How to use retarded Green's functions in de Sitter spacetime
Higuchi, Atsushi; Cheong, Lee Yen
2008-10-15
We demonstrate in examples that the covariant retarded Green's functions in electromagnetism and linearized gravity work as expected in de Sitter spacetime. We first clarify how retarded Green's functions should be used in spacetimes with spacelike past infinity such as de Sitter spacetime. In particular, we remind the reader of a general formula which gives the field for given initial data on a Cauchy surface and a given source (a charge or stress-energy tensor distribution) in its future. We then apply this formula to three examples: (i) electromagnetism in the future of a Cauchy surface in Minkowski spacetime, (ii) electromagnetism in de Sitter spacetime, and (iii) linearized gravity in de Sitter spacetime. In each example the field is reproduced correctly as predicted by the general argument. In the third example we construct a linearized gravitational field from two equal point masses located at the 'North and South Poles' which is nonsingular on the cosmological horizon and satisfies a covariant gauge condition and show that this field is reproduced by the retarded Green's function with corresponding gauge parameters.
More on the covariant retarded Green's function for the electromagnetic field in de Sitter spacetime
Higuchi, Atsushi; Lee, Yen Cheong; Nicholas, Jack R.
2009-11-15
In a recent paper 2 it was shown in examples that the covariant retarded Green's functions in certain gauges for electromagnetism and linearized gravity can be used to reproduce field configurations correctly in spite of the spacelike nature of past infinity in de Sitter spacetime. In this paper we extend the work of Ref. 2 concerning the electromagnetic field and show that the covariant retarded Green's function with an arbitrary value of the gauge parameter reproduces the electromagnetic field from two opposite charges at antipodal points of de Sitter spacetime.
General Retarded Contact Self-energies in and beyond the Non-equilibrium Green's Functions Method
NASA Astrophysics Data System (ADS)
Kubis, Tillmann; He, Yu; Andrawis, Robert; Klimeck, Gerhard
2016-03-01
Retarded contact self-energies in the framework of nonequilibrium Green's functions allow to model the impact of lead structures on the device without explicitly including the leads in the actual device calculation. Most of the contact self-energy algorithms are limited to homogeneous or periodic, semi-infinite lead structures. In this work, the complex absorbing potential method is extended to solve retarded contact self-energies for arbitrary lead structures, including irregular and randomly disordered leads. This method is verified for regular leads against common approaches and on physically equivalent, but numerically different irregular leads. Transmission results on randomly alloyed In0.5Ga0.5As structures show the importance of disorder in the leads. The concept of retarded contact self-energies is expanded to model passivation of atomically resolved surfaces without explicitly increasing the device's Hamiltonian.
Measuring nonequilibrium retarded spin-spin Green's functions in an ion-trap-based quantum simulator
NASA Astrophysics Data System (ADS)
Yoshimura, Bryce T.; Freericks, J. K.
2016-05-01
Recently a variant on Ramsey interferometry for coupled spin-1 /2 systems was proposed to directly measure the retarded spin-spin Green's function. In conventional experimental situations, the spin system is initially in a nonequilibrium state before the Ramsey interferometry is performed, so we examine the nonequilibrium retarded spin-spin Green's functions within the transverse-field Ising model. We derive the lowest four spectral moments to understand the short-time behavior and we employ a Lehmann-like representation to determine the spectral behavior. We simulate a Ramsey protocol for a nonequilibrium quantum spin system that consists of a coherent superposition of the ground state and diabatically excited higher-energy states via a temporally ramped transverse magnetic field. We then apply the Ramsey spectroscopy protocol to the final Hamiltonian, which has a constant transverse field. The short time allows us to extract the initial transport of many-body correlations, while the long-time behavior relates to the excitation spectra of the Hamiltonian. Compressive sensing is employed in the data analysis to efficiently extract that spectra.
Innovative green technique for preparing of flame retardant cotton
Technology Transfer Automated Retrieval System (TEKTRAN)
Due to its environmentally benign character, microwave-assisted or supercritical carbon dioxide high pressure reactors are considered in green chemistry as a substitute for organic solvents in chemical reactions. In this paper, an innovative approach for preparation of flame retardant cotton fabric ...
Green Flame Retardant Cotton Highlofts for Mattresses and Upholstered Furniture
Technology Transfer Automated Retrieval System (TEKTRAN)
Green flame retardant (FR) barrier fabric is environmentally-friendly because it is from a natural renewable resource, biodegradable, economical, employing greige cotton that is soft to touch. Greige unbleached cotton is cheaper and softer than bleached cotton, thus, increasing its marketability par...
Plasma-enhanced synthesis of green flame retardant cellulosic materials
NASA Astrophysics Data System (ADS)
Totolin, Vladimir
The natural fiber-containing fabrics and composites are more environmentally friendly, and are used in transportation (automobiles, aerospace), military applications, construction industries (ceiling paneling, partition boards), consumer products, etc. Therefore, the flammability characteristics of the composites based on polymers and natural fibers play an important role. This dissertation presents the development of plasma assisted - green flame retardant coatings for cellulosic substrates. The overall objective of this work was to generate durable flame retardant treatment on cellulosic materials. In the first approach sodium silicate layers were pre-deposited onto clean cotton substrates and cross linked using low pressure, non-equilibrium oxygen plasma. A statistical design of experiments was used to optimize the plasma parameters. The modified cotton samples were tested for flammability using an automatic 45° angle flammability test chamber. Aging tests were conducted to evaluate the coating resistance during the accelerated laundry technique. The samples revealed a high flame retardant behavior and good thermal stability proved by thermo-gravimetric analysis. In the second approach flame retardant cellulosic materials have been produced using a silicon dioxide (SiO2) network coating. SiO 2 network armor was prepared through hydrolysis and condensation of the precursor tetraethyl orthosilicate (TEOS), prior coating the substrates, and was cross linked on the surface of the substrates using atmospheric pressure plasma (APP) technique. Due to protection effects of the SiO2 network armor, the cellulosic based fibers exhibit enhanced thermal properties and improved flame retardancy. In the third approach, the TEOS/APP treatments were extended to linen fabrics. The thermal analysis showed a higher char content and a strong endothermic process of the treated samples compared with control ones, indicating a good thermal stability. Also, the surface analysis proved
NASA Astrophysics Data System (ADS)
Challis, Lawrie; Sheard, Fred
2003-12-01
In 1828, an English miller from Nottingham published a mathematical essay that generated little response. George Green's analysis, however, has since found applications in areas ranging from classical electrostatics to modern quantum field theory.
Green application of flame retardant cotton fabric using supercritical carbon dioxide
Technology Transfer Automated Retrieval System (TEKTRAN)
Due to its environmentally benign character, supercritical carbon dioxide (scCO2) is considered in green chemistry as a substitute for organic solvents in chemical reactions. In this poster, an innovative approach for preparation of flame retardant woven and nonwoven fabrics were obtained by utiliz...
Adaptive and intellectual functioning in autistic and nonautistic retarded children.
Carpentieri, S; Morgan, S B
1996-12-01
This study examined the relationship between adaptive functioning on the Vineland Adaptive Behaviour Scale (VABS) and intellectual functioning on the Stanford-Binet Intelligence Scale, 4th edition (SB-IV) in autistic children and nonautistic retarded children of comparable CA and SB-IV composite score (IQ). The autistic group had lower scores than the retarded group in VABS adaptive composite, Socialization domain, and Communication domain, and SB-IV Verbal Reasoning area. VABS domain scores yielded higher classification rates than the SB-IV area scores in discriminating the two groups. Correlations between the two measures were much higher for the autistic group than for the retarded group. Results support the conclusion that the cognitive impairment in autism is reflected in greater impairment in adaptive behaviors than in mental retardation without autism. PMID:8986847
Interferometric seismoelectric Green's function representations
NASA Astrophysics Data System (ADS)
de Ridder, Sjoerd A. L.; Slob, Evert; Wapenaar, Kees
2009-09-01
Interferometric Green's function representations can be used to retrieve a Green's function between two receiver stations, effectively turning one receiver into a source. Through reciprocity theorems of the convolution and correlation types, we derive interferometric Green's function representations for coupled electromagnetic and seismic wave propagation in 1-D. These representations express a symmetrized Green's function in terms of correlations of sources distributed throughout the domain of reciprocity and on its boundary. The main challenge for practical implementation is the necessity of sources throughout a domain. Numerical examples show how this constraint can be relaxed for different configurations. In a configuration of two layers bounded by a vacuum, seismic noise sources behind the interface can be used to recover seismoelectric reflection responses that suffer from small amplitude losses, but are not corrupted by spurious events.
Work function measurements of dispenser cathodes by retarding potential method
NASA Astrophysics Data System (ADS)
Khairnar, Rajendra S.; Chopra, A. K.
1992-11-01
The work function of dispenser cathode pellets has been determined by means of the retarding potential technique. A low-energy electron gun was fabricated which delivers a collimated beam of electrons on the pellet surface at normal incidence. The set up is calibrated by employing samples of known work function such as gold and tungsten, prior to determining the work function of the cathode pellets. This set up provides a rapid determination of the work function of cathode pellets.
GREEN'S FUNCTIONS OF VORTEX OPERATORS
Polchinski, Joseph
1980-08-01
We study the Euclidean Green's functions of the 't Hooft vortex operator, primarily for Abelian gauge theories. The operator is written in terms of elementary fields, with emphasis on a form in which it appears as the exponential of a surface integral, We explore the requirement that the Green's functions depend only on the boundary of this surface, The Dirac veto problem appears in a new guise, We present a two dimensional ''solvable model" of a Dirac string, which suggests a new solution of the veto problem. The renormalization of the Green's functions of the Abelian Wilson loop and Abelian vortex operator is studied with the aid of the operator product expansion. In each case. an overall multiplication of the operator makes all Green's functions finite; a surprising cancellation of divergences occurs with the vortex operator. We present a brief discussion of the relation between the nature of the vacuum and the cluster properties of the Green's functions of the Wilson and vortex operators. for a general gauge theory. The surface-like cluster property of the vortex operator in an Abelian Higgs theory is explored in more detail.
Work function measurements by the field emission retarding potential method
NASA Technical Reports Server (NTRS)
Swanson, L. W.; Strayer, R. W.; Mackie, W. A.
1971-01-01
Using the field emission retarding potential method true work functions have been measured for the following monocrystalline substrates: W(110), W(111), W(100), Nb(100), Ni(100), Cu(100), Ir(110) and Ir(111). The electron elastic and inelastic reflection coefficients from several of these surfaces have also been examined near zero primary beam energy.
Work function measurements by the field emission retarding potential method.
NASA Technical Reports Server (NTRS)
Strayer, R. W.; Mackie, W.; Swanson, L. W.
1973-01-01
Description of the theoretical foundation of the field electron retarding potential method, and review of its experimental application to the measurement of single crystal face work functions. The results obtained from several substrates are discussed. An interesting and useful fallout from the experimental approach described is the ability to accurately measure the elastic and inelastic reflection coefficient for impinging electrons to near zero-volt energy.
Work function measurements using a field emission retarding potential technique.
Hamanaka, M H M O; Dall'Agnol, F F; Pimentel, V L; Mammana, V P; Tatsch, P J; den Engelsen, D
2016-03-01
Herein we describe the measurement of the work function of a metal with advanced equipment based on the field emission retarding potential (FERP) method using a carbon nanotube (CNT) as cathode. The accuracy of the FERP method using a CNT emitter is described and a comparison between measurements of the work functions of aluminum, barium, calcium, gold, and platinum with published data will be presented. Our FERP equipment could be optimized with the aid of particle tracing simulations. These simulations led us to insert a magnetic collimator to improve the collection efficiency at the anode. PMID:27036828
Work function measurements using a field emission retarding potential technique
NASA Astrophysics Data System (ADS)
Hamanaka, M. H. M. O.; Dall'Agnol, F. F.; Pimentel, V. L.; Mammana, V. P.; Tatsch, P. J.; den Engelsen, D.
2016-03-01
Herein we describe the measurement of the work function of a metal with advanced equipment based on the field emission retarding potential (FERP) method using a carbon nanotube (CNT) as cathode. The accuracy of the FERP method using a CNT emitter is described and a comparison between measurements of the work functions of aluminum, barium, calcium, gold, and platinum with published data will be presented. Our FERP equipment could be optimized with the aid of particle tracing simulations. These simulations led us to insert a magnetic collimator to improve the collection efficiency at the anode.
Elementary introduction to the Green's function
NASA Technical Reports Server (NTRS)
Whitten, R. C.; Mccormick, P. T.
1975-01-01
A technique, using the method of variation of parameters for solving differential equations, is developed for introducing Green's functions early in an undergraduate curriculum. Various examples are presented.
Brownian dynamics without Green's functions
Delong, Steven; Donev, Aleksandar; Usabiaga, Florencio Balboa; Delgado-Buscalioni, Rafael; Griffith, Boyce E.
2014-04-07
We develop a Fluctuating Immersed Boundary (FIB) method for performing Brownian dynamics simulations of confined particle suspensions. Unlike traditional methods which employ analytical Green's functions for Stokes flow in the confined geometry, the FIB method uses a fluctuating finite-volume Stokes solver to generate the action of the response functions “on the fly.” Importantly, we demonstrate that both the deterministic terms necessary to capture the hydrodynamic interactions among the suspended particles, as well as the stochastic terms necessary to generate the hydrodynamically correlated Brownian motion, can be generated by solving the steady Stokes equations numerically only once per time step. This is accomplished by including a stochastic contribution to the stress tensor in the fluid equations consistent with fluctuating hydrodynamics. We develop novel temporal integrators that account for the multiplicative nature of the noise in the equations of Brownian dynamics and the strong dependence of the mobility on the configuration for confined systems. Notably, we propose a random finite difference approach to approximating the stochastic drift proportional to the divergence of the configuration-dependent mobility matrix. Through comparisons with analytical and existing computational results, we numerically demonstrate the ability of the FIB method to accurately capture both the static (equilibrium) and dynamic properties of interacting particles in flow.
Green's function methods in heavy ion shielding
NASA Technical Reports Server (NTRS)
Wilson, John W.; Costen, Robert C.; Shinn, Judy L.; Badavi, Francis F.
1993-01-01
An analytic solution to the heavy ion transport in terms of Green's function is used to generate a highly efficient computer code for space applications. The efficiency of the computer code is accomplished by a nonperturbative technique extending Green's function over the solution domain. The computer code can also be applied to accelerator boundary conditions to allow code validation in laboratory experiments.
Muehlhoff, Rainer
2011-02-15
Existence and uniqueness of advanced and retarded fundamental solutions (Green's functions) and of global solutions to the Cauchy problem is proved for a general class of first order linear differential operators on vector bundles over globally hyperbolic Lorentzian manifolds. This is a core ingredient to CAR-/CCR-algebraic constructions of quantum field theories on curved spacetimes, particularly for higher spin field equations.
Green's function calculations of light nuclei
NASA Astrophysics Data System (ADS)
Sun, ZhongHao; Wu, Qiang; Xu, FuRong
2016-09-01
The influence of short-range correlations in nuclei was investigated with realistic nuclear force. The nucleon-nucleon interaction was renormalized with V lowk technique and applied to the Green's function calculations. The Dyson equation was reformulated with algebraic diagrammatic constructions. We also analyzed the binding energy of 4He, calculated with chiral potential and CD-Bonn potential. The properties of Green's function with realistic nuclear forces are also discussed.
ERIC Educational Resources Information Center
Hauck, Friedrich
1985-01-01
A functional questionnaire on self-injurious behavior of mentally retarded children was examined for social validation by principals of special schools for the retarded. Results were considered promising for developing the questionnaire in the form chosen. (CL)
NASA Astrophysics Data System (ADS)
Do, Van-Nam
2014-09-01
We review fundamental aspects of the non-equilibrium Green function method in the simulation of nanometer electronic devices. The method is implemented into our recently developed computer package OPEDEVS to investigate transport properties of electrons in nano-scale devices and low-dimensional materials. Concretely, we present the definition of the four real-time Green functions, the retarded, advanced, lesser and greater functions. Basic relations among these functions and their equations of motion are also presented in detail as the basis for the performance of analytical and numerical calculations. In particular, we review in detail two recursive algorithms, which are implemented in OPEDEVS to solve the Green functions defined in finite-size opened systems and in the surface layer of semi-infinite homogeneous ones. Operation of the package is then illustrated through the simulation of the transport characteristics of a typical semiconductor device structure, the resonant tunneling diodes.
The sources of Schwinger's Green's functions
Schweber, Silvan S.
2005-01-01
Julian Schwinger's development of his Green's functions methods in quantum field theory is placed in historical context. The relation of Schwinger's quantum action principle to Richard Feynman's path-integral formulation of quantum mechanics is reviewed. The nonperturbative character of Schwinger's approach is stressed as well as the ease with which it can be extended to finite temperature situations. PMID:15930139
Generating functionals for Green's functions in gauge field theories
Bordag, M.; Kaschlun, L.; Matveev, V.A.; Robaschik, D.
1987-09-01
The structure of the generating functional of the one-particle-irreducible Green's functions in gauge field theories is investigated. Both axial as well as covariant gauge conditions are considered. For both cases, the general structure of the functionals is obtained, and a functional expansion with respect to nonlocal operators is given. The appearance of gauge-dependent operators in the case of the covariant gauge follows in a natural manner from the structure of the corresponding functional.
NASA Astrophysics Data System (ADS)
Dmitriev, K. V.
2015-11-01
Matrix Green's functions are introduced for a linearized system of hydrodynamic equations. The relations between the retarded and advanced Green's functions and Green's functions of the direct and conjugate operators of the system of hydrodynamic equations are determined. An expression for the reciprocity principle and a relation like the Marchenko equation are derived. The proposed mathematical apparatus is used to analyze scattering by a quasi-point refraction-density inhomogeneity of a medium. The phase and amplitude limitations are obtained for the scattering coefficients of such an inhomogeneity. The existence of the largest possible amplitude of the scattered field should be taken into account in designing metamaterials consisting of individual elements whose sizes are small compared to the wavelength, including those with resonance properties.
Electromagnetic Green's function for layered topological insulators
NASA Astrophysics Data System (ADS)
Crosse, J. A.; Fuchs, Sebastian; Buhmann, Stefan Yoshi
2015-12-01
The dyadic Green's function of the inhomogeneous vector Helmholtz equation describes the field pattern of a single frequency point source. It appears in the mathematical description of many areas of electromagnetism and optics including both classical and quantum, linear and nonlinear optics, dispersion forces (such as the Casimir and Casimir-Polder forces), and in the dynamics of trapped atoms and molecules. Here we compute the Green's function for a layered topological insulator. Via the magnetoelectric effect, topological insulators are able to mix the electric E and magnetic induction B fields and, hence, one finds that the TE and TM polarizations mix on reflection from or transmission through an interface. This leads to unusual field patterns close to the surface of a topological insulator.
Gluon Green functions free of quantum fluctuations
NASA Astrophysics Data System (ADS)
Athenodorou, A.; Boucaud, Ph.; De Soto, F.; Rodríguez-Quintero, J.; Zafeiropoulos, S.
2016-09-01
This letter reports on how the Wilson flow technique can efficaciously kill the short-distance quantum fluctuations of 2- and 3-gluon Green functions, remove the ΛQCD scale and destroy the transition from the confining non-perturbative to the asymptotically-free perturbative sector. After the Wilson flow, the behavior of the Green functions with momenta can be described in terms of the quasi-classical instanton background. The same behavior also occurs, before the Wilson flow, at low-momenta. This last result permits applications as, for instance, the detection of instanton phenomenological properties or a determination of the lattice spacing only from the gauge sector of the theory.
Green's function calculation from equipartition theorem.
Perton, Mathieu; Sánchez-Sesma, Francisco José
2016-08-01
A method is presented to calculate the elastodynamic Green's functions by using the equipartition principle. The imaginary parts are calculated as the average cross correlations of the displacement fields generated by the incidence of body and surface waves with amplitudes weighted by partition factors. The real part is retrieved using the Hilbert transform. The calculation of the partition factors is discussed for several geometrical configurations in two dimensional space: the full-space, a basin in a half-space and for layered media. For the last case, it results in a fast computation of the full Green's functions. Additionally, if the contribution of only selected states is desired, as for instance the surface wave part, the computation is even faster. Its use for full waveform inversion may then be advantageous. PMID:27586757
Quantum thermodynamics: a nonequilibrium Green's function approach.
Esposito, Massimiliano; Ochoa, Maicol A; Galperin, Michael
2015-02-27
We establish the foundations of a nonequilibrium theory of quantum thermodynamics for noninteracting open quantum systems strongly coupled to their reservoirs within the framework of the nonequilibrium Green's functions. The energy of the system and its coupling to the reservoirs are controlled by a slow external time-dependent force treated to first order beyond the quasistatic limit. We derive the four basic laws of thermodynamics and characterize reversible transformations. Stochastic thermodynamics is recovered in the weak coupling limit. PMID:25768745
PREFACE: Progress in Nonequilibrium Green's Functions IV
NASA Astrophysics Data System (ADS)
Bonitz, Michael; Balzer, Karsten
2010-04-01
This is the fourth volume1 of articles on the theory of Nonequilibrium Green's functions (NEGF) and their modern application in various fields such as plasma physics, semiconductor physics, molecular electronics and high energy physics. It contains 23 articles written by experts in many-body theory and quantum transport who summarize recent progress in their respective area of research. The articles are based on talks given at the interdisciplinary conference Progress in Nonequilibrium Green's functions IV which was held 17-21 August 2009 at the University of Glasgow, Scotland. This conference continues the tradition of the previous meetings which started in 1999 and which aimed at an informal exchange across field boundaries. The previous meetings and the earlier proceedings proved to be very stimulating not only for young researchers but also for experienced scientists, and we are convinced that this fourth volume will be as successful as the previous ones. As before, this volume includes only extended review-type papers which are written in a way that they are understandable to a broad interdisciplinary audience. All papers published in this volume of Journal of Physics: Conference Series have been peer reviewed through processes administrated by the Editors assuring highest scientific standards. In the review process some papers were substantially revised and improved and some were rejected. This conference would not have been possible without the remarkable work of the local organizing team around John Barker and Scott Roy and the generous financial support from the University of Glasgow and the Deutsche Forschungsgemeinschaft via SFB-Transregio 24. Michael Bonitz and Karsten Balzer Kiel, February 2010 1 The first two volumes are Progress in Nonequilibrium Green's functions, M Bonitz (ed) and Progress in Nonequilibrium Green's functions II, M Bonitz and D Semkat (eds), which were published by World Scientific (Singapore), in 2000 and 2003, respectively (ISBN
Relativistic dynamics, Green function and pseudodifferential operators
NASA Astrophysics Data System (ADS)
Cirilo-Lombardo, Diego Julio
2016-06-01
The central role played by pseudodifferential operators in relativistic dynamics is known very well. In this work, operators like the Schrodinger one (e.g., square root) are treated from the point of view of the non-local pseudodifferential Green functions. Starting from the explicit construction of the Green (semigroup) theoretical kernel, a theorem linking the integrability conditions and their dependence on the spacetime dimensions is given. Relativistic wave equations with arbitrary spin and the causality problem are discussed with the algebraic interpretation of the radical operator and their relation with coherent and squeezed states. Also we perform by means of pure theoretical procedures (based in physical concepts and symmetry) the relativistic position operator which satisfies the conditions of integrability: it is a non-local, Lorentz invariant and does not have the same problems as the "local"position operator proposed by Newton and Wigner. Physical examples, as zitterbewegung and rogue waves, are presented and deeply analyzed in this theoretical framework.
Functionality of Objectives in the Program and Education Plans of Persons with Mental Retardation.
ERIC Educational Resources Information Center
Keyes, Joseph B.; Karst, Ralph R.
This study examined the relationship between the functionality of training objectives established in Individual Program Plans (IPPs) and Individual Education Plans (IEPs) of persons with severe and profound mental retardation and different service delivery environments. Each training objective in the IPPs and IEPs of 78 individuals was classified…
Tremor Frequency Profile as a Function of Level of Mental Retardation
ERIC Educational Resources Information Center
Sprague, Robert L.; Deutsch, Katherine M.; Newell, Karl M.
2007-01-01
The characteristic slowness of movement initiation and execution in adult individuals with mental retardation may be driven by the slower frequency profile of the dynamics of the system. To investigate this hypothesis, we examined the resting and postural finger tremor frequency profile (single and dual limb) of adults as a function of level of…
Contour-ordered Green's functions in stochastic field theory
NASA Astrophysics Data System (ADS)
Honkonen, J.
2013-06-01
We briefly review the functional formulation of the perturbation theory for various Green's functions in quantum field theory. In particular, we discuss the contour-ordered representation of Green's functions at a finite temperature. We show that the perturbation expansion of time-dependent Green's functions at a finite temperature can be constructed using the standard Wick rules in the functional form without introducing complex time and evolution backward in time. We discuss the factorization problem for the corresponding functional integral. We construct the Green's functions of the solution of stochastic differential equations in the Schwinger-Keldysh form with a functional-integral representation with explicitly intertwined physical and auxiliary fields.
A Green's function quantum average atom model
Starrett, Charles Edward
2015-05-21
A quantum average atom model is reformulated using Green's functions. This allows integrals along the real energy axis to be deformed into the complex plane. The advantage being that sharp features such as resonances and bound states are broadened by a Lorentzian with a half-width chosen for numerical convenience. An implementation of this method therefore avoids numerically challenging resonance tracking and the search for weakly bound states, without changing the physical content or results of the model. A straightforward implementation results in up to a factor of 5 speed-up relative to an optimized orbital based code.
Dirac Green function for angular projection potentials.
Zeller, Rudolf
2015-11-25
The aim of this paper is twofold: first, it is shown that the angular dependence of the Dirac Green function can be described analytically for potentials with non-local dependence on the angular variables if they are chosen as projection potentials in angular momentum space. Because the local dependence on the radial variable can be treated to any precision with present computing capabilities, this means that the Green function can be calculated practically exactly. Second, it is shown that a result of this kind not only holds for a single angular projection potential but also more generally, for instance if space is divided into non-overlapping cells and a separate angular projection potential is used in each cell. This opens the way for relativistic density-functional calculations within a different perspective than the conventional one. Instead of trying to obtain the density for a given potential approximately as well as possible, the density is determined exactly for non-local potentials which can approximate arbitrary local potentials as well as desired. PMID:26523824
Dirac Green function for angular projection potentials
NASA Astrophysics Data System (ADS)
Zeller, Rudolf
2015-11-01
The aim of this paper is twofold: first, it is shown that the angular dependence of the Dirac Green function can be described analytically for potentials with non-local dependence on the angular variables if they are chosen as projection potentials in angular momentum space. Because the local dependence on the radial variable can be treated to any precision with present computing capabilities, this means that the Green function can be calculated practically exactly. Second, it is shown that a result of this kind not only holds for a single angular projection potential but also more generally, for instance if space is divided into non-overlapping cells and a separate angular projection potential is used in each cell. This opens the way for relativistic density-functional calculations within a different perspective than the conventional one. Instead of trying to obtain the density for a given potential approximately as well as possible, the density is determined exactly for non-local potentials which can approximate arbitrary local potentials as well as desired.
Green functions of graphene: An analytic approach
NASA Astrophysics Data System (ADS)
Lawlor, James A.; Ferreira, Mauro S.
2015-04-01
In this article we derive the lattice Green Functions (GFs) of graphene using a Tight Binding Hamiltonian incorporating both first and second nearest neighbour hoppings and allowing for a non-orthogonal electron wavefunction overlap. It is shown how the resulting GFs can be simplified from a double to a single integral form to aid computation, and that when considering off-diagonal GFs in the high symmetry directions of the lattice this single integral can be approximated very accurately by an algebraic expression. By comparing our results to the conventional first nearest neighbour model commonly found in the literature, it is apparent that the extended model leads to a sizeable change in the electronic structure away from the linear regime. As such, this article serves as a blueprint for researchers who wish to examine quantities where these considerations are important.
Lattice Green's functions in all dimensions
NASA Astrophysics Data System (ADS)
Guttmann, Anthony J.
2010-07-01
We give a systematic treatment of lattice Green's functions (LGF) on the d-dimensional diamond, simple cubic, body-centred cubic and face-centred cubic lattices for arbitrary dimensionality d >= 2 for the first three lattices, and for 2 <= d <= 5 for the hyper-fcc lattice. We show that there is a close connection between the LGF of the d-dimensional hyper-cubic lattice and that of the (d - 1)-dimensional diamond lattice. We give constant-term formulations of LGFs for each of these lattices in all dimensions. Through a still under-developed connection with Mahler measures, we point out an unexpected connection between the coefficients of the sc, bcc and diamond LGFs and some Ramanujan-type formulae for 1/π.
Green's function Monte Carlo in nuclear physics
Carlson, J.
1990-01-01
We review the status of Green's Function Monte Carlo (GFMC) methods as applied to problems in nuclear physics. New methods have been developed to handle the spin and isospin degrees of freedom that are a vital part of any realistic nuclear physics problem, whether at the level of quarks or nucleons. We discuss these methods and then summarize results obtained recently for light nuclei, including ground state energies, three-body forces, charge form factors and the coulomb sum. As an illustration of the applicability of GFMC to quark models, we also consider the possible existence of bound exotic multi-quark states within the framework of flux-tube quark models. 44 refs., 8 figs., 1 tab.
Convergence rate for numerical computation of the lattice Green's function.
Ghazisaeidi, M; Trinkle, D R
2009-03-01
Flexible boundary-condition methods couple an isolated defect to bulk through the bulk lattice Green's function. Direct computation of the lattice Green's function requires projecting out the singular subspace of uniform displacements and forces for the infinite lattice. We calculate the convergence rates for elastically isotropic and anisotropic cases for three different techniques: relative displacement, elastic Green's function correction, and discontinuity correction. The discontinuity correction has the most rapid convergence for the general case. PMID:19392089
Rossby wave Green's functions in an azimuthal wind
NASA Astrophysics Data System (ADS)
Webb, G. M.; Duba, C. T.; Hu, Q.
2016-05-01
Green's functions for Rossby waves in an azimuthal wind are obtained, in which the stream-function $\\psi$ depends on $r$, $\\phi$ and $t$, where $r$ is cylindrical radius and $\\phi$ is the azimuthal angle in the $\\beta$-plane relative to the easterly direction, in which the $x$-axis points east and the $y$-axis points north. The Rossby wave Green's function with no wind is obtained using Fourier transform methods, and is related to the previously known Green's function obtained for this case, which has a different but equivalent form to the Green's function obtained in the present paper. We emphasize the role of the wave eikonal solution, which plays an important role in the form of the solution. The corresponding Green's function for a rotating wind with azimuthal wind velocity ${\\bf u}=\\Omega r{\\bf e}_\\phi$ ($\\Omega=$const.) is also obtained by Fourier methods, in which the advective rotation operator in position space is transformed to a rotation operator in ${\\bf k}$ transform space. The finite Rossby deformation radius is included in the analysis. The physical characteristics of the Green's functions are delineated and applications are discussed. In the limit as $\\Omega\\to 0$, the rotating wind Green's function reduces to the Rossby wave Green function with no wind.
Green's function of the second order differential operator with involution
NASA Astrophysics Data System (ADS)
Ashyralyev, Allaberen; Sarsenbi, Abdisalam A.
2016-08-01
In the present paper, the Green's function of the second order differential operator L defined by formula L u =α u″ (x ) -u″ (-x ) =λ u (x ) ,-1
Deterministic retrieval of complex Green's functions using hard X rays.
Vine, D J; Paganin, D M; Pavlov, K M; Uesugi, K; Takeuchi, A; Suzuki, Y; Yagi, N; Kämpfe, T; Kley, E-B; Förster, E
2009-01-30
A massively parallel deterministic method is described for reconstructing shift-invariant complex Green's functions. As a first experimental implementation, we use a single phase contrast x-ray image to reconstruct the complex Green's function associated with Bragg reflection from a thick perfect crystal. The reconstruction is in excellent agreement with a classic prediction of dynamical diffraction theory. PMID:19257417
NASA Astrophysics Data System (ADS)
Jiang, Heping; Jiang, Jiao; Song, Yongli
In this paper, we firstly employ the normal form theory of delayed differential equations according to Faria and Magalhães to derive the normal form of saddle-node-Hopf bifurcation for the general retarded functional differential equations. Then, the dynamical behaviors of a Leslie-Gower predator-prey model with time delay and nonmonotonic functional response are considered. Specially, the dynamical classification near the saddle-node-Hopf bifurcation point is investigated by using the normal form and the center manifold approaches. Finally, the numerical simulations are employed to support the theoretical results.
Integral equation for gauge invariant quark Green's function
Sazdjian, H.
2008-08-29
We consider gauge invariant quark two-point Green's functions in which the gluonic phase factor follows a skew-polygonal line. Using a particular representation for the quark propagator in the presence of an external gluon field, functional relations between Green's functions with different numbers of segments of the polygonal lines are established. An integral equation is obtained for the Green's function having a phase factor along a single straight line. The related kernels involve Wilson loops with skew-polygonal contours and with functional derivatives along the sides of the contours.
Transient Thermoelectric Solution Employing Green's Functions
NASA Technical Reports Server (NTRS)
Mackey, Jon; Sehirlioglu, Alp; Dynys, Fred
2014-01-01
The study works to formulate convenient solutions to the problem of a thermoelectric couple operating under a time varying condition. Transient operation of a thermoelectric will become increasingly common as thermoelectric technology permits applications in an increasing number of uses. A number of terrestrial applications, in contrast to steady-state space applications, can subject devices to time varying conditions. For instance thermoelectrics can be exposed to transient conditions in the automotive industry depending on engine system dynamics along with factors like driving style. In an effort to generalize the thermoelectric solution a Greens function method is used, so that arbitrary time varying boundary and initial conditions may be applied to the system without reformulation. The solution demonstrates that in thermoelectric applications of a transient nature additional factors must be taken into account and optimized. For instance, the materials specific heat and density become critical parameters in addition to the thermal mass of a heat sink or the details of the thermal profile, such as oscillating frequency. The calculations can yield the optimum operating conditions to maximize power output andor efficiency for a given type of device.
Green's function evaluation for three-dimensional exponentially graded elasticity
Criado Portero, Rafael M; Gray, Leonard J; Mantic, Vladislav; Paris, Federico
2008-01-01
The numerical implementation of the Green's function for an isotropic exponentially graded three dimensional elastic solid is reported. The formulas for the nonsingular {\\lq}grading term{\\rq} in this Green's function, originally deduced by Martin et al., \\emph{Proc. R. Soc. Lond. A, 458, 1931-1947, 2000}, are quite complicated, and a small error in one of the formulas is corrected. The evaluation of the fundamental solution is tested by employing indirect boundary integral formulation using a Galerkin approximation to solve several problems having analytic solutions. The numerical results indicate that the Green's function formulas, and their evaluation, are correct.
On singular cases in the design derivative of Green's functional
NASA Technical Reports Server (NTRS)
Reiss, Robert
1987-01-01
The author's prior development of a general abstract representation for the design sensitivities of Green's functional for linear structural systems is extended to the case where the structural stiffness vanishes at an internal location. This situation often occurs in the optimal design of structures. Most optimality criteria require that optimally designed beams be statically determinate. For clamped-pinned beams, for example, this is possible only if the flexural stiffness vanishes at some intermediate location. The Green's function for such structures depends upon the stiffness and the location where it vanishes. A precise representation for Green's function's sensitivity to the location of vanishing stiffness is presented for beams and axisymmetric plates.
Introduction to Mental Retardation
ERIC Educational Resources Information Center
Arc of the United States, 2004
2004-01-01
The purpose of this document is to define mental retardation and answer questions related to this topic. According to the American Association on Mental Retardation (AAMR), mental retardation is a disability that occurs before age 18. It is characterized by significant limitations in intellectual functioning and adaptive behaviors as expressed in…
Flame-Retardant Paper from Wood Fibers Functionalized via Layer-by-Layer Assembly.
Köklükaya, Oruç; Carosio, Federico; Grunlan, Jaime C; Wågberg, Lars
2015-10-28
The highly flammable character of cellulose-rich fibers from wood limits their use in some advanced materials. To suppress the flammability and introduce flame-retardant properties to individual pulp fibers, we deposited nanometer thin films consisting of cationic chitosan (CH) and anionic poly(vinylphosphonic acid) (PVPA) on fibers using the layer-by-layer (LbL) technique. The buildup of the multilayer film was investigated in the presence and absence of salt (NaCl) using model cellulose surfaces and a quartz crystal microbalance technique. Fibers were then treated with the same strategy, and the treated fibers were used to prepare paper sheets. A horizontal flame test (HFT) and cone calorimetry were conducted to evaluate the combustion behavior of paper sheets as a function of the number of bilayers deposited on fibers. In HFT, paper made of fibers coated with 20 CH/PVPA bilayers (BL), self-extinguished the flame, while uncoated fibers were completely consumed. Scanning electron microscopy of charred paper after HFT revealed that a thin shell of the charred polymeric multilayer remained after the cellulose fibers had been completely oxidized. Cone calorimetry demonstrated that the phosphorus-containing thin films (20 BL is ∼25 nm) reduced the peak heat release rate by 49%. This study identifies a unique and highly effective way to impart flame-retardant characteristic to pulp fibers and the papers made from these fibers. PMID:26457504
NASA Astrophysics Data System (ADS)
LeBlanc, Victor G.
2016-02-01
In this paper, we study degenerate Hopf bifurcations in a class of parametrized retarded functional differential equations. Specifically, we are interested in the case where the eigenvalue crossing condition of the classical Hopf bifurcation theorem is violated. Our approach is based on center manifold reduction and Poincaré-Birkhoff normal forms, and a singularity theoretical classification of this degenerate Hopf bifurcation. Our results are applied to a recently developed SIS model incorporating a delayed behavioral response. We show the phenomenon of endemic bubbles, which is characterized by a branch of periodic solutions which bifurcates from the endemic equilibrium at some value of the basic reproduction number R_0, and then reconnects to the endemic equilibrium at a larger value of R_0, originates in a codimension-two organizing center where the eigenvalue crossing condition for the Hopf bifurcation theorem is violated.
Four-point Green functions in the Schwinger model
NASA Astrophysics Data System (ADS)
Radożycki, Tomasz; Namysłowski, Józef M.
1999-03-01
The evaluation of the four-point Green functions in the 1+1 Schwinger model is presented both in momentum and coordinate space representations. The crucial role in our calculations is played by two Ward identities: (i) the standard one and (ii) the chiral one. We demonstrate how the infinite set of Dyson-Schwinger equations is simplified, and is so reduced that a given n-point Green function is expressed only through itself and lower ones. For the four-point Green function, with two bosonic and two fermionic external ``legs,'' a compact solution is given both in momentum and coordinate space representations. For the four-fermion Green function a self-consistent equation is written down in the momentum representation and a concrete solution is given in the coordinate space. This exact solution is further analyzed and we show that it contains a pole corresponding to the Schwinger boson. All detailed considerations given for various four-point Green functions are easily generizable to higher functions.
Green's Function Retrieval with Absorbing Probes in Reverberating Cavities.
Davy, Matthieu; de Rosny, Julien; Besnier, Philippe
2016-05-27
The cross-correlation of a diffuse wave field converges toward the difference between the anticausal and causal Green's functions between two points. This property has paved the way to passive imaging using ambient noise sources. In this Letter, we investigate Green's function retrieval in electromagnetism. Using a model based on the fluctuation dissipation theorem, we demonstrate theoretically that the cross-correlation function strongly depends on the absorption properties of the receivers. This is confirmed in measurements within a reverberation chamber. In contrast to measurements with noninvasive probes, we show that only the anticausal Green's function can be retrieved with a matched antenna. Finally, we interpret this result as an equivalent time-reversal experiment with an electromagnetic sink. PMID:27284658
Floquet Green function formalism for harmonically driven Hamiltonians
NASA Astrophysics Data System (ADS)
Martinez, D. F.
2003-09-01
A method is proposed for the calculation of the Floquet-Green function of a general Hamiltonian with harmonic time dependence. We use matrix continued fractions to derive an expression for the 'dynamical effective potential' that can be used to calculate the Floquet-Green function of the system. We demonstrate the formalism for the simple case of a space-periodic (in the tight-binding approximation) Hamiltonian with a defect whose on-site energy changes harmonically with time. We study the local density of states for this system and the behaviour of the localized states as a function of the different parameters that characterize the system.
OPTIMIZING POTENTIAL GREEN REPLACEMENT CHEMICALS – BALANCING FUNCTION AND RISK
An important focus of green chemistry is the design of new chemicals that are inherently less toxic than the ones they might replace, but still retain required functional properties. A variety of methods exist to measure or model both functional and toxicity surrogates that could...
Green's functions for a CPn - 1 model with massless fermions
NASA Astrophysics Data System (ADS)
Schaposnik, F. A.
1983-07-01
We study the CPn - 1 model with massless fermions making a chiral change in the fermionic variables. We construct the generating functional and discuss relevant features of the theory. The factorization of a pure fermionic part shows a power law correction to the free fermion Green's function. The dynamical gauge field becomes massive and a screening phenomenon occurs. Member of CIC, Buenos Aires, Argentina
Theory of Green functions of free Dirac fermions in graphene
NASA Astrophysics Data System (ADS)
Hieu Nguyen, Van; Nguyen, Bich Ha; Dung Dinh, Ngoc
2016-03-01
This work is the beginning of our research on graphene quantum electrodynamics (GQED), based on the application of the methods of traditional quantum field theory to the study of the interacting system of quantized electromagnetic field and Dirac fermions in single-layer graphene. After a brief review of the known results concerning the lattice and electronic structures of single-layer graphene we perform the construction of the quantum fields of free Dirac fermions and the establishment of the corresponding Heisenberg quantum equations of these fields. We then elaborate the theory of Green functions of Dirac fermions in a free Dirac fermion gas at vanishing absolute temperature T = 0, the theory of Matsubara temperature Green functions and the Keldysh theory of non-equilibrium Green functions.
Parameterization of Star-Shaped Volumes Using Green's Functions
NASA Astrophysics Data System (ADS)
Xia, Jiazhi; He, Ying; Han, Shuchu; Fu, Chi-Wing; Luo, Feng; Gu, Xianfeng
Parameterizations have a wide range of applications in computer graphics, geometric design and many other fields of science and engineering. Although surface parameterizations have been widely studied and are well developed, little research exists on the volumetric data due to the intrinsic difficulties in extending surface parameterization algorithms to volumetric domain. In this paper, we present a technique for parameterizing star-shaped volumes using the Green's functions. We first show that the Green's function on the star shape has a unique critical point. Then we prove that the Green's functions can induce a diffeomorphism between two star-shaped volumes. We develop algorithms to parameterize star shapes to simple domains such as balls and star-shaped polycubes, and also demonstrate the volume parameterization applications: volumetric morphing, anisotropic solid texture transfer and GPU-based volumetric computation.
Gauge-invariant Green function dynamics: A unified approach
Swiecicki, Sylvia D. Sipe, J.E.
2013-11-15
We present a gauge-invariant description of Green function dynamics introduced by means of a generalized Peirels phase involving an arbitrary differentiable path in space–time. Two other approaches to formulating a gauge-invariant description of systems, the Green function treatment of Levanda and Fleurov [M. Levanda, V. Fleurov, J. Phys.: Condens. Matter 6 (1994) 7889] and the usual multipolar expansion for an atom, are shown to arise as special cases of our formalism. We argue that the consideration of paths in the generalized Peirels phase that do not lead to introduction of an effective gauge-invariant Hamiltonian with polarization and magnetization fields may prove useful for the treatment of the response of materials with short electron correlation lengths. -- Highlights: •Peirels phase for an arbitrary path in space–time established. •Gauge-invariant Green functions and the Power–Zienau–Wooley transformation connected. •Limitations on possible polarization and magnetization fields established.
Diffuse fields in open systems and the emergence of the Green's function (L)
NASA Astrophysics Data System (ADS)
Weaver, Richard L.; Lobkis, Oleg I.
2004-11-01
A definition of a diffuse field applicable to open heterogeneous systems is proposed. The identity between the Green's function of the structure and the diffuse field's correlations is proved. The Green's function that emerges from the correlation is found to be the full Green's function of the medium, symmetrized in time, with all reflections and scatterings and propagation modes. This is in contrast to suggestions that the correlation is the ballistic Green's function only, or the Green's function of a homogeneous effective medium. .
Relativistic extension of the complex scaled Green function method
NASA Astrophysics Data System (ADS)
Shi, Min; Guo, Jian-You; Liu, Quan; Niu, Zhong-Ming; Heng, Tai-Hua
2015-11-01
Resonances play a critical role in the formation of many physical phenomena. The complex scaled Green function method provides a powerful tool for the exploration of resonances. In the paper, we extend this method to the relativistic framework. With 120Sn as an example, we present the details of the scheme and seek resonant states in real nuclei. The results are compared, and are in satisfactory agreement with those from frequently used methods. In particular, the present method gathers the advantages of the complex scaling method and Green function method, and can be used to determine more accurately resonance parameters such as energy and lifetime of decay.
Green-function approach for scattering quantum walks
Andrade, F. M.; Luz, M. G. E. da
2011-10-15
In this work a Green-function approach for scattering quantum walks is developed. The exact formula has the form of a sum over paths and always can be cast into a closed analytic expression for arbitrary topologies and position-dependent quantum amplitudes. By introducing the step and path operators, it is shown how to extract any information about the system from the Green function. The method's relevant features are demonstrated by discussing in detail an example, a general diamond-shaped graph.
ERIC Educational Resources Information Center
Applegate, Heather; Matson, Johnny L.; Cherry, Katie E.
1999-01-01
A study used the Questions about Behavior Function Scale to examine the functions of five severe problem behaviors (self-injurious behavior, aggression, stereotypies, pica, and rumination) in 417 institutionalized persons with mental retardation. The most common function for all behaviors except aggression was nonsocial. Aggression was maintained…
Plant functional traits predict green roof ecosystem services.
Lundholm, Jeremy; Tran, Stephanie; Gebert, Luke
2015-02-17
Plants make important contributions to the services provided by engineered ecosystems such as green roofs. Ecologists use plant species traits as generic predictors of geographical distribution, interactions with other species, and ecosystem functioning, but this approach has been little used to optimize engineered ecosystems. Four plant species traits (height, individual leaf area, specific leaf area, and leaf dry matter content) were evaluated as predictors of ecosystem properties and services in a modular green roof system planted with 21 species. Six indicators of ecosystem services, incorporating thermal, hydrological, water quality, and carbon sequestration functions, were predicted by the four plant traits directly or indirectly via their effects on aggregate ecosystem properties, including canopy density and albedo. Species average height and specific leaf area were the most useful traits, predicting several services via effects on canopy density or growth rate. This study demonstrates that easily measured plant traits can be used to select species to optimize green roof performance across multiple key services. PMID:25599106
Nonlinear Green's function method for unsteady transonic flows
NASA Technical Reports Server (NTRS)
Tseng, K.; Morino, L.
1982-01-01
Advantages to employing Green's function in describing unsteady three-dimensional transonic flows are explored. The development of the function for application to linear subsonic and supersonic unsteady aerodynamics is reviewed. It is shown that unique solutions are possible for external flows, with all functional expressions being defined in Prandtl-Glauert space. The development of methods of using the Green's function for transonic flows is traced, noting the necessity of including the effects of significant nonlinear terms. The steady-state problem is considered to demonstrate the shock-capturing ability of the method and the usefulness of the function in the incompressible, subsonic, transonic, and supersonic areas of potential unsteady three-dimensional flows around complex configurations. Computational time is asserted to be an order of magnitude less than with finite difference methods.
Calibrating the ECCO ocean general circulation model using Green's functions
NASA Technical Reports Server (NTRS)
Menemenlis, D.; Fu, L. L.; Lee, T.; Fukumori, I.
2002-01-01
Green's functions provide a simple, yet effective, method to test and calibrate General-Circulation-Model(GCM) parameterizations, to study and quantify model and data errors, to correct model biases and trends, and to blend estimates from different solutions and data products.
Formation spectra of pionic atoms in the Green's function method
NASA Astrophysics Data System (ADS)
Ikeno, Natsumi; Yamagata-Sekihara, Junko; Nagahiro, Hideko; Hirenzaki, Satoru
2015-03-01
We study the formation spectra of deeply bound pionic atoms in the (d, ^3He) reactions using the Green's function method, stimulated by recent developments in experimental techniques. The Green's function method is considered to be a better theoretical formalism than the effective number approach to evaluate the formation rate of unstable systems. We compare the calculated results by the Green's function method with those by the effective number approach in various cases. We find that the differences between the results obtained by both methods are reasonably small and we can reaffirm that the effective number approach is a good theoretical method for the analyses of the previous experimental data with typical binding-energy errors of Δ B.E. ≳ 20keV for the deeply bound pionic atoms. On the other hand, we think that theoretical results using the Green's function method will be necessary in the near future to deduce precise information on the pion properties in nuclei from analyses of the pionic atom data with better accuracy than before.
Nonstandard formulation of perturbation theory for Green's function
Aliev, M.N.; Tagiev, V.S.
1989-01-01
Perturbation theory is developed for two-variable Green's functions (GF) when the initial GF is linked simultaneously to several higher-order GF. The total mass operator of the initial GF is obtained mathematically correctly in a form convenient for use. As an example of the application of this method, the mass operator of a nuclear spin anticommutator GF is calculated.
Chu, Yi-Zen
2014-09-15
Motivated by the desire to understand the causal structure of physical signals produced in curved spacetimes – particularly around black holes – we show how, for certain classes of geometries, one might obtain its retarded or advanced minimally coupled massless scalar Green's function by using the corresponding Green's functions in the higher dimensional Minkowski spacetime where it is embedded. Analogous statements hold for certain classes of curved Riemannian spaces, with positive definite metrics, which may be embedded in higher dimensional Euclidean spaces. The general formula is applied to (d ≥ 2)-dimensional de Sitter spacetime, and the scalar Green's function is demonstrated to be sourced by a line emanating infinitesimally close to the origin of the ambient (d + 1)-dimensional Minkowski spacetime and piercing orthogonally through the de Sitter hyperboloids of all finite sizes. This method does not require solving the de Sitter wave equation directly. Only the zero mode solution to an ordinary differential equation, the “wave equation” perpendicular to the hyperboloid – followed by a one-dimensional integral – needs to be evaluated. A topological obstruction to the general construction is also discussed by utilizing it to derive a generalized Green's function of the Laplacian on the (d ≥ 2)-dimensional sphere.
Growth, Hypothalamic Function, and Brain Ventricle Size in Mentally Retarded Subjects
ERIC Educational Resources Information Center
Leisti, S.; Iianainen, M.
1978-01-01
To determine whether moderate enlargement of the third brain ventricle or the temporal horns of the lateral ventricles was associated with hypothalamic dysfunction, 15 mentally retarded Ss (ages 12-25 years) with such characteristics were studies. (DLS)
Variational and Green`s function Monte Carlo calculations of few-body nuclei
Wiringa, R.B.; Carlson, J.; Pandharipande, V.R.; Pudliner, B.S.
1995-08-01
We performed an extensive series of variational Monte Carlo (VMC) and Green`s Function Monte Carlo (GFMC) calculations for few-body nuclei using a Hamiltonian, H, containing the new Argonne v{sub 18} NN interaction supplemented by a model three-nucleon (3N) potential. These calculations include the ground state binding energy of {sup 3}H, {sup 3}He, {sup 4}He, {sup 6}He, {sup 6}Li and {sup 6}Be, low-lying excited states in the A = 6 nuclei, and scattering states of {sup 5}He. The variational wave functions, {Psi}{sub v}(R), include central, spin, isospin, tensor, and spin-orbit two- and three-body correlations. These trial functions give upper bounds to the ground-state binding energy {approximately}2% above exact GFMC calculations in {sup 3}H and {sup 4}He.
NASA Astrophysics Data System (ADS)
Sabatini, Jesse J.; Poret, Jay C.; Broad, Russell N.
2011-10-01
The effect of using crystalline boron in green-colored handheld signal formulations is described. Due to its chemically inert nature, crystalline boron served to reduce the burn rates of the formulations. By adjusting crystalline boron percentages in the formulations, the pyrotechnic system could be tuned to meet burn time specifications.
Semitransparent one-dimensional potential: a Green's function approach
NASA Astrophysics Data System (ADS)
Maldonado-Villamizar, F. H.
2015-06-01
We study the unstable harmonic oscillator and the unstable linear potential in the presence of the point potential, which is the superposition of the Dirac δ (x) and its derivative {{δ }\\prime }(x). Using the physical boundary conditions for the Green's function we derive for both systems the resonance poles and the resonance wave functions. The matching conditions for the resonance wave functions coincide with those obtained by the self-adjoint extensions of the point potentials and also by the modelling of the {{δ }\\prime }(x) function. We find that, with our definitions, the pure b{{δ }\\prime }(x) barrier is semi-transparent independent of the value of b.
Two-dimensional Coulomb scattering of a quantum particle: Wave functions and Green's functions
NASA Astrophysics Data System (ADS)
Pupyshev, V. V.
2016-02-01
We solve the problem of the propagation of a charged quantum particle in a two-dimensional plane embedded in the three-dimensional coordinate space. We consider scattering of this particle by a stable Coulomb center situated in the same plane. We study the wave function of this particle, its Green's function, and all radial components of these functions. We derive uniform majorant bounds on absolute values of these functions and find the wave function representation in terms of regular radial Coulomb functions and the scattering amplitude representation via partial phases. We obtain integral representations of the Greens's function and all its radial components.
Green's Function Analysis of Periodic Structures in Computational Electromagnetics
NASA Astrophysics Data System (ADS)
Van Orden, Derek
2011-12-01
Periodic structures are used widely in electromagnetic devices, including filters, waveguiding structures, and antennas. Their electromagnetic properties may be analyzed computationally by solving an integral equation, in which an unknown equivalent current distribution in a single unit cell is convolved with a periodic Green's function that accounts for the system's boundary conditions. Fast computation of the periodic Green's function is therefore essential to achieve high accuracy solutions of complicated periodic structures, including analysis of modal wave propagation and scattering from external sources. This dissertation first presents alternative spectral representations of the periodic Green's function of the Helmholtz equation for cases of linear periodic systems in 2D and 3D free space and near planarly layered media. Although there exist multiple representations of the periodic Green's function, most are not efficient in the important case where the fields are observed near the array axis. We present spectral-spatial representations for rapid calculation of the periodic Green's functions for linear periodic arrays of current sources residing in free space as well as near a planarly layered medium. They are based on the integral expansion of the periodic Green's functions in terms of the spectral parameters transverse to the array axis. These schemes are important for the rapid computation of the interaction among unit cells of a periodic array, and, by extension, the complex dispersion relations of guided waves. Extensions of this approach to planar periodic structures are discussed. With these computation tools established, we study the traveling wave properties of linear resonant arrays placed near surfaces, and examine the coupling mechanisms that lead to radiation into guided waves supported by the surface. This behavior is especially important to understand the properties of periodic structures printed on dielectric substrates, such as periodic
Green's function approach for quantum graphs: An overview
NASA Astrophysics Data System (ADS)
Andrade, Fabiano M.; Schmidt, A. G. M.; Vicentini, E.; Cheng, B. K.; da Luz, M. G. E.
2016-08-01
Here we review the many aspects and distinct phenomena associated to quantum dynamics on general graph structures. For so, we discuss such class of systems under the energy domain Green's function (G) framework. This approach is particularly interesting because G can be written as a sum over classical-like paths, where local quantum effects are taken into account through the scattering matrix elements (basically, transmission and reflection amplitudes) defined on each one of the graph vertices. Hence, the exact G has the functional form of a generalized semiclassical formula, which through different calculation techniques (addressed in detail here) always can be cast into a closed analytic expression. It allows to solve exactly arbitrary large (although finite) graphs in a recursive and fast way. Using the Green's function method, we survey many properties of open and closed quantum graphs as scattering solutions for the former and eigenspectrum and eigenstates for the latter, also considering quasi-bound states. Concrete examples, like cube, binary trees and Sierpiński-like topologies are presented. Along the work, possible distinct applications using the Green's function methods for quantum graphs are outlined.
Relativistic central-field Green's functions for the RATIP package
NASA Astrophysics Data System (ADS)
Koval, Peter; Fritzsche, Stephan
2005-11-01
From perturbation theory, Green's functions are known for providing a simple and convenient access to the (complete) spectrum of atoms and ions. Having these functions available, they may help carry out perturbation expansions to any order beyond the first one. For most realistic potentials, however, the Green's functions need to be calculated numerically since an analytic form is known only for free electrons or for their motion in a pure Coulomb field. Therefore, in order to facilitate the use of Green's functions also for atoms and ions other than the hydrogen-like ions, here we provide an extension to the RATIP program which supports the computation of relativistic (one-electron) Green's functions in an—arbitrarily given—central-field potential V(r). Different computational modes have been implemented to define these effective potentials and to generate the radial Green's functions for all bound-state energies E<0. In addition, care has been taken to provide a user-friendly component of the RATIP package by utilizing features of the Fortran 90/95 standard such as data structures, allocatable arrays, or a module-oriented design. Program summaryTitle of program:XGREENS Catalogue number: ADWM Program summary URL:http://cpc.cs.qub.ac.uk/summaries/ADWM Program obtainable from: CPC Program Library, Queen's University of Belfast, N. Ireland Licensing provisions:None Computer for which the new version has been tested: PC Pentium II, III, IV, Athlon Installations: University of Kassel (Germany) Operating systems: SuSE Linux 8.2, SuSE Linux 9.0 Program language used in the new version: ANSI standard Fortran 90/95 Memory required to execute with typical data: On a standard grid (400 nodes), one central-field Green's function requires about 50 kBytes in RAM while approximately 3 MBytes are needed if saved as two-dimensional array on some external disc space No. of bits in a word: Real variables of double- and quad-precision are used Peripheral used: Disk for input
Analytic methods and free-space dyadic Green's functions
NASA Astrophysics Data System (ADS)
Weiglhofer, Werner S.
1993-09-01
A number of mathematical techniques are presented which have proven successful in obtaining analytic solutions to the differential equations for the dyadic Green's functions of electromagnetic theory. The emphasis is on infinite-medium (or free-space) time-harmonic solutions throughout, thus putting the focus on the physical medium in which the electromagnetic process takes place. The medium's properties enter Maxwell's equations through the constitutive relations, and a comprehensive listing of dyadic Green's functions for which closed-form solutions exist, is given. Presently, the list of media contains (achiral) isotropic, biisotropic (including chiral), generally uniaxial, electrically (or magnetically) gyrotropic, diffusive and moving media as well as certain plasmas. A critical evaluation of the achievements, successes, limits, and failures of the analytic techniques is provided, and a prognosis is put forward about the future place of analytic methods within the general context of the search for solutions to electromagnetic field problems.
Gauge-invariant Green function dynamics: A unified approach
NASA Astrophysics Data System (ADS)
Swiecicki, Sylvia D.; Sipe, J. E.
2013-11-01
We present a gauge-invariant description of Green function dynamics introduced by means of a generalized Peirels phase involving an arbitrary differentiable path in space-time. Two other approaches to formulating a gauge-invariant description of systems, the Green function treatment of Levanda and Fleurov [M. Levanda, V. Fleurov, J. Phys.: Condens. Matter 6 (1994) 7889] and the usual multipolar expansion for an atom, are shown to arise as special cases of our formalism. We argue that the consideration of paths in the generalized Peirels phase that do not lead to introduction of an effective gauge-invariant Hamiltonian with polarization and magnetization fields may prove useful for the treatment of the response of materials with short electron correlation lengths.
The straggling Green's function method for ion transport
NASA Astrophysics Data System (ADS)
Walker, Steven Andrew
For many years work has been conducted on developing a concise theory and method for HZE ion transport capable of being validated in the laboratory. Previous attempts have ignored dispersion and energy downshift associated with nuclear fragmentation and energy and range straggling. Here we present a Green's function approach to ion transport that incorporates these missing elements. This work forms the basis for a new version of GRNTRN, a Green's function transport code. Comparisons of GRNTRN predictions and laboratory results for an 56Fe ion beam with average energy at the target of one GeV/amu or more are presented for various targets. Quantities compared are the energy deposited spectra for an Aluminum target and Graphite-Epoxy mix target, the fraction of primary beam surviving and track average LET for these and various other targets.
Riley, M.E.
1998-03-01
This report describes the numerical procedure used to implement the Green`s function method for solving the Poisson equation in two-dimensional Cartesian coordinates. The procedure can determine the solution to a problem with any or all of applied voltage boundary conditions, dielectric media, floating (insulated) conducting media, dielectric surface charging, periodic (reflective) boundary conditions, and volumetric space charge. The numerical solution is reasonably fast, and the dimension of the linear problem to be solved is that of the number of elements needed to represent the surfaces, not the whole computational volume. The method of solution is useful in the simulation of plasma particle motion in the vicinity of complex surface structures as found in microelectronics plasma processing applications. A FORTRAN implementation of this procedure is available from the author.
Green`s function of Maxwell`s equations and corresponding implications for iterative methods
Singer, B.S.; Fainberg, E.B.
1996-12-31
Energy conservation law imposes constraints on the norm and direction of the Hilbert space vector representing a solution of Maxwell`s equations. In this paper, we derive these constrains and discuss the corresponding implications for the Green`s function of Maxwell`s equations in a dissipative medium. It is shown that Maxwell`s equations can be reduced to an integral equation with a contracting kernel. The equation can be solved using simple iterations. Software based on this algorithm have successfully been applied to a wide range of problems dealing with high contrast models. The matrix corresponding to the integral equation has a well defined spectrum. The equation can be symmetrized and solved using different approaches, for instance one of the conjugate gradient methods.
Two-dimensional Green`s function Poisson solution appropriate for cylindrical-symmetry simulations
Riley, M.E.
1998-04-01
This report describes the numerical procedure used to implement the Green`s function method for solving the Poisson equation in two-dimensional (r,z) cylindrical coordinates. The procedure can determine the solution to a problem with any or all of the applied voltage boundary conditions, dielectric media, floating (insulated) conducting media, dielectric surface charging, and volumetric space charge. The numerical solution is reasonably fast, and the dimension of the linear problem to be solved is that of the number of elements needed to represent the surfaces, not the whole computational volume. The method of solution is useful in the simulation of plasma particle motion in the vicinity of complex surface structures as found in microelectronics plasma processing applications. This report is a stand-alone supplement to the previous Sandia Technical Report SAND98-0537 presenting the two-dimensional Cartesian Poisson solver.
Approximate Green's function methods for HZE transport in multilayered materials
NASA Technical Reports Server (NTRS)
Wilson, John W.; Badavi, Francis F.; Shinn, Judy L.; Costen, Robert C.
1993-01-01
A nonperturbative analytic solution of the high charge and energy (HZE) Green's function is used to implement a computer code for laboratory ion beam transport in multilayered materials. The code is established to operate on the Langley nuclear fragmentation model used in engineering applications. Computational procedures are established to generate linear energy transfer (LET) distributions for a specified ion beam and target for comparison with experimental measurements. The code was found to be highly efficient and compared well with the perturbation approximation.
The Green function for the Duffin-Kemmer-Petiau equation
NASA Astrophysics Data System (ADS)
Boutabia-Chéraitia, B.; Boudjedaa, T.
2012-10-01
We present a calculation of the Green function for the Duffin-Kemmer-Petiau equation in the case of scalar and vectorial particles interacting with a square barrier potential, and relate it to that of the Klein-Gordon equation. A formal Hamiltonian of the Duffin-Kemmer-Petiau theory is first developed using the Feshbach-Villars analogy and the Sakata and Taketani decomposition. The coefficients of reflection and transmission are deduced.
Slogans and Euphemisms: The Functions of Semantics in Mental Health and Mental Retardation Care.
ERIC Educational Resources Information Center
Bachrach, Leona L.
The paper examines the way in which semantics relates to policies of deinstitutionalization of persons with mental illness and mental retardation. Different understandings of common terms in the field are illustrated and it is suggested that the government plays many games, both number games and word games, in dealing with homeless people, migrant…
The Assessment of Social Functioning in Individuals with Mental Retardation: A Review
ERIC Educational Resources Information Center
Bielecki, Joanne; Swender, Stephen L.
2004-01-01
Social skills deficits and excesses are a defining aspect of mental retardation (MR). Research indicates that there is an established relationship between social skills and maladaptive behaviors. A number of studies demonstrate that the social competence of individuals with MR and comorbid psychopathology can be enhanced with social skills…
ERIC Educational Resources Information Center
Pearson, Deborah A.; Santos, Cynthia W.; Casat, Charles D.; Lane, David M.; Jerger, Susan W.; Roache, John D.; Loveland, Katherine A.; Lachar, David; Faria, Laura P.; Payne, Christa D.; Cleveland, Lynne A.
2004-01-01
Objective: Cognitive effects of stimulant medication were investigated in children with mental retardation (MR) and attention-deficit/hyperactivity disorder (ADHD). Method: Performance on tasks tapping sustained attention, visual and auditory selective attention, inhibition, and immediate memory was assessed for 24 children (mean age 10.9 years)…
Functional Concepts in Mental Retardation: Finding the Natural Essence of an Artificial Category
ERIC Educational Resources Information Center
Greenspan, Stephen
2006-01-01
Although there have always been people considered to have mental retardation (MR), the category has proven surprisingly difficult to define adequately. This is because it includes a subcategory of mild MR whose members are part of a larger population of marginally competent people, some of whom may be considered to have other forms of disability…
ERIC Educational Resources Information Center
Soenen, Sarah; Van Berckelaer-Onnes, Ina; Scholte, Evert
2009-01-01
Many researchers have studied the population of individuals with mild mental retardation (MIMR) as if it is a clear entity. Few researchers have investigated potential subtypes within the MIMR population. The purpose of the present study was to investigate which subtypes can be identified on the basis of intellectual, adaptive and behavioral…
Kananenka, Alexei A; Welden, Alicia Rae; Lan, Tran Nguyen; Gull, Emanuel; Zgid, Dominika
2016-05-10
The popular, stable, robust, and computationally inexpensive cubic spline interpolation algorithm is adopted and used for finite temperature Green's function calculations of realistic systems. We demonstrate that with appropriate modifications the temperature dependence can be preserved while the Green's function grid size can be reduced by about 2 orders of magnitude by replacing the standard Matsubara frequency grid with a sparser grid and a set of interpolation coefficients. We benchmarked the accuracy of our algorithm as a function of a single parameter sensitive to the shape of the Green's function. Through numerous examples, we confirmed that our algorithm can be utilized in a systematically improvable, controlled, and black-box manner and highly accurate one- and two-body energies and one-particle density matrices can be obtained using only around 5% of the original grid points. Additionally, we established that to improve accuracy by an order of magnitude, the number of grid points needs to be doubled, whereas for the Matsubara frequency grid, an order of magnitude more grid points must be used. This suggests that realistic calculations with large basis sets that were previously out of reach because they required enormous grid sizes may now become feasible. PMID:27049642
Tan, William; Schauder, Curtis; Naryshkina, Tatyana; Minakhina, Svetlana; Steward, Ruth
2016-02-15
Fragile-X syndrome is the most commonly inherited cause of autism and mental disabilities. The Fmr1 (Fragile-X Mental Retardation 1) gene is essential in humans and Drosophila for the maintenance of neural stem cells, and Fmr1 loss results in neurological and reproductive developmental defects in humans and flies. FMRP (Fragile-X Mental Retardation Protein) is a nucleo-cytoplasmic shuttling protein, involved in mRNA silencing and translational repression. Both Zfrp8 and Fmr1 have essential functions in the Drosophila ovary. In this study, we identified FMRP, Nufip (Nuclear Fragile-X Mental Retardation Protein-interacting Protein) and Tral (Trailer Hitch) as components of a Zfrp8 protein complex. We show that Zfrp8 is required in the nucleus, and controls localization of FMRP in the cytoplasm. In addition, we demonstrate that Zfrp8 genetically interacts with Fmr1 and tral in an antagonistic manner. Zfrp8 and FMRP both control heterochromatin packaging, also in opposite ways. We propose that Zfrp8 functions as a chaperone, controlling protein complexes involved in RNA processing in the nucleus. PMID:26772998
Green's function of a free massive scalar field on the lattice
Borasoy, B.; Krebs, H.
2005-09-01
We propose a method to calculate the Green's function of a free massive scalar field on the lattice numerically to very high precision. For masses m<2 (in lattice units) the massive Green's function can be expressed recursively in terms of the massless Green's function and just two additional mass-independent constants.
Green polymer chemistry: enzyme catalysis for polymer functionalization.
Sen, Sanghamitra; Puskas, Judit E
2015-01-01
Enzyme catalyzed reactions are green alternative approaches to functionalize polymers compared to conventional methods. This technique is especially advantageous due to the high selectivity, high efficiency, milder reaction conditions, and recyclability of enzymes. Selected reactions can be conducted under solventless conditions without the application of metal catalysts. Hence this process is becoming more recognized in the arena of biomedical applications, as the toxicity created by solvents and metal catalyst residues can be completely avoided. In this review we will discuss fundamental aspects of chemical reactions biocatalyzed by Candida antarctica lipase B, and their application to create new functionalized polymers, including the regio- and chemoselectivity of the reactions. PMID:26007188
ERIC Educational Resources Information Center
Wright, Jennifer Adams
2010-01-01
This study investigated the relationship of mental health issues, adaptive functioning, and school outcomes for students with mild mental retardation (MMR). Mental health (MH) was measured using the Teacher Report Form (TRF) of the Achenbach System of Empirically Based Assessment (ASEBA). Teachers also completed the Adaptive Behavior Inventory…
Brazilian green propolis improves immune function in aged mice
Gao, Weina; Wu, Jianquan; Wei, Jingyu; Pu, Lingling; Guo, Changjiang; Yang, Jijun; Yang, Ming; Luo, Haiji
2014-01-01
Aging weakened innate and adaptive immunity both quantitatively and qualitatively. Some components in propolis could stimulate immune function in young animals or cultured immune cells in vitro. Few studies had been carried out in the aged. The present study was to evaluate the effects of Brazilian green propolis supplementation on the immunological parameters in aged mice. Eighty Kunming mice, aged 15–18 months, were randomly assigned to the control and three experimental groups supplemented with different doses (83.3, 157.4 and 352.9 mg/kg.bw respectively) of Brazilian green propolis. The experiment lasted for 4 weeks. Contents of total polyphenol, flavonoid, cinnamic acid and artepillin-C in Brazilian green propolis were analyzed. Splenic NK cytotoxic, T lymphocyte proliferation and antibody generation cells, as well as the phagocytosis of peritoneal macrophages, ear swelling, and serum contents of IgG, IgM, hemolysin and cytokines were measured. After 4 weeks of treatment, the phagocytosis of peritoneal macrophages was enhanced in 157.4 mg/kg and 352.9 mg/kg groups. Ear swelling increased in all propolis treatmented groups. Antibodies specific to sheep erythrocytes were higher in the groups receiving 157.4 and 352.9 mg/kg.bw than that of control group. IgG level dramatically increased in the groups receiving 83.3 and 157.4 mg/kg.bw in comparison to the control group. These results indicate that administration of Brazilian green propolis have a positive effect on innate and adaptive immunity in aged mice. PMID:25120274
Nonequilibrium Green's Function approach to time-resolved photoabsorption
NASA Astrophysics Data System (ADS)
Stefanucci, Gianluca; Perfetto, Enrico; Uimonen, Anna-Maija; van Leeuwen, Robert
We propose a nonequilibrium Green's function (NEGF) approach to calculate the time-resolved absorption spectrum of nanoscale systems. We can deal with arbitrary shape, intensity, duration and relative delay of the pump and probe fields and include ionization processes as well as hybridization effects due to surfaces. We present numerical simulations of atomic systems using different approximate self-energies and show that electron correlations are pivotal to reproduce important qualitative features. E.P. and G.S. acknowledge funding by MIUR FIRB Grant No. RBFR12SW0J. R.v.L. thanks the Academy of Finland for support.
Optical spectroscopy of molecular junctions: Nonequilibrium Green's functions perspective.
Gao, Yi; Galperin, Michael
2016-05-01
We consider optical spectroscopy of molecular junctions from the quantum transport perspective when radiation field is quantized and optical response of the system is simulated as photon flux. Using exact expressions for photon and electronic fluxes derived within the nonequilibrium Green function (NEGF) methodology and utilizing fourth order diagrammatic perturbation theory (PT) in molecular coupling to radiation field, we perform simulations employing realistic parameters. Results of the simulations are compared to the bare PT which is usually employed in studies on nonlinear optical spectroscopy to classify optical processes. We show that the bare PT violates conservation laws, while flux conserving NEGF formulation mixes optical processes. PMID:27155631
Optical spectroscopy of molecular junctions: Nonequilibrium Green's functions perspective
NASA Astrophysics Data System (ADS)
Gao, Yi; Galperin, Michael
2016-05-01
We consider optical spectroscopy of molecular junctions from the quantum transport perspective when radiation field is quantized and optical response of the system is simulated as photon flux. Using exact expressions for photon and electronic fluxes derived within the nonequilibrium Green function (NEGF) methodology and utilizing fourth order diagrammatic perturbation theory (PT) in molecular coupling to radiation field, we perform simulations employing realistic parameters. Results of the simulations are compared to the bare PT which is usually employed in studies on nonlinear optical spectroscopy to classify optical processes. We show that the bare PT violates conservation laws, while flux conserving NEGF formulation mixes optical processes.
Eddy current calculations using half-space Green's functions
NASA Astrophysics Data System (ADS)
Bowler, J. R.
1987-02-01
A simple scalar representation is used to describe the electromagnetic field in the quasi-static limit for an arbitrary time-harmonic source current above an imperfectly conducting half-space. Solutions are given in terms of half-space scalar and dyadic Green's functions. The general results are then used to derive analytical expressions for the fields arising from circular filaments and extended sources whose axes of symmetry are parallel to the surface of the conductor. These tangent coil solutions have applications in the theory of inductive sensors, particularly for eddy current nondestructive testing.
Surface state photoelectrons in topological insulators: Green's function approach.
Schmeltzer, D; Saxena, A
2015-12-01
We compute the photoemission intensity and polarization for the surface states in topological insulators. Due to the chirality and linear energy dispersion the effective electron-photon coupling is normalized by the tunneling amplitude (τ) into the vacuum. We investigate a chiral Dirac Hamiltonian for different cases: helical, Zeeman and warping, allowing us to study spin textures. Using the Green's function formalism we obtain exact results for the emitted photoelectrons to second order in the laser field. The number of emitted photoelectrons is sensitive to the laser coherent state intensity whereas the photoelectron polarization is sensitive to the surface topology of electronic states and incoming photon polarization. PMID:26565417
PREFACE: Progress in Nonequilibrium Green's Functions V (PNGF V)
NASA Astrophysics Data System (ADS)
van Leeuwen, Robert; Tuovinen, Riku; Bonitz, Michael
2013-03-01
(The PDF contains: an obituary and in memoriam for David C. Langreth, a list of the conference participants, a complete list of the conference talks and posters and several photographs taken during the conference. ) The fifth interdisciplinary conference 'Progress in Nonequilibrium Green's Functions' (PNGF5) was held at the University of Jyväskylä, Finland, on 27--31 August 2012. The conference continued the successful tradition of its predecessors (Rostock 1999, Dresden 2002, Kiel 2005 and Glasgow 2009) to bring together different communities for an interdisciplinary exchange of recent results and theoretical concepts. The conference focused on recent developments, current challenges and future perspectives in nonequilibrium Green's functions theory in various fields of physics but included also other many-body methods. Roughly 20 invited talks were given by some of the top scientists in the field, accompanied by 10 contributed talks. (Slides of several presentations can be found online at www.jyu.fi/physics/pngf5.) Also a poster session was set up to enhance scientific discussions, building up new collaborations and enriching views and ideas. As at the previous meetings, the atmosphere was interactive and stimulating, benefitting both experienced scientists and young researchers and students. The present volume contains 14 articles based on works presented at this conference. The articles partly have review character so they should be of use for an interdisciplinary community working or interested in nonequilibrium Green's functions. All papers were refereed according to high scientific standards. The conference would not have been possible without financial support from the Federation of Finnish Learned Societies, Finnish Academy of Science and Letters and Nanoscience Center of the university of Jyväskylä which are greatly acknowledged. The local organizing committee is also grateful to the administration personnel, Marjut Hilska and Riitta-Liisa Kuittinen
Free Electron Laser Theory Using Two Times Green Function Formalism
NASA Astrophysics Data System (ADS)
Takahashi, Hiroshi
2002-04-01
In this paper, we present a quatum theory for free electron laser obtained by firstly using the Two time's Green Function method developed by Matsubara for solid physics theory. The dispersion relation for the laser photon obtained is limited to the case of low intensity of the laser due to the decoupling the correlation function in low order. For the analysis of the self-amplified emission (SASE), the high intensity laser radiation which strongly affect the trajectory of the free electron is involved, the use of the classical approximation for laser can formulate the laser radiation with multiple frequency. To get the quantum effects in the high intensity laser, use of the perturbation theory, and the expansion methods of state function using the coherent, squeeze and super-radiant states have discussed.
SOURCE PULSE ENHANCEMENT BY DECONVOLUTION OF AN EMPIRICAL GREEN'S FUNCTION.
Mueller, Charles S.
1985-01-01
Observations of the earthquake source-time function are enhanced if path, recording-site, and instrument complexities can be removed from seismograms. Assuming that a small earthquake has a simple source, its seismogram can be treated as an empirical Green's function and deconvolved from the seismogram of a larger and/or more complex earthquake by spectral division. When the deconvolution is well posed, the quotient spectrum represents the apparent source-time function of the larger event. This study shows that with high-quality locally recorded earthquake data it is feasible to Fourier transform the quotient and obtain a useful result in the time domain. In practice, the deconvolution can be stabilized by one of several simple techniques. Application of the method is given. Refs.
Eco-friendly functionalized superhydrophobic recycled paper with enhanced flame-retardancy.
Si, Yifan; Guo, Zhiguang
2016-09-01
Recycled paper with superhydrophobicity and flame-retardancy has been demonstrated here due to the synergistic action of dopamine-silica trimethylsilyl modified gel powder and stearic acid modified Mg(OH)2. This multifunctional recycled paper displays great self-cleaning and anti-fouling ability and can be used for oil-water separation. Surprisingly, the absorbed organic can be reused as fuel via simple combustion method for multiple cycles. This work will not only expand the usable range of paper but also ease the energy and environment crisis. PMID:27244592
Green's function approach to edge states in transition metal dichalcogenides
NASA Astrophysics Data System (ADS)
Farmanbar, Mojtaba; Amlaki, Taher; Brocks, Geert
2016-05-01
The semiconducting two-dimensional transition metal dichalcogenides MX 2 show an abundance of one-dimensional metallic edges and grain boundaries. Standard techniques for calculating edge states typically model nanoribbons, and require the use of supercells. In this paper, we formulate a Green's function technique for calculating edge states of (semi-)infinite two-dimensional systems with a single well-defined edge or grain boundary. We express Green's functions in terms of Bloch matrices, constructed from the solutions of a quadratic eigenvalue equation. The technique can be applied to any localized basis representation of the Hamiltonian. Here, we use it to calculate edge states of MX 2 monolayers by means of tight-binding models. Aside from the basic zigzag and armchair edges, we study edges with a more general orientation, structurally modifed edges, and grain boundaries. A simple three-band model captures an important part of the edge electronic structures. An 11-band model comprising all valence orbitals of the M and X atoms is required to obtain all edge states with energies in the MX 2 band gap. Here, states of odd symmetry with respect to a mirror plane through the layer of M atoms have a dangling-bond character, and tend to pin the Fermi level.
2012-01-01
Background Animal and in vitro studies demonstrated a neurotoxic potential of brominated flame retardants, a group of chemicals used in many household and commercial products to prevent fire. Although the first reports of detrimental neurobehavioral effects in rodents appeared more than ten years ago, human data are sparse. Methods As a part of a biomonitoring program for environmental health surveillance in Flanders, Belgium, we assessed the neurobehavioral function with the Neurobehavioral Evaluation System (NES-3), and collected blood samples in a group of high school students. Cross-sectional data on 515 adolescents (13.6-17 years of age) was available for the analysis. Multiple regression models accounting for potential confounders were used to investigate the associations between biomarkers of internal exposure to brominated flame retardants [serum levels of polybrominated diphenyl ether (PBDE) congeners 47, 99, 100, 153, 209, hexabromocyclododecane (HBCD), and tetrabromobisphenol A (TBBPA)] and cognitive performance. In addition, we investigated the association between brominated flame retardants and serum levels of FT3, FT4, and TSH. Results A two-fold increase of the sum of serum PBDE’s was associated with a decrease of the number of taps with the preferred-hand in the Finger Tapping test by 5.31 (95% CI: 0.56 to 10.05, p = 0.029). The effects of the individual PBDE congeners on the motor speed were consistent. Serum levels above the level of quantification were associated with an average decrease of FT3 level by 0.18 pg/mL (95% CI: 0.03 to 0.34, p = 0.020) for PBDE-99 and by 0.15 pg/mL (95% CI: 0.004 to 0.29, p = 0.045) for PBDE-100, compared with concentrations below the level of quantification. PBDE-47 level above the level of quantification was associated with an average increase of TSH levels by 10.1% (95% CI: 0.8% to 20.2%, p = 0.033), compared with concentrations below the level of quantification. We did not observe effects of
ERIC Educational Resources Information Center
Baumeister, Alfred A., Ed.
Thirteen papers by different authors consider the application of research findings and theoretical formulations to the practical appraisal and treatment of mental retardation. All suggest methods for shaping appropriate and adaptive behaviors in retarded individuals. The papers include "Definition, Diagnosis, and Classification" by D.W. Brison,…
ERIC Educational Resources Information Center
Purpura, Dominick P.; And Others
Evidence today indicates that the causes of mental retardation are biological, psychological, and social in origin and that a combination of these causes frequently occur in a single individual. Mental retardation is identified clinically by the presence of several signs that include, but are not limited to, a significant impairment of…
Real-space Green;s function calculations of Compton profiles
Mattern, Brian A.; Seidler, Gerald T.; Kas, Joshua J.; Pacold, Joseph I.; Rehr, John J.
2012-09-05
We report the development of a first-principles, real-space Green's function method for calculation of Compton profiles in the impulse approximation. For crystalline Be, we find excellent agreement with prior theoretical treatments requiring periodicity, with prior experimental measurements of the Compton profile, and with present measurements of the dynamical structure factor via nonresonant inelastic x-ray scattering (often also called x-ray Thomson scattering in the plasma physics community). We also find good agreement with prior experimental results for the Compton profile of Cu. This approach can be extended to disordered and very high-temperature systems, such as 'warm dense matter,' where theories presently used for the interpretation of inelastic x-ray scattering include condensed phase effects only at a perturbative level.
Clay nanopaper with tough cellulose nanofiber matrix for fire retardancy and gas barrier functions.
Liu, Andong; Walther, Andreas; Ikkala, Olli; Belova, Lyuba; Berglund, Lars A
2011-03-14
Nacre-mimicking hybrids of high inorganic content (>50 wt %) tend to show low strain-to-failure. Therefore, we prepared clay nanopaper hybrid composite montmorillonite platelets in a continuous matrix of nanofibrillated cellulose (NFC) with the aim of harnessing the intrinsic toughness of fibrillar networks. Hydrocolloid mixtures were used in a filtration approach akin to paper processing. The resulting multilayered structure of the nanopaper was studied by FE-SEM, FTIR, and XRD. Uniaxial stress-strain curves measured in tension and thermal analysis were carried out by DMTA and TGA. In addition, fire retardance and oxygen permeability characteristics were measured. The continuous NFC matrix is a new concept and provides unusual ductility to the nanocomposite, allowing inorganic contents as high as 90% by weight. Clay nanopaper extends the property range of cellulose nanopaper and is of interest in self-extinguishing composites and in oxygen barrier layers. PMID:21291221
An improved version of the Green's function molecular dynamics method
NASA Astrophysics Data System (ADS)
Kong, Ling Ti; Denniston, Colin; Müser, Martin H.
2011-02-01
This work presents an improved version of the Green's function molecular dynamics method (Kong et al., 2009; Campañá and Müser, 2004 [1,2]), which enables one to study the elastic response of a three-dimensional solid to an external stress field by taking into consideration only atoms near the surface. In the previous implementation, the effective elastic coefficients measured at the Γ-point were altered to reduce finite size effects: their eigenvalues corresponding to the acoustic modes were set to zero. This scheme was found to work well for simple Bravais lattices as long as only atoms within the last layer were treated as Green's function atoms. However, it failed to function as expected in all other cases. It turns out that a violation of the acoustic sum rule for the effective elastic coefficients at Γ (Kong, 2010 [3]) was responsible for this behavior. In the new version, the acoustic sum rule is enforced by adopting an iterative procedure, which is found to be physically more meaningful than the previous one. In addition, the new algorithm allows one to treat lattices with bases and the Green's function slab is no longer confined to one layer. New version program summaryProgram title: FixGFC/FixGFMD v1.12 Catalogue identifier: AECW_v1_1 Program summary URL:http://cpc.cs.qub.ac.uk/summaries/AECW_v1_1.html Program obtainable from: CPC Program Library, Queen's University, Belfast, N. Ireland Licensing provisions: Standard CPC licence, http://cpc.cs.qub.ac.uk/licence/licence.html No. of lines in distributed program, including test data, etc.: 206 436 No. of bytes in distributed program, including test data, etc.: 4 314 850 Distribution format: tar.gz Programming language: C++ Computer: All Operating system: Linux Has the code been vectorized or parallelized?: Yes. Code has been parallelized using MPI directives. RAM: Depends on the problem Classification: 7.7 External routines: LAMMPS ( http://lammps.sandia.gov/), MPI ( http
Electron Systems Out of Equilibrium: Nonequilibrium Green's Function Approach
NASA Astrophysics Data System (ADS)
Špička, Václav Velický, Bedřich Kalvová, Anděla
2015-10-01
This review deals with the state of the art and perspectives of description of non-equilibrium many body systems using the non-equilibrium Green's function (NGF) method. The basic aim is to describe time evolution of the many-body system from its initial state over its transient dynamics to its long time asymptotic evolution. First, we discuss basic aims of transport theories to motivate the introduction of the NGF techniques. Second, this article summarizes the present view on construction of the electron transport equations formulated within the NGF approach to non-equilibrium. We discuss incorporation of complex initial conditions to the NGF formalism, and the NGF reconstruction theorem, which serves as a tool to derive simplified kinetic equations. Three stages of evolution of the non-equilibrium, the first described by the full NGF description, the second by a Non-Markovian Generalized Master Equation and the third by a Markovian Master Equation will be related to each other.
Coupled cluster Green function: Model involving single and double excitations
NASA Astrophysics Data System (ADS)
Bhaskaran-Nair, Kiran; Kowalski, Karol; Shelton, William A.
2016-04-01
In this paper, we report on the development of a parallel implementation of the coupled-cluster (CC) Green function formulation (GFCC) employing single and double excitations in the cluster operator (GFCCSD). A key aspect of this work is the determination of the frequency dependent self-energy, Σ(ω). The detailed description of the underlying algorithm is provided, including approximations used that preserve the pole structure of the full GFCCSD method, thereby reducing the computational costs while maintaining an accurate character of methodology. Furthermore, for systems with strong local correlation, our formulation reveals a diagonally dominate block structure where as the non-local correlation increases, the block size increases proportionally. To demonstrate the accuracy of our approach, several examples including calculations of ionization potentials for benchmark systems are presented and compared against experiment.
Dyadic Green's function of a cluster of spheres.
Moneda, Angela P; Chrissoulidis, Dimitrios P
2007-11-01
The electric dyadic Green's function (dGf) of a cluster of spheres is obtained by application of the superposition principle, dyadic algebra, and the indirect mode-matching method. The analysis results in a set of linear equations for the unknown, vector, wave amplitudes of the dGf; that set is solved by truncation and matrix inversion. The theory is exact in the sense that no simplifying assumptions are made in the analytical steps leading to the dGf, and it is general in the sense that any number, position, size and electrical properties can be considered for the spheres that cluster together. The point source can be anywhere, even within one of the spheres. Energy conservation, reciprocity, and other tests prove that this solution is correct. Numerical results are presented for an electric Hertz dipole radiating in the presence of an array of rexolite spheres, which manifests lensing and beam-forming capabilities. PMID:17975570
Coupled cluster Green function: Model involving single and double excitations.
Bhaskaran-Nair, Kiran; Kowalski, Karol; Shelton, William A
2016-04-14
In this paper, we report on the development of a parallel implementation of the coupled-cluster (CC) Green function formulation (GFCC) employing single and double excitations in the cluster operator (GFCCSD). A key aspect of this work is the determination of the frequency dependent self-energy, Σ(ω). The detailed description of the underlying algorithm is provided, including approximations used that preserve the pole structure of the full GFCCSD method, thereby reducing the computational costs while maintaining an accurate character of methodology. Furthermore, for systems with strong local correlation, our formulation reveals a diagonally dominate block structure where as the non-local correlation increases, the block size increases proportionally. To demonstrate the accuracy of our approach, several examples including calculations of ionization potentials for benchmark systems are presented and compared against experiment. PMID:27083702
Electron systems out of equilibrium: Nonequilibrium Green's function approach
NASA Astrophysics Data System (ADS)
Špička, Václav; Velický, Bedřich; Kalvová, Anděla
2014-07-01
This review deals with the state of the art and perspectives of description of nonequilibrium many-body systems using the nonequilibrium Green's function (NGF) method. The basic aim is to describe time evolution of the many-body system from its initial state over its transient dynamics to its long time asymptotic evolution. First, we discuss basic aims of transport theories to motivate the introduction of the NGF techniques. Second, this article summarizes the present view on construction of the electron transport equations formulated within the NGF approach to nonequilibrium. We discuss incorporation of complex initial conditions to the NGF formalism, and the NGF reconstruction theorem, which serves as a tool to derive simplified kinetic equations. Three stages of evolution of the nonequilibrium, the first described by the full NGF description, the second by a non-Markovian generalized master equation and the third by a Markovian master equation will be related to each other.
Integral equation for gauge invariant quark two-point Green's function in QCD
Sazdjian, H.
2008-02-15
Gauge invariant quark two-point Green's functions defined with path-ordered gluon field phase factors along skew-polygonal lines joining the quark to the antiquark are considered. Functional relations between Green's functions with different numbers of path segments are established. An integral equation is obtained for the Green's function defined with a phase factor along a single straight line. The equation implicates an infinite series of two-point Green's functions, having an increasing number of path segments; the related kernels involve Wilson loops with contours corresponding to the skew-polygonal lines of the accompanying Green's function and with functional derivatives along the sides of the contours. The series can be viewed as an expansion in terms of the global number of the functional derivatives of the Wilson loops. The lowest-order kernel, which involves a Wilson loop with two functional derivatives, provides the framework for an approximate resolution of the equation.
Retrieving time-dependent Green's functions in optics with low-coherence interferometry.
Badon, Amaury; Lerosey, Geoffroy; Boccara, Albert C; Fink, Mathias; Aubry, Alexandre
2015-01-16
We report on the passive measurement of time-dependent Green's functions in the optical frequency domain with low-coherence interferometry. Inspired by previous studies in acoustics and seismology, we show how the correlations of a broadband and incoherent wave field can directly yield the Green's functions between scatterers of a complex medium. Both the ballistic and multiple scattering components of the Green's function are retrieved. This approach opens important perspectives for optical imaging and characterization in complex scattering media. PMID:25635547
Plant Species and Functional Group Combinations Affect Green Roof Ecosystem Functions
Lundholm, Jeremy; MacIvor, J. Scott; MacDougall, Zachary; Ranalli, Melissa
2010-01-01
Background Green roofs perform ecosystem services such as summer roof temperature reduction and stormwater capture that directly contribute to lower building energy use and potential economic savings. These services are in turn related to ecosystem functions performed by the vegetation layer such as radiation reflection and transpiration, but little work has examined the role of plant species composition and diversity in improving these functions. Methodology/Principal Findings We used a replicated modular extensive (shallow growing- medium) green roof system planted with monocultures or mixtures containing one, three or five life-forms, to quantify two ecosystem services: summer roof cooling and water capture. We also measured the related ecosystem properties/processes of albedo, evapotranspiration, and the mean and temporal variability of aboveground biomass over four months. Mixtures containing three or five life-form groups, simultaneously optimized several green roof ecosystem functions, outperforming monocultures and single life-form groups, but there was much variation in performance depending on which life-forms were present in the three life-form mixtures. Some mixtures outperformed the best monocultures for water capture, evapotranspiration, and an index combining both water capture and temperature reductions. Combinations of tall forbs, grasses and succulents simultaneously optimized a range of ecosystem performance measures, thus the main benefit of including all three groups was not to maximize any single process but to perform a variety of functions well. Conclusions/Significance Ecosystem services from green roofs can be improved by planting certain life-form groups in combination, directly contributing to climate change mitigation and adaptation strategies. The strong performance by certain mixtures of life-forms, especially tall forbs, grasses and succulents, warrants further investigation into niche complementarity or facilitation as mechanisms
Implementation of Green's function molecular dynamics: An extension to LAMMPS
NASA Astrophysics Data System (ADS)
Kong, Ling Ti; Bartels, Guido; Campañá, Carlos; Denniston, Colin; Müser, Martin H.
2009-06-01
The Green's function molecular dynamics method, which enables one to study the elastic response of a three-dimensional solid to an external stress field by taking into consideration only the surface atoms, was implemented as an extension to an open source classical molecular dynamics simulation code LAMMPS. This was done in the style of fixes. The first fix, FixGFC, measures the elastic stiffness coefficients for a (small) solid block of a given material by making use of the fluctuation-dissipation theorem. With the help of the second fix, FixGFMD, the coefficients obtained from FixGFC can then be used to compute the elastic forces for a (large) block of the same material. Both fixes are designed to be run in parallel and to exploit the functions provided by LAMMPS. Program summaryProgram title: FixGFC/FixGFMD Catalogue identifier: AECW_v1_0 Program summary URL:http://cpc.cs.qub.ac.uk/summaries/AECW_v1_0.html Program obtainable from: CPC Program Library, Queen's University, Belfast, N. Ireland Licensing provisions: yes No. of lines in distributed program, including test data, etc.: 33 469 No. of bytes in distributed program, including test data, etc.: 1 383 631 Distribution format: tar.gz Programming language: C++ Computer: All Operating system: Linux Has the code been vectorized or parallelized?: Parallelized via MPI RAM: Depends on the problem Classification: 7.7 External routines: MPI, FFTW 2.1.5 ( http://www.fftw.org/), LAMMPS version May 21, 2008 ( http://lammps.sandia.gov/) Nature of problem: Using molecular dynamics to study elastically deforming solids imposes very high computational costs because portions of the solid far away from the interface or contact points need to be included in the simulation to reproduce the effects of long-range elastic deformations. Green's function molecular dynamics (GFMD) incorporates the full elastic response of semi-infinite solids so that only surface atoms have to be considered in molecular dynamics simulations, thus
Recursive evaluation of space-time lattice Green's functions
NASA Astrophysics Data System (ADS)
de Hon, Bastiaan P.; Arnold, John M.
2012-09-01
Up to a multiplicative constant, the lattice Green's function (LGF) as defined in condensed matter physics and lattice statistical mechanics is equivalent to the Z-domain counterpart of the finite-difference time-domain Green's function (GF) on a lattice. Expansion of a well-known integral representation for the LGF on a ν-dimensional hyper-cubic lattice in powers of Z-1 and application of the Chu-Vandermonde identity results in ν - 1 nested finite-sum representations for discrete space-time GFs. Due to severe numerical cancellations, these nested finite sums are of little practical use. For ν = 2, the finite sum may be evaluated in closed form in terms of a generalized hypergeometric function. For special lattice points, that representation simplifies considerably, while on the other hand the finite-difference stencil may be used to derive single-lattice-point second-order recurrence schemes for generating 2D discrete space-time GF time sequences on the fly. For arbitrary symbolic lattice points, Zeilberger's algorithm produces a third-order recurrence operator with polynomial coefficients of the sixth degree. The corresponding recurrence scheme constitutes the most efficient numerical method for the majority of lattice points, in spite of the fact that for explicit numeric lattice points the associated third-order recurrence operator is not the minimum recurrence operator. As regards the asymptotic bounds for the possible solutions to the recurrence scheme, Perron's theorem precludes factorial or exponential growth. Along horizontal lattices directions, rapid initial growth does occur, but poses no problems in augmented dynamic-range fixed precision arithmetic. By analysing long-distance wave propagation along a horizontal lattice direction, we have concluded that the chirp-up oscillations of the discrete space-time GF are the root cause of grid dispersion anisotropy. With each factor of ten increase in the lattice distance, one would have to roughly double
Green's function of compressible Petschek-type magnetic reconnection
NASA Astrophysics Data System (ADS)
Penz, Thomas; Semenov, V. S.; Ivanova, V. V.; Heyn, M. F.; Ivanov, I. B.; Biernat, H. K.
2006-05-01
We present a method to analyze the wave and shock structures arising from Petschek-type magnetic reconnection. Based on a time-dependent analytical approach developed by Heyn and Semenov [Phys. Plasmas 3, 2725 (1996)] and Semenov et al. [Phys. Plasmas 11, 62 (2004)], we calculate the perturbations caused by a delta function-shaped reconnection electric field, which allows us to achieve a representation of the plasma variables in the form of Green's functions. Different configurations for the initial conditions are considered. In the case of symmetric, antiparallel magnetic fields and symmetric plasma density, the well-known structure of an Alfvén discontinuity, a fast body wave, a slow shock, a slow wave, and a tube wave occurs. In the case of asymmetric, antiparallel magnetic fields, additionally surface waves are found. We also discuss the case of symmetric, antiparallel magnetic fields and asymmetric densities, which leads to a faster propagation in the lower half plane, causing side waves forming a Mach cone in the upper half plane. Complex effects like anisotropic propagation characteristics, intrinsic wave coupling, and the generation of different nonlinear and linear wave modes in a finite β plasma are retained. The temporal evolution of these wave and shock structures is shown.
Siphonaxanthin, a Green Algal Carotenoid, as a Novel Functional Compound
Sugawara, Tatsuya; Ganesan, Ponesakki; Li, Zhuosi; Manabe, Yuki; Hirata, Takashi
2014-01-01
Siphonaxanthin is a specific keto-carotenoid in green algae whose bio-functional properties are yet to be identified. This review focuses on siphonaxanthin as a bioactive compound and outlines the evidence associated with functionality. Siphonaxanthin has been reported to potently inhibit the viability of human leukemia HL-60 cells via induction of apoptosis. In comparison with fucoxanthin, siphonaxanthin markedly reduced cell viability as early as 6 h after treatment. The cellular uptake of siphonaxanthin was 2-fold higher than fucoxanthin. It has been proposed that siphonaxanthin possesses significant anti-angiogenic activity in studies using human umbilical vein endothelial cells and rat aortic ring. The results of these studies suggested that the anti-angiogenic effect of siphonaxanthin is due to the down-regulation of signal transduction by fibroblast growth factor receptor-1 in vascular endothelial cells. Siphonaxanthin also exhibited inhibitory effects on antigen-induced degranulation of mast cells. These findings open up new avenues for future research on siphonaxanthin as a bioactive compound, and additional investigation, especially in vivo studies, are required to validate these findings. In addition, further studies are needed to determine its bioavailability and metabolic fate. PMID:24950294
Green process for chemical functionalization of nanocellulose with carboxylic acids.
Espino-Pérez, Etzael; Domenek, Sandra; Belgacem, Naceur; Sillard, Cécile; Bras, Julien
2014-12-01
An environmentally friendly and simple method, named SolReact, has been developed for a solvent-free esterification of cellulose nanocrystals (CNC) surface by using two nontoxic carboxylic acids (CA), phenylacetic acid and hydrocinnamic acid. In this process, the carboxylic acids do not only act as grafting agent, but also as solvent media above their melting point. Key is the in situ solvent exchange by water evaporation driving the esterification reaction without drying the CNC. Atomic force microscopy and X-ray diffraction analyses showed no significant change in the CNC dimensions and crystallinity index after this green process. The presence of the grafted carboxylic was characterized by analysis of the "bulk" CNC with elemental analysis, infrared spectroscopy, and (13)C NMR. The ability to tune the surface properties of grafted nanocrystals (CNC-g-CA) was evaluated by X-ray photoelectron spectroscopy analysis. The hydrophobicity behavior of the functionalized CNC was studied through the water contact-angle measurements and vapor adsorption. The functionalization of these bionanoparticles may offer applications in composite manufacturing, where these nanoparticles have limited dispersibility in hydrophobic polymer matrices and as nanoadsorbers due to the presence of phenolic groups attached on the surface. PMID:25353612
NASA Astrophysics Data System (ADS)
Wapenaar, Kees; Thorbecke, Jan; van der Neut, Joost
2016-04-01
Green's theorem plays a fundamental role in a diverse range of wavefield imaging applications, such as holographic imaging, inverse scattering, time-reversal acoustics and interferometric Green's function retrieval. In many of those applications, the homogeneous Green's function (i.e. the Green's function of the wave equation without a singularity on the right-hand side) is represented by a closed boundary integral. In practical applications, sources and/or receivers are usually present only on an open surface, which implies that a significant part of the closed boundary integral is by necessity ignored. Here we derive a homogeneous Green's function representation for the common situation that sources and/or receivers are present on an open surface only. We modify the integrand in such a way that it vanishes on the part of the boundary where no sources and receivers are present. As a consequence, the remaining integral along the open surface is an accurate single-sided representation of the homogeneous Green's function. This single-sided representation accounts for all orders of multiple scattering. The new representation significantly improves the aforementioned wavefield imaging applications, particularly in situations where the first-order scattering approximation breaks down.
The Green's function for the three-dimensional linear Boltzmann equation via Fourier transform
NASA Astrophysics Data System (ADS)
Machida, Manabu
2016-04-01
The linear Boltzmann equation with constant coefficients in the three-dimensional infinite space is revisited. It is known that the Green's function can be calculated via the Fourier transform in the case of isotropic scattering. In this paper, we show that the three-dimensional Green's function can be computed with the Fourier transform even in the case of arbitrary anisotropic scattering.
NASA Astrophysics Data System (ADS)
Sarsenbi, Abdizhahan
2015-09-01
In this paper, the Green's function of a boundary boundary value problem with an involution is constructed. Applying the Green's function, a formula for expansion in the eigenfunctions of the spectral problem for a second order differential equation with an involution involving boundary conditions of Dirichlet type is presented.
A Green's function method for heavy ion beam transport
NASA Technical Reports Server (NTRS)
Shinn, J. L.; Wilson, J. W.; Schimmerling, W.; Shavers, M. R.; Miller, J.; Benton, E. V.; Frank, A. L.; Badavi, F. F.
1995-01-01
The use of Green's function has played a fundamental role in transport calculations for high-charge high-energy (HZE) ions. Two recent developments have greatly advanced the practical aspects of implementation of these methods. The first was the formulation of a closed-form solution as a multiple fragmentation perturbation series. The second was the effective summation of the closed-form solution through nonperturbative techniques. The nonperturbative methods have been recently extended to an inhomogeneous, two-layer transport media to simulate the lead scattering foil present in the Lawrence Berkeley Laboratories (LBL) biomedical beam line used for cancer therapy. Such inhomogeneous codes are necessary for astronaut shielding in space. The transport codes utilize the Langley Research Center atomic and nuclear database. Transport code and database evaluation are performed by comparison with experiments performed at the LBL Bevalac facility using 670 A MeV 20Ne and 600 A MeV 56Fe ion beams. The comparison with a time-of-flight and delta E detector measurement for the 20Ne beam and the plastic nuclear track detectors for 56Fe show agreement up to 35%-40% in water and aluminium targets, respectively.
An improved Green's function for ion beam transport.
Tweed, J; Wilson, J W; Tripathi, R K
2004-01-01
Ion beam transport theory allows testing of material transmission properties in the laboratory environment generated by particle accelerators. This is a necessary step in materials development and evaluation for space use. The approximations used in solving the Boltzmann transport equation for the space setting are often not sufficient for laboratory work and those issues are the main emphasis of the present work. In consequence, an analytic solution of the linear Boltzmann equation is pursued in the form of a Green's function allowing flexibility in application to a broad range of boundary value problems. It has been established that simple solutions can be found for high charge and energy (HZE) ions by ignoring nuclear energy downshifts and dispersion. Such solutions were found to be supported by experimental evidence with HZE ion beams when multiple scattering was added. Lacking from the prior solutions were range and energy straggling and energy downshift with dispersion associated with nuclear events. Recently, we have found global solutions including these effects providing a broader class of HZE ion solutions. PMID:15880918
An Improved Green's Function for Ion Beam Transport
NASA Technical Reports Server (NTRS)
Tweed, J.; Wilson, J. W.; Tripathi, R. K.
2003-01-01
Ion beam transport theory allows testing of material transmission properties in the laboratory environment generated by particle accelerators. This is a necessary step in materials development and evaluation for space use. The approximations used in solving the Boltzmann transport equation for the space setting are often not sufficient for laboratory work and those issues are the main emphasis of the present work. In consequence, an analytic solution of the linear Boltzmann equation is pursued in the form of a Green's function allowing flexibility in application to a broad range of boundary value problems. It has been established that simple solutions can be found for the high charge and energy (HZE) by ignoring nuclear energy downshifts and dispersion. Such solutions were found to be supported by experimental evidence with HZE ion beams when multiple scattering was added. Lacking from the prior solutions were range and energy straggling and energy downshift with dispersion associated with nuclear events. Recently, we have found global solutions including these effects providing a broader class of HZE ion solutions.
Quantitative imaging of lymphatic function with liposomal indocyanine green.
Proulx, Steven T; Luciani, Paola; Derzsi, Stefanie; Rinderknecht, Matthias; Mumprecht, Viviane; Leroux, Jean-Christophe; Detmar, Michael
2010-09-15
Lymphatic vessels play a major role in cancer progression and in postsurgical lymphedema, and several new therapeutic approaches targeting lymphatics are currently being developed. Thus, there is a critical need for quantitative imaging methods to measure lymphatic flow. Indocyanine green (ICG) has been used for optical imaging of the lymphatic system, but it is unstable in solution and may rapidly enter venous capillaries after local injection. We developed a novel liposomal formulation of ICG (LP-ICG), resulting in vastly improved stability in solution and an increased fluorescence signal with a shift toward longer wavelength absorption and emission. When injected intradermally to mice, LP-ICG was specifically taken up by lymphatic vessels and allowed improved visualization of deep lymph nodes. In a genetic mouse model of lymphatic dysfunction, injection of LP-ICG showed no enhancement of draining lymph nodes and slower clearance from the injection site. In mice bearing B16 luciferase-expressing melanomas expressing vascular endothelial growth factor-C (VEGF-C), sequential near-IR imaging of intradermally injected LP-ICG enabled quantification of lymphatic flow. Increased flow through draining lymph nodes was observed in mice bearing VEGF-C-expressing tumors without metastases, whereas a decreased flow pattern was seen in mice with a higher lymph node tumor burden. This new method will likely facilitate quantitative studies of lymphatic function in preclinical investigations and may also have potential for imaging of lymphedema or improved sentinel lymph detection in cancer. PMID:20823159
Combining molecular dynamics with mesoscopic Green's function reaction dynamics simulations
NASA Astrophysics Data System (ADS)
Vijaykumar, Adithya; Bolhuis, Peter G.; ten Wolde, Pieter Rein
2015-12-01
In many reaction-diffusion processes, ranging from biochemical networks, catalysis, to complex self-assembly, the spatial distribution of the reactants and the stochastic character of their interactions are crucial for the macroscopic behavior. The recently developed mesoscopic Green's Function Reaction Dynamics (GFRD) method enables efficient simulation at the particle level provided the microscopic dynamics can be integrated out. Yet, many processes exhibit non-trivial microscopic dynamics that can qualitatively change the macroscopic behavior, calling for an atomistic, microscopic description. We propose a novel approach that combines GFRD for simulating the system at the mesoscopic scale where particles are far apart, with a microscopic technique such as Langevin dynamics or Molecular Dynamics (MD), for simulating the system at the microscopic scale where reactants are in close proximity. This scheme defines the regions where the particles are close together and simulated with high microscopic resolution and those where they are far apart and simulated with lower mesoscopic resolution, adaptively on the fly. The new multi-scale scheme, called MD-GFRD, is generic and can be used to efficiently simulate reaction-diffusion systems at the particle level.
A Green's function approach to PIV Pressure estimates
NASA Astrophysics Data System (ADS)
Goushcha, Oleg; Ganatos, Peter; Elvin, Niell; Andreopoulos, Yiannis
2014-11-01
Spatial resolution of PIV data limits the ability to calculate the pressure along a solid boundary of a body immersed in a fluid and hence to accurately estimate the force exerted. Current methodologies solve numerically Navier-Stokes equations to calculate the pressure field from velocity data. An analytical approach has the potential of more accurate estimation of pressure in comparison to existing methods. A methodology has been developed to calculate the pressure distribution on the body in the flow by analytically solving the pressure Poisson Equation using a Green's function approach. The pressure is then extrapolated to the solid boundary resulting in an accurate pressure distribution and total net force on the boundary. This technique has been applied to the case of a flexible cantilever beam vibrating after interacting with a traveling vortex in an experimental setup to harvest energy from an air-flow. Time-resolved PIV has been used to acquire a two-dimensional velocity field which has been used to obtain a time-dependent pressure distribution acting on the surface of the beam and resultant forces. The analytical solution is compared to the force measured directly by a force sensor placed at the base of the beam as well as the power harvested. Sponsored by NSF Grant: CBET #1033117.
An improved Green's function for ion beam transport
NASA Technical Reports Server (NTRS)
Tweed, J.; Wilson, J. W.; Tripathi, R. K.
2004-01-01
Ion beam transport theory allows testing of material transmission properties in the laboratory environment generated by particle accelerators. This is a necessary step in materials development and evaluation for space use. The approximations used in solving the Boltzmann transport equation for the space setting are often not sufficient for laboratory work and those issues are the main emphasis of the present work. In consequence, an analytic solution of the linear Boltzmann equation is pursued in the form of a Green's function allowing flexibility in application to a broad range of boundary value problems. It has been established that simple solutions can be found for high charge and energy (HZE) ions by ignoring nuclear energy downshifts and dispersion. Such solutions were found to be supported by experimental evidence with HZE ion beams when multiple scattering was added. Lacking from the prior solutions were range and energy straggling and energy downshift with dispersion associated with nuclear events. Recently, we have found global solutions including these effects providing a broader class of HZE ion solutions. c2004 COSPAR. Published by Elsevier Ltd. All rights reserved.
Empirical Green's function analysis of recent moderate events in California
Hough, S.E.
2001-01-01
I use seismic data from portable digital stations and the broadband Terrascope network in southern California to investigate radiated earthquake source spectra and discuss the results in light of previous studies on both static stress drop and apparent stress. Applying the empirical Green's function (EGF) method to two sets of M 4-6.1 events, I obtain deconvolved source-spectra estimates and corner frequencies. The results are consistent with an ??2 source model and constant Brune stress drop. However, consideration of the raw spectral shapes of the largest events provides evidence for a high-frequency decay more shallow than ??2. The intermediate (???f-1) slope cannot be explained plausibly with attenuation or site effects and is qualitatively consistent with a model incorporating directivity effects and a fractional stress-drop rupture process, as suggested by Haddon (1996). However, the results obtained in this study are not consistent with the model of Haddon (1996) in that the intermediate slope is not revealed with EGF analysis. This could reflect either bandwidth limitations inherent in EGF analysis or perhaps a rupture process that is not self-similar. I show that a model with an intermediate spectral decay can also reconcile the apparent discrepancy between the scaling of static stress drop and that of apparent stress drop for moderate-to-large events.
Using SVD for improved interferometric Green's function retrieval
NASA Astrophysics Data System (ADS)
Melo, Gabriela; Malcolm, Alison; Mikesell, Dylan; van Wijk, Kasper
2013-09-01
Seismic interferometry (SI) is a technique used to estimate the Green's function (GF) between two receiver locations, as if there were a source at one of the receiver locations. However, in many applications, the requirements to recover the exact GF are not satisfied and SI yields a poor estimate of the GF. For these non-ideal cases, we improve the interferometric GFs, by applying singular value decomposition (SVD) to the cross-correlations before stacking. The SVD approach preserves energy that is stationary in the cross-correlations, which is the energy that contributes most to the GF recovery, and attenuates non-stationary energy, which leads to artefacts in the interferometric GF. We apply this method to construct virtual shot gathers (for both synthetic and field data) and demonstrate how using SVD enhances physical arrivals in these gathers. We also find that SVD is robust with respect to weakly correlated random noise, allowing a better recovery of events from noisy data, in some cases recovering energy that would otherwise be completely lost in the noise and that the standard SI technique fails to recover.
A Green's function method for heavy ion beam transport.
Shinn, J L; Wilson, J W; Schimmerling, W; Shavers, M R; Miller, J; Benton, E V; Frank, A L; Badavi, F F
1995-08-01
The use of Green's function has played a fundamental role in transport calculations for high-charge high-energy (HZE) ions. Two recent developments have greatly advanced the practical aspects of implementation of these methods. The first was the formulation of a closed-form solution as a multiple fragmentation perturbation series. The second was the effective summation of the closed-form solution through nonperturbative techniques. The nonperturbative methods have been recently extended to an inhomogeneous, two-layer transport media to simulate the lead scattering foil present in the Lawrence Berkeley Laboratories (LBL) biomedical beam line used for cancer therapy. Such inhomogeneous codes are necessary for astronaut shielding in space. The transport codes utilize the Langley Research Center atomic and nuclear database. Transport code and database evaluation are performed by comparison with experiments performed at the LBL Bevalac facility using 670 A MeV 20Ne and 600 A MeV 56Fe ion beams. The comparison with a time-of-flight and delta E detector measurement for the 20Ne beam and the plastic nuclear track detectors for 56Fe show agreement up to 35%-40% in water and aluminium targets, respectively. PMID:7480630
Computation of the lattice Green function for a dislocation
NASA Astrophysics Data System (ADS)
Tan, Anne Marie Z.; Trinkle, Dallas R.
2016-08-01
Modeling isolated dislocations is challenging due to their long-ranged strain fields. Flexible boundary condition methods capture the correct long-range strain field of a defect by coupling the defect core to an infinite harmonic bulk through the lattice Green function (LGF). To improve the accuracy and efficiency of flexible boundary condition methods, we develop a numerical method to compute the LGF specifically for a dislocation geometry; in contrast to previous methods, where the LGF was computed for the perfect bulk as an approximation for the dislocation. Our approach directly accounts for the topology of a dislocation, and the errors in the LGF computation converge rapidly for edge dislocations in a simple cubic model system as well as in BCC Fe with an empirical potential. When used within the flexible boundary condition approach, the dislocation LGF relaxes dislocation core geometries in fewer iterations than when the perfect bulk LGF is used as an approximation for the dislocation, making a flexible boundary condition approach more efficient.
Dyadic Green's function of an eccentrically stratified sphere.
Moneda, Angela P; Chrissoulidis, Dimitrios P
2014-03-01
The electric dyadic Green's function (dGf) of an eccentrically stratified sphere is built by use of the superposition principle, dyadic algebra, and the addition theorem of vector spherical harmonics. The end result of the analytical formulation is a set of linear equations for the unknown vector wave amplitudes of the dGf. The unknowns are calculated by truncation of the infinite sums and matrix inversion. The theory is exact, as no simplifying assumptions are required in any one of the analytical steps leading to the dGf, and it is general in the sense that any number, position, size, and electrical properties can be considered for the layers of the sphere. The point source can be placed outside of or in any lossless part of the sphere. Energy conservation, reciprocity, and other checks verify that the dGf is correct. A numerical application is made to a stratified sphere made of gold and glass, which operates as a lens. PMID:24690648
NASA Technical Reports Server (NTRS)
Troitzsch, J.
1988-01-01
The use of flame retardants in plastics has grown only slightly in recent years and will probably grow slowly in the future. The reasons for this are slow economic growth and the absence of fundamentally new requirements for future fire prevention. The trends are toward the increasing use of easily handled, dust-free and well-dispersed flame retardant compounds and master batches; there are no spectacular new developments. In the future, questions of smoke evolution, toxicity and corrosiveness of combustion gases will become increasingly important, especially due to new regulations and rising requirements for environmental protection.
ERIC Educational Resources Information Center
Gruen, Gerald E.
Three studies compared learning and problem-solving performances of normal and familially-retarded children on tasks differing in complexity, and one study investigated motivational-personality differences. Main purpose of the first three studies was to investigate the controversy between developmental and defect theorists in mental retardation.…
ERIC Educational Resources Information Center
Pilowsky, Tammy; Yirmiya, Nurit; Gross-Tsur, Varda; Shalev, Ruth S.
2007-01-01
Neuropsychological functioning of 30 siblings of children with autism (AU-S), 28 siblings of children with mental retardation of (MR-S), and 30 siblings of children with developmental language delay (DLD-S) was compared. Two siblings, both AU-S, received diagnoses of pervasive developmental disorder (PDD). More siblings with cognitive disabilities…
ERIC Educational Resources Information Center
Balthazar, Earl E.
The scoring form for functional independence skills for the mentally retarded includes a section for recording subjects' demographic characteristics as well as tests used, date administered, and raw score. Other sections provide for a brief description of the program being used, an item scoring sheet for the Eating Scales (dependent feeding,…
NASA Astrophysics Data System (ADS)
Xiang, Shang; Jiang, Weikang; Pan, Siwei
2015-12-01
A modified inverse patch transfer function (iPTF) method is used to reconstruct the normal velocities of the target source in a noisy environment. The iPTF method simplifies the Helmholtz integral equation to one term by constructing a Green's function satisfying Neumann boundary conditions for an enclosure, which is generally constructed by slowly convergent modal expansions. The main objective of the present work is to provide an evanescent Green's function to improve the convergence of calculations. A brief description of the iPTF method and two sets of Green's functions for a rectangular cavity are presented firstly. In simulations, both the Green's functions are used to calculate the condition numbers of impedance matrices describing the relation between source and measurement patches, and the time cost of calculation based on the two sets of Green's functions at 450 Hz is compared. Double pressure measurements are then employed as the input data instead of pressure and velocity measurements. The normal velocities of two baffled loudspeakers are reconstructed by the combination of a measurement method and a Green's function in the presence of a disturbing source in the frequency range of 50-1000 Hz. In addition, the double pressure measurements are examined by an experiment. The precise identification of the sources indicates that the double pressure measurements are capable of localizing sources in a noisy environment. It is also found that the reconstruction with the evanescent Green's functions is slightly better than that with the modal expansions.
NASA Astrophysics Data System (ADS)
Liu, Jun
2013-02-01
A least square based fitting scheme is proposed to extract an optimal one-particle spectral function from any one-particle temperature Green function. It uses the existing non-negative least square (NNLS) fit algorithm to do the fit, and Tikhonov regularization to help with possible numerical singular behaviors. By flexibly adding delta peaks to represent very sharp features of the target spectrum, this scheme guarantees a global minimization of the fitted residue. The performance of this scheme is manifested with diverse physical examples. The proposed scheme is shown to be comparable in performance to the standard Padé analytic continuation scheme.
Efficient computation of periodic and nonperiodic Green`s functions in layered media using the MPIE
Wilton, D.R.; Jackson, D.R.; Champagne, N.J.
1998-03-27
The mixed potential integral equation (MPIE) formulation is convenient for problems involving layered media because potential quantities involve low order singularities, in comparison to field quantities. For nonperiodic problems, the associated Green`s potentials involve spectral integrals of the Sommerfeld type, in the periodic case, discrete sums over sampled values of the same spectra are required. When source and observation points are in the same or in adjacent layers, the convergence of both representations is enhanced by isolating the direct and quasi-static image contributions associated with the nearby layers. In the periodic case, the convergence of direct and image contributions may be rapidly accelerated by means of the Ewadd method.
Hubbard one-particle Green function in the antiferromagnetic phase
NASA Astrophysics Data System (ADS)
Polatsek, G.; Becker, K. W.
1997-01-01
An analytic approach is presented of electronic one-particle spectra of the one-band Hubbard model at half filling in the antiferromagnetic phase. Starting from the strong-coupling regime U>>:t, a projection technique is used to set up self-consistent coupled equations for the electron Green function, which are valid down to values U~t. The self-consistent equation for the hole propagator is a direct generalization of the one found from the t-J model. This gives further support to the ``string'' picture, where propagation of holes creates strings of overturned spins with which the holes interact. In the present work hopping of holes (or electrons) with up spin on the down sublattice is also taken into acount, as well as transitions between the lower and upper Hubbard bands. These are shown to change significantly the incoherent part of the t-J model spectra, by smearing out the shake-off peaks, reminiscent of higher bound string states due to multispin scattering. Coherent (quasiparticle) peaks exist at the band edges, on both sides of the insulating gap. We show that with decreasing U the quasiparticle concept loses its meaning for wave vectors at the center of the magnetic Brillouin zone (MBZ). For large values of U the dispersion of the quasiparticle is found to scale with its band width, which is of order J. Extrema are always found at k=(π/2,π/2). The weight of the quasiparticle at this k value decreases logarithmically with increasing U. In the strong-coupling limit the spectrum tends to be symmetric, i.e., to become an even function of the frequency around the chemical potential, for any wave vector. For small values of U the dispersion at the edge of the MBZ flattens away, as expected when approaching the noninteracting limit. The spectral function in this regime, for wave vectors away from the edge of the MBZ, is concentrated mainly on one side of the chemical potential.
Green's-function formalism for waveguide QED applications
NASA Astrophysics Data System (ADS)
Schneider, Michael P.; Sproll, Tobias; Stawiarski, Christina; Schmitteckert, Peter; Busch, Kurt
2016-01-01
We present a quantum-field-theoretical framework based on path integrals and Feynman diagrams for the investigation of the quantum-optical properties of one-dimensional waveguiding structures with embedded quantum impurities. In particular, we obtain the Green's functions for a waveguide with an embedded two-level system in the single- and two-excitation sector for arbitrary dispersion relations both in the time and the frequency domains. In the single-excitation sector, we show how to sum the diagrammatic perturbation series to all orders and thus obtain explicit expressions for physical quantities such as the spectral density and the scattering matrix. In the two-excitation sector, we show that strictly linear dispersion relations exhibit the special property that the corresponding diagrammatic perturbation series terminates after two terms, again allowing for closed-form expressions for physical quantities. In the case of general dispersion relations, notably those exhibiting a band edge or waveguide cutoff frequencies, the perturbation series cannot be summed explicitly. Instead, we derive a self-consistent T -matrix equation that reduces the computational effort to that of a single-excitation computation. This analysis allows us to identify a Fano resonance between the occupied quantum impurity and a free photon in the waveguide as a unique signature of the few-photon nonlinearity inherent in such systems. In addition, our diagrammatic approach allows for the classification of different physical processes such as the creation of photon-photon correlations and interaction-induced radiation trapping, the latter being absent for strictly linear dispersion relations. Our framework can serve as the basis for further studies that involve more complex scenarios such as several and many-level quantum impurities, networks of coupled waveguides, disordered systems, and nonequilibrium effects.
Empirical Green's function analysis: Taking the next step
Hough, S.E.
1997-01-01
An extension of the empirical Green's function (EGF) method is presented that involves determination of source parameters using standard EGF deconvolution, followed by inversion for a common attenuation parameter for a set of colocated events. Recordings of three or more colocated events can thus be used to constrain a single path attenuation estimate. I apply this method to recordings from the 1995-1996 Ridgecrest, California, earthquake sequence; I analyze four clusters consisting of 13 total events with magnitudes between 2.6 and 4.9. I first obtain corner frequencies, which are used to infer Brune stress drop estimates. I obtain stress drop values of 0.3-53 MPa (with all but one between 0.3 and 11 MPa), with no resolved increase of stress drop with moment. With the corner frequencies constrained, the inferred attenuation parameters are very consistent; they imply an average shear wave quality factor of approximately 20-25 for alluvial sediments within the Indian Wells Valley. Although the resultant spectral fitting (using corner frequency and ??) is good, the residuals are consistent among the clusters analyzed. Their spectral shape is similar to the the theoretical one-dimensional response of a layered low-velocity structure in the valley (an absolute site response cannot be determined by this method, because of an ambiguity between absolute response and source spectral amplitudes). I show that even this subtle site response can significantly bias estimates of corner frequency and ??, if it is ignored in an inversion for only source and path effects. The multiple-EGF method presented in this paper is analogous to a joint inversion for source, path, and site effects; the use of colocated sets of earthquakes appears to offer significant advantages in improving resolution of all three estimates, especially if data are from a single site or sites with similar site response.
Green's functions of the scalar model of electromagnetic fields in sinusoidal superlattices
NASA Astrophysics Data System (ADS)
Ignatchenko, V. A.; Tsikalov, D. S.
2016-03-01
Problems of obtaining Green's function and using it for studying the structure of scalar electromagnetic fields in a sinusoidal superlattice are considered. An analytical solution of equation in the k-space for Green's function is found. Green's function in the r-space is obtained by both the numerical and the approximate analytical Fourier transformation of that solution. It is shown, that from the experimental study of Green's function in the k-space the position of the plane radiation source relative to the extremes of the dielectric permittivity ε(z) can be determined. The relief map of Green's function in the r-space shows that the structure of the field takes the form of chains of islets in the plane ωz, the number of which increases with increasing the distance from a radiation source. This effect leads to different frequency dependences of Green's function at different distances from the radiation source and can be used to measure the distance to the internal source. The real component of Green's function and its spatial decay in the forbidden zones in the near field is investigated. The local density of states, depending on the position of the source in the superlattice, is calculated.
Sanders, Marijke W; Fazzi, Gregorio E; Janssen, Ger M J; Blanco, Carlos E; De Mey, Jo G R
2005-07-01
A suboptimal fetal environment increases the risk to develop cardiovascular disease in the adult. We reported previously that intrauterine stress in response to reduced uteroplacental blood flow in the pregnant rat limits fetal growth and compromises renal development, leading to an altered renal function in the adult offspring. Here we tested the hypothesis that high dietary sodium intake in rats with impaired renal development attributable to intrauterine stress, results in increased blood pressure, altered renal function, and organ damage. In rats, intrauterine stress was induced by bilateral ligation of the uterine arteries at day 17 of pregnancy. At the age of 12 weeks, the offspring was given high-sodium drinking water (2% sodium chloride). At the age of 16 weeks, rats were instrumented for monitoring of blood pressure and renal function. After intrauterine stress, litter size and birth weight were reduced, whereas hematocrit at birth was increased. Renal blood flow, glomerular filtration rate, and the glomerular filtration fraction were increased significantly after intrauterine stress. High sodium intake did not change renal function and blood pressure in control animals. However, during high sodium intake in intrauterine stress offspring, renal blood flow, glomerular filtration rate, and the filtration fraction were decreased, and blood pressure was increased. In addition, these animals developed severe albuminuria, an important sign of renal dysfunction. Thus, a suboptimal fetal microenvironment, which impairs renal development, results in sodium-dependent hypertension and albuminuria. PMID:15956110
The green function of an infinite, fluid loaded membrane
NASA Astrophysics Data System (ADS)
Crighton, D. G.
1983-02-01
In this paper the response of a fluid loaded plane structure (a membrane) to a concentrated line force excitation is considered in great detail. The normalized velocity response—here called the Green function G—depends upon a dimensionless range x0= km| x|, where km is the free wavenumber on the membrane in a vacuum, on the Mach number M= {k 0}/{k m}, the ratio of wave phase speed ω/ km on the unloaded membrane to the sound speed ω/ k0, and on a parameter ɛ which can be regarded as a measure of fluid loading at the "coincidence" condition M=1. In the analogous problem involving a thin elastic plate, the corresponding parameter is independent of frequency and plate thickness and may be regarded as an intrinsic measure of fluid loading; moreover, in cases of common interest (steel in water, aluminium in air) that parameter is small. In the present paper, the asymptotic structure of G( x0, M, ɛ) is therefore sought in the limit ɛ → 0. Naturally, no single asymptotic expansion can be expected to be valid throughout the ( x0, M) plane, and the programme therefore involves the delineation of regions of that plane in which distinct asymptotic results apply, the construction and discussion of those results, and the asymptotic matching (according to the procedures of the method of matched asymptotic expansions) of results holding in adjoining regions. The Fourier integral for G is broken into surface wave and acoustic components, and the asymptotic structure obtained for each. Previously obtained results for the behaviour at large distances are recovered, with a demonstration that very large distances indeed ( x0 ≫ ɛ-2) may be needed for their validity for some ranges of M; and the drive point behaviour, of G( x0=0, M, ɛ) as ɛ → 0 qua function of M, is shown to correspond to that already discussed in the literature. Elsewhere, in the covering of the whole ( x0, M) plane by different asymptotic expressions, a wide variety of analytical results is found
Relativistic Green's Functions in Full-Potential Multiple-Scattering Theory
NASA Astrophysics Data System (ADS)
Liu, Xianglin; Wang, Yang; Eisenbach, Markus; Stocks, G. Malcolm
The Green's functions play a central role in MST based KKR method. Obtaining the Green's functions by solving the Dirac equation is appealing since it naturally incorporated the electron spin and the spin-orbit coupling effects. Here we implemented the full-potential relativistic KKR method using a technique called the sine and cosine matrices formalism. The charge density and the density of states of some pure element crystals have been calculated. Different expressions of the Green's functions have been investigated for numerical benefits.
The physiological consequences of early neonatal growth retardation in the kidney are investigated using DFMO (a-difluoromethylornithine), a specific irreversible inhibitor of ornithine decarboxylase (ODC), a key enzyme in the biosynthesis of polyamines. e administered 500 eg/kg/...
Rinaldi, Massimiliano
2007-11-15
We consider Green's functions associated to a scalar field propagating on a curved, ultrastatic background, in the presence of modified dispersion relations. The usual proper-time DeWitt-Schwinger procedure to obtain a series representation of Green's functions is doomed to failure because of higher order spatial derivatives in the Klein-Gordon operator. We show how to overcome this difficulty by considering a preferred frame, associated to a unit timelike vector. With respect to this frame, we can express Green's functions as an integral over all frequencies of a space-dependent function. The latter can be expanded in momentum space, as a series with geometric coefficients similar to the DeWitt-Schwinger ones. By integrating over all frequencies, we finally find the expansion of Green's function up to four derivatives of the metric tensor. The relation with the proper-time formalism is also discussed.
NASA Astrophysics Data System (ADS)
Tai, C.-T.
1981-09-01
The concept of equivalent layers of surface charges, surface current, and surface polarization associated with the discontinuous behavior of the eigenfunction expansion of various Green's functions in electromagnetic theory is discussed. Green's function pertaining to the potential function in electrostatics is considered first; a detailed analysis is then presented of an eigenfunction representation of a typical dyadic Green's function for time-varying harmonic fields. An eigenfunction expansion of a Green's function requires that a point singularity be replaced by an equivalent layer of surface singularity. Since this layered source is not present in the original Green's function, care must be taken when interpreting the results.
Sudhir, Dange Prasad; Saksena, Annapurna; Khurana, Nita
2016-01-01
Introduction Polarizing microscope plays a vital role in few but unique situations. A pair of cross polarizers is used to confirm the presence of birefringent substances. Also, a red retardation plate is needed to evaluate the sign of birefringence. However, a polarizing microscope especially with retardation plate is very expensive. Thus, an affordable yet effective substitute using the 3D Polaroid glasses used for ‘3D movies’ would enable widespread use of the polarizing system. Aim To study the use of 3D polaroid glasses procured from cinema halls in detecting birefringence substances and to study the red retardation plate function in them. Materials and Methods Passive 3D Polaroid glasses were procured from cinema halls. They were arranged in aspecific manner to obtain polarized light. Red retardation plate function can be obtained by changing the arrangement of the glasses. These glasses were used with various available models of different light microscope manufacturers. Various specimens observed included amyloid deposits, woven and lamellar bone, skeletal muscle striations, urate crystals, cholesterol crystals, suture material and glove powder. The comparison was based on subjective interpretation of intensity and quality of birefringence. Sign of birefringence was also determined whenever relevant. Results The birefringence observed by our system was comparable to the commercially available polarizing system with respect to intensity and quality. Also, there were no false positive /negative results when compared with the commercial Polarizing microscope. Moreover, the system had an inbuilt red retardation plate to determine sign of birefringence. Conclusion The system is efficient, cheap, easily accessible, portable and compatible with all models of light microscopes. PMID:26894072
Approximate analytical time-domain Green's functions for the Caputo fractional wave equation.
Kelly, James F; McGough, Robert J
2016-08-01
The Caputo fractional wave equation [Geophys. J. R. Astron. Soc. 13, 529-539 (1967)] models power-law attenuation and dispersion for both viscoelastic and ultrasound wave propagation. The Caputo model can be derived from an underlying fractional constitutive equation and is causal. In this study, an approximate analytical time-domain Green's function is derived for the Caputo equation in three dimensions (3D) for power law exponents greater than one. The Green's function consists of a shifted and scaled maximally skewed stable distribution multiplied by a spherical spreading factor 1/(4πR). The approximate one dimensional (1D) and two dimensional (2D) Green's functions are also computed in terms of stable distributions. Finally, this Green's function is decomposed into a loss component and a diffraction component, revealing that the Caputo wave equation may be approximated by a coupled lossless wave equation and a fractional diffusion equation. PMID:27586735
Kolek, Andrzej
2015-05-04
The formulas are derived that enable calculations of intersubband absorption coefficient within nonequilibrium Green's function method applied to a single-band effective-mass Hamiltonian with the energy dependent effective mass. The derivation provides also the formulas for the virtual valence band components of the two-band Green's functions which can be used for more exact estimation of the density of states and electrons and more reliable treatment of electronic transport in unipolar n-type heterostructure semiconductor devices.
Schulze-Halberg, Axel
2010-05-15
We study Green's functions of the generalized Sturm-Liouville problems that are related to each other by Darboux -equivalently, supersymmetrical - transformations. We establish an explicit relation between the corresponding Green's functions and derive a simple formula for their trace. The class of equations considered here includes the conventional Schroedinger equation and generalizations, such as for position-dependent mass and with linearly energy-dependent potential, as well as the stationary Fokker-Planck equation.
Colombi, Andrea; Boschi, Lapo; Roux, Philippe; Campillo, Michel
2014-03-01
Cross-correlations of ambient noise averaged at two receivers lead to the reconstruction of the two-point Green's function, provided that the wave-field is uniform azimuthally, and also temporally and spatially uncorrelated. This condition depends on the spatial distribution of the sources and the presence of heterogeneities that act as uncorrelated secondary sources. This study aims to evaluate the relative contributions of source distribution and medium complexity in the two-point cross-correlations by means of numerical simulations and laboratory experiments in a finite-size reverberant two-dimensional (2D) plate. The experiments show that the fit between the cross-correlation and the 2D Green's function depends strongly on the nature of the source used to excite the plate. A turbulent air-jet produces a spatially uncorrelated acoustic field that rapidly builds up the Green's function. On the other hand, extracting the Green's function from cross-correlations of point-like sources requires more realizations and long recordings to balance the effect of the most energetic first arrivals. When the Green's function involves other arrivals than the direct wave, numerical simulations confirm the better Green's function reconstruction with a spatially uniform source distribution than the typical contour-like source distribution surrounding the receivers that systematically gives rise to spurious phases. PMID:24606247
Semiclassical Green's function for electron motion in combined Coulomb and electric fields
NASA Astrophysics Data System (ADS)
Ambalampitiya, Harindranath; Fabrikant, Ilya
2016-05-01
We are developing an extension of the Green-function approach to the theory of ionization of a multielectron atom in a strong laser field by using the semiclassical Van Vleck-Gutzwiller propagator. For a static field the exact quantum mechanical Green's function can be calculated with an arbitrary accuracy. Therefore, as a first step towards solution of the problem, we apply the semiclassical method to the static field case for the energies above the ionization threshold where all classical trajectories contributing to the Green's function are real. Required trajectories are determined by solving the problem of finding initial velocity and traveling time corresponding to two position points. For the pure electric field case of two trajectories the semiclassical Green's function agrees very well with the exact Green's function. With the inclusion of the Coulomb field, the number of classical trajectories between two points grows rapidly and here we observe that the agreement between the semiclassical and exact Green's functions increases when more trajectories are included in the computation. Supported by the National Science Foundation.
Fortune, Brad; Cull, Grant; Reynaud, Juan; Wang, Lin; Burgoyne, Claude F.
2015-01-01
Purpose. To relate changes in retinal function and retinal nerve fiber layer (RNFL) retardance to loss of RNFL thickness and optic nerve axon counts in a nonhuman primate (NHP) model of experimental glaucoma (EG). Methods. Bilateral longitudinal measurements of peripapillary RNFL thickness (spectral-domain optical coherence tomography, SDOCT; Spectralis), retardance (GDxVCC), and multifocal electroretinography (mfERG; VERIS) were performed in 39 NHP at baseline (BL; median, 5 recordings; range, 3–10) and weekly after induction of unilateral EG by laser photocoagulation of the trabecular meshwork. Multifocal ERG responses were high-pass filtered (>75 Hz) to measure high- and low-frequency component (HFC and LFC) amplitudes, including LFC features N1, P1, and N2. High-frequency component amplitudes are known to specifically reflect retinal ganglion cell (RGC) function. Complete (100%) axon counts of orbital optic nerves were obtained in 31/39 NHP. Results. Postlaser follow-up was 10.4 ± 7.9 months; mean and peak IOP were 18 ± 5 and 41 ± 11 mm Hg in EG eyes, 11 ± 2 and 18 ± 6 mm Hg in control (CTL) eyes. At the final available time point, RNFL thickness had decreased from BL by 14 ± 14%, retardance by 20 ± 11%, and the mfERG HFC by 30 ± 17% (P < 0.0001 each). Longitudinal changes in retardance and HFC were linearly related to RNFL thickness change (R2 = 0.51, P < 0.0001 and R2 = 0.22, P = 0.002, respectively); LFC N2 was weakly related but N1 or P2 (N1: R2 = 0.07, P = 0.11; P1: R2 = 0.04, P = 0.24; N2: R2 = 0.13, P = 0.02). At zero change from BL for RNFL thickness (Y-intercept), retardance was reduced by 11% (95% confidence interval [CI]: −15.3% to −6.8%) and HFC by 21.5% (95% CI: −28.7% to −14.3%). Relative loss of RNFL thickness, retardance, and HFC (EG:CTL) were each related to axon loss (R2 = 0.66, P < 0.0001; R2 = 0.42, P < 0.0001; R2 = 0.42, P < 0.0001, respectively), but only retardance and HFC were significantly reduced at zero relative axon
Green's function of a heat problem with a periodic boundary condition
NASA Astrophysics Data System (ADS)
Erzhanov, Nurzhan E.
2016-08-01
In the paper, a nonlocal initial-boundary value problem for a non-homogeneous one-dimensional heat equation is considered. The domain under consideration is a rectangle. The classical initial condition with respect to t is put. A nonlocal periodic boundary condition by a spatial variable x is put. It is well-known that a solution of problem can be constructed in the form of convergent orthonormal series according to eigenfunctions of a spectral problem for an operator of multiple differentiation with periodic boundary conditions. Therefore Green's function can be also written in the form of an infinite series with respect to trigonometric functions (Fourier series). For classical first and second initial-boundary value problems there also exists a second representation of the Green's function by Jacobi function. In this paper we find the representation of the Green's function of the nonlocal initial-boundary value problem with periodic boundary conditions in the form of series according to exponents.
NASA Astrophysics Data System (ADS)
He, Yuan-Yao; Wu, Han-Qing; Meng, Zi Yang; Lu, Zhong-Yi
2016-05-01
Topological phase transitions in free fermion systems can be characterized by the closing of single-particle gap and the change in topological invariants. However, in the presence of electronic interactions, topological phase transitions can be more complicated. In paper I of this series [Phys. Rev. B 93, 195163 (2016), 10.1103/PhysRevB.93.195163], we have proposed an efficient scheme to evaluate the topological invariants based on the single-particle Green's function formalism. Here, in paper II, we demonstrate several interaction-driven topological phase transitions (TPTs) in two-dimensional (2D) interacting topological insulators (TIs) via large-scale quantum Monte Carlo (QMC) simulations, based on the scheme of evaluating topological invariants presented in paper I. Across these transitions, the defining symmetries of the TIs have been neither explicitly nor spontaneously broken. In the first two models, the topological invariants calculated from the Green's function formalism succeed in characterizing the topologically distinct phases and identifying interaction-driven TPTs. However, in the other two models, we find that the single-particle gap does not close and the topological invariants constructed from the single-particle Green's function acquire no change across the TPTs. Unexpected breakdown of the Green's function formalism in constructing the topological invariants is thus discovered. We thence classify the topological phase transitions in interacting TIs into two categories in practical computation: Those that have noninteracting correspondence can be characterized successfully by the topological invariants constructed from the Green's functions, while for the others that do not have noninteracting correspondence, the Green's function formalism experiences a breakdown, but more interesting and exciting phenomena, such as emergent collective critical modes at the transition, arise. Discussion on the success and breakdown of topological invariants
ERIC Educational Resources Information Center
Spitz, Herman H.; Winters, Emilia A.
1977-01-01
Available from: Ablex Publishing Corporation, 355 Chestnut Street, Norwood, New Jersey 07648. Two groups (36 Ss) of educable and trainable mentally retarded adolescents in an institution were compared with two groups (38 Ss) of nonretarded children (ages 8-9 years old) on a modified tic-tac-toe game for foresight in logical problem solving. (MH)
ERIC Educational Resources Information Center
Welch, Steven J.; Pear, Joseph J.
1980-01-01
Picture cards, photographs, and real objects were compared as training stimuli in order to determine which best facilitated the generalization of naming responses learned in a special training room to real objects in the natural environments of four severely retarded children (ages 5, 6, 9, and 14). (Author)
NASA Technical Reports Server (NTRS)
Leser, William P.; Yuan, Fuh-Gwo; Leser, William P.
2013-01-01
A method of numerically estimating dynamic Green's functions using the finite element method is proposed. These Green's functions are accurate in a limited frequency range dependent on the mesh size used to generate them. This range can often match or exceed the frequency sensitivity of the traditional acoustic emission sensors. An algorithm is also developed to characterize an acoustic emission source by obtaining information about its strength and temporal dependence. This information can then be used to reproduce the source in a finite element model for further analysis. Numerical examples are presented that demonstrate the ability of the band-limited Green's functions approach to determine the moment tensor coefficients of several reference signals to within seven percent, as well as accurately reproduce the source-time function.
Green's function theory of orbital magnetic moment of interacting electrons in solids
NASA Astrophysics Data System (ADS)
Aryasetiawan, F.; Karlsson, K.; Miyake, T.
2016-04-01
A general formula for the orbital magnetic moment of interacting electrons in solids is derived using the many-electron Green's function method. The formula factorizes into two parts, a part that contains the information about the one-particle band structure of the system and a part that contains the effects of exchange and correlations carried by the Green's function. The derived formula provides a convenient yet rigorous means of including the effects of exchange and correlations beyond the commonly used local density approximation of density functional theory.
Retrieving the Green's function of attenuating heterogeneous media by time-reversal modeling
NASA Astrophysics Data System (ADS)
Zhu, T.
2014-12-01
The Green's function between two locations within which seismograms that were not physically recorded, are retrieved by cross-correlation, convolution or deconvolution and summation of other recorded wavefields (also known as seismic interferometry). More recently seismic interferometry was applied in exploration seismology by Bakulin and Calvert (2006) and Schuster et al. (2004), in ultrasound by Weaver and Lobkis (2001), in crustal seismology by Campillo and Paul (2003), Sabra et al. (2005a, b), Roux et al. (2005) and Shapiro et al. (2005), and in helioseismology by Rickett and Claerbout (1999). Theory of the retrieval of Green's function can also be represented by time-reversal propagation because of time invariance of wave equations in the lossless media. In the presence of intrinsic attenuation in the media, however, the time invariance of wave equations is invalid. My previous work present methods of using novel viscoacoustic and viscoelastic wave equations to recover the time invariance property of such wave equations for viscoacoustic and viscoelastic time-reversal modeling. More importantly, attenuation effects are compensated for during time-reversal wave propagation. In this paper, I investigate the possibility of retrieving the Green's function through time-reversal modeling techniques in attenuating media. I consider two different models to illustrate the feasibility of Green's function retrieval in attenuating media. I consider the viscoacoustic as well as the viscoelastic situation. Numerical results show that the Green's function can be retrieved in the correct amplitude and phase by time-reversal modeling with compensating both amplitude loss and dispersion effects.
Scalar Green's-function derivation of the thermal blooming compensation instability equations
Morris, J.R. )
1989-12-01
Karr (J. Opt. Soc. Am. A {bold 6}, 1038 (1989)) recently derived an eigenvalue equation for the temporal growth rate of the thermal blooming compensation instability, using a Green's-function matrix formulation. A rigorous and concise derivation of all the Green's-function matrix elements is presented here for the case of arbitrary axial variation of the wind velocity and thermal blooming strength. Starting with the perturbation growth equation of the high-power beam in an arbitrary Galilean reference frame, the high-power and beacon-propagation equations are solved by the scalar Green's-function method. Although Green's function of the high-power beam equation has a closed form only in special cases, the general solution is useful as a rigorous basis for the Wentzel--Kramers--Brillouin approximation and for other approximations. Finally, the matrix closed-loop compensation equation is assembled from the Green's functions of the high-power beam, low-power beacon, and compensation subsystems.
Reimers, Jeffrey R; Solomon, Gemma C; Gagliardi, Alessio; Bilić, Ante; Hush, Noel S; Frauenheim, Thomas; Di Carlo, Aldo; Pecchia, Alessandro
2007-07-01
A review is presented of the nonequilibrium Green's function (NEGF) method "gDFTB" for evaluating elastic and inelastic conduction through single molecules employing the density functional tight-binding (DFTB) electronic structure method. This focuses on the possible advantages that DFTB implementations of NEGF have over conventional methods based on density functional theory, including not only the ability to treat large irregular metal-molecule junctions with high nonequilibrium thermal distributions but perhaps also the ability to treat dispersive forces, bond breakage, and open-shell systems and to avoid large band lineup errors. New results are presented indicating that DFTB provides a useful depiction of simple gold-thiol interactions. Symmetry is implemented in DFTB, and the advantages it brings in terms of large savings of computational resources with significant increase in numerical stability are described. The power of DFTB is then harnessed to allow the use of gDFTB as a real-time tool to discover the nature of the forces that control inelastic charge transport through molecules and the role of molecular symmetry in determining both elastic and inelastic transport. Future directions for the development of the method are discussed. PMID:17530826
NASA Astrophysics Data System (ADS)
Areshkin, Denis A.; Nikolić, Branislav K.
2010-04-01
The recent fabrication of graphene nanoribbon (GNR) field-effect transistors poses a challenge for first-principles modeling of carbon nanoelectronics due to many thousand atoms present in the device. The state of the art quantum transport algorithms, based on the nonequilibrium Green function formalism combined with the density-functional theory (NEGF-DFT), were originally developed to calculate self-consistent electron density in equilibrium and at finite bias voltage (as a prerequisite to obtain conductance or current-voltage characteristics, respectively) for small molecules attached to metallic electrodes where only a few hundred atoms are typically simulated. Here we introduce combination of two numerically efficient algorithms which make it possible to extend the NEGF-DFT framework to device simulations involving large number of atoms. Our first algorithm offers an alternative to the usual evaluation of the equilibrium part of electron density via numerical contour integration of the retarded Green function in the upper complex half-plane. It is based on the replacement of the Fermi function f(E) with an analytic function f˜(E) coinciding with f(E) inside the integration range along the real axis, but decaying exponentially in the upper complex half-plane. Although f˜(E) has infinite number of poles, whose positions and residues are determined analytically, only a finite number of those poles have non-negligible residues. We also discuss how this algorithm can be extended to compute the nonequilibrium contribution to electron density, thereby evading cumbersome real-axis integration (within the bias voltage window) of NEGFs which is very difficult to converge for systems with large number of atoms while maintaining current conservation. Our second algorithm combines the recursive formulas with the geometrical partitioning of an arbitrary multiterminal device into nonuniform segments in order to reduce the computational complexity of the retarded Green
Comparison of eigeninference based on one- and two-point Green's functions
NASA Astrophysics Data System (ADS)
Drogosz, Zbigniew; Jurkiewicz, Jerzy; Łukaszewski, Grzegorz; Nowak, Maciej A.
2015-08-01
We compare two methods of eigeninference from large sets of data. Our analysis points at the superiority of our eigeninference method based on one-point Green's functions and Padé approximants over a method based on fluctuations and two-point Green's functions. The first method is orders of magnitude faster than the second one; moreover, we found a source of potential instability of the second method and identified it as arising from the spurious zero and negative modes of the estimator for the variance operator of a certain multidimensional Gaussian distribution, inherent for that method. We also present eigeninference based on spectral moments of negative orders, for strictly positive spectra. Finally, we compare the cases of eigeninference of real-valued and complex-valued correlated Wishart distributions, reinforcing our conclusions on the advantage of the one-point Green's function method.
Efficient calculation of 1-D periodic Green's functions for leaky-wave applications.
Baccarelli, Paolo; Johnson, William Arthur; Paulotto, Simone; Jackson, David R.; Wilton, Donald R.; Galli, A.; Valero, G.; Celepcikay, F. T.
2010-08-01
In this paper an approach is described for the efficient computation of the mixed-potential scalar and dyadic Green's functions for a one-dimensional periodic (periodic along x direction) array of point sources embedded in a planar stratified structure. Suitable asymptotic extractions are performed on the slowly converging spectral series. The extracted terms are summed back through the Ewald method, modified and optimized to efficiently deal with all the different terms. The accelerated Green's functions allow for complex wavenumbers, and are thus suitable for application to leaky-wave antennas analysis. Suitable choices of the spectral integration paths are made in order to account for leakage effects and the proper/improper nature of the various space harmonics that form the 1-D periodic Green's function.
NASA Astrophysics Data System (ADS)
Petukhin, Anatoly; Miyakoshi, Ken; Tsurugi, Masato; Kawase, Hiroshi; Kamae, Katsuhiro
2016-01-01
We used simulation by the reciprocity method to visualize the distribution of Green's function amplitudes in the source of a megathrust earthquake in the Nankai Trough and considered the effects of various areas (asperities or strong motion generation areas) on the simulated long-period ground motions at Konohana in the Osaka basin. We employed a fault source model proposed for an anticipated M9-class event in the Nankai Trough and the 3D Japan Intergrated Velocity Structure Model developed for simulations of long-period ground motions in Japan. Green's functions were calculated for about 1400 subsources by combining the finite-difference method and the reciprocity approach. Depths, strikes, and dips of subsources were adjusted to the shape of the upper boundary of the Philippine Sea plate. Ground motions with periods of 4-20 s were considered. The simulated distribution of peak amplitudes of Green's functions identified two strongly anomalous areas: (1) a large along-strike elongated area just south of the Kii Peninsula and (2) a parallel area closer to the trench. The elongation of the anomalies corresponded well with depth isolines at the top of the Philippine Sea plate. Postulating that plate shape influences simulated ground motions, we investigated the effect on Green's function amplitudes of phenomena related to plate shape: radiation pattern; variations of medium properties (e.g., velocity and density) at subsource depths; depth, strike, and dip; and the effect of soft sediments. We suggest that the cumulative effect on Green's function amplitudes of subsource radiation patterns, medium properties at subsource depth, reflection from crustal interfaces, and passage through soft sedimentary layers plays a critical role in the formation of amplitude anomalies. Analysis of waveforms and the time delay of peak amplitude demonstrate that large-amplitude waves of Green's functions in shallow parts of the plate boundary are composed mostly of surface waves.
A Green's function formulation for a nonlinear potential flow solution applicable to transonic flow
NASA Technical Reports Server (NTRS)
Baker, A. J.; Fox, C. H., Jr.
1977-01-01
Routine determination of inviscid subsonic flow fields about wing-body-tail configurations employing a Green's function approach for numerical solution of the perturbation velocity potential equation is successfully extended into the high subsonic subcritical flow regime and into the shock-free supersonic flow regime. A modified Green's function formulation, valid throughout a range of Mach numbers including transonic, that takes an explicit accounting of the intrinsic nonlinearity in the parent governing partial differential equations is developed. Some considerations pertinent to flow field predictions in the transonic flow regime are discussed.
Probing resonances in deformed nuclei by using the complex-scaled Green's function method
NASA Astrophysics Data System (ADS)
Shi, Xin-Xing; Shi, Min; Niu, Zhong-Ming; Heng, Tai-Hua; Guo, Jian-You
2016-08-01
Resonance plays a key role in the formation of many physical phenomena. The complex-scaled Green's function method provides a powerful tool for exploring resonance. In this paper, we combine this method with the theory describing deformed nuclei with the formalism presented. Taking 45S as an example, we elaborate numerical details and demonstrate how to determine the resonance parameters. The results are compared with those obtained by the complex scaling method and the coupled-channel method and satisfactory agreement is obtained. In particular, the present scheme focuses on the advantages of the complex scaling method and the Green's function method and is more suitable for the exploration of resonance.
Functional Green-Tuned Proteorhodopsin from Modern Stromatolites
Albarracín, Virginia Helena; Kraiselburd, Ivana; Bamann, Christian; Wood, Phillip G.; Bamberg, Ernst; Farias, María Eugenia; Gärtner, Wolfgang
2016-01-01
The sequenced genome of the poly-extremophile Exiguobacterium sp. S17, isolated from modern stromatolites at Laguna Socompa (3,570 m), a High-Altitude Andean Lake (HAAL) in Argentinean Puna revealed a putative proteorhodopsin-encoding gene. The HAAL area is exposed to the highest UV irradiation on Earth, making the microbial community living in the stromatolites test cases for survival strategies under extreme conditions. The heterologous expressed protein E17R from Exiguobacterium (248 amino acids, 85% sequence identity to its ortholog ESR from E. sibiricum) was assembled with retinal displaying an absorbance maximum at 524 nm, which makes it a member of the green-absorbing PR-subfamily. Titration down to low pH values (eventually causing partial protein denaturation) indicated a pK value between two and three. Global fitting of data from laser flash-induced absorption changes gave evidence for an early red-shifted intermediate (its formation being below the experimental resolution) that decayed (τ1 = 3.5 μs) into another red-shifted intermediate. This species decayed in a two-step process (τ2 = 84 μs, τ3 = 11 ms), to which the initial state of E17-PR was reformed with a kinetics of 2 ms. Proton transport capability of the HAAL protein was determined by BLM measurements. Additional blue light irradiation reduced the proton current, clearly identifying a blue light absorbing, M-like intermediate. The apparent absence of this intermediate is explained by closely matching formation and decay kinetics. PMID:27187791
Functional Green-Tuned Proteorhodopsin from Modern Stromatolites.
Albarracín, Virginia Helena; Kraiselburd, Ivana; Bamann, Christian; Wood, Phillip G; Bamberg, Ernst; Farias, María Eugenia; Gärtner, Wolfgang
2016-01-01
The sequenced genome of the poly-extremophile Exiguobacterium sp. S17, isolated from modern stromatolites at Laguna Socompa (3,570 m), a High-Altitude Andean Lake (HAAL) in Argentinean Puna revealed a putative proteorhodopsin-encoding gene. The HAAL area is exposed to the highest UV irradiation on Earth, making the microbial community living in the stromatolites test cases for survival strategies under extreme conditions. The heterologous expressed protein E17R from Exiguobacterium (248 amino acids, 85% sequence identity to its ortholog ESR from E. sibiricum) was assembled with retinal displaying an absorbance maximum at 524 nm, which makes it a member of the green-absorbing PR-subfamily. Titration down to low pH values (eventually causing partial protein denaturation) indicated a pK value between two and three. Global fitting of data from laser flash-induced absorption changes gave evidence for an early red-shifted intermediate (its formation being below the experimental resolution) that decayed (τ1 = 3.5 μs) into another red-shifted intermediate. This species decayed in a two-step process (τ2 = 84 μs, τ3 = 11 ms), to which the initial state of E17-PR was reformed with a kinetics of 2 ms. Proton transport capability of the HAAL protein was determined by BLM measurements. Additional blue light irradiation reduced the proton current, clearly identifying a blue light absorbing, M-like intermediate. The apparent absence of this intermediate is explained by closely matching formation and decay kinetics. PMID:27187791
Kowalski, K.; Bhaskaran-Nair, K.; Shelton, W. A.
2014-09-07
In this paper we discuss a new formalism for producing an analytic coupled-cluster (CC) Green's function for an N-electron system by shifting the poles of similarity transformed Hamiltonians represented in N - 1 and N + 1 electron Hilbert spaces. Simple criteria are derived for the states in N - 1 and N + 1 electron spaces that are then corrected in the spectral resolution of the corresponding matrix representations of the similarity transformed Hamiltonian. The accurate description of excited state processes within a Green's function formalism would be of significant importance to a number of scientific communities ranging from physics and chemistry to engineering and the biological sciences. This is because the Green's function methodology provides a direct path for not only calculating properties whose underlying origins come from coupled many-body interactions but also provides a straightforward path for calculating electron transport, response, and correlation functions that allows for a direct link with experiment. Finally, as a special case of this general formulation, we discuss the application of this technique for Green's function defined by the CC with singles and doubles representation of the ground-state wave function.
Kowalski, K. Bhaskaran-Nair, K.; Shelton, W. A.
2014-09-07
In this paper we discuss a new formalism for producing an analytic coupled-cluster (CC) Green's function for an N-electron system by shifting the poles of similarity transformed Hamiltonians represented in N − 1 and N + 1 electron Hilbert spaces. Simple criteria are derived for the states in N − 1 and N + 1 electron spaces that are then corrected in the spectral resolution of the corresponding matrix representations of the similarity transformed Hamiltonian. The accurate description of excited state processes within a Green's function formalism would be of significant importance to a number of scientific communities ranging from physics and chemistry to engineering and the biological sciences. This is because the Green's function methodology provides a direct path for not only calculating properties whose underlying origins come from coupled many-body interactions but also provides a straightforward path for calculating electron transport, response, and correlation functions that allows for a direct link with experiment. As a special case of this general formulation, we discuss the application of this technique for Green's function defined by the CC with singles and doubles representation of the ground-state wave function.
Pinho, Pedro; Correia, Otília; Lecoq, Miguel; Munzi, Silvana; Vasconcelos, Sasha; Gonçalves, Paula; Rebelo, Rui; Antunes, Cristina; Silva, Patrícia; Freitas, Catarina; Lopes, Nuno; Santos-Reis, Margarida; Branquinho, Cristina
2016-05-01
Forested areas within cities host a large number of species, responsible for many ecosystem services in urban areas. The biodiversity in these areas is influenced by human disturbances such as atmospheric pollution and urban heat island effect. To ameliorate the effects of these factors, an increase in urban green areas is often considered sufficient. However, this approach assumes that all types of green cover have the same importance for species. Our aim was to show that not all forested green areas are equal in importance for species, but that based on a multi-taxa and functional diversity approach it is possible to value green infrastructure in urban environments. After evaluating the diversity of lichens, butterflies and other-arthropods, birds and mammals in 31 Mediterranean urban forests in south-west Europe (Almada, Portugal), bird and lichen functional groups responsive to urbanization were found. A community shift (tolerant species replacing sensitive ones) along the urbanization gradient was found, and this must be considered when using these groups as indicators of the effect of urbanization. Bird and lichen functional groups were then analyzed together with the characteristics of the forests and their surroundings. Our results showed that, contrary to previous assumptions, vegetation density and more importantly the amount of urban areas around the forest (matrix), are more important for biodiversity than forest quantity alone. This indicated that not all types of forested green areas have the same importance for biodiversity. An index of forest functional diversity was then calculated for all sampled forests of the area. This could help decision-makers to improve the management of urban green infrastructures with the goal of increasing functionality and ultimately ecosystem services in urban areas. PMID:26777032
Transition-Metal-Catalyzed Redox-Neutral and Redox-Green C-H Bond Functionalization.
Wang, Hongli; Huang, Hanmin
2016-08-01
Transition-metal-catalyzed C-H bond functionalization has become one of the most promising strategies to prepare complex molecules from simple precursors. However, the utilization of environmentally unfriendly oxidants in the oxidative C-H bond functionalization reactions reduces their potential applications in organic synthesis. This account describes our recent efforts in the development of a redox-neutral C-H bond functionalization strategy for direct addition of inert C-H bonds to unsaturated double bonds and a redox-green C-H bond functionalization strategy for realization of oxidative C-H functionalization with O2 as the sole oxidant, aiming to circumvent the problems posed by utilizing environmentally unfriendly oxidants. In principle, these redox-neutral and redox-green strategies pave the way for establishing new environmentally benign transition-metal-catalyzed C-H bond functionalization strategies. PMID:27258190
Hutchings, L.; Foxall, W.; Kasameyer, P.; Wu, F.T.; Rau, R.-J.; Jarpe, S.
1997-01-01
We synthesize strong ground motion from a M=7.25 earthquake along the NW-trending Sanyi-Tungshih-Puli seismic zone. This trend extends from Houlong to Taichung and forms a nearly continuous 78 km long seismic zone identified by the occurrence of M<5 events. It extends from a shallow depth all the way down to about 40 km. The entire length of the fault, if activated at one time, can lead to an event comparable to that the 1995 Kobe earthquake. With the improved digital CWBSN data now provided routinely by CWBSN, it becomes possible to use these data as empirical Green`s functions to synthesize potential ground motion for future large earthquakes. We developed a suite of 100 rupture scenarios for the earthquake and computed the commensurate strong ground motion time histories. We synthesized strong ground motion with physics-based solutions of earthquake rupture and applied physical bounds on rupture parameters. the synthesized ground motions obtained for a fixed magnitude and identifying the hazard to a site from the statistical distribution of engineering parameters, we have introduced a probabilistic component to the deterministic hazard calculation, The time histories suggested for engineering design are the ones that most closely match either the average or one standard deviation absolute acceleration response values.
Frequency-domain Green's functions for radar waves in heterogeneous 2.5D media
Ellefsen, K.J.; Croize, D.; Mazzella, A.T.; McKenna, J.R.
2009-01-01
Green's functions for radar waves propagating in heterogeneous 2.5D media might be calculated in the frequency domain using a hybrid method. The model is defined in the Cartesian coordinate system, and its electromagnetic properties might vary in the x- and z-directions, but not in the y-direction. Wave propagation in the x- and z-directions is simulated with the finite-difference method, and wave propagation in the y-direction is simulated with an analytic function. The absorbing boundaries on the finite-difference grid are perfectly matched layers that have been modified to make them compatible with the hybrid method. The accuracy of these numerical Greens functions is assessed by comparing them with independently calculated Green's functions. For a homogeneous model, the magnitude errors range from -4.16% through 0.44%, and the phase errors range from -0.06% through 4.86%. For a layered model, the magnitude errors range from -2.60% through 2.06%, and the phase errors range from -0.49% through 2.73%. These numerical Green's functions might be used for forward modeling and full waveform inversion. ?? 2009 Society of Exploration Geophysicists. All rights reserved.
Brazilian Green Propolis Improves Antioxidant Function in Patients with Type 2 Diabetes Mellitus.
Zhao, Liting; Pu, Lingling; Wei, Jingyu; Li, Jinghua; Wu, Jianquan; Xin, Zhonghao; Gao, Weina; Guo, Changjiang
2016-01-01
Propolis contains a variety of bioactive components and possesses many biological properties. This study was designed to evaluate potential effects of Brazilian green propolis on glucose metabolism and antioxidant function in patients with type 2 diabetes mellitus (T2DM). In the 18-week randomized controlled study, enrolled patients with T2DM were randomly assigned to Brazilian green propolis group (900 mg/day) (n = 32) and control group (n = 33). At the end of the study, no significant difference was found in serum glucose, glycosylated hemoglobin, insulin, aldose reductase or adiponectin between the two groups. However, serum GSH and total polyphenols were significantly increased, and serum carbonyls and lactate dehydrogenase activity were significantly reduced in the Brazilian green propolis group. Serum TNF-α was significantly decreased, whereas serum IL-1β and IL-6 were significantly increased in the Brazilian green propolis group. It is concluded that Brazilian green propolis is effective in improving antioxidant function in T2DM patients. PMID:27187435
Brazilian Green Propolis Improves Antioxidant Function in Patients with Type 2 Diabetes Mellitus
Zhao, Liting; Pu, Lingling; Wei, Jingyu; Li, Jinghua; Wu, Jianquan; Xin, Zhonghao; Gao, Weina; Guo, Changjiang
2016-01-01
Propolis contains a variety of bioactive components and possesses many biological properties. This study was designed to evaluate potential effects of Brazilian green propolis on glucose metabolism and antioxidant function in patients with type 2 diabetes mellitus (T2DM). In the 18-week randomized controlled study, enrolled patients with T2DM were randomly assigned to Brazilian green propolis group (900 mg/day) (n = 32) and control group (n = 33). At the end of the study, no significant difference was found in serum glucose, glycosylated hemoglobin, insulin, aldose reductase or adiponectin between the two groups. However, serum GSH and total polyphenols were significantly increased, and serum carbonyls and lactate dehydrogenase activity were significantly reduced in the Brazilian green propolis group. Serum TNF-α was significantly decreased, whereas serum IL-1β and IL-6 were significantly increased in the Brazilian green propolis group. It is concluded that Brazilian green propolis is effective in improving antioxidant function in T2DM patients. PMID:27187435
NASA Astrophysics Data System (ADS)
Kim, Young Eun; Kim, Yu-Na; Kim, Jung A.; Kim, Ho Min; Jung, Yongwon
2015-05-01
Supramolecular protein assemblies offer novel nanoscale architectures with molecular precision and unparalleled functional diversity. A key challenge, however, is to create precise nano-assemblies of functional proteins with both defined structures and a controlled number of protein-building blocks. Here we report a series of supramolecular green fluorescent protein oligomers that are assembled in precise polygonal geometries and prepared in a monodisperse population. Green fluorescent protein is engineered to be self-assembled in cells into oligomeric assemblies that are natively separated in a single-protein resolution by surface charge manipulation, affording monodisperse protein (nano)polygons from dimer to decamer. Several functional proteins are multivalently displayed on the oligomers with controlled orientations. Spatial arrangements of protein oligomers and displayed functional proteins are directly visualized by a transmission electron microscope. By employing our functional protein assemblies, we provide experimental insight into multivalent protein-protein interactions and tools to manipulate receptor clustering on live cell surfaces.
Green's functions for dislocations in bonded strips and related crack problems
NASA Technical Reports Server (NTRS)
Ballarini, R.; Luo, H. A.
1990-01-01
Green's functions are derived for the plane elastostatics problem of a dislocation in a bimaterial strip. Using these fundamental solutions as kernels, various problems involving cracks in a bimaterial strip are analyzed using singular integral equations. For each problem considered, stress intensity factors are calculated for several combinations of the parameters which describe loading, geometry and material mismatch.
Green's functions for dislocations in bonded strips and related crack problems
NASA Technical Reports Server (NTRS)
Ballarini, R.; Luo, H. A.
1991-01-01
Green's functions are derived for the plane elastostatics problem of a dislocation in a bimaterial strip. Using these fundamental solutions as kernels, various problems involving cracks in a bimaterial strip are analyzed using singular integral equations. For each problem considered, stress intensity factors are calculated for several combinations of the parameters which describe loading, geometry and material mismatch.
NASA Astrophysics Data System (ADS)
Simon, Emanuel; Foschum, Florian; Kienle, Alwin
2013-06-01
Time-resolved diffuse optical spectroscopy measurements of phantoms at small source-detector separations yield good results for the retrieved coefficients of reduced scattering and absorption when a hybrid Green's function of the radiative transfer equation for semi-infinite media is used.
The Prediction of Jet Noise Ground Effects Using an Acoustic Analogy and a Tailored Green's Function
NASA Technical Reports Server (NTRS)
Miller, Steven A. E.
2013-01-01
An assessment of an acoustic analogy for the mixing noise component of jet noise in the presence of an infinite surface is presented. The reflection of jet noise by the ground changes the distribution of acoustic energy and is characterized by constructive and destructive interference patterns. The equivalent sources are modeled based on the two-point cross- correlation of the turbulent velocity fluctuations and a steady Reynolds-Averaged Navier-Stokes (RANS) solution. Propagation effects, due to reflection by the surface and refaction by the jet shear layer, are taken into account by calculating the vector Green's function of the linearized Euler equations (LEE). The vector Green's function of the LEE is written in relation to Lilley's equation; that is, approximated with matched asymptotic solutions and the Green's function of the convective Helmholtz equation. The Green's function of the convective Helmholtz equation for an infinite flat plane with impedance is the Weyl-van der Pol equation. Predictions are compared with an unheated Mach 0.95 jet produced by a nozzle with an exit diameter of 0.3302 meters. Microphones are placed at various heights and distances from the nozzle exit in the peak jet noise direction above an acoustically hard and an asphalt surface. The predictions are shown to accurately capture jet noise ground effects that are characterized by constructive and destructive interference patterns in the mid- and far-field and capture overall trends in the near-field.
Localized axial Green's function method for the convection-diffusion equations in arbitrary domains
NASA Astrophysics Data System (ADS)
Lee, Wanho; Kim, Do Wan
2014-10-01
A localized axial Green's function method (LAGM) is proposed for the convection-diffusion equation. The axial Green's function method (AGM) enables us to calculate the numerical solution of a multi-dimensional problem using only one-dimensional Green's functions for the axially split differential operators. This AGM has been developed not only for the elliptic boundary value problems but also for the steady Stokes flows, however, this paper is concerned with the localization of the AGM. This localization of the method is needed for practical purpose when computing the axial Green's function, specifically for the convection-diffusion equation on a line segment that we call the local axial line. Although our focus is mainly on the convection-dominated cases in arbitrary domains, this method can solve other cases in a unified way. Numerical results show that, despite irregular types of discretization on an arbitrary domain, we can calculate the numerical solutions using the LAGM without loss of accuracy even in cases of large convection. In particular, it is also shown that randomly distributed axial lines are available in our LAGM and complicated domains are not a burden.
NASA Astrophysics Data System (ADS)
McMahon, N. D.; Chaput, J. A.; Knox, H. A.; Aster, R. C.; Kyle, P. R.
2013-12-01
Seismic interferometry has emerged in the past decade as a powerful technique for interpreting passive seismic data and has been particularly useful for retrieving portions of elastic Green's functions in continental settings and for detailing structure and monitoring temporal variations at microseism periods (e.g., near 8 Hz) at volcanoes. Coda wave interferometry studies to retrieve body waves have previously been performed on Erebus volcano utilizing Strombolian eruption coda signals to image the internal structure of the volcano using short period body waves. Here we demonstrate that short-period surface and body wave Green's functions can also be recovered by correlating icequake coda signals on this highly glaciated volcano. A dense network of 99 short-period, three-component seismometers were deployed in a 3x3-km array surrounding the summit crater during the 2008-2009 austral summer. Coda data from 44 small, near-surface source icequakes (likely crevassing events) recorded during the month of December 2008 were cross-correlated revealing both body- and surface-wave portions of the Green's functions across the array. Recovery of Green's functions from a small number of icequakes lends merit to the utilization of icequake coda to enhance recovery of structural details and possible monitoring applications on glaciated volcanoes.
Green's functions for a volume source in an elastic half-space.
Zabolotskaya, Evgenia A; Ilinskii, Yurii A; Hay, Todd A; Hamilton, Mark F
2012-03-01
Green's functions are derived for elastic waves generated by a volume source in a homogeneous isotropic half-space. The context is sources at shallow burial depths, for which surface (Rayleigh) and bulk waves, both longitudinal and transverse, can be generated with comparable magnitudes. Two approaches are followed. First, the Green's function is expanded with respect to eigenmodes that correspond to Rayleigh waves. While bulk waves are thus ignored, this approximation is valid on the surface far from the source, where the Rayleigh wave modes dominate. The second approach employs an angular spectrum that accounts for the bulk waves and yields a solution that may be separated into two terms. One is associated with bulk waves, the other with Rayleigh waves. The latter is proved to be identical to the Green's function obtained following the first approach. The Green's function obtained via angular spectrum decomposition is analyzed numerically in the time domain for different burial depths and distances to the receiver, and for parameters relevant to seismo-acoustic detection of land mines and other buried objects. PMID:22423682
GREEN'S Function and Super-Particle Methods for Kinetic Simulation of Heteroepitaxy
NASA Astrophysics Data System (ADS)
Lam, Chi-Hang; Lung, M. T.
Arrays of nanosized three dimensional islands are known to self-assemble spontaneously on strained heteroepitaxial thin films. We simulate the dynamics using kinetic Monte Carlo method based on a ball and spring lattice model. Green's function and super-particle methods which greatly enhance the computational efficiency are explained.
Bayesian source localization with uncertain Green's function in an uncertain shallow water ocean.
Le Gall, Yann; Dosso, Stan E; Socheleau, François-Xavier; Bonnel, Julien
2016-03-01
Matched-field acoustic source localization is a challenging task when environmental properties of the oceanic waveguide are not precisely known. Errors in the assumed environment (mismatch) can cause severe degradations in localization performance. This paper develops a Bayesian approach to improve robustness to environmental mismatch by considering the waveguide Green's function to be an uncertain random vector whose probability density accounts for environmental uncertainty. The posterior probability density is integrated over the Green's function probability density to obtain a joint marginal probability distribution for source range and depth, accounting for environmental uncertainty and quantifying localization uncertainty. Because brute-force integration in high dimensions can be costly, an efficient method is developed in which the multi-dimensional Green's function integration is approximated by one-dimensional integration over a suitably defined correlation measure. An approach to approximate the Green's function covariance matrix, which represents the environmental mismatch, is developed based on modal analysis. Examples are presented to illustrate the method and Monte-Carlo simulations are carried out to evaluate its performance relative to other methods. The proposed method gives efficient, reliable source localization and uncertainties with improved robustness toward environmental mismatch. PMID:27036237
Green Function Approach to the Calculation of the Local Density of States in the Graphitic Nanocone
NASA Astrophysics Data System (ADS)
Smotlacha, Jan; Pinčák, Richard
2016-02-01
Graphene and other nanostructures belong to the center of interest of today's physics research. The local density of states of the graphitic nanocone influenced by the spin-orbit interaction was calculated. Numerical calculations and the Green function approach were used to solve this problem. It was proven in the second case that the second order approximation is not sufficient for this purpose.
Toward proving a new identity for Green's functions in N = 1 supersymmetric electrodynamics
Stepanyantz, K. V.
2009-01-15
A method that may underlie an attempt at proving the previously proposed new identity for Green's functions is described for N = 1 supersymmetric massless electrodynamics regularized by higher derivatives. With the aid of this method, it is shown that some contributions to the identity in question do indeed vanish.
NASA Technical Reports Server (NTRS)
Plante, Ianik; Cucinotta, Francis A.
2011-01-01
Radiolytic species are formed approximately 1 ps after the passage of ionizing radiation through matter. After their formation, they diffuse and chemically react with other radiolytic species and neighboring biological molecules, leading to various oxidative damage. Therefore, the simulation of radiation chemistry is of considerable importance to understand how radiolytic species damage biological molecules [1]. The step-by-step simulation of chemical reactions is difficult, because the radiolytic species are distributed non-homogeneously in the medium. Consequently, computational approaches based on Green functions for diffusion-influenced reactions should be used [2]. Recently, Green functions for more complex type of reactions have been published [3-4]. We have developed exact random variate generators of these Green functions [5], which will allow us to use them in radiation chemistry codes. Moreover, simulating chemistry using the Green functions is which is computationally very demanding, because the probabilities of reactions between each pair of particles should be evaluated at each timestep [2]. This kind of problem is well adapted for General Purpose Graphic Processing Units (GPGPU), which can handle a large number of similar calculations simultaneously. These new developments will allow us to include more complex reactions in chemistry codes, and to improve the calculation time. This code should be of importance to link radiation track structure simulations and DNA damage models.
Green's function Monte Carlo calculation for the ground state of helium trimers
Cabral, F.; Kalos, M.H.
1981-02-01
The ground state energy of weakly bound boson trimers interacting via Lennard-Jones (12,6) pair potentials is calculated using a Monte Carlo Green's Function Method. Threshold coupling constants for self binding are obtained by extrapolation to zero binding.
NASA Astrophysics Data System (ADS)
Sheng, X.; Xiao, X.; Zhang, S.
2016-09-01
When dealing with wheel-rail interactions for a high-speed train using the time domain Green function of a railway track, it would be more reasonable to use the moving Green function associated with a reference frame moving with the train, since observed from this frame wheel/rail forces are stationary. In this paper, the time domain moving Green function of a railway track as an infinitely long periodic structure is defined, derived, discussed and applied. The moving Green function is defined as the Fourier transform, from the load frequency domain to the time domain, of the response of the rail due to a moving harmonic load. The response of the rail due to a moving harmonic load is calculated using the Fourier transform-based method. A relationship is established between the moving Green function and the conventional impulse response function of the track. Properties of the moving Green function are then explored which can largely simplify the calculation of the Green function. And finally, the moving Green function is applied to deal with interactions between wheels and a track with or without rail dampers, allowing non-linearity in wheel-rail contact and demonstrating the effect of the rail dampers.
Hutchings, L.
1992-01-01
This report outlines a method of using empirical Green's functions in an earthquake simulation program EMPSYN that provides realistic seismograms from potential earthquakes. The theory for using empirical Green's functions is developed, implementation of the theory in EMPSYN is outlined, and an example is presented where EMPSYN is used to synthesize observed records from the 1971 San Fernando earthquake. To provide useful synthetic ground motion data from potential earthquakes, synthetic seismograms should model frequencies from 0.5 to 15.0 Hz, the full wave-train energy distribution, and absolute amplitudes. However, high-frequency arrivals are stochastically dependent upon the inhomogeneous geologic structure and irregular fault rupture. The fault rupture can be modeled, but the stochastic nature of faulting is largely an unknown factor in the earthquake process. The effect of inhomogeneous geology can readily be incorporated into synthetic seismograms by using small earthquakes to obtain empirical Green's functions. Small earthquakes with source corner frequencies higher than the site recording limit f{sub max}, or much higher than the frequency of interest, effectively have impulsive point-fault dislocation sources, and their recordings are used as empirical Green's functions. Since empirical Green's functions are actual recordings at a site, they include the effects on seismic waves from all geologic inhomogeneities and include all recordable frequencies, absolute amplitudes, and all phases. They scale only in amplitude with differences in seismic moment. They can provide nearly the exact integrand to the representation relation. Furthermore, since their source events have spatial extent, they can be summed to simulate fault rupture without loss of information, thereby potentially computing the exact representation relation for an extended source earthquake.
Coulomb Green's function and image potential near a cylindrical diffuse interface
NASA Astrophysics Data System (ADS)
Xue, Changfeng; Huang, Qiongwei; Deng, Shaozhong
2015-12-01
In a preceding paper [Comput. Phys. Commun. 184 (1): 51-59, 2013], we revisited the problem of calculating Coulomb Green's function and image potential near a planar diffuse interface within which the dielectric permittivity of the inhomogeneous medium changes continuously along one Cartesian direction in a transition layer between two dissimilar dielectric materials. In the present paper, we consider a cylindrical diffuse interface within which the dielectric permittivity changes continuously along the radial direction instead. First we propose a specific cylindrical diffuse interface model, termed the quasi-harmonic diffuse interface model, that can admit analytical solution for the Green's function in terms of the modified Bessel functions. Then and more importantly we develop a robust numerical method for building Green's functions for any cylindrical diffuse interface models. The main idea of the numerical method is, after dividing a diffuse interface into multiple sublayers, to approximate the dielectric permittivity profile in each one of the sublayers by one of the quasi-harmonic functional form rather than simply by a constant value as one would normally do. Next we describe how to efficiently compute well-behaved ratios, products, and logarithmic derivatives of the modified Bessel functions so as to avoid direct evaluations of individual modified Bessel functions in our formulations. Finally we conduct numerical experiments to show the effectiveness of the quasi-harmonic diffuse interface model in overcoming the divergence of the image potential, to validate the numerical method in terms of its accuracy and convergence, and to demonstrate its capability for computing Green's functions for any cylindrical diffuse interface models.
Green's function for a Schroedinger operator and some related summation formulas
Keviczky, Attila B. von; Saad, Nasser; Hall, Richard L.
2005-07-01
Summation formulas are obtained for products of associated Lagurre polynomials by means of the Green's function K for the Hamiltonian H{sub 0}=-d{sup 2}/dx{sup 2}+x{sup 2}+Ax{sup -2} (A>0). K is constructed by an application of a Mercer-type theorem that arises in connection with integral equations. The approach introduced in this paper may be useful for the construction of wider classes of generating function.
NASA Astrophysics Data System (ADS)
Hernández, Alexis R.; Lewenkopf, Caio H.
2013-04-01
We study the nonlinear elastic quantum electronic transport properties of nanoscopic devices using the nonequilibrium Green's function (NEGF) method. The Green's function method allows us to expand the I- V characteristics of a given device to arbitrary powers of the applied voltages. By doing so, we are able to relate the NEGF method to the scattering approach, showing their similarities and differences and calculate the conductance coefficients to arbitrary order. We demonstrate that the electronic current given by NEGF is gauge invariant to all orders in powers of V, and discuss the requirements for gauge invariance in the standard density functional theory (DFT) implementations in molecular electronics. We also analyze the symmetries of the nonlinear conductance coefficients with respect to a magnetic field inversion and the violation of the Onsager reciprocity relations with increasing source-drain bias.
Green tea: a novel functional food for the oral health of older adults.
Gaur, Sumit; Agnihotri, Rupali
2014-04-01
Functional foods are foods with positive health effects that extend beyond their nutritional value. They affect the function of the body and help in the management of specific health conditions. Green tea, a time-honoured Chinese herb, might be regarded as a functional food because of its inherent anti-oxidant, anti-inflammatory, antimicrobial and antimutagenic properties. They are attributed to its reservoir of polyphenols, particularly the catechin, epigallocatechin-3-gallate. Owing to these beneficial actions, this traditional beverage was used in the management of chronic systemic diseases including cancer. Recently, it has been emphasized that the host immuno-inflammatory reactions destroy the oral tissues to a greater extent than the microbial activity alone. Green tea with its wide spectrum of activities could be a healthy alternative for controlling these damaging reactions seen in oral diseases, specifically, chronic periodontitis, dental caries and oral cancer, which are a common occurrence in the elderly population. PMID:24261512
Phytochrome from Green Plants: Properties and biological Function
Quail, Peter H.
2014-07-25
Pfr conformer reverses this activity upon initial light exposure, inducing the switch to photomorphogenic development. This reversal involves light-triggered translocation of the photoactivated phy molecule into the nucleus where it interacts with PIF-family members, inducing rapid phosphorylation and degradation of the PIFs via the ubiquitin-proteasome system. This degradation in turn elicits rapid alterations in gene expression that drive the deetiolation transition. This project has made considerable progress in defining phy-PIF signaling activity in controlling the SAR. The biological functions of the multiple PIF-family members in controlling the SAR, including dissection of the relative contributions of the individual PIFs to this process, as well as to diurnal growth-control oscillations, have been investigated using higher-order pif-mutant combinations. Using microarray analysis of a quadruple pif mutant we have defined the shade-induced, PIF-regulated transcriptional network genome-wide. This has revealed that a dynamic antagonism between the phys and PIFs generates selective reciprocal responses during deetiolation and the SAR in a rapidly light-responsive transcriptional network. Using integrated RNA-seq and ChIP-seq analysis of higher order pif-mutant combinations, we have defined the direct gene-targets of PIF transcriptional regulation, and have obtained evidence that this regulation involves differential direct targeting of rapidly light-responsive genes by the individual PIF-family members. This project has provided significant advances in our understanding of the molecular mechanisms by which the phy-PIF photosensory signaling pathway regulates an important bioenergy-related plant response to the light environment. The identification of molecular targets in the primary transcriptional-regulatory circuitry of this pathway has the potential to enable genetic or reverse-genetic manipulation of the partitioning of carbon between reproductive and
Dispersive and dissipative medium response to an ultrashort pulse: A Green's function approach
NASA Astrophysics Data System (ADS)
Wilhelmsson, Hans; Trombert, Jean-Hughes; Eloy, Jean-François
1995-07-01
The propagation of an ultrashort pulse in a dispersive and dissipative medium may conveniently be described by using a Green's function analysis. The advantage would be that all details of the initial pulse, however short, could be probed by an "infinitely" sharp δ-pulse and subsequently deciphered in a modified form, after the influence of the medium, at a later time and at a new observation point. The Green's function for a dispersive and dissipative, plasma or dielectric (molecular) medium, is constructed for an infinitely extended three-dimensional case by using symbolic algebra for time-differential operators. The solution consists of two parts: a displaced δ-function part and a Bessel-function part, describing a wake field which for dominating dispersion is of oscillatory nature. For a certain ratio between the dispersive and dissipative parameters (plasma frequency and damping) a critical limit is found where the wake oscillations disappear completely. In the particular limits of vanishing dispersion or vanishing dissipation one recovers from the generalized solution the well-known results for a pure conductor (metal) and a pure dispersive medium (cold collisionless plasma) described by the Klein-Gordon equation. The response of the medium to an initially localized ulrashort electromagnetic pulse, of an arbitrary shape, can be expressed by an integral in time and space, of the product of the Green's function and the initial pulse.
NASA Astrophysics Data System (ADS)
Pearson, L. W.
1983-04-01
The expansions of the electric and magnetic dyadic Green's functions are constructed in terms of the solenoidal Hansen vector wave functions in cylindrical coordinates. A static term is shown to arise in the course of conducting the radial spectral integral. This pole term has apparently not been identified in previously published expansions and is similar to recently identified static terms in Cartesian and spherical wave function expansions. The integration in the longitudinal spectral variable is considered, too, and forms which offer two alternative integration paths are constructed.
NASA Technical Reports Server (NTRS)
Baumeister, K. J.
1983-01-01
A time-dependent finite difference formulation to the inhomogeneous wave equation is derived for plane wave propagation with harmonic noise sources. The difference equation and boundary conditions are developed along with the techniques to simulate the Dirac delta function associated with a concentrated noise source. Example calculations are presented for the Green's function and distributed noise sources. For the example considered, the desired Fourier transformed acoustic pressures are determined from the transient pressures by use of a ramping function and an integration technique, both of which eliminates the nonharmonic pressure associated with the initial transient.
Quantum field theory in the presence of a medium: Green's function expansions
Kheirandish, Fardin; Salimi, Shahriar
2011-12-15
Starting from a Lagrangian and using functional-integration techniques, series expansions of Green's function of a real scalar field and electromagnetic field, in the presence of a medium, are obtained. The parameter of expansion in these series is the susceptibility function of the medium. Relativistic and nonrelativistic Langevin-type equations are derived. Series expansions for Lifshitz energy in finite temperature and for an arbitrary matter distribution are derived. Covariant formulations for both scalar and electromagnetic fields are introduced. Two illustrative examples are given.
A hybrid representation of the Green's function in an overmoded rectangular cavity
NASA Astrophysics Data System (ADS)
Wu, Doris I.; Chang, David C.
1988-09-01
A hybrid ray-mode representation of the Green's function in a rectangular cavity is developed using the finite Poisson summation formula. To obtain a numerically efficient scheme for computing the field generated by a point source in a large rectangular cavity, the conventional modal representation of the Green's function is modified in such a way that all the modes near resonance are retained while the truncated remainder of the mode series is expressed in terms of a weighted contribution of rays. For an electrically large cavity, the contribution of rays from distant images becomes small; therefore, the ray sum can be approximated by one or two dominant terms without a loss of numerical accuracy. To illustrate the accuracy and the computational simplification of this ray-mode representation, numerical examples are included with the conventional mode series (summed at the expense of long computation time) serving as a reference.
NASA Astrophysics Data System (ADS)
Alvermann, A.; Edwards, D. M.; Fehske, H.
2010-04-01
In classical Drude theory the conductivity is determined by the mass of the propagating particles and the mean free path between two scattering events. For a quantum particle this simple picture of diffusive transport loses relevance if strong correlations dominate the particle motion. We study a situation where the propagation of a fermionic particle is possible only through creation and annihilation of local bosonic excitations. This correlated quantum transport process is outside the Drude picture, since one cannot distinguish between free propagation and intermittent scattering. The characterization of transport is possible using the Drude weight obtained from the f-sum rule, although its interpretation in terms of free mass and mean free path breaks down. For the situation studied we calculate the Green's function and Drude weight using a Green's functions expansion technique, and discuss their physical meaning.
Svinarenko, A. A.; Loboda, A. V.; Sukharev, D. E.; Dubrovskaya, Yu. V.; Mudraya, N. V.; Serga, I. N.; Glushkov, A. V.
2010-05-04
We report the further development of an effective approach to construction of the electron Green's function (GF) for the Dirac equation with a complex energy and non-singular central nuclear potential. The nuclear charge distribution and the corresponding nuclear potential are received within the relativistic mean field (RMF) model. The Green's function is usually represented as a combination of two fundamental solutions of the Dirac equation. In the numerical procedure we use the Ivanov-Ivanova effective numerical algorithm and reduce a definition of the Dirac equation fundamental solutions to solving the system of differential equations, which includes the differential equations for the RMF nuclear potential too. As an application, we estimate the self-energy shift correction to atomic levels energies within the Mohr covariant procedure and presented GF approach and calculate the transitions energies for some heavy Li-like multi-charged ions within the QED many-body perturbation theory formalism.
Electronic states on a fractal: Exact Green's-function renormalization approach
NASA Astrophysics Data System (ADS)
Andrade, R. F. S.; Schellnhuber, H. J.
1991-12-01
A nontrivial tight-binding model for electron dynamics on the fractal Koch curve is investigated within the framework of the Green's-function formalism. The key result is the construction of a multiple exact renormalization group that allows one to derive all the rather unusual properties of the model. This group is generated by four nonequivalent decimation operations, which define distinct transformation rules for the 48 relevant parameters to be renormalized. The calculation of the density of states confirms the crucial results that were obtained recently using transfer-matrix methods: local self-affinity, dense gap structure, and singular electronic levels with infinite degeneracy. This demonstrates that the Green's-function approach is not inferior to other techniques even in topologically one-dimensional situations.
Thermal-wave fields in solid wedges using the Green function method: Theory and experiment
NASA Astrophysics Data System (ADS)
Tai, Rui; Zhang, Jie; Wang, Chinhua; Mandelis, Andreas
2013-04-01
In this work, we establish a theoretical model for a cylindrical rod of radius R with opening angle θ illuminated by a modulated incident beam. The model uses the Green function method in cylindrical coordinates. An analytical expression for the Green function and thermal-wave field in such a solid is presented. The theory is validated in the limit of reducing the arbitrary wedge geometrical structure to simpler geometries. For acute angle wedges, it is shown that the thermal-wave field near the edge exhibits confinement behavior and increased amplitude compared to a flat (reference) solid with θ = π. For obtuse angle wedges, it is shown that the opposite is true and relaxation of confinement occurs leading to lower amplitude thermal-wave fields. The theory provides a basis for quantitative thermophysical characterization of wedge-shaped objects and it is tested using an AISI 304 steel wedge and photothermal radiometry detection.
Born modeling for heterogeneous media using the Gaussian beam summation based Green's function
NASA Astrophysics Data System (ADS)
Huang, Xingguo; Sun, Hui; Sun, Jianguo
2016-08-01
Born approximation is a commonly used approximation in the simulation of seismic wave propagation. Calculation of the Green's function in Born approximation integral is essential for Born modeling. We derive a new Born formula based on the Gaussian beam representations of Green's functions. This procedure can be used to mitigate the problems like the caustic, shadow region, and multivalued traveltime caused by multipathing that traditional geometric ray theory cannot deal with. However, due to the characteristic of complex traveltime in the Gaussian beam, we present a new isochronous stack method for Gaussian beam based Born modeling. Additionally, two basic issues, background velocity and integral region selection, are discussed. Numerical results demonstrate the accuracy and efficiency of the Gaussian beam based Born theory and implementation.
NASA Astrophysics Data System (ADS)
Huang, Guobo; Fei, Zhengdong; Chen, Xiaoying; Qiu, Fangli; Wang, Xu; Gao, Jianrong
2012-10-01
A phosphorussbnd nitrogen containing compound, N-(2-(5,5-dimethyl-1,3,2-dioxaphosphinyl-2-ylamino)-hexylacetamide-2-propyl acid (PAHPA), is synthesized and characterized. A novel flame retardant, namely layered double hydroxides (LDHs) modified with PAHPA (PAHPA-LDHs), is prepared by ion-exchange of LDHs with PAHPA. The results from Fourier transform infrared spectroscopy, X-ray photoelectron spectroscopy and energy dispersive X-ray analysis with a high-angle annular dark-field scanning transmission electron microscope show that PAHPA intercalated LDHs. The X-ray diffraction and transmission electron microscopy (TEM) results show that PAHPA-LDHs achieve well dispersion in ethylene vinyl acetate copolymer (EVA) matrix and the EVA/PAHPA-LDHs nanocomposites (i.e. EVA filled with 5 wt% PAHPA-LDHs) are formed by polymer melt intercalation. Thermal stability and flammability properties are investigated by thermogravimetric analysis and cone calorimeter tests. The results show that the addition of PAHPA-LDHs improves thermal stability and reduces obviously the flammability of EVA resin. Compared with pure EVA resin, the peak heat release rate of the EVA/PAHPA-LDHs nanocomposites is reduced by about 43%. The results of scanning electron microscopy and TEM indicate that a compact and dense intumescent char is formed for the EVA/PAHPA-LDHs nanocomposites after combustion.
Welch, S J; Pear, J J
1980-01-01
Picture-cards, photographs, and real objects were compared as training stimuli in order to determine which best facilitated the generalization of naming responses learned in a special training room to real objects in the natural environments of four retarded children. The amount of transfer of naming behavior between the three stimulus modes and the average amount of training time required per stimulus mode were also assessed. Three of the four children displayed considerably more generalization to the real objects in the natural environment when they were trained with real objects. The fourth child displayed substantial generalization regardless of the training stimulus mode. No particular training stimulus mode clearly facilitated the transfer of naming responses to other modes or greatly reduced training time. The results of two supplementary procedures conducted with one child showed that: (1) training in several environments facilitated generalization to real objects in the natural environment when real objects were used as training stimuli but not when picture-cards were used, and (2) transfer from picture-cards to real objects was facilitated by training other picture-cards and the real objects portrayed by them at the same time. PMID:6451607
Extraction of Broadband Basin-Scale Green's Functions from the Ambient Seismic Field
NASA Astrophysics Data System (ADS)
Viens, L.; Koketsu, K.; Miyake, H.; Sakai, S.; Hirata, N.
2015-12-01
Many large cities in the world, including Tokyo and Los Angeles, are located atop sedimentary basins that have the potential to significantly amplify ground motions. The Kanto sedimentary basin, which underlies the Tokyo Metropolitan area, is filled by soft sediments and has a resonance period of 7-10 s, similar to the natural period of some tall buildings. To assess seismic hazard in this particularly seismically active area, we use the information carried by the ambient seismic field continuously recorded by more than 600 seismic stations that have been deployed in the basin. These stations equipped with three-component seismometers are a part of different networks, including the Metropolitan Seismic Observation network (MeSO-net), Hi-net and F-net of NIED, and the Japan Meteorological Agency (JMA) network. We extracted the 9 components of the Green's function tensors from the ambient seismic field using deconvolution for each pair of stations, regarding one as the virtual source and the other one as the receiver. We show that the extracted Green's functions contain body and surface waves having phase and amplification similar to the ones of earthquake records that occurred close to the virtual sources. For inter-station distances shorter than 30 km, time-frequency analyses suggest that Green's functions with energy higher than 1 Hz can be recovered. We use this dense array to investigate the effect of inter-station distance variations and azimuth dependences on the Green's function retrieval. Results show that the ambient seismic field recorded by stations situated at less than a few kilometers from each other can provide insights on seismic hazard assessment over a broad period range.
Fathi, S. M. Saberi
2010-12-15
In this paper we first show in the framework of quaternion analysis how the fundamental solutions of the Dirac operators with vector potential can be obtained. Then, we use the obtained results to present a derivation of the exact analytic Green function for the Helmholtz equation, i.e., ({Delta}+|a(x)|{sup 2})G{sub 0}(x)={delta}(x), for the case a(x) is a monogenic (analytic) vector potential.
Double plane wave reverse time migration with plane wave Green's function
NASA Astrophysics Data System (ADS)
Zhao, Z.; Sen, M. K.; Stoffa, P. L.
2015-12-01
Reverse time migration (RTM) is effective in obtaining complex subsurface structures from seismic data. By solving the two-way wave equation, RTM can use entire wavefield for imaging. Although powerful computer are becoming available, the conventional pre-stack shot gather RTM is still computationally expensive. Solving forward and backward wavefield propagation for each source location and shot gather is extremely time consuming, especially for large seismic datasets. We present an efficient, accurate and flexible plane wave RTM in the frequency domain where we utilize a compressed plane wave dataset, known as the double plane wave (DPW) dataset. Provided with densely sampled seismic dataset, shot gathers can be decomposed into source and receiver plane wave components with minimal artifacts. The DPW RTM is derived under the Born approximation and utilizes frequency domain plane wave Green's function for imaging. Time dips in the shot profiles can help to estimate the range of plane wave components present in shot gathers. Therefore, a limited number of plane wave Green's functions are needed for imaging. Plane wave Green's functions can be used for imaging both source and receiver plane waves. Source and receiver reciprocity can be used for imaging plane wave components at no cost and save half of the computation time. As a result, the computational burden for migration is substantially reduced. Plane wave components can be migrated independently to recover specific targets with given dips, and ray parameter common image gathers (CIGs) can be generated after migration directly. The ray parameter CIGs can be used to justify the correctness of velocity models. Subsurface anisotropy effects can also be included in our imaging condition, provided with plane wave Green's functions in the anisotropic media.
One- and two-dimensional dyadic Green's functions in chiral media
NASA Technical Reports Server (NTRS)
Engheta, Nader; Bassiri, Sassan
1989-01-01
The one-dimensional and two-dimensional dyadic Green functions are determined for an unbounded lossless reciprocal chiral medium which is electromagnetically described by a set of symmetric constitutive relations. It is shown that, as in the three-dimensional case, the medium supports two eigenmodes of propagation with two different wavenumbers, corresponding to the right- and left-circularly polarized waves, respectively. The eigenmode amplitudes a and b are similar to those of the three-dimensional case.
An analytic Green's function for a lined circular duct containing uniform mean flow
NASA Astrophysics Data System (ADS)
Rienstra, Sjoerd W.; Tester, Brian J.
2008-11-01
An analytic Green's function is derived for a lined circular duct, both hollow and annular, containing uniform mean flow, from first principles by Fourier transformation. The derived result takes the form of a common mode series. We show that the analytic Green's function for a lined hollow circular duct, containing uniform mean flow, is essentially identical to that used by Tester et al. in the Cargill splice scattering model. The explicit form of the Green's function for the annular duct is new. A more comprehensive causality analysis suggests the possibility of certain upstream modes being really downstream instabilities. As their growth rates are usually exceptionally large, including these modes as instabilities is both not practical and in disagreement with most (not all) experiments. Therefore, we outline the possibility but do not include them in the presented examples. We follow the "modelling assumption" that all modes decay in their respective direction of propagation. To illustrate the advantages of our analytic result compared to the matrix inversion technique of Alonso et al., we compute the mode amplitudes from both methods for a typical aircraft engine intake condition. The comparisons show good agreement without flow, irrespective of how many modes are included in the matrix inversion for the numerical mode amplitudes. With flow, the mode amplitudes do not agree but as the number of modes included in the matrix inversion is increased, enough to include any important surface waves, the numerically obtained modal amplitudes of Alonso et al. appear to be converging to the present analytical result. In practical applications our closed form analytic Green's function will be computationally more efficient, especially at high frequencies of practical interest to aero-engine applications, and the analytic form for the mode amplitudes could permit future modelling advances not possible from the numerical equivalent. It also may have application to post
NASA Astrophysics Data System (ADS)
Oh, Yun-Tak; Higashi, Yoichi; Chan, Ching-Kit; Han, Jung Hoon
2016-08-01
The Lang-Firsov Hamiltonian, a well-known solvable model of interacting fermion-boson system with sideband features in the fermion spectral weight, is generalized to have the time-dependent fermion-boson coupling constant. We show how to derive the two-time Green's function for the time-dependent problem in the adiabatic limit, defined as the slow temporal variation of the coupling over the characteristic oscillator period. The idea we use in deriving the Green's function is akin to the use of instantaneous basis states in solving the adiabatic evolution problem in quantum mechanics. With such "adiabatic Green's function" at hand we analyze the transient behavior of the spectral weight as the coupling is gradually tuned to zero. Time-dependent generalization of a related model, the spin-boson Hamiltonian, is analyzed in the same way. In both cases the sidebands arising from the fermion-boson coupling can be seen to gradually lose their spectral weights over time. Connections of our solution to the two-dimensional Dirac electrons coupled to quantized photons are discussed.
Green's Function Retrieval and Marchenko Imaging in a Dissipative Acoustic Medium.
Slob, Evert
2016-04-22
Single-sided Marchenko equations for Green's function construction and imaging relate the measured reflection response of a lossless heterogeneous medium to an acoustic wave field inside this medium. I derive two sets of single-sided Marchenko equations for the same purpose, each in a heterogeneous medium, with one medium being dissipative and the other a corresponding medium with negative dissipation. Double-sided scattering data of the dissipative medium are required as input to compute the surface reflection response in the corresponding medium with negative dissipation. I show that each set of single-sided Marchenko equations leads to Green's functions with a virtual receiver inside the medium: one exists inside the dissipative medium and one in the medium with negative dissipation. This forms the basis of imaging inside a dissipative heterogeneous medium. I relate the Green's functions to the reflection response inside each medium, from which the image can be constructed. I illustrate the method with a one-dimensional example that shows the image quality. The method has a potentially wide range of imaging applications where the material under test is accessible from two sides. PMID:27152808
Green's Function Retrieval and Marchenko Imaging in a Dissipative Acoustic Medium
NASA Astrophysics Data System (ADS)
Slob, Evert
2016-04-01
Single-sided Marchenko equations for Green's function construction and imaging relate the measured reflection response of a lossless heterogeneous medium to an acoustic wave field inside this medium. I derive two sets of single-sided Marchenko equations for the same purpose, each in a heterogeneous medium, with one medium being dissipative and the other a corresponding medium with negative dissipation. Double-sided scattering data of the dissipative medium are required as input to compute the surface reflection response in the corresponding medium with negative dissipation. I show that each set of single-sided Marchenko equations leads to Green's functions with a virtual receiver inside the medium: one exists inside the dissipative medium and one in the medium with negative dissipation. This forms the basis of imaging inside a dissipative heterogeneous medium. I relate the Green's functions to the reflection response inside each medium, from which the image can be constructed. I illustrate the method with a one-dimensional example that shows the image quality. The method has a potentially wide range of imaging applications where the material under test is accessible from two sides.
NASA Astrophysics Data System (ADS)
Dahm, T.; Heimann, S.; Kriegerowski, M.; Cesca, S.; Wang, R.
2015-12-01
The study of seismic sources from measured waveforms requires synthetic elementary seismograms (Green's functions, GFs) calculated for specific earth models and source receiver geometries. Since the calculation of GFs is computationally expensive and requires careful parameter testing and quality control, pre-calculated GF databases, which can be re-used for different types of applications, can be of advantage. We developed a GF database web platform for the seismological community, where a researcher can share Green's function stores and retrieve synthetic seismograms on the fly for various point and extended earthquake source models for many different earth models at local, regional and global scale. This web service is part of a rich new toolset for the creation and handling of Green's functions and synthetic seismograms. It can be used off-line or in client mode. We demonstrate core features of the GF platform with different applications on global, regional and local scales. These include the automatic inversion of kinematic source parameters from teleseismic body waves, the improved depth estimate of shallow induced earthquakes from regional seismological arrays, or the relative moment tensor inversion of volcanic earthquakes.
Three-dimensional Green's function for an anisotropic multi-layered half-space
NASA Astrophysics Data System (ADS)
Chen, Lin
2015-11-01
A new numerical approach is presented to calculate the Green's function for an anisotropic multi-layered half space. The formulation is explicit and unconditionally stable. It imposes no limit to the thickness of the layered medium and the magnitude of the frequency. In the analysis, the Fourier transform and the precise integration method (PIM) are employed. Here, the Fourier transform is employed to transform the wave motion equation from the spatial domain to the wavenumber domain. A second order ordinary differential equation (ODE) is observed. Then, the dual vector representation of the wave motion equation is used to reduce the second order ODE to first order. It is solved by the PIM. Finally, the Green's function in the wavenumber domain is obtained. For the evaluation of the Green's function in the spatial domain, the double inverse Fourier transform over the wavenumber is employed to derive the solutions. Especially, for the transversely isotropic medium, the double inverse Fourier transform can be further reduced to a single integral by the cylindrical polar coordinate transform. Numerical examples are provided. Comparisons with other methods are done. Very promising results are obtained.
NASA Astrophysics Data System (ADS)
Heimann, Sebastian; Kriegerowski, Marius; Dahm, Torsten; Simone, Cesca; Wang, Rongjiang
2016-04-01
The study of seismic sources from measured waveforms requires synthetic elementary seismograms (Green's functions, GF) calculated for specific earth models and source receiver geometries. Since the calculation of GFs is computationally expensive and requires careful parameter testing and quality control, pre-calculated GF databases, which can be re-used for different types of applications, can be of advantage. We developed a GF database web platform for the seismological community (http://kinherd.org/), where a researcher can share Green's function stores and retrieve synthetic seismograms on the fly for various point and extended earthquake source models for many different earth models at local, regional and global scale. This web service is part of a rich new toolset for the creation and handling of Green's functions and synthetic seismograms (http://emolch.github.com/pyrocko/gf). It can be used off-line or in client mode. We demonstrate core features of the GF platform with different applications on global, regional and local scales. These include the automatic inversion of kinematic source parameter from teleseismic body waves, the improved depth estimate of shallow induced earthquakes from regional seismological arrays, or the relative moment tensor inversion of local earthquakes from volcanic induced seismicity.
Suh, S H
1987-01-01
"The purpose of this paper is to suggest that, in evaluating the relevance of sustaining the green belt, we must pay more attention to the fact that the green belt amenities can accelerate rather than decelerate the population growth of a city. For this, this paper analyzes the case where there exist green belt amenities and the demand for land function is almost linear. In this case, it can be shown that the green belt is ineffective in restricting the population growth in the long run." PMID:12283599
NASA Technical Reports Server (NTRS)
Deshpande, M. D.
1997-01-01
The dyadic Green's function for an electric current source placed in a rectangular waveguide is derived using a magnetic vector potential approach. A complete solution for the electric and magnetic fields including the source location is obtained by simple differentiation of the vector potential around the source location. The simple differentiation approach which gives electric and magnetic fields identical to an earlier derivation is overlooked by the earlier workers in the derivation of the dyadic Green's function particularly around the source location. Numerical results obtained using the Green's function approach are compared with the results obtained using the Finite Element Method (FEM).
NASA Astrophysics Data System (ADS)
Grapenthin, R.
2014-01-01
CRUSDE is a plug-in based simulation framework written in C/C++ for Linux platforms (installation information, download and test cases: http://www.grapenthin.org/crusde). It utilizes Green's functions for simulations of the Earth's response to changes in surface loads. Such changes could involve, for example, melting glaciers, oscillating snow loads, or lava flow emplacement. The focus in the simulation could be the response of the Earth's crust in terms of stress changes, changes in strain rates, or simply uplift or subsidence and the respective horizontal displacements of the crust (over time). Rather than implementing a variety of specific models, CRUSDE approaches crustal deformation problems from a general formulation in which model elements (Green's function, load function, relaxation function, load history), operators, pre- and postprocessors, as well as input and output routines are independent, exchangeable, and reusable on the basis of a plug-in approach (shared libraries loaded at runtime). We derive the general formulation CRUSDE is based on, describe its architecture and use, and demonstrate its capabilities in a test case. With CRUSDE users can: (1) dynamically select software components to participate in a simulation (through XML experiment definitions), (2) extend the framework independently with new software components and reuse existing ones, and (3) exchange software components and experiment definitions with other users. CRUSDE's plug-in mechanism aims for straightforward extendability allowing modelers to add new Earth models/response functions. Current Green's function implementations include surface displacements due to the elastic response, final relaxed response, and pure thick plate response for a flat Earth. These can be combined to express exponential decay from elastic to final relaxed response, displacement rates due to one or multiple disks, irregular loads, or a combination of these. Each load can have its own load history and
Required distribution of noise sources for Green's function recovery in diffusive fields
NASA Astrophysics Data System (ADS)
Shamsalsadati, S.; Weiss, C. J.
2011-12-01
In the most general sense, noise is the part of the signal of little or no interest, due to a multitude of reasons such as operator error, imperfect instrumentation, experiment design, or inescapable background interference. Considering the latter, it has been shown that Green's function can be extracted from cross-correlation of the ambient, diffusive wavefields arising from background random noise sources. Pore pressure and low-frequency electromagnetic induction are two such examples of diffusive fields. In theory, applying Green's function method in geophysical exploration requires infinity of volumetrically distributed sources; however, in the real world the number of noise sources in an area is limited, and furthermore, unevenly distributed in time, space and spectral content. Hence, quantification of the requisite noise sources that enable us to calculate Green's function acceptably well remains an open research question. The purpose of this study is to find the area of noise sources that contribute most to the Green's function estimation in diffusive systems. We call such a region the Volume of Relevance (VoR). Our analysis builds upon recent work in 1D homogeneous system where it was shown that sources located between two receivers positions are the most important ones for the purpose of Green's function recovery. Our results confirm the previous finding but we also examine the effect of heterogeneity, dimensionality and receiver location in both 1D and 2D at a fixed frequency. We demonstrate that for receivers located symmetrically across an interface between regions of contrasting diffusivity, the VoR rapidly shifts from one side of the interface to the other, and back again, as receiver separation increases. We also demonstrate that where the receiver pair is located on the interface itself, the shifting is less rapid, and for moderate to high diffusivity contrasts, the VoR remains entirely on the more diffusive side. In addition, because classical
Density Functional Theory for Green Chemical Catalyst Supported on S-Terminated GaN(0001)
NASA Astrophysics Data System (ADS)
Yokoyama, Mami; Tsukamoto, Shiro; Ishii, Akira
2011-12-01
A novel function of nitried-based semiconductor is successfully developed for organic synthesis, in which palladium supported on the surface of S-terminated GaN(0001) serves as a unique green chemical catalyst. In this study we determined the structure of Pd-catalyst supported on S-terminated GaN(0001) surface by means of the density functional theory (DFT) within a Local Density Approximation (LDA). The important role of S on the case of GaN substrate is to make the number of the valence electron to be close to 0, it happened same way for GaAs substrate.
NASA Astrophysics Data System (ADS)
Sokolowski, Thomas; Bossen, Laurens; Miedema, Thomas; Becker, Nils
2010-09-01
Active transport of intracellular cargo on cytoskeletal polymers via ATP-driven motor proteins plays a key role in establishing well-defined spatial patterns of functional intracellular components, which can range from proteins to big organelles like mitochondria. It is the interplay between active transport, diffusive movement in the cytosol and the geometry of the cell and its cytoskeleton that finally determines the distribution of the transported objects. To analyze such phenomena we extend our Green's Function Reaction Dynamics (GFRD) framework to allow for an exact event-driven simulation of active transport on microtubules and interactions with the cell membrane.
Liu, Siyu; Zhao, Ning; Cheng, Zhen; Liu, Hongguang
2015-04-21
Amino-functionalized fluorescent carbon dots have been prepared by hydrothermal treatment of glucosamine with excess pyrophosphate. The produced carbon dots showed stabilized green emission fluorescence at various excitation wavelengths and pH environments. Herein, we demonstrate the surface energy transfer between the amino-functionalized carbon dots and negatively charged hyaluronate stabilized gold nanoparticles. Hyaluronidase can degrade hyaluronate and break down the hyaluronate stabilized gold nanoparticles to inhibit the surface energy transfer. The developed fluorescent carbon dot/gold nanoparticle system can be utilized as a biosensor for sensitive and selective detection of hyaluronidase by two modes which include fluorescence measurements and colorimetric analysis. PMID:25807038
Tuya, Fernando; Png-Gonzalez, Lydia; Riera, Rodrigo; Haroun, Ricardo; Espino, Fernando
2014-07-01
Marine vegetated habitats, e.g. seagrass meadows, deliver essential functions and services to coastal ecosystems and human welfare. Impacts induced by humans, however, have facilitated the replacement of seagrasses by alternative vegetation, e.g. green rhizophytic seaweeds. The implications of habitat shifts for ecosystem attributes and processes and the services they deliver remain poorly known. In this study, we compared ecosystem structure and function between Cymodocea nodosa seagrass meadows and bottoms dominated by Caulerpa prolifera, a green, native, rhizophytic seaweed, through 5 ecological proxies: (i) primary production (via community metabolism), (ii) composition and abundance of epifauna (a proxy for provision of habitat for epifauna), composition and abundance of (iii) small-sized (juvenile) and (iv) large-sized (adult) fishes (proxies for provision of habitat for fishes), and (v) sediment retention (a proxy for sediment stabilization). Four of these proxies were greater in C. nodosa seagrass meadows than in C. prolifera beds: gross primary productivity (∼1.4 times), the total abundance, species density and biomass of small-sized fishes (∼2.1, 1.3 and 1.3 times, respectively), the total abundance and species density of large-sized fishes (∼3.6 and 1.5 times, respectively), and sediment stabilization (∼1.4 times). In contrast, the total abundance and species density of epifauna was larger (∼3.1 and 1.7 times, respectively) in C. prolifera than in C. nodosa seagrass beds. These results suggest that ecosystem structure and function may differ if seagrasses are replaced by green rhizophytic seaweeds. Importantly, ecosystem functions may not be appropriate surrogates for one another. As a result, assessments of ecosystem services associated with ecosystem functions cannot be based on exclusively one service that is expected to benefit other services. PMID:24836641
Mental Retardation: The Search for Cures. Research Monograph Number 7.
ERIC Educational Resources Information Center
Menolascino, Frank J.; Neman, Ronald
The booklet describes the Association for Retarded Citizens' (ARC's) goal of coordinating efforts to seek a cure for mental retardation. Cures are defined as any intervention that would significantly increase intellectual functioning and adaptive behavior beyond the upper level of retardation. It is explained that because of the variety of causes…
Self-Consistent Green Function Calculations for Isospin Asymmetric Nuclear Matter
NASA Astrophysics Data System (ADS)
Mansour, H.; Gad, K.; Hassaneen, K. S. A.
2010-04-01
The one-body potentials for protons and neutrons are obtained from the self-consistent Green-function calculations of asymmetric nuclear matter, in particular their dependence on the degree of proton/neutron asymmetry. Results of the binding energy per nucleon as a function of the density and asymmetry parameter are presented for the self-consistent Green function approach using the CD-Bonn potential. For the sake of comparison, the same calculations are performed using the Brueckner-Hartree-Fock approximation. The contribution of the hole-hole terms leads to a repulsive contribution to the energy per nucleon which increases with the nuclear density. The incompressibility for asymmetric nuclear matter has been also investigated in the framework of the self-consistent Green-function approach using the CD-Bonn potential. The behavior of the incompressibility is studied for different values of the nuclear density and the neutron excess parameter. The nuclear symmetry potentia l at fixed nuclear density is also calculated and its value decreases with increasing the nucleon energy. In particular, the nuclear symmetry potential at saturation density changes from positive to negative values at nucleon kinetic energy of about 200 MeV. For the sake of comparison, the same calculations are performed using the Brueckner-Hartree-Fock approximation. The proton/neutron effective mass splitting in neutron-rich matter has been studied. The predicted isospin splitting of the proton/neutron effective mass splitting in neutron-rich matter is such that m(*_n) ≥ m(*_p) .
NASA Astrophysics Data System (ADS)
Liu, Siyu; Zhao, Ning; Cheng, Zhen; Liu, Hongguang
2015-04-01
Amino-functionalized fluorescent carbon dots have been prepared by hydrothermal treatment of glucosamine with excess pyrophosphate. The produced carbon dots showed stabilized green emission fluorescence at various excitation wavelengths and pH environments. Herein, we demonstrate the surface energy transfer between the amino-functionalized carbon dots and negatively charged hyaluronate stabilized gold nanoparticles. Hyaluronidase can degrade hyaluronate and break down the hyaluronate stabilized gold nanoparticles to inhibit the surface energy transfer. The developed fluorescent carbon dot/gold nanoparticle system can be utilized as a biosensor for sensitive and selective detection of hyaluronidase by two modes which include fluorescence measurements and colorimetric analysis.Amino-functionalized fluorescent carbon dots have been prepared by hydrothermal treatment of glucosamine with excess pyrophosphate. The produced carbon dots showed stabilized green emission fluorescence at various excitation wavelengths and pH environments. Herein, we demonstrate the surface energy transfer between the amino-functionalized carbon dots and negatively charged hyaluronate stabilized gold nanoparticles. Hyaluronidase can degrade hyaluronate and break down the hyaluronate stabilized gold nanoparticles to inhibit the surface energy transfer. The developed fluorescent carbon dot/gold nanoparticle system can be utilized as a biosensor for sensitive and selective detection of hyaluronidase by two modes which include fluorescence measurements and colorimetric analysis. Electronic supplementary information (ESI) available. See DOI: 10.1039/c5nr00070j
GreenPhylDB v2.0: comparative and functional genomics in plants.
Rouard, Mathieu; Guignon, Valentin; Aluome, Christelle; Laporte, Marie-Angélique; Droc, Gaëtan; Walde, Christian; Zmasek, Christian M; Périn, Christophe; Conte, Matthieu G
2011-01-01
GreenPhylDB is a database designed for comparative and functional genomics based on complete genomes. Version 2 now contains sixteen full genomes of members of the plantae kingdom, ranging from algae to angiosperms, automatically clustered into gene families. Gene families are manually annotated and then analyzed phylogenetically in order to elucidate orthologous and paralogous relationships. The database offers various lists of gene families including plant, phylum and species specific gene families. For each gene cluster or gene family, easy access to gene composition, protein domains, publications, external links and orthologous gene predictions is provided. Web interfaces have been further developed to improve the navigation through information related to gene families. New analysis tools are also available, such as a gene family ontology browser that facilitates exploration. GreenPhylDB is a component of the South Green Bioinformatics Platform (http://southgreen.cirad.fr/) and is accessible at http://greenphyl.cirad.fr. It enables comparative genomics in a broad taxonomy context to enhance the understanding of evolutionary processes and thus tends to speed up gene discovery. PMID:20864446
A Radiation Chemistry Code Based on the Greens Functions of the Diffusion Equation
NASA Technical Reports Server (NTRS)
Plante, Ianik; Wu, Honglu
2014-01-01
Ionizing radiation produces several radiolytic species such as.OH, e-aq, and H. when interacting with biological matter. Following their creation, radiolytic species diffuse and chemically react with biological molecules such as DNA. Despite years of research, many questions on the DNA damage by ionizing radiation remains, notably on the indirect effect, i.e. the damage resulting from the reactions of the radiolytic species with DNA. To simulate DNA damage by ionizing radiation, we are developing a step-by-step radiation chemistry code that is based on the Green's functions of the diffusion equation (GFDE), which is able to follow the trajectories of all particles and their reactions with time. In the recent years, simulations based on the GFDE have been used extensively in biochemistry, notably to simulate biochemical networks in time and space and are often used as the "gold standard" to validate diffusion-reaction theories. The exact GFDE for partially diffusion-controlled reactions is difficult to use because of its complex form. Therefore, the radial Green's function, which is much simpler, is often used. Hence, much effort has been devoted to the sampling of the radial Green's functions, for which we have developed a sampling algorithm This algorithm only yields the inter-particle distance vector length after a time step; the sampling of the deviation angle of the inter-particle vector is not taken into consideration. In this work, we show that the radial distribution is predicted by the exact radial Green's function. We also use a technique developed by Clifford et al. to generate the inter-particle vector deviation angles, knowing the inter-particle vector length before and after a time step. The results are compared with those predicted by the exact GFDE and by the analytical angular functions for free diffusion. This first step in the creation of the radiation chemistry code should help the understanding of the contribution of the indirect effect in the
Faber, C; Boulanger, P; Attaccalite, C; Duchemin, I; Blase, X
2014-03-13
Many-body Green's function perturbation theories, such as the GW and Bethe-Salpeter formalisms, are starting to be routinely applied to study charged and neutral electronic excitations in molecular organic systems relevant to applications in photovoltaics, photochemistry or biology. In parallel, density functional theory and its time-dependent extensions significantly progressed along the line of range-separated hybrid functionals within the generalized Kohn-Sham formalism designed to provide correct excitation energies. We give an overview and compare these approaches with examples drawn from the study of gas phase organic systems such as fullerenes, porphyrins, bacteriochlorophylls or nucleobases molecules. The perspectives and challenges that many-body perturbation theory is facing, such as the role of self-consistency, the calculation of forces and potential energy surfaces in the excited states, or the development of embedding techniques specific to the GW and Bethe-Salpeter equation formalisms, are outlined. PMID:24516185
Green's function solution to heat transfer of a transparent gas through a tube
NASA Technical Reports Server (NTRS)
Frankel, J. I.
1989-01-01
A heat transfer analysis of a transparent gas flowing through a circular tube of finite thickness is presented. This study includes the effects of wall conduction, internal radiative exchange, and convective heat transfer. The natural mathematical formulation produces a nonlinear, integrodifferential equation governing the wall temperature and an ordinary differential equation describing the gas temperature. This investigation proposes to convert the original system of equations into an equivalent system of integral equations. The Green's function method permits the conversion of an integrodifferential equation into a pure integral equation. The proposed integral formulation and subsequent computational procedure are shown to be stable and accurate.
Recent Developments in Three Dimensional Radiation Transport Using the Green's Function Technique
NASA Technical Reports Server (NTRS)
Rockell, Candice; Tweed, John; Blattnig, Steve R.; Mertens, Christopher J.
2010-01-01
In the future, astronauts will be sent into space for longer durations of time compared to previous missions. The increased risk of exposure to dangerous radiation, such as Galactic Cosmic Rays and Solar Particle Events, is of great concern. Consequently, steps must be taken to ensure astronaut safety by providing adequate shielding. In order to better determine and verify shielding requirements, an accurate and efficient radiation transport code based on a fully three dimensional radiation transport model using the Green's function technique is being developed
NASA Astrophysics Data System (ADS)
Dill, Robert; Klemann, Volker
2015-04-01
The influence of the elastic Earth properties on seasonal or shorter periodic surface mass loads due to atmospheric surface pressure and terrestrial water storage variations is usually modeled by applying a local isostatic model like a homogeneous half-space model, or by a one dimensional spherical Earth model like PREM from which a unique set of elastic load Love numbers, or alternatively, elastic Green's functions are derived. The drawbacks of these strategies are that, in the first case, the response according to the local Earth structure is valid only if load and observer almost coincide, or that, in the second case, only the response of an average Earth structure is considered. However, for surface loads with horizontal scales less than 2500 km2, as for instance, for strong localized hydrological signals associated with heavy precipitation events and river floods, the Earth elastic response becomes very sensitive to inhomogeneities in the Earth crustal structure. We derive a set of local Green's functions defined for every global 1°× 1° gridcell for the 3-layer crustal structure TEA12. Local Green's functions show standard deviations of ±12% in the vertical and ±21% in the horizontal directions for distances in the range from 0.1° to 0.5°. The application of local Green's functions introduces a variability of 0.5 - 1.0 mm into the hydrological loading displacements, both in vertical and in horizontal directions. Maximum changes due to the local crustal structures are from -25% to +26% in the vertical and -91% to +55% in the horizontal displacements. In addition, the horizontal displacement changes its direction significantly, even to the opposite. The modeling of a site-dependent crustal response to surface loads provides an alternative way to probe the density and elastic structure of the Earth's crust and mantle by means of observed surface deformations caused by mass re-distributions. In addition, realistic loading models allow the monitoring of mass
NASA Technical Reports Server (NTRS)
Shivakumar, V.; Forman, R. G.; Rosencranz, R., Jr.
1983-01-01
Stress-intensity factors are obtained for point loaded equal length cracks emanating from a circular hole in an infinite plate. A series approach and the Muskhelishvili formulation in the two-dimensional theory of elasticity are used to derive the solution. The applicability of the solution is demonstrated by using it as a Green's function to obtain stress-intensity factors in the case of (1) biaxial tension and pure shear of an infinite plate and (2) tension and pin loading of a plate with cracks emanating from one hole in a row of holes.
Green's functions of one-dimensional quasicrystal bi-material with piezoelectric effect
NASA Astrophysics Data System (ADS)
Zhang, Liangliang; Wu, Di; Xu, Wenshuai; Yang, Lianzhi; Ricoeur, Andreas; Wang, Zhibin; Gao, Yang
2016-09-01
Based on the Stroh formalism of one-dimensional quasicrystals with piezoelectric effect, the problems of an infinite plane composed of two different quasicrystal half-planes are taken into account. The solutions of the internal and interfacial Green's functions of quasicrystal bi-material are obtained. Moreover, numerical examples are analyzed for a quasicrystal bi-material subjected to line forces or line dislocations, showing the contour maps of the coupled fields. The impacts of changing material constants on the coupled field components are investigated.
A calculation method for finite depth free-surface green function
NASA Astrophysics Data System (ADS)
Liu, Yingyi; Iwashita, Hidetsugu; Hu, Changhong
2015-06-01
An improved boundary element method is presented for numerical analysis of hydrodynamic behavior of marine structures. A new algorithm for numerical solution of the finite depth free-surface Green function in three dimensions is developed based on multiple series representations. The whole range of the key parameter R/h is divided into four regions, within which different representation is used to achieve fast convergence. The well-known epsilon algorithm is also adopted to accelerate the convergence. The critical convergence criteria for each representation are investigated and provided. The proposed method is validated by several well-documented benchmark problems.
Two-point Green function of Chern-Simons gauge field in anyon gas
Hieu, N.V.; Son, N.H. )
1992-01-20
This paper reports on the quantum theory of the anyon gas that was developed in the framework of the field theoretical formalism. The existence of the classical background CS gauge field created by the quasiparticles below the Fermi level and acting as some effective magnetic field was taken into account. The expressions of the two-point Green functions of the free and interacting CS gauge fields were derived. It was shown that they determine the conductivity tensor of the anyon gas. The relevance to the FQHE was discussed.
NASA Astrophysics Data System (ADS)
Bakirci, Taciser; Kaslilar, Ayse; Kocaoglu, Argun
2014-05-01
Records of ambient seismic noise (ASN) field are widely used to obtain seismic velocity structures at both engineering and global scales. Two well-known methods commonly employed to obtain shear-wave velocity profiles, in engineering seismology, are the frequency-wavenumber (FK) transform and spatial auto-correlation (SPAC) methods that are based on the analysis of ASN field recorded by 2D sensor arrays. At global scale on the other hand, seismic velocity structure is determined by the Green's function retrieved from cross-correlation of the ASN recorded between two seismic stations. In the last decade, this approach has become complementary or almost alternative to the conventional methods of surface wave tomography used to investigate the velocity structure of the crust and upper mantle. Similarly, in recent years, the Green's functions estimated from ASN have also been used to investigate the shear-wave velocity structure of basins and their site amplification properties. This work presents the Rayleigh wave Green's functions retrieved from the vertical-component ASN data recorded in the Bursa and Adana basins of Turkey. This constitutes the first stage of our research whose objective is to investigate whether velocity structures of these basins can reliably be obtained from tomographic inversion. The continuous data used in our study were recorded between 2010 and 2013 by the national seismic networks operated by Kandilli Observatory and Earthquake Research Institute (KOERI) of Bosphorus University and Earthquake Research Department (ERD) of Disaster and Emergency Management Presidency of Turkey. For both basins, distances between station pairs are in the range of 30-200 km. In this distance range, the Green's functions reveal Rayleigh waves with the periods of 6 to 30 s. Group velocity dispersion analysis carried out by the multiple filtering technique show that the group velocities are estimated to be in the range of 2.5-4.0 km/s. Observed variation of group
Hutchings, L.; Wu, F. )
1990-02-10
Seismograms from 52 aftershocks of the 1971 San Fernando earthquake recorded at 25 stations distributed across the San Fernando Valley are examined to identify empirical Green's functions, and characterize the dependence of their waveforms on moment, focal mechanism, source and recording site spatial variations, recording site geology, and recorded frequency band. Recording distances ranged from 3.0 to 33.0 km, hypocentral separations ranged from 0.22 to 28.4 km, and recording site separations ranged from 0.185 to 24.2 km. The recording site geologies are diorite gneiss, marine and nonmarine sediments, and alluvium of varying thicknesses. Waveforms of events with moment below about 1.5 {times} 10{sup 21} dyn cm are independent of the source-time function and are termed empirical Green's functions. Waveforms recorded at a particular station from events located within 1.0 to 3.0 km of each other, depending upon site geology, with very similar focal mechanism solutions are nearly identical for frequencies up to 10 Hz. There is no correlation to waveforms between recording sites at least 1.2 km apart, and waveforms are clearly distinctive for two sites 0.185 km apart. The geologic conditions of the recording site dominate the character of empirical Green's functions. Even for source separations of up to 20.0 km, the empirical Green's functions at a particular site are consistent in frequency content, amplification, and energy distribution. Therefore, it is shown that empirical Green's functions can be used to obtain site response functions. The observations of empirical Green's functions are used as a basis for developing the theory for using empirical Green's functions in deconvolution for source pulses and synthesis of seismograms of larger earthquakes.
Green's function variational approach to orbital polarons in KCuF3
NASA Astrophysics Data System (ADS)
Bieniasz, Krzysztof; Berciu, Mona; Daghofer, Maria; Oleś, Andrzej M.
2016-08-01
We develop an eg orbital, t -J -like model of a single charge doped into a two-dimensional plane with ferromagnetic spin order and alternating orbital order, and present its solution by Green's functions in the variational approximation framework. The model is designed to represent the orbital physics within ferromagnetic (a ,b ) planes of KCuF3 and K2CuF4 . The variational approximation (VA) relies on the systematic generation of equations of motion for the Green's function, taking into account the real-space constraints coming from the exclusion of doubly occupied sites. This method is compared to the firmly established self-consistent Born approximation, and to the variational cluster approximation (VCA) which relies on the itinerant regime of the model. We find that the present variational approximation captures the essential aspects of the spectral weight distribution of the coherent quasiparticle state and gives a result similar to the VCA, while also reproducing well the momentum dependence of the spectral moments. In contrast, the spectral function obtained within the self-consistent Born approximation is more incoherent and its quasiparticle is heavier, at strong effective couplings, than observed with VCA and VA.
A DATABASE OF >20 keV ELECTRON GREEN'S FUNCTIONS OF INTERPLANETARY TRANSPORT AT 1 AU
Agueda, N.; Sanahuja, B.; Vainio, R.
2012-10-15
We use interplanetary transport simulations to compute a database of electron Green's functions, i.e., differential intensities resulting at the spacecraft position from an impulsive injection of energetic (>20 keV) electrons close to the Sun, for a large number of values of two standard interplanetary transport parameters: the scattering mean free path and the solar wind speed. The nominal energy channels of the ACE, STEREO, and Wind spacecraft have been used in the interplanetary transport simulations to conceive a unique tool for the study of near-relativistic electron events observed at 1 AU. In this paper, we quantify the characteristic times of the Green's functions (onset and peak time, rise and decay phase duration) as a function of the interplanetary transport conditions. We use the database to calculate the FWHM of the pitch-angle distributions at different times of the event and under different scattering conditions. This allows us to provide a first quantitative result that can be compared with observations, and to assess the validity of the frequently used term beam-like pitch-angle distribution.
Single fermion Green's function in the quantum ordered Fermi-system: Analytic solution
NASA Astrophysics Data System (ADS)
Mukhin, S. I.; Galimzyanov, T. R.
2012-06-01
An exact self-consistent solution for a finite temperature quantum-ordered state of correlated electron system found previously (Mukhin, 2009, 2011) is used to derive the fermionic single-particle Green's function. The quantum order parameter (QOP) found in the form of a periodic (elliptic Jacoby) function of the Matsubara's imaginary time (Mukhin, 2009), plays the role of effective scattering potential seen by electrons. The analytic solution for the Green's function demonstrates the following new features: (1) the pseudo-gap behavior of the single-electron density of states (DOS) near the (shifted) Fermi-level;(2) the side-bands of decreasing intensity away from the Fermi-level; (3) scaling of the quasi-particle energies with the QOP amplitude; (4) fermionic quasi-particles in the QOP state are combined from two confined “odd” and “even” fermions that separately would be unstable. The false-color plot of single-fermion DOS in the limit of a periodic kink-like Matsubara time-dependence of QOP is presented and could be used as prediction for the ARPES experiments. The plot of the DOS transfer between different energies at the “fermi-surface” momentum for a given kink-like QOP is also presented. Some possibly observable consequences of the found finger-prints are discussed.
A Green's-Function Approach to Exchange Spin Coupling As a New Tool for Quantum Chemistry.
Steenbock, Torben; Tasche, Jos; Lichtenstein, Alexander I; Herrmann, Carmen
2015-12-01
Exchange spin coupling is usually evaluated in quantum chemistry from the energy difference between a high-spin determinant and a Broken-Symmetry (BS) determinant in combination with Kohn-Sham density functional theory (KS-DFT), based on the work of Noodleman. As an alternative, an efficient approximate approach relying on Green's functions has been developed by one of the authors. This approach stems from solid-state physics and has never been systematically tested for molecular systems. We rederive a version of the Green's-function approach originally suggested by Han, Ozaki, and Yu. This new derivation employs local projection operators as common in quantum chemistry for defining local properties such as partial charges, rather than using a dual basis as in the Han-Ozaki-Yu approach. The result is a simple postprocessing procedure for KS-DFT calculations, which in contrast to the BS energy-difference approach requires the electronic structure of only one spin state. We show for several representative small molecules, diradicals, and dinuclear transition metal complexes that this method gives qualitatively consistent results with the BS energy-difference approach as long as it is applied to high-spin determinants and as long as structural relaxation effects in different spin states do not play an important role. PMID:26579585
Self-consistent second-order Green's function perturbation theory for periodic systems
NASA Astrophysics Data System (ADS)
Rusakov, Alexander A.; Zgid, Dominika
2016-02-01
Despite recent advances, systematic quantitative treatment of the electron correlation problem in extended systems remains a formidable task. Systematically improvable Green's function methods capable of quantitatively describing weak and at least qualitatively strong correlations appear as promising candidates for computational treatment of periodic systems. We present a periodic implementation of temperature-dependent self-consistent 2nd-order Green's function (GF2) method, where the self-energy is evaluated in the basis of atomic orbitals. Evaluating the real-space self-energy in atomic orbitals and solving the Dyson equation in k-space are the key components of a computationally feasible algorithm. We apply this technique to the one-dimensional hydrogen lattice — a prototypical crystalline system with a realistic Hamiltonian. By analyzing the behavior of the spectral functions, natural occupations, and self-energies, we claim that GF2 is able to recover metallic, band insulating, and at least qualitatively Mott regimes. We observe that the iterative nature of GF2 is essential to the emergence of the metallic and Mott phases.
Calculation of the vacuum Green's function valid for high toroidal mode number in tokamaks.
NASA Astrophysics Data System (ADS)
Chance, Morrell; Turnbull, Alan
2005-10-01
The present evaluation of the Green's function used for the magmetic scalar potential in vacuum calculations for axisymmetric geometry in the vacuum segments of gato, pest and other mhd stability codes has been found to be deficient for moderately high toroidal mode numbers. This was due to the loss of numerical precision arising from the upward recursion relation used for generating the functions to high mode numbers. The recursion is initiated from the complete elliptic integrals of the first and second kinds. To ameliorate this, a direct integration of the integral representation of the function was crafted to achieve the necessary high accuracy for moderately high mode numbers. At very high mode numbers the loss of numerical precision due to the oscillatory behavior of the integrand is further avoided by judiciously deforming the integration contour in the complex plane. Machine precision, roughly 14 -- 16 digits, accuracy can be achieved by using a combination of both these techniques.
NASA Astrophysics Data System (ADS)
Dong, Jianping
2014-12-01
Integral form of the space-time-fractional Schrödinger equation for the scattering problem in the fractional quantum mechanics is studied in this paper. We define the fractional Green's function for the space-time fractional Schrödinger equation and express it in terms of Fox's H-function and in a computable series form. The asymptotic formula of the Green's function for large argument is also obtained, and applied to study the fractional quantum scattering problem. We get the approximate scattering wave function with correction of every order.
ERIC Educational Resources Information Center
JORDAN, THOMAS E.
THIS BOOK PROVIDES A GUIDE TO THE BASIC CONCEPTS AND ISSUES IN THE FIELD OF MENTAL RETARDATION. THERE ARE MANY SOURCES OR CAUSES OF MENTAL RETARDATION AND THE FOLLOWING TYPES ARE EXPLAINED--(1) GENETIC OR CHEMICAL DISORDERS, (2) BIRTH TRAUMA, (3) SUBSEQUENT ACCIDENTS OR DISEASE, AND (4) ENVIRONMENTAL INFLUENCES. IT IS NOTED THAT MOST CASES INVOLVE…
Mental Retardation in Perspective.
ERIC Educational Resources Information Center
Horvath, Michael; And Others
This monograph presents a general introduction to the history, classification, and characteristics of mental retardation. It begins with a discussion of the history of mental retardation from ancient Greece and Rome to the present. The beginnings of special education are traced to the early 19th century in Europe. Major influences in treatment of…
Vignettes in Mental Retardation.
ERIC Educational Resources Information Center
Crissey, Marie Skodak
1983-01-01
The use of the family history chart and the "Binet-Simon Scale" to study mental retardation in the early 20th century are considered, along with the implications of this practice. With the thesis that mental retardation was primarily familial and hereditary, limiting reproduction and segregation were viewed as appropriate approaches. (SEW)
Brominated flame retardants (BFRs) belong to a large class of compounds known as organohalogens. BFRs are currently the largest marketed flame retardant group due to their high performance efficiency and low cost. In the commercial market, more than 75 different BFRs are recogniz...
Uncertainty of Green Functions for Waveform-based Earthquake Source Inversions
NASA Astrophysics Data System (ADS)
Gallovic, F.; Hallo, M.
2015-12-01
Green functions (GFs) are an essential ingredient in waveform-based earthquake source inversions. Hence, their error due to imprecise knowledge of a crustal model is the major source of uncertainty of the inferred earthquake source parameters. Strategies how to incorporate the modeling error (uncertainty) of the GFs in waveform inversions have been recently introduced (Yagi and Fukahata, 2011; Duputel et al., 2014). They rely on statistical description of the GFs uncertainty by means of the covariance matrix. This study is devoted to estimation of covariance matrix of full wavefield GFs, describing the effect of velocity model uncertainty. By means of Monte Carlo simulations in randomly perturbed 1D velocity models we analyze the dependence of the covariances on the strength of the perturbations, receiver-source distances, and frequency ranges. Since the covariance matrix estimation is numerically very expensive and thus hardly applicable in practice, we propose simplified approaches. The first simplification uses the „Approximate covariance function" based on GFs in the mean velocity model. The second possible simplification „Stacionarized covariance function" (i.e. averaged over time) leads to a simple analytical formula for covariance function. The both simplifications exhibit very good agreement with the Monte Carlo simulations, and may be easily implemented in currently existing inversion techniques. References:Duputel, Z., Agram, P.S., Simons, M., Minson, S.E. Beck, J.L., 2014. Accounting for prediction uncertainty when inferring subsurface fault slipl, Geophys. J. Int., 197 (1), 464-482.Yagi, Y. Fukahata, Y., 2011. Introduction of uncertainty of Green's function into waveform inversion for seismic source processes, Geophys. J. Int., 186 (2), 711-720.
Use of time space Green's functions in the computation of transient eddy current fields
Davey, K.; Turner, L.
1988-12-01
The utility of integral equations to solve eddy current problems has been borne out by numerous computations in the past few years, principally in sinusoidal steady-state problems. This paper attempts to examine the applicability of the integral approaches in both time and space for the more generic transient problem. The basic formulation for the time space Green's function approach is laid out. A technique employing Gauss-Laguerre integration is employed to realize the temporal solution, while Gauss--Legendre integration is used to resolve the spatial field character. The technique is then applied to the fusion electromagnetic induction experiments (FELIX) cylinder experiments in both two and three dimensions. It is found that quite accurate solutions can be obtained using rather coarse time steps and very few unknowns; the three-dimensional field solution worked out in this context used basically only four unknowns. The solution appears to be somewhat sensitive to the choice of time step, a consequence of a numerical instability imbedded in the Green's function near the origin.
The use of time space Green's functions in the computation of transient eddy current fields
NASA Astrophysics Data System (ADS)
Davey, Kent; Turner, Larry
1988-12-01
The utility of integral equations to solve eddy current problems has been borne out by numerous computations in the past few years, principally in sinusoidal steady-state problems. This paper attempts to examine the applicability of the integral approaches in both time and space for the more generic transient problem. The basic formulation for the time space Green's function approach is laid out. A technique employing Gauss-Laguerre integration is employed to realize the temporal solution, while Gauss-Legendre integration is used to resolve the spatial field character. The technique is then applied to the fusion electromagnetic induction experiments (FELIX) cylinder experiments in both two and three dimensions. It is found that quite accurate solutions can be obtained using rather coarse time steps and very few unknowns; the three-dimensional field solution worked out in this context used basically only four unknowns. The solution appears to be somewhat sensitive to the choice of time step, a consequence of a numerical instability imbedded in the Green's function near the origin.
Cancellation of spurious arrivals in Green's function extraction and the generalized optical theorem
Snieder, R.; Van Wijk, K.; Haney, M.; Calvert, R.
2008-01-01
The extraction of the Green's function by cross correlation of waves recorded at two receivers nowadays finds much application. We show that for an arbitrary small scatterer, the cross terms of scattered waves give an unphysical wave with an arrival time that is independent of the source position. This constitutes an apparent inconsistency because theory predicts that such spurious arrivals do not arise, after integration over a complete source aperture. This puzzling inconsistency can be resolved for an arbitrary scatterer by integrating the contribution of all sources in the stationary phase approximation to show that the stationary phase contributions to the source integral cancel the spurious arrival by virtue of the generalized optical theorem. This work constitutes an alternative derivation of this theorem. When the source aperture is incomplete, the spurious arrival is not canceled and could be misinterpreted to be part of the Green's function. We give an example of how spurious arrivals provide information about the medium complementary to that given by the direct and scattered waves; the spurious waves can thus potentially be used to better constrain the medium. ?? 2008 The American Physical Society.
A first-order time-domain Green's function approach to supersonic unsteady flow
NASA Technical Reports Server (NTRS)
Freedman, M. I.; Tseng, K.
1985-01-01
A time-domain Green's Function Method for unsteady supersonic potential flow around complex aircraft configurations is presented. The focus is on the supersonic range wherein the linear potential flow assumption is valid. The Green's function method is employed in order to convert the potential-flow differential equation into an integral one. This integral equation is then discretized, in space through standard finite-element technique, and in time through finite-difference, to yield a linear algebraic system of equations relating the unknown potential to its prescribed co-normalwash (boundary condition) on the surface of the aircraft. The arbitrary complex aircraft configuration is discretized into hyperboloidal (twisted quadrilateral) panels. The potential and co-normalwash are assumed to vary linearly within each panel. Consistent with the spatial linear (first-order) finite-element approximations, the potential and co-normalwash are assumed to vary linearly in time. The long range goal of our research is to develop a comprehensive theory for unsteady supersonic potential aerodynamics which is capable of yielding accurate results even in the low supersonic (i.e., high transonic) range.
NASA Astrophysics Data System (ADS)
Zimmermann, Anke; Kuhn, Sandra; Richter, Marten
2016-01-01
Often, the calculation of Coulomb coupling elements for quantum dynamical treatments, e.g., in cluster or correlation expansion schemes, requires the evaluation of a six dimensional spatial integral. Therefore, it represents a significant limiting factor in quantum mechanical calculations. If the size or the complexity of the investigated system increases, many coupling elements need to be determined. The resulting computational constraints require an efficient method for a fast numerical calculation of the Coulomb coupling. We present a computational method to reduce the numerical complexity by decreasing the number of spatial integrals for arbitrary geometries. We use a Green's function formulation of the Coulomb coupling and introduce a generalized scalar potential as solution of a generalized Poisson equation with a generalized charge density as the inhomogeneity. That enables a fast calculation of Coulomb coupling elements and, additionally, a straightforward inclusion of boundary conditions and arbitrarily spatially dependent dielectrics through the Coulomb Green's function. Particularly, if many coupling elements are included, the presented method, which is not restricted to specific symmetries of the model, presents a promising approach for increasing the efficiency of numerical calculations of the Coulomb interaction. To demonstrate the wide range of applications, we calculate internanostructure couplings, such as the Förster coupling, and illustrate the inclusion of symmetry considerations in the method for the Coulomb coupling between bound quantum dot states and unbound continuum states.
McCollom, Brittany A; Collis, Jon M
2014-09-01
A normal mode solution to the ocean acoustic problem of the Pekeris waveguide with an elastic bottom using a Green's function formulation for a compressional wave point source is considered. Analytic solutions to these types of waveguide propagation problems are strongly dependent on the eigenvalues of the problem; these eigenvalues represent horizontal wavenumbers, corresponding to propagating modes of energy. The eigenvalues arise as singularities in the inverse Hankel transform integral and are specified by roots to a characteristic equation. These roots manifest themselves as poles in the inverse transform integral and can be both subtle and difficult to determine. Following methods previously developed [S. Ivansson et al., J. Sound Vib. 161 (1993)], a root finding routine has been implemented using the argument principle. Using the roots to the characteristic equation in the Green's function formulation, full-field solutions are calculated for scenarios where an acoustic source lies in either the water column or elastic half space. Solutions are benchmarked against laboratory data and existing numerical solutions. PMID:25190379
Two-Flux Green's Function Analysis for Transient Spectral Radiation in a Composite
NASA Technical Reports Server (NTRS)
Siegel, Robert
1996-01-01
An analysis is developed for obtaining transient temperatures in a two-layer semitransparent composite with spectrally dependent properties. Each external boundary of the composite is subjected to radiation and convection. The two-flux radiative transfer equations are solved by deriving a Green's function. This yields the local radiative heat source needed to numerically solve the transient energy equation. An advantage of the two-flux method is that isotropic scattering is included without added complexity. The layer refractive indices are larger than one. This produces internal reflections at the boundaries and the internal interface; the reflections are assumed diffuse. Spectral results using the Green's function method are verified by comparing with numerical solutions using the exact radiative transfer equations. Transient temperature distributions are given to illustrate the effect of radiative heating on one side of a composite with external convective cooling. The protection of a material from incident radiation is illustrated by adding scattering to the layer adjacent to the radiative source.
Source analysis using regional empirical Green's functions: The 2008 Wells, Nevada, earthquake
Mendoza, C.; Hartzell, S.
2009-01-01
We invert three-component, regional broadband waveforms recorded for the 21 February 2008 Wells, Nevada, earthquake using a finite-fault methodology that prescribes subfault responses using eight MW∼4 aftershocks as empirical Green's functions (EGFs) distributed within a 20-km by 21.6-km fault area. The inversion identifies a seismic moment of 6.2 x 1024 dyne-cm (5.8 MW) with slip concentrated in a compact 6.5-km by 4-km region updip from the hypocenter. The peak slip within this localized area is 88 cm and the stress drop is 72 bars, which is higher than expected for Basin and Range normal faults in the western United States. The EGF approach yields excellent fits to the complex regional waveforms, accounting for strong variations in wave propagation and site effects. This suggests that the procedure is useful for studying moderate-size earthquakes with limited teleseismic or strong-motion data and for examining uncertainties in slip models obtained using theoretical Green's functions.
Shi, Yan; Wang, Hao Gang; Li, Long; Chan, Chi Hou
2008-10-01
A multilevel Green's function interpolation method based on two kinds of multilevel partitioning schemes--the quasi-2D and the hybrid partitioning scheme--is proposed for analyzing electromagnetic scattering from objects comprising both conducting and dielectric parts. The problem is formulated using the surface integral equation for homogeneous dielectric and conducting bodies. A quasi-2D multilevel partitioning scheme is devised to improve the efficiency of the Green's function interpolation. In contrast to previous multilevel partitioning schemes, noncubic groups are introduced to discretize the whole EM structure in this quasi-2D multilevel partitioning scheme. Based on the detailed analysis of the dimension of the group in this partitioning scheme, a hybrid quasi-2D/3D multilevel partitioning scheme is proposed to effectively handle objects with fine local structures. Selection criteria for some key parameters relating to the interpolation technique are given. The proposed algorithm is ideal for the solution of problems involving objects such as missiles, microstrip antenna arrays, photonic bandgap structures, etc. Numerical examples are presented to show that CPU time is between O(N) and O(N log N) while the computer memory requirement is O(N). PMID:18830332
Argani, L P; Bigoni, D; Capuani, D; Movchan, N V
2014-09-01
The infinite-body three-dimensional Green's function set (for incremental displacement and mean stress) is derived for the incremental deformation of a uniformly strained incompressible, nonlinear elastic body. Particular cases of the developed formulation are the Mooney-Rivlin elasticity and the J2-deformation theory of plasticity. These Green's functions are used to develop a boundary integral equation framework, by introducing an ad hoc potential, which paves the way for a boundary element formulation of three-dimensional problems of incremental elasticity. Results are used to investigate the behaviour of a material deformed near the limit of ellipticity and to reveal patterns of shear failure. In fact, within the investigated three-dimensional framework, localized deformations emanating from a perturbation are shown to be organized in conical geometries rather than in planar bands, so that failure is predicted to develop through curved and thin surfaces of intense shearing, as can for instance be observed in the cup-cone rupture of ductile metal bars. PMID:25197258
Singularity-free Green's function for EM sources embedded in a stratified medium
NASA Astrophysics Data System (ADS)
Weng, Ai-Hua; Liu, Yun-He; Yin, Chang-Chun; Jia, Ding-Yu
2016-03-01
We present a method to unify the calculation of Green's functions for an electromagnetic (EM) transmitting source embedded in a homogeneous stratified medium. A virtual interface parallel to layer interfaces is introduced through the source location. The potentials for Green's function are derived by decomposing the partial wave solutions to Helmholtz's equations into upward and downward within boundaries. The amplitudes of the potentials in each stratum are obtained recursively from the initial amplitudes at the source level. The initial amplitudes are derived by coupling with the transmitting sources and following the discontinuity of the tangential electric and magnetic fields at the source interface. Only the initial terms are related to the transmitting sources and thus need to be modified for different transmitters, whereas the kernel connected with the stratified media stays unchanged. Hence, the present method can be easily applied to EM transmitting sources with little modification. The application of the proposed method to the marine controlled-source electromagnetic method (MCSEM) demonstrates its simplicity and flexibility.
Representation theorems and Green's function retrieval for scattering in acoustic media.
Vasconcelos, Ivan; Snieder, Roel; Douma, Huub
2009-09-01
Reciprocity theorems for perturbed acoustic media are provided in the form of convolution- and correlation-type theorems. These reciprocity relations are particularly useful in the general treatment of both forward and inverse-scattering problems. Using Green's functions to describe perturbed and unperturbed waves in two distinct wave states, representation theorems for scattered waves are derived from the reciprocity relations. While the convolution-type theorems can be manipulated to obtain scattering integrals that are analogous to the Lippmann-Schwinger equation, the correlation-type theorems can be used to retrieve the scattering response of the medium by cross correlations. Unlike previous formulations of Green's function retrieval, the extraction of scattered-wave responses by cross correlations does not require energy equipartitioning. Allowing for uneven energy radiation brings experimental advantages to the retrieval of fields scattered by remote lossless and/or attenuative scatterers. These concepts are illustrated with a number of examples, including analytic solutions to a one-dimensional scattering problem, and a numerical example in the context of seismic waves recorded on the ocean bottom. PMID:19905236
Sebastian, Abin; Prasad, M N V
2013-01-01
Cadmium (Cd) uptake mediated alterations in functional components of photo assimilation during conversion of cow dung and poultry cast to vermicompost were studied in two Indian rice cultivars; MO 16 and MTU 7029. It was found that higher amount of Cd accumulate in plants grown in soil amended with vermicompost which in turn damaged functional components in photo assimilation. Enhancement of root growth was recognized as reason for Cd accumulation. Metabolic alterations noticed among plants were not taken place during application of raw materials used for vermicomposting such as cow dung and poultry cast amendment. Rice varieties accumulated Cd differentially where MTU 7029 accumulated more Cd compare to MO 16. It was also noticed that existence of negative correlation between zinc status of the plant and Cd accumulation. PMID:23819289
Consanguinity and mental retardation.
Madhavan, T; Narayan, J
1991-04-01
Consanguinity among parents as a cause of mental retardation in their children is debatable. The present study was conducted to find out the effect of consanguinity on mental retardation where the causative factor is not established. A total of 517 mentally retarded persons and their families were studied out of which 160 were born of consanguineous marriage and 357 were of non-consanguineous marriage. The results indicated that, when there is a history of mental retardation in the family and if the parents are consanguineously married, the risk of mental retardation in the offspring is significantly high (chi 2 = 11.52; P less than 0.001). Among the consanguineously married families, the blood relationship of uncle-niece seems to have the highest risk of affecting the offsprings. The implications are discussed in detail. PMID:2072392
NASA Astrophysics Data System (ADS)
Rajagopal, A. K.; Mochena, Mogus
2000-12-01
The group-theory framework developed by Fukutome for a systematic analysis of the various broken-symmetry types of Hartree-Fock solution exhibiting spin structures is here extended to the general many-body context using spinor Green function formalism for describing magnetic systems. Consequences of this theory are discussed for examining the magnetism of itinerant electrons in nanometric systems of current interest as well as bulk systems where a vector spin-density form is required, by specializing our work to spin-density-functional formalism. We also formulate the linear-response theory for such a system and compare and contrast our results with the recent results obtained for localized electron systems. The various phenomenological treatments of itinerant magnetic systems are here unified in this group-theoretical description. We apply this theory to the one-band Hubbard model to illustrate the usefulness of this approach.
Fire-Retardant, Decorative Inks
NASA Technical Reports Server (NTRS)
Kourtides, D.; Nir, Z.; Mikroyannidis, J.
1987-01-01
Effectiveness of fire-retardant additives evaluated. Fire retardance of decorative acrylic printing inks for aircraft interiors enhanced by certain commercial and experimental fire-retardant additives, according to study.
NASA Astrophysics Data System (ADS)
Tsaur, Gin-yih; Wang, Jyhpyng
2016-07-01
The Green function method is a powerful technique for solving the initial value problem in quantum mechanics. Once the Green function is solved the whole wavefunction evolution is represented in a concise form and can be evaluated conveniently by numerical integration. We present a method for constructing the Green functions systematically which is different from the conventional methods of eigenfunction expansion or path integration. By using variable changing, function substitution, and Fourier transforms, the time dependent Schrödinger equations can be simplified and the solutions for the simplified equations can be easily derived. We then obtain the Green functions for the original equations by the reverse transforms. The method is demonstrated for the linear potential, the harmonic oscillator, the centrifugal potential, and the centripetal barrier oscillator, where the Green function for the centripetal barrier oscillator has not been solved previously by conventional methods. The method and examples illustrated in this paper can be utilised to strengthen undergraduate courses on quantum mechanics and/or partial differential equation.
Khan, Akhtar Ali; Shah, Mohd Abas; Majid, Somina
2016-02-01
Aphis pomi De Geer, the green apple aphid, is an economic pest of apple and other rosaceae throughout the world. In the present study, functional responses of the syrphids Episyrphus balteatus De Geer, Eristalis tenax(L.), Eristalis interruptus (Poda), and Sphaerophoria scripta (L.), to A. pomi were studied under laboratory conditions to determine their relative predatory potential. The second- and third-instar larvae of the predators were exposed to increasing densities of similar-sized A. pomi nymphs in Petri dishes. Ep. balteatus was found to possess the highest consumption rate followed by Er. tenax, Er. interruptus, and S. scripta. All predator species and stages exhibited a Type II functional response. The coefficients of attack rate and handling time showed an insignificant variation between species and preying stages, suggesting equal potential of the four syrphid species to regulate A. pomi colonies. PMID:26578626
Elusive Structural, Functional, and Immunological Features of Act d 5, the Green Kiwifruit Kiwellin.
Offermann, Lesa R; Giangrieco, Ivana; Perdue, Makenzie L; Zuzzi, Sara; Santoro, Mario; Tamburrini, Maurizio; Cosgrove, Daniel J; Mari, Adriano; Ciardiello, Maria Antonietta; Chruszcz, Maksymilian
2015-07-29
Kiwellin (Act d 5) is an allergenic protein contained in kiwifruit pulp in high amounts. The aim of this study was to investigate the three-dimensional structure of the natural molecule from green kiwifruit and its possible function. Kiwellin was crystallized, and its structure, including post-translational modifications, was elucidated. The molecular weight and structural features, in solution, were analyzed by gel filtration and circular dichroism, respectively. Although structurally similar to expansin, kiwellin lacks expansin activity and carbohydrate binding. A specific algorithm was applied to investigate any possible IgE reactivity correlation between kiwellin and a panel of 102 allergens, including expansins and other carbohydrate-binding allergens. The available data suggest a strong dependence of the kiwellin structure on the environmental/experimental conditions. This dependence therefore poses challenges in detecting the correlations between structural, functional, and immunological features of this protein. PMID:26146952
Weighted two-particle Green's functions in the coherent-potential approximation
NASA Astrophysics Data System (ADS)
Schwabe, N. F.; Elliott, R. J.
1996-03-01
We extend the two-particle theory of disordered systems within the coherent-potential approximation to obtain weighted contributions to averaged two-particle resolvents which arise from separate alloy components. Starting from first principles in a model of diagonal disorder and the single-site approximation for a binary substitutional alloy AcB1-c we extend the approach of a fundamental paper by Velický to evaluate various weighted forms of a general class of two-particle Green's functions. Applications in a wide range of linear response theory are discussed in detail as well as the behavior of the weighted functions in a strong disorder limit. To exemplify our analytic calculations the optical absorption in a disordered model alloy is studied numerically.
Off-Shell Green Functions: One-Loop with Growing Legs
Bashir, A.; Concha-Sanchez, Y.; Delbourgo, R.; Tejeda-Yeomans, M. E.
2008-07-02
One loop calculations in gauge theories in arbitrary gauge and dimensions become exceedingly hard with growing number of external off-shell legs. Let alone higher point functions, such a calculation for even the three point one-loop vertices for quantum electrodynamics (QED) and quantum chromodynamics (QCD) has been made available only recently. In this article, we discuss how Ward-Fradkin-Green-Takahashi identities (WFGTI) may provide a helpful tool in these computations. After providing a glimpse of our suggestion for the case of the 3-point vertex, we present our preliminary findings towards our similar efforts for the 4-point function. We restrict ourselves to the example of scalar quantum electrodynamics (SQED)
Green's function multiple-scattering theory with a truncated basis set: An augmented-KKR formalism
Alam, Aftab; Khan, Suffian N.; Smirnov, A. V.; Nicholson, D. M.; Johnson, Duane D.
2014-11-04
Korringa-Kohn-Rostoker (KKR) Green's function, multiple-scattering theory is an ecient sitecentered, electronic-structure technique for addressing an assembly of N scatterers. Wave-functions are expanded in a spherical-wave basis on each scattering center and indexed up to a maximum orbital and azimuthal number L_{max} = (l,m)_{max}, while scattering matrices, which determine spectral properties, are truncated at L_{tr} = (l,m)_{tr} where phase shifts δl>l_{tr} are negligible. Historically, L_{max} is set equal to L_{tr}, which is correct for large enough L_{max} but not computationally expedient; a better procedure retains higher-order (free-electron and single-site) contributions for L_{max} > L_{tr} with δl>l_{tr} set to zero [Zhang and Butler, Phys. Rev. B 46, 7433]. We present a numerically ecient and accurate augmented-KKR Green's function formalism that solves the KKR equations by exact matrix inversion [R^{3} process with rank N(l_{tr} + 1)^{2}] and includes higher-L contributions via linear algebra [R^{2} process with rank N(l_{max} +1)^{2}]. Augmented-KKR approach yields properly normalized wave-functions, numerically cheaper basis-set convergence, and a total charge density and electron count that agrees with Lloyd's formula. We apply our formalism to fcc Cu, bcc Fe and L1_{0} CoPt, and present the numerical results for accuracy and for the convergence of the total energies, Fermi energies, and magnetic moments versus L_{max} for a given L_{tr}.
Green's function multiple-scattering theory with a truncated basis set: An augmented-KKR formalism
Alam, Aftab; Khan, Suffian N.; Smirnov, A. V.; Nicholson, D. M.; Johnson, Duane D.
2014-11-04
Korringa-Kohn-Rostoker (KKR) Green's function, multiple-scattering theory is an ecient sitecentered, electronic-structure technique for addressing an assembly of N scatterers. Wave-functions are expanded in a spherical-wave basis on each scattering center and indexed up to a maximum orbital and azimuthal number Lmax = (l,m)max, while scattering matrices, which determine spectral properties, are truncated at Ltr = (l,m)tr where phase shifts δl>ltr are negligible. Historically, Lmax is set equal to Ltr, which is correct for large enough Lmax but not computationally expedient; a better procedure retains higher-order (free-electron and single-site) contributions for Lmax > Ltr with δl>ltr set to zero [Zhang andmore » Butler, Phys. Rev. B 46, 7433]. We present a numerically ecient and accurate augmented-KKR Green's function formalism that solves the KKR equations by exact matrix inversion [R3 process with rank N(ltr + 1)2] and includes higher-L contributions via linear algebra [R2 process with rank N(lmax +1)2]. Augmented-KKR approach yields properly normalized wave-functions, numerically cheaper basis-set convergence, and a total charge density and electron count that agrees with Lloyd's formula. We apply our formalism to fcc Cu, bcc Fe and L10 CoPt, and present the numerical results for accuracy and for the convergence of the total energies, Fermi energies, and magnetic moments versus Lmax for a given Ltr.« less
Green's function multiple-scattering theory with a truncated basis set: An augmented-KKR formalism
NASA Astrophysics Data System (ADS)
Alam, Aftab; Khan, Suffian N.; Smirnov, A. V.; Nicholson, D. M.; Johnson, Duane D.
2014-11-01
The Korringa-Kohn-Rostoker (KKR) Green's function, multiple-scattering theory is an efficient site-centered, electronic-structure technique for addressing an assembly of N scatterers. Wave functions are expanded in a spherical-wave basis on each scattering center and indexed up to a maximum orbital and azimuthal number Lmax=(l,mmax), while scattering matrices, which determine spectral properties, are truncated at Lt r=(l,mt r) where phase shifts δl >ltr are negligible. Historically, Lmax is set equal to Lt r, which is correct for large enough Lmax but not computationally expedient; a better procedure retains higher-order (free-electron and single-site) contributions for Lmax>Lt r with δl >ltr set to zero [X.-G. Zhang and W. H. Butler, Phys. Rev. B 46, 7433 (1992), 10.1103/PhysRevB.46.7433]. We present a numerically efficient and accurate augmented-KKR Green's function formalism that solves the KKR equations by exact matrix inversion [R3 process with rank N (ltr+1 ) 2 ] and includes higher-L contributions via linear algebra [R2 process with rank N (lmax+1) 2 ]. The augmented-KKR approach yields properly normalized wave functions, numerically cheaper basis-set convergence, and a total charge density and electron count that agrees with Lloyd's formula. We apply our formalism to fcc Cu, bcc Fe, and L 1 0 CoPt and present the numerical results for accuracy and for the convergence of the total energies, Fermi energies, and magnetic moments versus Lmax for a given Lt r.
Cresti, Alessandro . E-mail: cresti@df.unipi.it; Grosso, Giuseppe . E-mail: grosso@df.unipi.it; Parravicini, Giuseppe Pastori . E-mail: pastori@fisicavolta.unipv.it
2006-05-15
We have derived closed analytic expressions for the Green's function of an electron in a two-dimensional electron gas threaded by a uniform perpendicular magnetic field, also in the presence of a uniform electric field and of a parabolic spatial confinement. A workable and powerful numerical procedure for the calculation of the Green's functions for a large infinitely extended quantum wire is considered exploiting a lattice model for the wire, the tight-binding representation for the corresponding matrix Green's function, and the Peierls phase factor in the Hamiltonian hopping matrix element to account for the magnetic field. The numerical evaluation of the Green's function has been performed by means of the decimation-renormalization method, and quite satisfactorily compared with the analytic results worked out in this paper. As an example of the versatility of the numerical and analytic tools here presented, the peculiar semilocal character of the magnetic Green's function is studied in detail because of its basic importance in determining magneto-transport properties in mesoscopic systems.
Baishya, Prasanta; Maji, Tarun K
2016-09-20
Starch based wood nanocomposites (WSNC) were prepared successfully from starch and soft wood with multi-walled carbon nanotube (MWCNT) as nano reinforcing agent through a completely green path. The most important part of this scheme was the use of water as the solvent. In this technique, starch was grafted with methylmethacrylate (MMA) and MWCNT was functionalised with hydroxyl groups (f-MWCNT). Dimethyloldihydroxyethyleneurea (DMDHEU) was used as a cross-linker to prepare the green material from methylmethacrylate grafted starch (MMA-g-starch), soft wood flour and functionalised MWCNT. The functionalization of MWCNT was confirmed by Fourier transform infrared spectroscopy (FTIR), thermogravimetric analysis (TGA) and Raman analysis. Different properties of the WSNC were investigated by varying the concentration of f-MWCNT. The prepared nanocomposites exhibited outstanding thermal stability, mechanical properties and water resistance capacity compared to untreated wood composites. The flammability of the wood composites decreased up to 30% with just addition of 0.50phr f-MWCNT. PMID:27261757
Structure, Function and Reconstitution of Antenna Complexes of Green Photosynthetic Bacteria
Blankenship, Robert E.
2005-06-10
Most chlorophyll-type pigments in a photosynthetic organism function as an antenna, absorbing light and transferring excitations to a photochemical reaction center where energy storage takes place by a series of chemical reactions. The green photosynthetic bacteria are characterized by large antenna complexes known as chlorosomes, in which pigment-pigment interactions are of dominant importance. The overall objective of this project is to determine the mechanisms of excitation transfer and regulation of this unique antenna system, including how it is integrated into the rest of the photosynthetic energy transduction apparatus. Techniques that are being used in this research include biochemical analysis, spectroscopy, microscopy, X-ray structural studies, and reconstitution from purified components. Our recent results indicate that the chlorosome baseplate structure, which is the membrane attachment site for the chlorosome to the membrane, is a unique pigment-protein that contains large amounts of carotenoids and small amounts of bacteriochlorophyll a. Reconstitution of directed energy transfer in chlorosomes will be carried out using purified baseplates and oligomeric pigments. The integral membrane B808-866 antenna complex from Chloroflexus aurantiacus and the Fenna-Matthews-Olson protein-reaction center complex from green sulfur bacteria will be characterized by spectroscopic and structural techniques.
Green tea polyphenol EGCG blunts androgen receptor function in prostate cancer
Siddiqui, Imtiaz A.; Asim, Mohammad; Hafeez, Bilal B.; Adhami, Vaqar M.; Tarapore, Rohinton S.; Mukhtar, Hasan
2011-01-01
Androgen deprivation therapy is the major treatment for advanced prostate cancer (PCa). However, it is a temporary remission, and the patients almost inevitably develop hormone refractory prostate cancer (HRPC). HRPC is almost incurable, although most HRPC cells still express androgen receptor (AR) and depend on the AR for growth, making AR a prime drug target. Here, we provide evidence that epigallocatechin-3-gallate (EGCG), the major polyphenol in green tea, is a direct antagonist of androgen action. In silico modeling and FRET-based competition assay showed that EGCG physically interacts with the ligand-binding domain of AR by replacing a high-affinity labeled ligand (IC50 0.4 μM). The functional consequence of this interaction was a decrease in AR-mediated transcriptional activation, which was due to EGCG mediated inhibition of interdomain N-C termini interaction of AR. Treatment with EGCG also repressed the transcriptional activation by a hotspot mutant AR (T877A) expressed ectopically as well as the endogenous AR mutant. As the physiological consequence of AR antagonism, EGCG repressed R1881-induced PCa cell growth. In a xenograft model, EGCG was found to inhibit AR nuclear translocation and protein expression. We also observed a significant down-regulation of androgen-regulated miRNA-21 and up-regulation of a tumor suppressor, miRNA-330, in tumors of mice treated with EGCG. Taken together, we provide evidence that EGCG functionally antagonizes androgen action at multiple levels, resulting in inhibition of PCa growth.—Siddiqui, I. A., Asim, M., Hafeez, B. B., Adhami, V. M., Tarapore, R. S., Mukhtar, H. Green tea polyphenol EGCG blunts androgen receptor function in prostate cancer. PMID:21177307
Rapid Estimates of the Source-Time Function and Mw using Empirical Green's Function Deconvolution
NASA Astrophysics Data System (ADS)
Benz, H.; Herrmann, R. B.
2010-12-01
The USGS’s National Earthquake Information Center uses a variety of network-averaged measures (e.g. mb, Ms) and waveform modeling (e.g., W-phase and CMT procedures) to determine the magnitude of an earthquake. Magnitude estimates are initially poorly constrained because the station sampling required for a robust estimate have not been reached. To provide faster and more accurate estimates of the moment magnitude within the first ten minutes of occurrence, NEIC is investigating the use of empirical Green’s function deconvolution to determine both the moment magnitude and the relative source-time function of the earthquake source. The procedure involves computing the expected source mechanism based on a moment tensor catalog, deconvolution of pre-computed Green’s function synthetic seismograms from the observed waveforms, network-averaging of the deconvolution results to determine the moment magnitude and a network averaged source time function. In addition, if waveform data are available for a previously modeled earthquake for which the moment tensor results are known and for which common stations observed the two events, an empirical Green’s function deconvolution of the two events is performed at each station to determine the relative moment-magnitude and source-time functions. In order to do these computations robustly and automatically, NEIC has had to develop new infrastructure to support these computations that includes a moment tensor catalog server from which composite mechanisms for the region can be estimated and a database of GSN and US Backbone waveforms for all events for which moment tensor solutions have been calculated since 1990. Initial results indicated that for most M6 or larger events worldwide, NEIC can compute within 10 minutes of origin time an initial moment magnitude that is typically within +/-0.2 of the final moment magnitude determined from waveform modeling (W-phase). In addition, the deconvolution processing provides an initial
Branch, Darren W.
2008-05-01
Recently, the generalized method for calculation of the 16-element Green's function for analysis of surface acoustic waves has proven crucial to develop more sophisticated transducers. The generalized Green's function provides a precise relationship between the acoustic stresses and electric displacement on the three mechanical displacements and electric potential. This generalized method is able to account for mass loading effects which is absent in the effective permittivity approach. However, the calculation is numerically intensive and may lead to numerical instabilities when solving for both the eigenvalues and eigenvectors simultaneously. In this work, the general eigenvalue problem was modified to eliminate the numerical instabilities in the solving procedure. An algorithm is also presented to select the proper eigenvalues rapidly to facilitate analysis for all types of acoustic propagation. The 4 x 4 Green's functions and effective permittivities were calculated for materials supporting Rayleigh, leaky, and leaky longitudinal waves as demonstration of the method.
Identification of a functional nuclear export signal in the green fluorescent protein asFP499
Mustafa, Huseyin . E-mail: huseyinm@hotmail.com; Strasser, Bernd; Rauth, Sabine; Irving, Robert A.; Wark, Kim L.
2006-04-21
The green fluorescent protein (GFP) asFP499 from Anemonia sulcata is a distant homologue of the GFP from Aequorea victoria. We cloned the asFP499 gene into a mammalian expression vector and showed that this protein was expressed in the human lymphoblast cell line Ramos RA1 and in the embryonic kidney 293T cell line (HEK 293T). In HEK 293T cells, asFP499 was localized mainly in the cytoplasm, suggesting that the protein was excluded from the nucleus. We identified {sub 194}LRMEKLNI{sub 201} as a candidate nuclear export signal in asFP499 and mutated the isoleucine at position 201 to an alanine. Unlike the wildtype form, the mutant protein was distributed throughout the cytoplasm and nucleus. This is First report of a GFP that contains a functional NES.
Hierarchy of correlations: Application to Green's functions and interacting topological phases
NASA Astrophysics Data System (ADS)
Gómez-León, Álvaro
2016-07-01
We study the many-body physics of different quantum systems using a hierarchy of correlations, which corresponds to a generalization of the 1 /Z hierarchy. The decoupling scheme obtained from this hierarchy is adapted to calculate double-time Green's functions and due to its nonperturbative nature, we describe quantum phase transition and topological features characteristic of strongly correlated phases. As concrete examples we consider spinless fermions in a dimerized chain and in a honeycomb lattice. We present analytical results which are valid for any dimension and can be generalized to different types of interactions (e.g., long-range interactions), which allows us to shed light on the effect of quantum correlations in a very systematic way. Furthermore, we show that this approach provides an efficient framework for the calculation of topological invariants in interacting systems.
Development of multi-functional streetscape green infrastructure using a performance index approach.
Tiwary, A; Williams, I D; Heidrich, O; Namdeo, A; Bandaru, V; Calfapietra, C
2016-01-01
This paper presents a performance evaluation framework for streetscape vegetation. A performance index (PI) is conceived using the following seven traits, specific to the street environments - Pollution Flux Potential (PFP), Carbon Sequestration Potential (CSP), Thermal Comfort Potential (TCP), Noise Attenuation Potential (NAP), Biomass Energy Potential (BEP), Environmental Stress Tolerance (EST) and Crown Projection Factor (CPF). Its application is demonstrated through a case study using fifteen street vegetation species from the UK, utilising a combination of direct field measurements and inventoried literature data. Our results indicate greater preference to small-to-medium size trees and evergreen shrubs over larger trees for streetscaping. The proposed PI approach can be potentially applied two-fold: one, for evaluation of the performance of the existing street vegetation, facilitating the prospects for further improving them through management strategies and better species selection; two, for planning new streetscapes and multi-functional biomass as part of extending the green urban infrastructure. PMID:26412197
Paolino, Marco; Gueye, Moussa; Pieri, Elisa; Manathunga, Madushanka; Fusi, Stefania; Cappelli, Andrea; Latterini, Loredana; Pannacci, Danilo; Filatov, Michael; Léonard, Jérémie; Olivucci, Massimo
2016-08-10
While rotary molecular switches based on neutral and cationic organic π-systems have been reported, structurally homologous anionic switches providing complementary properties have not been prepared so far. Here we report the design and preparation of a molecular switch mimicking the anionic p-HBDI chromophore of the green fluorescent protein. The investigation of the mechanism and dynamics of the E/Z switching function is carried out both computationally and experimentally. The data consistently support axial rotary motion occurring on a sub-picosecond time scale. Transient spectroscopy and trajectory simulations show that the nonadiabatic decay process occurs in the vicinity of a conical intersection (CInt) between a charge transfer state and a covalent/diradical state. Comparison of our anionic p-HBDI-like switch with the previously reported cationic N-alkyl indanylidene pyrrolinium switch mimicking visual pigments reveals that these similar systems translocate, upon vertical excitation, a similar net charge in the same axial direction. PMID:27322488
Electronic Structure Calculation of Permanent Magnets using the KKR Green's Function Method
NASA Astrophysics Data System (ADS)
Doi, Shotaro; Akai, Hisazumi
2014-03-01
Electronic structure and magnetic properties of permanent magnetic materials, especially Nd2Fe14B, are investigated theoretically using the KKR Green's function method. Important physical quantities in magnetism, such as magnetic moment, Curie temperature, and anisotropy constant, which are obtained from electronics structure calculations in both cases of atomic-sphere-approximation and full-potential treatment, are compared with past band structure calculations and experiments. The site preference of heavy rare-earth impurities are also evaluated through the calculation of formation energy with the use of coherent potential approximations. Further, the development of electronic structure calculation code using the screened KKR for large super-cells, which is aimed at studying the electronic structure of realistic microstructures (e.g. grain boundary phase), is introduced with some test calculations.
Green functions for generalized point interactions in one dimension: A scattering approach
Schmidt, Alexandre G.M.; Cheng, B.K.; Luz, M.G.E. da
2002-12-01
Recently, general point interactions in one dimension has been used to model a large number of different phenomena in quantum mechanics. Such potentials, however, require some sort of regularization to lead to meaningful results. The usual ways to do so rely on technicalities that may hide important physical aspects of the problem. In this work we present a method to calculate the exact Green functions for general point interactions in one dimension. Our approach differs from previous ones because it is based only on physical quantities, namely, the scattering coefficients R and T to construct G. Renormalization or particular mathematical prescriptions are not invoked. The simple formulation of the method makes it easy to extend to more general contexts, such as for lattices of N general point interactions, on a line, on a half-line, under periodic boundary conditions, and confined in a box.
NASA Astrophysics Data System (ADS)
Balzer, Karsten; Bauch, Sebastian; Bonitz, Michael
2010-04-01
In this contribution, we discuss the finite-element discrete variable representation (FE-DVR) of the nonequilibrium Green's function and its implications on the description of strongly inhomogeneous quantum systems. In detail, we show that the complementary features of FEs and the DVR allow for a notably more efficient solution of the two-time Schwinger/Keldysh/Kadanoff-Baym equations compared to a general basis approach. Particularly, the use of the FE-DVR leads to an essential speedup in computing the self-energies. As atomic and molecular examples we consider the He atom and the linear version of H+3 in one spatial dimension. For these closed-shell models we, in Hartree-Fock and second Born approximation, compute the ground-state properties and compare with the exact findings obtained from the solution of the few-particle time-dependent Schrödinger equation.
Optical absorption of dilute nitride alloys using self-consistent Green's function method
NASA Astrophysics Data System (ADS)
Seifikar, Masoud; O'Reilly, Eoin P.; Fahy, Stephen
2014-01-01
We have calculated the optical absorption for InGaNAs and GaNSb using the band anticrossing (BAC) model and a self-consistent Green's function (SCGF) method. In the BAC model, we include the interaction of isolated and pair N levels with the host matrix conduction and valence bands. In the SCGF approach, we include a full distribution of N states, with non-parabolic conduction and light-hole bands, and parabolic heavy-hole and spin-split-off bands. The comparison with experiments shows that the first model accounts for many features of the absorption spectrum in InGaNAs; including the full distribution of N states improves this agreement. Our calculated absorption spectra for GaNSb alloys predict the band edges correctly but show more features than are seen experimentally. This suggests the presence of more disorder in GaNSb alloys in comparison with InGaNAs.
Green's function theory for the Cheng-Schick model of 3He-4He mixtures
NASA Astrophysics Data System (ADS)
Siemann, R. P.; Boukahil, A.; Huber, D. L.
2014-08-01
In this paper, we outline a theory for the thermodynamic properties of 3He-4He mixtures in the neighborhood of the critical line and the tricritical point (TCP). The theory utilizes the Cheng-Schick (CS) lattice gas model where both the 3He and 4He atoms are treated as quantum particles on a lattice. The analysis is based on Green's function approach. Results are presented for the ordering susceptibility and the thermal averages of the occupation numbers of 3He and 4He atoms. We derive a self-consistent equation for the ordering susceptibility and use it to calculate the critical line and locate the TCP. Our findings are compared with the predictions obtained from high temperature series expansions, mean field theory and the random phase approximation (RPA).
A full-potential approach to the relativistic single-site Green's function
Liu, Xianglin; Wang, Yang; Eisenbach, Markus; Stocks, George Malcolm
2016-07-07
One major purpose of studying the single-site scattering problem is to obtain the scattering matrices and differential equation solutions indispensable to multiple scattering theory (MST) calculations. On the other hand, the single-site scattering itself is also appealing because it reveals the physical environment experienced by electrons around the scattering center. In this study, we demonstrate a new formalism to calculate the relativistic full-potential single-site Green's function. We implement this method to calculate the single-site density of states and electron charge densities. Lastly, the code is rigorously tested and with the help of Krein's theorem, the relativistic effects and full potentialmore » effects in group V elements and noble metals are thoroughly investigated.« less
A Green's function approach to the Casimir effect on topological insulators with planar symmetry
NASA Astrophysics Data System (ADS)
Martín-Ruiz, A.; Cambiaso, M.; Urrutia, L. F.
2016-03-01
We investigate the Casimir stress on a topological insulator (TI) between two metallic plates. The TI is assumed to be joined to one of the plates and its surface in front of the other is covered by a thin magnetic layer, which turns the TI into a full insulator. We also analyze the limit where one of the plates is sent to infinity yielding the Casimir stress between a conducting plate and a TI. To this end we employ a local approach in terms of the stress-energy tensor of the system, its vacuum expectation value being subsequently evaluated in terms of the appropriate Green's function. Finally, the construction of the renormalised vacuum stress-energy tensor in the region between the plates yields the Casimir stress. Numerical results are also presented.
Dynamics of charge transfer: Rate processes formulated with nonequilibrium Green's functions
Yeganeh, Sina; Ratner, Mark A.; Mujica, Vladimiro
2007-04-28
The authors examine the connection between electron transport under bias in a junction and nonadiabatic intramolecular electron transfer (ET). It is shown that under certain assumptions it is possible to define a stationary current that allows the computation of the intramolecular transfer rate using the same formalism that is employed in the description of transport. They show that the nonequilibrium Green's function formalism of quantum transport can be used to calculate the ET rate. The formal connection between electron transport and electron transfer is made, and they work out the simple case of an electronic level coupled to a vibrational mode representing a thermal bath and show that the result is the same as expected from a Fermi golden rule treatment, and in the high-temperature limit yields the Marcus electron transfer theory. The usefulness of this alternative formulation of rates is discussed.
A full-potential approach to the relativistic single-site Green's function.
Liu, Xianglin; Wang, Yang; Eisenbach, Markus; Malcolm Stocks, G
2016-09-01
One major purpose of studying the single-site scattering problem is to obtain the scattering matrices and differential equation solutions indispensable to multiple scattering theory (MST) calculations. On the other hand, the single-site scattering itself is also appealing because it reveals the physical environment experienced by electrons around the scattering center. In this paper we demonstrate a new formalism to calculate the relativistic full-potential single-site Green's function. We implement this method to calculate the single-site density of states and electron charge densities. The code is rigorously tested and with the help of Krein's theorem, the relativistic effects and full potential effects in group V elements and noble metals are thoroughly investigated. PMID:27388858
Investigation of spherical and cylindrical Luneburg lens antennas by the Green's function method
NASA Astrophysics Data System (ADS)
Knyazev, S.; Korotkov, A.; Panchenko, B.; Shabunin, S.
2016-03-01
Luneburg lens antenna radiation fields are calculated with Green's functions of spherical and cylindrical layered structures. Electric field components of spherical and cylindrical Luneburg lenses excited by linear and circular polarized incident field are analysed. Dipole, slot and aperture antennas are described by electric and magnetic extraneous currents. Radiation patterns of cylindrical and spherical Luneburg lens are analysed. Co-polarized and cross-polarized field radiation patterns are shown. The proposed method significantly reduces the computing time for multi-layered lenses in comparison with the most commonly used in antenna design. The first step antenna structure optimization may be performed for a shorter time. The results may be used as the first approximation for Ansys HFSS and other software.
Electronic structure of disordered graphene with Greenʼs function approach
NASA Astrophysics Data System (ADS)
Smotlacha, J.; Pincak, R.; Pudlak, M.
2012-10-01
The Green functions play a big role in the calculation of the local density of states of the carbon nanostructures. We investigate their nature for the variously oriented and disclinated graphene-like surface. Next, we investigate the case of a small perturbation generated by two heptagonal defects and from the character of the local density of states in the border sites of these defects we derive their minimal and maximal distances on the perturbed cylindrical surface. For this purpose, we transform the given surface into a chain using the Haydock recursion method. We will suppose only the nearest-neighbor interactions between the atom orbitals, in other words, the calculations suppose the short-range potential.
Global relativistic folding optical potential and the relativistic Green's function model
NASA Astrophysics Data System (ADS)
Ivanov, M. V.; Vignote, J. R.; Álvarez-Rodríguez, R.; Meucci, A.; Giusti, C.; Udías, J. M.
2016-07-01
Optical potentials provide critical input for calculations on a wide variety of nuclear reactions, in particular, for neutrino-nucleus reactions, which are of great interest in the light of the new neutrino oscillation experiments. We present the global relativistic folding optical potential (GRFOP) fits to elastic proton scattering data from 12C nucleus at energies between 20 and 1040 MeV. We estimate observables, such as the differential cross section, the analyzing power, and the spin rotation parameter, in elastic proton scattering within the relativistic impulse approximation. The new GRFOP potential is employed within the relativistic Green's function model for inclusive quasielastic electron scattering and for (anti)neutrino-nucleus scattering at MiniBooNE kinematics.
Bratu's problem: A novel approach using fixed-point iterations and Green's functions
NASA Astrophysics Data System (ADS)
Kafri, H. Q.; Khuri, S. A.
2016-01-01
In this article, the one-dimensional non-linear Bratu's boundary value problem is solved via a novel approach that combines Green's function and fixed point iterative schemes, such as Picard's and Krasnoselskii-Mann's. The convergence of the introduced iterative algorithm is proved using the contraction principle. The method is supported by considering a number of numerical examples that correspond to different cases of eigenvalues. The procedure underlying the strategy reduces calculations and provides highly accurate results in comparison with the exact solution and/or numerical solutions provided in the literature. The current method overcomes the difficulty of treating the problem for eigenvalues near and at the critical value, such as λ = 3 and λ = 3.51, and handles them reliably and very efficiently.
NASA Astrophysics Data System (ADS)
Mi, Bin-Zhou; Zhai, Liang-Jun; Hua, Ling-Ling
2016-01-01
The effect of magnetic spin correlation on the thermodynamic properties of Heisenberg ferromagnetic single-walled nanotubes are comprehensively investigated by use of the double-time Green's function method. The influence of temperature, spin quantum number, diameter of the tube, anisotropy strength and external magnetic field to internal energy, free energy, and magnon specific heat are carefully calculated. Compared to the mean field approximation, the consideration of the magnetic correlation effect significantly improves the internal energy values at finite temperature, while it does not so near zero temperature, and this effect is related to the diameter of the tube, anisotropy strength, and spin quantum number. The magnetic correlation effect lowers the internal energy at finite temperature. As a natural consequence of the reduction of the internal energy, the specific heat is reduced, and the free energy is elevated.
Green function method for the time domain simulation of pulse propagation.
Huang, Jing; Yao, Jianquan; Xu, Degang; Li, Runhua
2014-06-01
Based on the Green function method, the nonlinear Schrödinger equation is directly solved in the time domain (without Fourier transform). Because the dispersion and nonlinear effects are calculated simultaneously, it does not bring any spurious effect such as the split-step method in which the step size has to be carefully controlled by an error estimation. By this time domain solution, the pulse fission is analyzed, and we obtain the relationship between the minimum T₀ (the half-width at 1/e-intensity point of a pulse) and dispersion coefficients (β₂, β₃, and β₄). Thus the concrete dispersion values, which have an impact on ultrashort pulses (the quantity units is femtosecond or attosecond), are listed. It has been demonstrated that pulse fission occurs in the normal and anomalous dispersion regimes, even though fourth-order dispersion and the fifth-order nonlinear effects are not taken into account. PMID:24922431
A Study of Green's Function Methods Applied to Space Radiation Protection
NASA Technical Reports Server (NTRS)
Heinbockel, John H.
2001-01-01
The purpose of this research was to study the propagation of galactic ions through various materials. Galactic light ions result from the break up of heavy ion particles and their propagation through materials is modeled using the one-dimensional Boltzmann equation. When ions enter materials there can occur (i) the interaction of ions with orbital electrons which causes ionization within the material and (ii) ions collide with atoms causing production of secondary particles which penetrate deeper within the material. These processes are modeled by a continuum model. The basic idea is to place a control volume within the material and examine the change in ion flux across this control volume. In this way on can derive the basic equations for the transport of light and heavy ions in matter. Green's function perturbation methods can then be employed to solve the resulting equations using energy dependent nuclear cross sections.
Green's function method for single-particle resonant states in relativistic mean field theory
NASA Astrophysics Data System (ADS)
Sun, T. T.; Zhang, S. Q.; Zhang, Y.; Hu, J. N.; Meng, J.
2014-11-01
Relativistic mean field theory is formulated with the Green's function method in coordinate space to investigate the single-particle bound states and resonant states on the same footing. Taking the density of states for free particles as a reference, the energies and widths of single-particle resonant states are extracted from the density of states without any ambiguity. As an example, the energies and widths for single-neutron resonant states in 120Sn are compared with those obtained by the scattering phase-shift method, the analytic continuation in the coupling constant approach, the real stabilization method, and the complex scaling method. Excellent agreements with these methods are found for the energies and widths of single-neutron resonant states.
Structure, Function, and Regulation of Antenna Complexes of Green Photosynthetic Bacteria
Robert E. Blankenship
2001-04-27
This project is concerned with the structure and function of the chlorosome antennas found in green photosynthetic bacteria. Chlorosomes are ellipsoidal structures attached to the cytoplasmic side of the inner cell membrane. These antenna complexes provide a very large absorption cross section for light capture. Evidence is overwhelming that the chlorosome represents a very different type of antenna from that found in any other photosynthetic system yet studied. It is now clear that chlorosomes do not contain traditional pigment-proteins, in which the pigments bind to specific sites on proteins. Instead, the chlorosome pigments are organized in vivo into pigment oligomers in which direct pigment-pigment interactions are of dominant importance. Our group has used a multidisciplinary approach to investigate this unique system, including model systems, ultrafast spectroscopy, molecular biology, protein chemistry and X-ray crystallography.
Fotheringham, John B.
1974-01-01
Influences producing mental retardation can be divided into three categories: inherited factors, health problems and social-emotional influences. This article outlines steps which can be taken to reduce the first two categories, both pre and postnatally. PMID:20469133
Fire retardant polyisocyanurate foam
NASA Technical Reports Server (NTRS)
Riccitiello, S. R.; Parker, J. A.
1972-01-01
Fire retardant properties of low density polymer foam are increased. Foam has pendant nitrile groups which form thermally-stable heterocyclic structures at temperature below degradation temperature of urethane linkages.
Green polymer chemistry: The role of Candida antarctica lipase B in polymer functionalization
NASA Astrophysics Data System (ADS)
Castano Gil, Yenni Marcela
The synthesis of functional polymers with well-defined structure, end-group fidelity and physico-chemical properties useful for biomedical applications has proven challenging. Chemo-enzymatic methods are an alternative strategy to increase the diversity of functional groups in polymeric materials. Specifically, enzyme-catalyzed polymer functionalization carried out under solventless conditions is a great advancement in the design of green processes for biomedical applications, where the toxicity of solvents and catalyst residues need to be considered. Enzymes offer several distinct advantages, including high efficiency, catalyst recyclability, and mild reaction conditions. This reseach aimed to precisely functionalized polymers using two methods: enzyme-catalyzed functionalization via polymerization and chemo-enzymatic functionalization of pre-made polymers for drug delivery. In the first method, well-defined poly(caprolactone)s were generated using alkyne-based initiating systems catalyzed by CALB. Propargyl alcohol and 4-dibenzocyclooctynol (DIBO) were shown to efficiently initiate the ring opening polymerization of epsilon-caprolactone under metal free conditions and yielded polymers with Mn ~4 to 24 KDa and relatively narrow molecular mass distribution. In the second methodology, we present quantitative enzyme-catalyzed transesterification of vinyl esters and ethyl esters with poly(ethylene glycol)s (PEG)s that will serve as building blocks for dendrimer synthesis, followed by introducing a new process for the exclusive gamma-conjugation of folic acid. Specifically, fluorescein-acrylate was enzymatically conjugated with PEG. Additionally, halo-ester functionalized PEGs were successfully prepared by the transesterification of alkyl halo-esters with PEGs. 1H and 13C NMR spectroscopy, SEC and MALDI-ToF mass spectrometry confirmed the structure and purity of the products.
Earthquake source tensor inversion with the gCAP method and 3D Green's functions
NASA Astrophysics Data System (ADS)
Zheng, J.; Ben-Zion, Y.; Zhu, L.; Ross, Z.
2013-12-01
We develop and apply a method to invert earthquake seismograms for source properties using a general tensor representation and 3D Green's functions. The method employs (i) a general representation of earthquake potency/moment tensors with double couple (DC), compensated linear vector dipole (CLVD), and isotropic (ISO) components, and (ii) a corresponding generalized CAP (gCap) scheme where the continuous wave trains are broken into Pnl and surface waves (Zhu & Ben-Zion, 2013). For comparison, we also use the waveform inversion method of Zheng & Chen (2012) and Ammon et al. (1998). Sets of 3D Green's functions are calculated on a grid of 1 km3 using the 3-D community velocity model CVM-4 (Kohler et al. 2003). A bootstrap technique is adopted to establish robustness of the inversion results using the gCap method (Ross & Ben-Zion, 2013). Synthetic tests with 1-D and 3-D waveform calculations show that the source tensor inversion procedure is reasonably reliable and robust. As initial application, the method is used to investigate source properties of the March 11, 2013, Mw=4.7 earthquake on the San Jacinto fault using recordings of ~45 stations up to ~0.2Hz. Both the best fitting and most probable solutions include ISO component of ~1% and CLVD component of ~0%. The obtained ISO component, while small, is found to be a non-negligible positive value that can have significant implications for the physics of the failure process. Work on using higher frequency data for this and other earthquakes is in progress.
Ren, Xiaoying; Hu, Zhongai Hu, Haixiong; Qiang, Ruibin; Li, Li; Li, Zhimin; Yang, Yuying; Zhang, Ziyu; Wu, Hongying
2015-10-15
Graphical abstract: Electroactive methyl green (MG) is selected to functionalize reduced graphene oxide (RGO) through non-covalent modification and the composite achieves high specific capacitance, good rate capability and excellent long life cycle. - Highlights: • MG–RGO composites were firstly prepared through non-covalent modification. • The mass ratio in composites is a key for achieving high specific capacitance. • MG–RGO 5:4 exhibits the highest specific capacitance of 341 F g{sup −1}. • MG–RGO 5:4 shows excellent rate capability and long life cycle. - Abstract: In the present work, water-soluble electroactive methyl green (MG) has been used to non-covalently functionalize reduced graphene oxide (RGO) for enhancing supercapacitive performance. The microstructure, composition and morphology of MG–RGO composites are systematically characterized by UV–vis absorption, field emission scanning electron microscopy (FE-SEM), transmission electron microscopy (TEM) and X-ray diffraction (XRD). The electrochemical performances are investigated by cyclic voltammetry (CV), galvanostatic charge/discharge and electrochemical impedance spectroscopy (EIS). The fast redox reactions from MG could generate additional pseudocapacitance, which endows RGO higher capacitances. As a result, the MG–RGO composite (with the 5:4 mass ratio of MG:RGO) achieve a maximum value of 341 F g{sup −1} at 1 A g{sup −1} within the potential range from −0.25 to 0.75 V and provide a 180% enhancement in specific capacitance in comparison with pure RGO. Furthermore, excellent rate capability (72% capacitance retention from 1 A g{sup −1} to 20 A g{sup −1}) and long life cycle (12% capacitance decay after 5000 cycles) are achieved for the MG–RGO composite electrode.
NASA Astrophysics Data System (ADS)
Schaden, Martin; Spruch, Larry
2004-09-01
We derive the semiclassical approximation to Feynman's path integral representation of the energy Green function of a massless particle in the shadow region of an ideal obstacle in a medium. The wavelength of the particle is assumed to be comparable to or smaller than any relevant length of the problem. Classical paths with extremal length partially creep along the obstacle and their fluctuations are subject to non-holonomic constraints. If the medium is a vacuum, the asymptotic contribution from a single classical path of overall length L to the energy Green function at energy E is that of a non-relativistic particle of mass E/ c2 moving in the two-dimensional space orthogonal to the classical path for a time τ= L/ c. Dirichlet boundary conditions at the surface of the obstacle constrain the motion of the particle to the exterior half-space and result in an effective time-dependent but spatially constant force that is inversely proportional to the radius of curvature of the classical path. We relate the diffractive, classically forbidden motion in the "creeping" case to the classically allowed motion in the "whispering gallery" case by analytic continuation in the curvature of the classical path. The non-holonomic constraint implies that the surface of the obstacle becomes a zero-dimensional caustic of the particle's motion. We solve this problem for extremal rays with piecewise constant curvature and provide uniform asymptotic expressions that are approximately valid in the penumbra as well as in the deep shadow of a sphere.
NASA Technical Reports Server (NTRS)
Wilson, John C.
1995-01-01
Aerodynamic plates stop litter from spinning during hoisting by helicopter. Features of proposed litter-spinning retarders include convenience of deployment and independence from ground restraint. Retarder plate(s) folded flat against bottom of litter during storage or while litter is loaded. Plate(s) held in storage position by latch that releases manually or automatically as litter is hoisted. Upon release, springs move plates into deployed position.
NASA Astrophysics Data System (ADS)
Shendeleva, Margarita L.
2004-03-01
Diffuse photon-density waves generated by an instantaneous line source that is parallel to the interface between two semi-infinite turbid media are studied by use of the diffusion approximation. For two nonabsorbing media the Green functions for diffuse light are obtained based on the Green functions for temperature fields that were derived with the Cagniard-de Hoop method. The boundary conditions for diffuse light take into account the discontinuity in the specific intensity at the interface between two media with different refractive indices. The results of the calculations of the specific intensities and the gradient lines for different sets of parameters are presented.
Retardation Measurements of Infrared PVA Wave plate
NASA Astrophysics Data System (ADS)
Sun, Y.; Z, H.; W, D.; D, Y.; Z, Z.; S, J.
The wave plate made of Polyvinyl Alcohol PVA plastic film has several advantages such as its lower cost and insensitivity to temperature and incidence angle so it has been used in the Solar Multi-Channel Telescope SMCT in China But the important parameter retardations of PVA wave plates in the near infrared wavelength have never been provided In this paper a convenient and high precise instrument to get the retardations of discrete wavelengths or a continuous function of wavelength in near infrared is developed In this method the retardations of wave plates have been determined through calculating the maximum and minimum of light intensity The instrument error has been shown Additionally we can get the continuous direction of wavelength retardations in the ultraviolet visible or infrared spectral in another way
NASA Astrophysics Data System (ADS)
Stradi, Daniele; Martinez, Umberto; Blom, Anders; Brandbyge, Mads; Stokbro, Kurt
2016-04-01
Metal-semiconductor contacts are a pillar of modern semiconductor technology. Historically, their microscopic understanding has been hampered by the inability of traditional analytical and numerical methods to fully capture the complex physics governing their operating principles. Here we introduce an atomistic approach based on density functional theory and nonequilibrium Green's function, which includes all the relevant ingredients required to model realistic metal-semiconductor interfaces and allows for a direct comparison between theory and experiments via I -Vbias curve simulations. We apply this method to characterize an Ag/Si interface relevant for photovoltaic applications and study the rectifying-to-Ohmic transition as a function of the semiconductor doping. We also demonstrate that the standard "activation energy" method for the analysis of I -Vbias data might be inaccurate for nonideal interfaces as it neglects electron tunneling, and that finite-size atomistic models have problems in describing these interfaces in the presence of doping due to a poor representation of space-charge effects. Conversely, the present method deals effectively with both issues, thus representing a valid alternative to conventional procedures for the accurate characterization of metal-semiconductor interfaces.
NASA Astrophysics Data System (ADS)
Brix, H.; Menemenlis, D.; Hill, C.; Dutkiewicz, S.; Jahn, O.; Wang, D.; Bowman, K.; Zhang, H.
2015-11-01
The NASA Carbon Monitoring System (CMS) Flux Project aims to attribute changes in the atmospheric accumulation of carbon dioxide to spatially resolved fluxes by utilizing the full suite of NASA data, models, and assimilation capabilities. For the oceanic part of this project, we introduce ECCO2-Darwin, a new ocean biogeochemistry general circulation model based on combining the following pre-existing components: (i) a full-depth, eddying, global-ocean configuration of the Massachusetts Institute of Technology general circulation model (MITgcm), (ii) an adjoint-method-based estimate of ocean circulation from the Estimating the Circulation and Climate of the Ocean, Phase II (ECCO2) project, (iii) the MIT ecosystem model "Darwin", and (iv) a marine carbon chemistry model. Air-sea gas exchange coefficients and initial conditions of dissolved inorganic carbon, alkalinity, and oxygen are adjusted using a Green's Functions approach in order to optimize modeled air-sea CO2 fluxes. Data constraints include observations of carbon dioxide partial pressure (pCO2) for 2009-2010, global air-sea CO2 flux estimates, and the seasonal cycle of the Takahashi et al. (2009) Atlas. The model sensitivity experiments (or Green's Functions) include simulations that start from different initial conditions as well as experiments that perturb air-sea gas exchange parameters and the ratio of particulate inorganic to organic carbon. The Green's Functions approach yields a linear combination of these sensitivity experiments that minimizes model-data differences. The resulting initial conditions and gas exchange coefficients are then used to integrate the ECCO2-Darwin model forward. Despite the small number (six) of control parameters, the adjusted simulation is significantly closer to the data constraints (37% cost function reduction, i.e., reduction in the model-data difference, relative to the baseline simulation) and to independent observations (e.g., alkalinity). The adjusted air-sea gas
NASA Astrophysics Data System (ADS)
Leng, Xia; Yin, Huabing; Liang, Dongmei; Ma, Yuchen
2015-09-01
Organic semiconductors have promising and broad applications in optoelectronics. Understanding their electronic excited states is important to help us control their spectroscopic properties and performance of devices. There have been a large amount of experimental investigations on spectroscopies of organic semiconductors, but theoretical calculation from first principles on this respect is still limited. Here, we use density functional theory (DFT) and many-body Green's function theory, which includes the GW method and Bethe-Salpeter equation, to study the electronic excited-state properties and spectroscopies of one prototypical organic semiconductor, sexithiophene. The exciton energies of sexithiophene in both the gas and bulk crystalline phases are very sensitive to the exchange-correlation functionals used in DFT for ground-state structure relaxation. We investigated the influence of dynamical screening in the electron-hole interaction on exciton energies, which is found to be very pronounced for triplet excitons and has to be taken into account in first principles calculations. In the sexithiophene single crystal, the energy of the lowest triplet exciton is close to half the energy of the lowest singlet one. While lower-energy singlet and triplet excitons are intramolecular Frenkel excitons, higher-energy excitons are of intermolecular charge-transfer type. The calculated optical absorption spectra and Davydov splitting are in good agreement with experiments.
Fractional charge and spin errors in self-consistent Green's function theory
NASA Astrophysics Data System (ADS)
Phillips, Jordan J.; Kananenka, Alexei A.; Zgid, Dominika
2015-05-01
We examine fractional charge and spin errors in self-consistent Green's function theory within a second-order approximation (GF2). For GF2, it is known that the summation of diagrams resulting from the self-consistent solution of the Dyson equation removes the divergences pathological to second-order Møller-Plesset (MP2) theory for strong correlations. In the language often used in density functional theory contexts, this means GF2 has a greatly reduced fractional spin error relative to MP2. The natural question then is what effect, if any, does the Dyson summation have on the fractional charge error in GF2? To this end, we generalize our previous implementation of GF2 to open-shell systems and analyze its fractional spin and charge errors. We find that like MP2, GF2 possesses only a very small fractional charge error, and consequently minimal many electron self-interaction error. This shows that GF2 improves on the critical failings of MP2, but without altering the positive features that make it desirable. Furthermore, we find that GF2 has both less fractional charge and fractional spin errors than typical hybrid density functionals as well as random phase approximation with exchange.
Function and dynamics of aptamers: A case study on the malachite green aptamer
Wang, Tianjiao
2008-01-01
Aptamers are short single-stranded nucleic acids that can bind to their targets with high specificity and high affinity. To study aptamer function and dynamics, the malachite green aptamer was chosen as a model. Malachite green (MG) bleaching, in which an OH- attacks the central carbon (C1) of MG, was inhibited in the presence of the malachite green aptamer (MGA). The inhibition of MG bleaching by MGA could be reversed by an antisense oligonucleotide (AS) complementary to the MGA binding pocket. Computational cavity analysis of the NMR structure of the MGA-MG complex predicted that the OH^{-} is sterically excluded from the C1 of MG. The prediction was confirmed experimentally using variants of the MGA with changes in the MG binding pocket. This work shows that molecular reactivity can be reversibly regulated by an aptamer-AS pair based on steric hindrance. In addition to demonstrate that aptamers could control molecular reactivity, aptamer dynamics was studied with a strategy combining molecular dynamics (MD) simulation and experimental verification. MD simulation predicted that the MG binding pocket of the MGA is largely pre-organized and that binding of MG involves reorganization of the pocket and a simultaneous twisting of the MGA terminal stems around the pocket. MD simulation also provided a 3D-structure model of unoccupied MGA that has not yet been obtained by biophysical measurements. These predictions were consistent with biochemical and biophysical measurements of the MGA-MG interaction including RNase I footprinting, melting curves, thermodynamic and kinetic constants measurement. This work shows that MD simulation can be used to extend our understanding of the dynamics of aptamer-target interaction which is not evident from static 3D-structures. To conclude, I have developed a novel concept to control molecular reactivity by an aptamer based on steric protection and a strategy to study the dynamics of aptamer-target interaction by combining MD
NASA Astrophysics Data System (ADS)
Hassanzadeh, Pedram; Kuang, Zhiming
2016-09-01
A linear response function (LRF) determines the mean-response of a nonlinear climate system to weak imposed forcings, and an eddy flux matrix (EFM) determines the eddy momentum and heat flux responses to mean-flow changes. Neither LRF nor EFM can be calculated from first principles due the lack of a complete theory for turbulent eddies. Here the LRF and EFM for an idealized dry atmosphere are computed by applying numerous localized weak forcings, one at a time, to a GCM with Held-Suarez physics and calculating the mean-responses. The LRF and EFM for zonally-averaged responses are then constructed using these forcings and responses through matrix inversion. Tests demonstrate that LRF and EFM are fairly accurate. Spectral analysis of the LRF shows that the most excitable dynamical mode, the neutral vector, strongly resembles the model's Annular Mode. The framework described here can be employed to compute the LRF/EFM for zonally-asymmetric responses and more complex GCMs. The potential applications of the LRF/EFM constructed here are i) forcing a specified mean-flow for hypothesis-testing, ii) isolating/quantifying the eddy-feedbacks in complex eddy-mean flow interaction problems, and iii) evaluating/improving more generally-applicable methods currently used to construct LRFs or diagnose eddy-feedbacks in comprehensive GCMs or observations. As an example for iii, in Part 2, the LRF is also computed using the fluctuation-dissipation theorem (FDT), and the previously-calculated LRF is exploited to investigate why FDT performs poorly in some cases. It is shown that dimension-reduction using leading EOFs, which is commonly used to construct LRFs from the FDT, can significantly degrade the accuracy due to the non-normality of the operator.
2014-01-01
Background The built environment in which older people live plays an important role in promoting or inhibiting physical activity. Most work on this complex relationship between physical activity and the environment has excluded people with reduced physical function or ignored the difference between groups with different levels of physical function. This study aims to explore the role of neighbourhood green space in determining levels of participation in physical activity among elderly men with different levels of lower extremity physical function. Method Using data collected from the Caerphilly Prospective Study (CaPS) and green space data collected from high resolution Landmap true colour aerial photography, we first investigated the effect of the quantity of neighbourhood green space and the variation in neighbourhood vegetation on participation in physical activity for 1,010 men aged 66 and over in Caerphilly county borough, Wales, UK. Second, we explored whether neighbourhood green space affects groups with different levels of lower extremity physical function in different ways. Results Increasing percentage of green space within a 400 meters radius buffer around the home was significantly associated with more participation in physical activity after adjusting for lower extremity physical function, psychological distress, general health, car ownership, age group, marital status, social class, education level and other environmental factors (OR = 1.21, 95% CI 1.05, 1.41). A statistically significant interaction between the variation in neighbourhood vegetation and lower extremity physical function was observed (OR = 1.92, 95% CI 1.12, 3.28). Conclusion Elderly men living in neighbourhoods with more green space have higher levels of participation in regular physical activity. The association between variation in neighbourhood vegetation and regular physical activity varied according to lower extremity physical function. Subjects reporting poor lower extremity
Demuzere, M; Orru, K; Heidrich, O; Olazabal, E; Geneletti, D; Orru, H; Bhave, A G; Mittal, N; Feliu, E; Faehnle, M
2014-12-15
In order to develop climate resilient urban areas and reduce emissions, several opportunities exist starting from conscious planning and design of green (and blue) spaces in these landscapes. Green urban infrastructure has been regarded as beneficial, e.g. by balancing water flows, providing thermal comfort. This article explores the existing evidence on the contribution of green spaces to climate change mitigation and adaptation services. We suggest a framework of ecosystem services for systematizing the evidence on the provision of bio-physical benefits (e.g. CO2 sequestration) as well as social and psychological benefits (e.g. improved health) that enable coping with (adaptation) or reducing the adverse effects (mitigation) of climate change. The multi-functional and multi-scale nature of green urban infrastructure complicates the categorization of services and benefits, since in reality the interactions between various benefits are manifold and appear on different scales. We will show the relevance of the benefits from green urban infrastructures on three spatial scales (i.e. city, neighborhood and site specific scales). We will further report on co-benefits and trade-offs between the various services indicating that a benefit could in turn be detrimental in relation to other functions. The manuscript identifies avenues for further research on the role of green urban infrastructure, in different types of cities, climates and social contexts. Our systematic understanding of the bio-physical and social processes defining various services allows targeting stressors that may hamper the provision of green urban infrastructure services in individual behavior as well as in wider planning and environmental management in urban areas. PMID:25163601
ERIC Educational Resources Information Center
Kellow, J. Thomas; Frey, Georgia C.; Sandt, Dawn Rosser
2007-01-01
This study is a conceptual replication of previous work by Storey, Stern, & Parker (1990) that examined the influence of participation in integrated vs. segregated recreation/sports activities on evaluations of a person with mental retardation by persons without a disability. The Storey et al., (1990) study observed that people with mental…
Kleinert, H; Zatloukal, V
2013-11-01
The statistics of rare events, the so-called black-swan events, is governed by non-Gaussian distributions with heavy power-like tails. We calculate the Green functions of the associated Fokker-Planck equations and solve the related stochastic differential equations. We also discuss the subject in the framework of path integration. PMID:24329213
NASA Astrophysics Data System (ADS)
Koshanov, Bakytbek D.; Koshanova, Maira D.
2015-09-01
In this paper we construct an explicit form of the Green function of the Dirichlet problem for polyharmonic equations in a ball outside of the ball and, in the case of odd-dimensional space, and in the case of even dimension space 2m ≥ n by using a special expansion of the fundamental solution.
Manakov, N.L.; Nekipelov, A.A.; Fai-brevenshtei-breven, A.G.
1987-04-01
The method of the Sturm expansion of the relativistic Coulomb Green function G(E) is extended to the continuum range chemically bondEchemically bond>mc/sup 2/. The cross section for elastic and inelastic scattering of a ..gamma.. quantum by a hydrogenlike ion is calculated. Asymmetry effects in the polarization dependence of the scattering cross section are considered.
Nonequilibrium Green's functions and atom-surface dynamics: Simple views from a simple model system
NASA Astrophysics Data System (ADS)
Boström, E.; Hopjan, M.; Kartsev, A.; Verdozzi, C.; Almbladh, C.-O.
2016-03-01
We employ Non-equilibrium Green's functions (NEGF) to describe the real-time dynamics of an adsorbate-surface model system exposed to ultrafast laser pulses. For a finite number of electronic orbitals, the system is solved exactly and within different levels of approximation. Specifically i) the full exact quantum mechanical solution for electron and nuclear degrees of freedom is used to benchmark ii) the Ehrenfest approximation (EA) for the nuclei, with the electron dynamics still treated exactly. Then, using the EA, electronic correlations are treated with NEGF within iii) 2nd Born and with iv) a recently introduced hybrid scheme, which mixes 2nd Born self-energies with non-perturbative, local exchange- correlation potentials of Density Functional Theory (DFT). Finally, the effect of a semi-infinite substrate is considered: we observe that a macroscopic number of de-excitation channels can hinder desorption. While very preliminary in character and based on a simple and rather specific model system, our results clearly illustrate the large potential of NEGF to investigate atomic desorption, and more generally, the non equilibrium dynamics of material surfaces subject to ultrafast laser fields.
NASA Astrophysics Data System (ADS)
Jiang, Jin-Wu; Wang, Jian-Sheng; Li, Baowen
2011-01-01
The phonon and electron transport in single-walled carbon nanotubes (SWCNT) are investigated using the nonequilibrium Green's function approach. In zigzag SWCNT (n ,0) with mod(n ,3)≠0, the thermal conductance is mainly attributed to the phonon transport, while the electron only has few percentage contribution. The maximum value of the figure of merit (ZT) is about 0.2 in this type of SWCNT. The ZT is considerably larger in narrower SWCNT because of enhanced Seebeck coefficient. ZT is smaller in the armchair SWCNT, where Seebeck coefficient is small due to zero band gap. It is found that the cluster isotopic doping can reduce the phonon thermal conductance obviously and enhance the value of ZT. The uniaxial elongation and compress strain depresses phonons in whole frequency region, leading to the reduction in the phonon thermal conductance in whole temperature range. Interestingly, the elongation strain can affect the phonon transport more seriously than the compress strain, because the high frequency G mode is completely filtered out under elongation strain ɛ >0.05. The strain also has important effect on the subband edges of the electron band structure by smoothing the steps in the electron transmission function. The ZT is decreased by strain as the reduction in the electronic conductance overcomes the reduction in the thermal conductance.
Functional Rearrangement of the Light-Harvesting Antenna upon State Transitions in a Green Alga
Wlodarczyk, Lucyna M.; Snellenburg, Joris J.; Ihalainen, Janne A.; van Grondelle, Rienk; van Stokkum, Ivo H.M.; Dekker, Jan P.
2015-01-01
State transitions in the green alga Chlamydomonas reinhardtii serve to balance excitation energy transfer to photosystem I (PSI) and to photosystem II (PSII) and possibly play a role as a photoprotective mechanism. Thus, light-harvesting complex II (LHCII) can switch between the photosystems consequently transferring more excitation energy to PSII (state 1) or to PSI (state 2) or can end up in LHCII-only domains. In this study, low-temperature (77 K) steady-state and time-resolved fluorescence measured on intact cells of Chlamydomonas reinhardtii shows that independently of the state excitation energy transfer from LHCII to PSI or to PSII occurs on two main timescales of <15 ps and ∼100 ps. Moreover, in state 1 almost all LHCIIs are functionally connected to PSII, whereas the transition from state 1 to a state 2 chemically locked by 0.1 M sodium fluoride leads to an almost complete functional release of LHCIIs from PSII. About 2/3 of the released LHCIIs transfer energy to PSI and ∼1/3 of the released LHCIIs form a component designated X-685 peaking at 685 nm that decays with time constants of 0.28 and 5.8 ns and does not transfer energy to PSI or to PSII. A less complete state 2 was obtained in cells incubated under anaerobic conditions without chemical locking. In this state about half of all LHCIIs remained functionally connected to PSII, whereas the remaining half became functionally connected to PSI or formed X-685 in similar amounts as with chemical locking. We demonstrate that X-685 originates from LHCII domains not connected to a photosystem and that its presence introduces a change in the interpretation of 77 K steady-state fluorescence emission measured upon state transitions in Chalamydomonas reinhardtii. PMID:25606675
Retrieving the Green's Function by Cross-correlation: a Comparison of Approaches
NASA Astrophysics Data System (ADS)
Wapenaar, K.; Draganov, D.
2004-12-01
Recently it has been shown by various authors that the Green's function of a random medium can be obtained by cross-correlating the recordings of a diffuse wave field at two receiver positions (Weaver and Lobkis, 2001; van Tiggelen, 2003; Snieder, 2004). The resulting Green's function is the wave field that would be observed at one of these receiver positions if there were an impulsive source at the other. This theoretical result has first been demonstrated with ultrasonic measurements and later with seismic surface waves (Campillo and Paul, 2003). The accuracy of the reconstructed Green's function depends on the amount of disorder of the medium parameters and the duration of the signal. Ideally the cross-correlations should be done in the equipartitioned regime (where the net energy flux is equal to zero), which takes place after sufficiently long multiple scattering of the wave field between the heterogeneities in the disordered medium (Malcolm, Scales and van Tiggelen, 2004). An initially independent line of research, developed by exploration seismologists, deals with the reconstruction of the seismic reflection response of a deterministic medium from (passive) recordings of the transmission response. Already in 1968 Claerbout showed that the autocorrelation of the transmission response of a horizontally layered earth yields the superposition of the reflection response and its time-reversed version. The source in the subsurface may be a transient or a noise signal; in both cases the source signature in the reconstructed reflection response is the autocorrelation of the source signal in the subsurface. Claerbout's derivation was strictly one-dimensional. Later he conjectured for the 3-D situation that `by cross-correlating noise traces recorded at two locations on the surface, we can construct the wave field that would be recorded at one of the locations if there was a source at the other'. Although it was not explicitly stated, this conjecture applies to
NASA Astrophysics Data System (ADS)
Prüstel, Thorsten; Meier-Schellersheim, Martin
2012-08-01
We derive an exact Green's function of the diffusion equation for a pair of disk-shaped interacting particles in two dimensions subject to a backreaction boundary condition. Furthermore, we use the obtained function to calculate exact expressions for the survival probability and the time-dependent rate coefficient for the initially unbound pair and the survival probability of the bound state. The derived expressions will be of particular utility for the description of reversible membrane-bound reactions in cell biology.
NASA Astrophysics Data System (ADS)
Lee, Hyun C.
2016-07-01
The phonon dynamics of normal metal in the coherent regime of ultrafast spectroscopy is studied based on the non-equilibrium gauge invariant Green's function method. The non-equilibrium phonon self-energy is computed explicitly as a function of time in a gauge invariant way up to the second order of electric field of applied laser pulse. The extension beyond the coherent regime and the incorporation of correlation effects are discussed.
NASA Astrophysics Data System (ADS)
Klymko, Victor A.; Yakovlev, Alexander B.; Eshrah, Islam A.; Kishk, Ahmed A.; Glisson, Allen W.
2005-06-01
Green's function analysis of ideal hard surface circular waveguides is proposed with application to excitation and scattering problems. A decomposition of the hard surface waveguide into perfect electric conductor and perfect magnetic conductor waveguides allows the representation of dyadic Green's function in terms of transverse electric (TE) and transverse magnetic (TM) waveguide modes, respectively. In addition, a term corresponding to a transverse electromagnetic (TEM) mode is included in the representation of the Green's dyadic. The TEM term is extracted in closed form from the eigenmode expansion of TM and TE modes in the zero-cutoff limit. The electric field distribution due to an arbitrarily oriented electric dipole source is illustrated for representative TM, TE, and TEM modes propagating in the ideal hard surface circular waveguide. The derived Green's function is used in the method of moments analysis of an ideal hard surface waveguide excited by a half-wavelength strip dipole antenna. In addition, the scattering of the TEM mode by a thin strip is studied in the ideal hard surface circular waveguide.
ERIC Educational Resources Information Center
Giron, Maria D.; Salto, Rafael
2011-01-01
Structure-function relationship studies in proteins are essential in modern Cell Biology. Laboratory exercises that allow students to familiarize themselves with basic mutagenesis techniques are essential in all Genetic Engineering courses to teach the relevance of protein structure. We have implemented a laboratory course based on the…
Green's functions for the forced vibrations of cracked Euler-Bernoulli beams
NASA Astrophysics Data System (ADS)
Zhao, X.; Zhao, Y. R.; Gao, X. Z.; Li, X. Y.; Li, Y. H.
2016-02-01
In this paper, explicit expressions of the steady-state responses of a cracked Euler-Bernoulli beam submitted to a harmonic force are presented. The mechanical properties of cracked sections of the beam are characterized by five local stiffness models available in literature. Fundamental dynamic response of a beam with one crack is obtained by means of Green's function method. For a multi-cracked beam, the transfer matrix method is employed to derive the steady-state response, which can be readily reduced to those for a single-cracked beam. Numerical calculations are performed to validate the present solutions, to compare the dynamical behaviors of the beam corresponding to various classical local compliance models and to study the influences of crack geometry (depth and location) on the mechanical behavior of beam. Furthermore, the interactions of two cracks in the beam are particularly studied. The present analytical results can serve as a valuable benchmark to the future numerical simulations and experimental studies.
Snieder, Roel
2004-04-01
The Green's function of waves that propagate between two receivers can be found by cross-correlating multiply scattered waves recorded at these receivers. This technique obviates the need for a source at one of these locations, and is therefore called "passive imaging." This principle has been explained by assuming that the normal modes of the system are uncorrelated and that all carry the same amount of energy (equipartitioning). Here I present an alternative derivation of passive imaging of the ballistic wave that is not based on normal modes. The derivation is valid for scalar waves in three dimensions, and for elastic surface waves. Passive imaging of the ballistic wave is based on the destructive interference of waves radiated from scatterers away from the receiver line, and the constructive interference of waves radiated from secondary sources near the receiver line. The derivation presented here shows that the global requirement of the equipartitioning of normal modes can be relaxed to the local requirement that the scattered waves propagate on average isotropically near the receivers. PMID:15169121
Simulation of the radiolysis of water using Green's functions of the diffusion equation.
Plante, I; Cucinotta, F A
2015-09-01
Radiation chemistry is of fundamental importance in the understanding of the effects of ionising radiation, notably with regard to DNA damage by indirect effect (e.g. damage by ·OH radicals created by the radiolysis of water). In the recent years, Green's functions of the diffusion equation (GFDEs) have been used extensively in biochemistry, notably to simulate biochemical networks in time and space. In the present work, an approach based on the GFDE will be used to refine existing models on the indirect effect of ionising radiation on DNA. As a starting point, the code RITRACKS (relativistic ion tracks) will be used to simulate the radiation track structure and calculate the position of all radiolytic species formed during irradiation. The chemical reactions between these radiolytic species and with DNA will be done by using an efficient Monte Carlo sampling algorithm for the GFDE of reversible reactions with an intermediate state that has been developed recently. These simulations should help the understanding of the contribution of the indirect effect in the formation of DNA damage, particularly with regards to the formation of double-strand breaks. PMID:25897139
NASA Astrophysics Data System (ADS)
Minato, Shohei; Ghose, Ranajit
2016-04-01
The spatial heterogeneity along a fracture is a key determinant for fracture-associated mechanical and hydraulic properties of the subsurface. Laboratory experiments have been performed to test the applicability of the nonwelded interface representation to predict the frequency- and angle-dependent elastic response of a single fracture. The observation that nonwelded interface model can represent quite well the frequency- and angle-dependent reflection response of a fracture has led us to develop a new methodology for estimating the spatially heterogeneous fracture compliance from the reflection response along a fracture surface. A data-driven approach based on Marchenko equation coupled with inverse scattering to solve the nonwelded interface boundary condition has been formulated. The approach estimates the elastic wavefield along a fracture accurately, including the multiple reflections. As an extension, it offers the possibility to estimate fracture compliance using the multiple reflections. We illustrate the concept by numerically modeling 2-D SH waves sensing the heterogeneous tangential compliance of a fracture. The stationary phase method is applied to single and double spatial integrals to analyze the effect of source and receiver aperture on the Green's function retrieval. Our results show that the use of multiple reflections allows a better estimation of the heterogeneous fracture compliance than using primary reflections alone, especially for the far offsets on the fracture plane.
NASA Astrophysics Data System (ADS)
Moujaes, Elie A.; Khater, A.; Abou Ghantous, M.
2015-10-01
Ferromagnetic phase diagrams were, for a long time, unsuccessfully determined theoretically, despite the important Callen's 1963 [21] theoretical model. A great variety of experimental data for the magnetization over the entire range of temperature defining the ordered phase compared well with an empirical formula recently determined by Kuz'min (2005) [22]. Nonetheless, the Ising effective field theory (EFT), which can be of enormous support to both methods, was never given attention. The present work intends to show how the Ising EFT technique, when combined with the Green functions in Callen's work, is able to reconcile theoretical work with experimental data. The ratio kTc / JZS(S + 1) plays an important role in finding values for the exchange parameter J, whose first-principles calculation, often depending on the package used, is not properly done. J can be determined for a variety of ferromagnetic materials represented by general spin systems S with a number of nearest neighbours Z and critical temperature Tc, even for models including a percolative feature, characteristic of diluted interactive systems. We demonstrate that EFT is capable of estimating a value of J, which can substitute the use of more complex theoretical models or the performance of ab initio/DFT calculations.
Excitonic effects in GeC hybrid: Many-body Green's function calculations
NASA Astrophysics Data System (ADS)
Drissi, L. B.; Ramadan, F. Z.
2015-11-01
Many-body effects on the electronic and optical absorption properties of a GeC sheet are studied by means of first principle many-body Green's function and Bethe-Salpeter equation formalism. The absence of soft modes in the phonon-spectrum indicates the stability of the system. The inclusion of quasiparticle corrections increases significantly the band gap. The local field effects induce significant change in the absorption spectra for the out-plane polarization rendering the GeC monolayer transparent below 7 eV. The excitonic effects are significant on the optical absorption properties. A detailed analysis of the spectrum shows a strong binding energy of 1.82 eV assigned to the lowest-energy bound excitons that is characterized by an effective mass of 1.68m0 and a Bohr radius of 2 Å. The results of this study hold the promise for potential applications of the GeC hybrid in optoelectronics.
A self-force approach to the two-body problem: The Green function method
NASA Astrophysics Data System (ADS)
Casals, Marc
2016-06-01
The inspiral of a stellar-mass astrophysical object into a massive black hole may be modeled within perturbation theory of General Relativity via the so-called self-force. In this paper, we present a novel method for the calculation of the self-force which is based on the Green function (GF) of the wave equation satisfied by the field created by the smaller object. We review the results in [M. Casals, S. Dolan, A. C. Ottewill and B. Wardell, Phys. Rev. D 88 (2013) 044022; B. Wardell, C. R. Galley, A. Zenginoğlu, M. Casals, S. R. Dolan and A. C. Ottewill, Phys. Rev. D 89 (2014) 084021] on the GF and the self-force on a scalar charge (as a model for the gravitational case) moving on a Schwarzschild black hole spacetime. This GF method offers an appealing geometrical insight into the origin of the self-force and is a promising candidate for practical self-force calculations.
A Radiation Chemistry Code Based on the Green's Function of the Diffusion Equation
NASA Technical Reports Server (NTRS)
Plante, Ianik; Wu, Honglu
2014-01-01
Stochastic radiation track structure codes are of great interest for space radiation studies and hadron therapy in medicine. These codes are used for a many purposes, notably for microdosimetry and DNA damage studies. In the last two decades, they were also used with the Independent Reaction Times (IRT) method in the simulation of chemical reactions, to calculate the yield of various radiolytic species produced during the radiolysis of water and in chemical dosimeters. Recently, we have developed a Green's function based code to simulate reversible chemical reactions with an intermediate state, which yielded results in excellent agreement with those obtained by using the IRT method. This code was also used to simulate and the interaction of particles with membrane receptors. We are in the process of including this program for use with the Monte-Carlo track structure code Relativistic Ion Tracks (RITRACKS). This recent addition should greatly expand the capabilities of RITRACKS, notably to simulate DNA damage by both the direct and indirect effect.
NASA Technical Reports Server (NTRS)
Chrzanowski, P. L.; Misner, C. W.
1974-01-01
The scalar, electromagnetic, and gravitational geodesic-synchrotron-radiation (GSR) spectra are determined for the case of a test particle moving on a highly relativistic circular orbit about a rotating (Kerr) black hole. It is found that the spectral shape depends only weakly on the value of the angular-momentum parameter (a/M) of the black hole, but the total radiated power drops unexpectedly for a value of at least 0.95 and vanishes as the value approaches unity. A spin-dependent factor (involving the inner product of the polarization of a radiated quantum with the source) is isolated to explain the dependence of the spectral shape on the spin of the radiated field. Although the scalar wave equation is solved by separation of variables, this procedure is avoided for the vector and tensor cases by postulating a sum-over-states expansion for the Green's function similar to that found to hold in the scalar case. The terms in this sum, significant for GSR, can then be evaluated in the geometric-optics approximation without requiring the use of vector or tensor spherical harmonics.
Improved Temporal Resolution of Ambient Seismic Noise Monitoring without the Green's Function
NASA Astrophysics Data System (ADS)
Hadziioannou, Céline; Larose, Eric; Baig, Adam; Campillo, Michel
2010-05-01
Ambient noise crosscorrelations have been used on several occasions to monitor temporal variations in seismic velocity. In particular, Brenguier et al. (Science, 2008) find coseismic and postseismic velocity changes around a fault zone in Parkfield, California. In this study, and in others, it was initially assumed that a correct reconstruction of the Green's function is as necessary for temporal monitoring as it is for imaging. We show through laboratory experiments that a stable waveform reconstruction is sufficient to retrieve relative temporal variations. Armed with this knowledge, we revisit the data from Parkfield. One way to obtain a stable waveform, with an acceptable signal to noise ratio, is to average the correlations over a long period of time. However, for the application to monitoring one wants the possibility of following short-term variations. How can we resolve this conflict and improve temporal resolution without sacrificing SNR? We show that by applying an adaptive filter (Baig et al, J. Geophys. Res., 2009) to the Parkfield dataset the temporal resolution can be increased from 30 days up to 1 day. With this, we show that the velocity drop observed is coseismic with the Parkfield earthquake.
NASA Astrophysics Data System (ADS)
Martín-Ruiz, A.; Cambiaso, M.; Urrutia, L. F.
2015-12-01
Boundary effects produced by a Chern-Simons (CS) extension to electrodynamics are analyzed exploiting the Green's function (GF) method. We consider the electromagnetic field coupled to a θ term in a way that has been proposed to provide the correct low-energy effective action for topological insulators (TI). We take the θ term to be piecewise constant in different regions of space separated by a common interface Σ , which will be called the θ boundary. Features arising due to the presence of the boundary, such as magnetoelectric effects, are already known in CS extended electrodynamics, and solutions for some experimental setups have been found, each with its specific configuration of sources. In this work we illustrate a method to construct the GF that allows us to solve the CS modified field equations for a given θ boundary with otherwise arbitrary configuration of sources. The method is illustrated by solving the case of a planar θ boundary but can also be applied for cylindrical and spherical geometries for which the θ boundary can be characterized by a surface where a given coordinate remains constant. The static fields of a pointlike charge interacting with a planar TI, as described by a planar discontinuity in θ , are calculated and successfully compared with previously reported results. We also compute the force between the charge and the θ boundary by two different methods, using the energy-momentum tensor approach and the interaction energy calculated via the GF. The infinitely straight current-carrying wire is also analyzed.
A fast lattice Green's function method for solving viscous incompressible flows on unbounded domains
NASA Astrophysics Data System (ADS)
Liska, Sebastian; Colonius, Tim
2016-07-01
A computationally efficient method for solving three-dimensional, viscous, incompressible flows on unbounded domains is presented. The method formally discretizes the incompressible Navier-Stokes equations on an unbounded staggered Cartesian grid. Operations are limited to a finite computational domain through a lattice Green's function technique. This technique obtains solutions to inhomogeneous difference equations through the discrete convolution of source terms with the fundamental solutions of the discrete operators. The differential algebraic equations describing the temporal evolution of the discrete momentum equation and incompressibility constraint are numerically solved by combining an integrating factor technique for the viscous term and a half-explicit Runge-Kutta scheme for the convective term. A projection method that exploits the mimetic and commutativity properties of the discrete operators is used to efficiently solve the system of equations that arises in each stage of the time integration scheme. Linear complexity, fast computation rates, and parallel scalability are achieved using recently developed fast multipole methods for difference equations. The accuracy and physical fidelity of solutions are verified through numerical simulations of vortex rings.
NASA Astrophysics Data System (ADS)
Tang, Yong; Wu, Yue-Liang
2011-11-01
We perform an explicit one-loop calculation for the gravitational contributions to the two-, three- and four-point gauge Green's functions with paying attention to the quadratic divergences. It is shown for the first time in the diagrammatic calculation that the Slavnov-Taylor identities are preserved even if the quantum graviton effects are included at one-loop level, such a conclusion is independent of the choice of regularization schemes. We also present a regularization scheme independent calculation based on the gauge condition independent background field framework of Vilkovisky-DeWitt's effective action with focusing on both the quadratic divergence and quartic divergence that is not discussed before. With the harmonic gauge condition, the results computed by using the traditional background field method can consistently be recovered from the Vilkovisky-DeWitt's effective action approach by simply taking a limiting case, and are found to be the same as the ones yielded by the diagrammatic calculation. As a consequence, in all the calculations, the symmetry-preserving and divergent-behavior-preserving loop regularization method can consistently lead to a nontrivial gravitational contribution to the gauge coupling constant with an asymptotic free power-law running at one loop near the Planck scale.
Dyadic Green's functions for curved waveguides and cavities and their reformulation
NASA Astrophysics Data System (ADS)
Fan, Guo-Xin; Liu, Qing Huo
2002-10-01
Dyadic Green's functions (DGFs) for continuously curved waveguides are important for the feeding and radiation problems of cylindrically conformal slotted-waveguide arrays. The major difficulty in the construction of these DGFs in curved waveguides and cavities is that there are no entire-domain TE or TM modes with respect to the curving direction, while the longitudinal-section electric (LSE) and magnetic (LSM) modes do not have the complete orthogonality in terms of the dot product as required by the conventional Ohm-Rayleigh method as practiced in literature. Therefore, the conventional Ohm-Rayleigh method for constructing DGFs is not applicable to curved waveguides. In this work, the DGFs are constructed with the help of the Lorentz reciprocity theorem and the mode orthogonality based on the concept of power flow, and by adding the source singularity terms. To reduce the orders of singularity of DGFs in their application to waveguide walls, the common form of DGFs is then reformulated into a form convenient for numerical computation by both forward and backward derivation procedures. Finally, a general procedure is proposed for the reformulation of DGFs for common types of waveguides. The DGFs derived are applicable to problems with curved waveguide junctions, and coupling and radiating slots for conformal slotted-waveguide antennas.
NASA Astrophysics Data System (ADS)
Campañá, Carlos; Müser, Martin H.; Denniston, Colin; Qi, Yue; Perry, Thomas A.
2007-12-01
We study the contact mechanics of a flat, elastic wall pressed against a rigid substrate with Green's function molecular dynamics. The substrate's height profiles are parametrized from atomic force microscope topography measurements of two different aluminum-silicon alloys. In both samples, roughness lives on disparate length scales, i.e., on relatively large scales defined by size and mean separation of load-bearing silicon particles and on much smaller scales associated with the roughness on top of individual particles. The major differences between the two alloys are their silicon content and the typical silicon particle geometry. These differences lead to quite different stress distributions on both mesoscale and microscale in our calculations. A common feature is that the stress distribution decays exponentially for large stresses σ and not like a Gaussian. Persson's contact mechanics theory is generalized to the case where contact can only occur on silicon particles. This generalization predicts relatively accurate microscopic mean square stresses, however, it fails to predict accurate numbers for mean square stresses on the mesoscopic scales. Local overlap models are not accurate either, because they fail to describe the contact morphology.
Eigenfunction approach to the Green's function parabolic equation in outdoor sound: A tutorial.
Gilbert, Kenneth E
2016-03-01
Understanding the physics and mathematics underlying a computational algorithm such as the Green's function parabolic equation (GFPE) is both useful and worthwhile. To this end, the present article aims to give a more widely accessible derivation of the GFPE algorithm than was given originally by Gilbert and Di [(1993). J. Acoust. Soc. Am. 94, 2343-2352]. The present derivation, which uses mathematics familiar to most engineers and physicists, begins with the separation of variables method, a basic and well-known approach for solving partial differential equations. The method leads naturally to eigenvalue-eigenfunction equations. A step-by-step analysis arrives at relatively simple, analytic expressions for the horizontal and vertical eigenfunctions, which are sinusoids plus a surface wave. The eigenfunctions are superposed in an eigenfunction expansion to yield a one-way propagation solution. The one-way solution is generalized to obtain the GFPE algorithm. In addition, and equally important, the eigenfunctions are used to give concrete meaning to abstract operator solutions for one-way acoustic propagation. By using an eigenfunction expansion of the acoustic field, together with an operator solution, one can obtain the GFPE algorithm very directly and concisely. PMID:27036244
Aerodynamic interference effects on tilting proprotor aircraft. [using the Green function method
NASA Technical Reports Server (NTRS)
Soohoo, P.; Morino, L.; Noll, R. B.; Ham, N. D.
1977-01-01
The Green's function method was used to study tilting proprotor aircraft aerodynamics with particular application to the problem of the mutual interference of the wing-fuselage-tail-rotor wake configuration. While the formulation is valid for fully unsteady rotor aerodynamics, attention was directed to steady state aerodynamics, which was achieved by replacing the rotor with the actuator disk approximation. The use of an actuator disk analysis introduced a mathematical singularity into the formulation; this problem was studied and resolved. The pressure distribution, lift, and pitching moment were obtained for an XV-15 wing-fuselage-tail rotor configuration at various flight conditions. For the flight configurations explored, the effects of the rotor wake interference on the XV-15 tilt rotor aircraft yielded a reduction in the total lift and an increase in the nose-down pitching moment. This method provides an analytical capability that is simple to apply and can be used to investigate fuselage-tail rotor wake interference as well as to explore other rotor design problem areas.
Electron transport in extended carbon-nanotube/metal contacts: Ab initio based Green function method
NASA Astrophysics Data System (ADS)
Fediai, Artem; Ryndyk, Dmitry A.; Cuniberti, Gianaurelio
2015-04-01
We have developed a new method that is able to predict the electrical properties of the source and drain contacts in realistic carbon nanotube field effect transistors (CNTFETs). It is based on large-scale ab initio calculations combined with a Green function approach. For the first time, both internal and external parts of a realistic CNT-metal contact are taken into account at the ab initio level. We have developed the procedure allowing direct calculation of the self-energy for an extended contact. Within the method, it is possible to calculate the transmission coefficient through a contact of both finite and infinite length; the local density of states can be determined in both free and embedded CNT segments. We found perfect agreement with the experimental data for Pd and Al contacts. We have explained why CNTFETs with Pd electrodes are p -type FETs with ohmic contacts, which can carry current close to the ballistic limit (provided contact length is large enough), whereas in CNT-Al contacts transmission is suppressed to a significant extent, especially for holes.
High pressure pair distribution function studies of Green River oil shale.
Chapman, K. W.; Chupas, P. J.; Locke, D. R.; Winans, R. E.; Pugmire, R. J.; Univ. of Utah
2008-01-01
The compression behavior of a silicate-rich oil shale from the Green River formation in the pressure range 0.0-2.4 GPa was studied using in situ high pressure X-ray pair distribution function (PDF) measurements for the sample contained within a Paris-Edinburgh cell. The real-space local structural information in the PDF, G(r), was used to evaluate the compressibility of the oil shale. Specifically, the pressure-induced reduction in the medium- to long-range atom distances ({approx}6-20 {angstrom}) yielded an average sample compressibility corresponding to a bulk modulus of ca. 61-67 GPa. A structural model consisting of a three phase mixture of the principal crystalline oil shale components (quartz, albite and Illite) provided a good fit to the ambient pressure PDF data (R {approx} 30.7%). Indeed the features in the PDF beyond {approx} {angstrom}, were similarly well fit by a single phase model of the highest symmetry, highly crystalline quartz component. The factors influencing the observed compression behavior are discussed.
Fully relativistic surface green function and its application to surface spectroscopies
Tamura, E.
1993-06-30
A fully relativistic layer-KKR formalism was developed and implemented for calculating the single-particle Green function in atomic layers parallel to crystalline surfaces magnetic and non magnetic materials: The method was applied to the calculation surface spectroscopies, such as low energy electron diffraction (LEED), angle-resolve ultraviolet photo emission spectroscopy (UPS), and photoelectron scattering. Numeric tests were performed for non magnetic actinide surfaces and magnetic Fe surface Theoretical angle-resolved UPS spectra are presented for uranium monolayers on Pt(111) and for f.c.c. u(lll) surfaces. We find that u island formation can take place if a peak in the UPS spectra appears just before the Fermi energy immediately as u is deposited on P and we suggest an experimental procedure for testing this prediction. An intensity map photo excited electrons from the 2p{sub 3/2} core states of Fe(110) surface is also show Sizable magnetic anisotropy is found due to the interference between exchange and spin-orbit interaction, which is suitable for studying a possible surface-induced magnetism actinide adlayers.
A fast lattice Green's function method for solving viscous incompressible flows on unbounded domains
NASA Astrophysics Data System (ADS)
Liska, Sebastian; Colonius, Tim
2015-11-01
A novel, parallel, computationally efficient immersed boundary method for solving three-dimensional, viscous, incompressible flows on unbounded domains is presented. The method formally discretizes the incompressible Navier-Stokes equations on an infinite staggered Cartesian grid. Operations are limited to a finite computational domain through a lattice Green's function technique. This technique obtains solutions to inhomogeneous difference equations through the discrete convolution of source terms with the fundamental solutions of the discrete operators. The differential algebraic equations describing the temporal evolution of the discrete momentum equation, incompressibility constraint, and the no-slip constraint are numerically solved by combining an integrating factor technique for the viscous term and a half-explicit Runge-Kutta scheme for the convective term. A nested projection that exploits the mimetic and commutativity properties of the discrete operators is used to efficiently solve the system of equations that arises in each stage of the time integration scheme. Linear complexity, fast computation rate, and parallel scalability are achieved using recently developed fast multipole methods for difference equations. Results for three-dimensional test problems are presented, and the performance and scaling of the present implementation are discussed.
A Green's Function Approach to Simulate DNA Damage by the Indirect Effect
NASA Technical Reports Server (NTRS)
Plante, Ianik; Cicinotta, Francis A.
2013-01-01
The DNA damage is of fundamental importance in the understanding of the effects of ionizing radiation. DNA is damaged by the direct effect of radiation (e.g. direct ionization) and by indirect effect (e.g. damage by.OH radicals created by the radiolysis of water). Despite years of research, many questions on the DNA damage by ionizing radiation remains. In the recent years, the Green's functions of the diffusion equation (GFDE) have been used extensively in biochemistry [1], notably to simulate biochemical networks in time and space [2]. In our future work on DNA damage, we wish to use an approach based on the GFDE to refine existing models on the indirect effect of ionizing radiation on DNA. To do so, we will use the code RITRACKS [3] developed at the NASA Johnson Space Center to simulate the radiation track structure and calculate the position of radiolytic species after irradiation. We have also recently developed an efficient Monte-Carlo sampling algorithm for the GFDE of reversible reactions with an intermediate state [4], which can be modified and adapted to simulate DNA damage by free radicals. To do so, we will use the known reaction rate constants between radicals (OH, eaq, H,...) and the DNA bases, sugars and phosphates and use the sampling algorithms to simulate the diffusion of free radicals and chemical reactions with DNA. These techniques should help the understanding of the contribution of the indirect effect in the formation of DNA damage and double-strand breaks.
Structure, Function and Reconstitution of Antenna Complexes from Green Photosynthetic Bacteria
Robert E. Blankenship
2005-08-10
This project is concerned with the structure and function of the chlorosome antennas found in green photosynthetic bacteria. Chlorosomes are ellipsoidal structures attached to the cytoplasmic side of the inner cell membrane. These antenna complexes provide a very large absorption cross section for light capture. Evidence is overwhelming that the chlorosome represents a very different type of antenna from that found in any other photosynthetic system yet studied. It is now clear that chlorosomes do not contain traditional pigment-proteins, in which the pigments bind to specific sites on proteins. Instead, the chlorosome pigments are organized in vivo into pigment oligomers in which direct pigment-pigment interactions are of dominant importance. Our group has used a multidisciplinary approach to investigate this unique system, as well as the complexes that they directly interact with. Our work has included using model systems, numerous types of both steady-state and ultrafast spectroscopy, molecular biology, protein chemistry and X-ray crystallography. Details of our recent results using these approaches are given below and in the references. Numbers cited in the sections refer to DOE-sponsored publications that are listed below. Only publications dated 2001-2004 or later are included in this report. In addition to the primary literature reports, a comprehensive review of this area of research has been written as well as a commentary.
Ahmad, Mudasir; Baba, Waqas N; A Wani, Touseef; Gani, Asir; Gani, Adil; Shah, Umar; Wani, S M; Masoodi, F A
2015-09-01
Green tea powder (GTP) was incorporated in wheat flour at different levels (1, 2 and 4 %) and its effect on quality parameters of flour and cookies were studied. Thermal analysis showed that addition of GTP did not increase the onset temperature, end temperature and enthalpy of flour significantly. However, the increase in GTP content retarded the retro gradation of the gelatinized wheat flour gel and decreased the water absorption capacity, Oil absorption capacity, water solubility index, Foam capacity and foam stability significantly. The L* and b* values of cookies decreased from 53.63 to 33.23 and 29.02 to 24.39 respectively, while as, a* value showed an increase from 3.61 to 5.23 indirect proportion to quantity added. The addition of GTP to wheat flour increased the DPPH (2,2-diphenyl-1-picrylhydrazyl) percent inhibition and reducing power of cookies. Further, it also increases the acceptability for color, aroma and taste; however it loosened its structural integrity and decreased the fracture force. PMID:26344994
Factors affecting social integration of noninstitutionalized mentally retarded adults.
Reiter, S; Levi, A M
1980-07-01
The social integration of noninstitutionalized moderately and mildly mentally retarded young adults was investigated. A group of moderately and mildly retarded adults (study group) was compared with a group of borderline retarded (control group) adults on employability, behavior at work, social integration and social skills, personality, and self-concept. Findings indicated that the study group was less well integrated at work and in society than was the control group and showed lack of social skills. The retarded adults who had nonretarded friends showed better social-educational skills than did the other subjects. Findings suggest that even retarded individuals who grow up in the community need help in order to become socially independent. The existence of a special social club for retarded adults was found to fulfill the functions of a sheltered framework. Participants in the club showed more positive self-concepts; however, the club did not seem to prepare them for social integration in the general community. PMID:7446566
Vignettes in Mental Retardation.
ERIC Educational Resources Information Center
Crissey, Marie Skodak
1983-01-01
Described are turn-of-the-century (1900) efforts of E. Johnstone, Vineland Training School for the mentally retarded; H. Goddard, psychologist (also at Vineland); and C. Davenport, Carnegie Foundation biological laboratory, Coldspring Harbor; to identify the roles of genetic heredity and environmental impact, and thus to eradicate or ameliorate…
Epidemiology of Mental Retardation.
ERIC Educational Resources Information Center
Heber, Rick
Prevalence data on mental retardation is presented including international estimates on general prevalence, age directions, geographical variations within the United States, racial and ethnic variations, economic class distributions, family variations, and population distribution in institutions. Statistics are also provided in areas of specific…
Monkey Retardate Learning Analysis
ERIC Educational Resources Information Center
Chamove, A. S.; Molinaro, T. J.
1978-01-01
Seven rhesus monkeys reared on diets high in phenylalanine to induce phenylketonuria (PKU--a metabolic disorder associated with mental retardation if untreated) were compared with normal, pair-fed, and younger controls; frontal brain-lesioned monkeys; and those raised on high-tryptophan diets in three object discrimination tasks. (Author)
Hutchings, L.; Stavrakakis, G.N.; Ioannidou, E.; Wu, F.T.; Jarpe, S.; Kasameyer, P.
1998-01-01
We synthesize strong ground motion at three sites from a M=7.2 earthquake along the MW-trending Gulf of Cornith seismic zone. We model rupture along an 80 segment of the zone. The entire length of the fault, if activated at one time, can lead to an event comparable to that of the 1995 Kobe earthquake. With the improved digital data now routinely available, it becomes possible to use recordings of small earthquakes as empirical Green`s functions to synthesize potential ground motion for future large earthquakes. We developed a suite of 100 rupture scenarios for the earthquake and computed the commensurate strong ground motion time histories. We synthesized strong ground motion with physics-based solutions of earthquake rupture and applied physical bounds on rupture parameters. The synthesized ground motions obtained are source and site specific. By having a suite of rupture scenarios of hazardous earthquakes for a fixed magnitude and identifying the hazard to a site from the statistical distribution of engineering parameters, we have introduced a probabilistic component to the deterministic hazard calculation. The time histories suggested for engineering design are the ones that most closely match either the average or one standard deviation absolute accelerations response values.
NASA Astrophysics Data System (ADS)
Yedlin, M. J.; Virieux, J.; van Vorst, D. G.
2010-12-01
obtained by using the new uniform asymptotic expansion ansatz, which supplants the usual homogeneous transfer function employed. Examples will be presented for synthetic data sets, to illustrate the differences between these two transfer functions. References [1] E. Zauderer. 1971, Uniform asymptotic solutions of the reduced wave equation. Journal of Mathematical Analysis and Application 30, pp. 157-171. [2] M. J. Yedlin. 1987, Uniform asymptotic solution for the Green’s function for the two-dimensional acoustic equation. J. Acoust. Soc. Am. 81(2) pp. 238-243. [3] J. Tromp, C. Tape and Q. Liu. 2005, Seismic tomography, adjoint methods, time reversal and banana-doughnut kernels. Geophysical Journal International 160(1), pp. 195-216. [4] I. Iturbe, P. Roux, J. Virieux and B. Nicolas. 2009, Travel-time sensitivity kernels versus diffraction patterns obtained through double beam-forming in shallow water. J. Acoust. Soc. Am. 126(2), pp. 713-720. [5] J. R. Ernst, A. G. Green, H. Maurer and K. Holliger. 2007, Application of a new 2D time-domain full-waveform inversion scheme to crosshole radar data. Geophysics 72, pp. J53-J64.
Current breakthroughs in green nanotechnology are capable to transform many of the existing processes and products that enhance environmental quality, reduce pollution, and conserve natural and non-renewable resources. Noteworthy, successful use of metal nanoparticles and 10 nano...
Flame retardant spandex type polyurethanes
NASA Technical Reports Server (NTRS)
Howarth, J. T.; Sheth, S.; Sidman, K. R.; Massucco, A. A. (Inventor)
1978-01-01
Flame retardant elastomeric compositions were developed, comprised of: (1) spandex type polyurethane having incorporated into the polymer chain, halogen containing polyols; (2) conventional spandex type polyurethanes in physical admixture flame retardant additives; and (3) fluoroelastomeric resins in physical admixture with flame retardant additives. Methods of preparing fibers of the flame retardant elastomeric materials are presented and articles of manufacture comprised of the elastomeric materials are mentioned.
Technology Transfer Automated Retrieval System (TEKTRAN)
In this presentation, new approaches for flame retardant textile by using supercritical carbon dioxide (scCO2) and layer-by-layer processing will be discussed. Due to its environmentally benign character, the scCO2 is considered in green chemistry as a substitute for organic solvents in chemical rea...
Technology Transfer Automated Retrieval System (TEKTRAN)
In this presentation, new approaches for flame retardant textile by using supercritical carbon dioxide (scCO2) and layer-by-layer processing will be discussed. Due to its environmentally benign character, the scCO2 is considered in green chemistry as a substitute for organic solvents in chemical re...
Mental Retardation, Selected Conference Papers.
ERIC Educational Resources Information Center
Scheerenberger, R.C., Ed.
A compilation of selected papers includes the following: comprehensive diagnostic services; pediatric aspects of diagnosis; psychological evaluation of the severely retarded; use of social competency devices; diagnosis of the adult retarded; programing for the severely retarded; nursery school experiences for the trainable; a practical approach to…
Teaching the Educable Mentally Retarded.
ERIC Educational Resources Information Center
Love, Harold D.
The text discusses the behavior, evaluation, and education of mentally retarded children. Harold D. Love presents an overview of the retarded, a description of intelligence and personality tests, and a historical survey of retardation; Virginia Cantrell reviews the educational philosophies and methods of Itard, Seguin, and Montessori. Shirley K.…
Intrauterine radiation exposures and mental retardation
Miller, R.W.
1988-08-01
Small head size and mental retardation have been known as effects of intrauterine exposure to ionizing radiation since the 1920s. In the 1950s, studies of Japanese atomic-bomb survivors revealed that at 4-17 wk of gestation, the greater the dose, the smaller the brain (and head size), and that beginning at 0.5 Gy (50 rad) in Hiroshima, mental retardation increased in frequency with increasing dose. No other excess of birth defects was observed. Otake and Schull (1984) pointed out that the period of susceptibility to mental retardation coincided with that for proliferation and migration of neuronal elements from near the cerebral ventricles to the cortex. Mental retardation could be the result of interference with this process. Their analysis indicated that exposures at 8-15 wk to 0.01-0.02 Gy (1-2 rad) doubled the frequency of severe mental retardation. This estimate was based on small numbers of mentally retarded atomic-bomb survivors. Although nuclear accidents have occurred recently, new cases will hopefully be too rare to provide further information about the risk of mental retardation. It may be possible, however, to learn about lesser impairment. New psychometric tests may be helpful in detecting subtle deficits in intelligence or neurodevelopmental function. One such test is PEERAMID, which is being used in schools to identify learning disabilities due, for example, to deficits in attention, short- or long-term memory, or in sequencing information. This and other tests could be applied in evaluating survivors of intrauterine exposure to various doses of ionizing radiation. The results could change our understanding of the safety of low-dose exposures.
Sabra, Karim G
2010-06-01
It has been demonstrated theoretically and experimentally that an estimate of the Green's function between two receivers can be obtained by cross-correlating acoustic (or elastic) ambient noise recorded at these two receivers. Coherent wavefronts emerge from the noise cross-correlation time function due to the accumulated contributions over time from noise sources whose propagation path pass through both receivers. Previous theoretical studies of the performance of this passive imaging technique have assumed that no relative motion between noise sources and receivers occurs. In this article, the influence of noise sources motion (e.g., aircraft or ship) on this passive imaging technique was investigated theoretically in free space, using a stationary phase approximation, for stationary receivers. The theoretical results were extended to more complex environments, in the high-frequency regime, using first-order expansions of the Green's function. Although sources motion typically degrades the performance of wideband coherent processing schemes, such as time-delay beamforming, it was found that the Green's function estimated from ambient noise cross-correlations are not expected to be significantly affected by the Doppler effect, even for supersonic sources. Numerical Monte-Carlo simulations were conducted to confirm these theoretical predictions for both cases of subsonic and supersonic moving sources. PMID:20550258
COGNITIVE TRAINING WITH RETARDED CHILDREN, I. FINAL REPORT.
ERIC Educational Resources Information Center
CORTER, HAROLD M.; MCKINNEY, JAMES D.
THE MAJOR PURPOSE OF THIS RESEARCH WAS TO DETERMINE WHETHER TRAINING IN SPECIFIC COGNITIVE PROCESSES IS EFFECTIVE IN INCREASING THE COGNITIVE FUNCTIONING OF RETARDED CHILDREN. IN PHASE I OF THE PROJECT, 51 EDUCABLE RETARDED AND 18 NORMAL SUBJECTS RECEIVED A 20-DAY PROGRAM IN SIMILARITIES-DIFFERENCES CONCEPT FORMATION AND WERE COMPARED WITH 42…
Implicit Learning in Children and Adolescents with Mental Retardation.
ERIC Educational Resources Information Center
Vinter, Annie; Detable, Christelle
2003-01-01
A study compared the implicit learning of 58 children (ages 7-14) with mental retardation and 53 controls (ages 3-8). Individuals with mental retardation modified their behavior after an implicit training procedure similar to the controls. The effect of implicit learning did not vary as a function of IQ or age. (Contains references.) (Author/CR)
Defining Mental Retardation: A Matter of Life or Death
ERIC Educational Resources Information Center
Lichten, William; Simon, Elliot W.
2007-01-01
Because persons with mental retardation cannot be executed for murder, the diagnosis becomes a life and death matter. The American Association on Mental Retardation (now the American Association on Intellectual and Developmental Disabilities) and other associations agree that IQ alone is an insufficient criterion and adaptive functioning also…
45 CFR 1308.10 - Eligibility criteria: Mental retardation.
Code of Federal Regulations, 2010 CFR
2010-10-01
... DISABILITIES Health Services Performance Standards § 1308.10 Eligibility criteria: Mental retardation. (a) A child is classified as mentally retarded who exhibits significantly sub-average intellectual functioning and exhibits deficits in adaptive behavior which adversely affect learning. Adaptive behavior...
Defining Mental Retardation and Ensuring Access to the General Curriculum.
ERIC Educational Resources Information Center
Wehmeyer, Michael L.
2003-01-01
Discussion of trends in the American Association on Mental Retardation's definition of mental retardation notes a shift toward a support paradigm and a definition stressing the interaction between a person's independent functioning and the various contexts of the person's life. The current definition is seen to promote greater access to the…
TERMINOLOGY AND CONCEPTS IN APPRAISING THE MENTALLY RETARDED.
ERIC Educational Resources Information Center
LORGE, IRVING; AND OTHERS
THE OBJECTIVE OF THIS STUDY WAS TO MINIMIZE THE VARIABILITY IN LEGAL AND EDUCATIONAL CLASSIFICATION OF THE MENTALLY RETARDED. A SYSTEMATIC REVIEW WAS MADE OF THE SEMANTIC VARIATIONS IN THE DEFINITION OF THE MENTALLY RETARDED IN TERMS OF FUNCTIONAL ADEQUACY FOR EDUCATION, TRAINING, OR CUSTODIAL CARE. THE METHOD INVOLVED THE REVIEW OF STATUTES AND…
Becker, Peter A.; Das, Santabrata; Le, Truong E-mail: sbdas@iitg.ernet.in
2011-12-10
The acceleration of relativistic particles in a viscous accretion disk containing a standing shock is investigated as a possible explanation for the energetic outflows observed around radio-loud black holes. The energy/space distribution of the accelerated particles is computed by solving a transport equation that includes the effects of first-order Fermi acceleration, bulk advection, spatial diffusion, and particle escape. The velocity profile of the accreting gas is described using a model for shocked viscous disks recently developed by the authors, and the corresponding Green's function distribution for the accelerated particles in the disk and the outflow is obtained using a classical method based on eigenfunction analysis. The accretion-driven, diffusive shock acceleration scenario explored here is conceptually similar to the standard model for the acceleration of cosmic rays at supernova-driven shocks. However, in the disk application, the distribution of the accelerated particles is much harder than would be expected for a plane-parallel shock with the same compression ratio. Hence the disk environment plays a key role in enhancing the efficiency of the shock acceleration process. The presence of the shock helps to stabilize the disk by reducing the Bernoulli parameter, while channeling the excess binding energy into the escaping relativistic particles. In applications to M87 and Sgr A*, we find that the kinetic power in the jet is {approx}0.01 M-dot c{sup 2}, and the outflowing relativistic particles have a mean energy {approx}300 times larger than that of the thermal gas in the disk at the shock radius. Our results suggest that a standing shock may be an essential ingredient in accretion onto underfed black holes, helping to resolve the long-standing problem of the stability of advection-dominated accretion disks.
NASA Astrophysics Data System (ADS)
Choudhury, Pallabee; Chopra, Sumer; Roy, Ketan Singha; Sharma, Jyoti
2016-04-01
In this study, ground motions are estimated for scenario earthquakes of Mw 6.0, 6.5 and 7.0 at 17 sites in Gujarat region using Empirical Green's function technique. The Dholavira earthquake of June 19, 2012 (Mw 5.1) which occurred in the Kachchh region of Gujarat is considered as an element earthquake. We estimated the focal mechanism and source parameters of the element earthquake using standard methodologies. The moment tensor inversion technique is used to determine the fault plane solution (strike = 8°, dip = 51°, and rake = - 7°). The seismic moment and the stress drop are 5.6 × 1016 Nm and 120 bars respectively. The validity of the approach was tested for a smaller earthquake. A few possible directivity scenarios were also tested to find out the effect of directivity on the level of ground motions. Our study reveals that source complexities and site effects play a very important role in deciding the level of ground motions at a site which are difficult to model by GMPEs. Our results shed new light on the expected accelerations in the region and suggest that the Kachchh region can expect maximum acceleration of around 500 cm/s2 at few sites near source and around 200 cm/s2 at most of the sites located within 50 km from the epicentre for a Mw 7.0 earthquake. The estimated ground accelerations can be used by the administrators and planners for providing a guiding framework to undertake mitigation investments and activities in the region.
NASA Astrophysics Data System (ADS)
Williams, C. A.; Wallace, L. M.
2015-12-01
The Hikurangi subduction margin adjacent to the North Island, New Zealand, displays a variation in interseismic coupling behavior along strike, with shallow coupling in the north and deeper coupling in the south (Wallace et al., 2012). With new information such as an improved interface geometry, a New Zealand-wide seismic velocity model and an increased density and duration of geodetic networks, it is now possible to provide a much more detailed picture of interseismic coupling at the Hikurangi margin than in previous studies. In previous work (Williams and Wallace, 2015), we examined the effects of material property variations on slip estimates for slow slip events (SSEs) along the Hikurangi margin, and found that in cases where the slip is deep or there is good geodetic coverage above the slipping region, heterogeneous models generally predict about 20% less slip than elastic half-space models. Based on those results, we anticipate that interseismic coupling models that account for elastic heterogeneity will also predict similarly lower slip deficit rates in such regions. To explore these ideas, we are developing a new interseismic coupling model for the North Island. We use a New Zealand-wide seismic velocity model (Eberhart-Phillips et al., 2010) to provide elastic properties and an improved Hikurangi interface geometry (Williams et al., 2013) as the basis for our subduction geometry. In addition to the Hikurangi subduction interface, we generate finite element meshes for 20 additional faults that compose the North Island portion of the elastic block model of Wallace et al. (2012). We generate Green's functions for all faults using the PyLith finite element code (Aagaard et al., 2013), and then use the Defnode geodetic inversion code (McCaffrey, 1995; 2002) to invert for block rotation poles and interseismic coupling. Our revised coupling model should provide better constraints on interseismic coupling in the North Island, and should thus provide a better
Radiated Energy of Great Earthquakes from Teleseismic Empirical Green's Function Deconvolution
NASA Astrophysics Data System (ADS)
Baltay, Annemarie S.; Beroza, Gregory C.; Ide, Satoshi
2014-10-01
We expand on the empirical Green's function deconvolution method of Ide et al. (2011) to estimate radiated energy for the six largest earthquakes worldwide over the last 10 years: 2011 M w 9.0 Tohoku-Oki, 2004 M w 9.1 Sumatra, 2010 M w 8.8 Maule, 2005 M w 8.7 Nias, 2007 M w 8.5 Bengkulu, and 2012 M w 8.6 off-Sumatra. Deconvolution of P, SV and SH components gives consistent energy results that are comparable to estimates found independently by other researchers. Apparent stress for the five great thrust earthquakes is between 0.4 and 0.8 MPa, while the 2012 off-Sumatra strike-slip earthquake has a higher apparent stress of 3 MPa, which is consistent with other studies that find a tendency for strike-slip events to be more energetic. Our results are within the spread of apparent stress from the wider global earthquake population over a large magnitude range. The azimuthal distribution of energy in each case shows signs of directivity, and in some cases, shows less energy radiated in the trench-ward direction, which may suggest enhanced tsunami potential. We find that eGfs as small as ~M 6.5 can be used for teleseismic deconvolution, and that an eGf-mainshock magnitude difference of 1.5 units yields stable results. This implies that M 8 is the minimum mainshock size for which teleseismic eGf deconvolution will work well. We propose that a database of eGf events could be used to calculate radiated energy and apparent stress of great, hazardous events in near real time, i.e., promptly enough that it could contribute to rapid response measures.
NASA Astrophysics Data System (ADS)
Yao, X.; Zhang, W.
2011-12-01
The Mw 9.0 Honshu earthquake of March 11, 2011 is the largest earthquake ever recorded in Japan, and is among the 5 largest earthquakes recorded worldwide. It has been followed by a series of powerful aftershocks, with 31 events of magnitude larger than 6 in three days. It generated huge tsunami waves in the Pacific. The death toll as of April 2, 2011 exceeded 12,157 largely due to the tsunami whose amplitude overwhelmed coastal defences. In this study, we simulate the near-field strong ground motions of this earthquake by using empirical Green's function (EGF) method (Irikura, 1988) .Slip-distribution inversion results from USGS, ERI, etc. showed that there were two large asperities on the fault plane. According to these results, we selected two aftershocks whose source mechanisms were similar with the two asperities as the EGFs. Considering the epicenter distance of all selected stations is less than the fault dimension of the 2011 Honshu Earthquake, we did not estimate the parameter of EGF (C and N) by the source spectral fitting method, but directly applied the scaling relation (Somerville et al., 1999) to estimate the size of strong motion generation area (SMGA) in the rupture area of the main-shock, and then use the genetic algorithm (GA) to get the best values of the parameter of C (related the stress drop) and the source rise-time by fitting the envelope of the synthetic broadband waveforms with that of the observed records. Based on the source model, we simulated the near-field strong ground motions. Our result shows that most of the syntheti waveforms agreed well with the observed records in the frequency range from 0.5 Hz to 10 Hz. Our result also shows that the source rise-time we obtained is smaller than the extrapolation of the scaling law proposed by Somerville et al. (1999).
Nie, Chuanxiong; Cheng, Chong; Ma, Lang; Deng, Jie; Zhao, Changsheng
2016-06-14
Nanointerfacial decoration of silver nanoparticles (AgNPs) is an ideal protocol to improve the antibacterial efficiency of diverse nanomaterials, including carbon nanotube (CNT), graphene, and many other intensively studied nanoarchitectures, which provides a tremendous possibility for designing advanced antibacterial biomaterials and biomedical devices. However, the direct exposure of AgNPs will lead to potential mammalian cell apoptosis and death, which significantly limits their biological applications. In this study, we demonstrated a green and one-step approach to achieve robust antibacterial and highly biocompatible AgNP-CNT composites. AgNPs were produced via mussel-inspired "one-step" in situ reduction and coating process and were anchored onto the surface of a CNT. Simultaneously, protective polymer layers were formed to shield the AgNPs to improve their biocompatibility. Because of the bactericidal efficiency of AgNPs, the composites showed robust antibacterial efficiency in terms of both inhibition of bacterial cell growth and bacterial killing activity. Moreover, owing to the shielding effects of the polymer coatings, the nanocomposites exhibited much improved compatibility with human umbilical vein endothelial cells compared with bare AgNP-CNTs. Furthermore, the nanocomposites exhibited good stability in psychological solutions. With integrated excellent antibacterial activity, cell compatibility, and long-term stability, it is believed that the synthesized AgNP-CNT composites will be of promising potential in antibacterial applications. Meanwhile, the proposed strategies can also be applied to fabricate many other kinds of AgNP-based composites because of the versatile functionality of catecholic polymers. PMID:27189807
2-D Modeling of Nanoscale MOSFETs: Non-Equilibrium Green's Function Approach
NASA Technical Reports Server (NTRS)
Svizhenko, Alexei; Anantram, M. P.; Govindan, T. R.; Biegel, Bryan
2001-01-01
We have developed physical approximations and computer code capable of realistically simulating 2-D nanoscale transistors, using the non-equilibrium Green's function (NEGF) method. This is the most accurate full quantum model yet applied to 2-D device simulation. Open boundary conditions and oxide tunneling are treated on an equal footing. Electrons in the ellipsoids of the conduction band are treated within the anisotropic effective mass approximation. Electron-electron interaction is treated within Hartree approximation by solving NEGF and Poisson equations self-consistently. For the calculations presented here, parallelization is performed by distributing the solution of NEGF equations to various processors, energy wise. We present simulation of the "benchmark" MIT 25nm and 90nm MOSFETs and compare our results to those from the drift-diffusion simulator and the quantum-corrected results available. In the 25nm MOSFET, the channel length is less than ten times the electron wavelength, and the electron scattering time is comparable to its transit time. Our main results are: (1) Simulated drain subthreshold current characteristics are shown, where the potential profiles are calculated self-consistently by the corresponding simulation methods. The current predicted by our quantum simulation has smaller subthreshold slope of the Vg dependence which results in higher threshold voltage. (2) When gate oxide thickness is less than 2 nm, gate oxide leakage is a primary factor which determines off-current of a MOSFET (3) Using our 2-D NEGF simulator, we found several ways to drastically decrease oxide leakage current without compromising drive current. (4) Quantum mechanically calculated electron density is much smaller than the background doping density in the poly silicon gate region near oxide interface. This creates an additional effective gate voltage. Different ways to. include this effect approximately will be discussed.
Yin, Jie; Tao, Chao Cai, Peng; Liu, Xiaojun
2015-06-08
Acoustically inhomogeneous mediums with multiple scattering are often the nightmare of photoacoustic tomography. In order to break this limitation, a photoacoustic tomography scheme combining ultrasound interferometry and time reversal is proposed to achieve images in acoustically scattering medium. An ultrasound interferometry is developed to determine the unknown Green's function of strong scattering tissue. Using the determined Greens' function, a time-reversal process is carried out to restore images behind an acoustically inhomogeneous layer from the scattering photoacoustic signals. This method effectively decreases the false contrast, noise, and position deviation of images induced by the multiple scattering. Phantom experiment is carried out to validate the method. Therefore, the proposed method could have potential value in extending the biomedical applications of photoacoustic tomography in acoustically inhomogeneous tissue.
NASA Astrophysics Data System (ADS)
Lambot, Sébastien; Slob, Evert; Vereecken, Harry
2007-11-01
We propose an efficient integration path for the fast evaluation of the three-dimensional spatial-domain Green's function for electromagnetic wave propagation in layered media for the particular case of zero-offset, source-receiver proximal ground-penetrating radar (GPR) applications. The integration path is deformed in the complex plane of the integration variable k ρ so that the oscillations of the dominant exponential term in the spectral Green's function are minimized. The contour does not need to be closed back on the real k ρ axis as the complex integrand rapidly damps. The accuracy and efficiency of the technique have been confirmed by comparison with traditional elliptic integration contours. The proposed algorithm appears to be promising development for fast, full-wave modeling and inversion of GPR data.
NASA Astrophysics Data System (ADS)
Naber, R. R.; Bahai, H.; Jones, B. E.
2006-05-01
The ability to model acoustic emission (AE) plays an important role in advancing the reliability of AE source characterisation. In this paper, an efficient numerical approach is proposed for modelling AE waves in isotropic solids. The approach is based on evaluating the reciprocal band-limited Green's functions using the finite element (FE) method. In the first section, known analytical solutions of the Green's function for an elastic isotropic infinite plate subjected to point monopole surface loading are used to validate the approach. Then, a study investigating the effects of the spatial resolution of the FE model on the accuracy of the numerical solutions is presented. Furthermore, comparisons between numerical calculations and experimental measurements are presented for a glass plate subjected to two known AE sources (pencil lead break and ball impact). Finally, the reciprocal relation between the source and the receiver is confirmed using numerical simulations of a plane stress model of an elastic isotropic plate.
Prociuk, Alexander; Van Kuiken, Ben; Dunietz, Barry D
2006-11-28
Electronic transmission through a metal-molecule-metal system is calculated by employing a Green's function formalism in the scattering based scheme. Self-energy models representing the bulk and the potential bias are used to describe electron transport through the molecular system. Different self-energies can be defined by varying the partition between device and bulk regions of the metal-molecule-metal model system. In addition, the self-energies are calculated with different representations of the bulk through its Green's function. In this work, the dependence of the calculated transmission on varying the self-energy subspaces is benchmarked. The calculated transmission is monitored with respect to the different choices defining the self-energy model. In this report, we focus on one-dimensional model systems with electronic structures calculated at the density functional level of theory. PMID:17144733
ERIC Educational Resources Information Center
National Association for Retarded Children, Arlington, TX. South Central Regional Office.
The first of a series of four booklets on residential programing for the mentally retarded reviews for parents the prevailing definitions, attitudes and practices in the field. Mental retardation is defined as subaverage functioning which originates during the developmental period and is associated with impairment in adaptive behavior. The need…
NASA Astrophysics Data System (ADS)
Yedlin, Matthew; Virieux, Jean
2010-05-01
As data collection in both seismic data acquisition and radar continues to improve, more emphasis is being placed on data pre-processing and inversion, in particular frequency domain waveform inversion in seismology [1], and, for example, time-domain waveform inversion in crosshole radar measurements [2]. Complementary to these methods are the sensitivity kernel techniques established initially in seismology [3, 4]. However, these methods have also been employed in crosshole radar tomography [5]. The sensitivity kernel technique has most recently been applied to the analysis of diffraction of waves in shallow water [6]. Central to the sensitivity kernel techniques is the use of an appropriate Green's function in either two or three dimensions and a background model is assumed for the calculation of the Green's function. In some situations, the constant velocity Green's function is used [5] but in other situations a smooth background model is used in a ray-type approximation. In the case of the smooth background model, computation of a ray-tracing type Green's function is problematic since at the source point the rays convergence, creating a singularity in the computation of the Jacobian used in the amplitude calculation. In fact the source is an axial caustic in two dimensions and a point caustic in three dimensions [7]. To obviate this problem, we will create a uniform asymptotic ansatz [8], explaining in detail how it is obtained in two dimensions. We will then show how to extend the results to three dimensions. In both cases, the Green's function will be obtained in the frequency domain for the acoustic equation with smoothly varying density and bulk modulus. The application of the new Green's function technique will provide more flexibility in the computation of sensitivities, both in seismological and radar applications. References [1] R. G. Pratt. 1999, Seismic waveform inversion in the frequency domain, part 1: Theory and verification in a physical scale
READINESS AND READING FOR THE RETARDED CHILD.
ERIC Educational Resources Information Center
BERNSTEIN, BEBE
THIS TEACHER'S BOOK AND MANUAL, DESIGNED TO ACCOMPANY TWO WORKBOOKS, PRESENTS A FUNCTIONAL APPROACH TO READINESS AND READING FOR YOUNG EDUCABLE RETARDED CHILDREN. THE WORKBOOKS THEMSELVES OFFER PREPARATORY ACTIVITIES FOR CHILDREN AT THE READINESS LEVEL AND SEQUENTIAL ACTIVITIES AND MATERIALS FOR THOSE AT THE BEGINNING READING STAGE. THE TEACHER'S…
Green's function approximation from cross-correlations of 20-100 Hz noise during a tropical storm.
Brooks, Laura A; Gerstoft, Peter
2009-02-01
Approximation of Green's functions through cross-correlation of acoustic signals in the ocean, a method referred to as ocean acoustic interferometry, is potentially useful for estimating parameters in the ocean environment. Travel times of the main propagation paths between hydrophone pairs were estimated from interferometry of ocean noise data that were collected on three L-shaped arrays off the New Jersey coast while Tropical Storm Ernesto passed nearby. Examination of the individual noise spectra and their mutual coherence reveals that the coherently propagating noise is dominated by signals of less than 100 Hz. Several time and frequency noise normalization techniques were applied to the low frequency data in order to determine the effectiveness of each technique for ocean acoustic applications. Travel times corresponding to the envelope peaks of the noise cross-correlation time derivatives of data were extracted from all three arrays, and are shown to be in agreement with the expected direct, surface-reflected, and surface-bottom-reflected interarray hydrophone travel times. The extracted Green's function depends on the propagating noise. The Green's function paths that propagate horizontally are extracted from long distance shipping noise, and during the storm the more vertical paths are extracted from breaking waves. PMID:19206850
NASA Astrophysics Data System (ADS)
Phillips, Jordan J.; Zgid, Dominika
2014-06-01
We report an implementation of self-consistent Green's function many-body theory within a second-order approximation (GF2) for application with molecular systems. This is done by iterative solution of the Dyson equation expressed in matrix form in an atomic orbital basis, where the Green's function and self-energy are built on the imaginary frequency and imaginary time domain, respectively, and fast Fourier transform is used to efficiently transform these quantities as needed. We apply this method to several archetypical examples of strong correlation, such as a H32 finite lattice that displays a highly multireference electronic ground state even at equilibrium lattice spacing. In all cases, GF2 gives a physically meaningful description of the metal to insulator transition in these systems, without resorting to spin-symmetry breaking. Our results show that self-consistent Green's function many-body theory offers a viable route to describing strong correlations while remaining within a computationally tractable single-particle formalism.
Phillips, Jordan J. Zgid, Dominika
2014-06-28
We report an implementation of self-consistent Green's function many-body theory within a second-order approximation (GF2) for application with molecular systems. This is done by iterative solution of the Dyson equation expressed in matrix form in an atomic orbital basis, where the Green's function and self-energy are built on the imaginary frequency and imaginary time domain, respectively, and fast Fourier transform is used to efficiently transform these quantities as needed. We apply this method to several archetypical examples of strong correlation, such as a H{sub 32} finite lattice that displays a highly multireference electronic ground state even at equilibrium lattice spacing. In all cases, GF2 gives a physically meaningful description of the metal to insulator transition in these systems, without resorting to spin-symmetry breaking. Our results show that self-consistent Green's function many-body theory offers a viable route to describing strong correlations while remaining within a computationally tractable single-particle formalism.
Basin-scale Green's functions from the ambient seismic field recorded by MeSO-net stations
NASA Astrophysics Data System (ADS)
Viens, Loïc.; Koketsu, Kazuki; Miyake, Hiroe; Sakai, Shin'ichi; Nakagawa, Shigeki
2016-04-01
Seismic waves propagating through the Earth can be significantly affected by velocity structures such as sedimentary basins. We investigate the propagation characteristics of seismic waves across the Kanto basin, Japan, using Green's functions extracted from the ambient seismic field. We use two stations situated on the eastern and southern edges of the basin as virtual sources, and approximately 420 stations, which are mainly a part of the Metropolitan Seismic Observation network (MeSO-net), as receivers. Using seismometers aligned along two straight lines with the virtual sources, we find that several types of waves can be recovered, each with different sensitivities to the layers that compose the basin. We also show that after amplitude calibration, the extracted Green's functions can accurately simulate the seismic waves of two moderate Mw 4-5 shallow earthquakes that occurred close to the virtual sources. Furthermore, we find that the distribution of the 5% damped pseudovelocity response at a period of 6 s computed from the records of each event and the Green's function waveforms have similar amplification patterns. This study supports the fact that dense networks recording continuously the ambient seismic field in metropolitan areas can be used to accurately assess seismic hazard at high spatial resolution.
NASA Astrophysics Data System (ADS)
Drews, M. J.
Despite a reduction in Federal regulatory activity, research concerned with flame retardancy and smoke suppression in the private sector appears to be increasing. This trend seem related to the increased utilization of plastics for end uses which traditionally have employed metal or wood products. As a result, new markets have appeared for thermally stable and fire resistance thermoplastic materials, and this in turn has spurred research and development activity. In addition, public awareness of the dangers associated with fire has increased as a result of several highly publicized hotel and restaurant fires within the past two years. The consumers recognition of flammability characteristics as important materials property considerations has increased. The current status of fire and smoke retardant chemistry and research are summarized.
NASA Technical Reports Server (NTRS)
Thompson, C. M.; Smith, J. G., Jr.; Connell, J. W.; Hergenrother, P. M.; Lyon, R. E.
2004-01-01
As part of a program to develop fire resistant exterior composite structures for future subsonic commercial aircraft, flame retardant epoxy resins are under investigation. Epoxies and their curing agents (aromatic diamines) containing phosphorus were synthesized and used to prepare epoxy formulations. Phosphorus was incorporated within the backbone of the epoxy resin and not used as an additive. The resulting cured epoxies were characterized by thermogravimetric analysis, propane torch test, elemental analysis and microscale combustion calorimetry. Several formulations showed excellent flame retardation with phosphorous contents as low as 1.5% by weight. The fracture toughness of plaques of several cured formulations was determined on single-edge notched bend specimens. The chemistry and properties of these new epoxy formulations are discussed.
NASA Astrophysics Data System (ADS)
Sato, Haruo
2013-05-01
For imaging the earth structure, the cross-correlation function (CCF) of random waves as ambient noise or coda waves has been widely used for the estimation of the Green's function. We precisely study the condition for the Green's function retrieval in relation to the energy conservation for a single obstacle of arbitrary shape. When an obstacle is placed in a 2-D homogeneous medium, the Green's function is written by a double series expansion using Hankel functions of the first kind which represent outgoing waves. When two receivers and the scattering obstacle are illuminated by uncorrelated noise sources randomly and uniformly distributed on a closed circle of a large radius surrounding them, the lag-time derivative of the CCF of random waves at the two receivers can be written by a convolution of the antisymmetrized Green's function and the autocorrelation function of the noise source time function. We explicitly derive the constraint for the Hankel function expansion coefficients as the sufficient condition for the Green's function retrieval. We show that the constraint is equal to the generalized optical theorem derived from the energy conservation principle. Physical meaning of the generalized optical theorem becomes clear when the Hankel function expansion coefficients are transformed into scattering amplitudes in the framework of the conventional scattering theory. In the 3-D case, the Green's function is written by a double series expansion using spherical Hankel functions of the first kind and spherical harmonic functions. When two receivers and the scattering obstacle are illuminated by noise sources randomly and uniformly distributed on a closed spherical shell of a large radius surrounding them, we explicitly derive the constraint for the spherical Hankel function expansion coefficients for the Green's function retrieval and the energy conservation. We note that the derivation of the constraint does not assume that two receivers are in the far field of
NASA Astrophysics Data System (ADS)
Hopjan, M.; Karlsson, D.; Ydman, S.; Verdozzi, C.; Almbladh, C.-O.
2016-06-01
We propose a description of nonequilibrium systems via a simple protocol that combines exchange-correlation potentials from density functional theory with self-energies of many-body perturbation theory. The approach, aimed to avoid double counting of interactions, is tested against exact results in Hubbard-type systems, with respect to interaction strength, perturbation speed and inhomogeneity, and system dimensionality and size. In many regimes, we find significant improvement over adiabatic time dependent density functional theory or second Born nonequilibrium Green's function approximations. We briefly discuss the reasons for the residual discrepancies, and directions for future work.
Hopjan, M; Karlsson, D; Ydman, S; Verdozzi, C; Almbladh, C-O
2016-06-10
We propose a description of nonequilibrium systems via a simple protocol that combines exchange-correlation potentials from density functional theory with self-energies of many-body perturbation theory. The approach, aimed to avoid double counting of interactions, is tested against exact results in Hubbard-type systems, with respect to interaction strength, perturbation speed and inhomogeneity, and system dimensionality and size. In many regimes, we find significant improvement over adiabatic time dependent density functional theory or second Born nonequilibrium Green's function approximations. We briefly discuss the reasons for the residual discrepancies, and directions for future work. PMID:27341247
2012-01-01
Background Bathycoccus prasinos is an extremely small cosmopolitan marine green alga whose cells are covered with intricate spider's web patterned scales that develop within the Golgi cisternae before their transport to the cell surface. The objective of this work is to sequence and analyze its genome, and to present a comparative analysis with other known genomes of the green lineage. Research Its small genome of 15 Mb consists of 19 chromosomes and lacks transposons. Although 70% of all B. prasinos genes share similarities with other Viridiplantae genes, up to 428 genes were probably acquired by horizontal gene transfer, mainly from other eukaryotes. Two chromosomes, one big and one small, are atypical, an unusual synapomorphic feature within the Mamiellales. Genes on these atypical outlier chromosomes show lower GC content and a significant fraction of putative horizontal gene transfer genes. Whereas the small outlier chromosome lacks colinearity with other Mamiellales and contains many unknown genes without homologs in other species, the big outlier shows a higher intron content, increased expression levels and a unique clustering pattern of housekeeping functionalities. Four gene families are highly expanded in B. prasinos, including sialyltransferases, sialidases, ankyrin repeats and zinc ion-binding genes, and we hypothesize that these genes are associated with the process of scale biogenesis. Conclusion The minimal genomes of the Mamiellophyceae provide a baseline for evolutionary and functional analyses of metabolic processes in green plants. PMID:22925495
NASA Astrophysics Data System (ADS)
Grabchev, Ivo; Mokreva, Pavlina; Gancheva, Valeria; Terlemezyan, Levon
2013-04-01
Two new green fluorescence poly(propyleneamine) dendrimers from second generation, comprising eight 1,8-naphthalimide signaling units in their periphery have been synthesized and investigated. Тheir photophysical characteristics have been determined in organic solvents of different polarity. Particular attention has been paid to the spectral characteristics of the solid dendrimer films. The photostability of the dendrimers has also been studied.
NASA Astrophysics Data System (ADS)
Martín-Ruiz, A.; Cambiaso, M.; Urrutia, L. F.
2016-02-01
The Green's function method is used to analyze the boundary effects produced by a Chern-Simons extension to electrodynamics. We consider the electromagnetic field coupled to a θ term that is piecewise constant in different regions of space, separated by a common interface Σ , the θ boundary, model which we will refer to as θ electrodynamics. This model provides a correct low-energy effective action for describing topological insulators. Features arising due to the presence of the boundary, such as magnetoelectric effects, are already known in Chern-Simons extended electrodynamics, and solutions for some experimental setups have been found with a specific configuration of sources. In this work we construct the static Green's function in θ electrodynamics for different geometrical configurations of the θ boundary, namely, planar, spherical and cylindrical θ -interfaces. Also, we adapt the standard Green's theorem to include the effects of the θ boundary. These are the most important results of our work, since they allow one to obtain the corresponding static electric and magnetic fields for arbitrary sources and arbitrary boundary conditions in the given geometries. Also, the method provides a well-defined starting point for either analytical or numerical approximations in the cases where the exact analytical calculations are not possible. Explicit solutions for simple cases in each of the aforementioned geometries for θ boundaries are provided. On the one hand, the adapted Green's theorem is illustrated by studying the problem of a pointlike electric charge interacting with a planar topological insulator with prescribed boundary conditions. On the other hand, we calculate the electric and magnetic static fields produced by the following sources: (i) a pointlike electric charge near a spherical θ boundary, (ii) an infinitely straight current-carrying wire near a cylindrical θ boundary and (iii) an infinitely straight uniformly charged wire near a
Experimental Study of the Convergence of Two-Point Cross-Correlation Toward the Green's Function
NASA Astrophysics Data System (ADS)
Gouedard, P.; Roux, P.; Campillo, M.; Verdel, A.; Campman, X.
2007-12-01
It has been shown theoretically by several authors that cross-correlation of the seismic motion recorded at two points could yield the Green's Function (GF) between these points. Convergence of cross-correlations toward the GF depends on sources positions and/or the nature of the wavefield. Direct waves from an even distribution of sources can be used to retrieve the GF. On the other hand, in an inhomogeneous medium, recording the diffuse field (coda) is theoretically sufficient to retrieve the GF whatever the sources distribution is. Since none of these two conditions (even distribution of sources or a perfectly diffuse field) is satisfied in practice, the question of convergence toward the GF has to be investigated with real data. A 3D exploration survey with sources and receivers on a dense grid offers such an opportunity. We used a high- resolution survey recorded by Petroleum Development Oman in North Oman. The data have been obtained in a 1x1~km area covered with 1600 geophones located on a 25x25~m-cell grid. Records are 4-seconds long. A unique feature of this survey is that vibrators (working in the [8-120~Hz] frequency band), were located on a similar grid shifted with respect to the receiver grid by half a cell (12.5~m) in both directions. This allows us to compare estimated GF's with measured direct waves (GF's) between the geophones. The shallow subsurface is highly heterogeneous and records include seismic coda. From this dataset, we selected two receiver locations (Ra and Rb) distant from d=158~m. We used both different sets of source locations and time windows to compute the cross-correlation between these two receivers. Then we compared the derivatives of correlation functions with the actual GF measured in Rb (resp.~Ra) for a source close to Ra (resp.~Rb). By doing so, we show the actual influence of source locations and scattering (governed by the records' selected time window) on the Signal-to-Noise Ratio (SNR) of the reconstructed GF. When using
NASA Astrophysics Data System (ADS)
Pavao-Zuckerman, M.
2010-12-01
As rates of urbanization continue to rise and a greater proportion of the population lives in urban and suburban areas, the provision of ecological services and functions become increasingly important to sustain human and environmental health in urban ecosystems. Soils play a primary role in the healthy functioning of ecosystems that provide supporting, provisioning, regulating, preserving, and cultural ecosystem services, yet developing our understanding of how urban soils function to provide these services within an ecological context is just getting underway. Soils in urban ecosytems are highly heterogeneous, and are affected by both direct and indirect influences and local modifications which alter their functioning relative to non-urbanized local soils. Here I discuss the functioning of rain gardens in and around Tucson, AZ, that have been installed in the urban landscape with the purpose of providing various ecosystem services to local residents and the greater urban ecosystem. This reconnection of ecohydrologic flows in the city has the potential to alter the structure and function of urban ecosystems in positive (through the increase in water availability) and negative (through the import of pollutants to soils) ways. This study compares soil properties, microbial function, and ecosystem functions within the urban ecosystem to determine how urbanization alters soils in semi-arid environments, and to determine if green urban modifications in desert cities can improve soils and ecosystem services. Soils in rain gardens have nearly twice the organic matter contents of native and urban soils, and correspondingly, greater microbial function (as indicated through respiration potential), higher abundance (through substrate induced respiration), and community complexity (indicated by a 3x increase in metabolic diversity) in these green design modifications. Net N-mineralization rates are almost 1.5 times faster in the rain garden basins than urban soils in general
NASA Astrophysics Data System (ADS)
Chibani, Wael; Ren, Xinguo; Scheffler, Matthias; Rinke, Patrick
2016-04-01
We present an embedding scheme for periodic systems that facilitates the treatment of the physically important part (here a unit cell or a supercell) with advanced electronic structure methods, that are computationally too expensive for periodic systems. The rest of the periodic system is treated with computationally less demanding approaches, e.g., Kohn-Sham density-functional theory, in a self-consistent manner. Our scheme is based on the concept of dynamical mean-field theory formulated in terms of Green's functions. Our real-space dynamical mean-field embedding scheme features two nested Dyson equations, one for the embedded cluster and another for the periodic surrounding. The total energy is computed from the resulting Green's functions. The performance of our scheme is demonstrated by treating the embedded region with hybrid functionals and many-body perturbation theory in the GW approach for simple bulk systems. The total energy and the density of states converge rapidly with respect to the computational parameters and approach their bulk limit with increasing cluster (i.e., computational supercell) size.
Campos, Patricia M B G Maia; Gianeti, Mirela D; Mercurio, Daiane G; Gaspar, Lorena R
2014-09-01
This study aimed to evaluate the effects of cosmetic formulations containing green tea (GT) and/or Ginkgo biloba (GB) extracts by preclinical and clinical studies. For the preclinical study, histological analysis was performed after 5 day-period of formulations application on the dorsum of hairless mice. For the clinical study, the formulations were applied on the forearm skin of 48 volunteers, and assessed before and after 3 hours and after a 15 and 30 day-period of application. Histological analysis showed that the formulation with GT (FGT) and the association of GT and GB (FBlend) significantly enhanced viable epidermis thickness and the number of cell layers, suggesting a moisturizing effect in skin deeper layers and increased cell renewal. The clinical efficacy studies showed that the extracts had a moisturizing effect and improved skin microrelief. In addition they synergistically acted on the skin elasticity and skin barrier function. In conclusion, the formulation containing a combination of green tea and Ginkgo biloba extracts effectively improved skin conditions and the effect of formulation FBlend on the improvement of skin elasticity was more pronounced. Finally, the results of the present study revealed other important clinical benefits of Ginkgo biloba and green tea extracts on the skin besides their already known antioxidant action. PMID:25226010
Severino, Joyce Ferreira; Goodman, Bernard A; Kay, Christopher W M; Stolze, Klaus; Tunega, Daniel; Reichenauer, Thomas G; Pirker, Katharina F
2009-04-15
Electron paramagnetic resonance spectroscopy and density functional theory calculations have been used to investigate the redox properties of the green tea polyphenols (GTPs) (-)-epigallocatechin gallate (EGCG), (-)-epigallocatechin (EGC), and (-)-epicatechin gallate (ECG). Aqueous extracts of green tea and these individual phenols were autoxidized at alkaline pH and oxidized by superoxide anion (O(2)(-)) radicals in dimethyl sulfoxide. Several new aspects of the free radical chemistry of GTPs were revealed. EGCG can be oxidized on both the B and the D ring. The B ring was the main oxidation site during autoxidation, but the D ring was the preferred site for O(2)(-) oxidation. Oxidation of the D ring was followed by structural degradation, leading to generation of a radical identical to that of oxidized gallic acid. Alkaline autoxidation of green tea extracts produced four radicals that were related to products of the oxidation of EGCG, EGC, ECG, and gallic acid, whereas the spectra from O(2)(-) oxidation could be explained solely by radicals generated from EGCG. Assignments of hyperfine coupling constants were made by DFT calculations, allowing the identities of the radicals observed to be confirmed. PMID:19439236
Ghosh, Somdatta; Xie, Xiangjin; Dey, Abhishek; Sun, Yan; Scholes, Charles P.; Solomon, Edward I.
2009-01-01
A combination of spectroscopies and density functional theory calculations indicate that there are large temperature-dependent absorption spectral changes present in green nitrite reductases (NiRs) due to a thermodynamic equilibrium between a green and a blue type 1 (T1) copper site. The axial methionine (Met) ligand is unconstrained in the oxidized NiRs, which results in an enthalpically favored (ΔH ≈4.6 kcal/mol) Met-bound green copper site at low temperatures, and an entropically favored (TΔS ≈4.5 kcal/mol, at room temperature) Met-elongated blue copper site at elevated temperatures. In contrast to the NiRs, the classic blue copper sites in plastocyanin and azurin show no temperature-dependent behavior, indicating that a single species is present at all temperatures. For these blue copper proteins, the polypeptide matrix opposes the gain in entropy that would be associated with the loss of the weak axial Met ligand at physiological temperatures by constraining its coordination to copper. The potential energy surfaces of Met binding indicate that it stabilizes the oxidized state more than the reduced state. This provides a mechanism to tune down the reduction potential of blue copper sites by >200 mV. PMID:19282479
Activational Peaking in Educable and Trainable Mentally Retarded Persons
ERIC Educational Resources Information Center
Gargiulo, Richard M.; Uno, Tad
1977-01-01
A study involving 10 educable and 10 trainable mentally retarded adolescents indicated that levels of intellectual functioning influenced patterns of autonomic activation as measured by magnitude of the galvanic skin response. (CL)
Hierarchical Semantic Organization in Educable Mentally Retarded Children.
ERIC Educational Resources Information Center
Bender, Nila N.; Johnson, N. S.
1979-01-01
Investigates the extent to which educable mentally retarded (EMR) children make functional use of a hierarchical class inclusion system in a memory retrieval task that does not have experimenter-imposed input organization. (MP)
Cue Selection in Verbal Discrimination Learning of Retarded Subjects
ERIC Educational Resources Information Center
Ashford, Donnell C.; Baumeister, Alfred A.
1975-01-01
Presents a series of these experiments which examined cue function in trigram verbal discrimination learning by retarded subjects. The two variables of chief interest were: (1) trigram meaningfulness, and (2) reinforcement history. (Author/LLK)
Analysis of Laboratory Simulations of Volcanic Hybrid Earthquakes using Empirical Green's Functions
NASA Astrophysics Data System (ADS)
Harrington, R. M.; Benson, P. M.
2010-12-01
Volcanic hybrid earthquakes often precede explosive volcanic eruptions by hours to days, and are therefore frequently used for short term eruption forecasting. In spite of their predictive capabilities, their high-frequency onsets which transition to protracted low-frequency ringing make inferring a source mechanism a perplexing task. Complex models involving some combination of elastic shear, fluid, fluid shear, and their interactions are commonly invoked to explain their mechanism. However, some field observations suggest that the highly attenuating, complex travel path in a volcanic edifice may be responsible for some portion of the low-frequency part of the waveform. Resolving the ambiguity in the role of fluids in hybrid generation is an important factor in understanding eruption dynamics, as it would better facilitate our ability to provide accurate forecasts of how explosive a given eruption may be. Here we present a new analysis of experimental simulations of volcanic hybrid signals, in efforts to better understand their origin. We examine the waveforms of laboratory microseismic events generated during two rock deformation experiments performed on samples of Mt. Etna basalt to determine their source characteristics and establish evidence for a mode of failure. Events were recorded during deformation under (a), unsaturated (dry) conditions, and (b), samples saturated with water. We employ an empirical Green's function approach to isolate the acoustic emission source spectra from attenuation and travel path effects, and estimate the spectral corner frequency using a least-squares fit to a Brune spectral model. Spectral fits indicate that the acoustic emission events occurring under dry conditions follow the expected scaling of moment and corner frequency for standard brittle-failure in an elastic medium with constant stress drop, namely M0 ∝ fc-3. Events occurring during the decompression phase of the saturated experiment have estimated corner frequencies
NASA Astrophysics Data System (ADS)
Kevorkyants, S. S.
2012-11-01
The system of Biot vector equations in the frequency space includes two elliptic-type vector partial differential equations with unknown displacement vectors in the solid and liquid phases. Considering the Biot equations, alongside with Pride's equations, the key approaches to the theoretical study of the elastic waves in the two-phase fluid-saturated media, the author suggests an analytical solution for the inhomogeneous Biot equations in the frequency space, which is reduced to finding its fundamental solution (Green's function). The solution of this problem consists of solutions for two systems of Biot equations. In the first system, only the first equation is inhomogeneous, while in the second system, only the second equation is inhomogeneous and, as it is shown, its right-hand side is exclusively a potential function. The fundamental solution of the full system of inhomogeneous Biot equations (in which both equations are inhomogeneous) is represented in the form of Green's matrix-tensor, for the scalar elements of which the analytical relations are presented. The obtained formulas describing the elastic displacements of both the solid and liquid phases reflect three wave types, namely, compressional waves of the first and the second kind (the fast and the slow waves, respectively) and shear waves. Similar terms (those describing the same type of the elastic waves in the solid and liquid phases) in the expressions for Green's functions are linked with each other through the coefficient that links the components of the displacement vectors of the solid and liquid phases corresponding to the given wave type.
Intumescent Coatings as Fire Retardants
NASA Technical Reports Server (NTRS)
Parker, J. A.; Fohlen, G. M.; Sawko, P. M.; Fish, R. H.
1970-01-01
The development of fire-retardant coatings to protect surfaces which may be exposed to fire or extreme heat is a subject of intense interest to many industries. A fire-retardant paint has been developed which represents a new chemical approach for preparing intumescent coatings, and potentially, is very important to fire-prevention authorities. The requirements for a superior coating include ease of application, suitability to a wide variety of surfaces and finishes, and stability over an extended period of time within a broad range of ambient temperature and humidity conditions. These innovative coatings, when activated by the heat of a fire, react to form a thick, low-density, polymeric coating or char layer. Water vapor and sulphur dioxide are released during the intumescent reaction. Two fire-protection mechanisms thus become available: (1) the char layer retards the flow of heat, due to the extremely low thermal conductivity; and (2) water vapor and sulfur dioxide are released, providing fire quenching properties. Still another mechanism functions in cases where the char, by virtue of its high oxidation resistance and low thermal conductivity, reaches a sufficiently high temperature to re-radiate much of the incident heat load. The coatings consist of dispersions of selective salts of a nitro-amino-arornatic compound. Specifically, para-nitroaniline bisulfate and the ammonium salt of para-nitroaniline-ortho sulphuric acid (2-amino-5-nitrobenzenesulphuric acid) are used. Suitable vehicles are cellulose nitrate of lacquer grade, a nitrite-phenolic modified rubber, or epoxy-polysulfide copolymer. Three separate formulations have been developed. A solvent is usually employed, such as methylethyl ketone, butyl acetate, or toluene, which renders the coatings suitably thin and which evaporates after the coatings are applied. Generally, the intumescent material is treated as insoluble in the vehicle, and is ground and dispersed in the vehicle and solvent like an
Epidemiological issues in mental retardation.
Fryers, T
1987-12-01
The basic epidemiological issues have not changed fundamentally in 30 years but emphases are different. Clarity of concept and definition is essential; we need several definitions for different purposes, and should distinguish global criteria defining groups in some way specifically 'retarded' and partial criteria defining groups not exclusive to retardation. Of global definitions, we can distinguish Intellectual Impairment based on IQ, Learning Disability based on educational criteria, and Mental Handicap or Retardation based on service or administrative criteria. The first and second may be co-terminous for children. The first and third are usually co-terminous below a certain IQ level, conventionally 50, as SII and SMH/R. This is not so for higher ability groups: MII and MMR are conceived and defined differently, and suit different research purposes. There may be much unknown need because there have been so few studies of total IQ defined groups above 50. Although organic and psychological factors are very important, the study of MMR needs to recognize its primarily social nature, reflecting determinants of selection into MMR status in legal, organizational and professional structures, activities and attitudes characteristic of particular communities and cultures. If the primary focus is on aetiological factors, natural history, and preventive possibilities, study group should be aetiologically defined and preferably not limited to MR. The same applies to specific impairments, disabilities, diseases, behaviours and disadvantages. The services are also susceptible to epidemiological approaches, descriptive, analytic, interventionist and evaluative, but little is yet available on agency structure and function, professional activities, attitudes and training, legal contexts, and financial constraints. Rigorous outcome studies would greatly benefit rapidly developing services. We know quite a lot about the distribution and associations of SII/SMR, though more is
NASA Astrophysics Data System (ADS)
Lynn, J. E.
2016-03-01
I discuss our recent work on Green's function Monte Carlo (GFMC) calculations of light nuclei using local nucleon-nucleon interactions derived from chiral effective field theory (EFT) up to next-to-next-to-leading order (N2LO). I present the natural extension of this work to include the consistent three-nucleon (3N) forces at the same order in the chiral expansion. I discuss our choice of observables to fit the two low-energy constants which enter in the 3N sector at N2LO and present some results for light nuclei.
NASA Technical Reports Server (NTRS)
Plante, Ianik; Cucinotta, Francis A.
2011-01-01
The irradiation of biological systems leads to the formation of radiolytic species such as H(raised dot), (raised dot)OH, H2, H2O2, e(sup -)(sub aq), etc.[1]. These species react with neighboring molecules, which result in damage in biological molecules such as DNA. Radiation chemistry is there for every important to understand the radiobiological consequences of radiation[2]. In this work, we discuss an approach based on the exact Green Functions for diffusion-influenced reactions which may be used to simulate radiation chemistry and eventually extended to study more complex systems, including DNA.
NASA Astrophysics Data System (ADS)
Katcho, N. A.; Carrete, J.; Li, Wu; Mingo, N.
2014-09-01
We show that impurities and vacancies affect the thermal conductivity much more strongly than what is predicted by widely accepted models. When local distortions around point defects are strong, standard perturbative approaches fail, and phonon scattering can only be accounted for by an exact Green's function calculation. We apply the theory to the study, from first-principles, of nitrogen and vacancy defects in diamond. The thermal conductivity is computed by solving the linearized Boltzmann transport equation. The Born approximation underestimates the phonon scattering cross sections of nitrogen and vacancies by factors of 3 and 10, respectively. Thermal conductivity calculations are in good agreement with experiment.
NASA Astrophysics Data System (ADS)
Tewary, V. K.; Quardokus, Rebecca C.; DelRio, Frank W.
2016-04-01
A Green's function (GF) method is developed for interpreting scanning probe microscopy (SPM) measurements on new two-dimensional (2D) materials. GFs for the Laplace/Poisson equations are calculated by using a virtual source method for two separate cases of a finite material containing a rectangular defect and a hexagonal defect. The prescribed boundary values are reproduced almost exactly by the calculated GFs. It is suggested that the GF is not just a mathematical artefact but a basic physical characteristic of material systems, which can be measured directly by SPM for 2D solids. This should make SPM an even more powerful technique for characterization of 2D materials.
NASA Astrophysics Data System (ADS)
Shamsalsadati, Sharmin; Weiss, Chester J.
2012-09-01
From a theoretical perspective, perfect Green's function recovery in diffusive systems is based on cross-correlation of time-series measured at distinct locations arising from background fluctuations from an infinite set of uncorrelated sources, either naturally occurring or engineered. Clearly such a situation is impossible in practice, and a relevant question to ask, then, is how does an imperfect set of noise sources affect the quality of the resulting empirical Green's function (EGF)? We narrow down this broad question by exploring the effect of source location and make no distinction between whether the noise sources are natural or man made. Following the theory of EGF recovery, the only requirement is that the sources are uncorrelated and endowed with the same (or nearly so) frequency spectrum and amplitude. As such, our intuition suggests that noise sources proximal to the observation points are likely to contribute more to the Green's function estimate than distal ones. However, in what manner and over what spatial extent our intuition is less clear. Thus, in this short note we specifically ask the question, 'Where are the noise sources that contribute most to the Green's function estimate in heterogeneous, lossy systems?' We call such a region the volume of relevance (VoR). Our analysis builds upon recent work on 1-D homogeneous systems by examining the effect of heterogeneity, dimensionality and receiver location in both one and two dimensions. Following the strategy of previous work in the field, the analysis is conducted out of mathematical convenience in the frequency domain although we stress that the sources need not be monochromatic. We find that for receivers located symmetrically across an interface between regions of contrasting diffusivity, the VoR rapidly shifts from one side of the interface to the other, and back again, as receiver separation increases. For the case where the receiver pair is located on the interface itself, the shifting is
Tsai, V.C.
2010-01-01
Recent derivations have shown that when noise in a physical system has its energy equipartitioned into the modes of the system, there is a convenient relationship between the cross correlation of time-series recorded at two points and the Green's function of the system. Here, we show that even when energy is not fully equipartitioned and modes are allowed to be degenerate, a similar (though less general) property holds for equations with wave equation structure. This property can be used to understand why certain seismic noise correlation measurements are successful despite known degeneracy and lack of equipartition on the Earth. No claim to original US government works Journal compilation ?? 2010 RAS.
Collins, A M; Timlin, J A; Anthony, S M; Montaño, G A
2016-08-11
We describe the ability of a short-chain amphiphilic block copolymer to self-assemble to form an artificial supramolecular light-harvesting system. Specifically, we demonstrate that the 2.5 kDa, poly(ethylene oxide)-block-poly(butadiene) (PEO-b-PBD), exhibits sufficient morphological flexibility as a membrane material and enables generation of mimics of three-dimensional chlorosomes as well as supported membrane bilayers containing energy acceptors. This overall architecture replicates green bacterial light-harvesting function whereby these assemblies exhibit long-range order and three-dimensional morphology similar to native chlorosomes and are capable of energy transfer internally and to external acceptors, located in a supporting biomimetic polymer membrane. Unlike native green bacterial systems that use multiple lipids as a matrix to generate the appropriate environment for chlorosome assembly and function, the described system matrix is comprised entirely of a single polymer amphiphile. This work demonstrates the potential of short-chain amphiphilic block copolymers in generating self-assembled, bio-mimetic membrane architectures, and in doing so, generates scalable, spatial-energetic landscapes for photonic applications. Finally, the results presented provide evidence of minimal requirements to induce chlorosome-like organization and function. PMID:27481550
Educable Mentally Retarded, Level I.
ERIC Educational Resources Information Center
Suo, Minnie Alice; Willemin, Helen
Intended for teachers of special classes of educable mentally retarded children aged 6 to 8 (mental age = 3.5 to 4.9), the guide stresses skills necessary to the development of physical, personal and social, and vocational competency. An introduction defines philosophy and goals, outlines the educable mentally retarded program and the readiness…
China's Approach to Mental Retardation.
ERIC Educational Resources Information Center
Hittman, Stephan
History, tradition, culture, and superstition have played significant roles in influencing Chinese attitudes toward the mentally retarded. China's overwhelmingly rural, agricultural society has made it dependent upon a huge force of semi-skilled and unskilled labor, to which the retarded are capable of contribution. The stress on self-reliance,…
The Mentally Retarded in Sweden.
ERIC Educational Resources Information Center
Grunewald, Karl
Described are residential and educational services provided for mentally retarded (MC) children and adults in Sweden. Normalization is the focus of the services which make maximum use of mental and physical capacities to reduce the handicap of mental retardation. Described are general principles, and four stages involving development of services…
Flame retarded asphalt blend composition
Walters, R.B.
1987-04-21
This patent describes a flame retarded asphalt composition consisting essentially of a blend of: (a) thermoplastic elastomer modified bitumen; (b) 20-30 wt % inert filler; (c) 1-20 wt % of at least one halogenated flame retardant; and (d) 1-5 wt % of at least one inorganic phosphorus containing compound selected from the group consisting of ammonium phosphate compounds and red phosphorus.
THE PATHOLOGY OF MENTAL RETARDATION.
ERIC Educational Resources Information Center
CROME, L.; STERN, J.
DATA FROM RECENT COMPREHENSIVE STUDIES OF THE PATHOLOGY OF MENTAL RETARDATION ARE ASSEMBLED, INCLUDING MATERIAL ON ETIOLOGY, MORPHOLOGY, BIOCHEMISTRY, AND LABORATORY DIAGNOSIS. AREAS COVERED ARE (1) GENETIC CAUSES OF MENTAL RETARDATION, (2) DISORDERS OF GESTATION, (3) BIRTH INJURY, (4) GENERAL CONSIDERATIONS OF POSTNATAL CAUSES OF MENTAL…
High speed memory scanning in retarded and non-retarded adolescents.
Todman, J; Gibb, C M
1985-02-01
Four groups of 13-14-year-olds, classified on the basis of Raven's Progressive Matrices scores as intellectually above average, average, below average and retarded, were subjects in a Sternberg (1966) type memory scanning task in which memory sets of two, three and four letters were used. Slope values of the memory search function did not differ between groups, whereas intercept values decreased with higher intelligence up to the average intelligence level. There was an overall inverse relation between intercept values and intelligence (r = -0.77) and similar relations obtained within the three non-retarded groups (rs greater than or equal to -0.57), but not within the retarded group (r = -0.06). Possible connections between these results and findings from inspection time studies are discussed. PMID:3978355
NASA Astrophysics Data System (ADS)
Salvucci, Guido Daniel; Entekhabi, Dara
1994-09-01
The sharp wetting front model of infiltration (Green and Ampt, 1911; Philip, 1954) yields through simple integration an exact solution relating the infiltration rate (i), cumulative infiltration (I), and time (t). The relation, however, is implicit for i or I; i.e., it is of the form t = A[I - B ln (1 + I/B)]. Numerical iteration is required to find the infiltration rate, and furthermore, analytic manipulations are limited using this traditional formulation of the Green-Ampt infiltration. In this note we present an accurate expression for the infiltration rate in the form of a rapidly converging series in the variable τ = t/(t + χ). Truncating the series at four terms yields a useful expression for i(t). The proposed four-term expression gives less than 2% error at all times and is readily integrated to yield the cumulative infiltration I(t). In conjunction with the exact expression for time (t) given i or I, the proposed expression is useful in infiltration/runoff calculations that necessitate the time compression approximation (TCA).
Corellou, Florence; Schwartz, Christian; Motta, Jean-Paul; Djouani-Tahri, El Batoul; Sanchez, Frédéric; Bouget, François-Yves
2009-01-01
Biological rhythms that allow organisms to adapt to the solar cycle are generated by endogenous circadian clocks. In higher plants, many clock components have been identified and cellular rhythmicity is thought to be driven by a complex transcriptional feedback circuitry. In the small genome of the green unicellular alga Ostreococcus tauri, two of the master clock genes Timing of Cab expression1 (TOC1) and Circadian Clock-Associated1 (CCA1) appear to be conserved, but others like Gigantea or Early-Flowering4 are lacking. Stably transformed luciferase reporter lines and tools for gene functional analysis were therefore developed to characterize clock gene function in this simple eukaryotic system. This approach revealed several features that are comparable to those in higher plants, including the circadian regulation of TOC1, CCA1, and the output gene Chlorophyll a/b Binding under constant light, the relative phases of TOC1/CCA1 expression under light/dark cycles, arrhythmic overexpression phenotypes under constant light, the binding of CCA1 to a conserved evening element in the TOC1 promoter, as well as the requirement of the evening element for circadian regulation of TOC1 promoter activity. Functional analysis supports TOC1 playing a central role in the clock, but repression of CCA1 had no effect on clock function in constant light, arguing against a simple TOC1 /CCA1 one-loop clock in Ostreococcus. The emergence of functional genomics in a simple green cell with a small genome may facilitate increased understanding of how complex cellular processes such as the circadian clock have evolved in plants. PMID:19948792
Two-Flux and Green's Function Method for Transient Radiative Transfer in a Semi-Transparent Layer
NASA Technical Reports Server (NTRS)
Siegel, Robert
1995-01-01
A method using a Green's function is developed for computing transient temperatures in a semitransparent layer by using the two-flux method coupled with the transient energy equation. Each boundary of the layer is exposed to a hot or cold radiative environment, and is heated or cooled by convection. The layer refractive index is larger than one, and the effect of internal reflections is included with the boundaries assumed diffuse. The analysis accounts for internal emission, absorption, heat conduction, and isotropic scattering. Spectrally dependent radiative properties are included, and transient results are given to illustrate two-band spectral behavior with optically thin and thick bands. Transient results using the present Green's function method are verified for a gray layer by comparison with a finite difference solution of the exact radiative transfer equations; excellent agreement is obtained. The present method requires only moderate computing times and incorporates isotropic scattering without additional complexity. Typical temperature distributions are given to illustrate application of the method by examining the effect of strong radiative heating on one side of a layer with convective cooling on the other side, and the interaction of strong convective heating with radiative cooling from the layer interior.
NASA Astrophysics Data System (ADS)
Chen, M.; Masy, J.; Niu, F.; Levander, A.
2014-12-01
We present a high-resolution 3D crustal model of Eastern Venezuela from a full waveform inversion adjoint tomography technique, based on the spectral-element method. Empirical Green's functions (EGFs) of Rayleigh waves from ambient noise interferometry serve as the observed waveforms. Rayleigh wave signals in the period range of 10 - 50 s were extracted by cross-correlations of 48 stations from both Venezuelan national seismic network and the BOLIVAR project array. The synthetic Green's functions (SGFs) are calculated with an initial regional 3D shear wave model determined from ballistic Rayleigh wave tomography from earthquake records with periods longer than 20 s. The frequency-dependent traveltime time misfits between the SGFs and EGFs are minimized iteratively using adjoint tomography = to refine 3D crustal structure [Chen et al. 2014]. The final 3D model shows lateral shear wave velocity variations that are well correlated with the geological terranes within the continental interior. In particular, the final model reveals low velocities distributed along the axis of the Espino Graben, indicating that the graben has a substantially different crustal structure than the rest of the Eastern Venezuela Basin. We also observe high shear velocities in the lower crust beneath some of the subterranes of the Proterozoic-Archean Guayana Shield.
Allen, Joseph G.; MacNaughton, Piers; Satish, Usha; Santanam, Suresh; Vallarino, Jose; Spengler, John D.
2015-01-01
Background: The indoor built environment plays a critical role in our overall well-being because of both the amount of time we spend indoors (~90%) and the ability of buildings to positively or negatively influence our health. The advent of sustainable design or green building strategies reinvigorated questions regarding the specific factors in buildings that lead to optimized conditions for health and productivity. Objective: We simulated indoor environmental quality (IEQ) conditions in “Green” and “Conventional” buildings and evaluated the impacts on an objective measure of human performance: higher-order cognitive function. Methods: Twenty-four participants spent 6 full work days (0900–1700 hours) in an environmentally controlled office space, blinded to test conditions. On different days, they were exposed to IEQ conditions representative of Conventional [high concentrations of volatile organic compounds (VOCs)] and Green (low concentrations of VOCs) office buildings in the United States. Additional conditions simulated a Green building with a high outdoor air ventilation rate (labeled Green+) and artificially elevated carbon dioxide (CO2) levels independent of ventilation. Results: On average, cognitive scores were 61% higher on the Green building day and 101% higher on the two Green+ building days than on the Conventional building day (p < 0.0001). VOCs and CO2 were independently associated with cognitive scores. Conclusions: Cognitive function scores were significantly better under Green+ building conditions than in the Conventional building conditions for all nine functional domains. These findings have wide-ranging implications because this study was designed to reflect conditions that are commonly encountered every day in many indoor environments. Citation: Allen JG, MacNaughton P, Satish U, Santanam S, Vallarino J, Spengler JD. 2016. Associations of cognitive function scores with carbon dioxide, ventilation, and volatile organic compound
López-Téllez, J. M. Bruce, N. C.
2014-03-15
We present a method for using liquid-crystal variable retarders (LCVR’s) with continually varying voltage to measure the Stokes vector of a light beam. The LCVR's are usually employed with fixed retardance values due to the nonlinear voltage-retardance behavior that they show. The nonlinear voltage-retardance relationship is first measured and then a linear fit of the known retardance terms to the detected signal is performed. We use known waveplates (half-wave and quarter-wave) as devices to provide controlled polarization states to the Stokes polarimeter and we use the measured Stokes parameters as functions of the orientation of the axes of the waveplates as an indication of the quality of the polarimeter. Results are compared to a Fourier analysis method that does not take into account the nonlinear voltage-retardance relationship and also to a Fourier analysis method that uses experimental voltage values to give a linear retardance function with time. Also, we present results of simulations for comparison.
NASA Astrophysics Data System (ADS)
Anders, Frithjof B.; Schmitt, Sebastian
2010-04-01
Scattering states fulfill the correct boundary conditions of a current carrying open quantum system. Discretizing the energy continuum of these states allows for employing Wilson's numerical renormalization group approach without violating the boundary conditions by using a finite size system. We evolve the analytically known steady-state density operator for a non-interacting quantum-system at finite bias to the full interacting problem by the time-dependent numerical renormalization group after switching on the local charging energy. Using a newly developed algorithm for steady-state nonequilibrium Green functions, we can calculate the current I as function of bias voltage V for arbitrary temperature and magnetic field. A comparison with second-order and GW Kadanoff-Baym-Keldysh results shows excellent agreement for weak interaction strength U.
Spectral characterization and tuning with liquid-crystal retarders
NASA Astrophysics Data System (ADS)
Sánchez-López, María. del Mar; Moreno, Ignacio; Vargas, Asticio; García-Martínez, Pascuala
2015-09-01
An accurate characterization of the retardance function of liquid-crystal retarders (LCR) is essential for a proper use of instruments that include these devices. In this paper a simple technique to characterize the retardance of a LCR, both as a function of wavelength and applied voltage, is presented. With the proposed analysis we can describe the spectral modulation properties of the device using few parameters. The method is then extended to the case of non-normal incidence, thus allowing to distinguish between the extraordinary and ordinary axes. The accounting of Fabry-Perot interference effects are used to obtain a very accurate determination of the spectral phase shifts. Finally, such a full characterization of the LCR retardance is applied to a liquid-crystal spatial light modulator and an optical architecture is designed where the spectral content of the light beam can be engineered at will.
A Computer Program for the Computation of Running Gear Temperatures Using Green's Function
NASA Technical Reports Server (NTRS)
Koshigoe, S.; Murdock, J. W.; Akin, L. S.; Townsend, D. P.
1996-01-01
A new technique has been developed to study two dimensional heat transfer problems in gears. This technique consists of transforming the heat equation into a line integral equation with the use of Green's theorem. The equation is then expressed in terms of eigenfunctions that satisfy the Helmholtz equation, and their corresponding eigenvalues for an arbitrarily shaped region of interest. The eigenfunction are obtalned by solving an intergral equation. Once the eigenfunctions are found, the temperature is expanded in terms of the eigenfunctions with unknown time dependent coefficients that can be solved by using Runge Kutta methods. The time integration is extremely efficient. Therefore, any changes in the time dependent coefficients or source terms in the boundary conditions do not impose a great computational burden on the user. The method is demonstrated by applying it to a sample gear tooth. Temperature histories at representative surface locatons are given.
NASA Astrophysics Data System (ADS)
Matos, Catarina; Silveira, Graça; Custódio, Susana; Domingues, Ana; Dias, Nuno; Fonseca, João F. B.; Matias, Luís; Krueger, Frank; Carrilho, Fernando
2014-05-01
Noise cross-correlations are now widely used to extract Green functions between station pairs. But, do all the cross-correlations routinely computed produce successful Green Functions? What is the relationship between noise recorded in a couple of stations and the cross-correlation between them? During the last decade, we have been involved in the deployment of several temporary dense broadband (BB) networks within the scope of both national projects and international collaborations. From 2000 to 2002, a pool of 8 BB stations continuously operated in the Azores in the scope of the Memorandum of Understanding COSEA (COordinated Seismic Experiment in the Azores). Thanks to the Project WILAS (West Iberia Lithosphere and Astenosphere Structure, PTDC/CTE-GIX/097946/2008) we temporarily increased the number of BB deployed in mainland Portugal to more than 50 (permanent + temporary) during the period 2010 - 2012. In 2011/12 a temporary pool of 12 seismometers continuously recorded BB data in the Madeira archipelago, as part of the DOCTAR (Deep Ocean Test Array Experiment) project. Project CV-PLUME (Investigation on the geometry and deep signature of the Cape Verde mantle plume, PTDC/CTE-GIN/64330/2006) covered the archipelago of Cape Verde, North Atlantic, with 40 temporary BB stations in 2007/08. Project MOZART (Mozambique African Rift Tomography, PTDC/CTE-GIX/103249/2008), covered Mozambique, East Africa, with 30 temporary BB stations in the period 2011 - 2013. These networks, located in very distinct geographical and tectonic environments, offer an interesting opportunity to study seasonal and spatial variations of noise sources and their impact on Empirical Green functions computed from noise cross-correlation. Seismic noise recorded at different seismic stations is evaluated by computation of the probability density functions of power spectral density (PSD) of continuous data. To assess seasonal variations of ambient noise sources in frequency content, time-series of
NASA Astrophysics Data System (ADS)
Dey, N.; Dickman, S. R.
2010-09-01
A decade ago, a novel theoretical approach was developed (Dickman, 1998) for determining the dynamic response of the oceans to atmospheric pressure variations, a response nicknamed the "dynamic barometer" (DB), and the effects of that response on Earth's rotation. This approach employed a generalized, spherical harmonic ocean tide model to compute oceanic Green's functions, the oceans' fluid dynamic response to unit-amplitude pressure forcing on various spatial and temporal scales, and then construct rotational Green's functions, representing the rotational effects of that response. When combined with the observed atmospheric pressure field, the rotational Green's functions would yield the effects of the DB on Earth's rotation. The Green's functions reflect in some way the geographical and spectral sensitivity of the oceans to atmospheric pressure forcing. We have formulated a measure of that sensitivity using a simple combination of rotational Green's functions. We find that the DB response of the oceans to atmospheric pressure forcing depends significantly on geographic location and on frequency. Compared to the inverted barometer (IB) (the traditional static model), the DB effects differ slightly at long periods but become very different at shorter periods. Among all the responses, the prograde polar motion effects are the most dynamic, with large portions of the North Atlantic and some of the North Pacific no larger than one third of IB, but most of the Southern Hemisphere oceans at least 50% greater than IB.
Sadybekov, Makhmud A.; Torebek, Berikbol T.; Turmetov, Batirkhan Kh.
2014-08-20
The paper is devoted to the investigation of questions about constructing the explicit form of the Green’s function of the Robin problem. For constructing this function we use the representation of the fundamental solution of the Laplace equation in the form of a series. An integral representation of the Green function is obtained and for some values of the parameters, the problem is presented in elementary functions.
Qian, Zekan; Li, Rui; Hou, Shimin; Xue, Zengquan; Sanvito, Stefano
2007-11-21
An efficient self-consistent approach combining the nonequilibrium Green's function formalism with density functional theory is developed to calculate electron transport properties of molecular devices with quasi-one-dimensional (1D) electrodes. Two problems associated with the low dimensionality of the 1D electrodes, i.e., the nonequilibrium state and the uncertain boundary conditions for the electrostatic potential, are circumvented by introducing the reflectionless boundary conditions at the electrode-contact interfaces and the zero electric field boundary conditions at the electrode-molecule interfaces. Three prototypical systems, respectively, an ideal ballistic conductor, a high resistance tunnel junction, and a molecular device, are investigated to illustrate the accuracy and efficiency of our approach. PMID:18035901
Structural properties and digestion of green banana flour as a functional ingredient in pasta.
Zheng, Zeqi; Stanley, Roger; Gidley, Michael J; Dhital, Sushil
2016-02-01
Gluten free pasta was made from raw banana flour in combination with vegetable gums and protein for comparison to pasta similarly made from wheat flour. After cooking, it was found that the banana flour pasta was less susceptible to alpha-amylase digestion compared to conventional wheat flour pasta. Release of glucose by alpha-amylase digestion followed first order kinetics with an initial rapid rate of digestion and a subsequent second slower phase. The structure of green banana pasta starch at the inner and outer pasta surfaces was observed under confocal laser scanning microscopy (CLSM) and the viscosities of the flour mixtures were measured by a Rapid Visco Analyser (RVA). The digestibility of banana flour pasta was found to be related, not only to the properties of the starch granules, but also to the protein network of the surrounding food matrix. The effects of gums and proteins on pasta formation and digestibility are discussed in the context of its potential use as a gluten free lower glycaemic alternative to conventional wheat based pastas. PMID:26632017
Functional incorporation of green fluorescent protein into hepatitis B virus envelope particles
Lambert, Carsten; Thome, Nicole; Kluck, Christoph J.; Prange, Reinhild . E-mail: prange@mail.uni-mainz.de
2004-12-05
The envelope of hepatitis B virus (HBV), containing the L, M, and S proteins, is essential for virus entry and maturation. For direct visualization of HBV, we determined whether envelope assembly could accommodate the green fluorescent protein (GFP). While the C-terminal addition of GFP to S trans-dominant negatively inhibited empty envelope particle secretion, the N-terminal GFP fusion to S (GFP.S) was co-integrated into the envelope, giving rise to fluorescent particles. Microscopy and topogenesis analyses demonstrated that the proper intracellular distribution and folding of GFP.S, required for particle export were rescued by interprotein interactions with wild-type S. Thereby, a dual location of GFP, inside and outside the envelope, was observed. GFP.S was also efficiently packaged into the viral envelope, and these GFP-tagged virions retained the capacity for attachment to HBV receptor-positive cells in vitro. Together, GFP-tagged virions should be suitable to monitor HBV uptake and egress in live hepatocytes.
Neurotoxicity of brominated flame retardants
Polybrominated diphenyl ethers (PBDEs) have been commonly used as commercial flame retardants in a variety of products including plastics and textiles. Despite their decreasing usage worldwide, congeners continue to accumulate in the environment, including soil, dust, food, anima...
Can earthworms survive fire retardants?
Beyer, W.N.; Olson, A.
1996-01-01
Most common fire retardants are foams or are similar to common agricultural fertilizers, such as ammonium sulfate and ammonium phosphate. Although fire retardants are widely applied to soils, we lack basic information about their toxicities to soil organisms. We measured the toxicity of five fire retardants (Firetrol LCG-R, Firetrol GTS-R, Silv-Ex Foam Concentrate, Phos-chek D-75, and Phos-chek WD-881) to earthworms using the pesticide toxicity test developed for earthworms by the European Economic Community. None was lethal at 1,000 ppm in the soil, which was suggested as a relatively high exposure under normal applications. We concluded that the fire retardants tested are relatively nontoxic to soil organisms compared with other environmental chemicals and that they probably do not reduce earthworm populations when applied under usual firefighting conditions.
INTRODUCTION TO BROMINATED FLAME RETARDANTS
Brominated flame retardants (BFRs) are a large and diverse class of major industrial products used to provide fire safety. Tetrabromobisphenol A (TBBPA), Hexabromocylocodecane (HBCD), and Polybrominated Diphenyl Ethers (PBDEs) are the major commercial compounds. TBBPA is a react...
Intumescent Coatings as Fire Retardants
NASA Technical Reports Server (NTRS)
Fish, R. H.; Fohlen, G. M.; Parker, J. A.; Sawko, P. M.
1970-01-01
Fire-retardant paint, when activated by the heat of fire, reacts to form a thick, low-density, polymeric coating or char layer. Water vapor and sulphur dioxide are released during the intumescent reaction.
NASA Astrophysics Data System (ADS)
Krishnamurthy, Srini; Van Orden, Derek; Yu, Zhi-Gang
2016-04-01
We have developed a hybrid method that can be applied to study isolated defects in semiconductor compounds and superlattices. The method is a combination of (1) a long-range tight-binding (TB) Hamiltonian, (2) a first-principles Hamiltonian, and (3) a Green's function (GF) formalism. The calculation of the GF requires accurate energy band structure, wave functions, and defect potentials. The TB Hamiltonian with sp 3 orbitals basis ensures accurate band gaps and band masses while providing the functional form for the wave functions. We calculated the band gaps of InAs/GaSb and InAs/InAsSb strained-layer superlattices and found them to agree well with measurements. The change in potentials caused by native point defects (NPDs) was obtained from a first-principles method using Spanish Initiative for Electronic Simulations with Thousands of Atoms, which also uses sp 3 basis. We describe the method of calculating NPD energy levels in compounds and superlattices, obtain some defect levels in GaAs, InAs, InSb, and GaSb compounds, and provide details of the NPD-level calculations.
NASA Astrophysics Data System (ADS)
Krishnamurthy, Srini; Van Orden, Derek; Yu, Zhi-Gang
2016-09-01
We have developed a hybrid method that can be applied to study isolated defects in semiconductor compounds and superlattices. The method is a combination of (1) a long-range tight-binding (TB) Hamiltonian, (2) a first-principles Hamiltonian, and (3) a Green's function (GF) formalism. The calculation of the GF requires accurate energy band structure, wave functions, and defect potentials. The TB Hamiltonian with sp 3 orbitals basis ensures accurate band gaps and band masses while providing the functional form for the wave functions. We calculated the band gaps of InAs/GaSb and InAs/InAsSb strained-layer superlattices and found them to agree well with measurements. The change in potentials caused by native point defects (NPDs) was obtained from a first-principles method using Spanish Initiative for Electronic Simulations with Thousands of Atoms, which also uses sp 3 basis. We describe the method of calculating NPD energy levels in compounds and superlattices, obtain some defect levels in GaAs, InAs, InSb, and GaSb compounds, and provide details of the NPD-level calculations.
De Gasperi, Andrea; Mazza, Ernestina; Prosperi, Manlio
2016-01-01
Indocyanine green (ICG) kinetics (PDR/R15) used to quantitatively assess hepatic function in the perioperative period of major resective surgery and liver transplantation have been the object of an extensive, updated and critical review. New, non invasive bedside monitors (pulse dye densitometry technology) make this opportunity widely available in clinical practice. After having reviewed basic concepts of hepatic clearance, we analysed the most common indications ICG kinetic parameters have nowadays in clinical practice, focusing in particular on the diagnostic and prognostic role of PDR and R15 in the perioperative period of major liver surgery and liver transplantation. As recently pointed out, even if of extreme interest, ICG clearance parameters have still some limitations, to be considered when using these tests. PMID:26981173
Fullwave coupling to a 3D antenna code using Green's function formulation of wave-particle response
NASA Astrophysics Data System (ADS)
Wright, John; Bonoli, P. T.; Bilato, R.; Brambilla, M.; Maggiora, R.; Lancellotti, V.
2006-10-01
Using the fullwave code, TORIC, and the 3D antenna code, TOPICA, we construct a complete linear system for the RF driven plasma. The 3D finite element antenna code, TOPICA, requires an admittance, Y, for the plasma, where B=YE. In this work, TORIC was modified to allow excitation of the (Eη, Eζ) electric field components at the plasma surface, corresponding to a single poloidal and toroidal mode number combination (m,n). This leads to the tensor response: Yn= ( ll Yηη& YηζYζη& Yζζ), where each of the Yn submatrices is Nm in size. It is shown that the admittance matrix is equivalent to a Green's function calculation for the fullwave system and the net work done is less than twice a single fullwave calculation. The admittance calculation is used with loading calculation from TOPICA to construct self consistent plasma and antenna currents.
NASA Astrophysics Data System (ADS)
Toyoda, Takahiro; Sugiura, Nozomi; Masuda, Shuhei; Sasaki, Yuji; Igarashi, Hiromichi; Ishikawa, Yoichi; Hatayama, Takaki; Kawano, Takeshi; Kawai, Yoshimi; Kouketsu, Shinya; Katsumata, Katsuro; Uchida, Hiroshi; Doi, Toshimasa; Fukasawa, Masao; Awaji, Toshiyuki
2015-11-01
An improved vertical diffusivity scheme is introduced into an ocean general circulation model to better reproduce the observed features of water property distribution inherent in the deep Pacific Ocean structure. The scheme incorporates (a) a horizontally uniform background profile, (b) a parameterization depending on the local static stability, and (c) a parameterization depending on the bottom topography. Weighting factors for these parameterizations are optimally estimated based on the Green's function method. The optimized values indicate an important role of both the intense vertical diffusivity near rough topography and the background vertical diffusivity. This is consistent with recent reports that indicate the presence of significant vertical mixing associated with finite-amplitude internal wave breaking along the bottom slope and its remote effect. The robust simulation with less artificial trend of water properties in the deep Pacific Ocean illustrates that our approach offers a better modeling analysis for the deep ocean variability.
Castano, Marcela; Seo, Kwang Su; Kim, Eun Hye; Becker, Matthew L; Puskas, Judit E
2013-09-01
Halo-ester-functionalized poly(ethylene glycol)s (PEGs) are successfully prepared by the transesterification of alkyl halo-esters with PEGs using Candida antarctica lipase B (CALB) as a biocatalyst under the solventless conditions. Transesterifications of chlorine, bromine, and iodine esters with tetraethylene glycol monobenzyl ether (BzTEG) are quantitative in less than 2.5 h. The transesterification of halo-esters with PEGs are complete in 4 h. (1) H and (13) C NMR spectroscopy with MALDI-ToF and ESI mass spectrometry confirm the structure and purity of the products. This method provides a convenient and "green" process to effectively produce halo-ester PEGs. PMID:23877930
Lindskog, M. Wacker, A.; Wolf, J. M.; Liverini, V.; Faist, J.; Trinite, V.; Maisons, G.; Carras, M.; Aidam, R.; Ostendorf, R.
2014-09-08
We study the operation of an 8.5 μm quantum cascade laser based on GaInAs/AlInAs lattice matched to InP using three different simulation models based on density matrix (DM) and non-equilibrium Green's function (NEGF) formulations. The latter advanced scheme serves as a validation for the simpler DM schemes and, at the same time, provides additional insight, such as the temperatures of the sub-band carrier distributions. We find that for the particular quantum cascade laser studied here, the behavior is well described by simple quantum mechanical estimates based on Fermi's golden rule. As a consequence, the DM model, which includes second order currents, agrees well with the NEGF results. Both these simulations are in accordance with previously reported data and a second regrown device.
Recent Progress in the Development of a Multi-Layer Green's Function Code for Ion Beam Transport
NASA Technical Reports Server (NTRS)
Tweed, John; Walker, Steven A.; Wilson, John W.; Tripathi, Ram K.
2008-01-01
To meet the challenge of future deep space programs, an accurate and efficient engineering code for analyzing the shielding requirements against high-energy galactic heavy radiation is needed. To address this need, a new Green's function code capable of simulating high charge and energy ions with either laboratory or space boundary conditions is currently under development. The computational model consists of combinations of physical perturbation expansions based on the scales of atomic interaction, multiple scattering, and nuclear reactive processes with use of the Neumann-asymptotic expansions with non-perturbative corrections. The code contains energy loss due to straggling, nuclear attenuation, nuclear fragmentation with energy dispersion and downshifts. Previous reports show that the new code accurately models the transport of ion beams through a single slab of material. Current research efforts are focused on enabling the code to handle multiple layers of material and the present paper reports on progress made towards that end.
NASA Astrophysics Data System (ADS)
Kafri, H. Q.; Khuri, S. A.; Sayfy, A.
2016-03-01
In this paper, a novel approach is introduced for the solution of the non-linear Troesch's boundary value problem. The underlying strategy is based on Green's functions and fixed-point iterations, including Picard's and Krasnoselskii-Mann's schemes. The resulting numerical solutions are compared with both the analytical solutions and numerical solutions that exist in the literature. Convergence of the iterative schemes is proved via manipulation of the contraction principle. It is observed that the method handles the boundary layer very efficiently, reduces lengthy calculations, provides rapid convergence, and yields accurate results particularly for large eigenvalues. Indeed, to our knowledge, this is the first time that this problem is solved successfully for very large eigenvalues, actually the rate of convergence increases as the magnitude of the eigenvalues increases.
NASA Astrophysics Data System (ADS)
Gerstner, Candice Rockell
In the future, astronauts will be sent into space for longer durations of time compared to previous missions. The increased risk of exposure to ionizing radiation, such as Galactic Cosmic Rays and Solar Particle Events, is of great concern. Consequently, steps must be taken to ensure astronaut safety by providing adequate shielding. The shielding and exposure of space travelers is controlled by the transport properties of the radiation through the spacecraft, its onboard systems and the bodies of the individuals themselves. Meeting the challenge of future space programs will therefore require accurate and efficient methods for performing radiation transport calculations to analyze and predict shielding requirements. One such method, which is developed in this dissertation, is based on a three dimensional Green's function solution technique for the transport of heavy ions in both laboratory and space.
Marin, F. P.
2014-01-01
We study the I-V characteristic of mesoscopic systems or quantum dot (QD) attached to a pair of superconducting leads. Interaction effects in the QD are considered through the charging energy of the QD; that is, the treatment of current transport under a voltage bias is performed within a coupled Poisson nonequilibrium Green function (PNEGF) formalism. We derive the expression for the current in full generality but consider only the regime where transport occurs only via a single particle current. We show for this case and for various charging energies values U 0 and associated capacitances of the QD the effect on the I-V characteristic. Also the influence of the coupling constants on the I-V characteristic is investigated. Our approach puts forward a novel interpretation of experiments in the strong Coulomb regime. PMID:24977220
Mori, J.; Frankel, A.
1990-01-01
Using small events as empirical Green functions, source parameters were estimated for 25 ML 3.4 to 4.4 events associated with the 1986 North Palm Springs earthquake. The static stress drops ranged from 3 to 80 bars, for moments of 0.7 to 11 ?? 1021 dyne-cm. There was a spatial pattern to the stress drops of the aftershocks which showed increasing values along the fault plane toward the northwest compared to relatively low values near the hypocenter of the mainshock. The highest values were outside the main area of slip, and are believed to reflect a loaded area of the fault that still has an higher level of stress which was not released during the main shock. -from Authors
NASA Astrophysics Data System (ADS)
Riahi, Ali; Sadeghi, Hossein; Hosseini, Sayyed Keivan
2015-06-01
The 2003 Bam, Iran, earthquake (Mw = 6.6) was recorded by the BAM accelerometer station. Since the causative fault was located just below the city, the accelerometer recorded the main shock, a foreshock and several local aftershocks. To study the scenario of rupturing, we simulated all components of the observed main shock waveform via the empirical Green's function method. 28 selected aftershocks and the single foreshock are used to simulate the main shock in the frequency range of 0.5-5 Hz. Since the events were very close to the station, some small events may not have similar path effects to the main shock. Therefore, it is essential to employ some appropriate changes to the waveforms to alleviate path difference effects. The starting point of the rupture is identified in the centre of the strong motion generation area and is located approximately 5 km south of the BAM station and in depth of about 7 km. The horizontal simulated components imply that the main shock was located west of the BAM station. In contrast, significant variation in the ratio of amplitudes in EW and NS components may be used to discuss the possibility of dissimilarity in the focal mechanism of the small events. Most aftershocks with similar mechanisms to the main shock, that is similar EW/NS maximum amplitude ratio, have capacity to simulate certain peaks of their horizontal components. However, some small events with different mechanisms are only able to simulate the peaks of up to one horizontal component. Some changes were applied to the empirical Green's function method to incorporate two small events by using a combined fault model. While the two aftershocks have different mechanisms, some combinations may improve simulations. The rupture initiating point at the middle of the fault plane and improved simulations by combination of two fault surfaces with different focal mechanisms may suggest a bilateral rupture and combination of two focal mechanisms for the main shock of the Bam
NASA Technical Reports Server (NTRS)
Stammer, Detlef; Wunsch, Carl
1996-01-01
A Green's function method for obtaining an estimate of the ocean circulation using both a general circulation model and altimetric data is demonstrated. The fundamental assumption is that the model is so accurate that the differences between the observations and the model-estimated fields obey a linear dynamics. In the present case, the calculations are demonstrated for model/data differences occurring on very a large scale, where the linearization hypothesis appears to be a good one. A semi-automatic linearization of the Bryan/Cox general circulation model is effected by calculating the model response to a series of isolated (in both space and time) geostrophically balanced vortices. These resulting impulse responses or 'Green's functions' then provide the kernels for a linear inverse problem. The method is first demonstrated with a set of 'twin experiments' and then with real data spanning the entire model domain and a year of TOPEX/POSEIDON observations. Our present focus is on the estimate of the time-mean and annual cycle of the model. Residuals of the inversion/assimilation are largest in the western tropical Pacific, and are believed to reflect primarily geoid error. Vertical resolution diminishes with depth with 1 year of data. The model mean is modified such that the subtropical gyre is weakened by about 1 cm/s and the center of the gyre shifted southward by about 10 deg. Corrections to the flow field at the annual cycle suggest that the dynamical response is weak except in the tropics, where the estimated seasonal cycle of the low-latitude current system is of the order of 2 cm/s. The underestimation of observed fluctuations can be related to the inversion on the coarse spatial grid, which does not permit full resolution of the tropical physics. The methodology is easily extended to higher resolution, to use of spatially correlated errors, and to other data types.
Kokudo, Takashi; Hasegawa, Kiyoshi; Amikura, Katsumi; Uldry, Emilie; Shirata, Chikara; Yamaguchi, Takamune; Arita, Junichi; Kaneko, Junichi; Akamatsu, Nobuhisa; Sakamoto, Yoshihiro; Takahashi, Amane; Sakamoto, Hirohiko; Makuuchi, Masatoshi; Matsuyama, Yutaka; Demartines, Nicolas; Malagó, Massimo; Kokudo, Norihiro; Halkic, Nermin
2016-01-01
Background Most patients with hepatocellular carcinoma (HCC) have underlying liver disease, therefore, precise preoperative evaluation of the patient’s liver function is essential for surgical decision making. Methods We developed a grading system incorporating only two variables, namely, the serum albumin level and the indocyanine green retention rate at 15 minutes (ICG R15), to assess the preoperative liver function, based on the overall survival of 1868 patients with HCC who underwent liver resection. We then tested the model in a European cohort (n = 70) and analyzed the predictive power for the postoperative short-term outcome. Results The Albumin-Indocyanine Green Evaluation (ALICE) grading system was developed in a randomly assigned training cohort: linear predictor = 0.663 × log10ICG R15 (%)−0.0718 × albumin (g/L) (cut-off value: -2.20 and -1.39). This new grading system showed a predictive power for the overall survival similar to the Child-Pugh grading system in the validation cohort. Determination of the ALICE grade in Child-Pugh A patients allowed further stratification of the postoperative prognosis. This result was reproducible in the European cohort. Determination of the ALICE grade allowed better prediction of the risk of postoperative liver failure and mortality (ascites: grade 1, 2.1%; grade 2, 6.5%; grade 3, 16.0%; mortality: grade 1, 0%; grade 2, 1.3%; grade 3, 5.3%) than the previously reported model based on the presence/absence of portal hypertension. Conclusions This new grading system is a simple method for prediction of the postoperative long-term and short-term outcomes. PMID:27434062
Understanding and Teaching the Dependent Retarded Child.
ERIC Educational Resources Information Center
Rosenzweig, Louis E.; Long, Julia
Levels of mental retardation and school admission procedures for the dependent retarded (IQ's 30 to 50) are reviewed. Goals for all retarded and the application of goals to the dependent retarded are considered. Plans and procedures for both teacher and child activities along with suggestions for audiovisual and other materials are provided in the…
The Mentally Retarded Offender: Annotated Bibliography.
ERIC Educational Resources Information Center
Schilit, Jeffrey; And Others
An annotated bibliography of approximately 150 books and articles on the mentally retarded offender as well as 30 nonannotated entries are provided. Topics covered include such areas as characteristics of mentally retarded delinquents, rehabilitation of the retarded offender, community services for retarded persons, rights of the mentally…
Green fluorescent protein functions as a reporter for protein localization in Escherichia coli.
Feilmeier, B J; Iseminger, G; Schroeder, D; Webber, H; Phillips, G J
2000-07-01
The use of green fluorescent protein (GFP) as a reporter for protein localization in Escherichia coli was explored by creating gene fusions between malE (encoding maltose-binding protein [MBP]) and a variant of gfp optimized for fluorescence in bacteria (GFPuv). These constructs encode hybrid proteins composed of GFP fused to the carboxy-terminal end of MBP. Fluorescence was not detected when the hybrid protein was synthesized with the MBP signal sequence. In contrast, when the MBP signal sequence was deleted, fluorescence was observed. Cell fractionation studies showed that the fluorescent MBP-GFP hybrid protein was localized in the cytoplasm, whereas the nonfluorescent version was localized to the periplasmic space. Smaller MBP-GFP hybrid proteins, however, exhibited abnormal fractionation. Expression of the gene fusions in different sec mutants, as well as signal sequence processing assays, confirmed that the periplasmically localized hybrid proteins were exported by the sec-dependent pathway. The distinction between fluorescent and nonfluorescent colonies was exploited as a scorable phenotype to isolate malE signal sequence mutations. While expression of hybrid proteins comprised of full-length MBP did not result in overproduction lethality characteristic of some exported beta-galactosidase hybrid proteins, synthesis of shorter, exported hybrid proteins was toxic to the cells. Purification of MBP-GFP hybrid protein from the different cellular compartments indicated that GFP is improperly folded when localized outside of the cytoplasm. These results suggest that GFP could serve as a useful reporter for genetic analysis of bacterial protein export and of protein folding. PMID:10869087
Puch, Florence; Samson-Villeger, Sandrine; Guyonnet, Denis; Blachon, Jean-Luc; Rawlings, Anthony Vincent; Lassel, Taous
2008-08-01
As emerging studies show that skin functioning can be improved with orally imbibed ingredients, we decided to investigate a mixture of borage oil, catechins, vitamin E and probiotics, all known for their reported effects on epidermal function, in a fermented dairy product, for the first time. Gamma-linolenic acid (GLA) and catechins bioavailability and their effects on skin functionality have not been previously investigated from a fermented dairy product. Firstly, we assessed the bioavailability of GLA and catechins mixed in a fermented dairy matrix by measuring their levels in chylomicrons and plasma samples respectively. For the GLA contained in the dairy matrix, the area under the curve and time for maximal absorption were significantly different to the same kinetic parameters compared with absorption from the free oil indicating improved oral bioavailability. However, the overall absorption of catechins over the 6-h period was identical for both product forms. These results were sufficiently promising to warrant a 24 week skin nutrition intervention study in female volunteers having dry and sensitive skin. The product improved stratum corneum barrier function compared with a control product as early as 6 weeks after the consumption which continued throughout the rest of the study. The reduction in transepidermal water loss relative to control was maintained throughout the trial despite seasonal changes. Moreover, as a result of the enhanced bioavailability, a much greater effect on skin barrier function occurred than reported previously for the individual ingredients. Nevertheless, body mass index significantly influenced various outcome measurements of this study. PMID:18318715
Kwon, Woosung; Kim, Young-Hoon; Kim, Ji-Hee; Lee, Taehyung; Do, Sungan; Park, Yoonsang; Jeong, Mun Seok; Lee, Tae-Woo; Rhee, Shi-Woo
2016-01-01
Chemically derived graphene quantum dots (GQDs) to date have showed very broad emission linewidth due to many kinds of chemical bondings with different energy levels, which significantly degrades the color purity and color tunability. Here, we show that use of aniline derivatives to chemically functionalize GQDs generates new extrinsic energy levels that lead to photoluminescence of very narrow linewidths. We use transient absorption and time-resolved photoluminescence spectroscopies to study the electronic structures and related electronic transitions of our GQDs, which reveals that their underlying carrier dynamics is strongly related to the chemical properties of aniline derivatives. Using these functionalized GQDs as lumophores, we fabricate light-emitting didoes (LEDs) that exhibit green, orange, and red electroluminescence that has high color purity. The maximum current efficiency of 3.47 cd A(-1) and external quantum efficiency of 1.28% are recorded with our LEDs; these are the highest values ever reported for LEDs based on carbon-nanoparticle phosphors. This functionalization of GQDs with aniline derivatives represents a new method to fabricate LEDs that produce natural color. PMID:27048887
NASA Astrophysics Data System (ADS)
Plante, Ianik
2016-01-01
The exact Green's function of the diffusion equation (GFDE) is often considered to be the gold standard for the simulation of partially diffusion-controlled reactions. As the GFDE with angular dependency is quite complex, the radial GFDE is more often used. Indeed, the exact GFDE is expressed as a Legendre expansion, the coefficients of which are given in terms of an integral comprising Bessel functions. This integral does not seem to have been evaluated analytically in existing literature. While the integral can be evaluated numerically, the Bessel functions make the integral oscillate and convergence is difficult to obtain. Therefore it would be of great interest to evaluate the integral analytically. The first term was evaluated previously, and was found to be equal to the radial GFDE. In this work, the second term of this expansion was evaluated. As this work has shown that the first two terms of the Legendre polynomial expansion can be calculated analytically, it raises the question of the possibility that an analytical solution exists for the other terms.
Kwon, Woosung; Kim, Young-Hoon; Kim, Ji-Hee; Lee, Taehyung; Do, Sungan; Park, Yoonsang; Jeong, Mun Seok; Lee, Tae-Woo; Rhee, Shi-Woo
2016-01-01
Chemically derived graphene quantum dots (GQDs) to date have showed very broad emission linewidth due to many kinds of chemical bondings with different energy levels, which significantly degrades the color purity and color tunability. Here, we show that use of aniline derivatives to chemically functionalize GQDs generates new extrinsic energy levels that lead to photoluminescence of very narrow linewidths. We use transient absorption and time-resolved photoluminescence spectroscopies to study the electronic structures and related electronic transitions of our GQDs, which reveals that their underlying carrier dynamics is strongly related to the chemical properties of aniline derivatives. Using these functionalized GQDs as lumophores, we fabricate light-emitting didoes (LEDs) that exhibit green, orange, and red electroluminescence that has high color purity. The maximum current efficiency of 3.47 cd A−1 and external quantum efficiency of 1.28% are recorded with our LEDs; these are the highest values ever reported for LEDs based on carbon-nanoparticle phosphors. This functionalization of GQDs with aniline derivatives represents a new method to fabricate LEDs that produce natural color. PMID:27048887
NASA Astrophysics Data System (ADS)
Kwon, Woosung; Kim, Young-Hoon; Kim, Ji-Hee; Lee, Taehyung; Do, Sungan; Park, Yoonsang; Jeong, Mun Seok; Lee, Tae-Woo; Rhee, Shi-Woo
2016-04-01
Chemically derived graphene quantum dots (GQDs) to date have showed very broad emission linewidth due to many kinds of chemical bondings with different energy levels, which significantly degrades the color purity and color tunability. Here, we show that use of aniline derivatives to chemically functionalize GQDs generates new extrinsic energy levels that lead to photoluminescence of very narrow linewidths. We use transient absorption and time-resolved photoluminescence spectroscopies to study the electronic structures and related electronic transitions of our GQDs, which reveals that their underlying carrier dynamics is strongly related to the chemical properties of aniline derivatives. Using these functionalized GQDs as lumophores, we fabricate light-emitting didoes (LEDs) that exhibit green, orange, and red electroluminescence that has high color purity. The maximum current efficiency of 3.47 cd A‑1 and external quantum efficiency of 1.28% are recorded with our LEDs; these are the highest values ever reported for LEDs based on carbon-nanoparticle phosphors. This functionalization of GQDs with aniline derivatives represents a new method to fabricate LEDs that produce natural color.
Rakhmanova, I V; D'yakonova, I N; Sichinava, L G; Ledovskikh, Yu A
2015-01-01
The objective of the present work was to study the function of the retrocochlear auditory pathway in the premature infants with intrauterine growth retardation (IGR) in comparison to that of the normotrophics of a similar gestational age during the third and sixth months of life by recording auditory steady-state responses (ASSR). The audiological examination by the method of auditory steady-state response (ASSR) involved 127 children at the 3d month of life and in 97 children at the 6th month of life. It was shown that the ASSR thresholds at certain frequencies during the 3d and 6th months of life of the children born after the 32d week of pregnancy were significantly higher than in the children born after 32 weeks gestation. The comparison of the two objective audiological methods, viz. distortion-product otoacoustic emission (DPOAE) and ASSR, indicates that both should be used to evaluate the hearing function during the third and sixth months of life to compensate for the discrepancy between the results obtained by either technique. PMID:26978745
De Schamphelaere, Karel A C; Janssen, Colin R
2006-07-15
regression model may form a sound conceptual basis for modeling the toxicological bioavailability of copper to green algae in regulatory assessments, although a full mechanistic understanding is lacking and should be the focus of future studies. PMID:16903294
Development of novel fire retardants
NASA Astrophysics Data System (ADS)
Sigdel Regmi, Bhawani
Numerous candidate environmentally-friendly, water-soluble, and non-toxic fire retardants and fire-retarding processes were developed and tested according to the ASTM D 3801 flammability test and the NRL 8093 smoldering test. Flame retardants that passed the ASTM D 3801 flammability test with the highest V0 rating were boron esters of guanidinium hydroxycarboxylate (glycolate, salicylate and dihydroxybenzoate), zinc gluconate borate ester, and cyanoacetate salts of organic bases (melaminium, cyanoguanidinium, and ammonium). Several related compounds pass this test with the lower V1 rating. Two new synergistic flame and smolder retarding systems were developed in which the individual components were incapable of preventing flame spread or smoldering but in combination they were highly effective. These systems were mixtures of either guanyl urea phosphate and boric acid or beta-alanine and boric acid. Compositions leading to the maximum solubility of boron oxides in the ammonium borate/sodium borate system were determined at several temperatures and the formation of mixtures exceeding 50% dissolved boric acid equivalents was found possible. These mixtures were applied as flame retardants for wood, paper, and carbon-loaded polyurethane foam both directly and indirectly by in situ precipitation of boric acid or zinc borate by appropriate chemical treatments. These all passed the ASTM flammability test with V0 rating. The performance of the boron-containing fire retardants is likely due to deposition of protective boron oxide coatings at elevated temperatures except where phosphate was present and a protective boron phosphate was deposited instead. In all cases, the oxidation of carbonaceous char was strongly inhibited. The hydroxycarboxylate groups generally formed intumescent chars during thermal decomposition that also contributed to fire retardancy.
NASA Astrophysics Data System (ADS)
Levashov, V. A.
2014-11-01
In order to gain insight into the connection between the vibrational dynamics and the atomic-level Green-Kubo stress correlation function in liquids, we consider this connection in a model crystal instead. Of course, vibrational dynamics in liquids and crystals are quite different and it is not expected that the results obtained on a model crystal should be valid for liquids. However, these considerations provide a benchmark to which the results of the previous molecular dynamics simulations can be compared. Thus, assuming that vibrations are plane waves, we derive analytical expressions for the atomic-level stress correlation functions in the classical limit and analyze them. These results provide, in particular, a recipe for analysis of the atomic-level stress correlation functions in Fourier space and extraction of the wave-vector and frequency-dependent information. We also evaluate the energies of the atomic-level stresses. The energies obtained are significantly smaller than the energies previously determined in molecular dynamics simulations of several model liquids. This result suggests that the average energies of the atomic-level stresses in liquids and glasses are largely determined by the structural disorder. We discuss this result in the context of equipartition of the atomic-level stress energies. Analysis of the previously published data suggests that it is possible to speak about configurational and vibrational contributions to the average energies of the atomic-level stresses in a glass state. However, this separation in a liquid state is problematic. We also introduce and briefly consider the atomic-level transverse current correlation function. Finally, we address the broadening of the peaks in the pair distribution function with increase of distance. We find that the peaks' broadening (by ≈40 % ) occurs due to the transverse vibrational modes, while contribution from the longitudinal modes does not change with distance.
NASA Astrophysics Data System (ADS)
Kontar, E. P.; MacKinnon, A. L.; Schwartz, R. A.; Brown, J. C.
2006-02-01
The observed hard X-ray (HXR) flux spectrum I(ɛ) from solar flares is a combination of primary bremsstrahlung photons I_P(ɛ) with a spectrally modified component from photospheric Compton backscatter of downward primary emission. The latter can be significant, distorting or hiding the true features of the primary spectrum which are key diagnostics for acceleration and propagation of high energy electrons and of their energy budget. For the first time in solar physics, we use a Green's function approach to the backscatter spectral deconvolution problem, constructing a Green's matrix including photoelectric absorption. This approach allows spectrum-independent extraction of the primary spectrum for several HXR flares observed by the Ramaty High Energy Solar Spectroscopic Imager (RHESSI). We show that the observed and primary spectra differ very substantially for flares with hard spectra close to the disk centre. We show in particular that the energy dependent photon spectral index γ (ɛ)=-d log I/d log ɛ is very different for I_P(ɛ) and for I(ɛ) and that inferred mean source electron spectra F(E) differ greatly. Even for a forward fitting of a parametric F(E) to the data, a clear low-energy cutoff required to fit I(ɛ) essentially disappears when the fit is to I_P(ɛ) - i.e. when albedo correction is included. The self-consistent correction for backscattered photons is thus shown to be crucial in determining the energy spectra of flare accelerated electrons, and hence their total number and energy.
Chen, Shan Nan; Zhang, Xiao Wen; Li, Li; Ruan, Bai Ye; Huang, Bei; Huang, Wen Shu; Zou, Peng Fei; Fu, Jian Ping; Zhao, Li Juan; Li, Nan; Nie, Pin
2016-08-01
IFN-λ (IFNL), i.e. type III IFN genes were found in a conserved gene locus in tetrapod vertebrates. But, a unique locus containing IFNL was found in avian. In turtle and crocodile, IFNL genes were distributed in these two separate loci. As revealed in phylogenetic trees, IFN-λs in these two different loci and other amniotes were grouped into two different clades. The conservation in gene presence and gene locus was also observed for the receptors of IFN-λ, IFN-λR1 and IL-10RB in tetrapods. It is further revealed that in North American green anole lizard Anolis carolinensis, a single IFNL gene was situated collinearly in the conserved locus as in other tetrapods, together with its receptors IFN-λR1 and IL-10RB also identified in this study. The IFN-λ and its receptors were expressed in all examined organs/tissues, and their expression was stimulated following the injection of polyI:polyC. The ISREs in promoter of IFN-λ in lizard were responsible to IRF3 as demonstrated using luciferase report system, and IFN-λ in lizard functioned through the receptors, IFN-λR1 and IL-10RB, as the up-regulation of ISGs was observed in ligand-receptor transfected, and also in recombinant IFN-λ stimulated, cell lines. Taken together, it is concluded that the mechanisms involved in type III IFN ligand-receptor system, and in its signalling pathway and its down-stream genes may be conserved in green anole lizard, and may even be so in tetrapods from xenopus to human. PMID:27062970
NASA Astrophysics Data System (ADS)
Xu, Fuming; Wang, Bin; Wei, Yadong; Wang, Jian
2013-10-01
Orbital-free density functional theory (OFDFT) replaces the wavefunction in the kinetic energy by an explicit energy functional and thereby speeds up significantly the calculation of ground state properties of the solid state systems. So far, the application of OFDFT has been centered on closed systems and less attention is paid on the transport properties in open systems. In this paper, we use OFDFT and combine it with non-equilibrium Green's function to simulate equilibrium electronic transport properties in silicon nanostructures from first principles. In particular, we study ac transport properties of a silicon atomic junction consisting of a silicon atomic chain and two monoatomic leads. We have calculated the dynamic conductance of this atomic junction as a function of ac frequency with one to four silicon atoms in the central scattering region. Although the system is transmissive with dc conductance around 4 to 5 e2/h, capacitive-like behavior was found in the finite frequency regime. Our analysis shows that, up to 0.1 THz, this behavior can be characterized by a classic RC circuit consisting of two resistors and a capacitor. One resistor gives rise to dc resistance and the other one accounts for the charge relaxation resistance with magnitude around 0.2 h/e2 when the silicon chain contains two atoms. It was found that the capacitance is around 5 aF for the same system.
Method of Green's function of nonlinear vibration of corrugated shallow shells
NASA Astrophysics Data System (ADS)
Yuan, Hong
2008-06-01
Based on the dynamic equations of nonlinear large deflection of axisymmetric shallow shells of revolution, the nonlinear free vibration and forced vibration of a corrugated shallow shell under concentrated load acting at the center have been investigated. The nonlinear partial differential equations of shallow shell were reduced to the nonlinear integral-differential equations by using the method of Green’s function. To solve the integral-differential equations, the expansion method was used to obtain Green’s function. Then the integral-differential equations were reduced to the form with a degenerate core by expanding Green’s function as a series of characteristic function. Therefore, the integral-differential equations became nonlinear ordinary differential equations with regard to time. The amplitude-frequency relation, with respect to the natural frequency of the lowest order and the amplitude-frequency response under harmonic force, were obtained by considering single mode vibration. As a numerical example, nonlinear free and forced vibration phenomena of shallow spherical shells with sinusoidal corrugation were studied. The obtained solutions are available for reference to the design of corrugated shells.
Frequency-Domain Green's Functions for Radar Waves in Heterogeneous 2.5D Media
Green’s functions for radar waves propagating in heterogeneous media may be calculated in the frequency domain using a hybrid of two numerical methods. The model is defined in the Cartesian coordinate system, and its electromagnetic properties may vary in the x and z directions, ...
Allocation of Attention and Effect of Practice on Persons with and without Mental Retardation
ERIC Educational Resources Information Center
Oka, Kohei; Miura, Toshiaki
2008-01-01
Persons with mild and moderate mental retardation and CA-matched persons without mental retardation performed a dual-task, "pencil-and-paper task" (Baddeley, Della Sala, Gray, Papagno, & Spinnler (1997). Testing central executive functioning with a pencil-and-paper test. In Rabbit (Ed.), Methodology of Frontal and Executive Function (pp. 61-80).…