The discrete dipole approximation code DDscat.C++: features, limitations and plans
NASA Astrophysics Data System (ADS)
Choliy, V. Ya.
2013-08-01
We present a new freely available open-source C++ software for numerical solution of the electromagnetic waves absorption and scattering problems within the Discrete Dipole Approximation paradigm. The code is based upon the famous and free Fortan-90 code DDSCAT by B. Draine and P. Flatau. Started as a teaching project, the presented code DDscat.C++ differs from the parent code DDSCAT with a number of features, essential for C++ but quite seldom in Fortran. This article introduces the new code, explains its features, presents timing information and some plans for further development.
Approximate analysis of electromagnetically coupled microstrip dipoles
NASA Astrophysics Data System (ADS)
Kominami, M.; Yakuwa, N.; Kusaka, H.
1990-10-01
A new dynamic analysis model for analyzing electromagnetically coupled (EMC) microstrip dipoles is proposed. The formulation is based on an approximate treatment of the dielectric substrate. Calculations of the equivalent impedance of two different EMC dipole configurations are compared with measured data and full-wave solutions. The agreement is very good.
Photoelectron spectroscopy and the dipole approximation
Hemmers, O.; Hansen, D.L.; Wang, H.
1997-04-01
Photoelectron spectroscopy is a powerful technique because it directly probes, via the measurement of photoelectron kinetic energies, orbital and band structure in valence and core levels in a wide variety of samples. The technique becomes even more powerful when it is performed in an angle-resolved mode, where photoelectrons are distinguished not only by their kinetic energy, but by their direction of emission as well. Determining the probability of electron ejection as a function of angle probes the different quantum-mechanical channels available to a photoemission process, because it is sensitive to phase differences among the channels. As a result, angle-resolved photoemission has been used successfully for many years to provide stringent tests of the understanding of basic physical processes underlying gas-phase and solid-state interactions with radiation. One mainstay in the application of angle-resolved photoelectron spectroscopy is the well-known electric-dipole approximation for photon interactions. In this simplification, all higher-order terms, such as those due to electric-quadrupole and magnetic-dipole interactions, are neglected. As the photon energy increases, however, effects beyond the dipole approximation become important. To best determine the range of validity of the dipole approximation, photoemission measurements on a simple atomic system, neon, where extra-atomic effects cannot play a role, were performed at BL 8.0. The measurements show that deviations from {open_quotes}dipole{close_quotes} expectations in angle-resolved valence photoemission are observable for photon energies down to at least 0.25 keV, and are quite significant at energies around 1 keV. From these results, it is clear that non-dipole angular-distribution effects may need to be considered in any application of angle-resolved photoelectron spectroscopy that uses x-ray photons of energies as low as a few hundred eV.
Yurkin, Maxim A; Min, Michiel; Hoekstra, Alfons G
2010-09-01
We compared three formulations of the discrete dipole approximation (DDA) for simulation of light scattering by particles with refractive indices m=10+10i , 0.1+i , and 1.6+0.01i . These formulations include the filtered coupled dipoles (FCD), the lattice dispersion relation (LDR) and the radiative reaction correction. We compared the number of iterations required for the convergence of the iterative solver (proportional to simulation time) and the accuracy of final results. We showed that the LDR performance for m=10+10i is especially bad, while the FCD is a good option for all cases studied. Moreover, we analyzed the detailed structure of DDA errors and the spectrum of the DDA interaction matrix to understand the performance of the FCD. In particular, this spectrum, obtained with the FCD for particles smaller than the wavelength, falls into the bounds, physically implied for the spectrum of the infinite-dimensional integral scattering operator, contrary to two other DDA formulations. Finally, such extreme refractive indices can now be routinely simulated using modern desktop computers using the publicly available ADDA code, which includes an efficient implementation of the FCD. PMID:21230209
Discrete dipole approximation simulation of bead enhanced diffraction grating biosensor
NASA Astrophysics Data System (ADS)
Arif, Khalid Mahmood
2016-08-01
We present the discrete dipole approximation simulation of light scattering from bead enhanced diffraction biosensor and report the effect of bead material, number of beads forming the grating and spatial randomness on the diffraction intensities of 1st and 0th orders. The dipole models of gratings are formed by volume slicing and image processing while the spatial locations of the beads on the substrate surface are randomly computed using discrete probability distribution. The effect of beads reduction on far-field scattering of 632.8 nm incident field, from fully occupied gratings to very coarse gratings, is studied for various bead materials. Our findings give insight into many difficult or experimentally impossible aspects of this genre of biosensors and establish that bead enhanced grating may be used for rapid and precise detection of small amounts of biomolecules. The results of simulations also show excellent qualitative similarities with experimental observations.
Breakdown of the dipole approximation in strong-field ionization.
Ludwig, A; Maurer, J; Mayer, B W; Phillips, C R; Gallmann, L; Keller, U
2014-12-12
We report the breakdown of the electric dipole approximation in the long-wavelength limit in strong-field ionization with linearly polarized few-cycle mid-infrared laser pulses at intensities on the order of 10¹³ W/cm². Photoelectron momentum distributions were recorded by velocity map imaging and projected onto the beam propagation axis. We observe an increasing shift of the peak of this projection opposite to the beam propagation direction with increasing laser intensities. From a comparison with semiclassical simulations, we identify the combined action of the magnetic field of the laser pulse and the Coulomb potential as the origin of our observations. PMID:25541770
Discrete dipole approximation analysis of plasmonic core/alloy nanoparticles.
Wu, Wenjie; Maye, Mathew M
2014-08-25
The surface plasmon resonance (SPR) properties of Au/Au(x)Ag(1-x) core/alloy nanoparticles (NPs) have been investigated by means of the discrete dipole approximation. The core/alloy microstructure was varied by changing the shell alloy composition x, its thickness t(S), and the shell thickness to core radius ratio (t(S)/r(C)) in the range of 0.05-1.0. These changes resulted in a novel tuning of SPR shape, frequency, and extinction. These models were compared with experimental results for Au/Au(x)Ag(1-x) NPs prepared by a microwave-mediated hydrothermal processing method, which produces core/alloy NPs with SPR signatures closely resembling those of the models. PMID:24889191
Fretting about FRET: Failure of the Ideal Dipole Approximation
Muñoz-Losa, Aurora; Curutchet, Carles; Krueger, Brent P.; Hartsell, Lydia R.; Mennucci, Benedetta
2009-01-01
Abstract With recent growth in the use of fluorescence-detected resonance energy transfer (FRET), it is being applied to complex systems in modern and diverse ways where it is not always clear that the common approximations required for analysis are applicable. For instance, the ideal dipole approximation (IDA), which is implicit in the Förster equation, is known to break down when molecules get “too close” to each other. Yet, no clear definition exists of what is meant by “too close”. Here we examine several common fluorescent probe molecules to determine boundaries for use of the IDA. We compare the Coulombic coupling determined essentially exactly with a linear response approach with the IDA coupling to find the distance regimes over which the IDA begins to fail. We find that the IDA performs well down to roughly 20 Å separation, provided the molecules sample an isotropic set of relative orientations. However, if molecular motions are restricted, the IDA performs poorly at separations beyond 50 Å. Thus, isotropic probe motions help mask poor performance of the IDA through cancellation of error. Therefore, if fluorescent probe motions are restricted, FRET practitioners should be concerned with not only the well-known κ2 approximation, but also possible failure of the IDA. PMID:19527638
Fretting about FRET: failure of the ideal dipole approximation.
Muñoz-Losa, Aurora; Curutchet, Carles; Krueger, Brent P; Hartsell, Lydia R; Mennucci, Benedetta
2009-06-17
With recent growth in the use of fluorescence-detected resonance energy transfer (FRET), it is being applied to complex systems in modern and diverse ways where it is not always clear that the common approximations required for analysis are applicable. For instance, the ideal dipole approximation (IDA), which is implicit in the Förster equation, is known to break down when molecules get "too close" to each other. Yet, no clear definition exists of what is meant by "too close". Here we examine several common fluorescent probe molecules to determine boundaries for use of the IDA. We compare the Coulombic coupling determined essentially exactly with a linear response approach with the IDA coupling to find the distance regimes over which the IDA begins to fail. We find that the IDA performs well down to roughly 20 A separation, provided the molecules sample an isotropic set of relative orientations. However, if molecular motions are restricted, the IDA performs poorly at separations beyond 50 A. Thus, isotropic probe motions help mask poor performance of the IDA through cancellation of error. Therefore, if fluorescent probe motions are restricted, FRET practitioners should be concerned with not only the well-known kappa2 approximation, but also possible failure of the IDA. PMID:19527638
Two-electron ionization and stabilization beyond the dipole approximation
Staudt, Andreas; Keitel, Christoph H.
2006-04-15
A two-dimensional model atom is employed to study the ionization behavior of helium subjected to strong laser fields in the high-frequency regime. The evolution of the system is studied by means of numerical integration of the Schroedinger equation beyond the dipole approximation. Ionization probabilities of the two-electron atom in highly intense laser fields have been calculated for different pulse shapes. It is confirmed that the mutual repulsion between the two electrons as well as the length of the laser pulses significantly alter the ionization probabilities of the system. Nondipole effects are shown to lead to a considerable increase of the ionization probabilities. For certain laser pulse shapes, a regime of ionization suppression is investigated which exists in addition to two-electron stabilization. The applicability of our model scheme to the case of heliumlike systems is discussed, and it is shown that stabilization may also occur in these systems, and how it is altered in dependence of the nuclear charge.
Convergence analysis of the thermal discrete dipole approximation
NASA Astrophysics Data System (ADS)
Edalatpour, Sheila; Čuma, Martin; Trueax, Tyler; Backman, Roger; Francoeur, Mathieu
2015-06-01
The thermal discrete dipole approximation (T-DDA) is a numerical approach for modeling near-field radiative heat transfer in complex three-dimensional geometries. In this work, the convergence of the T-DDA is investigated by comparison against the exact results for two spheres separated by a vacuum gap. The error associated with the T-DDA is reported for various sphere sizes, refractive indices, and vacuum gap thicknesses. The results reveal that for a fixed number of subvolumes, the accuracy of the T-DDA degrades as the refractive index and the sphere diameter to gap ratio increase. A converging trend is observed as the number of subvolumes increases. The large computational requirements associated with increasing the number of subvolumes, and the shape error induced by large sphere diameter to gap ratios, are mitigated by using a nonuniform discretization scheme. Nonuniform discretization is shown to significantly accelerate the convergence of the T-DDA, and is thus recommended for near-field thermal radiation simulations. Errors less than 5% are obtained in 74% of the cases studied by using up to 82 712 subvolumes. Additionally, the convergence analysis demonstrates that the T-DDA is very accurate when dealing with surface polariton resonant modes dominating radiative heat transfer in the near field.
Approximate maximum likelihood decoding of block codes
NASA Technical Reports Server (NTRS)
Greenberger, H. J.
1979-01-01
Approximate maximum likelihood decoding algorithms, based upon selecting a small set of candidate code words with the aid of the estimated probability of error of each received symbol, can give performance close to optimum with a reasonable amount of computation. By combining the best features of various algorithms and taking care to perform each step as efficiently as possible, a decoding scheme was developed which can decode codes which have better performance than those presently in use and yet not require an unreasonable amount of computation. The discussion of the details and tradeoffs of presently known efficient optimum and near optimum decoding algorithms leads, naturally, to the one which embodies the best features of all of them.
First Hyperpolarizability of Collagen Using the Point Dipole Approximation.
Harczuk, Ignat; Vahtras, Olav; Ågren, Hans
2016-06-01
The application of localized hyperpolarizabilities to predict a total protein hyperpolarizability is presented for the first time, using rat-tail collagen as a demonstration example. We employ a model comprising the quadratic Applequist point-dipole approach, the so-called LoProp transformation, and a procedure with molecular fractionation using conjugate caps to determine the atomic and bond contributions to the net β tensor of the collagen [(PPG)10]3 triple-helix. By using Tholes exponential damping modification to the dyadic tensor in the Applequist equations, a correct qualitative agreement with experiment is found. The intensity of the βHRS signal and the depolarization ratios are best reproduced by decomposing the LoProp properties into the atomic positions and using Tholes exponential damping with the original damping parameter. Some ramifications of the model for general protein property optimization are briefly discussed. PMID:27203480
NASA Astrophysics Data System (ADS)
Moteki, N.
2015-12-01
Black carbon (BC) is a light-absorbing carbonaceous aerosol emitted from combustions of fossil fuels and biomasses and is estimated as the second most important contributor to positive climate forcing after the carbon dioxide. In the atmosphere, the fractal aggregate of BC-spherules may be mixed with non-absorbing (or weakly absorbing) compounds that forms morphologically complex "BC-containing particle". A reliable scattering code for BC-containing particles is necessary for predicting mass absorption efficiency of BC and designing/evaluating optical techniques for estimating microphysical properties (i.e., size distribution, mixing state, shape, refractive index) of BC-containing particles. The computational methods that derived from the volume-integral form of the Maxwell equation, such as discrete dipole approximation (DDA), are method of choice for morphologically complex object like BC-containing particles. In ordinary DDA, the entire particle volume is approximated as a collection of tiny cubical dipoles (with side length d) placed on a 3D cubic lattice. For several model BC-containing particles, the comparisons with numerically exact T-matrix method reveals that the ordinary DDA suffered from persistent positive systematic error (up to +30%) in absorption even under d <<λ. The cause of this DDA error is identified to be the shape error in BC-spherules. To eliminate the shape error in BC-spherules, we propose a new DDA methodology which may be called hybrid DDA (h-DDA): each primary BC sphere is assumed as a spherical dipole, while remaining particle volume of coating material is approximated by a collection of tiny cubical dipoles on a 3D cubic lattice. Positive absorption bias up to +30% in ordinary DDA is suppressed to within 3% in h-DDA. In h-DDA code, an efficient FFT-based algorithm for solving the matrix equation has been implemented, by utilizing the multilevel block-Toeplitz property of the submatrix corresponding to inter-dipole interaction within
Model of Jovian F region ionosphere (Saturnian ionosphere in offset dipole approximation)
NASA Technical Reports Server (NTRS)
Tan, A.
1991-01-01
Researchers investigated the offset effect of Saturn's dipole on its ionosphere. The magnetic field of Saturn is primarily that of a dipole closely aligned to the rotational axis, but displaced northward from the center by a distance approximately equal to 0.05 R sub S, R sub S being the reference radius of Saturn. This offset effect would manifest itself most prominently between the ionospheric profiles in the Northern and Southern Hemispheres of Saturn.
NASA Astrophysics Data System (ADS)
Draine, Bruce T.; Flatau, Piotr J.
2000-08-01
DDSCAT is a freely available software package which applies the "discrete dipole approximation" (DDA) to calculate scattering and absorption of electromagnetic waves by targets with arbitrary geometries and complex refractive index. The DDA approximates the target by an array of polarizable points. DDSCAT.5a requires that these polarizable points be located on a cubic lattice. DDSCAT allows accurate calculations of electromagnetic scattering from targets with "size parameters" 2 pi a/lambda < 15 provided the refractive index m is not large compared to unity (|m-1| < 1). The DDSCAT package is written in Fortran and is highly portable. The program supports calculations for a variety of target geometries (e.g., ellipsoids, regular tetrahedra, rectangular solids, finite cylinders, hexagonal prisms, etc.). Target materials may be both inhomogeneous and anisotropic. It is straightforward for the user to import arbitrary target geometries into the code, and relatively straightforward to add new target generation capability to the package. DDSCAT automatically calculates total cross sections for absorption and scattering and selected elements of the Mueller scattering intensity matrix for specified orientation of the target relative to the incident wave, and for specified scattering directions. This User Guide explains how to use DDSCAT to carry out EM scattering calculations. CPU and memory requirements are described.
Ionization dynamics beyond the dipole approximation induced by the pulse envelope
NASA Astrophysics Data System (ADS)
Simonsen, Aleksander Skjerlie; Kjellsson, Tor; Førre, Morten; Lindroth, Eva; Selstø, Sølve
2016-05-01
When atoms and molecules are ionized by laser pulses of finite duration and increasingly high intensities, the validity of the much-used dipole approximation, in which the spatial dependence and magnetic component of the external field are neglected, eventually breaks down. We report that, when going beyond the dipole approximation for the description of atoms exposed to ultraviolet light, the spatial dependence of the pulse shape, the envelope, provides the dominant correction, while the spatial dependence of the carrier is negligible. We present a first-order beyond-dipole correction to the Hamiltonian which accounts exclusively for nondipole effects stemming from the carrier envelope of the pulse. We demonstrate by ab initio calculations for hydrogen that this approximation, which we refer to as the envelope approximation, reproduces the full interaction beyond the dipole approximation for absolute and differential observables and proves to be valid for a broad range of high-frequency fields. This is done both for the Schrödinger and the Dirac equation. Moreover, it is demonstrated that the envelope approximation provides an interaction-term which gives rise to faster numerical convergence in terms of partial waves compared to its exact counterpart.
NASA Astrophysics Data System (ADS)
D'Agostino, Stefania; Della Sala, Fabio; Andreani, Lucio Claudio
2013-05-01
A theoretical control of the electromagnetic coupling between localized surface plasmons and pointlike sources of radiation is a relevant topic in nanoscience and nanophotonics. In this paper a numerical approach based on the discrete dipole approximation is presented as a practical and reliable computational tool to study the decay dynamics of a dipole when it is located in the near proximities of metallic nanoparticles whose shapes do not allow a fully analytical treatment. The method is first applied to Ag nanospheres and nanoshells, which represent two analytically solvable cases, and it is shown to lead to a very good agreement with exact results. The approach is then used to consider the response, in terms of perturbations induced on the radiative and nonradiative decay rates, of elongated nanoparticles, like Ag prolate spheroids and nanocones. Results demonstrate how the optical response of conically shaped nanoparticles can be affected by the distance and the orientation of the emitter of radiation, as well as by other geometrical parameters. The particular symmetry of these plasmonic objects results in peculiar features: the absorption efficiencies of the modes depend on the distance of the source of radiation in a counterintuitive way, and this is explained in terms of the excited charge density distributions. The possibility to simulate arbitrary-shaped nanostructures and several dipole-metal configurations presented here, could thus open new avenues for an aware use of surface plasmons in fluorescence spectroscopy applications or single photon emission studies.
Hydrogen atom excitation in intense attosecond laser field: Gauge dependence of dipole approximation
NASA Astrophysics Data System (ADS)
Aldarmaa, Ch.; Khenmedekh, L.; Lkhagva, O.
2014-03-01
It is assumed that, the atomic excitations probability can be calculated using first order perturbation theory and dipole approximations. The validity of the dipole approximations had been examined by comparing the results with the results obtained by exact calculations within the first order perturbation theory[2]. Figure 1 shows the time dependence of the transition probability in the dipole approximation. From these plots it is obvious that, the probabilities obtained in the length gauge are higher than that in the velocity gauge, in the interaction period (-τ/2
Hydrogen atom excitation in intense attosecond laser field: Gauge dependence of dipole approximation
Aldarmaa, Ch. E-mail: l-xemee@yahoo.com; Khenmedekh, L. E-mail: l-xemee@yahoo.com; Lkhagva, O.
2014-03-24
It is assumed that, the atomic excitations probability can be calculated using first order perturbation theory and dipole approximations. The validity of the dipole approximations had been examined by comparing the results with the results obtained by exact calculations within the first order perturbation theory[2]. Figure 1 shows the time dependence of the transition probability in the dipole approximation. From these plots it is obvious that, the probabilities obtained in the length gauge are higher than that in the velocity gauge, in the interaction period (−τ/2
Progressive Image Coding by Hierarchical Linear Approximation.
ERIC Educational Resources Information Center
Wu, Xiaolin; Fang, Yonggang
1994-01-01
Proposes a scheme of hierarchical piecewise linear approximation as an adaptive image pyramid. A progressive image coder comes naturally from the proposed image pyramid. The new pyramid is semantically more powerful than regular tessellation but syntactically simpler than free segmentation. This compromise between adaptability and complexity…
NASA Astrophysics Data System (ADS)
Yurkin, Maxim A.; de Kanter, David; Hoekstra, Alfons G.
2010-02-01
We studied the accuracy of the discrete dipole approximation (DDA) for simulations of absorption and scattering spectra by gold nanoparticles (spheres, cubes, and rods ranging in size from 10 to 100 nm). We varied the dipole resolution and applied two DDA formulations, employing the standard lattice dispersion relation (LDR) and the relatively new filtered coupled dipoles (FCD) approach. The DDA with moderate dipole resolutions is sufficiently accurate for scattering efficiencies or positions of spectral peaks, but very inaccurate for e.g. values of absorption efficiencies in the near-IR. To keep relative errors of the latter within 10% about 107 dipoles per sphere are required. Surprisingly, errors for cubes are about 10 times smaller than that for spheres or rods, which we explain in terms of shape errors. The FCD is generally more accurate and leads to up to 2 times faster computations than the LDR. Therefore, we recommend FCD as the DDA formulation of choice for gold and other metallic nanoparticles.
Lestrange, Patrick J.; Egidi, Franco; Li, Xiaosong
2015-12-21
The interaction between a quantum mechanical system and plane wave light is usually modeled within the electric dipole approximation. This assumes that the intensity of the incident field is constant over the length of the system and transition probabilities are described in terms of the electric dipole transition moment. For short wavelength spectroscopies, such as X-ray absorption, the electric dipole approximation often breaks down. Higher order multipoles are then included to describe transition probabilities. The square of the magnetic dipole and electric quadrupole are often included, but this results in an origin-dependent expression for the oscillator strength. The oscillator strength can be made origin-independent if all terms through the same order in the wave vector are retained. We will show the consequences and potential pitfalls of using either of these two expressions. It is shown that the origin-dependent expression may violate the Thomas-Reiche-Kuhn sum rule and the origin-independent expression can result in negative transition probabilities.
Lestrange, Patrick J; Egidi, Franco; Li, Xiaosong
2015-12-21
The interaction between a quantum mechanical system and plane wave light is usually modeled within the electric dipole approximation. This assumes that the intensity of the incident field is constant over the length of the system and transition probabilities are described in terms of the electric dipole transition moment. For short wavelength spectroscopies, such as X-ray absorption, the electric dipole approximation often breaks down. Higher order multipoles are then included to describe transition probabilities. The square of the magnetic dipole and electric quadrupole are often included, but this results in an origin-dependent expression for the oscillator strength. The oscillator strength can be made origin-independent if all terms through the same order in the wave vector are retained. We will show the consequences and potential pitfalls of using either of these two expressions. It is shown that the origin-dependent expression may violate the Thomas-Reiche-Kuhn sum rule and the origin-independent expression can result in negative transition probabilities. PMID:26696042
NASA Astrophysics Data System (ADS)
Lestrange, Patrick J.; Egidi, Franco; Li, Xiaosong
2015-12-01
The interaction between a quantum mechanical system and plane wave light is usually modeled within the electric dipole approximation. This assumes that the intensity of the incident field is constant over the length of the system and transition probabilities are described in terms of the electric dipole transition moment. For short wavelength spectroscopies, such as X-ray absorption, the electric dipole approximation often breaks down. Higher order multipoles are then included to describe transition probabilities. The square of the magnetic dipole and electric quadrupole are often included, but this results in an origin-dependent expression for the oscillator strength. The oscillator strength can be made origin-independent if all terms through the same order in the wave vector are retained. We will show the consequences and potential pitfalls of using either of these two expressions. It is shown that the origin-dependent expression may violate the Thomas-Reiche-Kuhn sum rule and the origin-independent expression can result in negative transition probabilities.
Lindsay, Sean S.; Wooden, Diane H.; Harker, David E.; Kelley, Michael S.; Woodward, Charles E.; Murphy, Jim R. E-mail: diane.h.wooden@nasa.gov E-mail: msk@astro.umd.edu E-mail: murphy@nmsu.edu
2013-03-20
We compute the absorption efficiency (Q{sub abs}) of forsterite using the discrete dipole approximation in order to identify and describe what characteristics of crystal grain shape and size are important to the shape, peak location, and relative strength of spectral features in the 8-40 {mu}m wavelength range. Using the DDSCAT code, we compute Q{sub abs} for non-spherical polyhedral grain shapes with a{sub eff} = 0.1 {mu}m. The shape characteristics identified are (1) elongation/reduction along one of three crystallographic axes; (2) asymmetry, such that all three crystallographic axes are of different lengths; and (3) the presence of crystalline faces that are not parallel to a specific crystallographic axis, e.g., non-rectangular prisms and (di)pyramids. Elongation/reduction dominates the locations and shapes of spectral features near 10, 11, 16, 23.5, 27, and 33.5 {mu}m, while asymmetry and tips are secondary shape effects. Increasing grain sizes (0.1-1.0 {mu}m) shifts the 10 and 11 {mu}m features systematically toward longer wavelengths and relative to the 11 {mu}m feature increases the strengths and slightly broadens the longer wavelength features. Seven spectral shape classes are established for crystallographic a-, b-, and c-axes and include columnar and platelet shapes plus non-elongated or equant grain shapes. The spectral shape classes and the effects of grain size have practical application in identifying or excluding columnar, platelet, or equant forsterite grain shapes in astrophysical environs. Identification of the shape characteristics of forsterite from 8 to 40 {mu}m spectra provides a potential means to probe the temperatures at which forsterite formed.
Relativistic quasiparticle time blocking approximation: Dipole response of open-shell nuclei
NASA Astrophysics Data System (ADS)
Litvinova, E.; Ring, P.; Tselyaev, V.
2008-07-01
The self-consistent relativistic quasiparticle random-phase approximation (RQRPA) is extended by the quasiparticle-phonon coupling (QPC) model using the quasiparticle time blocking approximation (QTBA). The method is formulated in terms of the Bethe-Salpeter equation (BSE) in the two-quasiparticle space with an energy-dependent two-quasiparticle residual interaction. This equation is solved either in the basis of Dirac states forming the self-consistent solution of the ground state or in the momentum representation. Pairing correlations are treated within the Bardeen-Cooper-Schrieffer (BCS) model with a monopole-monopole interaction. The same NL3 set of the coupling constants generates the Dirac-Hartree-BCS single-quasiparticle spectrum, the static part of the residual two-quasiparticle interaction and the quasiparticle-phonon coupling amplitudes. A quantitative description of electric dipole excitations in the chain of tin isotopes (Z=50) with the mass numbers A=100,106,114,116,120, and 130 and in the chain of isotones with (N=50) Sr88, Zr90, Mo92 is performed within this framework. The RQRPA extended by the coupling to collective vibrations generates spectra with a multitude of 2q⊗phonon (two quasiparticles plus phonon) states providing a noticeable fragmentation of the giant dipole resonance as well as of the soft dipole mode (pygmy resonance) in the nuclei under investigation. The results obtained for the photo absorption cross sections and for the integrated contributions of the low-lying strength to the calculated dipole spectra agree very well with the available experimental data.
Accelerated Broadband Spectra Using Transition Dipole Decomposition and Padé Approximants.
Bruner, Adam; LaMaster, Daniel; Lopata, Kenneth
2016-08-01
We present a method for accelerating the computation of UV-visible and X-ray absorption spectra in large molecular systems using real-time time-dependent density functional theory (TDDFT). This approach is based on deconvolution of the dipole into molecular orbital dipole pairs developed by Repisky, et al. [Repisky et al., J. Chem. Theory Comput. 2015, 11, 980-911] followed by Padé approximants to their Fourier transforms. By combining these two techniques, the required simulation time is reduced by a factor of 5 or more, and moreover, the transition dipoles yield the molecular orbital contributions to each transition, akin to the coefficients in linear-response TDDFT. We validate this method on valence and core-level spectra of gas-phase water and nickel porphyrin, where the results are essentially equivalent to conventional linear response. This approach makes real-time TDDFT competitive against linear response for large molecular and material systems with a high density of states. PMID:27359347
NASA Astrophysics Data System (ADS)
Førre, Morten; Simonsen, Aleksander Skjerlie
2016-01-01
The exact velocity-gauge minimal-coupling Hamiltonian describing the laser-matter interaction is transformed into another form by means of a series of gauge transformations. The Hamiltonian corresponding to this point of view is valid for an arbitrary time- and space-dependent laser field, also known as a nondipole field. In effect, the Hamiltonian represents a generalization of the original velocity-gauge minimal-coupling Hamiltonian in the sense that the particle's (classical) velocity in the laser propagation direction is also explicitly accounted for by a new operator term. Imposing the so-called long-wavelength approximation (LWA) on the field, i.e., assuming the laser wavelength being much larger than the extent of the atomic system, the spatial dependence of the field can be neglected and the interaction Hamiltonian reduces to a simpler form. Nevertheless, the resulting LWA Hamiltonian includes the effect of the magnetic-field component of the laser, which is in clear contrast with the usual dipole approximation Hamiltonian derived by imposing the LWA directly on the initial velocity-gauge minimal-coupling Hamiltonian. As such, the weak-field condition necessary to justify neglecting the magnetic field, and the LWA condition, can be considered independently in this formalism, making it an attractive alternative for a broad range of applications in strong-field physics. We demonstrate that, from a numerical perspective, this form of the light-matter interaction is advantageous compared to its standard velocity-gauge counterpart as it gives rise to faster convergence properties when describing ionization dynamics in superintense fields beyond the dipole approximation.
NASA Astrophysics Data System (ADS)
Lindsay, Sean Stephen
The shape, size, and composition of crystalline silicates observed in comet comae and external proto-planetary disks are indicative of the formation and evolution of the dust grains during the processes of planetary formation. In this dissertation, I present the 3 -- 40 mum absorption efficiencies( Qabs) of irregularly shaped forsterite crystals computed with the discrete dipole approximation (DDA) code DDSCAT developed by Draine and Flatau and run on the NASA Advanced Supercomputing facility Pleiades. An investigation of grain shapes ranging from spheroidal to irregular indicate that the strong spectral features from forsterite are sensitive to grain shape and are potentially degenerate with the effects of crystal solid state composition (Mg-content). The 10, 11, 18, 23, and 33.5 mum features are found to be the most crystal shape sensitive and should be avoided in determining Mg-content. The distinct spectral features for the three shape classes are connected with crystal formation environment using a condensation experiment by (Kobatake et al., 2008). The condensation experiment demonstrates that condensed forsterite crystal shapes are dependent on the condensation environmental temperature. I generate DDSCAT target analog shapes to the condensed crystal shapes. These analog shapes are represented by the three shape classes: 1) equant, 2) a, c-columns, and 3) b-shortened platelets. Each of these shape classes exhibit distinct spectral features that can be used to interpret grain shape characteristics from 8 --- 40 mum spectroscopy of astronomical objects containing crystalline silicates. Synthetic spectral energy distributions (SEDs) of the coma of Hale-Bopp at rh = 2.8 AU are generated by thermally modeling the flux contributions of 5 mineral species present in comets. The synthetic SEDs are constrained using a chi2- minimization technique. The mineral species are amorphous carbon, amorphous pyroxene, amorphous olivine, crystalline enstatite, and crystalline
NASA Astrophysics Data System (ADS)
Modarres, M.; Masouminia, M. R.; Hosseinkhani, H.; Olanj, N.
2016-01-01
In the spirit of performing a complete phenomenological investigation of the merits of Kimber-Martin-Ryskin (KMR) and Martin-Ryskin-Watt (MRW) unintegrated parton distribution functions (UPDF), we have computed the longitudinal structure function of the proton, FL (x, Q2), from the so-called dipole approximation, using the LO and the NLO-UPDF, prepared in the respective frameworks. The preparation process utilizes the PDF of Martin et al., MSTW2008-LO and MSTW2008-NLO, as the inputs. Afterwards, the numerical results are undergone a series of comparisons against the exact kt-factorization and the kt-approximate results, derived from the work of Golec-Biernat and Stasto, against each other and the experimental data from ZEUS and H1 Collaborations at HERA. Interestingly, our results show a much better agreement with the exact kt-factorization, compared to the kt-approximate outcome. In addition, our results are completely consistent with those prepared from embedding the KMR and MRW UPDF directly into the kt-factorization framework. One may point out that the FL, prepared from the KMR UPDF shows a better agreement with the exact kt-factorization. This is despite the fact that the MRW formalism employs a better theoretical description of the DGLAP evolution equation and has an NLO expansion. Such unexpected consequence appears, due to the different implementation of the angular ordering constraint in the KMR approach, which automatically includes the resummation of ln (1 / x), BFKL logarithms, in the LO-DGLAP evolution equation.
Discrete Dipole Approximation for Low-Energy Photoelectron Emission from NaCl Nanoparticles
Berg, Matthew J.; Wilson, Kevin R.; Sorensen, Chris; Chakrabarti, Amit; Ahmed, Musahid
2011-09-22
This work presents a model for the photoemission of electrons from sodium chloride nanoparticles 50-500 nm in size, illuminated by vacuum ultraviolet light with energy ranging from 9.4-10.9 eV. The discrete dipole approximation is used to calculate the electromagnetic field inside the particles, from which the two-dimensional angular distribution of emitted electrons is simulated. The emission is found to favor the particle?s geometrically illuminated side, and this asymmetry is compared to previous measurements performed at the Lawrence Berkeley National Laboratory. By modeling the nanoparticles as spheres, the Berkeley group is able to semi-quantitatively account for the observed asymmetry. Here however, the particles are modeled as cubes, which is closer to their actual shape, and the interaction of an emitted electron with the particle surface is also considered. The end result shows that the emission asymmetry for these low-energy electrons is more sensitive to the particle-surface interaction than to the specific particle shape, i.e., a sphere or cube.
Resonance fluorescence beyond the dipole approximation of a quantum dot in a plasmonic nanostructure
NASA Astrophysics Data System (ADS)
Yang, Chun-Jie; An, Jun-Hong
2016-05-01
The mesoscopic characteristics of a quantum dot (QD), which make the dipole approximation (DA) break down, provide a new dimension to manipulate light-matter interaction [M. L. Andersen et al., Nat. Phys. 7, 215 (2011)], 10.1038/nphys1870. Here we investigate the power spectrum and the second-order correlation property of the fluorescence from a resonantly driven QD placed on a planar metal. It is revealed that due to the pronounced QD spatial extension and the dramatic variation of the triggered surface plasmon near the metal, the fluorescence has a notable contribution from the quadrupole moment. The π -rotation symmetry of the fluorescence to the QD orientation under the DA is broken. By manipulating the QD orientation and quadrupole moment, the spectrum can be switched between the Mollow triplet and a single peak, and the fluorescence characterized by the antibunching in the second-order correlation function can be changed from the weak to the strong radiation regime. Our result is instructive for utilizing the unique mesoscopic effects to develop nanophotonic devices.
Classical dynamics of a charged particle in a laser field beyond the dipole approximation
NASA Astrophysics Data System (ADS)
Jameson, Paul; Khvedelidze, Arsen
2008-05-01
The classical dynamics of a charged particle traveling in a laser field modeled by an elliptically polarized monochromatic electromagnetic plane wave is discussed within the time reparametrization invariant form of the nonrelativistic Hamilton-Jacobi theory. The exact parametric representation for a particle’s orbit in an arbitrary plane wave background beyond the dipole approximation and including effect of the magnetic field is derived. For an elliptically polarized monochromatic plane wave the particle’s trajectory, as an explicit function of the laboratory frame’s time, is given in terms of the Jacobian elliptic functions, whose modulus is proportional to the laser’s intensity and depends on the polarization of radiation. It is shown that the system exposes the intensity duality, correspondence between the motion in the backgrounds with various intensities. In virtue of the modular properties of the Jacobian functions, by starting with the representative “fundamental solution” and applying a certain modular transformation one can obtain the particle’s orbit in the monochromatic plane wave background with arbitrarily prescribed characteristics.
Synthesis, Study, and Discrete Dipole Approximation Simulation of Ag-Au Bimetallic Nanostructures
NASA Astrophysics Data System (ADS)
Hu, Yang; Zhang, An-Qi; Li, Hui-Jun; Qian, Dong-Jin; Chen, Meng
2016-04-01
Water-soluble Ag-Au bimetallic nanostructures were prepared via co-reduction and seed-mediated growth routes employing poly-(4-styrenesulfonic acid-co-maleic acid) (PSSMA) as both a reductant and a stabilizer. Ag-Au alloy nanoparticles were obtained by the co-reduction of AgNO3 and HAuCl4, while Ag-Au core-shell nanostructures were prepared through seed-mediated growth using PSSMA-Au nanoparticle seeds in a heated AgNO3 solution. The optical properties of the Ag-Au alloy and core-shell nanostructures were studied, and the growth mechanism of the bimetallic nanoparticles was investigated. Plasmon resonance bands in the range 422 to 517 nm were observed for Ag-Au alloy nanoparticles, while two plasmon resonances were found in the Ag-Au core-shell nanostructures. Furthermore, discrete dipole approximation theoretical simulation was used to assess the optical property differences between the Ag-Au alloy and core-shell nanostructures. Composition and morphology studies confirmed that the synthesized materials were Ag-Au bimetallic nanostructures.
Synthesis, Study, and Discrete Dipole Approximation Simulation of Ag-Au Bimetallic Nanostructures.
Hu, Yang; Zhang, An-Qi; Li, Hui-Jun; Qian, Dong-Jin; Chen, Meng
2016-12-01
Water-soluble Ag-Au bimetallic nanostructures were prepared via co-reduction and seed-mediated growth routes employing poly-(4-styrenesulfonic acid-co-maleic acid) (PSSMA) as both a reductant and a stabilizer. Ag-Au alloy nanoparticles were obtained by the co-reduction of AgNO3 and HAuCl4, while Ag-Au core-shell nanostructures were prepared through seed-mediated growth using PSSMA-Au nanoparticle seeds in a heated AgNO3 solution. The optical properties of the Ag-Au alloy and core-shell nanostructures were studied, and the growth mechanism of the bimetallic nanoparticles was investigated. Plasmon resonance bands in the range 422 to 517 nm were observed for Ag-Au alloy nanoparticles, while two plasmon resonances were found in the Ag-Au core-shell nanostructures. Furthermore, discrete dipole approximation theoretical simulation was used to assess the optical property differences between the Ag-Au alloy and core-shell nanostructures. Composition and morphology studies confirmed that the synthesized materials were Ag-Au bimetallic nanostructures. PMID:27094823
Model of Jovian F region ionosphere (Jovian ionosphere model in offset dipole approximation)
NASA Technical Reports Server (NTRS)
Tan, A.
1990-01-01
The geomagnetic control of the Earth's atmosphere is well understood. In the F-region and the topside ionosphere, non-electrical forces transport plasma along the magnetic field lines only. In consequence, the worldwide distribution of ionization is strongly dependent on the dip angle. For example, the equatorial anomaly is roughly symmetrical about the dipole equator rather than the geographic. The same appears to be the case in the Jovian ionosphere (Mahajan, 1981). The influence of the magnetic field of Jupiter on its ionization pattern is one of several outstanding topics which need to be studied. Tan (1986) investigated the formation of the equatorial anomaly in the Jovian ionosphere under a centered dipole model. Tan (1988) further studied the effect of the tilt of the Jovian dipole. The results were in broad agreement with those of a diffusive equilibrium model (Tan and Wu, 1981). An off-centered dipole model is constructed and its effects on the ionization pattern are investigated.
Model of Jovian F region ionosphere (Jovian ionosphere model in offset dipole approximation)
NASA Astrophysics Data System (ADS)
Tan, A.
1990-10-01
The geomagnetic control of the Earth's atmosphere is well understood. In the F-region and the topside ionosphere, non-electrical forces transport plasma along the magnetic field lines only. In consequence, the worldwide distribution of ionization is strongly dependent on the dip angle. For example, the equatorial anomaly is roughly symmetrical about the dipole equator rather than the geographic. The same appears to be the case in the Jovian ionosphere (Mahajan, 1981). The influence of the magnetic field of Jupiter on its ionization pattern is one of several outstanding topics which need to be studied. Tan (1986) investigated the formation of the equatorial anomaly in the Jovian ionosphere under a centered dipole model. Tan (1988) further studied the effect of the tilt of the Jovian dipole. The results were in broad agreement with those of a diffusive equilibrium model (Tan and Wu, 1981). An off-centered dipole model is constructed and its effects on the ionization pattern are investigated.
Wei, Guoke; Wang, Jinliang; Chen, Yu
2015-01-01
The enhancement factor (EF) of surface-enhanced Raman scattering (SERS) from two-dimensional (2D) hexagonal silver nanorod (AgNR) arrays were investigated in terms of electromagnetic (EM) mechanism by using the discrete dipole approximation (DDA) method. The dependence of EF on several parameters, i.e., structure, length, excitation wavelength, incident angle and polarization, and gap size has been investigated. "Hotspots" were found distributed in the gaps between adjacent nanorods. Simulations of AgNR arrays of different lengths revealed that increasing the rod length from 374 to 937 nm (aspect ratio from 2.0 to 5.0) generated more "hotspots" but not necessarily increased EF under both 514 and 532 nm excitation. A narrow lateral gap (in the incident plane) was found to result in strong EF, while the dependence of EF on the diagonal gap (out of the incident plane) showed an oscillating behavior. The EF of the array was highly dependent on the angle and polarization of the incident light. The structure of AgNR and the excitation wavelength were also found to affect the EF. The EF of random arrays was stronger than that of an ordered one with the same average gap of 21 nm, which could be explained by the exponential dependence of EF on the lateral gap size. Our results also suggested that absorption rather than extinction or scattering could be a good indicator of EM enhancement. It is expected that the understanding of the dependence of local field enhancement on the structure of the nanoarrays and incident excitations will shine light on the optimal design of efficient SERS substrates and improved performance. PMID:25821708
Wei, Guoke; Wang, Jinliang
2015-01-01
Summary The enhancement factor (EF) of surface-enhanced Raman scattering (SERS) from two-dimensional (2D) hexagonal silver nanorod (AgNR) arrays were investigated in terms of electromagnetic (EM) mechanism by using the discrete dipole approximation (DDA) method. The dependence of EF on several parameters, i.e., structure, length, excitation wavelength, incident angle and polarization, and gap size has been investigated. “Hotspots” were found distributed in the gaps between adjacent nanorods. Simulations of AgNR arrays of different lengths revealed that increasing the rod length from 374 to 937 nm (aspect ratio from 2.0 to 5.0) generated more “hotspots” but not necessarily increased EF under both 514 and 532 nm excitation. A narrow lateral gap (in the incident plane) was found to result in strong EF, while the dependence of EF on the diagonal gap (out of the incident plane) showed an oscillating behavior. The EF of the array was highly dependent on the angle and polarization of the incident light. The structure of AgNR and the excitation wavelength were also found to affect the EF. The EF of random arrays was stronger than that of an ordered one with the same average gap of 21 nm, which could be explained by the exponential dependence of EF on the lateral gap size. Our results also suggested that absorption rather than extinction or scattering could be a good indicator of EM enhancement. It is expected that the understanding of the dependence of local field enhancement on the structure of the nanoarrays and incident excitations will shine light on the optimal design of efficient SERS substrates and improved performance. PMID:25821708
NASA Astrophysics Data System (ADS)
Moteki, Nobuhiro
2016-07-01
An accurate and efficient simulation of light scattering by an atmospheric black carbon (BC)-containing aerosol-a fractal-like cluster of hundreds of carbon monomers that is internally mixed with other aerosol compounds such as sulfates, organics, and water-remains challenging owing to the enormous diversities of such aerosols' size, shape, and mixing state. Although the discrete dipole approximation (DDA) is theoretically an exact numerical method that is applicable to arbitrary non-spherical inhomogeneous targets, in practice, it suffers from severe granularity-induced error and degradation of computational efficiency for such extremely complex targets. To solve this drawback, we propose herein a hybrid DDA method designed for arbitrary BC-containing aerosols: the monomer-dipole assumption is applied to a cluster of carbon monomers, whereas the efficient cubic-lattice discretization is applied to the remaining particle volume consisting of other materials. The hybrid DDA is free from the error induced by the surface granularity of carbon monomers that occurs in conventional cubic-lattice DDA. In the hybrid DDA, we successfully mitigate the artifact of neglecting the higher-order multipoles in the monomer-dipole assumption by incorporating the magnetic dipole in addition to the electric dipole into our DDA formulations. Our numerical experiments show that the hybrid DDA method is an efficient light-scattering solver for BC-containing aerosols in arbitrary mixing states. The hybrid DDA could be also useful for a cluster of metallic nanospheres associated with other dielectric materials.
Atoms and molecules in intense attosecond fields: beyond the dipole approximation
NASA Astrophysics Data System (ADS)
Førre, M.; Hansen, J. P.; Kocbach, L.; Selstø, S.; Kjeldsen, T. K.; Madsen, L. B.
2007-11-01
The exact non-dipole minimal-coupling Hamiltonian for an atomic system interacting with an explicitly time- and space-dependent laser field is transformed into the rest frame of a classical free electron in the laser field, i.e., into the Kramers-Henneberger frame. The new form of the Hamiltonian has been used to study the non-dipole dynamics of atoms and molecules in intense XUV laser pulses. The time-dependent Schrödinger equation is solved without any simplifications.
Barbieri, C.; Martinez-Pinedo, G.; Caurier, E.; Langanke, K.
2008-02-15
The occurrence of a pygmy dipole resonance in proton rich {sup 32,34}Ar is studied using the unitary correlator operator method interaction V{sub UCOM}, based on Argonne V18. Predictions from the random-phase approximation (RPA) and the shell model in a no-core basis are compared. It is found that the inclusion of configuration mixing up to two-particles-two-holes broadens the pygmy strength slightly and reduces sensibly its strength, as compared to the RPA predictions. For {sup 32}Ar, a clear peak associated with a pygmy resonance is found. For {sup 34}Ar, the pygmy states are obtained close to the giant dipole resonance and mix with it.
NASA Technical Reports Server (NTRS)
Omidvar, K.
1971-01-01
Expressions for the excitation cross section of the highly excited states of the hydrogenlike atoms by fast charged particles have been derived in the dipole approximation of the semiclassical impact parameter and the Born approximations, making use of a formula for the asymptotic expansion of the oscillator strength of the hydrogenlike atoms given by Menzel. When only the leading term in the asymptotic expansion is retained, the expression for the cross section becomes identical to the expression obtained by the method of the classical collision and correspondence principle given by Percival and Richards. Comparisons are made between the Bethe coefficients obtained here and the Bethe coefficients of the Born approximation for transitions where the Born calculation is available. Satisfactory agreement is obtained only for n yields n + 1 transitions, with n the principal quantum number of the excited state.
NASA Technical Reports Server (NTRS)
Draine, B. T.; Goodman, Jeremy
1993-01-01
We derive the dispersion relation for electromagnetic waves propagating on a lattice of polarizable points. From this dispersion relation we obtain a prescription for choosing dipole polarizabilities so that an infinite lattice with finite lattice spacing will mimic a continuum with dielectric constant. The discrete dipole approximation is used to calculate scattering and absorption by a finite target by replacing the target with an array of point dipoles. We compare different prescriptions for determining the dipole polarizabilities. We show that the most accurate results are obtained when the lattice dispersion relation is used to set the polarizabilities.
NASA Astrophysics Data System (ADS)
Predota, Milan; Cummings, Peter T.; Chialvo, Ariel A.
The adiabatic nuclear and electronic sampling method (ANES), originally formulated as an efficient Monte Carlo algorithm for systems with fluctuating charges, is applied to the simulation of a polarizable water model with induced dipole moments. Structural, thermodynamic and dipolar properties obtained by ANES and a newer algorithm, the pair approximation for polarization interaction (PAPI), are compared with full iteration. With the best parameters, the inaccuracy of both approximate methods was found to be comparable with the uncertainty of the full iteration. The PAPI method with iteration radius equal to the second minimum of the oxygen-oxygen correlation function is, depending on the convergence tolerance, 10-15 times faster than the full iteration for 256 molecules, and yields very accurate structure and thermodynamics with deviation about 0.3%. When the iteration radius is increased to the cutoff distance, exact results are recovered at the cost of decreased efficiency. The ANES method with small nuclear displacements proved to inefficiently sample the configurational space. Simulations at low electronic temperatures with large nuclear displacements are inaccurate for up to 100 electronic moves, and increasing this number would make the simulations as slow as the full iteration. The most accurate and efficient adiabatic ANES simulations are those with infinite electronic temperature, large nuclear displacements and 1-10 electronic moves. The extra freedom of induced dipoles in the ANES method at high electronic temperatures modifies the observed dipolar properties; however, the question of whether the dielectric constant is also modified needs further consideration.
NASA Astrophysics Data System (ADS)
Skorupski, Krzysztof
2015-05-01
Black carbon (BC) particles are a product of incomplete combustion of carbon-based fuels. One of the possibilities of studying the optical properties of BC structures is to use the DDA (Discrete Dipole Approximation) method. The main goal of this work was to investigate its accuracy and to approximate the most reliable simulation parameters. For the light scattering simulations the ADDA code was used and for the reference program the superposition T-Matrix code by Mackowski was selected. The study was divided into three parts. First, DDA simulations for a single particle (sphere) were performed. The results proved that the meshing algorithm can significantly affect the particle shape, and therefore, the extinction diagrams. The volume correction procedure is recommended for sparse or asymmetrical meshes. In the next step large fractal-like aggregates were investigated. When sparse meshes are used, the impact of the volume correction procedure cannot be easily predicted. In some cases it can even lead to more erroneous results. Finally, the optical properties of fractal-like aggregates composed of spheres in point contact were compared to much more realistic structures made up of connected, non-spherical primary particles.
abcpmc: Approximate Bayesian Computation for Population Monte-Carlo code
NASA Astrophysics Data System (ADS)
Akeret, Joel
2015-04-01
abcpmc is a Python Approximate Bayesian Computing (ABC) Population Monte Carlo (PMC) implementation based on Sequential Monte Carlo (SMC) with Particle Filtering techniques. It is extendable with k-nearest neighbour (KNN) or optimal local covariance matrix (OLCM) pertubation kernels and has built-in support for massively parallelized sampling on a cluster using MPI.
NASA Astrophysics Data System (ADS)
Haiwei, Mu; Jingwei, Lv; Zhaoting, Liu; Shijie, Zheng; Lin, Yang; Tao, Sun; Qiang, Liu; Chao, Liu
2016-04-01
Optical properties of localized surface plasmon resonances (LSPR) of Ag/ITO sliced nanosphere have been studied using discrete dipole approximation and plasmon hybridization theory. It is found that different morphologies of sliced nanosphere can induce distinctive features in the extinction spectra. In the meanwhile, gap distances and refractive index of the surrounding medium could modulate the plasmon hybridization and the LSPR shifting. At large separation, the shift of LSPR peaks for the nanosphere sliced in halves consisting of ITO and Ag is small and insensitive to the gap distance in the weak coupling, whereas smaller separation exhibits a distinct red shift. Additionally, multiple resonance peaks are excited for the nanosphere sliced in quarters consisting of ITO and Ag. In this situation, electric field is mainly distributed in the gap region of sliced nanosphere and the central point. These results indicate that different morphologies of sliced nanosphere could create abundant tunable LSPR modes, which provides potential for multiplex optical sensing.
Calculation of electric dipole hypershieldings at the nuclei in the Hellmann-Feynman approximation.
Soncini, Alessandro; Lazzeretti, Paolo; Bakken, Vebjørn; Helgaker, Trygve
2004-02-15
The third-rank electric hypershieldings at the nuclei of four small molecules have been evaluated at the Hartree-Fock level of theory in the Hellmann-Feynman approximation. The nuclear electric hypershieldings are closely related to molecular vibrational absorption intensities and a generalization of the atomic polar tensors (expanded in powers of the electric field strength) is proposed to rationalize these intensities. It is shown that the sum rules for rototranslational invariance and the constraints imposed by the virial theorem provide useful criteria for basis-set completeness and for near Hartree-Fock quality of nuclear shieldings and hypershieldings evaluated in the Hellmann-Feynman approximation. Twelve basis sets of different size and quality have been employed for the water molecule in an extended numerical test on the practicality of the proposed scheme. The best results are obtained with the R12 and R12+ basis sets, designed for the calculation of electronic energies by the explicitly correlated R12 method. The R12 basis set is subsequently used to investigate three other molecules, CO, N2, and NH3, verifying that the R12 basis consistently performs very well. PMID:15268466
NASA Astrophysics Data System (ADS)
Palade, D. I.; Baran, V.
2016-09-01
We generalize the schematic model based on the Random Phase Approximation (RPA) with separable interaction, to a collection of subspaces of ph excitations which interact with different coupling constants. This ansatz notably lowers the numerical effort involved, by reducing the RPA eigenvalue problem to a finite small dimensional system of equation. We derive the associated dispersion relation and the normalization condition for the newly defined unknowns of the system. In contrast with the standard separable approach, the present formalism is able to describe more than one collective excitation even in the degenerate limit, giving also access to the nature of the resonance. The theoretical framework is tested investigating the dipolar oscillations in various neutral and singly charged sodium clusters and C 60 fullerene with results in good agreement with full RPA calculations and experimental data. It is proven that the 40 eV resonance present in photoabsorption spectra of C 60 is a localized surface plasmon.
NASA Astrophysics Data System (ADS)
Bamler, Robert; Rosch, Achim
2015-06-01
The presence of (approximate) conservation laws can prohibit the fast relaxation of interacting many-particle quantum systems. We investigate this physics by studying the center-of-mass oscillations of two species of fermionic ultracold atoms in a harmonic trap. If their trap frequencies are equal, a dynamical symmetry (spectrum-generating algebra), closely related to Kohn's theorem, prohibits the relaxation of center-of-mass oscillations. A small detuning δ ω of the trap frequencies for the two species breaks the dynamical symmetry and ultimately leads to a damping of dipole oscillations driven by interspecies interactions. Using memory-matrix methods, we calculate the relaxation as a function of frequency difference, particle number, temperature, and strength of interspecies interactions. When interactions dominate, there is almost perfect drag between the two species and the dynamical symmetry is approximately restored. The drag can either arise from Hartree potentials or from friction. In the latter case (hydrodynamic limit), the center-of-mass oscillations decay with a tiny rate, 1 /τ ∝(δω ) 2/Γ , where Γ is a single-particle scattering rate.
Kleinig, W.; Nesterenko, V. O.; Kvasil, J.; Vesely, P.; Reinhard, P.-G.
2008-10-15
The E1(T=1) isovector dipole giant resonance (GDR) in heavy and superheavy deformed nuclei is analyzed over a sample of 18 rare-earth nuclei, four actinides, and three chains of superheavy elements (Z=102, 114, and 120). The basis of the description is the self-consistent separable random-phase approximation (SRPA) using the Skyrme force SLy6. The model well reproduces the experimental data in the rare-earth and actinide regions. The trend of the resonance peak energies follows the estimates from collective models, showing a bias to the volume mode for the rare-earth isotopes and a mix of volume and surface modes for actinides and superheavy elements. The widths of the GDR are mainly determined by the Landau fragmentation, which in turn is found to be strongly influenced by deformation. A deformation splitting of the GDR can contribute to about one-third of the width, and about 1 MeV further broadening can be associated with mechanisms beyond the SRPA description (e.g., escape widths and coupling with complex configurations)
Dumitru, Adrian; Jalilian-Marian, Jamal
2010-10-01
Present knowledge of QCD n-point functions of Wilson lines at high energies is rather limited. In practical applications, it is therefore customary to factorize higher n-point functions into products of two-point functions (dipoles) which satisfy the Balitsky-Kovchegov-evolution equation. We employ the Jalilian-Marian-Iancu-McLerran-Weigert-Leonidov-Kovner formalism to derive explicit evolution equations for the 4- and 6-point functions of fundamental Wilson lines and show that if the Gaussian approximation is carried out before the rapidity evolution step is taken, then many leading order N{sub c} contributions are missed. Our evolution equations could specifically be used to improve calculations of forward dijet angular correlations, recently measured by the STAR Collaboration in deuteron-gold collisions at the RHIC collider. Forward dijets in proton-proton collisions at the LHC probe QCD evolution at even smaller light-cone momentum fractions. Such correlations may provide insight into genuine differences between the Jalilian-Marian-Iancu-McLerran-Weigert-Leonidov-Kovner and Balitsky-Kovchegov approaches.
NASA Astrophysics Data System (ADS)
Konoshonkin, Alexander V.; Kustova, Natalia V.; Borovoi, Anatoli G.
2015-10-01
The open-source beam-splitting code is described which implements the geometric-optics approximation to light scattering by convex faceted particles. This code is written in C++ as a library which can be easy applied to a particular light scattering problem. The code uses only standard components, that makes it to be a cross-platform solution and provides its compatibility to popular Integrated Development Environments (IDE's). The included example of solving the light scattering by a randomly oriented ice crystal is written using Qt 5.1, consequently it is a cross-platform solution, too. Both physical and computational aspects of the beam-splitting algorithm are discussed. Computational speed of the beam-splitting code is obviously higher compared to the conventional ray-tracing codes. A comparison of the phase matrix as computed by our code with the ray-tracing code by A. Macke shows excellent agreement.
NASA Astrophysics Data System (ADS)
Nowell, Holly Kreutzer
Although spheres and spheroids have been used extensively by researchers as convenient models to approximate "snowflakes" when computing their microwave scattering properties, recent research indicates that the scattering properties of more accurately simulated snowflakes are fundamentally different from the simplified models. To resolve this well-recognized discrepancy, a new snowflake aggregation model is developed in this study and the microwave single-scattering properties of the modeled aggregate snowflakes are characterized for use in radiative transfer modeling and remote sensing algorithm development. Three different aggregate snowflake types (rounded, oblate and prolate) are generated by random aggregation of 6-bullet rosettes constrained by size-density relationships derived from previous field observations. Additionally, they are further constrained to empirically determined aspect ratios (ar) and fractal dimensions (df) of aggregate flakes. Due to random generation, aggregates may have the same size or mass, yet different morphology, allowing for a study into how detailed structure influences an individual flake's scattering properties. Single-scattering properties of the aggregates were investigated using discrete dipole approximation (DDA) at 10 frequencies: 10.65, 13.6, 18.7, 23.8, 35.6, 36.5, 89.0, 94.0, 165.5 and 183.31 GHz. All of these frequencies are currently used in instruments (radar and radiometers) aboard satellites involved in the research of atmospheric ice particles. Results from DDA were compared to those of Mie theory for solid and soft spheres (with a density 10% that of solid ice) and to T-matrix results for solid and soft spheroidal cases with ar values of 0.8 and 0.6 dependent on flake type (rounded, oblate or prolate). Analyzing modeling results, it is found that above size parameter 0.75, neither solid nor soft sphere and spheroidal approximations accurately represented the DDA results for all aggregate types. The asymmetry
NASA Astrophysics Data System (ADS)
Meath, William J.; Jagatap, B. N.
2011-10-01
One of the purposes of this paper is to develop an analytical many-level generalized rotating wave approximation (GRWA), including the effects of permanent dipoles, for the excitation of many-level molecules through the simultaneous absorption of two photons. Included are expressions for the two-photon laser-molecule coupling C, and its two components Cd and Cv corresponding to the direct permanent dipole and the virtual state excitation mechanisms, respectively, and related observables such as the time-dependent populations of the initial and final states of the excitation process and resonance profiles. This GRWA treatment also includes an energy shift parameter ɛ, which causes shifts in the position of the resonance energy as the laser intensity increases. The effects of permanent dipoles are very different in Cv and ɛ versus Cd. These effects have been discussed previously for Cd using analytic two-level RWA approaches. The analytical results for Cv and ɛ obtained here are new as is their use in discussing the influence of permanent dipoles in the parts of the two-photon excitation process involving virtual states. In the absence of permanent dipoles Cd is zero whereas Cv and ɛ are not; they equal the corresponding perturbation theory results. The GRWA and perturbative results are related by Bessel function damping functions which, for dipolar molecules, damp out the divergence of the perturbative results as the laser intensity increases. Illustrative examples are given for a two-photon excitation involving a model chromophore which has a significant virtual state contribution through both the laser-molecule coupling and the energy shift parameter.
NASA Astrophysics Data System (ADS)
Guillaume, Stéphane-Olivier; de Abajo, F. Javier García; Henrard, Luc
2013-12-01
An efficient procedure is introduced for the calculation of the optical response of individual and coupled metallic nanoparticles in the framework of the discrete-dipole approximation (DDA). We introduce a modal expansion in the basis set of discrete dipoles and show that a few suitably selected modes are sufficient to compute optical spectra with reasonable accuracy, thus reducing the required numerical effort relative to other DDA approaches. Our method offers a natural framework for the study of localized plasmon modes, including plasmon hybridization. As a proof of concept, we investigate optical extinction and electron energy-loss spectra of monomers, dimers, and quadrumers formed by flat silver squares. This method should find application to the previously prohibited simulation of complex particle arrays.
NASA Astrophysics Data System (ADS)
Feng, Bin; Zhang, Chengshuo; Xu, Baoshu; Shi, Zelin
2015-11-01
Artefacts and noise degrade the decoded image of a wavefront coding infrared imaging system, which usually results in the decoded image being inferior to the in-focus infrared image of a conventional infrared imaging system. The previous letter showed that the decoded image fell behind the in-focus infrared image. For comparison, a bar target experiment at temperature of 20°C and two groups of outdoor experiments at temperatures of 28°C and 70°C are respectively conducted. Experimental results prove that a wavefront coding infrared imaging system can achieve the decoded image being approximating to its corresponding in-focus infrared image.
Gambacurta, D.; Catara, F.
2011-09-15
Low-energy dipole excitations are analyzed for the stable isotopes {sup 40}Ca and {sup 48}Ca in the framework of the Skyrme-second random-phase approximation. The corresponding random-phase approximation calculations provide a negligible strength distribution for both nuclei in the energy region from 5 to 10 MeV. The inclusion and the coupling of 2 particle-2 hole configurations in the second random-phase approximation lead to an appreciable dipole response at low energies for the neutron-rich nucleus {sup 48}Ca. The presence of a neutron skin in the nucleus {sup 48}Ca would suggest the interpretation of the low-lying response in terms of a pygmy excitation. The composition of the excitation modes (content of 1 particle-1 hole and 2 particle-2 hole configurations), their transition densities and their collectivity (number and coherence of the different contributions) are analyzed. This analysis indicates that, in general, these excitations cannot be clearly interpreted in terms of oscillations of the neutron skin against the core with the exception of the peak with the largest B(E1) value, which is located at 9.09 MeV. For this peak the neutron transition density dominates and the neutron and proton transition densities oscillate out of phase in the internal part of the nucleus leading to a strong mixing of isoscalar and isovector components. Therefore, this state shows some features usually associated to pygmy resonances.
BILAM: a composite laminate failure-analysis code using bilinear stress-strain approximations
McLaughlin, P.V. Jr.; Dasgupta, A.; Chun, Y.W.
1980-10-01
The BILAM code which uses constant strain laminate analysis to generate in-plane load/deformation or stress/strain history of composite laminates to the point of laminate failure is described. The program uses bilinear stress-strain curves to model layer stress-strain behavior. Composite laminates are used for flywheels. The use of this computer code will help to develop data on the behavior of fiber composite materials which can be used by flywheel designers. In this program the stress-strain curves are modelled by assuming linear response in axial tension while using bilinear approximations (2 linear segments) for stress-strain response to axial compressive, transverse tensile, transverse compressive and axial shear loadings. It should be noted that the program attempts to empirically simulate the effects of the phenomena which cause nonlinear stress-strain behavior, instead of mathematically modelling the micromechanics involved. This code, therefore, performs a bilinear laminate analysis, and, in conjunction with several user-defined failure interaction criteria, is designed to provide sequential information on all layer failures up to and including the first fiber failure. The modus operandi is described. Code BILAM can be used to: predict the load-deformation/stress-strain behavior of a composite laminate subjected to a given combination of in-plane loads, and make analytical predictions of laminate strength.
List, Nanna Holmgaard Jensen, Hans Jørgen Aagaard; Kauczor, Joanna; Norman, Patrick; Saue, Trond
2015-06-28
We present a formulation of molecular response theory for the description of a quantum mechanical molecular system in the presence of a weak, monochromatic, linearly polarized electromagnetic field without introducing truncated multipolar expansions. The presentation focuses on a description of linear absorption by adopting the energy-loss approach in combination with the complex polarization propagator formulation of response theory. Going beyond the electric-dipole approximation is essential whenever studying electric-dipole-forbidden transitions, and in general, non-dipolar effects become increasingly important when addressing spectroscopies involving higher-energy photons. These two aspects are examined by our study of the near K-edge X-ray absorption fine structure of the alkaline earth metals (Mg, Ca, Sr, Ba, and Ra) as well as the trans-polyenes. In following the series of alkaline earth metals, the sizes of non-dipolar effects are probed with respect to increasing photon energies and a detailed assessment of results is made in terms of studying the pertinent transition electron densities and in particular their spatial extension in comparison with the photon wavelength. Along the series of trans-polyenes, the sizes of non-dipolar effects are probed for X-ray spectroscopies on organic molecules with respect to the spatial extension of the chromophore.
Martini, M.; Peru, S.; Dupuis, M.
2011-03-15
Low-energy dipole excitations in neon isotopes and N=16 isotones are calculated with a fully consistent axially-symmetric-deformed quasiparticle random phase approximation (QRPA) approach based on Hartree-Fock-Bogolyubov (HFB) states. The same Gogny D1S effective force has been used both in HFB and QRPA calculations. The microscopical structure of these low-lying resonances, as well as the behavior of proton and neutron transition densities, are investigated in order to determine the isoscalar or isovector nature of the excitations. It is found that the N=16 isotones {sup 24}O, {sup 26}Ne, {sup 28}Mg, and {sup 30}Si are characterized by a similar behavior. The occupation of the 2s{sub 1/2} neutron orbit turns out to be crucial, leading to nontrivial transition densities and to small but finite collectivity. Some low-lying dipole excitations of {sup 28}Ne and {sup 30}Ne, characterized by transitions involving the {nu}1d{sub 3/2} state, present a more collective behavior and isoscalar transition densities. A collective proton low-lying excitation is identified in the {sup 18}Ne nucleus.
O’Brien, Daniel B.; Massari, Aaron M.
2015-01-14
In the field of vibrational sum frequency generation spectroscopy (VSFG) applied to organic thin film systems, a significant challenge to data analysis is in the accurate description of optical interference effects. Herein, we provide experimental evidence that a model recently developed in our lab provides an accurate description of this phenomenon. We studied the organic small molecule N,N′-dioctyl-3,4,9,10-perylenedicarboximide vapor deposited as a thickness gradient on silicon wafer substrates with two oxide thicknesses and two surface preps. VSFG data were obtained using the ssp and the sps polarization combinations in the imide carbonyl stretching region as a function of organic thickness. In this first of two reports, the data are modeled and interpreted within the ubiquitous electric dipole approximation for VSFG. The intrinsic sample responses are parameterized during the fitting routines while optical interference effects are simply calculated from the model using known refractive indices, thin film thicknesses, and beam angles. The results indicate that the thin film model provides a good description of optical interferences, indicating that interfacial terms are significant. Inconsistencies between the fitting results within the bounds of the electric dipole response motivate deliberation for additional effects to be considered in the second report.
List, Nanna Holmgaard; Kauczor, Joanna; Saue, Trond; Jensen, Hans Jørgen Aagaard; Norman, Patrick
2015-06-28
We present a formulation of molecular response theory for the description of a quantum mechanical molecular system in the presence of a weak, monochromatic, linearly polarized electromagnetic field without introducing truncated multipolar expansions. The presentation focuses on a description of linear absorption by adopting the energy-loss approach in combination with the complex polarization propagator formulation of response theory. Going beyond the electric-dipole approximation is essential whenever studying electric-dipole-forbidden transitions, and in general, non-dipolar effects become increasingly important when addressing spectroscopies involving higher-energy photons. These two aspects are examined by our study of the near K-edge X-ray absorption fine structure of the alkaline earth metals (Mg, Ca, Sr, Ba, and Ra) as well as the trans-polyenes. In following the series of alkaline earth metals, the sizes of non-dipolar effects are probed with respect to increasing photon energies and a detailed assessment of results is made in terms of studying the pertinent transition electron densities and in particular their spatial extension in comparison with the photon wavelength. Along the series of trans-polyenes, the sizes of non-dipolar effects are probed for X-ray spectroscopies on organic molecules with respect to the spatial extension of the chromophore. PMID:26133414
NASA Astrophysics Data System (ADS)
O'Brien, Daniel B.; Massari, Aaron M.
2015-01-01
In the field of vibrational sum frequency generation spectroscopy (VSFG) applied to organic thin film systems, a significant challenge to data analysis is in the accurate description of optical interference effects. Herein, we provide experimental evidence that a model recently developed in our lab provides an accurate description of this phenomenon. We studied the organic small molecule N,N'-dioctyl-3,4,9,10-perylenedicarboximide vapor deposited as a thickness gradient on silicon wafer substrates with two oxide thicknesses and two surface preps. VSFG data were obtained using the ssp and the sps polarization combinations in the imide carbonyl stretching region as a function of organic thickness. In this first of two reports, the data are modeled and interpreted within the ubiquitous electric dipole approximation for VSFG. The intrinsic sample responses are parameterized during the fitting routines while optical interference effects are simply calculated from the model using known refractive indices, thin film thicknesses, and beam angles. The results indicate that the thin film model provides a good description of optical interferences, indicating that interfacial terms are significant. Inconsistencies between the fitting results within the bounds of the electric dipole response motivate deliberation for additional effects to be considered in the second report.
Calculations of the giant-dipole-resonance photoneutrons using a coupled EGS4-morse code
Liu, J.C.; Nelson, W.R.; Kase, K.R.; Mao, X.S.
1995-10-01
The production and transport of the photoneutrons from the giant-dipoleresonance reaction have been implemented in a coupled EGS4-MORSE code. The total neutron yield (including both the direct neutron and evaporation neutron components) is calculated by folding the photoneutron yield cross sections with the photon track length distribution in the target. Empirical algorithms based on the measurements have been developed to estimate the fraction and energy of the direct neutron component for each photon. The statistical theory in the EVAP4 code, incorporated as a MORSE subroutine, is used to determine the energies of the evaporation neutrons. These represent major improvements over other calculations that assumed no direct neutrons, a constant fraction of direct neutrons, monoenergetic direct neutron, or a constant nuclear temperature for the evaporation neutrons. It was also assumed that the slow neutrons (< 2.5 MeV) are emitted isotropically and the fast neutrons are emitted anisotropically in the form of 1+Csin{sup 2}{theta}, which have a peak emission at 900. Comparisons between the calculated and the measured photoneutron results (spectra of the direct, evaporation and total neutrons; nuclear temperatures; direct neutron fractions) for materials of lead, tungsten, tantalum and copper have been made. The results show that the empirical algorithms, albeit simple, can produce reasonable results over the interested photon energy range.
Determination of recombination radius in Si for binary collision approximation codes
Vizkelethy, Gyorgy; Foiles, Stephen M.
2015-09-11
Displacement damage caused by ions or neutrons in microelectronic devices can have significant effect on the performance of these devices. Therefore, it is important to predict not only the displacement damage profile, but also its magnitude precisely. Analytical methods and binary collision approximation codes working with amorphous targets use the concept of displacement energy, the energy that a lattice atom has to receive to create a permanent replacement. It was found that this “displacement energy” is direction dependent; it can range from 12 to 32 eV in silicon. Obviously, this model fails in BCA codes that work with crystalline targets, such as Marlowe. Marlowe does not use displacement energy; instead, it uses lattice binding energy only and then pairs the interstitial atoms with vacancies. Then based on the configuration of the Frenkel pairs it classifies them as close, near, or distant pairs, and considers the distant pairs the permanent replacements. Unfortunately, this separation is an ad hoc assumption, and the results do not agree with molecular dynamics calculations. After irradiation, there is a prompt recombination of interstitials and vacancies if they are nearby, within a recombination radius. In order to implement this recombination radius in Marlowe, we used the comparison of MD and Marlowe calculation in a range of ion energies in single crystal silicon target. As a result, the calculations showed that a single recombination radius of ~7.4 Å in Marlowe for a range of ion energies gives an excellent agreement with MD.
Determination of recombination radius in Si for binary collision approximation codes
NASA Astrophysics Data System (ADS)
Vizkelethy, Gyorgy; Foiles, Stephen M.
2016-03-01
Displacement damage caused by ions or neutrons in microelectronic devices can have significant effect on the performance of these devices. Therefore, it is important to predict not only the displacement damage profile, but also its magnitude precisely. Analytical methods and binary collision approximation codes working with amorphous targets use the concept of displacement energy, the energy that a lattice atom has to receive to create a permanent replacement. It was found that this "displacement energy" is direction dependent; it can range from 12 to 32 eV in silicon. Obviously, this model fails in BCA codes that work with crystalline targets, such as Marlowe. Marlowe does not use displacement energy; instead, it uses lattice binding energy only and then pairs the interstitial atoms with vacancies. Then based on the configuration of the Frenkel pairs it classifies them as close, near, or distant pairs, and considers the distant pairs the permanent replacements. Unfortunately, this separation is an ad hoc assumption, and the results do not agree with molecular dynamics calculations. After irradiation, there is a prompt recombination of interstitials and vacancies if they are nearby, within a recombination radius. In order to implement this recombination radius in Marlowe, we used the comparison of MD and Marlowe calculation in a range of ion energies in single crystal silicon target. The calculations showed that a single recombination radius of ∼7.4 Å in Marlowe for a range of ion energies gives an excellent agreement with MD.
Determination of recombination radius in Si for binary collision approximation codes
Vizkelethy, Gyorgy; Foiles, Stephen M.
2015-09-11
Displacement damage caused by ions or neutrons in microelectronic devices can have significant effect on the performance of these devices. Therefore, it is important to predict not only the displacement damage profile, but also its magnitude precisely. Analytical methods and binary collision approximation codes working with amorphous targets use the concept of displacement energy, the energy that a lattice atom has to receive to create a permanent replacement. It was found that this “displacement energy” is direction dependent; it can range from 12 to 32 eV in silicon. Obviously, this model fails in BCA codes that work with crystalline targets,more » such as Marlowe. Marlowe does not use displacement energy; instead, it uses lattice binding energy only and then pairs the interstitial atoms with vacancies. Then based on the configuration of the Frenkel pairs it classifies them as close, near, or distant pairs, and considers the distant pairs the permanent replacements. Unfortunately, this separation is an ad hoc assumption, and the results do not agree with molecular dynamics calculations. After irradiation, there is a prompt recombination of interstitials and vacancies if they are nearby, within a recombination radius. In order to implement this recombination radius in Marlowe, we used the comparison of MD and Marlowe calculation in a range of ion energies in single crystal silicon target. As a result, the calculations showed that a single recombination radius of ~7.4 Å in Marlowe for a range of ion energies gives an excellent agreement with MD.« less
NASA Astrophysics Data System (ADS)
Short, Mitchell R.
Nanotechnology has become so widely used it can be found in every aspect of life, from cell-phones and computers, to cars, and even athletic socks. As it permeates so many markets, the need for supplemental technologies has also increased. One such needed technology is in the area of nanoscale characterization. Current imaging methods are advanced; however, they do not have the capabilities to characterize the size, shape, composition, and arrangement of nanostructures and nanoparticles in a real-time, unobtrusive manner. The Polarized-Surface-Wave-Scattering system (PSWSS) is a method being researched at the University of Utah that can provide such characterization, although in order for the PSWSS to function accurately through inversion techniques, a predictive forward model must be developed and validated. This work explores the discrete dipole approximation with surface interaction (DDA-SI), an open source MATLAB toolbox, as a predictive model to calculate electromagnetic scattering by objects on a surface illuminated by an evanescent wave generated by total internal reflection (TIR). Far-field scattering predictions via DDA-SI are validated against scaled microwave experimental results for two objects on a surface: a sphere with a diameter of lambda/1.92 and a cube with a side length of lambda/1.785, where lambda refers to the wavelength. A good agreement between experiments and simulations is observed, especially when modified Fresnel reflection coefficients are employed by DDA-SI. Programs to calculate the amplitude scattering matrix and Mueller matrix elements have been also been created. Additionally, the sensitivity of four Mueller matrix elements (M11, M12, M21, and M22) to the particle size, material (gold and silver), shape (sphere and cube), and interparticle spacing, is analyzed. It is found that these four elements are sensitive to changes in shape and interparticle spacing, whereas prove insufficient to difference in material and sizes smaller than
NASA Technical Reports Server (NTRS)
Schmit, L. A.; Miura, H.
1975-01-01
The creation of an efficient automated capability for minimum weight design of structures is reported. The ACCESS 1 computer program combines finite element analysis techniques and mathematical programming algorithms using an innovative collection of approximation concepts. Design variable linking, constraint deletion techniques and approximate analysis methods are used to generate a sequence of small explicit mathematical programming problems which retain the essential features of the design problem. Organization of the finite element analysis is carefully matched to the design optimization task. The efficiency of the ACCESS 1 program is demonstrated by giving results for several example problems.
NASA Astrophysics Data System (ADS)
Brieger, M.; Renn, A.; Sodeik, A.; Hese, A.
1983-02-01
Continuing our Stark quantum beat experiments on 7LiH at electric field strengths of 100 kV/cm and above, we were le to observe quantum beat signals for the vibrational level v' = 5 of the A 1v+ state. The evaluation of these signals yields a field reduced splitting Δ W/ E2 = 1.157(70) kHz/(kV/cm) 2 which would correspond to an "effective" value of 1μ eff( v' = 5)1 = 0.051 (5) D for the dipole moment, if the ordinarily used formula were applicable. A serious check of all available data, however, shows that neighbouring vibrational levels of the A 1v+ state and also the sum over the levels of the electronic ground state X 1Σ +, though counteracting, have the main effect on the residual splitting thus preventing a straightforward evaluation for the dipole moment. Taking account of these polarizability effects and including the possibility for a slight shift of the theoretical dipole moment function a value of 1μ( v' = 5)1 = 0.089(14) D is the most probable one. In the case of 7LiD according to the usual formula an "effective" value of 1μ eff( v' = 6)1 = 0.425(20) D was deduced from a beat signal obtained at an electric field strength of 24 kV/cm. Here the influence of neighbouring vibrational levels and electronic states is only of minor importance leading to a corrected value of 1μ( v' = 6)1 = 0.43(2) D for the dipole moment. This value differs by 13% from the theoretical one calculated on the basis of the dipole moment function of 7LiH and the adiabatically corrected potential energy curve of 7LiD, thus indicating non-adiabatic effects.
ACCESS-2: Approximation Concepts Code for Efficient Structural Synthesis, user's guide
NASA Technical Reports Server (NTRS)
Miura, H.; Schmit, L. A., Jr.
1978-01-01
A user's guide is presented for the ACCESS-2 computer program. ACCESS-2 is a research oriented program which implements a collection of approximation concepts to achieve excellent efficiency in structural synthesis. The finite element method is used for structural analysis and general mathematical programming algorithms are applied in the design optimization procedure.
ACCESS 3. Approximation concepts code for efficient structural synthesis: User's guide
NASA Technical Reports Server (NTRS)
Fleury, C.; Schmit, L. A., Jr.
1980-01-01
A user's guide is presented for ACCESS-3, a research oriented program which combines dual methods and a collection of approximation concepts to achieve excellent efficiency in structural synthesis. The finite element method is used for structural analysis and dual algorithms of mathematical programming are applied in the design optimization procedure. This program retains all of the ACCESS-2 capabilities and the data preparation formats are fully compatible. Four distinct optimizer options were added: interior point penalty function method (NEWSUMT); second order primal projection method (PRIMAL2); second order Newton-type dual method (DUAL2); and first order gradient projection-type dual method (DUAL1). A pure discrete and mixed continuous-discrete design variable capability, and zero order approximation of the stress constraints are also included.
NASA Technical Reports Server (NTRS)
Miura, H.; Schmit, L. A., Jr.
1976-01-01
The program documentation and user's guide for the ACCESS-1 computer program is presented. ACCESS-1 is a research oriented program which implements a collection of approximation concepts to achieve excellent efficiency in structural synthesis. The finite element method is used for structural analysis and general mathematical programming algorithms are applied in the design optimization procedure. Implementation of the computer program, preparation of input data and basic program structure are described, and three illustrative examples are given.
NASA Astrophysics Data System (ADS)
Okita, Taishi; Takagi, Toshiyuki
2010-01-01
We analytically derive the solutions for electromagnetic fields of electric current dipole moment, which is placed in the exterior of the spherical homogeneous conductor, and is pointed along the radial direction. The dipole moment is driven in the low frequency f = 1 kHz and high frequency f = 1 GHz regimes. The electrical properties of the conductor are appropriately chosen in each frequency. Electromagnetic fields are rigorously formulated at an arbitrary point in a spherical geometry, in which the magnetic vector potential is straightforwardly given by the Biot-Savart formula, and the scalar potential is expanded with the Legendre polynomials, taking into account the appropriate boundary conditions at the spherical surface of the conductor. The induced electric fields are numerically calculated along the several paths in the low and high frequeny excitation. The self-consistent solutions obtained in this work will be of much importance in a wide region of electromagnetic induction problems.
Pygmy dipole resonance and dipole polarizability in {sup 90}Zr
Iwamoto, C.; Tamii, A.; Shima, T.; Hashimoto, T.; Suzuki, T.; Fujita, H.; Hatanaka, K.; Utsunomiya, H.; Akimune, H.; Yamagata, T.; Okamoto, A.; Kondo, T.; Nakada, H.; Kawabata, T.; Fujita, Y.; Matsubara, H.; Shimbara, Y.; Nagashima, M.; Sakuda, M.; Mori, T.; and others
2014-05-02
Electric dipole (E1) reduced transition probability B(E1) of {sup 90}Zr was obtained by the inelastic proton scattering near 0 degrees using a 295 MeV proton beam and multipole decomposition analysis of the angular distribution by the distorted-wave Born approximation with the Hartree-Fock plus random-phase approximation model and inclusion of El Coulomb excitation, and the E1 strength of the pygmy dipole resonance was found in the vicinity of the neutron threshold in the low-energy tail of the giant dipole resonance. Using the data, we plan to determine the precise dipole polarizability α{sub D} which is defined as an inversely energy-weighted sum value of the elecrric dipole strength. The dipole polarizability is expected to constrain the symmetry energy term of the neutron matter equation of state. Thus systematical measurement of the dipole polarizability is important.
NASA Astrophysics Data System (ADS)
Shedge, Sapana V.; Pal, Sourav; Köster, Andreas M.
2011-07-01
Recently, two non-iterative approaches have been proposed to calculate response properties within density functional theory (DFT). These approaches are auxiliary density perturbation theory (ADPT) and the non-iterative approach to the coupled-perturbed Kohn-Sham (NIA-CPKS) method. Though both methods are non-iterative, they use different techniques to obtain the perturbed Kohn-Sham matrix. In this Letter, for the first time, both of these two independent methods have been used for the calculation of dipole-quadrupole polarizabilities. To validate these methods, three tetrahedral molecules viz., P4,CH4 and adamantane (C10H16) have been used as examples. The comparison with MP2 and CCSD proves the reliability of the methodology.
Miyamoto, R.; Kopp, S.E.; Jansson, A.; Syphers, M.J.; /Fermilab
2007-06-01
The AC dipole is an oscillating dipole magnet which can induce large amplitude oscillations without the emittance growth and decoherence. These properties make it a good tool to measure optics of a hadron synchrotron. The vertical AC dipole for the Tevatron is powered by an inexpensive high power audio amplifier since its operating frequency is approximately 20 kHz. The magnet is incorporated into a parallel resonant system to maximize the current. The use of a vertical pinger magnet which has been installed in the Tevatron made the cost relatively inexpensive. Recently, the initial system was upgraded with a more powerful amplifier and oscillation amplitudes up to 2-3{sigma} were achieved with the 980 GeV proton beam. This paper discusses details of the Tevatron AC dipole system and also shows its test results.
NASA Astrophysics Data System (ADS)
Barbier, Jean; Schülke, Christophe; Krzakala, Florent
2015-05-01
We study the behavior of approximate message-passing (AMP), a solver for linear sparse estimation problems such as compressed sensing, when the i.i.d matrices—for which it has been specifically designed—are replaced by structured operators, such as Fourier and Hadamard ones. We show empirically that after proper randomization, the structure of the operators does not significantly affect the performances of the solver. Furthermore, for some specially designed spatially coupled operators, this allows a computationally fast and memory efficient reconstruction in compressed sensing up to the information-theoretical limit. We also show how this approach can be applied to sparse superposition codes, allowing the AMP decoder to perform at large rates for moderate block length.
NASA Technical Reports Server (NTRS)
Shambayati, Shervin
2001-01-01
In order to evaluate performance of strong channel codes in presence of imperfect carrier phase tracking for residual carrier BPSK modulation in this paper an approximate 'brick wall' model is developed which is independent of the channel code type for high data rates. It is shown that this approximation is reasonably accurate (less than 0.7dB for low FERs for (1784,1/6) code and less than 0.35dB for low FERs for (5920,1/6) code). Based on the approximation's accuracy, it is concluded that the effects of imperfect carrier tracking are more or less independent of the channel code type for strong channel codes. Therefore, the advantage that one strong channel code has over another with perfect carrier tracking translates to nearly the same advantage under imperfect carrier tracking conditions. This will allow the link designers to incorporate projected channel code performance of strong channel codes into their design tables without worrying about their behavior in the face of imperfect carrier phase tracking.
1998-08-03
The problem here is to model the three-dimensional response of an electromagnetic logging tool to a practical situation which is often encountered in oil and gas exploration. The DWELL code provide the electromagnetic fields on the axis of a borehole due to either an electric or a magnetic dipole located on the same axis. The borehole is cylindrical, and is located within a stratified formation in which the bedding planes are not horizontal. The anglemore » between the normal to the bedding planes and the axis of the borehole may assume any value, or in other words, the borehole axis may be tilted with respect to the bedding planes. Additionally, all of the formation layers may have invasive zones of drilling mud. The operating frequency of the source dipole(s) extends from a few Hertz to hundreds of Megahertz.« less
Newman, Gregory
1998-08-03
The problem here is to model the three-dimensional response of an electromagnetic logging tool to a practical situation which is often encountered in oil and gas exploration. The DWELL code provide the electromagnetic fields on the axis of a borehole due to either an electric or a magnetic dipole located on the same axis. The borehole is cylindrical, and is located within a stratified formation in which the bedding planes are not horizontal. The angle between the normal to the bedding planes and the axis of the borehole may assume any value, or in other words, the borehole axis may be tilted with respect to the bedding planes. Additionally, all of the formation layers may have invasive zones of drilling mud. The operating frequency of the source dipole(s) extends from a few Hertz to hundreds of Megahertz.
Yoriyaz, Helio; Moralles, Mauricio; Tarso Dalledone Siqueira, Paulo de; Costa Guimaraes, Carla da; Belonsi Cintra, Felipe; Santos, Adimir dos
2009-11-15
Purpose: Radiopharmaceutical applications in nuclear medicine require a detailed dosimetry estimate of the radiation energy delivered to the human tissues. Over the past years, several publications addressed the problem of internal dose estimate in volumes of several sizes considering photon and electron sources. Most of them used Monte Carlo radiation transport codes. Despite the widespread use of these codes due to the variety of resources and potentials they offered to carry out dose calculations, several aspects like physical models, cross sections, and numerical approximations used in the simulations still remain an object of study. Accurate dose estimate depends on the correct selection of a set of simulation options that should be carefully chosen. This article presents an analysis of several simulation options provided by two of the most used codes worldwide: MCNP and GEANT4. Methods: For this purpose, comparisons of absorbed fraction estimates obtained with different physical models, cross sections, and numerical approximations are presented for spheres of several sizes and composed as five different biological tissues. Results: Considerable discrepancies have been found in some cases not only between the different codes but also between different cross sections and algorithms in the same code. Maximum differences found between the two codes are 5.0% and 10%, respectively, for photons and electrons.Conclusion: Even for simple problems as spheres and uniform radiation sources, the set of parameters chosen by any Monte Carlo code significantly affects the final results of a simulation, demonstrating the importance of the correct choice of parameters in the simulation.
NASA Astrophysics Data System (ADS)
Griffiths, David J.
2011-08-01
We study stationary but time-dependent ideal (point) electric and magnetic dipoles, both the conventional type consisting of electric charges and currents and the hypothetical kind composed of magnetic monopoles and their currents. We derive their potentials and fields, and calculate the energy, momentum, and angular momentum they radiate.
Daura-Oller, Elias; Cabré, Maria; Montero, Miguel A.; Paternáin, José L.; Romeu, Antoni
2009-01-01
In the present study, a positive training set of 30 known human imprinted gene coding regions are compared with a set of 72 randomly sampled human nonimprinted gene coding regions (negative training set) to identify genomic features common to human imprinted genes. The most important feature of the present work is its ability to use multivariate analysis to look at variation, at coding region DNA level, among imprinted and non-imprinted genes. There is a force affecting genomic parameters that appears through the use of the appropriate multivariate methods (principle components analysis (PCA) and quadratic discriminant analysis (QDA)) to analyse quantitative genomic data. We show that variables, such as CG content, [bp]% CpG islands, [bp]% Large Tandem Repeats, and [bp]% Simple Repeats, are able to distinguish coding regions of human imprinted genes. PMID:19360135
Sukhovoj, A. M. Furman, W. I. Khitrov, V. A.
2008-06-15
The sums of radiative strength functions for primary dipole gamma transitions, k(E1) + k(M1), are approximated to a high precision by a superposition of two functional dependences in the energy range 0.5 < E{sub 1} < B{sub n} - 0.5 MeV for the {sup 40}K, {sup 60}Co, {sup 71,74}Ge, {sup 80}Br, {sup 114}Cd, {sup 118}Sn, {sup 124,125}Te, {sup 128}I, {sup 137,138,139}Ba, {sup 140}La, {sup 150}Sm, {sup 156,158}Gd, {sup 160}Tb, {sup 163,164,165}Dy, {sup 166}Ho, {sup 168}Er, {sup 170}Tm, {sup 174}Yb, {sup 176,177}Lu, {sup 181}Hf, {sup 182}Ta, {sup 183,184,185,187}W, {sup 188,190,191,193}Os, {sup 192}Ir, {sup 196}Pt, {sup 198}Au, and {sup 200}Hg nuclei. It is shown that, in any nuclei, radiative strength functions are a dynamical quantity and that the values of k(E1) + k(M1) for specific energies of gamma transitions and specific nuclei are determined by the structure of decaying and excited levels, at least up to the neutron binding energy B{sub n}.
Lithium electric dipole polarizability
Puchalski, M.; KePdziera, D.; Pachucki, K.
2011-11-15
The electric dipole polarizability of the lithium atom in the ground state is calculated including relativistic and quantum electrodynamics corrections. The obtained result {alpha}{sub E}=164.0740(5) a.u. is in good agreement with the less accurate experimental value of 164.19(1.08) a.u. The small uncertainty of about 3 parts per 10{sup 6} comes from the approximate treatment of quantum electrodynamics corrections. Our theoretical result can be considered as a benchmark for more general atomic structure methods and may serve as a reference value for the relative measurement of polarizabilities of the other alkali-metal atoms.
Remote Sensing of Dipole Rings
NASA Technical Reports Server (NTRS)
Hooker, Stanford B.; Mied, Richard P.; Brown, James W.; Kirwan, A. D., Jr.
1997-01-01
Historical satellite-derived sea surface temperature (SST) data are reanalyzed with a zebra color palette and a thermal separatrix method. The new results from this reanalysis are as follows: (a) Thirteen observational sequences of six rings from the Gulf Stream and the Brazil Current, which have historically been interpreted as solitary vortices or monopoles are shown to have a dipolar character; (b) some of these dipole rings have been observed in the open ocean, thereby eliminating the possibility that they are sustained by topographic interactions with the continental slope; (c) whether interacting with other features or evolving as isolated circulations, dipoles are seen to rotate within a relatively narrow range of approximately 4-8 deg/day (interacting) and 10-11 deg/day (isolated); and (d) feature tracking delineates energetic fluid in both vortices and eliminates the possibility of interpreting dipole rings as transient features produced by active monopoles and patches of entrained fluid.
Gedney, S.D.
1987-09-01
The electromagnetic pulse (EMP) produced by a high-altitude nuclear blast presents a severe threat to electronic systems due to its extreme characteristics. To test the vulnerability of large systems, such as airplanes, missiles, or satellites, they must be subjected to a simulated EMP environment. One type of simulator that has been used to approximate the EMP environment is the Large Parallel-Plate Bounded-Wave Simulator. It is a guided-wave simulator which has properties of a transmission line and supports a single TEM model at sufficiently low frequencies. This type of simulator consists of finite-width parallel-plate waveguides, which are excited by a wave launcher and terminated by a wave receptor. This study addresses the field distribution within a finite-width parallel-plate waveguide that is matched to a conical tapered waveguide at either end. Characteristics of a parallel-plate bounded-wave EMP simulator were developed using scattering theory, thin-wire mesh approximation of the conducting surfaces, and the Numerical Electronics Code (NEC). Background is provided for readers to use the NEC as a tool in solving thin-wire scattering problems.
Solvents level dipole moments.
Liang, Wenkel; Li, Xiaosong; Dalton, Larry R; Robinson, Bruce H; Eichinger, Bruce E
2011-11-01
The dipole moments of highly polar molecules measured in solution are usually smaller than the molecular dipole moments that are calculated with reaction field methods, whereas vacuum values are routinely calculated in good agreement with available vapor phase data. Whether from Onsager's theory (or variations thereof) or from quantum mechanical methods, the calculated molecular dipoles in solution are found to be larger than those measured. The reason, of course, is that experiments measure the net dipole moment of solute together with the polarized (perturbed) solvent "cloud" surrounding it. Here we show that the reaction field charges that are generated in the quantum mechanical self-consistent reaction field (SCRF) method give a good estimate of the net dipole moment of the solute molecule together with the moment arising from the reaction field charges. This net dipole is a better description of experimental data than the vacuum dipole moment and certainly better than the bare dipole moment of the polarized solute molecule. PMID:21923185
NASA Astrophysics Data System (ADS)
Dey, Supriyo; Aanandan, C. K.; Jose, K. A.; Mohanan, P.; Nair, K. G.
1992-12-01
A new wideband half-wave microstrip dipole antenna is described which operates in low-frequency range with more than 5 percent 2:1 VSWR bandwidth. The design is based on a stripline feeding mechanism to prevent radiation from the feeding structure and on proper end-loading of dipole arms to enhance the impedance bandwidth. It is concluded that this dipole can replace the conventional dipoles or existing microstrip antennas in phased array application.
Efficient treatment of induced dipoles.
Simmonett, Andrew C; Pickard, Frank C; Shao, Yihan; Cheatham, Thomas E; Brooks, Bernard R
2015-08-21
Most existing treatments of induced dipoles in polarizable molecular mechanics force field calculations use either the self-consistent variational method, which is solved iteratively, or the "direct" approximation that is non-iterative as a result of neglecting coupling between induced dipoles. The variational method is usually implemented using assumptions that are only strictly valid under tight convergence of the induced dipoles, which can be computationally demanding to enforce. In this work, we discuss the nature of the errors that result from insufficient convergence and suggest a strategy that avoids such problems. Using perturbation theory to reintroduce the mutual coupling into the direct algorithm, we present a computationally efficient method that combines the precision of the direct approach with the accuracy of the variational approach. By analyzing the convergence of this perturbation series, we derive a simple extrapolation formula that delivers a very accurate approximation to the infinite order solution at the cost of only a few iterations. We refer to the new method as extrapolated perturbation theory. Finally, we draw connections to our previously published permanent multipole algorithm to develop an efficient implementation of the electric field and Thole terms and also derive some necessary, but not sufficient, criteria that force field parameters must obey. PMID:26298123
Efficient treatment of induced dipoles
Simmonett, Andrew C.; Pickard, Frank C.; Shao, Yihan; Cheatham, Thomas E.; Brooks, Bernard R.
2015-01-01
Most existing treatments of induced dipoles in polarizable molecular mechanics force field calculations use either the self-consistent variational method, which is solved iteratively, or the “direct” approximation that is non-iterative as a result of neglecting coupling between induced dipoles. The variational method is usually implemented using assumptions that are only strictly valid under tight convergence of the induced dipoles, which can be computationally demanding to enforce. In this work, we discuss the nature of the errors that result from insufficient convergence and suggest a strategy that avoids such problems. Using perturbation theory to reintroduce the mutual coupling into the direct algorithm, we present a computationally efficient method that combines the precision of the direct approach with the accuracy of the variational approach. By analyzing the convergence of this perturbation series, we derive a simple extrapolation formula that delivers a very accurate approximation to the infinite order solution at the cost of only a few iterations. We refer to the new method as extrapolated perturbation theory. Finally, we draw connections to our previously published permanent multipole algorithm to develop an efficient implementation of the electric field and Thole terms and also derive some necessary, but not sufficient, criteria that force field parameters must obey. PMID:26298123
Efficient treatment of induced dipoles
NASA Astrophysics Data System (ADS)
Simmonett, Andrew C.; Pickard, Frank C.; Shao, Yihan; Cheatham, Thomas E.; Brooks, Bernard R.
2015-08-01
Most existing treatments of induced dipoles in polarizable molecular mechanics force field calculations use either the self-consistent variational method, which is solved iteratively, or the "direct" approximation that is non-iterative as a result of neglecting coupling between induced dipoles. The variational method is usually implemented using assumptions that are only strictly valid under tight convergence of the induced dipoles, which can be computationally demanding to enforce. In this work, we discuss the nature of the errors that result from insufficient convergence and suggest a strategy that avoids such problems. Using perturbation theory to reintroduce the mutual coupling into the direct algorithm, we present a computationally efficient method that combines the precision of the direct approach with the accuracy of the variational approach. By analyzing the convergence of this perturbation series, we derive a simple extrapolation formula that delivers a very accurate approximation to the infinite order solution at the cost of only a few iterations. We refer to the new method as extrapolated perturbation theory. Finally, we draw connections to our previously published permanent multipole algorithm to develop an efficient implementation of the electric field and Thole terms and also derive some necessary, but not sufficient, criteria that force field parameters must obey.
The Dipole Model and Phase Transitions in Biological Membranes
Almeida, Silverio P.; Bond, James D.; Ward, Thomas C.
1971-01-01
Assuming the dipole model for a membrane, approximate calculations are made which employ a dipole-dipole interaction energy. The calculations are based upon the assumption of cooperative coupling of membrane polar molecules and make use of the Bragg-Williams approximation. A theoretical estimate is made of the critical temperature at which phase changes might occur in certain biological membranes. Proposals are presented which explain how the dipole transition might relate to the sometimes observed thermal phase transitions in biological membranes. PMID:5134212
Precision measurement of the electromagnetic dipole strengths in Be11
NASA Astrophysics Data System (ADS)
Kwan, E.; Wu, C. Y.; Summers, N. C.; Hackman, G.; Drake, T. E.; Andreoiu, C.; Ashley, R.; Ball, G. C.; Bender, P. C.; Boston, A. J.; Boston, H. C.; Chester, A.; Close, A.; Cline, D.; Cross, D. S.; Dunlop, R.; Finlay, A.; Garnsworthy, A. B.; Hayes, A. B.; Laffoley, A. T.; Nano, T.; Navrátil, P.; Pearson, C. J.; Pore, J.; Quaglioni, S.; Svensson, C. E.; Starosta, K.; Thompson, I. J.; Voss, P.; Williams, S. J.; Wang, Z. M.
2014-05-01
The electromagnetic dipole strength in Be11 between the bound states has been measured using low-energy projectile Coulomb excitation at bombarding energies of 1.73 and 2.09 MeV/nucleon on a Pt196 target. An electric dipole transition probability B(E1;1/2-→1/2+)=0.102(2) e2fm was determined using the semi-classical code Gosia, and a value of 0.098(4) e2fm was determined using the Extended Continuum Discretized Coupled Channels method with the quantum mechanical code FRESCO. These extracted B(E1) values are consistent with the average value determined by a model-dependent analysis of intermediate energy Coulomb excitation measurements and are approximately 14% lower than that determined by a lifetime measurement. The much-improved precisions of 2% and 4% in the measured B(E1) values between the bound states deduced using Gosia and the Extended Continuum Discretized Coupled Channels method, respectively, compared to the previous accuracy of ˜10% will help in our understanding of and better improve the realistic inter-nucleon interactions.
NASA Astrophysics Data System (ADS)
Engel, D.; Klews, M.; Wunner, G.
2009-02-01
We have developed a new method for the fast computation of wavelengths and oscillator strengths for medium-Z atoms and ions, up to iron, at neutron star magnetic field strengths. The method is a parallelized Hartree-Fock approach in adiabatic approximation based on finite-element and B-spline techniques. It turns out that typically 15-20 finite elements are sufficient to calculate energies to within a relative accuracy of 10-5 in 4 or 5 iteration steps using B-splines of 6th order, with parallelization speed-ups of 20 on a 26-processor machine. Results have been obtained for the energies of the ground states and excited levels and for the transition strengths of astrophysically relevant atoms and ions in the range Z=2…26 in different ionization stages. Catalogue identifier: AECC_v1_0 Program summary URL:http://cpc.cs.qub.ac.uk/summaries/AECC_v1_0.html Program obtainable from: CPC Program Library, Queen's University, Belfast, N. Ireland Licensing provisions: Standard CPC licence, http://cpc.cs.qub.ac.uk/licence/licence.html No. of lines in distributed program, including test data, etc.: 3845 No. of bytes in distributed program, including test data, etc.: 27 989 Distribution format: tar.gz Programming language: MPI/Fortran 95 and Python Computer: Cluster of 1-26 HP Compaq dc5750 Operating system: Fedora 7 Has the code been vectorised or parallelized?: Yes RAM: 1 GByte Classification: 2.1 External routines: MPI/GFortran, LAPACK, PyLab/Matplotlib Nature of problem: Calculations of synthetic spectra [1] of strongly magnetized neutron stars are bedevilled by the lack of data for atoms in intense magnetic fields. While the behaviour of hydrogen and helium has been investigated in detail (see, e.g., [2]), complete and reliable data for heavier elements, in particular iron, are still missing. Since neutron stars are formed by the collapse of the iron cores of massive stars, it may be assumed that their atmospheres contain an iron plasma. Our objective is to fill the gap
Relativistic Dipole Matrix Element Zeros
NASA Astrophysics Data System (ADS)
Lajohn, L. A.; Pratt, R. H.
2002-05-01
There is a special class of relativistic high energy dipole matrix element zeros (RZ), whose positions with respect to photon energy ω , only depend on the bound state l quantum number according to ω^0=mc^2/(l_b+1) (independent of primary quantum number n, nuclear charge Z, central potential V and dipole retardation). These RZ only occur in (n,l_b,j_b)arrow (ɛ , l_b+1,j_b) transitions such as ns_1/2arrow ɛ p_1/2; np_3/2arrow ɛ d_3/2: nd_5/2arrow ɛ f_5/2 etc. The nonrelativistic limit of these matrix elements can be established explicitly in the Coulomb case. Within the general matrix element formalism (such as that in [1]); when |κ | is substituted for γ in analytic expressions for matrix elements, the zeros remain, but ω^0 now becomes dependent on n and Z. When the reduction to nonrelativistic form is completed by application of the low energy approximation ω mc^2 mc^2, the zeros disappear. This nonzero behavior was noted in nonrelativistic dipole Coulomb matrix elements by Fano and Cooper [2] and later proven by Oh and Pratt[3]. (J. H. Scofield, Phys. Rev. A 40), 3054 (1989 (U. Fano and J. W. Cooper, Rev. Mod. Phys. 40), 441 (1968). (D. Oh and R. H. Pratt, Phys. Rev. A 34), 2486 (1986); 37, 1524 (1988); 45, 1583 (1992).
Hendry, L B; Bransome, E D; Hutson, M S; Campbell, L K
1981-01-01
To examine the question of whether or not the genetic code has a stereochemical basis, we used artificial constructs of the topography and physicochemical features of unique "cavities" formed by removal of the second codon base in B-DNA. The effects of base changes on the stereochemistry of the cavities are consistent with the pattern of the genetic code. Fits into the cavities of the side chains of the 20 L amino acids involved in protein synthesis can be demonstrated by using conventional physicochemical principles of hydrogen bonding and steric constraints. The specificity of the fits is remarkably consistent with the genetic code. Images PMID:6950386
Olson, Peter; Amit, Hagay
2006-11-01
The dipole moment of Earth's magnetic field has decreased by nearly 9% over the past 150 years and by about 30% over the past 2,000 years according to archeomagnetic measurements. Here, we explore the causes and the implications of this rapid change. Maps of the geomagnetic field on the core-mantle boundary derived from ground-based and satellite measurements reveal that most of the present episode of dipole moment decrease originates in the southern hemisphere. Weakening and equatorward advection of normal polarity magnetic field by the core flow, combined with proliferation and growth of regions where the magnetic polarity is reversed, are reducing the dipole moment on the core-mantle boundary. Growth of these reversed flux regions has occurred over the past century or longer and is associated with the expansion of the South Atlantic Anomaly, a low-intensity region in the geomagnetic field that presents a radiation hazard at satellite altitudes. We address the speculation that the present episode of dipole moment decrease is a precursor to the next geomagnetic polarity reversal. The paleomagnetic record contains a broad spectrum of dipole moment fluctuations with polarity reversals typically occurring during dipole moment lows. However, the dipole moment is stronger today than its long time average, indicating that polarity reversal is not likely unless the current episode of moment decrease continues for a thousand years or more. PMID:16915369
NASA Astrophysics Data System (ADS)
Engel, D.; Klews, M.; Wunner, G.
2009-02-01
We have developed a new method for the fast computation of wavelengths and oscillator strengths for medium-Z atoms and ions, up to iron, at neutron star magnetic field strengths. The method is a parallelized Hartree-Fock approach in adiabatic approximation based on finite-element and B-spline techniques. It turns out that typically 15-20 finite elements are sufficient to calculate energies to within a relative accuracy of 10-5 in 4 or 5 iteration steps using B-splines of 6th order, with parallelization speed-ups of 20 on a 26-processor machine. Results have been obtained for the energies of the ground states and excited levels and for the transition strengths of astrophysically relevant atoms and ions in the range Z=2…26 in different ionization stages. Catalogue identifier: AECC_v1_0 Program summary URL:http://cpc.cs.qub.ac.uk/summaries/AECC_v1_0.html Program obtainable from: CPC Program Library, Queen's University, Belfast, N. Ireland Licensing provisions: Standard CPC licence, http://cpc.cs.qub.ac.uk/licence/licence.html No. of lines in distributed program, including test data, etc.: 3845 No. of bytes in distributed program, including test data, etc.: 27 989 Distribution format: tar.gz Programming language: MPI/Fortran 95 and Python Computer: Cluster of 1-26 HP Compaq dc5750 Operating system: Fedora 7 Has the code been vectorised or parallelized?: Yes RAM: 1 GByte Classification: 2.1 External routines: MPI/GFortran, LAPACK, PyLab/Matplotlib Nature of problem: Calculations of synthetic spectra [1] of strongly magnetized neutron stars are bedevilled by the lack of data for atoms in intense magnetic fields. While the behaviour of hydrogen and helium has been investigated in detail (see, e.g., [2]), complete and reliable data for heavier elements, in particular iron, are still missing. Since neutron stars are formed by the collapse of the iron cores of massive stars, it may be assumed that their atmospheres contain an iron plasma. Our objective is to fill the gap
Microstrip monpulse dipole array
NASA Astrophysics Data System (ADS)
Miccioli, W.; Toth, J.; Sa, N.; Lewis, M.
1985-01-01
The development of a microstrip radiating aperture utilizing multiple microstrip dipole radiators fed by a resonant feed configuration is described. This array combines an efficient capacitively coupled radiator feeding mechanism with a planar power divider configuration to achieve an extremely thin, lightweight antenna aperture. Linear array dipole matching theory and radiator bandwidth improvement techniques are also described. A quadrant based microstrip monopulse antenna was constructed. Experimental data from this array, its subassemblies and individual components are presented and compared to analytical predictions.
Toroidal dipole excitations in metamolecules formed by interacting plasmonic nanorods
NASA Astrophysics Data System (ADS)
Watson, Derek W.; Jenkins, Stewart D.; Ruostekoski, Janne; Fedotov, Vassili A.; Zheludev, Nikolay I.
2016-03-01
We show how the elusive toroidal dipole moment appears as a radiative excitation eigenmode in a metamolecule resonator that is formed by pairs of plasmonic nanorods. We analyze one such nanorod configuration—a toroidal metamolecule. We find that the radiative interactions in the toroidal metamolecule can be qualitatively represented by a theoretical model based on an electric point dipole arrangement. Both a finite-size rod model and the point dipole approximation demonstrate how the toroidal dipole moment is subradiant and difficult to excite by incident light. By means of breaking the geometric symmetry of the metamolecule, the toroidal mode can be excited by linearly polarized light and appears as a Fano resonance dip in the forward scattered light. We provide simple optimization protocols for maximizing the toroidal dipole mode excitation. This opens up possibilities for simplified control and driving of metamaterial arrays consisting of toroidal dipole unit-cell resonators.
Structure and melting behavior of classical bilayer crystals of dipoles
Lu Xin; Wu Changqin; Micheli, Andrea; Pupillo, Guido
2008-07-01
We study the structure and melting of a classical bilayer system of dipoles in a setup where the dipoles are oriented perpendicular to the planes of the layers and the density of dipoles is the same in each layer. Due to the anisotropic character of the dipole-dipole interactions, we find that the ground-state configuration is given by two hexagonal crystals positioned on top of each other, independent of the interlayer spacing and dipolar density. For large interlayer distances these crystals are independent, while in the opposite limit of small interlayer distances the system behaves as a two-dimensional crystal of paired dipoles. Within the harmonic approximation for the phonon excitations, the melting temperature of these crystalline configurations displays a nonmonotonic dependence on the interlayer distance, which is associated with a re-entrant melting behavior in the form of solid-liquid-solid-liquid transitions at fixed temperature.
Electric dipole transitions between Gamow-Teller and spin-dipole states
Suzuki, T.; Sagawa, H.; Van Giai, N.
1998-01-01
We study electric dipole transitions between Gamow-Teller (GT) and spin-dipole (SD) states. SD and GT excitations are calculated within the Hartree-Fock+Tamm-Dancoff approximation for {sup 48}Sc and {sup 90}Nb. The electric dipole transitions are found to be rather selective, and strong E1 transitions occur to some specific spin-dipole states. Calculated E1 transition strengths between GT and SD states are compared with the analytic sum rules within one-particle{endash}one-hole (1p-1h) configuration space and within both 1p-1h and 2p-2h model space. Possible implications for charge-exchange reactions may help to understand the quenching problem of spin excitations. {copyright} {ital 1998} {ital The American Physical Society}
Clinical coding. Code breakers.
Mathieson, Steve
2005-02-24
--The advent of payment by results has seen the role of the clinical coder pushed to the fore in England. --Examinations for a clinical coding qualification began in 1999. In 2004, approximately 200 people took the qualification. --Trusts are attracting people to the role by offering training from scratch or through modern apprenticeships. PMID:15768716
Kopeliovich, B.; Schmidt, I.; Siddikov, M.
2009-03-23
We study the DVCS amplitude within the color dipole approach employing a nonperturbative wave function for the real photon. We found that the model is able to decribe the absolute value of the cross section and the t-slope, but predicts too steep Q{sup 2}-dependence in comparison with H1 data.
Experiments with Dipole Antennas
ERIC Educational Resources Information Center
Kraftmakher, Yaakov
2009-01-01
Employment of a data-acquisition system for data collection and calculations makes experiments with antennas more convenient and less time consuming. The determined directional patterns of the dipole antennas of different lengths are in reasonable agreement with theory. The enhancement of the signal by using a reflector is demonstrated, and a…
Geometrical Simplification of the Dipole-Dipole Interaction Formula
ERIC Educational Resources Information Center
Kocbach, Ladislav; Lubbad, Suhail
2010-01-01
Many students meet dipole-dipole potential energy quite early on when they are taught electrostatics or magnetostatics and it is also a very popular formula, featured in encyclopedias. We show that by a simple rewriting of the formula it becomes apparent that, for example, by reorienting the two dipoles, their attraction can become exactly twice…
AutoDipole - Automated generation of dipole subtraction terms -
NASA Astrophysics Data System (ADS)
Hasegawa, K.; Moch, S.; Uwer, P.
2010-10-01
We present an automated generation of the subtraction terms for next-to-leading order QCD calculations in the Catani-Seymour dipole formalism. For a given scattering process with n external particles our Mathematica package generates all dipole terms, allowing for both massless and massive dipoles. The numerical evaluation of the subtraction terms proceeds with MadGraph, which provides Fortran code for the necessary scattering amplitudes. Checks of the numerical stability are discussed. Program summaryProgram title: AutoDipole Catalogue identifier: AEGO_v1_0 Program summary URL:http://cpc.cs.qub.ac.uk/summaries/AEGO_v1_0.html Program obtainable from: CPC Program Library, Queen's University, Belfast, N. Ireland Licensing provisions: Standard CPC licence, http://cpc.cs.qub.ac.uk/licence/licence.html No. of lines in distributed program, including test data, etc.: 138 042 No. of bytes in distributed program, including test data, etc.: 1 117 665 Distribution format: tar.gz Programming language: Mathematica and Fortran Computer: Computers running Mathematica (version 7.0) Operating system: The package should work on every Linux system supported by Mathematica. Detailed tests have been performed on Scientific Linux as supported by DESY and CERN and on openSUSE and Debian. RAM: Depending on the complexity of the problem, recommended at least 128 MB RAM Classification: 11.5 External routines: MadGraph (including HELAS library) available under http://madgraph.hep.uiuc.edu/ or http://madgraph.phys.ucl.ac.be/ or http://madgraph.roma2.infn.it/. A copy of the tar file, MG_ME_SA_V4.4.30, is included in the AutoDipole distribution package. Nature of problem: Computation of next-to-leading order QCD corrections to scattering cross sections, regularization of real emission contributions. Solution method: Catani-Seymour subtraction method for massless and massive partons [1,2]; Numerical evaluation of subtracted matrix elements interfaced to MadGraph [3-5] (stand-alone version) using
Microstrip dipoles on cylindrical structures
NASA Astrophysics Data System (ADS)
Alexopoulos, N. G.; Uslenghi, P. L. E.; Uzunoglu, N. K.
1981-12-01
An electric dipole tangent to the outer surface of a dielectric layer which coats a metallic cylinder is considered. Exact expressions are obtained for the electromagnetic field produced by the dipole, both inside the coating layer and in the surrounding free space. Asymptotic results are derived for a cylinder whose diameter is large compared to the wavelength. Arrays of elementary dipoles are discussed.
Electromagnetically coupled microstrip dipoles
NASA Astrophysics Data System (ADS)
Oltman, H. G.; Huebner, D. A.
1981-01-01
A new class of printed circuit radiator consisting of a microstrip dipole electromagnetically coupled to a microstrip feed line is described. Several configurations which differ in bandwidth, efficiency, and construction simplicity are presented. A geometry which has been found to be optimum for many applications is noted. Radiation characteristics of both isolated elements and arrays of elements are examined. Experimental and theoretical results are presented.
NASA Astrophysics Data System (ADS)
Holanda, B. A.; Cordeiro, R. C.; Blak, A. R.
2010-11-01
Dipole defects in gamma irradiated and thermally treated beryl (Be3Al2Si6O18) samples have been studied using the Thermally Stimulated Depolarization Currents (TSDC) technique. TSDC experiments were performed in pink (morganite), green (emerald), blue (aquamarine) and colourless (goshenite) natural beryl. TSDC spectra present dipole peaks at 190K, 220K, 280K and 310K that change after gamma irradiation and thermal treatments. In morganite samples, for thermal treatments between 700K and 1100K, the 280K peak increase in intensity and the band at 220K disappears. An increase of the 280K peak and a decrease of the 190K peak were observed in the TSDC spectra of morganite after a gamma irradiation of 25kGy performed after the thermal treatments. In the case of emerald samples, thermal treatments enhanced the 280K peak and gamma irradiation partially destroyed this band. The goshenite TSDC spectra present only one band at 280K that is not affected either by thermal treatments or by gamma irradiation. All the observed peaks are of dipolar origin because the intensity of the bands is linearly dependent on the polarization field, behaviour of dipole defects. The systematic study, by means of TSDC measurements, of ionizing irradiation effects and thermal treatments in these crystals makes possible a better understanding of the role played by the impurities in beryl crystals.
Simulation of Whistler Chorus in a Compressed Dipole Field
NASA Astrophysics Data System (ADS)
Wu, S.; Denton, R. E.; Hudson, M.
2015-12-01
Earth's dipole magnetic field is constantly compressed by the solar wind and the compression is enhanced during magnetic storm. We simulate whistler chorus in a compressed dipole field using a hybrid code. The hybrid code uses the particle-in-cell technique in generalized orthogonal coordinates. In the hybrid code, a small fraction of electrons are treated as particles with anisotropic temperature that leads to the whistler instability. Other electrons are treated as a cold fluid without mass. The density of the fluid electrons is large such that the plasma frequency exceeds the electron gyro frequency. Ions serve as a fixed background. We model the compressed dipole field by adding a constant magnetic field component to the dipole field. The direction of the compressed component is the same as that of the dipole field at the equator. This model of the compressed dipole field yields a magnetic field with off-equator minima and smaller inhomogeneity than the dipole field near the equator. The distribution of hot anisotropic electrons along the magnetic field is a function of adiabatic invariants that satisfies MHD force balance. In the compressed dipole field, the hot electron anisotropy, hot electron density and plasma beta in the direction parallel to the background magnetic field are the maximum at the minimum magnetic field. In our simulation, whistler chorus are generated at the minimum magnetic field with a peak frequency in agreement with the prediction by WHAMP, a local dispersion relation solver. The waves propagate in both directions along the magnetic field. Waves that propagate to higher magnetic latitude are damped at the boundary by the artificial resistive layers, while waves that propagate to lower latitude towards the equator continue to grow.
NLO evolution of color dipoles in N=4 SYM
Chirilli, Giovanni A.; Balitsky, Ian
2009-07-04
Here, high-energy behavior of amplitudes in a gauge theory can be reformulated in terms of the evolution of Wilson-line operators. In the leading logarithmic approximation it is given by the conformally invariant BK equation for the evolution of color dipoles. In QCD, the next-to-leading order BK equation has both conformal and non-conformal parts, the latter providing the running of the coupling constant. To separate the conformally invariant effects from the running-coupling effects, we calculate the NLO evolution of the color dipoles in the conformal ${\\cal N}$=4 SYM theory. We define the "composite dipole operator" with the rapidity cutoff preserving conformal invariance.
Dipole angular entropy techniques for intron-exon segregation in DNA
NASA Astrophysics Data System (ADS)
Subramanian, Nithya; Bose, R.
2012-04-01
We propose techniques for computing the angular entropies of DNA sequences, based on the orientations of the dipole moments of the nucleotide bases. The angles of the dipole moment vectors of the bases are used to compute the dipole angular entropy and the Fourier harmonics of the angles are used to compute the dipole angular spectral entropy for a given sequence. We also show that the coding (exons) and noncoding (introns) regions of the DNA can be segregated based on their dipole angular entropies and dipole angular spectral entropies. Segregation using these techniques is found to be computationally faster and more accurate than the previously reported methods. The proposed techniques can also be improvised to use the magnitude of the dipole moments of the bases in addition to the angles.
Superconducting dipole electromagnet
Purcell, John R.
1977-07-26
A dipole electromagnet of especial use for bending beams in particle accelerators is wound to have high uniformity of magnetic field across a cross section and to decrease evenly to zero as the ends of the electromagnet are approached by disposing the superconducting filaments of the coil in the crescent-shaped nonoverlapping portions of two intersecting circles. Uniform decrease at the ends is achieved by causing the circles to overlap increasingly in the direction of the ends of the coil until the overlap is complete and the coil is terminated.
Transverse current on strip dipole antenna
NASA Astrophysics Data System (ADS)
Wunsch, A. D.
1982-07-01
Analyses of the current of thin wire dipole antennas presuppose that the current is parallel to the antenna axis. It is pointed out that a component of current transverse to the antenna axis can exist for antennas having a noncircular cross section, such as the strip dipole. The present investigation is concerned with a perfectly conducting strip antenna which is center driven by a delta function generator, taking into account the surface current-density components Kx(x,z) and Kz(x,z). In the solution of the resulting integral equations, it is assumed that Kz is considerably stronger than the transverse surface current density Kx. After obtaining an approximation to Kz, the second integral equation is solved for Kx. Results for the normalized transverse surface current density are presented in graphs.
Geomagnetic dipole moment collapse by convective mixing in the core
NASA Astrophysics Data System (ADS)
Liu, Lijun; Olson, Peter
2009-05-01
Convective mixing in the fluid outer core can induce rapid transient decrease of the geomagnetic dipole. Here we determine rates of dipole moment decrease as a function of magnetic Reynolds number following convective instability in a numerical dynamo and in axisymmetric kinematic flows. Our calculations show that mixing flows induce reversed magnetic flux on the core-mantle boundary through expulsion of mostly poloidal magnetic field by convective upwellings. The dipole field collapse is accelerated by enhanced radial diffusion and meridional advection of magnetic flux below the core-mantle boundary. Magnetic energy cascades from the dipole to smaller scales during mixing, producing a filamentary magnetic field structure on the core-mantle boundary. We find that the maximum rate of dipole moment decrease on century time scales is weakly sensitive to the mixing flow pattern but varies with the velocity of the flow approximately as cRm β , with Rm the magnetic Reynolds number and (c, β) ≈ (0.2 ± 0.07, 0.78 ± 0.05). According to our calculations, a mixing flow in the outer core with Rm in the range of 200-300 can account for the historically-measured rate of decrease of the geomagnetic dipole moment, although it is unlikely that a single mixing flow event with this intensity would cause a full dipole collapse or polarity reversal.
A method for synthesis of small arrays of printed dipole antennas backed by a ground plane
NASA Astrophysics Data System (ADS)
Popovic, Branko D.
1987-11-01
A method is proposed for synthesis of antenna arrays consisting of narrow strip-dipole antennas printed on a thin dielectric substrate. Approximately antiresonant dipoles (i.e., dipoles about one wavelength long) are considered, because by moderate variation of their width and length their impedance can be varied in a wide range. A method for analysis of such arrays is described first, in which the printed strip dipoles are replaced by approximately equivalent circular-cylindrical dipoles with coaxial magnetic coating, using recently proposed generalization of equivalent radius of thin cylindrical antennas. An interactive optimization procedure is next applied for synthesis, which enables arrays to be obtained having array radiation pattern and, particularly, dipole impedances close to the desired.
Ferrofluid Photonic Dipole Contours
NASA Astrophysics Data System (ADS)
Snyder, Michael; Frederick, Jonathan
2008-03-01
Understanding magnetic fields is important to facilitate magnetic applications in diverse fields in industry, commerce, and space exploration to name a few. Large electromagnets can move heavy loads of metal. Magnetic materials attached to credit cards allow for fast, accurate business transactions. And the Earth's magnetic field gives us the colorful auroras observed near the north and south poles. Magnetic fields are not visible, and therefore often hard to understand or characterize. This investigation describes and demonstrates a novel technique for the visualization of magnetic fields. Two ferrofluid Hele-Shaw cells have been constructed to facilitate the imaging of magnetic field lines [1,2,3,4]. We deduce that magnetically induced photonic band gap arrays similar to electrostatic liquid crystal operation are responsible for the photographed images and seek to mathematically prove the images are of exact dipole nature. We also note by comparison that our photographs are very similar to solar magnetic Heliosphere photographs.
Highly Automated Dipole EStimation (HADES).
Campi, C; Pascarella, A; Sorrentino, A; Piana, M
2011-01-01
Automatic estimation of current dipoles from biomagnetic data is still a problematic task. This is due not only to the ill-posedness of the inverse problem but also to two intrinsic difficulties introduced by the dipolar model: the unknown number of sources and the nonlinear relationship between the source locations and the data. Recently, we have developed a new Bayesian approach, particle filtering, based on dynamical tracking of the dipole constellation. Contrary to many dipole-based methods, particle filtering does not assume stationarity of the source configuration: the number of dipoles and their positions are estimated and updated dynamically during the course of the MEG sequence. We have now developed a Matlab-based graphical user interface, which allows nonexpert users to do automatic dipole estimation from MEG data with particle filtering. In the present paper, we describe the main features of the software and show the analysis of both a synthetic data set and an experimental dataset. PMID:21437232
Cooperative Self-Assembly of Carbazole Derivatives Driven by Multiple Dipole-Dipole Interactions.
Ikeda, Toshiaki; Iijima, Tatsuya; Sekiya, Ryo; Takahashi, Osamu; Haino, Takeharu
2016-08-01
Carbazole possessing phenylisoxazoles self-assembled in a cooperative manner in decalin. X-ray crystal structure analysis revealed that the isoxazole dipoles align in a head-to-tail fashion. DFT calculations suggested that the linear array of dipoles induced the polarization of each dipole, leading to an increase in dipole-dipole interactions. This dipole polarization resulted in cooperative assembly. PMID:27391525
Magnetic Field of a Dipole and the Dipole-Dipole Interaction
ERIC Educational Resources Information Center
Kraftmakher, Yaakov
2007-01-01
With a data-acquisition system and sensors commercially available, it is easy to determine magnetic fields produced by permanent magnets and to study the dipole-dipole interaction for different separations and angular positions of the magnets. For sufficiently large distances, the results confirm the 1/R[superscript 3] law for the magnetic field…
Combined Panofsky Quadrupole & Corrector Dipole
George Biallas; Nathan Belcher; David Douglas; Tommy Hiatt; Kevin Jordan
2007-07-02
Two styles of Panofsky Quadrupoles with integral corrector dipole windings are in use in the electron beam line of the Free Electron Laser at Jefferson Lab. We combined steering and focusing functions into single magnets, adding hundreds of Gauss-cm dipole corrector capability to existing quadrupoles because space is at a premium along the beam line. Superposing a one part in 100 dipole corrector field on a 1 part in 1000, weak (600 to 1000 Gauss) quadrupole is possible because the parallel slab iron yoke of the Panofsky Quadrupole acts as a window frame style dipole yoke. The dipole field is formed when two electrically floating “current sources”, designed and made at JLab, add and subtract current from the two opposite quadrupole current sheet windings parallel to the dipole field direction. The current sources also drive auxiliary coils at the yoke’s inner corners that improve the dipole field. Magnet measurements yielded the control system field maps that characterize the two types of fields. Field analysis using TOSCA, construction and wiring details, magnet measurements and reference for the current source are presented.
Effect of the short-range interaction on low-energy collisions of ultracold dipoles
NASA Astrophysics Data System (ADS)
Zhang, Peng; Jie, Jianwen
2014-12-01
We consider the low-energy scattering of two ultracold polarized dipoles with both a short-range interaction (SRI) and a weak dipole-dipole interaction (DDI), which is far away from shape resonances. In previous analytical studies, the scattering amplitude in this system was often calculated via the first-order Born approximation (FBA). Our results show that significant derivations from this approximation can arise in some cases. In these cases, the SRI can significantly modify the interdipole scattering amplitudes even if the scattering amplitudes for the SRI alone are much smaller than the dipolar length of the DDI. We further obtain approximate analytical expressions for these interdipole scattering amplitudes.
Observation of Stueckelberg oscillations in dipole-dipole interactions
Ditzhuijzen, C. S. E. van; Tauschinsky, Atreju; Van Linden van den Heuvell, H. B.
2009-12-15
We have observed Stueckelberg oscillations in the dipole-dipole interaction between Rydberg atoms with an externally applied radio-frequency field. The oscillating rf field brings the interaction between cold Rydberg atoms in two separated volumes into resonance. We observe multiphoton transitions when varying the amplitude of the rf field and the static electric field offset. The angular momentum states we use show a quadratic Stark shift, which leads to a fundamentally different behavior than linearly shifting states. Both cases are studied theoretically using the Floquet approach and are compared. The amplitude of the sidebands, related to the interaction strength, is given by the Bessel function in the linearly shifting case and by the generalized Bessel function in the quadratically shifting case. The oscillatory behavior of both functions corresponds to Stueckelberg oscillations, an interference effect described by the semiclassical Landau-Zener-Stueckelberg model. The measurements prove coherent dipole-dipole interaction during at least 0.6 mus.
Fermion dipole moment and holography
NASA Astrophysics Data System (ADS)
Kulaxizi, Manuela; Rahman, Rakibur
2015-12-01
In the background of a charged AdS black hole, we consider a Dirac particle endowed with an arbitrary magnetic dipole moment. For non-zero charge and dipole coupling of the bulk fermion, we find that the dual boundary theory can be plagued with superluminal modes. Requiring consistency of the dual CFT amounts to constraining the strength of the dipole coupling by an upper bound. We briefly discuss the implications of our results for the physics of holographic non-Fermi liquids.
Analytic dipole moment geometric derivatives from nuclear electric shielding in molecules
NASA Astrophysics Data System (ADS)
Lazzeretti, P.; Zanasi, R.
1986-04-01
We present ab initio calculations of dipole moment geometric derivatives for some first-row atom hydrides. Dipole moment derivatives, in terms of atomic polar tensors (APT), are equivalent to nuclear electric shieldings and were determined analytically, within the random phase approximation (RPA). Polarized basis sets were used, which give accurate results with small computer effort.
Dipole-dipole interaction between rubidium Rydberg atoms
Altiere, Emily; Fahey, Donald P.; Noel, Michael W.; Smith, Rachel J.; Carroll, Thomas J.
2011-11-15
Ultracold Rydberg atoms in a static electric field can exchange energy via the dipole-dipole interaction. The Stark effect shifts the energy levels of the atoms which tunes the energy exchange into resonance at specific values of the electric field (Foerster resonances). We excite rubidium atoms to Rydberg states by focusing either a 480 nm beam from a tunable dye laser or a pair of diode lasers into a magneto-optical trap. The trap lies at the center of a configuration of electrodes. We scan the electric field by controlling the voltage on the electrodes while measuring the fraction of atoms that interact. Dipole-dipole interaction spectra are presented for initially excited rubidium nd states for n=31 to 46 and for four different pairs of initially excited rubidium ns states. We also present the dipole-dipole interaction spectra for individual rubidium 32d (j, m{sub j}) fine structure levels that have been selectively excited. The data are compared to calculated spectra.
Dipole-Strength Distributions up to the Giant Dipole Resonance Deduced from Photon Scattering
NASA Astrophysics Data System (ADS)
Schwengner, R.; Rusev, G.; Benouaret, N.; Beyer, R.; Dönau, F.; Erhard, M.; Grosse, E.; Junghans, A. R.; Kosev, K.; Klug, J.; Nair, C.; Nankov, N.; Schilling, K. D.; Wagner, A.
2008-04-01
Dipole-strength distributions up to the neutron-separation energies of the even-mass Mo isotopes from 92Mo to 100Mo and of the N = 50 isotones 88Sr, 89Y, 90Zr have been investigated in photon-scattering experiments using the bremsstrahlung facility at the superconducting electron accelerator ELBE of the Forschungszentrum Dresden-Rossendorf. A measurement using polarised bremsstrahlung impinging on 88Sr revealed that all resolved transitions with energies greater than 6 MeV in this nuclide except for one are E1 transitions. The intensity distributions obtained from the measured spectra after a correction for detector response and a subtraction of atomic background in the target contain a continuum part in addition to the resolved peaks. It turns out that the dipole strength in the resolved peaks amounts to about 30% of the total dipole strength while the continuum contains about 70%. In order to estimate the distribution of inelastic transitions and to correct the ground-state transitions for their branching ratios simulations of γ-ray cascades were performed. The photoabsorption cross sections obtained in this way connect smoothly to (γ, n) cross sections and give novel information about the strength on the low-energy tails of the Giant Dipole Resonances below the neutron-separation energies. The experimental cross sections are compared with predictions of a Quasiparticle-Random-Phase Approximation in a deformed basis. The calculations describe the experimentally observed increase of the dipole strengths with increasing neutron number of the Mo isotopes as a consequence of increasing nuclear deformation.
Screening of nucleon electric dipole moments in nuclei
NASA Astrophysics Data System (ADS)
Inoue, Satoru; Gudkov, Vladimir; Schindler, Matthias R.; Song, Young-Ho
2016-05-01
A partial screening of nucleon electric dipole moments (EDMs) in nuclear systems, which is related to the Schiff mechanism known for neutral atomic systems, is discussed. It is shown that the direct contribution from the neutron EDM to the deuteron EDM is partially screened by about 1% in a zero-range approximation calculation.
Simulation studies of the transverse dipole mode multibunch instability for the SSC Collider
Chen, S.; Lopez, G.
1993-01-01
A computer program that assumes a point-like structure of the bunches, called TADIMMI, has been devised to study the dipole mode multibunch instability in the Superconducting Super Collider (SSC) Collider ring due to a single Positron-Electron Project (PEP) test rf cavity and the resistive wall. For the rf cavity, the following cases are considered: symmetric filling, where good agreement is obtained with ZAP code; nonsymmetric filling; elimination of the most dangerous mode of the cavity; De-Q of the cavity, where a damping ratio is obtained for the cavity; and the feedback system, where it is verified that the proposed system for the Collider will work. For the resistive wall, a resonator impedance model approximation is used, which allows use of the same computer program to study the instabilities and the associated feedback system. Comparison with the analytical approach (ZAP) is also made.
NASA Technical Reports Server (NTRS)
Divsalar, D.; Pollara, F.
1995-01-01
A description is given of multiple turbo codes and a suitable decoder structure derived from an approximation to the maximum a posteriori probability (MAP) decision rule, which is substantially different from the decoder for two-code-based encoders.
NASA Astrophysics Data System (ADS)
Hashimoto, S.; Iwamoto, Y.; Sato, T.; Niita, K.; Boudard, A.; Cugnon, J.; David, J.-C.; Leray, S.; Mancusi, D.
2014-08-01
A new approach to describing neutron spectra of deuteron-induced reactions in the Monte Carlo simulation for particle transport has been developed by combining the Intra-Nuclear Cascade of Liège (INCL) and the Distorted Wave Born Approximation (DWBA) calculation. We incorporated this combined method into the Particle and Heavy Ion Transport code System (PHITS) and applied it to estimate (d,xn) spectra on natLi, 9Be, and natC targets at incident energies ranging from 10 to 40 MeV. Double differential cross sections obtained by INCL and DWBA successfully reproduced broad peaks and discrete peaks, respectively, at the same energies as those observed in experimental data. Furthermore, an excellent agreement was observed between experimental data and PHITS-derived results using the combined method in thick target neutron yields over a wide range of neutron emission angles in the reactions. We also applied the new method to estimate (d,xp) spectra in the reactions, and discussed the validity for the proton emission spectra.
Visualizing coherent intermolecular dipole-dipole coupling in real space.
Zhang, Yang; Luo, Yang; Zhang, Yao; Yu, Yun-Jie; Kuang, Yan-Min; Zhang, Li; Meng, Qiu-Shi; Luo, Yi; Yang, Jin-Long; Dong, Zhen-Chao; Hou, J G
2016-03-31
Many important energy-transfer and optical processes, in both biological and artificial systems, depend crucially on excitonic coupling that spans several chromophores. Such coupling can in principle be described in a straightforward manner by considering the coherent intermolecular dipole-dipole interactions involved. However, in practice, it is challenging to directly observe in real space the coherent dipole coupling and the related exciton delocalizations, owing to the diffraction limit in conventional optics. Here we demonstrate that the highly localized excitations that are produced by electrons tunnelling from the tip of a scanning tunnelling microscope, in conjunction with imaging of the resultant luminescence, can be used to map the spatial distribution of the excitonic coupling in well-defined arrangements of a few zinc-phthalocyanine molecules. The luminescence patterns obtained for excitons in a dimer, which are recorded for different energy states and found to resemble σ and π molecular orbitals, reveal the local optical response of the system and the dependence of the local optical response on the relative orientation and phase of the transition dipoles of the individual molecules in the dimer. We generate an in-line arrangement up to four zinc-phthalocyanine molecules, with a larger total transition dipole, and show that this results in enhanced 'single-molecule' superradiance from the oligomer upon site-selective excitation. These findings demonstrate that our experimental approach provides detailed spatial information about coherent dipole-dipole coupling in molecular systems, which should enable a greater understanding and rational engineering of light-harvesting structures and quantum light sources. PMID:27029277
An alternate method for designing dipole magnet ends
Pope, W.L.; Green, M.A.; Peters, C.; Caspi, S.; Taylor, C.E.
1988-08-01
Small bore superconducting dipole magnets, such as those for the SSC, often have problems in the ends. These problems can often be alleviated by spreading out the end windings so that the conductor sees less deformation. This paper presents a new procedure for designing dipole magnet ends which can be applied to magnets with either cylindrical or conical bulged ends to have integrated field multipoles which meet the constraints imposed by the SSC lattice. The method described here permits one to couple existing multiparameter optimization routines (i.e., MINUIT with suitable independent parameter constraints) with a computer code DIPEND, which describes the multiples, so that one can meet any reasonable objective (i.e., minimizing integrated sextupole and decapole). This paper will describe how the computer method was used to analyze the bulged conical ends for an SSC dipole. 6 refs, 6 figs, 2 tabs.
Measuring the Forces between Magnetic Dipoles
ERIC Educational Resources Information Center
Gayetsky, Lisa E.; Caylor, Craig L.
2007-01-01
We describe a simple undergraduate lab in which students determine how the force between two magnetic dipoles depends on their separation. We consider the case where both dipoles are permanent and the case where one of the dipoles is induced by the field of the other (permanent) dipole. Agreement with theoretically expected results is quite good.
Dispersion dipoles for coupled Drude oscillators
NASA Astrophysics Data System (ADS)
Odbadrakh, Tuguldur T.; Jordan, Kenneth D.
2016-01-01
We present the dispersion-induced dipole moments of coupled Drude oscillators obtained from two approaches. The first approach evaluates the dipole moment using the second-order Rayleigh-Schrödinger perturbation theory wave function allowing for dipole-dipole and dipole-quadrupole coupling. The second approach, based on response theory, employs an integral of the dipole-dipole polarizability of one oscillator and the dipole-dipole-quadrupole hyperpolarizability of the other oscillator over imaginary frequencies. The resulting dispersion dipoles exhibit an R-7 dependence on the separation between the two oscillators and are connected to the leading-order C6/R6 dispersion energy through the electrostatic Hellmann-Feynman theorem.
Circular current loops, magnetic dipoles and spherical harmonic analysis.
Alldredge, L.R.
1980-01-01
Spherical harmonic analysis (SHA) is the most used method of describing the Earth's magnetic field, even though spherical harmonic coefficients (SHC) almost completely defy interpretation in terms of real sources. Some moderately successful efforts have been made to represent the field in terms of dipoles placed in the core in an effort to have the model come closer to representing real sources. Dipole sources are only a first approximation to the real sources which are thought to be a very complicated network of electrical currents in the core of the Earth. -Author
Interaction of a vortex dipole with a deformable cantilevered plate
NASA Astrophysics Data System (ADS)
Zivkov, Eugene; Yarusevych, Serhiy; Peterson, Sean
2014-11-01
The coupled interaction of a vortex dipole impacting the tip of a deformable cantilevered plate is investigated both numerically and experimentally. Numerically, a strongly coupled fluid-structure interaction code is used to simulate the impact at three dipole Reynolds numbers, Re = 500, 1500, and 3000. These Reynolds numbers are representative of flows over small-scale energy harvesting devices, and the plate properties model an ionic polymer-metal composite. Of particular interest is the vortex dynamics and the attendant plate response, with the underlying implications to energy harvesting. As the dipole approaches the plate, secondary vortical structures are generated at the plate, with finer structures present at higher Reynolds number. The dipole breaks up after the initial impact, which is followed by complex vortex interactions of secondary structures. The initial impact produces the largest plate deflection, followed by a more complex response attributed to plate interaction with multiple secondary vortices. The plate response to the initial impact is not strongly dependent upon the Reynolds number. However, the secondary vortex dynamics, and the associated plate loadings, exhibit strong Reynolds number dependence. To validate the numerical results, a similar dipole-plate interaction is modelled experimentally and characterized using flow visualization and time resolved, planar particle image velocimetry.
Experimental static dipole-dipole polarizabilities of molecules
NASA Astrophysics Data System (ADS)
Hohm, U.
2013-12-01
A compilation of the static mean dipole-dipole polarizability α is given for 174 molecules. All data are evaluated from gas phase measurements. For some molecules like H2, N2, and O2 very precise experimental data exist with an uncertainty of better than 0.1%. In general however, the experimental error is much higher. There are also molecules like HI, CH2Cl2 or CH2Br2 for which the available data do not even overlap within their error bars. The present tabulations should be used if highly accurate experimental values are needed.
Atom-Pair Kinetics with Strong Electric-Dipole Interactions
NASA Astrophysics Data System (ADS)
Thaicharoen, N.; Gonçalves, L. F.; Raithel, G.
2016-05-01
Rydberg-atom ensembles are switched from a weakly to a strongly interacting regime via adiabatic transformation of the atoms from an approximately nonpolar into a highly dipolar quantum state. The resultant electric dipole-dipole forces are probed using a device akin to a field ion microscope. Ion imaging and pair-correlation analysis reveal the kinetics of the interacting atoms. Dumbbell-shaped pair-correlation images demonstrate the anisotropy of the binary dipolar force. The dipolar C3 coefficient, derived from the time dependence of the images, agrees with the value calculated from the permanent electric-dipole moment of the atoms. The results indicate many-body dynamics akin to disorder-induced heating in strongly coupled particle systems.
NLO evolution of color dipoles in N=4 SYM
Chirilli, Giovanni A.; Balitsky, Ian
2009-07-04
Here, high-energy behavior of amplitudes in a gauge theory can be reformulated in terms of the evolution of Wilson-line operators. In the leading logarithmic approximation it is given by the conformally invariant BK equation for the evolution of color dipoles. In QCD, the next-to-leading order BK equation has both conformal and non-conformal parts, the latter providing the running of the coupling constant. To separate the conformally invariant effects from the running-coupling effects, we calculate the NLO evolution of the color dipoles in the conformalmore » $${\\cal N}$$=4 SYM theory. We define the "composite dipole operator" with the rapidity cutoff preserving conformal invariance.« less
The pygmy dipole resonance in neutron-rich nuclei
NASA Astrophysics Data System (ADS)
Quang Hung, Nguyen; Kiet, Hoang Anh Tuan; Duc, Huynh Ngoc; Thi Chuong, Nguyen
2016-06-01
The pygmy dipole resonance (PDR), which has been observed via the enhancement of the electric dipole strength E1 of atomic nuclei, is studied within a microscopic collective model. The latter employs the Hartree-Fock (HF) method with effective nucleon-nucleon interactions of the Skyrme types plus the random-phase approximation (RPA). The results of the calculations obtained for various even-even nuclei such as 16-28O, 40-58Ca, 100-120Sn, and 182-218Pb show that the PDR is significantly enhanced when the number of neutrons outside the stable core of the nucleus is increased, that is, in the neutron-rich nuclei. As the result, the relative ratio between the energy weighted sum of the strength of the PDR and that of the GDR (giant dipole resonance) does not exceed 4%. The collectivity of the PDR and GDR states will be also discussed.
NLO evolution of color dipoles in N=4 SYM
Balitsky, Ian; Chirilli, Giovanni
2009-01-01
High-energy behavior of amplitudes in a gauge theory can be reformulated in terms of the evolution of Wilson-line operators. In the leading logarithmic approximation it is given by the conformally invariant BK equation for the evolution of color dipoles. In QCD, the next-to-leading order BK equation has both conformal and non-conformal parts, the latter providing the running of the coupling constant. To separate the conformally invariant effects from the running-coupling effects, we calculate the NLO evolution of the color dipoles in the conformal ${\\cal N}$=4 SYM theory. We define the ``composite dipole operator' with the rapidity cutoff preserving conformal invariance. The resulting M\\"obius invariant kernel agrees with the forward NLO BFKL calculation of Ref. 1
Atom-Pair Kinetics with Strong Electric-Dipole Interactions.
Thaicharoen, N; Gonçalves, L F; Raithel, G
2016-05-27
Rydberg-atom ensembles are switched from a weakly to a strongly interacting regime via adiabatic transformation of the atoms from an approximately nonpolar into a highly dipolar quantum state. The resultant electric dipole-dipole forces are probed using a device akin to a field ion microscope. Ion imaging and pair-correlation analysis reveal the kinetics of the interacting atoms. Dumbbell-shaped pair-correlation images demonstrate the anisotropy of the binary dipolar force. The dipolar C_{3} coefficient, derived from the time dependence of the images, agrees with the value calculated from the permanent electric-dipole moment of the atoms. The results indicate many-body dynamics akin to disorder-induced heating in strongly coupled particle systems. PMID:27284655
Radiation from an off-centred rotating dipole in vacuum
NASA Astrophysics Data System (ADS)
Pétri, J.
2016-08-01
When a neutron star forms, after the collapse of its progenitor, a strong magnetic field survives in its interior. This magnetic topology is usually assumed to be well approximated by a dipole located right at the centre of the star. However, there is no particular reason why this dipole should be attached to this very special point. A slight shift from the stellar centre could have strong implications for the surrounding electromagnetic field configuration leading to clear observational signatures. We study the effect of the most general off-centred dipole anchored in the neutron star interior. Exact analytical solutions are given in vacuum outside the star to any order of accuracy in the small parameter ɛ = d/R, where d is the displacement of the dipole from the stellar centre and R the neutron star radius. As a simple diagnostic of this decentred dipole, the spin-down luminosity and the torque exerted on its crust are computed to the lowest leading order in ɛ. Results are compared to earlier works and a discussion on repercussions on pulsar braking index and multi-wavelength light curves is proposed.
Coherent and incoherent dipole-dipole interactions between atoms
NASA Astrophysics Data System (ADS)
Robicheaux, Francis
2016-05-01
Results will be presented on the collective interaction between atoms due to the electric dipole-dipole coupling between states of different parity on two different atoms. A canonical example of this effect is when the electronic state of one atom has S-character and the state of another atom has P-character. The energy difference between the two states plays an important role in the interaction since the change in energy determines the wave number of a photon that would cause a transition between the states. If the atoms are much closer than the wave length of this photon, then the dipole-dipole interaction is in the near field and has a 1 /r3 dependence on atomic separation. If the atoms are farther apart than the wave length, then the interaction is in the far field and has a 1 / r dependence. When many atoms interact, collective effects can dominate the system with the character of the collective effect depending on whether the atomic separation leads to near field or far field coupling. As an example of the case where the atoms are in the far field, the line broadening of transitions and strong deviations from the Beer-Lambert law in a diffuse gas will be presented. As an example of near field collective behavior, the radiative properties of a Rydberg gas will be presented. Based upon work supported by the National Science Foundation under Grant No. 1404419-PHY in collaboration with R.T. Sutherland.
Dipole relaxation in an electric field
NASA Astrophysics Data System (ADS)
Neumann, Richard M.
1980-07-01
From Boltzmann's equation, S=k lnΩ, an expression for the orientational entropy, S of a rigid rod (electric dipole) is derived. The free energy of the dipole in an electric field is then calculated as a function of both the dipole's average orientation and the field strength. Application of the equilibrium criterion to the free energy yields the field dependence of the entropy of the dipole. Irreversible thermodynamics is used to derive the general form of the equation of motion of the dipole's average orientation. Subsequent application of Newton's second law of motion produces Debye's classical expression for the relaxation of an electric dipole in a viscous medium.
Numerical Based Linear Model for Dipole Magnets
Li,Y.; Krinsky, S.; Rehak, M.
2009-05-04
In this paper, we discuss an algorithm for constructing a numerical linear optics model for dipole magnets from a 3D field map. The difference between the numerical model and K. Brown's analytic approach is investigated and clarified. It was found that the optics distortion due to the dipoles' fringe focusing must be properly taken into account to accurately determine the chromaticities. In NSLS-II, there are normal dipoles with 35-mm gap and dipoles for infrared sources with 90-mm gap. This linear model of the dipole magnets is applied to the NSLS-II lattice design to match optics parameters between the DBA cells having dipoles with different gaps.
Takashima, S
1993-01-01
Previously, we discussed the calculation of the dipole moments of small proteins using the three-dimensional protein data-base. Our results demonstrate that the calculated dipole moments are in acceptable agreement with measured values. We, however, noted the difficulty of the calculation with larger proteins, in particular those consisting of several subunits. Hemoglobin (Hb) is a protein having a molecular weight of 64,000 that consists of four subunits, a typical case where the computation was found to be difficult. To circumvent the difficulties, we calculated the dipole moment of each subunit separately. The dipole moment of the whole protein was calculated by the vectorial summation of subunit moments. With this method, the calculated net dipole moment is in good agreement with the experimental value. Our calculation shows that the dipole moment vectors of subunits are, by and large, antiparallel in tetramers causing partial cancellation of the net dipole moment. In addition to normal HbA, the dipole moment of abnormal HbS was calculated using an approximate computational technique. Because of the loss of two negative changes as a result of the replacement of glutamic acid with valine in beta-chains, the dipole moment of HbS was found, experimentally and theoretically, to be significantly smaller than that of HbA. PMID:8324190
Torney, D. C.
2001-01-01
We have begun to characterize a variety of codes, motivated by potential implementation as (quaternary) DNA n-sequences, with letters denoted A, C The first codes we studied are the most reminiscent of conventional group codes. For these codes, Hamming similarity was generalized so that the score for matched letters takes more than one value, depending upon which letters are matched [2]. These codes consist of n-sequences satisfying an upper bound on the similarities, summed over the letter positions, of distinct codewords. We chose similarity 2 for matches of letters A and T and 3 for matches of the letters C and G, providing a rough approximation to double-strand bond energies in DNA. An inherent novelty of DNA codes is 'reverse complementation'. The latter may be defined, as follows, not only for alphabets of size four, but, more generally, for any even-size alphabet. All that is required is a matching of the letters of the alphabet: a partition into pairs. Then, the reverse complement of a codeword is obtained by reversing the order of its letters and replacing each letter by its match. For DNA, the matching is AT/CG because these are the Watson-Crick bonding pairs. Reversal arises because two DNA sequences form a double strand with opposite relative orientations. Thus, as will be described in detail, because in vitro decoding involves the formation of double-stranded DNA from two codewords, it is reasonable to assume - for universal applicability - that the reverse complement of any codeword is also a codeword. In particular, self-reverse complementary codewords are expressly forbidden in reverse-complement codes. Thus, an appropriate distance between all pairs of codewords must, when large, effectively prohibit binding between the respective codewords: to form a double strand. Only reverse-complement pairs of codewords should be able to bind. For most applications, a DNA code is to be bi-partitioned, such that the reverse-complementary pairs are separated
Induced dipole-dipole interactions in light diffusion from point dipoles
NASA Astrophysics Data System (ADS)
Cherroret, Nicolas; Delande, Dominique; van Tiggelen, Bart A.
2016-07-01
We develop a perturbative treatment of induced dipole-dipole interactions in the diffusive transport of electromagnetic waves through disordered atomic clouds. The approach is exact at order 2 in the atomic density and accounts for the vector character of light. It is applied to the calculations of the electromagnetic energy stored in the atomic cloud, which modifies the energy transport velocity, and of the light scattering and transport mean free paths. Results are compared to those obtained from a purely scalar model for light.
Acoustic dispersion in a two-dimensional dipole system
Golden, Kenneth I.; Kalman, Gabor J.; Donko, Zoltan; Hartmann, Peter
2008-07-15
We calculate the full density response function and from it the long-wavelength acoustic dispersion for a two-dimensional system of strongly coupled point dipoles interacting through a 1/r{sup 3} potential at arbitrary degeneracy. Such a system has no random-phase-approximation (RPA) limit and the calculation has to include correlations from the outset. We follow the quasilocalized charge (QLC) approach, accompanied by molecular-dynamics (MD) simulations. Similarly to what has been recently reported for the closely spaced classical electron-hole bilayer [G. J. Kalman et al., Phys. Rev. Lett. 98, 236801 (2007)] and in marked contrast to the RPA, we report a long-wavelength acoustic phase velocity that is wholly maintained by particle correlations and varies linearly with the dipole moment p. The oscillation frequency, calculated both in an extended QLC approximation and in the Singwi-Tosi-Land-Sjolander approximation [Phys. Rev. 176, 589 (1968)], is invariant in form over the entire classical to quantum domains all the way down to zero temperature. Based on our classical MD-generated pair distribution function data and on ground-state energy data generated by recent quantum Monte Carlo simulations on a bosonic dipole system [G. E. Astrakharchik et al., Phys. Rev. Lett. 98, 060405 (2007)], there is a good agreement between the QLC approximation kinetic sound speeds and the standard thermodynamic sound speeds in both the classical and quantum domains.
Mutual impedance computation between printed dipoles
NASA Astrophysics Data System (ADS)
Alexopoulos, N. G.; Rana, I. E.
1981-01-01
The mutual impedance between microstrip dipoles printed on a grounded substrate is computed. Results for the microstrip dipoles in broadside, collinear, and echelon arrangements are presented. The significance of surface wave to mutual coupling is discussed.
Chalasani, P.; Saias, I.; Jha, S.
1996-04-08
As increasingly large volumes of sophisticated options (called derivative securities) are traded in world financial markets, determining a fair price for these options has become an important and difficult computational problem. Many valuation codes use the binomial pricing model, in which the stock price is driven by a random walk. In this model, the value of an n-period option on a stock is the expected time-discounted value of the future cash flow on an n-period stock price path. Path-dependent options are particularly difficult to value since the future cash flow depends on the entire stock price path rather than on just the final stock price. Currently such options are approximately priced by Monte carlo methods with error bounds that hold only with high probability and which are reduced by increasing the number of simulation runs. In this paper the authors show that pricing an arbitrary path-dependent option is {number_sign}-P hard. They show that certain types f path-dependent options can be valued exactly in polynomial time. Asian options are path-dependent options that are particularly hard to price, and for these they design deterministic polynomial-time approximate algorithms. They show that the value of a perpetual American put option (which can be computed in constant time) is in many cases a good approximation to the value of an otherwise identical n-period American put option. In contrast to Monte Carlo methods, the algorithms have guaranteed error bounds that are polynormally small (and in some cases exponentially small) in the maturity n. For the error analysis they derive large-deviation results for random walks that may be of independent interest.
Critical behavior of isotropic three-dimensional systems with dipole-dipole interactions
Belim, S. M.
2013-06-15
The critical behavior of Heisenberg magnets with dipole-dipole interactions near the line of second-order phase transitions directly in three-dimensional space is investigated in terms of a field-theoretic approach. The dependences of critical exponents on the dipole-dipole interaction parameter are derived. Comparison with experimental facts is made.
A skull-based multiple dipole phantom for EEG and MEG studies
Spencer, M.E.; Leahy, R.M.; Mosher, J.C.
1996-07-01
A versatile phantom for use in evaluating forward and inverse methods for MEG and EEG has been designed and is currently being constructed. The phantom consists of three major components: (i) a 32-element cur- rent dipole array, (ii) a PC-controlled dipole driver with 32 isolated channels allowing independent control of each dipole, (iii) spherical and human-skull mounts in which the dipole array is placed. Materials were selected throughout the phantom to produce minimal field distortions and artifacts to enable acquisition of high quality EEG and MEG data. The dipoles are made from a rigid narrow (0.84 mm) stainless steel coax cable. The dipole drivers can be configured as either current or voltage sources, are independently programmable and fully isolated, and are capable of producing arbitrary bipolar waveforms up to a 200 Hz bandwidth. The spherical mount is a single shell sphere filled with conductive gelatin. The human skull mount has three shells: ``brain`` (conducting gelatin), ``skull`` (the skull is impregnated with a low conductivity conducting gelatin), and ``scalp`` (a thin layer of rubber latex mixed with NaCl to achieve a conductivity matched to the brain). The conductivities will be adjusted to achieve approximately an 80:1:80 ratio. Data collected to date from the spherical phantom shows excellent agreement between measured surface potentials and that predicted from theory (27 of the 32 dipoles give better than 99.9% rms fit) and negligible leakage between dipoles. We are currently completing construction of the skull mount.
NASA Astrophysics Data System (ADS)
Cregg, P. J.; Murphy, Kieran; Mardinoglu, Adil; Prina-Mello, Adriele
2010-08-01
The implant assisted magnetic targeted drug delivery system of Avilés, Ebner and Ritter is considered both experimentally ( in vitro) and theoretically. The results of a 2D mathematical model are compared with 3D experimental results for a magnetizable wire stent. In this experiment a ferromagnetic, coiled wire stent is implanted to aid collection of particles which consist of single domain magnetic nanoparticles (radius ≈10 nm). In order to model the agglomeration of particles known to occur in this system, the magnetic dipole-dipole and hydrodynamic interactions for multiple particles are included. Simulations based on this mathematical model were performed using open source C++ code. Different initial positions are considered and the system performance is assessed in terms of collection efficiency. The results of this model show closer agreement with the measured in vitro experimental results and with the literature. The implications in nanotechnology and nanomedicine are based on the prediction of the particle efficiency, in conjunction with the magnetizable stent, for targeted drug delivery.
Microwaves Probe Dipole Blockade and van der Waals Forces in a Cold Rydberg Gas.
Teixeira, R Celistrino; Hermann-Avigliano, C; Nguyen, T L; Cantat-Moltrecht, T; Raimond, J M; Haroche, S; Gleyzes, S; Brune, M
2015-07-01
We show that microwave spectroscopy of a dense Rydberg gas trapped on a superconducting atom chip in the dipole blockade regime reveals directly the dipole-dipole many-body interaction energy spectrum. We use this method to investigate the expansion of the Rydberg cloud under the effect of repulsive van der Waals forces and the breakdown of the frozen gas approximation. This study opens a promising route for quantum simulation of many-body systems and quantum information transport in chains of strongly interacting Rydberg atoms. PMID:26182093
Heat pipe transient response approximation
NASA Astrophysics Data System (ADS)
Reid, Robert S.
2002-01-01
A simple and concise routine that approximates the response of an alkali metal heat pipe to changes in evaporator heat transfer rate is described. This analytically based routine is compared with data from a cylindrical heat pipe with a crescent-annular wick that undergoes gradual (quasi-steady) transitions through the viscous and condenser boundary heat transfer limits. The sonic heat transfer limit can also be incorporated into this routine for heat pipes with more closely coupled condensers. The advantages and obvious limitations of this approach are discussed. For reference, a source code listing for the approximation appears at the end of this paper. .
Collectivity of dipole bands in {sup 196}Pb
Carpenter, M.P.; Liang, Y.; Janssens, R.V.F.
1995-08-01
The region of nuclei with mass {approximately} 190 was studied extensively over the last few years following the discovery of superdeformation in {sup 190}Hg. More recently, considerable interest in the neutron-deficient Pb isotopes developed with the discover of a number of bands at high spin connected by dipole transitions in both even {sup 192-200}Pb and odd {sup 197-201}Pb nuclei. The majority of the dipole bands are regular in character (i.e. transition energies increase smoothly with spin) while the remaining bands are referred to as irregular in character, due to the fact that the transition energies do not increase smoothly with spin. The properties of the dipole bands were interpreted in terms of high-K, moderately-deformed oblate states built on configurations involving high-J, shape-driving quasiproton excitations coupled to rotation-aligned quasineutrons. It was suggested that the difference between the regular and irregular dipole sequences is related to the deformation where the irregular sequences are thought to be less collective than their regular counterparts.
Constraining the neutrino magnetic dipole moment from white dwarf pulsations
NASA Astrophysics Data System (ADS)
Córsico, A. H.; Althaus, L. G.; Miller Bertolami, M. M.; Kepler, S. O.; García-Berro, E.
2014-08-01
Pulsating white dwarf stars can be used as astrophysical laboratories to constrain the properties of weakly interacting particles. Comparing the cooling rates of these stars with the expected values from theoretical models allows us to search for additional sources of cooling due to the emission of axions, neutralinos, or neutrinos with magnetic dipole moment. In this work, we derive an upper bound to the neutrino magnetic dipole moment (μν) using an estimate of the rate of period change of the pulsating DB white dwarf star PG 1351+489. We employ state-of-the-art evolutionary and pulsational codes which allow us to perform a detailed asteroseismological period fit based on fully DB white dwarf evolutionary sequences. Plasmon neutrino emission is the dominant cooling mechanism for this class of hot pulsating white dwarfs, and so it is the main contributor to the rate of change of period with time (Pi dot) for the DBV class. Thus, the inclusion of an anomalous neutrino emission through a non-vanishing magnetic dipole moment in these sequences notably influences the evolutionary timescales, and also the expected pulsational properties of the DBV stars. By comparing the theoretical Pi dot value with the rate of change of period with time of PG 1351+489, we assess the possible existence of additional cooling by neutrinos with magnetic dipole moment. Our models suggest the existence of some additional cooling in this pulsating DB white dwarf, consistent with a non-zero magnetic dipole moment with an upper limit of μν lesssim 10-11 μB. This bound is somewhat less restrictive than, but still compatible with, other limits inferred from the white dwarf luminosity function or from the color-magnitude diagram of the Globular cluster M5. Further improvements of the measurement of the rate of period change of the dominant pulsation mode of PG 1351+489 will be necessary to confirm our bound.
Constraining the neutrino magnetic dipole moment from white dwarf pulsations
Córsico, A.H.; Althaus, L.G.; García-Berro, E. E-mail: althaus@fcaglp.unlp.edu.ar E-mail: kepler@if.ufrgs.br
2014-08-01
Pulsating white dwarf stars can be used as astrophysical laboratories to constrain the properties of weakly interacting particles. Comparing the cooling rates of these stars with the expected values from theoretical models allows us to search for additional sources of cooling due to the emission of axions, neutralinos, or neutrinos with magnetic dipole moment. In this work, we derive an upper bound to the neutrino magnetic dipole moment (μ{sub ν}) using an estimate of the rate of period change of the pulsating DB white dwarf star PG 1351+489. We employ state-of-the-art evolutionary and pulsational codes which allow us to perform a detailed asteroseismological period fit based on fully DB white dwarf evolutionary sequences. Plasmon neutrino emission is the dominant cooling mechanism for this class of hot pulsating white dwarfs, and so it is the main contributor to the rate of change of period with time (Pidot) for the DBV class. Thus, the inclusion of an anomalous neutrino emission through a non-vanishing magnetic dipole moment in these sequences notably influences the evolutionary timescales, and also the expected pulsational properties of the DBV stars. By comparing the theoretical Pidot value with the rate of change of period with time of PG 1351+489, we assess the possible existence of additional cooling by neutrinos with magnetic dipole moment. Our models suggest the existence of some additional cooling in this pulsating DB white dwarf, consistent with a non-zero magnetic dipole moment with an upper limit of μ{sub ν} ∼< 10{sup -11} μ{sub B}. This bound is somewhat less restrictive than, but still compatible with, other limits inferred from the white dwarf luminosity function or from the color-magnitude diagram of the Globular cluster M5. Further improvements of the measurement of the rate of period change of the dominant pulsation mode of PG 1351+489 will be necessary to confirm our bound.
Presheaths in multi-dipole plasma
Hala, A.M.; Hershkowitz, N.
1998-12-31
Measurements of plasma presheath thickness as a function of pressure (0.5 to 2 mTorr) were made in a DC hot-filament produced multi-dipole plasma discharge. The presheath plasma potential near a negatively biased plate (D = 10 cm) was mapped with an emissive probe. The inflection point method in the limit of zero emission was used. The probe measurement of the plasma potential were accurate to approximately 0.1 V. Measurements were made in plasmas based on nitrogen, argon and combinations of both gases. Experimental results were similar to those found in ECR magnetized plasmas. The presheaths were found to be regions of approximately constant electric field with characteristic lengths the order of the ion-neutral collision lengths. The results show contraction of the presheath as the pressure increased. Two competing processes affect the presheath. These are ionization and collisions with ionization becoming more important at lower pressures. Experimental results are compared to various presheath models.
RHIC spin flipper AC dipole controller
Oddo, P.; Bai, M.; Dawson, C.; Gassner, D.; Harvey, M.; Hayes, T.; Mernick, K.; Minty, M.; Roser, T.; Severino, F.; Smith, K.
2011-03-28
The RHIC Spin Flipper's five high-Q AC dipoles which are driven by a swept frequency waveform require precise control of phase and amplitude during the sweep. This control is achieved using FPGA based feedback controllers. Multiple feedback loops are used to and dynamically tune the magnets. The current implementation and results will be presented. Work on a new spin flipper for RHIC (Relativistic Heavy Ion Collider) incorporating multiple dynamically tuned high-Q AC-dipoles has been developed for RHIC spin-physics experiments. A spin flipper is needed to cancel systematic errors by reversing the spin direction of the two colliding beams multiple times during a store. The spin flipper system consists of four DC-dipole magnets (spin rotators) and five AC-dipole magnets. Multiple AC-dipoles are needed to localize the driven coherent betatron oscillation inside the spin flipper. Operationally the AC-dipoles form two swept frequency bumps that minimize the effect of the AC-dipole dipoles outside of the spin flipper. Both AC bumps operate at the same frequency, but are phase shifted from each other. The AC-dipoles therefore require precise control over amplitude and phase making the implementation of the AC-dipole controller the central challenge.
Quantum synchronization of ultracold atoms with dipole-dipole interactions in an optical lattice
NASA Astrophysics Data System (ADS)
Zhu, Bihui; Restrepo, Juan; Rey, Ana Maria; Holland, Murray
2014-05-01
Ultracold atoms confined in an optical lattice have been utilized as a powerful platform to study versatile many-body physics both experimentally and theoretically. A recent research focus has been the novel phenomena that would emerge with long-range interactions, which become especially important for atomic clocks where ultrahigh precision can amplify these effects. We develop theoretical models treating the two-level atoms as oscillators and study the synchronization of phases among a large ensemble of atoms coupled by dipole-dipole interactions, where the effect of geometry becomes relevant. We investigate the onset of synchronization and the related phase diagram, and further discuss the parameter regime for potential experimental observation using ultracold atoms such as Strontium. By applying different numerical methods, eg., quantum trajectories and truncated Wigner approximations to compare with the mean-field results, we also explore the underlying role of quantum fluctuations. We acknowledge funding from NIST, JILA-NSF-PFC-1125844, NSF-PIF, ARO, ARO-DARPA-OLE, and AFOSR.
NASA Technical Reports Server (NTRS)
Bailey, M. C.
1985-01-01
A 6X6 array of fan-dipoles was designed to operate in the 510 to 660 MHz frequency range for aircraft flight test and evaluation of a UHF radiometer system. A broad-band dipole design operating near the first resonance is detailed. Measured VSWR and radiation patterns for the dipole array demonstrate achievable bandwidths in the 35 percent to 40 percent range.
Bose gas in a single-beam optical dipole trap
Simon, Lena; Strunz, Walter T.
2010-06-15
We study an ultracold Bose gas in an optical dipole trap consisting of one single focused laser beam. An analytical expression for the corresponding density of states beyond the usual harmonic approximation is obtained. We are thus able to discuss the existence of a critical temperature for Bose-Einstein condensation and find that the phase transition must be enabled by a cutoff near the threshold. Moreover, we study the dynamics of evaporative cooling and observe significant deviations from the findings for the well-established harmonic approximation. Furthermore, we investigate Bose-Einstein condensates in such a trap in Thomas-Fermi approximation and determine analytical expressions for chemical potential, internal energy, and Thomas-Fermi radii beyond the usual harmonic approximation.
Study of Collective Dipole Excitations below the Giant Dipole Resonance at HI{gamma}S
Tonchev, A. P.; Howell, C. R.; Tornow, W.; Angell, C.; Boswell, M.; Karwowski, H. J.; Chyzh, A.; Kelley, J. H.; Tsoneva, N.; Wu, Y. K.
2007-02-26
The High-Intensity Gamma-ray Source utilizing intra-cavity back-scattering of free electron laser photons from relativistic electrons allows one to produce a unique beam of high-flux gamma rays with 100% polarization and selectable energy and energy resolution which is ideal for low-energy {gamma}-ray scattering experiments. Nuclear resonance fluorescence experiments have been performed on N=82 nuclei. High sensitivity studies of E1 and M1 excitations at energies close to the neutron emission threshold have been performed. The method allows the determination of excitation energies, spin, parities, and decay branching ratios of the pygmy dipole mode of excitation. The observations are compared with calculations using statistical and quasi-particle random-phase approximations.
Top quark electromagnetic dipole moments
NASA Astrophysics Data System (ADS)
Bouzas, Antonio O.; Larios, F.
2015-11-01
The magnetic and electric dipole moments of the top quark are constrained indirectly by the Br(B → Xsγ) and the ACP(B → Xsγ) measurements. They can also be tested by top quark production and decay processes. The recent measurement of production by CDF are used to set direct constraints. The B → Xsγ measurements by themselves define an allowed parameter region that sets up stringent constraints on both dipole moments. The measurement by CDF has a ∼ 37% error that is too large to set any competitive bounds, for which a much lower 5% error would be required. For the LHC it is found that with its higher energy the same measurement could indeed further constrain the allowed parameter region given by the B → Xsγ measurement [1]. In addition, the proposed LHeC experiment (electron- proton) could provide even more stringent constraints than the LHC via the photoproduction channel [2].
Nuclear Electric Dipole Moment Calculations
NASA Astrophysics Data System (ADS)
Haxton, Wick
2010-11-01
One of the most important constraints on CP violation in the nucleon and NN interaction is provided by electric dipole moment (EDM) limits for neutral diamagnetic atoms, particularly 199Hg. To extract CP-violating couplings from experiment, one must relate the atomic EDM to the underlying nuclear CP-odd moments, a task complicated by the atomic response, which largely shields the nucleus from the applied external electric field. The residual response -- the Schiff moment -- depends on corrections such as the finite size of the nucleus. Conventional Schiff-moment calculations have largely ignored one consequence of the screening: the cancellation between direct and polarization diagrams, which yields an answer that is suppressed by two powers of RN/RA, where RN and RA are the nuclear and atomic sizes, requires one to identify all other terms that contribute to the same order in the RN/RA power counting. We show that such terms arise from nuclear excitations associated with the dipole charge and transverse electric multipole operators, and discuss the consequences. We also describe higher T-odd moments that contribute up to the same order in the counting, and point out interesting nuclear structure and experimental consequences.
Isospin properties of electric dipole excitations in 48Ca
NASA Astrophysics Data System (ADS)
Derya, V.; Savran, D.; Endres, J.; Harakeh, M. N.; Hergert, H.; Kelley, J. H.; Papakonstantinou, P.; Pietralla, N.; Ponomarev, V. Yu.; Roth, R.; Rusev, G.; Tonchev, A. P.; Tornow, W.; Wörtche, H. J.; Zilges, A.
2014-03-01
Two different experimental approaches were combined to study the electric dipole strength in the doubly-magic nucleus 48Ca below the neutron threshold. Real-photon scattering experiments using bremsstrahlung up to 9.9 MeV and nearly mono-energetic linearly polarized photons with energies between 6.6 and 9.51 MeV provided strength distribution and parities, and an (α,α‧γ) experiment at Eα=136 MeV gave cross sections for an isoscalar probe. The unexpected difference observed in the dipole response is compared to calculations using the first-order random-phase approximation and points to an energy-dependent isospin character. A strong isoscalar state at 7.6 MeV was identified for the first time supporting a recent theoretical prediction.
Dipole moments and electron distribution of furoxans and furazans
NASA Astrophysics Data System (ADS)
Všetečka, Václav; Fruttero, Roberta; Gasco, Alberto; Exner, Otto
1994-08-01
Dipole moments of a set of substituted 1,2,5-oxadiazoles (furazans) and 1,2,5-oxadiazole-2-oxides (furoxans) were measured in benzene solution. The dipole moment in furazan is oriented with the negative end towards oxygen in agreement with common opinion but contrary to the literature. Comparison of the two classes of compounds revealed a strong electron shift in furoxans, from the exocyclic oxygen back into the heterocyclic system, corresponding to a mesomeric moment of approximately 3D. However, the electron redistribution cannot be described in terms of simple mesomeric structures. The molecule of furoxan is well characterized as electron-overcrowded, particularly in the vicinity of the nitrogen atom N(2).
Spectral Distortions of the CMB Dipole
NASA Astrophysics Data System (ADS)
Balashev, S. A.; Kholupenko, E. E.; Chluba, J.; Ivanchik, A. V.; Varshalovich, D. A.
2015-09-01
We consider the distortions of the cosmic microwave background (CMB) dipole anisotropy related to primordial recombination radiation (PRR) and primordial y- and μ-distortions. The signals arise due to our motion relative to the CMB restframe and appear as a frequency-dependent distortion of the CMB temperature dipole. To leading order, the expected relative distortion of the CMB dipole does not depend on the particular observation directions and reaches the level of 10-6 for the PRR- and μ-distortions and 10-5 for the y-distortion in the frequency range 1-700 GHz. The temperature differences arising from the dipole anisotropy of the relic CMB distortions depend on the observation directions. For mutually opposite directions, collinear to the CMB dipole axis, the temperature differences due to the PRR- and μ-dipole anisotropy attain values {{Δ }}T≃ 10 {nK} in the considered range. The temperature difference arising from the y-dipole anisotropy may reach values of up to 1 μ {{K}}. The key features of the considered effect are as follow: (i) an observation of the effect does not require absolute calibration; (ii) patches of sky with minimal foreground contamination can be chosen. Future measurements of the CMB dipole distortion thus will provide an alternative method for direct detection of the PRR-, y-, and μ-distortions. The y-distortion dipole may be detectable with PIXIE at a few standard deviations.
Testing of a Single 11 T $Nb_3Sn$ Dipole Coil Using a Dipole Mirror Structure
Zlobin, Alexander; Andreev, Nicolai; Barzi, Emanuela; Chlachidze, Guram; Kashikhin, Vadim; Nobrega, Alfred; Novitski, Igor; Turrioni, Daniele; Karppinen, Mikko; Smekens, David
2014-07-01
FNAL and CERN are developing an 11 T Nb3Sn dipole suitable for installation in the LHC. To optimize coil design parameters and fabrication process and study coil performance, a series of 1 m long dipole coils is being fabricated. One of the short coils has been tested using a dipole mirror structure. This paper describes the dipole mirror magnetic and mechanical designs, and reports coil parameters and test results.
Microwave pump-probe spectroscopy of the dipole-dipole interaction in a cold Rydberg gas
NASA Astrophysics Data System (ADS)
Park, Hyunwook; Gallagher, T. F.; Pillet, P.
2016-05-01
Microwave pump-probe experiments starting with a cold gas of Rb 34 s atoms confirm that cusped line shapes observed in dipole-dipole broadened microwave transitions are due to atoms which are widely separated and exhibit small dipole-dipole energy shifts. When the experiments are interpreted in terms of a nearest-neighbor model, they demonstrate that it is possible to select pairs of atoms based on their separation and orientation.
Coupled-Channel Models of Direct-Semidirect Capture via Giant-Dipole Resonances
Thompson, I J; Escher, Jutta E; Arbanas, Goran
2013-01-01
Semidirect capture, a two-step process that excites a giant-dipole resonance followed by its radiative de-excitation, is a dominant process near giant-dipole resonances, that is, for incoming neutron energies within 5 20 MeV. At lower energies such processes may affect neutron capture rates that are relevant to astrophysical nucleosynthesis models. We implement a semidirect capture model in the coupled-channel reaction code Fresco and validate it by comparing the cross section for direct-semidirect capture 208Pb(n,g)209Pb to experimental data. We also investigate the effect of low-energy electric dipole strength in the pygmy resonance. We use a conventional single-particle direct-semidirect capture code Cupido for comparison. Furthermore, we present and discuss our results for direct-semidirect capture reaction 130Sn(n,g)131Sn, the cross section of which is known to have a significant effect on nucleosynthesis models.
Coupled-Channel Models of Direct-Semidirect Capture via Giant-Dipole Resonances
NASA Astrophysics Data System (ADS)
Thompson, I. J.; Escher, J. E.; Arbanas, G.
2014-04-01
Semidirect capture, a two-step process that excites a giant-dipole resonance followed by its radiative de-excitation, is a dominant process near giant-dipole resonances, that is, for incoming neutron energies within 5-20 MeV. At lower energies such processes may affect neutron capture rates that are relevant to astrophysical nucleosynthesis models. We implement a semidirect capture model in the coupled-channel reaction code Fresco and validate it by comparing the cross section for direct-semidirect capture 208Pb(n,γ)209Pb to experimental data. We also investigate the effect of low-energy electric dipole strength in the pygmy resonance. We use a conventional single-particle direct-semidirect capture code Cupido for comparison. Furthermore, we present and discuss our results for direct-semidirect capture reaction 130Sn(n,γ)131Sn, the cross section of which is known to have a significant effect on nucleosynthesis models.
Whistler choruswaves: Linear theory and nonlinear simulations in dipole geometry
NASA Astrophysics Data System (ADS)
Wu, Shuo
Whistler-mode chorus waves have recently drawn tremendous attention as an important mechanism for controlling the energetic electron flux in Earth's radiation belt. This dissertation aims to answer questions about whistler-mode chorus waves, such as "What is the effect of cold plasma density on the linear whistler instability? How do whistler mode chorus waves evolve in a meridional plane? How would chorus waves occur if the magnetosphere is compressed?" First, we derive the real dispersion relation and linear growth rate of whistler mode in mixed hot and cold plasma. We find that there is a peak in the temporal and convective growth rates with respect to cold plasma density. We model the relation between the linear growth rate and various plasma parameters and use this model to explain the observed modulation of chorus intensity by cold plasma density. Second, we simulate the nonlinear growth of whistler-mode chorus waves in a dipole field using a hybrid code. The hybrid code uses the particle-in-cell technique in generalized orthogonal coordinates. A small fraction of electrons is treated as particles with anisotropic temperature that leads to the whistler instability. Other electrons are treated as a cold fluid without mass. The rough validity of our model is confirmed by comparing results from our hybrid code and a full dynamics particle in cell code. Our 1-D simulations along the dipole field line reproduce chorus generation in agreement with observations and past studies. We find that it is easier to simulate temporal frequency variation in a scaled down system with greater magnetic field inhomogeneity. Our 2-D simulations reveal features of chorus propagation in a meridional plane and the effects of background plasma density on that propagation. These are the first 2-D first principles simulations of whistler-mode chorus waves in Earth's dipole field. Our preliminary simulation in a 1-D compressed dipole field is the first attempt to self
Mathematical algorithms for approximate reasoning
NASA Technical Reports Server (NTRS)
Murphy, John H.; Chay, Seung C.; Downs, Mary M.
1988-01-01
Most state of the art expert system environments contain a single and often ad hoc strategy for approximate reasoning. Some environments provide facilities to program the approximate reasoning algorithms. However, the next generation of expert systems should have an environment which contain a choice of several mathematical algorithms for approximate reasoning. To meet the need for validatable and verifiable coding, the expert system environment must no longer depend upon ad hoc reasoning techniques but instead must include mathematically rigorous techniques for approximate reasoning. Popular approximate reasoning techniques are reviewed, including: certainty factors, belief measures, Bayesian probabilities, fuzzy logic, and Shafer-Dempster techniques for reasoning. A group of mathematically rigorous algorithms for approximate reasoning are focused on that could form the basis of a next generation expert system environment. These algorithms are based upon the axioms of set theory and probability theory. To separate these algorithms for approximate reasoning various conditions of mutual exclusivity and independence are imposed upon the assertions. Approximate reasoning algorithms presented include: reasoning with statistically independent assertions, reasoning with mutually exclusive assertions, reasoning with assertions that exhibit minimum overlay within the state space, reasoning with assertions that exhibit maximum overlay within the state space (i.e. fuzzy logic), pessimistic reasoning (i.e. worst case analysis), optimistic reasoning (i.e. best case analysis), and reasoning with assertions with absolutely no knowledge of the possible dependency among the assertions. A robust environment for expert system construction should include the two modes of inference: modus ponens and modus tollens. Modus ponens inference is based upon reasoning towards the conclusion in a statement of logical implication, whereas modus tollens inference is based upon reasoning away
NASA Astrophysics Data System (ADS)
Gang, Yin; Yingtang, Zhang; Hongbo, Fan; Zhining, Li; Guoquan, Ren
2016-05-01
We have developed a method for automatic detection, localization and classification (DLC) of multiple dipole sources using magnetic gradient tensor data. First, we define modified tilt angles to estimate the approximate horizontal locations of the multiple dipole-like magnetic sources simultaneously and detect the number of magnetic sources using a fixed threshold. Secondly, based on the isotropy of the normalized source strength (NSS) response of a dipole, we obtain accurate horizontal locations of the dipoles. Then the vertical locations are calculated using magnitude magnetic transforms of magnetic gradient tensor data. Finally, we invert for the magnetic moments of the sources using the measured magnetic gradient tensor data and forward model. Synthetic and field data sets demonstrate effectiveness and practicality of the proposed method.
Jun, James Jaeyoon; Longtin, André; Maler, Leonard
2013-01-01
In order to survive, animals must quickly and accurately locate prey, predators, and conspecifics using the signals they generate. The signal source location can be estimated using multiple detectors and the inverse relationship between the received signal intensity (RSI) and the distance, but difficulty of the source localization increases if there is an additional dependence on the orientation of a signal source. In such cases, the signal source could be approximated as an ideal dipole for simplification. Based on a theoretical model, the RSI can be directly predicted from a known dipole location; but estimating a dipole location from RSIs has no direct analytical solution. Here, we propose an efficient solution to the dipole localization problem by using a lookup table (LUT) to store RSIs predicted by our theoretically derived dipole model at many possible dipole positions and orientations. For a given set of RSIs measured at multiple detectors, our algorithm found a dipole location having the closest matching normalized RSIs from the LUT, and further refined the location at higher resolution. Studying the natural behavior of weakly electric fish (WEF) requires efficiently computing their location and the temporal pattern of their electric signals over extended periods. Our dipole localization method was successfully applied to track single or multiple freely swimming WEF in shallow water in real-time, as each fish could be closely approximated by an ideal current dipole in two dimensions. Our optimized search algorithm found the animal’s positions, orientations, and tail-bending angles quickly and accurately under various conditions, without the need for calibrating individual-specific parameters. Our dipole localization method is directly applicable to studying the role of active sensing during spatial navigation, or social interactions between multiple WEF. Furthermore, our method could be extended to other application areas involving dipole source
Dipole spectrum structure of nonresonant nonpertubative driven two-level atoms
Picon, A.; Mompart, J.; Corbalan, R.; Roso, L.; Varela, O.; Plaja, L.; Ahufinger, V.
2010-03-15
We analyze the dipole spectrum of a two-level atom excited by a nonresonant intense monochromatic field under the electric dipole approximation and beyond the rotating wave approximation. We show that the apparently complex spectral structure can be completely described by two families: harmonic frequencies of the driving field and field-induced nonlinear fluorescence. Our formulation of the problem provides quantitative laws for the most relevant spectral features: harmonic ratios and phases, nonperturbative Stark shift, and frequency limits of the harmonic plateau. In particular, we demonstrate the locking of the harmonic phases at the wings of the plateau opening the possibility of ultrashort pulse generation through harmonic filtering.
Stripline dipole with dielectric covering
NASA Astrophysics Data System (ADS)
Wang, J.; Hansen, V.
The use of stripline antennas has greatly increased during the last ten years. In connection with an employment of the antennas, it is often necessary to provide an additional dielectric covering layer to protect the antenna against atmospheric conditions. Water or ice layers can also be described as dielectric layers. The present investigation is concerned with the effect of such additional layers on the radiation characteristics of stripline dipoles. A description is presented of a procedure for the calculation of all important antenna characteristics, taking into account current distribution, input impedance, radiation characteristics, the excitation of surface waves, and aspects of coupling. With the aid of a number of examples it is shown that even a thin covering layer can have a pronounced effect. Such layers can, therefore, also be employed to modify the antenna radiation characteristics to improve their suitability for a given application.
Dipole Relaxation in an Electric Field.
ERIC Educational Resources Information Center
Neumann, Richard M.
1980-01-01
Derives an expression for the orientational entropy of a rigid rod (electric dipole) from Boltzmann's equation. Subsequent application of Newton's second law of motion produces Debye's classical expression for the relaxation of an electric dipole in a viscous medium. (Author/GS)
How to Introduce the Magnetic Dipole Moment
ERIC Educational Resources Information Center
Bezerra, M.; Kort-Kamp, W. J. M.; Cougo-Pinto, M. V.; Farina, C.
2012-01-01
We show how the concept of the magnetic dipole moment can be introduced in the same way as the concept of the electric dipole moment in introductory courses on electromagnetism. Considering a localized steady current distribution, we make a Taylor expansion directly in the Biot-Savart law to obtain, explicitly, the dominant contribution of the…
Electric dipoles on the Bloch sphere
NASA Astrophysics Data System (ADS)
Vutha, Amar C.
2015-03-01
The time evolution of a two-level quantum mechanical system can be geometrically described using the Bloch sphere. By mapping the Bloch sphere evolution onto the dynamics of oscillating electric dipoles, we provide a physically intuitive link between classical electromagnetism and the electric dipole transitions of atomic and molecular physics.
Final Report: Levitated Dipole Experiment
Kesner, Jay; Mauel, Michael
2013-03-10
Since the very first experiments with the LDX, research progress was rapid and significant. Initial experiments were conducted with the high-field superconducting coil suspended by three thin rods. These experiments produced long-pulse, quasi-steady-state microwave discharges, lasting more than 10 s, having peak beta values of 20% [Garnier et al., Physics of Plasmas, 13 (2006) 056111]. High- beta, near steady-state discharges have been maintained in LDX for more than 20 seconds, and this capability made LDX the longest pulse fusion confinement experiment operating in the U.S. fusion program. A significant measure of progress in the LDX research program was the routine investigation of plasma confinement with a magnetically-levitated dipole and the resulting observations of confinement improvement. In both supported and levitated configurations, detailed measurements were made of discharge evolution, plasma dynamics and instability, and the roles of gas fueling, microwave power deposition profiles, and plasma boundary shape. High-temperature plasma was created by multi frequency electron cyclotron resonance heating at 2.45 GHz, 6.4 GHz, 10.5 GHz and 28 GHz allowing control of heating profiles. Depending upon neutral fueling rates, the LDX discharges contain a fraction of energetic electrons, with mean energies above 50 keV. Depending on whether or not the superconducting dipole was levitated or supported, the peak thermal electron temperature was estimated to exceed 500 eV and peak densities to approach 1e18 m^{-3}. We have found that levitation causes a strong inwards density pinch [Boxer et al., Nature Physics, 6 (2010) 207] and we have observed the central plasma density increase dramatically indicating a significant improvement in the confinement of a thermal plasma species.
Rasin, A.
1994-04-01
We discuss the idea of approximate flavor symmetries. Relations between approximate flavor symmetries and natural flavor conservation and democracy models is explored. Implications for neutrino physics are also discussed.
High-field dipoles for future accelerators
Wipf, S.L.
1984-09-01
This report presents the concept for building superconducting accelerator dipoles with record high fields. Economic considerations favor the highest possible current density in the windings. Further discussion indicates that there is an optimal range of pinning strength for a superconducting material and that it is not likely for multifilamentary conductors to ever equal the potential performance of tape conductors. A dipole design with a tape-wound, inner high-field winding is suggested. Methods are detailed to avoid degradation caused by flux jumps and to overcome problems with the dipole ends. Concerns for force support structure and field precision are also addressed. An R and D program leading to a prototype 11-T dipole is outlined. Past and future importance of superconductivity to high-energy physics is evident from a short historical survey. Successful dipoles in the 10- to 20-T range will allow interesting options for upgrading present largest accelerators.
Reappraisal of the Electric Dipole Moment Enhancement Factor for Thallium
Nataraj, H. S.; Sahoo, B. K.; Das, B. P.; Mukherjee, D.
2011-05-20
The electric dipole moment (EDM) enhancement factor of atomic Tl is of considerable interest as it has been used in determining the most accurate limit on the electron EDM to date. However, its value varies from -179 to -1041 in different approximations. In view of the large uncertainties associated with many of these calculations, we perform an accurate calculation employing the relativistic coupled-cluster theory and obtain -466, which in combination with the most accurate measurement of Tl EDM [Phys. Rev. Lett. 88, 071805 (2002)] yields a new limit for the electron EDM: |d{sub e}|<2.0x10{sup -27}e cm.
Parity-violating electric-dipole transitions in helium
NASA Technical Reports Server (NTRS)
Hiller, J.; Sucher, J.; Bhatia, A. K.; Feinberg, G.
1980-01-01
The paper examines parity-violating electric-dipole transitions in He in order to gain insight into the reliability of approximate calculations which are carried out for transitions in many-electron atoms. The contributions of the nearest-lying states are computed with a variety of wave functions, including very simple product wave functions, Hartree-Fock functions and Hylleraas-type wave functions with up to 84 parameters. It is found that values of the matrix elements of the parity-violating interaction can differ considerably from the values obtained from the good wave functions, even when these simple wave functions give accurate values for the matrix elements in question
Final Report: Levitated Dipole Experiment
Kesner, Jay; Mauel, Michael
2013-03-10
Since the very first experiments with the LDX, research progress was rapid and significant. Initial experiments were conducted with the high-field superconducting coil suspended by three thin rods. These experiments produced long-pulse, quasi-steady-state microwave discharges, lasting more than 10 s, having peak beta values of 20% [Garnier, Phys. Plasmas, v13, p. 056111, 2006]. High-beta, near steady-state discharges have been maintained in LDX for more than 20 seconds, and this capability makes LDX the longest pulse fusion confinement experiment now operating in the U.S. fusion program. In both supported and levitated configurations, detailed measurements are made of discharge evolution, plasma dynamics and instability, and the roles of gas fueling, microwave power deposition profiles, and plasma boundary shape. High-temperature plasma is created by multifrequency electron cyclotron resonance heating allowing control of heating profiles. Depending upon neutral fueling rates, the LDX discharges contain a fraction of energetic electrons, with mean energies above 50 keV. Depending on whether or not the superconducting dipole is levitated or supported, the peak thermal electron temperature is estimated to exceed 500 eV and peak densities reach 1.0E18 (1/m3). Several significant discoveries resulted from the routine investigation of plasma confinement with a magnetically-levitated dipole. For the first time, toroidal plasma with pressure approaching the pressure of the confining magnetic field was well-confined in steady-state without a toroidal magnetic field. Magnetic levitation proved to be reliable and is now routine. The dipole's cryostat allows up to three hours of "float time" between re-cooling with liquid helium and providing scientists unprecedented access to the physics of magnetizd plasma. Levitation eliminates field-aligned particle sources and sinks and results in a toroidal, magnetically-confined plasma where profiles are determined by cross
Dipole-dipole resonance line shapes in a cold Rydberg gas
NASA Astrophysics Data System (ADS)
Richards, B. G.; Jones, R. R.
2016-04-01
We have explored the dipole-dipole mediated, resonant energy transfer reaction, 32 p3 /2+32 p3 /2→32 s +33 s , in an ensemble of cold 85Rb Rydberg atoms. Stark tuning is employed to measure the population transfer probability as a function of the total electronic energy difference between the initial and final atom-pair states over a range of Rydberg densities, 2 ×108≤ρ ≤3 ×109 cm-3. The observed line shapes provide information on the role of beyond nearest-neighbor interactions, the range of Rydberg atom separations, and the electric field inhomogeneity in the sample. The widths of the resonance line shapes increase approximately linearly with the Rydberg density and are only a factor of 2 larger than expected for two-body, nearest-neighbor interactions alone. These results are in agreement with the prediction [B. Sun and F. Robicheaux, Phys. Rev. A 78, 040701(R) (2008), 10.1103/PhysRevA.78.040701] that beyond nearest-neighbor exchange interactions should not influence the population transfer process to the degree once thought. At low densities, Gaussian rather than Lorentzian line shapes are observed due to electric field inhomogeneities, allowing us to set an upper limit for the field variation across the Rydberg sample. At higher densities, non-Lorentzian, cusplike line shapes characterized by sharp central peaks and broad wings reflect the random distribution of interatomic distances within the magneto-optical trap (MOT). These line shapes are well reproduced by an analytic expression derived from a nearest-neighbor interaction model and may serve as a useful fingerprint for characterizing the position correlation function for atoms within the MOT.
Full kinetic simulations of plasma flow interactions with meso- and microscale magnetic dipoles
Ashida, Y.; Yamakawa, H.; Usui, H.; Miyake, Y.; Shinohara, I.; Funaki, I.; Nakamura, M.
2014-12-15
We examined the plasma flow response to meso- and microscale magnetic dipoles by performing three-dimensional full particle-in-cell simulations. We particularly focused on the formation of a magnetosphere and its dependence on the intensity of the magnetic moment. The size of a magnetic dipole immersed in a plasma flow can be characterized by a distance L from the dipole center to the position where the pressure of the local magnetic field becomes equal to the dynamic pressure of the plasma flow under the magnetohydrodynamics (MHD) approximation. In this study, we are interested in a magnetic dipole whose L is smaller than the Larmor radius of ions r{sub iL} calculated with the unperturbed dipole field at the distance L from the center. In the simulation results, we confirmed the clear formation of a magnetosphere consisting of a magnetopause and a tail region in the density profile, although the spatial scale is much smaller than the MHD scale. One of the important findings in this study is that the spatial profiles of the plasma density as well as the current flows are remarkably affected by the finite Larmor radius effect of the plasma flow, which is different from the Earth's magnetosphere. The magnetopause found in the upstream region is located at a position much closer to the dipole center than L. In the equatorial plane, we also found an asymmetric density profile with respect to the plasma flow direction, which is caused by plasma gyration in the dipole field region. The ion current layers are created in the inner region of the dipole field, and the electron current also flows in the region beyond the ion current layer because ions with a large inertia can closely approach the dipole center. Unlike the ring current structure of the Earth's magnetosphere, the current layers in the microscale dipole fields are not circularly closed around the dipole center. Since the major current is caused by the particle gyrations, the current is independently determined
The ROSAT X-ray background dipole
NASA Astrophysics Data System (ADS)
Plionis, M.; Georgantopoulos, I.
1999-06-01
We estimate the dipole of the diffuse 1.5-keV X-ray background from the ROSAT all-sky survey map of Snowden et al. We first subtract the diffuse Galactic emission by fitting an exponential scaleheight, finite-radius, disc model to the data. We further exclude regions of low galactic latitudes, of local X-ray emission (e.g. the North Polar Spur) and model them using two different methods. We find that the ROSAT X-ray background dipole points towards (l,b) ~ (288 deg 25 deg) +/- 19 deg in consistency with the cosmic microwave background (within ~ 30 deg) its direction is also in good agreement with the HEAO-1 X-ray dipole at harder energies. The normalized amplitude of the ROSAT XRB dipole is ~ 1.7 per cent. Subtracting from the ROSAT map the expected X-ray background dipole resulting from the reflex motion of the observer with respect to the cosmic rest frame (Compton-Getting effect) we find the large-scale dipole of the X-ray emitting extragalactic sources having an amplitude D_LSS ~ 0.9 D_XRB, in general agreement with the predictions of Lahav et al. We finally estimate that the Virgo cluster is responsible for ~ 20 per cent of the total measured XRB dipole amplitude.
Constraints on exotic dipole-dipole couplings between electrons at the micron scale
NASA Astrophysics Data System (ADS)
Kotler, Shlomi; Ozeri, Roee; Jackson Kimball, Derek
2015-05-01
Until recently, the magnetic dipole-dipole coupling between electrons had not been directly observed experimentally. This is because at the atomic scale dipole-dipole coupling is dominated by the exchange interaction and at larger distances the dipole-dipole coupling is overwhelmed by ambient magnetic field noise. In spite of these challenges, the magnetic dipole-dipole interaction between two electron spins separated by 2.4 microns was recently measured using the valence electrons of trapped Strontium ions [S. Kotler, N. Akerman, N. Navon, Y. Glickman, and R. Ozeri, Nature 510, 376 (2014)]. We have used this measurement to directly constrain exotic dipole-dipole interactions between electrons at the micron scale. For light bosons (mass 0.1 eV), we find that coupling constants describing pseudoscalar and axial-vector mediated interactions must be | gPegPe/4 πℏc | <= 1 . 5 × 10-3 and | gAegAe/4 πℏc | <= 1 . 2 × 10-17 , respectively, at the 90% confidence level. These bounds significantly improve on previous constraints in this mass range: for example, the constraints on axial-vector interactions are six orders of magnitude stronger than electron-positron constraints based on positronium spectroscopy. Supported by the National Science Foundation, I-Core: the Israeli excellence center, and the European Research Council.
Hexasubstituted Benzenes with Ultrastrong Dipole Moments.
Wudarczyk, Jakob; Papamokos, George; Margaritis, Vasilis; Schollmeyer, Dieter; Hinkel, Felix; Baumgarten, Martin; Floudas, George; Müllen, Klaus
2016-02-24
Hexasubstituted benzenes have been synthesized with the highest known dipole moments, as determined by dielectric spectroscopy and DFT methods. Based on the preparation of 4,5-diamino-3,6-dibromophthalonitrile, combined with a novel method to synthesize dihydrobenzimidazoles, these benzene derivatives have dipole moments in excess of 10 debye. Such dipole moments are desirable in ferroelectrics, nonlinear optics, and in organic photovoltaics. Structure determination was achieved through single-crystal X-ray crystallography, and the optical properties were determined by UV/Vis absorption and fluorescence spectroscopy. PMID:26836590
The field of a screened magnetic dipole
NASA Technical Reports Server (NTRS)
Greene, J. M.; Miller, R. L.
1994-01-01
The purpose of this note is to quantitatively study the asymptotic behavior of the dipole magnetic field in the tail region of a paraboloidal or cylindrical model of the magnetosphere, assuming the complete screening of the internal field by magnetopause currents. This screening assumption is equivalent to imposing the boundary condition that the normal component of the magnetic field is zero at the magnetopause. With this boundary condition, the screened dipole field falls off exponentially with distance down the tail, in sharp constrast to the bare dipole field. Analytic expressions for a cylindrical and paraboloidal magnetopause are given.
Axion induced oscillating electric dipole moments
Hill, Christopher T.
2015-06-24
In this study, the axion electromagnetic anomaly induces an oscillating electric dipole for any magnetic dipole. This is a low energy theorem which is a consequence of the space-time dependent cosmic background field of the axion. The electron will acquire an oscillating electric dipole of frequency m_{a} and strength ~ 10^{-32} e-cm, within four orders of magnitude of the present standard model DC limit, and two orders of magnitude above the nucleon, assuming standard axion model and dark matter parameters. This may suggest sensitive new experimental venues for the axion dark matter search.
Quadrupole radiation from terahertz dipole antennas.
Rudd, J V; Johnson, J L; Mittleman, D M
2000-10-15
We report what is to our knowledge the first detailed investigation of the polarization state of radiation from lens-coupled terahertz dipole antennas. The radiation exhibits a weak but measurable component that is polarized orthogonally to the orientation of the emitter dipole. The angular radiation pattern of this cross-polarized emission reveals that it is quadrupolar, rather than dipolar, in nature. One can understand this result by taking into account the photocurrent flowing in the strip lines that feed the dipole antenna. A Fresnel-Kirchhoff scalar diffraction calculation is used for calculating the frequency-dependent angular distribution of the radiation pattern, providing satisfactory agreement with the measurements. PMID:18066277
Magnetic dipole discharges. III. Instabilities
Stenzel, R. L.; Urrutia, J. M.; Ionita, C.; Schrittwieser, R.
2013-08-15
Instabilities in a cross-field discharge around a permanent magnet have been investigated. The permanent magnet serves as a cold cathode and the chamber wall as an anode. The magnet is biased strongly negative and emits secondary electrons due to impact of energetic ions. The electrons outside the sheath are confined by the strong dipolar magnetic field and by the ion-rich sheath surrounding the magnet. The electron energy peaks in the equatorial plane where most ionization occurs and the ions are trapped in a negative potential well. The discharge mechanism is the same as that of cylindrical and planar magnetrons, but here extended to a 3-D cathode geometry using a single dipole magnet. While the basic properties of the discharge are presented in a companion paper, the present focus is on various observed instabilities. The first is an ion sheath instability which oscillates the plasma potential outside the sheath below the ion plasma frequency. It arises in ion-rich sheaths with low electron supply, which is the case for low secondary emission yields. Sheath oscillations modulate the discharge current creating oscillating magnetic fields. The second instability is current-driven ion sound turbulence due to counter-streaming electrons and ions. The fluctuations have a broad spectrum and short correlation lengths in all directions. The third type of fluctuations is spiky potential and current oscillations in high density discharges. These appear to be due to unstable emission properties of the magnetron cathode.
Third Elementary Dipole Moment: Toroidal
NASA Astrophysics Data System (ADS)
Cordrey, Vincent; Eshete, Amanuel; Majewski, Walerian
2015-04-01
In this paper we study the generally unknown characteristics of toroids, magnets without magnetic poles. Toroids have never seemed interesting enough to be studied for their physical features in labs due to the fact that they have no magnetic fields on the outside, but rather a very strong magnetic field trapped inside. Toroidal solenoids or magnets (rings magnetized circumferentially) interact with the external magnetic field only through its curl, which can be created either by an electric current, or by a time-dependent electric flux. We confirmed a theoretical prediction, that a toroid would not interact with the curl-less magnetic field of a current-carrying wire running outside of the torus's hole. We used our toroids as magnetic curlmeters, measuring the torque on the toroid, when the current-carrying wire runs through the toroid. From this torque we found the toroidal dipole moment. We are experimenting on detecting the escape of the inner magnetic field of the toroid outside of it, when magnetic toroid rotates or when electric toroid is driven by AC voltage. We also will discuss toroidal (or anapole) moments of fundamental particles, nuclei and atoms, and toroids' applications in metamaterials.
Design of undercuts and dipole stabilizer rods for the CPHS RFQ accelerator
NASA Astrophysics Data System (ADS)
Cai, Jin-Chi; Xing, Qing-Zi; Guan, Xia-Ling; Du, Lei
2012-05-01
As part of the design and machining of the RFQ accelerator in the Compact Pulsed Hadron Source (CPHS) project at Tsinghua University, the design process of the undercuts and dipole stabilizer rods is presented in this paper. In particular, the relationship between the inter-vane voltage slope and the local frequency of the undercut section is described quantitatively. With the identification of modes existing in the cavity, the specific parameters are optimized by the SUPERFISH and MAFIA codes. In addition, the water-cooling requirement of the dipole stabilizer rods is briefly discussed.
Possibility of splitting APS dipoles to make more ID straights.
Borland, M.; Accelerator Systems Division
2009-09-29
Recently we were asked by Ercan Alp if it would be possible to use three dipoles in an APS sector to make a second ID beamline possible, much as was done for the APSx3 design. We've looked at this to see what might be possible without making too many changes to the ring. Ideally, we'd like to simply replace the one dipole with two shorter dipoles with an insertion device in the middle. Of course, we'd like to make the ID as long as possible, subject to limits on dipole strength, accelerator optics, and emittance. We used elegant [3] to match an insertion device consisting of two sectors. The second (BM) dipole of the first sector was split at the 1/8th point in terms of both angle and length. A zero length drift space was inserted that could then be stretched to create room for an ID. To simplify matters somewhat at this stage, we constrained the length of the two dipoles plus the drift to equal the original dipole length. I.e., we ignored for now the difference between arc and straight length. Our desire is to make the drift space as long as possible. If we limit the dipole field B to 2T, then the total length of the dipoles must be greater than L{sub min} = H{theta}/B, where H = 23.35Tm is the rigidity and {theta} = {pi}/40-0.001 is the total angle. L{sub min} is therefore 0.91 m, and hence the drift space can at most be 2.15 m. At least one, perhaps both, of the short dipoles will end up in a high-dispersion region, which will lead to emittance growth. Hence, we didn't want to drive the length too far and decided to limit it to 2 m, approximately the same as in the APSx3 lattice. Hence, as in that lattice we should be able to accommodate a 1-m-long insertion device. In addition to stretching the drift space, we allowed all twenty quadrupoles in the sectors to vary. Initial constraints included less than 20% deviation in lattice functions at the middle ID straight and less than 0.001% deviation in the final ID straight (to get a good match to the rest of the ring
NASA Astrophysics Data System (ADS)
Nguyen, Thanh Long; Celistrino Teixeira, Raul; Hermann Avigliano, Carla; Cantat Moltrecht, Tigrane; Raimond, Jean Michel; Haroche, Serge; Gleyzes, Sebastiens; Brune, Michel
2016-05-01
Dipole-dipole interactions between Rydberg atoms are a flourishing tool for quantum information processing and for quantum simulation of complex many-body problems. Microwave spectroscopy of a dense Rydberg gas trapped close to a superconducting atom chip in the strong dipole blockade regime reveals directly the many-body atomic interaction spectrum. We present here a direct measurement of the interaction energy distribution in the strong dipole blockade regime, based on microwave spectroscopy. We first apply this method to the observation of the excitation dynamics of the Rydberg gas, conditioned by dipole-dipole interactions, in either the strong blockade regime or the so-called facilitation regime. We also observe with this method the atomic cloud expansion driven by the repulsive Van der Waals interaction after excitation. This measurement, in good agreement with Monte Carlo simulations of the excitation process and of the cloud dynamics, reveals the limits of the frozen gas approximation. This method can help investigate self-organization and dynamical phase transitions in Rydberg-atom based quantum simulators. This study thus opens a promising route for quantum simulation of many-body systems and quantum information transport in chains of strongly interacting Rydberg atom.
Study on the connection between the rotating mass dipole and natural elongated bodies
NASA Astrophysics Data System (ADS)
Zeng, Xiangyuan; Jiang, Fanghua; Li, Junfeng; Baoyin, Hexi
2015-03-01
The focus of this paper is to connect the rotating mass dipole with natural elongated bodies. The dipole system is consisted with two point masses connected with a massless rod in a constant characteristic distance. A brief introduction on the dynamics near the rotating mass dipole is given with the distribution of its equilibrium points and zero-velocity curves. Five parameters of the dipole model are required to approximate the potential distribution of an elongated body out of the body's surface, including the mass ratio, system mass, spinning period, characteristic distance and the ratio between the gravitational and centrifugal forces. The method to obtain the five parameters is presented along with its application to the asteroid 1620 Geographos in detail. The accuracy of the dipole model is quantified with the relative tolerance of locations of the equilibrium points. Six more elongated asteroids and comets, such as 25143 Itokawa and 103P/Hartley-2, are illustrated to provide a reference for further studies. Model justification is evaluated through comparison between sample elongated bodies and their corresponding dipole models with regard to the external potential distribution, the stability and topological manifold structure of the equilibrium points.
Pygmy dipole mode in deformed neutron-rich Mg isotopes close to the drip line
Yoshida, Kenichi
2009-10-15
We investigate the microscopic structure of the low-lying isovector-dipole excitation mode in neutron-rich {sup 36,38,40}Mg close to the drip line by means of the deformed quasiparticle random-phase approximation employing the Skyrme and the local pairing energy-density functionals. It is found that the low-lying bump structure above the neutron emission-threshold energy develops when the drip line is approached, and that the isovector dipole strength at E{sub x}<10 MeV exhausts about 6.0% of the classical Thomas-Reiche-Kuhn dipole sum rule in {sup 40}Mg. We obtained the collective dipole modes at around 8-10 MeV in Mg isotopes, that consist of many two-quasiparticle excitations of the neutron. The transition density clearly shows an oscillation of the neutron skin against the isoscalar core. We found significant coupling effects between the dipole and octupole excitation modes due to the nuclear deformation. It is also found that the responses for the compressional dipole and isoscalar octupole excitations are much enhanced in the lower energy region.
JIMWLK evolution in the Gaussian approximation
NASA Astrophysics Data System (ADS)
Iancu, E.; Triantafyllopoulos, D. N.
2012-04-01
We demonstrate that the Balitsky-JIMWLK equations describing the high-energy evolution of the n-point functions of the Wilson lines (the QCD scattering amplitudes in the eikonal approximation) admit a controlled mean field approximation of the Gaussian type, for any value of the number of colors N c . This approximation is strictly correct in the weak scattering regime at relatively large transverse momenta, where it re-produces the BFKL dynamics, and in the strong scattering regime deeply at saturation, where it properly describes the evolution of the scattering amplitudes towards the respective black disk limits. The approximation scheme is fully specified by giving the 2-point function (the S-matrix for a color dipole), which in turn can be related to the solution to the Balitsky-Kovchegov equation, including at finite N c . Any higher n-point function with n ≥ 4 can be computed in terms of the dipole S-matrix by solving a closed system of evolution equations (a simplified version of the respective Balitsky-JIMWLK equations) which are local in the transverse coordinates. For simple configurations of the projectile in the transverse plane, our new results for the 4-point and the 6-point functions coincide with the high-energy extrapolations of the respective results in the McLerran-Venugopalan model. One cornerstone of our construction is a symmetry property of the JIMWLK evolution, that we notice here for the first time: the fact that, with increasing energy, a hadron is expanding its longitudinal support symmetrically around the light-cone. This corresponds to invariance under time reversal for the scattering amplitudes.
Study of atomic dipole-dipole interactions via measurement of atom-pair kinetics
NASA Astrophysics Data System (ADS)
Thaicharoen, Nithiwadee; Gonçalves, Luís Felipe; Raithel, Georg
2016-05-01
We observe atom-pair kinetics due to binary dipolar forces by direct imaging of the center-of-mass positions of the individual Rydberg atoms and pair-correlation analysis. To prepare a highly dipolar quantum state, Rydberg-atom ensembles are switched from a weakly- into a strongly-interacting regime via adiabatic state transformation. The transformed atoms exhibit a large permanent electric dipole moment that is locked to the direction of an applied electric field. The resultant electric dipole-dipole forces reveal dumbbell-shaped pair correlation images that demonstrate the anisotropy of the binary dipolar force. The dipole-dipole interaction coefficient C3, derived from the time dependence of the images, agrees with the value calculated from the known permanent electric-dipole moment of the atoms. The observations also show the dynamics reminiscent of disorder-induced heating in strongly coupled particle systems.
Dipole-fiber systems: radiation field patterns, effective magnetic dipoles, and induced cavity modes
NASA Astrophysics Data System (ADS)
Atakaramians, Shaghik; Miroshnichenko, Andrey E.; Shadrivov, Ilya V.; Monro, Tanya M.; Kivshar, Yuri S.; Afshar, Shahraam V.
2015-12-01
We study the radiation patterns produced by a dipole placed at the surface of a nanofiber and oriented perpendicular to it, either along the radial (r-oriented) or azimuthal (Φ-oriented) directions. We find that the dipole induces an effective circular cavity-like leaky mode in the nanofiber. The first radiation peak of the Φ-oriented dipole contributes only to TE radiation modes, while the radiation of the r-oriented dipole is composed of both TE and TM radiation modes, with relative contribution depending on the refractive index of the nanofiber. We reveal that the field pattern of the first resonance of a Φ-oriented dipole is associated with a magnetic dipole mode and strong magnetic response of an optical nanofiber.
The Effect of Dipole-Dipole Interaction on Tripartite Entanglement in Different Cavities
NASA Astrophysics Data System (ADS)
Khan, Salman; Jan, Munsif
2016-03-01
The effect of dipole-dipole interaction, the initial relative phase and the coupling strength with the cavity on the dynamics of three two level atoms in the good and the bad cavity regime are investigated. It is found that the presence of strong dipole-dipole interaction not only ensures avoiding entanglement sudden death but also retains entanglement for long time. The choice of the phase in the initial state is crucial to the operational regime of the cavity. Under specific conditions, the entanglement can be frozen in time to its initial values through strong dipole-dipole interaction. This trait of tripartite entanglement may prove helpful in engineering multiparticle entanglement for the practical realization of quantum technology.
NASA Astrophysics Data System (ADS)
Lazzeretti, P.; Malagoli, M.; Turci, L.; Zanasi, R.
1993-10-01
Theoretical methods based on the random-phase approximation have been applied to evaluate near Hartree-Fock dynamic electric polarizability and shielding tensors of carbon and hydrogen nuclei in the benzene molecule. Cauchy moments of the various properties have been determined. The results obtained in different gauges (dipole length, velocity, and acceleration) are reported.
Microstrip dipoles on electrically thick substrates
NASA Astrophysics Data System (ADS)
Jackson, D. R.; Alexopoulos, N. G.
1986-01-01
Certain basic radiation properties of microstrip dipoles on electrically thick substrates are investigated, and a comparison is made with the case of dipoles printed on a dielectric half-space. It is concluded that the microstrip dipole radiation properties become sensitive to substrate loss as the substrate thickness increases, with the half-space properties obtained for an adequate amount of loss. Asymptotic formulas for radiated power and efficiency are given for both the thick substrate and half-space problems, showing the behavior with increasing dielectric constant. The method of moments is used to extend the analysis to center-fed strip dipoles, and a method of improving both the efficiency and gain of a printed antenna by using a superstrate layer is discussed.
Tevatron optics measurements using an AC dipole
Miyamoto, R.; Kopp, S.E.; Jansson, A.; Syphers, M.J.; /Fermilab
2007-06-01
The AC dipole is a device to study beam optics of hadron synchrotrons. It can produce sustained large amplitude oscillations with virtually no emittance growth. A vertical AC dipole for the Tevatron is recently implemented and a maximum oscillation amplitude of 2{sigma} (4{sigma}) at 980 GeV (150 GeV) is achieved [1]. When such large oscillations are measured with the BPM system of the Tevatron (20 {micro}m resolution), not only linear but even nonlinear optics can be directly measured. This paper shows how to measure {beta} function using an AC dipole and the result is compared to the other measurement. The paper also shows a test to detect optics changes when small changes are made in the Tevatron. Since an AC dipole is nondestructive, it allows frequent measurements of the optics which is necessary for such an test.
NASA Technical Reports Server (NTRS)
Dutta, Soumitra
1988-01-01
A model for approximate spatial reasoning using fuzzy logic to represent the uncertainty in the environment is presented. Algorithms are developed which can be used to reason about spatial information expressed in the form of approximate linguistic descriptions similar to the kind of spatial information processed by humans. Particular attention is given to static spatial reasoning.
NASA Astrophysics Data System (ADS)
Gorobets, Yu. I.; Kulish, V. V.
2015-07-01
Dipole-exchange spin waves in nanotubes composed of uniaxial ferromagnets are studied. An equation for the magnetic potential of linear spin waves in uniaxial "easy plane" ferromagnets is obtained in the magnetostatic approximation taking into account magnetic dipole-dipole interactions, exchange interactions, and anisotropy effects. A solution is found for this equation and a dispersion relation for these types of spin waves is obtained. The dependence of the spin wave frequency on the total wave number is found for the case of a thin nanotube. An expression is derived for the transverse wave number spectrum.
Lawrie, J. J.; Lawrie, E. A.; Newman, R. T.; Sharpey-Schafer, J. F.; Smit, F. D.; Msezane, B.; Benatar, M.; Mabala, G. K.; Mutshena, K. P.; Federke, M.; Mullins, S. M.; Ncapayi, N. J.; Vymers, P.
2011-10-28
High spin states in {sup 196}Hg have been populated in the {sup 198}Pt({alpha},6n) reaction at 65 MeV and the level scheme has been extended. A new dipole band has been observed and a previously observed dipole has been confirmed. Excitation energies, spins and parities of these bands were determined from DCO ratio and linear polarization measurements. Possible quasiparticle excitations responsible for these structures are discussed.
Magnetic dipole transitions in the hydrogen molecule
Pachucki, Krzysztof; Komasa, Jacek
2011-03-15
In homonuclear molecules, such as H{sub 2}, the electric dipole transitions are strongly forbidden, and the transitions between rovibrational states are of the electric quadrupole type. We show, however, that magnetic dipole transitions also take place, although they are significantly weaker. We evaluate the probabilities of such transitions between several of the lowest rotational states and compare them with those of the corresponding electric quadrupole transitions.
Magnetic dipole interactions in crystals
NASA Astrophysics Data System (ADS)
Johnston, David C.
2016-01-01
The influence of magnetic dipole interactions (MDIs) on the magnetic properties of local-moment Heisenberg spin systems is investigated. A general formulation is presented for calculating the eigenvalues λ and eigenvectors μ ̂ of the MDI tensor of the magnetic dipoles in a line (one dimension, 1D), within a circle (2D) or a sphere (3D) of radius r surrounding a given moment μ⃗i for given magnetic propagation vectors k for collinear and coplanar noncollinear magnetic structures on both Bravais and non-Bravais spin lattices. Results are calculated for collinear ordering on 1D chains, 2D square and simple-hexagonal (triangular) Bravais lattices, 2D honeycomb and kagomé non-Bravais lattices, and 3D cubic Bravais lattices. The λ and μ ̂ values are compared with previously reported results. Calculations for collinear ordering on 3D simple tetragonal, body-centered tetragonal, and stacked triangular and honeycomb lattices are presented for c /a ratios from 0.5 to 3 in both graphical and tabular form to facilitate comparison of experimentally determined easy axes of ordering on these Bravais lattices with the predictions for MDIs. Comparisons with the easy axes measured for several illustrative collinear antiferromagnets (AFMs) are given. The calculations are extended to the cycloidal noncollinear 120∘ AFM ordering on the triangular lattice where λ is found to be the same as for collinear AFM ordering with the same k. The angular orientation of the ordered moments in the noncollinear coplanar AFM structure of GdB4 with a distorted stacked 3D Shastry-Sutherland spin-lattice geometry is calculated and found to be in disagreement with experimental observations, indicating the presence of another source of anisotropy. Similar calculations for the undistorted 2D and stacked 3D Shastry-Sutherland lattices are reported. The thermodynamics of dipolar magnets are calculated using the Weiss molecular field theory for quantum spins, including the magnetic transition
Magnetic dipole interactions in crystals
Johnston, David
2016-01-13
The influence of magnetic dipole interactions (MDIs) on the magnetic properties of local-moment Heisenberg spin systems is investigated. A general formulation is presented for calculating the eigenvalues λ and eigenvectors μ ˆ of the MDI tensor of the magnetic dipoles in a line (one dimension, 1D), within a circle (2D) or a sphere (3D) of radius r surrounding a given moment μ → i for given magnetic propagation vectors k for collinear and coplanar noncollinear magnetic structures on both Bravais and non-Bravais spin lattices. Results are calculated for collinear ordering on 1D chains, 2D square and simple-hexagonal (triangular) Bravais lattices,more » 2D honeycomb and kagomé non-Bravais lattices, and 3D cubic Bravais lattices. The λ and μ ˆ values are compared with previously reported results. Calculations for collinear ordering on 3D simple tetragonal, body-centered tetragonal, and stacked triangular and honeycomb lattices are presented for c/a ratios from 0.5 to 3 in both graphical and tabular form to facilitate comparison of experimentally determined easy axes of ordering on these Bravais lattices with the predictions for MDIs. Comparisons with the easy axes measured for several illustrative collinear antiferromagnets (AFMs) are given. The calculations are extended to the cycloidal noncollinear 120 ° AFM ordering on the triangular lattice where λ is found to be the same as for collinear AFM ordering with the same k. The angular orientation of the ordered moments in the noncollinear coplanar AFM structure of GdB 4 with a distorted stacked 3D Shastry-Sutherland spin-lattice geometry is calculated and found to be in disagreement with experimental observations, indicating the presence of another source of anisotropy. Similar calculations for the undistorted 2D and stacked 3D Shastry-Sutherland lattices are reported. The thermodynamics of dipolar magnets are calculated using the Weiss molecular field theory for quantum spins, including the magnetic
Controlling dipole-dipole frequency shifts in a lattice-based optical atomic clock
Chang, D.E.; Lukin, M.D.; Ye Jun
2004-02-01
Motivated by the ideas of using cold alkaline-earth atoms trapped in an optical lattice for realization of optical atomic clocks, we investigate theoretically the perturbative effects of atom-atom interactions on a clock transition frequency. These interactions are mediated by the dipole fields associated with the optically excited atoms. We predict resonancelike features in the frequency shifts when constructive interference among atomic dipoles occur. We theoretically demonstrate that by fine tuning the coherent dipole-dipole couplings in appropriately designed lattice geometries, the undesirable frequency shifts can be greatly suppressed.
Critical properties of entanglement in the Dicke model with the dipole-dipole interactions
NASA Astrophysics Data System (ADS)
Nie, J.; Huang, X. L.; Yi, X. X.
2009-04-01
In this paper, we investigate two aspects of entanglement properties of the ground state for the Dicke model with the dipole-dipole interaction between the atoms in the thermodynamic limit, and observe how they are affected by the quantum phase transition. The appearance of dipole-dipole interactions between the atoms does not change the maximum atom-field entanglement at the critical point, while it changes the maximum atom-atom entanglement at the critical point, and has an important influence on the atom-atom entanglement behavior.
electric dipole superconductor in bilayer exciton system
NASA Astrophysics Data System (ADS)
Sun, Qing-Feng; Jiang, Qing-Dong; Bao, Zhi-Qiang; Xie, X. C.
Recently, it was reported that the bilayer exciton systems could exhibit many new phenomena, including the large bilayer counterflow conductivity, the Coulomb drag, etc. These phenomena imply the formation of exciton condensate superfluid state. On the other hand, it is now well known that the superconductor is the condensate superfluid state of the Cooper pairs, which can be viewed as electric monopoles. In other words, the superconductor state is the electric monopole condensate superfluid state. Thus, one may wonder whether there exists electric dipole superfluid state. In this talk, we point out that the exciton in a bilayer system can be considered as a charge neutral electric dipole. And we derive the London-type and Ginzburg-Landau-type equations of electric dipole superconductivity. From these equations, we discover the Meissner-type effect (against spatial variation of magnetic fields), and the dipole current Josephson effect. The frequency in the AC Josephson effect of the dipole current is equal to that in the normal (monopole) superconductor. These results can provide direct evidence for the formation of exciton superfluid state in the bilayer systems and pave new ways to obtain the electric dipole current. We gratefully acknowledge the financial support by NBRP of China (2012CB921303 and 2015CB921102) and NSF-China under Grants Nos. 11274364 and 11574007.
Dipole-moment-driven cooperative supramolecular polymerization.
Kulkarni, Chidambar; Bejagam, Karteek K; Senanayak, Satyaprasad P; Narayan, K S; Balasubramanian, S; George, Subi J
2015-03-25
While the mechanism of self-assembly of π-conjugated molecules has been well studied to gain control over the structure and functionality of supramolecular polymers, the intermolecular interactions underpinning it are poorly understood. Here, we study the mechanism of self-assembly of perylene bisimide derivatives possessing dipolar carbonate groups as linkers. It was observed that the combination of carbonate linkers and cholesterol/dihydrocholesterol self-assembling moieties led to a cooperative mechanism of self-assembly. Atomistic molecular dynamics simulations of an assembly in explicit solvent strongly suggest that the dipole-dipole interaction between the carbonate groups imparts a macro-dipolar character to the assembly. This is confirmed experimentally through the observation of a significant polarization in the bulk phase for molecules following a cooperative mechanism. The cooperativity is attributed to the presence of dipole-dipole interaction in the assembly. Thus, anisotropic long-range intermolecular interactions such as dipole-dipole interaction can serve as a way to obtain cooperative self-assembly and aid in rationalizing and predicting the mechanisms in various synthetic supramolecular polymers. PMID:25756951
A Dipole Assisted IEC Neutron Source
Prajakti Joshi Shrestha
2005-11-28
A potential opportunity to enhance Inertial Electrostatic Confinement (IEC) fusion exists by augmenting it with a magnetic dipole configuration. The theory is that the dipole fields will enhance the plasma density in the center region of the IEC and the combined IEC and dipole confinement properties will reduce plasma losses. To demonstrate that a hybrid Dipole-IEC configuration can provide an improved neutron source vs. a stand alone IEC, a first model Dipole-IEC experiment was benchmarked against a reference IEC. A triple Langmuir probe was used to find the electron temperature and density. It was found that the magnetic field increases the electron density by a factor of 16, the electron temperature decreases in the presence of a magnetic field, the discharge voltage decreases in the presence of a magnetic field, the potential of the dipole strongly influences the densities obtained in the center. The experimental set-up and plasma diagnostics are discussed in detail, as well as the results, and the developmental issues.
750 GeV diphoton resonance and electric dipole moments
NASA Astrophysics Data System (ADS)
Choi, Kiwoon; Im, Sang Hui; Kim, Hyungjin; Mo, Doh Young
2016-09-01
We examine the implication of the recently observed 750 GeV diphoton excess for the electric dipole moments of the neutron and electron. If the excess is due to a spin zero resonance which couples to photons and gluons through the loops of massive vector-like fermions, the resulting neutron electric dipole moment can be comparable to the present experimental bound if the CP-violating angle α in the underlying new physics is of O (10-1). An electron EDM comparable to the present bound can be achieved through a mixing between the 750 GeV resonance and the Standard Model Higgs boson, if the mixing angle itself for an approximately pseudoscalar resonance, or the mixing angle times the CP-violating angle α for an approximately scalar resonance, is of O (10-3). For the case that the 750 GeV resonance corresponds to a composite pseudo-Nambu-Goldstone boson formed by a QCD-like hypercolor dynamics confining at ΛHC, the resulting neutron EDM can be estimated with α ∼(750 GeV /ΛHC) 2θHC, where θHC is the hypercolor vacuum angle.
Bayesian smoothing of dipoles in magneto-/electroencephalography
NASA Astrophysics Data System (ADS)
Vivaldi, Valentina; Sorrentino, Alberto
2016-04-01
We describe a novel method for dynamic estimation of multi-dipole states from magneto-/electroencephalography (M/EEG) time series. The new approach builds on the recent development of particle filters for M/EEG; these algorithms approximate, with samples and weights, the posterior distribution of the neural sources at time t given the data up to time t. However, for off-line inference purposes it is preferable to work with the smoothing distribution, i.e. the distribution for the neural sources at time t conditioned on the whole time series. In this study, we use a Monte Carlo algorithm to approximate the smoothing distribution for a time-varying set of current dipoles. We show, using numerical simulations, that the estimates provided by the smoothing distribution are more accurate than those provided by the filtering distribution, particularly at the appearance of the source. We validate the proposed algorithm using an experimental data set recorded from an epileptic patient. Improved localization of the source onset can be particularly relevant in source modeling of epileptic patients, where the source onset brings information on the epileptogenic zone.
Calculator Function Approximation.
ERIC Educational Resources Information Center
Schelin, Charles W.
1983-01-01
The general algorithm used in most hand calculators to approximate elementary functions is discussed. Comments on tabular function values and on computer function evaluation are given first; then the CORDIC (Coordinate Rotation Digital Computer) scheme is described. (MNS)
Reexamination of Lunar Exospheric Dust Estimates Using Discrete Dipole Scattering Simulations
NASA Astrophysics Data System (ADS)
Stubbs, T. J.; Glenar, D. A.; Richard, D. T.; Feldman, P. D.; Retherford, K. D.
2014-12-01
Analysis of Apollo regolith samples showed that lunar dust grains consist of a diverse set of shapes. Consequently, the optical scattering properties of these grains will differ from those predicted using the Mie approximation, which strictly applies only for spheres. Because it is analytically convenient and without shape ambiguity, Mie theory has been used routinely to estimate the concentration of dust or it's upper limits in the lunar exosphere from brightness measurements acquired during orbital dust searches. Utilizing the Discrete Dipole Approximation (DDA), we have computed a more realistic set of scattering parameters for a collection of sub-micron grain shapes that represents the ultra-fine fraction of lunar soil. Included in this suite are spheroids (oblate and prolate) and irregular geometries resembling isolated grains observed in Apollo samples. A subset of these models includes the addition of nanophase iron, in order to examine the influence of space weathering. Wavelength coverage of the DDA scattering computations extends from far-UV to near-IR. This range is diagnostic of grain size and shape, since scattering efficiency depends on both of these parameters. This collection of grain scattering models is used, together with an observing simulation code, to reexamine some prior estimates of exospheric dust concentration derived from Apollo-era limb brightness measurements (e.g., Apollo 15 coronal photography), as well as the subsequent Clementine star tracker search and a search for lunar horizon glow by LRO Lyman Alpha Mapping Project (LAMP). We compare our revised estimates of exospheric dust abundance with the results of these previous dust searches.
NASA Technical Reports Server (NTRS)
Dutta, Soumitra
1988-01-01
Much of human reasoning is approximate in nature. Formal models of reasoning traditionally try to be precise and reject the fuzziness of concepts in natural use and replace them with non-fuzzy scientific explicata by a process of precisiation. As an alternate to this approach, it has been suggested that rather than regard human reasoning processes as themselves approximating to some more refined and exact logical process that can be carried out with mathematical precision, the essence and power of human reasoning is in its capability to grasp and use inexact concepts directly. This view is supported by the widespread fuzziness of simple everyday terms (e.g., near tall) and the complexity of ordinary tasks (e.g., cleaning a room). Spatial reasoning is an area where humans consistently reason approximately with demonstrably good results. Consider the case of crossing a traffic intersection. We have only an approximate idea of the locations and speeds of various obstacles (e.g., persons and vehicles), but we nevertheless manage to cross such traffic intersections without any harm. The details of our mental processes which enable us to carry out such intricate tasks in such apparently simple manner are not well understood. However, it is that we try to incorporate such approximate reasoning techniques in our computer systems. Approximate spatial reasoning is very important for intelligent mobile agents (e.g., robots), specially for those operating in uncertain or unknown or dynamic domains.
Approximate kernel competitive learning.
Wu, Jian-Sheng; Zheng, Wei-Shi; Lai, Jian-Huang
2015-03-01
Kernel competitive learning has been successfully used to achieve robust clustering. However, kernel competitive learning (KCL) is not scalable for large scale data processing, because (1) it has to calculate and store the full kernel matrix that is too large to be calculated and kept in the memory and (2) it cannot be computed in parallel. In this paper we develop a framework of approximate kernel competitive learning for processing large scale dataset. The proposed framework consists of two parts. First, it derives an approximate kernel competitive learning (AKCL), which learns kernel competitive learning in a subspace via sampling. We provide solid theoretical analysis on why the proposed approximation modelling would work for kernel competitive learning, and furthermore, we show that the computational complexity of AKCL is largely reduced. Second, we propose a pseudo-parallelled approximate kernel competitive learning (PAKCL) based on a set-based kernel competitive learning strategy, which overcomes the obstacle of using parallel programming in kernel competitive learning and significantly accelerates the approximate kernel competitive learning for large scale clustering. The empirical evaluation on publicly available datasets shows that the proposed AKCL and PAKCL can perform comparably as KCL, with a large reduction on computational cost. Also, the proposed methods achieve more effective clustering performance in terms of clustering precision against related approximate clustering approaches. PMID:25528318
Zerilli, A.; Bisdorf, R.J.
1990-01-01
An interactive HP 9845B BASIC program transforms continuous polar dipole-dipole resistivity soundings to half-Schlumberger soundings. The program features graphic presentation of the field dipole-dipole data as well as the transformed half-Schlumberger data. An example of the transformation and its effectiveness in smoothing "high-frequency" noise is given. ?? 1990.
Dipole effects in a cold Rydberg gas
NASA Astrophysics Data System (ADS)
Han, Jianing
2009-12-01
This dissertation is a continuing study of the dipole effects between cold Rydberg atoms in a MOT (Magneto Optical Trap). The dipole-dipole interaction is commonly used to explain the plasma forming process and dipole blockade effects. However, no direct measurements have been made for such interaction. This dissertation is designed to directly measure this interaction and study the effects induced by the dipole interaction. To achieve this, a few experiments were carried out. First, a millimeter wave spectroscopy experiment was performed to determine quantum defects of higher angular momentum f and g states, which then allows us to accurately identify these states. Moreover, the higher angular momentum states play an important role in the plasma forming process. The next experiment examined the oscilloscope trace collected through field ionization pulses on which all our experiments are based, which leads to the conclusion that the side peaks other than the main peak can be due to the field ionization pulse sweeping through the resonances. Based on the knowledge of identifying states obtained from these two experiments, a third experiment was carried out to understand the interactions between cold Rydberg atoms. It was found that the second order dipole-dipole interaction, the van der Waals interaction, commonly exists between the atoms in our atomic sample, and when we excite the atoms from the ns to (n + 1)s states using a narrow band microwave pulse, an asymmetric broadening, which is attributed to the nsns to ns(n + 1) s molecular state transition, was observed. Furthermore, the van der Waals long range molecule is studied, which provides another way to study the two-body to multi-body transition.
NASA Astrophysics Data System (ADS)
Roostaei, B.; Ermler, W. C.
2012-03-01
A procedure for calculating electric dipole transition moments and permanent dipole moments from spin-orbit configuration interaction (SOCI) wave functions has been developed in the context of the COLUMBUS ab initio electronic structure programs. The SOCI procedure requires relativistic effective core potentials and their corresponding spin-orbit coupling operators to define the molecular Hamiltonian, electric dipole transition moment and permanent dipole moment matrices. The procedure can be used for any molecular system for which the COLUMBUS SOCI circuits are applicable. Example applications are reported for transition moments and dipole moments for a series of electronic states of LiBe and LiSr defined in diatomic relativistic ωω-coupling.
Plasmon-Induced Resonant Energy Transfer: a coherent dipole-dipole coupling mechanism
NASA Astrophysics Data System (ADS)
Bristow, Alan D.; Cushing, Scott K.; Li, Jiangtian; Wu, Nianqiang
Metal-insulator-semiconductor core-shell nanoparticles have been used to demonstrate a dipole-dipole coupling mechanism that is entirely dependent on the dephasing time of the localized plasmonic resonance. Consequently, the short-time scale of the plasmons leads to broad energy uncertainty that allows for excitation of charge carriers in the semiconductor via stimulation of photons with energies below the energy band gap. In addition, this coherent energy transfer process overcomes interfacial losses often associated with direct charge transfer. This work explores the efficiency of the energy transfer process, the dipole-dipole coupling strength with dipole separation, shell thickness and plasmonic resonance overlap. We demonstrate limits where the coherent nature of the coupling is switched off and charge transfer processes can dominate. Experiments are performed using transient absorption spectroscopy. Results are compared to calculations using a quantum master equation. These nanostructures show strong potential for improving solar light-harvesting for power and fuel generation.
Laser-Induced Magnetic Dipole Spectroscopy.
Hintze, Christian; Bücker, Dennis; Domingo Köhler, Silvia; Jeschke, Gunnar; Drescher, Malte
2016-06-16
Pulse electron paramagnetic resonance measurements of nanometer scale distance distributions have proven highly effective in structural studies. They exploit the magnetic dipole-dipole coupling between spin labels site-specifically attached to macromolecules. The most commonly applied technique is double electron-electron resonance (DEER, also called pulsed electron double resonance (PELDOR)). Here we present the new technique of laser-induced magnetic dipole (LaserIMD) spectroscopy based on optical switching of the dipole-dipole coupling. In a proof of concept experiment on a model peptide, we find, already at a low quantum yield of triplet excitation, the same sensitivity for measuring the distance between a porphyrin and a nitroxide label as in a DEER measurement between two nitroxide labels. On the heme protein cytochrome C, we demonstrate that LaserIMD allows for distance measurements between a heme prosthetic group and a nitroxide label, although the heme triplet state is not directly observable by an electron spin echo. PMID:27163749
Covariant approximation averaging
NASA Astrophysics Data System (ADS)
Shintani, Eigo; Arthur, Rudy; Blum, Thomas; Izubuchi, Taku; Jung, Chulwoo; Lehner, Christoph
2015-06-01
We present a new class of statistical error reduction techniques for Monte Carlo simulations. Using covariant symmetries, we show that correlation functions can be constructed from inexpensive approximations without introducing any systematic bias in the final result. We introduce a new class of covariant approximation averaging techniques, known as all-mode averaging (AMA), in which the approximation takes account of contributions of all eigenmodes through the inverse of the Dirac operator computed from the conjugate gradient method with a relaxed stopping condition. In this paper we compare the performance and computational cost of our new method with traditional methods using correlation functions and masses of the pion, nucleon, and vector meson in Nf=2 +1 lattice QCD using domain-wall fermions. This comparison indicates that AMA significantly reduces statistical errors in Monte Carlo calculations over conventional methods for the same cost.
Fast approximate motif statistics.
Nicodème, P
2001-01-01
We present in this article a fast approximate method for computing the statistics of a number of non-self-overlapping matches of motifs in a random text in the nonuniform Bernoulli model. This method is well suited for protein motifs where the probability of self-overlap of motifs is small. For 96% of the PROSITE motifs, the expectations of occurrences of the motifs in a 7-million-amino-acids random database are computed by the approximate method with less than 1% error when compared with the exact method. Processing of the whole PROSITE takes about 30 seconds with the approximate method. We apply this new method to a comparison of the C. elegans and S. cerevisiae proteomes. PMID:11535175
The Guiding Center Approximation
NASA Astrophysics Data System (ADS)
Pedersen, Thomas Sunn
The guiding center approximation for charged particles in strong magnetic fields is introduced here. This approximation is very useful in situations where the charged particles are very well magnetized, such that the gyration (Larmor) radius is small compared to relevant length scales of the confinement device, and the gyration is fast relative to relevant timescales in an experiment. The basics of motion in a straight, uniform, static magnetic field are reviewed, and are used as a starting point for analyzing more complicated situations where more forces are present, as well as inhomogeneities in the magnetic field -- magnetic curvature as well as gradients in the magnetic field strength. The first and second adiabatic invariant are introduced, and slowly time-varying fields are also covered. As an example of the use of the guiding center approximation, the confinement concept of the cylindrical magnetic mirror is analyzed.
Design and applications of flexible dipole rectenna for smart actuators and devices
NASA Astrophysics Data System (ADS)
Song, Kyo D.; Jones, Sean; Kim, Jae H.; Yang, Sang Y.; Choi, Sang H.
2006-03-01
Flexible dipole rectenna devices appeared to be attractive for this study because of the adaptability on complex structures; possibility for higher power density features, and ability of coupling. In this paper, design concepts and results of various flexible dipole rectennas will be discussed including their efficiencies. Using the result, some applications of the system will also be addressed. A typical output of a flexible dipole rectenna array produced up to 70 VDC and 300 mA with a 200W amplifier. The irradiance of the microwave power is measured as 20 - 200 mW/cm2 at the distance of 130 cm from the horn. In this research, a 4 x 5 flexible rectenna array was used for actuation of a propeller of MAV which is required approximately 3W as an input power. The design concept of various rectennas that depends on the requirements of input for propellers/actuators in a vehicle is discussed.
Measurement of the Dipole Polarizability of the Unstable Neutron-Rich Nucleus Ni68
NASA Astrophysics Data System (ADS)
Rossi, D. M.; Adrich, P.; Aksouh, F.; Alvarez-Pol, H.; Aumann, T.; Benlliure, J.; Böhmer, M.; Boretzky, K.; Casarejos, E.; Chartier, M.; Chatillon, A.; Cortina-Gil, D.; Datta Pramanik, U.; Emling, H.; Ershova, O.; Fernandez-Dominguez, B.; Geissel, H.; Gorska, M.; Heil, M.; Johansson, H. T.; Junghans, A.; Kelic-Heil, A.; Kiselev, O.; Klimkiewicz, A.; Kratz, J. V.; Krücken, R.; Kurz, N.; Labiche, M.; Le Bleis, T.; Lemmon, R.; Litvinov, Yu. A.; Mahata, K.; Maierbeck, P.; Movsesyan, A.; Nilsson, T.; Nociforo, C.; Palit, R.; Paschalis, S.; Plag, R.; Reifarth, R.; Savran, D.; Scheit, H.; Simon, H.; Sümmerer, K.; Wagner, A.; Waluś, W.; Weick, H.; Winkler, M.
2013-12-01
The E1 strength distribution in Ni68 has been investigated using Coulomb excitation in inverse kinematics at the RB3-LAND setup and by measuring the invariant mass in the one- and two-neutron decay channels. The giant dipole resonance and a low-lying peak (pygmy dipole resonance) have been observed at 17.1(2) and 9.55(17) MeV, respectively. The measured dipole polarizability is compared to relativistic random phase approximation calculations yielding a neutron-skin thickness of 0.17(2) fm. A method and analysis applicable to neutron-rich nuclei has been developed, allowing for a precise determination of neutron skins in nuclei as a function of neutron excess.
NASA Astrophysics Data System (ADS)
Schwengner, R.; Benouaret, N.; Beyer, R.; Dönau, F.; Erhard, M.; Frauendorf, S.; Grosse, E.; Junghans, A. R.; Klug, J.; Kosev, K.; Nair, C.; Nankov, N.; Rusev, G.; Schilling, K. D.; Wagner, A.
2007-05-01
Dipole-strength distributions in the nuclides 92Mo, 98Mo and 100Mo have been investigated in photon-scattering experiments with bremsstrahlung at the superconducting electron accelerator ELBE of the Forschungszentrum Rossendorf. A simulation of γ cascades was performed in order to estimate the distribution of inelastic transitions to low-lying states and thus to deduce the primary dipole-strength distribution up to the neutron-separation energies. The absorption cross sections obtained connect smoothly to ( γ, n) cross sections and give novel information about the low-energy tail of the Giant Dipole Resonance below the neutron-separation energies. The experimental cross sections are compared with predictions of a Quasiparticle-Random-Phase Approximation (QRPA) in a deformed basis. Photoactivation experiments were performed at various electron energies to study the 92Mo( γ, n), 92Mo( γ, p), 92Mo( γ, α) and 100Mo( γ, n) reactions. The deduced activation yields are compared with theoretical predictions.
Initial conditions for dipole evolution beyond the McLerran-Venugopalan model
NASA Astrophysics Data System (ADS)
Dumitru, Adrian; Petreska, Elena
2012-04-01
We derive the scattering amplitude N(r) for a QCD dipole on a dense target in the semi-classical approximation. We include the first subleading correction in the target thickness arising from ˜ρ4 operators in the effective action for the large-x valence charges. Our result for N(r) can be matched to a phenomenological proton fit by Albacete et al. over a broad range of dipole sizes r and provides a definite prediction for the A-dependence for heavy-ion targets. We find a suppression of N(r) for finite A for dipole sizes a few times smaller than the inverse saturation scale, corresponding to a suppression of the classical bremsstrahlung tail.
Quark contribution to the small-x evolution of color dipole
Ian Balitsky
2006-09-11
The small-x deep inelastic scattering in the saturation region is governed by the non-linear evolution of Wilson-lines operators. In the leading logarithmic approximation it is given by the BK equation for the evolution of color dipoles. In the NLO the nonlinear equation gets contributions from quark and gluon loops. In this paper I calculate the quark-loop contribution to small-x evolution of Wilson lines in the NLO. It turns out that there are no new operators at the one-loop level--just as at the tree level, the high-energy scattering can be described in terms of Wilson lines. In addition, from the analysis of quark loops I find that the argument of coupling constant in the BK equation is determined by the size of the parent dipole rather than by the size of produced dipoles. These results are to be supported by future calculation of gluon loops.
Measurement of the dipole polarizability of the unstable neutron-rich nucleus 68Ni.
Rossi, D M; Adrich, P; Aksouh, F; Alvarez-Pol, H; Aumann, T; Benlliure, J; Böhmer, M; Boretzky, K; Casarejos, E; Chartier, M; Chatillon, A; Cortina-Gil, D; Datta Pramanik, U; Emling, H; Ershova, O; Fernandez-Dominguez, B; Geissel, H; Gorska, M; Heil, M; Johansson, H T; Junghans, A; Kelic-Heil, A; Kiselev, O; Klimkiewicz, A; Kratz, J V; Krücken, R; Kurz, N; Labiche, M; Le Bleis, T; Lemmon, R; Litvinov, Yu A; Mahata, K; Maierbeck, P; Movsesyan, A; Nilsson, T; Nociforo, C; Palit, R; Paschalis, S; Plag, R; Reifarth, R; Savran, D; Scheit, H; Simon, H; Sümmerer, K; Wagner, A; Waluś, W; Weick, H; Winkler, M
2013-12-13
The E1 strength distribution in 68Ni has been investigated using Coulomb excitation in inverse kinematics at the R3B-LAND setup and by measuring the invariant mass in the one- and two-neutron decay channels. The giant dipole resonance and a low-lying peak (pygmy dipole resonance) have been observed at 17.1(2) and 9.55(17) MeV, respectively. The measured dipole polarizability is compared to relativistic random phase approximation calculations yielding a neutron-skin thickness of 0.17(2) fm. A method and analysis applicable to neutron-rich nuclei has been developed, allowing for a precise determination of neutron skins in nuclei as a function of neutron excess. PMID:24483648
Evolution of the pygmy dipole resonance in nuclei with neutron excess
Co', G.; Donno, V. De; Maieron, C.; Anguiano, M.; Lallena, A. M.
2009-07-15
The electric dipole excitation of various nuclei is calculated with a Random Phase Approximation phenomenological approach. The evolution of the strength distribution in various groups of isotopes of oxygen, calcium, zirconium, and tin is studied. The neutron excess produces E1 strength in the low-energy region. Indexes to measure the collectivity of the excitation are defined. We studied the behavior of proton and neutron transition densities to determine the isoscalar or isovector nature of the excitation. We observed that in medium-heavy nuclei the low-energy E1 excitation has characteristics rather different than those exhibited by the giant dipole resonance. This new type of excitation can be identified as a pygmy dipole resonance.
Cosmic microwave background dipole spectrum measured by the COBE FIRAS instrument
NASA Technical Reports Server (NTRS)
Fixsen, D. J.; Cheng, E. S.; Cottingham, D. A.; Eplee, R. E., Jr.; Isaacman, R. B.; Mather, J. C.; Meyer, S. S.; Noerdlinger, P. D.; Shafer, R. A.; Weiss, R.
1994-01-01
The Far-Infrared Absolute Spectrophotometer (FIRAS) instrument on the Cosmic Background Explorer (COBE) has determined the dipole spectrum of the cosmic microwave background radiation (CMBR) from 2 to 20/cm. For each frequency the signal is decomposed by fitting to a monopole, a dipole, and a Galactic template for approximately 60% of the sky. The overall dipole spectrum fits the derivative of a Planck function with an amplitude of 3.343 +/- 0.016 mK (95% confidence level), a temperature of 2.714 +/- 0.022 K (95% confidence level), and an rms deviation of 6 x 10(exp -9) ergs/sq cm/s/sr cm limited by a detector and cosmic-ray noise. The monopole temperature is consistent with that determined by direct measurement in the accompanying article by Mather et al.
Monotone Boolean approximation
Hulme, B.L.
1982-12-01
This report presents a theory of approximation of arbitrary Boolean functions by simpler, monotone functions. Monotone increasing functions can be expressed without the use of complements. Nonconstant monotone increasing functions are important in their own right since they model a special class of systems known as coherent systems. It is shown here that when Boolean expressions for noncoherent systems become too large to treat exactly, then monotone approximations are easily defined. The algorithms proposed here not only provide simpler formulas but also produce best possible upper and lower monotone bounds for any Boolean function. This theory has practical application for the analysis of noncoherent fault trees and event tree sequences.
NASA Astrophysics Data System (ADS)
Gomis, L.; Faye, I. G.; Diallo, S.; Tall, M. S.; Diedhiou, I.; Hibbert, A.; Daul, C. A.; Diatta, C. S.
2016-01-01
The quadrupole, monopole and dipole generalized oscillator strengths (GOSs) as a function of momentum transfer are respectively calculated for these 3p6 → 3p5 (4p, 5p, 6p) and 3p6 → 3p5 (4s, 5s, 6s) transitions. Configuration interaction (CI) and random phase approximation with exchange (RPAE) methods are used in the determination of these GOS, in the length and velocity forms. The code of Hibbert has been used to generate the wavefunctions from which a partial of argon GOSs are been computed. The present work has reduced the gap between the absolute values of the theoretical calculations of GOSs and those of the experimental results of Zhu et al for the quadrupole excitations to 3p5 (4p, 5p). The profile of our quadrupole GOS 3p6 → 3p55p transition agrees well with the experimental result of Zhu. The best agreement (0.7%) is observed between the (length) first maximum position and the experimental one for the quadrupole GOS 3p6 → 3p54p transition. The present velocity GOS minimum position for the dipole excitation in 3p6 → 3p54s and the calculated velocity GOS maximum position of the monopole 3p6 → 3p54p transition are in good agreement with the experimental observations (differences of 1.82% and 3.08%, respectively). Correlation effects decrease with increasing of the excited state principal quantum number and have no great influence on the extrema positions.
Bunched beam longitudinal instability: Coherent dipole motion
Zhang, S.Y.; Weng, W.T.
1993-04-23
In this paper, the authors present a new formulation for the longitudinal coherent dipole motion, where a quadrature response of the environmental impedance is shown to be the effective longitudinal impedance for the beam instability. The Robinson-Pedersen formulation for the longitudinal dipole motion is also presented, the difference of the two approaches is discussed in the comparison. The results by using the Sacherer integral equation for the coherent dipole motion can generate the same results as by using the other two approaches, except for a scaling difference. The formulation is further generalized to the rigid bunch motion using signal analysis method, where a form factor shows up naturally. Finally, the formulation is applied to solve the coupled bunch instabilities. Examples of the AGS Booster and the AGS coupled bunch instabilities are used to illustrate the applications of the formulation.
Relationships between dipole moments of diatomic molecules.
Hou, Shilin; Bernath, Peter F
2015-02-14
The dipole moment is one of the most important physical properties of a molecule. We present a combination rule for the dipole moments of related diatomic molecules. For molecules AB, AX, BY, and XY from two different element groups in the periodic table, if their elements make a small parallelogram, reliable predictions can be obtained. Our approach is particularly useful for systems with heavy atoms. For a large set of molecules tested, the average difference of the prediction from experimental data is less than 0.2 debye (D). The dipole moments for heavy molecules such as GaCl, InBr, SrCl, and SrS, for which no experimental data are available at present, are predicted to be 3.17, 3.76, 3.85 and 11.54 D, respectively. PMID:25588998
Acoustic Scattering by a Vortex Dipole
NASA Astrophysics Data System (ADS)
Zheng, Zhongquan; Zhang, Junjian
2015-11-01
Acoustic scattering in vortical flow has been an interesting and practical topic, with applications in problems such as acoustic scattering of turbulent flow. In this study, the linearized Euler equation model is employed to investigate sound wave propagation over a subsonic counter-rotating vortex dipole. Both the stationary and moving due to mutual induction vortex dipoles are studied. The numerical scheme uses a high-order WENO scheme to accommodate the highly convective background flow at high Mach numbers. The simulation results are compared with the analytical solutions and literature data. The theoretical study is focused on the effects of three characteristic length scales in this problem: the incident sound wave length, the vortex core size, and the vortex dipole size. The directivity and scaling laws related to the vortex scattering effects are discussed.
Overview of the Levitated Dipole Experiment
NASA Astrophysics Data System (ADS)
Mauel, M. E.; Garnier, D. T.; Hansen, A.; Pedersen, T. Sunn; Kesner, J.; Jones, C. M.; Karim, I.; Liptac, J.; Minervini, J.; Michael, P.; Radovinsky, A.; Schultz, J. H.; Smith, B. A.; Zhukovsky, A.
2001-10-01
The Levitated Dipole Experiment (LDX) [http://www.psfc.mit.edu/ldx/] will be the first experiment able to study high-beta plasma confined by a magnetic dipole with near classical energy confinement. LDX consists of three superconducting magnets and illustrates the role of innovative magnetic technology that makes possible explorations of entirely new confinement concepts. We describe the LDX machine design and detail the fabrication status of the superconducting floating-coil, charging-coil, and levitation-coil. In addition, we summarize (1) our procedure to cool, to inductively charge, and to levitate the 1.3 MA floating coil, (2) our initial diagnostic set, and (3) our experimental and physics plans that answer the key questions of high-beta stability and confinement in the dipole fusion concept.
Observation of the dipole-dipole interaction between cold Rydberg atoms by microwave spectroscopy
NASA Astrophysics Data System (ADS)
Park, Hyunwook
We measured the dipole-dipole interaction between nsnp pairs of atoms by the line broadening technique. The broadening rate relies on the atomic density, equivalently the average internuclear spacing Rav, and principal quantum number n. This measurement of the dipole-dipole broadening can be expressed in terms of n and provides a simple measure of line broadening due to increased atomic density in laboratory units. Calculation of the dipole-dipole interaction was compared to the observations. It was realized that the observations, which have smaller broadening rates than the calculation, stem from the spin-orbit coupling, which results in the shift-free and small-shift dipole-dipole energy levels as well as normal shift levels. As a result of the dipole-dipole interaction, the nsnp molecules form attractive and repulsive dipole-dipole potentials in which atoms are forced to move toward each other and farther apart, respectively. These motions of the atoms in the dipole potentials induce collisional ionization and trigger plasma formation from Rydberg atoms. The collisional ionization was systematically investigated by comparing the effects of the attractive, repulsive, and almost flat potentials. It turned out that atoms transferred to the attractive potential are ionized in a few microseconds, while those on the repulsive potential are not significantly ionized, similar to the flat potential case. Essentially the same result was observed again with an enhanced ion signal by extending the sampling to a broader range of internuclear separation via high microwave power. We also detected plasma fields by using the exaggerated property of Rydberg atoms responding to external electric fields. Rydberg atoms were injected into a plasma cloud, and the ns -- np microwave transition was driven to detect the plasma fields by measuring Stark shifts. We were able to measure a microscopic field as small as 0.1 V/cm. In the presence of a strong macroscopic field, the resonances
Plasma Physics Approximations in Ares
Managan, R. A.
2015-01-08
Lee & More derived analytic forms for the transport properties of a plasma. Many hydro-codes use their formulae for electrical and thermal conductivity. The coefficients are complex functions of Fermi-Dirac integrals, F_{n}( μ/θ ), the chemical potential, μ or ζ = ln(1+e^{ μ/θ} ), and the temperature, θ = kT. Since these formulae are expensive to compute, rational function approximations were fit to them. Approximations are also used to find the chemical potential, either μ or ζ . The fits use ζ as the independent variable instead of μ/θ . New fits are provided for A^{α} (ζ ),A^{β} (ζ ), ζ, f(ζ ) = (1 + e^{-μ/θ})F_{1/2}(μ/θ), F_{1/2}'/F_{1/2}, F_{c}^{α}, and F_{c}^{β}. In each case the relative error of the fit is minimized since the functions can vary by many orders of magnitude. The new fits are designed to exactly preserve the limiting values in the non-degenerate and highly degenerate limits or as ζ→ 0 or ∞. The original fits due to Lee & More and George Zimmerman are presented for comparison.
Approximating Integrals Using Probability
ERIC Educational Resources Information Center
Maruszewski, Richard F., Jr.; Caudle, Kyle A.
2005-01-01
As part of a discussion on Monte Carlo methods, which outlines how to use probability expectations to approximate the value of a definite integral. The purpose of this paper is to elaborate on this technique and then to show several examples using visual basic as a programming tool. It is an interesting method because it combines two branches of…
Multicriteria approximation through decomposition
Burch, C. |; Krumke, S.; Marathe, M.; Phillips, C.; Sundberg, E. |
1997-12-01
The authors propose a general technique called solution decomposition to devise approximation algorithms with provable performance guarantees. The technique is applicable to a large class of combinatorial optimization problems that can be formulated as integer linear programs. Two key ingredients of the technique involve finding a decomposition of a fractional solution into a convex combination of feasible integral solutions and devising generic approximation algorithms based on calls to such decompositions as oracles. The technique is closely related to randomized rounding. The method yields as corollaries unified solutions to a number of well studied problems and it provides the first approximation algorithms with provable guarantees for a number of new problems. The particular results obtained in this paper include the following: (1) The authors demonstrate how the technique can be used to provide more understanding of previous results and new algorithms for classical problems such as Multicriteria Spanning Trees, and Suitcase Packing. (2) They show how the ideas can be extended to apply to multicriteria optimization problems, in which they wish to minimize a certain objective function subject to one or more budget constraints. As corollaries they obtain first non-trivial multicriteria approximation algorithms for problems including the k-Hurdle and the Network Inhibition problems.
Multicriteria approximation through decomposition
Burch, C.; Krumke, S.; Marathe, M.; Phillips, C.; Sundberg, E.
1998-06-01
The authors propose a general technique called solution decomposition to devise approximation algorithms with provable performance guarantees. The technique is applicable to a large class of combinatorial optimization problems that can be formulated as integer linear programs. Two key ingredients of their technique involve finding a decomposition of a fractional solution into a convex combination of feasible integral solutions and devising generic approximation algorithms based on calls to such decompositions as oracles. The technique is closely related to randomized rounding. Their method yields as corollaries unified solutions to a number of well studied problems and it provides the first approximation algorithms with provable guarantees for a number of new problems. The particular results obtained in this paper include the following: (1) the authors demonstrate how the technique can be used to provide more understanding of previous results and new algorithms for classical problems such as Multicriteria Spanning Trees, and Suitcase Packing; (2) they also show how the ideas can be extended to apply to multicriteria optimization problems, in which they wish to minimize a certain objective function subject to one or more budget constraints. As corollaries they obtain first non-trivial multicriteria approximation algorithms for problems including the k-Hurdle and the Network Inhibition problems.
Dynamics of dipoles and vortices in nonlinearly coupled three-dimensional field oscillators
NASA Astrophysics Data System (ADS)
Driben, R.; Konotop, V. V.; Malomed, B. A.; Meier, T.
2016-07-01
The dynamics of a pair of harmonic oscillators represented by three-dimensional fields coupled with a repulsive cubic nonlinearity is investigated through direct simulations of the respective field equations and with the help of the finite-mode Galerkin approximation (GA), which represents the two interacting fields by a superposition of 3 +3 harmonic-oscillator p -wave eigenfunctions with orbital and magnetic quantum numbers l =1 and m =1 , 0, -1 . The system can be implemented in binary Bose-Einstein condensates, demonstrating the potential of the atomic condensates to emulate various complex modes predicted by classical field theories. First, the GA very accurately predicts a broadly degenerate set of the system's ground states in the p -wave manifold, in the form of complexes built of a dipole coaxial with another dipole or vortex, as well as complexes built of mutually orthogonal dipoles. Next, pairs of noncoaxial vortices and/or dipoles, including pairs of mutually perpendicular vortices, develop remarkably stable dynamical regimes, which feature periodic exchange of the angular momentum and periodic switching between dipoles and vortices. For a moderately strong nonlinearity, simulations of the coupled-field equations agree very well with results produced by the GA, demonstrating that the dynamics is accurately spanned by the set of six modes limited to l =1 .
Pygmy dipole resonance as a constraint on the neutron skin of heavy nuclei
Piekarewicz, J.
2006-04-15
The isotopic dependence of the isovector Pygmy dipole response in tin is studied within the framework of the relativistic random-phase approximation. Regarded as an oscillation of the neutron skin against the isospin-symmetric core, the pygmy dipole resonance may place important constraints on the neutron skin of heavy nuclei and, as a result, on the equation of state of neutron-rich matter. The present study centers around two questions. First, is there a strong correlation between the development of a neutron skin and the emergence of low-energy isovector dipole strength? Second, could one use the recently measured Pygmy dipole resonance in {sup 130}Sn and {sup 132}Sn to discriminate among theoretical models? For the first question we found that although a strong correlation between the neutron skin and the Pygmy dipole resonance exists, a mild anticorrelation develops beyond {sup 120}Sn. The answer to the second question suggests that models with overly large neutron skins--and thus stiff symmetry energies--are in conflict with experiment.
Effects of Head Models and Dipole Source Parameters on EEG Fields
Peng, Li; Peng, Mingming; Xu, Anhuai
2015-01-01
Head model and an efficient method for computing the forward EEG (electroencephalography)problem are essential to dipole source localization(DSL). In this paper, we use less expensive ovoid geometry to approximate human head, aiming at investigating the effects of head shape and dipole source parameters on EEG fields. The application of point least squares (PLS) based on meshless method was introduced for solving EEG forward problem and numerical simulation is implemented in three kinds of ovoid head models. We present the performances of the surface potential in the face of varying dipole source parameters in detail. The results show that the potential patterns are similar for different dipole position in different head shapes, but the peak value of potential is significantly influenced by the head shape. Dipole position induces a great effect on the peak value of potential and shift of peak potential. The degree of variation between sphere head model and non-sphere head models is seen at the same time. We also show that PLS method with the trigonometric basis is superior to the constant basis, linear basis, and quadratic basis functions in accuracy and efficiency. PMID:25893011
Dynamics of dipoles and vortices in nonlinearly coupled three-dimensional field oscillators.
Driben, R; Konotop, V V; Malomed, B A; Meier, T
2016-07-01
The dynamics of a pair of harmonic oscillators represented by three-dimensional fields coupled with a repulsive cubic nonlinearity is investigated through direct simulations of the respective field equations and with the help of the finite-mode Galerkin approximation (GA), which represents the two interacting fields by a superposition of 3+3 harmonic-oscillator p-wave eigenfunctions with orbital and magnetic quantum numbers l=1 and m=1, 0, -1. The system can be implemented in binary Bose-Einstein condensates, demonstrating the potential of the atomic condensates to emulate various complex modes predicted by classical field theories. First, the GA very accurately predicts a broadly degenerate set of the system's ground states in the p-wave manifold, in the form of complexes built of a dipole coaxial with another dipole or vortex, as well as complexes built of mutually orthogonal dipoles. Next, pairs of noncoaxial vortices and/or dipoles, including pairs of mutually perpendicular vortices, develop remarkably stable dynamical regimes, which feature periodic exchange of the angular momentum and periodic switching between dipoles and vortices. For a moderately strong nonlinearity, simulations of the coupled-field equations agree very well with results produced by the GA, demonstrating that the dynamics is accurately spanned by the set of six modes limited to l=1. PMID:27575123
NASA Astrophysics Data System (ADS)
Gersho, Allen
1990-05-01
Recent advances in algorithms and techniques for speech coding now permit high quality voice reproduction at remarkably low bit rates. The advent of powerful single-ship signal processors has made it cost effective to implement these new and sophisticated speech coding algorithms for many important applications in voice communication and storage. Some of the main ideas underlying the algorithms of major interest today are reviewed. The concept of removing redundancy by linear prediction is reviewed, first in the context of predictive quantization or DPCM. Then linear predictive coding, adaptive predictive coding, and vector quantization are discussed. The concepts of excitation coding via analysis-by-synthesis, vector sum excitation codebooks, and adaptive postfiltering are explained. The main idea of vector excitation coding (VXC) or code excited linear prediction (CELP) are presented. Finally low-delay VXC coding and phonetic segmentation for VXC are described.
Waves in space plasma dipole antenna subsystem
NASA Technical Reports Server (NTRS)
Thomson, Mark
1993-01-01
The Waves In Space Plasma (WISP) flight experiment requires a 50-meter-long deployable dipole antenna subsystem (DASS) to radiate radio frequencies from the STS Orbiter cargo bay. The transmissions are to excite outer ionospheric plasma between the dipole and a free-flying receiver (Spartan) for scientific purposes. This report describes the singular DASS design requirements and how the resulting design satisfies them. A jettison latch is described in some detail. The latch releases the antenna in case of any problems which might prevent the bay doors from closing for re-entry and landing of the Orbiter.
Microstrip dipole antennas on electrically thick substrates
NASA Astrophysics Data System (ADS)
Jackson, D. R.; Alexopoulos, N. G.
1985-10-01
Printed circuit antennas are attractive radiation sources both at microwave and millimeter wave frequencies. However, for millimeter wave applications where the substrate is likely to be electrically thick, it is important to understand the basic effects of a thick substrate on radiation characteristics. In particular, it is concluded here that dipole radiation properties become sensitive to loss as the substrate becomes thick. Furthermore, the efficiency of dipoles on thick substrates tends to be low, especially as the dielectric constant of the substrate increases. A method of improving both the efficiency and gain can be used for thick substrates, however, which uses a superstrate layer on top of the antenna.
Dipole strength distributions from HIGS Experiments
NASA Astrophysics Data System (ADS)
Werner, V.; Cooper, N.; Goddard, P. M.; Humby, P.; Ilieva, R. S.; Rusev, G.; Beller, J.; Bernards, C.; Crider, B. P.; Isaak, J.; Kelley, J. H.; Kwan, E.; Löher, B.; Peters, E. E.; Pietralla, N.; Romig, C.; Savran, D.; Scheck, M.; Tonchev, A. P.; Tornow, W.; Yates, S. W.; Zweidinger, M.
2015-05-01
A series of photon scattering experiments has been performed on the double-beta decay partners 76Ge and 76Se, in order to investigate their dipole response up to the neutron separation threshold. Gamma-ray beams from bremsstrahlung at the S-DALINAC and from Compton-backscattering at HIGS have been used to measure absolute cross sections and parities of dipole excited states, respectively. The HIGS data allows for indirect measurement of averaged branching ratios, which leads to significant corrections in the observed excitation cross sections. Results are compared to statistical calculations, to test photon strength functions and the Axel-Brink hypothesis
Real Compton scattering via color dipoles
Kopeliovich, B. Z.; Schmidt, Ivan; Siddikov, M.
2009-09-01
We study the photoabsorption reaction and real Compton scattering within the color dipole model. We rely on a photon wave function derived in the instanton-vacuum model and on the energy-dependent phenomenological elastic dipole amplitude. Data for the photoabsorption cross section at high energies agree with our parameter-free calculations. We also provide predictions for the differential real Compton scattering cross section. Although no data for small angle Compton scattering are available so far, this process can be measured in ultraperipheral hadronic and nuclear collisions at the LHC.
Neutron electric dipole moment and CP
Chang, Darwin; Chang, We-Fu; Frank, Mariana; Keung, Wai-Yee
2000-11-01
We analyze the neutron electric dipole moment (EDM) in the minimal supersymmetric standard model with explicit R-parity violating terms. The leading contribution to the EDM occurs at the two-loop level and is dominated by the chromoelectric dipole moments of quarks, assuming there is no tree-level mixings between sleptons and Higgs bosons or between leptons and gauginos. Based on the experimental constraint on the neutron EDM, we set limits on the imaginary parts of complex couplings {lambda}{sub ijk}{prime} and {lambda}{sub ijk} due to the virtual b loop or {tau} loop.
Microwave observations of the dipole-dipole interaction between cold Rydberg atoms
NASA Astrophysics Data System (ADS)
Afrousheh, K.; Bohlouli, P. Z.; Vagale, D.; Fedorov, M.; Mugford, A.; Martin, J. D. D.
2004-05-01
Neighboring Rydberg atoms may strongly interact through electric dipole-dipole couplings. Thus, temporary excitation to Rydberg states has been proposed for implementing elements of quantum information processing using cold neutral atoms. In this work we excited Rb atoms in a MOT to the 45d_5/2 Rydberg state. A microwave pulse was then used to transfer a variable amount of 45d_5/2 atoms to the 46p_3/2 state. Atoms in the 45d and 46p states strongly interact through an always resonant dipole-dipole interaction. We probe this by introducing a second microwave pulse which drives the 45d_5/2-46d_5/2 two photon transition. The dipole-dipole interaction between 46d and 46p states is relatively weak, so the observed spectra are dominated by the 45d-46p couplings between neighboring atoms. These results are discussed in the context of dipole-blockade, as proposed by Lukin et al., Phys. Rev. Lett., 87, 37901 (2001).
NASA Astrophysics Data System (ADS)
Arapiraca, A. F. C.; Jonsson, Dan; Mohallem, J. R.
2011-12-01
We report an upgrade of the Dalton code to include post Born-Oppenheimer nuclear mass corrections in the calculations of (ro-)vibrational averages of molecular properties. These corrections are necessary to achieve an accuracy of 10-4 debye in the calculations of isotopic dipole moments. Calculations on the self-consistent field level present this accuracy, while numerical instabilities compromise correlated calculations. Applications to HD, ethane, and ethylene isotopologues are implemented, all of them approaching the experimental values.
Arapiraca, A F C; Jonsson, Dan; Mohallem, J R
2011-12-28
We report an upgrade of the Dalton code to include post Born-Oppenheimer nuclear mass corrections in the calculations of (ro-)vibrational averages of molecular properties. These corrections are necessary to achieve an accuracy of 10(-4) debye in the calculations of isotopic dipole moments. Calculations on the self-consistent field level present this accuracy, while numerical instabilities compromise correlated calculations. Applications to HD, ethane, and ethylene isotopologues are implemented, all of them approaching the experimental values. PMID:22225162
Collective spin excitations in 2D paramagnet with dipole interaction
NASA Astrophysics Data System (ADS)
Tsiberkin, Kirill
2016-02-01
The collective spin excitations in the unbounded 2D paramagnetic system with dipole interactions are studied. The model Hamiltonian includes Zeeman energy and dipole interaction energy, while the exchange vanishes. The system is placed into a constant uniform magnetic field which is orthogonal to the lattice plane. It provides the equilibrium state with spin ordering along the field direction, and the saturation is reached at zero temperature. We consider the deviations of spin magnetic moments from its equilibrium position along the external field. The Holstein-Primakoff representation is applied to spin operators in low-temperature approximation. When the interaction between the spin waves is negligible and only two-magnon terms are taken into account, the Hamiltonian diagonalisation is possible. We obtain the dispersion relation for spin waves in the square and hexagonal honeycomb lattice. Bose-Einstein statistics determine the average number of spin deviations, and total system magnetization. The lattice structure does not influence on magnetization at the long-wavelength limit. The dependencies of the relative magnetization and longitudinal susceptibility on temperature and external field intensity are found. The internal energy and specific heat of the Bose gas of spin waves are calculated. The collective spin excitations play a significant role in the properties of the paramagnetic system at low temperature and strong external magnetic field.
Reorientable electric dipoles and cooperative phenomena in human tooth enamel.
Hitmi, N; Lamure-Plaino, E; Lamure, A; LaCabanne, C; Young, R A
1986-05-01
A preliminary investigation of electric dipole reorientability in human tooth enamel (TE) in comparison to that in hydroxyapatite (OHAp) has been made with the fractional-polarization form of the thermally stimulated currents (TSC) method. The reorientable dipoles are the structural OH-ions. The OHAp exhibited compensation phenomena at 211.5 degrees C and at 356 degrees C which are associated here with the hexagonal form becoming quasi-statically stabilized and dynamically stabilized, respectively, against the monoclinic form. TE specimens were pretreated at various temperatures. All showed the onset of cooperative motions that could quasi-statically stabilize the hexagonal form at the same temperature, approximately 212 degrees C, as did OHAp, even though the TE was already statically stabilized in the hexagonal form. Parts of the TSC spectra that did not conform to the 212 degrees C compensation changed progressively with pretreatment temperature. Loss of incorporated H2O is identified as the most probable cause of most of these changes. This work shows considerable promise for TSC as a tool for further quantitative investigation of TE. PMID:3013384
Non-free gas of dipoles of non-singular screw dislocations and the shear modulus near the melting
Malyshev, Cyril
2014-12-15
The behavior of the shear modulus caused by proliferation of dipoles of non-singular screw dislocations with finite-sized core is considered. The representation of two-dimensional Coulomb gas with smoothed-out coupling is used, and the stress–stress correlation function is calculated. A convolution integral expressed in terms of the modified Bessel function K{sub 0} is derived in order to obtain the shear modulus in approximation of interacting dipoles. Implications are demonstrated for the shear modulus near the melting transition which are due to the singularityless character of the dislocations. - Highlights: • Thermodynamics of dipoles of non-singular screw dislocations is studied below the melting. • The renormalization of the shear modulus is obtained for interacting dipoles. • Dependence of the shear modulus on the system scales is presented near the melting.
Optimizing the Zeldovich approximation
NASA Technical Reports Server (NTRS)
Melott, Adrian L.; Pellman, Todd F.; Shandarin, Sergei F.
1994-01-01
We have recently learned that the Zeldovich approximation can be successfully used for a far wider range of gravitational instability scenarios than formerly proposed; we study here how to extend this range. In previous work (Coles, Melott and Shandarin 1993, hereafter CMS) we studied the accuracy of several analytic approximations to gravitational clustering in the mildly nonlinear regime. We found that what we called the 'truncated Zeldovich approximation' (TZA) was better than any other (except in one case the ordinary Zeldovich approximation) over a wide range from linear to mildly nonlinear (sigma approximately 3) regimes. TZA was specified by setting Fourier amplitudes equal to zero for all wavenumbers greater than k(sub nl), where k(sub nl) marks the transition to the nonlinear regime. Here, we study the cross correlation of generalized TZA with a group of n-body simulations for three shapes of window function: sharp k-truncation (as in CMS), a tophat in coordinate space, or a Gaussian. We also study the variation in the crosscorrelation as a function of initial truncation scale within each type. We find that k-truncation, which was so much better than other things tried in CMS, is the worst of these three window shapes. We find that a Gaussian window e(exp(-k(exp 2)/2k(exp 2, sub G))) applied to the initial Fourier amplitudes is the best choice. It produces a greatly improved crosscorrelation in those cases which most needed improvement, e.g. those with more small-scale power in the initial conditions. The optimum choice of kG for the Gaussian window is (a somewhat spectrum-dependent) 1 to 1.5 times k(sub nl). Although all three windows produce similar power spectra and density distribution functions after application of the Zeldovich approximation, the agreement of the phases of the Fourier components with the n-body simulation is better for the Gaussian window. We therefore ascribe the success of the best-choice Gaussian window to its superior treatment
Dipole-dipole interactions in optical lattices do not follow an inverse cube power law
NASA Astrophysics Data System (ADS)
Wall, M. L.; Carr, L. D.
2013-12-01
We study the effective dipole-dipole interactions in ultracold quantum gases on optical lattices as a function of asymmetry in confinement along the principal axes of the lattice. In particular, we study the matrix elements of the dipole-dipole interaction in the basis of lowest band Wannier functions which serve as a set of low-energy states for many-body physics on the lattice. We demonstrate that, for shallow lattices in quasi-reduced dimensional scenarios, the effective interaction between dipoles in an optical lattice is non-algebraic in the inter-particle separation at short to medium distance on the lattice scale and has a long-range power-law tail, in contrast to the pure power-law behavior of the dipole-dipole interaction in free space. The modifications to the free-space interaction can be sizable; we identify differences of up to 36% from the free-space interaction at the nearest-neighbor distance in quasi-one-dimensional arrangements. The interaction difference depends essentially on asymmetry in confinement, due to the d-wave anisotropy of the dipole-dipole interaction. Our results do not depend on statistics, applying to both dipolar Bose-Einstein condensates and degenerate Fermi gases. Using matrix product state simulations, we demonstrate that use of the correct lattice dipolar interaction leads to significant deviations from many-body predictions using the free-space interaction. Our results are relevant to up and coming experiments with ultracold heteronuclear molecules, Rydberg atoms and strongly magnetic atoms in optical lattices.
Entanglement between two atoms in the presence of dipole-dipole interaction and atomic coherence
NASA Astrophysics Data System (ADS)
Bashkirov, Eugene K.; Litvinova, Darya V.
2015-03-01
We have investigated the influence of dipole-dipole interaction and initial atomic coherence on dynamics of two-atom systems. We have considered a model, in which only one atom is trapped in a cavity, and the other one can be spatially moved freely outside the cavity. We have shown the possibility of disappearance of the entanglement sudden death effect in the presence of the dipole interaction of atoms. We have also derived that the initial atomic coherence can be used for effective control of the degree of the atom-atom entanglement.
NASA Astrophysics Data System (ADS)
Oruç, Bülent
2010-01-01
The magnetic gradient tensor (MGT) provides gradient components of potential fields with mathematical properties which allow processing techniques e.g. analytic signal techniques. With MGT emerging as a new tool for geophysical exploration, the mathematical modelling of gradient tensor fields is necessary for interpretation of magnetic field measurements. The point-dipole and line of dipoles are used to approximate various magnetic objects. I investigate the maxima of the magnitude of magnetic vector components (MMVC) and analytic signals of magnetic gradient tensor (ASMGT) resulting from point-dipole and line of dipoles sources in determining horizontal locations. I also present a method in which depths of these sources are estimated from the ratio of the maximum of MMVC to the maximum of ASMGT. Theoretical examples have been carried out to test the feasibility of the method in obtaining source locations and depths. The method has been applied to the MMVC and ASMGT computed from the total field data over a basic/ultrabasic body at the emerald deposit of Socotó, Bahia, Brazil and buried water supply pipe near Jadaguda Township, India. In both field examples, the method produces good correlations with previous interpretations.
NASA Technical Reports Server (NTRS)
Pollara, Fabrizio; Hamkins, Jon; Dolinar, Sam; Andrews, Ken; Divsalar, Dariush
2006-01-01
This viewgraph presentation reviews uplink coding. The purpose and goals of the briefing are (1) Show a plan for using uplink coding and describe benefits (2) Define possible solutions and their applicability to different types of uplink, including emergency uplink (3) Concur with our conclusions so we can embark on a plan to use proposed uplink system (4) Identify the need for the development of appropriate technology and infusion in the DSN (5) Gain advocacy to implement uplink coding in flight projects Action Item EMB04-1-14 -- Show a plan for using uplink coding, including showing where it is useful or not (include discussion of emergency uplink coding).
NASA Technical Reports Server (NTRS)
Gliebe, P; Mani, R.; Shin, H.; Mitchell, B.; Ashford, G.; Salamah, S.; Connell, S.; Huff, Dennis (Technical Monitor)
2000-01-01
This report describes work performed on Contract NAS3-27720AoI 13 as part of the NASA Advanced Subsonic Transport (AST) Noise Reduction Technology effort. Computer codes were developed to provide quantitative prediction, design, and analysis capability for several aircraft engine noise sources. The objective was to provide improved, physics-based tools for exploration of noise-reduction concepts and understanding of experimental results. Methods and codes focused on fan broadband and 'buzz saw' noise and on low-emissions combustor noise and compliment work done by other contractors under the NASA AST program to develop methods and codes for fan harmonic tone noise and jet noise. The methods and codes developed and reported herein employ a wide range of approaches, from the strictly empirical to the completely computational, with some being semiempirical analytical, and/or analytical/computational. Emphasis was on capturing the essential physics while still considering method or code utility as a practical design and analysis tool for everyday engineering use. Codes and prediction models were developed for: (1) an improved empirical correlation model for fan rotor exit flow mean and turbulence properties, for use in predicting broadband noise generated by rotor exit flow turbulence interaction with downstream stator vanes: (2) fan broadband noise models for rotor and stator/turbulence interaction sources including 3D effects, noncompact-source effects. directivity modeling, and extensions to the rotor supersonic tip-speed regime; (3) fan multiple-pure-tone in-duct sound pressure prediction methodology based on computational fluid dynamics (CFD) analysis; and (4) low-emissions combustor prediction methodology and computer code based on CFD and actuator disk theory. In addition. the relative importance of dipole and quadrupole source mechanisms was studied using direct CFD source computation for a simple cascadeigust interaction problem, and an empirical combustor
NASA Astrophysics Data System (ADS)
Gao, Y. J.; Guo, Y. J.; Liu, J.-M.
2012-03-01
A double-domain model with long-range dipole-dipole interaction is proposed to investigate the self-oscillation of magnetization in nano-magnetic systems driven by self-controlled spin-polarized current. The dynamic behavior of magnetization oscillation is calculated by a modified Landau-Lifshitz-Gilbert equation in order to evaluate the effects of the long-range dipole-dipole interaction. While the self-oscillation of magnetization can be maintained substantially, several self-oscillation regions are experienced as the dipole-dipole interaction increases gradually.
Electromagnetic Force on a Moving Dipole
ERIC Educational Resources Information Center
Kholmetskii, Alexander L.; Missevitch, Oleg V.; Yarman, T.
2011-01-01
We analyse the force acting on a moving dipole due to an external electromagnetic field and show that the expression derived in Vekstein (1997 "Eur. J. Phys." 18 113) is erroneous and suggest the correct equation for the description of this force. We also discuss the physical meaning of the relativistic transformation of current for a closed…
Dipole operator constraints on composite Higgs models
NASA Astrophysics Data System (ADS)
König, Matthias; Neubert, Matthias; Straub, David M.
2014-07-01
Flavour- and CP-violating electromagnetic or chromomagnetic dipole operators in the quark sector are generated in a large class of new physics models and are strongly constrained by measurements of the neutron electric dipole moment and observables sensitive to flavour-changing neutral currents, such as the branching ratio and . After a model-independent discussion of the relevant constraints, we analyze these effects in models with partial compositeness, where the quarks get their masses by mixing with vector-like composite fermions. These scenarios can be seen as the low-energy limit of composite Higgs or warped extra dimensional models. We study different choices for the electroweak representations of the composite fermions motivated by electroweak precision tests as well as different flavour structures, including flavour anarchy and or flavour symmetries in the strong sector. In models with "wrong-chirality" Yukawa couplings, we find a strong bound from the neutron electric dipole moment, irrespective of the flavour structure. In the case of flavour anarchy, we also find strong bounds from flavour-violating dipoles, while these constraints are mild in the flavour-symmetric models.
Analysis of a microstrip dipole antenna
NASA Astrophysics Data System (ADS)
Rao, B. V.; Sabhnani, N. H.
1984-02-01
Assuming a quasi-TEM mode of wave propagation and using a conformal transformation technique, accurate and simple analytic expressions for the characteristic wave resistance and the effective dielectric constant of the microstrip dipole antenna in the mixed dielectric medium have been derived. The theoretical values are in close agreement with the experimental results.
Efficient analysis for infinite microstrip dipole arrays
NASA Astrophysics Data System (ADS)
Wright, S. M.; Lo, Y. T.
1983-11-01
A moment method analysis of infinite microstrip dipole arrays which uses an efficient technique to evaluate the generalized impedance matrix is described. A particularly simple formulation is obtained through the use of the periodic Green function. Results for the reflection coefficient magnitude against scan angle are given for a typical array.
The Case of the Disappearing Magnetic Dipole
ERIC Educational Resources Information Center
Gough, W.
2008-01-01
The problem of an oscillating magnetic dipole at the centre of a lossless dielectric spherical shell is considered. For simplicity, the free-space wavelength is taken to be much greater than the shell radii, but the relative permittivity [epsilon][subscript r] of the shell is taken as much greater than unity, so the wavelength in the shell could…
Dipole nano-laser: Theory and properties
Ghannam, T.
2014-03-31
In this paper we outline the main quantum properties of the system of nano-based laser called Dipole Nano-Laser emphasizing mainly on its ability to produce coherent light and for different configurations such as different embedding materials and subjecting it to an external classical electric field.
A Microstrip Reflect Array Using Crossed Dipoles
NASA Technical Reports Server (NTRS)
Pozar, David M.; Targonski, Stephen D.
1998-01-01
Microstrip reflect arrays offer a flat profile and light weight, combined with many of the electrical characteristics of reflector antennas. Previous work [1]-[7] has demonstrated a variety of microstrip reflect arrays, using different elements at a range of frequencies. In this paper we describe the use of crossed dipoles as reflecting elements in a microstrip reflectarray. Theory of the solution will be described, with experimental results for a 6" square reflectarray operating at 28 GHz. The performance of crossed dipoles will be directly compared with microstrip patches, in terms of bandwidth and loss. We also comment on the principle of operation of reflectarray elements, including crossed dipoles, patches of variable length, and patch elements with tuning stubs. This research was prompted by the proposed concept of overlaying a flat printed reflectarray on the surface of a spacecraft solar panel. Combining solar panel and antenna apertures in this way would lead to a reduction in weight and simpler deployment, with some loss of flexibility in independently pointing the solar panel and the antenna. Using crossed dipoles as reflectarray elements will minimize the aperture blockage of the solar cells, in contrast to the use of elements such as microstrip patches.
GenLocDip: A Generalized Program to Calculate and Visualize Local Electric Dipole Moments.
Groß, Lynn; Herrmann, Carmen
2016-09-30
Local dipole moments (i.e., dipole moments of atomic or molecular subsystems) are essential for understanding various phenomena in nanoscience, such as solvent effects on the conductance of single molecules in break junctions or the interaction between the tip and the adsorbate in atomic force microscopy. We introduce GenLocDip, a program for calculating and visualizing local dipole moments of molecular subsystems. GenLocDip currently uses the Atoms-In-Molecules (AIM) partitioning scheme and is interfaced to various AIM programs. This enables postprocessing of a variety of electronic structure output formats including cube and wavefunction files, and, in general, output from any other code capable of writing the electron density on a three-dimensional grid. It uses a modified version of Bader's and Laidig's approach for achieving origin-independence of local dipoles by referring to internal reference points which can (but do not need to be) bond critical points (BCPs). Furthermore, the code allows the export of critical points and local dipole moments into a POVray readable input format. It is particularly designed for fragments of large systems, for which no BCPs have been calculated for computational efficiency reasons, because large interfragment distances prevent their identification, or because a local partitioning scheme different from AIM was used. The program requires only minimal user input and is written in the Fortran90 programming language. To demonstrate the capabilities of the program, examples are given for covalently and non-covalently bound systems, in particular molecular adsorbates. © 2016 Wiley Periodicals, Inc. PMID:27416879
Candidate molecular ions for an electron electric dipole moment experiment
Meyer, Edmund R.; Bohn, John L.; Deskevich, Michael P.
2006-06-15
This paper is a theoretical work in support of a newly proposed experiment [R. Stutz and E. Cornell, Bull. Am. Soc. Phys. 89, 76 (2004)] that promises greater sensitivity to measurements of the electron's electric dipole moment (EDM) based on the trapping of molecular ions. Such an experiment requires the choice of a suitable molecule that is both experimentally feasible and possesses an expectation of a reasonable EDM signal. We find that the molecular ions PtH{sup +} and HfH{sup +} are both suitable candidates in their low-lying {sup 3}{delta} states. In particular, we anticipate that the effective electric fields generated inside these molecules are approximately 73 and -17 GV/cm, respectively. As a byproduct of this discussion, we also explain how to make estimates of the size of the effective electric field acting in a molecule, using commercially available nonrelativistic molecular structure software.
Standing slow magnetosonic waves in a dipole-like plasmasphere
NASA Astrophysics Data System (ADS)
Leonovich, A. S.; Kozlov, D. A.; Edemskiy, I. K.
2010-09-01
A problem of the structure and spectrum of standing slow magnetosonic waves in a dipole plasmasphere is solved. Both an analytical (in WKB approximation) and numerical solutions are found to the problem, for a distribution of the plasma parameters typical of the Earth's plasmasphere. The solutions allow us to treat the total electronic content oscillations registered above Japan as oscillations of one of the first harmonics of standing slow magnetosonic waves. Near the ionosphere the main components of the field of registered standing SMS waves are the plasma oscillations along magnetic field lines, plasma concentration oscillation and the related oscillations of the gas-kinetic pressure. The velocity of the plasma oscillations increases dramatically near the ionospheric conductive layer, which should result in precipitation of the background plasma particles. This may be accompanied by ionospheric F2 region airglows modulated with the periods of standing slow magnetosonic waves.
Spectroscopic Observation of Resonant Electric Dipole-Dipole Interactions between Cold Rydberg Atoms
NASA Astrophysics Data System (ADS)
Afrousheh, K.; Bohlouli-Zanjani, P.; Vagale, D.; Mugford, A.; Fedorov, M.; Martin, J. D.
2004-11-01
Resonant electric dipole-dipole interactions between cold Rydberg atoms were observed using microwave spectroscopy. Laser-cooled 85Rb atoms in a magneto-optical trap were optically excited to 45d5/2 Rydberg states using a pulsed laser. A microwave pulse transferred a fraction of these Rydberg atoms to the 46p3/2 state. A second microwave pulse then drove atoms in the 45d5/2 state to the 46d5/2 state, and was used as a probe of interatomic interactions. The spectral width of this two-photon probe transition was found to depend on the presence of the 46p3/2 atoms, and is due to the resonant electric dipole-dipole interaction between 45d5/2 and 46p3/2 Rydberg atoms.
Droplet formation in a Bose-Einstein condensate with strong dipole-dipole interaction
NASA Astrophysics Data System (ADS)
Xi, Kui-Tian; Saito, Hiroki
2016-01-01
Motivated by the recent experiment [H. Kadau et al., arXiv:1508.05007], we study roton instability and droplet formation in a Bose-Einstein condensate of 164Dy atoms with strong magnetic dipole-dipole interaction. We numerically solve the cubic-quintic Gross-Pitaevskii equation with dipole-dipole interaction, and show that the three-body interaction plays a significant role in the formation of droplet patterns. We numerically demonstrate the formation of droplet patterns and crystalline structures, decay of droplets, and hysteresis behavior, which are in good agreement with the experiment. Our numerical simulations provide the first prediction on the values of the three-body interaction in a 164Dy Bose-Einstein condensate. We also predict that the droplets remain stable during the time-of-flight expansion. From our results, further experiments investigating the three-body interaction in dipolar quantum gases are required.
Master equation with quantized atomic motion including dipole-dipole interactions
NASA Astrophysics Data System (ADS)
Damanet, François; Braun, Daniel; Martin, John
2016-05-01
We derive a markovian master equation for the internal dynamics of an ensemble of two-level atoms including all effects related to the quantization of their motion. Our equation provides a unifying picture of the consequences of recoil and indistinguishability of atoms beyond the Lamb-Dicke regime on both their dissipative and conservative dynamics, and is relevant for experiments with ultracold trapped atoms. We give general expressions for the decay rates and the dipole-dipole shifts for any motional states, and we find analytical formulas for a number of relevant states (Gaussian states, Fock states and thermal states). In particular, we show that the dipole-dipole interactions and cooperative photon emission can be modulated through the external state of motion. The effects predicted should be experimentally observable with Rydberg atoms. FD would like to thank the F.R.S.-FNRS for financial support. FD is a FRIA Grant holder of the Fonds de la Recherche Scientifique-FNRS.
Dipole evolution in rotating two-dimensional flow with bottom friction
NASA Astrophysics Data System (ADS)
Makarov, V. G.
2012-02-01
The evolution of a dipolar vortex in a quasi-two-dimensional rotating flow of barotropic fluid over a flat surface with a no-slip condition in the Ekman bottom layer is considered. The vorticity equation in this case becomes nonlinear. An effect of bottom friction is displayed mainly in cyclone-anticyclone asymmetry, which results in the expansion (diminution) of cyclonic (anticyclonic) local structures and in the stronger decay of positive vorticity. When a lateral viscosity is omitted, the vorticity equation has a solution in the form of vortex patches and hence a contour dynamics method may be used for numerical simulation. An approach of point vortices with decaying strengths is also discussed. In an approximation of two patches of opposite uniform vorticity, a three-parameter family of stationary (in an ideal fluid) orbital dipoles [V. G. Makarov and Z. Kizner, "Stability and evolution of uniform-vorticity dipoles," J. Fluid Mech. 672, 307 (2011)], 10.1017/S0022112010006026 consisting of patches with unequal areas and absolute values of vorticity is considered. A three-dimensional domain of instability for this family is numerically constructed. It is shown that the evolution of such dipoles in a flow with bottom friction is described with good accuracy by a properly matched trajectory in parameter space of ideal-fluid steady states. Explicit time-dependent formulae for this phase trajectory are obtained. All characteristics (including the patch's shapes) of the evolutionary dipole, and the same characteristics for the corresponding ideal-fluid stationary dipole, almost completely coincide, at least while the phase trajectory remains in the stability region. The evolution of stationary translating dipoles (with zero net circulation) that have continuously distributed vorticity inside a quasi-elliptical finite region is also examined. When the circular Lamb dipole is used as the initial condition, good qualitative agreement is observed between the asymmetric
Laboratory study of vortex dipoles interacting with step topography
NASA Astrophysics Data System (ADS)
Hinds, A. K.; Eames, I.; Johnson, E. R.; McDonald, N. R.
2009-06-01
Laboratory experiments are performed which study the behavior of two-dimensional vortex dipoles propagating toward a rectilinear step change in depth. The dipoles are formed in a homogeneous shallow water layer by an impulsive jet and approach the step from either relatively deep or shallow water at normal or oblique incidence. Qualitative observations agree well with previous theoretical predictions: At normal incidence the separation of the two vortices forming the dipole increases for a dipole crossing from deep water and decreases for a dipole crossing from shallow water. Dipoles with oblique angles of incidence refract toward the normal when passing into shallower water, and dipoles that cross the step into deep water refract away from the normal. Dipoles approaching from shallow water at sufficiently large angles of incidence reflect off the step.
Beyond the Kirchhoff approximation
NASA Technical Reports Server (NTRS)
Rodriguez, Ernesto
1989-01-01
The three most successful models for describing scattering from random rough surfaces are the Kirchhoff approximation (KA), the small-perturbation method (SPM), and the two-scale-roughness (or composite roughness) surface-scattering (TSR) models. In this paper it is shown how these three models can be derived rigorously from one perturbation expansion based on the extinction theorem for scalar waves scattering from perfectly rigid surface. It is also shown how corrections to the KA proportional to the surface curvature and higher-order derivatives may be obtained. Using these results, the scattering cross section is derived for various surface models.
Probing dipole-dipole interaction in a rubidium gas via double-quantum 2D spectroscopy.
Gao, Feng; Cundiff, Steven T; Li, Hebin
2016-07-01
We have implemented double-quantum 2D spectroscopy on a rubidium vapor and shown that this technique provides sensitive and background-free detection of the dipole-dipole interaction. The 2D spectra include signals from both individual atoms and interatomic interactions, allowing quantitative studies of the interaction. A theoretical model based on the optical Bloch equations is used to reproduce the experimental spectrum and confirm the origin of double-quantum signals. PMID:27367074
Mutual impedance of nonplanar-skew sinusoidal dipoles
NASA Technical Reports Server (NTRS)
Richmond, J. H.; Geary, N. H.
1974-01-01
The mutual impedance of nonplanar-skew sinusoidal dipoles is presented as a summation of several exponential integrals with complex arguments. Mathematical models are developed to show the near-zone field of the sinusoidal dipole. The mutual impedance of coupled dipoles is expressed as the sum of four monopole-mobopole impedances to simplify the analysis procedure. The subroutines for solving the parameters of the dipoles are discussed.
NASA Astrophysics Data System (ADS)
Cristea, M.
2016-04-01
Due to its non-centrosymmetric wurtzite crystal structure, the CdSe dot presents a permanent electric dipole moment. In this paper we study the effect of an electric applied field on the emission wavelength of a CdSe/ZnS core-shell quantum dot with a permanent electric dipole. The electron and hole single-particle energy and wave function in the presence of an electric dipole are obtained in the effective-mass and parabolic-band approximation for various electric field strengths. The Schrödinger equation was solved by use of the finite element method. The exciton binding energy is calculated in the first-order perturbation theory and the optical emission wavelengths are found and compared to the experimental values. We find that the photoluminescence emission can be tuned by varying the electric dipole size, the electric field strength and by an appropriate orientation between the permanent dipole moment and applied electric field.
On the decoder error probability of block codes
NASA Technical Reports Server (NTRS)
Cheung, Kar-Ming
1992-01-01
By using coding and combinational techniques, an explicit formula is derived which enumerates the complete weight distribution of decodable words of block codes using partially known weight distributions. Also an approximation formula for nonbinary block codes is obtained. These results in turn give exact and approximate expressions for the decoder error probability PE(u) of block codes.
Electric dipole moment in KH2PO4 systematically modified by proton irradiation
NASA Astrophysics Data System (ADS)
Jung Kweon, Jin; Eui Lee, Cheol; Noh, S. J.; Kim, H. S.
2012-01-01
We have carried out an impedance spectroscopy study on a series of proton-irradiated KH2PO4 (KDP) systems. A systematic modification was observed in the transverse dipole moment of the proton-irradiated KDP systems, associated with hydrogen-ion displacements, as obtained from dielectric constant measurements by using a mean-field approximation. Besides, intercorrelation of the charge transport with the dielectric properties was revealed, both having closely to do with the hydrogen-bond modification.
Approximate Green's function methods for HZE transport in multilayered materials
NASA Technical Reports Server (NTRS)
Wilson, John W.; Badavi, Francis F.; Shinn, Judy L.; Costen, Robert C.
1993-01-01
A nonperturbative analytic solution of the high charge and energy (HZE) Green's function is used to implement a computer code for laboratory ion beam transport in multilayered materials. The code is established to operate on the Langley nuclear fragmentation model used in engineering applications. Computational procedures are established to generate linear energy transfer (LET) distributions for a specified ion beam and target for comparison with experimental measurements. The code was found to be highly efficient and compared well with the perturbation approximation.
Permutation-invariant quantum codes
NASA Astrophysics Data System (ADS)
Ouyang, Yingkai
2014-12-01
A quantum code is a subspace of a Hilbert space of a physical system chosen to be correctable against a given class of errors, where information can be encoded. Ideally, the quantum code lies within the ground space of the physical system. When the physical model is the Heisenberg ferromagnet in the absence of an external magnetic field, the corresponding ground space contains all permutation-invariant states. We use techniques from combinatorics and operator theory to construct families of permutation-invariant quantum codes. These codes have length proportional to t2; one family of codes perfectly corrects arbitrary weight t errors, while the other family of codes approximately correct t spontaneous decay errors. The analysis of our codes' performance with respect to spontaneous decay errors utilizes elementary matrix analysis, where we revisit and extend the quantum error correction criterion of Knill and Laflamme, and Leung, Chuang, Nielsen and Yamamoto.
RHIC AC DIPOLE DESIGN AND CONSTRUCTION.
BAI,M.; METH,M.; PAI,C.; PARKER,B.; PEGGS,S.; ROSER,T.; SANDERS,R.; TRBOJEVIC,D.; ZALTSMAN,A.
2001-06-18
Two ac dipoles with vertical and horizontal magnetic field have been proposed at RHIC for applications in linear and non-linear beam dynamics and spin manipulations. A magnetic field amplitude of 380 Gm is required to produce a coherent oscillation of 5 times the rms beam size at the top energy. We take the ac dipole frequency to be 1.0% of the revolution frequency away from the betatron frequency. To achieve the strong magnetic field with minimum power loss, an air-core magnet with two seven turn winding of low loss Litz wire resonating at 64 kHz is designed. The system is also designed to allow one to connect the two magnet winding in series to resonate at 37 kHz for the spin manipulation. Measurements of a half length prototype magnet are also presented.
Generation of squeezing: magnetic dipoles on cantilevers
NASA Astrophysics Data System (ADS)
Seok, Hyojun; Singh, Swati; Steinke, Steven; Meystre, Pierre
2011-05-01
We investigate the generation of motional squeezed states in a nano-mechanical cantilever. Our model system consists of a nanoscale cantilever - whose center-of-mass motion is initially cooled to its quantum mechanical ground state - magnetically coupled a classically driven mechanical tuning fork. We show that the magnetic dipole-dipole interaction can produce significant phonon squeezing of the center-of-mass motion of the cantilever, and evaluate the effect of various dissipation channels, including the coupling of the cantilever to a heat bath and phase and amplitude fluctuations in the oscillating field driving the tuning fork. US National Science Foundation, the US Army Research Office, DARPA ORCHID program through a grant from AFOSR.
Dynamical dipole mode in fusion reactions
Pierroutsakou, D.; Boiano, A.; Romoli, M.; Martin, B.; Inglima, G.; La Commara, M.; Sandoli, M.; Agodi, C.; Alba, R.; Coniglione, R.; Zoppo, A. Del; Maiolino, C.; Piattelli, P.; Santonocito, D.; Sapienza, P.; Baran, V.; Glodariu, T.; Cardella, G.; De Filippo, E.; Pagano, A.
2009-05-04
We investigated the dynamical dipole mode, related with entrance channel charge asymmetry effects, in the {sup 40}Ar+{sup 92}Zr and {sup 36}Ar+{sup 96}Zr fusion reactions at E{sub lab} = 15.1 A and 16 A MeV, respectively. These reactions populate, through entrance channels having different charge asymmetries, a compound nucleus in the A = 126 mass energy region, identical spin distribution at an average excitation energy of about 280 MeV. The compound nucleus average excitation energy and average mass were deduced by the analysis of the light charged particle energy spectra. By studying the {gamma}-ray energy spectra and the {gamma}-ray angular distributions of the considered reactions, the dynamical nature of the prompt radiation related to the dynamical dipole mode was evidenced. The data are compared with calculations based on a collective bremsstrahlung analysis of the reaction dynamics.
Revisiting the NVSS number count dipole
NASA Astrophysics Data System (ADS)
Tiwari, Prabhakar; Nusser, Adi
2016-03-01
We present a realistic modeling of the dipole component of the projected sky distribution of NVSS radio galaxies. The modeling relies on mock catalogs generated within the context of ΛCDM cosmology, in the linear regime of structure formation. After removing the contribution from the solar motion, the mocks show that the remaining observed signal is mostly (70%) due to structures within z lesssim 0.1. The amplitude of the model signal depends on the bias factor b of the NVSS mock galaxies. For sources with flux density, S > 15 mJy, the bias recipe inferred from higher order moments is consistent with the observed dipole signal at 2.12σ. Flux thresholds above 20 mJy yield a disagreement close to the 3σ level. A constant high bias, b = 3 is needed to mitigate the tension to the ~ 2.3σ level.
NASA Technical Reports Server (NTRS)
1985-01-01
COSMIC MINIVER, a computer code developed by NASA for analyzing aerodynamic heating and heat transfer on the Space Shuttle, has been used by Marquardt Company to analyze heat transfer on Navy/Air Force missile bodies. The code analyzes heat transfer by four different methods which can be compared for accuracy. MINIVER saved Marquardt three months in computer time and $15,000.
Search for the electron electric dipole moment
De Mille, D.; Bickman, S.; Hamilton, P.; Jiang, Y.; Prasad, V.; Kawall, D.; Paolino, R.
2006-07-11
Extensions to the Standard Model (SM) typically include new heavy particles and new mechanisms for CP violation. These underlying phenomena can give rise to electric dipole moments of the electron and other particles. Tabletop-scale experiments used to search for these effects are described. Present experiments are already sensitive to new physics at the TeV scale, and new methods could extend this range dramatically. Such experiments could be among the first to show evidence for physics beyond the SM.
15 T And Beyond - Dipoles and Quadrupoles
Sabbi, GianLuca
2008-05-19
Starting with the invention of the cyclotron by Lawrence, accelerator-based experiments have been the primary source of new discoveries in particle physics. In order to progress toward higher energy and luminosity, higher field magnets are required. R&D programs are underway to take advantage of new developments in superconducting materials, achieve better efficiency and simplify magnet fabrication while preserving accelerator-class field quality. A review of recent progress on high field dipole and quadrupole magnets is presented.
Magnetic field modification of optical magnetic dipoles.
Armelles, Gaspar; Caballero, Blanca; Cebollada, Alfonso; Garcia-Martin, Antonio; Meneses-Rodríguez, David
2015-03-11
Acting on optical magnetic dipoles opens novel routes to govern light-matter interaction. We demonstrate magnetic field modification of the magnetic dipolar moment characteristic of resonant nanoholes in thin magnetoplasmonic films. This is experimentally shown through the demonstration of the magneto-optical analogue of Babinet's principle, where mirror imaged MO spectral dependencies are obtained for two complementary magnetoplasmonic systems: holes in a perforated metallic layer and a layer of disks on a substrate. PMID:25646869
Black Saturn with a dipole ring
Yazadjiev, Stoytcho S.
2007-09-15
We present a new stationary, asymptotically flat solution of 5D Einstein-Maxwell gravity describing a Saturn-like black object: a rotating black hole surrounded by a rotating dipole black ring. The solution is generated by combining the vacuum black Saturn solution and the vacuum black ring solution with appropriately chosen parameters. Some basic properties of the solution are analyzed and the basic quantities are calculated.
Toroidal Dipole Moment of a Massless Neutrino
Cabral-Rosetti, L. G.; Mondragon, M.; Perez, E. Reyes
2009-04-20
We obtain the toroidal dipole moment of a massless neutrino {tau}{sub v{sub I}}{sup M} using the results for the anapole moment of a massless Dirac neutrino a{sub v{sub I}}{sup D}, which was obtained in the context of the Standard Model of the electroweak interactions (SM)SU(2){sub L} x U(1){sub Y}.
Electric dipole moment of light nuclei
Gibson, Benjamin; Afnan, I R
2010-01-01
We examine the sensitivity of the deuteron Electric Dipole Moment (EDM) to variation in the nucleon-nucleon interaction. In particular, we write the EDM as a sum of two terms, one depends on the target wave function, the second on intermediate multiple scattering states in the {sup 3}P{sub 1} channel. This second contribution is sensitive to off-shell behavior of the {sup 3}P{sub 1} amplitude.
Electric dipole moment of light nuclei
Afnan, Iraj R.; Gibson, Benjamin F.
2010-07-27
We examine the sensitivity of the deuteron Electric Dipole Moment (EDM) to variation in the nucleon-nucleon interaction. In particular, we write the EDM as a sum of two terms, one depends on the target wave function, the second on intermediate multiple scattering states in the {sup 3}P{sub 1} channel. This second contribution is sensitive to off-shell behavior of the {sup 3}P{sub 1} amplitude.
The midpoint between dipole and parton showers
NASA Astrophysics Data System (ADS)
Höche, Stefan; Prestel, Stefan
2015-09-01
We present a new parton-shower algorithm. Borrowing from the basic ideas of dipole cascades, the evolution variable is judiciously chosen as the transverse momentum in the soft limit. This leads to a very simple analytic structure of the evolution. A weighting algorithm is implemented that allows one to consistently treat potentially negative values of the splitting functions and the parton distributions. We provide two independent, publicly available implementations for the two event generators P ythia and S herpa.
The midpoint between dipole and parton showers
Höche, Stefan; Prestel, Stefan
2015-09-28
We present a new parton-shower algorithm. Borrowing from the basic ideas of dipole cascades, the evolution variable is judiciously chosen as the transverse momentum in the soft limit. This leads to a very simple analytic structure of the evolution. A weighting algorithm is implemented that allows one to consistently treat potentially negative values of the splitting functions and the parton distributions. Thus, we provide two independent, publicly available implementations for the two event generators PYTHIA and SHERPA.
Trapped field internal dipole superconducting motor generator
Hull, John R.
2001-01-01
A motor generator including a high temperature superconductor rotor and an internally disposed coil assembly. The motor generator superconductor rotor is constructed of a plurality of superconductor elements magnetized to produce a dipole field. The coil assembly can be either a conventional conductor or a high temperature superconductor. The superconductor rotor elements include a magnetization direction and c-axis for the crystals of the elements and which is oriented along the magnetization direction.
Characterizing single atom optical dipole traps
NASA Astrophysics Data System (ADS)
Shih, Chung-Yu; Gibbons, Michael; Chapman, Michael
2012-06-01
Trapping and manipulating individual neutral atoms in far off-resonant traps (FORTs) is a promising approach for quantum information processing. It is important to characterize the trapping environment of the atom and the atomic level shifts due to the trapping fields. Using non-destructive measurement techniques,ootnotetextM. J. Gibbons et al., Phys. Rev. Lett 106, 133002 (2011). we have measured the level dependent AC Stark shifts, trap frequencies, and temperature of single rubidium atoms confined in optical dipole trap.
A simulation assessment of the thermodynamics of dense ion-dipole mixtures with polarization
Bastea, Sorin
2014-07-28
Molecular dynamics (MD) simulations are employed to ascertain the relative importance of various electrostatic interaction contributions, including induction interactions, to the thermodynamics of dense, hot ion-dipole mixtures. In the absence of polarization, we find that an MD-constrained free energy term accounting for the ion-dipole interactions, combined with well tested ionic and dipolar contributions, yields a simple, fairly accurate free energy form that may be a better option for describing the thermodynamics of such mixtures than the mean spherical approximation (MSA). Polarization contributions induced by the presence of permanent dipoles and ions are found to be additive to a good approximation, simplifying the thermodynamic modeling. We suggest simple free energy corrections that account for these two effects, based in part on standard perturbative treatments and partly on comparisons with MD simulation. Even though the proposed approximations likely need further study, they provide a first quantitative assessment of polarization contributions at high densities and temperatures and may serve as a guide for future modeling efforts.
Countably QC-Approximating Posets
Mao, Xuxin; Xu, Luoshan
2014-01-01
As a generalization of countably C-approximating posets, the concept of countably QC-approximating posets is introduced. With the countably QC-approximating property, some characterizations of generalized completely distributive lattices and generalized countably approximating posets are given. The main results are as follows: (1) a complete lattice is generalized completely distributive if and only if it is countably QC-approximating and weakly generalized countably approximating; (2) a poset L having countably directed joins is generalized countably approximating if and only if the lattice σc(L)op of all σ-Scott-closed subsets of L is weakly generalized countably approximating. PMID:25165730
Soft dipole excitations in 11Li
NASA Astrophysics Data System (ADS)
Esbensen, H.; Bertsch, G. F.
1992-06-01
A three-body model of 11Li is extended to include all interactions in unbound states in the continuum. We use a Green function technique to solve the three-body hamiltonian equation, and study the continuum dipole states produced by electromagnetic excitations of the ground state. The final-state interaction modifies the dipole strength function substantially, making it similar to an independent-particle strength function, but the total strength is enhanced by 50% due to ground-state correlations. The dipole strength is concentrated in a peak just above threshold, and the strength distribution is consistent with the measured beam energy dependence of the Coulomb dissociation cross section. This threshold peak also gives a narrow component in the neutron and the residual nucleus momentum distributions. The angular distributions of the neutrons emitted in Coulomb-induced reactions show a surprising anticorrelation, favoring emission with a large opening angle between the directions of the two neutrons in the rest frame of 11Li.
Bent Solenoids with Superimposed Dipole Fields
Meinke, Rainer, B.; Goodzeit, Carl, L.
2000-03-21
A conceptual design and manufacturing technique were developed for a superconducting bent solenoid magnet with a superimposed dipole field that would be used as a dispersion device in the cooling channel of a future Muon Collider. The considered bent solenoid is equivalent to a 180° section of a toroid with a major radius of ~610 mm and a coil aperture of ~416 mm. The required field components of this magnet are 4 tesla for the solenoid field and 1 tesla for the superimposed dipole field. A magnet of this size and shape, operating at these field levels, has to sustain large Lorentz forces resulting in a maximum magnetic pressure of about 2,000 psi. A flexible round mini-cable with 37 strands of Cu-NbTi was selected as the superconductor. Detailed magnetic analysis showed that it is possible to obtain the required superimposed dipole field by tilting the winding planes of the solenoid by ~25°. A complete structural analysis of the coil support system and the helium containment vessel under thermal, pressure, and Lorentz force loads was carried out using 3D finite element models of the structures. The main technical issues were studied and solutions were worked out so that a highly reliable magnet of this type can be produced at an affordable cost.
NASA Astrophysics Data System (ADS)
Schwengner, R.; Rusev, G.; Tsoneva, N.; Benouaret, N.; Beyer, R.; Erhard, M.; Grosse, E.; Junghans, A. R.; Klug, J.; Kosev, K.; Lenske, H.; Nair, C.; Schilling, K. D.; Wagner, A.
2008-12-01
The dipole response of the N=50 nucleus Zr90 was studied in photon-scattering experiments at the electron linear accelerator ELBE with bremsstrahlung produced at kinetic electron energies of 7.9, 9.0, and 13.2 MeV. We identified 189 levels up to an excitation energy of 12.9 MeV. Statistical methods were applied to estimate intensities of inelastic transitions and to correct the intensities of the ground-state transitions for their branching ratios. In this way we derived the photoabsorption cross section up to the neutron-separation energy. This cross section matches well the photoabsorption cross section obtained from (γ, n) data and thus provides information about the extension of the dipole-strength distribution toward energies below the neutron-separation energy. An enhancement of E1 strength has been found in the range of 6 to 11 MeV. Calculations within the framework of the quasiparticle-phonon model ascribe this strength to a vibration of the excessive neutrons against the N=Z neutron-proton core, giving rise to a pygmy dipole resonance.
Local electric dipole moments: A generalized approach.
Groß, Lynn; Herrmann, Carmen
2016-09-30
We present an approach for calculating local electric dipole moments for fragments of molecular or supramolecular systems. This is important for understanding chemical gating and solvent effects in nanoelectronics, atomic force microscopy, and intensities in infrared spectroscopy. Owing to the nonzero partial charge of most fragments, "naively" defined local dipole moments are origin-dependent. Inspired by previous work based on Bader's atoms-in-molecules (AIM) partitioning, we derive a definition of fragment dipole moments which achieves origin-independence by relying on internal reference points. Instead of bond critical points (BCPs) as in existing approaches, we use as few reference points as possible, which are located between the fragment and the remainder(s) of the system and may be chosen based on chemical intuition. This allows our approach to be used with AIM implementations that circumvent the calculation of critical points for reasons of computational efficiency, for cases where no BCPs are found due to large interfragment distances, and with local partitioning schemes other than AIM which do not provide BCPs. It is applicable to both covalently and noncovalently bound systems. © 2016 Wiley Periodicals, Inc. PMID:27520590
Radiation Q of dipole-generated fields
NASA Astrophysics Data System (ADS)
Grimes, Dale M.; Grimes, Craig A.
1999-03-01
The radiation Q of several dipole fields in free space are determined using the time-dependent Poynting theorem. Earlier works on this subject, recently summarized by McLean [1996], are based upon the complex Poynting theorem. It was previously shown [Grimes and Grimes, 1997] that the full complex Poynting theorem is correct only for single-mode radiation fields. The time-dependent theorem shows that three numbers are necessary to completely specify time-varying power, and complex numbers supply but two; the third piece of information, a phase, is discarded when complex notation is formed. Omissions inherent in the complex Poynting theorem affect the calculated value of standing energy about an antenna and hence the calculated value of Q. To avoid such omissions, we develop a method of determining Q based upon the time-dependent Poynting theorem that builds upon and extends our earlier work [Grimes and Grimes, 1997]. The purposes of this paper are to (1) provide a time domain basis for calculating Q in mixed modal radiation fields, (2) determine the Q of electric and magnetic dipoles, alone and in combination, and (3) demonstrate how source structure and relative phasing affect the physics of several combinations of electric and magnetic dipole radiation fields. The primary conclusion of this work is that the minimum possible Q of a radiation source established by Chu [1948] does not extend to properly mixed and phased multimodal radiation fields. A radiation source is presented for which, by our analysis, the radiation Q is zero.
Dynamics of two-dimensional dipole systems
Golden, Kenneth I.; Kalman, Gabor J.; Hartmann, Peter; Donko, Zoltan
2010-09-15
Using a combined analytical/molecular dynamics approach, we study the current fluctuation spectra and longitudinal and transverse collective mode dispersions of the classical two-dimensional (point) dipole system (2DDS) characterized by the {phi}{sub D}(r)={mu}{sup 2}/r{sup 3} repulsive interaction potential; {mu} is the electric dipole strength. The interest in the 2DDS is twofold. First, the quasi-long-range 1/r{sup 3} interaction makes the system a unique classical many-body system, with a remarkable collective mode behavior. Second, the system may be a good model for a closely spaced semiconductor electron-hole bilayer, a system that is in the forefront of current experimental interest. The longitudinal collective excitations, which are of primary interest for the liquid phase, are acoustic at long wavelengths. At higher wave numbers and for sufficiently high coupling strength, we observe the formation of a deep minimum in the dispersion curve preceded by a sharp maximum; this is identical to what has been observed in the dispersion of the zero-temperature bosonic dipole system, which in turn emulates so-called roton-maxon excitation spectrum of the superfluid {sup 4}He. The analysis we present gives an insight into the emergence of this apparently universal structure, governed by strong correlations. We study both the liquid and the crystalline solid state. We also observe the excitation of combination frequencies, resembling the roton-roton, roton-maxon, etc. structures in {sup 4}He.
Approximate Bayesian multibody tracking.
Lanz, Oswald
2006-09-01
Visual tracking of multiple targets is a challenging problem, especially when efficiency is an issue. Occlusions, if not properly handled, are a major source of failure. Solutions supporting principled occlusion reasoning have been proposed but are yet unpractical for online applications. This paper presents a new solution which effectively manages the trade-off between reliable modeling and computational efficiency. The Hybrid Joint-Separable (HJS) filter is derived from a joint Bayesian formulation of the problem, and shown to be efficient while optimal in terms of compact belief representation. Computational efficiency is achieved by employing a Markov random field approximation to joint dynamics and an incremental algorithm for posterior update with an appearance likelihood that implements a physically-based model of the occlusion process. A particle filter implementation is proposed which achieves accurate tracking during partial occlusions, while in cases of complete occlusion, tracking hypotheses are bound to estimated occlusion volumes. Experiments show that the proposed algorithm is efficient, robust, and able to resolve long-term occlusions between targets with identical appearance. PMID:16929730
Approximation by hinge functions
Faber, V.
1997-05-01
Breiman has defined {open_quotes}hinge functions{close_quotes} for use as basis functions in least squares approximations to data. A hinge function is the max (or min) function of two linear functions. In this paper, the author assumes the existence of smooth function f(x) and a set of samples of the form (x, f(x)) drawn from a probability distribution {rho}(x). The author hopes to find the best fitting hinge function h(x) in the least squares sense. There are two problems with this plan. First, Breiman has suggested an algorithm to perform this fit. The author shows that this algorithm is not robust and also shows how to create examples on which the algorithm diverges. Second, if the author tries to use the data to minimize the fit in the usual discrete least squares sense, the functional that must be minimized is continuous in the variables, but has a derivative which jumps at the data. This paper takes a different approach. This approach is an example of a method that the author has developed called {open_quotes}Monte Carlo Regression{close_quotes}. (A paper on the general theory is in preparation.) The author shall show that since the function f is continuous, the analytic form of the least squares equation is continuously differentiable. A local minimum is solved for by using Newton`s method, where the entries of the Hessian are estimated directly from the data by Monte Carlo. The algorithm has the desirable properties that it is quadratically convergent from any starting guess sufficiently close to a solution and that each iteration requires only a linear system solve.
Effect of rotational-state-dependent molecular alignment on the optical dipole force
NASA Astrophysics Data System (ADS)
Kim, Lee Yeong; Lee, Ju Hyeon; Kim, Hye Ah; Kwak, Sang Kyu; Friedrich, Bretislav; Zhao, Bum Suk
2016-07-01
The properties of molecule-optical elements such as lenses or prisms based on the interaction of molecules with optical fields depend in a crucial way on the molecular quantum state and its alignment created by the optical field. Herein, we consider the effects of state-dependent alignment in estimating the optical dipole force acting on the molecules and, to this end, introduce an effective polarizability which takes proper account of molecular alignment and is directly related to the alignment-dependent optical dipole force. We illustrate the significance of including molecular alignment in the optical dipole force by a trajectory study that compares previously used approximations with the present approach. The trajectory simulations were carried out for an ensemble of linear molecules subject to either propagating or standing-wave optical fields for a range of temperatures and laser intensities. The results demonstrate that the alignment-dependent effective polarizability can serve to provide correct estimates of the optical dipole force, on which a state-selection method applicable to nonpolar molecules could be based. We note that an analogous analysis of the forces acting on polar molecules subject to an inhomogeneous static electric field reveals a similarly strong dependence on molecular orientation.
Molecular Dipole Moments within the Incremental Scheme Using the Domain-Specific Basis-Set Approach.
Fiedler, Benjamin; Coriani, Sonia; Friedrich, Joachim
2016-07-12
We present the first implementation of the fully automated incremental scheme for CCSD unrelaxed dipole moments using the domain-specific basis-set approach. Truncation parameters are varied, and the accuracy of the method is statistically analyzed for a test set of 20 molecules. The local approximations introduce small errors at second order and negligible ones at third order. For a third-order incremental CCSD expansion with a CC2 error correction, a cc-pVDZ/SV domain-specific basis set (tmain = 3.5 Bohr), and the truncation parameter f = 30 Bohr, we obtain a mean error of 0.00 mau (-0.20 mau) and a standard deviation of 1.95 mau (2.17 mau) for the total dipole moments (Cartesian components of the dipole vectors). By analyzing incremental CCSD energies, we demonstrate that the MP2 and CC2 error correction schemes are an exclusive correction for the domain-specific basis-set error. Our implementation of the incremental scheme provides fully automated computations of highly accurate dipole moments at reduced computational cost and is fully parallelized in terms of the calculation of the increments. Therefore, one can utilize the incremental scheme, on the same hardware, to extend the basis set in comparison to standard CCSD and thus obtain a better total accuracy. PMID:27300371
Laarne, P H; Tenhunen-Eskelinen, M L; Hyttinen, J K; Eskola, H J
2000-01-01
The effect of number of EEG electrodes on the dipole localization was studied by comparing the results obtained using the 10-20 and 10-10 electrode systems. Two anatomically detailed models with resistivity values of 177.6 omega m and 67.0 omega m for the skull were applied. Simulated potential values generated by current dipoles were applied to different combinations of the volume conductors and electrode systems. High and low resistivity models differed slightly in favour of the lower skull resistivity model when dipole localization was based on noiseless data. The localization errors were approximately three times larger using low resistivity model for generating the potentials, but applying high resistivity model for the inverse solution. The difference between the two electrode systems was minor in favour of the 10-10 electrode system when simulated, noiseless potentials were used. In the presence of noise the dipole localization algorithm operated more accurately using the denser electrode system. In conclusion, increasing the number of recording electrodes seems to improve the localization accuracy in the presence of noise. The absolute skull resistivity value also affects the accuracy, but using an incorrect value in modelling calculations seems to be the most serious source of error. PMID:10912732
Observation of electric-dipole-forbidden infrared transitions in cold molecular ions
NASA Astrophysics Data System (ADS)
Germann, Matthias; Tong, Xin; Willitsch, Stefan
2014-11-01
Spectroscopic transitions in atoms and molecules that are not allowed within the electric-dipole approximation, but occur because of higher-order terms in the interaction between matter and radiation, are termed dipole-forbidden. These transitions are extremely weak and therefore exhibit very small natural linewidths. Dipole-forbidden optical transitions in atoms form the basis of next-generation atomic clocks and of high-fidelity qubits used in quantum information processors and quantum simulators. In molecules, however, such transitions are much less characterized, reflecting the considerable challenges to address them. Here, we report direct observation of dipole-forbidden, electric-quadrupole-allowed infrared (IR) transitions in a molecular ion. Their detection was enabled by the very long interrogation times of several minutes afforded by the sympathetic cooling of individual quantum-state-selected molecular ions into the nearly perturbation-free environment of a Coulomb crystal. The present work paves the way for new mid-IR frequency standards and precision spectroscopic measurements on single molecules in the IR domain.
Exact kinematics in the small-x evolution of the color dipole and gluon cascade
Motyka, Leszek; Stasto, Anna M.
2009-04-15
The problem of kinematic effects in gluon and color dipole cascades is addressed in the large N{sub c} limit of SU(N{sub c}) Yang-Mills theory. We investigate the tree-level multigluon components of the gluon light-cone wave functions in the light-cone gauge keeping the exact kinematics of the gluon emissions. We focus on the components with all helicities identical to the helicity of the incoming gluon. The recurrence relations for the gluon wave functions are derived. In the case when the virtuality of the incoming gluon is neglected the exact form of the multigluon wave function is obtained. Furthermore, we propose an approximate scheme to treat the kinematic effects in the color dipole evolution kernel. The new kernel entangles longitudinal and transverse degrees of freedom and leads to a reduced diffusion in the impact parameter. When evaluated in the next-to-leading logarithmic (NLL) accuracy, the kernel reproduces the correct form of the double logarithmic terms of the dipole size ratios present in the exact NLL dipole kernel. Finally, we analyze the scattering of the incoming gluon light-cone components off a gluon target and the fragmentation of the scattered state into the final state. The equivalence of the resulting amplitudes and the maximally helicity-violating amplitudes is demonstrated in the special case when the target gluon is far in rapidity from the evolved gluon wave function.
Self-Interaction Corrected Functional Calculations of a Dipole-Bound Molecular Anion.
Zhang, Yao; Weber, Peter M; Jónsson, Hannes
2016-06-01
A self-interaction corrected density functional is used to describe the ground state of the CH3CN(-) ion that includes a dipole bound electron with large spatial extent and low binding energy. Without the correction, some commonly used density functionals based on the generalized gradient approximation as well as hybrid functionals fail to give a bound ground state of the anion. A negative HOMO orbital energy of magnitude 0.013 eV is obtained using the self-interaction corrected PBE functional in good correspondence with the experimentally estimated binding energy of 0.019 eV. The dipole bound electron polarizes the CH3CN molecule and increases its dipole moment by 7% to 4.2 D. Because the computational effort increases slowly with system size, as the number of electrons cubed, the results presented here point to a viable approach to theoretical studies of dipole bound electrons in large and complex systems such as molecular clusters, biological systems, and solvated electrons. PMID:27166989
NASA Technical Reports Server (NTRS)
Kastner, S. O.; Wade, C.
1974-01-01
The Coulomb approximation tables of Oertel and Shomo, together with binding-energy values obtained by a screening approximation, have been used to produce values of the dipole and quadrupole radial integrals needed in obtaining transition probabilities for ions of six, seven, and eight electrons. Some comparisons with more rigorously calculated values show that the present values are quite accurate, especially for ions of higher atomic number.
New method to determine proton trajectories in the equatorial plane of a dipole magnetic field.
Ioanoviciu, Damaschin
2015-01-01
A parametric description of proton trajectories in the equatorial plane of Earth's dipole magnetic field has been derived. The exact expression of the angular coordinate contains an integral to be performed numerically. The radial coordinate results from the initial conditions by basic mathematical operations and by using trigonometric functions. With the approximate angular coordinate formula, applicable for a wide variety of cases of protons trapped in Earth's radiation belts, no numerical integration is needed. The results of exact and approximate expressions were compared for a specific case and small differences were found. PMID:25815248
An Exact Form of Lilley's Equation with a Velocity Quadrupole/Temperature Dipole Source Term
NASA Technical Reports Server (NTRS)
Goldstein, Marvin E.
2001-01-01
There have been several attempts to introduce approximations into the exact form of Lilley's equation in order to express the source term as the sum of a quadrupole whose strength is quadratic in the fluctuating velocities and a dipole whose strength is proportional to the temperature fluctuations. The purpose of this note is to show that it is possible to choose the dependent (i.e., the pressure) variable so that this type of result can be derived directly from the Euler equations without introducing any additional approximations.
Spatially Resolved Observation of Dipole-Dipole Interaction between Rydberg Atoms
Ditzhuijzen, C. S. E. van; Noordam, L. D.; Heuvell, H. B. van Linden van den; Koenderink, A. F.; Hernandez, J. V.; Robicheaux, F.
2008-06-20
We have observed resonant energy transfer between cold Rydberg atoms in spatially separated cylinders. Resonant dipole-dipole coupling excites the 49s atoms in one cylinder to the 49p state while the 41d atoms in the second cylinder are transferred down to the 42p state. We have measured the production of the 49p state as a function of separation of the cylinders (0-80 {mu}m) and the interaction time (0-25 {mu}s). In addition, we measured the width of the electric field resonances. A full many-body quantum calculation reproduces the main features of the experiments.
Gligoric, Goran; Hadzievski, Ljupco; Maluckov, Aleksandra; Malomed, Boris A.
2009-05-15
The stability and collapse of fundamental unstaggered bright solitons in the discrete Schroedinger equation with the nonpolynomial on-site nonlinearity, which models a nearly one-dimensional Bose-Einstein condensate trapped in a deep optical lattice, are studied in the presence of the long-range dipole-dipole (DD) interactions. The cases of both attractive and repulsive contact and DD interaction are considered. The results are summarized in the form of stability-collapse diagrams in the parametric space of the model, which demonstrate that the attractive DD interactions stabilize the solitons and help to prevent the collapse. Mobility of the discrete solitons is briefly considered too.
Finite amplitude method for the quasiparticle random-phase approximation
Avogadro, Paolo; Nakatsukasa, Takashi
2011-07-15
We present the finite amplitude method (FAM), originally proposed in Ref. [17], for superfluid systems. A Hartree-Fock-Bogoliubov code may be transformed into a code of the quasiparticle-random-phase approximation (QRPA) with simple modifications. This technique has advantages over the conventional QRPA calculations, such as coding feasibility and computational cost. We perform the fully self-consistent linear-response calculation for the spherical neutron-rich nucleus {sup 174}Sn, modifying the hfbrad code, to demonstrate the accuracy, feasibility, and usefulness of the FAM.
Electric dipole moments (EDM) of ionic atoms
NASA Astrophysics Data System (ADS)
Oshima, Sachiko
2010-03-01
Recent investigations show that the second-order perturbation calculations of electric dipole moments (EDM) from the finite nuclear size as well as the relativistic effects are all canceled out by the third-order perturbation effects and that this is due to electron screening. To derive the nucleon EDM from the nucleus, we propose to measure the EDM of an ionic system. In this case, it is shown that the nucleon EDM can survive by the reduction factor of 1/Z for the ionic system with one electron stripped off.
Revised cross section for RHIC dipole magnets
Thompson, P.A.; Gupta, R.C.; Kahn, S.A.; Hahn, H.; Morgan, G.H.; Wanderer, P.J.; Willen, E.
1991-01-01
Using the experience gained in designing and building Relativistic Heavy Ion Collider (RHIC) dipole prototype magnets an improved cross section has been developed. Significant features of this design include the use of only three wedges for field shaping and wedge cross sections which are sectors of an annulus. To aid in the understanding of the actual magnets, one has been sectioned, and detailed mechanical and photographic measurements made of the wire positions. The comparison of these measurements with the magnetic field measurements will is presented. 2 refs, 3 figs., 2 tabs.
NMR measurements in SSC dipole D00001
Kuchnir, M.; Schmidt, E.E.; Hanft, R.W.; Strait, J.B.
1986-09-12
The first 16.5 m long SSC dipole magnet (D00001) had its field intensity measured as a function of position with a custom made NMR magnetometer. A short description of the probe is presented. The data obtained (most of it near 2 T spaced apart by one inch) shows an average transfer function of 1.02830 T/KA with position dependent values deviating from the average by up to .00130 T/KA revealing contruction inhomogeneities that were measured with a sensitivity of 25 ppM.
Electric dipole moments (EDM) of ionic atoms
Oshima, Sachiko
2010-03-15
Recent investigations show that the second-order perturbation calculations of electric dipole moments (EDM) from the finite nuclear size as well as the relativistic effects are all canceled out by the third-order perturbation effects and that this is due to electron screening. To derive the nucleon EDM from the nucleus, we propose to measure the EDM of an ionic system. In this case, it is shown that the nucleon EDM can survive by the reduction factor of 1/Z for the ionic system with one electron stripped off.
SSC dipole vacuum vessel support placement analysis
Nicol, T.H.
1987-08-01
Early (superconducting super collider) SSC dipole model magnets were supported at five points along their length by feet welded to the vacuum vessel. The cold mass was supported at the same five points. The number of supports was determined such that the maximum cold mass deflection between supports was limited to 0.010 inches as specified in the first version of the SSC Design Criteria. The spacing between supports was determined to minimize the sag of the cold mass, given five supports. This paper analyzes the deflection of the cold mass and vacuum vessel as a result of these supports. 4 refs. (LSP)
Large muon electric dipole moment from flavor?
Hiller, Gudrun; Huitu, Katri; Rueppell, Timo; Laamanen, Jari
2010-11-01
We study the prospects and opportunities of a large muon electric dipole moment (EDM) of the order (10{sup -24}-10{sup -22}) ecm. We investigate how natural such a value is within the general minimal supersymmetric extension of the standard model with CP violation from lepton flavor violation in view of the experimental constraints. In models with hybrid gauge-gravity-mediated supersymmetry breaking, a large muon EDM is indicative for the structure of flavor breaking at the Planck scale, and points towards a high messenger scale.
Multilayer Microstrip Slot And Dipole Array Antenna
NASA Technical Reports Server (NTRS)
Tulintseff, Ann N.
1994-01-01
Multilayer antenna structure contains interleaved linear subarrays of microstrip dipole and slot radiating antenna elements to provide compact, dual-band antenna. Structure also contains associated microstrip transmission lines, plus high-power amplifiers for transmission and low-noise amplifiers for reception. Overall function is to transmit in horizontal polarization at frequency of 29.634 GHz and receive in vertical polarization at 19.914 GHz, in direction 44 degrees from broadside to antenna. Antenna structure is part of apparatus described in "Steerable K/Ka-band Antenna for Land-Mobile Satellite Applications," NPO-18772.
Geomagnetic Secular Variation Recorded in Volcanic Rocks: The End of the Geocentric Axial Dipole
NASA Astrophysics Data System (ADS)
Champion, D. E.; Turrin, B. D.; Robinson, J. E.
2015-12-01
Most paleomagnetic textbooks ascribe secular variation (SV) to the movement and waxing/waning of non-dipole magnetic features in the fluid core, perhaps joined by wobble of a geocentric axial dipole (GAD). The actuality of a GAD is profoundly limited by the existence of the static, solid inner core, and the dynamic nature of the fluid outer core. A study of >560 Brunhes Epoch Virtual Geomagnetic Poles (VGP) suggests that geomagnetic field behavior arises from the waxing/waning of three approximately "stationary" offset dipoles (OD) situated in the middle of the ring of the outer core. These OD have been loosely fixed to preferred longitudes of 40°E, 120°E, and 280°E for at least the past 17Ma. The three offset dipoles in these positions determine transitional and excursional paths, and also normal SV. An extended literature documents these longitude corridors as paths of preferred VGP movement, guided by the polarity inversion of one of the three OD. Analysis of volcanic rock and archeomagnetic SV records shows a three-fold symmetric movement of local magnetic directions, guided by the variation in strength of the three OD. Preliminary data indicates that in the recent past the dominant OD at a given time yields to the next OD in movement toward greater east longitude. The frequency of OD dominance exchange is ~400 years, with return to the original OD in ~1200 years. Archeomagnetic "jerks", not easily explained by a single dominant, inertial GAD, are more easily understood with 3 waxing/waning and exchanging OD. The particular analysis of Hawaiian SV with regard to the three OD suggests that tropical locales, far from the three spin axis-parallel OD, may still record true non-dipole influences.
Ravishankar, C., Hughes Network Systems, Germantown, MD
1998-05-08
Speech is the predominant means of communication between human beings and since the invention of the telephone by Alexander Graham Bell in 1876, speech services have remained to be the core service in almost all telecommunication systems. Original analog methods of telephony had the disadvantage of speech signal getting corrupted by noise, cross-talk and distortion Long haul transmissions which use repeaters to compensate for the loss in signal strength on transmission links also increase the associated noise and distortion. On the other hand digital transmission is relatively immune to noise, cross-talk and distortion primarily because of the capability to faithfully regenerate digital signal at each repeater purely based on a binary decision. Hence end-to-end performance of the digital link essentially becomes independent of the length and operating frequency bands of the link Hence from a transmission point of view digital transmission has been the preferred approach due to its higher immunity to noise. The need to carry digital speech became extremely important from a service provision point of view as well. Modem requirements have introduced the need for robust, flexible and secure services that can carry a multitude of signal types (such as voice, data and video) without a fundamental change in infrastructure. Such a requirement could not have been easily met without the advent of digital transmission systems, thereby requiring speech to be coded digitally. The term Speech Coding is often referred to techniques that represent or code speech signals either directly as a waveform or as a set of parameters by analyzing the speech signal. In either case, the codes are transmitted to the distant end where speech is reconstructed or synthesized using the received set of codes. A more generic term that is applicable to these techniques that is often interchangeably used with speech coding is the term voice coding. This term is more generic in the sense that the
Propagation of magnetic dipole radiation through a medium.
Arnoldus, Henk F; Xu, Zhangjin
2016-05-01
An oscillating magnetic dipole moment emits radiation. We assume that the dipole is embedded in a medium with relative permittivity ϵ_{r} and relative permeability μ_{r}, and we have studied the effects of the surrounding material on the flow lines of the emitted energy. For a linear dipole moment in free space the flow lines of energy are straight lines, coming out of the dipole. When located in a medium, these field lines curve toward the dipole axis, due to the imaginary part of μ_{r}. Some field lines end on the dipole axis, giving a nonradiating contribution to the energy flow. For a rotating dipole moment in free space, each field line of energy flow lies on a cone around the axis perpendicular to the plane of rotation of the dipole moment. The field line pattern is an optical vortex. When embedded in a material, the cone shape of the vortex becomes a funnel shape, and the windings are much less dense than for the pattern in free space. This is again due to the imaginary part of μ_{r}. When the real part of μ_{r} is negative, the field lines of the vortex swirl around the dipole axis opposite to the rotation direction of the dipole moment. For a near-single-negative medium, the spatial extent of the vortex becomes huge. We compare the results for the magnetic dipole to the case of an embedded electric dipole. PMID:27140885
Lunar magnetic field - Permanent and induced dipole moments
NASA Technical Reports Server (NTRS)
Russell, C. T.; Coleman, P. J., Jr.; Schubert, G.
1974-01-01
Apollo 15 subsatellite magnetic field observations have been used to measure both the permanent and the induced lunar dipole moments. Although only an upper limit of 1.3 x 10 to the 18th gauss-cubic centimeters has been determined for the permanent dipole moment in the orbital plane, there is a significant induced dipole moment which opposes the applied field, indicating the existence of a weak lunar ionosphere.
Two methods of computing molecular dipole and quadrupole derivatives
NASA Astrophysics Data System (ADS)
Lazzeretti, P.; Zanasi, R.; Fowler, P. W.
1988-01-01
Polarized basis sets are used to compute dipole and quadrupole derivatives of the hydrides LiH, CH4, NH3, H2O, and HF. Analytic calculation of derivatives is compared with calculation via the dipole and quadrupole electric shielding tensors. With these basis sets, violation of the Hellmann-Feynman theorem is only about 0.01 a.u. in dipole derivatives and 0.02 a.u. in quadrupole derivatives.
Dipole characterization of single neurons from their extracellular action potentials
Victor, Jonathan D.
2011-01-01
The spatial variation of the extracellular action potentials (EAP) of a single neuron contains information about the size and location of the dominant current source of its action potential generator, which is typically in the vicinity of the soma. Using this dependence in reverse in a three-component realistic probe + brain + source model, we solved the inverse problem of characterizing the equivalent current source of an isolated neuron from the EAP data sampled by an extracellular probe at multiple independent recording locations. We used a dipole for the model source because there is extensive evidence it accurately captures the spatial roll-off of the EAP amplitude, and because, as we show, dipole localization, beyond a minimum cell-probe distance, is a more accurate alternative to approaches based on monopole source models. Dipole characterization is separable into a linear dipole moment optimization where the dipole location is fixed, and a second, nonlinear, global optimization of the source location. We solved the linear optimization on a discrete grid via the lead fields of the probe, which can be calculated for any realistic probe + brain model by the finite element method. The global source location was optimized by means of Tikhonov regularization that jointly minimizes model error and dipole size. The particular strategy chosen reflects the fact that the dipole model is used in the near field, in contrast to the typical prior applications of dipole models to EKG and EEG source analysis. We applied dipole localization to data collected with stepped tetrodes whose detailed geometry was measured via scanning electron microscopy. The optimal dipole could account for 96% of the power in the spatial variation of the EAP amplitude. Among various model error contributions to the residual, we address especially the error in probe geometry, and the extent to which it biases estimates of dipole parameters. This dipole characterization method can be applied to
Mutual impedance of nonplanar-skew sinusoidal dipoles
NASA Technical Reports Server (NTRS)
Richmond, J. H.; Geary, N. H.
1975-01-01
The mutual impedance expressions for parallel dipoles in terms of sine-integrals and cosine-integrals have been published by King (1957). The investigation reported provides analogous expressions for nonparallel dipoles. The expressions presented are most useful when the monopoles are close together. The theory of moment methods shows an approach for employing the mutual impedance of filamentary sinusoidal dipoles to calculate the impedance and scattering properties of straight and bent wires with small but finite diameter.
PROBING THE UNIVERSE'S TILT WITH THE COSMIC INFRARED BACKGROUND DIPOLE
Fixsen, D. J.; Kashlinsky, A. E-mail: alexander.kashlinsky@nasa.gov
2011-06-10
Conventional interpretation of the observed cosmic microwave background (CMB) dipole is that all of it is produced by local peculiar motions. Alternative explanations requiring part of the dipole to be primordial have received support from measurements of large-scale bulk flows. A test of the two hypotheses is whether other cosmic dipoles produced by collapsed structures later than the last scattering coincide with the CMB dipole. One background is the cosmic infrared background (CIB) whose absolute spectrum was measured to {approx}30% by the COBE satellite. Over the 100-500 {mu}m wavelength range its spectral energy distribution can provide a probe of its alignment with the CMB. This is tested with the COBE FIRAS data set which is available for such a measurement because of its low noise and frequency resolution which are important for Galaxy subtraction. Although the FIRAS instrument noise is in principle low enough to determine the CIB dipole, the Galactic foreground is sufficiently close spectrally to keep the CIB dipole hidden. A similar analysis is performed with DIRBE, which-because of the limited frequency coverage-provides a poorer data set. We discuss strategies for measuring the CIB dipole with future instruments to probe the tilt and apply it to the Planck, Herschel, and the proposed Pixie missions. We demonstrate that a future FIRAS-like instrument with instrument noise a factor of {approx}10 lower than FIRAS would make a statistically significant measurement of the CIB dipole. We find that the Planck and Herschel data sets will not allow a robust CIB dipole measurement. The Pixie instrument promises a determination of the CIB dipole and its alignment with either the CMB dipole or the dipole galaxy acceleration vector.
Thermal Analysis of the Fair SIS300 Model Dipole
NASA Astrophysics Data System (ADS)
Sorbi, M.; Alessandria, F.; Bellomo, G.; Fabbricatore, P.; Farinon, S.; Gambardella, U.; Musenich, R.; Volpini, G.
2010-04-01
Design activities, conductor R&D and model coil construction are under way for the development of a curved superconducting dipole for the fast cycled SIS300 synchrotron at FAIR at GSI. The main target is the construction within 2009 of a half-length model magnet (cold mass fully integrated in a horizontal cryostat). This magnet is designed for a maximum central field of 4.5 T in a bore of 100 mm, with a ramp rate of 1 T/s. The magnetic length of the model is 3.9 m with a curvature radius of 66.67 m (27 mm of sagitta). This paper describes the thermal analysis of the magnet, based on the estimated values of the losses in the cold mass. The study has been performed with 2-D finite element codes, both in steady state and transient analysis. The study has been completed with measurements of overall thermal exchange coefficient between the kapton-insulated cables and the supercritical helium, in order to validate the adopted assumptions about the material thermal properties.
THERMAL ANALYSIS OF THE FAIR SIS300 MODEL DIPOLE
Sorbi, M.; Bellomo, G.; Alessandria, F.; Volpini, G.; Fabbricatore, P.; Farinon, S.; Musenich, R.; Gambardella, U.
2010-04-09
Design activities, conductor R and D and model coil construction are under way for the development of a curved superconducting dipole for the fast cycled SIS300 synchrotron at FAIR at GSI. The main target is the construction within 2009 of a half-length model magnet (cold mass fully integrated in a horizontal cryostat). This magnet is designed for a maximum central field of 4.5 T in a bore of 100 mm, with a ramp rate of 1 T/s. The magnetic length of the model is 3.9 m with a curvature radius of 66.67 m (27 mm of sagitta). This paper describes the thermal analysis of the magnet, based on the estimated values of the losses in the cold mass. The study has been performed with 2-D finite element codes, both in steady state and transient analysis. The study has been completed with measurements of overall thermal exchange coefficient between the kapton-insulated cables and the supercritical helium, in order to validate the adopted assumptions about the material thermal properties.
Information Content of the Low-Energy Electric Dipole Strength: Correlation Analysis
Reinhard, P.-G.; Nazarewicz, Witold
2013-01-01
Background: Recent experiments on the electric dipole (E1) polarizability in heavy nuclei have stimulated theoretical interest in the low-energy electric dipole strength, both isovector and isoscalar. Purpose: We study the information content carried by the electric dipole strength with respect to isovector and isoscalar indicators characterizing bulk nuclear matter and finite nuclei. To separate isoscalar and isovector modes, and low-energy strength and giant resonances, we analyze the E1 strength as a function of the excitation energy E and momentum transfer q. Methods: We use the self-consistent nuclear density functional theory with Skyrme energy density functionals, augmented by the random phase approximation, to compute the E1 strength and covariance analysis to assess correlations between observables. Calculations are performed for the spherical, doubly magic nuclei 208Pb and 132Sn. Results: We demonstrate that E1 transition densities in the low-energy region below the giant dipole resonance exhibit appreciable state dependence and multinodal structures, which are fingerprints of weak collectivity. The correlation between the accumulated low-energy strength and the symmetry energy is weak, and dramatically depends on the energy cutoff assumed. On the other hand, a strong correlation is predicted between isovector indicators and the accumulated isovector strength at E around 20 MeV and momentum transfer q 0.65 fm 1. Conclusions: Momentum- and coordinate-space patterns of the low-energy dipole modes indicate a strong fragmentation into individual particle-hole excitations. The global measure of low-energy dipole strength correlates poorly with the nuclear symmetry energy and other isovector characteristics. Consequently, our results do not support the suggestion that there exists a collective pygmy dipole resonance, which is a strong indicator of nuclear isovector properties. By considering nonzero values of momentum transfer, one can isolate individual
An alternate end design for SSC dipoles
Peters, C.; Caspi, S.; Taylor, C.
1989-02-01
Experience in the SSC dipole program has shown that fabrication of cylindrical coil ends is difficult. Cable stiffness requires large forces to maintain the proper position of the conductors in the end during winding. After winding, the coil ends remain distorted nd significant motion of the need conductors is required to force the coil end into the molding cavity. Local mechanical stresses are high during this process and extra pieces of insulation are required to prevent turn-to-turn shorts from developing during the winding and molding steps. Prior to assembly the coil end is compressed in a mold cavity and injected with a filler material to correct surface irregularities and fill voids in the end. LBL has developed an alternate design which permits the conductors to be wound over the end using minimal force and technician coerosion. The conductors are placed on a conical surface where the largest diameter over the outer layer conductors is 10 cm. No coil end spaces or insulation pieces between turns are required. The conductor geometry was analytically optimized to meet SSC multipole requirements for the ends. The first 1-m dipole utilizing this end geometry has been constructed and successfully tested. Design and construction data are presented. Also model test results, including training and multipole measurements of the end are given. 1 ref., 12 figs., 3 tabs.
Surface Dipole Control of Liquid Crystal Alignment.
Schwartz, Jeffrey J; Mendoza, Alexandra M; Wattanatorn, Natcha; Zhao, Yuxi; Nguyen, Vinh T; Spokoyny, Alexander M; Mirkin, Chad A; Baše, Tomáš; Weiss, Paul S
2016-05-11
Detailed understanding and control of the intermolecular forces that govern molecular assembly are necessary to engineer structure and function at the nanoscale. Liquid crystal (LC) assembly is exceptionally sensitive to surface properties, capable of transducing nanoscale intermolecular interactions into a macroscopic optical readout. Self-assembled monolayers (SAMs) modify surface interactions and are known to influence LC alignment. Here, we exploit the different dipole magnitudes and orientations of carboranethiol and -dithiol positional isomers to deconvolve the influence of SAM-LC dipolar coupling from variations in molecular geometry, tilt, and order. Director orientations and anchoring energies are measured for LC cells employing various carboranethiol and -dithiol isomer alignment layers. The normal component of the molecular dipole in the SAM, toward or away from the underlying substrate, was found to determine the in-plane LC director orientation relative to the anisotropy axis of the surface. By using LC alignment as a probe of interaction strength, we elucidate the role of dipolar coupling of molecular monolayers to their environment in determining molecular orientations. We apply this understanding to advance the engineering of molecular interactions at the nanoscale. PMID:27090503
Satellite sweeping in offset, tilted dipole fields
NASA Technical Reports Server (NTRS)
Paonessa, Mark T.; Cheng, Andrew F.
1987-01-01
The paper presents a theory for the longitudinally averaged satellite sweeping rate in an offset, tilted dipole magnetic field. It includes the reductions in the sweeping rate when the moon radius is not large compared to the gyroradius or the azimuthal drift distance during a bounce period. With a large tilt angle between the magnetic and rotation axes, moons make large excursions in dipole L value, and more than one moon can sweep at a given L. The sweeping rate peaks at the minimum L for each moon. If the gyroradius is large, additional peaks can occur when the particle mirrors near the moon latitude. To illustrate the theory, sweeping rates are evaluated for parameters relevant to the observations at Uranus by the Voyager 2 Low Energy Charged Particles Experiment. Calculated sweeping rates for ions and electrons are typically two or three orders of magnitude less than the strong-diffusion loss rate. The observation of sweeping signatures at Uranus would imply that pitch-angle scattering there occurs at a rate far below the strong-diffusion limit, contrasting with the situation for energetic ions in the inner Jovian magnetosphere.
Brownian dipole rotator in alternating electric field.
Rozenbaum, V M; Vovchenko, O Ye; Korochkova, T Ye
2008-06-01
The study addresses the azimuthal jumping motion of an adsorbed polar molecule in a periodic n -well potential under the action of an external alternating electric field. Starting from the perturbation theory of the Pauli equation with respect to the weak field intensity, explicit analytical expressions have been derived for the time dependence of the average dipole moment as well as the frequency dependences of polarizability and the average angular velocity, the three quantities exhibiting conspicuous stochastic resonance. As shown, unidirectional rotation can arise only provided simultaneous modulation of the minima and maxima of the potential by an external alternating field. For a symmetric potential of hindered rotation, the average angular velocity, if calculated by the second-order perturbation theory with respect to the field intensity, has a nonzero value only at n=2 , i.e., when two azimuthal wells specify a selected axis in the system. Particular consideration is given to the effect caused by the asymmetry of the two-well potential on the dielectric loss spectrum and other Brownian motion parameters. When the asymmetric potential in a system of dipole rotators arises from the average local fields induced by an orientational phase transition, the characteristics concerned show certain peculiarities which enable detection of the phase transition and determination of its parameters. PMID:18643221
Brownian dipole rotator in alternating electric field
NASA Astrophysics Data System (ADS)
Rozenbaum, V. M.; Vovchenko, O. Ye.; Korochkova, T. Ye.
2008-06-01
The study addresses the azimuthal jumping motion of an adsorbed polar molecule in a periodic n -well potential under the action of an external alternating electric field. Starting from the perturbation theory of the Pauli equation with respect to the weak field intensity, explicit analytical expressions have been derived for the time dependence of the average dipole moment as well as the frequency dependences of polarizability and the average angular velocity, the three quantities exhibiting conspicuous stochastic resonance. As shown, unidirectional rotation can arise only provided simultaneous modulation of the minima and maxima of the potential by an external alternating field. For a symmetric potential of hindered rotation, the average angular velocity, if calculated by the second-order perturbation theory with respect to the field intensity, has a nonzero value only at n=2 , i.e., when two azimuthal wells specify a selected axis in the system. Particular consideration is given to the effect caused by the asymmetry of the two-well potential on the dielectric loss spectrum and other Brownian motion parameters. When the asymmetric potential in a system of dipole rotators arises from the average local fields induced by an orientational phase transition, the characteristics concerned show certain peculiarities which enable detection of the phase transition and determination of its parameters.
Dipole Alignment in Rotating MHD Turbulence
NASA Technical Reports Server (NTRS)
Shebalin, John V.; Fu, Terry; Morin, Lee
2012-01-01
We present numerical results from long-term CPU and GPU simulations of rotating, homogeneous, magnetohydrodynamic (MHD) turbulence, and discuss their connection to the spherically bounded case. We compare our numerical results with a statistical theory of geodynamo action that has evolved from the absolute equilibrium ensemble theory of ideal MHD turbulence, which is based on the ideal MHD invariants are energy, cross helicity and magnetic helicity. However, for rotating MHD turbulence, the cross helicity is no longer an exact invariant, although rms cross helicity becomes quasistationary during an ideal MHD simulation. This and the anisotropy imposed by rotation suggests an ansatz in which an effective, nonzero value of cross helicity is assigned to axisymmetric modes and zero cross helicity to non-axisymmetric modes. This hybrid statistics predicts a large-scale quasistationary magnetic field due to broken ergodicity , as well as dipole vector alignment with the rotation axis, both of which are observed numerically. We find that only a relatively small value of effective cross helicity leads to the prediction of a dipole moment vector that is closely aligned (less than 10 degrees) with the rotation axis. We also discuss the effect of initial conditions, dissipation and grid size on the numerical simulations and statistical theory.
Splitting of the Pygmy Dipole Resonance
NASA Astrophysics Data System (ADS)
Endres, J.; Butler, P.; Harakeh, M. N.; Harissopulos, S.; Herzberg, R.-D.; Krücken, R.; Lagoyannis, A.; Litvinova, E.; Pietralla, N.; Ponomarev, V. Yu.; Popescu, L.; Ring, P.; Savran, D.; Scheck, M.; Sonnabend, K.; Stoica, V. I.; Wörtche, H. J.; Zilges, A.
2011-10-01
In recent years investigations have been made to study the electric Pygmy Dipole Resonance (PDR) systematically, mainly in semi-magic nuclei. For this purpose the well understood high resolution (γ,γ') photon scattering method is used. In complementary (α,α'γ) coincidence experiments at Eα = 136 MeV a similar γ-energy resolution and a high selectivity to E1 transitions can be obtained at the Big-Bite Spectrometer (BBS) at KVI, Groningen. In comparison to the (γ,γ') method a structural splitting of the PDR is observed in the N = 82 nuclei 138Ba and 140Ce and in the Z = 50 nucleus 124Sn. The low energy part is excited in (γ,γ') as well as in (α,α'γ) while the high energy part is observed in (γ,γ') only. The experimental results together with theoretical QPM and RQTBA calculations on 124Sn which are able to reproduce the splitting of the PDR qualitatively are presented. The low-lying group of Jπ = 1- states seem to represent the more isoscalar neutron-skin oscillation of the PDR while the energetically higher-lying states seemingly belong to the transitional region between the PDR and the isovector Giant Dipole Resonance (IVGDR).
Splitting of the Pygmy Dipole Resonance
Endres, J.; Zilges, A.; Butler, P.; Herzberg, R.-D.; Scheck, M.; Harakeh, M. N.; Harissopulos, S.; Lagoyannis, A.; Kruecken, R.; Ring, P.; Litvinova, E.; Pietralla, N.; Ponomarev, V. Yu.; Sonnabend, K.; Popescu, L.; Savran, D.; Stoica, V. I.; Woertche, H. J.
2011-10-28
In recent years investigations have been made to study the electric Pygmy Dipole Resonance (PDR) systematically, mainly in semi-magic nuclei. For this purpose the well understood high resolution ({gamma},{gamma}') photon scattering method is used. In complementary ({alpha},{alpha}'{gamma}) coincidence experiments at E{sub {alpha}} = 136 MeV a similar {gamma}-energy resolution and a high selectivity to E1 transitions can be obtained at the Big-Bite Spectrometer (BBS) at KVI, Groningen. In comparison to the ({gamma},{gamma}') method a structural splitting of the PDR is observed in the N = 82 nuclei {sup 138}Ba and {sup 140}Ce and in the Z = 50 nucleus {sup 124}Sn. The low energy part is excited in ({gamma},{gamma}') as well as in ({alpha},{alpha}'{gamma}) while the high energy part is observed in ({gamma},{gamma}') only. The experimental results together with theoretical QPM and RQTBA calculations on {sup 124}Sn which are able to reproduce the splitting of the PDR qualitatively are presented. The low-lying group of J{sup {pi}} = 1{sup -} states seem to represent the more isoscalar neutron-skin oscillation of the PDR while the energetically higher-lying states seemingly belong to the transitional region between the PDR and the isovector Giant Dipole Resonance (IVGDR).
Projected Dipole Model for Quantum Plasmonics
NASA Astrophysics Data System (ADS)
Yan, Wei; Wubs, Martijn; Asger Mortensen, N.
2015-09-01
Quantum effects of plasmonic phenomena have been explored through ab initio studies, but only for exceedingly small metallic nanostructures, leaving most experimentally relevant structures too large to handle. We propose instead an effective description with the computationally appealing features of classical electrodynamics, while quantum properties are described accurately through an infinitely thin layer of dipoles oriented normally to the metal surface. The nonlocal polarizability of the dipole layer—the only introduced parameter—is mapped from the free-electron distribution near the metal surface as obtained with 1D quantum calculations, such as time-dependent density-functional theory (TDDFT), and is determined once and for all. The model can be applied in two and three dimensions to any system size that is tractable within classical electrodynamics, while capturing quantum plasmonic aspects of nonlocal response and a finite work function with TDDFT-level accuracy. Applying the theory to dimers, we find quantum corrections to the hybridization even in mesoscopic dimers, as long as the gap itself is subnanometric.
Giant dipole resonance in hot rotating nuclei
NASA Astrophysics Data System (ADS)
Chakrabarty, D. R.; Dinh Dang, N.; Datar, V. M.
2016-05-01
Over the last several decades, extensive experimental and theoretical work has been done on the giant dipole resonance (GDR) in excited nuclei covering a wide range of temperature ( T), angular momentum ( J) and nuclear mass. A reasonable stability of the GDR centroid energy and an increase of the GDR width with T (in the range ˜ 1 - 3 MeV) and J are the two well-established results. Some experiments have indicated the saturation of the GDR width at high T . The gradual disappearance of the GDR vibration at much higher T has been observed. Experiments on the Jacobi transition and the GDR built on superdeformed shapes at high rotational frequencies have been reported in a few cases. Theoretical calculations on the damping of the collective dipole vibration, characterised by the GDR width, have been carried out within various models such as the thermal shape fluctuation model and the phonon damping model. These models offer different interpretations of the variation of the GDR width with T and J and have met with varying degrees of success in explaining the experimental data. In this review, the present experimental and theoretical status in this field will be discussed along with the future outlook. The interesting phenomenon of the pre-equilibrium GDR excitation in nuclear reactions will be briefly addressed.
Dipole Transport: a New Confinement Paradigm
NASA Astrophysics Data System (ADS)
Kesner, J.; Garnier, D.; Mauel, M.
2014-10-01
In a tokamak-like device turbulence will grow up to a level determined by non-linear processes. The associated transport, in combination with particle and energy sources then determines the density and temperature profiles of the plasma. This paradigm is fundamentally different for a plasma that is confined in a dipole field. In a dipole, levitated to avoid losses to the supports, the plasma will assume a stationary profile determined only by the specific volume, V (Ψ) , (which is determined by the magnetic geometry). Independent of the source and sink profiles for particles and energy, turbulence will grow up to a sufficient level so that diffusion and pinch dynamics will establish stationary profiles characterized by ne ~ 1 / V and p ~ 1 /V 5 / 3 . This process is observed in magnetospheric plasmas and we have observed it in the laboratory in LDX. For example, with edge fueling in LDX we observed that the stationary (peaked) density profile (n ~ 1 / V) was established by a turbulence-driven density pinch whereas in recent experiments with core (pellet) fueling turbulence was observed to relax the density back to the stationary profile on a similar timescale. Supported by the NSF-DOE Partnership in Plasma Science Grants DE-FG02-00ER54585 and PHY-1201896.
Projected Dipole Model for Quantum Plasmonics.
Yan, Wei; Wubs, Martijn; Asger Mortensen, N
2015-09-25
Quantum effects of plasmonic phenomena have been explored through ab initio studies, but only for exceedingly small metallic nanostructures, leaving most experimentally relevant structures too large to handle. We propose instead an effective description with the computationally appealing features of classical electrodynamics, while quantum properties are described accurately through an infinitely thin layer of dipoles oriented normally to the metal surface. The nonlocal polarizability of the dipole layer-the only introduced parameter-is mapped from the free-electron distribution near the metal surface as obtained with 1D quantum calculations, such as time-dependent density-functional theory (TDDFT), and is determined once and for all. The model can be applied in two and three dimensions to any system size that is tractable within classical electrodynamics, while capturing quantum plasmonic aspects of nonlocal response and a finite work function with TDDFT-level accuracy. Applying the theory to dimers, we find quantum corrections to the hybridization even in mesoscopic dimers, as long as the gap itself is subnanometric. PMID:26451583
SSC 50 mm collider dipole cryostat design
Nicol, T.H.
1992-04-01
The cryostat of a Superconducting Super Collider (SSC) dipole magnet consists of all magnet components except the magnet assembly itself. It serves to support the magnet accurately and reliably within the vacuum vessel, provide all required cryogenic piping, and to insulate the cold mass from heat radiated and conducted from the environment. It must function reliably during storage, shipping and handling, normal magnet operation, quenches, and seismic excitations, and must be manufacturable at low cost. The major components of the cryostat are the vacuum vessel, thermal shields, multilayer insulation system, cryogenic piping, interconnections, and suspension system. The overall design of a cryostat for superconducting accelerator magnets requires consideration of fluid flow, proper selection of materials for their thermal and structural performance at both ambient and operating temperature, and knowledge of the environment to which the magnets will be subjected over the course of their expected operating life. This paper describes the design of the current SSC dipole magnet cryostat and includes discussions on the structural and thermal considerations involved in the development of each of the major systems.
NASA Technical Reports Server (NTRS)
Baumeister, K. J.
1985-01-01
Analytical solutions for the three dimensional inhomogeneous wave equation with flow in a hardwall rectangular wind tunnel and in the free field are presented for a stationary monopole noise source. Dipole noise sources are calculated by combining two monopoles 180 deg out of phase. Numerical calculations for the modal content, spectral response and directivity for both monopole and dipole sources are presented. In addition, the effect of tunnel alterations, such as the addition of a mounting plate, on the tunnels reverberant response are considered. In the frequency range of practical importance for the turboprop response, important features of the free field directivity can be approximated in a hardwall wind tunnel with flow if the major lobe of the noise source is not directed upstream. However, for an omnidirectional source, such as a monopole, the hardwall wind tunnel and free field response are not comparable.
Polarity Reversal Time of the Magnetic Dipole Component of the Sun in Solar Cycle 24
NASA Astrophysics Data System (ADS)
Hakamada, Kazuyuki
2013-04-01
The Sun's general magnetic field has shown polarity reversal three times during the last three solar cycles. We attempt to estimate the upcoming polarity reversal time of the solar magnetic dipole by using the coronal field model and synoptic data of the photospheric magnetic field. The scalar magnetic potential of the coronal magnetic field is expanded into a spherical harmonic series. The long-term variations of the dipole component (g01) calculated from the data of National Solar Observatory/Kitt Peak and Wilcox Solar Observatory are compared with each other. It is found that the two g01 values show a similar tendency and an approximately linear increase between the Carrington rotation periods CR 2070 and CR 2118. The next polarity reversal is estimated by linear extrapolation to be between CR 2132.2 (December 2012) and CR2134.8 (March 2013).
Theoretical Study the Error Caused by Dipole Hypothesis of Large-loop TEM Response
NASA Astrophysics Data System (ADS)
Yan, S.; Xue, G.; Zhou, N.
2010-12-01
Transient electromagnetic method (Transient Electromagnetic Field is TEM for short) is an time domain artificial sources of electromagnetic detection method based on the principle of electromagnetic induction. This method has higher sensitivity for the anomalous body of low resistivity , a stimulating can cover the required frequency bands and greatly improve the work efficiency by using a rich spectrum component pulse waveform . Also because send magnetic moment is relatively large, so the loop source system TEM has been very widely used in geological exploration, engineering, geothermal and environmental exploration which belong to medium depth ( less than 2000m) exploration [1], especially the central-loop system TEM has become the preferred method in Coalfield Hydrogeology Exploration and metal ore exploration . In order to obtain greater depth of exploration, the launch frame side of loop system commonly use large-scale form , Now the imported equipments with a large number of applications are large-loop system which shall be accounted for about 80% of the share of middle-depth exploration on the ground , sush as V-5, V8, GDP-32, PROTEM, SIROTEM, PEM, etc. If only one point be observed in the frame center to move the whole system when the side of loop system reach to hundreds of meters, the work efficiency of TEM will be greatly reduced. In order to increase the production efficiency, we will observe the points from center of loop to 0ne third of loop in the actual production, which is to think that the field in this region is approximately homogeneous. So, we can derive large-loop center-model TEM system which is different from the center-loop TEM system in the conventional sense as well as large-loop source TEM system. Fixed loop source TEM sysetm has been built based on the theory of dipole infinitesimal, which can not show more correct character in near-field area, even though this kind of theory has played more important guide in TEM study. There exist
Dipole Tilt Angle Effects on Joule and Particle Heating in the Ionosphere
NASA Astrophysics Data System (ADS)
Chun, F. K.; Knipp, D. J.; McHarg, M. G.; Lu, G.; Emery, B. A.
2002-12-01
Previous work by Chun et al. [2002] presented spatial distributions of Joule heating as a function of the polar cap (PC) index and the season (summer, equinox, and winter). Noticeable differences in the Joule heating maps were observed with respect to both geomagnetic activity and the season. In this study, we present average patterns of height-integrated Pedersen and Hall conductivity, electric potential, Joule heating, and electron particle heating as a function of PC and dipole tilt angle using 56 days (approximately 12,800 individual patterns) of Assimilative Mapping of Ionospheric Electrodynamics (AMIE) data. We investigate differences in the spatial distributions as well as the hemispheric integrated Joule and particle heating. We also present spatial distributions of the ratios of the Joule to particle heating and the Hall to Pedersen conductance as a function of PC and dipole tilt angle.
NASA Technical Reports Server (NTRS)
Baumeister, K. J.
1986-01-01
Analytical solutions for the three dimensional inhomogeneous wave equation with flow in a hardwall rectangular wind tunnel and in the free field are presented for a stationary monopole noise source. Dipole noise sources are calculated by combining two monopoles 180 deg out of phase. Numerical calculations for the modal content, spectral response and directivity for both monopole and dipole sources are presented. In addition, the effect of tunnel alterations, such as the addition of a mounting plate, on the tunnels reverberant response are considered. In the frequency range of practical importance for the turboprop response, important features of the free field directivity can be approximated in a hardwall wind tunnel with flow if the major lobe of the noise source is not directed upstream. However, for an omnidirectional source, such as a monopole, the hardwall wind tunnel and free field response are not comparable.
Evidence of Soft Dipole Resonance in 11Li with Isoscalar Character
Kanungo, R.; Sanetullaev, A.; Jansen, Gustav R.; Tanaka, J.; Ishimoto, S.; Myo, T.; Suzuki, T.; Andreoiu, C.; Bender, P.; Chen, A. A.; et al
2015-05-12
The first conclusive evidence of a dipole resonance in 11Li having isoscalar character observed from inelastic scattering with a novel solid deuteron target is reported. The experiment was performed at the newly commissioned IRIS facility at TRIUMF. The results show a resonance peak at an excitation energy of 1.03±0.03 MeV with a width of 0.51±0.11 MeV (FWHM). The angular distribution is consistent with a dipole excitation in the distorted-wave Born approximation framework. The observed resonance energy together with shell model calculations show the first signature that the monopole tensor interaction is important in 11Li. The first ab initio calculations inmore » the coupled cluster framework are also included.« less
Evidence of Soft Dipole Resonance in ^{11}Li with Isoscalar Character
Kanungo, R.; Sanetullaev, A.; Jansen, Gustav R.; Tanaka, J.; Ishimoto, S.; Myo, T.; Suzuki, T.; Andreoiu, C.; Bender, P.; Chen, A. A.; Davids, B.; Fallis, J.; Fortin, J. P.; Galinski, N.; Gallant, A. T.; Garrett, P. E.; Hackman, G.; Hadinia, B.; Hagen, Gaute; Keefe, M.; Krucken, R.; Lighthall, J.; McNeice, E.; Miller, D.; Otsuka, T.; Purcell, J.; Randhawa, J. S.; Roger, T.; Rojas, A.; Savajols, H.; Shotter, A.; Tanihata, I.; Thompson, I. J.; Unsworth, C.; Voss, P.; Wang, Z.
2015-05-12
The first conclusive evidence of a dipole resonance in ^{11}Li having isoscalar character observed from inelastic scattering with a novel solid deuteron target is reported. The experiment was performed at the newly commissioned IRIS facility at TRIUMF. The results show a resonance peak at an excitation energy of 1.03±0.03 MeV with a width of 0.51±0.11 MeV (FWHM). The angular distribution is consistent with a dipole excitation in the distorted-wave Born approximation framework. The observed resonance energy together with shell model calculations show the first signature that the monopole tensor interaction is important in ^{11}Li. The first ab initio calculations in the coupled cluster framework are also included.
Experimental study on dipole motion of an ion plasma confined in a linear Paul trap
NASA Astrophysics Data System (ADS)
Ito, K.; Okano, T.; Moriya, K.; Fukushima, K.; Higaki, H.; Okamoto, H.
2015-11-01
The compact non-neutral plasma trap systems named "S-POD" have been developed at Hiroshima University as an experimental simulator of beam dynamics. S-POD is based either on a linear Paul trap or on a Penning trap and can approximately reproduce the collective motion of a relativistic charged-particle beam observed in the center-of-mass frame. We here employ the Paul trap system to investigate the behavior of an ion plasma near a dipole resonance. A simple method is proposed to calibrate the data of secular frequency measurements by using the dipole instability condition. We also show that the transverse density profile of an ion plasma in the trap can be estimated from the time evolution of ion losses caused by the resonance.
Terahertz radiation-induced sub-cycle field electron emission across a split-gap dipole antenna
Zhang, Jingdi; Averitt, Richard D. E-mail: raveritt@ucsd.edu; Zhao, Xiaoguang; Fan, Kebin; Wang, Xiaoning; Zhang, Xin E-mail: raveritt@ucsd.edu; Zhang, Gu-Feng; Geng, Kun
2015-12-07
We use intense terahertz pulses to excite the resonant mode (0.6 THz) of a micro-fabricated dipole antenna with a vacuum gap. The dipole antenna structure enhances the peak amplitude of the in-gap THz electric field by a factor of ∼170. Above an in-gap E-field threshold amplitude of ∼10 MV/cm{sup −1}, THz-induced field electron emission is observed as indicated by the field-induced electric current across the dipole antenna gap. Field emission occurs within a fraction of the driving THz period. Our analysis of the current (I) and incident electric field (E) is in agreement with a Millikan-Lauritsen analysis where log (I) exhibits a linear dependence on 1/E. Numerical estimates indicate that the electrons are accelerated to a value of approximately one tenth of the speed of light.
NASA Astrophysics Data System (ADS)
Desmarais, Jacques K.; Smith, Richard S.
2016-03-01
A novel automatic data interpretation algorithm is presented for modelling airborne electromagnetic (AEM) data acquired over resistive environments, using a single-component (vertical) transmitter, where the position and orientation of a dipole conductor is allowed to vary in three dimensions. The algorithm assumes that the magnetic fields produced from compact vortex currents are expressed as a linear combinations of the fields arising from dipoles in the subsurface oriented parallel to the [1, 0, 0], [0, 1, 0], and [0, 0, 1], unit vectors. In this manner, AEM responses can be represented as 12 terms. The relative size of each term in the decomposition can be used to determine geometrical information about the orientation of the subsurface conductivity structure. The geometrical parameters of the dipole (location, depth, dip, strike) are estimated using a combination of a look-up table and a matrix inverted in a least-squares sense. Tests on 703 synthetic models show that the algorithm is capable of extracting most of the correct geometrical parameters of a dipole conductor when three-component receiver data is included in the interpretation procedure. The algorithm is unstable when the target is perfectly horizontal, as the strike is undefined. Ambiguities may occur in predicting the orientation of the dipole conductor if y-component data is excluded from the analysis. Application of our approach to an anomaly on line 15 of the Reid Mahaffy test site yields geometrical parameters in reasonable agreement with previous authors. However, our algorithm provides additional information on the strike and offset from the traverse line of the conductor. Disparities in the values of predicted dip and depth are within the range of numerical precision. The index of fit was better when strike and offset were included in the interpretation procedure. Tests on the data from line 15701 of the Chibougamau MEGATEM survey shows that the algorithm is applicable to situations where
Detecting the dipole moment of a single carbon monoxide molecule
Schwarz, A. Köhler, A.; Grenz, J.; Wiesendanger, R.
2014-07-07
Using non-contact atomic force microscopy with metallic tips enabled us to detect the electrostatic dipole moment of single carbon monoxide (CO) molecules adsorbed on three very different substrates. The observed distance dependent contrast can be explained by an interplay between the attractive van der Waals interaction and the repulsive electrostatic interaction, respectively, with the latter stemming from antiparallel aligned dipoles in tip and molecule. Our results suggest that metallic as well as CO-functionalized tips are able to probe electrostatic properties of polar molecules and that repulsive dipole-dipole interactions have to be considered when interpreting complex contrast patterns.
Measurement of the b hadron lifetime with the dipole method
NASA Astrophysics Data System (ADS)
Buskulic, D.; de Bonis, I.; Decamp, D.; Ghez, P.; Goy, C.; Lees, J.-P.; Minard, M.-N.; Pietrzyk, B.; Ariztizabal, F.; Comas, P.; Crespo, J. M.; Delfino, M.; Efthymiopoulos, I.; Fernandez, E.; Fernandez-Bosman, M.; Gaitan, V.; Garrido, Ll.; Mattison, T.; Pacheco, A.; Padilla, C.; Pascual, A.; Creanza, D.; de Palma, M.; Farilla, A.; Iaselli, G.; Maggi, G.; Marinelli, N.; Natali, S.; Nuzzo, S.; Ranieri, A.; Raso, G.; Romano, F.; Ruggieri, F.; Selvaggi, G.; Silvestris, L.; Tempesta, P.; Zito, G.; Chai, Y.; Hu, H.; Huang, D.; Huang, X.; Lin, J.; Wang, T.; Xie, Y.; Xu, D.; Xu, R.; Zhang, J.; Zhang, L.; Zhao, W.; Bonvicini, G.; Boudreau, J.; Casper, D.; Drevermann, H.; Forty, R. W.; Ganis, G.; Gay, C.; Hagelberg, R.; Harvey, J.; Hilgart, J.; Jacobsen, R.; Jost, B.; Knobloch, J.; Lehraus, I.; Maggi, M.; Markou, C.; Martinez, M.; Mato, P.; Meinhard, H.; Minten, A.; Miquel, R.; Moser, H.-G.; Palazzi, P.; Pater, J. R.; Perlas, J. A.; Pusztaszeri, J.-F.; Ranjard, F.; Rolandi, L.; Rothberg, J.; Ruan, T.; Saich, M.; Schlatter, D.; Schmelling, M.; Sefkow, F.; Tejessy, W.; Tomalin, I. R.; Veenhof, R.; Wachsmuth, H.; Wasserbaech, S.; Wiedenmann, W.; Wildish, T.; Witzeling, W.; Wotschack, J.; Ajaltouni, Z.; Badaud, F.; Bardadin-Otwinowska, M.; El Fellous, R.; Falvard, A.; Gay, P.; Guicheney, C.; Henrard, P.; Jousset, J.; Michel, B.; Montret, J.-C.; Pallin, D.; Perret, P.; Podlyski, F.; Proriol, J.; Prulhière, F.; Saadi, F.; Fearnley, T.; Hansen, J. B.; Hansen, J. D.; Hansen, J. R.; Hansen, P. H.; Møllerud, R.; Nilsson, B. S.; Kyriakis, A.; Simopoulou, E.; Siotis, I.; Vayaki, A.; Zachariadou, K.; Badier, J.; Blondel, A.; Bonneaud, G.; Brient, J. C.; Bourdon, P.; Fouque, G.; Orteu, S.; Rougé, A.; Rumpf, M.; Tanaka, R.; Verderi, M.; Videau, H.; Candlin, D. J.; Parsons, M. I.; Veitch, E.; Focardi, E.; Moneta, L.; Parrini, G.; Corden, M.; Georgiopoulos, C.; Ikeda, M.; Levinthal, D.; Antonelli, A.; Baldini, R.; Bencivenni, G.; Bologna, G.; Bossi, F.; Campana, P.; Capon, G.; Cerutti, F.; Chiarella, V.; D'Ettorre-Piazzoli, B.; Felici, G.; Laurelli, P.; Mannocchi, G.; Murtas, F.; Murtas, G. P.; Passalacqua, L.; Pepe-Altarelli, M.; Picchi, P.; Colrain, P.; Ten Have, I.; Lynch, J. G.; Maitland, W.; Morton, W. T.; Raine, C.; Reeves, P.; Scarr, J. M.; Smith, K.; Smith, M. G.; Thompson, A. S.; Turnbull, R. M.; Brandl, B.; Braun, O.; Geweniger, C.; Hanke, P.; Hepp, V.; Kluge, E. E.; Maumary, Y.; Putzer, A.; Rensch, B.; Stahl, A.; Tittel, K.; Wunsch, M.; Beuselinck, R.; Binnie, D. M.; Cameron, W.; Cattaneo, M.; Colling, D. J.; Dornan, P. J.; Greene, A. M.; Hassard, J. F.; Lieske, N. M.; Moutoussi, A.; Nash, J.; Patton, S.; Payne, D. G.; Phillips, M. J.; San Martin, G.; Sedgbeer, J. K.; Wright, A. G.; Girtler, P.; Kuhn, D.; Rudolph, G.; Vogl, R.; Bowdery, C. K.; Brodbeck, T. J.; Finch, A. J.; Foster, F.; Hughes, G.; Jackson, D.; Keemer, N. R.; Nuttall, M.; Patel, A.; Sloan, T.; Snow, S. W.; Whelan, E. P.; Kleinknecht, K.; Raab, J.; Renk, B.; Sander, H.-G.; Schmidt, H.; Walther, S. M.; Wanke, R.; Wolf, B.; Zimmermann, A.; Bencheikh, A. M.; Benchouk, C.; Bonissent, A.; Carr, J.; Coyle, P.; Drinkard, J.; Etienne, F.; Nicod, D.; Papalexiou, S.; Payre, P.; Roos, L.; Rousseau, D.; Schwemling, P.; Talby, M.; Adlung, S.; Assmann, R.; Bauer, C.; Blum, W.; Brown, D.; Cattaneo, P.; Dehning, B.; Dietl, H.; Dydak, F.; Frank, M.; Halley, A. W.; Jakobs, K.; Lauber, J.; Lütjens, G.; Lutz, G.; Männer, W.; Richter, R.; Schröder, J.; Schwarz, A. S.; Settles, R.; Seywerd, H.; Stierlin, U.; Stiegler, U.; St. Denis, R.; Wolf, G.; Alemany, R.; Boucrot, J.; Callot, O.; Cordier, A.; Davier, M.; Duflot, L.; Grivaz, J.-F.; Heusse, Ph.; Jaffe, D. E.; Janot, P.; Kim, D. W.; Le Diberder, F.; Lefrançois, J.; Lutz, A.-M.; Schune, M.-H.; Veillet, J.-J.; Videau, I.; Zhang, Z.; Abbaneo, D.; Bagliesi, G.; Batignani, G.; Bottigli, U.; Bozzi, C.; Calderini, G.; Carpinelli, M.; Ciocci, M. A.; Ciulli, V.; Dell'Orso, R.; Ferrante, I.; Fidecaro, F.; Foà, L.; Forti, F.; Giassi, A.; Giorgi, M. A.; Gregorio, A.; Ligabue, F.; Lusiani, A.; Mannelli, E. B.; Marrocchesi, P. S.; Messineo, A.; Palla, F.; Rizzo, G.; Sanguinetti, G.; Spagnolo, P.; Steinberger, J.; Tenchini, R.; Tonelli, G.; Triggiani, G.; Valassi, A.; Vannini, C.; Venturi, A.; Verdini, P. G.; Walsh, J.; Betteridge, A. P.; Gao, Y.; Green, M. G.; March, P. V.; Mir, Ll. M.; Medcalf, T.; Quazi, I. S.; Strong, J. A.; West, L. R.; Botterill, D. R.; Clifft, R. W.; Edgecock, T. R.; Haywood, S.; Norton, P. R.; Thompson, J. C.; Bloch-Devaux, B.; Colas, P.; Duarte, H.; Emery, S.; Kozanecki, W.; Lançon, E.; Lemaire, M. C.; Locci, E.; Marx, B.; Perez, P.; Rander, J.; Renardy, J.-F.; Rosowsky, A.; Roussarie, A.; Schuller, J.-P.; Schwindling, J.; Si Mohand, D.; Vallage, B.; Johnson, R. P.; Litke, A. M.; Taylor, G.; Wear, J.; Ashman, J. G.; Babbage, W.; Booth, C. N.; Buttar, C.; Cartwright, S.; Combley, F.; Dawson, I.; Thompson, L. F.; Barbeiro, E.; Böhrer, A.; Brandt, S.; Cowan, G.; Grupen, C.; Lutters, G.; Rivera, F.; Schäfer, U.; Smolik, L.; Bosisio, L.; Della Marina, R.; Giannini, G.; Gobbo, B.; Ragusa, F.; Bellantoni, L.; Chen, W.; Conway, J. S.; Feng, Z.; Ferguson, D. P. S.; Gao, Y. S.; Grahl, J.; Harton, J. L.; Hayes, O. J.; Nachtman, J. M.; Pan, Y. B.; Saadi, Y.; Schmitt, M.; Scott, I.; Sharma, V.; Shi, Z. H.; Turk, J. D.; Walsh, A. M.; Weber, F. V.; Sau Lan Wu; Wu, X.; Zheng, M.; Zobernig, G.; Aleph Collaboration
1993-09-01
A measurement of the average lifetime of b hadrons has been performed with dipole method on a sample of 260 000 hadronic Z decays recorded with the ALEPH detector during 1991. The dipole is the distance between the vertices built in the opposite hemispheres. The mean dipole is extracted from all the events without attempting b enrichment. Comparing the average of the data dipole distribution with a Monte Carlo calibration curve obtained with different b lifetimes, an average b hadron lifetime of 1.51±0.08 ps is extracted.
New Insight into the Pygmy Dipole Resonance in Stable Nuclei
Neumann-Cosel, P. von
2008-11-11
Two examples of recent work on the structure of low-energy electric dipole modes are presented. The first part discusses the systematics of the pygmy dipole resonance (PDR) in stable tin isotopes deduced from high-resolution ({gamma},{gamma}') experiments. These help to distinguish between microscopic QRPA calculations based on either a relativistic or a nonrelativistic mean-field description, predicting significantly different properties of the PDR. The second part presents attempts to unravel the structure of dipoles modes at energies below the giant dipole resonance (GDR) in {sup 208}Pb with a high-resolution measurement of the (p-vector,p-vector') reaction under 0 deg.
Structural Analysis of the SHMS Cosine Theta Superconducting Dipole Force Collar
S.R. Lassiter, P.D. Brindza, M.J. Fowler, E. Sun, G. Markham
2009-06-01
Jefferson Laboratory is developing a set of innovative superconducting magnets for the 12 GeV upgrade in JLAB Hall C. We will report on the finite element analysis (FEA) of the force collar for the Super High Momentum Spectrometer Cosine Theta Dipole magnet. The force collar is designed with an interference fit and intended to provide enough pressure after cool down to operating temperature to counteract Lorentz forces acting on the dipole coil during operation. By counteracting the Lorentz forces and keeping the coil pack in overall compression, movement of the coils is expected to be minimized. The dimensional geometry of the cold mass is maintained in the commercial solid modeling code UG/I-DEAS while the magnetic field design is maintained in the commercial TOSCA code from Vector Fields. The three dimensional FEA was conducted in the commercial codes ANSYS and IDEAS. The method for converting the models and calculating the loads transferred to the structure is discussed. The results show the cold mass response to: force collar assembly preload, differential thermal contraction, and operational Lorentz loads. Evaluations are made for two candidate force collar materials and two candidate force collar designs.
The electric dipole moment of DNA-binding HU protein calculated by the use of an NMR database.
Takashima, S; Yamaoka, K
1999-08-30
Electric birefringence measurements indicated the presence of a large permanent dipole moment in HU protein-DNA complex. In order to substantiate this observation, numerical computation of the dipole moment of HU protein homodimer was carried out by using NMR protein databases. The dipole moments of globular proteins have hitherto been calculated with X-ray databases and NMR data have never been used before. The advantages of NMR databases are: (a) NMR data are obtained, unlike X-ray databases, using protein solutions. Accordingly, this method eliminates the bothersome question as to the possible alteration of the protein structure due to the transition from the crystalline state to the solution state. This question is particularly important for proteins such as HU protein which has some degree of internal flexibility; (b) the three-dimensional coordinates of hydrogen atoms in protein molecules can be determined with a sufficient resolution and this enables the N-H as well as C = O bond moments to be calculated. Since the NMR database of HU protein from Bacillus stearothermophilus consists of 25 models, the surface charge as well as the core dipole moments were computed for each of these structures. The results of these calculations show that the net permanent dipole moments of HU protein homodimer is approximately 500-530 D (1 D = 3.33 x 10(-30) Cm) at pH 7.5 and 600-630 D at the isoelectric point (pH 10.5). These permanent dipole moments are unusually large for a small protein of the size of 19.5 kDa. Nevertheless, the result of numerical calculations is compatible with the electro-optical observation, confirming a very large dipole moment in this protein. PMID:10483709
NASA Astrophysics Data System (ADS)
Goldman, Saul
1981-10-01
A thermodynamic perturbation theory that derives from the work of Gray, Gubbins, and Stell is used to analyze the influence of the permanent dipole and quadrupole moments in water on a variety of thermodynamic functions that characterize hydrophobic solvation and hydrophobic interactions. The model used for water was a generalized Stockmayer potential. Experimental values were used for the dipole moment and for the three components of the quadrupole tensor of water, and the parameters for the Lennard-Jones part of this potential were taken from Finney et al.'s polarizable electropole model for water. This potential function involves reduced dipole and quadrupole moments that are shown to be within the range of validity of Stell's Padé approximant. Induced moments were not considered. The solute-solute and solute-solvent pair potential functions were taken to be the same as the Lennard-Jones part of the solvent-solvent pair potential function. The effects of three types of anisotropies, namely, dipole forces only, generalized quadrupole forces only, dipole-dipole plus generalized quadrupole-generalized quadrupole plus dipole-generalized quadrupole forces, are considered separately. Values obtained for the Henry's law constant, the heat of solution, the partial molal volume, and the partial molal heat capacity, at infinite dilution, are compared with ranges of experimental values for these quantities for the rare gases in water. The closeness of our results to those data, for our solvent with all the anisotropies simultaneously turned on, is, with the exception of the partial molal volume, remarkable good. The reason for this one failure is discussed. Most surprising perhaps was the result, again for the solvent with the most complicated anisotropy, that it was possible, over a restricted temperature range, to mimic the drop in the osmotic second virial coefficient that is found in real aqueous systems at ordinary temperatures. A physical explanation for this
NASA Astrophysics Data System (ADS)
Yu, Yue; Luo, Zhuxi; Wang, Ziqiang
2014-07-01
We show that the dipole-dipole coupling between Wannier modes in cigar-shaped Bose-Einstein condensates (BECs) is significantly enhanced while the short-range coupling is strongly suppressed. As a result, the dipole-dipole interaction can become the dominant interaction between ultracold alkali Bose atoms. In the long length limit of a cigar-shaped BEC, the resulting effective one-dimensional models possess an effective inverse squared interacting potential, the Calogero-Sutherland potential, which plays a fundamental role in many fields of contemporary physics; but its direct experimental realization has been a challenge for a long time. We propose to realize the Calogero-Sutherland model in ultracold alkali Bose atoms and study the effects of the dipole-dipole interaction.
ERIC Educational Resources Information Center
Lai, Hsin-Chih; Chang, Chun-Yen; Li, Wen-Shiane; Fan, Yu-Lin; Wu, Ying-Tien
2013-01-01
This study presents an m-learning method that incorporates Integrated Quick Response (QR) codes. This learning method not only achieves the objectives of outdoor education, but it also increases applications of Cognitive Theory of Multimedia Learning (CTML) (Mayer, 2001) in m-learning for practical use in a diverse range of outdoor locations. When…
Study By Spin Tracking of A Storage Ring For Deuteron Electric Dipole Moment
Lin, F.; Malitsky, N. D.; Luccio, A. U.; Morse, W. M.; Semertzidis, Y. K.; Onderwater, C. J. G.; Orlov, Y. F.
2009-08-04
Spin tracking of polarized deuterons for a proposed experiment to measure a possible Electric Dipole Moment (EDM) of the deuteron was done by using the codes UAL and SPINK. In the experiment the direction of spin polarization will be frozen using crossed electric and magnetic fields. Systematics, in particular the effects of non-linearities of the lattice on a beam with finite emittance and energy spread, have been extensively simulated and the effect of sextuple corrections to increase the spin coherence time has been studied.
Bremmer, Rolf H; van Gemert, Martin J C; Faber, Dirk J; van Leeuwen, Ton G; Aalders, Maurice C G
2013-08-01
Diffuse reflectance spectra are used to determine the optical properties of biological samples. In medicine and forensic science, the turbid objects under study often possess large absorption and/or scattering properties. However, data analysis is frequently based on the diffusion approximation to the radiative transfer equation, implying that it is limited to tissues where the reduced scattering coefficient dominates over the absorption coefficient. Nevertheless, up to absorption coefficients of 20 mm-1 at reduced scattering coefficients of 1 and 11.5 mm-1, we observed excellent agreement (r2=0.994) between reflectance measurements of phantoms and the diffuse reflectance equation proposed by Zonios et al. [Appl. Opt.38, 6628-6637 (1999)], derived as an approximation to one of the diffusion dipole equations of Farrell et al. [Med. Phys.19, 879-888 (1992)]. However, two parameters were fitted to all phantom experiments, including strongly absorbing samples, implying that the reflectance equation differs from diffusion theory. Yet, the exact diffusion dipole approximation at high reduced scattering and absorption also showed agreement with the phantom measurements. The mathematical structure of the diffuse reflectance relation used, derived by Zonios et al. [Appl. Opt.38, 6628-6637 (1999)], explains this observation. In conclusion, diffuse reflectance relations derived as an approximation to the diffusion dipole theory of Farrell et al. can analyze reflectance ratios accurately, even for much larger absorption than reduced scattering coefficients. This allows calibration of fiber-probe set-ups so that the object's diffuse reflectance can be related to its absorption even when large. These findings will greatly expand the application of diffuse reflection spectroscopy. In medicine, it may allow the use of blue/green wavelengths and measurements on whole blood, and in forensic science, it may allow inclusion of objects such as blood stains and cloth at crime
NASA Astrophysics Data System (ADS)
Bremmer, Rolf H.; van Gemert, Martin J. C.; Faber, Dirk J.; van Leeuwen, Ton G.; Aalders, Maurice C. G.
2013-08-01
Diffuse reflectance spectra are used to determine the optical properties of biological samples. In medicine and forensic science, the turbid objects under study often possess large absorption and/or scattering properties. However, data analysis is frequently based on the diffusion approximation to the radiative transfer equation, implying that it is limited to tissues where the reduced scattering coefficient dominates over the absorption coefficient. Nevertheless, up to absorption coefficients of 20 m at reduced scattering coefficients of 1 and 11.5 mm-1, we observed excellent agreement (r2=0.994) between reflectance measurements of phantoms and the diffuse reflectance equation proposed by Zonios et al. [Appl. Opt.
NASA Astrophysics Data System (ADS)
Panahi, M.; Solookinejad, G.; Ahmadi Sangachin, E.; Hossein Asadpour, Seyyed
2016-07-01
The impact of the dipole-dipole interaction on the Goo-Hänchen (GH) shifts in reflected and transmitted lights is investigated. A weak probe beam is incident on a cavity containing the donor and acceptor quantum dots embedded in a nonlinear photonic crystal. We deduced that the GH shifts can be easily adjusted via controlling the corresponding parameters of the system in the presence or absence of dipole-dipole interaction. Our proposed model may be useful to developing the all-optical devices based on photonic materials doped with nanoparticles.
Modified Coulomb-Dipole Theory for 2e Photoionization
NASA Technical Reports Server (NTRS)
2004-01-01
In the light of recent experiment on 2e photoionization of Li near threshold, we have considered a modification of the Coulomb-dipole theory, retaining the basic assumption that the threshold is dominated by asymmetric events in phase space [implies r(sub 1), k(sub 1)) greater than or equal to 2(r(sub 2), k(sub )]. In this region [in a collinear model, 2/r(sub 12) approached + 2/(r(sub 1)+r(sub 2)] the interaction reduces to V(rIsub 1) is greater than or equal to 2r(sub 2) is identically equal to [(-Z/r(sub 2)-(A-1)/r(sub 1)] + [(-2r(sub 2)/r(sub 1 exp 2)] is identically equal to V(sub c)+[V(sub d)]. For two electron emission Z = 2, thus both electrons see a Coulomb potential (V(sub c)) asymptotically, albeit each seeing a different charge. The residual potential (V(sub d)) is dipole in character. Writing the total psi = psi (sub c) + psi(sub d) = delta psi, and noting that. (T+V(sub c)-E)psy(sub c) = 0 and (T+V(sub c))psi(sub d) = 0 can be solved exactly, we find, substituting psi into the complete Schrod. Eq., that delta psi = -(H-E)(exp -1)(V(sub d) psi(sub 0)+V(sub c psi (sub 1). Using the fact that the absolute value of V(sub c) is much more than the absolute value of V(sub d) in almost all of configuration space, we can replace H by H(sub 0) in 9H-E)(exp -1) to obtain an improved approximation psi (improved) = psi(sub c) + psi(sub d) -(H(sub 0)-E)(exp -1) (V(sub c) psi (sub 0) + V(sub c) psi(sub 1). Here's the Green's function (H(sub 0)-E)(exp -1), can be exhibited explicitly, but the last term in psi (improved) is small, compared to the first two terms. Inserting them into the transition matrix element, which one handles in the usual way, we obtain in the limit E approaches 0, the threshold law: Q(E) alpha E + M(E)E(exp 5/4) + higher order (Eq. 1a). The modulation function, M(E), is a well-defined (but very non-trivial integral, but it is expected to be well approximated by a sinusoidal function containing a dipole phase term (M(E) = c sin[alpha log (E
Legendre-tau approximations for functional differential equations
NASA Technical Reports Server (NTRS)
Ito, K.; Teglas, R.
1986-01-01
The numerical approximation of solutions to linear retarded functional differential equations are considered using the so-called Legendre-tau method. The functional differential equation is first reformulated as a partial differential equation with a nonlocal boundary condition involving time-differentiation. The approximate solution is then represented as a truncated Legendre series with time-varying coefficients which satisfy a certain system of ordinary differential equations. The method is very easy to code and yields very accurate approximations. Convergence is established, various numerical examples are presented, and comparison between the latter and cubic spline approximation is made.
Legendre-Tau approximations for functional differential equations
NASA Technical Reports Server (NTRS)
Ito, K.; Teglas, R.
1983-01-01
The numerical approximation of solutions to linear functional differential equations are considered using the so called Legendre tau method. The functional differential equation is first reformulated as a partial differential equation with a nonlocal boundary condition involving time differentiation. The approximate solution is then represented as a truncated Legendre series with time varying coefficients which satisfy a certain system of ordinary differential equations. The method is very easy to code and yields very accurate approximations. Convergence is established, various numerical examples are presented, and comparison between the latter and cubic spline approximations is made.
Relativistic Coulomb excitation within the time dependent superfluid local density approximation
Stetcu, I.; Bertulani, C. A.; Bulgac, A.; Magierski, P.; Roche, K. J.
2015-01-06
Within the framework of the unrestricted time-dependent density functional theory, we present for the first time an analysis of the relativistic Coulomb excitation of the heavy deformed open shell nucleus ^{238}U. The approach is based on the superfluid local density approximation formulated on a spatial lattice that can take into account coupling to the continuum, enabling self-consistent studies of superfluid dynamics of any nuclear shape. We compute the energy deposited in the target nucleus as a function of the impact parameter, finding it to be significantly larger than the estimate using the Goldhaber-Teller model. The isovector giant dipole resonance, the dipole pygmy resonance, and giant quadrupole modes are excited during the process. As a result, the one-body dissipation of collective dipole modes is shown to lead a damping width Γ↓≈0.4 MeV and the number of preequilibrium neutrons emitted has been quantified.
ANALYTICAL CALCULATION OF STOKES PROFILES OF ROTATING STELLAR MAGNETIC DIPOLE
Martinez Gonzalez, M. J.
2012-08-20
The observation of the polarization emerging from a rotating star at different phases opens up the possibility to map the magnetic field in the stellar surface thanks to the well-known Zeeman-Doppler imaging. When the magnetic field is sufficiently weak, the circular and linear polarization profiles locally in each point of the star are proportional to the first and second derivatives of the unperturbed intensity profile, respectively. We show that the weak-field approximation (for weak lines in the case of linear polarization) can be generalized to the case of a rotating star including the Doppler effect and taking into account the integration on the stellar surface. The Stokes profiles are written as a linear combination of wavelength-dependent terms expressed as series expansions in terms of Hermite polynomials. These terms contain the surface-integrated magnetic field and velocity components. The direct numerical evaluation of these quantities is limited to rotation velocities not larger than eight times the Doppler width of the local absorption profiles. Additionally, we demonstrate that in a rotating star, the circular polarization flux depends on the derivative of the intensity flux with respect to the wavelength and also on the profile itself. Likewise, the linear polarization depends on the profile and on its first and second derivatives with respect to the wavelength. We particularize the general expressions to a rotating dipole.
Isoscalar Giant Dipole Resonance within Fermi Liquid Drop Model
NASA Astrophysics Data System (ADS)
Pochivalov, Oleksiy; Shlomo, Shalom
2006-04-01
Recent highly accurate experimental data on Isoscalar Giant Dipole (ISGDR) and Monopole (ISGMR) Resonances in nuclei renewed interest in correct microscopic description of collective excitations. Hartree-Fock based Random-Phase-Approximation (HF-RPA) is a successful method of describing collective excitations in nuclei. However, recent fully self-consistent HF-RPA calculations, which reproduce the centroid energies of the ISGMR, systematically overestimate by 1.5-2.5 MeV results for the ISGDR energy comparing with experimentally obtained data. Also, the HF-RPA model does not provide description of the widths of giant resonances. We consider these issues within the semi-classical generalization of the mean field theory, namely, Fermi-Liquid-Drop-Model (FLDM). In this presentation, we provide description of the FLDM formalism in its application to ISGDR and ISGMR calculations. We present results of FLDM calculations for centroid energy and widths of the ISGDR and ISGMR in the four nuclei, namely, 90Zr, 116Sn, 144Sm, and 208Pb and compare with available experimental data.
Measuring the Electron Electric Dipole Moment Using Ytterbium Fluoride Molecules
NASA Astrophysics Data System (ADS)
Smallman, I. J.; Devlin, J. A.; Kara, D. M.; Hudson, J. J.; Sauer, B. E.; Tarbutt, M. R.; Hinds, E. A.
2013-06-01
It is well known that the existence of an electron electric dipole moment (eEDM) would violate time reversal symmetry. The Standard Model predicts an eEDM less than 10^{-38}e.cm, however many popular extensions predict values in the range 10^{-29}-10^{-24}e.cm. Our experiment currently has the potential to measure eEDMs down to approximately 10^{-29}e.cm, making it a precise probe for T-violation and physics beyond the Standard Model. We measure the eEDM by performing a type of separated oscillating field interferometry on a pulsed beam of YbF. The molecules are prepared such that the molecular spin is oriented perpendicular to an applied strong (10kV/cm) electric field. The spin is then allowed to precess about the electric field axis over a 0.5ms interaction period. We measure this angle of rotation, which is directly proportional to the eEDM. In order to measure the eEDM precisely and without error we use a complex switching technique wherein certain parameters, including the applied electric and magnetic fields, are reversed between individual molecular pulses. I will present our current technique and our most recent world leading result.
Model dependence of the {sup 2}H electric dipole moment
Afnan, I. R.; Gibson, B. F.
2010-12-15
Background: Direct measurement of the electric dipole moment (EDM) of the neutron is in the future; measurement of a nuclear EDM may well come first. The deuteron is one nucleus for which exact model calculations are feasible. Purpose: We explore the model dependence of deuteron EDM calculations. Methods: Using a separable potential formulation of the Hamiltonian, we examine the sensitivity of the deuteron EDM to variation in the nucleon-nucleon interaction. We write the EDM as the sum of two terms, the first depending on the target wave function with plane-wave intermediate states, and the second depending on intermediate multiple scattering in the {sup 3}P{sub 1} channel, the latter being sensitive to the off-shell behavior of the {sup 3}P{sub 1} amplitude. Results: We compare the full calculation with the plane-wave approximation result, examine the tensor force contribution to the model results, and explore the effect of short-range repulsion found in realistic, contemporary potential models of the deuteron. Conclusions: Because one-pion exchange dominates the EDM calculation, separable potential model calculations will provide an adequate description of the {sup 2}H EDM until such time as a measurement better than 10% is obtained.
Atomic electric dipole moments: The Schiff theorem and its corrections
Liu, C.-P.; Ramsey-Musolf, M. J.; Haxton, W. C.; Timmermans, R. G. E.; Dieperink, A. E. L.
2007-09-15
Searches for the permanent electric dipole moments (EDMs) of diamagnetic atoms provide powerful probes of CP-violating hadronic and semileptonic interactions. The theoretical interpretation of such experiments, however, requires careful implementation of a well-known theorem by Schiff that implies a vanishing net EDM for an atom built entirely from pointlike, nonrelativistic constituents that interact only electrostatically. Any experimental observation of a nonzero atomic EDM would result from corrections to the pointlike, nonrelativistic, electrostatic assumption. We reformulate Schiff's theorem at the operator level and delineate the electronic and nuclear operators whose atomic matrix elements generate corrections to 'Schiff screening'. We obtain a form for the operator responsible for the leading correction associated with finite nuclear size - the so-called Schiff moment operator - and observe that it differs from the corresponding operator used in previous Schiff moment computations. We show that the more general Schiff moment operator reduces to the previously employed operator only under certain approximations that are not generally justified. We also identify other corrections to Schiff screening that may not be included properly in previous theoretical treatments. We discuss practical considerations for obtaining a complete computation of corrections to Schiff screening in atomic EDM calculations.
The coupled dipole modes of the NLC accelerator structure
Bane, K.L.F.; Gluckstern, R.; Holtkamp, N.
1992-03-01
The proposed accelerator cavity of the Next Linear Collider (NLC) is a disk-loaded structure composed of 200 cells, operating at 11.42 GHz. The proposed mode of operation is to accelerate bunches in trains of 10, with a bunch spacing of 42 cm. One problem is that one bunch in a train can excite transverse wakefields in the accelerator cavity which, in turn, can deflect following bunches and result in emittance growth. A method of curing this problem is to detune the transverse modes of the cavity. Beam dynamics simulations for the NLC have shown that by keeping the transverse wakefield at the positions of the nine trailing bunches at or below 1 MW/nC/m{sup 2} we can void emittance growth. Earlier, approximate calculations of the wakefields, which did not include the cell-to-cell coupling of the modes, have shown that by the proper Gaussian detuning the above level of cancellation can be achieved. A specific goal of this report is to see if this conclusion still holds when coupling is included in the calculation. Note that in this paper we focus on the modes belonging to the first dipole passband, which are the most important. A special feature of these modes in the detuned NLC cavity is that the cell-to-cell coupling changes sign somewhere in the middle of the structure.
Near-Field Magnetic Dipole Moment Analysis
NASA Technical Reports Server (NTRS)
Harris, Patrick K.
2003-01-01
This paper describes the data analysis technique used for magnetic testing at the NASA Goddard Space Flight Center (GSFC). Excellent results have been obtained using this technique to convert a spacecraft s measured magnetic field data into its respective magnetic dipole moment model. The model is most accurate with the earth s geomagnetic field cancelled in a spherical region bounded by the measurement magnetometers with a minimum radius large enough to enclose the magnetic source. Considerably enhanced spacecraft magnetic testing is offered by using this technique in conjunction with a computer-controlled magnetic field measurement system. Such a system, with real-time magnetic field display capabilities, has been incorporated into other existing magnetic measurement facilities and is also used at remote locations where transport to a magnetics test facility is impractical.
Concentric Titled Double-Helix Dipole Magnets
Rainer Meinke, Ph.D; Carl Goodzeit; Millicent Ball, Ph.D
2003-09-05
The high magnetic fields required for future accelerator magnets can only be achieved with Nb3Sn, other A15 or HTS type conductors, which are brittle and sensitive to mechanical strain. The traditional ''cosine-theta'' dipole configuration has intrinsic drawbacks that make it difficult and expensive to employ such conductors in these designs. Some of these problems involve (1) difficulty in applying enough pre-stress to counteract Lorentz forces without compromising conductor performance; (2) small minimum bend radii of the conductor necessitating the intricate wind-and-react coil fabrication; (3) complex spacers in particular for coil ends and expensive tooling for coil fabrication; (4) typically only 2/3 of the coil aperture can be used with achievable field uniformity.
Magnetic field decay in model SSC dipoles
Gilbert, W.S.; Althaus, R.F.; Barale, P.J.; Benjegerdes, R.W.; Green, M.A.; Green, M.I.; Scanlan, R.M.
1988-08-01
We have observed that some of our model SSC dipoles have long time constant decays of the magnetic field harmonics with amplitudes large enough to result in significant beam loss, if they are not corrected. The magnets were run at constant current at the SSC injection field level of 0.3 tesla for one to three hours and changes in the magnetic field were observed. One explanation for the observed field decay is time dependent superconductor magnetization. Another explanation involves flux creep or flux flow. Data are presented on how the decay changes with previous flux history. Similar magnets with different Nb-Ti filament spacings and matrix materials have different long time field decay. A theoretical model using proximity coupling and flux creep for the observed field decay is discussed. 10 refs., 5 figs., 2 tabs.
Beam optical properties of the NSLS dipoles
Galayda, J.N.; Blumberg, L.N.; Heese, R.N.; Hsieh, H.C.H.
1981-01-01
Presently there is much interest in low energy (<1 GeV) electron storage rings as sources of synchrotron radiation and for studies of the free electron laser. The economics and physics of these storage rings favor the use of bending magnets with small radius of curvature and large bend angle. Some general features of such magnets and the results of magnetic measurements of the dipole magnets of the NSLS booster and storage rings are discussed. The magnetic measurements are interpreted in terms of the magnet geometry and saturation characteristics. Transport functions describing the linear and nonlinear focusing properties of the magnets, parametrized in terms of their curvature and fringe field length are discussed.
Systematic Study of the Pygmy Dipole Resonance
NASA Astrophysics Data System (ADS)
Derya, V.; Endres, J.; Harakeh, M. N.; Savran, D.; Wörtche, H. J.; Zilges, A.
2012-05-01
In recent years, a systematic comparative study of the pygmy dipole resonance (PDR) using the (γ,γ') and the (α,α'γ) reactions on the nuclei 140Ce, 138Ba, 124Sn, 94Mo, and 48Ca was performed. The aim of this systematic study is to explore the structure of the PDR by the usage of two complementary probes and several different nuclei. The real-photon scattering experiments were performed at the S-DALINAC in Darmstadt, Germany, while the (α, α'γ) coincidence experiments were performed at the Big-Bite Spectrometer (BBS) at KVI in Groningen, The Netherlands. The comparison of the results from both kinds of experiments showed an energetic splitting of the PDR into two parts that might be due to the different isospin character of these states. First experimental results of the (α, α'γ) experiments on the nuclei 94Mo and 48Ca will be presented.
Splitting of the Pygmy Dipole Resonance
NASA Astrophysics Data System (ADS)
Savran, D.; Endres, J.; Harakeh, M. N.; Pietralla, N.; Sonnabend, K.; Stoica, V. I.; Wörtche, H. J.; van den Berg, A. M.; Zilges, A.
2011-09-01
We report on experiments using the (α, α' γ) method to investigate the structure of the Pygmy Dipole Resonance (PDR) in the nuclei 94Mo, 124Sn, 138Ba and 140Ce. The experiments were performed with the Big-Bite Spectrometer (BBS) at the KVI at an incident energy of Eα = 136 MeV. The method allows a clean separation of the PDR from other excitations in the same energy region by selecting the ground-state γ-decay channel. In addition, the high resolution of the γ-ray spectroscopy using high-purity Germanium detectors allows a state-to-state analysis even in the case of the rather high level density of the investigated nuclei. The comparison to (γ,γ') experiments on the same nuclei reveals a splitting of the PDR into two groups of states with different underlying structure.
Novel Design of Superconducting Helical Dipole Magnet
NASA Astrophysics Data System (ADS)
Meinke, R.; Senti, M.; Stelzer, G.
1997-05-01
Superconducting helical dipole magnets with a nominal field of 4 Tesla are needed for the spin physics program at the Relativistic Heavy Ion Collider (RHIC) at Brookhaven National Laboratory. The magnets are required to operate at a relatively low current of 400 A since many of these magnets have to be independently controlled. The Advanced Magnet Lab, Inc., in Palm Bay, FL has designed and built two prototype magnets using advanced computer controlled coil winding technology. The AML design is extremely cost effective since it avoids magnet specific tooling despite the required complex coil pattern and any precision machined inserts or spacers. It is the first time an accelerator magnet of this technology has reached a field above 4 Tesla. Results from the prototype testing at BNL are presented.
Nuclear electric dipole moment of 3He
Stetcu, Ionel; Friar, J L; Hayes, A C; Liu, C P; Navratil, P
2008-01-01
In the no-core shell model (NCSM) framework, we calculate the {sup 3}He electric dipole moment (EDM) generated by parity- and time-reversal violation in the nucleon-nucleon interaction. While the results are somehow sensitive to the interaction model chosen for the strong two- and three-body interactions, we demonstrate the pion-exchange dominance to the EDM of {sup 3}He, if the coupling constants for {pi}, {rho} and {omega}-exchanges are of comparable magnitude, as expected. Finally, our results suggest that a measurement of {sup 3}He EDM would be complementary to the currently planned neutron and deuteron experiments, and would constitute a powerful constraint to the models of the pion P- and T-violating interactions.
Search for the Neutron Electric Dipole Moment
Plaster, Brad
2010-08-04
Searches for the neutron electric dipole moment (EDM) are motivated by their highly suppressed Standard Model value. The observation of a non-zero signal in the next generation of experiments would point unambiguously to the existence of new physics beyond the Standard Model. Several ongoing efforts worldwide hold the potential for an up to two-orders-of-magnitude improvement beyond the current upper limit on the neutron EDM of 2.9x10{sup -6} e-cm. In this talk, I review the basic measurement principles of neutron EDM searches, then discuss a new experiment to be carried out in the United States at the Spallation Neutron Source with ultracold neutrons and an in-situ '3He''co-magnetometer'.
Intrinsic surface dipole in topological insulators.
Fregoso, Benjamin M; Coh, Sinisa
2015-10-28
We calculate the local density of states of two prototypical topological insulators (Bi2Se3 and Bi2Te2Se) as a function of distance from the surface within density functional theory. We find that, in the absence of disorder or doping, there is a 2 nm thick surface dipole the origin of which is the occupation of the topological surface states above the Dirac point. As a consequence, the bottom of the conduction band is bent upward by about 75 meV near the surface, and there is a hump-like feature associated with the top of the valence band. We expect that band bending will occur in all pristine topological insulators as long as the Fermi level does not cross the Dirac point. Our results show that topological insulators are intrinsic Schottky barrier solar cells. PMID:26440802
Search for a Neutron Electric Dipole Moment
Golub, R.; Huffman, P. R.
2005-01-01
The possible existence of a nonzero electric dipole moment (EDM) of the neutron is of great fundamental interest in itself and directly impacts our understanding of the nature of electro-weak and strong interactions. The experimental search for this moment has the potential to reveal new sources of T and CP violation and to challenge calculations that propose extensions to the Standard Model. The goal of the current experiment is to significantly improve the measurement sensitivity to the neutron EDM over what is reported in the literature. The experiment has the potential to either measure the magnitude of the neutron EDM or to lower the current experimental limit by two orders of magnitude. Achieving these objectives will have a major impact on our understanding of the physics of both weak and strong interactions. PMID:27308116
Search for the Neutron Electric Dipole Moment
NASA Astrophysics Data System (ADS)
Plaster, Brad
2010-08-01
Searches for the neutron electric dipole moment (EDM) are motivated by their highly suppressed Standard Model value. The observation of a non-zero signal in the next generation of experiments would point unambiguously to the existence of new physics beyond the Standard Model. Several ongoing efforts worldwide hold the potential for an up to two-orders-of-magnitude improvement beyond the current upper limit on the neutron EDM of 2.9×10-6 e-cm. In this talk, I review the basic measurement principles of neutron EDM searches, then discuss a new experiment to be carried out in the United States at the Spallation Neutron Source with ultracold neutrons and an in-situ 3He "co-magnetometer".
Fission and dipole resonances in metal clusters
Martin, T. P.; Billas, I. M. L.; Branz, W.; Heinebrodt, M.; Tast, F.; Malinowski, N.
1997-06-20
It is not obvious that metal clusters should behave like atomic nuclei--but they do. Of course the energy and distance scales are quite different. But aside from this, the properties of these two forms of condensed matter are amazingly similar. The shell model developed by nuclear physicists describes very nicely the electronic properties of alkali metal clusters. The giant dipole resonances in the excitation spectra of nuclei have their analogue in the plasmon resonances of metal clusters. Finally, the droplet model describing the fission of unstable nuclei can be successively applied to the fragmentation of highly charged metal clusters. The similarity between clusters and nuclei is not accidental. Both systems consist of fermions moving, nearly freely, in a confined space.
Roll measurement of Tevatron dipoles and quadrupoles
Volk, J.T.; Elementi, L.; Gollwitzer, K.; Jostlein, H.; Nobrega, F.; Shiltsev, V.; Stefanski, R.
2006-09-01
In 2003 a simple digital level system was developed to allow for rapid roll measurements of all dipoles and quadrupoles in the Tevatron. The system uses a Mitutoyo digital level and a PC running MS WINDOWS XP and LAB VIEW to acquire data on the upstream and downstream roll of each magnet. The system is sufficiently simple that all 1,000 magnets in the Tevatron can be measured in less than 3 days. The data can be quickly processed allowing for correction of rolled magnets by the Fermilab alignment group. Data will be presented showing the state of the Tevatron in 2003 and the changes in rolls as measured in each shutdown since then.
Active flutter suppression using dipole filters
NASA Technical Reports Server (NTRS)
Srinathkumar, S.; Waszak, Martin R.
1992-01-01
By using traditional control concepts of gain root locus, the active suppression of a flutter mode of a flexible wing is examined. It is shown that the attraction of the unstable mode towards a critical system zero determines the degree to which the flutter mode can be stabilized. For control situations where the critical zero is adversely placed in the complex plane, a novel compensation scheme called a 'Dipole' filter is proposed. This filter ensures that the flutter mode is stabilized with acceptable control energy. The control strategy is illustrated by designing flutter suppression laws for an active flexible wing (AFW) wind-tunnel model, where minimal control effort solutions are mandated by control rate saturation problems caused by wind-tunnel turbulence.
Antenna impedance measurements in a magnetized plasma. II. Dipole antenna
Blackwell, David D.; Walker, David N.; Messer, Sarah J.; Amatucci, William E.
2007-09-15
This paper presents experimental impedance measurements of a dipole antenna immersed in a magnetized plasma. The impedance was derived from the magnitude and phase of the reflected power using a network analyzer over a frequency range of 1 MHz-1 GHz. The plasma density was varied between 10{sup 7} and 10{sup 10} cm{sup -3} in weakly ({omega}{sub ce}<{omega}{sub pe}) and strongly ({omega}{sub ce}>{omega}{sub pe}) magnetized plasmas in the Space Physics Simulation Chamber at the Naval Research Laboratory. Over this range of plasma conditions the wavelength in the plasma varies from the short dipole limit ({lambda}>>L) to the long dipole limit ({lambda}{approx}L). As with previous impedance measurements, there are two resonant frequencies observed as frequencies where the impedance of the antenna is real. Measurements have indicated that in the short dipole limit the majority of the power deposition takes place at the lower resonance frequency which lies between the cyclotron frequency and the upper hybrid frequency. These measured curves agree very well with the analytic theory for a short dipole in a magnetoplasma. In the long dipole regime, in addition to the short dipole effects still being present, there is resonant energy deposition which peaks at much higher frequencies and correlates to 1/2 and 3/2 wavelength dipole resonances. The wavelengths in the plasma predicted by these resonances are consistent with the antenna radiating R and L-waves.
Complete and rigorous analysis of electromagnetically coupled transverse microstrip dipole
NASA Astrophysics Data System (ADS)
Lepeltier, P.; Floc'h, J. M.; Citerne, J.
1987-07-01
A rigorous and complete analysis of the electromagnetically coupled transverse microstrip dipole is presented. This new feeding process offers an alternative solution, which is especially interesting when it is necessary to excite several dipoles from the same line. The theoretical results are compared to experimental measurements in X-band for the input impedance and the radiation patterns (co- and crosspolarization).
The transverse current on a strip dipole antenna
NASA Astrophysics Data System (ADS)
Wunsch, A. D.
1983-04-01
The magnitude and distribution of the current flow transverse to the axis of a small strip dipole antenna is evaluated numerically by means of the moment method. This current is found to be small compared to the axial current and to be a sensitive function of the dipole width.
The mathematical modeling of grouping the dipole water clusters
NASA Astrophysics Data System (ADS)
Shaidurov, Vladimir; Kornienko, Viktoria; Vyatkin, Alexander
2016-08-01
In the present paper, a physical-mathematical model and a computational algorithm implementing the model are proposed to study the behavior of particles having an electric dipole moment in an external electric field. Computational experiments demonstrate the orientation dynamics of water clusters with the increase of the generated field. The dipole properties of some water clusters were previously determined using Hyperchem program.
Helical dipole magnets for polarized protons in RHIC
Syphers, M.; Courant, E.; Fischer, W.
1997-07-01
Superconducting helical dipole magnets will be used in the Brookhaven Relativistic Heavy Ion Collider (RHIC) to maintain polarization of proton beams and to perform localized spin rotations at the two major experimental detector regions. Requirements for the helical dipole system are discussed, and magnet prototype work is reported.
Dipole modulation in tensor modes: signatures in CMB polarization
NASA Astrophysics Data System (ADS)
Zarei, Moslem
2015-06-01
In this work we consider a dipole asymmetry in tensor modes and study the effects of this asymmetry on the angular power spectra of CMB. We derive analytical expressions for the and in the presence of such dipole modulation in tensor modes for . We also discuss on the amplitude of modulation term and show that the is considerably modified due to this term.
Pygmy Dipole Strength and Neutron Skins in Exotic Nuclei
NASA Astrophysics Data System (ADS)
Klimkiewicz, A.; Paar, N.; Adrich, P.; Fallot, M.; Boretzky, K.; Aumann, T.; Cortina-Gil, D.; Pramanik, U. Datta; Elze, Th. W.; Emling, H.; Geissel, H.; Hellström, M.; Jones, K. L.; Kratz, J. V.; Kulessa, R.; Nociforo, C.; Palit, R.; Simon, H.; Surówka, G.; Sümmerer, K.; Vretenar, D.; Waluś, W.
2008-05-01
Dipole strength distributions were determined for the neutron-rich nuclei 129-132Sn and 133,134Sb from electromagnetic excitation in an experiment using the FRS-LAND setup. For all nuclei, a sizeable fraction of ``pygmy'' dipole strength at excitation energies well below the giant dipole resonance was observed. The integrated low-lying dipole strength of the nuclei with low neutron separation energies can be compared to results for stable nuclei (e.g. N = 82 isotopes) determined for the energy regime of 5-9 MeV. A clear increase of the dipole strength with increasing asymmetry of the nuclei is observed. Comparing the ratio of the low-lying dipole over the giant dipole strength to recent relativistic mean field calculations, values for the parameters a4 and p0 of the symmetry energy and for the neutron skin thickness are derived. Averaged over 130Sn and 132Sn we extract a4 = 31.8+/-1.3 MeV and p0 = 2.2+/-0.5 MeV/fm3. The neutron skin sizes are determined to Rn-Rp = 0.23+/-0.03 fm and 0.24+/-0.03 fm for 130Sn and 132Sn, respectively. For 208Pb a neutron skin thickness of Rn-Rp = 0.18+/-0.035 fm follows, when applying the same method and using earlier published experimental findings on the dipole strength.
Electric dipole moment of the electron and of the neutron
NASA Technical Reports Server (NTRS)
Barr, S. M.; Zee, A.
1990-01-01
It is shown that if Higgs-boson exchange mediates CP violation a significant electric dipole moment for the electron can result. Analogous effects can contribute to the neutron's electric dipole moment at a level competitive with Weinberg's three-gluon operator.
Multiple dipole modeling of spatio-temporal MEG (magnetoencephalogram) data
Mosher, J.C. . Systems Engineering and Development Div. University of Southern California, Los Angeles, CA . Signal and Image Processing Inst.); Lewis, P.S. ); Leahy, R. . Signal and Image Processing Inst.); Singh, M. (University of Southern Californi
1990-01-01
An array of SQUID biomagentometers may be used to measure the spatio-temporal neuromagnetic field produced by the brain in response to a given sensory stimulus. A popular model for the neural activity that produces these fields is a set of current dipoles. We present here a common linear algebraic framework for three common spatio-temporal dipole models: moving and rotating dipoles, rotating dipoles with fixed location, and dipoles with fixed orientation and location. Our intent here is not to argue the merits of one model over another, but rather show how each model may be solved efficiently, and within the same framework as the others. In all cases, we assume that the location, orientation, and magnitude of the dipoles are unknown. We present the parameter estimation problem for these three models in a common framework, and show how, in each case, the problem may be decomposed into the estimation of the dipole locations using nonlinear minimization followed by linear estimation of the associated moment time series. Numerically efficient means of calculating the cost function are presented, and problems of model order selection and missing moments are also investigated. The methods described are demonstrated in a simulated application to a three dipole problem. 21 refs., 2 figs., 1 tab.
Diagnostics of the Fermilab Tevatron using an AC dipole
Miyamoto, Ryoichi
2008-08-01
The Fermilab Tevatron is currently the world's highest energy colliding beam facility. Its counter-rotating proton and antiproton beams collide at 2 TeV center-of-mass. Delivery of such intense beam fluxes to experiments has required improved knowledge of the Tevatron's beam optical lattice. An oscillating dipole magnet, referred to as an AC dipole, is one of such a tool to non-destructively assess the optical properties of the synchrotron. We discusses development of an AC dipole system for the Tevatron, a fast-oscillating (f ~ 20 kHz) dipole magnet which can be adiabatically turned on and off to establish sustained coherent oscillations of the beam particles without affecting the transverse emittance. By utilizing an existing magnet and a higher power audio amplifier, the cost of the Tevatron AC dipole system became relatively inexpensive. We discuss corrections which must be applied to the driven oscillation measurements to obtain the proper interpretation of beam optical parameters from AC dipole studies. After successful operations of the Tevatron AC dipole system, AC dipole systems, similar to that in the Tevatron, will be build for the CERN LHC. We present several measurements of linear optical parameters (beta function and phase advance) for the Tevatron, as well as studies of non-linear perturbations from sextupole and octupole elements.
Measurement of coupling resonance driving terms with the AC dipole
Miyamoto, R.
2010-10-01
Resonance driving terms for linear coupled betatron motion in a synchrotron ring can be determined from corresponding spectral lines of an excited coherent beam motion. An AC dipole is one of instruments to excite such a motion. When a coherent motion is excited with an AC dipole, measured Courant-Snyder parameters and betatron phase advance have apparent modulations, as if there is an additional quadrupole field at the location of the AC dipole. Hence, measurements of these parameters using the AC dipole require a proper interpretation of observed quantities. The situation is similar in measurements of resonance driving terms using the AC dipole. In this note, we derive an expression of coupled betatron motion excited with two AC dipoles in presence of skew quadrupole fields, discuss an impact of this quadrupole like effect of the AC dipole on a measurement of coupling resonance driving terms, and present an analytical method to determine the coupling resonance driving terms from quantities observed using the AC dipole.
Dipole collapse and reversal precursors in a numerical dynamo
NASA Astrophysics Data System (ADS)
Olson, Peter; Driscoll, Peter; Amit, Hagay
2009-03-01
Precursors to extreme geomagnetic field changes are examined in a numerical dynamo with a reversing dipolar magnetic field. A dynamo model with compositional convection in a rotating spherical shell produces a strongly dipolar external magnetic field over 6 Myr of simulated paleomagnetic time, with stable polarity epochs and occasional dipole collapses, some of which result in polarity reversals or dipole axis excursions. We analyze the model behavior during two dipole collapses, one that leads to a polarity reversal and one that does not, focusing on observable precursors. Reversed magnetic field induced in the dynamo interior by intermittent convective variability is the primary cause of dipole collapse. Spots of reversed magnetic flux emerge on the outer boundary at an early stage, then re-emerge with greater intensity at the height of the collapse. The energy in the external field cascades to higher harmonics as these reversed patches appear. Butterfly diagrams showing the reversed and normal flux contributions to the axial dipole reveal poleward migration of the patches during dipole collapse. Axial dipole reduction by precursory reversed flux is several times larger in the reversing case, compared to the non-reversing case. A butterfly diagram of the geomagnetic field since 1840 shows high latitude reversed flux emerging on the core-mantle boundary. Although the reversed geomagnetic flux is presently too weak to be labeled a reversal precursor, it is consistent with early stage dipole collapse in the dynamo model.
Diagnostics of the Fermilab Tevatron using an AC dipole
NASA Astrophysics Data System (ADS)
Miyamoto, Ryoichi
The Fermilab Tevatron is currently the world's highest energy colliding beam facility. Its counter-rotating proton and antiproton beams collide at 2 TeV center-of-mass. Delivery of such intense beam fluxes to experiments has required improved knowledge of the Tevatron's beam optical lattice. An oscillating dipole magnet, referred to as an AC dipole, is one of such a tool to non-destructively assess the optical properties of the synchrotron. We discusses development of an AC dipole system for the Tevatron, a fast-oscillating (f˜20 kHz) dipole magnet which can be adiabatically turned on and off to establish sustained coherent oscillations of the beam particles without affecting the transverse emittance. By utilizing an existing magnet and a higher power audio amplifier, the cost of the Tevatron AC dipole system became relatively inexpensive. We discuss corrections which must be applied to the driven oscillation measurements to obtain the proper interpretation of beam optical parameters from AC dipole studies. After successful operations of the Tevatron AC dipole system, AC dipole systems, similar to that in the Tevatron, will be build for the CERN LHC. We present several measurements of linear optical parameters (beta function and phase advance) for the Tevatron, as well as studies of non-linear perturbations from sextupole and octupole elements.
Simulations of the angular dependence of the dipole-dipole interaction among Rydberg atoms
NASA Astrophysics Data System (ADS)
Bigelow, Jacob L.; Hollingsworth, Jacob; Paul, Jacob T.; Peleg, Matan; Sanford, Veronica L.; Carroll, Thomas J.; Noel, Michael W.
2016-05-01
The dipole-dipole interaction between two Rydberg atoms depends on the relative orientation of the atoms and on the change in the magnetic quantum number. We simulate the effect of this anisotropy on the energy transport in an amorphous many atom system of ultracold Rydberg atoms subject to a homogeneous applied electric field. We consider two experimentally feasible geometries and find that the effects should be measurable in current generation imaging experiments. We also examine evidence for Anderson localization. This work was supported by the National Science Foundation under Grants No. 1205895 and No. 1205897 and used the Extreme Science and Engineering Discovery Environment (XSEDE), which is supported by National Science Foundation Grant Number OCI-1053575.
Resonant electric dipole-dipole interactions between cold Rydberg atoms in a magnetic field
NASA Astrophysics Data System (ADS)
Afrousheh, Kourosh; Bohlouli-Zanjani, Parisa; Carter, Jeffery; Mugford, Ashton; Martin, James D. D.
2006-05-01
Laser cooled Rb atoms were optically excited to 46d5/2 Rydberg states. A microwave pulse transferred a fraction of the atoms to the 47p3/2 Rydberg state. The resonant electric dipole-dipole interactions between atoms in these two states were probed using the linewidth of the two-photon microwave transitions 46d5/2 -- 47d5/2. The presence of a weak magnetic field (roughly 1 G) reduced the observed line broadening, indicating that the interaction is suppressed by the field. The field removes some of the energy degeneracies responsible foe the resonant interaction, and this is the basis for a quantitative model of the resulting suppression. A technique for the calibration of magnetic field strengths using the 34s1/2 -- 34p1/2 one-photon transition is also presented.
Resonant electric dipole-dipole interactions between cold Rydberg atoms in a magnetic field
NASA Astrophysics Data System (ADS)
Afrousheh, K.; Bohlouli-Zanjani, P.; Carter, J. D.; Mugford, A.; Martin, J. D. D.
2006-06-01
Laser-cooled Rb85 atoms were optically excited to 46d5/2 Rydberg states. A microwave pulse transferred a fraction of the atoms to the 47p3/2 Rydberg state. The resonant electric dipole-dipole interactions between atoms in these two states were probed using the linewidth of the two-photon microwave transition 46d5/2-47d5/2 . The presence of a weak magnetic field ≈0.5G reduced the observed line broadening, indicating that the interaction is suppressed by the field. The field removes some of the energy degeneracies responsible for the resonant interaction, and this is the basis for a quantitative model of the resulting suppression. A technique for the calibration of magnetic field strengths using the 34s1/2-34p1/2 one-photon transition is also presented.
Controlling the dipole-dipole interaction using NMR composite rf pulses
Baudin, Emmanuel
2014-08-07
New composite rf pulses are proposed during which the average dipole-dipole interactions within a spin ensemble are controlled, while a global rotation is achieved. The method used to tailor the pulses is based on the average Hamiltonian theory and relies on the geometrical properties of the spin-spin dipolar interaction. I describe several such composite pulses and analyze quantitatively the improvement brought on the control of the NMR dynamics. Numerical simulations show that the magic sandwich pulse sequence, during which the average dipolar field is effectively reversed, is plagued by defects originating from the finite initial and final π/2 rf pulses. A numerical test based on a classical description of nuclear magnetic resonance is used to check that, when these pulses are replaced by magic composite pulses, the efficiency of the magic sandwich is improved.
Quantum defect theory for the van der Waals plus dipole-dipole interaction
NASA Astrophysics Data System (ADS)
Wang, Gao-Ren; Xie, Ting; Huang, Yin; Zhang, Wei; Cong, Shu-Lin
2012-12-01
We investigate the scattering dynamics governed by the long-range van der Waals plus dipole-dipole interaction potential, -C6/R6-C3/R3, which describes the long-range interaction between two polar molecules in an electric field. In the spirit of quantum defect theory, a set of parameters which are nearly constants in the threshold regime is defined to characterize the scattering process. Using appropriate boundary conditions for the scattering wave functions and relevant parameters, we explore the quantum reflection by and quantum tunneling through the long-range potential. As a sample application, the reactive collision rates of 40K87Rb + 40K87Rb are calculated.
Effect of resonance dipole-dipole interaction on spectra of adsorbed SF6 molecules.
Dobrotvorskaia, Anna N; Kolomiitsova, Tatiana D; Petrov, Sergey N; Shchepkin, Dmitriy N; Smirnov, Konstantin S; Tsyganenko, Alexey A
2015-09-01
Adsorption of SF6 on zinc oxide and on silicalite-1 was investigated by a combination of IR spectroscopy with the calculations of spectra by means of a modernized model, developed previously for liquids. Comparison of the experimental spectra and the results of modeling shows that the complex band shapes in spectra of adsorbed molecules with extremely high absorbance are due to the strong resonance dipole-dipole interaction (RDDI) rather that the surface heterogeneity or the presence of specific surface sites. Perfect agreement between calculated and observed spectra was found for ZnO, while some dissimilarity in band intensities for silicalite-1 was attributed to complicated geometry of molecular arrangement in the channels. PMID:25897721
Wideband dipole antenna with inter-digital capacitor
NASA Astrophysics Data System (ADS)
Xiong, Han; Hong, Jin-Song; Jin, Da-Lin
2013-04-01
A dipole antenna with wideband characteristics is presented. The proposed antenna consists of a dipole with periodic capacitive loading and a pair of coplanar striplines (CPSs) as an impedance transformer. By adding interlaced coupling lines at each section, periodic capacitive loading is realized. The periodic interlaced coupling lines divide each arm of the dipole into five sections, and currents are distributed on different sections at different frequencies, which is useful to achieve a wide impedance bandwidth. By parametric study using HFSS, the optimized parameters of this dipole antenna are obtained. In order to validate the simulation results, a prototype of the proposed dipole antenna is fabricated and tested. The results show that the proposed antenna can achieve a gain of 3.1 dB-5.1 dB and bandwidth of 51% for |S11| < -10 dB over the band of 3.9 GHz-6.6 GHz, indicating its good radiation performance and radiation efficiency.
Mesogen polarity effects on biaxial nematics. Centrally located dipoles.
Querciagrossa, Lara; Ricci, Matteo; Berardi, Roberto; Zannoni, Claudio
2013-11-21
We investigate the phase organisation of thermotropic biaxial Gay-Berne (GB) mesogens yielding a biaxial nematic (Nb) phase upon endowing them with a central point dipole. We study the effects of changing the strength and orientation of the dipole on the phase behaviour, and in particular we examine, using molecular dynamics (MD) simulations, the possibility of improving the stability of the Nb phase. After mapping the boundaries of the Nb phase, we find that the strength of the embedded dipole is the parameter with the strongest influence on the mesogenic properties, while its orientation plays a minor role. For these central dipole systems, we find that the Nb phase organisation is stable only for mesogens with relatively weak dipole moments, while it disappears if electrostatic interactions become comparable in magnitude with dispersion interactions. PMID:24100468
Dipole splitting algorithm: A practical algorithm to use the dipole subtraction procedure
NASA Astrophysics Data System (ADS)
Hasegawa, K.
2015-11-01
The Catani-Seymour dipole subtraction is a general and powerful procedure to calculate the QCD next-to-leading order corrections for collider observables. We clearly define a practical algorithm to use the dipole subtraction. The algorithm is called the dipole splitting algorithm (DSA). The DSA is applied to an arbitrary process by following well defined steps. The subtraction terms created by the DSA can be summarized in a compact form by tables. We present a template for the summary tables. One advantage of the DSA is to allow a straightforward algorithm to prove the consistency relation of all the subtraction terms. The proof algorithm is presented in the following paper [K. Hasegawa, arXiv:1409.4174]. We demonstrate the DSA in two collider processes, pp to μ -μ + and 2 jets. Further, as a confirmation of the DSA, it is shown that the analytical results obtained by the DSA in the Drell-Yan process exactly agree with the well known results obtained by the traditional method.
Universal Behavior of Dielectric Responses of Glass Formers: Role of Dipole-Dipole Interactions.
Paluch, M; Knapik, J; Wojnarowska, Z; Grzybowski, A; Ngai, K L
2016-01-15
From an exhaustive examination of the molecular dynamics in practically all van der Waals molecular glass formers ever probed by dielectric spectroscopy, we found that the width of the α-loss peak at or near the glass transition temperature T_{g} is strongly anticorrelated with the polarity of the molecule. The larger the dielectric relaxation strength Δε(T_{g}) of the system, the narrower is the α-loss peak. This remarkable property is explained by the contribution from the dipole-dipole interaction potential V_{dd}(r)=-Dr^{-6} to the attractive part of the intermolecular potential, making the resultant potential more harmonic, and the effect increases rapidly with the dipole moment μ and Δε(T_{g}) in view of the relation, D∝(μ^{4}/kT_{g})∝kT_{g}[Δε(T_{g})]^{2}. Since the novel correlation discovered encompasses practically all van der Waals molecular glass formers studied by dielectric spectroscopy, it impacts the large dielectric research community as well as those engaged in solving the glass transition problem. PMID:26824551
Universal Behavior of Dielectric Responses of Glass Formers: Role of Dipole-Dipole Interactions
NASA Astrophysics Data System (ADS)
Paluch, M.; Knapik, J.; Wojnarowska, Z.; Grzybowski, A.; Ngai, K. L.
2016-01-01
From an exhaustive examination of the molecular dynamics in practically all van der Waals molecular glass formers ever probed by dielectric spectroscopy, we found that the width of the α -loss peak at or near the glass transition temperature Tg is strongly anticorrelated with the polarity of the molecule. The larger the dielectric relaxation strength Δ ɛ (Tg) of the system, the narrower is the α -loss peak. This remarkable property is explained by the contribution from the dipole-dipole interaction potential Vd d(r )=-D r-6 to the attractive part of the intermolecular potential, making the resultant potential more harmonic, and the effect increases rapidly with the dipole moment μ and Δ ɛ (Tg) in view of the relation, D ∝(μ4/k Tg)∝k Tg[Δɛ (Tg)] 2 . Since the novel correlation discovered encompasses practically all van der Waals molecular glass formers studied by dielectric spectroscopy, it impacts the large dielectric research community as well as those engaged in solving the glass transition problem.
Dipole-Dipole Interactions of High-spin Paramagnetic Centers in Disordered Systems
Maryasov, Alexander G.; Bowman, Michael K.; Tsvetkov, Yuri D.
2007-09-13
Dipole-dipole interactions between distant paramagnetic centers (PCs) where at least one PC has spin S>1/2 are examined. The results provide a basis for the application of pulsed DEER or PELDOR methods to the measurement of distances between PC involving high-spin species. A projection operator technique based on spectral decomposition of the secular Hamiltonian is used to calculate EPR line splitting caused by the dipole coupling. This allows calculation of operators projecting arbitrary wavefunction onto high PC eigenstates when the eigenvectors of the Hamiltonian are not known. The effective spin vectors-that is, the expectation values for vector spin operators in the PC eigenstates-are calculated. The dependence of these effective spin vectors on the external magnetic field is calculated. There is a qualitative difference between pairs having at least one integer spin (non Karmers PC) and pairs of two half-integer (Kramers PC) spins. With the help of these effective spin vectors, the dipolar lineshape of EPR lines is calculated. Analytical relations are obtained for PCs with spin S=1/2 and 1. The dependence of Pake patterns on variations of zero field splitting, Zeeman energy, temperature and dipolar coupling are illustrated.
Li, Hui-zhen; Tao, Dong-liang; Qi, Jian; Wu, Jin-guang; Xu, Yi-zhuang; Noda, Isao
2014-04-24
Two-dimensional (2D) synchronous spectroscopy together with a new approach called "Orthogonal Sample Design Scheme" was used to study the dipole-dipole interactions in two representative ternary chemical systems (N,N-dimethyllformamide (DMF)/CH3COOC2H5/CCl4 and C60/CH3COOC2H5/CCl4). For the first system, dipole-dipole interactions among carbonyl groups from DMF and CH3COOC2H5 are characterized by using the cross peak in 2D Fourier Transform Infrared Radiation (FT-IR) spectroscopy. For the second system, intermolecular interaction among π-π transition from C60 and vibration transition from the carbonyl band of ethyl acetate is probed by using 2D spectra. The experimental results demonstrate that "Orthogonal Sample Design Scheme" can effectively remove interfering part that is not relevant to intermolecular interaction. Additional procedures are carried out to preclude the possibilities of producing interfering cross peaks by other reasons, such as experimental errors. Dipole-dipole interactions that manifest in the form of deviation from the Beer-Lambert law generate distinct cross peaks visualized in the resultant 2D synchronous spectra of the two chemical systems. This work demonstrates that 2D synchronous spectra coupled with orthogonal sample design scheme provide us an applicable experimental approach to probing and characterizing dipole-dipole interactions in complex molecular systems. PMID:24582337
Cavity approximation for graphical models.
Rizzo, T; Wemmenhove, B; Kappen, H J
2007-07-01
We reformulate the cavity approximation (CA), a class of algorithms recently introduced for improving the Bethe approximation estimates of marginals in graphical models. In our formulation, which allows for the treatment of multivalued variables, a further generalization to factor graphs with arbitrary order of interaction factors is explicitly carried out, and a message passing algorithm that implements the first order correction to the Bethe approximation is described. Furthermore, we investigate an implementation of the CA for pairwise interactions. In all cases considered we could confirm that CA[k] with increasing k provides a sequence of approximations of markedly increasing precision. Furthermore, in some cases we could also confirm the general expectation that the approximation of order k , whose computational complexity is O(N(k+1)) has an error that scales as 1/N(k+1) with the size of the system. We discuss the relation between this approach and some recent developments in the field. PMID:17677405
Approximate circuits for increased reliability
Hamlet, Jason R.; Mayo, Jackson R.
2015-08-18
Embodiments of the invention describe a Boolean circuit having a voter circuit and a plurality of approximate circuits each based, at least in part, on a reference circuit. The approximate circuits are each to generate one or more output signals based on values of received input signals. The voter circuit is to receive the one or more output signals generated by each of the approximate circuits, and is to output one or more signals corresponding to a majority value of the received signals. At least some of the approximate circuits are to generate an output value different than the reference circuit for one or more input signal values; however, for each possible input signal value, the majority values of the one or more output signals generated by the approximate circuits and received by the voter circuit correspond to output signal result values of the reference circuit.
Approximate circuits for increased reliability
Hamlet, Jason R.; Mayo, Jackson R.
2015-12-22
Embodiments of the invention describe a Boolean circuit having a voter circuit and a plurality of approximate circuits each based, at least in part, on a reference circuit. The approximate circuits are each to generate one or more output signals based on values of received input signals. The voter circuit is to receive the one or more output signals generated by each of the approximate circuits, and is to output one or more signals corresponding to a majority value of the received signals. At least some of the approximate circuits are to generate an output value different than the reference circuit for one or more input signal values; however, for each possible input signal value, the majority values of the one or more output signals generated by the approximate circuits and received by the voter circuit correspond to output signal result values of the reference circuit.
Structural optimization with approximate sensitivities
NASA Technical Reports Server (NTRS)
Patnaik, S. N.; Hopkins, D. A.; Coroneos, R.
1994-01-01
Computational efficiency in structural optimization can be enhanced if the intensive computations associated with the calculation of the sensitivities, that is, gradients of the behavior constraints, are reduced. Approximation to gradients of the behavior constraints that can be generated with small amount of numerical calculations is proposed. Structural optimization with these approximate sensitivities produced correct optimum solution. Approximate gradients performed well for different nonlinear programming methods, such as the sequence of unconstrained minimization technique, method of feasible directions, sequence of quadratic programming, and sequence of linear programming. Structural optimization with approximate gradients can reduce by one third the CPU time that would otherwise be required to solve the problem with explicit closed-form gradients. The proposed gradient approximation shows potential to reduce intensive computation that has been associated with traditional structural optimization.
Evolution of the virtual dipole moment through the Paleoarchean-Phanerozoic
NASA Astrophysics Data System (ADS)
Schreider, A. A.; Schreider, Al. A.; Varga, P.; Denis, C.
2015-03-01
In the context of the dipole model of the earth's magnetic field, the data from the international bank of digital information on the distribution of the virtual dipole moment (VDM) values in time, combined with the data obtained by subsequent investigations (7082 values in total), served as the basis for reconstructing its behavior through the Paleoarchean-Phanerozoic. The VDM behavior is characterized by a positive linear trend in the interval of 4.1 × 1022 Am2 (3.5 Ga ago) to 5.5 × 1022 Am2 (now). This background linear growth of the field strength is complicated by irregularly distributed VDM variations ranging in the amplitude from 1.7 × 1022 to 3.7 × 1022 Am2 with the wavelength varying from 220 to 920 Ma. The average wavelength of such fluctuations is estimated to be 570 Ma, which is approximately equal by duration to the Wilson geological cycles. The interval of 0.84-1.3 Ga is first established to be characterized by the relatively calm VDM region of 4.7-4.9 × 1022 Am2. The first defined deep minimum described by 10 data points with the extremum of 2.3 × 1022 Am2 (2.15 Ga ago) corresponds to the terminal phase in the formation of the earth's core geometry and initiation of the formation of the modern dipole field.
Pygmy Dipole Strength in Exotic Nuclei and the Equation of State
NASA Astrophysics Data System (ADS)
Klimkiewicz, A.; Paar, N.; Adrich, P.; Fallot, M.; le Bleis, T.; Rossi, D.; Boretzky, K.; Aumann, T.; Alvarez-Pol, H.; Aksouh, F.; Benlliure, J.; Berg, T.; Boehmer, M.; Casarejos, E.; Chartier, M.; Chatillon, A.; Cortina-Gil, D.; Pramanik, U. Datta; Elze, Th. W.; Emling, H.; Ershova, O.; Fernando-Dominguez, B.; Geissel, H.; Gorska, M.; Heil, M.; Hellström, M.; Johansson, H.; Jones, K. L.; Junghans, A.; Kiselev, O.; Kratz, J. V.; Kulessa, R.; Kurz, N.; Labiche, M.; Lemmon, R.; Litvinov, Y.; Mahata, K.; Maierbeck, P.; Nilsson, T.; Nociforo, C.; Palit, R.; Paschalis, S.; Plag, R.; Reifarth, R.; Simon, H.; Sümmerer, K.; Surówka, G.; Vretenar, D.; Wagner, A.; Waluś, W.; Weick, H.; Winkler, M.
2009-08-01
A concentration of dipole strength at energies below the giant dipole resonance was observed in neutron-rich nuclei around 132Sn in an experiment using the FRS-LAND setup. This so-called "pygmy" dipole strength can be related to the parameters of the symmetry energy and to the neutron skin thickness on the grounds of a relativistic quasiparticle random-phase approximation. Using this ansatz and the experimental findings for 130Sn and 132Sn, we derive a value of the symmetry energy pressure of p¯0 = 2.2±0.5 MeV/fm3. Neutron skin thicknesses of Rn-Rp = 0.23±0.03 fm and 0.24±0.03 fm for 130Sn and 132Sn, respectively, have been determined. Preliminary results on 68Ni from a similar experiment using an improved setup indicate an enhanced cross section at low energies, while the results for 58Ni are in accordance with results from photoabsorption measurements.
The effect of a permanent dipole moment on the polar molecule cavity quantum electrodynamics
NASA Astrophysics Data System (ADS)
Jing-Yun, Zhao; Li-Guo, Qin; Xun-Ming, Cai; Qiang, Lin; Zhong-Yang, Wang
2016-04-01
A dressed-state perturbation theory beyond the rotating wave approximation (RWA) is presented to investigate the interaction between a two-level electronic transition of polar molecules and a quantized cavity field. Analytical expressions can be explicitly derived for both the ground- and excited-state-energy spectrums and wave functions of the system, where the contribution of permanent dipole moments (PDM) and the counter-rotating wave term (CRT) can be shown separately. The validity of these explicit results is discussed by comparison with the direct numerical simulation. Compared to the CRT coupling, PDM results in the coupling of more dressed states and the energy shift is proportional to the square of the normalized permanent dipole difference, and a greater Bloch–Siegert shift can be produced in the giant dipole molecule cavity QED. In addition, our method can also be extended to the solution of the two-level atom Rabi model Hamiltonian beyond the RWA. Project supported by the Strategic Priority Research Program of the Chinese Academy of Sciences (Grant No. XDB01010200), the Hundred Talents Program of the Chinese Academy of Sciences (Grant No. Y321311401), the National Natural Science Foundation of China (Grant Nos. 61475139, 11347147, and 11247014), the National Basics Research Program of China (Grant No. 2013CB329501), and the Zhejiang Provincial Natural Science Foundation (Grant No. LQ13A040006).
Dipole-forbidden atomic transitions induced by superintense x-ray laser fields
NASA Astrophysics Data System (ADS)
Simonsen, Aleksander Skjerlie; Førre, Morten
2016-06-01
A hydrogen atom, initially prepared in the 2 s and/or 2 p (m =±1 ) states, is assumed irradiated by 0.8 keV (1.5 nm) photons in pulses of 1 -250 fs duration and intensities in the range 1020 to 1023W /cm2 . Solving the corresponding time-dependent Schrödinger equation from first principles, we show that the ionization and excitation dynamics of the laser-atom system is strongly influenced by interactions beyond the electric dipole approximation. A beyond-dipole two-photon Raman-like transition between the 2 s and 2 p (m =±1 ) states is found to completely dominate the underlying laser-matter interaction. It turns out that the large difference in the ionization rates of the 2 s and 2 p (m =±1 ) states is important in this context, effectively leading to a symmetry breaking in the corresponding (beyond-dipole) bound-bound dynamics with the result that a net population transfer between the states occurs throughout the laser-matter interaction period. Varying the x-ray exposure time as well as the laser intensity, we probe the phenomenon as the bound wave packet oscillates between having 2 s and 2 p (m =±1 ) character, eventually giving rise to a Rabi-like oscillation pattern in the populations.
NASA Astrophysics Data System (ADS)
Choi, Jun-Ho; Cho, Minhaeng
2013-05-01
The Hessian matrix reconstruction method initially developed to extract the basis mode frequencies, vibrational coupling constants, and transition dipoles of the delocalized amide I, II, and III vibrations of polypeptides and proteins from quantum chemistry calculation results is used to obtain those properties of delocalized O-H stretch modes in liquid water. Considering the water symmetric and asymmetric O-H stretch modes as basis modes, we here develop theoretical models relating vibrational frequencies, transition dipoles, and coupling constants of basis modes to local water configuration and solvent electric potential. Molecular dynamics simulation was performed to generate an ensemble of water configurations that was in turn used to construct vibrational Hamiltonian matrices. Obtaining the eigenvalues and eigenvectors of the matrices and using the time-averaging approximation method, which was developed by the Skinner group, to calculating the vibrational spectra of coupled oscillator systems, we could numerically simulate the O-H stretch IR spectrum of liquid water. The asymmetric line shape and weak shoulder bands were quantitatively reproduced by the present computational procedure based on vibrational exciton model, where the polarization effects on basis mode transition dipoles and inter-mode coupling constants were found to be crucial in quantitatively simulating the vibrational spectra of hydrogen-bond networking liquid water.
Diffusion-mediated dephasing in the dipole field around a single spherical magnetic object.
Buschle, Lukas R; Kurz, Felix T; Kampf, Thomas; Triphan, Simon M F; Schlemmer, Heinz-Peter; Ziener, Christian Herbert
2015-11-01
In this work, the time evolution of the free induction decay caused by the local dipole field of a spherical magnetic perturber is analyzed. The complicated treatment of the diffusion process is replaced by the strong-collision-approximation that allows a determination of the free induction decay in dependence of the underlying microscopic tissue parameters such as diffusion coefficient, sphere radius and susceptibility difference. The interplay between susceptibility- and diffusion-mediated effects yields several dephasing regimes of which, so far, only the classical regimes of motional narrowing and static dephasing for dominant and negligible diffusion, respectively, were extensively examined. Due to the asymmetric form of the dipole field for spherical objects, the free induction decay exhibits a complex component in contradiction to the cylindrical case, where the symmetric local dipole field only causes a purely real induction decay. Knowledge of the shape of the corresponding frequency distribution is necessary for the evaluation of more sophisticated pulse sequences and a detailed understanding of the off-resonance distribution allows improved quantification of transverse relaxation. PMID:26133269
Dipole radiation in a one-dimensional photonic crystal: TE polarization
NASA Astrophysics Data System (ADS)
Alvarado-Rodriguez, I.; Halevi, P.; Sánchez, Adán S.
2001-05-01
We study the power emitted by an oscillating dipole in a superlattice (SL) modeled by means of a periodic distribution of Dirac δ functions (Dirac comb SL). The radiation is permitted to propagate in all directions in space; however, it is restricted to the transverse electric (TE) polarization mode. The calculation is based on a classical theory of radiation in nonuniform dielectric media by Dowling and Bowden [Phys. Rev. A 46, 612 (1992)]. The emitted power is derived in terms of a single integral, with no approximations. A SL has no omnidirectional photonic band gaps, and therefore the power is always finite. The power spectrum exhibits slope discontinuities, which occur at the band edges for on-axis propagation. It also depends strongly on the dipole's position in the SL and on the grating strength that characterizes the Dirac comb model. The power peaks for low frequencies, and there can be large enhancement of emission as compared to free space. The closer the dipole is to a barrier (Dirac δ) and the greater the grating strength, the stronger the enhancement is. These conclusions are expected to be relevant for a real SL.
Electric transition dipole moment in pre-Born-Oppenheimer molecular structure theory.
Simmen, Benjamin; Mátyus, Edit; Reiher, Markus
2014-10-21
This paper presents the calculation of the electric transition dipole moment in a pre-Born-Oppenheimer framework. Electrons and nuclei are treated equally in terms of the parametrization of the non-relativistic total wave function, which is written as a linear combination of basis functions constructed from explicitly correlated Gaussian functions and the global vector representation. The integrals of the electric transition dipole moment are derived corresponding to these basis functions in both the length and the velocity representation. The calculations are performed in laboratory-fixed Cartesian coordinates without relying on coordinates which separate the center of mass from the translationally invariant degrees of freedom. The effect of the overall motion is eliminated through translationally invariant integral expressions. The electric transition dipole moment is calculated between two rovibronic levels of the H2 molecule assignable to the lowest rovibrational states of the X (1)Σ(g)(+) and B (1)Σ(u)(+) electronic states in the clamped-nuclei framework. This is the first evaluation of this quantity in a full quantum mechanical treatment without relying on the Born-Oppenheimer approximation. PMID:25338879
A New LLR Approximation for BICM Systems with HARQ
NASA Astrophysics Data System (ADS)
Kang, Jin Whan; Kim, Sang-Hyo; Yoon, Seokho; Han, Tae Hee; Choi, Hyoung Kee
In this letter, a new approximation of log-likelihood ratio (LLR) for soft input channel decoding is proposed. Conventional simplified LLR using log-sum approximation can degrade the performance of bit interleaved coded modulation (BICM) systems employing hybrid automatic repeat request (HARQ) at low SNR. The proposed LLR performs as well as the exact LLR, and at the same time, requires only a small number of elementary operations.
Near-field induction heating of metallic nanoparticles due to infrared magnetic dipole contribution
NASA Astrophysics Data System (ADS)
Chapuis, Pierre-Olivier; Laroche, Marine; Volz, Sebastian; Greffet, Jean-Jacques
2008-03-01
We revisit the electromagnetic heat transfer between a metallic nanoparticle and a highly conductive metallic semi-infinite substrate, commonly studied using the electric dipole approximation. For infrared and microwave frequencies, we find that the magnetic polarizability of the particle is larger than the electric one. We also find that the local density of states in the near field is dominated by the magnetic contribution. As a consequence, the power absorbed by the particle in the near field is due to dissipation by fluctuating eddy currents. These results show that a number of near-field effects involving metallic particles should be affected by the fluctuating magnetic fields.
Reflection and transmission properties of a metasurface composed of resonant loaded wire dipoles.
Awan, Z A
2016-05-20
A considered metasurface is assumed to consist of a two-dimensional periodic arrangement of inductively loaded wires. The effects of incident angles and inductive loads upon equivalent surface impedance, reflection, and transmission properties of this metasurface have been investigated using numerical simulations. It is shown that at a particular frequency and angle, a metasurface can be cloaked for the incoming incident wave with nearly zero reflection. It is further studied that this approximate zero reflection is independent of the inductances of the inductively loaded wire dipoles. PMID:27411153
Performance of initial full-length RHIC (Relativistic Heavy Ion Collider) dipoles
Dahl, P.; Cottingham, J.; Garber, M.; Ghosh, A.; Goodzeit, C.; Greene, A.; Herrera, J.; Kahn, S.; Kelly, E.; Morgan, G.
1987-01-01
The first four full-length (9.7 m) R and D dipoles for the proposed Relativistic Heavy Ion Collider (RHIC) have been successfully tested. The magnets reached a quench plateau of approximately 4.5 T with very reasonable training - a field level comfortably above the design field of 3.45 T required for operation with beams of 100 GeV/amu gold nuclei. Measured field multipoles are considered to be quite acceptable for this series of R and D magnets.
NASA Astrophysics Data System (ADS)
Safar, Anuar Mat; Aljunid, Syed Alwee; Arief, Amir Razif; Nordin, Junita; Saad, Naufal
2012-01-01
The use of minimal multiple access interference (MAI) in code design is investigated. Applying a projection and mapping techniques, a code that has a zero cross correlation (ZCC) between users in optical code division multiple access (OCDMA) is presented in this paper. The system is based on an incoherent light source—LED, spectral amplitude coding (SAC), and direct detection techniques at the receiver. Using power spectral density (PSD) function and Gaussian approximation, we obtain the signal-to-noise ratio (SNR) and the bit-error rate (BER) to measure the code performance. Making a comparison with other existing codes, e.g., Hadamard, MFH and MDW codes, we show that our code performs better at BER 10-9 in terms of number of simultaneous users. We also demonstrate the comparison between the theoretical and simulation analyses, where the results are close to one another.
An Empirical Evaluation of Coding Methods for Multi-Symbol Alphabets.
ERIC Educational Resources Information Center
Moffat, Alistair; And Others
1994-01-01
Evaluates the performance of different methods of data compression coding in several situations. Huffman's code, arithmetic coding, fixed codes, fast approximations to arithmetic coding, and splay coding are discussed in terms of their speed, memory requirements, and proximity to optimal performance. Recommendations for the best methods of…
Approximate Genealogies Under Genetic Hitchhiking
Pfaffelhuber, P.; Haubold, B.; Wakolbinger, A.
2006-01-01
The rapid fixation of an advantageous allele leads to a reduction in linked neutral variation around the target of selection. The genealogy at a neutral locus in such a selective sweep can be simulated by first generating a random path of the advantageous allele's frequency and then a structured coalescent in this background. Usually the frequency path is approximated by a logistic growth curve. We discuss an alternative method that approximates the genealogy by a random binary splitting tree, a so-called Yule tree that does not require first constructing a frequency path. Compared to the coalescent in a logistic background, this method gives a slightly better approximation for identity by descent during the selective phase and a much better approximation for the number of lineages that stem from the founder of the selective sweep. In applications such as the approximation of the distribution of Tajima's D, the two approximation methods perform equally well. For relevant parameter ranges, the Yule approximation is faster. PMID:17182733
CONSTRAINT ON LIGHT DIPOLE DARK MATTER FROM HELIOSEISMOLOGY
Lopes, Ilídio; Kadota, Kenji; Silk, Joseph E-mail: ilopes@uevora.pt E-mail: silk@astro.ox.ac.uk
2014-01-10
We investigate the effects of a magnetic dipole moment of asymmetric dark matter (DM) in the evolution of the Sun. The dipole interaction can lead to a sizable DM scattering cross section even for light DM, and asymmetric DM can lead to a large DM number density in the Sun. We find that solar model precision tests, using as diagnostic the sound speed profile obtained from helioseismology data, exclude dipolar DM particles with a mass larger than 4.3 GeV and magnetic dipole moment larger than 1.6 × 10{sup –17} e cm.
Electric Dipole States and Time Reversal Violation in Nuclei.
NASA Astrophysics Data System (ADS)
Auerbach, N.
2016-06-01
The nuclear Schiff moment is essential in the mechanism that induces a parity and time reversal violation in the atom. In this presentation we explore theoretically the properties and systematics of the isoscalar dipole in nuclei with the emphasis on the low-energy strength and the inverse energy weighted sum which determines the Schiff moment. We also study the influence of the isovector dipole strength distribution on the Schiff moment. The influence of a large neutron excess in nuclei is examined. The centroid energies of the isoscalar giant resonance (ISGDR) and the overtone of the isovector giant dipole resonance (OIVGDR) are given for a range of nuclei.
Propagation of the Lissajous singularity dipole in free space
NASA Astrophysics Data System (ADS)
Chen, Haitao; Gao, Zenghui; Zou, Xuefang; Xiao, Xi; Wang, Fanhou; Yang, Huajun
2014-01-01
The propagation properties of a pair of Lissajous singularities with opposite singularity indexes called the Lissajous singularity dipole (LSD) in free space are studied analytically and illustrated numerically. It is shown that the motion, creation, annihilation and change in the degree of polarization of the LSD, and change in the shape of Lissajous figures take place by suitably varying the waist width, off-axis distance or propagation distance. In particular, the creation and shift to infinity of a single Lissajous singularity may appear. A comparison with the free-space propagation of an optical vortex dipole and a C-dipole is also made.
Diatomic molecules in optical and microwave dipole traps
Lysebo, Marius; Veseth, Leif
2011-03-15
The dipole forces on rotating diatomic molecules are worked out in detail for optical as well as microwave radiation fields. The objective is in particular to investigate how the dipole forces and potentials depend on the subtle internal structure of the molecule, with special emphasis on hyperfine and Zeeman states. Dipole potentials are obtained from computations of the real part of the complex molecular polarizability, whereas the imaginary part yields the scattering force. Numerical examples are presented for {sup 23}Na{sub 2} and OH for optical (laser) fields related to strong electronic transitions and for microwave fields for the {Lambda} doubling in the OH ground state.
Equipotential transformation of multipole systems to dipole systems
NASA Technical Reports Server (NTRS)
Wang, W. X.
1987-01-01
The vector sum of fields produced by a set of magnetic dipoles with different magnetic moments that are both tilted from the planetary spin axis and offset from the planetary center by different amounts can be used to completely represent a planetary magnetic field in the conventional form of spherical harmonic expansion. The scalar equipotential transformation analytically results in 24 equations that may subsequently be solved for the 24 adjustable parameters in dipole systems with the predetermined main dipole. Attention is given to this method's application to the Jovian magnetic field.
Nuclear Electric Dipole Moment of 3He
Stetcu, I; P.Liu, C; Friar, J L; Hayes, A C; Navratil, P
2008-04-08
A permanent electric dipole moment (EDM) of a physical system would require time-reversal (T) violation, which is equivalent to charge-conjugation-parity (CP) violation by CPT invariance. Experimental programs are currently pushing the limits on EDMs in atoms, nuclei, and the neutron to regimes of fundamental theoretical interest. Nuclear EDMs can be studied at ion storage rings with sensitivities that may be competitive with atomic and neutron measurements. Here we calculate the magnitude of the CP-violating EDM of {sup 3}He and the expected sensitivity of such a measurement to the underlying CP-violating interactions. Assuming that the coupling constants are of comparable magnitude for {pi}-, {rho}-, and {omega}-exchanges, we find that the pion-exchange contribution dominates. Finally, our results suggest that a measurement of the {sup 3}He EDM is complementary to the planned neutron and deuteron experiments, and could provide a powerful constraint for the theoretical models of the pion-nucleon P,T-violating interaction.
An Efficient Coupled Dipole Method: TCDM
NASA Astrophysics Data System (ADS)
Kim, Hye-Young
2015-03-01
An overview of a memory-efficient and cost-effective method, called Trace-Coupled Dipole Method (TCDM), which can accurately predict the van der Waals (VDW) forces between dielectric materials will be presented. CDM is an intrinsically atomistic method which includes all the many-body interaction terms self-consistently. TCDM, an alternative way to execute CDM, is to obtain VDW interaction energy by calculating the trace of a 3NX3N matrix, rather than its eigenvalues. It will be demonstrated that the power series expansion in TCDM is equivalent to that of the perturbation theory. The advantage of adopting TCDM over the conventional perturbation theory or CDM will also be discussed. The use of TCDM will make it practical for any interested future users to calculate the accurate VDW interaction in large systems like those found in computer simulation studies without serious increase in computational burden. This research is supported by the Louisiana Board of Regents-RCS Grant (LEQSF(2012-15)-RD-A-19).
Magnetic dipole discharges. I. Basic properties
Stenzel, R. L.; Urrutia, J. M.; Teodorescu-Soare, C. T.; Ionita, C.; Schrittwieser, R.
2013-08-15
A simple discharge is described which uses a permanent magnet as a cold cathode and the metallic chamber wall as an anode. The magnet's equator is biased strongly negative, which produces secondary electrons due to the impact of energetic ions. The emitted electrons are highly confined by the strong dipolar magnetic field and the negative potential in the equatorial plane of the magnet. The emitted electrons ionize near the sheath and produce further electrons, which drift across field lines to the anode while the nearly unmagnetized ions are accelerated back to the magnet. A steady state discharge is maintained at neutral pressures above 10{sup −3} mbar. This is the principle of magnetron discharges, which commonly use cylindrical and planar cathodes rather than magnetic dipoles as cathodes. The discharge properties have been investigated in steady state and pulsed mode. Different magnets and geometries have been employed. The role of a background plasma has been investigated. Various types of instabilities have been observed such as sheath oscillations, current-driven turbulence, relaxation instabilities due to ionization, and high frequency oscillations created by sputtering impulses, which are described in more detail in companion papers. The discharge has also been operated in reactive gases and shown to be useful for sputtering applications.
Electric dipole polarizability and the neutral skin
Piechaczek, A.; Nazarewicz, Witold; Reinhard, P.-G.; Agrawal, Bijay K; Colo, Gianluca; Paar, Nils; Roca-Maza, X; Vretenar, Dario
2012-01-01
The recent high-resolution measurement of the electric dipole (E1) polarizability {alpha}{sub D} in {sup 208}Pb [A. Tamii et al. Phys. Rev. Lett. 107 062502 (2011)] provides a unique constraint on the neutron-skin thickness of this nucleus. The neutron-skin thickness r{sub skin} of {sup 208}Pb is a quantity of critical importance for our understanding of a variety of nuclear and astrophysical phenomena. To assess the model dependence of the correlation between {alpha}{sub D} and r{sub skin}, we carry out systematic calculations for {sup 208}Pb, {sup 132}Sn, and {sup 48}Ca based on the nuclear density functional theory using both nonrelativistic and relativistic energy density functionals. Our analysis indicates that whereas individual models exhibit a linear dependence between {alpha}{sub D} and r{sub skin}, this correlation is not universal when one combines predictions from a host of different models. By averaging over these model predictions, we provide estimates with associated systematic errors for r{sub skin} and {alpha}{sub D} for the nuclei under consideration. We conclude that precise measurements of r{sub skin} in both {sup 48}Ca and {sup 208}Pb - combined with the recent measurement of {alpha}{sub D} - should significantly constrain the isovector sector of the nuclear energy density functional.
Two flavors of the Indian Ocean Dipole
NASA Astrophysics Data System (ADS)
Endo, Satoru; Tozuka, Tomoki
2015-07-01
The Indian Ocean Dipole (IOD) is known as a climate mode in the tropical Indian Ocean accompanied by negative (positive) sea surface temperature (SST) anomalies over the eastern (western) pole during its positive phase. However, the western pole of the IOD is not always covered totally by positive SST anomalies. For this reason, the IOD is further classified into two types in this study based on SST anomalies in the western pole. The first type (hereafter "canonical IOD") is associated with negative (positive) SST anomalies in the eastern (central to western) tropical Indian Ocean. The second type (hereafter "IOD Modoki"), on the other hand, is associated with negative SST anomalies in the eastern and western tropical Indian Ocean and positive SST anomalies in the central tropical Indian Ocean. Based on composite analyses, it is found that easterly wind anomalies cover the whole equatorial Indian Ocean in the canonical IOD, and as a result, positive rainfall anomalies are observed over East Africa. Also, due to the basin-wide easterly wind anomalies, the canonical IOD is accompanied by strong sea surface height (SSH) anomalies. In contrast, zonal wind anomalies converge in the central tropical Indian Ocean in the IOD Modoki, and no significant precipitation anomalies are found over East Africa. Also, only weak SSH anomalies are seen, because equatorial downwelling anomalies induced by westerly wind anomalies in the west are counteracted by equatorial upwelling anomalies caused by easterly wind anomalies in the east.
The search for permanent electric dipole moments
Kirch, Klaus
2013-02-13
Permanent electric dipole moments (EDMs) of fundamental systems with spin - particles, nuclei, atoms or molecules violate parity and time reversal invariance. Invoking the CPT theorem, time reversal violation implies CP violation. Although CP-violation is implemented in the standard electro-weak theory, EDM generated this way remain undetectably small. However, this CP-violation also appears to fail explaining the observed baryon asymmetry of our universe. Extensions of the standard theory usually include new sources of CP violation and often predict sizeable EDMs. EDM searches in different systems are complementary and various efforts worldwide are underway and no finite value has been established yet. The prototype of an EDM search is the pursuit of the EDM of the neutron. It has the longest history and at the same time is at the forefront of present research. The talk aims at giving an overview of the field with emphasis on our efforts within an international collaboration at PSI, nedm.web.psi.ch.
Nuclear Electric Dipole Moment of ^{3}_He
Stetcu, I.; Liu, C.-P.; Friar, J. L.; Hayes, A. C.; Navratil, P.
2008-01-01
A permanent electric dipole moment (EDM) of a physical system would require time-reversal (T) violation, which is equivalent to charge-conjugation-parity (CP) violation by CPT invariance. Experimental programs are currently pushing the limits on EDMs in atoms, nuclei, and the neutron to regimes of fundamental theoretical interest. Nuclear EDMs can be studied at ion storage rings with sensitivities that may be competitive with atomic and neutron measurements. Here we calculate the magnitude of the CP-violating EDM of ^{3}_He and the expected sensitivity of such a measurement to the underlyng CP-violating interactions. Assuming that the coupling constants are of comparable magnitude for {\\pi}-, {\\rho}-, and {\\omega}-exchanges, we find that the pion-exchange contribution dominates. Our results suggest that a measurement of the ^{3}_He EDM is complementary to the planned neutron and deuteron experiments, and could provide a powerful constraint for the theoretical models of the pion-nucleon P,T-violating interaction.
Two flavors of the Indian Ocean Dipole
NASA Astrophysics Data System (ADS)
Endo, Satoru; Tozuka, Tomoki
2016-06-01
The Indian Ocean Dipole (IOD) is known as a climate mode in the tropical Indian Ocean accompanied by negative (positive) sea surface temperature (SST) anomalies over the eastern (western) pole during its positive phase. However, the western pole of the IOD is not always covered totally by positive SST anomalies. For this reason, the IOD is further classified into two types in this study based on SST anomalies in the western pole. The first type (hereafter "canonical IOD") is associated with negative (positive) SST anomalies in the eastern (central to western) tropical Indian Ocean. The second type (hereafter "IOD Modoki"), on the other hand, is associated with negative SST anomalies in the eastern and western tropical Indian Ocean and positive SST anomalies in the central tropical Indian Ocean. Based on composite analyses, it is found that easterly wind anomalies cover the whole equatorial Indian Ocean in the canonical IOD, and as a result, positive rainfall anomalies are observed over East Africa. Also, due to the basin-wide easterly wind anomalies, the canonical IOD is accompanied by strong sea surface height (SSH) anomalies. In contrast, zonal wind anomalies converge in the central tropical Indian Ocean in the IOD Modoki, and no significant precipitation anomalies are found over East Africa. Also, only weak SSH anomalies are seen, because equatorial downwelling anomalies induced by westerly wind anomalies in the west are counteracted by equatorial upwelling anomalies caused by easterly wind anomalies in the east.
Exponential approximations in optimal design
NASA Technical Reports Server (NTRS)
Belegundu, A. D.; Rajan, S. D.; Rajgopal, J.
1990-01-01
One-point and two-point exponential functions have been developed and proved to be very effective approximations of structural response. The exponential has been compared to the linear, reciprocal and quadratic fit methods. Four test problems in structural analysis have been selected. The use of such approximations is attractive in structural optimization to reduce the numbers of exact analyses which involve computationally expensive finite element analysis.
Approximate factorization with source terms
NASA Technical Reports Server (NTRS)
Shih, T. I.-P.; Chyu, W. J.
1991-01-01
A comparative evaluation is made of three methodologies with a view to that which offers the best approximate factorization error. While two of these methods are found to lead to more efficient algorithms in cases where factors which do not contain source terms can be diagonalized, the third method used generates the lowest approximate factorization error. This method may be preferred when the norms of source terms are large, and transient solutions are of interest.
NASA Astrophysics Data System (ADS)
Perrusson, G.; Lambert, M.; Lesselier, D.; Charalambopoulos, A.; Dassios, G.
2000-03-01
The field resulting from the illumination by a localized time-harmonic low-frequency source (typically a magnetic dipole) of a voluminous lossy dielectric body placed in a lossy dielectric embedding is determined within the framework of the localized nonlinear approximation by means of a low-frequency Rayleigh analysis. It is sketched (1) how one derives a low-frequency series expansion in positive integral powers of (jk), where k is the embedding complex wavenumber, of the depolarization dyad that relates the background electric field to the total electric field inside the body; (2) how this expansion is used to determine the magnetic field resulting outside the body and how the corresponding series expansion of this field, up to the power 5 in (jk), follows once the series expansion of the incident electric field in the body volume is known up to the same power; and (3) how the needed nonzero coefficients of the depolarization dyad (up to the power 3 in (jk)) are obtained, for a general triaxial ellipsoid and after careful reduction for the geometrically degenerate geometries, with the help of the elliptical harmonic theory. Numerical results obtained by this hybrid low-frequency approach illustrate its capability to provide accurate magnetic fields at low computational cost, in particular, in comparison with a general purpose method-of-moments code.
NASA Astrophysics Data System (ADS)
Abdullah, Alyasa Gan; Wah, Yap Bee
2015-02-01
The computation of the approximate values of the trigonometric sines was discovered by Bhaskara I (c. 600-c.680), a seventh century Indian mathematician and is known as the Bjaskara's I's sine approximation formula. The formula is given in his treatise titled Mahabhaskariya. In the 14th century, Madhava of Sangamagrama, a Kerala mathematician astronomer constructed the table of trigonometric sines of various angles. Madhava's table gives the measure of angles in arcminutes, arcseconds and sixtieths of an arcsecond. The search for more accurate formulas led to the discovery of the power series expansion by Madhava of Sangamagrama (c.1350-c. 1425), the founder of the Kerala school of astronomy and mathematics. In 1715, the Taylor series was introduced by Brook Taylor an English mathematician. If the Taylor series is centered at zero, it is called a Maclaurin series, named after the Scottish mathematician Colin Maclaurin. Some of the important Maclaurin series expansions include trigonometric functions. This paper introduces the genetic code of the sine of an angle without using power series expansion. The genetic code using square root approach reveals the pattern in the signs (plus, minus) and sequence of numbers in the sine of an angle. The square root approach complements the Pythagoras method, provides a better understanding of calculating an angle and will be useful for teaching the concepts of angles in trigonometry.
Approximating random quantum optimization problems
NASA Astrophysics Data System (ADS)
Hsu, B.; Laumann, C. R.; Läuchli, A. M.; Moessner, R.; Sondhi, S. L.
2013-06-01
We report a cluster of results regarding the difficulty of finding approximate ground states to typical instances of the quantum satisfiability problem k-body quantum satisfiability (k-QSAT) on large random graphs. As an approximation strategy, we optimize the solution space over “classical” product states, which in turn introduces a novel autonomous classical optimization problem, PSAT, over a space of continuous degrees of freedom rather than discrete bits. Our central results are (i) the derivation of a set of bounds and approximations in various limits of the problem, several of which we believe may be amenable to a rigorous treatment; (ii) a demonstration that an approximation based on a greedy algorithm borrowed from the study of frustrated magnetism performs well over a wide range in parameter space, and its performance reflects the structure of the solution space of random k-QSAT. Simulated annealing exhibits metastability in similar “hard” regions of parameter space; and (iii) a generalization of belief propagation algorithms introduced for classical problems to the case of continuous spins. This yields both approximate solutions, as well as insights into the free energy “landscape” of the approximation problem, including a so-called dynamical transition near the satisfiability threshold. Taken together, these results allow us to elucidate the phase diagram of random k-QSAT in a two-dimensional energy-density-clause-density space.
Diffusion approximation for modeling of 3-D radiation distributions
Zardecki, A.; Gerstl, S.A.W.; De Kinder, R.E. Jr.
1985-01-01
A three-dimensional transport code DIF3D, based on the diffusion approximation, is used to model the spatial distribution of radiation energy arising from volumetric isotropic sources. Future work will be concerned with the determination of irradiances and modeling of realistic scenarios, relevant to the battlefield conditions. 8 refs., 4 figs.
zeldovich-PLT: Zel'dovich approximation initial conditions generator
NASA Astrophysics Data System (ADS)
Eisenstein, Daniel; Garrison, Lehman
2016-05-01
zeldovich-PLT generates Zel'dovich approximation (ZA) initial conditions (i.e. first-order Lagrangian perturbation theory) for cosmological N-body simulations, optionally applying particle linear theory (PLT) corrections. The code uses double precision internally, but output format can be set to single or double precision.
Turbo Equalization Using Partial Gaussian Approximation
NASA Astrophysics Data System (ADS)
Zhang, Chuanzong; Wang, Zhongyong; Manchon, Carles Navarro; Sun, Peng; Guo, Qinghua; Fleury, Bernard Henri
2016-09-01
This paper deals with turbo-equalization for coded data transmission over intersymbol interference (ISI) channels. We propose a message-passing algorithm that uses the expectation-propagation rule to convert messages passed from the demodulator-decoder to the equalizer and computes messages returned by the equalizer by using a partial Gaussian approximation (PGA). Results from Monte Carlo simulations show that this approach leads to a significant performance improvement compared to state-of-the-art turbo-equalizers and allows for trading performance with complexity. We exploit the specific structure of the ISI channel model to significantly reduce the complexity of the PGA compared to that considered in the initial paper proposing the method.
Comparing numerical and analytic approximate gravitational waveforms
NASA Astrophysics Data System (ADS)
Afshari, Nousha; Lovelace, Geoffrey; SXS Collaboration
2016-03-01
A direct observation of gravitational waves will test Einstein's theory of general relativity under the most extreme conditions. The Laser Interferometer Gravitational-Wave Observatory, or LIGO, began searching for gravitational waves in September 2015 with three times the sensitivity of initial LIGO. To help Advanced LIGO detect as many gravitational waves as possible, a major research effort is underway to accurately predict the expected waves. In this poster, I will explore how the gravitational waveform produced by a long binary-black-hole inspiral, merger, and ringdown is affected by how fast the larger black hole spins. In particular, I will present results from simulations of merging black holes, completed using the Spectral Einstein Code (black-holes.org/SpEC.html), including some new, long simulations designed to mimic black hole-neutron star mergers. I will present comparisons of the numerical waveforms with analytic approximations.
Lugovtsov, A E; Nikitin, S Yu; Priezzhev, A V
2008-06-30
A theoretical model is developed and an algorithm is proposed for calculating far-field light scattering by a transparent dielectric particle significantly larger than a wavelength. The accuracy of this algorithm is close to that of the discrete dipole approximation. The calculation time for this algorithm in the case of particles with the size parameter higher than 50 is much lower than that for the discrete dipole approximation. Scattering diagrams for spheroidal particles of different sizes, orientations and refractive indices are calculated. The proposed algorithm has a great potential for quick calculations of parameters of light scattering by large biological particles such as erythrocytes and their aggregates, bacteria, etc. (special issue devoted to application of laser technologies in biophotonics and biomedical studies)
Nonexistence of the self-accelerating dipole and related questions
NASA Astrophysics Data System (ADS)
Steane, Andrew M.
2014-06-01
We calculate the self-force of a constantly accelerating electric dipole, showing, in particular, that classical electromagnetism does not predict that an electric dipole could self-accelerate, nor could it levitate in a gravitational field. We also resolve a paradox concerning the inertial mass of a longitudinally accelerating dipole, showing that the combined system of dipole plus field can be assigned a well-defined energy-momentum four-vector, so that the principle of relativity is satisfied. We then present some general features of electromagnetic phenomena in a reference frame described by the Rindler metric, showing in particular that an observer fixed in a gravitational field described everywhere by the Rindler metric will find any charged object supported in the gravitational field to possess an electromagnetic self-force equal to that observed by an inertial observer relative to which the body undergoes rigid hyperbolic motion. It follows that the principle of equivalence is satisfied by these systems.
Quantitative analysis on electric dipole energy in Rashba band splitting
NASA Astrophysics Data System (ADS)
Hong, Jisook; Rhim, Jun-Won; Kim, Changyoung; Ryong Park, Seung; Hoon Shim, Ji
2015-09-01
We report on quantitative comparison between the electric dipole energy and the Rashba band splitting in model systems of Bi and Sb triangular monolayers under a perpendicular electric field. We used both first-principles and tight binding calculations on p-orbitals with spin-orbit coupling. First-principles calculation shows Rashba band splitting in both systems. It also shows asymmetric charge distributions in the Rashba split bands which are induced by the orbital angular momentum. We calculated the electric dipole energies from coupling of the asymmetric charge distribution and external electric field, and compared it to the Rashba splitting. Remarkably, the total split energy is found to come mostly from the difference in the electric dipole energy for both Bi and Sb systems. A perturbative approach for long wave length limit starting from tight binding calculation also supports that the Rashba band splitting originates mostly from the electric dipole energy difference in the strong atomic spin-orbit coupling regime.
Warped AdS3/dipole-CFT duality
NASA Astrophysics Data System (ADS)
Song, Wei; Strominger, Andrew
2012-05-01
String theory contains solutions with {{SL}}( {{2},{R}} ){{R}} × {{U}}{( {1} )_L} -invariant warped AdS3 (WAdS3) factors arising as continuous deformations of ordinary AdS3 factors. We propose that some of these are holographically dual to the IR limits of nonlocal dipole-deformed 2D D-brane gauge theories, referred to as "dipole CFTs". Neither the bulk nor boundary theories are currently well-understood, and consequences of the proposed duality for both sides is investigated. The bulk entropy-area law suggests that dipole CFTs have (at large N) a high-energy density of states which does not depend on the deformation parameter. Putting the boundary theory on a spatial circle leads to closed timelike curves in the bulk, suggesting a relation of the latter to dipole-type nonlocality.
Development of Cellular Magnetic Dipoles in Magnetotactic Bacteria
Faivre, Damien; Fischer, Anna; Garcia-Rubio, Inés; Mastrogiacomo, Giovanni; Gehring, Andreas U.
2010-01-01
Magnetotactic bacteria benefit from their ability to form cellular magnetic dipoles by assembling stable single-domain ferromagnetic particles in chains as a means to navigate along Earth's magnetic field lines on their way to favorable habitats. We studied the assembly of nanosized membrane-encapsulated magnetite particles (magnetosomes) by ferromagnetic resonance spectroscopy using Magnetospirillum gryphiswaldense cultured in a time-resolved experimental setting. The spectroscopic data show that 1), magnetic particle growth is not synchronized; 2), the increase in particle numbers is insufficient to build up cellular magnetic dipoles; and 3), dipoles of assembled magnetosome blocks occur when the first magnetite particles reach a stable single-domain state. These stable single-domain particles can act as magnetic docks to stabilize the remaining and/or newly nucleated superparamagnetic particles in their adjacencies. We postulate that docking is a key mechanism for building the functional cellular magnetic dipole, which in turn is required for magnetotaxis in bacteria. PMID:20713012
WHT, DIPOL-2 polarimetry of Nova Sgr 2015b
NASA Astrophysics Data System (ADS)
Harvey, Eamonn; Berdyugin, Andrei; Redman, Matt
2015-09-01
We report polarimetry data from three nights observing of Nova Sgr 2015b (also PNV J18365700-2855420 or V5668 Sgr) with the William Herschel Telescope in the BVR passbands using the DIPOL-2 instrument.
Initial tests of an AC dipole for the Tevatron
Miyamoto, R.; Jansson, A.; Kopp, S.; Syphers, M.; /Fermilab
2006-06-01
The AC dipole is a device to diagnose transverse motions of a beam. It can achieve large-amplitude oscillations without two inevitable problems of conventional kicker/pinger magnets: decoherence and emittance growth. While not the first synchrotron to operate with an AC dipole, the Tevatron can now make use of its recently upgraded BPM system, providing unprecedented resolution for use with an AC dipole, to measure both linear and nonlinear properties of the accelerator. Plans are to provide AC dipole systems for both transverse degrees of freedom. Preliminary tests have been done using an audio power amplifier with an existing vertical pinger magnet, producing oscillation amplitudes up to 2{sigma} at 150 GeV. In this paper, we will present the configuration of this system. We also show the analysis of a first few data sets, including the direct measurement of beta functions at BPM locations.
Dipole Theory of Heat Production and Absorption in Nerve Axon
Wei, Ling Y.
1972-01-01
Exact formulas are derived for the energy change of a dipole system with two energy states (or bands) in a changing field in two cases: (a) no dipole flip-flop and (b) dipole flip-flop caused by stimulation. Based on these formulas, the positive and negative heats are calculated. The results are in good agreement with experiment in case b but are 60-180% larger in case a. Furthermore, the theory shows that the negative heat cannot be less than the positive heat in case a but can be either way in case b, the latter result being found prevalent in experiment. It is concluded that nerve excitation is most likely to involve dipole flip-flop at the membrane surface. The theory is consistent in the interpretations and correlations of the electrical, optical, and thermal effects observed in nerve axon. PMID:5056960