Multiple scattering tomography.
Modregger, Peter; Kagias, Matias; Peter, Silvia; Abis, Matteo; Guzenko, Vitaliy A; David, Christian; Stampanoni, Marco
2014-07-11
Multiple scattering represents a challenge for numerous modern tomographic imaging techniques. In this Letter, we derive an appropriate line integral that allows for the tomographic reconstruction of angular resolved scattering distributions, even in the presence of multiple scattering. The line integral is applicable to a wide range of imaging techniques utilizing various kinds of probes. Here, we use x-ray grating interferometry to experimentally validate the framework and to demonstrate additional structural sensitivity, which exemplifies the impact of multiple scattering tomography. PMID:25062159
Modeling Lidar Multiple Scattering
NASA Astrophysics Data System (ADS)
Sato, Kaori; Okamoto, Hajime; Ishimoto, Hiroshi
2016-06-01
A practical model to simulate multiply scattered lidar returns from inhomogeneous cloud layers are developed based on Backward Monte Carlo (BMC) simulations. The estimated time delay of the backscattered intensities returning from different vertical grids by the developed model agreed well with that directly obtained from BMC calculations. The method was applied to the Cloud-Aerosol Lidar and Infrared Pathfinder Satellite Observations (CALIPSO) satellite data to improve the synergetic retrieval of cloud microphysics with CloudSat radar data at optically thick cloud grids. Preliminary results for retrieving mass fraction of co-existing cloud particles and drizzle size particles within lowlevel clouds are demonstrated.
Multiple scattering in optical coherence microscopy.
Yadlowsky, M J; Schmitt, J M; Bonner, R F
1995-09-01
We show that the multiple-scatter rejection provided by optical coherence microscopy (low-coherence interferometry) can be incomplete in optically turbid media and that multiple scattering manifests itself in two distinct ways. Multiple small-angle scattering results in an effective probe field that is stronger than expected from a first-order beam extinction model, but that contains a distorted wave front that enhances the apparent reflectance of small structures relative to those that are larger than the unscattered incident beam. Multiple wide-angle scattering produces a broad diffuse haze that reduces the contrast of subsequent features. PMID:21060400
Multiple scattering of electromagnetic waves by rain
NASA Technical Reports Server (NTRS)
Tsolakis, A.; Stutzman, W. L.
1982-01-01
As the operating frequencies of communications systems move higher into the millimeter wave region, the effects of multiple scattering in precipitation media become more significant. In this paper, general formulations are presented for single, first-order multiple, and complete multiple scattering. Included specifically are distributions of particle size, shape, and orientation angle, as well as variation in the medium density along the direction of wave propagation. Calculations are performed for rain. It is shown that the effects of higher-order scattering are not noticeable in either attenuation or channel isolation on a dual-polarized system until frequencies of about 30 GHz are reached. The complete multiple-scattering formulation presented gives accurate results at high millimeter wave frequencies as well as including realistic medium parameter distributions. Furthermore, it is numerically efficient.
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.
Multiple Scattering Theory for Inelastic Processes
NASA Astrophysics Data System (ADS)
Braun, V. M.; Shabelski, Yu. M.
The review is devoted to the description of inelastic interactions of composite systems in the framework of the multiple scattering approach. Quasielastic scattering and multiple hadron production processes are considered for hadron-hadron, hadron-nucleus, and nucleus-nucleus collisions at high energies. We show that important information on inelastic processes follows on very general grounds from the classification of various intermediate states in the elastic amplitude, as similarly AGK cutting rules arise for reggeon diagrams. Attention is mainly given to the appropriate technique, which is illustrated with several examples of increasing complexity. The general formalism for the inelastic screening corrections is presented and its particular applications to various reactions. The review does not aim at the systematic study of numerous versions of the multiple scattering calculus confronting each other and to the extensive experimental data. Instead, we concentrate on a few simple examples to make clear the underlying physics and to work out the needed machinery employed in practical calculations.
Multiple Scattering in Transit Transmission Spectroscopy
NASA Astrophysics Data System (ADS)
Misra, Amit; Meadows, V.; Crisp, D.
2014-01-01
Exoplanet transit transmission spectroscopy is a powerful tool that has been used to characterize Jupiter and Neptune-sized transiting exoplanets, and a Super-Earth/Mini-Neptune. Because of the flat and featureless spectra for many of these planets, a large number of exoplanets are thought to have cloud or aerosol haze layers in their atmospheres. Clouds and aerosols lead to extinction of flux, but can also scatter photons into the beam to a distant observer. Most transit transmission spectroscopy models include extinction from cloud and aerosol particles, but do not include the effects of directional and multiple scattering from these particles. We have updated an existing transit transmission spectroscopy model to include a backwards Monte Carlo ray tracing scheme that simulates directional and multiple scattering from cloud and aerosol particles. For the paths which connect the host star to a distant observer, we generate a transit transmission spectrum using the calculated paths. We have run simulations for scattering functions ranging from isotropic to strongly forward scattering. We vary the optical depth from optically thin (max transmission of 10% on limb) to very optically thick (max transmission of 0.1%) and the particle vertical distribution from homogeneously distributed in the atmosphere to over a only one layer of the model atmosphere. We find that for a particle layer that is optically thin and confined to a narrow vertical extent, multiple scattering can lead to significant decreases in planetary absorption by nearly 30% when compared to model results with only extinction from clouds and aerosols.
Multiple Scattering Effects in Ionization Processes
NASA Astrophysics Data System (ADS)
Barrachina, R. O.
2011-10-01
The momentum distributions of electrons emitted in the ionization of atoms and molecules by the impact of photons or massive particles usually present interference patterns similar to those of the demonstrations with light proposed by Thomas Young more than two centuries ago. Furthermore, these cross sections also display richer structures due to the same multiple-scattering effects that are at the origin of different techniques to probe atomic aggregates and solid samples. In this talk, I will review these effects and discuss some of their most important characteristics, showing that they lead to distortions that are not fully replicated by non-scattering or even single-scattering approximations.
Benchmarking longwave multiple scattering in cirrus environments
NASA Astrophysics Data System (ADS)
Kuo, C.; Feldman, D.; Yang, P.; Flanner, M.; Huang, X.
2015-12-01
Many global climate models currently assume that longwave photons are non-scattering in clouds, and also have overly simplistic treatments of surface emissivity. Multiple scattering of longwave radiation and non-unit emissivity could lead to substantial discrepancies between the actual Earth's radiation budget and its parameterized representation in the infrared, especially at wavelengths longer than 15 µm. The evaluation of the parameterization of longwave spectral multiple scattering in radiative transfer codes for global climate models is critical and will require benchmarking across a wide range atmospheric conditions with more accurate, though computationally more expensive, multiple scattering models. We therefore present a line-by-line radiative transfer solver that includes scattering, run on a supercomputer from the National Energy Research Scientific Computing that exploits the embarrassingly parallel nature of 1-D radiative transfer solutions with high effective throughput. When paired with an advanced ice-particle optical property database with spectral values ranging from the 0.2 to 100 μm, a particle size and habit distribution derived from MODIS Collection 6, and a database for surface emissivity which extends to 100 μm, this benchmarking result can densely sample the thermodynamic and condensate parameter-space, and therefore accelerate the development of an advanced infrared radiative parameterization for climate models, which could help disentangle forcings and feedbacks in CMIP6.
Multiple scattering lidar returns from stratus clouds
NASA Technical Reports Server (NTRS)
Hutt, D. L.; Bissonnette, L. R.
1992-01-01
Multiple scattering lidar returns from stratus clouds were measured using a multi-field-of-view (MFOV) lidar operating at 1.054 microns. The detector consists of four concentric silicon photodiodes which define half-angle fields of view (FOV) of 3.8, 12.5, 25 and 38.5 mrad. The central FOV receives the conventional lidar signal, while the outer FOV's receive only multiply scattered contributions. The ratios of the signals in the outer FOV's to the signal in the central FOV is an indication of the lateral spreading of the scattered component of the laser pulse as it propagates through the cloud. MFOV lidar returns from stratus clouds measured between October 1991 and March 1992 can be divided into two distinct types, those with large multiple scattering ratios and those with small ratios. An example of each type of return is shown. Both measurements were made at an elevation angle of 45 degrees. Clouds with small multiple scattering signals probably have a high concentration of much larger particles on the order of hundreds of micrometers in size. This is a typical size range for suspended ice crystals or precipitations. Stratus clouds often have a high concentration of ice crystals even when there is no precipitation. Large ice crystals would give smaller signals in the outer FOV's because much of the scattered intensity is contained in a narrow diffraction peak with an angular width on the order of milliradians. The result is that for a given extinction, many more orders of scattering are required for the laser pulse to spread out. So far we have not been able to do simulations of MFOV lidar returns from ice crystal clouds because of uncertainties about the phase function of the crystals, particularly the magnitude of the backscatter peak at 180 degrees. On two occasions, MFOV lidar returns measured just prior to snowfall, showed a striking vertical profile. An example is shown. From 900 to 1300m, the multiply scattered signals are negligible compared to the
Multiple scattering of metallic wire structures
NASA Astrophysics Data System (ADS)
Zhan, T. R.; Chui, S. T.; Lin, Z. F.
2015-10-01
We describe how the electromagnetic resonance and scattering properties of complex structures of which metallic wire structures are constituents can be studied with multiple scattering theory. The t matrix of individual structures is calculated with our recently developed rigorous equivalent circuit theory in which retardation effects are taken into account. We illustrate our method with the example of a planar periodic array of split ring resonators. The transmission is calculated as a function of frequency. The result is found to agree well with that obtained by a commercial code (COMSOL) but our result is two orders of magnitude faster and requires much less memory.
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.
Multiple Scattering Measurements in the MICE Experiment
Carlisle, T.; Cobb, J.; Neuffer, D.; /Fermilab
2012-05-01
The international Muon Ionization Cooling Experiment (MICE), under construction at RAL, will test a prototype cooling channel for a future Neutrino Factory or Muon Collider. The cooling channel aims to achieve, using liquid hydrogen absorbers, a 10% reduction in transverse emittance. The change in 4D emittance will be determined with an accuracy of 1% by measuring muons individually. Step IV of MICE will make the first precise emittance-reduction measurements of the experiment. Simulation studies using G4MICE, based on GEANT4, find a significant difference in multiple scattering in low Z materials, compared with the standard expression quoted by the Particle Data Group. Direct measurement of multiple scattering using the scintillating-fibre trackers is found to be possible, but requires the measurement resolution to be unfolded from the data.
Multiple-scattering theory for electromagnetic waves
Wang, X. ); Zhang, X. ); Yu, Q.; Harmon, B.N. )
1993-02-15
In this paper, a multiple-scattering formalism for electromagnetic waves is presented. Its application to the three-dimensional periodic dielectric structures is given in a form similar to the usual Korringa-Kohn-Rostoker form of scalar waves. Using this approach, the band-structure results of touching spheres of diamond structure in a dielectric medium with dielectric constant 12.96 are calculated. The application to disordered systems under the coherent-potential approximation is discussed.
Multiple electron scattering routines for PEREGRINE
White, J A
1999-08-23
The Monte Carlo electron scattering routines solve multiple elastic scatters in a condensed history approach. The Goudsmit-Saunderson scattering model is used and its implementation is taken from Kawrakow and Bielajew[l]. The subroutines produce an exit angle representing a likely scattering angle of a single incident electron after scattering elastically over a given step size. Two input parameters, {lambda} and {eta}, that depend on the atomic species and incident energy must first be specified. The mapping from species and energy to 77 and {lambda} already existed in the PEREGRINE code and was not redone or modified in any way. The software has been validated by comparisons to Moliere and Goudsmit-Saunderson models of D.W.O. Rogers[2]. As required by licensing considerations, no public domain or copyrighted software has been used in any phase of the preparation of any of these sub-routines or data files. Apart from needing to have {eta} and {lambda} specified through PEREGRINE, the code provided is completely self-contained. Everything is written in the FORTRAN 77 language to simplify inclusion in the existing PEREGRINE package.
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.
Acoustic multiple scattering using recursive algorithms
NASA Astrophysics Data System (ADS)
Amirkulova, Feruza A.; Norris, Andrew N.
2015-10-01
Acoustic multiple scattering by a cluster of cylinders in an acoustic medium is considered. A fast recursive technique is described which takes advantage of the multilevel Block Toeplitz structure of the linear system. A parallelization technique is described that enables efficient application of the proposed recursive algorithm for solving multilevel Block Toeplitz systems on high performance computer clusters. Numerical comparisons of CPU time and total elapsed time taken to solve the linear system using the direct LAPACK and TOEPLITZ libraries on Intel FORTRAN, show the advantage of the TOEPLITZ solver. Computations are optimized by multi-threading which displays improved efficiency of the TOEPLITZ solver with the increase of the number of scatterers and frequency.
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.
Multiple scattering of laser beams in dense hydrosols
NASA Technical Reports Server (NTRS)
Zardecki, A.; Gerstl, S. A. W.; Unruh, W. P.; Stokes, G. H.; Stupin, D. M.; Elliott, N. E.; Weinman, J. A.
1986-01-01
The multiple scattering of laser beams is usually described within the framework of small-angle scattering theory. The validity of this approximation as well as improvements due to the incorporation of diffusion theory in the calculations were studied.
Multiple magnetic scattering in small-angle neutron scattering of Nd-Fe-B nanocrystalline magnet.
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
Multiple magnetic scattering in small-angle neutron scattering of Nd–Fe–B nanocrystalline magnet
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
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.
FEFF5: An ab initio multiple scattering XAFS code
Rehr, J.J.; Zabinsky, S.I.
1992-12-31
FEFF5 is an efficient automated code which calculates multiple scattering (MS) curved wave XAFS spectra for molecules and solids. The theoretical ingredients and approximations contained in the code are revised, with the aim of describing the how XAFS spectra are efficiently simulated. The FEFF5 code consists of 4 independent modules: a scattering potential and phase shift module, a path finder module, a scattering amplitude module and an XAFS module. Multiple scattering Debye-Waller factors are built in using a correlated Debye model.
Face recognition using multiple maximum scatter difference discrimination dictionary learning
NASA Astrophysics Data System (ADS)
Zhu, Yanyong; Dong, Jiwen; Li, Hengjian
2015-10-01
Based on multiple maximum scatter difference discrimination Dictionary learning, a novel face recognition algorithm is proposed. Dictionary used for sparse coding plays a key role in sparse representation classification. In this paper, a multiple maximum scatter difference discriminated criterion is used for dictionary learning. During the process of dictionary learning, the multiple maximum scatter difference computes its discriminated vectors from both the range of the between class scatter matrix and the null space of the within-class scatter matrix. The proposed algorithm is theoretically elegant and easy to calculate. Extensive experimental studies conducted on the AR database and Extended Yale Database B in comparison with existing basic sparse representation and other classification methods, it shows that the performance is a little better than the original sparse representation methods with lower complexity.
Method for measuring multiple scattering corrections between liquid scintillators
Verbeke, J. M.; Glenn, A. M.; Keefer, G. J.; Wurtz, R. E.
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.
A new screening length for small angle multiple scattering
NASA Astrophysics Data System (ADS)
Ikegami, Seiji
2013-09-01
A new screening length formulation that incorporates the charge state of the projectile is applied to multiple scattering. The present screening length is derived from an interatomic potential that accounts for electron-electron, electron-nuclear, and nuclear-nuclear interactions using the Thomas-Fermi-Moliere potential. We examined the charge state effect on multiple scattering angular distributions. We successfully estimate the charge state effects and predict angular distributions. The present screening length is compared with many low energy ion scattering experiments and with O'Connor-Biersack prediction values.
Method for measuring multiple scattering corrections between liquid scintillators
NASA Astrophysics Data System (ADS)
Verbeke, J. M.; Glenn, A. M.; Keefer, G. J.; Wurtz, R. E.
2016-07-01
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.
Convergence of the nucleus-nucleus Glauber multiple scattering series
Usmani, A.A.; Ahmad, I. )
1991-05-01
The Glauber {ital S}-matrix operator for nucleus-nucleus scattering is expressed as a finite series of matrix elements involving Bell's polynomials. Analyzing {alpha}{sup 4}He elastic-scattering data at the incident momentum of 4.32 GeV/{ital c}, we infer that our expansion is appreciably converging. Further, by applying closure over target and projectile states and neglecting a certain class of terms involving intermediate excitations, we arrive at a recurrence relation for nucleus-nucleus multiple scattering series terms, which invites further study as it seems to provide a simple method for calculating the nucleus-nucleus elastic-scattering cross section.
Effect of multiple scattering on Cerenkov radiation from energetic electrons
Zheng Jian
2013-01-15
Cerenkov radiation can be used as a diagnostic tool to study energetic electrons generated in ultra-intense laser matter interactions. However, electrons suffer scattering with nuclei as they move in a medium. In this article, we theoretically study the effect of multiple scattering on Cerenkov radiation, and obtain analytical formulas under some circumstances. The results show that when the speed of an energetic electron is not close to the light speed in the medium, Cerenkov radiation is just slightly decreased due to multiple scattering. In the case that the electron speed is very close to the light speed in the medium, the effect of multiple scattering becomes significant, and the radiation is dominated by bremsstrahlung.
Multiple scattering induced negative refraction of matter waves
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 scattering induced negative refraction of matter waves.
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
NASA Astrophysics Data System (ADS)
Kiran, K. U.; Ravindraswami, K.; Eshwarappa, K. M.; Somashekarappa, H. M.
2016-02-01
Multiple scattering of gamma photons obtained from 0.215 GBq 137Cs source in both forward and backward hemisphere for 4 elements viz., carbon, aluminium, iron and copper are detected by a 76 mm ×76 mm NaI(Tl) scintillation detector. The variation of saturation thicknesses of 4 elements are studied experimentally at 60°, 80°, 90°, 100°, 120° and 135°. Monte Carlo N-Particle (MCNP) simulation of multiple scattering and variation in saturation thicknesses is carried out for 40°, 60°, 80°, 90°, 100°, 120°, 135°, 160° and 180° for four elements. The variation of the intensity of multiple scattered photons in different scattering angles is found to be different in forward and backward hemispheres. The intensity of multiple scattered photons is found to be minimum at around 90°. Saturation thicknesses for 40° and 60° are found to be less than saturation thicknesses for 80°, 90°, 100°, 120°, 135°, 160° and 180° in spite of the fact that the scattered energy is more for lower scattering angles. The behaviour of variation of saturation thicknesses as a function of scattering angles obtained from MCNP simulation agrees well with experimentally obtained values.
Effect of multiple scattering on depolarization measurements with spaceborne lidars.
Reichardt, Susanne; Reichardt, Jens
2003-06-20
An analytical model based on the integration of the scattering-angle and light-path manifold has been developed to quantify the effect of multiple scattering on cirrus measurements obtained with elastic polarization lidars from space. Light scattering by molecules and by a horizontally homogeneous cloud is taken into account. Lidar parameter, including laser beam divergence, can be freely chosen. Up to 3 orders of scattering are calculated. Furthermore, an inversion technique for the retrieval of cloud extinction profiles from measurements with elastic-backscatter lidars is proposed that explicitly takes multiple scattering into account. It is found that for typical lidar system parameters such as those of the Cloud-Aerosol Lidar and Infrared Pathfinder Satellite Observations (CALIPSO) instrument multiple scattering does not significantly affect depolarization-ratio measurements in cirrus clouds with small to moderate optical depths. For all simulated clouds, the absolute value of the difference between measured and single-scattering volume depolarization ratio is < 0.006. The particle depolarization ratio can be calculated from the measured volume depolarization ratio and the retrieved backscatter ratio without degradation of accuracy; thus characterization of the various cirrus categories in terms of the particle depolarization ratio and retrieval of cloud microphysical properties is feasible from space. The results of this study apply to polar stratospheric clouds as well. PMID:12833968
About multiple scattering of high energy protons in crystal deflectors
NASA Astrophysics Data System (ADS)
Taratin, A. M.; Scandale, W.
2015-07-01
The process of multiple scattering of high energy protons in a silicon crystal at its amorphous orientation was studied by simulation of proton trajectories in the model of binary collisions and by a straight simulation of the sequences of proton collisions with atoms when their impact parameters are randomly and uniformly distributed on the symmetry cell for a given crystallography direction. The value of the RMS deflection of multiple scattering obtained by the simulation is in a good agreement with the experiment and more than 15% larger than it follows from the Moliere theory. The obtained RMS deflection used in the Gaussian approach of multiple scattering well describes dechanneling of protons in the frame of the planar potential model. Different number of proton collisions with atoms occurs along the same crystal length for different crystal orientations. However, the change of the collision number is compensated by the corresponding change of the mean square deflection in a single collision. Therefore, multiple scattering is the same for different crystal orientations. The generator of multiple scattering for amorphous crystal orientations was proposed.
Fingerprints of Multiple Electron Scatterings in Single-Layer Graphene
NASA Astrophysics Data System (ADS)
Jung, Minbok; Sohn, So-Dam; Park, Jonghyun; Lee, Keun-U.; Shin, Hyung-Joon
2016-03-01
The electrons in graphene exhibit unusual behaviours, which can be described by massless Dirac quasiparticles. Understanding electron scattering in graphene has been of significant importance for its future application in electronic devices because electron scattering determines electrical properties such as resistivity and electron transport. There are two types of electron scatterings in graphene: intervalley scattering and intravalley scattering. In single-layer graphene, to date, it has been difficult to observe intravalley scattering because of the suppression of backscattering resulting from the chiral nature of the electrons in graphene. Here, we report the multiple electron scattering behaviours in single-layer graphene on a metallic substrate. By applying one- and two-dimensional Fourier transforms to maps of the local density of states, we can distinguish individual scattering processes from complex interference patterns. These techniques enable us to provide direct evidence of intravalley scattering, revealing a linear dispersion relation with a Fermi velocity of ~7.4 × 105 m/s.
Fingerprints of Multiple Electron Scatterings in Single-Layer Graphene
Jung, Minbok; Sohn, So-Dam; Park, Jonghyun; Lee, Keun-U; Shin, Hyung-Joon
2016-01-01
The electrons in graphene exhibit unusual behaviours, which can be described by massless Dirac quasiparticles. Understanding electron scattering in graphene has been of significant importance for its future application in electronic devices because electron scattering determines electrical properties such as resistivity and electron transport. There are two types of electron scatterings in graphene: intervalley scattering and intravalley scattering. In single-layer graphene, to date, it has been difficult to observe intravalley scattering because of the suppression of backscattering resulting from the chiral nature of the electrons in graphene. Here, we report the multiple electron scattering behaviours in single-layer graphene on a metallic substrate. By applying one- and two-dimensional Fourier transforms to maps of the local density of states, we can distinguish individual scattering processes from complex interference patterns. These techniques enable us to provide direct evidence of intravalley scattering, revealing a linear dispersion relation with a Fermi velocity of ~7.4 × 105 m/s. PMID:26936521
Multiple parton scattering in nuclei: Beyond helicity amplitude approximation
Zhang, Ben-Wei; Wang, Xin-Nian
2003-01-21
Multiple parton scattering and induced parton energy loss in deeply inelastic scattering (DIS) off heavy nuclei is studied within the framework of generalized factorization in perturbative QCD with a complete calculation beyond the helicity amplitude (or soft bremsstrahlung) approximation. Such a calculation gives rise to new corrections to the modified quark fragmentation functions. The effective parton energy loss is found to be reduced by a factor of 5/6 from the result of helicity amplitude approximation.
Adjoint calculations for multiple scattering of Compton and Rayleigh effects
NASA Astrophysics Data System (ADS)
Fernández, J. E.; Sumini, M.
1992-08-01
As is well known, the experimental determination of the Compton profile requires a particular geometry with a scattering angle close to π. That situation involves a narrow multiple-scattering spectrum that overlaps the Compton peak, making it difficult to analyze the different contributions to the profile. We show how the solution of the adjoint problem can help in devising more useful experimental configurations, giving, through its classical "importance" meaning, a formally clear picture of the whole problem.
Efficient light propagation for multiple anisotropic volume scattering
Max, N. |
1993-12-01
Realistic rendering of participating media like clouds requires multiple anisotropic light scattering. This paper presents a propagation approximation for light scattered into M direction bins, which reduces the ``ray effect`` problem in the traditional ``discrete ordinates`` method. For a volume of n{sup 3} elements, it takes O(M n{sup 3} log n + M{sup 2} n{sup 3}) time and O(M n{sup 3}) space.
A covariant multiple scattering series for elastic projectile-target scattering
NASA Technical Reports Server (NTRS)
Gross, Franz; Maung-Maung, Khin
1989-01-01
A covariant formulation of the multiple scattering series for the optical potential is presented. The case of a scalar nucleon interacting with a spin zero isospin zero A-body target through meson exchange, is considered. It is shown that a covariant equation for the projectile-target t-matrix can be obtained which sums the ladder and crossed ladder diagrams efficiently. From this equation, a multiple scattering series for the optical potential is derived, and it is shown that in the impulse approximation, the two-body t-matrix associated with the first order optical potential is the one in which one particle is kept on mass-shell. The meaning of various terms in the multiple scattering series is given. The construction of the first-order optical potential for elastic scattering calculations is described.
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.
Bright-white beetle scales optimise multiple scattering of light.
Burresi, Matteo; Cortese, Lorenzo; Pattelli, Lorenzo; Kolle, Mathias; Vukusic, Peter; Wiersma, Diederik S; Steiner, Ullrich; Vignolini, Silvia
2014-01-01
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. PMID:25123449
Bright-White Beetle Scales Optimise Multiple Scattering of Light
Burresi, Matteo; Cortese, Lorenzo; Pattelli, Lorenzo; Kolle, Mathias; Vukusic, Peter; Wiersma, Diederik S.; Steiner, Ullrich; Vignolini, Silvia
2014-01-01
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. PMID:25123449
Role of multiple scattering in formation of OCT skin images
Kirillin, M Yu; Priezzhev, A V; Myllylae, R
2008-06-30
Optical coherence tomography (OCT) images of model human skin samples are obtained by using Monte Carlo simulations. The contributions of least and multiple scattering, diffusion and nondiffusion components and of separate scattering orders are studied by using a multilayer skin model based on experimental images. The model images are obtained by neglecting speckles or taking them into account. It is shown that least scattering forms the image of the upper skin layers, while the contribution of multiple scattering can be characterised as a blurred full image with a lower contrast. Repeated scattering mainly contributes to the OCT image at depths up to 1 mm. The diffusion component contributes to the image beginning from the epidermal basal layer. The partial image produced by this component is more blurred compared to the partial image produced by to multiple scattering. The nondiffusion component forms the OCT skin image at depths up to {approx}1.3 mm. (special issue devoted to application of laser technologies in biophotonics and biomedical studies)
Collective hypersonic excitations in strongly multiple scattering colloids.
Still, T; Gantzounis, G; Kiefer, D; Hellmann, G; Sainidou, R; Fytas, G; Stefanou, N
2011-04-29
Unprecedented low-dispersion high-frequency acoustic excitations are observed in dense suspensions of elastically hard colloids. The experimental phononic band structure for SiO(2) particles with different sizes and volume fractions is well represented by rigorous full-elastodynamic multiple-scattering calculations. The slow phonons, which do not relate to particle resonances, are localized in the surrounding liquid medium and stem from coherent multiple scattering that becomes strong in the close-packing regime. Such rich phonon-matter interactions in nanostructures, being still unexplored, can open new opportunities in phononics. PMID:21635048
Effects of multiple scattering on scintillation of transionospheric radio signals
NASA Technical Reports Server (NTRS)
Liu, C. H.; Yeh, K. C.; Youakim, M. Y.; Wernik, A. W.
1974-01-01
Recent development in the optical scintillation theory has been adapted to the ionospheric geometry in order to study the ionospheric scintillation phenomenon in the presence of multiple scattering. Under approximations well satisfied in typical ionospheres for a frequency above about 20 MHz, the first through fourth moment equations have been derived and some analytic solutions given. The fourth moment equation has also been solved numerically. The numerical results show clearly the occurrence of focusing and saturation phenomena. The new multiple-scatter effects are emphasized.
Multiple Scattering of Dirac Fermions in Two Dimensions
NASA Astrophysics Data System (ADS)
Asmar, Mahmoud M.; Ulloa, Sergio E.
2014-03-01
The low energy dispersion of electrons in graphene-as well as surface states of three dimensional topological insulators- are characterized by a linear dispersion, leading to interesting dynamical properties. The presence of potential scattering centers, such as impurities in real samples or artificially created gated regions, also reflect the ``massless'' nature of electrons in these materials. The study of Dirac fermion scattering from single potential obstacles is made possible through partial wave methods. In the case of closely-spaced potential obstacles (high defect concentration), one should consider multiple scattering effects. Using separation of variables, Graf's addition rules, and far field matching, one can generalize the partial wave method to the case of many scatterers, and obtain physical observables for such problem. We present our study of the scattering problem of Dirac fermions from multiple potential obstacles, with focus on the two-center problem. We discuss the dependence of the differential cross section on the separation, and different potential shifts caused by these obstacles, and compare these results with the differential cross section for a single scattering center. We also study the minimal conditions that allow the observation of Klein tunneling. Supported by MWN/CIAM-NSF and AvH.
NASA Astrophysics Data System (ADS)
Deharak, B. A.; Savich, J. L.; Roberts, H. M.; Brown, E. G.; McGill, M. R.; Kim, B. N.; Weaver, C. M.; Martin, N. L. S.
2016-05-01
We have conducted a series of Monte Carlo simulations of laser assisted free-free scattering experiments. The simulations make use of Kroll-Watson approximation to account for the effects of the laser field on the scattering process. The parameters for these simulations are believed to mimic the experimental conditions of the work reported by Wallbank and Holmes, particularly the target number density. The simulations account for the effects multiple scattering (i.e., the scattering of a single incident electron from multiple target atoms). We present a comparison of the results of these simulations to the experimental results of Wallbank and Holmes. This work was supported by the National Science Foundation under Grants Nos. PHY-0855040 (NLSM) and PHY-1402899 (BAd).
Multiple light scattering methods for multiphase flow diagnostics
NASA Astrophysics Data System (ADS)
Estevadeordal, Jordi
2015-11-01
Multiphase flows of gases and liquids containing droplets, bubbles, or particulates present light scattering imaging challenges due to the interference from each phase, such as secondary reflections, extinctions, absorptions, and refractions. These factors often prevent the unambiguous detection of each phase and also produce undesired beam steering. The effects can be especially complex in presence of dense phases, multispecies flows, and high pressure environments. This investigation reports new methods for overcoming these effects for quantitative measurements of velocity, density, and temperature fields. The methods are based on light scattering techniques combining Mie and filtered Rayleigh scattering and light extinction analyses and measurements. The optical layout is designed to perform multiple property measurements with improved signal from each phase via laser spectral and polarization characterization, etalon decontamination, and use of multiple wavelengths and imaging detectors.
Multiple scattering of a spherical acoustic wave from fluid spheres
NASA Astrophysics Data System (ADS)
Wu, J. H.; Liu, A. Q.; Chen, H. L.; Chen, T. N.
2006-02-01
The multiple scattering of a spherical acoustic wave from an arbitrary number of fluid spheres is investigated theoretically. The tool to attack the multiple scattering problem is a kind of addition formulas for the spherical wave functions, which are presented in the paper, based on the bicentric expansion form of Green function in the spherical coordinates. For an arbitrary configuration of N fluid spheres, the kind of addition formulas permits the field expansions (all referred to the center of each sphere). With these the sound fields scattered by each sphere can be described by a set of N equations. The interactions between any two fluid spheres are taken into account in these equations exactly and their coefficients are coupled through double sums in the spherical wave functions. By truncating the infinite series in the equations depending on certain calculation accuracy and solving the coefficients matrix by using the Gauss-Seidel iteration method, we can obtain the scattered sound field by the configuration of the fluid spheres. Finally, the scattering calculations by using the kind of addition formulas are carried out.
Nucleon-nucleon scattering within a multiple subtractive renormalization approach
Timoteo, V. S.; Frederico, T.; Delfino, A.; Tomio, Lauro
2011-06-15
We present a methodology to renormalize the nucleon-nucleon interaction in momentum space, using a recursive multiple subtraction approach that prescinds from a cutoff regularization, to construct the kernel of the scattering equation. The subtracted scattering equation is solved with the next-leading-order and next-to-next-leading-order interactions. The results are presented for all partial waves up to j=2, fitted to low-energy experimental data. In this renormalization group invariant approach, the subtraction energy emerges as a renormalization scale and the momentum associated with it comes to be about the QCD scale ({Lambda}{sub QCD}), irrespectively to the partial wave.
Correction to Molière's formula for multiple scattering
NASA Astrophysics Data System (ADS)
Lee, R. N.; Milstein, A. I.
2009-06-01
The semiclassical correction to Molière’s formula for multiple scattering is derived. The consideration is based on the scattering amplitude obtained with the first semiclassical correction taken into account for an arbitrary localized but not spherically symmetric potential. Unlike the leading term, the correction to Molière’s formula contains the target density n and thickness L not only in the combination nL (areal density). Therefore, this correction can be referred to as the bulk density correction. It turns out that the bulk density correction is small even for high density. This result explains the wide range of applicability of Molière’s formula.
Relativistic real-space multiple scattering calculations of EELS
NASA Astrophysics Data System (ADS)
Jorissen, K.; Rehr, J. J.; Sorini, A.; Levine, Z. H.
2006-03-01
We present an extension of the real space multiple scattering code FEFF8 for ab initio, relativistic calculations of electron energy loss spectra (EELS), which is applicable both to periodic and non-periodic systems. The approach explains the observed relativistic shifts in the magic angle. In addition, the method can account for experimental parameters such as collection and convergence angles of the microscope and sample orientation. We also discuss relativistic effects on inelastic electron scattering including the density correction to the stopping power. Our results are compared with other approaches and with experiment. B. Jouffrey, P. Schattschneider and C. Hebert, Ultramicroscopy 102, 61 (2004).
Diffusion and multiple anisotropic scattering for global illumination in clouds
Max, N L; Schussman, G; Miyazaki, R; Iwasaki, K; Nishita, T
2003-10-14
The diffusion method is a good approximation inside the dense core of a cloud, but not at the more tenuous boundary regions. Also, it breaks down in regions where the density of scattering droplets is zero. We have enhanced it by using hardware cell projection volume rendering at cloud border voxels to account for the straight line light transport across these empty regions. We have also used this hardware volume rendering at key voxels in the low-density boundary regions to account for the multiple anisotropic scattering of the environment.
Stimulated Raman scattering of laser dye mixtures dissolved in multiple scattering media
Yashchuk, V P; Komyshan, A O; Tikhonov, E A; Olkhovyk, L A
2014-10-31
Stimulated Raman scattering (SRS) of a mixture of rhodamine 6G and pyrromethene 605 laser dyes in vesicular films is studied. It is shown that a peculiar interaction of dyes occurs under conditions of multiple scattering of light from vesicles. This interaction manifests itself as SRS excitation of one of the dyes by random lasing of the other dye, provided that the random lasing spectrum overlaps the Stokes lines of the first dye. In addition, there is energy transfer between molecules of these dyes if their luminescence and absorption spectra overlap. The results obtained confirm that the mechanism of SRS from laser dyes in multiple scattering media is similar to that in coherent-active Raman spectroscopy. These results extend the possibility of determining the vibrational spectrum of dye molecules from their secondary radiation in these media. (nonlinear optical phenomena)
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
MODTRAN cloud and multiple scattering upgrades with application to AVIRIS
Berk, A.; Bernstein, L.S.; Acharya, P.K.; Robertson, D.C.; Adler-Golden, S.M.; Anderson, G.P.; Chetwynd, J.H.
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; the CK approach provides refined predictions for AVIRIS nadir and near-nadir viewing.
Interstitial integrals in the multiple-scattering model
Swanson, J.R.; Dill, D.
1982-08-15
We present an efficient method for the evaluation of integrals involving multiple-scattering wave functions over the interstitial region. Transformation of the multicenter interstitial wave functions to a single center representation followed by a geometric projection reduces the integrals to products of analytic angular integrals and numerical radial integrals. The projection function, which has the value 1 in the interstitial region and 0 elsewhere, has a closed-form partial-wave expansion. The method is tested by comparing its results with exact normalization and dipole integrals; the differences are 2% at worst and typically less than 1%. By providing an efficient means of calculating Coulomb integrals, the method allows treatment of electron correlations using a multiple scattering basis set.
Multiple-scattering corrections to the Beer-Lambert law
Zardecki, A.
1983-01-01
The effect of multiple scattering on the validity of the Beer-Lambert law is discussed for a wide range of particle-size parameters and optical depths. To predict the amount of received radiant power, appropriate correction terms are introduced. For particles larger than or comparable to the wavelength of radiation, the small-angle approximation is adequate; whereas for small densely packed particles, the diffusion theory is advantageously employed. These two approaches are used in the context of the problem of laser-beam propagation in a dense aerosol medium. In addition, preliminary results obtained by using a two-dimensional finite-element discrete-ordinates transport code are described. Multiple-scattering effects for laser propagation in fog, cloud, rain, and aerosol cloud are modeled.
Fully relativistic multiple scattering calculations for general potentials
NASA Astrophysics Data System (ADS)
Ebert, H.; Braun, J.; Ködderitzsch, D.; Mankovsky, S.
2016-02-01
The formal basis for fully relativistic Korringa-Kohn-Rostoker (KKR) or multiple scattering calculations for the electronic Green function in case of a general potential is discussed. Simple criteria are given to identify situations that require to distinguish between right- and left-hand-side solutions to the Dirac equation when setting up the electronic Green function. In addition, various technical aspects of an implementation of the relativistic KKR for general local and nonlocal potentials will be discussed.
Few-photon scattering in dispersive waveguides with multiple qubits.
Ekin Kocabaş, Şükrü
2016-06-01
We extend the Krylov-subspace-based time-dependent numerical simulation technique for a qubit interacting with photons in a waveguide to the multiple qubit case. We analyze photon scattering from two qubits and derive expressions for the bound states in the continuum (BICs). We show how the BIC can be excited. We use the BIC in a recent Pauli-Z gate proposal involving decoherence free subspaces and obtain the gate fidelity as a function of the gate parameters. The techniques presented in this Letter are useful for investigating the time evolution of quantum gates and other many-body systems with multiple quenches in the Hamiltonian. PMID:27244407
Few-photon scattering in dispersive waveguides with multiple qubits
NASA Astrophysics Data System (ADS)
Ekin Kocabaş, Şükrü
2016-06-01
We extend the Krylov-subspace based time-dependent numerical simulation technique for a qubit interacting with photons in a waveguide to the multiple qubit case. We analyze photon scattering from two qubits analytically and derive expressions for the bound states in the continuum (BIC). We show how the BIC can be excited. We use the BIC in a recent Pauli-Z gate proposal involving decoherence free subspaces and obtain the gate fidelity as a function of the gate parameters. The techniques presented in the paper are useful for investigating the time evolution of quantum gates and other many-body systems with multiple quenches in the Hamiltonian.
Generalization of the Booker-Gordon formula to include multiple scattering
NASA Astrophysics Data System (ADS)
Fante, R. L.
1982-12-01
A general expression, which includes multiple scattering, has been derived for the radiation scattered from a random medium. The result is examined numerically and compared to the results calculated via the Booker-Gordon formula which considers single scattering effects
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.
Proton radiography, nuclear cross sections and multiple scattering
NASA Astrophysics Data System (ADS)
Sjue, Sky; Lansce Proton Radiography Team
2015-10-01
Proton radiography is a valuable tool for assessing dynamic experiments over times as short as 100 nanoseconds. Facilities now exist or are in development in the China, Germany, Russia and the United States with proton energies ranging from 800 MeV to 50 GeV. The multiple Coulomb scattering distribution of protons and the cross sections for proton interactions with the nucleus both depend on the proton energy. A detailed understanding of these effects is necessary to gain the best possible quantitative information from proton generated radiographs. We will present an analysis of the integrated nuclear cross sections for various metals at 800 MeV kinetic energy using step wedges at Los Alamos Neutron Science Center at 800 MeV, along with results at 24 GeV from Alternating Gradient Synchrotron at 24 GeV. The results will be compared with models of multiple scattering and several models of the nuclear interactions. Finally, we will discuss trends in the interplay between nuclear attenuation and multiple scattering as a function of proton energy.
Does the multiple-scattering series in the pion-deuteron scattering actually converge?
Kudryavtsev, A. E. Romanov, A. I. Gani, V. A.
2013-07-15
It is demonstrated that the well-known answer for the multiple-scattering series (MSS) for a light particle interacting to a pair of static nucleons, calculated in the Fixed Centers Approximation (FCA), works well for a wide region of the two-body complex scattering length a. However, this approach is not applicable in a narrow region surrounding the real positive a half-axis, where the MSS does not converge. Simultaneously, for real positive a's the 3-body system forms an infinite set of bound states.
NASA Astrophysics Data System (ADS)
Nakatsuka, Takao; Nishimura, Jun
2008-08-01
The Molière theory of multiple Coulomb scattering is improved to take account of ionization loss by applying a differential formulation of the theory. Distributions for the deflection angle θ⃗ , as well as for any linear combination between θ⃗ and the lateral displacement r⃗ , under the ionization process are derived by a series expansion with the same universal functions f(n)(ϑ) of Molière, except that the values for both the expansion parameter B and the scale angle θM are corrected from those under the fixed-energy process. We find that Goudsmit-Saunderson angular distribution with ionization is also expressed by the same characteristic parameters B and θM derived above by the Molière theory. The transport mechanism of Molière process of multiple Coulomb scattering and the stochastic property of Molière series expansion are also investigated and discussed.
Multiple scattering in the remote sensing of natural surfaces
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 very 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.
Multiple electronic Raman scatterings in a single metallic carbon nanotube
NASA Astrophysics Data System (ADS)
Zhang, Daqi; Yang, Juan; Hasdeo, Eddwi H.; Liu, Can; Liu, Kaihui; Saito, Riichiro; Li, Yan
2016-06-01
We observe multiple electronic Raman scatterings (ERSs) in a single suspended metallic single-walled carbon nanotube. The ERS process originates from the inelastic scattering of photoexcited excitons by a continuum of low-lying electron-hole pairs. In previous work, the observed Fano factor of the G band line shape is always negative; however, in this work we find that the Fano factor can be either positive or negative depending on the relative position of the nearest ERS with respect to the G band. This supports the idea that the origin of the G band asymmetry is an interference between the discrete G band and the continuous ERS. We also report that the ERS position and intensity are sensitive to the nanotube bundling effect and the laser heating effect.
Multiple Scattering Approach to Continuum State with Generally Shaped Potential
Hatada, Keisuke; Hayakawa, Kuniko; Tenore, Antonio; Benfatto, Maurizio; Natoli, Calogero
2007-02-02
We present a new scheme for solving the scattering problem for an arbitrarily shaped potential cell that avoids the well known convergence problems in the angular momentum expansion of the cell shape function. Tests of the method against analytically soluble separable model potentials, with and without shape truncation, have been performed with success. By a judicious choice of the shape of the cells partitioning the whole molecular space and use of empty cells when necessary, we set up a multiple scattering scheme that leads to a straightforward generalization of the same equations in the muffin-tin approximation. For example lmax in the angular momentum expansion can still be chosen according to the rule lmax {approx} kR, where R is the radius of the bounding sphere of the cell and all the matrices appearing in the theory are square matrices.
Effects of Multiple Scattering for Millimeter-Wavelength Weather Radars
NASA Technical Reports Server (NTRS)
Kobayashi, Satoru; Tanelli, Simone; Im, Eastwood
2004-01-01
Effects of multiple scattering on the reflectivity measurement for millimeter-wavelength weather radars are studied, in which backscattering enhancement may play an important role. In the previous works, the backscattering enhancement has been studied for plane wave injection, the reflection of which is received at the infinite distance. In this paper, a finite beam width of a Gaussian antenna pattern along with spherical wave is taken into account. A time-independent second order theory is derived for a single layer of clouds of a uniform density. The ordinary second-order scattering (ladder term) and the second-order backscattering enhancement (cross term) are derived for both the copolarized and cross-polarized waves.
UV communications channel modeling incorporating multiple scattering interactions.
Drost, Robert J; Moore, Terrence J; Sadler, Brian M
2011-04-01
In large part because of advancements in the design and fabrication of UV LEDs, photodetectors, and filters, significant research interest has recently been focused on non-line-of-sight UV communication systems. This research in, for example, system design and performance prediction, can be greatly aided by accurate channel models that allow for the reproducibility of results, thus facilitating the fair and consistent comparison of different communication approaches. In this paper, we provide a comprehensive derivation of a multiple-scattering Monte Carlo UV channel model, addressing weaknesses in previous treatments. The resulting model can be used to study the contribution of different orders of scattering to the path loss and impulse response functions associated with general UV communication system geometries. Simulation results are provided that demonstrate the benefit of this approach. PMID:21478967
Multiple scattering of scalar waves by point scatterers in one dimension. I
Haacke, E.M.; Foldy, L.L.
1981-04-01
We discuss the problem of scalar wave multiple scattering in one dimension on a target of n identical fixed scatterers with delta-function potentials. We consider in detail a statistical ensemble of configurations of scatterers whose positions are uniformly distributed throughout the scattering region. We succeed in analytically performing a configurational average (over all scatterer positions) for the wave function for the problem of a transmitted wave with constant amplitude. We discuss the relationship between this problem and the standard problem of an incident wave with constant amplitude. From the simple closed form for the average of the wave function, the optical potential for the system is obtained. We then present the large and small incident particle wavelength limits (with respect to the length (L) of the scattering region) for both the average of the wave function and the optical potential. We also examine the question as to where the optical potential can be approximated by the form it takes in the limit of infinite n. (The question of where in parameter space this occurs and how well the transmitted and reflected waves can be predicted with this form is discussed in the following paper.) Furthermore, we consider the large incident particle wave number limit for the average wave function and the optical potential for a general distribution of the scatterer positions in the limit of both n and L approaching infinity but with n/L remaining fixed. Lastly, knowing the simple closed form for the average of the wave function, we prove that the effective field approximation becomes exact in the limit of infinite n with all other parameters held fixed.
NASA Astrophysics Data System (ADS)
Dzheparov, F. S.; Lvov, D. V.
2016-02-01
Multiple small-angle neutron scattering by a high-density system of inhomogeneities has been considered. A combined approach to the analysis of multiple small-angle neutron scattering has been proposed on the basis of the synthesis of the Zernike-Prince and Moliére formulas. This approach has been compared to the existing multiple small-angle neutron scattering theory based on the eikonal approximation. This comparison has shown that the results in the diffraction limit coincide, whereas differences exist in the refraction limit because the latter theory includes correlations between successive scattering events. It has been shown analytically that the existence of correlations in the spatial position of scatterers results in an increase in the number of unscattered neutrons. Thus, the narrowing of spectra of multiple small-angle neutron scattering observed experimentally and in numerical simulation has been explained.
Proton radiography, nuclear cross sections and multiple Coulomb scattering
Sjue, Sky K.
2015-11-04
The principles behind proton radiography including multiple Coulomb scattering are discussed for a purely imaginary square well nucleus in the eikonal approximation. It is found that a very crude model can reproduce the angular dependence of the cross sections measured at 24 GeV/c. The largest differences are ~3% for the 4.56 mrad data, and ~4% for the 6.68 mrad data. The prospect of understanding how to model deterministically high-energy proton radiography over a very large range of energies is promising, but it should be tested more thoroughly.
Multiple scattering of light in three-dimensional photonic quasicrystals.
Ledermann, Alexandra; Wiersma, Diederik S; Wegener, Martin; von Freymann, Georg
2009-02-01
Recent experiments on three-dimensional icosahedral dielectric photonic quasicrystals have shown several unexpected features: transmitted femtosecond pulses developed a trailing "diffusive" exponential tail and the sum of (zeroth-order) transmittance and reflectance was well below unity. These experimental findings have previously been ascribed to sample imperfections. Here, we analyze these findings by using 3D periodic approximants of the ideal photonic quasicrystals. We show that the experimental observations can be explained in terms of multiple scattering of light within these structures, i.e., in terms of intrinsic rather than purely extrinsic quasicrystal properties. PMID:19189014
Sky luminance/radiance model with multiple scattering effect
Kocifaj, M.
2009-10-15
Angular distribution of the diffuse light essentially varies with the physical state of a disperse media. The main factors influencing the optical behaviour of the Earth's atmosphere are the total optical thickness, the scattering ability of atmospheric layers, and also the reflectance of underlying surface. Any model aspiring to be more universal and still satisfactory accurate must at least account for these quantities. The paper presents the theoretically derived equation simulating the sky luminance/radiance under various meteorological conditions. Because the radiative transfer equation in plan-parallel atmosphere is solved exactly, the proposed approximation formula is physically well-founded. Compared with other, predominately empirical models, the presented approach accepts the basic principles of light scattering in a turbid environment and the model is spectral in its nature (contrary to empirical models in current use). In addition, the contribution of multiple scattering is taken into account. A set of free parameters, otherwise used as weighting factors for individual optical effects, makes the model easily scalable and applicable for a wide range of optical states of the atmosphere. (author)
Multiple scattering depolarization in marine stratus clouds: Lidar experiments
NASA Technical Reports Server (NTRS)
Sassen, K.; Petrilla, R. L.
1986-01-01
The depolarization of ruby lidar backscattering caused by multiple scattering in marine stratus clouds was examined systematically from a field site on the southern California coast. Investigated were the effects on the linear depolarization (delta) of lidar receiver field of view (FOV), elevation angle and laser beam pointing errors. An approximately linear increase in maximum delta values was observed with increasing receiver FOV, and the importance of accurate transmitter/receiver beam alignment was demonstrated during experiments in which the laser axis was deliberately misaligned. An elevation angle dependence to the delta values was observed as a consequence of the natural vertical inhomogeneity of water cloud content above the cloud base. Time histories of the depolarization characteristics of dissipating stratus clouds revealed significant spatial and temporal variability in delta values attributed to cloud composition variations. Employing a 1 mrad transmitter FOV, maximum delta values of 0.21 nd 0.33 were observed with 1 and 3 mrad receiver FOVs, respectively, from the low stratus clouds. The fundamental causes and effects on the lidar equation of multiple scattering are also discussed.
NASA Astrophysics Data System (ADS)
Fu, Qiang
1991-02-01
A radiation model has been developed to calculate the radiative fluxes and heating rates in plane parallel, vertically nonhomogeneous, multiple scattering atmospheres with an accuracy of better than 5%. This scheme is appropriate for use in climate and numerical prediction models to study the effect of cloud and radiation interactions. Parameterization of nongray gaseous absorption in vertically nonhomogeneous atmospheres has been developed based upon the correlated K-distribution method. The entire radiation spectrum is divided into 18 intervals: 6 in the solar and 12 in the infrared. By using a minimum number of quadrature points within each wavelength interval to represent the gaseous absorption and to treat overlap, we need to perform 121 spectral calculations for each vertical profile to obtain total radiative fluxes and heating rates. The treatment of gaseous absorption introduces errors less than 0.05 K/day in the heating rates below 30 km and and relative errors less than 0.5% in the fluxes. The single-scattering properties of water/ice clouds have been parameterized in terms of the effective size and liquid/ice water contents, based on Mie-scattering/ray -tracing computations with the best available size distributions. The parameterization gives an accuracy within about 1% in the solar and 5% in the infrared. By using the delta-four-stream approximation, a single algorithm has been developed for radiative transfer calculations. For vertically nonhomogeneous atmospheres, this code is numerically stable and computationally efficient. The accuracy of the algorithm is generally better than 5%, but it can produce more accurate results in the limit of no scattering. Compared with line-by-line results from clear -sky longwave calculations when all constituents were included, the errors in heating rates calculated by the new radiation model are less than 0.1 K/day in the troposphere and lower stratosphere. The errors in radiative fluxes are less than 1% both at
NASA Astrophysics Data System (ADS)
Okamoto, Hajime; Sato, Kaori; Makino, Toshiyuki; Nishizawa, Tomoaki; Sugimoto, Nobuo; Jin, Yoshitaka; Shimizu, Atsushi
2016-06-01
We have developed the Multiple Field of view Multiple Scattering Polarization Lidar (MFMSPL) system for the study of optically thick low-level clouds. It has 8 telescopes; 4 telescopes for parallel channels and another 4 for perpendicular channels. The MFMSPL is the first lidar system that can measure depolarization ratio for optically thick clouds where multiple scattering is dominant. Field of view of each channel was 10mrad and was mounted with different angles ranging from 0 mrad (vertical) to 30mrad. And footprint size from the total FOV was achieved to be close to that of Cloud-Aerosol Lidar and Infrared Pathfinder Satellite Observation (CALIPSO) lidar at the altitude of 1km in order to reproduce similar degree of multiple scattering effects as observed from space. The MFMSPL has started observations since June 2014 and has been continuously operated at National Institute for Environmental Studies (NIES) in Tsukuba, Japan. Observations proved expected performance such that measured depolarization ratio was comparable to the one observed by CALIPSO lidar.
NASA Astrophysics Data System (ADS)
Yashchuk, Vasil P.
2015-07-01
Random lasing (RL) and stimulated Raman scattering (SRS) of dye in multiple scattering media (MSM) appears simultaneously and each couple with other. This coupling has considerable influence on the SRS regularities of dye in MSM. The main feature of this impact is that RL radiation promotes the Raman lines revealing in the RL spectrum range as part of total radiation. SRS initiation occurs owing to the CARS-like mechanism provided by the two component pump: incident monochromatic radiation (laser pump) and RL radiation arising inside the MSM. It leads to important consequences: the RL spectrum must overlap with the spectral region of the possible Stokes lines of the dye; only those Stokes lines appear which are in a range of the RL spectrum; all conditions which promote RL assist SRS also. It is shown MSM promotes the best conditions for SRS and RL coupling due to optimal matching of RL localization regions and pump radiation.
Scattering Optical Elements: Stand-Alone Optical Elements Exploiting Multiple Light Scattering.
Park, Jongchan; Cho, Joong-Yeon; Park, Chunghyun; Lee, KyeoReh; Lee, Heon; Cho, Yong-Hoon; Park, YongKeun
2016-07-26
Optical design and fabrication techniques are crucial for making optical elements. From conventional lenses to diffractive optical elements and to recent metasurfaces, various types of optical elements have been proposed to manipulate light where optical materials are fabricated into desired structures. Here, we propose a scattering optical element (SOE) that exploits multiple light scattering and wavefront shaping. Instead of fabricating optical materials, the SOE consists of a disordered medium and a photopolymer-based wavefront recorder, with shapes impinging on light on demand. With the proposed stand-alone SOEs, we experimentally demonstrate control of various properties of light, including intensity, polarization, spectral frequency, and near field. Due to the tremendous freedom brought about by disordered media, the proposed approach will provide unexplored routes to manipulate arbitrary optical fields in stand-alone optical elements. PMID:27331616
Yashchuk, V P; Komyshan, A O; Smaliuk, A P; Prygodiuk, O A; Ishchenko, A A; Olkhovyk, L A
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, 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)
Multiple photon production in double parton scattering at the LHC
NASA Astrophysics Data System (ADS)
Palota da Silva, R.; Brenner Mariotto, C.; Goncalves, V. P.
2016-04-01
The high density of gluons in the initial state of hadronic collisions at LHC implies that the probability of multiple parton interactions within one proton-proton collision increases. In particular, the probability of having two or more hard interactions in a collision is not significantly suppressed with respect to the single interaction probability. In this contribution we study for the first time the production of prompt photons in double parton scattering processes. In particular, we estimate the rapidity distribution for the double Compton process, which leads to two photons plus two jets in the final state. Besides, we study the production of three and four photons in the final state, which are backgrounds to physics beyond the Standard Model.
The Expected Impact of Multiple Scattering on ATLID Signals
NASA Astrophysics Data System (ADS)
Donovan, D. P.
2016-06-01
ATLID stands for "ATmospheric LIDar" and is the lidar to be flown on the Earth Clouds and Radiation Explorer (EarthCARE) platform in 2018. ATLID is a High-Spectral Resolution (HSRL) system operating at 355nm with a narrower field-of-view and lower orbit than the CALIPSO lidar. In spite of the smaller footprint multiple-scattering (MS) will have an important impact on ATLID cloud signals and, in some aspects, the accurate treatment of MS will be more important for ATLID than CALIPSO. On the other hand, the relationship between integrated backscatter and integrated MS induced depolarization in water clouds will be similar between ATLID and CALIPSO indicating that a CALIPSO-like strategy for cloud-phase identification can be successfully applied to ATLID.
Multiple Scattering in Random Mechanical Systems and Diffusion Approximation
NASA Astrophysics Data System (ADS)
Feres, Renato; Ng, Jasmine; Zhang, Hong-Kun
2013-10-01
This paper is concerned with stochastic processes that model multiple (or iterated) scattering in classical mechanical systems of billiard type, defined below. From a given (deterministic) system of billiard type, a random process with transition probabilities operator P is introduced by assuming that some of the dynamical variables are random with prescribed probability distributions. Of particular interest are systems with weak scattering, which are associated to parametric families of operators P h , depending on a geometric or mechanical parameter h, that approaches the identity as h goes to 0. It is shown that ( P h - I)/ h converges for small h to a second order elliptic differential operator on compactly supported functions and that the Markov chain process associated to P h converges to a diffusion with infinitesimal generator . Both P h and are self-adjoint (densely) defined on the space of square-integrable functions over the (lower) half-space in , where η is a stationary measure. This measure's density is either (post-collision) Maxwell-Boltzmann distribution or Knudsen cosine law, and the random processes with infinitesimal generator respectively correspond to what we call MB diffusion and (generalized) Legendre diffusion. Concrete examples of simple mechanical systems are given and illustrated by numerically simulating the random processes.
Multiple scattering of proton via stochastic differential equations
NASA Astrophysics Data System (ADS)
Kia, M. R.; Noshad, Houshyar
2015-08-01
Multiple scattering of protons through a target is explained by a set of coupled stochastic differential equations. The motion of protons in matter is calculated by analytical random sampling from Moliere and Landau probability density functions (PDF). To satisfy the Vavilov theory, the moments for energy distribution of a 49.1 MeV proton beam in aluminum target are obtained. The skewness for the PDF of energy demonstrates that the energy distribution of protons in thin thickness becomes a Landau function, whereas, by increasing the thickness of the target it does not follow a Gaussian function completely. Afterwards, the depth-dose distributions are calculated for a 60 MeV proton beam traversing soft tissue and for a 160 MeV proton beam travelling through water. The results prove that when elastic scattering is taken into account, the Bragg-peak position is decreased, while the dose deposited in the Bragg region is increased. The results obtained in this article are benchmarked by comparison of our results with the experimental data reported in the literature.
Parameterization of radiative processes in vertically nonhomogeneous multiple scattering atmospheres
NASA Astrophysics Data System (ADS)
Fu, Qiang
1991-05-01
A radiation model has been developed to calculate the radiative fluxes and heating rates in plane parallel, vertically nonhomogeneous, multiple scattering atmospheres with an accuracy of better than 5 percent. This scheme is appropriate for use in climate and numerical prediction models to study the effect of cloud and radiation interactions. Parameterization of nongray gaseous absorption in vertically nonhomogeneous atmospheres has been developed based upon the correlated K-distribution method. The entire radiation spectrum is divided into 18 intervals: 6 in the solar and 12 in the infrared. By using a minimum number of quadrature points within each wavelength interval to represent the gaseous absorption and to treat overlap, we need to perform 121 spectral calculations for each vertical profile to obtain total radiative fluxes and heating rates. The treatment of gaseous absorption introduces errors less than 0.05 K/day in the heating rates below 30 km and relative errors less than 0.5 percent in the fluxes. The single-scattering properties of water/ice clouds have been parameterized in terms of the effective size and liquid/ice water contents, based on Mie-scattering/ray-tracing computations with the best available size distributions. The parameterization gives an accuracy within about 1 percent in the solar and 5 percent in the infrared. By using the delta-four-stream approximation, a single algorithm has been developed for radiative transfer calculations. For vertically nonhomogeneous atmospheres, this code is numerically stable and computationally efficient. The accuracy of the algorithm is generally better than 5 percent, but it can produce more accurate results in the limit of no scattering. Compared with line-by-line results from clear-sky longwave calculations when all constituents were included, the errors in heating rates calculated by the new radiation model are less than 0.1 K/day in the troposphere and lower stratosphere. The errors in radiative
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
Multiplicity moments in deep inelastic scattering at HERA
NASA Astrophysics Data System (ADS)
ZEUS Collaboration; Chekanov, S.; Derrick, M.; Krakauer, D.; Magill, S.; Musgrave, B.; Pellegrino, A.; Repond, J.; Stanek, R.; Yoshida, R.; Mattingly, M. C. K.; Antonioli, P.; Bari, G.; Basile, M.; Bellagamba, L.; Boscherini, D.; Bruni, A.; Bruni, G.; Cara Romeo, G.; Cifarelli, L.; Cindolo, F.; Contin, A.; Corradi, M.; De Pasquale, S.; Giusti, P.; Iacobucci, G.; Levi, G.; Margotti, A.; Massam, T.; Nania, R.; Palmonari, F.; Pesci, A.; Sartorelli, G.; Zichichi, A.; Aghuzumtsyan, G.; Brock, I.; Goers, S.; Hartmann, H.; Hilger, E.; Irrgang, P.; Jakob, H.-P.; Kappes, A.; Katz, U. F.; Kerger, R.; Kind, O.; Paul, E.; Rautenberg, J.; Schnurbusch, H.; Stifutkin, A.; Tandler, J.; Voss, K. C.; Weber, A.; Wieber, H.; Bailey, D. S.; Brook, N. H.; Cole, J. E.; Foster, B.; Heath, G. P.; Heath, H. F.; Robins, S.; Rodrigues, E.; Scott, J.; Tapper, R. J.; Wing, M.; Capua, M.; Mastroberardino, A.; Schioppa, M.; Susinno, G.; Jeoung, H. Y.; Kim, J. Y.; Lee, J. H.; Lim, I. T.; Ma, K. J.; Pac, M. Y.; Caldwell, A.; Helbich, M.; Liu, W.; Liu, X.; Mellado, B.; Paganis, S.; Sampson, S.; Schmidke, W. B.; Sciulli, F.; Chwastowski, J.; Eskreys, A.; Figiel, J.; Klimek, K.; Olkiewicz, K.; Przybycień, M. B.; Stopa, P.; Zawiejski, L.; Bednarek, B.; Jeleń, K.; Kisielewska, D.; Kowal, A. M.; Kowal, M.; Kowalski, T.; Mindur, B.; Przybycień, M.; Rulikowska-Zarȩbska, E.; Suszycki, L.; Szuba, D.; Kotański, A.; Bauerdick, L. A. T.; Behrens, U.; Borras, K.; Chiochia, V.; Crittenden, J.; Dannheim, D.; Desler, K.; Drews, G.; Fox-Murphy, A.; Fricke, U.; Geiser, A.; Goebel, F.; Göttlicher, P.; Graciani, R.; Haas, T.; Hain, W.; Hartner, G. F.; Hebbel, K.; Hillert, S.; Koch, W.; Kötz, U.; Kowalski, H.; Labes, H.; Löhr, B.; Mankel, R.; Martens, J.; Martínez, M.; Milite, M.; Moritz, M.; Notz, D.; Petrucci, M. C.; Polini, A.; Savin, A. A.; Schneekloth, U.; Selonke, F.; Stonjek, S.; Wolf, G.; Wollmer, U.; Whitmore, J. J.; Wichmann, R.; Youngman, C.; Zeuner, W.; Coldewey, C.; Lopez-Duran Viani, A.; Meyer, A.; Schlenstedt, S.; Barbagli, G.; Gallo, E.; Pelfer, P. G.; Bamberger, A.; Benen, A.; Coppola, N.; Markun, P.; Raach, H.; Wölfle, S.; Bell, M.; Bussey, P. J.; Doyle, A. T.; Glasman, C.; Lee, S. W.; Lupi, A.; McCance, G. J.; Saxon, D. H.; Skillicorn, I. O.; Bodmann, B.; Gendner, N.; Holm, U.; Salehi, H.; Wick, K.; Yildirim, A.; Ziegler, A.; Carli, T.; Garfagnini, A.; Gialas, I.; Lohrmann, E.; Foudas, C.; Gonçalo, R.; Long, K. R.; Metlica, F.; Miller, D. B.; Tapper, A. D.; Walker, R.; Cloth, P.; Filges, D.; Ishii, T.; Kuze, M.; Nagano, K.; Tokushuku, K.; Yamada, S.; Yamazaki, Y.; Barakbaev, A. N.; Boos, E. G.; Pokrovskiy, N. S.; Zhautykov, B. O.; Ahn, S. H.; Lee, S. B.; Park, S. K.; Lim, H.; Son, D.; Barreiro, F.; García, G.; González, O.; Labarga, L.; del Peso, J.; Redondo, I.; Terrón, J.; Vázquez, M.; Barbi, M.; Corriveau, F.; Padhi, S.; Stairs, D. G.; Tsurugai, T.; Antonov, A.; Bashkirov, V.; Danilov, P.; Dolgoshein, B. A.; Gladkov, D.; Sosnovtsev, V.; Suchkov, S.; Dementiev, R. K.; Ermolov, P. F.; Golubkov, Y. A.; Katkov, I. I.; Khein, L. A.; Korotkova, N. A.; Korzhavina, I. A.; Kuzmin, V. A.; Levchenko, B. B.; Lukina, O. Y.; Proskuryakov, A. S.; Shcheglova, L. M.; Solomin, A. N.; Vlasov, N. N.; Zotkin, S. A.; Bokel, C.; Botje, M.; Engelen, J.; Grijpink, S.; Koffeman, E.; Kooijman, P.; Schagen, S.; van Sighem, A.; Tassi, E.; Tiecke, H.; Tuning, N.; Velthuis, J. J.; Vossebeld, J.; Wiggers, L.; de Wolf, E.; Brümmer, N.; Bylsma, B.; Durkin, L. S.; Gilmore, J.; Ginsburg, C. M.; Kim, C. L.; Ling, T. Y.; Boogert, S.; Cooper-Sarkar, A. M.; Devenish, R. C. E.; Ferrando, J.; Große-Knetter, J.; Matsushita, T.; Rigby, M.; Ruske, O.; Sutton, M. R.; Walczak, R.; Bertolin, A.; Brugnera, R.; Carlin, R.; Dal Corso, F.; Dusini, S.; Limentani, S.; Longhin, A.; Parenti, A.; Posocco, M.; Stanco, L.; Turcato, M.; Adamczyk, L.; Iannotti, L.; Oh, B. Y.; Saull, P. R. B.; Toothacker, W. S.; Iga, Y.; D'Agostini, G.; Marini, G.; Nigro, A.; Cormack, C.; Hart, J. C.; McCubbin, N. A.; Epperson, D.; Heusch, C.; Sadrozinski, H. F.-W.; Seiden, A.; Williams, D. C.; Park, I. H.; Pavel, N.; Abramowicz, H.; Dagan, S.; Gabareen, A.; Kananov, S.; Kreisel, A.; Levy, A.; Abe, T.; Fusayasu, T.; Kohno, T.; Umemori, K.; Yamashita, T.; Hamatsu, R.; Hirose, T.; Inuzuka, M.; Kitamura, S.; Matsuzawa, K.; Nishimura, T.; Arneodo, M.; Cartiglia, N.; Cirio, R.; Costa, M.; Ferrero, M. I.; Maselli, S.; Monaco, V.; Peroni, C.; Ruspa, M.; Sacchi, R.; Solano, A.; Staiano, A.; Bailey, D. C.; Fagerstroem, C.-P.; Galea, R.; Koop, T.; Levman, G. M.; Martin, J. F.; Mirea, A.; Sabetfakhri, A.; Butterworth, J. M.; Gwenlan, C.; Hayes, M. E.; Heaphy, E. A.; Jones, T. W.; Lane, J. B.; West, B. J.; Ciborowski, J.; Ciesielski, R.; Grzelak, G.; Nowak, R. J.; Pawlak, J. M.; Plucinski, P.; Smalska, B.; Tymieniecka, T.; Ukleja, J.; Zakrzewski, J. A.; Z˙arnecki, A. F.; Adamus, M.; Sztuk, J.; Deppe, O.; Eisenberg, Y.; Gladilin, L. K.; Hochman, D.; Karshon, U.; Breitweg, J.; Chapin, D.; Cross, R.; Kçira, D.; Lammers, S.; Reeder, D. D.; Smith, W. H.; Deshpande, A.; Dhawan, S.; Hughes, V. W.; Straub, P. B.; Bhadra, S.; Catterall, C. D.; Frisken, W. R.; Hall-Wilton, R.; Khakzad, M.; Menary, S.
2001-06-01
Multiplicity moments of charged particles in deep inelastic e+p scattering have been measured with the ZEUS detector at HERA using an integrated luminosity of 38.4 pb-1. The moments for Q2>1000 GeV2 were studied in the current region of the Breit frame. The evolution of the moments was investigated as a function of restricted regions in polar angle and, for the first time, both in the transverse momentum and in absolute momentum of final-state particles. Analytic perturbative QCD predictions in conjunction with the hypothesis of Local Parton-Hadron Duality (LPHD) reproduce the trends of the moments in polar-angle regions, although some discrepancies are observed. For the moments restricted either in transverse or absolute momentum, the analytic results combined with the LPHD hypothesis show considerable deviations from the measurements. The study indicates a large influence of the hadronisation stage on the multiplicity distributions in the restricted phase-space regions studied here, which is inconsistent with the expectations of the LPHD hypothesis.
Suppression of multiple scattering with a CCD camera detection scheme
NASA Astrophysics Data System (ADS)
Zakharov, Pavel; Schurtenberger, Peter; Scheffold, Frank
2005-06-01
We introduce a CCD camera detection scheme in dynamic light scattering that provides information on the single-scattered auto-correlation function even for fairly turbid samples. Our approach allows access to the extensive range of systems that show low-order scattering by selective detection of the singly scattered light. Model experiments on slowly relaxing suspensions of latex spheres in glycerol were carried out to verify validity range of our approach.
Multiple scattering of ultrasound in weakly inhomogeneous media: application to human soft tissues.
Aubry, Alexandre; Derode, Arnaud
2011-01-01
Waves scattered by a weakly inhomogeneous random medium contain a predominant single-scattering contribution as well as a multiple-scattering contribution which is usually neglected, especially for imaging purposes. A method based on random matrix theory is proposed to separate the single- and multiple-scattering contributions. The experimental setup uses an array of sources/receivers placed in front of the medium. The impulse responses between every couple of transducers are measured and form a matrix. Single-scattering contributions are shown to exhibit a deterministic coherence along the antidiagonals of the array response matrix, whatever the distribution of inhomogeneities. This property is taken advantage of to discriminate single- from multiple-scattered waves. This allows one to evaluate the absorption losses and the scattering losses separately, by comparing the multiple-scattering intensity with a radiative transfer model. Moreover, the relative contribution of multiple scattering in the backscattered wave can be estimated, which serves as a validity test for the Born approximation. Experimental results are presented with ultrasonic waves in the megahertz range, on a synthetic sample (agar-gelatine gel) as well as on breast tissues. Interestingly, the multiple-scattering contribution is found to be far from negligible in the breast around 4.3 MHz. PMID:21303005
Coastal Zone Color Scanner atmospheric correction algorithm: multiple scattering effects.
Gordon, H R; Castaño, D J
1987-06-01
An analysis of the errors due to multiple scattering which are expected to be encountered in application of the current Coastal Zone Color Scanner (CZCS) atmospheric correction algorithm is presented in detail. This was prompted by the observations of others that significant errors would be encountered if the present algorithm were applied to a hypothetical instrument possessing higher radiometric sensitivity than the present CZCS. This study provides CZCS users sufficient information with which to judge the efficacy of the current algorithm with the current sensor and enables them to estimate the impact of the algorithm-induced errors on their applications in a variety of situations. The greatest source of error is the assumption that the molecular and aerosol contributions to the total radiance observed at the sensor can be computed separately. This leads to the requirement that a value epsilon'(lambda,lambda(0)) for the atmospheric correction parameter, which bears little resemblance to its theoretically meaningful counterpart, must usually be employed in the algorithm to obtain an accurate atmospheric correction. The behavior of '(lambda,lambda(0)) with the aerosol optical thickness and aerosol phase function is thoroughly investigated through realistic modeling of radiative transfer in a stratified atmosphere over a Fresnel reflecting ocean. A unique feature of the analysis is that it is carried out in scan coordinates rather than typical earth-sun coordinates allowing elucidation of the errors along typical CZCS scan lines; this is important since, in the normal application of the algorithm, it is assumed that the same value of can be used for an entire CZCS scene or at least for a reasonably large subscene. Two types of variation of ' are found in models for which it would be constant in the single scattering approximation: (1) variation with scan angle in scenes in which a relatively large portion of the aerosol scattering phase function would be examined
Average wavefunction method for multiple scattering theory and applications
Singh, H.
1985-01-01
A general approximation scheme, the average wavefunction approximation (AWM), applicable to scattering of atoms and molecules off multi-center targets, is proposed. The total potential is replaced by a sum of nonlocal, separable interactions. Each term in the sum projects the wave function onto a weighted average in the vicinity of a given scattering center. The resultant solution is an infinite order approximation to the true solution, and choosing the weighting function as the zeroth order solution guarantees agreement with the Born approximation to second order. In addition, the approximation also becomes increasingly more accurate in the low energy long wave length limit. A nonlinear, nonperturbative literature scheme for the wave function is proposed. An extension of the scheme to multichannel scattering suitable for treating inelastic scattering is also presented. The method is applied to elastic scattering of a gas off a solid surface. The formalism is developed for both periodic as well as disordered surfaces. Numerical results are presented for atomic clusters on a flat hard wall with a Gaussian like potential at each atomic scattering site. The effect of relative lateral displacement of two clusters upon the scattering pattern is shown. The ability of AWM to accommodate disorder through statistical averaging over cluster configuration is illustrated. Enhanced uniform back scattering is observed with increasing roughness on the surface. Finally, the AWM is applied to atom-molecule scattering.
Multiple scattering and charged-particle - hydrogen-atom collisions
NASA Technical Reports Server (NTRS)
Franco, V.; Thomas, B. K.
1979-01-01
Glauber-approximation scattering amplitudes for charged-particle - hydrogen-atom elastic and inelastic collisions are derived directly in terms of the known particle-electron and particle-proton Coulomb scattering amplitudes and the known hydrogen-atom form factors. It is shown that the particle-hydrogen amplitude contains no single-scattering term. The double-scattering term is obtained as a two-dimensional integral in momentum space. It is demonstrated how the result can be used as the starting point for an alternative and relatively simple derivation, in closed form, of the Glauber particle-hydrogen scattering amplitude for transitions from the ground state to an arbitrary (nlm) state.
μ-diff: An open-source Matlab toolbox for computing multiple scattering problems by disks
NASA Astrophysics Data System (ADS)
Thierry, Bertrand; Antoine, Xavier; Chniti, Chokri; Alzubaidi, Hasan
2015-07-01
The aim of this paper is to describe a Matlab toolbox, called μ-diff, for modeling and numerically solving two-dimensional complex multiple scattering by a large collection of circular cylinders. The approximation methods in μ-diff are based on the Fourier series expansions of the four basic integral operators arising in scattering theory. Based on these expressions, an efficient spectrally accurate finite-dimensional solution of multiple scattering problems can be simply obtained for complex media even when many scatterers are considered as well as large frequencies. The solution of the global linear system to solve can use either direct solvers or preconditioned iterative Krylov subspace solvers for block Toeplitz matrices. Based on this approach, this paper explains how the code is built and organized. Some complete numerical examples of applications (direct and inverse scattering) are provided to show that μ-diff is a flexible, efficient and robust toolbox for solving some complex multiple scattering problems.
Robustness of the fractal regime for the multiple-scattering structure factor
NASA Astrophysics Data System (ADS)
Katyal, Nisha; Botet, Robert; Puri, Sanjay
2016-08-01
In the single-scattering theory of electromagnetic radiation, the fractal regime is a definite range in the photon momentum-transfer q, which is characterized by the scaling-law behavior of the structure factor: S(q) ∝ 1 /q df. This allows a straightforward estimation of the fractal dimension df of aggregates in Small-Angle X-ray Scattering (SAXS) experiments. However, this behavior is not commonly studied in optical scattering experiments because of the lack of information on its domain of validity. In the present work, we propose a definition of the multiple-scattering structure factor, which naturally generalizes the single-scattering function S(q). We show that the mean-field theory of electromagnetic scattering provides an explicit condition to interpret the significance of multiple scattering. In this paper, we investigate and discuss electromagnetic scattering by three classes of fractal aggregates. The results obtained from the TMatrix method show that the fractal scaling range is divided into two domains: (1) a genuine fractal regime, which is robust; (2) a possible anomalous scaling regime, S(q) ∝ 1 /qδ, with exponent δ independent of df, and related to the way the scattering mechanism uses the local morphology of the scatterer. The recognition, and an analysis, of the latter domain is of importance because it may result in significant reduction of the fractal regime, and brings into question the proper mechanism in the build-up of multiple-scattering.
Multiple scattering of surface waves by cavities in a half-space
Phan, Haidang; Cho, Younho; Ju, Taeho; Achenbach, Jan D.
2014-02-18
Scattering of surface waves from multiple two-dimensional cavities at the surface of a homogenous, isotropic, linearly elastic half-space is analyzed in this work. For the case of multiple cavities, the scattered field is shown to be equivalent to the total radiation from the distributions of tractions, calculated from the incident wave, over the surfaces of the cavities. The multiple-scattering model is obtained from known single-scattering calculation for a cavity by the use of the self-consistent method. The second order approximation to the multiple-scattering problem by a random distribution of cavities is then considered and solved analytically. The vertical displacement at some distance from the cavities is calculated and verified by the solution of the same problem obtained by the boundary element method (BEM). The analytical and BEM results are graphically displayed and show good agreement when the depths of the cavities are small compared to the wavelength.
FEFF5: An ab initio multiple scattering XAFS code. [In FORTRAN 77
Rehr, J.J.; Zabinsky, S.I.
1992-01-01
FEFF5 is an efficient automated code which calculates multiple scattering (MS) curved wave XAFS spectra for molecules and solids. The theoretical ingredients and approximations contained in the code are revised, with the aim of describing the how XAFS spectra are efficiently simulated. The FEFF5 code consists of 4 independent modules: a scattering potential and phase shift module, a path finder module, a scattering amplitude module and an XAFS module. Multiple scattering Debye-Waller factors are built in using a correlated Debye model.
Multiple scattering of electrons in the reflex triode
Creedon, J.M. )
1990-12-01
Analytical theories and Monte Carlo calculations are used to treat the scattering and energy loss of electrons in the anode of a reflex triode. The solution of this scattering problem is combined with the equations for particle flow in vacuum to give a quantitative theory of triode operation. It is now possible to calculate several important properties of this device. These include the operating voltage in the constant voltage mode, the ratio of ion-to-electron current and the ion transit time.
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,
Multiple resonant scattering in the Compton upscatter model of gamma-ray bursts
NASA Technical Reports Server (NTRS)
Brainerd, J. J.
1992-01-01
Resonant Compton scattering, an increasingly popular mechanism for suppressing X-rays and producing gamma rays, must be treated as a multiple-scattering process for conditions thought characteristic of gamma-ray bursts. Photons that multiply scatter with a beamed power-law electron distribution in a uniform magnetic field produce a flat spectrum between the cyclotron frequency and an optical-depth-dependent critical energy; this critical energy ranges between several hundred keV and several MeV. Above this critical energy, the gamma-ray spectrum has a shape determined by the electron distribution and described by a single-scattering model. Only electron distributions that are nearly proportional to the electron momentum are able to simultaneously suppress X-rays and produce a single-scattering spectrum. As the Thomson optical depth approaches unity, photons that experience multiple scatterings often spawn additional photons at a rate that makes the model unphysical.
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.
Study of multiple scattering in high magnetic fields
NASA Astrophysics Data System (ADS)
Kaplan, Daniel M.; Roberts, Thomas J.
2013-02-01
Muon cooling for a neutrino factory or muon collider can be achieved using low-Z absorbers in strong focusing fields. Proposed cooling lattices place absorbers in solenoidal fields ranging up to 30 to 40 T. The cooling performance of these lattices is determined by the interplay of ionization energy loss and Molière scattering, but Bethe's classic treatment of Moliere scattering ignores the helical motion of charged particles in solenoidal fields. When this motion is taken into account, the performance of these lattices can be better than predicted by simulations using the standard treatment.
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.
Angular width of the Cherenkov radiation with inclusion of multiple scattering
NASA Astrophysics Data System (ADS)
Zheng, Jian
2016-06-01
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.
Multiple scattering of slow ions in a partially degenerate electron fluid
Popoff, Romain; Maynard, Gilles; Deutsch, Claude
2009-10-15
We extend former investigation to a partially degenerate electron fluid at any temperature of multiple slow ion scattering at T=0. We implement an analytic and mean-field interpolation of the target electron dielectric function between T=0 (Lindhard) and T{yields}{infinity} (Fried-Conte). A specific attention is given to multiple scattering of proton projectiles in the keV energy range, stopped in a hot-electron plasma at solid density.
Multiple scattering of scalar waves by point scatterers in one dimension. II
Haacke, E.M.; Foldy, L.L.
1981-04-01
In the first paper of this series, we studied the problem of scattering in one dimension of a wave interacting with n randomly distributed pointlike scatterers by delta-function potentials. Averaging the wave function for a constant amplitude transmitted wave over an ensemble of configurations allowed us to obtain an analytic expression for the optical potential which, in certain limits, took the form of the scatterer density (rho) times the scattering strength (GAMMA). We examine the domain in parameter space where rhoGAMMA can be regarded as a good approximation to the optical potential for both this problem and the problem in which the amplitude of the incident wave is constant. The conditions on the parameters are found to be the same in both the preceding problems. We then supplement rhoGAMMA by an appropriate imaginary part. The wave function predicted from this effective potential approximation to the optical potential is in good agreement with that from the exact solution.
Optimal control of light propagation through multiple-scattering media in the presence of noise
Yılmaz, Hasan; Vos, Willem L.; Mosk, Allard P.
2013-01-01
We study the control of coherent light propagation through multiple-scattering media in the presence of measurement noise. In our experiments, we use a two-step optimization procedure to find the optimal incident wavefront that generates a bright focal spot behind the medium. We conclude that the control of coherent light propagation through a multiple-scattering medium is only determined by the number of photoelectrons detected per optimized segment. The prediction of our model agrees well with the experimental results. Our results offer opportunities for imaging applications through scattering media such as biological tissue in the shot noise limit. PMID:24049696
Track fitting with multiple scattering: A new method
NASA Astrophysics Data System (ADS)
Billoir, Pierre
1984-08-01
An analytical calculation of the variance is performed, in some simple case, for standard least-squares estimators of track parameters (accounting for independent measurement errors only); comparison is made with optimal estimators (accounting also for scattering errors, correlated between one point and the following ones). A new method is proposed for optimal estimation: the points measured on the track are included backwards, one by one, in the fitting algorithm, and the scattering is handled locally at each step. The feasibility of the method is shown on real events, for which the geometrical resolution is improved. The algorithm is very flexible and allows fast programmation; moreover the computation time is merely proportional to the number of measured points, contrary to the other optimal estimators.
Vectorized polarization-sensitive model of non-line-of-sight multiple-scatter propagation.
Yin, Hongwei; Jia, Honghui; Zhang, Hailiang; Wang, Xiaofeng; Chang, Shengli; Yang, Juncai
2011-10-01
The existing Monte-Carlo-based non-line-of-sight (NLOS) multiple-scatter propagation model is extended to include polarization and also vectorized to improve the simulation speed by about 500 times. This model is validated by the noncoplanar single-scatter model; the results show a perfect match. Numerical examples for various polarization setups are obtained, and results show that the single-scatter and multiple-scatter signals are all polarization dependent. Therefore, NLOS polarized UV communication with a high data rate is achievable--the polarizing information is coded by a time-dependent polarizer, influenced by the atmospheric channel, and decoded according to the distribution characteristics of the scattered signals after the time-independent analyzers. PMID:21979512
Multiple scattering effects in Doppler optical coherence tomography of flowing blood
NASA Astrophysics Data System (ADS)
Kalkman, J.; Bykov, A. V.; Streekstra, G. J.; van Leeuwen, T. G.
2012-04-01
We investigate the effect of multiple scattering on the optical coherence tomography (OCT) signal and the Doppler OCT signal of flowing blood. Doppler OCT measurements at 1300 nm are performed on flowing diluted porcine blood with hematocrit ranging between 0% and 15%. Measured blood hematocrit and mean red blood cell volume are used to calculate, using the discrete dipole approximation model, the (single) scattering coefficient and scattering anisotropy of blood. Monte Carlo simulations, based on the calculated scattering coefficients and scattering anisotropies, are compared to Doppler OCT measurements for hematocrit smaller than 10%. Good quantitative agreement between Doppler OCT measurements and Monte Carlo simulations is observed. Our measurements, calculations and simulations explain the relatively low attenuation coefficients and well preserved flow profiles measured with Doppler OCT for flowing blood. Monte Carlo simulations demonstrate the effect of the scattering anisotropy of the medium on the strength of multiple scattering effects in Doppler OCT signals. With increasing scattering anisotropy the OCT attenuation decreases; the distortion of the flow profile is strongest at intermediate scattering anisotropies (≈0.6).
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.
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.
Scattering from phase-separated vesicles. I. An analytical form factor for multiple static domains
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 of 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.
Dependent and multiple scattering in transmission and backscattering optical coherence tomography.
Nguyen, V Duc; Faber, D J; van der Pol, E; van Leeuwen, T G; Kalkman, J
2013-12-01
We use transmission and backscattering optical coherence tomography (OCT) to distinguish and quantify dependent and multiple scattering effects in turbid media. With transmission OCT the dependent scattering coefficients for a range of monodisperse silica particle suspensions are determined. An excellent agreement is observed between the measured dependent scattering coefficients and calculations based on Mie calculations, the Percus-Yevick radial distribution function, and coherent light scattering theory. Backscattering OCT measurements are fitted using the extended Huygens-Fresnel (EHF) model with the dependent scattering coefficients obtained from the transmission OCT measurements as input parameters. Good agreement between the EHF model and the backscattering OCT measurements is observed. For large particles, the rms scattering angle θrms obtained from the EHF fit is in fair agreement with θrms calculated from the transmission OCT data. PMID:24514466
Multiple-collision rotational rainbow effect in molecule-surface scattering
Elber, R.; Gerber, R.B.
1983-10-15
Classical calculations of molecular scattering from smooth surfaces show that multiple rainbow spikes in the rotational intensities may occur where the peaks correspond, respectively, to single, double, etc. collisions of the molecule with the repulsive potential. Unlike single collision rainbows, this effect may cause multiple peaks even for homonuclear diatomics.
Multiple Point Dynamic Gas Density Measurements Using Molecular Rayleigh Scattering
NASA Technical Reports Server (NTRS)
Seasholtz, Richard; Panda, Jayanta
1999-01-01
A nonintrusive technique for measuring dynamic gas density properties is described. Molecular Rayleigh scattering is used to measure the time-history of gas density simultaneously at eight spatial locations at a 50 kHz sampling rate. The data are analyzed using the Welch method of modified periodograms to reduce measurement uncertainty. Cross-correlations, power spectral density functions, cross-spectral density functions, and coherence functions may be obtained from the data. The technique is demonstrated using low speed co-flowing jets with a heated inner jet.
Ultra-fast hybrid CPU-GPU multiple scatter simulation for 3-D PET.
Kim, Kyung Sang; Son, Young Don; Cho, Zang Hee; Ra, Jong Beom; Ye, Jong Chul
2014-01-01
Scatter correction is very important in 3-D PET reconstruction due to a large scatter contribution in measurements. Currently, one of the most popular methods is the so-called single scatter simulation (SSS), which considers single Compton scattering contributions from many randomly distributed scatter points. The SSS enables a fast calculation of scattering with a relatively high accuracy; however, the accuracy of SSS is dependent on the accuracy of tail fitting to find a correct scaling factor, which is often difficult in low photon count measurements. To overcome this drawback as well as to improve accuracy of scatter estimation by incorporating multiple scattering contribution, we propose a multiple scatter simulation (MSS) based on a simplified Monte Carlo (MC) simulation that considers photon migration and interactions due to photoelectric absorption and Compton scattering. Unlike the SSS, the MSS calculates a scaling factor by comparing simulated prompt data with the measured data in the whole volume, which enables a more robust estimation of a scaling factor. Even though the proposed MSS is based on MC, a significant acceleration of the computational time is possible by using a virtual detector array with a larger pitch by exploiting that the scatter distribution varies slowly in spatial domain. Furthermore, our MSS implementation is nicely fit to a parallel implementation using graphic processor unit (GPU). In particular, we exploit a hybrid CPU-GPU technique using the open multiprocessing and the compute unified device architecture, which results in 128.3 times faster than using a single CPU. Overall, the computational time of MSS is 9.4 s for a high-resolution research tomograph (HRRT) system. The performance of the proposed MSS is validated through actual experiments using an HRRT. PMID:24403412
Application of the 2-D discrete-ordinates method to multiple scattering of laser radiation
Zardecki, A.; Gerstl, S.A.W.; Embury, J.F.
1983-05-01
The discrete-ordinates finite-element radiation transport code twotran is applied to describe the multiple scattering of a laser beam from a reflecting target. For a model scenario involving a 99% relative humidity rural aerosol we compute the average intensity of the scattered radiation and correction factors to the Beer-Lambert law arising from multiple scattering. As our results indicate, 2-D x-y and r-z geometry modeling can reliably describe a realistic 3-D scenario. Specific results are presented for the two visual ranges of 1.52 and 0.76 km which show that, for sufficiently high aerosol concentrations (e.g., equivalent to V = 0.76 km), the target signature in a distant detector becomes dominated by multiply scattered radiation from interactions of the laser light with the aerosol environment. The merits of the scaling group and the delta-M approximation for the transfer equation are also explored.
On multiple scatterings of mesons in hot and cold QCD matter
NASA Astrophysics Data System (ADS)
Dominguez, Fabio; Marquet, Cyrille; Wu, Bin
2009-05-01
We study the propagation of a color singlet qq¯ pair undergoing multiple scatterings in hot and cold QCD matter. The interaction of the dipole with the nucleus or plasma is described with the McLerran-Venugopalan and Gyulassy-Wang models respectively. We find identical results when expressed in terms of the saturation momentum of either the nucleus or the plasma. We compare two kinds of multiple scatterings, elastic and inelastic with respect to the target. When allowing the target to scatter inelastically, the difference with the elastic case is suppressed by a 1/Nc2 factor. We also discuss some implications of our results in the following situations: the survival probability of quarkonia in a hot medium, the production of high- p heavy mesons in nucleus-nucleus collisions, and the production of vector mesons in deep inelastic scattering off nuclei.
Effect of the concentration of inhomogeneities on the multiple small-angle neutron scattering
Abov, Yu. G.; Dzheparov, F. S.; Elyutin, N. O.; Lvov, D. V. Tyulyusov, A. N.
2013-03-15
The interference effects manifested during multiple small-angle neutron scattering (MSANS) on a chaotically arranged close-packed ensemble of scatterers have been studied. MSANS measurements have been performed for mixtures of Al and Ti-Zr alloy powders. It is shown that the results can be satisfactorily described based on a theory that takes into account spatial correlations in the arrangement of powder grains.
NASA Technical Reports Server (NTRS)
Eloranta, E. W.; Piironen, P. K.
1996-01-01
Quantitative lidar measurements of aerosol scattering are hampered by the need for calibrations and the problem of correcting observed backscatter profiles for the effects of attenuation. The University of Wisconsin High Spectral Resolution Lidar (HSRL) addresses these problems by separating molecular scattering contributions from the aerosol scattering; the molecular scattering is then used as a calibration target that is available at each point in the observed profiles. While the HSRl approach has intrinsic advantages over competing techniques, realization of these advantages requires implementation of a technically demanding system which is potentially very sensitive to changes in temperature and mechanical alignments. This paper describes a new implementation of the HSRL in an instrumented van which allows measurements during field experiments. The HSRL was modified to measure depolarization. In addition, both the signal amplitude and depolarization variations with receiver field of view are simultaneously measured. This allows for discrimination of ice clouds from water clouds and observation of multiple scattering contributions to the lidar return.
Correlations among angular wave component amplitudes in elastic multiple-scattering random media.
Hoover, Brian G; Deslauriers, Louis; Grannell, Shawn M; Ahmed, Rizwan E; Dilworth, David S; Athey, Brian D; Leith, Emmett N
2002-02-01
The propagation of scalar waves through random media that provide multiple elastic scattering is considered by derivation of an expression for the angular correlation of the scattered wave amplitudes. Coherent wave transmission is shown to occur through a mechanism similar to that responsible for coherent backscattering. While the properties of the scattered wave are generally consistent with radiative-transfer theory for sufficiently small incident and scattering angles, coherent transmission provides corrections to radiative-transfer results at larger angles. The theoretical angular correlation curves are fit, by specifying the probability densities of two random variables that correspond to material parameters, to measured data of laser light scattering from various polymer microsphere suspensions. PMID:11863685
Supersymmetric and Kaluza-Klein Particles Multiple Scattering in the Earth
Albuquerque, Ivone; Klein, Spencer
2009-05-19
Neutrino telescopes with cubic kilometer volume have the potential to discover new particles. Among them are next to lightest supersymmetric (NLSPs) and next to lightest Kaluza-Klein (NLKPs) particles. Two NLSPs or NLKPs will transverse the detector simultaneously producing parallel charged tracks. The track separation inside the detector can be a few hundred meters. As these particles might propagate a few thousand kilometers before reaching the detector, multiple scattering could enhance the pair separation at the detector. We find that the multiple scattering will alter the separation distribution enough to increase the number of NLKP pairs separated by more than 100 meters (a reasonable experimental cut) by up to 46% depending on the NLKP mass. Vertical upcoming NLSPs will have their separation increased by 24% due to multiple scattering.
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. PMID:27308132
NASA Astrophysics Data System (ADS)
Lambert, Simon A.; Näsholm, Sven Peter; Nordsletten, David; Michler, Christian; Juge, Lauriane; Serfaty, Jean-Michel; Bilston, Lynne; Guzina, Bojan; Holm, Sverre; Sinkus, Ralph
2015-08-01
Wave scattering provides profound insight into the structure of matter. Typically, the ability to sense microstructure is determined by the ratio of scatterer size to probing wavelength. Here, we address the question of whether macroscopic waves can report back the presence and distribution of microscopic scatterers despite several orders of magnitude difference in scale between wavelength and scatterer size. In our analysis, monosized hard scatterers 5 μ m in radius are immersed in lossless gelatin phantoms to investigate the effect of multiple reflections on the propagation of shear waves with millimeter wavelength. Steady-state monochromatic waves are imaged in situ via magnetic resonance imaging, enabling quantification of the phase velocity at a voxel size big enough to contain thousands of individual scatterers, but small enough to resolve the wavelength. We show in theory, experiments, and simulations that the resulting coherent superposition of multiple reflections gives rise to power-law dispersion at the macroscopic scale if the scatterer distribution exhibits apparent fractality over an effective length scale that is comparable to the probing wavelength. Since apparent fractality is naturally present in any random medium, microstructure can thereby leave its fingerprint on the macroscopically quantifiable power-law exponent. Our results are generic to wave phenomena and carry great potential for sensing microstructure that exhibits intrinsic fractality, such as, for instance, vasculature.
Lambert, Simon A; Näsholm, Sven Peter; Nordsletten, David; Michler, Christian; Juge, Lauriane; Serfaty, Jean-Michel; Bilston, Lynne; Guzina, Bojan; Holm, Sverre; Sinkus, Ralph
2015-08-28
Wave scattering provides profound insight into the structure of matter. Typically, the ability to sense microstructure is determined by the ratio of scatterer size to probing wavelength. Here, we address the question of whether macroscopic waves can report back the presence and distribution of microscopic scatterers despite several orders of magnitude difference in scale between wavelength and scatterer size. In our analysis, monosized hard scatterers 5 μm in radius are immersed in lossless gelatin phantoms to investigate the effect of multiple reflections on the propagation of shear waves with millimeter wavelength. Steady-state monochromatic waves are imaged in situ via magnetic resonance imaging, enabling quantification of the phase velocity at a voxel size big enough to contain thousands of individual scatterers, but small enough to resolve the wavelength. We show in theory, experiments, and simulations that the resulting coherent superposition of multiple reflections gives rise to power-law dispersion at the macroscopic scale if the scatterer distribution exhibits apparent fractality over an effective length scale that is comparable to the probing wavelength. Since apparent fractality is naturally present in any random medium, microstructure can thereby leave its fingerprint on the macroscopically quantifiable power-law exponent. Our results are generic to wave phenomena and carry great potential for sensing microstructure that exhibits intrinsic fractality, such as, for instance, vasculature. PMID:26371655
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.
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.
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.
Multiple-source optical diffusion approximation for a multilayer scattering medium.
Hollmann, Joseph L; Wang, Lihong V
2007-08-10
A method for improving the accuracy of the optical diffusion theory for a multilayer scattering medium is presented. An infinitesimally narrow incident light beam is replaced by multiple isotropic point sources of different strengths that are placed in the scattering medium along the incident beam. The multiple sources are then used to develop a multilayer diffusion theory. Diffuse reflectance is then computed using the multilayer diffusion theory and compared with accurate data computed by the Monte Carlo method. This multisource method is found to be significantly more accurate than the previous single-source method. PMID:17694156
NASA Astrophysics Data System (ADS)
Zimnyakov, D. A.; Yuvchenko, S. A.; Taskina, L. A.; Alonova, M. V.; Isaeva, E. A.; Isaeva, A. A.; Ushakova, O. V.
2016-04-01
The effect of increase in the uncertainty of local polarization states of laser light forward scattered by random media was studied in the experiments with phantom scatterers. At macroscopic level this effect is related to decay in the degree of polarization of scattered light in the course of transition from single to multiple scattering. Gelatin layers with embedded titania particles were used as the phantom scatterers. Features of distributions of local polarization states in various polarization coordinates were considered.
Multiple magnetic impurities on surfaces: Scattering and quasiparticle interference
NASA Astrophysics Data System (ADS)
Mitchell, Andrew K.; Derry, Philip G.; Logan, David E.
2015-06-01
We study systems of multiple interacting quantum impurities deposited on a metallic surface in a three-dimensional host. For the real-space two-impurity problem, using numerical renormalization group calculations, a rich range of behavior is shown to arise due to the interplay between Kondo physics and effective Ruderman-Kittel-Kasuya-Yosida interactions—provided the impurity separation is small. Such calculations allow identification of the minimum impurity separation required for a description in terms of independent impurities, and thereby the onset of the "dilute-impurity limit" in many-impurity systems. A "dilute-cluster" limit is also identified in systems with higher impurity density, where interimpurity interactions are important only within independent clusters. We calculate the quasiparticle interference due to two and many impurities, and explore the consequences of the independent impurity and cluster paradigms. Our results provide a framework to investigate the effects of disorder due to interacting impurities at experimentally relevant surface coverages.
MULTIPLE-PLANET SCATTERING AND THE ORIGIN OF HOT JUPITERS
Beauge, C.; Nesvorny, D.
2012-06-01
Doppler and transit observations of exoplanets show a pile-up of Jupiter-size planets in orbits with a 3 day period. A fraction of these hot Jupiters have retrograde orbits with respect to the parent star's rotation, as evidenced by the measurements of the Rossiter-McLaughlin effect. To explain these observations we performed a series of numerical integrations of planet scattering followed by the tidal circularization and migration of planets that evolved into highly eccentric orbits. We considered planetary systems having three and four planets initially placed in successive mean-motion resonances, although the angles were taken randomly to ensure orbital instability in short timescales. The simulations included the tidal and relativistic effects, and precession due to stellar oblateness. Our results show the formation of two distinct populations of hot Jupiters. The inner population (Population I) is characterized by semimajor axis a < 0.03 AU and mainly formed in the systems where no planetary ejections occurred. Our follow-up integrations showed that this population was transient, with most planets falling inside the Roche radius of the star in <1 Gyr. The outer population of hot Jupiters (Population II) formed in systems where at least one planet was ejected into interstellar space. This population survives the effects of tides over >1 Gyr and fits nicely the observed 3 day pile-up. A comparison between our three-planet and four-planet runs shows that the formation of hot Jupiters is more likely in systems with more initial planets. Due to the large-scale chaoticity that dominates the evolution, high eccentricities and/or high inclinations are generated mainly by close encounters between the planets and not by secular perturbations (Kozai or otherwise). The relative proportion of retrograde planets seems of be dependent on the stellar age. Both the distribution of almost aligned systems and the simulated 3 day pile-up also fit observations better in our four
Multiple-scattering effects on spaceborne lidar dedicated to forests survey
NASA Astrophysics Data System (ADS)
Shang, Xiaoxia; Chazette, Patrick
2014-05-01
The role of forests in the climate balance of the Earth system leads us to consider their monitoring on a global scale. This militates towards the establishment of a long-term monitoring of both forest areas and their evolution, in accordance with the climatic scales. Lidar and radar are promising instruments for such observations from spaceborne stations and present strong complementarity via their use in synergy. Here, we will focus on lidar technology where one of the major difficulties is the choice of the emitted wavelength. In fact, for space observations, multiple-scattering may significantly affect the scattering of the propagating laser light through the forest canopy. Indeed, depending on the lidar system parameters (e.g. wavelength, field of view) and on the tree species, spaceborne lidar observations are more or less perturbed by multiple-scattering. To assess the multiple-scattering effects on lidar signal return, a Monte Carlo simulator has been built. The simulator is constraint by actual measurements performed by an airborne lidar using an ultraviolet wavelength (355 nm). The airborne lidar sampled forest types (e.g. oaks, maritime pines, poplars) representative of European mid-latitude forests to constitute a data base of extinction coefficient vertical profiles in the canopy. For the simulations, the leaves have been considered as Lambertian surfaces, but it is not a limitation for the statistic modelling. For example, the multiple-scattering may lead to a significant overestimation of the poplar crown depths, larger than 4 m. The footprint, accounting for the altitude of the satellite orbit, dimensions the amplitude of the multiple-scattering effects. It has to be assessed taking into account the ground slope. Results established using UV airborne lidar coupled with a Monte Carlo approach will be presented and discussed.
Multiple scattering dynamics of fermions at an isolated p-wave resonance
NASA Astrophysics Data System (ADS)
Thomas, R.; Roberts, K. O.; Tiesinga, E.; Wade, A. C. J.; Blakie, P. B.; Deb, A. B.; Kjærgaard, N.
2016-07-01
The wavefunction for indistinguishable fermions is anti-symmetric under particle exchange, which directly leads to the Pauli exclusion principle, and hence underlies the structure of atoms and the properties of almost all materials. In the dynamics of collisions between two indistinguishable fermions, this requirement strictly prohibits scattering into 90° angles. Here we experimentally investigate the collisions of ultracold clouds fermionic 40K atoms by directly measuring scattering distributions. With increasing collision energy we identify the Wigner threshold for p-wave scattering with its tell-tale dumb-bell shape and no 90° yield. Above this threshold, effects of multiple scattering become manifest as deviations from the underlying binary p-wave shape, adding particles either isotropically or axially. A shape resonance for 40K facilitates the separate observation of these two processes. The isotropically enhanced multiple scattering mode is a generic p-wave threshold phenomenon, whereas the axially enhanced mode should occur in any colliding particle system with an elastic scattering resonance.
Multiple scattering dynamics of fermions at an isolated p-wave resonance.
Thomas, R; Roberts, K O; Tiesinga, E; Wade, A C J; Blakie, P B; Deb, A B; Kjærgaard, N
2016-01-01
The wavefunction for indistinguishable fermions is anti-symmetric under particle exchange, which directly leads to the Pauli exclusion principle, and hence underlies the structure of atoms and the properties of almost all materials. In the dynamics of collisions between two indistinguishable fermions, this requirement strictly prohibits scattering into 90° angles. Here we experimentally investigate the collisions of ultracold clouds fermionic (40)K atoms by directly measuring scattering distributions. With increasing collision energy we identify the Wigner threshold for p-wave scattering with its tell-tale dumb-bell shape and no 90° yield. Above this threshold, effects of multiple scattering become manifest as deviations from the underlying binary p-wave shape, adding particles either isotropically or axially. A shape resonance for (40)K facilitates the separate observation of these two processes. The isotropically enhanced multiple scattering mode is a generic p-wave threshold phenomenon, whereas the axially enhanced mode should occur in any colliding particle system with an elastic scattering resonance. PMID:27396294
Enhanced multiple scattering in crystals with effective LR length in the micron range
NASA Astrophysics Data System (ADS)
Biryukov, V. M.
2008-01-01
Multiple Coulomb scattering in amorphous media can be characterised by radiation length LR. We find in computer simulations that particles can scatter in bent crystal lattices with effective LR length down to a few microns or up to 700 times shorter than in the corresponding amorphous media. The effect exists only within the angular range of the bent crystal arc. Outside this range LR is back to normal value. This makes the crystal a material with unique enhanced multiple scattering property easily switched on/off. We derive a theoretical estimate independent of energy for the effective LR that is in agreement with our simulations for C, Si, Ge and W crystal lattices. We show that in the ongoing collimation experiment at the Tevatron a crystal-based "super-scattering material" could outperform a channeling crystal in collimation efficiency reducing the local background rate by a factor of 40. The introduced "enhanced multiple scattering" materials could serve for new approaches to beam collimation in accelerators, especially at the high-energy frontier machines like the LHC and ILC.
NASA Astrophysics Data System (ADS)
Dorri-Nowkoorani, Farhad
1995-01-01
Scope and method of study. The purpose of this study was to examine different parameters such as transmission, back-scattering, off angle detection, polarization, and different ranges of optical thickness (low to high), in dynamic light scattering measurements from multiple scattering fluid/particle suspensions. In addition, the validity of correlation transfer (CT) theory was investigated and a methodology was provided for finding micron size spherical particle diameter. The experiment has been setup using an Argon-Ion laser, PMT, goiniometer, mirrors, lenses, and beam splitter. Solutions of 0.3 m latex particles mixed with water have been used as the test samples. The measurements have been compared to CT theory using exact and approximate numerical solutions. Findings and conclusions. It was found that the two-dimensional correlation function decays slower as compared to the one-dimensional situation. The correlation function decays faster as effective optical thickness increases. Polarization affects the back-scattering correlation function decay rate for all optical thicknesses, while it may be unimportant for transmission at high optical thicknesses. Transition from single scattering to multiple scattering appears to begin around an optical thickness of 0.05. In addition, the correlation function appears relatively insensitive to off angle detection for effective optical thicknesses of 3 or greater transmission and 1.5 or greater for back -scattering. However, for smaller optical thicknesses, the correlation function appears to be dependent on detection angle. The CT theory has demonstrated promise as a model to bridge the gap from single scattering to multiple scattering correlation. A methodology is proposed herein to allow the determination of particle size using data to match CT predictions, as long as two index of refraction changes at the boundaries and a realistic single scattering phase function are considered in the numerical results. A method of
NASA Technical Reports Server (NTRS)
Otterman, Joseph; Brakke, T. W.
1991-01-01
All orders of scattering are analyzed for two artifical canopies. The SHL canopy consists of Small Horizontal Leaves that are much smaller than the leaf-to-leaf spacing. The IHL canopy consists of Infinite Horizontal Layers, where each leaf is of infinite extent (a horizontal plane). Hemispheric leaf reflectances and transmittances independent of the direction of illumination lead to exact solutions for these models. Sunlight that penetrates to a given leaf area index level is much stronger in an SHL canopy than that in IHL; but the difference becomes muted when leaf transmittance is large. Multiple scattering enhances the hemispheric canopy reflectance more strongly in SHL than it does in IHL. The enhancement depends linearly on leaf transmittance in SHL and on the transmittance squared in IHL. Comparison with measured reflectances indicates that IHL model grossly underestimates multiple scattering in soybean canopies.
Simulation of multiple scattering in the systems with complicated phase function
NASA Astrophysics Data System (ADS)
Aksenova, E. V.; Kokorin, D. I.; Romanov, V. P.
2015-11-01
We consider simulation of multiple scattering of waves in isotropic and anisotropic media. The focus is on the construction of the phase function interpolation for the single scattering. The procedure is based on the construction of the adaptive partitioning of the angular variables that determine the phase function. The developed interpolation method allows us rather quickly to perform calculations for systems with very complicated phase function. Application of the proposed method is illustrated by calculating the multiple scattering of light in a nematic liquid crystal (NLC) which presents the uniaxial anisotropic system. For this system the grid corresponding to the adaptive partitioning is constructed and the transition to the diffusion regime for the photon distribution is presented.
Separation of multiple scatterers in NEWS experiments using Independent Component Analysis (ICA)
NASA Astrophysics Data System (ADS)
Vanaverbeke, S.; Van Den Abeele, K.; Nion, D.; De Lathauwer, L.
2010-01-01
Nonlinear elastic wave spectroscopy combined with imaging techniques such as acoustic time reversal (NEWS-TR) or sparse array tomography is a promising new methodology for detecting microdamage at an early stage. When dealing with structures which could potentially contain many point-like nonlinear scatterers, there is a need to develop techniques for separately imaging the defects using a distributed sensor network which can be used either in time-reversal imaging processes or for tomographic imaging.. In this contribution, we discuss the application of Independent Component Analysis (ICA) methods to solve the problem of separating multiple nonlinear scatterers distributed throughout a sample, either by combining ICA with time reversal or by using ICA in conjunction with a tomographic experiment. We illustrate the procedure for ICA based tomographic imaging of multiple scatterers in an infinite medium.
NASA Technical Reports Server (NTRS)
Davis, A. B.; Varnai, T.; Marshak, A.
2010-01-01
The primary goal of NASA's current ICESat and future ICESat2 missions is to map the altitude of the Earth's land ice with high accuracy using laser altimetry technology, and to measure sea ice freeboard. Ice however is a highly transparent optical medium with variable scattering and absorption properties. Moreover, it is often covered by a layer of snow with varying depth and optical properties largely dependent on its age. We describe a modeling framework for estimating the potential altimetry bias caused by multiple scattering in the layered medium. We use both a Monte Carlo technique and an analytical diffusion model valid for optically thick media. Our preliminary numerical results are consistent with estimates of the multiple scattering delay from laboratory measurements using snow harvested in Greenland, namely, a few cm. Planned refinements of the models are described.
NASA Astrophysics Data System (ADS)
Cheng, Ying; Liu, XiaoJun
2008-11-01
It was qualitatively demonstrated through finite-element full-wave simulations that acoustic cloak can be constructed by using concentric multilayered structure with alternating homogeneous isotropic materials [Y. Cheng et al., Appl. Phys. Lett. 92, 151913 (2008)]. Here we present a sequential in-depth analysis of the proposed cloak by means of the multiple-scattering algorithms. Calculated pressure fields demonstrate that the cloak possesses low-reflection and wavefront-bending properties. The scattering patterns further characterize the directional cloaking performance in the far field, which is consistent with the pressure fields. The mechanism of the cloaking is ascribed to a specific multiple-scattering process determined by the microscopic material distribution and structural details of the cloak. We also discuss the behavior of the multilayered cloak as a function of wavelength.
On the multiple scattering of VHF/UHF waves in the equatorial ionosphere
NASA Technical Reports Server (NTRS)
Vats, H. O.
1981-01-01
Using amplitude data of radio beacons at 40, 140, and 360 MHz from ATS 6 (phase II), an attempt has been made to study scattering of these waves in the equatorial ionosphere. A comparison of observed scintillation index S sub 4 with the theoretical results of the multiple scattering approach and variation of autocorrelation time with frequency indicates that this theory explains the results to a large extent. A comparison of power spectra of amplitude records with the ionograms of a nearby equatorial station has led to the following conclusions: the change from a weak scattering regime to a strong scattering regime is gradual and occurs because of the gradual decrease in the scale size of the irregularities (i.e., broadening of the spectra) and the gradual increase in the thickness of the irregular region.
Simulating the effects of multiple scattering on images of dense sprays and particle fields.
Jermy, Mark C; Allen, Andrew
2002-07-10
Most optical measurements in turbid media (including sprays, fogs, particulate and colloidal suspensions) assume single scattering of the detected photons. Multiple scattering introduces error, which has been quantified in very few systems. To quantify this error, we have written a flexible Monte Carlo photon transport simulation code capable of handling any three-dimensional geometry. Simulations of planar laser spray imaging with large, nonabsorbing particles show that up to 50% of the photons reaching the camera are multiply scattered. Because forward scattering dominates, the image is affected little. For particles with more absorption or with size closer to the wavelength of the light than those we have simulated, the effects are expected to be more serious. PMID:12141519
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.
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.
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
Multiple Scattering in Beam-line Detectors of the MUSE Experiment
NASA Astrophysics Data System (ADS)
Garland, Heather; Robinette, Clay; Strauch, Steffen; MUon Scattering Experiment (MUSE) Collaboration
2015-10-01
The charge radius of the proton has been obtained precisely from elastic electron-scattering data and spectroscopy of atomic hydrogen. However, a recent experiment using muonic hydrogen, designed for high-precision, presented a charge radius significantly smaller than the accepted value. This discrepancy certainly prompts a discussion of topics ranging from experimental methods to physics beyond the Standard Model. The MUon Scattering Experiment (MUSE) collaboration at the Paul Scherrer Institute, Switzerland, is planning an experiment to measure the charge radius of the proton in elastic scattering of electrons and muons of positive and negative charge off protons. In the layout for the proposed experiment, detectors will be placed in the beam line upstream of a hydrogen target. Using Geant4 simulations, we studied the effect of multiple scattering due to these detectors and determined the fraction of primary particles that hit the target for a muon beam at each beam momentum. Of the studied detectors, a quartz Cherenkov detector caused the largest multiple scattering. Our results will guide further optimization of the detector setup. Supported in parts by the U.S. National Science Foundation: NSF PHY-1205782.
Time-domain numerical simulations of multiple scattering to extract elastic effective wavenumbers
NASA Astrophysics Data System (ADS)
Chekroun, Mathieu; Le Marrec, Loïc; Lombard, Bruno; Piraux, Joël
2012-08-01
Elastic wave propagation is studied in a heterogeneous two-dimensional medium consisting of an elastic matrix containing randomly distributed circular elastic inclusions. The aim of this study is to determine the effective wavenumbers when the incident wavelength is similar to the radius of the inclusions. A purely numerical methodology is presented, with which the limitations usually associated with low scatterer concentrations can be avoided. The elastodynamic equations are integrated by a fourth-order time-domain numerical scheme. An immersed interface method is used to accurately discretize the interfaces on a Cartesian grid. The effective field is extracted from the simulated data, and signal-processing tools are used to obtain the complex effective wavenumbers. The numerical reference solution thus obtained can be used to check the validity of multiple scattering analytical models. The method is applied to the case of concrete. A parametric study is performed on longitudinal and transverse incident plane waves at various scatterer concentrations. The phase velocities and attenuations determined numerically are compared with predictions obtained with multiple scattering models, such as the Independent Scattering Approximation model, the Waterman-Truell model, and the more recent Conoir-Norris model.
Technology Transfer Automated Retrieval System (TEKTRAN)
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...
Scattering from phase-separated vesicles. I. An analytical form factor for multiple static domains
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
NASA Astrophysics Data System (ADS)
Li, Meng; Jiang, Li-Hui; Xiong, Xing-Long; Ma, Yu-Zhao; Liu, Jie-Sheng
2016-08-01
Layer boundaries detection with LIDAR is of great significance for the meteorological and environmental research. Apart from the background noise, multiple scattering can also seriously affect the detection results in LIDAR signal processing. To alleviate these issues, a novel approach was proposed based upon morphological filtering and multiple scattering correction with multiple iterations, which essentially acts as a weighted algorithm with multiple scattering factors in different filtering scales, and applies integral extinction coefficients as media to perform correction. Simulations on artificial signals and real LIDAR signals support this approach.
NASA Astrophysics Data System (ADS)
Li, Meng; Jiang, Li-Hui; Xiong, Xing-Long; Ma, Yu-Zhao; Liu, Jie-Sheng
2016-05-01
Layer boundaries detection with LIDAR is of great significance for the meteorological and environmental research. Apart from the background noise, multiple scattering can also seriously affect the detection results in LIDAR signal processing. To alleviate these issues, a novel approach was proposed based upon morphological filtering and multiple scattering correction with multiple iterations, which essentially acts as a weighted algorithm with multiple scattering factors in different filtering scales, and applies integral extinction coefficients as media to perform correction. Simulations on artificial signals and real LIDAR signals support this approach.
A multiple-scattering approach to transient electromagnetic interaction with plasmas
NASA Technical Reports Server (NTRS)
Bowhill, S. A.; Gray, K. G.
1978-01-01
A multiple-scattering method is described which is applicable to the transient plasma problem concerning the interaction between transient electromagnetic waves and plasmas. The method starts with the time-dependent wave fields scattered by a linear electric dipole when illuminated by a transient plane wave. It avoids the use of Fourier transform methods and provides additional physical insight into the origin of the frequency-dispersive properties of material media. The results are applicable only to cold plasmas since spatial dispersion is neglected, implying that effects due to thermal velocities of electrons - such as incoherent scatter - are not covered by the theory. The advantages of the method for initiation of the student into transient electromagnetics in dispersive media are identified as conceptual simplicity and computational simplicity. The entire analysis is in the time domain.
Quantum correlations of magnetic impurities by a multiple electron scattering in carbon nanotubes
NASA Astrophysics Data System (ADS)
Gamboa Angulo, Didier; Cordourier Maruri, Guillermo; de Coss Gómez, Romeo
In this work we analyze the quantum correlations and polarizations states of magnetic impurities spins, when a multiple electron scattering was taken place. A sequence of non-correlated electrons interacts through scattering producing quantum correlation which will have an impact on the electronic transmission. We consider a short range Heisenberg interaction between ballistic electron and static impurities. We analyze the cases when the electron scattering is produce by one and two impurities, obtaining the electronic transmission rates. Concurrence and fidelity calculations are performed to obtain the level of quantum entanglement and polarization correlations. We also discuss the possible application of this model to metallic and semiconductor carbon nanotubes, which could have important implications on spintronics and quantum information devices.
Filtering random matrices: the effect of incomplete channel control in multiple scattering.
Goetschy, A; Stone, A D
2013-08-01
We present an analytic random matrix theory for the effect of incomplete channel control on the measured statistical properties of the scattering matrix of a disordered multiple-scattering medium. When the fraction of the controlled input channels, m1, and output channels, m2, is decreased from unity, the density of the transmission eigenvalues is shown to evolve from the bimodal distribution describing coherent diffusion, to the distribution characteristic of uncorrelated Gaussian random matrices, with a rapid loss of access to the open eigenchannels. The loss of correlation is also reflected in an increase in the information capacity per channel of the medium. Our results have strong implications for optical and microwave experiments on diffusive scattering media. PMID:23971574
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.
Degree and plane of polarization of multiple scattered light. 2: Earth's atmosphere with aerosols
NASA Technical Reports Server (NTRS)
Plass, G. N.; Kattawar, G. W.
1972-01-01
The degree of polarization, as well as the direction of the plane of polarization, were calculated by a Monte Carlo method for the reflected and transmitted photons from the earth's atmosphere. The solar photons were observed during multiple collisions with aerosols and the Rayleigh scattering centers in the atmosphere. The aerosol number density, as well as the ratio of aerosol to Rayleigh scattering, varies with height. The proportion of aerosol to Rayleigh scattering was appropriately chosen at each wavelength 0.4 microns and 0.7 microns; ozone absorption was included where appropriate. Three different aerosol number densities were used to study the effects of aerosol variations. Results are given for a solar zenith angle of 81.37 deg and a surface albedo of zero. The polarization of the reflected and transmitted photons was found to be sensitive to the amount of aerosols in the atmosphere at certain angles of observation.
Research on multiple-scattering channel with Monte Carlo model in UV atmosphere communication.
Han, Dahai; Fan, Xing; Zhang, Kai; Zhu, Rui
2013-08-01
A non-line-of-sight (NLOS) ultraviolet (UV) communication channel model is established by using a Monte Carlo simulation method based on photon tracing. This method considers the multiple-scattering effects of UV signal propagation in the atmosphere, and simulates the condition of dual receivers for diversity reception. The channel characteristics of the UV communication are obtained by simulating the photon arrival probabilities. The model is employed to study the characteristics of NLOS UV scattering channels for a variety of scattering conditions, including the separation distance between transmitter and receiver, transmit/receive elevation angle, beam divergence, and field of view. The model has advantages in reliable prediction of UV communication for the dual-receiver condition, as validated by outdoor experiments at fixed elevation angles. PMID:23913073
NASA Astrophysics Data System (ADS)
Eshwarappa, Kunabevu Mallikarjunappa; Kiran, Kiggal Udayashankar; Ravindraswami, Kalladka; Somashekarappa, Hiriyur Mallaiah
2014-11-01
Saturation thickness for multiple scattering gamma rays from multiple sources has been measured experimentally and simulated using the Monte Carlo N-Particle (MCNP) Code. Experimental measurements were performed using a collimated beam of gamma-rays from 57Co, 203Hg, 133Ba, 22Na, 137Cs, 65Zn and 60Co sources. The gamma rays were directed at rectangular aluminium targets of varying thickness. A NaI (Tl) scintillation detector placed at a backscattering angle of 180° was used to detect the scattered photons. The measured and calculated saturation thickness increases with increasing energy of incident gamma-rays. Experimental and simulated values are compared and are in good agreement.
Multiple scattering from finite inhomogeneous media. [internal reflection of electromagnetic waves
NASA Technical Reports Server (NTRS)
Tang, C. C. H.
1974-01-01
Utilizing the characteristic information concerning the apparent phase constant difference between the electric and magnetic fields propagating in an inhomogeneous medium, a theoretical analysis of the multiple scattering of electromagnetic waves in finite inhomogeneous media is presented. The solution is obtained by first approximating the coefficients of a pair of exact coupled first-order differential equations and then solving the equations by first-order iteration. The present first-order approximate solution with multiple scattering considerations is shown to be more accurate than the WKB solution. Methods to improve the accuracy of the first-order solution further are discussed. Application of the solution to slowly varying finite media with periodic properties demonstrates the validity of the solution. The same approach can be extended to frequencies in the optical region by retaining additional terms in the coefficients of the coupled differential equations.
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.
NASA Technical Reports Server (NTRS)
Ben-David, Avishai
1992-01-01
Knowing the optical properties of aerosol dust is important for designing electro-optical systems and for modeling the effect on propagation of light in the atmosphere. As CO2 lidar technology becomes more advanced and is used for multiwavelength measurements, information on the wavelength dependent backscattering of aerosol dust particles is required. The volume backscattering coefficient of aerosols in the IR is relatively small. Thus, only a few field measurements of backscattering, usually at only a few wavelengths, are reported in the literature. We present spectral field measurements of backscattering of kaolin dust in the 9-11 micron wavelength range. As the quantity of dust increases, multiple scattering contributes more to the measured backscattered signal. The measurements show the effect of the dust quantity of the spectral backscatter measurements. A simple analytical two stream radiative transfer model is applied to confirm the measurements and to give insight to the multiple scattering spectra of backscattering.
Multiple-mode Lamb wave scattering simulations using 3D elastodynamic finite integration technique.
Leckey, Cara A C; Rogge, Matthew D; Miller, Corey A; Hinders, Mark K
2012-02-01
We have implemented three-dimensional (3D) elastodynamic finite integration technique (EFIT) simulations to model Lamb wave scattering for two flaw-types in an aircraft-grade aluminum plate, a rounded rectangle flat-bottom hole and a disbond of the same shape. The plate thickness and flaws explored in this work include frequency-thickness regions where several Lamb wave modes exist and sometimes overlap in phase and/or group velocity. For the case of the flat-bottom hole the depth was incrementally increased to explore progressive changes in multiple-mode Lamb wave scattering due to the damage. The flat-bottom hole simulation results have been compared to experimental data and are shown to provide key insight for this well-defined experimental case by explaining unexpected results in experimental waveforms. For the rounded rectangle disbond flaw, which would be difficult to implement experimentally, we found that Lamb wave behavior differed significantly from the flat-bottom hole flaw. Most of the literature in this field is restricted to low frequency-thickness regions due to difficulties in interpreting data when multiple modes exist. We found that benchmarked 3D EFIT simulations can yield an understanding of scattering behavior for these higher frequency-thickness regions and in cases that would be difficult to set up experimentally. Additionally, our results show that 2D simulations would not have been sufficient for modeling the complicated scattering that occurred. PMID:21908011
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.
Two-loop self-energy and multiple scattering at finite temperature
Kapusta, J. I.; Wong, S. M. H.
2001-08-15
One- and two-loop self-energies are worked out explicitly for a heavy scalar field interacting weakly with a light self-interacting scalar field at finite temperature. The ring or daisy diagrams and a set of necklace diagrams can be summed simultaneously. This simple model serves to illustrate the connection between multiloop self-energy diagrams and multiple scattering in a medium.
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.
Coulomb corrections to the parameters of the Molière multiple scattering theory
NASA Astrophysics Data System (ADS)
Kuraev, Eduard; Voskresenskaya, Olga; Tarasov, Alexander
2014-06-01
High-energy Coulomb corrections to the parameters of the Molière multiple scattering theory are obtained. Numerical calculations are presented in the range of the nuclear charge number of the target atom 6⪕Z⪕92. It is shown that these corrections have a large value for sufficiently heavy elements of the target material and should be taken into account in describing high-energy experiments with nuclear targets.
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.
Low-temperature lattice-scattering mobility in multiple heterojunctions: Phonon-drag enhancement
Lyo, S.K. )
1991-01-15
The temperature dependence of the low-temperature lattice-scattering mobility (LSM) of a heterojunction as well as a multiple-heterojunction structure is obtained. We show that the LSM of a multiple-heterojunction structure can be significantly enhanced as compared to that of a single heterojunction due to the phonon-drag effect. The high-temperature approximation employed for the LSM in the current literature is found to underestimate significantly the LSM as well as the deformation-potential coefficient.
Wandinger, U
1998-01-20
A formalism describing the influence of multiple scattering on cloud measurements with Raman and high-spectral-resolution lidars is presented. Model calculations including both particulate and molecular scattering processes are performed to describe the general effects of multiple scattering on both particulate and molecular lidar backscatter signals. It is found that, for typical measurement geometries of ground-based lidars, as many as five scattering orders contribute significantly to the backscattered light. The relative intensity of multiple-scattered light is generally larger in signals backscattered from molecules than in signals backscattered from particles. The multiple-scattering formalism is applied to measurements of water and ice clouds taken with a Raman lidar. Multiple-scattering errors of measured extinction coefficients are typically of the order of 50% at the bases of both water and ice clouds and decrease with increasing penetration depth to below 20%. In contrast, the multiple-scattering errors of backscatter coefficients are negligible in ice clouds and below 20% in water clouds. PMID:18268599
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.
Doc, Jean-Baptiste; Conoir, Jean-Marc; Marchiano, Régis; Fuster, Daniel
2016-04-01
The weakly nonlinear propagation of acoustic waves in monodisperse bubbly liquids is investigated numerically. A hydrodynamic model based on the averaged two-phase fluid equations is coupled with the Rayleigh-Plesset equation to model the dynamics of bubbles at the local scale. The present model is validated in the linear regime by comparing with the Foldy approximation. The analysis of the pressure signals in the linear regime highlights two resonance frequencies: the Minnaert frequency and a multiple scattering resonance that strongly depends on the bubble concentration. For weakly nonlinear regimes, the generation of higher harmonics is observed only for the Minnaert frequency. Linear combinations between the Minnaert harmonics and the multiple scattering resonance are also observed. However, the most significant effect observed is the appearance of softening-hardening effects that share some similarities with those observed for sandstones or cracked materials. These effects are related to the multiple scattering resonance. Downward or upward resonance frequency shifts can be observed depending on the characteristic of the incident wave when increasing the excitation amplitude. It is shown that the frequency shift can be explained assuming that the acoustic wave velocity depends on a law different from those usually encountered for sandstones or cracked materials. PMID:27106317
Generalization of the Gluckstern formulas II: Multiple scattering and non-zero dip angles
NASA Astrophysics Data System (ADS)
Valentan, M.; Regler, M.; Frühwirth, R.
2009-07-01
The first rules-of-thumb for the uncertainties in track momentum and direction of tracking detectors under inclusion of multiple scattering, as developed by Gluckstern [Nucl. Instr. and Meth. 24 (1963) 381] in the times of the bubble chamber, were limited to tracks with low curvature and equidistant measurement points with equal accuracy. The extension to strongly curved tracks with nonvanishing incident angle, arbitrary detector configuration and accuracy was published recently [M. Regler, R. Frühwirth, Nucl. Instr. and Meth. A 589 (2008) 109]. However, this extension is restricted to the (symmetry) plane with tracks with zero dip angle, perpendicular to the magnetic field, and does not treat multiple scattering. The present study extends the analytical approximate formulas for the calculation of uncertainties in track momentum and direction of “barrel” detectors to non-zero dip angles, including multiple scattering. The dip angle dependence of all terms of the error matrix is calculated. The results of a comparison with a linear least-squares fit are presented, showing excellent agreement. An open source implementation of the exact covariance matrices is described.
An hybrid computing approach to accelerating the multiple scattering theory based ab initio methods
NASA Astrophysics Data System (ADS)
Wang, Yang; Stocks, G. Malcolm
2014-03-01
The multiple scattering theory method, also known as the Korringa-Kohn-Rostoker (KKR) method, is considered an elegant approach to the ab initio electronic structure calculation for solids. Its convenience in accessing the one-electron Green function has led to the development of locally-self consistent multiple scattering (LSMS) method, a linear scaling ab initio method that allows for the electronic structure calculation for complex structures requiring tens of thousands of atoms in unit cell. It is one of the few applications that demonstrated petascale computing capability. In this presentation, we discuss our recent efforts in developing a hybrid computing approach for accelerating the full potential electronic structure calculation. Specifically, in the framework of our existing LSMS code in FORTRAN 90/95, we explore the many core resources on GPGPU accelerators by implementing the compute intensive functions (for the calculation of multiple scattering matrices and the single site solutions) in CUDA, and move the computational tasks to the GPGPUs if they are found available. We explain in details our approach to the CUDA programming and the code structure, and show the speed-up of the new hybrid code by comparing its performances on CPU/GPGPU and on CPU only. The work was supported in part by the Center for Defect Physics, a DOE-BES Energy Frontier Research Center.
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.
Multiple-scattering lidar from both sides of the clouds: Addressing internal structure
NASA Astrophysics Data System (ADS)
Davis, A. B.
2008-07-01
Multiple-scattering (a.k.a. "off-beam") lidar is an emerging technology in cloud remote sensing. It delivers, as in classic lidar ceilometry, cloud base altitude but also the cloud's physical thickness H as well as its optical depth τ (averaged over horizontal scales on the order of H). The value of τ in fact must lie beyond the range accessible by standard (i.e., single-scattering/on-beam) lidar profiling, namely, up to 3-4. A refined diffusion-theoretical model is presented here for signals from multiple-scattering lidar and applied, on the one hand, to retrieval algorithm development and, on the other hand, signal-to-noise ratio (SNR) estimation. SNRs are computed for LANL's ground-based Wide-Angle Imaging Lidar (WAIL) system and NASA's space-based Lidar-In-space Technology Experiment (LITE). The refinements are threefold and all about internal structure. First, the laser source is modeled as a collimated anisotropic exponentially distributed internal source rather than an isotropic point source at the cloud boundary; this opens the possibility of using δ-Eddington rescaling to capture the forward peaked phase function more effectively within the diffusion framework. Second, stratification of the scattering coefficient is modeled as an increasing function of distance to cloud base; this strongly differentiates the signals when observed from above or from below. Finally, Cairns' rescaling is applied to this conservative scattering problem to account for the systematic effects of random (turbulence-driven) internal variability at scales up to a few mean free paths.
Multiple-scattering analysis of laser-beam propagation in the atmosphere and through obscurants
Zardecki, A.; Gerstl, S.A.W.
1983-01-01
The general purpose, discrete-ordinates transport code TWOTRAN is applied to describe the propagation and multiple scattering of a laser beam in a nonhomogeneous aerosol medium. For the medium composed of smoke, haze, and a rain cloud, the problem of the target detectability in a realistic atmospheric scenario is addressed and solved. The signals reflected from the target vs the signals scattered from the smoke cloud are analyzed as a function of the smoke concentration. By calculating the average intensity and a correction factor in the x-y and r-z geometries, the consistency of the rectangular and cylindrical geometry models is assessed. Received power for a detector with a small field of view is computed on a sphere of 1-km radius around the laser source for the Air Force Geophysics Laboratory rural aerosol model with extinction coefficients of 4 km/sup -1/ and 10 km/sup -1/. This computation allows us to study the received power as a function of the angle between the detector and source axes. The correction factor describing the multiple-scattering enhancement with respect to the simple Lambert-Beer law is introduced, and its calculation is employed to validate the use of the small-angle approximation for the transmissometer configuration. An outline of the theory for a finite field of view detector is followed by numerical results pertaining to the received power and intensity for various aerosol models. Recommendations regarding future work are also formulated.
NASA Astrophysics Data System (ADS)
Bendali, Abderrahmane; Cocquet, Pierre-Henri; Tordeux, Sébastien
2016-03-01
The asymptotic analysis carried out in this paper for the problem of a multiple scattering in three dimensions of a time-harmonic wave by obstacles whose size is small as compared with the wavelength establishes that the effect of the small bodies can be approximated at any order of accuracy by the field radiated by point sources. Among other issues, this asymptotic expansion of the wave furnishes a mathematical justification with optimal error estimates of Foldy's method that consists in approximating each small obstacle by a point isotropic scatterer. Finally, it is shown how this theory can be further improved by adequately locating the center of phase of the point scatterers and the taking into account of self-interactions. In this way, it is established that the usual Foldy model may lead to an approximation whose asymptotic behavior is the same than that obtained when the multiple scattering effects are completely neglected.
NASA Astrophysics Data System (ADS)
Patterson, M.; Hughes, S.; Schulz, S.; Beggs, D. M.; White, T. P.; O'Faolain, L.; Krauss, T. F.
2009-11-01
Through a combined theoretical and experimental study of disorder-induced incoherent scattering losses in slow-light photonic crystal slab waveguides, we show the importance of Bloch mode reshaping and multiple scattering. We describe a convenient and fully three-dimensional theoretical treatment of disorder-induced extrinsic scattering, including the calculation of backscatter and out-of-plane losses per unit cell, and the extrapolation of the unit-cell loss to the loss for an entire disordered waveguide. The theoretical predictions, which are also compared with recent measurements on dispersion engineered silicon waveguides, demonstrate the failure of the Beer-Lambert law due to multiple scattering. We also explain why the previously assumed group velocity scalings of disorder-induced loss break down in general.
Riley, Jason; Boukari, Hacène; Gandjbakhche, Amir; Nossal, Ralph
2012-01-01
Abstract. Fluorescence correlation spectroscopy (FCS) is increasingly being used to assess the movement of particles diffusing in complex, optically dense surroundings, in which case measurement conditions may complicate data interpretation. It is considered how a single-photon FCS measurement can be affected if the sample properties result in scattering of the incident light. FCS autocorrelation functions of Atto 488 dye molecules diffusing in solutions of polystyrene beads are measured, which acted as scatterers. Data indicated that a scattering-linked increase in the illuminated volume, as much as two fold, resulted in minimal increase in diffusivity. To analyze the illuminated beam profile, Monte-Carlo simulations were employed, which indicated a larger broadening of the beam along the axial than the radial directions, and a reduction of the incident intensity at the focal point. The broadening of the volume in the axial direction has only negligible effect on the measured diffusion time, since intensity fluctuations due to diffusion events in the radial direction are dominant in FCS measurements. Collectively, results indicate that multiple scattering does not result in FCS measurement artifacts and thus, when sufficient signal intensity is attainable, single-photon FCS can be a useful technique for measuring probe diffusivity in optically dense media. PMID:23208294
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.
Zustiak, Silviya; Riley, Jason; Boukari, Hacène; Gandjbakhche, Amir; Nossal, Ralph
2012-12-01
Fluorescence correlation spectroscopy (FCS) is increasingly being used to assess the movement of particles diffusing in complex, optically dense surroundings, in which case measurement conditions may complicate data interpretation. It is considered how a single-photon FCS measurement can be affected if the sample properties result in scattering of the incident light. FCS autocorrelation functions of Atto 488 dye molecules diffusing in solutions of polystyrene beads are measured, which acted as scatterers. Data indicated that a scattering-linked increase in the illuminated volume, as much as two fold, resulted in minimal increase in diffusivity. To analyze the illuminated beam profile, Monte-Carlo simulations were employed, which indicated a larger broadening of the beam along the axial than the radial directions, and a reduction of the incident intensity at the focal point. The broadening of the volume in the axial direction has only negligible effect on the measured diffusion time, since intensity fluctuations due to diffusion events in the radial direction are dominant in FCS measurements. Collectively, results indicate that multiple scattering does not result in FCS measurement artifacts and thus, when sufficient signal intensity is attainable, single-photon FCS can be a useful technique for measuring probe diffusivity in optically dense media. PMID:23208294
NASA Astrophysics Data System (ADS)
Ushakova, O. V.; Kuznetsova, L. V.; Zimnyakov, D. A.
2007-05-01
Diffuse reflectance of polarized light is studied in application to characterization of multiple scattering anisotropic media (such as, e.g., the fibrous tissues) with the use of focused probe laser beam. The theoretical model for description of the transport properties (the values of transport scattering coefficients and effective refractive index for different polarization states of probe light) of closely packed systems of partially disordered dielectric cylinders is considered on the base of coherent potential approximation. The influence of structural and optical characteristics of fibrous systems (such as the volume fraction of cylindrical scatters, their average diameter, the degree of disorder, refractive indices of scatters and surrounding medium) on diagnostical parameters determined with the polarization videoreflectometry can be analyzed in the framework of the considered theoretical model. The obtained theoretical results satisfactorily agree with the experimental data on polarization videoreflectometry and spectral-polarization measurements in the transmittance mode of in-vitro samples of demineralized bone, muscular tissue and phantom samples (partially oriented polymer films).
Correction for multiple scattering of unpolarized photons in attenuation coefficient measurements
Fernandez, J.E.; Sumini, M.; Satori, R.
1995-01-01
Calculations of the diffusion of unpolarized photons in thin thickness targets have been performed with recourse to a vector transport model taking rigorously into account the polarization introduced by the scattering interactions. An order-of-interactions solution of the Boltzmann transport equation for photons was used to describe the multiple scattering terms due to the prevailing effects in the X-ray regime. An analytical expression for the correction factor to the attenuation coefficient is given in term of the solid angle subtended by the detector and the energy interval characterizing the detection response. Although the main corrections are due to the influence of the pure Rayleigh effect, first- and second-order chains involving the Rayleigh and Compton effects have been considered as possible sources of overlapping contributions to the transmitted intensity. The extent of the corrections is estimated and some examples are given for pure element targets.
A Bayesian approach for high resolution imaging of small changes in multiple scattering media.
Xie, Fan; Moreau, Ludovic; Zhang, Yuxiang; Larose, Eric
2016-01-01
This paper introduces a Bayesian approach to achieve high-resolution imaging of sub-wavelength changes in the presence of multiple scattering. The approach is based on the minimization of a cost function defined by the decorrelations induced in the measured waveforms by the apparition of a local changes. Minimization is achieved via a Monte Carlo Markov Chain (MCMC) algorithm combined to an analytical model that computes the sensitivity kernel of the medium. In the inversion procedure, the parameters to infer represent the physics of the problem, such as the diffusivity in the medium and/or the geometrical features of the reflector (position and scattering cross-section). The method is successfully compared to the linear inversion approach initially proposed for the so-called Locadiff imaging method through several examples, both numerical and experimental. PMID:26341851
Houamer, Salim; Popov, Yuri V.; Dal Cappello, Claude
2010-03-15
The first Born approximation is examined for different fast capture processes for the p+He system at incident energies of about 1 MeV. Calculations have been performed for the singly differential cross section (SDCS) for scattering angles 0-0.5 mrad in the laboratory frame. In the case of transfer ionization, we observe that the two-step-2 mechanism has a dominant contribution to the SDCS for the kinematics considered in this work. The present investigation demonstrates that the multiple peaking approximation is a very crude method which fails to describe the SDCS even at scattering angles below 0.5 mrad. We have also presented a doubly differential cross section for the fixed emission energy of 600 eV and compared our results with other theoretical calculations and experiments.
NASA Astrophysics Data System (ADS)
Sica, R. J.; Haefele, A.
2014-12-01
The measurement of temperature in the middle atmosphere with Rayleigh-scatter lidars is an important technique for assessing atmospheric change. Current retrieval schemes for these temperature have several shortcoming which can be overcome using an optimal estimation method (OEM). OEMs are applied to the retrieval of temperature from Rayleigh-scatter lidar measurements using both single and multiple channel measurements. Forward models are presented that completely characterize the measurement and allow the simultaneous retrieval of temperature, dead time and background. The method allows a full uncertainty budget to be obtained on a per profile basis that includes, in addition to the statistical uncertainties, the smoothing error and uncertainties due to Rayleigh extinction, ozone absorption, the lidar constant, nonlinearity in the counting system, variation of the Rayleigh-scatter cross section with altitude, pressure, acceleration due to gravity and the variation of mean molecular mass with altitude. The vertical resolution of the temperature profile is found at each height, and a quantitative determination is made of the maximum height to which the retrieval is valid. A single temperature profile can be retrieved from measurements with multiple channels that cover different height ranges, vertical resolutions and even different detection methods. The OEM employed is shown to give robust estimates of temperature consistent with previous methods, while requiring minimal computational time. This demonstrated success of lidar temperature retrievals using an OEM opens new possibilities in atmospheric science for measurement integration between active and passive remote sensing instruments. We are currently working on extending our method to simultaneously retrieve water vapour and temperature using Raman-scatter lidar measurements.
NASA Astrophysics Data System (ADS)
Moshe, Tomer; Firer, Michael A.; Abookasis, David
2015-05-01
In this paper, we present a hybrid method for improving the imaging quality of objects obscured within a scattering environment by combining multiple elliptical polarized speckle contrast projections with the use of optical clearing agents (OCAs). Elliptically polarized light enables the probing of subsurface volumes, where OCAs decrease light scattering while increasing photons' penetration depth through the medium. Experiments were conducted on object sample and prostate cancer cells embedded within ex vivo biological samples (chicken breasts) in reflection configuration. After immersion with OCAs, the medium was irradiated with an elliptically polarized laser beam and multiple polarized speckled images obtained from a lens array were first converted to speckled contrast images and then processed using a self-deconvolution shift-and-add algorithm. The conversion to contrast images and multiple perspectives acquisition was found to emphasize contrast. Analysis of image quality indicated improvement in object visualization by the combination of elliptical polarization and OCAs. This enhanced imaging strategy may advance the development of improved methods in biomedicine field, specifically biomedical tomography.
NASA Astrophysics Data System (ADS)
Mounaix, Mickael; Andreoli, Daria; Defienne, Hugo; Volpe, Giorgio; Katz, Ori; Grésillon, Samuel; Gigan, Sylvain
2016-06-01
We report the broadband characterization of the propagation of light through a multiple scattering medium by means of its multispectral transmission matrix. Using a single spatial light modulator, our approach enables the full control of both the spatial and spectral properties of an ultrashort pulse transmitted through the medium. We demonstrate spatiotemporal focusing of the pulse at any arbitrary position and time with any desired spectral shape. Our approach opens new perspectives for fundamental studies of light-matter interaction in disordered media, and has potential applications in sensing, coherent control, and imaging.
Overcoming the Diffraction Limit Using Multiple Light Scattering in a Highly Disordered Medium
Choi, Youngwoon; Yang, Taeseok Daniel; Fang-Yen, Christopher; Kang, Pilsung; Lee, Kyoung Jin; Dasari, Ramachandra R.; Feld, Michael S.; Choi, Wonshik
2012-01-01
We report that disordered media made of randomly distributed nanoparticles can be used to overcome the diffraction limit of a conventional imaging system. By developing a method to extract the original image information from the multiple scattering induced by the turbid media, we dramatically increase a numerical aperture of the imaging system. As a result, the the resolution is enhanced by more than five times over the diffraction limit and a field of view is extended over the physical area of the camera. Our technique lays the foundation to use a turbid medium as a far-field superlens. PMID:21797607
Mounaix, Mickael; Andreoli, Daria; Defienne, Hugo; Volpe, Giorgio; Katz, Ori; Grésillon, Samuel; Gigan, Sylvain
2016-06-24
We report the broadband characterization of the propagation of light through a multiple scattering medium by means of its multispectral transmission matrix. Using a single spatial light modulator, our approach enables the full control of both the spatial and spectral properties of an ultrashort pulse transmitted through the medium. We demonstrate spatiotemporal focusing of the pulse at any arbitrary position and time with any desired spectral shape. Our approach opens new perspectives for fundamental studies of light-matter interaction in disordered media, and has potential applications in sensing, coherent control, and imaging. PMID:27391722
Neumayer, P; Berger, R L; Divol, L; Froula, D H; London, R A; Macgowan, B J; Meezan, N B; Ross, J S; Sorce, C; Suter, L J; Glenzer, S H
2008-03-14
We demonstrate that multiple-ion-species plasmas greatly reduce stimulated Brillouin scattering (SBS) in high-electron temperature inertial confinement fusion hohlraums. Landau damping is increased by adding hydrogen to a CO(2) gas filled hohlraum. We find that the SBS reflectivity decreases monotonically with increasing hydrogen fraction from 18% to 3% with a simultaneous increase of laser beam transmission. Detailed simulations with a 3D laser-plasma interaction code are in agreement with the experimentally observed reduction in backscattered light. PMID:18352195
A High Performance Computing approach to model multiple Rayleigh scattering in the Earth atmosphere
NASA Astrophysics Data System (ADS)
Franssens, Ghislain; Dekemper, Emmanuel; Mateshivili, Nina; Vanhellemont, filip; fussen, didier; pieroux, didier
2016-04-01
The retrieval of atmospheric trace gases and aerosols in the Earth atmosphere from light scattering measurements typically involves an iterative inversion algorithm. A key part of this algorithm is its forward model, which takes care of calculating the amount of light that the remote sensing instrument will see, for any assumed atmosphere composition. The forward model is usually an atmospheric radiative transfer code. It is a serious challenge for a radiative transfer code to be, at the same time, sufficiently accurate and sufficiently fast, so that it can be included in the iterative retrieval loop of an operational service. An accurate code must be able to calculate multiple Rayleigh scattering (important in the UV and/or at lower altitudes) by the air in a spherical atmosphere. This is something that currently only a Monte Carlo algorithm can do. However, any Monte Carlo code is far too slow to be included in the retrieval loop, even if we make use of the currently available HPC power. We report some first results that were obtained by a new solution to this old problem. We first use a HPC cluster to tabulate multiple Rayleigh scattering in a standard Earth atmosphere, using a Monte Carlo code, as function of 6 parameters (albedo, view zenith angle, solar zenith angle, relative azimuth angle, altitude and wavelength). Then, a well chosen empirical function is fitted on the tabulated data. From this function, correction factors are derived and appropriately inserted in a fast single scattering algorithm, which so effectively becomes a multiple scattering algorithm. Since the evaluation of the empirical function is also very fast, we end up with a radiative transfer code that is both accurate and sufficiently fast for operational data production. Our conclusion is that commonly available and affordable HPC systems can still not directly solve the retrieval problem with sufficient accuracy in real time. However, the above described two step approach now becomes
NASA Astrophysics Data System (ADS)
Cohen, B. I.; Baldis, H. A.; Berger, R. L.; Williams, E. A.; Labaune, C.
1999-11-01
Multiple laser beam experiments with CH target foils at the LULI facility demonstrate anti-correlation of stimulated Brillouin and Raman backscatter (SBS and SRS).(C. Labaune, et al.), Phys. Plasmas 6, 2048 (1999). Detailed Thomson scattering diagnostics show that SBS precedes SRS, that secondary electron plasma waves can accompany SRS appropriate to the Langmuir Decay Instability (LDI), and that with multiple interaction beams the SBS signal in the primary laser beam is reduced while the SRS signal is enhanced and onsets earlier. Analysis and numerical calculations are presented that evaluate the influence of mode coupling (B. Cohen, et al.), Phys. Plasmas 5, 3402 (1998). of SBS and LDI ion waves and local pump depletion in laser hot spots. The modeling suggests that ponderomotive and thermal self-focusing should modify the probability distribution of intense speckles and enhance the local pump depletion and ion wave mode coupling.
Multiple solutions to dense systems in radar scattering using a preconditioned block GMRES solver
Boyse, W.E.
1996-12-31
Multiple right-hand sides occur in radar scattering calculations in the computation of the simulated radar return from a body at a large number of angles. Each desired angle requires a right-hand side vector to be computed and the solution generated. These right-hand sides are naturally smooth functions of the angle parameters and this property is utilized in a novel way to compute solutions an order of magnitude faster than LINPACK The modeling technique addressed is the Method of Moments (MOM), i.e. a boundary element method for time harmonic Maxwell`s equations. Discretization by this method produces general complex dense systems of rank 100`s to 100,000`s. The usual way to produce the required multiple solutions is via LU factorization and solution routines such as found in LINPACK. Our method uses the block GMRES iterative method to directly iterate a subset of the desired solutions to convergence.
Otsuki, Soichi
2016-02-01
This paper presents a theory describing totally incoherent multiple scattering of turbid spherical samples. It is proved that if reciprocity and mirror symmetry hold for single scattering by a particle, they also hold for multiple scattering in spherical samples. Monte Carlo simulations generate a reduced effective scattering Mueller matrix, which virtually satisfies reciprocity and mirror symmetry. The scattering matrix was factorized by using the symmetric decomposition in a predefined form, as well as the Lu-Chipman polar decomposition, approximately into a product of a pure depolarizer and vertically oriented linear retarding diattenuators. The parameters of these components were calculated as a function of the polar angle. While the turbid spherical sample is a pure depolarizer at low polar angles, it obtains more functions of the retarding diattenuator with increasing polar angle. PMID:26831777
A triple axis double crystal multiple reflection camera for ultra small angle X-ray scattering
NASA Astrophysics Data System (ADS)
Lambard, Jacques; Lesieur, Pierre; Zemb, Thomas
1992-06-01
To extend the domain of small angle X-ray scattering requires multiple reflection crystals to collimate the beam. A double crystal, triple axis X-ray camera using multiple reflection channel cut crystals is described. Procedures for measuring the desmeared scattering cross-section on absolute scale are described as well as the measurement from several typical samples : fibrils of collagen, 0.3 μm diameter silica spheres, 0.16 μm diameter interacting latex spheres, porous lignite coal, liquid crystals in a surfactant-water system, colloidal crystal of 0.32 μm diameter silica spheres. L'extension du domaine de diffusion des rayons-X vers les petits angles demande l'emploi de cristaux à réflexions multiples pour collimater le faisceau. Nous décrivons une caméra à rayons-X à trois axes où les réflexions multiples sont réalisées dans deux cristaux à gorge. Nous donnons ensuite les procédures de déconvolution pour obtenir la section efficace de diffusion en échelle absolue, ainsi que les résultats des mesures effectuées avec plusieurs échantillons typiques : fibres de collagène, sphères de silice de 0,3 μm de diamètre, sphères de latex de 0,16 μm de diamètre en interaction, charbon lignite poreux, cristaux liquides formés dans un système eau-tensioactif, solution colloïdale de sphères de silice de 0,32 μm de diamètre.
Multiple scattering of polarized light in turbid birefringent media: a Monte Carlo simulation.
Otsuki, Soichi
2016-07-20
Multiple scattering of polarized light in a birefringent turbid plane medium was studied using a Monte Carlo simulation. The reduced effective scattering Mueller matrix obtained in the simulation was factorized in two dimensions using the Lu-Chipman decomposition, yielding polarization parameters that exhibited dependences on the azimuth and the radial distance around the illumination point. We propose a double-scattering model for the propagation of polarized photons in turbid infinite plane media. When the birefringence slow axis is along the azimuth of 90° on the plane surface, the retardance becomes the largest negative along the azimuth of 0° and the largest positive along the azimuth of 90° and increases with increasing the azimuth from 0° to 90°. This azimuthal dependence may result from the overlap of the contributions from the light propagations vertical to, and lateral along, the plane surface. Thus, the dependences on the azimuth and the radial distance of the polarization parameters, such as the retardance, its orientation, optical rotation, and the depolarization coefficients, are correctly predicted. PMID:27463921
Inverse scattering solutions by a sinc basis, multiple source, moment method--Part I: Theory.
Johnson, S A; Tracy, M L
1983-10-01
A new method for solving the inverse scattering problem for the scalar, inhomogeneous, exact, Helmholtz wave equation is presented. No perturbation approximations are used and the method is applicable even for many cases where weak to moderate attenuation and moderate to strong refraction of incident fields occur. The ill-posed nature of the inverse scattering problem for a single monochromatic source is known. However, the use of multiple sources, the collection of redundant (i.e., overdetermined) data, and the constraining of the fields and complex refractive index to be spatially band limited constitutes a new problem. The cases we have tested by computer simulation indicate that the new problem is well posed, a unique solution, and is stable with noisy data. The method is an application of the well-known method of moments with sinc basis and delta testing functions to discretize the problem. The inverse scattering solution may be obtained by solving the resulting set of simultaneous, quadratic, multivariate equations. Several algorithms for solving these equations are given. PMID:6686901
Potential effect of resonant scattering from multiple swimbladders on audition in juvenile fish
NASA Astrophysics Data System (ADS)
Hastings, Mardi C.
2003-04-01
The swimbladder, a gas-filled chamber in the abdominal cavity of most bony fishes, is a hydrostatic organ that enables fish to maintain neutral buoyancy; however, it also responds to acoustic pressure and radiates a secondary acoustic field that enhances detection capability of the inner ear. Recent experiments have indicated that resonant response of the swimbladder may control the auditory bandwidth in at least four species of fish [Hastings et al., J. Acoust. Soc. Am. 110, 2640 (2001)]. The auditory bandwidths of these fishes, however, do not change appreciably while they grow even though the resonance frequency of the swimbladder decreases with increasing body length. Results of an analysis inspired by Feiullade et al. [J. Acoust. Soc. Am. 112, 2206 (2002)] show that the downward shift and broadening associated with resonance of the aggregate scattered field from multiple fish is perhaps sufficient enough to account for this discrepancy. Effects of resonant characteristics of a single swimbladder, fish length, and number of fish on the changes in the collective scattered field are presented. Thus the resonant scattered field created by relatively large schools of juvenile fish may enhance their auditory capability.
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.
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.
Modelling and rapid simulation of multiple red blood cell light scattering
Zohdi, T.I; Kuypers, F.A
2006-01-01
The goal of this work is to develop a computational framework to rapidly simulate the light scattering response of multiple red blood cells. Because the wavelength of visible light (3.8×10−7 m≤λ≤7.2×10−7 m) is approximately an order of magnitude smaller than the diameter of a typical red blood cell scatterer (d≈8×10−6 m), geometric ray-tracing theory is applicable, and can be used to quickly ascertain the amount of optical energy, characterized by the Poynting vector, that is reflected and absorbed by multiple red blood cells. The overall objective is to provide a straightforward approach that can be easily implemented by researchers in the field, using standard desktop computers. Three-dimensional examples are given to illustrate the approach and the results compare quite closely to experiments on blood samples conducted at the Children's Hospital Oakland Research Institute (CHORI). PMID:17015301
Green's function multiple-scattering theory with a truncated basis set: An augmented-KKR formalism
Alam, Aftab; Khan, Suffian N.; Smirnov, A. V.; Nicholson, D. M.; Johnson, Duane D.
2014-11-04
Korringa-Kohn-Rostoker (KKR) Green's function, multiple-scattering theory is an ecient sitecentered, electronic-structure technique for addressing an assembly of N scatterers. Wave-functions are expanded in a spherical-wave basis on each scattering center and indexed up to a maximum orbital and azimuthal number L_{max} = (l,m)_{max}, while scattering matrices, which determine spectral properties, are truncated at L_{tr} = (l,m)_{tr} where phase shifts δl>l_{tr} are negligible. Historically, L_{max} is set equal to L_{tr}, which is correct for large enough L_{max} but not computationally expedient; a better procedure retains higher-order (free-electron and single-site) contributions for L_{max} > L_{tr} with δl>l_{tr} set to zero [Zhang and Butler, Phys. Rev. B 46, 7433]. We present a numerically ecient and accurate augmented-KKR Green's function formalism that solves the KKR equations by exact matrix inversion [R^{3} process with rank N(l_{tr} + 1)^{2}] and includes higher-L contributions via linear algebra [R^{2} process with rank N(l_{max} +1)^{2}]. Augmented-KKR approach yields properly normalized wave-functions, numerically cheaper basis-set convergence, and a total charge density and electron count that agrees with Lloyd's formula. We apply our formalism to fcc Cu, bcc Fe and L1_{0} CoPt, and present the numerical results for accuracy and for the convergence of the total energies, Fermi energies, and magnetic moments versus L_{max} for a given L_{tr}.
Green's function multiple-scattering theory with a truncated basis set: An augmented-KKR formalism
Alam, Aftab; Khan, Suffian N.; Smirnov, A. V.; Nicholson, D. M.; Johnson, Duane D.
2014-11-04
Korringa-Kohn-Rostoker (KKR) Green's function, multiple-scattering theory is an ecient sitecentered, electronic-structure technique for addressing an assembly of N scatterers. Wave-functions are expanded in a spherical-wave basis on each scattering center and indexed up to a maximum orbital and azimuthal number Lmax = (l,m)max, while scattering matrices, which determine spectral properties, are truncated at Ltr = (l,m)tr where phase shifts δl>ltr are negligible. Historically, Lmax is set equal to Ltr, which is correct for large enough Lmax but not computationally expedient; a better procedure retains higher-order (free-electron and single-site) contributions for Lmax > Ltr with δl>ltr set to zero [Zhang andmore » Butler, Phys. Rev. B 46, 7433]. We present a numerically ecient and accurate augmented-KKR Green's function formalism that solves the KKR equations by exact matrix inversion [R3 process with rank N(ltr + 1)2] and includes higher-L contributions via linear algebra [R2 process with rank N(lmax +1)2]. Augmented-KKR approach yields properly normalized wave-functions, numerically cheaper basis-set convergence, and a total charge density and electron count that agrees with Lloyd's formula. We apply our formalism to fcc Cu, bcc Fe and L10 CoPt, and present the numerical results for accuracy and for the convergence of the total energies, Fermi energies, and magnetic moments versus Lmax for a given Ltr.« less
Green's function multiple-scattering theory with a truncated basis set: An augmented-KKR formalism
NASA Astrophysics Data System (ADS)
Alam, Aftab; Khan, Suffian N.; Smirnov, A. V.; Nicholson, D. M.; Johnson, Duane D.
2014-11-01
The Korringa-Kohn-Rostoker (KKR) Green's function, multiple-scattering theory is an efficient site-centered, electronic-structure technique for addressing an assembly of N scatterers. Wave functions are expanded in a spherical-wave basis on each scattering center and indexed up to a maximum orbital and azimuthal number Lmax=(l,mmax), while scattering matrices, which determine spectral properties, are truncated at Lt r=(l,mt r) where phase shifts δl >ltr are negligible. Historically, Lmax is set equal to Lt r, which is correct for large enough Lmax but not computationally expedient; a better procedure retains higher-order (free-electron and single-site) contributions for Lmax>Lt r with δl >ltr set to zero [X.-G. Zhang and W. H. Butler, Phys. Rev. B 46, 7433 (1992), 10.1103/PhysRevB.46.7433]. We present a numerically efficient and accurate augmented-KKR Green's function formalism that solves the KKR equations by exact matrix inversion [R3 process with rank N (ltr+1 ) 2 ] and includes higher-L contributions via linear algebra [R2 process with rank N (lmax+1) 2 ]. The augmented-KKR approach yields properly normalized wave functions, numerically cheaper basis-set convergence, and a total charge density and electron count that agrees with Lloyd's formula. We apply our formalism to fcc Cu, bcc Fe, and L 1 0 CoPt and present the numerical results for accuracy and for the convergence of the total energies, Fermi energies, and magnetic moments versus Lmax for a given Lt r.
NASA Astrophysics Data System (ADS)
Kondrat'ev, Andrei V.
2004-06-01
Variation in the correlation function of light multiply scattered by a random medium was observed with increasing the incident beam power. The light-induced motion of microparticles in suspension, caused by a high-power laser radiation, serves as an additional factor in the decorrelation of the scattered light. The experimental data are in good agreement with the results of theoretical analysis.
NASA Astrophysics Data System (ADS)
Qualls, R. J.; Zhao, W.
2004-05-01
Remote sensing technology has tremendous potential for use in natural resource studies, agriculture, water and land use management because of the spatial information contained in remote sensing images and because of the ease and/or frequency of acquiring vast amounts of surface information. However, the quantitative application of remotely sensed data is restricted by several problems. One of them is that the entities a remote sensor views are not single targets. For example, measurement show that the skin temperature of many crops can exhibit more than a 10° C difference between the leaves at the bottom and those at the top of the canopy, in addition to the usually large difference between leaves and soil substrate. Directional radiometric surface temperatures measured from above a crop represent neither the skin temperature of the crop nor the surface temperature of the soil substrate but a complex aggregate of all elements viewed. When a remote sensing device views a vegetated surface from different view angles, different combinations of canopy and soil elements at different temperatures will be seen, producing different values of "remotely sensed surface temperature." As the first step in a series of models to be developed to simulate energy balance, sensible and latent heat fluxes, and temperature profiles within a vegetation canopy, a multiple-layer canopy scattering model to estimate short wave radiation distribution within a wheat canopy was developed. This model incorporates processes of radiation penetration through gaps between leaves, and radiation absorption, reflection and transmission in leaf layers. It is able to simulate the multiple scattering processes that occur among different canopy layers, and determine the vertical distributions of upwelling, downwelling, and reflected short wave radiation within the canopy, and at the soil surface. One of the primary advantages of this model, in contrast to other models, is that the multiple scattering
Yang, S.; Park, S.; Makowski, L.; Roux, B.
2009-02-01
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 amino 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.
NASA Astrophysics Data System (ADS)
Liu, Z. Z.; Zhang, Q.; Xiao, J. J.
2016-01-01
We study the optical properties associated with both the polariton gap and the Bragg gap in periodic resonator-waveguide coupled systems, based on the temporal coupled mode theory and the transfer matrix method. Using the complex band and the transmission spectrum, it is feasible to tune the interaction between multiple Bragg scattering and local resonance, which may give rise to analogous phenomena of electromagnetically induced transparency (EIT). We further design a plasmonic slot waveguide side-coupled with local plasmonic resonators to demonstrate the EIT-like effects in the near-infrared band. Numerical calculations show that realistic amounts of metal Joule loss may destroy the interference and the total absorption is enhanced in the transparency window due to the near zero group velocity of the guiding wave.
Multiple Scattering of Seismic Waves from Ensembles of Upwardly Lossy Thin Flux Tubes
NASA Astrophysics Data System (ADS)
Hanson, Chris S.; Cally, Paul S.
2015-07-01
Our previous semi-analytic treatment of - and -mode multiple scattering from ensembles of thin flux tubes (Hanson and Cally, Astrophys. J. 781, 125, 2014a; 791, 129, 2014b) is extended by allowing both sausage and kink waves to freely escape at the top of the model using a radiative boundary condition there. As expected, this additional avenue of escape, supplementing downward loss into the deep solar interior, results in substantially greater absorption of incident - and -modes. However, less intuitively, it also yields mildly to substantially smaller phase shifts in waves emerging from the ensemble. This may have implications for the interpretation of seismic data for solar plage regions, and in particular their small measured phase shifts.
Multiple scattering filter: Application to plane defect detection in a nickel alloy
NASA Astrophysics Data System (ADS)
Trottier, Camille; Shahjhan, Sharfine; Schumm, Andreas; Aubry, Alexandre; Derode, Arnaud
2016-02-01
The ultrasonic inspection of polycrystalline media remains a challenge. The high noise levels due to interaction between the wave and the microstructure limit the efficiency of classical ultrasonic techniques to detect a defect in a coarse grain structure. The aim of this work is to reduce the influence of multiple scattering in order to increase the information obtained from the defect. The technique introduced here is based on array probes for the acquisition of the medium's response matrix by full matrix capture, after which a filter based on random matrix theory is applied. Here an improvement of this technique is applied on nickel-based alloy mock-ups that present an unfavourable grain structure and well known bulk and plane defects. The results in normal incidence and with an angle array probe of 128 elements and 5 MHz of central frequency are compared to classical phased array probe techniques.
NASA Astrophysics Data System (ADS)
Amamou, Manel L.
2016-05-01
This paper develops an analytical solution for sound, electromagnetic or any other wave propagation described by the Helmholtz equation in three-dimensional case. First, a theoretical investigation based on multipole expansion method and spherical wave functions was established, through which we show that the resolution of the problem is reduced to solving an infinite, complex and large linear system. Second, we explain how to suitably truncate the last infinite dimensional system to get an accurate stable and fast numerical solution of the problem. Then, we evaluate numerically the theoretical solution of scattering problem by multiple ideal rigid spheres. Finally, we made a numerical study to present the "Head related transfer function" with respect to different physical and geometrical parameters of the problem.
Self-interaction correction in multiple scattering theory: application to transition metal oxides
Daene, Markus W; Lueders, Martin; Ernst, Arthur; Diemo, Koedderitzsch; Temmerman, Walter M; Szotek, Zdzislawa; Wolfam, Hergert
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 the CPA approach and supercell calculations to study the electronic structure of NiO with cation vacancies.
NASA Technical Reports Server (NTRS)
Anderson, D. E., Jr.; Meier, R. R.; Hodges, R. R., Jr.; Tinsley, B. A.
1987-01-01
The H Balmer alpha nightglow is investigated by using Monte Carlo models of asymmetric geocoronal atomic hydrogen distributions as input to a radiative transfer model of solar Lyman-beta radiation in the thermosphere and atmosphere. It is shown that it is essential to include multiple scattering of Lyman-beta radiation in the interpretation of Balmer alpha airglow data. Observations of diurnal variation in the Balmer alpha airglow showing slightly greater intensities in the morning relative to evening are consistent with theory. No evidence is found for anything other than a single sinusoidal diurnal variation of exobase density. Dramatic changes in effective temperature derived from the observed Balmer alpha line profiles are expected on the basis of changing illumination conditions in the thermosphere and exosphere as different regions of the sky are scanned.
Vanadium K-edge XANES in vanadium-bearing model compounds: a full multiple scattering study.
Benzi, Federico; Giuli, Gabriele; Della Longa, Stefano; Paris, Eleonora
2016-07-01
A systematic study is presented on a set of vanadium-bearing model compounds, representative of the most common V coordination geometries and oxidation states, analysed by means of vanadium K-edge X-ray absorption near-edge spectroscopy calculations in the full multiple scattering (FMS) framework. Analysis and calibration of the free parameters of the theory under the muffin-tin approximation (muffin-tin overlap and interstitial potential) have been carried out by fitting the experimental spectra using the MXAN program. The analysis shows a correlation of the fit parameters with the V coordination geometry and oxidation state. By making use of this correlation it is possible to approach the study of unknown V-bearing compounds with useful preliminary information. PMID:27359143
Multiple-scattering effects in nucleus-nucleus reactions with Glauber theory
NASA Astrophysics Data System (ADS)
Hatakeyama, Shinya; Ebata, Shuichiro; Horiuchi, Wataru; Kimura, Masaaki
2014-09-01
A study of new unstable nuclei has become possible in new radioactive beam facilities. In order to understand the relationship between reaction observables and nuclear structure, we need reaction theory which exactly reflects the nuclear structure. The Glauber theory is a powerful tool of analyzing high energy nuclear reactions. The theory describes the multiple scattering processes, whereas the optical limit approximation (OLA), which is widely used, ignores those processes. Those effects are expected to play an important role in the nuclear collision involving unstable nuclei (see for example Phys. Rev. C 54, 1843 (1996)). Here we apply the Glauber theory to nucleus-nucleus reactions. The wave functions are generated by the Skyrme-Hartree-Fock method and are expressed in a Slater determinant that allows us to evaluate the complete Glauber amplitude easily. We calculate total reaction cross sections, elastic cross sections and differential elastic cross sections for 16~24O, 40~70Ca, 56,58Ni, 100~140Sn, 190~214Pb on proton, 4He, 12C targets and compare with experimental data. The Glauber theory gives much better description than the OLA, especially at larger scattering angles.
Reichardt, Jens; Reichardt, Susanne
2006-04-20
A method is presented that permits the determination of the cloud effective particle size from Raman- or Rayleigh-integration temperature measurements that exploits the dependence of the multiple-scattering contributions to the lidar signals from heights above the cloud on the particle size of the cloud. Independent temperature information is needed for the determination of size. By use of Raman-integration temperatures, the technique is applied to cirrus measurements. The magnitude of the multiple-scattering effect and the above-cloud lidar signal strength limit the method's range of applicability to cirrus optical depths from 0.1 to 0.5. Our work implies that records of stratosphere temperature obtained with lidar may be affected by multiple scattering in clouds up to heights of 30 km and beyond. PMID:16633433
Nagamatsu, S.; Ono, M.; Kera, S.; Okudaira, K. K.; Fujikawa, T.; Ueno, N.
2007-02-02
The polarization dependence of F K-edge X-ray absorption near edge structure (XANES) spectra of highly-oriented thin-film of polytetrafluoroethylene (PTFE) has been analyzed by using multiple scattering theory. The spectra show clear polarization dependence due to the highly-oriented structure. The multiple scattering calculations reflects a local structure around an absorbing atom. The calculated results obtained by considering intermolecular-interactions are in good agreement with the observed polarization-dependence. We have also analyzed structural models of the radiation damaged PTFE films.
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.
NASA Astrophysics Data System (ADS)
Perliski, Lori Mac
The ability to properly interpret UV-visible twilight absorption measurements of atmospheric chemical constituents is dependent on how well the optical path, or airmass factor, of light collected by the spectrometer is understood. In the case of direct light measurement, the airmass factor may be calculated from simple geometrical considerations for a spherical atmosphere. In the case of scattered light, a spherical radiative transfer model must be used. A simple single scattering model and a Monte Carlo radiative transfer scheme were developed to study the effects of multiple scattering, aerosol scattering, albedo and refraction on scattered light airmass factors. Stratospheric airmass factors are found to be relatively insensitive to multiple scattering, albedo, refraction and aerosol scattering by background aerosols at fairly short visible wavelengths (about 450 nm). Tropospheric airmass factors, on the other hand, are very sensitive to these processes. Ground albedo, refraction, multiple scattering and aerosol scattering are also important in determining photolysis rates of atmospheric species. It is found that one-dimensional photochemical model calculations of vertical column abundances of several stratospheric chemical constituents are relatively insensitive to changes in photolysis rates due to albedo, refraction and background aerosol scattering, although they are sensitive to multiple scattering. Following the June 1991 eruption of Mt. Pinatubo, OClO and BrO were observed at Fritz Peak Observatory for the first time every. The radiative and photochemical effects of the presence of Pinatubo volcanic aerosols are examined using a one-dimensional photochemical model coupled to a spherical matrix inversion radiative transfer model. Although the heterogeneous removal of NO(x) is not explicitly considered in the photochemical model, the photochemical effects of NO(x) removal may be studied by prescribing the amount of NO(x) removed by heterogeneous chemistry
NASA Astrophysics Data System (ADS)
Toft-Petersen, Rasmus; Groitl, Felix; Kure, Mathias; Lim, Joshua; Čermák, Petr; Alimov, Svyatoslav; Wilpert, Thomas; Le, Manh Duc; Quintero-Castro, Diana; Niedermayer, Christof; Schneidewind, Astrid; Habicht, Klaus
2016-09-01
A thorough experimental characterization of a multiplexing backend with multiple energy analysis on a cold-neutron triple axis spectrometer (cTAS) is presented. The prototype employs two angular segments (2 θ -segments) each containing five vertically scattering analyzers (energy channels), which simultaneously probe an energy transfer range of 2 meV at the corresponding two scattering angles. The feasibility and strength of such a vertically scattering multiple energy analysis setup is clearly demonstrated. It is shown, that the energy resolution near the elastic line is comparable to the energy resolution of a standard cTAS. The dispersion relation of the antiferromagnetic excitations in MnF2 has been mapped out by performing constant energy transfer maps. These results show that the tested setup is virtually spurion free. In addition, focusing effects due to (mis)matching of the instrumental resolution ellipsoid to the excitation branch are clearly evident.
Berginc, G
2013-11-30
We have developed a general formalism based on Green's functions to calculate the coherent electromagnetic field scattered by a random medium with rough boundaries. The approximate expression derived makes it possible to determine the effective permittivity, which is generalised for a layer of an inhomogeneous random medium with different types of particles and bounded with randomly rough interfaces. This effective permittivity describes the coherent propagation of an electromagnetic wave in a random medium with randomly rough boundaries. We have obtained an expression, which contains the Maxwell – Garnett formula at the low-frequency limit, and the Keller formula; the latter has been proved to be in good agreement with experiments for particles whose dimensions are larger than a wavelength. (coherent light scattering)
NASA Technical Reports Server (NTRS)
Tsang, Leung; Chen, Zhengxiao; Oh, Seho; Marks, Robert J., II; Chang, A. T. C.
1992-01-01
Simultaneous inversion of the three parameters was performed which included mean-grain size of ice particles in snow, snow density, and snow temperatures from five brightness temperatures. Good results for the inversion of parameters were obtained using the neural network based on the simulated data computed from the dense media radiative transfer equation that takes into account the effects of multiple scattering.
Prokudin, Alexey; Anselmino, Mauro; Boglione, Mariaelena; Melis, Stefano; Gonzalez, J. O.
2014-10-01
The unpolarised transverse momentum dependent distribution and fragmentation functions (TMDs) are extracted from HERMES and COMPASS experimental measurements of semi- inclusive deep inelastic scattering multiplicities for charged hadron production. A simple factorised functional form of the TMDs is adopted, with a Gaussian dependence on the intrinsic transverse momentum, which turns out to be quite adequate in shape.
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
X-ray absorption spectroscopy of hemes and hemeproteins in solution: multiple scattering analysis.
D'Angelo, Paola; Lapi, Andrea; Migliorati, Valentina; Arcovito, Alessandro; Benfatto, Maurizio; Roscioni, Otello Maria; Meyer-Klaucke, Wolfram; Della-Longa, Stefano
2008-11-01
A full quantitative analysis of Fe K-edge X-ray absorption spectra has been performed for hemes in two porphynato complexes, that is, iron(III) tetraphenylporphyrin chloride (Fe(III)TPPCl) and iron(III) tetraphenylporphyrin bis(imidazole) (Fe(III)TPP(Imid)2), in two protein complexes whose X-ray structure is known at atomic resolution (1.0 A), that is, ferrous deoxy-myoglobin (Fe(II)Mb) and ferric aquo-myoglobin (Fe(III)MbH2O), and in ferric cyano-myoglobin (Fe(III)MbCN), whose X-ray structure is known at lower resolution (1.4 A). The analysis has been performed via the multiple scattering approach, starting from a muffin tin approximation of the molecular potential. The Fe-heme structure has been obtained by analyzing independently the Extended X-ray Absorption Fine Structure (EXAFS) region and the X-ray Absorption Near Edge Structure (XANES) region. The EXAFS structural results are in full agreement with the crystallographic values of the models, with an accuracy of +/- 0.02 A for Fe-ligand distances, and +/-6 degrees for angular parameters. All the XANES features above the theoretical zero energy (in the lower rising edge) are well accounted for by single-channel calculations, for both Fe(II) and Fe(III) hemes, and the Fe-N p distance is determined with the same accuracy as EXAFS. XANES evaluations of Fe-5th and Fe-6th ligand distances are determined with 0.04-0.07 A accuracy; a small discrepancy with EXAFS (0.01 to 0.05 A beyond the statistical error), is found for protein compounds. Concerns from statistical correlation among parameters and multiple minima in the parameter space are discussed. As expected, the XANES accuracy is slightly lower than what was found for polarized XANES on Fe(III)MbCN single crystal (0.03-0.04 A), and states the actual state-of-the-art of XANES analysis when used to extract heme-normal parameters in a solution spectrum dominated by heme-plane scattering. PMID:18837548
Multiple-wavelength spectroscopic quantitation of light-absorbing species in scattering media
Nathel, Howard; Cartland, Harry E.; Colston, Jr., Billy W.; Everett, Matthew J.; Roe, Jeffery N.
2000-01-01
An oxygen concentration measurement system for blood hemoglobin comprises a multiple-wavelength low-coherence optical light source that is coupled by single mode fibers through a splitter and combiner and focused on both a target tissue sample and a reference mirror. Reflections from both the reference mirror and from the depths of the target tissue sample are carried back and mixed to produce interference fringes in the splitter and combiner. The reference mirror is set such that the distance traversed in the reference path is the same as the distance traversed into and back from the target tissue sample at some depth in the sample that will provide light attenuation information that is dependent on the oxygen in blood hemoglobin in the target tissue sample. Two wavelengths of light are used to obtain concentrations. The method can be used to measure total hemoglobin concentration [Hb.sub.deoxy +Hb.sub.oxy ] or total blood volume in tissue and in conjunction with oxygen saturation measurements from pulse oximetry can be used to absolutely quantify oxyhemoglobin [HbO.sub.2 ] in tissue. The apparatus and method provide a general means for absolute quantitation of an absorber dispersed in a highly scattering medium.
Local Lattice Distortion of Ge Impurity in Si (001): Multiple-Scattering EXAFS Study
Sun Zhihu; Yan Wensheng; Pan Zhiyun; Wei Shiqiang; Oyanagi, H.
2007-02-02
The local structure of dilute Ge impurity in the Si host has been studied by fluorescence x-ray absorption fine structure spectra through multiple-scattering data analysis method. Contrary to the elongation of 0.029 A for the Ge-Si distance in the first shell, the Ge-Si interatomic distance in the second shell shows a contraction of about 0.013 A relative to the corresponding Si-Si distance in the Si host. This coincides with the theoretical prediction by Mousseau and Thorpe [Phys. Rev. B 46, 15887 (1992)] which includes both the bond length mismatch and bond-angle deviation. It turns out that the contraction of the second-shell Ge-Si distance is due to the deviation of Ge-Si-Si bond-angle from the ideal tetrahedral angle. From the Ge-Si distances within the first three shells, it is revealed that the dilute Ge doped into Si host can lead to the local distortion rather than the average lattice change.
Local lattice distortion of Ge-dilute Ge-Si alloy: Multiple-scattering EXAFS study
Sun Zhihu; Yan Wensheng; Pan Zhiyu; Wei Shiqiang; Oyanagi, Hiroyuki
2006-09-01
The local structure of a Ge{sub 0.006}Si{sub 0.994} thin film with dilute Ge impurity in a Si host has been studied by fluorescence x-ray absorption fine structure spectroscopy in the temperature region of 10-300 K using the multiple-scattering data analysis method. Contrary to the elongation of 0.029 A ring for the Ge-Si distance in the first shell, the Ge-Si interatomic distance in the second shell shows a contraction of about 0.013 A ring relative to the corresponding Si-Si distance in the Si host. This coincides with the theoretical result calculated using the formula proposed by Mousseau and Thorpe [Phys. Rev. B 46, 15887 (1992)] which includes both the bond-length mismatch and bond-angle deviation. It turns out that the contraction of the second-shell Ge-Si distance is due to the deviation of the Ge-Si-Si bond angle from the ideal tetrahedral angle. From the obtained Ge-Si distances within the first three shells, it is revealed that dilute Ge doped into a Si host can lead to local distortion rather than an average lattice change.
NASA Astrophysics Data System (ADS)
Mondescu, Radu P.; Muthukumar, M.
1999-01-01
Based on the multiple scattering technique [K. F. Freed and M. Muthukumar, J. Chem. Phys. 69, 2657 (1978); 68, 2088 (1978); M. Muthukumar and K. H. Freed, J. Chem. Phys. 70, 5875 (1979)] previously applied to the study of suspensions of spheres and polymers, we propose an approach to the computation of the effective elastic properties of a composite material containing rigid, mono-sized, randomly dispersed, spherical particles. Our method incorporates the many-body, long-range elastic interactions among inclusions. The effective medium equations are constructed and numerically solved self-consistently. We have calculated the effective shear μ' and Young E' moduli, as well as the effective Poisson ratio σ', as functions of the particle volume fraction Φ and of the Poisson ratio σ of the continuous phase. Comparisons with two sets of experimental data—glass beads in a polymer matrix and tungsten carbide particles in a cobalt matrix (Wc/Co)—and to a previous theoretical solution, are also presented. Our model can predict the effective Poisson ratio of the Wc/Co system for Φ⩽1 and for the glass/polymer system for Φ⩽0.5. In particular, the present work describes accurately composites with a high volume fraction of inclusions, where a percolation transition occurs. Very good agreement with the experimental data are obtained for E' and μ' when Φ⩽0.4, for both systems.
Multiple-wavelength spectroscopic quantitation of light-absorbing species in scattering media
Nathel, H.; Cartland, H.E.; Colston, B.W. Jr.; Everett, M.J.; Roe, J.N.
2000-01-18
This invention relates to an oxygen concentration measurement system for blood hemoglobin comprises a multiple-wavelength low-coherence optical light source that is coupled by single mode fibers through a splitter and combiner and focused on both a target tissue sample and a reference mirror. Reflections from both the reference mirror and from the depths of the target tissue sample are carried back and mixed to produce interference fringes in the splitter and combiner. The reference mirror is set such that the distance traversed in the reference path is the same as the distance traversed into and back from the target tissue sample at some depth in the sample that will provide light attenuation information that is dependent on the oxygen in blood hemoglobin in the target tissue sample. Two wavelengths of light are used to obtain concentrations. The method can be used to measure total hemoglobin concentration [Hb(deoxy) + Hb(oxy)] or total blood volume in tissue and in conjunction with oxygen saturation measurements from pulse oximetry can be used to absolutely quantify oxyhemoglobin [HbO{sub 2}] in tissue. The apparatus and method provide a general means for absolute quantitation of an absorber dispersed in a highly scattering medium.
NASA Technical Reports Server (NTRS)
Guinness, Edward A.; Arvidson, Raymond E.; Irons, J. R.; Harding, D. J.
1991-01-01
Here, researchers apply the Hapke function to airborne bidirectional reflectance data collected over three terrestrial surfaces. The objectives of the study were to test the range of natural surfaces that the Hapke model fits and to evaluate model parameters in terms of known surface properties. The data used are multispectral and multiple emission angle data collected during the Geologic Remote Sensing Field Experiment (GRSFE) over a mud-cracked playa, an artificially roughened playa, and a basalt cobble strewn playa at Lunar Lake Playa in Nevada. Airborne remote sensing data and associated field measurements were acquired at the same time. The airborne data were acquired by the Advanced Solid State Array Spectroradiometer (ASAS) instrument, a 29-spectral band imaging system. ASAS reflectance data for a cobble-strewn surface and an artificially rough playa surface on Lunar Lake Playa can be explained with the Hanke model. The cobble and rough playa sites are distinguishable by a single scattering albedo, which is controlled by material composition; by the roughness parameter, which appears to be controlled by the surface texture and particle size; and the symmetry factor of the single particle phase function, which is controlled by particle size and shape. A smooth playa surface consisting of compacted, fine-grained particles has reflectance variations that are also distinct from either the cobble site or rough playa site. The smooth playa appears to behave more like a Lambertian surface that cannot be modeled with the Hapke function.
Effects of multiple scattering and surface albedo on the photochemistry of the troposphere
NASA Technical Reports Server (NTRS)
Augustsson, T. R.; Tiwari, S. N.
1981-01-01
The effect of treatment of incoming solar radiation on the photochemistry of the troposphere is discussed. A one dimensional photochemical model of the troposphere containing the species of the nitrogen, oxygen, carbon, hydrogen, and sulfur families was developed. The vertical flux is simulated by use of the parameterized eddy diffusion coefficients. The photochemical model is coupled to a radiative transfer model that calculates the radiation field due to the incoming solar radiation which initiates much of the photochemistry of the troposphere. Vertical profiles of tropospheric species were compared with the Leighton approximation, radiative transfer, matrix inversion model. The radiative transfer code includes the effects of multiple scattering due to molecules and aerosols, pure absorption, and surface albedo on the transfer of incoming solar radiation. It is indicated that significant differences exist for several key photolysis frequencies and species number density profiles between the Leighton approximation and the profiles generated with, radiative transfer, matrix inversion technique. Most species show enhanced vertical profiles when the more realistic treatment of the incoming solar radiation field is included
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.
NASA Astrophysics Data System (ADS)
Sha, Wei E. I.; Choy, Wallace C. H.; Liu, Yang G.; Cho Chew, Weng
2011-09-01
We investigate near-field multiple scattering effects of plasmonic nanospheres (NSPs) embedded into organic solar cells (OSCs). When NSPs are embedded into a spacer layer, the near-field scattering from the NSPs shows strong direction-dependent features, which significantly affects the optical absorption. When NSPs are embedded into an active layer, the absorption enhancement is attributed to the interplay between longitudinal and transverse modes supported by the NSP chain. The breakdown of electrostatic scaling law is confirmed by our theoretical model and should be accounted for optical designs of OSCs. The work provides the fundamental physical understanding and design guidelines for plasmonic photovoltaics.
Small angle multiple scattering of fast ions, physics, stochastic theory and numerical calculations
NASA Astrophysics Data System (ADS)
Amsel, G.; Battistig, G.; L'Hoir, A.
2003-02-01
We present the physical principles underlying small angle multiple scattering of ions (MS) along with a renewed and comprehensive analytical approach to MS, based on probability theory, more precisely on stochastic processes. New theoretical results are derived, bearing in particular on the combination of angular and lateral spread. The scattering of ions by the screened target nuclei is governed by cross sections decreasing slowly with angle: large deflections may occur with probabilities high enough to render the basic characteristics of MS radically different from energy loss processes. These large deflections induce behaviour that may at first appear paradoxical. The width of the angular distributions presents a power law type dependence on thickness t of matter crossed, far from the familiar t1/2 behaviour: it varies as t1/ ν, where the exponent ν increases from ≈0.4 for small t, but does not exceed ≈1.8 for large t. Mathematical concepts such as Lévy flights and fractals are briefly discussed for a deeper insight into the nature of MS. The paper is intended to be self-contained, starting from first principles to present the basic elements of the physical and theoretical concepts required to describe MS processes. Projected angular distributions and the corresponding probability densities of the lateral spread of the trajectories with respect to the initial axis are calculated theoretically and numerically for a large range of thicknesses, as well as the statistical dependence between angular and lateral spread and the linear combination of their effects. The cases of both mono- and multielemental media, as well as that of thick targets are examined and the validity of the theory for projectiles heavier than the atoms of the medium and for ions with very high energies is discussed. Typical applications of MS theory are described, with particular emphasis on depth profiling of elements or isotopes in ion beam analysis. A large number of numerical data
NASA Astrophysics Data System (ADS)
Carlsson Tedgren, Åsa; Plamondon, Mathieu; Beaulieu, Luc
2015-07-01
The aim of this work was to investigate how dose distributions calculated with the collapsed cone (CC) algorithm depend on the size of the water phantom used in deriving the point kernel for multiple scatter. A research version of the CC algorithm equipped with a set of selectable point kernels for multiple-scatter dose that had initially been derived in water phantoms of various dimensions was used. The new point kernels were generated using EGSnrc in spherical water phantoms of radii 5 cm, 7.5 cm, 10 cm, 15 cm, 20 cm, 30 cm and 50 cm. Dose distributions derived with CC in water phantoms of different dimensions and in a CT-based clinical breast geometry were compared to Monte Carlo (MC) simulations using the Geant4-based brachytherapy specific MC code Algebra. Agreement with MC within 1% was obtained when the dimensions of the phantom used to derive the multiple-scatter kernel were similar to those of the calculation phantom. Doses are overestimated at phantom edges when kernels are derived in larger phantoms and underestimated when derived in smaller phantoms (by around 2% to 7% depending on distance from source and phantom dimensions). CC agrees well with MC in the high dose region of a breast implant and is superior to TG43 in determining skin doses for all multiple-scatter point kernel sizes. Increased agreement between CC and MC is achieved when the point kernel is comparable to breast dimensions. The investigated approximation in multiple scatter dose depends on the choice of point kernel in relation to phantom size and yields a significant fraction of the total dose only at distances of several centimeters from a source/implant which correspond to volumes of low doses. The current implementation of the CC algorithm utilizes a point kernel derived in a comparatively large (radius 20 cm) water phantom. A fixed point kernel leads to predictable behaviour of the algorithm with the worst case being a source/implant located well within a patient
Tedgren, Åsa Carlsson; Plamondon, Mathieu; Beaulieu, Luc
2015-07-01
The aim of this work was to investigate how dose distributions calculated with the collapsed cone (CC) algorithm depend on the size of the water phantom used in deriving the point kernel for multiple scatter. A research version of the CC algorithm equipped with a set of selectable point kernels for multiple-scatter dose that had initially been derived in water phantoms of various dimensions was used. The new point kernels were generated using EGSnrc in spherical water phantoms of radii 5 cm, 7.5 cm, 10 cm, 15 cm, 20 cm, 30 cm and 50 cm. Dose distributions derived with CC in water phantoms of different dimensions and in a CT-based clinical breast geometry were compared to Monte Carlo (MC) simulations using the Geant4-based brachytherapy specific MC code Algebra. Agreement with MC within 1% was obtained when the dimensions of the phantom used to derive the multiple-scatter kernel were similar to those of the calculation phantom. Doses are overestimated at phantom edges when kernels are derived in larger phantoms and underestimated when derived in smaller phantoms (by around 2% to 7% depending on distance from source and phantom dimensions). CC agrees well with MC in the high dose region of a breast implant and is superior to TG43 in determining skin doses for all multiple-scatter point kernel sizes. Increased agreement between CC and MC is achieved when the point kernel is comparable to breast dimensions. The investigated approximation in multiple scatter dose depends on the choice of point kernel in relation to phantom size and yields a significant fraction of the total dose only at distances of several centimeters from a source/implant which correspond to volumes of low doses. The current implementation of the CC algorithm utilizes a point kernel derived in a comparatively large (radius 20 cm) water phantom. A fixed point kernel leads to predictable behaviour of the algorithm with the worst case being a source/implant located well within a patient
Malhotra, M.
1996-12-31
Finite-element discretizations of time-harmonic acoustic wave problems in exterior domains result in large sparse systems of linear equations with complex symmetric coefficient matrices. In many situations, these matrix problems need to be solved repeatedly for different right-hand sides, but with the same coefficient matrix. For instance, multiple right-hand sides arise in radiation problems due to multiple load cases, and also in scattering problems when multiple angles of incidence of an incoming plane wave need to be considered. In this talk, we discuss the iterative solution of multiple linear systems arising in radiation and scattering problems in structural acoustics by means of a complex symmetric variant of the BL-QMR method. First, we summarize the governing partial differential equations for time-harmonic structural acoustics, the finite-element discretization of these equations, and the resulting complex symmetric matrix problem. Next, we sketch the special version of BL-QMR method that exploits complex symmetry, and we describe the preconditioners we have used in conjunction with BL-QMR. Finally, we report some typical results of our extensive numerical tests to illustrate the typical convergence behavior of BL-QMR method for multiple radiation and scattering problems in structural acoustics, to identify appropriate preconditioners for these problems, and to demonstrate the importance of deflation in block Krylov-subspace methods. Our numerical results show that the multiple systems arising in structural acoustics can be solved very efficiently with the preconditioned BL-QMR method. In fact, for multiple systems with up to 40 and more different right-hand sides we get consistent and significant speed-ups over solving the systems individually.
Local ordering of nanostructured Pt probed by multiple-scattering XAFS
NASA Astrophysics Data System (ADS)
Witkowska, Agnieszka; di Cicco, Andrea; Principi, Emiliano
2007-09-01
We present detailed results of a multiple-scattering (MS) extended x-ray absorption fine structure (EXAFS) data analysis of crystalline and nanocrystalline platinum. Advanced MS EXAFS analysis has been applied to raw x-ray absorption data including the background, using the expansion of the absorption cross section in terms of local two-body and three-body configurations. Present EXAFS results on bulk Pt are found to be in agreement with previous structural and vibrational data, and has been used as a reference for reliable structural refinement of nanosized systems. EXAFS structural refinement of Pt nanoparticles has been performed in combination with electron microscopy and x-ray diffraction, showing the importance of considering the actual size distribution and morphology of the samples. Present samples were unsupported and supported Pt nanocrystalline systems with size distributions showing clusters of quasispherical shape in the 1-7nm range. In particular, EXAFS spectra have been analyzed accounting for the reduction of the coordination number and degeneracy of three-body configurations, resulting from the measured size distribution and expected surface atom contributions. The importance of a correct account of the reduction of the number of neighbors for calculating MS contributions is emphasized in the paper. EXAFS results have been found compatible with x-ray diffraction and transmission electron microscopy investigations. We estimate that EXAFS could be used to study cluster shapes only for sizes below 2nm using present methods and quality of the experimental data. We have also shown that the local distribution of distances and angles probed by EXAFS is broader than in bulk Pt, with first-neighbor bond length variance and asymmetry increasing upon reducing the particle size. Methods and results presented in this paper have been found to be successful for a robust structural refinement of monatomic nanocrystalline systems and represents a solid starting
NASA Astrophysics Data System (ADS)
Tauzin, B.; Trampert, J.; van der Hilst, R.; Wittlinger, G.; Vergne, J.
2011-12-01
Using data from the US Transportable Array, we combine observations of P-to-S single and multiple scattered waves to constrain the transition zone (TZ) structure beneath the Western US. From stacking the data by common conversion points along profiles, we produce depth images of seismic discontinuities. Systematic depth and amplitude measurements are performed for the '410', the '660', and some other minor seismic discontinuities identified as sharp reductions of wave velocities at ˜350 km depth (the '350') and ˜590 km depth (the '590'). The Gorda plate, subducted under Northern California, is traced back to the TZ where it seems to flatten and induces, due to cold temperatures or a high water content, a significant uplift of the '410' under Northern Nevada. The geographical maps of the '410'/'660' amplitude/topography reveal an anomalous TZ at the borders between Washington, Oregon and Idaho with: (i) a thickened TZ, (ii) a sharp jump in the topography of the '660' both in a South-North and West-East direction, and (iii) reduced '410' amplitudes at the North. Such anomalous structure might be inherited from the past history of plate subduction/accretion. A thinned TZ under the Yellowstone is likely the result of a deep hot thermal plume. Both the '350' and the '590' negative discontinuities extend over very large areas. They might be related either to an increased water content in the TZ and/or significant amount of oceanic material accumulated through the past 100 My. An estimation of the TZ water content is now possible based on observation of PPS reverberated phases on the '410' and '660' interfaces.
NASA Astrophysics Data System (ADS)
Kaina, Nadège; Lemoult, Fabrice; Fink, Mathias; Lerosey, Geoffroy
2015-09-01
Metamaterials, man-made composite media structured on a scale much smaller than a wavelength, offer surprising possibilities for engineering the propagation of waves. One of the most interesting of these is the ability to achieve superlensing--that is, to focus or image beyond the diffraction limit. This originates from the left-handed behaviour--the property of refracting waves negatively--that is typical of negative index metamaterials. Yet reaching this goal requires the design of `double negative' metamaterials, which act simultaneously on the permittivity and permeability in electromagnetics, or on the density and compressibility in acoustics; this generally implies the use of two different kinds of building blocks or specific particles presenting multiple overlapping resonances. Such a requirement limits the applicability of double negative metamaterials, and has, for example, hampered any demonstration of subwavelength focusing using left-handed acoustic metamaterials. Here we show that these strict conditions can be largely relaxed by relying on media that consist of only one type of single resonant unit cell. Specifically, we show with a simple yet general semi-analytical model that judiciously breaking the symmetry of a single negative metamaterial is sufficient to turn it into a double negative one. We then demonstrate that this occurs solely because of multiple scattering of waves off the metamaterial resonant elements, a phenomenon often disregarded in these media owing to their subwavelength patterning. We apply our approach to acoustics and verify through numerical simulations that it allows the realization of negative index acoustic metamaterials based on Helmholtz resonators only. Finally, we demonstrate the operation of a negative index acoustic superlens, achieving subwavelength focusing and imaging with spot width and resolution 7 and 3.5 times better than the diffraction limit, respectively. Our findings have profound implications for the
Kaina, Nadège; Lemoult, Fabrice; Fink, Mathias; Lerosey, Geoffroy
2015-09-01
Metamaterials, man-made composite media structured on a scale much smaller than a wavelength, offer surprising possibilities for engineering the propagation of waves. One of the most interesting of these is the ability to achieve superlensing--that is, to focus or image beyond the diffraction limit. This originates from the left-handed behavior--the property of refracting waves negatively--that is typical of negative index metamaterials. Yet reaching this goal requires the design of 'double negative' metamaterials, which act simultaneously on the permittivity and permeability in electromagnetics, or on the density and compressibility in acoustics; this generally implies the use of two different kinds of building blocks or specific particles presenting multiple overlapping resonances. Such a requirement limits the applicability of double negative metamaterials, and has, for example, hampered any demonstration of subwavelength focusing using left-handed acoustic metamaterials. Here we show that these strict conditions can be largely relaxed by relying on media that consist of only one type of single resonant unit cell. Specifically, we show with a simple yet general semi-analytical model that judiciously breaking the symmetry of a single negative metamaterial is sufficient to turn it into a double negative one. We then demonstrate that this occurs solely because of multiple scattering of waves off the metamaterial resonant elements, a phenomenon often disregarded in these media owing to their subwavelength patterning. We apply our approach to acoustics and verify through numerical simulations that it allows the realization of negative index acoustic metamaterials based on Helmholtz resonators only. Finally, we demonstrate the operation of a negative index acoustic superlens, achieving subwavelength focusing and imaging with spot width and resolution 7 and 3.5 times better than the diffraction limit, respectively. Our findings have profound implications for the
NASA Astrophysics Data System (ADS)
Chen, Duan; Cai, Wei; Zinser, Brian; Cho, Min Hyung
2016-09-01
In this paper, we develop an accurate and efficient Nyström volume integral equation (VIE) method for the Maxwell equations for a large number of 3-D scatterers. The Cauchy Principal Values that arise from the VIE are computed accurately using a finite size exclusion volume together with explicit correction integrals consisting of removable singularities. Also, the hyper-singular integrals are computed using interpolated quadrature formulae with tensor-product quadrature nodes for cubes, spheres and cylinders, that are frequently encountered in the design of meta-materials. The resulting Nyström VIE method is shown to have high accuracy with a small number of collocation points and demonstrates p-convergence for computing the electromagnetic scattering of these objects. Numerical calculations of multiple scatterers of cubic, spherical, and cylindrical shapes validate the efficiency and accuracy of the proposed method.
Diez Muino, R.; Rolles, D.; Garcia de Abajo, F.J.; Fadley, C.S.; Van Hove, M.A.
2001-09-06
We use multiple scattering in non-spherical potentials (MSNSP) to calculate the angular distributions of electrons photoemitted from the 1s-shells of CO and N2 gas-phase molecules with fixed-in-space orientations. For low photoelectron kinetic energies (E<50 eV), as appropriate to certain shape-resonances, the electron scattering must be represented by non-spherical scattering potentials, which are naturally included in our formalism. Our calculations accurately reproduce the experimental angular patterns recently measured by several groups, including those at the shape-resonance energies. The MSNSP theory thus enhances the sensitivity to spatial electronic distribution and dynamics, paving the way toward their determination from experiment.
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%.
Monte Carlo Code System for Calculation of Multiple Scattering of Neutrons in the Resonance Region.
1983-01-25
Version 00 MCRTOF systematically calculates capture and scattering probabilities for neutrons incident on a material disk, with neutron cross sections calculated from the resonance parameters. Capture, front and rear face scattering, transmission, etc., probabilities are obtained from the average destinations of the incident neutrons.
The role of multiple scattering in one-dimensional radiative transfer
NASA Technical Reports Server (NTRS)
Adamson, D.
1975-01-01
The usual methods of solving the radiative transfer equation yield answers which embrace all orders of scattering and thus shed little light on the underlying physical process. The present analysis examines the contributions of the various orders of scattering to the one dimensional transfer of radiation. In the one dimensional case an exact analytical solution exists and the problem reduces to that of expanding these exact solutions in powers of the albedo for single scattering. Formulas are given which permit the calculation of any order of scattering in an atmosphere of arbitrary optical thickness, particle albedo, and asymmetry parameter. The results should aid in identifying those physical situations where only the lowest orders of scattering play a significant role and where appropriate approximate methods might provide results of acceptable accuracy.
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.
NASA Astrophysics Data System (ADS)
Zhao, Yaqin; Zhong, Xin; Wu, Di; Zhang, Ye; Ren, Guanghui; Wu, Zhilu
2013-09-01
Optical code-division multiple access (OCDMA) systems usually allocate orthogonal or quasi-orthogonal codes to the active users. When transmitting through atmospheric scattering channel, the coding pulses are broadened and the orthogonality of the codes is worsened. In truly asynchronous case, namely both the chips and the bits are asynchronous among each active user, the pulse broadening affects the system performance a lot. In this paper, we evaluate the performance of a 2D asynchronous hard-limiting wireless OCDMA system through atmospheric scattering channel. The probability density function of multiple access interference in truly asynchronous case is given. The bit error rate decreases as the ratio of the chip period to the root mean square delay spread increases and the channel limits the bit rate to different levels when the chip period varies.
Multiple-order resonant Raman scattering of the localized molecular rose center in BaF 2
NASA Astrophysics Data System (ADS)
Deyhimi, Farzad; Bill, Hans
1983-11-01
The rose center in BaF 2 is investigated by resonant Raman scattering. The spectra obtained at liquid-helium temperature show multiple order and combination bands of the internal local modes (up to the sixth order), and associated side bands of the lattice. The temperature dependence of the linewidth of the local-mode transitions has been investigated and is explained as being due to anharmonic coupling to the lattice.
Khubchandani, Bhaskar Lachman
2014-08-15
Implications of spontaneous and stimulated Raman scattering (SSRS) and phase noise on the spatial evolution of multiple-order sidebands arising from four-wave mixing (FWM) along the length of an optical fiber are investigated. A modified split-step Fourier method is used to solve the governing coupled nonlinear Schrödinger equations. The phase noise overcomes the depletive nature of SSRS and stabilizes the FWM sidebands, in good agreement with experimental results. PMID:25121893
Haworth, Kevin J.; Fowlkes, J. Brian; Carson, Paul L.; Kripfgans, Oliver D.
2009-01-01
A theoretical shot noise model to describe the output of a time-reversal experiment in a multiple-scattering medium is developed. This (non-wave equation based) model describes the following process. An arbitrary waveform is transmitted through a high-order multiple-scattering environment and recorded. The recorded signal is arbitrarily windowed and then time-reversed. The processed signal is retransmitted into the environment and the resulting signal recorded. The temporal and spatial signal and noise of this process is predicted statistically. It is found that the time when the noise is largest depends on the arbitrary windowing and this noise peak can occur at times outside the main lobe. To determine further trends, a common set of parameters is applied to the general result. It is seen that as the duration of the input function increases, the signal-to-noise ratio (SNR) decreases (independent of signal bandwidth). It is also seen that longer persisting impulse responses result in increased main lobe amplitudes and SNR. Assumptions underpinning the generalized shot noise model are compared to an experimental realization of a multiple-scattering medium (a time-reversal chaotic cavity). Results from the model are compared to random number numerical simulation. PMID:19425655
Multiple-scattering calculations of the uranium L3-edge x-ray-absorption near-edge structure
NASA Astrophysics Data System (ADS)
Hudson, E. A.; Rehr, J. J.; Bucher, J. J.
1995-11-01
A theoretical study of the uranium L3-edge x-ray absorption near-edge structure (XANES) is presented for several uranium compounds, including oxides, intermetallics, uranyl fluoride, and α-uranium. Calculations were performed using feff6, an ab initio multiple-scattering (MS) code that includes the most important features of current theories. The results, which account for both the fine structure χ and the atomiclike background μ0 of the absorption coefficient μ, are compared to new and previously measured experimental spectra, reavealing very good agreement for most systems. For several compounds, a more detailed theoretical analysis determined the influence of cluster size and scattering order upon the calculated spectra. Results indicate that MS paths and scattering paths that include rather distant atoms make significant contributions for UO2, whereas XANES for crystals with lower symmetry and density can be modeled using only shorter single-scattering paths. In most cases, assumption of a screened final state in the calculation gives better agreement with experiment than use of an unscreened final state. The successful modeling of spectra for a variety of different uranium compounds, with differing spectral features, indicates that the semirelativistic treatment of XANES used here is adequate even for heavy elements. The well-known resonance, observed experimentally for uranyl (UO2+2) compounds ~=15 eV above the white line, is successfully modeled here for the first time, using multiple-scattering paths within the O-U-O axial bonds. Overlapping muffin-tin spheres were required in the calculation, probably as a result of the short uranyl axial bonds.
Chen, Y.; Garcia de Abajo, F.J.; Ynzunza, R.X.; Kaduwela, A.P.; Van Hove, M.A.; Fadley, C.S. |
1998-11-01
The Rehr-Albers (RA) separable Green{close_quote}s-function formalism, which is based on an expansion series, has been successful in speeding up multiple-scattering cluster calculations for photoelectron diffraction simulations, particularly in its second-order version. The performance of this formalism is explored here in terms of computational speed, convergence over orders of multiple scattering, over orders of approximation, and over cluster size, by comparison with exact cluster-based formalisms. It is found that the second-order RA approximation [characterized by (6{times}6) scattering matrices] is adequate for many situations, particularly if the initial state from which photoemission occurs is of {ital s} or {ital p} type. For the most general and quantitative applications, higher-order versions of RA may become necessary for {ital d} initial states [third-order, i.e., (10{times}10) matrices] and {ital f} initial states [fourth-order, i.e., (15{times}15) matrices]. However, the required RA order decreases as an electron wave proceeds along a multiple-scattering path, and this can be exploited, together with the selective and automated cutoff of weakly contributing matrix elements and paths, to yield computer time savings of at least an order of magnitude with no significant loss of accuracy. Cluster sizes of up to approximately 100 atoms should be sufficient for most problems that require about 5{percent} accuracy in diffracted intensities. Excellent sensitivity to structure is seen in comparisons of second-order theory with variable geometry to exact theory as a fictitious {open_quotes}experiment.{close_quotes} Our implementation of the Rehr-Albers formalism thus represents a versatile, quantitative, and efficient method for the accurate simulation of photoelectron diffraction. {copyright} {ital 1998} {ital The American Physical Society}
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.
NASA Technical Reports Server (NTRS)
Kobayashi, Satoru; Tanelli, Simone; Im, Eastwood
2005-01-01
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.
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.
NASA Astrophysics Data System (ADS)
Hirst, Evan; Thompson, Oliver; Andrews, Mike
2013-02-01
The retina/choroid structure is an example of a complex biological target featuring highly perfused tissues and vessel flows both near the surface and at some depth. Laser speckle imaging can be used to image blood flows but static scattering paths present a problem for extracting quantifiable data. The speckle contrast is artificially increased by any residual specular reflection and light paths where no moving scatterers are encountered. Here we present results from phantom experiments demonstrating that the static and dynamic contributions to laser speckle contrast can be separated when camera exposures of varying duration are used. The stationary contrast parameter follows the thickness and strength of the overlying scatterer while the dynamic proportion of the scatter resulting from vessel flows and Brownian motion is unchanged. The importance of separating the two scatter components is illustrated by in vivo measurements from a scarred human retina, where the effect of the un-perfused scar tissue can be decoupled from the dynamic speckle from the intact tissue beneath it.
NASA Astrophysics Data System (ADS)
Wang, Ruikang K.
2002-07-01
Multiple scattering is a major source that limits light penetration into biotissues, thereby preventing visualization of the deep microstructures for high-resolution optical imaging techniques. The optical clearing approach is a new adventure in biomedical optics for manipulating the optical properties of tissue; for example, the scattering coefficient and the degree of forward scattering of photons, by the use of the chemical administration method in order to improve the optical imaging depth, particularly for the recently developed optical coherence tomography (OCT). This paper investigates systematically how the multiple scattering affects signal attenuation and localization in general, and how the alterations of optical properties of tissue enhance the optical imaging depth and signal localization in particular, by the use of Monte Carlo simulations through the separate considerations of the least scattered photons (LSP) and multiple scattered photons (MSP). The LSP are those photons that contribute to the precise OCT signal, i.e. localization, and the MSP are those that degrade the OCT signal. It is shown that with either the reduction of the scattering coefficient or the increase of the degree of forward scattering, signal localization and imaging depth for OCT is enhanced. Whilst the increase of the anisotropic factor of the medium is more efficient in improving signal localization, it introduces more scattering events for the photons travelling within the tissue for both the LSP and MSP. It is also found that the OCT imaging resolution is almost reduced exponentially with the increase of the probing depth as opposed to the claimed system resolution. We demonstrate that optical clearing could be a useful tool to improve the imaging resolution when the light progressively penetrates the high scattering medium. Experimental results are also presented to show intuitively how multiple scattering affects OCT signal profiles by the use of intralipid solution and
Improved separation of soft and hard components in multiple Coulomb scattering
NASA Astrophysics Data System (ADS)
Bondarenco, M. V.
2016-02-01
Evaluation of the angular distribution function of particles scattered in an amorphous medium is improved by deforming the integration path in the Fourier integral representation into the complex plane. That allows us to present the distribution function as a sum of two positive components, soft and hard, the soft component being close to a Gaussian, and the hard component vanishing in the forward direction, while including the Rutherford asymptotics and all the power corrections to it at large scattering angles. Detailed properties of these components, and their interplay at intermediate deflection angles are discussed. Comparison with the Molière theory is given.
NASA Astrophysics Data System (ADS)
Neuville, C.; Tassin, V.; Pesme, D.; Monteil, M.-C.; Masson-Laborde, P.-E.; Baccou, C.; Fremerye, P.; Philippe, F.; Seytor, P.; Teychenné, D.; Seka, W.; Katz, J.; Bahr, R.; Depierreux, S.
2016-06-01
The indirect-drive scheme to inertial confinement fusion uses a large number of laser beams arranged in a symmetric angular distribution. Collective laser plasma instabilities can therefore develop that couple all the incident laser waves located in a cone to the daughter wave growing along the cone symmetry axis [D. F. DuBois et al., Phys. Fluids B 4, 241 (1992)]. With complementary diagnostics of Thomson scattering and of the scattered light, we demonstrate the occurrence of collective stimulated Brillouin sidescattering driving collective acoustic waves in indirect-drive experiments.
Neuville, C; Tassin, V; Pesme, D; Monteil, M-C; Masson-Laborde, P-E; Baccou, C; Fremerye, P; Philippe, F; Seytor, P; Teychenné, D; Seka, W; Katz, J; Bahr, R; Depierreux, S
2016-06-10
The indirect-drive scheme to inertial confinement fusion uses a large number of laser beams arranged in a symmetric angular distribution. Collective laser plasma instabilities can therefore develop that couple all the incident laser waves located in a cone to the daughter wave growing along the cone symmetry axis [D. F. DuBois et al., Phys. Fluids B 4, 241 (1992)]. With complementary diagnostics of Thomson scattering and of the scattered light, we demonstrate the occurrence of collective stimulated Brillouin sidescattering driving collective acoustic waves in indirect-drive experiments. PMID:27341238
Assessing multiple quality attributes of peaches using spectral absorption and scattering properties
Technology Transfer Automated Retrieval System (TEKTRAN)
The objective of this research was to measure the spectral absorption and reduced scattering coefficients of peaches, using a hyperspectral imaging-based spatially-resolved method, for maturity/quality assessment. A newly developed optical property measuring instrument was used for acquiring hypersp...
Brancewicz, Marek; Itou, Masayoshi; Sakurai, Yoshiharu
2016-01-01
The first results of multiple scattering simulations of polarized high-energy X-rays for Compton experiments using a new Monte Carlo program, MUSCAT, are presented. The program is developed to follow the restrictions of real experimental geometries. The new simulation algorithm uses not only well known photon splitting and interaction forcing methods but it is also upgraded with the new propagation separation method and highly vectorized. In this paper, a detailed description of the new simulation algorithm is given. The code is verified by comparison with the previous experimental and simulation results by the ESRF group and new restricted geometry experiments carried out at SPring-8. PMID:26698070
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
Fast and scalable algorithm for the simulation of multiple Mie scattering in optical systems.
Kalthoff, Oliver; Kampmann, Ronald; Streicher, Simon; Sinzinger, Stefan
2016-05-20
The Monte Carlo simulation of light propagation in optical systems requires the processing of a large number of photons to achieve a satisfactory statistical accuracy. Based on classical Mie scattering, we experimentally show that the independence of photons propagating through a turbid medium imposes a postulate for a concurrent and scalable programming paradigm of general purpose graphics processing units. This ensures that, without rewriting code, increasingly complex optical systems can be simulated if more processors are available in the future. PMID:27411111
NASA Astrophysics Data System (ADS)
Chaput, J.; Campillo, M.; Aster, R. C.; Roux, P.; Kyle, P. R.; Knox, H.; Czoski, P.
2015-02-01
We examine seismic coda from an unusually dense deployment of over 100 short-period and broadband seismographs in the summit region of Mount Erebus volcano on a network with an aperture of approximately 5 km. We investigate the energy-partitioning properties of the seismic wavefield generated by thousands of small icequake sources originating on the upper volcano and use them to estimate Green's functions via coda cross correlation. Emergent coda seismograms suggest that this locale should be particularly amenable to such methods. Using a small aperture subarray, we find that modal energy partition between S and P wave energy between ˜1 and 4 Hz occurs in just a few seconds after event onset and persists for tens of seconds. Spatially averaged correlograms display clear body and surface waves that span the full aperture of the array. We test for stable bidirectional Green's function recovery and note that good symmetry can be achieved at this site even with a geographically skewed distribution of sources. We estimate scattering and absorption mean free path lengths and find a power law decrease in mean free path between 1.5 and 3.3 Hz that suggests a quasi-Rayleigh or Rayleigh-Gans scattering situation. Finally, we demonstrate the existence of coherent backscattering (weak localization) for this coda wavefield. The remarkable properties of scattered seismic wavefields in the vicinity of active volcanoes suggests that the abundant small icequake sources may be used for illumination where temporal monitoring of such dynamic structures is concerned.
NASA Astrophysics Data System (ADS)
Nakatsuka, Takao; Okei, Kazuhide; Iyono, Atsushi; Bielajew, Alex F.
2015-12-01
Simultaneous distribution between the deflection angle and the lateral displacement of fast charged particles traversing through matter is derived by applying numerical inverse Fourier transforms on the Fourier spectral density solved analytically under the Molière theory of multiple scattering, taking account of ionization loss. Our results show the simultaneous Gaussian distribution at the region of both small deflection angle and lateral displacement, though they show the characteristic contour patterns of probability density specific to the single and the double scatterings at the regions of large deflection angle and/or lateral displacement. The influences of ionization loss on the distribution are also investigated. An exact simultaneous distribution is derived under the fixed energy condition based on a well-known model of screened single scattering, which indicates the limit of validity of the Molière theory applied to the simultaneous distribution. The simultaneous distribution will be valuable for improving the accuracy and the efficiency of experimental analyses and simulation studies relating to charged particle transports.
NASA Astrophysics Data System (ADS)
Li, Z. J.; Wu, Z. S.; Qu, T.; Shang, Q. C.; Bai, L.
2016-01-01
Based on the generalized multiparticle Mie theory, multiple scattering of an aggregate of uniaxial anisotropic spheres illuminated by a zero-order Bessel beam (ZOBB) with arbitrary propagation direction is investigated. The particle size and configuration are arbitrary. The arbitrary incident Bessel beam is expanded in terms of spherical vector wave functions (SVWFs). Utilizing the vector addition theorem of SVWFs, interactive and total scattering coefficients are derived through the continuous boundary conditions on which the interaction of the particles is considered. The accuracy of the theory and codes are verified by comparing results with those obtained for arbitrary plane wave incidence by CST simulation, and for ZOBB incidence by a numerical method. The effects of angle of incidence, pseudo-polarization angle, half-conical angle, beam center position, and permittivity tensor elements on the radar cross sections (RCSs) of several types of collective uniaxial anisotropic spheres, such as a linear chain, a 4×4×4 cube-shaped array, and other periodical structures consisting of massive spheres, are numerically analyzed. Selected results on the properties of typical particles such as TiO2, SiO2, or other particle lattices are calculated. This investigation could provide an effective test for further research on the scattering characteristics of an aggregate of anisotropic spheres by a high-order Bessel vortex beam. The results have important application in optical tweezers and particle manipulation.
Almasian, Mitra; Bosschaart, Nienke; van Leeuwen, Ton G; Faber, Dirk J
2015-12-01
Optical coherence tomography (OCT) has the potential to quantitatively measure optical properties of tissue such as the attenuation coefficient and backscattering coefficient. However, to obtain reliable values for strong scattering tissues, accurate consideration of the effects of multiple scattering and the nonlinear relation between the scattering coefficient and scatterer concentration (concentration-dependent scattering) is required. We present a comprehensive model for the OCT signal in which we quantitatively account for both effects, as well as our system parameters (confocal point spread function and sensitivity roll-off). We verify our model with experimental data from controlled phantoms of monodisperse silica beads (scattering coefficients between 1 and 30 mm(−1) and scattering anisotropy between 0.4 and 0.9). The optical properties of the phantoms are calculated using Mie theory combined with the Percus–Yevick structure factor to account for concentration-dependent scattering. We demonstrate excellent agreement between the OCT attenuation and backscattering coefficient predicted by our model and experimentally derived values. We conclude that this model enables us to accurately model OCT-derived parameters (i.e., attenuation and backscattering coefficients) in the concentration-dependent and multiple scattering regime for spherical monodisperse samples. PMID:26720868
NASA Astrophysics Data System (ADS)
Marouf, Essam A.; Wong, Kwok K.; French, Richard G.; Rappaport, Nicole J.; McGhee-French, Colleen A.
2014-11-01
Elongated and canted clusters of ring particles (gravitational wakes) are known to permeate the A- and B-Rings of Saturn. We constrain wake width W and height H, for given cant angle γ, using multiple 3.6 cm-λ Cassini radio occultations covering a range of ring opening angle B. We model the electromagnetic interaction problem as diffraction by randomly blocked screens constructed in the plane normal to the incidence direction (Marouf, DPS 1994, 1996, and 1997; Thomson and Marouf, Icarus, 2009). The screen’s transmittance is binary: the incident wave is either blocked or not blocked depending on the collective shadow area cast by the large particles and particle clusters. Wakes are modeled as monolayer of elliptical cylinders populated by random but uniform distribution of spherical particles. The cylinders can be immersed in a “halo” of loose spherical particles. Numerical simulations of diffraction patterns for a range of model parameters and viewing geometry reveal distinct diffracted cylindrical and spherical components. The first dominates at small scattering angles and originates from specific locations within the footprint of the spacecraft antenna. The second dominates at larger angles and originates from the full footprint. Its angular spectrum is in good agreement with theoretical predictions based on multiple scattering by classical ring models (Marouf et al., Icarus, 1982, 1983). We interpret Cassini measurements in the light of the simulation results, assuming that the measured scattered signal spectra can be modeled as superposition of diffracted spherical and cylindrical components. We compute and remove contribution of the first component assuming Voyager-like size distributions (Zebker et al., Icarus, 1985). In most cases, a large residual spectral component is interpreted as contribution of cylindrical (wake) diffraction. Its angular width determines a characteristic cylindrical shadow width that depends on the wake (W, H) and the viewing
NASA Technical Reports Server (NTRS)
Martin, D. L.; Perry, M. J.
1994-01-01
Water-leaving radiances and phytoplankton pigment concentrations are calculated from coastal zone color scanner (CZCS) radiance measurements by removing atmospheric Rayleigh and aerosol radiances from the total radiance signal measured at the satellite. The single greatest source of error in CZCS atmospheric correction algorithms in the assumption that these Rayleigh and aerosol radiances are separable. Multiple-scattering interactions between Rayleigh and aerosol components cause systematic errors in calculated aerosol radiances, and the magnitude of these errors is dependent on aerosol type and optical depth and on satellite viewing geometry. A technique was developed which extends the results of previous radiative transfer modeling by Gordon and Castano to predict the magnitude of these systematic errors for simulated CZCS orbital passes in which the ocean is viewed through a modeled, physically realistic atmosphere. The simulated image mathematically duplicates the exact satellite, Sun, and pixel locations of an actual CZCS image. Errors in the aerosol radiance at 443 nm are calculated for a range of aerosol optical depths. When pixels in the simulated image exceed an error threshhold, the corresponding pixels in the actual CZCS image are flagged and excluded from further analysis or from use in image compositing or compilation of pigment concentration databases. Studies based on time series analyses or compositing of CZCS imagery which do not address Rayleigh-aerosol multiple scattering should be interpreted cautiously, since the fundamental assumption used in their atmospheric correction algorithm is flawed.
NASA Astrophysics Data System (ADS)
Silván-Cárdenas, Jose L.; Corona-Romero, Nirani
2015-10-01
In this paper, we describe some results from a study on hyperspectral analysis of coniferous canopy scattering for the purpose of estimating forest biophysical and structural parameters. Georeferenced airborne hyperspectral measurements were taken from a flying helicopter over a coniferous forest dominated by Pinus hartweguii and Abies religiosa within the Federal District Conservation Land in Mexico City. Hyperspectral data was recorded in the optical range from 350 to 2500 nm at 1nm spectral resolution using the FieldSpec 4 (ASD Inc.). Spectral measurements were also carried out in the ground for vegetation and understory components, including leaf, bark, soil and grass. Measurements were then analyzed through a previously developed multiple scattering approximation (MSA) model, which represents above-canopy spectral reflectance through a non-linear combination of pure spectral components (endmembers), as well as through a set of photon recollision probabilities and interceptance fractions. In this paper we provide an expression for the canopy absorptance as the basis for estimating the components of canopy radiation budget using the MSA model. Furthermore, since MSA does not prescribe a priori the endmembers to incorporate in the model, a multiple endmember selection method (MESMSA) was developed and tested. Photon recollision probabilities and interceptance fractions were estimated by fitting the model to airborne spectral reflectance and selected endmembers where then used to estimate the canopy radiation budget at each measured location.
NASA Technical Reports Server (NTRS)
Ajello, J. M.; Pryor, W. R.; Barth, C. A.; Hord, C. W.; Stewart, A. I. F.; Simmons, K. E.; Hall, D. T.
1994-01-01
The Galileo Ultravilet Spectrometer Experiment (UVS) obtained a partial celestial sphere map of interplanetary Lyman-alpha (IP L alpha) on 13-14 December 1990 during the first Earth encounter. The Galileo spacecraft was near the downwind axis of the local interstellar medium flow. These UVS measurements sampled the downwind, anti-sunward hemisphere. The data were modeled using a hot model of the interplanetary hydrogen density distribution with the goal of studying multiple scattering effects in the inner solar system. The derived ratio in the downwind direction of the observed brightness and a single scattering model brightness, both normalized to unity in the upwind direction, is 1.82 +/- 0.2. This brightness ratio requires a multiple scattering correction which is 36% larger than can be accounted for by theoretical calculations. The hot model may require: (1) a temperature perturbation of the interstellar wind velocity distribution or (2) an additional downstream source of interplanetary hydrogen. However, a more likely exlanation which affects the hot model is the latitude dependence of the radiation pressure. This dependence, based on the known solar L alpha flux latitude variation at solar maximum, causes a downwind brightness enhancement by preferential focusing of H-atoms with trajectory planes containing the solar poles. This result implies that radiation pressure near the solar poles is nearly independent of solar cycle and is insufficient to lead to a net repulsion of hydrogen atoms by the sun, as can occur near the ecliptic plane during the solar maximum. In addition, the UVS performed 13 observations of IP L alpha while in cruise between Venus and the Earth in 3 directions fixed in ecliptic coordinates.
Bernstein, B. E.; Michels, P. A.; Kim, H.; Petra, P. H.; Hol, W. G.
1998-01-01
Phosphoglycerate kinase (PGK) catalyzes the phosphoryl transfer between 1,3 bis-phosphoglycerate and ADP to form 3-phosphoglycerate and ATP, undergoing significant conformational changes during catalysis. To more precisely document this reaction and the corresponding conformational changes, we have crystallized Trypanosoma brucei PGK in several crystal forms: (1) in the presence of 3-phosphoglycerate and MgADP, PGK crystallizes with four molecules in the asymmetric unit; (2) in the presence of the ATP analog, AMP-PNP, PGK crystallizes in a similar form; (3) in the presence of the bisubstrate analog, adenylyl 1,1,5,5-tetrafluoropentane-1,5-bisphosphonate, PGK crystals grow with one molecule in the asymmetric unit. Large scale expression and purification of T. brucei PGK from an E. coli overexpression system was required to obtain sufficient enzyme yields. Results from dynamic light scattering experiments allowed us to identify substrates and analogs which were amenable for crystallization. Ease of crystal growth and diffraction quality for a particular PGK-ligand complex is highly consistent with the apparent monodispersity of the complex in solution as judged by dynamic light scattering. The three-dimensional structures of the various enzyme-ligand complexes are currently being exploited to obtain a better understanding of PGK catalysis, as well as for structure based design of enzyme inhibitors to be used in the development of anti-trypanosomal agents. PMID:9521128
NASA Astrophysics Data System (ADS)
Cerussi, Albert E.; Gratton, Enrico; Fantini, Sergio
1999-07-01
Over the past few years, there has been significant research activity devoted to the application of fluorescence spectroscopy to strongly scattering media, where photons propagate diffusely. Much of this activity focused on fluorescence as a source of contrast enhancement in optical tomography. Our efforts have emphasized the quantitative recovery of fluorescence parameters for spectroscopy. Using a frequency-domain diffusion-based model, we have successfully recovered the lifetime, the absolute quantum yield, the fluorophore concentration, and the emission spectrum of the fluorophore, as well as the absorption and the reduced scattering coefficients at the emission wavelength of the medium in different measurements. In this contribution, we present a sensitive monitor of the binding between ethidium bromide and bovine cells in fresh milk. The spectroscopic contrast was the approximately tenfold increase in the ethidium bromide lifetime upon binding to DNA. The measurement clearly demonstrated that we could quantitatively measure the density of cells in the milk, which is an application vital to the tremendous economic burden of bovine subclinical mastitis detection. Furthermore, we may in principle use the spirit of this technique as a quantitative monitor of the binding of fluorescent drugs inside tissues. This is a first step towards lifetime spectroscopy in tissues.
NASA Astrophysics Data System (ADS)
Pukite, Janis; Dörner, Steffen; Wagner, Thomas
2015-04-01
The Scanning Imaging Absorption spectroMeter for Atmospheric CHartographY (SCIAMACHY) on the ENVISAT satellite probed the atmosphere at the day side of Earth in alternating sequences of nadir and limb measurements from August 2002 to April 2012. Limb measurements allow the retrieval of stratospheric profiles of various trace gases on a global scale. It has been shown that combining measurements of the same air volume from different viewing positions along the orbit, 2D distribution fields of stratospheric trace gases can be acquired in one inversion step. Since the atmospheric scattering and absorption processes are wavelength dependent, the spatial sensitivity for limb observations also varies with wavelength. In general, for longer wavelengths, photons from more remote areas along the line of sight are contributing stronger to the measurement than for shorter wavelengths because of the lower probability of Rayleigh scattering. In addition, the radiative transfer is modified by the ozone absorption structures making longer light paths less probable within strong ozone absorption bands. In this study, additional information on the spatial distribution of NO2 is investigated by analysing results obtained by Differential Optical Absorption Spectroscopy (DOAS) in various spectral fit windows. Combing the fit results in one profile retrieval algorithm helps to improve the spatial sensitivity and resolution of the measurements. The largest improvements for the spatial resolution and sensitivity are expected for the upper troposphere/ lower stratosphere (UTLS) region where the variation of the spatial sensitivity with wavelength is strongest.
Studies on laser beam propagation and stimulated scattering in multiple beam experiments
NASA Astrophysics Data System (ADS)
Labaune, C.; Lewis, K.; Bandulet, H.; Depierreux, S.; Hüller, S.; Masson-Laborde, P. E.; Pesme, D.; Riazuelo, G.
2006-06-01
The propagation and stimulated scattering of intense laser beams interacting with underdense plasmas are two important issues for inertial confinement fusion (ICF). The purpose of this work was to perform experiments under well-controlled interaction conditions and confront them with numerical simulations to test the physics included in the codes. Experimental diagnostics include time and space resolved images of incident and SBS light and of SBS-ion acoustic activity. New numerical diagnostics, including similar constraints as the experimental ones and the treatment of the propagation of the light between the emitting area and the detectors, have been developed. Particular care was put to include realistic plasma density and velocity profiles, as well as laser pulse shape in the simulations. In the experiments presented in this paper, the interaction beam was used with a random phase plate (RPP) to produce a statistical distribution of speckles in the focal volume. Stimulated Brillouin Scattering (SBS) was described using a decomposition of the spatial scales which provides a predictive modeling of SBS in an expanding mm-scale plasma. Spatial and temporal behavior of the SBS-ion acoustic waves was found to be in good agreement with the experimental ones for two laser intensities.
Johnson, S A; Zhou, Y; Tracy, M K; Berggren, M J; Stenger, F
1984-01-01
olving the inverse scattering problem for the Helmholtz wave equation without employing the Born or Rytov approximations is a challenging problem, but some slow iterative methods have been proposed. One such method suggested by us is based on solving systems of nonlinear algebraic equations that are derived by applying the method of moments to a sinc basis function expansion of the fields and scattering potential. In the past, we have solved these equations for a 2-D object of n by n pixels in a time proportional to n5. In the present paper, we demonstrate a new method based on FFT convolution and the concept of backprojection which solves these equations in time proportional to n3 X log(n). Several numerical examples are given for images up to 7 by 7 pixels in size. Analogous algorithms to solve the Riccati wave equation in n3 X log(n) time are also suggested, but not verified. A method is suggested for interpolating measurements from one detector geometry to a new perturbed detector geometry whose measurement points fall on a FFT accessible, rectangular grid and thereby render many detector geometrics compatible for use by our fast methods. PMID:6540908
A 3D point-kernel multiple scatter model for parallel-beam SPECT based on a gamma-ray buildup factor
NASA Astrophysics Data System (ADS)
Marinkovic, Predrag; Ilic, Radovan; Spaic, Rajko
2007-09-01
A three-dimensional (3D) point-kernel multiple scatter model for point spread function (PSF) determination in parallel-beam single-photon emission computed tomography (SPECT), based on a dose gamma-ray buildup factor, is proposed. This model embraces nonuniform attenuation in a voxelized object of imaging (patient body) and multiple scattering that is treated as in the point-kernel integration gamma-ray shielding problems. First-order Compton scattering is done by means of the Klein-Nishina formula, but the multiple scattering is accounted for by making use of a dose buildup factor. An asset of the present model is the possibility of generating a complete two-dimensional (2D) PSF that can be used for 3D SPECT reconstruction by means of iterative algorithms. The proposed model is convenient in those situations where more exact techniques are not economical. For the proposed model's testing purpose calculations (for the point source in a nonuniform scattering object for parallel beam collimator geometry), the multiple-order scatter PSF generated by means of the proposed model matched well with those using Monte Carlo (MC) simulations. Discrepancies are observed only at the exponential tails mostly due to the high statistic uncertainty of MC simulations in this area, but not because of the inappropriateness of the model.
NASA Astrophysics Data System (ADS)
Pedio, M.; Wu, Z. Y.; Benfatto, M.; Mascaraque, A.; Michel, E.; Ottaviani, C.; Crotti, C.; Peloi, M.; Zacchigna, M.; Comicioli, C.
2002-10-01
The high-energy resolution O K-edge absorption near-edge x-ray absorption fine structure spectrum has been measured for in situ prepared potassium superoxide. The experimental data have been analyzed in detail by multiple scattering calculations using self-consistent field potentials. In particular, the so-called π resonance at the rising edge, which presents a double-peak structure, has been totally resolved and reproduced by the calculations. This analysis indicates that the grown material is arranged in a KO2 structure with an O-O distance between 1.31 and 1.34 Å. Moreover, the calculation demonstrates both a complete ionic character of the bound between the O2- anion and K atoms and a strong interaction between the anion and solid-state matrices.
Biris, Alexandru S.; Boldor, Dorin; Palmer, Jason; Monroe, William T.; Mahmood, Meena; Dervishi, Enkeleda; Xu, Yang; Li, Zhongrui; Galanzha, Ekaterina I.; Zharov, Vladimir P.
2016-01-01
Nanophotothermolysis with long laser pulses for treatment of scattered cancer cells and their clusters is introduced with the main focus on real-time monitoring of temperature dynamics inside and around individual cancer cells labeled with carbon nanotubes. This technique utilizes advanced time- and spatially-resolved thermal radiometry imaging for the visualization of laser-induced temperature distribution in multiple-point absorbing targets. The capability of this approach was demonstrated for monitoring of thermal effects under long laser exposure (from millisecond to seconds, wavelength 1064 nm, maximum power 1 W) of cervical cancer HeLa cells labeled with carbon nanotubes in vitro. The applications are discussed with a focus on the nanophotothermolysis of small tumors, tumor margins, or micrometastases under the guidance of near-IR and microwave radiometry. PMID:19405720
NASA Astrophysics Data System (ADS)
Cantero, E. D.; Lantschner, G. H.; Eckardt, J. C.; Lovey, F. C.; Arista, N. R.
2010-04-01
Measurements of angular distributions and of the angular dependence of the energy loss of 4-, 6-, and 9-keV protons transmitted through thin Cu and Ag polycrystalline foils are presented. By means of standard multiple-scattering model calculations it is found that a V(r)∝r-2.8 potential leads to significantly better fits of the angular distributions than the standard Thomas Fermi, Lenz-Jensen, or Ziegler-Biersack-Littmark potentials. A theoretical model for the angular dependence of the energy loss based on considering geometric effects on a frictional inelastic energy loss plus an angular-dependent elastic contribution and the effects of foil roughness reproduces the experimental data. This agrees with previous results in Au and Al, therefore extending the applicability of the model to other metallic elements.
Moreno, M. S.; Egerton, R.F.; Rehr, J.J.; Midgley, P.A.
2005-01-15
The electronic structure of the tin oxides SnO and SnO{sub 2} is studied using the fine structure of the Sn-M{sub 4,5} and oxygen K-edges measured by electron energy loss spectroscopy (EELS). The experimental results are compared with real-space multiple scattering calculations. It is observed that both edges are overlapped. The calculations reveal that the observed fine structure is due largely to the oxygen states, and that it can be used to fingerprint each phase. The calculated densities of states are similar for both compounds and suggest a covalent nature. The structures appearing within the first 10 eV above the threshold arise from a covalent mixing of mainly O 2p and Sn 5s-p. For SnO the oxygen edge is satisfactorily reproduced. Discrepancies in the predicted energy position of the features in the EELS of SnO{sub 2} are briefly discussed.
Biris, Alexandru S; Boldor, Dorin; Palmer, Jason; Monroe, William T; Mahmood, Meena; Dervishi, Enkeleda; Xu, Yang; Li, Zhongrui; Galanzha, Ekaterina I; Zharov, Vladimir P
2009-01-01
Nanophotothermolysis with long laser pulses for treatment of scattered cancer cells and their clusters is introduced with the main focus on real-time monitoring of temperature dynamics inside and around individual cancer cells labeled with carbon nanotubes. This technique utilizes advanced time- and spatially-resolved thermal radiometry imaging for the visualization of laser-induced temperature distribution in multiple-point absorbing targets. The capability of this approach was demonstrated for monitoring of thermal effects under long laser exposure (from millisecond to seconds, wavelength 1,064 nm, maximum power 1 W) of cervical cancer HeLa cells labeled with carbon nanotubes in vitro. The applications are discussed with a focus on the nanophotothermolysis of small tumors, tumor margins, or micrometastases under the guidance of near-IR and microwave radiometry. PMID:19405720
Cantero, E. D.; Lantschner, G. H.; Eckardt, J. C.; Lovey, F. C.; Arista, N. R.
2010-04-15
Measurements of angular distributions and of the angular dependence of the energy loss of 4-, 6-, and 9-keV protons transmitted through thin Cu and Ag polycrystalline foils are presented. By means of standard multiple-scattering model calculations it is found that a V(r){proportional_to}r{sup -2.8} potential leads to significantly better fits of the angular distributions than the standard Thomas Fermi, Lenz-Jensen, or Ziegler-Biersack-Littmark potentials. A theoretical model for the angular dependence of the energy loss based on considering geometric effects on a frictional inelastic energy loss plus an angular-dependent elastic contribution and the effects of foil roughness reproduces the experimental data. This agrees with previous results in Au and Al, therefore extending the applicability of the model to other metallic elements.
Carp, Stefan A; Roche-Labarbe, Nadàege; Franceschini, Maria-Angela; Srinivasan, Vivek J; Sakadžić, Sava; Boas, David A
2011-07-01
We suggest that Diffuse Correlation Spectroscopy (DCS) measurements of tissue blood flow primarily probe relative red blood cell (RBC) motion, due to the occurrence of multiple sequential scattering events within blood vessels. The magnitude of RBC shear-induced diffusion is known to correlate with flow velocity, explaining previous reports of linear scaling of the DCS "blood flow index" with tissue perfusion despite the observed diffusion-like auto-correlation decay. Further, by modeling RBC mean square displacement using a formulation that captures the transition from ballistic to diffusive motion, we improve the fit to experimental data and recover effective diffusion coefficients and velocity de-correlation time scales in the range expected from previous blood rheology studies. PMID:21750779
Sica, R J; Haefele, A
2015-03-10
The measurement of temperature in the middle atmosphere with Rayleigh-scatter lidars is an important technique for assessing atmospheric change. Current retrieval schemes for this temperature have several shortcomings, which can be overcome by using an optimal estimation method (OEM). Forward models are presented that completely characterize the measurement and allow the simultaneous retrieval of temperature, dead time, and background. The method allows a full uncertainty budget to be obtained on a per profile basis that includes, in addition to the statistical uncertainties, the smoothing error and uncertainties due to Rayleigh extinction, ozone absorption, lidar constant, nonlinearity in the counting system, variation of the Rayleigh-scatter cross section with altitude, pressure, acceleration due to gravity, and the variation of mean molecular mass with altitude. The vertical resolution of the temperature profile is found at each height, and a quantitative determination is made of the maximum height to which the retrieval is valid. A single temperature profile can be retrieved from measurements with multiple channels that cover different height ranges, vertical resolutions, and even different detection methods. The OEM employed is shown to give robust estimates of temperature, which are consistent with previous methods, while requiring minimal computational time. This demonstrated success of lidar temperature retrievals using an OEM opens new possibilities in atmospheric science for measurement integration between active and passive remote sensing instruments. PMID:25968361
NASA Astrophysics Data System (ADS)
Egan, J.; McMillan, N. D.; Denieffe, D.; Riedel, S.; Doyle, G.; Farrell, G.
2005-09-01
The data-entropy quality-budget developed by the authors is used as an alternative to the conventional power budget. The traditional power budget approach is not capable of providing a full analysis of a system with different noise types and specifically providing a measure of signal quality. The quality-budget addressed this issue by applying its dimensionless 'bit measure' to integrate the analysis of all types of losses. A data-entropy visualisation is produced for each set of points in a reference and test signal. This data-entropy signal is a measure of signal disorder and reflects the power loss and types of signal degradation experienced by the test signal. To analyse the differences between two signals an algorithm known as phase-coherent data-scatter (PCDS) is used to assess levels of attenuation, dispersion, jitter, etc. Practical analysis of telecommunications signals using the new multiple-centroid (MC) PCDS is presented here for the first time. MC-PCDS is then used to analyse differences between sets of data-entropy signals and digital signals. The theory behind MC data-scatter is discussed and its advantages for the quantification of signal degradations are assessed. Finally, a brief consideration is given to the use of pattern recognition algorithms to measure optical signal degrading factors.
NASA Astrophysics Data System (ADS)
Drost, Robert J.; Moore, Terrence J.; Sadler, Brian M.
2011-06-01
Although the concept of non-line-of-sight (NLOS) ultraviolet (UV) communications has been studied for decades, recent advances in the design and manufacturing of light-emitting diodes, filters, and sensors have ignited new interest. In this paper, we discuss a Monte Carlo channel model for NLOS UV communications that accounts for the possibility that a transmitted photon experiences multiple scattering events before being received. By simulating the propagation of many photons based on probabilistic rules derived from physics considerations, a computationally efficient algorithm is obtained that allows for the study of the contribution of various orders of scattering to the received signal and to the system impulse response function. We then demonstrate the use of this channel model in the exploration of several system configurations. In particular, we examine the effect of the transmitter beam shape and receiver sensitivity function on the faithfulness of a well-known linear model of path loss versus distance for short-range NLOS UV systems, and we explore geometry design for interference reduction in a full-duplex link. The use of the model to study such diverse system implementations demonstrates its general applicability.
Rich, A.M.; Armstrong, R.S.; Ellis, P.J.; Freeman, H.C.; Lay, P.A.
1998-11-02
XAFS data in the range 0 {le} k {le} 14.5 {angstrom}{sup {minus}1} have been obtained from frozen aqueous solutions (10 K) of horse heart myoglobin (Mb) in the Fe(III) (aqua-met) and Fe(II) (deoxy) forms. The structures of the Fe sites have been refined using both single-scattering (SS) and multiple-scattering (MS) analyses. The XAFS MS analyses yield more precise Fe-ligand bond lengths (estimated error 0.02--0.03 {angstrom}) than those determined crystallographically (estimated errors {ge} 0.1 {angstrom}). For met-Mb, the MS analysis results in an average Fe-N(pyrrole) distance of 2.05 {angstrom}, an Fe-N(imidazole) distance of 2.17 {angstrom}, and an Fe-O(aqua) distance of 2.08 {angstrom}. For deoxy-Mb, the MS analysis results in Fe-N(pyrrole) and Fe-N(imidazole) distances of 2.06 and 2.16 {angstrom}, respectively. The final XAFS R values are 18.8% and 17.8% for met- and deoxy-Mb, respectively. The robustness of the refinements was tested by varying the starting models, constraints, restraints, and k ranges.
Electromagnetic-wave scattering by a sphere with multiple spherical inclusions.
Ioannidou, Melina P; Chrissoulidis, Dimitrios P
2002-03-01
An exact solution to the problem of electromagnetic-wave scattering from a sphere with an arbitrary number of nonoverlapping spherical inclusions is obtained by use of the indirect mode-matching technique. A set of linear equations for the wave amplitudes of the electric field intensity throughout the inhomogeneous sphere and in the surrounding empty space is determined. Numerical results are calculated by truncation and matrix inversion of that set of equations. Specific information about the truncation number pertaining to the multipole expansions of the electric field intensity is given. The theory and the accompanying computer code successfully reproduce the results of other pertinent papers. Some numerical results [Borghese et al., Appl. Opt. 33, 484 (1994)] were not reproduced well, and that discrepancy is discussed. Our numerical investigation is focused on an acrylic sphere with up to four spherical inclusions. This is the first time that numerical results are presented for a sphere with more than two spherical inclusions. Interesting remarks are made about the effect that the look direction and the structure of the inhomogeneity have on backscattering by the acrylic host sphere. PMID:11876314
Numerical Simulations of Single and Multiple Scattering by Fractal Ice Clusters
NASA Technical Reports Server (NTRS)
Dlugach, Janna M.; Mishchenko, Michael I.; Mackowski, Daniel W.
2011-01-01
We consider the scattering model in the form of a vertically and horizontally homogeneous particulate slab of an arbitrary optical thickness composed of widely separated fractal aggregates built of small spherical ice monomers. The aggregates are generated by applying three different approaches, including simulated cluster-cluster aggregation (CCA) and diffusion-limited aggregation (DLA) procedures. Having in mind radar remote-sensing applications, we report and analyze the results of computations of the backscattering circular polarization ratio obtained using efficient superposition T-matrix and vector radiative-transfer codes. The computations have been performed at a wavelength of 12.6 cm for fractal aggregates with the following characteristics: monomer refractive index m=1.78+i0.003, monomer radius r=1 cm, monomer packing density p=0.2, overall aggregate radii R in the range 4<=R<=10 cm and fractal dimensions D(sub f) 2.5 and 3. We show that for aggregates generated with simulated CCA and DLA procedures, the respective values of the backscattering circular polarization ratio differ weakly for D(sub f) 2.5, but the differences can increase somewhat for D(sub f)3, especially in case of an optically semi-infinite medium. For aggregates with a spheroidal overall shape, the dependence of the circular polarization ratio on the cluster morphology can be quite significant and increases with increasing the aspect ratio of the circumscribing spheroid.
Multiple scattering of electromagnetic waves by an aggregate of uniaxial anisotropic spheres.
Li, Zheng-Jun; Wu, Zhen-Sen; Shi, Yan'e; Bai, Lu; Li, Hai-Ying
2012-01-01
An exact analytical solution is obtained for the scattering of electromagnetic waves from a plane wave with arbitrary directions of propagation and polarization by an aggregate of interacting homogeneous uniaxial anisotropic spheres with parallel primary optical axes. The expansion coefficients of a plane wave with arbitrary directions of propagation and polarization, for both TM and TE modes, are derived in terms of spherical vector wave functions. The effects of the incident angle α and the polarization angle β on the radar cross sections (RCSs) of several types of collective uniaxial anisotropic spheres are numerically analyzed in detail. The characteristics of the forward and backward RCSs in relation to the incident wavelength are also numerically studied. Selected results on the forward and backward RCSs of several types of square arrays of SiO₂ spheres illuminated by a plane wave with different incident angles are described. The accuracy of the expansion coefficients of the incident fields is verified by comparing them with the results obtained from references when the plane wave is degenerated to a z-propagating and x- or y-polarized plane wave. The validity of the theory is also confirmed by comparing the numerical results with those provided by a CST simulation. PMID:22218348
NASA Astrophysics Data System (ADS)
Xu, Junqing; Natoli, Calogero R.; Krüger, Peter; Hayakawa, Kuniko; Sébilleau, Didier; Song, Li; Hatada, Keisuke
2016-06-01
We present an interface package, called ES2MS, for passing self-consistent charge density and potential from Electronic Structure (ES) codes To Multiple Scattering (MS) codes. MS theory is based on the partitioning of the space by atomic-size scattering sites, so that the code provides the charge densities and potentials for each scattering site. For pseudo potential codes, the interface solves Poisson equation to construct the all-electron potential on the radial mesh which is used to solve the transition operators (T-matrix) and Green's functions in MS codes. We show the algorithm of the interface and the example for X-ray absorption spectra of graphene.
Scattering characteristics of high-resolution meteor head echoes detected at multiple frequencies
NASA Astrophysics Data System (ADS)
Close, S.; Oppenheim, M.; Hunt, S.; Dyrud, L.
2002-10-01
Meteor data collected at the Kwajalein Missile Range (KMR) during the peak of the 1998 Leonid storm comprise the only simultaneous observations of meteor head echoes and trails using seven frequencies (very high frequency (VHF), ultrahigh frequency (UHF), L-, S-, C-, Ka-, and W-band spanning 160 MHz to 95 GHz). The primary sensor was the ARPA Long-Range Tracking and Instrumentation Radar (ALTAIR) radar operating at 160 MHz with 30 m range resolution and 422 MHz with 7.5 m range resolution, including both interferometric and polarization capabilities. This paper presents an analysis of this high-resolution data set with the following results: First, these observations support the theory that head echo scattering arises from an ionized region with a density sufficiently high that its plasma frequency exceeds the radar frequency (overdense reflection). Second, radar cross section (RCS) decreases rapidly with decreasing wavelength because higher frequencies must penetrate further into the increasing density of the plasma surrounding the meteoroid to reach its reflection point. Third, head echo angle measurements indicate that most of the observed meteors are sporadics not originating from the Leonid radiant. Fourth, polarization ratios showed that head echo reflections result from plasmas with a circular cross section. Fifth, the highest RCS values are detected near 105 km altitude, where the meteoroid gives up the most kinetic energy during its decent. This paper presents the first analyses of a three-frequency head echo as well as the polarization ratios and RCS characteristics from numerous two-frequency head echoes, which will allow us to develop a better understanding of meteor physics.
Bissonnette, Luc R; Roy, Gilles; Poutier, Laurent; Cober, Stewart G; Isaac, George A
2002-10-20
A multiple-field-of-view (MFOV) lidar measurement and solution technique has been developed to exploit the retrievable particle extinction and size information contained in the multiple-scattering contributions to aerosol lidar returns. We describe the proposed solution algorithm. The primary retrieved parameters are the extinction coefficient at the lidar wavelength and the effective particle diameter from which secondary products such as the extinction at other wavelengths and the liquid-water content (LWC) of liquid-phase clouds can be derived. The solutions are compared with true values in a series of Monte Carlo simulations and with in-cloud measurements. Good agreement is obtained for the simulations. For the field experiment, the retrieved effective droplet diameter and LWC for the available seven cases studied are on average 15% and 35% (worst case) smaller than the measured data, respectively. In the latter case, the analysis shows that the differences cannot be attributed solely to lidar inversion errors. Despite the limited penetration depth (150-300 m) of the lidar pulses, the results of the studied cases indicate that the retrieved lidar solutions remain statistically representative of measurements performed over the full cloud extent. Long-term MFOV lidar monitoring could thus become a practical and economical option for cloud statistical studies but more experimentation on more varied cloud conditions, especially for LWC, is still needed. PMID:12396180
Impact of multiple frequency scattering on GNSS performance under adverse ionospheric conditions
NASA Astrophysics Data System (ADS)
Das, Aditi; Paul, Ashik
and L5 frequencies are closely spaced, their correlation coeffcients show good correspondence. It was observed that the response of L2 and L5 are nearly correlated. But correlation coefficients of L1:L5 and L1:L2 are low during scintillations and shows good correspondence with CNO fades. Similar effects were observed on the SV24 link on April 13, 2013 and on SV1 link on April 16, 2013. During October 2013, scintillations were observed at L1, L2 and L5 on the SV25 and 27 links on October 13, 2013, on the SV25 link on October 18, 2013, SV27 link on October 19, 2013 and SV1 and 27 links on October 21, 2013 respectively. Uncorrelated values of S4 and CNO fluctuations at L1:L2 and L1:L5 indicate different scattering mechanisms even within the same L-band possibly due to dynamic evolving nature of equatorial ionospheric irregularities. This issue is of serious concern in view of application of frequency diversity techniques for scintillation mitigation.
NASA Astrophysics Data System (ADS)
Zhang, A.; Hohlmann, M.
2016-06-01
The geometric-mean method is often used to estimate the spatial resolution of a position-sensitive detector probed by tracks. It calculates the resolution solely from measured track data without using a detailed tracking simulation and without considering multiple Coulomb scattering effects. Two separate linear track fits are performed on the same data, one excluding and the other including the hit from the probed detector. The geometric mean of the widths of the corresponding exclusive and inclusive residual distributions for the probed detector is then taken as a measure of the intrinsic spatial resolution of the probed detector: σ=√σex·σin. The validity of this method is examined for a range of resolutions with a stand-alone Geant4 Monte Carlo simulation that specifically takes multiple Coulomb scattering in the tracking detector materials into account. Using simulated as well as actual tracking data from a representative beam test scenario, we find that the geometric-mean method gives systematically inaccurate spatial resolution results. Good resolutions are estimated as poor and vice versa. The more the resolutions of reference detectors and probed detector differ, the larger the systematic bias. An attempt to correct this inaccuracy by statistically subtracting multiple-scattering effects from geometric-mean results leads to resolutions that are typically too optimistic by 10–50%. This supports an earlier critique of this method based on simulation studies that did not take multiple scattering into account.
Li, Xiang-Guo; Chu, Iek-Heng; Zhang, X. -G.; Cheng, Hai-Ping
2015-05-28
Electron transport in graphene is along the sheet but junction devices are often made by stacking different sheets together in a “side-contact” geometry which causes the current to flow perpendicular to the sheets within the device. Such geometry presents a challenge to first-principles transport methods. We solve this problem by implementing a plane-wave-based multiple-scattering theory for electron transport. In this study, this implementation improves the computational efficiency over the existing plane-wave transport code, scales better for parallelization over large number of nodes, and does not require the current direction to be along a lattice axis. As a first application, wemore » calculate the tunneling current through a side-contact graphene junction formed by two separate graphene sheets with the edges overlapping each other. We find that transport properties of this junction depend strongly on the AA or AB stacking within the overlapping region as well as the vacuum gap between two graphene sheets. Finally, such transport behaviors are explained in terms of carbon orbital orientation, hybridization, and delocalization as the geometry is varied.« less
Weisser, Thomas; Groby, Jean-Philippe; Dazel, Olivier; Gaultier, François; Deckers, Elke; Futatsugi, Sideto; Monteiro, Luciana
2016-02-01
The acoustic response of a rigidly backed poroelastic layer with a periodic set of elastic cylindrical inclusions embedded is studied. A semi-analytical approach is presented, based on Biot's 1956 theory to account for the deformation of the skeleton, coupling mode matching technique, Bloch wave representation, and multiple scattering theory. This model is validated by comparing the derived absorption coefficients to finite element simulations. Numerical results are further exposed to investigate the influence of the properties of the inclusions (type, material properties, size) of this structure, while a modal analysis is performed to characterize the dynamic behaviors leading to high acoustic absorption. Particularly, in the case of thin viscoelastic membranes, an absorption coefficient larger than 0.8 is observed on a wide frequency band. This property is found to be due to the coupling between the first volume mode of the inclusion and the trapped mode induced by the periodic array and the rigid backing, for a wavelength in the air smaller than 11 times the material thickness. PMID:26936546
Valier-Brasier, Tony; Conoir, Jean-Marc; Coulouvrat, François; Thomas, Jean-Louis
2015-10-01
Sound propagation in dilute suspensions of small spheres is studied using two models: a hydrodynamic model based on the coupled phase equations and an acoustic model based on the ECAH (ECAH: Epstein-Carhart-Allegra-Hawley) multiple scattering theory. The aim is to compare both models through the study of three fundamental kinds of particles: rigid particles, elastic spheres, and viscous droplets. The hydrodynamic model is based on a Rayleigh-Plesset-like equation generalized to elastic spheres and viscous droplets. The hydrodynamic forces for elastic spheres are introduced by analogy with those of droplets. The ECAH theory is also modified in order to take into account the velocity of rigid particles. Analytical calculations performed for long wavelength, low dilution, and weak absorption in the ambient fluid show that both models are strictly equivalent for the three kinds of particles studied. The analytical calculations show that dilatational and translational mechanisms are modeled in the same way by both models. The effective parameters of dilute suspensions are also calculated. PMID:26520342
Li, Xiang-Guo; Chu, Iek-Heng; Zhang, X. -G.; Cheng, Hai-Ping
2015-05-28
Electron transport in graphene is along the sheet but junction devices are often made by stacking different sheets together in a “side-contact” geometry which causes the current to flow perpendicular to the sheets within the device. Such geometry presents a challenge to first-principles transport methods. We solve this problem by implementing a plane-wave-based multiple-scattering theory for electron transport. In this study, this implementation improves the computational efficiency over the existing plane-wave transport code, scales better for parallelization over large number of nodes, and does not require the current direction to be along a lattice axis. As a first application, we calculate the tunneling current through a side-contact graphene junction formed by two separate graphene sheets with the edges overlapping each other. We find that transport properties of this junction depend strongly on the AA or AB stacking within the overlapping region as well as the vacuum gap between two graphene sheets. Finally, such transport behaviors are explained in terms of carbon orbital orientation, hybridization, and delocalization as the geometry is varied.
NASA Astrophysics Data System (ADS)
Zhang, Y.; Tournat, V.; Abraham, O.; Durand, O.; Letourneur, S.; Le Duff, A.; Lascoup, B.
2013-02-01
An ultrasonic method providing for an efficient global detection of defects in complex media (multiple scattering or reverberating media) is reported herein; this method is based on the nonlinear acoustic mixing of coda waves (stemming from multiple scattering) with lower frequency-swept pump waves. Such a nonlinear mixing step is made possible by the presence of nonlinear scatterers, such as cracks and delamination, yet remains absent when the waves are scattered only by linear scatterers, as is the case in a complex but defect-free medium. A global inspection is achieved thanks to the use of wide-band coda and pump signals, which ensure the excitation of many resonances along with a homogeneous acoustic energy distribution in the medium. We introduce the existing sensitivity tools developed for Coda Wave Interferometry in extracting the pump amplitude-dependent parameters of the coda waves associated with effective nonlinear parameters of the medium. By comparing results at two damage levels, these effective nonlinear parameters are shown to be correlated with crack presence in glass samples. The mechanisms potentially responsible for the observed amplitude dependence on the tested elastic parameters and waveform modification are discussed.
Punegov, V. I.; Roshchupkin, D. V.
2012-01-15
The effect of multiple scattering on the formation of the {theta}-2{theta} scan curves for a crystal modulated by a surface acoustic wave (SAW), depending on the ultrasonic frequency, has been investigated in the frame-work of the dynamical theory of X-ray diffraction. A model of a Rayleigh surface wave has been analyzed as applied to X-ray diffraction with allowance for the transverse and longitudinal elastic lattice strains. Using the example of the 127 Degree-Sign Y Prime cut of the LiNbO{sub 3} crystal, it is established that the effects of multiple scattering can be neglected for ultrasonic frequencies above 650 MHz; this finding significantly simplifies the numerical calculations of X-ray diffraction from a crystal modulated by a short-wavelength SAW. A comparative quantitative analysis of the experimental data on synchrotron scattering from the 127 Degree-Sign Y Prime cut of a LiNbO{sub 3} crystal modulated by a 952-MHz SAW have been performed, both taking into account and neglecting the effects of multiple scattering. It is shown that the computation time can be reduced by 2 to 3 orders of magnitude.
Wojcik, J; Litniewski, J; Nowicki, A
2011-10-01
The integral equations that describe scattering in the media with step-rise changing parameters have been numerically solved for the trabecular bone model. The model consists of several hundred discrete randomly distributed elements. The spectral distribution of scattering coefficients in subsequent orders of scattering has been presented. Calculations were carried on for the ultrasonic frequency ranging from 0.5 to 3 MHz. Evaluation of the contribution of the first, second, and higher scattering orders to total scattering of the ultrasounds in trabecular bone was done. Contrary to the approaches that use the μCT images of trabecular structure to modeling of the ultrasonic wave propagation condition, the 3D numerical model consisting of cylindrical elements mimicking the spatial matrix of trabeculae, was applied. The scattering, due to interconnections between thick trabeculae, usually neglected in trabecular bone models, has been included in calculations when the structure backscatter was evaluated. Influence of the absorption in subsequent orders of scattering is also addressed. Results show that up to 1.5 MHz, the influence of higher scattering orders on the total scattered field characteristic can be neglected while for the higher frequencies, the relatively high amplitude interference peaks in higher scattering orders clearly occur. PMID:21973345
Shea, Jacob D.; Kosmas, Panagiotis; Hagness, Susan C.; Van Veen, Barry D.
2010-01-01
Purpose: Breast density measurement has the potential to play an important role in individualized breast cancer risk assessment and prevention decisions. Routine evaluation of breast density will require the availability of a low-cost, nonionizing, three-dimensional (3-D) tomographic imaging modality that exploits a strong properties contrast between dense fibroglandular tissue and less dense adipose tissue. The purpose of this computational study is to investigate the performance of 3-D tomography using low-power microwaves to reconstruct the spatial distribution of breast tissue dielectric properties and to evaluate the modality for application to breast density characterization. Methods: State-of-the-art 3-D numerical breast phantoms that are realistic in both structural and dielectric properties are employed. The test phantoms include one sample from each of four classes of mammographic breast density. Since the properties of these phantoms are known exactly, these testbeds serve as a rigorous benchmark for the imaging results. The distorted Born iterative imaging method is applied to simulated array measurements of the numerical phantoms. The forward solver in the imaging algorithm employs the finite-difference time-domain method of solving the time-domain Maxwell’s equations, and the dielectric profiles are estimated using an integral equation form of the Helmholtz wave equation. A multiple-frequency, bound-constrained, vector field inverse scattering solution is implemented that enables practical inversion of the large-scale 3-D problem. Knowledge of the frequency-dependent characteristic of breast tissues at microwave frequencies is exploited to obtain a parametric reconstruction of the dispersive dielectric profile of the interior of the breast. Imaging is performed on a high-resolution voxel basis and the solution is bounded by a known range of dielectric properties of the constituent breast tissues. The imaging method is validated using a breast
Nisbet, A. G. A.; Beutier, G.; Fabrizi, F.; Moser, B.; Collins, S. P.
2015-01-01
A new form of diffraction lines similar to Rutherford, Kikuchi and Kossel lines has been identified. They can be used to eliminate the need for sample/source matching in Lonsdale’s triple convergent line method in lattice-parameter determination. A new form of diffraction lines has been identified, similar to Rutherford, Kikuchi and Kossel lines. This paper highlights some of the properties of these lines and shows how they can be used to eliminate the need for sample/source matching in Lonsdale’s triple convergent line method in lattice-parameter determination.
Kondrat'ev, Andrei V
2004-06-30
Variation in the correlation function of light multiply scattered by a random medium was observed with increasing the incident beam power. The light-induced motion of microparticles in suspension, caused by a high-power laser radiation, serves as an additional factor in the decorrelation of the scattered light. The experimental data are in good agreement with the results of theoretical analysis. (light scattering)
Giachini, Lisa; Francia, Francesco; Mallardi, Antonia; Palazzo, Gerardo; Carpenè, Emilio; Boscherini, Federico; Venturoli, Giovanni
2005-01-01
Binding of transition metal ions to the reaction center (RC) protein of the photosynthetic bacterium Rhodobacter sphaeroides has been previously shown to slow light-induced electron and proton transfer to the secondary quinone acceptor molecule, QB. On the basis of x-ray diffraction at 2.5 Å resolution a site, formed by AspH124, HisH126, and HisH128, has been identified at the protein surface which binds Cd2+ or Zn2+. Using Zn K-edge x-ray absorption fine structure spectroscopy we report here on the local structure of Zn2+ ions bound to purified RC complexes embedded into polyvinyl alcohol films. X-ray absorption fine structure data were analyzed by combining ab initio simulations and multiparameter fitting; structural contributions up to the fourth coordination shell and multiple scattering paths (involving three atoms) have been included. Results for complexes characterized by a Zn to RC stoichiometry close to one indicate that Zn2+ binds two O and two N atoms in the first coordination shell. Higher shell contributions are consistent with a binding cluster formed by two His, one Asp residue, and a water molecule. Analysis of complexes characterized by ∼2 Zn ions per RC reveals a second structurally distinct binding site, involving one O and three N atoms, not belonging to a His residue. The local structure obtained for the higher affinity site nicely fits the coordination geometry proposed on the basis of x-ray diffraction data, but detects a significant contraction of the first shell. Two possible locations of the second new binding site at the cytoplasmic surface of the RC are proposed. PMID:15613631
NASA Astrophysics Data System (ADS)
Bednyakov, A. A.
2014-09-01
Several "misconceptions" regarding the theory of multiple scattering of fast charged particles in matter developed by Molière in 1947-1948 and its application in the analysis of experimental results are discussed. It is shown that the critics of this theory misinterpreted the Molière method for determining the cross section of particle scattering by atoms with the screening of their nuclear fields by electron shells described by the Thomas-Fermi statistical model. If the original Molière method is applied consistently, the obtained scattering cross section generally agrees with the results of later classical calculations carried out by Lindhard and his collaborators and other authors.
NASA Astrophysics Data System (ADS)
Singh, Tejbir; Singh, Parjit S.
2011-12-01
The pulse height spectra for different thicknesses of portland cement in the reflected geometry has been recorded with the help of a NaI(Tl) scintillator detector and 2 K MCA card using different gamma-ray sources such as Hg203 (279 keV), Cs137 (662 keV) and Co60 (1173 and 1332 keV). It has been observed that the multiple scatter peak for portland cement appears at 110 (±7) keV in all the spectra irrespective of different incident photon energies in the range 279-1332 keV from different gamma-ray sources. Further, the variation in the intensity of the multiple scatter peak with the thickness of portland cement in the backward semi-cylinders has been investigated.
Ibraeva, E. T.; Imambekov, O.
2015-07-15
Differential cross sections for elastic p{sup 6,8}He and p{sup 8,9}Li scattering at energies between 60 and 70 MeV per nucleon and at the energy of 700 MeV per nucleon were calculated. The calculations in question were performed with the wave functions found on the basis of the α–n–n (for {sup 6}He), α–t–n (for {sup 8}Li), and α–t–2n (for {sup 9}Li) three-body models and with the density from the large-scale shell model for the {sup 8}He nucleus. The respective matrix elements were derived either upon taking fully into account the multiple-scattering operator or in the optical-limit approximation. A comparison of the results of the precise and approximate calculations made it possible to estimate reliably the contribution of higher multiplicity collisions to the differential cross sections.
NASA Technical Reports Server (NTRS)
Lacis, Andrew A.; Oinas, Valdar
1991-01-01
A radiative transfer method for treating nongray gaseous absorption and thermal emission in vertically inhomogeneous multiple scattering atmospheres is described. Probability density distributions of absorption coefficient strength are derived from line-by-line calculations to construct line-by-line and band model based k distributions. The monotonic ordering of absorption coefficient strengths in these k distributions implicitly preserves the monochromatic structure of the atmosphere at different pressure levels, thus simulating monochromatic spectral integration at a fraction of the line-by-line computing cost. The k distribution approach also permits accurate modeling of overlapping absorption by different atmospheric gases and accurate treatment of nongray absorption in multiple scattering media. It is shown that the correlated k distribution method is capable of achieving numerical accuracy to within 1 percent of cooling rates obtained with line-by-line calculations throughout the troposphere and most of the stratosphere.
Froula, D H; Davis, P; Divol, L; Ross, J S; Meezan, N; Price, D; Glenzer, S H; Rousseaux, C
2005-11-01
The dispersion of ion-acoustic fluctuations has been measured using a novel technique that employs multiple color Thomson-scattering diagnostics to measure the frequency spectrum for two separate thermal ion-acoustic fluctuations with significantly different wave vectors. The plasma fluctuations are shown to become dispersive with increasing electron temperature. We demonstrate that this technique allows a time resolved local measurement of electron density and temperature in inertial confinement fusion plasmas. PMID:16383991
NASA Astrophysics Data System (ADS)
Chang, Xin
This dissertation proposal is concerned with the use of fast and broadband full-wave electromagnetic methods for modeling high speed interconnects (e.g, vertical vias and horizontal traces) and passive components (e.g, decoupling capacitors) for structures of PCB and packages, in 3D IC, Die-level packaging and SIW based devices, to effectively modeling the designs signal integrity (SI) and power integrity (PI) aspects. The main contributions finished in this thesis is to create a novel methodology, which hybridizes the Foldy-Lax multiple scattering equations based fast full wave method, method of moment (MoM) based 1D technology, modes decoupling based geometry decomposition and cavity modes expansions, to model and simulate the electromagnetic scattering effects for the irregular power/ground planes, multiple vias and traces, for fast and accurate analysis of link level simulation on multilayer electronic structures. For the modeling details, the interior massively-coupled multiple vias problem is modeled most-analytically by using the Foldy-Lax multiple scattering equations. The dyadic Green's functions of the magnetic field are expressed in terms of waveguide modes in the vertical direction and vector cylindrical wave expansions or cavity modes expansions in the horizontal direction, combined with 2D MoM realized by 1D technology. For the incident field of the case of vias in the arbitrarily shaped antipad in finite large cavity/waveguide, the exciting and scattering field coefficients are calculated based on the transformation which converts surface integration of magnetic surface currents in antipad into 1D line integration of surface charges on the vias and on the ground plane. Geometry decomposition method is applied to model and integrate both the vertical and horizontal interconnects/traces in arbitrarily shaped power/ground planes. Moreover, a new form of multiple scattering equations is derived for solving coupling effects among mixed metallic
Hudson, E.A.; Rehr, J.J.; Bucher, J.J.
1995-11-15
A theoretical study of the uranium {ital L}{sub 3}-edge x-ray absorption near-edge structure (XANES) is presented for several uranium compounds, including oxides, intermetallics, uranyl fluoride, and {alpha}-uranium. Calculations were performed using FEFF6, an {ital ab} {ital initio} multiple-scattering (MS) code that includes the most important features of current theories. The results, which account for both the fine structure {chi} and the atomiclike background {mu}{sub 0} of the absorption coefficient {mu}, are compared to new and previously measured experimental spectra, reavealing very good agreement for most systems. For several compounds, a more detailed theoretical analysis determined the influence of cluster size and scattering order upon the calculated spectra. Results indicate that MS paths and scattering paths that include rather distant atoms make significant contributions for UO{sub 2}, whereas XANES for crystals with lower symmetry and density can be modeled using only shorter single-scattering paths. In most cases, assumption of a screened final state in the calculation gives better agreement with experiment than use of an unscreened final state. The successful modeling of spectra for a variety of different uranium compounds, with differing spectral features, indicates that the semirelativistic treatment of XANES used here is adequate even for heavy elements. The well-known resonance, observed experimentally for uranyl (UO{sub 2}{sup 2+}) compounds {approx}15 eV above the white line, is successfully modeled here for the first time, using multiple-scattering paths within the O-U-O axial bonds. Overlapping muffin-tin spheres were required in the calculation, probably as a result of the short uranyl axial bonds.
Yashchuk, V P; Tikhonov, E A; Bukatar', A O; Prigodiuk, O A; Smalyuk, A P
2011-10-31
A method is described for deriving Raman spectra of organic dyes from their random lasing spectra. The method was tested using Rhodamine 6G. The Raman spectrum obtained for this dye agrees well with the spectra measured by standard techniques but is more structured, which allows unresolved features to be detected. The spectrum provides more detailed information owing to the interference between the Raman scattered light and amplified spontaneous emission of the dye molecules within a photon mean free path. One advantage of the method is that the luminescence of the dye helps to observe Raman lines, which allows one to work in the Stokes region and facilitates the measurement procedure. (nonlinear optical phenomena)
NASA Astrophysics Data System (ADS)
Omari, Khalid
This thesis investigated the development and assessment of a simple parameterization of the multiple scattering within canopies assuming the single scattering field is known and the background beneath the canopy is completely absorbing. The parameterization is based on the concept of spectral invariants related to recollision and escape probabilities from vegetation canopies. The simplified approach is evaluated against detailed 3-D ray tracing model, PARCINOPY, as well as reference datasets from the Radiation Modelling Intercomparison Experiment On-Line Checker. Comparison with homogenous canopies simulated with PARCINOPY showed that the model's performance is best in both the solar principal and perpendicular planes at low and mid LAI levels for all solar zenith angles. The comparison to the On-line Checker datasets shows also that the model is a suitable approach to describe the multiple scattering components of physically based models. This simple parameterization is then incorporated into the Four Scale Linear Model for Anisotropie Reflectance (FLAIR) canopy radiative transfer model to enhance the description of the spectrally dependant multiple scattered radiation field of a forest canopy. The contribution of the multiply scattered radiation between the canopy and the background is also added to the parameterization of the multiple scattering component. The validation of the new version of the FLAIR model was performed using the multi-angular data sets obtained by the airborne sensor POLarization and Directionality of the Earth's Reflectances (POLDER) during the BOReal Ecosystem-Atmosphere Study (BOREAS) campaign of 1994. The results indicate that this approach is well suited to the FLAIR model. It is also demonstrated that the multiple scattering problem can be parameterized by a limited number of architectural parameters and the leaf scattering coefficient. Finally, the combined canopy-leaf PROFLAIR (PROSPECT + FLAIR) model is used to investigate the
NASA Astrophysics Data System (ADS)
Randall, Summer Lockerbie
The investigation of Optical Low Coherence Reflectometry (OLCR) for evaluation of highly scattering suspensions involves a balance between the observation of real systems and theoretical development. The main focus of this work was the development and utilization of OLCR to investigate highly scattering solid-liquid suspensions over a wide range of particle sizes, using monodispersed, bimodal, and polydispersed polystyrene nanosphere suspensions and Department of Energy (DOE) waste surrogates. The results were the first experimental demonstration that coherent optical backscattering from media with randomly distributed spherical nanoparticles is dominated by Mie resonances. Industrial process samples of various sizes and dispersity were also measured to expand the applicability of OLCR to a wide range of process needs. Current research has focused on the deconvolution of sample parameters from the tailing decay profiles of highly scattering matrices. Significant progress has been made on data analysis methods for monodispersed and more complex compositions of polystyrene suspensions and these methods have been applied to HLW surrogate suspensions and several industrial models. The research described within this dissertation has implications for measurement needs on basic science, industrial, and national laboratory levels. The scope of this research includes advancements in both fundamental understanding of multiple scattering through analysis of model systems and in development and application of the technology to current measurement needs within industry.
NASA Astrophysics Data System (ADS)
Larin, Kirill V.; Ghosn, M. G.
2006-12-01
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 μm where most likely single scattering of light occurs in cornea. It is shown that 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)×10-5 and (1.71±0.51)×10-5 cm s-1, respectively.
NASA Astrophysics Data System (ADS)
Silies, Martin; Mascheck, Manfred; Leipold, David; Kollmann, Heiko; Schmidt, Slawa; Sartor, Janos; Yatsui, Takashi; Kitamura, Kokoro; Ohtsu, Motoicho; Kalt, Heinz; Runge, Erich; Lienau, Christoph
2016-07-01
We investigate the influence of the diameter and the filling factor of randomly arranged ZnO nanoneedles on the multiple scattering and localization of light in disordered dielectrics. Coherent, ultra-broadband second-harmonic (SH) microscopy is used to probe the spatial localization of light in representative nm-sized ZnO arrays of needles. We observe strong fluctuations of the SH intensity inside different ZnO needle geometries. Comparison of the SH intensity distributions with predictions based on a one-parameter scaling model indicate that SH fluctuations can be taken as a quantitative measure for the degree of localization. Interestingly, the strongest localization signatures are found for densely packed arrays of thin needles with diameters in the range of only 30 nm range, despite the small scattering cross section of these needles. FDTD simulations indicate that in this case coupling of electric near-fields between neighbouring needles governs the localization.
Helmeke, H J; Hundeshagen, H
1995-08-01
Due to scattering of protons or deuterons in the target gas the radius of beams increases with increasing penetration depth of the particles. The increase depends on the kind of beam particle, the energy, the target gas and its temperature and pressure. A Monte-Carlo program was developed for stimulation of multiple scattering. The initial beam has a particle distribution of variable sinusoidal shape behind the entrance window and may be cut off by the simulation of a collimator. The beam distribution is calculated for up to 14 planes representing energy values of the particles due to a predefined range from one plane to the next. The energy loss is calculated with the help of an integrated Bethe-Bloch routine. The distribution of the particles within the plane may be rearranged into profiles and transferred to a spreadsheet for further manipulation and graphical printout. Simulations are carried out for radionuclide production routes, commonly used for position emission tomography (PET). PMID:7633390
Fister, T. T.; Nagel, K. P.; Vila, F. D.; Seidler, G. T.; Hamner, C.; Cross, J. O.; Rehr, J. J.; Univ. Washington; Washington State Univ.
2009-01-01
We report measurements of the nonresonant inelastic x-ray scattering (NRIXS) from the O 1s orbitals in ice Ih, and also report calculations of the corresponding spectra for ice Ih and several other phases of water ice. We find that the intermediate-energy fine structure may be calculated well using an ab initio real-space full multiple scattering approach and that it provides a strong fingerprint of the intermediate-range order for some ice phases. Both experiment and theory find that the intermediate-range fine structure, unlike the near-edge structure, is independent of momentum transfer (q) to very high q. These results have important consequences for future NRIXS measurements of high-pressure phases of ice.
Technology Transfer Automated Retrieval System (TEKTRAN)
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...
Bendoula, Ryad; Gobrecht, Alexia; Moulin, Benoit; Roger, Jean-Michel; Bellon-Maurel, Veronique
2015-01-01
Near-infrared spectroscopy (NIRS) is a powerful non-destructive analytical method used to analyze major compounds in bulk materials and products and requiring no sample preparation. It is widely used in routine analysis and also in line in industries, in vivo with biomedical applications, or in field for agricultural and environmental applications. However, highly scattering samples subvert Beer-Lambert law's linear relationship between spectral absorbance and the concentration. Instead of spectral pre-processing, which is commonly used by NIR spectroscopists to mitigate the scattering effect, we put forward an optical method, i.e., coupling polarized light with NIR spectrometry, to free spectra from scattering effect. This should allow us to retrieve linear and steady conditions for spectral analysis. When tested in visible-NIR (Vis-NIR) range (400-800 nm) on model media, mixtures of scattering and absorbing particles, the setup provided significant improvements in absorber concentration estimation precision as well as in the quality and robustness of the calibration model. PMID:25498765
NASA Astrophysics Data System (ADS)
Bachmann, Charles M.; Peck, Douglas S.; Ambeau, Brittany; Harms, Justin; Schultz, Malachi
2015-09-01
Approximate solutions to the Radiative transfer equation for granular media have been previously developed1. To apply these models to coastal sediments, modifications are needed to account for observed phenomenology. This study uses a new hyperspectral goniometer system, the Goniometer of the Rochester Institute of Technology (GRIT), designed for both field and laboratory settings, to compare observed bidirectional reflectance distribution function (BRDF) measurements with outcomes predicted by the approximate radiative transfer solutions. In previous laboratory studies,2 using a more limited hyperspectral goniometer observing in the principle plane, we had seen that the degree of optical contrast between coastal sand constituents was indicative of whether these models accurately predict the observed BRDF dependence on sediment density. Our earlier measurements using another field hyperspectral goniometer also demonstrated results consistent with the laboratory measurements as well as with CASI- 1500 airborne hyperspectral measurements3,4. In our earlier work,2 the presence of highly contrasting constituents (translucent quartz and more opaque fractions composed of minerals such as magnetite) led to greater reflectance as density decreased, exactly the opposite of what was anticipated from radiative transfer models for a more uniform sand. The present study shows that the illumination zenith angle also plays a significant role in whether or not BRDF dependency exhibits behavior predicted by current radiative transfer theory, and this distinction is directly related to the degree of multiple scattering, which depends on the illumination zenith angle. We also investigate a novel sampling paradigm that constrains the measurements to constant phase angle and reveals when the multiple scattering component of models departs from the assumptions of current theory. For the multiple scattering term, we also propose and analyze a simple modification which removes the
NASA Astrophysics Data System (ADS)
Malden, Catharine H.; Speller, Robert. D.
2000-07-01
CdZnTe detectors were used to collect energy-dispersive diffraction spectra at a range of scatter angles, from sheets of explosives hidden in baggage. It is shown that the combined information from these `signatures' can be used to determine whether an explosive sample is present or not. The geometrical configuration of the collimation and the position of the baggage within the scanner must be taken into careful consideration when optimising the capabilities of such a system. The CdZnTe array lends itself well to the detection of explosives in baggage since multiple signals may be collected simultaneously providing more rapid detection than achieved using a single detector.
NASA Technical Reports Server (NTRS)
Stamnes, Knut; Tsay, S.-CHEE; Jayaweera, Kolf; Wiscombe, Warren
1988-01-01
The transfer of monochromatic radiation in a scattering, absorbing, and emitting plane-parallel medium with a specified bidirectional reflectivity at the lower boundary is considered. The equations and boundary conditions are summarized. The numerical implementation of the theory is discussed with attention given to the reliable and efficient computation of eigenvalues and eigenvectors. Ways of avoiding fatal overflows and ill-conditioning in the matrix inversion needed to determine the integration constants are also presented.
NASA Astrophysics Data System (ADS)
Stamnes, Knut; Tsay, S.-Chee; Jayaweera, Kolf; Wiscombe, Warren
1988-06-01
The transfer of monochromatic radiation in a scattering, absorbing, and emitting plane-parallel medium with a specified bidirectional reflectivity at the lower boundary is considered. The equations and boundary conditions are summarized. The numerical implementation of the theory is discussed with attention given to the reliable and efficient computation of eigenvalues and eigenvectors. Ways of avoiding fatal overflows and ill-conditioning in the matrix inversion needed to determine the integration constants are also presented.
Xia, H. Patterson, R.; Feng, Y.; Shrestha, S.; Conibeer, G.
2014-08-11
The rates of charge carrier relaxation by phonon emission are of substantial importance in the field of hot carrier solar cell, primarily in investigation of mechanisms to slow down hot carrier cooling. In this work, energy and momentum resolved deformation potentials relevant to electron-phonon scattering are computed for wurtzite InN and GaN as well as an InN/GaN multiple quantum well (MQW) superlattice using ab-initio methods. These deformation potentials reveal important features such as discontinuities across the electronic bandgap of the materials and variations over tens of eV. The energy dependence of the deformation potential is found to be very similar for wurtzite nitrides despite differences between the In and Ga pseudopotentials and their corresponding electronic band structures. Charge carrier relaxation by this mechanism is expected to be minimal for electrons within a few eV of the conduction band edge. However, hole scattering at energies more accessible to excitation by solar radiation is possible between heavy and light hole states. Moderate reductions in overall scattering rates are observed in MQW relative to the bulk nitride materials.
Amorati, Roberta; Rizzi, Rolando
2002-03-20
A fast-forward radiative transfer (RTF) model is presented that includes cloud-radiation interaction for any number of cloud layers. Layer cloud fraction and transmittance are treated separately and combined with that of gaseous transmittances. RTF is tested against a reference procedure that uses line-by-line gaseous transmittances and solves the radiative transfer equation by use of the adding-doubling method to handle multiple-scattering conditions properly. The comparison is carried out for channels 8, 12, and 14 of the High Resolution Infrared Radiation Sounder (HIRS/2) and for the geostationary satellite METEOSAT thermal infrared and water vapor channels. Fairly large differences in simulated radiances by the two schemes are found in clear conditions for upper- and mid-tropospheric channels; the cause of the differences is discussed. For cloudy situations an improved layer source function is shown to be required when rapid changes in atmospheric transmission are experienced within the model layers. The roles of scattering processes are discussed; results with and without scattering, both obtained by use of a reference code, are compared. Overall, the presented results show that the fast model is capable of reproducing the cloudy results of the much more complex and time-consuming reference scheme. PMID:11921787
NASA Astrophysics Data System (ADS)
Xia, H.; Patterson, R.; Feng, Y.; Shrestha, S.; Conibeer, G.
2014-08-01
The rates of charge carrier relaxation by phonon emission are of substantial importance in the field of hot carrier solar cell, primarily in investigation of mechanisms to slow down hot carrier cooling. In this work, energy and momentum resolved deformation potentials relevant to electron-phonon scattering are computed for wurtzite InN and GaN as well as an InN/GaN multiple quantum well (MQW) superlattice using ab-initio methods. These deformation potentials reveal important features such as discontinuities across the electronic bandgap of the materials and variations over tens of eV. The energy dependence of the deformation potential is found to be very similar for wurtzite nitrides despite differences between the In and Ga pseudopotentials and their corresponding electronic band structures. Charge carrier relaxation by this mechanism is expected to be minimal for electrons within a few eV of the conduction band edge. However, hole scattering at energies more accessible to excitation by solar radiation is possible between heavy and light hole states. Moderate reductions in overall scattering rates are observed in MQW relative to the bulk nitride materials.
Ren, X.; Senftleben, A.; Pflueger, T.; Dorn, A.; Ullrich, J.; Colgan, J.; Pindzola, M. S.; Al-Hagan, O.; Madison, D. H.; Bray, I.; Fursa, D. V.
2010-09-15
Absolutely normalized (e,2e) measurements for H{sub 2} and He covering the full solid angle of one ejected electron are presented for 16 eV sum energy of both final state continuum electrons. For both targets rich cross-section structures in addition to the binary and recoil lobes are identified and studied as a function of the fixed electron's emission angle and the energy sharing among both electrons. For H{sub 2} their behavior is consistent with multiple scattering of the projectile as discussed before [Al-Hagan et al., Nature Phys. 5, 59 (2009)]. For He the binary and recoil lobes are significantly larger than for H{sub 2} and partly cover the multiple scattering structures. To highlight these patterns we propose a alternative representation of the triply differential cross section. Nonperturbative calculations are in good agreement with the He results and show discrepancies for H{sub 2} in the recoil peak region. For H{sub 2} a perturbative approach reasonably reproduces the cross-section shape but deviates in absolute magnitude.
NASA Astrophysics Data System (ADS)
Xu, Junqing; Krüger, Peter; Natoli, Calogero R.; Hayakawa, Kuniko; Wu, Ziyu; Hatada, Keisuke
2015-09-01
The x-ray absorption near-edge structure of graphene, graphene oxide, and diamond is studied by the recently developed real-space full potential multiple scattering (FPMS) theory with space-filling cells. It is shown how accurate potentials for FPMS can be generated from self-consistent charge densities obtained with other schemes, especially the projector augmented wave method. Compared to standard multiple scattering calculations in the muffin-tin approximation, FPMS gives much better agreement with experiment. The effects of various structural modifications on the graphene spectra are well reproduced. (1) Stacking of graphene layers increases the peak intensity in the higher energy region. (2) The spectrum of the C atom located at the edge of a graphene sheet shows a prominent pre-edge structure. (3) Adsorption of oxygen gives rise to the so-called interlayer-state peak. Moreover, O K-edge spectra of graphene oxide are calculated for three types of bonding, C-OH, C-O-C, and C-O, and the proportions of these bondings at 800 ∘C are deduced by fitting them to the experimental spectrum.
Li, Yile; Mei, Chiang C
2007-07-01
We study the Bragg resonance of surface water waves by a two-dimensional array of vertical cylinders covering a large area of the sea. Starting from the resonance criterion known in the physics of solid state and crystallography, we employ asymptotic techniques to derive two-dimensional coupled-mode equations for the envelopes of scattered waves resonated by a plane incident wave. Explicit analytical solutions are obtained for a long strip of cylinder array which may be used for supporting a future offshore airport. Examples of both two-wave and three-wave resonances are discussed in detail. Roles of the band gaps are examined. PMID:17677558
NASA Astrophysics Data System (ADS)
Hizanidis, K.; Bairaktaris, F.; Valvis, S. I.; Ram, A. K.
2015-11-01
Radio frequency waves are of particular importance for heating and current drive in magnetized fusion plasmas. The scattering of these waves by a multitude of density fluctuations, such as blobs in the edge region, is studied by homogenizing the edge region populated by an ensemble of ellipsoidal plasma blobs immersed in an ambient background plasma. The effective permittivity tensor is formulated on the basis of a depolarization dyadic. In general, the interface between the homogenized slab and the ambient plasma is not necessarily aligned with the magnetic field line. The misalignment leads to changes in the propagation characteristics of the RF waves. The scattering of an incident wave is treated by considering the reflection and transmission through a composite plasma slab. This study is a generalization of; it applies to RF waves in plasmas interacting with ellipsoidal blobs of arbitrary shapes and sizes. Supported in part by the Hellenic National Programme on Controlled Thermonuclear Fusion associated with the EUROfusion Consortium, and by DoE.
Sica, R J; Haefele, A
2016-02-01
Lidar measurements of the atmospheric water vapor mixing ratio provide an excellent complement to radiosoundings and passive, ground-based remote sensors. Lidars are now routinely used that can make high spatial-temporal resolution measurements of water vapor from the surface to the stratosphere. Many of these systems can operate during the day and night, with operation only limited by clouds thick enough to significantly attenuate the laser beam. To enhance the value of these measurements for weather and climate studies, this paper presents an optimal estimation method (OEM) to retrieve the water vapor mixing ratio, aerosol optical depth profile, Ångstrom exponent, lidar constants, detector dead times, and measurement backgrounds from multichannel vibrational Raman-scatter lidars. The OEM retrieval provides the systematic uncertainties due to the overlap function, calibration factor, air density and Rayleigh-scatter cross sections, in addition to the random uncertainties of the retrieval due to measurement noise. The OEM also gives the vertical resolution of the retrieval as a function of height, as well as the height to which the contribution of the a priori is small. The OEM is applied to measurements made by the Meteoswiss Raman Lidar for Meteorological Observations (RALMO) in the day and night for clear and cloudy conditions. The retrieved water vapor mixing ratio is in excellent agreement with both the traditional lidar retrieval method and coincident radiosoundings. PMID:26836078
Cavalier, J.; Lemoine, N.; Bonhomme, G.; Tsikata, S.; Honore, C.; Gresillon, D.
2012-08-15
The effect of the collective light scattering diagnostic transfer function is considered in the context of the dispersion relation of the unstable E Multiplication-Sign B mode previously reported. This transfer function is found to have a contribution to the measured frequencies and mode amplitudes which is more or less significant depending on the measurement wavenumbers and angles. After deconvolution, the experimental data are found to be possibly compatible with the idea that the mode frequency in the jet frame (after subtraction of the Doppler effect due to the plasma motion along the thruster axis) is independent of the orientation of the wave vector in the plane orthogonal to the local magnetic field.
Learmonth, T.; McGuinness, C.; Glans, P.-A.; Downes, J.E.; Schmitt, T.; Duda, L.-C.; Guo, J.-H.; Chou, F.C.; Smith, K.E.
2007-10-29
Multiple Zhang-Rice type spectral features have been observed in resonant inelastic X-ray scattering (RIXS) from the quasi-one-dimensional cuprate charge transfer insulator Li{sub 2}CuO{sub 2}. The first feature appears at constant emission energy, and is associated with a Zhang-Rice singlet final state. The second is an interplaquette charge transfer excitation that results in a novel triplet Zhang-Rice-type final state. It is accompanied by the presence of a O 2p nonbonding to upper Hubbard band excitation at an energy close to that of a calculated triplet charge transfer Zhang-Rice-type excitation. The site selectivity and polarization rules associated with RIXS allows these two excitations to be distinguished.
Eisenbach, Markus; Larkin, Jeff; Lutjens, Justin; Rennich, Steven; Rogers, James H
2016-01-01
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. 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.
Peng, Yu; Zhang, Feng; Tao, Hongxun; Wang, Wei; Sun, Lianna; Chen, Wansheng; Wang, Changhong
2015-11-01
A traditional external standard method using HPLC coupled with evaporative light scattering detection has been developed for fast and accurate determination of seven platycosides in Platycodi Radix. However, inevitable difficulties in reference standards preparation process, which are quite costly and time consuming, have made its application limited. To avoid this inconvenience, a simultaneous determination of multiple components with a single reference standard strategy, which could be realized by calibrating the standard curve with internal standard and response factors, was introduced to the HPLC coupled with evaporative light scattering detection method. This is the first time that an incorporation of these two methods has been realized. Among seven ingredients, platycodin D was selected as the internal standard for its relatively easy preparation and low cost. Moreover, according to the investigation on concentration-dependent effects over response factors and robustness test, platycoside E, deapioplatycodin D, platycodin D, and polygalacin D2 were chosen to be the indicators for this novel method. The present method has not shown statistically significant differences with a traditional external standard method as verified sample analysis by the F-test (p = 95%, n = 6). PMID:26331296
Utsav, K C; Varghese, Philip L
2013-07-10
A multiple-pass cell is aligned to focus light at two regions at the center of the cell. The two "points" are separated by 2.0 mm. Each probe region is 200 μm×300 μm. The cell is used to amplify spontaneous Raman scattering from a CH4-air laminar flame. The signal gain is 20, and the improvement in signal-to-noise ratio varies according to the number of laser pulses used for signal acquisition. The temperature is inferred by curve fitting high-resolution spectra of the Stokes signal from N2. The model accounts for details, such as the angular dependence of Raman scattering, the presence of a rare isotope of N2 in air, anharmonic oscillator terms in the vibrational polarizability matrix elements, and the dependence of Herman-Wallis factors on the vibrational level. The apparatus function is modeled using a new line shape function that is the convolution of a trapezoid function and a Lorentzian. The uncertainty in the value of temperature arising from noise, the uncertainty in the model input parameters, and various approximations in the theory have been characterized. We estimate that the uncertainty in our measurement of flame temperature in the least noisy data is ±9 K. PMID:23852217
Cheng, M.C.; Rich, A.M.; Armstrong, R.S.; Ellis, P.J.; Lay, P.A.
1999-12-13
Cytochrome c (cyt c) is a small heme protein (MW 12 384) that functions as a biological electron-transfer agent. It consists of a single polypeptide chain and a prosthetic heme group and provides a pathway for the transfer of electrons from cyt c reductase to cyt c oxidase in the mitochondrial respiratory chain (oxidative phosphorylation). The protein participates in oxidation-reduction reactions with the heme iron alternating between the oxidized (ferric, Fe{sup III}) state and the reduced (ferrous, Fe{sup II}) state. X-ray absorption fine structure (XAFS) data were obtained from frozen aqueous solutions (10 K) of horse heart ferri- and ferrocyt c. Models of the structure about the Fe center were refined to optimize the fit between the observed XAFS in the range 0 {le} k {le} 16.3 {angstrom}{sup {minus}1} and the XAFS calculated using both single-scattering (SS) and multiple-scattering (MS) calculations. The bond lengths obtained are more accurate and precise than those determined previously for cyt c from various species using X-ray crystallography. The Fe-N bond lengths are 1.98--1.99 {angstrom} for both oxidation states of cyt c. The Fe-S bond of derricyt c (2.33 {angstrom}) is significantly longer than that of ferrocyt c (2.29 {angstrom}). The small changes in the bond lengths are consistent with the small reorganizational energy required for the fast electron-transfer reaction of cyt c.
Simon, Peter; Frankowski, Marcin; Bock, Nicole; Neukammer, Jörg
2016-06-21
We developed a microfluidic sensor for label-free flow cytometric cell differentiation by combined multiple AC electrical impedance and light scattering analysis. The measured signals are correlated to cell volume, membrane capacity and optical properties of single cells. For an improved signal to noise ratio, the microfluidic sensor incorporates two electrode pairs for differential impedance detection. One-dimensional sheath flow focusing was implemented, which allows single particle analysis at kHz count rates. Various monodisperse particles and differentiation of leukocytes in haemolysed samples served to benchmark the microdevice applying combined AC impedance and side scatter analyses. In what follows, we demonstrate that AC impedance measurements at selected frequencies allow label-free discrimination of platelets, erythrocytes, monocytes, granulocytes and lymphocytes in whole blood samples involving dilution only. Immunofluorescence staining was applied to validate the results of the label-free cell analysis. Reliable differentiation and enumeration of cells in whole blood by AC impedance detection have the potential to support medical diagnosis for patients with haemolysis resistant erythrocytes or abnormally sensitive leucocytes, i.e. for patients suffering from anaemia or leukaemia. PMID:27229300
Scheinost, A.C.; Sparks, D.L.
2000-03-15
Spectroscopic and microscopic studies have shown that Ni and Co sorption by clay minerals may proceed via formation of surface precipitates. Several studies employing X-ray absorption fine structure (XAFS) spectroscopy suggested the formation of turbostratic, a-type metal hydroxides, of layered double hydroxides (LDH) with Al-for-metal substitution, and of 1:1 or 2:1 phyllosilicates. Distinction of these phases is difficult because they have low crystallinity and/or a small mass compared to the sorbents, and because they have similar metal-metal distances in their hydroxide layers/sheets. Distinction of these phases is crucial, however, because they have substantially differing solubilities. In this paper the authors show that an XAFS beat pattern at about 8 {angstrom} {sup {minus}1} can be used as a fingerprint to unequivocally distinguish LDH from the {alpha}-type hydroxides and phyllosilicates. Full multiple-scattering simulations and experimental spectra of model compounds indicate that the beat pattern is due to focused multiple scattering at Me/Al ratios between 1 and 4(Me = Ni,Co). By applying the fingerprint method to new and to already published XAFS data on Ni and Co surface precipitates, the authors found that LDH preferentially forms in the presence of the Al-containing sorbents pyrophyllite, illite, kaolinite, gibbsite, and alumina above pH 7.0. However, {alpha}-type metal hydroxides form in the presence of the Al-free sorbents talc, silica, and rutile, and in the presence of the Al-containing clay minerals montmorillonite and vermiculite. The authors believe, that the high permanent charge of these latter minerals prevents or retards the release of Al. When Al is available, the formation of LDH seems to be thermodynamically and/or kinetically favored over the formation of {alpha}-type hydroxides.
Scheinost; Sparks
2000-03-15
Spectroscopic and microscopic studies have shown that Ni and Co sorption by clay minerals may proceed via formation of surface precipitates. Several studies employing X-ray absorption fine structure (XAFS) spectroscopy suggested the formation of turbostratic, alpha-type metal hydroxides, of layered double hydroxides (LDH) with Al-for-metal substitution, and of 1:1 or 2:1 phyllosilicates. Distinction of these phases is difficult because they have low crystallinity and/or a small mass compared to the sorbents, and because they have similar metal-metal distances in their hydroxide layers/sheets. Distinction of these phases is crucial, however, because they have substantially differing solubilities. In this paper we show that an XAFS beat pattern at about 8 Å(-1) can be used as a fingerprint to unequivocally distinguish LDH from the alpha-type hydroxides and phyllosilicates. Full multiple-scattering simulations and experimental spectra of model compounds indicate that the beat pattern is due to focused multiple scattering at Me/Al ratios between 1 and 4 (Me=Ni, Co). By applying the fingerprint method to new and to already published XAFS data on Ni and Co surface precipitates, we found that LDH preferentially forms in the presence of the Al-containing sorbents pyrophyllite, illite, kaolinite, gibbsite, and alumina above pH 7.0. However, alpha-type metal hydroxides form in the presence of the Al-free sorbents talc, silica, and rutile, and in the presence of the Al-containing clay minerals montmorillonite and vermiculite. We believe that the high permanent charge of these latter minerals prevents or retards the release of Al. When Al is available, the formation of LDH seems to be thermodynamically and/or kinetically favored over the formation of alpha-type hydroxides. Copyright 2000 Academic Press. PMID:10700399
Stamnes, K; Tsay, S C; Wiscombe, W; Jayaweera, K
1988-06-15
We summarize an advanced, thoroughly documented, and quite general purpose discrete ordinate algorithm for time-independent transfer calculations in vertically inhomogeneous, nonisothermal, plane-parallel media. Atmospheric applications ranging from the UV to the radar region of the electromagnetic spectrum are possible. The physical processes included are thermal emission, scattering, absorption, and bidirectional reflection and emission at the lower boundary. The medium may be forced at the top boundary by parallel or diffuse radiation and by internal and boundary thermal sources as well. We provide a brief account of the theoretical basis as well as a discussion of the numerical implementation of the theory. The recent advances made by ourselves and our collaborators-advances in both formulation and numerical solution-are all incorporated in the algorithm. Prominent among these advances are the complete conquest of two illconditioning problems which afflicted all previous discrete ordinate implementations: (1) the computation of eigenvalues and eigenvectors and (2) the inversion of the matrix determining the constants of integration. Copies of the FORTRAN program on microcomputer diskettes are available for interested users. PMID:20531783
Gao, Jiaxue; Ma, Lan; Lei, Zhen; Wang, Zhenxin
2016-03-01
The mapping of specific single nucleotide polymorphisms (SNPs) in patients' genome is a critical process for the development of personalized therapy. In this work, a DNA microarray-based resonance light scattering (RLS) assay has been developed for multiplexed detection of breast cancer related SNPs with high sensitivity and selectivity. After hybridization of the desired target single-stranded DNAs (ssDNAs) with the ssDNA probes on a microarray, the polyvalent ssDNA modified 13 nm gold nanoparticles (GNPs) are employed to label the hybridization reaction through the formation of a three-stranded DNA system. The H2O2-mediated enlargement of GNPs is then used to enhance the RLS signal. The microarray-based RLS assay provides a detection limit of 10 pM (S/N = 3) for the target ssDNA and determines an allele frequency as low as 1.0% in the target ssDNA cocktail. Combined with an asymmetric PCR technique, the proposed assay shows good accuracy and sensitivity in profiling 4 SNPs related to breast cancer of three selected cell lines. PMID:26899365
NASA Astrophysics Data System (ADS)
Garnier, A.; Pelon, J.; Vaughan, M. A.; Winker, D. M.; Trepte, C. R.; Dubuisson, P.
2015-07-01
Cirrus cloud absorption optical depths retrieved at 12.05 μm are compared to extinction optical depths retrieved at 0.532 μm from perfectly co-located observations of single-layered semi-transparent cirrus over ocean made by the Imaging Infrared Radiometer (IIR) and the Cloud and Aerosol Lidar with Orthogonal Polarization (CALIOP) flying on board the CALIPSO (Cloud-Aerosol Lidar and Infrared Pathfinder Satellite Observations) satellite. IIR infrared absorption optical depths are compared to CALIOP visible extinction optical depths when the latter can be directly derived from the measured apparent two-way transmittance through the cloud. An evaluation of the CALIOP multiple scattering factor is inferred from these comparisons after assessing and correcting biases in IIR and CALIOP optical depths reported in version 3 data products. In particular, the blackbody radiance taken in the IIR version 3 algorithm is evaluated, and IIR retrievals are corrected accordingly. Numerical simulations and IIR retrievals of ice crystal sizes suggest that the ratios of CALIOP extinction and IIR absorption optical depths should remain roughly constant with respect to temperature. Instead, these ratios are found to increase quasi-linearly by about 40 % as the temperature at the layer centroid altitude decreases from 240 to 200 K. It is discussed that this behavior can be explained by variations of the multiple scattering factor ηT applied to correct the measured apparent two-way transmittance for contribution of forward-scattering. While the CALIOP version 3 retrievals hold ηT fixed at 0.6, this study shows that ηT varies with temperature (and hence cloud particle size) from ηT = 0.8 at 200 K to ηT = 0.5 at 240 K for single-layered semi-transparent cirrus clouds with optical depth larger than 0.3. The revised parameterization of ηT introduces a concomitant temperature dependence in the simultaneously derived CALIOP lidar ratios that is consistent with observed changes in CALIOP
NASA Astrophysics Data System (ADS)
Klein, Miles
2008-03-01
Using an extension of BCS theory to a two-band superconductor, Leggett showed that if the relevant parameters obeyed certain conditions a collective mode would exist corresponding to the counter flow of the two condensates.^1 I have extended earlier work on electronic Raman in superconductors^2 to the multiple band case in order to incorporate Leggett's theory. The following effects have been included: (a) Vertex correction in the particle/hole channel where the Raman vertex acts. (b) Realistic parameters that apply to MgB2 yielding a counter flow mode that decays into the pair-breaking continuum associated with the lower gap π band. (c) Large finite wave-vector effects due to the relatively large Fermi velocity of the π band. (d) Integration over the wave-vector in part (c) necessitated by the exponential decay of the photon fields traveling into and out of the metallic sample. A comparison to the results of Blumberg^3 will be given. ^1A.J. Leggett, Progr. Theor. Phys. 36, 901 (1966). ^2M.V. Klein and S.B. Dierker, Phys. Rev. B29, 4976 (1984). ^3G. Blumberg et al., Phys. Rev. Lett. 99, (2007); arXiv:0710.2803.
NASA Astrophysics Data System (ADS)
Imitola, Jaime; Côté, Daniel; Rasmussen, Stine; Xie, X. Sunney; Liu, Yingru; Chitnis, Tanuja; Sidman, Richard L.; Lin, Charles. P.; Khoury, Samia J.
2011-02-01
Myelin loss and axonal degeneration predominate in many neurological disorders; however, methods to visualize them simultaneously in live tissue are unavailable. We describe a new imaging strategy combining video rate reflectance and fluorescence confocal imaging with coherent anti-Stokes Raman scattering (CARS) microscopy tuned to CH2 vibration of myelin lipids, applied in live tissue of animals with chronic experimental autoimmune encephalomyelitis (EAE). Our method allows monitoring over time of demyelination and neurodegeneration in brain slices with high spatial resolution and signal-to-noise ratio. Local areas of severe loss of lipid signal indicative of demyelination and loss of the reflectance signal from axons were seen in the corpus callosum and spinal cord of EAE animals. Even in myelinated areas of EAE mice, the intensity of myelin lipid signals is significantly reduced. Using heterozygous knock-in mice in which green fluorescent protein replaces the CX3CR1 coding sequence that labels central nervous system microglia, we find areas of activated microglia colocalized with areas of altered reflectance and CARS signals reflecting axonal injury and demyelination. Our data demonstrate the use of multimodal CARS microscopy for characterization of demyelinating and neurodegenerative pathology in a mouse model of multiple sclerosis, and further confirm the critical role of microglia in chronic inflammatory neurodegeneration.
Krüger, Peter; Lagos, Maureen J; Ke, Xiaoxing; Van Tendeloo, Gustaaf; Ewels, Chris; Umek, Polona; Guttmann, Peter
2012-01-01
Summary Recent advances in near-edge X-ray-absorption fine-structure spectroscopy coupled with transmission X-ray microscopy (NEXAFS–TXM) allow large-area mapping investigations of individual nano-objects with spectral resolution up to E/ΔE = 104 and spatial resolution approaching 10 nm. While the state-of-the-art spatial resolution of X-ray microscopy is limited by nanostructuring process constrains of the objective zone plate, we show here that it is possible to overcome this through close coupling with high-level theoretical modelling. Taking the example of isolated bundles of hydrothermally prepared sodium titanate nanotubes ((Na,H)TiNTs) we are able to unravel the complex nanoscale structure from the NEXAFS–TXM data using multichannel multiple-scattering calculations, to the extent of being able to associate specific spectral features in the O K-edge and Ti L-edge with oxygen atoms in distinct sites within the lattice. These can even be distinguished from the contribution of different hydroxyl groups to the electronic structure of the (Na,H)TiNTs. PMID:23213642
Bittencourt, Carla; Krüger, Peter; Lagos, Maureen J; Ke, Xiaoxing; Van Tendeloo, Gustaaf; Ewels, Chris; Umek, Polona; Guttmann, Peter
2012-01-01
Recent advances in near-edge X-ray-absorption fine-structure spectroscopy coupled with transmission X-ray microscopy (NEXAFS-TXM) allow large-area mapping investigations of individual nano-objects with spectral resolution up to E/ΔE = 10(4) and spatial resolution approaching 10 nm. While the state-of-the-art spatial resolution of X-ray microscopy is limited by nanostructuring process constrains of the objective zone plate, we show here that it is possible to overcome this through close coupling with high-level theoretical modelling. Taking the example of isolated bundles of hydrothermally prepared sodium titanate nanotubes ((Na,H)TiNTs) we are able to unravel the complex nanoscale structure from the NEXAFS-TXM data using multichannel multiple-scattering calculations, to the extent of being able to associate specific spectral features in the O K-edge and Ti L-edge with oxygen atoms in distinct sites within the lattice. These can even be distinguished from the contribution of different hydroxyl groups to the electronic structure of the (Na,H)TiNTs. PMID:23213642
NASA Astrophysics Data System (ADS)
Chen, Jeng-Tzong; Lee, Jia-Wei
2013-09-01
In this paper, we focus on the water wave scattering by an array of four elliptical cylinders. The null-field boundary integral equation method (BIEM) is used in conjunction with degenerate kernels and eigenfunctions expansion. The closed-form fundamental solution is expressed in terms of the degenerate kernel containing the Mathieu and the modified Mathieu functions in the elliptical coordinates. Boundary densities are represented by using the eigenfunction expansion. To avoid using the addition theorem to translate the Mathieu functions, the present approach can solve the water wave problem containing multiple elliptical cylinders in a semi-analytical manner by introducing the adaptive observer system. Regarding water wave problems, the phenomena of numerical instability of fictitious frequencies may appear when the BIEM/boundary element method (BEM) is used. Besides, the near-trapped mode for an array of four identical elliptical cylinders is observed in a special layout. Both physical (near-trapped mode) and mathematical (fictitious frequency) resonances simultaneously appear in the present paper for a water wave problem by an array of four identical elliptical cylinders. Two regularization techniques, the combined Helmholtz interior integral equation formulation (CHIEF) method and the Burton and Miller approach, are adopted to alleviate the numerical resonance due to fictitious frequency.
NASA Astrophysics Data System (ADS)
Cui, P. X.; Lian, F. L.; Wang, Y.; Wen, Yi; Chu, W. S.; Zhao, H. F.; Zhang, S.; Li, J.; Lin, D. H.; Wu, Z. Y.
2014-02-01
Prion-related protein (PrP), a cell-surface copper-binding glycoprotein, is considered to be responsible for a number of transmissible spongiform encephalopathies (TSEs). The structural conversion of PrP from the normal cellular isoform (PrPC) to the post-translationally modified form (PrPSc) is thought to be relevant to Cu2+ binding to histidine residues. Rabbits are one of the few mammalian species that appear to be resistant to TSEs, because of the structural characteristics of the rabbit prion protein (RaPrPC) itself. Here we determined the three-dimensional local structure around the C-terminal high-affinity copper-binding sites using X-ray absorption near-edge structure combined with ab initio calculations in the framework of the multiple-scattering (MS) theory. Result shows that two amino acid resides, Gln97 and Met108, and two histidine residues, His95 and His110, are involved in binding this copper(II) ion. It might help us understand the roles of copper in prion conformation conversions, and the molecular mechanisms of prion-involved diseases.
NASA Astrophysics Data System (ADS)
Perico, Angelo; La Ferla, Roberto; Freed, Karl F.
1987-05-01
Numerical calculations are presented for the frequency dependent Huggins coefficient based on the formal derivation provided in paper I using the dynamical multiple scattering theory for discrete Gaussian chains. The calculations employ fast Fourier transform methods and confirm the analytic complexity of this frequency dependence as previously anticipated from our calculations of the concentration dependence of the normal mode autocorrelation function. The harmonic spring model is considered because this simple limit is amenable to closed form solution, displaying the frequency dependence of the relaxation rates and providing a useful check on the difficult numerical computations for higher numbers n of beads. The steady state Huggins coefficient is also calculated with carefully optimized Gauss-Laguerre quadrature methods which permit extrapolation to n→∞. The calculated steady state value of 0.33 lies below experimental data for theta solutions, and an extensive discussion of the experimental data is provided to understand the discrepancy. One major factor, suggested by Schrag, arises from a strong concentration dependence of the individual bead friction coefficient.
NASA Astrophysics Data System (ADS)
Los, Victor F.; Los, Nicholas V.
2016-04-01
The exact expressions for an energy-dependent Green function (resolvent), space-time propagator and time-dependent solution for the wave function Ψ(r, t) of a particle moving in the presence of an asymmetric rectangular well/barrier potential are obtained. It is done by applying to this problem the multiple scattering theory (MST), which is different from previous such approaches by using the localized at the potential jumps effective potentials responsible for transmission through and reflection from the considered rectangular potential. This approach (alternative to the path-integral one) enables considering these processes from a particle (rather than a wave) point of view. The solution for the wave function describes these quantum phenomena as a function of time and is related to the fundamental issues (such as measuring time) of quantum mechanics. It is presented in terms of integrals of elementary functions and is a sum of the forward- and backward-moving components of the wave packet. The relative contribution of these components and their interference as well as of the potential asymmetry to the probability density |Ψ(x, t)|2 and particle dwell time is considered and numerically visualized for narrow and broad energy (momentum) distributions of the initial Gaussian wave packet. It is shown that in the case of a broad initial wave packet, the quantum mechanical counterintuitive effect of the influence of the backward-moving components on the considered quantities becomes significant.
Rouff, Ashaki A; Rabe, Stefan; Nachtegaal, Maarten; Vogel, Frédéric
2009-06-25
Phosphorus K-edge X-ray absorption fine structure (XAFS) was explored as a means to distinguish between aqueous and solid phosphates and to detect changes in phosphate protonation state. Data were collected for H(3)PO(4), KH(2)PO(4), K(2)HPO(4) and K(3)PO(4) solids and solutions and for the more complex phosphates, hydroxylapatite (HAP) and struvite (MAP). The X-ray absorption near-edge structure (XANES) spectra for solid samples are distinguishable from those of solutions by a shoulder at approximately 4.5 eV above the edge, caused by scattering from cation sites. For phosphate species, the intensity of the white line peak increased for solid and decreased for aqueous samples, respectively, with phosphate deprotonation. This was assigned to increasing charge delocalization in solid samples, and the effect of solvating water molecules on charge for aqueous samples. In the extended X-ray absorption fine structure (EXAFS), backscattering from first-shell O atoms dominated the chi(k) spectra. Multiple scattering (MS) via a four-legged P-O(1)-P-O(1)-P collinear path was localized in the lower k region at approximately 3.5 A(-1) and contributed significantly to the beat pattern of the first oscillation. For EXAFS analysis, increasing Debye-Waller factors suggest more disorder in the P-O shell with addition of protons to the crystal structure due to the lengthening effects of P-OH bonds. This disorder produces splitting in the hybridized P 3p-O 2p band in the density of states. For aqueous samples, however, increased protonation reduced the structural disorder within this shell. This was linked to a change from kosmotropic to chaotropic behavior of the phosphate species, with reduced effects of H bonding on structural distortion. The intensity of MS is correlated to the degree of disorder in the P-O shell, with more ordered structures exhibiting enhanced MS. The observed trends in the XAFS data can be used to distinguish between phosphate species in both solid and
NASA Technical Reports Server (NTRS)
Hong, Byungsik; Maung, Khin Maung; Wilson, John W.; Buck, Warren W.
1989-01-01
The derivations of the Lippmann-Schwinger equation and Watson multiple scattering are given. A simple optical potential is found to be the first term of that series. The number density distribution models of the nucleus, harmonic well, and Woods-Saxon are used without t-matrix taken from the scattering experiments. The parameterized two-body inputs, which are kaon-nucleon total cross sections, elastic slope parameters, and the ratio of the real to the imaginary part of the forward elastic scattering amplitude, are presented. The eikonal approximation was chosen as our solution method to estimate the total and absorptive cross sections for the kaon-nucleus scattering.
ERIC Educational Resources Information Center
Young, Andrew T.
1982-01-01
The correct usage of such terminology as "Rayleigh scattering,""Rayleigh lines,""Raman lines," and "Tyndall scattering" is resolved during an historical excursion through the physics of light-scattering by gas molecules. (Author/JN)
Surface wave dispersion from small vertical scatterers
NASA Astrophysics Data System (ADS)
van Wijk, K.; Levshin, A. L.
2004-10-01
Heterogeneity in the subsurface creates conflicting types of dispersion of seismic waves. A laboratory and numerical experiment show that multiple scattering of elastic waves from isolated heterogeneities near the surface not only attenuates, but also delays coherent events. Because scattering off these impedance contrasts is frequency dependent, multiple scattering is a source of dispersion. If ignored, multiple scattering dispersion could be erroneously attributed to a model with horizontal homogeneous layers of different wave speeds.
Rich, A M; Ellis, P J; Tennant, L; Wright, P E; Armstrong, R S; Lay, P A
1999-12-14
The NO adducts of leghemoglobin (Lb) are implicated in biological processes, but only the adduct with ferrous Lb (Lb(II)NO) has been characterized previously. We report the first characterization of ferric nitrosylleghemoglobin (Lb(III)NO) and XAS experiments performed on frozen aqueous solutions of Lb(II)NO and Lb(III)NO at 10 K. The XANES and electronic spectra of the NO adducts are similar in shape and energies to the myoglobin (Mb) analogues. The environment of the Fe atom has been refined using multiple-scattering (MS) analyses of the XAFS data. For Lb(II)NO, the MS analysis resulted in an averaged Fe-N(p)(pyrrole) distance of 2.02 A, an Fe-N(epsilon)(imidazole) distance of 1.98 A, an Fe-N(NO) distance of 1.77 A, and an Fe-N-O angle of 147 degrees. The Fe-N(NO) distance and Fe-N-O angle obtained from the analysis of Lb(II)NO are in good agreement with those determined crystallographically for [Fe(TPP)(NO)] (TPP, tetraphenylporphyrinato), with and without 1-methylimidazole (1-MeIm) as the sixth ligand, and the MS XAFS structures reported previously for the myoglobin (Mb(II)NO) analogue and [Fe(TPP)(NO)]. The MS analysis of Lb(III)NO yielded an average Fe-N(p) distance of 2.00 A, an Fe-N(epsilon) distance of 1.89 A, an Fe-N(NO) distance of 1.68 A, and an Fe-N-O angle of 173 degrees. These bond lengths and angles are consistent with those determined previously for the myoglobin analogue (Mb(III)NO) and the crystal structures of the model complexes, [Fe(III)(TPP)(NO)(OH(2))](+) and [Fe(OEP)(NO)](+) (OEP, octaethylporphyrinato). The final XAFS R values were 16.1 and 18.2% for Lb(II)NO and Lb(III)NO, respectively. PMID:10600110
NASA Astrophysics Data System (ADS)
Augustynek, T.; Battaglia, A.; Kollias, P.
2011-12-01
The primary goal of this work is to address several challenges related to spaceborne Doppler radars like future the EarthCARE mission and recent developments of data simulation, correction and processing. The 94 GHz Cloud Profiling Radar onboard the ESA EarthCARE mission will be the first radar in space with Doppler capability allowing mean Doppler velocity measurements. This will enable more accurate characterization of clouds and precipitation (classification, retrieval accuracy, dynamics). It is the only instrument of this kind planned for the immediate post-CloudSat era and represents an irreplaceable asset in regards to climate change studies. Meeting the scientific accuracy requirements of vertical motions of 1 m/s, with a horizontal resolution of 1 km, is very challenging. The five key factors that control the performance of spaceborne radar will be discussed, such as: contribution of multiple scattering (MS), attenuation, velocity folding, non uniform beam filling (NUBF) and effects of along track integration of the signal. The research utilizes an end-to-end simulator for spaceborne Doppler radars. The simulator uses a Monte Carlo module which accounts for MS and produces ideal Doppler spectra as measured by a spaceborne radar flying over 3D highly resolved scenes produced via WRF Model simulations. The estimates of the Doppler moments (reflectivity, mean Doppler velocity and spectrum width) are achieved via the pulse pair technique. The objective method for identification of MS-contaminated range-bins based purely on the reflectivity-derived variables is described, with most important one, cumulative integrated reflectivity, found to be 41 dBZ_int which serves as the threshold value for identification of radar range gates contaminated by MS. This is further demonstrated in a CloudSat case study with the threshold value for CloudSat is found to be 41.9 dBZ_int. The unfolding procedure of Doppler velocities will be presented. Then we will describe the
NASA Astrophysics Data System (ADS)
Fainstein, A.; Etchegoin, P.; Chamberlain, M. P.; Cardona, M.; Tötemeyer, K.; Eberl, K.
1995-05-01
We present a detailed experimental study of optical phonon Raman scattering in GaAs/AlAs multiple quantum wells for several in-plane geometries. By exploiting a waveguided structure, we performed 90°, forward, and backscattering experiments with dispersed light propagating along the layers. Using these geometries, phonons with various propagation directions and polarized both parallel and perpendicular to the growth axis can be probed. The 90° data complete and correct earlier results obtained for the same geometry by Zucker et al., bringing them into accord with later experimental and theoretical work. Moreover, in-plane forward scattering data are reportd as a complementary check to these experiments. We discuss selection rules and scattering mechanisms, and compare the results with phonon energies calculated within a continuum model based on linear combinations of LO, TO, and interface modes. We find a very good agreement between the experiment and the predictions of the established theory of phonon modes and Raman scattering in semiconductor heterostructures.
Resel, Roland; Bainschab, Markus; Pichler, Alexander; Dingemans, Theo; Simbrunner, Clemens; Stangl, Julian; Salzmann, Ingo
2016-01-01
Dynamical scattering effects are observed in grazing-incidence X-ray diffraction experiments using an organic thin film of 2,2′:6′,2′′-ternaphthalene grown on oxidized silicon as substrate. Here, a splitting of all Bragg peaks in the out-of-plane direction (z-direction) has been observed, the magnitude of which depends both on the incidence angle of the primary beam and the out-of-plane angle of the scattered beam. The incident angle was varied between 0.09° and 0.25° for synchrotron radiation of 10.5 keV. This study reveals comparable intensities of the split peaks with a maximum for incidence angles close to the critical angle of total external reflection of the substrate. This observation is rationalized by two different scattering pathways resulting in diffraction peaks at different positions at the detector. In order to minimize the splitting, the data suggest either using incident angles well below the critical angle of total reflection or angles well above, which sufficiently attenuates the contributions from the second scattering path. This study highlights that the refraction of X-rays in (organic) thin films has to be corrected accordingly to allow for the determination of peak positions with sufficient accuracy. Based thereon, a reliable determination of the lattice constants becomes feasible, which is required for crystallographic structure solutions from thin films. PMID:27140152
Resel, Roland; Bainschab, Markus; Pichler, Alexander; Dingemans, Theo; Simbrunner, Clemens; Stangl, Julian; Salzmann, Ingo
2016-05-01
Dynamical scattering effects are observed in grazing-incidence X-ray diffraction experiments using an organic thin film of 2,2':6',2''-ternaphthalene grown on oxidized silicon as substrate. Here, a splitting of all Bragg peaks in the out-of-plane direction (z-direction) has been observed, the magnitude of which depends both on the incidence angle of the primary beam and the out-of-plane angle of the scattered beam. The incident angle was varied between 0.09° and 0.25° for synchrotron radiation of 10.5 keV. This study reveals comparable intensities of the split peaks with a maximum for incidence angles close to the critical angle of total external reflection of the substrate. This observation is rationalized by two different scattering pathways resulting in diffraction peaks at different positions at the detector. In order to minimize the splitting, the data suggest either using incident angles well below the critical angle of total reflection or angles well above, which sufficiently attenuates the contributions from the second scattering path. This study highlights that the refraction of X-rays in (organic) thin films has to be corrected accordingly to allow for the determination of peak positions with sufficient accuracy. Based thereon, a reliable determination of the lattice constants becomes feasible, which is required for crystallographic structure solutions from thin films. PMID:27140152
Born approximation, scattering, and algorithm
NASA Astrophysics Data System (ADS)
Martinez, Alex; Hu, Mengqi; Gu, Haicheng; Qiao, Zhijun
2015-05-01
In the past few decades, there were many imaging algorithms designed in the case of the absence of multiple scattering. Recently, we discussed an algorithm for removing high order scattering components from collected data. This paper is a continuation of our previous work. First, we investigate 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 the target region for various frequencies. Furthermore, we propagate this energy through free space towards our antenna, and remove it from the collected data.
Katcho, N. A.; Lomba, E.; Urones-Garrote, E.; Otero-Diaz, L. C.; Landa-Canovas, A. R.
2006-06-01
In this work we present an investigation on the composition dependence of the local structure in Se{sub x}Te{sub 1-x} crystalline alloys analyzing their experimental energy-loss spectra with the aid of a real-space multiple-scattering modeling approach and first-principles molecular dynamics. The concourse of this latter technique is essential for a proper modeling of the alloy spectra. From our results, it can be inferred that Se{sub x}Te{sub 1-x} alloys exhibit a high degree of substitutional disorder ruling out the existence of fully ordered alternating copolymer chains of Se and Te atoms.
NASA Astrophysics Data System (ADS)
Katcho, N. A.; Lomba, E.; Urones-Garrote, E.; Landa-Cánovas, A. R.; Otero-Díaz, L. C.
2006-06-01
In this work we present an investigation on the composition dependence of the local structure in SexTe1-x crystalline alloys analyzing their experimental energy-loss spectra with the aid of a real-space multiple-scattering modeling approach and first-principles molecular dynamics. The concourse of this latter technique is essential for a proper modeling of the alloy spectra. From our results, it can be inferred that SexTe1-x alloys exhibit a high degree of substitutional disorder ruling out the existence of fully ordered alternating copolymer chains of Se and Te atoms.
Demchenko, I. N.; Denlinger, J. D.; Chernyshova, M.; Yu, K. M.; Speaks, D. T.; Olalde-Velasco, P.; Hemmers, O.; Walukiewicz, W.; Derkachova, A.; Lawniczak-Jablonska, K.
2010-07-05
X-ray absorption near edge structure (XANES) at the cadmium L3 and oxygen K edges for CdO thin films grown by pulsed laser deposition method, is interpreted within the real-space multiple scattering formalism, FEFF code. The features in the experimental spectra are well reproduced by calculations for a cluster of about six and ten coordination shells around the absorber for L3 edge of Cd and K edge of O, respectively. The calculated projected electronic density of states is found to be in good agreement with unoccupied electronic states in experimental data and allows to conclude that the orbital character of the lowest energy of the conductive band is Cd-5s-O-2p. The charge transfer has been quantified and not purely ionic bonding has been found. Combined XANES and resonant inelastic x-ray scattering measurements allow us to determine the direct and indirect band gap of investigated CdO films to be {approx}2.4-eV and {approx}0.9-eV, respectively.
Scattering of slow neutrons by bound nuclei
NASA Astrophysics Data System (ADS)
Nowak, Ernst
1982-09-01
The T-operator for scattering of slow neutrons by a system of bound nuclei is calculated up to quadratic terms in the scattering length. Binding effects as well as effects of multiple scattering have to be included in order to avoid inconsistencies. For the discussion of binding effects one can adopt methods developed by Dietze and Nowak [1] for treating scattering by an elastically bound nucleus. In particular the case of coherent elastic scattering is discussed: we show how the corrections can be expressed in terms of correlation functions and that binding effects are most important for scattering by light nuclei.
NASA Technical Reports Server (NTRS)
Schaetzel, Klaus
1989-01-01
Since the development of laser light sources and fast digital electronics for signal processing, the classical discipline of light scattering on liquid systems experienced a strong revival plus an enormous expansion, mainly due to new dynamic light scattering techniques. While a large number of liquid systems can be investigated, ranging from pure liquids to multicomponent microemulsions, this review is largely restricted to applications on Brownian particles, typically in the submicron range. Static light scattering, the careful recording of the angular dependence of scattered light, is a valuable tool for the analysis of particle size and shape, or of their spatial ordering due to mutual interactions. Dynamic techniques, most notably photon correlation spectroscopy, give direct access to particle motion. This may be Brownian motion, which allows the determination of particle size, or some collective motion, e.g., electrophoresis, which yields particle mobility data. Suitable optical systems as well as the necessary data processing schemes are presented in some detail. Special attention is devoted to topics of current interest, like correlation over very large lag time ranges or multiple scattering.
NASA Astrophysics Data System (ADS)
Schaetzel, Klaus
1989-08-01
Since the development of laser light sources and fast digital electronics for signal processing, the classical discipline of light scattering on liquid systems experienced a strong revival plus an enormous expansion, mainly due to new dynamic light scattering techniques. While a large number of liquid systems can be investigated, ranging from pure liquids to multicomponent microemulsions, this review is largely restricted to applications on Brownian particles, typically in the submicron range. Static light scattering, the careful recording of the angular dependence of scattered light, is a valuable tool for the analysis of particle size and shape, or of their spatial ordering due to mutual interactions. Dynamic techniques, most notably photon correlation spectroscopy, give direct access to particle motion. This may be Brownian motion, which allows the determination of particle size, or some collective motion, e.g., electrophoresis, which yields particle mobility data. Suitable optical systems as well as the necessary data processing schemes are presented in some detail. Special attention is devoted to topics of current interest, like correlation over very large lag time ranges or multiple scattering.
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.
NASA Astrophysics Data System (ADS)
Zilani, M. A. K.; Xu, H.; Liu, T.; Sun, Y. Y.; Feng, Y. P.; Wang, X.-S.; Wee, A. T. S.
2006-05-01
The electronic structure of cobalt-induced magic clusters grown on Si(111)-(7×7) is investigated by scanning tunneling microscopy, scanning tunneling spectroscopy, and real-space multiple-scattering calculations. Topographical images of a half unit cell of Si(111)-(7×7) with the cluster acquired at low bias voltages of ±0.4V show greatly reduced cluster heights; however, the heights of the corner adatoms are unchanged, indicative of the highly localized nature of the charge distribution. Spectroscopic studies of the clusters indicate a band gap of ˜0.8eV , suggesting localized nonmetallic behavior. The opening of such a band gap is suggested to be a stabilizing factor for the observed magic clusters. A 65-atom Co-Si cluster is constructed to calculate the momentum- and element-projected density of states. The calculated result identifies that the intense state below the Fermi level at -1.75V in the experimental spectroscopic curve is primarily due to localized 3d orbitals of Co atoms in the magic clusters.
Critical fluid light scattering
NASA Technical Reports Server (NTRS)
Gammon, Robert W.
1988-01-01
The objective is to measure the decay rates of critical density fluctuations in a simple fluid (xenon) very near its liquid-vapor critical point using laser light scattering and photon correlation spectroscopy. Such experiments were severely limited on Earth by the presence of gravity which causes large density gradients in the sample when the compressibility diverges approaching the critical point. The goal is to measure fluctuation decay rates at least two decades closer to the critical point than is possible on earth, with a resolution of 3 microK. This will require loading the sample to 0.1 percent of the critical density and taking data as close as 100 microK to the critical temperature. The minimum mission time of 100 hours will allow a complete range of temperature points to be covered, limited by the thermal response of the sample. Other technical problems have to be addressed such as multiple scattering and the effect of wetting layers. The experiment entails measurement of the scattering intensity fluctuation decay rate at two angles for each temperature and simultaneously recording the scattering intensities and sample turbidity (from the transmission). The analyzed intensity and turbidity data gives the correlation length at each temperature and locates the critical temperature. The fluctuation decay rate data from these measurements will provide a severe test of the generalized hydrodynamic theories of transport coefficients in the critical regions. When compared to equivalent data from binary liquid critical mixtures they will test the universality of critical dynamics.
Forward-peaked scattering of polarized light.
Clark, Julia P; Kim, Arnold D
2014-11-15
Polarized light propagation in a multiple scattering medium is governed by the vector radiative transfer equation. We analyze the vector radiative transfer equation in asymptotic limit of forward-peaked scattering and derive an approximate system of equations for the Stokes parameters, which we call the vector Fokker-Planck approximation. The vector Fokker-Planck approximation provides valuable insight into several outstanding issues regarding the forward-peaked scattering of polarized light such as the polarization memory phenomenon. PMID:25490484
Superresolution imaging from nonlinear inverse scattering
NASA Astrophysics Data System (ADS)
Ritter, R. Shane; Fiddy, M. A.
2015-09-01
Inverse scattering algorithms typically rely on weak scattering approximations and the inversion of far field data on an Ewald sphere. This, in turn, fixes the resolution of the computed image. However, it has long been observed that when multiple scattering occurs in a strongly interacting object, and a nonlinear inversion method is employed to image it, the resulting image can reveal subwavelength resolution. We have observed this phenomenon using a cepstral filtering approach and characterize it more fully here.
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.
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.
Separating Scattering from Intrinsic Attenuation
NASA Astrophysics Data System (ADS)
van Wijk, K.; Scales, J. A.
2003-12-01
The subsurface appears disordered at all length-scales. Therefore, wave propatation at seismic or ultrasonic frequencies is subject to complicated scatterings. A pulse propagating in the subsurface loses energy at each scattering off an impedance contrast, but also decreases in amplitude as the impulse interacts with fluids in the rock. We call the latter non-elastic effect "intrinsic Q", while the former is "scattering Q". It is often the fluids in the rocks that are of interest, but conventional reflection and transmission of the incident pulse only cannot deceipher the individual components of Q due to scattering and fluid movement in the pore-space. We present an approach that can unravel these two mechanisms, allowing a separate estimate of absorption. This method treats the propagation of the average intensity in the framework of radiative transfer (RT); the arrival of (what is left of) the incident pulse is modeled as the coherent energy, whereas the later arriving multiply scattered events form the incoherent intensity. The coherent pulse decays exponentially due to a combination of scattering and absorption, and so does the incoherent intensity. However, multiple scattering can re-direct energy back to the receiver, supplying a gain-term at later times that makes up the incoherent intensity. Strictly speaking, one can invert for scattering and absorption from the intensity at late times only, often modeled with the late-time equivalent of RT, diffusion. However, we will show that fitting both early- and late-time signal with RT constrains absorption and scattering constants more rigorously. These ideas are illustrated by laboratory and sonic-logging measurements.
Imaging deep within a scattering medium using collective accumulation of single-scattered waves
NASA Astrophysics Data System (ADS)
Kang, Sungsam; Jeong, Seungwon; Choi, Wonjun; Ko, Hakseok; Yang, Taeseok D.; Joo, Jang Ho; Lee, Jae-Seung; Lim, Yong-Sik; Park, Q.-Han; Choi, Wonshik
2015-04-01
Optical microscopy suffers from a loss of resolving power when imaging targets are embedded in thick scattering media because of the dominance of strong multiple-scattered waves over waves scattered only a single time by the targets. Here, we present an approach that maintains full optical resolution when imaging deep within scattering media. We use both time-gated detection and spatial input-output correlation to identify those reflected waves that conserve in-plane momentum, which is a property of single-scattered waves. By implementing a superradiance-like collective accumulation of the single-scattered waves, we enhance the ratio of the single scattering signal to the multiple scattering background by more than three orders of magnitude. An imaging depth of 11.5 times the scattering mean free path is achieved with a near-diffraction-limited resolution of 1.5 μm. Our method of distinguishing single- from multiple-scattered waves will open new routes to deep-tissue imaging and studying the physics of the interaction of light with complex media.
Interferometric Rayleigh Scattering Measurement System
NASA Technical Reports Server (NTRS)
Bivolaru, Daniel (Inventor); Danehy, Paul M. (Inventor); Lee, Joseph W. (Inventor)
2008-01-01
A method and apparatus for performing simultaneous multi-point measurements of multiple velocity components in a gas flow is described. Pulses of laser light are directed to a measurement region of unseeded gas to produce Rayleigh or Mie scattered light in a plurality of directions. The Rayleigh or Mie scattered light is collected from multiple directions and combined in a single collimated light beam. The Rayleigh or Mie scattered light is then mixed together with a reference laser light before it is passed through a single planar Fabry-Perot interferometer for spectral analysis. At the output of the interferometer, a high-sensitivity CCD camera images the interference fringe pattern. This pattern contains the spectral and spatial information from both the Rayleigh scattered light and the reference laser light. Interferogram processing software extracts and analyzes spectral profiles to determine the velocity components of the gas flow at multiple points in the measurement region. The Rayleigh light rejected by the interferometer is recirculated to increase the accuracy and the applicability of the method for measurements at high temperatures without requiring an increase in the laser energy.
Analytical optical scattering in clouds
NASA Technical Reports Server (NTRS)
Phanord, Dieudonne D.
1989-01-01
An analytical optical model for scattering of light due to lightning by clouds of different geometry is being developed. The self-consistent approach and the equivalent medium concept of Twersky was used to treat the case corresponding to outside illumination. Thus, the resulting multiple scattering problem is transformed with the knowledge of the bulk parameters, into scattering by a single obstacle in isolation. Based on the size parameter of a typical water droplet as compared to the incident wave length, the problem for the single scatterer equivalent to the distribution of cloud particles can be solved either by Mie or Rayleigh scattering theory. The super computing code of Wiscombe can be used immediately to produce results that can be compared to the Monte Carlo computer simulation for outside incidence. A fairly reasonable inverse approach using the solution of the outside illumination case was proposed to model analytically the situation for point sources located inside the thick optical cloud. Its mathematical details are still being investigated. When finished, it will provide scientists an enhanced capability to study more realistic clouds. For testing purposes, the direct approach to the inside illumination of clouds by lightning is under consideration. Presently, an analytical solution for the cubic cloud will soon be obtained. For cylindrical or spherical clouds, preliminary results are needed for scattering by bounded obstacles above or below a penetrable surface interface.
Scattering of electromagnetic waves from a turbulent plasma slab.
NASA Technical Reports Server (NTRS)
Liu, C. H.
1972-01-01
Scattering of electromagnetic waves from a turbulent plasma slab is studied. Part of the effects of the multiple scattering is taken into account. The reflection coefficient is found to be increased and its variation with respect to the slab thickness is smoothed out by the random scattering.
Basin topology in dissipative chaotic scattering.
Seoane, Jesús M; Aguirre, Jacobo; Sanjuán, Miguel A F; Lai, Ying-Cheng
2006-06-01
Chaotic scattering in open Hamiltonian systems under weak dissipation is not only of fundamental interest but also important for problems of current concern such as the advection and transport of inertial particles in fluid flows. Previous work using discrete maps demonstrated that nonhyperbolic chaotic scattering is structurally unstable in the sense that the algebraic decay of scattering particles immediately becomes exponential in the presence of weak dissipation. Here we extend the result to continuous-time Hamiltonian systems by using the Henon-Heiles system as a prototype model. More importantly, we go beyond to investigate the basin structure of scattering dynamics. A surprising finding is that, in the common case where multiple destinations exist for scattering trajectories, Wada basin boundaries are common and they appear to be structurally stable under weak dissipation, even when other characteristics of the nonhyperbolic scattering dynamics are not. We provide numerical evidence and a geometric theory for the structural stability of the complex basin topology. PMID:16822004
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.
Kegel, Gunter H.R.; Egan, James J
2007-04-18
This project covers four principal areas of research: Elastic and inelastic neutron scattering studies in odd-A terbium, thulium and other highly deformed nuclei near A=160 with special regard to interband transitions and to the investigation of the direct-interaction versus the compound-nucleus excitation process in these nuclei. Examination of new, fast photomultiplier tubes suitable for use in a miniaturized neutron-time-of-flight spectrometer. Measurement of certain inelastic cross sections of 238U. Determination of the multiplicity of prompt fission gamma rays in even-A fissile actinides. Energies and mean lives of fission isomers produced by fast fission of even-Z, even-A actinides. Study of the mean life of 7Be in different host matrices and its possible astro-physical significance.
Scattering apodizer for laser beams
Summers, M.A.; Hagen, W.F.; Boyd, R.D.
1984-01-01
A method is disclosed for apodizing a laser beam to smooth out the production of diffraction peaks due to optical discontinuities in the path of the laser beam, such method comprising introduction of a pattern of scattering elements for reducing the peak intensity in the region of such optical discontinuities, such pattern having smoothly tapering boundaries in which the distribution density of the scattering elements is tapered gradually to produce small gradients in the distribution density, such pattern of scattering elements being effective to reduce and smooth out the diffraction effects which would otherwise be produced. The apodizer pattern may be produced by selectively blasting a surface of a transparent member with fine abrasive particles to produce a multitude of minute pits. In one embodiment, a scattering apodizer pattern is employed to overcome diffraction patterns in a multiple element crystal array for harmonic conversion of a laser beam. The interstices and the supporting grid between the crystal elements are obscured by the gradually tapered apodizer pattern of scattering elements.
Scattering apodizer for laser beams
Summers, Mark A.; Hagen, Wilhelm F.; Boyd, Robert D.
1985-01-01
A method is disclosed for apodizing a laser beam to smooth out the production of diffraction peaks due to optical discontinuities in the path of the laser beam, such method comprising introduction of a pattern of scattering elements for reducing the peak intensity in the region of such optical discontinuities, such pattern having smoothly tapering boundaries in which the distribution density of the scattering elements is tapered gradually to produce small gradients in the distribution density, such pattern of scattering elements being effective to reduce and smooth out the diffraction effects which would otherwise be produced. The apodizer pattern may be produced by selectively blasting a surface of a transparent member with fine abrasive particles to produce a multitude of minute pits. In one embodiment, a scattering apodizer pattern is employed to overcome diffraction patterns in a multiple element crystal array for harmonic conversion of a laser beam. The interstices and the supporting grid between the crystal elements are obscured by the gradually tapered apodizer pattern of scattering elements.
Multiphonon scattering from surfaces
NASA Astrophysics Data System (ADS)
Manson, J. R.; Celli, V.; Himes, D.
1994-01-01
We consider the relationship between several different formalisms for treating the multiphonon inelastic scattering of atomic projectiles from surfaces. Starting from general principles of formal scattering theory, the trajectory approximation to the scattering intensity is obtained. From the trajectory approximation, the conditions leading to the fast-collision approximation for multiquantum inelastic scattering are systematically derived.
Generalized Rayleigh scattering. II. Matrix source functions.
NASA Astrophysics Data System (ADS)
Ivanov, V. V.; Kasaurov, A. M.; Loskutov, V. M.; Viik, T.
1995-11-01
Numerical and analytical data are presented on the matrix source functions S(τ) of the standard problem of multiple generalized Rayleigh scattering (GRS) in homogeneous semi-infinite atmospheres with uniformly distributed embedded primary sources of partially polarized radiation. The source matrices S(τ) are found by the discrete-ordinate solution of the relevant 2x2 matrix transfer equation and by albedo shifting technique, which is a version of the accelerated {LAMBDA}-iteration approach. The dependence of the solution of the matrix transfer equation on the parameters of the problem of multiple molecular scattering, albedo of single scattering λ_I_ and depolarization factor W, is carefully considered. (The value W=1 corresponds to Rayleigh scattering, while for scalar isotropic scattering W=0). From the pair of the parameters (λ_I_, W) we switch to (λ_I_, λ_Q_), with λ_Q_=0.7Wλ_I_, and instead of the physically natural domain of the parameter values, λ_Iin[0,1], λ_ Qin[0,0.7λ_I_], in GRS we consider a wider one, λ_ I_, λ_Qin[0,1]. On the plane with the axes (λ_I_, λ_Q_), or the λ-plane, there is a one-parameter family of curves, the isopols, along which S(0) remains constant. The λ-plane and the isopols are the basic instruments in our analysis. Along with presenting the numerical data we discuss the asymptotic behavior of S(τ) for τ->{infinity}. It is shown that the matrix counterpart of the usual scalar conservative isotropic scattering is not the ordinary conservative Rayleigh scattering (λ_I_=1, λ_ Q_=0.7), but the biconservative scattering, i.e., scattering with λ_I_=λ_Q_=1. The analysis of the remarkable properties of biconservative scattering naturally leads to matrix generalizations of the Hopf-Bronstein relation, the Hopf constant etc.
Reversibility of scattered fields (Conference Presentation)
NASA Astrophysics Data System (ADS)
Zhou, Renjie; Kim, Taewoo; Popescu, Gabriel
2016-03-01
In recent years, tremendous efforts have been spent on deep tissue imaging using phase conjugation, a technique used to undo the effects of light scattering in a thick tissue. Despite the early debates between Yariv and Wolf, it is still not well understood physically how deep can a field propagate into biological tissue and still be phase conjugated. In order to answer this question, we developed a light scattering theory to describe the evolution of the phase associated with a field scattered by a thick tissue block. The multiple scattering through the sample is simplified to a series of single scattering through consecutive thin tissue slices. With this theory, we identify the limits of the phase conjugation operation and recover the previous results by Yariv and Wolf, which asserts that phase conjugation is rooted in small angle approximation. Importantly, we discover the fundamental principle that rules phase conjugation: the mean axial wavenumber of a field progressively decreases to zero as it scatters multiple times. At this point, phase becomes a spatially random variable and phase conjugation becomes impossible. This result describes a fundamental phenomenon: the interaction between a deterministic object and a deterministic field can result in a random scattered field. We show that this phenomenon is rooted into Heisenberg's uncertainty principle.
[Inelastic electron scattering from surfaces]. [Progress report
Not Available
1993-10-01
This program uses ab-initio and multiple scattering to study surface dynamical processes; high-resolution electron-energy loss spectroscopy is used in particular. Off-specular excitation cross sections are much larger if electron energies are in the LEED range (50--300 eV). The analyses have been extended to surfaces of ordered alloys. Phonon eigenvectors and eigenfrequencies were used as inputs to electron-energy-loss multiple scattering cross section calculations. Work on low-energy electron and positron holography is mentioned.
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.
A new SERS: scattering enhanced Raman scattering
NASA Astrophysics Data System (ADS)
Bixler, Joel N.; Yakovlev, Vladislav V.
2014-03-01
Raman spectroscopy is a powerful technique that can be used to obtain detailed chemical information about a system without the need for chemical markers. It has been widely used for a variety of applications such as cancer diagnosis and material characterization. However, Raman scattering is a highly inefficient process, where only one in 1011 scattered photons carry the needed information. Several methods have been developed to enhance this inherently weak effect, including surface enhanced Raman scattering and coherent anti-Stokes Raman scattering. These techniques suffer from drawbacks limiting their commercial use, such as the need for spatial localization of target molecules to a `hot spot', or the need for complex laser systems. Here, we present a simple instrument to enhance spontaneous Raman scattering using elastic light scattering. Elastic scattering is used to substantially increase the interaction volume. Provided that the scattering medium exhibits very low absorption in the spectral range of interest, a large enhancement factor can be attained in a simple and inexpensive setting. In our experiments, we demonstrate an enhancement of 107 in Raman signal intensity. The proposed novel device is equally applicable for analyzing solids, liquids, and gases.
Technology Transfer Automated Retrieval System (TEKTRAN)
Multispectral scattering is a promising technique for nondestructive sensing of multiple quality attributes of apple fruit. This research developed new, improved methods for processing and analyzing multispectral scattering profiles in order to design and build a better multispectral imaging system ...
Light Scattering by Nonspherical Particles
NASA Technical Reports Server (NTRS)
Mishchenko, Michael I.; Travis, Larry D.; Hovenier, Joop W.
1998-01-01
Improved understanding of electromagnetic scattering by nonspherical particles is important to many science and engineering disciplines and was the subject of the Conference on Light Scattering by Nonspherical Particles: Theory, Measurements, and Applications. The conference was held 29 September-1 October 1998 at the Goddard Institute for Space Studies in New York City and brought together 115 participants from 18 countries. The main objective of the conference was to highlight and summarize the rapid advancements in the field, including numerical methods for computing the single and multiple scattering of electromagnetic radiation by nonspherical and heterogeneous particles, measurement approaches, knowledge of characteristic features in scattering patterns, retrieval and remote sensing techniques, nonspherical particle sizing, and various practical applications. The conference consisted of twelve oral and one poster sessions. The presentations were loosely grouped based on broad topical categories. In each of these categories invited review talks highlighted and summarized specific active areas of research. To ensure a high-quality conference, all abstracts submitted had been reviewed by members of the Scientific Organizing Committee for technical merit and content. The conference program was published in the June 1998 issue of the Bulletin of the American Meteorological Society and is available on the World Wide Web at http://www.giss.nasa.gov/-crmim/conference/program.html. Authors of accepted papers and review presentations contributed to a volume of preprints published by the American Meteorological Society' and distributed to participants at the conference.
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.
ERIC Educational Resources Information Center
di Francia, Giuliano Toraldo
1973-01-01
The art of deriving information about an object from the radiation it scatters was once limited to visible light. Now due to new techniques, much of the modern physical science research utilizes radiation scattering. (DF)
NASA Astrophysics Data System (ADS)
Bashkatov, A. N.; Genina, Elina A.; Kochubei, V. I.; Tuchin, Valerii V.
2006-12-01
Based on the digital image analysis and inverse Monte-Carlo method, the proximate analysis method is deve-loped and the optical properties of hairs of different types are estimated in three spectral ranges corresponding to three colour components. The scattering and absorption properties of hairs are separated for the first time by using the inverse Monte-Carlo method. The content of different types of melanin in hairs is estimated from the absorption coefficient. It is shown that the dominating type of melanin in dark hairs is eumelanin, whereas in light hairs pheomelanin dominates.
Electromagnetic scattering by impedance structures
NASA Technical Reports Server (NTRS)
Balanis, Constantine A.; Griesser, Timothy
1987-01-01
The scattering of electromagnetic waves from impedance structures is investigated, and current work on antenna pattern calculation is presented. A general algorithm for determining radiation patterns from antennas mounted near or on polygonal plates is presented. These plates are assumed to be of a material which satisfies the Leontovich (or surface impedance) boundary condition. Calculated patterns including reflection and diffraction terms are presented for numerious geometries, and refinements are included for antennas mounted directly on impedance surfaces. For the case of a monopole mounted on a surface impedance ground plane, computed patterns are compared with experimental measurements. This work in antenna pattern prediction forms the basis of understanding of the complex scattering mechanisms from impedance surfaces. It provides the foundation for the analysis of backscattering patterns which, in general, are more problematic than calculation of antenna patterns. Further proposed study of related topics, including surface waves, corner diffractions, and multiple diffractions, is outlined.
Incoherent image formation in the presence of scattering eye media.
Wesemann, W
1987-08-01
Incoherent image formation in human eyes that have scattering eye media is investigated as a function of the particle size and the optical density of the scattering medium and for test targets that differ in form and size. For single scattering by large particles (much greater than lambda), a point-spread function and the associated modulation-transfer function of the scattered light are derived from diffraction theory. It is shown that object structures with low spatial frequencies are also imaged by the scattered light. Following single scattering by small particles and/or multiple scattering, the scattered light forms an approximately uniform background. Consequently, the retinal contrast is reduced regardless of spatial frequency. The image quality is, contrary to what is found in normal image formation, extremely sensitive to the form and size of the test target. It is shown that the optimal readability of white-on-black letters is obtained at intermediate spatial frequencies. For an extended layer of arbitrary optical density and particle size, the influence of multiple scattering is approximated by using Hartel's scattering theory. It is shown that wavelength has only a small influence on retinal contrast for scattering by particles greater than lambda. PMID:3625324
Analytical scatter kernels for portal imaging at 6 MV.
Spies, L; Bortfeld, T
2001-04-01
X-ray photon scatter kernels for 6 MV electronic portal imaging are investigated using an analytical and a semi-analytical model. The models are tested on homogeneous phantoms for a range of uniform circular fields and scatterer-to-detector air gaps relevant for clinical use. It is found that a fully analytical model based on an exact treatment of photons undergoing a single Compton scatter event and an approximate treatment of second and higher order scatter events, assuming a multiple-scatter source at the center of the scatter volume, is accurate within 1% (i.e., the residual scatter signal is less than 1% of the primary signal) for field sizes up to 100 cm2 and air gaps over 30 cm, but shows significant discrepancies for larger field sizes. Monte Carlo results are presented showing that the effective multiple-scatter source is located toward the exit surface of the scatterer, rather than at its center. A second model is therefore investigated where second and higher-order scattering is instead modeled by fitting an analytical function describing a nonstationary isotropic point-scatter source to Monte Carlo generated data. This second model is shown to be accurate to within 1% for air gaps down to 20 cm, for field sizes up to 900 cm2 and phantom thicknesses up to 50 cm. PMID:11339752
Coherence effects in scattering order expansion of light by atomic clouds.
Rouabah, Mohamed-Taha; Samoylova, Marina; Bachelard, Romain; Courteille, Philippe W; Kaiser, Robin; Piovella, Nicola
2014-05-01
We interpret cooperative scattering by a collection of cold atoms as a multiple-scattering process. Starting from microscopic equations describing the response of N atoms to a probe light beam, we represent the total scattered field as an infinite series of multiple-scattering events. As an application of the method, we obtain analytical expressions of the coherent intensity in the double-scattering approximation for Gaussian density profiles. In particular, we quantify the contributions of coherent backward and forward scattering. PMID:24979635
Modelling dust scattering in our Galaxy
NASA Astrophysics Data System (ADS)
Murthy, Jayant
2016-06-01
I have used Monte Carlo models with multiple scattering to predict the dust scattered light from our Galaxy and have compared the predictions with data in two ultraviolet bands from the Galaxy Evolution Explorer spacecraft. I find that 90 per cent of the scattered light arises from less than 1000 stars with 25 per cent from the 10 brightest. About half of the diffuse radiation originates within 200 pc of the Sun with a maximum distance of 600 pc. Multiple scattering is important at any optical depth with 30 per cent of the flux being multiply scattered even at zero reddening. I find that the global distribution of the scattered light is insensitive to the dust distribution with grains of 0.3 < a < 0.5 and g < 0.6. There is an offset between the model and the data of 100 and 200 ph cm-2 s-1 sr-1 Å-1 in the FUV and NUV, respectively, at the poles rising to 200-400 ph cm-2 s-1 sr-1 Å-1 at lower latitudes. The Monte Carlo code and the models of diffuse radiation for different values of the optical constants are available for download.
Simulation of basic subcellular scattering in tissues
NASA Astrophysics Data System (ADS)
Spaeth, Juergen; Radina, Martin; Kessler, Manfred D.
2001-05-01
The main signals of light coming back from tissues result from multiple scattering interactions of the incoming light wave with the multipoles of subcellular particles. For a detailed knowledge of the systems, noninvasive optical measurement techniques in the microvolume (capillary, cellular and subcellular signals) are well established at the Institute of Physiology. Due to these methods, the scattering signals and their changes can be detected and analyzed quantitatively at the micrometers 3 volume. The scattering parameters of interest can be set separately and the results can be visualized by three dimensional imaging techniques. Mitochondria produce different scattering patterns by a change of their respiratory state due to different sizes. The algorism presented simulates this scattering. It allows fast predictions of effects like variation of particle size, variation of concentration and absorption at different geometries of lightguides. A comparison of the simulation with the measurements in microvolume shows correlation so that the algorism is reliable for qualitative and quantitative explanation of what happens in the tissue. A remarkable effect is that there are no big differences between measurements in 360- degree direction and 90 degrees because of massive multiple scattering effects.
Characterisation of porous materials by combining mercury porosimetry and scattering techniques
NASA Astrophysics Data System (ADS)
Stefanopoulos, K. L.; Steriotis, Th. A.; Mitropoulos, A. Ch.; Kanellopoulos, N. K.; Treimer, W.
2004-07-01
Small-angle neutron scattering (SANS), ultra small-angle neutron scattering (USANS) and mercury porosimetry have been used to fully characterise macroporous chalk as well as Si3N4 and BaTiO3 samples. For the scattering techniques, multiple scattering effects have been studied. In addition, the scattering data have been evaluated by using a generalised form of the indirect Fourier transformation technique suitable for concentrated systems. Pore size distributions are calculated and compared to the mercury porosimetry results.
Survey of background scattering from materials found in small-angle neutron scattering
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
Kotova, S P; Maiorov, I V; Maiorova, A M
2007-01-31
We analyse the possibilities of simultaneous measuring three optical parameters of scattering media, namely, the scattering and absorption coefficients and the scattering anisotropy parameter by the intensity profile of backscattered radiation by using the neural network inversion method and the method of adaptive-network-based fuzzy inference system. The measurement errors of the absorption and scattering coefficients and the scattering anisotropy parameter are 20%, 5%, and 10%, respectively. (special issue devoted to multiple radiation scattering in random media)
Electromagnetic inverse scattering
NASA Technical Reports Server (NTRS)
Bojarski, N. N.
1972-01-01
A three-dimensional electromagnetic inverse scattering identity, based on the physical optics approximation, is developed for the monostatic scattered far field cross section of perfect conductors. Uniqueness of this inverse identity is proven. This identity requires complete scattering information for all frequencies and aspect angles. A nonsingular integral equation is developed for the arbitrary case of incomplete frequence and/or aspect angle scattering information. A general closed-form solution to this integral equation is developed, which yields the shape of the scatterer from such incomplete information. A specific practical radar solution is presented. The resolution of this solution is developed, yielding short-pulse target resolution radar system parameter equations. The special cases of two- and one-dimensional inverse scattering and the special case of a priori knowledge of scatterer symmetry are treated in some detail. The merits of this solution over the conventional radar imaging technique are discussed.
SCAP. Point Kernel Single or Albedo Scatter
Disney, R.K.; Bevan, S.E.
1982-08-05
SCAP solves for radiation transport in complex geometries using the single or albedo-scatter point kernel method. The program is designed to calculate the neutron or gamma-ray radiation level at detector points located within or outside a complex radiation scatter source geometry or a user-specified discrete scattering volume. The geometry is described by zones bounded by intersecting quadratic surfaces with an arbitrary maximum number of boundary surfaces per zone. The anisotropic point sources are described as point-wise energy dependent distributions of polar angles on a meridian; isotropic point sources may be specified also. The attenuation function for gamma rays is an exponential function on the primary source leg and the scatter leg with a buildup factor approximation to account for multiple scatter on the scatter leg. The neutron attenuation function is an exponential function using neutron removal cross sections on the primary source leg and scatter leg. Line or volumetric sources can be represented as distributions of isotropic point sources, with uncollided line-of-sight attenuation and buildup calculated between each source point and the detector point.
The Scattering of Light III. External Scattering from a Finite Molecular Fluid
NASA Astrophysics Data System (ADS)
Hynne, F.; Bullough, R. K.
1990-03-01
We calculate the external incoherent scattering from a finite molecular fluid exposed to a weak, external, coherent electromagnetic field. The scattered field is detected outside the fluid and the system models a real scattering experiment in all its aspects. The analysis is based on a classical all order many-body theory developed in two previous papers. The theory is microscopic, i.e. is developed ab initio and in detail in terms of individual scattering processes in vacuo at a strictly molecular level. But it is shown that the collective action of these generates all of the macroscopic features expected in the external scattering: for example, the refractive index, as it was calculated previously from the many-body theory, plays much of its expected macroscopic role. These macroscopic results are reached by showing that the complete scattering process (from a wave incident in vacuo on the fluid to a wave in vacuo scattered from the fluid) separates into three independent collective processes compactly described by a particular quadrilinear form quadratic in a field E induced in the fluid by any coherent external field, and quadratic in a `weight' field ɛ describing the scattered field in the fluid. The internal fields E and ɛ couple separately to the external incoming field and to one representing the external scattered field respectively. In each case they account for all collective surface effects. The kernel of the quadrilinear form accounts for all of the internal scattering processes in the fluid. The weight field ɛ and the equations associated with it describe refraction and (multiple) internal reflection of the scattered light at the surface of the medium in all details: these collective surface effects are managed in a very effective way through a new reciprocity principle derived from the microscopic theory and containing a new form of optical extinction theorem for external scattering. The kernel of the quadrilinear form for internal scattering has
Decoherence due to Scattering Atoms
NASA Astrophysics Data System (ADS)
Uys, Hermann; Perreault, John; Cronin, Alex
2004-05-01
Coherent manipulation of a quantum system is difficult because of uncontrolled interactions with the system's environment. The study of decoherence so introduced is important for progress in quantum mechanical engineering, and for understanding the transition from quantum to classical behavior. We have observed loss of fringe contrast in a Mach-Zhender atom interferometer due to scattering background gas atoms and propose that this might be interpreted as quantum decoherence. Progress will be reported on the use of a general model of decoherence incorporating a semi-classical picture of atom scattering to explain the contrast loss [1]. A formal analogy is made to decoherence due to scattering photons from atoms in an interferometer [2]. [1] S.M. Tan, D.F. Waals, ``Loss of coherence in interferometry", Phys. Rev. A 47 p.4663 (1993) [2] D.A. Kokorowski, A.D. Cronin, T.D. Roberts, and D.E. Pritchard, ``From single- to multiple-photon decoherence in an atom interferometer", Phys. Rev. Lett. 86 p. 2191 (2001)
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Scattering theory for Floquet-Bloch states
NASA Astrophysics Data System (ADS)
Bilitewski, Thomas; Cooper, Nigel R.
2015-03-01
Motivated by recent experimental implementations of artificial gauge fields for gases of cold atoms, we study the scattering properties of particles that are subjected to time-periodic Hamiltonians. Making use of Floquet theory, we focus on translationally invariant situations in which the single-particle dynamics can be described in terms of spatially extended Floquet-Bloch waves. We develop a general formalism for the scattering of these Floquet-Bloch waves. An important role is played by the conservation of Floquet quasienergy, which is defined only up to the addition of integer multiples of ℏ ω for a Hamiltonian with period T =2 π /ω . We discuss the consequences of this for the interpretation of "elastic" and "inelastic" scattering in cases of physical interest. We illustrate our general results with applications to the scattering of a single particle in a Floquet-Bloch state from a static potential and the scattering of two bosonic particles in Floquet-Bloch states through their interparticle interaction. We analyze examples of these scattering processes that are closely related to the schemes used to generate artificial gauge fields in cold-atom experiments, through optical dressing of internal states, or through time-periodic modulations of tight-binding lattices. We show that the effects of scattering cannot, in general, be understood by an effective time-independent Hamiltonian, even in the limit ω →∞ of rapid modulation. We discuss the relative sizes of the elastic scattering (required to stabilize many-body phases) and of the inelastic scattering (leading to deleterious heating effects). In particular, we describe how inelastic processes that can cause significant heating in the current experimental setup can be switched off by additional confinement of transverse motion.
NASA Astrophysics Data System (ADS)
Sneha, Mahima; Gao, Hong; Zare, Richard N.; Jambrina, P. G.; Menéndez, M.; Aoiz, F. J.
2016-07-01
Differential cross sections (DCSs) for the H + D2 → HD(v' = 4, j') + D reaction at 3.26 eV collision energy have been measured using the photoloc technique, and the results have been compared with those from quantum and quasiclassical scattering calculations. The quantum mechanical DCSs are in good overall agreement with the experimental measurements. In common with previous results at 1.97 eV, clear interference patterns which appear as fingerlike structures have been found at 3.26 eV but in this case for vibrational states as high as v' = 4. The oscillatory structure is prominent for low rotational states and progressively disappears as j' increases. A detailed analysis, similar to that carried out at 1.97 eV, shows that the origin of these structures could be traced to interferences between well defined classical mechanisms. In addition, at this energy, we do not observe the anomalous positive j'-θ trend found for the v' = 4 manifold at lower collision energies, thus reinforcing our explanation that the anomalous distribution for HD(v' = 4, j') at 1.97 eV only takes place for those states associated with low product recoil energies.
Environment scattering in GADRAS.
Thoreson, Gregory G.; Mitchell, Dean James; Theisen, Lisa Anne; Harding, Lee T.
2013-09-01
Radiation transport calculations were performed to compute the angular tallies for scattered gamma-rays as a function of distance, height, and environment. Green's Functions were then used to encapsulate the results a reusable transformation function. The calculations represent the transport of photons throughout scattering surfaces that surround sources and detectors, such as the ground and walls. Utilization of these calculations in GADRAS (Gamma Detector Response and Analysis Software) enables accurate computation of environmental scattering for a variety of environments and source configurations. This capability, which agrees well with numerous experimental benchmark measurements, is now deployed with GADRAS Version 18.2 as the basis for the computation of scattered radiation.
ERIC Educational Resources Information Center
Simanihuruk, Mudin
2011-01-01
Multiplication facts are difficult to teach. Therefore many researchers have put a great deal of effort into finding multiplication strategies. Sherin and Fuson (2005) provided a good survey paper on the multiplication strategies research area. Kolpas (2002), Rendtorff (1908), Dabell (2001), Musser (1966) and Markarian (2009) proposed the finger…
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Acoustical and optical scattering and imaging of tissues: an overview
NASA Astrophysics Data System (ADS)
Ishimaru, Akira
2001-05-01
This talk will first give a general discussion on the ultrasound media characteristics of blood and spectral densities of tissues. The first-order scattering theory, multiple scattering theory, Doppler spectrum, cw and pulse scattering, focused beam, beam spot-size, speckle, texture, and rough interface effects will be presented. Imaging through tissues will then be discussed in terms of temporal and spatial resolutions, contrast, MTF (modulation transfer function), SAR and confocal imaging techniques, tomographic and holographic imaging, and inverse scattering. Next, we discuss optical diffusion in blood and tissues, radiative transfer theory, photon density waves, and polarization effects.
A Recursive Born Approach to Nonlinear Inverse Scattering
NASA Astrophysics Data System (ADS)
Kamilov, Ulugbek S.; Liu, Dehong; Mansour, Hassan; Boufounos, Petros T.
2016-08-01
The Iterative Born Approximation (IBA) is a well-known method for describing waves scattered by semi-transparent objects. In this paper, we present a novel nonlinear inverse scattering method that combines IBA with an edge-preserving total variation (TV) regularizer. The proposed method is obtained by relating iterations of IBA to layers of a feedforward neural network and developing a corresponding error backpropagation algorithm for efficiently estimating the permittivity of the object. Simulations illustrate that, by accounting for multiple scattering, the method successfully recovers the permittivity distribution where the traditional linear inverse scattering fails.
Recurrence relations of Kummer functions and Regge string scattering amplitudes
NASA Astrophysics Data System (ADS)
Lee, Jen-Chi; Mitsuka, Yoshihiro
2013-04-01
We discover an infinite number of recurrence relations among Regge string scattering amplitudes [11, 30] of different string states at arbitrary mass levels in the open bosonic string theory. As a result, all Regge string scattering amplitudes can be algebraically solved up to multiplicative factors. Instead of decoupling zero-norm states in the fixed angle regime, the calculation is based on recurrence relations and addition theorem of Kummer functions of the second kind. These recurrence relations among Regge string scattering amplitudes are dual to linear relations or symmetries among high-energy fixed angle string scattering amplitudes discovered previously.
Geist, William H.
2015-12-01
This set of slides begins by giving background and a review of neutron counting; three attributes of a verification item are discussed: ^{240}Pu_{eff} mass; α, the ratio of (α,n) neutrons to spontaneous fission neutrons; and leakage multiplication. It then takes up neutron detector systems – theory & concepts (coincidence counting, moderation, die-away time); detector systems – some important details (deadtime, corrections); introduction to multiplicity counting; multiplicity electronics and example distributions; singles, doubles, and triples from measured multiplicity distributions; and the point model: multiplicity mathematics.
Theoretical criteria for scattering dark states in nanostructured particles.
Hsu, Chia Wei; DeLacy, Brendan G; Johnson, Steven G; Joannopoulos, John D; Soljačić, Marin
2014-05-14
Nanostructures with multiple resonances can exhibit a suppressed or even completely eliminated scattering of light, called a scattering dark state. We describe this phenomenon with a general treatment of light scattering from a multiresonant nanostructure that is spherical or nonspherical but subwavelength in size. With multiple resonances in the same channel (i.e., same angular momentum and polarization), coherent interference always leads to scattering dark states in the low-absorption limit, regardless of the system details. The coupling between resonances is inevitable and can be interpreted as arising from far-field or near-field. This is a realization of coupled-resonator-induced transparency in the context of light scattering, which is related to but different from Fano resonances. Explicit examples are given to illustrate these concepts. PMID:24805881
Computing Scattering Matrices For Circular Waveguides
NASA Technical Reports Server (NTRS)
Hoppe, Daniel J.
1990-01-01
Scattering Matrix Program for Circular Waveguide Junctions computes scattering matrix for series of circular waveguide sections. Sections must have same axis, but radius and length of each section completely arbitrary. Devices analyzed include simple waveguide step discontinuity like that used in a dual-mode horn, stepped matching section, or corrugated waveguide section with constant or varying slot depth. Certain types of corrugated horns also analyzed with program. Mathematical model used in program accurately predicts reflection and transmission characteristics of such devices, taking into account excitation of modes of higher order as well as multiple reflections and energy stored at each discontinuity. Written in FORTRAN 77.
Critical concentrations of cumulative scattered damage
Ignatovich, S.R.
1995-12-01
A statistical model is constructed to describe the formation of associations (clusters) of several defects randomly scattered within a limited region of the material. The dependence of the number of such clusters on the total concentration of defects is determined. Two criteria of the limiting state are established for multiple fracture, these criteria corresponding to the critical concentrations of cumulative scattered damage. The critical concentrations are the threshold concentration at which individual defects begin to merge and the concentration characterizing the transition to the stage in which defects coalesce on a massive scale.
HADRONIC SCATTERING IN THE COLOR GLASS CONDENSATE.
VENUGOPALAN, R.
2005-05-15
Multi-particle production in QCD is dominated by higher twist contributions. The operator product expansion is not very effective here because the number of relevant operators grow rapidly with increasing twist. The Color Glass Condensate (CGC) provides a framework in QCD to systematically discuss ''classical'' (multiple scattering) and ''quantum'' evolution (shadowing) effects in multi-particle production. The apparently insuperable problem of nucleus-nucleus scattering in QCD simplifies greatly in the CGC. A few examples are discussed with emphasis on open problems.
Limitations in scatter propagation
NASA Astrophysics Data System (ADS)
Lampert, E. W.
1982-04-01
A short description of the main scatter propagation mechanisms is presented; troposcatter, meteor burst communication and chaff scatter. For these propagation modes, in particular for troposcatter, the important specific limitations discussed are: link budget and resulting hardware consequences, diversity, mobility, information transfer and intermodulation and intersymbol interference, frequency range and future extension in frequency range for troposcatter, and compatibility with other services (EMC).
Hartemann, F V
2008-12-01
An overview of linear and nonlinear Compton scattering is presented, along with a comparison with Thomson scattering. Two distinct processes play important roles in the nonlinear regime: multi-photon interactions, leading to the generation of harmonics, and radiation pressure, yielding a downshift of the radiated spectral features. These mechanisms, their influence on the source brightness, and different modeling strategies are also briefly discussed.
Berger, E.L.; Collins, J.C.; Soper, D.E.; Sterman, G.
1986-03-01
I discuss events in high energy hadron collisions that contain a hard scattering, in the sense that very heavy quarks or high P/sub T/ jets are produced, yet are diffractive, in the sense that one of the incident hadrons is scattered with only a small energy loss. 8 refs.
Resonance scattering by fish schools: A comparison of two models.
Raveau, M; Feuillade, C
2016-01-01
The effective medium method is used to investigate resonance scattering from schools of fish with gas-filled swim bladders, as a function of frequency and azimuth. Calculations are also performed with a coupled differential equation model, which incorporates both multiple scattering between fish and wave interference interactions of their scattered fields [Feuillade, Nero, and Love, J. Acoust. Soc. Am. 99, 196-208 (1996)]. A theoretical comparison of the models for idealized spherical schools shows good agreement over the entire resonance region in the forward direction, where interference interactions have a minimal effect. Good agreement is also seen in back scattering at low frequencies, where the wavelength λ≥4s, and s is the average nearest neighbor fish separation. If λ<4s, the models diverge in back scattering, and the effective medium method fails. This can be critically important when migrations of schools to deeper water cause the collective resonance frequency to increase. Multiple scattering interactions are negligible when |4πnf(b)(2)/k|⪅0.01, where n is the fish number density, f(b) is the individual fish scattering amplitude, and k=2π/λ. A comparison with forward scattering data shows very good agreement for both models, and indicates a method for estimating fish abundance. For back scattering data, the effective medium method diverges strongly when λ<4s. PMID:26827014
N-SAP and G-SAP neutron and gamma ray albedo model scatter shield analysis program
NASA Technical Reports Server (NTRS)
Sapovchak, B. J.; Stephenson, L. D.
1967-01-01
Computer program calculates neutron or gamma ray first order scattering from a plane or cylindrical surface to a detector point. The SAP Codes, G-SAP and N-SAP, constitute a multiple scatter albedo model shield analysis.
Aureolegraph internal scattering correction.
DeVore, John; Villanucci, Dennis; LePage, Andrew
2012-11-20
Two methods of determining instrumental scattering for correcting aureolegraph measurements of particulate solar scattering are presented. One involves subtracting measurements made with and without an external occluding ball and the other is a modification of the Langley Plot method and involves extrapolating aureolegraph measurements collected through a large range of solar zenith angles. Examples of internal scattering correction determinations using the latter method show similar power-law dependencies on scattering, but vary by roughly a factor of 8 and suggest that changing aerosol conditions during the determinations render this method problematic. Examples of corrections of scattering profiles using the former method are presented for a range of atmospheric particulate layers from aerosols to cumulus and cirrus clouds. PMID:23207299
Synthetic aperture methods for angular scatter imaging
NASA Astrophysics Data System (ADS)
Guenther, Drake A.; Ranganathan, Karthik; McAllister, Michael J.; Rigby, K. W.; Walker, William F.
2004-04-01
Angular scatter offers a new source of tissue contrast and an opportunity for tissue characterization in ultrasound imaging. We have previously described the application of the translating apertures algorithm (TAA) to coherently acquire angular scatter data over a range of scattering angles. While this approach works well at the focus, it suffers from poor depth of field (DOF) due to a finite aperture size. Furthermore, application of the TAA with large focused apertures entails a tradeoff between spatial resolution and scattering angle resolution. While large multielement apertures improve spatial resolution, they encompass many permutations of transmit/receive element pairs. This results in the simultaneous interrogation of multiple scattering angles, limiting angular resolution. We propose a synthetic aperture imaging scheme that achieves both high spatial resolution and high angular resolution. In backscatter acquisition mode, we transmit successively from single transducer elements, while receiving on the same element. Other scattering angles are interrogated by successively transmitting and receiving on different single elements chosen with the appropriate spatial separation between them. Thus any given image is formed using only transmit/receive element pairs at a single separation. This synthetic aperture approach minimizes averaging across scattering angles, and yields excellent angular resolution. Likewise, synthetic aperture methods allow us to build large effective apertures to maintain a high spatial resolution. Synthetic dynamic focusing and dynamic apodization are applied to further improve spatial resolution and DOF. We present simulation results and experimental results obtained using a GE Logiq 700MR system modified to obtain synthetic aperture TAA data. Images of wire targets exhibit high DOF and spatial resolution. We also present a novel approach for combining angular scatter data to effectively reduce grating lobes. With this approach we have
Scattering of light by molecules over a rough surface.
Long, Maureen; Khine, Michelle; Kim, Arnold D
2010-05-01
We present a theory for the multiple scattering of light by obstacles situated over a rough surface. This problem is important for applications in biological and chemical sensors. To keep the formulation of this theory simple, we study scalar waves. This theory requires knowledge of the scattering operator (t-matrix) for each of the obstacles as well as the reflection operator for the rough surface. The scattering operator gives the field scattered by the obstacle due to an exciting field incident on the scatterer. The reflection operator gives the field reflected by the rough surface due to an exciting field incident on the rough surface. We apply this general theory for the special case of point scatterers and a slightly rough surface with homogeneous Dirichlet and Neumann boundary conditions. We show examples that demonstrate the utility of this theory. PMID:20448766
NASA Astrophysics Data System (ADS)
Voronov, Aleksandr V.; Tret'yakov, Evgeniy V.; Shuvalov, Vladimir V.
2004-06-01
Based on the path-integration technique and the Metropolis method, the original calculation scheme is developed for solving the problem of light propagation through highly scattering objects. The elimination of calculations of 'unnecessary' realisations and the phenomenological description of processes of multiple small-angle scattering provided a drastic increase (by nine and more orders of magnitude) in the calculation rate, retaining the specific features of the problem (consideration of spatial inhomogeneities, boundary conditions, etc.). The scheme allows one to verify other fast calculation algorithms and to obtain information required to reconstruct the internal structure of highly scattering objects (of size ~1000 scattered lengths and more) by the method of diffusion optical tomography.
Inverse scattering by point-like scatterers in the Foldy regime
NASA Astrophysics Data System (ADS)
Prasad Challa, Durga; Sini, Mourad
2012-12-01
The scattering by point-like scatterers is described in the Born, Foldy and the intermediate regimes. We explain why the Foldy regime is, rigorously, a natural model for taking into account the multiple scattering. For each regime, we study the inverse problems for detecting these scatterers as well as the scattering strengths. In the first part, we do it for the acoustic case, and in the second, we study the corresponding models for the linearized isotropic elastic case. In this last case, we show how any of the two body waves, namely pressure waves P or shear waves S, is enough to solve the inverse problem. In the 3D case, it is shown that the shear horizontal part (SH) or the shear vertical part (SV) of the shear waves S is also enough for the detection. Finally, we provide extensive numerical tests justifying our findings and discuss the question of resolution in terms of the distance between the scatterers, the used frequency and the scattering strengths. In addition, a comparison study between the three mentioned regimes is also provided.
Calculates Thermal Neutron Scattering Kernel.
1989-11-10
Version 00 THRUSH computes the thermal neutron scattering kernel by the phonon expansion method for both coherent and incoherent scattering processes. The calculation of the coherent part is suitable only for calculating the scattering kernel for heavy water.
Restoration of antenna parameters in scattering environments using electromagnetic cloaking
NASA Astrophysics Data System (ADS)
Kwon, Do-Hoon; Werner, Douglas H.
2008-03-01
It is proposed that electromagnetic cloaks be used as effective shielding devices which enable improved antenna performance in highly scattering, multiple-antenna environments. In multiple frequency, multiple-antenna environments, each antenna is enclosed in a dispersive cloak that is designed to operate at the transmitting frequencies of the neighboring antennas. The loading effect of large objects in close proximity to a radiating antenna can be removed by enclosing the scatterer with a cloak. Application of cloaks to microwave antenna shielding only requires narrow band performance, which can be realized using currently available metamaterials technology.
Neutrons scattering studies in the actinide region
Kegel, G.H.R.; Egan, J.J.
1992-09-01
During the report period were investigated the following areas: prompt fission neutron energy spectra measurements; neutron elastic and inelastic scattering from [sup 239]Pu; neutron scattering in [sup 181]Ta and [sup 197]Au; response of a [sup 235]U fission chamber near reaction thresholds; two-parameter data acquisition system; black'' neutron detector; investigation of neutron-induced defects in silicon dioxide; and multiple scattering corrections. Four Ph.D. dissertations and one M.S. thesis were completed during the report period. Publications consisted of three journal articles, four conference papers in proceedings, and eleven abstracts of presentations at scientific meetings. There are currently four Ph.D. and one M.S. candidates working on dissertations directly associated with the project. In addition, three other Ph.D. candidates are working on dissertations involving other aspects of neutron physics in this laboratory.
Simultaneous CARS and Interferometric Rayleigh Scattering
NASA Technical Reports Server (NTRS)
Bivolaru, Daniel; Danehy, Paul M.; Grinstead, Keith D., Jr.; Tedder, Sarah; Cutler, Andrew D.
2006-01-01
This paper reports for the first time the combination of a dual-pump coherent anti-Stokes Raman scattering system with an interferometric Rayleigh scattering system (CARS - IRS) to provide time-resolved simultaneous measurement of multiple properties in combustion flows. The system uses spectrally narrow green (seeded Nd:YAG at 532 nm) and yellow (552.9 nm) pump beams and a spectrally-broad red (607 nm) beam as the Stokes beam. A spectrometer and a planar Fabry-Perot interferometer used in the imaging mode are used to record the spectrally broad CARS spectra and the spontaneous Rayleigh scattering spectra, respectively. Time-resolved simultaneous measurement of temperature, absolute mole fractions of N2, O2, and H2, and two components of velocity in a Hencken burner flame were performed to demonstrate the technique.
Neutrons scattering studies in the actinide region
NASA Astrophysics Data System (ADS)
Kegel, G. H. R.; Egan, J. J.
1992-09-01
During the last report period, we investigated the following areas: prompt fission neutron energy spectra measurements; neutron elastic and inelastic scattering from Pu-239; neutron scattering in Ta-181 and Au-197; response of a U-235 fission chamber near reaction thresholds; two-parameter data acquisition system; 'black' neutron detector; investigation of neutron-induced defects in silicon dioxide; and multiple scattering corrections. Four Ph.D. dissertations and one M.S. thesis were completed during the report period. Publications consisted of three journal articles, four conference papers in proceedings, and eleven abstracts of presentations at scientific meetings. There are currently four Ph.D. and one M.S. candidates working on dissertations directly associated with the project. In addition, three other Ph.D. candidates are working on dissertations involving other aspects of neutron physics in this laboratory.
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.
Kernel Integration Code System--Multigroup Gamma-Ray Scattering.
1988-02-15
GGG (G3) is the generic designation for a series of computer programs that enable the user to estimate gamma-ray scattering from a point source to a series of point detectors. Program output includes detector response due to each source energy, as well as a grouping by scattered energy in addition to a simple, unscattered beam result. Although G3 is basically a single-scatter program, it also includes a correction for multiple scattering by applying a buildupmore » factor for the path segment between the point of scatter and the detector point. Results are recorded with and without the buildup factor. Surfaces, defined by quadratic equations, are used to provide for a full three-dimensional description of the physical geometry. G3 evaluates scattering effects in those situations where more exact techniques are not economical. G3 was revised by Bettis and the name was changed to indicate that it was no longer identical to the G3 program. The name S3 was chosen since the scattering calculation has three steps: calculation of the flux arriving at the scatterer from the point source, calculation of the differential scattering cross section, and calculation of the scattered flux arriving at the detector.« less
Imaging scattering orientation with spatial frequency domain imaging
Konecky, Soren D.; Rice, Tyler; Durkin, Anthony J.; Tromberg, Bruce J.
2011-01-01
Optical imaging techniques based on multiple light scattering generally have poor sensitivity to the orientation and direction of microscopic light scattering structures. In order to address this limitation, we introduce a spatial frequency domain method for imaging contrast from oriented scattering structures by measuring the angular-dependence of structured light reflectance. The measurement is made by projecting sinusoidal patterns of light intensity on a sample, and measuring the degree to which the patterns are blurred as a function of the projection angle. We derive a spatial Fourier domain solution to an anisotropic diffusion model. This solution predicts the effects of bulk scattering orientation on the amplitude and phase of the projected patterns. We introduce a new contrast function based on a scattering orientation index (SOI) which is sensitive to the degree to which light scattering is directionally dependent. We validate the technique using tissue simulating phantoms, and ex vivo samples of muscle and brain. Our results show that SOI is independent of the overall amount of bulk light scattering and absorption, and that isotropic versus oriented scattering structures can be clearly distinguished. We determine the orientation of subsurface microscopic scattering structures located up to 600 μm beneath highly scattering (μ′s = 1.5 mm−1) material. PMID:22191918
Analysis of the Reconstructibility and Noise Properties of Scattered Photons in Tc-99m SPECT
Kadrmas, Dan J; Frey, Eric C; Tsui, Benjamin M W
2009-01-01
Since scattered photons carry degraded spatial information, scatter is typically considered a source of contamination in SPECT. However, with the advent of scatter modeling methods and reconstruction-based scatter compensation (RBSC), it may be possible to utilize scattered data in a productive manner. In this work we analyze the reconstructibility of scattered photon projection data and investigate the potential for using scattered photons to reduce the noise levels of SPECT images. We have simulated projection data for an elliptical phantom containing three cold rods in a uniform background of Tc-99m activity. A variety of photopeak and scatter energy windows were formed, as well as corresponding RBSC transfer matrices. Each statistically weighted matrix was decomposed using SVD and analyzed in terms of reconstructibility and noise properties. Results indicate that scattered photons contain sufficient information to reconstruct the source activity, but the scatter-only matrices are very poorly conditioned. We have also evaluated several methods of utilizing scattered events via RBSC, and compared them with other, idealized methods of handling scatter. It was found that scattered photons can be used productively when photopeak and non-photopeak data are separated through the use of multiple energy windows. The RBSC methods outperformed ideal scatter subtraction, but fell short of methods which assume perfect discrimination between scattered and primary events. The knowledge gained by this study may help guide future research and lead to better approaches to handling scatter in SPECT. PMID:9434303
Short-range order and near-field effects on optical scattering and structural coloration
Liew, S.F.; Forster, J.; Noh, H.; Schreck, C.F.; Saranathan, V.; Lu, X.; Yang, L.; Prum, Richard O.; OHern, C.S.; Dufresne, E.R.; Cao, H.
2012-03-26
We have investigated wavelength-dependent light scattering in biomimetic structures with short-range order. Coherent backscattering experiments are performed to measure the transport mean free path over a wide wavelength range. Overall scattering strength is reduced significantly due to short-range order and near-field effects. Our analysis explains why single scattering of light is dominant over multiple scattering in similar biological structures and is responsible for color generation.
Short-range Order and Near-field Effects on Optical Scattering and Structural Coloration
S Liew; J Forster; H Noh; C Schreck; V Saranathan; X Lu; L Yang; E Dufresne; H Cao; et al.
2011-12-31
We have investigated wavelength-dependent light scattering in biomimetic structures with short-range order. Coherent backscattering experiments are performed to measure the transport mean free path over a wide wavelength range. Overall scattering strength is reduced significantly due to short-range order and near-field effects. Our analysis explains why single scattering of light is dominant over multiple scattering in similar biological structures and is responsible for color generation.
Rayleigh Scattering Diagnostics Workshop
NASA Technical Reports Server (NTRS)
Seasholtz, Richard (Compiler)
1996-01-01
The Rayleigh Scattering Diagnostics Workshop was held July 25-26, 1995 at the NASA Lewis Research Center in Cleveland, Ohio. The purpose of the workshop was to foster timely exchange of information and expertise acquired by researchers and users of laser based Rayleigh scattering diagnostics for aerospace flow facilities and other applications. This Conference Publication includes the 12 technical presentations and transcriptions of the two panel discussions. The first panel was made up of 'users' of optical diagnostics, mainly in aerospace test facilities, and its purpose was to assess areas of potential applications of Rayleigh scattering diagnostics. The second panel was made up of active researchers in Rayleigh scattering diagnostics, and its purpose was to discuss the direction of future work.
NASA Astrophysics Data System (ADS)
Piwinski, A.
Intra-beam scattering is analysed and the rise times or damping times of the beam dimensions are derived. The theoretical results are compared with experimental values obtained on the CERN AA and SPS machines.
Electron scattering from pyrimidine
NASA Astrophysics Data System (ADS)
Colmenares, Rafael; Fuss, Martina C.; Oller, Juan C.; Muñoz, Antonio; Blanco, Francisco; Almeida, Diogo; Limão-Vieira, Paulo; García, Gustavo
2014-04-01
Electron scattering from pyrimidine (C4H4N2) was investigated over a wide range of energies. Following different experimental and theoretical approaches, total, elastic and ionization cross sections as well as electron energy loss distributions were obtained.
Cosmic Ray Scattering Radiography
NASA Astrophysics Data System (ADS)
Morris, C. L.
2015-12-01
Cosmic ray muons are ubiquitous, are highly penetrating, and can be used to measure material densities by either measuring the stopping rate or by measuring the scattering of transmitted muons. The Los Alamos team has studied scattering radiography for a number of applications. Some results will be shown of scattering imaging for a range of practical applications, and estimates will be made of the utility of scattering radiography for nondestructive assessments of large structures and for geological surveying. Results of imaging the core of the Toshiba Nuclear Critical Assembly (NCA) Reactor in Kawasaki, Japan and simulations of imaging the damaged cores of the Fukushima nuclear reactors will be presented. Below is an image made using muons of a core configuration for the NCA reactor.
NASA Technical Reports Server (NTRS)
Mceachran, R. P.; Horbatsch, M.; Stauffer, A. D.
1990-01-01
A 5-state close-coupling calculation (5s-5p-4d-6s-6p) was carried out for positron-Rb scattering in the energy range 3.7 to 28.0 eV. In contrast to the results of similar close-coupling calculations for positron-Na and positron-K scattering the (effective) total integrated cross section has an energy dependence which is contrary to recent experimental measurements.
Neutron spin echo scattering angle measurement (SESAME)
Pynn, R.; Fitzsimmons, M.R.; Fritzsche, H.; Gierlings, M.; Major, J.; Jason, A.
2005-05-15
We describe experiments in which the neutron spin echo technique is used to measure neutron scattering angles. We have implemented the technique, dubbed spin echo scattering angle measurement (SESAME), using thin films of Permalloy electrodeposited on silicon wafers as sources of the magnetic fields within which neutron spins precess. With 30-{mu}m-thick films we resolve neutron scattering angles to about 0.02 deg. with neutrons of 4.66 A wavelength. This allows us to probe correlation lengths up to 200 nm in an application to small angle neutron scattering. We also demonstrate that SESAME can be used to separate specular and diffuse neutron reflection from surfaces at grazing incidence. In both of these cases, SESAME can make measurements at higher neutron intensity than is available with conventional methods because the angular resolution achieved is independent of the divergence of the neutron beam. Finally, we discuss the conditions under which SESAME might be used to probe in-plane structure in thin films and show that the method has advantages for incident neutron angles close to the critical angle because multiple scattering is automatically accounted for.
Monte Carlo scatter correction for SPECT
NASA Astrophysics Data System (ADS)
Liu, Zemei
The goal of this dissertation is to present a quantitatively accurate and computationally fast scatter correction method that is robust and easily accessible for routine applications in SPECT imaging. A Monte Carlo based scatter estimation method is investigated and developed further. The Monte Carlo simulation program SIMIND (Simulating Medical Imaging Nuclear Detectors), was specifically developed to simulate clinical SPECT systems. The SIMIND scatter estimation (SSE) method was developed further using a multithreading technique to distribute the scatter estimation task across multiple threads running concurrently on multi-core CPU's to accelerate the scatter estimation process. An analytical collimator that ensures less noise was used during SSE. The research includes the addition to SIMIND of charge transport modeling in cadmium zinc telluride (CZT) detectors. Phenomena associated with radiation-induced charge transport including charge trapping, charge diffusion, charge sharing between neighboring detector pixels, as well as uncertainties in the detection process are addressed. Experimental measurements and simulation studies were designed for scintillation crystal based SPECT and CZT based SPECT systems to verify and evaluate the expanded SSE method. Jaszczak Deluxe and Anthropomorphic Torso Phantoms (Data Spectrum Corporation, Hillsborough, NC, USA) were used for experimental measurements and digital versions of the same phantoms employed during simulations to mimic experimental acquisitions. This study design enabled easy comparison of experimental and simulated data. The results have consistently shown that the SSE method performed similarly or better than the triple energy window (TEW) and effective scatter source estimation (ESSE) methods for experiments on all the clinical SPECT systems. The SSE method is proven to be a viable method for scatter estimation for routine clinical use.
NASA Astrophysics Data System (ADS)
Nakayama, J.; Sakata, M.; Ogura, H.
1981-09-01
The scattering of an electromagnetic wave from an infinite random surface is studied by the probabilistic method developed in a previous paper. For a vertical polarized plane wave incident on a slightly random and perfectly conductive surface a new stochastic wave solution involving multiple scattering is obtained. The stochastic solution is free from the divergence difficulty as in the small perturbation method but gives an anomaly such that for a grazing angle of incidence the coherent scattering almost disappears and instead the incoherent scattering becomes dominant. In terms of the stochastic solution, a number of statistical properties of the scattering are calculated concretely for a perfectly conductive surface, such as the complex amplitude of the coherent scattering, the variance of the electric field, the optical theorem describing the power relation between the coherent and the incoherent scattering, the angular distribution of the incoherent scattering, the scattering cross section per unit area, and the surface wave flow, which are all illustrated in the figures.
Scattered surface wave energy in the seismic coda
Zeng, Y.
2006-01-01
One of the many important contributions that Aki has made to seismology pertains to the origin of coda waves (Aki, 1969; Aki and Chouet, 1975). In this paper, I revisit Aki's original idea of the role of scattered surface waves in the seismic coda. Based on the radiative transfer theory, I developed a new set of scattered wave energy equations by including scattered surface waves and body wave to surface wave scattering conversions. The work is an extended study of Zeng et al. (1991), Zeng (1993) and Sato (1994a) on multiple isotropic-scattering, and may shed new insight into the seismic coda wave interpretation. The scattering equations are solved numerically by first discretizing the model at regular grids and then solving the linear integral equations iteratively. The results show that scattered wave energy can be well approximated by body-wave to body wave scattering at earlier arrival times and short distances. At long distances from the source, scattered surface waves dominate scattered body waves at surface stations. Since surface waves are 2-D propagating waves, their scattered energies should in theory follow a common decay curve. The observed common decay trends on seismic coda of local earthquake recordings particular at long lapse times suggest that perhaps later seismic codas are dominated by scattered surface waves. When efficient body wave to surface wave conversion mechanisms are present in the shallow crustal layers, such as soft sediment layers, the scattered surface waves dominate the seismic coda at even early arrival times for shallow sources and at later arrival times for deeper events.
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.
2010-01-01
Abstract Advances in the imaging and treatment of multiple myeloma have occurred over the past decade. This article summarises the current status and highlights how an understanding of both is necessary for optimum management. PMID:20159661
Multiple sclerosis (MS) is a nervous system disease that affects your brain and spinal cord. It damages the myelin sheath, the ... and your body, leading to the symptoms of MS. They can include Visual disturbances Muscle weakness Trouble ...
Plasma cell dyscrasia; Plasma cell myeloma; Malignant plasmacytoma; Plasmacytoma of bone; Myeloma - multiple ... myeloma most commonly causes a low red blood cell count ( anemia ), which can lead to fatigue and ...
Raab, Marc S; Podar, Klaus; Breitkreutz, Iris; Richardson, Paul G; Anderson, Kenneth C
2009-07-25
Multiple myeloma is characterised by clonal proliferation of malignant plasma cells, and mounting evidence indicates that the bone marrow microenvironment of tumour cells has a pivotal role in myeloma pathogenesis. This knowledge has already expanded treatment options for patients with multiple myeloma. Prototypic drugs thalidomide, bortezomib, and lenalidomide have each been approved for the treatment of this disease by targeting both multiple myeloma cells and the bone marrow microenvironment. Although benefit was first shown in relapsed and refractory disease, improved overall response, duration of response, and progression-free and overall survival can be achieved when these drugs are part of first-line regimens. This treatment framework promises to improve outcome not only for patients with multiple myeloma, but also with other haematological malignancies and solid tumours. PMID:19541364
Hashimoto, S.A.; Jiwa, Theresa I.
1991-01-01
Successful management of patients with multiple sclerosis depends upon the involvement of the family physician. All contacts with either a multiple sclerosis clinic or a neurologist should be made at the instigation of the family practitioner. Constant contact with the family physician ensures that the individual receives proper care. While specialty care is needed for many of the symptoms, psychosocial problems are dealt with best by the individual's own family physician. PMID:21229090
NASA Astrophysics Data System (ADS)
Hu, Zhijia; Zhang, Qun; Miao, Bo; Fu, Qiang; Zou, Gang; Chen, Yang; Luo, Yi; Zhang, Douguo; Wang, Pei; Ming, Hai; Zhang, Qijin
2012-12-01
We demonstrate the realization of a coherent random fiber laser (RFL) in the extremely weakly scattering regime, which contains a dispersive solution of polyhedral oligomeric silsesquioxanes nanoparticles (NPs) and laser dye pyrromethene 597 in carbon disulfide that was injected into a hollow optical fiber. Multiple scattering of polyhedral oligomeric silsesquioxanes NPs greatly enhanced by the waveguide confinement effect was experimentally verified to account for coherent lasing observed in our RFL system. This Letter extends the NPs-based RFLs from the incoherent regime to the coherent regime.
Scattering of electromagnetic waves from a half space of densely distributed dielectric scatterers
NASA Technical Reports Server (NTRS)
Tsang, L.; Kong, J. A.
1983-01-01
The scattering of a plane wave obliquely incident on a half space of densely distributed spherical dielectric scatterers is studied. The quasi-crystalline approximation is applied to truncate the hierarchy of multiple scattering equations, and the Percus-Yevick and the Verlet-Weis results are used to represent the pair distribution function. The coherent reflected wave is studied with these approximations. The incoherent scattered wave is calculated with the distorted Born approximation. In the low-frequency limit, closed-form expressions are obtained for the effective propagation constants, the coherent reflected wave, and the bistatic scattering coeficients. Results at higher frequencies are calculated numerically. The advantage of the present approach is that, in the low-frequency limit, it reproduces the effects of specular reflection, Fresnel reflection coefficient, Brewster angle, and Clausius-Mosotti relation. In addition to the classical results, the bistatic scattering coefficients are also calculated. The theory is also applied to match backscattering data from dry snow at microwave frequencies.
Light Scattering by Fractal Dust Aggregates. I. Angular Dependence of Scattering
NASA Astrophysics Data System (ADS)
Tazaki, Ryo; Tanaka, Hidekazu; Okuzumi, Satoshi; Kataoka, Akimasa; Nomura, Hideko
2016-06-01
In protoplanetary disks, micron-sized dust grains coagulate to form highly porous dust aggregates. Because the optical properties of these aggregates are not completely understood, it is important to investigate how porous dust aggregates scatter light. In this study, the light scattering properties of porous dust aggregates were calculated using a rigorous method, the T-matrix method, and the results were then compared with those obtained using the Rayleigh–Gans–Debye (RGD) theory and Mie theory with the effective medium approximation (EMT). The RGD theory is applicable to moderately large aggregates made of nearly transparent monomers. This study considered two types of porous dust aggregates—ballistic cluster–cluster agglomerates (BCCAs) and ballistic particle–cluster agglomerates. First, the angular dependence of the scattered intensity was shown to reflect the hierarchical structure of dust aggregates; the large-scale structure of the aggregates is responsible for the intensity at small scattering angles, and their small-scale structure determines the intensity at large scattering angles. Second, it was determined that the EMT underestimates the backward scattering intensity by multiple orders of magnitude, especially in BCCAs, because the EMT averages the structure within the size of the aggregates. It was concluded that the RGD theory is a very useful method for calculating the optical properties of BCCAs.
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.
Gasdynamic Multiple-Mirror Trap
NASA Astrophysics Data System (ADS)
Beklemishev, Alexei; Anikeev, Andrei; Bagryansky, Peter; Burdakov, Alexander; Gavrilenko, Dmitrii; Ivanov, Alexander; Polosatkin, Sergei; Sinitsky, Stanislav
2013-10-01
The new linear device for confinement of fusion plasmas, GDMT, is being developed at the Budker Institute of Nuclear Physics, Novosibirsk. The facility will combine features of existing GOL-3 and GDT devices: the central GDT-like cell with sloshing NBI ions, and the multiple-mirror plugs for suppression of axial losses. Such combination became feasible due to recent discoveries. In particular, the requirement of flute-mode stability can be relaxed by using vortex confinement, achieved by plasma biasing through open field lines. This allows the use of potentially destabilizing multiple-mirror sections. Another key effect is the enhanced multiple-mirror confinement at low densities, which is due to collective rather than coulomb scattering of ions. Hence the multiple-mirror plugs can work at pressures compatible with magnetic confinement. These two main technologies are supplemented by axial injection of pulsed electron beams. Besides additional plasma heating (like in GOL-3), such injection can be used for induced collective scattering in the multiple-mirror plugs and for plasma biasing. The new device is designed to be superconducting and modular. It will be built in stages, with the first stage, GDMT-T, intended for PMI studies. The work was financially supported by Ministry of Education and Science RF.
Erin A. Miller; Joseph A. Caggiano; Robert C. Runkle; Timothy A. White; Aaron M. Bevill
2011-03-01
As a complement to passive detection systems, radiographic inspection of cargo is an increasingly important tool for homeland security because it has the potential to detect highly attenuating objects associated with special nuclear material or surrounding shielding, in addition to screening for items such as drugs or contraband. Radiographic detection of such threat objects relies on high image contrast between regions of different density and atomic number (Z). Threat detection is affected by scatter of the interrogating beamin the cargo, the radiographic system itself, and the surrounding environment, which degrades image contrast. Here, we estimate the extent to which scatter plays a role in radiographic imaging of cargo containers. Stochastic transport simulations were performed to determine the details of the radiography equipment and surrounding environment, which are important in reproducing measured data and to investigate scatter magnitudes for typical cargo. We find that scatter plays a stronger role in cargo radiography than in typicalmedical imaging scenarios, even for low-density cargo, with scatter-toprimary ratios ranging from 0.14 for very low density cargo, to between 0.20 and 0.40 for typical cargo, and higher yet for dense cargo.
Depolarization of Light Scattered from Rough Cylindrical Surfaces
NASA Astrophysics Data System (ADS)
Aparicio, R.; Quintián, F. Perez; Rebollo, M. A.
2008-04-01
In this work we study the state of polarization of light scattered from rough cylindrical surfaces. The experimental results show that the amount of cross-polarized light at a particular observation angle is correlated with the roughness of the cylinders. We compare these results with those obtained using the Kirchhoff's vector theory and analyze if the differences can be modeled on multiple-scattering effects.
Multiple-illumination photoacoustic tomography
NASA Astrophysics Data System (ADS)
Barber, Quinn M.; Zemp, Roger J.
2016-03-01
Previously we described the potential for multiple illumination photoacoustic tomography to provide quantitative reconstructions, however this work used only simulated data. We have developed a custom photoacoustic-ultrasound tomography system capable of multiple illuminations and parallel acquisition from a 256 element 5 MHz transducer ring array with 8-cm diameter. The multiple illumination scheme uses a free-space light delivery geometry where a rotational stage scans a pulsed laser beam onto different incident locations around the sample. For each illumination location a photoacoustic image is reconstructed using a modified backprojection algorithm. Images from different source locations have the potential to be combined to form an improved deep-tissue image using our previously developed iterative algorithms. We complement the photoacoustic imaging data with unique ultrasound imaging data. Most previous ultrasound tomography methods have used migration algorithms, iterative ray-based analysis, wave-equation modeling, or frequency-based algorithms that all demand large amounts of data and computational power. We propose a new UST method that offers isotropic resolution, provides scattering contrast, as well as the potential for measuring ultrasound scattering anisotropy and decoupling density and compressibility contributions. The imaging system is driven by a Verasonics scan engine and programmed for both ultrasound and photoacoustic imaging modes. Resolution has been measured to be 150 μm for ultrasound and 200 μm for photoacoustic images. Imaging capabilities are demonstrated on phantoms with custom-tailored ultrasound scattering and optical properties, as well as in murine models.
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.
Compton scattering profile for in vivo XRF techniques.
Tartari, A; Baraldi, C; Felsteiner, J; Casnati, E
1991-05-01
The contribution from single Compton scattered photons to the background in in vivo x-ray fluorescence analysis is evaluated by taking into account the energy broadening of the scattered photons which reflects the momentum distribution of the target electrons. A general-purpose Monte Carlo evaluation of multiple scattering components, as well as accurate experimental verifications with 59.54 keV photons impinging on various targets of interest for real-life irradiation, confirm that the single Compton scattering profiles of the elements composing the biological matrix dominate the trend and amplitude of the background in the region of interest with near-backscatter configurations. Step features are likewise explained in terms of single Compton phenomenology. Other probable sources of background, such as photoelectron Bremsstrahlung and pile-up distribution, are studied both theoretically and experimentally in order to compare their amplitude and features with those of single Compton scattered photon profiles. PMID:2068224
Estimation of Anomalous Single Scatter Events in XENON100 Data
NASA Astrophysics Data System (ADS)
Lim, Kyungeun; Xenon100 Collaboration
2011-04-01
Anomalous single scatter events in XENON100 are events that have only one scintillation pulse (S1) and one ionization pulse (S2), but are multiple scatters in nature. Only one scatter takes place inside the detector's charge and light sensitive volume, resulting in a S2/S1 ratio that is lower than that of true single scatter events and typical of that expected from a WIMP interaction. The identification and suppression of these anomalous events is therefore essential for a sensitive dark matter search. I present results from a Monte Carlo (MC) study that was carried out to estimate the expected number of anomalous single scatter events in the XENON100 WIMP search data. The MC was validated with a comparison with Co-60 gamma-calibration data. We gratefully acknowledge support from NSF, DOE, SNF, the Volkswagen Foundation, FCT, and STCSM. We are grateful to the LNGS for hosting and supporting the XENON program.
UV Multi-scatter Propagation Model of Point Probability Method
NASA Astrophysics Data System (ADS)
Lu, Bai; Zhensen, Wu; Haiying, Li
Based on the multi-scatter propagation model of Monte Carlo, an improved geometric model is proposed. The model is ameliorated by using the point probability method. Comparison is made between the multiple scattering propagation models and the single-scatter propagation model in calculation time and relative error. The effect of complex weather, stumbling block and the transmitter and the receiver in different height are discussed. It is shown that although the single-scatter propagation model can be evaluated easily from standard numerical integration but this model cannot describe general non-line-of sight propagation problem. While the improved point probability multi-scatter Monte Carlo model may be used to more general case.
Study of erythrocyte membrane fluctuation using light scattering analysis
NASA Astrophysics Data System (ADS)
Lee, Hoyoon; Lee, Sangyun; Park, YongKeun; Shin, Sehyun
2016-03-01
It is commonly known that alteration of erythrocyte deformability lead to serious microcirculatory diseases such as retinopathy, nephropathy, etc. Various methods and technologies have been developed to diagnose such membrane properties of erythrocytes. In this study, we developed an innovative method to measure hemorheological characteristics of the erythrocyte membrane using a light scattering analysis with simplified optic setting and multi-cell analysis as well. Light scattering intensity through multiple erythrocytes and its power density spectrum were obtained. The results of light scattering analyses were compared in healthy control and artificially hardened sample which was treated with glutaraldehyde. These results were further compared with conventional assays to measure deformable property in hemorheology. We found that light scattering information would reflect the disturbance of membrane fluctuation in artificially damaged erythrocytes. Therefore, measuring fluctuation of erythrocyte membrane using light scattering signal could facilitate simple and precise diagnose of pathological state on erythrocyte as well as related complications.
Terrier, L-M; François, P
2016-06-01
Multiple meningiomas (MMs) or meningiomatosis are defined by the presence of at least 2 lesions that appear simultaneously or not, at different intracranial locations, without the association of neurofibromatosis. They present 1-9 % of meningiomas with a female predominance. The occurrence of multiple meningiomas is not clear. There are 2 main hypotheses for their development, one that supports the independent evolution of these tumors and the other, completely opposite, that suggests the propagation of tumor cells of a unique clone transformation, through cerebrospinal fluid. NF2 gene mutation is an important intrinsic risk factor in the etiology of multiple meningiomas and some exogenous risk factors have been suspected but only ionizing radiation exposure has been proven. These tumors can grow anywhere in the skull but they are more frequently observed in supratentorial locations. Their histologic types are similar to unique meningiomas of psammomatous, fibroblastic, meningothelial or transitional type and in most cases are benign tumors. The prognosis of these tumors is eventually good and does not differ from the unique tumors except for the cases of radiation-induced multiple meningiomas, in the context of NF2 or when diagnosed in children where the outcome is less favorable. Each meningioma lesion should be dealt with individually and their multiple character should not justify their resection at all costs. PMID:27234913
Electromagnetic scattering theory
NASA Technical Reports Server (NTRS)
Bird, J. F.; Farrell, R. A.
1986-01-01
Electromagnetic scattering theory is discussed with emphasis on the general stochastic variational principle (SVP) and its applications. The stochastic version of the Schwinger-type variational principle is presented, and explicit expressions for its integrals are considered. Results are summarized for scalar wave scattering from a classic rough-surface model and for vector wave scattering from a random dielectric-body model. Also considered are the selection of trial functions and the variational improvement of the Kirchhoff short-wave approximation appropriate to large size-parameters. Other applications of vector field theory discussed include a general vision theory and the analysis of hydromagnetism induced by ocean motion across the geomagnetic field. Levitational force-torque in the magnetic suspension of the disturbance compensation system (DISCOS), now deployed in NOVA satellites, is also analyzed using the developed theory.
Quaglioni, S; Navratil, P; Roth, R
2009-12-15
The exact treatment of nuclei starting from the constituent nucleons and the fundamental interactions among them has been a long-standing goal in nuclear physics. Above all nuclear scattering and reactions, which require the solution of the many-body quantum-mechanical problem in the continuum, represent an extraordinary theoretical as well as computational challenge for ab initio approaches.We present a new ab initio many-body approach which derives from the combination of the ab initio no-core shell model with the resonating-group method [4]. By complementing a microscopic cluster technique with the use of realistic interactions, and a microscopic and consistent description of the nucleon clusters, this approach is capable of describing simultaneously both bound and scattering states in light nuclei. We will discuss applications to neutron and proton scattering on sand light p-shell nuclei using realistic nucleon-nucleon potentials, and outline the progress toward the treatment of more complex reactions.
ZALIZNYAK,I.A.; LEE,S.H.
2004-07-30
Much of our understanding of the atomic-scale magnetic structure and the dynamical properties of solids and liquids was gained from neutron-scattering studies. Elastic and inelastic neutron spectroscopy provided physicists with an unprecedented, detailed access to spin structures, magnetic-excitation spectra, soft-modes and critical dynamics at magnetic-phase transitions, which is unrivaled by other experimental techniques. Because the neutron has no electric charge, it is an ideal weakly interacting and highly penetrating probe of matter's inner structure and dynamics. Unlike techniques using photon electric fields or charged particles (e.g., electrons, muons) that significantly modify the local electronic environment, neutron spectroscopy allows determination of a material's intrinsic, unperturbed physical properties. The method is not sensitive to extraneous charges, electric fields, and the imperfection of surface layers. Because the neutron is a highly penetrating and non-destructive probe, neutron spectroscopy can probe the microscopic properties of bulk materials (not just their surface layers) and study samples embedded in complex environments, such as cryostats, magnets, and pressure cells, which are essential for understanding the physical origins of magnetic phenomena. Neutron scattering is arguably the most powerful and versatile experimental tool for studying the microscopic properties of the magnetic materials. The magnitude of the cross-section of the neutron magnetic scattering is similar to the cross-section of nuclear scattering by short-range nuclear forces, and is large enough to provide measurable scattering by the ordered magnetic structures and electron spin fluctuations. In the half-a-century or so that has passed since neutron beams with sufficient intensity for scattering applications became available with the advent of the nuclear reactors, they have became indispensable tools for studying a variety of important areas of modern science
NASA Astrophysics Data System (ADS)
Gomez, Humberto
2016-06-01
The CHY representation of scattering amplitudes is based on integrals over the moduli space of a punctured sphere. We replace the punctured sphere by a double-cover version. The resulting scattering equations depend on a parameter Λ controlling the opening of a branch cut. The new representation of scattering amplitudes possesses an enhanced redundancy which can be used to fix, modulo branches, the location of four punctures while promoting Λ to a variable. Via residue theorems we show how CHY formulas break up into sums of products of smaller (off-shell) ones times a propagator. This leads to a powerful way of evaluating CHY integrals of generic rational functions, which we call the Λ algorithm.
Monopole-antimonopole scattering
NASA Astrophysics Data System (ADS)
Vachaspati, Tanmay
2016-02-01
We numerically study the head-on scattering of a 't Hooft-Polyakov magnetic monopole and antimonopole for a wide range of parameters. In contrast to the scattering of a λ ϕ4 kink and antikink in 1 +1 dimensions, we find that the monopole and antimonopole annihilate even when scattered at relativistic velocities. If the monopole and antimonopole have a relative twist, there is a repulsive force between them and they can initially be reflected. However, in every case we have examined, the reflected monopoles remain bound and eventually annihilate. We also calculate the magnetic helicity in the aftermath of monopole-antimonopole annihilation and confirm the conversion of relative twist to magnetic helicity as discussed earlier in the electroweak case.
Experimental studies of light propagation in active scattering media
NASA Astrophysics Data System (ADS)
Perkins, Amy Elizabeth
1998-10-01
Over the past several years there has been a great deal of renewed interest in multiple scattering systems with gain. Laser action has been demonstrated in systems containing high gain laser dyes mixed with passive scattering particles. In these materials, known as photonic paint, the scatterers redirect the light and provide the feedback mechanism to initiate lasing. A method of decreasing the linewidth which has been used in conventional laser systems is injection locking, in which a seed at the desired wavelength is introduced into the cavity to initiate lasing. Experiments are presented which demonstrate injection locking of this new laser system. It is also of particular interest to study the phenomenon of weak localization of light in these photonic paint systems. The interference between scattered light paths increases the probability of light traveling opposite to the direction of the incident light, and produces a cone of enhanced reflected light in that direction. In the presence of amplification, the coherent backscattering cone narrows. In this high gain scattering system, an unstudied regime can be achieved in which significant amplification takes place over one scattering length. The results of the coherent backscattering experiment in a high gain scattering system is discussed. There are certain intrinsic problems with inversion gain systems, such as photonic paint, which makes the narrowing of the coherent backscattering cone less pronounced. In Raman materials, these effects are greatly reduced. Experimental studies of the amplification of a probe beam in a disordered Raman scattering medium, and the Monte Carlo simulations of this experiment, are presented. It is also of interest to study absorptive scattering systems which appear in a number of different situations, including the determination of the excitation volume in a scattering gain system and the modeling of biological tissue. The addition of an absorbing species into a scattering medium
Confocal zero-angle dynamic depolarized light scattering.
Potenza, M A C; Sanvito, T; Alaimo, M D; Degiorgio, V; Giglio, M
2010-01-01
We present a novel Dynamic Depolarized Scattering method based on a tight confocal, zero scattering angle, heterodyne scheme. The method is highly immune from parasitic multiple-scattering contributions, so that it can operate with non-index-matched samples presenting large turbidity. It provides measurements of both rotational and translational diffusion coefficients, the latter via number fluctuation spectroscopy. In addition, the amplitude ratio between the two baselines for the fast rotational mode and the slow translational mode can be used to determine the particles intrinsic birefringence. PMID:20087622
Miller, Erin A.; Caggiano, Joseph A.; Runkle, Robert C.; White, Timothy A.; Bevill, Aaron M.
2011-03-01
As a complement to passive detection systems, radiographic inspection of cargo is an increasingly important tool for homeland security because it has the potential to detect highly attenuating objects associated with special nuclear material or surrounding shielding. Detecting such objects relies on high image contrast between regions of different density and atomic number (Z). Threat detection is affected by scatter of the interrogating beam, both in the cargo and surrounding objects, which degrades image contrast. Here, we work to determine the extent to which scatter plays a role in radiographic imaging of cargo containers.
Scattering with absorptive interaction
NASA Astrophysics Data System (ADS)
Cassing, W.; Stingl, M.; Weiguny, A.
1982-07-01
The S matrix for a wide class of complex and nonlocal potentials is studied, with special attention given to the motion of singularities in the complex k plane as a function of the imaginary coupling strength. Modifications of Levinson's theorem are obtained and discussed. Analytic approximations to the S matrix in the vicinity of narrow resonances are exhibited and compared to numerical results of resonating-group calculations. The problem of defining resonances in the case of complex interactions is discussed, making contact with the usual analysis of scattering in terms of Argand diagrams. NUCLEAR REACTIONS Scattering theory, S matrix for absorptive potentials.
Controlling single-photon Fock-state propagation through opaque scattering media
NASA Astrophysics Data System (ADS)
Huisman, Thomas J.; Huisman, Simon R.; Mosk, Allard P.; Pinkse, Pepijn W. H.
2014-09-01
The control of light scattering is essential in many quantum optical experiments. Wavefront shaping is a technique used for ultimate control over wave propagation through multiple-scattering media by adaptive manipulation of incident waves. We control the propagation of single-photon Fock states through opaque scattering media by spatial phase modulation of the incident wavefront. We enhance the probability that a single photon arrives in a target output mode with a factor 30. Our proof-of-principle experiment shows that the propagation of quantum light through multiple-scattering media can be controlled, with prospective applications in quantum communication and quantum cryptography.
AGK cutting rules and multiple scattering in hadronic collisions
NASA Astrophysics Data System (ADS)
Bartels, J.; Salvadore, M.; Vacca, G. P.
2005-07-01
We discuss the AGK rules for the exchange of an arbitrary number of reggeized gluons in perturbative QCD in the high-energy limit. The results include the cancellation of corrections to single jet and double jet inclusive cross sections, both for hard and soft rescattering contributions.
Multiple scattering calculations of relativistic electron energy loss spectra
NASA Astrophysics Data System (ADS)
Jorissen, K.; Rehr, J. J.; Verbeeck, J.
2010-04-01
A generalization of the real-space Green’s-function approach is presented for ab initio calculations of relativistic electron energy loss spectra (EELS) which are particularly important in anisotropic materials. The approach incorporates relativistic effects in terms of the transition tensor within the dipole-selection rule. In particular, the method accounts for relativistic corrections to the magic angle in orientation resolved EELS experiments. The approach is validated by a study of the graphite CK edge, for which we present an accurate magic angle measurement consistent with the predicted value.
Low-energy multiple-Coulomb scattering in thick foils
Morrill, S.M.
1984-01-01
Angular and energy distributions were taken using proton and ..cap alpha..-particle beams of energies 2 to 10 MeV incident on a variety of thick foils. Foils were chosen from commonly used materials and to span the periodic table. Foil thicknesses were chosen which resulted in approximately 20-60% energy losses. The lower-energy experiments were done using the Brigham Young University 4-MeV Van de Graaff accelerator while the higher-energy experiments were performed using the Triangle Universities Nuclear Laboratory (TUNL) tandem Van de Graaff. Angular distributions are characterized by the angles at which the distribution had dropped to the 1/e, 1/10, and 1/100 points of their initial values. Energy distributions are characterized by the mean energy and the width of the energy-straggling distribution of the emerging particle. Comparisons are made to the appropriate theories including the angular distribution theory of Nigam, Sundaresan, and Wu (NSW), and the straggling theory of Bethe. Improvements to the NSW method by using an effective energy and effective nuclear charge are discussed.