Atom-diatom scattering dynamics of spinning molecules
Energy Technology Data Exchange (ETDEWEB)
Eyles, C. J. [Institut für Chemie und Biochemie, Freie Universität Berlin, 14195 Berlin (Germany); Floß, J.; Averbukh, I. Sh. [Department of Chemical Physics, Weizmann Institute of Science, Rehovot 76100 (Israel); Leibscher, M. [Institut für Theoretische Physik, Leibniz Universität Hannover, 30167 Hannover (Germany)
2015-01-14
We present full quantum mechanical scattering calculations using spinning molecules as target states for nuclear spin selective atom-diatom scattering of reactive D+H{sub 2} and F+H{sub 2} collisions. Molecules can be forced to rotate uni-directionally by chiral trains of short, non-resonant laser pulses, with different nuclear spin isomers rotating in opposite directions. The calculations we present are based on rotational wavepackets that can be created in this manner. As our simulations show, target molecules with opposite sense of rotation are predominantly scattered in opposite directions, opening routes for spatially and quantum state selective scattering of close chemical species. Moreover, two-dimensional state resolved differential cross sections reveal detailed information about the scattering mechanisms, which can be explained to a large degree by a classical vector model for scattering with spinning molecules.
Energy Technology Data Exchange (ETDEWEB)
Quemener, G.; Launay, J.M. [Rennes-1 Univ., Institut de Physique de Rennes, UMR CNRS 6251, 35 (France); Quemener, G. [Nevada Las Vegas niv., Dept. of Chemistry, NV (United States); Honvault, P. [University of Franche-Comte, Institut UTINAM, UMR CNRS 6213, 25 - Besancon (France)
2008-08-15
The role of the atom-atom scattering length and of the symmetrization in ultracold atom-diatom collisions in one dimension is presented. For an ultracold atom-diatom collision and for a diatomic molecule in its highest vibrational state, inelastic rate coefficients vanish for a system composed of fermionic atoms as the atom-atom scattering length increases whereas they do not for a system composed of bosonic atoms. The differences come from the symmetrization of the wavefunction of the systems. We explain these differences by comparing the shape of the effective potentials of the atom-diatom approach. For the fermionic system, we use a zero-range interaction to model the adiabatic energies and we give a lower estimate of the atom-diatom scattering length as a function of the atom-atom scattering length. (authors)
Herman, Michael F.; Freed, Karl F.
1983-05-01
The self-consistent matrix propagator method of Laing and Freed is extended to treat semiclassical nonadiabatic scattering in the collinear atom-diatom system. Applications are made to a model system in which diabatic surfaces are parallel, so the nonadiabatic transitions are not well localized in space, thereby introducing difficulties in some previous nonadiabatic semiclassical methods. In the self-consistent matrix propagator method nonadiabatic transitions occur at the boundaries of Magnus regions, and the relative phases, associated with trajectories undergoing transitions at different boundaries, must accurately be determined. This necessitates the determination of the absolute phases of the uniformized classical S matrix, a phase which is unnecessary in single potential surface semiclassical scattering. Semiclassical calculations are compared with full close coupled quantum calculations of Schmalz. The agreement is very good even at relatively low energies. The largest errors enter, as anticipated, for highly classically forbidden transitions whose overall probabilities are, however, rather small. The self-consistent matrix propagator method becomes simpler to apply and more accurate as the total energy increases, i.e., as the fully quantum calculations become prohibitively large. The method has the physical appeal that the self-consistent trajectories follow essentially adiabatic surfaces in strongly interacting regions and diabatic surfaces in weakly interacting regions, with a self-consistent interpolation between these regions.
Warehime, Mick; Alexander, Millard H
2014-07-14
We restate the application of the finite element method to collinear triatomic reactive scattering dynamics with a novel treatment of the scattering boundary conditions. The method provides directly the reactive scattering wave function and, subsequently, the probability current density field. Visualizing these quantities provides additional insight into the quantum dynamics of simple chemical reactions beyond simplistic one-dimensional models. Application is made here to a symmetric reaction (H+H2), a heavy-light-light reaction (F+H2), and a heavy-light-heavy reaction (F+HCl). To accompany this article, we have written a MATLAB code which is fast, simple enough to be accessible to a wide audience, as well as generally applicable to any problem that can be mapped onto a collinear atom-diatom reaction. The code and user's manual are available for download from http://www2.chem.umd.edu/groups/alexander/FEM.
Energy Technology Data Exchange (ETDEWEB)
Warehime, Mick [Chemical Physics Program, University of Maryland, College Park, Maryland 20742-2021 (United States); Alexander, Millard H., E-mail: mha@umd.edu [Department of Chemistry and Biochemistry and Institute for Physical Science and Technology, University of Maryland, College Park, Maryland 20742-2021 (United States)
2014-07-14
We restate the application of the finite element method to collinear triatomic reactive scattering dynamics with a novel treatment of the scattering boundary conditions. The method provides directly the reactive scattering wave function and, subsequently, the probability current density field. Visualizing these quantities provides additional insight into the quantum dynamics of simple chemical reactions beyond simplistic one-dimensional models. Application is made here to a symmetric reaction (H+H{sub 2}), a heavy-light-light reaction (F+H{sub 2}), and a heavy-light-heavy reaction (F+HCl). To accompany this article, we have written a MATLAB code which is fast, simple enough to be accessible to a wide audience, as well as generally applicable to any problem that can be mapped onto a collinear atom-diatom reaction. The code and user's manual are available for download from http://www2.chem.umd.edu/groups/alexander/FEM.
2005-01-01
The long-range forces that act between three atoms are analysed in both atom-diatom and atom-atom-atom representations. Expressions for atom-diatom dispersion coefficients are obtained in terms of 3-body nonadditive coefficients. The anisotropy of atom-diatom C_6 dispersion coefficients arises primarily from nonadditive triple-dipole and quadruple-dipole forces, while pairwise-additive forces and nonadditive triple-dipole and dipole-dipole-quadrupole forces contribute significantly to atom-di...
Modelling Hyperboloid Sound Scattering
DEFF Research Database (Denmark)
Burry, Jane; Davis, Daniel; Peters, Brady;
2011-01-01
The Responsive Acoustic Surfaces workshop project described here sought new understandings about the interaction between geometry and sound in the arena of sound scattering. This paper reports on the challenges associated with modelling, simulating, fabricating and measuring this phenomenon using...
Dynamical approach to the statistical average of atom-diatom collision
Institute of Scientific and Technical Information of China (English)
无
2006-01-01
The dynamical Lie algebraic method is used for the description of statistical mechanics of the atom-diatom collision. A main advantage of this method is that it can not only give the expression for evolution operator in terms of the group parameter, but also provide the expression for the density operator for a given system. The group parameters can be determined by solving a set of coupled nonlinear differential equations. Thus, the expression of the statistical average values is derived in terms of the density operator formalism in statistical mechanics. And we can use the time evolution operator to calculate the transition probability. The method is applied to the collision of H2 with He. Comparing the results with the experimental results, we can see that the dynamical Lie algebraic method is useful for describing the molecule collision.
Energy Technology Data Exchange (ETDEWEB)
Zhao, Bin [Center for Theoretical and Computational Chemistry, and State Key Laboratory of Molecular Reaction Dynamics, Dalian Institute of Chemical Physics, Chinese Academy of Sciences, Dalian 116023 (China); Department of Chemistry and Chemical Biology, University of New Mexico, Albuquerque, New Mexico 87131 (United States); Sun, Zhigang, E-mail: zsun@dicp.ac.cn, E-mail: hguo@unm.edu [Center for Theoretical and Computational Chemistry, and State Key Laboratory of Molecular Reaction Dynamics, Dalian Institute of Chemical Physics, Chinese Academy of Sciences, Dalian 116023 (China); Guo, Hua, E-mail: zsun@dicp.ac.cn, E-mail: hguo@unm.edu [Department of Chemistry and Chemical Biology, University of New Mexico, Albuquerque, New Mexico 87131 (United States)
2014-06-21
A recently proposed transition-state wave packet method [R. Welsch, F. Huarte-Larrañaga, and U. Manthe, J. Chem. Phys. 136, 064117 (2012)] provides an efficient and intuitive framework to study reactive quantum scattering at the state-to-state level. It propagates a few transition-state wave packets, defined by the eigenfunctions of the low-rank thermal flux operator located near the transition state, into the asymptotic regions of the reactant and product arrangement channels separately using the corresponding Jacobi coordinates. The entire S-matrix can then be assembled from the corresponding flux-flux cross-correlation functions for all arrangement channels. Since the transition-state wave packets can be defined in a relatively small region, its transformation into either the reactant or product Jacobi coordinates is accurate and efficient. Furthermore, the grid/basis for the propagation, including the maximum helicity quantum number K, is much smaller than that required in conventional wave packet treatments of state-to-state reactive scattering. This approach is implemented for atom-diatom reactions using a time-dependent wave packet method and applied to the H + D{sub 2} reaction with all partial waves. Excellent agreement with benchmark integral and differential cross sections is achieved.
Zhao, Bin; Sun, Zhigang; Guo, Hua
2014-06-01
A recently proposed transition-state wave packet method [R. Welsch, F. Huarte-Larrañaga, and U. Manthe, J. Chem. Phys. 136, 064117 (2012)] provides an efficient and intuitive framework to study reactive quantum scattering at the state-to-state level. It propagates a few transition-state wave packets, defined by the eigenfunctions of the low-rank thermal flux operator located near the transition state, into the asymptotic regions of the reactant and product arrangement channels separately using the corresponding Jacobi coordinates. The entire S-matrix can then be assembled from the corresponding flux-flux cross-correlation functions for all arrangement channels. Since the transition-state wave packets can be defined in a relatively small region, its transformation into either the reactant or product Jacobi coordinates is accurate and efficient. Furthermore, the grid/basis for the propagation, including the maximum helicity quantum number K, is much smaller than that required in conventional wave packet treatments of state-to-state reactive scattering. This approach is implemented for atom-diatom reactions using a time-dependent wave packet method and applied to the H + D2 reaction with all partial waves. Excellent agreement with benchmark integral and differential cross sections is achieved.
Modeling fluctuations in scattered waves
Jakeman, E
2006-01-01
Fluctuations in scattered waves limit the performance of imaging and remote sensing systems that operate on all wavelengths of the electromagnetic spectrum. To better understand these fluctuations, Modeling Fluctuations in Scattered Waves provides a practical guide to the phenomenology, mathematics, and simulation of non-Gaussian noise models and discusses how they can be used to characterize the statistics of scattered waves.Through their discussion of mathematical models, the authors demonstrate the development of new sensing techniques as well as offer intelligent choices that can be made for system analysis. Using experimental results and numerical simulation, the book illustrates the properties and applications of these models. The first two chapters introduce statistical tools and the properties of Gaussian noise, including results on phase statistics. The following chapters describe Gaussian processes and the random walk model, address multiple scattering effects and propagation through an extended med...
Sethuraman, V.; Hunt, P. M.
1988-06-01
The adaptive multigrid technique in the finite element method of the solution of partial differential equations is examined in the context of model problems in atom-atom and collinear atom-diatom collisions. For the problem leading to scattering along an L-shaped region, the technique yields accurate results for regions of energy far from the threshold for excitation of a new channel without inclusion of virtual states. Close to the threshold, the cusplike structure of the transition probability (vs. energy) and the time delay associated with the onset of a resonance are recovered only by inclusion of the new (closed) channel in the finite element solution. For atom-diatom collinear collisions, use of an orthogonal coordinate system facilitates dicretization and adds no extra labor in the finite element method, compared to the usual mass-weighted system.
Quantum mechanical theory of a structured atom-diatom collision system - A + BC/1-Sigma/
Devries, P. L.; George, T. F.
1977-01-01
The problem of a 2-p state atom colliding with a singlet sigma state diatom, which involves multiple potential surfaces, is investigated. Within a diabatic representation for the electronic degrees of freedom (plus spin-orbit interaction), coupled scattering equations are derived in both space-fixed and body-fixed coordinate systems. Coefficients, analogous to Percival-Seaton coefficients, are obtained. Approximations to the exact equations, including angular momenta decoupling approximations, are discussed for both the space-fixed and body-fixed formalisms.
Multiple scattering Model in GEANT4
Urbàn, L
2002-01-01
We present a new multiple scattering (MSC) model to simulate the multiple scattering of charged particles in matter. This model does not use the Moliere formalism, it is based on the more complete Lewis theory. The model simulates the scattering of the particle after a given step, computes the path length correction and the lateral displacement as well.
Elastic scattering in geometrical model
Plebaniak, Zbigniew; Wibig, Tadeusz
2016-10-01
The experimental data on proton-proton elastic and inelastic scattering emerging from the measurements at the Large Hadron Collider, calls for an efficient model to fit the data. We have examined the optical, geometrical picture and we have found the simplest, linear dependence of this model parameters on the logarithm of the interaction energy with the significant change of the respective slopes at one point corresponding to the energy of about 300 GeV. The logarithmic dependence observed at high energies allows one to extrapolate the proton-proton elastic, total (and inelastic) cross sections to ultra high energies seen in cosmic rays events which makes a solid justification of the extrapolation to very high energy domain of cosmic rays and could help us to interpret the data from an astrophysical and a high energy physics point of view.
Efficient Finite Element Modelling of Elastodynamic Scattering
Velichko, A.; Wilcox, P. D.
2010-02-01
A robust and efficient technique for predicting the complete scattering behavior for an arbitrarily-shaped defect is presented that can be implemented in a commercial FE package. The spatial size of the modeling domain around the defect is as small as possible to minimize computational expense and a minimum number of models are executed. Example results for 2D and 3D scattering in isotropic material and guided wave scattering are presented.
Boundary scattering in the phi^4 model
Dorey, Patrick; Mercer, James; Romanczukiewicz, Tomasz; Shnir, Yasha
2015-01-01
We study boundary scattering in the phi^4 model on a half-line with a one-parameter family of Neumann-type boundary conditions. A rich variety of phenomena is observed, which extends previously-studied behaviour on the full line to include regimes of near-elastic scattering, the restoration of a missing scattering window, and the creation of a kink or oscillon through the collision-induced decay of a metastable boundary state.
Composed Scattering Model for Direct Volume Rendering
Institute of Scientific and Technical Information of China (English)
蔡文立; 石教英
1996-01-01
Based on the equation of transfer in transport theory of optical physics,a new volume rendering model,called composed scattering model(CSM),is presented.In calculating the scattering term of the equation,it is decomposed into volume scattering intensity and surface scattering intensity,and they are composed with the boundary detection operator as the weight function.This proposed model differs from the most current volume rendering models in the aspect that in CSM segmentation and illumination intensity calculation are taken as two coherent parts while in existing models they are regarded as two separate ones.This model has been applied to the direct volume rendering of 3D data sets obtained by CT and MRI.The resultant images show not only rich details but also clear boundary surfaces.CSM is demonstrated to be an accurate volume rendering model suitable for CT and MRI data sets.
Compton scattering in the Endpoint Model
Dagaonkar, Sumeet
2016-01-01
We use the Endpoint model for exclusive hadronic processes to study Compton scattering of the proton. The parameters of the Endpoint model are fixed using the data for $F_1$ and the ratio of Pauli and Dirac form factors ($F_2/F_1$) and then used to get numerical predictions for the differential scattering cross section. We studied the Compton scattering at fixed $\\theta_{CM}$ in the $s \\sim t \\gg \\Lambda_{QCD}$ limit and at fixed $s$ much larger than $t$ limit. We observed that the calculations in the Endpoint Model give a good fit with experimental data in both regions.
Rotational nuclear models and electron scattering
Energy Technology Data Exchange (ETDEWEB)
Moya de Guerra, E.
1986-05-01
A review is made of the basic formalism involved in the application of nuclear rotational models to the problem of electron scattering from axially symmetric deformed nuclei. Emphasis is made on the use of electron scattering to extract information on the nature of the collective rotational model. In this respect, the interest of using polarized beam and target is discussed with the help of illustrative examples. Concerning the nuclear structure four rotational models are considered: Two microscopic models, namely the Projected Hartree-Fock (PHF) and cranking models; and two collective models, the rigid rotor and the irrotational flow models. The problem of current conservation within the different models is also discussed.
Modelling the inelastic scattering of fast electrons
Energy Technology Data Exchange (ETDEWEB)
Allen, L.J., E-mail: lja@unimelb.edu.au [School of Physics, University of Melbourne, Parkville, Victoria 3010 (Australia); D' Alfonso, A.J., E-mail: a.j@dalfonso.com.au [School of Physics, University of Melbourne, Parkville, Victoria 3010 (Australia); Findlay, S.D. [School of Physics, Monash University, Clayton, Victoria 3800 (Australia)
2015-04-15
Imaging at atomic resolution based on the inelastic scattering of electrons has become firmly established in the last three decades. Harald Rose pioneered much of the early theoretical work on this topic, in particular emphasising the role of phase and the importance of a mixed dynamic form factor. In this paper we review how the modelling of inelastic scattering has subsequently developed and how numerical implementation has been achieved. A software package μSTEM is introduced, capable of simulating various imaging modes based on inelastic scattering in both scanning and conventional transmission electron microscopy. - Highlights: • Harald Rose was a pioneer of important work on atomic resolution imaging using inelastic scattering. • We review how the modelling of inelastic scattering has subsequently developed and been applied. • A software package μSTEM is introduced, capable of simulating various inelastic imaging modes.
Improving Pulsar Distances by Modelling Interstellar Scattering
Deshpande, A A
1998-01-01
We present here a method to study the distribution of electron density fluctuations in pulsar directions as well as to estimate pulsar distances. The method, based on a simple two-component model of the scattering medium discussed by Gwinn et al. (1993), uses scintillation & proper motion data in addition to the measurements of angular broadening & temporal broadening to solve for the model parameters, namely, the fractional distance to a discrete scatterer and the ascociated relative scattering strength. We show how this method can be used to estimate pulsar distances reliably, when the location of a discrete scatterer (e.g. an HII region), if any, is known. Considering the specific example of PSR B0736-40, we illustrate how a simple characterization of the Gum nebula region (using the data on the Vela pulsar) is possible and can be used along with the temporal broadening measurements to estimate pulsar distances.
Transparent alumina: A light scattering model
Apetz, R.; Van Bruggen, P.B.
2003-01-01
A model based on Rayleigh-Gans-Debye light scattering theory has been developed to describe the light transmission properties of fine-grained, fully dense polycrystalline ceramics consisting of birefringent crystals. This model extends light transmission models based on geometrical optics, which are
Quark model for kaon nucleon scattering
Indian Academy of Sciences (India)
Ahmed Osman
2011-12-01
Kaon nucleon elastic scattering is studied using chiral (3) quark model including antiquarks. Parameters of the present model are essentially based on nucleon–nucleon and nucleon–hyperon interactions. The mass of the scalar meson is taken as 635 MeV. Using this model, the phase shifts of the and partial waves of the kaon nucleon elastic scattering are investigated for isospins 0 and 1. The results of the numerical calculations of different partial waves are in good agreement with experimental data.
Arrangement transformation approach to state-to-state quantum reactive scattering H+DH→DH+H, HH+D
Institute of Scientific and Technical Information of China (English)
张怿慈; 战立欣; 谭哲民; 张庆刚; 张增辉
1999-01-01
Arrangement transformation approach (ATA) for doing state-to-state quantum reactive scattering calculations of atom-diatom systems is given. The state-to-state results of H + DH on LSTH potential energy surface are present. ed, and it can be deduced from the results that the ATA method can be used for the system with more than three atoms.
Scattering Amplitudes and Worldsheet Models of QFTs
CERN. Geneva
2016-01-01
I will describe recent progress on the study of scattering amplitudes via ambitwistor strings and the scattering equations. Ambitwistor strings are worldsheet models of quantum field theories, inspired by string theory. They naturally lead to a representation of amplitudes based on the scattering equations. While worldsheet models and related ideas have had a wide-ranging impact on the modern study of amplitudes, their direct application at loop level is a very recent success. I will show how a major difficulty in the loop-level story, the technicalities of higher-genus Riemann surfaces, can be avoided by turning the higher-genus surface into a nodal Riemann sphere, with the nodes representing the loop momenta. I will present new formulas for the one-loop integrands of gauge theory and gravity, with or without supersymmetry, and also some two-loop results.
Directional Dipole Model for Subsurface Scattering
DEFF Research Database (Denmark)
Frisvad, Jeppe Revall; Hachisuka, Toshiya; Kjeldsen, Thomas Kim
2014-01-01
Rendering translucent materials using Monte Carlo ray tracing is computationally expensive due to a large number of subsurface scattering events. Faster approaches are based on analytical models derived from diffusion theory. While such analytical models are efficient, they miss out on some...... point source diffusion. A ray source corresponds better to the light that refracts through the surface of a translucent material. Using this ray source, we are able to take the direction of the incident light ray and the direction toward the point of emergence into account. We use a dipole construction...... similar to that of the standard dipole model, but we now have positive and negative ray sources with a mirrored pair of directions. Our model is as computationally efficient as existing models while it includes single scattering without relying on a separate Monte Carlo simulation, and the rendered images...
Braided rings a scattering billiard model
Bénet, L
1999-01-01
We introduce a billiard scattering model consisting of two non-overlapping rotating discs in the context of the formation and structural properties of planetary rings. We show that due to the arrangement of the symmetric periodic orbits, stable orbits are found which in the configuration space lead to the appearance of patterns qualitatively similar to planetary rings. Rings associated with different stability regions are naturally braided; different braids may overlap displaying features similar to clumps. Erosion mechanisms within the model are discussed.
A sparse scattering model for nanoparticles on rough substrates
DEFF Research Database (Denmark)
Karamehmedovic, Mirza; Hansen, Poul-Erik; Wriedt, Thomas
2013-01-01
We present and validate an efficient forward scattering model for nanoparticles on rough contaminated substrates.......We present and validate an efficient forward scattering model for nanoparticles on rough contaminated substrates....
Microwave scattering and emission models for users
Fung, Adrian K
2009-01-01
Today, microwave remote sensing has evolved into a valuable and economical tool for a variety of applications. It is used in a wide range of areas, from geological sensing, geographical mapping, and weather monitoring, to GPS positioning, aircraft traffic, and mapping of oil pollution over the sea surface. This unique resource provides you with practical scattering and emission data models that represent the interaction between electromagnetic waves and a scene on the Earth surface in the microwave region. The book helps you understand and apply these models to your specific work in the field.
Analytic amplitude models for forward scattering
Kang, K; Ezhela, Vladimir V; Gauron, P; Kuyanov, Yu V; Lugovsky, S B; Nicolescu, Basarab; Tkachenko, N P; Kuyanov, Yu. V.
2002-01-01
We report on fits of a large class of analytic amplitude models for forward scattering against the comprehensive data for all available reactions. To differentiate the goodness of the fits of many possible parametrizations to a large sample of data, we developed and used a set of quantitative indicators measuring statistical quality of the fits over and beyond the typical criterion of the $\\Chi^2 /dof$. These indicators favor models with a universal $ log^2 s$ Pomeron term, which enables one to extend the fit down to $\\sqrt s = 4$ GeV.
Model of Light Scattering in Cavitation Area
Directory of Open Access Journals (Sweden)
S. P. Skvortsov
2015-01-01
Full Text Available The offered work presents analysis of extinction mechanisms and justification of light scattering model in ultrasonic cavitation area to justify a control method of ultrasonic cavitation through its optical sounding by low-intensity laser radiation and through photo-detector record of last radiation.The analysis of the extinction mechanisms has shown that the most essential mechanism causing a change of the transmission coefficient with time is dispersion on pulsating cavitation bubbles. Other extinction mechanisms lead to the time-constant reduction of last radiation intensity and can be taken into consideration by normalizing a recorded transmission coefficient for a previously measured liquid transmission coefficient when there is no cavitation.The feature of light scattering on the cavitation bubbles is primary dispersion in a forward direction that is connected with great values of bubbles radius from units to hundreds of micrometers. In case of single bubbles, dispersion can be described by Mi's theory, and, as to the cavitation area, it is reasonable to use the theory of V. Tversky for multiple light scattering. Thus, dispersion section, according to the paradox of extinction, can be considered to be equal to doubled geometrical section of a bubble. With increasing bubble radius the transmission coefficient monotonically decreases. So, the law of bubble pulsations and the model of light scattering define the law of changing transmission coefficient.Therefore, the cavitation area with its optical sounding acts as a peculiar opto-acoustic modulator. Thus, the demodulated signal of a photo-detector comprises information on pulsations of bubbles.The paper examines the influence of cavitation area thickness and bubbles concentration on the transmission coefficient. It shows a type of transmission coefficient dependence on the radius of cavitation bubbles.The optical sounding method is attractive because it allows us to obtain data on the
Hydrogen scattering from a cesiated surface model
Rutigliano, Maria; Palma, Amedeo; Sanna, Nico
2017-10-01
A cesiated surface model was considered to study the dynamics of hydrogen atom scattering using a semiclassical collisional method. Using dipole correction method, the work function of the considered surface, is calculated to be 1.81 eV (± 0.02) eV. The Potential Energy Surface for the interaction of H atoms with the surface was determined via first principle electronic structure calculations including the interaction with both Cs and Mo atoms of the surface. We found the scattered H atoms to have a negative partial charge of nearly 0.4 with the backscattered flux arising mainly from H atoms impinging directly (or very close) to Cs atoms on the surface. On the contrary, H atoms impinging in the voids between the Cs atoms propagate through the first Cs layer and remain adsorbed. The propagation occurs mainly in the vertical direction. The scattering probability after a very quick increase remains almost constant around an average value of 0.35.
A hybrid Scatter/Transform cloaking model
Directory of Open Access Journals (Sweden)
Gad Licht
2015-01-01
Full Text Available A new Scatter/Transform cloak is developed that combines the light bending of refraction characteristic of a Transform cloak with the scatter cancellation characteristic of a Scatter cloak. The hybrid cloak incorporates both Transform’s variable index of refraction with modified linear intrusions to maximize the Scatter cloak effect. Scatter/Transform improved the scattering cross-section of cloaking in a 2-dimensional space to 51.7% compared to only 39.6% or 45.1% respectively with either Scatter or Transform alone. Metamaterials developed with characteristics based on the new ST hybrid cloak will exhibit superior cloaking capabilities.
Astronomical Receiver Modelling Using Scattering Matrices
King, O G; Copley, C; Davis, R J; Leahy, J P; Leech, J; Muchovej, S J C; Pearson, T J; Taylor, Angela C
2014-01-01
Proper modelling of astronomical receivers is vital: it describes the systematic errors in the raw data, guides the receiver design process, and assists data calibration. In this paper we describe a method of analytically modelling the full signal and noise behaviour of arbitrarily complex radio receivers. We use electrical scattering matrices to describe the signal behaviour of individual components in the receiver, and noise correlation matrices to describe their noise behaviour. These are combined to produce the full receiver model. We apply this approach to a specified receiver architecture: a hybrid of a continous comparison radiometer and correlation polarimeter designed for the C-Band All-Sky Survey. We produce analytic descriptions of the receiver Mueller matrix and noise temperature, and discuss how imperfections in crucial components affect the raw data. Many of the conclusions drawn are generally applicable to correlation polarimeters and continuous comparison radiometers.
Modeling Scattering Polarization for Probing Solar Magnetism
Bueno, Javier Trujillo
2011-01-01
This paper considers the problem of modeling the light polarization that emerges from an astrophysical plasma composed of atoms whose excitation state is significantly influenced by the anisotropy of the incident radiation field. In particular, it highlights how radiative transfer simulations in three-dimensional models of the quiet solar atmosphere may help us to probe its thermal and magnetic structure, from the near equilibrium photosphere to the highly non-equilibrium upper chromosphere. The paper finishes with predictions concerning the amplitudes and magnetic sensitivities of the linear polarization signals produced by scattering processes in two transition region lines, which should encourage us to develop UV polarimeters for sounding rockets and space telescopes with the aim of opening up a new diagnostic window in astrophysics.
Modeling surface roughness scattering in metallic nanowires
Energy Technology Data Exchange (ETDEWEB)
Moors, Kristof, E-mail: kristof@itf.fys.kuleuven.be [KU Leuven, Institute for Theoretical Physics, Celestijnenlaan 200D, B-3001 Leuven (Belgium); IMEC, Kapeldreef 75, B-3001 Leuven (Belgium); Sorée, Bart [IMEC, Kapeldreef 75, B-3001 Leuven (Belgium); Physics Department, University of Antwerp, Groenenborgerlaan 171, B-2020 Antwerpen (Belgium); KU Leuven, Electrical Engineering (ESAT) Department, Kasteelpark Arenberg 10, B-3001 Leuven (Belgium); Magnus, Wim [IMEC, Kapeldreef 75, B-3001 Leuven (Belgium); Physics Department, University of Antwerp, Groenenborgerlaan 171, B-2020 Antwerpen (Belgium)
2015-09-28
Ando's model provides a rigorous quantum-mechanical framework for electron-surface roughness scattering, based on the detailed roughness structure. We apply this method to metallic nanowires and improve the model introducing surface roughness distribution functions on a finite domain with analytical expressions for the average surface roughness matrix elements. This approach is valid for any roughness size and extends beyond the commonly used Prange-Nee approximation. The resistivity scaling is obtained from the self-consistent relaxation time solution of the Boltzmann transport equation and is compared to Prange-Nee's approach and other known methods. The results show that a substantial drop in resistivity can be obtained for certain diameters by achieving a large momentum gap between Fermi level states with positive and negative momentum in the transport direction.
Relativistic models for quasielastic electron and neutrino-nucleus scattering
Directory of Open Access Journals (Sweden)
Meucci Andrea
2012-12-01
Full Text Available Relativistic models developed within the framework of the impulse approximation for quasielastic (QE electron scattering and successfully tested in comparison with electron-scattering data have been extended to neutrino-nucleus scattering. Different descriptions of final-state interactions (FSI in the inclusive scattering are compared. In the relativistic Green’s function (RGF model FSI are described consistently with the exclusive scattering using a complex optical potential. In the relativistic mean field (RMF model FSI are described by the same RMF potential which gives the bound states. The results of the models are compared for electron and neutrino scattering and, for neutrino scattering, with the recently measured charged-current QE (CCQE MiniBooNE cross sections.
Lorquet, J. C.
2014-04-01
We consider a triatomic system with zero total angular momentum and demonstrate that, no matter how complicated the anharmonic part of the potential energy function, classical dynamics in the vicinity of a saddle point is constrained by symmetry properties. At short times and at not too high energies, recrossing dynamics is largely determined by elementary local structural parameters and thus can be described in configuration space only. Conditions for recrossing are given in the form of inequalities involving structural parameters only. Explicit expressions for recrossing times, valid for microcanonical ensembles, are shown to obey interesting regularities. In a forward reaction, when the transition state is nonlinear and tight enough, one-fourth of the trajectories are expected to recross the plane R = R* (where R* denotes the position of the saddle point) within a short time. Another fourth of them are expected to have previously recrossed at a short negative time, i.e., close to the saddle point. These trajectories do not contribute to the reaction rate. The reactive trajectories that obey the transition state model are to be found in the remaining half. However, no conclusion can be derived for them, except that if recrossings occur, then they must either take place in the distant future or already have taken place in the remote past, i.e., far away from the saddle point. Trajectories that all cross the plane R = R* at time t = 0, with the same positive translational momentum P_{R_* } can be partitioned into two sets, distinguished by the parity of their initial conditions; both sets have the same average equation of motion up to and including terms cubic in time. Coordination is excellent in the vicinity of the saddle point but fades out at long (positive or negative) times, i.e., far away from the transition state.
Haïat, G; Naili, S
2011-02-01
Speed of sound measurements are used clinically to assess bone strength. Trabecular bone is an attenuating composite material in which negative values of velocity dispersion have been measured; this behavior remaining poorly explained physically. The aim of this work is to describe the ultrasonic propagation in trabecular bone modeled by infinite cylinders immersed in a saturating matrix and to derive the physical determinants of velocity dispersion. An original homogenization model accounting for the coupling of independent scattering and absorption phenomena allows the computation of phase velocity and of dispersion while varying bone properties. The first step of the model consists in the computation of the attenuation coefficient at all frequencies. The second step of the model corresponds to the application of the general Kramers-Krönig relationship to derive the frequency dependence of phase velocity. The model predicts negative values of velocity dispersion in agreement with experimental results obtained in phantoms mimicking trabecular bone. In trabecular bone, only negative values of velocity dispersion are predicted by the model, which span within the range of values measured experimentally. However, the comparison of the present results with results obtained in Haiat et al. (J Acoust Soc Am 124:4047-4058, 2008) assuming multiple scattering indicates that accounting for multiple scattering phenomena leads to a better prediction of velocity dispersion in trabecular bone.
Estimating seabed scattering mechanisms via Bayesian model selection.
Steininger, Gavin; Dosso, Stan E; Holland, Charles W; Dettmer, Jan
2014-10-01
A quantitative inversion procedure is developed and applied to determine the dominant scattering mechanism (surface roughness and/or volume scattering) from seabed scattering-strength data. The classification system is based on trans-dimensional Bayesian inversion with the deviance information criterion used to select the dominant scattering mechanism. Scattering is modeled using first-order perturbation theory as due to one of three mechanisms: Interface scattering from a rough seafloor, volume scattering from a heterogeneous sediment layer, or mixed scattering combining both interface and volume scattering. The classification system is applied to six simulated test cases where it correctly identifies the true dominant scattering mechanism as having greater support from the data in five cases; the remaining case is indecisive. The approach is also applied to measured backscatter-strength data where volume scattering is determined as the dominant scattering mechanism. Comparison of inversion results with core data indicates the method yields both a reasonable volume heterogeneity size distribution and a good estimate of the sub-bottom depths at which scatterers occur.
A surface-scattering model satisfying energy conservation and reciprocity
Sasihithlu, Karthik; Hugonin, Jean-Paul; Greffet, Jean-Jacques
2015-01-01
In order for surface scattering models to be accurate they must necessarily satisfy energy conservation and reciprocity principles. Roughness scattering models based on Kirchoff's approximation or perturbation theory do not satisfy these criteria in all frequency ranges. Here we present a surface scattering model based on analysis of scattering from a layer of particles on top of a substrate in the dipole approximation which satisfies both energy conservation and reciprocity and is thus accurate in all frequency ranges. The model takes into account the absorption in the substrate induced by the particles but does not take into account the near-field interactions between the particles.
A model for multiple scattering in GEANT4
Urbán, László
2006-01-01
We present a model to simulate the multiple scattering of charged particles in matter. The model is based on Lewis theory; it does not use the Moliere formalism. It simulates the scattering of a charged particle after a given step, computes the path length correction and the lateral displacement as well. This model is used in GEANT4.
Multi-scattering inversion for low model wavenumbers
Alkhalifah, Tariq Ali
2015-08-19
A successful full wavenumber inversion (FWI) implementation updates the low wavenumber model components first for proper wavefield propagation description, and slowly adds the high-wavenumber potentially scattering parts of the model. The low-wavenumber components can be extracted from the transmission parts of the recorded data given by direct arrivals or the transmission parts of the single and double-scattering wave-fields developed from a predicted scatter field. We develop a combined inversion of data modeled from the source and those corresponding to single and double scattering to update both the velocity model and the component of the velocity (perturbation) responsible for the single and double scattering. The combined inversion helps us access most of the potential model wavenumber information that may be embedded in the data. A scattering angle filter is used to divide the gradient of the combined inversion so initially the high wavenumber (low scattering angle) components of the gradient is directed to the perturbation model and the low wavenumber (high scattering angle) components to the velocity model. As our background velocity matures, the scattering angle divide is slowly lowered to allow for more of the higher wavenumbers to contribute the velocity model.
A Soluble Model for Scattering and Decay in Quaternionic Quantum Mechanics II Scattering
Horwitz, L P
1994-01-01
In a previous paper, it was shown that a soluble model can be constructed for the description of a decaying system in analogy to the Lee-Friedrichs model of complex quantum theory. It is shown here that this model also provides a soluble scattering theory, and therefore constitutes a model for a decay scattering system. Generalized second resolvent equations are obtained for quaternionic scattering theory. It is shown explicitly for this model, in accordance with a general theorem of Adler, that the scattering matrix is complex subalgebra valued. It is also shown that the method of Adler, using an effective optical potential in the complex sector to describe the effect of the quaternionic interactions, is equivalent to the general method of Green's functions described here.
Scattering for mixtures of hard spheres: comparison of total scattering intensities with model.
Anderson, B J; Gopalakrishnan, V; Ramakrishnan, S; Zukoski, C F
2006-03-01
The angular dependence of the intensity of x-rays scattered from binary and ternary hard sphere mixtures is investigated and compared to the predictions of two scattering models. Mixture ratio and total volume fraction dependent effects are investigated for size ratios equal to 0.51 and 0.22. Comparisons of model predictions with experimental results indicate the significant impact of the role of particle size distributions in interpreting the angular dependence of the scattering at wave vectors probing density fluctuations intermediate between the sizes of the particles in the mixture.
Exactly solvable models of scattering with SL(2, C) symmetry
Energy Technology Data Exchange (ETDEWEB)
Levay, P. [School of Physics, University of Melbourne, Parkville (Australia); Department of Theoretical Physics, Institute of Physics, Technical University, Budapest (Hungary)
2002-08-02
Using the theory of induced representations two exactly solvable models of non-relativistic scattering with SL(2, C) symmetry are presented. The first describes the scattering of a charged particle moving on the Poincare upper half space H under the influence of an SU(2) non-Abelian gauge potential with isospin s. The second deals with a one-dimensional coupled-channel scattering problem for a charged particle in a matrix-valued scalar potential containing Morse-like interaction terms. The coupled channel wavefunctions and the corresponding scattering matrices are calculated. A detailed description of the underlying geometric structures is also given and a generalization for restricting the motion to fundamental domains of H (three manifolds of constant negative sectional curvature) is outlined. Such models provide an interesting generalization to the known ones of multichannel scattering, quantum chaos and chaotic cosmology. (author)
Bi-Spectrum Scattering Model for Dielectric Randomly Rough Surface
Institute of Scientific and Technical Information of China (English)
刘宁; 李宗谦
2003-01-01
The bistatic scattering model is offen used for remote microwave sensing. The bi-spectrum model (BSM) for conducting surfaces was used to develop a scattering model for dielectric randomly rough surfaces to estimate their bistatic scattering coefficients. The model for dielectric rough surfaces differs from the BSM for a conducting surface by including Fresnell reflection and transmission from dielectric rough surfaces. The bistatic scattering coefficients were defined to satisfy the reciprocal theorem. Values calculated using the BSM for dielectric randomly rough surfaces compare well with those of the integral equation model (IEM) and with experimental data, showing that the BSM accuracy is acceptable and its range of validity is similar to that of IEM while the BSM expression is simpler than that of IEM.
Bi-Spectrum Scattering Model for Conducting Randomly Rough Surface
Institute of Scientific and Technical Information of China (English)
刘宁; 李宗谦
2002-01-01
A scattering model is developed to predict the scattering coefficient of a conducting randomly rough surface by analyzing the randomly rough surface in the spectral domain using the bi-spectrum method. For common randomly rough surfaces without obvious two-scale characteristics, a scale-compression filter can divide the auto-correlation spectrum into two parts with different correlation lengths. The Kirchhoff approximation and the small perturbation method are used to obtain the surface field, then a bistatic scattering model, the bi-spectrum model (BSM), is used to derive an explicit expression from the surface field. Examples using the integral equation model (IEM), finite difference of the time domain (FDTD) method, and BSM show that the BSM accuracy is acceptable and its range of validity is similar to IEM. BSM can also be extended to a scattering model for dielectric randomly rough surfaces.
Two body scattering length of Yukawa model on a lattice
De Soto, F; Roiesnel, C; Boucaud, P; Leroy, J P; Pène, O; Boucaud, Ph.
2007-01-01
The extraction of scattering parameters from Euclidean simulations of a Yukawa model in a finite volume with periodic boundary conditions is analyzed both in non relativistic quantum mechanics and in quantum field theory.
Dunkl operator, integrability, and pairwise scattering in rational Calogero model
Karakhanyan, David
2017-05-01
The integrability of the Calogero model can be expressed as zero curvature condition using Dunkl operators. The corresponding flat connections are non-local gauge transformations, which map the Calogero wave functions to symmetrized wave functions of the set of N free particles, i.e. it relates the corresponding scattering matrices to each other. The integrability of the Calogero model implies that any k-particle scattering is reduced to successive pairwise scatterings. The consistency condition of this requirement is expressed by the analog of the Yang-Baxter relation.
Fast sampling model for X-ray Rayleigh scattering
Grichine, V M
2013-01-01
A simple model for X-ray Rayleigh scattering is discussed in terms of the process total cross-section and the angular distribution of scattered X-ray photons. Comparisons with other calculations and experimental data are presented. The model is optimized for the simulation of X-ray tracking inside experimental setups with complex geometry where performance and memory volume are issues to be optimized. (C) 2013 Elsevier B.V. All rights reserved.
Crossing symmetric potential model of pion-nucleon scattering
Blankleider, B; Skawronski, T
2010-01-01
A crossing symmetric $\\pi N$ scattering amplitude is constructed through a complete attachment of two external pions to the dressed nucleon propagator of an underlying $\\pi N$ potential model. Our formulation automatically provides expressions also for the crossing symmetric and gauge invariant pion photoproduction and Compton scattering amplitudes. We show that our amplitudes are unitary if they coincide on-shell with the amplitudes obtained by attaching one pion to the dressed $\\pi NN$ vertex of the same potential model.
Validation of Compton Scattering Monte Carlo Simulation Models
Weidenspointner, Georg; Hauf, Steffen; Hoff, Gabriela; Kuster, Markus; Pia, Maria Grazia; Saracco, Paolo
2014-01-01
Several models for the Monte Carlo simulation of Compton scattering on electrons are quantitatively evaluated with respect to a large collection of experimental data retrieved from the literature. Some of these models are currently implemented in general purpose Monte Carlo systems; some have been implemented and evaluated for possible use in Monte Carlo particle transport for the first time in this study. Here we present first and preliminary results concerning total and differential Compton scattering cross sections.
Modeling plasmonic scattering combined with thin-film optics.
Schmid, M; Klenk, R; Lux-Steiner, M Ch; Topic, M; Krc, J
2011-01-14
Plasmonic scattering from metal nanostructures presents a promising concept for improving the conversion efficiency of solar cells. The determination of optimal nanostructures and their position within the solar cell is crucial to boost the efficiency. Therefore we established a one-dimensional optical model combining plasmonic scattering and thin-film optics to simulate optical properties of thin-film solar cells including metal nanoparticles. Scattering models based on dipole oscillations and Mie theory are presented and their integration in thin-film semi-coherent optical descriptions is explained. A plasmonic layer is introduced in the thin-film structure to simulate scattering properties as well as parasitic absorption in the metal nanoparticles. A proof of modeling concept is given for the case of metal-island grown silver nanoparticles on glass and ZnO:Al/glass substrates. Using simulations a promising application of the nanoparticle integration is shown for the case of CuGaSe(2) solar cells.
Neutrino-Electron Scattering and the Little Higgs Models
Institute of Scientific and Technical Information of China (English)
LI Na; YUE Chong-Xing; LI Xu-Xin
2011-01-01
The neutrino-electron scattering process is sensitive to the standard model (SM) and the new physics beyond the SM.We calculate the corrections of the littlest Higgs model and the SU(3) simple group model to the vee scattering cross section.Using the LSND experimental measured values,we obtain the bounds on the relevant free parameters,which might be compatible with those from the electroweak precision data.Neutrino-electron scattering is a simple and purely leptonic weak interaction process that can play an important role to perform precision tests of the standard model (SM) and probe various kinds of new physics models beyond the SM.[1-3] Thus,this process provides an ideal tool for electroweak studies.%The neutrino-electron scattering process is sensitive to the standard model (SM) and the new physics beyond the SM. We calculate the corrections of the littlest Higgs model and the SU(3) simple group model to the vee scattering cross section. Using the LSND experimental measured values, we obtain the bounds on the relevant free parameters, which might be compatible with those from the electroweak precision data.
Electromagnetic Model Reliably Predicts Radar Scattering Characteristics of Airborne Organisms
Mirkovic, Djordje; Stepanian, Phillip M.; Kelly, Jeffrey F.; Chilson, Phillip B.
2016-10-01
The radar scattering characteristics of aerial animals are typically obtained from controlled laboratory measurements of a freshly harvested specimen. These measurements are tedious to perform, difficult to replicate, and typically yield only a small subset of the full azimuthal, elevational, and polarimetric radio scattering data. As an alternative, biological applications of radar often assume that the radar cross sections of flying animals are isotropic, since sophisticated computer models are required to estimate the 3D scattering properties of objects having complex shapes. Using the method of moments implemented in the WIPL-D software package, we show for the first time that such electromagnetic modeling techniques (typically applied to man-made objects) can accurately predict organismal radio scattering characteristics from an anatomical model: here the Brazilian free-tailed bat (Tadarida brasiliensis). The simulated scattering properties of the bat agree with controlled measurements and radar observations made during a field study of bats in flight. This numerical technique can produce the full angular set of quantitative polarimetric scattering characteristics, while eliminating many practical difficulties associated with physical measurements. Such a modeling framework can be applied for bird, bat, and insect species, and will help drive a shift in radar biology from a largely qualitative and phenomenological science toward quantitative estimation of animal densities and taxonomic identification.
Light scattering by neutrophils: model, simulation, and experiment.
Orlova, Darya Yu; Yurkin, Maxim A; Hoekstra, Alfons G; Maltsev, Valeri P
2008-01-01
We studied the elastic light-scattering properties of human blood neutrophils, both experimentally and theoretically. The experimental study was performed with a scanning flow cytometer measuring the light-scattering patterns (LSPs) of individual cells over an angular range of 5-60 deg. We determined the absolute differential light-scattering cross sections of neutrophils. We also proposed an optical model for a neutrophil as a sphere filled by small spheres and prolate spheroids that correspond to granules and segmented nucleus, respectively. This model was used in simulations of LSPs using the discrete dipole approximation and different compositions of internal organelles. A comparison of experimentally measured and simulated LSPs gives a good qualitative agreement in LSP shape and quantitative agreement in overall magnitude of the differential light-scattering cross section.
Dual absorptive model and np elastic scattering at high energies
Energy Technology Data Exchange (ETDEWEB)
Saleem, M.; Fazal-e-Aleem
1980-06-01
The most recent measurements of the angular distribution and total cross-sections in np elastic scattering at high energies from 70 to 400 GeV/c have been fitted by using the dual absorptive model. Comparison has also been made with the Kane-Siedl model and the simple Regge pole model.
Geometric Feature Extraction and Model Reconstruction Based on Scattered Data
Institute of Scientific and Technical Information of China (English)
胡鑫; 习俊通; 金烨
2004-01-01
A method of 3D model reconstruction based on scattered point data in reverse engineering is presented here. The topological relationship of scattered points was established firstly, then the data set was triangulated to reconstruct the mesh surface model. The curvatures of cloud data were calculated based on the mesh surface, and the point data were segmented by edge-based method; Every patch of data was fitted by quadric surface of freeform surface, and the type of quadric surface was decided by parameters automatically, at last the whole CAD model was created. An example of mouse model was employed to confirm the effect of the algorithm.
Diffuse Scattering Model of Indoor Wideband Propagation
DEFF Research Database (Denmark)
Franek, Ondrej; Andersen, Jørgen Bach; Pedersen, Gert Frølund
2011-01-01
This paper presents a discrete-time numerical algorithm for computing field distribution in indoor environment by diffuse scattering from walls. Calculations are performed for a rectangular room with semi-reflective walls. The walls are divided into 0.5 x 0.5 m segments, resulting in 2272 wall...... segments in total and approximately 2 min running time on average computer. Frequency independent power levels at the walls around the circumference of the room and at four receiver locations in the middle of the room are observed. It is demonstrated that after finite period of initial excitation the field...... intensity in all locations eventually follows exponential decay with the same slope and approximately the same level for given delay. These observations are shown to be in good agreement with theory and previous measurements—the slopes of the decay curves for measurement, simulation and theory are found...
GNSS-Reflectometry: Forest canopies polarization scattering properties and modeling
Wu, Xuerui; Jin, Shuanggen
2014-09-01
Nowadays, GNSS-Reflectometry (GNSS-R) can be a new promising remote sensing tool in the ocean, snow/ice and land surfaces, e.g., vegetation biomass monitoring. Although GNSS-R provides a potentially special L-band multi-angular and multi-polarization measurement, the theoretical vegetation scattering properties and mechanisms for GNSS-R are not understood clearly. In this paper, the GNSS-R vegetation polarization scattering properties are studied and modeled at different incidence angles (specular direction). The bistatic scattering model Bi-mimics is employed, which is the first-order radiative transfer equation. As a kind of forest stand, the Aspen’s crown layer is composed of entire leaves, and its parameters in Mimics handbook are used as model input. The specular circular polarizations (co-polarization RR and cross-polarization LR) are simulated. For cross-polarization, the received polarization is assumed as a linear (horizontal and vertical) polarizations and ±45° linear polarizations. Therefore, the HR VR, +45R and -45R polarizations are simulated here. Contributions from different scattering components at RR, LR and VR polarization are also presented. For co-polarization, it is large in the whole specular angles (10-80°). The scattering trends of the other cross polarization (HR, LR, +45R and -45R) are a little similar when compared to the RR and RV. Therefore, the RHCP and V polarizations are more favorable to collect the reflected signals. The trunk heights and crown depths do not affect the scattering trends of RR, RV and RL, while the trunk height has some effect on the scattering amplitude of different polarizations. The azimuth angle has more effects on RR, RL and RV scattering, especially in lower than 50°. The observation angles and polarization combinations are extremely important for GNSS-R remote sensing.
Spermatozoa scattering by a microchannel feature: an elastohydrodynamic model
Montenegro-Johnson, Thomas; Smith, David J
2014-01-01
Sperm traverse their microenvironment through viscous fluid by propagating flagellar waves; the waveform emerges as a consequence of elastic structure, internal active moments, and low Reynolds number fluid dynamics. Engineered microchannels have recently been proposed as a method of sorting and manipulating motile cells; the interaction of cells with these artificial environments therefore warrants investigation. A numerical method is presented for the geometrically nonlinear elastohydrodynamic interaction of active swimmers with domain features. This method is employed to examine hydrodynamic scattering by a model microchannel backstep feature. Scattering is shown to depend on backstep height and the relative strength of viscous and elastic forces in the flagellum. In a 'high viscosity' parameter regime corresponding to human sperm in cervical mucus analogue, this hydrodynamic contribution to scattering is comparable in magnitude to recent data on contact effects, being of the order of 5-10 degrees. Scatter...
Velichko, A.; Wilcox, P. D.
2012-05-01
An efficient technique for predicting the complete scattering behavior for an arbitrarily-shaped scatterer is presented. The spatial size of the modeling domain around the scatterer is as small as possible to minimize computational expense and a minimum number of models are executed. This model uses non-reflecting boundary conditions on the surface surrounding the scatterer which are non-local in space. Example results for 2D and 3D scattering in isotropic material and guided wave scattering are presented.
A scattering model for surface-textured thin films
Jäger, K.; Zeman, M.
2009-01-01
We present a mathematical model that relates the surface morphology of randomly surface-textured thin films with the intensity distribution of scattered light. The model is based on the first order Born approximation [see e.g., M. Born and E. Wolf, Principles of Optics, 7th ed. (Cambridge University
A scattering model for surface-textured thin films
Jäger, K.; Zeman, M.
2009-01-01
We present a mathematical model that relates the surface morphology of randomly surface-textured thin films with the intensity distribution of scattered light. The model is based on the first order Born approximation [see e.g., M. Born and E. Wolf, Principles of Optics, 7th ed. (Cambridge University
Modelling of classical ghost images obtained using scattered light
Crosby, S.; Castelletto, S.; Aruldoss, C.; Scholten, R. E.; Roberts, A.
2007-08-01
The images obtained in ghost imaging with pseudo-thermal light sources are highly dependent on the spatial coherence properties of the incident light. Pseudo-thermal light is often created by reducing the coherence length of a coherent source by passing it through a turbid mixture of scattering spheres. We describe a model for simulating ghost images obtained with such partially coherent light, using a wave-transport model to calculate the influence of the scattering on initially coherent light. The model is able to predict important properties of the pseudo-thermal source, such as the coherence length and the amplitude of the residual unscattered component of the light which influence the resolution and visibility of the final ghost image. We show that the residual ballistic component introduces an additional background in the reconstructed image, and the spatial resolution obtainable depends on the size of the scattering spheres.
Modeling transmission and scatter for photon beam attenuators.
Ahnesjö, A; Weber, L; Nilsson, P
1995-11-01
The development of treatment planning methods in radiation therapy requires dose calculation methods that are both accurate and general enough to provide a dose per unit monitor setting for a broad variety of fields and beam modifiers. The purpose of this work was to develop models for calculation of scatter and transmission for photon beam attenuators such as compensating filters, wedges, and block trays. The attenuation of the beam is calculated using a spectrum of the beam, and a correction factor based on attenuation measurements. Small angle coherent scatter and electron binding effects on scattering cross sections are considered by use of a correction factor. Quality changes in beam penetrability and energy fluence to dose conversion are modeled by use of the calculated primary beam spectrum after passage through the attenuator. The beam spectra are derived by the depth dose effective method, i.e., by minimizing the difference between measured and calculated depth dose distributions, where the calculated distributions are derived by superposing data from a database for monoenergetic photons. The attenuator scatter is integrated over the area viewed from the calculation point of view using first scatter theory. Calculations are simplified by replacing the energy and angular-dependent cross-section formulas with the forward scatter constant r2(0) and a set of parametrized correction functions. The set of corrections include functions for the Compton energy loss, scatter attenuation, and secondary bremsstrahlung production. The effect of charged particle contamination is bypassed by avoiding use of dmax for absolute dose calibrations. The results of the model are compared with scatter measurements in air for copper and lead filters and with dose to a water phantom for lead filters for 4 and 18 MV. For attenuated beams, downstream of the buildup region, the calculated results agree with measurements on the 1.5% level. The accuracy was slightly less in situations
Modelling Nuclear Effects in Neutrino Scattering
Leitner, T; Mosel, U
2006-01-01
We have developed a model to describe the interactions of neutrinos with nucleons and nuclei via charged and neutral currents, focusing on the region of the quasielastic and Delta(1232) peaks. For neutrino nucleon collisions a fully relativistic formalism is used. The extension to finite nuclei has been done in the framework of a coupled-channel BUU transport model where we have studied exclusive channels taking into account in-medium effects and final state interactions.
Wave chaotic experiments and models for complicated wave scattering systems
Yeh, Jen-Hao
Wave scattering in a complicated environment is a common challenge in many engineering fields because the complexity makes exact solutions impractical to find, and the sensitivity to detail in the short-wavelength limit makes a numerical solution relevant only to a specific realization. On the other hand, wave chaos offers a statistical approach to understand the properties of complicated wave systems through the use of random matrix theory (RMT). A bridge between the theory and practical applications is the random coupling model (RCM) which connects the universal features predicted by RMT and the specific details of a real wave scattering system. The RCM gives a complete model for many wave properties and is beneficial for many physical and engineering fields that involve complicated wave scattering systems. One major contribution of this dissertation is that I have utilized three microwave systems to thoroughly test the RCM in complicated wave systems with varied loss, including a cryogenic system with a superconducting microwave cavity for testing the extremely-low-loss case. I have also experimentally tested an extension of the RCM that includes short-orbit corrections. Another novel result is development of a complete model based on the RCM for the fading phenomenon extensively studied in the wireless communication fields. This fading model encompasses the traditional fading models as its high-loss limit case and further predicts the fading statistics in the low-loss limit. This model provides the first physical explanation for the fitting parameters used in fading models. I have also applied the RCM to additional experimental wave properties of a complicated wave system, such as the impedance matrix, the scattering matrix, the variance ratio, and the thermopower. These predictions are significant for nuclear scattering, atomic physics, quantum transport in condensed matter systems, electromagnetics, acoustics, geophysics, etc.
Modeling diffuse reflectance measurements of light scattered by layered tissues
Rohde, Shelley B.
In this dissertation, we first present a model for the diffuse reflectance due to a continuous beam incident normally on a half space composed of a uniform scattering and absorbing medium. This model is the result of an asymptotic analysis of the radiative transport equation for strong scattering, weak absorption and a defined beam width. Through comparison with the diffuse reflectance computed using the numerical solution of the radiative transport equation, we show that this diffuse reflectance model gives results that are accurate for small source-detector separation distances. We then present an explicit model for the diffuse reflectance due to a collimated beam of light incident normally on layered tissues. This model is derived using the corrected diffusion approximation applied to a layered medium, and it takes the form of a convolution with an explicit kernel and the incident beam profile. This model corrects the standard diffusion approximation over all source-detector separation distances provided the beam is sufficiently wide compared to the scattering mean-free path. We validate this model through comparison with Monte Carlo simulations. Then we use this model to estimate the optical properties of an epithelial layer from Monte Carlo simulation data. Using measurements at small source-detector separations and this model, we are able to estimate the absorption coefficient, scattering coefficient and anisotropy factor of epithelial tissues efficiently with reasonable accuracy. Finally, we present an extension of the corrected diffusion approximation for an obliquely incident beam. This model is formed through a Fourier Series representation in the azimuthal angle which allows us to exhibit the break in axisymmetry when combined with the previous analysis. We validate this model with Monte Carlo simulations. This model can also be written in the form of a convolution of an explicit kernel with the incident beam profile. Additionally, it can be used to
Modeling of detective quantum efficiency considering scatter-reduction devices
Energy Technology Data Exchange (ETDEWEB)
Park, Ji Woong; Kim, Dong Woon; Kim, Ho Kyung [Pusan National University, Busan (Korea, Republic of)
2016-05-15
The reduction of signal-to-noise ratio (SNR) cannot be restored and thus has become a severe issue in digital mammography.1 Therefore, antiscatter grids are typically used in mammography. Scatter-cleanup performance of various scatter-reduction devices, such as air gaps,2 linear (1D) or cellular (2D) grids,3, 4 and slot-scanning devices,5 has been extensively investigated by many research groups. In the present time, a digital mammography system with the slotscanning geometry is also commercially available.6 In this study, we theoretically investigate the effect of scattered photons on the detective quantum efficiency (DQE) performance of digital mammography detectors by using the cascaded-systems analysis (CSA) approach. We show a simple DQE formalism describing digital mammography detector systems equipped with scatter reduction devices by regarding the scattered photons as additive noise sources. The LFD increased with increasing PMMA thickness, and the amounts of LFD indicated the corresponding SF. The estimated SFs were 0.13, 0.21, and 0.29 for PMMA thicknesses of 10, 20, and 30 mm, respectively. While the solid line describing the measured MTF for PMMA with 0 mm was the result of least-squares of regression fit using Eq. (14), the other lines were simply resulted from the multiplication of the fit result (for PMMA with 0 mm) with the (1-SF) estimated from the LFDs in the measured MTFs. Spectral noise-power densities over the entire frequency range were not much changed with increasing scatter. On the other hand, the calculation results showed that the spectral noise-power densities increased with increasing scatter. This discrepancy may be explained by that the model developed in this study does not account for the changes in x-ray interaction parameters for varying spectral shapes due to beam hardening with increasing PMMA thicknesses.
Geant4 models for simulation of multiple scattering
Ivanchenko, V N; Maire, M; Urban, L
2010-01-01
Recent progress in development of single and multiple scattering models within the Geant4 toolkit is presented. Different options available to users are discussed. The comparisons with the data are shown. The trade of precision versus CPU performance is discussed with the focus on LHC detectors simulation
Elastic scattering of surface plasmon polaritons: Modeling and experiment
DEFF Research Database (Denmark)
Bozhevolnyi, Sergey I.; Coello, V.
1998-01-01
excitation wavelengths (594 and 633 nm) and different metal (silver and gold) films. The near-field optical images obtained are related to the calculated SPP intensity distributions demonstrating that the model developed can be successfully used in studies of SPP elastic scattering, e.g., to design...
Effective single scattering albedo estimation using regional climate model
CSIR Research Space (South Africa)
Tesfaye, M
2011-09-01
Full Text Available In this study, by modifying the optical parameterization of Regional Climate model (RegCM), the authors have computed and compared the Effective Single-Scattering Albedo (ESSA) which is a representative of VIS spectral region. The arid, semi...
Three dimensional rigorous model for optical scattering problems
Wei, X.
2006-01-01
We present a three-dimensional model based on the finite element method for solving the time-harmonic Maxwell equation in optics. It applies to isotropic or anisotropic dielectrics and metals, and to many configurations such as an isolated scatterer in a multilayer, bi-gratings and crystals. We shal
Computational modeling of single particle scattering over large distances
Rapp, Rebecca; Plumley, Rajan; McCracken, Michael
2016-09-01
We present a Monte Carlo simulation of the propagation of a single particle through a large three-dimensional volume under the influence of individual scattering events. In such systems, short paths can be quickly and accurately simulated using random walks defined by individual scattering parameters, but the simulation time greatly increases as the size of the space grows. We present a method for reducing the overall simulation time by restricting the simulation to a cube of unit length; each `cell' is characterized by a set of parameters which dictate the distributions of allowable step lengths and polar scattering angles. We model propagation over large distances by constructing a lattice of cells with physical parameters that depend on position, such that the full set would represent a space within the entire volume available to the particle. With these, we propose the use of Markov chains to determine a probable path for the particle, thereby removing the need to simulate every step in the particle's path. For a single particle with constant velocity, we can use the step statistics to determine the travel time of the particle. We investigate the effect of scattering parameters such as average step distance and possible scattering angles on the probabilities of a cell.
Neutron scattering and models: Iron. Nuclear data and measurements series
Energy Technology Data Exchange (ETDEWEB)
Smith, A.B. [Argonne National Lab., IL (United States)
1995-08-01
Differential elastic and inelastic neutron-scattering cross sections of elemental iron are measured from 4.5 to 10 MeV in increments of {approx} 0.5 MeV. At each incident energy the measurements are made at forty or more scattering angles distributed between {approx} 17{degrees} and 160{degrees}, with emphasis on elastic scattering and inelastic scattering due to the excitation of the yrast 2{sup +} state. The measured data is combined with earlier lower-energy results from this laboratory, with recent high-precision {approx} 9.5 {yields} 15 MeV results from the Physilalisch Technische Bundesanstalt and with selected values from the literature to provide a detailed neutron-scattering data base extending from {approx} 1.5 to 26 MeV. This data is interpreted in the context of phenomenological spherical-optical and coupled-channels (vibrational and rotational) models, and physical implications discussed. Deformation, coupling, asymmetry and dispersive effects are explored. It is shown that, particularly in a collective context, a good description of the interaction of neutrons with iron is achieved over the energy range {approx} 0 {yields} 26 MeV, avoiding the dichotomy between high and low-energy interpretations found in previous work.
Institute of Scientific and Technical Information of China (English)
Lukas Graber; Diomar Infante; Michael Steurer; William W. Brey
2011-01-01
Careful analysis of transients in shipboard power systems is important to achieve long life times of the com ponents in future all-electric ships. In order to accomplish results with high accuracy, it is recommended to validate cable models as they have significant influence on the amplitude and frequency spectrum of voltage transients. The authors propose comparison of model and measurement using scattering parameters. They can be easily obtained from measurement and simulation and deliver broadband information about the accuracy of the model. The measurement can be performed using a vector network analyzer. The process to extract scattering parameters from simulation models is explained in detail. Three different simulation models of a 5 kV XLPE power cable have been validated. The chosen approach delivers an efficient tool to quickly estimate the quality of a model.
THEORETICAL-MODEL FOR THE SCATTERING OF LIGHT BY DENTIN AND COMPARISON WITH MEASUREMENTS
ZIJP, [No Value; TENBOSCH, JJ
1993-01-01
A theoretical model of the scattering of light by dentin is presented. The model that results is a superposition of several scattering contributions, i.e., scattering by mineral crystals, collagen fibrils, and dentinal tubules. These tubules are oriented so that they cause an asymmetrical scattering
A weak-scattering model for turbine-tone haystacking
McAlpine, A.; Powles, C. J.; Tester, B. J.
2013-08-01
Noise and emissions are critical technical issues in the development of aircraft engines. This necessitates the development of accurate models to predict the noise radiated from aero-engines. Turbine tones radiated from the exhaust nozzle of a turbofan engine propagate through turbulent jet shear layers which causes scattering of sound. In the far-field, measurements of the tones may exhibit spectral broadening, where owing to scattering, the tones are no longer narrow band peaks in the spectrum. This effect is known colloquially as 'haystacking'. In this article a comprehensive analytical model to predict spectral broadening for a tone radiated through a circular jet, for an observer in the far field, is presented. This model extends previous work by the authors which considered the prediction of spectral broadening at far-field observer locations outside the cone of silence. The modelling uses high-frequency asymptotic methods and a weak-scattering assumption. A realistic shear layer velocity profile and turbulence characteristics are included in the model. The mathematical formulation which details the spectral broadening, or haystacking, of a single-frequency, single azimuthal order turbine tone is outlined. In order to validate the model, predictions are compared with experimental results, albeit only at polar angle equal to 90°. A range of source frequencies from 4 to 20kHz, and jet velocities from 20 to 60ms-1, are examined for validation purposes. The model correctly predicts how the spectral broadening is affected when the source frequency and jet velocity are varied.
$^{-} - {}^{12}C$ elastic scattering above the resonance using diffraction model
Indian Academy of Sciences (India)
M R Arafah
2008-01-01
Phenomenological analysis of the $^{-}- ^{12}C$ elastic scattering differential cross-section at 400, 486, 500, 584, 663, 672 and 766 MeV is presented. The analysis is made in the diffraction model framework using the recently proposed parametrization of the phase-shift function. Good description of the experimental data is achieved at all energies. Microscopic interpretation of the parameters of the phase-shift function is provided in terms of Helm's model density parameters.
Deconstruction and Elastic pi pi Scattering in Higgsless Models
Chivukula, R S; Kurachi, M; Simmons, E H; Tanabashi, M; He, Hong-Jian; Kurachi, Masafumi; Simmons, Elizabeth H.; Tanabashi, Masaharu
2007-01-01
We study elastic pion-pion scattering in global linear moose models and apply the results to a variety of Higgsless models in flat and AdS space using the Equivalence Theorem. In order to connect the global moose to Higgsless models, we first introduce a block-spin transformation which corresponds, in the continuum, to the freedom to perform coordinate transformations in the Higgsless model. We show that it is possible to make an "f-flat" deconstruction in which all of the f-constants f_j of the linear moose model are identical; the phenomenologically relevant f-flat models are those in which the coupling constants of the groups at either end of the moose are small - corresponding to the global linear moose. In studying pion-pion scattering, we derive various sum rules, including one analogous to the KSRF relation, and use them in evaluating the low-energy and high-energy forms of the leading elastic partial wave scattering amplitudes. We obtain elastic unitarity bounds as a function of the mass of the lighte...
Duda, G; Kemper, A; Duda, Gintaras; Gondolo, Paolo; Kemper, Ann
2006-01-01
Theoretical calculations of neutralino cross sections with various nuclei are of great interest to direct dark matter searches such as CDMS, EDELWEISS, ZEPLIN, and other experiments. These cross sections and direct detection rates are generally computed with standard, one or two parameter model-dependent nuclear form factors, which may not exactly mirror the actual form factor for the particular nucleus in question. As is well known, elastic electron scattering can allow for very precise determinations of nuclear form factors and hence nuclear charge densities for spherical or near-spherical nuclei. We use charge densities derived from elastic electron scattering data to calculate model independent form factors for various target nuclei important in dark matter searches, such as Si, Ge, S, Ca and others. We have found that for nuclear recoils in the range of 1-100 keV significant differences in cross sections and rates exist when the model independent form factors are used. DarkSUSY, a publicly-available adva...
Impact of Scattering Model on Disdrometer Derived Attenuation Scaling
Zemba, Michael; Luini, Lorenzo; Nessel, James; Riva, Carlo
2016-01-01
NASA Glenn Research Center (GRC), the Air Force Research Laboratory (AFRL), and the Politecnico di Milano (POLIMI) are currently entering the third year of a joint propagation study in Milan, Italy utilizing the 20 and 40 GHz beacons of the Alphasat TDP#5 Aldo Paraboni scientific payload. The Ka- and Q-band beacon receivers were installed at the POLIMI campus in June of 2014 and provide direct measurements of signal attenuation at each frequency. Collocated weather instrumentation provides concurrent measurement of atmospheric conditions at the receiver; included among these weather instruments is a Thies Clima Laser Precipitation Monitor (optical disdrometer) which records droplet size distributions (DSD) and droplet velocity distributions (DVD) during precipitation events. This information can be used to derive the specific attenuation at frequencies of interest and thereby scale measured attenuation data from one frequency to another. Given the ability to both predict the 40 gigahertz attenuation from the disdrometer and the 20 gigahertz time-series as well as to directly measure the 40 gigahertz attenuation with the beacon receiver, the Milan terminal is uniquely able to assess these scaling techniques and refine the methods used to infer attenuation from disdrometer data. In order to derive specific attenuation from the DSD, the forward scattering coefficient must be computed. In previous work, this has been done using the Mie scattering model, however, this assumes a spherical droplet shape. The primary goal of this analysis is to assess the impact of the scattering model and droplet shape on disdrometer-derived attenuation predictions by comparing the use of the Mie scattering model to the use of the T-matrix method, which does not assume a spherical droplet. In particular, this paper will investigate the impact of these two scattering approaches on the error of the resulting predictions as well as on the relationship between prediction error and rain rate.
FDTD Modeling of Transient Scattering by Subsurface Targets
Institute of Scientific and Technical Information of China (English)
Gong Zhu-qian; Zhu Guo-qiang
2004-01-01
In this paper, a two-dimensional (2-D) finitedifference time-domain method (FDTD) scheme is used to simulate the transient scattering characteristics of buried objects, which are modeled by columns of arbitrary permittivities, conductivities, and sizes. The FDTD soil is modeled by isotropic, homogeneous and lossy media. The standing-trave-ling wave boundary condition (STWBC) that can simplify calculation and save CPU storage is used for modeling physical absorbers inside the FDTD computational domain. Reflection of electromagnetic pulses incident on a layered medium and transient scattering by the ground and an underground air square cylinder are computed. These results verify the validity of the FDTD scheme by comparisons with those shown in some references. Numerical results presented in the final part of this paper are desirable and meaningful, explicitly distinguishing echo waves stemming from the ground and the buried objects.
Gonçalves, O. D.; Boldt, S.; Kasch, K. U.
2016-09-01
This work aims at measuring the scattering cross sections for white beams and the verification of a semi-empirical model predicting scattered energy spectra of an X-ray beam produced by an industrial X-ray tube (Pantack Sievert, 120 kV, tungsten target) incident on a water sample. Both, theoretical and semi-empirical results presented are based on the form factor approach with results well corresponding to performed measurements. The elastic (Rayleigh) scattering cross sections are based on Thomson scattering with a form factor correction as published by Morin (1982). The inelastic (Compton) contribution is based on the Klein Nishina equation (Klein and Nishina, 1929) multiplied by the incoherent scattering factors calculated by Hubbel et al. (1975). Two major results are presented: first, the experimental integrated in energy cross sections corresponds with theoretical cross sections obtained at the mean energy of the measured scattered spectra at a given angle. Secondly, the measured scattered spectra at a given angle correspond to those obtained utilizing the semi-empirical model as proposed here. A good correspondence of experimental results and model predictions can be shown. The latter, therefore, proves to be a useful method to calculate the scattering contributions in a number of applications as for example cone beam tomography.
Phenomenological models of elastic nucleon scattering and predictions for LHC
Kundrat, V; Lokajicek, M; Prochazka, J
2011-01-01
The hitherto analyses of elastic collisions of charged nucleons involving common influence of Coulomb and hadronic scattering have been based practically on West and Yennie formula. However, this approach has been shown recently to be inadequate from experimental as well as theoretical points of view. The eikonal model enabling to determine physical characteristics in impact parameter space seems to be more pertinent. The contemporary phenomenological models admit, of course, different distributions of collision processes in the impact parameter space and cannot give any definite answer. Nevertheless, some predictions for the planned LHC energy that have been given on their basis may be useful, as well as the possibility of determining the luminosity from elastic scattering. (C) 2010 Elsevier B.V. All rights reserved.
Hybrid Modeling of Elastic Wave Scattering in a Welded Cylinder
Mahmoud, A.; Shah, A. H.; Popplewell, N.
2003-03-01
In the present study, a 3D hybrid method, which couples the finite element region with guided elastic wave modes, is formulated to investigate the scattering by a non-axisymmetric crack in a welded steel pipe. The algorithm is implemented on a parallel computing platform. Implementation is facilitated by the dynamic memory allocation capabilities of Fortran 90™ and the parallel processing directives of OpenMp™. The algorithm is validated against available numerical results. The agreement with a previous 2D hybrid model is excellent. Novel results are presented for the scattering of the first longitudinal mode from different non-axisymmetric cracks. The trend of the new results is consistent with the previous findings for the axisymmetric case. The developed model has potential application in ultrasonic nondestructive evaluation of welded steel pipes.
Scattering as a key to improved room acoustic computer modelling
DEFF Research Database (Denmark)
Rindel, Jens Holger; Christensen, Claus Lynge
1996-01-01
It has been known for a long time that surface scattering plays a very important role in room acoustics. With room acoustic computer models like ODEON it is possible to study the influence of scattering coefficients, which can be assigned to the surfaces of the room. In the latest version...... of the program an additional effect has been modelled, namely the attenuation of sound due to diffraction, which is particularly pronounced for small surfaces, low frequencies and long reflecting paths. The present paper describes a parameter study of how to optimize the choice of the number of rays...... room acoustic parameters. Results from two different halls have shown that a relative low number of rays are sufficient for reliable and stable calculation results. The optimum value of the transition order is two or three. The inclusion of diffraction effect leads to clearly improved results....
Nonrelativistic factorizable scattering theory of multicomponent Calogero-Sutherland model
Ahn, C; Nam, S; Ahn, Changrim; Lee, Kong Ju Bock; Nam, Soonkeon
1995-01-01
We relate two integrable models in (1+1) dimensions, namely, multicomponent Calogero-Sutherland model with particles and antiparticles interacting via the hyperbolic potential and the nonrelativistic factorizable S-matrix theory with SU(N)-invariance. We find complete solutions of the Yang-Baxter equations without implementing the crossing symmetry, and one of them is identified with the scattering amplitudes derived from the Schr\\"{o}dinger equation of the Calogero-Sutherland model. This particular solution is of interest in that it cannot be obtained as a nonrelativistic limit of any known relativistic solutions of the SU(N)-invariant Yang-Baxter equations.
A fully polarimetric scattering model for a coniferous forest
Karam, M. A.; Fung, A. K.; Lopes, A.; Mougin, E.
1991-01-01
For an elliptically polarized plane wave exciting a coniferous forested canopy a fully polarimetric scattering model has been developed to account for the size and orientation distributions of each forest constituent. A canopy is divided into three layers over a rough interface. The upper two layers represent the crown with its constituents (leaves, stems, and branches). The lower layer stands for the trunks and the rough interface is the canopy-ground interface. For a plane wave exciting the canopy, the explicit expressions for the bistatic scattering coefficient associated with each scattering mechanism are given. For an elliptically polarized incidence wave, the present model can be recast in a form suitable for polarimetric wave synthesis. The model validation is justified by comparing the measured and the calculated values of the backscattering coefficients for a linearly polarized incident wave. The comparison is made over a wide range of frequencies and incident angles. Numerical simulations are conducted to calculate the radar polarization signature of the canopy for different incident frequencies and angles.
Korda, V Y; Korda, L P
2005-01-01
We present a new procedure which enables to extract a scattering matrix $S(l)$ as a complex function of angular momentum directly from the scattering data, without any a priori model assumptions implied. The key ingredient of the procedure is the evolutionary algorithm with diffused mutation which evolves the population of the scattering matrices, via their smooth deformations, from the primary arbitrary analytical $S(l)$ shapes to the final ones giving high quality fits to the data. Due to the automatic monitoring of the scattering matrix derivatives, the final $S(l)$ shapes are monotonic and do not have any distortions. For the $^{16}$O-$^{16}$O elastic scattering data at 350 MeV, we show the independence of the final results of the primary $S(l)$ shapes. Contrary to the other approaches, our procedure provides an excellent fit by the $S(l)$ shapes which support the ``rainbow'' interpretation of the data under analysis.
Dynamics and Lax Phillips scattering for generalized Lamb models
Bertini, Massimo; Noja, Diego; Posilicano, Andrea
2006-12-01
This paper treats the dynamics and scattering of a model of coupled oscillating systems, a finite dimensional one and a wave field on the half line. The coupling is realized producing the family of self-adjoint extensions of the suitably restricted self-adjoint operator describing the uncoupled dynamics. The spectral theory of the family is studied and the associated quadratic forms constructed. The dynamics turns out to be Hamiltonian and the Hamiltonian is described, including the case in which the finite-dimensional systems comprise nonlinear oscillators; in this case, the dynamics is shown to exist as well. In the linear case, the system is equivalent, on a dense subspace, to a wave equation on the half line with higher order boundary conditions, described by a differential polynomial p(∂x) explicitly related to the model parameters. In terms of such structure, the Lax-Phillips scattering of the system is studied. In particular, we determine the scattering operator, which turns out to be unitarily equivalent to the multiplication operator given by the rational function -p(iκ)*/p(iκ), the incoming and outgoing translation representations and the Lax-Phillips semigroup, which describes the evolution of the states which are neither incoming in the past nor outgoing in the future.
Dynamics and Lax-Phillips scattering for generalized Lamb models
Energy Technology Data Exchange (ETDEWEB)
Bertini, Massimo [Dipartimento di Matematica, Universita di Milano, I-20133 Milan (Italy); Noja, Diego [Dipartimento di Matematica e Applicazioni, Universita di Milano-Bicocca, I-20126, Milan (Italy); Posilicano, Andrea [Dipartimento di Fisica e Matematica, Universita dell' Insubria, I-22100 Como (Italy)
2006-12-08
This paper treats the dynamics and scattering of a model of coupled oscillating systems, a finite dimensional one and a wave field on the half line. The coupling is realized producing the family of self-adjoint extensions of the suitably restricted self-adjoint operator describing the uncoupled dynamics. The spectral theory of the family is studied and the associated quadratic forms constructed. The dynamics turns out to be Hamiltonian and the Hamiltonian is described, including the case in which the finite-dimensional systems comprise nonlinear oscillators; in this case, the dynamics is shown to exist as well. In the linear case, the system is equivalent, on a dense subspace, to a wave equation on the half line with higher order boundary conditions, described by a differential polynomial p({partial_derivative}{sub x}) explicitly related to the model parameters. In terms of such structure, the Lax-Phillips scattering of the system is studied. In particular, we determine the scattering operator, which turns out to be unitarily equivalent to the multiplication operator given by the rational function -p(i{kappa})*/p(i{kappa}), the incoming and outgoing translation representations and the Lax-Phillips semigroup, which describes the evolution of the states which are neither incoming in the past nor outgoing in the future.
Multiple Scattering Model for Optical Coherence Tomography with Rytov Approximation
Li, Muxingzi
2017-04-24
Optical Coherence Tomography (OCT) is a coherence-gated, micrometer-resolution imaging technique that focuses a broadband near-infrared laser beam to penetrate into optical scattering media, e.g. biological tissues. The OCT resolution is split into two parts, with the axial resolution defined by half the coherence length, and the depth-dependent lateral resolution determined by the beam geometry, which is well described by a Gaussian beam model. The depth dependence of lateral resolution directly results in the defocusing effect outside the confocal region and restricts current OCT probes to small numerical aperture (NA) at the expense of lateral resolution near the focus. Another limitation on OCT development is the presence of a mixture of speckles due to multiple scatterers within the coherence length, and other random noise. Motivated by the above two challenges, a multiple scattering model based on Rytov approximation and Gaussian beam optics is proposed for the OCT setup. Some previous papers have adopted the first Born approximation with the assumption of small perturbation of the incident field in inhomogeneous media. The Rytov method of the same order with smooth phase perturbation assumption benefits from a wider spatial range of validity. A deconvolution method for solving the inverse problem associated with the first Rytov approximation is developed, significantly reducing the defocusing effect through depth and therefore extending the feasible range of NA.
Quantum inverse scattering and the lambda deformed principal chiral model
Appadu, Calan; Hollowood, Timothy J.; Price, Dafydd
2017-07-01
The lambda model is a one parameter deformation of the principal chiral model that arises when regularizing the non-compactness of a non-abelian T dual in string theory. It is a current-current deformation of a WZW model that is known to be integrable at the classical and quantum level. The standard techniques of the quantum inverse scattering method cannot be applied because the Poisson bracket is non ultra-local. Inspired by an approach of Faddeev and Reshetikhin, we show that in this class of models, there is a way to deform the symplectic structure of the theory leading to a much simpler theory that is ultra-local and can be quantized on the lattice whilst preserving integrability. This lattice theory takes the form of a generalized spin chain that can be solved by standard algebraic Bethe Ansatz techniques. We then argue that the IR limit of the lattice theory lies in the universality class of the lambda model implying that the spin chain provides a way to apply the quantum inverse scattering method to this non ultra-local theory. This points to a way of applying the same ideas to other lambda models and potentially the string world-sheet theory in the gauge-gravity correspondence.
The Quantum Inverse Scattering Method for Hubbard-like Models
Martins, M J
1997-01-01
This work is concerned with various aspects of the formulation of the quantum inverse scattering method for the one-dimensional Hubbard model. We first establish the essential tools to solve the eigenvalue problem for the transfer matrix of the classical ``covering'' Hubbard model within the algebraic Bethe Ansatz framework. The fundamental commutation rules exhibit a hidden 6-vertex symmetry which plays a crucial role in the whole algebraic construction. Next we apply this formalism to study the SU(2) highest weights properties of the eigenvectors and the solution of a related coupled spin model with twisted boundary conditions. The machinery developed in this paper is applicable to many other models, and as an example we present the algebraic solution of the Bariev XY coupled model.
The Empowerment of Plasma Modeling by Fundamental Electron Scattering Data
Kushner, Mark J.
2015-09-01
Modeling of low temperature plasmas addresses at least 3 goals - investigation of fundamental processes, analysis and optimization of current technologies, and prediction of performance of as yet unbuilt systems for new applications. The former modeling may be performed on somewhat idealized systems in simple gases, while the latter will likely address geometrically and electromagnetically intricate systems with complex gas mixtures, and now gases in contact with liquids. The variety of fundamental electron and ion scattering data (FSD) required for these activities increases from the former to the latter, while the accuracy required of that data probably decreases. In each case, the fidelity, depth and impact of the modeling depends on the availability of FSD. Modeling is, in fact, empowered by the availability and robustness of FSD. In this talk, examples of the impact of and requirements for FSD in plasma modeling will be discussed from each of these three perspectives using results from multidimensional and global models. The fundamental studies will focus on modeling of inductively coupled plasmas sustained in Ar/Cl2 where the electron scattering from feed gases and their fragments ultimately determine gas temperatures. Examples of the optimization of current technologies will focus on modeling of remote plasma etching of Si and Si3N4 in Ar/NF3/N2/O2 mixtures. Modeling of systems as yet unbuilt will address the interaction of atmospheric pressure plasmas with liquids Work was supported by the US Dept. of Energy (DE-SC0001939), National Science Foundation (CHE-124752), and the Semiconductor Research Corp.
Plasma Modeling Enabled Technology Development Empowered by Fundamental Scattering Data
Kushner, Mark J.
2016-05-01
Technology development increasingly relies on modeling to speed the innovation cycle. This is particularly true for systems using low temperature plasmas (LTPs) and their role in enabling energy efficient processes with minimal environmental impact. In the innovation cycle, LTP modeling supports investigation of fundamental processes that seed the cycle, optimization of newly developed technologies, and prediction of performance of unbuilt systems for new applications. Although proof-of-principle modeling may be performed for idealized systems in simple gases, technology development must address physically complex systems that use complex gas mixtures that now may be multi-phase (e.g., in contact with liquids). The variety of fundamental electron and ion scattering, and radiation transport data (FSRD) required for this modeling increases as the innovation cycle progresses, while the accuracy required of that data depends on the intended outcome. In all cases, the fidelity, depth and impact of the modeling depends on the availability of FSRD. Modeling and technology development are, in fact, empowered by the availability and robustness of FSRD. In this talk, examples of the impact of and requirements for FSRD in the innovation cycle enabled by plasma modeling will be discussed using results from multidimensional and global models. Examples of fundamental studies and technology optimization will focus on microelectronics fabrication and on optically pumped lasers. Modeling of systems as yet unbuilt will address the interaction of atmospheric pressure plasmas with liquids. Work supported by DOE Office of Fusion Energy Science and the National Science Foundation.
A Model for High Energy Scattering in Quantum Gravity
Banks, T; Banks, Tom; Fischler, Willy
1999-01-01
We present a model for high energy two body scattering in a quantum theory of gravity. The model is applicable for center of mass energies higher than the relevant Planck scale. At impact parameters smaller than the Schwarzchild radius appropriate to the center of mass energy and total charge of the initial state, the cross section is dominated by an inelastic process in which a single large black hole is formed. The black hole then decays by Hawking radiation. The elastic cross section is highly suppressed at these impact parameters because of the small phase space for thermal decay into a high energy two body state. For very large impact parameter the amplitude is dominated by eikonalized single graviton exchange. At intermediate impact parameters the scattering is more complicated, but since the Schwarzchild radius grows with energy, we speculate that a more sophisticated eikonal calculation which uses the nonlinear classical solutions of the field equations may provide a good approximation at all larger i...
Low-energy $^{6}$He scattering in a microscopic model
Descouvemont, P
2016-01-01
A microscopic version of the Continuum Discretized Coupled Channel (CDCC) method is used to investigate $^{6}$He scattering on $^{27}$Al, $^{58}$Ni, $^{120}$Sn, and $^{208}$Pb at energies around the Coulomb barrier. The $^{6}$He nucleus is described by an antisymmetric 6-nucleon wave function, defined in the Resonating Group Method. The $^{6}$He continuum is simulated by square-integrable positive-energy states. The model is based only on well known nucleon-target potentials, and is therefore does not depend on any adjustable parameter. I show that experimental elastic cross sections are fairly well reproduced. The calculation suggests that breakup effects increase for high target masses. For a light system such as $^{6}$He+$^{27}$Al, breakup effects are small, and a single-channel approximation provides fair results. This property is explained by a very simple model, based on the sharp-cut-off approximation for the scattering matrix. I also investigate the $^{6}$He-target optical potentials, which confirm th...
Quasi-one-dimensional scattering in a discrete model
Energy Technology Data Exchange (ETDEWEB)
Valiente, Manuel; Moelmer, Klaus [Lundbeck Foundation Theoretical Center for Quantum System Research, Department of Physics and Astronomy, Aarhus University, DK-8000 Aarhus C (Denmark)
2011-11-15
We study quasi-one-dimensional scattering of one and two particles with short-range interactions on a discrete lattice model in two dimensions. One of the directions is tightly confined by an arbitrary trapping potential. We obtain the collisional properties of these systems both at finite and zero Bloch quasimomenta, considering as well finite sizes and transversal traps that support a continuum of states. This is made straightforward by using the exact ansatz for the quasi-one-dimensional states from the beginning. In the more interesting case of genuine two-particle scattering, we find that more than one confinement-induced resonances appear due to the nonseparability of the center-of-mass and relative coordinates on the lattice. This is done by solving its corresponding Lippmann-Schwinger-like equation. We characterize the effective one-dimensional interaction and compare it with a model that includes only the effect of the dominant, broadest resonance, which amounts to a single-pole approximation for the interaction coupling constant.
Non-line-of-sight polarized single-scatter propagation model for noncoplanar geometries
Yin, Hongwei; Jia, Honghui; Luo, Jianfeng; Chang, Shengli; Yang, Juncai
2012-01-01
The classical model of non-line-of-sight (NLOS) single-scatter propagation for coplanar geometries was recently extended to include noncoplanar geometries; the calculation processes in the extended model are partly based on the Cartesian coordinate system and are somewhat complicated. A new NLOS single-scatter propagation model for noncoplanar geometries is presented based only on the prolate spheroidal coordinate system, which can be considered as the simplified version of the extended model mentioned above. Similar to the polarization-extension of the Monte-Carlo-based multiple-scatter model, the new single-scatter model for noncoplanar geometries is also extended to take polarization into account; the polarized single-scatter model is validated by the Monte-Carlo-based polarized model, results show perfect match. The theoretical feasibility of a 2-polarization UV communication link is validated based on the polarized single-scatter model.
Finite Element Modeling of scattered electromagnetic waves for stroke analysis.
Priyadarshini, N; Rajkumar, E R
2013-01-01
Stroke has become one of the leading causes of mortality worldwide and about 800 in every 100,000 people suffer from stroke each year. The occurrence of stroke is ranked third among the causes of acute death and first among the causes for neurological dysfunction. Currently, Neurological examinations followed by medical imaging with CT, MRI or Angiography are used to provide better identification of the location and the type of the stroke, however they are neither fast, cost-effective nor portable. Microwave technology has emerged to complement these modalities to diagnose stroke as it is sensitive to the differences between the distinct dielectric properties of the brain tissues and blood. This paper investigates the possibility of diagnosing the type of stroke using Finite Element Analysis (FEA). The object of interest is a simulated head phantom with stroke, created with its specifying material characteristics like electrical conductivity and relative permittivity. The phantom is then placed in an electromagnetic field generated by a dipole antenna radiating at 1 GHz. The FEM forward model solver computes the scattered electromagnetic field by finding the solution for the Maxwell's wave equation in the head volume. Subsequently the inverse scattering problem is solved using the Contrast Source Inversion (CSI) method to reconstruct the dielectric profile of the head phantom.
Fitting Data to Model: Structural Equation Modeling Diagnosis Using Two Scatter Plots
Yuan, Ke-Hai; Hayashi, Kentaro
2010-01-01
This article introduces two simple scatter plots for model diagnosis in structural equation modeling. One plot contrasts a residual-based M-distance of the structural model with the M-distance for the factor score. It contains information on outliers, good leverage observations, bad leverage observations, and normal cases. The other plot contrasts…
Exponential Disks from Stellar Scattering: III. Stochastic Models
Elmegreen, Bruce G
2016-01-01
Stellar scattering off irregularities in a galaxy disk has been shown to make an exponential radial profile, but no fundamental reason for this has been suggested. Here we show that exponentials are mathematically expected from random scattering in a disk when there is a slight inward bias in the scattering probability. Such a bias was present in our previous scattering experiments that formed exponential profiles. Double exponentials can arise when the bias varies with radius. This is a fundamental property of scattering and may explain why piece-wise exponential profiles are ubiquitous in galaxies, even after minor mergers and other disruptive events.
Modeling and simulation of HTS cables for scattering parameter analysis
Bang, Su Sik; Lee, Geon Seok; Kwon, Gu-Young; Lee, Yeong Ho; Chang, Seung Jin; Lee, Chun-Kwon; Sohn, Songho; Park, Kijun; Shin, Yong-June
2016-11-01
Most of modeling and simulation of high temperature superconducting (HTS) cables are inadequate for high frequency analysis since focus of the simulation's frequency is fundamental frequency of the power grid, which does not reflect transient characteristic. However, high frequency analysis is essential process to research the HTS cables transient for protection and diagnosis of the HTS cables. Thus, this paper proposes a new approach for modeling and simulation of HTS cables to derive the scattering parameter (S-parameter), an effective high frequency analysis, for transient wave propagation characteristics in high frequency range. The parameters sweeping method is used to validate the simulation results to the measured data given by a network analyzer (NA). This paper also presents the effects of the cable-to-NA connector in order to minimize the error between the simulated and the measured data under ambient and superconductive conditions. Based on the proposed modeling and simulation technique, S-parameters of long-distance HTS cables can be accurately derived in wide range of frequency. The results of proposed modeling and simulation can yield the characteristics of the HTS cables and will contribute to analyze the HTS cables.
The Use of Scattering Matrix to Model Multi-Modal Array Inspection with the Tfm
Zhang, J.; Drinkwater, B. W.; Wilcox, P. D.
2009-03-01
The scattering coefficient matrix describes the far field amplitude of scattered signals from a scatterer as a function of incident and scattering angles. In this paper an FE model is used to predict scattering matrices. By combining the predicted scattering coefficient matrix with a ray tracing model to predict the full matrix of array data, an efficient forward model of the complete array inspection process is presented. Longitudinal wave, shear waves and wave mode conversions are considered in the model. The TFM images for various wave mode combination cases from a weld sample are predicted and measured. Results show that by selecting the optimum array mode combination a good image for a given defect in the weld sample can be produced using an array. It is also shown how the model can be used to optimize the array inspection configuration.
An algebraic model of Coulomb scattering with spin
Energy Technology Data Exchange (ETDEWEB)
Levay, P. [School of Physics, University of Melbourne, Parkville (Australia); Department of Theoretical Physics, Institute of Physics, Technical University, Budapest (Hungary); Amos, K. [School of Physics, University of Melbourne, Parkville (Australia)
2001-05-11
A new matrix-valued realization for the so(3,1) algebra leads to a natural generalization of the Coulomb scattering problem of a particle with spin. The underlying su(2) gauge structure of this realization recasts the scattering problem into a familiar form, namely, the Coulomb scattering problem of a collection of dyons (particles having both electric and magnetic charges). Using this equivalent form and the results of Zwanziger for such systems, the scattering matrix can be calculated in the helicity formalism. (author)
Modelling grain-scattered ultrasound in austenitic stainless-steel welds: A hybrid model
Nowers, O.; Duxbury, D. J.; Velichko, A.; Drinkwater, B. W.
2015-03-01
The ultrasonic inspection of austenitic stainless steel welds can be challenging due to their coarse grain structure, charaterised by preferentially oriented, elongated grains. The anisotropy of the weld is manifested as both a `steering' of the beam and the back-scatter of energy due to the macroscopic granular structure of the weld. However, the influence of weld properties, such as mean grain size and orientation distribution, on the magnitude of scattered ultrasound is not well understood. A hybrid model has been developed to allow the study of grain-scatter effects in austenitic welds. An efficient 2D Finite Element (FE) method is used to calculate the complete scattering response from a single elliptical austenitic grain of arbitrary length and width as a function of the specific inspection frequency. A grain allocation model of the weld is presented to approximate the characteristic structures observed in austenitic welds and the complete scattering behaviour of each grain calculated. This model is incorporated into a semi-analytical framework for a single-element inspection of a typical weld in immersion. Experimental validation evidence is demonstrated indicating excellent qualitative agreement of SNR as a function of frequency and a minimum SNR difference of 2 dB at a centre frequency of 2.25 MHz. Additionally, an example Monte-Carlo study is presented detailing the variation of SNR as a function of the anisotropy distribution of the weld, and the application of confidence analysis to inform inspection development.
Light scattering by neutrophils: Model, simulation, and experiment
Orlova, D.Y.; Yurkin, M.A.; Hoekstra, A.G.; Maltsev, V.P.
2008-01-01
We studied the elastic light-scattering properties of human blood neutrophils, both experimentally and theoretically. The experimental study was performed with a scanning flow cytometer measuring the light-scattering patterns (LSPs) of individual cells over an angular range of 5-60 deg. We determine
Theoretical Models of Light Scattering Applied in Sizing Particles in Coal Water Slurry
Institute of Scientific and Technical Information of China (English)
王仁哲; 张荣曾; 徐志强
2004-01-01
Advantges and disadvantage of Mie scattering model and Fraunhofer diffraction model are discussed. The result shows that 1) the Fraunhofer diffraction model is simple in design and fast in operation, which is quite suitable for on-line control and 2) the intensity and energy distribution of diffracted light of both the Mie scattering model and the Fraunhofer theoretical model are compared and researched. Feasibility of using the Fraunhofer diffraction model to replace the Mie scattering model in measuring particles in coal water slurry is demonstrated.
Perkins, Stephen J; Wright, David W; Zhang, Hailiang; Brookes, Emre H; Chen, Jianhan; Irving, Thomas C; Krueger, Susan; Barlow, David J; Edler, Karen J; Scott, David J; Terrill, Nicholas J; King, Stephen M; Butler, Paul D; Curtis, Joseph E
2016-12-01
The capabilities of current computer simulations provide a unique opportunity to model small-angle scattering (SAS) data at the atomistic level, and to include other structural constraints ranging from molecular and atomistic energetics to crystallography, electron microscopy and NMR. This extends the capabilities of solution scattering and provides deeper insights into the physics and chemistry of the systems studied. Realizing this potential, however, requires integrating the experimental data with a new generation of modelling software. To achieve this, the CCP-SAS collaboration (http://www.ccpsas.org/) is developing open-source, high-throughput and user-friendly software for the atomistic and coarse-grained molecular modelling of scattering data. Robust state-of-the-art molecular simulation engines and molecular dynamics and Monte Carlo force fields provide constraints to the solution structure inferred from the small-angle scattering data, which incorporates the known physical chemistry of the system. The implementation of this software suite involves a tiered approach in which GenApp provides the deployment infrastructure for running applications on both standard and high-performance computing hardware, and SASSIE provides a workflow framework into which modules can be plugged to prepare structures, carry out simulations, calculate theoretical scattering data and compare results with experimental data. GenApp produces the accessible web-based front end termed SASSIE-web, and GenApp and SASSIE also make community SAS codes available. Applications are illustrated by case studies: (i) inter-domain flexibility in two- to six-domain proteins as exemplified by HIV-1 Gag, MASP and ubiquitin; (ii) the hinge conformation in human IgG2 and IgA1 antibodies; (iii) the complex formed between a hexameric protein Hfq and mRNA; and (iv) synthetic 'bottlebrush' polymers.
Non-line-of-sight ultraviolet single-scatter propagation model in random turbulent medium.
Xiao, Houfei; Zuo, Yong; Wu, Jian; Li, Yan; Lin, Jintong
2013-09-01
Non-line-of-sight (NLOS) ultraviolet communication (UVC) uses the atmosphere as a propagation medium. In previous literature, various scatter propagation models have been derived based on the premise that atmospheric turbulence was ignored and the atmosphere was considered as a turbid medium, also called random scatterers. In this Letter, a NLOS single-scatter propagation model is proposed to describe the singly scattered radiation in a turbulent medium, also called a random continuum, such as the clear atmosphere. The model is established based on the relationship between the scattered power and the characteristics of the random turbulent medium. The scattering cross section is further investigated in terms of different correlation distances and wavelengths. The received power dependence for NLOS UVC is also analyzed for different factors, including refractive-index structure parameter and transceiver range.
Rakotonarivo, S T; Walker, S C; Kuperman, W A; Roux, P
2011-12-01
A method to actively localize a small perturbation in a multiple scattering medium using a collection of remote acoustic sensors is presented. The approach requires only minimal modeling and no knowledge of the scatterer distribution and properties of the scattering medium and the perturbation. The medium is ensonified before and after a perturbation is introduced. The coherent difference between the measured signals then reveals all field components that have interacted with the perturbation. A simple single scatter filter (that ignores the presence of the medium scatterers) is matched to the earliest change of the coherent difference to localize the perturbation. Using a multi-source/receiver laboratory setup in air, the technique has been successfully tested with experimental data at frequencies varying from 30 to 60 kHz (wavelength ranging from 0.5 to 1 cm) for cm-scale scatterers in a scattering medium with a size two to five times bigger than its transport mean free path.
SEMIINCLUSIVE DEEP-INELASTIC LEPTON SCATTERING IN A PION CLOUD MODEL
DIEPERINK, AEL; POLLOCK, SJ
1994-01-01
In this note we explore the consequences of the pion cloud model for semi-inclusive deep inelastic lepton scattering. We argue that by scattering on a few-nucleon target, the detection of the recoiling target would provide a valuable test of the meson cloud model. We estimate the semi-inclusive cros
Numerical modelling of multiple scattering between two elastical particles
DEFF Research Database (Denmark)
Bjørnø, Irina; Jensen, Leif Bjørnø
1998-01-01
in suspension have been studied extensively since Foldy's formulation of his theory for isotropic scattering by randomly distributed scatterers. However, a number of important problems related to multiple scattering are still far from finding their solutions. A particular, but still unsolved, problem...... is higher than 20 g/l of sand particles. This paper reports an attempt to illuminate and to solve the proximity threshold question, by an in-depth numerical study of the interaction of ultrasonic signals with two canonically shaped elastic particles. Introductory experimental results seem to create evidence...
Coupled-channel scattering in 1+1 dimensional lattice model
Guo, Peng
2013-01-01
Based on the Lippmann-Schwinger equation approach, a generalized L\\"uscher's formula in 1+1 dimensions for two particles scattering in both the elastic and coupled-channel cases in moving frames is derived. A 2D coupled-channel scattering lattice model is presented, the model represents a two-coupled-channel resonant scattering scalars system. The Monte Carlo simulation is performed on finite lattices and in various moving frames. The 2D generalized L\\"uscher's formula is used to extract the scattering amplitudes for the coupled-channel system from the discrete finite-volume spectrum.
Generalized Chou-Yang Model and Meson-Proton Elastic Scattering at High Energies
Saleem, Mohammad; Aleem, Fazal-E.; Rashid, Haris
The various characteristics of meson-proton elastic scattering at high energies are explained by using the generalized Chou-Yang model which takes into consideration the anisotropic scattering of objects constituting pions(kaons) and protons. A new parametrization of the proton form factor consistent with the recent experimental data is proposed. It is then shown that all the data for meson-proton elastic scattering at 200 and 250 GeV/c are in agreement with theoretical computations. The physical picture of generalized Chou-Yang model which is based on multiple scattering theory is given in detail.
Generalized Chou-Yang model and meson-proton elastic scattering at high energies
Energy Technology Data Exchange (ETDEWEB)
Saleem, M.; Aleem, F.E.; Rashid, H.
1989-01-01
The various characteristics of meson-proton elastic scattering at high energies are explained by using the generalized Chou-Yang model which takes into consideration the anisotropic scattering of objects constituting pions(kaons) and protons. A new parametrization of the proton form factor consistent with the recent experimental data is proposed. It is then shown that all the data for meson-proton elastic scattering at 200 and 250 GeV/c are in agreement with theoretical computations. The physical picture of generalized Chou-Yang model which is based on multiple scattering theory is given in detail.
Ma, Shufen; Liu, Haiguang
2016-04-01
X-ray free-electron lasers generate intense femtosecond X-ray pulses, so that high-resolution structure determination becomes feasible from noncrystalline samples, such as single particles or single molecules. At the moment, the orientation of sample particles cannot be precisely controlled, and consequently the unknown orientation needs to be recovered using computational algorithms. This delays the model reconstruction until all the scattering patterns have been re-oriented, which often entails a long elapse of time and until the completion of the experiment. The scattering patterns from single particles or multiple particles can be summed to form a virtual powder diffraction pattern, and the low-resolution region, corresponding to the small-angle X-ray scattering (SAXS) regime, can be analysed using existing SAXS methods. This work presents a pipeline that converts single-particle data sets into SAXS data, from which real-time model reconstruction is achieved using the model retrieval approach implemented in the software package SASTBX [Liu, Hexemer & Zwart (2012). J. Appl. Cryst.45, 587-593]. To illustrate the applications, two case studies are presented with real experimental data sets collected at the Linac Coherent Light Source.
Kawauchi, Satoko; Sato, Shunichi; Ooigawa, Hidetoshi; Nawashiro, Hiroshi; Ishihara, Miya; Kikuchi, Makoto
2009-08-14
Measurement of intrinsic optical signals (IOSs) is an attractive technique for monitoring tissue viability in brains since it enables noninvasive, real-time monitoring of morphological characteristics as well as physiological and biochemical characteristics of tissue. We previously showed that light scattering signals reflecting cellular morphological characteristics were closely related to the IOSs associated with the redox states of cytochrome c oxidase in the mitochondrial respiratory chain. In the present study, we examined the relationship between light scattering and energy metabolism. Light scattering signals were transcranially measured in rat brains after oxygen and glucose deprivation, and the results were compared with concentrations of cerebral adenosine triphosphate (ATP) measured by luciferin-luciferase bioluminescence assay. Electrophysiological signal was also recorded simultaneously. After starting saline infusion, EEG activity ceased at 108+/-17s, even after which both the light scattering signal and ATP concentration remained at initial levels. However, light scattering started to change in three phases at 236+/-15s and then cerebral ATP concentration started to decrease at about 260s. ATP concentration significantly decreased during the triphasic scattering change, indicating that the start of scattering change preceded the loss of cerebral ATP. The mean time difference between the start of triphasic scattering change and the onset of ATP loss was about 24s in the present model. DC potential measurement showed that the triphasic scattering change was associated with anoxic depolarization. These findings suggest that light scattering signal can be used as an indicator of loss of tissue viability in brains.
Sharma, S. K.
2012-12-01
A number of experimental elastic light scattering studies have been performed in the past few years with the aim of developing automated in vivo tools for differentiating a healthy red blood cell from a Plasmodium falciparum infected cell. This paper examines some theoretical aspects of the problem. An attempt has been made to simulate the scattering patterns of healthy as well as infected individual red blood cells. Two models, namely, a homogeneous sphere model and a coated sphere model have been considered. The scattering patterns predicted by these models are examined. A possible method for discriminating infected red blood cells from healthy ones has been suggested.
Modeling quantum mechanical scattering with continuous analogue of the newton method
Directory of Open Access Journals (Sweden)
Algirdas Deveikis
2013-09-01
Full Text Available Computational modelling of potential and resonant scattering for short range and Coulomb potentials was investigated in this study. The resonant scattering problem is formulated with the short range potential composed of a spherically symmetric square well and spherically symmetric square barrier. An iteration scheme of a continuous analogue of the Newton method for continuous spectral problem with correct asymptotic in uncoupled partial waves has been developed. The nonlinear representation of the scattering problem for the normalized radial Schrödinger equation is solved numerically using the difference sweep technique. The second order accuracy scheme developed allow to find scattering phases and wave functions as well as investigate their numerical evolution. The scattering phases and wave functions dependence on the scattering problem parameters have been studied.
Imaging local scatterer concentrations by the Nakagami statistical model.
Tsui, Po-Hsiang; Chang, Chien-Cheng
2007-04-01
The ultrasonic B-mode image is an important clinical tool used to examine the internal structures of the biological tissue. Due to the fact that the conventional B-scans cannot fully reflect the nature of the tissue, some useful quantitative parameters have been applied to quantify the properties of the tissue. Among various possibilities, the Nakagami parameter was demonstrated to have an outstanding ability to detect the variation of the scatterer concentration. This study is aimed to develop a scatterer concentration image based on the Nakagami parameter map to assist in the B-mode image for tissue characterization. In particular, computer simulations are carried out to generate phantoms of different scatterer concentrations and echogenicity coefficients and their B-mode and Nakagami parametric images are compared to evaluate the performance of the Nakagami image in differentiating the properties of the scatterers. The simulated results show that the B-mode image would be affected by the system settings and user operations, whereas the Nakagami parametric image provides a comparatively consistent image result when different diagnosticians use different dynamic ranges and system gains. This is largely because the Nakagami image formation is only based on the backscattered statistics of the ultrasonic signals in local tissues. Such an imaging principle allows the Nakagami image to quantify the local scatterer concentrations in the tissue and to extract the backscattering information from the regions of the weaker echoes that may be lost in the B-mode image. These findings suggest that the Nakagami image can be combined with the use of the B-mode image simultaneously to visualize the tissue structures and the scatterer properties for a better medical diagnosis.
A wave-mechanical model of incoherent neutron scattering II. Role of the momentum transfer
Frauenfelder, Hans; Young, Robert D.; Fenimore, Paul W.
2015-01-01
We recently introduced a wave-mechanical model for quasi-elastic neutron scattering (QENS) in proteins. We call the model ELM for "Energy Landscape Model". We postulate that the spectrum of the scattered neutrons consists of lines of natural width shifted from the center by fluctuations. ELM is based on two facts: Neutrons are wave packets; proteins have low-lying substates that form the free-energy landscape (FEL). Experiments suggest that the wave packets are a few hundred micrometers long....
Improved Monte Carlo model for multiple scattering calculations
Institute of Scientific and Technical Information of China (English)
Weiwei Cai; Lin Ma
2012-01-01
The coupling between the Monte Carlo (MC) method and geometrical optics to improve accuracy is investigated.The results obtained show improved agreement with previous experimental data,demonstrating that the MC method,when coupled with simple geometrical optics,can simulate multiple scattering with enhanced fidelity.
An SVD Investigation of Modeling Scatter in Multiple Energy Windows for Improved SPECT Images.
Kadrmas, Dan J; Frey, Eric C; Tsui, Benjamin M W
1996-08-01
In this work singular value decomposition (SVD) techniques are used to investigate how the use of low energy photons and multiple energy windows affects the noise properties of Tc-99m SPECT imaging. We have previously shown that, when modeling scatter in the projector and backprojector of iterative reconstruction algorithms, simultaneous reconstruction from multiple energy window data can result in very different noise characteristics. Further, the properties depend upon the width and number of energy windows used. To investigate this further, we have generated photon transport matrices using models for scatter, an elliptical phantom containing cold rods of various sizes, and a number of multiple energy window acquisition schemes. Transfer matrices were also generated for the cases of perfect scatter rejection and ideal scatter subtraction. The matrices were decomposed using SVD, and signal power and projection space variance spectra were computed using the basis formed by the left singular vectors. Results indicate very different noise levels for the various energy window combinations. The perfect scatter rejection case resulted in the lowest variance spectrum, and reconstruction-based scatter compensation performed better than the scatter subtraction case. When including lower energy photons in reconstruction-based scatter compensation, using a series of multiple energy windows outperformed a single large energy window. One multiple window combination is presented which achieves a lower variance spectrum than the standard 20% energy window, indicating the potential for using low energy photons to improve the noise characteristics of SPECT images.
Standard model extensions for PV electron scattering, g-2, EDM: Overview
Erler, Jens
2011-01-01
I review how various extensions of the Standard Model, in particular supersymmetry and extra neutral gauge bosons, may affect low energy observables, including parity-violating electron scattering and related observables, as well as electric and magnetic dipole moments.
Constraint on Parameters of Inverse Compton Scattering Model for PSR B2319+60
Indian Academy of Sciences (India)
H. G. Wang; M. Lv
2011-03-01
Using the multifrequency radio profiles of pulsar PSR B2319+60, two parameters of inverse Compton scattering model, the initial Lorentz factor and the factor of energy loss of relativistic particles are constrained.
Accounting for scattering in the Landauer-Datta-Lundstrom transport model
Directory of Open Access Journals (Sweden)
Юрій Олексійович Кругляк
2015-03-01
Full Text Available Scattering of carriers in the LDL transport model during the changes of the scattering times in the collision processes is considered qualitatively. The basic relationship between the transmission coefficient T and the average mean free path is derived for 1D conductor. As an example, the experimental data for Si MOSFET are analyzed with the use of various models of reliability.
Velichko, A.; Wilcox, P. D.
2011-06-01
A robust and efficient technique for predicting the complete scattering behavior for an arbitrarily-shaped defect which is located near a free surface in an otherwise homogeneous anisotropic half-space is presented that can be implemented in a commercial FE package. The spatial size of the modeling domain around the defect is as small as possible to minimize computational expense and a minimum number of models are executed. Example results for 2D wave scattering in isotropic material are presented.
High Energy Proton-Proton Elastic Scattering in Reggeon-Pomeron Exchange Model
Institute of Scientific and Technical Information of China (English)
ZHOU Li-Juan; HU Zhao-Hui; MA Wei-Xing
2006-01-01
We initially propose a Reggeon-Pomeron exchange model to describe proton-proton elastic scattering at high energies in this short paper. A calculation for total cross section of proton-proton elastic scattering at high energies is performed without any free parameters. Our new finding from this work is that the Reggeon-Pomeron model gives a perfect fit to experimental data of the total cross section at the whole energy region where experimental data exist.
Alicki's model of scattering-induced decoherence derived from Hamiltonian dynamics
Energy Technology Data Exchange (ETDEWEB)
Hellmich, Mario [Faculty of Physics, University of Bielefeld, 33615 Bielefeld (Germany)
2004-09-10
We study a semiphenomenological model introduced by Alicki (2002 Phys. Rev. A 65 034104), describing environmental decoherence by scattering of a Brownian particle in a gas environment. For a slightly wider class of models, we prove that the semigroup describing the dynamics of the Brownian particle can be approximated by the reduced dynamics arising from a Hamiltonian interaction between the particle and an infinite fermionic thermal gas reservoir, provided the scattering process is isotropic.
Modelling optical scattering artefacts for varying pathlength in a gel dosimeter phantom.
Bosi, Stephen G; Brown, Saxby; Sarabipour, Sarvenaz; De Deene, Yves; Baldock, Clive
2009-01-21
A gelatin phantom containing an optically scattering funnel-shaped region of elevated optical density (OD) was used to examine light-scattering-induced artefacts in a cone-beam optical CT scanner used for gel dosimetry. To simulate polymer gel dosimeters, the opacity was introduced by adding a colloidal scatterer to the gelatin. Scatter results in an underestimate of OD (hence dose). In line profiles of OD taken from 3D reconstructions of the funnel, those profiles with a long pathlength through high OD regions exhibited a 'dishing' (or 'cupping') artefact, while those of short pathlength exhibited the opposite effect-'doming'. These phenomena are accounted for by a model that includes the effect of stray, scattered light.
Modelling optical scattering artefacts for varying pathlength in a gel dosimeter phantom
Energy Technology Data Exchange (ETDEWEB)
Bosi, Stephen G [Department of Radiation Oncology, Prince of Wales Hospital, Randwick, NSW 2031 (Australia); Brown, Saxby; Sarabipour, Sarvenaz; Baldock, Clive [Institute of Medical Physics, School of Physics, University of Sydney, NSW 2006 (Australia); De Deene, Yves [Division of Radiotherapy, University Hospital of Ghent, de Pintelaan 185, 9000 Ghent (Belgium)], E-mail: s.bosi@physics.usyd.edu.au
2009-01-21
A gelatin phantom containing an optically scattering funnel-shaped region of elevated optical density (OD) was used to examine light-scattering-induced artefacts in a cone-beam optical CT scanner used for gel dosimetry. To simulate polymer gel dosimeters, the opacity was introduced by adding a colloidal scatterer to the gelatin. Scatter results in an underestimate of OD (hence dose). In line profiles of OD taken from 3D reconstructions of the funnel, those profiles with a long pathlength through high OD regions exhibited a 'dishing' (or 'cupping') artefact, while those of short pathlength exhibited the opposite effect-'doming'. These phenomena are accounted for by a model that includes the effect of stray, scattered light.
Model Simulation and Eigen-Analysis for Polarimetric Scattering from Tree Canopy in SAR Imagery
Institute of Scientific and Technical Information of China (English)
无
2000-01-01
In this paper, a theoretical model of multi-level, non-spherical scatterers is develotped for fully polarimetric scattering from tree canopy in SAR imaging at C band. The amplitude functions of non-spherical particles with randomly spatial orientation are derived by the generalized Rayleigh Gans (GRG) approximation. The non-diagonal extinction matrix and the Mueller matrix solution are constructed. Numerical solutions of polarimetric scattering of four Stokes parametersfrom random, non-spherical scatterers are obtained. To physically identify polarimetric scattering of the Mueller matrix solution, the coherency matrix and its eigen-analysis are discussed. Functional dependence of the coherency matrix and entropy upon various parameters are obtained. As an application, the analysis of AirSAR images at P, L, C bands is discussed.
Evaluation of angular scattering models for electron-neutral collisions in Monte Carlo simulations
Janssen, J. F. J.; Pitchford, L. C.; Hagelaar, G. J. M.; van Dijk, J.
2016-10-01
In Monte Carlo simulations of electron transport through a neutral background gas, simplifying assumptions related to the shape of the angular distribution of electron-neutral scattering cross sections are usually made. This is mainly because full sets of differential scattering cross sections are rarely available. In this work simple models for angular scattering are compared to results from the recent quantum calculations of Zatsarinny and Bartschat for differential scattering cross sections (DCS’s) from zero to 200 eV in argon. These simple models represent in various ways an approach to forward scattering with increasing electron energy. The simple models are then used in Monte Carlo simulations of range, straggling, and backscatter of electrons emitted from a surface into a volume filled with a neutral gas. It is shown that the assumptions of isotropic elastic scattering and of forward scattering for the inelastic collision process yield results within a few percent of those calculated using the DCS’s of Zatsarinny and Bartschat. The quantities which were held constant in these comparisons are the elastic momentum transfer and total inelastic cross sections.
Optical modeling of plasma-deposited ZnO films: Electron scattering at different length scales
Energy Technology Data Exchange (ETDEWEB)
Knoops, Harm C. M., E-mail: H.C.M.Knoops@tue.nl; Loo, Bas W. H. van de; Smit, Sjoerd; Ponomarev, Mikhail V.; Weber, Jan-Willem; Sharma, Kashish [Department of Applied Physics, Eindhoven University of Technology, P.O. Box 513, 5600 MB Eindhoven (Netherlands); Kessels, Wilhelmus M. M.; Creatore, Mariadriana, E-mail: M.Creatore@tue.nl [Department of Applied Physics, Eindhoven University of Technology, P.O. Box 513, 5600 MB Eindhoven, The Netherlands and Solliance, High Tech Campus 5, 5656 AE Eindhoven (Netherlands)
2015-03-15
In this work, an optical modeling study on electron scattering mechanisms in plasma-deposited ZnO layers is presented. Because various applications of ZnO films pose a limit on the electron carrier density due to its effect on the film transmittance, higher electron mobility values are generally preferred instead. Hence, insights into the electron scattering contributions affecting the carrier mobility are required. In optical models, the Drude oscillator is adopted to represent the free-electron contribution and the obtained optical mobility can be then correlated with the macroscopic material properties. However, the influence of scattering phenomena on the optical mobility depends on the considered range of photon energy. For example, the grain-boundary scattering is generally not probed by means of optical measurements and the ionized-impurity scattering contribution decreases toward higher photon energies. To understand this frequency dependence and quantify contributions from different scattering phenomena to the mobility, several case studies were analyzed in this work by means of spectroscopic ellipsometry and Fourier transform infrared (IR) spectroscopy. The obtained electrical parameters were compared to the results inferred by Hall measurements. For intrinsic ZnO (i-ZnO), the in-grain mobility was obtained by fitting reflection data with a normal Drude model in the IR range. For Al-doped ZnO (Al:ZnO), besides a normal Drude fit in the IR range, an Extended Drude fit in the UV-vis range could be used to obtain the in-grain mobility. Scattering mechanisms for a thickness series of Al:ZnO films were discerned using the more intuitive parameter “scattering frequency” instead of the parameter “mobility”. The interaction distance concept was introduced to give a physical interpretation to the frequency dependence of the scattering frequency. This physical interpretation furthermore allows the prediction of which Drude models can be used in a specific
Directory of Open Access Journals (Sweden)
Sang-Eun Park
2012-05-01
Full Text Available In this paper, the three-component power decomposition for polarimetric SAR (PolSAR data with an adaptive volume scattering model is proposed. The volume scattering model is assumed to be reflection-symmetric but parameterized. For each image pixel, the decomposition first starts with determining the adaptive parameter based on matrix similarity metric. Then, a respective scattering power component is retrieved with the established procedure. It has been shown that the proposed method leads to complete elimination of negative powers as the result of the adaptive volume scattering model. Experiments with the PolSAR data from both the NASA/JPL (National Aeronautics and Space Administration/Jet Propulsion Laboratory Airborne SAR (AIRSAR and the JAXA (Japan Aerospace Exploration Agency ALOS-PALSAR also demonstrate that the proposed method not only obtains similar/better results in vegetated areas as compared to the existing Freeman-Durden decomposition but helps to improve discrimination of the urban regions.
Closed-form impulse response model of non-line-of-sight single-scatter propagation.
Sun, Yu; Zhan, Yafeng
2016-04-01
For optical scattering communication, a closed-form expression of channel impulse response (CIR) is favorable for further system design and channel capacity analysis. Combining the mean value theorem of integrals and L'Hôpital's rule, the exact non-line-of-sight (NLOS) single-scatter propagation model is simplified to a closed-form CIR model for a laser source with a narrow beam. Based on this model, by joint geometrical and empirical approaches, a piecewise CIR expression is presented under certain system NLOS geometries. Through numerical results on CIR for various NLOS geometries, the proposed model is verified with the exact NLOS single-scatter propagation model and the previous Gamma fitting model, showing that our model agrees better with the former than the latter.
Bio-physical modeling of time-resolved forward scattering by Listeria colonies
Bae, Euiwon; Banada, Padmapriya P.; Bhunia, Arun K.; Hirleman, E. Daniel
2006-10-01
We have developed a detection system and associated protocol based on optical forward scattering where the bacterial colonies of various species and strains growing on solid nutrient surfaces produced unique scatter signatures. The aim of the present investigation was to develop a bio-physical model for the relevant phenomena. In particular, we considered time-varying macroscopic morphological properties of the growing colonies and modeled the scattering using scalar diffraction theory. For the present work we performed detailed studies with three species of Listeria; L. innocua, L. monocytogenes, and L. ivanovii. The baseline experiments involved cultures grown on brain heart infusion (BHI) agar and the scatter images were captured every six hours for an incubation period of 42 hours. The morphologies of the colonies were studied by phase contrast microscopy, including measurement of the diameter of the colony. Growth curves, represented by colony diameter as a function of time, were compared with the time-evolution of scattering signatures. Similar studies were carried out with L. monocytogenes grown on different substrates. Non-dimensionalizing incubation time in terms of the time to reach stationary phase was effective in reducing the dimensionality of the model. Bio-physical properties of the colony such as diameter, bacteria density variation, surface curvature/profile, and transmission coefficient are important parameters in predicting the features of the forward scattering signatures. These parameters are included in a baseline model that treats the colony as a concentric structure with radial variations in phase modulation. In some cases azimuthal variations and random phase inclusions were included as well. The end result is a protocol (growth media, incubation time and conditions) that produces reproducible and distinguishable scatter patterns for a variety of harmful food borne pathogens in a short period of time. Further, the bio-physical model we
Monte Carlo Modeling of Computed Tomography Ceiling Scatter for Shielding Calculations.
Edwards, Stephen; Schick, Daniel
2016-04-01
Radiation protection for clinical staff and members of the public is of paramount importance, particularly in occupied areas adjacent to computed tomography scanner suites. Increased patient workloads and the adoption of multi-slice scanning systems may make unshielded secondary scatter from ceiling surfaces a significant contributor to dose. The present paper expands upon an existing analytical model for calculating ceiling scatter accounting for variable room geometries and provides calibration data for a range of clinical beam qualities. The practical effect of gantry, false ceiling, and wall attenuation in limiting ceiling scatter is also explored and incorporated into the model. Monte Carlo simulations were used to calibrate the model for scatter from both concrete and lead surfaces. Gantry attenuation experimental data showed an effective blocking of scatter directed toward the ceiling at angles up to 20-30° from the vertical for the scanners examined. The contribution of ceiling scatter from computed tomography operation to the effective dose of individuals in areas surrounding the scanner suite could be significant and therefore should be considered in shielding design according to the proposed analytical model.
Statistical-thermodynamic model for light scattering from eye lens protein mixtures
Bell, Michael M.; Ross, David S.; Bautista, Maurino P.; Shahmohamad, Hossein; Langner, Andreas; Hamilton, John F.; Lahnovych, Carrie N.; Thurston, George M.
2017-02-01
We model light-scattering cross sections of concentrated aqueous mixtures of the bovine eye lens proteins γB- and α-crystallin by adapting a statistical-thermodynamic model of mixtures of spheres with short-range attractions. The model reproduces measured static light scattering cross sections, or Rayleigh ratios, of γB-α mixtures from dilute concentrations where light scattering intensity depends on molecular weights and virial coefficients, to realistically high concentration protein mixtures like those of the lens. The model relates γB-γB and γB-α attraction strengths and the γB-α size ratio to the free energy curvatures that set light scattering efficiency in tandem with protein refractive index increments. The model includes (i) hard-sphere α-α interactions, which create short-range order and transparency at high protein concentrations, (ii) short-range attractive plus hard-core γ-γ interactions, which produce intense light scattering and liquid-liquid phase separation in aqueous γ-crystallin solutions, and (iii) short-range attractive plus hard-core γ-α interactions, which strongly influence highly non-additive light scattering and phase separation in concentrated γ-α mixtures. The model reveals a new lens transparency mechanism, that prominent equilibrium composition fluctuations can be perpendicular to the refractive index gradient. The model reproduces the concave-up dependence of the Rayleigh ratio on α/γ composition at high concentrations, its concave-down nature at intermediate concentrations, non-monotonic dependence of light scattering on γ-α attraction strength, and more intricate, temperature-dependent features. We analytically compute the mixed virial series for light scattering efficiency through third order for the sticky-sphere mixture, and find that the full model represents the available light scattering data at concentrations several times those where the second and third mixed virial contributions fail. The model
Mishchenko, Michael I; Yurkin, Maxim A; Bi, Lei; Cairns, Brian; Liu, Li; Panetta, R Lee; Travis, Larry D; Yang, Ping; Zakharova, Nadezhda T
2016-01-01
The main objective of this Report is to formulate the general theoretical framework of electromagnetic scattering by discrete random media rooted in the Maxwell-Lorentz electromagnetics and discuss its immediate analytical and numerical consequences. Starting from the microscopic Maxwell-Lorentz equations, we trace the development of the first-principles formalism enabling accurate calculations of monochromatic and quasi-monochromatic scattering by static and randomly varying multiparticle groups. We illustrate how this general framework can be coupled with state-of-the-art computer solvers of the Maxwell equations and applied to direct modeling of electromagnetic scattering by representative random multi-particle groups with arbitrary packing densities. This first-principles modeling yields general physical insights unavailable with phenomenological approaches. We discuss how the first-order-scattering approximation, the radiative transfer theory, and the theory of weak localization of electromagnetic waves ...
Yu, Ting; Chaix, Jean-François; Komatitsch, Dimitri; Garnier, Vincent; Audibert, Lorenzo; Henault, Jean-Marie
2017-02-01
Multiple scattering is important when ultrasounds propagate in a heterogeneous medium such as concrete, the scatterer size of which is in the order of the wavelength. The aim of this work is to build a 2D numerical model of ultrasonic wave propagation integrating the multiple scattering phenomena in SPECFEM software. The coherent field of multiple scattering could be obtained by averaging numerical wave fields, and it is used to determine the effective phase velocity and attenuation corresponding to an equivalent homogeneous medium. After the creation of numerical model under several assumptions, its validation is completed in a case of scattering by one cylinder through the comparison with analytical solution. Two cases of multiple scattering by a set of cylinders at different concentrations are simulated to perform a parametric study (of frequency, scatterer concentration, scatterer size). The effective properties are compared with the predictions of Waterman-Truell model as well, to verify its validity.
A. S. M. Zahid Kausar; Ahmed Wasif Reza; Lau Chun Wo; Harikrishnan Ramiah
2014-01-01
Although ray tracing based propagation prediction models are popular for indoor radio wave propagation characterization, most of them do not provide an integrated approach for achieving the goal of optimum coverage, which is a key part in designing wireless network. In this paper, an accelerated technique of three-dimensional ray tracing is presented, where rough surface scattering is included for making a more accurate ray tracing technique. Here, the rough surface scattering is represented...
Kausar, A. S. M. Zahid; Reza, Ahmed Wasif; Wo, Lau Chun; Ramiah, Harikrishnan
2014-01-01
Although ray tracing based propagation prediction models are popular for indoor radio wave propagation characterization, most of them do not provide an integrated approach for achieving the goal of optimum coverage, which is a key part in designing wireless network. In this paper, an accelerated technique of three-dimensional ray tracing is presented, where rough surface scattering is included for making a more accurate ray tracing technique. Here, the rough surface scattering is represented ...
Directory of Open Access Journals (Sweden)
Abel Palafox
2014-01-01
Full Text Available We address a prototype inverse scattering problem in the interface of applied mathematics, statistics, and scientific computing. We pose the acoustic inverse scattering problem in a Bayesian inference perspective and simulate from the posterior distribution using MCMC. The PDE forward map is implemented using high performance computing methods. We implement a standard Bayesian model selection method to estimate an effective number of Fourier coefficients that may be retrieved from noisy data within a standard formulation.
Nguyen, Jennifer; Hayakawa, Carole K; Mourant, Judith R; Venugopalan, Vasan; Spanier, Jerome
2016-05-01
We present a polarization-sensitive, transport-rigorous perturbation Monte Carlo (pMC) method to model the impact of optical property changes on reflectance measurements within a discrete particle scattering model. The model consists of three log-normally distributed populations of Mie scatterers that approximate biologically relevant cervical tissue properties. Our method provides reflectance estimates for perturbations across wavelength and/or scattering model parameters. We test our pMC model performance by perturbing across number densities and mean particle radii, and compare pMC reflectance estimates with those obtained from conventional Monte Carlo simulations. These tests allow us to explore different factors that control pMC performance and to evaluate the gains in computational efficiency that our pMC method provides.
Gamow shell model description of proton scattering on $^{18}$Ne
Jaganathen, Y; Płoszajczak, M
2014-01-01
We formulate the GSM in coupled-channel (GSM-CC) representation to describe low-energy elastic and inelastic scattering of protons on $^{18}$Ne. The GSM-CC formalism is applied to a translationally-invariant Hamiltonian with an effective finite-range two-body interaction. We discuss in details the GSM-CC formalism in coordinate space and give the description of the novel equivalent potential method for solving the GSM-CC system of integro-differential equations. We present the first application of the GSM-CC formalism for the calculation of excited states of $^{18}$Ne and $^{19}$Na, excitation function and the elastic/inelastic differential cross-sections in the $^{18}$Ne$(p,p')$ reaction at different energies.
Krems, Roman; Cui, Jie; Li, Zhiying
2016-05-01
We show how statistical learning techniques based on kriging (Gaussian Process regression) can be used for improving the predictions of classical and/or quantum scattering theory. In particular, we show how Gaussian Process models can be used for: (i) efficient non-parametric fitting of multi-dimensional potential energy surfaces without the need to fit ab initio data with analytical functions; (ii) obtaining scattering observables as functions of individual PES parameters; (iii) using classical trajectories to interpolate quantum results; (iv) extrapolation of scattering observables from one molecule to another; (v) obtaining scattering observables with error bars reflecting the inherent inaccuracy of the underlying potential energy surfaces. We argue that the application of Gaussian Process models to quantum scattering calculations may potentially elevate the theoretical predictions to the same level of certainty as the experimental measurements and can be used to identify the role of individual atoms in determining the outcome of collisions of complex molecules. We will show examples and discuss the applications of Gaussian Process models to improving the predictions of scattering theory relevant for the cold molecules research field. Work supported by NSERC of Canada.
A Model with Ellipsoidal Scatterers for Polarimetric Remote Sensing of Anisotropic Layered Media
Nghiem, S. V.; Kwok, R.; Kong, J. A.; Shin, R. T.
1993-01-01
This paper presents a model with ellipsoidal scatterers for applications to polarimetric remote sensing of anisotropic layered media at microwave frequencies. The physical configuration includes an isotropic layer covering an anisotropic layer above a homogeneous half space. The isotropic layer consists of randomly oriented spheroids. The anisotropic layer contains ellipsoidal scatterers with a preferential vertical alignment and random azimuthal orientations. Effective permittivities of the scattering media are calculated with the strong fluctuation theory extended to account for the nonspherical shapes and the scatterer orientation distributions. On the basis of the analytic wave theory, dyadic Green's functions for layered media are used to derive polarimetric backscattering coefficients under the distorted Born approximation. The ellipsoidal shape of the scatterers gives rise to nonzero cross-polarized returns from the untilted anisotropic medium in the first-order approximation. Effects of rough interfaces are estimated by an incoherent addition method. Theoretical results and experimental data are matched at 9 GHz for thick first-year sea ice with a bare surface and with a snow cover at Point Barrow, Alaska. The model is then used to study the sensitivity of polarimetric backscattering coefficients with respect to correlation lengths representing the geometry of brine inclusions. Polarimetric signatures of bare and snow-covered sea ice are also simulated based on the model to investigate effects of different scattering mechanisms.
Test of 600 and 750 MeV NN matrix on elastic scattering Glauber model calculations
Brissaud, I.
1980-09-01
The 600 and 750 MeV proton nucleus elastic scattering cross section and polarization calculations have been performed in the framework of the Glauber model to test the pp and pn scattering amplitudes deduced from a phase shift analysis by Bystricky, Lechanoine and Lehar. It is well known that up to now we do not possess a non-phenomenological NN scattering matrix at intermediate energies. However proton-nucleus scattering analyses are used to extract information about short range correlations1), Δ resonance2) or pion condensation presences)... etc. Most scattering calculations made at these energies have been done with phenomenological NN amplitudes having a gaussian q-dependence 10050_2005_Article_BF01438168_TeX2GIFE1.gif A(q) = {kσ }/{4π }(α + i) e^{ - β ^2 q^2 /2} and 10050_2005_Article_BF01438168_TeX2GIFE2.gif C(q) = {kσ }/{4π }iq(α + i) D_e - β ^2 q^2 /2 K and σ being respectively the projectile momentum and the total pN total cross section. The parameters α, β and D are badly known and are adjusted by fitting some specific reactions as p+4He elastic scattering4). Even when these amplitudes provide good fits to the data, our understanding of the dynamics of the scattering remains obscure.
Hulth$\\grave{e}$n potential models for $\\alpha−\\alpha$ and $\\alpha−He^3$ elastic scattering
Indian Academy of Sciences (India)
J BHOI; U LAHA
2017-03-01
Simple Hulth$\\grave{e}$n-type potential models are proposed to treat the $\\alpha−\\alpha$ and $\\alpha−He^3$ elastic scattering. The merit of our approach is examined by computing elastic scattering phases through the judicious use of the phase function method. Reasonable agreements in scattering phase shifts are obtained with the standard data.
Hulthén potential models for α-α and α-He 3 elastic scattering
BHOI, J.; LAHA, U.
2017-03-01
Simple Hulthén-type potential models are proposed to treat the α- α and α {-} {He}3 elastic scattering. The merit of our approach is examined by computing elastic scattering phases through the judicious use of the phase function method. Reasonable agreements in scattering phase shifts are obtained with the standard data.
A vehicle-to-infrastructure channel model for blind corner scattering environments
Chelli, Ali
2013-09-01
In this paper, we derive a new geometrical blind corner scattering model for vehicle-to-infrastructure (V2I) communications. The proposed model takes into account single-bounce and double-bounce scattering stemming from fixed scatterers located on both sides of the curved street. Starting from the geometrical blind corner model, the exact expression of the angle of departure (AOD) is derived. Based on this expression, the probability density function (PDF) of the AOD and the Doppler power spectrum are determined. Analytical expressions for the channel gain and the temporal autocorrelation function (ACF) are provided under non-line-of-sight (NLOS) conditions. Moreover, we investigate the impact of the position of transmitting vehicle relatively to the receiving road-side unit on the channel statistics. The proposed channel model is useful for the design and analysis of future V2I communication systems. Copyright © 2013 by the Institute of Electrical and Electronic Engineers, Inc.
Resonant Raman scattering theory for Kitaev models and their Majorana fermion boundary modes
Perreault, Brent; Knolle, Johannes; Perkins, Natalia B.; Burnell, F. J.
2016-09-01
We study the inelastic light scattering response in two- (2D) and three-dimensional (3D) Kitaev spin-liquid models with Majorana spinon band structures in the symmetry classes BDI and D leading to protected gapless surface modes. We present a detailed calculation of the resonant Raman/Brillouin scattering vertex relevant to iridate and ruthenate compounds whose low-energy physics is believed to be proximate to these spin-liquid phases. In the symmetry class BDI, we find that while the resonant scattering on thin films can detect the gapless boundary modes of spin liquids, the nonresonant processes do not couple to them. For the symmetry class D, however, we find that the coupling between both types of light-scattering processes and the low-energy surface states is strongly suppressed. Additionally, we describe the effect of weak time-reversal symmetry breaking perturbations on the bulk Raman response of these systems.
Forward and inverse models of electromagnetic scattering from layered media with rough interfaces
Tabatabaeenejad, Seyed Alireza
This work addresses the problem of electromagnetic scattering from layered dielectric structures with rough boundaries and the associated inverse problem of retrieving the subsurface parameters of the structure using the scattered field. To this end, a forward scattering model based on the Small Perturbation Method (SPM) is developed to calculate the first-order spectral-domain bistatic scattering coefficients of a two-layer rough surface structure. SPM requires the boundaries to be slightly rough compared to the wavelength, but to understand the range of applicability of this method in scattering from two-layer rough surfaces, its region of validity is investigated by comparing its output with that of a first principle solver that does not impose roughness restrictions. The Method of Moments (MoM) is used for this purpose. Finally, for retrieval of the model parameters of the layered structure using scattered field, an inversion scheme based on the Simulated Annealing method is investigated and a strategy is proposed to address convergence to local minimum.
Efficient scatter model for simulation of ultrasound images from computed tomography data
D'Amato, J. P.; Lo Vercio, L.; Rubi, P.; Fernandez Vera, E.; Barbuzza, R.; Del Fresno, M.; Larrabide, I.
2015-12-01
Background and motivation: Real-time ultrasound simulation refers to the process of computationally creating fully synthetic ultrasound images instantly. Due to the high value of specialized low cost training for healthcare professionals, there is a growing interest in the use of this technology and the development of high fidelity systems that simulate the acquisitions of echographic images. The objective is to create an efficient and reproducible simulator that can run either on notebooks or desktops using low cost devices. Materials and methods: We present an interactive ultrasound simulator based on CT data. This simulator is based on ray-casting and provides real-time interaction capabilities. The simulation of scattering that is coherent with the transducer position in real time is also introduced. Such noise is produced using a simplified model of multiplicative noise and convolution with point spread functions (PSF) tailored for this purpose. Results: The computational efficiency of scattering maps generation was revised with an improved performance. This allowed a more efficient simulation of coherent scattering in the synthetic echographic images while providing highly realistic result. We describe some quality and performance metrics to validate these results, where a performance of up to 55fps was achieved. Conclusion: The proposed technique for real-time scattering modeling provides realistic yet computationally efficient scatter distributions. The error between the original image and the simulated scattering image was compared for the proposed method and the state-of-the-art, showing negligible differences in its distribution.
Directory of Open Access Journals (Sweden)
E DU
2014-01-01
Full Text Available We developed a model to describe polarized photon scattering in biological tissues. In this model, tissues are simplified to a mixture of scatterers and surrounding medium. There are two types of scatterers in the model: solid spheres and infinitely long solid cylinders. Variables related to the scatterers include: the densities and sizes of the spheres and cylinders, the orientation and angular distribution of cylinders. Variables related to the surrounding medium include: the refractive index, absorption coefficient and birefringence. In this paper, as a development we introduce an optical activity effect to the model. By comparing experiments and Monte Carlo simulations, we analyze the backscattering Mueller matrix patterns of several tissue-like media, and summarize the different effects coming from anisotropic scattering and optical properties. In addition, we propose a possible method to extract the optical activity values for tissues. Both the experimental and simulated results show that, by analyzing the Mueller matrix patterns, the microstructure and optical properties of the medium can be obtained. The characteristic features of Mueller matrix patterns are potentially powerful tools for studying the contrast mechanisms of polarization imaging for medical diagnosis.
Comparison of models and measurements of angle-resolved scatter from irregular aerosols
Milstein, Adam B.; Richardson, Jonathan M.
2015-01-01
We have developed and validated a method for modeling the elastic scattering properties of biological and inert aerosols of irregular shape at near- and mid-wave infrared wavelengths. The method, based on Gaussian random particles, calculates the ensemble-average optical cross section and Mueller scattering matrix, using the measured aerodynamic size distribution and previously-reported refractive index as inputs. The utility of the Gaussian particle model is that it is controlled by only two parameters (σ and Γ) which we have optimized such that the model best reproduces the full angle-resolved Mueller scattering matrices measured at λ=1.55 μm in the Standoff Aerosol Active Signature Testbed (SAAST). The method has been applied to wet-generated singlet biological spore samples, dry-generated biological spore clusters, and kaolin. The scattering computation is performed using the Discrete Dipole Approximation (DDA), which requires significant computational resources, and is thus implemented on LLGrid, a large parallel grid computer. For the cases presented, the best fit Gaussian particle model is in good qualitative correspondence with microscopy images of the corresponding class of particles. The measured and computed cross sections agree well within a factor of two overall, with certain cases bearing closer correspondence. In particular, the DDA reproduces the shape of the measured scatter function more accurately than Mie predictions. The DDA-computed depolarization factors are also in good agreement with measurement.
A hybrid model for the three-dimensional scattering from objects in underwater waveguides
Zampolli, Mario; Burnett, David S.; Jensen, Finn B.; Schmidt, Henrik; Blottman, John B.
2003-10-01
The scattering from objects in underwater waveguides is a multi-scale problem, involving both near-field effects in the vicinity of the scatterer as well as long-range propagation through the waveguide. To solve this problem, 3-D Finite-Element STructural Acoustics software developed at SACLANTCEN (FESTA) and an underwater waveguide propagation model based on wavenumber integration developed at MIT (3-D OASES), are coupled into a hybrid model. In a three-step method, the propagation model is used to compute the incident acoustic field in the vicinity of the target, which may be floating, proud, partially buried or buried in the sediment. The incident field data is subsequently passed as an input to the finite-element tool to compute the target-scattered acoustic nearfield. In the final step, the scattered field is propagated through the waveguide by OASES. A second method of coupling between the two models is based on the characterization of the target scattering via spherical harmonic basis responses. The advantage of the second method is that the finite-element computations need to be performed only once for each frequency, regardless of the incident field. Results for different targets with multistatic source-receiver configurations and with focused acoustic incident fields are presented.
Chelli, Ali
2014-01-01
In this paper, we derive a new geometrical blind bend scattering model for vehicle-to- infrastructure (V2I) communications. The proposed model takes into account single-bounce and double- bounce scattering stemming from fixed scatterers located on both sides of a curved street. Starting from the geometrical blind bend model, the exact expression of the angle of departure (AOD) is derived. Based on this expression, the probability density function (PDF) of the AOD and the Doppler power spectrum are determined. Analytical expressions for the channel gain and the temporal autocorrelation function (ACF) are provided under non-line-of-sight (NLOS) conditions. Additionally, we investigate the impact of the position of transmitting vehicle relatively to the receiving road-side unit on the channel statistics. Moreover, we study the performance of different digital modulations over a sum of singly and doubly scattered (SSDS) channel. Note that the proposed V2I channel model falls under the umbrella of SSDS channels since the transmitted signal undergoes a combination of single-bounce and double-bounce scattering. We study some characteristic quantities of SSDS channels and derive expressions for the average symbol error probability of several modulation schemes over SSDS channels with and without diversity combining. The validity of these analytical expressions is confirmed by computer-based simulations.
Leavesley, Silas; Bayraktar, Bülent; Venkatapathi, Murugesan; Hirleman, E. Dan; Bhunia, Arun K.; Robinson, J. Paul; Hassler, Richard; Smith, Linda; Rajwa, Bartek
2007-02-01
Traditional biological and chemical methods for pathogen identification require complicated sample preparation for reliable results. Optical scattering technology has been used for identification of bacterial cells in suspension, but with only limited success. Our published reports have demonstrated that scattered light based identification of Listeria colonies growing on solid surfaces is feasible with proper pattern recognition tools. Recently we have extended this technique to classification of other bacterial genera including, Salmonella, Bacillus, and Vibrio. Our approach may be highly applicable to early detection and classification of pathogens in food-processing industry and in healthcare. The unique scattering patterns formed by colonies of different species are created through differences in colony microstructure (on the order of wavelength used), bulk optical properties, and the macroscopic morphology. While it is difficult to model the effect on scatter-signal patterns owing to the microstructural changes, the influence of bulk optical properties and overall shape of colonies can be modeled using geometrical optics. Our latest research shows that it is possible to model the scatter pattern of bacterial colonies using solid-element optical modeling software (TracePro), and theoretically assess changes in macro structure and bulk refractive indices. This study allows predicting the theoretical limits of resolution and sensitivity of our detection and classification methods. Moreover, quantification of changes in macro morphology and bulk refractive index provides an opportunity to study the response of colonies to various reagents and antibiotics.
Study of light scattering by a granulated coated sphere - a model of granulated blood cells
M.A. Yurkin; D. de Kanter; A.G. Hoekstra
2008-01-01
We performed extensive simulations of light scattering by granulated coated sphere model using the discrete dipole approximation and varying model parameters in the ranges of sizes and refractive indices of granulated blood cells. We compared these results with predictions of Maxwell-Garnett effecti
Quark-diquark model for p(\\bar p)-p elastic scattering at high energies
Grichine, V M; Zotov, N P
2012-01-01
A model for elastic scattering of protons at high energies based on the quark-diquark representation of the proton is discussed. The predictions of the model are compared with experimental data for the differential elastic cross-sections from available databases
Quark-diquark model for p(anti p) -p elastic scattering at high energies
Energy Technology Data Exchange (ETDEWEB)
Grichine, V.M.; Starkov, N.I. [Lebedev Physical Institute, Moscow (Russian Federation); Zotov, N.P. [Lomonosov Moscow State University, Skobeltsyn Institute of Nuclear Physics, Moscow (Russian Federation)
2013-02-15
A model for elastic scattering of protons at high energies based on the quark-diquark representation of the proton is discussed. The predictions of the model are compared with experimental data for the differential elastic cross-sections from available databases. (orig.)
Modeling of laser light scattering in a medium with spherical particles
Larionova, Nadezhda L.; Maksimova, Irina L.
2001-05-01
Laser light radiation scattered by the system of spheres with various parameters was theoretically investigated by using of the Mie theory of electromagnetic scattering by a single sphere. The calculations were performed for systems of particles whose coordinates were specifically realized in random fashion according to the specified probabilities defined by the approximation of hard spheres. The parameters of model are the same as in the eye lense biotissue and were carried out by using of medical data about internal structure of men lens and some animals. In general the studied model presents the system of homogeneous spherical particles which are randomly distributed in the layer of thickness. We study the optical properties such as scattering effective cross-section and function of correlation in different models.
Energy Technology Data Exchange (ETDEWEB)
Reutter, Bryan W.; Gullberg, Grant T.; Huesman, Ronald H.
2003-10-29
Quantitative analysis of uptake and washout of cardiac single photon emission computed tomography (SPECT) radiopharmaceuticals has the potential to provide better contrast between healthy and diseased tissue, compared to conventional reconstruction of static images. Previously, we used B-splines to model time-activity curves (TACs) for segmented volumes of interest and developed fast least-squares algorithms to estimate spline TAC coefficients and their statistical uncertainties directly from dynamic SPECT projection data. This previous work incorporated physical effects of attenuation and depth-dependent collimator response. In the present work, we incorporate scatter and use a computer simulation to study how scatter modeling affects directly estimated TACs and subsequent estimates of compartmental model parameters. An idealized single-slice emission phantom was used to simulate a 15 min dynamic {sup 99m}Tc-teboroxime cardiac patient study in which 500,000 events containing scatter were detected from the slice. When scatter was modeled, unweighted least-squares estimates of TACs had root mean square (RMS) error that was less than 0.6% for normal left ventricular myocardium, blood pool, liver, and background tissue volumes and averaged 3% for two small myocardial defects. When scatter was not modeled, RMS error increased to average values of 16% for the four larger volumes and 35% for the small defects. Noise-to-signal ratios (NSRs) for TACs ranged between 1-18% for the larger volumes and averaged 110% for the small defects when scatter was modeled. When scatter was not modeled, NSR improved by average factors of 1.04 for the larger volumes and 1.25 for the small defects, as a result of the better-posed (though more biased) inverse problem. Weighted least-squares estimates of TACs had slightly better NSR and worse RMS error, compared to unweighted least-squares estimates. Compartmental model uptake and washout parameter estimates obtained from the TACs were less
Efficient modeling of sun/shade canopy radiation dynamics explicitly accounting for scattering
Directory of Open Access Journals (Sweden)
P. Bodin
2012-04-01
Full Text Available The separation of global radiation (R_{g} into its direct (R_{b} and diffuse constituents (R_{g} is important when modeling plant photosynthesis because a high R_{d}:R_{g} ratio has been shown to enhance Gross Primary Production (GPP. To include this effect in vegetation models, the plant canopy must be separated into sunlit and shaded leaves. However, because such models are often too intractable and computationally expensive for theoretical or large scale studies, simpler sun-shade approaches are often preferred. A widely used and computationally efficient sun-shade model was developed by Goudriaan (1977 (GOU. However, compared to more complex models, this model's realism is limited by its lack of explicit treatment of radiation scattering.
Here we present a new model based on the GOU model, but which in contrast explicitly simulates radiation scattering by sunlit leaves and the absorption of this radiation by the canopy layers above and below (2-stream approach. Compared to the GOU model our model predicts significantly different profiles of scattered radiation that are in better agreement with measured profiles of downwelling diffuse radiation. With respect to these data our model's performance is equal to a more complex and much slower iterative radiation model while maintaining the simplicity and computational efficiency of the GOU model.
Efficient modeling of sun/shade canopy radiation dynamics explicitly accounting for scattering
Directory of Open Access Journals (Sweden)
P. Bodin
2011-08-01
Full Text Available The separation of global radiation (R_{g} into its direct (R_{b} and diffuse constituents (R_{d} is important when modeling plant photosynthesis because a high R_{d}:R_{g} ratio has been shown to enhance Gross Primary Production (GPP. To include this effect in vegetation models, the plant canopy must be separated into sunlit and shaded leaves, for example using an explicit 3-dimensional ray tracing model. However, because such models are often too intractable and computationally expensive for theoretical or large scale studies simpler sun-shade approaches are often preferred. A widely used and computationally efficient sun-shade model is a model originally developed by Goudriaan (1977 (GOU, which however does not explicitly account for radiation scattering.
Here we present a new model based on the GOU model, but which in contrast explicitly simulates radiation scattering by sunlit leaves and the absorption of this radiation by the canopy layers above and below (2-stream approach. Compared to the GOU model our model predicts significantly different profiles of scattered radiation that are in better agreement with measured profiles of downwelling diffuse radiation. With respect to these data our model's performance is equal to a more complex and much slower iterative radiation model while maintaining the simplicity and computational efficiency of the GOU model.
Micro-Doppler Effect of Extended Streamlined Targets Based on Sliding Scattering Centre Model
Directory of Open Access Journals (Sweden)
Bo Tang
2016-06-01
Full Text Available The scattering center of extended streamlined targets can slide when the direction of radiation is changed. The sliding scattering center has influence on the micro-Doppler effect of micro-motion of the extended streamlined target. This paper focused on the micro-Doppler of the extended streamlined target for the bistatic radar. Based on the analysis, the analytical expressions of the micro-Doppler of coning motion with sliding scattering center model were given for bistatic radar. And the results were validated by the simulated results of the scattering field based on the full-wave method of the electromagnetic computation. The results showed that the sliding of the scattering center can make the micro-Doppler be less and distorted, and the influence of the sliding is different for two different types of the sliding scattering centers: sliding on the surface and sliding on the bottom circle. The analytical expressions of the micro-Doppler are helpful to analyze the time-frequency presentations (TFR of the coning motion of the extended streamlined target and to estimate the parameters of the target.
Excitation function of elastic $pp$ scattering from a unitarily extended Bialas-Bzdak model
Nemes, F.; Csanád, M.
2015-01-01
The Bialas-Bzdak model of elastic proton-proton scattering assumes a purely imaginary forward scattering amplitude, which consequently vanishes at the diffractive minima. We extended the model to arbitrarily large real parts in a way that constraints from unitarity are satisfied. The resulting model is able to describe elastic $pp$ scattering not only at the lower ISR energies but also at $\\sqrt{s}=$7~TeV in a statistically acceptable manner, both in the diffractive cone and in the region of the first diffractive minimum. The total cross-section as well as the differential cross-section of elastic proton-proton scattering is predicted for the future LHC energies of $\\sqrt{s}=$13, 14, 15~TeV and also to 28~TeV. A non-trivial, significantly non-exponential feature of the differential cross-section of elastic proton-proton scattering is analyzed and the excitation function of the non-exponential behavior is predicted. The excitation function of the shadow profiles is discussed and related to saturation at small ...
Efficient methods to model the scattering of ultrasonic guided waves in 3D
Moreau, L.; Velichko, A.; Wilcox, P. D.
2010-03-01
The propagation of ultrasonic guided waves and their interaction with a defect is of interest to the nondestructive testing community. There is no general solution to the scattering problem and it is still an ongoing research topic. Due to the complexity of guided wave scattering problems, most existing models are related to the 2D case. However, thanks to the increase in computer calculation power, specific 3D problems can also be studied, with the help of numerical or semi-analytical methods. This paper describes two efficient methods aimed at modeling 3D scattering problems. The first method is the use of the Huygens' principle to reduce the size of finite element models. This principle allows the area of interest to be restricted to the very near field of the defect, for both the generation of the incident field and the modal decomposition of the scattered field. The second method consists of separating the 3D problem into two 2D problems for which the solutions are calculated and used to approximate the 3D solution. This can be used at low frequency-thickness products, where Lamb waves have a similar behavior to bulk waves. These two methods are presented briefly and compared on simple scattering cases.
Excitation function of elastic $pp$ scattering from a unitarily extended Bialas-Bzdak model
Nemes, F; Csanád, M
2014-01-01
The Bialas-Bzdak model of elastic proton-proton scattering assumes a purely imaginary forward scattering amplitude, which consequently vanishes at the diffractive minima. We extended the model to arbitrarily large real parts in a way that constraints from unitarity are satisfied. The resulting model is able to describe elastic $pp$ scattering not only at the lower ISR energies but also at $\\sqrt{s}=$7 TeV in a statistically acceptable manner, both in the diffractive cone and in the region of the first diffractive minimum. The total cross-section as well as the differential cross-section of elastic proton-proton scattering is predicted for the future LHC energies of $\\sqrt{s}=$8, 13, 14, 15 TeV and also to 28 TeV. A non-trivial, significantly non-exponential feature of the differential cross-section of elastic proton-proton scattering is analyzed and the excitation function of the non-exponential behavior is predicted. The excitation function of the shadow profiles is discussed and related to saturation at sma...
Mishchenko, Michael I.; Dlugach, Janna M.; Yurkin, Maxim A.; Bi, Lei; Cairns, Brian; Liu, Li; Panetta, R. Lee; Travis, Larry D.; Yang, Ping; Zakharova, Nadezhda T.
2016-05-01
A discrete random medium is an object in the form of a finite volume of a vacuum or a homogeneous material medium filled with quasi-randomly and quasi-uniformly distributed discrete macroscopic impurities called small particles. Such objects are ubiquitous in natural and artificial environments. They are often characterized by analyzing theoretically the results of laboratory, in situ, or remote-sensing measurements of the scattering of light and other electromagnetic radiation. Electromagnetic scattering and absorption by particles can also affect the energy budget of a discrete random medium and hence various ambient physical and chemical processes. In either case electromagnetic scattering must be modeled in terms of appropriate optical observables, i.e., quadratic or bilinear forms in the field that quantify the reading of a relevant optical instrument or the electromagnetic energy budget. It is generally believed that time-harmonic Maxwell's equations can accurately describe elastic electromagnetic scattering by macroscopic particulate media that change in time much more slowly than the incident electromagnetic field. However, direct solutions of these equations for discrete random media had been impracticable until quite recently. This has led to a widespread use of various phenomenological approaches in situations when their very applicability can be questioned. Recently, however, a new branch of physical optics has emerged wherein electromagnetic scattering by discrete and discretely heterogeneous random media is modeled directly by using analytical or numerically exact computer solutions of the Maxwell equations. Therefore, the main objective of this Report is to formulate the general theoretical framework of electromagnetic scattering by discrete random media rooted in the Maxwell-Lorentz electromagnetics and discuss its immediate analytical and numerical consequences. Starting from the microscopic Maxwell-Lorentz equations, we trace the development of
Energy Technology Data Exchange (ETDEWEB)
Mishchenko, Michael I., E-mail: michael.i.mishchenko@nasa.gov [NASA Goddard Institute for Space Studies, 2880 Broadway, New York, NY 10025 (United States); Dlugach, Janna M. [Main Astronomical Observatory of the National Academy of Sciences of Ukraine, 27 Zabolotny Str., 03680, Kyiv (Ukraine); Yurkin, Maxim A. [Voevodsky Institute of Chemical Kinetics and Combustion, SB RAS, Institutskaya str. 3, 630090 Novosibirsk (Russian Federation); Novosibirsk State University, Pirogova 2, 630090 Novosibirsk (Russian Federation); Bi, Lei [Department of Atmospheric Sciences, Texas A& M University, College Station, TX 77843 (United States); Cairns, Brian [NASA Goddard Institute for Space Studies, 2880 Broadway, New York, NY 10025 (United States); Liu, Li [NASA Goddard Institute for Space Studies, 2880 Broadway, New York, NY 10025 (United States); Columbia University, 2880 Broadway, New York, NY 10025 (United States); Panetta, R. Lee [Department of Atmospheric Sciences, Texas A& M University, College Station, TX 77843 (United States); Travis, Larry D. [NASA Goddard Institute for Space Studies, 2880 Broadway, New York, NY 10025 (United States); Yang, Ping [Department of Atmospheric Sciences, Texas A& M University, College Station, TX 77843 (United States); Zakharova, Nadezhda T. [Trinnovim LLC, 2880 Broadway, New York, NY 10025 (United States)
2016-05-16
A discrete random medium is an object in the form of a finite volume of a vacuum or a homogeneous material medium filled with quasi-randomly and quasi-uniformly distributed discrete macroscopic impurities called small particles. Such objects are ubiquitous in natural and artificial environments. They are often characterized by analyzing theoretically the results of laboratory, in situ, or remote-sensing measurements of the scattering of light and other electromagnetic radiation. Electromagnetic scattering and absorption by particles can also affect the energy budget of a discrete random medium and hence various ambient physical and chemical processes. In either case electromagnetic scattering must be modeled in terms of appropriate optical observables, i.e., quadratic or bilinear forms in the field that quantify the reading of a relevant optical instrument or the electromagnetic energy budget. It is generally believed that time-harmonic Maxwell’s equations can accurately describe elastic electromagnetic scattering by macroscopic particulate media that change in time much more slowly than the incident electromagnetic field. However, direct solutions of these equations for discrete random media had been impracticable until quite recently. This has led to a widespread use of various phenomenological approaches in situations when their very applicability can be questioned. Recently, however, a new branch of physical optics has emerged wherein electromagnetic scattering by discrete and discretely heterogeneous random media is modeled directly by using analytical or numerically exact computer solutions of the Maxwell equations. Therefore, the main objective of this Report is to formulate the general theoretical framework of electromagnetic scattering by discrete random media rooted in the Maxwell–Lorentz electromagnetics and discuss its immediate analytical and numerical consequences. Starting from the microscopic Maxwell–Lorentz equations, we trace the development
High Energy (-p)p and pp Elastic Scatterings in QCD Inspired Model
Institute of Scientific and Technical Information of China (English)
LU Juan; MA Wei-Xing; HE Xiao-Rong
2007-01-01
We propose QCD inspired model to calculate (p)p and pp elastic scatterings at high energies in this paper.A calculation for total cross section of (p)p and pp is performed in which the contributions from gluon-gluon,quark-quark,and gluon-quark interactions are included.Our results show that the QCD inspired model gives a perfect fit to experimental data of total cross section both for (p)p and pp elastic scatterings at the whole energy region where experimental data existed at FNAL and CERN.
Palazzi, E.; Premuda, M.; Petritoli, A.; Giovanelli, G.; Kostadinov, I.; Ravegnani, F.; Bortoli, D.
A correct interpretation of diffuse solar radiation measurements made by DOAS (Differential Optical Absorption Spectroscopy) remote sensors, requires the use of radiative transfer models of the atmosphere. The simplest models, the geometrical ones, consider radiation scattering in the atmosphere as a single scattering process. This means that the photons collected by the receiver have changed their direction from the sun only once. More realistic atmospheric models are those which consider multiple scattering: their application is useful and essential for the analysis of zenith and off-axis measurements regarding the lowest layers of the atmosphere, characterized by the highest values of air density and quantities of particles and aerosols acting as scattering nuclei. A new atmospheric model, called PROMSAR (PROcessing of Multi-Scattered Atmospheric Radiation), including multiple Rayleigh and Mie scattering, has recently been developed at the ISAC-CNR institute. It is based on a backward Monte Carlo technique, very suitable for studying the various interactions taking place in a complex and non-homogeneous system like the terrestrial atmosphere. PROMSAR code calculates the mean path of the radiation within each layer into which the atmosphere is sub-divided, taking into account the large variety of processes which solar radiation undergoes during propagation through the atmosphere. This quantity is then employed to work out the Air Mass Factor (AMF) of several trace gases, to simulate, both in zenith and off-axis configurations, their slant column amounts and to calculate the weighting functions from which information about the gas vertical distribution is obtained using inversion methods. Results from the model, simulations and comparisons with slant column measurements are presented and discussed.
Re-evaluation of model-based light-scattering spectroscopy for tissue spectroscopy
Lau, Condon; Šćepanović, Obrad; Mirkovic, Jelena; McGee, Sasha; Yu, Chung-Chieh; Fulghum, Stephen; Wallace, Michael; Tunnell, James; Bechtel, Kate; Feld, Michael
2009-01-01
Model-based light scattering spectroscopy (LSS) seemed a promising technique for in-vivo diagnosis of dysplasia in multiple organs. In the studies, the residual spectrum, the difference between the observed and modeled diffuse reflectance spectra, was attributed to single elastic light scattering from epithelial nuclei, and diagnostic information due to nuclear changes was extracted from it. We show that this picture is incorrect. The actual single scattering signal arising from epithelial nuclei is much smaller than the previously computed residual spectrum, and does not have the wavelength dependence characteristic of Mie scattering. Rather, the residual spectrum largely arises from assuming a uniform hemoglobin distribution. In fact, hemoglobin is packaged in blood vessels, which alters the reflectance. When we include vessel packaging, which accounts for an inhomogeneous hemoglobin distribution, in the diffuse reflectance model, the reflectance is modeled more accurately, greatly reducing the amplitude of the residual spectrum. These findings are verified via numerical estimates based on light propagation and Mie theory, tissue phantom experiments, and analysis of published data measured from Barrett’s esophagus. In future studies, vessel packaging should be included in the model of diffuse reflectance and use of model-based LSS should be discontinued. PMID:19405760
Deeply virtual Compton scattering in a relativistic quark model
Energy Technology Data Exchange (ETDEWEB)
Spitzenberg, T.
2007-09-15
This thesis is mainly concerned with a model calculation for generalized parton distributions (GPDs). We calculate vectorial- and axial GPDs for the N{yields}N and N{yields}{delta} transition in the framework of a light front quark model. This requires the elaboration of a connection between transition amplitudes and GPDs. We provide the first quark model calculations for N{yields}{delta} GPDs. The examination of transition amplitudes leads to various model independent consistency relations. These relations are not exactly obeyed by our model calculation since the use of the impulse approximation in the light front quark model leads to a violation of Poincare covariance. We explore the impact of this covariance breaking on the GPDs and form factors which we determine in our model calculation and find large effects. The reference frame dependence of our results which originates from the breaking of Poincare covariance can be eliminated by introducing spurious covariants. We extend this formalism in order to obtain frame independent results from our transition amplitudes. (orig.)
Ryan, Deirdre A.; Langdon, H. Scott; Beggs, John H.; Steich, David J.; Luebbers, Raymond J.; Kunz, Karl S.
1992-01-01
The approach chosen to model steady state scattering from jet engines with moving turbine blades is based upon the Finite Difference Time Domain (FDTD) method. The FDTD method is a numerical electromagnetic program based upon the direct solution in the time domain of Maxwell's time dependent curl equations throughout a volume. One of the strengths of this method is the ability to model objects with complicated shape and/or material composition. General time domain functions may be used as source excitations. For example, a plane wave excitation may be specified as a pulse containing many frequencies and at any incidence angle to the scatterer. A best fit to the scatterer is accomplished using cubical cells in the standard cartesian implementation of the FDTD method. The material composition of the scatterer is determined by specifying its electrical properties at each cell on the scatterer. Thus, the FDTD method is a suitable choice for problems with complex geometries evaluated at multiple frequencies. It is assumed that the reader is familiar with the FDTD method.
Laboratory light scattering from regolith surface and simulation of data by Hapke model
Deb, S
2015-01-01
The small atmosphereless objects of our solar system, such as asteroids, the moon are covered by layer of dust particles known as regolith, formed by meteoritic impact. The light scattering studies of such dust layer by laboratory experiment and numerical simulation are two important tools to investigate their physical properties. In the present work, the light scattered from a layer of dust particles, containing 0.3{\\mu}m Al2O3 at wavelength 632.8 nm is analysed. This work has been performed by using a light scattering instrument 'ellipsometer', at the Department of Physics, Assam Universiy, Silchar, India. Through this experiment, we generated in laboratory the photometric and polarimetric phase curves of light scattered from such a layer. In order to numerically simulate this data, we used Hapke's model combined with Mie's single particle scattering properties. The perpendicular and parallel components of single particle albedo and the phase function were derived from Mie theory. By using the Hapke's model...
Design of Wideband MIMO Car-to-Car Channel Models Based on the Geometrical Street Scattering Model
Directory of Open Access Journals (Sweden)
Nurilla Avazov
2012-01-01
Full Text Available We propose a wideband multiple-input multiple-output (MIMO car-to-car (C2C channel model based on the geometrical street scattering model. Starting from the geometrical model, a MIMO reference channel model is derived under the assumption of single-bounce scattering in line-of-sight (LOS and non-LOS (NLOS propagation environments. The proposed channel model assumes an infinite number of scatterers, which are uniformly distributed in two rectangular areas located on both sides of the street. Analytical solutions are presented for the space-time-frequency cross-correlation function (STF-CCF, the two-dimensional (2D space CCF, the time-frequency CCF (TF-CCF, the temporal autocorrelation function (ACF, and the frequency correlation function (FCF. An efficient sum-of-cisoids (SOCs channel simulator is derived from the reference model. It is shown that the temporal ACF and the FCF of the SOC channel simulator fit very well to the corresponding correlation functions of the reference model. To validate the proposed channel model, the mean Doppler shift and the Doppler spread of the reference model have been matched to real-world measurement data. The comparison results demonstrate an excellent agreement between theory and measurements, which confirms the validity of the derived reference model. The proposed geometry-based channel simulator allows us to study the effect of nearby street scatterers on the performance of C2C communication systems.
Spatial distribution of mineral dust single scattering albedo based on DREAM model
Kuzmanoski, Maja; Ničković, Slobodan; Ilić, Luka
2016-04-01
Mineral dust comprises a significant part of global aerosol burden. There is a large uncertainty in estimating role of dust in Earth's climate system, partly due to poor characterization of its optical properties. Single scattering albedo is one of key optical properties determining radiative effects of dust particles. While it depends on dust particle sizes, it is also strongly influenced by dust mineral composition, particularly the content of light-absorbing iron oxides and the mixing state (external or internal). However, an assumption of uniform dust composition is typically used in models. To better represent single scattering albedo in dust atmospheric models, required to increase accuracy of dust radiative effect estimates, it is necessary to include information on particle mineral content. In this study, we present the spatial distribution of dust single scattering albedo based on the Dust Regional Atmospheric Model (DREAM) with incorporated particle mineral composition. The domain of the model covers Northern Africa, Middle East and the European continent, with horizontal resolution set to 1/5°. It uses eight particle size bins within the 0.1-10 μm radius range. Focusing on dust episode of June 2010, we analyze dust single scattering albedo spatial distribution over the model domain, based on particle sizes and mineral composition from model output; we discuss changes in this optical property after long-range transport. Furthermore, we examine how the AERONET-derived aerosol properties respond to dust mineralogy. Finally we use AERONET data to evaluate model-based single scattering albedo. Acknowledgement We would like to thank the AERONET network and the principal investigators, as well as their staff, for establishing and maintaining the AERONET sites used in this work.
Quasi-one-dimensional scattering in a discrete model
DEFF Research Database (Denmark)
Valiente, Manuel; Mølmer, Klaus
2011-01-01
that more than one confinement-induced resonances appear due to the nonseparability of the center-of-mass and relative coordinates on the lattice. This is done by solving its corresponding Lippmann-Schwinger-like equation. We characterize the effective one-dimensional interaction and compare it with a model...
Simple Regge pole model for Compton scattering of protons
Energy Technology Data Exchange (ETDEWEB)
Saleem, M.; Fazal-e-Aleem
1978-08-01
It is shown that by a phenomenological choice of the residue functions, the differential cross section for ..gamma.. p ..-->.. ..gamma.. p, including the very recent measurements up to /sup -/t=4.3 (GeV/c)/sup 2/, can be explained at all measured energies greater than 2 GeV with simple Regge pole model.
Small-angle neutron scattering from multilamellar lipid bilayers: Theory, model, and experiment
DEFF Research Database (Denmark)
Lemmich, Jesper; Mortensen, Kell; Ipsen, John Hjorth
1996-01-01
Small-angle neutron scattering data obtained from fully hydrated, multilamellar phospholipid bilayers with deuterated acyl chains of different length are presented and analyzed within a paracrystalline theory and a geometric model that permit the bilayer structure to be determined under condition...
A Path Loss Model for Non-Line-of-Sight Ultraviolet Multiple Scattering Channels
2010-01-01
relevant model parameters. 2.3. Elementary Events for Photon RandomMigration. Gener- ally, it is impossible to predict with certainty the trajectory of a...Witt, “Multiple scattering in reflection nebulae—I: a Monte Carlo approach,” The Astrophysical Journal Supplement Series, vol. 35, pp. 1–6, 1977. [22] D
Distinguishing among models of strong WL WL scattering at the LHC
Energy Technology Data Exchange (ETDEWEB)
Kilgore, W.B.
1997-01-01
Using a multi-channel analysis of strong W{sub L} W{sub L} scattering signals, I study the LHC`s ability to distinguish among various models of strongly interacting electroweak symmetry breaking sectors. 9 refs., 1 fig., 3 tabs.
Van der Waals Type Model for Neutron-Proton Elastic Scattering at High Energies
Aleem, F.
1980-12-01
The most recent measurements of the angular distribution and total cross-section for neutron-proton elastic scattering between 70< pL <400 GeV/c with squared four momentum transfer -t ≤ 3.6 (GeV/c)2 have been explained using Van der Waals type model.
Simple Regge pole model for proton-proton elastic scattering at high energies
Energy Technology Data Exchange (ETDEWEB)
Saleem, M.; Fazal-e-Aleem
1979-06-01
It is shown that by a phenomemological choice of residue functions, the angular distribution in pp elastic scattering at high energies, including the most recent measurement at ..sqrt..s = 27.4 GeV with squared 4-momentum transfer, -t, extending up to 14 (GeV/c)/sup 2/, can be explained with simple Regge pole model.
Modelling small-angle scattering data from complex protein-lipid systems
DEFF Research Database (Denmark)
Kynde, Søren Andreas Røssell
geometric objects and the discrete approach were models are build from a large number of points. It is the basic hypothesis of this thesis, that analysis of smallangle scattering data can be approached in a way that combines the continuous and the discrete modelling methods, and that such an approach can...... the techniques very well suited for the study of the nanodisc system. Chapter 3 explains two different modelling approaches that can be used in the analysis of small-angle scattering data from lipid-protein complexes. These are the continuous approach where the system of interest is modelled as a few regular...... of bacteriorhodopsin and a continuous model of the nanodisc. The position and orientation of the membrane protein relative to the nanodisc is determined as well as the structural changes of the nanodisc. Paper II describes the use of the same approach to determine the relative position of a nanodisc and the membrane...
Universal Quantum Computation by Scattering in the Fermi-Hubbard Model
Bao, Ning; Salton, Grant; Thomas, Nathaniel
2014-01-01
The Hubbard model may be the simplest model of particles interacting on a lattice, but simulation of its dynamics remains beyond the reach of current numerical methods. In this article, we show that general quantum computations can be encoded into the physics of wave packets propagating through a planar graph, with scattering interactions governed by the fermionic Hubbard model. Therefore, simulating the model on planar graphs is as hard as simulating quantum computation. We give two different arguments, demonstrating that the simulation is difficult both for wave packets prepared as excitations of the fermionic vacuum, and for hole wave packets at filling fraction one-half in the limit of strong coupling. In the latter case, which is described by the t-J model, there is only reflection and no transmission in the scattering events, as would be the case for classical hard spheres. In that sense, the construction provides a quantum mechanical analog of the Fredkin-Toffoli billiard ball computer.
Renormalized scattering series for frequency-domain waveform modelling of strong velocity contrasts
Jakobsen, M.; Wu, R. S.
2016-08-01
An improved description of scattering and inverse scattering processes in reflection seismology may be obtained on the basis of a scattering series solution to the Helmoltz equation, which allows one to separately model primary and multiple reflections. However, the popular scattering series of Born is of limited seismic modelling value, since it is only guaranteed to converge if the global contrast is relatively small. For frequency-domain waveform modelling of realistic contrasts, some kind of renormalization may be required. The concept of renormalization is normally associated with quantum field theory, where it is absolutely essential for the treatment of infinities in connection with observable quantities. However, the renormalization program is also highly relevant for classical systems, especially when there are interaction effects that act across different length scales. In the scattering series of De Wolf, a renormalization of the Green's functions is achieved by a split of the scattering potential operator into fore- and backscattering parts; which leads to an effective reorganization and partially re-summation of the different terms in the Born series, so that their order better reflects the physics of reflection seismology. It has been demonstrated that the leading (single return) term in the De Wolf series (DWS) gives much more accurate results than the corresponding Born approximation, especially for models with high contrasts that lead to a large accumulation of phase changes in the forward direction. However, the higher order terms in the DWS that are associated with internal multiples have not been studied numerically before. In this paper, we report from a systematic numerical investigation of the convergence properties of the DWS which is based on two new operator representations of the DWS. The first operator representation is relatively similar to the original scattering potential formulation, but more global and explicit in nature. The second
Sabry, R.; Vachon, P. W.
2005-08-01
A Fourier-based technique for electromagnetic (EM) wave reconstruction with application to polarimetric airborne and spaceborne radar data exploitation is presented. The method is different from conventional modelling techniques for Synthetic Aperture Radar (SAR) applications as a result of the full electromagnetic treatment of field interactions with the scatterer, the possibility of introducing new and controllable feature classes for target classification, and accurate decomposition of the source impulse response function that avoids potential errors (e.g. loss of coherent information) associated with the spherical phase approximations. The capability of extracting scatterer information such as the coherent radar cross section (RCS) is explored.
Inelastic scattering in a local polaron model with quadratic coupling to bosons
DEFF Research Database (Denmark)
Olsen, Thomas
2009-01-01
We calculate the inelastic scattering probabilities in the wide band limit of a local polaron model with quadratic coupling to bosons. The central object is a two-particle Green's function which is calculated exactly using a purely algebraic approach. Compared with the usual linear interaction term...... a quadratic interaction term gives higher probabilities for inelastic scattering involving a large number of bosons. As an application we consider the problem hot-electron-mediated energy transfer at surfaces and use the delta self-consistent field extension of density-functional theory to calculate...
SAR Automatic Target Recognition Based on Numerical Scattering Simulation and Model-based Matching
Directory of Open Access Journals (Sweden)
Zhou Yu
2015-12-01
Full Text Available This study proposes a model-based Synthetic Aperture Radar (SAR automatic target recognition algorithm. Scattering is computed offline using the laboratory-developed Bidirectional Analytic Ray Tracing software and the same system parameter settings as the Moving and Stationary Target Acquisition and Recognition (MSTAR datasets. SAR images are then created by simulated electromagnetic scattering data. Shape features are extracted from the measured and simulated images, and then, matches are searched. The algorithm is verified using three types of targets from MSTAR data and simulated SAR images, and it is shown that the proposed approach is fast and easy to implement with high accuracy.
Swearingen, Michelle Elaine
2003-10-01
This thesis is a presentation of an analytic model, developed in cylindrical coordinates, for the scattering of a spherical wave off a semi infinite right cylinder placed normal to a ground surface. The model is developed to simulate a single tree and is developed as a first piece to creating a model for estimating attenuation in a forest based on scattering from individual tree trunks. Comparisons are made to the plane wave case, the transparent cylinder case, and the rigid and soft ground cases as a method of theoretically verifying the model. Agreement is excellent for these benchmark cases. Model sensitivity to five parameters is determined, which aids in error analysis, particularly when comparing the model results to experimental data, and offers insight into the inner workings of the model. An experiment was performed to collect real-world data on scattering from a cylinder normal to a ground surface. The data from the experiment is analyzed with a transfer function method into frequency and impulse responses. The model results are compared to the experimental data.
Falsifying models of new physics via WW scattering.
Distler, Jacques; Grinstein, Benjamin; Porto, Rafael A; Rothstein, Ira Z
2007-01-26
We show that the coefficients of operators in the electroweak chiral Lagrangian can be bounded if the underlying theory obeys the usual assumptions of Lorentz invariance, analyticity, unitarity, and crossing to arbitrarily short distances. Violations of these bounds can be explained by either the existence of new physics below the naive cutoff of the effective theory, or by the breakdown of one of these assumptions in the short distance theory. As a corollary, if no light resonances are found, then a measured violation of the bound would falsify generic models of string theory.
Model independent extraction of the proton magnetic radius from electron scattering
Epstein, Zachary; Paz, Gil; Roy, Joydeep
2014-10-01
We combine constraints from analyticity with experimental electron-proton scattering data to determine the proton magnetic radius without model-dependent assumptions on the shape of the form factor. We also study the impact of including electron-neutron scattering data, and ππ→NN ¯ data. Using representative data sets we find for a cut of Q2≤0.5 GeV2, rMp=0.91-0.06+0.03±0.02 fm using just proton scattering data; rMp=0.87-0.05+0.04±0.01 fm adding neutron data; and rMp=0.87-0.02+0.02 fm adding ππ data. We also extract the neutron magnetic radius from these data sets obtaining rMn=0.89-0.03+0.03 fm from the combined proton, neutron, and ππ data.
Comment on "More on Heisenberg's model for high energy nucleon-nucleon scattering"
Block, Martin M; Ha, Phuoc; Halzen, Francis
2016-01-01
We comment on the treatment of asymptotic black-disk scattering in a recent paper of Nastase and Sonnenschein, Phys.\\ Rev.\\ D\\ {\\bf 92}, 015028 (2015), on scattering in an updated version of the Heisenberg model which gives $pp$ and $\\bar{p}p$ cross sections which increase at very high energies as $\\ln^2s$. We show that the total cross section they define does not correspond to that measured in experiments, with the result that their limit for the ratio $\\sigma_{\\rm elas}/\\sigma_{\\rm tot}$ is too small by a factor 2. The correct ratio for black-disk scattering, $\\sigma_{\\rm elas}/\\sigma_{\\rm tot} \\rightarrow 1/2$ for $s\\rightarrow\\infty$, is strongly supported by experiment.
Energy Technology Data Exchange (ETDEWEB)
Lü, X.; Schrottke, L.; Grahn, H. T. [Paul-Drude-Institut für Festkörperelektronik, Leibniz-Institut im Forschungsverbund Berlin e. V., Hausvogteiplatz 5–7, 10117 Berlin (Germany)
2016-06-07
We present scattering rates for electrons at longitudinal optical phonons within a model completely formulated in the Fourier domain. The total intersubband scattering rates are obtained by averaging over the intrasubband electron distributions. The rates consist of the Fourier components of the electron wave functions and a contribution depending only on the intersubband energies and the intrasubband carrier distributions. The energy-dependent part can be reproduced by a rational function, which allows for the separation of the scattering rates into a dipole-like contribution, an overlap-like contribution, and a contribution which can be neglected for low and intermediate carrier densities of the initial subband. For a balance between accuracy and computation time, the number of Fourier components can be adjusted. This approach facilitates an efficient design of complex heterostructures with realistic, temperature- and carrier density-dependent rates.
Alvarado, Matthew J.; Lonsdale, Chantelle R.; Macintyre, Helen L.; Bian, Huisheng; Chin, Mian; Ridley, David A.; Heald, Colette L.; Thornhill, Kenneth L.; Anderson, Bruce E.; Cubison, Michael J.; Jimenez, Jose L.; Kondo, Yutaka; Sahu, Lokesh K.; Dibb, Jack E.; Wang, Chien
2016-07-01
Accurate modeling of the scattering and absorption of ultraviolet and visible radiation by aerosols is essential for accurate simulations of atmospheric chemistry and climate. Closure studies using in situ measurements of aerosol scattering and absorption can be used to evaluate and improve models of aerosol optical properties without interference from model errors in aerosol emissions, transport, chemistry, or deposition rates. Here we evaluate the ability of four externally mixed, fixed size distribution parameterizations used in global models to simulate submicron aerosol scattering and absorption at three wavelengths using in situ data gathered during the 2008 Arctic Research of the Composition of the Troposphere from Aircraft and Satellites (ARCTAS) campaign. The four models are the NASA Global Modeling Initiative (GMI) Combo model, GEOS-Chem v9-02, the baseline configuration of a version of GEOS-Chem with online radiative transfer calculations (called GC-RT), and the Optical Properties of Aerosol and Clouds (OPAC v3.1) package. We also use the ARCTAS data to perform the first evaluation of the ability of the Aerosol Simulation Program (ASP v2.1) to simulate submicron aerosol scattering and absorption when in situ data on the aerosol size distribution are used, and examine the impact of different mixing rules for black carbon (BC) on the results. We find that the GMI model tends to overestimate submicron scattering and absorption at shorter wavelengths by 10-23 %, and that GMI has smaller absolute mean biases for submicron absorption than OPAC v3.1, GEOS-Chem v9-02, or GC-RT. However, the changes to the density and refractive index of BC in GC-RT improve the simulation of submicron aerosol absorption at all wavelengths relative to GEOS-Chem v9-02. Adding a variable size distribution, as in ASP v2.1, improves model performance for scattering but not for absorption, likely due to the assumption in ASP v2.1 that BC is present at a constant mass fraction
Superradiant Forward Scattering in Multiple Scattering
Chabe, Julien; Bienaime, Tom; Bachelard, Romain; Piovella, Nicola; Kaiser, Robin
2012-01-01
We report on an interference effect in multiple scattering by resonant scatterers resulting in enhanced forward scattering, violating Ohm's law for photons. The underlying mechanism of this wave effect is superradiance, which we have investigated using cold atoms as a toy model. We present numerical and experimental evidences for this superradiant forward scattering, which is robust against disorder and configuration averaging.
Quantum statistics of Raman scattering model with Stokes mode generation
Tanatar, Bilal; Shumovsky, Alexander S.
1994-01-01
The model describing three coupled quantum oscillators with decay of Rayleigh mode into the Stokes and vibration (phonon) modes is examined. Due to the Manley-Rowe relations the problem of exact eigenvalues and eigenstates is reduced to the calculation of new orthogonal polynomials defined both by the difference and differential equations. The quantum statistical properties are examined in the case when initially: the Stokes mode is in the vacuum state; the Rayleigh mode is in the number state; and the vibration mode is in the number of or squeezed states. The collapses and revivals are obtained for different initial conditions as well as the change in time the sub-Poisson distribution by the super-Poisson distribution and vice versa.
Optical scatter imaging of cellular and mitochondrial swelling in brain tissue models of stroke
Johnson, Lee James
2001-08-01
The severity of brain edema resulting from a stroke can determine a patient's survival and the extent of their recovery. Cellular swelling is the microscopic source of a significant part of brain edema. Mitochondrial swelling also appears to be a determining event in the death or survival of the cells that are injured during a stroke. Therapies for reducing brain edema are not effective in many cases and current treatments of stroke do not address mitochondrial swelling at all. This dissertation is motivated by the lack of a complete understanding of cellular swelling resulting from stroke and the lack of a good method to begin to study mitochondrial swelling resulting from stroke in living brain tissue. In this dissertation, a novel method of detecting mitochondrial and cellular swelling in living hippocampal slices is developed and validated. The system is used to obtain spatial and temporal information about cellular and mitochondrial swelling resulting from various models of stroke. The effect of changes in water content on light scatter and absorption are examined in two models of brain edema. The results of this study demonstrate that optical techniques can be used to detect changes in water content. Mie scatter theory, the theoretical basis of the dual- angle scatter ratio imaging system, is presented. Computer simulations based on Mie scatter theory are used to determine the optimal angles for imaging. A detailed account of the early systems is presented to explain the motivations for the system design, especially polarization, wavelength and light path. Mitochondrial sized latex particles are used to determine the system response to changes in scattering particle size and concentration. The dual-angle scatter ratio imaging system is used to distinguish between osmotic and excitotoxic models of stroke injury. Such distinction cannot be achieved using the current techniques to study cellular swelling in hippocampal slices. The change in the scatter ratio is
Lindsley, E. H.; Farkas, D. L.
2008-02-01
We have designed and built an imaging elastic scattering spectroscopy endoscopic instrument for the purpose of detecting cancer in vivo. As part of our testing and validation of the system, known targets representing potential disease states of interest were constructed using polystyrene beads of known average diameter and TiO II crystals embedded in a two-layer agarose gel. Final construction geometry was verified using a dissection microscope. The phantoms were then imaged using the endoscopic probe at a known incident angle, and the results compared to model predictions. The mathematical model that was used combines classic ray-tracing optics with Mie scattering to predict the images that would be observed by the probe at a given physical distance from a Mie-regime scattering media. This model was used generate the expected observed response for a broad range of parameter values, and these results were then used as a library to fit the observed data from the phantoms. Compared against the theoretical library, the best matching signal correlated well with known phantom material dimensions. These results lead us to believe that imaging elastic scattering can be useful in detection/diagnosis, but further refinement of the device will be necessary to detect the weak signals in a real clinical setting.
Measurements and modelling of aerosol single-scattering albedo: progress, problems and prospects
Energy Technology Data Exchange (ETDEWEB)
Heintzenberg, J. [Institut fuer Troposphaerenforschung e.V. (IfT), Leipzig (Germany); Charlson, R.J.; Clarke, A.D.; Liousse, C.; Ramaswamy, V.; Shine, K.P.; Wendisch, M.; Helas, G.
1997-11-01
The net effect of atmospheric aerosols in the radiation balance is determined by both their scattering and absorption of solar radiation. The combined optical effect is expressed in the single scatter albedo, {omega}, of the particles. Currently available data on {omega} are insufficient for definitive use in climate models because most of them are not corrected for the method-dependent effect of the scattering portion of the aerosol on the measured absorption, most refer to the dry state of the aerosol, and the coverage of the globe is far from being complete. Standardisation and calibration of the measurements is needed. Modelling exercises using currently available data on {omega} should clearly state that corrections are required. The purpose of this review is not to suggest a particular range of values for single scatter albedo. Rather, it is to illustrate that the uncertainties are currently imbedded in various data sets because of the lack of calibration, the possibility that many of the extant methods systematically overestimate light absorption coefficients, and the necessity of including the influence of humidity in models. (orig.) 95 refs.
Jäger, K.; Fischer, M.; Van Swaaij, R.A.C.M.M.; Zeman, M.
2012-01-01
We present a scattering model based on the scalar scattering theory that allows estimating far field scattering properties in both transmission and reflection for nano-textured interfaces. We first discuss the theoretical formulation of the scattering model and validate it for nano-textures with dif
A washboard with moment of inertia model of gas-surface scattering.
Yan, Tianying; Hase, William L; Tully, John C
2004-01-08
A washboard with moment of inertia (WBMI) model for gas atom scattering from a flexible surface is proposed and applied. This model is a direct extension of the washboard model [J. Chem. Phys. 92, 680 (1990)] proposed for gas atom scattering from relatively rigid, corrugated surfaces. In addition, a moment of inertia is incorporated in the original washboard model to describe the flexibility of softer, more highly corrugated surfaces such as polymer or liquid surfaces. The moment of inertia of the effective surface object introduces a dependence of the efficiency of energy transfer on the position and direction of impact, a feature that has been shown to be critical by molecular dynamics simulations. The WBMI model is solved numerically by Monte Carlo integration, which makes the implementation of multiple impacts between a colliding atom and the surface very efficient. The model is applied to Ne and Ar atoms scattering from an alkylthiolate self-assembled monolayer surface and reproduces the major results obtained by classical trajectory simulation of the same system, i.e., a bimodal translation energy distribution P(E(f)) with the low-energy component well-fit with a Boltzmann distribution, but with a temperature that may (Ar) or may not (Ne) be the same as the surface temperature. This indicates that the WBMI model, with well-motivated physical assumptions and simplified interaction, reveals many of the major aspects of the gas-surface collision dynamics, though it does not take into account the real-time dynamics explicitly.
Zhang, Jin-Peng; Wu, Zhen-Sen; Zhao, Zhen-Wei; Zhang, Yu-Sheng; Wang, Bo
2012-10-01
The maritime tropospheric duct is a low-altitude anomalous refractivity structure over the ocean surface, and it can significantly affect the performance of many shore-based/shipboard radar and communication systems. We propose the idea that maritime tropospheric ducts can be retrieved from ocean forward-scattered low-elevation global positioning system (GPS) signals. Retrieval is accomplished by matching the measured power patterns of the signals to those predicted by the forward propagation model as a function of the modified refractivity profile. On the basis of a parabolic equation method and bistatic radar equation, we develop such a forward model for computing the trapped propagation characteristics of an ocean forward-scattered GPS signal within a tropospheric duct. A new GPS scattering initial field is defined for this model to start the propagation modeling. A preliminary test on the performance of this model is conducted using measured data obtained from a 2009-experiment in the South China Sea. Results demonstrate that this model can predict GPS propagation characteristics within maritime tropospheric ducts and serve as a forward model for duct inversion.
Institute of Scientific and Technical Information of China (English)
Zhang Jin-Peng; Wu Zhen-Sen; Zhao Zhen-Wei; Zhang Yu-Sheng; Wang Bo
2012-01-01
The maritime tropospheric duct is a low-altitude anomalous refractivity structure over the ocean surface,and it can significantly affect the performance of many shore-based/shipboard radar and communication systems. We propose the idea that maritime tropospheric ducts can be retrieved from ocean forward-scattered low-elevation global positioning system (GPS) signals.Retrieval is accomplished by matching the measured power patterns of the signals to those predicted by the forward propagation model as a function of the modified refractivity profile.On the basis of a parabolic equation method and bistatic radar equation,we develop such a forward model for computing the trapped propagation characteristics of an ocean forward-scattered GPS signal within a tropospheric duct.A new GPS scattering initial field is defined for this model to start the propagation modeling.A preliminary test on the performance of this model is conducted using measured data obtained from a 2009-experiment in the South China Sea.Results demonstrate that this model can predict GPS propagation characteristics within maritime tropospheric ducts and serve as a forward model for duct inversion.
Comparison of Geant4 multiple Coulomb scattering models with theory for radiotherapy protons
Makarova, Anastasia; Sauerwein, Wolfgang
2016-01-01
Usually, Monte Carlo models are validated against experimental data. However, models of multiple Coulomb scattering (MCS) in the Gaussian approximation are exceptional in that we have theories which are probably more accurate than the experiments which have, so far, been done to test them. In problems directly sensitive to the distribution of angles leaving the target, the relevant theory is the Moliere/Fano/Hanson variant of Moliere theory. For transverse spreading of the beam in the target itself, the theory of Preston and Koehler holds. Therefore, in this paper we compare Geant4 simulations, using the Urban and Wentzel models of MCS, with theory rather than experiment, revealing trends which would otherwise be obscured by experimental scatter. For medium-energy (radiotherapy) protons, and low-Z (water-like) target materials, Wentzel appears to be better than Urban in simulating the distribution of outgoing angles. For beam spreading in the target itself, the two models are essentially equal.
A Multiple Scattering Polarized Radiative Transfer Model: Application to HD 189733b
Kopparla, Pushkar; Zhang, Xi; Swain, Mark R; Wiktorowicz, Sloane J; Yung, Yuk L
2015-01-01
We present a multiple scattering vector radiative transfer model which produces disk integrated, full phase polarized light curves for reflected light from an exoplanetary atmosphere. We validate our model against results from published analytical and computational models and discuss a small number of cases relevant to the existing and possible near-future observations of the exoplanet HD 189733b. HD 189733b is arguably the most well observed exoplanet to date and the only exoplanet to be observed in polarized light, yet it is debated if the planet's atmosphere is cloudy or clear. We model reflected light from clear atmospheres with Rayleigh scattering, and cloudy or hazy atmospheres with Mie and fractal aggregate particles. We show that clear and cloudy atmospheres have large differences in polarized light as compared to simple flux measurements, though existing observations are insufficient to make this distinction. Futhermore, we show that atmospheres that are spatially inhomogeneous, such as being partial...
Sporre, John R.; Elg, Daniel T.; Kalathiparambil, Kishor K.; Ruzic, David N.
2016-01-01
A theoretical model for describing the propagation and scattering of energetic species in an extreme ultraviolet (EUV) light lithography source is presented. An EUV light emitting XTREME XTS 13-35 Z-pinch plasma source is modeled with a focus on the effect of chamber pressure and buffer gas mass on energetic ion and neutral debris transport. The interactions of the energetic debris species, which is generated by the EUV light emitting plasma, with the buffer gas and chamber walls are considered as scattering events in the model, and the trajectories of the individual atomic species involved are traced using a Monte Carlo algorithm. This study aims to establish the means by which debris is transported to the intermediate focus with the intent to verify the various mitigation techniques currently employed to increase EUV lithography efficiency. The modeling is compared with an experimental investigation.
Modelling small-angle scattering data from complex protein-lipid systems
DEFF Research Database (Denmark)
Kynde, Søren Andreas Røssell
the techniques very well suited for the study of the nanodisc system. Chapter 3 explains two different modelling approaches that can be used in the analysis of small-angle scattering data from lipid-protein complexes. These are the continuous approach where the system of interest is modelled as a few regular...... geometric objects and the discrete approach were models are build from a large number of points. It is the basic hypothesis of this thesis, that analysis of smallangle scattering data can be approached in a way that combines the continuous and the discrete modelling methods, and that such an approach can......This thesis consists of two parts. The rst part is divided into five chapters. Chapter 1 gives a general introduction to the bio-molecular systems that have been studied. These are membrane proteins and their lipid environments in the form of phospholipid nanodiscs. Membrane proteins...
A General Model of the Atmospheric Scattering in the Wavelength Interval 300 - 1100nm
Directory of Open Access Journals (Sweden)
K. Dimitrov
2009-12-01
Full Text Available We have presented and developed new theoretic-empirical models of the extinction coefficients of the molecular scattering in the lower, close to the ground troposphere. We have included the indicatrices of backscattering. The models have been presented using general analytical functions valid for the whole wavelength interval 300-1100 nm and for the whole interval of visibility from 0.1 km up to 50 km. The results have been compared in quantity with the model and experimental data of other authors. The modeling of troposphere scattering is necessary for the analysis and design of all optoelectronic free space systems: atmospheric optical communication systems, location systems for atmospheric research (LIDAR, optical radiometric systems.
Simulation of ultrasonic scattering from a fractal model of the liver
Phillips, Daniel Brian
The liver has been particularly resistant to ultrasonic tissue characterization of diffuse pathological processes. This may be due, in part, to the difficulty in determining the scattering contribution of a complex structure comprised of components that span a size range from sub-resolveable to many times larger than the insonating wavelength. Due to the inherent random nature of scattering from such a complex structure, statistical evaluation of the backscattered signals has been pursued by a number of investigators in order to gain a better understanding of their relationship to the underlying scattering sources within a liver which contains an intricate network of vascular components with significant collagen content. This study maintains that the collagenous structures represented by the vessels associated with the portal vasculature, including how they are spatially organized, is a major source of the observed features of backscattered ultrasound signals from the liver. To that end, a three dimensional geometric computer model of the human portal vascular system has been constructed based on accepted anatomical and physiological information and utilizing a fractal generation algorithm. The fractal methodology is used to determine the branching characteristics of the model, such as vessel numbers, locations and dimensions. This complex, three dimensional data set is used as a source for producing simulated ultrasound B-scans which are subsequently subjected to statistical analysis and evaluation in order to (1) verify that the model produced data with characteristics similar to those from actual backscattered signals from human liver, and (2) attempt to understand the relationship between the characteristics of the modeled vasculature and the resulting backscattered signals. The fractal implementation of the vasculature model will be discussed and results will be presented which indicate that simple variations in the characteristics of the model can produce
Energy Technology Data Exchange (ETDEWEB)
Saleem, M.; Fazal-E-Aleem; Azhar, I.A.
1988-06-01
The various characteristics of pp and antipp elastic scattering at high energies are explained by using the generalized Chou-Yang model which takes into consideration the anisotropic scattering of objects constituting colliding particles. The model is also used to extract the form factor and radius of the ..lambda.. particle.
A model-based scatter artifacts correction for cone beam CT
Energy Technology Data Exchange (ETDEWEB)
Zhao, Wei; Zhu, Jun; Wang, Luyao [Department of Biomedical Engineering, Huazhong University of Science and Technology, Hubei 430074 (China); Vernekohl, Don; Xing, Lei, E-mail: lei@stanford.edu [Department of Radiation Oncology, Stanford University, Stanford, California 94305 (United States)
2016-04-15
Purpose: Due to the increased axial coverage of multislice computed tomography (CT) and the introduction of flat detectors, the size of x-ray illumination fields has grown dramatically, causing an increase in scatter radiation. For CT imaging, scatter is a significant issue that introduces shading artifact, streaks, as well as reduced contrast and Hounsfield Units (HU) accuracy. The purpose of this work is to provide a fast and accurate scatter artifacts correction algorithm for cone beam CT (CBCT) imaging. Methods: The method starts with an estimation of coarse scatter profiles for a set of CBCT data in either image domain or projection domain. A denoising algorithm designed specifically for Poisson signals is then applied to derive the final scatter distribution. Qualitative and quantitative evaluations using thorax and abdomen phantoms with Monte Carlo (MC) simulations, experimental Catphan phantom data, and in vivo human data acquired for a clinical image guided radiation therapy were performed. Scatter correction in both projection domain and image domain was conducted and the influences of segmentation method, mismatched attenuation coefficients, and spectrum model as well as parameter selection were also investigated. Results: Results show that the proposed algorithm can significantly reduce scatter artifacts and recover the correct HU in either projection domain or image domain. For the MC thorax phantom study, four-components segmentation yields the best results, while the results of three-components segmentation are still acceptable. The parameters (iteration number K and weight β) affect the accuracy of the scatter correction and the results get improved as K and β increase. It was found that variations in attenuation coefficient accuracies only slightly impact the performance of the proposed processing. For the Catphan phantom data, the mean value over all pixels in the residual image is reduced from −21.8 to −0.2 HU and 0.7 HU for projection
Directory of Open Access Journals (Sweden)
Martin J Bishop
2014-09-01
Full Text Available Light scattering during optical imaging of electrical activation within the heart is known to significantlydistort the optically-recorded action potential (AP upstroke, as well as affecting the magnitude of the measured response of ventricular tissue to strong electric shocks. Modelling approaches based on the photondiffusion equation have recently been instrumental in quantifying and helping to understand the origin of the resulting distortion. However, they are unable to faithfully represent regions of non-scattering media, such assmall cavities within the myocardium which are filled with perfusate during experiments. Stochastic Monte Carlo (MC approaches allow simulation and tracking of individual photon `packets' as they propagate through tissuewith differing scattering properties. Here, we present a novel application of the MC method of photon scattering simulation, applied for the first time to the simulation of cardiac optical mapping signals withinunstructured, tetrahedral, finite element computational ventricular models. The method faithfully allows simulation of optical signals over highly-detailed, anatomically-complex MR-based models, includingrepresentations of fine-scale anatomy and intramural cavities. We show that optical action potential upstroke is prolonged close to large subepicardial vessels than further away from vessels, at times having a distinct `humped' morphology.Furthermore, we uncover a novel mechanism by which photon scattering effects around vessels cavities interact with `virtual-electrode' regions of strong de-/hyper-polarised tissue surrounding cavitiesduring shocks, significantly reducing the apparent optically-measured epicardial polarisation. We therefore demonstrate the importance of this novel optical mapping simulation approach along with highly anatomically-detailed models to fully investigate electrophysiological phenomena driven by fine-scale structural heterogeneity.
Stavenga, Doekele G; van der Kooi, Casper J.
2015-01-01
Main conclusion An absorbing-layer-stack model allows quantitative analysis of the light flux in flowers and the resulting reflectance spectra. It provides insight in how plants can optimize their flower coloration for attracting pollinators. The coloration of flowers is due to the combined effect of pigments and light-scattering structures. To interpret flower coloration, we applied an optical model that considers a flower as a stack of layers, where each layer can be treated with the Kubelk...
Scattering resonances and two-particle bound states of the extended Hubbard model
Energy Technology Data Exchange (ETDEWEB)
Valiente, M; Petrosyan, D [Institute of Electronic Structure and Laser, FORTH, 71110 Heraklion, Crete (Greece)
2009-06-28
We present a complete derivation of two-particle states of the one-dimensional extended Bose-Hubbard model involving attractive or repulsive on-site and nearest-neighbour interactions. We find that this system possesses scattering resonances and two families of energy-dependent interaction-bound states which are not present in the Hubbard model with the on-site interaction alone. (fast track communication)
Tan, S.; Tsang, L.; Xu, X.; Ding, K. H.
2015-12-01
In this paper we describe partial coherent model and fully coherent snowpack scattering model based on numerical simulation of Maxwell's equation. In medium characterization, we derive the correlation functions from the pair distribution functions of sticky spheres and multiple-size spheres used in QCA. We show that both the Percus-Yevick pair functions and the bicontinuous model have tails in the correlation functions that are distinctly different from the traditional exponential correlation functions. The methodologies of using ground measurements of grain size distributions and correlation functions to obtain model parameters are addressed. The DMRT theory has been extended to model the backscattering enhancement. We developed the methodology of cyclical corrections beyond first order to all orders of multiple scattering. This enables the physical modeling of combined active and passive microwave remote sensing of snow over the same scene. The bicontinuous /DMRT is applied to compare with data acquired in the NoSREx campaign, and the model results are validated against coincidental active and passive measurements using the same set of physical parameters of snow in all frequency and polarization channels. The DMRT is a partially coherent approach that one accounts for the coherent wave interaction only within few wavelengths as represented by phase matrix. However, the phase information of field is lost in propagating the specific intensity via RT and this hinders the use of DMRT in coherent synthetic aperture radar (SAR) analysis, including InSAR, PolInSAR and Tomo-SAR. One can alternatively calculate the scattering matrix of the terrestrial snowpack above ground by solving the volume integral equations directly with half space Green's function. The scattering matrix of the snowpack is computed for each realization giving rise to the speckle statistics. The resulting bistatic scattering automatically includes the backscattering enhancement effects. Tomograms of
Characterising Vegetation Canopies by means of optical data and Microwave Scattering models
Molina, Iñigo; Gonzalez, Constancio; Ormeño, Santiago; Morillo, Carmen; Garcia-Melendez, Eduardo
One of the main strengths of active microwave remote sensing, in relation to frequency, is its capacity to penetrate vegetation canopies, and reach the ground surface, so that information about the vegetation and hydrological properties of the surface can be drawn. All this infor-mation is gathered in the so called backscattering coefficient (σ 0 ), and in a vegetated medium, this coefficient reveals important information on the vegetation water content, geometry and/or structure of the canopy elements, above ground biomass, and soil roughness and moisture. In the scope of microwave frequencies, modeling the backscattering coefficient of vegetated terrain, involves taking into account scattering models that simulate the soil surface contribution by means of its physical variables, and the vegetation layer, through the knowledge of its biophys-ical properties. Soil surface scattering models require describing parameters of roughness, like soil profile height displacement standard deviation and correlation length, and moisture, which determines sur-face reflective properties. The knowledge of these parameters, allows to establishing surface scattering models with different validity ranges. Some frequently used models are divided into theoretical and empirical models. The vegetation canopy is usually regarded as a homogeneous, or random layer, at a certain height above terrain surface, and it is used to compute the attenuation through this layer. This requires a geometric generalization of the vegetation layer and its constituents, specifying additionally its electromagnetic properties. The main simulation models are based on Radiative Transfer theory, which allows for different approaches and simplifications. In this sense, somo of these models, can be efficiently adapted to any vegetated medium, and the constituents can by approximated by more general variables like Leaf Area Index (LAI), or Water total Content (WTC) of Vegetation. Moreover, in the microwave region
Ground moving target signal model and power calculation in forward scattering micro radar
Institute of Scientific and Technical Information of China (English)
LONG Teng; HU Cheng; MIKHAIL Cherniakov
2009-01-01
Forward scattering micro radar is used for situation awareness;its operational range is relatively short because of the battery power and local horizon,the free space propagation model is not appropriate.The ground moving targets,such as humans,cars and tanks,have only comparable size with the transmitted signal wavelength;the point target model and the linear change of observation angle are not applicable.In this paper,the signal model of ground moving target is developed based on the case of forward scattering micro radar,considering the two-ray propagation model and area target model,and nonlinear change of observation angle as well as high order phase error.Furthermore,the analytical form of the received power from moving target has been obtained.Using the simulated forward scattering radar cross section,the received power of theoretical calculation is near to that of measured data.In addition,the simulated signal model of ground moving target is perfectly matched with the experimented data.All these results show the correctness of analytical calculation completely.
A MULTIPLE SCATTERING POLARIZED RADIATIVE TRANSFER MODEL: APPLICATION TO HD 189733b
Energy Technology Data Exchange (ETDEWEB)
Kopparla, Pushkar; Yung, Yuk L. [Division of Geological and Planetary Sciences, California Institute of Technology, Pasadena, CA (United States); Natraj, Vijay; Swain, Mark R. [Jet Propulsion Laboratory (NASA-JPL), Pasadena, CA (United States); Zhang, Xi [Lunar and Planetary Laboratory, University of Arizona, Tucson, AZ (United States); Wiktorowicz, Sloane J., E-mail: pkk@gps.caltech.edu [Department of Astronomy and Astrophysics, University of California, Santa Cruz, CA (United States)
2016-01-20
We present a multiple scattering vector radiative transfer model that produces disk integrated, full phase polarized light curves for reflected light from an exoplanetary atmosphere. We validate our model against results from published analytical and computational models and discuss a small number of cases relevant to the existing and possible near-future observations of the exoplanet HD 189733b. HD 189733b is arguably the most well observed exoplanet to date and the only exoplanet to be observed in polarized light, yet it is debated if the planet’s atmosphere is cloudy or clear. We model reflected light from clear atmospheres with Rayleigh scattering, and cloudy or hazy atmospheres with Mie and fractal aggregate particles. We show that clear and cloudy atmospheres have large differences in polarized light as compared to simple flux measurements, though existing observations are insufficient to make this distinction. Futhermore, we show that atmospheres that are spatially inhomogeneous, such as being partially covered by clouds or hazes, exhibit larger contrasts in polarized light when compared to clear atmospheres. This effect can potentially be used to identify patchy clouds in exoplanets. Given a set of full phase polarimetric measurements, this model can constrain the geometric albedo, properties of scattering particles in the atmosphere, and the longitude of the ascending node of the orbit. The model is used to interpret new polarimetric observations of HD 189733b in a companion paper.
Richard, D. T.; Glenar, D. A.; Stubbs, T. J.; Davis, S. S.; Colaprete, A.
2011-11-01
It is suspected that the lunar exosphere has a dusty component dispersed above the surface by various physical mechanisms. Most of the evidence for this phenomenon comes from observations of "lunar horizon glow" (LHG), which is thought to be produced by the scattering of sunlight by this exospheric dust. The characterization of exospheric dust populations at the Moon is key to furthering our understanding of fundamental surface processes, as well as a necessary requirement for the planning of future robotic and human exploration. We present a model to simulate the scattering of sunlight by complex lunar dust grains (i.e. grains that are non-spherical and can be inhomogeneous in composition) to be used in the interpretation of remote sensing data from current and future lunar missions. We numerically model lunar dust grains with several different morphologies and compositions and compute their individual scattering signatures using the Discrete Dipole Approximation (DDA). These scattering properties are then used in a radiative transfer code to simulate the light scattering due to a dust size distribution, as would likely be observed in the lunar exosphere at high altitudes 10's of km. We demonstrate the usefulness and relevance of our model by examining mode: irregular grains, aggregate of spherical monomers and spherical grains with nano-phase iron inclusions. We subsequently simulate the scattering by two grain size distributions ( 0.1 and 0.3μm radius), and show the results normalized per-grain. A similar methodology can also be applied to the analysis of the LHG observations, which are believed to be produced by scattering from larger dust grains within about a meter of the surface. As expected, significant differences in scattering properties are shown between the analyses employing the widely used Mie theory and our more realistic grain geometries. These differences include large variations in intensity as well as a positive polarization of scattered
A More General Model for the Intrinsic Scatter in Type Ia Supernova Distance Moduli
Marriner, John; Bernstein, J. P.; Kessler, Richard; Lampeitl, Hubert; Miquel, Ramon; Mosher, Jennifer; Nichol, Robert C.; Sako, Masao; Schneider, Donald P.; Smith, Mathew
2011-10-01
We describe a new formalism to fit the parameters α and β that are used in the SALT2 model to determine the standard magnitudes of Type Ia supernovae (SNe Ia). The new formalism describes the intrinsic scatter in SNe Ia by a covariance matrix in place of the single parameter normally used. We have applied this formalism to the Sloan Digital Sky Survey Supernova Survey (SDSS-II) data and conclude that the data are best described by α = 0.135+.033 -.017 and β = 3.19+0.14 - 0.24, where the error is dominated by the uncertainty in the form of the intrinsic scatter matrix. Our result depends on the introduction of a more general form for the intrinsic scatter of the distance moduli of SNe Ia than is conventional, resulting in a larger value of β and a larger uncertainty than the conventional approach. Although this analysis results in a larger value of β and a larger error, the SDSS data differ (at a 98% confidence level) from β = 4.1, the value expected for extinction by the type of dust found in the Milky Way. We have modeled the distribution of SNe Ia in terms of their color and conclude that there is strong evidence that variation in color is a significant contributor to the scatter of SNe Ia around their standard candle magnitude.
Small-angle scattering from precipitates: Analysis by use of a polydisperse hard-sphere model
DEFF Research Database (Denmark)
Pedersen, J.S.
1993-01-01
A general polydisperse hard-sphere model for analyzing small-angle-scattering data from spherical precipitates in alloys is presented. In the model the size distribution is chosen as a Weibull density distribution and the hard-sphere interaction radius is taken as being proportional to the radius...... very good fits to the experimental data and the results are in agreement with a Li content of 25% in the precipitates. The concentration of Li in the matrix is also in good agreement with the phase diagram of Al-Li found in the literature. Results from the application of a monodisperse hard-sphere...... of the precipitates. The Weibull distribution is monomodal, and depending on the parameters describing the distribution, it can skew to either side. Small-angle x-ray- and neutron-scattering data, taken from the literature, from spherical delta' precipitates in Al-Li alloys have been analyzed with the model. It gives...
A quad-pol radar scattering model for use in remote sensing of lava flow morphology
Campbell, Bruce A.; Zisk, Stanley H.; Mouginis-Mark, Peter J.
1989-01-01
Mapping of spatial variations in surface roughness over large regions is required to understand the nature of volcanic terrains. An invertible scattering model for quad-polarization radar data is presented to assist in the remote-sensing analysis of lava flow surface morphology. This model permits separation of the polarized part of the radar echo into quasispecular, dihedral, and small-perturbation scatterin components, based on an assumed surface dielectric constant. Tests are presented for a quad-pol scene of Craters of the Moon National Monument in Idaho, where there are a number of basaltic lava flows of differing surface morphology. Comparison of calculated model components with the observed morphology of the lava flows suggests that this technique may be useful for the remote description of changes in surface roughness. The scattering mechanisms chosen to represent the polarizing behavior of the real surface display correlations which indicate that they are sensitive to the expected scales of roughness.
f-mode interaction with models of sunspot: near-field scattering and multifrequency effects
Daiffallah, Khalil
2016-07-01
We use numerical simulations to investigate the interaction of an f-mode wave packet with small and large models of a sunspot in a stratified atmosphere. While a loose cluster model has been largely studied before, we focus in this study on the scattering from an ensemble of tightly compact tubes. We showed that the small compact cluster produces a slight distorted scattered wave field in the transverse direction, which can be attributed to the simultaneous oscillations of the pairs of tubes within the cluster aligned in a perpendicular direction to the incoming wave. However, no signature of a multiple-scattering regime has been observed from this model, while it has been clearly observable for the large compact cluster model. Furthermore, we pointed out the importance of the geometrical shape of the monolithic model on the interaction of f-mode waves with a sunspot in a high-frequency range (ν = 5 mHz). These results are a contribution to the observational effort to distinguish seismically between different configurations of magnetic flux tubes within sunspots and plage.
Perkins, Stephen J; Okemefuna, Azubuike I; Nan, Ruodan; Li, Keying; Bonner, Alexandra
2009-10-06
X-ray and neutron-scattering techniques characterize proteins in solution and complement high-resolution structural studies. They are useful when either a large protein cannot be crystallized, in which case scattering yields a solution structure, or a crystal structure has been determined and requires validation in solution. These solution structures are determined by the application of constrained modelling methods based on known subunit structures. First, an appropriate starting model is generated. Next, its conformation is randomized to generate thousands of models for trial-and-error fits. Comparison with the experimental data identifies a small family of best-fit models. Finally, their significance for biological function is assessed. We illustrate this in application to structure determinations for secretory immunoglobulin A, the most prevalent antibody in the human body and a first line of defence in mucosal immunity. We also discuss the applications to the large multi-domain proteins of the complement system, most notably its major regulator factor H, which is important in age-related macular degeneration and renal diseases. We discuss the importance of complementary data from analytical ultracentrifugation, and structural studies of protein-protein complexes. We conclude that constrained scattering modelling makes useful contributions to our understanding of antibody and complement structure and function.
Structural model of the 50S subunit of E.Coli ribosomes from solution scattering
Energy Technology Data Exchange (ETDEWEB)
Svergun, D.I.; Koch, M.H.J. [Hamburg Outstation (Germany); Pedersen, J.S. [Riso National Laboratory, Roskilde (Denmark); Serdyuk, I.N. [Inst. of Protein Research, Moscow (Russian Federation)
1994-12-31
The application of new methods of small-angle scattering data interpretation to a contrast variation study of the 50S ribosomal subunit of Escherichia coli in solution is described. The X-ray data from contrast variation with sucrose are analyzed in terms of the basic scattering curves from the volume inaccessible to sucrose and from the regions inside this volume occupied mainly by RNA and by proteins. From these curves models of the shape of the 50S and its RNA-rich core are evaluated and positioned so that their difference produces a scattering curve which is in good agreement with the scattering from the protein moiety. Basing on this preliminary model, the X-ray and neutron contrast variation data of the 50S subunit in aqueous solutions are interpreted in the frame of the advanced two-phase model described by the shapes of the 50S subunit and its RNA-rich core taking into account density fluctuations inside the RNA and the protein moiety. The shape of the envelope of the 50S subunit and of the RNA-rich core are evaluated with a resolution of about 40A. The shape of the envelope is in good agreement with the models of the 50S subunit obtained from electron microscopy on isolated particles. The shape of the RNA-rich core correlates well with the model of the entire particle determined by the image reconstruction from ordered sheets indicating that the latter model which is based on the subjective contouring of density maps is heavily biased towards the RNA.
Korda, V. Yu.; Molev, A. S.; Klepikov, V. F.; Korda, L. P.
2015-02-01
Using the evolutionary model-independent S -matrix approach, we show that a simultaneous correct description of the pictures of nuclear rainbow, prerainbow, and anomalous large-angle scattering (ALAS) in the 4He-40Ca elastic scattering can be achieved with help of the S -matrix moduli and the real nuclear phases exhibiting smooth monotonic dependencies on angular momentum, while the quantum deflection functions have a form characteristic of the nuclear rainbow case. The special role of the surface partial waves in the formation of ALAS is revealed.
Neural Network Emulation of the Integral Equation Model with Multiple Scattering
Directory of Open Access Journals (Sweden)
Luca Pulvirenti
2009-10-01
Full Text Available The Integral Equation Model with multiple scattering (IEMM represents a well-established method that provides a theoretical framework for the scattering of electromagnetic waves from rough surfaces. A critical aspect is the long computational time required to run such a complex model. To deal with this problem, a neural network technique is proposed in this work. In particular, we have adopted neural networks to reproduce the backscattering coefficients predicted by IEMM at L- and C-bands, thus making reference to presently operative satellite radar sensors, i.e., that aboard ERS-2, ASAR on board ENVISAT (C-band, and PALSAR aboard ALOS (L-band. The neural network-based model has been designed for radar observations of both flat and tilted surfaces, in order to make it applicable for hilly terrains too. The assessment of the proposed approach has been carried out by comparing neural network-derived backscattering coefficients with IEMM-derived ones. Different databases with respect to those employed to train the networks have been used for this purpose. The outcomes seem to prove the feasibility of relying on a neural network approach to efficiently and reliably approximate an electromagnetic model of surface scattering.
Sekihara, Takayasu
2016-01-01
For a general two-body bound state in quantum mechanics, both in the stable and decaying cases, we establish a way to extract its two-body wave function in momentum space from the scattering amplitude of the constituent two particles. For this purpose, we first show that the two-body wave function of the bound state corresponds to the residue of the off-shell scattering amplitude at the bound state pole. Then, we examine our scheme to extract the two-body wave function from the scattering amplitude in several schematic models. As a result, the two-body wave functions from the Lippmann--Schwinger equation coincides with that from the Schr\\"{o}dinger equation for an energy-independent interaction. Of special interest is that the two-body wave function from the scattering amplitude is automatically scaled; the norm of the two-body wave function, to which we refer as the compositeness, is unity for an energy-independent interaction, while the compositeness deviates from unity for an energy-dependent interaction, ...
Modeling proton and alpha elastic scattering in liquid water in Geant4-DNA
Energy Technology Data Exchange (ETDEWEB)
Tran, H.N., E-mail: tranngochoang@tdt.edu.vn [Division of Nuclear Physics, Ton Duc Thang University, Tan Phong Ward, District 7, Ho Chi Minh City (Viet Nam); Faculty of Applied Sciences, Ton Duc Thang University, Tan Phong Ward, District 7, Ho Chi Minh City (Viet Nam); El Bitar, Z. [Institut Pluridisciplinaire Hubert Curien/IN2P3/CNRS, Strasbourg (France); Champion, C. [Univ. Bordeaux, CENBG, UMR 5797, F-33170 Gradignan (France); CNRS, IN2P3, CENBG, UMR 5797, F-33170 Gradignan (France); Karamitros, M. [Univ. Bordeaux, CENBG, UMR 5797, F-33170 Gradignan (France); CNRS, IN2P3, CENBG, UMR 5797, F-33170 Gradignan (France); CNRS, INCIA, UMR 5287, F-33400 Talence (France); Bernal, M.A. [Instituto de FísicaGleb Wataghin, Universida de Estadual de Campinas, SP (Brazil); Francis, Z. [Université Saint Joseph, Faculty of Science, Department of Physics, Beirut (Lebanon); The Open University, Faculty of Science, Department of Physical Sciences, Walton Hall, MK7 6AA Milton Keynes (United Kingdom); Ivantchenko, V. [Ecoanalytica, 119899 Moscow (Russian Federation); Lee, S.B.; Shin, J.I. [Proton Therapy Center, National Cancer Center, 323 Ilsan-ro, Ilsandong-gu, Goyang-si, Gyeonggi-do 410-769 (Korea, Republic of); Incerti, S. [Univ. Bordeaux, CENBG, UMR 5797, F-33170 Gradignan (France); CNRS, IN2P3, CENBG, UMR 5797, F-33170 Gradignan (France)
2015-01-15
Elastic scattering of protons and alpha (α) particles by water molecules cannot be neglected at low incident energies. However, this physical process is currently not available in the “Geant4-DNA” extension of the Geant4 Monte Carlo simulation toolkit. In this work, we report on theoretical differential and integral cross sections of the elastic scattering process for 100 eV–1 MeV incident protons and for 100 eV–10 MeV incident α particles in liquid water. The calculations are performed within the classical framework described by Everhart et al., Ziegler et al. and by the ICRU 49 Report. Then, we propose an implementation of the corresponding classes into the Geant4-DNA toolkit for modeling the elastic scattering of protons and α particles. Stopping powers as well as ranges are also reported. Then, it clearly appears that the account of the elastic scattering process in the slowing-down of the charged particle improves the agreement with the existing data in particular with the ICRU recommendations.
Kim, Kyuseok; Park, Soyoung; Kim, Guna; Cho, Hyosung; Je, Uikyu; Park, Chulkyu; Lim, Hyunwoo; Lee, Dongyeon; Lee, Hunwoo; Kang, Seokyoon
2017-03-01
In conventional mammography, contrast sensitivity remains limited due to the superimposition of breast tissue and scattered X-rays, which induces low visibility of lesions in the breast and, thus, an excessive number of false-positive findings. Several methods, including digital breast tomosynthesis as a multiplanar imaging modality, air-gap and slot techniques for the reduction of scatters, phase-contrast imaging as another image-contrast modality, etc., have been investigated in attempt to overcome these difficulties. However, those techniques typically require a higher imaging dose or special equipment. In this work, as an alternative, we propose a new image restoration method based on a radiographic scattering model in which the intensity of scattered X-rays and the direct transmission function of a given medium are estimated from a single projection by using the dark-channel prior. We implemented the proposed algorithm and performed an experiment to demonstrate its viability. Our results indicate that most of the structures in the examined breast were very discernable even with no adjustment in the display-window level, thus preserving superior image features and edge sharpening.
DEFF Research Database (Denmark)
Bjerrum-Niese, Christian; Jensen, Leif Bjørnø
1994-01-01
Temporal variations of scattering of high-frequency, monochromatic signals from the ocean surface has been studied numerically. In the high-frequency domain the dynamic scattering can be modeled by a coherence function of the scattered pressure field, which is based on the Kirchhoff integral...... for the Pierson–Moskowitz spectrum (for a fully developed sea) with computations for the JONSWAP spectrum (for fetch-limited seas). The following results, among other issues, have been obtained: As the fetch decreases, the surface waves become shorter, leading to increasing frequency shifting of the scattered...... signal. [Work sponsored by the Danish Technical Research Council and the EU/MAST programme.]...
2005-10-01
radar cross section (RCS), which is a measure of a target’s reflectivity. Assuming a specific imaging scene, we predict the SNR through the RCS of the...the effective length Lk of the scattering primitive. Many scattering geometries, such as dihedrals , corner reflectors , and cylinders, are...and M. T. Tuley. Radar Cross Section . Artech House, Boston, 1993. [4] E. R. Keydel, S. W. Lee and J. T. Moore. MSTAR extended operating conditions: a
Structure of liposome encapsulating proteins characterized by X-ray scattering and shell-modeling
Energy Technology Data Exchange (ETDEWEB)
Hirai, Mitsuhiro, E-mail: mhirai@gunma-u.ac.jp; Kimura, Ryota; Takeuchi, Kazuki; Hagiwara, Yoshihiko [Gunma University, 4-2 Aramaki, Maebashi, Gunma 371-8510 (Japan); Kawai-Hirai, Rika [Gunma University, 3-39-15 Shouwa, Maebashi 371-8512 (Japan); Ohta, Noboru [JASRI, 1-1-1 Kuoto, Sayo-cho, Sayo-gun, Hyogo 679-5198 (Japan); Igarashi, Noriyuki; Shimuzu, Nobutaka [KEK-PF, 1-1 Oho, Tsukuba, Ibaraki 305-0801 (Japan)
2013-11-01
Wide-angle X-ray scattering data using a third-generation synchrotron radiation source are presented. Lipid liposomes are promising drug delivery systems because they have superior curative effects owing to their high adaptability to a living body. Lipid liposomes encapsulating proteins were constructed and the structures examined using synchrotron radiation small- and wide-angle X-ray scattering (SR-SWAXS). The liposomes were prepared by a sequential combination of natural swelling, ultrasonic dispersion, freeze-throw, extrusion and spin-filtration. The liposomes were composed of acidic glycosphingolipid (ganglioside), cholesterol and phospholipids. By using shell-modeling methods, the asymmetric bilayer structure of the liposome and the encapsulation efficiency of proteins were determined. As well as other analytical techniques, SR-SWAXS and shell-modeling methods are shown to be a powerful tool for characterizing in situ structures of lipid liposomes as an important candidate of drug delivery systems.
Folding model study of the elastic $\\alpha + \\alpha$ scattering at low energies
Tan, Ngo Hai; Khoa, Dao T
2014-01-01
The folding model analysis of the elastic $\\alpha + \\alpha$ scattering at the incident energies below the reaction threshold of 34.7 MeV (in the lab system) has been done using the well-tested density dependent versions of the M3Y interaction and realistic choices for the $^4$He density. Because the absorption is negligible at the energies below the reaction threshold, we were able to probe the $\\alpha + \\alpha$ optical potential at low energies quite unambiguously and found that the $\\alpha + \\alpha$ overlap density used to construct the density dependence of the M3Y interaction is strongly distorted by the Pauli blocking. This result gives possible explanation of a long-standing inconsistency of the double-folding model in its study of the elastic $\\alpha + \\alpha$ and $\\alpha$-nucleus scattering at low energies using the same realistic density dependent M3Y interaction.
Pion scattering and electro-production on nucleons in the resonance region in chiral quark models
Sirca, Simon; Fiolhais, Manuel; Alberto, Pedro
2011-01-01
Pion scattering and electro-production amplitudes have been computed in a coupled-channel framework incorporating quasi-bound quark-model states, based on the Cloudy Bag model. All relevant low-lying nucleon resonances in the P33, P11, and S11 partial waves have been covered, including the Delta(1232), the N*(1440), N*(1535), and N*(1650). Consistent results have been obtained for elastic and inelastic scattering (two-pion, eta-N, and K-Lambda channels), as well as for electro-production. The meson cloud has been shown to play a major role, in particular in electro-magnetic observables in the P33 and P11 channels.
Scattering data for modelling positron tracks in gaseous and liquid water
Blanco, F.; Roldán, A. M.; Krupa, K.; McEachran, R. P.; White, R. D.; Marjanović, S.; Petrović, Z. Lj; Brunger, M. J.; Machacek, J. R.; Buckman, S. J.; Sullivan, J. P.; Chiari, L.; Limão-Vieira, P.; García, G.
2016-07-01
We present in this study a self-consistent set of scattering cross sections for positron collisions with water molecules, in the energy range 0.1-10 000 eV, with the prime motivation being to provide data for modelling purposes. The structure of the database is based on a new model potential calculation, including interference terms, which provides differential and integral elastic as well as integral inelastic positron scattering cross sections for water molecules over the whole energy range considered here. Experimental and theoretical data available in the literature have been integrated into the database after a careful analysis of their uncertainties and their self-consistency. These data have been used as input parameters for a step-by-step Monte Carlo simulation procedure, providing valuable information on energy deposition, positron range, and the relative percentages of specific interactions (e.g. positronium formation, direct ionisation, electronic, vibrational and rotational excitations) in gaseous and liquid water.
Coupled-Channel Model for $\\bar{K}N$ Scattering in the Resonant Region
Fernandez-Ramirez, C; Manley, D M; Mathieu, V; Szczepaniak, A P
2015-01-01
We present a unitary multichannel model for $\\bar{K}N$ scattering in the resonance region that fulfills unitarity. It has the correct analytical properties for the amplitudes once they are extended to the complex-$s$ plane and the partial waves have the right threshold behavior. To determine the parameters of the model, we have fitted single-energy partial waves up to $J=7/2$ and up to 2.15 GeV of energy in the center-of-mass reference frame obtaining the poles of the $\\Lambda^*$ and $\\Sigma^*$ resonances, which are compared to previous analyses. We provide the most comprehensive picture of the $S=-1$ hyperon spectrum to date. Important differences are found between the available analyses making the gathering of further experimental information on $\\bar{K}N$ scattering mandatory to make progress in the assessment of the hyperon spectrum.
A Soluble Model for Scattering and Decay in Quaternionic Quantum Mechanics I Decay
Horwitz, L P
1994-01-01
The Lee-Friedrichs model has been very useful in the study of decay-scattering systems in the framework of complex quantum mechanics. Since it is exactly soluble, the analytic structure of the amplitudes can be explicitly studied. It is shown in this paper that a similar model, which is also exactly soluble, can be constructed in quaternionic quantum mechanics. The problem of the decay of an unstable system is treated here. The use of the Laplace transform, involving quaternion-valued analytic functions of a variable with values in a complex subalgebra of the quaternion algebra, makes the analytic properties of the solution apparent; some analysis is given of the dominating structure in the analytic continuation to the lower half plane. A study of the corresponding scattering system will be given in a succeeding paper.
Fast-neutron total and scattering cross sections of sup 58 Ni and nuclear models
Energy Technology Data Exchange (ETDEWEB)
Smith, A.B.; Guenther, P.T.; Whalen, J.F. (Argonne National Lab., IL (United States)); Chiba, S. (Japan Atomic Energy Research Inst., Tokai, Ibaraki (Japan). Tokai Research Establishment)
1991-07-01
The neutron total cross sections of {sup 58}Ni were measured from {approx} 1 to > 10 MeV using white-source techniques. Differential neutron elastic-scattering cross sections were measured from {approx} 4.5 to 10 MeV at {approx} 0.5 MeV intervals with {ge} 75 differential values per distribution. Differential neutron inelastic-scattering cross sections were measured, corresponding to fourteen levels with excitations up to 4.8 MeV. The measured results, combined with relevant values available in the literature, were interpreted in terms of optical-statistical and coupled-channels model using both vibrational and rotational coupling schemes. The physical implications of the experimental results nd their interpretation are discussed in the contexts of optical-statistical, dispersive-optical, and coupled-channels models. 61 refs.
Double folding model analysis of elastic scattering of halo nucleus 11Be from 64Zn
Indian Academy of Sciences (India)
M Hemalatha
2014-05-01
Calculations of elastic scattering cross-sections for 9,10,11Be+64Zn at near-Coulomb barrier energy have been performed using a potential obtained from the double folding model and are compared with the experiment. In the framework of the double folding model, the nuclear matter densities of 9,10,11Be projectiles and a 64Zn target are folded with the complex energydependent effective M3Y interaction. The angular distributions of the differential cross-section for 9,10Be scattering from 64Zn at $E_{c.m.} ≈$24.5 MeV agree remarkably well with the data, while in case of 11Be, calculations show a Coulomb–nuclear interference peak which is not observed in the data.
Taxes in a Wealth Distribution Model by Inelastically Scattering of Particles
Directory of Open Access Journals (Sweden)
Sebastian Guala
2009-07-01
Full Text Available In this work we use an inelastic scattering process of particles to propose a model able to reproduce the salient features of the wealth distribution in an economy by including taxes to each trading process and redistributing that collected among the population according to a given criterion. Additionally, we show that different optimal levels of taxes may exist depending on the redistribution criterion.
A dense medium electromagnetic scattering model for the InSAR correlation of snow
Lei, Yang; Siqueira, Paul; Treuhaft, Robert
2016-05-01
Snow characteristics, such as snow water equivalent (SWE) and snow grain size, are important characteristics for the monitoring of the global hydrological cycle and as indicators of climate change. This paper derives an interferometric synthetic aperture radar (InSAR) scattering model for dense media, such as snow, which takes into account multiple scattering effects through the Quasi-Crystalline Approximation. The result of this derivation is a simplified version of the InSAR correlation model derived for relating the InSAR correlation measurements to the snowpack characteristics of grain size, volume fraction, and layer depth as well as those aspects of the volume-ground interaction that affects the interferometric observation (i.e., the surface topography and the ratio of ground-to-volume scattering). Based on the model, the sensitivity of the InSAR correlation measurements to the snow characteristics is explored by simulation. Through this process, it is shown that Ka-band InSAR phase has a good sensitivity to snow grain size and volume fraction, while for lower frequency signals (Ku-band to L-band), the InSAR correlation magnitude and phase have a sensitivity to snow depth. Since the formulation depends, in part, on the pair distribution function, three functional forms of the pair distribution function are implemented and their effects on InSAR phase measurements compared. The InSAR scattering model described in this paper is intended to be an observational prototype for future Ka-band and L-band InSAR missions, such as NASA's Surface Water and Ocean Topography and NASA-ISRO Synthetic Aperture Radar missions, planned for launch in the 2020-2021 time frame. This formulation also enables further investigation of the InSAR-based snow retrieval approaches.
Van der Waals Type Model and Structure in π-p Elastic Scattering at High Energies
Aleem, F.
1982-10-01
The most recent measurement of the angular distribution for π-p elastic scattering at pL =50 and 200 GeV/c which show a structure near -t ≈ 4(GeV/c)2, with squared four momentum transfer -t extended to 10(GeV/c)2, and the total cross section data for 50 ≤ pL ≤ 370 GeV/c have been simultaneously explained by using Van der Waal's type model.
Integrative structural modeling with small angle X-ray scattering profiles
Directory of Open Access Journals (Sweden)
Schneidman-Duhovny Dina
2012-07-01
Full Text Available Abstract Recent technological advances enabled high-throughput collection of Small Angle X-ray Scattering (SAXS profiles of biological macromolecules. Thus, computational methods for integrating SAXS profiles into structural modeling are needed more than ever. Here, we review specifically the use of SAXS profiles for the structural modeling of proteins, nucleic acids, and their complexes. First, the approaches for computing theoretical SAXS profiles from structures are presented. Second, computational methods for predicting protein structures, dynamics of proteins in solution, and assembly structures are covered. Third, we discuss the use of SAXS profiles in integrative structure modeling approaches that depend simultaneously on several data types.
Asymmetric Dark Matter and CP Violating Scatterings in a UV Complete Model
Baldes, Iason; Millar, Alexander J; Volkas, Raymond R
2015-01-01
We explore possible asymmetric dark matter models using CP violating scatterings to generate an asymmetry. In particular, we introduce a new model, based on DM fields coupling to the SM Higgs and lepton doublets, $\\overline{L}H$, and explore its UV completions. We study the CP violation and asymmetry formation of this model, to demonstrate that it is capable of producing the correct abundance of dark matter and the observed matter-antimatter asymmetry. Crucial to achieving this is the introduction of interactions which violate CP with a $T^{2}$ dependence.
The Dubna-Mainz-Taipei Dynamical Model for $\\pi N$ Scattering and $\\pi$ Electromagnetic Production
Yang, Shin Nan
2016-01-01
Some of the featured results of the Dubna-Mainz-Taipei (DMT) dynamical model for $\\pi N$ scattering and $\\pi^0$ electromagnetic production are summarized. These include results for threshold $\\pi^0$ production, deformation of $\\Delta(1232)$, and the extracted properties of higher resonances below 2 GeV. The excellent agreement of DMT model's predictions with threshold $\\pi^0$ production data, including the recent precision measurements from MAMI establishes results of DMT model as a benchmark for experimentalists and theorists in dealing with threshold pion production.
Energy Technology Data Exchange (ETDEWEB)
Candy, J V; Chambers, D H; Breitfeller, E F; Guidry, B L; Verbeke, J M; Axelrod, M A; Sale, K E; Meyer, A M
2010-03-02
The detection of radioactive contraband is a critical problem is maintaining national security for any country. Photon emissions from threat materials challenge both detection and measurement technologies especially when concealed by various types of shielding complicating the transport physics significantly. This problem becomes especially important when ships are intercepted by U.S. Coast Guard harbor patrols searching for contraband. The development of a sequential model-based processor that captures both the underlying transport physics of gamma-ray emissions including Compton scattering and the measurement of photon energies offers a physics-based approach to attack this challenging problem. The inclusion of a basic radionuclide representation of absorbed/scattered photons at a given energy along with interarrival times is used to extract the physics information available from the noisy measurements portable radiation detection systems used to interdict contraband. It is shown that this physics representation can incorporated scattering physics leading to an 'extended' model-based structure that can be used to develop an effective sequential detection technique. The resulting model-based processor is shown to perform quite well based on data obtained from a controlled experiment.
Pion-Nucleon Scattering in a Large-N Sigma Model
Mattis, M P; MATTIS, Michael P.; SILBAR, Richard R.
1995-01-01
We review the large-N_c approach to meson-baryon scattering, including recent interesting developments. We then study pion-nucleon scattering in a particular variant of the linear sigma-model, in which the couplings of the sigma and pi mesons to the nucleon are echoed by couplings to the entire tower of I=J baryons (including the Delta) as dictated by large-N_c group theory. We sum the complete set of multi-loop meson-exchange \\pi N --> \\pi N and \\pi N --> \\sigma N Feynman diagrams, to leading order in 1/N_c. The key idea, reviewed in detail, is that large-N_c allows the approximation of LOOP graphs by TREE graphs, so long as the loops contain at least one baryon leg; trees, in turn, can be summed by solving classical equations of motion. We exhibit the resulting partial-wave S-matrix and the rich nucleon and Delta resonance spectrum of this simple model, comparing not only to experiment but also to pion-nucleon scattering in the Skyrme model. The moral is that much of the detailed structure of the meson-bary...
Block-sparse Lamb wave structural health monitoring using generic scattering models
Levine, Ross M.; Michaels, Jennifer E.
2014-02-01
A well-known damage detection paradigm is the use of ultrasonic guided waves that are generated and recorded by a spatially-distributed array of piezoelectric transducers. This type of configuration is capable of interrogating a defect from a variety of angles and over a large region of interest by analyzing all pairwise transducer signals. By subtracting prerecorded baseline signals, differential signals are obtained that can be analyzed for the purpose of detecting, locating, and characterizing newly-introduced scatterers. Typical analysis techniques such as delay-and-sum imaging have the ability to detect flaws, but their performance is limited, especially when the potential scatterers may have high directionality or introduce phase shifts. Signal envelopes are frequently used to avoid the problem of unknown phase shifts, which further reduces performance. The sparsity-based technique described here uses a different approach, where each potential damage location has its own generic linear scattering model that allows for unknown variations in amplitude and phase between each transducer pair. The differential signals are then assumed to be a linear combination of a small number of these models, and an image is generated using a block-sparse reconstruction algorithm that splits the signals into location-based components. Results are presented for experimental data. The images exhibit smaller spot size and fewer artifacts than those obtained via delay-and-sum imaging, provided the model is reasonably well-matched to the data.
Directory of Open Access Journals (Sweden)
Qinghua Xie
2017-01-01
Full Text Available Recently, a general polarimetric model-based decomposition framework was proposed by Chen et al., which addresses several well-known limitations in previous decomposition methods and implements a simultaneous full-parameter inversion by using complete polarimetric information. However, it only employs four typical models to characterize the volume scattering component, which limits the parameter inversion performance. To overcome this issue, this paper presents two general polarimetric model-based decomposition methods by incorporating the generalized volume scattering model (GVSM or simplified adaptive volume scattering model, (SAVSM proposed by Antropov et al. and Huang et al., respectively, into the general decomposition framework proposed by Chen et al. By doing so, the final volume coherency matrix structure is selected from a wide range of volume scattering models within a continuous interval according to the data itself without adding unknowns. Moreover, the new approaches rely on one nonlinear optimization stage instead of four as in the previous method proposed by Chen et al. In addition, the parameter inversion procedure adopts the modified algorithm proposed by Xie et al. which leads to higher accuracy and more physically reliable output parameters. A number of Monte Carlo simulations of polarimetric synthetic aperture radar (PolSAR data are carried out and show that the proposed method with GVSM yields an overall improvement in the final accuracy of estimated parameters and outperforms both the version using SAVSM and the original approach. In addition, C-band Radarsat-2 and L-band AIRSAR fully polarimetric images over the San Francisco region are also used for testing purposes. A detailed comparison and analysis of decomposition results over different land-cover types are conducted. According to this study, the use of general decomposition models leads to a more accurate quantitative retrieval of target parameters. However, there
Institute of Scientific and Technical Information of China (English)
DENG Ruru; LIU Qinhuo; KE Ruiping; CHENG Lei; LIU Xiaoping
2004-01-01
It is a valid route for quantitatively remote sensing on water pollution to build a model according to the physical mechanisms of scattering and absorbing of suspended substance, pollutant, and molecules of water. Remote sensing model for water pollution based on single scattering is simple and easy to be used, but the precision is affected by turbidity of water. The characteristics of the energy composition of multiple scattering, are analyzed and it is proposed that, based on the model of single scattering, ifthe flux of the second scattering is considered additionally, the precision of the modelwill be remarkably improved and the calculation is still very simple. The factor of the second scattering is deduced to build a double scattering model, and the practical arithmetic for the calculation of the model is put forward. The result of applying this model in the water area around the Zhujiang(Pearl) River outfall shows that the precision is obviously improved. The result also shows that the seriously polluted water area is distributed in the northeast of Lingding Sea, the Victoria Bay of Hong Kong, and the Shengzhen Bay.
Voronoi diagram-based spheroid model for microwave scattering of complex snow aggregates
Honeyager, Ryan; Liu, Guosheng; Nowell, Holly
2016-02-01
Methods to model snow aggregate scattering properties at microwave frequencies can be divided into structurally explicit and implicit techniques. Explicit techniques, such as the discrete dipole approximation (DDA), determine scattering and backscatter cross-sections assuming full knowledge of a given snow particle's structure. Such calculations are computationally expensive. Implicit techniques, such as using the T-matrix method (TMM) with optically soft spheroids, model equivalent particles with variable mass, bulk density and aspect ratio according to an effective-medium approximation. It is highly desirable that there should be a good agreement between modeled aggregate cross-sections using both methods. A Voronoi bounding-neighbor algorithm is presented in this study to determine the bulk equivalent density of complex three-dimensional snow aggregates. While mass and aspect ratio are easily parameterized quantities, attempts to parameterize the bulk density of snowflakes have usually relied on a bounding ellipsoid, which can be determined from a flake's radius of gyration, root mean square mean or simply from its maximum diameter. We compared the Voronoi algorithm against existing bounding spheroid approaches and mass-effective density relations at ten frequencies from 10.65 to 183.31 GHz, using a set of 1005 aggregates with maximum dimensions from a few hundred microns to several centimeters. When using the Voronoi-determined effective density, the asymmetry parameter, scattering, and backscatter cross-sections determined using the TMM reasonably match those for DDA-computed snow aggregates. From Ku to W-band, soft spheroids can reproduce cross-sections for aggregates up to 9 mm in maximum dimension. Volume-integrated cross-sections always agree to within 25% of DDA. As the DDA is computationally expensive, this offers a fast alternative that efficiently evaluates scattering properties at microwave frequencies.
Calculation of accurate small angle X-ray scattering curves from coarse-grained protein models
Directory of Open Access Journals (Sweden)
Stovgaard Kasper
2010-08-01
Full Text Available Abstract Background Genome sequencing projects have expanded the gap between the amount of known protein sequences and structures. The limitations of current high resolution structure determination methods make it unlikely that this gap will disappear in the near future. Small angle X-ray scattering (SAXS is an established low resolution method for routinely determining the structure of proteins in solution. The purpose of this study is to develop a method for the efficient calculation of accurate SAXS curves from coarse-grained protein models. Such a method can for example be used to construct a likelihood function, which is paramount for structure determination based on statistical inference. Results We present a method for the efficient calculation of accurate SAXS curves based on the Debye formula and a set of scattering form factors for dummy atom representations of amino acids. Such a method avoids the computationally costly iteration over all atoms. We estimated the form factors using generated data from a set of high quality protein structures. No ad hoc scaling or correction factors are applied in the calculation of the curves. Two coarse-grained representations of protein structure were investigated; two scattering bodies per amino acid led to significantly better results than a single scattering body. Conclusion We show that the obtained point estimates allow the calculation of accurate SAXS curves from coarse-grained protein models. The resulting curves are on par with the current state-of-the-art program CRYSOL, which requires full atomic detail. Our method was also comparable to CRYSOL in recognizing native structures among native-like decoys. As a proof-of-concept, we combined the coarse-grained Debye calculation with a previously described probabilistic model of protein structure, TorusDBN. This resulted in a significant improvement in the decoy recognition performance. In conclusion, the presented method shows great promise for
Institute of Scientific and Technical Information of China (English)
Huang Hao; Pan Minghai; Lu Zhijun
2015-01-01
Hardware-in-the-loop (HWIL) simulation technology can verify and evaluate the radar by simulating the radio frequency environment in an anechoic chamber. The HWIL simulation technology of wide-band radar targets can accurately generate wide-band radar target echo which stands for the radar target scattering characteristics and pulse modulation of radar transmitting sig-nal. This paper analyzes the wide-band radar target scattering properties first. Since the responses of target are composed of many separate scattering centers, the target scattering characteristic is restructured by scattering centers model. Based on the scattering centers model of wide-band radar target, the wide-band radar target echo modeling and the simulation method are discussed. The wide-band radar target echo is reconstructed in real-time by convoluting the transmitting signal to the target scattering parameters. Using the digital radio frequency memory (DRFM) system, the HWIL simulation of wide-band radar target echo with high accuracy can be actualized. A typical wide-band radar target simulation is taken to demonstrate the preferable simulation effect of the reconstruction method of wide-band radar target echo. Finally, the radar target time-domain echo and high-resolution range profile (HRRP) are given. The results show that the HWIL simulation gives a high-resolution range distribution of wide-band radar target scattering centers.
A microscopic cluster model study of $^3$He+$p$ scatterings
Arai, K; Suzuki, Y
2008-01-01
We calculate $^3$He+$p$ scattering phase shifts in two different microscopic cluster models, Model T and Model C, in order to show the effects of tensor force as well as $D$-wave components in the cluster wave function. Model T employs a realistic nucleon-nucleon potential and includes the $D$-wave, whereas Model C employs an effective potential in which the tensor-force effect is considered to be renormalized into the central force and includes only the $S$-wave for the cluster intrinsic motion. The $S$- and $P$-wave elastic scattering phase shifts are obtained in the \\{$^3$He+$p$\\}+\\{$d$ + 2$p$\\} coupled-channels calculation. In Model T, the $d$ + 2$p$ channel plays a significant role in producing the $P$-wave resonant phase shifts but hardly affects the $S$-wave non-resonant phase shifts. In Model C, however, the effect of the $d$ + 2$p$ channel is suppressed in both of the $S$- and $P$-wave phase shifts, suggesting that it is renormalized mostly as the $^3$He(1/2$^+$)+$p$ channel in the resonance region.
Shekhar, Prabhanshu; Nanda, Hirsh; Lösche, Mathias; Heinrich, Frank
2011-11-15
Biological membranes are composed of a thermally disordered lipid matrix and therefore require non-crystallographic scattering approaches for structural characterization with x-rays or neutrons. Here we develop a continuous distribution (CD) model to refine neutron or x-ray reflectivity data from complex architectures of organic molecules. The new model is a flexible implementation of the composition-space refinement of interfacial structures to constrain the resulting scattering length density profiles. We show this model increases the precision with which molecular components may be localized within a sample, with a minimal use of free model parameters. We validate the new model by parameterizing all-atom molecular dynamics (MD) simulations of bilayers and by evaluating the neutron reflectivity of a phospholipid bilayer physisorbed to a solid support. The determination of the structural arrangement of a sparsely-tethered bilayer lipid membrane (stBLM) comprised of a multi-component phospholipid bilayer anchored to a gold substrate by a thiolated oligo(ethylene oxide) linker is also demonstrated. From the model we extract the bilayer composition and density of tether points, information which was previously inaccessible for stBLM systems. The new modeling strategy has been implemented into the ga_refl reflectivity data evaluation suite, available through the National Institute of Standards and Technology (NIST) Center for Neutron Research (NCNR).
Energy Technology Data Exchange (ETDEWEB)
Shekhar, Prabhanshu [Department of Physics, Carnegie Mellon University, 5000 Forbes Avenue, Pittsburgh, Pennsylvania 15213-3890 (United States); Nanda, Hirsh; Heinrich, Frank [Department of Physics, Carnegie Mellon University, 5000 Forbes Avenue, Pittsburgh, Pennsylvania 15213-3890 (United States); National Institute of Standards and Technology, Center for Neutron Research, Gaithersburg, Maryland 20899-6102 (United States); Loesche, Mathias [Department of Physics, Carnegie Mellon University, 5000 Forbes Avenue, Pittsburgh, Pennsylvania 15213-3890 (United States); Department of Biomedical Engineering, Carnegie Mellon University, 5000 Forbes Avenue, Pittsburgh, Pennsylvania 15213-3890 (United States); National Institute of Standards and Technology, Center for Neutron Research, Gaithersburg, Maryland 20899-6102 (United States)
2011-11-15
Biological membranes are composed of a thermally disordered lipid matrix and therefore require non-crystallographic scattering approaches for structural characterization with x-rays or neutrons. Here we develop a continuous distribution (CD) model to refine neutron or x-ray reflectivity data from complex architectures of organic molecules. The new model is a flexible implementation of the composition-space refinement of interfacial structures to constrain the resulting scattering length density profiles. We show this model increases the precision with which molecular components may be localized within a sample, with a minimal use of free model parameters. We validate the new model by parameterizing all-atom molecular dynamics (MD) simulations of bilayers and by evaluating the neutron reflectivity of a phospholipid bilayer physisorbed to a solid support. The determination of the structural arrangement of a sparsely-tethered bilayer lipid membrane (stBLM) comprised of a multi-component phospholipid bilayer anchored to a gold substrate by a thiolated oligo(ethylene oxide) linker is also demonstrated. From the model we extract the bilayer composition and density of tether points, information which was previously inaccessible for stBLM systems. The new modeling strategy has been implemented into the ga lowbar refl reflectivity data evaluation suite, available through the National Institute of Standards and Technology (NIST) Center for Neutron Research (NCNR).
Bai, Nan
A label-free and nondestructive optical elastic forward light scattering method has been extended for the analysis of microcolonies for food-borne bacteria detection and identification. To understand the forward light scattering phenomenon, a model based on the scalar diffraction theory has been employed: a bacterial colony is considered as a biological spatial light modulator with amplitude and phase modulation to the incoming light, which continues to propagate to the far-field to form a distinct scattering 'fingerprint'. Numerical implementation via angular spectrum method (ASM) and Fresnel approximation have been carried out through Fast Fourier Transform (FFT) to simulate this optical model. Sampling criteria to achieve unbiased and un-aliased simulation results have been derived and the effects of violating these conditions have been studied. Diffraction patterns predicted by these two methods (ASM and Fresnel) have been compared to show their applicability to different simulation settings. Through the simulation work, the correlation between the colony morphology and its forward scattering pattern has been established to link the number of diffraction rings and the half cone angle with the diameter and the central height of the Gaussian-shaped colonies. In order to experimentally prove the correlation, a colony morphology analyzer has been built and used to characterize the morphology of different bacteria genera and investigate their growth dynamics. The experimental measurements have demonstrated the possibility of differentiating bacteria Salmonella, Listeria, Escherichia in their early growth stage (100˜500 µm) based on their phenotypic characteristics. This conclusion has important implications in microcolony detection, as most bacteria of our interest need much less incubation time (8˜12 hours) to grow into this size range. The original forward light scatterometer has been updated to capture scattering patterns from microcolonies. Experiments have
Equilibrium model prediction for the scatter in the star-forming main sequence
Mitra, Sourav; Davé, Romeel; Simha, Vimal; Finlator, Kristian
2017-01-01
The analytic `equilibrium model' for galaxy evolution using a mass balance equation is able to reproduce mean observed galaxy scaling relations between stellar mass, halo mass, star formation rate (SFR), and metallicity across the majority of cosmic time with a small number of parameters related to feedback. Here, we aim to test this data-constrained model to quantify deviations from the mean relation between stellar mass and SFR, i.e. the star-forming galaxy main sequence (MS). We implement fluctuation in halo accretion rates parametrized from merger-based simulations, and quantify the intrinsic scatter introduced into the MS under the assumption that fluctuations in star formation follow baryonic inflow fluctuations. We predict the 1σ MS scatter to be ˜0.2-0.25 dex over the stellar mass range 108-1011 M⊙ and a redshift range 0.5 ≲ z ≲ 3 for SFRs averaged over 100 Myr. The scatter increases modestly at z ≳ 3, as well as by averaging over shorter time-scales. The contribution from merger-induced star formation is generally small, around 5 per cent today and 10-15 per cent during the peak epoch of cosmic star formation. These results are generally consistent with available observations, suggesting that deviations from the MS primarily reflect stochasticity in the inflow rate owing to halo mergers.
Zhang, Jianing; Bi, Lei; Liu, Jianping; Panetta, R. Lee; Yang, Ping; Kattawar, George W.
2016-07-01
Constructing an appropriate particle morphology model is essential for realistic simulation of optical properties of atmospheric particles. This paper presents a model for generating surface roughness based on a combination of methods from discrete differential geometry combined with a stochastic partial differential equation for surface evolution introduced by Edwards and Wilkinson. Scattering of light by roughened particles is simulated using the Invariant Imbedding T-Matrix (II-TM) method. The effects of surface roughness on the single-scattering properties, namely, the phase matrix, asymmetry factor, and extinction efficiency, are investigated for a single wavelength in the visible range and for a range of size parameters up to x=50. Three different smooth shapes are considered: spherical, spheroidal, and hexagonal, the latter two in just the "compact particle" case of unit aspect ratio. It is shown that roughness has negligible effects on the optical scattering properties for size parameters less than 20. For size parameters ranging from 20 to 50, the phase matrix elements are more sensitive to the surface roughness than are two important integral optical properties, the extinction efficiency and asymmetry factor. As has been seen in studies using other forms of roughening, the phase function is progressively smoothed as roughness increases. The effect on extinction efficiency is to increase it, and on asymmetry factor is to decrease it. Each of these effects is relatively modest in the size range considered, but the trend of results suggests that greater effects will be seen for size parameters larger than ones considered here.
Equilibrium model prediction for the scatter in the star-forming main sequence
Mitra, Sourav; Davé, Romeel; Simha, Vimal; Finlator, Kristian
2016-10-01
The analytic "equilibrium model" for galaxy evolution using a mass balance equation is able to reproduce mean observed galaxy scaling relations between stellar mass, halo mass, star formation rate (SFR) and metallicity across the majority of cosmic time with a small number of parameters related to feedback. Here we aim to test this data-constrained model to quantify deviations from the mean relation between stellar mass and SFR, i.e. the star-forming galaxy main sequence (MS). We implement fluctuation in halo accretion rates parameterised from merger-based simulations, and quantify the intrinsic scatter introduced into the MS under the assumption that fluctuations in star formation follow baryonic inflow fluctuations. We predict the 1-σ MS scatter to be ˜0.2 - 0.25 dex over the stellar mass range 108M⊙ to 1011M⊙ and a redshift range 0.5⪉ z⪉ 3 for SFRs averaged over 100 Myr. The scatter increases modestly at z⪆ 3, as well as by averaging over shorter timescales. The contribution from merger-induced star formation is generally small, around 5% today and 10 - 15% during the peak epoch of cosmic star formation. These results are generally consistent with available observations, suggesting that deviations from the MS primarily reflect stochasticity in the inflow rate owing to halo mergers.
Different Types of Solitary Wave Scattering in the Fermi-Pasta-Ulam Model
Institute of Scientific and Technical Information of China (English)
WEN Zhen-Ying; ZHAO Hong
2005-01-01
@@ We show that the scattering between two solitary waves in the Fermi-Pasta-Ulam model with interaction potential V(x) = αx2/2 + x4/4 can be classified into four types according to the configurations of the solitary waves. For three of the four types, the large solitary wave can lose energy and the small one can gain in average by collision.For the other one type in a special parameter region we encounter an anomalous scattering, i.e. the large solitary wave gains energy and the small one loses energy. Numerical investigations are performed for the anharmonic limit case of α = 0 and the general case of α≠ 0 and comparisons between them are made.
Scattering from Model Nonspherical Particles Theory and Applications to Environmental Physics
Borghese, Ferdinando; Saija, Rosalba
2007-01-01
The scattering of electromagnetic radiation by nonspherical particles has become an increasingly important research topic over the past 20 years. Instead of handling anisotropic particles of arbitrary shape, the authors consider the more amenable problem of aggregates of spherical particles. This is often a very satisfactory approach as the optical response of nonspherical particles depends more on their general symmetry and the quantity of refractive material than on the precise details of their shape. The book addresses a wide spectrum of applications, ranging from scattering properties of water droplets containing pollutants, atmospheric aerosols and ice crystals to the modeling of cosmic dust grains as aggregates. In this extended second edition the authors have encompassed all the new topics arising from their recent studies of cosmic dust grains. Thus many chapters were deeply revised and new chapters were added. The new material spans The description of the state of polarization of electromagnetic wave...
Folding model analysis of the nucleus–nucleus scattering based on Jacobi coordinates
Indian Academy of Sciences (India)
F PAKDEL; A A RAJABI; L NICKHAH
2016-12-01
This paper presents the results of scattering of $^{16}O+^{209}Bi interaction near the Coulomb barrier. The interaction potential between two nuclei is calculated using the double folding model with the effective nucleon–nucleon (NN) interaction. The calculations of the exchange part of the interaction were assumed to be of finite range and the density dependence of the $NN$ interaction is accounted for. Also the results are compared with thezero-range approximation. All these calculations are done using the wave functions of the two colliding nuclei in place of their density distributions. The wave functions are obtained by the $D$-dimensional wave equationusing the hyper spherical calculations on the basis of Jacobi coordinates. The numerical results for the interaction potential and the differential scattering are in good agreement with the previous works.
Heftberger, Peter; Heberle, Frederick A; Pan, Jianjun; Rappolt, Michael; Amenitsch, Heinz; Kucerka, Norbert; Katsaras, John; Pabst, Georg
2013-01-01
We adapted the highly successful scattering density pro?le (SDP) model, which is used to jointly analyze small angle x-ray and neutron scattering data from unilamellar vesicles, for use with data from fully hydrated, liquid crystalline multilamellar vesicles (MLVs). By using a genetic algorithm, this new method is capable of providing high resolution structural information, as well as determining bilayer elastic bending fluctuations from standalone x-ray data. Important structural parameters, such as bilayer thickness and area per lipid were determined for a series of saturated and unsaturated lipids, as well as binary mixtures with cholesterol. Results are in good agreement with previously reported SDP data, which used both neutron and x-ray data. The addition of deuterated and non-deuterated MLV neutron data to the analysis improved lipid backbone information, but did not improve, within experimental uncertainties, the structural information regarding bilayer thickness and area per lipid.
Mature red blood cells: from optical model to inverse light-scattering problem.
Gilev, Konstantin V; Yurkin, Maxim A; Chernyshova, Ekaterina S; Strokotov, Dmitry I; Chernyshev, Andrei V; Maltsev, Valeri P
2016-04-01
We propose a method for characterization of mature red blood cells (RBCs) morphology, based on measurement of light-scattering patterns (LSPs) of individual RBCs with the scanning flow cytometer and on solution of the inverse light-scattering (ILS) problem for each LSP. We considered a RBC shape model, corresponding to the minimal bending energy of the membrane with isotropic elasticity, and constructed an analytical approximation, which allows rapid simulation of the shape, given the diameter and minimal and maximal thicknesses. The ILS problem was solved by the nearest-neighbor interpolation using a preliminary calculated database of 250,000 theoretical LSPs. For each RBC in blood sample we determined three abovementioned shape characteristics and refractive index, which also allows us to calculate volume, surface area, sphericity index, spontaneous curvature, hemoglobin concentration and content.
Scattering amplitude and bosonization duality in general Chern-Simons vector models
Yokoyama, Shuichi
2016-09-01
We present the exact large N calculus of four point functions in general Chern-Simons bosonic and fermionic vector models. Applying the LSZ formula to the four point function we determine the two body scattering amplitudes in these theories taking a special care for a non-analytic term to achieve unitarity in the singlet channel. We show that the S-matrix enjoys the bosonization duality, an unusual crossing relation and a non-relativistic reduction to Aharonov-Bohm scattering. We also argue that the S-matrix develops a pole in a certain range of coupling constants, which disappears in the range where the theory reduces to the Chern-Simons theory interacting with free fermions.
Quesada, José Manuel; Capote, Roberto; Soukhovitski, Efrem S.; Chiba, Satoshi
2016-03-01
An extension for odd-A actinides of a previously derived dispersive coupledchannel optical model potential (OMP) for 238U and 232Th nuclei is presented. It is used to fit simultaneously all the available experimental databases including neutron strength functions for nucleon scattering on 232Th, 233,235,238U and 239Pu nuclei. Quasi-elastic (p,n) scattering data on 232Th and 238U to the isobaric analogue states of the target nucleus are also used to constrain the isovector part of the optical potential. For even-even (odd) actinides almost all low-lying collective levels below 1 MeV (0.5 MeV) of excitation energy are coupled. OMP parameters show a smooth energy dependence and energy independent geometry.
Ellison, Donald C; Bykov, Andrei M
2015-01-01
We include a general form for the scattering mean free path in a nonlinear Monte Carlo model of relativistic shock formation and Fermi acceleration. Particle-in-cell (PIC) simulations, as well as analytic work, suggest that relativistic shocks tend to produce short-scale, self-generated magnetic turbulence that leads to a scattering mean free path (mfp) with a stronger momentum dependence than the mfp ~ p dependence for Bohm diffusion. In unmagnetized shocks, this turbulence is strong enough to dominate the background magnetic field so the shock can be treated as parallel regardless of the initial magnetic field orientation, making application to gamma-ray bursts (GRBs), pulsar winds, Type Ibc supernovae, and extra-galactic radio sources more straightforward and realistic. In addition to changing the scale of the shock precursor, we show that, when nonlinear effects from efficient Fermi acceleration are taken into account, the momentum dependence of the mfp has an important influence on the efficiency of cosm...
Model of K/sup +/p elastic scattering at high energies
Energy Technology Data Exchange (ETDEWEB)
Fazal-e-Aleem
1985-07-01
Very recent measurements of the angular distribution for K/sup +/p elastic scattering which show a structure near -t = 3.8(GeV/c)/sup 2/, together with the total cross section and ratio of the real and imaginary parts of the scattering amplitude for 50< or =p/sub l/< or =280 GeV/c and with -t extending up to 8 (GeV/c)/sup 2/, have been fitted by using a simple Regge-pole model with phenomenological residue functions. The break in the slope near -t = 0.5 (GeV/c)/sup 2/ observed in the differential cross section has also been explained.
New results for antiproton-proton elastic scattering and various theoretical models
Energy Technology Data Exchange (ETDEWEB)
Fazal-e-Aleem; Saleem, M. (Centre for High Energy Physics, Punjab University, Lahore-54590, Pakistan (PK)); Yodh, G.B. (Department of Physics, University of California-Irvine, Irvine, CA 92717 (USA))
1991-07-01
The most recent measurements of the ratio {rho} of the real and imaginary parts of the forward-scattering amplitudes at 0.546 TeV, the total and elastic differential cross sections at 0.546 and 1.8 TeV for proton-antiproton scattering, are compared to the predictions of the generalized Chou-Yang and other theoretical models. For 1.8 TeV, the presence or absence of the break near {minus}{ital t}{approx}0.15 (GeV/{ital c}){sup 2} and of the dip in the vicinity of 0.6 (GeV/{ital c}){sup 2} are also discussed in the light of various predictions. The possibility of a further rise of the ratio {rho} at 1.8 TeV is also probed.
Chromospheric diagnosis with Ca II lines: forward modeling in forward scattering (I)
Carlin, E S
2014-01-01
This paper shows the first synthetic tomography of the quiet solar chromosphere formed by spatial maps of scattering polarization. It has been calculated for the CaII 8498, 8542 and 3934 A lines by solving the NLTE (non-local thermodynamical equilibrium) RT (radiative transfer) problem of the second kind in a 3D atmosphere model obtained from realistic MHD (magneto-hydrodynamical) simulations. Maps of circular polarization were calculated neglecting atomic polarization. Our investigation focuses on the linear polarization signals induced by kinematics, radiation field anisotropy and Hanle effect in forward-scattering geometry. Thus, instead of considering slit profiles at the limb as normally done in the study of the second solar spectrum, we synthetize and analyze spatial maps of polarization at disk center. It allows us to understand the spatial signatures of dynamics and magnetic field in the linear polarization for discriminating them observationally. Our results suggest new ideas for chromospheric diagno...
Energy Technology Data Exchange (ETDEWEB)
Engelhardt, Larry [Francis Marion University; Demmel, Franz [Rutherford Appleton Laboratory; Luban, Marshall [Ames Laboratory; Timco, Grigore A [The University of Manchester; Tuna, Floriana [The University of Manchester; Winpenny, Richard E [The University of Manchester
2014-06-01
We present a refined model of the {Fe9} tridiminished icosahedron magnetic molecule system. This molecule was originally modeled as being composed of two ({Fe3} and {Fe6}) clusters, with the Fe3+ ions within each cluster being coupled via exchange interactions, but with no coupling between the clusters. The present inelastic neutron scattering (INS) measurements were used to probe the low-lying energy spectrum of {Fe9}, and these results demonstrate that the previously published model of two uncoupled clusters is incomplete. To achieve agreement between the experiment and theory, we have augmented the model with relatively small exchange coupling between the clusters. A combination of Lanczos matrix diagonalization and quantum Monte Carlo simulations have been used to achieve good agreement between the experimental data and the improved model of the full {Fe9} system despite the complexity of this model (with Hilbert space dimension >107).
Palm, M.; Benedikt, M.; Dorda, U.
2013-01-01
The field of hadron therapy is growing rapidly with several facilities currently being planned, under construction or in commissioning worldwide. In the “active scanning” irradiation technique, the target is irradiated using a narrow pencil beam that is scanned transversally over the target while the penetration depth is altered with the beam energy. Together, the target dose can thereby be conformed in all three dimensions to the shape of the tumor. For applications where a sharp lateral beam penumbra is required in order to spare critical organs from unwanted dose, beam size blowup due to scattering in on-line beam diagnostic monitors, air gaps and passive elements like the ripple filter must be minimized. This paper presents a model for transverse scattering of therapeutic hadron beams along arbitrary multislab geometries. The conventional scattering formulation, which is only applicable to a drift space, is extended to not only take beam optics into account, but also non-Gaussian transverse beam profiles which are typically obtained from the slow resonant extraction from a synchrotron. This work has been carried out during the design phase of the beam delivery system for MedAustron, an Austrian hadron therapy facility with first patient treatment planned for the end of 2015. Irradiation will be performed using active scanning with proton and carbon ion beams. As a direct application of the scattering model, design choices for the MedAustron proton gantry and treatment nozzles are evaluated with respect to the transverse beam profile at the focal point; in air and at the Bragg peak.
Synthesis of lumped models from N-port scattering parameter data
Rautio, James C.
1994-03-01
A closed form technique is described which allows the synthesis of an N-node lumped network from N-port scattering parameter (S-parameter) data. The synthesis is appropriate for networks where N is very large, for example, high speed digital interconnect networks. The resulting lumped model can be used in SPICE and other simulators. The synthesis is valid for any structure that is small with respect to wavelength. Thus it is also appropriate for synthesizing lumped models of simple discontinuities, such as step junctions and cross junctions. A description of the theory and several examples are provided.
Weber, N; Monnin, P; Elandoy, C; Ding, S
2015-12-01
Given the contribution of scattered radiations to patient dose in CT, apron shielding is often used for radiation protection. In this study the efficiency of apron was assessed with a model-based approach of the contributions of the four scatter sources in CT, i.e. external scattered radiations from the tube and table, internal scatter from the patient and backscatter from the shielding. For this purpose, CTDI phantoms filled with thermoluminescent dosimeters were scanned without apron, and then with an apron at 0, 2.5 and 5 cm from the primary field. Scatter from the tube was measured separately in air. The scatter contributions were separated and mathematically modelled. The protective efficiency of the apron was low, only 1.5% in scatter dose reduction on average. The apron at 0 cm from the beam lowered the dose by 7.5% at the phantom bottom but increased the dose by 2% at the top (backscatter) and did not affect the centre. When the apron was placed at 2.5 or 5 cm, the results were intermediate to the one obtained with the shielding at 0 cm and without shielding. The apron effectiveness is finally limited to the small fraction of external scattered radiation.
Effects of Scattering on the Temperature Stratification in 3D Model Atmospheres of Late-Type Stars
Collet, R.; Hayek, W.; Asplund, M.
2011-12-01
Three-dimensional (3D) radiative hydrodynamic model atmospheres of metal-poor late-type stars predict cooler upper photospheric stratifications than their one-dimensional (1D) counterparts. This property of 3D model atmospheres affects the determination of elemental abundances from temperature-sensitive spectral features, with important consequences for galactic chemical evolution studies. In this contribution, we investigate the impact of different approximations of scattering in the solution of the radiative transfer equation on the temperature stratification of 3D model atmospheres of metal-poor red giants. We use the BIFROST code to construct 3D model atmospheres of metal-poor red giants using three different approximations of scattering. First, we self-consistently solve the radiative transfer equation for the general case of a source function with a coherent scattering term; second, we solve the radiative transfer equation assuming a Planckian source function and neglecting altogether the contribution of continuum scattering to extinction in the optically thin layers; third, we assume a Planckian source function and treat continuum scattering as pure absorption everywhere in the simulation's domain. We find that the second approach produces very similar temperature structures with cool upper photospheric layers as when treating scattering correctly, and at a much lower computational cost. In contrast, treating scattering as pure absorption leads to significantly hotter and shallower temperature stratifications.
The Investigation of EM Scattering from the Time-Varying Overturning Wave Crest Model by the IEM
Directory of Open Access Journals (Sweden)
Xiao Meng
2016-01-01
Full Text Available Investigation of the electromagnetic (EM scattering of time-varying overturning wave crests is a worthwhile endeavor. Overturning wave crest is one of the reasons of sea spike generation, which increases the probability of false radar alarms and reduces the performance of multitarget detection in the environment. A three-dimensional (3D time-varying overturning wave crest model is presented in this paper; this 3D model is an improvement of the traditional two-dimensional (2D time-varying overturning wave crest model. The integral equation method (IEM was employed to investigate backward scattering radar cross sections (RCS at various incident angles of the 3D overturning wave crest model. The super phenomenon, where the intensity of horizontal polarization scattering is greater than that of vertical polarization scattering, is an important feature of sea spikes. Simulation results demonstrate that super phenomena may occur in some time samples as variations in the overturning wave crest.
Cwik, Tom; Zuffada, Cinzia; Jamnejad, Vahraz
1996-01-01
Finite element modeling has proven useful for accurtely simulating scattered or radiated fields from complex three-dimensional objects whose geometry varies on the scale of a fraction of a wavelength.
Spectral and scattering theory for translation invariant models in quantum field theory
DEFF Research Database (Denmark)
Rasmussen, Morten Grud
This thesis is concerned with a large class of massive translation invariant models in quantum field theory, including the Nelson model and the Fröhlich polaron. The models in the class describe a matter particle, e.g. a nucleon or an electron, linearly coupled to a second quantised massive scalar...... of the essential energy-momentum spectrum and either the two-body threshold, if there are no exited isolated mass shells, or the one-body threshold pertaining to the first exited isolated mass shell, if it exists. For the model restricted to the vacuum and one-particle sectors, the absence of singular continuous...... spectrum is proven to hold globally and scattering theory of the model is studied using time-dependent methods, of which the main result is asymptotic completeness....
Yeh, Jen-Hao; Antonsen, Thomas M; Ott, Edward; Anlage, Steven M
2012-01-01
Fading is the time-dependent variation in transmitted signal strength through a complex medium due to interference or temporally evolving multipath scattering. In this paper we use random matrix theory (RMT) to establish a first-principles model for fading, including both universal and nonuniversal effects. This model provides a more general understanding of the most common statistical models (Rayleigh fading and Rice fading) and provides a detailed physical basis for their parameters. We also report experimental tests on two ray-chaotic microwave cavities. The results show that our RMT model agrees with the Rayleigh and Rice models in the high-loss regime, but there are strong deviations in low-loss systems where the RMT approach describes the data well.
Measurements and modeling of the volume scattering function in the coastal northern Adriatic Sea
Berthon, Jean-François; Shybanov, Eugeny; Lee, Michael E.-G.; Zibordi, Giuseppe
2007-08-01
We performed measurements of the volume scattering function (VSF) between 0.5° and 179° with an angular resolution of 0.3° in the northern Adriatic Sea onboard an oceanographic platform during three different seasons, using the multispectral volume scattering meter (MVSM) instrument. We observed important differences with respect to Petzold's commonly used functions, whereas the Fournier-Forand's analytical formulation provided a rather good description of the measured VSF. The comparison of the derived scattering, bp(λ) and backscattering, bbp(λ) coefficients for particles with the measurements performed with the classical AC-9 and Hydroscat-6 showed agreement to within 20%. The use of an empirical relationship for the derivation of bb(λ) from β(ψ,λ) at ψ=140° was validated for this coastal site although ψ=118° was confirmed to be the most appropriate angle. The low value of the factor used to convert β(ψ,λ) into bb(λ) within the Hydroscat-6 processing partially contributed to the underestimation of bb(λ) with respect to the MVSM. Finally, use of the Kopelevich model together with a measurement of bp(λ) at λ=555 nm allowed us to reconstruct the VSF with average rms percent differences between 8 and 15%.
Fluorescent and scattering contrast agents in a mouse model of colorectal cancer
Winkler, Amy M.; Rice, Photini F. S.; Troutman, Timothy S.; Backer, Marina V.; Backer, Joseph M.; Drezek, Rebekah A.; Romanowski, Marek; Barton, Jennifer K.
2008-02-01
In previous work we have demonstrated the utility of laser-induced fluorescence (LIF) and optical coherence tomography (OCT) to identify adenoma in mouse models of colorectal cancer with high sensitivity and specificity. However, improved sensitivity to early disease, as well as the ability to distinguish confounders (e.g. fecal contamination, natural variations in mucosal thickness), is desired. In this study, we investigated the signal enhancement of fluorescent and scattering contrast agents in the colons of AOM-treated mice. The fluorescent tracer scVEGF/Cy, targeted to receptors for vascular endothelial growth factor, was visualized on a dual modality OCT/LIF endoscopic system with 1300-nm center wavelength OCT source and 635-nm LIF excitation. Scattering agents were tested with an 890-nm center wavelength endoscopic OCT system. Agents included nanoshells, 120-nm in diameter, and nanorods, 20-nm in diameter by 80-nm in length. Following imaging, colons were excised. Tissue treated with fluorophore was imaged on an epifluorescence microscope. Histological sections were obtained and stained with H&E and silver enhancer to verify disease and identify regions of gold uptake, respectively. Non-specific signal enhancement was observed with the scattering contrast agents. Specificity for adenoma was seen with the scVEGF/Cy dye.
A single HII region model of the strong interstellar scattering towards Sgr A*
Sicheneder, Egid; Dexter, Jason
2017-01-01
Until recently, the strong interstellar scattering observed towards the Galactic center (GC) black hole, Sgr A*, was thought to come from dense gas within the GC region. The pulse broadening towards the transient magnetar SGR J1745-2900 near Sgr A* has shown that the source of the scattering is instead located much closer to Earth, possibly in a nearby spiral arm. We show that a single HII region along the line of sight, 1.5 - 4.8 kpc away from Earth with density ne of a few ˜eq 100 cm^{-3} and radius R ≃ 1.8 - 3.2 pc can explain the observed angular broadening of Sgr A*. Clouds closer to the GC overproduce the observed DM, providing an independent location constraint that agrees with that from the magnetar pulse broadening. Our model predicts that sources within ≲ 10 pc should show the same scattering origin as the magnetar and Sgr A*, while the nearest known pulsars with separations >20 pc should not. The radio spectrum of Sgr A* should show a cutoff from free-free absorption at 0.2 ≲ ν ≲ 1 GHz. For a magnetic field strength B ˜eq 15 - 70 {μ}G, the HII region could produce the rotation measure of the magnetar, the largest of any known pulsar, without requiring the gas near Sgr A* to be strongly magnetised.
A single H II region model of the strong interstellar scattering towards Sgr A*
Sicheneder, Egid; Dexter, Jason
2017-05-01
Until recently, the strong interstellar scattering observed towards the Galactic centre (GC) black hole, Sgr A*, was thought to come from dense gas within the GC region. The pulse broadening towards the transient magnetar SGR J1745-2900 near Sgr A* has shown that the source of the scattering is instead located much closer to Earth, possibly in a nearby spiral arm. We show that a single H II region along the line of sight, 1.5-4.8 kpc away from Earth with density ne of a few ≃ 100 cm^{-3} and radius R ≃ 1.8-3.2 pc can explain the observed angular broadening of Sgr A*. Clouds closer to the GC overproduce the observed disperson measure, providing an independent location constraint that agrees with that from the magnetar pulse broadening. Our model predicts that sources within ≲10 pc should show the same scattering origin as the magnetar and Sgr A*, while the nearest known pulsars with separations >20 pc should not. The radio spectrum of Sgr A* should show a cut-off from free-free absorption at 0.2 ≲ ν ≲ 1 GHz. For a magnetic field strength B ≃ 15-70 μG, the H II region could produce the rotation measure of the magnetar, the largest of any known pulsar, without requiring the gas near Sgr A* to be strongly magnetized.
Finite element modeling of guided wave scattering at delaminations in composite panels
Murat, B. I. S.; Fromme, P.
2016-04-01
Carbon fiber laminate composites, consisting of layers of polymer matrix reinforced with high strength carbon fibers, are increasingly employed for aerospace structures. They offer advantages for aerospace applications, e.g., good strength to weight ratio. However, impact during the operation and servicing of the aircraft can lead to barely visible and difficult to detect damage. Depending on the severity of the impact, delaminations can occur, reducing the load carrying capacity of the structure. Efficient structural health monitoring of composite panels can be achieved using guided ultrasonic waves propagating along the structure. The guided ultrasonic wave (A0 Lamb wave mode) scattering at delaminations was modelled using full three-dimensional Finite Element (FE) simulations. The influence of the delamination size was systematically investigated from a parameter study. The angular dependency of the scattered guided wave amplitude was calculated using a baseline subtraction method. A significant influence of the delamination width on the guided wave scattering was found. The sensitivity of guided waves for the detection of barely visible impact damage in composite panels has been predicted.
Chromospheric Diagnosis with Ca II Lines: Forward Modeling in Forward Scattering. I
Carlin, E. S.; Asensio Ramos, A.
2015-03-01
This paper presents a synthetic tomography of the quiet solar chromosphere formed by spatial maps of scattering polarization. It has been calculated for the Ca II 8498, 8542, and 3934 Å lines by solving the non-LTE radiative transfer problem of the second kind in a three-dimensional atmosphere model obtained from realistic magneto-hydrodynamical simulations. Our investigation focuses on the linear polarization signals induced by kinematics, radiation field anisotropy, and the Hanle effect in forward-scattering geometry. Thus, instead of considering slit profiles at the limb as normally done in the study of the second solar spectrum, we synthesize and analyze spatial maps of polarization at the disk center. This allows us to understand the spatial signatures of dynamics and magnetic field in the linear polarization in order to discriminate them observationally. Our results suggest some ideas for chromospheric diagnosis that will be developed throughout a series of papers. In particular, Hanle polarity inversion lines and dynamic Hanle diagrams are two concepts introduced in the present work. We find that chromospheric dynamics and magnetic field topology create spatial polarization fingerprints that trace the dynamic situation of the plasma and the magnetic field. This allows us to reconstruct the magnetic field intensity in the middle chromosphere using Stokes V along grooves of null linear polarization. We finally address the problems of diagnosing Hanle saturation and kinematic amplification of scattering signals using Hanle diagrams.
A Spectral Geometrical Model for Compton Scatter Tomography Based on the SSS Approximation
DEFF Research Database (Denmark)
Kazantsev, Ivan G.; Olsen, Ulrik Lund; Poulsen, Henning Friis
2016-01-01
annihilation event and undergoing a single scattering at a certain angle. The equations for single scatter calculation are derived using the Single Scatter Simulation approximation. We show that the three-dimensional slice-by-slice filtered backprojection algorithm is applicable for scatter data inversion...
Directory of Open Access Journals (Sweden)
A. S. M. Zahid Kausar
2014-01-01
Full Text Available Although ray tracing based propagation prediction models are popular for indoor radio wave propagation characterization, most of them do not provide an integrated approach for achieving the goal of optimum coverage, which is a key part in designing wireless network. In this paper, an accelerated technique of three-dimensional ray tracing is presented, where rough surface scattering is included for making a more accurate ray tracing technique. Here, the rough surface scattering is represented by microfacets, for which it becomes possible to compute the scattering field in all possible directions. New optimization techniques, like dual quadrant skipping (DQS and closest object finder (COF, are implemented for fast characterization of wireless communications and making the ray tracing technique more efficient. In conjunction with the ray tracing technique, probability based coverage optimization algorithm is accumulated with the ray tracing technique to make a compact solution for indoor propagation prediction. The proposed technique decreases the ray tracing time by omitting the unnecessary objects for ray tracing using the DQS technique and by decreasing the ray-object intersection time using the COF technique. On the other hand, the coverage optimization algorithm is based on probability theory, which finds out the minimum number of transmitters and their corresponding positions in order to achieve optimal indoor wireless coverage. Both of the space and time complexities of the proposed algorithm surpass the existing algorithms. For the verification of the proposed ray tracing technique and coverage algorithm, detailed simulation results for different scattering factors, different antenna types, and different operating frequencies are presented. Furthermore, the proposed technique is verified by the experimental results.
Resonant scattering as a sensitive diagnostic of current collisional plasma models
Ogorzalek, Anna; Zhuravleva, Irina; Allen, Steven W.; Pinto, Ciro; Werner, Norbert; Mantz, Adam; Canning, Rebecca; Fabian, Andrew C.; Kaastra, Jelle S.; de Plaa, Jelle
2017-08-01
Resonant scattering is a subtle process that suppresses fluxes of some of the brightest optically thick X-ray emission lines produced by collisional plasmas in galaxy clusters and massive early-type galaxies. The amplitude of the effect depends on the turbulent structure of the hot gas, making it a sensitive velocity probe. It is therefore crucial to properly model this effect in order to correctly interpret high resolution X-ray spectra. Our measurements of resonant scattering with XMM-Newton Reflection Grating Spectrometer in giant elliptical galaxies and with Hitomi in the center of Perseus Cluster show that the potentially rich inference from this effect is limited by the uncertainties in the atomic data underlying plasma codes such as APEC and SPEX. Typically, the effect is of the order of 10-20%, while the discrepancy between the two codes is of similar order or even higher. Precise knowledge of the emissivity and oscillator strengths of lines emitted by Fe XVII and Fe XXV, as well as their respective uncertainties propagated through plasma codes are key to understanding gas dynamics and microphysics in giant galaxies and cluster ICM, respectively. This is especially crucial for massive ellipticals, where sub-eV resolution would be needed to measure line broadening precisely, making resonant scattering an important velocity diagnostic in these systems for the foreseeable future. In this poster, I will summarize current status of resonant scattering measurements and show how they depend on the assumed atomic data. I will also discuss which improvements are essential to maximize scientific inference from future high resolution X-ray spectra.
submitter A model for the accurate computation of the lateral scattering of protons in water
Bellinzona, EV; Embriaco, A; Ferrari, A; Fontana, A; Mairani, A; Parodi, K; Rotondi, A; Sala, P; Tessonnier, T
2016-01-01
A pencil beam model for the calculation of the lateral scattering in water of protons for any therapeutic energy and depth is presented. It is based on the full Molière theory, taking into account the energy loss and the effects of mixtures and compounds. Concerning the electromagnetic part, the model has no free parameters and is in very good agreement with the FLUKA Monte Carlo (MC) code. The effects of the nuclear interactions are parametrized with a two-parameter tail function, adjusted on MC data calculated with FLUKA. The model, after the convolution with the beam and the detector response, is in agreement with recent proton data in water from HIT. The model gives results with the same accuracy of the MC codes based on Molière theory, with a much shorter computing time.
More on Heisenberg's model for high energy nucleon-nucleon scattering
Nastase, Horatiu
2015-01-01
We revisit Heisenberg's model for nucleon-nucleon scattering which admits a saturation of the Froissart bound. We examine its uniqueness, and find that up to certain natural generalizations, it is the only action that saturates the bound. We find that we can extract also sub-leading behaviour for $\\sigma_{\\rm tot}(s)$ from it, though that requires a knowledge of the wavefunction solution that is hard to obtain, and a black-disk model allows the calculation of $\\sigma_{elastic}(s)$ as well. The wavefunction solution is analyzed perturbatively, and its source is interpreted. Generalizations to several mesons, addition of vector mesons, and curved space regimes are also found. We discuss the relations between Heisenberg's model and holographic models that are dual to QCD-like theories.
Modeling and measurement of angle-beam wave propagation in a scatterer-free plate
Dawson, Alexander J.; Michaels, Jennifer E.; Michaels, Thomas E.
2017-02-01
Wavefield imaging has been shown to be a powerful tool for improving the understanding and characterization of wave propagation and scattering in plates. The complete measurement of surface displacement over a 2-D grid provided by wavefield imaging has the potential to serve as a useful means of validating ultrasonic models. Here, a preliminary study of ultrasonic angle-beam wave propagation in a scatterer-free plate using a combination of wavefield measurements and 2-D finite element models is described. Both wavefield imaging and finite element analysis are used to study the propagation of waves at a refracted angle of 56.8° propagating in a 6.35 mm thick aluminum plate. Wavefield imaging is performed using a laser vibrometer mounted on an XYZ scanning stage, which is programmed to move point-to-point on a rectilinear grid to acquire waveform data. The commercial finite element software package, PZFlex, which is specifically designed to handle large, complex ultrasonic problems, is used to create a 2-D cross-sectional model of the transducer and plate. For model validation, vertical surface displacements from both the wavefield measurements and the PZFlex finite element model are compared and found to be in excellent agreement. The validated PZFlex model is then used to explain the mechanism of Rayleigh wave generation by the angle-beam wedge. Since the wavefield measurements are restricted to the specimen surface, the cross-sectional PZFlex model is able to provide insights the wavefield data cannot. This study illustrates how information obtained from ultrasonic experiments and modeling results can be combined to improve understanding of angle-beam wave generation and propagation.
Recent advances in semi-analytical scattering models for NDT simulation
Darmon, M.; Chatillon, S.; Mahaut, S.; Calmon, P.; Fradkin, L. J.; Zernov, V.
2011-01-01
For several years, CEA-LIST and partners have been developing ultrasonic simulation tools with the aim of modelling non-destructive evaluation. The existing ultrasonic modules allow us to simulate fully real ultrasonic inspection scenarios in a range of applications which requires the computation of the propagated beam, as well as its interaction with flaws. To fulfil requirements of an intensive use (for parametric studies), the choice has been made to adopt mainly analytical approximate or exact methods to model the scattering of ultrasound by flaws. The applied analytical theories (Kirchhoff and Born approximations, GTD, SOV...) were already described in previous GDR communication. Over the years, this "semi-analytical" approach has been enriched by adaptations and improvements of the existing models or by new models, in order to extend the applicability of the simulation tools. This paper is devoted to the following recent advances performed in the framework of this approach: The SOV method based on the exact analytical model for the scattering from a cylindrical cavity has been extended in 3D to account for field variations along the cylinder. This new 3D model leads to an improvement in simulation of small side-drilled holes. Concerning the geometrical theories of diffraction (GTD), subroutines for calculation of the 2D wedge diffraction coefficients (for bulk or Rayleigh incident waves) have been developed by the Waves and Fields Group and uniform corrections (UAT and UTD) are under investigation. Modelling of the contribution of the head wave and creeping wave to the echoes arising from a wedge. Numerous experimental validations of the developed models are provided. New possibilities offered by these new developments are emphasized.
Radioactive Threat Detection with Scattering Physics: A Model-Based Application
Energy Technology Data Exchange (ETDEWEB)
Candy, J V; Chambers, D H; Breitfeller, E F; Guidry, B L; Verbeke, J M; Axelrod, M A; Sale, K E; Meyer, A M
2010-01-21
The detection of radioactive contraband is a critical problem in maintaining national security for any country. Emissions from threat materials challenge both detection and measurement technologies especially when concealed by various types of shielding complicating the transport physics significantly. The development of a model-based sequential Bayesian processor that captures both the underlying transport physics including scattering offers a physics-based approach to attack this challenging problem. It is shown that this processor can be used to develop an effective detection technique.
Modeling inelastic phonon scattering in atomic- and molecular-wire junctions
DEFF Research Database (Denmark)
Paulsson, Magnus; Frederiksen, Thomas; Brandbyge, Mads
2005-01-01
Computationally inexpensive approximations describing electron-phonon scattering in molecular-scale conductors are derived from the nonequilibrium Green's function method. The accuracy is demonstrated with a first-principles calculation on an atomic gold wire. Quantitative agreement between...... the full nonequilibrium Green's function calculation and the newly derived expressions is obtained while simplifying the computational burden by several orders of magnitude. In addition, analytical models provide intuitive understanding of the conductance including nonequilibrium heating and provide...... a convenient way of parameterizing the physics. This is exemplified by fitting the expressions to the experimentally observed conductances through both an atomic gold wire and a hydrogen molecule....
Bystritskiy, Yu M; Pervushin, V N; Volkov, M K
2009-01-01
The charge pion polarizability is calculated in the Nambu-Jona-Lasinio model, where the quark loops (in the mean field approximation) and the meson loops (in the $1/N_c$ approximation) are taken into account. We show that quark loop contribution dominates, because the meson loops strongly conceal each other. The sigma-pole contribution $(m^2_\\sigma-t)^{-1}$ plays the main role and contains strong t-dependence of the effective pion polarizability at the region $|t|\\geq 4M_\\pi^2$. Possibilities of experimental test of this sigma-pole effect in the reaction of Coulomb Nuclear Scattering are estimated for the COMPASS experiment.
Nuclear Slope Parameter Of pp and (-p)p Elastic Scattering in QCD Inspired Model
Institute of Scientific and Technical Information of China (English)
MA Shan-Jun; LU Juan; LU Hai-Liang; MA Wei-Xing; FAN Hong-Yi; HE Xiao-Rong
2008-01-01
Based on the quaxk-gluon structure of nucleon and the possible existence of Odderon in strong interaction process due to gluon self-interaction, the elastic scatterings of pp and pp at high energies axe studied. The contributions from individual terms of quark-quark, gluon-gluon interactions, quaxk-gluon interference, and the Odderon terms to the nuclear slope parameter B(s) are analyzed. Our results show that the QCD inspired model gives a good fit to the LHC experimental data of the nucleax slope parameter.
Design and synthesis of model transparent aqueous colloids with optimal scattering properties.
Perro, Adeline; Meng, Guangnan; Fung, Jerome; Manoharan, Vinothan N
2009-10-06
We demonstrate the synthesis and self-assembly of colloidal particles with independently controlled diameter and scattering cross section. We show that it is possible to prepare bulk colloidal suspensions that are nearly transparent in water, while the particles themselves can be individually resolved using optical microscopy. These particles may be ideal model colloids for real-space studies of self-assembly in aqueous media. Moreover, they illustrate the degree to which the optical properties of colloids can be engineered through straightforward chemistry.
Nonlinear kinetic modeling and simulations of Raman scattering in a two-dimensional geometry
Directory of Open Access Journals (Sweden)
Bénisti Didier
2013-11-01
Full Text Available In this paper, we present our nonlinear kinetic modeling of stimulated Raman scattering (SRS by the means of envelope equations, whose coefficients have been derived using a mixture of perturbative and adiabatic calculations. First examples of the numerical resolution of these envelope equations in a two-dimensional homogeneous plasma are given, and the results are compared against those of particle-in-cell (PIC simulations. These preliminary comparisons are encouraging since our envelope code provides threshold intensities consistent with those of PIC simulations while requiring computational resources reduced by 4 to 5 orders of magnitude compared to full-kinetic codes.
πN Elastic Scattering and Resonances in Quark Potential Model
Institute of Scientific and Technical Information of China (English)
CHEN Ju-Mei; WANG Hai-Jun; LI Cheng-Zu; SU Jun-Chen; LIANG Lin-Mei; CHEN Ping-Xing; DAI Hong-Yi
2008-01-01
The quark potential model is used to investigate the low-energy elastic scattering of π N system. The model potential consists of the t-channel and s-channel one-gluon exchange potentials and the harmonic oscillator confining potential. By means of the resonating group method, a nonlocal effective potential for the πN system is derived from the interquark potentials and used to calculate the π N elastic scattering phase shifts. By considering the effect of QCD renormalization, the suppression of the spin-orbital coupling and the contribution of the color octet of the clusters (qq) and (qqq), the numerical results are in fairly good agreement with the experimental data. The same model and method are employed to investigate the possible πN resonances. For this purpose, the resonating group equation is transformed into a standard Schrodinger equation in which the nonlocal effective πN interaction potential is included. Solving the Schrodinger equation by the variational method, we are able to reproduce the masses of some currently concerned πN resonances.
Yashkir, Yuri M.; Yashkir, Yuriy Y.
2004-09-01
We present a computer numerical model (virtual sub-nanosecond laser) utilizing intracavity stimulated Raman scattering. The goal of this work is to shorten laser output pulses (for which the highly nonlinear frequency conversion process stimulated Raman scattering is used) and to obtain high efficiency (which is enhanced by placing a Raman-active crystal inside the cavity where the fundamental laser frequency intensity is maximal). The following laser components were modeled: a diodepumped solidstate laser active medium (a crystal of the Nd3+:YLF type), a closed cavity for a wave on its fundamental frequency with a Q-switching element and an internal subcavity with a Ramanactive crystal with controlled output coupler transmission at the Raman frequency. The model components are: a numerical integrator of a set of three rate equations (for an inverse population of the laser medium and for the number of fundamental and Stokes frequency photons), random number sources for radiation seeding, and an interactive data input interface and graphic output. A wide range of parameters was investigated and output pulses as short as 0.8 ns were found. The optimal conditions for the maximal peak power of Stokes pulses were determined and the conditions for generating pulse trains for burst laser machining were identified.
A model for pion-pion scattering in large-N QCD arXiv
Veneziano, Gabriele; Onofri, Enrico
Following up on recent work by Caron-Huot et al. we consider a generalization of the old Lovelace-Shapiro model as a toy model for Pi-Pi scattering satisfying (most of) the properties expected to hold in ('t Hooft's) large-N limit of massless QCD. In particular, the model has asymptotically linear and parallel Regge trajectories at positive t, a positive leading Regge intercept $\\alpha_0 < 1$, and an effective bending of the trajectories in the negative-t region producing a fixed branch point at J=0 for $t < t_0 < 0$. Fixed (physical) angle scattering can be tuned to match the power-like (including logarithmic corrections) behavior predicted by perturbative QCD: $A(s,t) ~ s^{-\\beta} \\log(s)^{-\\gamma} F(\\theta)$. Tree-level unitarity (i.e. positivity of residues for all values of s and J) imposes strong constraints on the allowed region in the alpha_0-beta-gamma parameter space, which nicely includes a physically interesting region around $\\alpha_0 = 0.5$, $\\beta = 2$ and $\\gamma = 3$. The full consis...
Controlling the s-wave scattering length with non-resonant light: Predictions of an asymptotic model
Crubellier, Anne; Koch, Christiane P; Luc-Koenig, Eliane
2016-01-01
A pair of atoms interacts with non-resonant light via its anisotropic polarizability. This effect can be used to tune the scattering properties of the atoms. Although the light-atom interaction varies with interatomic separation as $1/R^{3}$, the effective s-wave potential decreases more rapidly, as $1/R^{4}$ such that the field-dressed scattering length can be determined without any formal difficulty. The scattering dynamics are essentially governed by the long-range part of the interatomic interaction and can thus be accurately described by an asymptotic model [Crubellier et al., New J. Phys. 17, 045020 (2015)]. Here we use the asymptotic model to determine the field-dressed scattering length from the s-wave radial component of a particular threshold wave function. Applying our theory to the scattering of two strontium isotopes, we calculate the variation of the scattering length with the intensity of the non-resonant light. Moreover, we predict the intensities at which the scattering length becomes infinit...
Abdellah, Marwan
2017-02-15
Background We present a visualization pipeline capable of accurate rendering of highly scattering fluorescent neocortical neuronal models. The pipeline is mainly developed to serve the computational neurobiology community. It allows the scientists to visualize the results of their virtual experiments that are performed in computer simulations, or in silico. The impact of the presented pipeline opens novel avenues for assisting the neuroscientists to build biologically accurate models of the brain. These models result from computer simulations of physical experiments that use fluorescence imaging to understand the structural and functional aspects of the brain. Due to the limited capabilities of the current visualization workflows to handle fluorescent volumetric datasets, we propose a physically-based optical model that can accurately simulate light interaction with fluorescent-tagged scattering media based on the basic principles of geometric optics and Monte Carlo path tracing. We also develop an automated and efficient framework for generating dense fluorescent tissue blocks from a neocortical column model that is composed of approximately 31000 neurons. Results Our pipeline is used to visualize a virtual fluorescent tissue block of 50 μm3 that is reconstructed from the somatosensory cortex of juvenile rat. The fluorescence optical model is qualitatively analyzed and validated against experimental emission spectra of different fluorescent dyes from the Alexa Fluor family. Conclusion We discussed a scientific visualization pipeline for creating images of synthetic neocortical neuronal models that are tagged virtually with fluorescent labels on a physically-plausible basis. The pipeline is applied to analyze and validate simulation data generated from neuroscientific in silico experiments.
Simplified models for new physics in vector boson scattering. Input for Snowmass 2013
Energy Technology Data Exchange (ETDEWEB)
Reuter, Juergen [Deutsches Elektronen-Synchrotron (DESY), Hamburg (Germany); Kilian, Wolfgang; Sekulla, Marco [Siegen Univ. (Germany). Theoretische Physik I
2013-07-15
In this contribution to the Snowmass process 2013 we give a brief review of how new physics could enter in the electroweak (EW) sector of the Standard Model (SM). This new physics, if it is directly accessible at low energies, can be parameterized by explicit resonances having certain quantum numbers. The extreme case is the decoupling limit where those resonances are very heavy and leave only traces in the form of deviations in the SM couplings. Translations are given into higher-dimensional operators leading to such deviations. As long as such resonances are introduced without a UV-complete theory behind it, these models suffer from unitarity violation of perturbative scattering amplitudes. We show explicitly how theoretically sane descriptions could be achieved by using a unitarization prescription that allows a correct description of such a resonance without specifying a UV-complete model.
Weakly nonlinear models for internal waves: inverse scattering transform and solitary wave contents
Chen, Shengqian
2016-01-01
The time evolution emanating from ``internal dam-break'' initial conditions is studied for a class of models of stratified Euler fluids in configurations close to two-homogeneous layers separated by a thin diffused interface. Direct numerical simulations and experiments in wave tanks show that such initial conditions eventually give rise to coherent structures that are close to solitary-wave solutions moving ahead of a region of dispersive wave motion and turbulent mixing close to the location of the initial dam step. A priori theoretical predictions of the main features of these solitary waves, such as their amplitudes and speeds, appear to be unavailable, even for simplified models of wave evolution in stratified fluids. With the aim of providing estimates of the existence, amplitude and speed of such solitary waves, an approach based on Inverse Scattering Transform (IST) for completely integrable models is developed here and tested against direct numerical simulations of Euler fluids and some of their mode...
Qiao, G J; Zhang, B; Han, J L
2001-01-01
The shapes of pulse profiles, especially their variations with respect to observing frequencies, are very important to understand emission mechanisms of pulsars, while no previous attempt has been made in interpreting the complicated phenomenology. In this paper, we present theoretical simulations for the integrated pulse profiles and their frequency evolution within the framework of the inverse Compton scattering (ICS) model proposed by Qiao (1988) and Qiao & Lin (1998). Using the phase positions of the pulse components predicted by the ``beam-frequency figure'' of the ICS model, we present Gaussian fits to the multi-frequency pulse profiles for some pulsars. It is shown that the model can reproduce various types of the frequency evolution behaviors of pulse profiles observed.
Lattice oscillator model, scattering theory and a many-body problem
Energy Technology Data Exchange (ETDEWEB)
Valiente, Manuel, E-mail: mvalien@phys.au.dk [Department of Physics and Astronomy, Lundbeck Foundation Theoretical Center for Quantum System Research, Aarhus University, DK-8000 Aarhus C (Denmark)
2011-11-18
We propose a model for the quantum harmonic oscillator on a discrete lattice which can be written in a supersymmetric form, in contrast with the more direct discretization of the harmonic oscillator. Its ground state is easily found to be annihilated by the annihilation operator defined here, and its excitation spectrum is obtained numerically. We then define an operator whose continuum limit corresponds to an angular momentum in terms of the creation-annihilation operators of our model. Coherent states with the correct continuum limit are also constructed. The versatility of the model is then used to calculate, in a simple way, the generalized position-dependent scattering length for a particle colliding with a single static impurity in a periodic potential and the exact ground state of an interacting many-body problem in a one-dimensional ring. (paper)
A model for two-proton emission induced by electron scattering
Energy Technology Data Exchange (ETDEWEB)
Anguiano, Marta [Dipartimento di Fisica, Universita di Lecce and Istituto Nazionale di Fisica Nucleare, sez. di Lecce, I-73100 Lecce (Italy); Giampaolo, Co' [Dipartimento di Fisica, Universita di Lecce and Istituto Nazionale di Fisica Nucleare, sez. di Lecce, I-73100 Lecce (Italy); Lallena, Antonio M [Departamento de Fisica Moderna, Universidad de Granada, E-18071 Granada (Spain)
2003-06-01
A model to study two-proton emission processes induced by electron scattering is developed. The process is induced by one-body electromagnetic operators acting together with short-range correlations, and by two-body {delta} currents. The model includes all the diagrams containing a single correlation function. A test of the sensitivity of the model to the various theoretical inputs is done. An investigation of the relevance of the {delta} currents is done by changing the final state angular momentum, excitation energy and momentum transfer. The sensitivity of the cross section to the details of the correlation function is studied by using realistic and schematic correlations. Results for {sup 12}C, {sup 16}O and {sup 40}Ca nuclei are presented.
W_L W_L Scattering in Higgsless Models: Identifying Better Effective Theories
Belyaev, Alexander S; Christensen, Neil D; Simmons, Elizabeth H; He, Hong-Jian; Kurachi, Masafumi; Tanabashi, Masaharu
2009-01-01
The three-site model has been offered as a benchmark for studying the collider phenomenology of Higgsless models. In this paper we analyze how well the three-site model performs as a general exemplar of Higgsless models in describing W_L W_L scattering, and which modifications can make it more representative. We employ general sum rules relating the masses and couplings of the Kaluza-Klein (KK) modes of the gauge fields in continuum and deconstructed Higgsless models as a way to compare the different theories. We show that the size of the four-point vertex for the (unphysical) Nambu-Goldstone modes and the degree to which the sum rules are saturated by contributions from the lowest-lying KK resonances both provide good measures of the extent to which a highly-deconstructed theory can accurately describe the low-energy physics of a continuum 5d Higgsless model. After comparing the three-site model to flat and warped continuum models, we analyze extensions of the three-site model to a longer open linear moose w...
Synthetic aperture radar imaging based on attributed scatter model using sparse recovery techniques
Institute of Scientific and Technical Information of China (English)
苏伍各; 王宏强; 阳召成
2014-01-01
The sparse recovery algorithms formulate synthetic aperture radar (SAR) imaging problem in terms of sparse representation (SR) of a small number of strong scatters’ positions among a much large number of potential scatters’ positions, and provide an effective approach to improve the SAR image resolution. Based on the attributed scatter center model, several experiments were performed with different practical considerations to evaluate the performance of five representative SR techniques, namely, sparse Bayesian learning (SBL), fast Bayesian matching pursuit (FBMP), smoothed l0 norm method (SL0), sparse reconstruction by separable approximation (SpaRSA), fast iterative shrinkage-thresholding algorithm (FISTA), and the parameter settings in five SR algorithms were discussed. In different situations, the performances of these algorithms were also discussed. Through the comparison of MSE and failure rate in each algorithm simulation, FBMP and SpaRSA are found suitable for dealing with problems in the SAR imaging based on attributed scattering center model. Although the SBL is time-consuming, it always get better performance when related to failure rate and high SNR.
Hierarchical Model for the Analysis of Scattering Data of Complex Materials
Oyedele, Akinola; Mcnutt, Nicholas W.; Rios, Orlando; Keffer, David J.
2016-06-01
Interpreting the results of scattering data for complex materials with a hierarchical structure in which at least one phase is amorphous presents a significant challenge. Often the interpretation relies on the use of large-scale molecular dynamics (MD) simulations, in which a structure is hypothesized and from which a radial distribution function (RDF) can be extracted and directly compared against an experimental RDF. This computationally intensive approach presents a bottleneck in the efficient characterization of the atomic structure of new materials. Here, we propose and demonstrate an approach for a hierarchical decomposition of the RDF in which MD simulations are replaced by a combination of tractable models and theory at the atomic scale and the mesoscale, which when combined yield the RDF. We apply the procedure to a carbon composite, in which graphitic nanocrystallites are distributed in an amorphous domain. We compare the model with the RDF from both MD simulation and neutron scattering data. This procedure is applicable for understanding the fundamental processing-structure-property relationships in complex magnetic materials.
Placati, Silvio; Guermandi, Marco; Samore, Andrea; Franchi Scarselli, Eleonora; Guerrieri, Roberto
2015-11-26
Diffuse Optical Tomography is an imaging technique based on evaluating how light propagates within the human head to obtain functional information about the brain. Precision in reconstructing such an optical properties map is highly affected by the accuracy of the light propagation model implemented, which needs to take into account the presence of clear and scattering tissues. We present a numerical solver based on the radiosity-diffusion model integrating the anatomical information provided by a structural MRI. The solver is designed to run on parallel heterogeneous platforms based on multiple GPUs and CPUs. We demonstrate how the solver provides a 7x speed-up over an isotropic-scattered parallel Monte Carlo engine based on a Radiative Transport Equation for a domain composed of 2 millions voxels, along with a significant improvement in accuracy. The speed-up greatly increases for larger domains, allowing us to compute the light distribution of a full human head ( 3 million voxels) in 116 seconds for the platform used.
Structural evaluation of an amyloid fibril model using small-angle x-ray scattering
Dahal, Eshan; Choi, Mina; Alam, Nadia; Bhirde, Ashwinkumar A.; Beaucage, Serge L.; Badano, Aldo
2017-08-01
Amyloid fibrils are highly structured protein aggregates associated with a wide range of diseases including Alzheimer’s and Parkinson’s. We report a structural investigation of an amyloid fibril model prepared from a commonly used plasma protein (bovine serum albumin (BSA)) using small-angle x-ray scattering (SAXS) technique. As a reference, the size estimates from SAXS are compared to dynamic light scattering (DLS) data and the presence of amyloid-like fibrils is confirmed using Congo red absorbance assay. Our SAXS results consistently show the structural transformation of BSA from spheroid to rod-like elongated structures during the fibril formation process. We observe the elongation of fibrils over two months with fibril length growing from 35.9 ± 3.0 nm to 51.5 ± 2.1 nm. Structurally metastable fibrils with distinct SAXS profiles have been identified. As proof of concept, we demonstrate the use of such distinct SAXS profiles to detect fibrils in the mixture solutions of two species by estimating their volume fractions. This easily detectable and well-characterized amyloid fibril model from BSA can be readily used as a control or standard reference to further investigate SAXS applications in the detection of structurally diverse amyloid fibrils associated with protein aggregation diseases.
Ellison, Donald C.; Warren, Donald C.; Bykov, Andrei M.
2016-03-01
We include a general form for the scattering mean free path, λmfp(p), in a nonlinear Monte Carlo model of relativistic shock formation and Fermi acceleration. Particle-in-cell simulations, as well as analytic work, suggest that relativistic shocks tend to produce short-scale, self-generated magnetic turbulence that leads to a scattering mean free path with a stronger momentum dependence than the λmfp ∝ p dependence for Bohm diffusion. In unmagnetized shocks, this turbulence is strong enough to dominate the background magnetic field so the shock can be treated as parallel regardless of the initial magnetic field orientation, making application to γ-ray bursts, pulsar winds, type Ibc supernovae, and extragalactic radio sources more straightforward and realistic. In addition to changing the scale of the shock precursor, we show that, when nonlinear effects from efficient Fermi acceleration are taken into account, the momentum dependence of λmfp(p) has an important influence on the efficiency of cosmic ray production as well as the accelerated particle spectral shape. These effects are absent in non-relativistic shocks and do not appear in relativistic shock models unless nonlinear effects are self-consistently described. We show, for limited examples, how the changes in Fermi acceleration translate to changes in the intensity and spectral shape of γ-ray emission from proton-proton interactions and pion-decay radiation.
Hooper, Andrew John
While conventional interferometric synthetic aperture radar (InSAR) is a very effective technique for measuring crustal deformation, almost any interferogram includes large areas where the signals decorrelate and no measurement is possible. Consequently, most InSAR studies to date have focused on areas that are dry and sparsely vegetated. A relatively new analysis technique, permanent scatterer InSAR, overcomes the decorrelation problem by identifying resolution elements whose echo is dominated by a single scatterer in a series of interferograms. This technique has been useful for analysis of urban areas, where angular structures produce efficient reflectors that dominate background scattering. However, man-made structures are absent from most of the Earth's surface. Furthermore, this technique requires, a priori, an approximate temporal model for the deformation, whereas characterizing the temporal pattern of deformation is commonly one of the aims of any study. We have developed a new method of analysis, StaMPS, using spatial correlation of interferogram phase to find a network of stable pixels in all terrains, with or without buildings. Prior knowledge of temporal variations in the deformation rate is not required. We refer to these pixels as persistent scatterers (PS). A key component of our method is the development of two algorithms to unwrap a three-dimensional series of interferograms. We observe temporally-variable deformation, using an initial version of StaMPS, in data acquired over Long Valley caldera in California, for a period when deformation rates varied significantly. The inferred displacements of the PS compare well with ground truth. Using an enhanced version of StaMPS, we detect a period of steady deflation within the Volcan Alcedo caldera in the Galapagos Islands between 1997 and 2001, which we model with a contracting ellipsoidal magma body. Conventional InSAR has been limited here until now by high rates of temporal decorrelation over much of
$f$-mode interaction with models of sunspot : near-field scattering and multi-frequency effects
Daiffallah, Khalil
2016-01-01
We use numerical simulations to investigate the interaction of an $f$-mode wave packet with small and large models of a sunspot in a stratified atmosphere. While a loose cluster model has been largely studied before, we focus in this study on the scattering from an ensemble of tightly compact tubes. We showed that the small compact cluster produces a slight distorted scattered wave field in the transverse direction, which can be attributed to the simultaneous oscillations of the pairs of tubes within the cluster aligned in a perpendicular direction to the incoming wave. However, no signature of a multiple-scattering regime has been observed from this model, while it has been clearly observable for the large compact cluster model. Furthermore, we pointed out the importance of the geometrical shape of the monolithic model on the interaction of $f$-mode waves with a sunspot in a high frequency range ($\
Modeling of Electromagnetic Waves Scattering from Snow Covered First Year Sea Ice
Komarov, A. S.; Barber, D. G.; Isleifson, D. K.
2011-12-01
Modeling of electromagnetic wave interaction with sea ice is required for various remote sensing applications, such as an interpretation of Synthetic Aperture Radar (SAR) imagery over sea ice. In this study, we present numerical modeling of the Normalized Radar Cross Section (NRCS) at vertical and horizontal polarizations from snow covered First Year (FY) sea ice. We consider sea ice as a layered medium with an arbitrary profile of dielectric constant, and the snow cover as a homogeneous layer on the top of the sea ice. Surface scattering at the snow-sea ice interface was taken into account by the first-order approximation of the small perturbation method. We obtained an analytical formulation for radar cross-sections at vertical and horizontal polarizations and conducted numerical modeling of the backscattering characteristics. The solution derived for NRCSs includes reflection coefficients from snow and sea ice. The calculation of reflection coefficients from the stratified sea ice is considered separately as an auxiliary problem. In-situ geophysical properties of snow and sea ice collected during the Circumpolar Flow Lead (CFL) system study project were used to estimate the dielectric constants of snow and sea ice for several case studies. The dielectric constant of the sea ice was calculated using the Polder-van-Santen/de Loor (PVD) mixture model, while the dielectric constant of the snow was estimated using a Debye-like model. The calculated angular dependencies of the NRCSs (HH- and VV- polarizations) and co-polarization ratios were compared with in-situ C-band scatterometer measurements. These comparisons demonstrate a good agreement between simulated and observed scattering characteristics.
Hu, Shuai; Gao, Taichang; Li, Hao; Yang, Bo; Jiang, Zidong; Liu, Lei; Chen, Ming
2017-10-01
The performance of absorbing boundary condition (ABC) is an important factor influencing the simulation accuracy of MRTD (Multi-Resolution Time-Domain) scattering model for non-spherical aerosol particles. To this end, the Convolution Perfectly Matched Layer (CPML), an excellent ABC in FDTD scheme, is generalized and applied to the MRTD scattering model developed by our team. In this model, the time domain is discretized by exponential differential scheme, and the discretization of space domain is implemented by Galerkin principle. To evaluate the performance of CPML, its simulation results are compared with those of BPML (Berenger's Perfectly Matched Layer) and ADE-PML (Perfectly Matched Layer with Auxiliary Differential Equation) for spherical and non-spherical particles, and their simulation errors are analyzed as well. The simulation results show that, for scattering phase matrices, the performance of CPML is better than that of BPML; the computational accuracy of CPML is comparable to that of ADE-PML on the whole, but at scattering angles where phase matrix elements fluctuate sharply, the performance of CPML is slightly better than that of ADE-PML. After orientation averaging process, the differences among the results of different ABCs are reduced to some extent. It also can be found that ABCs have a much weaker influence on integral scattering parameters (such as extinction and absorption efficiencies) than scattering phase matrices, this phenomenon can be explained by the error averaging process in the numerical volume integration.
Modeling of electromagnetic scattering by thin cylinders using Pattern Equation Method
Demin, D. B.; Kleev, A. I.; Kyurkchan, A. G.
2017-01-01
To solve the problem related to scattering by a perfectly conducting thin cylinder, approximate approach was developed based on use of Pattern Equation Method (PEM). Explicit formulas were obtained for total scattering cross-section applicable for cylindric scatterers of complex shape. It is shown that calculation accuracy controlled by calculating the balance of power flows for incident and scattered waves (checking the accomplishment of optical theorem) is quite sufficient for practice.
Riviere, Nicolas; Ceolato, Romain; Hespel, Laurent
2014-10-01
Onera, the French aerospace lab, develops and models active imaging systems to understand the relevant physical phenomena affecting these systems performance. As a consequence, efforts have been done on the propagation of a pulse through the atmosphere and on target geometries and surface properties. These imaging systems must operate at night in all ambient illumination and weather conditions in order to perform strategic surveillance for various worldwide operations. We have implemented codes for 2D and 3D laser imaging systems. As we aim to image a scene in the presence of rain, snow, fog or haze, we introduce such light-scattering effects in our numerical models and compare simulated images with measurements provided by commercial laser scanners.
The Tor Vergata Scattering Model Applied to L Band Backscatter During the Corn Growth Cycle
Joseph, A. T.; van der Velde, R.; Ferrazzoli, P.; Lang, R. H.; Gish, T.
2013-12-01
At the USDA's Optimizing Production Inputs for Economic and Environmental Enhancement (OPE3) experimental site in Beltsville (Maryland, USA) a field campaign took place throughout the 2002 corn growth cycle from May 10th (emergence of corn crops) to October 2nd (harvest). One of the microwave instruments deployed was the multi-frequency (X-, C- and L-band) quad-polarized (HH, HV, VV, VH) NASA GSFC / George Washington University (GWU) truck mounted radar. During the field campaign, this radar system provided once a week fully polarized C- and L-band (4.75 and 1.6 GHz) backscatter measurements from incidence angle of 15, 35, and 55 degrees. In support of these microwave observations, an extensive ground characterization took place, which included measurements of surface roughness, soil moisture, vegetation biomass and morphology. The field conditions during the campaign are characterized by several dry downs with a period of drought in the month of August. Peak biomass of the corn canopies was reached at July 24, 2002 with a total biomass of approximately 6.5 kg m-2. This dynamic range in both soil moisture and vegetation conditions within the data set is ideal for the validation of discrete medium vegetation scattering models. In this study, we compare the L band backscatter measurements with simulations by the Tor Vergata model (Bracaglia et al., 1995). The measured soil moisture, vegetation biomass and most reliably measured vegetation morphological parameters (e.g. number of leaves, number of stems and stem height) were used as input for the Tor Vergata model. The more uncertain model parameters (e.g. surface roughness, leaf thickness) and the stem diameter were optimized using a parameter estimation routine based on the Levenberg-Marquardt algorithm. As cost function for this optimization, the HH and VV polarized backscatter measured and simulated by the Tor Vergata model for incidence angle of 15, 35 and 55 degrees were used (6 measurements in total). The
Directory of Open Access Journals (Sweden)
Adam Wax
2008-01-01
Full Text Available Light scattering spectroscopy measurements can be used to determine the structure of tissue samples. Through refined data acquisition and signal processing techniques, quantitative nuclear morphology measurements may be obtained from light scattering data. These data have been used primarily as a biomarker of neoplastic change in a wide range of settings. Here, we review the application of light scattering to assessing the health status of tissues drawn from animal models of carcinogenesis, in particular, the rat esophagus and the golden Syrian hamster trachea carcinogenesis models. In addition, we present results from ex vivo human tissues to demonstrate the relevance of the use of animal models which are excellent surrogates for several human cancers. These models provide the opportunity to develop biomarkers and test chemopreventive and therapy strategies before application in humans.
Mathematical Model and Hybrid Scatter Search for Cost Driven Job-shop Scheduling Problem
Directory of Open Access Journals (Sweden)
Bai Jie
2011-07-01
Full Text Available Job-shop scheduling problem (JSP is one of the most well-known machine scheduling problems and one of the strongly NP-hard combinatorial optimization problems. Cost optimization is an attractive and critical research and development area for both academic and industrial societies. This paper presents a cost driven model of the job-shop scheduling problem in which the solutions are driven by business inputs, such as the cost of the product transitions, revenue loss due to the machine idle time and earliness/tardiness penalty. And then, a new hybrid scatter search algorithm is proposed to solve the cost driven job-shop scheduling problem by introducing the simulated annealing (SA into the improvement method of scatter search (SS. In order to illustrate the effectiveness of the hybrid method, some test problems are generated, and the performance of the proposed method is compared with other evolutionary algorithms such as genetic algorithm and simulated annealing. The experimental simulation tests show that the hybrid method is quite effective at solving the cost driven job-shop scheduling problem.
Cross-section model for cold neutron scattering in solid and liquid methane
Morishima, N
2002-01-01
Incoherent neutron scattering cross-sections for solid CH sub 4 in the temperature range of 20.4-90.7 K and liquid CH sub 4 at temperatures between 90.7 and 111.7 K are evaluated. A space-time correlation approach is used to describe a double-differential scattering cross-section which is basically expressed by a generalized frequency distribution. The cross-section model includes molecular translations and rotations as well as intramolecular vibrations. The former are concerned with very short-time free-gas like translation, short-lived vibration and long-time diffusion (only in liquid state). The latter consists of short-time free rotation and long-time isotropic rotational diffusion. Numerical calculations on double-differential and total cross-sections are carried out for incident neutron energies covered 0.1 mu eV to 10 eV. Good agreement with experimental results at many different temperatures is found.
Meson-Meson Scattering in the Relativistic Quark Model from Constraint Dynamics
Crater, Horace; Wong, Cheuk-Yin
2004-11-01
Previously, Crater and Van Alstine footnote H.W. Crater and P. Van Alstine, Ann. Phys. (N.Y.) Vol. 148, 57 (1983) employed Dirac's relativistic constraint dynamics to derive Two-Body Dirac equations which were subsequently applied successfully to obtain a covariant nonperturbative description of QED and QCD bound states footnote H.W. Crater, R.L. Becker, C.Y. Wong, and P. Van Alstine, Phys. Rev. D, Vol.46, 5117 (1992), H. Crater and P. Van Alstine to appear in Phys. Rev. D Vol 70 (hep-ph/0208186). We use this formalism to generalize the microscopic theory of meson-meson scattering developed by Barnes and Swanson footnote T. barnes and E.S. Swanson, Phys. Rev. D Vol. 46, 131 (1992) footnote C.Y. Wong, T. Barnes and E.S. Swanson, Phys. Rev. C Vol 62, 045201 (2001)from the nonrelativistic to the relativistic domain. The application of the present formalism will be demonstrated with a simple quark model for the scattering of mesons.
Energy Technology Data Exchange (ETDEWEB)
Bansil, Arun [Northeastern Univ., Boston, MA (United States)
2016-12-01
Basic-Energy Sciences of the Department of Energy (BES/DOE) has made large investments in x-ray sources in the U.S. (NSLS-II, LCLS, NGLS, ALS, APS) as powerful enabling tools for opening up unprecedented new opportunities for exploring properties of matter at various length and time scales. The coming online of the pulsed photon source literally allows us to see and follow the dynamics of processes in materials at their natural timescales. There is an urgent need therefore to develop theoretical methodologies and computational models for understanding how x-rays interact with matter and the related spectroscopies of materials. The present project addressed aspects of this grand challenge of X-ray science. In particular, our Collaborative Research Team (CRT) focused on understanding and modeling of elastic and inelastic resonant X-ray scattering processes. We worked to unify the three different computational approaches currently used for modeling X-ray scattering—density functional theory, dynamical mean-field theory, and small-cluster exact diagonalization—to achieve a more realistic material-specific picture of the interaction between X-rays and complex matter. To achieve a convergence in the interpretation and to maximize complementary aspects of different theoretical methods, we concentrated on the cuprates, where most experiments have been performed. Our team included both US and international researchers, and it fostered new collaborations between researchers currently working with different approaches. In addition, we developed close relationships with experimental groups working in the area at various synchrotron facilities in the US. Our CRT thus helped toward enabling the US to assume a leadership role in the theoretical development of the field, and to create a global network and community of scholars dedicated to X-ray scattering research.
Stieger, M.A.; Pedersen, J.S.; Lindner, P.; Richtering, W.
2004-01-01
The structure of concentrated temperature-sensitive poly(N-isopropylacrylamide) (PNiPAM) microgel suspensions has been investigated employing rheology and small-angle neutron scattering (SANS). A previously described model expression for the particle form factor Pinho(q) is extended by a model hard
Inline Modeling of Cross-Beam Energy Transfer and Raman Scattering in NIF Hohlraums
Strozzi, David; Bailey, D. S.; Thomas, C. A.; Sepke, S. M.; Kerbel, G. D.; Michel, P.; Divol, L.; Jones, O. S.
2015-11-01
Inline models of cross-beam energy transfer (CBET) and stimulated Raman Scattering (SRS) have been added to the radiation-hydrodynamics codes Hydra and Lasnex. Both processes are important in hohlraums with high gas fill density, particularly for implosion symmetry. Coupled-mode equations are solved along laser ray paths for both models. The inline model shows the SRS gain rate exceeds that of SRS light absorption along most of the laser ray path, and most SRS light escapes the target. Most SRS-driven Langmuir wave power is deposited slightly inside the laser entrance hole (LEH), which reduces how much inner-beam power reaches the equator. This also makes the LEH hotter, which affects CBET. Compared to removing SRS power from the incident laser, the inline SRS model does not change total x-ray drive but makes the drive stronger from the poles than the equatorial waist. This reduces the need to artificially clamp CBET in order to match implosion shape data, which has historically been needed for high gas fill hohlraums. We are applying the models to a set of NIF shots with varying gas fill densities. Work performed under the auspices of the U.S. Department of Energy by LLNL under Contract DE-AC52-07NA27344.
Application of the Tor Vergata Scattering Model to L Band Backscatter During the Corn Growth Cycle
Joseph, A. T.; vanderVelde, R.; ONeill, P. E.; Lang, R.; Gish, T.
2010-01-01
At the USDA's Optimizing Production Inputs for Economic and Environmental Enhancement (OPE3) experimental site in Beltsville, Maryland, USA) a field campaign took place throughout the 2002 corn growth cycle from May 10th (emergence of corn crops) to October 2nd (harvest). One of the microwave instruments deployed was the multi-frequency (X-, C- and L-band) quad-polarized (HH, HV, VV, VH) NASA GSFC/George Washington University (GWU) truck mounted radar. During the field campaign, this radar system provided once a week fully polarized C- and L-band (4.75 and 1.6 GHz) backscatter measurements from incidence angle of 15, 35, and 55 degrees. In support of microwave observations, an extensive ground characterization took place, which included measurements of surface roughness, soil moisture, vegetation biomass and morphology. The field conditions during the campaign are characterized by several dry downs with a period of drought in the month of August. Peak biomass the corn canopies was reached on July 24th with a total biomass of approximately 6.5 kg/sq m. This dynamic range in both soil moisture and vegetation conditions within the data set is ideal for the validation of discrete medium vegetation scattering models. In this study, we compare the L band backscatter measurements with simulations by the Tor Vergata model (ferrazzoli and Guerriero 1996). The measured soil moisture, vegetation biomass and most reliably measured vegetation morphological parameters (e.g. number of leaves, number of stems and stem height) were used as input for the Tor Vergata model. The more uncertain model parameters (e.g. surface roughness, leaf thickness) and the stem diameter were optimized using a parameter estimation routine based on the Levenberg-Marquardt algorithm. As cost function for this optimization, the HH and VV polarized backscatter measured and stimulated by the TOR Vergata model for incidence angle of 15, 35, and 55 degrees were used (6 measurements in total). The calibrated
Low Energy Pion-Pion Elastic Scattering in Sakai-Sugimoto Model
Parthasarathy, R
2008-01-01
We have considered the holographic large $N_c$ QCD model proposed by Sakai and Sugimoto and evaluated the non-Abelian DBI-action on the D8-brane upto $(\\alpha')^4$ terms. Restricting to the pion sector, these corrections give rise to four derivative contact terms for the pion field. We derive the Weinberg's phenemenological lagrangian. The coefficients of the four derivative terms are determined in terms of $g_{YM}^2$. The low energy pion-pion scattering amplitudes are evaluated. Numerical results are presented with the choice of $M_{KK}=0.94 GeV$ and $N_c=11$. The results are compared with the amplitudes calculated using the experimental phase shifts. The agreement with the experimental data is found to be satisfactory.
Energy deposition model based on electron scattering cross section data from water molecules
Energy Technology Data Exchange (ETDEWEB)
Munoz, A; Oiler, J C [Centra de Investigaciones Energeticas, Medioambientales y Tecnologicas (CIEMAT), Avenida Complutense 22, 28040 Madrid (Spain); Blanco, F [Departamento de Fisica Atomica, Molecular y Nuclear, Universidad Complutense de Madrid, Avenida Complutense s.n., 28040 Madrid (Spain); Gorfinkiel, J D [Department of Physiscs and Astronomy, The Open University, Walton Hall, Milton Keynes MK7 6AA (United Kingdom); Limao-Vieira, P [Departamento de Fisica, Universidade Nova de Lisboa, 2829-516 Caparica (Portugal); Maira-Vidal, A; Borge, M J G; Tengblad, O [Instituto de Estructura de la Materia, Consejo Superior de Investigaciones Cientificas (CSIC), Serrano 113-bis, 28006 Madrid, Spam (Spain); Huerga, C; Tellez, M [Hospital Universitario La Paz, paseo de la Castellana 261, 28046 Madrid (Spain); Garcia, G [Instituto de Matematicas y Fisica Fundamental, Consejo Superior de Investigaciones CientifIcas (CSIC), Serrano 113-bis, 28006 Madrid (Spain)], E-mail: g.garcia@imaff.cfmac.csic.es
2008-10-01
A complete set of electrons scattering cross sections by water molecules over a broad energy range, from the me V to the Me V ranges, is presented in this study. These data have been obtained by combining experiments and calculations and cover most relevant processes, both elastic and inelastic, which can take place in the considered energy range. A new Monte Carlo simulation programme has been developed using as input parameter these cross sectional data as well as experimental energy loss spectra. The simulation procedure has been applied to obtain electron tracks and energy deposition plots in water when irradiated by a Ru-106 plaque as those used for brachytherapy of ocular tumours. Finally, the low energy electron tracks provided by the present model have been compared with those obtained with other codes available in the literature.
Polarimetric entropy of the ocean surface with a two-scale scattering model
Institute of Scientific and Technical Information of China (English)
WANG Wenguang; LI Haiyan; SONG Xingai
2014-01-01
The relationships among an ocean wave spectrum, a fully polarimetric coherence matrix, and radar pa-rameters are deduced with an electromagnetic wave theory. Furthermore, the relationship between the polarimetric entropy and ocean wave spectrum is established based on the definition of entropy and a two-scale scattering model of the ocean surface. It is the first time that the polarimetric entropy of the ocean surface is presented in theory. Meanwhile, the relationships among the fully polarimetric entropy and the parameters related to radar and ocean are discussed. The study is the basis of further monitoring targets on the ocean surface and deriving oceanic information with the entropy from the ocean surface. The con-trast enhancement between human-made targets and the ocean surface with the entropy is presented with quad-pol airborne synthetic aperture radar (AIRSAR) data.
Source-model technique analysis of electromagnetic scattering by surface grooves and slits.
Trotskovsky, Konstantin; Leviatan, Yehuda
2011-04-01
A computational tool, based on the source-model technique (SMT), for analysis of electromagnetic wave scattering by surface grooves and slits is presented. The idea is to use a superposition of the solution of the unperturbed problem and local corrections in the groove/slit region (the grooves and slits are treated as perturbations). In this manner, the solution is obtained in a much faster way than solving the original problem. The proposed solution is applied to problems of grooves and slits in otherwise planar or periodic surfaces. Grooves and slits of various shapes, both smooth ones as well as ones with edges, empty or filled with dielectric material, are considered. The obtained results are verified against previously published data.
Two-photon-exchange effects in the unpolarized $\\mu p$ scattering within the hadronic model
Zhou, Hai-Qing
2016-01-01
In this work, the two-photon-exchange (TPE) effects in the unpolarized $\\mu p$ scattering are discussed within the hadronic model where the intermediate states $N,\\Delta$ and $\\sigma$ are considered. The contribution from the $N$ intermediate is close to the results given by Ref. \\cite{Tomalak2014} at the small $Q$ and there is a sizeable difference when $Q>0.25$GeV (where $Q^2$ is the four momentum transfer). The contributions from the $\\Delta$ and the $\\sigma$ intermediate states are much smaller than that from the $N$ intermediate at the small $Q$. In the kinematic region with $k_i\\subseteq [0.01,0.3]$ GeV and $Q \\leq0.4$GeV (where $k_i$ is the three momentum of initial muon at Lab frame), a naive expression for the TPE contributions is given, which can be used directly for other analysis.
A Physical Optics Approach to the Electromagnetic Field Scattered by Simplified Ship-Sea Models.
1977-11-01
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Turolla, Andrea; Santoro, Domenico; de Bruyn, John R; Crapulli, Ferdinando; Antonelli, Manuela
2016-01-01
A computational fluid dynamic (CFD) model was developed to describe the process performance of a semi-batch annular TiO2-UV photoreactor in an Eulerian framework. The model accounted for the optical behaviour of titanium dioxide (TiO2) suspensions, the flow distribution and the oxalic acid degradation in the reactor. The scattering component of the optical model, explicitly included in the CFD simulations using a TiO2-specific scattering phase function integrated in the radiative transfer equation, was calibrated using an optical goniometer by comparing simulated scattering light profiles against irradiance measurements collected for various TiO2 concentrations and UV wavelengths and subsequently solved by the discrete ordinate (DO) radiation model. Several scattering phase functions were tested against the goniometric measurements confirming that the Henyey-Greenstein (HG) equation was the most appropriate angular distribution function at 254 and 355 nm, irrespective of the TiO2 concentration. Using the calibrated HG function, a new approach for quantifying the absolute values of absorption and scattering coefficients in TiO2 suspensions was proposed. It consists of iteratively solving, using the DO model, the radiative transfer equation for various combinations of absorption and scattering coefficients until the error between observed and predicted angular irradiance measurements is minimized. The accuracy of the optical parameters was verified with independent CFD simulations carried out for an annular photoreactor and already available in the literature. Predicted and simulated irradiance and oxalic acid degradation data were found to be in excellent agreement, confirming the considerable potential of the integrated modelling approach presented in this paper for the design, optimization and scale-up of photocatalytic technologies for water and wastewater treatment applications.
Electron scattering cross sections for the modelling of oxygen-containing plasmas
Lemos Alves, Luís; Coche, Philippe; Ridenti, Marco Antonio; Guerra, Vasco
2016-05-01
This work proposes a set of electron scattering cross sections for molecular and atomic oxygen, with interest for the modelling of oxygen-containing plasmas. These cross sections, compiled for kinetic energies up to 1 keV, are part of the IST-LISBON database with LXCat, being used as input data to the LoKI (LisbOn KInetics) numerical code. The cross sections for ground-state molecular oxygen describe elastic and inelastic collision mechanisms, the latter including rotational excitations/de-excitations (treated using either a discrete or a continuous approach), vibrational and electronic excitations (including dissociation), dissociative attachment and ionisation. This set yields calculated swarm parameters that reproduce measurements within 5-20% (transport parameters) and within a factor of 2 difference (Townsend coefficients), for reduced electric fields in the range 10-3-103 Td. The cross sections describing the kinetics of atomic oxygen by electron-impact comprise elastic mechanisms, electronic excitation and ionisation from O(3P) ground-state, dissociation of O2(X,a,b) (including dissociative ionisation and attachment) and of O3, and detachment. These cross sections are indirectly validated, together with other elementary data for oxygen, by comparing the densities of O((4S0)3p 5P) obtained from the self-consistent modelling and from calibrated optical emission spectroscopy diagnostics of microwave-sustained micro-plasmas in dry air (80% N2: 20% O2), produced using a surface-wave excitation (2.45 GHz frequency) within a small radius capillary (R = 345 μm) at low pressure (p = 300 Pa). The calculated densities are in good qualitative agreement with measurements, overestimating them by a factor ˜1.5. Contribution to the Topical Issue "Advances in Positron and Electron Scattering", edited by Paulo Limao-Vieira, Gustavo Garcia, E. Krishnakumar, James Sullivan, Hajime Tanuma and Zoran Petrovic.
Directory of Open Access Journals (Sweden)
D. J. Goossens
2015-01-01
Full Text Available Diffuse scattering from a crystal contains valuable information about the two-body correlations (related to the nanoscale order in the material. Despite years of development, the detailed analysis of single crystal diffuse scattering (SCDS has yet to become part of the everyday toolbox of the structural scientist. Recent decades have seen the pair distribution function approach to diffuse scattering (in fact, total scattering from powders become a relatively routine tool. However, analysing the detailed, complex, and often highly anisotropic three-dimensional distribution of SCDS remains valuable yet rare because there is no routine method for undertaking the analysis. At present, analysis requires significant investment of time to develop specialist expertise, which means that the analysis of diffuse scattering, which has much to offer, is not incorporated thorough studies of many compounds even though it has the potential to be a very useful adjunct to existing techniques. This article endeavours to outline in some detail how the diffuse scattering from a molecular crystal can be modelled relatively quickly and largely using existing software tools. It is hoped this will provide a template for other studies. To enable this, the entire simulation is included as deposited material.
Bhattacharya, Bhubanjyoti; Tropiano, Anthony J
2015-01-01
Understanding the charged current quasielestic (CCQE) neutrino-nucleus interaction is important for precision studies of neutrino oscillations. The theoretical description of the interaction depends on the combination of a nuclear model with the knowledge of form factors. While the former has received considerable attention, the latter, in particular the axial form factor, is implemented using the historical dipole model. Instead, we use a model-independent approach, presented in a previous study, to analyze the muon antineutrino CCQE mineral oil data published by the MiniBooNE collaboration. We combine the cross section for scattering of antineutrinos off protons in carbon and hydrogen, using the same axial form factor for both. The extracted value of the axial mass parameter $m_A = 0.84^{+0.12}_{-0.04} \\pm {0.11} \\, {\\rm GeV}$ is in very good agreement with the model-independent value extracted from MiniBooNE's neutrino data. Going beyond a one-parameter description of the axial form factor, we extract valu...
A hybrid transport-diffusion model for radiative transfer in absorbing and scattering media
Energy Technology Data Exchange (ETDEWEB)
Roger, M., E-mail: maxime.roger@insa-lyon.fr [Université de Lyon, CNRS, INSA-Lyon, CETHIL, UMR5008, F-69621 Villeurbanne (France); Caliot, C. [PROMES-UPR CNRS 6144, 7 rue du Four Solaire, 66120 Font Romeu Odeillo (France); Crouseilles, N. [INRIA-Rennes Bretagne-Atlantique (IPSO Project) and Université de Rennes 1 (IRMAR), Campus de Beaulieu, 35042 Rennes Cedex (France); Coelho, P.J. [Mechanical Engineering Department, LAETA, IDMEC, Instituto Superior Técnico, Universidade de Lisboa, Av. Rovisco Pais 1, 1049-001, Lisboa (Portugal)
2014-10-15
A new multi-scale hybrid transport-diffusion model for radiative transfer is proposed in order to improve the efficiency of the calculations close to the diffusive regime, in absorbing and strongly scattering media. In this model, the radiative intensity is decomposed into a macroscopic component calculated by the diffusion equation, and a mesoscopic component. The transport equation for the mesoscopic component allows to correct the estimation of the diffusion equation, and then to obtain the solution of the linear radiative transfer equation. In this work, results are presented for stationary and transient radiative transfer cases, in examples which concern solar concentrated and optical tomography applications. The Monte Carlo and the discrete-ordinate methods are used to solve the mesoscopic equation. It is shown that the multi-scale model allows to improve the efficiency of the calculations when the medium is close to the diffusive regime. The proposed model is a good alternative for radiative transfer at the intermediate regime where the macroscopic diffusion equation is not accurate enough and the radiative transfer equation requires too much computational effort.
Time-domain compressive dictionary of attributed scattering center model for sparse representation
Institute of Scientific and Technical Information of China (English)
ZHONG Jin-rong; WEN Gong-jian
2016-01-01
Parameter estimation of the attributed scattering center (ASC) model is significant for automatic target recognition (ATR). Sparse representation based parameter estimation methods have developed rapidly. Construction of the separable dictionary is a key issue for sparse representation technology. A compressive time-domain dictionary (TD) for ASC model is presented. Two-dimensional frequency domain responses of the ASC are produced and transformed into the time domain. Then these time domain responses are cutoff and stacked into vectors. These vectored time-domain responses are amalgamated to form the TD. Compared with the traditional frequency-domain dictionary (FD), the TD is a matrix that is quite spare and can markedly reduce the data size of the dictionary. Based on the basic TD construction method, we present four extended TD construction methods, which are available for different applications. In the experiments, the performance of the TD, including the basic model and the extended models, has been firstly analyzed in comparison with the FD. Secondly, an example of parameter estimation from SAR synthetic aperture radar (SAR) measurements of a target collected in an anechoic room is exhibited. Finally, a sparse image reconstruction example is from two apart apertures. Experimental results demonstrate the effectiveness and efficiency of the proposed TD.
Institute of Scientific and Technical Information of China (English)
无
2003-01-01
The authors first establish a quantum microscopic scattering matrix model in multidimen-sional wave-vector space, which relates the phase space density of each superlattice cell withthat of the neighbouring cells. Then, in the limit of a large number of cells, a SHE (SphericalHarmonics Expansion)-type model of diffusion equations for the particle number density in theposition-energy space is obtained. The crucial features of diffusion constants on retaining thememory of the quantum scattering characteristics of the superlattice elementary cell (like e.g.transmission resonances) are shown in order. Two examples are treated with the analyticallycomputation of the diffusion constants.
Fauchez, Thomas; Davis, Anthony B.; Cornet, Celine; Szczap, Frederic; Platnick, Steven; Dubuisson, Philippe; Thieuleux, Francois
2017-01-01
We investigate the impact of cirrus cloud heterogeneity on the direct emission by cloud or surface and on the scattering by ice particles in the thermal infrared (TIR). Realistic 3-D cirri are modeled with the 3DCLOUD code, and top-of-atmosphere radiances are simulated by the 3-D Monte Carlo radiative transfer (RT) algorithm 3DMCPOL for two (8.65 micrometers and 12.05 micrometers) channels of the Imaging Infrared Radiometer on CALIPSO. At nadir, comparisons of 1-D and 3-D RT show that 3-D radiances are larger than their 1-D counterparts for direct emission but smaller for scattered radiation. For our cirrus cases, 99% of the 3-D total radiance is computed by the third scattering order, which corresponds to 90% of the total computational effort, but larger optical thicknesses need more scattering orders. To radically accelerate the 3-D RT computations (using only few percent of 3-D RT time with a Monte Carlo code), even in the presence of large optical depths, we develop a hybrid model based on exact 3-D direct emission, the first scattering order from 1-D in each homogenized column, and an empirical adjustment linearly dependent on the optical thickness to account for higher scattering orders. Good agreement is found between the hybrid model and the exact 3-D radiances for two very different cirrus models without changing the empirical parameters. We anticipate that a future deterministic implementation of the hybrid model will be fast enough to process multiangle thermal imagery in a practical tomographic reconstruction of 3-D cirrus fields.
Nucleon scattering on actinides using a dispersive optical model with extended couplings
SoukhovitskiÄ©, E. Sh.; Capote, R.; Quesada, J. M.; Chiba, S.; Martyanov, D. S.
2016-12-01
The Tamura coupling model [Rev. Mod. Phys. 37, 679 (1965), 10.1103/RevModPhys.37.679] has been extended to consider the coupling of additional low-lying rotational bands to the ground-state band. Rotational bands are built on vibrational bandheads (even-even targets) or single-particle bandheads (odd-A targets) including both axial and nonaxial deformations. These additional excitations are introduced as a perturbation to the underlying axially symmetric rigid-rotor structure of the ground-state rotational band. Coupling matrix elements of the generalized optical model are derived for extended multiband transitions in even-even and odd-A nuclei. Isospin symmetric formulation of the optical model is employed. A coupled-channels optical-model potential (OMP) containing a dispersive contribution is used to fit simultaneously all available optical experimental databases including neutron strength functions for nucleon scattering on 232Th,233,235,238U, and 239Pu nuclei. Quasielastic (p ,n ) scattering data on 232Th and 238U to the isobaric analog states of the target nucleus are also used to constrain the isovector part of the optical potential. Lane consistent OMP is derived for all actinides if corresponding multiband coupling schemes are defined. For even-even (odd-A ) actinides almost all low-lying collective levels below 1 MeV (0.5 MeV) of excitation energy are coupled. OMP parameters show a smooth energy dependence and energy-independent geometry. A phenomenological optical-model potential that couples multiple bands in odd-A actinides is published for a first time. Calculations using the derived OMP potential reproduce measured total cross-section differences between several actinide pairs within experimental uncertainty for incident neutron energies from 50 keV up to 150 MeV. The importance of extended coupling is studied. Multiband coupling is stronger in even-even targets owing to the collective nature of the coupling; the impact of extended coupling on
Sharf, I V; Sokhrannyi, G O; Yatkin, K V; Rusov, V D
2009-01-01
The method for taking into account the interference contributions to hadron inelastic scattering cross-section is developed within the framework of the simplest multiperipheral model. This method is based on the self-acting scalar fi^3 field theory and the Laplace method using. It was shown that the considered in [1] mechanism of virtuality diminishing at the energy sqrt(s) growth with consideration of all considerable interference contributions into account can be responsible for the total hadron scattering cross-section growth which is experimentally observed. The offered model reproduces well at qualitative level the experimental dependence of total scattering cross-section on energy sqrt(s) with a characteristic minimum in the range sqrt(s) around 10 GeV.
Fukukawa, K.; Fujiwara, Y.
2011-05-01
The S-wave effective-range parameters of the neutron-deuteron (nd) scattering are calculated in the Faddeev formalism using a nonlocal Gaussian potential based on the quark-model baryon-baryon interaction fss2. The spin-doublet low-energy eigenphase shift is sufficiently attractive to reproduce predictions by the AV18 plus Urbana three-body force, yielding almost correct values of the scattering length and the triton binding energy without the three-nucleon force. This feature is due to the strong distortion effect of the deuteron in this spin channel, which is very sensitive to the nonlocal description of the short-range repulsion in the quark-model nucleon-nucleon interaction. We incorporate the Coulomb force by extending the framework of the Coulomb externally corrected approximation and calculate the differential cross sections of the pd scattering.
Practical methods to define scattering coefficients in a room acoustics computer model
DEFF Research Database (Denmark)
Zeng, Xiangyang; Christensen, Claus Lynge; Rindel, Jens Holger
2006-01-01
To predict acoustics of rooms using computer programs based on geometrical assumptions, it is important that scattering is included in the calculations. Therefore scattering is usually included in terms of scattering coefficients which are assigned to each surface telling the software the ratio...... between the part of the reflected energy which is not being reflected specularily and the total reflected energy. However the effective scattering coefficient of a surface depends not only on the roughness of the surface material indeed diffraction caused by limited dimensions of the surface as well...
Energy Technology Data Exchange (ETDEWEB)
Kucerka, Norbert [Canadian Neutron Beam Centre and Comelius University (Slovakia); Holland, B [University of Guelph; Gray, C.G [University of Guelph; Tomberli, B [Brandon University; Katsaras, John [ORNL
2012-01-01
We combine molecular dynamics (MD) simulations and experiment, both small-angle neutron (SANS) and small-angle X-ray scattering (SAXS), to determine the precise structure of bilayers composed of 1-palmitoyl-2-oleoyl-sn-glycero-3-phosphatidylglycerol (POPG), a lipid commonly encountered in bacterial membranes. Experiment and simulation are used to develop a one-dimensional scattering density profile (SDP) model suitable for the analysis of experimental data. The joint refinement of such data (i.e., SANS and SAXS) results in the area per lipid that is then used in the fixed-area simulations. In the final step, the direct comparison of simulated-to-experimental data gives rise to the detailed structure of POPG bilayers. From these studies we conclude that POPG s molecular area is 66.0 +/- 1.3 ^2, its overall bilayer thickness is 36.7 +/- 0.7 , and its hydrocarbon region thickness is 27.9 ( 0.6 , assuming a simulated value of 1203 ^3 for the total lipid volume.
A tissue-engineered 3D model of light scattering in atherosclerotic plaques
Levitz, David; Hinds, Monica T.; Wang, Ruikang K.; Ma, Zhenhe; Ishii, Katsu; Tran, Noi; McCarty, Owen J. T.; Hanson, Stephen R.; Jacques, Steven L.
2007-02-01
The development of atherosclerotic plaques includes changes in the cellular and extracellular composition of the arterial wall. Although these changes in composition affect the manner in which light scatters in the vessel wall and thus affect any optical signal, experimentally determining how features of atherosclerosis affect optical signals has remained elusive. Using current tissue-engineering methods, we developed a 3D tissue construct model for assessing how certain features of atherosclerosis (the increased concentrations of lipids and macrophages) affect optical signals. The model is based on vascular tissue constructs made of smooth muscle cells (SMCs) and macrophages (M\\Fgr s) that are co-cultured inside a 3D scaffold matrix of collagen fibers with interspersed lipids. To make the scaffold matrix, powdered collagen was dissolved in acetic acid, homogenized, and neutralized by sequential dialyses to yield a soft gel of 2 μm thick collagen fibers in which cells were seeded. In "normal" constructs, only SMCs were seeded in the collagen gel; in "athero-like" constructs, both SMCs and M\\Fgr s (loaded or unloaded with lipid) were seeded in the gel. To demonstrate the use of this model, sets of slab-shaped normal and athero-like constructs were imaged by optical coherence tomography (OCT) and qualitatively analyzed. 2D frames from 3D OCT image cubes were compared to 2D histology sections. Our results indicate that the cellular composition of the construct affects morphological features of the OCT image.
Exploring Higgs Triplet Models via Vector Boson Scattering at the LHC
Godfrey, Stephen
2010-01-01
We present the results of a study of Higgs triplet boson production arising in the Littlest Higgs, Left-Right Symmetric, and Georgi-Machacek models in the W^\\pm W^\\pm, W^\\pm Z, W^+ W^-, and Z Z channels at the LHC. We focus on the "gold-plated" purely leptonic decay modes and consider the irreducible electroweak, QCD, and t-quark backgrounds, applying a combination of forward-jet-tagging, central-jet-vetoing, and stringent leptonic cuts to suppress the backgrounds. We find that, given the constraints on the triplet vacuum expectation value (vev), considerable luminosity is required to observe Higgs triplet bosons in vector boson scattering. Observing a Higgs triplet at the LHC is most promising in the Georgi-Machacek model due to a weaker constraint on the triplet vev. In this model, we find that a Higgs triplet boson with a mass of 1.0 (1.5) TeV can be observed at the LHC with an integrated luminosity as low as 41 (119) fb^{-1} in the W^\\pm W^\\pm channel and as low as 171 (474) fb^{-1} in the W^\\pm Z channel...
Venkatapathi, Murugesan; Rajwa, Bartek; Ragheb, Kathy; Banada, Padmapriya P.; Lary, Todd; Robinson, J. Paul; Hirleman, E. Daniel
2008-02-01
We describe a model-based instrument design combined with a statistical classification approach for the development and realization of high speed cell classification systems based on light scatter. In our work, angular light scatter from cells of four bacterial species of interest, Bacillus subtilis, Escherichia coli, Listeria innocua, and Enterococcus faecalis, was modeled using the discrete dipole approximation. We then optimized a scattering detector array design subject to some hardware constraints, configured the instrument, and gathered experimental data from the relevant bacterial cells. Using these models and experiments, it is shown that optimization using a nominal bacteria model (i.e., using a representative size and refractive index) is insufficient for classification of most bacteria in realistic applications. Hence the computational predictions were constituted in the form of scattering-data-vector distributions that accounted for expected variability in the physical properties between individual bacteria within the four species. After the detectors were optimized using the numerical results, they were used to measure scatter from both the known control samples and unknown bacterial cells. A multivariate statistical method based on a support vector machine (SVM) was used to classify the bacteria species based on light scatter signatures. In our final instrument, we realized correct classification of B. subtilis in the presence of E. coli,L. innocua, and E. faecalis using SVM at 99.1%, 99.6%, and 98.5%, respectively, in the optimal detector array configuration. For comparison, the corresponding values for another set of angles were only 69.9%, 71.7%, and 70.2% using SVM, and more importantly, this improved performance is consistent with classification predictions.
Venkatapathi, Murugesan; Rajwa, Bartek; Ragheb, Kathy; Banada, Padmapriya P; Lary, Todd; Robinson, J Paul; Hirleman, E Daniel
2008-02-10
We describe a model-based instrument design combined with a statistical classification approach for the development and realization of high speed cell classification systems based on light scatter. In our work, angular light scatter from cells of four bacterial species of interest, Bacillus subtilis, Escherichia coli, Listeria innocua, and Enterococcus faecalis, was modeled using the discrete dipole approximation. We then optimized a scattering detector array design subject to some hardware constraints, configured the instrument, and gathered experimental data from the relevant bacterial cells. Using these models and experiments, it is shown that optimization using a nominal bacteria model (i.e., using a representative size and refractive index) is insufficient for classification of most bacteria in realistic applications. Hence the computational predictions were constituted in the form of scattering-data-vector distributions that accounted for expected variability in the physical properties between individual bacteria within the four species. After the detectors were optimized using the numerical results, they were used to measure scatter from both the known control samples and unknown bacterial cells. A multivariate statistical method based on a support vector machine (SVM) was used to classify the bacteria species based on light scatter signatures. In our final instrument, we realized correct classification of B. subtilis in the presence of E. coli,L. innocua, and E. faecalis using SVM at 99.1%, 99.6%, and 98.5%, respectively, in the optimal detector array configuration. For comparison, the corresponding values for another set of angles were only 69.9%, 71.7%, and 70.2% using SVM, and more importantly, this improved performance is consistent with classification predictions.
Energy Technology Data Exchange (ETDEWEB)
Cwik, T.; Jamnejad, V.; Zuffada, C. [California Institute of Technology, Pasadena, CA (United States)
1994-12-31
The usefulness of finite element modeling follows from the ability to accurately simulate the geometry and three-dimensional fields on the scale of a fraction of a wavelength. To make this modeling practical for engineering design, it is necessary to integrate the stages of geometry modeling and mesh generation, numerical solution of the fields-a stage heavily dependent on the efficient use of a sparse matrix equation solver, and display of field information. The stages of geometry modeling, mesh generation, and field display are commonly completed using commercially available software packages. Algorithms for the numerical solution of the fields need to be written for the specific class of problems considered. Interior problems, i.e. simulating fields in waveguides and cavities, have been successfully solved using finite element methods. Exterior problems, i.e. simulating fields scattered or radiated from structures, are more difficult to model because of the need to numerically truncate the finite element mesh. To practically compute a solution to exterior problems, the domain must be truncated at some finite surface where the Sommerfeld radiation condition is enforced, either approximately or exactly. Approximate methods attempt to truncate the mesh using only local field information at each grid point, whereas exact methods are global, needing information from the entire mesh boundary. In this work, a method that couples three-dimensional finite element (FE) solutions interior to the bounding surface, with an efficient integral equation (IE) solution that exactly enforces the Sommerfeld radiation condition is developed. The bounding surface is taken to be a surface of revolution (SOR) to greatly reduce computational expense in the IE portion of the modeling.
Tornquist, Mattias
The research presented in this thesis covers wave-particle interactions for relativistic (0.5-10 MeV) electrons in Earth's outer radiation belt (r = 3-7 RE, or L-shells: L = 3-7) interacting with magnetospheric Pc-5 (ULF) waves. This dissertation focuses on ideal models for short and long term electron energy and radial position scattering caused by interactions with ULF waves. We use test particle simulations to investigate these wave-particle interactions with ideal wave and magnetic dipole fields. We demonstrate that the wave-particle phase can cause various patterns in phase space trajectories, i.e. local acceleration, and that for a global electron population, for all initial conditions accounted for, has a negligible net energy scattering. Working with GSM polar coordinates, the relevant wave field components are EL, Ephi and Bz, where we find that the maximum energy scattering is 3-10 times more effective for Ephi compared to EL in a magnetic dipole field with a realistic dayside compression amplitude. We also evaluate electron interactions with two coexisting waves for a set of small frequency separations and phases, where it is confirmed that multi-resonant transport is possible for overlapping resonances in phase space when the Chirikov criterion is met (stochasticity parameter K = 1). The electron energy scattering enhances with decreasing frequency separation, i.e. increasing K, and is also dependent on the phases of the waves. The global acceleration is non-zero, can be onset in about 1 hour and last for > 4 hours. The adiabatic wave-particle interaction discussed up to this point can be regarded as short-term scattering ( tau ˜ hours ). When the physical problem extends to longer time scales (tau ˜ days ) the process ceases to be adiabatic due to the introduction of stochastic element in the system and becomes a diffusive process. We show that any mode in a broadband spectrum can contribute to the total diffusion rate for a particular drift
A novel transport based model for wire media and its application to scattering problems
Forati, Ebrahim
Artificially engineered materials, known as metamaterials, have attracted the interest of researchers because of the potential for novel applications. Effective modeling of metamaterials is a crucial step for analyzing and synthesizing devices. In this thesis, we focus on wire medium (both isotropic and uniaxial) and validate a novel transport based model for them. Scattering problems involving wire media are computationally intensive due to the spatially dispersive nature of homogenized wire media. However, it will be shown that using the new model to solve scattering problems can simplify the calculations a great deal. For scattering problems, an integro-differential equation based on a transport formulation is proposed instead of the convolution-form integral equation that directly comes from spatial dispersion. The integro-differential equation is much faster to solve than the convolution equation form, and its effectiveness is confirmed by solving several examples in one-, two-, and three-dimensions. Both the integro-differential equation formulation and the homogenized wire medium parameters are experimentaly confirmed. To do so, several isotropic connected wire medium spheres have been fabricated using a rapid-prototyping machine, and their measured extinction cross sections are compared with simulation results. Wire parameters (period and diameter) are varied to the point where homogenization theory breaks down, which is observed in the measurements. The same process is done for three-dimensional cubical objects made of a uniaxail wire medium, and their measured results are compared with the numerical results based on the new model. The new method is extremely fast compared to brute-force numerical methods such as FDTD, and provides more physical insight (within the limits of homogenization), including the idea of a Debye length for wire media. The limits of homogenization are examined by comparing homogenization results and measurement. Then, a novel
Le Bihan, Nicolas; Margerin, Ludovic
2009-07-01
In this paper, we present a nonparametric method to estimate the heterogeneity of a random medium from the angular distribution of intensity of waves transmitted through a slab of random material. Our approach is based on the modeling of forward multiple scattering using compound Poisson processes on compact Lie groups. The estimation technique is validated through numerical simulations based on radiative transfer theory.
Bihan, Nicolas Le
2009-01-01
In this paper, we present a nonparametric method to estimate the heterogeneity of a random medium from the angular distribution of intensity transmitted through a slab of random material. Our approach is based on the modeling of forward multiple scattering using Compound Poisson Processes on compact Lie groups. The estimation technique is validated through numerical simulations based on radiative transfer theory.
Aleem, F.
1980-03-01
The most recent measurements of the angular distribution in proton-proton elastic scattering at sqrt{s}=27.4, 45 and 62GeV with squared four momentum transfer, -t, extending up to 14(GeV/c)2, have been explained using Van der Waals type model.
Forward modeling of an atmospheric scenario: path characterization in terms of scattering intensity
Energy Technology Data Exchange (ETDEWEB)
Bosisio, Ada Vittoria; Cadeddu, Maria P.; Fionda, Ermanno; Ciotti, Piero
2016-01-01
The knowledge of possible impairments due to atmospheric propagation is of importance in the framework of future 5G mobile networks that use spectrum resource up to the W band. Here, the authors propose the scalar Scatter Indicator (SI), defined as the difference between the simulated TB at 72 GHz and the TB value at the same frequency estimated from a combination of TBs values at 23.8 and 31.4 GHz under assumed scatter-free condition. On the basis of radiosonde profiles observed in Milan, Linate (Italy) in 2005, clear-sky scenarios are used as reference to define a scatter-free TB’s database. A second database of simulated TBs including scattering effects is generated with ARTS to build the SI. Numerical results show that the SI assumes significant positive values with increasing drop effective radius and total liquid water LWP and it can be used to identify the scattering due to hydrometeor
The measurement and modelling of light scattering by phytoplankton cells at narrow forward angles
MacCallum, Iain; Cunningham, Alex; McKee, David
2004-07-01
A procedure has been devised for measuring the angular dependence of light scattering from suspensions of phytoplankton cells at forward angles from 0.25° to 8°. The cells were illuminated with a spatially-filtered laser beam and the angular distribution of scattered light measured by tracking a photodetector across the Fourier plane of a collecting lens using a stepper-motor driven stage. The procedure was calibrated by measuring scattering from latex bead suspensions with known size distributions. It was then used to examine the scattering from cultures of the unicellular algae Isochrysis galbana (4 µm × 5 µm), Dunaliella primolecta (6 µm × 7 µm) and Rhinomonas reticulata (5 µm × 11 µm). The results were compared with the predictions of Mie theory. Excellent agreement was obtained for spherical particles. A suitable choice of spherical-equivalent scattering parameters was required to enable reasonable agreement within the first diffraction lobe for ellipsoidal particles.
Optical model predictions for total cross sections for scattering of neutrons from {sup 40}Ca
Energy Technology Data Exchange (ETDEWEB)
Chinn C.R.; Elster, C.; Thaler, R.M.
1993-10-01
Measurements of neutron total cross sections are both extensive and extremely accurate. Although they should place a strong constraint on theoretically constructed optical models, there are relatively few comparisons of optical model predictions with those experiments. We have calculated total cross sections for neutron scattering from {sup 40}Ca as a function of energy from 100 - 600 MeV laboratory energy with a microscopic first order optical potential derived within the framework of the Watson expansion. Although the results are already in qualitative agreement with the data, the inclusion of medium corrections to the propagator using a recently derived microscopic mean field approach, is essential for correctly predicting the energy dependence given by the experiment. In the region below 200 MeV, where our off-shell tp calculations over predict the experiment, the modification due to the nuclear medium reduces the calculated values, whereas above 200 MeV, these corrections tend to compensate for the under prediction of the off-shell t{rho} results.
Solving a novel multi-skilled project scheduling model by scatter search
Directory of Open Access Journals (Sweden)
Kazemipoor, H.
2013-05-01
Full Text Available A multi-skilled project scheduling problem (MSPSP has generally been presented to schedule information technology projects in deterministic conditions. The contribution of this model is to consider the resources, called staff members. These members are regarded as valuable, renewable, and discrete resources with different multiple skills. The different skills of staff members, as well as the project networks activity requirement of different skills, cause this problem to become a special type of multi-mode resource-constrained project scheduling problem (MM-RCPSP, with a huge number of modes. Taking into account the importance of this issue and the few studies performed on this problem, a novel mathematical model for the MSPSP is presented. Since the complexity of this problem is NP-hard, an efficient scatter search (SS algorithm is developed to solve such a difficult problem. This proposed SS is capable of generating optimised solutions in small sizes, and the excellent solutions in large sizes are compared with the solutions reported by a proposed Tabu search (TS algorithm.
Multi-component modeling of quasielastic neutron scattering from phospholipid membranes
Energy Technology Data Exchange (ETDEWEB)
Wanderlingh, U., E-mail: uwanderlingh@unime.it; D’Angelo, G.; Branca, C.; Trimarchi, A.; Rifici, S.; Finocchiaro, D. [Dipartimento di Fisica e Scienze della Terra, University of Messina, I-98166 Messina (Italy); Conti Nibali, V. [Institute for Physical Chemistry II, Ruhr-University Bochum, Bochum (Germany); Crupi, C. [IPCF-V.le F. Stagno D’Alcontres, n. 37, Messina 98158 (Italy); Ollivier, J. [Institut Laue-Langevin, 6 rue J. Horowitz, BP 156, F-38042 Grenoble (France); Middendorf, H. D. [Clarendon Laboratory, University of Oxford, Oxford (United Kingdom)
2014-05-07
We investigated molecular motions in the 0.3–350 ps time range of D{sub 2}O-hydrated bilayers of 1-palmitoyl-oleoyl-sn-glycero-phosphocholine and 1,2-dimyristoyl-sn-glycero-phosphocholine in the liquid phase by quasielastic neutron scattering. Model analysis of sets of spectra covering scale lengths from 4.8 to 30 Å revealed the presence of three types of motion taking place on well-separated time scales: (i) slow diffusion of the whole phospholipid molecules in a confined cylindrical region; (ii) conformational motion of the phospholipid chains; and (iii) fast uniaxial rotation of the hydrogen atoms around their carbon atoms. Based on theoretical models for the hydrogen dynamics in phospholipids, the spatial extent of these motions was analysed in detail and the results were compared with existing literature data. The complex dynamics of protons was described in terms of elemental dynamical processes involving different parts of the phospholipid chain on whose motions the hydrogen atoms ride.
Cui, Jie; Li, Zhiying; Krems, Roman V
2015-10-21
We consider a problem of extrapolating the collision properties of a large polyatomic molecule A-H to make predictions of the dynamical properties for another molecule related to A-H by the substitution of the H atom with a small molecular group X, without explicitly computing the potential energy surface for A-X. We assume that the effect of the -H →-X substitution is embodied in a multidimensional function with unknown parameters characterizing the change of the potential energy surface. We propose to apply the Gaussian Process model to determine the dependence of the dynamical observables on the unknown parameters. This can be used to produce an interval of the observable values which corresponds to physical variations of the potential parameters. We show that the Gaussian Process model combined with classical trajectory calculations can be used to obtain the dependence of the cross sections for collisions of C6H5CN with He on the unknown parameters describing the interaction of the He atom with the CN fragment of the molecule. The unknown parameters are then varied within physically reasonable ranges to produce a prediction uncertainty of the cross sections. The results are normalized to the cross sections for He - C6H6 collisions obtained from quantum scattering calculations in order to provide a prediction interval of the thermally averaged cross sections for collisions of C6H5CN with He.
Mcphaden, Michael J.; Busalacchi, Antonio J.; Picaut, Joel; Raymond, Gary
1988-01-01
A linear multiple vertical-mode model described by McPhaden et al. (1988) is used to examine potential errors due to data scatter around expendable bathythermograph (XBT) transects in the tropical Pacific. Two methods of sampling are compared. In the first, the model was sampled along approximately straight lines of grid points corresponding to the mean positions of XBT tracks in the eastern, central, and western Pacific; in the second, the model was sampled again at the dates and locations of actual XTB casts for 1979-1983. The model indicates that the data scattered zonally around XBT transects in general can lead to about 2 dyn cm error in dynamic height in composite sections of XBT data. Errors larger than 2 dyn cm occurred in regions where XBT sample spacing in the zonal direction was insufficient to resolve Rossby wave variations in the model.
Hann, Raiford E.
1991-01-01
An equivalent circuit model (ECM) approach is used to predict the scattering behavior of temperature-activated, electrically lossy dielectric layers. The total electrical response of the dielectric (relaxation + conductive) is given by the ECM and used in combination with transmission line theory to compute reflectance spectra for a Dallenbach layer configuration. The effects of thermally-activated relaxation processes on the scattering properties is discussed. Also, the effect of relaxation and conduction activation energy on the electrical properties of the dielectric is described.
Fukukawa, Kenji
2010-01-01
The S-wave effective range parameters of the neutron-deuteron (nd) scattering are derived in the Faddeev formalism, using a nonlocal Gaussian potential based on the quark-model baryon-baryon interaction fss2. The spin-doublet low-energy eigenphase shift is sufficiently attractive to reproduce predictions by the AV18 plus Urbana three-nucleon force, yielding the observed value of the doublet scattering length and the correct differential cross sections below the deuteron breakup threshold. This conclusion is consistent with the previous result for the triton binding energy, which is nearly reproduced by fss2 without reinforcing it with the three-nucleon force.
Rodríguez, Edith; Montilla, Elena; Jaramillo, Mauricio; Solarte, Efraín; Bastidas, Alvaro
2005-10-01
Aerosols are among the most spatially variable components of the atmosphere, and thus their study requires their monitoring over a broad geographic range. The backscattering of light from suspended solid and liquid particles in the atmosphere obeys Mie scattering theory. Light attenuation in the spectral region from 300 to 4000 nm due to Mie scattering exceeds that due to molecular (Rayleigh) scattering and ozone absorption combined. This occurs despite the fact that aerosol particle concentrations in the atmosphere are many orders of magnitude smaller than molecular concentrations. Starting from the characteristics of urban aerosols measured over the city of Cali (Colombia), 3° 30' N, 76° 30' W, with a PM10 particle selector, along with information on meteorological conditions typical of the region, we present the results of a study of light scattering properties generated using a model applied Mie scattering theory to size parameter between 0 and 50, with an increment of 0.01, and Matlab computer code, to simulate and predict measurements with a Lidar system operating at 532 nm.
Energy Technology Data Exchange (ETDEWEB)
Ewen, G.B.L. [Department of Atmospheric, Oceanic and Planetary Physics, University of Oxford, Clarendon Laboratory, Parks Road, Oxford, OX1 3PU (United Kingdom)]. E-mail: gewen@atm.ox.ac.uk; Grainger, R.G. [Department of Atmospheric, Oceanic and Planetary Physics, University of Oxford, Clarendon Laboratory, Parks Road, Oxford, OX1 3PU (United Kingdom); Lambert, A. [National Center for Atmospheric Research (NCAR), Boulder, CO (United States); Baran, A.J. [Met Office, Exeter (United Kingdom)
2005-11-15
The Monte Carlo cloud scattering forward model (McClouds{sub F}M) has been developed to simulate limb radiative transfer in the presence of cirrus clouds, for the purposes of simulating cloud contaminated measurements made by an infrared limb sounding instrument, e.g. the Michelson Interferometer for Passive Atmospheric Sounding (MIPAS). A reverse method three-dimensional Monte Carlo transfer model is combined with a line-by-line model for radiative transfer through the non-cloudy atmosphere to explicitly account for the effects of multiple scattering by the clouds. The ice cloud microphysics are characterised by a size distribution of randomly oriented ice crystals, with the single scattering properties of the distribution determined by accurate calculations accounting for non-spherical habit. A comparison of McClouds{sub F}M simulations and real MIPAS spectra of cirrus shows good agreement. Of particular interest are several noticeable spectral features (i.e. H{sub 2}O absorption lines) in the data that are replicated in the simulations: these can only be explained by upwelling tropospheric radiation scattered into the line-of-sight by the cloud ice particles.
A coupled channel model of scattering with SO(3,1) symmetry
Energy Technology Data Exchange (ETDEWEB)
Levay, P. [School of Physics, University of Melbourne, Parkville (Australia); Department of Theoretical Physics, Institute of Physics, Technical University, Budapest (Hungary); Amos, K. [School of Physics, University of Melbourne, Parkville (Australia)
2001-08-31
An exactly solvable coupled channel scattering problem with SO(3,1) symmetry is presented describing the helicity scattering of a particle with spin s. It is shown that the coupled channel wavefunction is a matrix-valued function with definite group theoretical properties. The scattering phase shifts are calculated for the special values of s=1/2, 1 and 3/2 and the result for general s is conjectured. It is also demonstrated that for an algebraic description of this coupled channel problem both of the independent Casimir operators are needed. (author)
Energy Technology Data Exchange (ETDEWEB)
Nguyen, Hung T. [BioMaPS Institute for Quantitative Biology, Rutgers University, Piscataway, New Jersey 08854 (United States); Pabit, Suzette A.; Meisburger, Steve P.; Pollack, Lois [School of Applied and Engineering Physics, Cornell University, Ithaca, New York 14853 (United States); Case, David A., E-mail: case@biomaps.rutgers.edu [BioMaPS Institute for Quantitative Biology, Rutgers University, Piscataway, New Jersey 08854 (United States); Department of Chemistry and Chemical Biology, Rutgers University, Piscataway, New Jersey 08854 (United States)
2014-12-14
A new method is introduced to compute X-ray solution scattering profiles from atomic models of macromolecules. The three-dimensional version of the Reference Interaction Site Model (RISM) from liquid-state statistical mechanics is employed to compute the solvent distribution around the solute, including both water and ions. X-ray scattering profiles are computed from this distribution together with the solute geometry. We describe an efficient procedure for performing this calculation employing a Lebedev grid for the angular averaging. The intensity profiles (which involve no adjustable parameters) match experiment and molecular dynamics simulations up to wide angle for two proteins (lysozyme and myoglobin) in water, as well as the small-angle profiles for a dozen biomolecules taken from the BioIsis.net database. The RISM model is especially well-suited for studies of nucleic acids in salt solution. Use of fiber-diffraction models for the structure of duplex DNA in solution yields close agreement with the observed scattering profiles in both the small and wide angle scattering (SAXS and WAXS) regimes. In addition, computed profiles of anomalous SAXS signals (for Rb{sup +} and Sr{sup 2+}) emphasize the ionic contribution to scattering and are in reasonable agreement with experiment. In cases where an absolute calibration of the experimental data at q = 0 is available, one can extract a count of the excess number of waters and ions; computed values depend on the closure that is assumed in the solution of the Ornstein–Zernike equations, with results from the Kovalenko–Hirata closure being closest to experiment for the cases studied here.
Ratio of Real to Imaginary for pp and (p)p Elastic Scatterings in QCD Inspired Model
Institute of Scientific and Technical Information of China (English)
LU Juan; MA Wei-Xing; HE Xiao-Rong
2007-01-01
We use the QCD inspired model to analyze the ratio of the real to the imaginary for pp and 5p elastic scatterings. A calculation for the ratio of the real to the imaginary is performed in which the contributions from gluongluon interaction, quark-quark interaction, quark-gluon interaction, and odd eikonal profile function are included. Our results show that the QCD inspired model gives a good fit to the LHC experimental data.
Nonlinear kinetic modeling of stimulated Raman scattering in a multidimensional geometry
Energy Technology Data Exchange (ETDEWEB)
Benisti, D.; Morice, O.; Gremillet, L.; Friou, A.; Lefebvre, E. [CEA, DAM, DIF F-91297 Arpajon (France)
2012-05-15
In this paper, we derive coupled envelope equations modeling the growth of stimulated Raman scattering (SRS) in a multi-dimensional geometry and accounting for nonlinear kinetic effects. In particular, our envelope equations allow for the nonlinear reduction of the Landau damping rate, whose decrease with the plasma wave amplitude depends on the rate of side-loss. Account is also made of the variations in the extent of the plasma wave packet entailed by the collisionless dissipation due to trapping. The dephasing between the electron plasma wave (EPW) and the laser drive, as well as the self-focussing of the plasma wave, both induced by the EPW nonlinear frequency shift, are also included in our envelope equations. These equations are solved in a multi-dimensional geometry using our code dubbed BRAMA, whose predictions regarding the evolution of Raman reflectivity as a function of the laser intensity are compared against previously published particle in cell results, thus illustrating the ability of BRAMA simulations to provide the correct laser threshold intensity for SRS as well as the right order of magnitude of Raman reflectivity above threshold.
Two-photon-exchange effects in the unpolarized μ p scattering within a hadronic model
Zhou, Hai-Qing
2017-02-01
In this work, the two-photon-exchange (TPE) effects in the unpolarized μ p scattering are discussed within the hadronic model where the intermediate states N ,Δ , and σ are considered. The contribution from the N intermediate is close to the results given by Tomalak and Vanderhaeghen [Phys. Rev. D 90, 013006 (2014)], 10.1103/PhysRevD.90.013006 at small Q , and there is a sizable difference when Q >0.25 GeV (where Q2 is the four-momentum transfer). The contributions from the Δ and the σ intermediate states are much smaller than that from the N intermediate at small Q . In the kinematic region with ki⊆[0.01 ,0.3 ] GeV and Q ≤0.4 GeV (where ki is the three-momentum of initial muon in the laboratory frame), a naive expression for the TPE contributions is given, which can be used directly for other analysis.
Jacques, David A; Guss, J Mitchell; Svergun, Dmitri I; Trewhella, Jill
2012-06-01
Small-angle scattering is becoming a mainstream technique for structural molecular biology. As such, it is important to establish guidelines for publication that will ensure that there is adequate reporting of the data and its treatment so that reviewers and readers can independently assess the quality of the data and the basis for any interpretations presented. This article presents a set of preliminary guidelines that emerged after consultation with the IUCr Commission on Small-Angle Scattering and other experts in the field and discusses the rationale for their application. At the 2011 Congress of the IUCr in Madrid, the Commission on Journals agreed to adopt these preliminary guidelines for the presentation of biomolecular structures from small-angle scattering data in IUCr publications. Here, these guidelines are outlined and the reasons for standardizing the way in which small-angle scattering data are presented.
A Model-Based Scatter Artifacts Correction for Cone Beam CT
Zhao, Wei; Zhu, Jun; Wang, Luyao; Xing, Lei
2016-01-01
The purpose of this work is to provide a fast and accurate scatter artifacts correction algorithm for cone beam CT (CBCT) imaging. The method starts with an estimation of coarse scatter profiles for a set of CBCT data in either image domain or projection domain. A denoising algorithm designed specifically for Poisson signals is then applied to derive the final scatter distribution. Qualitative and quantitative evaluations using thorax and abdomen phantoms with Monte Carlo (MC) simulations, experimental Catphan phantom data, and in vivo human data acquired for a clinical image guided radiation therapy were performed. Results show that the proposed algorithm can significantly reduce scatter artifacts and recover the correct HU in either projection domain or image domain. For the MC thorax phantom study, four components segmentation yield the best results, while the results of three components segmentation are still acceptable. For the Catphan phantom data, the mean value over all pixels in the residual image is...
Energy Technology Data Exchange (ETDEWEB)
Webber, J. Beau W., E-mail: J.B.W.Webber@kent.ac.uk
2013-05-15
Neutron scattering offers a length-scale-independent method of probing structured matter on an atomic scale through nano-scale to meso-scale. A protocol is presented that provides a versatile method of determining structure, by comparison of measured and calculated neutron scattering, for any structural distribution that can be described algebraically or numerically, requiring no particular model other than the model of the structure, and needing no adjustable parameters other than the scale and other parameters describing the physical model. The method enables the direct comparison of measured and calculated scattering from structured matter: from simple finite and infinite bodies, from extended regular array of pores, or from extended arrays of pores with a partially randomised character. Examples are given for the radial distributions of a range of regular bodies, of large arrays of highly ordered porous materials such as templated SBA-15 and MCM-41 silicas, as well as for more disordered materials such as sol–gel silicas. Monte Carlo integration of the calculated scattering for ensembles of up to about 100,000 pores has been studied using these techniques. The method enables the calculation of the solid–solid density correlation function G(r) for model systems, and hence, by Fourier transformation, the expected scattering. Example measured scattering is compared with the calculated scattering, with further data presented in a related paper. The technique allows the direct calculation and comparison with measurement of all three of the main pore structural parameters: lattice spacing, pore diameter, and pore-wall thickness. Example SBA-15 wide and small angle neutron scattering (SANS) data, measured on NIMROD (the Near and InterMediate Range Order Diffractometer at ISIS), is used as an initial evaluation of the applicability of the techniques. The method is also applicable to determining structure by comparing calculating with measured diffraction broadening
Gyöngy, Miklós; Makra, Ákos
2015-06-01
The shift-invariant convolution model of ultrasound is widely used in the literature, for instance to generate fast simulations of ultrasound images. However, comparison of the resulting simulations with experiments is either qualitative or based on aggregate descriptors such as envelope statistics or spectral components. In the current work, a planar arrangement of 49-μm polystyrene microspheres was imaged using macrophotography and a 4.7-MHz ultrasound linear array. The macrophotograph allowed estimation of the scattering function (SF) necessary for simulations. Using the coefficient of determination R(2) between real and simulated ultrasound images, different estimates of the SF and point spread function (PSF) were tested. All estimates of the SF performed similarly, whereas the best estimate of the PSF was obtained by Hanningwindowing the deconvolution of the real ultrasound image with the SF: this yielded R(2) = 0.43 for the raw simulated image and R(2) = 0.65 for the envelope-detected ultrasound image. R(2) was highly dependent on microsphere concentration, with values of up to 0.99 for regions with scatterers. The results validate the use of the shift-invariant convolution model for the realistic simulation of ultrasound images. However, care needs to be taken in experiments to reduce the relative effects of other sources of scattering such as from multiple reflections, either by increasing the concentration of imaged scatterers or by more careful experimental design.
Kiss, Annamaria; Kuramoto, Yoshio; Hoshino, Shintaro
2011-01-01
Accurate numerical results are derived for transport properties of Kondo impurity systems with potential scattering and orbital degeneracy. Using the continuous-time quantum Monte Carlo (CT-QMC) method, static and dynamic physical quantities are derived in a wide temperature range across the Kondo temperature T_K. With strong potential scattering, the resistivity tends to decrease with decreasing temperature, in contrast to the ordinary Kondo effect. Correspondingly, the quasi-particle densit...
Perera, M. Nilusha M. N.; Schmidt, Daniel; Gibbs, W. E. Keith; Juodkazis, Saulius; Stoddart, Paul R.
2016-09-01
Surface-enhanced Raman scattering (SERS) is drawing increasing interest in fields such as chemical and biomolecular sensing, nanoscale plasmonic engineering and surface science. In addition to the electromagnetic and chemical enhancements in SERS, several studies have reported a "back-side" enhancement when nanostructures are excited through a transparent base rather than directly through air. This additional enhancement has been attributed to a local increase in the electric field for propagation from high to low refractive index media. In this study, Mueller matrix ellipsometry was used to derive the effective optical constants of Ag nanostructures fabricated by thermal evaporation at oblique angles. The results confirm that the effective optical constants of the nanostructured Ag film depart substantially from the bulk properties. Detailed analysis suggests that the optical constants of the nano-island Ag structures exhibit uniaxial optical properties with the optical axis inclined from the substrate normal towards the deposition direction of the vapour flux. The substrates were functionalized with thiophenol and used to measure the wavelength dependence of the additional SERS signal. Further, a model based on the Fresnel equations was developed, using the Ag film optical constants and thickness as determined by ellipsometry. Both experimental data and the model show a significant additional enhancement in the back-side SERS, blue shifted from the plasmon resonance of the nanostructures. This information will be useful for a range of applications where it is necessary to understand the effective optical behaviour of thin films and in designing miniaturized optical fibre sensors for remote sensing applications.
Electron scattering cross sections for the modelling of oxygen-containing plasmas*
Alves, Luís Lemos; Coche, Philippe; Ridenti, Marco Antonio; Guerra, Vasco
2016-06-01
This work proposes a set of electron scattering cross sections for molecular and atomic oxygen, with interest for the modelling of oxygen-containing plasmas. These cross sections, compiled for kinetic energies up to 1 keV, are part of the IST-LISBON database with LXCat, being used as input data to the LoKI (LisbOn KInetics) numerical code. The cross sections for ground-state molecular oxygen describe elastic and inelastic collision mechanisms, the latter including rotational excitations/de-excitations (treated using either a discrete or a continuous approach), vibrational and electronic excitations (including dissociation), dissociative attachment and ionisation. This set yields calculated swarm parameters that reproduce measurements within 5-20% (transport parameters) and within a factor of 2 difference (Townsend coefficients), for reduced electric fields in the range 10-3-103 Td. The cross sections describing the kinetics of atomic oxygen by electron-impact comprise elastic mechanisms, electronic excitation and ionisation from O(3P) ground-state, dissociation of O2(X,a,b) (including dissociative ionisation and attachment) and of O3, and detachment. These cross sections are indirectly validated, together with other elementary data for oxygen, by comparing the densities of O((4S0)3 p 5P) obtained from the self-consistent modelling and from calibrated optical emission spectroscopy diagnostics of microwave-sustained micro-plasmas in dry air (80% N2: 20% O2), produced using a surface-wave excitation (2.45 GHz frequency) within a small radius capillary ( R = 345 μm) at low pressure ( p = 300 Pa). The calculated densities are in good qualitative agreement with measurements, overestimating them by a factor ˜1.5.
Note on neutron scattering and the optical model near A = 208. [0. 6 to 1. 0 MeV
Energy Technology Data Exchange (ETDEWEB)
Guenther, P.; Havel, D.; Smith, A.
1976-09-01
Elastic neutron scattering cross sections of /sup 206/Pb, /sup 207/Pb, /sup 208/Pb and /sup 209/Bi are measured at incident neutron energy intervals of approx. 25 keV from 0.6 to 1.0 MeV with resolutions of approx. 25 keV. Optical model parameters are obtained from the energy-averaged experimental results for each of the isotopes. The observed elastic-neutron-scattering distributions and derived parameters for the lead isotopes (doubly magic or neutron holes in the closed shell) tend to differ from those of /sup 209/Bi (doubly closed shell plus a proton). These potentials, derived in the approx. spherical region of A approximately 208, are extrapolated for the analysis of total and scattering cross sections of /sup 238/U introducing only a small N-Z/A dependence and the known deformation of /sup 238/U. Good descriptions of /sup 238/U total cross sections are obtained from a few hundred keV to 10.0 MeV and the prediction of measured scattering distributions in the low MeV region are as suitable as frequently reported with other specially developed potentials.
Bouzin, Margaux; Sironi, Laura; Chirico, Giuseppe; D'Alfonso, Laura; Inverso, Donato; Pallavicini, Piersandro; Collini, Maddalena
2015-12-01
Anisotropic metallic nanoparticles have been devised as powerful potential tools for in vivo imaging, photothermal therapy, and drug delivery thanks to plasmon-enhanced absorption and scattering cross sections, ease in synthesis and functionalization, and controlled cytotoxicity. The rational design of all these applications requires the characterization of the nanoparticles intracellular trafficking pathways. In this work, we exploit live-cell time-lapse confocal reflectance microscopy and image correlation in both direct and reciprocal space to investigate the intracellular transport of branched gold nanostars (GNSs). Different transport mechanisms, spanning from pure Brownian diffusion to (sub-)ballistic superdiffusion, are revealed by temporal and spatio-temporal image correlation spectroscopy on the tens-of-seconds timescale. According to these findings, combined with numerical simulations and with a Bayesian (hidden Markov model-based) analysis of single particle tracking data, we ascribe the superdiffusive, subballistic behavior characterizing the GNSs dynamics to a two-state switching between Brownian diffusion in the cytoplasm and molecular motor-mediated active transport. For the investigation of intermittent-type transport phenomena, we derive an analytical theoretical framework for Fourier-space image correlation spectroscopy (kICS). At first, we evaluate the influence of all the dynamic and kinetic parameters (the diffusion coefficient, the drift velocity, and the transition rates between the diffusive and the active transport regimes) on simulated kICS correlation functions. Then we outline a protocol for data analysis and employ it to derive whole-cell maps for each parameter underlying the GNSs intracellular dynamics. Capable of identifying even simpler transport phenomena, whether purely diffusive or ballistic, our intermittent kICS approach allows an exhaustive investigation of the dynamics of GNSs and biological macromolecules.
Advanced ensemble modelling of flexible macromolecules using X-ray solution scattering.
Tria, Giancarlo; Mertens, Haydyn D T; Kachala, Michael; Svergun, Dmitri I
2015-03-01
Dynamic ensembles of macromolecules mediate essential processes in biology. Understanding the mechanisms driving the function and molecular interactions of 'unstructured' and flexible molecules requires alternative approaches to those traditionally employed in structural biology. Small-angle X-ray scattering (SAXS) is an established method for structural characterization of biological macromolecules in solution, and is directly applicable to the study of flexible systems such as intrinsically disordered proteins and multi-domain proteins with unstructured regions. The Ensemble Optimization Method (EOM) [Bernadó et al. (2007 ▶). J. Am. Chem. Soc. 129, 5656-5664] was the first approach introducing the concept of ensemble fitting of the SAXS data from flexible systems. In this approach, a large pool of macromolecules covering the available conformational space is generated and a sub-ensemble of conformers coexisting in solution is selected guided by the fit to the experimental SAXS data. This paper presents a series of new developments and advancements to the method, including significantly enhanced functionality and also quantitative metrics for the characterization of the results. Building on the original concept of ensemble optimization, the algorithms for pool generation have been redesigned to allow for the construction of partially or completely symmetric oligomeric models, and the selection procedure was improved to refine the size of the ensemble. Quantitative measures of the flexibility of the system studied, based on the characteristic integral parameters of the selected ensemble, are introduced. These improvements are implemented in the new EOM version 2.0, and the capabilities as well as inherent limitations of the ensemble approach in SAXS, and of EOM 2.0 in particular, are discussed.
Advanced ensemble modelling of flexible macromolecules using X-ray solution scattering
Directory of Open Access Journals (Sweden)
Giancarlo Tria
2015-03-01
Full Text Available Dynamic ensembles of macromolecules mediate essential processes in biology. Understanding the mechanisms driving the function and molecular interactions of `unstructured' and flexible molecules requires alternative approaches to those traditionally employed in structural biology. Small-angle X-ray scattering (SAXS is an established method for structural characterization of biological macromolecules in solution, and is directly applicable to the study of flexible systems such as intrinsically disordered proteins and multi-domain proteins with unstructured regions. The Ensemble Optimization Method (EOM [Bernadó et al. (2007. J. Am. Chem. Soc. 129, 5656–5664] was the first approach introducing the concept of ensemble fitting of the SAXS data from flexible systems. In this approach, a large pool of macromolecules covering the available conformational space is generated and a sub-ensemble of conformers coexisting in solution is selected guided by the fit to the experimental SAXS data. This paper presents a series of new developments and advancements to the method, including significantly enhanced functionality and also quantitative metrics for the characterization of the results. Building on the original concept of ensemble optimization, the algorithms for pool generation have been redesigned to allow for the construction of partially or completely symmetric oligomeric models, and the selection procedure was improved to refine the size of the ensemble. Quantitative measures of the flexibility of the system studied, based on the characteristic integral parameters of the selected ensemble, are introduced. These improvements are implemented in the new EOM version 2.0, and the capabilities as well as inherent limitations of the ensemble approach in SAXS, and of EOM 2.0 in particular, are discussed.
Dong, R; Zhu, Z; Hartmann, L; Whitney, B; Brandt, T; Muto, T; Hashimoto, J; Grady, C; Follette, K; Kuzuhara, M; Tanii, R; Itoh, Y; Thalmann, C; Wisniewski, J; Mayama, S; Janson, M; Abe, L; Brandner, W; Carson, J; Egner, S; Feldt, M; Goto, M; Guyon, O; Hayano, Y; Hayashi, M; Hayashi, S; Henning, T; Hodapp, K W; Honda, M; Inutsuka, S; Ishii, M; Iye, M; Kandori, R; Knapp, G R; Kudo, T; Kusakabe, N; Matsuo, T; McElwain, M W; Miyama, S; Morino, J -I; Moro-Martin, A; Nishimura, T; Pyo, T -S; Suto, H; Suzuki, R; Takami, M; Takato, N; Terada, H; Tomono, D; Turner, E L; Watanabe, M; Yamada, T; Takami, H; Usuda, T; Tamura, M
2012-01-01
Transitional circumstellar disks around young stellar objects have a distinctive infrared deficit around 10 microns in their Spectral Energy Distributions (SED), recently measured by the Spitzer Infrared Spectrograph (IRS), suggesting dust depletion in the inner regions. These disks have been confirmed to have giant central cavities by imaging of the submillimeter (sub-mm) continuum emission using the Submillimeter Array (SMA). However, the polarized near-infrared scattered light images for most objects in a systematic IRS/SMA cross sample, obtained by HiCIAO on the Subaru telescope, show no evidence for the cavity, in clear contrast with SMA and Spitzer observations. Radiative transfer modeling indicates that many of these scattered light images are consistent with a smooth spatial distribution for micron-sized grains, with little discontinuity in the surface density of the micron-sized grains at the cavity edge. Here we present a generic disk model that can simultaneously account for the general features in...
Armstrong, Cameron R; David, John A; Thompson, John R
2015-07-13
We present a simple numerical model that is used in conjunction with a systematic algorithm for parameter optimization to understand the three-dimensional stochastic intensity dynamics of stimulated Brillouin scattering in a two-mode optical fiber. The primary factors driving the complex dynamics appear to be thermal density fluctuations, transverse pump fluctuations, and asymmetric transverse mode fractions over the beam cross-section.
The one-pion-exchange potential in the three-body model of nucleon-nucleon scattering
Garcilazo, Humberto
1981-02-01
We derive the one-pion-exchange potential in the three-body model of nucleon-nucleon scattering in which the nucleon is treated as a bound state of a pion and a nucleon, and show that it has the same form as the usual Yukawa OPEP derived from field theory, except that its range is energy dependent and it becomes complex above the pion-production threshold.
Van der Waals Type Model and Structure in bar{p}p Elastic Scattering at High Energies
Aleem, F.
1983-10-01
The most recent measurements of the angular distribution for bar{p}p elastic scattering at pL=50, 100 and 200 GeV/ c which show a structure near -t=1.4 (GeV/ c)2, with squared four momentum transter -t extended to 5(GeV/ c)2, and the total cross section data for 50 <= pL <= 280GeV/ c have been simultaneously fitted by using the Van der Waals type model.
Dupuis, M.; Karataglidis, S.; Bauge, E.; Delaroche, J.-P.; Gogny, D.
2008-07-01
Differential cross sections from fully microscopic calculations of inelastic proton scattering off 208Pb are compared to experimental scattering data for incident proton energies between 65 and 201 MeV. The required nucleon-nucleus interactions were formed by folding nuclear structure information with a reliable nucleon-nucleon effective interaction that has no adjustable parameter. The absence of phenomenological normalisation in our approach offers the possibility to interpret with confidence the calculated results in terms of the quality of the underlying nuclear structure description: a feature that had been reserved, until recently, to the electron probe. We have used this method to investigate the effect of long range correlations embedded in excited states on calculated inelastic observables and demonstrate the sensitivity of nucleon scattering predictions to details of the nuclear structure.
Kondratyuk, S; Kubodera, K; Myhrer, F; Scholten, O
2004-01-01
The Adler-Weisberger and Goldberger-Miyazawa-Oehme sum rules are calculated within a relativistic, unitary and crossing symmetric dynamical model for pion-nucleon scattering using two different methods: (1) by evaluating the scattering amplitude at the corresponding low-energy kinematics and (2) by
Indian Academy of Sciences (India)
I Ahmad; M R Arafah
2006-03-01
Elastic scattering of 800 MeV/c pions by 12C has been studied in the diffraction model with a view to determine pion optical potential by the method of inversion. Finding an earlier diffraction model analysis to be deficient in some respects, we propose a Glauber model based parametrization for the elastic -matrix and show that it provides an exceedingly good fit to the pion-carbon data. The proposed elastic -matrix gives a closed expression for the pion-12C optical potential by the method of inversion in the high energy approximation.
A simple nonbinary scattering model applicable to atomic collisions is crystals at 1ow energies
DEFF Research Database (Denmark)
Andersen, Hans Henrik; Sigmund, Peter
1966-01-01
the elliptic to the spherical potential are investigated. Special attention is paid to proper definitions of collision time and collision length which are important in collisions in crystals. Limitations to classical scattering arising from the uncertainty principle prove to be more serious than assumed......Presents the solution of a special scattering problem which may be important in the theory of slowing-down of atomic particles in crystals. A projectile moves along the centre axis of a regular ring of n equal atoms which are free and do not interact with each other. The interaction between...
Institute of Scientific and Technical Information of China (English)
Cao Meng; Wang Fang; Liu Jing; Zhang Hai-Bo
2012-01-01
We present a novel numerical model and simulate preliminarily the charging process of a polymer subjected to electron irradiation of several 10 keV.The model includes the simultaneous processes of electron scattering and ambipolar transport and the influence of a self-consistent electric field on the scattering distribution of electrons.The dynamic spatial distribution of charges is obtained and validated by existing experimental data.Our simulations show that excess negative charges are concentrated near the edge of the electron range.However,the formed region of high charge density may extend to the surface and bottom of a kapton sample,due to the effects of the electric field on electron scattering and charge transport,respectively.Charge trapping is then demonstrated to significantly influence the charge motion.The charge distribution can be extended to the bottom as the trap density decreases.Charge accumulation is therefore balanced by the appearance and increase of leakage current.Accordingly,our model and numerical simulation provide a comprehensive insight into the charging dynamics of a polymer irradiated by electrons in the complex space environment.
Radak, Brian K; Yockel, Scott; Kim, Dongwook; Schatz, George C
2009-07-01
To better understand the reactivity of gases with liquid surfaces, experimentalists have recently probed the reactive scattering of atomic fluorine at the surface of liquid squalane (C(30)H(62)). In this paper we further this research by simulating this scattering process at collision energies of 0.5 and 1.0 eV using a hybrid QM/MM molecular dynamics scheme. To model the structure of the liquid surface, classical molecular dynamics calculations were performed utilizing the OPLS-AA force field. During the F + squalane molecular dynamics simulation, QM/MM calculations are performed at every trajectory step by combining the MSINDO semiempirical Hamiltonian with OPLS-AA and using a dynamic partitioning of the atoms in the QM or MM regions via a "seed atom" method. This computational model provides a type of "on-the-fly" direct dynamics applicable to larger scale chemical processes that include the making/breaking of chemical bonds not available in standard force field models. Our results show that H abstraction is the only reactive scattering pathway and that most trajectories result in reactive scattering. Reaction statistics at the squalane surface are discussed, including variation of the results with incident angle and collision energy, and the probability of reaction as a function of carbon atom type, collision depth, and residence time. Product states, including angular distributions and final translational and rovibrational energies, are also considered and found to be significantly affected by the exothermic reaction energy for H abstraction. The vibrational distributions are in good agreement with recent experiments, but the rotational distributions are dominated by a nonthermal component while the experiments, which involve thermal incident energies, show comparable thermal and nonthermal contributions. Results for O + squalane at 1.0 eV, which we also present, show analogous comparisons with experiment, with OH vibrational distributions which are cold and
Incoherent neutron-scattering determination of hydrogen content: Theory and modeling
Perego, R.C.; Blaauw, M.
2005-01-01
Hydrogen concentrations of 0 up to 350 mg/kg in a titanium alloy have been determined at National Institute of Standards and Technology (NIST) with neutron incoherent scattering (NIS) and with cold neutron prompt gamma activation analysis. The latter is a well-established technique, while the former
Variations in the optical scattering properties of skin in murine animal models
Calabro, Katherine; Curtis, Allison; Galarneau, Jean-Rene; Krucker, Thomas; Bigio, Irving J.
2011-03-01
In the work presented here, the optical scattering properties of mouse skin are investigated in depth with the use of Elastic Scattering Spectroscopy (ESS). In particular, sources of variation that lead to experimental error are identified and examined. The thickness of the dermal layer of the skin is determined to be the primary source of variation due to its high collagen content. Specifically, gender differences in skin thickness are found to cause increases in the reflectance and scattering coefficient value by a factor of two in males as opposed to females. Changes in the hair growth cycle are found to influence scattering strength not only due to changes in skin thickness, but also from melanin collection in hair follicles. Because direct and/or indirect measurement of mouse skin is common in the development of novel biomedical optics techniques (optical biopsy, molecular imaging, in vivo monitoring of glucose/blood oxygenation, etc.), the purpose of this work is to identify sources of experimental variation that may arise in these studies such that care can be taken to avoid or compensate for their affects.
Van Heijkamp, L.F.
2011-01-01
In this study non-invasive neutron scattering techniques are used on soft condensed matter, probing colloidal length scales. Neutrons penetrate deeply into matter and have a different interaction with hydrogen and deuterium, allowing for tunable contrast using light and heavy water as solvents. The
2017-03-06
which amount to discrete finite-differencing of the Green functions) can be used to produce arbitrary (user-prescribed) algebraic convergence order...high-order algorithm for the solution of surface scattering problems: basic implementation, tests and applications, J. Computat. Phys. 169, 80–110
Van Heijkamp, L.F.
2011-01-01
In this study non-invasive neutron scattering techniques are used on soft condensed matter, probing colloidal length scales. Neutrons penetrate deeply into matter and have a different interaction with hydrogen and deuterium, allowing for tunable contrast using light and heavy water as solvents. The
A Model Independent Approach to Semi-Inclusive Deep Inelastic Scattering
Christova, E; Christova, Ekaterina; Leader, Elliot
2005-01-01
We present a method for extraction of detailed information on polarized quark densities from semi-inclusive deep inelastic scattering l+N -> l+h+X, in both LO and NLO QCD without any assumptions about fragmentation functions and polarized sea densities. The only symmetries utilised are charge conjugation and isotopic spin invariance of strong interactions.
A Benchmark Calculation for the Nd Scattering with a Model Three-Body Force
Phyu, Aye Mya; Golak, Jacek; Oo, Htun Htun; Witala, Henryk; Gloeckle, Walter
2012-01-01
Using the complex energy method, the problem of nucleon-deuteron scattering is solved with a simple three-body force having a separable form. Our results are compared with the results of modern direct two-variable calculations and a good agreement is found. This forms a firm base for other applications of the complex energy method.
Somerville, W R C; Ru, E C Le
2015-01-01
We provide a detailed user guide for SMARTIES, a suite of Matlab codes for the calculation of the optical properties of oblate and prolate spheroidal particles, with comparable capabilities and ease-of-use as Mie theory for spheres. SMARTIES is a Matlab implementation of an improved T-matrix algorithm for the theoretical modelling of electromagnetic scattering by particles of spheroidal shape. The theory behind the improvements in numerical accuracy and convergence is briefly summarised, with reference to the original publications. Instructions of use, and a detailed description of the code structure, its range of applicability, as well as guidelines for further developments by advanced users are discussed in separate sections of this user guide. The code may be useful to researchers seeking a fast, accurate and reliable tool to simulate the near-field and far-field optical properties of elongated particles, but will also appeal to other developers of light-scattering software seeking a reliable benchmark for...
Kanematsu, Nobuyuki
2008-01-01
Dose calculation in treatment planning of radiotherapy with protons and heavier ions deals with a large volume of path integrals involving a scattering power of body tissue. This work provides a simple formulation for such demanding applications. Empirical linearity between RMS end-point displacement and range of incident particles in water was translated into a linear formula, from which a simple scattering power was derived. The simplicity enabled analytical formulation for ions stopping in water, which was designed to be equivalent with the extended Highland model and agreed with measurements better than 2% or 0.02 cm in RMS displacement. The simplicity will also improve the efficiency of numerical path integrals in the presence of heterogeneity.
Elastic scattering phenomenology
Energy Technology Data Exchange (ETDEWEB)
Mackintosh, R.S. [The Open University, School of Physical Sciences, Milton Keynes (United Kingdom)
2017-04-15
We argue that, in many situations, fits to elastic scattering data that were historically, and frequently still are, considered ''good'', are not justifiably so describable. Information about the dynamics of nucleon-nucleus and nucleus-nucleus scattering is lost when elastic scattering phenomenology is insufficiently ambitious. It is argued that in many situations, an alternative approach is appropriate for the phenomenology of nuclear elastic scattering of nucleons and other light nuclei. The approach affords an appropriate means of evaluating folding models, one that fully exploits available empirical data. It is particularly applicable for nucleons and other light ions. (orig.)
Shell-model study on event rates of lightest supersymmetric particles scattering off 83Kr and 125Te
Pirinen, P.; Srivastava, P. C.; Suhonen, J.; Kortelainen, M.
2016-05-01
We investigate the elastic and inelastic scattering of lightest supersymmetric particle (LSP) dark matter off two possible target nuclei, 83Kr and 125Te. For the nuclear-structure calculations, we employ the nuclear shell model using recently generated realistic interactions. We have condensed the nuclear-physics contribution to a set of nuclear-structure factors that are independent of the adopted supersymmetric (SUSY) model. Total event rates are then easily calculated by combining the nuclear-structure factors with SUSY parameters of choice. In particular, 125Te shows promise as a detector material with both the elastic and inelastic channels yielding an appreciable nuclear response.
Yang, Shin Nan; Tiator, L
2011-01-01
We present the results on P11 resonances obtained with Dubna-Mainz-Taipei (DMT) dynamical model for pion-nucleon scattering and pion electromagnetic production. The extracted values agree well, in general, with PDG values. One pole is found corresponding to the Roper resonance and two more resonances are definitely needed in DMT model. We further find indication for a narrow P11 resonance at around 1700 MeV with a width of around 50 MeV in both pi-N and gamma-pi reactions.
Unified Model for Small-t and High-t Scattering at High Energies: Predictions at RHIC and LHC
Martynov, Evgenij
2007-01-01
The urgency of predictions in large-t region at LHC stimulated us to present a unified model of small and high t scattering at high energies. Our model is based upon a safe theoretical ground: analyticity, unitarity, Regge behavior, gluon exchange and saturation of bounds established in axiomatic quantum field theory. We make precise predictions for the behavior of the differential cross sections at high t, the evolution of the dip-shoulder structure localized in the region of -t between 0.5 and 0.8 GeV**2 and the radical violation of the exponential behavior of the first diffraction cone at small t.
Pinel, Nicolas; Bourlier, Christophe; Le Bastard, Cédric
2014-05-01
This paper presents the rigorous efficient PILE (Propagation-Inside-Layer Expansion) numerical method [1] and an extension of the Ament model [2] to calculate the field scattered by three homogeneous media separated by two random rough surfaces. Here, the study is applied to ground penetrating radar (GPR) (nadir angle, wide band) for nondestructive survey by taking the roughness of the surfaces into account and by calculating the contribution of each echo coming from the multiple scattering inside the layer. Applications to roadways and geoscience are investigated. The PILE method starts from the Method of Moments (MoM), and the impedance matrix is inverted by blocks from the Taylor series expansion of the inverse of the Schur complement. Its great advantage is that it is rigorous, with a simple formulation and has a straightforward physical interpretation. Actually, this last property relies on the fact that each block of the impedance matrix is linked to a particular and quasi-independent physical process occurring during the multiple scattering between the two rough surfaces. Furthermore, the PILE method allows us to use any acceleration algorithm (MLFMM, BMIA/CAG, Forward-Backward with or without Spectral Acceleration, etc.) developed for a single interface. In addition, an asymptotic approach is extended to rough layered media: the scalar Kirchhoff-tangent plane approximation (SKA), for calculating the coherent scattering from the rough layer. The numerical rigorous PILE method is used as a reference to validate this asymptotic model. The study focuses on 2D problems with so-called 1D surfaces, for computational ease of the reference numerical method. Nevertheless, it must be highlighted that the SKA approach can readily be applied to 3D problems. This approach is applied to rough layers with two slightly rough surfaces characterized by either Gaussian or exponential correlation functions. The height probability density function (PDF) is assumed to be Gaussian
Energy Technology Data Exchange (ETDEWEB)
Kostorz, G. [Eidgenoessische Technische Hochschule, Angewandte Physik, Zurich (Switzerland)
1996-12-31
While Bragg scattering is characteristic for the average structure of crystals, static local deviations from the average lattice lead to diffuse elastic scattering around and between Bragg peaks. This scattering thus contains information on the occupation of lattice sites by different atomic species and on static local displacements, even in a macroscopically homogeneous crystalline sample. The various diffuse scattering effects, including those around the incident beam (small-angle scattering), are introduced and illustrated by typical results obtained for some Ni alloys. (author) 7 figs., 41 refs.
Analysis of acoustic scattering from fluid bodies using a multipoint source model.
Boag, A; Leviatan, Y
1989-01-01
A moment-method solution is presented for the problem of acoustic scattering from homogeneous fluid bodies. It uses fictitious isotropic point sources to simulate both the field scattered by the body and the field inside the body and, in turn, point-matches the continuity conditions for the normal component of the velocity and for the pressure across the surface of the body. The procedure is simple to execute and is general in that bodies of arbitrary smooth shape can be handled effectively. Perfectly rigid bodies are treated as reduced cases of the general procedure. Results are given and compared with available analytic solutions, which demonstrate the very good performance of the procedure.
Scattering of electromagnetic waves by many thin cylinders: theory and computational modeling
Ramm, A G
2015-01-01
Electromagnetic (EM) wave scattering by many parallel infinite cylinders is studied asymptotically as a tends to 0, where a is the radius of the cylinders. It is assumed that the centres of the cylinders are distributed so that their numbers is determined by some positive function N(x). The function N(x) >= 0 is a given continuous function. An equation for the self-consistent (limiting) field is derived as a tends to 0. The cylinders are assumed perfectly conducting. Formula for the effective refraction coefficient of the new medium, obtained by embedding many thin cylinders into a given region, is derived. The numerical results presented demonstrate the validity of the proposed approach and its efficiency for solving the many-body scattering problems, as well as the possibility to create media with negative refraction coefficients.
A simple nonbinary scattering model applicable to atomic collisions is crystals at 1ow energies
DEFF Research Database (Denmark)
Andersen, Hans Henrik; Sigmund, Peter
1966-01-01
Presents the solution of a special scattering problem which may be important in the theory of slowing-down of atomic particles in crystals. A projectile moves along the centre axis of a regular ring of n equal atoms which are free and do not interact with each other. The interaction between...... the projectile and each ring atom is described by a Born-Mayer potential, and the scattering is assumed to be elastic and governed by the classical equations of motion. Because of symmetry, the problem can be reduced to plane motion of a particle in a potential of elliptic symmetry. The elliptic force field...... the asymptotic velocities of the ring atoms as well as the energy loss of the projectile. Furthermore, it can be decided whether the projectile is reflected by the ring. Both the feasibility of assumptions specifying the problem and the validity of different approximations made in the transformation from...
On the angular dependence and scattering model of polar mesospheric summer echoes at VHF
Sommer, Svenja; Stober, Gunter; Chau, Jorge L.
2016-01-01
We present measurements of the angular dependence of polar mesospheric summer echoes (PMSE) with the Middle Atmosphere Alomar Radar System in Northern Norway (69.30° N, 16.04° E). Our results are based on multireceiver and multibeam observations using beam pointing directions with off-zenith angles up to 25° as well as on spatial correlation analysis (SCA) from vertical beam observations. We consider a beam filling effect at the upper and lower boundaries of PMSE in tilted beams, which determines the effective mean angle of arrival. Comparing the average power of the vertical beam to the oblique beams suggests that PMSE are mainly not as aspect sensitive as in contrast to previous studies. However, from SCA, times of enhanced correlation are found, indicating aspect sensitivity or a localized scattering mechanism. Our results suggest that PMSE consist of nonhomogeneous isotropic scattering and previously reported aspect sensitivity values might have been influenced by the inhomogeneous nature of PMSE.
Skar-Gislinge, Nicholas; Arleth, Lise
2011-02-28
Nanodiscs™ consist of small phospholipid bilayer discs surrounded and stabilized by amphiphilic protein belts. Nanodiscs and their confinement and stabilization of nanometer sized pieces of phospholipid bilayer are highly interesting from a membrane physics point of view. We demonstrate how the detailed structure of Di-Lauroyl-Phosphatidyl Choline (DLPC) nanodiscs may be determined by simultaneous fitting of a structural model to small-angle scattering data from the nanodiscs as investigated in three different contrast situations, respectively two SANS contrasts and one SAXS contrast. The article gives a detailed account of the underlying structural model for the nanodiscs and describe how additional chemical and biophysical information can be incorporated in the model in terms of molecular constraints. We discuss and quantify the contribution from the different elements of the structural model and provide very strong experimental support for the nanodiscs as having an elliptical cross-section and with poly-histidine tags protruding out from the rim of the protein belt. The analysis also provides unprecedented information about the structural conformation of the phospholipids when these are localized in the nanodiscs. The model paves the first part of the way in order to reach our long term goal of using the nanodiscs as a platform for small-angle scattering based structural investigations of membrane proteins in solution.
Characterization of Model Polyimide/Silver Interphases Using Surface- Enhanced Raman Scattering
1990-06-01
investigated SERS from bilayers of polystyrene (PS), diglycidyl ether of bisphenol-A ( DGEBA ), poly (4-vinyl pyridine) (PVP), and poly (styrene sulfonate...PSS). Samples were prepared by spin-coating films of PS, DGEBA , or PVP were spun onto silver island films from dilute solutions and then overcoating...solution. Otherwise, SERS was only observed from the first layer (PS, DGEBA , or PVP) even though the PSS films were strong Raman scatters. These results
Modelling of the acoustic field of a multi-element HIFU array scattered by human ribs
Energy Technology Data Exchange (ETDEWEB)
Gelat, Pierre [National Physical Laboratory, Hampton Road, Teddington TW11 0LW (United Kingdom); Ter Haar, Gail [Therapeutic Ultrasound Group, Physics Department, Institute of Cancer Research, Sutton SM2 5NG (United Kingdom); Saffari, Nader, E-mail: Pierre.Gelat@npl.co.uk [Department of Mechanical Engineering, University College London, Torrington Place, London WC1E 7JE (United Kingdom)
2011-09-07
The efficacy of high-intensity focused ultrasound (HIFU) for the treatment of a range of different cancers, including those of the liver, prostate and breast, has been demonstrated. As a non-invasive focused therapy, HIFU offers considerable advantages over techniques such as chemotherapy and surgical resection in terms of reduced risk of harmful side effects. Despite this, there are a number of significant challenges which currently hinder its widespread clinical application. One of these challenges is the need to transmit sufficient energy through the rib cage to induce tissue necrosis in the required volume whilst minimizing the formation of side lobes. Multi-element random-phased arrays are currently showing great promise in overcoming the limitations of single-element transducers. Nevertheless, successful treatment of a patient with liver tumours requires a thorough understanding of the way in which the ultrasonic pressure field from a HIFU array is scattered by the rib cage. In order to address this, a boundary element approach based on a generalized minimal residual (GMRES) implementation of the Burton-Miller formulation was used in conjunction with phase conjugation techniques to focus the field of a 256-element random HIFU array behind human ribs at locations requiring intercostal and transcostal treatment. Simulations were carried out on a 3D mesh of quadratic pressure patches generated using CT scan anatomical data for adult ribs 9-12 on the right side. The methodology was validated on spherical and cylindrical scatterers. Field calculations were also carried out for idealized ribs, consisting of arrays of strip-like scatterers, demonstrating effects of splitting at the focus. This method has the advantage of fully accounting for the effect of scattering and diffraction in 3D under continuous wave excitation.
Monte Carlo modeling of photon propagation reveals highly scattering coral tissue
Directory of Open Access Journals (Sweden)
Daniel Wangpraseurt
2016-09-01
Full Text Available Corals are very efficient at using solar radiation, with photosynthetic quantum efficiencies approaching theoretical limits. Here, we investigated potential mechanisms underlying such outstanding photosynthetic performance through extracting inherent optical properties of the living coral tissue and skeleton in a massive faviid coral. Using Monte Carlo simulations developed for medical tissue optics it is shown that for the investigated faviid coral, the coral tissue was a strongly light scattering matrix with a reduced scattering coefficient of µs’ =10 cm-1 (at 636 nm. In contrast, the scattering coefficient of the coral skeleton was µs’ =3.4 cm-1, which facilitated the efficient propagation of light to otherwise shaded coral tissue layers, thus supporting photosynthesis in lower tissues. Our study provides a quantification of coral tissue optical properties in a massive faviid coral and suggests a novel light harvesting strategy, where tissue and skeletal optics act in concert to optimize the illumination of the photosynthesizing algal symbionts embedded within the living coral tissue.
Spectral Softening in X-ray Afterglow of GRB 130925A as Predicted by Dust Scattering Model
Zhao, Yi-Nan
2014-01-01
Gamma-ray bursts (GRBs) usually occurs in a dense star-forming region with massive circum-burst medium. The small-angle scattering of intense prompt X-ray emission off the surrounding dust grains will have observable consequences, and sometimes can dominate the X-ray afterglow. In most of the previous studies, only Rayleigh-Gans (RG) approximation is employed for describing the scattering process, which works accurately for the typical size of grains (with radius $a\\leq 0.1\\,{\\rm \\mu m}$) in the diffuse interstellar medium. When the size of the grains may significantly increase as in a more dense region where GRBs would occur, the RG approximation may not be valid enough for modeling detailed observational data. In order to study the temporal and spectral properties of the scattered X-ray emission more accurately with potentially larger dust grains, we provide a practical approach using the series expansions of anomalous diffraction (AD) approximation based on the complicated Mie theory. We apply our calculat...
Ivanov, M V; Caballero, J A; Antonov, A N; de Guerra, E Moya; Gaidarov, M K
2008-01-01
The superscaling analysis using the scaling function obtained within the coherent density fluctuation model is extended to calculate charge-changing neutrino and antineutrino scattering on $^{12}$C at energies from 1 to 2 GeV not only in the quasielastic but also in the delta excitation region. The results are compared with those obtained using the scaling functions from the relativistic Fermi gas model and from the superscaling analysis of inclusive scattering of electrons from nuclei.
Yueh, S. H.; Nghiem, S. V.; Kwok, R.; Li, F. K.
1993-01-01
Recently, it has been observed that the brightness temperatures of sea surfaces correlate with the azimuth angle of the ocean wind vector, indicating that ocean wind direction can not only be retrieved from the microwave backscatter, but also from the brightness temperature measurements. In this paper, comparison of the theoretical result calculated from a two-scale emission and scattering model with the Seasat and SSM/I model functions and aircraft measurements is presented and potential applications of microwave polarimetry are discussed. In our two-scale model, the modified reflectivities of large scale surfaces are calculated by extending the small perturbation method to the second order for small scale perturbation with anisotropic directional spectrum. It was found that the modified reflectivities derived from the second-order scattered field agree excellently well with the results obtained from a Monte Carlo simulation technique which numerically calculates the polarimetric reflectivities of one-dimensional random rough surfaces with a power-law spectrum. Without the second-order correction, the modified reflectivities of the rough surfaces are significantly over-estimated and sign errors are observed in the third and fourth Stokes parameters for thermal emissions. The surface spectrum parameters and two-scale cutoff are selected so that the calculated scattering and emission signatures agree with the reported model functions for Seasat and SSM/I. Subsequently, the polarimetric signatures of sea surfaces are illustrated to indicate the possibility of reducing the number of azimuthal looks required for spaceborne sensors in the remote sensing of ocean wind by using the polarimetric information. Furthermore, it is found that contrary to the dependence of backscattering coefficients on incidence angles, polarimetric brightness temperatures display a stronger wind direction dependence in the near nadir-looking direction than away from nadir. Finally, we discuss
Directory of Open Access Journals (Sweden)
T. Deutschmann
2009-04-01
Full Text Available We present a new technique for the quantitative simulation of the "Ring effect" for scattered light observations from various platforms and under different atmospheric situations. The method is based on radiative transfer calculations at only one wavelength λ_{0} in the wavelength range under consideration, and is thus computationally fast. The strength of the Ring effect is calculated from statistical properties of the photon paths for a given situation, which makes Monte Carlo radiative transfer models in particular appropriate. We quantify the Ring effect by the so called rotational Raman scattering probability, the probability that an observed photon has undergone a rotational Raman scattering event. The Raman scattering probability is independent from the spectral resolution of the instrument and can easily be converted into various definitions used to characterise the strength of the Ring effect. We compare the results of our method to the results of previous studies and in general good quantitative agreement is found. In addition to the simulation of the Ring effect, we developed a detailed retrieval strategy for the analysis of the Ring effect based on DOAS retrievals, which allows the precise determination of the strength of the Ring effect for a specific wavelength while using the spectral information within a larger spectral interval around the selected wavelength. Using our technique, we simulated synthetic satellite observation of an atmospheric scenario with a finite cloud illuminated from different sun positions. The strength of the Ring effect depends systematically on the measurement geometry, and is strongest if the satellite points to the side of the cloud which lies in the shadow of the sun.
von Bismarck, J.; Fischer, J.
2011-12-01
Raman scattering of the solar lightfield, due to energy absorption by vibrational modes of water molecules, may contribute significantly to the signals observed by remote sensing satellites over water. The inelastic fraction of the water-leaving radiance for clear water reaches values of 30% in the red part of the visible spectrum, and still reaches values of several percent in moderately turbid waters. Furthermore, inelastic scattering due to chlorophyll and yellow substance fluorescence adds to this fraction. For these reasons the inclusion of inelastic scattering sources into radiative-transfer models, used in ocean remote sensing applications or atmosphere remote sensing over the ocean, can be important. MOMO is a computer code based on the matrix-operator method designed to calculate the lightfield in the stratified atmosphere-ocean system. It has been developed at the Institute for Space Sciences of the Freie Universität Berlin and provides the full polarization state (in the newest version) and an air-sea interface accounting for radiative effects of the wind roughened water surface. The inclusion of Raman scattering effects is done by a processing module, that starts a primary MOMO program run with a high spectral resolution, to calculate the radiative energy available for inelastic scattering at each model layer boundary. The processing module then calculates the first order Raman source-terms for every observation wavelength at every layer boundary, accounting for the non-isotropicity (including the azimuthal dependence) of the Raman phase-function, the spectral redistribution, and the spectral dependence of the Raman scattering coefficient. These elementary source-terms then serve as input for the second program run, which then calculates the source-terms of all model layers, using the doubling-adding method, and the resulting radiance field. Higher orders of the Raman contribution can be computed with additional program runs. Apart from the Raman
A Modified Two-scale Microwave Scattering Model for a Dielectric Randomly Rough Surface(in English
Directory of Open Access Journals (Sweden)
Yu Fan
2015-10-01
Full Text Available In this paper, we present a Modified Two-Scale Microwave (MTSM scattering model to describe the scattering coefficient of naturally rough surfaces. The surface roughness is assumed to be Gaussian in the proposed model so that the surface height z(x, y can be split into large- and small-scale components by the wavelet packet transform according to electromagnetic wavelength. We used the Kirchhoff Model(KM and Small Perturbation Method (SPM to estimate the backscattering coefficient of large- and small-scale roughness, respectively. The tilting effect caused by the slope of large-scale roughness was corrected when calculating the contribution of backscattering to small-scale roughness. The backscattering coefficient of the MTSM comprised the total backscattering contributions of surfaces with both scales of roughness. The MTSM was tested and validated using the Advanced Integral Equation Model (AIEM for dielectric randomly rough surfaces. The accuracy of the MTSM showed favorable agreement with AIEM, both when the incident angle was less than 30° (θi<30° and when the surface roughness was small (ks=0.354.
Strauss, Y
1999-01-01
We apply the quantum Lax-Phillips scattering theory to a relativistically covariant quantum field theoretical form of the (soluble) Lee model. We construct the translation representations with the help of the wave operators, and show that the resulting Lax-Phillips $S$-matrix is an inner function (the Lax-Phillips theory is essentially a theory of translation invariant subspaces). We then discuss the non-relativistic limit of this theory, and show that the resulting kinematic relations coincide with the conditions required for the Galilean description of a decaying system.
Spectral model of time-domain coherent anti-Stokes Raman scattering
Marrocco, Michele
2014-01-01
We show that the increasingly popular nonlinear optical technique of time-domain coherent anti-Stokes Raman scattering (CARS), which is usually understood in terms of the semiclassical time-dependent third-order polarization, can be equally explained in terms of the time-delayed version of the Yuratich equation so popular in traditional frequency-domain CARS. The method brings out the strong dependence of CARS time traces and time-delayed CARS lineshapes on the spectral envelope of the probe laser electric field. Examples are analytically shown for experimental results that are otherwise treated by means of numerical methods only.
Scattering from inclusions in Marine Sediments: SAX04 Data/Model Comparisons
2008-07-14
spheres can be found, e.g., in [Hickling 1962, Morse and Ingard 1968, Medwin and Clay 1998]. There is no exact solution for non-spherical particles of...H. Medwin and C.S. Clay (1998), Fundamentals of Acoustical Oceanography, Academic Press, Boston. [28] P.M. Morse and K.U. Ingard (1968...from discrete scatterers on the ocean bottom, Sov.Phys.Acoust., 35, 5-11 (1989). 11. P.M. Morse and K.U. Ingard , Theoretical acoustics, McGraw-Hill
2013-09-01
during a gas-surface collision, and Rc is a critical value of Reff. For a given incident translational energy Etr , Reff is estimated from the one...dimensional (1D) approximation Etr εLJ ≈ ( r0 Reff )12 − 2 ( r0 Reff )6 , (7) where εLJ is the Lennard-Jones (LJ) well-depth parameter for the interaction...tr > Etr . This phenomenon is termed super-elastic scattering, and describes the case where the gas molecule picks up thermal energy from the surface
Ikegami, Seiji
2017-09-01
The switching model (PSM) developed in the previous paper is extended to obtain an ;extended switching model (ESM). In the ESM, the mixt electronic-and-nuclear energy-loss region, in addition to the electronic and nuclear energy-loss regions in PSM, is taken into account analytically and appropriately. This model is combined with a small-angle multiple scattering range theory considering both nuclear and electronic stopping effects developed by Marwick-Sigmund and Valdes-Arista to formulate a improved range theory. The ESM is also combined with the multiple scattering theory with non-small angle approximation by Goudsmit-Saunderson. Furthermore, we applied ESM to lateral spread model of Marwick-Sigmund. Numerical calculations of the entire distribution functions including one of the mixt region are roughly and approximately possible. However, exact numerical calculation may be impossible. Consequently, several preliminary numerical calculations of the electronic, mixt, and nuclear regions are performed to examine their underlying behavior with respect to the incident energy, the scattering angle, the outgoing projectile intensity, and the target thickness. We show the numerical results not only of PSM and but also of ESM. Both numerical results are shown in the present paper for the first time. Since the theoretical relations are constructed using reduced variables, the calculations are made only on the case of C colliding on C.
Yona, Guy; Meitav, Nizan; Kahn, Itamar; Shoham, Shy
2016-01-01
In recent years, optogenetics has become a central tool in neuroscience research. Estimating the transmission of visible light through brain tissue is of crucial importance for controlling the activation levels of neurons in different depths, designing optical systems, and avoiding lesions from excessive power density. The Kubelka-Munk model and Monte Carlo simulations have previously been used to model light propagation through rodents' brain tissue, however, these prior attempts suffer from fundamental shortcomings. Here, we introduce and study two modified approaches for modeling the distributions of light emanating from a multimode fiber and scattering through tissue, using both realistic numerical Monte Carlo simulations and an analytical approach based on the beam-spread function approach. We demonstrate a good agreement of the new methods' predictions both with recently published data, and with new measurements in mouse brain cortical slices, where our results yield a new cortical scattering length estimate of ∼47 µm at λ = 473 nm, significantly shorter than ordinarily assumed in optogenetic applications.
Jones, A. P.; Köhler, M.; Ysard, N.; Dartois, E.; Godard, M.; Gavilan, L.
2016-04-01
Context. The observed cloudshine and coreshine (C-shine) have been explained in terms of grain growth leading to enhanced scattering from clouds in the J, H, and K photometric bands and the Spitzer IRAC 3.6 and 4.5 μm bands. Aims: Using our global dust-modelling approach THEMIS (The Heterogeneous dust Evolution Model at the IaS), we explore the effects of dust evolution in dense clouds, through aliphatic-rich carbonaceous mantle formation and grain-grain coagulation. Methods: We model the effects of wide band gap a-C:H mantle formation and the low-level aggregation of diffuse interstellar medium dust in the moderately-extinguished outer regions of molecular clouds. Results: The formation of wide band gap a-C:H mantles on amorphous silicate and amorphous carbon (a-C) grains leads to a decrease in their absorption cross-sections but no change in their scattering cross-sections at near-infrared wavelengths, resulting in higher albedos. Conclusions: The evolution of dust, with increasing density and extinction in the diffuse-to-dense molecular cloud transition, through mantle formation and grain aggregation, appears to be a likely explanation for the observed C-shine.
Internal motions in proteins: A combined neutron scattering and molecular modelling approach
Indian Academy of Sciences (India)
M-C Bellissent-Funel
2004-07-01
It is well-known that water plays a major role in the stability and catalytic function of proteins. Both the effect of hydration water on the dynamics of proteins and that of proteins on the dynamics of water have been studied using inelastic neutron scattering. Inelastic neutron scattering is the most direct probe of diffusive protein dynamics on the picosecond{nanosecond time-scale. We present here results relative to a photosynthetic globular protein, the C-phycocyanin, that can be obtained in protonated and deuterated forms. Diffusive motions have been studied using the protonated C-phycocyanin, protein. Molecular dynamics simulation and analytical theory have been combined to analyse the data and get a detailed description of diffusive motions for protein. The simulation-derived dynamic structure factors are in good agreement with experiment. The dynamical parameters are shown to present a smooth variation with distance from the core of the protein. The collective dynamics has been investigated using the fully deuterated C-phycocyanin protein. Both the experimental and calculated spectra exhibit a dynamic relaxation with a characteristic time of about 10 ps.
Internal motions in proteins: A combined neutron scattering and molecular modelling approach
Bellissent-Funel, M.-C.
2004-07-01
It is well-known that water plays a major role in the stability and catalytic function of proteins. Both the effect of hydration water on the dynamics of proteins and that of proteins on the dynamics of water have been studied using inelastic neutron scatter- ing. Inelastic neutron scattering is the most direct probe of diffusive protein dynamics on the picosecond-nanosecond time-scale. We present here results relative to a photosynthetic globular protein, the C-phycocyanin, that can be obtained in protonated and deuterated forms. Diffusive motions have been studied using the protonated C-phycocyanin, protein. Molecular dynamics simulation and analytical theory have been combined to analyse the data and get a detailed description of diffusive motions for protein. The simulation-derived dynamic structure factors are in good agreement with experiment. The dynamical param- eters are shown to present a smooth variation with distance from the core of the protein. The collective dynamics has been investigated using the fully deuterated C-phycocyanin protein. Both the experimental and calculated spectra exhibit a dynamic relaxation with a characteristic time of about 10 ps.
Modelling of Electromagnetic Scattering by a Hypersonic Cone-Like Body in Near Space
Directory of Open Access Journals (Sweden)
Ji-Wei Qian
2017-01-01
Full Text Available A numerical procedure for analysis of electromagnetic scattering by a hypersonic cone-like body flying in the near space is presented. First, the fluid dynamics equation is numerically solved to obtain the electron density, colliding frequency, and the air temperature around the body. They are used to calculate the complex relative dielectric constants of the plasma sheath. Then the volume-surface integral equation method is adopted to analyze the scattering properties of the body plus the plasma sheath. The Backscattering Radar Cross-Sections (BRCS for the body flying at different speeds, attack angles, and elevations are examined. Numerical results show that the BRCS at a frequency higher than 300 MHz is only slightly affected if the speed is smaller than 7 Mach. The BRCS at 1 GHz would be significantly reduced if the speed is greater than 7 Mach and is continuously increased, which can be attributed to the absorption by the lossy plasma sheath. Typically, the BRCS is influenced by 5~10 dBm for a change of attack angle within 0~15 degrees, or for a change of elevation within 30~70 km above the ground.
Energy Technology Data Exchange (ETDEWEB)
Tang, Robert Y., E-mail: rx-tang@laurentian.ca [Biomolecular Sciences Program, Laurentian University, 935 Ramsey Lake Road, Sudbury, Ontario P3E 2C6 (Canada); Laamanen, Curtis, E-mail: cx-laamanen@laurentian.ca; McDonald, Nancy, E-mail: mcdnancye@gmail.com [Department of Physics, Laurentian University, 935 Ramsey Lake Road, Sudbury, Ontario P3E 2C6 (Canada); LeClair, Robert J., E-mail: rleclair@laurentian.ca [Department of Physics, Laurentian University, 935 Ramsey Lake Road, Sudbury, Ontario P3E 2C6, Canada and Biomolecular Sciences Program, Laurentian University, 935 Ramsey Lake Road, Sudbury, Ontario P3E 2C6 (Canada)
2014-05-15
Purpose: Develop a method to subtract fat tissue contributions to wide-angle x-ray scatter (WAXS) signals of breast biopsies in order to estimate the differential linear scattering coefficients μ{sub s} of fatless tissue. Cancerous and fibroglandular tissue can then be compared independent of fat content. In this work phantom materials with known compositions were used to test the efficacy of the WAXS subtraction model. Methods: Each sample 5 mm in diameter and 5 mm thick was interrogated by a 50 kV 2.7 mm diameter beam for 3 min. A 25 mm{sup 2} by 1 mm thick CdTe detector allowed measurements of a portion of the θ = 6° scattered field. A scatter technique provided means to estimate the incident spectrum N{sub 0}(E) needed in the calculations of μ{sub s}[x(E, θ)] where x is the momentum transfer argument. Values of μ{sup ¯}{sub s} for composite phantoms consisting of three plastic layers were estimated and compared to the values obtained via the sum μ{sup ¯}{sub s}{sup ∑}(x)=ν{sub 1}μ{sub s1}(x)+ν{sub 2}μ{sub s2}(x)+ν{sub 3}μ{sub s3}(x), where ν{sub i} is the fractional volume of the ith plastic component. Water, polystyrene, and a volume mixture of 0.6 water + 0.4 polystyrene labelled as fibphan were chosen to mimic cancer, fat, and fibroglandular tissue, respectively. A WAXS subtraction model was used to remove the polystyrene signal from tissue composite phantoms so that the μ{sub s} of water and fibphan could be estimated. Although the composite samples were layered, simulations were performed to test the models under nonlayered conditions. Results: The well known μ{sub s} signal of water was reproduced effectively between 0.5 < x < 1.6 nm{sup −1}. The μ{sup ¯}{sub s} obtained for the heterogeneous samples agreed with μ{sup ¯}{sub s}{sup ∑}. Polystyrene signals were subtracted successfully from composite phantoms. The simulations validated the usefulness of the WAXS models for nonlayered biopsies. Conclusions: The methodology to
PROBING THE STANDARD MODEL AND NUCLEON STRUCTURE VIA PARITY VIOLATING ELECTRON SCATTERING
Energy Technology Data Exchange (ETDEWEB)
Humensky, T
2003-10-28
Parity-violating electron scattering has developed over the last 25 years into a tool to study both the structure of electroweak interactions and the structure of nucleons. Work on two parity-violation experiments is reported in this thesis. They are the Hall A Proton Parity EXperiment (HAPPEX), which ran at Jefferson Laboratory in 1998-1999, and SLAC E-158, which had its first physics running in 2002. HAPPEX measured the parity-violating asymmetry in elastic e-p scattering at a momentum transfer squared of Q{sup 2} = 0.477 GeV{sup 2} and a scattering angle of 12{sup o}. This asymmetry is sensitive to the presence of strange sea quarks in the proton. In particular, it is sensitive to the proton's strange elastic form factors. An asymmetry of A{sub LR}{sup ep} = -15.05 {+-} 0.98 {+-} 0.56 ppm was measured, where the first error is statistical and the second error is systematic. Combining this asymmetry measurement with existing measurements of the electromagnetic form factors of the proton and neutron allowed HAPPEX to set new constraints on the strange elastic form factors of the proton G{sub E}{sup s} + 0.392G{sub M}{sup s} = 0.025 {+-} 0.020 {+-} 0.014, where G{sub E}{sup s} and G{sub M}{sup s} are the strange electric and magnetic form factors of the proton, respectively. The first error is the quadrature sum of the experimental errors and the second error is due to uncertainty in the electromagnetic form factors. This result is consistent with the absence of a contribution from strange quarks. This thesis reports an analysis of the 1999 data set, with a particular focus on the determination of the raw asymmetry and the corrections to the raw asymmetry to account for helicity-correlated asymmetries in properties of the electron beam.
Schwab, Hans-Martin; Beckmann, Martin F; Schmitz, Georg
2016-04-01
Photoacoustic imaging aims to visualize light absorption properties of biological tissue by receiving a sound wave that is generated inside the observed object as a result of the photoacoustic effect. In clinical applications, the strong light absorption in human skin is a major problem. When high amplitude photoacoustic waves that originate from skin absorption propagate into the tissue, they are reflected back by acoustical scatterers and the reflections contribute to the received signal. The artifacts associated with these reflected waves are referred to as clutter or skin echo and limit the applicability of photoacoustic imaging for medical applications severely. This study seeks to exploit the acoustic tissue information gained by plane wave ultrasound measurements with a linear array in order to correct for reflections in the photoacoustic image. By deriving a theory for clutter waves in k-space and a matching inversion approach, photoacoustic measurements compensated for clutter are shown to be recovered.
Buono, A.; Nunziata, F.; Migliaccio, M.; Li, X.; Wei, Y.; Shen, D.
2016-08-01
The Yellow River (in Chinese, Huang He) is the most sediment-filled river and the sixth-longest one in the world. The Yellow River is of paramount importance for safe navigation, local economy and environment due to the presence of floods, farms, aquacultures and pollution. Nonetheless, its delta area it is characterized by of several physical phenomena due to both natural and anthropogenic processes: sedimentation, erosion, floods, pollution, etc.In this study, actual partially overlapped L-/C-band FP SAR data collected from Radarsat-2 and ALOS PalSAR-2, respectively, are used to investigate the scattering properties of the Yellow River delta, whose very challenging area is characterized by different scenarios as recorded by ground truth data acquired during an in-situ campaign. 10 different classes have been codified: sea, river, forest, pond, swamp, tide-land, sand, saline soil, rural and industrial urban areas. However, no ground truth data is available in some codified areas.
Garg, S; Porcar, L; Woodka, A C; Butler, P D; Perez-Salas, U
2011-07-20
Proper cholesterol transport is essential to healthy cellular activity and any abnormality can lead to several fatal diseases. However, complete understandings of cholesterol homeostasis in the cell remains elusive, partly due to the wide variability in reported values for intra- and intermembrane cholesterol transport rates. Here, we used time-resolved small-angle neutron scattering to measure cholesterol intermembrane exchange and intramembrane flipping rates, in situ, without recourse to any external fields or compounds. We found significantly slower transport kinetics than reported by previous studies, particularly for intramembrane flipping where our measured rates are several orders of magnitude slower. We unambiguously demonstrate that the presence of chemical tags and extraneous compounds employed in traditional kinetic measurements dramatically affect the system thermodynamics, accelerating cholesterol transport rates by an order of magnitude. To our knowledge, this work provides new insights into cholesterol transport process disorders, and challenges many of the underlying assumptions used in most cholesterol transport studies to date.
Structure of raft-model membrane by using the inverse contrast variation neutron scattering method
Energy Technology Data Exchange (ETDEWEB)
Hirai, Mitsuhiro [Department of Physics, Gunma University, Maebashi 371-8510 (Japan); Hirai, Harutaka [Department of Physics, Gunma University, Maebashi 371-8510 (Japan); Koizumi, Masaharu [Department of Physics, Gunma University, Maebashi 371-8510 (Japan); Kasahara, Kohji [Tokyo Metropolitan Institute of Medical Science, Tokyo 113-8613 (Japan); Yuyama, Kohei [Tokyo Metropolitan Institute of Medical Science, Tokyo 113-8613 (Japan); Suzuki, Naoko [Tokyo Metropolitan Institute of Medical Science, Tokyo 113-8613 (Japan)
2006-11-15
By means of the inverse contrast variation method in small-angle neutron scattering, we have studied the structure of a small unilamellar vesicle (SUV) composed of ganglioside, cholesterol and dipalmitoyl-phosphocholine. The SUV treated has a similar lipid composition as in a plasma membrane with microdomains, so-called rafts. The present results indicate an asymmetric distribution of lipid components within the bilayer of the vesicle, that is, a predominant distribution of ganglioside and cholesterol at the outer leaflet of the vesicle bilayer. The deviation from the linearity in a pseudo-Stuhrmannplot strongly suggests the presence of a large heterogeneity of lipid composition in a bilayer, namely a clustering of ganglioside and cholesterol molecules. This deviation is enhanced by temperature elevation, meaning that ganglioside-cholesterol clusters become larger with holding liquid-ordered (L{sub o}) phase.
Modeling of fibrin gels based on confocal microscopy and light-scattering data.
Magatti, Davide; Molteni, Matteo; Cardinali, Barbara; Rocco, Mattia; Ferri, Fabio
2013-03-01
Fibrin gels are biological networks that play a fundamental role in blood coagulation and other patho/physiological processes, such as thrombosis and cancer. Electron and confocal microscopies show a collection of fibers that are relatively monodisperse in diameter, not uniformly distributed, and connected at nodal points with a branching order of ∼3-4. Although in the confocal images the hydrated fibers appear to be quite straight (mass fractal dimension D(m) = 1), for the overall system 1, joined at randomly distributed nodal points. The resulting 3D network strikingly resembles real fibrin gels and can be sketched as an assembly of densely packed fractal blobs, i.e., regions of size ξ, where the fiber concentration is higher than average. The blobs are placed at a distance ξ0 between their centers of mass so that they are overlapped by a factor η =ξ/ξ0 and have D(m) ∼1.2-1.6. The in silico gels' structure is quantitatively analyzed by its 3D spatial correlation function g(3D)(r) and corresponding power spectrum I(q) = FFT(3D[g3D(r)]), from which ρ, d, D(m), η, and ξ0 can be extracted. In particular, ξ0 provides an excellent estimate of the gel mesh size. The in silico gels' I(q) compares quite well with real gels' elastic light-scattering measurements. We then derived an analytical form factor for accurately fitting the scattering data, which allowed us to directly recover the gels' structural parameters.
Grishaev, Alexander; Guo, Liang; Irving, Thomas; Bax, Ad
2010-11-10
A new procedure, AXES, is introduced for fitting small-angle X-ray scattering (SAXS) data to macromolecular structures and ensembles of structures. By using explicit water models to account for the effect of solvent, and by restricting the adjustable fitting parameters to those that dominate experimental uncertainties, including sample/buffer rescaling, detector dark current, and, within a narrow range, hydration layer density, superior fits between experimental high resolution structures and SAXS data are obtained. AXES results are found to be more discriminating than standard Crysol fitting of SAXS data when evaluating poorly or incorrectly modeled protein structures. AXES results for ensembles of structures previously generated for ubiquitin show improved fits over fitting of the individual members of these ensembles, indicating these ensembles capture the dynamic behavior of proteins in solution.
Montagnon, Emmanuel; Hadj-Henni, Anis; Schmitt, Cédric; Cloutier, Guy
2013-04-07
This paper presents a semi-analytical model of shear wave scattering by a viscoelastic elliptical structure embedded in a viscoelastic medium, and its application in the context of dynamic elastography imaging. The commonly used assumption of mechanical homogeneity in the inversion process is removed introducing a priori geometrical information to model physical interactions of plane shear waves with the confined mechanical heterogeneity. Theoretical results are first validated using the finite element method for various mechanical configurations and incidence angles. Secondly, an inverse problem is formulated to assess viscoelastic parameters of both the elliptic inclusion and its surrounding medium, and applied in vitro to characterize mechanical properties of agar-gelatin phantoms. The robustness of the proposed inversion method is then assessed under various noise conditions, biased geometrical parameters and compared to direct inversion, phase gradient and time-of-flight methods. The proposed elastometry method appears reliable in the context of estimating confined lesion viscoelastic parameters.
Institute of Scientific and Technical Information of China (English)
沈鸿雁; 李庆春; 边建民
2014-01-01
Seismic reflection imaging result is not satisfactory when the underground geological conditions are much complex,and the conventional reflection seismic exploration would be ineffective.In the paper,one 2D seismic scattering wave imaging method is achieved from the time-distance curve equation of 2D scattering wave based on the seismic-earth model of point scattering,and the seismic scattering wave kinematics law is ana-lyzed.With the processing results of fault model and a set of real seismic data,the characteristics of the seismic scattering wave imaging technique is discussed,and the imaging results of traditional reflection imaging tech-nique are compared to prove the effectiveness of this method.%地下地质条件比较复杂时，地震反射波成像效果不理想，致使常规反射地震勘探难以奏效。本文基于点散射地震－地质模型，推导出2D散射波时距曲线方程，分析了地震散射波的运动学规律；在此基础上，提出了2D地震散射波成像的方法与技术；结合断层模型和一套实际地震资料处理，讨论了散射波地震成像的特点，并与传统反射波成像结果进行了比较，证明了该方法的有效性。
Celik, I H; Demirel, G; Sukhachev, D; Erdeve, O; Dilmen, U
2013-02-01
Neonatal sepsis remains an important clinical syndrome despite advances in neonatology. Current hematology analyzers can determine cell volume (V), conductivity for internal composition of cell (C) and light scatter for cytoplasmic granularity and nuclear structure (S), and standard deviations which are effective in the diagnosis of sepsis. Statistical models can be used to strengthen the diagnosis. Effective modeling of molecular activity (EMMA) uses combinatorial algorithm of the selection parameters for regression equation based on modified stepwise procedure. It allows obtaining different regression models with different combinations of parameters. We investigated these parameters in screening of neonatal sepsis. We used LH780 hematological analyzer (Beckman Coulter, Fullerton, CA, USA). We combined these parameters with interleukin-6 (IL-6) and C-reactive protein (CRP) and developed models by EMMA. A total of 304 newborns, 76 proven sepsis, 130 clinical sepsis and 98 controls, were enrolled in the study. Mean neutrophil volume (MNV) and volume distribution width (VDW) were higher in both proven and clinical sepsis groups. We developed three models using MNV, VDW, IL-6, and CRP. These models gave more sensitivity and specificity than the usage of each marker alone. We suggest to use the combination of MNV and VDW with markers such as CRP and IL-6, and use diagnostic models created by EMMA. © 2012 Blackwell Publishing Ltd.
Collet, Remo; Hayek, Wolfgang; Asplund, Martin
2011-08-01
We study the effects of different approximations of scattering in 3D radiation-hydrodynamics simulations on the photospheric temperature stratification of metal-poor red giant stars. We find that assuming a Planckian source function and neglecting the contribution of scattering to extinction in optically thin layers provides a good approximation of the effects of coherent scattering on the photospheric temperature balance.
RADIATIVE TRANSFER MODELING OF THE ENIGMATIC SCATTERING POLARIZATION IN THE SOLAR Na i D{sub 1} LINE
Energy Technology Data Exchange (ETDEWEB)
Belluzzi, Luca [Istituto Ricerche Solari Locarno, CH-6605 Locarno Monti (Switzerland); Bueno, Javier Trujillo [Instituto de Astrofísica de Canarias, E-38205 La Laguna, Tenerife (Spain); Degl’Innocenti, Egidio Landi [Dipartimento di Fisica e Astronomia, Università di Firenze, I-50125 Firenze (Italy)
2015-12-01
The modeling of the peculiar scattering polarization signals observed in some diagnostically important solar resonance lines requires the consideration of the detailed spectral structure of the incident radiation field as well as the possibility of ground level polarization, along with the atom's hyperfine structure and quantum interference between hyperfine F-levels pertaining either to the same fine structure J-level, or to different J-levels of the same term. Here we present a theoretical and numerical approach suitable for solving this complex non-LTE radiative transfer problem. This approach is based on the density-matrix metalevel theory (where each level is viewed as a continuous distribution of sublevels) and on accurate formal solvers of the transfer equations and efficient iterative methods. We show an application to the D-lines of Na i, with emphasis on the enigmatic D{sub 1} line, pointing out the observable signatures of the various physical mechanisms considered. We demonstrate that the linear polarization observed in the core of the D{sub 1} line may be explained by the effect that one gets when the detailed spectral structure of the anisotropic radiation responsible for the optical pumping is taken into account. This physical ingredient is capable of introducing significant scattering polarization in the core of the Na i D{sub 1} line without the need for ground-level polarization.
Toniolo, Giuliano R.; Fargnoli, H. G.; Brito, L. C. T.; Scarpelli, A. P. Baêta
2017-02-01
S-matrix amplitudes for the electron-electron scattering are calculated in order to verify the physical equivalence between two Lorentz-breaking dual models. We begin with an extended Quantum Electrodynamics which incorporates CPT-even Lorentz-violating kinetic and mass terms. Then, in a process of gauge embedding, its gauge-invariant dual model is obtained. The physical equivalence of the two models is established at tree level in the electron-electron scattering and the unpolarized cross section is calculated up to second order in the Lorentz-violating parameter.
Energy Technology Data Exchange (ETDEWEB)
Toniolo, Giuliano R.; Fargnoli, H.G.; Brito, L.C.T. [Universidade Federal de Lavras, Departamento de Fisica, Caixa Postal 3037, Lavras, Minas Gerais (Brazil); Scarpelli, A.P.B. [Setor Tecnico-Cientifico, Departamento de Policia Federal, Sao Paulo (Brazil)
2017-02-15
S-matrix amplitudes for the electron-electron scattering are calculated in order to verify the physical equivalence between two Lorentz-breaking dual models. We begin with an extended Quantum Electrodynamics which incorporates CPT-even Lorentz-violating kinetic and mass terms. Then, in a process of gauge embedding, its gauge-invariant dual model is obtained. The physical equivalence of the two models is established at tree level in the electron-electron scattering and the unpolarized cross section is calculated up to second order in the Lorentz-violating parameter. (orig.)
Optimization of Scatterer Concentration in High-Gain Scattering Media
Institute of Scientific and Technical Information of China (English)
ZHU Jiu-Gao; ZHU He-Yuan; SUN Die-Chi; DU Ge-Guo; LI Fu-Ming
2001-01-01
We report the scatterer concentration-dependent behaviour of laser action in high-gain scattering media. Amodified model of a random laser is proposed to explain the experimental results in good agreement. We mayuse this modified model to design and optimize the random laser system. A further detailed model is needed toquantitatively analyse the far-field distribution of random laser action.
Energy Technology Data Exchange (ETDEWEB)
Larsson, Anne [Department of Radiation Sciences, Radiation Physics, Umeaa University, SE-901 87 Umeaa (Sweden); Ljungberg, Michael [Medical Radiation Physics, Department of Clinical Sciences, Lund, Lund University, SE-221 85 Lund (Sweden); Mo, Susanna Jakobson [Department of Radiation Sciences, Diagnostic Radiology, Umeaa University, SE-901 87 Umeaa (Sweden); Riklund, Katrine [Department of Radiation Sciences, Diagnostic Radiology, Umeaa University, SE-901 87 Umeaa (Sweden); Johansson, Lennart [Department of Radiation Sciences, Radiation Physics, Umeaa University, SE-901 87 Umeaa (Sweden)
2006-11-21
Scatter and septal penetration deteriorate contrast and quantitative accuracy in single photon emission computed tomography (SPECT). In this study four different correction techniques for scatter and septal penetration are evaluated for {sup 123}I brain SPECT. One of the methods is a form of model-based compensation which uses the effective source scatter estimation (ESSE) for modelling scatter, and collimator-detector response (CDR) including both geometric and penetration components. The other methods, which operate on the 2D projection images, are convolution scatter subtraction (CSS) and two versions of transmission dependent convolution subtraction (TDCS), one of them proposed by us. This method uses CSS for correction for septal penetration, with a separate kernel, and TDCS for scatter correction. The corrections are evaluated for a dopamine transporter (DAT) study and a study of the regional cerebral blood flow (rCBF), performed with {sup 123}I. The images are produced using a recently developed Monte Carlo collimator routine added to the program SIMIND which can include interactions in the collimator. The results show that the method included in the iterative reconstruction is preferable to the other methods and that the new TDCS version gives better results compared with the other 2D methods.
Lizzit, D.; Badami, O.; Specogna, R.; Esseni, D.
2017-06-01
We present a new model for surface roughness (SR) scattering in n-type multi-gate FETs (MuGFETs) and gate-all-around nanowire FETs with fairly arbitrary cross-sections, its implementation in a complete device simulator, and the validation against experimental electron mobility data. The model describes the SR scattering matrix elements as non-linear transformations of interface fluctuations, which strongly influences the root mean square value of the roughness required to reproduce experimental mobility data. Mobility simulations are performed via the deterministic solution of the Boltzmann transport equation for a 1D-electron gas and including the most relevant scattering mechanisms for electronic transport, such as acoustic, polar, and non-polar optical phonon scattering, Coulomb scattering, and SR scattering. Simulation results show the importance of accounting for arbitrary cross-sections and biasing conditions when compared to experimental data. We also discuss how mobility is affected by the shape of the cross-section as well as by its area in gate-all-around and tri-gate MuGFETs.
Larsson, Anne; Ljungberg, Michael; Mo, Susanna Jakobson; Riklund, Katrine; Johansson, Lennart
2006-11-21
Scatter and septal penetration deteriorate contrast and quantitative accuracy in single photon emission computed tomography (SPECT). In this study four different correction techniques for scatter and septal penetration are evaluated for 123I brain SPECT. One of the methods is a form of model-based compensation which uses the effective source scatter estimation (ESSE) for modelling scatter, and collimator-detector response (CDR) including both geometric and penetration components. The other methods, which operate on the 2D projection images, are convolution scatter subtraction (CSS) and two versions of transmission dependent convolution subtraction (TDCS), one of them proposed by us. This method uses CSS for correction for septal penetration, with a separate kernel, and TDCS for scatter correction. The corrections are evaluated for a dopamine transporter (DAT) study and a study of the regional cerebral blood flow (rCBF), performed with 123I. The images are produced using a recently developed Monte Carlo collimator routine added to the program SIMIND which can include interactions in the collimator. The results show that the method included in the iterative reconstruction is preferable to the other methods and that the new TDCS version gives better results compared with the other 2D methods.
Larsson, Anne; Ljungberg, Michael; Jakobson Mo, Susanna; Riklund, Katrine; Johansson, Lennart
2006-11-01
Scatter and septal penetration deteriorate contrast and quantitative accuracy in single photon emission computed tomography (SPECT). In this study four different correction techniques for scatter and septal penetration are evaluated for 123I brain SPECT. One of the methods is a form of model-based compensation which uses the effective source scatter estimation (ESSE) for modelling scatter, and collimator-detector response (CDR) including both geometric and penetration components. The other methods, which operate on the 2D projection images, are convolution scatter subtraction (CSS) and two versions of transmission dependent convolution subtraction (TDCS), one of them proposed by us. This method uses CSS for correction for septal penetration, with a separate kernel, and TDCS for scatter correction. The corrections are evaluated for a dopamine transporter (DAT) study and a study of the regional cerebral blood flow (rCBF), performed with 123I. The images are produced using a recently developed Monte Carlo collimator routine added to the program SIMIND which can include interactions in the collimator. The results show that the method included in the iterative reconstruction is preferable to the other methods and that the new TDCS version gives better results compared with the other 2D methods.
Directory of Open Access Journals (Sweden)
S. Yu. Makarov
2015-01-01
Full Text Available The article dwells on a development of new non-invasive measurement methods of optical parameters of biological tissues, which are responsible for the scattering and absorption of monochromatic radiation. It is known from the theory of radiation transfer [1] that for strongly scattering media, to which many biological tissues pertain, such parameters are parameters of diffusion approximation, as well as a scattering coefficient and an anisotropy parameter.Based on statistical modeling the paper examines a spread of non-directional radiation from a Lambert light beam with the natural polarization that illuminates a surface of the biological tissue. Statistical modeling is based on the Monte Carlo method [2]. Thus, to have the correct energy coefficient values of Fresnel reflection and transmission in simulation of such radiation by Monte Carlo method the author uses his finding that is a function of the statistical representation for the incidence of model photons [3]. The paper describes in detail a principle of fixing the power transmitted by the non-directional radiation into biological tissue [3], and the equations of a power balance in this case.Further, the paper describes the diffusion approximation of a radiation transfer theory, often used in simulation of radiation propagation in strongly scattering media and shows its application in case of fixing the power transmitted into the tissue. Thus, to represent an uneven power distribution is used an approximating expression in conditions of fixing a total input power. The paper reveals behavior peculiarities of solution on the surface of the biological tissue inside and outside of the incident beam. It is shown that the solution in the region outside of the incident beam (especially far away from it, essentially, depends neither on the particular power distribution across the surface, being a part of the tissue, nor on the refractive index of the biological tissue. It is determined only by
Solodovnyk, Anastasiia; Lipovšek, Benjamin; Forberich, Karen; Stern, Edda; Krč, Janez; Batentschuk, Miroslaw; Topič, Marko; Brabec, Christoph J.
2015-12-01
We studied the optical properties of polymer layers filled with phosphor particles in two aspects. First, we used two different polymer binders with refractive indices n = 1.46 and n = 1.61 (λ = 600 nm) to decrease Δn with the phosphor particles (n = 1.81). Second, we prepared two particle size distributions D50 = 12 μm and D50 = 19 μm. The particles were dispersed in both polymer binders in several volume concentrations and coated onto glass with thicknesses of 150 - 600 μm. We present further a newly developed optical model for simulation and optimization of such luminescent down-shifting (LDS) layers. The model is developed within the ray tracing framework of the existing optical simulator CROWM (Combined Ray Optics / Wave Optics Model), which enables simulation of standalone LDS layers as well as complete solar cells (including thick and thin layers) enhanced by the LDS layers for an improved solar spectrum harvesting. Experimental results and numerical simulations show that the layers of the higher refractive index binder with larger particles result in the highest optical transmittance in the visible light spectrum. Finally we proved that scattering of the phosphor particles in the LDS layers may increase the overall light harvesting in the solar cell. We used numerical simulations to determine optimal layer composition for application in realistic thin-film photovoltaic devices. Surprisingly LDS layers with lower measured optical transmittance are more efficient when applied onto the solar cells due to graded refractive index and efficient light scattering. Therefore, our phosphor-filled LDS layers could possibly complement other light-coupling techniques in photovoltaics.
Lupi, Laura; Comez, Lucia; Paolantoni, Marco; Fioretto, Daniele; Ladanyi, Branka M
2012-06-28
Extended depolarized light scattering (EDLS) measurements have been recently employed to investigate the dynamics of water solvating biological molecules, giving evidence of the presence of two different dynamical regimes among water molecules. An interpretation of EDLS has been proposed that provides an independent estimate of the retardation factor of slowdown with respect to fast water molecules and of the number of solvent molecules affected by this slowing down. Nevertheless this measure is an inherently complex one, due to the collective nature of the physical property probed. In the present work a molecular dynamics (MD) approach has been used to more deeply understand experimental results. Time correlation functions of the collective polarizability anisotropy have been calculated for the prototype disaccharide trehalose in aqueous solutions as a function of concentration. The unique capability of MD to disentangle the contributions to the dynamics arising from solute, solvent, and cross terms between the two allowed us to check the reliability of an interpretation that assumes a spectral separation of water and sugar dynamics, as well as to highlight the very presence of two distinct relaxation processes in water. The two processes have been attributed to the dynamics of bulk and hydration water, respectively. A retardation factor of ~5 and concentration dependent hydration numbers have been observed, in good agreement with experimental results [Paolantoni, M.; et al. J. Phys. Chem. B 2009, 113, 7874-7878].
A semi-numerical model for near-critical angle scattering.
Fradkin, Larissa Ju; Darmon, Michel; Chatillon, Sylvain; Calmon, Pierre
2016-01-01
Numerous phenomena in the fields of physics and mathematics as seemingly different as seismology, ultrasonics, crystallography, photonics, relativistic quantum mechanics, and analytical number theory are described by integrals with oscillating integrands that contain three coalescing criticalities, a branch point, stationary phase point, and pole as well as accumulation points at which the speed of integrand oscillation is infinite. Evaluating such integrals is a challenge addressed in this paper. A fast and efficient numerical scheme based on the regularized composite Simpson's rule is proposed, and its efficacy is demonstrated by revisiting the scattering of an elastic plane wave by a stress-free half-plane crack embedded in an isotropic and homogeneous solid. In this canonical problem, the head wave, edge diffracted wave, and reflected (or compensating) wave each can be viewed as a respective contribution of a branch point, stationary phase point, and pole. The proposed scheme allows for a description of the non-classical diffraction effects near the "critical" rays (rays that separate regions irradiated by the head waves from their respective shadow zones). The effects include the spikes present in diffraction coefficients at the critical angles in the far field as well as related interference ripples in the near field.
Abnormal absorption and scattering effect of human ear model for electromagnetic waves
Institute of Scientific and Technical Information of China (English)
NIE Min; PEI Changxing; LI Jiandong; MA Chen; YANG Zhen
2005-01-01
@@ To explore the effect of human ear outline structure for electromagnetic waves, two human ear's models, a big one (model 1) and a small one (model 2), were made in proportion as real human ears (Fig. 1). The installation picture is shown in Fig. 2, and its geometry structure and size are shown in Figs. 3 and 4, respectively.
Scattering and duality in the 2 dimensional OSP(2|2) Gross Neveu and sigma models
Saleur, H
2009-01-01
We write the thermodynamic Bethe ansatz for the massive OSp(2|2) Gross Neveu and sigma models. We find evidence that the GN S matrix proposed by Bassi and Leclair [12] is the correct one. We determine features of the sigma model S matrix, which seem highly unconventional; we conjecture in particular a relation between this sigma model and the complex sine-Gordon model at a particular value of the coupling. We uncover an intriguing duality between the OSp(2|2) GN (resp. sigma) model on the one hand, and the SO(4) sigma (resp. GN model) on the other, somewhat generalizing to the massive case recent results on OSp(4|2). Finally, we write the TBA for the (SUSY version of the) flow into the random bond Ising model proposed by Cabra et al. [39], and conclude that their S matrix cannot be correct.
Pham, A. T.; Nguyen, C. D.; Jungemann, C.; Meinerzhagen, B.
2006-04-01
A new semiempirical surface scattering model for electrons in strained Si devices including a quantum correction has been developed and implemented into our FBMC simulator. The strain is assumed to be consistent with pseudomorphic growth on a relaxed SiGe buffer. By introducing a few additional terms into the physical scattering rates which depend on the Ge-content in the SiGe buffer, the new surface scattering model can excellently reproduce low-field inversion layer mobility measurements for a wide range of Ge-content (0-30%) and substrate doping levels (10 16-5.5 × 10 18 cm -3). As a device example, an NMOSFET with 23 nm gate length with and without a strained Si channel has been simulated by the new FBMC model.
Institute of Scientific and Technical Information of China (English)
GUO Xia; L(U) Daren; L(U) Yao
2007-01-01
Here we present a study focusing on atmospheric limb-scattered radiative characteristics in the ultraviolet band by using a limb-scan spherically-layered radiative-transfer-model based on the single-scattering approximation, which was developed by the present authors. We have applied an accurate numerical integration technique involving an auto-adaptive modified-space step, which assured high accuracy and simplification.Comparisons were made to the newly released spherical radiative transfer model, SCIATRAN2.0, which was developed by Institute of Remote Sensing/Institute of Environmental Physics (IUP/IFE) at University of Bremen and to measurements collected via an ultraviolet spectrometer on the Solar Mesospheric Explorer (SME) satellite, which was launched in October, 1981. Preliminary results indicate that the present model provides a good interpretation of the earth-limb scattered ultraviolet radiance, and thus, is suitable for the study of the ultraviolet-limb radiative-transfer problem with high accuracy.
Energy Technology Data Exchange (ETDEWEB)
Stirling, W.G. [Liverpool Univ., Dep. of Physics, Liverpool (United Kingdom); Perry, S.C. [Keele Univ. (United Kingdom). Dept. of Physics
1996-12-31
We outline the theoretical and experimental background to neutron scattering studies of critical phenomena at magnetic and structural phase transitions. The displacive phase transition of SrTiO{sub 3} is discussed, along with examples from recent work on magnetic materials from the rare-earth (Ho, Dy) and actinide (NpAs, NpSb, USb) classes. The impact of synchrotron X-ray scattering is discussed in conclusion. (author) 13 figs., 18 refs.
Double parton scattering: A study of the effective cross section within a Light-Front quark model
Directory of Open Access Journals (Sweden)
Matteo Rinaldi
2016-01-01
Full Text Available We present a calculation of the effective cross section σeff, an important ingredient in the description of double parton scattering in proton–proton collisions. Our theoretical approach makes use of a Light-Front quark model as a framework to calculate the double parton distribution functions at low-resolution scale. QCD evolution is implemented to reach the experimental scale. The obtained values of σeff in the valence region are consistent with the present experimental scenario, in particular with the sets of data which include the same kinematical range. However the result of the complete calculation shows a dependence of σeff on xi, a feature not easily seen in the available data, probably because of their low accuracy. Measurements of σeff in restricted xi regions are addressed to obtain indications on double parton correlations, a novel and interesting aspect of the three dimensional structure of the nucleon.
Energy Technology Data Exchange (ETDEWEB)
Champion, C. [Universite Paul Verlaine-Metz, Laboratoire de Physique Moleculaire et des Collisions, 1 Boulevard Arago, Technopole 2000, 57078 Metz (France)], E-mail: champion@univ-metz.fr; Incerti, S. [CNRS/IN2P3, Centre d' Etudes Nucleaires de Bordeaux-Gradignan, UMR 5797, Gradignan F-33175 (France); Universite de Bordeaux, Centre d' Etudes Nucleaires de Bordeaux-Gradignan, UMR 5797, Gradignan F-33175 (France); Aouchiche, H.; Oubaziz, D. [Universite M. Mammeri, Laboratoire de Mecanique, Structure et Energetique, BP 17, Tizi-Ouzou 15000 (Algeria)
2009-09-15
The present work provides an accurate description of the elastic scattering process for low-energy electrons (10 eV-10 keV) in liquid water by means of a free-parameter quantum-mechanical treatment. The calculations are performed in the partial-wave formalism by means of a total interaction potential taking into account a static contribution as well as fine effects like exchange and polarization contributions. The obtained results in terms of singly differential and total cross sections exhibit relatively good agreement with available experimental data (in gaseous water). They have been incorporated into the Geant4 toolkit, which has been recently extended with physics processes for microdosimetry applications in liquid water down to the electronvolt scale. They offer an improved alternative to the semi-empirical and to the screened Rutherford models already available in this very low-energy extension.
Institute of Scientific and Technical Information of China (English)
TU Juan; GUAN J.F.; MATULA T.J.; Crum L.A.; WEI Rong-jue
2008-01-01
The dynamic behaviour of SonoVue microbubbles a new generation ultrasound contrast agent is investigated in real time with light scattering method.Highly diluted SonoVue microbubbles are injected into a diluted gel made of xanthan gum and water.The responses of individual SonoVue bubbles to driven ultrasound pulses are measured.Both linear and nonlinear bubble oscillations are observed and the results suggest that SonoVue microbubbles can generate strong nonlinear responses.By fitting the experimental data of individual bubble responses with Sarkar's model,the shell coating parameter of the bubbles and dilatational viscosity is estimated to be 7.0 nm·s·Pa.
Cooksley, Geraint; Arnaud, Alain; Banwell, Marie-Josée
2013-04-01
Increasingly, geohazard risk managers are looking to satellite observations as a promising option for supporting their risk management and mitigation strategies. The Terrafirma project, aimed at supporting civil protection agencies, local authorities in charge of risk assessment and mitigation is a pan-European ground motion information service funded by the European Space Agency's Global Monitoring for Environment and Security initiative. Over 100 services were delivered to organizations over the last ten years. Terrafirma promotes the use of Synthetic Aperture Radar Interferometry (InSAR) and Persistent Scatterer InSAR (PSI) within three thematic areas for terrain motion analysis: Tectonics, Flooding and Hydrogeology (ground water, landslides and inactive mines), as well as the innovative Wide Area mapping service, aimed at measuring land deformation over very large areas. Terrafirma's thematic services are based on advanced satellite interferometry products; however they exploit additional data sources, including non-EO, coupled with expert interpretation specific to each thematic line. Based on the combination of satellite-derived ground-motion information products with expert motion interpretation, a portfolio of services addressing geo-hazard land motion issues was made available to users. Although not a thematic in itself, the Wide Area mapping product constitutes the fourth quarter of the Terrafirma activities. The wide area processing chain is nearly fully automatic and requires only a little operator interaction. The service offers an operational PSI processing for wide-area mapping with mm accuracy of ground-deformation measurement at a scale of 1:250,000 (i.e. one cm in the map corresponds to 2.5 Km on the ground) on a country or continent level. The WAP was demonstrated using stripmap ERS data however it is foreseen to be a standard for the upcoming Sentinel-1 mission that will be operated in Terrain Observation by Progressive Scan (TOPS) mode. Within
The study of correlation among different scattering parameters in an aggregate dust model
Mazarbhuiya, A. M.; Das, H. S.
2017-09-01
We study the light scattering properties of aggregate particles in a wide range of complex refractive indices (m = n + i k, where 1.4 ≤ n ≤ 2.0, 0.001 ≤ k ≤1.0) and wavelengths (0.45 ≤ λ≤1.25 μ m) to investigate the correlation among different parameters e.g., the positive polarization maximum (P_{max}), the amplitude of the negative polarization (P_{min}), geometric albedo (A), (n,k) and λ. Numerical computations are performed by the Superposition T-matrix code with Ballistic Cluster-Cluster Aggregate (BCCA) particles of 128 monomers and Ballistic Aggregates (BA) particles of 512 monomers, where monomer's radius of aggregates is considered to be 0.1 μm. At a fixed value of k, P_{max} and n are correlated via a quadratic regression equation and this nature is observed at all wavelengths. Further, P_{max} and k are found to be related via a polynomial regression equation when n is taken to be fixed. The degree of the equation depends on the wavelength, higher the wavelength lower is the degree. We find that A and P_{max} are correlated via a cubic regression at λ= 0.45 μ m whereas this correlation is quadratic at higher wavelengths. We notice that |P_{min}| increases with the decrease of P_{max} and a strong linear correlation between them is observed when n is fixed at some value and k is changed from higher to lower value. Further, at a fix value of k, P_{min} and P_{max} can be fitted well via a quartic regression equation when n is changed from higher to lower value. We also find that P_{max} increases with λ and they are correlated via a quartic regression.
Moreau, Ludovic; Caleap, Mihaï; Velichko, Alexander; Wilcox, Paul D.
2012-01-01
International audience; This paper presents an analytical model for the three-dimensional scattering of Lamb and SH waves by a partly through-thickness, flat-bottomed cavity with an irregular shape. In this model, both the scattered field and the standing field in the thinner plate beneath the cavity are decomposed on the basis of Lamb and SH waves, by including propagating and evanescent modes. The amplitude of the modes is calculated after writing the nullity of the total stress at the boun...
Kondratyuk, S; Myhrer, F; Scholten, O
2004-01-01
The Adler-Weisberger and Goldberger-Miyazawa-Oehme sum rules are calculated within a relativistic, unitary and crossing symmetric dynamical model for pion-nucleon scattering using two different methods: 1) by evaluating of the scattering amplitude at the corresponding low-energy kinematics and 2) by evaluating the sum-rule integrals with the calculated total cross section. The discrepancy between the results of the two methods provides a measure of the breaking of analyticity and chiral symmetry in the model. The contribution of the $\\Delta$ resonance, including its dressing with meson loops, is discussed in some detail and found to be small.
Scattering and duality in the 2 dimensional OSp(2|2) gross neveu and sigma models
Saleur, H.; Pozsgay, B.
2010-01-01
We write the thermodynamic Bethe ansatz for the massive OSp(2|2) Gross Neveu and sigma models. We find evidence that the GN S matrix proposed by Bassi and Leclair [12] is the correct one. We determine features of the sigma model S matrix, which seem highly unconventional; we conjecture in particular
A New Empirical Model for Radar Scattering from Bare Soil Surfaces
Directory of Open Access Journals (Sweden)
Nicolas Baghdadi
2016-11-01
Full Text Available The objective of this paper is to propose a new semi-empirical radar backscattering model for bare soil surfaces based on the Dubois model. A wide dataset of backscattering coefficients extracted from synthetic aperture radar (SAR images and in situ soil surface parameter measurements (moisture content and roughness is used. The retrieval of soil parameters from SAR images remains challenging because the available backscattering models have limited performances. Existing models, physical, semi-empirical, or empirical, do not allow for a reliable estimate of soil surface geophysical parameters for all surface conditions. The proposed model, developed in HH, HV, and VV polarizations, uses a formulation of radar signals based on physical principles that are validated in numerous studies. Never before has a backscattering model been built and validated on such an important dataset as the one proposed in this study. It contains a wide range of incidence angles (18°–57° and radar wavelengths (L, C, X, well distributed, geographically, for regions with different climate conditions (humid, semi-arid, and arid sites, and involving many SAR sensors. The results show that the new model shows a very good performance for different radar wavelengths (L, C, X, incidence angles, and polarizations (RMSE of about 2 dB. This model is easy to invert and could provide a way to improve the retrieval of soil parameters.
The gap probability model for canopy thermal infrared emission with non-scattering approximation
Institute of Scientific and Technical Information of China (English)
牛铮; 柳钦火; 高彦春; 张庆员; 王长耀
2000-01-01
To describe canopy emitting thermal radiance precisely and physically is one of the key researches in retrieving land surface temperature (LSI) over vegetation-covered regions by remote sensing technology. This work is aimed at establishing gap probability models to describe the thermal emission characteristics in continuous plant, including the basic model and the sunlit model. They are suitable respectively in the nighttime and in the daytime. The sunlit model is the basic model plus a sunlit correcting item which takes the hot spot effect into account. The researches on the directional distribution of radiance and its relationship to canopy structural parameters, such as the leaf area index (LAI) and leaf angle distribution (LAD), were focused. The characteristics of directional radiance caused by temperature differences among components in canopy, such as those between leaf and soil, and between sunlit leaf or soil and shadowed leaf or soil, were analyzed. A well fitting between experimental data an
Dremin, I M
2012-01-01
When colliding, the high energy hadrons can either produce new particles or scatter elastically without change of their quantum num- bers and other particles produced. Namely elastic scattering of hadrons is considered in this review paper. Even though the inelastic processes dominate at high energies, the elastic scattering constitutes the notice- able part of the total cross section ranging between 18 and 25% with some increase at higher energies. The scattering proceeds mostly at small angles and reveals peculiar dependences at larger angles disclos- ing the geometrical structure of the colliding particles and di?erent dynamical mechanisms. The fast decreasing Gaussian peak at small angles is followed by the exponential (Orear) regime with some shoul- ders and dips and then by the power-like decrease. Results of various theoretical approaches are compared with exper- imental data. Phenomenological models pretending to describe this process are reviewed. The unitarity condition requires the exponen- tial re...
Modeling interface roughness scattering in a layered seabed for normal-incident chirp sonar signals.
Tang, Dajun; Hefner, Brian T
2012-04-01
Downward looking sonar, such as the chirp sonar, is widely used as a sediment survey tool in shallow water environments. Inversion of geo-acoustic parameters from such sonar data precedes the availability of forward models. An exact numerical model is developed to initiate the simulation of the acoustic field produced by such a sonar in the presence of multiple rough interfaces. The sediment layers are assumed to be fluid layers with non-intercepting rough interfaces.
A model for the propagation and scattering of ultrasound in tissue
DEFF Research Database (Denmark)
Jensen, Jørgen Arendt
1991-01-01
of the field from typical transducers used in clinical ultrasound to yield a model for the received pulse-echo pressure field. Analytic expressions are found in the literature for a number of transducers, and any transducer excitation can be incorporated into the model. An example is given for a concave......, nonapodized transducer in which the predicted pressure field is compared to a measured field....
Indian Academy of Sciences (India)
J Tomkinson
2008-10-01
The role that model compounds can play in understanding the vibrational eigenvectors of molecules is discussed. Assigning the spectra of model compounds is of particular importance and the individual-scaling approach, that has been used with isolated molecule ab-initio calculations, is outlined. Special emphasis is given to recent work on assigning the spectra of three 5-6 heterobicyclic systems; indole, benzimidazole and isatin.
The gap probability model for canopy thermal infrared emission with non-scattering approximation
Institute of Scientific and Technical Information of China (English)
无
2000-01-01
To describe canopy emitting thermal radiance precisely and physically is one of the key researches in retrieving land surface temperature (LST) over vegetation-covered regions by remote sensing technology.This work is aimed at establishing gap probability models to describe the thermal emission characteristics in continuous plant,including the basic model and the sunlit model.They are suitable respectively in the nighttime and in the daytime.The sunlit model is the basic model plus a sunlit correcting item which takes the hot spot effect into account.The researches on the directional distribution of radiance and its relationship to canopy structural parameters,such as the leaf area index (LAI) and leaf angle distribution (LAD),were focused.The characteristics of directional radiance caused by temperature differences among components in canopy,such as those between leaf and soil,and between sunlit leaf or soil and shadowed leaf or soil,were analyzed.A well fitting between experimental data and the theoretical calculations shows that the models are able to illustrate the canopy thermal emission generally.
Julia-Diaz, B; Matsuyama, A; Sato, T
2007-01-01
As a first step to analyze the electromagnetic meson production reactions in the nucleon resonance region, the parameters of the hadronic interactions of a dynamical coupled-channel model, developed in {\\it Physics Reports 439, 193 (2007)}, are determined by fitting the empirical $\\pi N$ elastic scattering amplitudes of SAID up to 2 GeV. The channels included in the calculations are $\\pi N$, $\\eta N$ and $\\pi\\pi N$ which has $\\pi\\Delta$, $\\rho N$, and $\\sigma N$ resonant components. The non-resonant meson-baryon interactions of the model are derived from a set of Lagrangians by using a unitary transformation method. One or two bare excited nucleon states in each of $S$, $P$, $D$, and $F$ partial waves are included to generate the resonant amplitudes in the fits. The predicted total cross sections of $\\pi N$ reactions and $\\pi N\\to \\eta N$ reactions are in good agreement with the data. Applications of the constructed model in analyzing the electromagnetic meson production data as well as the future development...
Energy Technology Data Exchange (ETDEWEB)
Gol' danskii, V.I.; Krupyanskii, Yu.F.; Fleurov, V.N.
1986-06-01
Specific features of the Rayleigh Scattering of Moessbauer Radiation (RSMR) technique in the study of biological systems are described. Experimental data show that the temperature and hydration degree are the principal parameters which influence intramolecular mobility in biopolymers. Data on temperature dependencies of elastic fraction, f, and spectrum line-shape do not fit neither Debye or Einstein models of solids nor the free diffusion in liquids and demand for their explanation a multimode approximation (i.e. a wide spectrum of correlation times, at T=293 K from 10/sup -6/s to 10/sup -12/-10/sup -13/s). On the basis of RSMR, low temperature specific heat and X-ray dynamic analysis data and from the general conditions that information macromolecule must be in a non-equilibrium state (an independent confirmation of this fact comes from the kinetic model of protein folding) a glass-like dynamical model of biopolymers is formulated. A possible interpretation of RSMR data shows that fluctuatively prepared tunneling between quasiequilibrium positions (QEP) can prevail activated transitions up to a room temperature.
Dynamical Coupled-Channel Model of pi-N scattering in te W < 2 GeV Nucleon Resonane Region
Energy Technology Data Exchange (ETDEWEB)
Lee, T S.H.; Julia-diaz, B; Matsuyama, A; Sato, T
2007-12-01
As a first step to analyze the electromagnetic meson production reactions in the nucleon resonance region, the parameters of the hadronic interactions of a dynamical coupled-channel model, developed in {\\it Physics Reports 439, 193 (2007)}, are determined by fitting the empirical $\\pi N$ elastic scattering amplitudes of SAID up to 2 GeV. The channels included in the calculations are $\\pi N$, $\\eta N$ and $\\pi\\pi N$ which has $\\pi\\Delta$, $\\rho N$, and $\\sigma N$ resonant components. The non-resonant meson-baryon interactions of the model are derived from a set of Lagrangians by using a unitary transformation method. One or two bare excited nucleon states in each of $S$, $P$, $D$, and $F$ partial waves are included to generate the resonant amplitudes in the fits. The predicted total cross sections of $\\pi N$ reactions and $\\pi N\\rightarrow \\eta N$ reactions are in good agreement with the data. Applications of the constructed model in analyzing the electromagnetic meson production data as well as the future developments are discussed.
Energy Technology Data Exchange (ETDEWEB)
Soto, F. de [Laboratoire Physique Subatomique et Cosmologie, 53 av. des Martyrs, 38026 Grenoble (France)]|[Dpto. Sistemas Fisicos, Quimicos y Naturales, U. Pablo de Olavide, 41013 Sevilla (Spain); Carbonell, J. [Laboratoire Physique Subatomique et Cosmologie, 53 av. des Martyrs, 38026 Grenoble (France)
2007-04-15
The numerical solutions of the non-relativistic Yukawa model on a 3-dimensional size lattice with periodic boundary conditions are obtained. The possibility to extract the corresponding - infinite space - low energy parameters and bound state binding energies from eigenstates computed at finite lattice size is discussed. The results have been obtained with a non relativistic model, which is justified by the small energies involved in the calculations. Despite its simplicity, the model considered contains an essential ingredient of the hadron-hadron interaction - its finite range - which plays a relevant role in view of extracting the low energy parameters from the finite volume spectra. It offers a wieldy and physically sound tool to test the validity of the different approaches discussed in the literature to study the low energy scattering of baryon-baryon or meson-baryon systems from a lattice simulations in QCD. The results presented in this work have been essentially limited to the ground state of central attractive interactions, depending only on one parameter. The method can be easily applied to more involved interactions, like hard core repulsive terms or non central potentials leading to coupled channel equations. (authors)
Calvet, Marie
2008-01-01
We propose to model the uppermost inner core as an aggregate of randomly oriented anisotropic ``patches''. A patch is defined as an assemblage of a possibly large number of crystals with identically oriented crystallographic axes. This simple model accounts for the observed velocity isotropy of short period body waves, and offers a reasonable physical interpretation for the scatterers detected at the top of the inner core. From rigorous multiple scattering modeling of seismic wave propagation through the aggregate, we obtain strong constraints on both the size and the elastic constants of iron patches. We perform a systematic search for iron models compatible with measured seismic velocities and attenuations. An iron model is characterized by its symmetry (cubic or hexagonal), elastic constants, and patch size. Independent of the crystal symmetry, we infer a most likely size of patch of the order of 400 m. Recent {\\it bcc} iron models from the literature are in very good agreement with the most probable elast...
Relativistic model of 2p-2h meson exchange currents in (anti)neutrino scattering
Simo, I Ruiz; Barbaro, M B; De Pace, A; Caballero, J A; Donnelly, T W
2016-01-01
We develop a model of relativistic, charged meson-exchange currents (MEC) for neutrino-nucleus interactions. The two-body current is the sum of seagull, pion-in-flight, pion-pole and $\\Delta$-pole operators. These operators are obtained from the weak pion-production amplitudes for the nucleon derived in the non-linear $\\sigma$-model together with weak excitation of the $\\Delta(1232)$ resonance and its subsequent decay into $N\\pi$. With these currents we compute the five 2p-2h response functions contributing to $(\
Wijk, J.J. van; Spoelder, H.J.W.; Knibbe, W.-J.J.; Shahroudi, K.E.
1997-01-01
We present a system where visualization and the control of the simulation are integrated to facilitate interactive exploration and modeling of large data sets. The system was developed to estimate properties of the atmosphere of Venus from comparison between measured and simulated data. Reuse of res
Power-Law Scattering Models and Nonlinear Parametric Estimation for Super-Resolution Radar
2010-08-26
multiplicities. This is the decomposition, Eq. 3, where P is any matrix. That is, the JNF is the result of a nonunique similarity transform taking A into upper...important feature in the system engineering of real-time systems. - Because it addresses the problem of power law models directly, it is not subject to