Improved Abel transform inversion: First application to COSMIC/FORMOSAT-3
NASA Astrophysics Data System (ADS)
Aragon-Angel, A.; Hernandez-Pajares, M.; Juan, J.; Sanz, J.
2007-05-01
In this paper the first results of Ionospheric Tomographic inversion are presented, using the Improved Abel Transform on the COSMIC/FORMOSAT-3 constellation of 6 LEO satellites, carrying on-board GPS receivers.[- 4mm] The Abel transform inversion is a wide used technique which in the ionospheric context makes it possible to retrieve electron densities as a function of height based of STEC (Slant Total Electron Content) data gathered from GPS receivers on board of LEO (Low Earth Orbit) satellites. Within this precise use, the classical approach of the Abel inversion is based on the assumption of spherical symmetry of the electron density in the vicinity of an occultation, meaning that the electron content varies in height but not horizontally. In particular, one implication of this assumption is that the VTEC (Vertical Total Electron Content) is a constant value for the occultation region. This assumption may not always be valid since horizontal ionospheric gradients (a very frequent feature in some ionosphere problematic areas such as the Equatorial region) could significantly affect the electron profiles. [- 4mm] In order to overcome this limitation/problem of the classical Abel inversion, a studied improvement of this technique can be obtained by assuming separability in the electron density (see Hernández-Pajares et al. 2000). This means that the electron density can be expressed by the multiplication of VTEC data and a shape function which assumes all the height dependency in it while the VTEC data keeps the horizontal dependency. Actually, it is more realistic to assume that this shape fuction depends only on the height and to use VTEC information to take into account the horizontal variation rather than considering spherical symmetry in the electron density function as it has been carried out in the classical approach of the Abel inversion.[-4mm] Since the above mentioned improved Abel inversion technique has already been tested and proven to be a useful
Abel inversion method for cometary atmospheres.
NASA Astrophysics Data System (ADS)
Hubert, Benoit; Opitom, Cyrielle; Hutsemekers, Damien; Jehin, Emmanuel; Munhoven, Guy; Manfroid, Jean; Bisikalo, Dmitry V.; Shematovich, Valery I.
2016-04-01
Remote observation of cometary atmospheres produces a measurement of the cometary emissions integrated along the line of sight joining the observing instrument and the gas of the coma. This integration is the so-called Abel transform of the local emission rate. We develop a method specifically adapted to the inversion of the Abel transform of cometary emissions, that retrieves the radial profile of the emission rate of any unabsorbed emission, under the hypothesis of spherical symmetry of the coma. The method uses weighted least squares fitting and analytical results. A Tikhonov regularization technique is applied to reduce the possible effects of noise and ill-conditioning, and standard error propagation techniques are implemented. Several theoretical tests of the inversion techniques are carried out to show its validity and robustness, and show that the method is only weakly dependent on any constant offset added to the data, which reduces the dependence of the retrieved emission rate on the background subtraction. We apply the method to observations of three different comets observed using the TRAPPIST instrument: 103P/ Hartley 2, F6/ Lemmon and A1/ Siding spring. We show that the method retrieves realistic emission rates, and that characteristic lengths and production rates can be derived from the emission rate for both CN and C2 molecules. We show that the emission rate derived from the observed flux of CN emission at 387 nm and from the C2 emission at 514.1 nm of comet Siding Spring both present an easily-identifiable shoulder that corresponds to the separation between pre- and post-outburst gas. As a general result, we show that diagnosing properties and features of the coma using the emission rate is easier than directly using the observed flux. We also determine the parameters of a Haser model fitting the inverted data and fitting the line-of-sight integrated observation, for which we provide the exact analytical expression of the line-of-sight integration
Bayesian Abel Inversion in Quantitative X-Ray Radiography
Howard, Marylesa; Fowler, Michael; Luttman, Aaron; Mitchell, Stephen E.; Hock, Margaret C.
2016-05-19
A common image formation process in high-energy X-ray radiography is to have a pulsed power source that emits X-rays through a scene, a scintillator that absorbs X-rays and uoresces in the visible spectrum in response to the absorbed photons, and a CCD camera that images the visible light emitted from the scintillator. The intensity image is related to areal density, and, for an object that is radially symmetric about a central axis, the Abel transform then gives the object's volumetric density. Two of the primary drawbacks to classical variational methods for Abel inversion are their sensitivity to the type and scale of regularization chosen and the lack of natural methods for quantifying the uncertainties associated with the reconstructions. In this work we cast the Abel inversion problem within a statistical framework in order to compute volumetric object densities from X-ray radiographs and to quantify uncertainties in the reconstruction. A hierarchical Bayesian model is developed with a likelihood based on a Gaussian noise model and with priors placed on the unknown density pro le, the data precision matrix, and two scale parameters. This allows the data to drive the localization of features in the reconstruction and results in a joint posterior distribution for the unknown density pro le, the prior parameters, and the spatial structure of the precision matrix. Results of the density reconstructions and pointwise uncertainty estimates are presented for both synthetic signals and real data from a U.S. Department of Energy X-ray imaging facility.
Bayesian Abel Inversion in Quantitative X-Ray Radiography
Howard, Marylesa; Fowler, Michael; Luttman, Aaron; ...
2016-05-19
A common image formation process in high-energy X-ray radiography is to have a pulsed power source that emits X-rays through a scene, a scintillator that absorbs X-rays and uoresces in the visible spectrum in response to the absorbed photons, and a CCD camera that images the visible light emitted from the scintillator. The intensity image is related to areal density, and, for an object that is radially symmetric about a central axis, the Abel transform then gives the object's volumetric density. Two of the primary drawbacks to classical variational methods for Abel inversion are their sensitivity to the type andmore » scale of regularization chosen and the lack of natural methods for quantifying the uncertainties associated with the reconstructions. In this work we cast the Abel inversion problem within a statistical framework in order to compute volumetric object densities from X-ray radiographs and to quantify uncertainties in the reconstruction. A hierarchical Bayesian model is developed with a likelihood based on a Gaussian noise model and with priors placed on the unknown density pro le, the data precision matrix, and two scale parameters. This allows the data to drive the localization of features in the reconstruction and results in a joint posterior distribution for the unknown density pro le, the prior parameters, and the spatial structure of the precision matrix. Results of the density reconstructions and pointwise uncertainty estimates are presented for both synthetic signals and real data from a U.S. Department of Energy X-ray imaging facility.« less
NASA Astrophysics Data System (ADS)
Chou, Min Yang; Lin, Charles C. H.; Tsai, Ho Fang; Lin, Chi Yen
2017-01-01
The Abel inversion of ionospheric electron density profiles with the assumption of spherical symmetry applied for radio occultation soundings could introduce a greater systematic error or sometimes artifacts if the occultation rays trespass regions with larger horizontal gradients in electron density. The aided Abel inversions have been proposed by considering the asymmetry ratio derived from ionospheric total electron content (TEC) or peak density (NmF2) of reconstructed observation maps since knowledge of the horizontal asymmetry in ambient ionospheric density could mitigate the inversion error. Here we propose a new aided Abel inversion using three-dimensional time-dependent electron density (Ne) based on the climatological maps constructed from previous observations, as it has an advantage of providing altitudinal information on the horizontal asymmetry. Improvement of proposed Ne-aided Abel inversion and comparisons with electron density profiles inverted from the NmF2- and TEC-aided inversions are studied using observation system simulation experiments. Comparison results show that all three aided Abel inversions improve the ionospheric profiling by mitigating the artificial plasma caves and negative electron density in the daytime E region. The equatorial ionization anomaly crests in the F region become more distinct. The statistical results show that the Ne-aided Abel inversion has less mean and RMS error of error percentage above 250 km altitudes, and the performances for all aided Abel inversions are similar below 250 km altitudes.
Abel Inversion of Deflectometric Measurements in Dynamic Flows
NASA Technical Reports Server (NTRS)
Agrawal, Ajay K.; Albers, Burt W.; Griffin, DeVon W.
1999-01-01
We present an Abel-inversion algorithm to reconstruct mean and rms refractive-index profiles from spatially resolved statistical measurements of the beam-deflection angle in time-dependent, axisymmetric flows. An oscillating gas-jet diffusion flame was investigated as a test case for applying the algorithm. Experimental data were obtained across the whole field by a rainbow schlieren apparatus. Results show that simultaneous multipoint measurements are necessary to reconstruct the rms refractive index accurately.
The Filtered Abel Transform and Its Application in Combustion Diagnostics
NASA Technical Reports Server (NTRS)
Simons, Stephen N. (Technical Monitor); Yuan, Zeng-Guang
2003-01-01
Many non-intrusive combustion diagnosis methods generate line-of-sight projections of a flame field. To reconstruct the spatial field of the measured properties, these projections need to be deconvoluted. When the spatial field is axisymmetric, commonly used deconvolution method include the Abel transforms, the onion peeling method and the two-dimensional Fourier transform method and its derivatives such as the filtered back projection methods. This paper proposes a new approach for performing the Abel transform method is developed, which possesses the exactness of the Abel transform and the flexibility of incorporating various filters in the reconstruction process. The Abel transform is an exact method and the simplest among these commonly used methods. It is evinced in this paper that all the exact reconstruction methods for axisymmetric distributions must be equivalent to the Abel transform because of its uniqueness and exactness. Detailed proof is presented to show that the two dimensional Fourier methods when applied to axisymmetric cases is identical to the Abel transform. Discrepancies among various reconstruction method stem from the different approximations made to perform numerical calculations. An equation relating the spectrum of a set of projection date to that of the corresponding spatial distribution is obtained, which shows that the spectrum of the projection is equal to the Abel transform of the spectrum of the corresponding spatial distribution. From the equation, if either the projection or the distribution is bandwidth limited, the other is also bandwidth limited, and both have the same bandwidth. If the two are not bandwidth limited, the Abel transform has a bias against low wave number components in most practical cases. This explains why the Abel transform and all exact deconvolution methods are sensitive to high wave number noises. The filtered Abel transform is based on the fact that the Abel transform of filtered projection data is equal
Serre duality, Abel's theorem, and Jacobi inversion for supercurves over a thick superpoint
NASA Astrophysics Data System (ADS)
Rothstein, Mitchell J.; Rabin, Jeffrey M.
2015-04-01
The principal aim of this paper is to extend Abel's theorem to the setting of complex supermanifolds of dimension 1 | q over a finite-dimensional local supercommutative C-algebra. The theorem is proved by establishing a compatibility of Serre duality for the supercurve with Poincaré duality on the reduced curve. We include an elementary algebraic proof of the requisite form of Serre duality, closely based on the account of the reduced case given by Serre in Algebraic groups and class fields, combined with an invariance result for the topology on the dual of the space of répartitions. Our Abel map, taking Cartier divisors of degree zero to the dual of the space of sections of the Berezinian sheaf, modulo periods, is defined via Penkov's characterization of the Berezinian sheaf as the cohomology of the de Rham complex of the sheaf D of differential operators. We discuss the Jacobi inversion problem for the Abel map and give an example demonstrating that if n is an integer sufficiently large that the generic divisor of degree n is linearly equivalent to an effective divisor, this need not be the case for all divisors of degree n.
Inverting ion images without Abel inversion: maximum entropy reconstruction of velocity maps.
Dick, Bernhard
2014-01-14
A new method for the reconstruction of velocity maps from ion images is presented, which is based on the maximum entropy concept. In contrast to other methods used for Abel inversion the new method never applies an inversion or smoothing to the data. Instead, it iteratively finds the map which is the most likely cause for the observed data, using the correct likelihood criterion for data sampled from a Poissonian distribution. The entropy criterion minimizes the information content in this map, which hence contains no information for which there is no evidence in the data. Two implementations are proposed, and their performance is demonstrated with simulated and experimental data: Maximum Entropy Velocity Image Reconstruction (MEVIR) obtains a two-dimensional slice through the velocity distribution and can be compared directly to Abel inversion. Maximum Entropy Velocity Legendre Reconstruction (MEVELER) finds one-dimensional distribution functions Q(l)(v) in an expansion of the velocity distribution in Legendre polynomials P((cos θ) for the angular dependence. Both MEVIR and MEVELER can be used for the analysis of ion images with intensities as low as 0.01 counts per pixel, with MEVELER performing significantly better than MEVIR for images with low intensity. Both methods perform better than pBASEX, in particular for images with less than one average count per pixel.
Mass dependent galaxy transformation mechanisms in the complex environment of SuperGroup Abell 1882
NASA Astrophysics Data System (ADS)
Sengupta, Aparajita
We present our data and results from panchromatic photometry and optical spectrometry of the nearest (extremely rich) filamentary large scale structure, SuperGroup Abell 1882. It is a precursor of a cluster and is an inevitable part of the narrative in the study of galaxy transformations. There has been strong empirical evidence over the past three decades that galaxy environment affects galaxy properties. Blue disky galaxies transform into red bulge-like galaxies as they traverse into the deeper recesses of a cluster. However, we have little insight into the story of galaxy evolution in the early stages of cluster formation. Besides, in relaxed clusters that have been studied extensively, several evolutionary mechanisms take effect on similar spatial and temporal scales, making it almost impossible to disentangle different local and global mechanisms. A SuperGroup on the other hand, has a shallower dark-matter potential. Here, the accreting galaxies are subjected to evolutionary mechanisms over larger time and spatial scales. This separates processes that are otherwise superimposed in rich cluster-filament interfaces. As has been found from cluster studies, galaxy color and morphology tie very strongly with local galaxy density even in a complex and nascent structure like Abell 1882. Our major results indicate that there is a strong dependence of galaxy transformations on the galaxy masses themselves. Mass- dependent evolutionary mechanisms affect galaxies at different spatial scales. The galaxy color also varies with radial projected distance from the assumed center of the structure for a constant local galaxy density, indicating the underlying large scale structure as a second order evolutionary driver. We have looked for clues to the types of mechanisms that might cause the transformations at various mass regimes. We have found the thoroughly quenched low mass galaxies confined to the groups, whereas there are evidences of intermediate-mass quenched galaxies
Inversion and approximation of Laplace transforms
NASA Technical Reports Server (NTRS)
Lear, W. M.
1980-01-01
A method of inverting Laplace transforms by using a set of orthonormal functions is reported. As a byproduct of the inversion, approximation of complicated Laplace transforms by a transform with a series of simple poles along the left half plane real axis is shown. The inversion and approximation process is simple enough to be put on a programmable hand calculator.
Inversion: A Most Useful Kind of Transformation.
ERIC Educational Resources Information Center
Dubrovsky, Vladimir
1992-01-01
The transformation assigning to every point its inverse with respect to a circle with given radius and center is called an inversion. Discusses inversion with respect to points, circles, angles, distances, space, and the parallel postulate. Exercises related to these topics are included. (MDH)
An approximation for inverse Laplace transforms
NASA Technical Reports Server (NTRS)
Lear, W. M.
1981-01-01
Programmable calculator runs simple finite-series approximation for Laplace transform inversions. Utilizing family of orthonormal functions, approximation is used for wide range of transforms, including those encountered in feedback control problems. Method works well as long as F(t) decays to zero as it approaches infinity and so is appliable to most physical systems.
Inversion of the circular averages transform using the Funk transform
NASA Astrophysics Data System (ADS)
Evren Yarman, Can; Yazıcı, Birsen
2011-06-01
The integral of a function defined on the half-plane along the semi-circles centered on the boundary of the half-plane is known as the circular averages transform. Circular averages transform arises in many tomographic image reconstruction problems. In particular, in synthetic aperture radar (SAR) when the transmitting and receiving antennas are colocated, the received signal is modeled as the integral of the ground reflectivity function of the illuminated scene over the intersection of spheres centered at the antenna location and the surface topography. When the surface topography is flat the received signal becomes the circular averages transform of the ground reflectivity function. Thus, SAR image formation requires inversion of the circular averages transform. Apart from SAR, circular averages transform also arises in thermo-acoustic tomography and sonar inverse problems. In this paper, we present a new inversion method for the circular averages transform using the Funk transform. For a function defined on the unit sphere, its Funk transform is given by the integrals of the function along the great circles. We used hyperbolic geometry to establish a diffeomorphism between the circular averages transform, hyperbolic x-ray and Funk transforms. The method is exact and numerically efficient when fast Fourier transforms over the sphere are used. We present numerical simulations to demonstrate the performance of the inversion method. Dedicated to Dennis Healy, a friend of Applied Mathematics and Engineering.
An efficient and flexible Abel-inversion method for noisy data
NASA Astrophysics Data System (ADS)
Antokhin, Igor I.
2016-12-01
We propose an efficient and flexible method for solving the Abel integral equation of the first kind, frequently appearing in many fields of astrophysics, physics, chemistry, and applied sciences. This equation represents an ill-posed problem, thus solving it requires some kind of regularization. Our method is based on solving the equation on a so-called compact set of functions and/or using Tikhonov's regularization. A priori constraints on the unknown function, defining a compact set, are very loose and can be set using simple physical considerations. Tikhonov's regularization in itself does not require any explicit a priori constraints on the unknown function and can be used independently of such constraints or in combination with them. Various target degrees of smoothness of the unknown function may be set, as required by the problem at hand. The advantage of the method, apart from its flexibility, is that it gives uniform convergence of the approximate solution to the exact solution, as the errors of input data tend to zero. The method is illustrated on several simulated models with known solutions. An example of astrophysical application of the method is also given.
Kelvin transformation and inverse multipoles in electrostatics
NASA Astrophysics Data System (ADS)
Amaral, R. L. P. G.; Ventura, O. S.; Lemos, N. A.
2017-03-01
The inversion in the sphere or Kelvin transformation, which exchanges the radial coordinate for its inverse, is used as a guide to relate distinct electrostatic problems with dual features. The exact solution of some nontrivial problems are obtained through the mapping from simple highly symmetric systems. In particular, the concept of multipole expansion is revisited from a point of view opposed to the usual one: the sources are distributed in a region far from the origin while the electrostatic potential is described at points close to it.
Smoothing Technique and Variance Propagation for Abel Inversion of Scattered Data
1977-04-01
data and determination of the coefficients and transformation matrix. The bulk of this work is accomplished in SUB- ROUTINE COVCAL. However, subsequent...I 11111 I I I i I I I I I H i i I i l I i l i l i i i i l l l t ! i l 72 AE DC-T Ro76-163 I CALL INPUT I 1 1 C) A.4.0 FLOW CHARTS...2.0515~ 1D -03 . . . . . . . L S k I I 4 ? O - U . . . 3 , 7 0 6 9 9 4 0 - 0 3 4 , 1 1 0 7 8 6 0 - 0 3 3 , 6 9 7 1 1 6 D - 0 3 • . 2 ,5221~4D
Hirota difference equation: Inverse scattering transform, darboux transformation, and solitons
NASA Astrophysics Data System (ADS)
Pogrebkov, A. K.
2014-12-01
We consider the direct and inverse problems for the Hirota difference equation. We introduce the Jost solutions and scattering data and describe their properties. In a special case, we show that the Darboux transformation allows finding the evolution in discrete time and obtaining a recursive procedure for sequentially constructing the Jost solution at an arbitrary time for a given initial value. We consider some properties of the soliton solutions.
NASA Astrophysics Data System (ADS)
Syndergaard, S.; Kirchengast, G.
2016-03-01
We have developed a formula for the retrieval of the line-of-sight (l.o.s.) wind speed from future low Earth orbit (LEO) satellite-to-satellite infrared laser occultation measurements. The formula involves an Abelian integral transform akin to the Abel transform widely used for deriving refractive index from bending angle in Global Navigation Satellite System radio occultation measurements. Besides the Abelian integral transform, the formula is derived from a truncated series expansion of the volume absorption coefficient as a function of frequency and includes a simple absorption-line-asymmetry correction term. A first-order formulation (referred to as the standard formula) is complemented by higher-order terms that can be used for high-accuracy computations. Under the assumptions of spherical symmetry and perfect knowledge of spectroscopy, the residual l.o.s. wind error from using the standard formula rather than the high-accuracy formula is assessed to be small compared to that anticipated from measurement errors in a real experiment. Applying the new formula just in standard form to future infrared laser transmission profiles would therefore enable the retrieval of l.o.s. stratospheric wind profiles with an accuracy limited mainly by measurement errors, residual spectroscopic errors, and deviations from spherical symmetry.
Rapid Inversion of Angular Deflection Data for Certain Axisymmetric Refractive Index Distributions
NASA Technical Reports Server (NTRS)
Rubinstein, R.; Greenberg, P. S.
1994-01-01
Certain functions useful for representing axisymmetric refractive-index distributions are shown to have exact solutions for Abel transformation of the resulting angular deflection data. An advantage of this procedure over direct numerical Abel inversion is that least-squares curve fitting is a smoothing process that reduces the noise sensitivity of the computation
Numerical Laplace Transform Inversion Employing the Gaver-Stehfest Algorithm.
ERIC Educational Resources Information Center
Jacquot, Raymond G.; And Others
1985-01-01
Presents a technique for the numerical inversion of Laplace Transforms and several examples employing this technique. Limitations of the method in terms of available computer word length and the effects of these limitations on approximate inverse functions are also discussed. (JN)
LETTER TO THE EDITOR: Explicit finite inverse Hilbert transforms
NASA Astrophysics Data System (ADS)
You, Jiangsheng; Zeng, Gengsheng L.
2006-06-01
Recently, Noo and coworkers discovered an explicit inversion formula for the finite Hilbert transform, which is very important to accurate reconstruction from truncated projections. This letter presents two formulae for the finite inverse Hilbert transform using some elementary complex variable analysis. The new formulae do not contain the constant C and the singular endpoints that exist in the formula in Noo et al (2004 Phys. Med. Biol. 49 3903-23).
Inverse Fourier Transform in the Gamma Coordinate System
Wei, Yuchuan; Yu, Hengyong; Wang, Ge
2011-01-01
This paper provides auxiliary results for our general scheme of computed tomography. In 3D parallel-beam geometry, we first demonstrate that the inverse Fourier transform in different coordinate systems leads to different reconstruction formulas and explain why the Radon formula cannot directly work with truncated projection data. Also, we introduce a gamma coordinate system, analyze its properties, compute the Jacobian of the coordinate transform, and define weight functions for the inverse Fourier transform assuming a simple scanning model. Then, we generate Orlov's theorem and a weighted Radon formula from the inverse Fourier transform in the new system. Furthermore, we present the motion equation of the frequency plane and the conditions for sharp points of the instantaneous rotation axis. Our analysis on the motion of the frequency plane is related to the Frenet-Serret theorem in the differential geometry. PMID:21076520
Structural and aerodynamic data transformation using inverse isoparametric mapping
NASA Astrophysics Data System (ADS)
Pidaparti, R. M. V.
1992-06-01
The inverse isoparametric mapping is presently used to transform such state variables as displacement, load, stress, pressure, temperature, etc., from structural grid points to aerodynamic grid points. The wing plane's form can be represented by either four-node or eight-node isoparametric finite elements. Extrapolation to the case of control surfaces becomes possible via combination of well-known extrapolation techniques and the inverse-mapping procedure.
Book review: Nonlinear ocean waves and the inverse scattering transform
Geist, Eric L.
2011-01-01
Nonlinear Ocean Waves and the Inverse Scattering Transform is a comprehensive examination of ocean waves built upon the theory of nonlinear Fourier analysis. The renowned author, Alfred R. Osborne, is perhaps best known for the discovery of internal solitons in the Andaman Sea during the 1970s. In this book, he provides an extensive treatment of nonlinear water waves based on a nonlinear spectral theory known as the inverse scattering transform. The writing is exceptional throughout the book, which is particularly useful in explaining some of the more difficult mathematical concepts. Review info: Nonlinear Ocean Waves and the Inverse Scattering Transform. By Alfred R. Osborne, 2010. ISBN: 978-125286299, 917 pp.
Numerical inversion of the Funk transform on the rotation group
NASA Astrophysics Data System (ADS)
Hielscher, Ralf
2013-12-01
The reconstruction of a function on the rotation group from mean values along all geodesics is an overdetermined problem, i.e. it is sufficient to know the mean values for a three-dimensional subset of all geodesics on the rotation group. In this paper we give a Fourier slice theorem for the restricted problem. Based on the Fourier slice theorem and fast Fourier transforms on the rotation group and the sphere we introduce a fast algorithm for the forward transform. Analyzing the inverse problem we come up with an exact inversion formula for bandlimited functions on the rotation group. Unfortunately this inversion formula turns out to be extremely ill conditioned. Therefore we introduce an iterative approach which makes use of regularization and the fast algorithm for the forward transform. Numerical experiments indicate the applicability of our algorithms.
Wavelet transform analysis of the small-scale X-ray structure of the cluster Abell 1367
NASA Technical Reports Server (NTRS)
Grebeney, S. A.; Forman, W.; Jones, C.; Murray, S.
1995-01-01
We have developed a new technique based on a wavelet transform analysis to quantify the small-scale (less than a few arcminutes) X-ray structure of clusters of galaxies. We apply this technique to the ROSAT position sensitive proportional counter (PSPC) and Einstein high-resolution imager (HRI) images of the central region of the cluster Abell 1367 to detect sources embedded within the diffuse intracluster medium. In addition to detecting sources and determining their fluxes and positions, we show that the wavelet analysis allows a characterization of the sources extents. In particular, the wavelet scale at which a given source achieves a maximum signal-to-noise ratio in the wavelet images provides an estimate of the angular extent of the source. To account for the widely varying point response of the ROSAT PSPC as a function of off-axis angle requires a quantitative measurement of the source size and a comparison to a calibration derived from the analysis of a Deep Survey image. Therefore, we assume that each source could be described as an isotropic two-dimensional Gaussian and used the wavelet amplitudes, at different scales, to determine the equivalent Gaussian Full Width Half-Maximum (FWHM) (and its uncertainty) appropriate for each source. In our analysis of the ROSAT PSPC image, we detect 31 X-ray sources above the diffuse cluster emission (within a radius of 24 min), 16 of which are apparently associated with cluster galaxies and two with serendipitous, background quasars. We find that the angular extents of 11 sources exceed the nominal width of the PSPC point-spread function. Four of these extended sources were previously detected by Bechtold et al. (1983) as 1 sec scale features using the Einstein HRI. The same wavelet analysis technique was applied to the Einstein HRI image. We detect 28 sources in the HRI image, of which nine are extended. Eight of the extended sources correspond to sources previously detected by Bechtold et al. Overall, using both the
Non-thermal Hard X-Ray Emission from Coma and Several Abell Clusters
Correa, C
2004-02-05
We report results of hard X-Ray observations of the clusters Coma, Abell 496, Abell754, Abell 1060, Abell 1367, Abell2256 and Abell3558 using RXTE data from the NASA HEASARC public archive. Specifically we searched for clusters with hard x-ray emission that can be fitted by a power law because this would indicate that the cluster is a source of non-thermal emission. We are assuming the emission mechanism proposed by Vahk Petrosian where the inter cluster space contains clouds of relativistic electrons that by themselves create a magnetic field and emit radio synchrotron radiation. These relativistic electrons Inverse-Compton scatter Microwave Background photons up to hard x-ray energies. The clusters that were found to be sources of non-thermal hard x-rays are Coma, Abell496, Abell754 and Abell 1060.
Kinugawa, Tohru
2014-02-15
This paper presents a simple but nontrivial generalization of Abel's mechanical problem, based on the extended isochronicity condition and the superposition principle. There are two primary aims. The first one is to reveal the linear relation between the transit-time T and the travel-length X hidden behind the isochronicity problem that is usually discussed in terms of the nonlinear equation of motion (d{sup 2}X)/(dt{sup 2}) +(dU)/(dX) =0 with U(X) being an unknown potential. Second, the isochronicity condition is extended for the possible Abel-transform approach to designing the isochronous trajectories of charged particles in spectrometers and/or accelerators for time-resolving experiments. Our approach is based on the integral formula for the oscillatory motion by Landau and Lifshitz [Mechanics (Pergamon, Oxford, 1976), pp. 27–29]. The same formula is used to treat the non-periodic motion that is driven by U(X). Specifically, this unknown potential is determined by the (linear) Abel transform X(U) ∝ A[T(E)], where X(U) is the inverse function of U(X), A=(1/√(π))∫{sub 0}{sup E}dU/√(E−U) is the so-called Abel operator, and T(E) is the prescribed transit-time for a particle with energy E to spend in the region of interest. Based on this Abel-transform approach, we have introduced the extended isochronicity condition: typically, τ = T{sub A}(E) + T{sub N}(E) where τ is a constant period, T{sub A}(E) is the transit-time in the Abel type [A-type] region spanning X > 0 and T{sub N}(E) is that in the Non-Abel type [N-type] region covering X < 0. As for the A-type region in X > 0, the unknown inverse function X{sub A}(U) is determined from T{sub A}(E) via the Abel-transform relation X{sub A}(U) ∝ A[T{sub A}(E)]. In contrast, the N-type region in X < 0 does not ensure this linear relation: the region is covered with a predetermined potential U{sub N}(X) of some arbitrary choice, not necessarily obeying the Abel-transform relation. In discussing
2001-03-01
A unique ASIC was designed implementing the Haar Wavelet transform for image compression/decompression. ASIC operations include performing the Haar... wavelet transform on a 512 by 512 square pixel image, preparing the image for transmission by quantizing and thresholding the transformed data, and...performing the inverse Haar wavelet transform , returning the original image with only minor degradation. The ASIC is based on an existing four-chip FPGA
Improved FFT-based numerical inversion of Laplace transforms via fast Hartley transform algorithm
NASA Technical Reports Server (NTRS)
Hwang, Chyi; Lu, Ming-Jeng; Shieh, Leang S.
1991-01-01
The disadvantages of numerical inversion of the Laplace transform via the conventional fast Fourier transform (FFT) are identified and an improved method is presented to remedy them. The improved method is based on introducing a new integration step length Delta(omega) = pi/mT for trapezoidal-rule approximation of the Bromwich integral, in which a new parameter, m, is introduced for controlling the accuracy of the numerical integration. Naturally, this method leads to multiple sets of complex FFT computations. A new inversion formula is derived such that N equally spaced samples of the inverse Laplace transform function can be obtained by (m/2) + 1 sets of N-point complex FFT computations or by m sets of real fast Hartley transform (FHT) computations.
Real Variable Inversion of Laplace Transforms: An Application in Plasma Physics.
ERIC Educational Resources Information Center
Bohn, C. L.; Flynn, R. W.
1978-01-01
Discusses the nature of Laplace transform techniques and explains an alternative to them: the Widder's real inversion. To illustrate the power of this new technique, it is applied to a difficult inversion: the problem of Landau damping. (GA)
Jiang, Hua; Lu, Wenke; Zhang, Guoan
2013-07-01
In this paper, we propose a low insertion loss and miniaturization wavelet transform and inverse transform processor using surface acoustic wave (SAW) devices. The new SAW wavelet transform devices (WTDs) use the structure with two electrode-widths-controlled (EWC) single phase unidirectional transducers (SPUDT-SPUDT). This structure consists of the input withdrawal weighting interdigital transducer (IDT) and the output overlap weighting IDT. Three experimental devices for different scales 2(-1), 2(-2), and 2(-3) are designed and measured. The minimum insertion loss of the three devices reaches 5.49dB, 4.81dB, and 5.38dB respectively which are lower than the early results. Both the electrode width and the number of electrode pairs are reduced, thus making the three devices much smaller than the early devices. Therefore, the method described in this paper is suitable for implementing an arbitrary multi-scale low insertion loss and miniaturization wavelet transform and inverse transform processor using SAW devices.
A numerical inversion of a the Laplace transform solution to radial dispersion in a porous medium.
Moench, A.F.; Ogata, A.
1981-01-01
A special form of the numerical inversion of the Laplace transform described by Stehfest (1970) is applied to the transformed solution of dispersion in a radial flow system in a porous medium. The inversion is extremely simple to use because the weighting coefficients depend only on the number of terms used in the computation and not upon the transform solution as required by most numerical inversion techniques.-from Authors
Fair and Square Computation of Inverse "Z"-Transforms of Rational Functions
ERIC Educational Resources Information Center
Moreira, M. V.; Basilio, J. C.
2012-01-01
All methods presented in textbooks for computing inverse "Z"-transforms of rational functions have some limitation: 1) the direct division method does not, in general, provide enough information to derive an analytical expression for the time-domain sequence "x"("k") whose "Z"-transform is "X"("z"); 2) computation using the inversion integral…
Implementing wavelet inverse-transform processor with surface acoustic wave device.
Lu, Wenke; Zhu, Changchun; Liu, Qinghong; Zhang, Jingduan
2013-02-01
The objective of this research was to investigate the implementation schemes of the wavelet inverse-transform processor using surface acoustic wave (SAW) device, the length function of defining the electrodes, and the possibility of solving the load resistance and the internal resistance for the wavelet inverse-transform processor using SAW device. In this paper, we investigate the implementation schemes of the wavelet inverse-transform processor using SAW device. In the implementation scheme that the input interdigital transducer (IDT) and output IDT stand in a line, because the electrode-overlap envelope of the input IDT is identical with the one of the output IDT (i.e. the two transducers are identical), the product of the input IDT's frequency response and the output IDT's frequency response can be implemented, so that the wavelet inverse-transform processor can be fabricated. X-112(0)Y LiTaO(3) is used as a substrate material to fabricate the wavelet inverse-transform processor. The size of the wavelet inverse-transform processor using this implementation scheme is small, so its cost is low. First, according to the envelope function of the wavelet function, the length function of the electrodes is defined, then, the lengths of the electrodes can be calculated from the length function of the electrodes, finally, the input IDT and output IDT can be designed according to the lengths and widths for the electrodes. In this paper, we also present the load resistance and the internal resistance as the two problems of the wavelet inverse-transform processor using SAW devices. The solutions to these problems are achieved in this study. When the amplifiers are subjected to the input end and output end for the wavelet inverse-transform processor, they can eliminate the influence of the load resistance and the internal resistance on the output voltage of the wavelet inverse-transform processor using SAW device.
Optimal inversion of the generalized Anscombe transformation for Poisson-Gaussian noise.
Mäkitalo, Markku; Foi, Alessandro
2013-01-01
Many digital imaging devices operate by successive photon-to-electron, electron-to-voltage, and voltage-to-digit conversions. These processes are subject to various signal-dependent errors, which are typically modeled as Poisson-Gaussian noise. The removal of such noise can be effected indirectly by applying a variance-stabilizing transformation (VST) to the noisy data, denoising the stabilized data with a Gaussian denoising algorithm, and finally applying an inverse VST to the denoised data. The generalized Anscombe transformation (GAT) is often used for variance stabilization, but its unbiased inverse transformation has not been rigorously studied in the past. We introduce the exact unbiased inverse of the GAT and show that it plays an integral part in ensuring accurate denoising results. We demonstrate that this exact inverse leads to state-of-the-art results without any notable increase in the computational complexity compared to the other inverses. We also show that this inverse is optimal in the sense that it can be interpreted as a maximum likelihood inverse. Moreover, we thoroughly analyze the behavior of the proposed inverse, which also enables us to derive a closed-form approximation for it. This paper generalizes our work on the exact unbiased inverse of the Anscombe transformation, which we have presented earlier for the removal of pure Poisson noise.
New Type Continuities via Abel Convergence
Albayrak, Mehmet
2014-01-01
We investigate the concept of Abel continuity. A function f defined on a subset of ℝ, the set of real numbers, is Abel continuous if it preserves Abel convergent sequences. Some other types of continuities are also studied and interesting result is obtained. It turned out that uniform limit of a sequence of Abel continuous functions is Abel continuous and the set of Abel continuous functions is a closed subset of continuous functions. PMID:24883393
An inverse scattering transform for the MKdV equation with non-vanishing boundary value
NASA Astrophysics Data System (ADS)
Huang, Nian-Ning; Chen, Zong-Yun; Chen, Xiang-Jun
1997-01-01
The MKdV equation of normal dispersion with non-vanishing boundary value is solved by the inverse scattering transform method. An affine parameter is introduced to avoid double-valued functions of the usual spectral parameter. In terms of it the inverse scattering transform is performed and the inverse scattering equation of Zakharov-Shabat form as well as of Marchenko form is derived. Dark multi-soliton solutions are found formally by means of the Binet-Cauchy formula. The asymptotic behaviors in the limits of |t|→∞ are derived as expected.
NASA Technical Reports Server (NTRS)
Friedrich, R.; Drewelow, W.
1978-01-01
An algorithm is described that is based on the method of breaking the Laplace transform down into partial fractions which are then inverse-transformed separately. The sum of the resulting partial functions is the wanted time function. Any problems caused by equation system forms are largely limited by appropriate normalization using an auxiliary parameter. The practical limits of program application are reached when the degree of the denominator of the Laplace transform is seven to eight.
Arikan and Alamouti matrices based on fast block-wise inverse Jacket transform
NASA Astrophysics Data System (ADS)
Lee, Moon Ho; Khan, Md Hashem Ali; Kim, Kyeong Jin
2013-12-01
Recently, Lee and Hou (IEEE Signal Process Lett 13: 461-464, 2006) proposed one-dimensional and two-dimensional fast algorithms for block-wise inverse Jacket transforms (BIJTs). Their BIJTs are not real inverse Jacket transforms from mathematical point of view because their inverses do not satisfy the usual condition, i.e., the multiplication of a matrix with its inverse matrix is not equal to the identity matrix. Therefore, we mathematically propose a fast block-wise inverse Jacket transform of orders N = 2 k , 3 k , 5 k , and 6 k , where k is a positive integer. Based on the Kronecker product of the successive lower order Jacket matrices and the basis matrix, the fast algorithms for realizing these transforms are obtained. Due to the simple inverse and fast algorithms of Arikan polar binary and Alamouti multiple-input multiple-output (MIMO) non-binary matrices, which are obtained from BIJTs, they can be applied in areas such as 3GPP physical layer for ultra mobile broadband permutation matrices design, first-order q-ary Reed-Muller code design, diagonal channel design, diagonal subchannel decompose for interference alignment, and 4G MIMO long-term evolution Alamouti precoding design.
On the convergence of the inverse diffraction transform kernel using Cesàro summability
NASA Astrophysics Data System (ADS)
Pallotta, M.
1995-12-01
In diffraction tomography, optical information processing, and, more generally, Fourier optics, the diffraction transform solves both the direct and the inverse boundary value propagation problem for the Helmholtz equation. Its kernel is itself an integral. It is the representation of the evolution operator associated with translations of a constrained Cartesian coordinate. This fact threatens the inverse scattering problem with a divergence if the transform kernel is understood as a Cauchy integral. The kernel is, however, everywhere convergent if its integral representation is interpreted as a summable integral.
Image reconstruction in optical tomography using Radon transform and its inverse
NASA Astrophysics Data System (ADS)
Petrehus, Viorel; Gavrila, Camelia; Gruia, Ion
2009-10-01
Optical tomography is a new medical imaging modality that is at the threshold of realization. A large amount of clinical work has shown the very real benefits that such a method could provide. At the same time a considerable effort has been put into theoretical studies of its probable success. At present there exist gaps between these two realms. In this paper we review some general approaches to inverse problems to set the context for optical tomography. An essential requirement is to treat the problem in a nonlinear fashion, by using an iterative method. The inverse problem is approached by numerical solutions methods using MathCad program. The Radon transform is the basic tool of the computerized tomography. In the sequel we introduce this transform, review some properties and present a numerical program for its inversion. We show some results that represent the most complex and realistic simulations of optical tomography yet developed.
Numerical inversion of the Laplace transform in some problems of granular media dynamics
NASA Astrophysics Data System (ADS)
Yavich, Nikolay B.
2004-04-01
Approximated value for the vertical displacement of a surface bounding a half space and a layer laying on rigid foundation filled with granular medium caused by a vertical symmetric load is received here. The results obtained for Kandaurov standard linear medium model are used. This model takes in account an internal friction. The Papoulis method of numerical inversion of the Laplace transform is applied.
NASA Technical Reports Server (NTRS)
Chang, F.-C.; Mott, H.
1974-01-01
This paper presents a technique for the partial-fraction expansion of functions which are ratios of polynomials with real coefficients. The expansion coefficients are determined by writing the polynomials as Taylor's series and obtaining the Laurent series expansion of the function. The general formula for the inverse Laplace transform is also derived.
ERIC Educational Resources Information Center
Brown, Malcolm
2009-01-01
Inversions are fascinating phenomena. They are reversals of the normal or expected order. They occur across a wide variety of contexts. What do inversions have to do with learning spaces? The author suggests that they are a useful metaphor for the process that is unfolding in higher education with respect to education. On the basis of…
A real-time inverse quantised transform for multi-standard with dynamic resolution support
NASA Astrophysics Data System (ADS)
Sun, Chi-Chia; Lin, Chun-Ying; Zhang, Ce
2016-06-01
In this paper, a real-time configurable intelligent property (IP) core is presented for image/video decoding process in compatibility with the standard MPEG-4 Visual and the standard H.264/AVC. The inverse quantised discrete cosine and integer transform can be used to perform inverse quantised discrete cosine transform and inverse quantised inverse integer transforms which only required shift and add operations. Meanwhile, COordinate Rotation DIgital Computer iterations and compensation steps are adjustable in order to compensate for the video compression quality regarding various data throughput. The implementations are embedded in publicly available software XVID Codes 1.2.2 for the standard MPEG-4 Visual and the H.264/AVC reference software JM 16.1, where the experimental results show that the balance between the computational complexity and video compression quality is retained. At the end, FPGA synthesised results show that the proposed IP core can bring advantages to low hardware costs and also provide real-time performance for Full HD and 4K-2K video decoding.
NASA Astrophysics Data System (ADS)
Zhang, Yu-Juan; Zhao, Dun; Ma, Wen-Xiu
2017-01-01
We present the inverse scattering transformation for a nonisospectral AKNS hierarchy in which the spectral parameter is determined by an ordinary differential equation with polynomial nonlinearity, and thus, we give a unified treatment for the local and nonlocal nonautonomous Gross-Pitaevskii equations which possess the parity-time ( PT ) symmetric invariance. We find that unlike the local case, the PT -symmetry of the nonlocal Gross-Pitaevskii equation allows two different choices of the symmetry relations of the eigenfunctions which guarantee two different kinds of inverse scattering solutions.
Biondini, Gino; Kovačič, Gregor
2014-03-15
The inverse scattering transform for the focusing nonlinear Schrödinger equation with non-zero boundary conditions at infinity is presented, including the determination of the analyticity of the scattering eigenfunctions, the introduction of the appropriate Riemann surface and uniformization variable, the symmetries, discrete spectrum, asymptotics, trace formulae and the so-called theta condition, and the formulation of the inverse problem in terms of a Riemann-Hilbert problem. In addition, the general behavior of the soliton solutions is discussed, as well as the reductions to all special cases previously discussed in the literature.
Liao, Ke; Zhu, Min; Ding, Lei
2013-08-01
The present study investigated the use of transform sparseness of cortical current density on human brain surface to improve electroencephalography/magnetoencephalography (EEG/MEG) inverse solutions. Transform sparseness was assessed by evaluating compressibility of cortical current densities in transform domains. To do that, a structure compression method from computer graphics was first adopted to compress cortical surface structure, either regular or irregular, into hierarchical multi-resolution meshes. Then, a new face-based wavelet method based on generated multi-resolution meshes was proposed to compress current density functions defined on cortical surfaces. Twelve cortical surface models were built by three EEG/MEG softwares and their structural compressibility was evaluated and compared by the proposed method. Monte Carlo simulations were implemented to evaluate the performance of the proposed wavelet method in compressing various cortical current density distributions as compared to other two available vertex-based wavelet methods. The present results indicate that the face-based wavelet method can achieve higher transform sparseness than vertex-based wavelet methods. Furthermore, basis functions from the face-based wavelet method have lower coherence against typical EEG and MEG measurement systems than vertex-based wavelet methods. Both high transform sparseness and low coherent measurements suggest that the proposed face-based wavelet method can improve the performance of L1-norm regularized EEG/MEG inverse solutions, which was further demonstrated in simulations and experimental setups using MEG data. Thus, this new transform on complicated cortical structure is promising to significantly advance EEG/MEG inverse source imaging technologies.
Chen, Xiang-Jun; Lam, Wa Kun
2004-06-01
An inverse scattering transform for the derivative nonlinear Schrödinger equation with nonvanishing boundary conditions is derived by introducing an affine parameter to avoid constructing Riemann sheets. A one-soliton solution simpler than that in the literature is obtained, which is a breather and degenerates to a bright or dark soliton as the discrete eigenvalue becomes purely imaginary. The solution is mapped to that of the modified nonlinear Schrödinger equation by a gaugelike transformation, predicting some sub-picosecond solitons in optical fibers.
Friedline, Terri; Masa, Rainier D; Chowa, Gina A N
2015-01-01
The natural log and categorical transformations commonly applied to wealth for meeting the statistical assumptions of research may not always be appropriate for adjusting for skewness given wealth's unique properties. Finding and applying appropriate transformations is becoming increasingly important as researchers consider wealth as a predictor of well-being. We present an alternative transformation-the inverse hyperbolic sine (IHS)-for simultaneously dealing with skewness and accounting for wealth's unique properties. Using the relationship between household wealth and youth's math achievement as an example, we apply the IHS transformation to wealth data from US and Ghanaian households. We also explore non-linearity and accumulation thresholds by combining IHS transformed wealth with splines. IHS transformed wealth relates to youth's math achievement similarly when compared to categorical and natural log transformations, indicating that it is a viable alternative to other transformations commonly used in research. Non-linear relationships and accumulation thresholds emerge that predict youth's math achievement when splines are incorporated. In US households, accumulating debt relates to decreases in math achievement whereas accumulating assets relates to increases in math achievement. In Ghanaian households, accumulating assets between the 25th and 50th percentiles relates to increases in youth's math achievement.
A comparison of techniques for inversion of radio-ray phase data in presence of ray bending
NASA Technical Reports Server (NTRS)
Wallio, H. A.; Grossi, M. D.
1972-01-01
Derivations are presented of the straight-line Abel transform and the seismological Herglotz-Wiechert transform (which takes ray bending into account) that are used in the reconstruction of refractivity profiles from radio-wave phase data. Profile inversion utilizing these approaches, performed in computer-simulated experiments, are compared for cases of positive, zero, and negative ray bending. For thin atmospheres and ionospheres, such as the Martian atmosphere and ionosphere, radio wave signals are shown to be inverted accurately with both methods. For dense media, such as the solar corona or the lower Venus atmosphere, the refractive recovered by the seismological Herglotz-Wiechert transform provide a significant improvement compared with the straight-line Abel transform.
NASA Astrophysics Data System (ADS)
Matsueda, Hiroaki
2016-11-01
We examine holographic renormalization by singular value decomposition (SVD) of matrix data generated by a Monte Carlo snapshot of the two-dimensional (2D) classical Ising model at criticality. Taking the continuous limit of the SVD enables us to find the mathematical form of each SVD component by the inverse Mellin transformation as well as the power-law behavior of the SVD spectrum. We find that each SVD component is characterized by the two-point spin correlator with a finite correlation length. Then, the continuous limit of the decomposition index in the SVD corresponds to the inverse of the correlation length. These features strongly indicate that the SVD contains the same mathematical structure as the holographic renormalization.
NASA Astrophysics Data System (ADS)
Migukin, Artem; Katkovnik, Vladimir; Astola, Jaakko
2010-04-01
The phase retrieval is formulated as an inverse problem, where the forward propagation is defined by Discrete Diffraction Transform (DDT) [1], [2]. This propagation model is precise and aliasing free for pixelwise invariant (pixelated) wave field distributions in the sensor and object planes. Because of finite size of sensors DDT can be ill-conditioned and the regularization is an important component of the inverse. The proposed algorithm is designed for multiple plane observations and can be treated as a generalization of the Gerchberg-Saxton iterative algorithm. The proposed algorithm is studied by numerical experiments produced for phase and amplitude modulated object distributions. Comparison versus the conventional forward propagation models such as the angular spectrum decomposition and the convolutional model used in the algorithm of the same structure shows a clear advantage of DDT enabling better accuracy and better imaging.
NASA Astrophysics Data System (ADS)
Engel, Megan C.; Ritchie, Dustin B.; Foster, Daniel A. N.; Beach, Kevin S. D.; Woodside, Michael T.
2014-12-01
The energy landscapes that drive structure formation in biopolymers are difficult to measure. Here we validate experimentally a novel method to reconstruct landscape profiles from single-molecule pulling curves using an inverse Weierstrass transform (IWT) of the Jarzysnki free-energy integral. The method was applied to unfolding measurements of a DNA hairpin, replicating the results found by the more-established weighted histogram (WHAM) and inverse Boltzmann methods. Applying both WHAM and IWT methods to reconstruct the folding landscape for a RNA pseudoknot having a stiff energy barrier, we found that landscape features with sharper curvature than the force probe stiffness could not be recovered with the IWT method. The IWT method is thus best for analyzing data from stiff force probes such as atomic force microscopes.
A method extracting solar cell parameters from spectral response by inverse laplace transform
NASA Astrophysics Data System (ADS)
Tuominen, E.; Acerbis, M.; Hovinen, A.; Siirtola, T.; Sinkkonen, J.
1997-01-01
A mathematical method to interpret spectral responses measured from solar cells has been developed. Taking an inverse Laplace transform from the spectral response of a solar cell the spatial dependent collection efficiency of the cell can be obtained. Several important material parameters of the solar cell can be extracted from this function. Applying this method the properties of the solar cell can be investigated without applying characterization methods to the cell itself. We have applied the method both to simulated solar cells andto real solar cells.
Conn, Charlotte E.; Ces, Oscar; Mulet, Xavier; Seddon, John M.; Templer, Richard H.; Finet, Stephanie; Winter, Roland
2006-03-17
The liquid crystalline lamellar (L{sub {alpha}}) to double-diamond inverse bicontinuous cubic (Q{sub II}{sup D}) phase transition for the amphiphile monoelaidin in excess water exhibits a remarkable sequence of structural transformations for pressure or temperature jumps. Our data imply that the transition dynamics depends on a coupling between changes in molecular shape and the geometrical and topological constraints of domain size. We propose a qualitative model for this coupling based on theories of membrane fusion via stalks and existing knowledge of the structure and energetics of bicontinuous cubic phases.
An N-soliton solution to the DNLS equation based on revised inverse scattering transform
NASA Astrophysics Data System (ADS)
Zhou, Guo-Quan; Huang, Nian-Ning
2007-11-01
Based on a revised version of inverse scattering transform for the derivative nonlinear Schrödinger (DNLS) equation with vanishing boundary condition (VBC), the explicit N-soliton solution has been derived by some algebra techniques of some special matrices and determinants, especially the Binet-Cauchy formula. The one- and two-soliton solutions have been given as the illustration of the general formula of the N-soliton solution. Moreover, the asymptotic behaviors of the N-soliton solution have been discussed.
Prediction inverse d'un front de solidification dans un four de transformation a haute temperature
NASA Astrophysics Data System (ADS)
Marois, Marc-Andre
Ce projet de recherche porte sur une methode numerique permettant de predire l'evolution du profil 2D de la couche solide qui recouvre l'interieur des parois de plusieurs fours de transformation a haute temperature. Un modele mathematique base sur la formulation faible de l'energie est d'abord developpe et valide. Une methode de transfert thermique inverse reposant sur ce modele est ensuite developpee afin d'obtenir une mesure rapide et continue de l'evolution du profil de cette couche solide. Vu la grande inertie thermique du systeme a l'etude, differentes strategies sont proposees afin de faciliter la mise en uvre de cette methode numerique. Finalement, cette approche inverse est confrontee aux resultats experimentaux obtenus a l'aide d'un reacteur metallurgique. Une etude preliminaire montre que les fours de transformation presentent une tres grande inertie thermique qui limite grandement l'utilisation des methodes inverses. En effet, la sensibilite de cette methode numerique repose essentiellement sur le delai temporel observe entre la variation du profil du banc et la fluctuation de la temperature a la surface externe de la paroi du four. Les resultats obtenus demontrent qu'une partie de ce delai est proportionnel a la chaleur latente de fusion lorsque le materiau a changement de phase est constitue d'un melange non eutectique. Afin de limiter l'impact de ce delai temporel, deux astuces numeriques sont proposees : reutiliser plus d'une fois les mesures de temperature et modifier le probleme thermique dans les regions pateuse et liquide. D'une part, le concept de chevauchement propose permet de reduire le temps d'acquisition des donnees entre chacune des predictions. D'autre part, l'approche virtuelle developpee permet de reduire l'inertie thermique du systeme et, par le fait meme, le delai temporel associe a la diffusion de la chaleur. Ces deux strategies ont permis de predire efficacement l'evolution 1D de l'epaisseur de la couche de gelee qui se solidifie a
Oncogenic transformation through the cell cycle and the LET dependent inverse dose rate effect
NASA Technical Reports Server (NTRS)
Geard, C. R.; Miller, R. C.; Brenner, D. J.; Hall, E. J.; Wachholz, B. W. (Principal Investigator)
1994-01-01
Synchronised populations of mouse C3H/10T-1/2 cells were obtained by a stringent mitotic dislodgment procedure. Mitotic cells rapidly attach and progress sequentially through the cell cycle. Irradiation (3 Gy of X rays) was carried out at intervals from 0 to 18 h after initiating cell cycle progression of the mitotic cells. Oncogenic transformation was enhanced 10-fold over cells irradiated soon after replating (G1 and S phases) for cells in a near 2 h period corresponding to cells in G2 phase but not in mitosis. The cell surviving fraction had a 2-1/2-fold variation with resistant peaks corresponding to the late G1 and late S phases. These findings provide experimental support for the hypothesis initiated by Rossi and Kellerer and developed by Brenner and Hall to explain the LET dependent inverse dose rate effect for oncogenic transformation.
NASA Astrophysics Data System (ADS)
Ouyang, Wei; Mao, Weijian; Li, Xuelei; Li, Wuqun
2014-08-01
Sound velocity inversion problem based on scattering theory is formulated in terms of a nonlinear integral equation associated with scattered field. Because of its nonlinearity, in practice, linearization algorisms (Born/single scattering approximation) are widely used to obtain an approximate inversion solution. However, the linearized strategy is not congruent with seismic wave propagation mechanics in strong perturbation (heterogeneous) medium. In order to partially dispense with the weak perturbation assumption of the Born approximation, we present a new approach from the following two steps: firstly, to handle the forward scattering by taking into account the second-order Born approximation, which is related to generalized Radon transform (GRT) about quadratic scattering potential; then to derive a nonlinear quadratic inversion formula by resorting to inverse GRT. In our formulation, there is a significant quadratic term regarding scattering potential, and it can provide an amplitude correction for inversion results beyond standard linear inversion. The numerical experiments demonstrate that the linear single scattering inversion is only good in amplitude for relative velocity perturbation () of background media up to 10 %, and its inversion errors are unacceptable for the perturbation beyond 10 %. In contrast, the quadratic inversion can give more accurate amplitude-preserved recovery for the perturbation up to 40 %. Our inversion scheme is able to manage double scattering effects by estimating a transmission factor from an integral over a small area, and therefore, only a small portion of computational time is added to the original linear migration/inversion process.
Inversion of the broken ray transform in the case of energy-dependent attenuation.
Krylov, R; Katsevich, A
2015-06-07
Broken Ray transform (BRT) arises when one considers a narrow x-ray beam propagating through medium under the assumption of single scattering. Previous algorithms for inverting the BRT assumed that the medium is characterized by a single attenuation coefficient μ. However x-rays lose their energy after Compton scattering and the energy loss depends on the scattering angle. Since the attenuation coefficient depends on energy, the μ's before and after scattering are different. When there are three or more detectors one should distinguish not only between μ's that are 'seen' by x-rays before and after scattering, but also between μ's that are 'seen' by x-rays traveling towards different detectors.The main thrust of this paper is inversion of the BRT with N ⩾ 3 detectors under the assumption that the attenuation coefficient can be accurately approximated by a linear function of energy within the window of relevant energies. When the number of detectors is four or greater, we derive a family of inversion formulas. If N > 4, we find the optimal formula, which provides the best stability with respect to noise in the data. If N = 4, the family collapses into a single formula and no optimization is possible. If μ is independent of energy, N = 3 is sufficient for inversion. We also develop iterative reconstruction algorithms that can use global and local data. The results of testing the algorithms are presented.
NASA Astrophysics Data System (ADS)
Li, Guo; Xia, Jun; Li, Lei; Wang, Lidai; Wang, Lihong V.
2015-03-01
Linear transducer arrays are readily available for ultrasonic detection in photoacoustic computed tomography. They offer low cost, hand-held convenience, and conventional ultrasonic imaging. However, the elevational resolution of linear transducer arrays, which is usually determined by the weak focus of the cylindrical acoustic lens, is about one order of magnitude worse than the in-plane axial and lateral spatial resolutions. Therefore, conventional linear scanning along the elevational direction cannot provide high-quality three-dimensional photoacoustic images due to the anisotropic spatial resolutions. Here we propose an innovative method to achieve isotropic resolutions for three-dimensional photoacoustic images through combined linear and rotational scanning. In each scan step, we first elevationally scan the linear transducer array, and then rotate the linear transducer array along its center in small steps, and scan again until 180 degrees have been covered. To reconstruct isotropic three-dimensional images from the multiple-directional scanning dataset, we use the standard inverse Radon transform originating from X-ray CT. We acquired a three-dimensional microsphere phantom image through the inverse Radon transform method and compared it with a single-elevational-scan three-dimensional image. The comparison shows that our method improves the elevational resolution by up to one order of magnitude, approaching the in-plane lateral-direction resolution. In vivo rat images were also acquired.
Current methods of radio occultation data inversion
NASA Technical Reports Server (NTRS)
Kliore, A. J.
1972-01-01
The methods of Abel integral transform and ray-tracing inversion have been applied to data received from radio occultation experiments as a means of obtaining refractive index profiles of the ionospheres and atmospheres of Mars and Venus. In the case of Mars, certain simplifications are introduced by the assumption of small refractive bending in the atmosphere. General inversion methods, independent of the thin atmosphere approximation, have been used to invert the data obtained from the radio occultation of Mariner 5 by Venus; similar methods will be used to analyze data obtained from Jupiter with Pioneers F and G, as well as from the other outer planets in the Outer Planet Grand Tour Missions.
Lightweight Floating-Point Arithmetic: Case Study of Inverse Discrete Cosine Transform
NASA Astrophysics Data System (ADS)
Fang, Fang; Chen, Tsuhan; Rutenbar, Rob A.
2002-12-01
To enable floating-point (FP) signal processing applications in low-power mobile devices, we propose lightweight floating-point arithmetic. It offers a wider range of precision/power/speed/area trade-offs, but is wrapped in forms that hide the complexity of the underlying implementations from both multimedia software designers and hardware designers. Libraries implemented in C++ and Verilog provide flexible and robust floating-point units with variable bit-width formats, multiple rounding modes and other features. This solution bridges the design gap between software and hardware, and accelerates the design cycle from algorithm to chip by avoiding the translation to fixed-point arithmetic. We demonstrate the effectiveness of the proposed scheme using the inverse discrete cosine transform (IDCT), in the context of video coding, as an example. Further, we implement lightweight floating-point IDCT into hardware and demonstrate the power and area reduction.
Rank-Based Inverse Normal Transformations are Increasingly Used, But are They Merited?
Beasley, T. Mark; Erickson, Stephen; Allison, David B.
2010-01-01
Many complex traits studied in genetics have markedly non-normal distributions. This often implies that the assumption of normally distributed residuals has been violated. Recently, inverse normal transformations (INTs) have gained popularity among genetics researchers and are implemented as an option in several software packages. Despite this increasing use, we are unaware of extensive simulations or mathematical proofs showing that INTs have desirable statistical properties in the context of genetic studies. We show that INTs do not necessarily maintain proper Type 1 error control and can also reduce statistical power in some circumstances. Many alternatives to INTs exist. Therefore, we contend that there is a lack of justification for performing parametric statistical procedures on INTs with the exceptions of simple designs with moderate to large sample sizes, which makes permutation testing computationally infeasible and where maximum likelihood testing is used. Rigorous research evaluating the utility of INTs seems warranted. PMID:19526352
NASA Astrophysics Data System (ADS)
Malezan, A.; Tomal, A.; Antoniassi, M.; Watanabe, P. C. A.; Albino, L. D.; Poletti, M. E.
2015-11-01
In this work, a spectral reconstruction methodology for diagnostic X-ray, using Laplace inverse transform of the attenuation, was successfully applied to dental X-ray equipments. The attenuation curves of 8 commercially available dental X-ray equipment, from 3 different manufactures (Siemens, Gnatus and Dabi Atlante), were obtained by using an ionization chamber and high purity aluminium filters, while the kVp was obtained with a specific meter. A computational routine was implemented in order to adjust a model function, whose inverse Laplace transform is analytically known, to the attenuation curve. This methodology was validated by comparing the reconstructed and the measured (using semiconductor detector of cadmium telluride) spectra of a given dental X-ray unit. The spectral reconstruction showed the Dabi Atlante equipments generating similar shape spectra. This is a desirable feature from clinic standpoint because it produces similar levels of image quality and dose. We observed that equipments from Siemens and Gnatus generate significantly different spectra, suggesting that, for a given operating protocol, these units will present different levels of image quality and dose. This fact claims for the necessity of individualized operating protocols that maximize image quality and dose. The proposed methodology is suitable to perform a spectral reconstruction of dental X-ray equipments from the simple measurements of attenuation curve and kVp. The simplified experimental apparatus and the low level of technical difficulty make this methodology accessible to a broad range of users. The knowledge of the spectral distribution can help in the development of operating protocols that maximize image quality and dose.
An inversion method for cometary atmospheres
NASA Astrophysics Data System (ADS)
Hubert, B.; Opitom, C.; Hutsemékers, D.; Jehin, E.; Munhoven, G.; Manfroid, J.; Bisikalo, D. V.; Shematovich, V. I.
2016-10-01
Remote observation of cometary atmospheres produces a measurement of the cometary emissions integrated along the line of sight. This integration is the so-called Abel transform of the local emission rate. The observation is generally interpreted under the hypothesis of spherical symmetry of the coma. Under that hypothesis, the Abel transform can be inverted. We derive a numerical inversion method adapted to cometary atmospheres using both analytical results and least squares fitting techniques. This method, derived under the usual hypothesis of spherical symmetry, allows us to retrieve the radial distribution of the emission rate of any unabsorbed emission, which is the fundamental, physically meaningful quantity governing the observation. A Tikhonov regularization technique is also applied to reduce the possibly deleterious effects of the noise present in the observation and to warrant that the problem remains well posed. Standard error propagation techniques are included in order to estimate the uncertainties affecting the retrieved emission rate. Several theoretical tests of the inversion techniques are carried out to show its validity and robustness. In particular, we show that the Abel inversion of real data is only weakly sensitive to an offset applied to the input flux, which implies that the method, applied to the study of a cometary atmosphere, is only weakly dependent on uncertainties on the sky background which has to be subtracted from the raw observations of the coma. We apply the method to observations of three different comets observed using the TRAPPIST telescope: 103P/ Hartley 2, F6/ Lemmon and A1/ Siding Spring. We show that the method retrieves realistic emission rates, and that characteristic lengths and production rates can be derived from the emission rate for both CN and C2 molecules. We show that the retrieved characteristic lengths can differ from those obtained from a direct least squares fitting over the observed flux of radiation, and
An inverse scattering transform for the Landau-Lifshitz equation for a spin chain with an easy plane
NASA Astrophysics Data System (ADS)
Yue, Hong; Chen, Xiang-Jun; Huang, Nian-Ning
1998-03-01
The Landau-Lifshitz equation for a spin chain with an easy plane in the case of spin non-flip is solved by the method of inverse scattering transform. To avoid complexity caused by the Riemann surface of the usual spectral parameter, a particular parameter k is introduced. After performing a gauge transformation corresponding to 0305-4470/31/10/021/img1, the resulting Lax pair is independent of particular solutions in this limit. An inverse scattering transform is then developed in terms of k. A system of linear equations is derived in the reflectionless case. An expression of the gauge transformation and hence expressions of multi-soliton solutions are found explicitly by using the Binet-Cauchy formula. As an example, an explicit expression of the 1-soliton is given in terms of elementary functions of x and t.
ERIC Educational Resources Information Center
Debnath, Lokenath
2007-01-01
This paper deals with a brief introduction to major remarkable discoveries of the "soliton" and the "inverse scattering transform" in the 1960s. The discovery of the soliton (or the solitary waves) began with the famous physical experiments of the Scottish Engineer and Naval Architect John Scott Russell in the Glasgow-Edinburgh…
MASS SUBSTRUCTURE IN ABELL 3128
McCleary, J.; Dell’Antonio, I.; Huwe, P.
2015-05-20
We perform a detailed two-dimensional weak gravitational lensing analysis of the nearby (z = 0.058) galaxy cluster Abell 3128 using deep ugrz imaging from the Dark Energy Camera (DECam). We have designed a pipeline to remove instrumental artifacts from DECam images and stack multiple dithered observations without inducing a spurious ellipticity signal. We develop a new technique to characterize the spatial variation of the point-spread function that enables us to circularize the field to better than 0.5% and thereby extract the intrinsic galaxy ellipticities. By fitting photometric redshifts to sources in the observation, we are able to select a sample of background galaxies for weak-lensing analysis free from low-redshift contaminants. Photometric redshifts are also used to select a high-redshift galaxy subsample with which we successfully isolate the signal from an interloping z = 0.44 cluster. We estimate the total mass of Abell 3128 by fitting the tangential ellipticity of background galaxies with the weak-lensing shear profile of a Navarro–Frenk–White (NFW) halo and also perform NFW fits to substructures detected in the 2D mass maps of the cluster. This study yields one of the highest resolution mass maps of a low-z cluster to date and is the first step in a larger effort to characterize the redshift evolution of mass substructures in clusters.
Fast and Scalable Computation of the Forward and Inverse Discrete Periodic Radon Transform.
Carranza, Cesar; Llamocca, Daniel; Pattichis, Marios
2016-01-01
The discrete periodic radon transform (DPRT) has extensively been used in applications that involve image reconstructions from projections. Beyond classic applications, the DPRT can also be used to compute fast convolutions that avoids the use of floating-point arithmetic associated with the use of the fast Fourier transform. Unfortunately, the use of the DPRT has been limited by the need to compute a large number of additions and the need for a large number of memory accesses. This paper introduces a fast and scalable approach for computing the forward and inverse DPRT that is based on the use of: a parallel array of fixed-point adder trees; circular shift registers to remove the need for accessing external memory components when selecting the input data for the adder trees; an image block-based approach to DPRT computation that can fit the proposed architecture to available resources; and fast transpositions that are computed in one or a few clock cycles that do not depend on the size of the input image. As a result, for an N × N image (N prime), the proposed approach can compute up to N(2) additions per clock cycle. Compared with the previous approaches, the scalable approach provides the fastest known implementations for different amounts of computational resources. For example, for a 251×251 image, for approximately 25% fewer flip-flops than required for a systolic implementation, we have that the scalable DPRT is computed 36 times faster. For the fastest case, we introduce optimized just 2N + ⌈log(2) N⌉ + 1 and 2N + 3 ⌈log(2) N⌉ + B + 2 cycles, architectures that can compute the DPRT and its inverse in respectively, where B is the number of bits used to represent each input pixel. On the other hand, the scalable DPRT approach requires more 1-b additions than for the systolic implementation and provides a tradeoff between speed and additional 1-b additions. All of the proposed DPRT architectures were implemented in VHSIC Hardware Description Language
Inverse scattering transform analysis of rogue waves using local periodization procedure
Randoux, Stéphane; Suret, Pierre; El, Gennady
2016-01-01
The nonlinear Schrödinger equation (NLSE) stands out as the dispersive nonlinear partial differential equation that plays a prominent role in the modeling and understanding of the wave phenomena relevant to many fields of nonlinear physics. The question of random input problems in the one-dimensional and integrable NLSE enters within the framework of integrable turbulence, and the specific question of the formation of rogue waves (RWs) has been recently extensively studied in this context. The determination of exact analytic solutions of the focusing 1D-NLSE prototyping RW events of statistical relevance is now considered as the problem of central importance. Here we address this question from the perspective of the inverse scattering transform (IST) method that relies on the integrable nature of the wave equation. We develop a conceptually new approach to the RW classification in which appropriate, locally coherent structures are specifically isolated from a globally incoherent wave train to be subsequently analyzed by implementing a numerical IST procedure relying on a spatial periodization of the object under consideration. Using this approach we extend the existing classifications of the prototypes of RWs from standard breathers and their collisions to more general nonlinear modes characterized by their nonlinear spectra. PMID:27385164
Inverse scattering transform analysis of rogue waves using local periodization procedure.
Randoux, Stéphane; Suret, Pierre; El, Gennady
2016-07-07
The nonlinear Schrödinger equation (NLSE) stands out as the dispersive nonlinear partial differential equation that plays a prominent role in the modeling and understanding of the wave phenomena relevant to many fields of nonlinear physics. The question of random input problems in the one-dimensional and integrable NLSE enters within the framework of integrable turbulence, and the specific question of the formation of rogue waves (RWs) has been recently extensively studied in this context. The determination of exact analytic solutions of the focusing 1D-NLSE prototyping RW events of statistical relevance is now considered as the problem of central importance. Here we address this question from the perspective of the inverse scattering transform (IST) method that relies on the integrable nature of the wave equation. We develop a conceptually new approach to the RW classification in which appropriate, locally coherent structures are specifically isolated from a globally incoherent wave train to be subsequently analyzed by implementing a numerical IST procedure relying on a spatial periodization of the object under consideration. Using this approach we extend the existing classifications of the prototypes of RWs from standard breathers and their collisions to more general nonlinear modes characterized by their nonlinear spectra.
Cai, Xiaoyu; Li, Huiyun; Liu, Aiyi
2016-08-30
The increase in incidence of obesity and chronic diseases and their health care costs have raised the importance of quality diet on the health policy agendas. The healthy eating index is an important measure for diet quality which consists of 12 components derived from ratios of dependent variables with distributions hard to specify, measurement errors and excessive zero observations difficult to model parametrically. Hypothesis testing involving data of such nature poses challenges because the widely used multiple comparison procedures such as Hotelling's T(2) test and Bonferroni correction may suffer from substantial loss of efficiency. We propose a marginal rank-based inverse normal transformation approach to normalizing the marginal distribution of the data before employing a multivariate test procedure. Extensive simulation was conducted to demonstrate the ability of the proposed approach to adequately control the type I error rate as well as increase the power of the test, with data particularly from non-symmetric or heavy-tailed distributions. The methods are exemplified with data from a dietary intervention study for type I diabetic children. Published 2016. This article is a U.S. Government work and is in the public domain in the USA.
NASA Astrophysics Data System (ADS)
Gao, Yingjie; Zhang, Jinhai; Yao, Zhenxing
2016-06-01
The symplectic integration method is popular in high-accuracy numerical simulations when discretizing temporal derivatives; however, it still suffers from time-dispersion error when the temporal interval is coarse, especially for long-term simulations and large-scale models. We employ the inverse time dispersion transform (ITDT) to the third-order symplectic integration method to reduce the time-dispersion error. First, we adopt the pseudospectral algorithm for the spatial discretization and the third-order symplectic integration method for the temporal discretization. Then, we apply the ITDT to eliminate time-dispersion error from the synthetic data. As a post-processing method, the ITDT can be easily cascaded in traditional numerical simulations. We implement the ITDT in one typical exiting third-order symplectic scheme and compare its performances with the performances of the conventional second-order scheme and the rapid expansion method. Theoretical analyses and numerical experiments show that the ITDT can significantly reduce the time-dispersion error, especially for long travel times. The implementation of the ITDT requires some additional computations on correcting the time-dispersion error, but it allows us to use the maximum temporal interval under stability conditions; thus, its final computational efficiency would be higher than that of the traditional symplectic integration method for long-term simulations. With the aid of the ITDT, we can obtain much more accurate simulation results but with a lower computational cost.
Inverse scattering transform analysis of rogue waves using local periodization procedure
NASA Astrophysics Data System (ADS)
Randoux, Stéphane; Suret, Pierre; El, Gennady
2016-07-01
The nonlinear Schrödinger equation (NLSE) stands out as the dispersive nonlinear partial differential equation that plays a prominent role in the modeling and understanding of the wave phenomena relevant to many fields of nonlinear physics. The question of random input problems in the one-dimensional and integrable NLSE enters within the framework of integrable turbulence, and the specific question of the formation of rogue waves (RWs) has been recently extensively studied in this context. The determination of exact analytic solutions of the focusing 1D-NLSE prototyping RW events of statistical relevance is now considered as the problem of central importance. Here we address this question from the perspective of the inverse scattering transform (IST) method that relies on the integrable nature of the wave equation. We develop a conceptually new approach to the RW classification in which appropriate, locally coherent structures are specifically isolated from a globally incoherent wave train to be subsequently analyzed by implementing a numerical IST procedure relying on a spatial periodization of the object under consideration. Using this approach we extend the existing classifications of the prototypes of RWs from standard breathers and their collisions to more general nonlinear modes characterized by their nonlinear spectra.
NASA Astrophysics Data System (ADS)
Chen, Siyu; Zhang, Hanming; Li, Lei; Xi, Xiaoqi; Han, Yu; Yan, Bin
2016-10-01
X-ray computed tomography (CT) has been extensively applied in industrial non-destructive testing (NDT). However, in practical applications, the X-ray beam polychromaticity often results in beam hardening problems for image reconstruction. The beam hardening artifacts, which manifested as cupping, streaks and flares, not only debase the image quality, but also disturb the subsequent analyses. Unfortunately, conventional CT scanning requires that the scanned object is completely covered by the field of view (FOV), the state-of-art beam hardening correction methods only consider the ideal scanning configuration, and often suffer problems for interior tomography due to the projection truncation. Aiming at this problem, this paper proposed a beam hardening correction method based on radon inversion transform for interior tomography. Experimental results show that, compared to the conventional correction algorithms, the proposed approach has achieved excellent performance in both beam hardening artifacts reduction and truncation artifacts suppression. Therefore, the presented method has vitally theoretic and practicable meaning in artifacts correction of industrial CT.
NASA Technical Reports Server (NTRS)
Chung, W. W.; Mcneill, W. E.; Stortz, M. W.
1993-01-01
The nonlinear inverse transformation flight control system design method is applied to the Lockheed Ft. Worth Company's E-7D short takeoff and vertical land (STOVL) supersonic fighter/attack aircraft design with a modified General Electric F110 engine which has augmented propulsive lift capability. The system is fully augmented to provide flight path control and velocity control, and rate command attitude hold for angular axes during the transition and hover operations. In cruise mode, the flight control system is configured to provide direct thrust command, rate command attitude hold for pitch and roll axes, and sideslip command with turn coordination. A control selector based on the nonlinear inverse transformation method is designed specifically to be compatible with the propulsion system's physical configuration which has a two dimensional convergent-divergent aft nozzle, a vectorable ventral nozzle, and a thrust augmented ejector. The nonlinear inverse transformation is used to determine the propulsive forces and nozzle deflections, which in combination with the aerodynamic forces and moments (including propulsive induced contributions), and gravitational force, are required to achieve the longitudinal and vertical acceleration commands. The longitudinal control axes are fully decoupled within the propulsion system's performance envelope. A piloted motion-base flight simulation was conducted on the Vertical Motion Simulator (VMS) at NASA Ames Research Center to examine the handling qualities of this design. Based on results of the simulation, refinements to the control system have been made and will also be covered in the report.
SHOCKING TAILS IN THE MAJOR MERGER ABELL 2744
Owers, Matt S.; Couch, Warrick J.; Nulsen, Paul E. J.; Randall, Scott W.
2012-05-01
We identify four rare 'jellyfish' galaxies in Hubble Space Telescope imagery of the major merger cluster Abell 2744. These galaxies harbor trails of star-forming knots and filaments which have formed in situ in gas tails stripped from the parent galaxies, indicating they are in the process of being transformed by the environment. Further evidence for rapid transformation in these galaxies comes from their optical spectra, which reveal starburst, poststarburst, and active galactic nucleus features. Most intriguingly, three of the jellyfish galaxies lie near intracluster medium features associated with a merging 'Bullet-like' subcluster and its shock front detected in Chandra X-ray images. We suggest that the high-pressure merger environment may be responsible for the star formation in the gaseous tails. This provides observational evidence for the rapid transformation of galaxies during the violent core passage phase of a major cluster merger.
Shocking Tails in the Major Merger Abell 2744
NASA Astrophysics Data System (ADS)
Owers, Matt S.; Couch, Warrick J.; Nulsen, Paul E. J.; Randall, Scott W.
2012-05-01
We identify four rare "jellyfish" galaxies in Hubble Space Telescope imagery of the major merger cluster Abell 2744. These galaxies harbor trails of star-forming knots and filaments which have formed in situ in gas tails stripped from the parent galaxies, indicating they are in the process of being transformed by the environment. Further evidence for rapid transformation in these galaxies comes from their optical spectra, which reveal starburst, poststarburst, and active galactic nucleus features. Most intriguingly, three of the jellyfish galaxies lie near intracluster medium features associated with a merging "Bullet-like" subcluster and its shock front detected in Chandra X-ray images. We suggest that the high-pressure merger environment may be responsible for the star formation in the gaseous tails. This provides observational evidence for the rapid transformation of galaxies during the violent core passage phase of a major cluster merger.
NASA Astrophysics Data System (ADS)
Windhari, Ayuty; Handayani, Gunawan
2015-04-01
The 3D inversion gravity anomaly to estimate topographical density using a matlab source code from gridded data provided by Parker Oldenburg algorithm based on fast Fourier transform was computed. We extend and improved the source code of 3DINVERT.M invented by Gomez Ortiz and Agarwal (2005) using the relationship between Fourier transform of the gravity anomaly and the sum of the Fourier transform from the topography density. We gave density contrast between the two media to apply the inversion. FFT routine was implemented to construct amplitude spectrum to the given mean depth. The results were presented as new graphics of inverted topography density, the gravity anomaly due to the inverted topography and the difference between the input gravity data and the computed ones. It terminates when the RMS error is lower than pre-assigned value used as convergence criterion or until maximum of iterations is reached. As an example, we used the matlab program on gravity data of Banten region, Indonesia.
NASA Astrophysics Data System (ADS)
Balogh, Michael L.; Morris, Simon L.
2000-11-01
We present the results of a search for strong Hα emission line galaxies (rest frame equivalent widths greater than 50Å) in the z~0.23 cluster Abell 2390. The survey contains 1189galaxies over 270arcmin2, and is 50per cent complete at Mr~-17.5+5logh. The fraction of galaxies in which Hα is detected at the 2σ level rises from 0.0 in the central regions (excluding the cD galaxy) to 12.5+/-8per cent at R200. For 165 of the galaxies in our catalogue, we compare the Hα equivalent widths with their [Oii] λ3727 equivalent widths, from the Canadian Network for Observational Cosmology (CNOC1) spectra. The fraction of strong Hα emission line galaxies is consistent with the fraction of strong [Oii] emission galaxies in the CNOC1 sample: only 2+/-1per cent have no detectable [Oii] emission and yet significant (>2σ) Hα equivalent widths. Dust obscuration, non-thermal ionization, and aperture effects are all likely to contribute to this non-correspondence of emission lines. We identify six spectroscopically `secure' k+a galaxies [W0(Oii)<5Å and W0(Hδ)>~5Å] at least two of these show strong signs in Hα of star formation in regions that are covered by the slit from which the spectra were obtained. Thus, some fraction of galaxies classified as k+a based on spectra shortward of 6000Å are likely to be undergoing significant star formation. These results are consistent with a `strangulation' model for cluster galaxy evolution, in which star formation in cluster galaxies is gradually decreased, and is neither enhanced nor abruptly terminated by the cluster environment.
Goerg, Georg M
2015-01-01
I present a parametric, bijective transformation to generate heavy tail versions of arbitrary random variables. The tail behavior of this heavy tail Lambert W × F X random variable depends on a tail parameter δ ≥ 0: for δ = 0, Y ≡ X, for δ > 0 Y has heavier tails than X. For X being Gaussian it reduces to Tukey's h distribution. The Lambert W function provides an explicit inverse transformation, which can thus remove heavy tails from observed data. It also provides closed-form expressions for the cumulative distribution (cdf) and probability density function (pdf). As a special case, these yield analytic expression for Tukey's h pdf and cdf. Parameters can be estimated by maximum likelihood and applications to S&P 500 log-returns demonstrate the usefulness of the presented methodology. The R package Lambert W implements most of the introduced methodology and is publicly available on CRAN.
Goerg, Georg M.
2015-01-01
I present a parametric, bijective transformation to generate heavy tail versions of arbitrary random variables. The tail behavior of this heavy tail Lambert W × FX random variable depends on a tail parameter δ ≥ 0: for δ = 0, Y ≡ X, for δ > 0 Y has heavier tails than X. For X being Gaussian it reduces to Tukey's h distribution. The Lambert W function provides an explicit inverse transformation, which can thus remove heavy tails from observed data. It also provides closed-form expressions for the cumulative distribution (cdf) and probability density function (pdf). As a special case, these yield analytic expression for Tukey's h pdf and cdf. Parameters can be estimated by maximum likelihood and applications to S&P 500 log-returns demonstrate the usefulness of the presented methodology. The R package LambertW implements most of the introduced methodology and is publicly available on CRAN. PMID:26380372
NASA Technical Reports Server (NTRS)
Mutterperl, William
1944-01-01
A method of conformal transformation is developed that maps an airfoil into a straight line, the line being chosen as the extended chord line of the airfoil. The mapping is accomplished by operating directly with the airfoil ordinates. The absence of any preliminary transformation is found to shorten the work substantially over that of previous methods. Use is made of the superposition of solutions to obtain a rigorous counterpart of the approximate methods of thin-airfoils theory. The method is applied to the solution of the direct and inverse problems for arbitrary airfoils and pressure distributions. Numerical examples are given. Applications to more general types of regions, in particular to biplanes and to cascades of airfoils, are indicated. (author)
Abel's Theorem Simplifies Reduction of Order
ERIC Educational Resources Information Center
Green, William R.
2011-01-01
We give an alternative to the standard method of reduction or order, in which one uses one solution of a homogeneous, linear, second order differential equation to find a second, linearly independent solution. Our method, based on Abel's Theorem, is shorter, less complex and extends to higher order equations.
Bakhos, Tania; Saibaba, Arvind K.; Kitanidis, Peter K.
2015-10-15
We consider the problem of estimating parameters in large-scale weakly nonlinear inverse problems for which the underlying governing equations is a linear, time-dependent, parabolic partial differential equation. A major challenge in solving these inverse problems using Newton-type methods is the computational cost associated with solving the forward problem and with repeated construction of the Jacobian, which represents the sensitivity of the measurements to the unknown parameters. Forming the Jacobian can be prohibitively expensive because it requires repeated solutions of the forward and adjoint time-dependent parabolic partial differential equations corresponding to multiple sources and receivers. We propose an efficient method based on a Laplace transform-based exponential time integrator combined with a flexible Krylov subspace approach to solve the resulting shifted systems of equations efficiently. Our proposed solver speeds up the computation of the forward and adjoint problems, thus yielding significant speedup in total inversion time. We consider an application from Transient Hydraulic Tomography (THT), which is an imaging technique to estimate hydraulic parameters related to the subsurface from pressure measurements obtained by a series of pumping tests. The algorithms discussed are applied to a synthetic example taken from THT to demonstrate the resulting computational gains of this proposed method.
NASA Astrophysics Data System (ADS)
Boerner, W. M.; Brand, H.; Cram, L. A.; Giessing, D. T.; Jordan, A. K.
The present conference considers mathematical inverse methods and transient techniques, the topological approach to inverse scattering in remote sensing, the numerical resolution of inverse problems via functional derivatives, the application of almost periodic functions to inverse scattering theory, application of the Abel transform in remote sensing, the inverse diffraction problem, recent advances in the theory of inverse scattering with sparse data, direct and inverse halfspace scalar diffraction, approximation of input response, maximum entropy methods in electromagnetic/geophysical/ultrasonic imaging, time-dependent radar target signatures, the synthesis and detection of authenticity features, singularities in quasi-geometrical imaging, and polarization utilization in the electromagnetic vector inverse problem. Also discussed are polarization-dependence in angle tracking systems, polarization vector signal processing for radar clutter suppression, the radiative transfer approach in electromagnetic imaging, inverse methods in microwave target imaging, inversion in SAR imaging, fast mm-wave imaging, electromagnetic imaging of dielectric targets, tomographic imaging methods, diffraction tomography, phase-comparison monopulse side-scan radar, and far field-to-near field transforms in spherical coordinates.
The clusters Abell 222 and Abell 223: a multi-wavelength view
NASA Astrophysics Data System (ADS)
Durret, F.; Laganá, T. F.; Adami, C.; Bertin, E.
2010-07-01
Context. The Abell 222 and 223 clusters are located at an average redshift z ~ 0.21 and are separated by 0.26 deg. Signatures of mergers have been previously found in these clusters, both in X-rays and at optical wavelengths, thus motivating our study. In X-rays, they are relatively bright, and Abell 223 shows a double structure. A filament has also been detected between the clusters both at optical and X-ray wavelengths. Aims: We analyse the optical properties of these two clusters based on deep imaging in two bands, derive their galaxy luminosity functions (GLFs) and correlate these properties with X-ray characteristics derived from XMM-Newton data. Methods: The optical part of our study is based on archive images obtained with the CFHT Megaprime/Megacam camera, covering a total region of about 1 deg2, or 12.3 × 12.3 Mpc2 at a redshift of 0.21. The X-ray analysis is based on archive XMM-Newton images. Results: The GLFs of Abell 222 in the g' and r' bands are well fit by a Schechter function; the GLF is steeper in r' than in g'. For Abell 223, the GLFs in both bands require a second component at bright magnitudes, added to a Schechter function; they are similar in both bands. The Serna & Gerbal method allows to separate well the two clusters. No obvious filamentary structures are detected at very large scales around the clusters, but a third cluster at the same redshift, Abell 209, is located at a projected distance of 19.2 Mpc. X-ray temperature and metallicity maps reveal that the temperature and metallicity of the X-ray gas are quite homogeneous in Abell 222, while they are very perturbed in Abell 223. Conclusions: The Abell 222/Abell 223 system is complex. The two clusters that form this structure present very different dynamical states. Abell 222 is a smaller, less massive and almost isothermal cluster. On the other hand, Abell 223 is more massive and has most probably been crossed by a subcluster on its way to the northeast. As a consequence, the
Liu, Runna; Hu, Hong; Xu, Shanshan; Huo, Rui; Wang, Supin; Wan, Mingxi
2015-06-01
The quality of ultrafast active cavitation imaging (UACI) using plane wave transmission is hindered by low transmission pressure, which is necessary to prevent bubble destruction. In this study, a UACI method that combined wavelet transform with pulse inversion (PI) was proposed to enhance the contrast between the cavitation bubbles and surrounding tissues. The main challenge in using wavelet transform is the selection of the optimum mother wavelet. A mother wavelet named "cavitation bubble wavelet" and constructed according to Rayleigh-Plesset-Noltingk-Neppiras-Poritsky model was expected to obtain a high correlation between the bubbles and beamformed echoes. The method was validated by in vitro experiments. Results showed that the image quality was associated with the initial radius of bubble and the scale. The signal-to-noise ratio (SNR) of the best optimum cavitation bubble wavelet transform (CBWT) mode image was improved by 3.2 dB compared with that of the B-mode image in free-field experiments. The cavitation-to-tissue ratio of the best optimum PI-based CBWT mode image was improved by 2.3 dB compared with that of the PI-based B-mode image in tissue experiments. Furthermore, the SNR versus initial radius curve had the potential to estimate the size distribution of cavitation bubbles.
NASA Technical Reports Server (NTRS)
Kurtz, M. J.; Huchra, J. P.; Beers, T. C.; Geller, M. J.; Gioia, I. M.
1985-01-01
X-ray and optical observations of the cluster of galaxies Abell 744 are presented. The X-ray flux (assuming H(0) = 100 km/s per Mpc) is about 9 x 10 to the 42nd erg/s. The X-ray source is extended, but shows no other structure. Photographic photometry (in Kron-Cousins R), calibrated by deep CCD frames, is presented for all galaxies brighter than 19th magnitude within 0.75 Mpc of the cluster center. The luminosity function is normal, and the isopleths show little evidence of substructure near the cluster center. The cluster has a dominant central galaxy, which is classified as a normal brightest-cluster elliptical on the basis of its luminosity profile. New redshifts were obtained for 26 galaxies in the vicinity of the cluster center; 20 appear to be cluster members. The spatial distribution of redshifts is peculiar; the dispersion within the 150 kpc core radius is much greater than outside. Abell 744 is similar to the nearby cluster Abell 1060.
A Strong Merger Shock in Abell 665
NASA Technical Reports Server (NTRS)
Dasadia, S.; Sun, M.; Sarazin, C.; Morandi, A.; Markevitch, M.; Wik, D.; Feretti, L.; Giovannini, G.; Govoni, F.
2016-01-01
Deep (103 ks) Chandra observations of Abell 665 have revealed rich structures in this merging galaxy cluster, including a strong shock and two cold fronts. The newly discovered shock has a Mach number of M =?3.0 +/- 0.6, propagating in front of a cold disrupted cloud. This makes Abell 665 the second cluster, after the Bullet cluster, where a strong merger shock of M is approximately 3 has been detected. The shock velocity from jump conditions is consistent with (2.7 +/- 0.7) × 10(exp 3) km s(exp -1). The new data also reveal a prominent southern cold front with potentially heated gas ahead of it. Abell 665 also hosts a giant radio halo. There is a hint of diffuse radio emission extending to the shock at the north, which needs to be examined with better radio data. This new strong shock provides a great opportunity to study the reacceleration model with the X-ray and radio data combined.
ROSAT HRI images of Abell 85 and Abell 496: Evidence for inhomogeneities in cooling flows
NASA Technical Reports Server (NTRS)
Prestwich, Andrea H.; Guimond, Stephen J.; Luginbuhl, Christian; Joy, Marshall
1994-01-01
We present ROSAT HRI images of two clusters of galaxies with cooling flows, Abell 496 and Abell 85. In these clusters, x-ray emission on small scales above the general cluster emission is significant at the 3 sigma level. There is no evidence for optical counterparts. The enhancements may be associated with lumps of gas at a lower temperature and higher density than the ambient medium, or hotter, denser gas perhaps compressed by magnetic fields. These observations can be used to test models of how thermal instabilities form and evolve in cooling flows.
An improved inversion for FORMOSAT-3/COSMIC ionosphere electron density profiles
NASA Astrophysics Data System (ADS)
Pedatella, N. M.; Yue, X.; Schreiner, W. S.
2015-10-01
An improved method to retrieve electron density profiles from Global Positioning System (GPS) radio occultation (RO) data is presented and applied to Constellation Observing System for Meteorology, Ionosphere, and Climate (COSMIC) observations. The improved inversion uses a monthly grid of COSMIC F region peak densities (NmF2), which are obtained via the standard Abel inversion, to aid the Abel inversion by providing information on the horizontal gradients in the ionosphere. This lessens the impact of ionospheric gradients on the retrieval of GPS RO electron density profiles, reducing the dominant error source in the standard Abel inversion. Results are presented that demonstrate the NmF2 aided retrieval significantly improves the quality of the COSMIC electron density profiles. Improvements are most notable at E region altitudes, where the improved inversion reduces the artificial plasma cave that is generated by the Abel inversion spherical symmetry assumption at low latitudes during the daytime. Occurrence of unphysical negative electron densities at E region altitudes is also reduced. Furthermore, the NmF2 aided inversion has a positive impact at F region altitudes, where it results in a more distinct equatorial ionization anomaly. COSMIC electron density profiles inverted using our new approach are currently available through the University Corporation for Atmospheric Research COSMIC Data Analysis and Archive Center. Owing to the significant improvement in the results, COSMIC data users are encouraged to use electron density profiles based on the improved inversion rather than those inverted by the standard Abel inversion.
The cluster of galaxies Abell 376
NASA Astrophysics Data System (ADS)
Proust, D.; Capelato, H. V.; Hickel, G.; Sodré, L., Jr.; Lima Neto, G. B.; Cuevas, H.
2003-08-01
We present a dynamical analysis of the galaxy cluster Abell 376 based on a set of 73 velocities, most of them measured at Pic du Midi and Haute-Provence observatories and completed with data from the literature. Data on individual galaxies are presented and the accuracy of the determined velocities is discussed as well as some properties of the cluster. We obtained an improved mean redshift value z = 0.0478+0.005-0.006 and velocity dispersion sigma = 852+120-76 km s-1. Our analysis indicates that inside a radius of ~ 900 h70-1 kpc ( ~ 15 arcmin) the cluster is well relaxed without any remarkable features and the X-ray emission traces fairly well the galaxy distribution. A possible substructure is seen at 20 arcmin from the centre towards the Southwest direction, but is not confirmed by the velocity field. This SW clump is, however, kinematically bound to the main structure of Abell 376. A dense condensation of galaxies is detected at 46 arcmin (projected distance 2.6 h70-1 Mpc) from the centre towards the Northwest and analysis of the apparent luminosity distribution of its galaxies suggests that this clump is part of the large scale structure of Abell 376. X-ray spectroscopic analysis of ASCA data resulted in a temperature kT = 4.3 +/- 0.4 keV and metal abundance Z = 0.32 +/- 0.08 Zsun. The velocity dispersion corresponding to this temperature using the TX-sigma scaling relation is in agreement with the measured galaxies velocities. Based on observations made Haute-Provence and Pic du Midi Observatories (France). Table 1 is also available in electronic form at the CDS via anonymous ftp to cdsarc.u-strasbg.fr (130.79.128.5) or via http://cdsweb.u-strasbg.fr/cgi-bin/qcat?J/A+A/407/31
The cluster Abell 780: an optical view
NASA Astrophysics Data System (ADS)
Durret, F.; Slezak, E.; Adami, C.
2009-11-01
Context: The Abell 780 cluster, better known as the Hydra A cluster, has been thouroughly analyzed in X-rays. However, little is known about its optical properties. Aims: We propose to derive the galaxy luminosity function (GLF) in this apparently relaxed cluster and to search for possible environmental effects by comparing the GLFs in various regions and by looking at the galaxy distribution at large scale around Abell 780. Methods: Our study is based on optical images obtained with the ESO 2.2m telescope and WFI camera in the B and R bands, covering a total region of 67.22 × 32.94 arcmin^2, or 4.235 × 2.075 Mpc2 for a cluster redshift of 0.0539. Results: In a region of 500 kpc radius around the cluster center, the GLF in the R band shows a double structure, with a broad and flat bright part and a flat faint end that can be fit by a power law with an index α ~ - 0.85 ± 0.12 in the 20.25 ≤ R ≤ 21.75 interval. If we divide this 500 kpc radius region in north+south or east+west halves, we find no clear difference between the GLFs in these smaller regions. No obvious large-scale structure is apparent within 5 Mpc from the cluster, based on galaxy redshifts and magnitudes collected from the NED database in a much larger region than that covered by our data, suggesting that there is no major infall of material in any preferential direction. However, the Serna-Gerbal method reveals a gravitationally bound structure of 27 galaxies, which includes the cD, and of a more strongly gravitationally bound structure of 14 galaxies. Conclusions: These optical results agree with the overall relaxed structure of Abell 780 previously derived from X-ray analyses. Based on observations obtained at the European Southern Observatory, program ESO 68.A-0084(A), P. I. E. Slezak. This research has made use of the NASA/IPAC Extragalactic Database (NED), which is operated by the Jet Propulsion Laboratory, California Institute of Technology, under contract with the National Aeronautics
NASA Technical Reports Server (NTRS)
Schlegel, Todd T.; Cortez, Daniel
2010-01-01
Our primary objective was to ascertain which commonly used 12-to-Frank-lead transformation yields spatial QRS-T angle values closest to those obtained from simultaneously collected true Frank-lead recordings. Simultaneous 12-lead and Frank XYZ-lead recordings were analyzed for 100 post-myocardial infarction patients and 50 controls. Relative agreement, with true Frank-lead results, of 12-to-Frank-lead transformed results for the spatial QRS-T angle using Kors regression versus inverse Dower was assessed via ANOVA, Lin s concordance and Bland-Altman plots. Spatial QRS-T angles from the true Frank leads were not significantly different than those derived from the Kors regression-related transformation but were significantly smaller than those derived from the inverse Dower-related transformation (P less than 0.001). Independent of method, spatial mean QRS-T angles were also always significantly larger than spatial maximum (peaks) QRS-T angles. Spatial QRS-T angles are best approximated by regression-related transforms. Spatial mean and spatial peaks QRS-T angles should also not be used interchangeably.
The Abell 85 BCG: A Nucleated, Coreless Galaxy
NASA Astrophysics Data System (ADS)
Madrid, Juan P.; Donzelli, Carlos J.
2016-03-01
New high-resolution r-band imaging of the brightest cluster galaxy (BCG) in Abell 85 (Holm 15A) was obtained using the Gemini Multi Object Spectrograph. These data were taken with the aim of deriving an accurate surface brightness profile of the BCG of Abell 85, in particular, its central region. The new Gemini data show clear evidence of a previously unreported nuclear emission that is evident as a distinct light excess in the central kiloparsec of the surface brightness profile. We find that the light profile is never flat nor does it present a downward trend toward the center of the galaxy. That is, the new Gemini data show a different physical reality from the featureless, “evacuated core” recently claimed for the Abell 85 BCG. After trying different models, we find that the surface brightness profile of the BCG of Abell 85 is best fit by a double Sérsic model.
THE ABELL 85 BCG: A NUCLEATED, CORELESS GALAXY
Madrid, Juan P.
2016-03-01
New high-resolution r-band imaging of the brightest cluster galaxy (BCG) in Abell 85 (Holm 15A) was obtained using the Gemini Multi Object Spectrograph. These data were taken with the aim of deriving an accurate surface brightness profile of the BCG of Abell 85, in particular, its central region. The new Gemini data show clear evidence of a previously unreported nuclear emission that is evident as a distinct light excess in the central kiloparsec of the surface brightness profile. We find that the light profile is never flat nor does it present a downward trend toward the center of the galaxy. That is, the new Gemini data show a different physical reality from the featureless, “evacuated core” recently claimed for the Abell 85 BCG. After trying different models, we find that the surface brightness profile of the BCG of Abell 85 is best fit by a double Sérsic model.
The magnitude-redshift relation for 561 Abell clusters
NASA Technical Reports Server (NTRS)
Postman, M.; Huchra, J. P.; Geller, M. J.; Henry, J. P.
1985-01-01
The Hubble diagram for the 561 Abell clusters with measured redshifts has been examined using Abell's (1958) corrected photo-red magnitudes for the tenth-ranked cluster member (m10). After correction for the Scott effect and K dimming, the data are in good agreement with a linear magnitude-redshift relation with a slope of 0.2 out to z = 0.1. New redshift data are also presented for 20 Abell clusters. Abell's m10 is suitable for redshift estimation for clusters with m10 of no more than 16.5. At fainter m10, the number of foreground galaxies expected within an Abell radius is large enough to make identification of the tenth-ranked galaxy difficult. Interlopers bias the estimated redshift toward low values at high redshift. Leir and van den Bergh's (1977) redshift estimates suffer from this same bias but to a smaller degree because of the use of multiple cluster parameters. Constraints on deviations of cluster velocities from the mean cosmological flow require greater photometric accuracy than is provided by Abell's m10 magnitudes.
A model-assisted radio occultation data inversion method based on data ingestion into NeQuick
NASA Astrophysics Data System (ADS)
Shaikh, M. M.; Nava, B.; Kashcheyev, A.
2017-01-01
Inverse Abel transform is the most common method to invert radio occultation (RO) data in the ionosphere and it is based on the assumption of the spherical symmetry for the electron density distribution in the vicinity of an occultation event. It is understood that this 'spherical symmetry hypothesis' could fail, above all, in the presence of strong horizontal electron density gradients. As a consequence, in some cases wrong electron density profiles could be obtained. In this work, in order to incorporate the knowledge of horizontal gradients, we have suggested an inversion technique based on the adaption of the empirical ionospheric model, NeQuick2, to RO-derived TEC. The method relies on the minimization of a cost function involving experimental and model-derived TEC data to determine NeQuick2 input parameters (effective local ionization parameters) at specific locations and times. These parameters are then used to obtain the electron density profile along the tangent point (TP) positions associated with the relevant RO event using NeQuick2. The main focus of our research has been laid on the mitigation of spherical symmetry effects from RO data inversion without using external data such as data from global ionospheric maps (GIM). By using RO data from Constellation Observing System for Meteorology Ionosphere and Climate (FORMOSAT-3/COSMIC) mission and manually scaled peak density data from a network of ionosondes along Asian and American longitudinal sectors, we have obtained a global improvement of 5% with 7% in Asian longitudinal sector (considering the data used in this work), in the retrieval of peak electron density (NmF2) with model-assisted inversion as compared to the Abel inversion. Mean errors of NmF2 in Asian longitudinal sector are calculated to be much higher compared to American sector.
NASA Astrophysics Data System (ADS)
Ding, J. Y.
2013-12-01
This note illustrates, in the context of Brutsaert-Nieber (1977) model: -dQ/dt = aQb, the utility of a newly rediscovered inverse fractional power (IFP) transform of the flow rates. This method of streamflow recession analysis dates back a half-century. The IFP transform Δb on an operand Q is defined as Δb Q = 1/Qb-1. Brutsaert-Nieber model by IFP transform thus becomes: ΔbQ(t) = ΔbQ(0) + (b-1) at, if b ≠ 1. The IFP transformed recession curve appears as a straight line on a semi-IFP plot. The method has both the advantage of being independent of the size of computational time step, and the disadvantage of being depending on the parameter b value. This is used to calibrate the Brutsaert-Nieber recession flow model in which b is a slope (or shape) parameter, and a is an intercept (or a scale parameter). It is applied to four observed events on the Spoon River in Illinois (4237 km2). The results show that the IFP transform method gives a narrower range of parameter b values than the regression method in a recession plot. Theoretically, an IFP transformed recession curve for large watersheds falls between those performed by the reciprocal of the cubic root (RoCR) transform and the reciprocal of the square root (RoSR) one. In general, the forgotten IFP transform method merits a fresh look, especially for hillslopes and zero-order catchments, the building blocks of a watershed system. In particular, because of its origin in hillslope hydrology, the 1-parameter RoSR transform need be falsified or verified for application to headwater catchments.
NASA Technical Reports Server (NTRS)
Rummel, R.; Sjoeberg, L.; Rapp, R. H.
1978-01-01
A numerical method for the determination of gravity anomalies from geoid heights is described using the inverse Stokes formula. This discrete form of the inverse Stokes formula applies a numerical integration over the azimuth and an integration over a cubic interpolatory spline function which approximates the step function obtained from the numerical integration. The main disadvantage of the procedure is the lack of a reliable error measure. The method was applied on geoid heights derived from GEOS-3 altimeter measurements in the calibration area of the GEOS-3 satellite.
Cool Core Disruption in Abell 1763
NASA Astrophysics Data System (ADS)
Douglass, Edmund; Blanton, Elizabeth L.; Clarke, Tracy E.; Randall, Scott W.; Edwards, Louise O. V.; Sabry, Ziad
2017-01-01
We present the analysis of a 20 ksec Chandra archival observation of the massive galaxy cluster Abell 1763. A model-subtracted image highlighting excess cluster emission reveals a large spiral structure winding outward from the core to a radius of ~950 kpc. We measure the gas of the inner spiral to have significantly lower entropy than non-spiral regions at the same radius. This is consistent with the structure resulting from merger-induced motion of the cluster’s cool core, a phenomenon seen in many systems. Atypical of spiral-hosting clusters, an intact cool core is not detected. Its absence suggests the system has experienced significant disruption since the initial dynamical encounter that set the sloshing core in motion. Along the major axis of the elongated ICM distribution we detect thermal features consistent with the merger event most likely responsible for cool core disruption. The merger-induced transition towards non-cool core status will be discussed. The interaction between the powerful (P1.4 ~ 1026 W Hz-1) cluster-center WAT radio source and its ICM environment will also be discussed.
The SAMI Pilot Survey: stellar kinematics of galaxies in Abell 85, 168 and 2399
NASA Astrophysics Data System (ADS)
Fogarty, L. M. R.; Scott, N.; Owers, M. S.; Croom, S. M.; Bekki, K.; Houghton, R. C. W.; van de Sande, J.; D'Eugenio, F.; Cecil, G. N.; Colless, M. M.; Bland-Hawthorn, J.; Brough, S.; Cortese, L.; Davies, R. L.; Jones, D. H.; Pracy, M.; Allen, J. T.; Bryant, J. J.; Goodwin, M.; Green, A. W.; Konstantopoulos, I. S.; Lawrence, J. S.; Lorente, N. P. F.; Richards, S.; Sharp, R. G.
2015-12-01
We present the SAMI Pilot Survey, consisting of integral field spectroscopy of 106 galaxies across three galaxy clusters, Abell 85, Abell 168 and Abell 2399. The galaxies were selected by absolute magnitude to have Mr < -20.25 mag. The survey, using the Sydney-AAO Multi-object Integral field spectrograph (SAMI), comprises observations of galaxies of all morphological types with 75 per cent of the sample being early-type galaxies (ETGs) and 25 per cent being late-type galaxies (LTGs). Stellar velocity and velocity dispersion maps are derived for all 106 galaxies in the sample. The λR parameter, a proxy for the specific stellar angular momentum, is calculated for each galaxy in the sample. We find a trend between λR and galaxy concentration such that LTGs are less concentrated higher angular momentum systems, with the fast-rotating ETGs (FRs) more concentrated and lower in angular momentum. This suggests that some dynamical processes are involved in transforming LTGs to FRs, though a significant overlap between the λR distributions of these classes of galaxies implies that this is just one piece of a more complicated picture. We measure the kinematic misalignment angle, Ψ, for the ETGs in the sample, to probe the intrinsic shapes of the galaxies. We find the majority of FRs (83 per cent) to be aligned, consistent with them being oblate spheroids (i.e. discs). The slow rotating ETGs (SRs), on the other hand, are significantly more likely to show kinematic misalignment (only 38 per cent are aligned). This confirms previous results that SRs are likely to be mildly triaxial systems.
NASA Astrophysics Data System (ADS)
Ross, M. P.; Shumlak, U.
2016-10-01
The ZaP-HD flow Z-pinch project provides a platform to explore how shear flow stabilized Z-pinches could scale to high-energy-density plasma (plasma with pressures exceeding 1 Mbar) and fusion reactor conditions. The Z-pinch is a linear plasma confinement geometry in which the plasma carries axial electric current and is confined by its self-induced magnetic field. ZaP-HD generates shear stabilized, axisymmetric Z-pinches with stable lifetimes approaching 60 μs. The goal of the project is to increase the plasma density and temperature compared to the previous ZaP project by compressing the plasma to smaller radii (≈1 mm). Radial and axial plasma electron density structure is measured using digital holographic interferometry (DHI), which provides the necessary fine spatial resolution. ZaP-HD's DHI system uses a 2 ns Nd:YAG laser pulse with a second harmonic generator (λ = 532 nm) to produce holograms recorded by a Nikon D3200 digital camera. The holograms are numerically reconstructed with the Fresnel transform reconstruction method to obtain the phase shift caused by the interaction of the laser beam with the plasma. This provides a two-dimensional map of line-integrated electron density, which can be Abel inverted to determine the local number density. The DHI resolves line-integrated densities down to 3 × 1020 m-2 with spatial resolution near 10 μm. This paper presents the first application of Fresnel transform reconstruction as an analysis technique for a plasma diagnostic, and it analyzes the method's accuracy through study of synthetic data. It then presents an Abel inversion procedure that utilizes data on both sides of a Z-pinch local number density profile to maximize profile symmetry. Error estimation and Abel inversion are applied to the measured data.
The Dark Matter filament between Abell 222/223
NASA Astrophysics Data System (ADS)
Dietrich, Jörg P.; Werner, Norbert; Clowe, Douglas; Finoguenov, Alexis; Kitching, Tom; Miller, Lance; Simionescu, Aurora
2016-10-01
Weak lensing detections and measurements of filaments have been elusive for a long time. The reason is that the low density contrast of filaments generally pushes the weak lensing signal to unobservably low scales. To nevertheless map the dark matter in filaments exquisite data and unusual systems are necessary. SuprimeCam observations of the supercluster system Abell 222/223 provided the required combination of excellent seeing images and a fortuitous alignment of the filament with the line-of-sight. This boosted the lensing signal to a detectable level and led to the first weak lensing mass measurement of a large-scale structure filament. The filament connecting Abell 222 and Abell 223 is now the only one traced by the galaxy distribution, dark matter, and X-ray emission from the hottest phase of the warm-hot intergalactic medium. The combination of these data allows us to put the first constraints on the hot gas fraction in filaments.
An efficient and fast parallel method for Volterra integral equations of Abel type
NASA Astrophysics Data System (ADS)
Capobianco, Giovanni; Conte, Dajana
2006-05-01
In this paper we present an efficient and fast parallel waveform relaxation method for Volterra integral equations of Abel type, obtained by reformulating a nonstationary waveform relaxation method for systems of equations with linear coefficient constant kernel. To this aim we consider the Laplace transform of the equation and here we apply the recurrence relation given by the Chebyshev polynomial acceleration for algebraic linear systems. Back in the time domain, we obtain a three term recursion which requires, at each iteration, the evaluation of convolution integrals, where only the Laplace transform of the kernel is known. For this calculation we can use a fast convolution algorithm. Numerical experiments have been done also on problems where it is not possible to use the original nonstationary method, obtaining good results in terms of improvement of the rate of convergence with respect the stationary method.
A 1400-MHz survey of 1478 Abell clusters of galaxies
NASA Technical Reports Server (NTRS)
Owen, F. N.; White, R. A.; Hilldrup, K. C.; Hanisch, R. J.
1982-01-01
Observations of 1478 Abell clusters of galaxies with the NRAO 91-m telescope at 1400 MHz are reported. The measured beam shape was deconvolved from the measured source Gaussian fits in order to estimate the source size and position angle. All detected sources within 0.5 corrected Abell cluster radii are listed, including the cluster number, richness class, distance class, magnitude of the tenth brightest galaxy, redshift estimate, corrected cluster radius in arcmin, right ascension and error, declination and error, total flux density and error, and angular structure for each source.
LensPerfect Analysis of Abell 1689
NASA Astrophysics Data System (ADS)
Coe, Dan A.
2007-12-01
I present the first massmap to perfectly reproduce the position of every gravitationally-lensed multiply-imaged galaxy detected to date in ACS images of Abell 1689. This massmap was obtained using a powerful new technique made possible by a recent advance in the field of Mathematics. It is the highest resolution assumption-free Dark Matter massmap to date, with the resolution being limited only by the number of multiple images detected. We detect 8 new multiple image systems and identify multiple knots in individual galaxies to constrain a grand total of 168 knots within 135 multiple images of 42 galaxies. No assumptions are made about mass tracing light, and yet the brightest visible structures in A1689 are reproduced in our massmap, a few with intriguing positional offsets. Our massmap probes radii smaller than that resolvable in current Dark Matter simulations of galaxy clusters. And at these radii, we observe slight deviations from the NFW and Sersic profiles which describe simulated Dark Matter halos so well. While we have demonstrated that our method is able to recover a known input massmap (to limited resolution), further tests are necessary to determine the uncertainties of our mass profile and positions of massive subclumps. I compile the latest weak lensing data from ACS, Subaru, and CFHT, and attempt to fit a single profile, either NFW or Sersic, to both the observed weak and strong lensing. I confirm the finding of most previous authors, that no single profile fits extremely well to both simultaneously. Slight deviations are revealed, with the best fits slightly over-predicting the mass profile at both large and small radius. Our easy-to-use software, called LensPerfect, will be made available soon. This research was supported by the European Commission Marie Curie International Reintegration Grant 017288-BPZ and the PNAYA grant AYA2005-09413-C02.
NASA Astrophysics Data System (ADS)
Brendlé, E.; Papirer, E.
1998-05-01
Inverse Gas Chromatography (IGC) is a method well suited for the study of the surface properties of divided solids and of the modifications that result from applied treatments. In this instance, IGC was used to follow the surface properties variations (adsorption energy of alkanes, nanomorphology, acid-base behavior) that occur when goethite, upon heat treatment, transforms into hematite. La chromatographie Gazeuse Inverse (CGI) s'avère comme une méthode de choix pour l'étude des propriétés de surface de solides divisés et des modifications qui accompagnent les traitements auxquels on les soumet. Dans cette étude, la CGI est utilisée pour suivre les variations des propriétés de surface (énergie d'adsorption des alcanes, nanomorphologie, caractère acide-base) se produisant lors de la transformation de la goethite en hématite consécutive à un traitement thermique.
Barysz, Maria; Mentel, Lukasz; Leszczynski, Jerzy
2009-04-28
The two-component Hamiltonian of the infinite-order two-component (IOTC) theory is obtained by a unitary block-diagonalizing transformation of the Dirac-Hamiltonian. Once the IOTC spin orbitals are calculated, they can be back transformed into four-component solutions. The transformed four component solutions are then used to evaluate different moments of the electron density distribution. This formally exact method may, however, suffer from certain approximations involved in its numerical implementation. As shown by the present study, with sufficiently large basis set of Gaussian functions, the Dirac values of these moments are fully recovered in spite of using the approximate identity resolution into eigenvectors of the p{sup 2} operator.
ERIC Educational Resources Information Center
Iqbal, M.
2002-01-01
In this paper we have converted the Laplace transform into an integral equation of the first kind of convolution type, which is an ill-posed problem, and used a statistical regularization method to solve it. The method is applied to three examples. It gives a good approximation to the true solution and compares well with the method given by…
Retrieval Performance and Indexing Differences in ABELL and MLAIB
ERIC Educational Resources Information Center
Graziano, Vince
2012-01-01
Searches for 117 British authors are compared in the Annual Bibliography of English Language and Literature (ABELL) and the Modern Language Association International Bibliography (MLAIB). Authors are organized by period and genre within the early modern era. The number of records for each author was subdivided by format, language of publication,…
LACKS,S.A.
2003-10-09
Transformation, which alters the genetic makeup of an individual, is a concept that intrigues the human imagination. In Streptococcus pneumoniae such transformation was first demonstrated. Perhaps our fascination with genetics derived from our ancestors observing their own progeny, with its retention and assortment of parental traits, but such interest must have been accelerated after the dawn of agriculture. It was in pea plants that Gregor Mendel in the late 1800s examined inherited traits and found them to be determined by physical elements, or genes, passed from parents to progeny. In our day, the material basis of these genetic determinants was revealed to be DNA by the lowly bacteria, in particular, the pneumococcus. For this species, transformation by free DNA is a sexual process that enables cells to sport new combinations of genes and traits. Genetic transformation of the type found in S. pneumoniae occurs naturally in many species of bacteria (70), but, initially only a few other transformable species were found, namely, Haemophilus influenzae, Neisseria meningitides, Neisseria gonorrheae, and Bacillus subtilis (96). Natural transformation, which requires a set of genes evolved for the purpose, contrasts with artificial transformation, which is accomplished by shocking cells either electrically, as in electroporation, or by ionic and temperature shifts. Although such artificial treatments can introduce very small amounts of DNA into virtually any type of cell, the amounts introduced by natural transformation are a million-fold greater, and S. pneumoniae can take up as much as 10% of its cellular DNA content (40).
Cleaver, J.E. )
1989-01-01
Human cells transformed by simian virus 40 (SV40) are more sensitive to killing by ultraviolet light when grown in caffeine after irradiation. The degree of sensitization at 2 mM caffeine (expressed as the ratio of the 37% survival dose for control cells divided by the 37% survival dose for cells grown in caffeine, i.e., the dose modification factor) was approximately 1.9 in transformed normal cells and 3.8-5.8 in excision-defective xeroderma pigmentosum (XP) groups A, C, and D cells. A large dose modification factor of 12 was observed in a transformed XP variant cell line. Chinese hamster ovary cells were not significantly different from transformed normal human cells, with a maximum dose modification factor of 1.5. Two radioresistant XP revertants that do not excise cyclobutane dimers gave different responses; one resembled its group A parent in being sensitized by caffeine, and one did not. These results can be interpreted on the basis of a single hypothesis that cells are killed as a result of attempts to replicate damaged DNA. Increased replication rates caused by transformation, increased numbers of replication forks in DNA caused by caffeine, and increased numbers of damaged sites ahead of replication forks in excision-defective cells are all processes that will consequently increase killing according to this hypothesis. A corollary is that the XP variant may be highly sensitized to caffeine because of excision defects at the DNA replication forks, an idea that may be important in designing cloning strategies for the XP variant gene.
Bracken, Robert E.
2004-01-01
A subroutine (FFTDC2) coded in Fortran 77 is described, which performs a Fast Fourier Transform or Discrete Fourier Transform together with necessary conditioning steps of trend removal, extension, and windowing. The source code for the entire library of required subroutines is provided with the digital release of this report. But, there is only one required entry point, the subroutine call to FFTDC2; all the other subroutines are operationally transparent to the user. Complete instructions for use of FFTDC2.F (as well as for all the other subroutines) and some practical theoretical discussions are included as comments at the beginning of the source code. This subroutine is intended to be an efficient tool for the programmer in a variety of production-level signal-processing applications.
Baker, W.R.
1959-08-25
Transformers of a type adapted for use with extreme high power vacuum tubes where current requirements may be of the order of 2,000 to 200,000 amperes are described. The transformer casing has the form of a re-entrant section being extended through an opening in one end of the cylinder to form a coaxial terminal arrangement. A toroidal multi-turn primary winding is disposed within the casing in coaxial relationship therein. In a second embodiment, means are provided for forming the casing as a multi-turn secondary. The transformer is characterized by minimized resistance heating, minimized external magnetic flux, and an economical construction.
Zhan, X.
2005-01-01
A parallel Fortran-MPI (Message Passing Interface) software for numerical inversion of the Laplace transform based on a Fourier series method is developed to meet the need of solving intensive computational problems involving oscillatory water level's response to hydraulic tests in a groundwater environment. The software is a parallel version of ACM (The Association for Computing Machinery) Transactions on Mathematical Software (TOMS) Algorithm 796. Running 38 test examples indicated that implementation of MPI techniques with distributed memory architecture speedups the processing and improves the efficiency. Applications to oscillatory water levels in a well during aquifer tests are presented to illustrate how this package can be applied to solve complicated environmental problems involved in differential and integral equations. The package is free and is easy to use for people with little or no previous experience in using MPI but who wish to get off to a quick start in parallel computing. ?? 2004 Elsevier Ltd. All rights reserved.
Basis set expansion for inverse problems in plasma diagnostic analysis
Jones, B.; Ruiz, C. L.
2013-07-15
A basis set expansion method [V. Dribinski, A. Ossadtchi, V. A. Mandelshtam, and H. Reisler, Rev. Sci. Instrum. 73, 2634 (2002)] is applied to recover physical information about plasma radiation sources from instrument data, which has been forward transformed due to the nature of the measurement technique. This method provides a general approach for inverse problems, and we discuss two specific examples relevant to diagnosing fast z pinches on the 20–25 MA Z machine [M. E. Savage, L. F. Bennett, D. E. Bliss, W. T. Clark, R. S. Coats, J. M. Elizondo, K. R. LeChien, H. C. Harjes, J. M. Lehr, J. E. Maenchen, D. H. McDaniel, M. F. Pasik, T. D. Pointon, A. C. Owen, D. B. Seidel, D. L. Smith, B. S. Stoltzfus, K. W. Struve, W. A. Stygar, L. K. Warne, J. R. Woodworth, C. W. Mendel, K. R. Prestwich, R. W. Shoup, D. L. Johnson, J. P. Corley, K. C. Hodge, T. C. Wagoner, and P. E. Wakeland, in Proceedings of the Pulsed Power Plasma Sciences Conference (IEEE, 2007), p. 979]. First, Abel inversion of time-gated, self-emission x-ray images from a wire array implosion is studied. Second, we present an approach for unfolding neutron time-of-flight measurements from a deuterium gas puff z pinch to recover information about emission time history and energy distribution. Through these examples, we discuss how noise in the measured data limits the practical resolution of the inversion, and how the method handles discontinuities in the source function and artifacts in the projected image. We add to the method a propagation of errors calculation for estimating uncertainties in the inverted solution.
Basis set expansion for inverse problems in plasma diagnostic analysis
NASA Astrophysics Data System (ADS)
Jones, B.; Ruiz, C. L.
2013-07-01
A basis set expansion method [V. Dribinski, A. Ossadtchi, V. A. Mandelshtam, and H. Reisler, Rev. Sci. Instrum. 73, 2634 (2002)], 10.1063/1.1482156 is applied to recover physical information about plasma radiation sources from instrument data, which has been forward transformed due to the nature of the measurement technique. This method provides a general approach for inverse problems, and we discuss two specific examples relevant to diagnosing fast z pinches on the 20-25 MA Z machine [M. E. Savage, L. F. Bennett, D. E. Bliss, W. T. Clark, R. S. Coats, J. M. Elizondo, K. R. LeChien, H. C. Harjes, J. M. Lehr, J. E. Maenchen, D. H. McDaniel, M. F. Pasik, T. D. Pointon, A. C. Owen, D. B. Seidel, D. L. Smith, B. S. Stoltzfus, K. W. Struve, W. A. Stygar, L. K. Warne, J. R. Woodworth, C. W. Mendel, K. R. Prestwich, R. W. Shoup, D. L. Johnson, J. P. Corley, K. C. Hodge, T. C. Wagoner, and P. E. Wakeland, in Proceedings of the Pulsed Power Plasma Sciences Conference (IEEE, 2007), p. 979]. First, Abel inversion of time-gated, self-emission x-ray images from a wire array implosion is studied. Second, we present an approach for unfolding neutron time-of-flight measurements from a deuterium gas puff z pinch to recover information about emission time history and energy distribution. Through these examples, we discuss how noise in the measured data limits the practical resolution of the inversion, and how the method handles discontinuities in the source function and artifacts in the projected image. We add to the method a propagation of errors calculation for estimating uncertainties in the inverted solution.
NASA Astrophysics Data System (ADS)
Zhang, Taiping; Stackhouse, Paul W.; Gupta, Shashi K.; Cox, Stephen J.; Mikovitz, J. Colleen
2017-02-01
Occasionally, a need arises to downscale a time series of data from a coarse temporal resolution to a finer one, a typical example being from monthly means to daily means. For this case, daily means derived as such are used as inputs of climatic or atmospheric models so that the model results may exhibit variance on the daily time scale and retain the monthly mean of the original data set without an abrupt change from the end of one month to the beginning of the next. Different methods have been developed which often need assumptions, free parameters and the solution of simultaneous equations. Here we derive a generalized formulation by means of Fourier transform and inversion so that it can be used to directly compute daily means from a series of an arbitrary number of monthly means. The formulation can be used to transform any coarse temporal resolution to a finer one. From the derived results, the original data can be recovered almost identically. As a real application, we use this method to derive the daily counterpart of the MAC-v1 aerosol climatology that provides monthly mean aerosol properties for 18 shortwave bands and 12 longwave bands for the years from 1860 to 2100. The derived daily means are to be used as inputs of the shortwave and longwave algorithms of the NASA GEWEX SRB project.
X-Ray Imaging-Spectroscopy of Abell 1835
NASA Technical Reports Server (NTRS)
Peterson, J. R.; Paerels, F. B. S.; Kaastra, J. S.; Arnaud, M.; Reiprich T. H.; Fabian, A. C.; Mushotzky, R. F.; Jernigan, J. G.; Sakelliou, I.
2000-01-01
We present detailed spatially-resolved spectroscopy results of the observation of Abell 1835 using the European Photon Imaging Cameras (EPIC) and the Reflection Grating Spectrometers (RGS) on the XMM-Newton observatory. Abell 1835 is a luminous (10(exp 46)ergs/s), medium redshift (z = 0.2523), X-ray emitting cluster of galaxies. The observations support the interpretation that large amounts of cool gas are present in a multi-phase medium surrounded by a hot (kT(sub e) = 8.2 keV) outer envelope. We detect O VIII Ly(alpha) and two Fe XXIV complexes in the RGS spectrum. The emission measure of the cool gas below kT(sub e) = 2.7 keV is much lower than expected from standard cooling-flow models, suggesting either a more complicated cooling process than simple isobaric radiative cooling or differential cold absorption of the cooler gas.
The GenABEL Project for statistical genomics
Karssen, Lennart C.; van Duijn, Cornelia M.; Aulchenko, Yurii S.
2016-01-01
Development of free/libre open source software is usually done by a community of people with an interest in the tool. For scientific software, however, this is less often the case. Most scientific software is written by only a few authors, often a student working on a thesis. Once the paper describing the tool has been published, the tool is no longer developed further and is left to its own device. Here we describe the broad, multidisciplinary community we formed around a set of tools for statistical genomics. The GenABEL project for statistical omics actively promotes open interdisciplinary development of statistical methodology and its implementation in efficient and user-friendly software under an open source licence. The software tools developed withing the project collectively make up the GenABEL suite, which currently consists of eleven tools. The open framework of the project actively encourages involvement of the community in all stages, from formulation of methodological ideas to application of software to specific data sets. A web forum is used to channel user questions and discussions, further promoting the use of the GenABEL suite. Developer discussions take place on a dedicated mailing list, and development is further supported by robust development practices including use of public version control, code review and continuous integration. Use of this open science model attracts contributions from users and developers outside the “core team”, facilitating agile statistical omics methodology development and fast dissemination. PMID:27347381
SPITZER OBSERVATIONS OF ABELL 1763. I. INFRARED AND OPTICAL PHOTOMETRY
Edwards, Louise O. V.; Fadda, Dario; Biviano, Andrea
2010-02-15
We present a photometric analysis of the galaxy cluster Abell 1763 at visible and infrared wavelengths. Included are fully reduced images in r', J, H, and K{sub s} obtained using the Palomar 200in telescope, as well as the IRAC and MIPS images from Spitzer. The cluster is covered out to approximately 3 virial radii with deep 24 {mu}m imaging (a 5{sigma} depth of 0.2 mJy). This same field of {approx}40' x 40' is covered in all four IRAC bands as well as the longer wavelength MIPS bands (70 and 160 {mu}m). The r' imaging covers {approx}0.8 deg{sup 2} down to 25.5 mag, and overlaps with most of the MIPS field of view. The J, H, and K{sub s} images cover the cluster core and roughly half of the filament galaxies, which extend toward the neighboring cluster, Abell 1770. This first, in a series of papers on Abell 1763, discusses the data reduction methods and source extraction techniques used for each data set. We present catalogs of infrared sources (with 24 and/or 70 {mu}m emission) and their corresponding emission in the optical (u', g', r', i', z'), and near- to far-IR (J, H, K{sub s} , IRAC, and MIPS 160 {mu}m). We provide the catalogs and reduced images to the community through the NASA/IPAC Infrared Science Archive.
A Generalization of the Spherical Inversion
ERIC Educational Resources Information Center
Ramírez, José L.; Rubiano, Gustavo N.
2017-01-01
In the present article, we introduce a generalization of the spherical inversion. In particular, we define an inversion with respect to an ellipsoid, and prove several properties of this new transformation. The inversion in an ellipsoid is the generalization of the elliptic inversion to the three-dimensional space. We also study the inverse images…
RADIO AND DEEP CHANDRA OBSERVATIONS OF THE DISTURBED COOL CORE CLUSTER ABELL 133
Randall, S. W.; Nulsen, P. E. J.; Forman, W. R.; Murray, S. S.; Clarke, T. E.; Owers, M. S.; Sarazin, C. L.
2010-10-10
We present results based on new Chandra and multi-frequency radio observations of the disturbed cool core cluster Abell 133. The diffuse gas has a complex bird-like morphology, with a plume of emission extending from two symmetric wing-like features. The plume is capped with a filamentary radio structure that has been previously classified as a radio relic. X-ray spectral fits in the region of the relic indicate the presence of either high-temperature gas or non-thermal emission, although the measured photon index is flatter than would be expected if the non-thermal emission is from inverse Compton scattering of the cosmic microwave background by the radio-emitting particles. We find evidence for a weak elliptical X-ray surface brightness edge surrounding the core, which we show is consistent with a sloshing cold front. The plume is consistent with having formed due to uplift by a buoyantly rising radio bubble, now seen as the radio relic, and has properties consistent with buoyantly lifted plumes seen in other systems (e.g., M87). Alternatively, the plume may be a gas sloshing spiral viewed edge-on. Results from spectral analysis of the wing-like features are inconsistent with the previous suggestion that the wings formed due to the passage of a weak shock through the cool core. We instead conclude that the wings are due to X-ray cavities formed by displacement of X-ray gas by the radio relic. The central cD galaxy contains two small-scale cold gas clumps that are slightly offset from their optical and UV counterparts, suggestive of a galaxy-galaxy merger event. On larger scales, there is evidence for cluster substructure in both optical observations and the X-ray temperature map. We suggest that the Abell 133 cluster has recently undergone a merger event with an interloping subgroup, initialing gas sloshing in the core. The torus of sloshed gas is seen close to edge-on, leading to the somewhat ragged appearance of the elliptical surface brightness edge. We show
NASA Astrophysics Data System (ADS)
Edwards, L. O. V.; Alpert, H. S.; Trierweiler, I. L.; Abraham, T.; Beizer, V. G.
2016-09-01
We present the first results from an integral field unit (IFU) spectroscopic survey of a ˜75 kpc region around three brightest cluster galaxies (BCGs), combining over 100 IFU fibres to study the intracluster light (ICL). We fit population synthesis models to estimate age and metallicity. For Abell 85 and Abell 2457, the ICL is best-fit with a fraction of old, metal-rich stars like in the BCG, but requires 30-50 per cent young and metal-poor stars, a component not found in the BCGs. This is consistent with the ICL having been formed by a combination of interactions with less massive, younger, more metal-poor cluster members in addition to stars that form the BCG. We find that the three galaxies are in different stages of evolution and may be the result of different formation mechanisms. The BCG in Abell 85 is near a relatively young, metal-poor galaxy, but the dynamical friction time-scale is long and the two are unlikely to be undergoing a merger. The outer regions of Abell 2457 show a higher relative fraction of metal-poor stars, and we find one companion, with a higher fraction of young, metal-poor stars than the BCG, which is likely to merge within a gigayear. Several luminous red galaxies are found at the centre of the cluster IIZw108, with short merger time-scales, suggesting that the system is about to embark on a series of major mergers to build up a dominant BCG. The young, metal-poor component found in the ICL is not found in the merging galaxies.
The Origin of Dwarf Galaxies in Clusters: The Faint-End Slope of Abell 85 Galaxy Luminosity Function
NASA Astrophysics Data System (ADS)
Agulli, I.; Aguerri, J. A. L.; Barrena, R.; Diaferio, A.; Sánchez-Janssen, R.
2016-10-01
Dwarf galaxies (Mb>-18) are important because of their cosmological interest as tests of hierarchical theories. The formation of these galaxies is still an open question but red dwarf galaxies are preferentially located in high density environments, indicating that they are end-products of galaxy transformations in clusters. Deep spectroscopic studies of galaxy clusters are needed to put some constraints on dwarf galaxy formation and evolution. We have observed and analyzed Abell 85, a nearby (z = 0.055) and massive cluster down to M*+6, using the MOS instruments VIMOS@VLT and AF2@WHT. The first and powerful tool to study the characteristics of galaxies and compare with different density environments is the galaxy luminosity function. The comparison of the results for Abell 85 with literature outcomes for clusters and field, allows us to conclude that, at least for this cluster, the environment plays a major role in the nature of the faint-end galaxies, transforming blue dwarfs in the field into red ones in the cluster, but not in the formation of the luminosity function slope.
Soni, M.H.; Cooks, R.G. )
1994-08-01
Broad-band excitation of ions is accomplished in the quadrupole ion trap mass spectrometer using notched waveforms created by the SWIFT (stored waveform inverse Fourier transform) technique. A series of notched SWIFT pulses are applied during the period of ion injection from an external Cs[sup +] source to resonantly eject all ions whose resonance frequencies fall within the frequency range of the pulse while injecting only those analyte ions whose resonance frequencies fall within the limits of the notch. This allows selective injection and accumulation of the ions of interest and continuous ejection of the unwanted ions. This is shown to result in significant improvement in S/N ratio, resolution, and sensitivity for the analyte ions of interest. Selective ion injection is demonstrated by injecting the protonated molecules of peptides VSV and gramicidin S and the intact cation of l-carnitine hydrochloride, using singly notched SWIFT pulses. Multiply notched SWIFT pulses are used to simultaneously inject ions of different m/z values of l-carnitine hydrochloride into the ion trap. A new coarse/fine ion isolation procedure, which employs a doubly notched SWIFT pulse, is demonstrated for isolating ions of a single m/z value of 4-bromobiphenyl from a population of trapped ions. 36 refs., 10 figs., 2 tabs.
NASA Astrophysics Data System (ADS)
Ganguly, A.; Das, A.
2014-11-01
We consider one-dimensional stationary position-dependent effective mass quantum model and derive a generalized Korteweg-de Vries (KdV) equation in (1+1) dimension through Lax pair formulation, one being the effective mass Schrödinger operator and the other being the time-evolution of wave functions. We obtain an infinite number of conserved quantities for the generated nonlinear equation and explicitly show that the new generalized KdV equation is an integrable system. Inverse scattering transform method is applied to obtain general solution of the nonlinear equation, and then N-soliton solution is derived for reflectionless potentials. Finally, a special choice has been made for the variable mass function to get mass-deformed soliton solution. The influence of position and time-dependence of mass and also of the different representations of kinetic energy operator on the nature of such solitons is investigated in detail. The remarkable features of such solitons are demonstrated in several interesting figures and are contrasted with the conventional KdV-soliton associated with constant-mass quantum model.
The Distribution of Dark and Luminous Matter in the Galaxy Cluster Merger Abell 2146
NASA Astrophysics Data System (ADS)
King, Lindsay; Clowe, Douglas; Coleman, Joseph E.; Russell, Helen; Santana, Rebecca; White, Jacob; Canning, Rebecca; Deering, Nicole; Fabian, Andrew C.; Lee, Brandyn; Li, Baojiu; McNamara, Brian R.
2017-01-01
Abell 2146 (z = 0.232) consists of two galaxy clusters undergoing a major merger, presenting two large shock fronts on Chandra X-ray Observatory maps. These observations are consistent with a collision close to the plane of the sky, caught soon after first core passage. Here we outline the weak gravitational lensing analysis of the total mass in the system, using the distorted shapes of distant galaxies seen with Hubble Space Telescope. The highest peak in the mass reconstruction is centred on the brightest cluster galaxy in Abell 2146-A. The mass associated with Abell 2146-B is more extended. The best-fitting mass model with two components has a mass ratio of ~3:1 for the two clusters. From the weak lensing analysis, Abell 2146-A is the primary halo component, and the origin of the apparent discrepancy with the X-ray analysis where Abell 2146-B is the primary halo will be discussed.
The discovery of diffuse steep spectrum sources in Abell 2256
NASA Astrophysics Data System (ADS)
van Weeren, R. J.; Intema, H. T.; Oonk, J. B. R.; Röttgering, H. J. A.; Clarke, T. E.
2009-12-01
Context: Hierarchical galaxy formation models indicate that during their lifetime galaxy clusters undergo several mergers. An example of such a merging cluster is Abell 2256. Here we report on the discovery of three diffuse radio sources in the periphery of Abell 2256, using the Giant Metrewave Radio Telescope (GMRT). Aims: The aim of the observations was to search for diffuse ultra-steep spectrum radio sources within the galaxy cluster Abell 2256. Methods: We have carried out GMRT 325 MHz radio continuum observations of Abell 2256. V, R and I band images of the cluster were taken with the 4.2 m William Herschel Telescope (WHT). Results: We have discovered three diffuse elongated radio sources located about 1 Mpc from the cluster center. Two are located to the west of the cluster center, and one to the southeast. The sources have a measured physical extent of 170, 140 and 240 kpc, respectively. The two western sources are also visible in deep low-resolution 115-165 MHz Westerbork Synthesis Radio Telescope (WSRT) images, although they are blended into a single source. For the combined emission of the blended source we find an extreme spectral index (α) of -2.05 ± 0.14 between 140 and 351 MHz. The extremely steep spectral index suggests these two sources are most likely the result of adiabatic compression of fossil radio plasma due to merger shocks. For the source to the southeast, we find that {α < -1.45} between 1369 and 325 MHz. We did not find any clear optical counterparts to the radio sources in the WHT images. Conclusions: The discovery of the steep spectrum sources implies the existence of a population of faint diffuse radio sources in (merging) clusters with such steep spectra that they have gone unnoticed in higher frequency (⪆1 GHz) observations. Simply considering the timescales related to the AGN activity, synchrotron losses, and the presence of shocks, we find that most massive clusters should possess similar sources. An exciting possibility
Hierarchical Velocity Structure in the Core of Abell 2597
NASA Technical Reports Server (NTRS)
Still, Martin; Mushotzky, Richard
2004-01-01
We present XMM-Newton RGS and EPIC data of the putative cooling flow cluster Abell 2597. Velocities of the low-ionization emission lines in the spectrum are blue shifted with respect to the high-ionization lines by 1320 (sup +660) (sub -210) kilometers per second, which is consistent with the difference in the two peaks of the galaxy velocity distribution and may be the signature of bulk turbulence, infall, rotation or damped oscillation in the cluster. A hierarchical velocity structure such as this could be the direct result of galaxy mergers in the cluster core, or the injection of power into the cluster gas from a central engine. The uniform X-ray morphology of the cluster, the absence of fine scale temperature structure and the random distribution of the the galaxy positions, independent of velocity, suggests that our line of sight is close to the direction of motion. These results have strong implications for cooling flow models of the cluster Abell 2597. They give impetus to those models which account for the observed temperature structure of some clusters using mergers instead of cooling flows.
The Noble-Abel Stiffened-Gas equation of state
NASA Astrophysics Data System (ADS)
Le Métayer, Olivier; Saurel, Richard
2016-04-01
Hyperbolic two-phase flow models have shown excellent ability for the resolution of a wide range of applications ranging from interfacial flows to fluid mixtures with several velocities. These models account for waves propagation (acoustic and convective) and consist in hyperbolic systems of partial differential equations. In this context, each phase is compressible and needs an appropriate convex equation of state (EOS). The EOS must be simple enough for intensive computations as well as boundary conditions treatment. It must also be accurate, this being challenging with respect to simplicity. In the present approach, each fluid is governed by a novel EOS named "Noble Abel stiffened gas," this formulation being a significant improvement of the popular "Stiffened Gas (SG)" EOS. It is a combination of the so-called "Noble-Abel" and "stiffened gas" equations of state that adds repulsive effects to the SG formulation. The determination of the various thermodynamic functions and associated coefficients is the aim of this article. We first use thermodynamic considerations to determine the different state functions such as the specific internal energy, enthalpy, and entropy. Then we propose to determine the associated coefficients for a liquid in the presence of its vapor. The EOS parameters are determined from experimental saturation curves. Some examples of liquid-vapor fluids are examined and associated parameters are computed with the help of the present method. Comparisons between analytical and experimental saturation curves show very good agreement for wide ranges of temperature for both liquid and vapor.
ERIC Educational Resources Information Center
Grimm, C. A.
This document contains two units that examine integral transforms and series expansions. In the first module, the user is expected to learn how to use the unified method presented to obtain Laplace transforms, Fourier transforms, complex Fourier series, real Fourier series, and half-range sine series for given piecewise continuous functions. In…
Brig. Gen. Richard F. Abel and Col. Natan J. Lindsay answering questions
NASA Technical Reports Server (NTRS)
1982-01-01
Brigadier General Richard F. Abel, right, director of public affairs for the Air Force, and Colonel Nathan J. Lindsay of the USAF's space division, answer questions concerning STS-4 during a press conference at JSC on May 20, 1982.
Giant ringlike radio structures around galaxy cluster Abell 3376.
Bagchi, Joydeep; Durret, Florence; Neto, Gastão B Lima; Paul, Surajit
2006-11-03
In the current paradigm of cold dark matter cosmology, large-scale structures are assembling through hierarchical clustering of matter. In this process, an important role is played by megaparsec (Mpc)-scale cosmic shock waves, arising in gravity-driven supersonic flows of intergalactic matter onto dark matter-dominated collapsing structures such as pancakes, filaments, and clusters of galaxies. Here, we report Very Large Array telescope observations of giant ( approximately 2 Mpc by 1.6 Mpc), ring-shaped nonthermal radio-emitting structures, found at the outskirts of the rich cluster of galaxies Abell 3376. These structures may trace the elusive shock waves of cosmological large-scale matter flows, which are energetic enough to power them. These radio sources may also be the acceleration sites where magnetic shocks are possibly boosting cosmic-ray particles with energies of up to 10(18) to 10(19) electron volts.
Comparison of four stable numerical methods for Abel's integral equation
NASA Technical Reports Server (NTRS)
Murio, Diego A.; Mejia, Carlos E.
1991-01-01
The 3-D image reconstruction from cone-beam projections in computerized tomography leads naturally, in the case of radial symmetry, to the study of Abel-type integral equations. If the experimental information is obtained from measured data, on a discrete set of points, special methods are needed in order to restore continuity with respect to the data. A new combined Regularized-Adjoint-Conjugate Gradient algorithm, together with two different implementations of the Mollification Method (one based on a data filtering technique and the other on the mollification of the kernal function) and a regularization by truncation method (initially proposed for 2-D ray sample schemes and more recently extended to 3-D cone-beam image reconstruction) are extensively tested and compared for accuracy and numerical stability as functions of the level of noise in the data.
Ram pressure induced star formation in Abell 3266
NASA Astrophysics Data System (ADS)
Bonsall, Brittany
An X-ray observation of the merging galaxy cluster Abell 3266 was obtained via the ROSAT PSPC. This information, along with spectroscopic data from the WIde-field Nearby Galaxy-clusters Survey (i.e. WINGS), were used to investigate whether ram pressure is a mechanism that influences star formation. Galaxies exhibiting ongoing star formation are identified by the presence of strong Balmer lines (Hbeta), known to correspond to early type stars. Older galaxies where a rapid increase in star formation has recently ceased, known as E+A galaxies, are identified by strong Hbeta absorption coupled with little to no [OII] emission. The correlation between recent star formation and "high" ram pressure, as defined by Kapferer et al. (2009) as ≥ 5 x 10-11 dyn cm-2, was tested and lead to a contradiction of the previously held belief that ram pressure influences star formation on the global cluster scale.
ABEL description and implementation of cyber net system
NASA Astrophysics Data System (ADS)
Lu, Jiyuan; Jing, Liang
2013-03-01
Cyber net system is a subclass of Petri Nets. It has more powerful description capability and more complex properties compared with P/T system. Due to its nonlinear relation, it can't use analysis techniques of other net systems directly. This influences the research on cyber net system. In this paper, the author uses hardware description language to describe cyber net system. Simulation analysis is carried out through EDA software tools to disclose properties of the system. This method is introduced in detail through cyber net system model of computing Fibonacci series. ABEL source codes and simulation wave are also presented. The source codes are compiled, optimized, fit design and downloaded to the Programmable Logic Device. Thus ASIC of computing Fibonacci series is obtained. It will break a new path for the analysis and application study of cyber net system.
The distribution of dark and luminous matter in the unique galaxy cluster merger Abell 2146
NASA Astrophysics Data System (ADS)
King, Lindsay J.; Clowe, Douglas I.; Coleman, Joseph E.; Russell, Helen R.; Santana, Rebecca; White, Jacob A.; Canning, Rebecca E. A.; Deering, Nicole J.; Fabian, Andrew C.; Lee, Brandyn E.; Li, Baojiu; McNamara, Brian R.
2016-06-01
Abell 2146 (z = 0.232) consists of two galaxy clusters undergoing a major merger. The system was discovered in previous work, where two large shock fronts were detected using the Chandra X-ray Observatory, consistent with a merger close to the plane of the sky, caught soon after first core passage. A weak gravitational lensing analysis of the total gravitating mass in the system, using the distorted shapes of distant galaxies seen with Advanced Camera for Surveys - Wide Field Channel on Hubble Space Telescope, is presented. The highest peak in the reconstruction of the projected mass is centred on the brightest cluster galaxy (BCG) in Abell 2146-A. The mass associated with Abell 2146-B is more extended. Bootstrapped noise mass reconstructions show the mass peak in Abell 2146-A to be consistently centred on the BCG. Previous work showed that BCG-A appears to lag behind an X-ray cool core; although the peak of the mass reconstruction is centred on the BCG, it is also consistent with the X-ray peak given the resolution of the weak lensing mass map. The best-fitting mass model with two components centred on the BCGs yields M200 = 1.1^{+0.3}_{-0.4} × 1015 and 3^{+1}_{-2} × 1014 M⊙ for Abell 2146-A and Abell 2146-B, respectively, assuming a mass concentration parameter of c = 3.5 for each cluster. From the weak lensing analysis, Abell 2146-A is the primary halo component, and the origin of the apparent discrepancy with the X-ray analysis where Abell 2146-B is the primary halo is being assessed using simulations of the merger.
GHRS observations of mass-loaded flows in Abell 78
NASA Technical Reports Server (NTRS)
Harrington, J. Patrick; Borkowski, Kazimierz J.; Tsvetanov, Zlatan
1995-01-01
Spectroscopic observations of the central star of the planetary nebula Abell 78 were obtained with the Goddard High Resolution Spectrograph (GHRS) onboard the Hubble Space Telescope (HST) in the vicinity of the C IV lambda 1548.2, 1550.8 doublet. We find a series of narrow absorption features superposed on the broad, P Cygni stellar wind profile. These features are seen in both components of the doublet at heliocentric radial velocities of -18, -71, -131, and -192 km/s. At higher velocities, individual components are no longer distinct but, rather, merge into a continuous absorption extending to approximately -385 km/s. This is among the highest velocities ever detected for gas in a planetary nebula. The -18 km/s feature originates in an outer envelope of normal composition, while the -71 km/s feature is produced in the wind-swept shell encircling an irregular wind-blown bubble in the planetary nebula center. The hydrogen-poor ejecta of Abell 78, consisting of dense knots with wind-blown tails, are located in the bubble's interior, in the vicinity of the stellar wind termination shock. The high-velocity C IV lambda 154 absorption features can be explained as due to parcels of ejecta being accelerated to high velocities as they are swept up by the stellar wind during its interaction with dense condensations of H-poor ejecta. As the ablated material is accelerated, it will partially mix with the stellar wind, creating a mass-loaded flow. The abundance anomalies seen at the rim of the bubble attest to the transport of H-poor knot material by such a flow.
Dirken, J J; Vlaanderen, W
1994-01-01
Inversion of the uterus is a rare complication of childbirth. A primigravida aged 21 and a multigravida aged 32, hospitalized as emergency cases because of inversion of the uterus with major blood loss, were treated with infusion of liquids (to combat shock), repositioning of the uterus under anaesthesia and prevention of reinversion by uterine tonics. Inversion of the uterus should be part of the differential diagnosis in every case of fluxus post partum.
Mass, velocity anisotropy, and pseudo phase-space density profiles of Abell 2142
NASA Astrophysics Data System (ADS)
Munari, E.; Biviano, A.; Mamon, G. A.
2014-06-01
Aims: We aim to compute the mass and velocity anisotropy profiles of Abell 2142 and, from there, the pseudo phase-space density profile Q(r) and the density slope - velocity anisotropy β - γ relation, and then to compare them with theoretical expectations. Methods: The mass profiles were obtained by using three techniques based on member galaxy kinematics, namely the caustic method, the method of dispersion-kurtosis, and MAMPOSSt. Through the inversion of the Jeans equation, it was possible to compute the velocity anisotropy profiles. Results: The mass profiles, as well as the virial values of mass and radius, computed with the different techniques agree with one another and with the estimates coming from X-ray and weak lensing studies. A combined mass profile is obtained by averaging the lensing, X-ray, and kinematics determinations. The cluster mass profile is well fitted by an NFW profile with c = 4.0 ± 0.5. The population of red and blue galaxies appear to have a different velocity anisotropy configuration, since red galaxies are almost isotropic, while blue galaxies are radially anisotropic, with a weak dependence on radius. The Q(r) profile for the red galaxy population agrees with the theoretical results found in cosmological simulations, suggesting that any bias, relative to the dark matter particles, in velocity dispersion of the red component is independent of radius. The β - γ relation for red galaxies matches the theoretical relation only in the inner region. The deviations might be due to the use of galaxies as tracers of the gravitational potential, unlike the non-collisional tracer used in the theoretical relation.
An optical view of the filament region of Abell 85
NASA Astrophysics Data System (ADS)
Boué, G.; Durret, F.; Adami, C.; Mamon, G. A.; Ilbert, O.; Cayatte, V.
2008-10-01
Aims: We present an optical investigation of the Abell 85 cluster filament (z = 0.055) previously interpreted in X-rays as groups falling on to the main cluster. We compare the distribution of galaxies with the X-ray filament, and investigate the galaxy luminosity functions in several bands and in several regions. We search for galaxies where star formation may have been triggered by interactions with intracluster gas or tidal pressure due to the cluster potential when entering the cluster. Methods: Our analysis is based on images covering the South tip of Abell 85 and its infalling filament, obtained with CFHT MegaPrime/MegaCam (1×1 deg2 field) in four bands (u^*, g', r', i') and ESO 2.2 m WFI (38×36 arcmin2 field) in a narrow band filter corresponding to the redshifted Hα line and in an RC broad band filter. The LFs are estimated by statistically subtracting a reference field. Background contamination is minimized by cutting out galaxies redder than the observed red sequence in the g'-i' versus i' colour-magnitude diagram. Results: The galaxy distribution shows a significantly flattened cluster, whose principal axis is slightly offset from the X-ray filament. The analysis of the broad band galaxy luminosity functions shows that the filament region is well populated. The filament is also independently detected as a gravitationally bound structure by the Serna & Gerbal (1996, A&A, 309, 65) hierarchical method. 101 galaxies are detected in the Hα filter, among which 23 have spectroscopic redshifts in the cluster, 2 have spectroscopic redshifts higher than the cluster and 58 have photometric redshifts that tend to indicate that they are background objects. One galaxy that is not detected in the Hα filter probably because of the filter low wavelength cut but shows Hα emission in its SDSS spectrum in the cluster redshift range has been added to our sample. The 24 galaxies with spectroscopic redshifts in the cluster are mostly concentrated in the South part of the
The merging cluster of galaxies Abell 3376: an optical view
NASA Astrophysics Data System (ADS)
Durret, F.; Perrot, C.; Lima Neto, G. B.; Adami, C.; Bertin, E.; Bagchi, J.
2013-12-01
Context. The cluster Abell 3376 is a merging cluster of galaxies at redshift z = 0.046. It is famous mostly for its giant radio arcs, and shows an elongated and highly substructured X-ray emission, but has not been analysed in detail at optical wavelengths. Aims: To improve our understanding of the effects of the major cluster merger on the galaxy properties, we analyse the galaxy luminosity function (GLF) in the B band in several regions as well as the dynamical properties of the substructures. Methods: We have obtained wide field images of Abell 3376 in the B band and derive the GLF applying a statistical subtraction of the background in three regions: a circle of 0.29 deg radius (1.5 Mpc) encompassing the whole cluster, and two circles centred on each of the two brightest galaxies (BCG2, northeast, coinciding with the peak of X-ray emission, and BCG1, southwest) of radii 0.15 deg (0.775 Mpc). We also compute the GLF in the zone around BCG1, which is covered by the WINGS survey in the B and V bands, by selecting cluster members in the red sequence in a (B - V) versus V diagram. Finally, we discuss the dynamical characteristics of the cluster implied by an analysis based on the Serna & Gerbal (SG) method. Results: The GLFs are not well fit by a single Schechter function, but satisfactory fits are obtained by summing a Gaussian and a Schechter function. The GLF computed by selecting galaxies in the red sequence in the region surrounding BCG1 can also be fit by a Gaussian plus a Schechter function. An excess of galaxies in the brightest bins is detected in the BCG1 and BCG2 regions. The dynamical analysis based on the SG method shows the existence of a main structure of 82 galaxies that can be subdivided into two main substructures of 25 and six galaxies. A smaller structure of six galaxies is also detected. Conclusions: The B band GLFs of Abell 3376 are clearly perturbed, as already found in other merging clusters. The dynamical properties are consistent with the
NASA Technical Reports Server (NTRS)
Kastner, S. O.; Rothe, E. D.; Neupert, W. M.
1976-01-01
Intensities of Fe XIV and Fe XIII EUV emission lines obtained at coronal locations beyond the limb by the Goddard spectroheliograph on the OSO 7 satellite have been corrected for the wavelength dependence of the instrument's sensitivity and have been Abel-inverted to provide a valid comparison with theoretical predictions for each ion. Details of the Abel-inversion procedure are given, including explicit formulas for application of Bracewell's (1956) method. The intensity ratios of pairs of lines originating from a common level are compared with expected theoretical transition probability ratios over a range of heliocentric distance; deviations in some cases yield information about adjacent unclassified lines. Comparison of the observations with predictions for Fe XIV and Fe XIII shows generally good agreement, with a few interesting discrepancies that may imply a corresponding need for more accurate collisional excitation cross sections. The same comparison yields the variation of electron density with heliocentric radius for each ion separately; the two density functions are found to agree within a factor of three.
The merging cluster Abell 1758: an optical and dynamical view
NASA Astrophysics Data System (ADS)
Monteiro-Oliveira, Rogerio; Serra Cypriano, Eduardo; Machado, Rubens; Lima Neto, Gastao B.
2015-08-01
The galaxy cluster Abell 1758-North (z=0.28) is a binary system composed by the sub-structures NW and NE. This is supposed to be a post-merging cluster due to observed detachment between the NE BCG and the respective X-ray emitting hot gas clump in a scenario very close to the famous Bullet Cluster. On the other hand, the projected position of the NW BCG coincides with the local hot gas peak. This system was been targeted previously by several studies, using multiple wavelengths and techniques, but there is still no clear picture of the scenario that could have caused this unusual configuration. To help solving this complex puzzle we added some pieces: firstly, we have used deep B, RC and z' Subaru images to perform both weak lensing shear and magnification analysis of A1758 (including here the South component that is not in interaction with A1758-North) modeling each sub-clump as an NFW profile in order to constrain masses and its center positions through MCMC methods; the second piece is the dynamical analysis using radial velocities available in the literature (143) plus new Gemini-GMOS/N measurements (68 new redshifts).From weak lensing we found that independent shear and magnification mass determinations are in excellent agreement between them and combining both we could reduce mass error bar by ~30% compared to shear alone. By combining this two weak-lensing probes we found that the position of both Northern BCGs are consistent with the masses centers within 2σ and and the NE hot gas peak to be offseted of the respective mass peak (M200=5.5 X 1014 M⊙) with very high significance. The most massive structure is NW (M200=7.95 X 1014 M⊙ ) where we observed no detachment between gas, DM and BCG.We have calculated a low line-of-sight velocity difference (<300 km/s) between A1758 NW and NE. We have combined it with the projected velocity of 1600 km/s which was estimated by previous X-ray analysis (David & Kempner 2004) and we have obtained a small angle between
The planetary nebula Abell 48 and its [WN] nucleus
NASA Astrophysics Data System (ADS)
Frew, David J.; Bojičić, I. S.; Parker, Q. A.; Stupar, M.; Wachter, S.; DePew, K.; Danehkar, A.; Fitzgerald, M. T.; Douchin, D.
2014-05-01
We have conducted a detailed multi-wavelength study of the peculiar nebula Abell 48 and its central star. We classify the nucleus as a helium-rich, hydrogen-deficient star of type [WN4-5]. The evidence for either a massive WN or a low-mass [WN] interpretation is critically examined, and we firmly conclude that Abell 48 is a planetary nebula (PN) around an evolved low-mass star, rather than a Population I ejecta nebula. Importantly, the surrounding nebula has a morphology typical of PNe, and is not enriched in nitrogen, and thus not the `peeled atmosphere' of a massive star. We estimate a distance of 1.6 kpc and a reddening, E(B - V) = 1.90 mag, the latter value clearly showing the nebula lies on the near side of the Galactic bar, and cannot be a massive WN star. The ionized mass (˜0.3 M⊙) and electron density (700 cm-3) are typical of middle-aged PNe. The observed stellar spectrum was compared to a grid of models from the Potsdam Wolf-Rayet (PoWR) grid. The best-fitting temperature is 71 kK, and the atmospheric composition is dominated by helium with an upper limit on the hydrogen abundance of 10 per cent. Our results are in very good agreement with the recent study of Todt et al., who determined a hydrogen fraction of 10 per cent and an unusually large nitrogen fraction of ˜5 per cent. This fraction is higher than any other low-mass H-deficient star, and is not readily explained by current post-AGB models. We give a discussion of the implications of this discovery for the late-stage evolution of intermediate-mass stars. There is now tentative evidence for two distinct helium-dominated post-AGB lineages, separate to the helium- and carbon-dominated surface compositions produced by a late thermal pulse. Further theoretical work is needed to explain these recent discoveries.
The Sunyaev-Zeldovich Effect in Abell 370
NASA Technical Reports Server (NTRS)
Grego, Laura; Carlstrom, John E.; Joy, Marshall K.; Reese, Erik D.; Holder, Gilbert P.; Patel, Sandeep; Cooray, Asantha R.; Holzappel, William L.
2000-01-01
We present interferometric measurements of the Sunyaev-Zeldovich (SZ) effect toward the galaxy cluster Abell 370. These measurements, which directly probe the pressure of the cluster's gas, show the gas distribution to be strongly aspherical, as do the X-ray and gravitational lensing observations. We calculate the cluster's gas mass fraction in two ways. We first compare the gas mass derived from the SZ measurements to the lensing-derived gravitational mass near the critical lensing radius. We also calculate the gas mass fraction from the SZ data by deprojecting the three-dimensional gas density distribution and deriving the total mass under the assumption that the gas is in hydrostatic equilibrium (HSE). We test the assumptions in the HSE method by comparing the total cluster mass implied by the two methods and find that they agree within the errors of the measurement. We discuss the possible system- atic errors in the gas mass fraction measurement and the constraints it places on the matter density parameter, Omega(sub M).
ABELL 1201: A MINOR MERGER AT SECOND CORE PASSAGE
Ma Chengjiun; Nulsen, Paul E. J.; McNamara, Brian R.; Murray, Stephen S.; Owers, Matt; Couch, Warrick J.
2012-06-20
We present an analysis of the structures and dynamics of the merging cluster Abell 1201, which has two sloshing cold fronts around a cooling core, and an offset gas core approximately 500 kpc northwest of the center. New Chandra and XMM-Newton data reveal a region of enhanced brightness east of the offset core, with breaks in surface brightness along its boundary to the north and east. This is interpreted as a tail of gas stripped from the offset core. Gas in the offset core and the tail is distinguished from other gas at the same distance from the cluster center chiefly by having higher density, hence lower entropy. In addition, the offset core shows marginally lower temperature and metallicity than the surrounding area. The metallicity in the cool core is high and there is an abrupt drop in metallicity across the southern cold front. We interpret the observed properties of the system, including the placement of the cold fronts, the offset core, and its tail in terms of a simple merger scenario. The offset core is the remnant of a merging subcluster, which first passed pericenter southeast of the center of the primary cluster and is now close to its second pericenter passage, moving at {approx_equal} 1000 km s{sup -1}. Sloshing excited by the merger gave rise to the two cold fronts and the disposition of the cold fronts reveals that we view the merger from close to the plane of the orbit of the offset core.
A series of shocks and edges in Abell 2219
NASA Astrophysics Data System (ADS)
Canning, R. E. A.; Allen, S. W.; Applegate, D. E.; Kelly, P. L.; von der Linden, A.; Mantz, A.; Million, E.; Morris, R. G.; Russell, H. R.
2017-01-01
We present deep, 170 ks, Chandra X-ray observations of Abell 2219 (z = 0.23), one of the hottest and most X-ray luminous clusters known, and which is experiencing a major merger event. We discover a `horseshoe' of high-temperature gas surrounding the ram-pressure-stripped, bright, hot, X-ray cores. We confirm an X-ray shock front located north-west of the X-ray centroid and along the projected merger axis. We also find a second shock front to the south-east of the X-ray centroid making this only the second cluster where both the shock and reverse shock are confirmed with X-ray temperature measurements. We also present evidence for a possible sloshing cold front in the `remnant tail' of one of the sub-cluster cores. The cold front and north-west shock front geometrically bound the radio halo and appear to be directly influencing the radio properties of the cluster.
Chandra Observations of Point Sources in Abell 2255
NASA Technical Reports Server (NTRS)
Davis, David S.; Miller, Neal A.; Mushotzky, Richard F.
2003-01-01
In our search for "hidden" AGN we present results from a Chandra observation of the nearby cluster Abell 2255. Eight cluster galaxies are associated with point-like X-ray emission, and we classify these galaxies based on their X-ray, radio, and optical properties. At least three are associated with active galactic nuclei (AGN) with no optical signatures of nuclear activity, with a further two being potential AGN. Of the potential AGN, one corresponds to a galaxy with a post-starburst optical spectrum. The remaining three X-ray detected cluster galaxies consist of two starbursts and an elliptical with luminous hot gas. Of the eight cluster galaxies five are associated with luminous (massive) galaxies and the remaining three lie in much lower luminosity systems. We note that the use of X-ray to optical flux ratios for classification of X-ray sources is often misleading, and strengthen the claim that the fraction of cluster galaxies hosting an AGN based on optical data is significantly lower than the fraction based on X-ray and radio data.
Detection of a radio bridge in Abell 3667
NASA Astrophysics Data System (ADS)
Carretti, E.; Brown, S.; Staveley-Smith, L.; Malarecki, J. M.; Bernardi, G.; Gaensler, B. M.; Haverkorn, M.; Kesteven, M. J.; Poppi, S.
2013-04-01
We have detected a radio bridge of unpolarized synchrotron emission connecting the NW relic of the galaxy cluster Abell 3667 to its central regions. We used data at 2.3 GHz from the S-band Polarization All Sky Survey and at 3.3 GHz from a follow-up observation, both conducted with the Parkes radio telescope. This emission is further aligned with a diffuse X-ray tail, and represents the most compelling evidence for an association between intracluster medium turbulence and diffuse synchrotron emission. This is the first clear detection of a bridge associated both with an outlying cluster relic and X-ray diffuse emission. All the indicators point towards the synchrotron bridge being related to the post-shock turbulent wake trailing the shock front generated by a major merger in a massive cluster. Although predicted by simulations, this is the first time such emission is detected with high significance and clearly associated with the path of a confirmed shock. Although the origin of the relativistic electrons is still unknown, the turbulent re-acceleration model provides a natural explanation for the large-scale emission. The equipartition magnetic field intensity of the bridge is Beq = 2.2 ± 0.3 μG. We further detect diffuse emission coincident with the central regions of the cluster for the first time.
A shock at the radio relic position in Abell 115
NASA Astrophysics Data System (ADS)
Botteon, A.; Gastaldello, F.; Brunetti, G.; Dallacasa, D.
2016-07-01
We analysed a deep Chandra observation (334 ks) of the galaxy cluster Abell 115 and detected a shock cospatial with the radio relic. The X-ray surface brightness profile across the shock region presents a discontinuity, corresponding to a density compression factor C=2.0± 0.1, leading to a Mach number M=1.7± 0.1 (M=1.4-2 including systematics). Temperatures measured in the upstream and downstream regions are consistent with what expected for such a shock: Tu=4.3+1.0-0.6 keV and Td=7.9+1.4-1.1 keV, respectively, implying a Mach number M=1.8+0.5-0.4. So far, only few other shocks discovered in galaxy clusters are consistently detected from both density and temperature jumps. The spatial coincidence between this discontinuity and the radio relic edge strongly supports the view that shocks play a crucial role in powering these synchrotron sources. We suggest that the relic is originated by shock re-acceleration of relativistic electrons rather than acceleration from the thermal pool. The position and curvature of the shock and the associated relic are consistent with an off-axis merger with unequal mass ratio where the shock is expected to bend around the core of the less massive cluster.
Shedding light on the matter of Abell 781
NASA Astrophysics Data System (ADS)
Wittman, D.; Dawson, William; Benson, Bryant
2014-02-01
The galaxy cluster Abell 781 West has been viewed as a challenge to weak gravitational lensing mass calibration, as Cook & dell'Antonio found that the weak lensing signal-to-noise ratio in three independent sets of observations was consistently lower than expected from mass models based on X-ray and dynamical measurements. We correct some errors in statistical inference in Cook & dell'Antonio and show that their own results agree well with the dynamical mass and exhibit at most 2.2-2.9σ low compared to the X-ray mass, similar to the tension between the dynamical and X-ray masses. Replacing their simple magnitude cut with weights based on source photometric redshifts eliminates the tension between lensing and X-ray masses; in this case the weak lensing mass estimate is actually higher than, but still in agreement with, the dynamical estimate. A comparison of lensing analyses with and without photometric redshifts shows that a 1-2σ chance alignment of low-redshift sources lowers the signal-to-noise ratio observed by all previous studies which used magnitude cuts rather than photometric redshifts. The fluctuation is unexceptional, but appeared to be highly significant in Cook & dell'Antonio due to the errors in statistical interpretation.
The Sunyaev-Zel'dovich Effect Spectrum of Abell 2163
NASA Technical Reports Server (NTRS)
LaRoque, S. J.; Carlstrom, J. E.; Reese, E. D.; Holder, G. P.; Holzapfel, W. L.; Joy, M.; Grego, L.; Six, N. Frank (Technical Monitor)
2002-01-01
We present an interferometric measurement of the Sunyaev-Zel'dovich effect (SZE) at 1 cm for the galaxy cluster Abell 2163. We combine this data point with previous measurements at 1.1, 1.4, and 2.1 mm from the SuZIE experiment to construct the most complete SZE spectrum to date. The intensity in four wavelength bands is fit to determine the Compton y-parameter (y(sub 0)) and the peculiar velocity (v(sub p)) for this cluster. Our results are y(sub 0) = 3.56((sup +0.41+0.27)(sub -0.41-0.19)) X 10(exp -4) and v(sub p) = 410((sup +1030+460) (sub -850-440)) km s(exp -1) where we list statistical and systematic uncertainties, respectively, at 68% confidence. These results include corrections for contamination by Galactic dust emission. We find less contamination by dust emission than previously reported. The dust emission is distributed over much larger angular scales than the cluster signal and contributes little to the measured signal when the details of the SZE observing strategy are taken into account.
Linking star formation and galaxy kinematics in the massive cluster Abell 2163
NASA Astrophysics Data System (ADS)
Menacho, Veronica; Verdugo, Miguel
2015-02-01
The origin of the morphology-density relation is still an open question in galaxy evolution. It is most likely driven by the combination of the efficient star formation in the highest peaks of the mass distribution at high-z and the transformation by environmental processes at later times as galaxies fall into more massive halos. To gain additional insights about these processes we study the kinematics, star formation and structural properties of galaxies in Abell 2163 a very massive (~4×1015 M⊙, Holz & Perlmutter 2012) merging cluster at z = 0.2. We use high resolution spectroscopy with VLT/VIMOS to derive rotation curves and dynamical masses for galaxies that show regular kinematics. Galaxies that show irregular rotation are also analysed to study the origin of their distortion. This information is combined with stellar masses and structural parameters obtained from high quality CFHT imaging. From narrow band photometry (2.2m/WFI), centered on the redshifted Hα line, we obtain star formation rates. Although our sample is still small, field and cluster galaxies lie in a similar Tully-Fisher relation as local galaxies. Controlling by additional parameters like SFRs or bulge-to-disk ratio do not affect this result. We find however that ~50% of the cluster galaxies display irregular kinematics in contrast to what is found in the field at similar redshifts (~30%, Böhm et al. 2004) and in agreement with other studies in clusters (e.g. Bösch et al. 2013, Kutdemir et al. 2010) which points out to additional processes operating in clusters that distort the galaxy kinematics.
Strzemiecka, B; Voelkel, A; Zięba-Palus, J; Lachowicz, T
2014-09-12
The chemical changes occurring in the phenol-formaldehyde resins (resol and novolac type) during their storage were investigated. In this paper the FT-IR, py-GCMS and inverse gas chromatography methods were applied for assessment of the changes occurring during storage of the phenolic resins. We have found that during storage some examined resins occurred partial curing. The results from all techniques applied are consistent. Py-GCMS is useful technique for screening the storage processes but IGC seems to be most sensitive one.
Narrow-angle tail radio sources and the distribution of galaxy orbits in Abell clusters
NASA Technical Reports Server (NTRS)
O'Dea, Christopher P.; Sarazin, Craig L.; Owen, Frazer N.
1987-01-01
The present data on the orientations of the tails with respect to the cluster centers of a sample of 70 narrow-angle-tail (NAT) radio sources in Abell clusters show the distribution of tail angles to be inconsistent with purely radial or circular orbits in all the samples, while being consistent with isotropic orbits in (1) the whole sample, (2) the sample of NATs far from the cluster center, and (3) the samples of morphologically regular Abell clusters. Evidence for very radial orbits is found, however, in the sample of NATs near the cluster center. If these results can be generalized to all cluster galaxies, then the presence of radial orbits near the center of Abell clusters suggests that violent relaxation may not have been fully effective even within the cores of the regular clusters.
Bubbles and B-Flats: A Deep Observation of Abell 2052
NASA Astrophysics Data System (ADS)
Blanton, Elizabeth
2004-09-01
The cooling flow cluster Abell 2052 has, arguably, the morphology most similar to the Perseus cluster as seen with Chandra images. Two clear bubbles to the N and S of the center of Abell 2052 are filled with the radio lobes associated with 3C 317. An unsharp-masked image reveals faint ripple features similar to those seen in the Perseus cluster which may represent the propagation of sound waves into the cluster from the radio source. We propose to observe Abell 2052 much more deeply to study the ripple features, search for ghost bubbles, search for cooling gas in the bright shells around the radio source that may link the X-ray and H-alpha emission, detect hot gas within the X-ray holes, and directly compare the star formation and cooling rates in the cluster center.
New machine-readable version of Abell catalog of clusters of galaxies
NASA Astrophysics Data System (ADS)
Kalinkov, M.; Stavrev, K. Y.; Kuneva, I. F.
An improved version of the magnetic-tape catalog of Abell and Zwicky clusters of galaxies (Kalinkov et al., 1976) is briefly characterized, with an emphasis on the distance-calibration and homogenization techniques employed in its compilation. The distance calibration is improved by performing regression analyses on clusters of known Bautz-Morgan type; parameter and standard-deviation values are presented in a table. Selection effects are investigated, and it is shown that the increase in absolute magnitude estimates with distance is less pronounced for the values based on the photored magnitude of the first-rank galaxy (Leir and van den Bergh, 1977) than for those determined by Abell (1958).
Angular cross-relations of Abell clusters in different distance classes
NASA Technical Reports Server (NTRS)
Szalay, A. S.; Hollosi, J.; Toth, G.
1989-01-01
The angular autocorrelation and cross-correlation functions of the D = 1 ... 4, D = 5, and D = 6 distance class Abell clusters are estimated. There is a strong anticorrelation between the most distant D = 6 and the closest D = 1 ... 4 subsamples. It is suggested that an artifact of the cluster identification process presumably due to the finite angular size of the cluster. This anticorrelation seems to contradict some recent estimations of projection contaminations in the Abell catalog. The angular proximity of a foreground cluster may have caused a background cluster not to be counted as it was thought to be a subcluster or it was erroneously assigned to a nearer distance class.
The nearby Abell clusters. III - Luminosity functions for eight rich clusters
NASA Technical Reports Server (NTRS)
Oegerle, William R.; Hoessel, John G.
1989-01-01
Red photographic data on eight rich Abell clusters are combined with previous results on four other Abell clusters to study the luminosity functions of the clusters. The results produce a mean value of the characteristic galaxy magnitude (M asterisk) that is consistent with previous results. No relation is found between the magnitude of the first-ranked cluster galaxy and M asterisk, suggesting that the value of M asterisk is not changed by dynamical evolution. The faint ends of the luminosity functions for many of the clusters are quite flat, validating the nonuniversality in the parametrization of Schechter (1976) functions for rich clusters of galaxies.
U(1)-invariant membranes: The geometric formulation, Abel, and pendulum differential equations
Zheltukhin, A. A.; Trzetrzelewski, M.
2010-06-15
The geometric approach to study the dynamics of U(1)-invariant membranes is developed. The approach reveals an important role of the Abel nonlinear differential equation of the first type with variable coefficients depending on time and one of the membrane extendedness parameters. The general solution of the Abel equation is constructed. Exact solutions of the whole system of membrane equations in the D=5 Minkowski space-time are found and classified. It is shown that if the radial component of the membrane world vector is only time dependent, then the dynamics is described by the pendulum equation.
The nearby Abell clusters. III. Luminosity functions for eight rich clusters
Oegerle, W.R.; Hoessel, J.G. Washburn Observatory, Madison, WI )
1989-11-01
Red photographic data on eight rich Abell clusters are combined with previous results on four other Abell clusters to study the luminosity functions of the clusters. The results produce a mean value of the characteristic galaxy magnitude (M asterisk) that is consistent with previous results. No relation is found between the magnitude of the first-ranked cluster galaxy and M asterisk, suggesting that the value of M asterisk is not changed by dynamical evolution. The faint ends of the luminosity functions for many of the clusters are quite flat, validating the nonuniversality in the parametrization of Schechter (1976) functions for rich clusters of galaxies. 40 refs.
The Sunyaev-Zel'dovich Effect in Abell 370
NASA Technical Reports Server (NTRS)
Grego, Laura; Carlstrom, John E.; Joy, Marshall K.; Reese, Erik D.; Holder, Gilbert P.; Patel, Sandeep; Holzapfel, William L.; Cooray, Asantha K.
1999-01-01
We present interferometric measurements of the Sunyaev-Zel'dovich (SZ) effect towards the galaxy cluster Abell 370. These measurements, which directly probe the pressure of the cluster's gas, show the gas is strongly aspherical, on agreement with the morphology revealed by x-ray and gravitational lensing observations. We calculate the cluster's gas mass fraction by comparing the gas mass derived from the SZ measurements to the lensing-derived gravitational mass near the critical lensing radius. We also calculate the gas mass fraction from the SZ data by deriving the total mass under the assumption that the gas is in hydrostatic equilibrium (HSE). We test the assumptions in the HSE method by comparing the total cluster mass implied by the two methods. The Hubble constant derived for this cluster, when the known systematic uncertainties are included, has a very wide range of values and therefore does not provide additional constraints on the validity of the assumptions. We examine carefully the possible systematic errors in the gas fraction measurement. The gas fraction is a lower limit to the cluster's baryon fraction and so we compare the gas mass fraction, calibrated by numerical simulations to approximately the virial radius, to measurements of the global mass fraction of baryonic matter, OMEGA(sub B)/OMEGA(sub matter). Our lower limit to the cluster baryon fraction is f(sub B) = (0.043 +/- 0.014)/h (sub 100). From this, we derive an upper limit to the universal matter density, OMEGA(sub matter) <= 0.72/h(sub 100), and a likely value of OMEGA(sub matter) <= (0.44(sup 0.15, sub -0.12)/h(sub 100).
THE GALAXY POPULATION OF LOW-REDSHIFT ABELL CLUSTERS
Barkhouse, Wayne A.; Yee, H. K. C.; Lopez-Cruz, Omar E-mail: hyee@astro.utoronto.c
2009-10-01
We present a study of the luminosity and color properties of galaxies selected from a sample of 57 low-redshift Abell clusters. We utilize the non-parametric dwarf-to-giant ratio (DGR) and the blue galaxy fraction (f{sub b} ) to investigate the clustercentric radial-dependent changes in the cluster galaxy population. Composite cluster samples are combined by scaling the counting radius by r {sub 200} to minimize radius selection bias. The separation of galaxies into a red and blue population was achieved by selecting galaxies relative to the cluster color-magnitude relation. The DGR of the red and blue galaxies is found to be independent of cluster richness (B {sub gc}), although the DGR is larger for the blue population at all measured radii. A decrease in the DGR for the red and red+blue galaxies is detected in the cluster core region, while the blue galaxy DGR is nearly independent of radius. The f{sub b} is found not to correlate with B {sub gc}; however, a steady decline toward the inner-cluster region is observed for the giant galaxies. The dwarf galaxy f{sub b} is approximately constant with clustercentric radius except for the inner-cluster core region where f{sub b} decreases. The clustercentric radial dependence of the DGR and the galaxy blue fraction indicates that it is unlikely that a simple scenario based on either pure disruption or pure fading/reddening can describe the evolution of infalling dwarf galaxies; both outcomes are produced by the cluster environment.
Deep Westerbork observations of Abell 2256 at 350 MHz
NASA Astrophysics Data System (ADS)
Brentjens, M. A.
2008-10-01
Deep polarimetric Westerbork observations of the galaxy cluster Abell 2256 are presented, covering a frequency range of 325-377 MHz. The central halo source has a diameter of the order of 1.2 Mpc (18´), which is somewhat larger than at 1.4 GHz. With α = -1.61±0.04, the halo spectrum between 1.4 GHz and 22.25 MHz is less steep than previously thought. The centre of the ultra steep spectrum source in the eastern part of the cluster exhibits a spectral break near 400 MHz. It is estimated to be at least 51 million years old, but possibly older than 125 million years. A final measurement requires observations in the 10-150 MHz range. It remains uncertain whether the source is a radio tail of Fabricant galaxy 122, situated in the northeastern tip of the source. Faraday rotation measure synthesis revealed no polarized flux at all in the cluster. The polarization fraction of the brightest parts of the relic area is less than 1%. The RM-synthesis nevertheless revealed 9 polarized sources in the field enabling an accurate measurement of the Galactic Faraday rotation (-33±2 rad m-2 in front of the relic). Based on its depolarization on longer wavelengths, the line-of-sight magnetic field in relic filament G is estimated to be between 0.02 and 2 μG. A value of 0.2 μG appears most reasonable given the currently available data.
Merger shocks in Abell 3667 and the Cygnus A cluster
NASA Astrophysics Data System (ADS)
Sarazin, C. L.; Finoguenov, A.; Wik, D. R.
2013-04-01
We present new XMM-Newton observations of the northwest (NW) radio relic region in the cluster Abell 3667. We detect a jump in the X-ray surface brightness and X-ray temperature at the sharp outer edge of the radio relic which indicate that this is the location of a merger shock with a Mach number of about 2. Comparing the radio emission to the shock properties implies that approximately 0.2% of the dissipated shock kinetic energy goes into accelerating relativistic electrons. This is an order of magnitude smaller than the efficiency of shock acceleration in many Galactic supernova remnants, which may be due to the lower Mach numbers of cluster merger shocks. The X-ray and radio properties indicate that the magnetic field strength in the radio relic is ⪆ 3 μG, which is a very large field at a projected distance of ˜ 2.2 Mpc from the center of a cluster. The radio spectrum is relatively flat at the shock, and steepens dramatically with distance behind the shock. This is consistent with radiative losses by the electrons and the post-shock speed determined from the X-ray properties. The Cygnus A radio source is located in a merging cluster of galaxies. This appears to be an early-stage merger. Our recent Suzaku observation confirm the presence of a hot region between the two subclusters which agrees with the predicted shocked region. The high spectral resolution of the CCDs on Suzaku allowed us to measure the radial component of the merger velocity, Δ v_r ≈ 2650 km s-1.
Aluminum could be transported via phloem in Camellia oleifera Abel.
Zeng, Qi Long; Chen, Rong Fu; Zhao, Xue Qiang; Shen, Ren Fang; Noguchi, Akira; Shinmachi, Fumie; Hasegawa, Isao
2013-01-01
Aluminum (Al) accumulation and long-distance transport in oil tea (Camellia oleifera Abel.), known to be an Al accumulator, was investigated. The average Al concentration in the embryo of oil tea seeds was 389 mg Al kg(-1) dry weight, which was higher than seeds of other Al accumulators. By partially suppressing leaf transpiration in the field, Al accumulation in leaves was depressed, which clarified the importance of xylem transport to Al accumulation in leaves. However, the effects of xylem transport alone could not sufficiently explain the high Al accumulation in the seasons when the leaf transpiration is weak, which hints the necessity of phloem transport working. Aluminum content in phloem exudates of barks provides another evidence of phloem transport. Images from scanning electron microscopy and energy-dispersive analysis also showed that Al was present in the phloem of oil tea petioles. Aluminum in oil tea could also be redistributed: higher concentrations of Al were found in leaves when Al was supplied to a different leaf of the same plant. In addition, Al was present in newly emerging roots of oil tea seedlings in which all original roots were excised prior to treatment, and a positive correlation existed between Al content in the newly formed roots and that in the leaves. The results using the empty seed coat technique showed that Al unloading via the phloem occurred during seed development. In conclusion, the results demonstrated that Al could be redistributed between leaves, from seeds to leaves, leaves to roots and leaves to seeds, which indicates that Al can be transported via the phloem in oil tea.
Discovery of a Star Formation Region in Abell 2052
NASA Astrophysics Data System (ADS)
Martel, André R.; Sparks, William B.; Allen, Mark G.; Koekemoer, Anton M.; Baum, Stefi A.
2002-03-01
We report the discovery of an ultraviolet filament detected in a new Space Telescope Imaging Spectrograph (STIS) NUV-MAMA image of the cD galaxy UGC 9799, located in the cooling-flow cluster Abell 2052 and host to the radio source 3C 317. The filament is ~2 kpc in length and is located at a distance of ~4 kpc from the nucleus along a north-south axis. It consists of three knots embedded along the edges of a diffuse filamentary halo. The northern half of the filament is narrow (~100 pc) and straight while the southern half is bent and more diffuse. The blue color (NUV-V~-2.4) and morphology of the filament are most consistent with a recent episode of star formation (T~5 Myr). Only a few×104 Msolar of young stars or a star formation rate of ~10-3 Msolar yr-1 is required to produce the feature. A steep ultraviolet halo is detected around the unresolved nucleus, and it may be associated with an old stellar component. No ultraviolet features are identified at the location of the extended emission-line nebulae observed from the ground, indicating that OB stars are not the primary source of ionization in these regions. We consider cooling flows and a merger with a satellite galaxy the trigger for the starburst regions and conclude that the latter is the more consistent with the chaotic dust lanes spread throughout the host galaxy. The star formation observed is orders of magnitude less than the inferred cooling rate in the cooling flow scenario. Based on observations made with the NASA/ESA Hubble Space Telescope, which is operated by the Association of Universities for Research in Astronomy, Inc., under NASA contract NAS 5-26555.
NASA Astrophysics Data System (ADS)
Liu, Junjie; Bowman, Kevin W.; Lee, Meemong
2016-11-01
Ensemble Kalman filter (EnKF) and 4D-Variational (4D-Var) are two advanced data assimilation methods that are the basis of numerical weather prediction and have been extensively used in trace gas assimilation and inverse modeling. In this study, we compare 4D-Var and the Local Ensemble Transform Kalman Filter (LETKF), one type of EnKF, in estimating CO2 fluxes with both simulated and real satellite data from Greenhouse gases Observing Satellite (GOSAT) and propose a method to calculate flux changes and flux error reductions from assimilating each observation within the LETKF. The results show that the mean posterior flux accuracy across 11 land regions defined by the Atmospheric Tracer Transport Model Intercomparison Project is comparable between 4D-Var and the LETKF, as shown in the Observing System Simulation Experiment, but the differences between the LETKF and 4D-Var are relatively larger over data sparse regions. We show that this is most likely due to the fact that the observations from a much broader region have impact on flux estimation in 4D-Var than in the LETKF. As a result, the posterior fluxes from 4D-Var are more consistent with the atmospheric CO2 growth rate. We find that the inversion results are less dependent on inversion methods with the increase of observations. With real GOSAT observations, we show that the posterior flux changes in 2011 relative to 2010 are more consistent between these two methods than the absolute estimates.
The mass distribution of the unusual merging cluster Abell 2146 from strong lensing
NASA Astrophysics Data System (ADS)
Coleman, Joseph E.; King, Lindsay J.; Oguri, Masamune; Russell, Helen R.; Canning, Rebecca E. A.; Leonard, Adrienne; Santana, Rebecca; White, Jacob A.; Baum, Stefi A.; Clowe, Douglas I.; Edge, Alastair; Fabian, Andrew C.; McNamara, Brian R.; O'Dea, Christopher P.
2017-01-01
Abell 2146 consists of two galaxy clusters that have recently collided close to the plane of the sky, and it is unique in showing two large shocks on Chandra X-ray Observatory images. With an early stage merger, shortly after first core passage, one would expect the cluster galaxies and the dark matter to be leading the X-ray emitting plasma. In this regard, the cluster Abell 2146-A is very unusual in that the X-ray cool core appears to lead, rather than lag, the brightest cluster galaxy (BCG) in their trajectories. Here we present a strong-lensing analysis of multiple-image systems identified on Hubble Space Telescope images. In particular, we focus on the distribution of mass in Abell 2146-A in order to determine the centroid of the dark matter halo. We use object colours and morphologies to identify multiple-image systems; very conservatively, four of these systems are used as constraints on a lens mass model. We find that the centroid of the dark matter halo, constrained using the strongly lensed features, is coincident with the BCG, with an offset of ≈2 kpc between the centres of the dark matter halo and the BCG. Thus from the strong-lensing model, the X-ray cool core also leads the centroid of the dark matter in Abell 2146-A, with an offset of ≈30 kpc.
A weak-lensing analysis of the Abell 383 cluster
NASA Astrophysics Data System (ADS)
Huang, Z.; Radovich, M.; Grado, A.; Puddu, E.; Romano, A.; Limatola, L.; Fu, L.
2011-05-01
Aims: We use deep CFHT and SUBARU uBVRIz archival images of the Abell 383 cluster (z = 0.187) to estimate its mass by weak-lensing. Methods: To this end, we first use simulated images to check the accuracy provided by our Kaiser-Squires-Broadhurst (KSB) pipeline. These simulations include shear testing programme (STEP) 1 and 2 simulations, as well as more realistic simulations of the distortion of galaxy shapes by a cluster with a Navarro-Frenk-White (NFW) profile. From these simulations we estimate the effect of noise on shear measurement and derive the correction terms. The R-band image is used to derive the mass by fitting the observed tangential shear profile with an NFW mass profile. Photometric redshifts are computed from the uBVRIz catalogs. Different methods for the foreground/background galaxy selection are implemented, namely selection by magnitude, color, and photometric redshifts, and the results are compared. In particular, we developed a semi-automatic algorithm to select the foreground galaxies in the color-color diagram, based on the observed colors. Results: Using color selection or photometric redshifts improves the correction of dilution from foreground galaxies: this leads to higher signals in the inner parts of the cluster. We obtain a cluster mass Mvir = 7.5+2.7_{-1.9 × 1014} M⊙: this value is 20% higher than previous estimates and is more consistent the mass expected from X-ray data. The R-band luminosity function of the cluster is computed and gives a total luminosity Ltot = (2.14 ± 0.5) × 1012 L⊙ and a mass-to-luminosity ratio M/L 300 M⊙/L⊙. Based on: data collected with the Subaru Telescope (University of Tokyo) and obtained from the SMOKA, which is operated by the Astronomy Data Center, National Astronomical Observatory of Japan; observations obtained with MegaPrime/MegaCam, a joint project of CFHT and CEA/DAPNIA, at the Canada-France-Hawaii Telescope (CFHT), which is operated by the National Research Council (NRC) of Canada
MUSE observations of the lensing cluster Abell 1689
NASA Astrophysics Data System (ADS)
Bina, D.; Pelló, R.; Richard, J.; Lewis, J.; Patrício, V.; Cantalupo, S.; Herenz, E. C.; Soto, K.; Weilbacher, P. M.; Bacon, R.; Vernet, J. D. R.; Wisotzki, L.; Clément, B.; Cuby, J. G.; Lagattuta, D. J.; Soucail, G.; Verhamme, A.
2016-05-01
Context. This paper presents the results obtained with the Multi Unit Spectroscopic Explorer (MUSE) for the core of the lensing cluster Abell 1689, as part of MUSE's commissioning at the ESO Very Large Telescope. Aims: Integral-field observations with MUSE provide a unique view of the central 1 × 1 arcmin2 region at intermediate spectral resolution in the visible domain, allowing us to conduct a complete census of both cluster galaxies and lensed background sources. Methods: We performed a spectroscopic analysis of all sources found in the MUSE data cube. Two hundred and eighty-two objects were systematically extracted from the cube based on a guided-and-manual approach. We also tested three different tools for the automated detection and extraction of line emitters. Cluster galaxies and lensed sources were identified based on their spectral features. We investigated the multiple-image configuration for all known sources in the field. Results: Previous to our survey, 28 different lensed galaxies displaying 46 multiple images were known in the MUSE field of view, most of them were detected through photometric redshifts and lensing considerations. Of these, we spectroscopically confirm 12 images based on their emission lines, corresponding to 7 different lensed galaxies between z = 0.95 and 5.0. In addition, 14 new galaxies have been spectroscopically identified in this area thanks to MUSE data, with redshifts ranging between 0.8 and 6.2. All background sources detected within the MUSE field of view correspond to multiple-imaged systems lensed by A1689. Seventeen sources in total are found at z ≥ 3 based on their Lyman-α emission, with Lyman-α luminosities ranging between 40.5 ≲ log (Lyα) ≲ 42.5 after correction for magnification. This sample is particularly sensitive to the slope of the luminosity function toward the faintest end. The density of sources obtained in this survey is consistent with a steep value of α ≤ -1.5, although this result still
NASA Astrophysics Data System (ADS)
Sergienko, Olga
2013-04-01
Since Doug MacAyeal's pioneering studies of the ice-stream basal traction optimizations by control methods, inversions for unknown parameters (e.g., basal traction, accumulation patterns, etc) have become a hallmark of the present-day ice-sheet modeling. The common feature of such inversion exercises is a direct relationship between optimized parameters and observations used in the optimization procedure. For instance, in the standard optimization for basal traction by the control method, ice-stream surface velocities constitute the control data. The optimized basal traction parameters explicitly appear in the momentum equations for the ice-stream velocities (compared to the control data). The inversion for basal traction is carried out by minimization of the cost (or objective, misfit) function that includes the momentum equations facilitated by the Lagrange multipliers. Here, we build upon this idea, and demonstrate how to optimize for parameters indirectly related to observed data using a suite of nested constraints (like Russian dolls) with additional sets of Lagrange multipliers in the cost function. This method opens the opportunity to use data from a variety of sources and types (e.g., velocities, radar layers, surface elevation changes, etc.) in the same optimization process.
Nabais, João-Maria
2008-12-01
Abel Salazar was a true renaissance spirit, scientist, doctor, humanist, artist and writer. His paintings combined realism with a very strong social sense. This article looks at his art and the influence that he had through it on his contemporaries.
2007-02-12
Young University, Department of Mathematics, 292 TMCB, Provo, Utah 84602 USA, rachaelp@byu.net 1 Report Documentation Page Form ApprovedOMB No. 0704...and simulation utilize the same forward measurement operator P , allowing for the possibility of an exact solution, modulo the effects of data noise...solution, modulo the effects of data noise. 13 Table 4: Test Set 2: Object Configurations. Object Materials Edge Locations (cm) 2a [Fe, Teflon, Fe
Inversions. Popular Lectures in Mathematics.
ERIC Educational Resources Information Center
Bakel'man, I. Ya
Inversions are transformations of geometric figures, under which straight lines may be mapped to circles, and conversely. The use of such mapping allows development of a unified method of solution for many of the problems of elementary geometry, especially those concerning constructions and "pencils" of curves. This book discusses the inversion…
An Investigation into the Spectral Imaging of Hall Thruster Plumes
2015-07-01
neutral particles for various thruster operating conditions. Abel inversion analysis was applied to the photographs to examine the emission as a function...neutral parti- cles for various thruster operating conditions. Abel inversion analysis was applied to the photographs to examine the emission as a... inverse Abel transformation. In this study, a 16 bit camera with optical interference bandwidth filters was used to examine the plasma structure of the
Detection of large-scale alignment of Lick counts around Abell clusters
NASA Technical Reports Server (NTRS)
Argyres, P. C.; Groth, E. J.; Peebles, P. J. E.; Struble, M. F.
1986-01-01
The possible tendency of galaxies to be distributed in an aligned fashion, on sheets or filaments, on scales greater than the Abell radius, has been tested by a variety of statistics. The subject remains controversial because the statistical tests have either not been sensitive to the alignment or capable of unambiguously signalling alignment in a general, clumpy distribution of galaxies. The present approach combines ideas of Bingelli (1982) and Fry and Peebles (1980) in an examination of the cross correlation of Lick counts relative to the preferred direction defined by the cluster. This can substantially reduce the noise, and it is suggested on this basis that alignment has been found on large scales for Lick galaxy counts and Abell cluster positions and their angles.
Complete Measurement of S(1D2) Photofragment Alignment from Abel-Invertible Ion Images
NASA Astrophysics Data System (ADS)
Rakitzis, T. Peter; Samartzis, Peter C.; Kitsopoulos, Theofanis N.
2001-09-01
A novel method to measure directly the photofragment alignment from Abel-invertible two-dimensional ion images, as a function of photofragment recoil velocity, is demonstrated for S(1D2) atoms from the photodissociation of carbonyl sulfide at 223 nm. The results are analyzed in terms of coherent and incoherent contributions from two dissociative states, showing that the phase differences of the asymptotic wave functions of the fast and slow recoil-velocity channel are approximately π/2 and 0, respectively.
The extraordinary amount of substructure in the Hubble Frontier Fields cluster Abell 2744
NASA Astrophysics Data System (ADS)
Jauzac, M.; Eckert, D.; Schwinn, J.; Harvey, D.; Baugh, C. M.; Robertson, A.; Bose, S.; Massey, R.; Owers, M.; Ebeling, H.; Shan, H. Y.; Jullo, E.; Kneib, J.-P.; Richard, J.; Atek, H.; Clément, B.; Egami, E.; Israel, H.; Knowles, K.; Limousin, M.; Natarajan, P.; Rexroth, M.; Taylor, P.; Tchernin, C.
2016-12-01
We present a joint optical/X-ray analysis of the massive galaxy cluster Abell 2744 (z = 0.308). Our strong- and weak-lensing analysis within the central region of the cluster, i.e. at R < 1 Mpc from the brightest cluster galaxy, reveals eight substructures, including the main core. All of these dark matter haloes are detected with a significance of at least 5σ and feature masses ranging from 0.5 to 1.4 × 1014 M⊙ within R < 150 kpc. Merten et al. and Medezinski et al. substructures are also detected by us. We measure a slightly higher mass for the main core component than reported previously and attribute the discrepancy to the inclusion of our tightly constrained strong-lensing mass model built on Hubble Frontier Fields data. X-ray data obtained by XMM-Newton reveal four remnant cores, one of them a new detection, and three shocks. Unlike Merten et al., we find all cores to have both dark and luminous counterparts. A comparison with clusters of similar mass in the Millennium XXL simulations yields no objects with as many massive substructures as observed in Abell 2744, confirming that Abell 2744 is an extreme system. We stress that these properties still do not constitute a challenge to Λ cold dark matter, as caveats apply to both the simulation and the observations: for instance, the projected mass measurements from gravitational lensing and the limited resolution of the subhaloes finders. We discuss implications of Abell 2744 for the plausibility of different dark matter candidates and, finally, measure a new upper limit on the self-interaction cross-section of dark matter of σDM < 1.28 cm2 g-1 (68 per cent CL), in good agreement with previous results from Harvey et al.
Spectroscopic observations of the distant cluster of galaxies Abell 370 - A catalogue of 84 spectra
NASA Astrophysics Data System (ADS)
Soucail, G.; Mellier, Y.; Fort, B.; Cailloux, M.
1988-06-01
Spectroscopic and photometric data are presented on 84 objects in the field of the distant cluster of galaxies Abell 370 (z = 0.374) obtained with the multiaperture spectroscopic systems PUMA developed at the Toulouse Observatory for the CFHT and ESO. The redshift and the spectral types as well as CCD photometry in the B and R bands are given with a discussion on the accuracy of the different data and measurements.
Search for post-starburst (E+A) galaxies in the cluster Abell 3266
NASA Astrophysics Data System (ADS)
Zhang, Zhongyu
The objective of this work is to use spectroscopic techniques to further the understanding of the dynamical state of the galaxy cluster Abell 3266. This is a very rich cluster in the southern skies that has been extensively studied by many groups. The cluster shows evidence of a merger of substructure in its midst, but the geometry, dynamics, and age of this merger remain uncertain. Low resolution, fiber spectra of galaxies in Abell 3266 were analyzed and searched for “E+A” (post-starburst) galaxies, from which we selected two candidate “E+A” galaxies for follow-up high-resolution spectroscopy. The 2 candidate galaxies are confirmed as “E+A” galaxies with high-resolution, slit spectra. The ages of these “E+A” galaxies (i.e. time since their starburst occurred) are determined with the method developed by Leonardi & Rose (1996). We find that both galaxies had a major starburst in the past, but they occurred at significantly different epochs. If the starbursts are related to the recent merger history of Abell 3266, instead of being just isolated events, they would indicate that there may have been more than one merger in this cluster in the past 3 Gyr or so. This might explain the rather disparate conclusions that have been obtained in the past about the merger history of this cluster. To compare with other nearby clusters, “E+A” galaxies were also searched for among nearly 2400 galaxies in 26 clusters fields. Only 4 candidates are found. This result is consistent with the general observational fact that there are substantially fewer spectroscopically disturbed galaxies in nearby clusters than in distant clusters. The result is also in quantitative agreement with the findings in the larger, more homogeneous Las Campanas Redshift Survey, confirming the reliability of our identification in Abell 3266. The impact of these statistical analyses on the understanding of galaxy evolution in cluster environment is also discussed.
Gas Sloshing in Abell 2204: Constraining the Properties of the Magnetized Intracluster Medium
NASA Astrophysics Data System (ADS)
Chen, Huanqing; Jones, Christine; Andrade-Santos, Felipe; ZuHone, John A.; Li, Zhiyuan
2017-03-01
The rich galaxy cluster Abell 2204 exhibits edges in its X-ray surface brightness at ∼65 and 35 {kpc} west and east of its center, respectively. The presence of these edges, which were interpreted as sloshing cold fronts, implies that the intracluster medium (ICM) was recently disturbed. We analyze the properties of the ICM using multiple Chandra observations of Abell 2204. We find a density ratio of {n}{in}/{n}{out}=2.05+/- 0.05 and a temperature ratio of {T}{out}/{T}{in}=1.91+/- 0.27 (projected, or 1.87 ± 0.56 deprojected) across the western edge, and correspondingly {n}{in}/{n}{out}=1.96+/- 0.05 and {T}{out}/{T}{in}=1.45+/- 0.15 (projected, or 1.25 ± 0.26 deprojected) across the eastern edge. These values are typical of cold fronts in galaxy clusters. This, together with the spiral pattern observed in the cluster core, supports the sloshing scenario for Abell 2204. No Kelvin–Helmholtz eddies are observed along the cold front surfaces, indicating that they are effectively suppressed by some physical mechanism. We argue that the suppression is likely facilitated by the magnetic fields amplified in the sloshing motion and deduce from the measured gas properties that the magnetic field strength should be greater than 24 ± 6 μG and 32 ± 8 μG along the west and east cold fronts, respectively.
On the Evolutionary Status of the Early-type Galaxy Population in Abell 2390
NASA Astrophysics Data System (ADS)
Fritz, Alexander; Ziegler, Bodo L.; Bower, Richard G.; Smail, Ian; Davies, Roger L.
2003-08-01
Using a combination of Multi-Object-Spectroscopy (MOS) with MOSCA at the 3.5m telescope on Calar Alto Observatory, deep ground-based imaging with the 5.1m Hale telescope at Palomar Observatory and HST observations in the F555W (B) and F814W (I) filters, a large sample of N=51 early-type galaxies in the rich cluster Abell 2390 at a redshift z=0.23 is investigated. Our study spans both a broad range in luminosity (-19.3>=M_{B}>=-22.3) and a wide field-of-view (10' x 10'). Therefore, the environmental dependence of different formation scenarios can be analysed in detail as a function of radius from the cluster centre as well as for different sub-populations. In this article we present the motivation for this investigation, give an overview of the sample selection and observations and present our findings for the Fundamental Plane of early-type galaxies for the intermediate redshift clusters Abell 2218 and Abell 2390 at z~0.2.
Mass Distrubtion from Strong Gravitational Lensing of Merging Cluster Abell 2146
NASA Astrophysics Data System (ADS)
Coleman, Joseph E.; King, Lindsay J.; Oguri, Masamune; Russell, Helen
2017-01-01
The merging cluster Abell 2146 consists of two galaxy clusters that have recently collided close to the plane of the sky. In images from Chandra X-ray Observatory there are two distinct shock fronts in the intracluster medium. An unusual feature of one of the clusters is that the peak in the X-ray is leading the brightest cluster galaxy. The dark matter component is coincident with the brightest cluster galaxy (BCG). Shortly after first core passage one would typically expect the dark matter and BCG to lead the X-ray emitting plasma, however, that is not the case with Abell 2146. Strong lensing features were identified on images taken by the Hubble Space Telescope. These features were used as constraints on a lens model that maps the matter distribution of the system. We focus on the cluster Abell 2146-A to determine the dark matter centroid near BCG-A and the peak in the X-ray. The results from the strong lensing model indicate the X-ray cool core leads both the dark matter centroid and BCG-A. The dark matter centroid and BCG-A are separated by ≈ 2 kpc. The X-ray peak and dark matter centroid are separated by ≈ 30 kpc.
Chandra Observation of Abell 1142: A Cool-core Cluster Lacking a Central Brightest Cluster Galaxy?
NASA Astrophysics Data System (ADS)
Su, Yuanyuan; Buote, David A.; Gastaldello, Fabio; van Weeren, Reinout
2016-04-01
Abell 1142 is a low-mass galaxy cluster at low redshift containing two comparable brightest cluster galaxies (BCGs) resembling a scaled-down version of the Coma Cluster. Our Chandra analysis reveals an X-ray emission peak, roughly 100 kpc away from either BCG, which we identify as the cluster center. The emission center manifests itself as a second beta-model surface brightness component distinct from that of the cluster on larger scales. The center is also substantially cooler and more metal-rich than the surrounding intracluster medium (ICM), which makes Abell 1142 appear to be a cool-core cluster. The redshift distribution of its member galaxies indicates that Abell 1142 may contain two subclusters, each of which contain one BCG. The BCGs are merging at a relative velocity of ≈1200 km s-1. This ongoing merger may have shock-heated the ICM from ≈2 keV to above 3 keV, which would explain the anomalous LX-TX scaling relation for this system. This merger may have displaced the metal-enriched “cool core” of either of the subclusters from the BCG. The southern BCG consists of three individual galaxies residing within a radius of 5 kpc in projection. These galaxies should rapidly sink into the subcluster center due to the dynamical friction of a cuspy cold dark matter halo.
CHANDRA OBSERVATION OF ABELL 1142: A COOL-CORE CLUSTER LACKING A CENTRAL BRIGHTEST CLUSTER GALAXY?
Su, Yuanyuan; Weeren, Reinout van; Buote, David A.; Gastaldello, Fabio
2016-04-10
Abell 1142 is a low-mass galaxy cluster at low redshift containing two comparable brightest cluster galaxies (BCGs) resembling a scaled-down version of the Coma Cluster. Our Chandra analysis reveals an X-ray emission peak, roughly 100 kpc away from either BCG, which we identify as the cluster center. The emission center manifests itself as a second beta-model surface brightness component distinct from that of the cluster on larger scales. The center is also substantially cooler and more metal-rich than the surrounding intracluster medium (ICM), which makes Abell 1142 appear to be a cool-core cluster. The redshift distribution of its member galaxies indicates that Abell 1142 may contain two subclusters, each of which contain one BCG. The BCGs are merging at a relative velocity of ≈1200 km s{sup −1}. This ongoing merger may have shock-heated the ICM from ≈2 keV to above 3 keV, which would explain the anomalous L{sub X}–T{sub X} scaling relation for this system. This merger may have displaced the metal-enriched “cool core” of either of the subclusters from the BCG. The southern BCG consists of three individual galaxies residing within a radius of 5 kpc in projection. These galaxies should rapidly sink into the subcluster center due to the dynamical friction of a cuspy cold dark matter halo.
Integral inversion to Fraunhofer diffraction for particle sizing.
Cao, Zhang; Xu, Lijun; Ding, Jie
2009-09-01
A new solution to the inversion of Fraunhofer diffraction for particle sizing was introduced. Compared with the well-known Chin-Shifrin inversion, it is an inversion of the form of integral transform and less sensitive to noise. Simulation results with noise-contaminated data were obtained and showed that the new inversion is better than the Chin-Shifrin inversion. Especially when the particle diameter was small, the new inversion still performed well, whereas the Chin-Shifrin inversion did not converge.
NASA Astrophysics Data System (ADS)
Nath, Saurabh; Mukherjee, Anish; Chatterjee, Souvick; Ganguly, Ranjan; Sen, Swarnendu; Mukhopadhyay, Achintya; Boreyko, Jonathan
2014-11-01
We have observed that capillarity forces may cause floatation in a few non-intuitive configurations. These may be divided into 2 categories: i) floatation of heavier liquid droplets on lighter immiscible ones and ii) fully submerged floatation of lighter liquid droplets in a heavier immiscible medium. We call these counter-intuitive because of the inverse floatation configuration. For case (i) we have identified and studied in detail the several factors affecting the shape and maximum volume of the floating drop. We used water and vegetable oil combinations as test fluids and established the relation between Bond Number and maximum volume contained in a floating drop (in the order of μL). For case (ii), we injected vegetable oil drop-wise into a pool of water. The fully submerged configuration of the drop is not stable and a slight perturbation to the system causes the droplet to burst and float in partially submerged condition. Temporal variation of a characteristic length of the droplet is analyzed using MATLAB image processing. The constraint of small Bond Number establishes the assumption of lubrication regime in the thin gap. A brief theoretical formulation also shows the temporal variation of the gap thickness. Jadavpur University, Jagadis Bose Centre of Excellence, Virginia Tech.
Probing single biomolecules in solution using the Anti-Brownian ELectrokinetic (ABEL) trap
Wang, Quan; Goldsmith, Randall H.; Jiang, Yan; Bockenhauer, Samuel D.; Moerner, W.E.
2012-01-01
Conspectus Single-molecule fluorescence measurements allow researchers to study asynchronous dynamics and expose molecule-to-molecule structural and behavioral diversity, which contributes to the understanding of biological macromolecules. To provide measurements that are most consistent with the native environment of biomolecules, researchers would like to conduct these measurements in the solution phase if possible. However, diffusion typically limits the observation time to approximately one millisecond in many solution-phase single-molecule assays. Although surface immobilization is widely used to address this problem, this process can perturb the system being studied and contribute to the observed heterogeneity. Combining the technical capabilities of high-sensitivity single-molecule fluorescence microscopy, realtime feedback control and electrokinetic flow in a microfluidic chamber, we have developed a device called the Anti-Brownian ELectrokinetic (ABEL) trap to significantly prolong the observation time of single biomolecules in solution. We have applied the ABEL trap method to explore the photodynamics and enzymatic properties of a variety of biomolecules in aqueous solution and present four examples: the photosynthetic antenna allophycocyanin, the chaperonin enzyme TRiC, a G protein-coupled receptor protein, and the blue nitrite reductase redox enzyme. These examples illustrate the breadth and depth of information which we can extract in studies of single biomolecules with the ABEL trap. When confined in the ABEL trap, the photosynthetic antenna protein allophycocyanin exhibits rich dynamics both in its emission brightness and its excited state lifetime. As each molecule discontinuously converts from one emission/lifetime level to another in a primarily correlated way, it undergoes a series of state changes. We studied the ATP binding stoichiometry of the multi-subunit chaperonin enzyme TRiC in the ABEL trap by counting the number of hydrolyzed Cy3-ATP
Probing single biomolecules in solution using the anti-Brownian electrokinetic (ABEL) trap.
Wang, Quan; Goldsmith, Randall H; Jiang, Yan; Bockenhauer, Samuel D; Moerner, W E
2012-11-20
Single-molecule fluorescence measurements allow researchers to study asynchronous dynamics and expose molecule-to-molecule structural and behavioral diversity, which contributes to the understanding of biological macromolecules. To provide measurements that are most consistent with the native environment of biomolecules, researchers would like to conduct these measurements in the solution phase if possible. However, diffusion typically limits the observation time to approximately 1 ms in many solution-phase single-molecule assays. Although surface immobilization is widely used to address this problem, this process can perturb the system being studied and contribute to the observed heterogeneity. Combining the technical capabilities of high-sensitivity single-molecule fluorescence microscopy, real-time feedback control and electrokinetic flow in a microfluidic chamber, we have developed a device called the anti-Brownian electrokinetic (ABEL) trap to significantly prolong the observation time of single biomolecules in solution. We have applied the ABEL trap method to explore the photodynamics and enzymatic properties of a variety of biomolecules in aqueous solution and present four examples: the photosynthetic antenna allophycocyanin, the chaperonin enzyme TRiC, a G protein-coupled receptor protein, and the blue nitrite reductase redox enzyme. These examples illustrate the breadth and depth of information which we can extract in studies of single biomolecules with the ABEL trap. When confined in the ABEL trap, the photosynthetic antenna protein allophycocyanin exhibits rich dynamics both in its emission brightness and its excited state lifetime. As each molecule discontinuously converts from one emission/lifetime level to another in a primarily correlated way, it undergoes a series of state changes. We studied the ATP binding stoichiometry of the multi-subunit chaperonin enzyme TRiC in the ABEL trap by counting the number of hydrolyzed Cy3-ATP using stepwise
Solitons and the Inverse Scattering Transform
1980-01-01
the Airy equation ; it arises in certain problems in optics. Part (b) is the time - dependent Schr6dinger equation , with no potential. Part (c) is the...of these special nonlinear evolution equations are quite predictable, and can be computed explicitly (especially for large times ) once the initial data...ifferertial equations , even before time - dependence is brought into the picture! Fortunately, another miracle occurs, and there is a change of variables
Acoustic Inverse Scattering for Breast Cancer Microcalcification Detection. Addendum
2011-12-01
elliptical Radon transform have been developed. We conclude that inverse scattering algorithms for detecting microcalfications in heterogeneous tissue may be...bistatic ultrasound imaging geometry is the elliptical Radon transform (ERT). Small transducers can be modelled as having no directional sensitivity...elliptical Radon transform - a model for bistatic ultrasound array imaging in the breast One possible definition for the elliptical Radon transform would
The merging cluster Abell 1758 revisited: multi-wavelength observations and numerical simulations
NASA Astrophysics Data System (ADS)
Durret, F.; Laganá, T. F.; Haider, M.
2011-05-01
Context. Cluster properties can be more distinctly studied in pairs of clusters, where we expect the effects of interactions to be strong. Aims: We here discuss the properties of the double cluster Abell 1758 at a redshift z ~ 0.279. These clusters show strong evidence for merging. Methods: We analyse the optical properties of the North and South cluster of Abell 1758 based on deep imaging obtained with the Canada-France-Hawaii Telescope (CFHT) archive Megaprime/Megacam camera in the g' and r' bands, covering a total region of about 1.05 × 1.16 deg2, or 16.1 × 17.6 Mpc2. Our X-ray analysis is based on archive XMM-Newton images. Numerical simulations were performed using an N-body algorithm to treat the dark-matter component, a semi-analytical galaxy-formation model for the evolution of the galaxies and a grid-based hydrodynamic code with a parts per million (PPM) scheme for the dynamics of the intra-cluster medium. We computed galaxy luminosity functions (GLFs) and 2D temperature and metallicity maps of the X-ray gas, which we then compared to the results of our numerical simulations. Results: The GLFs of Abell 1758 North are well fit by Schechter functions in the g' and r' bands, but with a small excess of bright galaxies, particularly in the r' band; their faint-end slopes are similar in both bands. In contrast, the GLFs of Abell 1758 South are not well fit by Schechter functions: excesses of bright galaxies are seen in both bands; the faint-end of the GLF is not very well defined in g'. The GLF computed from our numerical simulations assuming a halo mass-luminosity relation agrees with those derived from the observations. From the X-ray analysis, the most striking features are structures in the metal distribution. We found two elongated regions of high metallicity in Abell 1758 North with two peaks towards the centre. In contrast, Abell 1758 South shows a deficit of metals in its central regions. Comparing observational results to those derived from numerical
GENERATING FRACTAL PATTERNS BY USING p-CIRCLE INVERSION
NASA Astrophysics Data System (ADS)
Ramírez, José L.; Rubiano, Gustavo N.; Zlobec, Borut Jurčič
2015-10-01
In this paper, we introduce the p-circle inversion which generalizes the classical inversion with respect to a circle (p = 2) and the taxicab inversion (p = 1). We study some basic properties and we also show the inversive images of some basic curves. We apply this new transformation to well-known fractals such as Sierpinski triangle, Koch curve, dragon curve, Fibonacci fractal, among others. Then we obtain new fractal patterns. Moreover, we generalize the method called circle inversion fractal be means of the p-circle inversion.
Embedded Spiral Patterns in the Cool Core of the Massive Cluster of Galaxies Abell 1835
NASA Astrophysics Data System (ADS)
Ueda, Shutaro; Kitayama, Tetsu; Dotani, Tadayasu
2017-03-01
We present the properties of an intracluster medium (ICM) in the cool core of the massive cluster of galaxies, Abell 1835, obtained with the data from the Chandra X-ray Observatory. We find distinctive spiral patterns with a radius of 70 kpc (or 18″) as a whole in the residual image of the X-ray surface brightness after the two-dimensional ellipse model of surface brightness is subtracted. The size is smaller by a factor of 2–4 than that of other clusters that are known to have a similar pattern. The spiral patterns consist of two arms. One of them appears as positive, and the other appears as negative excesses in the residual image. Their X-ray spectra show that the ICM temperatures in the positive- and negative-excess regions are {5.09}-0.13+0.12 keV and {6.52}-0.15+0.18 keV, respectively. In contrast, no significant difference is found in the abundance or pressure, the latter of which suggests that the ICM in the two regions of the spiral patterns is near or is in pressure equilibrium. The spatially resolved X-ray spectroscopy of the central region (r< 40\\prime\\prime ), divided into 92 sub-regions indicates that Abell 1835 is a typical cool core cluster. We also find that the spiral patterns extend from the cool core out to the hotter surrounding ICM. The residual image reveals some lumpy substructures in the cool core. The line of sight component of the disturbance velocity that is responsible for the substructures is estimated to be lower than 600 km s‑1. Abell 1835 may now be experiencing an off-axis minor merger.
Temperature and elemental abundances in the Abell cluster A 576 derived from X-ray observations
NASA Technical Reports Server (NTRS)
Rothenflug, R.; Vigroux, L.; Mushotzky, R. F.; Holt, S. S.
1983-01-01
Results of Einstein solid state spectrometer observations of the central region of Abell 576 combined with HEAO 1 spectra of the total cluster are given. Line emission was detected due to Fe, Si, and S from a hot plasma in the central region. The temperature of the total cluster spectrum may be in conflict with the central temperature. This difference can be explained either if cooling takes place in the center, or if part of the measured emission is due to individual galaxies. If the X-ray emission comes from the intergalactic gas only, there is some difficulty in producing all the silicon observed in the galaxies of A 576.
Abell 2069 - An X-ray cluster of galaxies with multiple subcondensations
NASA Technical Reports Server (NTRS)
Gioia, I. M.; Maccacaro, T.; Geller, M. J.; Huchra, J. P.; Stocke, J.; Steiner, J. E.
1982-01-01
X-ray and optical observations of the cluster Abell 2069 are presented. The cluster is at a mean redshift of 0.116. The cluster shows multiple condensations in both the X-ray emission and in the galaxy surface density and, thus, does not appear to be relaxed. There is a close correspondence between the gas and galaxy distributions which indicates that the galaxies in this system do map the mass distribution, contrary to what might be expected if low-mass neutrinos dominate the cluster mass.
Chandra Observation of the WAT Radio Source/ICM Interaction in Abell 623
NASA Astrophysics Data System (ADS)
Anand, Gagandeep; Blanton, Elizabeth L.; Randall, Scott W.; Paterno-Mahler, Rachel; Douglass, Edmund
2017-01-01
Galaxy clusters are important objects for studying the physics of the intracluster medium (ICM), galaxy formation and evolution, and cosmological parameters. Clusters containing wide-angle tail (WAT) radio sources are particularly valuable for studies of the interaction between these sources and the surrounding ICM. These sources are thought to form when the ram pressure from the ICM caused by the relative motion between the host radio galaxy and the cluster bends the radio lobes into a distinct wide-angle morphology. We present our results from the analysis of a Chandra observation of the nearby WAT hosting galaxy cluster Abell 623. A clear decrement in X-ray emission is coincident with the southern radio lobe, consistent with being a cavity carved out by the radio source. We present profiles of surface brightness, temperature, density, and pressure and find evidence for a possible shock. Based on the X-ray pressure in the vicinity of the radio lobes and assumptions about the content of the lobes, we estimate the relative ICM velocity required to bend the lobes into the observed angle. We also present spectral model fits to the overall diffuse cluster emission and see no strong signature for a cool core. The sum of the evidence indicates that Abell 623 may be undergoing a large scale cluster-cluster merger.
The X-ray luminosity functions of Abell clusters from the Einstein Cluster Survey
NASA Technical Reports Server (NTRS)
Burg, R.; Giacconi, R.; Forman, W.; Jones, C.
1994-01-01
We have derived the present epoch X-ray luminosity function of northern Abell clusters using luminosities from the Einstein Cluster Survey. The sample is sufficiently large that we can determine the luminosity function for each richness class separately with sufficient precision to study and compare the different luminosity functions. We find that, within each richness class, the range of X-ray luminosity is quite large and spans nearly a factor of 25. Characterizing the luminosity function for each richness class with a Schechter function, we find that the characteristic X-ray luminosity, L(sub *), scales with richness class as (L(sub *) varies as N(sub*)(exp gamma), where N(sub *) is the corrected, mean number of galaxies in a richness class, and the best-fitting exponent is gamma = 1.3 +/- 0.4. Finally, our analysis suggests that there is a lower limit to the X-ray luminosity of clusters which is determined by the integrated emission of the cluster member galaxies, and this also scales with richness class. The present sample forms a baseline for testing cosmological evolution of Abell-like clusters when an appropriate high-redshift cluster sample becomes available.
MINOR MERGER-INDUCED COLD FRONTS IN ABELL 2142 AND RXJ1720.1+2638
Owers, Matt S.; Couch, Warrick J.; Nulsen, Paul E. J.
2011-11-10
We present evidence for the existence of substructure in the 'relaxed appearing' cold front clusters Abell 2142 and RXJ1720.1+2638. The detection of these substructures was made possible by comprehensive multi-object optical spectroscopy obtained with the Hectospec and DEep Imaging Multi-Object Spectrograph instruments on the 6.5 m MMT and 10 m Keck II telescope, respectively. These observations produced 956 and 400 spectroscopically confirmed cluster members within a projected radius of 3 Mpc from the centers of A2142 and RXJ1720.1+2638, respectively. The substructure manifests itself as local peaks in the spatial distribution of member galaxies and also as regions of localized velocity substructure. For both Abell 2142 and RXJ1720.1+2638, we identify group-scale substructures which, when considering the morphology of the cold fronts and the time since pericentric passage of a perturber estimated from the cold front radii, could plausibly have perturbed the cluster cores and generated the cold fronts observed in Chandra images. The results presented here are consistent with cold fronts being the result of merger activity and with cold fronts in relaxed appearing clusters being due to minor merger activity.
The Evolutionary Status of Early-type Galaxies in Abell 2390
NASA Astrophysics Data System (ADS)
Fritz, A.; Ziegler, B. L.; Bower, R. G.; Smail, I.; Davies, R. L.
We explore the evolution of the early-type galaxy population in the rich cluster Abell 2390 at z=0.23. For this purpose, we have obtained spectroscopic data of 51 elliptical and lenticular galaxies with MOSCA at the 3.5 m telescope on Calar Alto Observatory. As our investigation spans both a broad range in luminosity (-22.3<=MB<=-:19.3) and a wide field of view (10'×10'), the environmental dependence of different formation scenarios can be analysed in detail as a function of radius from the cluster center. In this paper, we present first results on the Faber-Jackson relation and, for a subsample of 14 galaxies with morphological and structural parameters from HST, we also investigate the evolution of the Kormendy relation and the Fundamental Plane. We find a mild luminosity evolution of the early-type galaxies in Abell 2390: our objects are on average brighter by mB~0.4 mag.
Revisiting Abell 2744: a powerful synergy of GLASS spectroscopy and HFF photometry
NASA Astrophysics Data System (ADS)
Wang, Xin; Wang
We present new emission line identifications and improve the lensing reconstruction of the mass distribution of galaxy cluster Abell 2744 using the Grism Lens-Amplified Survey from Space (GLASS) spectroscopy and the Hubble Frontier Fields (HFF) imaging. We performed blind and targeted searches for faint line emitters on all objects, including the arc sample, within the field of view (FoV) of GLASS prime pointings. We report 55 high quality spectroscopic redshifts, 5 of which are for arc images. We also present an extensive analysis based on the HFF photometry, measuring the colors and photometric redshifts of all objects within the FoV, and comparing the spectroscopic and photometric redshift estimates. In order to improve the lens model of Abell 2744, we develop a rigorous algorithm to screen arc images, based on their colors and morphology, and selecting the most reliable ones to use. As a result, 25 systems (corresponding to 72 images) pass the screening process and are used to reconstruct the gravitational potential of the cluster pixellated on an adaptive mesh. The resulting total mass distribution is compared with a stellar mass map obtained from the Spitzer Frontier Fields data in order to study the relative distribution of stars and dark matter in the cluster.
Redshift observations of Abell/ACO galaxy clusters in two candidate superclusters
NASA Astrophysics Data System (ADS)
Batuski, D. J.; Maurogordato, S.; Balkowski, C.; Olowin, R. P.
1995-02-01
The results of spectroscopic observations of five R greater than or equal to 1 clusters of galaxies from the Abell (1958) and Abell et al. (1989) (hereafter ACO) catalogs are presented. The observations were conducted at the ESO 3.6m telescope with the EFOSC spectrograph and PUMA hole-punch aperture plates. Two of the clusters (A2576 and A2628) had been identified as members of one candidate supercluster that appears particularly dense in projection, and the other three clusters (A3802, A3817, and A3834) were in another candidate supercluster, based on redshifts estimated from the magnitudes of tenth brightest galaxies. Our observations confirm very similar redshifts for A2576 and A2628 ( z = 0.1875 and z = 0.1858, respectively) and for A3802 and A3834 (z = 0.1579 and z = 0.1518). From the agreement in redshifts and the proximity on the sky, it is suggestive that both pairs are indeed components of superclusters, although redshifts of other nearby candidates must be measured to determine the significance of the structure present. The fifth cluster, A3817, has a mean redshift of z = 0.2115, and so appears to be background to any possible A3802/A3834 supercluster. We note that the complex of clusters around A2576 and A2628 is a region of high spatial density, even ignoring the many clusters with unmeasured redshift. The region is an exceptional opportunity for large-scale structure study.
Zhao, Daomu; Zhu, Yingbin
2009-04-01
Generalized propagation formulas for the elements of the cross-spectral density matrix of stochastic electromagnetic beams on inverse propagation through an axially symmetrical or nonsymmetrical optical system are derived with the help of Fourier transform and inverse Fourier transform. As an example, we apply the formula to the inverse source problem of stochastic electromagnetic Gaussian Schell-model beams.
A Modal/WKB Inversion Method for Determining Sound Speed Profiles in the Ocean and Ocean Bottom
1988-06-01
0 and z = z0 with harmonic time dependence ezp(-iwt), satisfies the inhomogeneous Helmholtz equation : 1 [ (r) + -2 + k2(z)] p(r,z, zo) = -2 6(z- Zo...P(z) = 0. (5.2) Substituting v(z) = P(z)/V/ i gives the Schr ~ dinger type equation [36] d2 V(z) + (k(z) + pi(z) - k2) v(z) = 0 (5.3) where ) p/ 2(z...input data used in generating a profile dependent functional relationship for the phase integral. The Abel integral equation based inversion relations
Locative Inversion in Cantonese.
ERIC Educational Resources Information Center
Mok, Sui-Sang
This study investigates the phenomenon of "Locative Inversion" in Cantonese. The term "Locative Inversion" indicates that the locative phrase (LP) syntactic process in Cantonese and the appears at the sentence-initial position and its logical subject occurs postverbally. It is demonstrated that this Locative Inversion is a…
A Statistical Study of Multiply Imaged Systems in the Lensing Cluster Abell 68
NASA Astrophysics Data System (ADS)
Richard, Johan; Kneib, Jean-Paul; Jullo, Eric; Covone, Giovanni; Limousin, Marceau; Ellis, Richard; Stark, Daniel; Bundy, Kevin; Czoske, Oliver; Ebeling, Harald; Soucail, Geneviève
2007-06-01
We have carried out an extensive spectroscopic survey with the Keck and VLT telescopes, targeting lensed galaxies in the background of the massive cluster Abell 68. Spectroscopic measurements are obtained for 26 lensed images, including a distant galaxy at z=5.4. Redshifts have been determined for 5 out of 7 multiple-image systems. Through a careful modeling of the mass distribution in the strongly lensed regime, we derive a mass estimate of 5.3×1014 Msolar within 500 kpc. Our mass model is then used to constrain the redshift distribution of the remaining multiply imaged and singly imaged sources. This enables us to examine the physical properties for a subsample of 7 Lyα emitters at 1.7<~z<~5.5, whose unlensed luminosities of ~=1041 ergs s-1 are fainter than similar objects found in blank fields. Of particular interest is an extended Lyα emission region surrounding a highly magnified source at z=2.6, detected in VIMOS integral field spectroscopy data. The physical scale of the most distant lensed source at z=5.4 is very small (<300 pc), similar to the lensed z~5.6 emitter reported by Ellis et al. in Abell 2218. New photometric data available for Abell 2218 allow for a direct comparison between these two unique objects. Our survey illustrates the practicality of using lensing clusters to probe the faint end of the z~2-5 Lyα luminosity function in a manner that is complementary to blank-field narrowband surveys. Data presented herein were obtained at the W. M. Keck Observatory, which is operated as a scientific partnership among the California Institute of Technology, the University of California and the National Aeronautics and Space Administration. The Observatory was made possible by the generous financial support of the W. M. Keck Foundation. Also based on observations collected at the Very Large Telescope (Antu/UT1 and Melipal/UT3), European Southern Observatory, Paranal, Chile (ESO programs 070.A-0643 and 073.A-0774), the NASA/ESA Hubble Space Telescope
Matrix-inversion method: Applications to Möbius inversion adn deconvolution
NASA Astrophysics Data System (ADS)
Xie, Qian; Chen, Nan-Xian
1995-12-01
The purpose of this paper is threefold. The first is to show the matrix inversion method as a joint basis for the inversion of two important transforms: the Möbius and Laplace transforms. It is found that the Möbius transform is related to a multiplicative operator while the Laplace transform is related to an additive operator. The second is to show that the matrix inverison method is a useful tool for inverse problems not only in statistical physics but also in applied physics by means of adding two other applications, one the derivation of the Fuoss-Kirkwood formulas for relaxation spectra in studies of anelasticity and dielectrics and the other the reconstruction of real signal in signal processing. The third is to indicate the potentiality of the matrix inversion method as a rough algorithm for numerical solution of the convolution integral equation. The numerical examples given include the inversion of Laplace transform and the signal reconstruction with a Gaussian point spread kernel. (c) 1995 The American Physical Society
Inversion Concept of the Origin of Life
NASA Astrophysics Data System (ADS)
Kompanichenko, V. N.
2012-06-01
The essence of the inversion concept of the origin of life can be narrowed down to the following theses: 1) thermodynamic inversion is the key transformation of prebiotic microsystems leading to their transition into primary forms of life; 2) this transformation might occur only in the microsystems oscillating around the bifurcation point under far-from-equilibrium conditions. The transformation consists in the inversion of the balance "free energy contribution / entropy contribution", from negative to positive values. At the inversion moment the microsystem radically reorganizes in accordance with the new negentropy (i.e. biological) way of organization. According to this approach, the origin-of-life process on the early Earth took place in the fluctuating hydrothermal medium. The process occurred in two successive stages: a) spontaneous self-assembly of initial three-dimensional prebiotic microsystems composed mainly of hydrocarbons, lipids and simple amino acids, or their precursors, within the temperature interval of 100-300°C (prebiotic stage); b) non-spontaneous synthesis of sugars, ATP and nucleic acids started at the inversion moment under the temperature 70-100°C (biotic stage). Macro- and microfluctuations of thermodynamic and physico-chemical parameters able to sustain this way of chemical conversion have been detected in several contemporary hydrothermal systems. A minimal self-sufficient unit of life on the early Earth was a community of simplest microorganisms (not a separate microorganism).
Inversion concept of the origin of life.
Kompanichenko, V N
2012-06-01
The essence of the inversion concept of the origin of life can be narrowed down to the following theses: 1) thermodynamic inversion is the key transformation of prebiotic microsystems leading to their transition into primary forms of life; 2) this transformation might occur only in the microsystems oscillating around the bifurcation point under far-from-equilibrium conditions. The transformation consists in the inversion of the balance "free energy contribution / entropy contribution", from negative to positive values. At the inversion moment the microsystem radically reorganizes in accordance with the new negentropy (i.e. biological) way of organization. According to this approach, the origin-of-life process on the early Earth took place in the fluctuating hydrothermal medium. The process occurred in two successive stages: a) spontaneous self-assembly of initial three-dimensional prebiotic microsystems composed mainly of hydrocarbons, lipids and simple amino acids, or their precursors, within the temperature interval of 100-300°C (prebiotic stage); b) non-spontaneous synthesis of sugars, ATP and nucleic acids started at the inversion moment under the temperature 70-100°C (biotic stage). Macro- and microfluctuations of thermodynamic and physico-chemical parameters able to sustain this way of chemical conversion have been detected in several contemporary hydrothermal systems. A minimal self-sufficient unit of life on the early Earth was a community of simplest microorganisms (not a separate microorganism).
X-ray constraints on the shape of the dark matter in five Abell clusters
NASA Technical Reports Server (NTRS)
Buote, David A.; Canizares, Claude R.
1992-01-01
X-ray observations obtained with the Einstein Observatory are used to constrain the shape of the dark matter in the inner regions of Abell clusters A401, A426, A1656, A2029, and A2199, each of which exhibits highly flattened optical isopleths. The dark matter is modeled as an ellipsoid with a mass density of about r exp -2. The possible shapes of the dark matter is constrained by comparing these model isophotes to the image isophotes. The X-ray isophotes, and therefore the gravitational potentials, have ellipticities of about 0.1-0.2. The dark matter within the central 1 Mpc is found to be substantially rounder for all the clusters. It is concluded that the shape of the galaxy distributions in these clusters traces neither the gravitational potential nor the gravitating matter.
Television documentary, history and memory. An analysis of Sergio Zavoli's The Gardens of Abel
Foot, John
2014-01-01
This article examines a celebrated documentary made for Italian state TV in 1968 and transmitted in 1969 to an audience of millions. The programme – The Gardens of Abel – looked at changes introduced by the radical psychiatrist Franco Basaglia in an asylum in the north-east of Italy (Gorizia). The article examines the content of this programme for the first time, questions some of the claims that have been made for it, and outlines the sources used by the director, Sergio Zavoli. The article argues that the film was as much an expression of Zavoli's vision and ideas as it was linked to those of Franco Basaglia himself. Finally, the article highlights the way that this programme has become part of historical discourse and popular memory. PMID:25937804
Television documentary, history and memory. An analysis of Sergio Zavoli's The Gardens of Abel.
Foot, John
2014-10-20
This article examines a celebrated documentary made for Italian state TV in 1968 and transmitted in 1969 to an audience of millions. The programme - The Gardens of Abel - looked at changes introduced by the radical psychiatrist Franco Basaglia in an asylum in the north-east of Italy (Gorizia). The article examines the content of this programme for the first time, questions some of the claims that have been made for it, and outlines the sources used by the director, Sergio Zavoli. The article argues that the film was as much an expression of Zavoli's vision and ideas as it was linked to those of Franco Basaglia himself. Finally, the article highlights the way that this programme has become part of historical discourse and popular memory.
Early-type Galaxies in the Cluster Abell 2390 at z = 0.23
NASA Astrophysics Data System (ADS)
Fritz, A.; Ziegler, B. L.; Bower, R. G.; Smail, I.; Davies, R. L.
To examine the evolution of the early-type galaxy population in the rich cluster Abell 2390 at z = 0.23 we have gained spectroscopic data of 51 elliptical and lenticular galaxies with MOSCA at the 3.5 m telescope on Calar Alto Observatory. This investigation spans both a broad range in luminosity (-19.3 >˜MB >˜-22.3) and uses a wide field of view of 10'× 10', therefore the environmental dependence of different formation scenarios can be analysed in detail as a function of radius from the cluster centre. Here we present results on the surface brightness modelling of galaxies where morphological and structural information is available in the F814W filter aboard the Hubble Space Telescope (HST) and investigate for this subsample the evolution of the Fundamental Plane.
Inhibition of α-glucosidase by polysaccharides from the fruit hull of Camellia oleifera Abel.
Zhang, Sheng; Li, Xiang-Zhou
2015-01-22
We isolated and purified polysaccharides from the Camellia oleifera Abel. fruit hull and studied its hypoglycemic potential. Our results revealed six polysaccharides (CFPA-1-5 & CFPB) from the aqueous extract from the defatted C. oleifera fruit hull. Purified polysaccharides (purity >90%) were investigated for the inhibition of α-glucosidase activity in vitro. Two polysaccharides, CFPB and CFPA-3 were present in high concentration in the fruit hull and showed a dose-dependent inhibition of α-glucosidase activity, with IC50 concentrations of 11.80 and 10.95 μg/mL, respectively. This result suggests that polysaccharides (CFP) extracted from the fruit hull of C. oleifera may have potential as functional foods with featuring a hypoglycemic effect.
The Herschel Lensing Survey (HLS): A Bright Lensed Submillimeter Galaxy in the Field of Abell 773
NASA Astrophysics Data System (ADS)
Rawle, Tim; Egami, E.; Rex, M.; Combes, F.; Boone, F.; Smail, I.; Lensing Survey, Herschel
2012-05-01
The Herschel Lensing Survey (HLS; PI: Egami) is observing more than 50 massive galaxy clusters with deep PACS and SPIRE (100-500um) imaging, and a further 500 clusters in a SPIRE snapshot program ( 20 deg^2 of far-infrared cluster observations in total). Here, we present a discussion of an exceptionally bright ( 200mJy at 500um) source behind the cluster Abell 773, which is a strongly lensed submillimeter galaxy (SMG) at z=5.2. The source has an intrinsic infrared luminosity L_FIR 1e13 L_sun, with a total magnification factor of 11. We combine Herschel-SMA-IRAM observations of the dust continuum and gas excitation line emission, including multiple CO transitions, [CII] and [NII] (detected for the first time at high-z), to explore the morphology, star formation and ISM in this SMG.
Narrow-angle tail radio sources and evidence for radial orbits in Abell clusters
NASA Technical Reports Server (NTRS)
O'Dea, Christopher P.; Owen, Frazer N.; Sarazin, Craig L.
1986-01-01
Published observational data on the tail orientations (TOs) of 60 narrow-angle-tail (NAT) radio sources in Abell clusters of galaxies are analyzed statistically using a maximum-likelihood approach. The results are presented in a table, and it is found that the observed TO distributions in the whole sample and in subsamples of morphologically regular NATs and NATs with pericentric distances d greater than 500 kpc are consistent with isotropic orbits, whereas the TOs for NATs with d less than 500 kpc are consistent with highly radial orbits. If radial orbits were observed near the centers of other types of cluster galaxies as well, it could be inferred that violent relaxation during cluster formation was incomplete, and that clusters form by spherical collapse and secondary infall, as proposed by Gunn (1977).
Shocks, Ripples, and Bubbles: A Very Deep Observation of Abell 2052
NASA Astrophysics Data System (ADS)
Blanton, Elizabeth
2008-09-01
The cooling flow cluster A2052 has, arguably, the morphology most similar to the Perseus cluster as seen with Chandra. Two clear bubbles to the N and S of the center of A2052 are filled with the radio lobes associated with 3C 317. Surface brightness discontinuities consistent with shocks with Mach numbers of 1.8 and 1.2 are seen near the cluster center. These may be isothermal shocks. We propose to observe Abell 2052 much more deeply to study these shock features, ripple features due to sound waves that may be found at larger radii, possible ghost bubbles, cooling gas in the bright shells around the radio source that may link the X-ray and H-alpha emission, and possible hot gas within the X-ray holes. We will directly compare the star formation and cooling rates in the cluster center.
Cheng, Yu-Ting; Lu, Chi-Cheng; Yen, Gow-Chin
2015-01-01
Epidemiological studies have shown that increased dietary intake of natural antioxidants is beneficial for health because of their bioactivities, including antioxidant and anti-inflammation actions. Camellia oil made from tea seed (Camellia oleifera Abel.) is commonly used as an edible oil and a traditional medicine in Taiwan and China. Until now, the camellia oil has been widely considered as a dietary oil for heath. In this review, we summarize the protective effects of camellia oil with antioxidant activity against oxidative stress leading to hepatic damage and gastrointestinal ulcers. The information in this review leads to the conclusion that camellia oil is not only an edible oil but also a vegetable oil with a potential function for human health.
ASCA detection of iron line emission from the distant galaxy cluster Abell 370
NASA Technical Reports Server (NTRS)
Bautz, Marshall W.; Mushotzky, Richard; Fabian, Andrew C.; Yamashita, Koujun; Gendreau, Keith C.; Arnaud, Keith A.; Crew, Geoffrey B.; Tawara, Yuzuru
1994-01-01
ASCA observations of the gravitational lens and Butcher-Oemler cluster Abell 370 (z = 0.37) give kT = 8.8 +/- 0.8 keV and A = 0.5 +/- 0.1 cosmic. If the gas were isothermal the implied cluster mass would be M(sub vir) = (1.5 +/- 0.4) x 10(exp 15) solar masses, a value consistent with the optically-determined virial mass. We detect iron K line emission with high confidence. This measurement increases, by a large factor, the lookback time at which the presence of iron in the intracluster medium has been established. The iron abundance is marginally higher than that of low-redshift clusters of similar temperature, so our results are consistent with models in which all enrichment occurs before the epoch corresponding to z = 0.37.
2009-12-01
reserved. Printed in the U.S.A. ASTROMETRY WITH THE HUBBLE SPACE TELESCOPE: TRIGONOMETRIC PARALLAXES OF PLANETARY NEBULA NUCLEI NGC 6853, NGC 7293, ABELL 31...present absolute parallaxes and relative proper motions for the central stars of the planetary nebulae NGC 6853 (The Dumbbell), NGC 7293 (The Helix...Abell 31, and DeHt 5. This paper details our reduction and analysis using DeHt 5 as an example. We obtain these planetary nebula nuclei (PNNi
NASA Technical Reports Server (NTRS)
Patel, Sandeep K.; Joy, Marshall; Carlstrom, John E.; Holder, Gilbert P.; Reese, Erik D.; Gomez, Percy L.; Hughes, John P.; Grego, Laura; Holzapfel, William L.
2000-01-01
We present multi-wavelength observations of the Abell 1995 galaxy cluster. From analysis of x-ray spectroscopy and imaging data we derive the electron temperature, cluster core radius, and central electron number density. Using optical spectroscopy of 15 cluster members, we derive an accurate cluster redshift and velocity dispersion. Finally, the interferometric imaging of the SZE toward Abell 1995 at 28.5 GHz provides a measure of the integrated pressure through the cluster.
On the merging cluster Abell 578 and its central radio galaxy 4C+67.13
Hagino, K.; Stawarz, Ł.; Siemiginowska, A.; ...
2015-05-26
Here we analyze radio, optical, and X-ray data for the peculiar cluster Abell 578. This cluster is not fully relaxed and consists of two merging sub-systems. The brightest cluster galaxy (BCG), CGPG 0719.8+6704, is a pair of interacting ellipticals with projected separation ~10 kpc, the brighter of which hosts the radio source 4C+67.13. The Fanaroff–Riley type-II radio morphology of 4C+67.13 is unusual for central radio galaxies in local Abell clusters. Our new optical spectroscopy revealed that both nuclei of the CGPG 0719.8+6704 pair are active, albeit at low accretion rates corresponding to the Eddington ratiomore » $$\\sim {{10}^{-4}}$$ (for the estimated black hole masses of $$\\sim 3\\times {{10}^{8}}\\;{{M}_{\\odot }}$$ and $$\\sim {{10}^{9}}\\;{{M}_{\\odot }}$$). The gathered X-ray (Chandra) data allowed us to confirm and to quantify robustly the previously noted elongation of the gaseous atmosphere in the dominant sub-cluster, as well as a large spatial offset (~60 kpc projected) between the position of the BCG and the cluster center inferred from the modeling of the X-ray surface brightness distribution. Detailed analysis of the brightness profiles and temperature revealed also that the cluster gas in the vicinity of 4C+67.13 is compressed (by a factor of about ~1.4) and heated (from $$\\simeq 2.0$$ keV up to 2.7 keV), consistent with the presence of a weak shock (Mach number ~1.3) driven by the expanding jet cocoon. As a result, this would then require the jet kinetic power of the order of $$\\sim {{10}^{45}}$$ erg s–1, implying either a very high efficiency of the jet production for the current accretion rate, or a highly modulated jet/accretion activity in the system.« less
The galaxy population of Abell 1367: the stellar mass-metallicity relation
NASA Astrophysics Data System (ADS)
Mouhcine, M.; Kriwattanawong, W.; James, P. A.
2011-04-01
Using wide baseline broad-band photometry, we analyse the stellar population properties of a sample of 72 galaxies, spanning a wide range of stellar masses and morphological types, in the nearby spiral-rich and dynamically young galaxy cluster Abell 1367. The sample galaxies are distributed from the cluster centre out to approximately half the cluster Abell radius. The optical/near-infrared colours are compared with simple stellar population synthesis models from which the luminosity-weighted stellar population ages and metallicities are determined. The locus of the colours of elliptical galaxies traces a sequence of varying metallicity at a narrow range of luminosity-weighted stellar ages. Lenticular galaxies in the red sequence, however, exhibit a substantial spread of luminosity-weighted stellar metallicities and ages. For red-sequence lenticular galaxies and blue cloud galaxies, low-mass galaxies tend to be on average dominated by stellar populations of younger luminosity-weighted ages. Sample galaxies exhibit a strong correlation between integrated stellar mass and luminosity-weighted stellar metallicity. Galaxies with signs of morphological disturbance and ongoing star formation activity, tend to be underabundant with respect to passive galaxies in the red sequence of comparable stellar masses. We argue that this could be due to tidally driven gas flows towards the star-forming regions, carrying less enriched gas and diluting the pre-existing gas to produce younger stellar populations with lower metallicities than would be obtained prior to the interaction. Finally, we find no statistically significant evidence for changes in the luminosity-weighted ages and metallicities for either red-sequence or blue-cloud galaxies, at fixed stellar mass, with location within the cluster. We dedicate this work to the memory of our friend and colleague C. Moss who died suddenly recently.
Galaxy Luminosity Function of the Dynamically Young Abell 119 Cluster: Probing the Cluster Assembly
NASA Astrophysics Data System (ADS)
Lee, Youngdae; Rey, Soo-Chang; Hilker, Michael; Sheen, Yun-Kyeong; Yi, Sukyoung K.
2016-05-01
We present the galaxy luminosity function (LF) of the Abell 119 cluster down to {M}r˜ -14 mag based on deep images in the u, g, and r bands taken by using MOSAIC II CCD mounted on the Blanco 4 m telescope at the CTIO. The cluster membership was accurately determined based on the radial velocity information and on the color-magnitude relation for bright galaxies and the scaling relation for faint galaxies. The overall LF exhibits a bimodal behavior with a distinct dip at r˜ 18.5 mag ({M}r˜ -17.8 mag), which is more appropriately described by a two-component function. The shape of the LF strongly depends on the clustercentric distance and on the local galaxy density. The LF of galaxies in the outer, low-density region exhibits a steeper slope and more prominent dip compared with that of counterparts in the inner, high-density region. We found evidence for a substructure in the projected galaxy distribution in which several overdense regions in the Abell 119 cluster appear to be closely associated with the surrounding, possible filamentary structure. The combined LF of the overdense regions exhibits a two-component function with a distinct dip, while the LF of the central region is well described by a single Schechter function. We suggest that, in the context of the hierarchical cluster formation scenario, the observed overdense regions are the relics of galaxy groups, retaining their two-component LFs with a dip, which acquired their shapes through a galaxy merging process in group environments, before they fall into a cluster.
Tracing low-mass galaxy clusters using radio relics: the discovery of Abell 3527-bis
NASA Astrophysics Data System (ADS)
de Gasperin, F.; Intema, H. T.; Ridl, J.; Salvato, M.; van Weeren, R.; Bonafede, A.; Greiner, J.; Cassano, R.; Brüggen, M.
2017-01-01
Context. Galaxy clusters undergo mergers that can generate extended radio sources called radio relics. Radio relics are the consequence of merger-induced shocks that propagate in the intra cluster medium (ICM). Aims: In this paper we analyse the radio, optical and X-ray data from a candidate galaxy cluster that has been selected from the radio emission coming from a candidate radio relic detected in NRAO VLA Sky Survey (NVSS). Our aim is to clarify the nature of this source and prove that under certain conditions radio emission from radio relics can be used to trace relatively low-mass galaxy clusters. Methods: We observed the candidate galaxy cluster with the Giant Meterwave Radio Telescope (GMRT) at three different frequencies. These datasets have been analysed together with archival data from ROSAT in the X-ray and with archival data from the Gamma-Ray Burst Optical/Near-Infrared Detector (GROND) telescope in four different optical bands. Results: We confirm the presence of a 1 Mpc long radio relic located in the outskirts of a previously unknown galaxy cluster. We confirm the presence of the galaxy cluster through dedicated optical observations and using archival X-ray data. Due to its proximity and similar redshift to a known Abell cluster, we named it Abell 3527-bis. The galaxy cluster is amongst the least massive clusters known to host a radio relic. Conclusions: We showed that radio relics can be effectively used to trace a subset of relatively low-mass galaxy clusters that might have gone undetected in X-ray or Sunyaev-Zel'dovich (SZ) surveys. This technique might be used in future deep, low-frequency surveys such as those carried on by the Low Frequency Array (LOFAR), the Upgraded GMRT (uGMRT) and, ultimately, the Square Kilometre Array (SKA).
A Multiply-Imaged z ˜ 6.3 Lyman Alpha Emitter candidate behind Abell 2261
NASA Astrophysics Data System (ADS)
Rydberg, Claes-Erik; Zitrin, Adi; Zackrisson, Erik; Melinder, Jens; Whalen, Daniel J.; Klessen, Ralf S.; Gonzalez, Juan; Östlin, Göran; Carollo, Daniela
2017-01-01
While the Lyman-α (Lyα) emission line serves as an important tool in the study of galaxies at z ≲ 6, finding Lyα emitters (LAE) at significantly higher redshifts has been more challenging, probably because of the increasing neutrality of the intergalactic medium above z ˜ 6. Galaxies with extremely high rest-frame Lyα equivalent widths, EW(Lyα) ≳ 150 Å, at z > 6 are good candidates for Lyα follow-up observations, and can stand out in multiband imaging surveys because of their unusual colors. We have conducted a photometric search for such objects in the Cluster Lensing And Supernova survey with Hubble (CLASH), and report here the identification of three likely gravitationally-lensed images of a single LAE candidate at z ˜ 6.3, behind the galaxy cluster Abell 2261 (z = 0.225). In the process, we also measured with Keck/MOSFIRE the first spectroscopic redshift of a multiply-imaged galaxy behind Abell 2261, at z = 3.337. This allows us to calibrate the lensing model, which in turn is used to study the properties of the candidate LAE. Population III galaxy spectral energy distribution (SED) model fits to the CLASH broadband photometry of the possible LAE provide a slightly better fit than Population I/II models. The best fitted model suggests intrinsic EW(Lyα) ≈160 Å after absorption in the interstellar and intergalactic medium. Future spectroscopic observations will examine this prediction as well as shed more light on the morphology of this object, which indicates it may be a merger of two smaller galaxies.
Deep spectroscopy of nearby galaxy clusters - I. Spectroscopic luminosity function of Abell 85
NASA Astrophysics Data System (ADS)
Agulli, I.; Aguerri, J. A. L.; Sánchez-Janssen, R.; Dalla Vecchia, C.; Diaferio, A.; Barrena, R.; Dominguez Palmero, L.; Yu, H.
2016-05-01
We present a new deep spectroscopic catalogue for Abell 85, within 3.0 × 2.6 Mpc2 and down to Mr ˜ Mr^{ast } +6. Using the Visible Multi-Object Spectrograph at the Very Large Telescope and the AutoFiber 2 at the William Herschel Telescope, we obtained almost 1430 new redshifts for galaxies with mr ≤ 21 mag and <μe,r> ≤ 24 mag arcsec-2. These redshifts, together with Sloan Digital Sky Survey Data Release 6 and NASA/IPAC Extragaalctic Database spectroscopic information, result in 460 confirmed cluster members. This data set allows the study of the luminosity function (LF) of the cluster galaxies covering three orders of magnitudes in luminosities. The total and radial LFs are best modelled by a double Schechter function. The normalized LFs show that their bright (Mr ≤ -21.5) and faint (Mr ≥ -18.0) ends are independent of clustercentric distance and similar to the field LFs unlike the intermediate luminosity range (-21.5 ≤ Mr ≤ -18.0). Similar results are found for the LFs of the dominant types of galaxies: red, passive, virialized and early-infall members. On the contrary, the LFs of blue, star forming, non-virialized and recent-infall galaxies are well described by a single Schechter function. These populations contribute to a small fraction of the galaxy density in the innermost cluster region. However, in the outskirts of the cluster, they have similar densities to red, passive, virialized and early-infall members at the LF faint end. These results confirm a clear dependence of the colour and star formation of Abell 85 members in the cluster centric distance.
A plethora of diffuse steep spectrum radio sources in Abell 2034 revealed by LOFAR
NASA Astrophysics Data System (ADS)
Shimwell, T. W.; Luckin, J.; Brüggen, M.; Brunetti, G.; Intema, H. T.; Owers, M. S.; Röttgering, H. J. A.; Stroe, A.; van Weeren, R. J.; Williams, W. L.; Cassano, R.; de Gasperin, F.; Heald, G. H.; Hoang, D. N.; Hardcastle, M. J.; Sridhar, S. S.; Sabater, J.; Best, P. N.; Bonafede, A.; Chyży, K. T.; Enßlin, T. A.; Ferrari, C.; Haverkorn, M.; Hoeft, M.; Horellou, C.; McKean, J. P.; Morabito, L. K.; Orrù, E.; Pizzo, R.; Retana-Montenegro, E.; White, G. J.
2016-06-01
With Low-Frequency Array (LOFAR) observations, we have discovered a diverse assembly of steep spectrum emission that is apparently associated with the intracluster medium (ICM) of the merging galaxy cluster Abell 2034. Such a rich variety of complex emission associated with the ICM has been observed in few other clusters. This not only indicates that Abell 2034 is a more interesting and complex system than previously thought but it also demonstrates the importance of sensitive and high-resolution, low-frequency observations. These observations can reveal emission from relativistic particles which have been accelerated to sufficient energy to produce observable emission or have had their high energy maintained by mechanisms in the ICM. The most prominent feature in our maps is a bright bulb of emission connected to two steep spectrum filamentary structures, the longest of which extends perpendicular to the merger axis for 0.5 Mpc across the south of the cluster. The origin of these objects is unclear, with no shock detected in the X-ray images and no obvious connection with cluster galaxies or AGNs. We also find that the X-ray bright region of the cluster coincides with a giant radio halo with an irregular morphology and a very steep spectrum. In addition, the cluster hosts up to three possible radio relics, which are misaligned with the cluster X-ray emission. Finally, we have identified multiple regions of emission with a very steep spectral index that seem to be associated with either tailed radio galaxies or a shock.
On the merging cluster Abell 578 and its central radio galaxy 4C+67.13
Hagino, K.; Stawarz, Ł.; Siemiginowska, A.; Cheung, C. C.; Kozieł-Wierzbowska, D.; Szostek, A.; Madejski, G.; Harris, D. E.; Simionescu, A.; Takahashi, T.
2015-05-26
Here we analyze radio, optical, and X-ray data for the peculiar cluster Abell 578. This cluster is not fully relaxed and consists of two merging sub-systems. The brightest cluster galaxy (BCG), CGPG 0719.8+6704, is a pair of interacting ellipticals with projected separation ~10 kpc, the brighter of which hosts the radio source 4C+67.13. The Fanaroff–Riley type-II radio morphology of 4C+67.13 is unusual for central radio galaxies in local Abell clusters. Our new optical spectroscopy revealed that both nuclei of the CGPG 0719.8+6704 pair are active, albeit at low accretion rates corresponding to the Eddington ratio $\\sim {{10}^{-4}}$ (for the estimated black hole masses of $\\sim 3\\times {{10}^{8}}\\;{{M}_{\\odot }}$ and $\\sim {{10}^{9}}\\;{{M}_{\\odot }}$). The gathered X-ray (Chandra) data allowed us to confirm and to quantify robustly the previously noted elongation of the gaseous atmosphere in the dominant sub-cluster, as well as a large spatial offset (~60 kpc projected) between the position of the BCG and the cluster center inferred from the modeling of the X-ray surface brightness distribution. Detailed analysis of the brightness profiles and temperature revealed also that the cluster gas in the vicinity of 4C+67.13 is compressed (by a factor of about ~1.4) and heated (from $\\simeq 2.0$ keV up to 2.7 keV), consistent with the presence of a weak shock (Mach number ~1.3) driven by the expanding jet cocoon. As a result, this would then require the jet kinetic power of the order of $\\sim {{10}^{45}}$ erg s^{–1}, implying either a very high efficiency of the jet production for the current accretion rate, or a highly modulated jet/accretion activity in the system.
Revisiting Abell 2744: a powerful synergy of the GLASS spectroscopy and the HFF photometry.
NASA Astrophysics Data System (ADS)
Wang, Xin; Borello Schmidt, Kasper; Treu, Tommaso
2015-08-01
We present new emission line identifications and improve the strong lensing reconstruction of the massive cluster Abell 2744 using the Grism Lens-Amplified Survey from Space (GLASS) observations and the full depth of the Hubble Frontier Fields (HFF) imaging. We performed a blind and targeted search for emission lines in objects within the full field of view (FoV) of the GLASS prime pointings, including all the previously known multiple arc images. We report over 50 high quality spectroscopic redshifts, 4 of which are for the arc images. We also present an extensive analysis based on the HFF photometry, measuring the colors and photometric redshifts of all objects within the FoV, and comparing the spectroscopic and photometric results of the same ensemble of sources. In order to improve the lens model of Abell 2744, we develop a rigorous alogorithm to screen arc images, based on their colors and morphology, and selecting the most reliable ones to use. As a result, 21 systems (corresponding to 59 images) pass the screening process and are used to reconstruct the gravitational potential of the cluster pixellated on an adaptive mesh. The resulting total mass distribution is compared with a stellar mass map obtained from the deep Spitzer Frontier Fields data in a fashion very similar to the reduction of the Spitzer UltRa Faint SUrvey Program (SURFS UP) clusters, in order to study the relative distribution of stars and dark matter in the cluster. The maps of convergence, shear, and magnification are made publicly available in the standard HFF format.
Search for a non-equilibrium plasma in the merging galaxy cluster Abell 754
NASA Astrophysics Data System (ADS)
Inoue, Shota; Hayashida, Kiyoshi; Ueda, Shutaro; Nagino, Ryo; Tsunemi, Hiroshi; Koyama, Katsuji
2016-06-01
Abell 754 is a galaxy cluster in which an ongoing merger is evident on the plane of the sky, from the southeast to the northwest. We study the spatial variation of the X-ray spectra observed with Suzaku along the merging direction, centering on the Fe Ly α/Fe He α line ratio to search for possible deviation from ionization equilibrium. Fitting with a single-temperature collisional non-equilibrium plasma model shows that the electron temperature increases from the southeast to the northwest. The ionization parameter is consistent with that in equilibrium (net > 1013 s cm-3) except for the specific region with the highest temperature (kT=13.3_{-1.1}^{+1.4}keV) where n_et=10^{11.6_{-1.7}^{+0.6}}s cm-3. The elapsed time from the plasma heating estimated from the ionization parameter is 0.36-76 Myr at the 90% confidence level. This timescale is quite short but consistent with the traveling time of a shock to pass through that region. We thus interpret that the non-equilibrium ionization plasma in Abell 754 observed is a remnant of the shock heating in the merger process. However, we note that the X-ray spectrum of the specific region where the non-equilibrium is found can also be fitted with a collisional ionization plasma model with two temperatures, low kT=4.2^{+4.2}_{-1.5}keV and very high kT >19.3 keV. The very high temperature component is alternatively fitted with a power-law model. Either of these spectral models is interpreted as a consequence of the ongoing merger process as in the case of the non-equilibrium ionization plasma.
Inverse heat mimicking of given objects
NASA Astrophysics Data System (ADS)
Alwakil, Ahmed; Zerrad, Myriam; Bellieud, Michel; Amra, Claude
2017-03-01
We address a general inverse mimicking problem in heat conduction. The objects to cloak and mimic are chosen beforehand; these objects identify a specific set of space transformations. The shapes that can be mimicked are derived from the conductivity matrices. Numerical calculation confirms all of the analytical predictions. The technique provides key advantages for applications and can be extended to the field of waves.
Transformational Learners: Transformational Teachers
ERIC Educational Resources Information Center
Jones, Marguerite
2009-01-01
Transformational learning, according to Mezirow (1981), involves transforming taken-for-granted frames of reference into more discriminating, flexible "habits of mind". In teacher education, transformative learning impacts on the development of students' action theories, self-efficacy and professional attributes. Although considered…
Ionospheric profile inversion using oblique-incidence ionograms
NASA Technical Reports Server (NTRS)
Nielson, D. L.; Watt, T. M.
1972-01-01
Some of the elementary methods used in deriving true-height profiles from oblique-incidence ionograms are reviewed. The two principal methods presented are oblique-to-vertical transformation and direct inversion of the oblique-incidence ionogram. Limitations in oblique-incidence inversion due to magnetic-field effects, horizontal gradients, and absolute time delay are discussed.
MEERSCHAERT, MARK M.; STRAKA, PETER
2013-01-01
The inverse stable subordinator provides a probability model for time-fractional differential equations, and leads to explicit solution formulae. This paper reviews properties of the inverse stable subordinator, and applications to a variety of problems in mathematics and physics. Several different governing equations for the inverse stable subordinator have been proposed in the literature. This paper also shows how these equations can be reconciled. PMID:25045216
Generalized Uncertainty Quantification for Linear Inverse Problems in X-ray Imaging
Fowler, Michael James
2014-04-25
In industrial and engineering applications, X-ray radiography has attained wide use as a data collection protocol for the assessment of material properties in cases where direct observation is not possible. The direct measurement of nuclear materials, particularly when they are under explosive or implosive loading, is not feasible, and radiography can serve as a useful tool for obtaining indirect measurements. In such experiments, high energy X-rays are pulsed through a scene containing material of interest, and a detector records a radiograph by measuring the radiation that is not attenuated in the scene. One approach to the analysis of these radiographs is to model the imaging system as an operator that acts upon the object being imaged to produce a radiograph. In this model, the goal is to solve an inverse problem to reconstruct the values of interest in the object, which are typically material properties such as density or areal density. The primary objective in this work is to provide quantitative solutions with uncertainty estimates for three separate applications in X-ray radiography: deconvolution, Abel inversion, and radiation spot shape reconstruction. For each problem, we introduce a new hierarchical Bayesian model for determining a posterior distribution on the unknowns and develop efficient Markov chain Monte Carlo (MCMC) methods for sampling from the posterior. A Poisson likelihood, based on a noise model for photon counts at the detector, is combined with a prior tailored to each application: an edge-localizing prior for deconvolution; a smoothing prior with non-negativity constraints for spot reconstruction; and a full covariance sampling prior based on a Wishart hyperprior for Abel inversion. After developing our methods in a general setting, we demonstrate each model on both synthetically generated datasets, including those from a well known radiation transport code, and real high energy radiographs taken at two U. S. Department of Energy
NASA Astrophysics Data System (ADS)
Bockenhauer, Samuel; Fuerstenberg, Alexandre; Yao, Xiao Jie; Kobilka, Brian K.; Moerner, W. E.
2012-02-01
The ABEL trap allows trapping of single biomolecules in solution for extended observation without immobilization. The essential idea combines fluorescence-based position estimation with fast electrokinetic feedback in a microfluidic geometry to counter the Brownian motion of a single nanoscale object, hence maintaining its position in the field of view for hundreds of milliseconds to seconds. Such prolonged observation of single proteins allows access to slow dynamics, as probed by any available photophysical observables. We have used the ABEL trap to study conformational dynamics of the β2-adrenergic receptor, a key G-protein coupled receptor and drug target, in the absence and presence of agonist. A single environment-sensitive dye reports on the receptor microenvironment, providing a real-time readout of conformational change for each trapped receptor. The focus of this paper will be a quantitative comparison of the ligandfree and agonist-bound receptor data from our ABEL trap experiments. We observe a small but clearly detectable shift in conformational equilibria and a lengthening of fluctuation timescales upon binding of agonist. In order to quantify the shift in state distributions and timescales, we apply nonparametric statistical tests to place error bounds on the resulting single-molecule distributions.
Yao, Jie; Lesage, Anne-Cécile; Hussain, Fazle; Bodmann, Bernhard G.; Kouri, Donald J.
2014-12-15
The reversion of the Born-Neumann series of the Lippmann-Schwinger equation is one of the standard ways to solve the inverse acoustic scattering problem. One limitation of the current inversion methods based on the reversion of the Born-Neumann series is that the velocity potential should have compact support. However, this assumption cannot be satisfied in certain cases, especially in seismic inversion. Based on the idea of distorted wave scattering, we explore an inverse scattering method for velocity potentials without compact support. The strategy is to decompose the actual medium as a known single interface reference medium, which has the same asymptotic form as the actual medium and a perturbative scattering potential with compact support. After introducing the method to calculate the Green’s function for the known reference potential, the inverse scattering series and Volterra inverse scattering series are derived for the perturbative potential. Analytical and numerical examples demonstrate the feasibility and effectiveness of this method. Besides, to ensure stability of the numerical computation, the Lanczos averaging method is employed as a filter to reduce the Gibbs oscillations for the truncated discrete inverse Fourier transform of each order. Our method provides a rigorous mathematical framework for inverse acoustic scattering with a non-compact support velocity potential.
ERIC Educational Resources Information Center
Bedard, Catherine; Belin, Pascal
2004-01-01
Voice is the carrier of speech but is also an ''auditory face'' rich in information on the speaker's identity and affective state. Three experiments explored the possibility of a ''voice inversion effect,'' by analogy to the classical ''face inversion effect,'' which could support the hypothesis of a voice-specific module. Experiment 1 consisted…
Teaching about Inverse Functions
ERIC Educational Resources Information Center
Esty, Warren
2005-01-01
In their sections on inverses most precalculus texts emphasize an algorithm for finding f [superscript -1] given f. However, inspection of precalculus and calculus texts shows that students will never again use the algorithm, which suggests the textbook emphasis may be misplaced. Inverses appear primarily when equations need to be solved, which…
Dewpoint temperature inversions analyzed
NASA Technical Reports Server (NTRS)
Ashby, W. C.; Bogner, M. A.; Moses, H.
1969-01-01
Dewpoint temperature inversion, with regard to other simultaneous meteorological conditions, was examined to establish the influence of meteorological variables on the variation of dewpoint temperature with height. This report covers instrumentation and available data, all the climatological features of dewpoint inversions, and specific special cases.
Structure of Abell 1995 from optical and X-ray data: a galaxy cluster with an elongated radio halo
NASA Astrophysics Data System (ADS)
Boschin, W.; Girardi, M.; Barrena, R.
2012-11-01
Context. Abell 1995 is a puzzling galaxy cluster hosting a powerful radio halo, but it has not yet been recognized as a obvious cluster merger, as usually expected for clusters with diffuse radio emission. Aims: We aim at an exhaustive analysis of the internal structure of Abell 1995 to verify that this cluster is really dynamically relaxed, as reported in previous studies. Methods: We base our analysis on new and archival spectroscopic and photometric data for 126 galaxies in the field of Abell 1995. The study of the hot intracluster medium was performed on X-ray archival data. Results: Based on 87 fiducial cluster members, we have computed the average cluster redshift ⟨z⟩ = 0.322 and the global radial velocity dispersion σV ~ 1300 km s-1. We detect two main optical subclusters separated by 1.5'that cause the known NE-SW elongation of the galaxy distribution and a significant velocity gradient in the same direction. As for the X-ray analysis, we confirm that the intracluster medium is mildly elongated, but we also detect three X-ray peaks. Two X-ray peaks are offset with respect to the two galaxy peaks and lie between them, thus suggesting a bimodal merger caught in a phase of post core-core passage. The third X-ray peak lies between the NE galaxy peak and a third, minor galaxy peak suggesting a more complex merger. The difficulty of separating the two main systems leads to a large uncertainty on the line-of-sight (LOS) velocity separation and the system mass: ΔVrf,LOS = 600-2000 km s-1and Msys = 2-5×1015 h70-1 M⊙, respectively. Simple analytical arguments suggest a merging scenario for Abell 1995, where two main subsystems are seen just after the collision with an intermediate projection angle. Conclusions: The high mass of Abell 1995 and the evidence of merging suggest it is not atypical among clusters with known radio halos. Interestingly, our findings reinforce the previous evidence for the peculiar dichotomy between the dark matter and galaxy
A Census of Star Formation and Active Galactic Nuclei Populations in Abell 1689
NASA Astrophysics Data System (ADS)
Jones, Logan H.; Atlee, David Wesley
2016-01-01
A recent survey of low-z galaxy clusters observed a disjunction between X-ray and mid-infrared selected populations of active galactic nuclei (X-ray and IR AGNs) (Atlee+ 2011, ApJ 729, 22.). Here we present an analysis of near-infrared spectroscopic data of star-forming galaxies in cluster Abell 1689 in order to confirm the identity of some of their IR AGN and to provide a check on their reported star formation rates. Our sample consists of 24 objects in Abell 1689. H and K band spectroscopic observations of target objects and standard stars were obtained by David Atlee between 2010 May 17 and 2011 June 6 using the Large Binocular Telescope's LUCI instrument. After undergoing initial reductions, standard stars were corrected for telluric absorption using TelFit (Gullikson+ 2014, AJ, 158, 53). Raw detector counts were converted to physical units using the wavelength-dependent response of the grating and the star's reported H and K band magnitudes to produce conversion factors that fully correct for instrumental effects. Target spectra were flux-calibrated using the airmass-corrected transmission profiles produced by TelFit and the associated H band conversion factor (or the average of the two factors, for nights with two standard stars). Star formation rates were calculated using the SFR-L(Ha) relation reported in Kennicutt (1998), with the measured luminosity of the Pa-a emission line at the luminosity distance of the cluster used as a proxy for L(Ha) (Kennicutt 1998, ARA&A 36, 189; Hummer & Stoney 1987, MNRAS 346, 1055). The line ratios H2 2.121 mm/Brg and [FeII]/Pab were used to classify targets as starburst galaxies, AGNs, or LINERs (Rodriguez-Ardila+ 2005, MNRAS, 364, 1041). Jones was supported by the NOAO/KPNO Research Experience for Undergraduates (REU) Program, which is funded by the National Science Foundation Research Experiences for Undergraduates Program (AST-1262829).
SPECTRAL INDEX STUDIES OF THE DIFFUSE RADIO EMISSION IN ABELL 2256: IMPLICATIONS FOR MERGER ACTIVITY
Kale, Ruta; Dwarakanath, K. S. E-mail: dwaraka@rri.res.i
2010-08-01
We present a multi-wavelength analysis of the merging rich cluster of galaxies, Abell 2256 (A2256). We have observed A2256 at 150 MHz using the Giant Metrewave Radio Telescope and successfully detected the diffuse radio halo and the relic emission over a {approx}1.2 Mpc{sup 2} extent. Using this 150 MHz image and the images made using archival observations from the Very Large Array (VLA; 1369 MHz) and the Westerbrok Synthesis Radio Telescope (WSRT; 330 MHz), we have produced spectral index images of the diffuse radio emission in A2256. These spectral index images show a distribution of flat spectral index (S {proportional_to} {nu}{sup {alpha}}, {alpha} in the range -0.7 to -0.9) plasma in the region NW of the cluster center. Regions showing steep spectral indices ({alpha} in the range -1.0 to -2.3) are toward the SE of the cluster center. These spectral indices indicate synchrotron lifetimes for the relativistic plasmas in the range 0.08-0.4 Gyr. We interpret this spectral behavior as resulting from a merger event along the direction SE to NW within the last 0.5 Gyr or so. A shock may be responsible for the NW relic in A2256 and the megaparsec scale radio halo toward the SE is likely to be generated by the turbulence injected by mergers. Furthermore, the diffuse radio emission shows spectral steepening toward lower frequencies. This low-frequency spectral steepening is consistent with a combination of spectra from two populations of relativistic electrons created at two epochs (two mergers) within the last {approx}0.5 Gyr. Earlier interpretations of the X-ray and the optical data also suggested that there were two mergers in Abell 2256 in the last 0.5 Gyr, consistent with the current findings. Also highlighted in this study is the futility of correlating the average temperatures of thermal gas and the average spectral indices of diffuse radio emission in the respective clusters.
On the Merging Cluster Abell 578 and Its Central Radio Galaxy 4C+67.13
NASA Astrophysics Data System (ADS)
Hagino, K.; Stawarz, Ł.; Siemiginowska, A.; Cheung, C. C.; Kozieł-Wierzbowska, D.; Szostek, A.; Madejski, G.; Harris, D. E.; Simionescu, A.; Takahashi, T.
2015-06-01
Here we analyze radio, optical, and X-ray data for the peculiar cluster Abell 578. This cluster is not fully relaxed and consists of two merging sub-systems. The brightest cluster galaxy (BCG), CGPG 0719.8+6704, is a pair of interacting ellipticals with projected separation ˜10 kpc, the brighter of which hosts the radio source 4C+67.13. The Fanaroff-Riley type-II radio morphology of 4C+67.13 is unusual for central radio galaxies in local Abell clusters. Our new optical spectroscopy revealed that both nuclei of the CGPG 0719.8+6704 pair are active, albeit at low accretion rates corresponding to the Eddington ratio ˜ {{10}-4} (for the estimated black hole masses of ˜ 3× {{10}8} {{M}⊙ } and ˜ {{10}9} {{M}⊙ }). The gathered X-ray (Chandra) data allowed us to confirm and to quantify robustly the previously noted elongation of the gaseous atmosphere in the dominant sub-cluster, as well as a large spatial offset (˜60 kpc projected) between the position of the BCG and the cluster center inferred from the modeling of the X-ray surface brightness distribution. Detailed analysis of the brightness profiles and temperature revealed also that the cluster gas in the vicinity of 4C+67.13 is compressed (by a factor of about ˜1.4) and heated (from ≃ 2.0 keV up to 2.7 keV), consistent with the presence of a weak shock (Mach number ˜1.3) driven by the expanding jet cocoon. This would then require the jet kinetic power of the order of ˜ {{10}45} erg s-1, implying either a very high efficiency of the jet production for the current accretion rate, or a highly modulated jet/accretion activity in the system. Based on service observations made with the WHT operated on the island of La Palma by the Isaac Newton Group in the Spanish Observatorio del Roque de los Muchachos of the Instituto de Astrofísica de Canarias.
Suzaku observations of the merging galaxy cluster Abell 2255: The northeast radio relic
NASA Astrophysics Data System (ADS)
Akamatsu, H.; Mizuno, M.; Ota, N.; Zhang, Y.-Y.; van Weeren, R. J.; Kawahara, H.; Fukazawa, Y.; Kaastra, J. S.; Kawaharada, M.; Nakazawa, K.; Ohashi, T.; Röttgering, H. J. A.; Takizawa, M.; Vink, J.; Zandanel, F.
2017-04-01
We present the results of deep 140 ks Suzaku X-ray observations of the north-east (NE) radio relic of the merging galaxy cluster Abell 2255. The temperature structure of Abell 2255 is measured out to 0.9 times the virial radius (1.9 Mpc) in the NE direction for the first time. The Suzaku temperature map of the central region suggests a complex temperature distribution, which agrees with previous work. Additionally, on a larger-scale, we confirm that the temperature drops from 6 keV around the cluster center to 3 keV at the outskirts, with two discontinuities at r 5' (450 kpc) and 12' (1100 kpc) from the cluster center. Their locations coincide with surface brightness discontinuities marginally detected in the XMM-Newton image, which indicates the presence of shock structures. From the temperature drop, we estimate the Mach numbers to be ℳinner 1.2 and, ℳouter 1.4. The first structure is most likely related to the large cluster core region ( 350-430 kpc), and its Mach number is consistent with the XMM-Newton observation (ℳ 1.24: Sakelliou & Ponman 2006, MNRAS, 367, 1409). Our detection of the second temperature jump, based on the Suzaku key project observation, shows the presence of a shock structure across the NE radio relic. This indicates a connection between the shock structure and the relativistic electrons that generate radio emission. Across the NE radio relic, however, we find a significantly lower temperature ratio (T1/T2 1.44 ± 0.16 corresponds to ℳX-ray 1.4) than the value expected from radio wavelengths, based on the standard diffusive shock acceleration mechanism (T1/T2> 3.2 or ℳRadio> 2.8). This may suggest that under some conditions, in particular the NE relic of A2255 case, the simple diffusive shock acceleration mechanism is unlikely to be valid, and therefore, more a sophisticated mechanism is required.
A system model and inversion for synthetic aperture radar imaging.
Soumekh, M
1992-01-01
A system model and its corresponding inversion for synthetic aperture radar (SAR) imaging are presented. The system model incorporates the spherical nature of a radar's radiation pattern at far field. The inverse method based on this model performs a spatial Fourier transform (Doppler processing) on the recorded signals with respect to the available coordinates of a translational radar (SAR) or target (inverse SAR). It is shown that the transformed data provide samples of the spatial Fourier transform of the target's reflectivity function. The inverse method can be modified to incorporate deviations of the radar's motion from its prescribed straight line path. The effects of finite aperture on resolution, reconstruction, and sampling constraints for the imaging problem are discussed.
A redshift survey of the strong-lensing cluster ABELL 383
Geller, Margaret J.; Hwang, Ho Seong; Kurtz, Michael J.; Diaferio, Antonaldo; Coe, Dan; Rines, Kenneth J. E-mail: hhwang@cfa.harvard.edu E-mail: diaferio@ph.unito.it E-mail: kenneth.rines@wwu.edu
2014-03-01
Abell 383 is a famous rich cluster (z = 0.1887) imaged extensively as a basis for intensive strong- and weak-lensing studies. Nonetheless, there are few spectroscopic observations. We enable dynamical analyses by measuring 2360 new redshifts for galaxies with r {sub Petro} ≤ 20.5 and within 50' of the Brightest Cluster Galaxy (BCG; R.A.{sub 2000} = 42.°014125, decl.{sub 2000} = –03.°529228). We apply the caustic technique to identify 275 cluster members within 7 h {sup –1} Mpc of the hierarchical cluster center. The BCG lies within –11 ± 110 km s{sup –1} and 21 ± 56 h {sup –1} kpc of the hierarchical cluster center; the velocity dispersion profile of the BCG appears to be an extension of the velocity dispersion profile based on cluster members. The distribution of cluster members on the sky corresponds impressively with the weak-lensing contours of Okabe et al. especially when the impact of foreground and background structure is included. The values of R {sub 200} = 1.22 ± 0.01 h {sup –1} Mpc and M {sub 200} = (5.07 ± 0.09) × 10{sup 14} h {sup –1} M {sub ☉} obtained by application of the caustic technique agree well with recent completely independent lensing measures. The caustic estimate extends direct measurement of the cluster mass profile to a radius of ∼5 h {sup –1} Mpc.
X-Ray Spectroscopy of the Cluster of Galaxies Abell 1795 with XMM-Newton
NASA Technical Reports Server (NTRS)
Tamura, T.; Kaastra, J. S.; Peterson, J. R.; Paerels, F.; Mittaz, J. P. D.; Trudolyubov, S. P.; Stewart, G.; Fabian, A. C.; Mushotzky, R. F.; Lumb, D. H.
2000-01-01
The initial results from XMM-Newton observations of the rich cluster of galaxies Abell 1795 are presented. The spatially-resolved X-ray spectra taken by the European Photon Imaging Cameras (EPIC) show a temperature drop at a radius of - 200 kpc from the cluster center, indicating that the ICM is cooling. Both the EPIC and the Reflection Grating Spectrometers (RGS) spectra extracted from the cluster center can be described by an isothermal model with a temperature of approx. 4 keV. The volume emission measure of any cool component (less than 1 keV) is less than a few % of the hot component at the cluster center. A strong O VIII Lyman alpha line was detected with the RGS from the cluster core. The O abundance of the ICM is 0.2-0.5 times the solar value. The O to Fe ratio at the cluster center is 0.5 - 1.5 times the solar ratio.
Separating galaxies from the cluster dark matter halo in Abell 611
NASA Astrophysics Data System (ADS)
Monna, A.; Seitz, S.; Geller, M. J.; Zitrin, A.; Mercurio, A.; Suyu, S. H.; Postman, M.; Fabricant, D. G.; Hwang, H. S.; Koekemoer, A.
2017-03-01
We investigate the mass content of galaxies in the core of the galaxy cluster Abell 611. We perform a strong lensing analysis of the cluster core and use velocity dispersion measurements for individual cluster members as additional constraints. Despite the small number of multiply-imaged systems and cluster members with central velocity dispersions available in the core of A611, the addition of velocity dispersion measurements leads to tighter constraints on the mass associated with the galaxy component, and as a result, on the mass associated with the dark matter halo. Without the spectroscopic velocity dispersions, we would overestimate the mass of the galaxy component by a factor of ∼1.5, or, equivalently, we would underestimate the mass of the cluster dark halo by ∼5 per cent. We perform an additional lensing analysis using surface brightness (SB) reconstruction of the tangential giant arc. This approach improves the constraints on the mass parameters of the five galaxies close to the arc by a factor up to ∼10. The resulting parameters are in good agreement with the σ-rtr scaling relation derived in the pointlike analysis. The galaxy velocity dispersions resulting from the SB analysis are consistent at the 1σ confidence level with the spectroscopic measurements. In contrast, the truncation radii for 2-3 galaxies depart significantly from the galaxy scaling relation and suggest differences in the stripping history from galaxy to galaxy.
Disentangling the ICL with the CHEFs: Abell 2744 as a Case Study
NASA Astrophysics Data System (ADS)
Jiménez-Teja, Y.; Dupke, R.
2016-03-01
Measurements of the intracluster light (ICL) are still prone to methodological ambiguities, and there are multiple techniques in the literature to address them, mostly based on the binding energy, the local density distribution, or the surface brightness. A common issue with these methods is the a priori assumption of a number of hypotheses on either the ICL morphology, its surface brightness level, or some properties of the brightest cluster galaxy (BCG). The discrepancy in the results is high, and numerical simulations just place a boundary on the ICL fraction in present-day galaxy clusters in the range 10%-50%. We developed a new algorithm based on the Chebyshev-Fourier functions to estimate the ICL fraction without relying on any a priori assumption about the physical or geometrical characteristics of the ICL. We are able to not only disentangle the ICL from the galactic luminosity but mark out the limits of the BCG from the ICL in a natural way. We test our technique with the recently released data of the cluster Abell 2744, observed by the Frontier Fields program. The complexity of this multiple merging cluster system and the formidable depth of these images make it a challenging test case to prove the efficiency of our algorithm. We found a final ICL fraction of 19.17 ± 2.87%, which is very consistent with numerical simulations.
Uniform Contribution of Supernova Explosions to the Chemical Enrichment of Abell 3112 out to R 200
NASA Astrophysics Data System (ADS)
Ezer, Cemile; Bulbul, Esra; Nihal Ercan, E.; Smith, Randall K.; Bautz, Mark W.; Loewenstein, Mike; McDonald, Mike; Miller, Eric D.
2017-02-01
The spatial distribution of the metals residing in the intra-cluster medium (ICM) of galaxy clusters records all the information on a cluster’s nucleosynthesis and chemical enrichment history. We present measurements from a total of 1.2 Ms Suzaku XIS and 72 ks Chandra observations of the cool-core galaxy cluster Abell 3112 out to its virial radius (∼1470 kpc). We find that the ratio of the observed supernova type Ia explosions to the total supernova explosions has a uniform distribution at a level of 12%–16% out to the cluster’s virial radius. The observed fraction of type Ia supernova explosions is in agreement with the corresponding fraction found in our Galaxy and the chemical enrichment of our Galaxy. The non-varying supernova enrichment suggests that the ICM in cluster outskirts was enriched by metals at an early stage before the cluster itself was formed during a period of intense star formation activity. Additionally, we find that the 2D delayed detonation model CDDT produce significantly worse fits to the X-ray spectra compared to simple 1D W7 models. This is due to the relative overestimate of Si, and the underestimate of Mg in these models with respect to the measured abundances.
Antioxidant activity and bioactive compounds of tea seed (Camellia oleifera Abel.) oil.
Lee, Chia-Pu; Yen, Gow-Chin
2006-02-08
The oil of tea seed (Camellia oleifera Abel.) is used extensively in China as cooking oil. The objectives of this study were to investigate the antioxidant activity of tea seed oil and its active compounds. Of the five solvent extracts, methanol extract of tea seed oil exhibited the highest yield and the strongest antioxidant activity as determined by DPPH scavenging activity and Trolox equivalent antioxidant capacity (TEAC). Two peaks separated from the methanol extract by HPLC contributed the most significant antioxidant activity. These two peaks were further identified as sesamin and a novel compound: 2,5-bis-benzo[1,3]dioxol-5-yl-tetrahydro-furo [3,4-d][1,3]dioxine (named compound B) by UV absorption and characterized by MS, IR, 1H NMR, and 13C NMR techniques. Sesamin and compound B decreased H2O2-mediated formation of reactive oxygen species in red blood cells (RBCs), inhibited RBCs hemolysis induced by AAPH, and increased the lag time of conjugated dienes formation in human low-density lipoprotein. The results indicate that both compounds isolated from tea seed oil exhibit remarkable antioxidant activity. Apart from the traditional pharmacological effects of Camellia oleifera, the oil of tea seed may also act as a prophylactic agent to prevent free radical related diseases.
Star formation quenching and stellar mass in the cluster Abell 85
NASA Astrophysics Data System (ADS)
Fadda, Dario; Habas, Rebecca; Marleau, Francine; Biviano, Andrea; Durret, Florence
2017-01-01
We report the discovery of a group of galaxies falling into the cluster Abell 85 showing a decrease in star formation limited to its dwarf galaxy population. We covered the cluster and its surroundings with a multi-wavelength survey from the UV to the far-IR using ground and space telescopes (including GALEX, Spitzer, and Herschel) and followed-up these observations with spectroscopic surveys with the WIYN/Hydra and VLT/VIMOS instruments. We were able to obtain spectra for 522 members down to r'=20, 30% of them showing H-alpha emission. We estimated the variation in star formation rate by using two different estimators based on continuum (UV) and line (H-alpha) emission. While massive infalling galaxies continue to produce stars during the infall, the star formation in dwarf galaxies appear to be quenched by the cluster environment. Considering the different time-scales of the two estimators, we can estimate that the quenching happens in a period of approximately 10 Myr.
Systematic Uncertainties in Characterizing Cluster Outskirts: The Case of Abell 133
NASA Astrophysics Data System (ADS)
Paine, Jennie; Ogrean, Georgiana A.; Nulsen, Paul; Farrah, Duncan
2016-01-01
The outskirts of galaxy clusters have low surface brightness compared to the X-ray background, making accurate background subtraction particularly important for analyzing cluster spectra out to and beyond the virial radius. We analyze the thermodynamic properties of the intracluster medium (ICM) of Abell 133 and assess the extent to which uncertainties on background subtraction affect measured quantities. We implement two methods of analyzing the ICM spectra: one in which the blank-sky background is subtracted, and another in which the sky background is modeled. We find that the two methods are consistent within the 90% confidence ranges. We were able to measure the thermodynamic properties of the cluster up to R500. Even at R500, the systematic uncertainties associated with the sky background in the direction of A133 are small, despite the ICM signal constituting only ~25% of the total signal. This work was supported in part by the NSF REU and DoD ASSURE programs under NSF grant no. 1262851 and by the Smithsonian Institution. GAO acknowledges support by NASA through a Hubble Fellowship grant HST-HF2-51345.001-A awarded by the Space Telescope Science Institute, which is operated by the Association of Universities for Research in Astronomy, Incorporated, under NASA contract NAS5-26555.
DISENTANGLING THE ICL WITH THE CHEFs: ABELL 2744 AS A CASE STUDY
Jiménez-Teja, Y.; Dupke, R.
2016-03-20
Measurements of the intracluster light (ICL) are still prone to methodological ambiguities, and there are multiple techniques in the literature to address them, mostly based on the binding energy, the local density distribution, or the surface brightness. A common issue with these methods is the a priori assumption of a number of hypotheses on either the ICL morphology, its surface brightness level, or some properties of the brightest cluster galaxy (BCG). The discrepancy in the results is high, and numerical simulations just place a boundary on the ICL fraction in present-day galaxy clusters in the range 10%–50%. We developed a new algorithm based on the Chebyshev–Fourier functions to estimate the ICL fraction without relying on any a priori assumption about the physical or geometrical characteristics of the ICL. We are able to not only disentangle the ICL from the galactic luminosity but mark out the limits of the BCG from the ICL in a natural way. We test our technique with the recently released data of the cluster Abell 2744, observed by the Frontier Fields program. The complexity of this multiple merging cluster system and the formidable depth of these images make it a challenging test case to prove the efficiency of our algorithm. We found a final ICL fraction of 19.17 ± 2.87%, which is very consistent with numerical simulations.
The SAMI Galaxy Survey: Galaxy Interactions and Kinematic Anomalies in Abell 119
NASA Astrophysics Data System (ADS)
Oh, Sree; Yi, Sukyoung K.; Cortese, Luca; van de Sande, Jesse; Mahajan, Smriti; Jeong, Hyunjin; Sheen, Yun-Kyeong; Allen, James T.; Bekki, Kenji; Bland-Hawthorn, Joss; Bloom, Jessica V.; Brough, Sarah; Bryant, Julia J.; Colless, Matthew; Croom, Scott M.; Fogarty, L. M. R.; Goodwin, Michael; Green, Andy; Konstantopoulos, Iraklis S.; Lawrence, Jon; López-Sánchez, Á. R.; Lorente, Nuria P. F.; Medling, Anne M.; Owers, Matt S.; Richards, Samuel; Scott, Nicholas; Sharp, Rob; Sweet, Sarah M.
2016-11-01
Galaxy mergers are important events that can determine the fate of a galaxy by changing its morphology, star formation activity and mass growth. Merger systems have commonly been identified from their disturbed morphologies, and we now can employ integral field spectroscopy to detect and analyze the impact of mergers on stellar kinematics as well. We visually classified galaxy morphology using deep images ({μ }{{r}}=28 {mag} {{arcsec}}-2) taken by the Blanco 4 m telescope at the Cerro Tololo Inter-American Observatory. In this paper we investigate 63 bright ({M}{{r}}\\lt -19.3) spectroscopically selected galaxies in Abell 119, of which 53 are early type and 20 show a disturbed morphology by visual inspection. A misalignment between the major axes in the photometric image and the kinematic map is conspicuous in morphologically disturbed galaxies. Our sample is dominated by early-type galaxies, yet it shows a surprisingly tight Tully-Fisher relation except for the morphologically disturbed galaxies which show large deviations. Three out of the eight slow rotators in our sample are morphologically disturbed. The morphologically disturbed galaxies are generally more asymmetric, visually as well as kinematically. Our findings suggest that galaxy interactions, including mergers and perhaps fly-bys, play an important role in determining the orientation and magnitude of a galaxy’s angular momentum.
The Velocity Dispersion Function of Very Massive Galaxy Clusters: Abell 2029 and Coma
NASA Astrophysics Data System (ADS)
Sohn, Jubee; Geller, Margaret J.; Zahid, H. Jabran; Fabricant, Daniel G.; Diaferio, Antonaldo; Rines, Kenneth J.
2017-04-01
Based on an extensive redshift survey for galaxy clusters Abell 2029 and Coma, we measure the luminosity functions (LFs) and stellar mass functions (SMFs) for the entire cluster member galaxies. Most importantly, we measure the velocity dispersion functions (VDFs) for quiescent members. The MMT/Hectospec redshift survey for galaxies in A2029 identifies 982 spectroscopic members; for 838 members, we derive the central velocity dispersion from the spectroscopy. Coma is the only other cluster surveyed as densely. The LFs, SMFs, and VDFs for A2029 and Coma are essentially identical. The SMFs of the clusters are consistent with simulations. The A2029 and Coma VDFs for quiescent galaxies have a significantly steeper slope than those of field galaxies for velocity dispersion ≲ 100 {km} {{{s}}}-1. The cluster VDFs also exceed the field at velocity dispersion ≳ 250 {km} {{{s}}}-1. The differences between cluster and field VDFs are potentially important tests of simulations and of the formation of structure in the universe.
STRONG GRAVITATIONAL LENSING BY THE SUPER-MASSIVE cD GALAXY IN ABELL 3827
Carrasco, E. R.; Gomez, P. L.; Lee, H.; Diaz, R.; Bergmann, M.; Turner, J. E. H.; Miller, B. W.; West, M. J.; Verdugo, T.
2010-06-01
We have discovered strong gravitational lensing features in the core of the nearby cluster Abell 3827 by analyzing Gemini South GMOS images. The most prominent strong lensing feature is a highly magnified, ring-shaped configuration of four images around the central cD galaxy. GMOS spectroscopic analysis puts this source at z {approx} 0.2. Located {approx}20'' away from the central galaxy is a secondary tangential arc feature which has been identified as a background galaxy with z {approx} 0.4. We have modeled the gravitational potential of the cluster core, taking into account the mass from the cluster, the brightest cluster galaxy (BCG), and other galaxies. We derive a total mass of (2.7 {+-} 0.4) x 10{sup 13} M {sub sun} within 37 h {sup -1} kpc. This mass is an order of magnitude larger than that derived from X-ray observations. The total mass derived from lensing data suggests that the BCG in this cluster is perhaps the most massive galaxy in the nearby universe.
Canibalismo Extremo y Lente Gravitacional Intensa en el Cúmulo de Galaxias Abell 3827
NASA Astrophysics Data System (ADS)
Díaz, R. J.; West, M.; Bergmann, M.; Carrasco, E. R.; Gomez, P.; Lee, H.; Miller, B.; Turner, J.
Abell 3827 is one of the most massive known clusters and at its center we observe an extreme example of galactic canibalism: a super giant elliptical galaxy in its formation process, devoring five massive galaxies at the same time. Using high spatial resolution Gemini+GMOS imagery and multi-object spectroscopy, we derived the redshift (z=0.099) and the radial velocity dispersion of the 55 brightest galaxies in the cluster central region (1134 +- 125 km/s). The estimated virial mass is ~ 1E14 M(sun) inside a radius of 300 kpc of the cluster center. We have also found features corresponding to a strong gravitational lense, four anular features arranged in an Einstein Ring from a galaxy (z=0.2) at double redshift than the cluster, and a fifth arclet feature corresponding to the lensed light of a farther galaxy (z=0.4). The possible Einstein Ring is of small angular size and the gravitational lense morphology would confirm that the cluster is indeed very massive and dense. FULL TEXT IN SPANISH.
A Cosmic Train Wreck: JVLA Radio Observations of the HST Frontier Fields Cluster Abell 2744
NASA Astrophysics Data System (ADS)
Pearce, Connor; Van Weeren, Reinout J.; Jones, Christine; Forman, William R.; Ogrean, Georgiana A.; Andrade-Santos, Felipe; Kraft, Ralph P.; Dawson, William; Brüggen, Marcus; Roediger, Elke; Bulbul, Esra; Mroczkowski, Tony
2016-01-01
The galaxy cluster mergers observed in the HST Frontier Fields represent some of the most energetic events in the Universe. Major cluster mergers leave distinct signatures in the ICM in the form of shocks, turbulence, and diffuse cluster radio sources. These diffuse radio sources, so-called radio relics and halos, provide evidence for the acceleration of relativistic particles and the presence of large scale magnetic fields in the ICM. Observations of these halos and relics allow us to (i) study the physics of particle acceleration and its relation with shocks and turbulence in the ICM and (ii) constrain the dynamical evolution of the merger eventsWe present Jansky Very Large Array 1-4 GHz observations of the Frontier cluster Abell 2744. We confirm the presence of the known giant radio halo and radio relic via our deep radio images. Owing to the much greater sensitivity of the JVLA compared to previous observations, we are able to detect a previously unobserved long Mpc-size filament of synchrotron emission to the south west of the cluster core. We also present a radio spectral index image of the diffuse cluster emission to test the origin of the radio relic and halo, related to the underlying particle acceleration mechanism. Finally, we carry out a search for radio emission from the 'jellyfish' galaxies in A2744 to estimate their star formation rate. These highly disturbed galaxies are likely influenced by the cluster merger event, although the precise origin of these galaxies is still being debated.
Characterizing the inverses of block tridiagonal, block Toeplitz matrices
NASA Astrophysics Data System (ADS)
Boffi, Nicholas M.; Hill, Judith C.; Reuter, Matthew G.
2015-01-01
We consider the inversion of block tridiagonal, block Toeplitz matrices and comment on the behaviour of these inverses as one moves away from the diagonal. Using matrix Möbius transformations, we first present an O(1) representation (with respect to the number of block rows and block columns) for the inverse matrix and subsequently use this representation to characterize the inverse matrix. There are four symmetry-distinct cases where the blocks of the inverse matrix (i) decay to zero on both sides of the diagonal, (ii) oscillate on both sides, (iii) decay on one side and oscillate on the other and (iv) decay on one side and grow on the other. This characterization exposes the necessary conditions for the inverse matrix to be numerically banded and may also aid in the design of preconditioners and fast algorithms. Finally, we present numerical examples of these matrix types.
The inverse electroencephalography pipeline
NASA Astrophysics Data System (ADS)
Weinstein, David Michael
The inverse electroencephalography (EEG) problem is defined as determining which regions of the brain are active based on remote measurements recorded with scalp EEG electrodes. An accurate solution to this problem would benefit both fundamental neuroscience research and clinical neuroscience applications. However, constructing accurate patient-specific inverse EEG solutions requires complex modeling, simulation, and visualization algorithms, and to date only a few systems have been developed that provide such capabilities. In this dissertation, a computational system for generating and investigating patient-specific inverse EEG solutions is introduced, and the requirements for each stage of this Inverse EEG Pipeline are defined and discussed. While the requirements of many of the stages are satisfied with existing algorithms, others have motivated research into novel modeling and simulation methods. The principal technical results of this work include novel surface-based volume modeling techniques, an efficient construction for the EEG lead field, and the Open Source release of the Inverse EEG Pipeline software for use by the bioelectric field research community. In this work, the Inverse EEG Pipeline is applied to three research problems in neurology: comparing focal and distributed source imaging algorithms; separating measurements into independent activation components for multifocal epilepsy; and localizing the cortical activity that produces the P300 effect in schizophrenia.
Function representation with circle inversion map systems
NASA Astrophysics Data System (ADS)
Boreland, Bryson; Kunze, Herb
2017-01-01
The fractals literature develops the now well-known concept of local iterated function systems (using affine maps) with grey-level maps (LIFSM) as an approach to function representation in terms of the associated fixed point of the so-called fractal transform. While originally explored as a method to achieve signal (and 2-D image) compression, more recent work has explored various aspects of signal and image processing using this machinery. In this paper, we develop a similar framework for function representation using circle inversion map systems. Given a circle C with centre õ and radius r, inversion with respect to C transforms the point p˜ to the point p˜', such that p˜ and p˜' lie on the same radial half-line from õ and d(õ, p˜)d(õ, p˜') = r2, where d is Euclidean distance. We demonstrate the results with an example.
Inverse heat mimicking of given objects
Alwakil, Ahmed; Zerrad, Myriam; Bellieud, Michel; Amra, Claude
2017-01-01
We address a general inverse mimicking problem in heat conduction. The objects to cloak and mimic are chosen beforehand; these objects identify a specific set of space transformations. The shapes that can be mimicked are derived from the conductivity matrices. Numerical calculation confirms all of the analytical predictions. The technique provides key advantages for applications and can be extended to the field of waves. PMID:28252031
NASA Technical Reports Server (NTRS)
Mclyman, W. T.
1977-01-01
In space, power system transformer components are frequently the heaviest and bulkiest items in the power conversion circuit. They also have a significant effect upon the overall performance and efficiency of the system. Accordingly, the design of such transformers has an important effect on overall system weight, power-inversion efficiency, and cost. Relationships were between the parameters used by transformer designers that can be used as new tools to standardize and simplify transformer design. They can be used to optimize the design either for small size and weight or efficiency. The metric system of units, rather than the familiar English units, is used; however, material is presented to assist the reader in the transition from one system to the other.
Globular Clusters, Ultracompact Dwarfs, and Dwarf Galaxies in Abell 2744 at a Redshift of 0.308
NASA Astrophysics Data System (ADS)
Lee, Myung Gyoon; Jang, In Sung
2016-11-01
We report a photometric study of globular clusters (GCs), ultracompact dwarfs (UCDs), and dwarf galaxies in the giant merging galaxy cluster Abell 2744 at z = 0.308. Color-magnitude diagrams of the point sources derived from deep F814W (rest frame r‧) and F105W (rest frame I) images of Abell 2744 in the Hubble Space Telescope Frontier Field show a rich population of point sources, which have colors that are similar to those of typical GCs. These sources are as bright as -14.9\\lt {M}r\\prime ≤slant -11.4 (26.0 < F814W(Vega) ≤ 29.5) mag, being mostly UCDs and bright GCs in Abell 2744. The luminosity function (LF) of these sources shows a break at {M}r\\prime ≈ -12.9 (F814W ≈ 28.0) mag, indicating a boundary between UCDs and bright GCs. The numbers of GCs and UCDs are estimated to be 1,711,640+589,760 -430,500 and 147 ± 26, respectively. The clustercentric radial number density profiles of the UCDs and bright GCs show similar slopes, but these profiles are much steeper than those of the dwarf galaxies and the mass density profile based on gravitational lensing analysis. We derive an LF of the red sequence galaxies for -22.9\\lt {M}r\\prime ≤slant -13.9 mag. The faint end of this LF is fit well by a flat power law with α =-1.14+/- 0.08, showing no faint upturn. These results support the galaxy-origin scenario for bright UCDs: they are the nuclei of dwarf galaxies that are stripped when they pass close to the center of massive galaxies or a galaxy cluster, while some of the faint UCDs are at the bright end of the GCs.
One dimensional acoustic direct nonlinear inversion using the Volterra inverse scattering series
NASA Astrophysics Data System (ADS)
Yao, Jie; Lesage, Anne-Cécile; Bodmann, Bernhard G.; Hussain, Fazle; Kouri, Donald J.
2014-06-01
Direct inversion of acoustic scattering problems is nonlinear. One way to treat the inverse scattering problem is based on the reversion of the Born-Neumann series solution of the Lippmann-Schwinger equation. An important issue for this approach is the radius of convergence of the Born-Neumann series for the forward problem. However, this issue can be tackled by employing a renormalization technique to transform the Lippmann-Schwinger equation from a Fredholm to a Volterra integral form. The Born series of a Volterra integral equation converges absolutely and uniformly in the entire complex plane. We present a further study of this new mathematical framework. A Volterra inverse scattering series (VISS) using both reflection and transmission data is derived and tested for several acoustic velocity models. For large velocity contrast, series summation techniques (e.g., Cesàro summation, Euler transform, etc) are employed to improve the rate of convergence of VISS. It is shown that the VISS method with summation techniques can provide a relatively good estimation of the velocity profile. The method is fully data-driven in the respect that no prior information of the model is required. Besides, no internal multiple removal is needed. This one dimensional VISS approach is useful for inverse scattering and serves as an important step for studying more complicated and realistic inversions.
Structure and Formation of cD Galaxies: NGC 6166 in ABELL 2199
NASA Astrophysics Data System (ADS)
Bender, Ralf; Kormendy, John; Cornell, Mark E.; Fisher, David B.
2015-07-01
Hobby-Eberly Telescope (HET) spectroscopy is used to measure the velocity dispersion profile of the nearest prototypical cD galaxy, NGC 6166 in the cluster Abell 2199. We also present composite surface photometry from many telescopes. We confirm the defining feature of a cD galaxy; i.e., (we suggest), a halo of stars that fills the cluster center and that is controlled dynamically by cluster gravity, not by the central galaxy. Our HET spectroscopy shows that the velocity dispersion of NGC 6166 rises from σ ≃ 300 km s-1 in the inner r˜ 10\\prime\\prime to σ =865+/- 58 km s-1 at r ˜ 100″ in the cD halo. This extends published observations of an outward σ increase and shows for the first time that σ rises all the way to the cluster velocity dispersion of 819 ± 32 km s-1. We also observe that the main body of NGC 6166 moves at +206 ± 39 km s-1 with respect to the cluster mean velocity, but the velocity of the inner cD halo is ˜70 km s-1 closer to the cluster velocity. These results support our picture that cD halos consist of stars that were stripped from individual cluster galaxies by fast tidal encounters. However, our photometry does not confirm the widespread view that cD halos are identifiable as an extra, low-surface-brightness component that is photometrically distinct from the inner, steep-Sérsic-function main body of an otherwise-normal giant elliptical galaxy. Instead, all of the brightness profile of NGC 6166 outside its core is described to ±0.037 V mag arcsec-2 by a single Sérsic function with index n≃ 8.3. The cD halo is not recognizable from photometry alone. This blurs the distinction between cluster-dominated cD halos and the similarly-large-Sérsic-index halos of giant, core-boxy-nonrotating ellipticals. These halos are believed to be accreted onto compact, high-redshift progenitors (“red nuggets”) by large numbers of minor mergers. They belong dynamically to their central galaxies. Still, cDs and core-boxy-nonrotating Es
Detection of a pair of prominent X-ray cavities in Abell 3847
NASA Astrophysics Data System (ADS)
Vagshette, Nilkanth D.; Naik, Sachindra; Patil, Madhav. K.; Sonkamble, Satish S.
2017-04-01
We present the results obtained from a detailed analysis of a deep Chandra observation of the bright FRII radio galaxy 3C 444 in Abell 3847 cluster. A pair of huge X-ray cavities are detected along the north and south directions from the centre of 3C 444. X-ray and radio images of the cluster reveal peculiar positioning of the cavities and radio bubbles. The radio lobes and X-ray cavities are apparently not spatially coincident and exhibit offsets by ∼61 and 77 kpc from each other along the north and south directions, respectively. Radial temperature and density profiles reveal the presence of a cool core in the cluster. Imaging and spectral studies showed the removal of substantial amount of matter from the core of the cluster by the radio jets. A detailed analysis of the temperature and density profiles showed the presence of a rarely detected elliptical shock in the cluster. Detection of inflating cavities at an average distance of ∼55 kpc from the centre implies that the central engine feeds a remarkable amount of radio power (∼6.3 × 1044 erg s-1) into the intra-cluster medium over ∼108 yr, the estimated age of cavity. The cooling luminosity of the cluster was estimated to be ∼8.30 × 1043 erg s-1 , which confirms that the AGN power is sufficient to quench the cooling. Ratios of mass accretion rate to Eddington and Bondi rates were estimated to be ∼0.08 and 3.5 × 104, respectively. This indicates that the black hole in the core of the cluster accretes matter through chaotic cold accretion.
The merger history of the complex cluster Abell 1758: a combined weak lensing and spectroscopic view
NASA Astrophysics Data System (ADS)
Monteiro-Oliveira, R.; Cypriano, E. S.; Machado, R. E. G.; Lima Neto, G. B.; Ribeiro, A. L. B.; Sodré, L.; Dupke, R.
2017-04-01
We present a weak-lensing and dynamical study of the complex cluster Abell 1758 (A1758, bar{z} = 0.278) supported by hydrodynamical simulations. This cluster is composed of two main structures called A1758N and A1758S. The northern structure is composed of A1758NW and A1758NE, with lensing determined masses of 7.90_{-1.55}^{+1.89} × 1014 M⊙ and 5.49_{-1.33}^{+1.67} × 1014 M⊙, respectively. They show a remarkable feature: while in A1758NW, there is a spatial agreement among weak-lensing mass distribution, intracluster medium and its brightest cluster galaxy (BCG), in A1758NE, the X-ray peak is located 96_{-15}^{+14} arcsec away from the mass peak and BCG positions. Given the detachment between gas and mass, we could use the local surface mass density to estimate an upper limit for the dark matter self-interaction cross-section: σ/m < 5.83 cm2 g-1. Combining our velocity data with hydrodynamical simulations, we have shown that A1758 NW and NE had their closest approach 0.27 Gyr ago and their merger axis is 21° ± 12° from the plane of the sky. In the A1758S system, we have measured a total mass of 4.96_{-1.19}^{+1.08} × 10^{14} M⊙ and, using radial velocity data, we found that the main merger axis is located at 70° ± 4° from the plane of the sky, therefore closest to the line of sight.
The Merger in Abell 576: A Line-of-Sight Bullet Cluster?
NASA Astrophysics Data System (ADS)
Dupke, Renato A.; Mirabal, Nestor; Bregman, Joel N.; Evrard, August E.
2007-10-01
Using a combination of Chandra and XMM-Newton observations, we confirmed the presence of a significant velocity gradient along the northeast-southwest direction in the intracluster gas of the cluster Abell 576. The results are consistent with a previous ASCA SIS analysis of this cluster. The error-weighted average over the ACIS-S3 and EPIC MOS1 and MOS2 spectrometers for the maximum velocity difference is >3.3×103 km s-1 at the 90% confidence level, similar to the velocity limits estimated indirectly for the Bullet Cluster (1E 0657-56). The probability that the velocity gradient is generated by standard random gain fluctuations with Chandra and XMM-Newton is <0.1%. The regions of maximum velocity gradient are in CCD zones that have the lowest temporal gain variations. It is unlikely that the velocity gradient is due to Hubble distance differences between projected clusters (probability <~0.01%). We mapped the distribution of elemental abundance ratios across the cluster and detected a strong chemical discontinuity using the abundance ratio of silicon to iron, equivalent to a variation from 100% SN Ia iron mass fraction in the west-northwest regions to 32% in the eastern region. The ``center'' of the cluster is located at the chemical discontinuity boundary, which is inconsistent with the radially symmetric chemical gradient found in some regular clusters, but consistent with a cluster merging scenario. We predict that the velocity gradient as measured will produce a variation of the cosmic microwave background (CMB) temperature toward the east of the core of the cluster that will be detectable by current and near-future bolometers. The measured velocity gradient opens up the possibility that this cluster is passing through a near line-of-sight merger stage where the cores have recently crossed.
Can standard cosmological models explain the observed Abell cluster bulk flow?
NASA Technical Reports Server (NTRS)
Strauss, Michael A.; Cen, Renyue; Ostriker, Jeremiah P.; Laure, Tod R.; Postman, Marc
1995-01-01
Lauer and Postman (LP) observed that all Abell clusters with redshifts less than 15,000 km/s appear to be participating in a bulk flow of 689 km/s with respect to the cosmic microwave background. We find this result difficult to reconcile with all popular models for large-scale structure formation that assume Gaussian initial conditions. This conclusion is based on Monte Carlo realizations of the LP data, drawn from large particle-mesh N-body simulations for six different models of the initial power spectrum (standard, tilted, and Omega(sub 0) = 0.3 cold dark matter, and two variants of the primordial baryon isocurvature model). We have taken special care to treat properly the longest-wavelength components of the power spectra. The simulations are sampled, 'observed,' and analyzed as identically as possible to the LP cluster sample. Large-scale bulk flows as measured from clusters in the simulations are in excellent agreement with those measured from the grid: the clusters do not exhibit any strong velocity bias on large scales. Bulk flows with amplitude as large as that reported by LP are not uncommon in the Monte Carlo data stes; the distribution of measured bulk flows before error bias subtraction is rougly Maxwellian, with a peak around 400 km/s. However the chi squared of the observed bulk flow, taking into account the anisotropy of the error ellipsoid, is much more difficult to match in the simulations. The models examined are ruled out at confidence levels between 94% and 98%.
The dust in the hydrogen-poor ejecta of Abell 30
NASA Technical Reports Server (NTRS)
Borkowski, Kazimierz J.; Harrington, J. Patrick; Blair, William P.; Bregman, Jesse D.
1994-01-01
We present new optical and near-infrared images of the hydrogen-poor planetary nebula Abell 30 and produce detailed models that account for the major observed morphological and IR properties. By imaging the nebula in the K band, we confirm the presence of hot dust in an expanding equatorial ring of H-poor gas. No emission was detected from the H-poor polar knots, suggesting a dust deficiency htere relative to the equatorial ring. The near-IR emission is attributed to small carbonaceous dust grains which are stochastically heated by stellar ultraviolet photons. Using an adaptive version of a matrix method devised by Guhathakurta & Draine (1989) to model stochastic heating, we find that the near-IR spectrum observed by Dinerstein & Lester (1984) requires the presence of dust grains down to approximately 0.0007 microns in radius. This minimum grain radius is in excellent agreement with our calculations of the grain destruction by energetic stellar UV photons: we find that carbon clusters with less than approximately 140 atoms (0.0007 microns in radius) are destroyed by stellar UV photons in approximately 1000 yr, the kinematic age of H-poor ejecta. Modeling of the far-IR dust emission implies that the bulk of the dust mass in A30 must reside at distances several times greater than the distance of the equatorial ring from the central star. This spatial dust distribution is attributed to the interaction of the stellar wind with the inhomogeneous H-poor ejecta. Most of the H-poor gas and dust has been apparently carried outward by the stellar wind, leaving behing dense, H-poor knots with prominent wind-blown tails in the equatorial ring and in the polar knots. This picture is supported by the presence of a stellar wind-blown bubble within the H-rich envelope in our optical images.
Abundance and temperature distributions in the hot intra-cluster gas of Abell 4059
NASA Astrophysics Data System (ADS)
Mernier, F.; de Plaa, J.; Lovisari, L.; Pinto, C.; Zhang, Y.-Y.; Kaastra, J. S.; Werner, N.; Simionescu, A.
2015-03-01
Using the EPIC and RGS data from a deep (200 ks) XMM-Newton observation, we investigate the temperature structure (kT and σT) and the abundances of nine elements (O, Ne, Mg, Si, S, Ar, Ca, Fe, and Ni) of the intra-cluster medium (ICM) in the nearby (z = 0.046) cool-core galaxy cluster Abell 4059. Next to a deep analysis of the cluster core, a careful modelling of the EPIC background allows us to build radial profiles up to 12' (~650 kpc) from the core. Probably because of projection effects, the temperature ICM is not found to be in single phase, even in the outer parts of the cluster. The abundances of Ne, Si, S, Ar, Ca, and Fe, but also O are peaked towards the core. The elements Fe and O are still significantly detected in the outermost annuli, which suggests that the enrichment by both type Ia and core-collapse SNe started in the early stages of the cluster formation. However, the particularly high Ca/Fe ratio that we find in the core is not well reproduced by the standard SNe yield models. Finally, 2D maps of temperature and Fe abundance are presented and confirm the existence of a denser, colder, and Fe-rich ridge south-west of the core, previously observed by Chandra. The origin of this asymmetry in the hot gas of the cluster core is still unclear, but it might be explained by a past intense ram-pressure stripping event near the central cD galaxy. Appendices are available in electronic form at http://www.aanda.org
A multiwavelength view of the galaxy cluster Abell 523 and its peculiar diffuse radio source
NASA Astrophysics Data System (ADS)
Girardi, M.; Boschin, W.; Gastaldello, F.; Giovannini, G.; Govoni, F.; Murgia, M.; Barrena, R.; Ettori, S.; Trasatti, M.; Vacca, V.
2016-03-01
We study the structure of the galaxy cluster Abell 523 (A523) at z = 0.104 using new spectroscopic data for 132 galaxies acquired at the Telescopio Nazionale Galileo, new photometric data from the Isaac Newton Telescope, and X-ray and radio data from the Chandra and Very Large Array archives. We estimate the velocity dispersion of the galaxy population, σ _V=949_{-60}^{+80} km s-1, and the X-ray temperature of the hot intracluster medium, kT = 5.3 ± 0.3 keV. We infer that A523 is a massive system: M200 ˜ 7-9 × 1014 M⊙. The analysis of the optical data confirms the presence of two subclusters, 0.75 Mpc apart, tracing the SSW-NNE direction and dominated by the two brightest cluster galaxies (BCG1 and BCG2). The X-ray surface brightness is strongly elongated towards the NNE direction, and its peak is clearly offset from both the brightest cluster galaxies (BCGs). We confirm the presence of a 1.3 Mpc large radio halo, elongated in the ESE-WNW direction and perpendicular to the optical/X-ray elongation. We detect a significant radio/X-ray offset and radio polarization, two features which might be the result of a magnetic field energy spread on large spatial scales. A523 is found consistent with most scaling relations followed by clusters hosting radio haloes, but quite peculiar in the Pradio-LX relation: it is underluminous in the X-rays or overluminous in radio. A523 can be described as a binary head-on merger caught after a collision along the SSW-NNE direction. However, minor optical and radio features suggest a more complex cluster structure, with A523 forming at the crossing of two filaments along the SSW-NNE and ESE-WNW directions.
An Approach to Poetry Through Transformational Processes
ERIC Educational Resources Information Center
Thompson, Charles Lamar; Weiner, Charles
1972-01-01
Author details why the psychological studies of Jean Piaget have specific relevance to the teaching of poetry, especially his thought matrix which consists of four transformational processes: identity, inversion, reciprocity and correlation. (Author)
Inverse Thermal Analysis of Titanium GTA Welds Using Multiple Constraints
NASA Astrophysics Data System (ADS)
Lambrakos, S. G.; Shabaev, A.; Huang, L.
2015-06-01
Inverse thermal analysis of titanium gas-tungsten-arc welds using multiple constraint conditions is presented. This analysis employs a methodology that is in terms of numerical-analytical basis functions for inverse thermal analysis of steady-state energy deposition in plate structures. The results of this type of analysis provide parametric representations of weld temperature histories that can be adopted as input data to various types of computational procedures, such as those for prediction of solid-state phase transformations. In addition, these temperature histories can be used to construct parametric function representations for inverse thermal analysis of welds corresponding to other process parameters or welding processes whose process conditions are within similar regimes. The present study applies an inverse thermal analysis procedure that provides for the inclusion of constraint conditions associated with both solidification and phase transformation boundaries.
NASA Astrophysics Data System (ADS)
Rodney, Steven A.; Patel, Brandon; Scolnic, Daniel; Foley, Ryan J.; Molino, Alberto; Brammer, Gabriel; Jauzac, Mathilde; Bradač, Maruša; Broadhurst, Tom; Coe, Dan; Diego, Jose M.; Graur, Or; Hjorth, Jens; Hoag, Austin; Jha, Saurabh W.; Johnson, Traci L.; Kelly, Patrick; Lam, Daniel; McCully, Curtis; Medezinski, Elinor; Meneghetti, Massimo; Merten, Julian; Richard, Johan; Riess, Adam; Sharon, Keren; Strolger, Louis-Gregory; Treu, Tommaso; Wang, Xin; Williams, Liliya L. R.; Zitrin, Adi
2015-09-01
SN HFF14Tom is a Type Ia SN discovered at z=1.3457+/- 0.0001 behind the galaxy cluster Abell 2744 (z = 0.308). In a cosmology-independent analysis, we find that HFF14Tom is 0.77 ± 0.15 mag brighter than unlensed Type Ia SNe at similar redshift, implying a lensing magnification of {μ }{obs}=2.03+/- 0.29. This observed magnification provides a rare opportunity for a direct empirical test of galaxy cluster lens models. Here we test 17 lens models, 13 of which were generated before the SN magnification was known, qualifying as pure “blind tests.” The models are collectively fairly accurate: 8 of the models deliver median magnifications that are consistent with the measured μ to within 1σ. However, there is a subtle systematic bias: the significant disagreements all involve models overpredicting the magnification. We evaluate possible causes for this mild bias, and find no single physical or methodological explanation to account for it. We do find that model accuracy can be improved to some extent with stringent quality cuts on multiply imaged systems, such as requiring that a large fraction have spectroscopic redshifts. In addition to testing model accuracies as we have done here, Type Ia SN magnifications could also be used as inputs for future lens models of Abell 2744 and other clusters, providing valuable constraints in regions where traditional strong- and weak-lensing information is unavailable.
Bolens, Guillemette
2011-01-01
This article grapples with the question of the corpse through two particular literary texts. Rather than an elucidation of the physiological principle of the human body by means of dissection, the play Mactatio Abel, written in England in the 15th century, stages the difficulty of the relation to the corpse, via an amplification of the biblical narrative of Abel's murder by Cain. As for Chaucer's work, The Book of the Duchess, it rewrites Ovid's and Machaut's texts featuring the figure of Morpheus in a way that distinguishes between an imitation of the living and its simulacrum in the sense Wolfgang Iser gives this concept. Chaucer's Morpheus, instead of promoting verisimilitude, forbids it. Indeed, he animates a corpse from within instead of simulating an apparition of the deceased. The simulacrum, rather than a mimetic copy of the real, blocks all representational illusion, in order to formulate absence. The readability of the corpse in both works is relational. Both literary texts express the corpse as being always already grounded in a relational and narratorial space.
NASA Astrophysics Data System (ADS)
Munari, E.; Grillo, C.; De Lucia, G.; Biviano, A.; Annunziatella, M.; Borgani, S.; Lombardi, M.; Mercurio, A.; Rosati, P.
2016-08-01
In this Letter we compare the abundance of the member galaxies of a rich, nearby (z = 0.09) galaxy cluster, Abell 2142, with that of halos of comparable virial mass extracted from sets of state-of-the-art numerical simulations, both collisionless at different resolutions and with the inclusion of baryonic physics in the form of cooling, star formation, and feedback by active galactic nuclei. We also use two semi-analytical models to account for the presence of orphan galaxies. The photometric and spectroscopic information, taken from the Sloan Digital Sky Survey Data Release 12 database, allows us to estimate the stellar velocity dispersion of member galaxies of Abell 2142. This quantity is used as proxy for the total mass of secure cluster members and is properly compared with that of subhalos in simulations. We find that simulated halos have a statistically significant (≳ 7 sigma confidence level) smaller amount of massive (circular velocity above 200 {km} {{{s}}}-1) subhalos, even before accounting for the possible incompleteness of observations. These results corroborate the findings from a recent strong lensing study of the Hubble Frontier Fields galaxy cluster MACS J0416 and suggest that the observed difference is already present at the level of dark matter (DM) subhalos and is not solved by introducing baryonic physics. A deeper understanding of this discrepancy between observations and simulations will provide valuable insights into the impact of the physical properties of DM particles and the effect of baryons on the formation and evolution of cosmological structures.
The close binary central star of the planetary nebula Abell 41 - A helium-rich subdwarf primary
NASA Astrophysics Data System (ADS)
Green, R. F.; Liebert, J.; Wesemael, F.
1984-05-01
He II, He I, and H absorption features were detected in spectroscopy with 2 A resolution of the Abell 41 planetary nebula central star, which was recently reported by Grauer and Bond to be a close binary with a 2 hour 43 minute period. This subdwarf O spectrum has been analyzed with a grid of hot, high-gravity, LTE atmosphere models. T(eff) = 50,000 + or 5000 K, log g = 6 + or - 1, n(He)/n(H) = 10 exp -1.0 + or - 1. This temperature is a factor of 1.4-2.9 lower than the range used by Grauer and Bond, and the required secondary star heating is considerably reduced. Nevertheless, close agreement is found with their estimates for the distance, reddening, and the systemic parameters for the binary star. Their interpretation of Abell 41 as a precataclysmic variable object remains valid for a cool main-sequence or hotter evolved secondary star. The object should be a promising target for high-resolution (coude/echelle) follow-up spectroscopy.
ERIC Educational Resources Information Center
Rodgers, Joann Ellison
2010-01-01
The notion that vitamins, minerals, and other "supplemental" nutrients profoundly change behavior, mood, and intellect has origins as old as recorded history. Research has indeed suggested connections between nutrient deficiencies and behavior problems, but correlations are not the same as causality. This "Abell Report" is an…
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2010-10-08
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Inverse heat conduction problems
NASA Astrophysics Data System (ADS)
Orlande, Helcio Rangel Barreto
We present the solution of the following inverse problems: (1) Inverse Problem of Estimating Interface Conductance Between Periodically Contacting Surfaces; (2) Inverse Problem of Estimating Interface Conductance During Solidification via Conjugate Gradient Method; (3) Determination of the Reaction Function in a Reaction-Diffusion Parabolic Problem; and (4) Simultaneous Estimation of Thermal Diffusivity and Relaxation Time with Hyperbolic Heat Conduction Model. Also, we present the solution of a direct problem entitled: Transient Thermal Constriction Resistance in a Finite Heat Flux Tube. The Conjugate Gradient Method with Adjoint Equation was used in chapters 1-3. The more general function estimation approach was treated in these chapters. In chapter 1, we solve the inverse problem of estimating the timewise variation of the interface conductance between periodically contacting solids, under quasi-steady-state conditions. The present method is found to be more accurate than the B-Spline approach for situations involving small periods, which are the most difficult on which to perform the inverse analysis. In chapter 2, we estimate the timewise variation of the interface conductance between casting and mold during the solidification of aluminum. The experimental apparatus used in this study is described. In chapter 3, we present the estimation of the reaction function in a one dimensional parabolic problem. A comparison of the present function estimation approach with the parameter estimation technique, wing B-Splines to approximate the reaction function, revealed that the use of function estimation reduces the computer time requirements. In chapter 4 we present a finite difference solution for the transient constriction resistance in a cylinder of finite length with a circular contact surface. A numerical grid generation scheme was used to concentrate grid points in the regions of high temperature gradients in order to reduce discretization errors. In chapter 6, we
Disentangling the ICL with the CHEFs: Abell 2744 as a case study
NASA Astrophysics Data System (ADS)
Jimenez-Teja, Yolanda; Dupke, Renato a.
2015-08-01
The intracluster light (ICL) is important for understanding the metal enrichment of the intracluster gas and constraining cosmological parameters independently of the other methods. However, its measurement it is not trivial due to the necessity of disentangling the light of stars locked up in galaxies from the proper ICL. Currently, there is no standard method to efficiently measure the ICL (Rudick et al. 2011, ApJ, 732, 48), and different approaches relying on the binding energy of the cluster galaxies, the density of the material, or the surface brightness distribution, have been tried. Moreover, a suitable way to disentangle the limits of the brightest cluster galaxy (BCG) and the ICL still has not been developed.The CHEFs (from Chebyshev-Fourier bases, Jiménez-Teja & Benítez 2012, ApJ, 745, 150) are a mathematical tool especially designed to model the two-dimensional light distribution of galaxies. We use the CHEFs and tools from differential geometry to infer the light contribution of the ICL to the total brightness, without imposing any artificial thresholds and avoiding the ambiguity introduced by free parameters that are usually set in these studies (Rudick et al. 2011).We use the extremely deep optical images from Abell 2744, the Pandora cluster, a multi-cluster merger, observed by the Hubble Frontier Fields project to show the efficiency of this new method. The CHEFs can accurately fit and remove all the galaxies close to the cluster center, including the BCG. The limits of the BCG are marked out by determining the points where the surface curvature changes, thus disentangling the ICL from the BCG light in a completely natural way. Once we have the residual image just containing ICL and background, we extrapolate the value of this latter from images of individual pointings close to the main Pandora field. We finally estimate the ICL to be ~24% of the total light, which is very consistent with the predictions from numerical simulations (Montes
Inverse Functions and their Derivatives.
ERIC Educational Resources Information Center
Snapper, Ernst
1990-01-01
Presented is a method of interchanging the x-axis and y-axis for viewing the graph of the inverse function. Discussed are the inverse function and the usual proofs that are used for the function. (KR)
Intersections, ideals, and inversion
Vasco, D.W.
1998-10-01
Techniques from computational algebra provide a framework for treating large classes of inverse problems. In particular, the discretization of many types of integral equations and of partial differential equations with undetermined coefficients lead to systems of polynomial equations. The structure of the solution set of such equations may be examined using algebraic techniques.. For example, the existence and dimensionality of the solution set may be determined. Furthermore, it is possible to bound the total number of solutions. The approach is illustrated by a numerical application to the inverse problem associated with the Helmholtz equation. The algebraic methods are used in the inversion of a set of transverse electric (TE) mode magnetotelluric data from Antarctica. The existence of solutions is demonstrated and the number of solutions is found to be finite, bounded from above at 50. The best fitting structure is dominantly onedimensional with a low crustal resistivity of about 2 ohm-m. Such a low value is compatible with studies suggesting lower surface wave velocities than found in typical stable cratons.
Modelling and inversion -progress, problems, and challenges
NASA Astrophysics Data System (ADS)
Raiche, Art
1994-03-01
Researchers in the field of electromagnetic modelling and inversion have taken advantage of the impressive improvements of new computer hardware to explore exciting new initiatives and solid extensions of older ideas. Finite-difference time-stepping methods have been successfully applied to full-domain 3D models. Another new method combines time-stepping with spatial frequency solutions. The 2D model 3D source (2.5D) problem is also receiving fresh attention both for continental and sea floor applications. The 3D inversion problem is being attacked by several researchers using distorted Born approximation methods. Q-domain inversions using transformation to pseudo-wave field and travel time tomography have also been successfully tested for low contrast problems. Subspace methods have been successful in dramatically reducing the computational burden of the under-determined style of inversion. Static magnetic field interpretation methods are proving useful for delineating the position of closely-spaced multiple targets. Novel (“appeals to nature”) methods are also being investigated. Neural net algorithms have been tested for determining the depth and offset of buried pipes from EM ellipticity data. Genetic algorithms and simulated annealing have been tested for extremal model construction. The failure of researchers to take adequate account of the properties of the mathematical transformation from algorithms to the number domain represented by the computing process remains a major stumbling block. Structured programming, functional languages, and other software tools and methods are presented as an essential part of the serial process leading from EM theory to geological interpretation.
NASA Astrophysics Data System (ADS)
Trigub, R. M.
2015-08-01
We study the convergence of linear means of the Fourier series \\sumk=-∞+∞λk,\\varepsilon\\hat{f}_keikx of a function f\\in L1 \\lbrack -π,π \\rbrack to f(x) as \\varepsilon\\searrow0 at all points at which the derivative \\bigl(\\int_0^xf(t) dt\\bigr)' exists (i.e. at the d-points). Sufficient conditions for the convergence are stated in terms of the factors \\{λk,\\varepsilon\\} and, in the case of λk,\\varepsilon=\\varphi(\\varepsilon k), in terms of the condition that the functions \\varphi and x\\varphi'(x) belong to the Wiener algebra A( R). We also study a new problem concerning the convergence of means of the Abel-Poisson type, \\sumk=-∞^∞r\\psi(\\vert k\\vert)\\hat{f}_keikx, as r\
The ASTRODEEP Frontier Fields catalogues. I. Multiwavelength photometry of Abell-2744 and MACS-J0416
NASA Astrophysics Data System (ADS)
Merlin, E.; Amorín, R.; Castellano, M.; Fontana, A.; Buitrago, F.; Dunlop, J. S.; Elbaz, D.; Boucaud, A.; Bourne, N.; Boutsia, K.; Brammer, G.; Bruce, V. A.; Capak, P.; Cappelluti, N.; Ciesla, L.; Comastri, A.; Cullen, F.; Derriere, S.; Faber, S. M.; Ferguson, H. C.; Giallongo, E.; Grazian, A.; Lotz, J.; Michałowski, M. J.; Paris, D.; Pentericci, L.; Pilo, S.; Santini, P.; Schreiber, C.; Shu, X.; Wang, T.
2016-05-01
Context. The Frontier Fields survey is a pioneering observational program aimed at collecting photometric data, both from space (Hubble Space Telescope and Spitzer Space Telescope) and from ground-based facilities (VLT Hawk-I), for six deep fields pointing at clusters of galaxies and six nearby deep parallel fields, in a wide range of passbands. The analysis of these data is a natural outcome of the Astrodeep project, an EU collaboration aimed at developing methods and tools for extragalactic photometry and creating valuable public photometric catalogues. Aims: We produce multiwavelength photometric catalogues (from B to 4.5 μm) for the first two of the Frontier Fields, Abell-2744 and MACS-J0416 (plus their parallel fields). Methods: To detect faint sources even in the central regions of the clusters, we develop a robust and repeatable procedure that uses the public codes Galapagos and Galfit to model and remove most of the light contribution from both the brightest cluster members, and the intra-cluster light. We perform the detection on the processed HST H160 image to obtain a pure H-selected sample, which is the primary catalogue that we publish. We also add a sample of sources which are undetected in the H160 image but appear on a stacked infrared image. Photometry on the other HST bands is obtained using SExtractor, again on processed images after the procedure for foreground light removal. Photometry on the Hawk-I and IRAC bands is obtained using our PSF-matching deconfusion code t-phot. A similar procedure, but without the need for the foreground light removal, is adopted for the Parallel fields. Results: The procedure of foreground light subtraction allows for the detection and the photometric measurements of ~2500 sources per field. We deliver and release complete photometric H-detected catalogues, with the addition of the complementary sample of infrared-detected sources. All objects have multiwavelength coverage including B to H HST bands, plus K
GALAXY AND MASS ASSEMBLY (GAMA): WITNESSING THE ASSEMBLY OF THE CLUSTER ABELL 1882
Owers, M. S.; Bauer, A. E.; Cluver, M. E.; Hopkins, A. M.; Lara-Lopez, M. A.; Baldry, I. K.; Bland-Hawthorn, J.; Pimbblet, K. A.; Brown, M. J. I.; Colless, M.; Robotham, A. S. G.; Driver, S. P.; Edge, A. C.; Van Kampen, E.; Liske, J.; Loveday, J.; Ponman, T.
2013-08-01
We present a combined optical and X-ray analysis of the rich cluster ABELL 1882 (A1882) with the aim of identifying merging substructure and understanding the recent assembly history of this system. Our optical data consist of spectra drawn from the Galaxy and Mass Assembly survey, which lends itself to this kind of detailed study thanks to its depth and high spectroscopic completeness. We use 283 spectroscopically confirmed cluster members to detect and characterize substructure. We complement the optical data with X-ray data taken with both Chandra and XMM. Our analysis reveals that A1882 harbors two main components, A1882A and A1882B, which have a projected separation of {approx}2 Mpc and a line of sight velocity difference of v{sub los}{approx}-428{sup +187}{sub -139} km s{sup -1}. The primary system, A1882A, has velocity dispersion {sigma}{sub v}=500{sub -26}{sup +23} km s{sup -1} and Chandra (XMM) temperature kT = 3.57 {+-} 0.17 keV (3.31{sup +0.28}{sub -0.27} keV) while the secondary, A1882B, has {sigma}{sub v}=457{sup +108}{sub -101} km s{sup -1} and Chandra (XMM) temperature kT = 2.39 {+-} 0.28 keV (2.12 {+-} 0.20 keV). The optical and X-ray estimates for the masses of the two systems are consistent within the uncertainties and indicate that there is twice as much mass in A1882A (M{sub 500} = 1.5-1.9 Multiplication-Sign 10{sup 14} M{sub Sun }) when compared with A1882B (M{sub 500} = 0.8-1.0 Multiplication-Sign 10{sup 14} M{sub Sun }). We interpret the A1882A/A1882B system as being observed prior to a core passage. Supporting this interpretation is the large projected separation of A1882A and A1882B and the dearth of evidence for a recent (<2 Gyr) major interaction in the X-ray data. Two-body analyses indicate that A1882A and A1882B form a bound system with bound incoming solutions strongly favored. We compute blue fractions of f{sub b} = 0.28 {+-} 0.09 and 0.18 {+-} 0.07 for the spectroscopically confirmed member galaxies within r{sub 500} of the centers
The XMM Cluster Outskirts Project (X-COP): Physical conditions of Abell 2142 up to the virial radius
NASA Astrophysics Data System (ADS)
Tchernin, C.; Eckert, D.; Ettori, S.; Pointecouteau, E.; Paltani, S.; Molendi, S.; Hurier, G.; Gastaldello, F.; Lau, E. T.; Nagai, D.; Roncarelli, M.; Rossetti, M.
2016-10-01
Context. Galaxy clusters are continuously growing through the accretion of matter in their outskirts. This process induces inhomogeneities in the gas density distribution (clumping) that need to be taken into account to recover the physical properties of the intracluster medium (ICM) at large radii. Aims: We studied the thermodynamic properties in the outskirts (R > R500) of the massive galaxy cluster Abell 2142 by combining the Sunyaev Zel'dovich (SZ) effect with the X-ray signal. Methods: We combined the SZ pressure profile measured by Planck with the XMM-Newton gas density profile to recover radial profiles of temperature, entropy, and hydrostatic mass out to 2 × R500. We used a method that is insensitive to clumping to recover the gas density, and we compared the results with traditional X-ray measurement techniques. Results: When taking clumping into account, our joint X-SZ entropy profile is consistent with the predictions from pure gravitational collapse, whereas a significant entropy flattening is found when the effect of clumping is neglected. The hydrostatic mass profile recovered using joint X-SZ data agrees with that obtained from spectroscopic X-ray measurements and with mass reconstructions obtained through weak lensing and galaxy kinematics. Conclusions: We found that clumping can explain the entropy flattening observed by Suzaku in the outskirts of several clusters. When using a method that is insensitive to clumping for the reconstruction of the gas density, the thermodynamic properties of Abell 2142 are compatible with the assumption that the thermal gas pressure sustains gravity and that the entropy is injected at accretion shocks, with no need to evoke more exotic physics. Our results highlight the need for X-ray observations with sufficient spatial resolution, and large collecting area, to understand the processes at work in cluster outer regions.
The near-infrared Tully-Fisher relation - A preliminary study of the Coma and Abell 400 clusters
NASA Technical Reports Server (NTRS)
Guhathakurta, Puragra; Bernstein, Gary; Raychaudhury, Somak; Haynes, Martha; Giovanelli, Riccardo; Herter, Terry; Vogt, Nicole
1993-01-01
We have started a large project to study the NIR Tully-Fisher (TF) relation using H- and I-band surface photometry of spiral galaxies. A preliminary study of 20 spirals in the Coma and Abell 400 clusters is presented. The NIR images have been used to derive accurate inclinations and total magnitudes, and rotational linewidths are measured from high-quality 21-cm Arecibo data. The scatter in the Coma TF plot is found to be 0.19 mag in the H band and 0.20 mag in the I band for a set of 13 galaxies, if we assume that they are all at the same distance. The deviation of the Coma galaxies from the best-fit Tully-Fisher relation is correlated with their redshift, indicating that some of the galaxies are not bound to the cluster. Indeed, if we treat all the galaxies in the Coma sample as undergoing free Hubble expansion, the TF scatter drops to 0.12 and 0.13 mag for the H- and I-band datasets, respectively. The Abell 400 sample is best fit by a common distance model, yielding a scatter of 0.12 mag for seven galaxies in H using a fixed TF slope. We are in the process of studying cluster and field spirals out to about 10,000 km/s in order to calibrate the NIR TF relation and will apply it to more nearby galaxies to measure the peculiar velocity field in the local universe.
NASA Astrophysics Data System (ADS)
Cortese, L.; Gavazzi, G.; Iglesias-Paramo, J.; Boselli, A.; Carrasco, L.
2003-04-01
Optical spectroscopy of 93 galaxies, 60 projected in the direction of Abell 1367, 21 onto the Coma cluster and 12 on Virgo, is reported. The targets were selected because they were detected in previous Hα , UV or r' surveys. The present observations bring to 100% the redshift completeness of Hα selected galaxies in the Coma region and to 75% in Abell 1367. All observed galaxies except one show Hα emission and belong to the clusters. This confirms previous determinations of the Hα luminosity function of the two clusters that were based on the assumption that all Hα detected galaxies were cluster members. Using the newly obtained data we re-determine the UV luminosity function of Coma and we compute for the first time the UV luminosity function of A1367. Their faint end slopes remain uncertain (-2.00
The Fourier Transform on Quantum Euclidean Space
NASA Astrophysics Data System (ADS)
Coulembier, Kevin
2011-05-01
We study Fourier theory on quantum Euclidean space. A modified version of the general definition of the Fourier transform on a quantum space is used and its inverse is constructed. The Fourier transforms can be defined by their Bochner's relations and a new type of q-Hankel transforms using the first and second q-Bessel functions. The behavior of the Fourier transforms with respect to partial derivatives and multiplication with variables is studied. The Fourier transform acts between the two representation spaces for the harmonic oscillator on quantum Euclidean space. By using this property it is possible to define a Fourier transform on the entire Hilbert space of the harmonic oscillator, which is its own inverse and satisfies the Parseval theorem.
Optical properties of silicon inverse opals
NASA Astrophysics Data System (ADS)
Wei, Hong
Silicon inverse opals are artificial structures in which nearly monodisperse, close-packed air bubbles are embedded in a silicon matrix. If properly tailored, this structure can exhibit a photonic band gap (PBG) in the near infrared spectral region. The PBG can block light propagation in any direction, allowing the control of light flow in the material. Silicon inverse opals can be fabricated by infiltrating amorphous silicon into silica colloidal crystals and then etching away the silica. In this thesis, the structural defects of silica colloidal crystals and the optical properties of silicon inverse opals are studied. First, by using laser-scanning confocal microscopy, the concentration and distribution of stacking faults and vacancies were quantified in silica colloidal crystals. It's shown that silica colloidal crystals show strong tendency toward face-center-cubic structure with the vacancy density as small as 5 x 10-4. Second, by combining optical microscopy and Fourier Transform Infrared (FTIR) spectroscopy, the transmission and reflection spectra of silicon inverse opals along the [111] direction were measured. Combined with the calculation of transmission and reflection spectra by Transfer Matrix Methods, it is concluded that the strong light attenuation in silicon inverse opals is due to the enhanced absorption (>600%) in silicon materials. Third, by using optical pump-probe techniques, the photo-induced ultra-fast reflection changes in silicon inverse opals were examined. The pump-generated free carriers cause the reflection in the band gap region to change after ˜0.5 ps. For the first few ps, the main effect is a decrease in reflectivity due to nonlinear absorption. After ˜5 ps, this effect disappears and an unexpected blue spectral shift is seen in the photonic band gap. The refractive index decreases due to optically-induced strain born the thermal expansion mismatch between silicon and its native oxide. Finally, by infiltrating silicon inverse
Structures for time-reversed inversion in filter banks
NASA Astrophysics Data System (ADS)
Vaidyanathan, P. P.; Chen, Tsuhan
1994-12-01
Anticausal inversion of IIR transfer functions has gained importance in recent years, in the efficient implementation of IIR digital filter banks. In this paper we first introduce the idea of a causal dual, as an intermediate step in the implementation of anticausal IIR inverses. With time reversal operators at the input and output of the causal dual, we get the anticausal inverse of the original structure. The causal dual eliminates the need for similarity transformations, during a key step called blockwise state transfer, in implementing anticausal inverses. In the paper we identify efficient structures for causal duals of standard structures like the direct-form, cascade-form, coupled form, and IIR lattice structures, including the tapped lattice.
Inverse Thermal Analysis of Refractory Metal Laser Welds
NASA Astrophysics Data System (ADS)
Lambrakos, S. G.
2013-09-01
Case study inverse thermal analyses of Vanadium and Tantalum laser welds are presented. These analyses employ a methodology that is in terms of analytic basis functions for inverse thermal analysis of steady-state energy deposition in plate structures. The results of the case studies presented provide parametric representations of weld temperature histories that can be adopted as input data to various types of computational procedures, such as those for prediction of solid-state phase transformations. In addition, these temperature histories can be used to construct parametric-function representations for inverse thermal analysis of welds corresponding to other process parameters or welding processes process conditions of which fall within similar regimes. This study also discusses specific aspects the inverse-analysis methodology relevant to further development of algorithms for its application in practice.
Analysis of Raman lasing without inversion
NASA Astrophysics Data System (ADS)
Sheldon, Paul Martin
1999-12-01
Properties of lasing without inversion were studied analytically and numerically using Maple computer assisted algebra software. Gain for probe electromagnetic field without population inversion in detuned three level atomic schemes has been found. Matter density matrix dynamics and coherence is explored using Pauli matrices in 2-level systems and Gell-Mann matrices in 3-level systems. It is shown that extreme inversion produces no coherence and hence no lasing. Unitary transformation from the strict field-matter Hamiltonian to an effective two-photon Raman Hamiltonian for multilevel systems has been derived. Feynman diagrams inherent in the derivation show interesting physics. An additional picture change was achieved and showed cw gain possible. Properties of a Raman-like laser based on injection of 3- level coherently driven Λ-type atoms whose Hamiltonian contains the Raman Hamiltonian and microwave coupling the two bottom states have been studied in the limits of small and big photon numbers in the drive field. Another picture change removed the microwave coupler to all orders and simplified analysis. New possibilities of inversionless generation were found.
Hicks, H.R.; Dory, R.A.; Holmes, J.A.
1983-01-01
We illustrate in some detail a 2D inverse-equilibrium solver that was constructed to analyze tokamak configurations and stellarators (the latter in the context of the average method). To ensure that the method is suitable not only to determine equilibria, but also to provide appropriately represented data for existing stability codes, it is important to be able to control the Jacobian, tilde J is identical to delta(R,Z)/delta(rho, theta). The form chosen is tilde J = J/sub 0/(rho)R/sup l/rho where rho is a flux surface label, and l is an integer. The initial implementation is for a fixed conducting-wall boundary, but the technique can be extended to a free-boundary model.
NASA Technical Reports Server (NTRS)
Ostro, Steven J.; Connelly, Robert
1987-01-01
One of the most fundamental physical properties of any asteroid is its shape. Lightcurves provide the only source of shape information for most asteroids. Unfortunately, the functional form of a lightcurve is determined by the viewing/illumination geometry and the asteroid's light scattering characteristics as well as its shape, and in general it is impossible to determine an asteroid's shape from lightcurves. A technique called convex-profile inversion (CPI) that obtains a convex profile, P, from any lightcurve is introduced. If certain ideal conditions are satisfied, then P is an estimator for the asteroid's mean cross section, C, a convex set defined as the average of all cross sections C(z) cut by planes a distance z above the asteroids's equatorial plane. C is therefore a 2-D average of the asteroid's 3-D shape.
NASA Astrophysics Data System (ADS)
Coddington, O.; Pilewskie, P.; Schmidt, S.
2013-12-01
The upwelling shortwave irradiance measured by the airborne Solar Spectral Flux Radiometer (SSFR) flying above a cloud and aerosol layer is influenced by the properties of the cloud and aerosol particles below, just as would the radiance measured from satellite. Unlike satellite measurements, those from aircraft provide the unique capability to fly a lower-level leg above the cloud, yet below the aerosol layer, to characterize the extinction of the aerosol layer and account for its impact on the measured cloud albedo. Previous work [Coddington et al., 2010] capitalized on this opportunity to test the effects of aerosol particles (or more appropriately, the effects of neglecting aerosols in forward modeling calculations) on cloud retrievals using data obtained during the Intercontinental Chemical Transport Experiment/Intercontinental Transport and Chemical Transformation of anthropogenic pollution (INTEX-A/ITCT) study. This work showed aerosols can cause a systematic bias in the cloud retrieval and that such a bias would need to be distinguished from a true aerosol indirect effect (i.e. the brightening of a cloud due to aerosol effects on cloud microphysics) as theorized by Haywood et al., [2004]. The effects of aerosols on clouds are typically neglected in forward modeling calculations because their pervasiveness, variable microphysical properties, loading, and lifetimes makes forward modeling calculations under all possible combinations completely impractical. Using a general inverse theory technique, which propagates separate contributions from measurement and forward modeling errors into probability distributions of retrieved cloud optical thickness and droplet effective radius, we have demonstrated how the aerosol presence can be introduced as a spectral systematic error in the distributions of the forward modeling solutions. The resultant uncertainty and bias in cloud properties induced by the aerosols is identified by the shape and peak of the posteriori
Hard X-Ray Properties of the Merging Cluster Abell 3667 as Observed with Suzaku
2008-08-01
highest sensitivity at around 100 keV using the novel narrow-field-of-view Compton camera concept. It will open a new window to the widely distributed non...GeV energy are under- going cooling due to synchrotron and inverse Compton (IC) emissions. In every case, the radio halos/relics are found in...center and the north-west relic, with the highest sensitivity in the 10–40 keV band. In addition, the X-ray CCD cameras (XISs: Koyama et al. 2007
NASA Technical Reports Server (NTRS)
Warren, Wayne H., Jr.
1989-01-01
The machine readable version of the compilation, as it is currently being distributed from the Astronomical Data Center, is described. The catalog contains redshifts and velocity dispersions for all Abell clusters for which these data had been published up to 1986 July. Also included are 1950 equatorial coordinates for the centers of the listed clusters, numbers of observations used to determine the redshifts, and bibliographical references citing the data sources.
Modular theory of inverse systems
NASA Technical Reports Server (NTRS)
1979-01-01
The relationship between multivariable zeros and inverse systems was explored. A definition of zero module is given in such a way that it is basis independent. The existence of essential right and left inverses were established. The way in which the abstract zero module captured previous definitions of multivariable zeros is explained and examples are presented.
Inverse problem in hydrogeology
NASA Astrophysics Data System (ADS)
Carrera, Jesús; Alcolea, Andrés; Medina, Agustín; Hidalgo, Juan; Slooten, Luit J.
2005-03-01
The state of the groundwater inverse problem is synthesized. Emphasis is placed on aquifer characterization, where modelers have to deal with conceptual model uncertainty (notably spatial and temporal variability), scale dependence, many types of unknown parameters (transmissivity, recharge, boundary conditions, etc.), nonlinearity, and often low sensitivity of state variables (typically heads and concentrations) to aquifer properties. Because of these difficulties, calibration cannot be separated from the modeling process, as it is sometimes done in other fields. Instead, it should be viewed as one step in the process of understanding aquifer behavior. In fact, it is shown that actual parameter estimation methods do not differ from each other in the essence, though they may differ in the computational details. It is argued that there is ample room for improvement in groundwater inversion: development of user-friendly codes, accommodation of variability through geostatistics, incorporation of geological information and different types of data (temperature, occurrence and concentration of isotopes, age, etc.), proper accounting of uncertainty, etc. Despite this, even with existing codes, automatic calibration facilitates enormously the task of modeling. Therefore, it is contended that its use should become standard practice. L'état du problème inverse des eaux souterraines est synthétisé. L'accent est placé sur la caractérisation de l'aquifère, où les modélisateurs doivent jouer avec l'incertitude des modèles conceptuels (notamment la variabilité spatiale et temporelle), les facteurs d'échelle, plusieurs inconnues sur différents paramètres (transmissivité, recharge, conditions aux limites, etc.), la non linéarité, et souvent la sensibilité de plusieurs variables d'état (charges hydrauliques, concentrations) des propriétés de l'aquifère. A cause de ces difficultés, le calibrage ne peut êtreséparé du processus de modélisation, comme c'est le
X-ray cavities and temperature jumps in the environment of the strong cool core cluster Abell 2390
NASA Astrophysics Data System (ADS)
Sonkamble, S. S.; Vagshette, N. D.; Pawar, P. K.; Patil, M. K.
2015-10-01
We present results based on the systematic analysis of high resolution 95 ks Chandra observations of the strong cool core cluster Abell 2390 at the redshift of z = 0.228 that hosts an energetic radio AGN. This analysis has enabled us to investigate five X-ray deficient cavities in the atmosphere of Abell 2390 within central 30''. Presence of these cavities have been confirmed through a variety of image processing techniques like, the surface brightness profiles, unsharp masked image, as well as 2D elliptical model subtracted residual map. Temperature profile as well as 2D temperature map revealed structures in the distribution of ICM, in the sense that ICM in the NW direction is cooler than that on the SE direction. Temperature jump in all directions is evident near 25'' (90.5 kpc) corresponding to the average Mach number 1.44± 0.05, while another jump from 7.47 keV to 9.10 keV at 68'' (246 kpc) in the north-west direction, corresponding to Mach number 1.22± 0.06 and these jumps are associated with the cold fronts. Tricolour map as well as hardness ratio map detects cool gas clumps in the central 30 kpc region of temperature 4.45_{-0.10}^{+0.16} keV. The entropy profile derived from the X-ray analysis is found to fall systematically inward in a power-law fashion and exhibits a floor near 12.20± 2.54 keV cm2 in the central region. This flattening of the entropy profile in the core region confirms the intermittent heating at the centre by AGN. The diffuse radio emission map at 1.4 GHz using VLA L-band data exhibits highly asymmetric morphology with an edge in the north-west direction coinciding with the X-ray edge seen in the unsharp mask image. The mechanical power injected by the AGN in the form of X-ray cavities is found to be 5.94× 10^{45} erg s^{-1} and is roughly an order of magnitude higher than the energy lost by the ICM in the form of X-ray emission, confirming that AGN feedback is capable enough to quench the cooling flow in this cluster.
A new fractional wavelet transform
NASA Astrophysics Data System (ADS)
Dai, Hongzhe; Zheng, Zhibao; Wang, Wei
2017-03-01
The fractional Fourier transform (FRFT) is a potent tool to analyze the time-varying signal. However, it fails in locating the fractional Fourier domain (FRFD)-frequency contents which is required in some applications. A novel fractional wavelet transform (FRWT) is proposed to solve this problem. It displays the time and FRFD-frequency information jointly in the time-FRFD-frequency plane. The definition, basic properties, inverse transform and reproducing kernel of the proposed FRWT are considered. It has been shown that an FRWT with proper order corresponds to the classical wavelet transform (WT). The multiresolution analysis (MRA) associated with the developed FRWT, together with the construction of the orthogonal fractional wavelets are also presented. Three applications are discussed: the analysis of signal with time-varying frequency content, the FRFD spectrum estimation of signals that involving noise, and the construction of fractional Harr wavelet. Simulations verify the validity of the proposed FRWT.
ERIC Educational Resources Information Center
Denning, Peter J.; Hiles, John E.
2006-01-01
Transformational Events is a new pedagogic pattern that explains how innovations (and other transformations) happened. The pattern is three temporal stages: an interval of increasingly unsatisfactory ad hoc solutions to a persistent problem (the "mess"), an offer of an invention or of a new way of thinking, and a period of widespread adoption and…
ERIC Educational Resources Information Center
Reeves, Melinda
2006-01-01
The parents of students who attend Decatur High School thought that there was little hope of their kids going on to college. After a year or so in Decatur's reading program, their sons and daughters were both transformed and college bound. In this article, the author describes how Decatur was able to successfully transform their students. Seven…
Joint inversion of surface and borehole magnetic amplitude data
NASA Astrophysics Data System (ADS)
Li, Zelin; Yao, Changli; Zheng, Yuanman; Yuan, Xiaoyu
2016-04-01
3D magnetic inversion for susceptibility distribution is a powerful tool in quantitative interpretation of magnetic data in mineral exploration. However, the inversion and interpretation of such data are faced with two problems. One problem is the poor imaging results of deep sources when only surface data are inverted. The other is the unknown total magnetization directions of sources when strong remanence exists. To deal with these problems simultaneously, we propose a method through the joint inversion of surface and borehole magnetic amplitude data. In this method, we first transform both surface and borehole magnetic data to magnetic amplitude data that are less sensitive to the directions of total magnetization, and then preform a joint inversion of the whole amplitude data to generate a 3D susceptibility distribution. The amplitude inversion algorithm uses Tikhonov regularization and imposes a positivity constraint on the effective susceptibility defined as the ratio of magnetization magnitude over the geomagnetic field strength. In addition, a distance-based weighting function is used to make the algorithm applicable to joint data sets. To solve this positivity-constraint inversion problem efficiently, an appropriate optimization method must be chosen. We first use an interior-point method to incorporate the positivity constraint into the total objective function, and then minimize the objective function via a Gauss-Newton method due to the nonlinearity introduced by the positivity constraint and the amplitude data. To further improve the efficiency of the inversion algorithm, we use a conjugate gradient method to carry out the fast matrix-vector multiplication during the minimization. To verify the utility of the proposed method, we invert the synthetic and field data using three inversion methods, including the joint inversion of surface and borehole three-component magnetic data, the inversion of surface magnetic amplitude data, and the proposed joint
Inverse problems in mathematical physics
NASA Astrophysics Data System (ADS)
Glasko, V. B.
Procedures for the correct formulation and solution of inverse problems, which usually belong to the class of ill-posed problems, are discussed. Attention is given to the concept of the conditionally correct statement of a problem, the concept of quasi-solution, and the fundamentals of regularization theory. The discussion also covers the uniqueness of solutions to inverse problems in mathematical physics, with consideration given to problems involving layered media, impedance problems, gravimetric problems, and inverse problems of heat conduction. The problem of stability and regularizing operators are also discussed.
Rafa, M.J.
1993-04-19
In NiAl, we have succeeded in determining the complete Ginzburg-Landau strain free energy function necessary to model the cubic to tetragonal martensite transformation in a sample of any size. We believe that this is the first time that the parameters of a Ginzburg-Landau functional and the complete strain spinodal for any three-dimensional displacive transformation were used in simulating the transformation near a crack tip under Mode I loading; the transformation pattern and toughening are different from standard transformation toughening theories. Furthermore, the strain spinodal has an approximately conical shape which can be specified by two material dependent experimentally accessible parameters, rather than the ellipsoidal shape in standard theories. Stress induced martensitic transformation in a polycrystalline sample of NiAl was simulated. In the ZrO[sub 2] system, first principles calculations to determine the semi-empirical potentials for simulating the cubic-tetragonal and tetragonal-monoclinic transformations have been started by doing a more elaborate total energy calculation.In the Al[sub 2]0[sub 3] system, we have discovered that the first principles calculations and semi-empirical potentials have just been completed byanother group in England which we will use instead to base our molecular dynamics simulations on.
DISCOVERY OF ULTRA-STEEP SPECTRUM GIANT RADIO GALAXY WITH RECURRENT RADIO JET ACTIVITY IN ABELL 449
Hunik, Dominika; Jamrozy, Marek
2016-01-20
We report a discovery of a 1.3 Mpc diffuse radio source with extremely steep spectrum fading radio structures in the vicinity of the Abell 449 cluster of galaxies. Its extended diffuse lobes are bright only at low radio frequencies and their synchrotron age is about 160 Myr. The parent galaxy of the extended relic structure, which is the dominant galaxy within the cluster, is starting a new jet activity. There are three weak X-rays sources in the vicinity of the cluster as found in the ROSAT survey, however it is not known if they are connected with this cluster of galaxies. Just a few radio galaxy relics are currently known in the literature, as finding them requires sensitive and high angular resolution low-frequency radio observations. Objects of this kind, which also are starting a new jet activity, are important for understanding the life cycle and evolution of active galactic nuclei. A new 613 MHz map as well as the archival radio data pertaining to this object are presented and analyzed.
NASA Technical Reports Server (NTRS)
Oegerle, William R.; Jewison, Michael S.; Hoessel, John G.
1987-01-01
The luminosity and spatial distributions of galaxies in the nearby Abell clusters A2175, A2256, and A2384 have been studied using an automated object detection, classification, and photometry system. Schecter functions have been fit to the observed luminosity functions of these clusters. Values of the characteristic magnitude Mr(asterisk) at the 'break' in the luminosity function (LF) are found that are within about 0.25 mag of the so-called 'universal' value of Mr(asterisk) for A2256 and A2384. The faint ends of the LFs of these two clusters are fairly flat, with a value of -1.6 that is steeper than the universal value of -1.25. The spatial distributions of galaxies in all three clusters seem to be described fairly well by power laws, with no evidence for constant-density cores, when the cluster center is assumed to be the central D or cD galaxy. These results indicate a strong correlation between the density distribution of galaxies and the presence of a dominant D or cD galaxy in the cluster.
NASA Technical Reports Server (NTRS)
Corbelli, Edvige; Salpeter, Edwin E.; Dickey, John M.
1991-01-01
Visual and IRAS data for an optically selected sample of 183 late-type galaxies are compiled in tables and graphs and analyzed in detail to determine the joint FIR-optical luminosity function Psi from the FIR/blue luminosity ratio, r = L(FIR)/L(B). It is found that Psi can be approximated by a function of a single variable psi(r-prime), where r-prime is defined as r times L(B)/L(asterisk) exp -delta, with L(asterisk) a constant and delta = about 0.08. A lognormal curve peaking at r-prime = 0.35 and with dispersion of 0.28 is shown to give a good fit to psi(r-prime). From a lack of galaxies with very low r-prime in the present sample it is inferred that there are few spiral galaxies with low interstellar-dust abundances. Also included are data on the distribution function of r-prime for the more distant clusters Abell 400 and Cancer.
Zong, Jianfa; Wang, Ruilong; Bao, Guanhu; Ling, Tiejun; Zhang, Liang; Zhang, Xinfu; Hou, Ruyan
2015-07-01
Four oleanane-type triterpenoid saponins were isolated from the seed cake of Camellia oleifera Abel.: camelliasaponin B1 and three new saponins, oleiferasaponin C1-C3 (1-3). Their structures were identified as 22-O-angeloyl-camelliagenin B 3-O-[β-d-galactopyranosyl-(1→2)]-[β-d-galactopyranosyl-(1→2)-α-l-arabinopyranosyl-(1→3)]-β-d-glucopyranosiduronic acid methyl ester (1); 22-O-angeloyl-camelliagenin A 3-O-[β-d-galactopyranosyl-(1→2)]-[β-d-glucopyranosyl-(1→2)-β-d-galactopyranosyl-(1→3)]-β-d-glucopyranosiduronic acid methyl ester (2); and 28-O-cinnamoyl-camelliagenin B 3-O-[β-d-galactopyranosylz-(1→2)] [β-d-galactopyranosyl(1→2)-α-l-arabinopyranosyl-(1→3)]-β-d-glucopyranosiduronic acid methyl ester (3) through 1D and 2D NMR, HR-ESI-MS, as well as GC-MS spectroscopic methods. The anti-proliferative activities of these four compounds were investigated on five human tumor cell lines (BEL-7402, BGC-823, MCF-7, HL-60 and KB). Compounds 1 and 2 and camelliasaponin B1 showed significant cytotoxic activities.
Zong, Jian-Fa; Peng, Yun-Ru; Bao, Guan-Hu; Hou, Ru-Yan; Wan, Xiao-Chun
2016-02-04
Two new oleanane-type saponins, named oleiferasaponins C₄ (1) and C₅ (2), were isolated from Camellia oleifera Abel. seed cake residue. Their respective structures were identified as 16α-hydroxy-22α-O-angeloyl-23α-aldehyde-28-dihydroxymethylene-olean-12-ene-3β-O-[β-d-galacto-pyranosyl-(1→2)]-[β-d-glucopyranosyl-(1→2)-β-d-galactopyranosy-(1→3)]-β-d-glucopyranosid-uronic acid methyl ester (1) and 16α-hydroxy-22α-O-angeloyl-23α-aldehyde-28-dihydroxy-methylene-olean-12-ene-3β-O-[β-d-galactopyranosyl-(1→2)]-[β-d-galactopyranosyl-(1→3)]-β-d-glucopyranosiduronic acid methyl ester (2) through 1D- and 2D-NMR, HR-ESI-MS, and GC-MS spectroscopic methods. The two compounds exhibited potent cytotoxic activities against five human tumor cell lines (BEL-7402, BGC-823, MCF-7, HL-60 and KB).
Use of switched capacitor filters to implement the discrete wavelet transform
NASA Technical Reports Server (NTRS)
Kaiser, Kraig E.; Peterson, James N.
1993-01-01
This paper analyzes the use of IIR switched capacitor filters to implement the discrete wavelet transform and the inverse transform, using quadrature mirror filters (QMF) which have the necessary symmetry for reconstruction of the data. This is done by examining the sensitivity of the QMF transforms to the manufacturing variance in the desired capacitances. The performance is evaluated at the outputs of the separate filter stages and the error in the reconstruction of the inverse transform is compared with the desired results.
NASA Technical Reports Server (NTRS)
Alexandrov, Mikhail D.; Cairns, Brian; Mishchenko, Michael I.
2012-01-01
We present a novel technique for remote sensing of cloud droplet size distributions. Polarized reflectances in the scattering angle range between 135deg and 165deg exhibit a sharply defined rainbow structure, the shape of which is determined mostly by single scattering properties of cloud particles, and therefore, can be modeled using the Mie theory. Fitting the observed rainbow with such a model (computed for a parameterized family of particle size distributions) has been used for cloud droplet size retrievals. We discovered that the relationship between the rainbow structures and the corresponding particle size distributions is deeper than it had been commonly understood. In fact, the Mie theory-derived polarized reflectance as a function of reduced scattering angle (in the rainbow angular range) and the (monodisperse) particle radius appears to be a proxy to a kernel of an integral transform (similar to the sine Fourier transform on the positive semi-axis). This approach, called the rainbow Fourier transform (RFT), allows us to accurately retrieve the shape of the droplet size distribution by the application of the corresponding inverse transform to the observed polarized rainbow. While the basis functions of the proxy-transform are not exactly orthogonal in the finite angular range, this procedure needs to be complemented by a simple regression technique, which removes the retrieval artifacts. This non-parametric approach does not require any a priori knowledge of the droplet size distribution functional shape and is computationally fast (no look-up tables, no fitting, computations are the same as for the forward modeling).
Mahan, G. D.
2014-09-21
We calculate the binding energy of an electron bound to a donor in a semiconductor inverse opal. Inverse opals have two kinds of cavities, which we call octahedral and tetrahedral, according to their group symmetry. We put the donor in the center of each of these two cavities and obtain the binding energy. The binding energies become very large when the inverse opal is made from templates with small spheres. For spheres less than 50 nm in diameter, the donor binding can increase to several times its unconfined value. Then electrons become tightly bound to the donor and are unlikely to be thermally activated to the semiconductor conduction band. This conclusion suggests that inverse opals will be poor conductors.
NASA Astrophysics Data System (ADS)
Mahan, G. D.
2014-09-01
We calculate the binding energy of an electron bound to a donor in a semiconductor inverse opal. Inverse opals have two kinds of cavities, which we call octahedral and tetrahedral, according to their group symmetry. We put the donor in the center of each of these two cavities and obtain the binding energy. The binding energies become very large when the inverse opal is made from templates with small spheres. For spheres less than 50 nm in diameter, the donor binding can increase to several times its unconfined value. Then electrons become tightly bound to the donor and are unlikely to be thermally activated to the semiconductor conduction band. This conclusion suggests that inverse opals will be poor conductors.
Testing Earthquake Source Inversion Methodologies
NASA Astrophysics Data System (ADS)
Page, Morgan; Mai, P. Martin; Schorlemmer, Danijel
2011-03-01
Source Inversion Validation Workshop; Palm Springs, California, 11-12 September 2010; Nowadays earthquake source inversions are routinely performed after large earthquakes and represent a key connection between recorded seismic and geodetic data and the complex rupture process at depth. The resulting earthquake source models quantify the spatiotemporal evolution of ruptures. They are also used to provide a rapid assessment of the severity of an earthquake and to estimate losses. However, because of uncertainties in the data, assumed fault geometry and velocity structure, and chosen rupture parameterization, it is not clear which features of these source models are robust. Improved understanding of the uncertainty and reliability of earthquake source inversions will allow the scientific community to use the robust features of kinematic inversions to more thoroughly investigate the complexity of the rupture process and to better constrain other earthquake-related computations, such as ground motion simulations and static stress change calculations.
Temperature Inversions Have Cold Bottoms.
ERIC Educational Resources Information Center
Bohren, Craig F.; Brown, Gail M.
1982-01-01
Uses discussion and illustrations of several demonstrations on air temperature differences and atmospheric stability to explain the phenomena of temperature inversions. Relates this to the smog in Los Angeles and discusses the implications. (DC)
Inversion layer MOS solar cells
NASA Technical Reports Server (NTRS)
Ho, Fat Duen
1986-01-01
Inversion layer (IL) Metal Oxide Semiconductor (MOS) solar cells were fabricated. The fabrication technique and problems are discussed. A plan for modeling IL cells is presented. Future work in this area is addressed.
Testing earthquake source inversion methodologies
Page, M.; Mai, P.M.; Schorlemmer, D.
2011-01-01
Source Inversion Validation Workshop; Palm Springs, California, 11-12 September 2010; Nowadays earthquake source inversions are routinely performed after large earthquakes and represent a key connection between recorded seismic and geodetic data and the complex rupture process at depth. The resulting earthquake source models quantify the spatiotemporal evolution of ruptures. They are also used to provide a rapid assessment of the severity of an earthquake and to estimate losses. However, because of uncertainties in the data, assumed fault geometry and velocity structure, and chosen rupture parameterization, it is not clear which features of these source models are robust. Improved understanding of the uncertainty and reliability of earthquake source inversions will allow the scientific community to use the robust features of kinematic inversions to more thoroughly investigate the complexity of the rupture process and to better constrain other earthquakerelated computations, such as ground motion simulations and static stress change calculations.
NASA Astrophysics Data System (ADS)
Khan, Farrukh I.; Schinn, Dustin S.
2013-08-01
A new business plan that enables policy transformation and resource mobilization at the national and international level, while improving access to resources, will allow the Green Climate Fund to integrate development goals and action on climate change.
Inversion-symmetric topological insulators
NASA Astrophysics Data System (ADS)
Hughes, Taylor L.; Prodan, Emil; Bernevig, B. Andrei
2011-06-01
We analyze translationally invariant insulators with inversion symmetry that fall outside the current established classification of topological insulators. These insulators exhibit no edge or surface modes in the energy spectrum and hence they are not edge metals when the Fermi level is in the bulk gap. However, they do exhibit protected modes in the entanglement spectrum localized on the cut between two entangled regions. Their entanglement entropy cannot be made to vanish adiabatically, and hence the insulators can be called topological. There is a direct connection between the inversion eigenvalues of the Hamiltonian band structure and the midgap states in the entanglement spectrum. The classification of protected entanglement levels is given by an integer N, which is the difference between the negative inversion eigenvalues at inversion symmetric points in the Brillouin zone, taken in sets of 2. When the Hamiltonian describes a Chern insulator or a nontrivial time-reversal invariant topological insulator, the entirety of the entanglement spectrum exhibits spectral flow. If the Chern number is zero for the former, or time reversal is broken in the latter, the entanglement spectrum does not have spectral flow, but, depending on the inversion eigenvalues, can still exhibit protected midgap bands similar to impurity bands in normal semiconductors. Although spectral flow is broken (implying the absence of real edge or surface modes in the original Hamiltonian), the midgap entanglement bands cannot be adiabatically removed, and the insulator is “topological.” We analyze the linear response of these insulators and provide proofs and examples of when the inversion eigenvalues determine a nontrivial charge polarization, a quantum Hall effect, an anisotropic three-dimensional (3D) quantum Hall effect, or a magnetoelectric polarization. In one dimension, we establish a link between the product of the inversion eigenvalues of all occupied bands at all inversion
Forward and inverse kinematics of double universal joint robot wrists
NASA Technical Reports Server (NTRS)
Williams, Robert L., II
1991-01-01
A robot wrist consisting of two universal joints can eliminate the wrist singularity problem found on many individual robots. Forward and inverse position and velocity kinematics are presented for such a wrist having three degrees of freedom. Denavit-Hartenberg parameters are derived to find the transforms required for the kinematic equations. The Omni-Wrist, a commercial double universal joint robot wrist, is studied in detail. There are four levels of kinematic parameters identified for this wrist; three forward and three inverse maps are presented for both position and velocity. These equations relate the hand coordinate frame to the wrist base frame. They are sufficient for control of the wrist standing alone. When the wrist is attached to a manipulator arm; the offset between the two universal joints complicates the solution of the overall kinematics problem. All wrist coordinate frame origins are not coincident, which prevents decoupling of position and orientation for manipulator inverse kinematics.
Luzinski, Craig
2011-12-01
This month, the director of the Magnet Recognition Program® takes an in-depth look at the Magnet® model component transformational leadership. The author examines the expectations for Magnet organizations around this component. What are the qualities that make a nursing leader truly transformational, and what is the best approach to successfully lead a healthcare organization through today's volatile healthcare environment?
Computation of inverse magnetic cascades
NASA Technical Reports Server (NTRS)
Montgomery, D.
1981-01-01
Inverse cascades of magnetic quantities for turbulent incompressible magnetohydrodynamics are reviewed, for two and three dimensions. The theory is extended to the Strauss equations, a description intermediate between two and three dimensions appropriate to Tokamak magnetofluids. Consideration of the absolute equilibrium Gibbs ensemble for the system leads to a prediction of an inverse cascade of magnetic helicity, which may manifest itself as a major disruption. An agenda for computational investigation of this conjecture is proposed.
Inversion Algorithms for Geophysical Problems
1987-12-16
ktdud* Sccumy Oass/Kjoon) Inversion Algorithms for Geophysical Problems (U) 12. PERSONAL AUTHOR(S) Lanzano, Paolo 13 «. TYPE OF REPORT Final 13b...spectral density. 20. DISTRIBUTION/AVAILABILITY OF ABSTRACT 13 UNCLASSIFIED/UNLIMITED D SAME AS RPT n OTIC USERS 22a. NAME OF RESPONSIBLE...Research Laboratory ’^^ SSZ ’.Washington. DC 20375-5000 NRLrMemorandum Report-6138 Inversion Algorithms for Geophysical Problems p. LANZANO Space
3D parallel inversion of time-domain airborne EM data
NASA Astrophysics Data System (ADS)
Liu, Yun-He; Yin, Chang-Chun; Ren, Xiu-Yan; Qiu, Chang-Kai
2016-12-01
To improve the inversion accuracy of time-domain airborne electromagnetic data, we propose a parallel 3D inversion algorithm for airborne EM data based on the direct Gauss-Newton optimization. Forward modeling is performed in the frequency domain based on the scattered secondary electrical field. Then, the inverse Fourier transform and convolution of the transmitting waveform are used to calculate the EM responses and the sensitivity matrix in the time domain for arbitrary transmitting waves. To optimize the computational time and memory requirements, we use the EM "footprint" concept to reduce the model size and obtain the sparse sensitivity matrix. To improve the 3D inversion, we use the OpenMP library and parallel computing. We test the proposed 3D parallel inversion code using two synthetic datasets and a field dataset. The time-domain airborne EM inversion results suggest that the proposed algorithm is effective, efficient, and practical.
Inverse polynomial reconstruction method in DCT domain
NASA Astrophysics Data System (ADS)
Dadkhahi, Hamid; Gotchev, Atanas; Egiazarian, Karen
2012-12-01
The discrete cosine transform (DCT) offers superior energy compaction properties for a large class of functions and has been employed as a standard tool in many signal and image processing applications. However, it suffers from spurious behavior in the vicinity of edge discontinuities in piecewise smooth signals. To leverage the sparse representation provided by the DCT, in this article, we derive a framework for the inverse polynomial reconstruction in the DCT expansion. It yields the expansion of a piecewise smooth signal in terms of polynomial coefficients, obtained from the DCT representation of the same signal. Taking advantage of this framework, we show that it is feasible to recover piecewise smooth signals from a relatively small number of DCT coefficients with high accuracy. Furthermore, automatic methods based on minimum description length principle and cross-validation are devised to select the polynomial orders, as a requirement of the inverse polynomial reconstruction method in practical applications. The developed framework can considerably enhance the performance of the DCT in sparse representation of piecewise smooth signals. Numerical results show that denoising and image approximation algorithms based on the proposed framework indicate significant improvements over wavelet counterparts for this class of signals.
Floppy Molecules with Internal Rotation and Inversion
NASA Astrophysics Data System (ADS)
Kreglewski, Marek
2016-06-01
There are different ways to analyze rovibrational structure of molecules having several large amplitude motions of different type, like internal rotation and inversion or ring-puckering. In my research group we have developed and used methods starting from potential surfaces for large amplitude motions but also applied purely effective Hamiltonians, where tunneling splittings were key parameters. Whatever is the method the following problems must be solved when addressing a rovibrational problem with large amplitude vibrations: 1) a definition of the permutation-inversion molecular symmetry group, 2) a choice of the internal coordinates and their transformation in the symmetry group, 3) derivation of the Hamiltonian in chosen coordinates, 4) calculation of the Hamiltonian matrix elements in a symmetrized basis set. These points will be discussed. The advantage of methods which start from the geometry and potential surface for large amplitude vibrations give much clearer picture of internal dynamics of molecules but generally the fit to experimental data is much poorer. The fitting procedure is strongly non-linear and the iteration procedure much longer. The effective Hamiltonians the fit is generally much better since almost all optimized parameters are linear but the parameters have no clear physical meaning. This method is very useful in the assignment of experimental spectra. Results of the application of both method to methylamine and hydrazine will be presented.
Tensor Inversion of Intrinsic Permeabilities for Heterogeneous Reservoirs
NASA Astrophysics Data System (ADS)
Jiao, J.; Zhang, Y.
2013-12-01
An inverse method has been developed using hybrid formulations and coordinate transform techniques to simultaneously estimate multiple intrinsic permeability tensors (k), flow field, and boundary conditions for a heterogeneous reservoir under non-pumping or pumping conditions [Jiao & Zhang, 2013]. Unlike the objective-function-based approaches, the inverse method does not require forward flow simulations to assess the data-model misfits; thus the knowledge of reservoir boundary conditions is not needed. The method directly incorporates noisy observed data (i.e., fluid heads, Darcy fluxes, or well rates) at the measurement locations, without solving a boundary value problem. Given sufficient measurement data, it yields well-posed systems of equations that can be solved efficiently with coarse inverse grids and nonlinear optimization. When pumping and injection are active, the well rates can be used as measurements and subsurface flux sampling is not needed. Also, local grid refinement at the well locations is not needed for the inversion to succeed. The method is successfully tested for reservoir problems with regular and irregular geometries, different petrofacies patterns, and permeability anisotropy ratios. All problems yield stable solutions under increasing measurement errors. For a given set of the observation data, inversion accuracy is most affected by the permeability anisotropy ratio. Accuracy in estimating k is also affected by the flow pattern: within a given petrofacies, when the Darcy flux component is extremely small, the corresponding directional permeability perpendicular to streamlines becomes less identifiable. Finally, inversion is successful even if the location of the reservoir boundaries is unknown. In this case, the problem domain for inversion is defined by the location of the measurement data. Select problems are presented below in a set of figures and a table (the relevant quantities have a consistent set of units and are thus not labeled
Multidimensional NMR inversion without Kronecker products: Multilinear inversion
NASA Astrophysics Data System (ADS)
Medellín, David; Ravi, Vivek R.; Torres-Verdín, Carlos
2016-08-01
Multidimensional NMR inversion using Kronecker products poses several challenges. First, kernel compression is only possible when the kernel matrices are separable, and in recent years, there has been an increasing interest in NMR sequences with non-separable kernels. Second, in three or more dimensions, the singular value decomposition is not unique; therefore kernel compression is not well-defined for higher dimensions. Without kernel compression, the Kronecker product yields matrices that require large amounts of memory, making the inversion intractable for personal computers. Finally, incorporating arbitrary regularization terms is not possible using the Lawson-Hanson (LH) or the Butler-Reeds-Dawson (BRD) algorithms. We develop a minimization-based inversion method that circumvents the above problems by using multilinear forms to perform multidimensional NMR inversion without using kernel compression or Kronecker products. The new method is memory efficient, requiring less than 0.1% of the memory required by the LH or BRD methods. It can also be extended to arbitrary dimensions and adapted to include non-separable kernels, linear constraints, and arbitrary regularization terms. Additionally, it is easy to implement because only a cost function and its first derivative are required to perform the inversion.
Inversion of tsunami waveforms and tsunami warning
NASA Astrophysics Data System (ADS)
An, Chao
Ever since the 2004 Indian Ocean tsunami, the technique of inversion of tsunami data and the importance of tsunami warning have drawn the attention of many researchers. However, since tsunamis are rare and extreme events, developed inverse techniques lack validation, and open questions rise when they are applied to a real event. In this study, several of those open questions are investigated, i.e., the wave dispersion, bathymetry grid size and subfault division. First, tsunami records from three large tsunami events -- 2010 Maule, 2011 Tohoku and 2012 Haida Gwaii -- are analyzed to extract the main characteristics of the leading tsunami waves. Using the tool of wavelet transforming, the instant wave period can be obtained and thus the dispersive parameter mu2 can be calculated. mu2 is found to be smaller than 0.02 for all records, indicating that the wave dispersion is minor for the propagation of tsunami leading waves. Second, inversions of tsunami data are carried out for three tsunami events -- 2011 Tohoku, 2012 Haida Gwaii and 2014 Iquique. By varying the subfault size and the bathymetry grid size in the inversions, general rules are established for choosing those two parameters. It is found that the choice of bathymetry grid size depends on various parameters, such as the subfault size and the depth of subfaults. The global bathymetry data GEBCO with spatial resolution of 30 arcsec is generally good if the subfault size is larger than 40 km x 40 km; otherwise, bathymetry data with finer resolution is desirable. Detailed instructions of choosing the bathymetry size can be found in Chapter 2. By contrast, the choice of subfault size has much more freedom; our study shows that the subfault size can be very large without significant influence on the predicted tsunami waves. For earthquakes with magnitude of 8.0 ˜ 9.0, the subfault size can be 60 km ˜ 100 km. In our study, the maximum subfault size results in 9 ˜ 16 subfault patches on the ruptured fault surface
q-CALCULUS and the Discrete Inverse Scattering
NASA Astrophysics Data System (ADS)
Karlo, T.; Jacob, H.; Tripathy, K. C.
The discrete inverse scattering in one dimension has been re-identified with lattice calculus. By transforming the deformation parameter, the coordinate and the partial derivatives from lattice space to q-space, the Schrödinger equation with a potential is systematically analyzed. The potential having explicit q-dependence is derived from the knowledge of the spectral measure. The role of q to generate simulation is also highlighted.
Polynomial compensation, inversion, and approximation of discrete time linear systems
NASA Technical Reports Server (NTRS)
Baram, Yoram
1987-01-01
The least-squares transformation of a discrete-time multivariable linear system into a desired one by convolving the first with a polynomial system yields optimal polynomial solutions to the problems of system compensation, inversion, and approximation. The polynomial coefficients are obtained from the solution to a so-called normal linear matrix equation, whose coefficients are shown to be the weighting patterns of certain linear systems. These, in turn, can be used in the recursive solution of the normal equation.
NASA Astrophysics Data System (ADS)
Franssens, Ghislain; de Maziére, Martine; Fonteyn, Dominique
2000-08-01
A new derivation is presented for the analytical inversion of aerosol spectral extinction data to size distributions. It is based on the complex analytic extension of the anomalous diffraction approximation (ADA). We derive inverse formulas that are applicable to homogeneous nonabsorbing and absorbing spherical particles. Our method simplifies, generalizes, and unifies a number of results obtained previously in the literature. In particular, we clarify the connection between the ADA transform and the Fourier and Laplace transforms. Also, the effect of the particle refractive-index dispersion on the inversion is examined. It is shown that, when Lorentz s model is used for this dispersion, the continuous ADA inverse transform is mathematically well posed, whereas with a constant refractive index it is ill posed. Further, a condition is given, in terms of Lorentz parameters, for which the continuous inverse operator does not amplify the error.
Franssens, G; De Maziére, M; Fonteyn, D
2000-08-20
A new derivation is presented for the analytical inversion of aerosol spectral extinction data to size distributions. It is based on the complex analytic extension of the anomalous diffraction approximation (ADA). We derive inverse formulas that are applicable to homogeneous nonabsorbing and absorbing spherical particles. Our method simplifies, generalizes, and unifies a number of results obtained previously in the literature. In particular, we clarify the connection between the ADA transform and the Fourier and Laplace transforms. Also, the effect of the particle refractive-index dispersion on the inversion is examined. It is shown that, when Lorentz's model is used for this dispersion, the continuous ADA inverse transform is mathematically well posed, whereas with a constant refractive index it is ill posed. Further, a condition is given, in terms of Lorentz parameters, for which the continuous inverse operator does not amplify the error.
Psychoanalytic transformations.
Riolo, Fernando
2007-12-01
The author describes how Bion took Freud's conception of dreams as a form of thought and used it as the basis of his theory of transformations. Bion developed an expanded theory of 'dream thought', understood as a process of selection and transformation of sensory and emotional experiences. In this theory, the work of analysis is in turn conceived as a process not only of deciphering symbols, of revealing already existing unconscious meanings, but also of symbol production--of a process for generating thoughts and conferring meaning on experiences that have never been conscious and never been repressed because they have never been 'thought'. Analysis, in its specific operational sense, becomes a system of transformation whereby unconscious somatopsychic processes acquire the conditions for representability and become capable of translation into thoughts, words and interpretations. The rules of transformation applied by the patient in his representations and those applied by the analyst in his interpretations have the same importance for the analytic process as those described by Freud for the process of dreaming. The author discusses the broad categories of transformation adduced by Bion (rigid motion, projective, and in hallucinosis) and introduces some further distinctions within them.
Resolving spectral information from time domain induced polarization data through 2-D inversion
NASA Astrophysics Data System (ADS)
Fiandaca, Gianluca; Ramm, James; Binley, Andrew; Gazoty, Aurélie; Christiansen, Anders Vest; Auken, Esben
2013-02-01
Field-based time domain (TD) induced polarization (IP) surveys are usually modelled by taking into account only the integral chargeability, thus disregarding spectral content. Furthermore, the effect of the transmitted waveform is commonly neglected, biasing inversion results. Given these limitations of conventional approaches, a new 2-D inversion algorithm has been developed using the full voltage decay of the IP response, together with an accurate description of the transmitter waveform and receiver transfer function. This allows reconstruction of the spectral information contained in the TD decay series. The inversion algorithm is based around a 2-D complex conductivity kernel that is computed over a range of frequencies and converted to the TD through a fast Hankel transform. Two key points in the implementation ensure that computation times are minimized. First, the speed of the Jacobian computation, time transformed from frequency domain through the same transformation adopted for the forward response is optimized. Secondly, the reduction of the number of frequencies where the forward response and Jacobian are calculated: cubic splines are used to interpolate the responses to the frequency sampling necessary in the fast Hankel transform. These features, together with parallel computation, ensure inversion times comparable with those of direct current algorithms. The algorithm has been developed in a laterally constrained inversion scheme, and handles both smooth and layered inversions; the latter being helpful in sedimentary environments, where quasi-layered models often represent the actual geology more accurately than smooth minimum-structure models. In the layered inversion approach, a general method to derive the thickness derivative from the complex conductivity Jacobian is also proposed. One synthetic example of layered inversion and one field example of smooth inversion show the capability of the algorithm and illustrates a complete uncertainty
Global inversion for anisotropy during full-waveform inversion
NASA Astrophysics Data System (ADS)
Debens, H. A.; Warner, M.; Umpleby, A.
2015-12-01
Full-waveform inversion (FWI) is a powerful tool for quantitative estimation of high-resolution high-fidelity models of subsurface seismic parameters, typically P-wave velocity. The solution to FWI's posed nonlinear inverse problem is obtained via an iterative series of linearized local updates to a start model, assuming this model lies within the basin of attraction to the global minimum. Thanks to many successful published applications to three-dimensional (3D) field datasets, its advance has been rapid and driven in large-part by the oil and gas industry. The consideration of seismic anisotropy during FWI is of vital importance, as it holds influence over both the kinematics and dynamics of seismic waveforms. If not appropriately taken into account then inadequacies in the anisotropy model are likely to manifest as significant error in the recovered velocity model. Conventionally, anisotropic FWI employs either an a priori anisotropy model, held fixed during FWI, or it uses a multi-parameter local inversion scheme to recover the anisotropy as part of the FWI; both of these methods can be problematic. Constructing an anisotropy model prior to FWI often involves intensive (and hence expensive) iterative procedures, such as travel-time tomography or moveout velocity analysis. On the other hand, introducing multiple parameters to FWI itself increases the complexity of what is already an underdetermined inverse problem. We propose that global rather than local FWI can be used to recover the long-wavelength acoustic anisotropy model, and that this can then be followed by more-conventional local FWI to recover the detailed model. We validate this approach using a full 3D field dataset, demonstrating that it avoids problems associated to crosstalk that can bedevil local inversion schemes, and reconciles well with in situ borehole measurements. Although our approach includes a global inversion for anisotropy, it is nonetheless affordable and practical for 3D field data.
1981-02-01
using the standard Fouuier inversion method. Thep- reins concernIng the Fourier transformation of a tr-ncated and/or averaged visi- bility function are...is reviewed. Basic properties of the two-dimensional Fourier transform are reviewed, and the standard Fourier inversion method is presented. This...averaging are illustrated for a double Gaussian model source using the standard Fourier inversion method. Theorems concerning the Fourier transforma- tion
NASA Technical Reports Server (NTRS)
Birkinshaw, M.; Hughes, J. P.; Arnaud, K. A.
1991-01-01
A comparison of the X-ray properties and the Sunyaev-Zel'dovich (SZ) effect for a cluster of galaxies can be used to measure the distance of the cluster and hence the Hubble constant. This method was applied to the rich cluster Abell 665. The relative normalization of X-ray and SZ-effect data leads to an estimated Hubble constant of H sub 0 = 40 + or - 9 km/s Mpc if only the random errors are included. When the possible systematic errors are added in quadrature, the range of possible values of the Hubble constants expands to (40 to 50) + or - 12 km/s Mpc.
Kirkpatrick, C. C.; McNamara, B. R.; Kazemzadeh, F.; Cavagnolo, K. W.; Rafferty, D. A.; BIrzan, L.; Nulsen, P. E. J.; Wise, M. W.; Gitti, M.
2009-05-20
The brightest cluster galaxy (BCG) in the Abell 1664 cluster is unusually blue and is forming stars at a rate of {approx} 23 M {sub sun} yr{sup -1}. The BCG is located within 5 kpc of the X-ray peak, where the cooling time of 3.5 x 10{sup 8} yr and entropy of 10.4 keV cm{sup 2} are consistent with other star-forming BCGs in cooling flow clusters. The center of A1664 has an elongated, 'barlike' X-ray structure whose mass is comparable to the mass of molecular hydrogen, {approx}10{sup 10} M {sub sun} in the BCG. We show that this gas is unlikely to have been stripped from interloping galaxies. The cooling rate in this region is roughly consistent with the star formation rate, suggesting that the hot gas is condensing onto the BCG. We use the scaling relations of BIrzan et al. to show that the active galactic nucleus (AGN) is underpowered compared to the central X-ray cooling luminosity by roughly a factor of three. We suggest that A1664 is experiencing rapid cooling and star formation during a low state of an AGN feedback cycle that regulates the rates of cooling and star formation. Modeling the emission as a single-temperature plasma, we find that the metallicity peaks 100 kpc from the X-ray center, resulting in a central metallicity dip. However, a multi-temperature cooling flow model improves the fit to the X-ray emission and is able to recover the expected, centrally peaked metallicity profile.
NASA Astrophysics Data System (ADS)
George, L. T.; Dwarakanath, K. S.; Johnston-Hollitt, M.; Hurley-Walker, N.; Hindson, L.; Kapińska, A. D.; Tingay, S. J.; Bell, M.; Callingham, J. R.; For, Bi-Qing; Hancock, P. J.; Lenc, E.; McKinley, B.; Morgan, J.; Offringa, A.; Procopio, P.; Staveley-Smith, L.; Wayth, R. B.; Wu, Chen; Zheng, Q.; Bernardi, G.; Bowman, J. D.; Briggs, F.; Cappallo, R. J.; Corey, B. E.; Deshpande, A. A.; Emrich, D.; Goeke, R.; Greenhill, L. J.; Hazelton, B. J.; Kaplan, D. L.; Kasper, J. C.; Kratzenberg, E.; Lonsdale, C. J.; Lynch, M. J.; McWhirter, S. R.; Mitchell, D. A.; Morales, M. F.; Morgan, E.; Oberoi, D.; Ord, S. M.; Prabu, T.; Rogers, A. E. E.; Roshi, A.; Shankar, N. Udaya; Srivani, K. S.; Subrahmanyan, R.; Waterson, M.; Webster, R. L.; Whitney, A. R.; Williams, A.; Williams, C. L.
2015-08-01
We have carried out multiwavelength observations of the nearby (z = 0.046) rich, merging galaxy cluster Abell 3376 with the Murchison Widefield Array (MWA). As a part of the GaLactic and Extragalactic All-sky MWA Survey, this cluster was observed at 88, 118, 154, 188, and 215 MHz. The known radio relics, towards the eastern and western peripheries of the cluster, were detected at all the frequencies. The relics, with a linear extent of ˜1 Mpc each, are separated by ˜2 Mpc. Combining the current observations with those in the literature, we have obtained the spectra of these relics over the frequency range 80-1400 MHz. The spectra follow power laws, with α = -1.17 ± 0.06 and -1.37 ± 0.08 for the west and east relics, respectively (S∝να). Assuming the break frequency to be near the lower end of the spectrum we estimate the age of the relics to be ˜0.4 Gyr. No diffuse radio emission from the central regions of the cluster (halo) was detected. The upper limit on the radio power of any possible halo that might be present in the cluster is a factor of 35 lower than that expected from the radio power and X-ray luminosity correlation for cluster haloes. From this we conclude that the cluster halo is very extended (>500 kpc) and/or most of the radio emission from the halo has decayed. The current limit on the halo radio power is a factor of 10 lower than the existing upper limits with possible implications for models of halo formation.
NASA Astrophysics Data System (ADS)
Terlevich, Roberto; Melnick, Jorge; Terlevich, Elena; Chávez, Ricardo; Telles, Eduardo; Bresolin, Fabio; Plionis, Manolis; Basilakos, Spyros; Fernández Arenas, David; González Morán, Ana Luisa; Díaz, Ángeles I.; Aretxaga, Itziar
2016-08-01
ID11 is an actively star-forming, extremely compact galaxy and Lyα emitter at z = 3.117 that is gravitationally magnified by a factor of ~17 by the cluster of galaxies Hubble Frontier Fields AS1063. The observed properties of this galaxy resemble those of low luminosity HII galaxies or giant HII regions such as 30 Doradus in the Large Magellanic Cloud. Using the tight correlation correlation between the Balmer-line luminosities and the width of the emission lines (typically L(Hβ) - σ(Hβ)), which are valid for HII galaxies and giant HII regions to estimate their total luminosity, we are able to measure the lensing amplification of ID11. We obtain an amplification of 23 ± 11 that is similar within errors to the value of ~17 estimated or predicted by the best lensing models of the massive cluster Abell S1063. We also compiled, from the literature, luminosities and velocity dispersions for a set of lensed compact star-forming regions. There is more scatter in the L-σ correlation for these lensed systems, but on the whole the results tend to support the lensing model estimates of the magnification. Our result indicates that the amplification can be independently measured using the L - σ relation in lensed giant HII regions or HII galaxies. It also supports the suggestion, even if lensing is model dependent, that the L - σ relation is valid for low luminosity high-z objects. Ad hoc observations of lensed star-forming systems are required to determine the lensing amplification accurately.
Inversion strategies for visco-acoustic waveform inversion
NASA Astrophysics Data System (ADS)
Kamei, R.; Pratt, R. G.
2013-08-01
Visco-acoustic waveform inversion can potentially yield quantitative images of the distribution of both velocity and the attenuation parameters from seismic data. Intrinsic P-wave attenuation has been of particular interest, but has also proven challenging. Frequency-domain inversion allows attenuation and velocity relations to be easily incorporated, and allows a natural multiscale approach. The Laplace-Fourier approach extends this to allow the natural damping of waveforms to enhance early arrivals. Nevertheless, simultaneous inversion of velocity and attenuation leads to significant `cross-talk' between the resulting images, reflecting a lack of parameter resolution and indicating the need for pre-conditioning and regularization of the inverse problem. We analyse the cross-talk issue by partitioning the inversion parameters into two classes; the velocity parameter class, and the attenuation parameter class. Both parameters are defined at a reference frequency, and a dispersion relation is assumed that describes these parameters at any other frequency. We formulate the model gradients at a forward modelling frequency, and convert them to the reference frequency by employing the Jacobian of the coordinate change represented by the dispersion relation. We show that at a given modelling frequency, the Fréchet derivatives corresponding to these two parameter classes differ only by a 90° phase shift, meaning that the magnitudes of resulting model updates will be unscaled, and will not reflect the expected magnitudes in realistic (Q-1 ≪ 1) media. Due to the lack of scaling, cross-talk will be enhanced by poor subsurface illumination, by errors in kinematics, and by data noise. To solve these issues, we introduce an attenuation scaling term (the inverse of a penalty term) that is used to pre-condition the gradient by controlling the magnitudes of the updates to the attenuation parameters. Initial results from a suite of synthetic cross-hole tests using a three
Optimization and geophysical inverse problems
Barhen, J.; Berryman, J.G.; Borcea, L.; Dennis, J.; de Groot-Hedlin, C.; Gilbert, F.; Gill, P.; Heinkenschloss, M.; Johnson, L.; McEvilly, T.; More, J.; Newman, G.; Oldenburg, D.; Parker, P.; Porto, B.; Sen, M.; Torczon, V.; Vasco, D.; Woodward, N.B.
2000-10-01
A fundamental part of geophysics is to make inferences about the interior of the earth on the basis of data collected at or near the surface of the earth. In almost all cases these measured data are only indirectly related to the properties of the earth that are of interest, so an inverse problem must be solved in order to obtain estimates of the physical properties within the earth. In February of 1999 the U.S. Department of Energy sponsored a workshop that was intended to examine the methods currently being used to solve geophysical inverse problems and to consider what new approaches should be explored in the future. The interdisciplinary area between inverse problems in geophysics and optimization methods in mathematics was specifically targeted as one where an interchange of ideas was likely to be fruitful. Thus about half of the participants were actively involved in solving geophysical inverse problems and about half were actively involved in research on general optimization methods. This report presents some of the topics that were explored at the workshop and the conclusions that were reached. In general, the objective of a geophysical inverse problem is to find an earth model, described by a set of physical parameters, that is consistent with the observational data. It is usually assumed that the forward problem, that of calculating simulated data for an earth model, is well enough understood so that reasonably accurate synthetic data can be generated for an arbitrary model. The inverse problem is then posed as an optimization problem, where the function to be optimized is variously called the objective function, misfit function, or fitness function. The objective function is typically some measure of the difference between observational data and synthetic data calculated for a trial model. However, because of incomplete and inaccurate data, the objective function often incorporates some additional form of regularization, such as a measure of smoothness
ERIC Educational Resources Information Center
Cookson, Peter W., Jr., Ed.; Schneider, Barbara, Ed.
The authors in this book address the issues that relate to the crisis in American education and review some of the proposed solutions. To transform education, schools must be examined as social systems that are interrelated with families, communities, and the world of work. Following the introduction, section 1, "Conditions for Educational…
Transformation & Metamorphosis
ERIC Educational Resources Information Center
Lott, Debra
2009-01-01
The sculptures of Canadian artist Brian Jungen are a great inspiration for a lesson on creating new forms. Jungen transforms found objects into unique creations without fully concealing their original form or purpose. Frank Stella's sculpture series, including "K.132,2007" made of stainless steel and spray paint, is another great example of…
ERIC Educational Resources Information Center
Cronin, C. H.; Feldman, Phillip
1994-01-01
Presents comparisons between the traditional curriculum and the essential learnings curriculum implemented at the Moss Point School District in Moss Point, Mississippi. Describes in detail the curriculum transformation process. Provides insight into the role of technology in the reading/language arts curriculum. (RS)
ERIC Educational Resources Information Center
Berry, John N., III
2007-01-01
The program for the march by librarians on America's capital for the American Library Association (ALA) conference is predictably loaded with lobbying, legislation, and DC tours. It also abounds with professional opportunity and reflects the impact of Leslie Burger, one of the most activist ALA presidents in recent history. Her "Transformation"…
ERIC Educational Resources Information Center
Popham, W. James
2008-01-01
If you're at all skeptical that "formative assessment" is just another buzzword, then here's a book that will change the way you think about the role that formative assessment can play in transforming education into a more powerful and positive process. Renowned expert W. James Popham clarifies what formative assessment really is, why…
Probabilistic inversion: a preliminary discussion
NASA Astrophysics Data System (ADS)
Battista Rossi, Giovanni; Crenna, Francesco
2015-02-01
We continue the discussion on the possibility of interpreting probability as a logic, that we have started in the previous IMEKO TC1-TC7-TC13 Symposium. We show here how a probabilistic logic can be extended up to including direct and inverse functions. We also discuss the relationship between this framework and the Bayes-Laplace rule, showing how the latter can be formally interpreted as a probabilistic inversion device. We suggest that these findings open a new perspective in the evaluation of measurement uncertainty.
Thermoelectric properties of inverse opals
NASA Astrophysics Data System (ADS)
Mahan, G. D.; Poilvert, N.; Crespi, V. H.
2016-02-01
Rayleigh's method [Philos. Mag. Ser. 5 34, 481 (1892)] is used to solve for the classical thermoelectric equations in inverse opals. His theory predicts that in an inverse opal, with periodic holes, the Seebeck coefficient and the figure of merit are identical to that of the bulk material. We also provide a major revision to Rayleigh's method, in using the electrochemical potential as an important variable, instead of the electrostatic potential. We also show that in some cases, the thermal boundary resistance is important in the effective thermal conductivity.
Statistical inference for inverse problems
NASA Astrophysics Data System (ADS)
Bissantz, Nicolai; Holzmann, Hajo
2008-06-01
In this paper we study statistical inference for certain inverse problems. We go beyond mere estimation purposes and review and develop the construction of confidence intervals and confidence bands in some inverse problems, including deconvolution and the backward heat equation. Further, we discuss the construction of certain hypothesis tests, in particular concerning the number of local maxima of the unknown function. The methods are illustrated in a case study, where we analyze the distribution of heliocentric escape velocities of galaxies in the Centaurus galaxy cluster, and provide statistical evidence for its bimodality.
Chemical Shift Anisotropy Selective Inversion*
Caporini, Marc. A.; Turner, Christopher. J.; Bielecki, Anthony; Griffin, Robert G.
2009-01-01
Magic Angle Spinning (MAS) is used in solid-state NMR to remove the broadening effects of the chemical shift anisotropy (CSA). In this work we investigate a technique that can reintroduce the CSA in order to selectively invert transverse magnetization. The technique involves an amplitude sweep of the radio frequency field through a multiple of the spinning frequency. The selectivity of this inversion mechanism is determined by the size of the CSA. We develop a theoretical framework to describe this process and demonstrate the CSA selective inversion with numerical simulations and experimental data. We combine this approach with cross polarization (CP) for potential applications in multi-dimensional MAS NMR. PMID:19648036
Multiphase inverse modeling: An Overview
Finsterle, S.
1998-03-01
Inverse modeling is a technique to derive model-related parameters from a variety of observations made on hydrogeologic systems, from small-scale laboratory experiments to field tests to long-term geothermal reservoir responses. If properly chosen, these observations contain information about the system behavior that is relevant to the performance of a geothermal field. Estimating model-related parameters and reducing their uncertainty is an important step in model development, because errors in the parameters constitute a major source of prediction errors. This paper contains an overview of inverse modeling applications using the ITOUGH2 code, demonstrating the possibilities and limitations of a formalized approach to the parameter estimation problem.
Population inversion by chirped pulses
Lu Tianshi
2011-09-15
In this paper, we analyze the condition for complete population inversion by a chirped pulse over a finite duration. The nonadiabatic transition probability is mapped in the two-dimensional parameter space of coupling strength and detuning amplitude. Asymptotic forms of the probability are derived by the interference of nonadiabatic transitions for sinusoidal and triangular pulses. The qualitative difference between the maps for the two types of pulses is accounted for. The map is used for the design of stable inversion pulses under specific accuracy thresholds.
Slant plane CSAR processing using Householder transform.
Burki, Jehanzeb; Barnes, Christopher F
2008-10-01
Fourier analysis-based focusing of synthetic aperture radar (SAR) data collected during circular flight path is a recent advancement in SAR signal processing. This paper uses the Householder transform to obtain a ground plane circular SAR (CSAR) signal phase history from the slant plane CSAR phase history by inverting the linear shift-varying system model, thereby circumventing the need for explicitly computing a pseudo-inverse. The Householder transform has recently been shown to have improved error bounds and stability as an underdetermined and ill-conditioned system solver, and the Householder transform is computationally efficient.
A practical Hadamard transform spectrometer for astronomical application
NASA Technical Reports Server (NTRS)
Tai, M. H.
1977-01-01
The mathematical properties of Hadamard matrices and their application to spectroscopy are discussed. A comparison is made between Fourier and Hadamard transform encoding in spectrometry. The spectrometer is described and its laboratory performance evaluated. The algorithm and programming of inverse transform are given. A minicomputer is used to recover the spectrum.
Andersson, Karl E.; Peterson, J.R.; Madejski, G.M.; /SLAC /KIPAC, Menlo Park
2007-04-17
We propose a new Monte Carlo method to study extended X-ray sources with the European Photon Imaging Camera (EPIC) aboard XMM Newton. The Smoothed Particle Inference (SPI) technique, described in a companion paper, is applied here to the EPIC data for the clusters of galaxies Abell 1689, Centaurus and RXJ 0658-55 (the ''bullet cluster''). We aim to show the advantages of this method of simultaneous spectral-spatial modeling over traditional X-ray spectral analysis. In Abell 1689 we confirm our earlier findings about structure in temperature distribution and produce a high resolution temperature map. We also confirm our findings about velocity structure within the gas. In the bullet cluster, RXJ 0658-55, we produce the highest resolution temperature map ever to be published of this cluster allowing us to trace what looks like the motion of the bullet in the cluster. We even detect a south to north temperature gradient within the bullet itself. In the Centaurus cluster we detect, by dividing up the luminosity of the cluster in bands of gas temperatures, a striking feature to the north-east of the cluster core. We hypothesize that this feature is caused by a subcluster left over from a substantial merger that slightly displaced the core. We conclude that our method is very powerful in determining the spatial distributions of plasma temperatures and very useful for systematic studies in cluster structure.
Action Understanding as Inverse Planning
ERIC Educational Resources Information Center
Baker, Chris L.; Saxe, Rebecca; Tenenbaum, Joshua B.
2009-01-01
Humans are adept at inferring the mental states underlying other agents' actions, such as goals, beliefs, desires, emotions and other thoughts. We propose a computational framework based on Bayesian inverse planning for modeling human action understanding. The framework represents an intuitive theory of intentional agents' behavior based on the…
Wave-equation dispersion inversion
NASA Astrophysics Data System (ADS)
Li, Jing; Feng, Zongcai; Schuster, Gerard
2017-03-01
We present the theory for wave-equation inversion of dispersion curves, where the misfit function is the sum of the squared differences between the wavenumbers along the predicted and observed dispersion curves. The dispersion curves are obtained from Rayleigh waves recorded by vertical-component geophones. Similar to wave-equation traveltime tomography, the complicated surface wave arrivals in traces are skeletonized as simpler data, namely the picked dispersion curves in the phase-velocity and frequency domains. Solutions to the elastic wave equation and an iterative optimization method are then used to invert these curves for 2-D or 3-D S-wave velocity models. This procedure, denoted as wave-equation dispersion inversion (WD), does not require the assumption of a layered model and is significantly less prone to the cycle-skipping problems of full waveform inversion. The synthetic and field data examples demonstrate that WD can approximately reconstruct the S-wave velocity distributions in laterally heterogeneous media if the dispersion curves can be identified and picked. The WD method is easily extended to anisotropic data and the inversion of dispersion curves associated with Love waves.
NASA Astrophysics Data System (ADS)
Ouyang, Wei; Mao, Weijian; Li, Wuqun; Zhang, Pan
2016-11-01
An approach for approximate direct quadratic nonlinear inversion in two-parameter (density and bulk modulus) heterogeneous acoustic media is being presented and discussed in this paper. The approach consists of two parts: the first is a linear generalized Radon transform (GRT) migration procedure based on the weighted true-amplitude summation of pre-stack seismic scattered data that is adapted to a virtually arbitrary observing system, and the second is a non-iterative quadratic inversion operation, produced from the explicit expression of amplitude radiation pattern that is acting on the migrated data. This ensures the asymptotic inversion can continue to simultaneously locate the discontinuities and reconstruct the size of the discontinuities in the perturbation parameters describing the acoustic media. We identify that the amplitude radiation pattern is the binary quadratic combination of the parameters in the process of formulating nonlinear inverse scattering problems based on second-order Born approximation. The coefficients of the quadratic terms are computed by appropriately handling the double scattering effects. These added quadratic terms provide a better amplitude correction for the parameters inversion. Through numerical tests, we show that for strong perturbations, the errors of the linear inversion are significant and unacceptable. In contrast, the quadratic nonlinear inversion can give fairly accurate inversion results and keep almost the same computational complexity as conventional GRT liner inversion.
NASA Astrophysics Data System (ADS)
Ouyang, Wei; Mao, Weijian; Li, Wuqun; Zhang, Pan
2017-02-01
An approach for approximate direct quadratic non-linear inversion in two-parameter (density and bulk modulus) heterogeneous acoustic media is being presented and discussed in this paper. The approach consists of two parts: the first is a linear generalized Radon transform (GRT) migration procedure based on the weighted true-amplitude summation of pre-stack seismic scattered data that is adapted to a virtually arbitrary observing system, and the second is a non-iterative quadratic inversion operation, produced from the explicit expression of amplitude radiation pattern that is acting on the migrated data. This ensures the asymptotic inversion can continue to simultaneously locate the discontinuities and reconstruct the size of the discontinuities in the perturbation parameters describing the acoustic media. We identify that the amplitude radiation pattern is the binary quadratic combination of the parameters in the process of formulating non-linear inverse scattering problems based on second-order Born approximation. The coefficients of the quadratic terms are computed by appropriately handling the double scattering effects. These added quadratic terms provide a better amplitude correction for the parameters inversion. Through numerical tests, we show that for strong perturbations, the errors of the linear inversion are significant and unacceptable. In contrast, the quadratic non-linear inversion can give fairly accurate inversion results and keep almost the same computational complexity as conventional GRT liner inversion.
Extracting Low-Frequency Information from Time Attenuation in Elastic Waveform Inversion
NASA Astrophysics Data System (ADS)
Guo, Xuebao; Liu, Hong; Shi, Ying; Wang, Weihong
2017-03-01
Low-frequency information is crucial for recovering background velocity, but the lack of low-frequency information in field data makes inversion impractical without accurate initial models. Laplace-Fourier domain waveform inversion can recover a smooth model from real data without low-frequency information, which can be used for subsequent inversion as an ideal starting model. In general, it also starts with low frequencies and includes higher frequencies at later inversion stages, while the difference is that its ultralow frequency information comes from the Laplace-Fourier domain. Meanwhile, a direct implementation of the Laplace-transformed wavefield using frequency domain inversion is also very convenient. However, because broad frequency bands are often used in the pure time domain waveform inversion, it is difficult to extract the wavefields dominated by low frequencies in this case. In this paper, low-frequency components are constructed by introducing time attenuation into the recorded residuals, and the rest of the method is identical to the traditional time domain inversion. Time windowing and frequency filtering are also applied to mitigate the ambiguity of the inverse problem. Therefore, we can start at low frequencies and to move to higher frequencies. The experiment shows that the proposed method can achieve a good inversion result in the presence of a linear initial model and records without low-frequency information.
ERIC Educational Resources Information Center
Eberhart, Linda; Barnes, Tara
2014-01-01
The community of East Lake, home to Charles R. Drew Charter School (Drew), is 6 miles from downtown Atlanta. In 1995, crime in East Lake was 19 times higher than the national average. Now, violent crime is down 95 percent. In 1995, 88 percent of residents were unemployed. Now, only 5 percent receive welfare. In 1995, just 5 percent of fifth…
Smith, James L.; Helenberg, Harold W.; Kilsdonk, Dennis J.
1979-01-01
There is provided an improved RF transformer having a single-turn secondary of cylindrical shape and a coiled encapsulated primary contained within the secondary. The coil is tapered so that the narrowest separation between the primary and the secondary is at one end of the coil. The encapsulated primary is removable from the secondary so that a variety of different capacity primaries can be utilized with one secondary.
NASA Astrophysics Data System (ADS)
Kadic, Muamer; Guenneau, Sébastien; Enoch, Stefan; Huidobro, Paloma A.; Martín-Moreno, Luis; García-Vidal, Francisco J.; Renger, Jan; Quidant, Romain
2012-07-01
Surface plasmons polaritons (SPPs) at metal/dielectric interfaces have raised lots of expectations in the on-going quest towards scaling down optical devices. SPP optics offers a powerful and flexible platform for real two-dimensional integrated optics, capable of supporting both light and electrons. Yet, a full exploitation of the features of SPPs is conditioned by an accurate control of their flow. Most efforts have so far focused on the extrapolation of concepts borrowed from guided optics. This strategy has already led to many important breakthroughs but a fully deterministic control of SPP modes remains a challenge. Recently, the field of optics was stimulated by a novel paradigm, transformation optics, which offers the capability to control light flow in any desired fashion. While it has already significantly contributed to the design of metamaterials with unprecedented optical properties, its versatility offers new opportunities towards a fully deterministic control of SPPs and the design of a new class of plasmonic functionalities. Here, we review recent progress in the application of transformation optics to SPPs. We first briefly describe the theoretical formalism of transformation plasmonics, focusing on its specificities over its three-dimensional optical counterpart. Numerical simulations are then used to illustrate its capability to tame SPP flows at a metal interface patterned with a dielectric load. Finally, we review recent experimental implementations leading to unique SPP functionalities at optical frequencies.
Time Domain Viscoelastic Full Waveform Inversion
NASA Astrophysics Data System (ADS)
Fabien-Ouellet, Gabriel; Gloaguen, Erwan; Giroux, Bernard
2017-03-01
Viscous attenuation can have a strong impact on seismic wave propagation, but it is rarely taken into account in full waveform inversion (FWI). When viscoelasticity is considered in time domain FWI, the displacement formulation of the wave equation is usually used instead of the popular velocity-stress formulation. However, inversion schemes rely on the adjoint equations, which are quite different for the velocity-stress formulation than for the displacement formulation. In this paper, we apply the adjoint state method to the isotropic viscoelastic wave equation in the velocity-stress formulation based on the generalized standard linear solid rheology. By applying linear transformations to the wave equation before deriving the adjoint state equations, we obtain two symmetric sets of partial differential equations for the forward and adjoint variables. The resulting sets of equations only differ by a sign change and can be solved by the same numerical implementation. We also investigate the crosstalk between parameter classes (velocity and attenuation) of the viscoelastic equation. More specifically, we show that the attenuation levels can be used to recover the quality factors of P- and S- waves, but that they are very sensitive to velocity errors. Finally, we present a synthetic example of viscoelastic FWI in the context of monitoring CO2 geological sequestration. We show that FWI based on our formulation can indeed recover P- and S- wave velocities and their attenuation levels when attenuation is high enough. Both changes in velocity and attenuation levels recovered with FWI can be used to track the CO2 plume during and after injection. Further studies are required to evaluate the performance of viscoelastic FWI on real data.
Lewis inverse design code (LINDES): Users manual
NASA Technical Reports Server (NTRS)
Sanz, Jose M.
1987-01-01
The method of complex characteristics and hodograph transformation for the design of shockless airfoils was introduced by Bauer, Garabedian, and Korn and has been extended by the author to design subcritical and supercritical cascades with high solidities and large inlet angles. This new capability was achieved by introducing a new conformal mapping of the hodograph domain onto an ellipse and expanding the solution in terms of Chebyshev polynomials. A new computer code, the NASA Lewis inverse design code, was developed based on this idea. This new design code is an efficient method for the design of airfoils in cascade. In particular, the design of subcritical cascades of airfoils is a very fast, robust, and versatile process. The inverse design code can be made to interact with a turbulent boundary layer calculation to obtain airfoils with no separated flows at the design condition. This report is intended to serve as a users manual for this design code. Material previously reported by the author is included here for completeness and quick access to the user. The manual contains a description of the method followed by a discussion of the design procedure and examples. The input parameters necessary to run the code are then described and their default values given. Output listings corresponding to six different blade shapes designed with the code are given, as well as the necessary input data to reproduce the computer runs. The examples have been chosen to show that a wide range of applications can be covered with the code, ranging from supercritical propeller sections to wind tunnel turning vanes that can operate with a large inlet flow angle range.
Zhukovsky, K.
2014-01-01
We present a general method of operational nature to analyze and obtain solutions for a variety of equations of mathematical physics and related mathematical problems. We construct inverse differential operators and produce operational identities, involving inverse derivatives and families of generalised orthogonal polynomials, such as Hermite and Laguerre polynomial families. We develop the methodology of inverse and exponential operators, employing them for the study of partial differential equations. Advantages of the operational technique, combined with the use of integral transforms, generating functions with exponentials and their integrals, for solving a wide class of partial derivative equations, related to heat, wave, and transport problems, are demonstrated. PMID:24892051
Resolution enhancement of robust Bayesian pre-stack inversion in the frequency domain
NASA Astrophysics Data System (ADS)
Yin, Xingyao; Li, Kun; Zong, Zhaoyun
2016-10-01
AVO/AVA (amplitude variation with an offset or angle) inversion is one of the most practical and useful approaches to estimating model parameters. So far, publications on AVO inversion in the Fourier domain have been quite limited in view of its poor stability and sensitivity to noise compared with time-domain inversion. For the resolution and stability of AVO inversion in the Fourier domain, a novel robust Bayesian pre-stack AVO inversion based on the mixed domain formulation of stationary convolution is proposed which could solve the instability and achieve superior resolution. The Fourier operator will be integrated into the objective equation and it avoids the Fourier inverse transform in our inversion process. Furthermore, the background constraints of model parameters are taken into consideration to improve the stability and reliability of inversion which could compensate for the low-frequency components of seismic signals. Besides, the different frequency components of seismic signals can realize decoupling automatically. This will help us to solve the inverse problem by means of multi-component successive iterations and the convergence precision of the inverse problem could be improved. So, superior resolution compared with the conventional time-domain pre-stack inversion could be achieved easily. Synthetic tests illustrate that the proposed method could achieve high-resolution results with a high degree of agreement with the theoretical model and verify the quality of anti-noise. Finally, applications on a field data case demonstrate that the proposed method could obtain stable inversion results of elastic parameters from pre-stack seismic data in conformity with the real logging data.
Alamo-Martínez, K. A.; González-Lópezlira, R. A.; Blakeslee, J. P.; Côté, P.; Ferrarese, L.; Jee, M. J.; Jordán, A.; Meurer, G. R.; Peng, E. W.; West, M. J.
2013-09-20
We study the rich globular cluster (GC) system in the center of the massive cluster of galaxies Abell 1689 (z = 0.18), one of the most powerful gravitational lenses known. With 28 Hubble Space Telescope/Advanced Camera for Surveys orbits in the F814W bandpass, we reach a magnitude I{sub 814} = 29 with ∼>90% completeness and sample the brightest ∼5% of the GC system. Assuming the well-known Gaussian form of the GC luminosity function (GCLF), we estimate a total population of N{sup total}{sub GC}= 162,850{sup +75,450}{sub -51,310} GCs within a projected radius of 400 kpc. As many as half of the GCs may comprise an intracluster component. Even with the sizable uncertainties, which mainly result from the uncertain GCLF parameters, this system is by far the largest GC population studied to date. The specific frequency S{sub N} is high, but not uncommon for central galaxies in massive clusters, rising from S{sub N} ≈ 5 near the center to ∼12 at large radii. Passive galaxy fading would increase S{sub N} by ∼20% at z = 0. We construct the radial mass profiles of the GCs, stars, intracluster gas, and lensing-derived total mass, and we compare the mass fractions as a function of radius. The estimated mass in GCs, M{sub GC}{sup total} = 3.9 × 10{sup 10} M{sub ☉}, is comparable to ∼80% of the total stellar mass of the Milky Way. The shape of the GC mass profile appears intermediate between those of the stellar light and total cluster mass. Despite the extreme nature of this system, the ratios of the GC mass to the baryonic and total masses, and thus the GC formation efficiency, are typical of those in other rich clusters when comparing at the same physical radii. The GC formation efficiency is not constant, but varies with radius, in a manner that appears similar for different clusters; we speculate on the reasons for this similarity in profile.
NASA Astrophysics Data System (ADS)
Castellano, M.; Amorín, R.; Merlin, E.; Fontana, A.; McLure, R. J.; Mármol-Queraltó, E.; Mortlock, A.; Parsa, S.; Dunlop, J. S.; Elbaz, D.; Balestra, I.; Boucaud, A.; Bourne, N.; Boutsia, K.; Brammer, G.; Bruce, V. A.; Buitrago, F.; Capak, P.; Cappelluti, N.; Ciesla, L.; Comastri, A.; Cullen, F.; Derriere, S.; Faber, S. M.; Giallongo, E.; Grazian, A.; Grillo, C.; Mercurio, A.; Michałowski, M. J.; Nonino, M.; Paris, D.; Pentericci, L.; Pilo, S.; Rosati, P.; Santini, P.; Schreiber, C.; Shu, X.; Wang, T.
2016-05-01
Aims: We present the first public release of photometric redshifts, galaxy rest frame properties and associated magnification values in the cluster and parallel pointings of the first two Frontier Fields, Abell-2744 and MACS-J0416. The released catalogues aim to provide a reference for future investigations of extragalactic populations in these legacy fields: from lensed high-redshift galaxies to cluster members themselves. Methods: We exploit a multiwavelength catalogue, ranging from Hubble Space Telescope (HST) to ground-based K and Spitzer IRAC, which is specifically designed to enable detection and measurement of accurate fluxes in crowded cluster regions. The multiband information is used to derive photometric redshifts and physical properties of sources detected either in the H-band image alone, or from a stack of four WFC3 bands. To minimize systematics, median photometric redshifts are assembled from six different approaches to photo-z estimates. Their reliability is assessed through a comparison with available spectroscopic samples. State-of-the-art lensing models are used to derive magnification values on an object-by-object basis by taking into account sources positions and redshifts. Results: We show that photometric redshifts reach a remarkable ~3-5% accuracy. After accounting for magnification, the H-band number counts are found to be in agreement at bright magnitudes with number counts from the CANDELS fields, while extending the presently available samples to galaxies that, intrinsically, are as faint as H ~ 32-33, thanks to strong gravitational lensing. The Frontier Fields allow the galaxy stellar mass distribution to be probed, depending on magnification, at 0.5-1.5 dex lower masses with respect to extragalactic wide fields, including sources at Mstar ~ 107-108 M⊙ at z > 5. Similarly, they allow the detection of objects with intrinsic star formation rates (SFRs) >1 dex lower than in the CANDELS fields reaching 0.1-1 M⊙/yr at z ~ 6-10. The
Probing the dynamical and X-ray mass proxies of the cluster of galaxies Abell S1101
NASA Astrophysics Data System (ADS)
Rabitz, Andreas; Zhang, Yu-Ying; Schwope, Axel; Verdugo, Miguel; Reiprich, Thomas H.; Klein, Matthias
2017-01-01
Context. The galaxy cluster Abell S1101 (S1101 hereafter) deviates significantly from the X-ray luminosity versus velocity dispersion relation (L-σ) of galaxy clusters in our previous study. Given reliable X-ray luminosity measurement combining XMM-Newton and ROSAT, this could most likely be caused by the bias in the velocity dispersion due to interlopers and low member statistic in the previous sample of member galaxies, which was solely based on 20 galaxy redshifts drawn from the literature. Aims: We intend to increase the galaxy member statistics to perform precision measurements of the velocity dispersion and dynamical mass of S1101. We aim for a detailed substructure and dynamical state characterization of this cluster, and a comparison of mass estimates derived from (i) the velocity dispersion (Mvir), (ii) the caustic mass computation (Mcaustic), and (iii) mass proxies from X-ray observations and the Sunyaev-Zel'dovich (SZ) effect. Methods: We carried out new optical spectroscopic observations of the galaxies in this cluster field with VIMOS, obtaining a sample of 60 member galaxies for S1101. We revised the cluster redshift and velocity dispersion measurements based on this sample and also applied the Dressler-Shectman substructure test. Results: The completeness of cluster members within r200 was significantly improved for this cluster. Tests for dynamical substructure do not show evidence of major disturbances or merging activities in S1101. We find good agreement between the dynamical cluster mass measurements and X-ray mass estimates, which confirms the relaxed state of the cluster displayed in the 2D substructure test. The SZ mass proxy is slightly higher than the other estimates. The updated measurement of σ erased the deviation of S1101 in the L-σ relation. We also noticed a background structure in the cluster field of S1101. This structure is a galaxy group that is very close to the cluster S1101 in projection but at almost twice its redshift
A bright z = 5.2 lensed submillimeter galaxy in the field of Abell 773. HLSJ091828.6+514223
NASA Astrophysics Data System (ADS)
Combes, F.; Rex, M.; Rawle, T. D.; Egami, E.; Boone, F.; Smail, I.; Richard, J.; Ivison, R. J.; Gurwell, M.; Casey, C. M.; Omont, A.; Berciano Alba, A.; Dessauges-Zavadsky, M.; Edge, A. C.; Fazio, G. G.; Kneib, J.-P.; Okabe, N.; Pelló, R.; Pérez-González, P. G.; Schaerer, D.; Smith, G. P.; Swinbank, A. M.; van der Werf, P.
2012-02-01
During our Herschel Lensing Survey (HLS) of massive galaxy clusters, we have discovered an exceptionally bright source behind the z = 0.22 cluster Abell 773, which appears to be a strongly lensed submillimeter galaxy (SMG) at z = 5.2429. This source is unusual compared to most other lensed sources discovered by Herschel so far, because of its higher submm flux (~200 mJy at 500 μm) and its high redshift. The dominant lens is a foreground z = 0.63 galaxy, not the cluster itself. The source has a far-infrared (FIR) luminosity of LFIR = 1.1 × 1014/μ L⊙, where μ is the magnification factor, likely ~11. We report here the redshift identification through CO lines with the IRAM-30 m, and the analysis of the gas excitation, based on CO(7-6), CO(6-5), CO(5-4) detected at IRAM and the CO(2-1) at the EVLA. All lines decompose into a wide and strong red component, and a narrower and weaker blue component, 540 km s-1 apart. Assuming the ultraluminous galaxy (ULIRG) CO-to-H2 conversion ratio, the H2 mass is 5.8 × 1011/μ M⊙, of which one third is in a cool component. From the C I(3P2-3P1) line we derive a C I/H2 number abundance of 6 × 10-5 similar to that in other ULIRGs. The H2Op(2,0,2-1,1,1) line is strong only in the red velocity component, with an intensity ratio I(H2O)/I(CO) ~ 0.5, suggesting a strong local FIR radiation field, possibly from an active nucleus (AGN) component. We detect the [NII]205 μm line for the first time at high-z. It shows comparable blue and red components, with a strikingly broad blue one, suggesting strong ionized gas flows.
Goal Directed Model Inversion: A Study of Dynamic Behavior
NASA Technical Reports Server (NTRS)
Colombano, Silvano P.; Compton, Michael; Raghavan, Bharathi; Lum, Henry, Jr. (Technical Monitor)
1994-01-01
Goal Directed Model Inversion (GDMI) is an algorithm designed to generalize supervised learning to the case where target outputs are not available to the learning system. The output of the learning system becomes the input to some external device or transformation, and only the output of this device or transformation can be compared to a desired target. The fundamental driving mechanism of GDMI is to learn from success. Given that a wrong outcome is achieved, one notes that the action that produced that outcome 0 "would have been right if the outcome had been the desired one." The algorithm then proceeds as follows: (1) store the action that produced the wrong outcome as a "target" (2) redefine the wrong outcome as a desired goal (3) submit the new desired goal to the system (4) compare the new action with the target action and modify the system by using a suitable algorithm for credit assignment (Back propagation in our example) (5) resubmit the original goal. Prior publications by our group in this area focused on demonstrating empirical results based on the inverse kinematic problem for a simulated robotic arm. In this paper we apply the inversion process to much simpler analytic functions in order to elucidate the dynamic behavior of the system and to determine the sensitivity of the learning process to various parameters. This understanding will be necessary for the acceptance of GDMI as a practical tool.
NASA Astrophysics Data System (ADS)
Mazanec, M.; Kletetschka, G.
2014-12-01
The largest fragment of Chelyabinsk meteorite fell into the Russian lake Chebarkul on February 15, 2013. We used magnetic scanner constructed by Youngwood Science and Engineering (YSE, see Kletetschka et al 2013) to obtain micromagnetic maps of one of the Chelyabinsk's meteorite fragment. Our instrument has a Hall effect magnetic sensor and maps vertical component of the magnetic field approximately 0.3 mm above the planar surface of meteorite sample. Advantage of this instrument is a constant background field due to static position of the sensor. We applied fast Fourier transform inversion technique developed by Lima et al (2013). This technique is tailored for scanning magnetic microscopy (SMM), but may be also modified for aeromagnetic or satellite survey. It retrieves planar unidirectional magnetization distribution from micromagnetic field map. With this technique we achieved verifiable information about the source of the magnetic anomalies in our meteorite sample. Specific areas of detected magnetization were used for compositional analyses by scanning electron microscopy (SEM). This way we obtain the ground truth for the source of magnetic anomalies of our meteorite thin section. Measurement of chemical composition of magnetic grains can be directly linked to the amount of magnetization for the specific magnetic mineralogy. The inversion technique was extended for interpretation of real magnetic anomalies on Mars. Lima, E. A., B. P. Weiss, L. Baratchart,D. P.Hardin, and E. B. Saff (2013), Fast inversion ofmagnetic field maps of unidirectional planar geological magnetization, J. Geophys. Res. Solid Earth, 118, 2723-2752, doi:10.1002/jgrb.50229.Kletetschka, G., Schnabl, P., Sifnerova, K., Tasaryova, Z., Manda, S., and Pruner, P., 2013, Magnetic scanning and interpretation of paleomagnetic data from Prague Synform's volcanics: Studia Geophysica Et Geodaetica, v. 57, no. 1, p. 103-117.
Bainitelike transformations in some oxide ceramics
NASA Astrophysics Data System (ADS)
Nakanishi, N.; Shigematsu, T.; Furukawa, T.; Machida, N.
1994-12-01
The authors show two examples of “bainitelike” transformations in some oxide ceramics. A bainitelike transformation means that a shear (martensitic) mechanism is controlled by, or together with, ionic diffusion in the lattice as well as the case of lower bainite in steel. The first example is a tetragonal-to-monoclinic transformation in ZrO2-Y2O3 ceramics, where the bainitelike transformation must be characterized by (1) the increase in concentration of oxygen vacancies caused by the substitution of Zr4+ ions by Y3+ ions, (2) a fairly high mobility of oxygen ions through their vacancies, and (3) the formation of clusters composed of oxygen vacancies and oxygen ions. The second case is an inverse spinel to corundum structural change observed in γ Fe2O3 to α Fe2O3, in which the bainitelike transformation may be explained by cooperative movements of oxygen and ferric ions, which are sandwiched between oxygen layers.
NASA Technical Reports Server (NTRS)
Backus, George
1987-01-01
Let R be the real numbers, R(n) the linear space of all real n-tuples, and R(infinity) the linear space of all infinite real sequences x = (x sub 1, x sub 2,...). Let P sub n :R(infinity) approaches R(n) be the projection operator with P sub n (x) = (x sub 1,...,x sub n). Let p(infinity) be a probability measure on the smallest sigma-ring of subsets of R(infinity) which includes all of the cylinder sets P sub n(-1) (B sub n), where B sub n is an arbitrary Borel subset of R(n). Let p sub n be the marginal distribution of p(infinity) on R(n), so p sub n(B sub n) = p(infinity)(P sub n to the -1(B sub n)) for each B sub n. A measure on R(n) is isotropic if it is invariant under all orthogonal transformations of R(n). All members of the set of all isotropic probability distributions on R(n) are described. The result calls into question both stochastic inversion and Bayesian inference, as currently used in many geophysical inverse problems.
NASA Astrophysics Data System (ADS)
Usher, P. D.
1997-12-01
William Shakespeare's Hamlet has much evidence to suggest that the Bard was aware of the cosmological models of his time, specifically the geocentric bounded Ptolemaic and Tychonic models, and the infinite Diggesian. Moreover, Shakespeare describes how the Ptolemaic model is to be transformed to the Diggesian. Hamlet's "transformation" is the reason that Claudius, who personifies the Ptolemaic model, summons Rosencrantz and Guildenstern, who personify the Tychonic. Pantometria, written by Leonard Digges and his son Thomas in 1571, contains the first technical use of the word "transformation." At age thirty, Thomas Digges went on to propose his Perfit Description, as alluded to in Act Five where Hamlet's age is given as thirty. In Act Five as well, the words "bore" and "arms" refer to Thomas' vocation as muster-master and his scientific interest in ballistics. England's leading astronomer was also the father of the poet whose encomium introduced the First Folio of 1623. His oldest child Dudley became a member of the Virginia Company and facilitated the writing of The Tempest. Taken as a whole, such manifold connections to Thomas Digges support Hotson's contention that Shakespeare knew the Digges family. Rosencrantz and Guildenstern in Hamlet bear Danish names because they personify the Danish model, while the king's name is latinized like that of Claudius Ptolemaeus. The reason Shakespeare anglicized "Amleth" to "Hamlet" was because he saw a parallel between Book Three of Saxo Grammaticus and the eventual triumph of the Diggesian model. But Shakespeare eschewed Book Four, creating this particular ending from an infinity of other possibilities because it "suited his purpose," viz. to celebrate the concept of a boundless universe of stars like the Sun.
NASA Technical Reports Server (NTRS)
McLyman, Colonel Wm. T.
1996-01-01
None given. From first Par: Many spacecraft (S/C) and surface rovers require the transfer of signals and power across rotating interfaces. Science instruments, antennas and solar arrays are elements needing rotary power transfer for certain (S/C) configurations. Delivery of signal and power has mainly been done by using the simplest means, the slip ring approach. This approach, although simple, leaves debris generating noise over a period of time...The rotary transformer is a good alternative to slip rings for signal and power transfer.
Wolfgang, F.; Nicol, J.
1962-11-01
Transformer apparatus is designed for measuring the amount of a paramagnetic substance dissolved or suspended in a diamagnetic liquid. The apparatus consists of a cluster of tubes, some of which are closed and have sealed within the diamagnetic substance without any of the paramagnetic material. The remaining tubes are open to flow of the mix- ture. Primary and secondary conductors are wrapped around the tubes in such a way as to cancel noise components and also to produce a differential signal on the secondaries based upon variations of the content of the paramagnetic material. (AEC)
Momentum resolution in inverse photoemission
Zumbülte, A.; Schmidt, A. B.; Donath, M.
2015-01-15
We present a method to determine the electron beam divergence, and thus the momentum resolution, of an inverse-photoemission setup directly from a series of spectra measured on Cu(111). Simulating these spectra with different beam divergences shows a distinct influence of the divergence on the appearance of the Shockley surface state. Upon crossing the Fermi level, its rise in intensity can be directly linked with the beam divergence. A comparison of measurement and simulation enables us to quantify the momentum resolution independent of surface quality, energy resolution, and experimental geometry. With spin resolution, a single spectrum taken around the Fermi momentum of a spin-split surface state, e.g., on Au(111), is sufficient to derive the momentum resolution of an inverse-photoemission setup.
NASA Technical Reports Server (NTRS)
Hedland, D. A.; Degonia, P. K.
1974-01-01
The RAE-1 spacecraft inversion performed October 31, 1972 is described based upon the in-orbit dynamical data in conjunction with results obtained from previously developed computer simulation models. The computer simulations used are predictive of the satellite dynamics, including boom flexing, and are applicable during boom deployment and retraction, inter-phase coast periods, and post-deployment operations. Attitude data, as well as boom tip data, were analyzed in order to obtain a detailed description of the dynamical behavior of the spacecraft during and after the inversion. Runs were made using the computer model and the results were analyzed and compared with the real time data. Close agreement between the actual recorded spacecraft attitude and the computer simulation results was obtained.
Broadband synthetic aperture geoacoustic inversion.
Tan, Bien Aik; Gerstoft, Peter; Yardim, Caglar; Hodgkiss, William S
2013-07-01
A typical geoacoustic inversion procedure involves powerful source transmissions received on a large-aperture receiver array. A more practical approach is to use a single moving source and/or receiver in a low signal to noise ratio (SNR) setting. This paper uses single-receiver, broadband, frequency coherent matched-field inversion and exploits coherently repeated transmissions to improve estimation of the geoacoustic parameters. The long observation time creates a synthetic aperture due to relative source-receiver motion. This approach is illustrated by studying the transmission of multiple linear frequency modulated (LFM) pulses which results in a multi-tonal comb spectrum that is Doppler sensitive. To correlate well with the measured field across a receiver trajectory and to incorporate transmission from a source trajectory, waveguide Doppler and normal mode theory is applied. The method is demonstrated with low SNR, 100-900 Hz LFM pulse data from the Shallow Water 2006 experiment.
Inverse statistics and information content
NASA Astrophysics Data System (ADS)
Ebadi, H.; Bolgorian, Meysam; Jafari, G. R.
2010-12-01
Inverse statistics analysis studies the distribution of investment horizons to achieve a predefined level of return. This distribution provides a maximum investment horizon which determines the most likely horizon for gaining a specific return. There exists a significant difference between inverse statistics of financial market data and a fractional Brownian motion (fBm) as an uncorrelated time-series, which is a suitable criteria to measure information content in financial data. In this paper we perform this analysis for the DJIA and S&P500 as two developed markets and Tehran price index (TEPIX) as an emerging market. We also compare these probability distributions with fBm probability, to detect when the behavior of the stocks are the same as fBm.
NASA Astrophysics Data System (ADS)
Gershanov, V. Yu.; Garmashov, S. I.
2015-01-01
We prove the existence of an effect inverse to the Gibbs-Thomson effect for mass transfer in systems consisting of a solid phase and the solution of the solid phase material in a certain solvent. The effect involves a change in the shape of the interface due to a variation of the equilibrium concentrations under it, which is induced by external conditions, and exists in the presence of a negative feedback for mass transfer associated with capillary effects.
Viscoacoustic anisotropic full waveform inversion
NASA Astrophysics Data System (ADS)
Qu, Yingming; Li, Zhenchun; Huang, Jianping; Li, Jinli
2017-01-01
A viscoacoustic vertical transverse isotropic (VTI) quasi-differential wave equation, which takes account for both the viscosity and anisotropy of media, is proposed for wavefield simulation in this study. The finite difference method is used to solve the equations, for which the attenuation terms are solved in the wavenumber domain, and all remaining terms in the time-space domain. To stabilize the adjoint wavefield, robust regularization operators are applied to the wave equation to eliminate the high-frequency component of the numerical noise produced during the backward propagation of the viscoacoustic wavefield. Based on these strategies, we derive the corresponding gradient formula and implement a viscoacoustic VTI full waveform inversion (FWI). Numerical tests verify that our proposed viscoacoustic VTI FWI can produce accurate and stable inversion results for viscoacoustic VTI data sets. In addition, we test our method's sensitivity to velocity, Q, and anisotropic parameters. Our results show that the sensitivity to velocity is much higher than that to Q and anisotropic parameters. As such, our proposed method can produce acceptable inversion results as long as the Q and anisotropic parameters are within predefined thresholds.
An Involution of Lorentz Transformations
NASA Astrophysics Data System (ADS)
Lubkin, Elihu
2000-04-01
Quadrilateral(axis, joystick) creates a proper Lorentz transformation dual to Quadrilateral(joystick, axis). The joystick is a line through axis and coaxis, selecting on them the intrinsic velocity and the intrinsic angle, respectively.(E. Lubkin, ``Reversed 3velocities'', APR99.) (Thing and co-thing are skew perpendicular with inverse nearest points.) This involution may be interesting: axis, coaxis, joystick, and cojoystick indeed do close in a quadrilateral. And this came up in multiplying coaxial Lorentz transformations A and B to get C. When result C is surprisingly not coaxial with A and B---this happens when A, B are improper of opposite types---the result is an (intrinsic) aboutface whose new axis is of old joystick form.
Optimal control theory for unitary transformations
Palao, Jose P.; Kosloff, Ronnie
2003-12-01
The dynamics of a quantum system driven by an external field is well described by a unitary transformation generated by a time-dependent Hamiltonian. The inverse problem of finding the field that generates a specific unitary transformation is the subject of study. The unitary transformation which can represent an algorithm in a quantum computation is imposed on a subset of quantum states embedded in a larger Hilbert space. Optimal control theory is used to solve the inversion problem irrespective of the initial input state. A unified formalism based on the Krotov method is developed leading to a different scheme. The schemes are compared for the inversion of a two-qubit Fourier transform using as registers the vibrational levels of the X {sup 1}{sigma}{sub g}{sup +} electronic state of Na{sub 2}. Raman-like transitions through the A {sup 1}{sigma}{sub u}{sup +} electronic state induce the transitions. Light fields are found that are able to implement the Fourier transform within a picosecond time scale. Such fields can be obtained by pulse-shaping techniques of a femtosecond pulse. Of the schemes studied, the square modulus scheme converges fastest. A study of the implementation of the Q qubit Fourier transform in the Na{sub 2} molecule was carried out for up to five qubits. The classical computation effort required to obtain the algorithm with a given fidelity is estimated to scale exponentially with the number of levels. The observed moderate scaling of the pulse intensity with the number of qubits in the transformation is rationalized.
Sequential Geoacoustic Filtering and Geoacoustic Inversion
2014-09-30
1 DISTRIBUTION STATEMENT A. Approved for public release; distribution is unlimited. Sequential Geoacoustic Filtering and Geoacoustic Inversion ...geoacoustic inversion methods, their use in the analysis of shallow water experimental data, and evaluation of geoacoustic model and parameter...uncertainties including the mapping of these uncertainties through to system performance uncertainties. OBJECTIVES Analysis of geoacoustic inversion
On the Magic Square and Inverse
ERIC Educational Resources Information Center
Elzaidi, S. M.
2005-01-01
In this note, we give a method for finding the inverse of a three by three magic square matrix without using the usual methods for finding the inverse of a matrix. Also we give a method for finding the inverse of a three by three magic square matrix whose entries are also matrices. By using these ideas, we can construct large matrices whose…
Scattering and inverse scattering for a left-definite Sturm-Liouville problem
NASA Astrophysics Data System (ADS)
Bennewitz, C.; Brown, B. M.; Weikard, R.
This work develops a scattering and an inverse scattering theory for the Sturm-Liouville equation -u″+qu=λwu where w may change sign but q⩾0. Thus the left-hand side of the equation gives rise to a positive quadratic form and one is led to a left-definite spectral problem. The crucial ingredient of the approach is a generalized transform built on the Jost solutions of the problem and hence termed the Jost transform and the associated Paley-Wiener theorem linking growth properties of transforms with support properties of functions. One motivation for this investigation comes from the Camassa-Holm equation for which the solution of the Cauchy problem can be achieved by the inverse scattering transform for -u″+1/4u=λwu.
Inverse problem for in vivo NMR spatial localization
Hasenfeld, A.C.
1985-11-01
The basic physical problem of NMR spatial localization is considered. To study diseased sites, one must solve the problem of adequately localizing the NMR signal. We formulate this as an inverse problem. As the NMR Bloch equations determine the motion of nuclear spins in applied magnetic fields, a theoretical study is undertaken to answer the question of how to design magnetic field configurations to achieve these localized excited spin populations. Because of physical constraints in the production of the relevant radiofrequency fields, the problem factors into a temporal one and a spatial one. We formulate the temporal problem as a nonlinear transformation, called the Bloch Transform, from the rf input to the magnetization response. In trying to invert this transformation, both linear (for the Fourier Transform) and nonlinear (for the Bloch Transform) modes of radiofrequency excitation are constructed. The spatial problem is essentially a statics problem for the Maxwell equations of electromagnetism, as the wavelengths of the radiation considered are on the order of ten meters, and so propagation effects are negligible. In the general case, analytic solutions are unavailable, and so the methods of computer simulation are used to map the rf field spatial profiles. Numerical experiments are also performed to verify the theoretical analysis, and experimental confirmation of the theory is carried out on the 0.5 Tesla IBM/Oxford Imaging Spectrometer at the LBL NMR Medical Imaging Facility. While no explicit inverse is constructed to ''solve'' this problem, the combined theoretical/numerical analysis is validated experimentally, justifying the approximations made. 56 refs., 31 figs.
Matrix methods for reflective inverse diffusion
NASA Astrophysics Data System (ADS)
Burgi, Kenneth W.; Marciniak, Michael A.; Nauyoks, Stephen E.; Oxley, Mark E.
2016-09-01
Reflective inverse diffusion is a method of refocusing light scattered by a rough surface. An SLM is used to shape the wavefront of a HeNe laser at 632.8-nm wavelength to produce a converging phase front after reflection. Iterative methods previously demonstrated intensity enhancements of the focused spot over 100 times greater than the surrounding background speckle. This proof-of-concept method was very time consuming and the algorithm started over each time the desired location of the focus spot in the observation plane was moved. Transmission matrices have been developed to control light scattered by transmission through a turbid media. Time varying phase maps are applied to an SLM and used to interrogate the phase scattering properties of the material. For each phase map, the resultant speckle intensity pattern is recorded less than 1 mm from the material surface and represents an observation plane of less than 0.02 mm2. Fourier transforms are used to extract the phase scattering properties of the material from the intensity measurements. We investigate the effectiveness this method for constructing the reflection matrix (RM) of a diffuse reflecting medium where the propagation distances and observation plane are almost 1,000 times greater than the previous work based on transmissive scatter. The RM performance is based on its ability to refocus reflectively scattered light to a single focused spot or multiple foci in the observation plane. Diffraction-based simulations are used to corroborate experimental results.
Fourier analysis and signal processing by use of the Moebius inversion formula
NASA Technical Reports Server (NTRS)
Reed, Irving S.; Yu, Xiaoli; Shih, Ming-Tang; Tufts, Donald W.; Truong, T. K.
1990-01-01
A novel Fourier technique for digital signal processing is developed. This approach to Fourier analysis is based on the number-theoretic method of the Moebius inversion of series. The Fourier transform method developed is shown also to yield the convolution of two signals. A computer simulation shows that this method for finding Fourier coefficients is quite suitable for digital signal processing. It competes with the classical FFT (fast Fourier transform) approach in terms of accuracy, complexity, and speed.
Dynamically consistent Jacobian inverse for mobile manipulators
NASA Astrophysics Data System (ADS)
Ratajczak, Joanna; Tchoń, Krzysztof
2016-06-01
By analogy to the definition of the dynamically consistent Jacobian inverse for robotic manipulators, we have designed a dynamically consistent Jacobian inverse for mobile manipulators built of a non-holonomic mobile platform and a holonomic on-board manipulator. The endogenous configuration space approach has been exploited as a source of conceptual guidelines. The new inverse guarantees a decoupling of the motion in the operational space from the forces exerted in the endogenous configuration space and annihilated by the dual Jacobian inverse. A performance study of the new Jacobian inverse as a tool for motion planning is presented.
NASA Astrophysics Data System (ADS)
Smith, Russell J.; Lucey, John R.; Edge, Alastair C.
2017-01-01
Abell 1201 is a massive galaxy cluster at z=0.169 with a brightest cluster galaxy (BCG) that acts as a gravitational lens to a background source at z=0.451. The lensing configuration is unusual, with a single bright arc formed at small radius (˜2 arcsec), where stars and dark matter are both expected to contribute substantially to the total lensing mass. Here, we present deep spectroscopic observations of the Abell 1201 BCG with MUSE, which reveal emission lines from a faint counter-image, opposite to the main arc, at a radius of 0.6 arcsec. We explore models in which the lensing mass is described by a combination of stellar mass and a standard dark-matter halo. The counter-image is not predicted in such models, unless the dark-matter component is negligible, which would imply an extremely heavy stellar initial mass function (IMF) in this galaxy. We consider two modifications to the model which can produce the observed configuration without resorting to extreme IMFs. Imposing a radial gradient in the stellar mass-to-light ratio, Υ, can generate a counter-image close to the observed position if Υ increases by ≳60 per cent within the inner ˜1 arcsec (e.g. variation from a Milky-Way-like to a Salpeter-like IMF). Alternatively, the counter-image can be produced by introducing a central super-massive black hole. The required mass is MBH = (1.3±0.6)× 1010 M⊙, which is comparable to the largest black holes known to date, several of which are also hosted by BCGs. We comment on future observations which promise to distinguish between these alternatives.
NASA Astrophysics Data System (ADS)
Schirmer, M.; Carrasco, E. R.; Pessev, P.; Garrel, V.; Winge, C.; Neichel, B.; Vidal, F.
2015-04-01
We have observed two of the six Frontier Fields galaxy clusters, MACS J0416.1-2403 and Abell 2744, using the Gemini Multi-Conjugate Adaptive Optics System (GeMS) and the Gemini South Adaptive Optics Imager (GSAOI). With 0.″ 08-0.″ 10 FWHM our data are nearly diffraction-limited over a 100\\prime\\prime × 100\\prime\\prime wide area. GeMS/GSAOI complements the Hubble Space Telescope (HST) redwards of 1.6 μm with twice the angular resolution. We reach a 5σ depth of {{K}s}˜ 25.6 mag (AB) for compact sources. In this paper, we describe the observations, data processing, and initial public data release. We provide fully calibrated, co-added images matching the native GSAOI pixel scale as well as the larger plate scales of the HST release, adding to the legacy value of the Frontier Fields. Our work demonstrates that even for fields at high galactic latitude where natural guide stars are rare, current multi-conjugated adaptive optics technology at 8 m telescopes has opened a new window on the distant universe. Observations of a third Frontier Field, Abell 370, are planned. Based on observations obtained at the Gemini Observatory, which is operated by the Association of Universities for Research in Astronomy, Inc., under a cooperative agreement with the NSF on behalf of the Gemini partnership: the National Science Foundation (United States), the Science and Technology Facilities Council (United Kingdom), the National Research Council (Canada), CONICYT (Chile), the Australian Research Council (Australia), Ministério da Ciência, Tecnologia e Inovação (Brazil) and Ministerio de Ciencia, Tecnología e Innovación Productiva (Argentina). Based on observations made with ESO Telescopes at the La Silla and Paranal Observatories, Chile.
Tiling spaces are inverse limits
NASA Astrophysics Data System (ADS)
Sadun, Lorenzo
2003-11-01
Let M be an arbitrary Riemannian homogeneous space, and let Ω be a space of tilings of M, with finite local complexity (relative to some symmetry group Γ) and closed in the natural topology. Then Ω is the inverse limit of a sequence of compact finite-dimensional branched manifolds. The branched manifolds are (finite) unions of cells, constructed from the tiles themselves and the group Γ. This result extends previous results of Anderson and Putnam, of Ormes, Radin, and Sadun, of Bellissard, Benedetti, and Gambaudo, and of Gähler. In particular, the construction in this paper is a natural generalization of Gähler's.
The Inverse of Banded Matrices
2013-01-01
of Br,n. For these sequences to be well-defined, we assume that none of the denominators kis are zero (which is equivalent to the below-defined U...numbers of summed or subtracted terms in computing the inverse of a term of an upper (lower) triangular matrix are the generalized order-k Fibonacci ... Fibonacci numbers are the usual Fibonacci numbers, that is, f 2m = Fm (mth Fibonacci number). When also k = 3, c1 = c2 = c3 = 1, then the generalized order-3
A survey of the physical optics inverse scattering identity
NASA Astrophysics Data System (ADS)
Bojarski, N. N.
1982-09-01
An inverse scattering identity relating the characteristic function of a scatterer to the three-dimensional spatial Fourier transform of the augmented far field scattering amplitude is derived by applying the physical optics approximation to the acoustic and electromagnetic direct scattering integral representation. Because this identity requires full scattering data for all frequencies and aspect angles, an integral equation is developed for incomplete scattering data which solves for the unknown characteristic function of the scatterer in terms of the known incomplete scattering data. A regularized analytic closed form solution to this integral equation is obtained, and synthesized numerico-experimental results verifying the solution are presented.
Simultaneous Gaussian and exponential inversion for improved analysis of shales by NMR relaxometry
Washburn, Kathryn E.; Anderssen, Endre; Vogt, Sarah J.; Seymour, Joseph D.; Birdwell, Justin E.; Kirkland, Catherine M.; Codd, Sarah L.
2014-01-01
Nuclear magnetic resonance (NMR) relaxometry is commonly used to provide lithology-independent porosity and pore-size estimates for petroleum resource evaluation based on fluid-phase signals. However in shales, substantial hydrogen content is associated with solid and fluid signals and both may be detected. Depending on the motional regime, the signal from the solids may be best described using either exponential or Gaussian decay functions. When the inverse Laplace transform, the standard method for analysis of NMR relaxometry results, is applied to data containing Gaussian decays, this can lead to physically unrealistic responses such as signal or porosity overcall and relaxation times that are too short to be determined using the applied instrument settings. We apply a new simultaneous Gaussian-Exponential (SGE) inversion method to simulated data and measured results obtained on a variety of oil shale samples. The SGE inversion produces more physically realistic results than the inverse Laplace transform and displays more consistent relaxation behavior at high magnetic field strengths. Residuals for the SGE inversion are consistently lower than for the inverse Laplace method and signal overcall at short T2 times is mitigated. Beyond geological samples, the method can also be applied in other fields where the sample relaxation consists of both Gaussian and exponential decays, for example in material, medical and food sciences.
Simultaneous Gaussian and exponential inversion for improved analysis of shales by NMR relaxometry.
Washburn, Kathryn E; Anderssen, Endre; Vogt, Sarah J; Seymour, Joseph D; Birdwell, Justin E; Kirkland, Catherine M; Codd, Sarah L
2015-01-01
Nuclear magnetic resonance (NMR) relaxometry is commonly used to provide lithology-independent porosity and pore-size estimates for petroleum resource evaluation based on fluid-phase signals. However in shales, substantial hydrogen content is associated with solid and fluid signals and both may be detected. Depending on the motional regime, the signal from the solids may be best described using either exponential or Gaussian decay functions. When the inverse Laplace transform, the standard method for analysis of NMR relaxometry results, is applied to data containing Gaussian decays, this can lead to physically unrealistic responses such as signal or porosity overcall and relaxation times that are too short to be determined using the applied instrument settings. We apply a new simultaneous Gaussian-Exponential (SGE) inversion method to simulated data and measured results obtained on a variety of oil shale samples. The SGE inversion produces more physically realistic results than the inverse Laplace transform and displays more consistent relaxation behavior at high magnetic field strengths. Residuals for the SGE inversion are consistently lower than for the inverse Laplace method and signal overcall at short T2 times is mitigated. Beyond geological samples, the method can also be applied in other fields where the sample relaxation consists of both Gaussian and exponential decays, for example in material, medical and food sciences.
Dynamic data integration and stochastic inversion of a confined aquifer
NASA Astrophysics Data System (ADS)
Wang, D.; Zhang, Y.; Irsa, J.; Huang, H.; Wang, L.
2013-12-01
Much work has been done in developing and applying inverse methods to aquifer modeling. The scope of this paper is to investigate the applicability of a new direct method for large inversion problems and to incorporate uncertainty measures in the inversion outcomes (Wang et al., 2013). The problem considered is a two-dimensional inverse model (50×50 grid) of steady-state flow for a heterogeneous ground truth model (500×500 grid) with two hydrofacies. From the ground truth model, decreasing number of wells (12, 6, 3) were sampled for facies types, based on which experimental indicator histograms and directional variograms were computed. These parameters and models were used by Sequential Indicator Simulation to generate 100 realizations of hydrofacies patterns in a 100×100 (geostatistical) grid, which were conditioned to the facies measurements at wells. These realizations were smoothed with Simulated Annealing, coarsened to the 50×50 inverse grid, before they were conditioned with the direct method to the dynamic data, i.e., observed heads and groundwater fluxes at the same sampled wells. A set of realizations of estimated hydraulic conductivities (Ks), flow fields, and boundary conditions were created, which centered on the 'true' solutions from solving the ground truth model. Both hydrofacies conductivities were computed with an estimation accuracy of ×10% (12 wells), ×20% (6 wells), ×35% (3 wells) of the true values. For boundary condition estimation, the accuracy was within × 15% (12 wells), 30% (6 wells), and 50% (3 wells) of the true values. The inversion system of equations was solved with LSQR (Paige et al, 1982), for which coordinate transform and matrix scaling preprocessor were used to improve the condition number (CN) of the coefficient matrix. However, when the inverse grid was refined to 100×100, Gaussian Noise Perturbation was used to limit the growth of the CN before the matrix solve. To scale the inverse problem up (i.e., without smoothing
Rotation and inversion in nitrosamines
NASA Astrophysics Data System (ADS)
Kirste, Karl; Rademacher, Paul
1981-04-01
Geometry optimizations of the ground states as well as of the transition states for internal rotation and inversion have been performed by the semiempirical MNDO method for dimethyl nitrosamine (1), perfluordimethyl nitrosamine (2), N-nitroso aziridine (3), and N-nitroso azetidine (4). It was found that the potential barrier to internal rotation about the N-N bond is always of lower energy than that to inversion on the nitroso nitrogen. While the ground states tend to adopt structures which enable mesomerism, the lowest transition state is characterized by a pyramidal sp3-hybridized amino nitrogen. In accordance with experimental results the low barriers to rotation of 2 (7.96 kcal mol -1), 3 (3.38 kcal mol -1) and 4 (9.97 kcal mol -1) in comparison with 1 (12.54 kcal mol -1) indicate that in donor-acceptor molecules the transfer of charge can be limited by electronic and stereochemical effects. In particular, the equivalence of the α-methylene hydrogens which was observed in the NMR-spectrum of 3 is due to unhindered rotation and ring inveirsion.
Numerical solution of 2D-vector tomography problem using the method of approximate inverse
NASA Astrophysics Data System (ADS)
Svetov, Ivan; Maltseva, Svetlana; Polyakova, Anna
2016-08-01
We propose a numerical solution of reconstruction problem of a two-dimensional vector field in a unit disk from the known values of the longitudinal and transverse ray transforms. The algorithm is based on the method of approximate inverse. Numerical simulations confirm that the proposed method yields good results of reconstruction of vector fields.
Transformer regulated self-stabilizing chopper
NASA Technical Reports Server (NTRS)
Raposa, F. L. (Inventor)
1969-01-01
A self-stabilizing voltage regulator is described. Direct current voltage regulation employing a series transistor rendered conductive during various portions of a cycle is controlled by saturation of an autotransformer. The constant volt-second capacity of the transformer provides conduction time inverse to the input voltage whereby average output voltage is maintained constant. Conduction commenced in response to short gate signals, and resistor feedback for degenerative turn-off of the transistor was after transformer saturation. Standard output filters are also included.
Subband/transform functions for image processing
NASA Technical Reports Server (NTRS)
Glover, Daniel
1993-01-01
Functions for image data processing written for use with the MATLAB(TM) software package are presented. These functions provide the capability to transform image data with block transformations (such as the Walsh Hadamard) and to produce spatial frequency subbands of the transformed data. Block transforms are equivalent to simple subband systems. The transform coefficients are reordered using a simple permutation to give subbands. The low frequency subband is a low resolution version of the original image, while the higher frequency subbands contain edge information. The transform functions can be cascaded to provide further decomposition into more subbands. If the cascade is applied to all four of the first stage subbands (in the case of a four band decomposition), then a uniform structure of sixteen bands is obtained. If the cascade is applied only to the low frequency subband, an octave structure of seven bands results. Functions for the inverse transforms are also given. These functions can be used for image data compression systems. The transforms do not in themselves produce data compression, but prepare the data for quantization and compression. Sample quantization functions for subbands are also given. A typical compression approach is to subband the image data, quantize it, then use statistical coding (e.g., run-length coding followed by Huffman coding) for compression. Contour plots of image data and subbanded data are shown.
Constrained and joint inversion on unstructured meshes
NASA Astrophysics Data System (ADS)
Doetsch, J.; Jordi, C.; Rieckh, V.; Guenther, T.; Schmelzbach, C.
2015-12-01
Unstructured meshes allow for inclusion of arbitrary surface topography, complex acquisition geometry and undulating geological interfaces in the inversion of geophysical data. This flexibility opens new opportunities for coupling different geophysical and hydrological data sets in constrained and joint inversions. For example, incorporating geological interfaces that have been derived from high-resolution geophysical data (e.g., ground penetrating radar) can add geological constraints to inversions of electrical resistivity data. These constraints can be critical for a hydrogeological interpretation of the inversion results. For time-lapse inversions of geophysical data, constraints can be derived from hydrological point measurements in boreholes, but it is difficult to include these hard constraints in the inversion of electrical resistivity monitoring data. Especially mesh density and the regularization footprint around the hydrological point measurements are important for an improved inversion compared to the unconstrained case. With the help of synthetic and field examples, we analyze how regularization and coupling operators should be chosen for time-lapse inversions constrained by point measurements and for joint inversions of geophysical data in order to take full advantage of the flexibility of unstructured meshes. For the case of constraining to point measurements, it is important to choose a regularization operator that extends beyond the neighboring cells and the uncertainty in the point measurements needs to be accounted for. For joint inversion, the choice of the regularization depends on the expected subsurface heterogeneity and the cell size of the parameter mesh.
Kanter, Rosabeth Moss
2008-01-01
Large corporations have long been seen as lumbering, inflexible, bureaucratic--and clueless about global developments. But recently some multinationals seem to be transforming themselves: They're engaging employees, moving quickly, and introducing innovations that show true connection with the world. Harvard Business School's Kanter ventured with a research team inside a dozen global giants--including IBM, Procter & Gamble, Omron, CEMEX, Cisco, and Banco Real--to discover what has been driving the change. After conducting more than 350 interviews on five continents, she and her colleagues came away with a strong sense that we are witnessing the dawn of a new model of corporate power: The coordination of actions and decisions on the front lines now appears to stem from widely shared values and a sturdy platform of common processes and technology, not from top-down decrees. In particular, the values that engage the passions of far-flung workforces stress openness, inclusion, and making the world a better place. Through this shift in what might be called their guidance systems, the companies have become as creative and nimble as much smaller ones, even while taking on social and environmental challenges of a scale that only large enterprises could attempt. IBM, for instance, has created a nonprofit partnership, World Community Grid, through which any organization or individual can donate unused computing power to research projects and see what is being done with the donation in real time. IBM has gained an inspiring showcase for its new technology, helped business partners connect with the company in a positive way, and offered individuals all over the globe the chance to contribute to something big.
Magnetic interface forward and inversion method based on Padé approximation
NASA Astrophysics Data System (ADS)
Zhang, Chong; Huang, Da-Nian; Zhang, Kai; Pu, Yi-Tao; Yu, Ping
2016-12-01
The magnetic interface forward and inversion method is realized using the Taylor series expansion to linearize the Fourier transform of the exponential function. With a large expansion step and unbounded neighborhood, the Taylor series is not convergent, and therefore, this paper presents the magnetic interface forward and inversion method based on Padé approximation instead of the Taylor series expansion. Compared with the Taylor series, Padé's expansion's convergence is more stable and its approximation more accurate. Model tests show the validity of the magnetic forward modeling and inversion of Padé approximation proposed in the paper, and when this inversion method is applied to the measured data of the Matagami area in Canada, a stable and reasonable distribution of underground interface is obtained.
Wake Vortex Inverse Model User's Guide
NASA Technical Reports Server (NTRS)
Lai, David; Delisi, Donald
2008-01-01
NorthWest Research Associates (NWRA) has developed an inverse model for inverting landing aircraft vortex data. The data used for the inversion are the time evolution of the lateral transport position and vertical position of both the port and starboard vortices. The inverse model performs iterative forward model runs using various estimates of vortex parameters, vertical crosswind profiles, and vortex circulation as a function of wake age. Forward model predictions of lateral transport and altitude are then compared with the observed data. Differences between the data and model predictions guide the choice of vortex parameter values, crosswind profile and circulation evolution in the next iteration. Iterations are performed until a user-defined criterion is satisfied. Currently, the inverse model is set to stop when the improvement in the rms deviation between the data and model predictions is less than 1 percent for two consecutive iterations. The forward model used in this inverse model is a modified version of the Shear-APA model. A detailed description of this forward model, the inverse model, and its validation are presented in a different report (Lai, Mellman, Robins, and Delisi, 2007). This document is a User's Guide for the Wake Vortex Inverse Model. Section 2 presents an overview of the inverse model program. Execution of the inverse model is described in Section 3. When executing the inverse model, a user is requested to provide the name of an input file which contains the inverse model parameters, the various datasets, and directories needed for the inversion. A detailed description of the list of parameters in the inversion input file is presented in Section 4. A user has an option to save the inversion results of each lidar track in a mat-file (a condensed data file in Matlab format). These saved mat-files can be used for post-inversion analysis. A description of the contents of the saved files is given in Section 5. An example of an inversion input
Torgasheva, Anna A; Rubtsov, Nikolai B; Borodin, Pavel M
2013-03-01
Homologous chromosome synapsis in inversion heterozygotes results in the formation of inversion loops. These loops might be transformed into straight, non-homologously paired bivalents via synaptic adjustment. Synaptic adjustment was discovered 30 years ago; however, its relationship with recombination has remained unclear. We analysed this relationship in female mouse embryos heterozygous for large paracentric inversion In(1)1Rk using immunolocalisation of the synaptonemal complex (SYCP3) and mature recombination nodules (MLH1) proteins. The frequency of cells containing bivalents with inversion loops decreased from 69 % to 28 % during pachytene. If an MLH1 focus was present in the non-homologously paired inverted region of the straight bivalent, it was always located in the middle of the inversion. Most of the small, incompletely adjusted loops contained MLH1 foci near the points at which pairing partners were switched. This observation indicates that the degree of synaptic adjustment depended on the crossover position. Complete synaptic adjustment was only possible if a crossover (CO) was located exactly in the middle of the inversion. If a CO was located at any other site, this interrupted synaptic adjustment and resulted in inversion loops of different sizes with an MLH1 focus at or near the edge of the remaining loop.
MARE2DEM: a 2-D inversion code for controlled-source electromagnetic and magnetotelluric data
NASA Astrophysics Data System (ADS)
Key, Kerry
2016-10-01
This work presents MARE2DEM, a freely available code for 2-D anisotropic inversion of magnetotelluric (MT) data and frequency-domain controlled-source electromagnetic (CSEM) data from onshore and offshore surveys. MARE2DEM parametrizes the inverse model using a grid of arbitrarily shaped polygons, where unstructured triangular or quadrilateral grids are typically used due to their ease of construction. Unstructured grids provide significantly more geometric flexibility and parameter efficiency than the structured rectangular grids commonly used by most other inversion codes. Transmitter and receiver components located on topographic slopes can be tilted parallel to the boundary so that the simulated electromagnetic fields accurately reproduce the real survey geometry. The forward solution is implemented with a goal-oriented adaptive finite-element method that automatically generates and refines unstructured triangular element grids that conform to the inversion parameter grid, ensuring accurate responses as the model conductivity changes. This dual-grid approach is significantly more efficient than the conventional use of a single grid for both the forward and inverse meshes since the more detailed finite-element meshes required for accurate responses do not increase the memory requirements of the inverse problem. Forward solutions are computed in parallel with a highly efficient scaling by partitioning the data into smaller independent modeling tasks consisting of subsets of the input frequencies, transmitters and receivers. Non-linear inversion is carried out with a new Occam inversion approach that requires fewer forward calls. Dense matrix operations are optimized for memory and parallel scalability using the ScaLAPACK parallel library. Free parameters can be bounded using a new non-linear transformation that leaves the transformed parameters nearly the same as the original parameters within the bounds, thereby reducing non-linear smoothing effects. Data
Single-receiver geoacoustic inversion using modal reversal.
Bonnel, J; Gervaise, C; Nicolas, B; Mars, J I
2012-01-01
This paper introduces a single-receiver geoacoustic-inversion method based on dispersion analysis and adapted to low-frequency impulsive sources in shallow-water environments. In this context, most existing methods take advantage of the modal dispersion curves in the time-frequency domain. Inversion is usually performed by matching estimated dispersion curves with simulated replicas. The method proposed here is different. It considers the received modes in the frequency domain. The modes are transformed using an operator called modal reversal, which is parameterized using environmental parameters. When modal reversal is applied using parameters that match the real environment, dispersion is compensated for in all of the modes. In this case, the reversed modes are in phase and add up constructively, which is not the case when modal reversal is ill-parameterized. To use this phenomenon, a criterion that adds up the reversed modes has been defined. The geoacoustic inversion is finally performed by maximizing this criterion. The proposed method is benchmarked against simulated data, and it is applied to experimental data recorded during the Shallow Water 2006 experiment.
Self-similarity and self-inversion of quasicrystals
NASA Astrophysics Data System (ADS)
Madison, A. E.
2014-08-01
The discovery of quasicrystals played a revolutionary role in the condensed matter science and forced to renounce the dogma of the classical crystallography that the regular filling of the space by identical blocks is reduced solely to the Fedorov space groups. It is shown that aperiodic crystals, apart from the similarity, exhibit the self-inversion property. In a broadened sense, the self-inversion implies the possible composition of the inversion with translations, rotations, and homothety, whereas pure reflection by itself in a circle can be absent as an independent symmetry element. It is demonstrated that the symmetry of aperiodic tilings is described by Schottky groups (which belong to a particular type of Kleinian groups generated by the linear fractional Möbius transformations); in the theory of aperiodic crystals, the Schottky groups play the same role that the Fedorov groups play in the theory of crystal lattices. The local matching rules for the Penrose fractal tiling are derived, the problem of choice of the fundamental region of the group of motions of a quasicrystal is discussed, and the relation between the symmetry of aperiodic tilings and the symmetry of constructive fractals is analyzed.
Inverse groundwater modeling with emphasis on model parameterization
NASA Astrophysics Data System (ADS)
Kourakos, George; Mantoglou, Aristotelis
2012-05-01
This study develops an inverse method aiming to circumvent the subjective decision regarding model parameterization and complexity in inverse groundwater modeling. The number of parameters is included as a decision variable along with parameter values. A parameterization based on B-spline surfaces (BSS) is selected to approximate transmissivity, and genetic algorithms were selected to perform error minimization. A transform based on linear least squares (LLS) is developed, so that different parameterizations may be combined by standard genetic algorithm operators. First, three applications, with isotropic, anisotropic, and zoned aquifer parameters, are examined in a single objective optimization problem and the estimated transmissivity is found to be near the true one. Interestingly, in the anisotropic case, the algorithm converged to a solution with an anisotropic distribution of control points. Next, a single objective optimization with regularization, penalizing complex models, is considered, and last, the problem is expressed in a multiobjective optimization framework (MOO), where the goals are simultaneous minimization of calibration error and model complexity. The result of MOO is a Pareto set of potential solutions where the user can examine the tradeoffs between calibration error and model complexity and select the most suitable model. By comparing calibration with prediction errors, it appears, that the most promising models are the ones near a region where the rate of decrease of calibration error as model complexity increases drops (bend of error curve). This is a useful result of practical interest in real inverse modeling applications.
Inversion of multiwavelength radiometer measurements by three-dimensional filtering
NASA Technical Reports Server (NTRS)
Rosenkranz, P. W.; Baumann, W. T.
1980-01-01
Remote sensing data from satellites typically have three dimensions: scan position, spacecraft position, and wavelength. Inversion of the radiometric data to infer geophysical parameters is a filtering problem in which the dimension of wavelength (or channel number) is transformed into a dimension of geophysical parameters, and the most general solution is a three-dimensional filter. Linear filters have the advantages of computational speed and easily described transfer functions; but often the measurements are nonlinear functions of the parameters to be inferred. To the extent that the nonlinear inversion problem is overdetermined, it can be modeled by a critically determined linear problem. As an example, inversion of Scanning Multichannel Microwave Radiometer (SMMR) data by means of a three-dimensional Wiener Filter is described. Atmospheric water vapor content, rain liquid water content, surface wind speed and surface temperature are the parameters inferred from the measurements. Nonprecipitating liquid water and water vapor scale height are also modeled but not retrieved. The a priori statistics on which the filter is trained have the effect of governing the selection of a trade-off point of noise as a function of resolution (in all three retrieval dimensions).
Is current disruption associated with an inverse cascade?
NASA Astrophysics Data System (ADS)
Vörös, Z.; Runov, A.; Leubner, M. P.; Baumjohann, W.; Volwerk, M.
2010-06-01
Current disruption (CD) and the related kinetic instabilities in the near-Earth magnetosphere represent physical mechanisms which can trigger multi-scale substorm activity including global reorganizations of the magnetosphere. Lui et al. (2008) proposed a CD scenario in which the kinetic scale linear modes grow and reach the typical dipolarization scales through an inverse cascade. The experimental verification of the inverse nonlinear cascade is based on wavelet analysis. In this paper the Hilbert-Huang transform is used which is suitable for nonlinear systems and allows to reconstruct the time-frequency representation of empirical decomposed modes in an adaptive manner. It was found that, in the Lui et al. (2008) event, the modes evolve globally from high-frequencies to low-frequencies. However, there are also local frequency evolution trends oriented towards high-frequencies, indicating that the underlying processes involve multi-scale physics and non-stationary fluctuations for which the simple inverse cascade scenario is not correct.
Inverse planning incorporating organ motion.
Li, J G; Xing, L
2000-07-01
Accurate targeting is important in intensity-modulated radiation therapy (IMRT). The positional uncertainties of structures with respect to the external beams arise in part from random organ motion and patient setup errors. While it is important to improve immobilization and reduce the influence of organ motion, the residual effects should be included in the IMRT plan design. Current inverse planning algorithms follow the conventional approach and include uncertainties by assuming population-based margins to the target and sensitive structures. Margin around a structure represents a "hard boundary" and the fact that a structure has a spatial probability distribution has been completely ignored. With increasing understanding of spatial uncertainties of structures and the technical capability of fine-tuning the dose distribution on an individual beamlet level in IMRT, it seems timely and important to fully utilize the information in the planning process. This will reduce the "effective" margins of the structures and facilitate dose escalation. Instead of specifying a "hard margin," we describe an inverse planning algorithm which takes into consideration positional uncertainty in terms of spatial probability distribution. The algorithm was demonstrated by assuming that the random organ motion can be represented by a three-dimensional Gaussian distribution function. Other probability distributions can be dealt with similarly. In particular, the commonly used "hard margin" is a special case of the current approach with a uniform probability distribution within a specified range. The algorithm was applied to plan treatment for a prostate case and a pancreatic case. The results were compared with those obtained by adding a margin to the clinical target volume. Better sparing of the sensitive structures were obtained in both cases using the proposed method for approximately the same target coverage.
Inversion methods for interpretation of asteroid lightcurves
NASA Technical Reports Server (NTRS)
Kaasalainen, Mikko; Lamberg, L.; Lumme, K.
1992-01-01
We have developed methods of inversion that can be used in the determination of the three-dimensional shape or the albedo distribution of the surface of a body from disk-integrated photometry, assuming the shape to be strictly convex. In addition to the theory of inversion methods, we have studied the practical aspects of the inversion problem and applied our methods to lightcurve data of 39 Laetitia and 16 Psyche.
Adaptation through chromosomal inversions in Anopheles
Ayala, Diego; Ullastres, Anna; González, Josefa
2014-01-01
Chromosomal inversions have been repeatedly involved in local adaptation in a large number of animals and plants. The ecological and behavioral plasticity of Anopheles species—human malaria vectors—is mirrored by high amounts of polymorphic inversions. The adaptive significance of chromosomal inversions has been consistently attested by strong and significant correlations between their frequencies and a number of phenotypic traits. Here, we provide an extensive literature review of the different adaptive traits associated with chromosomal inversions in the genus Anopheles. Traits having important consequences for the success of present and future vector control measures, such as insecticide resistance and behavioral changes, are discussed. PMID:24904633
Inverse Problem;Litho_Inversion; Geology and Geophysics
NASA Astrophysics Data System (ADS)
Antonio, Guillen; Gabriel, Courrioux; Bernard, Bourgine
2015-04-01
Subsurface modeling is a key tool to describe, understand and quantify geological processes. As the subsurface is inaccessible and its observation is limited by acquisition methods, 3D models of the subsurface are usually built from the interpretation of sparse data with limited resolution. Therefore, uncertainties occur during the model building process, due to possible cognitive human biais, natural variability of geological objects and intrinsic uncertainties of data. In such context, the predictibility of models is limited by uncertainties, which must be assessed in order to reduce economical and human risks linked to the use of models. This work focuses more specifically on uncertainties about geological structures. In this context, a stochastic method is developed for generating structural models with various fault and horizon geometries as well as fault connections. Realistic geological objects are obtained using implicit modeling that represents a surface by an equipotential of a volumetric scalar field. Faults have also been described by a reduced set of uncertain parameters, which opens the way to the inversion of structural objects using geophysical data by baysian methods.
Using field inversion to quantify functional errors in turbulence closures
NASA Astrophysics Data System (ADS)
Singh, Anand Pratap; Duraisamy, Karthik
2016-04-01
A data-informed approach is presented with the objective of quantifying errors and uncertainties in the functional forms of turbulence closure models. The approach creates modeling information from higher-fidelity simulations and experimental data. Specifically, a Bayesian formalism is adopted to infer discrepancies in the source terms of transport equations. A key enabling idea is the transformation of the functional inversion procedure (which is inherently infinite-dimensional) into a finite-dimensional problem in which the distribution of the unknown function is estimated at discrete mesh locations in the computational domain. This allows for the use of an efficient adjoint-driven inversion procedure. The output of the inversion is a full-field of discrepancy that provides hitherto inaccessible modeling information. The utility of the approach is demonstrated by applying it to a number of problems including channel flow, shock-boundary layer interactions, and flows with curvature and separation. In all these cases, the posterior model correlates well with the data. Furthermore, it is shown that even if limited data (such as surface pressures) are used, the accuracy of the inferred solution is improved over the entire computational domain. The results suggest that, by directly addressing the connection between physical data and model discrepancies, the field inversion approach materially enhances the value of computational and experimental data for model improvement. The resulting information can be used by the modeler as a guiding tool to design more accurate model forms, or serve as input to machine learning algorithms to directly replace deficient modeling terms.
The advantages of logarithmically scaled data for electromagnetic inversion
NASA Astrophysics Data System (ADS)
Wheelock, Brent; Constable, Steven; Key, Kerry
2015-06-01
Non-linear inversion algorithms traverse a data misfit space over multiple iterations of trial models in search of either a global minimum or some target misfit contour. The success of the algorithm in reaching that objective depends upon the smoothness and predictability of the misfit space. For any given observation, there is no absolute form a datum must take, and therefore no absolute definition for the misfit space; in fact, there are many alternatives. However, not all misfit spaces are equal in terms of promoting the success of inversion. In this work, we appraise three common forms that complex data take in electromagnetic geophysical methods: real and imaginary components, a power of amplitude and phase, and logarithmic amplitude and phase. We find that the optimal form is logarithmic amplitude and phase. Single-parameter misfit curves of log-amplitude and phase data for both magnetotelluric and controlled-source electromagnetic methods are the smoothest of the three data forms and do not exhibit flattening at low model resistivities. Synthetic, multiparameter, 2-D inversions illustrate that log-amplitude and phase is the most robust data form, converging to the target misfit contour in the fewest steps regardless of starting model and the amount of noise added to the data; inversions using the other two data forms run slower or fail under various starting models and proportions of noise. It is observed that inversion with log-amplitude and phase data is nearly two times faster in converging to a solution than with other data types. We also assess the statistical consequences of transforming data in the ways discussed in this paper. With the exception of real and imaginary components, which are assumed to be Gaussian, all other data types do not produce an expected mean-squared misfit value of 1.00 at the true model (a common assumption) as the errors in the complex data become large. We recommend that real and imaginary data with errors larger than 10 per
NASA Astrophysics Data System (ADS)
Wang, Kang-Ning; Sun, Zan-Dong; Dong, Ning
2015-12-01
Economic shale gas production requires hydraulic fracture stimulation to increase the formation permeability. Hydraulic fracturing strongly depends on geomechanical parameters such as Young's modulus and Poisson's ratio. Fracture-prone sweet spots can be predicted by prestack inversion, which is an ill-posed problem; thus, regularization is needed to obtain unique and stable solutions. To characterize gas-bearing shale sedimentary bodies, elastic parameter variations are regarded as an anisotropic Markov random field. Bayesian statistics are adopted for transforming prestack inversion to the maximum posterior probability. Two energy functions for the lateral and vertical directions are used to describe the distribution, and the expectation-maximization algorithm is used to estimate the hyperparameters of the prior probability of elastic parameters. Finally, the inversion yields clear geological boundaries, high vertical resolution, and reasonable lateral continuity using the conjugate gradient method to minimize the objective function. Antinoise and imaging ability of the method were tested using synthetic and real data.
Fast 3D inversion of gravity data using solution space priorconditioned lanczos bidiagonalization
NASA Astrophysics Data System (ADS)
Rezaie, Mohammad; Moradzadeh, Ali; Kalateh, Ali Nejati
2017-01-01
Inversion of gravity data is one of the most important steps in the quantitative interpretation of practical data. Inversion is a mathematical technique that automatically constructs a subsurface geophysical model from measured data, incorporating some priori information. Inversion of gravity data is time consuming because of increase in data and model parameters. Some efforts have been made to deal with this problem, one of them is using fast algorithms for solving system of equations in inverse problem. Lanczos bidiagonalization method is a fast algorithm that works based on Krylov subspace iterations and projection method, but cannot always provide a good basis for a projection method. So in this study, we combined the Krylov method with a regularization method applied to the low-dimensional projected problem. To achieve the goal, the orthonormal basis vectors of the discrete cosine transform (DCT) were used to build the low-dimensional subspace. The forward operator matrix replaced with a matrix of lower dimension, thus, the required memory and running time of the inverse modeling is decreased by using the proposed algorithm. It is shown that this algorithm can be appropriate to solve a Tikhonov cost function for inversion of gravity data. The proposed method has been applied on a noise-corrupted synthetic data and field gravity data (Mobrun gravity data) to demonstrate its reliability for three dimensional (3D) gravity inversion. The obtained results of 3D inversion both synthetic and field gravity data (Mobrun gravity data) indicate the proposed inversion algorithm could produce density models consistent with true structures.
Inversion in Mathematical Thinking and Learning
ERIC Educational Resources Information Center
Greer, Brian
2012-01-01
Inversion is a fundamental relational building block both within mathematics as the study of structures and within people's physical and social experience, linked to many other key elements such as equilibrium, invariance, reversal, compensation, symmetry, and balance. Within purely formal arithmetic, the inverse relationships between addition and…
Prestack seismic inversion and reservoir property prediction
NASA Astrophysics Data System (ADS)
Chi, Xingang
In this dissertation, I have applied the method of prestack seismic inversion with uncertainty analysis. Also, I have developed the methods of the rock physics template analysis, the fluid modulus inversion and the reservoir property inversion from AVO attributes with and without constraint to improve the technique of reservoir characterization. I use the prestack seismic inversion to invert the elastic properties and use the statistical method to derive the posterior probability of the inverted elastic properties for the uncertainty analysis. I use the rock physics template drawn in the cross-plot of the inverted elastic properties to analyze the lithology and fluid property in the target reservoir. I develop the fluid modulus inversion method based on the simplified Gassmann's equation and the empirical rock physics relationship. Using the inverted fluid modulus, I estimate the gas saturation of the target reservoir before drilling. The reservoir property inversion is to predict the porosity, shale volume and water saturation of the reservoir from AVO attributes to enhance the reservoir interpretation and characterization. I apply this method with the statistical analysis together to execute the uncertainty analysis for the inversion results. Two methods of reservoir property inversion from AVO attributes are attempted in this dissertation: one is performed without constraint and the other is performed with the constrained relationship of the porosity and shale volume.
Bayesian Inversion of Seabed Scattering Data
2014-09-30
Bayesian Inversion of Seabed Scattering Data (Special Research Award in Ocean Acoustics ) Gavin A.M.W. Steininger School of Earth & Ocean...Figure 1: Schematic diagram of the environmental parameterizations for the monostatic- scattering kernel and reflection- coefficient forward and inverse...frequencies. Left two columns: scattering data; right two columns: reflection- coefficient data. 3 layers, hence accounting for the uncertainty of
An exact inverse method for subsonic flows
NASA Technical Reports Server (NTRS)
Daripa, Prabir
1988-01-01
A new inverse method for the aerodynamic design of airfoils is presented for subcritical flows. The pressure distribution in this method can be prescribed as a function of the arclength of the still unknown body. It is shown that this inverse problem is mathematically equivalent to solving only one nonlinear boundary value problem subject to known Dirichlet data on the boundary.
Recursive inversion of externally defined linear systems
NASA Technical Reports Server (NTRS)
Bach, Ralph E., Jr.; Baram, Yoram
1988-01-01
The approximate inversion of an internally unknown linear system, given by its impulse response sequence, by an inverse system having a finite impulse response, is considered. The recursive least squares procedure is shown to have an exact initialization, based on the triangular Toeplitz structure of the matrix involved. The proposed approach also suggests solutions to the problems of system identification and compensation.
CHAMP climate data based on the inversion of monthly average bending angles
NASA Astrophysics Data System (ADS)
Danzer, J.; Gleisner, H.; Healy, S. B.
2014-12-01
Global Navigation Satellite System Radio Occultation (GNSS-RO) refractivity climatologies for the stratosphere can be obtained from the Abel inversion of monthly average bending-angle profiles. The averaging of large numbers of profiles suppresses random noise and this, in combination with simple exponential extrapolation above an altitude of 80 km, circumvents the need for a "statistical optimization" step in the processing. Using data from the US-Taiwanese COSMIC mission, which provides ~1500-2000 occultations per day, it has been shown that this average-profile inversion (API) technique provides a robust method for generating stratospheric refractivity climatologies. Prior to the launch of COSMIC in mid-2006, the data records rely on data from the CHAMP (CHAllenging Mini-satellite Payload) mission. In order to exploit the full range of available RO data, the usage of CHAMP data is also required. CHAMP only provided ~200 profiles per day, and the measurements were noisier than COSMIC. As a consequence, the main research question in this study was to see if the average bending-angle approach is also applicable to CHAMP data. Different methods for the suppression of random noise - statistical and through data quality prescreening - were tested. The API retrievals were compared with the more conventional approach of averaging individual refractivity profiles, produced with the implementation of statistical optimization used in the EUMETSAT (European Organisation for the Exploitation of Meteorological Satellites) Radio Occultation Meteorology Satellite Application Facility (ROM SAF) operational processing. In this study it is demonstrated that the API retrieval technique works well for CHAMP data, enabling the generation of long-term stratospheric RO climate data records from August 2001 and onward. The resulting CHAMP refractivity climatologies are found to be practically identical to the standard retrieval at the DMI (Danish Meteorological Institute) below
Inverse magnetic/shear catalysis
NASA Astrophysics Data System (ADS)
McInnes, Brett
2016-05-01
It is well known that very large magnetic fields are generated when the Quark-Gluon Plasma is formed during peripheral heavy-ion collisions. Lattice, holographic, and other studies strongly suggest that these fields may, for observationally relevant field values, induce ;inverse magnetic catalysis;, signalled by a lowering of the critical temperature for the chiral/deconfinement transition. The theoretical basis of this effect has recently attracted much attention; yet so far these investigations have not included another, equally dramatic consequence of the peripheral collision geometry: the QGP acquires a large angular momentum vector, parallel to the magnetic field. Here we use holographic techniques to argue that the angular momentum can also, independently, have an effect on transition temperatures, and we obtain a rough estimate of the relative effects of the presence of both a magnetic field and an angular momentum density. We find that the shearing angular momentum reinforces the effect of the magnetic field at low values of the baryonic chemical potential, but that it can actually decrease that effect at high chemical potentials.
Inversion based on computational simulations
Hanson, K.M.; Cunningham, G.S.; Saquib, S.S.
1998-09-01
A standard approach to solving inversion problems that involve many parameters uses gradient-based optimization to find the parameters that best match the data. The authors discuss enabling techniques that facilitate application of this approach to large-scale computational simulations, which are the only way to investigate many complex physical phenomena. Such simulations may not seem to lend themselves to calculation of the gradient with respect to numerous parameters. However, adjoint differentiation allows one to efficiently compute the gradient of an objective function with respect to all the variables of a simulation. When combined with advanced gradient-based optimization algorithms, adjoint differentiation permits one to solve very large problems of optimization or parameter estimation. These techniques will be illustrated through the simulation of the time-dependent diffusion of infrared light through tissue, which has been used to perform optical tomography. The techniques discussed have a wide range of applicability to modeling including the optimization of models to achieve a desired design goal.
MODEL SELECTION FOR SPECTROPOLARIMETRIC INVERSIONS
Asensio Ramos, A.; Manso Sainz, R.; Martinez Gonzalez, M. J.; Socas-Navarro, H.; Viticchie, B.
2012-04-01
Inferring magnetic and thermodynamic information from spectropolarimetric observations relies on the assumption of a parameterized model atmosphere whose parameters are tuned by comparison with observations. Often, the choice of the underlying atmospheric model is based on subjective reasons. In other cases, complex models are chosen based on objective reasons (for instance, the necessity to explain asymmetries in the Stokes profiles) but it is not clear what degree of complexity is needed. The lack of an objective way of comparing models has, sometimes, led to opposing views of the solar magnetism because the inferred physical scenarios are essentially different. We present the first quantitative model comparison based on the computation of the Bayesian evidence ratios for spectropolarimetric observations. Our results show that there is not a single model appropriate for all profiles simultaneously. Data with moderate signal-to-noise ratios (S/Ns) favor models without gradients along the line of sight. If the observations show clear circular and linear polarization signals above the noise level, models with gradients along the line are preferred. As a general rule, observations with large S/Ns favor more complex models. We demonstrate that the evidence ratios correlate well with simple proxies. Therefore, we propose to calculate these proxies when carrying out standard least-squares inversions to allow for model comparison in the future.
NASA Technical Reports Server (NTRS)
Patel, Sandeep K.; Joy, Marshall; Carlstrom, John E.; Holder, Gilbert P.; Reese, Erik D.; Gomez, Percy L.; Hughes, John P.; Grego, Laura; Holzapfel, William L.
2000-01-01
We present multiwavelength observations of the Abell 1995 galaxy cluster. From an analysis of X-ray spectroscopy and imaging data, we derive the electron temperature, cluster core radius, and central electron number density. Using optical spectroscopy of 15 cluster members, we derive an accurate cluster redshift and velocity dispersion. Finally, the interferometric imaging of the Sunyaev-Zeldovich effect toward Abell 1995 at 28.5 GHz provides a measure of the integrated pressure through the cluster. The X-ray and Sunyaev-Zeldovich effect observations are combined to determine the angular diameter distance to the cluster of D(sub A) = 1294(sup +294 +438, sub -283 -458) Mpc (Statistical followed by systematic uncertainty), implying a Hubble constant of H(sub 0) = 52.2(sup +11.4 +18.5, sub -11.9 -17.7) km/s.Mpc for Omega(sub M) = 0.3 and Omega(sub lambda) = 0.7. We find a best-fit H(sub 0) of 46 km/s.Mpc for the Omega(sub M) = 1 and Omega(sub lambda) = 0 cosmology, and 48 km/s.Mpc for Omega(sub M) = 0.3 and Omega(sub lambda) = 0.0. The X-ray data are also used to derive a total cluster mass of M(sup HSE, sub tot)(r(sub 500)) = 5.18(sup +0.62, sub -0.48) x 10(exp 14)/h solar mass; the optical velocity dispersion yields an independent and consistent estimate of M(sup virial, sub tot)(r(sub 500)) = 6.35(sup +1.51, sub -1.19) X 10(exp 14) /h solar mass. Both of the total mass estimates are evaluated at a fiducial radius, r(sub 500) = 830 /h kpc, where the overdensity is 500 times the critical density. The total cluster mass is then combined with gas mass measurements to determine a cluster gas mass fraction of F(sub g) = 0.056(sup +0.010, sub -0.013) /h(sup 3/2) in combination with recent baryon density constraints, the measured gas mass fraction yields an upper limit on the mass density parameter of Omega(sub M) h(sup 1/2) <= 0.34(sup +/0.06, sub 0.05.
NASA Technical Reports Server (NTRS)
Benedict, G. F.; McArthur, Barbara E.; Napiwotzki, Ralf; Harrison, Thomas E.; Harris, Hugh C.; Nelan, Edmund; Bond, Howard E; Patterson, Richard J.; Ciardullo, Robin
2009-01-01
We present absolute parallaxes and relative proper motions for the central stars of the planetary nebulae NGC 6853 (The Dumbbell), NGC 7293 (The Helix), Abell 31, and DeHt 5. This paper details our reduction and analysis using DeHt 5 as an example. We obtain these planetary nebula nuclei (PNNi) parallaxes with astrometric data from Fine Guidance Sensors FGS 1r and FGS 3, white-light interferometers on the Hubble Space Telescope. Proper motions, spectral classifications and VJHKT2M and DDO51 photometry of the stars comprising the astrometric reference frames provide spectrophotometric estimates of reference star absolute parallaxes. Introducing these into our model as observations with error, we determine absolute parallaxes for each PNN. Weighted averaging with previous independent parallax measurements yields an average parallax precision, sigma (sub pi)/ pi = 5%. Derived distances are: d(sub NGC6853) = 405(exp +28 sub -25) pc, d(sub NGC7293) = 216(exp +14 sub -12) pc, d(sub Abell31) = 621(exp +91 sub -70) pc, and d(sub DeHt5) = 345(exp +19 sub -17) pc. These PNNi distances are all smaller than previously derived from spectroscopic analyses of the central stars. To obtain absolute magnitudes from these distances requires estimates of interstellar extinction. We average extinction measurements culled from the literature, from reddening based on PNNi intrinsic colors derived from model SEDs, and an assumption that each PNN experiences the same rate of extinction as a function of distance as do the reference stars nearest (in angular separation) to each central star. We also apply Lutz-Kelker bias corrections. The absolute magnitudes and effective temperatures permit estimates of PNNi radii through both the Stefan-Boltzmann relation and Eddington fluxes. Comparing absolute magnitudes with post-AGB models provides mass estimates. Masses cluster around 0.57 solar Mass, close to the peak of the white dwarf mass distribution. Adding a few more PNNi with well
NASA Astrophysics Data System (ADS)
Benedict, G. Fritz; McArthur, Barbara E.; Napiwotzki, Ralf; Harrison, Thomas E.; Harris, Hugh C.; Nelan, Edmund; Bond, Howard E.; Patterson, Richard J.; Ciardullo, Robin
2009-12-01
We present absolute parallaxes and relative proper motions for the central stars of the planetary nebulae NGC 6853 (The Dumbbell), NGC 7293 (The Helix), Abell 31, and DeHt 5. This paper details our reduction and analysis using DeHt 5 as an example. We obtain these planetary nebula nuclei (PNNi) parallaxes with astrometric data from Fine Guidance Sensors FGS 1r and FGS 3, white-light interferometers on the Hubble Space Telescope. Proper motions, spectral classifications and VJHKT2M and DDO51 photometry of the stars comprising the astrometric reference frames provide spectrophotometric estimates of reference star absolute parallaxes. Introducing these into our model as observations with error, we determine absolute parallaxes for each PNN. Weighted averaging with previous independent parallax measurements yields an average parallax precision, σπ/π = 5%. Derived distances are: d NGC 6853 = 405+28 -25 pc, d NGC 7293 = 216+14 -12 pc, d Abell 31 = 621+91 -70 pc, and d DeHt 5 = 345+19 -17 pc. These PNNi distances are all smaller than previously derived from spectroscopic analyses of the central stars. To obtain absolute magnitudes from these distances requires estimates of interstellar extinction. We average extinction measurements culled from the literature, from reddening based on PNNi intrinsic colors derived from model SEDs, and an assumption that each PNN experiences the same rate of extinction as a function of distance as do the reference stars nearest (in angular separation) to each central star. We also apply Lutz-Kelker bias corrections. The absolute magnitudes and effective temperatures permit estimates of PNNi radii through both the Stefan-Boltzmann relation and Eddington fluxes. Comparing absolute magnitudes with post-AGB models provides mass estimates. Masses cluster around 0.57 M_{⊙}, close to the peak of the white dwarf mass distribution. Adding a few more PNNi with well-determined distances and masses, we compare all the PNNi with cooler white dwarfs
Fast wavelet based sparse approximate inverse preconditioner
Wan, W.L.
1996-12-31
Incomplete LU factorization is a robust preconditioner for both general and PDE problems but unfortunately not easy to parallelize. Recent study of Huckle and Grote and Chow and Saad showed that sparse approximate inverse could be a potential alternative while readily parallelizable. However, for special class of matrix A that comes from elliptic PDE problems, their preconditioners are not optimal in the sense that independent of mesh size. A reason may be that no good sparse approximate inverse exists for the dense inverse matrix. Our observation is that for this kind of matrices, its inverse entries typically have piecewise smooth changes. We can take advantage of this fact and use wavelet compression techniques to construct a better sparse approximate inverse preconditioner. We shall show numerically that our approach is effective for this kind of matrices.
Rapid approximate inversion of airborne TEM
NASA Astrophysics Data System (ADS)
Fullagar, Peter K.; Pears, Glenn A.; Reid, James E.; Schaa, Ralf
2015-11-01
Rapid interpretation of large airborne transient electromagnetic (ATEM) datasets is highly desirable for timely decision-making in exploration. Full solution 3D inversion of entire airborne electromagnetic (AEM) surveys is often still not feasible on current day PCs. Therefore, two algorithms to perform rapid approximate 3D interpretation of AEM have been developed. The loss of rigour may be of little consequence if the objective of the AEM survey is regional reconnaissance. Data coverage is often quasi-2D rather than truly 3D in such cases, belying the need for `exact' 3D inversion. Incorporation of geological constraints reduces the non-uniqueness of 3D AEM inversion. Integrated interpretation can be achieved most readily when inversion is applied to a geological model, attributed with lithology as well as conductivity. Geological models also offer several practical advantages over pure property models during inversion. In particular, they permit adjustment of geological boundaries. In addition, optimal conductivities can be determined for homogeneous units. Both algorithms described here can operate on geological models; however, they can also perform `unconstrained' inversion if the geological context is unknown. VPem1D performs 1D inversion at each ATEM data location above a 3D model. Interpretation of cover thickness is a natural application; this is illustrated via application to Spectrem data from central Australia. VPem3D performs 3D inversion on time-integrated (resistive limit) data. Conversion to resistive limits delivers a massive increase in speed since the TEM inverse problem reduces to a quasi-magnetic problem. The time evolution of the decay is lost during the conversion, but the information can be largely recovered by constructing a starting model from conductivity depth images (CDIs) or 1D inversions combined with geological constraints if available. The efficacy of the approach is demonstrated on Spectrem data from Brazil. Both separately and in
Maps for Lorentz transformations of spin
Jordan, Thomas F.; Shaji, Anil; Sudarshan, E. C. G.
2006-03-15
Lorentz transformations of spin density matrices for a particle with positive mass and spin 1/2 are described by maps of the kind used in open quantum dynamics. They show how the Lorentz transformations of the spin depend on the momentum. Since the spin and momentum generally are not independent, the maps generally are not completely positive and act in limited domains. States with two momentum values are considered, so the maps are for the spin qubit correlated with the qubit made from the two momentum values, and results from the open quantum dynamics of two coupled qubits can be applied. Inverses are used to show that every Lorentz transformation completely removes the spin polarization, and so completely removes the information, from a number of spin density matrices. The size of the spin polarization that is removed is calculated for particular cases.
Dispersive Fourier transformation femtosecond stimulated Raman scattering
NASA Astrophysics Data System (ADS)
Dobner, Sven; Fallnich, Carsten
2016-11-01
We present the first proof-of-principle spectroscopic measurements with purely passive dispersive Fourier transformation femtosecond stimulated Raman scattering. In femtosecond stimulated Raman scattering, the full Raman scattering spectrum is efficiently obtained, as all Raman transitions are coherently excited with the combination of a narrow-bandwidth and a broad-bandwidth (femtosecond) pulse at once. Currently, the detection speed of the spectra is limited by the read-out time of classical, comparably slow CCD-based spectrometers. We show a reduction in the acquisition time of Raman signatures by applying the dispersive Fourier transformation, a method employing wavelength-to-time transformation, in order to record the spectral composition of a single pulse with a single fast photodiode. This arrangement leads to an acquisition time of Raman signatures, scaling inversely with the repetition frequency of the applied laser system, which in our case corresponds to the order of microseconds.
Saito, Hiroshi; Hayashi, Hisao
2015-11-01
Ferritin iron, hemosiderin iron, total iron stores and transformation rate were determined by serum ferritin kinetics. The transformation rate between ferritin and hemosiderin is motivated by the potential difference between them. The transformer determines transformation rate according to the potential difference in iron mobilization and deposition. The correlations between transformation rate and iron stores were studied in 11 patients with chronic hepatitis C (CHC), 1 patent with treated iron deficiency anemia (TIDA), 9 patients with hereditary hemochromatosis (HH) and 4 patients with transfusion-dependent anemia (TD). The power regression curve of approximation showed an inverse correlation between transformation rate and ferritin iron, hemosiderin iron in part and total iron stores in HH. Such an inverse correlation between transformation rate and iron stores implies that the larger the amount of iron stores, the smaller the transformation of iron stores. On the other hand, a minimal inverse correlation between transformation rate and ferritin iron and no correlation between transformation rate and hemosiderin iron or total iron stores in CHC indicate the derangement of storage iron metabolism in the cells with CHC. Radio-iron fixation on the iron storing tissue in iron overload was larger than that in normal subjects by ferrokinetics. This is consistent with the inverse correlation between transformation rate and total iron stores in HH. The characteristics of iron turnover between ferritin and hemosiderin were disclosed from the correlation between transformation rate and ferritin iron, hemosiderin iron or total iron stores.
Gravity Inversion with Geological Modeling Constraint and Its Application in the Okinawa Trough
NASA Astrophysics Data System (ADS)
Zhang, S.
2014-12-01
The satellite altimetry gravity data is used to recover the 3D distribution of oceanic lithosphere density in the Okinawa Trough and its neighbor region. It's difficult to use only gravity data to invert complex geological structure and density distribution by 3D gravity Inversion method. In order to improve the vertical resolution of the density inversion result, 3D geological modeling method is used to build structural model for the inversion, prior constraint conditions can be applied to solve the non-unique problem. In the Okinawa Trough, it is proved by earthquake data that the Philippine plate dives beneath the Okinawa Trough, which result in the upwelling of mantel material and decrease of the crust thickness. The Benioff zone clearly shows the plate's subduction parameter, such as direction, dip, transformation. Therefore, a structural subduction model is created by geological modeling method and works as the initial model and as constraint condition in gravity inversion. The 3D gravity inversion result and seismology CMT data are both used to explain the oceanic lithosphere structure in the Okinawa Trough. The inversion result illustrates high density anomaly under the Okinawa Trough. Affected by small scale mantle convections, the continental lithosphere is separated, which result in the spreading of back-arc basin and the formation of the Okinawa Trough.
Freyhult, Eva; Moulton, Vincent; Ardell, David H
2006-01-01
Sequence logos are stacked bar graphs that generalize the notion of consensus sequence. They employ entropy statistics very effectively to display variation in a structural alignment of sequences of a common function, while emphasizing its over-represented features. Yet sequence logos cannot display features that distinguish functional subclasses within a structurally related superfamily nor do they display under-represented features. We introduce two extensions to address these needs: function logos and inverse logos. Function logos display subfunctions that are over-represented among sequences carrying a specific feature. Inverse logos generalize both sequence logos and function logos by displaying under-represented, rather than over-represented, features or functions in structural alignments. To make inverse logos, a compositional inverse is applied to the feature or function frequency distributions before logo construction, where a compositional inverse is a mathematical transform that makes common features or functions rare and vice versa. We applied these methods to a database of structurally aligned bacterial tDNAs to create highly condensed, birds-eye views of potentially all so-called identity determinants and antideterminants that confer specific amino acid charging or initiator function on tRNAs in bacteria. We recovered both known and a few potentially novel identity elements. Function logos and inverse logos are useful tools for exploratory bioinformatic analysis of structure-function relationships in sequence families and superfamilies.
Inverse Cerenkov experiment. Final report
Kimura, W.D.
1993-09-30
The final report describes work performed to investigate inverse Cherenkov acceleration (ICA) as a promising method for laser particle acceleration. In particular, an improved configuration of ICA is being tested in a experiment presently underway on the Accelerator Test Facility (ATF). In the experiment, the high peak power ({approximately} 10 GW) linearly polarized ATF CO{sub 2} laser beam is converted to a radially polarized beam. This is beam is focused with an axicon at the Cherenkov angle onto the ATF 50-MeV e-beam inside a hydrogen gas cell, where the gas acts as the phase matching medium of the interaction. An energy gain of {approximately}12 MeV is predicted assuming a delivered laser peak power of 5 GW. The experiment is divided into two phases. The Phase I experiments, which were completed in the spring of 1992, were conducted before the ATF e-beam was available and involved several successful tests of the optical systems. Phase II experiments are with the e-beam and laser beam, and are still in progress. The ATF demonstrated delivery of the e-beam to the experiment in Dec. 1992. A preliminary ``debugging`` run with the e-beam and laser beam occurred in May 1993. This revealed the need for some experimental modifications, which have been implemented. The second run is tentatively scheduled for October or November 1993. In parallel to the experimental efforts has been ongoing theoretical work to support the experiment and investigate improvement and/or offshoots. One exciting offshoot has been theoretical work showing that free-space laser acceleration of electrons is possible using a radially-polarized, axicon-focused laser beam, but without any phase-matching gas. The Monte Carlo code used to model the ICA process has been upgraded and expanded to handle different types of laser beam input profiles.
Time parameters and Lorentz transformations of relativistic stochastic processes.
Dunkel, Jörn; Hänggi, Peter; Weber, Stefan
2009-01-01
Rules for the transformation of time parameters in relativistic Langevin equations are derived and discussed. In particular, it is shown that, if a coordinate-time-parametrized process approaches the relativistic Jüttner-Maxwell distribution, the associated proper-time-parametrized process converges to a modified momentum distribution, differing by a factor proportional to the inverse energy.
Plane Transformations in a Complex Setting III: Similarities
ERIC Educational Resources Information Center
Dana-Picard, Thierry
2009-01-01
This is the third part of a study of plane transformations described in a complex setting. After the study of homotheties, translations, rotations and reflections, we proceed now to the study of plane similarities, either direct or inverse. Their group theoretical properties are described, and their action on classical geometrical objects is…
The Funk transform as a Penrose transform
NASA Astrophysics Data System (ADS)
Bailey, Toby N.; Eastwood, Michael G.; Gover, A. Rod; Mason, Lionel J.
1999-01-01
The Funk transform is the integral transform from the space of smooth even functions on the unit sphere S2[subset or is implied by][open face R]3 to itself defined by integration over great circles. One can regard this transform as a limit in a certain sense of the Penrose transform from [open face C][open face P]2 to [open face C][open face P]*ast;2. We exploit this viewpoint by developing a new proof of the bijectivity of the Funk transform which proceeds by considering the cohomology of a certain involutive (or formally integrable) structure on an intermediate space. This is the simplest example of what we hope will prove to be a general method of obtaining results in real integral geometry by means of complex holomorphic methods derived from the Penrose transform.
Prismatic and full-waveform joint inversion
NASA Astrophysics Data System (ADS)
Qu, Ying-Ming; Li, Zhen-Chun; Huang, Jian-Ping; Li, Jin-Li
2016-09-01
Prismatic wave is that it has three reflection paths and two reflection points, one of which is located at the reflection interface and the other is located at the steep dip angle reflection layer, so that contains a lot of the high and steep reflection interface information that primary cannot reach. Prismatic wave field information can be separated by applying Born approximation to traditional reverse time migration profile, and then the prismatic wave is used to update velocity to improve the inversion efficiency for the salt dame flanks and some other high and steep structure. Under the guidance of this idea, a prismatic waveform inversion method is proposed (abbreviated as PWI). PWI has a significant drawback that an iteration time of PWI is more than twice as that of FWI, meanwhile, the full wave field information cannot all be used, for this problem, we propose a joint inversion method to combine prismatic waveform inversion with full waveform inversion. In this method, FWI and PWI are applied alternately to invert the velocity. Model tests suggest that the joint inversion method is less dependence on the high and steep structure information in the initial model and improve high inversion efficiency and accuracy for the model with steep dip angle structure.
Using emulsion inversion in industrial processes.
Salager, Jean-Louis; Forgiarini, Ana; Márquez, Laura; Peña, Alejandro; Pizzino, Aldo; Rodriguez, María P; Rondón-González, Marianna
2004-05-20
Emulsion inversion is a complex phenomenon, often perceived as an instability that is essentially uncontrollable, although many industrial processes make use of it. A research effort that started 2 decades ago has provided the two-dimensional and three-dimensional description, the categorization and the theoretical interpretation of the different kinds of emulsion inversion. A clear-cut phenomenological approach is currently available for understanding its characteristics, the factors that influence it and control it, the importance of fine-tuning the emulsification protocol, and the crucial occurrence of organized structures such as liquid crystals or multiple emulsions. The current know-how is used to analyze some industrial processes involving emulsion inversion, e.g. the attainment of a fine nutrient or cosmetic emulsion by temperature or formulation-induced transitional inversion, the preparation of a silicone oil emulsion by catastrophic phase inversion, the manufacture of a viscous polymer latex by combined inversion and the spontaneous but enigmatic inversion of emulsions used in metal working operations such as lathing or lamination.
Bayesian AVO inversion with consistent angle parameters
NASA Astrophysics Data System (ADS)
Li, Chao; Zhang, Jinmiao; Zhu, Zhenyu
2017-04-01
Amplitude versus offset (AVO) inversion has been extensively used in seismic exploration. Many different elastic parameters can be inverted by incorporating corresponding reflection coefficient approximations. Although efforts have been made to improve the accuracy of AVO inversions for years, there is still one problem that has long been ignored. In most methods, the angle in the approximation and the angle used in seismic angle gather extractions are not the same one. This inconsistency leads to inaccurate inversion results. In this paper, a Bayesian AVO inversion method with consistent angles is proposed to solve the problem and improve inversion accuracy. Firstly, a linearized P-wave reflection coefficient approximation with consistent angles is derived based on angle replacements. The equivalent form of the approximation in terms moduli and density is derived so that moduli can be inverted for reservoir characterization. Then, by convoluting it with seismic wavelets as the forward solver, a probabilistic prestack seismic inversion method with consistent angles is presented in a Bayesian scheme. The synthetic test proves that the accuracy of this method is higher than the traditional one. The real data example shows that the inversion result fits better with well log interpretation data, which verifies the feasibility of the proposed method.
Magnetotelluric inversion based on mutual information
NASA Astrophysics Data System (ADS)
Mandolesi, Eric; Jones, Alan G.
2014-10-01
Joint inversion of different geophysical data sets is becoming a more popular and powerful tool, and it has been performed on data sensitive both to the same physical parameter and to different physical parameters. Joint inversion is undertaken to reduce acceptable model space and to increase sensitivity to model parameters that one method alone is unable to resolve adequately. We examine and implement a novel hybrid joint inversion approach. In our inversion scheme a model-the reference model-is fixed, and the information shared with the subsurface structure obtained from another method will be maximized; in our case conductivity structures from magnetotelluric (MT) inversion. During inversion, the joint probability distribution of the MT and the specified reference model is estimated and its entropy minimized in order to guide the inversion result towards a solution that is statistically compatible with the reference model. The powerful feature of this technique is that no explicit relationships between estimated model parameters and reference model ones are presumed: if a link exists in data then it is highlighted in the estimation of the joint probability distribution, if no link is required, then none is enforced. Tests performed verify the robustness of this method and the advantages of it in a 1-D anisotropic scenario are demonstrated. A case study was performed with data from Central Germany, effectively fitting an MT data set from a single station within as minimal an amount of anisotropy as required.
NASA Astrophysics Data System (ADS)
Hindson, L.; Johnston-Hollitt, M.; Hurley-Walker, N.; Buckley, K.; Morgan, J.; Carretti, E.; Dwarakanath, K. S.; Bell, M.; Bernardi, G.; Bhat, N. D. R.; Bowman, J. D.; Briggs, F.; Cappallo, R. J.; Corey, B. E.; Deshpande, A. A.; Emrich, D.; Ewall-Wice, A.; Feng, L.; Gaensler, B. M.; Goeke, R.; Greenhill, L. J.; Hazelton, B. J.; Jacobs, D.; Kaplan, D. L.; Kasper, J. C.; Kratzenberg, E.; Kudryavtseva, N.; Lenc, E.; Lonsdale, C. J.; Lynch, M. J.; McWhirter, S. R.; McKinley, B.; Mitchell, D. A.; Morales, M. F.; Morgan, E.; Oberoi, D.; Ord, S. M.; Pindor, B.; Prabu, T.; Procopio, P.; Offringa, A. R.; Riding, J.; Rogers, A. E. E.; Roshi, A.; Shankar, N. Udaya; Srivani, K. S.; Subrahmanyan, R.; Tingay, S. J.; Waterson, M.; Wayth, R. B.; Webster, R. L.; Whitney, A. R.; Williams, A.; Williams, C. L.
2014-11-01
We present the first Murchison Widefield Array observations of the well-known cluster of galaxies Abell 3667 (A3667) between 105 and 241 MHz. A3667 is one of the best known examples of a galaxy cluster hosting a double radio relic and has been reported to contain a faint radio halo and bridge. The origin of radio haloes, relics and bridges is still unclear, however galaxy cluster merger seems to be an important factor. We clearly detect the north-west (NW) and south-east radio relics in A3667 and find an integrated flux density at 149 MHz of 28.1 ± 1.7 and 2.4 ± 0.1 Jy, respectively, with an average spectral index, between 120 and 1400 MHz, of -0.9 ± 0.1 for both relics. We find evidence of a spatial variation in the spectral index across the NW relic steepening towards the centre of the cluster, which indicates an ageing electron population. These properties are consistent with higher frequency observations. We detect emission that could be associated with a radio halo and bridge. However, due to the presence of poorly sampled large-scale Galactic emission and blended point sources we are unable to verify the exact nature of these features.
NASA Astrophysics Data System (ADS)
Kale, Ruta; Gitti, Myriam
2017-03-01
We report the discovery of a fourth eastern arc (Arc E) towards the cool-core cluster Abell 2626 using 610 MHz Giant Metrewave Radio Telescope observations. Three arcs towards north, west and south were known from earlier works at 1400 MHz and proposed to have originated in precessing radio jets of the central active galactic nucleus. The 610-1400 MHz integrated spectral indices of the arcs are in the range 3.2-3.6 and the spectral index map shows uniform distribution along the lengths of the arcs. If associated with A2626, the arcs have linear extents in the range 79-152 kpc. The detection of Arc E favours the scenario in which a pair of bipolar precessing jets were active and halted to produce the arc system. Based on the morphological symmetry and spectral similarity, we indicate a possible role of gravitational lensing. Further, high-resolution low-frequency observations and measurements of the mass of the system are needed to disentangle the mystery of this source.
On the inversion-indel distance
2013-01-01
Background The inversion distance, that is the distance between two unichromosomal genomes with the same content allowing only inversions of DNA segments, can be computed thanks to a pioneering approach of Hannenhalli and Pevzner in 1995. In 2000, El-Mabrouk extended the inversion model to allow the comparison of unichromosomal genomes with unequal contents, thus insertions and deletions of DNA segments besides inversions. However, an exact algorithm was presented only for the case in which we have insertions alone and no deletion (or vice versa), while a heuristic was provided for the symmetric case, that allows both insertions and deletions and is called the inversion-indel distance. In 2005, Yancopoulos, Attie and Friedberg started a new branch of research by introducing the generic double cut and join (DCJ) operation, that can represent several genome rearrangements (including inversions). Among others, the DCJ model gave rise to two important results. First, it has been shown that the inversion distance can be computed in a simpler way with the help of the DCJ operation. Second, the DCJ operation originated the DCJ-indel distance, that allows the comparison of genomes with unequal contents, considering DCJ, insertions and deletions, and can be computed in linear time. Results In the present work we put these two results together to solve an open problem, showing that, when the graph that represents the relation between the two compared genomes has no bad components, the inversion-indel distance is equal to the DCJ-indel distance. We also give a lower and an upper bound for the inversion-indel distance in the presence of bad components. PMID:24564182
Sparse CSEM inversion driven by seismic coherence
NASA Astrophysics Data System (ADS)
Guo, Zhenwei; Dong, Hefeng; Kristensen, Åge
2016-12-01
Marine controlled source electromagnetic (CSEM) data inversion for hydrocarbon exploration is often challenging due to high computational cost, physical memory requirement and low resolution of the obtained resistivity map. This paper aims to enhance both the speed and resolution of CSEM inversion by introducing structural geological information in the inversion algorithm. A coarse mesh is generated for Occam’s inversion, where the parameters are fewer than in the fine regular mesh. This sparse mesh is defined as a coherence-based irregular (IC) sparse mesh, which is based on vertices extracted from available geological information. Inversion results on synthetic data illustrate that the IC sparse mesh has a smaller inversion computational cost compared to the regular dense (RD) mesh. It also has a higher resolution than with a regular sparse (RS) mesh for the same number of estimated parameters. In order to study how the IC sparse mesh reduces the computational time, four different meshes are generated for Occam’s inversion. As a result, an IC sparse mesh can reduce the computational cost while it keeps the resolution as good as a fine regular mesh. The IC sparse mesh reduces the computational cost of the matrix operation for model updates. When the number of estimated parameters reduces to a limited value, the computational cost is independent of the number of parameters. For a testing model with two resistive layers, the inversion result using an IC sparse mesh has higher resolution in both horizontal and vertical directions. Overall, the model representing significant geological information in the IC mesh can improve the resolution of the resistivity models obtained from inversion of CSEM data.
Steerable Discrete Fourier Transform
NASA Astrophysics Data System (ADS)
Fracastoro, Giulia; Magli, Enrico
2017-03-01
Directional transforms have recently raised a lot of interest thanks to their numerous applications in signal compression and analysis. In this letter, we introduce a generalization of the discrete Fourier transform, called steerable DFT (SDFT). Since the DFT is used in numerous fields, it may be of interest in a wide range of applications. Moreover, we also show that the SDFT is highly related to other well-known transforms, such as the Fourier sine and cosine transforms and the Hilbert transforms.
Inverse Raman effect: applications and detection techniques
Hughes, L.J. Jr.
1980-08-01
The processes underlying the inverse Raman effect are qualitatively described by comparing it to the more familiar phenomena of conventional and stimulated Raman scattering. An experession is derived for the inverse Raman absorption coefficient, and its relationship to the stimulated Raman gain is obtained. The power requirements of the two fields are examined qualitatively and quantitatively. The assumption that the inverse Raman absorption coefficient is constant over the interaction length is examined. Advantages of the technique are discussed and a brief survey of reported studies is presented.
An inverse problem in thermal imaging
NASA Technical Reports Server (NTRS)
Bryan, Kurt; Caudill, Lester F., Jr.
1994-01-01
This paper examines uniqueness and stability results for an inverse problem in thermal imaging. The goal is to identify an unknown boundary of an object by applying a heat flux and measuring the induced temperature on the boundary of the sample. The problem is studied both in the case in which one has data at every point on the boundary of the region and the case in which only finitely many measurements are available. An inversion procedure is developed and used to study the stability of the inverse problem for various experimental configurations.
Monte Carlo inversion of seismic data
NASA Technical Reports Server (NTRS)
Wiggins, R. A.
1972-01-01
The analytic solution to the linear inverse problem provides estimates of the uncertainty of the solution in terms of standard deviations of corrections to a particular solution, resolution of parameter adjustments, and information distribution among the observations. It is shown that Monte Carlo inversion, when properly executed, can provide all the same kinds of information for nonlinear problems. Proper execution requires a relatively uniform sampling of all possible models. The expense of performing Monte Carlo inversion generally requires strategies to improve the probability of finding passing models. Such strategies can lead to a very strong bias in the distribution of models examined unless great care is taken in their application.
Population inversion in a stationary recombining plasma
Otsuka, M.
1980-12-01
Population inversion, which occurs in a recombining plasma when a stationary He plasma is brought into contact with a neutral gas, is examined. With hydrogen as a contact gas, noticeable inversion between low-lying levels of H as been found. The overpopulation density is of the order of 10/sup 8/ cm/sup -3/, which is much higher then that (approx. =10/sup 5/ cm/sup -3/) obtained previously with He as a contact gas. Relations between these experimental results and the conditions for population inversion are discussed with the CR model.
An Inversion Recovery NMR Kinetics Experiment.
Williams, Travis J; Kershaw, Allan D; Li, Vincent; Wu, Xinping
2011-05-01
A convenient laboratory experiment is described in which NMR magnetization transfer by inversion recovery is used to measure the kinetics and thermochemistry of amide bond rotation. The experiment utilizes Varian spectrometers with the VNMRJ 2.3 software, but can be easily adapted to any NMR platform. The procedures and sample data sets in this article will enable instructors to use inversion recovery as a laboratory activity in applied NMR classes and provide research students with a convenient template with which to acquire inversion recovery data on research samples.
An Inversion Recovery NMR Kinetics Experiment
Williams, Travis J.; Kershaw, Allan D.; Li, Vincent; Wu, Xinping
2011-01-01
A convenient laboratory experiment is described in which NMR magnetization transfer by inversion recovery is used to measure the kinetics and thermochemistry of amide bond rotation. The experiment utilizes Varian spectrometers with the VNMRJ 2.3 software, but can be easily adapted to any NMR platform. The procedures and sample data sets in this article will enable instructors to use inversion recovery as a laboratory activity in applied NMR classes and provide research students with a convenient template with which to acquire inversion recovery data on research samples. PMID:21552343
BOOK REVIEW: Inverse Problems. Activities for Undergraduates
NASA Astrophysics Data System (ADS)
Yamamoto, Masahiro
2003-06-01
This book is a valuable introduction to inverse problems. In particular, from the educational point of view, the author addresses the questions of what constitutes an inverse problem and how and why we should study them. Such an approach has been eagerly awaited for a long time. Professor Groetsch, of the University of Cincinnati, is a world-renowned specialist in inverse problems, in particular the theory of regularization. Moreover, he has made a remarkable contribution to educational activities in the field of inverse problems, which was the subject of his previous book (Groetsch C W 1993 Inverse Problems in the Mathematical Sciences (Braunschweig: Vieweg)). For this reason, he is one of the most qualified to write an introductory book on inverse problems. Without question, inverse problems are important, necessary and appear in various aspects. So it is crucial to introduce students to exercises in inverse problems. However, there are not many introductory books which are directly accessible by students in the first two undergraduate years. As a consequence, students often encounter diverse concrete inverse problems before becoming aware of their general principles. The main purpose of this book is to present activities to allow first-year undergraduates to learn inverse theory. To my knowledge, this book is a rare attempt to do this and, in my opinion, a great success. The author emphasizes that it is very important to teach inverse theory in the early years. He writes; `If students consider only the direct problem, they are not looking at the problem from all sides .... The habit of always looking at problems from the direct point of view is intellectually limiting ...' (page 21). The book is very carefully organized so that teachers will be able to use it as a textbook. After an introduction in chapter 1, sucessive chapters deal with inverse problems in precalculus, calculus, differential equations and linear algebra. In order to let one gain some insight
Analysis of Temperature Distributions in Nighttime Inversions
NASA Astrophysics Data System (ADS)
Telyak, Oksana; Krasouski, Aliaksandr; Svetashev, Alexander; Turishev, Leonid; Barodka, Siarhei
2015-04-01
Adequate prediction of temperature inversion in the atmospheric boundary layer is one of prerequisites for successful forecasting of meteorological parameters and severe weather events. Examples include surface air temperature and precipitation forecasting as well as prediction of fog, frosts and smog with hazardous levels of atmospheric pollution. At the same time, reliable forecasting of temperature inversions remains an unsolved problem. For prediction of nighttime inversions over some specific territory, it is important to study characteristic features of local circulation cells formation and to properly take local factors into account to develop custom modeling techniques for operational use. The present study aims to investigate and analyze vertical temperature distributions in tropospheric inversions (isotherms) over the territory of Belarus. We study several specific cases of formation, evolution and decay of deep nighttime temperature inversions in Belarus by means of mesoscale numerical simulations with WRF model, considering basic mechanisms of isothermal and inverse temperature layers formation in the troposphere and impact of these layers on local circulation cells. Our primary goal is to assess the feasibility of advance prediction of inversions formation with WRF. Modeling results reveal that all cases under consideration have characteristic features of radiative inversions (e.g., their formation times, development phases, inversion intensities, etc). Regions of "blocking" layers formation are extensive and often spread over the entire territory of Belarus. Inversions decay starts from the lowermost (near surface) layer (altitudes of 5 to 50 m). In all cases, one can observe formation of temperature gradients that substantially differ from the basic inversion gradient, i.e. the layer splits into smaller layers, each having a different temperature stratification (isothermal, adiabatic, etc). As opposed to various empirical techniques as well as
Inversion of spinning sound fields.
Carley, Michael
2009-02-01
A method is presented for the reconstruction of rotating monopole source distributions using acoustic pressures measured on a sideline parallel to the source axis. The method requires no a priori assumptions about the source other than that its strength at the frequency of interest varies sinusoidally in azimuth on the source disk so that the radiated acoustic field is composed of a single circumferential mode. When multiple azimuthal modes are present, the acoustic field can be decomposed into azimuthal modes and the method applied to each mode in sequence. The method proceeds in two stages, first finding an intermediate line source derived from the source distribution and then inverting this line source to find the radial variation in source strength. A far-field form of the radiation integrals is derived, showing that the far-field pressure is a band-limited Fourier transform of the line source, establishing a limit on the quality of source reconstruction, which can be achieved using far-field measurements. The method is applied to simulated data representing wind-tunnel testing of a ducted rotor system (tip Mach number of 0.74) and to control of noise from an automotive cooling fan (tip Mach number of 0.14), studies which have appeared in the literature of source identification.
Case of paracentric inversion 19p
Bettio, D.; Rizzi, N.; Giardino, D.
1995-09-25
Paracentric inversions have been described less frequently than pericentric ones. It is not known whether this is due to their rarity or rather to difficulty in detecting intra-arm rearrangements. Paracentric inversions have been noted in all chromosomes except chromosome 19; the short arm was involved in 21 cases and the long arm in 87. We describe the first case of paracentric inversion in chromosome 19. The patient, a 29-year-old man, was referred for cytogenetic investigation because his wife had had 3 spontaneous abortions. No history of subfertility was recorded. Chromosome studies on peripheral blood lymphocytes demonstrated an abnormal QFQ banding pattern in the short arm of one chromosome 19. The comparison between QFQ, GTG and RBA banding led us to suspect a paracentric inversion involving the chromosome 19 short arm. CBG banding resulted in an apparently normal position of the centromere. Parental chromosome studies showed the same anomaly in the patient`s mother. 4 refs.
AVO migration and inversion: Are they commutable?
Beydoun, W.B.; Jin, S.; Hanitzsch, C.
1994-12-31
With the increasing ambition of characterizing hydrocarbon traps in more subtle or complex reservoirs, Amplitude Variation with Offset (AVO) techniques are becoming a valuable seismic tool for quantitative seismic discrimination of lithologies and fluids. One of the biggest remaining challenges is to acquire and process the data in an amplitude preserved fashion and in multi-dimensional geology. This study is a component of this puzzle, and attempts to address the following processing question: what are the benefits of prestack migration before AVO inversion (process 1) versus performing an AVO inversion followed by a poststack migration (process 2)? The comparison is done on a 2-D synthetic model which is valid for process 2. The technique used for process 1 is the prestack depth AVO migration/inversion described in the text which estimates reflectivities and incidence angles in multi-dimensions from the data prior to AVO inversion. Process 2 results are derived using a commercial seismic processing software package.
FNAS/Rapid Spectral Inversion Methods
NASA Technical Reports Server (NTRS)
Poularikas, Alexander
1997-01-01
The purpose of this investigation was to study methods and ways for rapid inversion programs involving the correlated k-method, and to study the infrared observations of Saturn from the Cassini orbiter.
Inverse Born series for the Calderon problem
NASA Astrophysics Data System (ADS)
Arridge, Simon; Moskow, Shari; Schotland, John C.
2012-03-01
We propose a direct reconstruction method for the Calderon problem based on inversion of the Born series. We characterize the convergence, stability and approximation error of the method and illustrate its use in numerical reconstructions.
Electromagnetic inverse applications for functional brain imaging
Wood, C.C.
1997-10-01
This is the final report of a one-year, Laboratory Directed Research and Development (LDRD) project at Los Alamos National Laboratory (LANL). This project addresses an important mathematical and computational problem in functional brain imaging, namely the electromagnetic {open_quotes}inverse problem.{close_quotes} Electromagnetic brain imaging techniques, magnetoencephalography (MEG) and electroencephalography (EEG), are based on measurements of electrical potentials and magnetic fields at hundreds of locations outside the human head. The inverse problem is the estimation of the locations, magnitudes, and time-sources of electrical currents in the brain from surface measurements. This project extends recent progress on the inverse problem by combining the use of anatomical constraints derived from magnetic resonance imaging (MRI) with Bayesian and other novel algorithmic approaches. The results suggest that we can achieve significant improvements in the accuracy and robustness of inverse solutions by these two approaches.
Inverse Doppler Effects in Broadband Acoustic Metamaterials
NASA Astrophysics Data System (ADS)
Zhai, S. L.; Zhao, X. P.; Liu, S.; Shen, F. L.; Li, L. L.; Luo, C. R.
2016-08-01
The Doppler effect refers to the change in frequency of a wave source as a consequence of the relative motion between the source and an observer. Veselago theoretically predicted that materials with negative refractions can induce inverse Doppler effects. With the development of metamaterials, inverse Doppler effects have been extensively investigated. However, the ideal material parameters prescribed by these metamaterial design approaches are complex and also challenging to obtain experimentally. Here, we demonstrated a method of designing and experimentally characterising arbitrary broadband acoustic metamaterials. These omni-directional, double-negative, acoustic metamaterials are constructed with ‘flute-like’ acoustic meta-cluster sets with seven double meta-molecules; these metamaterials also overcome the limitations of broadband negative bulk modulus and mass density to provide a region of negative refraction and inverse Doppler effects. It was also shown that inverse Doppler effects can be detected in a flute, which has been popular for thousands of years in Asia and Europe.
Inverse Doppler Effects in Broadband Acoustic Metamaterials.
Zhai, S L; Zhao, X P; Liu, S; Shen, F L; Li, L L; Luo, C R
2016-08-31
The Doppler effect refers to the change in frequency of a wave source as a consequence of the relative motion between the source and an observer. Veselago theoretically predicted that materials with negative refractions can induce inverse Doppler effects. With the development of metamaterials, inverse Doppler effects have been extensively investigated. However, the ideal material parameters prescribed by these metamaterial design approaches are complex and also challenging to obtain experimentally. Here, we demonstrated a method of designing and experimentally characterising arbitrary broadband acoustic metamaterials. These omni-directional, double-negative, acoustic metamaterials are constructed with 'flute-like' acoustic meta-cluster sets with seven double meta-molecules; these metamaterials also overcome the limitations of broadband negative bulk modulus and mass density to provide a region of negative refraction and inverse Doppler effects. It was also shown that inverse Doppler effects can be detected in a flute, which has been popular for thousands of years in Asia and Europe.
An Inverse Problem Statistical Methodology Summary
2008-01-12
R. Vogel, Computational Methods for Inverse Problems, SIAM, Philadelphia, 2002. [36] D. D. Wackerly, W. Mendenhall III, and R. L. Scheaffer , Mathematical Statistics with Applications, Duxbury Thompson Learning, USA, 2002. 56
Inverse problem of electro-seismic conversion
NASA Astrophysics Data System (ADS)
Chen, Jie; Yang, Yang
2013-11-01
When a porous rock is saturated with an electrolyte, electrical fields are coupled with seismic waves via the electro-seismic conversion. Pride (1994 Phys. Rev. B 50 15678-96) derived the governing models, in which Maxwell equations are coupled with Biot's equations through the electro-kinetic mobility parameter. The inverse problem of the linearized electro-seismic conversion consists in two steps, namely the inversion of Biot's equations and the inversion of Maxwell equations. We analyze the reconstruction of conductivity and electro-kinetic mobility parameter in Maxwell equations with internal measurements, while the internal measurements are provided by the results of the inversion of Biot's equations. We show that knowledge of two internal data based on well-chosen boundary conditions uniquely determines these two parameters. Moreover, a Lipschitz-type stability is proved based on the same sets of well-chosen boundary conditions.
Inverse agonism and its therapeutic significance
Khilnani, Gurudas; Khilnani, Ajeet Kumar
2011-01-01
A large number of G-protein-coupled receptors (GPCRs) show varying degrees of basal or constitutive activity. This constitutive activity is usually minimal in natural receptors but is markedly observed in wild type and mutated (naturally or induced) receptors. According to conventional two-state drug receptor interaction model, binding of a ligand may initiate activity (agonist with varying degrees of positive intrinsic activity) or prevent the effect of an agonist (antagonist with zero intrinsic activity). Inverse agonists bind with the constitutively active receptors, stabilize them, and thus reduce the activity (negative intrinsic activity). Receptors of many classes (α-and β-adrenergic, histaminergic, GABAergic, serotoninergic, opiate, and angiotensin receptors) have shown basal activity in suitable in vitro models. Several drugs that have been conventionally classified as antagonists (β-blockers, antihistaminics) have shown inverse agonist effects on corresponding constitutively active receptors. Nearly all H1 and H2 antihistaminics (antagonists) have been shown to be inverse agonists. Among the β-blockers, carvedilol and bucindolol demonstrate low level of inverse agonism as compared to propranolol and nadolol. Several antipsychotic drugs (D2 receptors antagonist), antihypertensive (AT1 receptor antagonists), antiserotoninergic drugs and opioid antagonists have significant inverse agonistic activity that contributes partly or wholly to their therapeutic value. Inverse agonism may also help explain the underlying mechanism of beneficial effects of carvedilol in congestive failure, naloxone-induced withdrawal syndrome in opioid dependence, clozapine in psychosis, and candesartan in cardiac hypertrophy. Understanding inverse agonisms has paved a way for newer drug development. It is now possible to develop agents, which have only desired therapeutic value and are devoid of unwanted adverse effect. Pimavanserin (ACP-103), a highly selective 5-HT2A inverse
Linearity, resolution, and covariance in GRT inversions for anisotropic elastic moduli
NASA Astrophysics Data System (ADS)
Spencer, Carl; de Hoop, Maarten V.; Burridge, Robert
1995-09-01
This paper is concerned with the linearized inversion of elastic wave data using the Generalized Radon Transformation to give anisotropic medium parameters. Assumptions of linearity are examined by comparing linearized reflection coefficients calculated using the Born approximation with full plane-wave reflection coefficients. In typical sand/shale models we have found that the linearity assumption is valid only to approximately 60 degrees from the normal. Linear dependencies between the scattering patterns produced by individual moduli result in an ill-posed inverse problem. Utilizing P-wave data, we find that for the Transversely Isotropic case similarities in the C55 and C13 scattering directivity mean that they cannot be distinguished. C11 is best observed at wide-angle and hence estimates made using limited aperture data are subject to large error. Quasi-Monte Carlo techniques are adapted to carry out the 4D inversion integral.
On the Extraction of Seismic AVF Information and the Inversion of Anelastic Reflectivity
NASA Astrophysics Data System (ADS)
Bird, C.; Innanen, K. A.; Lines, L.; Naghizadeh, M.
2011-12-01
Strongly dispersive seismic anomalies associated with highly absorptive targets have been observed in seismic data. A frequency by frequency method (AVF) for determining the anelasticity of highly absorptive targets from measurements of the dispersive reflection coefficient is reviewed in this paper. In order to implement the AVF inversion technique, it is necessary that we have a method of estimating the local spectra of recorded seismic reflection events. We demonstrate AVF inversion using a calibrated, fast, non-redundant S-transform (FST) algorithm to estimate the local spectra of dispersive reflection coefficients. We test the effectiveness of the FST for estimating the spectrum of reflection coefficients by comparing with the analytic reflection coefficient. Using forward modeling to generate synthetic seismic traces with anelstic reflection coefficients, we observe accurate results of the AVF inversion using the FST.
Inversion of elastic impedance for unconsolidated sediments
Lee, Myung W.
2006-01-01
Elastic properties of gas-hydrate-bearing sediments are important for quantifying gas hydrate amounts as well as discriminating the gas hydrate effect on velocity from free gas or pore pressure. This paper presents an elastic inversion method for estimating elastic properties of gas-hydrate-bearing sediments from angle stacks using sequential inversion of P-wave impedance from the zero-offset stack and S-wave impedance from the far-offset stack without assuming velocity ratio.
Inverse Kinematics for a Parallel Myoelectric Elbow
2001-10-25
Inverse Kinematics for a Parallel Myoelectric Elbow A. Z. Escudero, Ja. Álvarez, L. Leija. Center of Research and Advanced Studies of the IPN...replacement above elbow are serial mechanisms driven by a DC motor and they include only one active articulation for the elbow [1]. Parallel mechanisms...are rather scarce [2]. The inverse kinematics model of a 3-degree of freedom parallel prosthetic elbow mechanism is reported. The mathematical