in the Dirac theory with Schiöberg and Manning-Rosen potentials within the framework of spin and pseudospin symmetries using the Nikiforov-Uvarov method. The bound state energy spectra and the radial wave functions have been approximately obtained in the case of spin and pseudospin symmetries. We have also reported some numerical results and figures to show the effects these tensor interactions.

Conformational heterogeneity within the Michaelis complex of lactate dehydrogenase†

PubMed Central

Deng, Hua; Vu, Dung V.; Clinch, Keith; Desamero, Ruel; Dyer, R. Brian; Callender, Robert

2011-01-01

A series of isotope edited IR measurements, both static as well as temperature jump relaxation spectroscopy, are performed on lactate dehydrogenase (LDH) to determine the ensemble of structures available to its Michaelis complex. There clearly has been a substantial reduction in the number of states available to the pyruvate substrate (as modeled by the substrate mimic, oxamate) and NADH when bound to protein compared to dissolved in solution, as determined by the bandwidths and positions of the critical C2=O band of bound substrate mimic and the C4-H stretch of NADH reduced nicotinamide group. Moreover, it is found that a strong ionic bond (characterized by a signature IR band discovered in this study) is formed between the carboxyl group of bound pyruvate with (presumably) Arg171, forming a strong ‘anchor’ within the protein matrix. However, conformational heterogeneity within the Michaelis complex is found that has an impact on both catalytic efficiency and thermodynamics of the enzyme. PMID:21568287

On existence and approximate solutions for stochastic differential equations in the framework of G-Brownian motion

NASA Astrophysics Data System (ADS)

Ullah, Rahman; Faizullah, Faiz

2017-10-01

This investigation aims at studying a Euler-Maruyama (EM) approximate solutions scheme for stochastic differential equations (SDEs) in the framework of G-Brownian motion. Subject to the growth condition, it is shown that the EM solutions Z^q(t) are bounded, in particular, Z^q(t)\\in M_G^2([t_0,T];R^n) . Letting Z( t) as a unique solution to SDEs in the G-framework and utilizing the growth and Lipschitz conditions, the convergence of Z^q(t) to Z( t) is revealed. The Burkholder-Davis-Gundy (BDG) inequalities, Hölder's inequality, Gronwall's inequality and Doobs martingale's inequality are used to derive the results. In addition, without assuming a solution of the stated SDE, we have shown that the Euler-Maruyama approximation sequence {Z^q(t)} is Cauchy in M_G^2([t_0,T];R^n) thus converges to a limit which is a unique solution to SDE in the G-framework.

Nonadiabatic Josephson current pumping by chiral microwave irradiation

NASA Astrophysics Data System (ADS)

Venitucci, B.; Feinberg, D.; Mélin, R.; Douçot, B.

2018-05-01

Irradiating a Josephson junction with microwaves can operate not only on the amplitude but also on the phase of the Josephson current. This requires breaking time-inversion symmetry, which is achieved by introducing a phase lapse between the microwave components acting on the two sides of the junction. General symmetry arguments and the solution of a specific single-level quantum dot model show that this induces chirality in the Cooper pair dynamics due to the topology of the Andreev bound-state wave function. Another essential condition is to break electron-hole symmetry within the junction. A shift of the current-phase relation is obtained, which is controllable in sign and amplitude with the microwave phase and an electrostatic gate, thus producing a "chiral" Josephson transistor. The dot model is solved in the infinite-gap limit by Floquet theory and in the general case with Keldysh nonequilibrium Green's functions. The chiral current is nonadiabatic: it is extremal and changes sign close to resonant chiral transitions between the Andreev bound states.

Solution of two-body relativistic bound state equations with confining plus Coulomb interactions

NASA Technical Reports Server (NTRS)

Maung, Khin Maung; Kahana, David E.; Norbury, John W.

1992-01-01

Studies of meson spectroscopy have often employed a nonrelativistic Coulomb plus Linear Confining potential in position space. However, because the quarks in mesons move at an appreciable fraction of the speed of light, it is necessary to use a relativistic treatment of the bound state problem. Such a treatment is most easily carried out in momentum space. However, the position space Linear and Coulomb potentials lead to singular kernels in momentum space. Using a subtraction procedure we show how to remove these singularities exactly and thereby solve the Schroedinger equation in momentum space for all partial waves. Furthermore, we generalize the Linear and Coulomb potentials to relativistic kernels in four dimensional momentum space. Again we use a subtraction procedure to remove the relativistic singularities exactly for all partial waves. This enables us to solve three dimensional reductions of the Bethe-Salpeter equation. We solve six such equations for Coulomb plus Confining interactions for all partial waves.

Dynamics of a New 5D Hyperchaotic System of Lorenz Type

NASA Astrophysics Data System (ADS)

Zhang, Fuchen; Chen, Rui; Wang, Xingyuan; Chen, Xiusu; Mu, Chunlai; Liao, Xiaofeng

Ultimate boundedness of chaotic dynamical systems is one of the fundamental concepts in dynamical systems, which plays an important role in investigating the stability of the equilibrium, estimating the Lyapunov dimension of attractors and the Hausdorff dimension of attractors, the existence of periodic solutions, chaos control, chaos synchronization. However, it is often difficult to obtain the bounds of the hyperchaotic systems due to the complex algebraic structure of the hyperchaotic systems. This paper has investigated the boundedness of solutions of a nonlinear hyperchaotic system. We have obtained the global exponential attractive set and the ultimate bound set for this system. To obtain the ellipsoidal ultimate bound, the ultimate bound of the proposed system is theoretically estimated using Lagrange multiplier method, Lyapunov stability theory and optimization theory. To show the ultimate bound region, numerical simulations are provided.

Resource Constrained Planning of Multiple Projects with Separable Activities

NASA Astrophysics Data System (ADS)

Fujii, Susumu; Morita, Hiroshi; Kanawa, Takuya

In this study we consider a resource constrained planning problem of multiple projects with separable activities. This problem provides a plan to process the activities considering a resource availability with time window. We propose a solution algorithm based on the branch and bound method to obtain the optimal solution minimizing the completion time of all projects. We develop three methods for improvement of computational efficiency, that is, to obtain initial solution with minimum slack time rule, to estimate lower bound considering both time and resource constraints and to introduce an equivalence relation for bounding operation. The effectiveness of the proposed methods is demonstrated by numerical examples. Especially as the number of planning projects increases, the average computational time and the number of searched nodes are reduced.

Topological sources of soliton mass and supersymmetry breaking

NASA Astrophysics Data System (ADS)

Haas, Patrick A.

2018-06-01

We derive the Smarr formulae for two five-dimensional solutions of supergravity, which are asymptotically ; in particular, one has a magnetic ‘bolt’ in its center, and one is a two-center solution. We show for both spacetimes that supersymmetry—and so the BPS-bound—is broken by the holonomy and how each topological feature of a space-like hypersurface enters Smarr’s mass formula, with emphasis on the ones that give rise to the stated violation of the BPS-bound. In this light, we question if any violating extra-mass term in a spacetime with such asymptotics is only evident in the ADM mass while the Komar mass per se ‘tries’ to preserve BPS. Finally, we derive the cohomological fluxes for each situation and examine in a more general fashion how the breaking of supersymmetry—and so the BPS-bound violation—is associated with their topologies. In the second (and more complicated) scenario, we especially focus on the compact cycle linking the centers, and the contribution of non-vanishing bulk terms in the mass formula to the breaking of supersymmetry.

Approximate labeling via graph cuts based on linear programming.

PubMed

Komodakis, Nikos; Tziritas, Georgios

2007-08-01

A new framework is presented for both understanding and developing graph-cut-based combinatorial algorithms suitable for the approximate optimization of a very wide class of Markov Random Fields (MRFs) that are frequently encountered in computer vision. The proposed framework utilizes tools from the duality theory of linear programming in order to provide an alternative and more general view of state-of-the-art techniques like the \\alpha-expansion algorithm, which is included merely as a special case. Moreover, contrary to \\alpha-expansion, the derived algorithms generate solutions with guaranteed optimality properties for a much wider class of problems, for example, even for MRFs with nonmetric potentials. In addition, they are capable of providing per-instance suboptimality bounds in all occasions, including discrete MRFs with an arbitrary potential function. These bounds prove to be very tight in practice (that is, very close to 1), which means that the resulting solutions are almost optimal. Our algorithms' effectiveness is demonstrated by presenting experimental results on a variety of low-level vision tasks, such as stereo matching, image restoration, image completion, and optical flow estimation, as well as on synthetic problems.

Universal bounds on charged states in 2d CFT and 3d gravity

DOE Office of Scientific and Technical Information (OSTI.GOV)

Benjamin, Nathan; Dyer, Ethan; Fitzpatrick, A. Liam

2016-08-04

We derive an explicit bound on the dimension of the lightest charged state in two dimensional conformal field theories with a global abelian symmetry. We find that the bound scales with c and provide examples that parametrically saturate this bound. We also prove that any such theory must contain a state with charge-to-mass ratio above a minimal lower bound. As a result, we comment on the implications for charged states in three dimensional theories of gravity.

Photon-assisted tunneling through a topological superconductor with Majorana bound states

DOE Office of Scientific and Technical Information (OSTI.GOV)

Tang, Han-Zhao; Zhang, Ying-Tao, E-mail: zhangyt@mail.hebtu.edu.cn; Liu, Jian-Jun, E-mail: liujj@mail.hebtu.edu.cn

Employing the Keldysh Nonequilibrium Green’s function method, we investigate time-dependent transport through a topological superconductor with Majorana bound states in the presence of a high frequency microwave field. It is found that Majorana bound states driven by photon-assisted tunneling can absorb(emit) photons and the resulting photon-assisted tunneling side band peaks can split the Majorana bound state that then appears at non-zero bias. This splitting breaks from the current opinion that Majorana bound states appear only at zero bias and thus provides a new experimental method for detecting Majorana bound states in the Non-zero-energy mode. We not only demonstrate that themore » photon-assisted tunneling side band peaks are due to Non-zero-energy Majorana bound states, but also that the height of the photon-assisted tunneling side band peaks is related to the intensity of the microwave field. It is further shown that the time-varying conductance induced by the Majorana bound states shows negative values for a certain period of time, which corresponds to a manifestation of the phase coherent time-varying behavior in mesoscopic systems.« less

Conformational dynamics of a G-protein α subunit is tightly regulated by nucleotide binding.

PubMed

Goricanec, David; Stehle, Ralf; Egloff, Pascal; Grigoriu, Simina; Plückthun, Andreas; Wagner, Gerhard; Hagn, Franz

2016-06-28

Heterotrimeric G proteins play a pivotal role in the signal-transduction pathways initiated by G-protein-coupled receptor (GPCR) activation. Agonist-receptor binding causes GDP-to-GTP exchange and dissociation of the Gα subunit from the heterotrimeric G protein, leading to downstream signaling. Here, we studied the internal mobility of a G-protein α subunit in its apo and nucleotide-bound forms and characterized their dynamical features at multiple time scales using solution NMR, small-angle X-ray scattering, and molecular dynamics simulations. We find that binding of GTP analogs leads to a rigid and closed arrangement of the Gα subdomain, whereas the apo and GDP-bound forms are considerably more open and dynamic. Furthermore, we were able to detect two conformational states of the Gα Ras domain in slow exchange whose populations are regulated by binding to nucleotides and a GPCR. One of these conformational states, the open state, binds to the GPCR; the second conformation, the closed state, shows no interaction with the receptor. Binding to the GPCR stabilizes the open state. This study provides an in-depth analysis of the conformational landscape and the switching function of a G-protein α subunit and the influence of a GPCR in that landscape.

Conformational dynamics of a G-protein α subunit is tightly regulated by nucleotide binding

PubMed Central

Goricanec, David; Stehle, Ralf; Egloff, Pascal; Grigoriu, Simina; Wagner, Gerhard; Hagn, Franz

2016-01-01

Heterotrimeric G proteins play a pivotal role in the signal-transduction pathways initiated by G-protein–coupled receptor (GPCR) activation. Agonist–receptor binding causes GDP-to-GTP exchange and dissociation of the Gα subunit from the heterotrimeric G protein, leading to downstream signaling. Here, we studied the internal mobility of a G-protein α subunit in its apo and nucleotide-bound forms and characterized their dynamical features at multiple time scales using solution NMR, small-angle X-ray scattering, and molecular dynamics simulations. We find that binding of GTP analogs leads to a rigid and closed arrangement of the Gα subdomain, whereas the apo and GDP-bound forms are considerably more open and dynamic. Furthermore, we were able to detect two conformational states of the Gα Ras domain in slow exchange whose populations are regulated by binding to nucleotides and a GPCR. One of these conformational states, the open state, binds to the GPCR; the second conformation, the closed state, shows no interaction with the receptor. Binding to the GPCR stabilizes the open state. This study provides an in-depth analysis of the conformational landscape and the switching function of a G-protein α subunit and the influence of a GPCR in that landscape. PMID:27298341

Level Density in the Complex Scaling Method

NASA Astrophysics Data System (ADS)

Suzuki, R.; Myo, T.; Katō, K.

2005-06-01

It is shown that the continuum level density (CLD) at unbound energies can be calculated with the complex scaling method (CSM), in which the energy spectra of bound states, resonances and continuum states are obtained in terms of L(2) basis functions. In this method, the extended completeness relation is applied to the calculation of the Green functions, and the continuum-state part is approximately expressed in terms of discretized complex scaled continuum solutions. The obtained result is compared with the CLD calculated exactly from the scattering phase shift. The discretization in the CSM is shown to give a very good description of continuum states. We discuss how the scattering phase shifts can inversely be calculated from the discretized CLD using a basis function technique in the CSM.

Optimum measurement for unambiguously discriminating two mixed states: General considerations and special cases

NASA Astrophysics Data System (ADS)

Herzog, Ulrike; Bergou, János A.

2006-04-01

Based on our previous publication [U. Herzog and J. A. Bergou, Phys. Rev. A 71, 050301(R)(2005)] we investigate the optimum measurement for the unambiguous discrimination of two mixed quantum states that occur with given prior probabilities. Unambiguous discrimination of nonorthogonal states is possible in a probabilistic way, at the expense of a nonzero probability of inconclusive results, where the measurement fails. Along with a discussion of the general problem, we give an example illustrating our method of solution. We also provide general inequalities for the minimum achievable failure probability and discuss in more detail the necessary conditions that must be fulfilled when its absolute lower bound, proportional to the fidelity of the states, can be reached.

Driven neutron star collapse: Type I critical phenomena and the initial black hole mass distribution

NASA Astrophysics Data System (ADS)

Noble, Scott C.; Choptuik, Matthew W.

2016-01-01

We study the general relativistic collapse of neutron star (NS) models in spherical symmetry. Our initially stable models are driven to collapse by the addition of one of two things: an initially ingoing velocity profile, or a shell of minimally coupled, massless scalar field that falls onto the star. Tolman-Oppenheimer-Volkoff (TOV) solutions with an initially isentropic, gamma-law equation of state serve as our NS models. The initial values of the velocity profile's amplitude and the star's central density span a parameter space which we have surveyed extensively and which we find provides a rich picture of the possible end states of NS collapse. This parameter space survey elucidates the boundary between Type I and Type II critical behavior in perfect fluids which coincides, on the subcritical side, with the boundary between dispersed and bound end states. For our particular model, initial velocity amplitudes greater than 0.3 c are needed to probe the regime where arbitrarily small black holes can form. In addition, we investigate Type I behavior in our system by varying the initial amplitude of the initially imploding scalar field. In this case we find that the Type I critical solutions resemble TOV solutions on the 1-mode unstable branch of equilibrium solutions, and that the critical solutions' frequencies agree well with the fundamental mode frequencies of the unstable equilibria. Additionally, the critical solution's scaling exponent is shown to be well approximated by a linear function of the initial star's central density.

Determining partial differential cross sections for low-energy electron photodetachment involving conical intersections using the solution of a Lippmann-Schwinger equation constructed with standard electronic structure techniques.

PubMed

Han, Seungsuk; Yarkony, David R

2011-05-07

A method for obtaining partial differential cross sections for low energy electron photodetachment in which the electronic states of the residual molecule are strongly coupled by conical intersections is reported. The method is based on the iterative solution to a Lippmann-Schwinger equation, using a zeroth order Hamiltonian consisting of the bound nonadiabatically coupled residual molecule and a free electron. The solution to the Lippmann-Schwinger equation involves only standard electronic structure techniques and a standard three-dimensional free particle Green's function quadrature for which fast techniques exist. The transition dipole moment for electron photodetachment, is a sum of matrix elements each involving one nonorthogonal orbital obtained from the solution to the Lippmann-Schwinger equation. An expression for the electron photodetachment transition dipole matrix element in terms of Dyson orbitals, which does not make the usual orthogonality assumptions, is derived.

Semiclassical Dynamicswith Exponentially Small Error Estimates

NASA Astrophysics Data System (ADS)

Hagedorn, George A.; Joye, Alain

We construct approximate solutions to the time-dependent Schrödingerequation for small values of ħ. If V satisfies appropriate analyticity and growth hypotheses and , these solutions agree with exact solutions up to errors whose norms are bounded by for some C and γ>0. Under more restrictive hypotheses, we prove that for sufficiently small T', implies the norms of the errors are bounded by for some C', γ'>0, and σ > 0.

On the boundedness and integration of non-oscillatory solutions of certain linear differential equations of second order.

PubMed

Tunç, Cemil; Tunç, Osman

2016-01-01

In this paper, certain system of linear homogeneous differential equations of second-order is considered. By using integral inequalities, some new criteria for bounded and [Formula: see text]-solutions, upper bounds for values of improper integrals of the solutions and their derivatives are established to the considered system. The obtained results in this paper are considered as extension to the results obtained by Kroopnick (2014) [1]. An example is given to illustrate the obtained results.

Proton transfer from C-6 of uridine 5'-monophosphate catalyzed by orotidine 5'-monophosphate decarboxylase: formation and stability of a vinyl carbanion intermediate and the effect of a 5-fluoro substituent.

PubMed

Tsang, Wing-Yin; Wood, B McKay; Wong, Freeman M; Wu, Weiming; Gerlt, John A; Amyes, Tina L; Richard, John P

2012-09-05

The exchange for deuterium of the C-6 protons of uridine 5'-monophosphate (UMP) and 5-fluorouridine 5'-monophosphate (F-UMP) catalyzed by yeast orotidine 5'-monophosphate decarboxylase (ScOMPDC) at pD 6.5-9.3 and 25 °C was monitored by (1)H NMR spectroscopy. Deuterium exchange proceeds by proton transfer from C-6 of the bound nucleotide to the deprotonated side chain of Lys-93 to give the enzyme-bound vinyl carbanion. The pD-rate profiles for k(cat) give turnover numbers for deuterium exchange into enzyme-bound UMP and F-UMP of 1.2 × 10(-5) and 0.041 s(-1), respectively, so that the 5-fluoro substituent results in a 3400-fold increase in the first-order rate constant for deuterium exchange. The binding of UMP and F-UMP to ScOMPDC results in 0.5 and 1.4 unit decreases, respectively, in the pK(a) of the side chain of the catalytic base Lys-93, showing that these nucleotides bind preferentially to the deprotonated enzyme. We also report the first carbon acid pK(a) values for proton transfer from C-6 of uridine (pK(CH) = 28.8) and 5-fluorouridine (pK(CH) = 25.1) in aqueous solution. The stabilizing effects of the 5-fluoro substituent on C-6 carbanion formation in solution (5 kcal/mol) and at ScOMPDC (6 kcal/mol) are similar. The binding of UMP and F-UMP to ScOMPDC results in a greater than 5 × 10(9)-fold increase in the equilibrium constant for proton transfer from C-6, so that ScOMPDC stabilizes the bound vinyl carbanions, relative to the bound nucleotides, by at least 13 kcal/mol. The pD-rate profile for k(cat)/K(m) for deuterium exchange into F-UMP gives the intrinsic second-order rate constant for exchange catalyzed by the deprotonated enzyme as 2300 M(-1) s(-1). This was used to calculate a total rate acceleration for ScOMPDC-catalyzed deuterium exchange of 3 × 10(10) M(-1), which corresponds to a transition-state stabilization for deuterium exchange of 14 kcal/mol. We conclude that a large portion of the total transition-state stabilization for the decarboxylation of orotidine 5'-monophosphate can be accounted for by stabilization of the enzyme-bound vinyl carbanion intermediate of the stepwise reaction.

Proton Transfer from C-6 of Uridine 5′-Monophosphate Catalyzed by Orotidine 5′-Monophosphate Decarboxylase: Formation and Stability of a Vinyl Carbanion Intermediate and the Effect of a 5-Fluoro Substituent

PubMed Central

Tsang, Wing-Yin; Wood, B. McKay; Wong, Freeman M.; Wu, Weiming; Gerlt, John A.; Amyes, Tina L.; Richard, John P.

2012-01-01

The exchange for deuterium of the C-6 protons of uridine 5′-monophosphate (UMP) and 5-fluorouridine 5′-monophosphate (F-UMP) catalyzed by yeast orotidine 5′-monophosphate decarboxylase (ScOMPDC) at pD 6.5 – 9.3 and 25 °C was monitored by 1H NMR spectroscopy. Deuterium exchange proceeds by proton transfer from C-6 of the bound nucleotide to the deprotonated side chain of Lys-93 to give the enzyme-bound vinyl carbanion. The pD-rate profiles for kcat give turnover numbers for deuterium exchange into enzyme-bound UMP and F-UMP of 1.2 × 10−5 and 0.041 s−1, respectively, so that the 5-fluoro substituent results in a 3400-fold increase in the first-order rate constant for deuterium exchange. The binding of UMP and F-UMP to ScOMPDC results in 0.5 and 1.4 unit decreases, respectively, in the pKa of the side chain of the catalytic base Lys-93, showing that these nucleotides bind preferentially to the deprotonated enzyme. We also report the first carbon acid pKas for proton transfer from C-6 of uridine (pKCH = 28.8) and 5-fluorouridine (pKCH = 25.1) in aqueous solution. The stabilizing effects of the 5-fluoro substituent on C-6 carbanion formation in solution (5 kcal/mol) and at ScOMPDC (6 kcal/mol) are similar. The binding of UMP and F-UMP to ScOMPDC results in a greater than 5 × 109-fold increase in the equilibrium constant for proton transfer from C-6 so that ScOMPDC stabilizes the bound vinyl carbanions, relative to the bound nucleotides, by at least 13 kcal/mol. The pD-rate profile for kcat/Km for deuterium exchange into F-UMP gives the intrinsic second-order rate constant for exchange catalyzed by the deprotonated enzyme as 2300 M−1 s−1. This was used to calculate a total rate acceleration for ScOMPDC-catalyzed deuterium exchange of 3 × 1010 M−1, which corresponds to a transition state stabilization for deuterium exchange of 14 kcal/mol. We conclude that a large portion of the total transition state stabilization for the decarboxylation of orotidine 5′-monophosphate can be accounted for by stabilization of the enzyme-bound vinyl carbanion intermediate of the stepwise reaction. PMID:22812629

Analyzing Thioflavin T Binding to Amyloid Fibrils by an Equilibrium Microdialysis-Based Technique

PubMed Central

Kuznetsova, Irina M.; Sulatskaya, Anna I.; Uversky, Vladimir N.; Turoverov, Konstantin K.

2012-01-01

A new approach for the determination of the amyloid fibril – thioflavin T (ThT) binding parameters (the number of binding modes, stoichiometry, and binding constants of each mode) is proposed. This approach is based on the absorption spectroscopy determination of the concentration of free and bound to fibril dye in solutions, which are prepared by equilibrium microdialysis. Furthermore, the proposed approach allowed us, for the first time, to determine the absorption spectrum, molar extinction coefficient, and fluorescence quantum yield of the ThT bound to fibril by each binding modes. This approach is universal and can be used for determining the binding parameters of any dye interaction with a receptor, such as ANS binding to proteins in the molten globule state or to protein amorphous aggregates. PMID:22383971

Analyzing thioflavin T binding to amyloid fibrils by an equilibrium microdialysis-based technique.

PubMed

Kuznetsova, Irina M; Sulatskaya, Anna I; Uversky, Vladimir N; Turoverov, Konstantin K

2012-01-01

A new approach for the determination of the amyloid fibril - thioflavin T (ThT) binding parameters (the number of binding modes, stoichiometry, and binding constants of each mode) is proposed. This approach is based on the absorption spectroscopy determination of the concentration of free and bound to fibril dye in solutions, which are prepared by equilibrium microdialysis. Furthermore, the proposed approach allowed us, for the first time, to determine the absorption spectrum, molar extinction coefficient, and fluorescence quantum yield of the ThT bound to fibril by each binding modes. This approach is universal and can be used for determining the binding parameters of any dye interaction with a receptor, such as ANS binding to proteins in the molten globule state or to protein amorphous aggregates.

A Study of Strong Stability of Distributed Systems. Ph.D. Thesis

NASA Technical Reports Server (NTRS)

Cataltepe, Tayfun

1989-01-01

The strong stability of distributed systems is studied and the problem of characterizing strongly stable semigroups of operators associated with distributed systems is addressed. Main emphasis is on contractive systems. Three different approaches to characterization of strongly stable contractive semigroups are developed. The first one is an operator theoretical approach. Using the theory of dilations, it is shown that every strongly stable contractive semigroup is related to the left shift semigroup on an L(exp 2) space. Then, a decomposition for the state space which identifies strongly stable and unstable states is introduced. Based on this decomposition, conditions for a contractive semigroup to be strongly stable are obtained. Finally, extensions of Lyapunov's equation for distributed parameter systems are investigated. Sufficient conditions for weak and strong stabilities of uniformly bounded semigroups are obtained by relaxing the equivalent norm condition on the right hand side of the Lyanupov equation. These characterizations are then applied to the problem of feedback stabilization. First, it is shown via the state space decomposition that under certain conditions a contractive system (A,B) can be strongly stabilized by the feedback -B(*). Then, application of the extensions of the Lyapunov equation results in sufficient conditions for weak, strong, and exponential stabilizations of contractive systems by the feedback -B(*). Finally, it is shown that for a contractive system, the first derivative of x with respect to time = Ax + Bu (where B is any linear bounded operator), there is a related linear quadratic regulator problem and a corresponding steady state Riccati equation which always has a bounded nonnegative solution.

[Effects of Low-Molecular-Weight Organic Acids on the Speciation of Pb in Purple Soil and Soil Solution].

PubMed

Liu, Jiang; Jiang, Tao; Huang, Rong; Zhang, Jin-zhong; Chen, Hong

2016-04-15

Lead (Pb) in purple soil was selected as the research target, using one-step extraction method with 0.01 mol · L⁻¹ sodium nitrate as the background electrolyte to study the release effect of citric acid (CA), tartaric acid (TA) and acetic acid (AC) with different concentrations. Sequential extraction and geochemical model (Visual Minteq v3.0) were applied to analyze and predict the speciation of Pb in soil solid phase and soil solution phase. Then the ebvironmental implications and risks of low-molecule weight organic acid (LMWOA) on soil Pb were analyzed. The results indicated that all three types of LMWOA increased the desorption capacity of Pb in purple soil, and the effect followed the descending order of CA > TA > AC. After the action of LMWOAs, the exchangeable Pb increased; the carbonate-bound Pb and Fe-Mn oxide bound Pb dropped in soil solid phase. Organic bound Pb was the main speciation in soil solution phase, accounting for 45.16%-75.05%. The following speciation of Pb in soil solution was free Pb, accounting for 22.71%-50.25%. For CA and TA treatments, free Pb ions and inorganic bound Pb in soil solution increased with increasing LMWOAs concentration, while organic bound Pb suffered a decrease in this process. An opposite trend for AC treatment was observed compared with CA and TA treatments. Overall, LMWOAs boosted the bioavailability of Pb in purple soil and had a potential risk to contaminate underground water. Among the three LMWOAs in this study, CA had the largest potential to activate soil Pb.

Segmented strings and the McMillan map

DOE PAGES

Gubser, Steven S.; Parikh, Sarthak; Witaszczyk, Przemek

2016-07-25

We present new exact solutions describing motions of closed segmented strings in AdS 3 in terms of elliptic functions. The existence of analytic expressions is due to the integrability of the classical equations of motion, which in our examples reduce to instances of the McMillan map. Here, we also obtain a discrete evolution rule for the motion in AdS 3 of arbitrary bound states of fundamental strings and D1-branes in the test approximation.

Transient and steady state viscoelastic rolling contact

NASA Technical Reports Server (NTRS)

Padovan, J.; Paramadilok, O.

1985-01-01

Based on moving total Lagrangian coordinates, a so-called traveling Hughes type contact strategy is developed. Employing the modified contact scheme in conjunction with a traveling finite element strategy, an overall solution methodology is developed to handle transient and steady viscoelastic rolling contact. To verify the scheme, the results of both experimental and analytical benchmarking is presented. The experimental benchmarking includes the handling of rolling tires up to their upper bound behavior, namely the standing wave response.

Determining the Orientation and Localization of Membrane-Bound Peptides

PubMed Central

Hohlweg, Walter; Kosol, Simone; Zangger, Klaus

2012-01-01

Many naturally occurring bioactive peptides bind to biological membranes. Studying and elucidating the mode of interaction is often an essential step to understand their molecular and biological functions. To obtain the complete orientation and immersion depth of such compounds in the membrane or a membrane-mimetic system, a number of methods are available, which are separated in this review into four main classes: solution NMR, solid-state NMR, EPR and other methods. Solution NMR methods include the Nuclear Overhauser Effect (NOE) between peptide and membrane signals, residual dipolar couplings and the use of paramagnetic probes, either within the membrane-mimetic or in the solvent. The vast array of solid state NMR methods to study membrane-bound peptide orientation and localization includes the anisotropic chemical shift, PISA wheels, dipolar waves, the GALA, MAOS and REDOR methods and again the use of paramagnetic additives on relaxation rates. Paramagnetic additives, with their effect on spectral linewidths, have also been used in EPR spectroscopy. Additionally, the orientation of a peptide within a membrane can be obtained by the anisotropic hyperfine tensor of a rigidly attached nitroxide label. Besides these magnetic resonance techniques a series of other methods to probe the orientation of peptides in membranes has been developed, consisting of fluorescence-, infrared- and oriented circular dichroism spectroscopy, colorimetry, interface-sensitive X-ray and neutron scattering and Quartz crystal microbalance. PMID:22044140

Low pH overrides the need of calcium ions for the shape-function relationship of calmodulin: resolving prevailing debates.

PubMed

Pandey, Kalpana; Dhoke, Reema R; Rathore, Yogendra Singh; Nath, Samir K; Verma, Neha; Bawa, Simranjot; Ashish

2014-05-15

Calmodulin (CaM) regulates numerous cellular functions by sensing Ca(2+) levels inside cells. Although its structure as a function of the Ca(2+)-bound state remains hotly debated, no report is available on how pH independently or in interaction with Ca(2+) ions regulates shape and function of CaM. From SAXS data analysis of CaM at different levels of Ca(2+)-ion concentration and buffer pH, we found that (1) CaM molecules possess a Gaussian-chain-like shape in solution even in the presence of Ca(2+) ion or at low pH, (2) the global shape of apo CaM is very similar to its NMR structure rather than the crystal structures, (3) about 16 Ca(2+) ions or more are required per CaM molecule in solution to achieve the four-Ca(2+)-bound crystal structure, (4) low pH alone can impart shape changes in CaM similar to Ca(2+) ions, and (5) at different [Ca(2+)]/[CaM] ratio or pH values, the predominant shape of CaM is essentially a weighted average of its apo and fully activated shape. Results were further substantiated by analysis of sedimentation coefficient values from analytical ultracentrifugation and peptide binding assays using two peptides, each known to preferentially bind the apo or the Ca(2+)-activated state.

Structural and dynamical properties of recombining ultracold neutral plasma

NASA Astrophysics Data System (ADS)

Tiwari, Sanat Kumar; Shaffer, Nathaniel R.; Baalrud, Scott D.

2017-10-01

An ultracold plasma (UCP) is an evolving collection of free charges and bound charges (Rydberg atoms). Over time, bound species concentration increases due to recombination. We present the structural and dynamical properties of an evolving UCP using classical molecular dynamics simulation. Coulomb collapse is avoided using a repulsive core with the attractive Coulomb potential. The repulsive core size controls the concentration of bound states, as it determines the depth of the potential well between opposite charges. We vary the repulsive core size to emulate the quasi-static state of plasma at different time during the evolution. Binary, chain and ring-like bound states are observed in the simulation carried out at different coupling strengths and repulsive core size. The effect of bound states can be seen as molecular peaks in the radial distribution function (RDF). The thermodynamic properties associated with the free charges can be analyzed from RDF by separating free from bound states. These bound states also change the dynamical properties of the plasma. The electron velocity auto-correlation displays oscillations due to the orbital motion in bound states. These bound states act like a neutral species, damping electron plasmon modes and broadening the ion acoustic mode. This work is supported by AFOSR Grant Number FA9550-16-1-0221. It used computational resources by XSEDE, which is supported by NSF Grant Number ACI-1053575.

Nanostructures and nanosecond dynamics at the polymer/filler interface

NASA Astrophysics Data System (ADS)

Koga, Tad; Barkley, Deborah; Endoh, Maya; Masui, Tomomi; Kishimoto, Hiroyuki; Nagao, Michihiro; Taniguchi, Takashi

We report in-situ nanostructures and nanosecond dynamics of polybutadiene (PB) chains bound to carbon black (CB) fillers (the so-called ``bound polymer layer (BPL)'') in polymer solutions (from dilute to concentrated solutions). The BPL on the CB fillers were extracted by solvent leaching of a CB-filled PB compound and subsequently dispersed in deuterated toluene (a good solvent) to label the BPL for ``contrast-matching'' small-angle neutron scattering (SANS) and neutron spin echo (NSE) techniques. The SANS results demonstrate that the BPL is composed of two regions regardless of molecular weights of PB: the inner unswollen region of 0.5 nm thick and outer swollen region where the polymer chains display a parabolic profile with a diffuse tail. In addition, the NSE results show that the dynamics of the swollen bound chains in the polymer solutions can be explained by the collective dynamics, the so-called ``breathing mode''. Intriguingly, it was also indicative that the collective dynamics is independent of the polymer concentrations and is much faster than that predicted from the solution viscosity. We will discuss the mechanism at the bound polymer-free polymer interface at the nanometer scale. T.K. acknowledges the financial support from NSF Grant (CMMI-1332499).

A tight upper bound for quadratic knapsack problems in grid-based wind farm layout optimization

NASA Astrophysics Data System (ADS)

Quan, Ning; Kim, Harrison M.

2018-03-01

The 0-1 quadratic knapsack problem (QKP) in wind farm layout optimization models possible turbine locations as nodes, and power loss due to wake effects between pairs of turbines as edges in a complete graph. The goal is to select up to a certain number of turbine locations such that the sum of selected node and edge coefficients is maximized. Finding the optimal solution to the QKP is difficult in general, but it is possible to obtain a tight upper bound on the QKP's optimal value which facilitates the use of heuristics to solve QKPs by giving a good estimate of the optimality gap of any feasible solution. This article applies an upper bound method that is especially well-suited to QKPs in wind farm layout optimization due to certain features of the formulation that reduce the computational complexity of calculating the upper bound. The usefulness of the upper bound was demonstrated by assessing the performance of the greedy algorithm for solving QKPs in wind farm layout optimization. The results show that the greedy algorithm produces good solutions within 4% of the optimal value for small to medium sized problems considered in this article.

Concentration-Dependent Exchange of Replication Protein A on Single-Stranded DNA Revealed by Single-Molecule Imaging

PubMed Central

Gibb, Bryan; Ye, Ling F.; Gergoudis, Stephanie C.; Kwon, YoungHo; Niu, Hengyao; Sung, Patrick; Greene, Eric C.

2014-01-01

Replication protein A (RPA) is a ubiquitous eukaryotic single-stranded DNA (ssDNA) binding protein necessary for all aspects of DNA metabolism involving an ssDNA intermediate, including DNA replication, repair, recombination, DNA damage response and checkpoint activation, and telomere maintenance [1], [2], [3]. The role of RPA in most of these reactions is to protect the ssDNA until it can be delivered to downstream enzymes. Therefore a crucial feature of RPA is that it must bind very tightly to ssDNA, but must also be easily displaced from ssDNA to allow other proteins to gain access to the substrate. Here we use total internal reflection fluorescence microscopy and nanofabricated DNA curtains to visualize the behavior of Saccharomyces cerevisiae RPA on individual strands of ssDNA in real-time. Our results show that RPA remains bound to ssDNA for long periods of time when free protein is absent from solution. In contrast, RPA rapidly dissociates from ssDNA when free RPA is present in solution allowing rapid exchange between the free and bound states. In addition, the S. cerevisiae DNA recombinase Rad51 and E. coli single-stranded binding protein (SSB) also promote removal of RPA from ssDNA. These results reveal an unanticipated exchange between bound and free RPA suggesting a binding mechanism that can confer exceptionally slow off rates, yet also enables rapid displacement through a direct exchange mechanism that is reliant upon the presence of free ssDNA-binding proteins in solution. Our results indicate that RPA undergoes constant microscopic dissociation under all conditions, but this is only manifested as macroscopic dissociation (i.e. exchange) when free proteins are present in solution, and this effect is due to mass action. We propose that the dissociation of RPA from ssDNA involves a partially dissociated intermediate, which exposes a small section of ssDNA allowing other proteins to access to the DNA. PMID:24498402

Comment on "exact solutions of the derivative nonlinear Schrödinger equation for a nonlinear transmission line".

PubMed

Nickel, J; Schürmann, H W

2007-03-01

In a recent article Kengne and Liu [Phys. Rev. E 73, 026603 (2006)] have presented a number of exact elliptic solutions for a derivative nonlinear Schrödinger equation. It is the aim of this Comment to point out that all these solutions given in Secs. II and III of this article (referred to as KL in the following) are subcases of the general solution of Eq. (KL.9). Conditions for the parameters A-E of the solutions given by Kengne and Liu can be found from general conditions for solitary and periodic elliptic solutions as shown in the following. Positive and bounded solutions can be found by considering the phase diagram. Therefore, the comment of Kengne and Liu that "we find its particular positive bounded solutions" can be specified.

Stabilizing a solution of the 2D Navier-Stokes system in the exterior of a bounded domain by means of a control on the boundary

DOE Office of Scientific and Technical Information (OSTI.GOV)

Gorshkov, Aleksei V

2012-09-30

The problem of stabilizing a solution of the 2D Navier-Stokes system defined in the exterior of a bounded domain with smooth boundary is investigated. For a given initial velocity field a control on the boundary of the domain must be constructed such that the solution stabilizes to a prescribed vortex solution or trivial solution at the rate of 1/t{sup k}. On the way, related questions are investigated, concerning the behaviour of the spectrum of an operator under a relatively compact perturbation and the existence of attracting invariant manifolds. Bibliography: 21 titles.

BBPH: Using progressive hedging within branch and bound to solve multi-stage stochastic mixed integer programs

DOE PAGES

Barnett, Jason; Watson, Jean -Paul; Woodruff, David L.

2016-11-27

Progressive hedging, though an effective heuristic for solving stochastic mixed integer programs (SMIPs), is not guaranteed to converge in this case. Here, we describe BBPH, a branch and bound algorithm that uses PH at each node in the search tree such that, given sufficient time, it will always converge to a globally optimal solution. Additionally, to providing a theoretically convergent “wrapper” for PH applied to SMIPs, computational results demonstrate that for some difficult problem instances branch and bound can find improved solutions after exploring only a few nodes.

Non-predictor control of a class of feedforward nonlinear systems with unknown time-varying delays

NASA Astrophysics Data System (ADS)

Koo, Min-Sung; Choi, Ho-Lim

2016-08-01

This paper generalises the several recent results on the control of feedforward time-delay nonlinear systems. First, in view of system formulation, there are unknown time-varying delays in both states and main control input. Also, the considered nonlinear system has extended feedforward nonlinearities. Second, in view of control solution, our proposed controller is a non-predictor feedback controller whereas smith-predictor type controllers are used in the several existing results. Moreover, our controller does not need any information on the unknown delays except their upper bounds. Thus, our result has certain merits in both system formulation and control solution perspective. The analysis and example are given for clear illustration.

Bound states in string nets

NASA Astrophysics Data System (ADS)

Schulz, Marc Daniel; Dusuel, Sébastien; Vidal, Julien

2016-11-01

We discuss the emergence of bound states in the low-energy spectrum of the string-net Hamiltonian in the presence of a string tension. In the ladder geometry, we show that a single bound state arises either for a finite tension or in the zero-tension limit depending on the theory considered. In the latter case, we perturbatively compute the binding energy as a function of the total quantum dimension. We also address this issue in the honeycomb lattice where the number of bound states in the topological phase depends on the total quantum dimension. Finally, the internal structure of these bound states is analyzed in the zero-tension limit.

Study of molecular N D bound states in the Bethe-Salpeter equation approach

NASA Astrophysics Data System (ADS)

Wang, Zhen-Yang; Qi, Jing-Juan; Guo, Xin-Heng; Wei, Ke-Wei

2018-05-01

We study the Λc(2595 )+ and Σc(2800 )0 states as the N D bound systems in the Bethe-Salpeter formalism in the ladder and instantaneous approximations. With the kernel induced by ρ , ω and σ exchanges, we solve the Bethe-Salpeter equations for the N D bound systems numerically and find that the bound states may exist. We assume that the observed states Λc(2595 )+ and Σc(2800 )0 are S -wave N D molecular bound states and calculate the decay widths of Λc(2595 )+→Σc0π+ and Σc(2800 )0→Λc+π-.

Strong Dependence of Hydration State of F-Actin on the Bound Mg(2+)/Ca(2+) Ions.

PubMed

Suzuki, Makoto; Imao, Asato; Mogami, George; Chishima, Ryotaro; Watanabe, Takahiro; Yamaguchi, Takaya; Morimoto, Nobuyuki; Wazawa, Tetsuichi

2016-07-21

Understanding of the hydration state is an important issue in the chemomechanical energetics of versatile biological functions of polymerized actin (F-actin). In this study, hydration-state differences of F-actin by the bound divalent cations are revealed through precision microwave dielectric relaxation (DR) spectroscopy. G- and F-actin in Ca- and Mg-containing buffer solutions exhibit dual hydration components comprising restrained water with DR frequency f2 (fw). The hydration state of F-actin is strongly dependent on the ionic composition. In every buffer tested, the HMW signal Dhyme (≡ (f1 - fw)δ1/(fwδw)) of F-actin is stronger than that of G-actin, where δw is DR-amplitude of bulk solvent and δ1 is that of HMW in a fixed-volume ellipsoid containing an F-actin and surrounding water in solution. Dhyme value of F-actin in Ca2.0-buffer (containing 2 mM Ca(2+)) is markedly higher than in Mg2.0-buffer (containing 2 mM Mg(2+)). Moreover, in the presence of 2 mM Mg(2+), the hydration state of F-actin is changed by adding a small fraction of Ca(2+) (∼0.1 mM) and becomes closer to that of the Ca-bound form in Ca2.0-buffer. This is consistent with the results of the partial specific volume and the Cotton effect around 290 nm in the CD spectra, indicating a change in the tertiary structure and less apparent change in the secondary structure of actin. The number of restrained water molecules per actin (N2) is estimated to be 1600-2100 for Ca2.0- and F-buffer and ∼2500 for Mg2.0-buffer at 10-15 °C. These numbers are comparable to those estimated from the available F-actin atomic structures as in the first water layer. The number of HMW molecules is roughly explained by the volume between the equipotential surface of -kT/2e and the first water layer of the actin surface by solving the Poisson-Boltzmann equation using UCSF Chimera.

Approximation of traveling wave solutions in wall-bounded flows using resolvent modes

NASA Astrophysics Data System (ADS)

McKeon, Beverley; Graham, Michael; Moarref, Rashad; Park, Jae Sung; Sharma, Ati; Willis, Ashley

2014-11-01

Significant recent attention has been devoted to computing and understanding exact traveling wave solutions of the Navier-Stokes equations. These solutions can be interpreted as the state-space skeleton of turbulence and are attractive benchmarks for studying low-order models of wall turbulence. Here, we project such solutions onto the velocity response (or resolvent) modes supplied by the gain-based resolvent analysis outlined by McKeon & Sharma (JFM, 2010). We demonstrate that in both pipe (Pringle et al., Phil. Trans. R. Soc. A, 2009) and channel (Waleffe, JFM, 2001) flows, the solutions can be well-described by a small number of resolvent modes. Analysis of the nonlinear forcing modes sustaining these solutions reveals the importance of small amplitude forcing, consistent with the large amplifications admitted by the resolvent operator. We investigate the use of resolvent modes as computationally cheap ``seeds'' for the identification of further traveling wave solutions. The support of AFOSR under Grants FA9550-09-1-0701, FA9550-12-1-0469, FA9550-11-1-0094 and FA9550-14-1-0042 (program managers Rengasamy Ponnappan, Doug Smith and Gregg Abate) is gratefully acknowledged.

Distinguishing topological Majorana bound states from trivial Andreev bound states: Proposed tests through differential tunneling conductance spectroscopy

NASA Astrophysics Data System (ADS)

Liu, Chun-Xiao; Sau, Jay D.; Das Sarma, S.

2018-06-01

Trivial Andreev bound states arising from chemical-potential variations could lead to zero-bias tunneling conductance peaks at finite magnetic field in class-D nanowires, precisely mimicking the predicted zero-bias conductance peaks arising from the topological Majorana bound states. This finding raises a serious question on the efficacy of using zero-bias tunneling conductance peaks, by themselves, as evidence supporting the existence of topological Majorana bound states in nanowires. In the current work, we provide specific experimental protocols for tunneling spectroscopy measurements to distinguish between Andreev and Majorana bound states without invoking more demanding nonlocal measurements which have not yet been successfully performed in nanowire systems. In particular, we discuss three distinct experimental schemes involving the response of the zero-bias peak to local perturbations of the tunnel barrier, the overlap of bound states from the wire ends, and, most compellingly, introducing a sharp localized potential in the wire itself to perturb the zero-bias tunneling peaks. We provide extensive numerical simulations clarifying and supporting our theoretical predictions.

Microscopic observation of magnon bound states and their dynamics.

PubMed

Fukuhara, Takeshi; Schauß, Peter; Endres, Manuel; Hild, Sebastian; Cheneau, Marc; Bloch, Immanuel; Gross, Christian

2013-10-03

The existence of bound states of elementary spin waves (magnons) in one-dimensional quantum magnets was predicted almost 80 years ago. Identifying signatures of magnon bound states has so far remained the subject of intense theoretical research, and their detection has proved challenging for experiments. Ultracold atoms offer an ideal setting in which to find such bound states by tracking the spin dynamics with single-spin and single-site resolution following a local excitation. Here we use in situ correlation measurements to observe two-magnon bound states directly in a one-dimensional Heisenberg spin chain comprising ultracold bosonic atoms in an optical lattice. We observe the quantum dynamics of free and bound magnon states through time-resolved measurements of two spin impurities. The increased effective mass of the compound magnon state results in slower spin dynamics as compared to single-magnon excitations. We also determine the decay time of bound magnons, which is probably limited by scattering on thermal fluctuations in the system. Our results provide a new way of studying fundamental properties of quantum magnets and, more generally, properties of interacting impurities in quantum many-body systems.

Multi-component Wronskian solution to the Kadomtsev-Petviashvili equation

NASA Astrophysics Data System (ADS)

Xu, Tao; Sun, Fu-Wei; Zhang, Yi; Li, Juan

2014-01-01

It is known that the Kadomtsev-Petviashvili (KP) equation can be decomposed into the first two members of the coupled Ablowitz-Kaup-Newell-Segur (AKNS) hierarchy by the binary non-linearization of Lax pairs. In this paper, we construct the N-th iterated Darboux transformation (DT) for the second- and third-order m-coupled AKNS systems. By using together the N-th iterated DT and Cramer's rule, we find that the KPII equation has the unreduced multi-component Wronskian solution and the KPI equation admits a reduced multi-component Wronskian solution. In particular, based on the unreduced and reduced two-component Wronskians, we obtain two families of fully-resonant line-soliton solutions which contain arbitrary numbers of asymptotic solitons as y → ∓∞ to the KPII equation, and the ordinary N-soliton solution to the KPI equation. In addition, we find that the KPI line solitons propagating in parallel can exhibit the bound state at the moment of collision.

Topologically protected bound states in photonic parity-time-symmetric crystals.

PubMed

Weimann, S; Kremer, M; Plotnik, Y; Lumer, Y; Nolte, S; Makris, K G; Segev, M; Rechtsman, M C; Szameit, A

2017-04-01

Parity-time (PT)-symmetric crystals are a class of non-Hermitian systems that allow, for example, the existence of modes with real propagation constants, for self-orthogonality of propagating modes, and for uni-directional invisibility at defects. Photonic PT-symmetric systems that also support topological states could be useful for shaping and routing light waves. However, it is currently debated whether topological interface states can exist at all in PT-symmetric systems. Here, we show theoretically and demonstrate experimentally the existence of such states: states that are localized at the interface between two topologically distinct PT-symmetric photonic lattices. We find analytical closed form solutions of topological PT-symmetric interface states, and observe them through fluorescence microscopy in a passive PT-symmetric dimerized photonic lattice. Our results are relevant towards approaches to localize light on the interface between non-Hermitian crystals.

Quantitative conditions for time evolution in terms of the von Neumann equation

NASA Astrophysics Data System (ADS)

Wang, WenHua; Cao, HuaiXin; Chen, ZhengLi; Wang, Lie

2018-07-01

The adiabatic theorem describes the time evolution of the pure state and gives an adiabatic approximate solution to the Schödinger equation by choosing a single eigenstate of the Hamiltonian as the initial state. In quantum systems, states are divided into pure states (unite vectors) and mixed states (density matrices, i.e., positive operators with trace one). Accordingly, mixed states have their own corresponding time evolution, which is described by the von Neumann equation. In this paper, we discuss the quantitative conditions for the time evolution of mixed states in terms of the von Neumann equation. First, we introduce the definitions for uniformly slowly evolving and δ-uniformly slowly evolving with respect to mixed states, then we present a necessary and sufficient condition for the Hamiltonian of the system to be uniformly slowly evolving and we obtain some upper bounds for the adiabatic approximate error. Lastly, we illustrate our results in an example.

Solution Structures of Mycobacterium tuberculosis Thioredoxin C and Models of the Intact Thioredoxin System Suggest New Approaches to Inhibitor and Drug Design

PubMed Central

Olson, Andrew L.; Neumann, Terrence S.; Cai, Sheng; Sem, Daniel S.

2012-01-01

Here we report the NMR solution structures of Mycobacterium tuberculosis (M. tuberculosis) thioredoxin C in both oxidized and reduced states, with discussion of structural changes that occur in going between redox states. The NMR solution structure of the oxidized TrxC corresponds closely to that of the crystal structure, except in the C-terminal region. It appears that crystal packing effects have caused an artifactual shift in the α4 helix in the previously reported crystal structure, compared to the solution structure. Based on these TrxC structures, chemical shift mapping, a previously reported crystal structure of the M. tuberculosis thioredoxin reductase (not bound to a Trx) and structures for intermediates in the E. coli thioredoxin catalytic cycle, we have modeled the complete M. tuberculosis thioredoxin system for the various steps in the catalytic cycle. These structures and models reveal pockets at the TrxR/TrxC interface in various steps in the catalytic cycle, which can be targeted in the design of uncompetitive inhibitors as potential anti-mycobacterial agents, or as chemical genetic probes of function. PMID:23229911

Generation of bound states of pulses in a SESAM mode-locked Cr:ZnSe laser

NASA Astrophysics Data System (ADS)

Bu, Xiangbao; Shi, Yuhang; Xu, Jia; Li, Huijuan; Wang, Pu

2018-06-01

We report on the generation of bound states of pulses in a SESAM mode-locked Cr:ZnSe laser around 2415 nm. A thulium-doped double-clad fiber laser at 1908 nm was used as the pump source. Bound states with various pulse separations at different dispersion regimes were obtained. Especially, in the anomalous dispersion regime, vibrating bound state of solitons exhibiting an evolving phase was obtained.

Bound entangled states with a private key and their classical counterpart.

PubMed

Ozols, Maris; Smith, Graeme; Smolin, John A

2014-03-21

Entanglement is a fundamental resource for quantum information processing. In its pure form, it allows quantum teleportation and sharing classical secrets. Realistic quantum states are noisy and their usefulness is only partially understood. Bound-entangled states are central to this question--they have no distillable entanglement, yet sometimes still have a private classical key. We present a construction of bound-entangled states with a private key based on classical probability distributions. From this emerge states possessing a new classical analogue of bound entanglement, distinct from the long-sought bound information. We also find states of smaller dimensions and higher key rates than previously known. Our construction has implications for classical cryptography: we show that existing protocols are insufficient for extracting private key from our distributions due to their "bound-entangled" nature. We propose a simple extension of existing protocols that can extract a key from them.

77 FR 31830 - Opportunity for Designation in the West Sacramento, CA; Frankfort, IN; Indianapolis, IN; and...

Federal Register 2010, 2011, 2012, 2013, 2014

2012-05-30

... eastern California State line; Bounded on the East by the eastern California State line south to the... lines west to the western California State line; and Bounded on the West by the western California State...; Bounded on the East by the eastern Fulton County line south to State Route 19; State Route 19 south to...

Probing Structural Changes among Analogous Inhibitor-Bound Forms of HIV-1 Protease and a Drug-Resistant Mutant in Solution by Nuclear Magnetic Resonance.

PubMed

Khan, Shahid N; Persons, John D; Paulsen, Janet L; Guerrero, Michel; Schiffer, Celia A; Kurt-Yilmaz, Nese; Ishima, Rieko

2018-03-13

In the era of state-of-the-art inhibitor design and high-resolution structural studies, detection of significant but small protein structural differences in the inhibitor-bound forms is critical to further developing the inhibitor. Here, we probed differences in HIV-1 protease (PR) conformation among darunavir and four analogous inhibitor-bound forms and compared them with a drug-resistant mutant using nuclear magnetic resonance chemical shifts. Changes in amide chemical shifts of wild-type (WT) PR among these inhibitor-bound forms, ΔCSP, were subtle but detectable and extended >10 Å from the inhibitor-binding site, asymmetrically between the two subunits of PR. Molecular dynamics simulations revealed differential local hydrogen bonding as the molecular basis of this remote asymmetric change. Inhibitor-bound forms of the drug-resistant mutant also showed a similar long-range ΔCSP pattern. Differences in ΔCSP values of the WT and the mutant (ΔΔCSPs) were observed at the inhibitor-binding site and in the surrounding region. Comparing chemical shift changes among highly analogous inhibitors and ΔΔCSPs effectively eliminated local environmental effects stemming from different chemical groups and enabled exploitation of these sensitive parameters to detect subtle protein conformational changes and to elucidate asymmetric and remote conformational effects upon inhibitor interaction.

On flows of viscoelastic fluids under threshold-slip boundary conditions

NASA Astrophysics Data System (ADS)

Baranovskii, E. S.

2018-03-01

We investigate a boundary-value problem for the steady isothermal flow of an incompressible viscoelastic fluid of Oldroyd type in a 3D bounded domain with impermeable walls. We use the Fujita threshold-slip boundary condition. This condition states that the fluid can slip along a solid surface when the shear stresses reach a certain critical value; otherwise the slipping velocity is zero. Assuming that the flow domain is not rotationally symmetric, we prove an existence theorem for the corresponding slip problem in the framework of weak solutions. The proof uses methods for solving variational inequalities with pseudo-monotone operators and convex functionals, the method of introduction of auxiliary viscosity, as well as a passage-to-limit procedure based on energy estimates of approximate solutions, Korn’s inequality, and compactness arguments. Also, some properties and estimates of weak solutions are established.

Describing the strongly interacting quark-gluon plasma through the Friedberg-Lee model

DOE Office of Scientific and Technical Information (OSTI.GOV)

Shu Song; Li Jiarong; Institute of Particle Physics, Hua-Zhong Normal University, Wuhan 430079

2010-10-15

The Friedberg-Lee (FL) model is studied at finite temperature and density. The soliton solutions of the FL model in the deconfinement phase transition are solved and thoroughly discussed for certain boundary conditions. We indicate that the solitons before and after the deconfinement have different physical meanings: the soliton before deconfinement represents hadrons, while the soliton after the deconfinement represents the bound state of quarks which leads to a strongly interacting quark-gluon plasma phase. The corresponding phase diagram is given.

Distinguishing Majorana bound states and Andreev bound states with microwave spectra

NASA Astrophysics Data System (ADS)

Zhang, Zhen-Tao

2018-04-01

Majorana fermions are a fascinating and not yet confirmed quasiparticles in condensed matter physics. Here we propose using microwave spectra to distinguish Majorana bound states (MBSs) from topological trivial Andreev bound states. By numerically calculating the transmission and Zeeman field dependence of the many-body excitation spectrum of a 1D Josephson junction, we find that the two kinds of bound states have distinct responses to variations in the related parameters. Furthermore, the singular behaviors of the MBSs spectrum could be attributed to the robust fractional Josephson coupling and nonlocality of MBSs. Our results provide a feasible method to verify the existence of MBSs and could accelerate its application to topological quantum computation.

Gravitationally self-bound quantum states in unstable potentials

NASA Astrophysics Data System (ADS)

Jääskeläinen, Markku

2018-04-01

Quantum mechanics at present cannot be unified with the theory of gravity at the deepest level, and to guide research towards the solution of this fundamental problem, we need to look for ways to observe or refute predictions originating from attempts to combine quantum theory with gravity. The influence of the gravitational field created by the material density given by the wave function itself gives rise to nontrivial phenomena. In this study I consider the wave function for the center-of-mass coordinate of a spherical mass distribution under the influence of the self-interaction of Newtonian gravity. I solve numerically for the ground state in the presence of an unstable potential and find that the energy of the free-space bound state can be lowered despite the nontrapping character of the potential. The center-of-mass ground state becomes increasingly localized for the used unstable potentials, although only in a limited parameter regime. The feebleness of the energy shift makes the observation of these effects demanding and requires further developments in the cooling of material particles. In addition, the influence of gravitational perturbations that are present in typical laboratory settings necessitates the use of extremely quiet and controlled environments such as those provided by recently proposed space-borne experiments.

A mechanistic study of the interaction of water-soluble borate glass with apatite-bound heterocyclic nitrogen-containing bisphosphonates.

PubMed

Pramanik, Chandrani; Sood, Parveen; Niu, Li-Na; Yuan, He; Ghoshal, Sushanta; Henderson, Walter; Liu, Yaodong; Jang, Seung Soon; Kumar, Satish; Pashley, David H; Tay, Franklin R

2016-02-01

Long-term oral and intravenous use of nitrogen-containing bisphosphonates (N-BPs) is associated with osteonecrosis of the jaw. Although N-BPs bind strongly to bone surfaces via non-covalent bonds, it is possible for extrinsic ions to dissociate bound N-BPs from mineralized bone by competitive desorption. Here, we investigate the effects and mechanism of using an ionic cocktail derived from borate bioactive glass for sequestration of heterocyclic N-BPs bound to apatite. By employing solid-state and solution-state analytical techniques, we confirmed that sequestration of N-BPs from bisphosphonate-bound apatite occurs in the presence of the borate-containing ionic cocktail. Simulations by density functional theory computations indicate that magnesium cation and borate anion are well within the extent of the risedronate or zoledronate anion to form precipitate complexes. The sequestration mechanism is due to the borate anion competing with bisphosphonates for similar electron-deficient sites on the apatite surface for binding. Thus, application of the borate-containing ionic cocktail represents a new topical lavage approach for removing apatite-bound heterocyclic N-BPs from exposed necrotic bone in bisphosphonate-related osteonecrosis of the jaw. Long-term oral consumption and injections of nitrogen-containing bisphosphonates (N-BPs) may result in death of the jaw bone when there is traumatic injury to the bone tissues. To date, there is no effective treatment for such a condition. This work reported the use of an ionic cocktail derived from water-soluble borate glass microfibers to displace the most potent type of N-BPs that are bound strongly to the mineral component on bone surfaces. The mechanism responsible for such an effect has been identified to be cation-mediated complexation of borate anions with negatively-charged N-BPs, allowing them to be released from the mineral surface. This borate-containing cocktail may be developed into a novel topical rinse for removing mineral-bound N-BPs from exposed dead bone. Copyright © 2015 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.

A solution-based single-molecule study of surface-bound PBIs: solvent-mediated environmental effects on molecular flexibility.

PubMed

Lee, Ji-Eun; Han, Ye Ri; Ham, Sujin; Jun, Chul-Ho; Kim, Dongho

2017-11-08

We have investigated the fundamental photophysical properties of surface-bound perylene bisimide (PBI) molecules in a solution-phase at the single-molecule level. By efficient immobilization of single PBIs on glass, we were able to simultaneously monitor fluorescence intensity trajectories, fluorescence lifetimes, and emission spectra of individual PBIs in organic and aqueous media using confocal microscopy. We showed that the fluorescence dynamics of single PBIs in the solution phase is highly dependent on their local and chemical environments. Furthermore, we visualized different spatial-fluctuations of surface-bound PBIs using defocused wide-field imaging. While PBIs show more steric flexibility in organic media, the flexible motion of PBI molecules in aqueous solution is relatively prohibited due to a cage effect by a hydrogen bonding network, which is previously unobserved. Our method opens up a new possibility to investigate the photophysical properties of multi-chromophoric systems in various solvents at the single-molecule level for developing optimal molecular devices such as water-proof devices.

Absolute Lower Bound on the Bounce Action

NASA Astrophysics Data System (ADS)

Sato, Ryosuke; Takimoto, Masahiro

2018-03-01

The decay rate of a false vacuum is determined by the minimal action solution of the tunneling field: bounce. In this Letter, we focus on models with scalar fields which have a canonical kinetic term in N (>2 ) dimensional Euclidean space, and derive an absolute lower bound on the bounce action. In the case of four-dimensional space, we show the bounce action is generically larger than 24 /λcr, where λcr≡max [-4 V (ϕ )/|ϕ |4] with the false vacuum being at ϕ =0 and V (0 )=0 . We derive this bound on the bounce action without solving the equation of motion explicitly. Our bound is derived by a quite simple discussion, and it provides useful information even if it is difficult to obtain the explicit form of the bounce solution. Our bound offers a sufficient condition for the stability of a false vacuum, and it is useful as a quick check on the vacuum stability for given models. Our bound can be applied to a broad class of scalar potential with any number of scalar fields. We also discuss a necessary condition for the bounce action taking a value close to this lower bound.

The NorM MATE transporter from N. gonorrhoeae: insights into drug and ion binding from atomistic molecular dynamics simulations.

PubMed

Leung, Yuk Ming; Holdbrook, Daniel A; Piggot, Thomas J; Khalid, Syma

2014-07-15

The multidrug and toxic compound extrusion transporters extrude a wide variety of substrates out of both mammalian and bacterial cells via the electrochemical gradient of protons and cations across the membrane. The substrates transported by these proteins include toxic metabolites and antimicrobial drugs. These proteins contribute to multidrug resistance in both mammalian and bacterial cells and are therefore extremely important from a biomedical perspective. Although specific residues of the protein are known to be responsible for the extrusion of solutes, mechanistic details and indeed structures of all the conformational states remain elusive. Here, we report the first, to our knowledge, simulation study of the recently resolved x-ray structure of the multidrug and toxic compound extrusion transporter, NorM from Neisseria gonorrhoeae (NorM_NG). Multiple, atomistic simulations of the unbound and bound forms of NorM in a phospholipid lipid bilayer allow us to identify the nature of the drug-protein/ion-protein interactions, and secondly determine how these interactions contribute to the conformational rearrangements of the protein. In particular, we identify the molecular rearrangements that occur to enable the Na(+) ion to enter the cation-binding cavity even in the presence of a bound drug molecule. These include side chain flipping of a key residue, GLU-261 from pointing toward the central cavity to pointing toward the cation binding side when bound to a Na(+) ion. Our simulations also provide support for cation binding in the drug-bound and apo states of NorM_NG. Copyright © 2014 Biophysical Society. Published by Elsevier Inc. All rights reserved.

The NorM MATE Transporter from N. gonorrhoeae: Insights into Drug and Ion Binding from Atomistic Molecular Dynamics Simulations

PubMed Central

Leung, Yuk Ming; Holdbrook, Daniel A.; Piggot, Thomas J.; Khalid, Syma

2014-01-01

The multidrug and toxic compound extrusion transporters extrude a wide variety of substrates out of both mammalian and bacterial cells via the electrochemical gradient of protons and cations across the membrane. The substrates transported by these proteins include toxic metabolites and antimicrobial drugs. These proteins contribute to multidrug resistance in both mammalian and bacterial cells and are therefore extremely important from a biomedical perspective. Although specific residues of the protein are known to be responsible for the extrusion of solutes, mechanistic details and indeed structures of all the conformational states remain elusive. Here, we report the first, to our knowledge, simulation study of the recently resolved x-ray structure of the multidrug and toxic compound extrusion transporter, NorM from Neisseria gonorrhoeae (NorM_NG). Multiple, atomistic simulations of the unbound and bound forms of NorM in a phospholipid lipid bilayer allow us to identify the nature of the drug-protein/ion-protein interactions, and secondly determine how these interactions contribute to the conformational rearrangements of the protein. In particular, we identify the molecular rearrangements that occur to enable the Na+ ion to enter the cation-binding cavity even in the presence of a bound drug molecule. These include side chain flipping of a key residue, GLU-261 from pointing toward the central cavity to pointing toward the cation binding side when bound to a Na+ ion. Our simulations also provide support for cation binding in the drug-bound and apo states of NorM_NG. PMID:25028887

Analytical Dimensional Reduction of a Fuel Optimal Powered Descent Subproblem

NASA Technical Reports Server (NTRS)

Rea, Jeremy R.; Bishop, Robert H.

2010-01-01

Current renewed interest in exploration of the moon, Mars, and other planetary objects is driving technology development in many fields of space system design. In particular, there is a desire to land both robotic and human missions on the moon and elsewhere. The landing guidance system must be able to deliver the vehicle to a desired soft landing while meeting several constraints necessary for the safety of the vehicle. Due to performance limitations of current launch vehicles, it is desired to minimize the amount of fuel used. In addition, the landing site may change in real-time in order to avoid previously undetected hazards which become apparent during the landing maneuver. This complicated maneuver can be broken into simpler subproblems that bound the full problem. One such subproblem is to find a minimum-fuel landing solution that meets constraints on the initial state, final state, and bounded thrust acceleration magnitude. With the assumptions of constant gravity and negligible atmosphere, the form of the optimal steering law is known, and the equations of motion can be integrated analytically, resulting in a system of five equations in five unknowns. It is shown that this system of equations can be reduced analytically to two equations in two unknowns. With an additional assumption of constant thrust acceleration magnitude, this system can be reduced further to one equation in one unknown. It is shown that these unknowns can be bounded analytically. An algorithm is developed to quickly and reliably solve the resulting one-dimensional bounded search, and it is used as a real-time guidance applied to a lunar landing test case.

Prediction of triple-charm molecular pentaquarks

NASA Astrophysics Data System (ADS)

Chen, Rui; Hosaka, Atsushi; Liu, Xiang

2017-12-01

In a one-boson-exchange model, we study molecular states of double-charm baryon [Ξc c(3621 )] and a charmed meson (D and D*). Our model indicates that there exist two possible triple-charm molecular pentaquarks, a Ξc cD state with I (JP)=0 (1 /2-), and a Ξc cD* state with I (JP)=0 (3 /2-), and we do not find bound solutions for isotriplet states. In addition, we also extend our formula to explore Ξc cB¯(*), Ξc cD¯(*), and Ξc cB(*) systems and find more possible heavy flavor molecular pentaquarks, a Ξc cB ¯ state with I (JP)=0 (1 /2-), a Ξc cB¯* state with I (JP)=0 (3 /2-), and Ξc cD¯*/Ξc cB* states with I (JP)=0 (1 /2-). Experimental research for these predicted triple-charm molecular pentaquarks is encouraged.

The study of nonlinear almost periodic differential equations without recourse to the H-classes of these equations

DOE Office of Scientific and Technical Information (OSTI.GOV)

Slyusarchuk, V. E., E-mail: V.E.Slyusarchuk@gmail.com, E-mail: V.Ye.Slyusarchuk@NUWM.rv.ua

2014-06-01

The well-known theorems of Favard and Amerio on the existence of almost periodic solutions to linear and nonlinear almost periodic differential equations depend to a large extent on the H-classes and the requirement that the bounded solutions of these equations be separated. The present paper provides different conditions for the existence of almost periodic solutions. These conditions, which do not depend on the H-classes of the equations, are formulated in terms of a special functional on the set of bounded solutions of the equations under consideration. This functional is used, in particular, to test whether solutions are separated. Bibliography: 24more » titles. (paper)« less

A duality approach for solving bounded linear programming problems with fuzzy variables based on ranking functions and its application in bounded transportation problems

NASA Astrophysics Data System (ADS)

Ebrahimnejad, Ali

2015-08-01

There are several methods, in the literature, for solving fuzzy variable linear programming problems (fuzzy linear programming in which the right-hand-side vectors and decision variables are represented by trapezoidal fuzzy numbers). In this paper, the shortcomings of some existing methods are pointed out and to overcome these shortcomings a new method based on the bounded dual simplex method is proposed to determine the fuzzy optimal solution of that kind of fuzzy variable linear programming problems in which some or all variables are restricted to lie within lower and upper bounds. To illustrate the proposed method, an application example is solved and the obtained results are given. The advantages of the proposed method over existing methods are discussed. Also, one application of this algorithm in solving bounded transportation problems with fuzzy supplies and demands is dealt with. The proposed method is easy to understand and to apply for determining the fuzzy optimal solution of bounded fuzzy variable linear programming problems occurring in real-life situations.

Quantum Discord for d⊗2 Systems

PubMed Central

Ma, Zhihao; Chen, Zhihua; Fanchini, Felipe Fernandes; Fei, Shao-Ming

2015-01-01

We present an analytical solution for classical correlation, defined in terms of linear entropy, in an arbitrary system when the second subsystem is measured. We show that the optimal measurements used in the maximization of the classical correlation in terms of linear entropy, when used to calculate the quantum discord in terms of von Neumann entropy, result in a tight upper bound for arbitrary systems. This bound agrees with all known analytical results about quantum discord in terms of von Neumann entropy and, when comparing it with the numerical results for 106 two-qubit random density matrices, we obtain an average deviation of order 10−4. Furthermore, our results give a way to calculate the quantum discord for arbitrary n-qubit GHZ and W states evolving under the action of the amplitude damping noisy channel. PMID:26036771

Soliton interactions and complexes for coupled nonlinear Schrödinger equations.

PubMed

Jiang, Yan; Tian, Bo; Liu, Wen-Jun; Sun, Kun; Li, Min; Wang, Pan

2012-03-01

Under investigation in this paper are the coupled nonlinear Schrödinger (CNLS) equations, which can be used to govern the optical-soliton propagation and interaction in such optical media as the multimode fibers, fiber arrays, and birefringent fibers. By taking the 3-CNLS equations as an example for the N-CNLS ones (N≥3), we derive the analytic mixed-type two- and three-soliton solutions in more general forms than those obtained in the previous studies with the Hirota method and symbolic computation. With the choice of parameters for those soliton solutions, soliton interactions and complexes are investigated through the asymptotic and graphic analysis. Soliton interactions and complexes with the bound dark solitons in a mode or two modes are observed, including that (i) the two bright solitons display the breatherlike structures while the two dark ones stay parallel, (ii) the two bright and dark solitons all stay parallel, and (iii) the states of the bound solitons change from the breatherlike structures to the parallel one even with the distance between those solitons smaller than that before the interaction with the regular one soliton. Asymptotic analysis is also used to investigate the elastic and inelastic interactions between the bound solitons and the regular one soliton. Furthermore, some discussions are extended to the N-CNLS equations (N>3). Our results might be helpful in such applications as the soliton switch, optical computing, and soliton amplification in the nonlinear optics.

Stationary and oscillatory bound states of dissipative solitons created by third-order dispersion

NASA Astrophysics Data System (ADS)

Sakaguchi, Hidetsugu; Skryabin, Dmitry V.; Malomed, Boris A.

2018-06-01

We consider the model of fiber-laser cavities near the zero-dispersion point, based on the complex Ginzburg-Landau equation with the cubic-quintic nonlinearity, including the third-order dispersion (TOD) term. It is well known that this model supports stable dissipative solitons. We demonstrate that the same model gives rise to several families of robust bound states of the solitons, which exists only in the presence of the TOD. There are both stationary and dynamical bound states, with oscillating separation between the bound solitons. Stationary states are multistable, corresponding to different values of the separation. With the increase of the TOD coefficient, the bound state with the smallest separation gives rise the oscillatory state through the Hopf bifurcation. Further growth of TOD leads to a bifurcation transforming the oscillatory limit cycle into a strange attractor, which represents a chaotically oscillating dynamical bound state. Families of multistable three- and four-soliton complexes are found too, the ones with the smallest separation between the solitons again ending by a transition to oscillatory states through the Hopf bifurcation.

Impurity bound states in d-wave superconductors with subdominant order parameters

NASA Astrophysics Data System (ADS)

Mashkoori, Mahdi; Björnson, Kristofer; Black-Schaffer, Annica

Single magnetic impurity induces intra-gap bound states in conventional s-wave superconductors (SCs) but, in d-wave SCs only virtual bound states can be induced. However, in small cuprate islands a fully gapped spectrum has recently been discovered. In this work, we investigate the real bound states due to potential and magnetic impurities in the two candidate fully gapped states for this system: the topologically trivial d + is -wave state and the topologically non-trivial d + id' -wave (chiral d-wave state). Using the analytic T-matrix formalism and self-consistent numerical tight-binding lattice calculations, we show that potential and magnetic impurities create entirely different intra-gap bound states in d + is -wave and chiral d-wave SCs. Therefore, our results suggest that the bound states mainly depend on the subdominant order parameter. Considering that recent experiments have demonstrated an access to adjustable coupling J, impurities thus offer an intriguing way to clearly distinguish between the chiral d-wave and topologically trivial d + is -wave state. This work was supported by Swedish Research Council, Swedish Foundation for Strategic Research, the Wallenberg Academy Fellows program and the Göran Gustafsson Foundation. The computations were performed on resources provided by SNIC at LUNARC.

A two-level approach to large mixed-integer programs with application to cogeneration in energy-efficient buildings

DOE PAGES

Lin, Fu; Leyffer, Sven; Munson, Todd

2016-04-12

We study a two-stage mixed-integer linear program (MILP) with more than 1 million binary variables in the second stage. We develop a two-level approach by constructing a semi-coarse model that coarsens with respect to variables and a coarse model that coarsens with respect to both variables and constraints. We coarsen binary variables by selecting a small number of prespecified on/off profiles. We aggregate constraints by partitioning them into groups and taking convex combination over each group. With an appropriate choice of coarsened profiles, the semi-coarse model is guaranteed to find a feasible solution of the original problem and hence providesmore » an upper bound on the optimal solution. We show that solving a sequence of coarse models converges to the same upper bound with proven finite steps. This is achieved by adding violated constraints to coarse models until all constraints in the semi-coarse model are satisfied. We demonstrate the effectiveness of our approach in cogeneration for buildings. Here, the coarsened models allow us to obtain good approximate solutions at a fraction of the time required by solving the original problem. Extensive numerical experiments show that the two-level approach scales to large problems that are beyond the capacity of state-of-the-art commercial MILP solvers.« less

A two-level approach to large mixed-integer programs with application to cogeneration in energy-efficient buildings

DOE Office of Scientific and Technical Information (OSTI.GOV)

Lin, Fu; Leyffer, Sven; Munson, Todd

We study a two-stage mixed-integer linear program (MILP) with more than 1 million binary variables in the second stage. We develop a two-level approach by constructing a semi-coarse model that coarsens with respect to variables and a coarse model that coarsens with respect to both variables and constraints. We coarsen binary variables by selecting a small number of prespecified on/off profiles. We aggregate constraints by partitioning them into groups and taking convex combination over each group. With an appropriate choice of coarsened profiles, the semi-coarse model is guaranteed to find a feasible solution of the original problem and hence providesmore » an upper bound on the optimal solution. We show that solving a sequence of coarse models converges to the same upper bound with proven finite steps. This is achieved by adding violated constraints to coarse models until all constraints in the semi-coarse model are satisfied. We demonstrate the effectiveness of our approach in cogeneration for buildings. Here, the coarsened models allow us to obtain good approximate solutions at a fraction of the time required by solving the original problem. Extensive numerical experiments show that the two-level approach scales to large problems that are beyond the capacity of state-of-the-art commercial MILP solvers.« less

Anarchy with linear and bilinear interactions

NASA Astrophysics Data System (ADS)

Da Rold, Leandro

2017-10-01

Composite Higgs models with anarchic partial compositeness require a scale of new physics O(10-100) TeV, with the bounds being dominated by the dipole moments and ɛ K . The presence of anarchic bilinear interactions can change this picture. We show a solution to the SM flavor puzzle where the electron and the Right-handed quarks of the first generation have negligible linear interactions, and the bilinear interactions account for most of their masses, whereas the other chiral fermions follow a similar pattern to anarchic partial compositeness. We compute the bounds from flavor and CP violation and show that neutron and electron dipole moments, as well as ɛ K and μ → eγ, are compatible with a new physics scale below the TeV. Δ F = 2 operators involving Left-handed quarks and Δ F = 1 operators with d L give the most stringent bounds in this scenario. Their Wilson coefficients have the same origin as in anarchic partial compositeness, requiring the masses of the new states to be larger than O(6-7) TeV.

Electron teleportation via Majorana bound states in a mesoscopic superconductor.

PubMed

Fu, Liang

2010-02-05

Zero-energy Majorana bound states in superconductors have been proposed to be potential building blocks of a topological quantum computer, because quantum information can be encoded nonlocally in the fermion occupation of a pair of spatially separated Majorana bound states. However, despite intensive efforts, nonlocal signatures of Majorana bound states have not been found in charge transport. In this work, we predict a striking nonlocal phase-coherent electron transfer process by virtue of tunneling in and out of a pair of Majorana bound states. This teleportation phenomenon only exists in a mesoscopic superconductor because of an all-important but previously overlooked charging energy. We propose an experimental setup to detect this phenomenon in a superconductor-quantum-spin-Hall-insulator-magnetic-insulator hybrid system.

Bound states of moving potential wells in discrete wave mechanics

NASA Astrophysics Data System (ADS)

Longhi, S.

2017-10-01

Discrete wave mechanics describes the evolution of classical or matter waves on a lattice, which is governed by a discretized version of the Schrödinger equation. While for a vanishing lattice spacing wave evolution of the continuous Schrödinger equation is retrieved, spatial discretization and lattice effects can deeply modify wave dynamics. Here we discuss implications of breakdown of exact Galilean invariance of the discrete Schrödinger equation on the bound states sustained by a smooth potential well which is uniformly moving on the lattice with a drift velocity v. While in the continuous limit the number of bound states does not depend on the drift velocity v, as one expects from the covariance of ordinary Schrödinger equation for a Galilean boost, lattice effects can lead to a larger number of bound states for the moving potential well as compared to the potential well at rest. Moreover, for a moving potential bound states on a lattice become rather generally quasi-bound (resonance) states.

Kodiak: An Implementation Framework for Branch and Bound Algorithms

NASA Technical Reports Server (NTRS)

Smith, Andrew P.; Munoz, Cesar A.; Narkawicz, Anthony J.; Markevicius, Mantas

2015-01-01

Recursive branch and bound algorithms are often used to refine and isolate solutions to several classes of global optimization problems. A rigorous computation framework for the solution of systems of equations and inequalities involving nonlinear real arithmetic over hyper-rectangular variable and parameter domains is presented. It is derived from a generic branch and bound algorithm that has been formally verified, and utilizes self-validating enclosure methods, namely interval arithmetic and, for polynomials and rational functions, Bernstein expansion. Since bounds computed by these enclosure methods are sound, this approach may be used reliably in software verification tools. Advantage is taken of the partial derivatives of the constraint functions involved in the system, firstly to reduce the branching factor by the use of bisection heuristics and secondly to permit the computation of bifurcation sets for systems of ordinary differential equations. The associated software development, Kodiak, is presented, along with examples of three different branch and bound problem types it implements.

Interacting quantum walkers: two-body bosonic and fermionic bound states

NASA Astrophysics Data System (ADS)

Krapivsky, P. L.; Luck, J. M.; Mallick, K.

2015-11-01

We investigate the dynamics of bound states of two interacting particles, either bosons or fermions, performing a continuous-time quantum walk on a one-dimensional lattice. We consider the situation where the distance between both particles has a hard bound, and the richer situation where the particles are bound by a smooth confining potential. The main emphasis is on the velocity characterizing the ballistic spreading of these bound states, and on the structure of the asymptotic distribution profile of their center-of-mass coordinate. The latter profile generically exhibits many internal fronts.

Exact quantum numbers of collapsed and non-collapsed two-string solutions in the spin-1/2 Heisenberg spin chain

NASA Astrophysics Data System (ADS)

Deguchi, Tetsuo; Ranjan Giri, Pulak

2016-04-01

Every solution of the Bethe-ansatz equations (BAEs) is characterized by a set of quantum numbers, by which we can evaluate it numerically. However, no general rule is known how to give quantum numbers for the physical solutions of BAE. For the spin-1/2 XXX chain we rigorously derive all the quantum numbers for the complete set of the Bethe-ansatz eigenvectors in the two down-spin sector with any chain length N. Here we obtain them both for real and complex solutions. We also show that all the solutions associated with them are distinct. Consequently, we prove the completeness of the Bethe ansatz and give an exact expression for the number of real solutions which correspond to collapsed bound-state solutions (i.e., two-string solutions) in the sector: 2[(N-1)/2-(N/π ){{tan}}-1(\\sqrt{N-1})] in terms of Gauss’ symbol. Moreover, we prove in the sector the scheme conjectured by Takahashi for solving BAE systematically. We also suggest that by applying the present method we can derive the quantum numbers for the spin-1/2 XXZ chain.

Exact Analytic Solution for a Ballistic Orbiting Wind

NASA Astrophysics Data System (ADS)

Wilkin, Francis P.; Hausner, Harry

2017-07-01

Much theoretical and observational work has been done on stellar winds within binary systems. We present a new solution for a ballistic wind launched from a source in a circular orbit. The solution is that of a single wind—no second wind is included in the system and the shocks that arise are those due to the orbiting wind interacting with itself. Our method emphasizes the curved streamlines in the corotating frame, where the flow is steady-state, allowing us to obtain an exact solution for the mass density at all pre-shock locations. Assuming an initially isotropic wind, fluid elements launched from the interior hemisphere of the wind will be the first to cross other streamlines, resulting in a spiral structure bounded by two shock surfaces. Streamlines from the outer wind hemisphere later intersect these shocks as well. An analytic solution is obtained for the geometry of the two shock surfaces. Although the inner and outer shock surfaces asymptotically trace Archimedean spirals, our tail solution suggests many crossings where the shocks overlap, beyond which the analytic solution cannot be continued. Our solution can be readily extended to an initially anisotropic wind.

Gravitating Q-balls in the Affleck-Dine mechanism

DOE Office of Scientific and Technical Information (OSTI.GOV)

Tamaki, Takashi; Sakai, Nobuyuki; Department of Education, Yamagata University, Yamagata 990-8560

2011-04-15

We investigate how gravity affects ''Q-balls'' with the Affleck-Dine potential V{sub AD}({phi}):=(m{sup 2}/2){phi}{sup 2} [1+Kln(({phi}/M)){sup 2}]. Contrary to the flat case, in which equilibrium solutions exist only if K<0, we find three types of gravitating solutions as follows. In the case that K<0, ordinary Q-ball solutions exist; there is an upper bound of the charge due to gravity. In the case that K=0, equilibrium solutions called (mini-)boson stars appear due to gravity; there is an upper bound of the charge, too. In the case that K>0, equilibrium solutions appear, too. In this case, these solutions are not asymptotically flat butmore » surrounded by Q-matter. These solutions might be important in considering a dark matter scenario in the Affleck-Dine mechanism.« less

Bifurcation Analysis Using Rigorous Branch and Bound Methods

NASA Technical Reports Server (NTRS)

Smith, Andrew P.; Crespo, Luis G.; Munoz, Cesar A.; Lowenberg, Mark H.

2014-01-01

For the study of nonlinear dynamic systems, it is important to locate the equilibria and bifurcations occurring within a specified computational domain. This paper proposes a new approach for solving these problems and compares it to the numerical continuation method. The new approach is based upon branch and bound and utilizes rigorous enclosure techniques to yield outer bounding sets of both the equilibrium and local bifurcation manifolds. These sets, which comprise the union of hyper-rectangles, can be made to be as tight as desired. Sufficient conditions for the existence of equilibrium and bifurcation points taking the form of algebraic inequality constraints in the state-parameter space are used to calculate their enclosures directly. The enclosures for the bifurcation sets can be computed independently of the equilibrium manifold, and are guaranteed to contain all solutions within the computational domain. A further advantage of this method is the ability to compute a near-maximally sized hyper-rectangle of high dimension centered at a fixed parameter-state point whose elements are guaranteed to exclude all bifurcation points. This hyper-rectangle, which requires a global description of the bifurcation manifold within the computational domain, cannot be obtained otherwise. A test case, based on the dynamics of a UAV subject to uncertain center of gravity location, is used to illustrate the efficacy of the method by comparing it with numerical continuation and to evaluate its computational complexity.

Molecular Basis for Structural Heterogeneity of an Intrinsically Disordered Protein Bound to a Partner by Combined ESI-IM-MS and Modeling

NASA Astrophysics Data System (ADS)

D'Urzo, Annalisa; Konijnenberg, Albert; Rossetti, Giulia; Habchi, Johnny; Li, Jinyu; Carloni, Paolo; Sobott, Frank; Longhi, Sonia; Grandori, Rita

2015-03-01

Intrinsically disordered proteins (IDPs) form biologically active complexes that can retain a high degree of conformational disorder, escaping structural characterization by conventional approaches. An example is offered by the complex between the intrinsically disordered NTAIL domain and the phosphoprotein X domain (PXD) from measles virus (MeV). Here, distinct conformers of the complex are detected by electrospray ionization-mass spectrometry (ESI-MS) and ion mobility (IM) techniques yielding estimates for the solvent-accessible surface area (SASA) in solution and the average collision cross-section (CCS) in the gas phase. Computational modeling of the complex in solution, based on experimental constraints, provides atomic-resolution structural models featuring different levels of compactness. The resulting models indicate high structural heterogeneity. The intermolecular interactions are predominantly hydrophobic, not only in the ordered core of the complex, but also in the dynamic, disordered regions. Electrostatic interactions become involved in the more compact states. This system represents an illustrative example of a hydrophobic complex that could be directly detected in the gas phase by native mass spectrometry. This work represents the first attempt to modeling the entire NTAIL domain bound to PXD at atomic resolution.

Generalizing the ADM computation to quantum field theory

NASA Astrophysics Data System (ADS)

Mora, P. J.; Tsamis, N. C.; Woodard, R. P.

2012-01-01

The absence of recognizable, low energy quantum gravitational effects requires that some asymptotic series expansion be wonderfully accurate, but the correct expansion might involve logarithms or fractional powers of Newton’s constant. That would explain why conventional perturbation theory shows uncontrollable ultraviolet divergences. We explore this possibility in the context of the mass of a charged, gravitating scalar. The classical limit of this system was solved exactly in 1960 by Arnowitt, Deser and Misner, and their solution does exhibit nonanalytic dependence on Newton’s constant. We derive an exact functional integral representation for the mass of the quantum field theoretic system, and then develop an alternate expansion for it based on a correct implementation of the method of stationary phase. The new expansion entails adding an infinite class of new diagrams to each order and subtracting them from higher orders. The zeroth-order term of the new expansion has the physical interpretation of a first quantized Klein-Gordon scalar which forms a bound state in the gravitational and electromagnetic potentials sourced by its own probability current. We show that such bound states exist and we obtain numerical results for their masses.

Multi-soliton interaction of a generalized Schrödinger-Boussinesq system in a magnetized plasma

NASA Astrophysics Data System (ADS)

Zhao, Xue-Hui; Tian, Bo; Chai, Jun; Wu, Xiao-Yu; Guo, Yong-Jiang

2017-04-01

Under investigation in this paper is a generalized Schrödinger-Boussinesq system, which describes the stationary propagation of coupled upper-hybrid waves and magnetoacoustic waves in a magnetized plasma. Bilinear forms, one-, two- and three-soliton solutions are derived by virtue of the Hirota method and symbolic computation. Propagation and interaction for the solitons are illustrated graphically: Coefficients β1^{} and β2^{} can affect the velocities and propagation directions of the solitary waves. Amplitude, velocity and shape of the one solitary wave keep invariant during the propagation, implying that the transport of the energy is stable in the upper-hybrid and magnetoacoustic waves, and amplitude of the upper-hybrid wave is bigger than that of the magnetoacoustic wave. For the upper-hybrid and magnetoacoustic waves, head-on, overtaking and bound-state interaction between the two solitary waves are asymptotically depicted, respectively, indicating that the interaction between the two solitary waves is elastic. Elastic interaction between the bound-state soliton and a single one soliton is also displayed, and interaction among the three solitary waves is all elastic.

The effect of covalently linked RGD peptide on the conformation of polysaccharides in aqueous solutions.

PubMed

Bernstein-Levi, Ortal; Ochbaum, Guy; Bitton, Ronit

2016-01-01

Covalently modified polysaccharides are routinely used in tissue engineering due to their tailored biofunctionality. Understanding the effect of single-chain level modification on the solution conformation of the single chain, and more importantly on the self-assembly and aggregation of the ensemble of chains is expected to improve our ability to control network topology and the properties of the resulting gels. Attaching an RGD peptide to a polysaccharide backbone is a common procedure used to promote cell adhesion in hydrogel scaffolds. Recently it has been shown that the spatial presentation of the RGD sequences affects the cell behavior; thus, understanding the effects of grafted RGD on the conformational properties of the solvated polysaccharide chains is a prerequisite for rational design of polysaccharide-peptide based biomaterials. Here we investigate the effect of covalently linked G4RGDS on the conformational state of the individual chain and chain assemblies of alginate, chitosan, and hyaluronic acid (HA) in aqueous solutions. Two peptide fractions were studied using small-angle X-ray scattering (SAXS) and rheology. In all cases, upon peptide conjugation structural differences were observed. Analysis of the scattering data shows evidence of clustering for a higher fraction of bound peptide. Moreover for all three polysaccharides the typical shear thinning behavior of the natural polysaccharide solutions is replaced by a Newtonian fluid behavior for the lower fraction conjugated peptide while a more pronounced shear thinning behavior is observed for the higher fraction. These results indicate that the fraction of the bounded peptide, determines the behavior of a polysaccharide-peptide conjugates in solution, regardless of the specific nature of the polysaccharide. Copyright © 2015 Elsevier B.V. All rights reserved.

Approximating the 0-1 Multiple Knapsack Problem with Agent Decomposition and Market Negotiation

DOE Office of Scientific and Technical Information (OSTI.GOV)

Smolinski, B.

The 0-1 multiple knapsack problem appears in many domains from financial portfolio management to cargo ship stowing. Methods for solving it range from approximate algorithms, such as greedy algorithms, to exact algorithms, such as branch and bound. Approximate algorithms have no bounds on how poorly they perform and exact algorithms can suffer from exponential time and space complexities with large data sets. This paper introduces a market model based on agent decomposition and market auctions for approximating the 0-1 multiple knapsack problem, and an algorithm that implements the model (M(x)). M(x) traverses the solution space rather than getting caught inmore » a local maximum, overcoming an inherent problem of many greedy algorithms. The use of agents ensures that infeasible solutions are not considered while traversing the solution space and that traversal of the solution space is not just random, but is also directed. M(x) is compared to a bound and bound algorithm (BB) and a simple greedy algorithm with a random shuffle (G(x)). The results suggest that M(x) is a good algorithm for approximating the 0-1 Multiple Knapsack problem. M(x) almost always found solutions that were close to optimal in a fraction of the time it took BB to run and with much less memory on large test data sets. M(x) usually performed better than G(x) on hard problems with correlated data.« less

Impurity bound states in fully gapped d-wave superconductors with subdominant order parameters

PubMed Central

Mashkoori, Mahdi; Björnson, Kristofer; Black-Schaffer, Annica M.

2017-01-01

Impurities in superconductors and their induced bound states are important both for engineering novel states such as Majorana zero-energy modes and for probing bulk properties of the superconducting state. The high-temperature cuprates offer a clear advantage in a much larger superconducting order parameter, but the nodal energy spectrum of a pure d-wave superconductor only allows virtual bound states. Fully gapped d-wave superconducting states have, however, been proposed in several cuprate systems thanks to subdominant order parameters producing d + is- or d + id′-wave superconducting states. Here we study both magnetic and potential impurities in these fully gapped d-wave superconductors. Using analytical T-matrix and complementary numerical tight-binding lattice calculations, we show that magnetic and potential impurities behave fundamentally different in d + is- and d + id′-wave superconductors. In a d + is-wave superconductor, there are no bound states for potential impurities, while a magnetic impurity produces one pair of bound states, with a zero-energy level crossing at a finite scattering strength. On the other hand, a d + id′-wave symmetry always gives rise to two pairs of bound states and only produce a reachable zero-energy level crossing if the normal state has a strong particle-hole asymmetry. PMID:28281570

Comment on “Approximate solutions of the Dirac equation for the Rosen-Morse potential including the spin-orbit centrifugal term” [J. Math. Phys. 51, 023525 (2010)

DOE Office of Scientific and Technical Information (OSTI.GOV)

Ghoumaid, A.; Benamira, F.; Guechi, L.

2016-02-15

It is shown that the application of the Nikiforov-Uvarov method by Ikhdair for solving the Dirac equation with the radial Rosen-Morse potential plus the spin-orbit centrifugal term is inadequate because the required conditions are not satisfied. The energy spectra given is incorrect and the wave functions are not physically acceptable. We clarify the problem and prove that the spinor wave functions are expressed in terms of the generalized hypergeometric functions {sub 2}F{sub 1}(a, b, c; z). The energy eigenvalues for the bound states are given by the solution of a transcendental equation involving the hypergeometric function.

MARKOV: A methodology for the solution of infinite time horizon MARKOV decision processes

USGS Publications Warehouse

Williams, B.K.

1988-01-01

Algorithms are described for determining optimal policies for finite state, finite action, infinite discrete time horizon Markov decision processes. Both value-improvement and policy-improvement techniques are used in the algorithms. Computing procedures are also described. The algorithms are appropriate for processes that are either finite or infinite, deterministic or stochastic, discounted or undiscounted, in any meaningful combination of these features. Computing procedures are described in terms of initial data processing, bound improvements, process reduction, and testing and solution. Application of the methodology is illustrated with an example involving natural resource management. Management implications of certain hypothesized relationships between mallard survival and harvest rates are addressed by applying the optimality procedures to mallard population models.

Optimal Least-Squares Unidimensional Scaling: Improved Branch-and-Bound Procedures and Comparison to Dynamic Programming

ERIC Educational Resources Information Center

Brusco, Michael J.; Stahl, Stephanie

2005-01-01

There are two well-known methods for obtaining a guaranteed globally optimal solution to the problem of least-squares unidimensional scaling of a symmetric dissimilarity matrix: (a) dynamic programming, and (b) branch-and-bound. Dynamic programming is generally more efficient than branch-and-bound, but the former is limited to matrices with…

A Self-Stabilizing Hybrid Fault-Tolerant Synchronization Protocol

NASA Technical Reports Server (NTRS)

Malekpour, Mahyar R.

2015-01-01

This paper presents a strategy for solving the Byzantine general problem for self-stabilizing a fully connected network from an arbitrary state and in the presence of any number of faults with various severities including any number of arbitrary (Byzantine) faulty nodes. The strategy consists of two parts: first, converting Byzantine faults into symmetric faults, and second, using a proven symmetric-fault tolerant algorithm to solve the general case of the problem. A protocol (algorithm) is also present that tolerates symmetric faults, provided that there are more good nodes than faulty ones. The solution applies to realizable systems, while allowing for differences in the network elements, provided that the number of arbitrary faults is not more than a third of the network size. The only constraint on the behavior of a node is that the interactions with other nodes are restricted to defined links and interfaces. The solution does not rely on assumptions about the initial state of the system and no central clock nor centrally generated signal, pulse, or message is used. Nodes are anonymous, i.e., they do not have unique identities. A mechanical verification of a proposed protocol is also present. A bounded model of the protocol is verified using the Symbolic Model Verifier (SMV). The model checking effort is focused on verifying correctness of the bounded model of the protocol as well as confirming claims of determinism and linear convergence with respect to the self-stabilization period.

A lower bound on the solutions of Kapustin-Witten equations

NASA Astrophysics Data System (ADS)

Huang, Teng

2016-11-01

In this article, we consider the Kapustin-Witten equations on a closed four-manifold. We study certain analytic properties of solutions to the equations on a closed manifold. The main result is that there exists an L2 -lower bound on the extra fields over a closed four-manifold satisfying certain conditions if the connections are not ASD connections. Furthermore, we also obtain a similar result about the Vafa-Witten equations.

Strong solutions for an incompressible Navier-Stokes/Allen-Cahn system with different densities

NASA Astrophysics Data System (ADS)

Li, Yinghua; Huang, Mingxia

2018-06-01

In this paper, we investigate a coupled Navier-Stokes/Allen-Cahn system describing a diffuse interface model for two-phase flow of viscous incompressible fluids with different densities in a bounded domain Ω \\subset R^N(N=2,3). We prove the existence and uniqueness of local strong solutions to the initial boundary value problem when the initial density function ρ _0 has a positive lower bound.

Theory of space-charge polarization for determining ionic constants of electrolytic solutions

NASA Astrophysics Data System (ADS)

Sawada, Atsushi

2007-06-01

A theoretical expression of the complex dielectric constant attributed to space-charge polarization has been derived under an electric field calculated using Poisson's equation considering the effects of bound charges on ions. The frequency dependence of the complex dielectric constant of chlorobenzene solutions doped with tetrabutylammonium tetraphenylborate (TBATPB) has been analyzed using the theoretical expression, and the impact of the bound charges on the complex dielectric constant has been clarified quantitatively in comparison with a theory that does not consider the effect of the bound charges. The Stokes radius of TBA +(=TPB-) determined by the present theory shows a good agreement with that determined by conductometry in the past; hence, the present theory should be applicable to the direct determination of the mobility of ion species in an electrolytic solution without the need to measure ionic limiting equivalent conductance and transport number.

Several reverse-time integrable nonlocal nonlinear equations: Rogue-wave solutions

NASA Astrophysics Data System (ADS)

Yang, Bo; Chen, Yong

2018-05-01

A study of rogue-wave solutions in the reverse-time nonlocal nonlinear Schrödinger (NLS) and nonlocal Davey-Stewartson (DS) equations is presented. By using Darboux transformation (DT) method, several types of rogue-wave solutions are constructed. Dynamics of these rogue-wave solutions are further explored. It is shown that the (1 + 1)-dimensional fundamental rogue-wave solutions in the reverse-time NLS equation can be globally bounded or have finite-time blowing-ups. It is also shown that the (2 + 1)-dimensional line rogue waves in the reverse-time nonlocal DS equations can be bounded for all space and time or develop singularities in critical time. In addition, the multi- and higher-order rogue waves exhibit richer structures, most of which have no counterparts in the corresponding local nonlinear equations.

Improved pedagogy for linear differential equations by reconsidering how we measure the size of solutions

NASA Astrophysics Data System (ADS)

Tisdell, Christopher C.

2017-11-01

For over 50 years, the learning of teaching of a priori bounds on solutions to linear differential equations has involved a Euclidean approach to measuring the size of a solution. While the Euclidean approach to a priori bounds on solutions is somewhat manageable in the learning and teaching of the proofs involving second-order, linear problems with constant co-efficients, we believe it is not pedagogically optimal. Moreover, the Euclidean method becomes pedagogically unwieldy in the proofs involving higher-order cases. The purpose of this work is to propose a simpler pedagogical approach to establish a priori bounds on solutions by considering a different way of measuring the size of a solution to linear problems, which we refer to as the Uber size. The Uber form enables a simplification of pedagogy from the literature and the ideas are accessible to learners who have an understanding of the Fundamental Theorem of Calculus and the exponential function, both usually seen in a first course in calculus. We believe that this work will be of mathematical and pedagogical interest to those who are learning and teaching in the area of differential equations or in any of the numerous disciplines where linear differential equations are used.

Asymptotic Behavior of Solutions of Systems of Neutral and Convolution Equations

NASA Astrophysics Data System (ADS)

Basit, Bolis; Günzler, Hans

1998-10-01

Suppose J=[α, ∞) for someα∈R or J=R and letXbe a Banach space. We study asymptotic behavior of solutions on J of neutral system of equations with values inX. This reduces to questions concerning the behavior of solutions of convolution equations (*)H∗Ω=b, whereH=(Hj, k) is anr×rmatrix,Hj, k∈D‧L1,b=(bj) andbj∈D‧(R, X), for 1⩽j, k⩽r. We prove that ifΩis a bounded uniformly continuous solution of (*) withbfrom some translation invariant suitably closed class A, thenΩbelongs to A, provided, for example, that det Hhas countably many zeros on R andc0⊄X. In particular, ifbis (asymptotically) almost periodic, almost automorphic or recurrent,Ωis too. Our results extend theorems of Bohr, Neugebauer, Bochner, Doss, Basit, and Zhikov and also, certain theorems of Fink, Madych, Staffans, and others. Also, we investigate bounded solutions of (*). This leads to an extension of the known classes of almost periodicity to larger classes called mean-classes. We explore mean-classes and prove that bounded solutions of (*) belong to mean-classes provided certain conditions hold. These results seem new even for the simplest difference equationΩ(t+1)-Ω(t)=b(t) with J=X=R andbStepanoff almost periodic.

Activating distillation with an infinitesimal amount of bound entanglement.

PubMed

Vollbrecht, Karl Gerd H; Wolf, Michael M

2002-06-17

We show that bipartite quantum states of any dimension, which do not have a positive partial transpose (NPPT), become 1-distillable when one adds an infinitesimal amount of bound entanglement. To this end we investigate the activation properties of a new class of symmetric bound entangled states of full rank. It is shown that in this set there exist universal activator states capable of activating the distillation of any NPPT state. The result shows that even a small amount of bound entanglement can be useful for quantum information purposes.

Search for bound states of the eta-meson in light nuclei

NASA Technical Reports Server (NTRS)

Chrien, R. E.; Bart, S.; Pile, P.; Sutter, R.; Tsoupas, N.; Funsten, H. O.; Finn, J. M.; Lyndon, C.; Punjabi, V.; Perdrisat, C. F.

1988-01-01

A search for nuclear-bound states of the eta meson was carried out. Targets of lithium, carbon, oxygen, and aluminum were placed in a pion(+) beam at 800 MeV/c. A predicted eta bound state in O-15* (E sub x approx. = 540 MeV) with a width of approx. 9 MeV was not observed. A bound state of a size 1/3 of the predicted cross section would have been seen in this experiment at a confidence level of 3sigma (P is greater than 0.9987).

BPS objects in D = 7 supergravity and their M-theory origin

NASA Astrophysics Data System (ADS)

Dibitetto, Giuseppe; Petri, Nicolò

2017-12-01

We study several different types of BPS flows within minimal N=1 , D = 7 supergravity with SU(2) gauge group and non-vanishing topological mass. After reviewing some known domain wall solutions involving only the metric and the ℝ+ scalar field, we move to considering more general flows involving a "dyonic" profile for the 3-form gauge potential. In this context, we consider flows featuring a Mkw3 as well as an AdS3 slicing, write down the corresponding flow equations, and integrate them analytically to obtain many examples of asymptotically AdS7 solutions in presence of a running 3-form. Furthermore, we move to adding the possibility of non-vanishing vector fields, find the new corresponding flows and integrate them numerically. Finally, we discuss the eleven-dimensional interpretation of the aforementioned solutions as effective descriptions of M2 - M5 bound states.

Ultrafast dynamics of electrons in ammonia.

PubMed

Vöhringer, Peter

2015-04-01

Solvated electrons were first discovered in solutions of metals in liquid ammonia. The physical and chemical properties of these species have been studied extensively for many decades using an arsenal of electrochemical, spectroscopic, and theoretical techniques. Yet, in contrast to their hydrated counterpart, the ultrafast dynamics of ammoniated electrons remained completely unexplored until quite recently. Femtosecond pump-probe spectroscopy on metal-ammonia solutions and femtosecond multiphoton ionization spectroscopy on the neat ammonia solvent have provided new insights into the optical properties and the reactivities of this fascinating species. This article reviews the nature of the optical transition, which gives the metal-ammonia solutions their characteristic blue appearance, in terms of ultrafast relaxation processes involving bound and continuum excited states. The recombination processes following the injection of an electron via photoionization of the solvent are discussed in the context of the electronic structure of the liquid and the anionic defect associated with the solvated electron.

Dissipative discrete breathers: periodic, quasiperiodic, chaotic, and mobile.

PubMed

Martínez, P J; Meister, M; Floría, L M; Falo, F

2003-06-01

The properties of discrete breathers in dissipative one-dimensional lattices of nonlinear oscillators subject to periodic driving forces are reviewed. We focus on oscillobreathers in the Frenkel-Kontorova chain and rotobreathers in a ladder of Josephson junctions. Both types of exponentially localized solutions are easily obtained numerically using adiabatic continuation from the anticontinuous limit. Linear stability (Floquet) analysis allows the characterization of different types of bifurcations experienced by periodic discrete breathers. Some of these bifurcations produce nonperiodic localized solutions, namely, quasiperiodic and chaotic discrete breathers, which are generally impossible as exact solutions in Hamiltonian systems. Within a certain range of parameters, propagating breathers occur as attractors of the dissipative dynamics. General features of these excitations are discussed and the Peierls-Nabarro barrier is addressed. Numerical scattering experiments with mobile breathers reveal the existence of two-breather bound states and allow a first glimpse at the intricate phenomenology of these special multibreather configurations. (c) 2003 American Institute of Physics.

FRW Solutions and Holography from Uplifted AdS/CFT

DOE Office of Scientific and Technical Information (OSTI.GOV)

Dong, Xi; Horn, Bart; /Stanford U., ITP /Stanford U., Phys. Dept. /SLAC

2012-02-15

Starting from concrete AdS/CFT dual pairs, one can introduce ingredients which produce cosmological solutions, including metastable de Sitter and its decay to non-accelerating FRW. We present simple FRW solutions sourced by magnetic flavor branes and analyze correlation functions and particle and brane dynamics. To obtain a holographic description, we exhibit a time-dependent warped metric on the solution and interpret the resulting redshifted region as a Lorentzian low energy effective field theory in one fewer dimension. At finite times, this theory has a finite cutoff, a propagating lower dimensional graviton and a finite covariant entropy bound, but at late times themore » lower dimensional Planck mass and entropy go off to infinity in a way that is dominated by contributions from the low energy effective theory. This opens up the possibility of a precise dual at late times. We reproduce the time-dependent growth of the number of degrees of freedom in the system via a count of available microscopic states in the corresponding magnetic brane construction.« less

FRW solutions and holography from uplifted AdS/CFT systems

NASA Astrophysics Data System (ADS)

Dong, Xi; Horn, Bart; Matsuura, Shunji; Silverstein, Eva; Torroba, Gonzalo

2012-05-01

Starting from concrete AdS/CFT dual pairs, one can introduce ingredients which produce cosmological solutions, including metastable de Sitter and its decay to nonaccelerating Friedmann-Robertson-Walker. We present simple Friedmann-Robertson-Walker solutions sourced by magnetic flavor branes and analyze correlation functions and particle and brane dynamics. To obtain a holographic description, we exhibit a time-dependent warped metric on the solution and interpret the resulting redshifted region as a Lorentzian low energy effective field theory in one fewer dimension. At finite times, this theory has a finite cutoff, a propagating lower-dimensional graviton, and a finite covariant entropy bound, but at late times the lower-dimensional Planck mass and entropy go off to infinity in a way that is dominated by contributions from the low energy effective theory. This opens up the possibility of a precise dual at late times. We reproduce the time-dependent growth of the number of degrees of freedom in the system via a count of available microscopic states in the corresponding magnetic brane construction.

Expansion in higher harmonics of boson stars using a generalized Ruffini-Bonazzola approach. Part 1. Bound states

NASA Astrophysics Data System (ADS)

Eby, Joshua; Suranyi, Peter; Wijewardhana, L. C. R.

2018-04-01

The method pioneered by Ruffini and Bonazzola (RB) to describe boson stars involves an expansion of the boson field which is linear in creation and annihilation operators. In the nonrelativistic limit, the equation of motion of RB is equivalent to the nonlinear Schrödinger equation. Further, the RB expansion constitutes an exact solution to a non-interacting field theory, and has been used as a reasonable ansatz for an interacting one. In this work, we show how one can go beyond the RB ansatz towards an exact solution of the interacting operator Klein-Gordon equation, which can be solved iteratively to ever higher precision. Our Generalized Ruffini-Bonazzola approach takes into account contributions from nontrivial harmonic dependence of the wavefunction, using a sum of terms with energy k E0, where k>=1 and E0 is the chemical potential of a single bound axion. The method critically depends on an expansion in a parameter Δ ≡ √1 ‑ E02/m2 < 1, where m is the mass of the boson. In the case of the axion potential, we calculate corrections which are relevant for axion stars in the transition or dense branches of solutions. We find with high precision the local minimum of the mass, Mmin≈ 463 f2/m, at Δ≈0.27, where f is the axion decay constant. This point marks the crossover from the transition branch to the dense branch of solutions, and a corresponding crossover from structural instability to stability.

Model-free nuclear magnetic resonance study of intermolecular free energy landscapes in liquids with paramagnetic Ln3+ spotlights: theory and application to Arg-Gly-Asp.

PubMed

Fries, Pascal H

2012-01-28

We propose an easily applicable method for investigating the pair distribution function of a lanthanide Ln(3+) complex LnL (L = ligand) with respect to any solvent or solute molecule A carrying observable nuclear spins. Let r be the distance of Ln(3+) to the observed nuclear spin I. We derive a simple expression of the experimental value of the configurational average of 1/r(6) in terms of longitudinal paramagnetic relaxation (rate) enhancements (PREs) of the spin I measured on a standard high-resolution NMR spectrometer and due to well-chosen concentrations of LnL complexes in which Ln(3+) is a fast-relaxing paramagnetic lanthanide or the slowly-relaxing gadolinium Gd(3+). The derivation is justified in the general case of a molecule A which is by turns in a bound state where it follows the complex and a free state where it moves independently. It rests on the expression of the underlying PRE theory in terms of the angle-dependent pair distribution function of LnL and A. The simplifications of this theory in the high-field regime and under the condition of fast exchange between bound and free states are carefully discussed. We also show that original information on the angle dependence of the molecular pair distribution function can be gained from the measured paramagnetic dipolar shifts induced by complexed fast-relaxing Ln(3+) ions. The method is illustrated by the case study of the anionic Lnttha(3-) = [Ln(3+)(ttha)](3-) (ttha(6-) = triethylene tetraamine hexacetate) complex interacting with the biologically important tripeptide Arg-Gly-Asp (RGD) which carries peripheral ionic groups. The usefulness of an auxiliary reference outer sphere probe solute is emphasized. © 2012 American Institute of Physics

New effects of a long-lived negatively charged massive particle on big bang nucleosynthesis

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kusakabe, Motohiko; Kim, K. S.; Cheoun, Myung-Ki

Primordial {sup 7}Li abundance inferred from observations of metal-poor stars is a factor of about 3 lower than the theoretical value of standard big bang nucleosynthesis (BBN) model. One of the solutions to the Li problem is {sup 7}Be destruction during the BBN epoch caused by a long-lived negatively charged massive particle, X{sup −}. The particle can bind to nuclei, and X-bound nuclei (X-nuclei) can experience new reactions. The radiative X{sup −} capture by {sup 7}Be nuclei followed by proton capture of the bound state of {sup 7}Be and X{sup −} ({sup 7}Be{sub x}) is a possible {sup 7}Be destructionmore » reaction. Since the primordial abundance of {sup 7}Li originates mainly from {sup 7}Li produced via the electron capture of {sup 7}Be after BBN, the {sup 7}Be destruction provides a solution to the {sup 7}Li problem. We suggest a new route of {sup 7}Be{sub x} formation, that is the {sup 7}Be charge exchange at the reaction of {sup 7}Be{sup 3+} ion and X{sup −}. The formation rate depends on the ionization fraction of {sup 7}Be{sup 3+} ion, the charge exchange cross section of {sup 7}Be{sup 3+}, and the probability that excited states {sup 7}Be{sub x}* produced at the charge exchange are converted to the ground state. We find that this reaction can be equally important as or more important than ordinary radiative recombination of {sup 7}Be and X{sup −}. The effect of this new route is shown in a nuclear reaction network calculation.« less

Bayesian refinement of protein structures and ensembles against SAXS data using molecular dynamics

PubMed Central

Shevchuk, Roman; Hub, Jochen S.

2017-01-01

Small-angle X-ray scattering is an increasingly popular technique used to detect protein structures and ensembles in solution. However, the refinement of structures and ensembles against SAXS data is often ambiguous due to the low information content of SAXS data, unknown systematic errors, and unknown scattering contributions from the solvent. We offer a solution to such problems by combining Bayesian inference with all-atom molecular dynamics simulations and explicit-solvent SAXS calculations. The Bayesian formulation correctly weights the SAXS data versus prior physical knowledge, it quantifies the precision or ambiguity of fitted structures and ensembles, and it accounts for unknown systematic errors due to poor buffer matching. The method further provides a probabilistic criterion for identifying the number of states required to explain the SAXS data. The method is validated by refining ensembles of a periplasmic binding protein against calculated SAXS curves. Subsequently, we derive the solution ensembles of the eukaryotic chaperone heat shock protein 90 (Hsp90) against experimental SAXS data. We find that the SAXS data of the apo state of Hsp90 is compatible with a single wide-open conformation, whereas the SAXS data of Hsp90 bound to ATP or to an ATP-analogue strongly suggest heterogenous ensembles of a closed and a wide-open state. PMID:29045407

Ensemble-based characterization of unbound and bound states on protein energy landscape

PubMed Central

Ruvinsky, Anatoly M; Kirys, Tatsiana; Tuzikov, Alexander V; Vakser, Ilya A

2013-01-01

Physicochemical description of numerous cell processes is fundamentally based on the energy landscapes of protein molecules involved. Although the whole energy landscape is difficult to reconstruct, increased attention to particular targets has provided enough structures for mapping functionally important subspaces associated with the unbound and bound protein structures. The subspace mapping produces a discrete representation of the landscape, further called energy spectrum. We compiled and characterized ensembles of bound and unbound conformations of six small proteins and explored their spectra in implicit solvent. First, the analysis of the unbound-to-bound changes points to conformational selection as the binding mechanism for four proteins. Second, results show that bound and unbound spectra often significantly overlap. Moreover, the larger the overlap the smaller the root mean square deviation (RMSD) between the bound and unbound conformational ensembles. Third, the center of the unbound spectrum has a higher energy than the center of the corresponding bound spectrum of the dimeric and multimeric states for most of the proteins. This suggests that the unbound states often have larger entropy than the bound states. Fourth, the exhaustively long minimization, making small intrarotamer adjustments (all-atom RMSD ≤ 0.7 Å), dramatically reduces the distance between the centers of the bound and unbound spectra as well as the spectra extent. It condenses unbound and bound energy levels into a thin layer at the bottom of the energy landscape with the energy spacing that varies between 0.8–4.6 and 3.5–10.5 kcal/mol for the unbound and bound states correspondingly. Finally, the analysis of protein energy fluctuations showed that protein vibrations itself can excite the interstate transitions, including the unbound-to-bound ones. PMID:23526684

Solution NMR investigation of the response of the lactose repressor core domain dimer to hydrostatic pressure.

PubMed

Fuglestad, Brian; Stetz, Matthew A; Belnavis, Zachary; Wand, A Joshua

2017-12-01

Previous investigations of the sensitivity of the lac repressor to high-hydrostatic pressure have led to varying conclusions. Here high-pressure solution NMR spectroscopy is used to provide an atomic level view of the pressure induced structural transition of the lactose repressor regulatory domain (LacI* RD) bound to the ligand IPTG. As the pressure is raised from ambient to 3kbar the native state of the protein is converted to a partially unfolded form. Estimates of rotational correlation times using transverse optimized relaxation indicates that a monomeric state is never reached and that the predominate form of the LacI* RD is dimeric throughout this pressure change. Spectral analysis suggests that the pressure-induced transition is localized and is associated with a volume change of approximately -115mlmol -1 and an average pressure dependent change in compressibility of approximately 30mlmol -1 kbar -1 . In addition, a subset of resonances emerge at high-pressures indicating the presence of a non-native but folded alternate state. Copyright © 2017 Elsevier B.V. All rights reserved.

Extremely efficient internal exciton dissociation through edge states in layered 2D perovskites

NASA Astrophysics Data System (ADS)

Blancon, J.-C.; Tsai, H.; Nie, W.; Stoumpos, C. C.; Pedesseau, L.; Katan, C.; Kepenekian, M.; Soe, C. M. M.; Appavoo, K.; Sfeir, M. Y.; Tretiak, S.; Ajayan, P. M.; Kanatzidis, M. G.; Even, J.; Crochet, J. J.; Mohite, A. D.

2017-03-01

Understanding and controlling charge and energy flow in state-of-the-art semiconductor quantum wells has enabled high-efficiency optoelectronic devices. Two-dimensional (2D) Ruddlesden-Popper perovskites are solution-processed quantum wells wherein the band gap can be tuned by varying the perovskite-layer thickness, which modulates the effective electron-hole confinement. We report that, counterintuitive to classical quantum-confined systems where photogenerated electrons and holes are strongly bound by Coulomb interactions or excitons, the photophysics of thin films made of Ruddlesden-Popper perovskites with a thickness exceeding two perovskite-crystal units (>1.3 nanometers) is dominated by lower-energy states associated with the local intrinsic electronic structure of the edges of the perovskite layers. These states provide a direct pathway for dissociating excitons into longer-lived free carriers that substantially improve the performance of optoelectronic devices.

Gauss Seidel-type methods for energy states of a multi-component Bose Einstein condensate

NASA Astrophysics Data System (ADS)

Chang, Shu-Ming; Lin, Wen-Wei; Shieh, Shih-Feng

2005-01-01

In this paper, we propose two iterative methods, a Jacobi-type iteration (JI) and a Gauss-Seidel-type iteration (GSI), for the computation of energy states of the time-independent vector Gross-Pitaevskii equation (VGPE) which describes a multi-component Bose-Einstein condensate (BEC). A discretization of the VGPE leads to a nonlinear algebraic eigenvalue problem (NAEP). We prove that the GSI method converges locally and linearly to a solution of the NAEP if and only if the associated minimized energy functional problem has a strictly local minimum. The GSI method can thus be used to compute ground states and positive bound states, as well as the corresponding energies of a multi-component BEC. Numerical experience shows that the GSI converges much faster than JI and converges globally within 10-20 steps.

Structural mechanism of JH delivery in hemolymph by JHBP of silkworm, Bombyx mori

PubMed Central

Suzuki, Rintaro; Fujimoto, Zui; Shiotsuki, Takahiro; Tsuchiya, Wataru; Momma, Mitsuru; Tase, Akira; Miyazawa, Mitsuhiro; Yamazaki, Toshimasa

2011-01-01

Juvenile hormone (JH) plays crucial roles in many aspects of the insect life. All the JH actions are initiated by transport of JH in the hemolymph as a complex with JH-binding protein (JHBP) to target tissues. Here, we report structural mechanism of JH delivery by JHBP based upon the crystal and solution structures of apo and JH-bound JHBP. In solution, apo-JHBP exists in equilibrium of multiple conformations with different orientations of the gate helix for the hormone-binding pocket ranging from closed to open forms. JH-binding to the gate-open form results in the fully closed JHBP-JH complex structure where the bound JH is completely buried inside the protein. JH-bound JHBP opens the gate helix to release the bound hormone likely by sensing the less polar environment at the membrane surface of target cells. This is the first report that provides structural insight into JH signaling. PMID:22355650

Relativistic symmetries in the Rosen—Morse potential and tensor interaction using the Nikiforov—Uvarov method

NASA Astrophysics Data System (ADS)

Sameer, M. Ikhdair; Majid, Hamzavi

2013-04-01

Approximate analytical bound-state solutions of the Dirac particle in the fields of attractive and repulsive Rosen—Morse (RM) potentials including the Coulomb-like tensor (CLT) potential are obtained for arbitrary spin-orbit quantum number κ. The Pekeris approximation is used to deal with the spin-orbit coupling terms κ (κ± 1)r-2. In the presence of exact spin and pseudospin (p-spin) symmetries, the energy eigenvalues and the corresponding normalized two-component wave functions are found by using the parametric generalization of the Nikiforov—Uvarov (NU) method. The numerical results show that the CLT interaction removes degeneracies between the spin and p-spin state doublets.

On a Free Boundary Problem for the Curvature Flow with Driving Force

NASA Astrophysics Data System (ADS)

Guo, Jong-Shenq; Matano, Hiroshi; Shimojo, Masahiko; Wu, Chang-Hong

2016-03-01

We study a free boundary problem associated with the curvature dependent motion of planar curves in the upper half plane whose two endpoints slide along the horizontal axis with prescribed fixed contact angles. Our first main result concerns the classification of solutions; every solution falls into one of the three categories, namely, area expanding, area bounded and area shrinking types. We then study in detail the asymptotic behavior of solutions in each category. Among other things we show that solutions are asymptotically self-similar both in the area expanding and the area shrinking cases, while solutions converge to either a stationary solution or a traveling wave in the area bounded case. We also prove results on the concavity properties of solutions. One of the main tools of this paper is the intersection number principle, however in order to deal with solutions with free boundaries, we introduce what we call "the extended intersection number principle", which turns out to be exceedingly useful in handling curves with moving endpoints.

Reaching the Quantum Cramér-Rao Bound for Transmission Measurements

NASA Astrophysics Data System (ADS)

Woodworth, Timothy; Chan, Kam Wai Clifford; Marino, Alberto

2017-04-01

The quantum Cramér-Rao bound (QCRB) is commonly used to quantify the lower bound for the uncertainty in the estimation of a given parameter. Here, we calculate the QCRB for transmission measurements of an optical system probed by a beam of light. Estimating the transmission of an optical element is important as it is required for the calibration of optimal states for interferometers, characterization of high efficiency photodetectors, or as part of other measurements, such as those in plasmonic sensors or in ellipsometry. We use a beam splitter model for the losses introduced by the optical system to calculate the QCRB for different input states. We compare the bound for a coherent state, a two-mode squeezed-state (TMSS), a single-mode squeezed-state (SMSS), and a Fock state and show that it is possible to obtain an ultimate lower bound, regardless of the state used to probe the system. We prove that the Fock state gives the lowest possible uncertainty in estimating the transmission for any state and demonstrate that the TMSS and SMSS approach this ultimate bound for large levels of squeezing. Finally, we show that a simple measurement strategy for the TMSS, namely an intensity difference measurement, is able to saturate the QCRB. Work supported by the W.M. Keck Foundation.

Validating Clusters with the Lower Bound for Sum-of-Squares Error

ERIC Educational Resources Information Center

Steinley, Douglas

2007-01-01

Given that a minor condition holds (e.g., the number of variables is greater than the number of clusters), a nontrivial lower bound for the sum-of-squares error criterion in K-means clustering is derived. By calculating the lower bound for several different situations, a method is developed to determine the adequacy of cluster solution based on…

Search for a hidden strange baryon-meson bound state from ϕ production in a nuclear medium

NASA Astrophysics Data System (ADS)

Gao, Haiyan; Huang, Hongxia; Liu, Tianbo; Ping, Jialun; Wang, Fan; Zhao, Zhiwen

2017-05-01

We investigate the hidden strange light baryon-meson system. With the resonating-group method, two bound states, η'-N and ϕ -N , are found in the quark delocalization color screening model. Focusing on the ϕ -N bound state around 1950 MeV, we obtain the total decay width of about 4 MeV by calculating the phase shifts in the resonance scattering processes. To study the feasibility of an experimental search for the ϕ -N bound state, we perform a Monte Carlo simulation of the bound state production with an electron beam and a gold target. In the simulation, we use the CLAS12 detector with the Forward Tagger and the BONUS12 detector in Hall B at Jefferson Lab. Both the signal and the background channels are estimated. We demonstrate that the signal events can be separated from the background with some momentum cuts. Therefore it is feasible to experimentally search for the ϕ -N bound state through the near threshold ϕ meson production from heavy nuclei.

Global boundedness of solutions to a two-species chemotaxis system

NASA Astrophysics Data System (ADS)

Zhang, Qingshan; Li, Yuxiang

2015-02-01

In this paper, we consider the chemotaxis system of two species which are attracted by the same signal substance under homogeneous Neumann boundary conditions in a smooth bounded domain . We prove that if the nonnegative initial data and for some r > n, the system possesses a unique global uniformly bounded solution under some conditions on the chemotaxis sensitivity functions χ 1( w), χ 2( w) and the logistic growth coefficients μ 1, μ 2.

Bounded fractional diffusion in geological media: Definition and Lagrangian approximation

NASA Astrophysics Data System (ADS)

Zhang, Yong; Green, Christopher T.; LaBolle, Eric M.; Neupauer, Roseanna M.; Sun, HongGuang

2016-11-01

Spatiotemporal fractional-derivative models (FDMs) have been increasingly used to simulate non-Fickian diffusion, but methods have not been available to define boundary conditions for FDMs in bounded domains. This study defines boundary conditions and then develops a Lagrangian solver to approximate bounded, one-dimensional fractional diffusion. Both the zero-value and nonzero-value Dirichlet, Neumann, and mixed Robin boundary conditions are defined, where the sign of Riemann-Liouville fractional derivative (capturing nonzero-value spatial-nonlocal boundary conditions with directional superdiffusion) remains consistent with the sign of the fractional-diffusive flux term in the FDMs. New Lagrangian schemes are then proposed to track solute particles moving in bounded domains, where the solutions are checked against analytical or Eulerian solutions available for simplified FDMs. Numerical experiments show that the particle-tracking algorithm for non-Fickian diffusion differs from Fickian diffusion in relocating the particle position around the reflective boundary, likely due to the nonlocal and nonsymmetric fractional diffusion. For a nonzero-value Neumann or Robin boundary, a source cell with a reflective face can be applied to define the release rate of random-walking particles at the specified flux boundary. Mathematical definitions of physically meaningful nonlocal boundaries combined with bounded Lagrangian solvers in this study may provide the only viable techniques at present to quantify the impact of boundaries on anomalous diffusion, expanding the applicability of FDMs from infinite domains to those with any size and boundary conditions.

Boundary control of elliptic solutions to enforce local constraints

NASA Astrophysics Data System (ADS)

Bal, G.; Courdurier, M.

We present a constructive method to devise boundary conditions for solutions of second-order elliptic equations so that these solutions satisfy specific qualitative properties such as: (i) the norm of the gradient of one solution is bounded from below by a positive constant in the vicinity of a finite number of prescribed points; (ii) the determinant of gradients of n solutions is bounded from below in the vicinity of a finite number of prescribed points. Such constructions find applications in recent hybrid medical imaging modalities. The methodology is based on starting from a controlled setting in which the constraints are satisfied and continuously modifying the coefficients in the second-order elliptic equation. The boundary condition is evolved by solving an ordinary differential equation (ODE) defined via appropriate optimality conditions. Unique continuations and standard regularity results for elliptic equations are used to show that the ODE admits a solution for sufficiently long times.

Pattern Formation in Keller-Segel Chemotaxis Models with Logistic Growth

NASA Astrophysics Data System (ADS)

Jin, Ling; Wang, Qi; Zhang, Zengyan

In this paper, we investigate pattern formation in Keller-Segel chemotaxis models over a multidimensional bounded domain subject to homogeneous Neumann boundary conditions. It is shown that the positive homogeneous steady state loses its stability as chemoattraction rate χ increases. Then using Crandall-Rabinowitz local theory with χ being the bifurcation parameter, we obtain the existence of nonhomogeneous steady states of the system which bifurcate from this homogeneous steady state. Stability of the bifurcating solutions is also established through rigorous and detailed calculations. Our results provide a selection mechanism of stable wavemode which states that the only stable bifurcation branch must have a wavemode number that minimizes the bifurcation value. Finally, we perform extensive numerical simulations on the formation of stable steady states with striking structures such as boundary spikes, interior spikes, stripes, etc. These nontrivial patterns can model cellular aggregation that develop through chemotactic movements in biological systems.

Quantum and classical dynamics in adiabatic computation

NASA Astrophysics Data System (ADS)

Crowley, P. J. D.; Äńurić, T.; Vinci, W.; Warburton, P. A.; Green, A. G.

2014-10-01

Adiabatic transport provides a powerful way to manipulate quantum states. By preparing a system in a readily initialized state and then slowly changing its Hamiltonian, one may achieve quantum states that would otherwise be inaccessible. Moreover, a judicious choice of final Hamiltonian whose ground state encodes the solution to a problem allows adiabatic transport to be used for universal quantum computation. However, the dephasing effects of the environment limit the quantum correlations that an open system can support and degrade the power of such adiabatic computation. We quantify this effect by allowing the system to evolve over a restricted set of quantum states, providing a link between physically inspired classical optimization algorithms and quantum adiabatic optimization. This perspective allows us to develop benchmarks to bound the quantum correlations harnessed by an adiabatic computation. We apply these to the D-Wave Vesuvius machine with revealing—though inconclusive—results.

Small Body GN&C Research Report: A Robust Model Predictive Control Algorithm with Guaranteed Resolvability

NASA Technical Reports Server (NTRS)

Acikmese, Behcet A.; Carson, John M., III

2005-01-01

A robustly stabilizing MPC (model predictive control) algorithm for uncertain nonlinear systems is developed that guarantees the resolvability of the associated finite-horizon optimal control problem in a receding-horizon implementation. The control consists of two components; (i) feedforward, and (ii) feedback part. Feed-forward control is obtained by online solution of a finite-horizon optimal control problem for the nominal system dynamics. The feedback control policy is designed off-line based on a bound on the uncertainty in the system model. The entire controller is shown to be robustly stabilizing with a region of attraction composed of initial states for which the finite-horizon optimal control problem is feasible. The controller design for this algorithm is demonstrated on a class of systems with uncertain nonlinear terms that have norm-bounded derivatives, and derivatives in polytopes. An illustrative numerical example is also provided.

A robust model predictive control algorithm for uncertain nonlinear systems that guarantees resolvability

NASA Technical Reports Server (NTRS)

Acikmese, Ahmet Behcet; Carson, John M., III

2006-01-01

A robustly stabilizing MPC (model predictive control) algorithm for uncertain nonlinear systems is developed that guarantees resolvability. With resolvability, initial feasibility of the finite-horizon optimal control problem implies future feasibility in a receding-horizon framework. The control consists of two components; (i) feed-forward, and (ii) feedback part. Feed-forward control is obtained by online solution of a finite-horizon optimal control problem for the nominal system dynamics. The feedback control policy is designed off-line based on a bound on the uncertainty in the system model. The entire controller is shown to be robustly stabilizing with a region of attraction composed of initial states for which the finite-horizon optimal control problem is feasible. The controller design for this algorithm is demonstrated on a class of systems with uncertain nonlinear terms that have norm-bounded derivatives and derivatives in polytopes. An illustrative numerical example is also provided.

A Monomeric Membrane Peptide that Lives in Three Worlds: In Solution, Attached to, and Inserted across Lipid Bilayers

PubMed Central

Reshetnyak, Yana K.; Segala, Michael; Andreev, Oleg A.; Engelman, Donald M.

2007-01-01

The membrane peptide pH (low) insertion peptide (pHLIP) lives in three worlds, being soluble in aqueous solution at pH 7.4, binding to the surface of lipid bilayers, and inserting as a transbilayer helix at low pH. With low pH driving the process, pHLIP can translocate cargo molecules attached to its C-terminus via a disulfide and release them in the cytoplasm of a cell. Here we examine a key aspect of the mechanism, showing that pHLIP is monomeric in each of its three major states: soluble in water near neutral pH (state I), bound to the surface of a membrane near neutral pH (state II), and inserted across the membrane as an α-helix at low pH (state III). The peptide does not induce fusion or membrane leakage. The unique properties of pHLIP made it attractive for the biophysical investigation of membrane protein folding in vitro and for the development of a novel class of delivery peptides for the transport of therapeutic and diagnostic agents to acidic tissue sites associated with various pathological processes in vivo. PMID:17557792

Exponential growth and Gaussian—like fluctuations of solutions of stochastic differential equations with maximum functionals

NASA Astrophysics Data System (ADS)

Appleby, J. A. D.; Wu, H.

2008-11-01

In this paper we consider functional differential equations subjected to either instantaneous state-dependent noise, or to a white noise perturbation. The drift of the equations depend linearly on the current value and on the maximum of the solution. The functional term always provides positive feedback, while the instantaneous term can be mean-reverting or can exhibit positive feedback. We show in the white noise case that if the instantaneous term is mean reverting and dominates the history term, then solutions are recurrent, and upper bounds on the a.s. growth rate of the partial maxima of the solution can be found. When the instantaneous term is weaker, or is of positive feedback type, we determine necessary and sufficient conditions on the diffusion coefficient which ensure the exact exponential growth of solutions. An application of these results to an inefficient financial market populated by reference traders and speculators is given, in which the difference between the current instantaneous returns and maximum of the returns over the last few time units is used to determine trading strategies.

Bound states for magic state distillation in fault-tolerant quantum computation.

PubMed

Campbell, Earl T; Browne, Dan E

2010-01-22

Magic state distillation is an important primitive in fault-tolerant quantum computation. The magic states are pure nonstabilizer states which can be distilled from certain mixed nonstabilizer states via Clifford group operations alone. Because of the Gottesman-Knill theorem, mixtures of Pauli eigenstates are not expected to be magic state distillable, but it has been an open question whether all mixed states outside this set may be distilled. In this Letter we show that, when resources are finitely limited, nondistillable states exist outside the stabilizer octahedron. In analogy with the bound entangled states, which arise in entanglement theory, we call such states bound states for magic state distillation.

Effects of bias and temperature on the intersubband absorption in very long wavelength GaAs/AlGaAs quantum well infrared photodetectors

DOE Office of Scientific and Technical Information (OSTI.GOV)

Liu, X. H.; Zhou, X. H., E-mail: xhzhou@mail.sitp.ac.cn; Li, N.

2014-03-28

The temperature- and bias-dependent photocurrent spectra of very long wavelength GaAs/AlGaAs quantum well infrared photodetectors (QWIPs) are studied using spectroscopic measurements and corresponding theoretical calculations. It is found that the peak response wavelength will shift as the bias and temperature change. Aided by band structure calculations, we propose a model of the double excited states and explain the experimental observations very well. In addition, the working mechanisms of the quasi-bound state confined in the quantum well, including the processes of tunneling and thermionic emission, are also investigated in detail. We confirm that the first excited state, which belongs to themore » quasi-bound state, can be converted into a quasi-continuum state induced by bias and temperature. These obtained results provide a full understanding of the bound-to-quasi-bound state and the bound-to-quasi-continuum state transition, and thus allow for a better optimization of QWIPs performance.« less

Propagating bound states in the continuum in dielectric gratings

NASA Astrophysics Data System (ADS)

Bulgakov, E. N.; Maksimov, D. N.; Semina, P. N.; Skorobogatov, S. A.

2018-06-01

We consider propagating bound states in the continuum in dielectric gratings. The gratings consist of a slab with ridges periodically arranged ether on top or on the both sides of the slab. Based on the Fourier modal approach we recover the leaky zones above the line of light to identify the geometries of the gratings supporting Bloch bound states propagating in the direction perpendicular to the ridges. Most importantly, it is demonstrated that if a two-side grating possesses either mirror or glide symmetry the Bloch bound states are stable to variation of parameters as far as the above symmetries are preserved.

On an aggregation in birth-and-death stochastic dynamics

NASA Astrophysics Data System (ADS)

Finkelshtein, Dmitri; Kondratiev, Yuri; Kutoviy, Oleksandr; Zhizhina, Elena

2014-06-01

We consider birth-and-death stochastic dynamics of particle systems with attractive interaction. The heuristic generator of the dynamics has a constant birth rate and density-dependent decreasing death rate. The corresponding statistical dynamics is constructed. Using the Vlasov-type scaling we derive the limiting mesoscopic evolution and prove that this evolution propagates chaos. We study a nonlinear non-local kinetic equation for the first correlation function (density of population). The existence of uniformly bounded solutions as well as solutions growing inside of a bounded domain and expanding in the space are shown. These solutions describe two regimes in the mesoscopic system: regulation and aggregation.

Gradient estimates on the weighted p-Laplace heat equation

NASA Astrophysics Data System (ADS)

Wang, Lin Feng

2018-01-01

In this paper, by a regularization process we derive new gradient estimates for positive solutions to the weighted p-Laplace heat equation when the m-Bakry-Émery curvature is bounded from below by -K for some constant K ≥ 0. When the potential function is constant, which reduce to the gradient estimate established by Ni and Kotschwar for positive solutions to the p-Laplace heat equation on closed manifolds with nonnegative Ricci curvature if K ↘ 0, and reduce to the Davies, Hamilton and Li-Xu's gradient estimates for positive solutions to the heat equation on closed manifolds with Ricci curvature bounded from below if p = 2.

Better bounds on optimal measurement and entanglement recovery, with applications to uncertainty and monogamy relations

NASA Astrophysics Data System (ADS)

Renes, Joseph M.

2017-10-01

We extend the recent bounds of Sason and Verdú relating Rényi entropy and Bayesian hypothesis testing (arXiv:1701.01974.) to the quantum domain and show that they have a number of different applications. First, we obtain a sharper bound relating the optimal probability of correctly distinguishing elements of an ensemble of states to that of the pretty good measurement, and an analogous bound for optimal and pretty good entanglement recovery. Second, we obtain bounds relating optimal guessing and entanglement recovery to the fidelity of the state with a product state, which then leads to tight tripartite uncertainty and monogamy relations.

Spatiotemporal evolution in a (2+1)-dimensional chemotaxis model

NASA Astrophysics Data System (ADS)

Banerjee, Santo; Misra, Amar P.; Rondoni, L.

2012-01-01

Simulations are performed to investigate the nonlinear dynamics of a (2+1)-dimensional chemotaxis model of Keller-Segel (KS) type, with a logistic growth term. Because of its ability to display auto-aggregation, the KS model has been widely used to simulate self-organization in many biological systems. We show that the corresponding dynamics may lead to steady-states, to divergencies in a finite time as well as to the formation of spatiotemporal irregular patterns. The latter, in particular, appears to be chaotic in part of the range of bounded solutions, as demonstrated by the analysis of wavelet power spectra. Steady-states are achieved with sufficiently large values of the chemotactic coefficient (χ) and/or with growth rates r below a critical value rc. For r>rc, the solutions of the differential equations of the model diverge in a finite time. We also report on the pattern formation regime, for different values of χ, r and of the diffusion coefficient D.

Exact-Output Tracking Theory for Systems with Parameter Jumps

NASA Technical Reports Server (NTRS)

Devasia, Santosh; Paden, Brad; Rossi, Carlo

1996-01-01

In this paper we consider the exact output tracking problem for systems with parameter jumps. Necessary and sufficient conditions are derived for the elimination of switching-introduced output transient. Previous works have studied this problem by developing a regulator that maintains exact tracking through parameter jumps (switches). Such techniques are, however, only applicable to minimum-phase systems. In contrast, our approach is applicable to nonminimum-phase systems and obtains bounded but possibly non-causal solutions. If the reference trajectories are generated by an exo-system, then we develop an exact-tracking controller in a feedback form. As in standard regulator theory, we obtain a linear map from the states of the exo-system to the desired system state which is defined via a matrix differential equation. The constant solution of this differential equation provides asymptotic tracking, and coincides with the feedback law used in standard regulator theory. The obtained results are applied to a simple flexible manipulator with jumps in the pay-load mass.

Exact-Output Tracking Theory for Systems with Parameter Jumps

NASA Technical Reports Server (NTRS)

Devasia, Santosh; Paden, Brad; Rossi, Carlo

1997-01-01

We consider the exact output tracking problem for systems with parameter jumps. Necessary and sufficient conditions are derived for the elimination of switching-introduced output transient. Previous works have studied this problem by developing a regulator that maintains exact tracking through parameter jumps (switches). Such techniques are, however, only applicable to minimum-phase systems. In contrast, our approach is applicable to non-minimum-phase systems and it obtains bounded but possibly non-causal solutions. If the reference trajectories are generated by an exosystem, then we develop an exact-tracking controller in a feed-back form. As in standard regulator theory, we obtain a linear map from the states of the exosystem to the desired system state which is defined via a matrix differential equation. The constant solution of this differential equation provides asymptotic tracking, and coincides with the feedback law used in standard regulator theory. The obtained results are applied to a simple flexible manipulator with jumps in the pay-load mass.

Analytical Solutions of the Schrödinger Equation for the Manning-Rosen plus Hulthén Potential Within SUSY Quantum Mechanics

NASA Astrophysics Data System (ADS)

Ahmadov, A. I.; Naeem, Maria; Qocayeva, M. V.; Tarverdiyeva, V. A.

2018-02-01

In this paper, the bound state solution of the modified radial Schrödinger equation is obtained for the Manning-Rosen plus Hulthén potential by implementing the novel improved scheme to surmount the centrifugal term. The energy eigenvalues and corresponding radial wave functions are defined for any l ≠ 0 angular momentum case via the Nikiforov-Uvarov (NU) and supersymmetric quantum mechanics (SUSYQM) methods. By using these two different methods, equivalent expressions are obtained for the energy eigenvalues, and the expression of radial wave functions transformations to each other is demonstrated. The energy levels are worked out and the corresponding normalized eigenfunctions are represented in terms of the Jacobi polynomials for arbitrary l states. A closed form of the normalization constant of the wave functions is also found. It is shown that, the energy eigenvalues and eigenfunctions are sensitive to nr radial and l orbital quantum numbers.

Upper bounds on the error probabilities and asymptotic error exponents in quantum multiple state discrimination

NASA Astrophysics Data System (ADS)

Audenaert, Koenraad M. R.; Mosonyi, Milán

2014-10-01

We consider the multiple hypothesis testing problem for symmetric quantum state discrimination between r given states σ1, …, σr. By splitting up the overall test into multiple binary tests in various ways we obtain a number of upper bounds on the optimal error probability in terms of the binary error probabilities. These upper bounds allow us to deduce various bounds on the asymptotic error rate, for which it has been hypothesized that it is given by the multi-hypothesis quantum Chernoff bound (or Chernoff divergence) C(σ1, …, σr), as recently introduced by Nussbaum and Szkoła in analogy with Salikhov's classical multi-hypothesis Chernoff bound. This quantity is defined as the minimum of the pairwise binary Chernoff divergences min _{j

Effects of Catalytic Action and Ligand Binding on Conformational Ensembles of Adenylate Kinase.

PubMed

Onuk, Emre; Badger, John; Wang, Yu Jing; Bardhan, Jaydeep; Chishti, Yasmin; Akcakaya, Murat; Brooks, Dana H; Erdogmus, Deniz; Minh, David D L; Makowski, Lee

2017-08-29

Crystal structures of adenylate kinase (AdK) from Escherichia coli capture two states: an "open" conformation (apo) obtained in the absence of ligands and a "closed" conformation in which ligands are bound. Other AdK crystal structures suggest intermediate conformations that may lie on the transition pathway between these two states. To characterize the transition from open to closed states in solution, X-ray solution scattering data were collected from AdK in the apo form and with progressively increasing concentrations of five different ligands. Scattering data from apo AdK are consistent with scattering predicted from the crystal structure of AdK in the open conformation. In contrast, data from AdK samples saturated with Ap5A do not agree with that calculated from AdK in the closed conformation. Using cluster analysis of available structures, we selected representative structures in five conformational states: open, partially open, intermediate, partially closed, and closed. We used these structures to estimate the relative abundances of these states for each experimental condition. X-ray solution scattering data obtained from AdK with AMP are dominated by scattering from AdK in the open conformation. For AdK in the presence of high concentrations of ATP and ADP, the conformational ensemble shifts to a mixture of partially open and closed states. Even when AdK is saturated with Ap5A, a significant proportion of AdK remains in a partially open conformation. These results are consistent with an induced-fit model in which the transition of AdK from an open state to a closed state is initiated by ATP binding.

Existence and amplitude bounds for irrotational water waves in finite depth

NASA Astrophysics Data System (ADS)

Kogelbauer, Florian

2017-12-01

We prove the existence of solutions to the irrotational water-wave problem in finite depth and derive an explicit upper bound on the amplitude of the nonlinear solutions in terms of the wavenumber, the total hydraulic head, the wave speed and the relative mass flux. Our approach relies upon a reformulation of the water-wave problem as a one-dimensional pseudo-differential equation and the Newton-Kantorovich iteration for Banach spaces. This article is part of the theme issue 'Nonlinear water waves'.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Preston, Leiph

Although using standard Taylor series coefficients for finite-difference operators is optimal in the sense that in the limit of infinitesimal space and time discretization, the solution approaches the correct analytic solution to the acousto-dynamic system of differential equations, other finite-difference operators may provide optimal computational run time given certain error bounds or source bandwidth constraints. This report describes the results of investigation of alternative optimal finite-difference coefficients based on several optimization/accuracy scenarios and provides recommendations for minimizing run time while retaining error within given error bounds.

Observation of topologically protected bound states in photonic quantum walks.

PubMed

Kitagawa, Takuya; Broome, Matthew A; Fedrizzi, Alessandro; Rudner, Mark S; Berg, Erez; Kassal, Ivan; Aspuru-Guzik, Alán; Demler, Eugene; White, Andrew G

2012-06-06

Topological phases exhibit some of the most striking phenomena in modern physics. Much of the rich behaviour of quantum Hall systems, topological insulators, and topological superconductors can be traced to the existence of robust bound states at interfaces between different topological phases. This robustness has applications in metrology and holds promise for future uses in quantum computing. Engineered quantum systems--notably in photonics, where wavefunctions can be observed directly--provide versatile platforms for creating and probing a variety of topological phases. Here we use photonic quantum walks to observe bound states between systems with different bulk topological properties and demonstrate their robustness to perturbations--a signature of topological protection. Although such bound states are usually discussed for static (time-independent) systems, here we demonstrate their existence in an explicitly time-dependent situation. Moreover, we discover a new phenomenon: a topologically protected pair of bound states unique to periodically driven systems.

Some Surprises and Paradoxes Revealed by Inverse Problem Approach and Notion about Qualitative Solutions of SCHRÖDINGER Equations “IN MIND”

NASA Astrophysics Data System (ADS)

Zakhariev, B. N.; Chabanov, V. M.

It was an important examination to give a review talk at the previous Conference on Inverse Quantum Scattering (1996, Lake Balaton) about computer visualization of this science in front of its fathers — creators, B. M. Levitan and V. A. Marchenko. We have achieved a new understanding that the discovered main rules of transformations of a single wave function bump, e.g., for the ground bound states of one dimensional quantum systems are applicable to any state of any potential with arbitrary number of bumps from finite to unlimited ones as scattering states and bound states embedded into continuum. It appeared that we need only to repeat the rule mentally the necessary number of times. That uttermost simplification and unification of physical notion of spectral, scattering and decay control for any potential have got an obligatory praise from B. M. Levitan at the conference and was a mighty stimulus for our further research After that we have written both Russian (2002) and improved English editions of “Submissive Quantum Mechanics. New Status of the Theory in Inverse Problem Approach”1 (appeared at the very end of 2007). This book was written for correction of the present defect in quantum education throughout the world. Recently the quantum IP intuition helped us to discover a new concept of permanent wave resonance with potential spatial oscillations.2 This means the constant wave swinging frequency on the whole energy intervals of spectral forbidden zones destroying physical solutions and deepening the theory of waves in periodic potentials. It also shows the other side of strengthening the fundamentally important magic structures. A ‘new language’ of wave bending will be presented to enrich our quantum intuition, e.g., the paradoxical effective attraction of barriers and repulsion of wells in multichannel systems, etc.

Expansion in higher harmonics of boson stars using a generalized Ruffini-Bonazzola approach. Part 1. Bound states

DOE Office of Scientific and Technical Information (OSTI.GOV)

Eby, Joshua; Suranyi, Peter; Wijewardhana, L. C. R.

The method pioneered by Ruffini and Bonazzola (RB) to describe boson stars involves an expansion of the boson field which is linear in creation and annihilation operators. This expansion constitutes an exact solution to a non-interacting field theory, and has been used as a reasonable ansatz for an interacting one. In this work, we show how one can go beyond the RB ansatz towards an exact solution of the interacting operator Klein-Gordon equation, which can be solved iteratively to ever higher precision. Our Generalized Ruffini-Bonazzola approach takes into account contributions from nontrivial harmonic dependence of the wavefunction, using a sum of terms with energymore » $$k\\,E_0$$, where $$k\\geq1$$ and $$E_0$$ is the chemical potential of a single bound axion. The method critically depends on an expansion in a parameter $$\\Delta \\equiv \\sqrt{1-E_0{}^2/m^2}<1$$, where $m$ is the mass of the boson. In the case of the axion potential, we calculate corrections which are relevant for axion stars in the transition or dense branches. We find with high precision the local minimum of the mass, $$M_{min}\\approx 463\\,f^2/m$$, at $$\\Delta\\approx0.27$$, where $f$ is the axion decay constant. This point marks the crossover from transition to dense branches of solutions, and a corresponding crossover from structural instability to stability.« less

Expansion in higher harmonics of boson stars using a generalized Ruffini-Bonazzola approach. Part 1. Bound states

DOE PAGES

Eby, Joshua; Suranyi, Peter; Wijewardhana, L. C. R.

2018-04-10

The method pioneered by Ruffini and Bonazzola (RB) to describe boson stars involves an expansion of the boson field which is linear in creation and annihilation operators. This expansion constitutes an exact solution to a non-interacting field theory, and has been used as a reasonable ansatz for an interacting one. In this work, we show how one can go beyond the RB ansatz towards an exact solution of the interacting operator Klein-Gordon equation, which can be solved iteratively to ever higher precision. Our Generalized Ruffini-Bonazzola approach takes into account contributions from nontrivial harmonic dependence of the wavefunction, using a sum of terms with energymore » $$k\\,E_0$$, where $$k\\geq1$$ and $$E_0$$ is the chemical potential of a single bound axion. The method critically depends on an expansion in a parameter $$\\Delta \\equiv \\sqrt{1-E_0{}^2/m^2}<1$$, where $m$ is the mass of the boson. In the case of the axion potential, we calculate corrections which are relevant for axion stars in the transition or dense branches. We find with high precision the local minimum of the mass, $$M_{min}\\approx 463\\,f^2/m$$, at $$\\Delta\\approx0.27$$, where $f$ is the axion decay constant. This point marks the crossover from transition to dense branches of solutions, and a corresponding crossover from structural instability to stability.« less

Backbone conformational preferences of an intrinsically disordered protein in solution.

PubMed

Espinoza-Fonseca, L Michel; Ilizaliturri-Flores, Ian; Correa-Basurto, José

2012-06-01

We have performed a 4-μs molecular dynamics simulation to investigate the native conformational preferences of the intrinsically disordered kinase-inducible domain (KID) of the transcription factor CREB in solution. There is solid experimental evidence showing that KID does not possess a bound-like structure in solution; however, it has been proposed that coil-to-helix transitions upon binding to its binding partner (CBP) are template-driven. While these studies indicate that IDPs possess a bias towards the bound structure, they do not provide direct evidence on the time-dependent conformational preferences of IDPs in atomic detail. Our simulation captured intrinsic conformational characteristics of KID that are in good agreement with experimental data such as a very small percentage of helical structure in its segment α(B) and structural disorder in solution. We used dihedral principal component analysis dPCA to map the conformations of KID in the microsecond timescale. By using principal components as reaction coordinates, we further constructed dPCA-based free energy landscapes of KID. Analysis of the free energy landscapes showed that KID is best characterized as a conformational ensemble of rapidly interconverting conformations. Interestingly, we found that despite the conformational heterogeneity of the backbone and the absence of substantial secondary structure, KID does not randomly sample the conformational space in solution: analysis of the (Φ, Ψ) dihedral angles showed that several individual residues of KID possess a strong bias toward the helical region of the Ramachandran plot. We suggest that the intrinsic conformational preferences of KID provide a bias toward the folded state without having to populate bound-like conformations before binding. Furthermore, we argue that these conformational preferences do not represent actual structural constraints which drive binding through a single pathway, which allows for specific interactions with multiple binding partners. Based on this evidence, we propose that the backbone conformational preferences of KID provide a thermodynamic advantage for folding and binding without negatively affecting the kinetics of binding. We further discuss the relation of our results to previous studies to rationalize the functional implications of the conformational preferences of IDPs, such as the optimization of structural disorder in protein-protein interactions. This study illustrates the importance in obtaining atomistic information of intrinsically disordered proteins in real time to reveal functional features arising from their complex conformational space.

Ability of a beta-casein phosphopeptide to modulate the precipitation of calcium phosphate by forming amorphous dicalcium phosphate nanoclusters.

PubMed Central

Holt, C; Wahlgren, N M; Drakenberg, T

1996-01-01

The ability of casein in the form of colloidal-sized casein micelles to modulate the phase separation of calcium phosphate during milk secretion is adapted to produce nanometre-sized particles of calcium phosphate stabilized by a casein phosphopeptide (nanoclusters). The nanoclusters were prepared from an undersaturated solution of salts and the peptide by raising the pH homogeneously from about 5.5 to 6.7 with urea plus urease. Chemical analysis and IR spectroscopy showed that they comprise an amorphous dicalcium phosophate bound to the phosphopeptide. Multinuclear NMR spectroscopy of the cluster solutions showed that the small ions and free peptide in the solution were in a state of dynamic exchange with the nanoclusters. The peptide is linked to the calcium phosphate through its sequence of phosphorylated residues, but, in a proportion of adsorbed conformational states, the termini retain the conformational freedom of the unbound peptide. The ability of casein to form nanoclusters in milk suggests a more general mechanism for avoiding pathological calcification and regulating calcium flow in tissues and biological fluids exposed to or containing high concentrations of calcium. PMID:8615755

Convex relaxations for gas expansion planning

DOE PAGES

Borraz-Sanchez, Conrado; Bent, Russell Whitford; Backhaus, Scott N.; ...

2016-01-01

Expansion of natural gas networks is a critical process involving substantial capital expenditures with complex decision-support requirements. Here, given the non-convex nature of gas transmission constraints, global optimality and infeasibility guarantees can only be offered by global optimisation approaches. Unfortunately, state-of-the-art global optimisation solvers are unable to scale up to real-world size instances. In this study, we present a convex mixed-integer second-order cone relaxation for the gas expansion planning problem under steady-state conditions. The underlying model offers tight lower bounds with high computational efficiency. In addition, the optimal solution of the relaxation can often be used to derive high-quality solutionsmore » to the original problem, leading to provably tight optimality gaps and, in some cases, global optimal solutions. The convex relaxation is based on a few key ideas, including the introduction of flux direction variables, exact McCormick relaxations, on/off constraints, and integer cuts. Numerical experiments are conducted on the traditional Belgian gas network, as well as other real larger networks. The results demonstrate both the accuracy and computational speed of the relaxation and its ability to produce high-quality solution« less

Three-body spectrum in a finite volume: The role of cubic symmetry

DOE PAGES

Doring, M.; Hammer, H. -W.; Mai, M.; ...

2018-06-15

The three-particle quantization condition is partially diagonalized in the center-of-mass frame by using cubic symmetry on the lattice. To this end, instead of spherical harmonics, the kernel of the Bethe-Salpeter equation for particle-dimer scattering is expanded in the basis functions of different irreducible representations of the octahedral group. Such a projection is of particular importance for the three-body problem in the finite volume due to the occurrence of three-body singularities above breakup. Additionally, we study the numerical solution and properties of such a projected quantization condition in a simple model. It is shown that, for large volumes, these solutions allowmore » for an instructive interpretation of the energy eigenvalues in terms of bound and scattering states.« less

Three-body spectrum in a finite volume: The role of cubic symmetry

DOE Office of Scientific and Technical Information (OSTI.GOV)

Doring, M.; Hammer, H. -W.; Mai, M.

The three-particle quantization condition is partially diagonalized in the center-of-mass frame by using cubic symmetry on the lattice. To this end, instead of spherical harmonics, the kernel of the Bethe-Salpeter equation for particle-dimer scattering is expanded in the basis functions of different irreducible representations of the octahedral group. Such a projection is of particular importance for the three-body problem in the finite volume due to the occurrence of three-body singularities above breakup. Additionally, we study the numerical solution and properties of such a projected quantization condition in a simple model. It is shown that, for large volumes, these solutions allowmore » for an instructive interpretation of the energy eigenvalues in terms of bound and scattering states.« less

Tunable hybridization of Majorana bound states at the quantum spin Hall edge

NASA Astrophysics Data System (ADS)

Keidel, Felix; Burset, Pablo; Trauzettel, Björn

2018-02-01

Confinement at the helical edge of a topological insulator is possible in the presence of proximity-induced magnetic (F) or superconducting (S) order. The interplay of both phenomena leads to the formation of localized Majorana bound states (MBS) or likewise (under certain resonance conditions) the formation of ordinary Andreev bound states (ABS). We investigate the properties of bound states in junctions composed of alternating regions of F or S barriers. Interestingly, the direction of magnetization in F regions and the relative superconducting phase between S regions can be exploited to hybridize MBS or ABS at will. We show that the local properties of MBS translate into a particular nonlocal superconducting pairing amplitude. Remarkably, the symmetry of the pairing amplitude contains information about the nature of the bound state that it stems from. Hence this symmetry can in principle be used to distinguish MBS from ABS, owing to the strong connection between local density of states and nonlocal pairing in our setup.

STATIC QUARK ANTI-QUARK FREE AND INTERNAL ENERGY IN 2-FLAVOR QCD AND BOUND STATES IN THE QGP.

DOE Office of Scientific and Technical Information (OSTI.GOV)

ZANTOW, F.; KACZMAREK, O.

2005-07-25

We present results on heavy quark free energies in 2-flavour QCD. The temperature dependence of the interaction between static quark anti-quark pairs will be analyzed in terms of temperature dependent screening radii, which give a first estimate on the medium modification of (heavy quark) bound states in the quark gluon plasma. Comparing those radii to the (zero temperature) mean squared charge radii of chasmonium states indicates that the J/{Psi} may survive the phase transition as a bound state, while {chi}{sub c} and {Psi}{prime} are expected to show significant thermal modifications at temperatures close to the transition. Furthermore we will analyzemore » the relation between heavy quark free energies, entropy contributions and internal energy and discuss their relation to potential models used to analyze the melting of heavy quark bound states above the deconfinement temperature. Results of different groups and various potential models for bound states in the deconfined phase of QCD are compared.« less

Pleural tissue hyaluronan produced by postmortem ventilation in rabbits.

PubMed

Wang, P M; Lai-Fook, S J

2000-01-01

We developed a method that used Alcian blue bound to hyaluronan to measure pleural hyaluronan in rabbits postmortem. Rabbits were killed, then ventilated with 21% O2--5% CO2--74% N2 for 3 h. The pleural liquid was removed by suction and 5 ml Alcian blue stock solution (0.33 mg/ml, 3.3 pH) was injected into each chest cavity. After 10 min, the Alcian blue solution was removed and the unbound Alcian blue solution (supernatant) separated by centrifugation and filtration. The supernatant transmissibility (T) was measured spectrophotometrically at 613 nm. Supernatant Alcian blue concentration (Cab) was obtained from a calibration curve of T versus dilutions of stock solution Cab. Alcian blue bound to pleural tissue hyaluronan was obtained by subtracting supernatant Cab from stock solution Cab. Pleural tissue hyaluronan was obtained from a calibration curve of hyaluronan versus Alcian blue bound to hyaluronan. Compared with control rabbits, pleural tissue hyaluronan (0.21 +/- 0.04 mg/kg) increased twofold, whereas pleural liquid volume decreased by 30% after 3 h of ventilation. Pleural effusions present 3 h postmortem without ventilation did not change pleural tissue hyaluronan from control values. Thus ventilation-induced pleural liquid shear stress, not increased filtration, was the stimulus for the increased hyaluronan produced from pleural mesothelial cells.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Azunre, P.

Here in this paper, two novel techniques for bounding the solutions of parametric weakly coupled second-order semilinear parabolic partial differential equations are developed. The first provides a theorem to construct interval bounds, while the second provides a theorem to construct lower bounds convex and upper bounds concave in the parameter. The convex/concave bounds can be significantly tighter than the interval bounds because of the wrapping effect suffered by interval analysis in dynamical systems. Both types of bounds are computationally cheap to construct, requiring solving auxiliary systems twice and four times larger than the original system, respectively. An illustrative numerical examplemore » of bound construction and use for deterministic global optimization within a simple serial branch-and-bound algorithm, implemented numerically using interval arithmetic and a generalization of McCormick's relaxation technique, is presented. Finally, problems within the important class of reaction-diffusion systems may be optimized with these tools.« less

Observation of three-photon bound states in a quantum nonlinear medium

NASA Astrophysics Data System (ADS)

Liang, Qi-Yu; Venkatramani, Aditya V.; Cantu, Sergio H.; Nicholson, Travis L.; Gullans, Michael J.; Gorshkov, Alexey V.; Thompson, Jeff D.; Chin, Cheng; Lukin, Mikhail D.; Vuletić, Vladan

2018-02-01

Bound states of massive particles, such as nuclei, atoms, or molecules, constitute the bulk of the visible world around us. By contrast, photons typically only interact weakly. We report the observation of traveling three-photon bound states in a quantum nonlinear medium where the interactions between photons are mediated by atomic Rydberg states. Photon correlation and conditional phase measurements reveal the distinct bunching and phase features associated with three-photon and two-photon bound states. Such photonic trimers and dimers possess shape-preserving wave functions that depend on the constituent photon number. The observed bunching and strongly nonlinear optical phase are described by an effective field theory of Rydberg-induced photon-photon interactions. These observations demonstrate the ability to realize and control strongly interacting quantum many-body states of light.

Transfer Function Bounds for Partial-unit-memory Convolutional Codes Based on Reduced State Diagram

NASA Technical Reports Server (NTRS)

Lee, P. J.

1984-01-01

The performance of a coding system consisting of a convolutional encoder and a Viterbi decoder is analytically found by the well-known transfer function bounding technique. For the partial-unit-memory byte-oriented convolutional encoder with m sub 0 binary memory cells and (k sub 0 m sub 0) inputs, a state diagram of 2(K) (sub 0) was for the transfer function bound. A reduced state diagram of (2 (m sub 0) +1) is used for easy evaluation of transfer function bounds for partial-unit-memory codes.

Distinguishing Majorana bound states from localized Andreev bound states by interferometry

NASA Astrophysics Data System (ADS)

Hell, Michael; Flensberg, Karsten; Leijnse, Martin

2018-04-01

Experimental evidence for Majorana bound states (MBSs) is so far mainly based on the robustness of a zero-bias conductance peak. However, similar features can also arise due to Andreev bound states (ABSs) localized at the end of an island. We show that these two scenarios can be distinguished by an interferometry experiment based on embedding a Coulomb-blockaded island into an Aharonov-Bohm ring. For two ABSs, when the ground state is nearly degenerate, cotunneling can change the state of the island, and interference is suppressed. By contrast, for two MBSs the ground state is nondegenerate, and cotunneling has to preserve the island state, which leads to h /e -periodic conductance oscillations with magnetic flux. Such interference setups can be realized with semiconducting nanowires or two-dimensional electron gases with proximity-induced superconductivity and may also be a useful spectroscopic tool for parity-flip mechanisms.

Universal bounds on current fluctuations.

PubMed

Pietzonka, Patrick; Barato, Andre C; Seifert, Udo

2016-05-01

For current fluctuations in nonequilibrium steady states of Markovian processes, we derive four different universal bounds valid beyond the Gaussian regime. Different variants of these bounds apply to either the entropy change or any individual current, e.g., the rate of substrate consumption in a chemical reaction or the electron current in an electronic device. The bounds vary with respect to their degree of universality and tightness. A universal parabolic bound on the generating function of an arbitrary current depends solely on the average entropy production. A second, stronger bound requires knowledge both of the thermodynamic forces that drive the system and of the topology of the network of states. These two bounds are conjectures based on extensive numerics. An exponential bound that depends only on the average entropy production and the average number of transitions per time is rigorously proved. This bound has no obvious relation to the parabolic bound but it is typically tighter further away from equilibrium. An asymptotic bound that depends on the specific transition rates and becomes tight for large fluctuations is also derived. This bound allows for the prediction of the asymptotic growth of the generating function. Even though our results are restricted to networks with a finite number of states, we show that the parabolic bound is also valid for three paradigmatic examples of driven diffusive systems for which the generating function can be calculated using the additivity principle. Our bounds provide a general class of constraints for nonequilibrium systems.

Local quenches and quantum chaos from higher spin perturbations

NASA Astrophysics Data System (ADS)

David, Justin R.; Khetrapal, Surbhi; Kumar, S. Prem

2017-10-01

We study local quenches in 1+1 dimensional conformal field theories at large- c by operators carrying higher spin charge. Viewing such states as solutions in Chern-Simons theory, representing infalling massive particles with spin-three charge in the BTZ back-ground, we use the Wilson line prescription to compute the single-interval entanglement entropy (EE) and scrambling time following the quench. We find that the change in EE is finite (and real) only if the spin-three charge q is bounded by the energy of the perturbation E, as | q| /c < E 2 /c 2. We show that the Wilson line/EE correlator deep in the quenched regime and its expansion for small quench widths overlaps with the Regge limit for chaos of the out-of-time-ordered correlator. We further find that the scrambling time for the two-sided mutual information between two intervals in the thermofield double state increases with increasing spin-three charge, diverging when the bound is saturated. For larger values of the charge, the scrambling time is shorter than for pure gravity and controlled by the spin-three Lyapunov exponent 4 π/β. In a CFT with higher spin chemical potential, dual to a higher spin black hole, we find that the chemical potential must be bounded to ensure that the mutual information is a concave function of time and entanglement speed is less than the speed of light. In this case, a quench with zero higher spin charge yields the same Lyapunov exponent as pure Einstein gravity.

Family of nonlocal bound entangled states

NASA Astrophysics Data System (ADS)

Yu, Sixia; Oh, C. H.

2017-03-01

Bound entanglement, being entangled yet not distillable, is essential to our understanding of the relations between nonlocality and entanglement besides its applications in certain quantum information tasks. Recently, bound entangled states that violate a Bell inequality have been constructed for a two-qutrit system, disproving a conjecture by Peres that bound entanglement is local. Here we construct this kind of nonlocal bound entangled state for all finite dimensions larger than two, making possible their experimental demonstration in most general systems. We propose a Bell inequality, based on a Hardy-type argument for nonlocality, and a steering inequality to identify their nonlocality. We also provide a family of entanglement witnesses to detect their entanglement beyond the Bell inequality and the steering inequality.

Optimization of Error-Bounded Lossy Compression for Hard-to-Compress HPC Data

DOE Office of Scientific and Technical Information (OSTI.GOV)

Di, Sheng; Cappello, Franck

Since today’s scientific applications are producing vast amounts of data, compressing them before storage/transmission is critical. Results of existing compressors show two types of HPC data sets: highly compressible and hard to compress. In this work, we carefully design and optimize the error-bounded lossy compression for hard-tocompress scientific data. We propose an optimized algorithm that can adaptively partition the HPC data into best-fit consecutive segments each having mutually close data values, such that the compression condition can be optimized. Another significant contribution is the optimization of shifting offset such that the XOR-leading-zero length between two consecutive unpredictable data points canmore » be maximized. We finally devise an adaptive method to select the best-fit compressor at runtime for maximizing the compression factor. We evaluate our solution using 13 benchmarks based on real-world scientific problems, and we compare it with 9 other state-of-the-art compressors. Experiments show that our compressor can always guarantee the compression errors within the user-specified error bounds. Most importantly, our optimization can improve the compression factor effectively, by up to 49% for hard-tocompress data sets with similar compression/decompression time cost.« less

Extension of the lower bound of monitor solutions of maximally permissive supervisors to non-α net systems

NASA Astrophysics Data System (ADS)

Wu, W. H.; Chao, D. Y.

2016-07-01

Traditional region-based liveness-enforcing supervisors focus on (1) maximal permissiveness of not losing legal states, (2) structural simplicity of minimal number of monitors, and (3) fast computation. Lately, a number of similar approaches can achieve minimal configuration using efficient linear programming. However, it is unclear as to the relationship between the minimal configuration and the net structure. It is important to explore the structures involved for the fewest monitors required. Once the lower bound is achieved, further iteration to merge (or reduce the number of) monitors is not necessary. The minimal strongly connected resource subnet (i.e., all places are resources) that contains the set of resource places in a basic siphon is an elementary circuit. Earlier, we showed that the number of monitors required for liveness-enforcing and maximal permissiveness equals that of basic siphons for a subclass of Petri nets modelling manufacturing, called α systems. This paper extends this to systems more powerful than the α one so that the number of monitors in a minimal configuration remains to be lower bounded by that of basic siphons. This paper develops the theory behind and shows examples.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Ho, M.; Shi, W; Rinaldo-Mathis, A

Inhibition of human purine nucleoside phosphorylase (PNP) stops growth of activated T-cells and the formation of 6-oxypurine bases, making it a target for leukemia, autoimmune disorders, and gout. Four generations of ribocation transition-state mimics bound to PNP are structurally characterized. Immucillin-H (K*{sub i} = 58 pM, first-generation) contains an iminoribitol cation with four asymmetric carbons. DADMe-Immucillin-H (K*{sub i} = 9 pM, second-generation), uses a methylene-bridged dihydroxypyrrolidine cation with two asymmetric centers. DATMe-Immucillin-H (K*{sub i} = 9 pM, third-generation) contains an open-chain amino alcohol cation with two asymmetric carbons. SerMe-ImmH (K*{sub i} = 5 pM, fourth-generation) uses achiral dihydroxyaminoalcohol seramide asmore » the ribocation mimic. Crystal structures of PNPs establish features of tight binding to be; (1) ion-pair formation between bound phosphate (or its mimic) and inhibitor cation, (2) leaving-group interactions to N1, O6, and N7 of 9-deazahypoxanthine, (3) interaction between phosphate and inhibitor hydroxyl groups, and (4) His257 interacting with the 5{prime}-hydroxyl group. The first generation analogue is an imperfect fit to the catalytic site with a long ion pair distance between the iminoribitol and bound phosphate and weaker interactions to the leaving group. Increasing the ribocation to leaving-group distance in the second- to fourth-generation analogues provides powerful binding interactions and a facile synthetic route to powerful inhibitors. Despite chemical diversity in the four generations of transition-state analogues, the catalytic site geometry is almost the same for all analogues. Multiple solutions in transition-state analogue design are available to convert the energy of catalytic rate enhancement to binding energy in human PNP.« less

Extremely efficient internal exciton dissociation through edge states in layered 2D perovskites

DOE PAGES

Blancon, Jean -Christophe Robert; Tsai, Hsinhan; Nie, Wanyi; ...

2017-03-09

Understanding and controlling charge and energy flow in state-of-the-art semiconductor quantum wells has enabled high-efficiency optoelectronic devices. Two-dimensional (2D) Ruddlesden-Popper perovskites are solution-processed quantum wells wherein the band gap can be tuned by varying the perovskite-layer thickness, which modulates the effective electron-hole confinement. We report that, counterintuitive to classical quantum-confined systems where photogenerated electrons and holes are strongly bound by Coulomb interactions or excitons, the photophysics of thin films made of Ruddlesden-Popper perovskites with a thickness exceeding two perovskite-crystal units (>1.3 nanometers) is dominated by lower-energy states associated with the local intrinsic electronic structure of the edges of the perovskitemore » layers. Furthermore, these states provide a direct pathway for dissociating excitons into longer-lived free carriers that substantially improve the performance of optoelectronic devices.« less

Bounded fractional diffusion in geological media: Definition and Lagrangian approximation

USGS Publications Warehouse

Zhang, Yong; Green, Christopher T.; LaBolle, Eric M.; Neupauer, Roseanna M.; Sun, HongGuang

2016-01-01

Spatiotemporal Fractional-Derivative Models (FDMs) have been increasingly used to simulate non-Fickian diffusion, but methods have not been available to define boundary conditions for FDMs in bounded domains. This study defines boundary conditions and then develops a Lagrangian solver to approximate bounded, one-dimensional fractional diffusion. Both the zero-value and non-zero-value Dirichlet, Neumann, and mixed Robin boundary conditions are defined, where the sign of Riemann-Liouville fractional derivative (capturing non-zero-value spatial-nonlocal boundary conditions with directional super-diffusion) remains consistent with the sign of the fractional-diffusive flux term in the FDMs. New Lagrangian schemes are then proposed to track solute particles moving in bounded domains, where the solutions are checked against analytical or Eularian solutions available for simplified FDMs. Numerical experiments show that the particle-tracking algorithm for non-Fickian diffusion differs from Fickian diffusion in relocating the particle position around the reflective boundary, likely due to the non-local and non-symmetric fractional diffusion. For a non-zero-value Neumann or Robin boundary, a source cell with a reflective face can be applied to define the release rate of random-walking particles at the specified flux boundary. Mathematical definitions of physically meaningful nonlocal boundaries combined with bounded Lagrangian solvers in this study may provide the only viable techniques at present to quantify the impact of boundaries on anomalous diffusion, expanding the applicability of FDMs from infinite do mains to those with any size and boundary conditions.

Selective determination of aluminum bound with tannin in tea infusion.

PubMed

Erdemoğlu, Sema B; Güçer, Seref

2005-08-01

In this study, an analytical method for indirect measurement of Al bound with tannin in tea infusion was studied. This method utilizes the ability of the tannins to precipitate with protein. Separation conditions were investigated using model solutions. This method is uncomplicated, inexpensive and suitable for real samples. About 34% of the total Al in brew extracted from commercially available teas was bound to condensed and hydrolyzable tannins.

Model reduction of dynamical systems by proper orthogonal decomposition: Error bounds and comparison of methods using snapshots from the solution and the time derivatives [Proper orthogonal decomposition model reduction of dynamical systems: error bounds and comparison of methods using snapshots from the solution and the time derivatives

DOE PAGES

Kostova-Vassilevska, Tanya; Oxberry, Geoffrey M.

2017-09-17

In this study, we consider two proper orthogonal decomposition (POD) methods for dimension reduction of dynamical systems. The first method (M1) uses only time snapshots of the solution, while the second method (M2) augments the snapshot set with time-derivative snapshots. The goal of the paper is to analyze and compare the approximation errors resulting from the two methods by using error bounds. We derive several new bounds of the error from POD model reduction by each of the two methods. The new error bounds involve a multiplicative factor depending on the time steps between the snapshots. For method M1 themore » factor depends on the second power of the time step, while for method 2 the dependence is on the fourth power of the time step, suggesting that method M2 can be more accurate for small between-snapshot intervals. However, three other factors also affect the size of the error bounds. These include (i) the norm of the second (for M1) and fourth derivatives (M2); (ii) the first neglected singular value and (iii) the spectral properties of the projection of the system’s Jacobian in the reduced space. Because of the interplay of these factors neither method is more accurate than the other in all cases. Finally, we present numerical examples demonstrating that when the number of collected snapshots is small and the first neglected singular value has a value of zero, method M2 results in a better approximation.« less

Model reduction of dynamical systems by proper orthogonal decomposition: Error bounds and comparison of methods using snapshots from the solution and the time derivatives [Proper orthogonal decomposition model reduction of dynamical systems: error bounds and comparison of methods using snapshots from the solution and the time derivatives

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kostova-Vassilevska, Tanya; Oxberry, Geoffrey M.

In this study, we consider two proper orthogonal decomposition (POD) methods for dimension reduction of dynamical systems. The first method (M1) uses only time snapshots of the solution, while the second method (M2) augments the snapshot set with time-derivative snapshots. The goal of the paper is to analyze and compare the approximation errors resulting from the two methods by using error bounds. We derive several new bounds of the error from POD model reduction by each of the two methods. The new error bounds involve a multiplicative factor depending on the time steps between the snapshots. For method M1 themore » factor depends on the second power of the time step, while for method 2 the dependence is on the fourth power of the time step, suggesting that method M2 can be more accurate for small between-snapshot intervals. However, three other factors also affect the size of the error bounds. These include (i) the norm of the second (for M1) and fourth derivatives (M2); (ii) the first neglected singular value and (iii) the spectral properties of the projection of the system’s Jacobian in the reduced space. Because of the interplay of these factors neither method is more accurate than the other in all cases. Finally, we present numerical examples demonstrating that when the number of collected snapshots is small and the first neglected singular value has a value of zero, method M2 results in a better approximation.« less

Obtaining lower bounds from the progressive hedging algorithm for stochastic mixed-integer programs

DOE PAGES

Gade, Dinakar; Hackebeil, Gabriel; Ryan, Sarah M.; ...

2016-04-02

We present a method for computing lower bounds in the progressive hedging algorithm (PHA) for two-stage and multi-stage stochastic mixed-integer programs. Computing lower bounds in the PHA allows one to assess the quality of the solutions generated by the algorithm contemporaneously. The lower bounds can be computed in any iteration of the algorithm by using dual prices that are calculated during execution of the standard PHA. In conclusion, we report computational results on stochastic unit commitment and stochastic server location problem instances, and explore the relationship between key PHA parameters and the quality of the resulting lower bounds.

Photophysics of aggregated 9-methylthiacarbocyanine bound to polyanions

NASA Astrophysics Data System (ADS)

Chibisov, Alexander K.; Görner, Helmut

2002-05-01

The photophysical properties of 3,3 '-diethyl-9-methylthiacarbocyanine (DTC) were studied in the presence of polystyrene sulfonate (PSS), polyacrylic acid (PAA) and polymethacrylic acid (PMA). The absorption spectra reflect a monomer/dimer equilibrium in neat aqueous solution and a shift towards bound H-aggregates, bound dimers and bound monomers on increasing the ratio of polyanion residue to dye concentrations ( r). These equilibria also determine the photodeactivation modes of DTC. The fluorescence intensity is reduced, when dimers and aggregates are present and strongly enhanced for low dye loading ( r=10 4). In contrast, the quantum yield of intersystem crossing is enhanced for bound dimers ( r=10 3).

What Information Theory Says about Bounded Rational Best Response

NASA Technical Reports Server (NTRS)

Wolpert, David H.

2005-01-01

Probability Collectives (PC) provides the information-theoretic extension of conventional full-rationality game theory to bounded rational games. Here an explicit solution to the equations giving the bounded rationality equilibrium of a game is presented. Then PC is used to investigate games in which the players use bounded rational best-response strategies. Next it is shown that in the continuum-time limit, bounded rational best response games result in a variant of the replicator dynamics of evolutionary game theory. It is then shown that for team (shared-payoff) games, this variant of replicator dynamics is identical to Newton-Raphson iterative optimization of the shared utility function.

Resin-Bound Crypto-Thioester for Native Chemical Ligation.

PubMed

Naruse, Naoto; Ohkawachi, Kento; Inokuma, Tsubasa; Shigenaga, Akira; Otaka, Akira

2018-04-20

The resin-bound N-sulfanylethylanilide (SEAlide) peptide was found to function as a crypto-thioester peptide. Exposure of the peptide resin to an aqueous solution under neutral conditions in the presence of thiols affords thioesters without accompanying racemization of C-terminal amino acids. Furthermore, the resin-bound SEAlide peptides react with N-terminal cysteinyl peptides in the absence of phosphate salts to afford ligated products, whereas soluble SEAlide peptides do not. This unexpected difference in reactivity of the SEAlide peptides allows for a one-pot/three-fragment ligation using resin-bound and unbound peptides.

Upper bounds on the error probabilities and asymptotic error exponents in quantum multiple state discrimination

DOE Office of Scientific and Technical Information (OSTI.GOV)

Audenaert, Koenraad M. R., E-mail: koenraad.audenaert@rhul.ac.uk; Department of Physics and Astronomy, University of Ghent, S9, Krijgslaan 281, B-9000 Ghent; Mosonyi, Milán, E-mail: milan.mosonyi@gmail.com

2014-10-01

We consider the multiple hypothesis testing problem for symmetric quantum state discrimination between r given states σ₁, …, σ{sub r}. By splitting up the overall test into multiple binary tests in various ways we obtain a number of upper bounds on the optimal error probability in terms of the binary error probabilities. These upper bounds allow us to deduce various bounds on the asymptotic error rate, for which it has been hypothesized that it is given by the multi-hypothesis quantum Chernoff bound (or Chernoff divergence) C(σ₁, …, σ{sub r}), as recently introduced by Nussbaum and Szkoła in analogy with Salikhov'smore » classical multi-hypothesis Chernoff bound. This quantity is defined as the minimum of the pairwise binary Chernoff divergences min{sub j« less

How actin binds and assembles onto plasma membranes from Dictyostelium discoideum

PubMed Central

1988-01-01

We have shown previously (Schwartz, M. A., and E. J. Luna. 1986. J. Cell Biol. 102: 2067-2075) that actin binds with positive cooperativity to plasma membranes from Dictyostelium discoideum. Actin is polymerized at the membrane surface even at concentrations well below the critical concentration for polymerization in solution. Low salt buffer that blocks actin polymerization in solution also prevents actin binding to membranes. To further explore the relationship between actin polymerization and binding to membranes, we prepared four chemically modified actins that appear to be incapable of polymerizing in solution. Three of these derivatives also lost their ability to bind to membranes. The fourth derivative (EF actin), in which histidine-40 is labeled with ethoxyformic anhydride, binds to membranes with reduced affinity. Binding curves exhibit positive cooperativity, and cross- linking experiments show that membrane-bound actin is multimeric. Thus, binding and polymerization are tightly coupled, and the ability of these membranes to polymerize actin is dramatically demonstrated. EF actin coassembles weakly with untreated actin in solution, but coassembles well on membranes. Binding by untreated actin and EF actin are mutually competitive, indicating that they bind to the same membrane sites. Hill plots indicate that an actin trimer is the minimum assembly state required for tight binding to membranes. The best explanation for our data is a model in which actin oligomers assemble by binding to clustered membrane sites with successive monomers on one side of the actin filament bound to the membrane. Individual binding affinities are expected to be low, but the overall actin-membrane avidity is high, due to multivalency. Our results imply that extracellular factors that cluster membrane proteins may create sites for the formation of actin nuclei and thus trigger actin polymerization in the cell. PMID:3392099

The nucleotide-free state of heterotrimeric G proteins α-subunit adopts a highly stable conformation.

PubMed

Andhirka, Sai Krishna; Vignesh, Ravichandran; Aradhyam, Gopala Krishna

2017-08-01

Deciphering the mechanism of activation of heterotrimeric G proteins by their cognate receptors continues to be an intriguing area of research. The recently solved crystal structure of the ternary complex captured the receptor-bound α-subunit in an open conformation, without bound nucleotide has improved our understanding of the activation process. Despite these advancements, the mechanism by which the receptor causes GDP release from the α-subunit remains elusive. To elucidate the mechanism of activation, we studied guanine nucleotide-induced structural stability of the α-subunit (in response to thermal/chaotrope-mediated stress). Inherent stabilities of the inactive (GDP-bound) and active (GTP-bound) forms contribute antagonistically to the difference in conformational stability whereas the GDP-bound protein is able to switch to a stable intermediate state, GTP-bound protein loses this ability. Partial perturbation of the protein fold reveals the underlying influence of the bound nucleotide providing an insight into the mechanism of activation. An extra stable, pretransition intermediate, 'empty pocket' state (conformationally active-state like) in the unfolding pathway of GDP-bound protein mimics a gating system - the activation process having to overcome this stable intermediate state. We demonstrate that a relatively more complex conformational fold of the GDP-bound protein is at the core of the gating system. We report capturing this threshold, 'metastable empty pocket' conformation (the gate) of α-subunit of G protein and hypothesize that the receptor activates the G protein by enabling it to achieve this structure through mild structural perturbation. © 2017 Federation of European Biochemical Societies.

Numerical uncertainty in computational engineering and physics

DOE Office of Scientific and Technical Information (OSTI.GOV)

Hemez, Francois M

2009-01-01

Obtaining a solution that approximates ordinary or partial differential equations on a computational mesh or grid does not necessarily mean that the solution is accurate or even 'correct'. Unfortunately assessing the quality of discrete solutions by questioning the role played by spatial and temporal discretizations generally comes as a distant third to test-analysis comparison and model calibration. This publication is contributed to raise awareness of the fact that discrete solutions introduce numerical uncertainty. This uncertainty may, in some cases, overwhelm in complexity and magnitude other sources of uncertainty that include experimental variability, parametric uncertainty and modeling assumptions. The concepts ofmore » consistency, convergence and truncation error are overviewed to explain the articulation between the exact solution of continuous equations, the solution of modified equations and discrete solutions computed by a code. The current state-of-the-practice of code and solution verification activities is discussed. An example in the discipline of hydro-dynamics illustrates the significant effect that meshing can have on the quality of code predictions. A simple method is proposed to derive bounds of solution uncertainty in cases where the exact solution of the continuous equations, or its modified equations, is unknown. It is argued that numerical uncertainty originating from mesh discretization should always be quantified and accounted for in the overall uncertainty 'budget' that supports decision-making for applications in computational physics and engineering.« less

Quantum defect theory for the orbital Feshbach resonance

NASA Astrophysics Data System (ADS)

Cheng, Yanting; Zhang, Ren; Zhang, Peng

2017-01-01

In the ultracold gases of alkali-earth-metal-like atoms, a new type of Feshbach resonance, i.e., the orbital Feshbach resonance (OFR), has been proposed and experimentally observed in ultracold 173Yb atoms [R. Zhang et al., Phys. Rev. Lett. 115, 135301 (2015), 10.1103/PhysRevLett.115.135301]. When the OFR of the 173Yb atoms occurs, the energy gap between the open and closed channels is smaller by two orders of magnitude than the van der Waals energy. As a result, quantitative accurate results for the low-energy two-body problems can be obtained via multichannel quantum defect theory (MQDT), which is based on the exact solution of the Schrödinger equation with the van der Waals potential. In this paper we use MQDT to calculate the two-atom scattering length, effective range, and binding energy of two-body bound states for the systems with OFR. With these results we further study the clock-transition spectrum for the two-body bound states, which can be used to experimentally measure the binding energy. Our results are helpful for the quantitative theoretical and experimental research for the ultracold gases of alkali-earth-metal-like atoms with OFR.

Harmonic oscillator representation in the theory of scattering and nuclear reactions

NASA Technical Reports Server (NTRS)

Smirnov, Yuri F.; Shirokov, A. M.; Lurie, Yuri, A.; Zaitsev, S. A.

1995-01-01

The following questions, concerning the application of the harmonic oscillator representation (HOR) in the theory of scattering and reactions, are discussed: the formulation of the scattering theory in HOR; exact solutions of the free motion Schroedinger equation in HOR; separable expansion of the short range potentials and the calculation of the phase shifts; 'isolated states' as generalization of the Wigner-von Neumann bound states embedded in continuum; a nuclear coupled channel problem in HOR; and the description of true three body scattering in HOR. As an illustration the soft dipole mode in the (11)Li nucleus is considered in a frame of the (9)Li+n+n cluster model taking into account of three body continuum effects.

Completing the physical representation of quantum algorithms provides a retrocausal explanation of the speedup

NASA Astrophysics Data System (ADS)

Castagnoli, Giuseppe

2017-05-01

The usual representation of quantum algorithms, limited to the process of solving the problem, is physically incomplete as it lacks the initial measurement. We extend it to the process of setting the problem. An initial measurement selects a problem setting at random, and a unitary transformation sends it into the desired setting. The extended representation must be with respect to Bob, the problem setter, and any external observer. It cannot be with respect to Alice, the problem solver. It would tell her the problem setting and thus the solution of the problem implicit in it. In the representation to Alice, the projection of the quantum state due to the initial measurement should be postponed until the end of the quantum algorithm. In either representation, there is a unitary transformation between the initial and final measurement outcomes. As a consequence, the final measurement of any ℛ-th part of the solution could select back in time a corresponding part of the random outcome of the initial measurement; the associated projection of the quantum state should be advanced by the inverse of that unitary transformation. This, in the representation to Alice, would tell her, before she begins her problem solving action, that part of the solution. The quantum algorithm should be seen as a sum over classical histories in each of which Alice knows in advance one of the possible ℛ-th parts of the solution and performs the oracle queries still needed to find it - this for the value of ℛ that explains the algorithm's speedup. We have a relation between retrocausality ℛ and the number of oracle queries needed to solve an oracle problem quantumly. All the oracle problems examined can be solved with any value of ℛ up to an upper bound attained by the optimal quantum algorithm. This bound is always in the vicinity of 1/2 . Moreover, ℛ =1/2 always provides the order of magnitude of the number of queries needed to solve the problem in an optimal quantum way. If this were true for any oracle problem, as plausible, it would solve the quantum query complexity problem.

Evidence for a bound on the lifetime of de Sitter space

NASA Astrophysics Data System (ADS)

Freivogel, Ben; Lippert, Matthew

2008-12-01

Recent work has suggested a surprising new upper bound on the lifetime of de Sitter vacua in string theory. The bound is parametrically longer than the Hubble time but parametrically shorter than the recurrence time. We investigate whether the bound is satisfied in a particular class of de Sitter solutions, the KKLT vacua. Despite the freedom to make the supersymmetry breaking scale exponentially small, which naively would lead to extremely stable vacua, we find that the lifetime is always less than about exp(1022) Hubble times, in agreement with the proposed bound. This result, however, is contingent on several estimates and assumptions; in particular, we rely on a conjectural upper bound on the Euler number of the Calabi-Yau fourfolds used in KKLT compactifications.

Magnetoconductance signatures of chiral domain-wall bound states in magnetic topological insulators

NASA Astrophysics Data System (ADS)

Tiwari, Kunal L.; Coish, W. A.; Pereg-Barnea, T.

2017-12-01

Recent magnetoconductance measurements performed on magnetic topological insulator candidates have revealed butterfly-shaped hysteresis. This hysteresis has been attributed to the formation of gapless chiral domain-wall bound states during a magnetic-field sweep. We treat this phenomenon theoretically, providing a link between microscopic magnetization dynamics and butterfly hysteresis in magnetoconductance. Further, we illustrate how a spatially resolved conductance measurement can probe the most striking feature of the domain-wall bound states: their chirality. This work establishes a regime where a definitive link between butterfly hysteresis in longitudinal magneto-conductance and domain-wall bound states can be made. This analysis provides an important tool for the identification of magnetic topological insulators.

Cosmological implications of Dark Matter bound states

DOE Office of Scientific and Technical Information (OSTI.GOV)

Mitridate, Andrea; Redi, Michele; Smirnov, Juri

2017-05-01

We present generic formulæ for computing how Sommerfeld corrections together with bound-state formation affects the thermal abundance of Dark Matter with non-abelian gauge interactions. We consider DM as a fermion 3plet (wino) or 5plet under SU(2) {sub L} . In the latter case bound states raise to 11.5 TeV the DM mass required to reproduce the cosmological DM abundance and give indirect detection signals such as (for this mass) a dominant γ-line around 70 GeV. Furthermore, we consider DM co-annihilating with a colored particle, such as a squark or a gluino, finding that bound state effects are especially relevant inmore » the latter case.« less

Search-based optimization

NASA Technical Reports Server (NTRS)

Wheeler, Ward C.

2003-01-01

The problem of determining the minimum cost hypothetical ancestral sequences for a given cladogram is known to be NP-complete (Wang and Jiang, 1994). Traditionally, point estimations of hypothetical ancestral sequences have been used to gain heuristic, upper bounds on cladogram cost. These include procedures with such diverse approaches as non-additive optimization of multiple sequence alignment, direct optimization (Wheeler, 1996), and fixed-state character optimization (Wheeler, 1999). A method is proposed here which, by extending fixed-state character optimization, replaces the estimation process with a search. This form of optimization examines a diversity of potential state solutions for cost-efficient hypothetical ancestral sequences and can result in greatly more parsimonious cladograms. Additionally, such an approach can be applied to other NP-complete phylogenetic optimization problems such as genomic break-point analysis. c2003 The Willi Hennig Society. Published by Elsevier Science (USA). All rights reserved.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Blancon, Jean -Christophe Robert; Tsai, Hsinhan; Nie, Wanyi

Understanding and controlling charge and energy flow in state-of-the-art semiconductor quantum wells has enabled high-efficiency optoelectronic devices. Two-dimensional (2D) Ruddlesden-Popper perovskites are solution-processed quantum wells wherein the band gap can be tuned by varying the perovskite-layer thickness, which modulates the effective electron-hole confinement. We report that, counterintuitive to classical quantum-confined systems where photogenerated electrons and holes are strongly bound by Coulomb interactions or excitons, the photophysics of thin films made of Ruddlesden-Popper perovskites with a thickness exceeding two perovskite-crystal units (>1.3 nanometers) is dominated by lower-energy states associated with the local intrinsic electronic structure of the edges of the perovskitemore » layers. Furthermore, these states provide a direct pathway for dissociating excitons into longer-lived free carriers that substantially improve the performance of optoelectronic devices.« less

Self-consistent quantum kinetic theory of diatomic molecule formation

DOE Office of Scientific and Technical Information (OSTI.GOV)

Forrey, Robert C.

2015-07-14

A quantum kinetic theory of molecule formation is presented which includes three-body recombination and radiative association for a thermodynamically closed system which may or may not exchange energy with its surrounding at a constant temperature. The theory uses a Sturmian representation of a two-body continuum to achieve a steady-state solution of a governing master equation which is self-consistent in the sense that detailed balance between all bound and unbound states is rigorously enforced. The role of quasibound states in catalyzing the molecule formation is analyzed in complete detail. The theory is used to make three predictions which differ from conventionalmore » kinetic models. These predictions suggest significant modifications may be needed to phenomenological rate constants which are currently in wide use. Implications for models of low and high density systems are discussed.« less

Extremal equilibria for reaction-diffusion equations in bounded domains and applications

NASA Astrophysics Data System (ADS)

Rodríguez-Bernal, Aníbal; Vidal-López, Alejandro

We show the existence of two special equilibria, the extremal ones, for a wide class of reaction-diffusion equations in bounded domains with several boundary conditions, including non-linear ones. They give bounds for the asymptotic dynamics and so for the attractor. Some results on the existence and/or uniqueness of positive solutions are also obtained. As a consequence, several well-known results on the existence and/or uniqueness of solutions for elliptic equations are revisited in a unified way obtaining, in addition, information on the dynamics of the associated parabolic problem. Finally, we ilustrate the use of the general results by applying them to the case of logistic equations. In fact, we obtain a detailed picture of the positive dynamics depending on the parameters appearing in the equation.

Relative affinities of divalent polyamines and of their N-methylated analogues for helical DNA determined by sup 23 Na NMR

DOE Office of Scientific and Technical Information (OSTI.GOV)

Padmanabhan, S.; Brushaber, V.M.; Anderson, C.F.

1991-07-30

Interactions of divalent polyamines with double-helical DNA in aqueous solution are investigated by monitoring the decrease in {sup 23}Na NMR relaxation rates as NaDNA is titrated with H{sub 3}N{sup +}-(CH{sub 2}){sub m}-{sup +}NH{sup 3}, where m = 3, 4, 5, or 6. Analogous measurements are made for the same homologous series of methylated polyamines (methonium ions). The dependence of the {sup 23}Na relaxation rates on the amount of added divalent cation (M{sup 2+}) is analyzes quantitatively in terms of a two-state model. The sodium ions are assumed to be in rapid exchange between a bound state, where they are closemore » enough to DNA so that it affects their relaxation rate, and a free state in bulk solution, where their relaxation rate is the same as in solutions containing no DNA. (1) For polyamines and methonium ions of the same m, D{sub H} exceeds D{sub Me} by factors that are significantly larger for m = 3 and 4 than for m = 5 and 6. (2) D{sub H} for m = 3 and 4 is larger than D{sub H} for m = 5 and 6. (3) D{sub Me} for m = 3 and 4 is smaller than D{sub Me} for m = 5 and 6.« less

T -matrix approach to quark-gluon plasma

NASA Astrophysics Data System (ADS)

Liu, Shuai Y. F.; Rapp, Ralf

2018-03-01

A self-consistent thermodynamic T -matrix approach is deployed to study the microscopic properties of the quark-gluon plasma (QGP), encompassing both light- and heavy-parton degrees of freedom in a unified framework. The starting point is a relativistic effective Hamiltonian with a universal color force. The input in-medium potential is quantitatively constrained by computing the heavy-quark (HQ) free energy from the static T -matrix and fitting it to pertinent lattice-QCD (lQCD) data. The corresponding T -matrix is then applied to compute the equation of state (EoS) of the QGP in a two-particle irreducible formalism, including the full off-shell properties of the selfconsistent single-parton spectral functions and their two-body interaction. In particular, the skeleton diagram functional is fully resummed to account for emerging bound and scattering states as the critical temperature is approached from above. We find that the solution satisfying three sets of lQCD data (EoS, HQ free energy, and quarkonium correlator ratios) is not unique. As limiting cases we discuss a weakly coupled solution, which features color potentials close to the free energy, relatively sharp quasiparticle spectral functions and weak hadronic resonances near Tc, and a strongly coupled solution with a strong color potential (much larger than the free energy), resulting in broad nonquasiparticle parton spectral functions and strong hadronic resonance states which dominate the EoS when approaching Tc.

Probing structurally altered and aggregated states of therapeutically relevant proteins using GroEL coupled to bio-layer interferometry.

PubMed

Naik, Subhashchandra; Kumru, Ozan S; Cullom, Melissa; Telikepalli, Srivalli N; Lindboe, Elizabeth; Roop, Taylor L; Joshi, Sangeeta B; Amin, Divya; Gao, Phillip; Middaugh, C Russell; Volkin, David B; Fisher, Mark T

2014-10-01

The ability of a GroEL-based bio-layer interferometry (BLI) assay to detect structurally altered and/or aggregated species of pharmaceutically relevant proteins is demonstrated. Assay development included optimizing biotinylated-GroEL immobilization to streptavidin biosensors, combined with biophysical and activity measurements showing native and biotinylated GroEL are both stable and active. First, acidic fibroblast growth factor (FGF-1) was incubated under conditions known to promote (40°C) and inhibit (heparin addition) molten globule formation. Heat exposed (40°C) FGF-1 exhibited binding to GroEL-biosensors, which was significantly diminished in the presence of heparin. Second, a polyclonal human IgG solution containing 6-8% non-native dimer showed an increase in higher molecular weight aggregates upon heating by size exclusion chromatography (SEC). The poly IgG solution displayed binding to GroEL-biosensors initially with progressively increased binding upon heating. Enriched preparations of the IgG dimers or monomers showed significant binding to GroEL-biosensors. Finally, a thermally treated IgG1 monoclonal antibody (mAb) solution also demonstrated increased GroEL-biosensor binding, but with different kinetics. The bound complexes could be partially to fully dissociated after ATP addition (i.e., specific GroEL binding) depending on the protein, environmental stress, and the assay's experimental conditions. Transmission electron microscopy (TEM) images of GroEL-mAb complexes, released from the biosensor, also confirmed interaction of bound complexes at the GroEL binding site with heat-stressed mAb. Results indicate that the GroEL-biosensor-BLI method can detect conformationally altered and/or early aggregation states of proteins, and may potentially be useful as a rapid, stability-indicating biosensor assay for monitoring the structural integrity and physical stability of therapeutic protein candidates. © 2014 The Protein Society.

Probing structurally altered and aggregated states of therapeutically relevant proteins using GroEL coupled to bio-layer interferometry

PubMed Central

Naik, Subhashchandra; Kumru, Ozan S; Cullom, Melissa; Telikepalli, Srivalli N; Lindboe, Elizabeth; Roop, Taylor L; Joshi, Sangeeta B; Amin, Divya; Gao, Phillip; Middaugh, C Russell; Volkin, David B; Fisher, Mark T

2014-01-01

The ability of a GroEL-based bio-layer interferometry (BLI) assay to detect structurally altered and/or aggregated species of pharmaceutically relevant proteins is demonstrated. Assay development included optimizing biotinylated-GroEL immobilization to streptavidin biosensors, combined with biophysical and activity measurements showing native and biotinylated GroEL are both stable and active. First, acidic fibroblast growth factor (FGF-1) was incubated under conditions known to promote (40°C) and inhibit (heparin addition) molten globule formation. Heat exposed (40°C) FGF-1 exhibited binding to GroEL-biosensors, which was significantly diminished in the presence of heparin. Second, a polyclonal human IgG solution containing 6–8% non-native dimer showed an increase in higher molecular weight aggregates upon heating by size exclusion chromatography (SEC). The poly IgG solution displayed binding to GroEL-biosensors initially with progressively increased binding upon heating. Enriched preparations of the IgG dimers or monomers showed significant binding to GroEL-biosensors. Finally, a thermally treated IgG1 monoclonal antibody (mAb) solution also demonstrated increased GroEL-biosensor binding, but with different kinetics. The bound complexes could be partially to fully dissociated after ATP addition (i.e., specific GroEL binding) depending on the protein, environmental stress, and the assay’s experimental conditions. Transmission electron microscopy (TEM) images of GroEL-mAb complexes, released from the biosensor, also confirmed interaction of bound complexes at the GroEL binding site with heat-stressed mAb. Results indicate that the GroEL-biosensor-BLI method can detect conformationally altered and/or early aggregation states of proteins, and may potentially be useful as a rapid, stability-indicating biosensor assay for monitoring the structural integrity and physical stability of therapeutic protein candidates. PMID:25043635

Probing Gαi1 Protein Activation at Single Amino Acid Resolution

PubMed Central

Sun, Dawei; Maeda, Shoji; Matkovic, Milos; Mendieta, Sandro; Mayer, Daniel; Dawson, Roger; Schertler, Gebhard F.X.; Madan Babu, M.; Veprintsev, Dmitry B.

2016-01-01

We present comprehensive single amino acid resolution maps of the residues stabilising the human Gαi1 subunit in nucleotide- and receptor-bound states. We generated these maps by measuring the effects of alanine mutations on the stability of Gαi1 and of the rhodopsin-Gαi1 complex. We identified stabilization clusters in the GTPase and helical domains responsible for structural integrity and the conformational changes associated with activation. In activation cluster I, helices α1 and α5 pack against strands β1-3 to stabilize the nucleotide-bound states. In the receptor-bound state, these interactions are replaced by interactions between α5 and strands β4-6. Key residues in this cluster are Y320, crucial for the stabilization of the receptor-bound state, and F336, which stabilizes nucleotide-bound states. Destabilization of helix α1, caused by rearrangement of this activation cluster, leads to the weakening of the inter-domain interface and release of GDP. PMID:26258638

Lower bounds of concurrence for N-qubit systems and the detection of k-nonseparability of multipartite quantum systems

NASA Astrophysics Data System (ADS)

Qi, Xianfei; Gao, Ting; Yan, Fengli

2017-01-01

Concurrence, as one of the entanglement measures, is a useful tool to characterize quantum entanglement in various quantum systems. However, the computation of the concurrence involves difficult optimizations and only for the case of two qubits, an exact formula was found. We investigate the concurrence of four-qubit quantum states and derive analytical lower bound of concurrence using the multiqubit monogamy inequality. It is shown that this lower bound is able to improve the existing bounds. This approach can be generalized to arbitrary qubit systems. We present an exact formula of concurrence for some mixed quantum states. For even-qubit states, we derive an improved lower bound of concurrence using a monogamy equality for qubit systems. At the same time, we show that a multipartite state is k-nonseparable if the multipartite concurrence is larger than a constant related to the value of k, the qudit number and the dimension of the subsystems. Our results can be applied to detect the multipartite k-nonseparable states.

Generalized Hofmann quantum process fidelity bounds for quantum filters

NASA Astrophysics Data System (ADS)

Sedlák, Michal; Fiurášek, Jaromír

2016-04-01

We propose and investigate bounds on the quantum process fidelity of quantum filters, i.e., probabilistic quantum operations represented by a single Kraus operator K . These bounds generalize the Hofmann bounds on the quantum process fidelity of unitary operations [H. F. Hofmann, Phys. Rev. Lett. 94, 160504 (2005), 10.1103/PhysRevLett.94.160504] and are based on probing the quantum filter with pure states forming two mutually unbiased bases. Determination of these bounds therefore requires far fewer measurements than full quantum process tomography. We find that it is particularly suitable to construct one of the probe bases from the right eigenstates of K , because in this case the bounds are tight in the sense that if the actual filter coincides with the ideal one, then both the lower and the upper bounds are equal to 1. We theoretically investigate the application of these bounds to a two-qubit optical quantum filter formed by the interference of two photons on a partially polarizing beam splitter. For an experimentally convenient choice of factorized input states and measurements we study the tightness of the bounds. We show that more stringent bounds can be obtained by more sophisticated processing of the data using convex optimization and we compare our methods for different choices of the input probe states.

Symmetry-breaking instability of quadratic soliton bound states

DOE Office of Scientific and Technical Information (OSTI.GOV)

Delque, Michaeel; Departement d'Optique P.M. Duffieux, Institut FEMTO-ST, Universite de Franche-Comte, CNRS UMR 6174, F-25030 Besancon; Fanjoux, Gil

We study both numerically and experimentally two-dimensional soliton bound states in quadratic media and demonstrate their symmetry-breaking instability. The experiment is performed in a potassium titanyl phosphate crystal in a type-II configuration. The bound state is generated by the copropagation of the antisymmetric fundamental beam locked in phase with the symmetrical second harmonic one. Experimental results are in good agreement with numerical simulations of the nonlinear wave equations.

Bounded solutions in a T-shaped waveguide and the spectral properties of the Dirichlet ladder

NASA Astrophysics Data System (ADS)

Nazarov, S. A.

2014-08-01

The Dirichlet problem is considered on the junction of thin quantum waveguides (of thickness h ≪ 1) in the shape of an infinite two-dimensional ladder. Passage to the limit as h → +0 is discussed. It is shown that the asymptotically correct transmission conditions at nodes of the corresponding one-dimensional quantum graph are Dirichlet conditions rather than the conventional Kirchhoff transmission conditions. The result is obtained by analyzing bounded solutions of a problem in the T-shaped waveguide that the boundary layer phenomenon.

Long-distance measurement-device-independent quantum key distribution with coherent-state superpositions.

PubMed

Yin, H-L; Cao, W-F; Fu, Y; Tang, Y-L; Liu, Y; Chen, T-Y; Chen, Z-B

2014-09-15

Measurement-device-independent quantum key distribution (MDI-QKD) with decoy-state method is believed to be securely applied to defeat various hacking attacks in practical quantum key distribution systems. Recently, the coherent-state superpositions (CSS) have emerged as an alternative to single-photon qubits for quantum information processing and metrology. Here, in this Letter, CSS are exploited as the source in MDI-QKD. We present an analytical method that gives two tight formulas to estimate the lower bound of yield and the upper bound of bit error rate. We exploit the standard statistical analysis and Chernoff bound to perform the parameter estimation. Chernoff bound can provide good bounds in the long-distance MDI-QKD. Our results show that with CSS, both the security transmission distance and secure key rate are significantly improved compared with those of the weak coherent states in the finite-data case.

Antiproton--neutron bound state

DOE Office of Scientific and Technical Information (OSTI.GOV)

Ju, I.; Tomozawa, Y.

1972-08-01

The possibility of an antiproton-neutron bound state for explaining a narrow peak which was found recently in the experiment p + n yields 4 pi and 6 pi is discussed. It is pointed out that the state is likely to be a /sup 1/P/ sub 1/ state or a higher angular momentum state. (auth)

Global a priori estimates for the inhomogeneous Landau equation with moderately soft potentials

NASA Astrophysics Data System (ADS)

Cameron, Stephen; Silvestre, Luis; Snelson, Stanley

2018-05-01

We establish a priori upper bounds for solutions to the spatially inhomogeneous Landau equation in the case of moderately soft potentials, with arbitrary initial data, under the assumption that mass, energy and entropy densities stay under control. Our pointwise estimates decay polynomially in the velocity variable. We also show that if the initial data satisfies a Gaussian upper bound, this bound is propagated for all positive times.

A Posteriori Bounds for Linear-Functional Outputs of Crouzeix-Raviart Finite Element Discretizations of the Incompressible Stokes Problem

NASA Technical Reports Server (NTRS)

Patera, Anthony T.; Paraschivoiu, Marius

1998-01-01

We present a finite element technique for the efficient generation of lower and upper bounds to outputs which are linear functionals of the solutions to the incompressible Stokes equations in two space dimensions; the finite element discretization is effected by Crouzeix-Raviart elements, the discontinuous pressure approximation of which is central to our approach. The bounds are based upon the construction of an augmented Lagrangian: the objective is a quadratic "energy" reformulation of the desired output; the constraints are the finite element equilibrium equations (including the incompressibility constraint), and the intersubdomain continuity conditions on velocity. Appeal to the dual max-min problem for appropriately chosen candidate Lagrange multipliers then yields inexpensive bounds for the output associated with a fine-mesh discretization; the Lagrange multipliers are generated by exploiting an associated coarse-mesh approximation. In addition to the requisite coarse-mesh calculations, the bound technique requires solution only of local subdomain Stokes problems on the fine-mesh. The method is illustrated for the Stokes equations, in which the outputs of interest are the flowrate past, and the lift force on, a body immersed in a channel.

A fast and robust computational method for the ionization cross sections of the driven Schrödinger equation using an O (N) multigrid-based scheme

NASA Astrophysics Data System (ADS)

Cools, S.; Vanroose, W.

2016-03-01

This paper improves the convergence and robustness of a multigrid-based solver for the cross sections of the driven Schrödinger equation. Adding a Coupled Channel Correction Step (CCCS) after each multigrid (MG) V-cycle efficiently removes the errors that remain after the V-cycle sweep. The combined iterative solution scheme (MG-CCCS) is shown to feature significantly improved convergence rates over the classical MG method at energies where bound states dominate the solution, resulting in a fast and scalable solution method for the complex-valued Schrödinger break-up problem for any energy regime. The proposed solver displays optimal scaling; a solution is found in a time that is linear in the number of unknowns. The method is validated on a 2D Temkin-Poet model problem, and convergence results both as a solver and preconditioner are provided to support the O (N) scalability of the method. This paper extends the applicability of the complex contour approach for far field map computation (Cools et al. (2014) [10]).

Probabilistic Approach to Enable Extreme-Scale Simulations under Uncertainty and System Faults. Final Technical Report

DOE Office of Scientific and Technical Information (OSTI.GOV)

Knio, Omar

2017-05-05

The current project develops a novel approach that uses a probabilistic description to capture the current state of knowledge about the computational solution. To effectively spread the computational effort over multiple nodes, the global computational domain is split into many subdomains. Computational uncertainty in the solution translates into uncertain boundary conditions for the equation system to be solved on those subdomains, and many independent, concurrent subdomain simulations are used to account for this bound- ary condition uncertainty. By relying on the fact that solutions on neighboring subdomains must agree with each other, a more accurate estimate for the global solutionmore » can be achieved. Statistical approaches in this update process make it possible to account for the effect of system faults in the probabilistic description of the computational solution, and the associated uncertainty is reduced through successive iterations. By combining all of these elements, the probabilistic reformulation allows splitting the computational work over very many independent tasks for good scalability, while being robust to system faults.« less

Solution of the Fokker-Planck equation with a logarithmic potential and mixed eigenvalue spectrum

NASA Astrophysics Data System (ADS)

Guarnieri, F.; Moon, W.; Wettlaufer, J. S.

2017-09-01

Motivated by a problem in climate dynamics, we investigate the solution of a Bessel-like process with a negative constant drift, described by a Fokker-Planck equation with a potential V (x ) =-[b ln(x ) +a x ] , for b >0 and a <0 . The problem belongs to a family of Fokker-Planck equations with logarithmic potentials closely related to the Bessel process that has been extensively studied for its applications in physics, biology, and finance. The Bessel-like process we consider can be solved by seeking solutions through an expansion into a complete set of eigenfunctions. The associated imaginary-time Schrödinger equation exhibits a mix of discrete and continuous eigenvalue spectra, corresponding to the quantum Coulomb potential describing the bound states of the hydrogen atom. We present a technique to evaluate the normalization factor of the continuous spectrum of eigenfunctions that relies solely upon their asymptotic behavior. We demonstrate the technique by solving the Brownian motion problem and the Bessel process both with a constant negative drift. We conclude with a comparison to other analytical methods and with numerical solutions.

Immortal solution of the Ricci flow

NASA Astrophysics Data System (ADS)

Ruan, Qihua; Chen, Zhihua

2005-12-01

For any complete noncompact K$\\ddot{a}$hler manifold with nonnegative and bounded holomorphic bisectional curvature,we provide the necessary and sufficient condition for non-ancient solution to the Ricci flow in this paper.

Distribution-dependent robust linear optimization with applications to inventory control

PubMed Central

Kang, Seong-Cheol; Brisimi, Theodora S.

2014-01-01

This paper tackles linear programming problems with data uncertainty and applies it to an important inventory control problem. Each element of the constraint matrix is subject to uncertainty and is modeled as a random variable with a bounded support. The classical robust optimization approach to this problem yields a solution with guaranteed feasibility. As this approach tends to be too conservative when applications can tolerate a small chance of infeasibility, one would be interested in obtaining a less conservative solution with a certain probabilistic guarantee of feasibility. A robust formulation in the literature produces such a solution, but it does not use any distributional information on the uncertain data. In this work, we show that the use of distributional information leads to an equally robust solution (i.e., under the same probabilistic guarantee of feasibility) but with a better objective value. In particular, by exploiting distributional information, we establish stronger upper bounds on the constraint violation probability of a solution. These bounds enable us to “inject” less conservatism into the formulation, which in turn yields a more cost-effective solution (by 50% or more in some numerical instances). To illustrate the effectiveness of our methodology, we consider a discrete-time stochastic inventory control problem with certain quality of service constraints. Numerical tests demonstrate that the use of distributional information in the robust optimization of the inventory control problem results in 36%–54% cost savings, compared to the case where such information is not used. PMID:26347579

Secure key from bound entanglement.

PubMed

Horodecki, Karol; Horodecki, Michał; Horodecki, Paweł; Oppenheim, Jonathan

2005-04-29

We characterize the set of shared quantum states which contain a cryptographically private key. This allows us to recast the theory of privacy as a paradigm closely related to that used in entanglement manipulation. It is shown that one can distill an arbitrarily secure key from bound entangled states. There are also states that have less distillable private keys than the entanglement cost of the state. In general, the amount of distillable key is bounded from above by the relative entropy of entanglement. Relationships between distillability and distinguishability are found for a class of states which have Bell states correlated to separable hiding states. We also describe a technique for finding states exhibiting irreversibility in entanglement distillation.

Ab initio investigation on the valence and dipole-bound states of CNa - and SiNa -

NASA Astrophysics Data System (ADS)

Kalcher, Josef; Sax, Alexander F.

2000-08-01

CNa - and SiNa - have been studied by the CAS-ACPF method. The 3Σ- ground states have binding energies of 5420 and 7517 cm -1, respectively. The 5Σ- excited states are 494 and 1551 cm -1 above the respective ground states. The 1Δ , 3Π , and 1Π valence-excited states for SiNa - should be at least metastable. CNa - and SiNa - possess dipole-bound 5Σ- and 3Σ- states. Binding energies of these states in CNa - are 217 and 236 cm -1, respectively. SiNa - has two stable 5Σ- dipole-bound states, whose binding energies are 246 and 118 cm -1, respectively.

Effects of forcefield and sampling method in all-atom simulations of inherently disordered proteins: Application to conformational preferences of human amylin

PubMed Central

Peng, Enxi; Todorova, Nevena

2017-01-01

Although several computational modelling studies have investigated the conformational behaviour of inherently disordered protein (IDP) amylin, discrepancies in identifying its preferred solution conformations still exist between various forcefields and sampling methods used. Human islet amyloid polypeptide has long been a subject of research, both experimentally and theoretically, as the aggregation of this protein is believed to be the lead cause of type-II diabetes. In this work, we present a systematic forcefield assessment using one of the most advanced non-biased sampling techniques, Replica Exchange with Solute Tempering (REST2), by comparing the secondary structure preferences of monomeric amylin in solution. This study also aims to determine the ability of common forcefields to sample a transition of the protein from a helical membrane bound conformation into the disordered solution state of amylin. Our results demonstrated that the CHARMM22* forcefield showed the best ability to sample multiple conformational states inherent for amylin. It is revealed that REST2 yielded results qualitatively consistent with experiments and in quantitative agreement with other sampling methods, however far more computationally efficiently and without any bias. Therefore, combining an unbiased sampling technique such as REST2 with a vigorous forcefield testing could be suggested as an important step in developing an efficient and robust strategy for simulating IDPs. PMID:29023509

Dynamic reduction with applications to mathematical biology and other areas.

PubMed

Sacker, Robert J; Von Bremen, Hubertus F

2007-10-01

In a difference or differential equation one is usually interested in finding solutions having certain properties, either intrinsic properties (e.g. bounded, periodic, almost periodic) or extrinsic properties (e.g. stable, asymptotically stable, globally asymptotically stable). In certain instances it may happen that the dependence of these equations on the state variable is such that one may (1) alter that dependency by replacing part of the state variable by a function from a class having some of the above properties and (2) solve the 'reduced' equation for a solution having the remaining properties and lying in the same class. This then sets up a mapping Τ of the class into itself, thus reducing the original problem to one of finding a fixed point of the mapping. The procedure is applied to obtain a globally asymptotically stable periodic solution for a system of difference equations modeling the interaction of wild and genetically altered mosquitoes in an environment yielding periodic parameters. It is also shown that certain coupled periodic systems of difference equations may be completely decoupled so that the mapping Τ is established by solving a set of scalar equations. Periodic difference equations of extended Ricker type and also rational difference equations with a finite number of delays are also considered by reducing them to equations without delays but with a larger period. Conditions are given guaranteeing the existence and global asymptotic stability of periodic solutions.

Effects of forcefield and sampling method in all-atom simulations of inherently disordered proteins: Application to conformational preferences of human amylin.

PubMed

Peng, Enxi; Todorova, Nevena; Yarovsky, Irene

2017-01-01

Although several computational modelling studies have investigated the conformational behaviour of inherently disordered protein (IDP) amylin, discrepancies in identifying its preferred solution conformations still exist between various forcefields and sampling methods used. Human islet amyloid polypeptide has long been a subject of research, both experimentally and theoretically, as the aggregation of this protein is believed to be the lead cause of type-II diabetes. In this work, we present a systematic forcefield assessment using one of the most advanced non-biased sampling techniques, Replica Exchange with Solute Tempering (REST2), by comparing the secondary structure preferences of monomeric amylin in solution. This study also aims to determine the ability of common forcefields to sample a transition of the protein from a helical membrane bound conformation into the disordered solution state of amylin. Our results demonstrated that the CHARMM22* forcefield showed the best ability to sample multiple conformational states inherent for amylin. It is revealed that REST2 yielded results qualitatively consistent with experiments and in quantitative agreement with other sampling methods, however far more computationally efficiently and without any bias. Therefore, combining an unbiased sampling technique such as REST2 with a vigorous forcefield testing could be suggested as an important step in developing an efficient and robust strategy for simulating IDPs.

Lactose binding to galectin-1 modulates structural dynamics, increases conformational entropy, and occurs with apparent negative cooperativity.

PubMed

Nesmelova, Irina V; Ermakova, Elena; Daragan, Vladimir A; Pang, Mabel; Menéndez, Margarita; Lagartera, Laura; Solís, Dolores; Baum, Linda G; Mayo, Kevin H

2010-04-16

Galectins are a family of lectins with a conserved carbohydrate recognition domain that interacts with beta-galactosides. By binding cell surface glycoconjugates, galectin-1 (gal-1) is involved in cell adhesion and migration processes and is an important regulator of tumor angiogenesis. Here, we used heteronuclear NMR spectroscopy and molecular modeling to investigate lactose binding to gal-1 and to derive solution NMR structures of gal-1 in the lactose-bound and unbound states. Structure analysis shows that the beta-strands and loops around the lactose binding site, which are more open and dynamic in the unbound state, fold in around the bound lactose molecule, dampening internal motions at that site and increasing motions elsewhere throughout the protein to contribute entropically to the binding free energy. CD data support the view of an overall more open structure in the lactose-bound state. Analysis of heteronuclear single quantum coherence titration binding data indicates that lactose binds the two carbohydrate recognition domains of the gal-1 dimer with negative cooperativity, in that the first lactose molecule binds more strongly (K(1)=21+/-6 x 10(3) M(-1)) than the second (K(2)=4+/-2 x 10(3) M(-1)). Isothermal calorimetry data fit using a sequential binding model present a similar picture, yielding K(1)=20+/-10 x 10(3) M(-1) and K(2)=1.67+/-0.07 x 10(3) M(-1). Molecular dynamics simulations provide insight into structural dynamics of the half-loaded lactose state and, together with NMR data, suggest that lactose binding at one site transmits a signal through the beta-sandwich and loops to the second binding site. Overall, our results provide new insight into gal-1 structure-function relationships and to protein-carbohydrate interactions in general. Copyright (c) 2010. Published by Elsevier Ltd.

Existence and numerical simulation of periodic traveling wave solutions to the Casimir equation for the Ito system

NASA Astrophysics Data System (ADS)

Abbasbandy, S.; Van Gorder, R. A.; Hajiketabi, M.; Mesrizadeh, M.

2015-10-01

We consider traveling wave solutions to the Casimir equation for the Ito system (a two-field extension of the KdV equation). These traveling waves are governed by a nonlinear initial value problem with an interesting nonlinearity (which actually amplifies in magnitude as the size of the solution becomes small). The nonlinear problem is parameterized by two initial constant values, and we demonstrate that the existence of solutions is strongly tied to these parameter values. For our interests, we are concerned with positive, bounded, periodic wave solutions. We are able to classify parameter regimes which admit such solutions in full generality, thereby obtaining a nice existence result. Using the existence result, we are then able to numerically simulate the positive, bounded, periodic solutions. We elect to employ a group preserving scheme in order to numerically study these solutions, and an outline of this approach is provided. The numerical simulations serve to illustrate the properties of these solutions predicted analytically through the existence result. Physically, these results demonstrate the existence of a type of space-periodic structure in the Casimir equation for the Ito model, which propagates as a traveling wave.

Why there is something rather than nothing: cosmological constant from summing over everything in lorentzian quantum gravity.

PubMed

Barvinsky, A O

2007-08-17

The density matrix of the Universe for the microcanonical ensemble in quantum cosmology describes an equipartition in the physical phase space of the theory (sum over everything), but in terms of the observable spacetime geometry this ensemble is peaked about the set of recently obtained cosmological instantons limited to a bounded range of the cosmological constant. This suggests the mechanism of constraining the landscape of string vacua and a possible solution to the dark energy problem in the form of the quasiequilibrium decay of the microcanonical state of the Universe.

Probing the coordination environment of Ti(3+) ions coordinated to nitrogen-containing Lewis bases.

PubMed

Morra, E; Maurelli, S; Chiesa, M; Van Doorslaer, S

2015-08-28

Multi-frequency continuous-wave and pulsed EPR techniques are employed to investigate the coordination of nitrogen-containing ligands to Ti(3+)-chloro complexes. Frozen solutions of TiCl3 and TiCl3(Py)3 dissolved in nitrogen-containing solvents have been investigated together with the TiCl3(Py)3 solid-state complex. For these different systems, the hyperfine and nuclear quadrupole data of Ti(3+)-bound (14)N nuclei are reported and discussed in the light of DFT computations, allowing for a detailed description of the microscopic structure of these systems.

Efficiency of autonomous soft nanomachines at maximum power.

PubMed

Seifert, Udo

2011-01-14

We consider nanosized artificial or biological machines working in steady state enforced by imposing nonequilibrium concentrations of solutes or by applying external forces, torques, or electric fields. For unicyclic and strongly coupled multicyclic machines, efficiency at maximum power is not bounded by the linear response value 1/2. For strong driving, it can even approach the thermodynamic limit 1. Quite generally, such machines fall into three different classes characterized, respectively, as "strong and efficient," "strong and inefficient," and "balanced." For weakly coupled multicyclic machines, efficiency at maximum power has lost any universality even in the linear response regime.

Effect of antibodies on pathogen dynamics with delays and two routes of infection

NASA Astrophysics Data System (ADS)

Elaiw, A. M.; Almatrafi, A. A.; Hobiny, A. D.

2018-06-01

We study the global stability of pathogen dynamics models with saturated pathogen-susceptible and infected-susceptible incidence. The models incorporate antibody immune response and three types of discrete or distributed time delays. We first show that the solutions of the model are nonnegative and ultimately bounded. We determine two threshold parameters, the basic reproduction number and antibody response activation number. We establish the existence and stability of the steady states. We study the global stability analysis of models using Lyapunov method. The numerical simulations have shown that antibodies can reduce the pathogen progression.

Proton NMR studies of functionalized nanoparticles in aqueous environments

NASA Astrophysics Data System (ADS)

Tataurova, Yulia Nikolaevna

Nanoscience is an emerging field that can provide potential routes towards addressing critical issues such as clean and sustainable energy, environmental remediation and human health. Specifically, porous nanomaterials, such as zeolites and mesoporous silica, are found in a wide range of applications including catalysis, drug delivery, imaging, environmental protection, and sensing. The characterization of the physical and chemical properties of nanocrystalline materials is essential to the realization of these innovative applications. The great advantage of porous nanocrystals is their increased external surface area that can control their biological, chemical and catalytic activities. Specific functional groups synthesized on the surface of nanoparticles are able to absorb heavy metals from the solution or target disease cells, such as cancer cells. In these studies, three main issues related to functionalized nanomaterials will be addressed through the application of nuclear magnetic resonance (NMR) techniques including: 1) surface composition and structure of functionalized nanocrystalline particles; 2) chemical properties of the guest molecules on the surface of nanomaterials, and 3) adsorption and reactivity of surface bound functional groups. Nuclear magnetic resonance (NMR) is one of the major spectroscopic techniques available for the characterization of molecular structure and conformational dynamics with atomic level detail. This thesis deals with the application of 1H solution state NMR to porous nanomaterial in an aqueous environment. Understanding the aqueous phase behavior of functionalized nanomaterials is a key factor in the design and development of safe nanomaterials because their interactions with living systems are always mediated through the aqueous phase. This is often due to a lack of fundamental knowledge in interfacial chemical and physical phenomena that occur on the surface of nanoparticles. The use of solution NMR spectroscopy results in high-resolution NMR spectra. This technique is selective for protons on the surface organic functional groups due to their motional averaging in solution. In this study, 1H solution NMR spectroscopy was used to investigate the interface of the organic functional groups in D2O. The pKa for these functional groups covalently bound to the surface of nanoparticles was determined using an NMR-pH titration method based on the variation in the proton chemical shift for the alkyl group protons closest to the amine group with pH. The adsorption of toxic contaminants (chromate and arsenate anions) on the surface of functionalized silicalite-1 and mesoporous silica nanoparticles has been studied by 1H solution NMR spectroscopy. With this method, the surface bound contaminants are detected. The analysis of the intensity and position of these peaks allows quantitative assessment of the relative amounts of functional groups with adsorbed metal ions. These results demonstrate the sensitivity of solution NMR spectroscopy to the electronic environment and structure of the surface functional groups on porous nanomaterials.

Goldstonic pseudoscalar mesons in Bethe-Salpeter-inspired setting

NASA Astrophysics Data System (ADS)

Lucha, Wolfgang; Schöberl, Franz F.

2018-03-01

For a two-particle bound-state equation closer to its Bethe-Salpeter origins than Salpeter’s equation, with effective interaction kernel deliberately forged such as to ensure, in the limit of zero mass of the bound-state constituents, the vanishing of the arising bound-state mass, we scrutinize the emerging features of the lightest pseudoscalar mesons for their agreement with the behavior predicted by a generalization of the Gell-Mann-Oakes-Renner relation.

Minichaperone (GroEL191-345) mediated folding of MalZ proceeds by binding and release of native and functional intermediates.

PubMed

Jain, Neha; Knowles, Timothy J; Lund, Peter A; Chaudhuri, Tapan K

2018-06-02

The isolated apical domain of GroEL consisting of residues 191-345 (known as "minichaperone") binds and assists the folding of a wide variety of client proteins without GroES and ATP, but the mechanism of its action is still unknown. In order to probe into the matter, we have examined minichaperone-mediated folding of a large aggregation prone protein Maltodextrin-glucosidase (MalZ). The key objective was to identify whether MalZ exists free in solution, or remains bound to, or cycling on and off the minichaperone during the refolding process. When GroES was introduced during refolding process, production of the native MalZ was inhibited. We also observed the same findings with a trap mutant of GroEL, which stably captures a predominantly non-native MalZ released from minichaperone during refolding process, but does not release it. Tryptophan and ANS fluorescence measurements indicated that refolded MalZ has the same structure as the native MalZ, but that its structure when bound to minichaperone is different. Surface plasmon resonance measurements provide an estimate for the equilibrium dissociation constant KD for the MalZ-minichaperone complex of 0.21 ± 0.04 μM, which are significantly higher than for most GroEL clients. This showed that minichaperone interacts loosely with MalZ to allow the protein to change its conformation and fold while bound during the refolding process. These observations suggest that the minichaperone works by carrying out repeated cycles of binding aggregation-prone protein MalZ in a relatively compact conformation and in a partially folded but active state, and releasing them to attempt to fold in solution. Copyright © 2018 Elsevier B.V. All rights reserved.

Spherical D-brane by tachyon condensation

NASA Astrophysics Data System (ADS)

Asakawa, Tsuguhiko; Matsuura, So

2018-03-01

We find a novel tachyon condensation which provides a D-brane system with spherical worldvolume in the flat spacetime. The tachyon profile is a deformation of a known D0-brane solution on non-BPS D3-branes in type IIA superstring theory, which realizes a bound state of a spherical D2-brane and a D0-brane. The D0-brane is resolved into the sphere as a U(1) monopole flux of the unit magnetic charge. We show that the system has the correct tension and the RR-coupling. Although the low-energy effective action of the system is the same as that of the dual description of the fuzzy sphere solution of multiple D0-branes, our system cannot be equivalent to the fuzzy sphere. The use of projective modules in describing the tachyon condensation is emphasized.

Sinc-interpolants in the energy plane for regular solution, Jost function, and its zeros of quantum scattering

NASA Astrophysics Data System (ADS)

Annaby, M. H.; Asharabi, R. M.

2018-01-01

In a remarkable note of Chadan [Il Nuovo Cimento 39, 697-703 (1965)], the author expanded both the regular wave function and the Jost function of the quantum scattering problem using an interpolation theorem of Valiron [Bull. Sci. Math. 49, 181-192 (1925)]. These expansions have a very slow rate of convergence, and applying them to compute the zeros of the Jost function, which lead to the important bound states, gives poor convergence rates. It is our objective in this paper to introduce several efficient interpolation techniques to compute the regular wave solution as well as the Jost function and its zeros approximately. This work continues and improves the results of Chadan and other related studies remarkably. Several worked examples are given with illustrations and comparisons with existing methods.

Multigrid solution of compressible turbulent flow on unstructured meshes using a two-equation model

NASA Technical Reports Server (NTRS)

Mavriplis, D. J.; Matinelli, L.

1994-01-01

The steady state solution of the system of equations consisting of the full Navier-Stokes equations and two turbulence equations has been obtained using a multigrid strategy of unstructured meshes. The flow equations and turbulence equations are solved in a loosely coupled manner. The flow equations are advanced in time using a multistage Runge-Kutta time-stepping scheme with a stability-bound local time step, while turbulence equations are advanced in a point-implicit scheme with a time step which guarantees stability and positivity. Low-Reynolds-number modifications to the original two-equation model are incorporated in a manner which results in well-behaved equations for arbitrarily small wall distances. A variety of aerodynamic flows are solved, initializing all quantities with uniform freestream values. Rapid and uniform convergence rates for the flow and turbulence equations are observed.

Interrelationship between flexoelectricity and strain gradient elasticity in ferroelectric nanofilms: A phase field study

NASA Astrophysics Data System (ADS)

Jiang, Limei; Xu, Xiaofei; Zhou, Yichun

2016-12-01

With the development of the integrated circuit technology and decreasing of the device size, ferroelectric films used in nano ferroelectric devices become thinner and thinner. Along with the downscaling of the ferroelectric film, there is an increasing influence of two strain gradient related terms. One is the strain gradient elasticity and the other one is flexoelectricity. To investigate the interrelationship between flexoelectricity and strain gradient elasticity and their combined effect on the domain structure in ferroelectric nanofilms, a phase field model of flexoelectricity and strain gradient elasticity on the ferroelectric domain evolution is developed based on Mindlin's theory of strain-gradient elasticity. Weak form is derived and implemented in finite element formulations for numerically solving the model equations. The simulation results show that upper bounds for flexoelectric coefficients can be enhanced by increasing strain gradient elasticity coefficients. While a large flexoelectricity that exceeds the upper bound can induce a transition from a ferroelectric state to a modulated/incommensurate state, a large enough strain gradient elasticity may lead to a conversion from an incommensurate state to a ferroelectric state. Strain gradient elasticity and the flexoelectricity have entirely opposite effects on polarization. The observed interrelationship between the strain gradient elasticity and flexoelectricity is rationalized by an analytical solution of the proposed theoretical model. The model proposed in this paper could help us understand the mechanism of phenomena observed in ferroelectric nanofilms under complex electromechanical loads and provide some guides on the practical application of ferroelectric nanofilms.

Parameter estimation of qubit states with unknown phase parameter

NASA Astrophysics Data System (ADS)

Suzuki, Jun

2015-02-01

We discuss a problem of parameter estimation for quantum two-level system, qubit system, in presence of unknown phase parameter. We analyze trade-off relations for mean square errors (MSEs) when estimating relevant parameters with separable measurements based on known precision bounds; the symmetric logarithmic derivative (SLD) Cramér-Rao (CR) bound and Hayashi-Gill-Massar (HGM) bound. We investigate the optimal measurement which attains the HGM bound and discuss its properties. We show that the HGM bound for relevant parameters can be attained asymptotically by using some fraction of given n quantum states to estimate the phase parameter. We also discuss the Holevo bound which can be attained asymptotically by a collective measurement.

Propagation of waves in a bounded random layer with laminar structure

NASA Technical Reports Server (NTRS)

Karam, M. A.; Fung, A. K.

1985-01-01

A closed form solution has been developed to obtain the intensity propagating in a bounded layer with laminar structure. Then, the brightness temperature due to an arbitrary temperature profile has been derived. Results are specialized to a half space to compare with those reported in the literature.

Minimum-error quantum distinguishability bounds from matrix monotone functions: A comment on 'Two-sided estimates of minimum-error distinguishability of mixed quantum states via generalized Holevo-Curlander bounds' [J. Math. Phys. 50, 032106 (2009)

DOE Office of Scientific and Technical Information (OSTI.GOV)

Tyson, Jon

2009-06-15

Matrix monotonicity is used to obtain upper bounds on minimum-error distinguishability of arbitrary ensembles of mixed quantum states. This generalizes one direction of a two-sided bound recently obtained by the author [J. Tyson, J. Math. Phys. 50, 032106 (2009)]. It is shown that the previously obtained special case has unique properties.

An Algebraic Approach to Guarantee Harmonic Balance Method Using Gröbner Base

NASA Astrophysics Data System (ADS)

Yagi, Masakazu; Hisakado, Takashi; Okumura, Kohshi

Harmonic balance (HB) method is well known principle for analyzing periodic oscillations on nonlinear networks and systems. Because the HB method has a truncation error, approximated solutions have been guaranteed by error bounds. However, its numerical computation is very time-consuming compared with solving the HB equation. This paper proposes an algebraic representation of the error bound using Gröbner base. The algebraic representation enables to decrease the computational cost of the error bound considerably. Moreover, using singular points of the algebraic representation, we can obtain accurate break points of the error bound by collisions.

Big Ideas and Small Solutions

ERIC Educational Resources Information Center

Tennant, Roy

2004-01-01

Small solutions solve discrete, well-bounded problems and can be pieces of larger solutions. They can move things forward by mixing and matching available components in new and previously unimagined ways. A number of innovations, which at first glance are completely unrelated, can come together and create important synergics. This article…

Unliganded HIV-1 gp120 core structures assume the CD4-bound conformation with regulation by quaternary interactions and variable loops

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kwon, Young Do; Finzi, Andrés; Wu, Xueling

2013-03-04

The HIV-1 envelope (Env) spike (gp120{sub 3}/gp41{sub 3}) undergoes considerable structural rearrangements to mediate virus entry into cells and to evade the host immune response. Engagement of CD4, the primary human receptor, fixes a particular conformation and primes Env for entry. The CD4-bound state, however, is prone to spontaneous inactivation and susceptible to antibody neutralization. How does unliganded HIV-1 maintain CD4-binding capacity and regulate transitions to the CD4-bound state? To define this mechanistically, we determined crystal structures of unliganded core gp120 from HIV-1 clades B, C, and E. Notably, all of these unliganded HIV-1 structures resembled the CD4-bound state. Conformationalmore » fixation with ligand selection and thermodynamic analysis of full-length and core gp120 interactions revealed that the tendency of HIV-1 gp120 to adopt the CD4-bound conformation was restrained by the V1/V2- and V3-variable loops. In parallel, we determined the structure of core gp120 in complex with the small molecule, NBD-556, which specifically recognizes the CD4-bound conformation of gp120. Neutralization by NBD-556 indicated that Env spikes on primary isolates rarely assume the CD4-bound conformation spontaneously, although they could do so when quaternary restraints were loosened. Together, the results suggest that the CD4-bound conformation represents a 'ground state' for the gp120 core, with variable loop and quaternary interactions restraining unliganded gp120 from 'snapping' into this conformation. A mechanism of control involving deformations in unliganded structure from a functionally critical state (e.g., the CD4-bound state) provides advantages in terms of HIV-1 Env structural diversity and resistance to antibodies and inhibitors, while maintaining elements essential for entry.« less

Impact of iron-site defects on superconductivity in LiFeAs

DOE PAGES

Chi, Shun; Aluru, Ramakrishna; Singh, Udai Raj; ...

2016-10-19

In conventional s -wave superconductors, only magnetic impurities exhibit impurity bound states, whereas for an s ± order parameter they can occur for both magnetic and nonmagnetic impurities. Impurity bound states in superconductors can thus provide important insight into the order parameter. We present a combined experimental and theoretical study of native and engineered iron-site defects in LiFeAs. A detailed comparison of tunneling spectra measured on impurities with spin-fluctuation theory reveals a continuous evolution from negligible impurity-bound-state features for weaker scattering potential to clearly detectable states for somewhat stronger scattering potentials. Furthermore, all bound states for these intermediate strengthmore » potentials are pinned at or close to the gap edge of the smaller gap, a phenomenon that we explain and ascribe to multiorbital physics.« less

Controllable reductive method for synthesizing metal-containing particles

DOE Office of Scientific and Technical Information (OSTI.GOV)

Moon, Ji-Won; Jung, Hyunsung; Phelps, Tommy Joe

The invention is directed to a method for producing metal-containing particles, the method comprising subjecting an aqueous solution comprising a metal salt, E.sub.h, lowering reducing agent, pH adjusting agent, and water to conditions that maintain the E.sub.h value of the solution within the bounds of an E.sub.h-pH stability field corresponding to the composition of the metal-containing particles to be produced, and producing said metal-containing particles in said aqueous solution at a selected E.sub.h value within the bounds of said E.sub.h-pH stability field. The invention is also directed to the resulting metal-containing particles as well as devices in which they aremore » incorporated.« less

Tunneling spectroscopy of quasiparticle bound states in a spinful Josephson junction.

PubMed

Chang, W; Manucharyan, V E; Jespersen, T S; Nygård, J; Marcus, C M

2013-05-24

The spectrum of a segment of InAs nanowire, confined between two superconducting leads, was measured as function of gate voltage and superconducting phase difference using a third normal-metal tunnel probe. Subgap resonances for odd electron occupancy-interpreted as bound states involving a confined electron and a quasiparticle from the superconducting leads, reminiscent of Yu-Shiba-Rusinov states-evolve into Kondo-related resonances at higher magnetic fields. An additional zero-bias peak of unknown origin is observed to coexist with the quasiparticle bound states.

Application of Ring-Closing Metathesis to Grb2 SH3 Domain-Binding Peptides | Center for Cancer Research

Cancer.gov

In silico-generated hypothetical interactions of a ring-closing metathesis-macrocylized peptide bound to the amino terminal SH3 domain of the growth factor receptor bound protein 2 (Grb2). The complex was derived from the NMR solution structure of the bound parent peptide, Ac-V-P-P-P-V-P-P-R-R-R-amide (Protein Data Bank: 3GBQ). The protein surface is shown as electrostatic

The Consensus Problem in Unreliable Distributed Systems (A Brief Survey).

DTIC Science & Technology

1983-06-01

they might also reach conflicting conclusions about the outcome of the election and hence fail to reach agreement. Davies and Wakerly [21 realized this...15], and part (b) was shown by Dolev and Reischuk [10]. For practical applications , these bounds are not very encouraging, especially the t+I bound on...solutions is f2(n + t2)). Theorem 7, part (b) shows this bound "best possible" for authenticated algorithms. 6. Applications of Agreement Protocols The

A Posteriori Finite Element Bounds for Sensitivity Derivatives of Partial-Differential-Equation Outputs. Revised

NASA Technical Reports Server (NTRS)

Lewis, Robert Michael; Patera, Anthony T.; Peraire, Jaume

1998-01-01

We present a Neumann-subproblem a posteriori finite element procedure for the efficient and accurate calculation of rigorous, 'constant-free' upper and lower bounds for sensitivity derivatives of functionals of the solutions of partial differential equations. The design motivation for sensitivity derivative error control is discussed; the a posteriori finite element procedure is described; the asymptotic bounding properties and computational complexity of the method are summarized; and illustrative numerical results are presented.

Dissociative recombination of HCl+

NASA Astrophysics Data System (ADS)

Larson, Åsa; Fonseca dos Santos, Samantha; E. Orel, Ann

2017-08-01

The dissociative recombination of HCl+, including both the direct and indirect mechanisms, is studied. For the direct process, the relevant electronic states are calculated ab initio by combining electron scattering calculations to obtain resonance positions and autoionization widths with multi-reference configuration interaction calculations of the ion and Rydberg states. The cross section for the direct dissociation along electronic resonant states is computed by solution of the time-dependent Schrödinger equation. For the indirect process, an upper bound value for the cross section is obtained using a vibrational frame transformation of the elements of the scattering matrix at energies just above the ionization threshold. Vibrational excitations of the ionic core from the ground vibrational state, v = 0 , to the first three excited vibrational states, v = 1 , v = 2 , and v = 3 , are considered. Autoionization is neglected and the effect of the spin-orbit splitting of the ionic potential energy upon the indirect dissociative recombination cross section is considered. The calculated cross sections are compared to measurements.

Dissociative recombination of HCl.

PubMed

Larson, Åsa; Fonseca Dos Santos, Samantha; E Orel, Ann

2017-08-28

The dissociative recombination of HCl + , including both the direct and indirect mechanisms, is studied. For the direct process, the relevant electronic states are calculated ab initio by combining electron scattering calculations to obtain resonance positions and autoionization widths with multi-reference configuration interaction calculations of the ion and Rydberg states. The cross section for the direct dissociation along electronic resonant states is computed by solution of the time-dependent Schrödinger equation. For the indirect process, an upper bound value for the cross section is obtained using a vibrational frame transformation of the elements of the scattering matrix at energies just above the ionization threshold. Vibrational excitations of the ionic core from the ground vibrational state, v = 0, to the first three excited vibrational states, v = 1, v = 2, and  v = 3, are considered. Autoionization is neglected and the effect of the spin-orbit splitting of the ionic potential energy upon the indirect dissociative recombination cross section is considered. The calculated cross sections are compared to measurements.

Heat kernel for the elliptic system of linear elasticity with boundary conditions

NASA Astrophysics Data System (ADS)

Taylor, Justin; Kim, Seick; Brown, Russell

2014-10-01

We consider the elliptic system of linear elasticity with bounded measurable coefficients in a domain where the second Korn inequality holds. We construct heat kernel of the system subject to Dirichlet, Neumann, or mixed boundary condition under the assumption that weak solutions of the elliptic system are Hölder continuous in the interior. Moreover, we show that if weak solutions of the mixed problem are Hölder continuous up to the boundary, then the corresponding heat kernel has a Gaussian bound. In particular, if the domain is a two dimensional Lipschitz domain satisfying a corkscrew or non-tangential accessibility condition on the set where we specify Dirichlet boundary condition, then we show that the heat kernel has a Gaussian bound. As an application, we construct Green's function for elliptic mixed problem in such a domain.

Role of glutamate-104 in generating a transition state analogue inhibitor at the active site of cytidine deaminase.

PubMed

Carlow, D C; Short, S A; Wolfenden, R

1996-01-23

The 19F-NMR resonance of 5-[19F]fluoropyrimidin-2-one ribonucleoside moves upfield when it is bound by wild-type cytidine deaminase from Escherichia coli, in agreement with UV and X-ray spectroscopic indications that this inhibitor is bound as the rate 3,4-hydrated species 5-fluoro-3,4-dihydrouridine, a transition state analogue inhibitor resembling an intermediate in direct water attack on 5-fluorocytidine. Comparison of pKa values of model compounds indicates that the equilibrium constant for 3,4-hydration of this inhibitor in free solution is 3.5 x 10(-4) M, so that the corrected dissociation constant of 5-fluoro-3,4-dihydrouridine from the wild-type enzyme is 3.9 x 10(-11) M. Very different behavior is observed for a mutant enzyme in which alanine replaces Glu-104 at the active site, and kcat has been reduced by a factor of 10(8). 5-[19F]Fluoropyrimidin-2-one ribonucleoside is strongly fluorescent, making it possible to observe that the mutant enzyme binds this inhibitor even more tightly (Kd = 4.4 x 10(-8) M) than does the native enzyme (Kd = 1.1 x 10(-7) M). 19F-NMR indicates, however, that the E104A mutant enzyme binds the inhibitor without modification, in a form that resembles the substrate in the ground state. These results are consistent with a major role for Glu-104, not only in stabilizing the ES++ complex in the transition state, but also in destabilizing the ES complex in the ground state.

Mixed matrix hollow fiber membranes for removal of protein-bound toxins from human plasma.

PubMed

Tijink, Marlon S L; Wester, Maarten; Glorieux, Griet; Gerritsen, Karin G F; Sun, Junfen; Swart, Pieter C; Borneman, Zandrie; Wessling, Matthias; Vanholder, Raymond; Joles, Jaap A; Stamatialis, Dimitrios

2013-10-01

In end stage renal disease (ESRD) waste solutes accumulate in body fluid. Removal of protein bound solutes using conventional renal replacement therapies is currently very poor while their accumulation is associated with adverse outcomes in ESRD. Here we investigate the application of a hollow fiber mixed matrix membrane (MMM) for removal of these toxins. The MMM hollow fiber consists of porous macro-void free polymeric inner membrane layer well attached to the activated carbon containing outer MMM layer. The new membranes have permeation properties in the ultrafiltration range. Under static conditions, they adsorb 57% p-cresylsulfate, 82% indoxyl sulfate and 94% of hippuric acid from spiked human plasma in 4 h. Under dynamic conditions, they adsorb on average 2.27 mg PCS/g membrane and 3.58 mg IS/g membrane in 4 h in diffusion experiments and 2.68 mg/g membrane PCS and 12.85 mg/g membrane IS in convection experiments. Based on the dynamic experiments we estimate that our membranes would suffice to remove the daily production of these protein bound solutes. Copyright © 2013 Elsevier Ltd. All rights reserved.

Who is Mr. HAMLET? Interaction of human alpha-lactalbumin with monomeric oleic acid.

PubMed

Knyazeva, Ekaterina L; Grishchenko, Valery M; Fadeev, Roman S; Akatov, Vladimir S; Permyakov, Sergei E; Permyakov, Eugene A

2008-12-09

A specific state of the human milk Ca(2+) binding protein alpha-lactalbumin (hLA) complexed with oleic acid (OA) prepared using an OA-pretreated ion-exchange column (HAMLET) triggers several cell death pathways in various tumor cells. The possibility of preparing a hLA-OA complex with structural and cytotoxic properties similar to those of the HAMLET but under solution conditions has been explored. The complex was formed by titration of hLA by OA at pH 8.3 up to OA critical micelle concentration. We have shown that complex formation strongly depends on calcium, ionic strength, and temperature; the optimal conditions were established. The spectrofluorimetrically estimated number of OA molecules irreversibly bound per hLA molecule (after dialysis of the OA-loaded preparation against water followed by lyophilization) depends upon temperature: 2.9 at 17 degrees C (native apo-hLA; resulting complex referred to as LA-OA-17 state) and 9 at 45 degrees C (thermally unfolded apo-hLA; LA-OA-45). Intrinsic tryptophan fluorescence measurements revealed substantially decreased thermal stability of Ca(2+)-free forms of HAMLET, LA-OA-45, and OA-saturated protein. The irreversibly bound OA does not affect the Ca(2+) association constant of the protein. Phase plot analysis of fluorimetric and CD data indicates that the OA binding process involves several hLA intermediates. The effective pseudoequilibrium OA association constants for Ca(2+)-free hLA were estimated. The far-UV CD spectra of Ca(2+)-free hLA show that all OA-bound forms of the protein are characterized by elevated content of alpha-helical structure. The various hLA-OA complexes possess similar cytotoxic activities against human epidermoid larynx carcinoma cells. Overall, the LA-OA-45 complex possesses physicochemical, structural, and cytotoxic properties closely resembling those of HAMLET. The fact that the HAMLET-like complex can be formed in aqueous solution makes the process of its preparation more transparent and controllable, opening up opportunities for formation of active complexes with specific properties.

Generator for ionic gallium-68 based on column chromatography

DOEpatents

Neirinckx, Rudi D.; Davis, Michael A.

1981-01-01

A physiologically acceptable solution of gallium-68 fluorides, having an activity of 0.1 to 50 millicuries per milliliter of solution is provided. The solution is obtained from a generator comprising germanium-68 hexafluoride bound to a column of an anion exchange resin which forms gallium-68 in situ by eluting the column with an acid solution to form a solution containing .sup.68 Ga-fluorides. The solution then is neutralized prior to administration.

Radiopharmaceutical composition containing tantalum-178 and process therefor

DOEpatents

Neirinckx, Rudi D.; Holman, B. Leonard; Davis, Michael A.; Harris, Gale I.

1989-05-16

A physiologically acceptable solution of tantalum-178 having an activity of 0.1 to 200 millicuries per milliliter of tantalum-178 solution is provided. The solution is obtained from tungsten-178 bound to a column of an anion exchange resin which forms tantalum-178 in situ by eluting the column with a hydrochloric acid solution containing hydrogen peroxide to form an acidic solution of tantalum-178. The acidic solution of tantalum-178 then is neutralized.

I. Aspects of the Dark Matter Problem. II. Fermion Balls

NASA Astrophysics Data System (ADS)

Tetradis, Nikolaos Athanassiou

The first part of this thesis deals with the dark matter problem. A simple non-supersymmetric extension of the standard model is presented, which provides dark matter candidates not excluded by the existing dark matter searches. The simplest candidate is the neutral component of a zero hypercharge triplet, with vector gauge interactions. The upper bound on its mass is a few TeV. We also discuss possible modifications of the standard freeze-out scenario, induced by the presence of a phase transition. More specifically, if the critical temperature of the electroweak phase transition is sufficiently small, it can change the final abundances of heavy dark matter particles, by keeping them massless for a long time. Recent experimental bounds on the Higgs mass from LEP imply that this is not the case in the minimal standard model. In the second part we discuss non-trivial configurations, involving fermions which obtain their mass through Yukawa interactions with a scalar field. Under certain conditions, the vacuum expectation value of the scalar field is shifted from the minimum of the effective potential, in regions of high fermion density. This may result in the formation of fermion bound states. We study two such cases: (a) Using the non-linear SU(3)L times SU(3)R chiral Lagrangian coupled to a field theory of nuclear forces, we show that a bound state of baryons with a well defined surface may concievably form in the presence of kaon condensation. This state is of similar density to ordinary nuclei, but has net strangeness equal to about two thirds the baryon number. We discuss the properties of lumps of strange baryon matter with baryon number between ~20 and ~10 57 where gravitational effects become important. (b) The Higgs field near a very heavy top quark or any other heavy fermion is expected to be significantly deformed. By computing explicit solutions of the classical equations of motion for a spherically symmetric configuration without gauge fields, we show that in the standard model this cannot happen without violating either vacuum stability or perturbation theory at energies very close to the top quark mass.

Tightening Quantum Speed Limits for Almost All States.

PubMed

Campaioli, Francesco; Pollock, Felix A; Binder, Felix C; Modi, Kavan

2018-02-09

Conventional quantum speed limits perform poorly for mixed quantum states: They are generally not tight and often significantly underestimate the fastest possible evolution speed. To remedy this, for unitary driving, we derive two quantum speed limits that outperform the traditional bounds for almost all quantum states. Moreover, our bounds are significantly simpler to compute as well as experimentally more accessible. Our bounds have a clear geometric interpretation; they arise from the evaluation of the angle between generalized Bloch vectors.

Two-polariton bound states in the Jaynes-Cummings-Hubbard model

DOE Office of Scientific and Technical Information (OSTI.GOV)

Wong, Max T. C.; Law, C. K.

2011-05-15

We examine the eigenstates of the one-dimensional Jaynes-Cummings-Hubbard model in the two-excitation subspace. We discover that two-excitation bound states emerge when the ratio of vacuum Rabi frequency to the tunneling rate between cavities exceeds a critical value. We determine the critical value as a function of the quasimomentum quantum number, and indicate that the bound states carry a strong correlation in which the two polaritons appear to be spatially confined together.

The light bound states of N=1 supersymmetric SU(3) Yang-Mills theory on the lattice

NASA Astrophysics Data System (ADS)

Ali, Sajid; Bergner, Georg; Gerber, Henning; Giudice, Pietro; Montvay, Istvan; Münster, Gernot; Piemonte, Stefano; Scior, Philipp

2018-03-01

In this article we summarise our results from numerical simulations of N=1 supersymmetric Yang-Mills theory with gauge group SU(3). We use the formulation of Curci and Veneziano with clover-improved Wilson fermions. The masses of various bound states have been obtained at different values of the gluino mass and gauge coupling. Extrapolations to the limit of vanishing gluino mass indicate that the bound states form mass-degenerate supermultiplets.

Analytically Solvable Model of Spreading Dynamics with Non-Poissonian Processes

NASA Astrophysics Data System (ADS)

Jo, Hang-Hyun; Perotti, Juan I.; Kaski, Kimmo; Kertész, János

2014-01-01

Non-Poissonian bursty processes are ubiquitous in natural and social phenomena, yet little is known about their effects on the large-scale spreading dynamics. In order to characterize these effects, we devise an analytically solvable model of susceptible-infected spreading dynamics in infinite systems for arbitrary inter-event time distributions and for the whole time range. Our model is stationary from the beginning, and the role of the lower bound of inter-event times is explicitly considered. The exact solution shows that for early and intermediate times, the burstiness accelerates the spreading as compared to a Poisson-like process with the same mean and same lower bound of inter-event times. Such behavior is opposite for late-time dynamics in finite systems, where the power-law distribution of inter-event times results in a slower and algebraic convergence to a fully infected state in contrast to the exponential decay of the Poisson-like process. We also provide an intuitive argument for the exponent characterizing algebraic convergence.

Bound states of dipolar bosons in one-dimensional systems

NASA Astrophysics Data System (ADS)

Volosniev, A. G.; Armstrong, J. R.; Fedorov, D. V.; Jensen, A. S.; Valiente, M.; Zinner, N. T.

2013-04-01

We consider one-dimensional tubes containing bosonic polar molecules. The long-range dipole-dipole interactions act both within a single tube and between different tubes. We consider arbitrary values of the externally aligned dipole moments with respect to the symmetry axis of the tubes. The few-body structures in this geometry are determined as a function of polarization angles and dipole strength by using both essentially exact stochastic variational methods and the harmonic approximation. The main focus is on the three-, four- and five-body problems in two or more tubes. Our results indicate that in the weakly coupled limit the intertube interaction is similar to a zero-range term with a suitable rescaled strength. This allows us to address the corresponding many-body physics of the system by constructing a model where bound chains with one molecule in each tube are the effective degrees of freedom. This model can be mapped onto one-dimensional Hamiltonians for which exact solutions are known.

Interactions of a designed peptide with lipopolysaccharide: Bound conformation and anti-endotoxic activity

DOE Office of Scientific and Technical Information (OSTI.GOV)

Bhunia, Anirban; Chua, Geok Lin; Domadia, Prerna N.

Designed peptides that would selectively interact with lipopolysaccharide (LPS) or endotoxin and fold into specific conformations could serve as important scaffolds toward the development of antisepsis compounds. Here, we describe solution structure of a designed amphipathic peptide, H{sub 2}N-YVKLWRMIKFIR-CONH{sub 2} (YW12D) in complex with endotoxin as determined by transferred nuclear Overhauser effect spectroscopy. The conformation of the isolated peptide is highly flexible, but undergoes a dramatic structural stabilization in the presence of LPS. Structure calculations reveal that the peptide presents two amphipathic surfaces in its bound state to LPS whereby each surface is characterized by two positive charges and amore » number of aromatic and/or aliphatic residues. ITC data suggests that peptide interacts with two molecules of lipid A. In activity assays, YW12D exhibits neutralization of LPS toxicity with very little hemolysis of red blood cells. Structural and functional properties of YW12D would be applicable in designing low molecular weight non-toxic antisepsis molecules.« less

Structural insights into the intertwined dimer of fyn SH2.

PubMed

Huculeci, Radu; Garcia-Pino, Abel; Buts, Lieven; Lenaerts, Tom; van Nuland, Nico

2015-12-01

Src homology 2 domains are interaction modules dedicated to the recognition of phosphotyrosine sites incorporated in numerous proteins found in intracellular signaling pathways. Here we provide for the first time structural insight into the dimerization of Fyn SH2 both in solution and in crystalline conditions, providing novel crystal structures of both the dimer and peptide-bound structures of Fyn SH2. Using nuclear magnetic resonance chemical shift analysis, we show how the peptide is able to eradicate the dimerization, leading to monomeric SH2 in its bound state. Furthermore, we show that Fyn SH2's dimer form differs from other SH2 dimers reported earlier. Interestingly, the Fyn dimer can be used to construct a completed dimer model of Fyn without any steric clashes. Together these results extend our understanding of SH2 dimerization, giving structural details, on one hand, and suggesting a possible physiological relevance of such behavior, on the other hand. © 2015 The Protein Society.

Germanium films by polymer-assisted deposition

DOEpatents

Jia, Quanxi; Burrell, Anthony K.; Bauer, Eve; Ronning, Filip; McCleskey, Thomas Mark; Zou, Guifu

2013-01-15

Highly ordered Ge films are prepared directly on single crystal Si substrates by applying an aqueous coating solution having Ge-bound polymer onto the substrate and then heating in a hydrogen-containing atmosphere. A coating solution was prepared by mixing water, a germanium compound, ethylenediaminetetraacetic acid, and polyethyleneimine to form a first aqueous solution and then subjecting the first aqueous solution to ultrafiltration.

Dynamic spin injection into a quantum well coupled to a spin-split bound state

NASA Astrophysics Data System (ADS)

Maslova, N. S.; Rozhansky, I. V.; Mantsevich, V. N.; Arseyev, P. I.; Averkiev, N. S.; Lähderanta, E.

2018-05-01

We present a theoretical analysis of dynamic spin injection due to spin-dependent tunneling between a quantum well (QW) and a bound state split in spin projection due to an exchange interaction or external magnetic field. We focus on the impact of Coulomb correlations at the bound state on spin polarization and sheet density kinetics of the charge carriers in the QW. The theoretical approach is based on kinetic equations for the electron occupation numbers taking into account high order correlation functions for the bound state electrons. It is shown that the on-site Coulomb repulsion leads to an enhanced dynamic spin polarization of the electrons in the QW and a delay in the carriers tunneling into the bound state. The interplay of these two effects leads to nontrivial dependence of the spin polarization degree, which can be probed experimentally using time-resolved photoluminescence experiments. It is demonstrated that the influence of the Coulomb interactions can be controlled by adjusting the relaxation rates. These findings open a new way of studying the Hubbard-like electron interactions experimentally.

Stylolitization as source of cement in Mississippian Salem Limestone, west-central Indiana

DOE Office of Scientific and Technical Information (OSTI.GOV)

Finkel, E.A.; Wilkinson, B.H.

The Mississippian Salem Limestone of west-central Indiana is a homogeneous cross-bedded grainstone containing numerous stylolites with amplitudes ranging up to 25 cm. Petrographic and geochemical analyses of closely spaced samples from four 1-m thick stylolite-bounded units document spatial trends in grainstone texture and composition, which correlate with proximity to bounding solution seams. Textural data indicate that stylolitization was locally preceded by grain compaction and that seam solution preferentially occurred within layers where grain packing was tightest. Amount of cement largely corresponds to volume of available pore space, and remaining porosity varies inversely to stylolite proximity. Trace-element compositions demonstrate that intergranularmore » spar is enriched in Mn and depleted in Mg relative to grains, and suggest a significant contribution of carbonate cement to grainstone pores from bounding solution seams. Data on grainstone and stylolite insoluble contents indicate that stylolite amplitude records 43% of actual section shortening. On average, seam solution within the Salem Limestone could have provided no less than 47% and no more than 90% of the CaCO{sub 3}, Fe, and Mn mass now in grainstone pores as intergranular spar cement. As such, stylolitization has played an important role during burial diagenesis, porosity occlusion, and permeability reduction within this Mississippian grainstone sequence. 17 figs., 1 tab.« less

Boundary causality versus hyperbolicity for spherical black holes in Gauss-Bonnet gravity

NASA Astrophysics Data System (ADS)

Andrade, Tomás; Cáceres, Elena; Keeler, Cynthia

2017-07-01

We explore the constraints boundary causality places on the allowable Gauss-Bonnet gravitational couplings in asymptotically AdS spaces, specifically considering spherical black hole solutions. We additionally consider the hyperbolicity properties of these solutions, positing that hyperbolicity-violating solutions are sick solutions whose causality properties provide no information about the theory they reside in. For both signs of the Gauss-Bonnet coupling, spherical black holes violate boundary causality at smaller absolute values of the coupling than planar black holes do. For negative coupling, as we tune the Gauss-Bonnet coupling away from zero, both spherical and planar black holes violate hyperbolicity before they violate boundary causality. For positive coupling, the only hyperbolicity-respecting spherical black holes which violate boundary causality do not do so appreciably far from the planar bound. Consequently, eliminating hyperbolicity-violating solutions means the bound on Gauss-Bonnet couplings from the boundary causality of spherical black holes is no tighter than that from planar black holes.

a Bounded Finite-Difference Discretization of a Two-Dimensional Diffusion Equation with Logistic Nonlinear Reaction

NASA Astrophysics Data System (ADS)

Macías-Díaz, J. E.

In the present manuscript, we introduce a finite-difference scheme to approximate solutions of the two-dimensional version of Fisher's equation from population dynamics, which is a model for which the existence of traveling-wave fronts bounded within (0,1) is a well-known fact. The method presented here is a nonstandard technique which, in the linear regime, approximates the solutions of the original model with a consistency of second order in space and first order in time. The theory of M-matrices is employed here in order to elucidate conditions under which the method is able to preserve the positivity and the boundedness of solutions. In fact, our main result establishes relatively flexible conditions under which the preservation of the positivity and the boundedness of new approximations is guaranteed. Some simulations of the propagation of a traveling-wave solution confirm the analytical results derived in this work; moreover, the experiments evince a good agreement between the numerical result and the analytical solutions.

Improving the efficiency of branch-and-bound complete-search NMR assignment using the symmetry of molecules and spectra

DOE Office of Scientific and Technical Information (OSTI.GOV)

Bernal, Andrés; Patiny, Luc; Castillo, Andrés M.

2015-02-21

Nuclear magnetic resonance (NMR) assignment of small molecules is presented as a typical example of a combinatorial optimization problem in chemical physics. Three strategies that help improve the efficiency of solution search by the branch and bound method are presented: 1. reduction of the size of the solution space by resort to a condensed structure formula, wherein symmetric nuclei are grouped together; 2. partitioning of the solution space based on symmetry, that becomes the basis for an efficient branching procedure; and 3. a criterion of selection of input restrictions that leads to increased gaps between branches and thus faster pruningmore » of non-viable solutions. Although the examples chosen to illustrate this work focus on small-molecule NMR assignment, the results are generic and might help solving other combinatorial optimization problems.« less

Maximum and minimum entropy states yielding local continuity bounds

NASA Astrophysics Data System (ADS)

Hanson, Eric P.; Datta, Nilanjana

2018-04-01

Given an arbitrary quantum state (σ), we obtain an explicit construction of a state ρɛ * ( σ ) [respectively, ρ * , ɛ ( σ ) ] which has the maximum (respectively, minimum) entropy among all states which lie in a specified neighborhood (ɛ-ball) of σ. Computing the entropy of these states leads to a local strengthening of the continuity bound of the von Neumann entropy, i.e., the Audenaert-Fannes inequality. Our bound is local in the sense that it depends on the spectrum of σ. The states ρɛ * ( σ ) and ρ * , ɛ (σ) depend only on the geometry of the ɛ-ball and are in fact optimizers for a larger class of entropies. These include the Rényi entropy and the minimum- and maximum-entropies, providing explicit formulas for certain smoothed quantities. This allows us to obtain local continuity bounds for these quantities as well. In obtaining this bound, we first derive a more general result which may be of independent interest, namely, a necessary and sufficient condition under which a state maximizes a concave and Gâteaux-differentiable function in an ɛ-ball around a given state σ. Examples of such a function include the von Neumann entropy and the conditional entropy of bipartite states. Our proofs employ tools from the theory of convex optimization under non-differentiable constraints, in particular Fermat's rule, and majorization theory.

The lifespan of 3D radial solutions to the non-isentropic relativistic Euler equations

NASA Astrophysics Data System (ADS)

Wei, Changhua

2017-10-01

This paper investigates the lower bound of the lifespan of three-dimensional spherically symmetric solutions to the non-isentropic relativistic Euler equations, when the initial data are prescribed as a small perturbation with compact support to a constant state. Based on the structure of the hyperbolic system, we show the almost global existence of the smooth solutions to Eulerian flows (polytropic gases and generalized Chaplygin gases) with genuinely nonlinear characteristics. While for the Eulerian flows (Chaplygin gas and stiff matter) with mild linearly degenerate characteristics, we show the global existence of the radial solutions, moreover, for the non-strictly hyperbolic system (pressureless perfect fluid) satisfying the mild linearly degenerate condition, we prove the blowup phenomenon of the radial solutions and show that the lifespan of the solutions is of order O(ɛ ^{-1}), where ɛ denotes the width of the perturbation. This work can be seen as a complement of our work (Lei and Wei in Math Ann 367:1363-1401, 2017) for relativistic Chaplygin gas and can also be seen as a generalization of the classical Eulerian fluids (Godin in Arch Ration Mech Anal 177:497-511, 2005, J Math Pures Appl 87:91-117, 2007) to the relativistic Eulerian fluids.

Spherically symmetric vacuum in covariant F (T )=T +α/2 T2+O (Tγ) gravity theory

NASA Astrophysics Data System (ADS)

DeBenedictis, Andrew; Ilijić, Saša

2016-12-01

Recently, a fully covariant version of the theory of F (T ) torsion gravity has been introduced by M. Kršśák and E. Saridakis [Classical Quantum Gravity 33, 115009 (2016)]. In covariant F (T ) gravity, the Schwarzschild solution is not a vacuum solution for F (T )≠T , and therefore determining the spherically symmetric vacuum is an important open problem. Within the covariant framework, we perturbatively solve the spherically symmetric vacuum gravitational equations around the Schwarzschild solution for the scenario with F (T )=T +(α /2 )T2 , representing the dominant terms in theories governed by Lagrangians analytic in the torsion scalar. From this, we compute the perihelion shift correction to solar system planetary orbits as well as perturbative gravitational effects near neutron stars. This allows us to set an upper bound on the magnitude of the coupling constant, α , which governs deviations from general relativity. We find the bound on this nonlinear torsion coupling constant by specifically considering the uncertainty in the perihelion shift of Mercury. We also analyze a bound from a similar comparison with the periastron orbit of the binary pulsar PSR J0045-7319 as an independent check for consistency. Setting bounds on the dominant nonlinear coupling is important in determining if other effects in the Solar System or greater universe could be attributable to nonlinear torsion.

Threshold singularities in a Fermi gas with attractive potential in one dimension

DOE PAGES

Schlottmann, P.; Zvyagin, A. A.

2015-01-15

We consider the one-dimensional gas of fermions with spin S interacting via an attractive δ-function potential using the Bethe Ansatz solution. In zero magnetic field the atoms form bound states of N=2S + 1 fermions, i.e. generalized Cooper states with each atom having a different spin component. For low energy excitations the system is a Luttinger liquid and is properly described by a conformal field theory with conformal charge c=1. The linear dispersion of a Luttinger liquid is asymptotically exact in the low-energy limit where the band curvature terms in the dispersion are irrelevant. For higher energy excitations, however, themore » spectral function displays deviations in the neighborhood of the single-particle (hole) energy, which can be described by an effective X-ray edge type model. Using the Bethe Ansatz solution we obtain expressions for the critical exponents for the single-particle (hole) Green’s function. This model can be relevant in the context of ultracold atoms with effective total spin S confined to an elongated optical trap.« less

Bounds on the entanglement entropy of droplet states in the XXZ spin chain

NASA Astrophysics Data System (ADS)

Beaud, V.; Warzel, S.

2018-01-01

We consider a class of one-dimensional quantum spin systems on the finite lattice Λ ⊂Z , related to the XXZ spin chain in its Ising phase. It includes in particular the so-called droplet Hamiltonian. The entanglement entropy of energetically low-lying states over a bipartition Λ = B ∪ Bc is investigated and proven to satisfy a logarithmic bound in terms of min{n, |B|, |Bc|}, where n denotes the maximal number of down spins in the considered state. Upon addition of any (positive) random potential, the bound becomes uniformly constant on average, thereby establishing an area law. The proof is based on spectral methods: a deterministic bound on the local (many-body integrated) density of states is derived from an energetically motivated Combes-Thomas estimate.

Relativistic many-body bound systems: electromagnetic properties. Monograph report

DOE Office of Scientific and Technical Information (OSTI.GOV)

Danos, M.; Gillet, V.

1977-04-01

The formulae for the calculation of the electron scattering form factors, and of the static magnetic dipole and electric quadrupole moments, of relativistic many-body bound systems are derived. The framework, given in NBS Monograph 147, is relativistic quantum field theory in the Schrodinger picture; the physical particles, i.e., the solutions of the interacting fields, are given as linear combinations of the solutions of the free fields, called the parton fields. The parton--photon interaction is taken as given by minimal coupling. In addition, the contribution of the photon--vector meson vertex of the vector dominance model is derived.

Geodesic motion around traversable wormholes supported by a massless conformally coupled scalar field

NASA Astrophysics Data System (ADS)

Willenborg, Felix; Grunau, Saskia; Kleihaus, Burkhard; Kunz, Jutta

2018-06-01

We consider a traversable wormhole solution of Einstein's gravity conformally coupled to a massless scalar field, a solution derived by Barcelo and Visser based on the Janis-Newman-Winicour-Wyman spacetime. We study the geodesic motion of timelike and spacelike particles in this spacetime. We solve the equations of motion analytically in terms of the Weierstraß functions and discuss all possible orbit types and their parameter dependence. Interestingly, bound orbits occur for timelike geodesics only in one of the two worlds. Moreover, under no conditions there exist timelike two world bound orbits.

Absorption enhancement in type-II coupled quantum rings due to existence of quasi-bound states

NASA Astrophysics Data System (ADS)

Hsieh, Chi-Ti; Lin, Shih-Yen; Chang, Shu-Wei

2018-02-01

The absorption of type-II nanostructures is often weaker than type-I counterpart due to spatially separated electrons and holes. We model the bound-to-continuum absorption of type-II quantum rings (QRs) using a multiband source-radiation approach using the retarded Green function in the cylindrical coordinate system. The selection rules due to the circular symmetry for allowed transitions of absorption are utilized. The bound-tocontinuum absorptions of type-II GaSb coupled and uncoupled QRs embedded in GaAs matrix are compared here. The GaSb QRs act as energy barriers for electrons but potential wells for holes. For the coupled QR structure, the region sandwiched between two QRs forms a potential reservoir of quasi-bound electrons. Electrons in these states, though look like bound ones, would ultimately tunnel out of the reservoir through barriers. Multiband perfectly-matched layers are introduced to model the tunneling of quasi-bound states into open space. Resonance peaks are observed on the absorption spectra of type-II coupled QRs due to the formation of quasi-bound states in conduction bands, but no resonance exist in the uncoupled QR. The tunneling time of these metastable states can be extracted from the resonance and is in the order of ten femtoseconds. Absorption of coupled QRs is significantly enhanced as compared to that of uncoupled ones in certain spectral windows of interest. These features may improve the performance of photon detectors and photovoltaic devices based on type-II semiconductor nanostructures.

Supramolecular Amino Acid Based Hydrogels: Probing the Contribution of Additive Molecules using NMR Spectroscopy

PubMed Central

Ramalhete, Susana M.; Nartowski, Karol P.; Sarathchandra, Nichola; Foster, Jamie S.; Round, Andrew N.; Angulo, Jesús

2017-01-01

Abstract Supramolecular hydrogels are composed of self‐assembled solid networks that restrict the flow of water. l‐Phenylalanine is the smallest molecule reported to date to form gel networks in water, and it is of particular interest due to its crystalline gel state. Single and multi‐component hydrogels of l‐phenylalanine are used herein as model materials to develop an NMR‐based analytical approach to gain insight into the mechanisms of supramolecular gelation. Structure and composition of the gel fibres were probed using PXRD, solid‐state NMR experiments and microscopic techniques. Solution‐state NMR studies probed the properties of free gelator molecules in an equilibrium with bound molecules. The dynamics of exchange at the gel/solution interfaces was investigated further using high‐resolution magic angle spinning (HR‐MAS) and saturation transfer difference (STD) NMR experiments. This approach allowed the identification of which additive molecules contributed in modifying the material properties. PMID:28401991

Quantum Black Hole Model and HAWKING’S Radiation

NASA Astrophysics Data System (ADS)

Berezin, Victor

The black hole model with a self-gravitating charged spherical symmetric dust thin shell as a source is considered. The Schroedinger-type equation for such a model is derived. This equation appeared to be a finite differences equation. A theory of such an equation is developed and general solution is found and investigated in details. The discrete spectrum of the bound state energy levels is obtained. All the eigenvalues appeared to be infinitely degenerate. The ground state wave functions are evaluated explicitly. The quantum black hole states are selected and investigated. It is shown that the obtained black hole mass spectrum is compatible with the existence of Hawking’s radiation in the limit of low temperatures both for large and nearly extreme Reissner-Nordstrom black holes. The above mentioned infinite degeneracy of the mass (energy) eigenvalues may appeared helpful in resolving the well known information paradox in the black hole physics.

Quantum-Fluctuation-Driven Crossover from a Dilute Bose-Einstein Condensate to a Macrodroplet in a Dipolar Quantum Fluid

NASA Astrophysics Data System (ADS)

Chomaz, L.; Baier, S.; Petter, D.; Mark, M. J.; Wächtler, F.; Santos, L.; Ferlaino, F.

2016-10-01

In a joint experimental and theoretical effort, we report on the formation of a macrodroplet state in an ultracold bosonic gas of erbium atoms with strong dipolar interactions. By precise tuning of the s -wave scattering length below the so-called dipolar length, we observe a smooth crossover of the ground state from a dilute Bose-Einstein condensate to a dense macrodroplet state of more than 2 ×104 atoms . Based on the study of collective excitations and loss features, we prove that quantum fluctuations stabilize the ultracold gas far beyond the instability threshold imposed by mean-field interactions. Finally, we perform expansion measurements, showing that although self-bound solutions are prevented by losses, the interplay between quantum stabilization and losses results in a minimal time-of-flight expansion velocity at a finite scattering length.

Search for weakly decaying Λn ‾ and ΛΛ exotic bound states in central Pb-Pb collisions at √{sNN} = 2.76 TeV

NASA Astrophysics Data System (ADS)

Adam, J.; Adamová, D.; Aggarwal, M. M.; Aglieri Rinella, G.; Agnello, M.; Agrawal, N.; Ahammed, Z.; Ahmed, I.; Ahn, S. U.; Aimo, I.; Aiola, S.; Ajaz, M.; Akindinov, A.; Alam, S. N.; Aleksandrov, D.; Alessandro, B.; Alexandre, D.; Alfaro Molina, R.; Alici, A.; Alkin, A.; Alme, J.; Alt, T.; Altinpinar, S.; Altsybeev, I.; Alves Garcia Prado, C.; Andrei, C.; Andronic, A.; Anguelov, V.; Anielski, J.; Antičić, T.; Antinori, F.; Antonioli, P.; Aphecetche, L.; Appelshäuser, H.; Arcelli, S.; Armesto, N.; Arnaldi, R.; Aronsson, T.; Arsene, I. C.; Arslandok, M.; Augustinus, A.; Averbeck, R.; Azmi, M. D.; Bach, M.; Badalà, A.; Baek, Y. W.; Bagnasco, S.; Bailhache, R.; Bala, R.; Baldisseri, A.; Ball, M.; Baltasar Dos Santos Pedrosa, F.; Baral, R. C.; Barbano, A. M.; Barbera, R.; Barile, F.; Barnaföldi, G. G.; Barnby, L. S.; Barret, V.; Bartalini, P.; Bartke, J.; Bartsch, E.; Basile, M.; Bastid, N.; Basu, S.; Bathen, B.; Batigne, G.; Batista Camejo, A.; Batyunya, B.; Batzing, P. C.; Bearden, I. G.; Beck, H.; Bedda, C.; Behera, N. K.; Belikov, I.; Bellini, F.; Bello Martinez, H.; Bellwied, R.; Belmont, R.; Belmont-Moreno, E.; Belyaev, V.; Bencedi, G.; Beole, S.; Berceanu, I.; Bercuci, A.; Berdnikov, Y.; Berenyi, D.; Bertens, R. A.; Berzano, D.; Betev, L.; Bhasin, A.; Bhat, I. R.; Bhati, A. K.; Bhattacharjee, B.; Bhom, J.; Bianchi, L.; Bianchi, N.; Bianchin, C.; Bielčík, J.; Bielčíková, J.; Bilandzic, A.; Biswas, S.; Bjelogrlic, S.; Blanco, F.; Blau, D.; Blume, C.; Bock, F.; Bogdanov, A.; Bøggild, H.; Boldizsár, L.; Bombara, M.; Book, J.; Borel, H.; Borissov, A.; Borri, M.; Bossú, F.; Botje, M.; Botta, E.; Böttger, S.; Braun-Munzinger, P.; Bregant, M.; Breitner, T.; Broker, T. A.; Browning, T. A.; Broz, M.; Brucken, E. J.; Bruna, E.; Bruno, G. E.; Budnikov, D.; Buesching, H.; Bufalino, S.; Buncic, P.; Busch, O.; Buthelezi, Z.; Buxton, J. T.; Caffarri, D.; Cai, X.; Caines, H.; Calero Diaz, L.; Caliva, A.; Calvo Villar, E.; Camerini, P.; Carena, F.; Carena, W.; Castillo Castellanos, J.; Castro, A. J.; Casula, E. A. R.; Cavicchioli, C.; Ceballos Sanchez, C.; Cepila, J.; Cerello, P.; Chang, B.; Chapeland, S.; Chartier, M.; Charvet, J. L.; Chattopadhyay, S.; Chattopadhyay, S.; Chelnokov, V.; Cherney, M.; Cheshkov, C.; Cheynis, B.; Chibante Barroso, V.; Chinellato, D. D.; Chochula, P.; Choi, K.; Chojnacki, M.; Choudhury, S.; Christakoglou, P.; Christensen, C. H.; Christiansen, P.; Chujo, T.; Chung, S. U.; Cicalo, C.; Cifarelli, L.; Cindolo, F.; Cleymans, J.; Colamaria, F.; Colella, D.; Collu, A.; Colocci, M.; Conesa Balbastre, G.; Conesa del Valle, Z.; Connors, M. E.; Contreras, J. G.; Cormier, T. M.; Corrales Morales, Y.; Cortés Maldonado, I.; Cortese, P.; Cosentino, M. R.; Costa, F.; Crochet, P.; Cruz Albino, R.; Cuautle, E.; Cunqueiro, L.; Dahms, T.; Dainese, A.; Danu, A.; Das, D.; Das, I.; Das, S.; Dash, A.; Dash, S.; De, S.; De Caro, A.; de Cataldo, G.; de Cuveland, J.; De Falco, A.; De Gruttola, D.; De Marco, N.; De Pasquale, S.; Deisting, A.; Deloff, A.; Dénes, E.; D'Erasmo, G.; Di Bari, D.; Di Mauro, A.; Di Nezza, P.; Diaz Corchero, M. A.; Dietel, T.; Dillenseger, P.; Divià, R.; Djuvsland, Ø.; Dobrin, A.; Dobrowolski, T.; Domenicis Gimenez, D.; Dönigus, B.; Dordic, O.; Dubey, A. K.; Dubla, A.; Ducroux, L.; Dupieux, P.; Ehlers, R. J.; Elia, D.; Engel, H.; Erazmus, B.; Erhardt, F.; Eschweiler, D.; Espagnon, B.; Estienne, M.; Esumi, S.; Evans, D.; Evdokimov, S.; Eyyubova, G.; Fabbietti, L.; Fabris, D.; Faivre, J.; Fantoni, A.; Fasel, M.; Feldkamp, L.; Felea, D.; Feliciello, A.; Feofilov, G.; Ferencei, J.; Fernández Téllez, A.; Ferreiro, E. G.; Ferretti, A.; Festanti, A.; Figiel, J.; Figueredo, M. A. S.; Filchagin, S.; Finogeev, D.; Fionda, F. M.; Fiore, E. M.; Fleck, M. G.; Floris, M.; Foertsch, S.; Foka, P.; Fokin, S.; Fragiacomo, E.; Francescon, A.; Frankenfeld, U.; Fuchs, U.; Furget, C.; Furs, A.; Fusco Girard, M.; Gaardhøje, J. J.; Gagliardi, M.; Gago, A. M.; Gallio, M.; Gangadharan, D. R.; Ganoti, P.; Gao, C.; Garabatos, C.; Garcia-Solis, E.; Gargiulo, C.; Gasik, P.; Germain, M.; Gheata, A.; Gheata, M.; Ghosh, P.; Ghosh, S. K.; Gianotti, P.; Giubellino, P.; Giubilato, P.; Gladysz-Dziadus, E.; Glässel, P.; Gomez Ramirez, A.; González-Zamora, P.; Gorbunov, S.; Görlich, L.; Gotovac, S.; Grabski, V.; Graczykowski, L. K.; Grelli, A.; Grigoras, A.; Grigoras, C.; Grigoriev, V.; Grigoryan, A.; Grigoryan, S.; Grinyov, B.; Grion, N.; Grosse-Oetringhaus, J. F.; Grossiord, J.-Y.; Grosso, R.; Guber, F.; Guernane, R.; Guerzoni, B.; Gulbrandsen, K.; Gulkanyan, H.; Gunji, T.; Gupta, A.; Gupta, R.; Haake, R.; Haaland, Ø.; Hadjidakis, C.; Haiduc, M.; Hamagaki, H.; Hamar, G.; Hanratty, L. D.; Hansen, A.; Harris, J. W.; Hartmann, H.; Harton, A.; Hatzifotiadou, D.; Hayashi, S.; Heckel, S. T.; Heide, M.; Helstrup, H.; Herghelegiu, A.; Herrera Corral, G.; Hess, B. A.; Hetland, K. F.; Hilden, T. E.; Hillemanns, H.; Hippolyte, B.; Hristov, P.; Huang, M.; Humanic, T. J.; Hussain, N.; Hussain, T.; Hutter, D.; Hwang, D. S.; Ilkaev, R.; Ilkiv, I.; Inaba, M.; Ionita, C.; Ippolitov, M.; Irfan, M.; Ivanov, M.; Ivanov, V.; Izucheev, V.; Jachołkowski, A.; Jacobs, P. M.; Jahnke, C.; Jang, H. J.; Janik, M. A.; Jayarathna, P. H. S. Y.; Jena, C.; Jena, S.; Jimenez Bustamante, R. T.; Jones, P. G.; Jung, H.; Jusko, A.; Kalinak, P.; Kalweit, A.; Kamin, J.; Kang, J. H.; Kaplin, V.; Kar, S.; Karasu Uysal, A.; Karavichev, O.; Karavicheva, T.; Karpechev, E.; Kebschull, U.; Keidel, R.; Keijdener, D. L. D.; Keil, M.; Khan, K. H.; Khan, M. M.; Khan, P.; Khan, S. A.; Khanzadeev, A.; Kharlov, Y.; Kileng, B.; Kim, B.; Kim, D. W.; Kim, D. J.; Kim, H.; Kim, J. S.; Kim, M.; Kim, M.; Kim, S.; Kim, T.; Kirsch, S.; Kisel, I.; Kiselev, S.; Kisiel, A.; Kiss, G.; Klay, J. L.; Klein, C.; Klein, J.; Klein-Bösing, C.; Kluge, A.; Knichel, M. L.; Knospe, A. G.; Kobayashi, T.; Kobdaj, C.; Kofarago, M.; Köhler, M. K.; Kollegger, T.; Kolojvari, A.; Kondratiev, V.; Kondratyeva, N.; Kondratyuk, E.; Konevskikh, A.; Kouzinopoulos, C.; Kovalenko, V.; Kowalski, M.; Kox, S.; Koyithatta Meethaleveedu, G.; Kral, J.; Králik, I.; Kravčáková, A.; Krelina, M.; Kretz, M.; Krivda, M.; Krizek, F.; Kryshen, E.; Krzewicki, M.; Kubera, A. M.; Kučera, V.; Kucheriaev, Y.; Kugathasan, T.; Kuhn, C.; Kuijer, P. G.; Kulakov, I.; Kumar, J.; Kumar, L.; Kurashvili, P.; Kurepin, A.; Kurepin, A. B.; Kuryakin, A.; Kushpil, S.; Kweon, M. J.; Kwon, Y.; La Pointe, S. L.; La Rocca, P.; Lagana Fernandes, C.; Lakomov, I.; Langoy, R.; Lara, C.; Lardeux, A.; Lattuca, A.; Laudi, E.; Lea, R.; Leardini, L.; Lee, G. R.; Lee, S.; Legrand, I.; Lehnert, J.; Lemmon, R. C.; Lenti, V.; Leogrande, E.; León Monzón, I.; Leoncino, M.; Lévai, P.; Li, S.; Li, X.; Lien, J.; Lietava, R.; Lindal, S.; Lindenstruth, V.; Lippmann, C.; Lisa, M. A.; Ljunggren, H. M.; Lodato, D. F.; Loenne, P. I.; Loggins, V. R.; Loginov, V.; Loizides, C.; Lopez, X.; López Torres, E.; Lowe, A.; Lu, X.-G.; Luettig, P.; Lunardon, M.; Luparello, G.; Maevskaya, A.; Mager, M.; Mahajan, S.; Mahmood, S. M.; Maire, A.; Majka, R. D.; Malaev, M.; Maldonado Cervantes, I.; Malinina, L.; Mal'Kevich, D.; Malzacher, P.; Mamonov, A.; Manceau, L.; Manko, V.; Manso, F.; Manzari, V.; Marchisone, M.; Mareš, J.; Margagliotti, G. V.; Margotti, A.; Margutti, J.; Marín, A.; Markert, C.; Marquard, M.; Martashvili, I.; Martin, N. A.; Martin Blanco, J.; Martinengo, P.; Martínez, M. I.; Martínez García, G.; Martinez Pedreira, M.; Martynov, Y.; Mas, A.; Masciocchi, S.; Masera, M.; Masoni, A.; Massacrier, L.; Mastroserio, A.; Matyja, A.; Mayer, C.; Mazer, J.; Mazzoni, M. A.; Mcdonald, D.; Meddi, F.; Menchaca-Rocha, A.; Meninno, E.; Mercado Pérez, J.; Meres, M.; Miake, Y.; Mieskolainen, M. M.; Mikhaylov, K.; Milano, L.; Milosevic, J.; Minervini, L. M.; Mischke, A.; Mishra, A. N.; Miśkowiec, D.; Mitra, J.; Mitu, C. M.; Mohammadi, N.; Mohanty, B.; Molnar, L.; Montaño Zetina, L.; Montes, E.; Morando, M.; Moretto, S.; Morreale, A.; Morsch, A.; Muccifora, V.; Mudnic, E.; Mühlheim, D.; Muhuri, S.; Mukherjee, M.; Müller, H.; Mulligan, J. D.; Munhoz, M. G.; Murray, S.; Musa, L.; Musinsky, J.; Nandi, B. K.; Nania, R.; Nappi, E.; Naru, M. U.; Nattrass, C.; Nayak, K.; Nayak, T. K.; Nazarenko, S.; Nedosekin, A.; Nellen, L.; Ng, F.; Nicassio, M.; Niculescu, M.; Niedziela, J.; Nielsen, B. S.; Nikolaev, S.; Nikulin, S.; Nikulin, V.; Noferini, F.; Nomokonov, P.; Nooren, G.; Norman, J.; Nyanin, A.; Nystrand, J.; Oeschler, H.; Oh, S.; Oh, S. K.; Ohlson, A.; Okatan, A.; Okubo, T.; Olah, L.; Oleniacz, J.; Oliveira Da Silva, A. C.; Oliver, M. H.; Onderwaater, J.; Oppedisano, C.; Ortiz Velasquez, A.; Oskarsson, A.; Otwinowski, J.; Oyama, K.; Ozdemir, M.; Pachmayer, Y.; Pagano, P.; Paić, G.; Pajares, C.; Pal, S. K.; Pan, J.; Pandey, A. K.; Pant, D.; Papikyan, V.; Pappalardo, G. S.; Pareek, P.; Park, W. J.; Parmar, S.; Passfeld, A.; Paticchio, V.; Paul, B.; Pawlak, T.; Peitzmann, T.; Pereira Da Costa, H.; Pereira De Oliveira Filho, E.; Peresunko, D.; Pérez Lara, C. E.; Peskov, V.; Pestov, Y.; Petráček, V.; Petrov, V.; Petrovici, M.; Petta, C.; Piano, S.; Pikna, M.; Pillot, P.; Pinazza, O.; Pinsky, L.; Piyarathna, D. B.; Płoskoń, M.; Planinic, M.; Pluta, J.; Pochybova, S.; Podesta-Lerma, P. L. M.; Poghosyan, M. G.; Polichtchouk, B.; Poljak, N.; Poonsawat, W.; Pop, A.; Porteboeuf-Houssais, S.; Porter, J.; Pospisil, J.; Prasad, S. K.; Preghenella, R.; Prino, F.; Pruneau, C. A.; Pshenichnov, I.; Puccio, M.; Puddu, G.; Pujahari, P.; Punin, V.; Putschke, J.; Qvigstad, H.; Rachevski, A.; Raha, S.; Rajput, S.; Rak, J.; Rakotozafindrabe, A.; Ramello, L.; Raniwala, R.; Raniwala, S.; Räsänen, S. S.; Rascanu, B. T.; Rathee, D.; Razazi, V.; Read, K. F.; Real, J. S.; Redlich, K.; Reed, R. J.; Rehman, A.; Reichelt, P.; Reicher, M.; Reidt, F.; Ren, X.; Renfordt, R.; Reolon, A. R.; Reshetin, A.; Rettig, F.; Revol, J.-P.; Reygers, K.; Riabov, V.; Ricci, R. A.; Richert, T.; Richter, M.; Riedler, P.; Riegler, W.; Riggi, F.; Ristea, C.; Rivetti, A.; Rocco, E.; Rodríguez Cahuantzi, M.; Rodriguez Manso, A.; Røed, K.; Rogochaya, E.; Rohr, D.; Röhrich, D.; Romita, R.; Ronchetti, F.; Ronflette, L.; Rosnet, P.; Rossi, A.; Roukoutakis, F.; Roy, A.; Roy, C.; Roy, P.; Rubio Montero, A. J.; Rui, R.; Russo, R.; Ryabinkin, E.; Ryabov, Y.; Rybicki, A.; Sadovsky, S.; Šafařík, K.; Sahlmuller, B.; Sahoo, P.; Sahoo, R.; Sahoo, S.; Sahu, P. K.; Saini, J.; Sakai, S.; Saleh, M. A.; Salgado, C. A.; Salzwedel, J.; Sambyal, S.; Samsonov, V.; Sanchez Castro, X.; Šándor, L.; Sandoval, A.; Sano, M.; Santagati, G.; Sarkar, D.; Scapparone, E.; Scarlassara, F.; Scharenberg, R. P.; Schiaua, C.; Schicker, R.; Schmidt, C.; Schmidt, H. R.; Schuchmann, S.; Schukraft, J.; Schulc, M.; Schuster, T.; Schutz, Y.; Schwarz, K.; Schweda, K.; Scioli, G.; Scomparin, E.; Scott, R.; Seeder, K. S.; Seger, J. E.; Sekiguchi, Y.; Selyuzhenkov, I.; Senosi, K.; Seo, J.; Serradilla, E.; Sevcenco, A.; Shabanov, A.; Shabetai, A.; Shadura, O.; Shahoyan, R.; Shangaraev, A.; Sharma, A.; Sharma, N.; Shigaki, K.; Shtejer, K.; Sibiriak, Y.; Siddhanta, S.; Sielewicz, K. M.; Siemiarczuk, T.; Silvermyr, D.; Silvestre, C.; Simatovic, G.; Simonetti, G.; Singaraju, R.; Singh, R.; Singha, S.; Singhal, V.; Sinha, B. C.; Sinha, T.; Sitar, B.; Sitta, M.; Skaali, T. B.; Slupecki, M.; Smirnov, N.; Snellings, R. J. M.; Snellman, T. W.; Søgaard, C.; Soltz, R.; Song, J.; Song, M.; Song, Z.; Soramel, F.; Sorensen, S.; Spacek, M.; Spiriti, E.; Sputowska, I.; Spyropoulou-Stassinaki, M.; Srivastava, B. K.; Stachel, J.; Stan, I.; Stefanek, G.; Steinpreis, M.; Stenlund, E.; Steyn, G.; Stiller, J. H.; Stocco, D.; Strmen, P.; Suaide, A. A. P.; Sugitate, T.; Suire, C.; Suleymanov, M.; Sultanov, R.; Šumbera, M.; Symons, T. J. M.; Szabo, A.; Szanto de Toledo, A.; Szarka, I.; Szczepankiewicz, A.; Szymanski, M.; Takahashi, J.; Tanaka, N.; Tangaro, M. A.; Tapia Takaki, J. D.; Tarantola Peloni, A.; Tariq, M.; Tarzila, M. G.; Tauro, A.; Tejeda Muñoz, G.; Telesca, A.; Terasaki, K.; Terrevoli, C.; Teyssier, B.; Thäder, J.; Thomas, D.; Tieulent, R.; Timmins, A. R.; Toia, A.; Trogolo, S.; Trubnikov, V.; Trzaska, W. H.; Tsuji, T.; Tumkin, A.; Turrisi, R.; Tveter, T. S.; Ullaland, K.; Uras, A.; Usai, G. L.; Utrobicic, A.; Vajzer, M.; Vala, M.; Valencia Palomo, L.; Vallero, S.; Van Der Maarel, J.; Van Hoorne, J. W.; van Leeuwen, M.; Vanat, T.; Vande Vyvre, P.; Varga, D.; Vargas, A.; Vargyas, M.; Varma, R.; Vasileiou, M.; Vasiliev, A.; Vauthier, A.; Vechernin, V.; Veen, A. M.; Veldhoen, M.; Velure, A.; Venaruzzo, M.; Vercellin, E.; Vergara Limón, S.; Vernet, R.; Verweij, M.; Vickovic, L.; Viesti, G.; Viinikainen, J.; Vilakazi, Z.; Villalobos Baillie, O.; Vinogradov, A.; Vinogradov, L.; Vinogradov, Y.; Virgili, T.; Vislavicius, V.; Viyogi, Y. P.; Vodopyanov, A.; Völkl, M. A.; Voloshin, K.; Voloshin, S. A.; Volpe, G.; von Haller, B.; Vorobyev, I.; Vranic, D.; Vrláková, J.; Vulpescu, B.; Vyushin, A.; Wagner, B.; Wagner, J.; Wang, H.; Wang, M.; Wang, Y.; Watanabe, D.; Weber, M.; Weber, S. G.; Wessels, J. P.; Westerhoff, U.; Wiechula, J.; Wikne, J.; Wilde, M.; Wilk, G.; Wilkinson, J.; Williams, M. C. S.; Windelband, B.; Winn, M.; Yaldo, C. G.; Yamaguchi, Y.; Yang, H.; Yang, P.; Yano, S.; Yasnopolskiy, S.; Yin, Z.; Yokoyama, H.; Yoo, I.-K.; Yurchenko, V.; Yushmanov, I.; Zaborowska, A.; Zaccolo, V.; Zaman, A.; Zampolli, C.; Zanoli, H. J. C.; Zaporozhets, S.; Zarochentsev, A.; Závada, P.; Zaviyalov, N.; Zbroszczyk, H.; Zgura, I. S.; Zhalov, M.; Zhang, H.; Zhang, X.; Zhang, Y.; Zhao, C.; Zhigareva, N.; Zhou, D.; Zhou, Y.; Zhou, Z.; Zhu, H.; Zhu, J.; Zhu, X.; Zichichi, A.; Zimmermann, A.; Zimmermann, M. B.; Zinovjev, G.; Zyzak, M.

2016-01-01

We present results of a search for two hypothetical strange dibaryon states, i.e. the H-dibaryon and the possible Λn ‾ bound state. The search is performed with the ALICE detector in central (0-10%) Pb-Pb collisions at √{sNN} = 2.76 TeV, by invariant mass analysis in the decay modes Λn ‾ → d ‾π+ and H-dibaryon → Λpπ-. No evidence for these bound states is observed. Upper limits are determined at 99% confidence level for a wide range of lifetimes and for the full range of branching ratios. The results are compared to thermal, coalescence and hybrid UrQMD model expectations, which describe correctly the production of other loosely bound states, like the deuteron and the hypertriton.

Search for weakly decaying Λ n - and ΛΛ exotic bound states in central Pb–Pb collisions at s NN = 2.76  TeV

DOE Office of Scientific and Technical Information (OSTI.GOV)

Adam, J.; Adamová, D.; Aggarwal, M. M.

Here, we present results of a search for two hypothetical strange dibaryon states, i.e. the H-dibaryon and the possiblemore » $$\\overline{Λn}$$ bound state. The search is performed with the ALICE detector in central (0-10%) Pb-Pb collisions at $$\\sqrt{s}$$$_ {NN}$$ = 2.76 TeV, by invariant mass analysis in the decay modes $$\\overline{Λn}$$ → $$\\bar{d}$$π + and H-dibaryon →Λpπ -. No evidence for these bound states is observed. Upper limits are determined at 99% confidence level for a wide range of lifetimes and for the full range of branching ratios. The results are compared to thermal, coalescence and hybrid UrQMD model expectations, which describe correctly the production of other loosely bound states, like the deuteron and the hypertriton.« less

Emergent gauge field for a chiral bound state on curved surface

NASA Astrophysics Data System (ADS)

Shi, Zhe-Yu; Zhai, Hui

2017-09-01

Emergent physics is one of the most important concepts in modern physics, and one of the most intriguing examples is the emergent gauge field. Here we show that a gauge field emerges for a chiral bound state formed by two attractively interacting particles on a curved surface. We demonstrate explicitly that the center-of-mass wave function of such a deeply bound state is monopole harmonic instead of spherical harmonic, which means that the bound state experiences a magnetic monopole at the center of the sphere. This emergent gauge field is due to the coupling between the center-of-mass and the relative motion on a curved surface, and our results can be generalized to an arbitrary curved surface. This result establishes an intriguing connection between the space curvature and gauge field, and paves an alternative way to engineer a topological state with space curvature, and may be observed in a cold atom system.

Search for weakly decaying Λ n - and ΛΛ exotic bound states in central Pb–Pb collisions at s NN = 2.76  TeV

DOE PAGES

Adam, J.; Adamová, D.; Aggarwal, M. M.; ...

2016-11-28

Here, we present results of a search for two hypothetical strange dibaryon states, i.e. the H-dibaryon and the possiblemore » $$\\overline{Λn}$$ bound state. The search is performed with the ALICE detector in central (0-10%) Pb-Pb collisions at $$\\sqrt{s}$$$_ {NN}$$ = 2.76 TeV, by invariant mass analysis in the decay modes $$\\overline{Λn}$$ → $$\\bar{d}$$π + and H-dibaryon →Λpπ -. No evidence for these bound states is observed. Upper limits are determined at 99% confidence level for a wide range of lifetimes and for the full range of branching ratios. The results are compared to thermal, coalescence and hybrid UrQMD model expectations, which describe correctly the production of other loosely bound states, like the deuteron and the hypertriton.« less

Pump-dump iterative squeezing of vibrational wave packets.

PubMed

Chang, Bo Y; Sola, Ignacio R

2005-12-22

The free motion of a nonstationary vibrational wave packet in an electronic potential is a source of interesting quantum properties. In this work we propose an iterative scheme that allows continuous stretching and squeezing of a wave packet in the ground or in an excited electronic state, by switching the wave function between both potentials with pi pulses at certain times. Using a simple model of displaced harmonic oscillators and delta pulses, we derive the analytical solution and the conditions for its possible implementation and optimization in different molecules and electronic states. We show that the main constraining parameter is the pulse bandwidth. Although in principle the degree of squeezing (or stretching) is not bounded, the physical resources increase quadratically with the number of iterations, while the achieved squeezing only increases linearly.

Classical heat transport in anharmonic molecular junctions: exact solutions.

PubMed

Liu, Sha; Agarwalla, Bijay Kumar; Wang, Jian-Sheng; Li, Baowen

2013-02-01

We study full counting statistics for classical heat transport through anharmonic or nonlinear molecular junctions formed by interacting oscillators. An analytical result of the steady-state heat flux for an overdamped anharmonic junction with arbitrary temperature bias is obtained. It is found that the thermal conductance can be expressed in terms of a temperature-dependent effective force constant. The role of anharmonicity is identified. We also give the general formula for the second cumulant of heat in steady state, as well as the average geometric heat flux when two system parameters are modulated adiabatically. We present an anharmonic example for which all cumulants for heat can be obtained exactly. For a bounded single oscillator model with mass we found that the cumulants are independent of the nonlinear potential.

Distributing Earthquakes Among California's Faults: A Binary Integer Programming Approach

NASA Astrophysics Data System (ADS)

Geist, E. L.; Parsons, T.

2016-12-01

Statement of the problem is simple: given regional seismicity specified by a Gutenber-Richter (G-R) relation, how are earthquakes distributed to match observed fault-slip rates? The objective is to determine the magnitude-frequency relation on individual faults. The California statewide G-R b-value and a-value are estimated from historical seismicity, with the a-value accounting for off-fault seismicity. UCERF3 consensus slip rates are used, based on geologic and geodetic data and include estimates of coupling coefficients. The binary integer programming (BIP) problem is set up such that each earthquake from a synthetic catalog spanning millennia can occur at any location along any fault. The decision vector, therefore, consists of binary variables, with values equal to one indicating the location of each earthquake that results in an optimal match of slip rates, in an L1-norm sense. Rupture area and slip associated with each earthquake are determined from a magnitude-area scaling relation. Uncertainty bounds on the UCERF3 slip rates provide explicit minimum and maximum constraints to the BIP model, with the former more important to feasibility of the problem. There is a maximum magnitude limit associated with each fault, based on fault length, providing an implicit constraint. Solution of integer programming problems with a large number of variables (>105 in this study) has been possible only since the late 1990s. In addition to the classic branch-and-bound technique used for these problems, several other algorithms have been recently developed, including pre-solving, sifting, cutting planes, heuristics, and parallelization. An optimal solution is obtained using a state-of-the-art BIP solver for M≥6 earthquakes and California's faults with slip-rates > 1 mm/yr. Preliminary results indicate a surprising diversity of on-fault magnitude-frequency relations throughout the state.

Ammonium Ion Binding to DNA G-Quadruplexes: Do Electrospray Mass Spectra Faithfully Reflect the Solution-Phase Species?

NASA Astrophysics Data System (ADS)

Balthasart, Françoise; Plavec, Janez; Gabelica, Valérie

2013-01-01

G-quadruplex nucleic acids can bind ammonium ions in solution, and these complexes can be detected by electrospray mass spectrometry (ESI-MS). However, because ammonium ions are volatile, the extent to which ESI-MS quantitatively could provide an accurate reflection of such solution-phase equilibria is unclear. Here we studied five G-quadruplexes having known solution-phase structure and ammonium ion binding constants: the bimolecular G-quadruplexes (dG4T4G4)2, (dG4T3G4)2, and (dG3T4G4)2, and the intramolecular G-quadruplexes dG4(T4G4)3 and dG2T2G2TGTG2T2G2 (thrombin binding aptamer). We found that not all mass spectrometers are equally suited to reflect the solution phase species. Ion activation can occur in the electrospray source, or in a high-pressure traveling wave ion mobility cell. When the softest instrumental conditions are used, ammonium ions bound between G-quartets, but also additional ammonium ions bound at specific sites outside the external G-quartets, can be observed. However, even specifically bound ammonium ions are in some instances too labile to be fully retained in the gas phase structures, and although the ammonium ion distribution observed by ESI-MS shows biases at specific stoichiometries, the relative abundances in solution are not always faithfully reflected. Ion mobility spectrometry results show that all inter-quartet ammonium ions are necessary to preserve the G-quadruplex fold in the gas phase. Ion mobility experiments, therefore, help assign the number of inner ammonium ions in the solution phase structure.[Figure not available: see fulltext.

Numerical Implementation of the Cohesive Soil Bounding Surface Plasticity Model. Volume I.

DTIC Science & Technology

1983-02-01

AD-R24 866 NUMERICAL IMPLEMENTATION OF THE COHESIVE SOIL BOUNDING 1/2 SURFACE PLASTICITY ..(U) CALIFORNIA UNIV DAVIS DEPT OF CIVIL ENGINEERING L R...a study of various numerical means for implementing the bounding surface plasticity model for cohesive soils is presented. A comparison is made of... Plasticity Models 17 3.4 Selection Of Methods For Comparison 17 3.5 Theory 20 3.5.1 Solution Methods 20 3.5.2 Reduction Of The Number Of Equation

Study of weak solutions for parabolic variational inequalities with nonstandard growth conditions.

PubMed

Dong, Yan

2018-01-01

In this paper, we study the degenerate parabolic variational inequality problem in a bounded domain. First, the weak solutions of the variational inequality are defined. Second, the existence and uniqueness of the solutions in the weak sense are proved by using the penalty method and the reduction method.

S-matrix method for the numerical determination of bound states.

NASA Technical Reports Server (NTRS)

Bhatia, A. K.; Madan, R. N.

1973-01-01

A rapid numerical technique for the determination of bound states of a partial-wave-projected Schroedinger equation is presented. First, one needs to integrate the equation only outwards as in the scattering case, and second, the number of trials necessary to determine the eigenenergy and the corresponding eigenfunction is considerably less than in the usual method. As a nontrivial example of the technique, bound states are calculated in the exchange approximation for the e-/He+ system and l equals 1 partial wave.

On bound-states of the Gross Neveu model with massive fundamental fermions

NASA Astrophysics Data System (ADS)

Frishman, Yitzhak; Sonnenschein, Jacob

2018-01-01

In the search for QFT's that admit boundstates, we reinvestigate the two dimensional Gross-Neveu model, but with massive fermions. By computing the self-energy for the auxiliary boundstate field and the effective potential, we show that there are no bound states around the lowest minimum, but there is a meta-stable bound state around the other minimum, a local one. The latter decays by tunneling. We determine the dependence of its lifetime on the fermion mass and coupling constant.

(Quasi)-convexification of Barta's (multi-extrema) bounding theorem: Inf_x\\big(\\ssty\\frac{H\\Phi(x)}{\\Phi(x)} \\big) \\le E_gr \\le Sup_x \\big(\\ssty\\frac{H\\Phi(x)}{\\Phi(x)} \\big)

NASA Astrophysics Data System (ADS)

Handy, C. R.

2006-03-01

There has been renewed interest in the exploitation of Barta's configuration space theorem (BCST) (Barta 1937 C. R. Acad. Sci. Paris 204 472) which bounds the ground-state energy, Inf_x\\big({{H\\Phi(x)}\\over {\\Phi(x)}} \\big ) \\leq E_gr \\leq Sup_x \\big({{H\\Phi(x)}\\over {\\Phi(x)}}\\big) , by using any Φ lying within the space of positive, bounded, and sufficiently smooth functions, {\\cal C} . Mouchet's (Mouchet 2005 J. Phys. A: Math. Gen. 38 1039) BCST analysis is based on gradient optimization (GO). However, it overlooks significant difficulties: (i) appearance of multi-extrema; (ii) inefficiency of GO for stiff (singular perturbation/strong coupling) problems; (iii) the nonexistence of a systematic procedure for arbitrarily improving the bounds within {\\cal C} . These deficiencies can be corrected by transforming BCST into a moments' representation equivalent, and exploiting a generalization of the eigenvalue moment method (EMM), within the context of the well-known generalized eigenvalue problem (GEP), as developed here. EMM is an alternative eigenenergy bounding, variational procedure, overlooked by Mouchet, which also exploits the positivity of the desired physical solution. Furthermore, it is applicable to Hermitian and non-Hermitian systems with complex-number quantization parameters (Handy and Bessis 1985 Phys. Rev. Lett. 55 931, Handy et al 1988 Phys. Rev. Lett. 60 253, Handy 2001 J. Phys. A: Math. Gen. 34 5065, Handy et al 2002 J. Phys. A: Math. Gen. 35 6359). Our analysis exploits various quasi-convexity/concavity theorems common to the GEP representation. We outline the general theory, and present some illustrative examples.

The charge conserving Poisson-Boltzmann equations: Existence, uniqueness, and maximum principle

DOE Office of Scientific and Technical Information (OSTI.GOV)

Lee, Chiun-Chang, E-mail: chlee@mail.nhcue.edu.tw

2014-05-15

The present article is concerned with the charge conserving Poisson-Boltzmann (CCPB) equation in high-dimensional bounded smooth domains. The CCPB equation is a Poisson-Boltzmann type of equation with nonlocal coefficients. First, under the Robin boundary condition, we get the existence of weak solutions to this equation. The main approach is variational, based on minimization of a logarithm-type energy functional. To deal with the regularity of weak solutions, we establish a maximum modulus estimate for the standard Poisson-Boltzmann (PB) equation to show that weak solutions of the CCPB equation are essentially bounded. Then the classical solutions follow from the elliptic regularity theorem.more » Second, a maximum principle for the CCPB equation is established. In particular, we show that in the case of global electroneutrality, the solution achieves both its maximum and minimum values at the boundary. However, in the case of global non-electroneutrality, the solution may attain its maximum value at an interior point. In addition, under certain conditions on the boundary, we show that the global non-electroneutrality implies pointwise non-electroneutrality.« less

Surface complexation of carboxylate adheres Cryptosporidium parvum öocysts to the hematite-water interface

USGS Publications Warehouse

Gao, X.; Metge, D.W.; Ray, C.; Harvey, R.W.; Chorover, J.

2009-01-01

The interaction of viable Cryptosporidium parvum öocysts at the hematite (α-Fe2O3)−water interface was examined over a wide range in solution chemistry using in situ attenuated total reflectance Fourier transform infrared (ATR-FTIR) spectroscopy. Spectra for hematite-sorbed öocysts showed distinct changes in carboxylate group vibrations relative to spectra obtained in the absence of hematite, indicative of direct chemical bonding between carboxylate groups and Fe metal centers of the hematite surface. The data also indicate that complexation modes vary with solution chemistry. In NaCl solution, öocysts are bound to hematite via monodentate and binuclear bidentate complexes. The former predominates at low pH, whereas the latter becomes increasingly prevalent with increasing pH. In a CaCl2 solution, only binuclear bidentate complexes are observed. When solution pH is above the point of zero net proton charge (PZNPC) of hematite, öocyst surface carboxylate groups are bound to the mineral surface via outer-sphere complexes in both electrolyte solutions.

Bound and resonance states of the dipolar anion of hydrogen cyanide: Competition between threshold effects and rotation in an open quantum system

DOE PAGES

Fossez, K.; Michel, N.; Nazarewicz, W.; ...

2015-01-12

In this paper, bound and resonance states of the dipole-bound anion of hydrogen cyanide HCN – are studied using a nonadiabatic pseudopotential method and the Berggren expansion technique involving bound states, decaying resonant states, and nonresonant scattering continuum. We devise an algorithm to identify the resonant states in the complex energy plane. To characterize spatial distributions of electronic wave functions, we introduce the body-fixed density and use it to assign families of resonant states into collective rotational bands. We find that the nonadiabatic coupling of electronic motion to molecular rotation results in a transition from the strong-coupling to weak-coupling regime.more » In the strong-coupling limit, the electron moving in a subthreshold, spatially extended halo state follows the rotational motion of the molecule. Above the ionization threshold, the electron's motion in a resonance state becomes largely decoupled from molecular rotation. Finally, the widths of resonance-band members depend primarily on the electron orbital angular momentum.« less

Interaction of Huntingtin Exon-1 Peptides with Lipid-Based Micellar Nanoparticles Probed by Solution NMR and Q-Band Pulsed EPR.

PubMed

Ceccon, Alberto; Schmidt, Thomas; Tugarinov, Vitali; Kotler, Samuel A; Schwieters, Charles D; Clore, G Marius

2018-05-23

Lipid-based micellar nanoparticles promote aggregation of huntingtin exon-1 peptides. Here we characterize the interaction of two such peptides, htt NT Q  7 and htt NT Q  10 comprising the N-terminal amphiphilic domain of huntingtin followed by 7 and 10 glutamine repeats, respectively, with 8 nm lipid micelles using NMR chemical exchange saturation transfer (CEST), circular dichroism and pulsed Q-band EPR. Exchange between free and micelle-bound htt NT Q  n peptides occurs on the millisecond time scale with a K D ∼ 0.5-1 mM. Upon binding micelles, residues 1-15 adopt a helical conformation. Oxidation of Met 7 to a sulfoxide reduces the binding affinity for micelles ∼3-4-fold and increases the length of the helix by a further two residues. A structure of the bound monomer unit is calculated from the backbone chemical shifts of the micelle-bound state obtained from CEST. Pulsed Q-band EPR shows that a monomer-dimer equilibrium exists on the surface of the micelles and that the two helices of the dimer adopt a parallel orientation, thereby bringing two disordered polyQ tails into close proximity which may promote aggregation upon dissociation from the micelle surface.

The role of bound potassium ions in the hydrolysis of low concentrations of adenosine triphosphate by preparations of membrane fragments from ox brain cerebral cortex

PubMed Central

Goldfarb, P. S. G.; Rodnight, R.

1970-01-01

1. The intrinsic Na+, K+, Mg2+ and Ca2+ contents of a preparation of membrane fragments from ox brain were determined by emission flame photometry. 2. Centrifugal washing of the preparation with imidazole-buffered EDTA solutions decreased the bound Na+ from 90±20 to 24±12, the bound K+ from 27±3 to 7±2, the bound Mg2+ from 20±2 to 3±1 and the bound calcium from 8±1 to <1nmol/mg of protein. 3. The activities of the Na++K++Mg2+-stimulated adenosine triphosphatase and the Na+-dependent reaction forming bound phosphate were compared in the unwashed and washed preparations at an ATP concentration of 2.5μm (ATP/protein ratio 12.5pmol/μg). 4. The Na+-dependent hydrolysis of ATP as well as the plateau concentration of bound phosphate and the rate of dephosphorylation were decreased in the washed preparation. The time-course of formation and decline of bound phosphate was fully restored by the addition of 2.5μm-magnesium chloride and 2μm-potassium chloride. Addition of 2.5μm-magnesium chloride alone fully restored the plateau concentration of bound phosphate, but the rate of dephosphorylation was only slightly increased. Na+-dependent ATP hydrolysis was partly restored with 2.5μm-magnesium chloride; addition of K+ in the range 2–10μm-potassium chloride then further restored hydrolysis but not to the control rate. 5. Pretreatment of the washed preparation at 0°C with 0.5nmol of K+/mg of protein so that the final added K+ in the reaction mixture was 0.1μm restored the Na+-dependent hydrolysis of ATP and the time-course of the reaction forming bound phosphate. 6. The binding of [42K]potassium chloride by the washed membrane preparation was examined. Binding in a solution containing 10nmol of K+/mg of protein was linear over a period of 20min and was inhibited by Na+. Half-maximal inhibition of 42K+-binding required a 100-fold excess of sodium chloride. 7. It was concluded (a) that a significant fraction of the apparent Na+-dependent hydrolysis of ATP observed in the unwashed preparation is due to activation by bound K+ and Mg2+ of the Na++K++Mg2+-stimulated adenosine triphosphatase system and (b) that the enzyme system is able to bind K+ from a solution of 0.5μm-potassium chloride. PMID:4250237

Majorana bound states in the finite-length chain

NASA Astrophysics Data System (ADS)

Zvyagin, A. A.

2015-08-01

Recent experiments investigating edge states in ferromagnetic atomic chains on superconducting substrate are analyzed. In particular, finite size effects are considered. It is shown how the energy of the Majorana bound state depends on the length of the chain, as well as on the parameters of the model. Oscillations of the energy of the bound edge state in the chain as a function of the length of the chain, and as a function of the applied voltage (or the chemical potential) are studied. In particular, it has been shown that oscillations can exist only for some values of the effective potential.

Evolution of complexity following a global quench

NASA Astrophysics Data System (ADS)

Moosa, Mudassir

2018-03-01

The rate of complexification of a quantum state is conjectured to be bounded from above by the average energy of the state. A different conjecture relates the complexity of a holographic CFT state to the on-shell gravitational action of a certain bulk region. We use `complexity equals action' conjecture to study the time evolution of the complexity of the CFT state after a global quench. We find that the rate of growth of complexity is not only consistent with the conjectured bound, but it also saturates the bound soon after the system has achieved local equilibrium.

Subgap in the Surface Bound States Spectrum of Superfluid (3) 3 He-B with Rough Surface

NASA Astrophysics Data System (ADS)

Nagato, Y.; Higashitani, S.; Nagai, K.

2018-03-01

The subgap structure in the surface bound states spectrum of superfluid ^3He-B with rough surface is discussed. The subgap is formed by the level repulsion between the surface bound state and the continuum states in the course of multiple scattering by the surface roughness. We show that the level repulsion is originated from the nature of the wave function of the surface bound state that is now recognized as Majorana fermion. We study the superfluid ^3He-B with a rough surface and in a magnetic field perpendicular to the surface using the quasi-classical Green function together with a random S-matrix model. We calculate the self-consistent order parameters, the spin polarization density and the surface density of states. It is shown that the subgap is found also in a magnetic field perpendicular to the surface. The magnetic field dependence of the transverse acoustic impedance is also discussed.

Shooting quasiparticles from Andreev bound states in a superconducting constriction

DOE Office of Scientific and Technical Information (OSTI.GOV)

Riwar, R.-P.; Houzet, M.; Meyer, J. S.

2014-12-15

A few-channel superconducting constriction provides a set of discrete Andreev bound states that may be populated with quasiparticles. Motivated by recent experimental research, we study the processes in an a.c. driven constriction whereby a quasiparticle is promoted to the delocalized states outside the superconducting gap and flies away. We distinguish two processes of this kind. In the process of ionization, a quasiparticle present in the Andreev bound state is transferred to the delocalized states leaving the constriction. The refill process involves two quasiparticles: one flies away while another one appears in the Andreev bound state. We notice an interesting asymmetrymore » of these processes. The electron-like quasiparticles are predominantly emitted to one side of the constriction while the hole-like ones are emitted to the other side. This produces a charge imbalance of accumulated quasiparticles, that is opposite on opposite sides of the junction. The imbalance may be detected with a tunnel contact to a normal metal lead.« less

SURE - SEMI-MARKOV UNRELIABILITY RANGE EVALUATOR (VAX VMS VERSION)

NASA Technical Reports Server (NTRS)

Butler, R. W.

1994-01-01

The Semi-Markov Unreliability Range Evaluator, SURE, is an analysis tool for reconfigurable, fault-tolerant systems. Traditional reliability analyses are based on aggregates of fault-handling and fault-occurrence models. SURE provides an efficient means for calculating accurate upper and lower bounds for the death state probabilities for a large class of semi-Markov models, not just those which can be reduced to critical-pair architectures. The calculated bounds are close enough (usually within 5 percent of each other) for use in reliability studies of ultra-reliable computer systems. The SURE bounding theorems have algebraic solutions and are consequently computationally efficient even for large and complex systems. SURE can optionally regard a specified parameter as a variable over a range of values, enabling an automatic sensitivity analysis. Highly reliable systems employ redundancy and reconfiguration as methods of ensuring operation. When such systems are modeled stochastically, some state transitions are orders of magnitude faster than others; that is, fault recovery is usually faster than fault arrival. SURE takes these time differences into account. Slow transitions are described by exponential functions and fast transitions are modeled by either the White or Lee theorems based on means, variances, and percentiles. The user must assign identifiers to every state in the system and define all transitions in the semi-Markov model. SURE input statements are composed of variables and constants related by FORTRAN-like operators such as =, +, *, SIN, EXP, etc. There are a dozen major commands such as READ, READO, SAVE, SHOW, PRUNE, TRUNCate, CALCulator, and RUN. Once the state transitions have been defined, SURE calculates the upper and lower probability bounds for entering specified death states within a specified mission time. SURE output is tabular. The mathematical approach chosen to solve a reliability problem may vary with the size and nature of the problem. Although different solution techniques are utilized on different programs, it is possible to have a common input language. The Systems Validation Methods group at NASA Langley Research Center has created a set of programs that form the basis for a reliability analysis workstation. The set of programs are: SURE reliability analysis program (COSMIC program LAR-13789, LAR-14921); the ASSIST specification interface program (LAR-14193, LAR-14923), PAWS/STEM reliability analysis programs (LAR-14165, LAR-14920); and the FTC fault tree tool (LAR-14586, LAR-14922). FTC is used to calculate the top-event probability for a fault tree. PAWS/STEM and SURE are programs which interpret the same SURE language, but utilize different solution methods. ASSIST is a preprocessor that generates SURE language from a more abstract definition. SURE, ASSIST, and PAWS/STEM are also offered as a bundle. Please see the abstract for COS-10039/COS-10041, SARA - SURE/ASSIST Reliability Analysis Workstation, for pricing details. SURE was originally developed for DEC VAX series computers running VMS and was later ported for use on Sun computers running SunOS. The VMS version (LAR13789) is written in PASCAL, C-language, and FORTRAN 77. The standard distribution medium for the VMS version of SURE is a 9-track 1600 BPI magnetic tape in VMSINSTAL format. It is also available on a TK50 tape cartridge in VMSINSTAL format. Executables are included. The Sun UNIX version (LAR14921) is written in ANSI C-language and PASCAL. An ANSI compliant C compiler is required in order to compile the C portion of this package. The standard distribution medium for the Sun version of SURE is a .25 inch streaming magnetic tape cartridge in UNIX tar format. Both Sun3 and Sun4 executables are included. SURE was developed in 1988 and last updated in 1992. DEC, VAX, VMS, and TK50 are trademarks of Digital Equipment Corporation. TEMPLATE is a registered trademark of Template Graphics Software, Inc. UNIX is a registered trademark of AT&T Bell Laboratories. Sun3 and Sun4 are trademarks of Sun Microsystems, Inc.

SURE - SEMI-MARKOV UNRELIABILITY RANGE EVALUATOR (SUN VERSION)

NASA Technical Reports Server (NTRS)

Butler, R. W.

1994-01-01

The Semi-Markov Unreliability Range Evaluator, SURE, is an analysis tool for reconfigurable, fault-tolerant systems. Traditional reliability analyses are based on aggregates of fault-handling and fault-occurrence models. SURE provides an efficient means for calculating accurate upper and lower bounds for the death state probabilities for a large class of semi-Markov models, not just those which can be reduced to critical-pair architectures. The calculated bounds are close enough (usually within 5 percent of each other) for use in reliability studies of ultra-reliable computer systems. The SURE bounding theorems have algebraic solutions and are consequently computationally efficient even for large and complex systems. SURE can optionally regard a specified parameter as a variable over a range of values, enabling an automatic sensitivity analysis. Highly reliable systems employ redundancy and reconfiguration as methods of ensuring operation. When such systems are modeled stochastically, some state transitions are orders of magnitude faster than others; that is, fault recovery is usually faster than fault arrival. SURE takes these time differences into account. Slow transitions are described by exponential functions and fast transitions are modeled by either the White or Lee theorems based on means, variances, and percentiles. The user must assign identifiers to every state in the system and define all transitions in the semi-Markov model. SURE input statements are composed of variables and constants related by FORTRAN-like operators such as =, +, *, SIN, EXP, etc. There are a dozen major commands such as READ, READO, SAVE, SHOW, PRUNE, TRUNCate, CALCulator, and RUN. Once the state transitions have been defined, SURE calculates the upper and lower probability bounds for entering specified death states within a specified mission time. SURE output is tabular. The mathematical approach chosen to solve a reliability problem may vary with the size and nature of the problem. Although different solution techniques are utilized on different programs, it is possible to have a common input language. The Systems Validation Methods group at NASA Langley Research Center has created a set of programs that form the basis for a reliability analysis workstation. The set of programs are: SURE reliability analysis program (COSMIC program LAR-13789, LAR-14921); the ASSIST specification interface program (LAR-14193, LAR-14923), PAWS/STEM reliability analysis programs (LAR-14165, LAR-14920); and the FTC fault tree tool (LAR-14586, LAR-14922). FTC is used to calculate the top-event probability for a fault tree. PAWS/STEM and SURE are programs which interpret the same SURE language, but utilize different solution methods. ASSIST is a preprocessor that generates SURE language from a more abstract definition. SURE, ASSIST, and PAWS/STEM are also offered as a bundle. Please see the abstract for COS-10039/COS-10041, SARA - SURE/ASSIST Reliability Analysis Workstation, for pricing details. SURE was originally developed for DEC VAX series computers running VMS and was later ported for use on Sun computers running SunOS. The VMS version (LAR13789) is written in PASCAL, C-language, and FORTRAN 77. The standard distribution medium for the VMS version of SURE is a 9-track 1600 BPI magnetic tape in VMSINSTAL format. It is also available on a TK50 tape cartridge in VMSINSTAL format. Executables are included. The Sun UNIX version (LAR14921) is written in ANSI C-language and PASCAL. An ANSI compliant C compiler is required in order to compile the C portion of this package. The standard distribution medium for the Sun version of SURE is a .25 inch streaming magnetic tape cartridge in UNIX tar format. Both Sun3 and Sun4 executables are included. SURE was developed in 1988 and last updated in 1992. DEC, VAX, VMS, and TK50 are trademarks of Digital Equipment Corporation. TEMPLATE is a registered trademark of Template Graphics Software, Inc. UNIX is a registered trademark of AT&T Bell Laboratories. Sun3 and Sun4 are trademarks of Sun Microsystems, Inc.

Low-dimensional Representation of Error Covariance

NASA Technical Reports Server (NTRS)

Tippett, Michael K.; Cohn, Stephen E.; Todling, Ricardo; Marchesin, Dan

2000-01-01

Ensemble and reduced-rank approaches to prediction and assimilation rely on low-dimensional approximations of the estimation error covariances. Here stability properties of the forecast/analysis cycle for linear, time-independent systems are used to identify factors that cause the steady-state analysis error covariance to admit a low-dimensional representation. A useful measure of forecast/analysis cycle stability is the bound matrix, a function of the dynamics, observation operator and assimilation method. Upper and lower estimates for the steady-state analysis error covariance matrix eigenvalues are derived from the bound matrix. The estimates generalize to time-dependent systems. If much of the steady-state analysis error variance is due to a few dominant modes, the leading eigenvectors of the bound matrix approximate those of the steady-state analysis error covariance matrix. The analytical results are illustrated in two numerical examples where the Kalman filter is carried to steady state. The first example uses the dynamics of a generalized advection equation exhibiting nonmodal transient growth. Failure to observe growing modes leads to increased steady-state analysis error variances. Leading eigenvectors of the steady-state analysis error covariance matrix are well approximated by leading eigenvectors of the bound matrix. The second example uses the dynamics of a damped baroclinic wave model. The leading eigenvectors of a lowest-order approximation of the bound matrix are shown to approximate well the leading eigenvectors of the steady-state analysis error covariance matrix.

Phonon coupling in optical transitions for singlet-triplet pairs of bound excitons in semiconductors

NASA Astrophysics Data System (ADS)

Pistol, M. E.; Monemar, B.

1986-05-01

A model is presented for the observed strong difference in selection rules for coupling of phonons in the one-phonon sideband of optical spectra related to bound excitons in semiconductors. The present treatment is specialized to the case of a closely spaced pair of singlet-triplet character as the lowest electronic states, as is common for bound excitons associated with neutral complexes in materials like GaP and Si. The optical transition for the singlet bound-exciton state is found to couple strongly only to symmetric A1 modes. The triplet state has a similar coupling strength to A1 modes, but in addition strong contributions are found for replicas corresponding to high-density-of-states phonons TAX, LAX, and TOX. This can be explained by a treatment of particle-phonon coupling beyond the ordinary adiabatic approximation. A weak mixing between the singlet and triplet states is mediated by the phonon coupling, as described in first-order perturbation theory. The model derived in this work, for such phonon-induced mixing of closely spaced electronic states, is shown to explain the observed phonon coupling for several bound-exciton systems of singlet-triplet character in GaP. In addition, the observed oscillator strength of the forbidden triplet state may be explained as partly derived from phonon-induced mixing with the singlet state, which has a much larger oscillator strength.

Exchangeability of N termini in the ligand-gated porins of Escherichia coli.

PubMed

Scott, D C; Cao, Z; Qi, Z; Bauler, M; Igo, J D; Newton, S M; Klebba, P E

2001-04-20

The ferric siderophore transporters of the Gram-negative bacterial outer membrane manifest a unique architecture: Their N termini fold into a globular domain that lodges within, and physically obstructs, a transmembrane porin beta-barrel formed by their C termini. We exchanged and deleted the N termini of two such siderophore receptors, FepA and FhuA, which recognize and transport ferric enterobactin and ferrichrome, respectively. The resultant chimeric proteins and empty beta-barrels avidly bound appropriate ligands, including iron complexes, protein toxins, and viruses. Thus, the ability to recognize and discriminate these molecules fully originates in the transmembrane beta-barrel domain. Both the hybrid and the deletion proteins also transported the ferric siderophore that they bound. The FepA constructs showed less transport activity than wild type receptor protein, but the FhuA constructs functioned with turnover numbers that were equivalent to wild type. The mutant proteins displayed the full range of transport functionalities, despite their aberrant or missing N termini, confirming (Braun, M., Killmann, H., and Braun, V. (1999) Mol. Microbiol. 33, 1037-1049) that the globular domain within the pore is dispensable to the siderophore internalization reaction, and when present, acts without specificity during solute uptake. These and other data suggest a transport process in which siderophore receptors undergo multiple conformational states that ultimately expel the N terminus from the channel concomitant with solute internalization.

Comparision of Incidental Reflection From Containerized Maintenance/Housekeeping Solutions and One Inch of Water

DOE Office of Scientific and Technical Information (OSTI.GOV)

Chapman, Bryan Scott; MacQuigg, Michael Robert; Wysong, Andrew Russell

This document addresses the incidental reflector reactivity worth of containerized maintenance/housekeeping fluids for use in PF-4 at Los Alamos National Laboratory (LANL). The intent of the document is to analyze containerized maintenance/housekeeping fluids which will be analyzed as water that may be present under normal conditions of an operation. The reactivity worth is compared to the reactivity worth due to I-inch of close-fitting 4n water reflection and I-inch of close-fitting radial water reflection. Both have been used to bound incidental reflection by 2-liter bottles in criticality safety evaluations. The conclusion is that, when the maintenance/housekeeping fluids are containerized the reactivitymore » increase from a configuration which is bounding of normal conditions (up to eight bottles modeled with 2-liters of solution at varying diameter) is bound by I-inch of close fitting 4n water relection.« less

Real-time spectral interferometry probes the internal dynamics of femtosecond soliton molecules

NASA Astrophysics Data System (ADS)

Herink, G.; Kurtz, F.; Jalali, B.; Solli, D. R.; Ropers, C.

2017-04-01

Solitons, particle-like excitations ubiquitous in many fields of physics, have been shown to exhibit bound states akin to molecules. The formation of such temporal soliton bound states and their internal dynamics have escaped direct experimental observation. By means of an emerging time-stretch technique, we resolve the evolution of femtosecond soliton molecules in the cavity of a few-cycle mode-locked laser. We track two- and three-soliton bound states over hundreds of thousands of consecutive cavity roundtrips, identifying fixed points and periodic and aperiodic molecular orbits. A class of trajectories acquires a path-dependent geometrical phase, implying that its dynamics may be topologically protected. These findings highlight the importance of real-time detection in resolving interactions in complex nonlinear systems, including the dynamics of soliton bound states, breathers, and rogue waves.

Internal structure of acceptor-bound excitons in wide-band-gap wurtzite semiconductors

NASA Astrophysics Data System (ADS)

Gil, Bernard; Bigenwald, Pierre; Paskov, Plamen P.; Monemar, Bo

2010-02-01

We describe the internal structure of acceptor-bound excitons in wurtzite semiconductors. Our approach consists in first constructing, in the context of angular momentum algebra, the wave functions of the two-hole system that fulfill Pauli’s exclusion’s principle. Second, we construct the acceptor-bound exciton states by adding the electron states in a similar manner that two-hole states are constructed. We discuss the optical selection rules for the acceptor-bound exciton recombination. Finally, we compare our theory with experimental data for CdS and GaN. In the specific case of CdS for which much experimental information is available, we demonstrate that, compared with cubic semiconductors, the sign of the short-range hole-exchange interaction is reversed and more than one order of magnitude larger. The whole set of data is interpreted in the context of a large value of the short-range hole-exchange interaction Ξ0=3.4±0.2meV . This value dictates the splitting between the ground-state line I1 and the other transitions. The values we find for the electron-hole spin-exchange interaction and of the crystal-field splitting of the two-hole state are, respectively, -0.4±0.1 and 0.2±0.1meV . In the case of GaN, the experimental data for the acceptor-bound excitons in the case of Mg and Zn acceptors, show more than one bound-exciton line. We discuss a possible assignment of these states.

Aggregation work at polydisperse micellization: ideal solution and "dressed micelle" models comparing to molecular dynamics simulations.

PubMed

Burov, S V; Shchekin, A K

2010-12-28

General thermodynamic relations for the work of polydisperse micelle formation in the model of ideal solution of molecular aggregates in nonionic surfactant solution and the model of "dressed micelles" in ionic solution have been considered. In particular, the dependence of the aggregation work on the total concentration of nonionic surfactant has been analyzed. The analogous dependence for the work of formation of ionic aggregates has been examined with regard to existence of two variables of a state of an ionic aggregate, the aggregation numbers of surface active ions and counterions. To verify the thermodynamic models, the molecular dynamics simulations of micellization in nonionic and ionic surfactant solutions at two total surfactant concentrations have been performed. It was shown that for nonionic surfactants, even at relatively high total surfactant concentrations, the shape and behavior of the work of polydisperse micelle formation found within the model of the ideal solution at different total surfactant concentrations agrees fairly well with the numerical experiment. For ionic surfactant solutions, the numerical results indicate a strong screening of ionic aggregates by the bound counterions. This fact as well as independence of the coefficient in the law of mass action for ionic aggregates on total surfactant concentration and predictable behavior of the "waterfall" lines of surfaces of the aggregation work upholds the model of "dressed" ionic aggregates.

Explicit formula for the Holevo bound for two-parameter qubit-state estimation problem

DOE Office of Scientific and Technical Information (OSTI.GOV)

Suzuki, Jun, E-mail: junsuzuki@uec.ac.jp

The main contribution of this paper is to derive an explicit expression for the fundamental precision bound, the Holevo bound, for estimating any two-parameter family of qubit mixed-states in terms of quantum versions of Fisher information. The obtained formula depends solely on the symmetric logarithmic derivative (SLD), the right logarithmic derivative (RLD) Fisher information, and a given weight matrix. This result immediately provides necessary and sufficient conditions for the following two important classes of quantum statistical models; the Holevo bound coincides with the SLD Cramér-Rao bound and it does with the RLD Cramér-Rao bound. One of the important results ofmore » this paper is that a general model other than these two special cases exhibits an unexpected property: the structure of the Holevo bound changes smoothly when the weight matrix varies. In particular, it always coincides with the RLD Cramér-Rao bound for a certain choice of the weight matrix. Several examples illustrate these findings.« less

The Structure of a High Fidelity DNA Polymerase Bound to a Mismatched Nucleotide Reveals an “Ajar” Intermediate Conformation in the Nucleotide Selection Mechanism*

PubMed Central

Wu, Eugene Y.; Beese, Lorena S.

2011-01-01

To achieve accurate DNA synthesis, DNA polymerases must rapidly sample and discriminate against incorrect nucleotides. Here we report the crystal structure of a high fidelity DNA polymerase I bound to DNA primer-template caught in the act of binding a mismatched (dG:dTTP) nucleoside triphosphate. The polymerase adopts a conformation in between the previously established “open” and “closed” states. In this “ajar” conformation, the template base has moved into the insertion site but misaligns an incorrect nucleotide relative to the primer terminus. The displacement of a conserved active site tyrosine in the insertion site by the template base is accommodated by a distinctive kink in the polymerase O helix, resulting in a partially open ternary complex. We suggest that the ajar conformation allows the template to probe incoming nucleotides for complementarity before closure of the enzyme around the substrate. Based on solution fluorescence, kinetics, and crystallographic analyses of wild-type and mutant polymerases reported here, we present a three-state reaction pathway in which nucleotides either pass through this intermediate conformation to the closed conformation and catalysis or are misaligned within the intermediate, leading to destabilization of the closed conformation. PMID:21454515

Hydrated Electron Transfer to Nucleobases in Aqueous Solutions Revealed by Ab Initio Molecular Dynamics Simulations.

PubMed

Zhao, Jing; Wang, Mei; Fu, Aiyun; Yang, Hongfang; Bu, Yuxiang

2015-08-03

We present an ab initio molecular dynamics (AIMD) simulation study into the transfer dynamics of an excess electron from its cavity-shaped hydrated electron state to a hydrated nucleobase (NB)-bound state. In contrast to the traditional view that electron localization at NBs (G/A/C/T), which is the first step for electron-induced DNA damage, is related only to dry or prehydrated electrons, and a fully hydrated electron no longer transfers to NBs, our AIMD simulations indicate that a fully hydrated electron can still transfer to NBs. We monitored the transfer dynamics of fully hydrated electrons towards hydrated NBs in aqueous solutions by using AIMD simulations and found that due to solution-structure fluctuation and attraction of NBs, a fully hydrated electron can transfer to a NB gradually over time. Concurrently, the hydrated electron cavity gradually reorganizes, distorts, and even breaks. The transfer could be completed in about 120-200 fs in four aqueous NB solutions, depending on the electron-binding ability of hydrated NBs and the structural fluctuation of the solution. The transferring electron resides in the π*-type lowest unoccupied molecular orbital of the NB, which leads to a hydrated NB anion. Clearly, the observed transfer of hydrated electrons can be attributed to the strong electron-binding ability of hydrated NBs over the hydrated electron cavity, which is the driving force, and the transfer dynamics is structure-fluctuation controlled. This work provides new insights into the evolution dynamics of hydrated electrons and provides some helpful information for understanding the DNA-damage mechanism in solution. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

A position-dependent mass model for the Thomas–Fermi potential: Exact solvability and relation to δ-doped semiconductors

DOE Office of Scientific and Technical Information (OSTI.GOV)

Schulze-Halberg, Axel, E-mail: xbataxel@gmail.com; García-Ravelo, Jesús; Pacheco-García, Christian

We consider the Schrödinger equation in the Thomas–Fermi field, a model that has been used for describing electron systems in δ-doped semiconductors. It is shown that the problem becomes exactly-solvable if a particular effective (position-dependent) mass distribution is incorporated. Orthogonal sets of normalizable bound state solutions are constructed in explicit form, and the associated energies are determined. We compare our results with the corresponding findings on the constant-mass problem discussed by Ioriatti (1990) [13]. -- Highlights: ► We introduce an exactly solvable, position-dependent mass model for the Thomas–Fermi potential. ► Orthogonal sets of solutions to our model are constructed inmore » closed form. ► Relation to delta-doped semiconductors is discussed. ► Explicit subband bottom energies are calculated and compared to results obtained in a previous study.« less

Challenges and solutions for the analysis of in situ , in crystallo micro-spectrophotometric data

DOE PAGES

Dworkowski, Florian S. N.; Hough, Michael A.; Pompidor, Guillaume; ...

2015-01-01

Combining macromolecular crystallography with in crystallo micro-spectrophotometry yields valuable complementary information on the sample, including the redox states of metal cofactors, the identification of bound ligands and the onset and strength of undesired photochemistry, also known as radiation damage. However, the analysis and processing of the resulting data differs significantly from the approaches used for solution spectrophotometric data. The varying size and shape of the sample, together with the suboptimal sample environment, the lack of proper reference signals and the general influence of the X-ray beam on the sample have to be considered and carefully corrected for. In the presentmore » article, we discuss how to characterize and treat these sample-dependent artefacts in a reproducible manner and we demonstrate the SLS-APE in situ, in crystallo optical spectroscopy data-analysis toolbox.« less

Chemical stabilization of graphite surfaces

DOE Office of Scientific and Technical Information (OSTI.GOV)

Bistrika, Alexander A.; Lerner, Michael M.

Embodiments of a device, or a component of a device, including a stabilized graphite surface, methods of stabilizing graphite surfaces, and uses for the devices or components are disclosed. The device or component includes a surface comprising graphite, and a plurality of haloaryl ions and/or haloalkyl ions bound to at least a portion of the graphite. The ions may be perhaloaryl ions and/or perhaloalkyl ions. In certain embodiments, the ions are perfluorobenzenesulfonate anions. Embodiments of the device or component including stabilized graphite surfaces may maintain a steady-state oxidation or reduction surface current density after being exposed to continuous oxidation conditionsmore » for a period of at least 1-100 hours. The device or component is prepared by exposing a graphite-containing surface to an acidic aqueous solution of the ions under oxidizing conditions. The device or component can be exposed in situ to the solution.« less

Replica Exchange with Solute Tempering: Efficiency in Large Scale Systems

PubMed Central

Huang, Xuhui; Hagen, Morten; Kim, Byungchan; Friesner, Richard A.; Zhou, Ruhong; Berne, B. J.

2009-01-01

We apply the recently developed replica exchange with solute tempering (REST) to three large solvated peptide systems: an α-helix, a β-hairpin, and a TrpCage, with these peptides defined as the “central group”. We find that our original implementation of REST is not always more efficient than the replica exchange method (REM). Specifically, we find that exchanges between folded (F) and unfolded (U) conformations with vastly different structural energies are greatly reduced by the nonappearance of the water self-interaction energy in the replica exchange acceptance probabilities. REST, however, is expected to remain useful for a large class of systems for which the energy gap between the two states is not large, such as weakly bound protein–ligand complexes. Alternatively, a shell of water molecules can be incorporated into the central group, as discussed in the original paper. PMID:17439169

Exact PDF equations and closure approximations for advective-reactive transport

DOE Office of Scientific and Technical Information (OSTI.GOV)

Venturi, D.; Tartakovsky, Daniel M.; Tartakovsky, Alexandre M.

2013-06-01

Mathematical models of advection–reaction phenomena rely on advective flow velocity and (bio) chemical reaction rates that are notoriously random. By using functional integral methods, we derive exact evolution equations for the probability density function (PDF) of the state variables of the advection–reaction system in the presence of random transport velocity and random reaction rates with rather arbitrary distributions. These PDF equations are solved analytically for transport with deterministic flow velocity and a linear reaction rate represented mathematically by a heterog eneous and strongly-correlated random field. Our analytical solution is then used to investigate the accuracy and robustness of the recentlymore » proposed large-eddy diffusivity (LED) closure approximation [1]. We find that the solution to the LED-based PDF equation, which is exact for uncorrelated reaction rates, is accurate even in the presence of strong correlations and it provides an upper bound of predictive uncertainty.« less

Atom-field dressed states in slow-light waveguide QED

NASA Astrophysics Data System (ADS)

Calajó, Giuseppe; Ciccarello, Francesco; Chang, Darrick; Rabl, Peter

2016-03-01

We discuss the properties of atom-photon bound states in waveguide QED systems consisting of single or multiple atoms coupled strongly to a finite-bandwidth photonic channel. Such bound states are formed by an atom and a localized photonic excitation and represent the continuum analog of the familiar dressed states in single-mode cavity QED. Here we present a detailed analysis of the linear and nonlinear spectral features associated with single- and multiphoton dressed states and show how the formation of bound states affects the waveguide-mediated dipole-dipole interactions between separated atoms. Our results provide both a qualitative and quantitative description of the essential strong-coupling processes in waveguide QED systems, which are currently being developed in the optical and microwave regimes.

W-Z-top-quark bags

DOE Office of Scientific and Technical Information (OSTI.GOV)

Crichigno, Marcos P.; Shuryak, Edward; Flambaum, Victor V.

2010-10-01

We discuss a new family of multiquanta-bound states in the standard model which exist due to the mutual Higgs-based attraction of the heaviest members of the standard model, namely, gauge quanta W, Z, and (anti)top quarks, t, t. We use a self-consistent mean-field approximation, up to a rather large particle number N. In this paper we do not focus on weakly bound, nonrelativistic bound states, but rather on 'bags' in which the Higgs vacuum expectation value is significantly modified or depleted. The minimal number N above which such states appear strongly depends on the ratio of the Higgs mass tomore » the masses of W, Z, t, t: For a light Higgs mass, m{sub H{approx}}50 GeV, bound states start from N{approx}O(10), but for a ''realistic'' Higgs mass, m{sub H{approx}}100 GeV, one finds metastable/bound W, Z bags only for N{approx}O(1000). We also found that in the latter case pure top bags disappear for all N, although top quarks can still be well bound to the W bags. Anticipating the cosmological applications (discussed in the following Article [Phys. Rev. D 82, 073019]) of these bags as 'doorway states' for baryosynthesis, we also consider here the existence of such metastable bags at finite temperatures, when standard-model parameters such as Higgs, gauge, and top masses are significantly modified.« less

The bound states of ultracold KRb molecules

NASA Astrophysics Data System (ADS)

Julienne, Paul; Hanna, Thomas

2009-03-01

Recently ultracold vibrational ground state ^40K^87Rb polar molecules have been made using magnetoassociation of two cold atoms to a weakly bound Feshbach molecule, followed by a two-color optical STIRAP process to transfer molecules to the molecular ground state [1]. We have used accurate potential energy curves for the singlet and triplet states of the KRb molecule [2] with coupled channels calculations to calculate all of the bound states of the ^40K^87Rb molecule as a function of magnetic field from the cold atom collision threshold to the v=0 ground state. We have also developed approximate models for understanding the changing properties of the molecular bound states as binding energy increases. Some overall conclusions from these calculations will be presented. [1] K.-K. Ni, S. Ospelkaus, M. H. G. de Miranda, A. Peer, B. Neyenhuis, J. J. Zirbel, S. Kotochigova, P. S. Julienne, D. S. Jin, and J. Ye, Science, 2008, 322, 231--235. [2] A. Pashov, O. Docenko, M. Tamanis, R. Ferber, H. Kn"ockel, and E. Tiemann, Phys. Rev. A, 2007, 76, 022511.

Resolving the Spatial Structures of Bound Hole States in Black Phosphorus.

PubMed

Qiu, Zhizhan; Fang, Hanyan; Carvalho, Alexandra; Rodin, A S; Liu, Yanpeng; Tan, Sherman J R; Telychko, Mykola; Lv, Pin; Su, Jie; Wang, Yewu; Castro Neto, A H; Lu, Jiong

2017-11-08

Understanding the local electronic properties of individual defects and dopants in black phosphorus (BP) is of great importance for both fundamental research and technological applications. Here, we employ low-temperature scanning tunnelling microscope (LT-STM) to probe the local electronic structures of single acceptors in BP. We demonstrate that the charge state of individual acceptors can be reversibly switched by controlling the tip-induced band bending. In addition, acceptor-related resonance features in the tunnelling spectra can be attributed to the formation of Rydberg-like bound hole states. The spatial mapping of the quantum bound states shows two distinct shapes evolving from an extended ellipse shape for the 1s ground state to a dumbbell shape for the 2p x excited state. The wave functions of bound hole states can be well-described using the hydrogen-like model with anisotropic effective mass, corroborated by our theoretical calculations. Our findings not only provide new insight into the many-body interactions around single dopants in this anisotropic two-dimensional material but also pave the way to the design of novel quantum devices.

Optical transitions in two-dimensional topological insulators with point defects

NASA Astrophysics Data System (ADS)

Sablikov, Vladimir A.; Sukhanov, Aleksei A.

2016-12-01

Nontrivial properties of electronic states in topological insulators are inherent not only to the surface and boundary states, but to bound states localized at structure defects as well. We clarify how the unusual properties of the defect-induced bound states are manifested in optical absorption spectra in two-dimensional topological insulators. The calculations are carried out for defects with short-range potential. We find that the defects give rise to the appearance of specific features in the absorption spectrum, which are an inherent property of topological insulators. They have the form of two or three absorption peaks that are due to intracenter transitions between electron-like and hole-like bound states.

Photochemical Dynamics of Intramolecular Singlet Fission

NASA Astrophysics Data System (ADS)

Lin, Zhou; Iwasaki, Hikari; Van Voorhis, Troy

2017-06-01

Singlet fission (SF) converts a singlet exciton (S_1) into a pair of triplet ones (T_1) via a ``multi-exciton'' (ME) intermediate: S_1 \\longleftrightarrow ^1ME \\longleftrightarrow ^1(T_1T_1) \\longrightarrow 2T_1. In exothermic cases, e.g., crystalline pentacene or its derivatives, the quantum yield of SF can reach 200%. With SF doubling the electric current generated by an incident high-energy photon, the solar conversion efficiency in pentacene-based organic photovoltaics (OPVs) can exceed the Shockley-Queisser limit of 33.7%. The ME state is popularly considered to be a dimeric state with significant charge transfer (CT) character that is strongly coupled to both S_1 and ^1(T_1T_1), while this local model lacks strong support from full quantum dynamics studies. Intramolecular SF (ISF) occurring to covalently-bound dimers in the solution phase is an excellent model for a straightforward dynamics simulation of local excitons. In the present study, we investigate the ISF mechanisms for three covalently-bound dimers of pentacene derivatives, including ortho-, meta-, and para-bis(6,13-bis(triisopropylsilylethynyl)pentacene)benzene, in non-protic solvents. Specifically, we propagate the real-time, non-adiabatic quantum mechanical/molecular mechanical (QM/MM) dynamics on the potential energy surfaces associated with the states of S_1, ^1(T_1T_1) and CT. We explore how the energies of these ISF-relevant states and the non-adiabatic couplings between each other fluctuate with time and the instantaneous molecular configuration (e.g., intermonomer distance and orientation). We also quantitatively compare Condon and non-Condon ISF dynamics with solution-phase spectroscopic data. Our results allow us to understand the roles of CT energy levels in the ISF mechanism and propose a design strategy to maximize ISF efficiency. M. B. Smith and J. Michl, Chem. Rev. 110, 6891 (2010). W. Shockley and H. J. Queisser, J. Appl. Phys. 32, 510 (1961). T. C. Berkelbach, M. S. Hybertsen, and D. R. Reichman, J. Chem. Phys. 141, 074705 (2014). M. G. Mavros, D. Hait, and T. A. Van Voorhis, J. Chem. Phys. 145, 214105 (2016). V. Vaissier, and T. A. Van Voorhis, in preparation.

Non-Abelian fermion parity interferometry of Majorana bound states in a Fermi sea

NASA Astrophysics Data System (ADS)

Dahan, Daniel; Tanhayi Ahari, Mostafa; Ortiz, Gerardo; Seradjeh, Babak; Grosfeld, Eytan

We study the quantum dynamics of Majorana and regular fermion bound states coupled to a one-dimensional lead. The dynamics following the quench in the coupling to the lead exhibits a series of dynamical revivals as the bound state propagates in the lead and reflects from the boundaries. We show that the nature of revivals for a single Majorana bound state depends uniquely on the presence of a resonant level in the lead. When two spatially separated Majorana modes are coupled to the lead, the revivals depend only on the phase difference between their host superconductors. Remarkably, the quench in this case effectively performs a fermion-parity interferometry between Majorana bound states, revealing their unique non-Abelian braiding. Using both analytical and numerical techniques, we find the pattern of fermion parity transfers following the quench, study its evolution in the presence of disorder and interactions, and thus, ascertain the fate of Majorana in a rough Fermi sea. Work supported in part by BSF Grant No. 2014345, ISF Grant Nos. 401/12 and 1626/16, EU Seventh Framework Programme (FP7/2007-2013) Grant No. 303742, NSF CAREER Grant DMR-1350663 and the College of Arts and Sciences at Indiana University.

The hyperbolic step potential: Anti-bound states, SUSY partners and Wigner time delays

DOE Office of Scientific and Technical Information (OSTI.GOV)

Gadella, M.; Kuru, Ş.; Negro, J., E-mail: jnegro@fta.uva.es

We study the scattering produced by a one dimensional hyperbolic step potential, which is exactly solvable and shows an unusual interest because of its asymmetric character. The analytic continuation of the scattering matrix in the momentum representation has a branch cut and an infinite number of simple poles on the negative imaginary axis which are related with the so called anti-bound states. This model does not show resonances. Using the wave functions of the anti-bound states, we obtain supersymmetric (SUSY) partners which are the series of Rosen–Morse II potentials. We have computed the Wigner reflection and transmission time delays formore » the hyperbolic step and such SUSY partners. Our results show that the more bound states a partner Hamiltonian has the smaller is the time delay. We also have evaluated time delays for the hyperbolic step potential in the classical case and have obtained striking similitudes with the quantum case. - Highlights: • The scattering matrix of hyperbolic step potential is studied. • The scattering matrix has a branch cut and an infinite number of poles. • The poles are associated to anti-bound states. • Susy partners using antibound states are computed. • Wigner time delays for the hyperbolic step and partner potentials are compared.« less

Electron accommodation dynamics in the DNA base thymine

NASA Astrophysics Data System (ADS)

King, Sarah B.; Stephansen, Anne B.; Yokoi, Yuki; Yandell, Margaret A.; Kunin, Alice; Takayanagi, Toshiyuki; Neumark, Daniel M.

2015-07-01

The dynamics of electron attachment to the DNA base thymine are investigated using femtosecond time-resolved photoelectron imaging of the gas phase iodide-thymine (I-T) complex. An ultraviolet pump pulse ejects an electron from the iodide and prepares an iodine-thymine temporary negative ion that is photodetached with a near-IR probe pulse. The resulting photoelectrons are analyzed with velocity-map imaging. At excitation energies ranging from -120 meV to +90 meV with respect to the vertical detachment energy (VDE) of 4.05 eV for I-T, both the dipole-bound and valence-bound negative ions of thymine are observed. A slightly longer rise time for the valence-bound state than the dipole-bound state suggests that some of the dipole-bound anions convert to valence-bound species. No evidence is seen for a dipole-bound anion of thymine at higher excitation energies, in the range of 0.6 eV above the I-T VDE, which suggests that if the dipole-bound anion acts as a "doorway" to the valence-bound anion, it only does so at excitation energies near the VDE of the complex.

Electron accommodation dynamics in the DNA base thymine.

PubMed

King, Sarah B; Stephansen, Anne B; Yokoi, Yuki; Yandell, Margaret A; Kunin, Alice; Takayanagi, Toshiyuki; Neumark, Daniel M

2015-07-14

The dynamics of electron attachment to the DNA base thymine are investigated using femtosecond time-resolved photoelectron imaging of the gas phase iodide-thymine (I(-)T) complex. An ultraviolet pump pulse ejects an electron from the iodide and prepares an iodine-thymine temporary negative ion that is photodetached with a near-IR probe pulse. The resulting photoelectrons are analyzed with velocity-map imaging. At excitation energies ranging from -120 meV to +90 meV with respect to the vertical detachment energy (VDE) of 4.05 eV for I(-)T, both the dipole-bound and valence-bound negative ions of thymine are observed. A slightly longer rise time for the valence-bound state than the dipole-bound state suggests that some of the dipole-bound anions convert to valence-bound species. No evidence is seen for a dipole-bound anion of thymine at higher excitation energies, in the range of 0.6 eV above the I(-)T VDE, which suggests that if the dipole-bound anion acts as a "doorway" to the valence-bound anion, it only does so at excitation energies near the VDE of the complex.

Tightening the entropic uncertainty bound in the presence of quantum memory

NASA Astrophysics Data System (ADS)

Adabi, F.; Salimi, S.; Haseli, S.

2016-06-01

The uncertainty principle is a fundamental principle in quantum physics. It implies that the measurement outcomes of two incompatible observables cannot be predicted simultaneously. In quantum information theory, this principle can be expressed in terms of entropic measures. M. Berta et al. [Nat. Phys. 6, 659 (2010), 10.1038/nphys1734] have indicated that uncertainty bound can be altered by considering a particle as a quantum memory correlating with the primary particle. In this article, we obtain a lower bound for entropic uncertainty in the presence of a quantum memory by adding an additional term depending on the Holevo quantity and mutual information. We conclude that our lower bound will be tightened with respect to that of Berta et al. when the accessible information about measurements outcomes is less than the mutual information about the joint state. Some examples have been investigated for which our lower bound is tighter than Berta et al.'s lower bound. Using our lower bound, a lower bound for the entanglement of formation of bipartite quantum states has been obtained, as well as an upper bound for the regularized distillable common randomness.

33 CFR 151.2040 - What are the mandatory ballast water management requirements for vessels equipped with ballast...

Code of Federal Regulations, 2010 CFR

2010-07-01

... United States and are bound for ports or places in the United States? 151.2040 Section 151.2040... Water Management for Control of Nonindigenous Species in Waters of the United States § 151.2040 What are... operate in the waters of the United States and are bound for ports or places in the United States? (a) A...