The forward rainbow scattering of low energy protons by a graphene sheet

NASA Astrophysics Data System (ADS)

Ćosić, M.; Petrović, S.; Nešković, N.

2018-05-01

This article studies the rainbow scattering of 5-keV protons by the single sheet of free-standing graphene and its possible use as a tool for investigation of the ion-graphene interaction. The proton-graphene interaction potential was constructed by using the Doyle-Turner, ZBL, and Molière proton-carbon interaction potentials. The thermal motion of carbon atoms was included by averaging the potentials according to the Debye model. Proton trajectories were obtained by numerical solution of the corresponding Newton equations of motion. They were used to obtain the mapping of the proton initial positions to their scattering angles. Morphological properties of the introduced mapping including its multiplicity and the rainbow singularities were used to explain important features of the obtained angular distributions of transmitted protons.

Full-potential multiple scattering theory with space-filling cells for bound and continuum states.

PubMed

Hatada, Keisuke; Hayakawa, Kuniko; Benfatto, Maurizio; Natoli, Calogero R

2010-05-12

We present a rigorous derivation of a real-space full-potential multiple scattering theory (FP-MST) that is free from the drawbacks that up to now have impaired its development (in particular the need to expand cell shape functions in spherical harmonics and rectangular matrices), valid both for continuum and bound states, under conditions for space partitioning that are not excessively restrictive and easily implemented. In this connection we give a new scheme to generate local basis functions for the truncated potential cells that is simple, fast, efficient, valid for any shape of the cell and reduces to the minimum the number of spherical harmonics in the expansion of the scattering wavefunction. The method also avoids the need for saturating 'internal sums' due to the re-expansion of the spherical Hankel functions around another point in space (usually another cell center). Thus this approach provides a straightforward extension of MST in the muffin-tin (MT) approximation, with only one truncation parameter given by the classical relation l(max) = kR(b), where k is the electron wavevector (either in the excited or ground state of the system under consideration) and R(b) is the radius of the bounding sphere of the scattering cell. Moreover, the scattering path operator of the theory can be found in terms of an absolutely convergent procedure in the l(max) --> ∞ limit. Consequently, this feature provides a firm ground for the use of FP-MST as a viable method for electronic structure calculations and makes possible the computation of x-ray spectroscopies, notably photo-electron diffraction, absorption and anomalous scattering among others, with the ease and versatility of the corresponding MT theory. Some numerical applications of the theory are presented, both for continuum and bound states.

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

Liu, Xianglin; Wang, Yang; Eisenbach, Markus

One major purpose of studying the single-site scattering problem is to obtain the scattering matrices and differential equation solutions indispensable to multiple scattering theory (MST) calculations. On the other hand, the single-site scattering itself is also appealing because it reveals the physical environment experienced by electrons around the scattering center. In this study, we demonstrate a new formalism to calculate the relativistic full-potential single-site Green's function. We implement this method to calculate the single-site density of states and electron charge densities. Lastly, the code is rigorously tested and with the help of Krein's theorem, the relativistic effects and full potentialmore » effects in group V elements and noble metals are thoroughly investigated.« less

Multiple magnetic scattering in small-angle neutron scattering of Nd-Fe-B nanocrystalline magnet.

PubMed

Ueno, Tetsuro; Saito, Kotaro; Yano, Masao; Ito, Masaaki; Shoji, Tetsuya; Sakuma, Noritsugu; Kato, Akira; Manabe, Akira; Hashimoto, Ai; Gilbert, Elliot P; Keiderling, Uwe; Ono, Kanta

2016-06-20

We have investigated the influence of multiple scattering on the magnetic small-angle neutron scattering (SANS) from a Nd-Fe-B nanocrystalline magnet. We performed sample-thickness- and neutron-wavelength-dependent SANS measurements, and observed the scattering vector dependence of the multiple magnetic scattering. It is revealed that significant multiple scattering exists in the magnetic scattering rather than the nuclear scattering of Nd-Fe-B nanocrystalline magnet. It is considered that the mean free path of the neutrons for magnetic scattering is rather short in Nd-Fe-B magnets. We analysed the SANS data by the phenomenological magnetic correlation model considering the magnetic microstructures and obtained the microstructural parameters.

Multiple magnetic scattering in small-angle neutron scattering of Nd–Fe–B nanocrystalline magnet

PubMed Central

Ueno, Tetsuro; Saito, Kotaro; Yano, Masao; Ito, Masaaki; Shoji, Tetsuya; Sakuma, Noritsugu; Kato, Akira; Manabe, Akira; Hashimoto, Ai; Gilbert, Elliot P.; Keiderling, Uwe; Ono, Kanta

2016-01-01

We have investigated the influence of multiple scattering on the magnetic small-angle neutron scattering (SANS) from a Nd–Fe–B nanocrystalline magnet. We performed sample-thickness- and neutron-wavelength-dependent SANS measurements, and observed the scattering vector dependence of the multiple magnetic scattering. It is revealed that significant multiple scattering exists in the magnetic scattering rather than the nuclear scattering of Nd–Fe–B nanocrystalline magnet. It is considered that the mean free path of the neutrons for magnetic scattering is rather short in Nd–Fe–B magnets. We analysed the SANS data by the phenomenological magnetic correlation model considering the magnetic microstructures and obtained the microstructural parameters. PMID:27321149

Self-interaction correction in multiple scattering theory: application to transition metal oxides

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

Daene, Markus W; Lueders, Martin; Ernst, Arthur

2009-01-01

We apply to transition metal monoxides the self-interaction corrected (SIC) local spin density (LSD) approximation, implemented locally in the multiple scattering theory within the Korringa-Kohn-Rostoker (KKR) band structure method. The calculated electronic structure and in particular magnetic moments and energy gaps are discussed in reference to the earlier SIC results obtained within the LMTO-ASA band structure method, involving transformations between Bloch and Wannier representations to solve the eigenvalue problem and calculate the SIC charge and potential. Since the KKR can be easily extended to treat disordered alloys, by invoking the coherent potential approximation (CPA), in this paper we compare themore » CPA approach and supercell calculations to study the electronic structure of NiO with cation vacancies.« less

MsSpec-1.0: A multiple scattering package for electron spectroscopies in material science

NASA Astrophysics Data System (ADS)

Sébilleau, Didier; Natoli, Calogero; Gavaza, George M.; Zhao, Haifeng; Da Pieve, Fabiana; Hatada, Keisuke

2011-12-01

We present a multiple scattering package to calculate the cross-section of various spectroscopies namely photoelectron diffraction (PED), Auger electron diffraction (AED), X-ray absorption (XAS), low-energy electron diffraction (LEED) and Auger photoelectron coincidence spectroscopy (APECS). This package is composed of three main codes, computing respectively the cluster, the potential and the cross-section. In the latter case, in order to cover a range of energies as wide as possible, three different algorithms are provided to perform the multiple scattering calculation: full matrix inversion, series expansion or correlation expansion of the multiple scattering matrix. Numerous other small Fortran codes or bash/csh shell scripts are also provided to perform specific tasks. The cross-section code is built by the user from a library of subroutines using a makefile. Program summaryProgram title: MsSpec-1.0 Catalogue identifier: AEJT_v1_0 Program summary URL:http://cpc.cs.qub.ac.uk/summaries/AEJT_v1_0.html Program obtainable from: CPC Program Library, Queen's University, Belfast, N. Ireland Licensing provisions: Standard CPC licence, http://cpc.cs.qub.ac.uk/licence/licence.html No. of lines in distributed program, including test data, etc.: 504 438 No. of bytes in distributed program, including test data, etc.: 14 448 180 Distribution format: tar.gz Programming language: Fortran 77 Computer: Any Operating system: Linux, MacOs RAM: Bytes Classification: 7.2 External routines: Lapack ( http://www.netlib.org/lapack/) Nature of problem: Calculation of the cross-section of various spectroscopies. Solution method: Multiple scattering. Running time: The test runs provided only take a few seconds to run.

Surface wave scattering from sharp lateral discontinuities

NASA Astrophysics Data System (ADS)

Pollitz, Fred F.

1994-11-01

The problem of surface wave scattering is re-explored, with quasi-degenerate normal mode coupling as the starting point. For coupling among specified spheroidal and toroidal mode dispersion branches, a set of coupled wave equations is derived in the frequency domain for first-arriving Rayleigh and Love waves. The solutions to these coupled wave equations using linear perturbation theory are surface integrals over the unit sphere covering the lateral distribution of perturbations in Earth structure. For isotropic structural perturbations and surface topographic perturbations, these solutions agree with the Born scattering theory previously obtained by Snieder and Romanowicz. By transforming these surface integrals into line integrals along the boundaries of the heterogeneous regions in the case of sharp discontinuities, and by using uniformly valid Green's functions, it is possible to extend the solution to the case of multiple scattering interactions. The proposed method allows the relatively rapid calculation of exact second order scattered wavefield potentials for scattering by sharp discontinuities, and it has many advantages not realized in earlier treatments. It employs a spherical Earth geometry, uses no far field approximation, and implicitly contains backward as well as forward scattering. Comparisons of asymptotic scattering and an exact solution with single scattering and multiple scattering integral formulations show that the phase perturbation predicted by geometrical optics breaks down for scatterers less than about six wavelengths in diameter, and second-order scattering predicts well both the amplitude and phase pattern of the exact wavefield for sufficiently small scatterers, less than about three wavelengths in diameter for anomalies of a few percent.

Optical-model abrasion cross sections for high-energy heavy ions

NASA Technical Reports Server (NTRS)

Townsend, L. W.

1981-01-01

Within the context of eikonal scattering theory, a generalized optical model potential approximation to the nucleus-nucleus multiple scattering series is used in an abrasion-ablation collision model to predict abrasion cross sections for relativistic projectile heavy ions. Unlike the optical limit of Glauber theory, which cannot be used for very light nuclei, the abrasion formalism is valid for any projectile target combination at any incident kinetic energy for which eikonal scattering theory can be utilized. Results are compared with experimental results and predictions from Glauber theory.

X-ray solution scattering combined with computation characterizing protein folds and multiple conformational states : computation and application.

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

Yang, S.; Park, S.; Makowski, L.

Small angle X-ray scattering (SAXS) is an increasingly powerful technique to characterize the structure of biomolecules in solution. We present a computational method for accurately and efficiently computing the solution scattering curve from a protein with dynamical fluctuations. The method is built upon a coarse-grained (CG) representation of the protein. This CG approach takes advantage of the low-resolution character of solution scattering. It allows rapid determination of the scattering pattern from conformations extracted from CG simulations to obtain scattering characterization of the protein conformational landscapes. Important elements incorporated in the method include an effective residue-based structure factor for each aminomore » acid, an explicit treatment of the hydration layer at the surface of the protein, and an ensemble average of scattering from all accessible conformations to account for macromolecular flexibility. The CG model is calibrated and illustrated to accurately reproduce the experimental scattering curve of Hen egg white lysozyme. We then illustrate the computational method by calculating the solution scattering pattern of several representative protein folds and multiple conformational states. The results suggest that solution scattering data, when combined with a reliable computational method, have great potential for a better structural description of multi-domain complexes in different functional states, and for recognizing structural folds when sequence similarity to a protein of known structure is low. Possible applications of the method are discussed.« less

Regularized wave equation migration for imaging and data reconstruction

NASA Astrophysics Data System (ADS)

Kaplan, Sam T.

The reflection seismic experiment results in a measurement (reflection seismic data) of the seismic wavefield. The linear Born approximation to the seismic wavefield leads to a forward modelling operator that we use to approximate reflection seismic data in terms of a scattering potential. We consider approximations to the scattering potential using two methods: the adjoint of the forward modelling operator (migration), and regularized numerical inversion using the forward and adjoint operators. We implement two parameterizations of the forward modelling and migration operators: source-receiver and shot-profile. For both parameterizations, we find requisite Green's function using the split-step approximation. We first develop the forward modelling operator, and then find the adjoint (migration) operator by recognizing a Fredholm integral equation of the first kind. The resulting numerical system is generally under-determined, requiring prior information to find a solution. In source-receiver migration, the parameterization of the scattering potential is understood using the migration imaging condition, and this encourages us to apply sparse prior models to the scattering potential. To that end, we use both a Cauchy prior and a mixed Cauchy-Gaussian prior, finding better resolved estimates of the scattering potential than are given by the adjoint. In shot-profile migration, the parameterization of the scattering potential has its redundancy in multiple active energy sources (i.e. shots). We find that a smallest model regularized inverse representation of the scattering potential gives a more resolved picture of the earth, as compared to the simpler adjoint representation. The shot-profile parameterization allows us to introduce a joint inversion to further improve the estimate of the scattering potential. Moreover, it allows us to introduce a novel data reconstruction algorithm so that limited data can be interpolated/extrapolated. The linearized operators are expensive, encouraging their parallel implementation. For the source-receiver parameterization of the scattering potential this parallelization is non-trivial. Seismic data is typically corrupted by various types of noise. Sparse coding can be used to suppress noise prior to migration. It is a method that stems from information theory and that we apply to noise suppression in seismic data.

Full multiple-scattering calculations on silicates and oxides at the Al K edge

NASA Astrophysics Data System (ADS)

Cabaret, Delphine; Sainctavit, Philippe; Ildefonse, Philippe; Flank, Anne-Marie

1996-05-01

We present full multiple-scattering calculations at the aluminium K edge that we compare with experiments for four crystalline silicates and oxide minerals. In the different minerals aluminium atoms are either fourfold or sixfold coordinated to oxygen atoms in Al sites that are poorly symmetric. The calculations are based on different choices of one-electron potentials according to aluminium coordinations and crystallographic structures of the compounds. Hence it is possible to determine how the near-edge spectral features are a sensitive probe of the effective potential seen by the photoelectron in the molecular environment. The purpose of this work is to determine on the one hand the relation between Al K-edge spectral features and the geometrical arrangements around the aluminium sites, and on the other hand the electronic structure of the compounds.

Enhanced backscattering of optical waves due to densely distributed scatterers

NASA Astrophysics Data System (ADS)

Ma, Yushieh; Varadan, Vijay K.; Varadan, Vasundara V.

1988-01-01

Using multiple scattering theory, the T matrix of a pair of scatterers which takes all back-and-forth scattering between the pair members into account and considers multiple scattering effects in the intensity calculation is used to calculate the magnitude and the width of the backscattered intensity peak. Generally, at low concentrations, both the magnitude of the scattered intensity and multiple scattering contributions are not sufficiently strong to reach the enhanced-backscattering threshold. The results obtained are consistent with those yielded by optical experiments.

Exploring the Potential of Smartphones and Tablets for Performance Support in Food Chemistry Laboratory Classes

ERIC Educational Resources Information Center

van der Kolk, Koos; Hartog, Rob; Beldman, Gerrit; Gruppen, Harry

2013-01-01

Increasingly, mobile applications appear on the market that can support students in chemistry laboratory classes. In a multiple app-supported laboratory, each of these applications covers one use-case. In practice, this leads to situations in which information is scattered over different screens and written materials. Such a multiple app-supported…

Frequency-domain method for measuring spectral properties in multiple-scattering media: methemoglobin absorption spectrum in a tissuelike phantom

NASA Astrophysics Data System (ADS)

Fishkin, Joshua B.; So, Peter T. C.; Cerussi, Albert E.; Gratton, Enrico; Fantini, Sergio; Franceschini, Maria Angela

1995-03-01

We have measured the optical absorption and scattering coefficient spectra of a multiple-scattering medium (i.e., a biological tissue-simulating phantom comprising a lipid colloid) containing methemoglobin by using frequency-domain techniques. The methemoglobin absorption spectrum determined in the multiple-scattering medium is in excellent agreement with a corrected methemoglobin absorption spectrum obtained from a steady-state spectrophotometer measurement of the optical density of a minimally scattering medium. The determination of the corrected methemoglobin absorption spectrum takes into account the scattering from impurities in the methemoglobin solution containing no lipid colloid. Frequency-domain techniques allow for the separation of the absorbing from the scattering properties of multiple-scattering media, and these techniques thus provide an absolute

Cloud Effects in Hyperspectral Imagery from First-Principles Scene Simulations

DTIC Science & Technology

2009-01-01

SPIE. One print or electronic copy may be made for personal use only. Systematic or multiple reproduction, or distribution to multiple locations...scattering and absorption, scattering events, surface scattering with material-dependent bidirectional reflectances, multiple surface adjacency...aerosols or clouds, they may be absorbed, or they may reflect off the ground or an object. A given photon may undergo multiple scattering events

The importance of scattering, surface potential, and vanguard counter-potential in terahertz emission from gallium arsenide

NASA Astrophysics Data System (ADS)

Cortie, D. L.; Lewis, R. A.

2012-06-01

It is well established that under excitation by short (<1 ps), above-band-gap optical pulses, semiconductor surfaces may emit terahertz-frequency electromagnetic radiation via photocarrier diffusion (the dominant mechanism in InAs) or photocarrier drift (dominant in GaAs). Our three-dimensional ensemble Monte Carlo simulations allow multiple physical parameters to vary over wide ranges and provide unique direct insight into the factors controlling terahertz emission. We find for GaAs (in contrast to InAs), scattering and the surface potential are key factors. We further delineate in GaAs (as in InAs) the role of a vanguard counter-potential. The effects of varying dielectric constant, band-gap, and effective mass are similar in both emitter types.

Foreign body detection in food materials using compton scattered x-rays

NASA Astrophysics Data System (ADS)

McFarlane, Nigel James Bruce

This thesis investigated the application of X-ray Compton scattering to the problem of foreign body detection in food. The methods used were analytical modelling, simulation and experiment. A criterion was defined for detectability, and a model was developed for predicting the minimum time required for detection. The model was used to predict the smallest detectable cubes of air, glass, plastic and steel. Simulations and experiments were performed on voids and glass in polystyrene phantoms, water, coffee and muesli. Backscatter was used to detect bones in chicken meat. The effects of geometry and multiple scatter on contrast, signal-to-noise, and detection time were simulated. Compton scatter was compared with transmission, and the effect of inhomogeneity was modelled. Spectral shape was investigated as a means of foreign body detection. A signal-to-noise ratio of 7.4 was required for foreign body detection in food. A 0.46 cm cube of glass or a 1.19 cm cube of polystyrene were detectable in a 10 cm cube of water in one second. The minimum time to scan a whole sample varied as the 7th power of the foreign body size, and the 5th power of the sample size. Compton scatter inspection produced higher contrasts than transmission, but required longer measurement times because of the low number of photon counts. Compton scatter inspection of whole samples was very slow compared to production line speeds in the food industry. There was potential for Compton scatter in applications which did not require whole-sample scanning, such as surface inspection. There was also potential in the inspection of inhomogeneous samples. The multiple scatter fraction varied from 25% to 55% for 2 to 10 cm cubes of water, but did not have a large effect on the detection time. The spectral shape gave good contrasts and signal-to-noise ratios in the detection of chicken bones.

CO2, H2O, and chlorophyll fluorescence retrieved from OCO-2 measurements using a fast radiative transfer model approximating multiple scattering effects

NASA Astrophysics Data System (ADS)

Reuter, Maximilian; Bovensmann, Heinrich; Buchwitz, Michael; Burrows, John P.; Heymann, Jens; Noël, Stefan; Rozanov, Vladimir; Schneising, Oliver

2017-04-01

Carbon dioxide is the most important anthropogenic greenhouse gas. Its global increasing concentration in the Earth's atmosphere is the main driver for global climate change. In spite of its importance, there are still large uncertainties on its global sources and sinks. Satellite measurements have the potential to reduce these surface flux uncertainties. However, the demanding accuracy requirements usually involve the need for precise radiative transfer calculations in a scattering atmosphere. These can be computationally so expensive that hundreds or thousands of CPU cores are need to keep up with the data stream of an instrument like OCO-2. Future instruments will further increase the amount of soundings at least by an order of magnitude. A radiative transfer model has been developed approximating scattering effects by multiple scattering at an optically thin scattering layer reducing the computational costs by several orders of magnitude. The model can be used to simulate the radiance in all three OCO-2 spectral bands allowing the simultaneous retrieval of CO2, H2O, and chlorophyll fluorescence. First retrieval results for OCO-2 data will be presented.

MIMO nonlinear ultrasonic tomography by propagation and backpropagation method.

PubMed

Dong, Chengdong; Jin, Yuanwei

2013-03-01

This paper develops a fast ultrasonic tomographic imaging method in a multiple-input multiple-output (MIMO) configuration using the propagation and backpropagation (PBP) method. By this method, ultrasonic excitation signals from multiple sources are transmitted simultaneously to probe the objects immersed in the medium. The scattering signals are recorded by multiple receivers. Utilizing the nonlinear ultrasonic wave propagation equation and the received time domain scattered signals, the objects are to be reconstructed iteratively in three steps. First, the propagation step calculates the predicted acoustic potential data at the receivers using an initial guess. Second, the difference signal between the predicted value and the measured data is calculated. Third, the backpropagation step computes updated acoustical potential data by backpropagating the difference signal to the same medium computationally. Unlike the conventional PBP method for tomographic imaging where each source takes turns to excite the acoustical field until all the sources are used, the developed MIMO-PBP method achieves faster image reconstruction by utilizing multiple source simultaneous excitation. Furthermore, we develop an orthogonal waveform signaling method using a waveform delay scheme to reduce the impact of speckle patterns in the reconstructed images. By numerical experiments we demonstrate that the proposed MIMO-PBP tomographic imaging method results in faster convergence and achieves superior imaging quality.

Dual wavelength multiple-angle light scattering system for cryptosporidium detection

NASA Astrophysics Data System (ADS)

Buaprathoom, S.; Pedley, S.; Sweeney, S. J.

2012-06-01

A simple, dual wavelength, multiple-angle, light scattering system has been developed for detecting cryptosporidium suspended in water. Cryptosporidium is a coccidial protozoan parasite causing cryptosporidiosis; a diarrheal disease of varying severity. The parasite is transmitted by ingestion of contaminated water, particularly drinking-water, but also accidental ingestion of bathing-water, including swimming pools. It is therefore important to be able to detect these parasites quickly, so that remedial action can be taken to reduce the risk of infection. The proposed system combines multiple-angle scattering detection of a single and two wavelengths, to collect relative wavelength angle-resolved scattering phase functions from tested suspension, and multivariate data analysis techniques to obtain characterizing information of samples under investigation. The system was designed to be simple, portable and inexpensive. It employs two diode lasers (violet InGaN-based and red AlGaInP-based) as light sources and silicon photodiodes as detectors and optical components, all of which are readily available. The measured scattering patterns using the dual wavelength system showed that the relative wavelength angle-resolved scattering pattern of cryptosporidium oocysts was significantly different from other particles (e.g. polystyrene latex sphere, E.coli). The single wavelength set up was applied for cryptosporidium oocysts'size and relative refractive index measurement and differential measurement of the concentration of cryptosporidium oocysts suspended in water and mixed polystyrene latex sphere suspension. The measurement results showed good agreement with the control reference values. These results indicate that the proposed method could potentially be applied to online detection in a water quality control system.

A multiwave range test for obstacle reconstructions with unknown physical properties

NASA Astrophysics Data System (ADS)

Potthast, Roland; Schulz, Jochen

2007-08-01

We develop a new multiwave version of the range test for shape reconstruction in inverse scattering theory. The range test [R. Potthast, et al., A `range test' for determining scatterers with unknown physical properties, Inverse Problems 19(3) (2003) 533-547] has originally been proposed to obtain knowledge about an unknown scatterer when the far field pattern for only one plane wave is given. Here, we extend the method to the case of multiple waves and show that the full shape of the unknown scatterer can be reconstructed. We further will clarify the relation between the range test methods, the potential method [A. Kirsch, R. Kress, On an integral equation of the first kind in inverse acoustic scattering, in: Inverse Problems (Oberwolfach, 1986), Internationale Schriftenreihe zur Numerischen Mathematik, vol. 77, Birkhauser, Basel, 1986, pp. 93-102] and the singular sources method [R. Potthast, Point sources and multipoles in inverse scattering theory, Habilitation Thesis, Gottingen, 1999]. In particular, we propose a new version of the Kirsch-Kress method using the range test and a new approach to the singular sources method based on the range test and potential method. Numerical examples of reconstructions for all four methods are provided.

Method and apparatus for fiber optic multiple scattering suppression

NASA Technical Reports Server (NTRS)

Ackerson, Bruce J. (Inventor)

2000-01-01

The instant invention provides a method and apparatus for use in laser induced dynamic light scattering which attenuates the multiple scattering component in favor of the single scattering component. The preferred apparatus utilizes two light detectors that are spatially and/or angularly separated and which simultaneously record the speckle pattern from a single sample. The recorded patterns from the two detectors are then cross correlated in time to produce one point on a composite single/multiple scattering function curve. By collecting and analyzing cross correlation measurements that have been taken at a plurality of different spatial/angular positions, the signal representative of single scattering may be differentiated from the signal representative of multiple scattering, and a near optimum detector separation angle for use in taking future measurements may be determined.

A Markov Chain-based quantitative study of angular distribution of photons through turbid slabs via isotropic light scattering

NASA Astrophysics Data System (ADS)

Li, Xuesong; Northrop, William F.

2016-04-01

This paper describes a quantitative approach to approximate multiple scattering through an isotropic turbid slab based on Markov Chain theorem. There is an increasing need to utilize multiple scattering for optical diagnostic purposes; however, existing methods are either inaccurate or computationally expensive. Here, we develop a novel Markov Chain approximation approach to solve multiple scattering angular distribution (AD) that can accurately calculate AD while significantly reducing computational cost compared to Monte Carlo simulation. We expect this work to stimulate ongoing multiple scattering research and deterministic reconstruction algorithm development with AD measurements.

Variational treatment of electron-polyatomic-molecule scattering calculations using adaptive overset grids

NASA Astrophysics Data System (ADS)

Greenman, Loren; Lucchese, Robert R.; McCurdy, C. William

2017-11-01

The complex Kohn variational method for electron-polyatomic-molecule scattering is formulated using an overset-grid representation of the scattering wave function. The overset grid consists of a central grid and multiple dense atom-centered subgrids that allow the simultaneous spherical expansions of the wave function about multiple centers. Scattering boundary conditions are enforced by using a basis formed by the repeated application of the free-particle Green's function and potential Ĝ0+V ̂ on the overset grid in a Born-Arnoldi solution of the working equations. The theory is shown to be equivalent to a specific Padé approximant to the T matrix and has rapid convergence properties, in both the number of numerical basis functions employed and the number of partial waves employed in the spherical expansions. The method is demonstrated in calculations on methane and CF4 in the static-exchange approximation and compared in detail with calculations performed with the numerical Schwinger variational approach based on single-center expansions. An efficient procedure for operating with the free-particle Green's function and exchange operators (to which no approximation is made) is also described.

Measurement and modeling of the acoustic field near an underwater vehicle and implications for acoustic source localization.

PubMed

Lepper, Paul A; D'Spain, Gerald L

2007-08-01

The performance of traditional techniques of passive localization in ocean acoustics such as time-of-arrival (phase differences) and amplitude ratios measured by multiple receivers may be degraded when the receivers are placed on an underwater vehicle due to effects of scattering. However, knowledge of the interference pattern caused by scattering provides a potential enhancement to traditional source localization techniques. Results based on a study using data from a multi-element receiving array mounted on the inner shroud of an autonomous underwater vehicle show that scattering causes the localization ambiguities (side lobes) to decrease in overall level and to move closer to the true source location, thereby improving localization performance, for signals in the frequency band 2-8 kHz. These measurements are compared with numerical modeling results from a two-dimensional time domain finite difference scheme for scattering from two fluid-loaded cylindrical shells. Measured and numerically modeled results are presented for multiple source aspect angles and frequencies. Matched field processing techniques quantify the source localization capabilities for both measurements and numerical modeling output.

Evolutions Of Diff-Tomo For Sensing Subcanopy Deformations And Height-Varying Temporal Coherence

NASA Astrophysics Data System (ADS)

Lombardini, Fabrizio; Cai, Francesco

2012-01-01

Interest is continuing to grow in advanced interferometric SAR methods for sensing complex scenarios with multiple (layover or volumetric) scatterers mapped in the SAR cell. Multibaseline SAR tomographic (3D) elevation beam forming is a promising technique in this field. Recently, the Tomo concept has been integrated with the differential interferometry concept, producing the advanced “differential tomography” (Diff-Tomo, “4D”) processing mode which furnishes “space-time” signatures of multiple scatterer dynamics in the SAR cell. Advances in the application of this new framework are investigated for complex volume scattering scenarios including temporal signal variations, both from scatterer temporal decorrelation and deformation motions. In particular, new results are reported concerning the potentials of Diff-Tomo for the analysis of forest scenarios, based on the original concept of the space-time signatures of temporal decorrelation. E-SAR P-band data results are expanded of tomography robust to temporal decorrelation, and first trials are reported of separation of different temporal decorrelation mechanisms of canopy and ground, and of sensing possible sub-canopy subsidences.

A wavelet analysis for the X-ray absorption spectra of molecules

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

Penfold, T. J.; Ecole polytechnique Federale de Lausanne, Laboratoire de chimie et biochimie computationnelles, ISIC, FSB-BCH, CH-1015 Lausanne; SwissFEL, Paul Scherrer Inst, CH-5232 Villigen

2013-01-07

We present a Wavelet transform analysis for the X-ray absorption spectra of molecules. In contrast to the traditionally used Fourier transform approach, this analysis yields a 2D correlation plot in both R- and k-space. As a consequence, it is possible to distinguish between different scattering pathways at the same distance from the absorbing atom and between the contributions of single and multiple scattering events, making an unambiguous assignment of the fine structure oscillations for complex systems possible. We apply this to two previously studied transition metal complexes, namely iron hexacyanide in both its ferric and ferrous form, and a rheniummore » diimine complex, [ReX(CO){sub 3}(bpy)], where X = Br, Cl, or ethyl pyridine (Etpy). Our results demonstrate the potential advantages of using this approach and they highlight the importance of multiple scattering, and specifically the focusing phenomenon to the extended X-ray absorption fine structure (EXAFS) spectra of these complexes. We also shed light on the low sensitivity of the EXAFS spectrum to the Re-X scattering pathway.« less

Vegetable Oil-Loaded Nanocapsules: Innovative Alternative for Incorporating Drugs for Parenteral Administration.

PubMed

Venturinil, C G; Bruinsmann, A; Oliveira, C P; Contri, R V; Pohlmann, A R; Guterres, S S

2016-02-01

An innovative nanocapsule formulation for parenteral administration using selected vegetable oils (mango, jojoba, pequi, oat, annatto, calendula, and chamomile) was developed that has the potential to encapsulate various drugs. The vegetable oil-loaded nanocapsules were prepared by interfacial deposition and compared with capric/caprylic triglyceride-loaded lipid core nanocapsules. The major objective was to investigate the effect of vegetable oils on particle size distribution and physical stability and to determine the hemolytic potential of the nanocapsules, considering their applicability for intravenous administration. Taking into account the importance of accurately determining particle size for the selected route of administration, different size characterization techniques were employed, such as Laser Diffraction, Dynamic Light Scattering, Multiple Light Scattering, Nanoparticle Tracking Analysis, and Transmission Electronic Microscopy. Laser diffraction studies indicated that the mean particle size of all nanocapsules was below 300 nm. For smaller particles, the laser diffraction and multiple light scattering data were in agreement (D[3,2]-130 nm). Dynamic light scattering and nanoparticle tracking analysis, two powerful techniques that complement each other, exhibited size values between 180 and 259 nm for all nanoparticles. Stability studies demonstrated a tendency of particle creaming for jojoba-nanocapsules and sedimentation for the other nanoparticles; however, no size variation occurred over 30 days. The hemolysis test proved the hemocompatibility of all nanosystems, irrespective of the type of oil. Although all developed nanocapsules presented the potential for parenteral administration, jojoba oil-loaded nanocapsules were selected as the most promising nanoformulation due to their low average size and high particle size homogeneity.

Theory of Multiple Coulomb Scattering from Extended Nuclei

DOE R&D Accomplishments Database

Cooper, L. N.; Rainwater, J.

1954-08-01

Two independent methods are described for calculating the multiple scattering distribution for projected angle scattering resulting when very high energy charged particles traverse a thick scatterer. The results are compared with the theories of Moliere and Olbert.

Extrinsic extinction cross-section in the multiple acoustic scattering by fluid particles

NASA Astrophysics Data System (ADS)

Mitri, F. G.

2017-04-01

Cross-sections (and their related energy efficiency factors) are physical parameters used in the quantitative analysis of different phenomena arising from the interaction of waves with a particle (or multiple particles). Earlier works with the acoustic scattering theory considered such quadratic (i.e., nonlinear) quantities for a single scatterer, although a few extended the formalism for a pair of scatterers but were limited to the scattering cross-section only. Therefore, the standard formalism applied to viscous particles is not suitable for the complete description of the cross-sections and energy balance of the multiple-particle system because both absorption and extinction phenomena arise during the multiple scattering process. Based upon the law of the conservation of energy, this work provides a complete comprehensive analysis for the extrinsic scattering, absorption, and extinction cross-sections (i.e., in the far-field) of a pair of viscous scatterers of arbitrary shape, immersed in a nonviscous isotropic fluid. A law of acoustic extinction taking into consideration interparticle effects in wave propagation is established, which constitutes a generalized form of the optical theorem in multiple scattering. Analytical expressions for the scattering, absorption, and extinction cross-sections are derived for plane progressive waves with arbitrary incidence. The mathematical expressions are formulated in partial-wave series expansions in cylindrical coordinates involving the angle of incidence, the addition theorem for the cylindrical wave functions, and the expansion coefficients of the scatterers. The analysis shows that the multiple scattering cross-section depends upon the expansion coefficients of both scatterers in addition to an interference factor that depends on the interparticle distance. However, the extinction cross-section depends on the expansion coefficients of the scatterer located in a particular system of coordinates, in addition to the interference term. Numerical examples illustrate the analysis for two viscous fluid circular cylindrical cross-sections immersed in a non-viscous fluid. Computations for the (non-dimensional) scattering, absorption, and extinction cross-section factors are performed with particular emphasis on varying the angle of incidence, the interparticle distance, and the sizes, and the physical properties of the particles. A symmetric behavior is observed for the dimensionless multiple scattering cross-section, while asymmetries arise for both the dimensionless absorption and extinction cross-sections with respect to the angle of incidence. The present analysis provides a complete analytical and computational method for the prediction of cross-section and energy efficiency factors in multiple acoustic scattering of plane waves of arbitrary incidence by a pair of scatterers. The results can be used as a priori information in the direct or inverse characterization of multiple scattering systems such as acoustically engineered fluid metamaterials with reconfigurable periodicities, cloaking devices, liquid crystals, and other applications.

Closed-loop multiple-scattering imaging with sparse seismic measurements

NASA Astrophysics Data System (ADS)

Berkhout, A. J. Guus

2018-03-01

In the theoretical situation of noise-free, complete data volumes (`perfect data'), seismic data matrices are fully filled and multiple-scattering operators have the minimum-phase property. Perfect data allow direct inversion methods to be successful in removing surface and internal multiple scattering. Moreover, under these perfect data conditions direct source wavefields realize complete illumination (no irrecoverable shadow zones) and, therefore, primary reflections (first-order response) can provide us with the complete seismic image. However, in practice seismic measurements always contain noise and we never have complete data volumes at our disposal. We actually deal with sparse data matrices that cannot be directly inverted. The message of this paper is that in practice multiple scattering (including source ghosting) must not be removed but must be utilized. It is explained that in the real world we badly need multiple scattering to fill the illumination gaps in the subsurface. It is also explained that the proposed multiple-scattering imaging algorithm gives us the opportunity to decompose both the image and the wavefields into order-based constituents, making the multiple scattering extension easy to apply. Last but not least, the algorithm allows us to use the minimum-phase property to validate and improve images in an objective way.

Multiple scattering and the density distribution of a Cs MOT.

PubMed

Overstreet, K; Zabawa, P; Tallant, J; Schwettmann, A; Shaffer, J

2005-11-28

Multiple scattering is studied in a Cs magneto-optical trap (MOT). We use two Abel inversion algorithms to recover density distributions of the MOT from fluorescence images. Deviations of the density distribution from a Gaussian are attributed to multiple scattering.

Effects of multiple scattering on time- and depth-resolved signals in airborne lidar systems

NASA Technical Reports Server (NTRS)

Punjabi, A.; Venable, D. D.

1986-01-01

A semianalytic Monte Carlo radiative transfer model (SALMON) is employed to probe the effects of multiple-scattering events on the time- and depth-resolved lidar signals from homogeneous aqueous media. The effective total attenuation coefficients in the single-scattering approximation are determined as functions of dimensionless parameters characterizing the lidar system and the medium. Results show that single-scattering events dominate when these parameters are close to their lower bounds and that when their values exceed unity multiple-scattering events dominate.

Intermediate energy proton-deuteron elastic scattering

NASA Technical Reports Server (NTRS)

Wilson, J. W.

1973-01-01

A fully symmetrized multiple scattering series is considered for the description of proton-deuteron elastic scattering. An off-shell continuation of the experimentally known twobody amplitudes that retains the exchange symmeteries required for the calculation is presented. The one boson exchange terms of the two body amplitudes are evaluated exactly in this off-shell prescription. The first two terms of the multiple scattering series are calculated explicitly whereas multiple scattering effects are obtained as minimum variance estimates from the 146-MeV data of Postma and Wilson. The multiple scattering corrections indeed consist of low order partial waves as suggested by Sloan based on model studies with separable interactions. The Hamada-Johnston wave function is shown consistent with the data for internucleon distances greater than about 0.84 fm.

Improvements in simulation of multiple scattering effects in ATLAS fast simulation

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

Basalaev, A. E., E-mail: artem.basalaev@cern.ch

Fast ATLAS Tracking Simulation (Fatras) package was verified on single layer geometry with respect to full simulation with GEANT4. Fatras hadronic interactions and multiple scattering simulation were studied in comparison with GEANT4. Disagreement was found in multiple scattering distributions of primary charged particles (μ, π, e). A new model for multiple scattering simulation was implemented in Fatras. The model was based on R. Frühwirth’s mixture models. New model was tested on single layer geometry and a good agreement with GEANT4 was achieved. Also a comparison of reconstructed tracks’ parameters was performed for Inner Detector geometry, and Fatras with new multiplemore » scattering model proved to have better agreement with GEANT4. New model of multiple scattering was added as a part of Fatras package in the development release of ATLAS software—ATHENA.« less

Airborne Polarized Lidar Detection of Scattering Layers in the Ocean

NASA Astrophysics Data System (ADS)

Vasilkov, Alexander P.; Goldin, Yury A.; Gureev, Boris A.; Hoge, Frank E.; Swift, Robert N.; Wright, C. Wayne

2001-08-01

A polarized lidar technique based on measurements of waveforms of the two orthogonal-polarized components of the backscattered light pulse is proposed to retrieve vertical profiles of the seawater scattering coefficient. The physical rationale for the polarized technique is that depolarization of backscattered light originating from a linearly polarized laser beam is caused largely by multiple small-angle scattering from particulate matter in seawater. The magnitude of the small-angle scattering is determined by the scattering coefficient. Therefore information on the vertical distribution of the scattering coefficient can be derived potentially from measurements of the timedepth dependence of depolarization in the backscattered laser pulse. The polarized technique was verified by field measurements conducted in the Middle Atlantic Bight of the western North Atlantic Ocean that were supported by in situ measurements of the beam attenuation coefficient. The airborne polarized lidar measured the timedepth dependence of the backscattered laser pulse in two orthogonal-polarized components. Vertical profiles of the scattering coefficient retrieved from the timedepth depolarization of the backscattered laser pulse were compared with measured profiles of the beam attenuation coefficient. The comparison showed that retrieved profiles of the scattering coefficient clearly reproduce the main features of the measured profiles of the beam attenuation coefficient. Underwater scattering layers were detected at depths of 2025 m in turbid coastal waters. The improvement in dynamic range afforded by the polarized lidar technique offers a strong potential benefit for airborne lidar bathymetric applications.

The potential influence of multiple scattering on longwave flux and heating rate simulations with clouds

NASA Astrophysics Data System (ADS)

Kuo, C. P.; Yang, P.; Huang, X.; Feldman, D.; Flanner, M.; Kuo, C.; Mlawer, E. J.

2017-12-01

Clouds, which cover approximately 67% of the globe, serve as one of the major modulators in adjusting radiative energy on the Earth. Since rigorous radiative transfer computations including multiple scattering are costly, only absorption is considered in the longwave spectral bands in the radiation sub-models of the general circulation models (GCMs). Quantification of the effect of ignoring longwave scattering for flux and heating rate simulations is performed by using the GCM version of the Longwave Rapid Radiative Transfer Model (RRTMG_LW) with an implementation with the 16-stream Discrete Ordinates Radiative Transfer (DISORT) Program for a Multi-Layered Plane-Parallel Medium in conjunction with the 2010 CCCM products that merge satellite observations from the Cloud-Aerosol Lidar and Infrared Pathfinder Satellite Observation (CALIPSO), the CloudSat, the Clouds and the Earth's Radiant Energy System (CERES) and the Moderate Resolution Imaging Spectrometer (MODIS). One-year global simulations show that neglecting longwave scattering overestimates upward flux at the top of the atmosphere (TOA) and underestimates downward flux at the surface by approximately 2.63 and 1.15 W/m2, respectively. Furthermore, when longwave scattering is included in the simulations, the tropopause is cooled by approximately 0.018 K/day and the surface is heated by approximately 0.028 K/day. As a result, the radiative effects of ignoring longwave scattering and doubling CO2 are comparable in magnitude.

Lidar inelastic multiple-scattering parameters of cirrus particle ensembles determined with geometrical-optics crystal phase functions.

PubMed

Reichardt, J; Hess, M; Macke, A

2000-04-20

Multiple-scattering correction factors for cirrus particle extinction coefficients measured with Raman and high spectral resolution lidars are calculated with a radiative-transfer model. Cirrus particle-ensemble phase functions are computed from single-crystal phase functions derived in a geometrical-optics approximation. Seven crystal types are considered. In cirrus clouds with height-independent particle extinction coefficients the general pattern of the multiple-scattering parameters has a steep onset at cloud base with values of 0.5-0.7 followed by a gradual and monotonic decrease to 0.1-0.2 at cloud top. The larger the scattering particles are, the more gradual is the rate of decrease. Multiple-scattering parameters of complex crystals and of imperfect hexagonal columns and plates can be well approximated by those of projected-area equivalent ice spheres, whereas perfect hexagonal crystals show values as much as 70% higher than those of spheres. The dependencies of the multiple-scattering parameters on cirrus particle spectrum, base height, and geometric depth and on the lidar parameters laser wavelength and receiver field of view, are discussed, and a set of multiple-scattering parameter profiles for the correction of extinction measurements in homogeneous cirrus is provided.

Study of coherent reflectometer for imaging internal structures of highly scattering media

NASA Astrophysics Data System (ADS)

Poupardin, Mathieu; Dolfi, Agnes

1996-01-01

Optical reflectometers are potentially useful tools for imaging internal structures of turbid media, particularly of biological media. To get a point by point image, an active imaging system has to distinguish light scattered from a sample volume and light scattered by other locations in the media. Operating this discrimination of light with reflectometers based on coherence can be realized in two ways: assuring a geometric selection or a temporal selection. In this paper we present both methods, showing in each case the influence of the different parameters on the size of the sample volume under the assumption of single scattering. We also study the influence on the detection efficiency of the coherence loss of the incident light resulting from multiple scattering. We adapt a model, first developed for atmospheric lidar in turbulent atmosphere, to get an analytical expression of this detection efficiency in the function of the optical coefficients of the media.

Analysis of multiple scattering contributions in electron-impact ionization of molecular hydrogen

NASA Astrophysics Data System (ADS)

Ren, Xueguang; Hossen, Khokon; Wang, Enliang; Pindzola, M. S.; Dorn, Alexander; Colgan, James

2017-10-01

We report a combined experimental and theoretical study on the low-energy (E 0 = 31.5 eV) electron-impact ionization of molecular hydrogen (H2). Triple differential cross sections are measured for a range of fixed emission angles of one outgoing electron between {θ }1=-70^\\circ and -130° covering the full 4π solid angle of the second electron. The energy sharing of the outgoing electrons varies from symmetric ({E}1={E}2=8 eV) to highly asymmetric (E 1 = 1 eV and E 2 = 15 eV). In addition to the binary and recoil lobes, a structure is observed perpendicular to the incoming beam direction which is due to multiple scattering of the projectile inside the molecular potential. The absolutely normalized experimental cross sections are compared with results from the time-dependent close-coupling (TDCC) calculations. Molecular alignment dependent TDCC results demonstrate that these structures are only present if the molecule axis is lying in the scattering plane.

Modeling lidar waveforms with time-dependent stochastic radiative transfer theory for remote estimations of forest structure

NASA Astrophysics Data System (ADS)

Kotchenova, Svetlana Y.; Shabanov, Nikolay V.; Knyazikhin, Yuri; Davis, Anthony B.; Dubayah, Ralph; Myneni, Ranga B.

2003-08-01

Large footprint waveform-recording laser altimeters (lidars) have demonstrated a potential for accurate remote sensing of forest biomass and structure, important for regional and global climate studies. Currently, radiative transfer analyses of lidar data are based on the simplifying assumption that only single scattering contributes to the return signal, which may lead to errors in the modeling of the lower portions of recorded waveforms in the near-infrared spectrum. In this study we apply time-dependent stochastic radiative transfer (RT) theory to model the propagation of lidar pulses through forest canopies. A time-dependent stochastic RT equation is formulated and solved numerically. Such an approach describes multiple scattering events, allows for realistic representation of forest structure including foliage clumping and gaps, simulates off-nadir and multiangular observations, and has the potential to provide better approximations of return waveforms. The model was tested with field data from two conifer forest stands (southern old jack pine and southern old black spruce) in central Canada and two closed canopy deciduous forest stands (with overstory dominated by tulip poplar) in eastern Maryland. Model-simulated signals were compared with waveforms recorded by the Scanning Lidar Imager of Canopies by Echo Recovery (SLICER) over these regions. Model simulations show good agreement with SLICER signals having a slow decay of the waveform. The analysis of the effects of multiple scattering shows that multiply scattered photons magnify the amplitude of the reflected signal, especially that originating from the lower portions of the canopy.

Multiple scattering effects with cyclical terms in active remote sensing of vegetated surface using vector radiative transfer theory

USDA-ARS?s Scientific Manuscript database

The energy transport in a vegetated (corn) surface layer is examined by solving the vector radiative transfer equation using a numerical iterative approach. This approach allows a higher order that includes the multiple scattering effects. Multiple scattering effects are important when the optical t...

Charge transfer in single and multiple scattering events at metal surfaces: a wavepacket study of the Na(+)/Cu(100) system.

PubMed

Sindona, A; Pisarra, M; Maletta, S; Riccardi, P; Falcone, G

2010-12-01

Resonant neutralization of hyperthermal energy Na(+) ions impinging on Cu(100) surfaces is studied, focusing on two specific collision events: one in which the projectile is reflected off the surface, the other in which the incident atom penetrates the outer surface layers initiating a series of scattering processes, within the target, and coming out together with a single surface atom. A semi-empirical model potential is adopted that embeds: (i) the electronic structure of the sample, (ii) the central field of the projectile, and (iii) the contribution of the Cu atom ejected in multiple scattering events. The evolution of the ionization orbital of the scattered atom is simulated, backwards in time, using a wavepacket propagation algorithm. The output of the approach is the neutralization probability, obtained by projecting the time-reversed valence wavefunction of the projectile onto the initially filled conduction band states. The results are in agreement with available data from the literature (Keller et al 1995 Phys. Rev. Lett. 75 1654) indicating that the motion of surface atoms, exiting the targets with kinetic energies of the order of a few electronvolts, plays a significant role in the final charge state of projectiles.

The multiple Coulomb scattering of very heavy charged particles.

PubMed

Wong, M; Schimmerling, W; Phillips, M H; Ludewigt, B A; Landis, D A; Walton, J T; Curtis, S B

1990-01-01

An experiment was performed at the Lawrence Berkeley Laboratory BEVALAC to measure the multiple Coulomb scattering of 650-MeV/A uranium nuclei in 0.19 radiation lengths of a Cu target. Differential distributions in the projected multiple scattering angle were measured in the vertical and horizontal planes using silicon position-sensitive detectors to determine particle trajectories before and after target scattering. The results were compared with the multiple Coulomb scattering theories of Fermi and Molière, and with a modification of the Fermi theory, using a Monte Carlo simulation. These theories were in excellent agreement with experiment at the 2 sigma level. The best quantitative agreement is obtained with the Gaussian distribution predicted by the modified Fermi theory.

Born approximation, multiple scattering, and butterfly algorithm

NASA Astrophysics Data System (ADS)

Martinez, Alex; Qiao, Zhijun

2014-06-01

Many imaging algorithms have been designed assuming the absence of multiple scattering. In the 2013 SPIE proceeding, we discussed an algorithm for removing high order scattering components from collected data. In this paper, our goal is to continue this work. First, we survey the current state of multiple scattering in SAR. Then, we revise our method and test it. Given an estimate of our target reflectivity, we compute the multi scattering effects in our target region for various frequencies. Furthermore, we propagate this energy through free space towards our antenna, and remove it from the collected data.

Analytical multiple scattering correction to the Mie theory: Application to the analysis of the lidar signal

NASA Technical Reports Server (NTRS)

Flesia, C.; Schwendimann, P.

1992-01-01

The contribution of the multiple scattering to the lidar signal is dependent on the optical depth tau. Therefore, the radar analysis, based on the assumption that the multiple scattering can be neglected is limited to cases characterized by low values of the optical depth (tau less than or equal to 0.1) and hence it exclude scattering from most clouds. Moreover, all inversion methods relating lidar signal to number densities and particle size must be modified since the multiple scattering affects the direct analysis. The essential requests of a realistic model for lidar measurements which include the multiple scattering and which can be applied to practical situations follow. (1) Requested are not only a correction term or a rough approximation describing results of a certain experiment, but a general theory of multiple scattering tying together the relevant physical parameter we seek to measure. (2) An analytical generalization of the lidar equation which can be applied in the case of a realistic aerosol is requested. A pure analytical formulation is important in order to avoid the convergency and stability problems which, in the case of numerical approach, are due to the large number of events that have to be taken into account in the presence of large depth and/or a strong experimental noise.

Application of a multiple scattering model to estimate optical depth, lidar ratio and ice crystal effective radius of cirrus clouds observed with lidar.

NASA Astrophysics Data System (ADS)

Gouveia, Diego; Baars, Holger; Seifert, Patric; Wandinger, Ulla; Barbosa, Henrique; Barja, Boris; Artaxo, Paulo; Lopes, Fabio; Landulfo, Eduardo; Ansmann, Albert

2018-04-01

Lidar measurements of cirrus clouds are highly influenced by multiple scattering (MS). We therefore developed an iterative approach to correct elastic backscatter lidar signals for multiple scattering to obtain best estimates of single-scattering cloud optical depth and lidar ratio as well as of the ice crystal effective radius. The approach is based on the exploration of the effect of MS on the molecular backscatter signal returned from above cloud top.

An iterative fullwave simulation approach to multiple scattering in media with randomly distributed microbubbles

NASA Astrophysics Data System (ADS)

Joshi, Aditya; Lindsey, Brooks D.; Dayton, Paul A.; Pinton, Gianmarco; Muller, Marie

2017-05-01

Ultrasound contrast agents (UCA), such as microbubbles, enhance the scattering properties of blood, which is otherwise hypoechoic. The multiple scattering interactions of the acoustic field with UCA are poorly understood due to the complexity of the multiple scattering theories and the nonlinear microbubble response. The majority of bubble models describe the behavior of UCA as single, isolated microbubbles suspended in infinite medium. Multiple scattering models such as the independent scattering approximation can approximate phase velocity and attenuation for low scatterer volume fractions. However, all current models and simulation approaches only describe multiple scattering and nonlinear bubble dynamics separately. Here we present an approach that combines two existing models: (1) a full-wave model that describes nonlinear propagation and scattering interactions in a heterogeneous attenuating medium and (2) a Paul-Sarkar model that describes the nonlinear interactions between an acoustic field and microbubbles. These two models were solved numerically and combined with an iterative approach. The convergence of this combined model was explored in silico for 0.5 × 106 microbubbles ml-1, 1% and 2% bubble concentration by volume. The backscattering predicted by our modeling approach was verified experimentally with water tank measurements performed with a 128-element linear array transducer. An excellent agreement in terms of the fundamental and harmonic acoustic fields is shown. Additionally, our model correctly predicts the phase velocity and attenuation measured using through transmission and predicted by the independent scattering approximation.

Second-order multiple-scattering theory associated with backscattering enhancement for a millimeter wavelength weather radar with a finite beam width

NASA Astrophysics Data System (ADS)

Kobayashi, Satoru; Tanelli, Simone; Im, Eastwood

2005-12-01

Effects of multiple scattering on reflectivity are studied for millimeter wavelength weather radars. A time-independent vector theory, including up to second-order scattering, is derived for a single layer of hydrometeors of a uniform density and a uniform diameter. In this theory, spherical waves with a Gaussian antenna pattern are used to calculate ladder and cross terms in the analytical scattering theory. The former terms represent the conventional multiple scattering, while the latter terms cause backscattering enhancement in both the copolarized and cross-polarized components. As the optical thickness of the hydrometeor layer increases, the differences from the conventional plane wave theory become more significant, and essentially, the reflectivity of multiple scattering depends on the ratio of mean free path to radar footprint radius. These results must be taken into account when analyzing radar reflectivity for use in remote sensing.

Focusing of light energy inside a scattering medium by controlling the time-gated multiple light scattering

NASA Astrophysics Data System (ADS)

Jeong, Seungwon; Lee, Ye-Ryoung; Choi, Wonjun; Kang, Sungsam; Hong, Jin Hee; Park, Jin-Sung; Lim, Yong-Sik; Park, Hong-Gyu; Choi, Wonshik

2018-05-01

The efficient delivery of light energy is a prerequisite for the non-invasive imaging and stimulating of target objects embedded deep within a scattering medium. However, the injected waves experience random diffusion by multiple light scattering, and only a small fraction reaches the target object. Here, we present a method to counteract wave diffusion and to focus multiple-scattered waves at the deeply embedded target. To realize this, we experimentally inject light into the reflection eigenchannels of a specific flight time to preferably enhance the intensity of those multiple-scattered waves that have interacted with the target object. For targets that are too deep to be visible by optical imaging, we demonstrate a more than tenfold enhancement in light energy delivery in comparison with ordinary wave diffusion cases. This work will lay a foundation to enhance the working depth of imaging, sensing and light stimulation.

A Persistent Feature of Multiple Scattering of Waves in the Time-Domain: A Tutorial

NASA Technical Reports Server (NTRS)

Lock, James A.; Mishchenko, Michael I.

2015-01-01

The equations for frequency-domain multiple scattering are derived for a scalar or electromagnetic plane wave incident on a collection of particles at known positions, and in the time-domain for a plane wave pulse incident on the same collection of particles. The calculation is carried out for five different combinations of wave types and particle types of increasing geometrical complexity. The results are used to illustrate and discuss a number of physical and mathematical characteristics of multiple scattering in the frequency- and time-domains. We argue that frequency-domain multiple scattering is a purely mathematical construct since there is no temporal sequencing information in the frequency-domain equations and since the multi-particle path information can be dispelled by writing the equations in another mathematical form. However, multiple scattering becomes a definite physical phenomenon in the time-domain when the collection of particles is illuminated by an appropriately short localized pulse.

Laplace Transform Based Radiative Transfer Studies

NASA Astrophysics Data System (ADS)

Hu, Y.; Lin, B.; Ng, T.; Yang, P.; Wiscombe, W.; Herath, J.; Duffy, D.

2006-12-01

Multiple scattering is the major uncertainty for data analysis of space-based lidar measurements. Until now, accurate quantitative lidar data analysis has been limited to very thin objects that are dominated by single scattering, where photons from the laser beam only scatter a single time with particles in the atmosphere before reaching the receiver, and simple linear relationship between physical property and lidar signal exists. In reality, multiple scattering is always a factor in space-based lidar measurement and it dominates space- based lidar returns from clouds, dust aerosols, vegetation canopy and phytoplankton. While multiple scattering are clear signals, the lack of a fast-enough lidar multiple scattering computation tool forces us to treat the signal as unwanted "noise" and use simple multiple scattering correction scheme to remove them. Such multiple scattering treatments waste the multiple scattering signals and may cause orders of magnitude errors in retrieved physical properties. Thus the lack of fast and accurate time-dependent radiative transfer tools significantly limits lidar remote sensing capabilities. Analyzing lidar multiple scattering signals requires fast and accurate time-dependent radiative transfer computations. Currently, multiple scattering is done with Monte Carlo simulations. Monte Carlo simulations take minutes to hours and are too slow for interactive satellite data analysis processes and can only be used to help system / algorithm design and error assessment. We present an innovative physics approach to solve the time-dependent radiative transfer problem. The technique utilizes FPGA based reconfigurable computing hardware. The approach is as following, 1. Physics solution: Perform Laplace transform on the time and spatial dimensions and Fourier transform on the viewing azimuth dimension, and convert the radiative transfer differential equation solving into a fast matrix inversion problem. The majority of the radiative transfer computation goes to matrix inversion processes, FFT and inverse Laplace transforms. 2. Hardware solutions: Perform the well-defined matrix inversion, FFT and Laplace transforms on highly parallel, reconfigurable computing hardware. This physics-based computational tool leads to accurate quantitative analysis of space-based lidar signals and improves data quality of current lidar mission such as CALIPSO. This presentation will introduce the basic idea of this approach, preliminary results based on SRC's FPGA-based Mapstation, and how we may apply it to CALIPSO data analysis.

Backscattering from a randomly rough dielectric surface

NASA Technical Reports Server (NTRS)

Fung, Adrian K.; Li, Zongqian; Chen, K. S.

1992-01-01

A backscattering model for scattering from a randomly rough dielectric surface is developed based on an approximate solution of a pair of integral equations for the tangential surface fields. Both like and cross-polarized scattering coefficients are obtained. It is found that the like polarized scattering coefficients contain two types of terms: single scattering terms and multiple scattering terms. The single scattering terms in like polarized scattering are shown to reduce the first-order solutions derived from the small perturbation method when the roughness parameters satisfy the slightly rough conditions. When surface roughnesses are large but the surface slope is small, only a single scattering term corresponding to the standard Kirchhoff model is significant. If the surface slope is large, the multiple scattering term will also be significant. The cross-polarized backscattering coefficients satisfy reciprocity and contain only multiple scattering terms. The difference between vertical and horizontal scattering coefficients is found to increase with the dielectric constant and is generally smaller than that predicted by the first-order small perturbation model. Good agreements are obtained between this model and measurements from statistically known surfaces.

Spin-analyzed SANS for soft matter applications

NASA Astrophysics Data System (ADS)

Chen, W. C.; Barker, J. G.; Jones, R.; Krycka, K. L.; Watson, S. M.; Gagnon, C.; Perevozchivoka, T.; Butler, P.; Gentile, T. R.

2017-06-01

The small angle neutron scattering (SANS) of nearly Q-independent nuclear spin-incoherent scattering from hydrogen present in most soft matter and biology samples may raise an issue in structure determination in certain soft matter applications. This is true at high wave vector transfer Q where coherent scattering is much weaker than the nearly Q-independent spin-incoherent scattering background. Polarization analysis is capable of separating coherent scattering from spin-incoherent scattering, hence potentially removing the nearly Q-independent background. Here we demonstrate SANS polarization analysis in conjunction with the time-of-flight technique for separation of coherent and nuclear spin-incoherent scattering for a sample of silver behenate back-filled with light water. We describe a complete procedure for SANS polarization analysis for separating coherent from incoherent scattering for soft matter samples that show inelastic scattering. Polarization efficiency correction and subsequent separation of the coherent and incoherent scattering have been done with and without a time-of-flight technique for direct comparisons. In addition, we have accounted for the effect of multiple scattering from light water to determine the contribution of nuclear spin-incoherent scattering in both the spin flip channel and non-spin flip channel when performing SANS polarization analysis. We discuss the possible gain in the signal-to-noise ratio for the measured coherent scattering signal using polarization analysis with the time-of-flight technique compared with routine unpolarized SANS measurements.

Influence of multiple scattering on CloudSat measurements in snow: A model study

NASA Astrophysics Data System (ADS)

Matrosov, Sergey Y.; Battaglia, Alessandro

2009-06-01

The effects of multiple scattering on larger precipitating hydrometers have an influence on measurements of the spaceborne W-band (94 GHz) CloudSat radar. This study presents initial quantitative estimates of these effects in “dry” snow using radiative transfer calculations for appropriate snowfall models. It is shown that these effects become significant (i.e., greater than approximately 1 dB) when snowfall radar reflectivity factors are greater than about 10-15 dBZ. Reflectivity enhancement due to multiple scattering can reach 4-5 dB in heavier stratiform snowfalls. Multiple scattering effects counteract signal attenuation, so the observed CloudSat reflectivity factors in snowfall could be relatively close to the values that would be observed in the case of single scattering and the absence of attenuation.

Computing wave functions in multichannel collisions with non-local potentials using the R-matrix method

NASA Astrophysics Data System (ADS)

Bonitati, Joey; Slimmer, Ben; Li, Weichuan; Potel, Gregory; Nunes, Filomena

2017-09-01

The calculable form of the R-matrix method has been previously shown to be a useful tool in approximately solving the Schrodinger equation in nuclear scattering problems. We use this technique combined with the Gauss quadrature for the Lagrange-mesh method to efficiently solve for the wave functions of projectile nuclei in low energy collisions (1-100 MeV) involving an arbitrary number of channels. We include the local Woods-Saxon potential, the non-local potential of Perey and Buck, a Coulomb potential, and a coupling potential to computationally solve for the wave function of two nuclei at short distances. Object oriented programming is used to increase modularity, and parallel programming techniques are introduced to reduce computation time. We conclude that the R-matrix method is an effective method to predict the wave functions of nuclei in scattering problems involving both multiple channels and non-local potentials. Michigan State University iCER ACRES REU.

Method for measuring multiple scattering corrections between liquid scintillators

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

Verbeke, J. M.; Glenn, A. M.; Keefer, G. J.

2016-04-11

In this study, a time-of-flight method is proposed to experimentally quantify the fractions of neutrons scattering between scintillators. An array of scintillators is characterized in terms of crosstalk with this method by measuring a californium source, for different neutron energy thresholds. The spectral information recorded by the scintillators can be used to estimate the fractions of neutrons multiple scattering. With the help of a correction to Feynman's point model theory to account for multiple scattering, these fractions can in turn improve the mass reconstruction of fissile materials under investigation.

Relativistic corrections to the multiple scattering effect on the Sunyaev-Zel'dovich effect in the isotropic approximation

NASA Astrophysics Data System (ADS)

Itoh, Naoki; Kawana, Youhei; Nozawa, Satoshi; Kohyama, Yasuharu

2001-10-01

We extend the formalism for the calculation of the relativistic corrections to the Sunyaev-Zel'dovich effect for clusters of galaxies and include the multiple scattering effects in the isotropic approximation. We present the results of the calculations by the Fokker-Planck expansion method as well as by the direct numerical integration of the collision term of the Boltzmann equation. The multiple scattering contribution is found to be very small compared with the single scattering contribution. For high-temperature galaxy clusters of kBTe~15keV, the ratio of both the contributions is -0.2 per cent in the Wien region. In the Rayleigh-Jeans region the ratio is -0.03 per cent. Therefore the multiple scattering contribution is safely neglected for the observed galaxy clusters.

Multiple scattering corrections to the Beer-Lambert law. 1: Open detector.

PubMed

Tam, W G; Zardecki, A

1982-07-01

Multiple scattering corrections to the Beer-Lambert law are analyzed by means of a rigorous small-angle solution to the radiative transfer equation. Transmission functions for predicting the received radiant power-a directly measured quantity in contrast to the spectral radiance in the Beer-Lambert law-are derived. Numerical algorithms and results relating to the multiple scattering effects for laser propagation in fog, cloud, and rain are presented.

Nonlinear coupled mode approach for modeling counterpropagating solitons in the presence of disorder-induced multiple scattering in photonic crystal waveguides

NASA Astrophysics Data System (ADS)

Mann, Nishan; Hughes, Stephen

2018-02-01

We present the analytical and numerical details behind our recently published article [Phys. Rev. Lett. 118, 253901 (2017), 10.1103/PhysRevLett.118.253901], describing the impact of disorder-induced multiple scattering on counterpropagating solitons in photonic crystal waveguides. Unlike current nonlinear approaches using the coupled mode formalism, we account for the effects of intraunit cell multiple scattering. To solve the resulting system of coupled semilinear partial differential equations, we introduce a modified Crank-Nicolson-type norm-preserving implicit finite difference scheme inspired by the transfer matrix method. We provide estimates of the numerical dispersion characteristics of our scheme so that optimal step sizes can be chosen to either minimize numerical dispersion or to mimic the exact dispersion. We then show numerical results of a fundamental soliton propagating in the presence of multiple scattering to demonstrate that choosing a subunit cell spatial step size is critical in accurately capturing the effects of multiple scattering, and illustrate the stochastic nature of disorder by simulating soliton propagation in various instances of disordered photonic crystal waveguides. Our approach is easily extended to include a wide range of optical nonlinearities and is applicable to various photonic nanostructures where power propagation is bidirectional, either by choice, or as a result of multiple scattering.

Multilevel fast multipole method based on a potential formulation for 3D electromagnetic scattering problems.

PubMed

Fall, Mandiaye; Boutami, Salim; Glière, Alain; Stout, Brian; Hazart, Jerome

2013-06-01

A combination of the multilevel fast multipole method (MLFMM) and boundary element method (BEM) can solve large scale photonics problems of arbitrary geometry. Here, MLFMM-BEM algorithm based on a scalar and vector potential formulation, instead of the more conventional electric and magnetic field formulations, is described. The method can deal with multiple lossy or lossless dielectric objects of arbitrary geometry, be they nested, in contact, or dispersed. Several examples are used to demonstrate that this method is able to efficiently handle 3D photonic scatterers involving large numbers of unknowns. Absorption, scattering, and extinction efficiencies of gold nanoparticle spheres, calculated by the MLFMM, are compared with Mie's theory. MLFMM calculations of the bistatic radar cross section (RCS) of a gold sphere near the plasmon resonance and of a silica coated gold sphere are also compared with Mie theory predictions. Finally, the bistatic RCS of a nanoparticle gold-silver heterodimer calculated with MLFMM is compared with unmodified BEM calculations.

Microscopic optical potentials derived from ab initio translationally invariant nonlocal one-body densities

NASA Astrophysics Data System (ADS)

Gennari, Michael; Vorabbi, Matteo; Calci, Angelo; Navrátil, Petr

2018-03-01

Background: The nuclear optical potential is a successful tool for the study of nucleon-nucleus elastic scattering and its use has been further extended to inelastic scattering and other nuclear reactions. The nuclear density of the target nucleus is a fundamental ingredient in the construction of the optical potential and thus plays an important role in the description of the scattering process. Purpose: In this paper we derive a microscopic optical potential for intermediate energies using ab initio translationally invariant nonlocal one-body nuclear densities computed within the no-core shell model (NCSM) approach utilizing two- and three-nucleon chiral interactions as the only input. Methods: The optical potential is derived at first order within the spectator expansion of the nonrelativistic multiple scattering theory by adopting the impulse approximation. Nonlocal nuclear densities are derived from the NCSM one-body densities calculated in the second quantization. The translational invariance is generated by exactly removing the spurious center-of-mass (COM) component from the NCSM eigenstates. Results: The ground-state local and nonlocal densities of He 4 ,6 ,8 , 12C, and 16O are calculated and applied to optical potential construction. The differential cross sections and the analyzing powers for the elastic proton scattering off these nuclei are then calculated for different values of the incident proton energy. The impact of nonlocality and the COM removal is discussed. Conclusions: The use of nonlocal densities has a substantial impact on the differential cross sections and improves agreement with experiment in comparison to results generated with the local densities especially for light nuclei. For the halo nuclei 6He and 8He, the results for the differential cross section are in a reasonable agreement with the data although a more sophisticated model for the optical potential is required to properly describe the analyzing powers.

Multiple-Fiber-Optic Probe For Light-Scattering Measurements

NASA Technical Reports Server (NTRS)

Dhadwal, Harbans Singh; Ansari, Rafat R.

1996-01-01

Multiple-fiber-optical probe developed for use in measuring light scattered at various angles from specimens of materials. Designed for both static and dynamic light-scattering measurements of colloidal dispersions. Probe compact, rugged unit containing no moving parts and remains stationary during operation. Not restricted to operation in controlled, research-laboratory environment. Positioned inside or outside light-scattering chamber. Provides simultaneous measurements at small angular intervals over range of angles, made to include small scattering angles by orienting probe in appropriate direction.

In vivo diagnosis of skin cancer using polarized and multiple scattered light spectroscopy

NASA Astrophysics Data System (ADS)

Bartlett, Matthew Allen

This thesis research presents the development of a non-invasive diagnostic technique for distinguishing between skin cancer, moles, and normal skin using polarized and multiple scattered light spectroscopy. Polarized light incident on the skin is single scattered by the epidermal layer and multiple scattered by the dermal layer. The epidermal light maintains its initial polarization while the light from the dermal layer becomes randomized and multiple scattered. Mie theory was used to model the epidermal light as the scattering from the intercellular organelles. The dermal signal was modeled as the diffusion of light through a localized semi-homogeneous volume. These models were confirmed using skin phantom experiments, studied with in vitro cell cultures, and applied to human skin for in vivo testing. A CCD-based spectroscopy system was developed to perform all these experiments. The probe and the theory were tested on skin phantoms of latex spheres on top of a solid phantom. We next extended our phantom study to include in vitro cells on top of the solid phantom. Optical fluorescent microscope images revealed at least four distinct scatterers including mitochondria, nucleoli, nuclei, and cell membranes. Single scattering measurements on the mammalian cells consistently produced PSD's in the size range of the mitochondria. The clinical portion of the study consisted of in vivo measurements on cancer, mole, and normal skin spots. The clinical study combined the single scattering model from the phantom and in vitro cell studies with the diffusion model for multiple scattered light. When parameters from both layers were combined, we found that a sensitivity of 100% and 77% can be obtained for detecting cancers and moles, respectively, given the number of lesions examined.

Effects of absorption on multiple scattering by random particulate media: exact results.

PubMed

Mishchenko, Michael I; Liu, Li; Hovenier, Joop W

2007-10-01

We employ the numerically exact superposition T-matrix method to perform extensive computations of elec nottromagnetic scattering by a volume of discrete random medium densely filled with increasingly absorbing as well as non-absorbing particles. Our numerical data demonstrate that increasing absorption diminishes and nearly extinguishes certain optical effects such as depolarization and coherent backscattering and increases the angular width of coherent backscattering patterns. This result corroborates the multiple-scattering origin of such effects and further demonstrates the heuristic value of the concept of multiple scattering even in application to densely packed particulate media.

Angular width of the Cherenkov radiation with inclusion of multiple scattering

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

Zheng, Jian, E-mail: jzheng@ustc.edu.cn

2016-06-15

Visible Cherenkov radiation can offer a method of the measurement of the velocity of charged particles. The angular width of the radiation is important since it determines the resolution of the velocity measurement. In this article, the angular width of Cherenkov radiation with inclusion of multiple scattering is calculated through the path-integral method, and the analytical expressions are presented. The condition that multiple scattering processes dominate the angular distribution is obtained.

Electromagnetic Scattering by Multiple Cavities Embedded in the Infinite 2D Ground Plane

DTIC Science & Technology

2014-07-01

Electromagnetic Scattering by Multiple Cavities Embedded in the Infinite 2D Ground Plane Peijun Li 1 and Aihua W. Wood 2 1 Department of...of the electromagnetic wave scattering by multiple open cavities, which are embedded in an infinite two-dimensional ground plane . By introducing a...equation, variational formulation. I. INTRODUCTION A cavity is referred to as a local perturbation of the infinite ground plane . Given the cavity

Correlation between Satellite-Derived Aerosol Characteristics and Oceanic Dimethylsulfide (DMS)

DTIC Science & Technology

1988-12-01

intensity gained by multiple scattering into the beam from all directions and the beam addition term accounting for single scattering events. The physical...the extinction and scattering coefficients are the integracion over radius of the product of the cross sectional area of aerosol particles, the...the same photon more than once is small. Therefore, the multiple interaction term can be neglected and a single scattering approximation is made. The

Huygens-Fresnel picture for electron-molecule elastic scattering★

NASA Astrophysics Data System (ADS)

Baltenkov, Arkadiy S.; Msezane, Alfred Z.

2017-11-01

The elastic scattering cross sections for a slow electron by C2 and H2 molecules have been calculated within the framework of the non-overlapping atomic potential model. For the amplitudes of the multiple electron scattering by a target the wave function of the molecular continuum is represented as a combination of a plane wave and two spherical waves generated by the centers of atomic spheres. This wave function obeys the Huygens-Fresnel principle according to which the electron wave scattering by a system of two centers is accompanied by generation of two spherical waves; their interaction creates a diffraction pattern far from the target. Each of the Huygens waves, in turn, is a superposition of the partial spherical waves with different orbital angular momenta l and their projections m. The amplitudes of these partial waves are defined by the corresponding phases of electron elastic scattering by an isolated atomic potential. In numerical calculations the s- and p-phase shifts are taken into account. So the number of interfering electron waves is equal to eight: two of which are the s-type waves and the remaining six waves are of the p-type with different m values. The calculation of the scattering amplitudes in closed form (rather than in the form of S-matrix expansion) is reduced to solving a system of eight inhomogeneous algebraic equations. The differential and total cross sections of electron scattering by fixed-in-space molecules and randomly oriented ones have been calculated as well. We conclude by discussing the special features of the S-matrix method for the case of arbitrary non-spherical potentials. Contribution to the Topical Issue "Low energy positron and electron interactions", edited by James Sullivan, Ron White, Michael Bromley, Ilya Fabrikant, and David Cassidy.

Simple aerosol correction technique based on the spectral relationships of the aerosol multiple-scattering reflectances for atmospheric correction over the oceans.

PubMed

Ahn, Jae-Hyun; Park, Young-Je; Kim, Wonkook; Lee, Boram

2016-12-26

An estimation of the aerosol multiple-scattering reflectance is an important part of the atmospheric correction procedure in satellite ocean color data processing. Most commonly, the utilization of two near-infrared (NIR) bands to estimate the aerosol optical properties has been adopted for the estimation of the effects of aerosols. Previously, the operational Geostationary Color Ocean Imager (GOCI) atmospheric correction scheme relies on a single-scattering reflectance ratio (SSE), which was developed for the processing of the Sea-viewing Wide Field-of-view Sensor (SeaWiFS) data to determine the appropriate aerosol models and their aerosol optical thicknesses. The scheme computes reflectance contributions (weighting factor) of candidate aerosol models in a single scattering domain then spectrally extrapolates the single-scattering aerosol reflectance from NIR to visible (VIS) bands using the SSE. However, it directly applies the weight value to all wavelengths in a multiple-scattering domain although the multiple-scattering aerosol reflectance has a non-linear relationship with the single-scattering reflectance and inter-band relationship of multiple scattering aerosol reflectances is non-linear. To avoid these issues, we propose an alternative scheme for estimating the aerosol reflectance that uses the spectral relationships in the aerosol multiple-scattering reflectance between different wavelengths (called SRAMS). The process directly calculates the multiple-scattering reflectance contributions in NIR with no residual errors for selected aerosol models. Then it spectrally extrapolates the reflectance contribution from NIR to visible bands for each selected model using the SRAMS. To assess the performance of the algorithm regarding the errors in the water reflectance at the surface or remote-sensing reflectance retrieval, we compared the SRAMS atmospheric correction results with the SSE atmospheric correction using both simulations and in situ match-ups with the GOCI data. From simulations, the mean errors for bands from 412 to 555 nm were 5.2% for the SRAMS scheme and 11.5% for SSE scheme in case-I waters. From in situ match-ups, 16.5% for the SRAMS scheme and 17.6% scheme for the SSE scheme in both case-I and case-II waters. Although we applied the SRAMS algorithm to the GOCI, it can be applied to other ocean color sensors which have two NIR wavelengths.

Analysis of dense-medium light scattering with applications to corneal tissue: experiments and Monte Carlo simulations.

PubMed

Kim, K B; Shanyfelt, L M; Hahn, D W

2006-01-01

Dense-medium scattering is explored in the context of providing a quantitative measurement of turbidity, with specific application to corneal haze. A multiple-wavelength scattering technique is proposed to make use of two-color scattering response ratios, thereby providing a means for data normalization. A combination of measurements and simulations are reported to assess this technique, including light-scattering experiments for a range of polystyrene suspensions. Monte Carlo (MC) simulations were performed using a multiple-scattering algorithm based on full Mie scattering theory. The simulations were in excellent agreement with the polystyrene suspension experiments, thereby validating the MC model. The MC model was then used to simulate multiwavelength scattering in a corneal tissue model. Overall, the proposed multiwavelength scattering technique appears to be a feasible approach to quantify dense-medium scattering such as the manifestation of corneal haze, although more complex modeling of keratocyte scattering, and animal studies, are necessary.

Analytic approximation for random muffin-tin alloys

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

Mills, R.; Gray, L.J.; Kaplan, T.

1983-03-15

The methods introduced in a previous paper under the name of ''traveling-cluster approximation'' (TCA) are applied, in a multiple-scattering approach, to the case of a random muffin-tin substitutional alloy. This permits the iterative part of a self-consistent calculation to be carried out entirely in terms of on-the-energy-shell scattering amplitudes. Off-shell components of the mean resolvent, needed for the calculation of spectral functions, are obtained by standard methods involving single-site scattering wave functions. The single-site TCA is just the usual coherent-potential approximation, expressed in a form particularly suited for iteration. A fixed-point theorem is proved for the general t-matrix TCA, ensuringmore » convergence upon iteration to a unique self-consistent solution with the physically essential Herglotz properties.« less

Multiple scattering contribution to the diffuse light of a night sky: A model which embraces all orders of scattering

NASA Astrophysics Data System (ADS)

Kocifaj, Miroslav

2018-02-01

The mechanism in which multiple scattering influences the radiance of a night sky has been poorly quantified until recently, or even completely unknown from the theoretical point of view. In this paper, the relative contribution of higher-scattering radiances to the total sky radiance is treated analytically for all orders of scattering, showing that a fast and accurate numerical solution to the problem exists. Unlike a class of ray tracing codes in which CPU requirements increase tremendously with each new scattering mode, the solution developed here requires the same processor time for each scattering mode. This allows for rapid estimation of higher-scattering radiances and residual error that is otherwise unknown if these radiances remain undetermined. Such convergence testing is necessary to guarantee accuracy and the stability of the numerical predictions. The performance of the method developed here is demonstrated in a set of numerical experiments aiming to uncover the relative importance of higher-scattering radiances at different distances from a light source. We have shown, that multiple scattering effects are generally low if distance to the light source is below 30 km. At large distances the multiple scattering can become important at the dark sky elements situated opposite to the light source. However, the brightness at this part of sky is several orders of magnitude smaller than that of a glowing dome of light over a city, so we do not expect that a partial increase or even doubling the radiance of otherwise dark sky elements can noticeably affect astronomical observations or living organisms (including humans). Single scattering is an appropriate approximation to the sky radiance of a night sky in the vast majority of cases.

Imaging complex objects using learning tomography

NASA Astrophysics Data System (ADS)

Lim, JooWon; Goy, Alexandre; Shoreh, Morteza Hasani; Unser, Michael; Psaltis, Demetri

2018-02-01

Optical diffraction tomography (ODT) can be described using the scattering process through an inhomogeneous media. An inherent nonlinearity exists relating the scattering medium and the scattered field due to multiple scattering. Multiple scattering is often assumed to be negligible in weakly scattering media. This assumption becomes invalid as the sample gets more complex resulting in distorted image reconstructions. This issue becomes very critical when we image a complex sample. Multiple scattering can be simulated using the beam propagation method (BPM) as the forward model of ODT combined with an iterative reconstruction scheme. The iterative error reduction scheme and the multi-layer structure of BPM are similar to neural networks. Therefore we refer to our imaging method as learning tomography (LT). To fairly assess the performance of LT in imaging complex samples, we compared LT with the conventional iterative linear scheme using Mie theory which provides the ground truth. We also demonstrate the capacity of LT to image complex samples using experimental data of a biological cell.

Coherent Multiple Light Scattering in Ultracold Atomic Rb

NASA Astrophysics Data System (ADS)

Kulatunga, Pasad; Sukenik, C. I.; Balik, Salim; Havey, M. D.; Kupriyanov, D. V.; Sokolov, I. M.

2003-05-01

Wave transport in mesoscopic systems can be strongly influenced by coherent multiple scattering,which can lead to novel magneto-optic, transmission, and backscattering effects of light in atomic vapors. Although related to traditional studies of radiation trapping, in ultracold vapors negligible frequency or phase redistribution takes place in the scattering, and high-order coherent light scattering occurs. Among other things, this leads to enhancement of the influence of otherwise small non-resonant terms in the scattering amplitudes. We report investigation of multiple coherent light scattering from ultracold Rb atoms confined in a magneto-optic trap (MOT). In experimental studies, measurements are made of the angular, spectral, and polarization-dependent coherent backscattering profile of a low-intensity probe beam tuned near the F = 3 - F' = 4 hyperfine transition. The influence of higher probe beam intensity is also studied. In a theoretical study of angular intensity enhancement of backscattered light, we consider scattering orders up to 10 and a realistic and asymmetric Gaussian atom distribution in the MOT. Supported by NSF, NATO, and RFBR.

An empirical correction for moderate multiple scattering in super-heterodyne light scattering.

PubMed

Botin, Denis; Mapa, Ludmila Marotta; Schweinfurth, Holger; Sieber, Bastian; Wittenberg, Christopher; Palberg, Thomas

2017-05-28

Frequency domain super-heterodyne laser light scattering is utilized in a low angle integral measurement configuration to determine flow and diffusion in charged sphere suspensions showing moderate to strong multiple scattering. We introduce an empirical correction to subtract the multiple scattering background and isolate the singly scattered light. We demonstrate the excellent feasibility of this simple approach for turbid suspensions of transmittance T ≥ 0.4. We study the particle concentration dependence of the electro-kinetic mobility in low salt aqueous suspension over an extended concentration regime and observe a maximum at intermediate concentrations. We further use our scheme for measurements of the self-diffusion coefficients in the fluid samples in the absence or presence of shear, as well as in polycrystalline samples during crystallization and coarsening. We discuss the scope and limits of our approach as well as possible future applications.

Multi-beam effects on backscatter and its saturation in experiments with conditions relevant to ignition

DOE PAGES

Kirkwood, R. K.; Michel, P.; London, R.; ...

2011-05-26

To optimize the coupling to indirect drive targets in the National Ignition Campaign (NIC) at the National Ignition Facility, a model of stimulated scattering produced by multiple laser beams is used. The model has shown that scatter of the 351 nm beams can be significantly enhanced over single beam predictions in ignition relevant targets by the interaction of the multiple crossing beams with a millimeter scale length, 2.5 keV, 0.02 - 0.05 x critical density, plasma. The model uses a suite of simulation capabilities and its key aspects are benchmarked with experiments at smaller laser facilities. The model has alsomore » influenced the design of the initial targets used for NIC by showing that both the stimulated Brillouin scattering (SBS) and stimulated Raman scattering (SRS) can be reduced by the reduction of the plasma density in the beam intersection volume that is caused by an increase in the diameter of the laser entrance hole (LEH). In this model, a linear wave response leads to a small gain exponent produced by each crossing quad of beams (<~1 per quad) which amplifies the scattering that originates in the target interior where the individual beams are separated and crosses many or all other beams near the LEH as it exits the target. As a result all 23 crossing quads of beams produce a total gain exponent of several or greater for seeds of light with wavelengths in the range that is expected for scattering from the interior (480 to 580 nm for SRS). This means that in the absence of wave saturation, the overall multi-beam scatter will be significantly larger than the expectations for single beams. The potential for non-linear saturation of the Langmuir waves amplifying SRS light is also analyzed with a two dimensional, vectorized, particle in cell code (2D VPIC) that is benchmarked by amplification experiments in a plasma with normalized parameters similar to ignition targets. The physics of cumulative scattering by multiple crossing beams that simultaneously amplify the same SBS light wave is further demonstrated in experiments that benchmark the linear models for the ion waves amplifying SBS. Here, the expectation from this model and its experimental benchmarks is shown to be consistent with observations of stimulated Raman scatter in the first series of energetic experiments with ignition targets, confirming the importance of the multi-beam scattering model for optimizing coupling.« less

Coherent transmission of an ultrasonic shock wave through a multiple scattering medium.

PubMed

Viard, Nicolas; Giammarinaro, Bruno; Derode, Arnaud; Barrière, Christophe

2013-08-01

We report measurements of the transmitted coherent (ensemble-averaged) wave resulting from the interaction of an ultrasonic shock wave with a two-dimensional random medium. Despite multiple scattering, the coherent waveform clearly shows the steepening that is typical of nonlinear harmonic generation. This is taken advantage of to measure the elastic mean free path and group velocity over a broad frequency range (2-15 MHz) in only one experiment. Experimental results are found to be in good agreement with a linear theoretical model taking into account spatial correlations between scatterers. These results show that nonlinearity and multiple scattering are both present, yet uncoupled.

Numerical Model of Multiple Scattering and Emission from Layering Snowpack for Microwave Remote Sensing

NASA Astrophysics Data System (ADS)

Jin, Y.; Liang, Z.

2002-12-01

The vector radiative transfer (VRT) equation is an integral-deferential equation to describe multiple scattering, absorption and transmission of four Stokes parameters in random scatter media. From the integral formal solution of VRT equation, the lower order solutions, such as the first-order scattering for a layer medium or the second order scattering for a half space, can be obtained. The lower order solutions are usually good at low frequency when high-order scattering is negligible. It won't be feasible to continue iteration for obtaining high order scattering solution because too many folds integration would be involved. In the space-borne microwave remote sensing, for example, the DMSP (Defense Meterological Satellite Program) SSM/I (Special Sensor Microwave/Imager) employed seven channels of 19, 22, 37 and 85GHz. Multiple scattering from the terrain surfaces such as snowpack cannot be neglected at these channels. The discrete ordinate and eigen-analysis method has been studied to take into account for multiple scattering and applied to remote sensing of atmospheric precipitation, snowpack etc. Snowpack was modeled as a layer of dense spherical particles, and the VRT for a layer of uniformly dense spherical particles has been numerically studied by the discrete ordinate method. However, due to surface melting and refrozen crusts, the snowpack undergoes stratifying to form inhomegeneous profiles of the ice grain size, fractional volume and physical temperature etc. It becomes necessary to study multiple scattering and emission from stratified snowpack of dense ice grains. But, the discrete ordinate and eigen-analysis method cannot be simply applied to multi-layers model, because numerically solving a set of multi-equations of VRT is difficult. Stratifying the inhomogeneous media into multi-slabs and employing the first order Mueller matrix of each thin slab, this paper developed an iterative method to derive high orders scattering solutions of whole scatter media. High order scattering and emission from inhomogeneous stratifying media of dense spherical particles are numerically obtained. The brightness temperature at low frequency such as 5.3 GHz without high order scattering and at SSM/I channels with high order scattering are obtained. This approach is also compared with the conventional discrete ordinate method for an uniform layer model. Numerical simulation for inhomogeneous snowpack is also compared with the measurements of microwave remote sensing.

Tissue polarimetry: concepts, challenges, applications, and outlook.

PubMed

Ghosh, Nirmalya; Vitkin, I Alex

2011-11-01

Polarimetry has a long and successful history in various forms of clear media. Driven by their biomedical potential, the use of the polarimetric approaches for biological tissue assessment has also recently received considerable attention. Specifically, polarization can be used as an effective tool to discriminate against multiply scattered light (acting as a gating mechanism) in order to enhance contrast and to improve tissue imaging resolution. Moreover, the intrinsic tissue polarimetry characteristics contain a wealth of morphological and functional information of potential biomedical importance. However, in a complex random medium-like tissue, numerous complexities due to multiple scattering and simultaneous occurrences of many scattering and polarization events present formidable challenges both in terms of accurate measurements and in terms of analysis of the tissue polarimetry signal. In order to realize the potential of the polarimetric approaches for tissue imaging and characterization/diagnosis, a number of researchers are thus pursuing innovative solutions to these challenges. In this review paper, we summarize these and other issues pertinent to the polarized light methodologies in tissues. Specifically, we discuss polarized light basics, Stokes-Muller formalism, methods of polarization measurements, polarized light modeling in turbid media, applications to tissue imaging, inverse analysis for polarimetric results quantification, applications to quantitative tissue assessment, etc.

Fully-relativistic full-potential multiple scattering theory: A pathology-free scheme

NASA Astrophysics Data System (ADS)

Liu, Xianglin; Wang, Yang; Eisenbach, Markus; Stocks, G. Malcolm

2018-03-01

The Green function plays an essential role in the Korringa-Kohn-Rostoker(KKR) multiple scattering method. In practice, it is constructed from the regular and irregular solutions of the local Kohn-Sham equation and robust methods exist for spherical potentials. However, when applied to a non-spherical potential, numerical errors from the irregular solutions give rise to pathological behaviors of the charge density at small radius. Here we present a full-potential implementation of the fully-relativistic KKR method to perform ab initio self-consistent calculation by directly solving the Dirac differential equations using the generalized variable phase (sine and cosine matrices) formalism Liu et al. (2016). The pathology around the origin is completely eliminated by carrying out the energy integration of the single-site Green function along the real axis. By using an efficient pole-searching technique to identify the zeros of the well-behaved Jost matrices, we demonstrated that this scheme is numerically stable and computationally efficient, with speed comparable to the conventional contour energy integration method, while free of the pathology problem of the charge density. As an application, this method is utilized to investigate the crystal structures of polonium and their bulk properties, which is challenging for a conventional real-energy scheme. The noble metals are also calculated, both as a test of our method and to study the relativistic effects.

Fully-relativistic full-potential multiple scattering theory: A pathology-free scheme

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

Liu, Xianglin; Wang, Yang; Eisenbach, Markus

The Green function plays an essential role in the Korringa–Kohn–Rostoker(KKR) multiple scattering method. In practice, it is constructed from the regular and irregular solutions of the local Kohn–Sham equation and robust methods exist for spherical potentials. However, when applied to a non-spherical potential, numerical errors from the irregular solutions give rise to pathological behaviors of the charge density at small radius. Here we present a full-potential implementation of the fully-relativistic KKR method to perform ab initio self-consistent calculation by directly solving the Dirac differential equations using the generalized variable phase (sine and cosine matrices) formalism Liu et al. (2016). Themore » pathology around the origin is completely eliminated by carrying out the energy integration of the single-site Green function along the real axis. Here, by using an efficient pole-searching technique to identify the zeros of the well-behaved Jost matrices, we demonstrated that this scheme is numerically stable and computationally efficient, with speed comparable to the conventional contour energy integration method, while free of the pathology problem of the charge density. As an application, this method is utilized to investigate the crystal structures of polonium and their bulk properties, which is challenging for a conventional real-energy scheme. The noble metals are also calculated, both as a test of our method and to study the relativistic effects.« less

Fully-relativistic full-potential multiple scattering theory: A pathology-free scheme

DOE PAGES

Liu, Xianglin; Wang, Yang; Eisenbach, Markus; ...

2017-10-28

The Green function plays an essential role in the Korringa–Kohn–Rostoker(KKR) multiple scattering method. In practice, it is constructed from the regular and irregular solutions of the local Kohn–Sham equation and robust methods exist for spherical potentials. However, when applied to a non-spherical potential, numerical errors from the irregular solutions give rise to pathological behaviors of the charge density at small radius. Here we present a full-potential implementation of the fully-relativistic KKR method to perform ab initio self-consistent calculation by directly solving the Dirac differential equations using the generalized variable phase (sine and cosine matrices) formalism Liu et al. (2016). Themore » pathology around the origin is completely eliminated by carrying out the energy integration of the single-site Green function along the real axis. Here, by using an efficient pole-searching technique to identify the zeros of the well-behaved Jost matrices, we demonstrated that this scheme is numerically stable and computationally efficient, with speed comparable to the conventional contour energy integration method, while free of the pathology problem of the charge density. As an application, this method is utilized to investigate the crystal structures of polonium and their bulk properties, which is challenging for a conventional real-energy scheme. The noble metals are also calculated, both as a test of our method and to study the relativistic effects.« less

Intermolecular correlations are necessary to explain diffuse scattering from protein crystals

DOE PAGES

Peck, Ariana; Poitevin, Frederic; Lane, Thomas Joseph

2018-02-21

Conformational changes drive protein function, including catalysis, allostery, and signaling. X-ray diffuse scattering from protein crystals has frequently been cited as a probe of these correlated motions, with significant potential to advance our understanding of biological dynamics. However, recent work challenged this prevailing view, suggesting instead that diffuse scattering primarily originates from rigid body motions and could therefore be applied to improve structure determination. To investigate the nature of the disorder giving rise to diffuse scattering, and thus the potential applications of this signal, a diverse repertoire of disorder models was assessed for its ability to reproduce the diffuse signalmore » reconstructed from three protein crystals. This comparison revealed that multiple models of intramolecular conformational dynamics, including ensemble models inferred from the Bragg data, could not explain the signal. Models of rigid body or short-range liquid-like motions, in which dynamics are confined to the biological unit, showed modest agreement with the diffuse maps, but were unable to reproduce experimental features indicative of long-range correlations. Extending a model of liquid-like motions to include disorder across neighboring proteins in the crystal significantly improved agreement with all three systems and highlighted the contribution of intermolecular correlations to the observed signal. These findings anticipate a need to account for intermolecular disorder in order to advance the interpretation of diffuse scattering to either extract biological motions or aid structural inference.« less

Intermolecular correlations are necessary to explain diffuse scattering from protein crystals

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

Peck, Ariana; Poitevin, Frederic; Lane, Thomas Joseph

Conformational changes drive protein function, including catalysis, allostery, and signaling. X-ray diffuse scattering from protein crystals has frequently been cited as a probe of these correlated motions, with significant potential to advance our understanding of biological dynamics. However, recent work challenged this prevailing view, suggesting instead that diffuse scattering primarily originates from rigid body motions and could therefore be applied to improve structure determination. To investigate the nature of the disorder giving rise to diffuse scattering, and thus the potential applications of this signal, a diverse repertoire of disorder models was assessed for its ability to reproduce the diffuse signalmore » reconstructed from three protein crystals. This comparison revealed that multiple models of intramolecular conformational dynamics, including ensemble models inferred from the Bragg data, could not explain the signal. Models of rigid body or short-range liquid-like motions, in which dynamics are confined to the biological unit, showed modest agreement with the diffuse maps, but were unable to reproduce experimental features indicative of long-range correlations. Extending a model of liquid-like motions to include disorder across neighboring proteins in the crystal significantly improved agreement with all three systems and highlighted the contribution of intermolecular correlations to the observed signal. These findings anticipate a need to account for intermolecular disorder in order to advance the interpretation of diffuse scattering to either extract biological motions or aid structural inference.« less

Wave multiple scattering by a finite number of unclosed circular cylinders

NASA Technical Reports Server (NTRS)

Veliyev, E. I.; Veremey, V. V.

1984-01-01

The boundary value problem of plane H-polarized electromagnetic wave multiple scattering by a finite number of unclosed circular cylinders is solved. The solution is obtained by two different methods: the method of successive scattering and the method of partial matrix inversion for simultaneous dual equations. The advantages of the successive scattering method are shown. Computer calculations of the suface currents and the total cross section are presented for the structure of two screens.

Measurement and Modeling of Ultrasonic Pitch/catch Grain Noise

NASA Astrophysics Data System (ADS)

Margetan, F. J.; Gray, T. A.; Thompson, R. B.

2008-02-01

Ultrasonic grain noise arises from the scattering of sound waves by microstructural boundaries, and can limit the detection of weakly-reflecting internal defects in metals. In some cases of practical interest, such as focused-transducer inspections of aircraft engine components, so-called "single scattering" or "independent scatterer" models have proven to be reasonably accurate in predicting grain noise characteristics. In pulse/echo inspections it is difficult to experimentally assess the relative contributions of single scattering and multiple scattering, because both can generally contribute to the backscattered noise seen at any given observation time. For pitch/catch inspections, however, it is relatively easy to construct inspection geometries for which single-scattered noise should be insignificant, and hence any observed noise is presumably due to multiple scattering. This concept is demonstrated using pitch/catch shear-wave measurements performed on a well-characterized stainless-steel specimen. The inspection geometry allows us to control the overlap volume of the intersecting radiation fields of the two transducers. As we proceed from maximally overlapping fields to zero overlap, the single-scattering contribution to the observed grain noise is expected to decrease. Measurements are compared to the predictions of a single-scatterer model, and the relative contributions of single and multiple scattering to the observed grain noise are estimated.

Quasi-elastic nuclear scattering at high energies

NASA Technical Reports Server (NTRS)

Cucinotta, Francis A.; Townsend, Lawrence W.; Wilson, John W.

1992-01-01

The quasi-elastic scattering of two nuclei is considered in the high-energy optical model. Energy loss and momentum transfer spectra for projectile ions are evaluated in terms of an inelastic multiple-scattering series corresponding to multiple knockout of target nucleons. The leading-order correction to the coherent projectile approximation is evaluated. Calculations are compared with experiments.

Dynamic mineral clouds on HD 189733b. II. Monte Carlo radiative transfer for 3D cloudy exoplanet atmospheres: combining scattering and emission spectra

NASA Astrophysics Data System (ADS)

Lee, G. K. H.; Wood, K.; Dobbs-Dixon, I.; Rice, A.; Helling, Ch.

2017-05-01

Context. As the 3D spatial properties of exoplanet atmospheres are being observed in increasing detail by current and new generations of telescopes, the modelling of the 3D scattering effects of cloud forming atmospheres with inhomogeneous opacity structures becomes increasingly important to interpret observational data. Aims: We model the scattering and emission properties of a simulated cloud forming, inhomogeneous opacity, hot Jupiter atmosphere of HD 189733b. We compare our results to available Hubble Space Telescope (HST) and Spitzer data and quantify the effects of 3D multiple scattering on observable properties of the atmosphere. We discuss potential observational properties of HD 189733b for the upcoming Transiting Exoplanet Survey Satellite (TESS) and CHaracterising ExOPlanet Satellite (CHEOPS) missions. Methods: We developed a Monte Carlo radiative transfer code and applied it to post-process output of our 3D radiative-hydrodynamic, cloud formation simulation of HD 189733b. We employed three variance reduction techniques, I.e. next event estimation, survival biasing, and composite emission biasing, to improve signal to noise of the output. For cloud particle scattering events, we constructed a log-normal area distribution from the 3D cloud formation radiative-hydrodynamic results, which is stochastically sampled in order to model the Rayleigh and Mie scattering behaviour of a mixture of grain sizes. Results: Stellar photon packets incident on the eastern dayside hemisphere show predominantly Rayleigh, single-scattering behaviour, while multiple scattering occurs on the western hemisphere. Combined scattered and thermal emitted light predictions are consistent with published HST and Spitzer secondary transit observations. Our model predictions are also consistent with geometric albedo constraints from optical wavelength ground-based polarimetry and HST B band measurements. We predict an apparent geometric albedo for HD 189733b of 0.205 and 0.229, in the TESS and CHEOPS photometric bands respectively. Conclusions: Modelling the 3D geometric scattering effects of clouds on observables of exoplanet atmospheres provides an important contribution to the attempt to determine the cloud properties of these objects. Comparisons between TESS and CHEOPS photometry may provide qualitative information on the cloud properties of nearby hot Jupiter exoplanets.

Physics Model-Based Scatter Correction in Multi-Source Interior Computed Tomography.

PubMed

Gong, Hao; Li, Bin; Jia, Xun; Cao, Guohua

2018-02-01

Multi-source interior computed tomography (CT) has a great potential to provide ultra-fast and organ-oriented imaging at low radiation dose. However, X-ray cross scattering from multiple simultaneously activated X-ray imaging chains compromises imaging quality. Previously, we published two hardware-based scatter correction methods for multi-source interior CT. Here, we propose a software-based scatter correction method, with the benefit of no need for hardware modifications. The new method is based on a physics model and an iterative framework. The physics model was derived analytically, and was used to calculate X-ray scattering signals in both forward direction and cross directions in multi-source interior CT. The physics model was integrated to an iterative scatter correction framework to reduce scatter artifacts. The method was applied to phantom data from both Monte Carlo simulations and physical experimentation that were designed to emulate the image acquisition in a multi-source interior CT architecture recently proposed by our team. The proposed scatter correction method reduced scatter artifacts significantly, even with only one iteration. Within a few iterations, the reconstructed images fast converged toward the "scatter-free" reference images. After applying the scatter correction method, the maximum CT number error at the region-of-interests (ROIs) was reduced to 46 HU in numerical phantom dataset and 48 HU in physical phantom dataset respectively, and the contrast-noise-ratio at those ROIs increased by up to 44.3% and up to 19.7%, respectively. The proposed physics model-based iterative scatter correction method could be useful for scatter correction in dual-source or multi-source CT.

Spatial fragment distribution from a therapeutic pencil-like carbon beam in water.

PubMed

Matsufuji, Naruhiro; Komori, Masataka; Sasaki, Hitomi; Akiu, Kengo; Ogawa, Masako; Fukumura, Akifumi; Urakabe, Eriko; Inaniwa, Taku; Nishio, Teiji; Kohno, Toshiyuki; Kanai, Tatsuaki

2005-07-21

The latest heavy ion therapy tends to require information about the spatial distribution of the quality of radiation in a patient's body in order to make the best use of any potential advantage of swift heavy ions for the therapeutic treatment of a tumour. The deflection of incident particles is described well by Molière's multiple-scattering theory of primary particles; however, the deflection of projectile fragments is not yet thoroughly understood. This paper reports on our investigation of the spatial distribution of fragments produced from a therapeutic carbon beam through nuclear reactions in thick water. A DeltaE-E counter telescope system, composed of a plastic scintillator, a gas-flow proportional counter and a BGO scintillator, was rotated around a water target in order to measure the spatial distribution of the radiation quality. The results revealed that the observed deflection of fragment particles exceeded the multiple scattering effect estimated by Molière's theory. However, the difference can be sufficiently accounted for by considering one term involved in the multiple-scattering formula; this term corresponds to a lateral 'kick' at the point of production of the fragment. This kick is successfully explained as a transfer of the intra-nucleus Fermi momentum of a projectile to the fragment; the extent of the kick obeys the expectation derived from the Goldhaber model.

A Multiple Scattering Polarized Radiative Transfer Model: Application to HD 189733b

NASA Astrophysics Data System (ADS)

Kopparla, Pushkar; Natraj, Vijay; Zhang, Xi; Swain, Mark R.; Wiktorowicz, Sloane J.; Yung, Yuk L.

2016-01-01

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.

Analytical study of the effects of clouds on the light produced by lightning

NASA Technical Reports Server (NTRS)

Phanord, Dieudonne D.

1990-01-01

Researchers consider the scattering of visible and infrared light due to lightning by cubic, cylindrical and spherical clouds. The researchers extend to cloud physics the work by Twersky for single and multiple scattering of electromagnetic waves. They solve the interior problem separately to obtain the bulk parameters for the scatterer equivalent to the ensemble of spherical droplets. With the interior solution or the equivalent medium approach, the multiple scattering problem is reduced to that of a single scatterer in isolation. Hence, the computing methods of Wiscombe or Bohren specialized to Mie scattering with the possibility for absorption were used to generate numerical results in short computer time.

The polarization signature from the circumstellar disks of classical Be stars

NASA Astrophysics Data System (ADS)

Halonen, R. J.; Jones, C. E.

2012-05-01

The scattering of light in the nonspherical circumstellar envelopes of classical Be stars produces distinct polarimetric properties that can be used to investigate the physical nature of the scattering environment. Both the continuum and emission line polarization are potentially important diagnostic tools in the modeling of these systems. We combine the use of a new multiple scattering code with an established non-LTE radiative transfer code to study the characteristic wavelength-dependence of the intrinsic polarization of classical Be stars. We construct models using realistic chemical composition and self-consistent calculations of the thermal structure of the disk, and then determine the fraction of emergent polarized light. In particular, the aim of this theoretical research project is to investigate the effect of gas density and metallicity on the observed polarization properties of classical Be stars.

Enhancement factor in low-coherence enhanced backscattering and its applications for characterizing experimental skin carcinogenesis

NASA Astrophysics Data System (ADS)

Liu, Jingjing; Xu, Zhengbin; Song, Qinghai; Konger, Raymond L.; Kim, Young L.

2010-05-01

We experimentally study potential mechanisms by which the enhancement factor in low-coherence enhanced backscattering (LEBS) can probe subtle variations in radial intensity distribution in weakly scattering media. We use enhanced backscattering of light by implementing either (1) low spatial coherence illumination or (2) multiple spatially independent detections using a microlens array under spatially coherent illumination. We show that the enhancement factor in these configurations is a measure of the integrated intensity within the localized coherence or detection area, which can exhibit strong dependence on small perturbations in scattering properties. To further evaluate the utility of the LEBS enhancement factor, we use a well-established animal model of cutaneous two-stage chemical carcinogenesis. In this pilot study, we demonstrate that the LEBS enhancement factor can be substantially altered at a stage of preneoplasia. Our animal result supports the idea that early carcinogenesis can cause subtle alterations in the scattering properties that can be captured by the LEBS enhancement factor. Thus, the LEBS enhancement factor has the potential as an easily measurable biomarker in skin carcinogenesis.

Acoustic attraction, repulsion and radiation force cancellation on a pair of rigid particles with arbitrary cross-sections in 2D: Circular cylinders example

NASA Astrophysics Data System (ADS)

Mitri, F. G.

2017-11-01

The acoustic radiation forces arising on a pair of sound impenetrable cylindrical particles of arbitrary cross-sections are derived. Plane progressive, standing or quasi-standing waves with an arbitrary incidence angle are considered. Multiple scattering effects are described using the multipole expansion formalism and the addition theorem of cylindrical wave functions. An effective incident acoustic field on a particular object is determined, and used with the scattered field to derive closed-form analytical expressions for the radiation force vector components. The mathematical expressions for the radiation force components are exact, and have been formulated in partial-wave series expansions in cylindrical coordinates involving the angle of incidence, the reflection coefficient forming the progressive or the (quasi)standing wave field, the addition theorem, and the expansion coefficients. Numerical examples illustrate the analysis for two rigid circular cross-sections immersed in a non-viscous fluid. Computations for the dimensionless radiation force functions are performed with emphasis on varying the angle of incidence, the interparticle distance, the sizes of the particles as well as the characteristics of the incident field. Depending on the interparticle distance and angle of incidence, one of the particles yields neutrality; it experiences no force and becomes unresponsive (i.e., ;invisible;) to the linear momentum transfer of the effective incident field due to multiple scattering cancellation effects. Moreover, attractive or repulsive forces between the two particles may arise depending on the interparticle distance, the angle of incidence and size parameters of the particles. This study provides a complete analytical method and computations for the axial and transverse radiation force components in multiple acoustic scattering encompassing the cases of plane progressive, standing or quasi-standing waves of arbitrary incidence by a pair of scatterers. Potential applications concern the prediction of the forces used in acoustically-engineered metamaterials with reconfigurable periodicities, cloaking devices, and liquid crystals to name a few examples.

On the theory and simulation of multiple Coulomb scattering of heavy-charged particles.

PubMed

Striganov, S I

2005-01-01

The Moliere theory of multiple Coulomb scattering is modified to take into account the difference between processes of scattering off atomic nuclei and electrons. A simple analytical expression for angular distribution of charged particles passing through a thick absorber is found. It does not assume any special form for a differential scattering cross section and has a wider range of applicability than a gaussian approximation. A well-known method to simulate multiple Coulomb scatterings is based on treating 'soft' and 'hard' collisions differently. An angular deflection in a large number of 'soft' collisions is sampled using the proposed distribution function, a small number of 'hard' collision are simulated directly. A boundary between 'hard' and 'soft' collisions is defined, providing a precise sampling of a scattering angle (1% level) and a small number of 'hard' collisions. A corresponding simulating module takes into account projectile and nucleus charged distributions and exact kinematics of a projectile-electron interaction.

Polarimetric scattering from layered media with multiple species of scatterers

NASA Technical Reports Server (NTRS)

Nghiem, S. V.; Kwok, R.; Yueh, S. H.; Kong, J. A.; Hsu, C. C.; Tassoudji, M. A.; Shin, R. T.

1995-01-01

Geophysical media are usually heterogeneous and contain multiple species of scatterers. In this paper a model is presented to calculate effective permittivities and polarimetric backscattering coefficients of multispecies-layered media. The same physical description is consistently used in the derivation of both permittivities and scattering coefficients. The strong permittivity fluctuation theory is extended to account for the multiple species of scatterers with a general ellipsoidal shape whose orientations are randomly distributed. Under the distorted Born approximation, polarimetric scattering coefficients are obtained. These calculations are applicable to the special cases of spheroidal and spherical scatterers. The model is used to study effects of scatterer shapes and multispecies mixtures on polarimetric signatures of heterogeneous media. The multispecies model accounts for moisture content in scattering media such as snowpack in an ice sheet. The results indicate a high sensitivity of backscatter to moisture with a stronger dependence for drier snow and ice grain size is important to the backscatter. For frost-covered saline ice, model results for bare ice are compared with measured data at C band and then the frost flower formation is simulated with a layer of fanlike ice crystals including brine infiltration over a rough interface. The results with the frost cover suggest a significant increase in scattering coefficients and a polarimetric signature closer to isotropic characteristics compared to the thin saline ice case.

Impurity-limited resistance and phase interference of localized impurities under quasi-one dimensional nano-structures

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

Sano, Nobuyuki, E-mail: sano@esys.tsukuba.ac.jp

2015-12-28

The impurity-limited resistance and the effect of the phase interference among localized multiple impurities in the quasi-one dimensional (quasi-1D) nanowire structures are systematically investigated under the framework of the scattering theory. We derive theoretical expressions of the impurity-limited resistance in the nanowire under the linear response regime from the Landauer formula and from the Boltzmann transport equation (BTE) with the relaxation time approximation. We show that the formula from the BTE exactly coincides with that from the Landauer approach with the weak-scattering limit when the energy spectrum of the in-coming electrons from the reservoirs is narrow and, thus, point outmore » a possibility that the distinction of the impurity-limited resistances derived from the Landauer formula and that of the BTE could be made clear. The derived formulas are applied to the quasi-1D nanowires doped with multiple localized impurities with short-range scattering potential and the validity of various approximations on the resistance are discussed. It is shown that impurity scattering becomes so strong under the nanowire structures that the weak-scattering limit breaks down in most cases. Thus, both phase interference and phase randomization simultaneously play a crucial role in determining the impurity-limited resistance even under the fully coherent framework. When the impurity separation along the wire axis direction is small, the constructive phase interference dominates and the resistance is much greater than the average resistance. As the separation becomes larger, however, it approaches the series resistance of the single-impurity resistance due to the phase randomization. Furthermore, under the uniform configuration of impurities, the space-average resistance of multiple impurities at room temperature is very close to the series resistance of the single-impurity resistance, and thus, each impurity could be regarded as an independent scattering center. The physical origin of this “self-averaging” under the fully coherent environments is attributed to the broadness of the energy spectrum of the in-coming electrons from the reservoirs.« less

Energy-loss cross sections for inclusive charge-exchange reactions at intermediate energies

NASA Technical Reports Server (NTRS)

Cucinotta, Francis A.; Townsend, Lawrence W.; Dubey, Rajendra R.

1993-01-01

Charge-exchange reactions for scattering to the continuum are considered in a high-energy multiple scattering model. Calculations for (p,n) and (He-3,H-3) reactions are made and compared with experimental results for C-12, O-16, and Al-27 targets. Coherent effects are shown to lead to an important role for inelastic multiple scattering terms when light projectiles are considered.

Full wave two-dimensional modeling of scattering and inverse scattering for layered rough surfaces with buried objects

NASA Astrophysics Data System (ADS)

Kuo, Chih-Hao

Efficient and accurate modeling of electromagnetic scattering from layered rough surfaces with buried objects finds applications ranging from detection of landmines to remote sensing of subsurface soil moisture. The formulation of a hybrid numerical/analytical solution to electromagnetic scattering from layered rough surfaces is first presented in this dissertation. The solution to scattering from each rough interface is sought independently based on the extended boundary condition method (EBCM), where the scattered fields of each rough interface are expressed as a summation of plane waves and then cast into reflection/transmission matrices. To account for interactions between multiple rough boundaries, the scattering matrix method (SMM) is applied to recursively cascade reflection and transmission matrices of each rough interface and obtain the composite reflection matrix from the overall scattering medium. The validation of this method against the Method of Moments (MoM) and Small Perturbation Method (SPM) is addressed and the numerical results which investigate the potential of low frequency radar systems in estimating deep soil moisture are presented. Computational efficiency of the proposed method is also discussed. In order to demonstrate the capability of this method in modeling coherent multiple scattering phenomena, the proposed method has been employed to analyze backscattering enhancement and satellite peaks due to surface plasmon waves from layered rough surfaces. Numerical results which show the appearance of enhanced backscattered peaks and satellite peaks are presented. Following the development of the EBCM/SMM technique, a technique which incorporates a buried object in layered rough surfaces by employing the T-matrix method and the cylindrical-to-spatial harmonics transformation is proposed. Validation and numerical results are provided. Finally, a multi-frequency polarimetric inversion algorithm for the retrieval of subsurface soil properties using VHF/UHF band radar measurements is devised. The top soil dielectric constant is first determined using an L-band inversion algorithm. For the retrieval of subsurface properties, a time-domain inversion technique is employed together with a parameter optimization for the pulse shape of time delay echoes from VHF/UHF band radar observations. Numerical studies to investigate the accuracy of the proposed inversion technique in presence of errors are addressed.

Colorimetry and magnitudes of asteroids

NASA Technical Reports Server (NTRS)

Bowell, E.; Lumme, K.

1979-01-01

In the present paper, 1500 UBV observations are analyzed by a new rather general multiple scattering theory which provided clear insight into previously poorly-recognized optical nature of asteroid surfaces. Thus, phase curves are shown to consist of a surface-texture controlled component, due to singly scattered light, and a component due to multiple scattering. Phase curve shapes can be characterized by a single parameter, the multiple scattering factor, Q. As Q increases, the relative importance of the opposition effect diminishes. Asteroid surfaces are particulate and strikingly similar to texture, being moderately porous and moderately rough on a scale greater than the wavelength of light. In concequence, Q (and also the phase coefficient) correlate well with geometric albedo, and there exists a purely photometric means of determining albedos and diameters.

On the evaluation of air mass factors for atmospheric near-ultraviolet and visible absorption spectroscopy

NASA Technical Reports Server (NTRS)

Perliski, Lori M.; Solomon, Susan

1993-01-01

The interpretation of UV-visible twilight absorption measurements of atmospheric chemical constituents is dependent on how well the optical path, or air mass factor, of light collected by the spectrometer is understood. A simple single scattering model and a Monte Carlo radiative transfer scheme have been developed to study the effects of multiple scattering, aerosol scattering, surface albedo and refraction on air mass factors for scattered light observations. At fairly short visible wavelengths (less than about 450 nm), stratospheric air mass factors are found to be relatively insensitive to multiple scattering, surface albedo and refraction, as well as aerosol scattering by background aerosols. Longer wavelengths display greater sensitivity to refraction and aerosol scattering. Tropospheric air mass factors are found to be highly dependent on aerosol scattering, surface albedo and, at long visible wavelengths (about 650 nm), refraction. Absorption measurements of NO2 and O4 are shown to support these conclusions.

Effect of Multiple Scattering on the Compton Recoil Current Generated in an EMP, Revisited

DOE PAGES

Farmer, William A.; Friedman, Alex

2015-06-18

Multiple scattering has historically been treated in EMP modeling through the obliquity factor. The validity of this approach is examined here. A simplified model problem, which correctly captures cyclotron motion, Doppler shifting due to the electron motion, and multiple scattering is first considered. The simplified problem is solved three ways: the obliquity factor, Monte-Carlo, and Fokker-Planck finite-difference. Because of the Doppler effect, skewness occurs in the distribution. It is demonstrated that the obliquity factor does not correctly capture this skewness, but the Monte-Carlo and Fokker-Planck finite-difference approaches do. Here, the obliquity factor and Fokker-Planck finite-difference approaches are then compared inmore » a fuller treatment, which includes the initial Klein-Nishina distribution of the electrons, and the momentum dependence of both drag and scattering. It is found that, in general, the obliquity factor is adequate for most situations. However, as the gamma energy increases and the Klein-Nishina becomes more peaked in the forward direction, skewness in the distribution causes greater disagreement between the obliquity factor and a more accurate model of multiple scattering.« less

Multispectral imaging of absorption and scattering properties of in vivo exposed rat brain using a digital red-green-blue camera.

PubMed

Yoshida, Keiichiro; Nishidate, Izumi; Ishizuka, Tomohiro; Kawauchi, Satoko; Sato, Shunichi; Sato, Manabu

2015-05-01

In order to estimate multispectral images of the absorption and scattering properties in the cerebral cortex of in vivo rat brain, we investigated spectral reflectance images estimated by the Wiener estimation method using a digital RGB camera. A Monte Carlo simulation-based multiple regression analysis for the corresponding spectral absorbance images at nine wavelengths (500, 520, 540, 560, 570, 580, 600, 730, and 760 nm) was then used to specify the absorption and scattering parameters of brain tissue. In this analysis, the concentrations of oxygenated hemoglobin and that of deoxygenated hemoglobin were estimated as the absorption parameters, whereas the coefficient a and the exponent b of the reduced scattering coefficient spectrum approximated by a power law function were estimated as the scattering parameters. The spectra of absorption and reduced scattering coefficients were reconstructed from the absorption and scattering parameters, and the spectral images of absorption and reduced scattering coefficients were then estimated. In order to confirm the feasibility of this method, we performed in vivo experiments on exposed rat brain. The estimated images of the absorption coefficients were dominated by the spectral characteristics of hemoglobin. The estimated spectral images of the reduced scattering coefficients had a broad scattering spectrum, exhibiting a larger magnitude at shorter wavelengths, corresponding to the typical spectrum of brain tissue published in the literature. The changes in the estimated absorption and scattering parameters during normoxia, hyperoxia, and anoxia indicate the potential applicability of the method by which to evaluate the pathophysiological conditions of in vivo brain due to the loss of tissue viability.

Fast analytical scatter estimation using graphics processing units.

PubMed

Ingleby, Harry; Lippuner, Jonas; Rickey, Daniel W; Li, Yue; Elbakri, Idris

2015-01-01

To develop a fast patient-specific analytical estimator of first-order Compton and Rayleigh scatter in cone-beam computed tomography, implemented using graphics processing units. The authors developed an analytical estimator for first-order Compton and Rayleigh scatter in a cone-beam computed tomography geometry. The estimator was coded using NVIDIA's CUDA environment for execution on an NVIDIA graphics processing unit. Performance of the analytical estimator was validated by comparison with high-count Monte Carlo simulations for two different numerical phantoms. Monoenergetic analytical simulations were compared with monoenergetic and polyenergetic Monte Carlo simulations. Analytical and Monte Carlo scatter estimates were compared both qualitatively, from visual inspection of images and profiles, and quantitatively, using a scaled root-mean-square difference metric. Reconstruction of simulated cone-beam projection data of an anthropomorphic breast phantom illustrated the potential of this method as a component of a scatter correction algorithm. The monoenergetic analytical and Monte Carlo scatter estimates showed very good agreement. The monoenergetic analytical estimates showed good agreement for Compton single scatter and reasonable agreement for Rayleigh single scatter when compared with polyenergetic Monte Carlo estimates. For a voxelized phantom with dimensions 128 × 128 × 128 voxels and a detector with 256 × 256 pixels, the analytical estimator required 669 seconds for a single projection, using a single NVIDIA 9800 GX2 video card. Accounting for first order scatter in cone-beam image reconstruction improves the contrast to noise ratio of the reconstructed images. The analytical scatter estimator, implemented using graphics processing units, provides rapid and accurate estimates of single scatter and with further acceleration and a method to account for multiple scatter may be useful for practical scatter correction schemes.

Virtual Excitation and Multiple Scattering Correction Terms to the Neutron Index of Refraction for Hydrogen.

PubMed

Schoen, K; Snow, W M; Kaiser, H; Werner, S A

2005-01-01

The neutron index of refraction is generally derived theoretically in the Fermi approximation. However, the Fermi approximation neglects the effects of the binding of the nuclei of a material as well as multiple scattering. Calculations by Nowak introduced correction terms to the neutron index of refraction that are quadratic in the scattering length and of order 10(-3) fm for hydrogen and deuterium. These correction terms produce a small shift in the final value for the coherent scattering length of H2 in a recent neutron interferometry experiment.

Multiple Coulomb scattering in thin silicon

NASA Astrophysics Data System (ADS)

Berger, N.; Buniatyan, A.; Eckert, P.; Förster, F.; Gredig, R.; Kovalenko, O.; Kiehn, M.; Philipp, R.; Schöning, A.; Wiedner, D.

2014-07-01

We present a measurement of multiple Coulomb scattering of 1 to 6 GeV/c electrons in thin (50-140 μm) silicon targets. The data were obtained with the EUDET telescope Aconite at DESY and are compared to parametrisations as used in the Geant4 software package. We find good agreement between data and simulation in the scattering distribution width but large deviations in the shape of the distribution. In order to achieve a better description of the shape, a new scattering model based on a Student's t distribution is developed and compared to the data.

Strong scattering of short-period seismic waves by the core-mantle boundary and the P-diffracted wave

NASA Astrophysics Data System (ADS)

Bataille, Klaus; Lund, Fernando

We interpret the long-tail-in-time (up to 3 minutes) decay of short-period Pdiff as being due to multiple scattering within D″, which, for this purpose, is assumed to be an heterogeneous region with a low velocity zone just next to the core-mantle boundary. A simple multiple scattering theory, generalized for a two-dimensional spherical geometry, provides good agreement with observations for values of the scattering and attenuation coefficients (η) of about 10-3 km-1.

Multiple scattering induced negative refraction of matter waves

PubMed Central

Pinsker, Florian

2016-01-01

Starting from fundamental multiple scattering theory it is shown that negative refraction indices are feasible for matter waves passing a well-defined ensemble of scatterers. A simple approach to this topic is presented and explicit examples for systems of scatterers in 1D and 3D are stated that imply negative refraction for a generic incoming quantum wave packet. Essential features of the effective scattering field, densities and frequency spectrum of scatterers are considered. Additionally it is shown that negative refraction indices allow perfect transmission of the wave passing the ensemble of scatterers. Finally the concept of the superlens is discussed, since it is based on negative refraction and can be extended to matter waves utilizing the observations presented in this paper which thus paves the way to ‘untouchable’ quantum systems in analogy to cloaking devices for electromagnetic waves. PMID:26857266

Multiple Acquisition InSAR Analysis: Persistent Scatterer and Small Baseline Approaches

NASA Astrophysics Data System (ADS)

Hooper, A.

2006-12-01

InSAR techniques that process data from multiple acquisitions enable us to form time series of deformation and also allow us to reduce error terms present in single interferograms. There are currently two broad categories of methods that deal with multiple images: persistent scatterer methods and small baseline methods. The persistent scatterer approach relies on identifying pixels whose scattering properties vary little with time and look angle. Pixels that are dominated by a singular scatterer best meet these criteria; therefore, images are processed at full resolution to both increase the chance of there being only one dominant scatterer present, and to reduce the contribution from other scatterers within each pixel. In images where most pixels contain multiple scatterers of similar strength, even at the highest possible resolution, the persistent scatterer approach is less optimal, as the scattering characteristics of these pixels vary substantially with look angle. In this case, an approach that interferes only pairs of images for which the difference in look angle is small makes better sense, and resolution can be sacrificed to reduce the effects of the look angle difference by band-pass filtering. This is the small baseline approach. Existing small baseline methods depend on forming a series of multilooked interferograms and unwrapping each one individually. This approach fails to take advantage of two of the benefits of processing multiple acquisitions, however, which are usually embodied in persistent scatterer methods: the ability to find and extract the phase for single-look pixels with good signal-to-noise ratio that are surrounded by noisy pixels, and the ability to unwrap more robustly in three dimensions, the third dimension being that of time. We have developed, therefore, a new small baseline method to select individual single-look pixels that behave coherently in time, so that isolated stable pixels may be found. After correction for various error terms, the phase values of the selected pixels are unwrapped using a new three-dimensional algorithm. We apply our small baseline method to an area in southern Iceland that includes Katla and Eyjafjallajökull volcanoes, and retrieve a time series of deformation that shows transient deformation due to intrusion of magma beneath Eyjafjallajökull. We also process the data using the Stanford method for persistent scatterers (StaMPS) for comparison.

An efficient algorithm for the generalized Foldy-Lax formulation

NASA Astrophysics Data System (ADS)

Huang, Kai; Li, Peijun; Zhao, Hongkai

2013-02-01

Consider the scattering of a time-harmonic plane wave incident on a two-scale heterogeneous medium, which consists of scatterers that are much smaller than the wavelength and extended scatterers that are comparable to the wavelength. In this work we treat those small scatterers as isotropic point scatterers and use a generalized Foldy-Lax formulation to model wave propagation and capture multiple scattering among point scatterers and extended scatterers. Our formulation is given as a coupled system, which combines the original Foldy-Lax formulation for the point scatterers and the regular boundary integral equation for the extended obstacle scatterers. The existence and uniqueness of the solution for the formulation is established in terms of physical parameters such as the scattering coefficient and the separation distances. Computationally, an efficient physically motivated Gauss-Seidel iterative method is proposed to solve the coupled system, where only a linear system of algebraic equations for point scatterers or a boundary integral equation for a single extended obstacle scatterer is required to solve at each step of iteration. The convergence of the iterative method is also characterized in terms of physical parameters. Numerical tests for the far-field patterns of scattered fields arising from uniformly or randomly distributed point scatterers and single or multiple extended obstacle scatterers are presented.

Intrinsic acoustical cross sections in the multiple scattering by a pair of rigid cylindrical particles in 2D

NASA Astrophysics Data System (ADS)

Mitri, F. G.

2017-08-01

The multiple scattering effects occurring between two scatterers are described based upon the multipole expansion formalism as well as the addition theorem of cylindrical wave functions. An original approach is presented in which an effective incident acoustic field on a particular object, which includes both the primary and re-scattered waves from the other particle is determined first, and then used with the scattered field to derive closed-form analytical expressions for the inherent (i.e. intrinsic) cross-sections based on the far-field scattering. This method does not introduce any approximation in the calculation of the intrinsic cross-sections since the procedure is reduced to the one-body problem. The mathematical expressions for the intrinsic cross-sections are formulated in partial-wave series expansions (PWSEs) in cylindrical coordinates involving the angle of incidence, the addition theorem for the cylindrical wave functions, and the expansion coefficients of the scatterers. Numerical examples illustrate the analysis for two rigid circular cylindrical cross-sections with different radii immersed in a non-viscous fluid. Computations for the dimensionless extrinsic and intrinsic extinction cross-section factors are evaluated with particular emphasis on varying the angle of incidence, the interparticle distance, as well as the sizes of the particles. A symmetric behavior is observed for the dimensionless extrinsic extinction cross-section, while asymmetry arises for the intrinsic extinction cross-section of each particle with respect to the angle of incidence. The present analysis provides a complete analytical and computational method for the prediction of the intrinsic (local) scattering, absorption and extinction cross-sections in the multiple acoustic scatterings of plane progressive waves of arbitrary incidence by a pair of scatterers. The results and computational analyses can be used as a priori information for future applications to guide the direct or inverse characterization of multiple scattering systems in acoustically-engineered metamaterials, cloaking devices, particle dynamics, levitation, manipulation and handling, and other areas.

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

Ray, L.; Hoffmann, G.W.; Thaler, R.M.

The treatment of the Coulomb interaction in the multiple scattering theories of Kerman-McManus-Thaler and Watson is examined in detail. By neglecting virtual Coulomb excitations, the lowest order Coulomb term in the Watson optical potential is shown to be a convolution of the point Coulomb interaction with the distributed nuclear charge, while the equivalent Kerman-McManus-Thaler Coulomb potential is obtained from an averaged, single-particle Coulombic T matrix. The Kerman-McManus-Thaler Coulomb potential is expressed as the Watson Coulomb term plus additional Coulomb-nuclear and Coulomb-Coulomb cross terms, and the omission of the extra terms in usual Kerman-McManus-Thaler applications leads to negative infinite total reactionmore » cross section predictions and incorrect pure Coulomb scattering limits. Approximations are presented which eliminate these anomalies. Using the two-potential formula, the full projectile-nucleus T matrix is separated into two terms, one resulting from the distributed nuclear charge and the other being a Coulomb distorted nuclear T matrix. It is shown that the error resulting from the omission of the Kerman-McManus-Thaler Coulomb terms is effectively removed when the pure Coulomb T matrix in Kerman-McManus-Thaler is replaced by the analogous quantity in the Watson approach. Using the various approximations, theoretical angular distributions are obtained for 800 MeV p+/sup 208/Pb elastic scattering and compared with experimental data.« less

Theory of bright-field scanning transmission electron microscopy for tomography

NASA Astrophysics Data System (ADS)

Levine, Zachary H.

2005-02-01

Radiation transport theory is applied to electron microscopy of samples composed of one or more materials. The theory, originally due to Goudsmit and Saunderson, assumes only elastic scattering and an amorphous medium dominated by atomic interactions. For samples composed of a single material, the theory yields reasonable parameter-free agreement with experimental data taken from the literature for the multiple scattering of 300-keV electrons through aluminum foils up to 25μm thick. For thin films, the theory gives a validity condition for Beer's law. For thick films, a variant of Molière's theory [V. G. Molière, Z. Naturforschg. 3a, 78 (1948)] of multiple scattering leads to a form for the bright-field signal for foils in the multiple-scattering regime. The signal varies as [tln(e1-2γt/τ)]-1 where t is the path length of the beam, τ is the mean free path for elastic scattering, and γ is Euler's constant. The Goudsmit-Saunderson solution interpolates numerically between these two limits. For samples with multiple materials, elemental sensitivity is developed through the angular dependence of the scattering. From the elastic scattering cross sections of the first 92 elements, a singular-value decomposition of a vector space spanned by the elastic scattering cross sections minus a delta function shows that there is a dominant common mode, with composition-dependent corrections of about 2%. A mathematically correct reconstruction procedure beyond 2% accuracy requires the acquisition of the bright-field signal as a function of the scattering angle. Tomographic reconstructions are carried out for three singular vectors of a sample problem with four elements Cr, Cu, Zr, and Te. The three reconstructions are presented jointly as a color image; all four elements are clearly identifiable throughout the image.

Influence of multiple scattering and absorption on the full scattering profile and the isobaric point in tissue

NASA Astrophysics Data System (ADS)

Duadi, Hamootal; Fixler, Dror

2015-05-01

Light reflectance and transmission from soft tissue has been utilized in noninvasive clinical measurement devices such as the photoplethysmograph (PPG) and reflectance pulse oximeter. Incident light on the skin travels into the underlying layers and is in part reflected back to the surface, in part transferred and in part absorbed. Most methods of near infrared (NIR) spectroscopy focus on the volume reflectance from a semi-infinite sample, while very few measure transmission. We have previously shown that examining the full scattering profile (angular distribution of exiting photons) provides more comprehensive information when measuring from a cylindrical tissue. Furthermore, an isobaric point was found which is not dependent on changes in the reduced scattering coefficient. The angle corresponding to this isobaric point depends on the tissue diameter. We investigated the role of multiple scattering and absorption on the full scattering profile of a cylindrical tissue. First, we define the range in which multiple scattering occurs for different tissue diameters. Next, we examine the role of the absorption coefficient in the attenuation of the full scattering profile. We demonstrate that the absorption linearly influences the intensity at each angle of the full scattering profile and, more importantly, the absorption does not change the position of the isobaric point. The findings of this work demonstrate a realistic model for optical tissue measurements such as NIR spectroscopy, PPG, and pulse oximetery.

Ultrafast carrier capture and Auger recombination in single GaN/InGaN multiple quantum well nanowires

DOE PAGES

Boubanga-Tombet, Stephane; Wright, Jeremy B.; Lu, Ping; ...

2016-11-04

Ultrafast optical microscopy is an important tool for examining fundamental phenomena in semiconductor nanowires with high temporal and spatial resolution. In this paper, we used this technique to study carrier dynamics in single GaN/InGaN core–shell nonpolar multiple quantum well nanowires. We find that intraband carrier–carrier scattering is the main channel governing carrier capture, while subsequent carrier relaxation is dominated by three-carrier Auger recombination at higher densities and bimolecular recombination at lower densities. Finally, the Auger constants in these nanowires are approximately 2 orders of magnitude lower than in planar InGaN multiple quantum wells, highlighting their potential for future light-emitting devices.

A fast calculating two-stream-like multiple scattering algorithm that captures azimuthal and elevation variations

NASA Astrophysics Data System (ADS)

Fiorino, Steven T.; Elmore, Brannon; Schmidt, Jaclyn; Matchefts, Elizabeth; Burley, Jarred L.

2016-05-01

Properly accounting for multiple scattering effects can have important implications for remote sensing and possibly directed energy applications. For example, increasing path radiance can affect signal noise. This study describes the implementation of a fast-calculating two-stream-like multiple scattering algorithm that captures azimuthal and elevation variations into the Laser Environmental Effects Definition and Reference (LEEDR) atmospheric characterization and radiative transfer code. The multiple scattering algorithm fully solves for molecular, aerosol, cloud, and precipitation single-scatter layer effects with a Mie algorithm at every calculation point/layer rather than an interpolated value from a pre-calculated look-up-table. This top-down cumulative diffusivity method first considers the incident solar radiance contribution to a given layer accounting for solid angle and elevation, and it then measures the contribution of diffused energy from previous layers based on the transmission of the current level to produce a cumulative radiance that is reflected from a surface and measured at the aperture at the observer. Then a unique set of asymmetry and backscattering phase function parameter calculations are made which account for the radiance loss due to the molecular and aerosol constituent reflectivity within a level and allows for a more accurate characterization of diffuse layers that contribute to multiple scattered radiances in inhomogeneous atmospheres. The code logic is valid for spectral bands between 200 nm and radio wavelengths, and the accuracy is demonstrated by comparing the results from LEEDR to observed sky radiance data.

Real-time absorption and scattering characterization of slab-shaped turbid samples obtained by a combination of angular and spatially resolved measurements.

PubMed

Dam, Jan S; Yavari, Nazila; Sørensen, Søren; Andersson-Engels, Stefan

2005-07-10

We present a fast and accurate method for real-time determination of the absorption coefficient, the scattering coefficient, and the anisotropy factor of thin turbid samples by using simple continuous-wave noncoherent light sources. The three optical properties are extracted from recordings of angularly resolved transmittance in addition to spatially resolved diffuse reflectance and transmittance. The applied multivariate calibration and prediction techniques are based on multiple polynomial regression in combination with a Newton--Raphson algorithm. The numerical test results based on Monte Carlo simulations showed mean prediction errors of approximately 0.5% for all three optical properties within ranges typical for biological media. Preliminary experimental results are also presented yielding errors of approximately 5%. Thus the presented methods show a substantial potential for simultaneous absorption and scattering characterization of turbid media.

On scattering from the one-dimensional multiple Dirac delta potentials

NASA Astrophysics Data System (ADS)

Erman, Fatih; Gadella, Manuel; Uncu, Haydar

2018-05-01

In this paper, we propose a pedagogical presentation of the Lippmann–Schwinger equation as a powerful tool, so as to obtain important scattering information. In particular, we consider a one-dimensional system with a Schrödinger-type free Hamiltonian decorated with a sequence of N attractive Dirac delta interactions. We first write the Lippmann–Schwinger equation for the system and then solve it explicitly in terms of an N × N matrix. Then, we discuss the reflection and the transmission coefficients for an arbitrary number of centres and study the threshold anomaly for the N = 2 and N = 4 cases. We also study further features like the quantum metastable states and resonances, including their corresponding Gamow functions and virtual or antibound states. The use of the Lippmann–Schwinger equation simplifies our analysis enormously and gives exact results for an arbitrary number of Dirac delta potentials.

New approach to CT pixel-based photon dose calculations in heterogeneous media

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

Wong, J.W.; Henkelman, R.M.

The effects of small cavities on dose in water and the dose in a homogeneous nonunit density medium illustrate that inhomogeneities do not act independently in photon dose perturbation, and serve as two constraints which should be satisfied by approximate methods of computed tomography (CT) pixel-based dose calculations. Current methods at best satisfy only one of the two constraints and show inadequacies in some intermediate geometries. We have developed an approximate method that satisfies both these constraints and treats much of the synergistic effect of multiple inhomogeneities correctly. The method calculates primary and first-scatter doses by first-order ray tracing withmore » the first-scatter contribution augmented by a component of second scatter that behaves like first scatter. Multiple-scatter dose perturbation values extracted from small cavity experiments are used in a function which approximates the small residual multiple-scatter dose. For a wide range of geometries tested, our method agrees very well with measurements. The average deviation is less than 2% with a maximum of 3%. In comparison, calculations based on existing methods can have errors larger than 10%.« less

Relative importance of multiple scattering by air molecules and aerosols in forming the atmospheric path radiance in the visible and near-infrared parts of the spectrum.

PubMed

Antoine, D; Morel, A

1998-04-20

Single and multiple scattering by molecules or by atmospheric aerosols only (homogeneous scattering), and heterogeneous scattering by aerosols and molecules, are recorded in Monte Carlo simulations. It is shown that heterogeneous scattering (1) always contributes significantly to the path reflectance (rho(path)), (2) is realized at the expense of homogeneous scattering, (3) decreases when aerosols are absorbing, and (4) introduces deviations in the spectral dependencies of reflectances compared with the Rayleigh exponent and the aerosol angstrom exponent. The ratio of rho(path) to the Rayleigh reflectance for an aerosol-free atmosphere is linearly related to the aerosol optical thickness. This result provides a basis for a new scheme for atmospheric correction of remotely sensed ocean color observations.

Visualization of hemodynamics and light scattering in exposed brain of rat using multispectral image reconstruction based on Wiener estimation method

NASA Astrophysics Data System (ADS)

Nishidate, Izumi; Ishizuka, Tomohiro; Yoshida, Keiichiro; Kawauchi, Satoko; Sato, Shunichi; Sato, Manabu

2015-07-01

We investigate a method to estimate the spectral images of reduced scattering coefficients and the absorption coefficients of in vivo exposed brain tissues in the range from visible to near-infrared wavelength (500-760 nm) based on diffuse reflectance spectroscopy using a digital RGB camera. In the proposed method, the multi-spectral reflectance images of in vivo exposed brain are reconstructed from the digital red, green, blue images using the Wiener estimation algorithm. The Monte Carlo simulation-based multiple regression analysis for the absorbance spectra is then used to specify the absorption and scattering parameters of brain tissue. In this analysis, the concentration of oxygenated hemoglobin and that of deoxygenated hemoglobin are estimated as the absorption parameters whereas the scattering amplitude a and the scattering power b in the expression of μs'=aλ-b as the scattering parameters, respectively. The spectra of absorption and reduced scattering coefficients are reconstructed from the absorption and scattering parameters, and finally, the spectral images of absorption and reduced scattering coefficients are estimated. We performed simultaneous recordings of spectral diffuse reflectance images and of the electrophysiological signals for in vivo exposed rat brain during the cortical spreading depression evoked by the topical application of KCl. Changes in the total hemoglobin concentration and the tissue oxygen saturation imply the temporary change in cerebral blood flow during CSD. Change in the reduced scattering coefficient was observed before the profound increase in the total hemoglobin concentration, and its occurrence was synchronized with the negative dc shift of the local field potential.

Approximating Reflectance and Transmittance of Vegetation Using Multiple Spectral Invariants

NASA Astrophysics Data System (ADS)

Mottus, M.

2011-12-01

Canopy spectral invariants, eigenvalues of the radiative transfer equation and photon recollision probability are some of the new theoretical tools that have been applied in remote sensing of vegetation and atmosphere. The theoretical approach based on spectral invariants, informally also referred to as the p-theory, owns its attractivity to several factors. Firstly, it provides a rapid and physically-based way of describing canopy scattering. Secondly, the p-theory aims at parameterizing canopy structure in reflectance models using a simple and intuitive concept which can be applied at various structural levels, from shoot to tree crown. The theory has already been applied at scales from the molecular level to forest stands. The most important shortcoming of the p-theory lies in its inability to predict the directionality of scattering. The theory is currently based on only one physical parameter, the photon recollision probability p. It is evident that one parameter cannot contain enough information to reasonably predict the observed complex reflectance patterns produced by natural vegetation canopies. Without estimating scattering directionality, however, the theory cannot be compared with even the most simple (and well-tested) two-stream vegetation reflectance models. In this study, we evaluate the possibility to use additional parameters to fit the measured reflectance and transmittance of a vegetation stand. As a first step, the parameters are applied to separate canopy scattering into reflectance and transmittance. New parameters are introduced following the general approach of eigenvector expansion. Thus, the new parameters are coined higher-order spectral invariants. Calculation of higher-order invariants is based on separating first-order scattering from total scattering. Thus, the method explicitly accounts for different view geometries with different fractions of visible sunlit canopy (e.g., hot-spot). It additionally allows to produce different irradiation levels on leaf surfaces for direct and diffuse incidence, thus (in theory) allowing more accurate calculation of potential photosynthesis rates. Similarly to the p-theory, the use of multiple spectral invariants facilitates easy parametrization of canopy structure and scaling between different structural levels (leaf-shoot-stand). Spectral invariant-based remote sensing approaches are well suited for relatively large pixels even when no detailed ground truth information is available. In a case study, the theory of multiple spectral invariants was applied to measured canopy scattering. Spectral reflectance and transmittance measurements were carried out in gray alder (Alnus incana) plantation at Tartu Observatory, Estonia, in August 2006. The equations produced by the theory of spectral invariants were fitted to measured radiation fluxes. Preliminary results indicate that quantities with invariant-like behavior may indeed be used to approximate canopy scattering directionality.

Simulation of multiple scattering in a medium with an anisotropic scattering pattern

NASA Astrophysics Data System (ADS)

Kuzmin, V. L.; Val'kov, A. Yu.

2017-03-01

Multiple backscattering from layers with various thicknesses, including the case of half-space, is numerically simulated and a comparative analysis is performed for systems with the anisotropy of scattering described by the Henyey-Greenstein and Rayleigh-Gans phase functions. It is shown that the intensity of backscattering depends on the form of the phase function; the difference between the intensities obtained within the two models increases with anisotropy.

Improved atmospheric 3D BSDF model in earthlike exoplanet using ray-tracing based method

NASA Astrophysics Data System (ADS)

Ryu, Dongok; Kim, Sug-Whan; Seong, Sehyun

2012-10-01

The studies on planetary radiative transfer computation have become important elements to disk-averaged spectral characterization of potential exoplanets. In this paper, we report an improved ray-tracing based atmospheric simulation model as a part of 3-D earth-like planet model with 3 principle sub-components i.e. land, sea and atmosphere. Any changes in ray paths and their characteristics such as radiative power and direction are computed as they experience reflection, refraction, transmission, absorption and scattering. Improved atmospheric BSDF algorithms uses Q.Liu's combined Rayleigh and aerosol Henrey-Greenstein scattering phase function. The input cloud-free atmosphere model consists of 48 layers with vertical absorption profiles and a scattering layer with their input characteristics using the GIOVANNI database. Total Solar Irradiance data are obtained from Solar Radiation and Climate Experiment (SORCE) mission. Using aerosol scattering computation, we first tested the atmospheric scattering effects with imaging simulation with HRIV, EPOXI. Then we examined the computational validity of atmospheric model with the measurements of global, direct and diffuse radiation taken from NREL(National Renewable Energy Laboratory)s pyranometers and pyrheliometers on a ground station for cases of single incident angle and for simultaneous multiple incident angles of the solar beam.

Potential Elevation Biases for Laser Altimeters from Subsurface Scattered Photons: Laboratory and Model Exploration of Green Light Scattering in Snow

NASA Astrophysics Data System (ADS)

Greeley, A.; Neumann, T.; Markus, T.; Kurtz, N. T.; Cook, W. B.

2015-12-01

Existing visible light laser altimeters such as MABEL (Multiple Altimeter Beam Experimental Lidar) - a single photon counting simulator for ATLAS (Advanced Topographic Laser Altimeter System) on NASA's upcoming ICESat-2 mission - and ATM (Airborne Topographic Mapper) on NASA's Operation IceBridge mission provide scientists a view of Earth's ice sheets, glaciers, and sea ice with unprecedented detail. Precise calibration of these instruments is needed to understand rapidly changing parameters like sea ice freeboard and to measure optical properties of surfaces like snow covered ice sheets using subsurface scattered photons. Photons travelling into snow, ice, or water before scattering back to the altimeter receiving system (subsurface photons) travel farther and longer than photons scattering off the surface only, causing a bias in the measured elevation. We seek to identify subsurface photons in a laboratory setting using a flight-tested laser altimeter (MABEL) and to quantify their effect on surface elevation estimates for laser altimeter systems. We also compare these estimates with previous laboratory measurements of green laser light transmission through snow, as well as Monte Carlo simulations of backscattered photons from snow.

Predicting X-ray diffuse scattering from translation–libration–screw structural ensembles

PubMed Central

Van Benschoten, Andrew H.; Afonine, Pavel V.; Terwilliger, Thomas C.; Wall, Michael E.; Jackson, Colin J.; Sauter, Nicholas K.; Adams, Paul D.; Urzhumtsev, Alexandre; Fraser, James S.

2015-01-01

Identifying the intramolecular motions of proteins and nucleic acids is a major challenge in macromolecular X-ray crystallography. Because Bragg diffraction describes the average positional distribution of crystalline atoms with imperfect precision, the resulting electron density can be compatible with multiple models of motion. Diffuse X-ray scattering can reduce this degeneracy by reporting on correlated atomic displacements. Although recent technological advances are increasing the potential to accurately measure diffuse scattering, computational modeling and validation tools are still needed to quantify the agreement between experimental data and different parameterizations of crystalline disorder. A new tool, phenix.diffuse, addresses this need by employing Guinier’s equation to calculate diffuse scattering from Protein Data Bank (PDB)-formatted structural ensembles. As an example case, phenix.diffuse is applied to translation–libration–screw (TLS) refinement, which models rigid-body displacement for segments of the macromolecule. To enable the calculation of diffuse scattering from TLS-refined structures, phenix.tls_as_xyz builds multi-model PDB files that sample the underlying T, L and S tensors. In the glycerophos­phodiesterase GpdQ, alternative TLS-group partitioning and different motional correlations between groups yield markedly dissimilar diffuse scattering maps with distinct implications for molecular mechanism and allostery. These methods demonstrate how, in principle, X-ray diffuse scattering could extend macromolecular structural refinement, validation and analysis. PMID:26249347

Predicting X-ray diffuse scattering from translation–libration–screw structural ensembles

DOE PAGES

Van Benschoten, Andrew H.; Afonine, Pavel V.; Terwilliger, Thomas C.; ...

2015-07-28

Identifying the intramolecular motions of proteins and nucleic acids is a major challenge in macromolecular X-ray crystallography. Because Bragg diffraction describes the average positional distribution of crystalline atoms with imperfect precision, the resulting electron density can be compatible with multiple models of motion. Diffuse X-ray scattering can reduce this degeneracy by reporting on correlated atomic displacements. Although recent technological advances are increasing the potential to accurately measure diffuse scattering, computational modeling and validation tools are still needed to quantify the agreement between experimental data and different parameterizations of crystalline disorder. A new tool, phenix.diffuse, addresses this need by employing Guinier'smore » equation to calculate diffuse scattering from Protein Data Bank (PDB)-formatted structural ensembles. As an example case, phenix.diffuse is applied to translation–libration–screw (TLS) refinement, which models rigid-body displacement for segments of the macromolecule. To enable the calculation of diffuse scattering from TLS-refined structures, phenix.tls_as_xyz builds multi-model PDB files that sample the underlying T, L and S tensors. In the glycerophosphodiesterase GpdQ, alternative TLS-group partitioning and different motional correlations between groups yield markedly dissimilar diffuse scattering maps with distinct implications for molecular mechanism and allostery. In addition, these methods demonstrate how, in principle, X-ray diffuse scattering could extend macromolecular structural refinement, validation and analysis.« less

Pulsed holographic system for imaging through spatially extended scattering media

NASA Astrophysics Data System (ADS)

Kanaev, A. V.; Judd, K. P.; Lebow, P.; Watnik, A. T.; Novak, K. M.; Lindle, J. R.

2017-10-01

Imaging through scattering media is a highly sought capability for military, industrial, and medical applications. Unfortunately, nearly all recent progress was achieved in microscopic light propagation and/or light propagation through thin or weak scatterers which is mostly pertinent to medical research field. Sensing at long ranges through extended scattering media, for example turbid water or dense fog, still represents significant challenge and the best results are demonstrated using conventional approaches of time- or range-gating. The imaging range of such systems is constrained by their ability to distinguish a few ballistic photons that reach the detector from the background, scattered, and ambient photons, as well as from detector noise. Holography can potentially enhance time-gating by taking advantage of extra signal filtering based on coherence properties of the ballistic photons as well as by employing coherent addition of multiple frames. In a holographic imaging scheme ballistic photons of the imaging pulse are reflected from a target and interfered with the reference pulse at the detector creating a hologram. Related approaches were demonstrated previously in one-way imaging through thin biological samples and other microscopic scale scatterers. In this work, we investigate performance of holographic imaging systems under conditions of extreme scattering (less than one signal photon per pixel signal), demonstrate advantages of coherent addition of images recovered from holograms, and discuss image quality dependence on the ratio of the signal and reference beam power.

Stationary phase method and delay times for relativistic and non-relativistic tunneling particles

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

Bernardini, A.E.

2009-06-15

The stationary phase method is frequently adopted for calculating tunneling phase times of analytically-continuous Gaussian or infinite-bandwidth step pulses which collide with a potential barrier. This report deals with the basic concepts on deducing transit times for quantum scattering: the stationary phase method and its relation with delay times for relativistic and non-relativistic tunneling particles. After reexamining the above-barrier diffusion problem, we notice that the applicability of this method is constrained by several subtleties in deriving the phase time that describes the localization of scattered wave packets. Using a recently developed procedure - multiple wave packet decomposition - for somemore » specifical colliding configurations, we demonstrate that the analytical difficulties arising when the stationary phase method is applied for obtaining phase (traversal) times are all overcome. In this case, we also investigate the general relation between phase times and dwell times for quantum tunneling/scattering. Considering a symmetrical collision of two identical wave packets with an one-dimensional barrier, we demonstrate that these two distinct transit time definitions are explicitly connected. The traversal times are obtained for a symmetrized (two identical bosons) and an antisymmetrized (two identical fermions) quantum colliding configuration. Multiple wave packet decomposition shows us that the phase time (group delay) describes the exact position of the scattered particles and, in addition to the exact relation with the dwell time, leads to correct conceptual understanding of both transit time definitions. At last, we extend the non-relativistic formalism to the solutions for the tunneling zone of a one-dimensional electrostatic potential in the relativistic (Dirac to Klein-Gordon) wave equation where the incoming wave packet exhibits the possibility of being almost totally transmitted through the potential barrier. The conditions for the occurrence of accelerated and, eventually, superluminal tunneling transmission probabilities are all quantified and the problematic superluminal interpretation based on the non-relativistic tunneling dynamics is revisited. Lessons concerning the dynamics of relativistic tunneling and the mathematical structure of its solutions suggest revealing insights into mathematically analogous condensed-matter experiments using electrostatic barriers in single- and bi-layer graphene, for which the accelerated tunneling effect deserves a more careful investigation.« less

Speckle noise attenuation in optical coherence tomography by compounding images acquired at different positions of the sample

NASA Astrophysics Data System (ADS)

Popescu, Dan P.; Hewko, Mark D.; Sowa, Michael G.

2007-01-01

This study demonstrates a simple method for attenuating the speckle noise generated by coherent multiple-scattered photons in optical-coherence tomography images. The method could be included among the space-diversity techniques used for speckle reduction. It relies on displacing the sample along a weakly focused beam in the sample arm of the interferometer, acquiring a coherent image for each sample position and adding the individual images to form a compounded image. It is proven that the compounded image displays a reduction in the speckle noise generated by multiple scattered photons and an enhancement in the intensity signal caused by single-backscattered photons. To evaluate its potential biomedical applications, the method is used to investigate in vitro a caries lesion affecting the enamel layer of a wisdom tooth. Because of the uncorrelated nature of the speckle noise the compounded image provides a better mapping of the lesion compared to a single (coherent) image.

In-flight radiometric calibration of the Airborne Visible/Infrared Imaging Spectrometer (AVIRIS)

NASA Technical Reports Server (NTRS)

Conel, James E.; Green, Robert O.; Alley, Ronald E.; Bruegge, Carol J.; Carrere, Veronique; Margolis, Jack S.; Vane, Gregg; Chrien, Thomas G.; Slater, Philip N.; Biggard, Stuart F.

1988-01-01

A reflectance-based method was used to provide an analysis of the in-flight radiometric performance of AVIRIS. Field spectral reflectance measurements of the surface and extinction measurements of the atmosphere using solar radiation were used as input to atmospheric radiative transfer calculations. Five separate codes were used in the analysis. Four include multiple scattering, and the computed radiances from these for flight conditions were in good agreement. Code-generated radiances were compared with AVIRIS-predicted radiances based on two laboratory calibrations (pre- and post-season of flight) for a uniform highly reflecting natural dry lake target. For one spectrometer (C), the pre- and post-season calibration factors were found to give identical results, and to be in agreement with the atmospheric models that include multiple scattering. This positive result validates the field and laboratory calibration technique. Results for the other spectrometers (A, B and D) were widely at variance with the models no matter which calibration factors were used. Potential causes of these discrepancies are discussed.

Localization of a small change in a multiple scattering environment without modeling of the actual medium.

PubMed

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. © 2011 Acoustical Society of America

Focusing light through strongly scattering media by controlling binary amplitude optimization using genetic algorithm

NASA Astrophysics Data System (ADS)

Liu, Zhipeng; Zhang, Bin; Feng, Qi; Chen, Zhaoyang; Lin, Chengyou; Ding, Yingchun

2017-06-01

Focusing light through strongly scattering media plays an important role in biomedical imaging and therapy. Here, we experimentally demonstrate light focusing through ZnO sample by controlling binary amplitude optimization using genetic algorithm. In the experiment, we use a Micro Electro-Mechanical System (MEMS)-based digital micromirror device (DMD) which is in amplitude-only modulation mode. The DMD consists of 1920×1080 square mirrors that can be independently controlled to reflect light to a desired position. We control only 160 thousand mirrors which are divided into 400 segments to modulate light focusing through the scattering media using advanced genetic algorithm. Light intensity at the target position is enhanced up to 50+/-5 times the average speckle intensity. The diameters of focusing spot can be changed ranging from 7 μm to 70 μm at arbitrary positions and multiple foci are obtained simultaneously. The spatial arrangement of multiple foci can be flexibly controlled. The advantage of DMDs lies in their switching speed up to 30 kHz, which has the potential to generate a focus in an ultra-short period of time. Our work provides a reference for the study of high speed wavefront shaping that is required in vivo tissues imaging.

Local measurements of the diffusion constant in multiple scattering media: Application to human trabecular bone imaging

NASA Astrophysics Data System (ADS)

Aubry, Alexandre; Derode, Arnaud; Padilla, Frédéric

2008-03-01

We present local measurements of the diffusion constant for ultrasonic waves undergoing multiple scattering. The experimental setup uses a coherent array of programmable transducers. By achieving Gaussian beamforming at emission and reception, an array of virtual sources and receivers located in the near field is constructed. A matrix treatment is proposed to separate the incoherent intensity from the coherent backscattering peak. Local measurements of the diffusion constant D are then achieved. This technique is applied to a real case: a sample of human trabecular bone for which the ultrasonic characterization of multiple scattering is an issue.

Photometry of icy satellites: How important is multiple scattering in diluting shadows?

NASA Technical Reports Server (NTRS)

Buratti, B.; Veverka, J.

1984-01-01

Voyager observations have shown that the photometric properties of icy satellites are influenced significantly by large-scale roughness elements on the surfaces. While recent progress was made in treating the photometric effects of macroscopic roughness, it is still the case that even the most complete models do not account for the effects of multiple scattering fully. Multiple scattering dilutes shadows caused by large-scale features, yet for any specific model it is difficult to calculate the amount of dilution as a function of albedo. Accordingly, laboratory measurements were undertaken using the Cornell Goniometer to evaluate the magnitude of the effect.

Comparison of multiplicity distributions to the negative binomial distribution in muon-proton scattering

NASA Astrophysics Data System (ADS)

Arneodo, M.; Arvidson, A.; Aubert, J. J.; Badełek, B.; Beaufays, J.; Bee, C. P.; Benchouk, C.; Berghoff, G.; Bird, I.; Blum, D.; Böhm, E.; de Bouard, X.; Brasse, F. W.; Braun, H.; Broll, C.; Brown, S.; Brück, H.; Calen, H.; Chima, J. S.; Ciborowski, J.; Clifft, R.; Coignet, G.; Combley, F.; Coughlan, J.; D'Agostini, G.; Dahlgren, S.; Dengler, F.; Derado, I.; Dreyer, T.; Drees, J.; Düren, M.; Eckardt, V.; Edwards, A.; Edwards, M.; Ernst, T.; Eszes, G.; Favier, J.; Ferrero, M. I.; Figiel, J.; Flauger, W.; Foster, J.; Ftáčnik, J.; Gabathuler, E.; Gajewski, J.; Gamet, R.; Gayler, J.; Geddes, N.; Grafström, P.; Grard, F.; Haas, J.; Hagberg, E.; Hasert, F. J.; Hayman, P.; Heusse, P.; Jaffré, M.; Jachołkowska, A.; Janata, F.; Jancsó, G.; Johnson, A. S.; Kabuss, E. M.; Kellner, G.; Korbel, V.; Krüger, J.; Kullander, S.; Landgraf, U.; Lanske, D.; Loken, J.; Long, K.; Maire, M.; Malecki, P.; Manz, A.; Maselli, S.; Mohr, W.; Montanet, F.; Montgomery, H. E.; Nagy, E.; Nassalski, J.; Norton, P. R.; Oakham, F. G.; Osborne, A. M.; Pascaud, C.; Pawlik, B.; Payre, P.; Peroni, C.; Peschel, H.; Pessard, H.; Pettinghale, J.; Pietrzyk, B.; Pietrzyk, U.; Pönsgen, B.; Pötsch, M.; Renton, P.; Ribarics, P.; Rith, K.; Rondio, E.; Sandacz, A.; Scheer, M.; Schlagböhmer, A.; Schiemann, H.; Schmitz, N.; Schneegans, M.; Schneider, A.; Scholz, M.; Schröder, T.; Schultze, K.; Sloan, T.; Stier, H. E.; Studt, M.; Taylor, G. N.; Thénard, J. M.; Thompson, J. C.; de La Torre, A.; Toth, J.; Urban, L.; Urban, L.; Wallucks, W.; Whalley, M.; Wheeler, S.; Williams, W. S. C.; Wimpenny, S. J.; Windmolders, R.; Wolf, G.

1987-09-01

The multiplicity distributions of charged hadrons produced in the deep inelastic muon-proton scattering at 280 GeV are analysed in various rapidity intervals, as a function of the total hadronic centre of mass energy W ranging from 4 20 GeV. Multiplicity distributions for the backward and forward hemispheres are also analysed separately. The data can be well parameterized by binomial distributions, extending their range of applicability to the case of lepton-proton scattering. The energy and the rapidity dependence of the parameters is presented and a smooth transition from the negative binomial distribution via Poissonian to the ordinary binomial is observed.

A FDTD solution of scattering of laser beam with orbital angular momentum by dielectric particles: Far-field characteristics

NASA Astrophysics Data System (ADS)

Sun, Wenbo; Hu, Yongxiang; Weimer, Carl; Ayers, Kirk; Baize, Rosemary R.; Lee, Tsengdar

2017-02-01

Electromagnetic (EM) beams with orbital angular momentum (OAM) may have great potential applications in communication technology and in remote sensing of the Earth-atmosphere system and outer planets. Study of their interaction with optical lenses and dielectric or metallic objects, or scattering of them by particles in the Earth-atmosphere system, is a necessary step to explore the advantage of the OAM EM beams. In this study, the 3-dimensional (3D) scattered-field (SF) finite-difference time domain (FDTD) technique with the convolutional perfectly matched layer (CPML) absorbing boundary conditions (ABC) is applied to calculate the scattering of the purely azimuthal (the radial mode number is assumed to be zero) Laguerre-Gaussian (LG) beams with the OAM by dielectric particles. We found that for OAM beam's interaction with dielectric particles, the forward-scattering peak in the conventional phase function (P11) disappears, and light scattering peak occurs at a scattering angle of 15° to 45°. The disappearance of forward-scattering peak means that, in laser communications most of the particle-scattered noise cannot enter the receiver, thus the received light is optimally the original OAM-encoded signal. This feature of the OAM beam also implies that in lidar remote sensing of the atmospheric particulates, most of the multiple-scattering energy will be off lidar sensors, and this may result in an accurate profiling of particle layers in the atmosphere or in the oceans by lidar, or even in the ground when a ground penetration radar (GPR) with the OAM is applied. This far-field characteristics of the scattered OAM light also imply that the optical theorem, which is derived from plane-parallel wave scattering case and relates the forward scattering amplitude to the total cross section of the scatterer, is invalid for the scattering of OAM beams by dielectric particles.

Radiance and polarization of multiple scattered light from haze and clouds.

PubMed

Kattawar, G W; Plass, G N

1968-08-01

The radiance and polarization of multiple scattered light is calculated from the Stokes' vectors by a Monte Carlo method. The exact scattering matrix for a typical haze and for a cloud whose spherical drops have an average radius of 12 mu is calculated from the Mie theory. The Stokes' vector is transformed in a collision by this scattering matrix and the rotation matrix. The two angles that define the photon direction after scattering are chosen by a random process that correctly simulates the actual distribution functions for both angles. The Monte Carlo results for Rayleigh scattering compare favorably with well known tabulated results. Curves are given of the reflected and transmitted radiances and polarizations for both the haze and cloud models and for several solar angles, optical thicknesses, and surface albedos. The dependence on these various parameters is discussed.

Bright-White Beetle Scales Optimise Multiple Scattering of Light

NASA Astrophysics Data System (ADS)

Burresi, Matteo; Cortese, Lorenzo; Pattelli, Lorenzo; Kolle, Mathias; Vukusic, Peter; Wiersma, Diederik S.; Steiner, Ullrich; Vignolini, Silvia

2014-08-01

Whiteness arises from diffuse and broadband reflection of light typically achieved through optical scattering in randomly structured media. In contrast to structural colour due to coherent scattering, white appearance generally requires a relatively thick system comprising randomly positioned high refractive-index scattering centres. Here, we show that the exceptionally bright white appearance of Cyphochilus and Lepidiota stigma beetles arises from a remarkably optimised anisotropy of intra-scale chitin networks, which act as a dense scattering media. Using time-resolved measurements, we show that light propagating in the scales of the beetles undergoes pronounced multiple scattering that is associated with the lowest transport mean free path reported to date for low-refractive-index systems. Our light transport investigation unveil high level of optimisation that achieves high-brightness white in a thin low-mass-per-unit-area anisotropic disordered nanostructure.

Scattering in discrete random media with implications to propagation through rain. Ph.D. Thesis George Washingtion Univ., Washington, D.C.

NASA Technical Reports Server (NTRS)

Ippolito, L. J., Jr.

1977-01-01

The multiple scattering effects on wave propagation through a volume of discrete scatterers were investigated. The mean field and intensity for a distribution of scatterers was developed using a discrete random media formulation, and second order series expansions for the mean field and total intensity derived for one-dimensional and three-dimensional configurations. The volume distribution results were shown to proceed directly from the one-dimensional results. The multiple scattering intensity expansion was compared to the classical single scattering intensity and the classical result was found to represent only the first three terms in the total intensity expansion. The Foldy approximation to the mean field was applied to develop the coherent intensity, and was found to exactly represent all coherent terms of the total intensity.

A novel sampling method for multiple multiscale targets from scattering amplitudes at a fixed frequency

NASA Astrophysics Data System (ADS)

Liu, Xiaodong

2017-08-01

A sampling method by using scattering amplitude is proposed for shape and location reconstruction in inverse acoustic scattering problems. Only matrix multiplication is involved in the computation, thus the novel sampling method is very easy and simple to implement. With the help of the factorization of the far field operator, we establish an inf-criterion for characterization of underlying scatterers. This result is then used to give a lower bound of the proposed indicator functional for sampling points inside the scatterers. While for the sampling points outside the scatterers, we show that the indicator functional decays like the bessel functions as the sampling point goes away from the boundary of the scatterers. We also show that the proposed indicator functional continuously depends on the scattering amplitude, this further implies that the novel sampling method is extremely stable with respect to errors in the data. Different to the classical sampling method such as the linear sampling method or the factorization method, from the numerical point of view, the novel indicator takes its maximum near the boundary of the underlying target and decays like the bessel functions as the sampling points go away from the boundary. The numerical simulations also show that the proposed sampling method can deal with multiple multiscale case, even the different components are close to each other.

Nanowire Electron Scattering Spectroscopy

NASA Technical Reports Server (NTRS)

Hunt, Brian; Bronikowsky, Michael; Wong, Eric; VonAllmen, Paul; Oyafuso, Fablano

2009-01-01

Nanowire electron scattering spectroscopy (NESS) has been proposed as the basis of a class of ultra-small, ultralow-power sensors that could be used to detect and identify chemical compounds present in extremely small quantities. State-of-the-art nanowire chemical sensors have already been demonstrated to be capable of detecting a variety of compounds in femtomolar quantities. However, to date, chemically specific sensing of molecules using these sensors has required the use of chemically functionalized nanowires with receptors tailored to individual molecules of interest. While potentially effective, this functionalization requires labor-intensive treatment of many nanowires to sense a broad spectrum of molecules. In contrast, NESS would eliminate the need for chemical functionalization of nanowires and would enable the use of the same sensor to detect and identify multiple compounds. NESS is analogous to Raman spectroscopy, the main difference being that in NESS, one would utilize inelastic scattering of electrons instead of photons to determine molecular vibrational energy levels. More specifically, in NESS, one would exploit inelastic scattering of electrons by low-lying vibrational quantum states of molecules attached to a nanowire or nanotube.

Multiple sclerosis - etiology and diagnostic potential.

PubMed

Kamińska, Joanna; Koper, Olga M; Piechal, Kinga; Kemona, Halina

2017-06-30

Multiple sclerosis (MS) is a chronic inflammatory and demyelinating disease of autoimmune originate. The main agents responsible for the MS development include exogenous, environmental, and genetic factors. MS is characterized by multifocal and temporally scattered central nervous system (CNS) damage which lead to the axonal damage. Among clinical courses of MS it can be distinguish relapsing-remitting multiple sclerosis (RRMS), secondary progressive multiple sclerosis (SPSM), primary progressive multiple sclerosis (PPMS), and progressive-relapsing multiple sclerosis (RPMS). Depending on the severity of signs and symptoms MS can be described as benign MS or malignant MS. MS diagnosis is based on McDonald's diagnostic criteria, which link clinical manifestation with characteristic lesions demonstrated by magnetic resonance imaging (MRI), cerebrospinal fluid (CSF) analysis, and visual evoked potentials. Among CSF laboratory tests used to the MS diagnosis are applied: Tibbling & Link IgG index, reinbegrams, and CSF isoelectrofocusing for oligoclonal bands detection. It should be emphasized, that despite huge progress regarding MS as well as the availability of different diagnostics methods this disease is still a diagnostic challenge. It may result from fact that MS has diverse clinical course and there is a lack of single test, which would be of appropriate diagnostic sensitivity and specificity for quick and accurate diagnosis.

Fundamentals of angled-beam ultrasonic NDE for potential characterization of hidden regions of impact damage in composites

NASA Astrophysics Data System (ADS)

Aldrin, John C.; Wertz, John N.; Welter, John T.; Wallentine, Sarah; Lindgren, Eric A.; Kramb, Victoria; Zainey, David

2018-04-01

In this study, the use of angled-beam ultrasonic NDE was explored for the potential characterization of the hidden regions of impact damage in composites. Simulated studies using CIVA FIDEL 2D were used to explore this inspection problem. Quasi-shear (qS) modes can be generated over a wide range of angles and used to reflect off the backwall and interrogate under the top delaminations of impact damage. Secondary probe signals that do propagate normal to the surface were found to be significant under certain probe conditions, and can potentially interfere with weakly scattered signals from within the composite panel. Simulations were used to evaluate the source of the multiple paths of reflections from the edge of a delamination; time-of-flight and amplitude will depend on the depth of the delamination and location of neighboring delaminations. For angled-beam inspections, noise from both the top surface roughness and internal features was found to potentially mask the detection of signals from the edge of delaminations. Lastly, the study explored the potential of generating "guided" waves along the backwall using an angled-beam source and subsequently measuring scattered signals from a far surface crack hidden under a delamination.

Light scattering and random lasing in aqueous suspensions of hexagonal boron nitride nanoflakes

NASA Astrophysics Data System (ADS)

O'Brien, S. A.; Harvey, A.; Griffin, A.; Donnelly, T.; Mulcahy, D.; Coleman, J. N.; Donegan, J. F.; McCloskey, D.

2017-11-01

Liquid phase exfoliation allows large scale production of 2D materials in solution. The particles are highly anisotropic and strongly scatter light. While spherical particles can be accurately and precisely described by a single parameter—the radius, 2D nanoflakes, however, cannot be so easily described. We investigate light scattering in aqueous solutions of 2D hexagonal boron nitride nanoflakes in the single and multiple scattering regimes. In the single scattering regime, the anisotropic 2D materials show a much stronger depolarization of light when compared to spherical particles of similar size. In the multiple scattering regime, the scattering as a function of optical path for hexagonal boron nitride nanoflakes of a given lateral length was found to be qualitatively equivalent to scattering from spheres with the same diameter. We also report the presence of random lasing in high concentration suspensions of aqueous h-BN mixed with Rhodamine B dye. The h-BN works as a scattering agent and Rhodamine B as a gain medium for the process. We observed random lasing at 587 nm with a threshold energy of 0.8 mJ.

Light scattering and random lasing in aqueous suspensions of hexagonal boron nitride nanoflakes.

PubMed

O'Brien, S A; Harvey, A; Griffin, A; Donnelly, T; Mulcahy, D; Coleman, J N; Donegan, J F; McCloskey, D

2017-11-24

Liquid phase exfoliation allows large scale production of 2D materials in solution. The particles are highly anisotropic and strongly scatter light. While spherical particles can be accurately and precisely described by a single parameter-the radius, 2D nanoflakes, however, cannot be so easily described. We investigate light scattering in aqueous solutions of 2D hexagonal boron nitride nanoflakes in the single and multiple scattering regimes. In the single scattering regime, the anisotropic 2D materials show a much stronger depolarization of light when compared to spherical particles of similar size. In the multiple scattering regime, the scattering as a function of optical path for hexagonal boron nitride nanoflakes of a given lateral length was found to be qualitatively equivalent to scattering from spheres with the same diameter. We also report the presence of random lasing in high concentration suspensions of aqueous h-BN mixed with Rhodamine B dye. The h-BN works as a scattering agent and Rhodamine B as a gain medium for the process. We observed random lasing at 587 nm with a threshold energy of 0.8 mJ.

Acoustic Coherent Backscatter Enhancement from Aggregations of Point Scatterers

DTIC Science & Technology

2015-09-30

and far-field acoustic multiple scattering from two- and now three-dimensional aggregations of omnidirectional point scatterers to determine the...an aggregation of omnidirectional point scatterers [1]. If ψ(r) is the harmonic acoustic pressure field at frequency ω at the point r and ψ0(r) is... scattered field and is given by the sum in (1), N is the number of scatterers , gn is the scattering coefficient of the nth scatterer , ψn(rn) is the field

Interpretation of light scattering and turbidity measurements in aggregated systems: effect of intra-cluster multiple-light scattering.

PubMed

Soos, Miroslav; Lattuada, Marco; Sefcik, Jan

2009-11-12

In this work we studied the effect of intracluster multiple-light scattering on the scattering properties of a population of fractal aggregates. To do so, experimental data of diffusion-limited aggregation for three polystyrene latexes with similar surface properties but different primary particle diameters (equal to 118, 420, and 810 nm) were obtained by static light scattering and by means of a spectrophotometer. In parallel, a population balance equation (PBE) model, which takes into account the effect of intracluster multiple-light scattering by solving the T-matrix and the mean-field version of T-matrix, was formulated and validated against time evolution of the root mean radius of gyration, , of the zero angle intensity of scattered light, I(0), and of the turbidity, tau. It was found that the mean-field version of the T-matrix theory is able to correctly predict the time evolution of all measured light scattering quantities for all sizes of primary particles without any adjustable parameter. The structure of the aggregates, characterized by fractal dimension, d(f), was independent of the primary particle size and equal to 1.7, which is in agreement with values found in literature. Since the mean-field version of the T-matrix theory used is rather complicated and requires advanced knowledge of cluster structure (i.e., the particle-particle correlation function), a simplified version of the light scattering model was proposed and tested. It was found that within the range of operating conditions investigated, the simplified version of the light scattering model was able to describe with reasonable accuracy the time evolution of all measured light scattering quantities of the cluster mass distribution (CMD) for all three sizes of primary particles and two values of the laser wavelength.

Electronic structure of alloys

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

Ehrenreich, H.; Schwartz, L.M.

1976-01-01

The description of electronic properties of binary substitutional alloys within the single particle approximation is reviewed. Emphasis is placed on a didactic exposition of the equilibrium properties of the transport and magnetic properties of such alloys. Topics covered include: multiple scattering theory; the single band alloy; formal extensions of the theory; the alloy potential; realistic model state densities; the s-d model; and the muffin tin model. 43 figures, 3 tables, 151 references. (GHT)

A Case for More Multiple Scattering Lidar from Space: Analysis of Four LITE Pulses Returned from a Marine Stratocumulus Deck

NASA Technical Reports Server (NTRS)

Davis, Anthony B.; Winker, David M.

2011-01-01

Outline: (1) Signal Physics for Multiple-Scattering Cloud Lidar, (2) SNR Estimation (3) Cloud Property Retrievals (3a) several techniques (3b) application to Lidar-In-space Technology Experiment (LITE) data (3c) relation to O2 A-band

Modeling Cometary Coma with a Three Dimensional, Anisotropic Multiple Scattering Distributed Processing Code

NASA Technical Reports Server (NTRS)

Luchini, Chris B.

1997-01-01

Development of camera and instrument simulations for space exploration requires the development of scientifically accurate models of the objects to be studied. Several planned cometary missions have prompted the development of a three dimensional, multi-spectral, anisotropic multiple scattering model of cometary coma.

Atmospheric aerosols: Their Optical Properties and Effects (supplement)

NASA Technical Reports Server (NTRS)

1976-01-01

A digest of technical papers is presented. Topics include aerosol size distribution from spectral attenuation with scattering measurements; comparison of extinction and backscattering coefficients for measured and analytic stratospheric aerosol size distributions; using hybrid methods to solve problems in radiative transfer and in multiple scattering; blue moon phenomena; absorption refractive index of aerosols in the Denver pollution cloud; a two dimensional stratospheric model of the dispersion of aerosols from the Fuego volcanic eruption; the variation of the aerosol volume to light scattering coefficient; spectrophone in situ measurements of the absorption of visible light by aerosols; a reassessment of the Krakatoa volcanic turbidity, and multiple scattering in the sky radiance.

Laser Light Scattering with Multiple Scattering Suppression Used to Measure Particle Sizes

NASA Technical Reports Server (NTRS)

Meyer, William V.; Tin, Padetha; Lock, James A.; Cannell, David S.; Smart, Anthony E.; Taylor, Thomas W.

1999-01-01

Laser light scattering is the technique of choice for noninvasively sizing particles in a fluid. The members of the Advanced Technology Development (ATD) project in laser light scattering at the NASA Lewis Research Center have invented, tested, and recently enhanced a simple and elegant way to extend the concentration range of this standard laboratory particle-sizing technique by several orders of magnitude. With this technique, particles from 3 nm to 3 mm can be measured in a solution. Recently, laser light scattering evolved to successfully size particles in both clear solutions and concentrated milky-white solutions. The enhanced technique uses the property of light that causes it to form tall interference patterns at right angles to the scattering plane (perpendicular to the laser beam) when it is scattered from a narrow laser beam. Such multiple-scattered light forms a broad fuzzy halo around the focused beam, which, in turn, forms short interference patterns. By placing two fiber optics on top of each other and perpendicular to the laser beam (see the drawing), and then cross-correlating the signals they produce, only the tall interference patterns formed by singly scattered light are detected. To restate this, unless the two fiber optics see the same interference pattern, the scattered light is not incorporated into the signal. With this technique, only singly scattered light is seen (multiple-scattered light is rejected) because only singly scattered light has an interference pattern tall enough to span both of the fiber-optic pickups. This technique is simple to use, easy to align, and works at any angle. Placing a vertical slit in front of the signal collection fibers enhanced this approach. The slit serves as an optical mask, and it significantly shortens the time needed to collect good data by selectively masking out much of the unwanted light before cross-correlation is applied.

Tropospheric haze and colors of the clear twilight sky.

PubMed

Lee, Raymond L; Mollner, Duncan C

2017-07-01

At the earth's surface, clear-sky colors during civil twilights depend on the combined spectral effects of molecular scattering, extinction by tropospheric aerosols, and absorption by ozone. Molecular scattering alone cannot produce the most vivid twilight colors near the solar horizon, for which aerosol scattering and absorption are also required. However, less well known are haze aerosols' effects on twilight sky colors at larger scattering angles, including near the antisolar horizon. To analyze this range of colors, we compare 3D Monte Carlo simulations of skylight spectra with hyperspectral measurements of clear twilight skies over a wide range of aerosol optical depths. Our combined measurements and simulations indicate that (a) the purest antisolar twilight colors would occur in a purely molecular, multiple-scattering atmosphere, whereas (b) the most vivid solar-sky colors require at least some turbidity. Taken together, these results suggest that multiple scattering plays an important role in determining the redness of the antitwilight arch.

Inverse atmospheric radiative transfer problems - A nonlinear minimization search method of solution. [aerosol pollution monitoring

NASA Technical Reports Server (NTRS)

Fymat, A. L.

1976-01-01

The paper studies the inversion of the radiative transfer equation describing the interaction of electromagnetic radiation with atmospheric aerosols. The interaction can be considered as the propagation in the aerosol medium of two light beams: the direct beam in the line-of-sight attenuated by absorption and scattering, and the diffuse beam arising from scattering into the viewing direction, which propagates more or less in random fashion. The latter beam has single scattering and multiple scattering contributions. In the former case and for single scattering, the problem is reducible to first-kind Fredholm equations, while for multiple scattering it is necessary to invert partial integrodifferential equations. A nonlinear minimization search method, applicable to the solution of both types of problems has been developed, and is applied here to the problem of monitoring aerosol pollution, namely the complex refractive index and size distribution of aerosol particles.

Low-energy Auger electron diffraction: influence of multiple scattering and angular momentum

NASA Astrophysics Data System (ADS)

Chassé, A.; Niebergall, L.; Kucherenko, Yu.

2002-04-01

The angular dependence of Auger electrons excited from single-crystal surfaces is treated theoretically within a multiple-scattering cluster model taking into account the full Auger transition matrix elements. In particular the model has been used to discuss the influence of multiple scattering and angular momentum of the Auger electron wave on Auger electron diffraction (AED) patterns in the region of low kinetic energies. Theoretical results of AED patterns are shown and discussed in detail for Cu(0 0 1) and Ni(0 0 1) surfaces, respectively. Even though Cu and Ni are very similar in their electronic and scattering properties recently strong differences have been found in AED patterns measured in the low-energy region. It is shown that the differences may be caused to superposition of different electron diffraction effects in an energy-integrated experiment. A good agreement between available experimental and theoretical results has been achieved.

Auger electron diffraction in thin CoO films on Au(1 1 1)

NASA Astrophysics Data System (ADS)

Chassé, A.; Niebergall, L.; Heiler, M.; Neddermeyer, H.; Schindler, K.-M.

The local structure of thin CoO films grown on a single crystal Au(1 1 1) surface has been studied by Auger electron diffraction (AED). Therefore, the angular dependence of the Auger electron intensity of Co-LMM and O-KLL Auger electrons was recorded in the total half-space above the film. Such 2 π-scans immediately reflect the symmetry of the surface and the local structure of the film. The experimental data are compared to multiple-scattering cluster calculations, where both the influence of multiple-scattering effects and effects of Auger transition matrix elements have been investigated. We have found that the AED patterns of a CoO film in forward-scattering conditions do not always provide straightforward information on the local structure of the film, whereas the multiple-scattering approximation applied gives very good agreement between experimental and theoretical results.

Scattering from phase-separated vesicles. I. An analytical form factor for multiple static domains

DOE PAGES

Heberle, Frederick A.; Anghel, Vinicius N. P.; Katsaras, John

2015-08-18

This is the first in a series of studies considering elastic scattering from laterally heterogeneous lipid vesicles containing multiple domains. Unique among biophysical tools, small-angle neutron scattering can in principle give detailed information about the size, shape and spatial arrangement of domains. A general theory for scattering from laterally heterogeneous vesicles is presented, and the analytical form factor for static domains with arbitrary spatial configuration is derived, including a simplification for uniformly sized round domains. The validity of the model, including series truncation effects, is assessed by comparison with simulated data obtained from a Monte Carlo method. Several aspects ofmore » the analytical solution for scattering intensity are discussed in the context of small-angle neutron scattering data, including the effect of varying domain size and number, as well as solvent contrast. Finally, the analysis indicates that effects of domain formation are most pronounced when the vesicle's average scattering length density matches that of the surrounding solvent.« less

The influence of current neutralization and multiple Coulomb scattering on the spatial dynamics of resistive sausage instability of a relativistic electron beam propagating in ohmic plasma

NASA Astrophysics Data System (ADS)

Kolesnikov, E. K.; Manuilov, A. S.; Petrov, V. S.; Klyushnikov, G. N.; Chernov, S. V.

2017-06-01

The influence of the current neutralization process, the phase mixing of the trajectories of electrons and multiple Coulomb scattering of electrons beam on the atoms of the background medium on the spatial increment of the growth of sausage instability of a relativistic electron beam propagating in ohmic plasma channel has been considered. It has been shown that the amplification of the current neutralization leads to a significant increase in this instability, and phase mixing and the process of multiple scattering of electrons beam on the atoms of the background medium are the stabilizing factor.

Effects of mixing states on the multiple-scattering properties of soot aerosols.

PubMed

Cheng, Tianhai; Wu, Yu; Gu, Xingfa; Chen, Hao

2015-04-20

The radiative properties of soot aerosols are highly sensitive to the mixing states of black carbon particles and other aerosol components. Light absorption properties are enhanced by the mixing state of soot aerosols. Quantification of the effects of mixing states on the scattering properties of soot aerosol are still not completely resolved, especially for multiple-scattering properties. This study focuses on the effects of the mixing state on the multiple scattering of soot aerosols using the vector radiative transfer model. Two types of soot aerosols with different mixing states such as external mixture soot aerosols and internal mixture soot aerosols are studied. Upward radiance/polarization and hemispheric flux are studied with variable soot aerosol loadings for clear and haze scenarios. Our study showed dramatic changes in upward radiance/polarization due to the effects of the mixing state on the multiple scattering of soot aerosols. The relative difference in upward radiance due to the different mixing states can reach 16%, whereas the relative difference of upward polarization can reach 200%. The effects of the mixing state on the multiple-scattering properties of soot aerosols increase with increasing soot aerosol loading. The effects of the soot aerosol mixing state on upwelling hemispheric flux are much smaller than in upward radiance/polarization, which increase with increasing solar zenith angle. The relative difference in upwelling hemispheric flux due to the different soot aerosol mixing states can reach 18% when the solar zenith angle is 75°. The findings should improve our understanding of the effects of mixing states on the optical properties of soot aerosols and their effects on climate. The mixing mechanism of soot aerosols is of critical importance in evaluating the climate effects of soot aerosols, which should be explicitly included in radiative forcing models and aerosol remote sensing.

Stand-alone scattering optical device using holographic photopolymer (Conference Presentation)

NASA Astrophysics Data System (ADS)

Park, Jongchan; Lee, KyeoReh; Park, YongKeun

2016-03-01

When a light propagates through highly disordered medium, its optical parameters such as amplitude, phase and polarization states are completely scrambled because of multiple scattering events. Since the multiple scattering is a fundamental optical process that contains extremely high degrees of freedom, optical information of a transmitted light is totally mingled. Until recently, the presence of multiple scattering in an inhomogeneous medium is considered as a major obstacle when manipulating a light transmitting through the medium. However, a recent development of wavefront shaping techniques enable us to control the propagation of light through turbid media; a light transmitting through a turbid medium can be effectively controlled by modulating the spatial profile of the incident light using spatial light modulator. In this work, stand-alone scattering optical device is proposed; a holographic photopolymer film, which is much economic compared to the other digital spatial light modulators, is used to record and reconstruct permanent wavefront to generate optical field behind a scattering medium. By employing our method, arbitrary optical field can be generated since the scattering medium completely mixes all the optical parameters which allow us to access all the optical information only by modulating spatial phase profile of the impinging wavefront. The method is experimentally demonstrated in both the far-field and near-field regime where it shows promising fidelity and stability. The proposed stand-alone scattering optical device will opens up new avenues for exploiting the randomness inherent in disordered medium.

High Spectral Resolution Lidar Measurements of Multiple Scattering

NASA Technical Reports Server (NTRS)

Eloranta, E. W.; Piironen, P.

1996-01-01

The University of Wisconsin High Spectral Resolution Lidar (HSRL) provides unambiguous measurements of backscatter cross section, backscatter phase function, depolarization, and optical depth. This is accomplished by dividing the lidar return into separate particulate and molecular contributions. The molecular return is then used as a calibration target. We have modified the HSRL to use an I2 molecular absorption filter to separate aerosol and molecular signals. This allows measurement in dense clouds. Useful profiles extend above the cloud base until the two way optical depth reaches values between 5 and 6; beyond this, photon counting errors become large. In order to observe multiple scattering, the HSRL includes a channel which records the combined aerosol and molecular lidar return simultaneously with the spectrometer channel measurements of optical properties. This paper describes HSRL multiple scattering measurements from both water and ice clouds. These include signal strengths and depolarizations as a function of receiver field of view. All observations include profiles of extinction and backscatter cross sections. Measurements are also compared to predictions of a multiple scattering model based on small angle approximations.

Second order nonlinear QED processes in ultra-strong laser fields

NASA Astrophysics Data System (ADS)

Mackenroth, Felix

2017-10-01

In the interaction of ultra-intense laser fields with matter the ever increasing peak laser intensities render nonlinear QED effects ever more important. For long, ultra-intense laser pulses scattering large systems, like a macroscopic plasma, the interaction time can be longer than the scattering time, leading to multiple scatterings. These are usually approximated as incoherent cascades of single-vertex processes. Under certain conditions, however, this common cascade approximation may be insufficient, as it disregards several effects such as coherent processes, quantum interferences or pulse shape effects. Quantifying deviations of the full amplitude of multiple scatterings from the commonly employed cascade approximations is a formidable, yet unaccomplished task. In this talk we are going to discuss how to compute second order nonlinear QED amplitudes and relate them to the conventional cascade approximation. We present examples for typical second order processes and benchmark the full result against common approximations. We demonstrate that the approximation of multiple nonlinear QED scatterings as a cascade of single interactions has certain limitations and discuss these limits in light of upcoming experimental tests.

Coherent backscattering of light by complex random media of spherical scatterers: numerical solution

NASA Astrophysics Data System (ADS)

Muinonen, Karri

2004-07-01

Novel Monte Carlo techniques are described for the computation of reflection coefficient matrices for multiple scattering of light in plane-parallel random media of spherical scatterers. The present multiple scattering theory is composed of coherent backscattering and radiative transfer. In the radiative transfer part, the Stokes parameters of light escaping from the medium are updated at each scattering process in predefined angles of emergence. The scattering directions at each process are randomized using probability densities for the polar and azimuthal scattering angles: the former angle is generated using the single-scattering phase function, whereafter the latter follows from Kepler's equation. For spherical scatterers in the Rayleigh regime, randomization proceeds semi-analytically whereas, beyond that regime, cubic spline presentation of the scattering matrix is used for numerical computations. In the coherent backscattering part, the reciprocity of electromagnetic waves in the backscattering direction allows the renormalization of the reversely propagating waves, whereafter the scattering characteristics are computed in other directions. High orders of scattering (~10 000) can be treated because of the peculiar polarization characteristics of the reverse wave: after a number of scatterings, the polarization state of the reverse wave becomes independent of that of the incident wave, that is, it becomes fully dictated by the scatterings at the end of the reverse path. The coherent backscattering part depends on the single-scattering albedo in a non-monotonous way, the most pronounced signatures showing up for absorbing scatterers. The numerical results compare favourably to the literature results for nonabsorbing spherical scatterers both in and beyond the Rayleigh regime.

Predicting X-ray diffuse scattering from translation–libration–screw structural ensembles

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

Van Benschoten, Andrew H.; Afonine, Pavel V.; Terwilliger, Thomas C.

2015-07-28

A method of simulating X-ray diffuse scattering from multi-model PDB files is presented. Despite similar agreement with Bragg data, different translation–libration–screw refinement strategies produce unique diffuse intensity patterns. Identifying the intramolecular motions of proteins and nucleic acids is a major challenge in macromolecular X-ray crystallography. Because Bragg diffraction describes the average positional distribution of crystalline atoms with imperfect precision, the resulting electron density can be compatible with multiple models of motion. Diffuse X-ray scattering can reduce this degeneracy by reporting on correlated atomic displacements. Although recent technological advances are increasing the potential to accurately measure diffuse scattering, computational modeling andmore » validation tools are still needed to quantify the agreement between experimental data and different parameterizations of crystalline disorder. A new tool, phenix.diffuse, addresses this need by employing Guinier’s equation to calculate diffuse scattering from Protein Data Bank (PDB)-formatted structural ensembles. As an example case, phenix.diffuse is applied to translation–libration–screw (TLS) refinement, which models rigid-body displacement for segments of the macromolecule. To enable the calculation of diffuse scattering from TLS-refined structures, phenix.tls-as-xyz builds multi-model PDB files that sample the underlying T, L and S tensors. In the glycerophosphodiesterase GpdQ, alternative TLS-group partitioning and different motional correlations between groups yield markedly dissimilar diffuse scattering maps with distinct implications for molecular mechanism and allostery. These methods demonstrate how, in principle, X-ray diffuse scattering could extend macromolecular structural refinement, validation and analysis.« less

Experimental observation of multiphoton Thomson scattering

NASA Astrophysics Data System (ADS)

Yan, Wenchao; Golovin, Grigory; Fruhling, Colton; Haden, Daniel; Zhang, Ping; Zhang, Jun; Zhao, Baozhen; Liu, Cheng; Chen, Shouyuan; Banerjee, Sudeep; Umstadter, Donald

2016-10-01

With the advent of high-power lasers, several multiphoton processes have been reported involving electrons in strong fields. For electrons that were initially bound to atoms, both multiphoton ionization and scattering have been reported. However, for free electrons, only low-order harmonic generation has been observed until now. This limitation stems from past difficulty in achieving the required ultra-high-field strengths in scattering experiments. Highly relativistic laser intensities are required to reach the multiphoton regime of Thomson scattering, and generate high harmonics from free electrons. The scaling parameter is the normalized vector potential (a0). Previous experiments have observed phenomena in the weakly relativistic case (a0 >> 1). In ultra-intense fields (a0 >>1), the anomalous electron trajectory is predicted to produce a spectrum characterized by the merging of multiple high-order harmonic generation into a continuum. This may be viewed as the multiphoton Thomson scattering regime analogous to the wiggler of a synchrotron. Thus, the light produced reflects the electrons behavior in an ultra-intense lase field. We discuss the first experiments in the highly relativistic case (a0 15). This material is based upon work supported by NSF No. PHY-153700; US DOE, Office of Science, BES, # DE-FG02-05ER15663; AFOSR # FA9550-11-1-0157; and DHS DNDO # HSHQDC-13-C-B0036.

An explicit canopy BRDF model and inversion. [Bidirectional Reflectance Distribution Function

NASA Technical Reports Server (NTRS)

Liang, Shunlin; Strahler, Alan H.

1992-01-01

Based on a rigorous canopy radiative transfer equation, the multiple scattering radiance is approximated by the asymptotic theory, and the single scattering radiance calculation, which requires an numerical intergration due to considering the hotspot effect, is simplified. A new formulation is presented to obtain more exact angular dependence of the sky radiance distribution. The unscattered solar radiance and single scattering radiance are calculated exactly, and the multiple scattering is approximated by the delta two-stream atmospheric radiative transfer model. The numerical algorithms prove that the parametric canopy model is very accurate, especially when the viewing angles are smaller than 55 deg. The Powell algorithm is used to retrieve biospheric parameters from the ground measured multiangle observations.

Advanced Thomson scattering system for high-flux linear plasma generator

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

Meiden, H. J. van der; Lof, A. R.; Berg, M. A. van den

2012-12-15

An advanced Thomson scattering system has been built for a linear plasma generator for plasma surface interaction studies. The Thomson scattering system is based on a Nd:YAG laser operating at the second harmonic and a detection branch featuring a high etendue (f /3) transmission grating spectrometer equipped with an intensified charged coupled device camera. The system is able to measure electron density (n{sub e}) and temperature (T{sub e}) profiles close to the output of the plasma source and, at a distance of 1.25 m, just in front of a target. The detection system enables to measure 50 spatial channels ofmore » about 2 mm each, along a laser chord of 95 mm. By summing a total of 30 laser pulses (0.6 J, 10 Hz), an observational error of 3% in n{sub e} and 6% in T{sub e} (at n{sub e}= 9.4 Multiplication-Sign 10{sup 18} m{sup -3}) can be obtained. Single pulse Thomson scattering measurements can be performed with the same accuracy for n{sub e} > 2.8 Multiplication-Sign 10{sup 20} m{sup -3}. The minimum measurable density and temperature are n{sub e} < 1 Multiplication-Sign 10{sup 17} m{sup -3} and T{sub e} < 0.07 eV, respectively. In addition, using the Rayleigh peak, superimposed on the Thomson scattered spectrum, the neutral density (n{sub 0}) of the plasma can be measured with an accuracy of 25% (at n{sub 0}= 1 Multiplication-Sign 10{sup 20} m{sup -3}). In this report, the performance of the Thomson scattering system will be shown along with unprecedented accurate Thomson-Rayleigh scattering measurements on a low-temperature argon plasma expansion into a low-pressure background.« less

Retrieval of Droplet size Density Distribution from Multiple field of view Cross polarized Lidar Signals: Theory and Experimental Validation

DTIC Science & Technology

2016-06-02

Retrieval of droplet-size density distribution from multiple-field-of-view cross-polarized lidar signals: theory and experimental validation...theoretical and experimental studies of mul- tiple scattering and multiple-field-of-view (MFOV) li- dar detection have made possible the retrieval of cloud...droplet cloud are typical of Rayleigh scattering, with a signature close to a dipole (phase function quasi -flat and a zero-depolarization ratio

A Two-Dimensional Helmholtz Equation Solution for the Multiple Cavity Scattering Problem

DTIC Science & Technology

2013-02-01

obtained by using the block Gauss – Seidel iterative meth- od. To show the convergence of the iterative method, we define the error between two...models to the general multiple cavity setting. Numerical examples indicate that the convergence of the Gauss – Seidel iterative method depends on the...variational approach. A block Gauss – Seidel iterative method is introduced to solve the cou- pled system of the multiple cavity scattering problem, where

The Statistical Sobolev-Rosseland Mean and the Effects of Frequency Redistribution on Wolf-Rayet Wind Driving

NASA Astrophysics Data System (ADS)

Onifer, A. J.; Gayley, K. G.

2003-06-01

The optically thick character of Wolf-Rayet winds implies that stellar continuum photons are multiply scattered, as a result of both free electron opacity and overlapping wind-broadened spectral lines. This allows the wind to accumulate a substantial excess in momentum flux relative to the driving radiation field, as is observationally required. Nevertheless, sustaining such a high degree of multiple scattering requires not only a large optical depth spatially but also substantial spectral blanketing. The latter is difficult to maintain when redistribution during scattering allows radiative flux to shift preferentially into spectral regions with fewer lines, since then the channels carrying much of the flux are also the least well blanketed. This paper parameterizes the potential severity of this effect in simple terms, using a generalization of the Rosseland mean treated in the Sobolev approximation. We show that our approach provides an informative starting point for characterizing and conceptualizing nongray effects in optically thick supersonic flows.

The observed properties of Fast Radio Bursts

NASA Astrophysics Data System (ADS)

Ravi, Vikram

2018-06-01

I present an empirical study of the properties of fast radio bursts (FRBs): Gigahertz-frequency, dispersed pulses of extragalactic origin. I focus my investigation on a sample of seventeen FRBs detected at the Parkes radio telescope with largely self-consistent instrumentation. Of this sample, six are temporally unresolved, eight exhibit evidence for scattering in inhomogeneous plasma, and five display potentially intrinsic temporal structure. The characteristic scattering timescales at a frequency of 1 GHz range between 0.005 ms and 32 ms; moderate evidence exists for a relation between FRB scattering timescales and dispersion measures. Additionally, I present constraints on the fluences of Parkes FRBs, accounting for their uncertain sky-positions, and use the multiple-beam detection of FRB 010724 (the Lorimer burst) to measure its fluence to be 800 ± 400 Jy ms. FRBs, including the repeating FRB 121102, appear to manifest with a plethora of characteristics, and it is uncertain at present whether they share a common class of progenitor object, or arise from a selection of independent progenitors.

Multiple-scattering coefficients and absorption controlled diffusive processes

NASA Astrophysics Data System (ADS)

Godoy, Salvador; García-Colín, L. S.; Micenmacher, Victor

1999-11-01

Multiple-scattering transmission and reflection coefficients (T,R) are introduced in addition to the diffusion coefficient D for the description of ballistic diffusion in the presence of absorption. For 1D (one-dimensional) systems, the measurement of only one between T and D imposes restrictions on the possible values of the other. If D is measured, then T is bounded between the Landauer and Lambert-Beer equations. Measurements of both (T,D) imply the theoretical knowledge of the microscopic absorption Σa and scattering rΣs cross sections.

Multiple Light Scattering Probes of Soft Materials

NASA Astrophysics Data System (ADS)

Scheffold, Frank

2007-02-01

I will discuss both static and dynamic properties of diffuse waves. In practical applications the optical properties of colloidal systems play an important role, for example in commercial products such as sunscreen lotions, food (drinks), coatings but also in medicine for example in cataract formation (eye lens turbidity). It is thus of importance to know the key parameters governing optical turbidity from the single to the multiple scattering regime. Temporal fluctuations of multiply scattered light are studied with photon correlation spectroscopy (Diffusing Wave Spectroscopy). This DWS method and its various implementations will be treated.

Relativistic scattered wave calculations on UF6

NASA Technical Reports Server (NTRS)

Case, D. A.; Yang, C. Y.

1980-01-01

Self-consistent Dirac-Slater multiple scattering calculations are presented for UF6. The results are compared critically to other relativistic calculations, showing that the results of all molecular orbital calculations are in qualitative agreement, as measured by energy levels, population analyses, and spin-orbit splittings. A detailed comparison is made to the relativistic X alpha(RX alpha) method of Wood and Boring, which also uses multiple scattering theory, but incorporates relativistic effects in a more approximate fashion. For the most part, the RX alpha results are in agreement with the present results.

Determination of effective atomic number of biomedical samples using Gamma ray back-scattering

NASA Astrophysics Data System (ADS)

Singh, Inderjeet; Singh, Bhajan; Sandhu, B. S.; Sabharwal, Arvind D.

2018-05-01

The study of effective atomic number of biomedical sample has been carried out by using a non-destructive multiple back-scattering technique. Also radiation characterization method is used to compare the tissue equivalent material as human tissue. Response function of 3″ × 3″ NaI(Tl) scintillation detector is implemented on recorded pulse-height distribution to boost the counts under the photo-peak and help to reduce the uncertainty in the experimental result. Monte Carlo calculation for multiple back-scattered events supports the reported experimental work.

Monte Carlo calculation of large and small-angle electron scattering in air

NASA Astrophysics Data System (ADS)

Cohen, B. I.; Higginson, D. P.; Eng, C. D.; Farmer, W. A.; Friedman, A.; Grote, D. P.; Larson, D. J.

2017-11-01

A Monte Carlo method for angle scattering of electrons in air that accommodates the small-angle multiple scattering and larger-angle single scattering limits is introduced. The algorithm is designed for use in a particle-in-cell simulation of electron transport and electromagnetic wave effects in air. The method is illustrated in example calculations.

Active probing of cloud multiple scattering, optical depth, vertical thickness, and liquid water content using wide-angle imaging lidar

NASA Astrophysics Data System (ADS)

Love, Steven P.; Davis, Anthony B.; Rohde, Charles A.; Tellier, Larry; Ho, Cheng

2002-09-01

At most optical wavelengths, laser light in a cloud lidar experiment is not absorbed but merely scattered out of the beam, eventually escaping the cloud via multiple scattering. There is much information available in this light scattered far from the input beam, information ignored by traditional 'on-beam' lidar. Monitoring these off-beam returns in a fully space- and time-resolved manner is the essence of our unique instrument, Wide Angle Imaging Lidar (WAIL). In effect, WAIL produces wide-field (60-degree full-angle) 'movies' of the scattering process and records the cloud's radiative Green functions. A direct data product of WAIL is the distribution of photon path lengths resulting from multiple scattering in the cloud. Following insights from diffusion theory, we can use the measured Green functions to infer the physical thickness and optical depth of the cloud layer, and, from there, estimate the volume-averaged liquid water content. WAIL is notable in that it is applicable to optically thick clouds, a regime in which traditional lidar is reduced to ceilometry. Here we present recent WAIL data on various clouds and discuss the extension of WAIL to full diurnal monitoring by means of an ultra-narrow magneto-optic atomic line filter for daytime measurements.

Diffuse optical microscopy for quantification of depth-dependent epithelial backscattering in the cervix

NASA Astrophysics Data System (ADS)

Bodenschatz, Nico; Lam, Sylvia; Carraro, Anita; Korbelik, Jagoda; Miller, Dianne M.; McAlpine, Jessica N.; Lee, Marette; Kienle, Alwin; MacAulay, Calum

2016-06-01

A fiber optic imaging approach is presented using structured illumination for quantification of almost pure epithelial backscattering. We employ multiple spatially modulated projection patterns and camera-based reflectance capture to image depth-dependent epithelial scattering. The potential diagnostic value of our approach is investigated on cervical ex vivo tissue specimens. Our study indicates a strong backscattering increase in the upper part of the cervical epithelium caused by dysplastic microstructural changes. Quantization of relative depth-dependent backscattering is confirmed as a potentially useful diagnostic feature for detection of precancerous lesions in cervical squamous epithelium.

MODTRAN cloud and multiple scattering upgrades with application to AVIRIS

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

Berk, A.; Bernstein, L.S.; Acharya, P.K.

1998-09-01

Recent upgrades to the MODTRAN atmospheric radiation code improve the accuracy of its radiance predictions, especially in the presence of clouds and thick aerosols, and for multiple scattering in regions of strong molecular line absorption. The current public-released version of MODTRAN (MODTRAN3.7) features a generalized specification of cloud properties, while the current research version of MODTRAN (MODTRAN4) implements a correlated-k (CK) approach for more accurate calculation of multiple scattered radiance. Comparisons to cloud measurements demonstrate the viability of the CK approach. The impact of these upgrades on predictions for AVIRIS viewing scenarios is discussed for both clear and clouded skies;more » the CK approach provides refined predictions for AVIRIS nadir and near-nadir viewing.« less

Coupling of Multiple Coulomb Scattering with Energy Loss and Straggling in HZETRN

NASA Technical Reports Server (NTRS)

Mertens, Christopher J.; Wilson, John W.; Walker, Steven A.; Tweed, John

2007-01-01

The new version of the HZETRN deterministic transport code based on Green's function methods, and the incorporation of ground-based laboratory boundary conditions, has lead to the development of analytical and numerical procedures to include off-axis dispersion of primary ion beams due to small-angle multiple Coulomb scattering. In this paper we present the theoretical formulation and computational procedures to compute ion beam broadening and a methodology towards achieving a self-consistent approach to coupling multiple scattering interactions with ionization energy loss and straggling. Our initial benchmark case is a 60 MeV proton beam on muscle tissue, for which we can compare various attributes of beam broadening with Monte Carlo simulations reported in the open literature.

Piezoelectric T-matrix approach and multiple scattering of electroacoustic waves in thin plates

NASA Astrophysics Data System (ADS)

Darabi, Amir; Ruzzene, Massimo; Leamy, Michael J.

2017-12-01

Metamaterial-enhanced harvesting (MEH) of wave energy in thin plates and other structures has appeared recently for powering small sensors and devices. To support continued MEH concept development, this paper proposes a fully coupled T-matrix formulation for analyzing scattering of incident wave energy from a piezoelectric patch attached to a thin plate. More generally, the T-matrix represents an input-output relationship between incident and reflected waves from inclusions in a host layer, and is introduced herein for a piezoelectric patch connected to an external circuit. The utility of a T-matrix formalism is most apparent in scenarios employing multiple piezoelectric harvesters, where it can be re-used with other T-matrices (such as those previously formulated for rigid, void, and elastic inclusions) in a multiple scattering context to compute the total wavefield and other response quantities, such as harvested power. Following development of the requisite T-matrix, harvesting in an example funnel-shaped metamaterial waveguide structure is predicted using the multiple scattering approach. Enhanced wave energy harvesting predictions are verified through comparisons to experimental results of a funnel-shaped waveguide formed by placing rigid aluminum inclusions in, and multiple piezoelectric harvesters on, a Lexan plate. Good agreement with predicted response quantities is noted.

Electron-phonon interactions in semiconductor nanostructures

NASA Astrophysics Data System (ADS)

Yu, Segi

In this dissertation, electron-phonon interactions are studied theoretically in semiconductor nanoscale heterostructures. Interactions of electrons with interface optical phonons dominate over other electron-phonon interactions in narrow width heterostructures. Hence, a transfer matrix method is used to establish a formalism for determining the dispersion relations and electrostatic potentials of the interface phonons for multiple-interface heterostructure within the macroscopic dielectric continuum model. This method facilitates systematic calculations for complex structures where the conventional method is difficult to implement. Several specific cases are treated to illustrate advantages of the formalism. Electrophonon resonance (EPR) is studied in cylindrical quantum wires using the confined/interface optical phonons representation and bulk phonon representation. It has been found that interface phonon contribution to EPR is small compared with confined phonon. Different selection rules for bulk phonons and confined phonons result in different EPR behaviors as the radius of cylindrical wire changes. Experiment is suggested to test which phonon representation is appropriate for EPR. The effects of phonon confinement on elect ron-acoustic-phonon scattering is studied in cylindrical and rectangular quantum wires. In the macroscopic elastic continuum model, the confined-phonon dispersion relations are obtained for several crystallographic directions with free-surface and clamped-surface boundary conditions in cylindrical wires. The scattering rates due to the deformation potential are obtained for these confined phonons and are compared with those of bulk-like phonons. The results show that the inclusion of acoustic phonon confinement may be crucial for calculating accurate low-energy electron scattering rates. Furthermore, it has been found that there is a scaling rule governing the directional dependence of the scattering rates. The Hamiltonian describing the deformation-potential of confined acoustic phonons is derived by quantizing the appropriate, experimentally verified approximate compressional acoustic-phonon modes in a free-standing rectangular quantum wire. The scattering rate is obtained for GaAs quantum wires with a range of cross-sectional dimensions. The results demonstrate that a proper treatment of confined acoustic phonons may be essential to correctly model electron scattering rates at low energies in nanoscale structures.

Electronic confining effects in Sierpiński triangle fractals

NASA Astrophysics Data System (ADS)

Wang, Hao; Zhang, Xue; Jiang, Zhuoling; Wang, Yongfeng; Hou, Shimin

2018-03-01

Electron confinement in fractal Sierpiński triangles (STs) on Ag(111) is investigated using scanning tunneling spectroscopy and theoretically simulated by employing an improved two-dimensional (2D) multiple scattering theory in which the energy-dependent phase shifts are explicitly calculated from the electrostatic potentials of the molecular building block of STs. Well-defined bound surface states are observed in three kinds of triangular cavities with their sides changing at a scale factor of 2. The decrease in length of the cavities results in an upshift of the resonances that deviates from an expected inverse quadratic dependence on the cavity length due to the less efficient confinement of smaller triangular cavities. Differential conductance maps at some specific biases present a series of alternative bright and dark rounded triangles preserving the symmetry of the boundary. Our improved 2D multiple scattering model reproduces the characteristics of the standing wave patterns and all features in the differential conductance spectra measured in experiments, illustrating that the elastic loss boundary scattering dominates the resonance broadening in these ST quantum corrals. Moreover, the self-similar structure of STs, that a larger central cavity is surrounded by three smaller ones with a half side length, gives rise to interactions of surface states confined in neighboring cavities, which are helpful for the suppression of the linewidth in differential conductance spectra.

A comparative study of Conroy and Monte Carlo methods applied to multiple quadratures and multiple scattering

NASA Technical Reports Server (NTRS)

Deepak, A.; Fluellen, A.

1978-01-01

An efficient numerical method of multiple quadratures, the Conroy method, is applied to the problem of computing multiple scattering contributions in the radiative transfer through realistic planetary atmospheres. A brief error analysis of the method is given and comparisons are drawn with the more familiar Monte Carlo method. Both methods are stochastic problem-solving models of a physical or mathematical process and utilize the sampling scheme for points distributed over a definite region. In the Monte Carlo scheme the sample points are distributed randomly over the integration region. In the Conroy method, the sample points are distributed systematically, such that the point distribution forms a unique, closed, symmetrical pattern which effectively fills the region of the multidimensional integration. The methods are illustrated by two simple examples: one, of multidimensional integration involving two independent variables, and the other, of computing the second order scattering contribution to the sky radiance.

Band structures in a two-dimensional phononic crystal with rotational multiple scatterers

NASA Astrophysics Data System (ADS)

Song, Ailing; Wang, Xiaopeng; Chen, Tianning; Wan, Lele

2017-03-01

In this paper, the acoustic wave propagation in a two-dimensional phononic crystal composed of rotational multiple scatterers is investigated. The dispersion relationships, the transmission spectra and the acoustic modes are calculated by using finite element method. In contrast to the system composed of square tubes, there exist a low-frequency resonant bandgap and two wide Bragg bandgaps in the proposed structure, and the transmission spectra coincide with band structures. Specially, the first bandgap is based on locally resonant mechanism, and the simulation results agree well with the results of electrical circuit analogy. Additionally, increasing the rotation angle can remarkably influence the band structures due to the transfer of sound pressure between the internal and external cavities in low-order modes, and the redistribution of sound pressure in high-order modes. Wider bandgaps are obtained in arrays composed of finite unit cells with different rotation angles. The analysis results provide a good reference for tuning and obtaining wide bandgaps, and hence exploring the potential applications of the proposed phononic crystal in low-frequency noise insulation.

Lectures on the scattering of light. [by dielectric sphere

NASA Technical Reports Server (NTRS)

Saxon, D. S.

1974-01-01

The exact (Mie) theory for the scattering of a plane wave by a dielectric sphere is presented. Since this infinite series solution is computationally impractical for large spheres, another formulation is given in terms of an integral equation valid for a bounded, but otherwise general array of scatterers. This equation is applied to the scattering by a single sphere, and several methods are suggested for approximating the scattering cross section in closed form. A tensor scattering matrix is introduced, in terms of which some general scattering theorems are derived. The application of the formalism to multiple scattering is briefly considered.

Modeling of the competition of stimulated Raman and Brillouin scatter in multiple beam experiments

NASA Astrophysics Data System (ADS)

Cohen, Bruce I.; Baldis, Hector A.; Berger, Richard L.; Estabrook, Kent G.; Williams, Edward A.; Labaune, Christine

2001-02-01

Multiple laser beam experiments with plastic target foils at the Laboratoire pour L'Utilisation des Lasers Intenses (LULI) facility [Baldis et al., Phys. Rev. Lett. 77, 2957 (1996)] demonstrated anticorrelation of stimulated Brillouin and Raman backscatter (SBS and SRS). Detailed Thomson scattering diagnostics showed that SBS always precedes SRS, that secondary electron plasma waves sometimes accompanied SRS appropriate to the Langmuir Decay Instability (LDI), and that, with multiple interaction laser beams, the SBS direct backscatter signal in the primary laser beam was reduced while the SRS backscatter signal was enhanced and occurred earlier in time. Analysis and numerical calculations are presented here that evaluate the influences on the competition of SBS and SRS, of local pump depletion in laser hot spots due to SBS, of mode coupling of SBS and LDI ion waves, and of optical mixing of secondary and primary laser beams. These influences can be significant. The calculations take into account simple models of the laser beam hot-spot intensity probability distributions and assess whether ponderomotive and thermal self-focusing are significant. Within the limits of the model, which omits several other potentially important nonlinearities, the calculations suggest the effectiveness of local pump depletion, ion wave mode coupling, and optical mixing in affecting the LULI observations.

Multiple Scattering Principal Component-based Radiative Transfer Model (PCRTM) from Far IR to UV-Vis

NASA Astrophysics Data System (ADS)

Liu, X.; Wu, W.; Yang, Q.

2017-12-01

Modern satellite hyperspectral satellite remote sensors such as AIRS, CrIS, IASI, CLARREO all require accurate and fast radiative transfer models that can deal with multiple scattering of clouds and aerosols to explore the information contents. However, performing full radiative transfer calculations using multiple stream methods such as discrete ordinate (DISORT), doubling and adding (AD), successive order of scattering order of scattering (SOS) are very time consuming. We have developed a principal component-based radiative transfer model (PCRTM) to reduce the computational burden by orders of magnitudes while maintain high accuracy. By exploring spectral correlations, the PCRTM reduce the number of radiative transfer calculations in frequency domain. It further uses a hybrid stream method to decrease the number of calls to the computational expensive multiple scattering calculations with high stream numbers. Other fast parameterizations have been used in the infrared spectral region reduce the computational time to milliseconds for an AIRS forward simulation (2378 spectral channels). The PCRTM has been development to cover spectral range from far IR to UV-Vis. The PCRTM model have been be used for satellite data inversions, proxy data generation, inter-satellite calibrations, spectral fingerprinting, and climate OSSE. We will show examples of applying the PCRTM to single field of view cloudy retrievals of atmospheric temperature, moisture, traces gases, clouds, and surface parameters. We will also show how the PCRTM are used for the NASA CLARREO project.

Calibration of multivariate scatter plots for exploratory analysis of relations within and between sets of variables in genomic research.

PubMed

Graffelman, Jan; van Eeuwijk, Fred

2005-12-01

The scatter plot is a well known and easily applicable graphical tool to explore relationships between two quantitative variables. For the exploration of relations between multiple variables, generalisations of the scatter plot are useful. We present an overview of multivariate scatter plots focussing on the following situations. Firstly, we look at a scatter plot for portraying relations between quantitative variables within one data matrix. Secondly, we discuss a similar plot for the case of qualitative variables. Thirdly, we describe scatter plots for the relationships between two sets of variables where we focus on correlations. Finally, we treat plots of the relationships between multiple response and predictor variables, focussing on the matrix of regression coefficients. We will present both known and new results, where an important original contribution concerns a procedure for the inclusion of scales for the variables in multivariate scatter plots. We provide software for drawing such scales. We illustrate the construction and interpretation of the plots by means of examples on data collected in a genomic research program on taste in tomato.

Light scattering and transmission measurement using digital imaging for online analysis of constituents in milk

NASA Astrophysics Data System (ADS)

Jain, Pranay; Sarma, Sanjay E.

2015-05-01

Milk is an emulsion of fat globules and casein micelles dispersed in an aqueous medium with dissolved lactose, whey proteins and minerals. Quantification of constituents in milk is important in various stages of the dairy supply chain for proper process control and quality assurance. In field-level applications, spectrophotometric analysis is an economical option due to the low-cost of silicon photodetectors, sensitive to UV/Vis radiation with wavelengths between 300 - 1100 nm. Both absorption and scattering are witnessed as incident UV/Vis radiation interacts with dissolved and dispersed constituents in milk. These effects can in turn be used to characterize the chemical and physical composition of a milk sample. However, in order to simplify analysis, most existing instrument require dilution of samples to avoid effects of multiple scattering. The sample preparation steps are usually expensive, prone to human errors and unsuitable for field-level and online analysis. This paper introduces a novel digital imaging based method of online spectrophotometric measurements on raw milk without any sample preparation. Multiple LEDs of different emission spectra are used as discrete light sources and a digital CMOS camera is used as an image sensor. The extinction characteristic of samples is derived from captured images. The dependence of multiple scattering on power of incident radiation is exploited to quantify scattering. The method has been validated with experiments for response with varying fat concentrations and fat globule sizes. Despite of the presence of multiple scattering, the method is able to unequivocally quantify extinction of incident radiation and relate it to the fat concentrations and globule sizes of samples.

A programmable metasurface with dynamic polarization, scattering and focusing control

NASA Astrophysics Data System (ADS)

Yang, Huanhuan; Cao, Xiangyu; Yang, Fan; Gao, Jun; Xu, Shenheng; Li, Maokun; Chen, Xibi; Zhao, Yi; Zheng, Yuejun; Li, Sijia

2016-10-01

Diverse electromagnetic (EM) responses of a programmable metasurface with a relatively large scale have been investigated, where multiple functionalities are obtained on the same surface. The unit cell in the metasurface is integrated with one PIN diode, and thus a binary coded phase is realized for a single polarization. Exploiting this anisotropic characteristic, reconfigurable polarization conversion is presented first. Then the dynamic scattering performance for two kinds of sources, i.e. a plane wave and a point source, is carefully elaborated. To tailor the scattering properties, genetic algorithm, normally based on binary coding, is coupled with the scattering pattern analysis to optimize the coding matrix. Besides, inverse fast Fourier transform (IFFT) technique is also introduced to expedite the optimization process of a large metasurface. Since the coding control of each unit cell allows a local and direct modulation of EM wave, various EM phenomena including anomalous reflection, diffusion, beam steering and beam forming are successfully demonstrated by both simulations and experiments. It is worthwhile to point out that a real-time switch among these functionalities is also achieved by using a field-programmable gate array (FPGA). All the results suggest that the proposed programmable metasurface has great potentials for future applications.

A programmable metasurface with dynamic polarization, scattering and focusing control

PubMed Central

Yang, Huanhuan; Cao, Xiangyu; Yang, Fan; Gao, Jun; Xu, Shenheng; Li, Maokun; Chen, Xibi; Zhao, Yi; Zheng, Yuejun; Li, Sijia

2016-01-01

Diverse electromagnetic (EM) responses of a programmable metasurface with a relatively large scale have been investigated, where multiple functionalities are obtained on the same surface. The unit cell in the metasurface is integrated with one PIN diode, and thus a binary coded phase is realized for a single polarization. Exploiting this anisotropic characteristic, reconfigurable polarization conversion is presented first. Then the dynamic scattering performance for two kinds of sources, i.e. a plane wave and a point source, is carefully elaborated. To tailor the scattering properties, genetic algorithm, normally based on binary coding, is coupled with the scattering pattern analysis to optimize the coding matrix. Besides, inverse fast Fourier transform (IFFT) technique is also introduced to expedite the optimization process of a large metasurface. Since the coding control of each unit cell allows a local and direct modulation of EM wave, various EM phenomena including anomalous reflection, diffusion, beam steering and beam forming are successfully demonstrated by both simulations and experiments. It is worthwhile to point out that a real-time switch among these functionalities is also achieved by using a field-programmable gate array (FPGA). All the results suggest that the proposed programmable metasurface has great potentials for future applications. PMID:27774997

A programmable metasurface with dynamic polarization, scattering and focusing control.

PubMed

Yang, Huanhuan; Cao, Xiangyu; Yang, Fan; Gao, Jun; Xu, Shenheng; Li, Maokun; Chen, Xibi; Zhao, Yi; Zheng, Yuejun; Li, Sijia

2016-10-24

Diverse electromagnetic (EM) responses of a programmable metasurface with a relatively large scale have been investigated, where multiple functionalities are obtained on the same surface. The unit cell in the metasurface is integrated with one PIN diode, and thus a binary coded phase is realized for a single polarization. Exploiting this anisotropic characteristic, reconfigurable polarization conversion is presented first. Then the dynamic scattering performance for two kinds of sources, i.e. a plane wave and a point source, is carefully elaborated. To tailor the scattering properties, genetic algorithm, normally based on binary coding, is coupled with the scattering pattern analysis to optimize the coding matrix. Besides, inverse fast Fourier transform (IFFT) technique is also introduced to expedite the optimization process of a large metasurface. Since the coding control of each unit cell allows a local and direct modulation of EM wave, various EM phenomena including anomalous reflection, diffusion, beam steering and beam forming are successfully demonstrated by both simulations and experiments. It is worthwhile to point out that a real-time switch among these functionalities is also achieved by using a field-programmable gate array (FPGA). All the results suggest that the proposed programmable metasurface has great potentials for future applications.

Rayleigh imaging in spectral mammography

NASA Astrophysics Data System (ADS)

Berggren, Karl; Danielsson, Mats; Fredenberg, Erik

2016-03-01

Spectral imaging is the acquisition of multiple images of an object at different energy spectra. In mammography, dual-energy imaging (spectral imaging with two energy levels) has been investigated for several applications, in particular material decomposition, which allows for quantitative analysis of breast composition and quantitative contrast-enhanced imaging. Material decomposition with dual-energy imaging is based on the assumption that there are two dominant photon interaction effects that determine linear attenuation: the photoelectric effect and Compton scattering. This assumption limits the number of basis materials, i.e. the number of materials that are possible to differentiate between, to two. However, Rayleigh scattering may account for more than 10% of the linear attenuation in the mammography energy range. In this work, we show that a modified version of a scanning multi-slit spectral photon-counting mammography system is able to acquire three images at different spectra and can be used for triple-energy imaging. We further show that triple-energy imaging in combination with the efficient scatter rejection of the system enables measurement of Rayleigh scattering, which adds an additional energy dependency to the linear attenuation and enables material decomposition with three basis materials. Three available basis materials have the potential to improve virtually all applications of spectral imaging.

Charged particle multiplicities in deep inelastic scattering at HERA

NASA Astrophysics Data System (ADS)

Aid, S.; Anderson, M.; Andreev, V.; Andrieu, B.; Appuhn, R.-D.; Babaev, A.; Bähr, J.; Bán, J.; Ban, Y.; Baranov, P.; Barrelet, E.; Barschke, R.; Bartel, W.; Barth, M.; Bassler, U.; Beck, H. P.; Behrend, H.-J.; Belousov, A.; Berger, Ch.; Bernardi, G.; Bertrand-Coremans, G.; Besançon, M.; Beyer, R.; Biddulph, P.; Bispham, P.; Bizot, J. C.; Blobel, V.; Borras, K.; Botterweck, F.; Boudry, V.; Braemer, A.; Braunschweig, W.; Brisson, V.; Bruel, P.; Bruncko, D.; Brune, C.; Buchholz, R.; Büngener, L.; Bürger, J.; Büsser, F. W.; Buniatian, A.; Burke, S.; Burton, M. J.; Calvet, D.; Campbell, A. J.; Carli, T.; Charlet, M.; Clarke, D.; Clegg, A. B.; Clerbaux, B.; Cocks, S.; Contreras, J. G.; Cormack, C.; Coughlan, J. A.; Courau, A.; Cousinou, M.-C.; Cozzika, G.; Criegee, L.; Cussans, D. G.; Cvach, J.; Dagoret, S.; Dainton, J. B.; Dau, W. D.; Daum, K.; David, M.; Davis, C. L.; Delcourt, B.; de Roeck, A.; de Wolf, E. A.; Dirkmann, M.; Dixon, P.; di Nezza, P.; Dlugosz, W.; Dollfus, C.; Dowell, J. D.; Dreis, H. B.; Droutskoi, A.; Dünger, O.; Duhm, H.; Ebert, J.; Ebert, T. R.; Eckerlin, G.; Efremenko, V.; Egli, S.; Eichler, R.; Eisele, F.; Eisenhandler, E.; Elsen, E.; Erdmann, M.; Erdmann, W.; Evrard, E.; Fahr, A. B.; Favart, L.; Fedotov, A.; Feeken, D.; Felst, R.; Feltesse, J.; Ferencei, J.; Ferrarotto, F.; Flamm, K.; Fleischer, M.; Flieser, M.; Flügge, G.; Fomenko, A.; Fominykh, B.; Formánek, J.; Foster, J. M.; Franke, G.; Fretwurst, E.; Gabathuler, E.; Gabathuler, K.; Gaede, F.; Garvey, J.; Gayler, J.; Gebauer, M.; Genzel, H.; Gerhards, R.; Glazov, A.; Goerlach, U.; Goerlich, L.; Gogitidze, N.; Goldberg, M.; Goldner, D.; Golec-Biernat, K.; Gonzalez-Pineiro, B.; Gorelov, I.; Grab, C.; Grässler, H.; Greenshaw, T.; Griffiths, R. K.; Grindhammer, G.; Gruber, A.; Gruber, C.; Haack, J.; Hadig, T.; Haidt, D.; Hajduk, L.; Hampel, M.; Haynes, W. J.; Heinzelmann, G.; Henderson, R. C. W.; Henschel, H.; Herynek, I.; Hess, M. F.; Hewitt, K.; Hildesheim, W.; Hiller, K. H.; Hilton, C. D.; Hladký, J.; Hoeger, K. C.; Höppner, M.; Hoffmann, D.; Holtom, T.; Horisberger, R.; Hudgson, V. L.; Hütte, M.; Ibbotson, M.; Itterbeck, H.; Jacholkowska, A.; Jacobsson, C.; Jaffre, M.; Janoth, J.; Jansen, T.; Jönsson, L.; Johnson, D. P.; Jung, H.; Kalmus, P. I. P.; Kander, M.; Kant, D.; Kaschowitz, R.; Kathage, U.; Katzy, J.; Kaufmann, H. H.; Kaufmann, O.; Kazarian, S.; Kenyon, I. R.; Kermiche, S.; Keuker, C.; Kiesling, C.; Klein, M.; Kleinwort, C.; Knies, G.; Köhler, T.; Köhne, J. H.; Kolanoski, H.; Kole, F.; Kolya, S. D.; Korbel, V.; Korn, M.; Kostka, P.; Kotelnikov, S. K.; Krämerkämper, T.; Krasny, M. W.; Krehbiel, H.; Krücker, D.; Küster, H.; Kuhlen, M.; Kurča, T.; Kurzhöfer, J.; Lacour, D.; Laforge, B.; Lander, R.; Landon, M. P. J.; Lange, W.; Langenegger, U.; Laporte, J.-F.; Lebedev, A.; Lehner, F.; Levonian, S.; Lindström, G.; Lindstroem, M.; Link, J.; Linsel, F.; Lipinski, J.; List, B.; Lobo, G.; Lomas, J. W.; Lopez, G. C.; Lubimov, V.; Lüke, D.; Magnussen, N.; Malinovski, E.; Mani, S.; Maraček, R.; Marage, P.; Marks, J.; Marshall, R.; Martens, J.; Martin, G.; Martin, R.; Martyn, H.-U.; Martyniak, J.; Mavroidis, T.; Maxfield, S. J.; McMahon, S. J.; Mehta, A.; Meier, K.; Meyer, A.; Meyer, A.; Meyer, H.; Meyer, J.; Meyer, P.-O.; Migliori, A.; Mikocki, S.; Milstead, D.; Moeck, J.; Moreau, F.; Morris, J. V.; Mroczko, E.; Müller, D.; Müller, G.; Müller, K.; Müller, M.; Murín, P.; Nagovizin, V.; Nahnhauer, R.; Naroska, B.; Naumann, Th.; Négri, I.; Newman, P. R.; Newton, D.; Nguyen, H. K.; Nicholls, T. C.; Niebergall, F.; Niebuhr, C.; Niedzballa, Ch.; Niggli, H.; Nisius, R.; Nowak, G.; Noyes, G. W.; Nyberg-Werther, M.; Oakden, M.; Oberlack, H.; Olsson, J. E.; Ozerov, D.; Palmen, P.; Panaro, E.; Panitch, A.; Pascaud, C.; Patel, G. D.; Pawletta, H.; Peppel, E.; Perez, E.; Phillips, J. P.; Pieuchot, A.; Pitzl, D.; Pope, G.; Prell, S.; Rabbertz, K.; Rädel, G.; Reimer, P.; Reinshagen, S.; Rick, H.; Riech, V.; Riedlberger, J.; Riepenhausen, F.; Riess, S.; Rizvi, E.; Robertson, S. M.; Robmann, P.; Roloff, H. E.; Roosen, R.; Rosenbauer, K.; Rostovtsev, A.; Rouse, F.; Royon, C.; Rüter, K.; Rusakov, S.; Rybicki, K.; Sankey, D. P. C.; Schacht, P.; Schiek, S.; Schleif, S.; Schleper, P.; von Schlippe, W.; Schmidt, D.; Schmidt, G.; Schöning, A.; Schröder, V.; Schuhmann, E.; Schwab, B.; Sefkow, F.; Seidel, M.; Sell, R.; Semenov, A.; Shekelyan, V.; Sheviakov, I.; Shtarkov, L. N.; Siegmon, G.; Siewert, U.; Sirois, Y.; Skillicorn, I. O.; Smirnov, P.; Smith, J. R.; Solochenko, V.; Soloviev, Y.; Specka, A.; Spiekermann, J.; Spielman, S.; Spitzer, H.; Squinabol, F.; Steenbock, M.; Steffen, P.; Steinberg, R.; Steiner, H.; Steinhart, J.; Stella, B.; Stellberger, A.; Stier, J.; Stiewe, J.; Stößlein, U.; Stolze, K.; Straumann, U.; Struczinski, W.; Sutton, J. P.; Tapprogge, S.; Taševský, M.; Tchernyshov, V.; Tchetchelnitski, S.; Theissen, J.; Thiebaux, C.; Thompson, G.; Truöl, P.; Tsipolitis, G.; Turnau, J.; Tutas, J.; Uelkes, P.; Usik, A.; Valkár, S.; Valkárová, A.; Vallée, C.; Vandenplas, D.; van Esch, P.; van Mechelen, P.; Vazdik, Y.; Verrecchia, P.; Villet, G.; Wacker, K.; Wagener, A.; Wagener, M.; Walther, A.; Waugh, B.; Weber, G.; Weber, M.; Wegener, D.; Wegner, A.; Wengler, T.; Werner, M.; West, L. R.; Wilksen, T.; Willard, S.; Winde, M.; Winter, G.-G.; Wittek, C.; Wobisch, M.; Wünsch, E.; Žáček, J.; Zarbock, D.; Zhang, Z.; Zhokin, A.; Zini, P.; Zomer, F.; Zsembery, J.; Zuber, K.; Zurnedden, M.

1996-12-01

Using the H1 detector at HERA, charged particle multiplicity distributions in deep inelastic e + p scattering have been measured over a large kinematical region. The evolution with W and Q 2 of the multiplicity distribution and of the multiplicity moments in pseudorapidity domains of varying size is studied in the current fragmentation region of the hadronic centre-of-mass frame. The results are compared with data from fixed target lepton-nucleon interactions, e + e - annihilations and hadron-hadron collisions as well as with expectations from QCD based parton models. Fits to the Negative Binomial and Lognormal distributions are presented.

Monte Carlo calculation of large and small-angle electron scattering in air

DOE PAGES

Cohen, B. I.; Higginson, D. P.; Eng, C. D.; ...

2017-08-12

A Monte Carlo method for angle scattering of electrons in air that accommodates the small-angle multiple scattering and larger-angle single scattering limits is introduced. In this work, the algorithm is designed for use in a particle-in-cell simulation of electron transport and electromagnetic wave effects in air. The method is illustrated in example calculations.

Inverse scattering theory: Inverse scattering series method for one dimensional non-compact support potential

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

Yao, Jie, E-mail: yjie2@uh.edu; Lesage, Anne-Cécile; Hussain, Fazle

2014-12-15

The reversion of the Born-Neumann series of the Lippmann-Schwinger equation is one of the standard ways to solve the inverse acoustic scattering problem. One limitation of the current inversion methods based on the reversion of the Born-Neumann series is that the velocity potential should have compact support. However, this assumption cannot be satisfied in certain cases, especially in seismic inversion. Based on the idea of distorted wave scattering, we explore an inverse scattering method for velocity potentials without compact support. The strategy is to decompose the actual medium as a known single interface reference medium, which has the same asymptoticmore » form as the actual medium and a perturbative scattering potential with compact support. After introducing the method to calculate the Green’s function for the known reference potential, the inverse scattering series and Volterra inverse scattering series are derived for the perturbative potential. Analytical and numerical examples demonstrate the feasibility and effectiveness of this method. Besides, to ensure stability of the numerical computation, the Lanczos averaging method is employed as a filter to reduce the Gibbs oscillations for the truncated discrete inverse Fourier transform of each order. Our method provides a rigorous mathematical framework for inverse acoustic scattering with a non-compact support velocity potential.« less

Dense fog on the highway: Visual range monitoring in cars?

NASA Technical Reports Server (NTRS)

Hahn, W.; Krichbaumer, W.; Streicher, J.; Werner, CH.

1992-01-01

This paper reports on the development of a new sensor. Laser range-finders are currently installed in cars and trucks to measure the distance to a proceeding car (LEICA). A modification of such a sensor to measure visibility was made. The problems that had to be solved were: (1) choice of wavelength with relation to the human eye for visibility measurements; (2) dependency of the wavelength on atmospheric turbidity; (3) laser eye-safety; and (4) influence of multiple scattering at visibilities smaller than 200 m. The wavelength used for lidar sensors in the near infrared presents no real problems because the object to be sensed is fog appearing white which means that scattering from fog is wavelength independent. There are however differences in backscatter-to-extinction ratio for different fog and weather situations. The two solutions to these problems are polarization and multiple scattering. As known from airport operations of a laser ceilometer, one can use this multiple scattering contribution to determine the visibility.

Particle Identification in Nuclear Emulsion by Measuring Multiple Coulomb Scattering

NASA Astrophysics Data System (ADS)

Than Tint, Khin; Nakazawa, Kazuma; Yoshida, Junya; Kyaw Soe, Myint; Mishina, Akihiro; Kinbara, Shinji; Itoh, Hiroki; Endo, Yoko; Kobayashi, Hidetaka; E07 Collaboration

2014-09-01

We are developing particle identification techniques for single charged particles such as Xi, proton, K and π by measuring multiple Coulomb scattering in nuclear emulsion. Nuclear emulsion is the best three dimensional detector for double strangeness (S = -2) nuclear system. We expect to accumulate about 10000 Xi-minus stop events which produce double lambda hypernucleus in J-PARC E07 emulsion counter hybrid experiment. The purpose of this particle identification (PID) in nuclear emulsion is to purify Xi-minus stop events which gives information about production probability of double hypernucleus and branching ratio of decay mode. Amount of scattering parameterized as angular distribution and second difference is inversely proportional to the momentum of particle. We produced several thousands of various charged particle tracks in nuclear emulsion stack via Geant4 simulation. In this talk, PID with some measuring methods for multiple scattering will be discussed by comparing with simulation data and real Xi-minus stop events in KEK-E373 experiment.

XAFS Debye-Waller Factors Temperature-Dependent Expressions for Fe+2-Porphyrin Complexes

NASA Astrophysics Data System (ADS)

Dimakis, Nicholas; Bunker, Grant

2007-02-01

We present an efficient and accurate method for directly calculating single and multiple scattering X-ray absorption fine structure (XAFS) thermal Debye-Waller factors for Fe+2 -porphiryn complexes. The number of multiple scattering Debye-Waller factors on metal porphyrin centers exceeds the number of available parameters that XAFS experimental data can support during fitting with simulated spectra. Using the Density Functional Theory (DFT) under the hybrid functional of X3LYP, phonon normal mode spectrum properties are used to express the mean square variation of the half-scattering path length for a Fe+2 -porphiryn complex as a function of temperature for the most important single and multiple scattering paths of the complex thus virtually eliminating them from the fitting procedure. Modeled calculations are compared with corresponding values obtained from DFT-built and optimized Fe+2 -porphyrin bis-histidine structure as well as from experimental XAFS spectra previously reported. An excellent agreement between calculated and reference Debye-Waller factors for Fe+2-porphyrins is obtained.

On the Angular Variation of Solar Reflectance of Snow

NASA Technical Reports Server (NTRS)

Chang, A. T. C.; Choudhury, B. J.

1979-01-01

Spectral and integrated solar reflectance of nonhomogeneous snowpacks were derived assuming surface reflection of direct radiation and subsurface multiple scattering. For surface reflection, a bidirectional reflectance distribution function derived for an isotropic Gaussian faceted surface was considered and for subsurface multiple scattering, an approximate solution of the radiative transfer equation was studied. Solar radiation incident on the snowpack was decomposed into direct and atmospherically scattered radiation. Spectral attenuation coefficients of ozone, carbon dioxide, water vapor, aerosol and molecular scattering were included in the calculation of incident solar radiation. Illustrative numerical results were given for a case of North American winter atmospheric conditions. The calculated dependence of spectrally integrated directional reflectance (or albedo) on solar elevation was in qualitative agreement with available observations.

Multiple-scattering model for inclusive proton production in heavy ion collisions

NASA Technical Reports Server (NTRS)

Cucinotta, Francis A.

1994-01-01

A formalism is developed for evaluating the momentum distribution for proton production in nuclear abrasion during heavy ion collisions using the Glauber multiple-scattering series. Several models for the one-body density matrix of nuclei are considered for performing numerical calculations. Calculations for the momentum distribution of protons in abrasion are compared with experimental data for inclusive proton production.

Phase matrix induced symmetrics for multiple scattering using the matrix operator method

NASA Technical Reports Server (NTRS)

Hitzfelder, S. J.; Kattawar, G. W.

1973-01-01

Entirely rigorous proofs of the symmetries induced by the phase matrix into the reflection and transmission operators used in the matrix operator theory are given. Results are obtained for multiple scattering in both homogeneous and inhomogeneous atmospheres. These results will be useful to researchers using the method since large savings in computer time and storage are obtainable.

A semi-analytical model of a time reversal cavity for high-amplitude focused ultrasound applications

NASA Astrophysics Data System (ADS)

Robin, J.; Tanter, M.; Pernot, M.

2017-09-01

Time reversal cavities (TRC) have been proposed as an efficient approach for 3D ultrasound therapy. They allow the precise spatio-temporal focusing of high-power ultrasound pulses within a large region of interest with a low number of transducers. Leaky TRCs are usually built by placing a multiple scattering medium, such as a random rod forest, in a reverberating cavity, and the final peak pressure gain of the device only depends on the temporal length of its impulse response. Such multiple scattering in a reverberating cavity is a complex phenomenon, and optimisation of the device’s gain is usually a cumbersome process, mostly empirical, and requiring numerical simulations with extremely long computation times. In this paper, we present a semi-analytical model for the fast optimisation of a TRC. This model decouples ultrasound propagation in an empty cavity and multiple scattering in a multiple scattering medium. It was validated numerically and experimentally using a 2D-TRC and numerically using a 3D-TRC. Finally, the model was used to determine rapidly the optimal parameters of the 3D-TRC which had been confirmed by numerical simulations.

A multiple maximum scatter difference discriminant criterion for facial feature extraction.

PubMed

Song, Fengxi; Zhang, David; Mei, Dayong; Guo, Zhongwei

2007-12-01

Maximum scatter difference (MSD) discriminant criterion was a recently presented binary discriminant criterion for pattern classification that utilizes the generalized scatter difference rather than the generalized Rayleigh quotient as a class separability measure, thereby avoiding the singularity problem when addressing small-sample-size problems. MSD classifiers based on this criterion have been quite effective on face-recognition tasks, but as they are binary classifiers, they are not as efficient on large-scale classification tasks. To address the problem, this paper generalizes the classification-oriented binary criterion to its multiple counterpart--multiple MSD (MMSD) discriminant criterion for facial feature extraction. The MMSD feature-extraction method, which is based on this novel discriminant criterion, is a new subspace-based feature-extraction method. Unlike most other subspace-based feature-extraction methods, the MMSD computes its discriminant vectors from both the range of the between-class scatter matrix and the null space of the within-class scatter matrix. The MMSD is theoretically elegant and easy to calculate. Extensive experimental studies conducted on the benchmark database, FERET, show that the MMSD out-performs state-of-the-art facial feature-extraction methods such as null space method, direct linear discriminant analysis (LDA), eigenface, Fisherface, and complete LDA.

An optical model description of momentum transfer in heavy ion collisions

NASA Technical Reports Server (NTRS)

Khan, F.; Khandelwal, G. S.; Townsend, Lawrence W.; Wilson, J. W.; Norbury, John W.

1989-01-01

An optical model description of momentum transfer in relativistic heavy ion collisions, based upon composite particle multiple scattering theory, is presented. The imaginary component of the complex momentum transfer, which comes from the absorptive part of the optical potential, is identified as the longitudinal momentum downshift of the projectile. Predictions of fragment momentum distribution observables are made and compared with experimental data. Use of the model as a tool for estimating collision impact parameters is discussed.

The effects of external planets on inner systems: multiplicities, inclinations and pathways to eccentric warm Jupiters

NASA Astrophysics Data System (ADS)

Mustill, Alexander J.; Davies, Melvyn B.; Johansen, Anders

2017-07-01

We study how close-in systems such as those detected by Kepler are affected by the dynamics of bodies in the outer system. We consider two scenarios: outer systems of giant planets potentially unstable to planet-planet scattering and wide binaries that may be capable of driving Kozai or other secular variations of outer planets' eccentricities. Dynamical excitation of planets in the outer system reduces the multiplicity of Kepler-detectable planets in the inner system in ˜20-25 per cent of our systems. Accounting for the occurrence rates of wide-orbit planets and binary stars, ≈18 per cent of close-in systems could be destabilized by their outer companions in this way. This provides some contribution to the apparent excess of systems with a single transiting planet compared to multiple; however, it only contributes at most 25 per cent of the excess. The effects of the outer dynamics can generate systems similar to Kepler-56 (two coplanar planets significantly misaligned with the host star) and Kepler-108 (two significantly non-coplanar planets in a binary). We also identify three pathways to the formation of eccentric warm Jupiters resulting from the interaction between outer and inner systems: direct inelastic collision between an eccentric outer and an inner planet; secular eccentricity oscillations that may 'freeze out' when scattering resolves in the outer system; and scattering in the inner system followed by 'uplift', where inner planets are removed by interaction with the outer planets. In these scenarios, the formation of eccentric warm Jupiters is a signature of a past history of violent dynamics among massive planets beyond ˜1 au.

Suppression of stimulated Brillouin instability of a beat-wave of two lasers in multiple-ion-species plasmas

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

Yadav, Pinki; Gupta, D. N., E-mail: dngupta@physics.du.ac.in; Avinash, K.

2016-01-15

Stimulated Brillouin instability of a beat-wave of two lasers in plasmas with multiple-ion-species (negative-ions) was studied. The inclusion of negative-ions affects the growth of ion-acoustic wave in Brillouin scattering. Thus, the growth rate of instability is suppressed significantly by the density of negative-ions. To obey the phase-matching condition, the growth rate of the instability attains a maxima for an appropriate scattering angle (angle between the pump and scattered sideband waves). This study would be technologically important to have diagnostics in low-temperature plasmas.

Scattering of exocomets by a planet chain: exozodi levels and the delivery of cometary material to inner planets

NASA Astrophysics Data System (ADS)

Marino, Sebastian; Bonsor, Amy; Wyatt, Mark C.; Kral, Quentin

2018-06-01

Exocomets scattered by planets have been invoked to explain observations in multiple contexts, including the frequently found near- and mid-infrared excess around nearby stars arising from exozodiacal dust. Here we investigate how the process of inward scattering of comets originating in an outer belt, is affected by the architecture of a planetary system, to determine whether this could lead to observable exozodi levels or deliver volatiles to inner planets. Using N-body simulations, we model systems with different planet mass and orbital spacing distributions in the 1-50 AU region. We find that tightly packed (Δap < 20RH, m) low mass planets are the most efficient at delivering material to exozodi regions (5-7% of scattered exocomets end up within 0.5 AU at some point), although the exozodi levels do not vary by more than a factor of ˜7 for the architectures studied here. We suggest that emission from scattered dusty material in between the planets could provide a potential test for this delivery mechanism. We show that the surface density of scattered material can vary by two orders of magnitude (being highest for systems of low mass planets with medium spacing), whilst the exozodi delivery rate stays roughly constant, and that future instruments such as JWST could detect it. In fact for η Corvi, the current Herschel upper limit rules our the scattering scenario by a chain of ≲30 M⊕ planets. Finally, we show that exocomets could be efficient at delivering cometary material to inner planets (0.1-1% of scattered comets are accreted per inner planet). Overall, the best systems at delivering comets to inner planets are the ones that have low mass outer planets and medium spacing (˜20RH, m).

Propagation of laser beams in scattering media.

PubMed

Zuev, V E; Kabanov, M V; Savelev, B A

1969-01-01

Experimental investigations have been undertaken of some aspects of the propagation of helium-neon gas laser radiation at lambda = 0.63 micro for different scattering media (artificial water fogs, wood smokes, model media). It has been shown that the attenuation coefficients practically coincide when coherent and incoherent radiation is scattered. The applicability limits of Bouguer-Beer's law for describing the attenuation of radiation in scattering media are investigated and the intensity of multiple forward-scattered light for different geometrical parameters of the source and radiation receiver are measured. The applicability of single scattering theory formulas for describing forward-scattered light intensity are discussed.

Two-dimensional and 3-D images of thick tissue using time-constrained times-of-flight and absorbance spectrophotometry

NASA Astrophysics Data System (ADS)

Benaron, David A.; Lennox, M.; Stevenson, David K.

1992-05-01

Reconstructing deep-tissue images in real time using spectrophotometric data from optically diffusing thick tissues has been problematic. Continuous wave applications (e.g., pulse oximetry, regional cerebral saturation) ignore both the multiple paths traveled by the photons through the tissue and the effects of scattering, allowing scalar measurements but only under limited conditions; interferometry works poorly in thick, highly-scattering media; frequency- modulated approaches may not allow full deconvolution of scattering and absorbance; and pulsed-light techniques allow for preservation of information regarding the multiple paths taken by light through the tissue, but reconstruction is both computation intensive and limited by the relative surface area available for detection of photons. We have developed a picosecond times-of-flight and absorbance (TOFA) optical system, time-constrained to measure only photons with a narrow range of path lengths and arriving within a narrow angel of the emitter-detector axis. The delay until arrival of the earliest arriving photons is a function of both the scattering and absorbance of the tissues in a direct line between the emitter and detector, reducing the influence of surrounding tissues. Measurement using a variety of emitter and detector locations produces spatial information which can be analyzed in a standard 2-D grid, or subject to computer reconstruction to produce tomographic images representing 3-D structure. Using such a technique, we have been able to demonstrate the principles of tc-TOFA, detect and localize diffusive and/or absorptive objects suspended in highly scattering media (such as blood admixed with yeast), and perform simple 3-D reconstructions using phantom objects. We are now attempting to obtain images in vivo. Potential future applications include use as a research tool, and as a continuous, noninvasive, nondestructive monitor in diagnostic imaging, fetal monitoring, neurologic and cardiac assessment. The technique may lead to real-time optical imaging and quantitation of tissues oxygen delivery.

Calculation of the angular radiance distribution for a coupled atmosphere and canopy

NASA Technical Reports Server (NTRS)

Liang, Shunlin; Strahler, Alan H.

1993-01-01

The radiative transfer equations for a coupled atmosphere and canopy are solved numerically by an improved Gauss-Seidel iteration algorithm. The radiation field is decomposed into three components: unscattered sunlight, single scattering, and multiple scattering radiance for which the corresponding equations and boundary conditions are set up and their analytical or iterational solutions are explicitly derived. The classic Gauss-Seidel algorithm has been widely applied in atmospheric research. This is its first application for calculating the multiple scattering radiance of a coupled atmosphere and canopy. This algorithm enables us to obtain the internal radiation field as well as radiances at boundaries. Any form of bidirectional reflectance distribution function (BRDF) as a boundary condition can be easily incorporated into the iteration procedure. The hotspot effect of the canopy is accommodated by means of the modification of the extinction coefficients of upward single scattering radiation and unscattered sunlight using the formulation of Nilson and Kuusk. To reduce the computation for the case of large optical thickness, an improved iteration formula is derived to speed convergence. The upwelling radiances have been evaluated for different atmospheric conditions, leaf area index (LAI), leaf angle distribution (LAD), leaf size and so on. The formulation presented in this paper is also well suited to analyze the relative magnitude of multiple scattering radiance and single scattering radiance in both the visible and near infrared regions.

Instrumentation on Multi-Scaled Scattering of Bio-Macromolecular Solutions

PubMed Central

Chu, Benjamin; Fang, Dufei; Mao, Yimin

2015-01-01

The design, construction and initial tests on a combined laser light scattering and synchrotron X-ray scattering instrument can cover studies of length scales from atomic sizes in Angstroms to microns and dynamics from microseconds to seconds are presented. In addition to static light scattering (SLS), dynamic light scattering (DLS), small angle X-ray scattering (SAXS) and wide angle X-ray diffraction (WAXD), the light scattering instrument is being developed to carry out studies in mildly turbid solutions, in the presence of multiple scattering. Three-dimensional photon cross correlation function (3D-PCCF) measurements have been introduced to couple with synchrotron X-ray scattering to study the structure, size and dynamics of macromolecules in solution. PMID:25946340

Coastal Zone Color Scanner atmospheric correction algorithm - Multiple scattering effects

NASA Technical Reports Server (NTRS)

Gordon, Howard R.; Castano, Diego J.

1987-01-01

Errors due to multiple scattering which are expected to be encountered in application of the current Coastal Zone Color Scanner (CZCS) atmospheric correction algorithm are analyzed. The analysis is based on radiative transfer computations in model atmospheres, in which the aerosols and molecules are distributed vertically in an exponential manner, with most of the aerosol scattering located below the molecular scattering. A unique feature of the analysis is that it is carried out in scan coordinates rather than typical earth-sun coordinates, making it possible to determine the errors along typical CZCS scan lines. Information provided by the analysis makes it possible to judge the efficacy of the current algorithm with the current sensor and to estimate the impact of the algorithm-induced errors on a variety of applications.

Multiple-Point Mass Flux Measurement System Using Rayleigh Scattering

NASA Technical Reports Server (NTRS)

Mielke, Amy F.; Elam, Kristie A.; Clem, Michelle M.

2009-01-01

A multiple-point Rayleigh scattering diagnostic is being developed to provide mass flux measurements in gas flows. Spectroscopic Rayleigh scattering is an established flow diagnostic that has the ability to provide simultaneous density, temperature, and velocity measurements. Rayleigh scattered light from a focused 18 Watt continuous-wave laser beam is directly imaged through a solid Fabry-Perot etalon onto a CCD detector which permits spectral analysis of the light. The spatial resolution of the measurements is governed by the locations of interference fringes, which can be changed by altering the etalon characteristics. A prototype system has been used to acquire data in a Mach 0.56 flow to demonstrate feasibility of using this system to provide mass flux measurements. Estimates of measurement uncertainty and recommendations for system improvements are presented

The Born approximation, multiple scattering, and the butterfly algorithm

NASA Astrophysics Data System (ADS)

Martinez, Alejandro F.

Radar works by focusing a beam of light and seeing how long it takes to reflect. To see a large region the beam is pointed in different directions. The focus of the beam depends on the size of the antenna (called an aperture). Synthetic aperture radar (SAR) works by moving the antenna through some region of space. A fundamental assumption in SAR is that waves only bounce once. Several imaging algorithms have been designed using that assumption. The scattering process can be described by iterations of a badly behaving integral. Recently a method for efficiently evaluating these types of integrals has been developed. We will give a detailed implementation of this algorithm and apply it to study the multiple scattering effects in SAR using target estimates from single scattering algorithms.

Time-domain Brillouin scattering assisted by diffraction gratings

NASA Astrophysics Data System (ADS)

Matsuda, Osamu; Pezeril, Thomas; Chaban, Ievgeniia; Fujita, Kentaro; Gusev, Vitalyi

2018-02-01

Absorption of ultrashort laser pulses in a metallic grating deposited on a transparent sample launches coherent compression/dilatation acoustic pulses in directions of different orders of acoustic diffraction. Their propagation is detected by delayed laser pulses, which are also diffracted by the metallic grating, through the measurement of the transient intensity change of the first-order diffracted light. The obtained data contain multiple frequency components, which are interpreted by considering all possible angles for the Brillouin scattering of light achieved through multiplexing of the propagation directions of light and coherent sound by the metallic grating. The emitted acoustic field can be equivalently presented as a superposition of plane inhomogeneous acoustic waves, which constitute an acoustic diffraction grating for the probe light. Thus the obtained results can also be interpreted as a consequence of probe light diffraction by both metallic and acoustic gratings. The realized scheme of time-domain Brillouin scattering with metallic gratings operating in reflection mode provides access to wide range of acoustic frequencies from minimal to maximal possible values in a single experimental optical configuration for the directions of probe light incidence and scattered light detection. This is achieved by monitoring the backward and forward Brillouin scattering processes in parallel. Potential applications include measurements of the acoustic dispersion, simultaneous determination of sound velocity and optical refractive index, and evaluation of samples with a single direction of possible optical access.

Experimental Evaluation of Turbidity Impact on the Fluence Rate Distribution in a UV Reactor Using a Microfluorescent Silica Detector.

PubMed

Li, Mengkai; Li, Wentao; Wen, Dong; Qiang, Zhimin; Blatchley, Ernest R

2017-11-21

Turbidity is a common parameter used to assess particle concentration in water using visible light. However, the fact that particles play multiple roles (e.g., scattering, refraction, and reflection) in influencing the optical properties of aqueous suspensions complicates examinations of their effects on ultraviolet (UV) photoreactor performance. To address this issue, UV fluence rate (FR) distributions in a photoreactor containing various particle suspensions (SiO 2 , MgO, and TiO 2 ) were measured using a microfluorescent silica detector (MFSD). Reflectance of solid particles, as well as transmittance and scattering properties of the suspensions were characterized at UV, visible, and infrared (IR) wavelengths. The results of these measurements indicated that the optical properties of all three particle types were similar at visible and IR wavelengths, but obvious differences were evident in the UV range. The FR results indicated that for turbidity associated with SiO 2 and MgO suspensions, the weighted average FR (WAFR) increased relative to deionized water. These increases were attributed to low particle photon absorption and strong scattering. In contrast, the WAFR values decreased with increasing turbidity for TiO 2 suspensions because of their high particle photon absorption and low scattering potential. The findings also indicate that measurements of scattering and transmittance at UV wavelengths can be used to quantify the effects of turbidity on UV FR distributions.

Radiation Transport of Heliospheric Lyman-alpha from Combined Cassini and Voyager Data Sets

NASA Technical Reports Server (NTRS)

Pryor, W.; Gangopadhyay, P.; Sandel, B.; Forrester, T.; Quemerais, E.; Moebius, E.; Esposito, L.; Stewart, I.; McClintock, W.; Jouchoux, A.;

Apparatus for measuring particle properties

DOEpatents

Rader, Daniel J.; Castaneda, Jaime N.; Grasser, Thomas W.; Brockmann, John E.

1998-01-01

An apparatus for determining particle properties from detected light scattered by the particles. The apparatus uses a light beam with novel intensity characteristics to discriminate between particles that pass through the beam and those that pass through an edge of the beam. The apparatus can also discriminate between light scattered by one particle and light scattered by multiple particles. The particle's size can be determined from the intensity of the light scattered. The particle's velocity can be determined from the elapsed time between various intensities of the light scattered.

FAST TRACK PAPER: A construct of internal multiples from surface data only: the concept of virtual seismic events

NASA Astrophysics Data System (ADS)

Ikelle, Luc T.

2006-02-01

We here describe one way of constructing internal multiples from surface seismic data only. The key feature of our construct of internal multiples is the introduction of the concept of virtual seismic events. Virtual events here are events, which are not directly recorded in standard seismic data acquisition, but their existence allows us to construct internal multiples with scattering points at the sea surface; the standard construct of internal multiples does not include any scattering points at the sea surface. The mathematical and computational operations invoked in our construction of virtual events and internal multiples are similar to those encountered in the construction of free-surface multiples based on the Kirchhoff or Born scattering theory. For instance, our construct operates on one temporal frequency at a time, just like free-surface demultiple algorithms; other internal multiple constructs tend to require all frequencies for the computation of an internal multiple at a given frequency. It does not require any knowledge of the subsurface nor an explicit knowledge of specific interfaces that are responsible for the generation of internal multiples in seismic data. However, our construct requires that the data be divided into two, three or four windows to avoid generating primaries. This segmentation of the data also allows us to select a range of periods of internal multiples that one wishes to construct because, in the context of the attenuation of internal multiples, it is important to avoid generating short-period internal multiples that may constructively average to form primaries at the seismic scale.

A new look at photometry of the Moon

USGS Publications Warehouse

Goguen, J.D.; Stone, T.C.; Kieffer, H.H.; Buratti, B.J.

2010-01-01

We use ROLO photometry (Kieffer, H.H., Stone, T.C. [2005]. Astron. J. 129, 2887-2901) to characterize the before and after full Moon radiance variation for a typical highlands site and a typical mare site. Focusing on the phase angle range 45??. ) to calculate the scattering matrix and solve the radiative transfer equation for I/. F. The mean single scattering albedo is ??=0.808, the asymmetry parameter is ???cos. ?????=0.77 and the phase function is very strongly peaked in both the forward and backward scattering directions. The fit to the observations for the highland site is excellent and multiply scattered photons contribute 80% of I/. F. We conclude that either model, roughness or multiple scattering, can match the observations, but that the strongly anisotropic phase functions of realistic particles require rigorous calculation of many orders of scattering or spurious photometric roughness estimates are guaranteed. Our multiple scattering calculation is the first to combine: (1) a regolith model matched to the measured particle size distribution and index of refraction of the lunar soil, (2) a rigorous calculation of the particle phase function and solution of the radiative transfer equation, and (3) application to lunar photometry with absolute radiance calibration. ?? 2010 Elsevier Inc.

Multi-Component, Multi-Point Interferometric Rayleigh/Mie Doppler Velocimeter

NASA Technical Reports Server (NTRS)

Danehy, Paul M.; Lee, Joseph W.; Bivolaru, Daniel

2012-01-01

An interferometric Rayleigh scattering system was developed to enable the measurement of multiple, orthogonal velocity components at several points within very-high-speed or high-temperature flows. The velocity of a gaseous flow can be optically measured by sending laser light into the gas flow, and then measuring the scattered light signal that is returned from matter within the flow. Scattering can arise from either gas molecules within the flow itself, known as Rayleigh scattering, or from particles within the flow, known as Mie scattering. Measuring Mie scattering is the basis of all commercial laser Doppler and particle imaging velocimetry systems, but particle seeding is problematic when measuring high-speed and high-temperature flows. The velocimeter is designed to measure the Doppler shift from only Rayleigh scattering, and does not require, but can also measure, particles within the flow. The system combines a direct-view, large-optic interferometric setup that calculates the Doppler shift from fringe patterns collected with a digital camera, and a subsystem to capture and re-circulate scattered light to maximize signal density. By measuring two orthogonal components of the velocity at multiple positions in the flow volume, the accuracy and usefulness of the flow measurement increase significantly over single or nonorthogonal component approaches.

LAI inversion from optical reflectance using a neural network trained with a multiple scattering model

NASA Technical Reports Server (NTRS)

Smith, James A.

1992-01-01

The inversion of the leaf area index (LAI) canopy parameter from optical spectral reflectance measurements is obtained using a backpropagation artificial neural network trained using input-output pairs generated by a multiple scattering reflectance model. The problem of LAI estimation over sparse canopies (LAI < 1.0) with varying soil reflectance backgrounds is particularly difficult. Standard multiple regression methods applied to canopies within a single homogeneous soil type yield good results but perform unacceptably when applied across soil boundaries, resulting in absolute percentage errors of >1000 percent for low LAI. Minimization methods applied to merit functions constructed from differences between measured reflectances and predicted reflectances using multiple-scattering models are unacceptably sensitive to a good initial guess for the desired parameter. In contrast, the neural network reported generally yields absolute percentage errors of <30 percent when weighting coefficients trained on one soil type were applied to predicted canopy reflectance at a different soil background.

UAV remote sensing atmospheric degradation image restoration based on multiple scattering APSF estimation

NASA Astrophysics Data System (ADS)

Qiu, Xiang; Dai, Ming; Yin, Chuan-li

2017-09-01

Unmanned aerial vehicle (UAV) remote imaging is affected by the bad weather, and the obtained images have the disadvantages of low contrast, complex texture and blurring. In this paper, we propose a blind deconvolution model based on multiple scattering atmosphere point spread function (APSF) estimation to recovery the remote sensing image. According to Narasimhan analytical theory, a new multiple scattering restoration model is established based on the improved dichromatic model. Then using the L0 norm sparse priors of gradient and dark channel to estimate APSF blur kernel, the fast Fourier transform is used to recover the original clear image by Wiener filtering. By comparing with other state-of-the-art methods, the proposed method can correctly estimate blur kernel, effectively remove the atmospheric degradation phenomena, preserve image detail information and increase the quality evaluation indexes.

Characterizing riverbed sediment using high-frequency acoustics 1: spectral properties of scattering

USGS Publications Warehouse

Buscombe, Daniel D.; Grams, Paul E.; Kaplinski, Matt A.

2014-01-01

Bed-sediment classification using high-frequency hydro-acoustic instruments is challenging when sediments are spatially heterogeneous, which is often the case in rivers. The use of acoustic backscatter to classify sediments is an attractive alternative to analysis of topography because it is potentially sensitive to grain-scale roughness. Here, a new method is presented which uses high-frequency acoustic backscatter from multibeam sonar to classify heterogeneous riverbed sediments by type (sand, gravel,rock) continuously in space and at small spatial resolution. In this, the first of a pair of papers that examine the scattering signatures from a heterogeneous riverbed, methods are presented to construct spatially explicit maps of spectral properties from geo-referenced point clouds of geometrically and radiometrically corrected echoes. Backscatter power spectra are computed to produce scale and amplitude metrics that collectively characterize the length scales of stochastic measures of riverbed scattering, termed ‘stochastic geometries’. Backscatter aggregated over small spatial scales have spectra that obey a power-law. This apparently self-affine behavior could instead arise from morphological- and grain-scale roughnesses over multiple overlapping scales, or riverbed scattering being transitional between Rayleigh and geometric regimes. Relationships exist between stochastic geometries of backscatter and areas of rough and smooth sediments. However, no one parameter can uniquely characterize a particular substrate, nor definitively separate the relative contributions of roughness and acoustic impedance (hardness). Combinations of spectral quantities do, however, have the potential to delineate riverbed sediment patchiness, in a data-driven approach comparing backscatter with bed-sediment observations (which is the subject of part two of this manuscript).

Computational Modeling of Micro-Crack Induced Attenuation in CFRP Composites

NASA Technical Reports Server (NTRS)

Roberts, R. A.; Leckey, C. A. C.

2012-01-01

A computational study is performed to determine the contribution to ultrasound attenuation in carbon fiber reinforced polymer composite laminates of linear elastic scattering by matrix micro-cracking. Multiple scattering approximations are benchmarked against exact computational approaches. Results support linear scattering as the source of observed increased attenuation in the presence of micro-cracking.

Direct Simulation of Multiple Scattering by Discrete Random Media Illuminated by Gaussian Beams

NASA Technical Reports Server (NTRS)

Mackowski, Daniel W.; Mishchenko, Michael I.

2011-01-01

The conventional orientation-averaging procedure developed in the framework of the superposition T-matrix approach is generalized to include the case of illumination by a Gaussian beam (GB). The resulting computer code is parallelized and used to perform extensive numerically exact calculations of electromagnetic scattering by volumes of discrete random medium consisting of monodisperse spherical particles. The size parameters of the scattering volumes are 40, 50, and 60, while their packing density is fixed at 5%. We demonstrate that all scattering patterns observed in the far-field zone of a random multisphere target and their evolution with decreasing width of the incident GB can be interpreted in terms of idealized theoretical concepts such as forward-scattering interference, coherent backscattering (CB), and diffuse multiple scattering. It is shown that the increasing violation of electromagnetic reciprocity with decreasing GB width suppresses and eventually eradicates all observable manifestations of CB. This result supplements the previous demonstration of the effects of broken reciprocity in the case of magneto-optically active particles subjected to an external magnetic field.

Scattering properties of alumina particle clusters with different radius of monomers in aerocraft plume

NASA Astrophysics Data System (ADS)

Li, Jingying; Bai, Lu; Wu, Zhensen; Guo, Lixin; Gong, Yanjun

2017-11-01

In this paper, diffusion limited aggregation (DLA) algorithm is improved to generate the alumina particle cluster with different radius of monomers in the plume. Scattering properties of these alumina clusters are solved by the multiple sphere T matrix method (MSTM). The effect of the number and radius of monomers on the scattering properties of clusters of alumina particles is discussed. The scattering properties of two types of alumina particle clusters are compared, one has different radius of monomers that follows lognormal probability distribution, another has the same radius of monomers that equals the mean of lognormal probability distribution. The result show that the scattering phase functions and linear polarization degrees of these two types of alumina particle clusters are of great differences. For the alumina clusters with different radius of monomers, the forward scatterings are bigger and the linear polarization degree has multiple peaks. Moreover, the vary of their scattering properties do not have strong correlative with the change of number of monomers. For larger booster motors, 25-38% of the plume being condensed alumina. The alumina can scatter radiation from other sources present in the plume and effect on radiation transfer characteristics of plume. In addition, the shape, size distribution and refractive index of the particles in the plume are estimated by linear polarization degree. Therefore, accurate scattering properties calculation is very important to decrease the deviation in the related research.

Modeling Radar Scattering by Planetary Regoliths for Varying Angles of Incidence

NASA Astrophysics Data System (ADS)

Prem, P.; Patterson, G. W.; Zimmerman, M. I.

2017-12-01

Bistatic radar observations can play an important role in characterizing the texture and composition of planetary regoliths. Multiple scattering within a closely-packed particulate medium, such as a regolith, can lead to a response referred to as the Coherent Backscatter Opposition Effect (CBOE), associated with an increase in the intensity of backscattered radiation and an increase in Circular Polarization Ratio (CPR) at small bistatic angles. The nature of the CBOE is thought to depend not only on regolith properties, but also on the angle of incidence (Mishchenko, 1992). The latter factor is of particular interest in light of recent radar observations of the Moon over a range of bistatic and incidence angles by the Mini-RF instrument (on board the Lunar Reconnaissance Orbiter), operating in bistatic mode with a ground-based transmitter at the Arecibo Observatory. These observations have led to some intriguing results that are not yet well-understood ­- for instance, the lunar South Polar crater Cabeus shows an elevated CPR at only some combinations of incidence angle/bistatic angle, a potential clue to the depth distribution of water ice at the lunar poles (Patterson et al., 2017). Our objective in this work is to develop a model for radar scattering by planetary regoliths that can assist in the interpretation of Mini-RF observations. We approach the problem by coupling the Multiple Sphere T-Matrix (MSTM) code of Mackowski and Mishchenko (2011) to a Monte Carlo radiative transfer model. The MSTM code is based on the solution of Maxwell's equations for the propagation of electromagnetic waves in the presence of a cluster of scattering/absorbing spheres, and can be used to model the scattering of radar waves by an aggregation of nominal regolith particles. The scattering properties thus obtained serve as input to the Monte Carlo model, which is used to simulate radar scattering at larger spatial scales. The Monte Carlo approach has the advantage of being able to readily accommodate varying incidence angles, as well as heterogeneities in regolith composition and properties - factors that may be of interest in both lunar and other contexts. We will report on the development and validation of the coupled MSTM-Monte Carlo model, and discuss its application to problems of interest.

Inelastic scattering in planetary atmospheres. I - The Ring effect, without aerosols

NASA Technical Reports Server (NTRS)

Kattawar, G. W.; Young, A. T.; Humphreys, T. J.

1981-01-01

The contribution of inelastic molecular scattering (Rayleigh-Brillouin and rotational Raman scattering) to the filling-in of Fraunhofer lines in the light of the blue sky is studied. Aerosol fluorescence is shown to be negligible, and aerosol scattering is ignored. The angular and polarization dependences of the filling-in detail for single scattering are discussed. An approximate treatment of multiple scattering, using a backward Monte Carlo technique, makes it possible to investigate the effects of the ground albedo. As the molecular scatterings alone produce more line-filling than is observed, it seems likely that aerosols dilute the effect by contributing unaltered sunlight to the observed spectra.

Absolute Definition of Phase Shift in the Elastic Scattering of a Particle from Compound Systems

NASA Technical Reports Server (NTRS)

Temkin, A.

1961-01-01

The projection of the target wave function on the total wave function of a scattered particle interacting with the target system is used to define an absolute phase shift including any multiples of pi. With this definition of the absolute phase shift, one can prove rigorously in the limit of zero energy for s-wave electrons scattered from atomic hydrogen that the triplet phase shift must approach a nonzero multiple of pi. One can further show that at least one pi of this phase shift is not connected with the existence of a bound state of the H- ion.

Precise determination of the refractive index of suspended particles: light transmission as a function of refractive index mismatch

NASA Astrophysics Data System (ADS)

McClymer, J. P.

2016-08-01

Many fluids appear white because refractive index differences lead to multiple scattering. In this paper, we use safe, low-cost commercial index matching fluids to quantitatively study light transmission as a function of index mismatch, reduce multiple scattering to allow single scattering probes, and to precisely determine the index of refraction of suspended material. The transmission profile is compared with Rayleigh-Gans and Mie theory predictions. The procedure is accessible as a student laboratory project, while providing advantages over other standard methods of measuring the refractive index of an unknown nanoparticle, making it valuable to researchers.

Polarimetric and Structural Properties of a Boreal Forest at P-Band and L-Band

NASA Astrophysics Data System (ADS)

Tebaldini, S.; Rocca, F.

2010-12-01

With this paper we investigate the structural and polarimetric of the boreal forest within the Krycklan river catchment, Northern Sweden, basing on multi-polarimetric and multi-baseline SAR surveys at P-Band and L-Band collected in the framework of the ESA campaign BioSAR 2008. The analysis has been carried out by applying the Algebraic Synthesis (AS) technique, recently introduced in literature, which provides a theoretical framework for the decomposition of the backscattered signal into ground-only and volume-only contributions, basing on both baseline and polarization diversity. The availability of multiple baselines allows the formation of a synthetic aperture not only along the azimuth direction but also in elevation. Accordingly, the backscattered echoes can be focused not only in the slant range, azimuth plane, but in the whole 3D space. This is the rationale of the SAR Tomography (T-SAR) concept, which has been widely considered in the literature of the last years. It follows that, as long as the penetration in the scattering volume is guaranteed, the vertical profile of the vegetation layer is retrieved by separating backscatter contributions along the vertical direction, which is the main reason for the exploitation of Tomographic techniques at longer wavelengths. Still, the capabilities of T-SAR are limited to imaging the global vertical structure of the electromagnetic scattering in a certain polarization. It then becomes important to develop methodologies for the investigation of the vertical structure of different Scattering Mechanisms (SMs), such as ground and volume scattering, in such a way as to derive information that can be delivered also outside the field of Radar processing. This is an issue that may become relevant at longer wavelengths, such as P-Band, where the presence of multiple scattering arising from the interaction with terrain could hinder the correct reconstruction of the forest structure. The availability of multiple polarizations allows to overcome this limitation, thus providing a way to obtain the vertical structures associated with volume-only contributions. Experimental results will be provided showing the following. At P-Band the most relevant scattering contributions are observed at the ground level, not only in the co-polar channels, but also in HV, consistently with he first BioSAR campaign. L-Band data have shown a remarkable difference, resulting in a more uniform distribution of the backscattered power along the vertical direction. Volume top height has been observed to be substantially invariant to the choice of the solution for volume-only scattering. These results underline the validity of modeling a forest scenario as being constituted by volume and ground (or rather ground-locked) scattering, and the importance of forest top height as the most robust indicator of the forest structure as imaged through microwaves measurements. Nevertheless, it has also been shown that different solutions for volume scattering correspond to dramatically different vertical structures. In this framework, tomography represents a powerful tool for investigating the potential solutions, as it allows to see what kind of vertical structure has been retrieved. On this basis, a solution has been proposed as a criterion to emphasize volume contributions at P-Band.

Multifunctional Metallosupramolecular Materials

DTIC Science & Technology

2011-02-28

supramolecular polymers based on 16 and Zn(NTf2)2 using small- angle X - ray scattering (SAXS) and transmission electron microscopy (TEM), carried out by...The SAXS data (Figure 13a) show multiple strong Bragg diffraction maxima at integer multiples of the scattering vector of the primary diffraction ...a minor amount of residual double bonds in the poly(ethylene-co-butylene) core. The metallopolymers 16·[Zn(NTf2)2] x exhibit similar traces, but do

Character of the opposition effect and negative polarization

NASA Technical Reports Server (NTRS)

Pieters, Carle M.; Shkuratov, Yu. G.; Stankevich, D. G.

1991-01-01

Photometric and polarimetric properties at small phase angles were measured for silicates with controlled surface properties in order to distinguish properties that are associated with surface reflection from those that are associated with multiple scattering from internal grain boundaries. These data provide insight into the causes and conditions of photometric properties observed at small phase angles for dark bodies of the solar system. Obsidian was chosen to represent a silicate dielectric with no internal scattering boundaries. Because obsidian is free of internal scatterers, light reflected from both the rough and smooth obsidian samples is almost entirely single and multiple Fresnel reflections form surface facets with no body component. Surface structure alone cannot produce an opposition effect. Comparison of the obsidian and basalt results indicates that for an opposition effect to occur, surface texture must be both rough and contain internal scattering interfaces. Although the negative polarization observed for the obsidian samples indicates single and multiple reflections are part of negative polarization, the longer inversion angle of the multigrain inversion samples implies that internal reflections must also contribute a significant negative polarization component.

Expanding Lorentz and spectrum corrections to large volumes of reciprocal space for single-crystal time-of-flight neutron diffraction

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

Michels-Clark, Tara M.; Savici, Andrei T.; Lynch, Vickie E.

Evidence is mounting that potentially exploitable properties of technologically and chemically interesting crystalline materials are often attributable to local structure effects, which can be observed as modulated diffuse scattering (mDS) next to Bragg diffraction (BD). BD forms a regular sparse grid of intense discrete points in reciprocal space. Traditionally, the intensity of each Bragg peak is extracted by integration of each individual reflection first, followed by application of the required corrections. In contrast, mDS is weak and covers expansive volumes of reciprocal space close to, or between, Bragg reflections. For a representative measurement of the diffuse scattering, multiple sample orientationsmore » are generally required, where many points in reciprocal space are measured multiple times and the resulting data are combined. The common post-integration data reduction method is not optimal with regard to counting statistics. A general and inclusive data processing method is needed. In this contribution, a comprehensive data analysis approach is introduced to correct and merge the full volume of scattering data in a single step, while correctly accounting for the statistical weight of the individual measurements. Lastly, development of this new approach required the exploration of a data treatment and correction protocol that includes the entire collected reciprocal space volume, using neutron time-of-flight or wavelength-resolved data collected at TOPAZ at the Spallation Neutron Source at Oak Ridge National Laboratory.« less

Expanding Lorentz and spectrum corrections to large volumes of reciprocal space for single-crystal time-of-flight neutron diffraction

DOE PAGES

Michels-Clark, Tara M.; Savici, Andrei T.; Lynch, Vickie E.; ...

2016-03-01

Evidence is mounting that potentially exploitable properties of technologically and chemically interesting crystalline materials are often attributable to local structure effects, which can be observed as modulated diffuse scattering (mDS) next to Bragg diffraction (BD). BD forms a regular sparse grid of intense discrete points in reciprocal space. Traditionally, the intensity of each Bragg peak is extracted by integration of each individual reflection first, followed by application of the required corrections. In contrast, mDS is weak and covers expansive volumes of reciprocal space close to, or between, Bragg reflections. For a representative measurement of the diffuse scattering, multiple sample orientationsmore » are generally required, where many points in reciprocal space are measured multiple times and the resulting data are combined. The common post-integration data reduction method is not optimal with regard to counting statistics. A general and inclusive data processing method is needed. In this contribution, a comprehensive data analysis approach is introduced to correct and merge the full volume of scattering data in a single step, while correctly accounting for the statistical weight of the individual measurements. Lastly, development of this new approach required the exploration of a data treatment and correction protocol that includes the entire collected reciprocal space volume, using neutron time-of-flight or wavelength-resolved data collected at TOPAZ at the Spallation Neutron Source at Oak Ridge National Laboratory.« less

Multiphoton Scattering Tomography with Coherent States.

PubMed

Ramos, Tomás; García-Ripoll, Juan José

2017-10-13

In this work we develop an experimental procedure to interrogate the single- and multiphoton scattering matrices of an unknown quantum system interacting with propagating photons. Our proposal requires coherent state laser or microwave inputs and homodyne detection at the scatterer's output, and provides simultaneous information about multiple-elastic and inelastic-segments of the scattering matrix. The method is resilient to detector noise and its errors can be made arbitrarily small by combining experiments at various laser powers. Finally, we show that the tomography of scattering has to be performed using pulsed lasers to efficiently gather information about the nonlinear processes in the scatterer.

Two-potential approach for electron-molecular collisions at intermediate and high energies - Application to e-N2 scatterings

NASA Technical Reports Server (NTRS)

Choi, B. H.; Poe, R. T.; Sun, J. C.; Shan, Y.

1979-01-01

A general theoretical approach is proposed for the calculation of elastic, vibrational, and rotational transitions for electron-molecule scattering at intermediate and high-electron-impact energies. In this formulation, contributions to the scattering process come from the incoherent sum of two dominant potentials: a short-range shielded nuclear Coulomb potential from individual atomic centers, and a permanent/induced long-range potential. Application to e-N2 scattering from 50-500 eV incident electron energies has yielded good agreement with absolutely calibrated experiments. Comparisons with other theoretical approaches are made. The physical picture as well as the general features of electron-molecule scattering process are discussed within the framework of the two-potential approach.

Stochastic description of geometric phase for polarized waves in random media

NASA Astrophysics Data System (ADS)

Boulanger, Jérémie; Le Bihan, Nicolas; Rossetto, Vincent

2013-01-01

We present a stochastic description of multiple scattering of polarized waves in the regime of forward scattering. In this regime, if the source is polarized, polarization survives along a few transport mean free paths, making it possible to measure an outgoing polarization distribution. We consider thin scattering media illuminated by a polarized source and compute the probability distribution function of the polarization on the exit surface. We solve the direct problem using compound Poisson processes on the rotation group SO(3) and non-commutative harmonic analysis. We obtain an exact expression for the polarization distribution which generalizes previous works and design an algorithm solving the inverse problem of estimating the scattering properties of the medium from the measured polarization distribution. This technique applies to thin disordered layers, spatially fluctuating media and multiple scattering systems and is based on the polarization but not on the signal amplitude. We suggest that it can be used as a non-invasive testing method.

Estimation of the intrinsic absorption and scattering attenuation in Northeastern Venezuela (Southeastern Caribbean) using coda waves

USGS Publications Warehouse

Ugalde, A.; Pujades, L.G.; Canas, J.A.; Villasenor, A.

1998-01-01

Northeastern Venezuela has been studied in terms of coda wave attenuation using seismograms from local earthquakes recorded by a temporary short-period seismic network. The studied area has been separated into two subregions in order to investigate lateral variations in the attenuation parameters. Coda-Q-1 (Q(c)-1) has been obtained using the single-scattering theory. The contribution of the intrinsic absorption (Q(i)-1) and scattering (Q(s)-1) to total attenuation (Q(t)-1) has been estimated by means of a multiple lapse time window method, based on the hypothesis of multiple isotropic scattering with uniform distribution of scatterers. Results show significant spatial variations of attenuation: the estimates for intermediate depth events and for shallow events present major differences. This fact may be related to different tectonic characteristics that may be due to the presence of the Lesser Antilles subduction zone, because the intermediate depth seismic zone may be coincident with the southern continuation of the subducting slab under the arc.

Non-Gaussian Correlations between Reflected and Transmitted Intensity Patterns Emerging from Opaque Disordered Media

NASA Astrophysics Data System (ADS)

Starshynov, I.; Paniagua-Diaz, A. M.; Fayard, N.; Goetschy, A.; Pierrat, R.; Carminati, R.; Bertolotti, J.

2018-04-01

The propagation of monochromatic light through a scattering medium produces speckle patterns in reflection and transmission, and the apparent randomness of these patterns prevents direct imaging through thick turbid media. Yet, since elastic multiple scattering is fundamentally a linear and deterministic process, information is not lost but distributed among many degrees of freedom that can be resolved and manipulated. Here, we demonstrate experimentally that the reflected and transmitted speckle patterns are robustly correlated, and we unravel all the complex and unexpected features of this fundamentally non-Gaussian and long-range correlation. In particular, we show that it is preserved even for opaque media with thickness much larger than the scattering mean free path, proving that information survives the multiple scattering process and can be recovered. The existence of correlations between the two sides of a scattering medium opens up new possibilities for the control of transmitted light without any feedback from the target side, but using only information gathered from the reflected speckle.

A proposed study of multiple scattering through clouds up to 1 THz

NASA Technical Reports Server (NTRS)

Gerace, G. C.; Smith, E. K.

1992-01-01

A rigorous computation of the electromagnetic field scattered from an atmospheric liquid water cloud is proposed. The recent development of a fast recursive algorithm (Chew algorithm) for computing the fields scattered from numerous scatterers now makes a rigorous computation feasible. A method is presented for adapting this algorithm to a general case where there are an extremely large number of scatterers. It is also proposed to extend a new binary PAM channel coding technique (El-Khamy coding) to multiple levels with non-square pulse shapes. The Chew algorithm can be used to compute the transfer function of a cloud channel. Then the transfer function can be used to design an optimum El-Khamy code. In principle, these concepts can be applied directly to the realistic case of a time-varying cloud (adaptive channel coding and adaptive equalization). A brief review is included of some preliminary work on cloud dispersive effects on digital communication signals and on cloud liquid water spectra and correlations.

Urban Monitoring Based on SENTINEL-1 Data Using Permanent Scatterer Interferometry and SAR Tomography

NASA Astrophysics Data System (ADS)

Crosetto, M.; Budillon, A.; Johnsy, A.; Schirinzi, G.; Devanthéry, N.; Monserrat, O.; Cuevas-González, M.

2018-04-01

A lot of research and development has been devoted to the exploitation of satellite SAR images for deformation measurement and monitoring purposes since Differential Interferometric Synthetic Apertura Radar (InSAR) was first described in 1989. In this work, we consider two main classes of advanced DInSAR techniques: Persistent Scatterer Interferometry and Tomographic SAR. Both techniques make use of multiple SAR images acquired over the same site and advanced procedures to separate the deformation component from the other phase components, such as the residual topographic component, the atmospheric component, the thermal expansion component and the phase noise. TomoSAR offers the advantage of detecting either single scatterers presenting stable proprieties over time (Persistent Scatterers) and multiple scatterers interfering within the same range-azimuth resolution cell, a significant improvement for urban areas monitoring. This paper addresses a preliminary inter-comparison of the results of both techniques, for a test site located in the metropolitan area of Barcelona (Spain), where interferometric Sentinel-1 data were analysed.

Ab initio optical potentials and nucleon scattering on medium mass nuclei

NASA Astrophysics Data System (ADS)

Idini, A.; Barbieri, C.; Navrátil, P.

2018-03-01

We show first results for the elastic scattering of neutrons off oxygen and calcium isotopes obtained from ab initio optical potentials. The potential is derived using self-consistent Green’s function theory (SCGF) with the saturating chiral interaction NNLOsat. Calculations are compared to available scattering data and show that it is possible to reproduce low energy scattering observables in medium mass nuclei from first principles.

A New String Model: NEXUS 3

NASA Astrophysics Data System (ADS)

Werner, K.; Liu, F. M.; Ostapchenko, S.; Pierog, T.

2004-11-01

After discussing conceptual problems with the conventional string model, we present a new approach, based on a theoretically consistent multiple scattering formalism. First results for proton-proton scattering at 158 GeV are discussed.

Depolarization and Scattering of Electromagnetic Waves. Appendices.

DTIC Science & Technology

1986-06-30

for both specular point scattering and Bragg scattering in a self-consistent manner is used to express the total cross section of the flake as a...by Arbitrarily Oriented Composite Rough Surfaces. In this work the full wave approach is used to determine the modu- lations of the like and cross...analyze multiple scattering using the equation of radiative transfer with the general Stokes’ parameters. Our ultimate goal is to develop codes which will

A multiple scattering theory for EM wave propagation in a dense random medium

NASA Technical Reports Server (NTRS)

Karam, M. A.; Fung, A. K.; Wong, K. W.

1985-01-01

For a dense medium of randomly distributed scatterers an integral formulation for the total coherent field has been developed. This formulation accounts for the multiple scattering of electromagnetic waves including both the twoand three-particle terms. It is shown that under the Markovian assumption the total coherent field and the effective field have the same effective wave number. As an illustration of this theory, the effective wave number and the extinction coefficient are derived in terms of the polarizability tensor and the pair distribution function for randomly distributed small spherical scatterers. It is found that the contribution of the three-particle term increases with the particle size, the volume fraction, the frequency and the permittivity of the particle. This increase is more significant with frequency and particle size than with other parameters.

Surface complexation and precipitate geometry for aqueous Zn(II) sorption on ferrihydrite: II. XANES analysis and simulation

USGS Publications Warehouse

Waychunas, G.A.; Fuller, C.C.; Davis, J.A.; Rehr, J.J.

2003-01-01

X-ray absorption near-edge spectroscopy (XANES) analysis of sorption complexes has the advantages of high sensitivity (10- to 20-fold greater than extended X-ray absorption fine structure [EXAFS] analysis) and relative ease and speed of data collection (because of the short k-space range). It is thus a potentially powerful tool for characterization of environmentally significant surface complexes and precipitates at very low surface coverages. However, quantitative analysis has been limited largely to "fingerprint" comparison with model spectra because of the difficulty of obtaining accurate multiple-scattering amplitudes for small clusters with high confidence. In the present work, calculations of the XANES for 50- to 200-atom clusters of structure from Zn model compounds using the full multiple-scattering code Feff 8.0 accurately replicate experimental spectra and display features characteristic of specific first-neighbor anion coordination geometry and second-neighbor cation geometry and number. Analogous calculations of the XANES for small molecular clusters indicative of precipitation and sorption geometries for aqueous Zn on ferrihydrite, and suggested by EXAFS analysis, are in good agreement with observed spectral trends with sample composition, with Zn-oxygen coordination and with changes in second-neighbor cation coordination as a function of sorption coverage. Empirical analysis of experimental XANES features further verifies the validity of the calculations. The findings agree well with a complete EXAFS analysis previously reported for the same sample set, namely, that octahedrally coordinated aqueous Zn2+ species sorb as a tetrahedral complex on ferrihydrite with varying local geometry depending on sorption density. At significantly higher densities but below those at which Zn hydroxide is expected to precipitate, a mainly octahedral coordinated Zn2+ precipitate is observed. An analysis of the multiple scattering paths contributing to the XANES demonstrates the importance of scattering paths involving the anion sublattice. We also describe the specific advantages of complementary quantitative XANES and EXAFS analysis and estimate limits on the extent of structural information obtainable from XANES analysis. ?? 2003 Elsevier Science Ltd.

Pushing, pulling and electromagnetic radiation force cloaking by a pair of conducting cylindrical particles

NASA Astrophysics Data System (ADS)

Mitri, F. G.

2018-02-01

The present analysis shows that two conducting cylindrical particles illuminated by an axially-polarized electric field of plane progressive waves at arbitrary incidence will attract, repel or become totally cloaked (i.e., invisible to the transfer of linear momentum carried by the incident waves), depending on their sizes, the interparticle distance as well as the angle of incidence of the incident field. Based on the rigorous multipole expansion method and the translational addition theorem of cylindrical wave functions, the electromagnetic (EM) radiation forces arising from multiple scattering effects between a pair of perfectly conducting cylindrical particles of circular cross-sections are derived and computed. An effective incident field on a particular particle is determined first, and used subsequently with its corresponding scattered field to derive the closed-form analytical expressions for the radiation force vector components. The mathematical expressions for the EM radiation force components (i.e. longitudinal and transverse) are exact, and have been formulated in partial-wave series expansions in cylindrical coordinates involving the angle of incidence, the interparticle distance and the expansion coefficients. Numerical examples illustrate the analysis for two perfectly conducting circular cylinders in a homogeneous nonmagnetic medium of wave propagation. The computations for the dimensionless radiation force functions are performed with particular emphasis on varying the angle of incidence, the interparticle distance, and the sizes of the particles. Depending on the interparticle distance and angle of incidence, the cylinders yield total neutrality (or invisibility); they experience no force and become unresponsive to the transfer of the EM linear momentum due to multiple scattering cancellation effects. Moreover, pushing or pulling EM forces between the two cylinders arise depending on the interparticle distance, the angle of incidence and their size parameters. This study provides a complete analytical method and computations for the longitudinal and transverse radiation force components in the multiple scattering of EM plane progressive waves with potential applications in particle manipulation, optically-engineered metamaterials with reconfigurable periodicities and cloaking devices to name a few examples.

Sub-diffusive scattering parameter maps recovered using wide-field high-frequency structured light imaging.

PubMed

Kanick, Stephen Chad; McClatchy, David M; Krishnaswamy, Venkataramanan; Elliott, Jonathan T; Paulsen, Keith D; Pogue, Brian W

2014-10-01

This study investigates the hypothesis that structured light reflectance imaging with high spatial frequency patterns [Formula: see text] can be used to quantitatively map the anisotropic scattering phase function distribution [Formula: see text] in turbid media. Monte Carlo simulations were used in part to establish a semi-empirical model of demodulated reflectance ([Formula: see text]) in terms of dimensionless scattering [Formula: see text] and [Formula: see text], a metric of the first two moments of the [Formula: see text] distribution. Experiments completed in tissue-simulating phantoms showed that simultaneous analysis of [Formula: see text] spectra sampled at multiple [Formula: see text] in the frequency range [0.05-0.5] [Formula: see text] allowed accurate estimation of both [Formula: see text] in the relevant tissue range [0.4-1.8] [Formula: see text], and [Formula: see text] in the range [1.4-1.75]. Pilot measurements of a healthy volunteer exhibited [Formula: see text]-based contrast between scar tissue and surrounding normal skin, which was not as apparent in wide field diffuse imaging. These results represent the first wide-field maps to quantify sub-diffuse scattering parameters, which are sensitive to sub-microscopic tissue structures and composition, and therefore, offer potential for fast diagnostic imaging of ultrastructure on a size scale that is relevant to surgical applications.

Modelling NDE pulse-echo inspection of misorientated planar rough defects using an elastic finite element method

NASA Astrophysics Data System (ADS)

Pettit, J. R.; Walker, A. E.; Lowe, M. J. S.

2015-03-01

Pulse-echo ultrasonic NDE examination of large pressure vessel forgings is a design and construction code requirement in the power generation industry. Such inspections aim to size and characterise potential defects that may have formed during the forging process. Typically these defects have a range of orientations and surface roughnesses which can greatly affect ultrasonic wave scattering behaviour. Ultrasonic modelling techniques can provide insight into defect response and therefore aid in characterisation. However, analytical approaches to solving these scattering problems can become inaccurate, especially when applied to increasingly complex defect geometries. To overcome these limitations a elastic Finite Element (FE) method has been developed to simulate pulse-echo inspections of embedded planar defects. The FE model comprises a significantly reduced spatial domain allowing for a Monte-Carlo based approach to consider multiple realisations of defect orientation and surface roughness. The results confirm that defects aligned perpendicular to the path of beam propagation attenuate ultrasonic signals according to the level of surface roughness. However, for defects orientated away from this plane, surface roughness can increase the magnitude of the scattered component propagating back along the path of the incident beam. This study therefore highlights instances where defect roughness increases the magnitude of ultrasonic scattered signals, as opposed to attenuation which is more often assumed.

Development of a human eye model incorporated with intraocular scattering for visual performance assessment

NASA Astrophysics Data System (ADS)

Chen, Yi-Chun; Jiang, Chong-Jhih; Yang, Tsung-Hsun; Sun, Ching-Cherng

2012-07-01

A biometry-based human eye model was developed by using the empirical anatomic and optical data of ocular parameters. The gradient refractive index of the crystalline lens was modeled by concentric conicoid isoindical surfaces and was adaptive to accommodation and age. The chromatic dispersion of ocular media was described by Cauchy equations. The intraocular scattering model was composed of volumetric Mie scattering in the cornea and the crystalline lens, and a diffusive-surface model at the retina fundus. The retina was regarded as a Lambertian surface and was assigned its corresponding reflectance at each wavelength. The optical performance of the eye model was evaluated in CodeV and ASAP and presented by the modulation transfer functions at single and multiple wavelengths. The chromatic optical powers obtained from this model resembled that of the average physiological eyes. The scattering property was assessed by means of glare veiling luminance and compared with the CIE general disability glare equation. By replacing the transparent lens with a cataractous lens, the disability glare curve of cataracts was generated to compare with the normal disability glare curve. This model has high potential for investigating visual performance in ordinary lighting and display conditions and under the influence of glare sources.

Proton energy and scattering angle radiographs to improve proton treatment planning: a Monte Carlo study

NASA Astrophysics Data System (ADS)

Biegun, A. K.; Takatsu, J.; Nakaji, T.; van Goethem, M. J.; van der Graaf, E. R.; Koffeman, E. N.; Visser, J.; Brandenburg, S.

2016-12-01

The novel proton radiography imaging technique has a large potential to be used in direct measurement of the proton energy loss (proton stopping power, PSP) in various tissues in the patient. The uncertainty of PSPs, currently obtained from translation of X-ray Computed Tomography (xCT) images, should be minimized from 3-5% or higher to less than 1%, to make the treatment plan with proton beams more accurate, and thereby better treatment for the patient. With Geant4 we simulated a proton radiography detection system with two position-sensitive and residual energy detectors. A complex phantom filled with various materials (including tissue surrogates), was placed between the position sensitive detectors. The phantom was irradiated with 150 MeV protons and the energy loss radiograph and scattering angles were studied. Protons passing through different materials in the phantom lose energy, which was used to create a radiography image of the phantom. The multiple Coulomb scattering of a proton traversing different materials causes blurring of the image. To improve image quality and material identification in the phantom, we selected protons with small scattering angles. A good quality proton radiography image, in which various materials can be recognized accurately, and in combination with xCT can lead to more accurate relative stopping powers predictions.

Neutron-deuteron analyzing power data at En=22.5 MeV

NASA Astrophysics Data System (ADS)

Weisel, G. J.; Tornow, W.; Crowell, A. S.; Esterline, J. H.; Hale, G. M.; Howell, C. R.; O'Malley, P. D.; Tompkins, J. R.; Witała, H.

2014-05-01

We present measurements of n-d analyzing power, Ay(θ), at En=22.5 MeV. The experiment uses a shielded neutron source which produced polarized neutrons via the 2H(d⃗,n⃗)3He reaction. It also uses a deuterated liquid-scintillator center detector and six pairs of liquid-scintillator neutron side detectors. Elastic neutron scattering events are identified by using time-of-flight techniques and by setting a window in the center detector pulse-height spectrum. The beam polarization is monitored by using a high-pressure helium gas cell and an additional pair of liquid-scintillator side detectors. The n-d Ay(θ) data were corrected for finite-geometry and multiple-scattering effects using a Monte Carlo simulation of the experiment. The 22.5-MeV data demonstrate that the three-nucleon analyzing power puzzle also exists at this energy. They show a significant discrepancy with predictions of high-precision nucleon-nucleon potentials alone or combined with Tucscon-Melbourne or Urbana IX three-nucleon forces, as well as currently available effective-field theory based potentials of next-to-next-to-next-to-leading order.

A Real-Time Clinical Endoscopic System for Intraluminal, Multiplexed Imaging of Surface-Enhanced Raman Scattering Nanoparticles

PubMed Central

Garai, Ellis; Loewke, Nathan O.; Rogalla, Stephan; Mandella, Michael J.; Felt, Stephen A.; Friedland, Shai; Liu, Jonathan T. C.; Gambhir, Sanjiv S.; Contag, Christopher H.

2015-01-01

The detection of biomarker-targeting surface-enhanced Raman scattering (SERS) nanoparticles (NPs) in the human gastrointestinal tract has the potential to improve early cancer detection; however, a clinically relevant device with rapid Raman-imaging capability has not been described. Here we report the design and in vivo demonstration of a miniature, non-contact, opto-electro-mechanical Raman device as an accessory to clinical endoscopes that can provide multiplexed molecular data via a panel of SERS NPs. This device enables rapid circumferential scanning of topologically complex luminal surfaces of hollow organs (e.g., colon and esophagus) and produces quantitative images of the relative concentrations of SERS NPs that are present. Human and swine studies have demonstrated the speed and simplicity of this technique. This approach also offers unparalleled multiplexing capabilities by simultaneously detecting the unique spectral fingerprints of multiple SERS NPs. Therefore, this new screening strategy has the potential to improve diagnosis and to guide therapy by enabling sensitive quantitative molecular detection of small and otherwise hard-to-detect lesions in the context of white-light endoscopy. PMID:25923788

Apparatus for measuring particle properties

DOEpatents

Rader, D.J.; Castaneda, J.N.; Grasser, T.W.; Brockmann, J.E.

1998-08-11

An apparatus is described for determining particle properties from detected light scattered by the particles. The apparatus uses a light beam with novel intensity characteristics to discriminate between particles that pass through the beam and those that pass through an edge of the beam. The apparatus can also discriminate between light scattered by one particle and light scattered by multiple particles. The particle`s size can be determined from the intensity of the light scattered. The particle`s velocity can be determined from the elapsed time between various intensities of the light scattered. 11 figs.

Modeling of scattering from ice surfaces

NASA Astrophysics Data System (ADS)

Dahlberg, Michael Ross

Theoretical research is proposed to study electromagnetic wave scattering from ice surfaces. A mathematical formulation that is more representative of the electromagnetic scattering from ice, with volume mechanisms included, and capable of handling multiple scattering effects is developed. This research is essential to advancing the field of environmental science and engineering by enabling more accurate inversion of remote sensing data. The results of this research contributed towards a more accurate representation of the scattering from ice surfaces, that is computationally more efficient and that can be applied to many remote-sensing applications.

Numerical solution of inverse scattering for near-field optics.

PubMed

Bao, Gang; Li, Peijun

2007-06-01

A novel regularized recursive linearization method is developed for a two-dimensional inverse medium scattering problem that arises in near-field optics, which reconstructs the scatterer of an inhomogeneous medium located on a substrate from data accessible through photon scanning tunneling microscopy experiments. Based on multiple frequency scattering data, the method starts from the Born approximation corresponding to weak scattering at a low frequency, and each update is obtained by continuation on the wavenumber from solutions of one forward problem and one adjoint problem of the Helmholtz equation.

Nonparametric estimation of the heterogeneity of a random medium using compound Poisson process modeling of wave multiple scattering.

PubMed

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.

Label-free tomographic reconstruction of optically thick structures using GLIM (Conference Presentation)

NASA Astrophysics Data System (ADS)

Kandel, Mikhail E.; Kouzehgarani, Ghazal N.; Ngyuen, Tan H.; Gillette, Martha U.; Popescu, Gabriel

2017-02-01

Although the contrast generated in transmitted light microscopy is due to the elastic scattering of light, multiple scattering scrambles the image and reduces overall visibility. To image both thin and thick samples, we turn to gradient light interference microscopy (GLIM) to simultaneously measure morphological parameters such as cell mass, volume, and surfaces as they change through time. Because GLIM combines multiple intensity images corresponding to controlled phase offsets between laterally sheared beams, incoherent contributions from multiple scattering are implicitly cancelled during the phase reconstruction procedure. As the interfering beams traverse near identical paths, they remain comparable in power and interfere with optimal contrast. This key property lets us obtain tomographic parameters from wide field z-scans after simple numerical processing. Here we show our results on reconstructing tomograms of bovine embryos, characterizing the time-lapse growth of HeLa cells in 3D, and preliminary results on imaging much larger specimen such as brain slices.

Magnetotransport of multiple-band nearly antiferromagnetic metals due to hot-spot scattering

DOE PAGES

Koshelev, A. E.

2016-09-30

Multiple-band electronic structure and proximity to antiferromagnetic (AF) instability are the key properties of iron-based superconductors. In this paper, we explore the influence of scattering by the AF spin fluctuations on transport of multiple-band metals above the magnetic transition. A salient feature of scattering on the AF fluctuations is that it is strongly enhanced at the Fermi surface locations where the nesting is perfect (“hot spots” or “hot lines”). We review derivation of the collision integral for the Boltzmann equation due to AF-fluctuations scattering. In the paramagnetic state, the enhanced scattering rate near the hot lines leads to anomalous behaviormore » of electronic transport in magnetic field. We explore this behavior by analytically solving the Boltzmann transport equation with approximate transition rates. This approach accounts for return scattering events and is more accurate than the relaxation-time approximation. The magnetic-field dependences are characterized by two very different field scales: the lower scale is set by the hot-spot width and the higher scale is set by the total scattering amplitude. A conventional magnetotransport behavior is limited to magnetic fields below the lower scale. In the wide range in-between these two scales, the longitudinal conductivity has linear dependence on the magnetic field and the Hall conductivity has quadratic dependence. The linear dependence of the diagonal component reflects growth of the Fermi-surface area affected by the hot spots proportional to the magnetic field. Finally, we discuss applicability of this theoretical framework for describing of anomalous magnetotransport properties in different iron pnictides and chalcogenides in the paramagnetic state.« less

Age scatter in cosmogenic exposure-age chronologies in the McMurdo Dry Valleys, Antarctica: implications for regional glacial history and sampling strategies

NASA Astrophysics Data System (ADS)

Swanger, K. M.; Schaefer, J. M.; Winckler, G.; Lamp, J. L.; Marchant, D. R.

2016-12-01

Based on surface exposure dating of moraines and drifts, East Antarctic outlet glaciers in the McMurdo Dry Valleys (MDV) advanced during the mid-Pliocene and/or early-Pleistocene. However, scatter in exposure ages is common for these deposits (and other glacial drifts throughout Antarctica), making it difficult to tie glacial advances to specific climate intervals. In order to constrain the sources of scatter, we mapped and dated 15 cold-based drifts in Taylor Valley and the Olympus Range in the MDV. A secondary goal was to build a regional climate record, for comparison with fluctuations of the local outlet glaciers. Our alpine drift record is confined to the late-Pleistocene, with glacial advances during interglacial periods. Based on 54 3He exposure dates on alpine drifts, age scatter is common in the MDV on both recent and ancient deposits. Where it occurs, age scatter is likely caused by inheritance of cosmogenic nuclides previous to glacial entrainment and stacking of multiple cold-based drifts. Nuclide inheritance of >1 Myr is possible, but this is relatively rare and confined to regions where englacial debris is sourced from stable, high-elevation plateaus. On the other hand, drifts associated with glaciers bound by steep cirque headwalls and arêtes exhibit significantly less age scatter. Given the cold-based nature of MDV alpine and outlet glaciers, deposition of multiple stacked drift sheets also contributes to age scatter, with the implication that it might be possible to date multiple advances of cold-based ice. These results serve to inform better sampling strategies on cold-based drifts throughout Antarctica.

Mesoporous multi-shelled ZnO microspheres for the scattering layer of dye sensitized solar cell with a high efficiency

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

Xia, Weiwei; Mei, Chao; Zeng, Xianghua, E-mail: xhzeng@yzu.edu.cn

2016-03-14

Both light scattering and dye adsorbing are important for the power conversion efficiency PCE performance of dye sensitized solar cell (DSSC). Nanostructured scattering layers with a large specific surface area are regarded as an efficient way to improve the PCE by increasing dye adsorbing, but excess adsorbed dye will hinder light scattering and light penetration. Thus, how to balance the dye adsorbing and light penetration is a key problem to improve the PCE performance. Here, multiple-shelled ZnO microspheres with a mesoporous surface are fabricated by a hydrothermal method and are used as scattering layers on the TiO{sub 2} photoanode ofmore » the DSSC in the presence of N719 dye and iodine–based electrolyte, and the results reveal that the DSSCs based on triple shelled ZnO microsphere with a mesoporous surface exhibit an enhanced PCE of 7.66%, which is 13.0% higher than those without the scattering layers (6.78%), indicating that multiple-shelled microspheres with a mesoporous surface can ensure enough light scattering between the shells, and a favorable concentration of the adsorbed dye can improve the light penetration. These results may provide a promising pathway to obtain the high efficient DSSCs.« less

Generalized Landauer equation: Absorption-controlled diffusion processes

NASA Astrophysics Data System (ADS)

Godoy, Salvador; García-Colín, L. S.; Micenmacher, Victor

1999-05-01

The exact expression of the one-dimensional Boltzmann multiple-scattering coefficients, for the passage of particles through a slab of a given material, is obtained in terms of the single-scattering cross section of the material, including absorption. The remarkable feature of the result is that for multiple scattering in a metal, free from absorption, one recovers the well-known Landauer result for conduction electrons. In the case of particles, such as neutrons, moving through a weak absorbing media, Landuer's formula is modified due to the absorption cross section. For photons, in a strong absorbing media, one recovers the Lambert-Beer equation. In this latter case one may therefore speak of absorption-controlled diffusive processes.

Experimental verification of nanofluid shear-wave reconversion in ultrasonic fields.

PubMed

Forrester, Derek Michael; Huang, Jinrui; Pinfield, Valerie J; Luppé, Francine

2016-03-14

Here we present the verification of shear-mediated contributions to multiple scattering of ultrasound in suspensions. Acoustic spectroscopy was carried out with suspensions of silica of differing particle sizes and concentrations in water to find the attenuation at a broad range of frequencies. As the particle sizes approach the nanoscale, commonly used multiple scattering models fail to match experimental results. We develop a new model, taking into account shear mediated contributions, and find excellent agreement with the attenuation spectra obtained using two types of spectrometer. The results determine that shear-wave phenomena must be considered in ultrasound characterisation of nanofluids at even relatively low concentrations of scatterers that are smaller than one micrometre in diameter.

Neutron crosstalk between liquid scintillators

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

Verbeke, J. M.; Prasad, M. K.; Snyderman, N. J.

2015-05-01

We propose a method to quantify the fractions of neutrons scattering between liquid scintillators. Using a spontaneous fission source, this method can be utilized to quickly characterize an array of liquid scintillators in terms of crosstalk. The point model theory due to Feynman is corrected to account for these multiple scatterings. Using spectral information measured by the liquid scintillators, fractions of multiple scattering can be estimated, and mass reconstruction of fissile materials under investigation can be improved. Monte Carlo simulations of mono-energetic neutron sources were performed to estimate neutron crosstalk. A californium source in an array of liquid scintillators wasmore » modeled to illustrate the improvement of the mass reconstruction.« less

Ratioed scatter diagrams - An erotetic method for phase identification on complex surfaces using scanning Auger microscopy

NASA Technical Reports Server (NTRS)

Browning, R.

1984-01-01

By ratioing multiple Auger intensities and plotting a two-dimensional occupational scatter diagram while digitally scanning across an area, the number and elemental association of surface phases can be determined. This can prove a useful tool in scanning Auger microscopic analysis of complex materials. The technique is illustrated by results from an anomalous region on the reaction zone of a SiC/Ti-6Al-4V metal matrix composite material. The anomalous region is shown to be a single phase associated with sulphur and phosphorus impurities. Imaging of a selected phase from the ratioed scatter diagram is possible and may be a useful technique for presenting multiple scanning Auger images.

Polarized BRDF for coatings based on three-component assumption

NASA Astrophysics Data System (ADS)

Liu, Hong; Zhu, Jingping; Wang, Kai; Xu, Rong

2017-02-01

A pBRDF(polarized bidirectional reflection distribution function) model for coatings is given based on three-component reflection assumption in order to improve the polarized scattering simulation capability for space objects. In this model, the specular reflection is given based on microfacet theory, the multiple reflection and volume scattering are given separately according to experimental results. The polarization of specular reflection is considered from Fresnel's law, and both multiple reflection and volume scattering are assumed depolarized. Simulation and measurement results of two satellite coating samples SR107 and S781 are given to validate that the pBRDF modeling accuracy can be significantly improved by the three-component model given in this paper.

Scattering Models and Basic Experiments in the Microwave Regime

NASA Technical Reports Server (NTRS)

Fung, A. K.; Blanchard, A. J. (Principal Investigator)

1985-01-01

The objectives of research over the next three years are: (1) to develop a randomly rough surface scattering model which is applicable over the entire frequency band; (2) to develop a computer simulation method and algorithm to simulate scattering from known randomly rough surfaces, Z(x,y); (3) to design and perform laboratory experiments to study geometric and physical target parameters of an inhomogeneous layer; (4) to develop scattering models for an inhomogeneous layer which accounts for near field interaction and multiple scattering in both the coherent and the incoherent scattering components; and (5) a comparison between theoretical models and measurements or numerical simulation.

Ultrasound scatter in heterogeneous 3D microstructures: Parameters affecting multiple scattering

NASA Astrophysics Data System (ADS)

Engle, B. J.; Roberts, R. A.; Grandin, R. J.

2018-04-01

This paper reports on a computational study of ultrasound propagation in heterogeneous metal microstructures. Random spatial fluctuations in elastic properties over a range of length scales relative to ultrasound wavelength can give rise to scatter-induced attenuation, backscatter noise, and phase front aberration. It is of interest to quantify the dependence of these phenomena on the microstructure parameters, for the purpose of quantifying deleterious consequences on flaw detectability, and for the purpose of material characterization. Valuable tools for estimation of microstructure parameters (e.g. grain size) through analysis of ultrasound backscatter have been developed based on approximate weak-scattering models. While useful, it is understood that these tools display inherent inaccuracy when multiple scattering phenomena significantly contribute to the measurement. It is the goal of this work to supplement weak scattering model predictions with corrections derived through application of an exact computational scattering model to explicitly prescribed microstructures. The scattering problem is formulated as a volume integral equation (VIE) displaying a convolutional Green-function-derived kernel. The VIE is solved iteratively employing FFT-based con-volution. Realizations of random microstructures are specified on the micron scale using statistical property descriptions (e.g. grain size and orientation distributions), which are then spatially filtered to provide rigorously equivalent scattering media on a length scale relevant to ultrasound propagation. Scattering responses from ensembles of media representations are averaged to obtain mean and variance of quantities such as attenuation and backscatter noise levels, as a function of microstructure descriptors. The computational approach will be summarized, and examples of application will be presented.

Sensitive SERS detection of DNA methyltransferase by target triggering primer generation-based multiple signal amplification strategy.

PubMed

Li, Ying; Yu, Chuanfeng; Han, Huixia; Zhao, Caisheng; Zhang, Xiaoru

2016-07-15

A novel and sensitive surface-enhanced Raman scattering (SERS) method is proposed for the assay of DNA methyltransferase (MTase) activity and evaluation of inhibitors by developing a target triggering primer generation-based multiple signal amplification strategy. By using of a duplex substrate for Dam MTase, two hairpin templates and a Raman probe, multiple signal amplification mode is achieved. Once recognized by Dam MTase, the duplex substrate can be cleaved by Dpn I endonuclease and two primers are released for triggering the multiple signal amplification reaction. Consequently, a wide dynamic range and remarkably high sensitivity are obtained under isothermal conditions. The detection limit is 2.57×10(-4)UmL(-1). This assay exhibits an excellent selectivity and is successfully applied in the screening of inhibitors for Dam MTase. In addition, this novel sensing system is potentially universal as the recognition element can be conveniently designed for other target analytes by changing the substrate of DNA MTase. Copyright © 2016 Elsevier B.V. All rights reserved.

Comparisons between GRNTRN simulations and beam measurements of proton lateral broadening distributions

NASA Astrophysics Data System (ADS)

Mertens, Christopher; Moyers, Michael; Walker, Steven; Tweed, John

Recent developments in NASA's High Charge and Energy Transport (HZETRN) code have included lateral broadening of primary ion beams due to small-angle multiple Coulomb scattering, and coupling of the ion-nuclear scattering interactions with energy loss and straggling. The new version of HZETRN based on Green function methods, GRNTRN, is suitable for modeling transport with both space environment and laboratory boundary conditions. Multiple scattering processes are a necessary extension to GRNTRN in order to accurately model ion beam experiments, to simulate the physical and biological-effective radiation dose, and to develop new methods and strategies for light ion radiation therapy. In this paper we compare GRNTRN simulations of proton lateral scattering distributions with beam measurements taken at Loma Linda Medical University. The simulated and measured lateral proton distributions will be compared for a 250 MeV proton beam on aluminum, polyethylene, polystyrene, bone, iron, and lead target materials.

Algorithms for radiative transfer simulations for aerosol retrieval

NASA Astrophysics Data System (ADS)

Mukai, Sonoyo; Sano, Itaru; Nakata, Makiko

2012-11-01

Aerosol retrieval work from satellite data, i.e. aerosol remote sensing, is divided into three parts as: satellite data analysis, aerosol modeling and multiple light scattering calculation in the atmosphere model which is called radiative transfer simulation. The aerosol model is compiled from the accumulated measurements during more than ten years provided with the world wide aerosol monitoring network (AERONET). The radiative transfer simulations take Rayleigh scattering by molecules and Mie scattering by aerosols in the atmosphere, and reflection by the Earth surface into account. Thus the aerosol properties are estimated by comparing satellite measurements with the numerical values of radiation simulations in the Earth-atmosphere-surface model. It is reasonable to consider that the precise simulation of multiple light-scattering processes is necessary, and needs a long computational time especially in an optically thick atmosphere model. Therefore efficient algorithms for radiative transfer problems are indispensable to retrieve aerosols from space.

Time-reversal MUSIC imaging of extended targets.

PubMed

Marengo, Edwin A; Gruber, Fred K; Simonetti, Francesco

2007-08-01

This paper develops, within a general framework that is applicable to rather arbitrary electromagnetic and acoustic remote sensing systems, a theory of time-reversal "MUltiple Signal Classification" (MUSIC)-based imaging of extended (nonpoint-like) scatterers (targets). The general analysis applies to arbitrary remote sensing geometry and sheds light onto how the singular system of the scattering matrix relates to the geometrical and propagation characteristics of the entire transmitter-target-receiver system and how to use this effect for imaging. All the developments are derived within exact scattering theory which includes multiple scattering effects. The derived time-reversal MUSIC methods include both interior sampling, as well as exterior sampling (or enclosure) approaches. For presentation simplicity, particular attention is given to the time-harmonic case where the informational wave modes employed for target interrogation are purely spatial, but the corresponding generalization to broadband fields is also given. This paper includes computer simulations illustrating the derived theory and algorithms.

Using Monte Carlo ray tracing simulations to model the quantum harmonic oscillator modes observed in uranium nitride

NASA Astrophysics Data System (ADS)

Lin, J. Y. Y.; Aczel, A. A.; Abernathy, D. L.; Nagler, S. E.; Buyers, W. J. L.; Granroth, G. E.

2014-04-01

Recently an extended series of equally spaced vibrational modes was observed in uranium nitride (UN) by performing neutron spectroscopy measurements using the ARCS and SEQUOIA time-of-flight chopper spectrometers [A. A. Aczel et al., Nat. Commun. 3, 1124 (2012), 10.1038/ncomms2117]. These modes are well described by three-dimensional isotropic quantum harmonic oscillator (QHO) behavior of the nitrogen atoms, but there are additional contributions to the scattering that complicate the measured response. In an effort to better characterize the observed neutron scattering spectrum of UN, we have performed Monte Carlo ray tracing simulations of the ARCS and SEQUOIA experiments with various sample kernels, accounting for nitrogen QHO scattering, contributions that arise from the acoustic portion of the partial phonon density of states, and multiple scattering. These simulations demonstrate that the U and N motions can be treated independently, and show that multiple scattering contributes an approximate Q-independent background to the spectrum at the oscillator mode positions. Temperature-dependent studies of the lowest few oscillator modes have also been made with SEQUOIA, and our simulations indicate that the T dependence of the scattering from these modes is strongly influenced by the uranium lattice.

Atmospheric neutrino oscillations from upward throughgoing muon multiple scattering in MACRO

NASA Astrophysics Data System (ADS)

MACRO Collaboration; Ambrosio, M.; Antolini, R.; Bakari, D.; Baldini, A.; Barbarino, G. C.; Barish, B. C.; Battistoni, G.; Becherini, Y.; Bellotti, R.; Bemporad, C.; Bernardini, P.; Bilokon, H.; Bloise, C.; Bower, C.; Brigida, M.; Bussino, S.; Cafagna, F.; Calicchio, M.; Campana, D.; Carboni, M.; Caruso, R.; Cecchini, S.; Cei, F.; Chiarella, V.; Chiarusi, T.; Choudhary, B. C.; Coutu, S.; Cozzi, M.; de Cataldo, G.; Dekhissi, H.; de Marzo, C.; de Mitri, I.; Derkaoui, J.; de Vincenzi, M.; di Credico, A.; Favuzzi, C.; Forti, C.; Fusco, P.; Giacomelli, G.; Giannini, G.; Giglietto, N.; Giorgini, M.; Grassi, M.; Grillo, A.; Gustavino, C.; Habig, A.; Hanson, K.; Heinz, R.; Iarocci, E.; Katsavounidis, E.; Katsavounidis, I.; Kearns, E.; Kim, H.; Kumar, A.; Kyriazopoulou, S.; Lamanna, E.; Lane, C.; Levin, D. S.; Lipari, P.; Longo, M. J.; Loparco, F.; Maaroufi, F.; Mancarella, G.; Mandrioli, G.; Manzoor, S.; Margiotta, A.; Marini, A.; Martello, D.; Marzari-Chiesa, A.; Mazziotta, M. N.; Michael, D. G.; Mikheyev, S.; Monacelli, P.; Montaruli, T.; Monteno, M.; Mufson, S.; Musser, J.; Nicolò, D.; Nolty, R.; Orth, C.; Osteria, G.; Palamara, O.; Patera, V.; Patrizii, L.; Pazzi, R.; Peck, C. W.; Perrone, L.; Petrera, S.; Popa, V.; Rainò, A.; Reynoldson, J.; Ronga, F.; Rrhioua, A.; Satriano, C.; Scapparone, E.; Scholberg, K.; Sciubba, A.; Serra, P.; Sioli, M.; Sirri, G.; Sitta, M.; Spinelli, P.; Spinetti, M.; Spurio, M.; Steinberg, R.; Stone, J. L.; Sulak, L. R.; Surdo, A.; Tarlè, G.; Togo, V.; Vakili, M.; Walter, C. W.; Webb, R.

2003-07-01

The energy of atmospheric neutrinos detected by MACRO was estimated using multiple Coulomb scattering of upward throughgoing muons. This analysis allows a test of atmospheric neutrino oscillations, relying on the distortion of the muon energy distribution. These results have been combined with those coming from the upward throughgoing muon angular distribution only. Both analyses are independent of the neutrino flux normalization and provide strong evidence, above the /4σ level, in favour of neutrino oscillations.

Adaptation of the University of Wisconsin High Spectral Resolution Lidar for Polarization and Multiple Scattering Measurements

NASA Technical Reports Server (NTRS)

Eloranta, E. W.; Piironen, P. K.

1992-01-01

A new implementation of the High Spectral Resolution Lidar (HSRL) in an instrument van which allows measurements during field experiments is described. The instrument was modified to provide measurements of depolarization. In addition, both the signal amplitude and depolarization variations with receiver field of view are simultaneously measured. These modifications allow discrimination of ice clouds from water clouds and observation of multiple scattering contributions to the lidar return.

Perspectives: Nanofibers and nanowires for disordered photonics

NASA Astrophysics Data System (ADS)

Pisignano, Dario; Persano, Luana; Camposeo, Andrea

2017-03-01

As building blocks of microscopically non-homogeneous materials, semiconductor nanowires and polymer nanofibers are emerging component materials for disordered photonics, with unique properties of light emission and scattering. Effects found in assemblies of nanowires and nanofibers include broadband reflection, significant localization of light, strong and collective multiple scattering, enhanced absorption of incident photons, synergistic effects with plasmonic particles, and random lasing. We highlight recent related discoveries, with a focus on material aspects. The control of spatial correlations in complex assemblies during deposition, the coupling of modes with efficient transmission channels provided by nanofiber waveguides, and the embedment of random architectures into individually coded nanowires will allow the potential of these photonic materials to be fully exploited, unconventional physics to be highlighted, and next-generation optical devices to be achieved. The prospects opened by this technology include enhanced random lasing and mode-locking, multi-directionally guided coupling to sensors and receivers, and low-cost encrypting miniatures for encoders and labels.

Fluorescence-Raman Dual Modal Endoscopic System for Multiplexed Molecular Diagnostics

NASA Astrophysics Data System (ADS)

Jeong, Sinyoung; Kim, Yong-Il; Kang, Homan; Kim, Gunsung; Cha, Myeong Geun; Chang, Hyejin; Jung, Kyung Oh; Kim, Young-Hwa; Jun, Bong-Hyun; Hwang, Do Won; Lee, Yun-Sang; Youn, Hyewon; Lee, Yoon-Sik; Kang, Keon Wook; Lee, Dong Soo; Jeong, Dae Hong

2015-03-01

Optical endoscopic imaging, which was recently equipped with bioluminescence, fluorescence, and Raman scattering, allows minimally invasive real-time detection of pathologies on the surface of hollow organs. To characterize pathologic lesions in a multiplexed way, we developed a dual modal fluorescence-Raman endomicroscopic system (FRES), which used fluorescence and surface-enhanced Raman scattering nanoprobes (F-SERS dots). Real-time, in vivo, and multiple target detection of a specific cancer was successful, based on the fast imaging capability of fluorescence signals and the multiplex capability of simultaneously detected SERS signals using an optical fiber bundle for intraoperative endoscopic system. Human epidermal growth factor receptor 2 (HER2) and epidermal growth factor receptor (EGFR) on the breast cancer xenografts in a mouse orthotopic model were successfully detected in a multiplexed way, illustrating the potential of FRES as a molecular diagnostic instrument that enables real-time tumor characterization of receptors during routine endoscopic procedures.

Transparent, flexible surface enhanced Raman scattering substrates based on Ag-coated structured PET (polyethylene terephthalate) for in-situ detection

NASA Astrophysics Data System (ADS)

Zuo, Zewen; Zhu, Kai; Gu, Chuan; Wen, Yibing; Cui, Guanglei; Qu, Jun

2016-08-01

Transparent, flexible surface-enhanced Raman scattering (SERS) substrates were fabricated by metalization of structured polyethylene terephthalate (PET) sheets. The resultant Ag-coated structured PET SERS substrates were revealed to be highly sensitive with good reproducibility and stability, an enhancement factor of 3 × 106 was acquired, which can be attributed mainly to the presence of plentiful multiple-type hot spots within the quasi-three-dimensional surface of the structured PET obtained by oxygen plasma etching. In addition, detections of model molecules on fruit skin were also carried out, demonstrating the great potential of the Ag-coated structured PET in in-situ detection of analyte on irregular objects. Importantly, the technique used for the preparation of such substrate is completely compatible with well-established silicon device technologies, and large-area fabrication with low cost can be readily realized.

Low-temperature thermoelectric power factor enhancement by controlling nanoparticle size distribution.

PubMed

Zebarjadi, Mona; Esfarjani, Keivan; Bian, Zhixi; Shakouri, Ali

2011-01-12

Coherent potential approximation is used to study the effect of adding doped spherical nanoparticles inside a host matrix on the thermoelectric properties. This takes into account electron multiple scatterings that are important in samples with relatively high volume fraction of nanoparticles (>1%). We show that with large fraction of uniform small size nanoparticles (∼1 nm), the power factor can be enhanced significantly. The improvement could be large (up to 450% for GaAs) especially at low temperatures when the mobility is limited by impurity or nanoparticle scattering. The advantage of doping via embedded nanoparticles compared to the conventional shallow impurities is quantified. At the optimum thermoelectric power factor, the electrical conductivity of the nanoparticle-doped material is larger than that of impurity-doped one at the studied temperature range (50-500 K) whereas the Seebeck coefficient of the nanoparticle doped material is enhanced only at low temperatures (∼50 K).

Simulating propagation of coherent light in random media using the Fredholm type integral equation

NASA Astrophysics Data System (ADS)

Kraszewski, Maciej; Pluciński, Jerzy

2017-06-01

Studying propagation of light in random scattering materials is important for both basic and applied research. Such studies often require usage of numerical method for simulating behavior of light beams in random media. However, if such simulations require consideration of coherence properties of light, they may become a complex numerical problems. There are well established methods for simulating multiple scattering of light (e.g. Radiative Transfer Theory and Monte Carlo methods) but they do not treat coherence properties of light directly. Some variations of these methods allows to predict behavior of coherent light but only for an averaged realization of the scattering medium. This limits their application in studying many physical phenomena connected to a specific distribution of scattering particles (e.g. laser speckle). In general, numerical simulation of coherent light propagation in a specific realization of random medium is a time- and memory-consuming problem. The goal of the presented research was to develop new efficient method for solving this problem. The method, presented in our earlier works, is based on solving the Fredholm type integral equation, which describes multiple light scattering process. This equation can be discretized and solved numerically using various algorithms e.g. by direct solving the corresponding linear equations system, as well as by using iterative or Monte Carlo solvers. Here we present recent development of this method including its comparison with well-known analytical results and a finite-difference type simulations. We also present extension of the method for problems of multiple scattering of a polarized light on large spherical particles that joins presented mathematical formalism with Mie theory.

Temporal evolution of the Green's function reconstruction in the seismic coda

NASA Astrophysics Data System (ADS)

Clerc, V.; Roux, P.; Campillo, M.

2013-12-01

In presence of multiple scattering, the wavefield evolves towards an equipartitioned state, equivalent to ambient noise. CAMPILLO and PAUL (2003) reconstructed the surface wave part of the Green's function between three pairs of stations in Mexico. The data indicate that the time asymmetry between causal and acausal part of the Green's function is less pronounced when the correlation is performed in the later windows of the coda. These results on the correlation of diffuse waves provide another perspective on the reconstruction of Green function which is independent of the source distribution and which suggests that if the time of observation is long enough, a single source could be sufficient. The paper by ROUX et al. (2005) provides a theoretical frame for the reconstruction of the Green's function in a homogeneous middle. In a multiple scattering medium with a single source, scatterers behave as secondary sources according to the Huygens principle. Coda waves are relevant to multiple scattering, a regime which can be approximated by diffusion for long lapse times. We express the temporal evolution of the correlation function between two receivers as a function of the secondary sources. We are able to predict the effect of the persistence of the net flux of energy observed by CAMPILLO and PAUL (2003) in numerical simulations. This method is also effective in order to retrieve the scattering mean free path. We perform a partial reconstruction of the Green's function in a strongly scattering medium in numerical simulations. The prediction of the flux asymmetry allows defining the parts of the coda providing the same information as ambient noise cross correlation.

Hadron multiplicity variation with Q2 and scale breaking of the Hadron distributions in deep inelastic muon-proton scattering

NASA Astrophysics Data System (ADS)

Arneodo, M.; Arvidson, A.; Aubert, J. J.; Badelek, B.; Beaufays, J.; Bee, C. P.; Benchouk, C.; Berghoff, G.; Bird, I.; Blum, D.; Böhm, E.; de Bouard, X.; Brasse, F. W.; Braun, H.; Broll, C.; Brown, S.; Brück, H.; Calen, H.; Chima, J. S.; Ciborowski, J.; Clifft, R.; Coignet, G.; Combley, F.; Coughlan, J.; D'Agostini, G.; Dahlgren, S.; Dengler, F.; Derado, I.; Dreyer, T.; Drees, J.; Düren, M.; Eckardt, V.; Edwards, A.; Edwards, M.; Ernst, T.; Eszes, G.; Favier, J.; Ferrero, M. I.; Figiel, J.; Flauger, W.; Foster, J.; Gabathuler, E.; Gajewski, J.; Gamet, R.; Gayler, J.; Geddes, N.; Giubellino, P.; Grafström, P.; Grard, F.; Haas, J.; Hagberg, E.; Hamacher, K.; Hasert, F. J.; Hayman, P.; Heusse, P.; Jaffré, M.; Jacholkowska, A.; Janata, F.; Jancso, G.; Johnson, A. S.; Kabuss, E. M.; Kellner, G.; Korbel, V.; Korzen, B.; Krüger, J.; Kullander, S.; Landgraf, U.; Lanske, D.; Loken, J.; Long, K.; Malecki, P.; Maire, M.; Manz, A.; Maselli, S.; Mohr, W.; Montanet, F.; Montgomery, H. E.; Nagy, E.; Nassalski, J.; Norton, P. R.; Oakham, F. G.; Osborne, A. M.; Pascaud, C.; Pawlik, B.; Payre, P.; Peroni, C.; Peschel, H.; Pessard, H.; Pettingale, J.; Pietrzyk, B.; Pietrzyk, U.; Pönsgen, B.; Pötsch, M.; Preissner, H.; Renton, P.; Ribarics, P.; Rith, K.; Rondio, E.; Scheer, M.; Schlagböhmer, A.; Schiemann, H.; Schmitz, N.; Schneegans, M.; Schneider, A.; Sholz, M.; Schröder, T.; Schouten, M.; Schultze, K.; Sloan, T.; Stier, H. E.; Stockhausen, W.; Studt, M.; Taylor, G. N.; Thénard, J. M.; Thompson, J. C.; de La Torre, A.; Toth, J.; Urban, L.; Urban, L.; Wallucks, W.; Whalley, M.; Wheeler, S.; Williams, W. S. C.; Wimpenny, S. J.; Windmolders, R.; Wolf, G.

1985-12-01

Measurements are presented of the variation with Q2 (scaling violation) of the hadron multiplicity in deep inelastic muon-proton scattering. An increase in the average multiplicity of both the charged hadrons and K0 mesons is observed with increasing Q2 or xBj for fixed centre-of-mass energy W. The study of the shape of the effective fragmentation function Dh (z, W, Q2) shows that the increase of the particle yield with Q2 takes place for low z particles. The variation of the hadron distributions with Q2 is also studied in the current fragmentation region where a decrease in multiplicity is observed. Such effects are expected from QCD.

Atmospheric Multiple Scattering Effects on GLAS Altimetry. Part 2; Analysis of Expected Errors in Antarctic Altitude Measurements

NASA Technical Reports Server (NTRS)

Mahesh, Ashwin; Spinhirne, James D.; Duda, David P.; Eloranta, Edwin W.; Starr, David O'C (Technical Monitor)

2001-01-01

The altimetry bias in GLAS (Geoscience Laser Altimeter System) or other laser altimeters resulting from atmospheric multiple scattering is studied in relationship to current knowledge of cloud properties over the Antarctic Plateau. Estimates of seasonal and interannual changes in the bias are presented. Results show the bias in altitude from multiple scattering in clouds would be a significant error source without correction. The selective use of low optical depth clouds or cloudfree observations, as well as improved analysis of the return pulse such as by the Gaussian method used here, are necessary to minimize the surface altitude errors. The magnitude of the bias is affected by variations in cloud height, cloud effective particle size and optical depth. Interannual variations in these properties as well as in cloud cover fraction could lead to significant year-to-year variations in the altitude bias. Although cloud-free observations reduce biases in surface elevation measurements from space, over Antarctica these may often include near-surface blowing snow, also a source of scattering-induced delay. With careful selection and analysis of data, laser altimetry specifications can be met.

Shadows cast on the transition disk of HD 135344B. Multiwavelength VLT/SPHERE polarimetric differential imaging

NASA Astrophysics Data System (ADS)

Stolker, T.; Dominik, C.; Avenhaus, H.; Min, M.; de Boer, J.; Ginski, C.; Schmid, H. M.; Juhasz, A.; Bazzon, A.; Waters, L. B. F. M.; Garufi, A.; Augereau, J.-C.; Benisty, M.; Boccaletti, A.; Henning, Th.; Langlois, M.; Maire, A.-L.; Ménard, F.; Meyer, M. R.; Pinte, C.; Quanz, S. P.; Thalmann, C.; Beuzit, J.-L.; Carbillet, M.; Costille, A.; Dohlen, K.; Feldt, M.; Gisler, D.; Mouillet, D.; Pavlov, A.; Perret, D.; Petit, C.; Pragt, J.; Rochat, S.; Roelfsema, R.; Salasnich, B.; Soenke, C.; Wildi, F.

2016-11-01

Context. The protoplanetary disk around the F-type star HD 135344B (SAO 206462) is in a transition stage and shows many intriguing structures both in scattered light and thermal (sub-)millimeter emission which are possibly related to planet formation processes. Aims: We aim to study the morphology and surface brightness of the disk in scattered light to gain insight into the innermost disk regions, the formation of protoplanets, planet-disk interactions traced in the surface and midplane layers, and the dust grain properties of the disk surface. Methods: We have carried out high-contrast polarimetric differential imaging (PDI) observations with VLT/SPHERE and obtained polarized scattered light images with ZIMPOL in the R and I-bands and with IRDIS in the Y and J-bands. The scattered light images and surface brightness profiles are used to study in detail structures in the disk surface and brightness variations. We have constructed a 3D radiative transfer model to support the interpretation of several detected shadow features. Results: The scattered light images reveal with unprecedented angular resolution and sensitivity the spiral arms as well as the 25 au cavity of the disk. Multiple shadow features are discovered on the outer disk with one shadow only being present during the second observation epoch. A positive surface brightness gradient is observed in the stellar irradiation corrected (r2-scaled) images in southwest direction possibly due to an azimuthally asymmetric perturbation of the temperature and/or surface density by the passing spiral arms. The disk integrated polarized flux, normalized to the stellar flux, shows a positive trend towards longer wavelengths which we attribute to large (2πa ≳ λ) aggregate dust grains in the disk surface. Part of the non-azimuthal polarization signal in the Uφ image of the J-band observation can be attributed to multiple scattering in the disk. Conclusions: The detected shadow features and their possible variability have the potential to provide insight into the structure of and processes occurring in the innermost disk regions. Possible explanations for the presence of the shadows include a 22° misaligned inner disk, a warped disk region that connects the inner disk with the outer disk, and variable or transient phenomena such as a perturbation of the inner disk or an asymmetric accretion flow. The spiral arms are best explained by one or multiple protoplanets in the exterior of the disk although no gap is detected beyond the spiral arms up to 1.''0. Based on observations collected at the European Southern Observatory, Chile, ESO No. 095.C-0273(A) and 095.C-0273(D).

Scattering and Diffraction of Electromagnetic Radiation: An Effective Probe to Material Structure

NASA Technical Reports Server (NTRS)

Xu, Yu-Lin

2016-01-01

Scattered electromagnetic waves from material bodies of different forms contain, in an intricate way, precise information on the intrinsic, geometrical and physical properties of the objects. Scattering theories, ever deepening, aim to provide dependable interpretation and prediction to the complicated interaction of electromagnetic radiation with matter. There are well-established multiple-scattering formulations based on classical electromagnetic theories. An example is the Generalized Multi-particle Mie-solution (GMM), which has recently been extended to a special version ? the GMM-PA approach, applicable to finite periodic arrays consisting of a huge number (e.g., >>106) of identical scattering centers [1]. The framework of the GMM-PA is nearly complete. When the size of the constituent unit scatterers becomes considerably small in comparison with incident wavelength, an appropriate array of such small element volumes may well be a satisfactory representation of a material entity having an arbitrary structure. X-ray diffraction is a powerful characterization tool used in a variety of scientific and technical fields, including material science. A diffraction pattern is nothing more than the spatial distribution of scattered intensity, determined by the distribution of scattering matter by way of its Fourier transform [1]. Since all linear dimensions entered into Maxwell's equations are normalized by wavelength, an analogy exists between optical and X-ray diffraction patterns. A large set of optical diffraction patterns experimentally obtained can be found in the literature [e.g., 2,3]. Theoretical results from the GMM-PA have been scrutinized using a large collection of publically accessible, experimentally obtained Fraunhofer diffraction patterns. As far as characteristic structures of the patterns are concerned, theoretical and experimental results are in uniform agreement; no exception has been found so far. Closely connected with the spatial distribution of scattered intensities are cross sections, such as for extinction, scattering, absorption, and radiation pressure, as a critical type of key quantity addressed in most theoretical and experimental studies of radiative scattering. Cross sections predicted from different scattering theories are supposed to be in general agreement. For objects of irregular shape, the GMM-PA solutions can be compared with the highly flexible Discrete Dipole Approximation (DDA) [4,5] when dividing a target to no more than 106 unit cells. Also, there are different ways to calculate the cross sections in the GMM-PA, providing an additional means to examine the accuracy of the numerical solutions and to unveil potential issues concerning the theoretical formulations and numerical aspects. To solve multiple scattering by an assembly of material volumes through classical theories such as the GMM-PA, the radiative properties of the component scatterers, the complex refractive index in particular, must be provided as input parameters. When using a PA to characterize a material body, this involves the use of an adequate theoretical tool, an effective medium theory, to connect Maxwell's phenomenogical theory with the atomistic theory of matter. In the atomic theory, one regards matter as composed of interacting particles (atoms and molecules) embedded in the vacuum [6]. However, the radiative properties of atomic-scaled particles are known to be substantially different from bulk materials. Intensive research efforts in the fields of cluster science and nanoscience attempt to bridge the gap between bulk and atom and to understand the transition from classical to quantum physics. The GMM-PA calculations, which place virtually no restriction on the component-particle size, might help to gain certain insight into the transition.

Re-Analysis of the Solar Phase Curves of the Icy Galilean Satellites

NASA Technical Reports Server (NTRS)

Domingue, Deborah; Verbiscer, Anne

1997-01-01

Re-analysis of the solar phase curves of the icy Galilean satellites demonstrates that the quantitative results are dependent on the single particle scattering function incorporated into the photometric model; however, the qualitative properties are independent. The results presented here show that the general physical characteristics predicted by a Hapke model (B. Hapke, 1986, Icarus 67, 264-280) incorporating a two parameter double Henyey-Greenstein scattering function are similar to the predictions given by the same model incorporating a three parameter double Henyey-Greenstein scattering function as long as the data set being modeled has adequate coverage in phase angle. Conflicting results occur when the large phase angle coverage is inadequate. Analysis of the role of isotropic versus anisotropic multiple scattering shows that for surfaces as bright as Europa the two models predict very similar results over phase angles covered by the data. Differences arise only at those phase angles for which there are no data. The single particle scattering behavior between the leading and trailing hemispheres of Europa and Ganymede is commensurate with magnetospheric alterations of their surfaces. Ion bombardment will produce more forward scattering single scattering functions due to annealing of potential scattering centers within regolith particles (N. J. Sack et al., 1992, Icarus 100, 534-540). Both leading and trailing hemispheres of Europa are consistent with a high porosity model and commensurate with a frost surface. There are no strong differences in predicted porosity between the two hemispheres of Callisto, both are consistent with model porosities midway between that deduced for Europa and the Moon. Surface roughness model estimates predict that surface roughness increases with satellite distance from Jupiter, with lunar surface roughness values falling midway between those measured for Ganymede and Callisto. There is no obvious variation in predicted surface roughness with hemisphere for any of the Galilean satellites.

On the Discrete Spectrum of the Nonstationary Schrödinger Equation and Multipole Lumps of the Kadomtsev-Petviashvili I Equation

NASA Astrophysics Data System (ADS)

Villarroel, Javier; Ablowitz, Mark J.

The discrete spectrum of the nonstationary Schrödinger equation and localized solutions of the Kadomtsev-Petviashvili-I (KPI) equation are studied via the inverse scattering transform. It is shown that there exist infinitely many real and rationally decaying potentials which correspond to a discrete spectrum whose related eigenfunctions have multiple poles in the spectral parameter. An index or winding number is asssociated with each of these solutions. The resulting localized solutions of KPI behave as collection of individual humps with nonuniform dynamics.

Potential New Lidar Observations for Cloud Studies

NASA Technical Reports Server (NTRS)

Winker, Dave; Hu, Yong; Narir, Amin; Cai, Xia

2015-01-01

The response of clouds to global warming represents a major uncertainty in estimating climate sensitivity. These uncertainties have been tracked to shallow marine clouds in the tropics and subtropics. CALIOP observations have already been used extensively to evaluate model predictions of shallow cloud fraction and top height (Leahy et al. 2013; Nam et al 2012). Tools are needed to probe the lowest levels of the troposphere. The large footprint of satellite lidars gives large multiple scattering from clouds which presents new possibilities for cloud retrievals to constrain model predictions.

Nuclear fragmentation energy and momentum transfer distributions in relativistic heavy-ion collisions

NASA Technical Reports Server (NTRS)

Khandelwal, Govind S.; Khan, Ferdous

1989-01-01

An optical model description of energy and momentum transfer in relativistic heavy-ion collisions, based upon composite particle multiple scattering theory, is presented. Transverse and longitudinal momentum transfers to the projectile are shown to arise from the real and absorptive part of the optical potential, respectively. Comparisons of fragment momentum distribution observables with experiments are made and trends outlined based on our knowledge of the underlying nucleon-nucleon interaction. Corrections to the above calculations are discussed. Finally, use of the model as a tool for estimating collision impact parameters is indicated.

Analytical transition-matrix treatment of electric multipole polarizabilities of hydrogen-like atoms

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

Kharchenko, V.F., E-mail: vkharchenko@bitp.kiev.ua

2015-04-15

The direct transition-matrix approach to the description of the electric polarization of the quantum bound system of particles is used to determine the electric multipole polarizabilities of the hydrogen-like atoms. It is shown that in the case of the bound system formed by the Coulomb interaction the corresponding inhomogeneous integral equation determining an off-shell scattering function, which consistently describes virtual multiple scattering, can be solved exactly analytically for all electric multipole polarizabilities. Our method allows to reproduce the known Dalgarno–Lewis formula for electric multipole polarizabilities of the hydrogen atom in the ground state and can also be applied to determinemore » the polarizability of the atom in excited bound states. - Highlights: • A new description for electric polarization of hydrogen-like atoms. • Expression for multipole polarizabilities in terms of off-shell scattering functions. • Derivation of integral equation determining the off-shell scattering function. • Rigorous analytic solving the integral equations both for ground and excited states. • Study of contributions of virtual multiple scattering to electric polarizabilities.« less

Influence of reabsorption and reemission on stimulated Raman scattering of polymethine dyes in multiple scattering media

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

Yashchuk, V P; Komyshan, A O; Smaliuk, A P

2013-12-31

It is shown that reabsorption of the luminescence radiation in the range of its overlapping with the absorption spectrum and the following reemission to a long-wavelength range may noticeably affect the process of stimulated Raman scattering (SRS) in polymethine dyes in multiple scattering media (MSM). This is related to the fact that SRS in such media occurs jointly with the random lasing (RL), which favors SRS and makes up with it a united nonlinear process. Reemission into the long-wavelength spectrum range amplified in MSM causes the RL spectrum to shift to longer wavelengths and initiates the long-wavelength band of RL,more » in which a main part of the lasing energy is concentrated. This weakens or completely stops the SRS if the band is beyond the range of possible spectral localisation of Stokes lines. This process depends on the efficiency of light scattering, dye concentration, temperature and pump intensity; hence, there exist optimal values of these parameters for obtaining SRS in MSM. (nonlinear optical phenomena)« less

Light Scattering by Lunar Exospheric Dust: What could be Learned from LRO LAMP and LADEE UVS?

NASA Astrophysics Data System (ADS)

Glenar, D. A.; Stubbs, T. J.; Richard, D. T.; Stern, S. A.; Retherford, K. D.; Gladstone, R.; Feldman, P. D.; Colaprete, A.; Delory, G. T.

2011-12-01

Two complementary spectrometers, namely the Lunar Reconnaissance Orbiter, Lyman Alpha Mapping Project (LAMP) and the planned Lunar Atmosphere and Dust Environment Explorer (LADEE) Ultraviolet Explorer (UVS) will carry out sensitive searches for high altitude exospheric dust, via detection of scattered sunlight. The combined spectral coverage of these instruments extends from far-UV to near-IR wavelengths. Over this wavelength range, grain size parameter (X=2πr/λ, with r the grain radius and λ the wavelength) changes dramatically, which makes broad wavelength coverage a good diagnostic of grain size. Utilizing different pointing geometries, both LAMP and UVS are able to observe dust over a range of scattering angles, as well as measure the dust vertical profile via limb measurements at multiple tangent heights. We summarize several categories of information that can be inferred from the data sets, using broadband simulations of horizon glow as observed at the limb. Grain scattering properties used in these simulations were computed for multiple grain shapes using Discrete-Dipole theory. Some cautionary remarks are included regarding the use of Mie theory to interpret scattering measurements.

High-speed imaging using compressed sensing and wavelength-dependent scattering (Conference Presentation)

NASA Astrophysics Data System (ADS)

Shin, Jaewook; Bosworth, Bryan T.; Foster, Mark A.

2017-02-01

The process of multiple scattering has inherent characteristics that are attractive for high-speed imaging with high spatial resolution and a wide field-of-view. A coherent source passing through a multiple-scattering medium naturally generates speckle patterns with diffraction-limited features over an arbitrarily large field-of-view. In addition, the process of multiple scattering is deterministic allowing a given speckle pattern to be reliably reproduced with identical illumination conditions. Here, by exploiting wavelength dependent multiple scattering and compressed sensing, we develop a high-speed 2D time-stretch microscope. Highly chirped pulses from a 90-MHz mode-locked laser are sent through a 2D grating and a ground-glass diffuser to produce 2D speckle patterns that rapidly evolve with the instantaneous frequency of the chirped pulse. To image a scene, we first characterize the high-speed evolution of the generated speckle patterns. Subsequently we project the patterns onto the microscopic region of interest and collect the total light from the scene using a single high-speed photodetector. Thus the wavelength dependent speckle patterns serve as high-speed pseudorandom structured illumination of the scene. An image sequence is then recovered using the time-dependent signal received by the photodetector, the known speckle pattern evolution, and compressed sensing algorithms. Notably, the use of compressed sensing allows for reconstruction of a time-dependent scene using a highly sub-Nyquist number of measurements, which both increases the speed of the imager and reduces the amount of data that must be collected and stored. We will discuss our experimental demonstration of this approach and the theoretical limits on imaging speed.

Multiple scattering in the remote sensing of natural surfaces

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

Li, Wen-Hao; Weeks, R.; Gillespie, A.R.

1996-07-01

Radiosity models predict the amount of light scattered many times (multiple scattering) among scene elements in addition to light interacting with a surface only once (direct reflectance). Such models are little used in remote sensing studies because they require accurate digital terrain models and, typically, large amounts of computer time. We have developed a practical radiosity model that runs relatively quickly within suitable accuracy limits, and have used it to explore problems caused by multiple-scattering in image calibration, terrain correction, and surface roughness estimation for optical images. We applied the radiosity model to real topographic surfaces sampled at two verymore » different spatial scales: 30 m (rugged mountains) and 1 cm (cobbles and gravel on an alluvial fan). The magnitude of the multiple-scattering (MS) effect varies with solar illumination geometry, surface reflectivity, sky illumination and surface roughness. At the coarse scale, for typical illumination geometries, as much as 20% of the image can be significantly affected (>5%) by MS, which can account for as much as {approximately}10% of the radiance from sunlit slopes, and much more for shadowed slopes, otherwise illuminated only by skylight. At the fine scale, radiance from as much as 30-40% of the scene can have a significant MS component, and the MS contribution is locally as high as {approximately}70%, although integrating to the meter scale reduces this limit to {approximately}10%. Because the amount of MS increases with reflectivity as well as roughness, MS effects will distort the shape of reflectance spectra as well as changing their overall amplitude. The change is proportional to surface roughness. Our results have significant implications for determining reflectivity and surface roughness in remote sensing.« less

An electrical analogy to Mie scattering

PubMed Central

Caridad, José M.; Connaughton, Stephen; Ott, Christian; Weber, Heiko B.; Krstić, Vojislav

2016-01-01

Mie scattering is an optical phenomenon that appears when electromagnetic waves, in particular light, are elastically scattered at a spherical or cylindrical object. A transfer of this phenomenon onto electron states in ballistic graphene has been proposed theoretically, assuming a well-defined incident wave scattered by a perfectly cylindrical nanometer scaled potential, but experimental fingerprints are lacking. We present an experimental demonstration of an electrical analogue to Mie scattering by using graphene as a conductor, and circular potentials arranged in a square two-dimensional array. The tabletop experiment is carried out under seemingly unfavourable conditions of diffusive transport at room-temperature. Nonetheless, when a canted arrangement of the array with respect to the incident current is chosen, cascaded Mie scattering results robustly in a transverse voltage. Its response on electrostatic gating and variation of potentials convincingly underscores Mie scattering as underlying mechanism. The findings presented here encourage the design of functional electronic metamaterials. PMID:27671003

Assessment of the biophysical characteristics of rangeland community using scatterometer and optical measurements

NASA Technical Reports Server (NTRS)

Kanemasu, E. T.; Asrar, Ghassem; Myneni, Ranga; Martin, Robert, Jr.; Burnett, R. Bruce

1987-01-01

Research activities for the following study areas are summarized: single scattering of parallel direct and axially symmetric diffuse solar radiation in vegetative canopies; the use of successive orders of scattering approximations (SOSA) for treating multiple scattering in a plant canopy; reflectance of a soybean canopy using the SOSA method; and C-band scatterometer measurements of the Konza tallgrass prairie.

Effective Tree Scattering and Opacity at L-Band

NASA Technical Reports Server (NTRS)

Kurum, Mehmet; O'Neill, Peggy E.; Lang, Roger H.; Joseph, Alicia T.; Cosh, Michael H.; Jackson, Thomas J.

2011-01-01

This paper investigates vegetation effects at L-band by using a first-order radiative transfer (RT) model and truck-based microwave measurements over natural conifer stands to assess the applicability of the tau-omega) model over trees. The tau-omega model is a zero-order RT solution that accounts for vegetation effects with effective vegetation parameters (vegetation opacity and single-scattering albedo), which represent the canopy as a whole. This approach inherently ignores multiple-scattering effects and, therefore, has a limited validity depending on the level of scattering within the canopy. The fact that the scattering from large forest components such as branches and trunks is significant at L-band requires that zero-order vegetation parameters be evaluated (compared) along with their theoretical definitions to provide a better understanding of these parameters in the retrieval algorithms as applied to trees. This paper compares the effective vegetation opacities, computed from multi-angular pine tree brightness temperature data, against the results of two independent approaches that provide theoretical and measured optical depths. These two techniques are based on forward scattering theory and radar corner reflector measurements, respectively. The results indicate that the effective vegetation opacity values are smaller than but of similar magnitude to both radar and theoretical estimates. The effective opacity of the zero-order model is thus set equal to the theoretical opacity and an explicit expression for the effective albedo is then obtained from the zero- and first- order RT model comparison. The resultant albedo is found to have a similar magnitude as the effective albedo value obtained from brightness temperature measurements. However, it is less than half of that estimated using the theoretical calculations (0.5 - 0.6 for tree canopies at L-band). This lower observed albedo balances the scattering darkening effect of the large theoretical albedo with a first-order multiple-scattering contribution. The retrieved effective albedo is different from theoretical definitions and not the albedo of single forest elements anymore, but it becomes a global parameter, which depends on all the processes taking place within the canopy, including multiple-scattering.

On the Mathematical Modeling of Single and Multiple Scattering of Ultrasonic Guided Waves by Small Scatterers: A Structural Health Monitoring Measurement Model

NASA Astrophysics Data System (ADS)

Strom, Brandon William

In an effort to assist in the paradigm shift from schedule based maintenance to conditioned based maintenance, we derive measurement models to be used within structural health monitoring algorithms. Our models are physics based, and use scattered Lamb waves to detect and quantify pitting corrosion. After covering the basics of Lamb waves and the reciprocity theorem, we develop a technique for the scattered wave solution. The first application is two-dimensional, and is employed in two different ways. The first approach integrates a traction distribution and replaces it by an equivalent force. The second approach is higher order and uses the actual traction distribution. We find that the equivalent force version of the solution technique holds well for small pits at low frequencies. The second application is three-dimensional. The equivalent force caused by the scattered wave of an arbitrary equivalent force is calculated. We obtain functions for the scattered wave displacements as a function of equivalent forces, equivalent forces as a function of incident wave, and scattered wave amplitudes as a function of incident amplitude. The third application uses self-consistency to derive governing equations for the scattered waves due to multiple corrosion pits. We decouple the implicit set of equations and solve explicitly by using a recursive series solution. Alternatively, we solve via an undetermined coefficient method which results in an interaction operator and solution via matrix inversion. The general solution is given for N pits including mode conversion. We show that the two approaches are equivalent, and give a solution for three pits. Various approximations are advanced to simplify the problem while retaining the leading order physics. As a final application, we use the multiple scattering model to investigate resonance of Lamb waves. We begin with a one-dimensional problem and progress to a three-dimensional problem. A directed graph enables interpretation of the interaction operator, and we show that a series solution converges due to loss of energy in the system. We see that there are four causes of resonance and plot the modulation depth as a function of spacing between the pits.

Acoustic and elastic multiple scattering and radiation from cylindrical structures

NASA Astrophysics Data System (ADS)

Amirkulova, Feruza Abdukadirovna

Multiple scattering (MS) and radiation of waves by a system of scatterers is of great theoretical and practical importance and is required in a wide variety of physical contexts such as the implementation of "invisibility" cloaks, the effective parameter characterization, and the fabrication of dynamically tunable structures, etc. The dissertation develops fast, rapidly convergent iterative techniques to expedite the solution of MS problems. The formulation of MS problems reduces to a system of linear algebraic equations using Graf's theorem and separation of variables. The iterative techniques are developed using Neumann expansion and Block Toeplitz structure of the linear system; they are very general, and suitable for parallel computations and a large number of MS problems, i.e. acoustic, elastic, electromagnetic, etc., and used for the first time to solve MS problems. The theory is implemented in Matlab and FORTRAN, and the theoretical predictions are compared to computations obtained by COMSOL. To formulate the MS problem, the transition matrix is obtained by analyzing an acoustic and an elastic single scattering of incident waves by elastic isotropic and anisotropic solids. The mathematical model of wave scattering from multilayered cylindrical and spherical structures is developed by means of an exact solution of dynamic 3D elasticity theory. The recursive impedance matrix algorithm is derived for radially heterogeneous anisotropic solids. An explicit method for finding the impedance in piecewise uniform, transverse-isotropic material is proposed; the solution is compared to elasticity theory solutions involving Buchwald potentials. Furthermore, active exterior cloaking devices are modeled for acoustic and elastic media using multipole sources. A cloaking device can render an object invisible to some incident waves as seen by some external observer. The active cloak is generated by a discrete set of multipole sources that destructively interfere with an incident wave to produce zero total field over a finite spatial region. The approach precisely determines the necessary source amplitudes and enables a cloaked region to be determined using Graf's theorem. To apply the approach, the infinite series of multipole expansions are truncated, and the accuracy of cloaking is studied by modifying the truncation parameter.

Numerical Green's functions in optical potential calculations for positron scattering from argon and neon

NASA Technical Reports Server (NTRS)

Bartschat, K.; Mceachran, R. P.; Stauffer, A. D.

1990-01-01

An optical potential method was applied to the calculation of positron scattering from the noble gases in order to determine the effect of open excitation channels on the shape of differential scattering cross sections.

Electromagnetic field scattering by a triangular aperture.

PubMed

Harrison, R E; Hyman, E

1979-03-15

The multiple Laplace transform has been applied to analysis and computation of scattering by a double triangular aperture. Results are obtained which match far-field intensity distributions observed in experiments. Arbitrary polarization components, as well as in-phase and quadrature-phase components, may be determined, in the transform domain, as a continuous function of distance from near to far-field for any orientation, aperture, and transformable waveform. Numerical results are obtained by application of numerical multiple inversions of the fully transformed solution.

Windowing of Full Wavefield Data in Multiple Domains to Characterize Angle-Beam Shear Wave Scattering (Postprint)

DTIC Science & Technology

2017-02-01

OMB control number. PLEASE DO NOT RETURN YOUR FORM TO THE ABOVE ADDRESS. 1. REPORT DATE (DD-MM-YY) 2. REPORT TYPE 3 . DATES COVERED (From - To) 19...September 2016 Interim 3 March 2014 – 19 August 2016 4. TITLE AND SUBTITLE WINDOWING OF FULL WAVEFIELD DATA IIN MULTIPLE DOMAINS TO CHARACTERIZE...wavefield baseline subtraction before and after the introduction of a scatterer [2]. Next, a 3 -D Fourier transform is performed to convert the residual

Multiple scattering calculation of the middle ultraviolet reaching the ground. [SST effects on ozone layer

NASA Technical Reports Server (NTRS)

Shettle, E. P.; Green, A. E. S.

1974-01-01

An investigation is conducted regarding the increase in the UV radiation as a function of wavelength due to changes in the amounts of ozone and various other parameters affecting the radiation in the atmosphere. Attention is given to the methods that can be used to solve the problem of the transfer of radiation through an absorbing and scattering atmosphere which includes aerosols. The multiple channel solution reported by Mudgett and Richards' (1971) is extended to vertically inhomogeneous atmospheres.

A Multiple Sphere T-Matrix Fortran Code for Use on Parallel Computer Clusters

NASA Technical Reports Server (NTRS)

Mackowski, D. W.; Mishchenko, M. I.

2011-01-01

A general-purpose Fortran-90 code for calculation of the electromagnetic scattering and absorption properties of multiple sphere clusters is described. The code can calculate the efficiency factors and scattering matrix elements of the cluster for either fixed or random orientation with respect to the incident beam and for plane wave or localized- approximation Gaussian incident fields. In addition, the code can calculate maps of the electric field both interior and exterior to the spheres.The code is written with message passing interface instructions to enable the use on distributed memory compute clusters, and for such platforms the code can make feasible the calculation of absorption, scattering, and general EM characteristics of systems containing several thousand spheres.

Effects of molecular and particle scatterings on the model parameter for remote-sensing reflectance.

PubMed

Lee, ZhongPing; Carder, Kendall L; Du, KePing

2004-09-01

For optically deep waters, remote-sensing reflectance (r(rs)) is traditionally expressed as the ratio of the backscattering coefficient (b(b)) to the sum of absorption and backscattering coefficients (a + b(b)) that multiples a model parameter (g, or the so-called f'/Q). Parameter g is further expressed as a function of b(b)/(a + b(b)) (or b(b)/a) to account for its variation that is due to multiple scattering. With such an approach, the same g value will be derived for different a and b(b) values that provide the same ratio. Because g is partially a measure of the angular distribution of upwelling light, and the angular distribution from molecular scattering is quite different from that of particle scattering; g values are expected to vary with different scattering distributions even if the b(b)/a ratios are the same. In this study, after numerically demonstrating the effects of molecular and particle scatterings on the values of g, an innovative r(rs) model is developed. This new model expresses r(rs) in two separate terms: one governed by the phase function of molecular scattering and one governed by the phase function of particle scattering, with a model parameter introduced for each term. In this way the phase function effects from molecular and particle scatterings are explicitly separated and accounted for. This new model provides an analytical tool to understand and quantify the phase-function effects on r(rs), and a platform to calculate r(rs) spectrum quickly and accurately that is required for remote-sensing applications.

Accelerated x-ray scatter projection imaging using multiple continuously moving pencil beams

NASA Astrophysics Data System (ADS)

Dydula, Christopher; Belev, George; Johns, Paul C.

2017-03-01

Coherent x-ray scatter varies with angle and photon energy in a manner dependent on the chemical composition of the scattering material, even for amorphous materials. Therefore, images generated from scattered photons can have much higher contrast than conventional projection radiographs. We are developing a scatter projection imaging prototype at the BioMedical Imaging and Therapy (BMIT) facility of the Canadian Light Source (CLS) synchrotron in Saskatoon, Canada. The best images are obtained using step-and-shoot scanning with a single pencil beam and area detector to capture sequentially the scatter pattern for each primary beam location on the sample. Primary x-ray transmission is recorded simultaneously using photodiodes. The technological challenge is to acquire the scatter data in a reasonable time. Using multiple pencil beams producing partially-overlapping scatter patterns reduces acquisition time but increases complexity due to the need for a disentangling algorithm to extract the data. Continuous sample motion, rather than step-and-shoot, also reduces acquisition time at the expense of introducing motion blur. With a five-beam (33.2 keV, 3.5 mm2 beam area) continuous sample motion configuration, a rectangular array of 12 x 100 pixels with 1 mm sampling width has been acquired in 0.4 minutes (3000 pixels per minute). The acquisition speed is 38 times the speed for single beam step-and-shoot. A system model has been developed to calculate detected scatter patterns given the material composition of the object to be imaged. Our prototype development, image acquisition of a plastic phantom and modelling are described.

Replacing backscattering with reduced scattering. A better formulation of reflectance function?

NASA Astrophysics Data System (ADS)

Piskozub, Jacek; McKee, David; Freda, Wlodzimierz

2014-05-01

Modern reflectance formulas all involve backscattering coefficient divided by absorption coefficient (bb/a). The backscattering (or backward scattering) coefficient describes how much of the incident radiation is scattered at angles between 90 and 180 deg. However, water leaving photons are not necessarily backscattered because it is possible for a variable fraction to exit after multiple forward scattering events. Therefore the whole angular function of scattering probability (phase function) influences the reflectance signal. This is the reason why phase functions of identical backscattering ratio may result in different reflectance values, contrary to the universally used formula. This creates the question whether there may exist a better formula using a parameter better describing phase function shape than backscattering ratio. The asymmetry parameter g (the average scattering cosine) is commonly used to parametrize phase functions. A replacement for backscattering should decrease with increasing g. Therefore, the simplest candidate to replace backscattering has the form of b(1-g), where b is the scattering coefficient. Such a parameter is well known in biomedical optics under the name of reduced scattering (sometimes transport scattering). It has even been used in parametrizing reflectance in (highly turbid) human tissues. However no attempt has been made to check its usefulness in marine optics. We perform Monte Carlo radiative transfer calculations of reflectance for multiple combinations of inherent optical properties, including different phase functions. The results are used to create a new reflectance formula as a function of reduced scattering and absorption and test its robustness to changes in phase function shape compared to the traditional bb/a formula. We discuss its usefulness as well as advantages and disadvantages compared to the traditional formulation.

Characterization of the Lung Parenchyma Using Ultrasound Multiple Scattering.

PubMed

Mohanty, Kaustav; Blackwell, John; Egan, Thomas; Muller, Marie

2017-05-01

The purpose of the study described here was to showcase the application of ultrasound to quantitative characterization of the micro-architecture of the lung parenchyma to predict the extent of pulmonary edema. The lung parenchyma is a highly complex and diffusive medium for which ultrasound techniques have remained qualitative. The approach presented here is based on ultrasound multiple scattering and exploits the complexity of ultrasound propagation in the lung structure. The experimental setup consisted of a linear transducer array with an 8-MHz central frequency placed in contact with the lung surface. The diffusion constant D and transport mean free path L* of the lung parenchyma were estimated by separating the incoherent and coherent intensities in the near field and measuring the growth of the incoherent diffusive halo over time. Significant differences were observed between the L* values obtained in healthy and edematous rat lungs in vivo. In the control rat lung, L* was found to be 332 μm (±48.8 μm), whereas in the edematous lung, it was 1040 μm (±90 μm). The reproducibility of the measurements of L* and D was tested in vivo and in phantoms made of melamine sponge with varying air volume fractions. Two-dimensional finite difference time domain numerical simulations were carried out on rabbit lung histology images with varying degrees of lung collapse. Significant correlations were observed between air volume fraction and L* in simulation (r = -0.9542, p < 0.0117) and sponge phantom (r = -0.9932, p < 0.0068) experiments. Ex vivo measurements of a rat lung in which edema was simulated by adding phosphate-buffered saline revealed a linear relationship between the fluid volume fraction and L*. These results illustrate the potential of methods based on ultrasound multiple scattering for the quantitative characterization of the lung parenchyma. Copyright © 2017 World Federation for Ultrasound in Medicine & Biology. Published by Elsevier Inc. All rights reserved.

Survey of background scattering from materials found in small-angle neutron scattering.

PubMed

Barker, J G; Mildner, D F R

2015-08-01

Measurements and calculations of beam attenuation and background scattering for common materials placed in a neutron beam are presented over the temperature range of 300-700 K. Time-of-flight (TOF) measurements have also been made, to determine the fraction of the background that is either inelastic or quasi-elastic scattering as measured with a 3 He detector. Other background sources considered include double Bragg diffraction from windows or samples, scattering from gases, and phonon scattering from solids. Background from the residual air in detector vacuum vessels and scattering from the 3 He detector dome are presented. The thickness dependence of the multiple scattering correction for forward scattering from water is calculated. Inelastic phonon background scattering at small angles for crystalline solids is both modeled and compared with measurements. Methods of maximizing the signal-to-noise ratio by material selection, choice of sample thickness and wavelength, removal of inelastic background by TOF or Be filters, and removal of spin-flip scattering with polarized beam analysis are discussed.

Survey of background scattering from materials found in small-angle neutron scattering

PubMed Central

Barker, J. G.; Mildner, D. F. R.

2015-01-01

Measurements and calculations of beam attenuation and background scattering for common materials placed in a neutron beam are presented over the temperature range of 300–700 K. Time-of-flight (TOF) measurements have also been made, to determine the fraction of the background that is either inelastic or quasi-elastic scattering as measured with a 3He detector. Other background sources considered include double Bragg diffraction from windows or samples, scattering from gases, and phonon scattering from solids. Background from the residual air in detector vacuum vessels and scattering from the 3He detector dome are presented. The thickness dependence of the multiple scattering correction for forward scattering from water is calculated. Inelastic phonon background scattering at small angles for crystalline solids is both modeled and compared with measurements. Methods of maximizing the signal-to-noise ratio by material selection, choice of sample thickness and wavelength, removal of inelastic background by TOF or Be filters, and removal of spin-flip scattering with polarized beam analysis are discussed. PMID:26306088

Scattering of accelerated wave packets

NASA Astrophysics Data System (ADS)

Longhi, S.; Horsley, S. A. R.; Della Valle, G.

2018-03-01

Wave-packet scattering from a stationary potential is significantly modified when the wave packet is subject to an external time-dependent force during the interaction. In the semiclassical limit, wave-packet motion is simply described by Newtonian equations, and the external force can, for example, cancel the potential force, making a potential barrier transparent. Here we consider wave-packet scattering from reflectionless potentials, where in general the potential becomes reflective when probed by an accelerated wave packet. In the particular case of the recently introduced class of complex Kramers-Kronig potentials we show that a broad class of time-dependent forces can be applied without inducing any scattering, while there is a breakdown of the reflectionless property when there is a broadband distribution of initial particle momentum, involving both positive and negative components.

Multiple light scattering in metallic ejecta produced under intense shockwave compression.

PubMed

Franzkowiak, J-E; Mercier, P; Prudhomme, G; Berthe, L

2018-04-10

A roughened metallic plate, subjected to intense shock wave compression, gives rise to an expanding ejecta particle cloud. Photonic Doppler velocimetry (PDV), a fiber-based heterodyne velocimeter, is often used to track ejecta velocities in dynamic compression experiments and on nanosecond time scales. Shortly after shock breakout at the metal-vacuum interface, a particular feature observed in many experiments in the velocity spectrograms is what appear to be slow-moving ejecta, below the free-surface velocity. Using Doppler Monte Carlo simulations incorporating the transport of polarization in the ejecta, we show that this feature is likely to be explained by the multiple scattering of light, rather than by possible collisions among particles, slowing down the ejecta. As the cloud expands in a vacuum, the contribution of multiple scattering decreases due to the limited field of view of the pigtailed collimator used to probe the ejecta, showing that the whole geometry of the system must be taken into account in the calculations to interpret and predict PDV measurements.

Modelling NDE pulse-echo inspection of misorientated planar rough defects using an elastic finite element method

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

Pettit, J. R.; Lowe, M. J. S.; Walker, A. E.

2015-03-31

Pulse-echo ultrasonic NDE examination of large pressure vessel forgings is a design and construction code requirement in the power generation industry. Such inspections aim to size and characterise potential defects that may have formed during the forging process. Typically these defects have a range of orientations and surface roughnesses which can greatly affect ultrasonic wave scattering behaviour. Ultrasonic modelling techniques can provide insight into defect response and therefore aid in characterisation. However, analytical approaches to solving these scattering problems can become inaccurate, especially when applied to increasingly complex defect geometries. To overcome these limitations a elastic Finite Element (FE) methodmore » has been developed to simulate pulse-echo inspections of embedded planar defects. The FE model comprises a significantly reduced spatial domain allowing for a Monte-Carlo based approach to consider multiple realisations of defect orientation and surface roughness. The results confirm that defects aligned perpendicular to the path of beam propagation attenuate ultrasonic signals according to the level of surface roughness. However, for defects orientated away from this plane, surface roughness can increase the magnitude of the scattered component propagating back along the path of the incident beam. This study therefore highlights instances where defect roughness increases the magnitude of ultrasonic scattered signals, as opposed to attenuation which is more often assumed.« less

Asymmetric scattering by non-Hermitian potentials

NASA Astrophysics Data System (ADS)

Ruschhaupt, A.; Dowdall, T.; Simón, M. A.; Muga, J. G.

2017-10-01

The scattering of quantum particles by non-Hermitian (generally non-local) potentials in one dimension may result in asymmetric transmission and/or reflection from left and right incidence. After extending the concept of symmetry for non-Hermitian potentials, eight generalized symmetries based on the discrete Klein's four-group (formed by parity, time reversal, their product, and unity) are found. Together with generalized unitarity relations they determine selection rules for the possible and/or forbidden scattering asymmetries. Six basic device types are identified when the scattering coefficients (squared moduli of scattering amplitudes) adopt zero/one values, and transmission and/or reflection are asymmetric. They can pictorically be described as a one-way mirror, a one-way barrier (a Maxwell pressure demon), one-way (transmission or reflection) filters, a mirror with unidirectional transmission, and a transparent, one-way reflector. We design potentials for these devices and also demonstrate that the behavior of the scattering coefficients can be extended to a broad range of incident momenta.

Superparamagnetic enhancement of thermoelectric performance.

PubMed

Zhao, Wenyu; Liu, Zhiyuan; Sun, Zhigang; Zhang, Qingjie; Wei, Ping; Mu, Xin; Zhou, Hongyu; Li, Cuncheng; Ma, Shifang; He, Danqi; Ji, Pengxia; Zhu, Wanting; Nie, Xiaolei; Su, Xianli; Tang, Xinfeng; Shen, Baogen; Dong, Xiaoli; Yang, Jihui; Liu, Yong; Shi, Jing

2017-09-13

The ability to control chemical and physical structuring at the nanometre scale is important for developing high-performance thermoelectric materials. Progress in this area has been achieved mainly by enhancing phonon scattering and consequently decreasing the thermal conductivity of the lattice through the design of either interface structures at nanometre or mesoscopic length scales or multiscale hierarchical architectures. A nanostructuring approach that enables electron transport as well as phonon transport to be manipulated could potentially lead to further enhancements in thermoelectric performance. Here we show that by embedding nanoparticles of a soft magnetic material in a thermoelectric matrix we achieve dual control of phonon- and electron-transport properties. The properties of the nanoparticles-in particular, their superparamagnetic behaviour (in which the nanoparticles can be magnetized similarly to a paramagnet under an external magnetic field)-lead to three kinds of thermoelectromagnetic effect: charge transfer from the magnetic inclusions to the matrix; multiple scattering of electrons by superparamagnetic fluctuations; and enhanced phonon scattering as a result of both the magnetic fluctuations and the nanostructures themselves. We show that together these effects can effectively manipulate electron and phonon transport at nanometre and mesoscopic length scales and thereby improve the thermoelectric performance of the resulting nanocomposites.

Forming images with thermal neutrons

NASA Astrophysics Data System (ADS)

Vanier, Peter E.; Forman, Leon

2003-01-01

Thermal neutrons passing through air have scattering lengths of about 20 meters. At further distances, the majority of neutrons emanating from a moderated source will scatter multiple times in the air before being detected, and will not retain information about the location of the source, except that their density will fall off somewhat faster than 1/r2. However, there remains a significant fraction of the neutrons that will travel 20 meters or more without scattering and can be used to create an image of the source. A few years ago, a proof-of-principle "camera" was demonstrated that could produce images of a scene containing sources of thermalized neutrons and could locate a source comparable in strength with an improvised nuclear device at ranges over 60 meters. The instrument makes use of a coded aperture with a uniformly redundant array of openings, analogous to those used in x-ray and gamma cameras. The detector is a position-sensitive He-3 proportional chamber, originally used for neutron diffraction. A neutron camera has many features in common with those designed for non-focusable photons, as well as some important differences. Potential applications include detecting nuclear smuggling, locating non-metallic land mines, assaying nuclear waste, and surveying for health physics purposes.

Light Scattering by Fractal Dust Aggregates. II. Opacity and Asymmetry Parameter

NASA Astrophysics Data System (ADS)

Tazaki, Ryo; Tanaka, Hidekazu

2018-06-01

Optical properties of dust aggregates are important at various astrophysical environments. To find a reliable approximation method for optical properties of dust aggregates, we calculate the opacity and the asymmetry parameter of dust aggregates by using a rigorous numerical method, the T-Matrix Method, and then the results are compared to those obtained by approximate methods: the Rayleigh–Gans–Debye (RGD) theory, the effective medium theory (EMT), and the distribution of hollow spheres method (DHS). First of all, we confirm that the RGD theory breaks down when multiple scattering is important. In addition, we find that both EMT and DHS fail to reproduce the optical properties of dust aggregates with fractal dimensions of 2 when the incident wavelength is shorter than the aggregate radius. In order to solve these problems, we test the mean field theory (MFT), where multiple scattering can be taken into account. We show that the extinction opacity of dust aggregates can be well reproduced by MFT. However, it is also shown that MFT is not able to reproduce the scattering and absorption opacities when multiple scattering is important. We successfully resolve this weak point of MFT, by newly developing a modified mean field theory (MMF). Hence, we conclude that MMF can be a useful tool to investigate radiative transfer properties of various astrophysical environments. We also point out an enhancement of the absorption opacity of dust aggregates in the Rayleigh domain, which would be important to explain the large millimeter-wave opacity inferred from observations of protoplanetary disks.

Using Monte Carlo ray tracing simulations to model the quantum harmonic oscillator modes observed in uranium nitride

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

Lin, J. Y. Y.; Aczel, Adam A; Abernathy, Douglas L

2014-01-01

Recently an extended series of equally spaced vibrational modes was observed in uranium nitride (UN) by performing neutron spectroscopy measurements using the ARCS and SEQUOIA time-of- flight chopper spectrometers [A.A. Aczel et al, Nature Communications 3, 1124 (2012)]. These modes are well described by 3D isotropic quantum harmonic oscillator (QHO) behavior of the nitrogen atoms, but there are additional contributions to the scattering that complicate the measured response. In an effort to better characterize the observed neutron scattering spectrum of UN, we have performed Monte Carlo ray tracing simulations of the ARCS and SEQUOIA experiments with various sample kernels, accountingmore » for the nitrogen QHO scattering, contributions that arise from the acoustic portion of the partial phonon density of states (PDOS), and multiple scattering. These simulations demonstrate that the U and N motions can be treated independently, and show that multiple scattering contributes an approximate Q-independent background to the spectrum at the oscillator mode positions. Temperature dependent studies of the lowest few oscillator modes have also been made with SEQUOIA, and our simulations indicate that the T-dependence of the scattering from these modes is strongly influenced by the uranium lattice.« less

Method of virtual quanta and gravitational radiation

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

Matzner, R.A.; Nutku, Y.

1974-02-01

The radio signals received from pulsars are pulses which are frequently broadened as a result of scattering in the interstellar medium. This broadening is examined theoretically using a diffraction theory of wave propagation in weakly irregular media. The theory is valid for all distances in the scattering medium, and particular attention is paid to the transition from the regime where single scattering predominates to that where all the radiation has been multiply- scattered. Typical pulse shapes are calculated and the results are compared with the theory of pulse broadening based on geometrical optics which represents the limiting case for extrememore » multiple scatter. (auth)« less

Atmospheric scattering of middle uv radiation from an internal source.

PubMed

Meier, R R; Lee, J S; Anderson, D E

1978-10-15

A Monte Carlo model has been developed which simulates the multiple-scattering of middle-uv radiation in the lower atmosphere. The source of radiation is assumed to be monochromatic and located at a point. The physical effects taken into account in the model are Rayleigh and Mie scattering, pure absorption by particulates and trace atmospheric gases, and ground albedo. The model output consists of the multiply scattered radiance as a function of look-angle of a detector located within the atmosphere. Several examples are discussed, and comparisons are made with direct-source and single-scattered contributions to the signal received by the detector.

EXTINCTION LAWS TOWARD STELLAR SOURCES WITHIN A DUSTY CIRCUMSTELLAR MEDIUM AND IMPLICATIONS FOR TYPE IA SUPERNOVAE

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

Nagao, Takashi; Maeda, Keiichi; Nozawa, Takaya, E-mail: nagao@kusastro.kyoto-u.ac.jp

Many astronomical objects are surrounded by dusty environments. In such dusty objects, multiple scattering processes of photons by circumstellar (CS) dust grains can effectively alter extinction properties. In this paper, we systematically investigate the effects of multiple scattering on extinction laws for steady-emission sources surrounded by the dusty CS medium using a radiation transfer simulation based on the Monte Carlo technique. In particular, we focus on whether and how the extinction properties are affected by properties of CS dust grains by adopting various dust grain models. We confirm that behaviors of the (effective) extinction laws are highly dependent on themore » properties of CS grains, especially the total-to-selective extinction ratio R{sub V}, which characterizes the extinction law and can be either increased or decreased and compared with the case without multiple scattering. We find that the criterion for this behavior is given by a ratio of albedos in the B and V bands. We also find that either small silicate grains or polycyclic aromatic hydrocarbons are necessary for realizing a low value of R{sub V} as often measured toward SNe Ia if the multiple scattering by CS dust is responsible for their non-standard extinction laws. Using the derived relations between the properties of dust grains and the resulting effective extinction laws, we propose that the extinction laws toward dusty objects could be used to constrain the properties of dust grains in CS environments.« less

Polarized Light Scattering from Perfect and Perturbed Surfaces and Fundamental Scattering Systems

DTIC Science & Technology

1992-02-29

ob- one frequency, an extension of it to multiple-field interac- served in the elastically scattered light emitted from glass tions would follow the...that 8. V CeIll . A. A. Maradudin, A. M. Marvin, and A. R. McGurn, can explain only gross scattering features. It is inde "Some aspects of light...and a surface of index n a 10.0 - 0.01. Such a surface could be made with a series of 1/4-wave dielectric layers on a glass substrate. It Is more

Measurement of multiplicities of charged hadrons, pions and kaons in DIS at COMPASS

NASA Astrophysics Data System (ADS)

Mitrofanov, Nikolai

2018-04-01

Precise measurements of multiplicities of charged hadrons, pions and kaons in deep inelastic scattering were performed. The data were obtained by the COMPASS Collaboration by scattering 160 GeV muons off an isoscalar 6LiD target. The results were obtained in three-dimensional bins of the Bjorken scaling variable x, the relative virtual-photon energy y, and the fraction z of the virtual-photon energy carried by the produced hadron. A leading-order pQCD analysis was performed using the pion multiplicity results to extract quark fragmentation functions into pions. The results for the sum of the z-integrated multiplicities for pions and for kaons, differ from earlier results from the HERMES experiment. The results from the sum of the z-integrated K+ and K- multiplicities at high x point to a value of the non-strange quark fragmentation function larger than obtained by the earlier DSS fit.

New Insight into the Local Structure of Hydrous Ferric Arsenate Using Full-Potential Multiple Scattering Analysis, Density Functional Theory Calculations, and Vibrational Spectroscopy.

PubMed

Wang, Shaofeng; Ma, Xu; Zhang, Guoqing; Jia, Yongfeng; Hatada, Keisuke

2016-11-15

Hydrous ferric arsenate (HFA) is an important arsenic-bearing precipitate in the mining-impacted environment and hydrometallurgical tailings. However, there is no agreement on its local atomic structure. The local structure of HFA was reprobed by employing a full-potential multiple scattering (FPMS) analysis, density functional theory (DFT) calculations, and vibrational spectroscopy. The FPMS simulations indicated that the coordination number of the As-Fe, Fe-As, or both in HFA was approximately two. The DFT calculations constructed a structure of HFA with the formula of Fe(HAsO 4 ) x (H 2 AsO 4 ) 1-x (OH) y ·zH 2 O. The presence of protonated arsenate in HFA was also evidenced by vibrational spectroscopy. The As and Fe K-edge X-ray absorption near-edge structure spectra of HFA were accurately reproduced by FPMS simulations using the chain structure, which was also a reasonable model for extended X-Ray absorption fine structure fitting. The FPMS refinements indicated that the interatomic Fe-Fe distance was approximately 5.2 Å, consistent with that obtained by Mikutta et al. (Environ. Sci. Technol. 2013, 47 (7), 3122-3131) using wavelet analysis. All of the results suggested that HFA was more likely to occur as a chain with AsO 4 tetrahedra and FeO 6 octahedra connecting alternately in an isolated bidentate-type fashion. This finding is of significance for understanding the fate of arsenic and the formation of ferric arsenate minerals in an acidic environment.

Qualitative and quantitative analysis of heparin and low molecular weight heparins using size exclusion chromatography with multiple angle laser scattering/refractive index and inductively coupled plasma/mass spectrometry detectors.

PubMed

Ouyang, Yilan; Zeng, Yangyang; Yi, Lin; Tang, Hong; Li, Duxin; Linhardt, Robert J; Zhang, Zhenqing

2017-11-03

Heparin, a highly sulfated glycosaminoglycan, has been used as a clinical anticoagulant over 80 years. Low molecular weight heparins (LMWHs), heparins partially depolymerized using different processes, are widely used as clinical anticoagulants. Qualitative molecular weight (MW) and quantitative mass content analysis are two important factors that contribute to LMWH quality control. Size exclusion chromatography (SEC), relying on multiple angle laser scattering (MALS)/refractive index (RI) detectors, has been developed for accurate analysis of heparin MW in the absence of standards. However, the cations, which ion-pair with the anionic polysaccharide chains of heparin and LMWHs, had not been considered in previous reports. In this study, SEC with MALS/RI and inductively coupled plasma/mass spectrometry detectors were used in a comprehensive analytical approach taking both anionic polysaccharide and ion-paired cations heparin products. This approach was also applied to quantitative analysis of heparin and LMWHs. Full profiles of MWs and mass recoveries for three commercial heparin/LMWH products, heparin sodium, enoxaparin sodium and nadroparin calcium, were obtained and all showed higher MWs than previously reported. This important improvement more precisely characterized the MW properties of heparin/LMWHs and potentially many other anionic polysaccharides. Copyright © 2017 Elsevier B.V. All rights reserved.

Simulation of ultrasonic NCF composites testing using 3D finite element model

NASA Astrophysics Data System (ADS)

Liu, Z.; Saffari, N.; Fromme, P.

2012-04-01

Composite materials offer many advantages for aerospace applications, e.g., good strength to weight ratio. Different types of composites, such as non-crimp fabrics (NCF), are currently being investigated as they offer reduced manufacturing costs and improved damage tolerance as compared to traditional pre-impregnated composite materials. NCF composites are made from stitched fiber bundles (tows), which typically have a width and thickness in the order of millimeter. This results in strongly inhomogeneous and anisotropic material properties. Different types of manufacturing imperfections, such as porosity, resin pockets, tow crimp and misalignment can lead to reduced material strength and thus to defects following excessive loads or impact, e.g. fracture and delaminations. The ultrasonic non-destructive testing of NCF composites is difficult, as the tow size is comparable to the wavelength, leading to multiple scattering in this inherently three-dimensional structure. For typical material properties and geometry of an NCF composite, a full three-dimensional Finite Element (FE) model has been developed in ABAQUS. The propagation of longitudinal ultrasonic waves has been simulated and the effect of multiple scattering at the fiber tows investigated. The effect of porosity as a typical manufacturing imperfection has been considered. The potential for the detection and quantification of such defects is discussed based on the observed influence on the ultrasonic wave propagation and attenuation.

Sub-100 nm gold nanohole-enhanced Raman scattering on flexible PDMS sheets.

PubMed

Lee, Seunghyun; Ongko, Andry; Kim, Ho Young; Yim, Sang-Gu; Jeon, Geumhye; Jeong, Hee Jin; Lee, Seungwoo; Kwak, Minseok; Yang, Seung Yun

2016-08-05

Surface-enhanced Raman spectroscopy (SERS) is a highly sensitive vibrational spectroscopy technique enabling detection of multiple analytes at the molecular level in a nondestructive and rapid manner. In this work, we introduce a new approach to fabricate deep subwavelength-scaled (sub-100 nm) metallic nanohole arrays (quasi-3D metallic nanoholes) on flexible and highly efficient SERS substrates. Target structures have been fabricated using a two-step process consisting of (i) direct pattern transfer of spin-coated polymer films onto polydimethylsiloxane (PDMS) substrates by plasma etching with transferred anodic aluminum oxide masks, and (ii) producing SERS-active substrates by functionalization of the etched polymeric films followed by Au deposition. Such an all-dry, top-down lithographic approach enables on-demand patterning of SERS-active metallic nanoholes with high structural fidelity even onto flexible and stretchable substrates, thus making possible multiple sensing modes in a versatile fashion. For example, metallic nanoholes on flexible PDMS substrates are highly amenable to their integration with curved glass sticks, which can be used in optical fiber-integrated SERS systems. Au surfaces immobilized by probe DNA molecules show a selective enhancement of Raman scattering with Cy5-labeled complementary DNA (as compared to flat Au surfaces), demonstrating the potential of using the quasi-3D Au nanohole arrays for bio-sensing applications.

Sub-100 nm gold nanohole-enhanced Raman scattering on flexible PDMS sheets

NASA Astrophysics Data System (ADS)

Lee, Seunghyun; Ongko, Andry; Kim, Ho Young; Yim, Sang-Gu; Jeon, Geumhye; Jeong, Hee Jin; Lee, Seungwoo; Kwak, Minseok; Yang, Seung Yun

2016-08-01

Surface-enhanced Raman spectroscopy (SERS) is a highly sensitive vibrational spectroscopy technique enabling detection of multiple analytes at the molecular level in a nondestructive and rapid manner. In this work, we introduce a new approach to fabricate deep subwavelength-scaled (sub-100 nm) metallic nanohole arrays (quasi-3D metallic nanoholes) on flexible and highly efficient SERS substrates. Target structures have been fabricated using a two-step process consisting of (i) direct pattern transfer of spin-coated polymer films onto polydimethylsiloxane (PDMS) substrates by plasma etching with transferred anodic aluminum oxide masks, and (ii) producing SERS-active substrates by functionalization of the etched polymeric films followed by Au deposition. Such an all-dry, top-down lithographic approach enables on-demand patterning of SERS-active metallic nanoholes with high structural fidelity even onto flexible and stretchable substrates, thus making possible multiple sensing modes in a versatile fashion. For example, metallic nanoholes on flexible PDMS substrates are highly amenable to their integration with curved glass sticks, which can be used in optical fiber-integrated SERS systems. Au surfaces immobilized by probe DNA molecules show a selective enhancement of Raman scattering with Cy5-labeled complementary DNA (as compared to flat Au surfaces), demonstrating the potential of using the quasi-3D Au nanohole arrays for bio-sensing applications.

Sensitivity booster for DOI-PET scanner by utilizing Compton scattering events between detector blocks

NASA Astrophysics Data System (ADS)

Yoshida, Eiji; Tashima, Hideaki; Yamaya, Taiga

2014-11-01

In a conventional PET scanner, coincidence events are measured with a limited energy window for detection of photoelectric events in order to reject Compton scatter events that occur in a patient, but Compton scatter events caused in detector crystals are also rejected. Scatter events within the patient causes scatter coincidences, but inter crystal scattering (ICS) events have useful information for determining an activity distribution. Some researchers have reported the feasibility of PET scanners based on a Compton camera for tracing ICS into the detector. However, these scanners require expensive semiconductor detectors for high-energy resolution. In the Anger-type block detector, single photons interacting with multiple detectors can be obtained for each interacting position and complete information can be gotten just as for photoelectric events in the single detector. ICS events in the single detector have been used to get coincidence, but single photons interacting with multiple detectors have not been used to get coincidence. In this work, we evaluated effect of sensitivity improvement using Compton kinetics in several types of DOI-PET scanners. The proposed method promises to improve the sensitivity using coincidence events of single photons interacting with multiple detectors, which are identified as the first interaction (FI). FI estimation accuracy can be improved to determine FI validity from the correlation between Compton scatter angles calculated on the coincidence line-of-response. We simulated an animal PET scanner consisting of 42 detectors. Each detector block consists of three types of scintillator crystals (LSO, GSO and GAGG). After the simulation, coincidence events are added as information for several depth-of-interaction (DOI) resolutions. From the simulation results, we concluded the proposed method promises to improve the sensitivity considerably when effective atomic number of a scintillator is low. Also, we showed that FI estimate accuracy is improved, as DOI resolution is high.

Multiple scattering in particulate planetary surfaces

NASA Astrophysics Data System (ADS)

Muinonen, Karri; Peltoniemi, Jouni; Markkanen, Johannes; Penttilä, Antti; Videen, Gorden

2015-08-01

There are two ubiquitous phenomena observed at small solar phase angles (the Sun-Object-Observer angle) from, for example, asteroids and transneptunian objects. First, a nonlinear increase of brightness is observed toward the zero phase angle in the magnitude scale that is commonly called the opposition effect. Second, the scattered light is observed to be partially linearly polarized parallel to the Sun-Object-Observer plane that iscommonly called the negative polarization surge.The observations can be interpreted using a radiative-transfer coherent-backscattering Monte Carlo method (RT-CB, Muinonen 2004) that makes use of a so-called phenomenological fundamental single scatterer (Muinonen and Videen 2012). For the validity of RT-CB, see Muinonen et al. (2012). The method can allow us to put constraints on the size, shape, and refractive index of the fundamental scatterers.In the present work, we extend the RT-CB method for the specific case of a macroscopic medium of electric dipole scatterers. For the computation of the interactions, the far-field approximation inherent in the RT-CB method is replaced by an exact treatment, allowing us to account for, e.g., the so-called near-field effects. The present method constitutes the first milestone in the development of a multiple-scattering method, where the so-called ladder and maximally crossed cyclical diagrams of the multiple electromagnetic interactions are rigorously computed. We expect to utilize the new methods in the spectroscopic, photometric, and polarimetric studies of asteroids, as well as in the interpretation of radar echoes from small Solar System bodies.Acknowledgments. The research is funded by the ERC Advanced Grant No 320773 entitled Scattering and Absorption of Electromagnetic Waves in Particulate Media (SAEMPL).K. Muinonen, Waves in Random Media 14, 365 (2004).K. Muinonen, K., and G. Videen, JQSRT 113, 2385 (2012).K. Muinonen, M. I. Mishchenko, J. M. Dlugach, E. Zubko, A. Penttilä,and G. Videen, ApJ 760, 118 (2012).

Coherent light depolarization by multiple scattering media and tissues: some fundamentals and applications

NASA Astrophysics Data System (ADS)

Zimnyakov, Dmitry A.; Tuchin, Valery V.; Yodh, Arjun G.; Mishin, Alexey A.; Peretochkin, Igor S.

1998-04-01

Relationships between decorrelation and depolarization of coherent light scattered by disordered media are examined by using the conception of the photon paths distribution functions. Analysis of behavior of the autocorrelation functions of the scattered field fluctuations and their polarization properties allows us to introduce generalized parameter of scattering media such as specific correlation time. Determination of specific correlation time has been carried out for phantom scattering media (water suspensions of polystyrene spheres). Results of statistical, correlation and polarization analysis of static and dynamic speckle patterns carried out in the experiments with human sclera with artificially controlled optical transmittance are presented. Some possibilities of applications of such polarization- correlation technique for monitoring and visualization of non- single scattering tissue structures are discussed.

Robust statistical reconstruction for charged particle tomography

DOEpatents

Schultz, Larry Joe; Klimenko, Alexei Vasilievich; Fraser, Andrew Mcleod; Morris, Christopher; Orum, John Christopher; Borozdin, Konstantin N; Sossong, Michael James; Hengartner, Nicolas W

2013-10-08

Systems and methods for charged particle detection including statistical reconstruction of object volume scattering density profiles from charged particle tomographic data to determine the probability distribution of charged particle scattering using a statistical multiple scattering model and determine a substantially maximum likelihood estimate of object volume scattering density using expectation maximization (ML/EM) algorithm to reconstruct the object volume scattering density. The presence of and/or type of object occupying the volume of interest can be identified from the reconstructed volume scattering density profile. The charged particle tomographic data can be cosmic ray muon tomographic data from a muon tracker for scanning packages, containers, vehicles or cargo. The method can be implemented using a computer program which is executable on a computer.

Nondestructive prediction of pork freshness parameters using multispectral scattering images

NASA Astrophysics Data System (ADS)

Tang, Xiuying; Li, Cuiling; Peng, Yankun; Chao, Kuanglin; Wang, Mingwu

2012-05-01

Optical technology is an important and immerging technology for non-destructive and rapid detection of pork freshness. This paper studied on the possibility of using multispectral imaging technique and scattering characteristics to predict the freshness parameters of pork meat. The pork freshness parameters selected for prediction included total volatile basic nitrogen (TVB-N), color parameters (L *, a *, b *), and pH value. Multispectral scattering images were obtained from pork sample surface by a multispectral imaging system developed by ourselves; they were acquired at the selected narrow wavebands whose center wavelengths were 517,550, 560, 580, 600, 760, 810 and 910nm. In order to extract scattering characteristics from multispectral images at multiple wavelengths, a Lorentzian distribution (LD) function with four parameters (a: scattering asymptotic value; b: scattering peak; c: scattering width; d: scattering slope) was used to fit the scattering curves at the selected wavelengths. The results show that the multispectral imaging technique combined with scattering characteristics is promising for predicting the freshness parameters of pork meat.

Using Monte Carlo Ray tracing to Understand the Vibrational Response of UN as Measured by Neutron Spectroscopy

NASA Astrophysics Data System (ADS)

Lin, J. Y. Y.; Aczel, A. A.; Abernathy, D. L.; Nagler, S. E.; Buyers, W. J. L.; Granroth, G. E.

2014-03-01

Recently neutron spectroscopy measurements, using the ARCS and SEQUOIA time-of-flight chopper spectrometers, observed an extended series of equally spaced modes in UN that are well described by quantum harmonic oscillator behavior of the N atoms. Additional contributions to the scattering are also observed. Monte Carlo ray tracing simulations with various sample kernels have allowed us to distinguish between the response from the N oscillator scattering, contributions that arise from the U partial phonon density of states (PDOS), and all forms of multiple scattering. These simulations confirm that multiple scattering contributes an ~ Q -independent background to the spectrum at the oscillator mode positions. All three of the aforementioned contributions are necessary to accurately model the experimental data. These simulations were also used to compare the T dependence of the oscillator modes in SEQUOIA data to that predicted by the binary solid model. This work was sponsored by the Scientific User Facilities Division, Office of Basic Energy Sciences, U.S. Department of Energy.

The effective propagation constants of SH wave in composites reinforced by dispersive parallel nanofibers

NASA Astrophysics Data System (ADS)

Qiang, FangWei; Wei, PeiJun; Li, Li

2012-07-01

In the present paper, the effective propagation constants of elastic SH waves in composites with randomly distributed parallel cylindrical nanofibers are studied. The surface stress effects are considered based on the surface elasticity theory and non-classical interfacial conditions between the nanofiber and the host are derived. The scattering waves from individual nanofibers embedded in an infinite elastic host are obtained by the plane wave expansion method. The scattering waves from all fibers are summed up to obtain the multiple scattering waves. The interactions among random dispersive nanofibers are taken into account by the effective field approximation. The effective propagation constants are obtained by the configurational average of the multiple scattering waves. The effective speed and attenuation of the averaged wave and the associated dynamical effective shear modulus of composites are numerically calculated. Based on the numerical results, the size effects of the nanofibers on the effective propagation constants and the effective modulus are discussed.

A random Q-switched fiber laser

PubMed Central

Tang, Yulong; Xu, Jianqiu

2015-01-01

Extensive studies have been performed on random lasers in which multiple-scattering feedback is used to generate coherent emission. Q-switching and mode-locking are well-known routes for achieving high peak power output in conventional lasers. However, in random lasers, the ubiquitous random cavities that are formed by multiple scattering inhibit energy storage, making Q-switching impossible. In this paper, widespread Rayleigh scattering arising from the intrinsic micro-scale refractive-index irregularities of fiber cores is used to form random cavities along the fiber. The Q-factor of the cavity is rapidly increased by stimulated Brillouin scattering just after the spontaneous emission is enhanced by random cavity resonances, resulting in random Q-switched pulses with high brightness and high peak power. This report is the first observation of high-brightness random Q-switched laser emission and is expected to stimulate new areas of scientific research and applications, including encryption, remote three-dimensional random imaging and the simulation of stellar lasing. PMID:25797520

Strategies for Multi-Modal Analysis

NASA Astrophysics Data System (ADS)

Hexemer, Alexander; Wang, Cheng; Pandolfi, Ronald; Kumar, Dinesh; Venkatakrishnan, Singanallur; Sethian, James; Camera Team

This section on soft materials will be dedicated to discuss the extraction of the chemical distribution and spatial arrangement of constituent elements and functional groups at multiple length scales and, thus, the examination of collective dynamics, transport, and electronic ordering phenomena. Traditional measures of structure in soft materials have relied heavily on scattering and imaging based techniques due to their capacity to measure nanoscale dimensions and their capacity to monitor structure under conditions of dynamic stress loading. Special attentions are planned to focus on the application of resonant x-ray scattering, contrast-varied neutron scattering, analytical transmission electron microscopy, and their combinations. This session aims to bring experts in both scattering and electron microscope fields to discuss recent advances in selectively characterizing structural architectures of complex soft materials, which have often multi-components with a wide range of length scales and multiple functionalities, and thus hopes to foster novel ideas to decipher a higher level of structural complexity in soft materials in future. CAMERA, Early Career Award.

Modeling radiative transfer with the doubling and adding approach in a climate GCM setting

NASA Astrophysics Data System (ADS)

Lacis, A. A.

2017-12-01

The nonlinear dependence of multiply scattered radiation on particle size, optical depth, and solar zenith angle, makes accurate treatment of multiple scattering in the climate GCM setting problematic, due primarily to computational cost issues. In regard to the accurate methods of calculating multiple scattering that are available, their computational cost is far too prohibitive for climate GCM applications. Utilization of two-stream-type radiative transfer approximations may be computationally fast enough, but at the cost of reduced accuracy. We describe here a parameterization of the doubling/adding method that is being used in the GISS climate GCM, which is an adaptation of the doubling/adding formalism configured to operate with a look-up table utilizing a single gauss quadrature point with an extra-angle formulation. It is designed to closely reproduce the accuracy of full-angle doubling and adding for the multiple scattering effects of clouds and aerosols in a realistic atmosphere as a function of particle size, optical depth, and solar zenith angle. With an additional inverse look-up table, this single-gauss-point doubling/adding approach can be adapted to model fractional cloud cover for any GCM grid-box in the independent pixel approximation as a function of the fractional cloud particle sizes, optical depths, and solar zenith angle dependence.

Unified double- and single-sided homogeneous Green’s function representations

PubMed Central

van der Neut, Joost; Slob, Evert

2016-01-01

In wave theory, the homogeneous Green’s function consists of the impulse response to a point source, minus its time-reversal. It can be represented by a closed boundary integral. In many practical situations, the closed boundary integral needs to be approximated by an open boundary integral because the medium of interest is often accessible from one side only. The inherent approximations are acceptable as long as the effects of multiple scattering are negligible. However, in case of strongly inhomogeneous media, the effects of multiple scattering can be severe. We derive double- and single-sided homogeneous Green’s function representations. The single-sided representation applies to situations where the medium can be accessed from one side only. It correctly handles multiple scattering. It employs a focusing function instead of the backward propagating Green’s function in the classical (double-sided) representation. When reflection measurements are available at the accessible boundary of the medium, the focusing function can be retrieved from these measurements. Throughout the paper, we use a unified notation which applies to acoustic, quantum-mechanical, electromagnetic and elastodynamic waves. We foresee many interesting applications of the unified single-sided homogeneous Green’s function representation in holographic imaging and inverse scattering, time-reversed wave field propagation and interferometric Green’s function retrieval. PMID:27436983

Unified double- and single-sided homogeneous Green's function representations

NASA Astrophysics Data System (ADS)

Wapenaar, Kees; van der Neut, Joost; Slob, Evert

2016-06-01

In wave theory, the homogeneous Green's function consists of the impulse response to a point source, minus its time-reversal. It can be represented by a closed boundary integral. In many practical situations, the closed boundary integral needs to be approximated by an open boundary integral because the medium of interest is often accessible from one side only. The inherent approximations are acceptable as long as the effects of multiple scattering are negligible. However, in case of strongly inhomogeneous media, the effects of multiple scattering can be severe. We derive double- and single-sided homogeneous Green's function representations. The single-sided representation applies to situations where the medium can be accessed from one side only. It correctly handles multiple scattering. It employs a focusing function instead of the backward propagating Green's function in the classical (double-sided) representation. When reflection measurements are available at the accessible boundary of the medium, the focusing function can be retrieved from these measurements. Throughout the paper, we use a unified notation which applies to acoustic, quantum-mechanical, electromagnetic and elastodynamic waves. We foresee many interesting applications of the unified single-sided homogeneous Green's function representation in holographic imaging and inverse scattering, time-reversed wave field propagation and interferometric Green's function retrieval.

Validation of the MCNP6 electron-photon transport algorithm: multiple-scattering of 13- and 20-MeV electrons in thin foils

NASA Astrophysics Data System (ADS)

Dixon, David A.; Hughes, H. Grady

2017-09-01

This paper presents a validation test comparing angular distributions from an electron multiple-scattering experiment with those generated using the MCNP6 Monte Carlo code system. In this experiment, a 13- and 20-MeV electron pencil beam is deflected by thin foils with atomic numbers from 4 to 79. To determine the angular distribution, the fluence is measured down range of the scattering foil at various radii orthogonal to the beam line. The characteristic angle (the angle for which the max of the distribution is reduced by 1/e) is then determined from the angular distribution and compared with experiment. Multiple scattering foils tested herein include beryllium, carbon, aluminum, copper, and gold. For the default electron-photon transport settings, the calculated characteristic angle was statistically distinguishable from measurement and generally broader than the measured distributions. The average relative difference ranged from 5.8% to 12.2% over all of the foils, source energies, and physics settings tested. This validation illuminated a deficiency in the computation of the underlying angular distributions that is well understood. As a result, code enhancements were made to stabilize the angular distributions in the presence of very small substeps. However, the enhancement only marginally improved results indicating that additional algorithmic details should be studied.

Acoustic and electromagnetic wave interaction in the detection and identification of buried objects

NASA Astrophysics Data System (ADS)

Lawrence, Daniel Edward

2002-09-01

In order to facilitate the development of a hybrid acoustic and electromagnetic (EM) system for buried object detection, a number of analytical solutions and a novel numerical technique are developed to analyze the complex interaction between acoustic and EM scattering. The essence of the interaction lies in the fact that identifiable acoustic properties of an object, such as acoustic resonances, can be observed in the scattered EM Doppler spectrum. Using a perturbation approach, analytical solutions are derived for the EM scattering from infinitely long circular cylinders, both metallic and dielectric, under acoustic vibration in a homogeneous background medium. Results indicate that both the shape variation and dielectric constant contribute to the scattered EM Doppler spectrum. To model the effect of a cylinder beneath an acoustically excited half-space, a new analytical solution is presented for EM scattering from a cylinder beneath a slightly rough surface. The solution is achieved by using plane-wave expansion of the fields and an iterative technique to account for the multiple interactions between the cylinder and rough surface. Following a similar procedure, a novel solution for elastic-wave scattering from a solid cylinder embedded in a solid half-space is developed and used to calculate the surface displacement. Simulations indicate that only a finite range of spatial surface frequencies, corresponding to surface roughness on the order of the EM wavelength; affect the EM scattering from buried objects and suggest that object detection can be improved if the acoustic excitation induces surface roughness outside this range. To extend the study to non-canonical scenarios, a novel numerical approach is introduced in which time-varying impedance boundary conditions (IBCs) are used in conjunction with the method of moments (MoM) to model the EM scattering from vibrating metallic objects of arbitrary shape. It is shown that the standard IBC provides a first order solution for TM polarization, but a second order IBC is needed for TE polarization. The crucial factor in the calculation of the potentially small Doppler components is that the time-varying nature of the cylinder boundary, contained within the surface impedance expressions, can be isolated from the unperturbed terms in the scattered field.

Calculations of Total Classical Cross Sections for a Central Field

NASA Astrophysics Data System (ADS)

Tsyganov, D. L.

2018-07-01

In order to find the total collision cross-section a direct method of the effective potential (EPM) in the framework of classical mechanics was proposed. EPM allows to over come both the direct scattering problem (calculation of the total collision cross-section) and the inverse scattering problem (reconstruction of the scattering potential) quickly and effectively. A general analytical expression was proposed for the generalized Lennard-Jones potentials: (6-3), (9-3), (12-3), (6-4), (8-4), (12-4), (8-6), (12-6), (18-6). The values for the scattering potential of the total cross section for pairs such as electron-N2, N-N, and O-O2 were obtained in a good approximation.

A mesh-free approach to acoustic scattering from multiple spheres nested inside a large sphere by using diagonal translation operators.

PubMed

Hesford, Andrew J; Astheimer, Jeffrey P; Greengard, Leslie F; Waag, Robert C

2010-02-01

A multiple-scattering approach is presented to compute the solution of the Helmholtz equation when a number of spherical scatterers are nested in the interior of an acoustically large enclosing sphere. The solution is represented in terms of partial-wave expansions, and a linear system of equations is derived to enforce continuity of pressure and normal particle velocity across all material interfaces. This approach yields high-order accuracy and avoids some of the difficulties encountered when using integral equations that apply to surfaces of arbitrary shape. Calculations are accelerated by using diagonal translation operators to compute the interactions between spheres when the operators are numerically stable. Numerical results are presented to demonstrate the accuracy and efficiency of the method.

A mesh-free approach to acoustic scattering from multiple spheres nested inside a large sphere by using diagonal translation operators

PubMed Central

Hesford, Andrew J.; Astheimer, Jeffrey P.; Greengard, Leslie F.; Waag, Robert C.

2010-01-01

A multiple-scattering approach is presented to compute the solution of the Helmholtz equation when a number of spherical scatterers are nested in the interior of an acoustically large enclosing sphere. The solution is represented in terms of partial-wave expansions, and a linear system of equations is derived to enforce continuity of pressure and normal particle velocity across all material interfaces. This approach yields high-order accuracy and avoids some of the difficulties encountered when using integral equations that apply to surfaces of arbitrary shape. Calculations are accelerated by using diagonal translation operators to compute the interactions between spheres when the operators are numerically stable. Numerical results are presented to demonstrate the accuracy and efficiency of the method. PMID:20136208

Photometric studies of Saturn's ring and eclipses of the Galilean satellites

NASA Technical Reports Server (NTRS)

Brunk, W. E.

1972-01-01

Reliable data defining the photometric function of the Saturn ring system at visual wavelengths are interpreted in terms of a simple scattering model. To facilitate the analysis, new photographic photometry of the ring has been carried out and homogeneous measurements of the mean surface brightness are presented. The ring model adopted is a plane parallel slab of isotropically scattering particles; the single scattering albedo and the perpendicular optical thickness are both arbitrary. Results indicate that primary scattering is inadequate to describe the photometric properties of the ring: multiple scattering predominates for all angles of tilt with respect to the Sun and earth. In addition, the scattering phase function of the individual particles is significantly anisotropic: they scatter preferentially towards the sun. Photoelectric photometry of Ganymede during its eclipse by Jupiter indicate that neither a simple reflecting-layer model nor a semi-infinite homogeneous scattering model provides an adequate physical description of the Jupiter atmosphere.

MUSIC algorithms for rebar detection

NASA Astrophysics Data System (ADS)

Solimene, Raffaele; Leone, Giovanni; Dell'Aversano, Angela

2013-12-01

The MUSIC (MUltiple SIgnal Classification) algorithm is employed to detect and localize an unknown number of scattering objects which are small in size as compared to the wavelength. The ensemble of objects to be detected consists of both strong and weak scatterers. This represents a scattering environment challenging for detection purposes as strong scatterers tend to mask the weak ones. Consequently, the detection of more weakly scattering objects is not always guaranteed and can be completely impaired when the noise corrupting data is of a relatively high level. To overcome this drawback, here a new technique is proposed, starting from the idea of applying a two-stage MUSIC algorithm. In the first stage strong scatterers are detected. Then, information concerning their number and location is employed in the second stage focusing only on the weak scatterers. The role of an adequate scattering model is emphasized to improve drastically detection performance in realistic scenarios.

Using seismic coda waves to resolve intrinsic and scattering attenuation

NASA Astrophysics Data System (ADS)

Wang, W.; Shearer, P. M.

2016-12-01

Seismic attenuation is caused by two factors, scattering and intrinsic absorption. Characterizing scattering and absorbing properties and the power spectrum of crustal heterogeneity is a fundamental problem for informing strong ground motion estimates at high frequencies, where scattering and attenuation effects are critical. Determining the relative amount of attenuation caused by scattering and intrinsic absorption has been a long-standing problem in seismology. The wavetrain following the direct body wave phases is called the coda, which is caused by scattered energy. Many studies have analyzed the coda of local events to constrain crustal and upper-mantle scattering strength and intrinsic attenuation. Here we examine two popular attenuation inversion methods, the Multiple Lapse Time Window Method (MLTWM) and the Coda Qc Method. First, based on our previous work on California attenuation structure, we apply an efficient and accurate method, the Monte Carlo Approach, to synthesize seismic envelope functions. We use this code to generate a series of synthetic data based on several complex and realistic forward models. Although the MLTWM assumes a uniform whole space, we use the MLTWM to invert for both scattering and intrinsic attenuation from the synthetic data to test how accurately it can recover the attenuation models. Results for the coda Qc method depend on choices for the length and starting time of the coda-wave time window. Here we explore the relation between the inversion results for Qc, the windowing parameters, and the intrinsic and scattering Q structure of our synthetic model. These results should help assess the practicality and accuracy of the Multiple Lapse Time Window Method and Coda Qc Method when applied to realistic crustal velocity and attenuation models.

Diffusion approximation with polarization and resonance effects for the modelling of seismic waves in strongly scattering small-scale media

NASA Astrophysics Data System (ADS)

Margerin, Ludovic

2013-01-01

This paper presents an analytical study of the multiple scattering of seismic waves by a collection of randomly distributed point scatterers. The theory assumes that the energy envelopes are smooth, but does not require perturbations to be small, thereby allowing the modelling of strong, resonant scattering. The correlation tensor of seismic coda waves recorded at a three-component sensor is decomposed into a sum of eigenmodes of the elastodynamic multiple scattering (Bethe-Salpeter) equation. For a general moment tensor excitation, a total number of four modes is necessary to describe the transport of seismic waves polarization. Their spatio-temporal dependence is given in closed analytical form. Two additional modes transporting exclusively shear polarizations may be excited by antisymmetric moment tensor sources only. The general solution converges towards an equipartition mixture of diffusing P and S waves which allows the retrieval of the local Green's function from coda waves. The equipartition time is obtained analytically and the impact of absorption on Green's function reconstruction is discussed. The process of depolarization of multiply scattered waves and the resulting loss of information is illustrated for various seismic sources. It is shown that coda waves may be used to characterize the source mechanism up to lapse times of the order of a few mean free times only. In the case of resonant scatterers, a formula for the diffusivity of seismic waves incorporating the effect of energy entrapment inside the scatterers is obtained. Application of the theory to high-contrast media demonstrates that coda waves are more sensitive to slow rather than fast velocity anomalies by several orders of magnitude. Resonant scattering appears as an attractive physical phenomenon to explain the small values of the diffusion constant of seismic waves reported in volcanic areas.

Characterization of random scattering media and related information retrieval

NASA Astrophysics Data System (ADS)

Wang, Zhenyu

There has been substantial interest in optical imaging in and through random media in applications as diverse as environmental sensing and tumor detection. The rich scatter environment also leads to multiple paths or channels, which may provide higher capacity for communication. Coherent light passing through random media produces an intensity speckle pattern when imaged, as a result of multiple scatter and the imaging optics. When polarized coherent light is used, the speckle pattern is sensitive to the polarization state, depending on the amount of scatter, and such measurements provide information about the random medium. This may form the basis for enhanced imaging of random media and provide information on the scatterers themselves. Second and third order correlations over laser scan frequency are shown to lead to the ensemble averaged temporal impulse response, with sensitivity to the polarization state in the more weakly scattering regime. A new intensity interferometer is introduced that provides information about two signals incident on a scattering medium. The two coherent beams, which are not necessarily overlapping, interfere in a scattering medium. A sinusoidal modulation in the second order intensity correlation with laser scan frequency is shown to be related to the relative delay of the two incident beams. An intensity spatial correlation over input position reveals that decorrelation occurs over a length comparable to the incident beam size. Such decorrelation is also related to the amount of scatter. Remarkably, with two beams incident at different angles, the intensity correlation over the scan position has a sinusoidal modulation that is related to the incidence angle difference between the two input beams. This spatial correlation over input position thus provides information about input wavevectors.

5 MeV Mott Polarimeter Development at Jefferson Lab

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

Price, J. S.; Sinclair, C. K.; Cardman, L. S.

1997-01-01

Low energy (E{sub k}=100 keV) Mott scattering polarimeters are ill- suited to support operations foreseen for the polarized electron injector at Jefferson Lab. One solution is to measure the polarization at 5 MeV where multiple and plural scattering are unimportant and precision beam monitoring is straightforward. The higher injector beam current offsets the lower cross-sections. Recent improvements in the CEBAF injector polarimeter scattering chamber have improved signal to noise.

Final state interactions and inclusive nuclear collisions

NASA Technical Reports Server (NTRS)

Cucinotta, Francis A.; Dubey, Rajendra R.

1993-01-01

A scattering formalism is developed in a multiple scattering model to describe inclusive momentum distributions for high-energy projectiles. The effects of final state interactions on response functions and momentum distributions are investigated. Calculations for high-energy protons that include shell model response functions are compared with experiments.

Resonant states for the scattering of slow particles by screened potentials

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

Bruk, Yu. M., E-mail: yubruk@gmail.com; Voloshchuk, A. N.

2016-09-15

Partial resonant situations for the scattering of slow particles with nonzero angular momenta by short-range screened Yukawa and Buckingham potentials are considered. The problem of electron scattering by a hydrogen atom placed in a plasma medium is discussed. A general scheme of resonances has been constructed in the Pais approximation.

Propagation of elastic wave in nanoporous material with distributed cylindrical nanoholes

NASA Astrophysics Data System (ADS)

Qiang, FangWei; Wei, PeiJun; Liu, XiQiang

2013-08-01

The effective propagation constants of plane longitudinal and shear waves in nanoporous material with random distributed parallel cylindrical nanoholes are studied. The surface elastic theory is used to consider the surface stress effects and to derive the nontraditional boundary condition on the surface of nanoholes. The plane wave expansion method is used to obtain the scattering waves from the single nanohole. The multiple scattering effects are taken into consideration by summing the scattered waves from all scatterers and performing the configuration averaging of random distributed scatterers. The effective propagation constants of coherent waves along with the associated dynamic effective elastic modulus are numerically evaluated. The influences of surface stress are discussed based on the numerical results.

Tissue structure characterization of biotissue phantom by use of the speckle-correlometric technique

NASA Astrophysics Data System (ADS)

Isaeva, A. A.; Isaeva, E. A.; Zimnyakov, D. A.; Pantyukov, A. V.; Agapova, Y. V.; Macheyev, M. A.

2017-03-01

Speckle correlometry gives the possibilities to visualize tissue scattering structure analyzing the correlation characteristics of speckle-modulated images. In this work, the inhomogeneous multiple scattering medium with the "dynamic" long inclusions was investigated like a blood vessels in living tissue. The scattering media is 0.28% weight fraction of gelatin dissolved in water and 1 gram per liter (gL-1) and 100 mg per liter (gL-1) of TiO2 for optical scattering. The movement of fluid (distilled water) in the cylindrical hole with given radius simulate a blood motion in the vessel. It was shown the possibility to determinate the depth location of dynamic inhomogeneities inside a scattering medium.

Electromagnetic Scattering by Spheroidal Volumes of Discrete Random Medium

NASA Technical Reports Server (NTRS)

Dlugach, Janna M.; Mishchenko, Michael I.

2017-01-01

We use the superposition T-matrix method to compare the far-field scattering matrices generated by spheroidal and spherical volumes of discrete random medium having the same volume and populated by identical spherical particles. Our results fully confirm the robustness of the previously identified coherent and diffuse scattering regimes and associated optical phenomena exhibited by spherical particulate volumes and support their explanation in terms of the interference phenomenon coupled with the order-of-scattering expansion of the far-field Foldy equations. We also show that increasing non-sphericity of particulate volumes causes discernible (albeit less pronounced) optical effects in forward and backscattering directions and explain them in terms of the same interference/multiple-scattering phenomenon.

Development of Multi-Field of view-Multiple-Scattering-Polarization Lidar ： analysis of angular resolved backscattered signals

NASA Astrophysics Data System (ADS)

Makino, T.; Okamoto, H.; Sato, K.; Tanaka, K.; Nishizawa, T.; Sugimoto, N.; Matsui, I.; Jin, Y.; Uchiyama, A.; Kudo, R.

2014-12-01

We have developed a new type of ground-based lidar, Multi-Field of view-Multiple-Scattering-Polarization Lidar (MFMSPL), to analyze multiple scattering contribution due to low-level clouds. One issue of the ground based lidar is the limitation of optical thickness of about 3 due to the strong attenuation in the lidar signals so that only the cloud bottom part can be observed. In order to overcome the problem, we have proposed the MFMSPL that has been designed to observe similar degree of multiple scattering contribution expected from space-borne lidar CALIOP on CALIPSO satellite. The system consists of eight detectors; four telescopes for parallel channels and four for perpendicular channels. The four pairs of telescope have been mounted with four different off-beam angles, ranging from -5 to 35mrad, where the angle is defined as the one between the direction of laser beam and the direction of telescope. Consequently, similar large foot print (100m) as CALIOP can be achieved in the MFMSPL observations when the altitude of clouds is located at about 1km. The use of multi-field of views enables to measure depolarization ratio from optically thick clouds. The outer receivers attached with larger angles generally detect backscattered signals from clouds located at upper altitudes due to the enhanced multiple scattering compared with the inner receiver that detects signals only from cloud bottom portions. Therefore the information of cloud microphysics from optically thicker regions is expected by the MFMSPL observations compared with the conventional lidar with small FOV. The MFMSPL have been continuously operated in Tsukuba, Japan since June 2014.Initial analyses have indicated expected performances from the theoretical estimation by backward Monte-Carlo simulations. The depolarization ratio from deeper part of the clouds detected by the receiver with large off-beam angle showed much larger values than those from the one with small angle. The calibration procedures and summary of initial observations will be presented. The observed data obtained by the MFMSPL will be used to develop and evaluate the retrieval algorithms for cloud microphysics applied to the CALIOP data.

Weak scattering of scalar and electromagnetic random fields

NASA Astrophysics Data System (ADS)

Tong, Zhisong

This dissertation encompasses several studies relating to the theory of weak potential scattering of scalar and electromagnetic random, wide-sense statistically stationary fields from various types of deterministic or random linear media. The proposed theory is largely based on the first Born approximation for potential scattering and on the angular spectrum representation of fields. The main focus of the scalar counterpart of the theory is made on calculation of the second-order statistics of scattered light fields in cases when the scattering medium consists of several types of discrete particles with deterministic or random potentials. It is shown that the knowledge of the correlation properties for the particles of the same and different types, described with the newly introduced pair-scattering matrix, is crucial for determining the spectral and coherence states of the scattered radiation. The approach based on the pair-scattering matrix is then used for solving an inverse problem of determining the location of an "alien" particle within the scattering collection of "normal" particles, from several measurements of the spectral density of scattered light. Weak scalar scattering of light from a particulate medium in the presence of optical turbulence existing between the scattering centers is then approached using the combination of the Born's theory for treating the light interaction with discrete particles and the Rytov's theory for light propagation in extended turbulent medium. It is demonstrated how the statistics of scattered radiation depend on scattering potentials of particles and the power spectra of the refractive index fluctuations of turbulence. This theory is of utmost importance for applications involving atmospheric and oceanic light transmission. The second part of the dissertation includes the theoretical procedure developed for predicting the second-order statistics of the electromagnetic random fields, such as polarization and linear momentum, scattered from static media. The spatial distribution of these properties of scattered fields is shown to be substantially dependent on the correlation and polarization properties of incident fields and on the statistics of the refractive index distribution within the scatterers. Further, an example is considered which illustrates the usefulness of the electromagnetic scattering theory of random fields in the case when the scattering medium is a thin bio-tissue layer with the prescribed power spectrum of the refractive index fluctuations. The polarization state of the scattered light is shown to be influenced by correlation and polarization states of the illumination as well as by the particle size distribution of the tissue slice.

Design of Multi-Resonant Cavities Based on Metal-Coated Dielectric Nanocylinders

NASA Astrophysics Data System (ADS)

Dong, Junyuan; Yu, Guanxia; Fu, Jingjing; Luo, Min; Du, Wenwen

2018-06-01

In this paper, the light scattering properties for multiple silver-coated dielectric nanocylinders with the symmetrical distribution were investigated. Based on the transfer matrix method, we derive the general transmission and reflection coefficient matrices for multiple dielectric nanocylinders. When the incident light frequencies are less than the plasma frequencies, the surface plasmons (SPs) appear in the interface between the silver and dielectrics. Numerical simulations show that there are three peaks of absorption cross-section (ACS) in the relationship between the ACS and the frequencies of the incident light, when the distance between the silver-coated dielectric nanocylinders is chosen properly. These SPs resonance peaks are characterised as resonances intrinsic to the cylindrically periodic system corresponding to different inner cavity structures. These multi-resonant cavities may have potential applications in integrated devices, optical sensors and optical storage devices.

Accurate in situ measurement of complex refractive index and particle size in intralipid emulsions

NASA Astrophysics Data System (ADS)

Dong, Miao L.; Goyal, Kashika G.; Worth, Bradley W.; Makkar, Sorab S.; Calhoun, William R.; Bali, Lalit M.; Bali, Samir

2013-08-01

A first accurate measurement of the complex refractive index in an intralipid emulsion is demonstrated, and thereby the average scatterer particle size using standard Mie scattering calculations is extracted. Our method is based on measurement and modeling of the reflectance of a divergent laser beam from the sample surface. In the absence of any definitive reference data for the complex refractive index or particle size in highly turbid intralipid emulsions, we base our claim of accuracy on the fact that our work offers several critically important advantages over previously reported attempts. First, our measurements are in situ in the sense that they do not require any sample dilution, thus eliminating dilution errors. Second, our theoretical model does not employ any fitting parameters other than the two quantities we seek to determine, i.e., the real and imaginary parts of the refractive index, thus eliminating ambiguities arising from multiple extraneous fitting parameters. Third, we fit the entire reflectance-versus-incident-angle data curve instead of focusing on only the critical angle region, which is just a small subset of the data. Finally, despite our use of highly scattering opaque samples, our experiment uniquely satisfies a key assumption behind the Mie scattering formalism, namely, no multiple scattering occurs. Further proof of our method's validity is given by the fact that our measured particle size finds good agreement with the value obtained by dynamic light scattering.

Accurate in situ measurement of complex refractive index and particle size in intralipid emulsions.

PubMed

Dong, Miao L; Goyal, Kashika G; Worth, Bradley W; Makkar, Sorab S; Calhoun, William R; Bali, Lalit M; Bali, Samir

2013-08-01

A first accurate measurement of the complex refractive index in an intralipid emulsion is demonstrated, and thereby the average scatterer particle size using standard Mie scattering calculations is extracted. Our method is based on measurement and modeling of the reflectance of a divergent laser beam from the sample surface. In the absence of any definitive reference data for the complex refractive index or particle size in highly turbid intralipid emulsions, we base our claim of accuracy on the fact that our work offers several critically important advantages over previously reported attempts. First, our measurements are in situ in the sense that they do not require any sample dilution, thus eliminating dilution errors. Second, our theoretical model does not employ any fitting parameters other than the two quantities we seek to determine, i.e., the real and imaginary parts of the refractive index, thus eliminating ambiguities arising from multiple extraneous fitting parameters. Third, we fit the entire reflectance-versus-incident-angle data curve instead of focusing on only the critical angle region, which is just a small subset of the data. Finally, despite our use of highly scattering opaque samples, our experiment uniquely satisfies a key assumption behind the Mie scattering formalism, namely, no multiple scattering occurs. Further proof of our method's validity is given by the fact that our measured particle size finds good agreement with the value obtained by dynamic light scattering.

On the radiative properties of soot aggregates part 1: Necking and overlapping

NASA Astrophysics Data System (ADS)

Yon, J.; Bescond, A.; Liu, F.

2015-09-01

There is a strong interest in accurately modelling the radiative properties of soot aggregates (also known as black carbon particles) emitted from combustion systems and fires to gain improved understanding of the role of black carbon to global warming. This study conducted a systematic investigation of the effects of overlapping and necking between neighbouring primary particles on the radiative properties of soot aggregates using the discrete dipole approximation. The degrees of overlapping and necking are quantified by the overlapping and necking parameters. Realistic soot aggregates were generated numerically by constructing overlapping and necking to fractal aggregates formed by point-touch primary particles simulated using a diffusion-limited cluster aggregation algorithm. Radiative properties (differential scattering, absorption, total scattering, specific extinction, asymmetry factor and single scattering albedo) were calculated using the experimentally measured soot refractive index over the spectral range of 266-1064 nm for 9 combinations of the overlapping and necking parameters. Overlapping and necking affect significantly the absorption and scattering properties of soot aggregates, especially in the near UV spectrum due to the enhanced multiple scattering effects within an aggregate. By using correctly modified aggregate properties (fractal dimension, prefactor, primary particle radius, and the number of primary particle) and by accounting for the effects of multiple scattering, the simple Rayleigh-Debye-Gans theory for fractal aggregates can reproduce reasonably accurate radiative properties of realistic soot aggregates.

Charged particle tracking without magnetic field: Optimal measurement of track momentum by a Bayesian analysis of the multiple measurements of deflections due to multiple scattering

NASA Astrophysics Data System (ADS)

Frosini, Mikael; Bernard, Denis

2017-09-01

We revisit the precision of the measurement of track parameters (position, angle) with optimal methods in the presence of detector resolution, multiple scattering and zero magnetic field. We then obtain an optimal estimator of the track momentum by a Bayesian analysis of the filtering innovations of a series of Kalman filters applied to the track. This work could pave the way to the development of autonomous high-performance gas time-projection chambers (TPC) or silicon wafer γ-ray space telescopes and be a powerful guide in the optimization of the design of the multi-kilo-ton liquid argon TPCs that are under development for neutrino studies.

Entanglement entropy in Fermi gases and Anderson's orthogonality catastrophe.

PubMed

Ossipov, A

2014-09-26

We study the ground-state entanglement entropy of a finite subsystem of size L of an infinite system of noninteracting fermions scattered by a potential of finite range a. We derive a general relation between the scattering matrix and the overlap matrix and use it to prove that for a one-dimensional symmetric potential the von Neumann entropy, the Rényi entropies, and the full counting statistics are robust against potential scattering, provided that L/a≫1. The results of numerical calculations support the validity of this conclusion for a generic potential.

Emitter and absorber assembly for multiple self-dual operation and directional transparency

NASA Astrophysics Data System (ADS)

Kalozoumis, P. A.; Morfonios, C. V.; Kodaxis, G.; Diakonos, F. K.; Schmelcher, P.

2017-03-01

We demonstrate how to systematically design wave scattering systems with simultaneous coherent perfect absorbing and lasing operation at multiple and prescribed frequencies. The approach is based on the recursive assembly of non-Hermitian emitter and absorber units into self-dual emitter-absorber trimers at different composition levels, exploiting the simple structure of the corresponding transfer matrices. In particular, lifting the restriction to parity-time-symmetric setups enables the realization of emitter and absorber action at distinct frequencies and provides flexibility with respect to the choice of realistic parameters. We further show how the same assembled scatterers can be rearranged to produce unidirectional and bidirectional transparency at the selected frequencies. With the design procedure being generically applicable to wave scattering in single-channel settings, we demonstrate it with concrete examples of photonic multilayer setups.

Time-dependent Second Order Scattering Theory for Weather Radar with a Finite Beam Width

NASA Technical Reports Server (NTRS)

Kobayashi, Satoru; Tanelli, Simone; Im, Eastwood; Ito, Shigeo; Oguchi, Tomohiro

2006-01-01

Multiple scattering effects from spherical water particles of uniform diameter are studied for a W-band pulsed radar. The Gaussian transverse beam-profile and the rectangular pulse-duration are used for calculation. An second-order analytical solution is derived for a single layer structure, based on a time-dependent radiative transfer theory as described in the authors' companion paper. When the range resolution is fixed, increase in footprint radius leads to increase in the second order reflectivity that is defined as the ratio of the second order return to the first order one. This feature becomes more serious as the range increases. Since the spaceborne millimeter-wavelength radar has a large footprint radius that is competitive to the mean free path, the multiple scattering effect must be taken into account for analysis.

Statistical reconstruction for cosmic ray muon tomography.

PubMed

Schultz, Larry J; Blanpied, Gary S; Borozdin, Konstantin N; Fraser, Andrew M; Hengartner, Nicolas W; Klimenko, Alexei V; Morris, Christopher L; Orum, Chris; Sossong, Michael J

2007-08-01

Highly penetrating cosmic ray muons constantly shower the earth at a rate of about 1 muon per cm2 per minute. We have developed a technique which exploits the multiple Coulomb scattering of these particles to perform nondestructive inspection without the use of artificial radiation. In prior work [1]-[3], we have described heuristic methods for processing muon data to create reconstructed images. In this paper, we present a maximum likelihood/expectation maximization tomographic reconstruction algorithm designed for the technique. This algorithm borrows much from techniques used in medical imaging, particularly emission tomography, but the statistics of muon scattering dictates differences. We describe the statistical model for multiple scattering, derive the reconstruction algorithm, and present simulated examples. We also propose methods to improve the robustness of the algorithm to experimental errors and events departing from the statistical model.

Investigation of multiple scattering effects in aerosols

NASA Technical Reports Server (NTRS)

Deepak, A.

1980-01-01

The results are presented of investigations on the various aspects of multiple scattering effects on visible and infrared laser beams transversing dense fog oil aerosols contained in a chamber (4' x 4' x 9'). The report briefly describes: (1) the experimental details and measurements; (2) analytical representation of the aerosol size distribution data by two analytical models (the regularized power law distribution and the inverse modified gamma distribution); (3) retrieval of aerosol size distributions from multispectral optical depth measurements by two methods (the two and three parameter fast table search methods and the nonlinear least squares method); (4) modeling of the effects of aerosol microphysical (coagulation and evaporation) and dynamical processes (gravitational settling) on the temporal behavior of aerosol size distribution, and hence on the extinction of four laser beams with wavelengths 0.44, 0.6328, 1.15, and 3.39 micrometers; and (5) the exact and approximate formulations for four methods for computing the effects of multiple scattering on the transmittance of laser beams in dense aerosols, all of which are based on the solution of the radiative transfer equation under the small angle approximation.

Investigation of multiple scattering effects in aerosols

NASA Astrophysics Data System (ADS)

Deepak, A.

1980-05-01

The results are presented of investigations on the various aspects of multiple scattering effects on visible and infrared laser beams transversing dense fog oil aerosols contained in a chamber (4' x 4' x 9'). The report briefly describes: (1) the experimental details and measurements; (2) analytical representation of the aerosol size distribution data by two analytical models (the regularized power law distribution and the inverse modified gamma distribution); (3) retrieval of aerosol size distributions from multispectral optical depth measurements by two methods (the two and three parameter fast table search methods and the nonlinear least squares method); (4) modeling of the effects of aerosol microphysical (coagulation and evaporation) and dynamical processes (gravitational settling) on the temporal behavior of aerosol size distribution, and hence on the extinction of four laser beams with wavelengths 0.44, 0.6328, 1.15, and 3.39 micrometers; and (5) the exact and approximate formulations for four methods for computing the effects of multiple scattering on the transmittance of laser beams in dense aerosols, all of which are based on the solution of the radiative transfer equation under the small angle approximation.

On the size dependence of the scattering greenhouse effect of CO2 ice particles

NASA Astrophysics Data System (ADS)

Kitzmann, D.; Patzer, A. B. C.; Rauer, H.

2011-10-01

In this contribution we study the potential greenhouse effect due to scattering of CO2 ice clouds for atmospheric conditions of terrestrial extrasolar planets. Therefore, we calculate the scattering and absorption properties of CO2 ice particles using Mie theory for assumed particle size distributions with different effective radii and particle densities to determine the scattering and absorption characteristics of such clouds. Implications especially in view of a potential greenhouse warming of the planetary surface are discussed.

Plane-dependent ML scatter scaling: 3D extension of the 2D simulated single scatter (SSS) estimate.

PubMed

Rezaei, Ahmadreza; Salvo, Koen; Vahle, Thomas; Panin, Vladimir; Casey, Michael; Boada, Fernando; Defrise, Michel; Nuyts, Johan

2017-07-24

Scatter correction is typically done using a simulation of the single scatter, which is then scaled to account for multiple scatters and other possible model mismatches. This scaling factor is determined by fitting the simulated scatter sinogram to the measured sinogram, using only counts measured along LORs that do not intersect the patient body, i.e. 'scatter-tails'. Extending previous work, we propose to scale the scatter with a plane dependent factor, which is determined as an additional unknown in the maximum likelihood (ML) reconstructions, using counts in the entire sinogram rather than only the 'scatter-tails'. The ML-scaled scatter estimates are validated using a Monte-Carlo simulation of a NEMA-like phantom, a phantom scan with typical contrast ratios of a 68 Ga-PSMA scan, and 23 whole-body 18 F-FDG patient scans. On average, we observe a 12.2% change in the total amount of tracer activity of the MLEM reconstructions of our whole-body patient database when the proposed ML scatter scales are used. Furthermore, reconstructions using the ML-scaled scatter estimates are found to eliminate the typical 'halo' artifacts that are often observed in the vicinity of high focal uptake regions.

Color from hierarchy: Diverse optical properties of micron-sized spherical colloidal assemblies.

PubMed

Vogel, Nicolas; Utech, Stefanie; England, Grant T; Shirman, Tanya; Phillips, Katherine R; Koay, Natalie; Burgess, Ian B; Kolle, Mathias; Weitz, David A; Aizenberg, Joanna

2015-09-01

Materials in nature are characterized by structural order over multiple length scales have evolved for maximum performance and multifunctionality, and are often produced by self-assembly processes. A striking example of this design principle is structural coloration, where interference, diffraction, and absorption effects result in vivid colors. Mimicking this emergence of complex effects from simple building blocks is a key challenge for man-made materials. Here, we show that a simple confined self-assembly process leads to a complex hierarchical geometry that displays a variety of optical effects. Colloidal crystallization in an emulsion droplet creates micron-sized superstructures, termed photonic balls. The curvature imposed by the emulsion droplet leads to frustrated crystallization. We observe spherical colloidal crystals with ordered, crystalline layers and a disordered core. This geometry produces multiple optical effects. The ordered layers give rise to structural color from Bragg diffraction with limited angular dependence and unusual transmission due to the curved nature of the individual crystals. The disordered core contributes nonresonant scattering that induces a macroscopically whitish appearance, which we mitigate by incorporating absorbing gold nanoparticles that suppress scattering and macroscopically purify the color. With increasing size of the constituent colloidal particles, grating diffraction effects dominate, which result from order along the crystal's curved surface and induce a vivid polychromatic appearance. The control of multiple optical effects induced by the hierarchical morphology in photonic balls paves the way to use them as building blocks for complex optical assemblies--potentially as more efficient mimics of structural color as it occurs in nature.

Feasibility study for combination of field-flow fractionation (FFF)-based separation of size-coded particle probes with amplified surface enhanced Raman scattering (SERS) tagging for simultaneous detection of multiple miRNAs.

PubMed

Shin, Kayeong; Choi, Jaeyeong; Kim, Yeoju; Lee, Yoonjeong; Kim, Joohoon; Lee, Seungho; Chung, Hoeil

2018-06-29

We propose a new analytical scheme in which field-flow fractionation (FFF)-based separation of target-specific polystyrene (PS) particle probes of different sizes are incorporated with amplified surface-enhanced Raman scattering (SERS) tagging for the simultaneous and sensitive detection of multiple microRNAs (miRNAs). For multiplexed detection, PS particles of three different diameters (15, 10, 5 μm) were used for the size-coding, and a probe single stranded DNA (ssDNA) complementary to a target miRNA was conjugated on an intended PS particle. After binding of a target miRNA on PS probe, polyadenylation reaction was executed to generate a long tail composed of adenine (A) serving as a binding site to thymine (T) conjugated Au nanoparticles (T-AuNPs) to increase SERS intensity. The three size-coded PS probes bound with T-AuNPs were then separated in a FFF channel. With the observation of extinction-based fractograms, separation of three size-coded PS probes was clearly confirmed, thereby enabling of measuring three miRNAs simultaneously. Raman intensities of FFF fractions collected at the peak maximum of 15, 10 and 5 μm PS probes varied fairy quantitatively with the change of miRNA concentrations, and the reproducibility of measurement was acceptable. The proposed method is potentially useful for simultaneous detection of multiple miRNAs with high sensitivity. Copyright © 2018 Elsevier B.V. All rights reserved.

Color from hierarchy: Diverse optical properties of micron-sized spherical colloidal assemblies

PubMed Central

Vogel, Nicolas; Utech, Stefanie; England, Grant T.; Shirman, Tanya; Phillips, Katherine R.; Koay, Natalie; Burgess, Ian B.; Kolle, Mathias; Weitz, David A.; Aizenberg, Joanna

2015-01-01

Materials in nature are characterized by structural order over multiple length scales have evolved for maximum performance and multifunctionality, and are often produced by self-assembly processes. A striking example of this design principle is structural coloration, where interference, diffraction, and absorption effects result in vivid colors. Mimicking this emergence of complex effects from simple building blocks is a key challenge for man-made materials. Here, we show that a simple confined self-assembly process leads to a complex hierarchical geometry that displays a variety of optical effects. Colloidal crystallization in an emulsion droplet creates micron-sized superstructures, termed photonic balls. The curvature imposed by the emulsion droplet leads to frustrated crystallization. We observe spherical colloidal crystals with ordered, crystalline layers and a disordered core. This geometry produces multiple optical effects. The ordered layers give rise to structural color from Bragg diffraction with limited angular dependence and unusual transmission due to the curved nature of the individual crystals. The disordered core contributes nonresonant scattering that induces a macroscopically whitish appearance, which we mitigate by incorporating absorbing gold nanoparticles that suppress scattering and macroscopically purify the color. With increasing size of the constituent colloidal particles, grating diffraction effects dominate, which result from order along the crystal’s curved surface and induce a vivid polychromatic appearance. The control of multiple optical effects induced by the hierarchical morphology in photonic balls paves the way to use them as building blocks for complex optical assemblies—potentially as more efficient mimics of structural color as it occurs in nature. PMID:26290583

Using Directional Emissivity as a Probe of Particle Microphysical Properties

NASA Astrophysics Data System (ADS)

Pitman, K. M.; Wolff, M. J.; Bandfield, J. L.; Clayton, G. C.

2002-09-01

Real surfaces are not expected to be diffuse emitters, thus observed emissivity values are a function of viewing geometry. This fact has strong implications for analyses of the MGS/TES emission phase function (EPF) sequences and the upcoming Mars Exploration Rover mini-TES dataset. As reviewed previously [1], in the absence of strong thermal gradients, directional emissivity may be obtained via a combination of reciprocity and Kirchhoff's Law. Here we focus on the potential utility of directional emissivity as a direct probe of surface particle microphysical properties. We explore the effects of particle size and composition on observed radiances in the TES spectral regime using a combination of multiple scattering radiative transfer and Mie scattering algorithms. Comparisons of these simulated spectra to TES EPF observations of typical surface units (e.g., high and low albedo regions) will also be made. This work is supported through NASA grant NAGS-9820 (MJW) and LSU Board of Regents (KMP). [1] Pitman, K.M., et al. (2001), AAS-DPS meeting # 33, # 36.01.

Daytime sky polarization calibration limitations

NASA Astrophysics Data System (ADS)

Harrington, David M.; Kuhn, Jeffrey R.; Ariste, Arturo López

2017-01-01

The daytime sky has recently been demonstrated as a useful calibration tool for deriving polarization cross-talk properties of large astronomical telescopes. The Daniel K. Inouye Solar Telescope and other large telescopes under construction can benefit from precise polarimetric calibration of large mirrors. Several atmospheric phenomena and instrumental errors potentially limit the technique's accuracy. At the 3.67-m AEOS telescope on Haleakala, we performed a large observing campaign with the HiVIS spectropolarimeter to identify limitations and develop algorithms for extracting consistent calibrations. Effective sampling of the telescope optical configurations and filtering of data for several derived parameters provide robustness to the derived Mueller matrix calibrations. Second-order scattering models of the sky show that this method is relatively insensitive to multiple-scattering in the sky, provided calibration observations are done in regions of high polarization degree. The technique is also insensitive to assumptions about telescope-induced polarization, provided the mirror coatings are highly reflective. Zemax-derived polarization models show agreement between the functional dependence of polarization predictions and the corresponding on-sky calibrations.

Optical Imaging of Flow Pattern and Phantom

NASA Technical Reports Server (NTRS)

Galland, Pierre A.; Liang, X.; Wang, L.; Ho, P. P.; Alfano, R. R.; Breisacher, K.

1999-01-01

Time-resolved optical imaging technique has been used to image the spatial distribution of small droplets and jet sprays in a highly scattering environment. The snake and ballistic components of the transmitted pulse are less scattered, and contain direct information about the sample to facilitate image formation as opposed to the diffusive components which are due to multiple collisions as a light pulse propagates through a scattering medium. In a time-gated imaging scheme, these early-arriving, image-bearing components of the incident pulse are selected by opening a gate for an ultrashort period of time and a shadowgram image is detected. Using a single shot cooled CCD camera system, the formation of water droplets is monitored as a function of time. Picosecond time-gated image of drop in scattering cells, spray droplets as a function of let speed and gas pressure, and model calcification samples consisted of calcium carbonate particles of irregular shapes ranging in size from 0. 1 to 1.5 mm affixed to a microscope slide have been measured. Formation produced by an impinging jet will be further monitored using a CCD with 1 kHz framing illuminated with pulsed light. The desired image resolution of the fuel droplets is on the 20 pm scale using early light through a highly scattering medium. A 10(exp -6)m displacement from a jet spray with a flow speed of 100 m/sec introduced by the ns grating pulse used in the imaging is negligible. Early ballistic/snake light imaging offers nondestructive and noninvasive method to observe the spatial distribution of hidden objects inside a highly scattering environment for space, biomedical, and materials applications. In this paper, the techniques we will present are time-resolved K-F transillumination imaging and time-gated scattered light imaging. With a large dynamic range and high resolution, time-gated early light imaging has the potential for improving rocket/aircraft design by determining jets shape and particle sizes. Refinements to these techniques may enable drop size measurements in the highly scattering, optically dense region of multi-element rocket injectors. These types of measurements should greatly enhance the design of stable, and higher performing rocket engines.

Quantum non-Abelian hydrodynamics: Anyonic or spin-orbital entangled liquids, nonunitarity of scattering matrix and charge fractionalization

NASA Astrophysics Data System (ADS)

Pareek, Tribhuvan Prasad

2015-09-01

In this article, we develop an exact (nonadiabatic, nonperturbative) density matrix scattering theory for a two component quantum liquid which interacts or scatters off from a generic spin-dependent quantum potential. The generic spin dependent quantum potential [Eq. (1)] is a matrix potential, hence, adiabaticity criterion is ill-defined. Therefore the full matrix potential should be treated nonadiabatically. We succeed in doing so using the notion of vectorial matrices which allows us to obtain an exact analytical expression for the scattered density matrix (SDM), ϱsc [Eq. (30)]. We find that the number or charge density in scattered fluid, Tr(ϱsc), expressions in Eqs. (32) depends on nontrivial quantum interference coefficients, Qα β 0ijk, which arises due to quantum interference between spin-independent and spin-dependent scattering amplitudes and among spin-dependent scattering amplitudes. Further it is shown that Tr(ϱsc) can be expressed in a compact form [Eq. (39)] where the effect of quantum interference coefficients can be included using a vector Qαβ, which allows us to define a vector order parameterQ. Since the number density is obtained using an exact scattered density matrix, therefore, we do not need to prove that Q is non-zero. However, for sake of completeness, we make detailed mathematical analysis for the conditions under which the vector order parameterQ would be zero or nonzero. We find that in presence of spin-dependent interaction the vector order parameterQ is necessarily nonzero and is related to the commutator and anti-commutator of scattering matrix S with its dagger S† [Eq. (78)]. It is further shown that Q≠0, implies four physically equivalent conditions,i.e., spin-orbital entanglement is nonzero, non-Abelian scattering phase, i.e., matrices, scattering matrix is nonunitary and the broken time reversal symmetry for SDM. This also implies that quasi particle excitation are anyonic in nature, hence, charge fractionalization is a natural consequence. This aspect has also been discussed from the perspective of number or charge density conservation, which implies i.e., Tr(ϱ} sc) = Tr(ϱin). On the other hand Q = 0 turns out to be a mathematically forced unphysical solution in presence of spin-dependent potential or scattering which is equivalent to Abelian hydrodynamics, unitary scattering matrix, absence of spin-space entanglement and preserved time reversal symmetry. We have formulated the theory using mesoscopic language, specifically, we have considered two terminal systems connected to spin-dependent scattering region, which is equivalent to having two potential wells separated by a generic spin-dependent potential barrier. The formulation using mesoscopic language is practically useful because it leads directly to the measured quantities such as conductance and spin-polarization density in the leads, however, the presented formulation is not limited to the mesoscopic system only, its generality has been stressed at various places in this article.

Development and Application of Chemical Probes for Vibrational Imaging by Stimulated Raman Scattering

NASA Astrophysics Data System (ADS)

Hu, Fanghao

During the last decade, Raman microscopy is experiencing rapid development and increasingly applied in biological and medical systems. Especially, stimulated Raman scattering (SRS) microscopy, which significantly improves the sensitivity of Raman scattering through stimulated emission, has allowed direct visualization of many species that are previously challenging with conventional fluorescence imaging. Compared to fluorescence, SRS imaging requires no label or small label on the target molecule, thus with minimal perturbation to the molecule of interest. Moreover, Raman scattering is free from complicated photophysical and photochemical processes such as photobleaching, and has intrinsically narrower linewidth than fluorescence emission. This allows multiplexed Raman imaging with minimal spectral crosstalk and excellent photo-stability. To achieve the full potential of Raman microscopy, vibrational probes have been developed for Raman imaging. Multiple Raman probes with a few atoms in size are applied in Raman imaging with high sensitivity and specificity. An overview of both fluorescence and Raman microscopy and their imaging probes is given in Chapter 1 with a brief discussion on the SRS theory. Built on the current progress of Raman microscopy and vibrational probes, I write on my research in the development of carbon-deuterium, alkyne and nitrile probes for visualizing choline metabolism (Chapter 2), glucose uptake activity (Chapter 3), complex brain metabolism (Chapter 4) and polymeric nanoparticles (Chapter 5) in live cells and tissues, as well as the development of polyyne-based vibrational probes for super-multiplexed imaging, barcoding and analysis (Chapter 6).

Extension and applications of switching model: Range theory, multiple scattering model of Goudsmit-Saunderson, and lateral spread treatment of Marwick-Sigmund

NASA Astrophysics Data System (ADS)

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.

Aerosol analysis with the Coastal Zone Color Scanner: a simple method for including multiple scattering effects.

PubMed

Gordon, H R; Castaño, D J

1989-04-01

For measurement of aerosols over the ocean, the total radiance L(t) backscattered from the top of a stratified atmosphere which contains both stratospheric and tropospheric aerosols of various types has been computed. A similar computation is carried out for an aerosol-free atmosphere yielding the Rayleigh scattered radiance L(r). The difference L(t) - L(r) is shown to be linearly related to the radiance L(as), which the aerosol would produce in the single scattering approximation. This greatly simplifies the application of aerosol models to aerosol analysis by satellite since adding to, or in some way changing, the aerosol model requires no additional multiple scattering computations. In fact, the only multiple computations required for aerosol analysis are those for determining L(r), which can be performed once and for all. The computations are explicitly applied to Band 4 of the CZCS, which, because of its high radiometric sensitivity and excellent calibration, is ideal for studying aerosols over the ocean. Specifically, the constant A in the relationship L(as) = A(-1)(L(t) - L(r)) is given as a function of position along the scan for four typical orbital-solar position scenarios. The computations show that L(as) can be retrieved from L(t) - L(r) with an average error of no more than 5-7% except at the very edges of the scan.

Phase-shift parametrization and extraction of asymptotic normalization constants from elastic-scattering data

NASA Astrophysics Data System (ADS)

Ramírez Suárez, O. L.; Sparenberg, J.-M.

2017-09-01

We introduce a simplified effective-range function for charged nuclei, related to the modified K matrix but differing from it in several respects. Negative-energy zeros of this function correspond to bound states. Positive-energy zeros correspond to resonances and "echo poles" appearing in elastic-scattering phase-shifts, while its poles correspond to multiple-of-π phase shifts. Padé expansions of this function allow one to parametrize phase shifts on large energy ranges and to calculate resonance and bound-state properties in a very simple way, independently of any potential model. The method is first tested on a d -wave 12C+α potential model. It is shown to lead to a correct estimate of the subthreshold-bound-state asymptotic normalization constant (ANC) starting from the elastic-scattering phase shifts only. Next, the 12C+α experimental p -wave and d -wave phase shifts are analyzed. For the d wave, the relatively large error bars on the phase shifts do not allow one to improve the ANC estimate with respect to existing methods. For the p wave, a value agreeing with the 12C(6Li,d )16O transfer-reaction measurement and with the recent remeasurement of the 16Nβ -delayed α decay is obtained, with improved accuracy. However, the method displays two difficulties: the results are sensitive to the Padé-expansion order and the simplest fits correspond to an imaginary ANC, i.e., to a negative-energy "echo pole," the physical meaning of which is still debatable.

Inclusion of electron correlation for the target wave function in low-energy e sup minus +N sub 2 scattering

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

Meyer, H.; Pal, S.; Riss, U.V.

1992-07-01

The interaction of a scattering electron with a correlated but frozen'' target may be called the correlated static-exchange interaction. There are two prior investigations (J.R. Rumble, W.J. Stevens, and D. Truhlar, J. Phys. B 17, 3151 (1984); C Weatherford, F.B. Brown, and A. Temkin, Phys. Rev. A 35, 4561 (1987)) on scattering off the correlated static-exchange potential. Both of these investigations concentrated on {ital e}{sup {minus}}+N{sub 2} scattering, and both have found that the correlated static-exchange potential is less attractive than the static-exchange potential. We will show, however, that the correlated static-exchange potential is more attractive than the static-exchange one---atmore » least for {ital e}{sup {minus}}+N{sub 2} scattering in {sup 2}{Pi}{sub {ital g}} symmetry. The two prior investigations were misled by an improper degree of correlation and by an improper treatment of the exchange.« less

Measurement and modeling of polarized specular neutron reflectivity in large magnetic fields.

PubMed

Maranville, Brian B; Kirby, Brian J; Grutter, Alexander J; Kienzle, Paul A; Majkrzak, Charles F; Liu, Yaohua; Dennis, Cindi L

2016-08-01

The presence of a large applied magnetic field removes the degeneracy of the vacuum energy states for spin-up and spin-down neutrons. For polarized neutron reflectometry, this must be included in the reference potential energy of the Schrödinger equation that is used to calculate the expected scattering from a magnetic layered structure. For samples with magnetization that is purely parallel or antiparallel to the applied field which defines the quantization axis, there is no mixing of the spin states (no spin-flip scattering) and so this additional potential is constant throughout the scattering region. When there is non-collinear magnetization in the sample, however, there will be significant scattering from one spin state into the other, and the reference potentials will differ between the incoming and outgoing wavefunctions, changing the angle and intensities of the scattering. The theory of the scattering and recommended experimental practices for this type of measurement are presented, as well as an example measurement.

Measurement and modeling of polarized specular neutron reflectivity in large magnetic fields

PubMed Central

Maranville, Brian B.; Kirby, Brian J.; Grutter, Alexander J.; Kienzle, Paul A.; Majkrzak, Charles F.; Liu, Yaohua; Dennis, Cindi L.

2016-01-01

The presence of a large applied magnetic field removes the degeneracy of the vacuum energy states for spin-up and spin-down neutrons. For polarized neutron reflectometry, this must be included in the reference potential energy of the Schrödinger equation that is used to calculate the expected scattering from a magnetic layered structure. For samples with magnetization that is purely parallel or antiparallel to the applied field which defines the quantization axis, there is no mixing of the spin states (no spin-flip scattering) and so this additional potential is constant throughout the scattering region. When there is non-collinear magnetization in the sample, however, there will be significant scattering from one spin state into the other, and the reference potentials will differ between the incoming and outgoing wavefunctions, changing the angle and intensities of the scattering. The theory of the scattering and recommended experimental practices for this type of measurement are presented, as well as an example measurement. PMID:27504074

Measurement and modeling of polarized specular neutron reflectivity in large magnetic fields

DOE PAGES

Maranville, Brian B.; Kirby, Brian J.; Grutter, Alexander J.; ...

2016-06-09

The presence of a large applied magnetic field removes the degeneracy of the vacuum energy states for spin-up and spin-down neutrons. For polarized neutron reflectometry, this must be included in the reference potential energy of the Schrödinger equation that is used to calculate the expected scattering from a magnetic layered structure. For samples with magnetization that is purely parallel or antiparallel to the applied field which defines the quantization axis, there is no mixing of the spin states (no spin-flip scattering) and so this additional potential is constant throughout the scattering region. When there is non-collinear magnetization in the sample,more » however, there will be significant scattering from one spin state into the other, and the reference potentials will differ between the incoming and outgoing wavefunctions, changing the angle and intensities of the scattering. In conclusion, the theory of the scattering and recommended experimental practices for this type of measurement are presented, as well as an example measurement.« less

Rapid calculation of radiative heating rates and photodissociation rates in inhomogeneous multiple scattering atmospheres

NASA Technical Reports Server (NTRS)

Toon, Owen B.; Mckay, C. P.; Ackerman, T. P.; Santhanam, K.

1989-01-01

The solution of the generalized two-stream approximation for radiative transfer in homogeneous multiple scattering atmospheres is extended to vertically inhomogeneous atmospheres in a manner which is numerically stable and computationally efficient. It is shown that solar energy deposition rates, photolysis rates, and infrared cooling rates all may be calculated with the simple modifications of a single algorithm. The accuracy of the algorithm is generally better than 10 percent, so that other uncertainties, such as in absorption coefficients, may often dominate the error in calculation of the quantities of interest to atmospheric studies.

Gaussian basis functions for highly oscillatory scattering wavefunctions

NASA Astrophysics Data System (ADS)

Mant, B. P.; Law, M. M.

2018-04-01

We have applied a basis set of distributed Gaussian functions within the S-matrix version of the Kohn variational method to scattering problems involving deep potential energy wells. The Gaussian positions and widths are tailored to the potential using the procedure of Bačić and Light (1986 J. Chem. Phys. 85 4594) which has previously been applied to bound-state problems. The placement procedure is shown to be very efficient and gives scattering wavefunctions and observables in agreement with direct numerical solutions. We demonstrate the basis function placement method with applications to hydrogen atom–hydrogen atom scattering and antihydrogen atom–hydrogen atom scattering.

Single and Multiple Scattered Solar Radiation

DTIC Science & Technology

1982-08-30

so that factor can be expected to vary considerably from one scattering point to the next. The monochromatic intensity at the observer due to all of...the single scattering sources within the line-of-sight is obtained by summing over the optical path the product of the source function and the...the observer. Using a dot product 1)etwecen position_ vectors on the unit sphere, it can be Chown that cosA cost coss cost) cos4o + 0 S 0 0 "+ cost

A Path Loss Model for Non-Line-of-Sight Ultraviolet Multiple Scattering Channels

DTIC Science & Technology

2010-01-01

scattering is self -governed, and the distances and angles for different scattering events are conditioned on previous quantities. Therefore, the arrival...solid angle of the receiver determined by the receiver area and distance rn. Note that no integration over rn is needed because it is a function of...www.eurasip.org). This year edition will take place in Barcelona, capital city of Catalonia (Spain), and will be jointly organized by the Centre Tecnològic de

Parity Nonconservation in Proton-water Scattering at 800 MeV

DOE R&D Accomplishments Database

Nagle, D. E.; Bowman, J. D.; Carlini, R.; Mischke, R. E.; Frauenfelder, H.; Harper, R. W.; Yuan, V.; McDonald, A. B.; Talaga, R.

1982-01-01

A search has been made for parity nonconservation in the scattering of 800 MeV polarized protons from an unpolarized water target. The result is for the longitudinal asymmetry, A{sub L} = +(6.6 +- 3.2) x 10{sup -7}. Control runs with Pb, using a thickness which gave equivalent beam broadening from Coulomb multiple scattering, but a factor of ten less nuclear interactions than the water target, gave A{sub L} = -(0.5 +- 6.0) x 10{sup -7}.

Spaceborne lidar for cloud monitoring

NASA Astrophysics Data System (ADS)

Werner, Christian; Krichbaumer, W.; Matvienko, Gennadii G.

1994-12-01

Results of laser cloud top measurements taken from space in 1982 (called PANTHER) are presented. Three sequences of land, water, and cloud data are selected. A comparison with airborne lidar data shows similarities. Using the single scattering lidar equation for these spaceborne lidar measurements one can misinterpret the data if one doesn't correct for multiple scattering.

Surface-enhanced Raman scattering (SERS) detection of multiple viral antigens using magnetic capture of SERS-active nanoparticles

USDA-ARS?s Scientific Manuscript database

A highly sensitive immunoassay based on surface-enhanced Raman scattering (SERS) spectroscopy has been developed for multiplex detection of surface envelope and capsid antigens of the viral zoonotic pathogens West Nile virus (WNV) and Rift Valley fever virus (RVFV). Detection was mediated by antibo...

Possible limits of plasma linear colliders

NASA Astrophysics Data System (ADS)

Zimmermann, F.

2017-07-01

Plasma linear colliders have been proposed as next or next-next generation energy-frontier machines for high-energy physics. I investigate possible fundamental limits on energy and luminosity of such type of colliders, considering acceleration, multiple scattering off plasma ions, intrabeam scattering, bremsstrahlung, and betatron radiation. The question of energy efficiency is also addressed.

Charactrisation of particle assemblies by 3D cross correlation light scattering and diffusing wave spectroscopy

NASA Astrophysics Data System (ADS)

Scheffold, Frank

2014-08-01

To characterize the structural and dynamic properties of soft materials and small particles, information on the relevant mesoscopic length scales is required. Such information is often obtained from traditional static and dynamic light scattering (SLS/DLS) experiments in the single scattering regime. In many dense systems, however, these powerful techniques frequently fail due to strong multiple scattering of light. Here I will discuss some experimental innovations that have emerged over the last decade. New methods such as 3D static and dynamic light scattering (3D LS) as well as diffusing wave spectroscopy (DWS) can cover a much extended range of experimental parameters ranging from dilute polymer solutions, colloidal suspensions to extremely opaque viscoelastic emulsions.

A hybrid asymptotic-modal analysis of the EM scattering by an open-ended S-shaped rectangular waveguide cavity

NASA Technical Reports Server (NTRS)

Law, P. H.; Burkholder, R. J.; Pathak, P. H.

1988-01-01

The electromagnetic fields (EM) backscatter from a 3-dimensional perfectly conducting S-shaped open-ended cavity with a planar interior termination is analyzed when it is illuminated by an external plane wave. The analysis is based on a self-consistent multiple scattering method which accounts for the multiple wave interactions between the open end and the interior termination. The scattering matrices which described the reflection and transmission coefficients of the waveguide modes reflected and transmitted at each junction between the different waveguide sections, as well at the scattering from the edges at the open end are found via asymptotic high frequency methods such as the geometrical and physical theories of diffraction used in conjunction with the equivalent current method. The numerical results for an S-shaped inlet cavity are compared with the backscatter from a straight inlet cavity; the backscattered patterns are different because the curvature of an S-shaped inlet cavity redistributes the energy reflected from the interior termination in a way that is different from a straight inlet cavity.

Multiple scattering in chiral media: border effects, reduced depolarization, and sensitivity limit

NASA Astrophysics Data System (ADS)

Delplancke, Francoise; Badoz, Jacques P.; Boccara, A. Claude

1997-10-01

Suspensions of polystyrene latex beads in chiral solutions were investigated. The rotatory power, induced by solubilized sucrose, in near-forward scattering was measured via a method using polarization modulation by photo-elastic modulator. The sensitivity of the measurement was enhanced and optimized in order to measure sucrose concentrations as low as 5 mg/ml in a cell 5 mm thick only. Different concentrations and diameters of latex particles were used in combination with different sucrose concentrations going from 1 mg/ml up to saturation. The experiments showed that the apparent rotatory power is enhanced by multiple scattering, that depolarization effects are less important with highly concentrated sucrose solutions and that attention has to be paid to cell border effects in order to avoid important artifacts, in case of highly scattering suspensions. Qualitative and theoretical explanations of those observations are presented. One possible application of this method is to measure the sugar content in human blood, in vivo, non-invasively, through the skin. The concentration to be evaluated is at the sensitivity limit. So any artifact has to be removed carefully, e.g. skin cell birefringence or chirality.

Degree and Direction of Polarization of Multiple Scattered Light. 2: Earth's Atmosphere with Aerosols.

PubMed

Plass, G N; Kattawar, G W

1972-12-01

The degree of polarization as well as the direction of the polarization are calculated by a Monte Carlo method for the reflected and transmitted photons from the earth's atmosphere. The solar photons are followed through multiple collisions with the aerosols and the Rayleigh scattering centers in the atmosphere. The aerosol number density as well as the ratio of aerosol to Rayleigh scattering vary with height. The aerosol index of refraction is assumed to be 1.55. The proportion of aerosol to Rayleigh scattering is appropriately chosen at each wavelength (lambda = 0.4 micro and 0.7 micro); ozone absorption is included where appropriate. Three different aerosol number densities are used to study the effects of aerosol variations. Results are given for a solar zenith angle of 81.37 degrees and various surface albedos. The radiance and polarization of the reflected and transmitted photons is particularly sensitive to the amount of aerosols in the atmosphere at certain angles of observation. The direction of pola ization shows little dependence on the surface albedo.

Multiple emitters in a waveguide: Nonreciprocity and correlated photons at perfect elastic transmission

NASA Astrophysics Data System (ADS)

Fang, Yao-Lung L.; Baranger, Harold U.

2017-07-01

We investigate interference and correlation effects when several detuned emitters are placed along a one-dimensional photonic waveguide. Such a setup allows multiple interactions between the photons and the strongly coupled emitters, and underlies proposed devices for quantum information processing. We show, first, that a pair of detuned two-level systems (2LS) separated by a half wavelength mimic a driven Λ -type three-level system (3LS) in both the single- and two-photon sectors. There is an interference-induced transparency peak at which the fluorescence is quenched, leaving the transmitted photons completely uncorrelated. Slightly away from this separation, we find that the inelastic scattering (fluorescence) is large, leading to nonlinear effects such as nonreciprocity (rectification). We connect this nonreciprocity to inelastic scattering caused by driving a dark pole and so derive a condition for maximum rectification. Finally, by placing a true 3LS midway between the two 2LS, we show that elastic scattering produces only transmission, but inelastic scattering nevertheless occurs (the fluorescence is not quenched) causing substantial photon correlations.

Evaluation of the telegrapher's equation and multiple-flux theories for calculating the transmittance and reflectance of a diffuse absorbing slab.

PubMed

Kong, Steven H; Shore, Joel D

2007-03-01

We study the propagation of light through a medium containing isotropic scattering and absorption centers. With a Monte Carlo simulation serving as the benchmark solution to the radiative transfer problem of light propagating through a turbid slab, we compare the transmission and reflection density computed from the telegrapher's equation, the diffusion equation, and multiple-flux theories such as the Kubelka-Munk and four-flux theories. Results are presented for both normally incident light and diffusely incident light. We find that we can always obtain very good results from the telegrapher's equation provided that two parameters that appear in the solution are set appropriately. We also find an interesting connection between certain solutions of the telegrapher's equation and solutions of the Kubelka-Munk and four-flux theories with a small modification to how the phenomenological parameters in those theories are traditionally related to the optical scattering and absorption coefficients of the slab. Finally, we briefly explore how well the theories can be extended to the case of anisotropic scattering by multiplying the scattering coefficient by a simple correction factor.

Semiempirical potentials for positron scattering by atoms

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

Assafrao, Denise; Walters, H. R. J.; Arretche, Felipe

2011-08-15

We report calculations of differential and integral cross sections for positron scattering by noble gas and alkaline-earth atoms within the same methodology. The scattering potentials are constructed by scaling adiabatic potentials so that their minima coincide with the covalent radii of the target atoms. Elastic differential and integral cross sections are calculated for Ne, Ar, Be, and Mg, and the results are very close to experimental and best theoretical data. Particularly, elastic differential cross sections for Be and Mg at low energies are reported.

Alternative Measurement Configurations for Extracting Bulk Optical Properties Using an Integrating Sphere Setup.

PubMed

Thennadil, Suresh N; Chen, Yi-Chieh

2017-02-01

The usual approach for estimating bulk optical properties using an integrating sphere measurement setup is by acquiring spectra from three measurement modes namely collimated transmittance (T c ), total transmittance (T d ), and total diffuse reflectance (R d ), followed by the inversion of these measurements using the adding-doubling method. At high scattering levels, accurate acquisition of T c becomes problematic due to the presence of significant amounts of forward-scattered light in this measurement which is supposed to contain only unscattered light. In this paper, we propose and investigate the effectiveness of using alternative sets of integrating sphere measurements that avoid the use of T c and could potentially increase the upper limit of concentrations of suspensions at which bulk optical property measurements can be obtained in the visible-near-infrared (Vis-NIR) region of the spectrum. We examine the possibility of replacing T c with one or more reflectance measurements at different sample thicknesses. We also examine the possibility of replacing both the collimated (T c ) and total transmittance (T d ) measurements with reflectance measurements taken from different sample thicknesses. The analysis presented here indicates that replacing T c with a reflectance measurement can reduce the errors in the bulk scattering properties when scattering levels are high. When only multiple reflectance measurements are used, good estimates of the bulk optical properties can be obtained when the absorption levels are low. In addition, we examine whether there is any advantage in using three measurements instead of two to obtain the reduced bulk scattering coefficient and the bulk absorption coefficient. This investigation is made in the context of chemical and biological suspensions which have a much larger range of optical properties compared to those encountered with tissue.

Impact of calcification state on the inherent optical properties of Emiliania huxleyi coccoliths and coccolithophores

NASA Astrophysics Data System (ADS)

Bi, Lei; Yang, Ping

2015-04-01

Understanding the inherent optical properties (IOPs) of coccoliths and coccolithophores is important in oceanic radiative transfer simulations and remote sensing implementations. In this study, the invariant imbedding T-matrix method (II-TM) is employed to investigate the IOPs of coccoliths and coccolithophores. The Emiliania huxleyi (Ehux) coccolith and coccolithophore models are built based on observed biometric parameters including the eccentricity, the number of slits, and the rim width of detached coccoliths. The calcification state that specifies the amount of calcium of a single coccolith is critical in the determination of the size-volume/mass relationship (note, the volume/mass of coccoltihs at different calcification states are different although the diameters are the same). The present results show that the calcification state, namely, under-calcification, normal-calcification, or over-calcification, significantly influences the backscattering cross section and the phase matrix. Furthermore, the linear depolarization ratio of the light scattered by coccoliths is sensitive to the degree of calcification, and provides a potentially valuable parameter for interpreting oceanic remote sensing data. The phase function of an ensemble of randomly oriented coccolithophores has a similar pattern to that of individual coccoliths, but the forward scattering is dominant in the coccolithophores due to the large geometric cross sections. The linear depolarization ratio associated with coccolithophores is found to be larger than that for coccoliths as polarization is more sensitive to multiple scattering than the phase function. The simulated coccolithophore phase matrix numerical results are compared with laboratory measurements. For scattering angles larger than 100°, an increase of the phase function with respect to the scattering angle is confirmed based on the present coccolithophore model while the spherical approximation fails.

Characterization of single particle aerosols by elastic light scattering at multiple wavelengths

NASA Astrophysics Data System (ADS)

Lane, P. A.; Hart, M. B.; Jain, V.; Tucker, J. E.; Eversole, J. D.

2018-03-01

We describe a system to characterize individual aerosol particles using stable and repeatable measurement of elastic light scattering. The method employs a linear electrodynamic quadrupole (LEQ) particle trap. Charged particles, continuously injected by electrospray into this system, are confined to move vertically along the stability line in the center of the LEQ past a point where they are optically interrogated. Light scattered in the near forward direction was measured at three different wavelengths using time-division multiplexed collinear laser beams. We validated our method by comparing measured silica microsphere data for four selected diameters (0.7, 1.0, 1.5 and 2.0 μm) to a model of collected scattered light intensities based upon Lorenz-Mie scattering theory. Scattered light measurements at the different wavelengths are correlated, allowing us to distinguish and classify inhomogeneous particles.

Multi-property isotropic intermolecular potentials and predicted spectral lineshapes of collision-induced absorption (CIA), collision-induced light scattering (CILS) and collision-induced hyper-Rayleigh scattering (CIHR) for H2sbnd Ne, -Kr and -Xe

NASA Astrophysics Data System (ADS)

El-Kader, M. S. A.; Godet, J.-L.; Gustafsson, M.; Maroulis, G.

2018-04-01

Quantum mechanical lineshapes of collision-induced absorption (CIA), collision-induced light scattering (CILS) and collision-induced hyper-Rayleigh scattering (CIHR) at room temperature (295 K) are computed for gaseous mixtures of molecular hydrogen with neon, krypton and xenon. The induced spectra are detected using theoretical values for induced dipole moment, pair-polarizability trace and anisotropy, hyper-polarizability and updated intermolecular potentials. Good agreement is observed for all spectra when the literature and the present potentials which are constructed from the transport and thermo-physical properties are used.

Quantum threshold reflection is not a consequence of a region of the long-range attractive potential with rapidly varying de Broglie wavelength

NASA Astrophysics Data System (ADS)

Petersen, Jakob; Pollak, Eli; Miret-Artes, Salvador

2018-04-01

Quantum threshold reflection is a well-known quantum phenomenon which prescribes that at threshold, except for special circumstances, a quantum particle scattering from any potential, even if attractive at long range, will be reflected with unit probability. In the past, this property had been associated with the so-called badlands region of the potential, where the semiclassical description of the scattering fails due to a rapid spatial variation of the de Broglie wavelength. This badlands region occurs far from the strong interaction region of the potential and has therefore been used to "explain" the quantum reflection phenomenon. In this paper we show that the badlands region of the interaction potential is immaterial. The extremely long wavelength of the scattered particle at threshold is much longer than the spatial extension of the badlands region, which therefore does not affect the scattering. For this purpose, we review and generalize the proof for the existence of quantum threshold reflection to stress that it is only a consequence of continuity and boundary conditions. The nonlocal character of the scattering implies that the whole interaction potential is involved in the phenomenon. We then provide a detailed numerical study of the threshold scattering of a particle by a Morse potential and an Eckart potential, especially in the time domain. We compare exact quantum computations with incoherent results obtained from a classical Wigner approximation. This study shows that close to threshold the time-dependent amplitude of the scattered particle is negligible in the badlands region and is the same whether the potential has a reflecting wall as in the Morse potential or a steplike structure as in the Eckart smooth step potential. The mean flight time of the particle is not shortened due to a local reflection from the badlands region or due to the lower density of the wave function at short distances. This study should serve to definitely rule out the badlands region as a qualitative guide to the properties of quantum threshold reflection.

Scattering of charged particles on two spatially separated time-periodic optical fields

NASA Astrophysics Data System (ADS)

Szabó, Lóránt Zs.; Benedict, Mihály G.; Földi, Péter

2017-12-01

We consider a monoenergetic beam of moving charged particles interacting with two separated oscillating electric fields. Time-periodic linear potential is assumed to model the light-particle interaction using a nonrelativistic, quantum mechanical description based on Gordon-Volkov states. Applying Floquet theory, we calculate transmission probabilities as a function of the laser field parameters. The transmission resonances in this Ramsey-like setup are interpreted as if they originated from a corresponding static double-potential barrier with heights equal to the ponderomotive potential resulting from the oscillating field. Due to the opening of new "Floquet channels," the resonances are repeated at input energies when the corresponding frequency is shifted by an integer multiple of the exciting frequency. These narrow resonances can be used as precise energy filters. The fine structure of the transmission spectra is determined by the phase difference between the two oscillating light fields, allowing for the optical control of the transmission.

Relative role of intrinsic and scattering attenuation beneath the Andaman Islands, India and tectonic implications

NASA Astrophysics Data System (ADS)

Singh, Chandrani; Biswas, Rahul; Srijayanthi, G.; Ravi Kumar, M.

2017-10-01

The attenuation characteristics of seismic waves traversing the Andaman Nicobar subduction zone (ANSZ) are investigated using high quality data from a network of broadband stations operational since 2009. We initially studied the Coda wave attenuation (Qc-1) under the assumption of a single isotropic scattering model. Subsequently, following the multiple isotropic scattering hypothesis, we isolated the relative contributions of intrinsic (Qi-1) and scattering (Qsc-1) attenuation employing the Multiple Lapse Time Window Analysis (MLTWA) method within a frequency range 1.5-18 Hz. Results reveal a highly attenuative nature of the crust, with the values of Qc being frequency dependent. The intrinsic absorption is mostly found to be predominant compared to scattering attenuation. The dominance of Qi-1 in the crust may be attributed to the presence of fluids associated with the subducted slab. Our results are consistent with the low velocity zone reported for the region. A comparison of our results with those from other regions of the globe shows that the ANSZ falls under the category of high intrinsic attenuation zone. Interestingly, the character of ANSZ is identical to that of eastern Himalaya and southern Tibet, but entirely different from the Garhwal-Kumaun Himalaya and the source zone of Chamoli earthquake, due to the underlying mechanisms causing high attenuation.

Spatially Correlated Sparse MIMO Channel Path Delay Estimation in Scattering Environments Based on Signal Subspace Tracking

PubMed Central

Chargé, Pascal; Bazzi, Oussama; Ding, Yuehua

2018-01-01

A parametric scheme for spatially correlated sparse multiple-input multiple-output (MIMO) channel path delay estimation in scattering environments is presented in this paper. In MIMO outdoor communication scenarios, channel impulse responses (CIRs) of different transmit–receive antenna pairs are often supposed to be sparse due to a few significant scatterers, and share a common sparse pattern, such that path delays are assumed to be equal for every transmit–receive antenna pair. In some existing works, an exact common support condition is exploited, where the path delays are considered equal for every transmit–receive antenna pair, meanwhile ignoring the influence of scattering. A more realistic channel model is proposed in this paper, where due to scatterers in the environment, the received signals are modeled as clusters of multi-rays around a nominal or mean time delay at different antenna elements, resulting in a non-strictly exact common support phenomenon. A method for estimating the channel mean path delays is then derived based on the subspace approach, and the tracking of the effective dimension of the signal subspace that changes due to the wireless environment. The proposed method shows an improved channel mean path delays estimation performance in comparison with the conventional estimation methods. PMID:29734797

Spatially Correlated Sparse MIMO Channel Path Delay Estimation in Scattering Environments Based on Signal Subspace Tracking.

PubMed

Mohydeen, Ali; Chargé, Pascal; Wang, Yide; Bazzi, Oussama; Ding, Yuehua

2018-05-06

A parametric scheme for spatially correlated sparse multiple-input multiple-output (MIMO) channel path delay estimation in scattering environments is presented in this paper. In MIMO outdoor communication scenarios, channel impulse responses (CIRs) of different transmit⁻receive antenna pairs are often supposed to be sparse due to a few significant scatterers, and share a common sparse pattern, such that path delays are assumed to be equal for every transmit⁻receive antenna pair. In some existing works, an exact common support condition is exploited, where the path delays are considered equal for every transmit⁻receive antenna pair, meanwhile ignoring the influence of scattering. A more realistic channel model is proposed in this paper, where due to scatterers in the environment, the received signals are modeled as clusters of multi-rays around a nominal or mean time delay at different antenna elements, resulting in a non-strictly exact common support phenomenon. A method for estimating the channel mean path delays is then derived based on the subspace approach, and the tracking of the effective dimension of the signal subspace that changes due to the wireless environment. The proposed method shows an improved channel mean path delays estimation performance in comparison with the conventional estimation methods.

Ab initio structure determination from prion nanocrystals at atomic resolution by MicroED

PubMed Central

Sawaya, Michael R.; Rodriguez, Jose; Cascio, Duilio; Collazo, Michael J.; Shi, Dan; Reyes, Francis E.; Gonen, Tamir; Eisenberg, David S.

2016-01-01

Electrons, because of their strong interaction with matter, produce high-resolution diffraction patterns from tiny 3D crystals only a few hundred nanometers thick in a frozen-hydrated state. This discovery offers the prospect of facile structure determination of complex biological macromolecules, which cannot be coaxed to form crystals large enough for conventional crystallography or cannot easily be produced in sufficient quantities. Two potential obstacles stand in the way. The first is a phenomenon known as dynamical scattering, in which multiple scattering events scramble the recorded electron diffraction intensities so that they are no longer informative of the crystallized molecule. The second obstacle is the lack of a proven means of de novo phase determination, as is required if the molecule crystallized is insufficiently similar to one that has been previously determined. We show with four structures of the amyloid core of the Sup35 prion protein that, if the diffraction resolution is high enough, sufficiently accurate phases can be obtained by direct methods with the cryo-EM method microelectron diffraction (MicroED), just as in X-ray diffraction. The success of these four experiments dispels the concern that dynamical scattering is an obstacle to ab initio phasing by MicroED and suggests that structures of novel macromolecules can also be determined by direct methods. PMID:27647903

Studying time of flight imaging through scattering media across multiple size scales (Conference Presentation)

NASA Astrophysics Data System (ADS)

Velten, Andreas

2017-05-01

Light scattering is a primary obstacle to optical imaging in a variety of different environments and across many size and time scales. Scattering complicates imaging on large scales when imaging through the atmosphere when imaging from airborne or space borne platforms, through marine fog, or through fog and dust in vehicle navigation, for example in self driving cars. On smaller scales, scattering is the major obstacle when imaging through human tissue in biomedical applications. Despite the large variety of participating materials and size scales, light transport in all these environments is usually described with very similar scattering models that are defined by the same small set of parameters, including scattering and absorption length and phase function. We attempt a study of scattering and methods of imaging through scattering across different scales and media, particularly with respect to the use of time of flight information. We can show that using time of flight, in addition to spatial information, provides distinct advantages in scattering environments. By performing a comparative study of scattering across scales and media, we are able to suggest scale models for scattering environments to aid lab research. We also can transfer knowledge and methodology between different fields.

Investigation of condensed matter by means of elastic thermal-neutron scattering

NASA Astrophysics Data System (ADS)

Abov, Yu. G.; Dzheparov, F. S.; Elyutin, N. O.; Lvov, D. V.; Tyulyusov, A. N.

2016-07-01

The application of elastic thermal-neutron scattering in investigations of condensed matter that were performed at the Institute for Theoretical and Experimental Physics is described. An account of diffraction studies with weakly absorbing crystals, including studies of the anomalous-absorption effect and coherent effects in diffuse scattering, is given. Particular attention is given to exposing the method of multiple small-angle neutron scattering (MSANS). It is shown how information about matter inhomogeneities can be obtained by this method on the basis of Molière's theory. Prospects of the development of this method are outlined, and MSANS theory is formulated for a high concentration of matter inhomogeneities.

Characteristics of large particles and their effects on the submarine light field

NASA Astrophysics Data System (ADS)

Hou, Weilin

Large particles play important roles in the ocean by modifying the underwater light field and effecting material transfer. The particle size distribution of large particles has been measured in-situ with multiple- camera video microscopy and the automated particle sizing and recognition software developed. Results show that there are more large particles in coastal waters than previously thaught, based upon by a hyperbolic size- distribution curve with a (log-log) slope parameter of close to 3 instead of 4 for the particles larger than 100μm diameter. Larger slopes are more typical for particles in the open ocean. This slope permits estimation of the distribution into the small-particle size range for use in correcting the beam-attenuation measurements for near-forward scattering. The large- particle slope and c-meter were used to estimate the small-particle size distributions which nearly matched those measured with a Coulter Counteroler (3.05%). There is also a fair correlation (r2=0.729) between the slope of the distribution and its concentration parameters. Scattering by large particles is influenced by not only the concentrations of these particles, but also the scattering phase functions. This first in-situ measurement of large-particle scattering with multiple angles reveals that they scatter more in the backward direction than was previously believed, and the enhanced backscattering can be explained in part by multiple scattering of aggregated particles. Proper identification of these large particles can be of great help in understanding the status of the ecosystem. By extracting particle features using high-resolution video images via moment-invariant functions and applying this information to lower-resolution images, we increase the effective sample volume without severely degrading classification efficiency. Traditional pattern recognition algorithms of images classified zooplankton with results within 24% of zooplankton collected using bottle samples. A faster particle recognition scheme using optical scattering is introduced and test results are satisfactory with an average error of 32%. This method promises given that the signal-to-noise ratio of the observations can be improved.

Classical theory of atom-surface scattering: The rainbow effect

NASA Astrophysics Data System (ADS)

Miret-Artés, Salvador; Pollak, Eli

2012-07-01

The scattering of heavy atoms and molecules from surfaces is oftentimes dominated by classical mechanics. A large body of experiments have gathered data on the angular distributions of the scattered species, their energy loss distribution, sticking probability, dependence on surface temperature and more. For many years these phenomena have been considered theoretically in the framework of the “washboard model” in which the interaction of the incident particle with the surface is described in terms of hard wall potentials. Although this class of models has helped in elucidating some of the features it left open many questions such as: true potentials are clearly not hard wall potentials, it does not provide a realistic framework for phonon scattering, and it cannot explain the incident angle and incident energy dependence of rainbow scattering, nor can it provide a consistent theory for sticking. In recent years we have been developing a classical perturbation theory approach which has provided new insight into the dynamics of atom-surface scattering. The theory includes both surface corrugation as well as interaction with surface phonons in terms of harmonic baths which are linearly coupled to the system coordinates. This model has been successful in elucidating many new features of rainbow scattering in terms of frictions and bath fluctuations or noise. It has also given new insight into the origins of asymmetry in atomic scattering from surfaces. New phenomena deduced from the theory include friction induced rainbows, energy loss rainbows, a theory of super-rainbows, and more. In this review we present the classical theory of atom-surface scattering as well as extensions and implications for semiclassical scattering and the further development of a quantum theory of surface scattering. Special emphasis is given to the inversion of scattering data into information on the particle-surface interactions.

Classical theory of atom-surface scattering: The rainbow effect

NASA Astrophysics Data System (ADS)

Miret-Artés, Salvador; Pollak, Eli

The scattering of heavy atoms and molecules from surfaces is oftentimes dominated by classical mechanics. A large body of experiments have gathered data on the angular distributions of the scattered species, their energy loss distribution, sticking probability, dependence on surface temperature and more. For many years these phenomena have been considered theoretically in the framework of the "washboard model" in which the interaction of the incident particle with the surface is described in terms of hard wall potentials. Although this class of models has helped in elucidating some of the features it left open many questions such as: true potentials are clearly not hard wall potentials, it does not provide a realistic framework for phonon scattering, and it cannot explain the incident angle and incident energy dependence of rainbow scattering, nor can it provide a consistent theory for sticking. In recent years we have been developing a classical perturbation theory approach which has provided new insight into the dynamics of atom-surface scattering. The theory includes both surface corrugation as well as interaction with surface phonons in terms of harmonic baths which are linearly coupled to the system coordinates. This model has been successful in elucidating many new features of rainbow scattering in terms of frictions and bath fluctuations or noise. It has also given new insight into the origins of asymmetry in atomic scattering from surfaces. New phenomena deduced from the theory include friction induced rainbows, energy loss rainbows, a theory of super-rainbows, and more. In this review we present the classical theory of atom-surface scattering as well as extensions and implications for semiclassical scattering and the further development of a quantum theory of surface scattering. Special emphasis is given to the inversion of scattering data into information on the particle-surface interactions.

Molecular t-matrices for Low-Energy Electron Diffraction (TMOL v1.1)

NASA Astrophysics Data System (ADS)

Blanco-Rey, Maria; de Andres, Pedro; Held, Georg; King, David A.

2004-08-01

We describe a FORTRAN-90 program that computes scattering t-matrices for a molecule. These can be used in a Low-Energy Electron Diffraction program to solve the molecular structural problem very efficiently. The intramolecular multiple scattering is computed within a Dyson-like approach, using free space Green propagators in a basis of spherical waves. The advantage of this approach is related to exploiting the chemical identity of the molecule, and to the simplicity to translate and rotate these t-matrices without performing a new multiple-scattering calculation for each configuration. FORTRAN-90 routines for rotating the resulting t-matrices using Wigner matrices are also provided. Program summaryTitle of program: TMOL Catalogue number: ADUF Program summary URL:http://cpc.cs.qub.ac.uk/summaries/ADUF Program obtainable from: CPC Program Library, Queen's University of Belfast, N. Ireland. Computers: Alpha ev6-21264 (700 MHz) and Pentium-IV. Operating systems: Digital UNIX V5.0 and Linux (Red Hat 8.0). Programming language: FORTRAN-90/95 (Compaq True64 compiler, and Intel Fortran Compiler 7.0 for Linux). High-speed storage required for the test run: minimum 64 Mbytes, it can grow to more depending on the system considered. Disk storage required: None. No. of bits in a word: 64 and 32. No. of lines in distributed program, including test data etc.: 5404 No. of bytes in distributed program, including test data etc.: 59 856 Distribution format: tar.gz Nature of problem: We describe the FORTRAN-90 program TMOL (v1.1) for the computation of non-diagonal scattering t-matrices for molecules or any other poly-atomic sub-unit of surface structures. These matrices can be used in an standard Low-Energy Electron Diffraction program, such as LEED90 or CLEED. Method of solution: A general non-diagonal t-matrix is assumed for the atoms or more general scatterers forming the molecule. The molecular t-matrix is solved adding the possible intramolecular multiple scattering events using Green's propagator formalism. The resulting t-matrix is referred to the mass centre of the molecule and can be easily translated with these propagators and rotated applying Wigner matrices. Typical running time: Calculating the t-matrix for a single energy takes a few seconds. Time depends on the maximum angular momentum quantum number, lmax, and the number of scatterers in the molecule, N. Running time scales as lmax6 and N3. References: [1] S. Andersson, J.B. Pendry, J. Phys. C: Solid St. Phys. 13 (1980) 3547. [2] A. Gonis, W.H. Butler, Multiple Scattering in Solids, Springer-Verlag, Berlin/New York, 2000.

Multiple scattered radiation emerging from Rayleigh and continental haze layers. I - Radiance, polarization, and neutral points

NASA Technical Reports Server (NTRS)

Kattawar, G. W.; Plass, G. N.; Hitzfelder, S. J.

1976-01-01

The matrix operator method was used to calculate the polarization of radiation scattered on layers of various optical thicknesses, with results compared for Rayleigh scattering and for scattering from a continental haze. In both cases, there are neutral points arising from the zeros of the polarization of single scattered photons at scattering angles of zero and 180 degrees. The angular position of these Rayleigh-like neutral points (RNP) in the sky shows appreciable variation with the optical thickness of the scattering layer for a Rayleigh phase matrix, but only a small variation for haze L phase matrix. Another type of neutral point exists for non-Rayleigh phase functions that is associated with the zeros of the polarization for single scattering which occurs between the end points of the curve. A comparison of radiances calculated from the complete theory of radiative transfer using Stokes vectors with those obtained from the scalar theory shows that differences of the order of 23% may be obtained for Rayleigh scattering, while the largest difference found for a haze L phase function was of the order of 0.1%.

GPU acceleration of the Locally Selfconsistent Multiple Scattering code for first principles calculation of the ground state and statistical physics of materials

NASA Astrophysics Data System (ADS)

Eisenbach, Markus; Larkin, Jeff; Lutjens, Justin; Rennich, Steven; Rogers, James H.

2017-02-01

The Locally Self-consistent Multiple Scattering (LSMS) code solves the first principles Density Functional theory Kohn-Sham equation for a wide range of materials with a special focus on metals, alloys and metallic nano-structures. It has traditionally exhibited near perfect scalability on massively parallel high performance computer architectures. We present our efforts to exploit GPUs to accelerate the LSMS code to enable first principles calculations of O(100,000) atoms and statistical physics sampling of finite temperature properties. We reimplement the scattering matrix calculation for GPUs with a block matrix inversion algorithm that only uses accelerator memory. Using the Cray XK7 system Titan at the Oak Ridge Leadership Computing Facility we achieve a sustained performance of 14.5PFlop/s and a speedup of 8.6 compared to the CPU only code.

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

Zeylikovich, I.; Xu, M., E-mail: mxu@fairfield.edu

The phase of multiply scattered light has recently attracted considerable interest. Coherent backscattering is a striking phenomenon of multiple scattered light in which the coherence of light survives multiple scattering in a random medium and is observable in the direction space as an enhancement of the intensity of backscattered light within a cone around the retroreflection direction. Reciprocity also leads to enhancement of backscattering light in the spatial space. The random medium behaves as a reciprocity mirror which robustly converts a diverging incident beam into a converging backscattering one focusing at a conjugate spot in space. Here we first analyzemore » theoretically this coherent backscattering mirror (CBM) phenomenon and then demonstrate the capability of CBM compensating and correcting both static and dynamic phase distortions occurring along the optical path. CBM may offer novel approaches for high speed dynamic phase corrections in optical systems and find applications in sensing and navigation.« less

Interstellar scintillation observations for PSR B0355+54

NASA Astrophysics Data System (ADS)

Xu, Y. H.; Lee, K. J.; Hao, L. F.; Wang, H. G.; Liu, Z. Y.; Yue, Y. L.; Yuan, J. P.; Li, Z. X.; Wang, M.; Dong, J.; Tan, J. J.; Chen, W.; Bai, J. M.

2018-06-01

In this paper, we report our investigation of pulsar scintillation phenomena by monitoring PSR B0355+54 at 2.25 GHz for three successive months using the Kunming 40-m radio telescope. We measured the dynamic spectrum, the two-dimensional correlation function and the secondary spectrum. These observations have a high signal-to-noise ratio (S/N ≥ 100). We detected scintillation arcs, which are rarely observable using such a small telescope. The sub-microsecond scale width of the scintillation arc indicates that the transverse scale of the structures on the scattering screen is as compact as astronomical unit size. Our monitoring shows that the scintillation bandwidth, the time-scale and the arc curvature of PSR B0355+54 were varying temporally. A plausible explanation would need to invoke a multiple-scattering-screen or multiple-scattering-structure scenario, in which different screens or ray paths dominate the scintillation process at different epochs.

Multiple coherent light scattering in ultracold rubidium

NASA Astrophysics Data System (ADS)

Kulatunga, P.; Sukenik, C. I.; Havey, M. D.; Kupriyanov, D. V.; Sokolov, I. M.

2001-11-01

We report investigation of multiple coherent light scattering from ^85Rb atoms confined in a magneto-optic trap. In a theoretical study of intensity enhancement of near-resonant backscattered light from cold ^85,87Rb atoms, we consider the dominant mode of double scattering only. Enhancement factors are calculated for all D1 and D2 hyperfine components and for both isotopes. In experimental studies, measurements are made of coherent backscattering of a low-intensity probe beam tuned near the F = 3 - F' = 4 transition in ^85Rb atoms. Polarization of backscattered light is determined by a backscattering polarimeter; the spatial distribution of light intensity is measured by a liquid-nitrogen cooled CCD camera set in the focal plane of the analyzing optics. The instrument has angular resolution of about 100 micro-radians, and a polarization analyzing power of roughly 1000. In this paper we describe the instrument details, including calibration procedures, and progress towards observation of atomic coherent backscattering.

Dynamic coherent backscattering mirror

NASA Astrophysics Data System (ADS)

Zeylikovich, I.; Xu, M.

2016-02-01

The phase of multiply scattered light has recently attracted considerable interest. Coherent backscattering is a striking phenomenon of multiple scattered light in which the coherence of light survives multiple scattering in a random medium and is observable in the direction space as an enhancement of the intensity of backscattered light within a cone around the retroreflection direction. Reciprocity also leads to enhancement of backscattering light in the spatial space. The random medium behaves as a reciprocity mirror which robustly converts a diverging incident beam into a converging backscattering one focusing at a conjugate spot in space. Here we first analyze theoretically this coherent backscattering mirror (CBM) phenomenon and then demonstrate the capability of CBM compensating and correcting both static and dynamic phase distortions occurring along the optical path. CBM may offer novel approaches for high speed dynamic phase corrections in optical systems and find applications in sensing and navigation.

Multiple coherent light scattering in ultracold rubidium

NASA Astrophysics Data System (ADS)

Havey, M. D.; Sukenik, C. I.; Kulatunga, P.; Kupriyanov, D. V.; Sokolov, I. M.

2001-05-01

We report investigation of multiple coherent light scattering from ^85Rb atoms confined in a magneto-optic trap. In a theoretical study of intensity enhancement of near-resonant backscattered light from cold ^85,87Rb atoms, we consider the dominant mode of double scattering only. Enhancement factors are calculated for all D1 and D2 hyperfine components and for both isotopes. In experimental studies, measurements are made of coherent backscattering of a low-intensity probe beam tuned near the F = 3 - F' = 4 transition in ^85Rb atoms. Polarization of backscattered light is determined by a backscattering polarimeter; the spatial distribution of light intensity is measured by a liquid-nitrogen cooled CCD camera set in the focal plane of the analyzing optics. The instrument has angular resolution of about 100 micro-radians, and a polarization analyzing power of roughly 1000. In this paper we describe the instrument details, including calibration procedures, and progress towards observation of atomic coherent backscattering.

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

Larin, Kirill V; Ghosn, M G

The passive diffusion of drugs through the epithelial surfaces of an eye (the most widespread method for medical treatment of various diseases) is considered. The permeability of water and drugs through rabbit cornea was measured in the isolated cornea (separate from an eye) and in the whole cornea. The permeability coefficients of water and dexamethasone were estimated by the method of optical coherence tomography (OCT). Because multiple photon scattering introduces noise and distortions to the OCT signal, measurements were performed at depths up to 500 {mu}m where most likely single scattering of light occurs in cornea. It is shown thatmore » the permeability coefficients in the isolated and whole cornea strongly differ from each other. For example, the water permeability in the isolated and whole cornea is (7.09{+-}0.12)x10{sup -5} and (1.71{+-}0.51)x10{sup -5} cm s{sup -1}, respectively. (special issue devoted to multiple radiation scattering in random media)« less

GPU acceleration of the Locally Selfconsistent Multiple Scattering code for first principles calculation of the ground state and statistical physics of materials

DOE PAGES

Eisenbach, Markus; Larkin, Jeff; Lutjens, Justin; ...

2016-07-12

The Locally Self-consistent Multiple Scattering (LSMS) code solves the first principles Density Functional theory Kohn–Sham equation for a wide range of materials with a special focus on metals, alloys and metallic nano-structures. It has traditionally exhibited near perfect scalability on massively parallel high performance computer architectures. In this paper, we present our efforts to exploit GPUs to accelerate the LSMS code to enable first principles calculations of O(100,000) atoms and statistical physics sampling of finite temperature properties. We reimplement the scattering matrix calculation for GPUs with a block matrix inversion algorithm that only uses accelerator memory. Finally, using the Craymore » XK7 system Titan at the Oak Ridge Leadership Computing Facility we achieve a sustained performance of 14.5PFlop/s and a speedup of 8.6 compared to the CPU only code.« less

Investigating acoustic-induced deformations in a foam using multiple light scattering.

PubMed

Erpelding, M; Guillermic, R M; Dollet, B; Saint-Jalmes, A; Crassous, J

2010-08-01

We have studied the effect of an external acoustic wave on bubble displacements inside an aqueous foam. The signature of the acoustic-induced bubble displacements is found using a multiple light scattering technique, and occurs as a modulation on the photon correlation curve. Measurements for various sound frequencies and amplitudes are compared to analytical predictions and numerical simulations. These comparisons finally allow us to elucidate the nontrivial acoustic displacement profile inside the foam; in particular, we find that the acoustic wave creates a localized shear in the vicinity of the solid walls holding the foam, as a consequence of inertial contributions. This study of how bubbles "dance" inside a foam as a response to sound turns out to provide new insights on foam acoustics and sound transmission into a foam, foam deformation at high frequencies, and analysis of light scattering data in samples undergoing nonhomogeneous deformations.

Investigation of hydrophobic interactions mediating the self-assembly of supramolecular host/guest polymer complexes utilizing Simultaneous Multiple Sample Light Scattering (SMSLS)

NASA Astrophysics Data System (ADS)

Payne, Molly; Jarand, Curtis; Grayson, Scott; Reed, Wayne

While living systems spontaneously heal injuries, most man made materials cannot recover from damage. Incorporating self-healing properties into synthetic polymers could significantly extend product lifetime, safety, and applications. Most reported approaches to incorporate healing into synthetic materials, however, require external stimuli such as chemical additives, heat, and light exposure. Although dynamic bonds have been explored, particularly using a hydrogen bond motif, this has not been fully investigated in an aqueous environment. To address this, hosts and guests that dynamically associate in water have been investigated to build aqueous self-healing materials. These association values were probed for various host/guest complexes using Simultaneous Multiple Sample Light Scattering (SMSLS), a technique that measures the size of aggregates via light scattering while varying concentration and other environmental factors. NSF EPSCoR IIA1430280.

Wideband Scattering Diffusion by using Diffraction of Periodic Surfaces and Optimized Unit Cell Geometries

PubMed Central

Costa, Filippo; Monorchio, Agostino; Manara, Giuliano

2016-01-01

A methodology to obtain wideband scattering diffusion based on periodic artificial surfaces is presented. The proposed surfaces provide scattering towards multiple propagation directions across an extremely wide frequency band. They comprise unit cells with an optimized geometry and arranged in a periodic lattice characterized by a repetition period larger than one wavelength which induces the excitation of multiple Floquet harmonics. The geometry of the elementary unit cell is optimized in order to minimize the reflection coefficient of the fundamental Floquet harmonic over a wide frequency band. The optimization of FSS geometry is performed through a genetic algorithm in conjunction with periodic Method of Moments. The design method is verified through full-wave simulations and measurements. The proposed solution guarantees very good performance in terms of bandwidth-thickness ratio and removes the need of a high-resolution printing process. PMID:27181841

Enhancement of multiple-phonon resonant Raman scattering in Co-doped ZnO nanorods

NASA Astrophysics Data System (ADS)

Phan, The-Long; Vincent, Roger; Cherns, David; Dan, Nguyen Huy; Yu, Seong-Cho

2008-08-01

We have studied Raman scattering in Co-doped ZnO nanorods prepared by thermal diffusion. Experimental results show that the features of their non-resonant spectra are similar to Raman spectra from Co-doped ZnO materials investigated previously. Under resonant conditions, however, there is a strong enhancement of multiple-phonon Raman scattering processes. Longitudinal optical (LO)-phonon overtones up to eleventh order are observed. The modes become more obvious when the Co concentration diffused into ZnO nanorods goes to an appropriate value. This phenomenon is explained due to the shift of the band-gap energy and also due to the decrease in the intensity of near-band-edge luminescence. Our observation is in agreement with the prediction [J. F. Scott, Phys. Rev. B 2, 1209 (1970)] that the number of LO-phonon lines in ZnO is higher than that observed for CdS.

Single Molecule Raman Spectroscopy Under High Pressure

NASA Astrophysics Data System (ADS)

Fu, Yuanxi; Dlott, Dana

2014-06-01

Pressure effects on surface-enhanced Raman scattering spectra of Rhdoamine 6G adsorbed on silver nanoparticle surfaces was studied using a confocal Raman microscope. Colloidal silver nanoparticles were treated with Rhodamine 6G (R6G) and its isotopically substituted partner, R6G-d4. Mixed isotopomers let us identify single-molecule spectra, since multiple-molecule spectra would show vibrational transitions from both species. The nanoparticles were embedded into a poly vinyl alcohol film, and loaded into a diamond anvil cell for the high-pressure Raman scattering measurement. Argon was the pressure medium. Ambient pressure Raman scattering spectra showed few single-molecule spectra. At moderately high pressure ( 1GPa), a surprising effect was observed. The number of sites with observable spectra decreased dramatically, and most of the spectra that could be observed were due to single molecules. The effects of high pressure suppressed the multiple-molecule Raman sites, leaving only the single-molecule sites to be observed.

Effects of multiple scattering in cold nuclear matter on J / ψ suppression and in heavy ion collisions

NASA Astrophysics Data System (ADS)

Glenn, A. M.; Nagle, J. L.; Molnar, Denes

2007-01-01

Coherent multiple scatterings of ccbar quark pairs in the environment of heavy ion collisions have been used in a previous work by Qiu et al. [J. Qiu, J.P. Vary, X. Zhang, Phys. Rev. Lett. 88 (2002) 232301; J. Qiu, J.P. Vary, X. Zhang, Nucl. Phys. A 698 (2002) 571, nucl-th/0106040] to study J / ψ suppression. That model suggests that heavy quark re-scatterings in a cold nuclear medium can completely explain the centrality dependence of the observed J / ψ suppression in Pb + Pb collisions at the SPS [M.C. Abreu, et al., NA50 Collaboration, Phys. Lett. B 521 (2001) 195]. Their calculations also revealed significant differences under the assumptions of a color singlet or color octet production mechanism. A more recent analytic calculation [H. Fujii, Phys. Rev. C 67 (2003) 031901], which includes incoherent final-state re-scatterings with explicit momentum transfer fluctuations in three dimensions, indicates much less suppression and little sensitivity to the production mechanism. In this Letter, we study simultaneously both the J / ψ suppression and pT modifications, at SPS and RHIC energies. We mainly focus on incoherent momentum transfer fluctuations in two dimensions, which is more appropriate for the heavy-ion collision kinematics. Our analytic and Monte Carlo calculations reinforce the analytic results in [H. Fujii, Phys. Rev. C 67 (2003) 031901]. Additionally, we find that the experimental J / ψ suppression and from nucleus-nucleus collisions at the SPS or RHIC cannot simultaneously be described in this incoherent multiple scattering framework for any value of the fluctuation strength parameter .

Theory of lasing in a multiple-scattering medium

NASA Astrophysics Data System (ADS)

John, Sajeev; Pang, Gendi

1996-10-01

In several recent experiments, isotropic lasing action was observed in paints that contain rhodamine 640 dye molecules in methanol solution as gain media and titania particles as optical scatterers. These so-called paint-on laser systems are extraordinary because they are highly disordered systems. The microscopic mechanism for laser activity and the coherence properties of light emission in this multiple-light-scattering medium have not yet been elucidated. In this paper we derive the emission intensity properties of a model dye system with excited singlet and triplet electronic energy levels, which is immersed in a multiple-scattering medium with transport mean free path l*. Using physically reasonable estimates for the absorption and emission cross section for the singlet and triplet manifolds, and the singlet-triplet intersystem crossing rate, we solve the nonlinear laser rate equations for the dye molecules. This leads to a diffusion equation for the light intensity in the medium with a nonlinear intensity-dependent gain coefficient. Using this model we are able to account for nearly all of the experimentally observed properties of laser paint reported so far when l*>>λ0, the emission wavelength. This includes the dependence of the peak intensity of amplified emission on the mean free path l*, the dye concentration ρ, and the pump intensity characteristics. Our model recaptures the collapse of the emission linewidth at a specific threshold pump intensity and describes how this threshold intensity varies with l*. In addition, our model predicts a dramatic increase in the peak intensity and a further lowering of the lasing threshold for the strong scattering limit l*-->λ0. This suggests a striking enhancement of the characteristics of laser paint near the photon localization threshold in a disordered medium.

Optical properties of the Martian aerosols as derived from Imager for Mars Pathfinder midday sky brightness data

NASA Astrophysics Data System (ADS)

Shalygina, O. S.; Markiewicz, W. J.; Hviid, S. F.

2012-09-01

It is well known that the aerosol play a major role in the energy budget of the Martian atmosphere. The importance of the aerosols for the radiative loading of the atmosphere has hence, direct impact on the Martian present weather and its seasonal cycle as well as consequences for its long term climate. Very accurate models of the sky brightness are required to separate the atmospheric illumination from the spectrum of the Martian surface, and hence to understand the mineralogy of the surface rocks and soil. Such accurate models are only possible if the optical properties of the Martian aerosols are known. In this work we analyze the images of the brightness of the Martian sky at midday acquired from the surface of the Mars during the Mars Pathfinder mission. The Imager for Mars Pathfinder (IMP) obtained data in filters centered at 443.6, 481.0, 670.8, 896.1 and 965.3 nm. Useful data sets were returned on sols 27, 40, 56, 65, 68, 74 and 82. Although the coverage in scattering angles of this sequence is limited to about 100°, having the Sun near zenith minimizes multiple scattering. This property should help in accuracy of constraining the size distribution and material properties. The shape of the particles can be expected to be less well constrained, as scattering events at angles around 150° are only present through multiple scattering. Data from sol 56 (Figure 1) were fitted with multiple scattering radiative transfer calculations to extract the size distribution, optical properties, and shape of the aerosols suspended in the atmosphere [1].

Analysis of 4He+40Ca and 4He+44Ti scattering using different optical model potentials

NASA Astrophysics Data System (ADS)

Ibraheem, Awad A.

2016-09-01

Elastic scattering of 4He+40Ca and 4He+44Ti reactions at backward angles has been analyzed using two differentmodels, microscopic and semimicroscopic folding potentials. The derived real potentials supplemented with phenomenological Woods-Saxon imaginary potentials, provide good agreement with the experimental data at energy E c.m. = 21.8 MeV without need to renormalize the potentials. Coupledchannels calculations are used to extract the inelastic scattering cross section to the low-lying state 2+ (1.083 MeV) of 44Ti. The deformation length is obtained and compared with the electromagnetic measurement values as well as those obtained from previous studies.

Strength of the interatomic potential derived from angular scans in LEIS

NASA Astrophysics Data System (ADS)

Primetzhofer, D.; Markin, S. N.; Draxler, M.; Beikler, R.; Taglauer, E.; Bauer, P.

2008-09-01

Angular scans were performed for a Cu(1 0 0) single crystal and He + ions. The results were compared to MARLOWE, KALYPSO and FAN simulations to obtain information on the interaction potential. The influence of the used evaluation procedure on the deduced scattering potential was investigated. The scattering potential is found to be weaker than what is predicted by an uncorrected TFM potential. It was found that the use of a single screening correction factor is applicable in a wide range of impact parameters. It is further shown that selection of single scattering trajectories and a limitation of information depth to the surface layers is possible for neutral and charge integrated spectra.

Quantum oscillation and the Aharonov-Bohm effect in a multiply connected normal-conductor loop

NASA Astrophysics Data System (ADS)

Takai, Daisuke; Ohta, Kuniichi

1994-12-01

The magnetostatic and electrostatic Aharonov-Bohm (AB) effects in multiply connected normal-conductor rings are studied. A previously developed model of a single mesoscopic ring is generalized to include an arbitrary number of rings, and the oscillatory behavior of the total transmission coefficients for the serially connected N (N is equal to integer) rings are derived as a function of the magnetic flux threading each ring and as a function of the electrostatic potential applied to the rings. It is shown that quantum oscillation of multiple rings exhibits greater variety of behavior than in periodic superlattices. We investigate the influence of the scattering at a junction and the number of atoms in the ring in both magnetostatic and electrostatic oscillation of multiring systems. For the electrostatic AB effects, when scattering occurs at the junctions between the connecting wire and the ring, the conductance in the AB oscillation is modified to an N-1 peaked shape. It is shown that this oscillatory behavior is greatly influenced by the number of atoms in the ring and is controlled by the electrostatic potential or magnetic flux that is applied to the ring. We discuss the behavior of the quantum oscillations upon varying the number of connected rings and the number of minibands.

Plane-dependent ML scatter scaling: 3D extension of the 2D simulated single scatter (SSS) estimate

NASA Astrophysics Data System (ADS)

Rezaei, Ahmadreza; Salvo, Koen; Vahle, Thomas; Panin, Vladimir; Casey, Michael; Boada, Fernando; Defrise, Michel; Nuyts, Johan

2017-08-01

Scatter correction is typically done using a simulation of the single scatter, which is then scaled to account for multiple scatters and other possible model mismatches. This scaling factor is determined by fitting the simulated scatter sinogram to the measured sinogram, using only counts measured along LORs that do not intersect the patient body, i.e. ‘scatter-tails’. Extending previous work, we propose to scale the scatter with a plane dependent factor, which is determined as an additional unknown in the maximum likelihood (ML) reconstructions, using counts in the entire sinogram rather than only the ‘scatter-tails’. The ML-scaled scatter estimates are validated using a Monte-Carlo simulation of a NEMA-like phantom, a phantom scan with typical contrast ratios of a 68Ga-PSMA scan, and 23 whole-body 18F-FDG patient scans. On average, we observe a 12.2% change in the total amount of tracer activity of the MLEM reconstructions of our whole-body patient database when the proposed ML scatter scales are used. Furthermore, reconstructions using the ML-scaled scatter estimates are found to eliminate the typical ‘halo’ artifacts that are often observed in the vicinity of high focal uptake regions.

One-step formation of multiple Pickering emulsions stabilized by self-assembled poly(dodecyl acrylate-co-acrylic acid) nanoparticles.

PubMed

Zhu, Ye; Sun, Jianhua; Yi, Chenglin; Wei, Wei; Liu, Xiaoya

2016-09-13

In this study, a one-step generation of stable multiple Pickering emulsions using pH-responsive polymeric nanoparticles as the only emulsifier was reported. The polymeric nanoparticles were self-assembled from an amphiphilic random copolymer poly(dodecyl acrylate-co-acrylic acid) (PDAA), and the effect of the copolymer content on the size and morphology of PDAA nanoparticles was determined by dynamic light scattering (DLS) and transmission electron microscopy (TEM). The emulsification study of PDAA nanoparticles revealed that multiple Pickering emulsions could be generated through a one-step phase inversion process by using PDAA nanoparticles as the stabilizer. Moreover, the emulsification performance of PDAA nanoparticles at different pH values demonstrated that multiple emulsions with long-time stability could only be stabilized by PDAA nanoparticles at pH 5.5, indicating that the surface wettability of PDAA nanoparticles plays a crucial role in determining the type and stability of the prepared Pickering emulsions. Additionally, the polarity of oil does not affect the emulsification performance of PDAA nanoparticles, and a wide range of oils could be used as the oil phase to prepare multiple emulsions. These results demonstrated that multiple Pickering emulsions could be generated via the one-step emulsification process using self-assembled polymeric nanoparticles as the stabilizer, and the prepared multiple emulsions have promising potential to be applied in the cosmetic, medical, and food industries.

Geant4 simulations of soft proton scattering in X-ray optics. A tentative validation using laboratory measurements

NASA Astrophysics Data System (ADS)

Fioretti, Valentina; Mineo, Teresa; Bulgarelli, Andrea; Dondero, Paolo; Ivanchenko, Vladimir; Lei, Fan; Lotti, Simone; Macculi, Claudio; Mantero, Alfonso

2017-12-01

Low energy protons (< 300 keV) can enter the field of view of X-ray telescopes, scatter on their mirror surfaces at small incident angles, and deposit energy on the detector. This phenomenon can cause intense background flares at the focal plane decreasing the mission observing time (e.g. the XMM-Newton mission) or in the most extreme cases, damaging the X-ray detector. A correct modelization of the physics process responsible for the grazing angle scattering processes is mandatory to evaluate the impact of such events on the performance (e.g. observation time, sensitivity) of future X-ray telescopes as the ESA ATHENA mission. The Remizovich model describes particles reflected by solids at glancing angles in terms of the Boltzmann transport equation using the diffuse approximation and the model of continuous slowing down in energy. For the first time this solution, in the approximation of no energy losses, is implemented, verified, and qualitatively validated on top of the Geant4 release 10.2, with the possibility to add a constant energy loss to each interaction. This implementation is verified by comparing the simulated proton distribution to both the theoretical probability distribution and with independent ray-tracing simulations. Both the new scattering physics and the Coulomb scattering already built in the official Geant4 distribution are used to reproduce the latest experimental results on grazing angle proton scattering. At 250 keV multiple scattering delivers large proton angles and it is not consistent with the observation. Among the tested models, the single scattering seems to better reproduce the scattering efficiency at the three energies but energy loss obtained at small scattering angles is significantly lower than the experimental values. In general, the energy losses obtained in the experiment are higher than what obtained by the simulation. The experimental data are not completely representative of the soft proton scattering experienced by current X-ray telescopes because of the lack of measurements at low energies (< 200 keV) and small reflection angles, so we are not able to address any of the tested models as the one that can certainly reproduce the scattering behavior of low energy protons expected for the ATHENA mission. We can, however, discard multiple scattering as the model able to reproduce soft proton funnelling, and affirm that Coulomb single scattering can represent, until further measurements at lower energies are available, the best approximation of the proton scattered angular distribution at the exit of X-ray optics.

Thermoelectric band engineering: The role of carrier scattering

NASA Astrophysics Data System (ADS)

Witkoske, Evan; Wang, Xufeng; Lundstrom, Mark; Askarpour, Vahid; Maassen, Jesse

2017-11-01

Complex electronic band structures, with multiple valleys or bands at the same or similar energies, can be beneficial for thermoelectric performance, but the advantages can be offset by inter-valley and inter-band scattering. In this paper, we demonstrate how first-principles band structures coupled with recently developed techniques for rigorous simulation of electron-phonon scattering provide the capabilities to realistically assess the benefits and trade-offs associated with these materials. We illustrate the approach using n-type silicon as a model material and show that intervalley scattering is strong. This example shows that the convergence of valleys and bands can improve thermoelectric performance, but the magnitude of the improvement depends sensitively on the relative strengths of intra- and inter-valley electron scattering. Because anisotropy of the band structure also plays an important role, a measure of the benefit of band anisotropy in the presence of strong intervalley scattering is presented.

Multiple scattered radiation emerging from continental haze layers. 1: Radiance, polarization, and neutral points

NASA Technical Reports Server (NTRS)

Kattawar, G. W.; Plass, G. N.; Hitzfelder, S. J.

1975-01-01

The complete radiation field is calculated for scattering layers of various optical thicknesses. Results obtained for Rayleigh and haze scattering are compared. Calculated radiances show differences as large as 23% compared to the approximate scalar theory of radiative transfer, while the same differences are approximately 0.1% for a continental haze phase function. The polarization of reflected and transmitted radiation is given for various optical thicknesses, solar zenith angles, and surface albedos. Two types of neutral points occur for aerosol phase functions. Rayleigh-like neutral points arise from zero polarization that occurs at scattering angles of 0 deg and 180 deg. For Rayleigh phase functions, the position of these points varies with the optical thickness of the scattering layer. Non-Rayleigh neutral points are associated with the zeros of polarization which occur between the end points of the single scattering curve, and are found over a wide range of azimuthal angles.

Effective phase function of light scattered at small angles by polydisperse particulate media

NASA Astrophysics Data System (ADS)

Turcu, I.

2008-06-01

Particles with typical dimensions higher than the light wavelength and relative refraction indexes close to one, scatter light mainly in the forward direction where the scattered light intensity has a narrow peak. For particulate media accomplishing these requirements the light scattered at small angles in a far-field detecting set-up can be described analytically by an effective phase function (EPF) even in the multiple scattering regime. The EPF model which was built for monodispersed systems has been extended to polydispersed media. The main ingredients consist in the replacement of the single particle phase function and of the optical thickness with their corresponding averaged values. Using a Gamma particle size distribution (PSD) as a testing model, the effect of polydispersity was systematically investigated. The increase of the average radius or/and of the PSD standard deviation leads to the decrease of the angular spreading of the small angle scattered light.

Use of the Wigner representation in scattering problems

NASA Technical Reports Server (NTRS)

Bemler, E. A.

1975-01-01

The basic equations of quantum scattering were translated into the Wigner representation, putting quantum mechanics in the form of a stochastic process in phase space, with real valued probability distributions and source functions. The interpretative picture associated with this representation is developed and stressed and results used in applications published elsewhere are derived. The form of the integral equation for scattering as well as its multiple scattering expansion in this representation are derived. Quantum corrections to classical propagators are briefly discussed. The basic approximation used in the Monte-Carlo method is derived in a fashion which allows for future refinement and which includes bound state production. Finally, as a simple illustration of some of the formalism, scattering is treated by a bound two body problem. Simple expressions for single and double scattering contributions to total and differential cross-sections as well as for all necessary shadow corrections are obtained.

Solar system applications of Mie theory and of radiative transfer of polarized light

NASA Technical Reports Server (NTRS)

Whitehill, L. P.

1972-01-01

A theory of the multiple scattering of polarized light is discussed using the doubling method of van de Hulst. The concept of the Stokes parameters is derived and used to develop the form of the scattering phase matrix of a single particle. The diffuse reflection and transmission matrices of a single scattering plane parallel atmosphere are expressed as a function of the phase matrix, and the symmetry properties of these matrices are examined. Four matrices are required to describe scattering and transmission. The scattering matrix that results from the addition of two identical layers is derived. Using the doubling method, the scattering and transmission matrices of layers of arbitrary optical thickness can be derived. The doubling equations are then rewritten in terms of their Fourier components. Computation time is reduced since each Fourier component doubles independently. Computation time is also reduced through the use of symmetry properties.

Matrix Approach of Seismic Wave Imaging: Application to Erebus Volcano

NASA Astrophysics Data System (ADS)

Blondel, T.; Chaput, J.; Derode, A.; Campillo, M.; Aubry, A.

2017-12-01

This work aims at extending to seismic imaging a matrix approach of wave propagation in heterogeneous media, previously developed in acoustics and optics. More specifically, we will apply this approach to the imaging of the Erebus volcano in Antarctica. Volcanoes are actually among the most challenging media to explore seismically in light of highly localized and abrupt variations in density and wave velocity, extreme topography, extensive fractures, and the presence of magma. In this strongly scattering regime, conventional imaging methods suffer from the multiple scattering of waves. Our approach experimentally relies on the measurement of a reflection matrix associated with an array of geophones located at the surface of the volcano. Although these sensors are purely passive, a set of Green's functions can be measured between all pairs of geophones from ice-quake coda cross-correlations (1-10 Hz) and forms the reflection matrix. A set of matrix operations can then be applied for imaging purposes. First, the reflection matrix is projected, at each time of flight, in the ballistic focal plane by applying adaptive focusing at emission and reception. It yields a response matrix associated with an array of virtual geophones located at the ballistic depth. This basis allows us to get rid of most of the multiple scattering contribution by applying a confocal filter to seismic data. Iterative time reversal is then applied to detect and image the strongest scatterers. Mathematically, it consists in performing a singular value decomposition of the reflection matrix. The presence of a potential target is assessed from a statistical analysis of the singular values, while the corresponding eigenvectors yield the corresponding target images. When stacked, the results obtained at each depth give a three-dimensional image of the volcano. While conventional imaging methods lead to a speckle image with no connection to the actual medium's reflectivity, our method enables to highlight a chimney-shaped structure inside Erebus volcano with true positive rates ranging from 80% to 95%. Although computed independently, the results at each depth are spatially consistent, substantiating their physical reliability. The identified structure is therefore likely to describe accurately the internal structure of the Erebus volcano.

Regional Cerebral Blood Flow Analysis in Patients with Multiple Sclerosis Using TC-99M Hmpao and a Three - Spect System.

NASA Astrophysics Data System (ADS)

D'Souza, Maximian Felix

1995-01-01

The purpose of the present study was to determine the changes in regional cerebral blood flow (rCBF) with a cognitive task of semantic word retrieval (verbal fluency) in patients with multiple sclerosis (MS) and compare with the rCBF distribution of normal controls. Two groups of patients with low and high verbal fluency scores and two groups of normal controls were selected to determine a relationship between rCBF and verbal performance. A three-detector gamma camera (TRIAD 88) was used with radiotracer Tc-99m HMPAO and single photon emission computed tomography (SPECT) to obtain 3D rCBF maps. The performance characteristics of the camera was comprehensively studied before being utilized for clinical studies. In addition, technical improvements were implemented in the form of scatter correction and MRI-SPECT coregistration to potentially enhance the quantitative accuracy of the rCBF data. The performance analysis of the gamma camera showed remarkable consistency among the three-detector heads and yielded results that were consistent with the manufacturer's specification. Measurements of physical objects also showed excellent image quality. The coregistration of SPECT and MRI images allowed more accurate anatomical localization for extraction of regional blood flow information. The validation of the scatter correction technique with physical phantoms indicated marked improvements in quantitative accuracy. There was marked difference in activation patterns between patients and normals. In normals, individually subjects showed either an increase or a decrease in blood flow to left frontal and temporal, however, on average, there was not a statistically significant change. The lack of significant change may suggest large variability among subjects chosen or that the individual changes are not large enough to be significant. The results from MS patients showed several left cortical areas with statistically significant change in blood flow after cognitive activation, especially in the low fluent group, with decreased flow. Scatter corrected data yielded mostly right sided significant increases in blood flow. Further studies must be conducted to further evaluate the scatter correction technique. Additional studies on MS patients must focus on correlating lesion volume, location and number to the rCBF distribution.

An experimental study of energy dependence of saturation thickness of multiply scattered gamma rays in binary alloys

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

Singh, Gurvinderjit; Singh, Bhajan, E-mail: bhajan2k1@yahoo.co.in; Sandhu, B. S.

2015-08-28

The present measurements are carried out to investigate the multiple scattering of 662 keV gamma photons emerging from targets of binary alloys (brass and soldering material). The scattered photons are detected by 51 mm × 51 mm NaI(Tl) scintillation detector whose response unscrambling converting the observed pulse–height distribution to a true photon energy spectrum, is obtained with the help of 10 × 10 inverse response matrix. The numbers of multiply scattered events, having same energy as in the singly scattered distribution, first increases with target thickness and then saturate. The application of response function of scintillation detector does not result in anymore » change of measured saturation thickness. Monte Carlo calculation supports the present experimental results.« less

Coherent-backscatter effect - A vector formulation accounting for polarization and absorption effects and small or large scatterers

NASA Technical Reports Server (NTRS)

Peters, Kenneth J.

1992-01-01

Previous theoretical work on the coherent-backscatter effect in the context of speckle time autocorrelation has gone beyond the diffusion approximation and the assumption of isotropic (point) scatterers. This paper extends the theory to include the effects of polarization and absorption, and to give the angular line shape. The results are expressions for angular variations valid for small and large scatterers and linear and circular polarizations, in lossless or lossy media. Calculations show that multiple anisotropic scattering results in the preservation of incident polarization. Application to a problem in radar astronomy is considered. It is shown that the unusual radar measurements (high reflectivity and polarization ratios) of Jupiter's icy Galilean satellites can be explained by coherent backscatter from anisotropic (forward) scatterers.

Quantum dynamical simulation of the scattering of Ar from a frozen LiF(100) surface based on a first principles interaction potential

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

Azuri, Asaf; Pollak, Eli, E-mail: eli.pollak@weizmann.ac.il

2015-07-07

In-plane two and three dimensional diffraction patterns are computed for the vertical scattering of an Ar atom from a frozen LiF(100) surface. Suitable collimation of the incoming wavepacket serves to reveal the quantum mechanical diffraction. The interaction potential is based on a fit to an ab initio potential calculated using density functional theory with dispersion corrections. Due to the potential coupling found between the two horizontal surface directions, there are noticeable differences between the quantum angular distributions computed for two and three dimensional scattering. The quantum results are compared to analogous classical Wigner computations on the same surface and withmore » the same conditions. The classical dynamics largely provides the envelope for the quantum diffractive scattering. The classical results also show that the corrugation along the [110] direction of the surface is smaller than along the [100] direction, in qualitative agreement with experimental observations of unimodal and bimodal scattering for the [110] and [100] directions, respectively.« less

Determination of scattering structures from spatial coherence measurements.

PubMed

Zarubin, A M

1996-03-01

A new method of structure determination and microscopic imaging with short-wavelength radiations (charged particles, X-rays, neutrons), based on measurements of the modulus and the phase of the degree of spatial coherence of the scattered radiation, is developed. The underlying principle of the method--transfer of structural information about the scattering potential via spatial coherence of the secondary (scattering) source of radiation formed by this potential--is expressed by the generalization of the van Cittert-Zernike theorem to wave and particle scattering [A.M. Zarubin, Opt. Commun. 100 (1993) 491; Opt. Commun. 102 (1993) 543]. Shearing interferometric techniques are proposed for implementing the above measurements; the limits of spatial resolution attainable by reconstruction of the absolute square of a 3D scattering potential and its 2D projections from the measurements are analyzed. It is shown theoretically that 3D imaging with atomic resolution can be realized in a "synthetic aperture" electron or ion microscope and that a 3D resolution of about 6 nm can be obtained with a "synthetic aperture" X-ray microscope. A proof-of-principle optical experiment is presented.

Cascaded Brillouin lasing in monolithic barium fluoride whispering gallery mode resonators

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

Lin, Guoping, E-mail: guoping.lin@femto-st.fr; Diallo, Souleymane; Saleh, Khaldoun

2014-12-08

We report the observation of stimulated Brillouin scattering and lasing at 1550 nm in barium fluoride (BaF{sub 2}) crystal. Brillouin lasing was achieved with ultra-high quality (Q) factor monolithic whispering gallery mode mm-size disk resonators. Overmoded resonators were specifically used to provide cavity resonances for both the pump and all Brillouin Stokes waves. Single and multiple Brillouin Stokes radiations with frequency shift ranging from 8.2 GHz up to 49 GHz have been generated through cascaded Brillouin lasing. BaF{sub 2} resonator-based Brillouin lasing can find potential applications for high-coherence lasers and microwave photonics.

Determination of electron-nucleus collisions geometry with forward neutrons

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

Zheng, L.; Aschenauer, E.; Lee, J. H.

2014-12-29

There are a large number of physics programs one can explore in electron-nucleus collisions at a future electron-ion collider. Collision geometry is very important in these studies, while the measurement for an event-by-event geometric control is rarely discussed in the prior deep-inelastic scattering experiments off a nucleus. This paper seeks to provide some detailed studies on the potential of tagging collision geometries through forward neutron multiplicity measurements with a zero degree calorimeter. As a result, this type of geometry handle, if achieved, can be extremely beneficial in constraining nuclear effects for the electron-nucleus program at an electron-ion collider.

Physics of neutrino flavor transformation through matter-neutrino resonances

NASA Astrophysics Data System (ADS)

Wu, Meng-Ru; Duan, Huaiyu; Qian, Yong-Zhong

2016-01-01

In astrophysical environments such as core-collapse supernovae and neutron star-neutron star or neutron star-black hole mergers where dense neutrino media are present, matter-neutrino resonances (MNRs) can occur when the neutrino propagation potentials due to neutrino-electron and neutrino-neutrino forward scattering nearly cancel each other. We show that neutrino flavor transformation through MNRs can be explained by multiple adiabatic solutions similar to the Mikheyev-Smirnov-Wolfenstein mechanism. We find that for the normal neutrino mass hierarchy, neutrino flavor evolution through MNRs can be sensitive to the shape of neutrino spectra and the adiabaticity of the system, but such sensitivity is absent for the inverted hierarchy.

Memory sparing, fast scattering formalism for rigorous diffraction modeling

NASA Astrophysics Data System (ADS)

Iff, W.; Kämpfe, T.; Jourlin, Y.; Tishchenko, A. V.

2017-07-01

The basics and algorithmic steps of a novel scattering formalism suited for memory sparing and fast electromagnetic calculations are presented. The formalism, called ‘S-vector algorithm’ (by analogy with the known scattering-matrix algorithm), allows the calculation of the collective scattering spectra of individual layered micro-structured scattering objects. A rigorous method of linear complexity is applied to model the scattering at individual layers; here the generalized source method (GSM) resorting to Fourier harmonics as basis functions is used as one possible method of linear complexity. The concatenation of the individual scattering events can be achieved sequentially or in parallel, both having pros and cons. The present development will largely concentrate on a consecutive approach based on the multiple reflection series. The latter will be reformulated into an implicit formalism which will be associated with an iterative solver, resulting in improved convergence. The examples will first refer to 1D grating diffraction for the sake of simplicity and intelligibility, with a final 2D application example.

Fully nonlocal inelastic scattering computations for spectroscopical transmission electron microscopy methods

NASA Astrophysics Data System (ADS)

Rusz, Ján; Lubk, Axel; Spiegelberg, Jakob; Tyutyunnikov, Dmitry

2017-12-01

The complex interplay of elastic and inelastic scattering amenable to different levels of approximation constitutes the major challenge for the computation and hence interpretation of TEM-based spectroscopical methods. The two major approaches to calculate inelastic scattering cross sections of fast electrons on crystals—Yoshioka-equations-based forward propagation and the reciprocal wave method—are founded in two conceptually differing schemes—a numerical forward integration of each inelastically scattered wave function, yielding the exit density matrix, and a computation of inelastic scattering matrix elements using elastically scattered initial and final states (double channeling). Here, we compare both approaches and show that the latter is computationally competitive to the former by exploiting analytical integration schemes over multiple excited states. Moreover, we show how to include full nonlocality of the inelastic scattering event, neglected in the forward propagation approaches, at no additional computing costs in the reciprocal wave method. Detailed simulations show in some cases significant errors due to the z -locality approximation and hence pitfalls in the interpretation of spectroscopical TEM results.

Multiple scattering by infinitely long cylindrical glass inclusions in a saturated Biot porous medium of glass beads.

PubMed

Trabelsi, W; Franklin, H; Tinel, A

2016-05-01

The resonance spectrum of sets of two to five infinitely long parallel cylindrical glass inclusions in a fluid saturated porous matrix of unconsolidated glass beads is investigated. The ratio of bead diameters to inclusion diameters is 1/5. The far field form functions and the related phase derivatives are calculated by using an exact multiple scattering formalism and by assuming that the porous medium obeys Biot's model. In order to validate this hypothesis, comparisons between theory and experiments are done in the special case of a fast incident wave on a set of two and three inclusions.

Single Charged Particle Identification in Nuclear Emulsion Using Multiple Coulomb Scattering Method

NASA Astrophysics Data System (ADS)

Tint, Khin T.; Endo, Yoko; Hoshino, Kaoru; Ito, Hiroki; Itonaga, Kazunori; Kinbara, Shinji; Kobayashi, Hidetaka; Mishina, Akihiro; Soe, Myint K.; Yoshida, Junya; Nakazawa, Kazuma

Development of particle identification technique for single charged particles such as Ξ- hyperon, proton, K- and π- mesons is on-going by measuring multiple Coulomb scattering in nuclear emulsion. We generated several thousands of tracks of the single charged particles in nuclear emulsion stacks with GEANT 4 simulation and obtained second difference in constant Sagitta Method. We found that recognition of Ξ- hyperon from π- mesons is well satisfied, although that from K- and proton are a little difficult. On the other hand, the consistency of second difference of real Ξ- hyperon and pi meson tracks and simulation results were also confirmed.

Gauge invariance and kaon production in deep inelastic scattering at low scales

NASA Astrophysics Data System (ADS)

Guerrero, Juan V.; Accardi, Alberto

2018-06-01

This paper focuses on hadron mass effects in calculations of semi-inclusive kaon production in lepton-Deuteron deeply inelastic scattering at HERMES and COMPASS kinematics. In the collinear factorization framework, the corresponding cross section is shown to factorize, at leading order and leading twist, into products of parton distributions and fragmentation functions evaluated in terms of kaon- and nucleon-mass-dependent scaling variables, and to respect gauge invariance. It is found that hadron mass corrections for integrated kaon multiplicities sizeably reduce the apparent large discrepancy between measurements of K++K- multiplicities performed by the two collaborations, and fully reconcile their K+/K- ratios.

Muon energy estimate through multiple scattering with the MACRO detector

NASA Astrophysics Data System (ADS)

Ambrosio, M.; Antolini, R.; Auriemma, G.; Bakari, D.; Baldini, A.; Barbarino, G. C.; Barish, B. C.; Battistoni, G.; Becherini, Y.; Bellotti, R.; Bemporad, C.; Bernardini, P.; Bilokon, H.; Bloise, C.; Bower, C.; Brigida, M.; Bussino, S.; Cafagna, F.; Calicchio, M.; Campana, D.; Candela, A.; Carboni, M.; Caruso, R.; Cassese, F.; Cecchini, S.; Cei, F.; Chiarella, V.; Choudhary, B. C.; Coutu, S.; Cozzi, M.; de Cataldo, G.; de Deo, M.; Dekhissi, H.; de Marzo, C.; de Mitri, I.; Derkaoui, J.; de Vincenzi, M.; di Credico, A.; Dincecco, M.; Erriquez, O.; Favuzzi, C.; Forti, C.; Fusco, P.; Giacomelli, G.; Giannini, G.; Giglietto, N.; Giorgini, M.; Grassi, M.; Gray, L.; Grillo, A.; Guarino, F.; Gustavino, C.; Habig, A.; Hanson, K.; Heinz, R.; Iarocci, E.; Katsavounidis, E.; Katsavounidis, I.; Kearns, E.; Kim, H.; Kyriazopoulou, S.; Lamanna, E.; Lane, C.; Levin, D. S.; Lindozzi, M.; Lipari, P.; Longley, N. P.; Longo, M. J.; Loparco, F.; Maaroufi, F.; Mancarella, G.; Mandrioli, G.; Margiotta, A.; Marini, A.; Martello, D.; Marzari-Chiesa, A.; Mazziotta, M. N.; Michael, D. G.; Monacelli, P.; Montaruli, T.; Monteno, M.; Mufson, S.; Musser, J.; Nicolo, D.; Nolty, R.; Orth, C.; Osteria, G.; Palamara, O.; Patera, V.; Patrizii, L.; Pazzi, R.; Peck, C. W.; Perrone, L.; Petrera, S.; Pistilli, P.; Popa, V.; Raino, A.; Reynoldson, J.; Ronga, F.; Rrhioua, A.; Satriano, C.; Scapparone, E.; Scholberg, K.; Sciubba, A.; Serra, P.; Sioli, M.; Sirri, G.; Sitta, M.; Spinelli, P.; Spinetti, M.; Spurio, M.; Steinberg, R.; Stone, J. L.; Sulak, L. R.; Surdo, A.; Tarle, G.; Tatananni, E.; Togo, V.; Vakili, M.; Walter, C. W.; Webb, R.; MACRO Collaboration

2002-10-01

Muon energy measurement represents an important issue for any experiment addressing neutrino-induced up-going muon studies. Since the neutrino oscillation probability depends on the neutrino energy, a measurement of the muon energy adds an important piece of information concerning the neutrino system. We show in this paper how the MACRO limited streamer tube system can be operated in drift mode by using the TDCs included in the QTPs, an electronics designed for magnetic monopole search. An improvement of the space resolution is obtained, through an analysis of the multiple scattering of muon tracks as they pass through our detector. This information can be used further to obtain an estimate of the energy of muons crossing the detector. Here we present the results of two dedicated tests, performed at CERN PS-T9 and SPS-X7 beam lines, to provide a full check of the electronics and to exploit the feasibility of such a multiple scattering analysis. We show that by using a neural network approach, we are able to reconstruct the muon energy for E μ<40 GeV. The test beam data provide an absolute energy calibration, which allows us to apply this method to MACRO data.

Multiple molecular scattering and albedo action on the solar spectral irradiance in the region of the UVB (less than or equal to 320 nm): A preliminary inventory

NASA Astrophysics Data System (ADS)

Nicolet, Marcel

A study comparing, in the spectral UVB region, the various components of the solar radiation field in order to explain the large difference obtained in Apr. 1939 by Goetz in Chur (green meadows), Nicolet in Arosa (adequate location in the snow) and Penndorf on the Weisshorn (above the ski slopes) (Switzerland) is presented. Numerical results from detailed theoretical calculations aimed at evaluating the various absolute effects associated with height, solar zenith angle and surface albedo were obtained for the standard atmosphere. The variations with solar zenith angles from 0 to 90 deg and albedos between 0 and 1 are presented for a spherical terrestrial atmosphere at selected wavelengths between 301 and 325 nm in the UVB region. From simultaneous measurements made at the same solar zenith angles, it was found that the values obtained in Arosa were between 5 and 10 times those obtained in Chur and on the Weisshorn. Such results are explained by a maximum of reflectivity of the snow covering the slope facing the relatively low Sun and its associated multiple scattered radiation in addition to the multiple molecular scattering of the atmosphere.

Multiple image x-radiography for functional lung imaging

NASA Astrophysics Data System (ADS)

Aulakh, G. K.; Mann, A.; Belev, G.; Wiebe, S.; Kuebler, W. M.; Singh, B.; Chapman, D.

2018-01-01

Detection and visualization of lung tissue structures is impaired by predominance of air. However, by using synchrotron x-rays, refraction of x-rays at the interface of tissue and air can be utilized to generate contrast which may in turn enable quantification of lung optical properties. We utilized multiple image radiography, a variant of diffraction enhanced imaging, at the Canadian light source to quantify changes in unique x-ray optical properties of lungs, namely attenuation, refraction and ultra small-angle scatter (USAXS or width) contrast ratios as a function of lung orientation in free-breathing or respiratory-gated mice before and after intra-nasal bacterial endotoxin (lipopolysaccharide) instillation. The lung ultra small-angle scatter and attenuation contrast ratios were significantly higher 9 h post lipopolysaccharide instillation compared to saline treatment whereas the refraction contrast decreased in magnitude. In ventilated mice, end-expiratory pressures result in an increase in ultra small-angle scatter contrast ratio when compared to end-inspiratory pressures. There were no detectable changes in lung attenuation or refraction contrast ratio with change in lung pressure alone. In effect, multiple image radiography can be applied towards following optical properties of lung air-tissue barrier over time during pathologies such as acute lung injury.

Investigation of spin-zero bosons in q-deformed relativistic quantum mechanics

NASA Astrophysics Data System (ADS)

Sobhani, H.; Chung, W. S.; Hassanabadi, H.

2018-04-01

In this article, Scattering states of Klein-Gordon equation for three scatter potentials of single and double Dirac delta and a potential well in the q-deformed formalism of relativistic quantum mechanics have been derived. At first, we discussed how q-deformed formalism can be constructed and used. Postulates of this q-deformed quantum mechanics are noted. Then scattering problems for spin-zero bosons are studied.

[Laser speckle suppression due to dynamic multiple scattering scheme introduced by oblique incidence].

PubMed

Xu, Mei-fang; Gao, Wen-hong; Shi, Yun-bo; Wang, Hao-quan; Du, Bin-bin

2014-06-01

Speckle suppression has been the research focus in laser display technology. In the present paper, the relation between multiple scattering and the size of speckle grains is established by analyzing the properties of speckle generated by the laser beam through SiO2 suspension. Combined with dynamic light scattering theory, laser speckle suppression due to dynamic multiple scattering scheme introduced by oblique incidence is proposed. A speckle suppression element consists of a static diffuser and a light pipe containing the water suspension of SiO2 microspheres with a diameter of 300 nm and a molar concentration of 3.0 x 10(-4) μm3, which is integrated with the laser display system. The laser beam with different incident angles into the SiO2 suspension affecting the contrast of the speckle images is analyzed by the experiments. The results demonstrate that the contrast of the speckle image can be reduced to 0.067 from 0.43 when the beam with the incident angle of approximately 8 degrees illuminates into the SiO2 suspension. The spatial average of speckle granules and the temporal average of speckle images were achieved by the proposed method, which improved the effect of speckle suppression. The proposed element for speckle suppression improved the reliability and reduced the cost of laser projection system, since no mechanical vibration is needed and it is convenient to integrate the element with the existing projection system.

Relativistic optical model on the basis of the Moscow potential and lower phase shifts for nucleon-nucleon scattering at laboratory energies of up to 3 GeV

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

Knyr, V. A.; Neudatchin, V. G.; Khokhlov, N. A.

Data of a partial-wave analysis of nucleon-nucleon scattering at energies of up to E{sub lab} = 3 GeV (lower partial waves) and the properties of the deuteron are described within the relativistic optical model based on deep attractive quasipotentials involving forbidden states (as exemplified by the Moscow potential). Partial-wave potentials are derived by the inverse-scattering-problem method based on the Marchenko equation by using present-day data from the partial-wave analysis of nucleon-nucleon scattering at energies of up to 3 GeV. Channel coupling is taken into account. The imaginary parts of the potentials are deduced from the phase equation of the variable-phasemore » approach. The general situation around the manifestation of quark effects in nucleon-nucleon interaction is discussed.« less

Transport and breakdown analysis for improved figure-of-merit for AlGaN power devices

NASA Astrophysics Data System (ADS)

Coltrin, Michael E.; Kaplar, Robert J.

2017-02-01

Mobility and critical electric field for bulk AlxGa1-xN alloys across the full composition range (0 ≤ x ≤ 1) are analyzed to address the potential application of this material system for power electronics. Calculation of the temperature-dependent electron mobility includes the potential limitations due to different scattering mechanisms, including alloy, optical polar phonon, deformation potential, and piezoelectric scattering. The commonly used unipolar figure of merit (appropriate for vertical-device architectures), which increases strongly with increasing mobility and critical electric field, is examined across the alloy composition range to estimate the potential performance in power electronics applications. Alloy scattering is the dominant limitation to mobility and thus also for the unipolar figure of merit. However, at higher alloy compositions, the limitations due to alloy scattering are overcome by increased critical electric field. These trade-offs, and their temperature dependence, are quantified in the analysis.

Light Scattering in Exoplanet Transits

NASA Astrophysics Data System (ADS)

Robinson, Tyler D.; Fortney, Jonathan J.

2016-10-01

Transit spectroscopy is currently the leading technique for studying exoplanet atmospheric composition, and has led to the detection of molecular species, clouds, and/or hazes for numerous worlds outside the Solar System. The field of exoplanet transit spectroscopy will be revolutionized with the anticipated launch of NASA's James Webb Space Telescope (JWST) in 2018. Over the course of the design five year mission for JWST, the observatory is expected to provide in-depth observations of many tens of transiting exoplanets, including some worlds in the poorly understood 2-4 Earth-mass regime. As the quality of transit spectrum observations continues to improve, so should models of exoplanet transits. Thus, certain processes initially thought to be of second-order importance should be revisited and possibly added to modeling tools. For example, atmospheric refraction, which was commonly omitted from early transit spectrum models, has recently been shown to be of critical importance in some terrestrial exoplanet transits. Beyond refraction, another process that has seen little study with regards to exoplanet transits is light multiple scattering. In most cases, scattering opacity in exoplanet transits has been treated as equivalent to absorption opacity. However, this equivalence cannot always hold, such as in the case of a strongly forward scattering, weakly absorbing aerosol. In this presentation, we outline a theory of exoplanet transit spectroscopy that spans the geometric limit (used in most modern models) to a fully multiple scattering approach. We discuss a new technique for improving model efficiency that effectively separates photon paths, which tend to vary slowly in wavelength, from photon absorption, which can vary rapidly in wavelength. Using this newly developed approach, we explore situations where cloud or haze scattering may be important to JWST observations of gas giants, and comment on the conditions necessary for scattering to become a major influence on an exoplanet transit spectrum.

Excitation of phonons in medium-energy electron diffraction

NASA Astrophysics Data System (ADS)

Alvarez, M. A. Vicente; Ascolani, H.; Zampieri, G.

1996-03-01

The ``elastic'' backscattering of electrons from crystalline surfaces presents two regimes: a low-energy regime, in which the characteristic low-energy electron diffraction (LEED) pattern is observed, and a medium-energy regime, in which the diffraction pattern is similar to those observed in x-ray photoemission diffraction (XPD) and Auger electron diffraction (AED) experiments. We present a model for the electron scattering which, including the vibrational degrees of freedom of the crystal, contains both regimes and explains the passage from one regime to the other. Our model is based on a separation of the electron and atomic motions (adiabatic approximation) and on a cluster-type formulation of the multiple scattering of the electron. The inelastic scattering events (excitation and/or absorption of phonons) are treated as coherent processes and no break of the phase relation between the incident and the exit paths of the electron is assumed. The LEED and the medium-energy electron diffraction regimes appear naturally in this model as the limit cases of completely elastic scattering and of inelastic scattering with excitation and/or absorption of multiple phonons. Intensity patterns calculated with this model are in very good agreement with recent experiments of electron scattering on Cu(001) at low and medium energies. We show that there is a correspondence between the type of intensity pattern and the mean number of phonons excited and/or absorbed during the scattering: a LEED-like pattern is observed when this mean number is less than 2, LEED-like and XPD/AED-like features coexist when this number is 3-4, and a XPD/AED-like pattern is observed when this number is greater than 5-6.

Radiation transfer in plant canopies - Scattering of solar radiation and canopy reflectance

NASA Technical Reports Server (NTRS)

Verstraete, Michel M.

1988-01-01

The one-dimensional vertical model of radiation transfer in a plant canopy described by Verstraete (1987) is extended to account for the transfer of diffuse radiation. This improved model computes the absorption and scattering of both visible and near-infrared radiation in a multilayer canopy as a function of solar position and leaf orientation distribution. Multiple scattering is allowed, and the spectral reflectance of the vegetation stand is predicted. The results of the model are compared to those of other models and actual observations.

Properties of dust and clouds in the Mars atmosphere: Analysis of Viking IRTM emission phase function sequences

NASA Technical Reports Server (NTRS)

Clancy, R. T.; Lee, S. W.

1991-01-01

An analysis of emission-phase-function (EPF) observations from the Viking Orbiter Infrared Thermal Mapper (IRTM) yields a wide variety of results regarding dust and cloud scattering in the Mars atmosphere and atmospheric-corrected albedos for the surface of Mars. A multiple scattering radiative transfer model incorporating a bidirectional phase function for the surface and atmospheric scattering by dust and clouds is used to derive surface albedos and dust and ice optical properties and optical depths for these various conditions on Mars.

Measurement of the magneto-optical correlation length in turbid media

NASA Astrophysics Data System (ADS)

Lenke, Ralf; Eisenmann, Christoph; Reinke, Daniel; Maret, Georg

2002-11-01

In multiple light scattering media, magnetic field induced circular birefringence (Faraday effect) influences interference effects such as speckle pattern or coherent backscattering. It was predicted that in the diffusive regime the relevant correlation length with respect to the Faraday rotation l*F differs, in general, from the transport mean free path l*. We have experimentally verified the prediction that the ratio l*F/l* equals 2 for Rayleigh scattering and decreases to 1 with increasing scatterer size. We also discuss the influence of the structure factor on l*F.

Experimental measurements with Monte Carlo corrections and theoretical calculations of neutron inelastic scattering cross section of 115In

NASA Astrophysics Data System (ADS)

Wang, Chao; Xiao, Jun; Luo, Xiaobing

2016-10-01

The neutron inelastic scattering cross section of 115In has been measured by the activation technique at neutron energies of 2.95, 3.94, and 5.24 MeV with the neutron capture cross sections of 197Au as an internal standard. The effects of multiple scattering and flux attenuation were corrected using the Monte Carlo code GEANT4. Based on the experimental values, the 115In neutron inelastic scattering cross sections data were theoretically calculated between the 1 and 15 MeV with the TALYS software code, the theoretical results of this study are in reasonable agreement with the available experimental results.